/*
 * Streams for CLISP
 * Bruno Haible 1990-2008, 2016-2020
 * Sam Steingold 1998-2011, 2016-2017
 * Generic Streams: Marcus Daniels 8.4.1994
 * SCREEN package for Win32: Arseny Slobodjuck 2001-02-14
 * German comments translated into English: Stefan Kain 2001-11-02
 */

#include "lispbibl.c"
#include "arilev0.c"            /* for R_sign */

#if 0
  #define DEBUG_OUT(x)  do { printf x; fflush(stdout); } while(0)
#else
  #define DEBUG_OUT(x)
#endif

#ifdef GNU_READLINE
  #include <readline/readline.h>
  #include <readline/history.h>
#endif

/* off_t is a signed type, defined in <sys/types.h> and <fcntl.h>, denoting
 a file descriptor's position. Here we also need the unsigned equivalent. */
#if SIZEOF_OFF_T > 4
  typedef uint64 uoff_t;
#else
  typedef uint32 uoff_t;
#endif

/* Converts an uoff_t value into an Integer >=0.
 uoff_t_to_I(value)
 > value: value in the range of uoff_t
 < result: Integer with that value.
 can trigger GC */
#if SIZEOF_OFF_T > 4
  #define uoff_to_I UQ_to_I
#else
  #define uoff_to_I UL_to_I
#endif

/* Converts an Integer >=0 into an uoff_t value.
 I_to_uoff_t(obj)
 > obj: an object, should be an Integer >=0, <= ~(uoff_t)0
 < result: the Integer's value as an uoff_t */
#if SIZEOF_OFF_T > 4
  #define I_to_uoff_t I_to_UQ
#else
  #define I_to_uoff_t I_to_UL
#endif

/* Test for an Integer that fits into an uoff_t.
 uoff_t_p(obj)
 > obj: an object
 < result: true if it's an integer >=0, <= ~(uoff_t)0 */
#if SIZEOF_OFF_T > 4
  #define uoff_t_p uint64_p
#else
  #define uoff_t_p uint32_p
#endif

/* once again the structure of Streams:
 strmflags = Flags
 Bits in the Flags:
   define strmflags_open_bit_B  0  - set, if the Stream is open
   define strmflags_immut_bit_B 1  - set if read literals are immutable
   define strmflags_fasl_bit_B  2  - Read-Eval is allowed, \r=#\Return */
  #define strmflags_unread_bit_B 3  /* set while strm_rd_ch_last is back */
/* define strmflags_rd_by_bit_B 4  - set if READ-BYTE is possible
   define strmflags_wr_by_bit_B 5  - set if WRITE-BYTE is possible
   define strmflags_rd_ch_bit_B 6  - set if READ-CHAR is possible
   define strmflags_wr_ch_bit_B 7  - set if WRITE-CHAR is possible
 Bitmasks in the Flags:
   define strmflags_open_B  bit(strmflags_open_bit_B) */
  #define strmflags_immut_B  bit(strmflags_immut_bit_B)
  #define strmflags_fasl_B   bit(strmflags_fasl_bit_B)
  #define strmflags_unread_B bit(strmflags_unread_bit_B)
/* define strmflags_rd_by_B bit(strmflags_rd_by_bit_B)
   define strmflags_wr_by_B bit(strmflags_wr_by_bit_B)
   define strmflags_rd_ch_B bit(strmflags_rd_ch_bit_B)
   define strmflags_wr_ch_B bit(strmflags_wr_ch_bit_B)
   define strmflags_rd_B  (strmflags_rd_by_B | strmflags_rd_ch_B)
   define strmflags_wr_B  (strmflags_wr_by_B | strmflags_wr_ch_B) */
  #define strmflags_by_B  (strmflags_rd_by_B | strmflags_wr_by_B)
  #define strmflags_ch_B  (strmflags_rd_ch_B | strmflags_wr_ch_B)
  #define strmflags_rdwr_B (strmflags_rd_B | strmflags_wr_B)
/* strmtype = further Typinfo. See LISPBIBL.D. */

/* individual fields:
   strm_rd_by         pseudofunction for READ-BYTE
   strm_rd_by_array   pseudofunction for READ-BYTE-SEQUENCE
   strm_wr_by         pseudofunction for WRITE-BYTE
   strm_wr_by_array   pseudofunction for WRITE-BYTE-SEQUENCE
   strm_rd_ch         pseudofunction for READ-CHAR
   strm_pk_ch         pseudofunction for PEEK-CHAR
   strm_rd_ch_array   pseudofunction for READ-CHAR-SEQUENCE
   strm_rd_ch_last    last character read by READ-CHAR, NIL if none has been
                      read upto now, eof_value after EOF has been seen.
                      After UNREAD-CHAR, additionally the bit
                      strmflags_unread_bit_B is set.
   strm_wr_ch         pseudofunction for WRITE-CHAR
   strm_wr_ch_array   pseudofunction for WRITE-CHAR-SEQUENCE
   strm_wr_ch_npnl        pseudofunction for WRITE-CHAR, when
                          no pending newline
   strm_wr_ch_array_npnl  pseudofunction for WRITE-CHAR-SEQUENCE, when
                          no pending newline
   strm_wr_ch_lpos    line-position in the current line after last WRITE-CHAR,
                      a fixnum >=0
 further (type-specific) components:
  See in LISPBIBL.D and at the Stream-Types.

 =============================================================================
                           S T R E A M S

 Since MAKE-TWO-WAY-STREAM possibly can return a Stream that is, e.g.,
 Character-Input and Byte-Output, and therewith in particular all
 READ-/WRITE-Operations must run efficiently, Streams are built up
 as follows:
    - Type of the Stream,
    - Components for READ-BYTE, READ-BYTE-SEQUENCE,
    - Components for WRITE-BYTE, WRITE-BYTE-SEQUENCE,
    - Components for READ-CHAR, READ-CHAR-SEQUENCE,
    - Components for WRITE-CHAR, WRITE-CHAR-SEQUENCE,
    - Components, depending on the Type of the Stream.

 Specification of the nine Types of Pseudo-Functions:

 Specification for READ-BYTE - Pseudo-Function:
 fun(stream)
 > stream: Stream
 < result: read Integer (eof_value at EOF)
 can trigger GC */
typedef maygc object (* rd_by_Pseudofun) (object stream);

/* Specification for READ-BYTE-ARRAY - Pseudo-Function:
   fun(&stream,&bytearray,start,len,persev)
   > stream: stream
   > object bytearray: simple-8bit-vector
   > uintL start: start index of byte sequence to be filled
   > uintL len: length of byte sequence to be filled, >0
   > perseverance_t persev: how to react on incomplete I/O
   < uintL result: number of bytes that have been filled
 can trigger GC */
typedef maygc uintL (* rd_by_array_Pseudofun) (const gcv_object_t* stream_, const gcv_object_t* bytearray_, uintL start, uintL len, perseverance_t persev);

/* Specification for WRITE-BYTE - Pseudo-Function:
 fun(stream,obj)
 > stream: Stream
 > obj: Integer to be written
 can trigger GC */
typedef maygc void (* wr_by_Pseudofun) (object stream, object obj);

/* Specification for WRITE-BYTE-ARRAY - Pseudo-Function:
 fun(&stream,&bytearray,start,len,persev)
 > stream: stream
 > object bytearray: simple-8bit-vector
 > uintL start: start index of byte sequence to be written
 > uintL len: length of byte sequence to be written, >0
 > perseverance_t persev: how to react on incomplete I/O
 can trigger GC */
typedef maygc uintL (* wr_by_array_Pseudofun) (const gcv_object_t* stream_, const gcv_object_t* bytearray_, uintL start, uintL len, perseverance_t persev);

/* Specification for READ-CHAR - Pseudo-Function:
 fun(&stream)
 > stream: Stream
 < stream: Stream
 < result: read Character (eof_value at EOF)
 can trigger GC */
typedef maygc object (* rd_ch_Pseudofun) (const gcv_object_t* stream_);

/* Specification for PEEK-CHAR - Pseudo-Function:
 fun(&stream)
 Like READ-CHAR with sequencing UNREAD-CHAR. Only side-effects up
 to the next real READ-CHAR are retarded (if possible).
 > stream: Stream (with strmflags_unread_bit_B deleted)
 < stream: Stream
 < result: read Character (eof_value at EOF)
 can trigger GC */
typedef maygc object (* pk_ch_Pseudofun) (const gcv_object_t* stream_);

/* Specification for READ-CHAR-ARRAY - Pseudo-Function:
 fun(&stream,&chararray,start,len)
 > stream: stream
 > object chararray: a mutable string that is or was simple
 > uintL start: start index of character sequence to be filled
 > uintL len: length of character sequence to be filled, >0
 < uintL result: number of characters that have been filled
 can trigger GC */
typedef maygc uintL (* rd_ch_array_Pseudofun) (const gcv_object_t* stream_, const gcv_object_t* chararray_, uintL start, uintL len);

/* Specification for WRITE-CHAR - Pseudo-Function:
 fun(&stream,obj)
 > stream: Stream
 < stream: Stream
 > obj: Character to be written
 can trigger GC */
typedef maygc void (* wr_ch_Pseudofun) (const gcv_object_t* stream_, object obj);

/* Specification for WRITE-CHAR-ARRAY - Pseudo-Function:
   fun(&stream,&chararray,start,len)
   > stream: stream
   > object chararray: not-reallocated simple-string
   > uintL start: start index of character sequence to be written
   > uintL len: length of character sequence to be written, >0 */
typedef maygc void (* wr_ch_array_Pseudofun) (const gcv_object_t* stream_, const gcv_object_t* chararray_, uintL start, uintL len);

/* extract Pseudo-Functions out of a Stream: */
#define rd_by(strm)       \
        (*(rd_by_Pseudofun)(ThePseudofun(TheStream(strm)->strm_rd_by)))
#define rd_by_array(strm) \
  (*(rd_by_array_Pseudofun)(ThePseudofun(TheStream(strm)->strm_rd_by_array)))
#define wr_by(strm)       \
        (*(wr_by_Pseudofun)(ThePseudofun(TheStream(strm)->strm_wr_by)))
#define wr_by_array(strm) \
  (*(wr_by_array_Pseudofun)(ThePseudofun(TheStream(strm)->strm_wr_by_array)))
#define rd_ch(strm)       \
        (*(rd_ch_Pseudofun)(ThePseudofun(TheStream(strm)->strm_rd_ch)))
#define pk_ch(strm)       \
        (*(pk_ch_Pseudofun)(ThePseudofun(TheStream(strm)->strm_pk_ch)))
#define rd_ch_array(strm) \
  (*(rd_ch_array_Pseudofun)(ThePseudofun(TheStream(strm)->strm_rd_ch_array)))
#define wr_ch(strm)       \
        (*(wr_ch_Pseudofun)(ThePseudofun(TheStream(strm)->strm_wr_ch)))
#define wr_ch_array(strm) \
  (*(wr_ch_array_Pseudofun)(ThePseudofun(TheStream(strm)->strm_wr_ch_array)))

/*Possible Types of Streams               Additional Components
  -------------------------               ---------------------
  Synonym-Stream                          Symbol
  Broadcast-(Output-)Stream               list of streams
  Concatenated-(Input-)Stream             list of streams
  Two-Way-Stream                          Stream for Input, Stream for Output
  Echo-Stream                             Stream for Input, Stream for Output
  String-Input-Stream                     total string, character counter
  String-Output-Stream                    Buffer (Semi-Simple-String)
  String-Push-Stream                      String with Fill-Pointer
  Pretty-Printer-Helper-Stream            List of Buffers, Mode
  Buffered-Input-Stream                   fun, mode, String, character counter
  Buffered-Output-Stream                  fun, Buffer (Semi-Simple-String)
#ifdef GENERIC_STREAMS
  Generic-Stream                          Private Controller Object
#endif
  Keyboard-Stream
  Interactive Terminal Stream             input-buffer, character counter
  File-Stream                             Handle, Pathname, File-Position,
  (Input, Output, I/O, Closed=Probe)      Buffer, [Bit-Buffer]
  Window-Stream                           ---
#ifdef PRINTER
  Printer-Stream
#endif
  File-Handle-Stream                      Handle, Pathname
#ifdef PIPES
  Pipe-Input-Stream                       Pid, Handle
  Pipe-Output-Stream                      Pid, Handle
#endif
#ifdef X11SOCKETS
  X11-Socket-Stream                       Info, Handle
#endif
#ifdef SOCKET_STREAMS
  Socket-Stream                           Host, Port
#endif

Additionally a list of all open File-Streams is maintained (for safety). */

/* error-message, if a Stream-Operation on a Stream is not allowed.
 error_illegal_streamop(caller,stream);
 > caller: Caller (a Symbol)
 > stream: Stream */
global _Noreturn void error_illegal_streamop (object caller, object stream) {
  pushSTACK(stream); /* STREAM-ERROR slot STREAM */
  pushSTACK(stream);
  pushSTACK(caller);
  error(stream_error,GETTEXT("~S on ~S is illegal"));
}

/* Dummy-Pseudo-Functions, that signal errors: */
local object rd_by_error (object stream)
{ error_illegal_streamop(S(read_byte),stream); }

local uintL rd_by_array_error (const gcv_object_t* stream_,
                               const gcv_object_t* bytearray_,
                               uintL start, uintL len, perseverance_t persev)
{
  unused(bytearray_); unused(start); unused(len); unused(persev);
  error_illegal_streamop(S(read_byte),*stream_);
}

local maygc uintL rd_by_array_dummy (const gcv_object_t* stream_,
                                     const gcv_object_t* bytearray_,
                                     uintL start, uintL len,
                                     perseverance_t persev) {
  var uintL end = start + len;
  var uintL index = start;
  do {
    var object stream = *stream_;
    if ((persev == persev_immediate || persev == persev_bonus)
        && LISTEN_AVAIL != listen_byte(stream))
      break;
    var object obj = rd_by(stream)(stream);
    if (eq(obj,eof_value))
      break;
    obj = check_uint8(obj);
    TheSbvector(*bytearray_)->data[index] =
      (uintB)(as_oint(obj) >> oint_data_shift);
    index++;
    if (persev == persev_partial)
      persev = persev_bonus;
  } while (index < end);
  return index - start;
}

local void wr_by_error (object stream, object obj)
{
  unused(obj);
  error_illegal_streamop(S(write_byte),stream);
}

local void wr_by_array_error (const gcv_object_t* stream_,
                              const gcv_object_t* bytearray_,
                              uintL start, uintL len, perseverance_t persev)
{
  unused(bytearray_); unused(start); unused(len); unused(persev);
  error_illegal_streamop(S(write_byte),*stream_);
}

local uintL wr_by_array_dummy (const gcv_object_t* stream_,
                              const gcv_object_t* bytearray_,
                              uintL start, uintL len, perseverance_t persev) {
  var uintL end = start + len;
  var uintL index = start;
  if (persev != persev_full) /* FIXME: need write_byte_will_hang_p() */
    error_illegal_streamop(S(write_byte_sequence),*stream_);
  do {
    var object stream = *stream_;
    wr_by(stream)(stream,fixnum(TheSbvector(*bytearray_)->data[index]));
    index++;
  } while (index < end);
  return len;
}

local object rd_ch_error (const gcv_object_t* stream_)
{ error_illegal_streamop(S(read_char),*stream_); }

local object pk_ch_dummy (const gcv_object_t* stream_) {
  var object newch = rd_ch(*stream_)(stream_);
  TheStream(*stream_)->strm_rd_ch_last = newch;
  if (!eq(newch,eof_value))
    TheStream(*stream_)->strmflags |= strmflags_unread_B;
  return newch;
}

local uintL rd_ch_array_error (const gcv_object_t* stream_,
                               const gcv_object_t* chararray_,
                               uintL start, uintL len)
{
  unused(chararray_); unused(start); unused(len);
  error_illegal_streamop(S(read_char),*stream_);
}

local uintL rd_ch_array_dummy (const gcv_object_t* stream_,
                               const gcv_object_t* chararray_,
                               uintL start, uintL len) {
  var uintL end = start + len;
  var uintL index = start;
  do {
    var object obj = rd_ch(*stream_)(stream_);
    if (eq(obj,eof_value))
      break;
    if (!charp(obj))
      error_char(obj);
    sstring_store(*chararray_,index,char_code(obj));
    index++;
  } while (index < end);
  return index - start;
}

local void wr_ch_error (const gcv_object_t* stream_, object obj)
{
  unused(obj);
  error_illegal_streamop(S(write_char),*stream_);
}

local void wr_ch_array_error (const gcv_object_t* stream_,
                              const gcv_object_t* chararray_,
                              uintL start, uintL len)
{
  unused(chararray_); unused(start); unused(len);
  error_illegal_streamop(S(write_char),*stream_);
}

local maygc void wr_ch_array_dummy (const gcv_object_t* stream_,
                                    const gcv_object_t* chararray_,
                                    uintL start, uintL len) {
  var uintL end = start + len;
  var uintL index = start;
  SstringDispatch(*chararray_,X, {
    do {
      write_char(stream_,code_char(as_chart(((SstringX)TheVarobject(*chararray_))->data[index])));
      index++;
    } while (index < end);
  });
}

/* check whether the stream is a terminal stream */
global bool terminal_stream_p (object stream) {
  if (!streamp(stream)) return false;
  if (eq(stream,Symbol_value(S(terminal_read_stream)))) return true;
  if (!builtin_stream_p(stream)) return false;
  if (TheStream(stream)->strmtype == strmtype_terminal) return true;
  if (TheStream(stream)->strmtype == strmtype_synonym)
    return terminal_stream_p(Symbol_value /* get_synonym_stream */
                             (TheStream(stream)->strm_synonym_symbol));
 #if 0
  if (TheStream(stream)->strmtype == strmtype_concat) {
    /* this is a gross hack for the CLISP kludge
     of reading the first line with READ-LINE for *KEY-BINDINGS*
     and then concatenating the line with the terminal stream */
    var object list = TheStream(stream)->strm_concat_list;
    while (consp(list)) {
      if (terminal_stream_p(Car(list)))
        return true;
      list = Cdr(list);
    }
    return false;
  }
 #endif
  return false;
}

/* At the end of a wr_ch_array, update the Line-Position:
 wr_ss_lpos(stream,ptr,len);
 > stream: Builtin-Stream, not the Terminal-Stream
 > ptr: Pointer to the End(!) of the already written characters to the Stream
 > len: number of characters, >0
 < result: true, if a NL is among the characters, else false */
local bool wr_ss_lpos (object stream, const chart* ptr, uintL len) {
 #ifdef TERMINAL_USES_KEYBOARD
  if (TheStream(stream)->strmtype == strmtype_terminal)
    return false; /* On the Atari wr_ch_terminal() would do this. */
 #endif
  /* Add together the widths of the characters since the last NL: */
  var bool result;
  var uintV pos = 0;
  var uintL count;
  dotimespL(count,len, {
    if (chareq(*--ptr,ascii(NL)))
      goto found_NL;
    pos++;
  });
  if (false) {
  found_NL: /* pos characters since the last NL */
    ptr++; len = pos; pos = 0; result = true;
  } else { /* pos==len */
    pos = posfixnum_to_V(TheStream(stream)->strm_wr_ch_lpos); result = false;
  }
  /* There were len characters starting from ptr, pos is the Position there. */
 #ifdef TERMINAL_USES_KEYBOARD
  pos += len;
 #else
  if (len > 0) {
    if (TheStream(stream)->strmtype == strmtype_terminal) {
      dotimespL(count,len, {
        var chart c = *ptr++;
        /* How do the control characters effect at that Position? */
        if (chareq(c,ascii(BS))) {
          /* Backspace ==> decrement Line Position, if possible: */
          if (pos > 0)
            pos--;
        } else if (chareq(c,ascii(TAB))) {
          /* Tabs have width 8 in Unix culture. */
          pos = (pos | (8 - 1)) + 1;
        } else
          pos += char_width(c);
      });
    } else {
      dotimespL(count,len, {
        var chart c = *ptr++;
        if (chareq(c,ascii(TAB))) {
          /* Tabs have width 8 in Unix culture. */
          pos = (pos | (8 - 1)) + 1;
        } else
          pos += char_width(c);
      });
    }
  }
 #endif
  TheStream(stream)->strm_wr_ch_lpos = fixnum(pos);
  return result;
}

/* Function: Returns the last character read (and not yet unread) from a stream.
 stream_get_lastchar(stream)
 > stream: a stream
 < result: the last character read, or NIL
 can trigger GC */
global maygc object stream_get_lastchar (object stream) {
  if (builtin_stream_p(stream)) {
    return TheStream(stream)->strm_rd_ch_last;
  } else {
    /* (SLOT-VALUE stream '$lastchar): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(lastchar),TheClass(clas)->slot_location_table,false);
    if (!eq(slotinfo,nullobj))
      return TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)];
    else
      return NIL;
  }
}

/* Function: Sets the last character read (and not yet unread) of a stream.
 stream_set_lastchar(stream,ch);
 > stream: a non-builtin stream
 > ch: an object (usually a character or NIL)
 can trigger GC */
local maygc void stream_set_lastchar (object stream, object ch) {
  ASSERT(!builtin_stream_p(stream));
  /* (SETF (SLOT-VALUE stream '$lastchar) ch): */
  pushSTACK(ch);
  var object stream_forwarded = stream;
  instance_un_realloc(stream_forwarded);
  instance_update(stream,stream_forwarded);
  var object cv = TheInstance(stream_forwarded)->inst_class_version;
  var object clas = TheClassVersion(cv)->cv_class;
  var object slotinfo = gethash(S(lastchar),TheClass(clas)->slot_location_table,false);
  ch = popSTACK();
  if (!eq(slotinfo,nullobj))
    TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)] = ch;
}

/* Reads a Byte from a Stream.
 read_byte(stream)
 > stream: Stream
 < result: read Integer (eof_value at EOF)
 can trigger GC */
global maygc object read_byte (object stream) {
  if (builtin_stream_p(stream)) {
    if (TheStream(stream)->strmflags & strmflags_unread_B) {
      /* UNREAD-CHAR was followed by a (SETF STREAM-ELEMENT-TYPE)
       thus we _know_ that the stream element type is ([UN]SIGNED-BYTE 8) */
     #ifdef ENABLE_UNICODE
      var object enc = TheStream(stream)->strm_encoding;
      var chart ch = char_code(TheStream(stream)->strm_rd_ch_last);
      var uintB buf[4]; /* are there characters longer than 4 bytes?! */
      var uintL char_len = cslen(enc,&ch,1);
      ASSERT(char_len <= sizeof(buf));
      if (char_len == 0) { /* the char corresponds to no bytes at all */
        TheStream(stream)->strmflags &= ~strmflags_unread_B;
        TheStream(stream)->strm_rd_ch_last = NIL;
        goto do_read_byte;
      }
      cstombs(enc,&ch,1,buf,char_len);
      var uint8 code = buf[0];
      if (char_len == 1) { /* the char was just one byte */
        TheStream(stream)->strmflags &= ~strmflags_unread_B;
        TheStream(stream)->strm_rd_ch_last = NIL;
      } else { /* encode the rest */
        var const uintB* cbuf = buf+1; /* skip the first byte */
        var chart* cptr = &ch;
        Encoding_mbstowcs(enc)(enc,stream,&cbuf,buf+char_len,&cptr,cptr+1);
        TheStream(stream)->strm_rd_ch_last = code_char(*cptr);
      }
     #else /* no ENABLE_UNICODE */
      var uint8 code = as_cint(char_code(TheStream(stream)->strm_rd_ch_last));
      TheStream(stream)->strmflags &= ~strmflags_unread_B;
      TheStream(stream)->strm_rd_ch_last = NIL;
     #endif
      var object eltype = TheStream(stream)->strm_eltype;
      if (eq(eltype,S(signed_byte))
          || (mconsp(eltype) && eq(Car(eltype),S(signed_byte))))
        return sfixnum((sint8)code);
      else
        return fixnum((uint8)code);
    } else {
     do_read_byte:
      return rd_by(stream)(stream);
    }
  } else {
    /* Call the generic function (STREAM-READ-BYTE stream): */
    pushSTACK(stream); funcall(S(stream_read_byte),1);
    var object result = value1;
    if (eq(result,S(Keof)))
      return eof_value;
    else
      return result;
  }
}

/* UP: check that the return value of STREAM-READ-BYTE-SEQUENCE et al
 > value: the value to be checked
 > caller: the function which returned the value
 > minval, maxval: the permissible range
 < an integer in [minval;maxval]
 can trigger GC */
local maygc uintL check_value_range (object value, object caller,
                                     uintL minval, uintL maxval) {
  var uintV result;
  if (posfixnump(value)
      && (result = posfixnum_to_V(value),
          result >= minval && result <= maxval))
    return result;
  /* should we make this continuable? continue == return maxval */
  pushSTACK(fixnum(maxval));
  pushSTACK(fixnum(minval));
  pushSTACK(caller);
  pushSTACK(value);
  error(error_condition,GETTEXT("Return value ~S of call to ~S should be an integer between ~S and ~S."));
}

/* Function: Reads several bytes from a stream.
 read_byte_array(&stream,&bytearray,start,len,persev)
 > stream: stream (on the STACK)
 > object bytearray: simple-8bit-vector (on the STACK)
 > uintL start: start index of byte sequence to be filled
 > uintL len: length of byte sequence to be filled
 > perseverance_t persev: how to react on incomplete I/O
 < uintL result: number of bytes that have been filled
 can trigger GC */
modexp maygc uintL read_byte_array
(const gcv_object_t* stream_, const gcv_object_t* bytearray_,
 uintL start, uintL len, perseverance_t persev) {
  if (len==0)
    return 0;
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    return rd_by_array(stream)(stream_,bytearray_,start,len,persev);
  } else {
    /* Call the generic function
     (STREAM-READ-BYTE-SEQUENCE stream bytearray start start+len no-hang interactive): */
    pushSTACK(stream); pushSTACK(*bytearray_);
    pushSTACK(fixnum(start)); pushSTACK(fixnum(start+len));
    pushSTACK(persev == persev_immediate || persev == persev_bonus ? T : NIL);
    pushSTACK(persev == persev_partial ? T : NIL);
    funcall(S(stream_read_byte_sequence),6);
    return check_value_range(value1,S(stream_read_byte_sequence),
                             start,start+len) - start;
  }
}

/* Writes a Byte to a Stream.
 write_byte(stream,byte);
 > stream: Stream
 > byte: Integer to be written
 can trigger GC */
global maygc void write_byte (object stream, object byte) {
  if (builtin_stream_p(stream)) {
    wr_by(stream)(stream,byte);
  } else {
    /* Call the generic function (STREAM-WRITE-BYTE stream byte): */
    pushSTACK(stream); pushSTACK(byte); funcall(S(stream_write_byte),2);
  }
}

/* Function: Writes several bytes to a stream.
 write_byte_array(&stream,&bytearray,start,len,persev)
 > stream: Stream (on the STACK)
 > object bytearray: simple-8bit-vector (on the STACK)
 > uintL start: start index of byte sequence to be written
 > uintL len: length of byte sequence to be written
 > perseverance_t persev: how to react on incomplete I/O
 < uintL result: number of bytes that have been written
 can trigger GC */
modexp maygc uintL write_byte_array
(const gcv_object_t* stream_, const gcv_object_t* bytearray_,
 uintL start, uintL len, perseverance_t persev) {
  if (len==0)
    return 0;
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    return wr_by_array(stream)(stream_,bytearray_,start,len,persev);
  } else {
    /* Call the generic function
     (STREAM-WRITE-BYTE-SEQUENCE stream bytearray start start+len no-hang interactive): */
    pushSTACK(stream); pushSTACK(*bytearray_);
    pushSTACK(fixnum(start)); pushSTACK(fixnum(start+len));
    pushSTACK(persev == persev_immediate || persev == persev_bonus ? T : NIL);
    pushSTACK(persev == persev_partial ? T : NIL);
    funcall(S(stream_write_byte_sequence),6);
    if (mv_count >= 2)
      /* second return value is index of first unwritten byte
         have to change that here into #bytes written */
      return check_value_range(value2,S(stream_write_byte_sequence),
                               start,start+len) - start;
    else
      return len;
  }
}

/* Reads a Character from a Stream.
 read_char(&stream)
 > stream: Stream
 < stream: Stream
 < result: read Character (eof_value at EOF)
 can trigger GC */
global maygc object read_char (const gcv_object_t* stream_) {
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    if (!(TheStream(stream)->strmflags & strmflags_unread_B)) { /* Char after UNREAD ? */
      /* no -> fetch next character: */
      var object newch = rd_ch(stream)(stream_);
      stream = *stream_;
      TheStream(stream)->strm_rd_ch_last = newch; /* and store */
      TheStream(stream)->strmflags &= ~strmflags_unread_B;
      return newch;
    } else {
      /* yes -> deleteFlagbit and fetch last character: */
      var object ret = TheStream(stream)->strm_rd_ch_last; /* immediate */
      TheStream(stream)->strmflags &= ~strmflags_unread_B;
      switch (TheStream(stream)->strmtype) {
        case strmtype_concat:
          /* presence of rd_ch_last indicates that concat_list is non-NIL */
          stream = Car(TheStream(stream)->strm_concat_list);
          goto read_char_recurse;
        case strmtype_echo:
        case strmtype_twoway:
          stream = TheStream(stream)->strm_twoway_input;
        read_char_recurse:
          pushSTACK(stream);
          var object new_ch = read_char(&STACK_0);
          ASSERT(eq(new_ch,ret));
          skipSTACK(1);
      }
      return ret;
    }
  } else {
    pushSTACK(stream);
    /* Call the generic function (STREAM-READ-CHAR stream): */
    pushSTACK(stream); funcall(S(stream_read_char),1);
    var object result = value1;
    if (eq(result,S(Keof)))
      result = eof_value;
    /* Store the result as slot $lastchar: */
    stream = STACK_0; STACK_0 = result;
    stream_set_lastchar(stream,result);
    return popSTACK();
  }
}

/* pushes the last read Character back to the Stream.
 unread_char(&stream,ch);
 > ch: last read Character
 > stream: Stream
 < stream: Stream
 can trigger GC */
global maygc void unread_char (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    if (eq(TheStream(stream)->strm_rd_ch_last,ch)
        && !(TheStream(stream)->strmflags & strmflags_unread_B)) {
      /* composite streams operate on their constituent streams */
      switch (TheStream(stream)->strmtype) {
        case strmtype_concat:
          /* presence of rd_ch_last indicates that concat_list is non-NIL */
          pushSTACK(Car(TheStream(stream)->strm_concat_list));
          goto unread_char_recurse;
        case strmtype_echo:
        case strmtype_twoway:
          pushSTACK(TheStream(stream)->strm_twoway_input);
        unread_char_recurse:
          unread_char(&STACK_0,ch);
          skipSTACK(1);
          stream = *stream_;
          /*FALLTHROUGH*/
        default:
          TheStream(stream)->strmflags |= strmflags_unread_B; /* set Flagbit */
      }
    } else {
      if (!nullp(TheStream(stream)->strm_rd_ch_last)
          && !(TheStream(stream)->strmflags & strmflags_unread_B)) {
        pushSTACK(stream); /* STREAM-ERROR slot STREAM */
        pushSTACK(ch);
        pushSTACK(stream);
        pushSTACK(S(unread_char));
        error(stream_error,GETTEXT("~S: the last character read from ~S was not ~S"));
      } else {
        pushSTACK(stream); /* STREAM-ERROR slot STREAM */
        pushSTACK(S(read_char));
        pushSTACK(stream);
        pushSTACK(S(unread_char));
        error(stream_error,GETTEXT("~S from ~S without ~S before it"));
      }
    }
  } else {
    pushSTACK(stream);
    /* Call the generic function (STREAM-UNREAD-CHAR stream ch): */
    pushSTACK(stream); pushSTACK(ch); funcall(S(stream_unread_char),2);
    /* Set $lastchar := NIL: */
    stream_set_lastchar(popSTACK(),NIL);
  }
}

/* Reads a Character from a Stream, without consuming it.
 peek_char(&stream)
 > stream: Stream
 < stream: Stream
 < result: read Character (eof_value at EOF)
 can trigger GC */
global maygc object peek_char (const gcv_object_t* stream_) {
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    if (!(TheStream(stream)->strmflags & strmflags_unread_B)) /* Char after UNREAD ? */
      /* no -> fetch new character: */
      return pk_ch(stream)(stream_);
    else
      /* yes -> fetch last character: */
      return TheStream(stream)->strm_rd_ch_last;
  } else {
    /* Call the generic function (STREAM-PEEK-CHAR stream): */
    pushSTACK(stream); funcall(S(stream_peek_char),1);
    var object result = value1;
    if (eq(result,S(Keof)))
      return eof_value;
    else
      return result;
  }
}

/* Function: Reads several characters from a stream.
 read_char_array(&stream,&chararray,start,len)
 > stream: stream (on the STACK)
 > object chararray: a mutable string that is or was simple (on the STACK)
 > uintL start: start index of character sequence to be filled
 > uintL len: length of character sequence to be filled
 < uintL result: number of characters that have been filled
 can trigger GC */
global maygc uintL read_char_array (const gcv_object_t* stream_,
                                    const gcv_object_t* chararray_,
                                    uintL start, uintL len) {
  if (len==0)
    return 0;
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    var object lastchar = TheStream(stream)->strm_rd_ch_last;
    if (eq(lastchar,eof_value)) /* EOF ? */
      return 0;
    var uintL index = start;
    if (TheStream(stream)->strmflags & strmflags_unread_B) {
      if (!charp(lastchar))
        error_char(lastchar);
      sstring_store(*chararray_,index++,char_code(lastchar));
      stream = *stream_;
      len--;
      if (len==0) {
        TheStream(stream)->strmflags &= ~strmflags_unread_B;
        return 1;
      }
    }
    var uintL count = rd_ch_array(stream)(stream_,chararray_,index,len);
    index += count;
    stream = *stream_;
    if (count == len) {
      var object chararray = *chararray_;
      sstring_un_realloc(chararray);
      var chart last_ch = schar(chararray,index-1);
      TheStream(stream)->strm_rd_ch_last = code_char(last_ch);
    } else
      TheStream(stream)->strm_rd_ch_last = eof_value;
    TheStream(stream)->strmflags &= ~strmflags_unread_B;
    return index - start;
  } else {
    pushSTACK(stream);
    /* Call the generic function
     (STREAM-READ-CHAR-SEQUENCE stream chararray start start+len): */
    pushSTACK(stream); pushSTACK(*chararray_);
    pushSTACK(fixnum(start)); pushSTACK(fixnum(start+len));
    funcall(S(stream_read_char_sequence),4);
    var uintV result =
      check_value_range(value1,S(stream_read_char_sequence),start,start+len);
    /* Set the stream's $lastchar := last char or #<EOF>: */
    var object lastchar;
    if (result-start == len) {
      var object chararray = *chararray_;
      sstring_un_realloc(chararray);
      lastchar = code_char(schar(chararray,result-1));
    } else
      lastchar = eof_value;
    stream_set_lastchar(popSTACK(),lastchar);
    return result-start;
  }
}

/* Function that handles the pending newline before doing the real job. */
local maygc void wr_ch_pending_newline (const gcv_object_t* stream_, object obj)
{
  var object stream = *stream_;
  TheStream(stream)->strm_wr_ch = TheStream(stream)->strm_wr_ch_npnl;
  TheStream(stream)->strm_wr_ch_array = TheStream(stream)->strm_wr_ch_array_npnl;
  if (!eq(obj,ascii_char(NL))) {
    pushSTACK(obj);
    write_char(stream_,ascii_char(NL));
    obj = popSTACK();
  }
  write_char(stream_,obj);
}

/* writes a Character to a Stream.
 write_char(&stream,ch);
 > ch: Character to be written
 > stream: Stream
 < stream: Stream
 can trigger GC */
global maygc void write_char (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    var chart c = char_code(ch);
    /* write Char: */
    wr_ch(stream)(stream_,ch);
    /* update Line Position: */
    var object stream = *stream_;
    if (!(TheStream(stream)->strmtype == strmtype_terminal)) {
      /* not the Terminal-Stream */
      if (chareq(c,ascii(NL))) /* After Newline: Line Position := 0 */
        TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
      else if (chareq(c,ascii(TAB))) /* Tab width is 8 in Unix culture. */
        TheStream(stream)->strm_wr_ch_lpos =
          fixnum_inc(TheStream(stream)->strm_wr_ch_lpos,
                     8 - fixnum_to_V(TheStream(stream)->strm_wr_ch_lpos) % 8);
      else /* increment line position */
        TheStream(stream)->strm_wr_ch_lpos =
          fixnum_inc(TheStream(stream)->strm_wr_ch_lpos,char_width(c));
    } else { /* it is the Terminal-Stream */
     #ifdef TERMINAL_USES_KEYBOARD
      /* On the Atari, wr_ch_terminal() would do this. */
     #else
      /* How do the control-characters effect in that Position? */
      if (chareq(c,ascii(NL))) { /* Newline -> Line Position := 0 */
        TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
      } else if (chareq(c,ascii(BS))) {
        /* Backspace -> Line Position, if possible, decrement: */
        if (!eq(TheStream(stream)->strm_wr_ch_lpos,Fixnum_0))
          TheStream(stream)->strm_wr_ch_lpos =
            fixnum_inc(TheStream(stream)->strm_wr_ch_lpos,-1);
      } else if (chareq(c,ascii(TAB))) /* Tab width is 8 in Unix culture. */
        TheStream(stream)->strm_wr_ch_lpos =
          fixnum_inc(TheStream(stream)->strm_wr_ch_lpos,
                     8 - fixnum_to_V(TheStream(stream)->strm_wr_ch_lpos) % 8);
      else /* increment line position */
        TheStream(stream)->strm_wr_ch_lpos =
          fixnum_inc(TheStream(stream)->strm_wr_ch_lpos,char_width(c));
     #endif
    }
  } else {
    pushSTACK(stream); pushSTACK(ch);
    /* Test (SLOT-VALUE stream '$penl): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(penl),TheClass(clas)->slot_location_table,false);
    if (!nullp(TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)])) {
      TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)] = NIL;
      if (!eq(STACK_0,ascii_char(NL))) {
        /* Call the generic function (STREAM-WRITE-CHAR stream #\Newline): */
        pushSTACK(STACK_1); pushSTACK(ascii_char(NL));
        funcall(S(stream_write_char),2);
      }
    }
    /* Call the generic function (STREAM-WRITE-CHAR stream ch): */
    funcall(S(stream_write_char),2);
  }
}

/* Function that handles the pending newline before doing the real job. */
local maygc void wr_ch_array_pending_newline (const gcv_object_t* stream_,
                                              const gcv_object_t* chararray_,
                                              uintL start, uintL len) {
  var object stream = *stream_;
  TheStream(stream)->strm_wr_ch = TheStream(stream)->strm_wr_ch_npnl;
  TheStream(stream)->strm_wr_ch_array = TheStream(stream)->strm_wr_ch_array_npnl;
  var bool next_is_NL;
  SstringDispatch(*chararray_,X, {
    next_is_NL = chareq(as_chart(((SstringX)TheVarobject(*chararray_))->data[start]),ascii(NL));
  });
  if (!next_is_NL)
    write_char(stream_,ascii_char(NL));
  write_char_array(stream_,chararray_,start,len);
}

/* Function: Writes several characters to a stream.
 write_char_array(&stream,&chararray,start,len)
 > stream: stream (on the STACK)
 > object chararray: not-reallocated simple-string (on the STACK)
 > uintL start: start index of character sequence to be written
 > uintL len: length of character sequence to be written
 can trigger GC */
global maygc void write_char_array (const gcv_object_t* stream_,
                                    const gcv_object_t* chararray_,
                                    uintL start, uintL len) {
  if (len==0)
    return;
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    wr_ch_array(stream)(stream_,chararray_,start,len);
  } else {
    /* Test (SLOT-VALUE stream '$penl): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(penl),TheClass(clas)->slot_location_table,false);
    if (!nullp(TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)])) {
      TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)] = NIL;
      var bool next_is_NL;
      SstringDispatch(*chararray_,X, {
        next_is_NL = chareq(as_chart(((SstringX)TheVarobject(*chararray_))->data[start]),ascii(NL));
      });
      if (!next_is_NL) {
        /* Call the generic function (STREAM-WRITE-CHAR stream #\Newline): */
        pushSTACK(*stream_); pushSTACK(ascii_char(NL));
        funcall(S(stream_write_char),2);
      }
    }
    /* Call the generic function
     (STREAM-WRITE-CHAR-SEQUENCE stream chararray start start+len): */
    pushSTACK(*stream_); pushSTACK(*chararray_);
    pushSTACK(fixnum(start)); pushSTACK(fixnum(start+len));
    funcall(S(stream_write_char_sequence),4);
  }
}

/* Outputs a real newline if an elastic newline is pending on the stream.
 harden_elastic_newline(&stream);
 > stream: Stream
 < stream: Stream
 can trigger GC */
local maygc void harden_elastic_newline (const gcv_object_t* stream_) {
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    if (eq(TheStream(stream)->strm_wr_ch,P(wr_ch_pending_newline))) {
      TheStream(stream)->strm_wr_ch = TheStream(stream)->strm_wr_ch_npnl;
      TheStream(stream)->strm_wr_ch_array = TheStream(stream)->strm_wr_ch_array_npnl;
      write_char(stream_,ascii_char(NL));
    }
  } else {
    /* Test (SLOT-VALUE stream '$penl): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(penl),TheClass(clas)->slot_location_table,false);
    if (!nullp(TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)])) {
      /* (SETF (SLOT-VALUE stream '$penl) NIL): */
      TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)] = NIL;
      write_char(stream_,ascii_char(NL));
    }
  }
}

/* UP: when closing, fill the stream with the dummy pseudo-functions
     and remove the capability flags
 close_dummys(stream);
 > stream: Stream */
#define close_dummys(s)                                                 \
  stream_dummy_fill(s);                                                 \
  /* delete capability flags                                              */\
  TheStream(s)->strmflags &= ~(strmflags_open_B|strmflags_unread_B)

/* fill the stream with dummy pseudo-functions */
local void stream_dummy_fill (object stream) {
  var Stream s = TheStream(stream);
  s->strm_rd_by = P(rd_by_error);
  s->strm_rd_by_array = P(rd_by_array_error);
  s->strm_wr_by = P(wr_by_error);
  s->strm_wr_by_array = P(wr_by_array_error);
  s->strm_rd_ch = P(rd_ch_error);
  s->strm_pk_ch = P(pk_ch_dummy);
  s->strm_rd_ch_array = P(rd_ch_array_error);
  s->strm_rd_ch_last = NIL; /* Lastchar := NIL */
  s->strm_wr_ch_lpos = Fixnum_0;
  s->strm_wr_ch = s->strm_wr_ch_npnl = P(wr_ch_error);
  s->strm_wr_ch_array = s->strm_wr_ch_array_npnl = P(wr_ch_array_error);
}

/* returns error-message, if the value of the Symbol sym is not a Stream. */
local _Noreturn void error_value_stream (object sym);
/* see below */

/* UP: Returns the Stream, that is the value of a Variable.
 var_stream(sym,streamflags)
 > sym: Variable (Symbol)
 > streamflags: set of Operations, that are to be possible on the Stream
 < result: Stream */
global object var_stream (object sym, uintB streamflags) {
  var object stream;
 recurse:
  stream = Symbol_value(sym);
  if (builtin_stream_p(stream)) {
    if ((streamflags | strmflags_open_B) & ~ TheStream(stream)->strmflags)
      error_value_stream(sym);
    if (TheStream(stream)->strmtype == strmtype_synonym) {
      sym = TheStream(stream)->strm_synonym_symbol;
      goto recurse;
    }
  } else if (instanceof(stream,O(class_fundamental_stream))) {
    /* Among instances of FUNDAMENTAL-STREAM:
     Only instances of FUNDAMENTAL-INPUT-STREAM can do input.
     Only instances of FUNDAMENTAL-OUTPUT-STREAM can do output. */
    if (((streamflags & strmflags_rd_B)
         && !instanceof(stream,O(class_fundamental_input_stream)))
        || ((streamflags & strmflags_wr_B)
            && !instanceof(stream,O(class_fundamental_output_stream))))
      error_value_stream(sym);
  } else
    error_value_stream(sym);
  return stream;
}

/* (SYSTEM::SYMBOL-STREAM symbol [direction])
 returns the Stream, that is the value of the Symbol, and checks, if it is an
 open Stream with Direction direction (:PROBE, :INPUT, :OUTPUT or :IO) . */
LISPFUN(symbol_stream,seclass_read,1,1,norest,nokey,0,NIL) {
  var object symbol = check_symbol(STACK_1);
  var object direction = STACK_0; skipSTACK(2);
  VALUES1(var_stream(symbol,(uintB)(
       eq(direction,S(Kinput)) ? strmflags_rd_ch_B : /* :INPUT */
       eq(direction,S(Koutput)) ? strmflags_wr_ch_B : /* :OUTPUT */
       eq(direction,S(Kio)) ?
       strmflags_rd_ch_B | strmflags_wr_ch_B : /* :IO */
       0))); /* :PROBE or not given */
}

/* signal an error if for some obscure reason a WRITE should not work: */
local _Noreturn void error_unwritable (object caller, object stream)
{
  pushSTACK(stream); /* FILE-ERROR slot PATHNAME */
  pushSTACK(stream);
  pushSTACK(caller);
  error(file_error,GETTEXT("~S: cannot output to ~S"));
}

/* signal an error if an Object is not the needed type:
 error_write(stream,obj,type); */
local _Noreturn void error_write (object stream, object obj, object type) {
  pushSTACK(obj);               /* TYPE-ERROR slot DATUM */
  pushSTACK(type);              /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(type); pushSTACK(stream); pushSTACK(obj);
  pushSTACK(TheSubr(subr_self)->name);
  error(type_error,GETTEXT("~S: cannot output ~S into ~S, not of type ~S"));
}

/* WRITE-CHAR pseudo-function for output streams of element type NIL */
local maygc void wr_ch_forbidden (const gcv_object_t* stream_, object ch)
{
  error_write(*stream_,ch,NIL);
}

/* WRITE-CHAR-ARRAY pseudo-function for output streams of element type NIL */
local maygc void wr_ch_array_forbidden (const gcv_object_t* stream_,
                                        const gcv_object_t* chararray_,
                                        uintL start, uintL len)
{
  unused start;
  unused len;
  error_write(*stream_,*chararray_,NIL);
}

#define check_wr_char(s,c)  if(!charp(c)) error_write(s,c,S(character))

/* signal an error if an Integer is out of range:
 error_bad_integer(stream,obj); */
local _Noreturn void error_bad_integer (object stream, object obj) {
  pushSTACK(stream); /* STREAM-ERROR slot STREAM */
  pushSTACK(stream); pushSTACK(obj);
  error(stream_error,GETTEXT("integer ~S is out of range, cannot be output onto ~S"));
}

/* Error message and get a replacement for an argument
   which isn't a stream of the requested stream-type:
 get_streamtype_replacement(obj,type);
 > obj: the faulty argument
 > type: requested stream-type
 can trigger GC */
local maygc object get_streamtype_replacement (object obj, object type) {
  pushSTACK(NIL);  /* no PLACE */
  pushSTACK(obj);  /* TYPE-ERROR slot DATUM */
  pushSTACK(type); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(type); pushSTACK(obj); pushSTACK(TheSubr(subr_self)->name);
  check_value(type_error,GETTEXT("~S: argument ~S is not a stream of type ~S"));
  return value1;
}

/* barf if the object is not a stream of the specific type */
#define CHECK_streamtype(obj,type,test)                         \
  while(!(test)) obj = get_streamtype_replacement(obj,type)
/* barf if the object is not a built-in stream */
#define CHECK_builtin_stream(obj)                               \
  CHECK_streamtype(obj,O(type_builtin_stream),(builtin_stream_p(obj)))
/* barf of the object is not an integer */
#define ASSERT_wr_int(stream,obj)                               \
  if (!integerp(obj)) error_write(stream,obj,S(integer))

/* UP: checks, if Arguments are Streams.
 check_stream_args(args_pointer,argcount);
 > args_pointer: Pointer to the Arguments
 > argcount: number of Arguments
 can trigger GC */
local maygc void check_stream_args (gcv_object_t* args_pointer, uintC argcount) {
  while (argcount--) {
    var gcv_object_t *next_arg_ptr = &NEXT(args_pointer);
    *next_arg_ptr = check_stream(*next_arg_ptr);
  };
}

/* forward declaration */
local object resolve_synonym_stream (object stream);

/* Function: Tests whether an object is an input-stream.
 input_stream_p(stream)
 > stream: object */
local bool input_stream_p (object stream) {
  stream = resolve_synonym_stream(stream);
  return (builtin_stream_p(stream) ?
          (TheStream(stream)->strmflags & strmflags_rd_B) != 0
          : instanceof(stream,O(class_fundamental_input_stream)));
}

/* Function: Tests whether an object is an output-stream.
 output_stream_p(stream)
 > stream: object */
local bool output_stream_p (object stream) {
  stream = resolve_synonym_stream(stream);
  return (builtin_stream_p(stream) ?
          (TheStream(stream)->strmflags & strmflags_wr_B) != 0
          : instanceof(stream,O(class_fundamental_output_stream)));
}

/* UP: checks an Input-Stream.
 test_input_stream(stream);
 > stream: Stream */
#define test_input_stream(stream)  \
    if (!input_stream_p(stream)) error_input_stream(stream);
local _Noreturn void error_input_stream (object stream) {
  pushSTACK(stream);               /* TYPE-ERROR slot DATUM */
  pushSTACK(O(type_input_stream)); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(stream); pushSTACK(TheSubr(subr_self)->name);
  error(type_error,GETTEXT("~S: argument ~S should be an input stream"));
}

/* UP: checks an Output-Stream.
 test_output_stream(stream);
 > stream: Stream */
#define test_output_stream(stream)  \
    if (!output_stream_p(stream)) error_output_stream(stream);
local _Noreturn void error_output_stream (object stream) {
  pushSTACK(stream);                /* TYPE-ERROR slot DATUM */
  pushSTACK(O(type_output_stream)); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(stream); pushSTACK(TheSubr(subr_self)->name);
  error(type_error,GETTEXT("~S: argument ~S should be an output stream"));
}

/* UP: checks, if Arguments are Input-Streams.
 test_input_stream_args(args_pointer,argcount);
 > args_pointer: Pointer to the Arguments
 > argcount: number of Arguments */
#define test_input_stream_args(args_pointer,argcount)   \
    if (argcount > 0) {                                 \
      var gcv_object_t* pointer = (args_pointer);       \
      var uintC count;                                  \
      dotimespC(count,argcount, {                       \
        var object arg = Next(pointer);                 \
        NEXT(pointer) = arg = check_stream(arg);        \
        test_input_stream(arg);                         \
      });                                               \
    }

/* UP: checks, if Arguments are Output-Streams.
 test_output_stream_args(args_pointer,argcount);
 > args_pointer: Pointer to the Arguments
 > argcount: number of Arguments */
#define test_output_stream_args(args_pointer,argcount)  \
    if (argcount > 0) {                                 \
      var gcv_object_t* pointer = (args_pointer);       \
      var uintC count;                                  \
      dotimespC(count,argcount, {                       \
        var object arg = Next(pointer);                 \
        NEXT(pointer) = arg = check_stream(arg);        \
        test_output_stream(arg);                        \
      });                                               \
    }


/* Synonym-Stream
   ==============

 Additional Components:
 define strm_synonym_symbol  strm_other[0]  - Symbol, whose value is referred to

 Macro: Returns the value of a Symbol, a Stream.
 get_synonym_stream(sym)
 > sym: Symbol, a variable
 < result: its value, a Stream */
#define get_synonym_stream(sym)                 \
    (!streamp(Symbol_value(sym))                \
     ? (error_value_stream(sym), unbound)      \
     : (object)Symbol_value(sym))

/* Macro: resolve the synonym stream */
#define resolve_as_synonym(stream)                              \
  do { object symbol = TheStream(stream)->strm_synonym_symbol;  \
       stream = get_synonym_stream(symbol); } while (0)

/* Function: resolve the synonym stream */
local object resolve_synonym_stream (object stream) {
  while (builtin_stream_p(stream)
         && TheStream(stream)->strmtype == strmtype_synonym) {
    var object symbol = TheStream(stream)->strm_synonym_symbol;
    stream = get_synonym_stream(symbol);
  }
  return stream;
}

/* READ-BYTE - Pseudo-Function for Synonym-Streams: */
local maygc object rd_by_synonym (object stream) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  return read_byte(get_synonym_stream(symbol));
}

/* READ-BYTE-ARRAY - Pseudo-Function for Synonym-Streams: */
local maygc uintL rd_by_array_synonym (const gcv_object_t* stream_,
                                       const gcv_object_t* bytearray_,
                                       uintL start, uintL len,
                                       perseverance_t persev) {
  check_SP(); check_STACK();
  var object symbol = TheStream(*stream_)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  var uintL result = read_byte_array(&STACK_0,bytearray_,start,len,persev);
  skipSTACK(1);
  return result;
}

/* WRITE-BYTE - Pseudo-Function for Synonym-Streams: */
local maygc void wr_by_synonym (object stream, object obj) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  write_byte(get_synonym_stream(symbol),obj);
}

/* WRITE-BYTE-ARRAY - Pseudo-Function for Synonym-Streams: */
local maygc uintL wr_by_array_synonym (const gcv_object_t* stream_,
                                       const gcv_object_t* bytearray_,
                                       uintL start, uintL len,
                                       perseverance_t persev) {
  check_SP(); check_STACK();
  var object symbol = TheStream(*stream_)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  var uintL result = write_byte_array(&STACK_0,bytearray_,start,len,persev);
  skipSTACK(1);
  return result;
}

/* READ-CHAR - Pseudo-Function for Synonym-Streams: */
local maygc object rd_ch_synonym (const gcv_object_t* stream_) {
  check_SP(); check_STACK();
  var object stream = *stream_;
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  var object result = read_char(&STACK_0);
  skipSTACK(1);
  return result;
}

/* PEEK-CHAR - Pseudo-Function for Synonym-Streams: */
local maygc object pk_ch_synonym (const gcv_object_t* stream_) {
  check_SP(); check_STACK();
  var object stream = *stream_;
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  var object result = peek_char(&STACK_0);
  skipSTACK(1);
  return result;
}

/* READ-CHAR-ARRAY - Pseudo-Function for Synonym-Streams: */
local maygc uintL rd_ch_array_synonym (const gcv_object_t* stream_,
                                       const gcv_object_t* chararray_,
                                       uintL start, uintL len) {
  check_SP(); check_STACK();
  var object symbol = TheStream(*stream_)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  var uintL result = read_char_array(&STACK_0,chararray_,start,len);
  skipSTACK(1);
  return result;
}

/* WRITE-CHAR - Pseudo-Function for Synonym-Streams: */
local maygc void wr_ch_synonym (const gcv_object_t* stream_, object obj) {
  check_SP(); check_STACK();
  var object stream = *stream_;
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  write_char(&STACK_0,obj);
  skipSTACK(1);
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for Synonym-Streams: */
local maygc void wr_ch_array_synonym (const gcv_object_t* stream_,
                                      const gcv_object_t* chararray_,
                                      uintL start, uintL len) {
  check_SP(); check_STACK();
  var object symbol = TheStream(*stream_)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  write_char_array(&STACK_0,chararray_,start,len);
  skipSTACK(1);
  /* No need to update wr_ch_lpos here. (See get_line_position().) */
}

/* Closes a Synonym-Stream.
 close_synonym(stream, abort);
 > stream : Synonym-Stream
 > abort: flag: non-0 => ignore errors */
#ifdef X3J13_014
  #define close_synonym(stream,abort)
#else
  local maygc void close_synonym (object stream, uintB abort) {
    check_SP(); check_STACK();
    var object symbol = TheStream(stream)->strm_synonym_symbol;
    var int argcount = 1;
    pushSTACK(get_synonym_stream(symbol));
    if (abort) { pushSTACK(S(Kabort)); pushSTACK(T); argcount=3; }
    funcall(S(closeL),argcount);
  }
#endif

/* Reads a line of characters from a synonym-stream.
 read_line_synonym(stream,&buffer)
 > stream: synonym-stream
 > buffer: a semi-simple string
 < buffer: contains the read characters, excluding the terminating #\Newline
 < result: true if EOF was seen before newline, else false
 can trigger GC */
local maygc bool read_line_synonym (object stream, const gcv_object_t* buffer_)
{
  check_SP(); check_STACK();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  pushSTACK(get_synonym_stream(symbol));
  var bool eofp = read_line(&STACK_0,buffer_);
  skipSTACK(1);
  return eofp;
}

/* Determines, if a character is available on the Synonym-Stream.
 listen_char_synonym(stream)
 > stream : Synonym-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_char_synonym (object stream) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  return listen_char(get_synonym_stream(symbol));
}

/* UP: Deletes already entered interactive Input from a Synonym-Stream.
 clear_input_synonym(stream)
 > stream: Synonym-Stream
 < result: true if Input was deleted
 can trigger GC */
local maygc bool clear_input_synonym (object stream) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  return clear_input(get_synonym_stream(symbol));
}

/* Determines, if a Byte is available on a Synonym-Stream.
 listen_byte_synonym(stream)
 > stream : Synonym-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_byte_synonym (object stream) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  return listen_byte(get_synonym_stream(symbol));
}

/* UP: bring pending Output of a Synonym-Stream to the destination.
 finish_output_synonym(stream);
 > stream: Synonym-Stream
 can trigger GC */
local maygc void finish_output_synonym (object stream) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  finish_output(get_synonym_stream(symbol));
}

/* UP: bring pending Output of a Synonym-Stream to the destination.
 force_output_synonym(stream);
 > stream: Synonym-Stream
 can trigger GC */
local maygc void force_output_synonym (object stream) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  force_output(get_synonym_stream(symbol));
}

/* UP: delete the pending Output of a Synonym-Stream.
 clear_output_synonym(stream);
 > stream: Synonym-Stream
 can trigger GC */
local maygc void clear_output_synonym (object stream) {
  check_SP();
  var object symbol = TheStream(stream)->strm_synonym_symbol;
  clear_output(get_synonym_stream(symbol));
}

/* Returns a Synonym-Stream for a Symbol.
 make_synonym_stream(symbol)
 > symbol : Symbol
 < result : new Synonym-Stream
 can trigger GC */
local maygc object make_synonym_stream (object symbol) {
  pushSTACK(symbol); /* save Symbol */
  var object stream = /* new Stream, all Operations permitted */
    allocate_stream(strmflags_rdwr_B,strmtype_synonym,strm_len+1,0);
  TheStream(stream)->strm_rd_by = P(rd_by_synonym);
  TheStream(stream)->strm_rd_by_array = P(rd_by_array_synonym);
  TheStream(stream)->strm_wr_by = P(wr_by_synonym);
  TheStream(stream)->strm_wr_by_array = P(wr_by_array_synonym);
  TheStream(stream)->strm_rd_ch = P(rd_ch_synonym);
  TheStream(stream)->strm_pk_ch = P(pk_ch_synonym);
  TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_synonym);
  TheStream(stream)->strm_rd_ch_last = NIL;
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_synonym);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_synonym);
  TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
  TheStream(stream)->strm_synonym_symbol = popSTACK();
  return stream;
}

LISPFUNNR(make_synonym_stream,1)
{ /* (MAKE-SYNONYM-STREAM symbol), CLTL p. 329 */
  var object arg = popSTACK();
  if (!symbolp(arg)) {
    pushSTACK(arg);       /* TYPE-ERROR slot DATUM */
    pushSTACK(S(symbol)); /* TYPE-ERROR slot EXPECTED-TYPE */
    pushSTACK(arg); pushSTACK(TheSubr(subr_self)->name);
    error(type_error,GETTEXT("~S: argument should be a symbol, not ~S"));
  }
  VALUES1(make_synonym_stream(arg));
}

LISPFUNNF(synonym_stream_p,1)
{ /* (SYS::SYNONYM-STREAM-P stream) == (TYPEP stream 'SYNONYM-STREAM) */
  var object arg = popSTACK();
  VALUES_IF(builtin_stream_p(arg)
            && (TheStream(arg)->strmtype == strmtype_synonym));
}

LISPFUNNR(synonym_stream_symbol,1)
{ /* (SYNONYM-STREAM-SYMBOL stream), CLtL2 p. 507 */
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(synonym_stream),
                   (builtin_stream_p(stream)
                    && (TheStream(stream)->strmtype == strmtype_synonym)));
  VALUES1(TheStream(stream)->strm_synonym_symbol);
}


/* Broadcast-Stream
   ================

 Additional Components:
  define strm_broad_list  strm_other[0] - list of streams

 WRITE-BYTE - Pseudo-Function for Broadcast-Streams: */
local maygc void wr_by_broad (object stream, object obj) {
  check_SP(); check_STACK();
  pushSTACK(obj);
  { /* list of streams */
    var object streamlist = TheStream(stream)->strm_broad_list;
    /* write obj to each Stream on the List: */
    while (consp(streamlist)) {
      pushSTACK(Cdr(streamlist)); /* remaining Streams */
      write_byte(Car(streamlist),STACK_1); /* write obj */
      streamlist = popSTACK();
    }
  }
  skipSTACK(1);
}

/* WRITE-BYTE-ARRAY - Pseudo-Function for Broadcast-Streams: */
local maygc uintL wr_by_array_broad (const gcv_object_t* stream_,
                                     const gcv_object_t* bytearray_,
                                     uintL start, uintL len,
                                     perseverance_t persev) {
  /* what happens if different streams write different amounts?
     Only persev_full is supported for broadcast streams. */
  if (persev != persev_full) {
    error_illegal_streamop(S(write_byte_sequence),*stream_);
  }
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_broad_list); /* list of streams */
  var object streamlist;
  while (streamlist = STACK_0, consp(streamlist)) {
    STACK_0 = Cdr(streamlist);
    pushSTACK(Car(streamlist));
    write_byte_array(&STACK_0,bytearray_,start,len,persev);
    skipSTACK(1);
  }
  skipSTACK(1);
  return len;
}

/* WRITE-CHAR - Pseudo-Function for Broadcast-Streams: */
local maygc void wr_ch_broad (const gcv_object_t* stream_, object obj) {
  check_SP(); check_STACK();
  pushSTACK(obj);
  pushSTACK(NIL); /* dummy */
  pushSTACK(TheStream(*stream_)->strm_broad_list); /* list of streams */
  /* write obj to each Stream on the List: */
  while (mconsp(STACK_0)) {
    /* Stack Layout: obj, dummy, streamlistr. */
    STACK_1 = Car(STACK_0); /* a Stream from the Liste */
    write_char(&STACK_1,STACK_2); /* write obj */
    STACK_0 = Cdr(STACK_0);
  }
  skipSTACK(3);
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for Broadcast-Streams: */
local maygc void wr_ch_array_broad (const gcv_object_t* stream_,
                                    const gcv_object_t* chararray_,
                                    uintL start, uintL len) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_broad_list); /* list of streams */
  pushSTACK(NIL); /* dummy */
  var object streamlist;
  while (streamlist = STACK_1, consp(streamlist)) {
    STACK_1 = Cdr(streamlist);
    STACK_0 = Car(streamlist);
    write_char_array(&STACK_0,chararray_,start,len);
  }
  skipSTACK(2);
  /* No need to update wr_ch_lpos here. (See get_line_position().) */
}

/* UP: Moves the pending Output of a Broadcast-Stream to the destination.
 finish_output_broad(stream);
 > stream: Broadcast-Stream
 can trigger GC */
local maygc void finish_output_broad (object stream) {
  check_SP(); check_STACK();
  var object streamlist = TheStream(stream)->strm_broad_list;
  /* treat each Stream from the List separately: */
  while (consp(streamlist)) {
    pushSTACK(Cdr(streamlist)); /* remaining Streams */
    finish_output(Car(streamlist));
    streamlist = popSTACK();
  }
}

/* UP: Moves the pending Output of a Broadcast-Stream to the destination.
 force_output_broad(stream);
 > stream: Broadcast-Stream
 can trigger GC */
local maygc void force_output_broad (object stream) {
  check_SP(); check_STACK();
  var object streamlist = TheStream(stream)->strm_broad_list;
  /* treat each Stream from the List separately: */
  while (consp(streamlist)) {
    pushSTACK(Cdr(streamlist)); /* remaining Streams */
    force_output(Car(streamlist));
    streamlist = popSTACK();
  }
}

/* UP: Deletes the pending Output of a Broadcast-Stream.
 clear_output_broad(stream);
 > stream: Broadcast-Stream
 can trigger GC */
local maygc void clear_output_broad (object stream) {
  check_SP(); check_STACK();
  var object streamlist = TheStream(stream)->strm_broad_list;
  /* treat each Stream from the List separately: */
  while (consp(streamlist)) {
    pushSTACK(Cdr(streamlist)); /* remaining Streams */
    clear_output(Car(streamlist));
    streamlist = popSTACK();
  }
}

/* Returns a Broadcast-Stream for a list of Streams.
 make_broadcast_stream(list)
 > list : list of streams
 < result : Broadcast-Stream
 Thereby the List list is destroyed.
 can trigger GC */
local maygc object make_broadcast_stream (object list) {
  pushSTACK(list); /* save list */
  var object stream = /* new Stream, only WRITEs allowed */
    allocate_stream(strmflags_wr_B,strmtype_broad,strm_len+1,0);
  list = popSTACK();
  stream_dummy_fill(stream);
  TheStream(stream)->strm_wr_by = P(wr_by_broad);
  TheStream(stream)->strm_wr_by_array = P(wr_by_array_broad);
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_broad);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_broad);
  TheStream(stream)->strm_broad_list = list;
  return stream;
}

/* returns a Broadcast-Stream for Stream stream.
 make_broadcast1_stream(stream)
 > stream : Stream
 < result : Broadcast-Stream
 can trigger GC */
global maygc object make_broadcast1_stream (object oldstream) {
  pushSTACK(oldstream);
  /* pack oldstream in a one-element List: */
  var object new_cons = allocate_cons();
  Car(new_cons) = STACK_0;
  var object stream = make_broadcast_stream(new_cons); /* new Stream */
  oldstream = popSTACK();
  /* take over Line-Position: */
  TheStream(stream)->strm_wr_ch_lpos = TheStream(oldstream)->strm_wr_ch_lpos;
  return stream;
}

LISPFUN(make_broadcast_stream,seclass_read,0,0,rest,nokey,0,NIL)
{ /* (MAKE-BROADCAST-STREAM {stream}), CLTL p. 329 */
  /* check that all Arguments are Streams: */
  test_output_stream_args(rest_args_pointer,argcount);
  /* collect to one List: */
  var object list = listof(argcount);
  /* build Stream: */
  VALUES1(make_broadcast_stream(list));
}

LISPFUNNF(broadcast_stream_p,1)
{ /* (SYS::BROADCAST-STREAM-P stream) == (TYPEP stream 'BROADCAST-STREAM) */
  var object arg = popSTACK();
  VALUES_IF(builtin_stream_p(arg)
            && (TheStream(arg)->strmtype == strmtype_broad));
}

LISPFUNNR(broadcast_stream_streams,1)
{ /* (BROADCAST-STREAM-STREAMS stream), CLtL2 p. 507 */
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(broadcast_stream),
                   (builtin_stream_p(stream)
                    && (TheStream(stream)->strmtype == strmtype_broad)));
  /* copy List of Streams as a precaution */
  VALUES1(copy_list(TheStream(stream)->strm_broad_list));
}

/* (car (last (broadcast_stream stream)))
 this is necessary for issue 021
 <http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Issues/iss021.html> */
local object broadcast_stream_last (object stream)
{
  var object stream_list = TheStream(stream)->strm_broad_list;
  if (consp(stream_list)) {
    do {   stream = Car(stream_list);
      stream_list = Cdr(stream_list);
    } while (consp(stream_list));
    return stream;
  } else return nullobj;
}

/* Concatenated-Stream
   ===================

 Additional Components:
 define strm_concat_list       strm_other[0]  - list of not exhausted streams */
#define strm_concat_totallist  strm_other[1]  /* list of all streams */

/* READ-BYTE - Pseudo-Function for Concatenated-Streams: */
local maygc object rd_by_concat (object stream) {
  check_SP(); check_STACK();
  pushSTACK(stream);
  var object streamlist = TheStream(stream)->strm_concat_list;
  var object result;
  while (consp(streamlist)) {
    result = read_byte(Car(streamlist)); /* read Integer */
    if (!eq(result,eof_value)) /* not EOF ? */
      goto OK;
    /* EOF reached -> remove emptied Stream from the List: */
    stream = STACK_0;
    streamlist = TheStream(stream)->strm_concat_list =
             Cdr(TheStream(stream)->strm_concat_list);
  }
  /* all Streams emptied -> return EOF: */
  { result = eof_value; }
 OK:
  skipSTACK(1);
  return result;
}

/* READ-BYTE-ARRAY - Pseudo-Function for Concatenated-Streams: */
local maygc uintL rd_by_array_concat (const gcv_object_t* stream_,
                                      const gcv_object_t* bytearray_,
                                      uintL start, uintL len,
                                      perseverance_t persev) {
  check_SP(); check_STACK();
  var uintL result = 0;
  var object stream = *stream_;
  var object streamlist = TheStream(stream)->strm_concat_list;
  while (consp(streamlist)) {
    pushSTACK(Car(streamlist));
    var uintL count = read_byte_array(&STACK_0,bytearray_,start,len,persev);
    skipSTACK(1);
    result += count;
    start += count; len -= count;
    if (len == 0)
      break;
    /* EOF reached -> remove emptied stream from the list: */
    stream = *stream_;
    streamlist = TheStream(stream)->strm_concat_list =
             Cdr(TheStream(stream)->strm_concat_list);
    if (persev == persev_partial && result > 0)
      persev = persev_bonus;
  }
  return result;
}

/* READ-CHAR - Pseudo-Function for Concatenated-Streams: */
local maygc object rd_ch_concat (const gcv_object_t* stream_) {
  check_SP(); check_STACK();
  var object streamlist = TheStream(*stream_)->strm_concat_list;
  while (consp(streamlist)) {
    pushSTACK(Car(streamlist));
    var object result = read_char(&STACK_0); /* read Character */
    skipSTACK(1);
    if (!eq(result,eof_value))
      return result;
    /* EOF reached -> remove emptied stream from the list: */
    var object stream = *stream_;
    streamlist = TheStream(stream)->strm_concat_list =
             Cdr(TheStream(stream)->strm_concat_list);
  }
  /* all Streams emptied -> return EOF: */
  return eof_value;
}

/* PEEK-CHAR - Pseudo-Function for Concatenated-Streams: */
local maygc object pk_ch_concat (const gcv_object_t* stream_) {
  check_SP(); check_STACK();
  var object streamlist = TheStream(*stream_)->strm_concat_list;
  while (consp(streamlist)) {
    pushSTACK(Car(streamlist));
    var object result = peek_char(&STACK_0); /* read Character */
    skipSTACK(1);
    if (!eq(result,eof_value))
      return result;
    /* EOF reached -> remove emptied stream from the list: */
    var object stream = *stream_;
    streamlist = TheStream(stream)->strm_concat_list =
             Cdr(TheStream(stream)->strm_concat_list);
  }
  /* all Streams emptied -> return EOF: */
  return eof_value;
}

/* READ-CHAR-ARRAY - Pseudo-Function for Concatenated-Streams: */
local maygc uintL rd_ch_array_concat (const gcv_object_t* stream_,
                                      const gcv_object_t* chararray_,
                                      uintL start, uintL len) {
  check_SP(); check_STACK();
  var uintL result = 0;
  var object stream = *stream_;
  var object streamlist = TheStream(stream)->strm_concat_list;
  while (consp(streamlist)) {
    pushSTACK(Car(streamlist));
    var uintL count = read_char_array(&STACK_0,chararray_,start,len);
    skipSTACK(1);
    result += count;
    start += count; len -= count;
    if (len == 0)
      break;
    /* EOF reached -> remove emptied stream from the list: */
    stream = *stream_;
    streamlist = TheStream(stream)->strm_concat_list =
             Cdr(TheStream(stream)->strm_concat_list);
  }
  return result;
}

/* Determines, if a character is available on the Concatenated-Stream.
 listen_char_concat(stream)
 > stream : Concatenated-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_char_concat (object stream) {
  pushSTACK(stream);
  var object streamlist = TheStream(stream)->strm_concat_list;
  var listen_t result;
  while (consp(streamlist)) {
    result = listen_char(Car(streamlist));
    if (result != LISTEN_EOF) /* not EOF ? */
      goto OK;
    /* EOF reached -> remove emptied stream from the list: */
    stream = STACK_0;
    streamlist = TheStream(stream)->strm_concat_list =
             Cdr(TheStream(stream)->strm_concat_list);
  }
  /* all Streams emptied -> return EOF: */
  result = LISTEN_EOF;
 OK:
  skipSTACK(1);
  return result;
}

/* UP: Deletes already entered interactive Input from a
 Concatenated-Stream.
 clear_input_concat(stream)
 > stream: Concatenated-Stream
 < result: true if Input was deleted
 can trigger GC */
local maygc bool clear_input_concat (object stream) {
  var bool result = false; /* no Input deleted yet */
  /* treat all Streams separately: */
  var object streamlist = TheStream(stream)->strm_concat_list;
  while (consp(streamlist)) {
    pushSTACK(Cdr(streamlist)); /* remaining list ofStreams */
    result |= clear_input(Car(streamlist)); /* delete all Input of the sub-streams */
    streamlist = popSTACK();
  }
  return result;
}

/* Determines, if a Byte is available on the Concatenated-Stream.
 listen_byte_concat(stream)
 > stream : Concatenated-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_byte_concat (object stream) {
  pushSTACK(stream);
  var object streamlist = TheStream(stream)->strm_concat_list;
  var listen_t result;
  while (consp(streamlist)) {
    result = listen_byte(Car(streamlist));
    if (result != LISTEN_EOF) /* not EOF ? */
      goto OK;
    /* EOF reached -> remove emptied stream from the list: */
    stream = STACK_0;
    streamlist = TheStream(stream)->strm_concat_list =
             Cdr(TheStream(stream)->strm_concat_list);
  }
  /* all Streams emptied -> return EOF: */
  result = LISTEN_EOF;
 OK:
  skipSTACK(1);
  return result;
}

/* Returns a Concatenated-Stream for a list of Stream.
 make_concatenated_stream(list)
 > list : list of streams
 < result : Concatenated-Stream
 Thereby the List list is destroyed.
 can trigger GC */
local maygc object make_concatenated_stream (object list) {
  pushSTACK(list); /* save list */
  var object stream = /* new Stream, only READs allowed */
    allocate_stream(strmflags_rd_B,strmtype_concat,strm_len+2,0);
  stream_dummy_fill(stream);
  TheStream(stream)->strm_rd_by = P(rd_by_concat);
  TheStream(stream)->strm_rd_by_array = P(rd_by_array_concat);
  TheStream(stream)->strm_rd_ch = P(rd_ch_concat);
  TheStream(stream)->strm_pk_ch = P(pk_ch_concat);
  TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_concat);
  TheStream(stream)->strm_concat_list =
    TheStream(stream)->strm_concat_totallist = popSTACK();
  return stream;
}

LISPFUN(make_concatenated_stream,seclass_read,0,0,rest,nokey,0,NIL)
{ /* (MAKE-CONCATENATED-STREAM {stream}), CLTL p. 329 */
  /* check that all Arguments are Streams: */
  test_input_stream_args(rest_args_pointer,argcount);
  /* collect to one List: */
  var object list = listof(argcount);
  /* build Stream: */
  VALUES1(make_concatenated_stream(list));
}

LISPFUNNF(concatenated_stream_p,1)
{ /* (SYS::CONCATENATED-STREAM-P stream)
     == (TYPEP stream 'CONCATENATED-STREAM) */
  var object arg = popSTACK();
  VALUES_IF(builtin_stream_p(arg)
            && (TheStream(arg)->strmtype == strmtype_concat));
}

LISPFUNNR(concatenated_stream_streams,1)
{ /* (CONCATENATED-STREAM-STREAMS stream), CLtL2 p. 507 */
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(concatenated_stream),
                   (builtin_stream_p(stream)
                    && (TheStream(stream)->strmtype == strmtype_concat)));
  /* copy List of Streams as a precaution */
  VALUES1(copy_list(TheStream(stream)->strm_concat_list));
}


/* Two-Way-Stream, Echo-Stream
   ===========================

 Additional Components:
   define strm_twoway_input   strm_other[0]  - Stream for Input
   define strm_twoway_output  strm_other[1]  - Stream for Output

 WRITE-BYTE - Pseudo-Function for Two-Way- and Echo-Streams: */
local maygc void wr_by_twoway (object stream, object obj) {
  check_SP();
  write_byte(TheStream(stream)->strm_twoway_output,obj);
}

/* WRITE-BYTE-ARRAY - Pseudo-Function for Two-Way- and Echo-Streams: */
local maygc uintL wr_by_array_twoway (const gcv_object_t* stream_,
                                      const gcv_object_t* bytearray_,
                                      uintL start, uintL len,
                                      perseverance_t persev) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_output);
  var uintL result = write_byte_array(&STACK_0,bytearray_,start,len,persev);
  skipSTACK(1);
  return result;
}

/* WRITE-CHAR - Pseudo-Function for Two-Way- and Echo-Streams: */
local maygc void wr_ch_twoway (const gcv_object_t* stream_, object obj) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_output);
  write_char(&STACK_0,obj);
  skipSTACK(1);
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for Two-Way- and Echo-Streams: */
local maygc void wr_ch_array_twoway (const gcv_object_t* stream_,
                                     const gcv_object_t* chararray_,
                                     uintL start, uintL len) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_output);
  write_char_array(&STACK_0,chararray_,start,len);
  skipSTACK(1);
  /* No need to update wr_ch_lpos here. (See get_line_position().) */
}

/* Determines, if a Character is available on a Two-Way- or Echo-Stream.
 listen_char_twoway(stream)
 > stream : Two-Way- or Echo-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_char_twoway (object stream) {
  check_SP();
  return listen_char(TheStream(stream)->strm_twoway_input);
}

/* UP: Deletes already entered interactive Input from a Two-Way-
 or Echo-Stream.
 clear_input_twoway(stream)
 > stream: Two-Way- or Echo-Stream
 < result: true if Input was deleted
 can trigger GC */
local maygc bool clear_input_twoway (object stream) {
  check_SP();
  return clear_input(TheStream(stream)->strm_twoway_input);
}

/* Determines, if a Byte is available on a Two-Way- or Echo-Stream.
 listen_byte_twoway(stream)
 > stream : Two-Way- or Echo-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_byte_twoway (object stream) {
  check_SP();
  return listen_byte(TheStream(stream)->strm_twoway_input);
}

/* UP: Moves the pending Output of a Two-Way- or Echo-Stream to the destination.
 finish_output_twoway(stream);
 > stream: Two-Way- or Echo-Stream
 can trigger GC */
local maygc void finish_output_twoway (object stream) {
  check_SP();
  finish_output(TheStream(stream)->strm_twoway_output);
}

/* UP: Moves the pending Output of a Two-Way- or Echo-Stream to the destination.
 force_output_twoway(stream);
 > stream: Two-Way- or Echo-Stream
 can trigger GC */
local maygc void force_output_twoway (object stream) {
  check_SP();
  force_output(TheStream(stream)->strm_twoway_output);
}

/* UP: Deletes the pending Output of a Two-Way- or Echo-Stream.
 clear_output_twoway(stream);
 > stream: Two-Way- or Echo-Stream
 can trigger GC */
local maygc void clear_output_twoway (object stream) {
  check_SP();
  clear_output(TheStream(stream)->strm_twoway_output);
}

/* Two-Way-Stream
   ==============

 READ-BYTE - Pseudo-Function for Two-Way-Streams: */
local maygc object rd_by_twoway (object stream) {
  check_SP();
  return read_byte(TheStream(stream)->strm_twoway_input);
}

/* READ-BYTE-ARRAY - Pseudo-Function for Two-Way-Streams: */
local maygc uintL rd_by_array_twoway (const gcv_object_t* stream_,
                                      const gcv_object_t* bytearray_,
                                      uintL start, uintL len,
                                      perseverance_t persev) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_input);
  var uintL result = read_byte_array(&STACK_0,bytearray_,start,len,persev);
  skipSTACK(1);
  return result;
}

/* READ-CHAR - Pseudo-Function for Two-Way-Streams: */
local maygc object rd_ch_twoway (const gcv_object_t* stream_) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_input);
  var object result = read_char(&STACK_0);
  skipSTACK(1);
  return result;
}

/* PEEK-CHAR - Pseudo-Function for Two-Way-Streams: */
local maygc object pk_ch_twoway (const gcv_object_t* stream_) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_input);
  var object result = peek_char(&STACK_0);
  skipSTACK(1);
  return result;
}

/* READ-CHAR-ARRAY - Pseudo-Function for Two-Way-Streams: */
local maygc uintL rd_ch_array_twoway (const gcv_object_t* stream_,
                                      const gcv_object_t* chararray_,
                                      uintL start, uintL len) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_input);
  var uintL result = read_char_array(&STACK_0,chararray_,start,len);
  skipSTACK(1);
  return result;
}

/* Reads a line of characters from a two-way-stream.
 read_line_twoway(stream,&buffer)
 > stream: two-way-stream
 > buffer: a semi-simple string
 < buffer: contains the read characters, excluding the terminating #\Newline
 < result: true if EOF was seen before newline, else false
 can trigger GC */
local maygc bool read_line_twoway (object stream, const gcv_object_t* buffer_) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(stream)->strm_twoway_input);
  var bool eofp = read_line(&STACK_0,buffer_);
  skipSTACK(1);
  return eofp;
}

/* Returns a Two-Way-Stream for an Input-Stream and an Output-Stream.
 make_twoway_stream(input_stream,output_stream)
 > input_stream : Input-Stream
 > output_stream : Output-Stream
 < result : Two-Way-Stream
 can trigger GC */
global maygc object make_twoway_stream (object input_stream,
                                        object output_stream) {
  pushSTACK(input_stream); pushSTACK(output_stream); /* save Streams */
  var uintB flags = strmflags_rdwr_B
    | (TheStream(input_stream)->strmflags & strmflags_immut_B);
  var object stream = /* new Stream, all Operations allowed */
    allocate_stream(flags,strmtype_twoway,strm_len+2,0);
  TheStream(stream)->strm_rd_by = P(rd_by_twoway);
  TheStream(stream)->strm_rd_by_array = P(rd_by_array_twoway);
  TheStream(stream)->strm_wr_by = P(wr_by_twoway);
  TheStream(stream)->strm_wr_by_array = P(wr_by_array_twoway);
  TheStream(stream)->strm_rd_ch = P(rd_ch_twoway);
  TheStream(stream)->strm_pk_ch = P(pk_ch_twoway);
  TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_twoway);
  TheStream(stream)->strm_rd_ch_last = NIL;
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_twoway);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_twoway);
  output_stream = popSTACK(); input_stream = popSTACK(); /* put back Streams */
  TheStream(stream)->strm_wr_ch_lpos =
    TheStream(output_stream)->strm_wr_ch_lpos;
  TheStream(stream)->strm_twoway_input = input_stream;
  TheStream(stream)->strm_twoway_output = output_stream;
  return stream;
}

LISPFUNNR(make_two_way_stream,2)
{ /* (MAKE-TWO-WAY-STREAM input-stream output-stream), CLTL p. 329 */
  /* check that both are Streams: */
  check_stream_args(args_end_pointer STACKop 2, 2);
  var object output_stream = popSTACK();
  var object input_stream = popSTACK();
  test_input_stream(input_stream);
  test_output_stream(output_stream);
  /* build Stream: */
  VALUES1(make_twoway_stream(input_stream,output_stream));
}

/* check whether the stream S is a two-way-stream */
#define stream_twoway_p(s)                                              \
  (builtin_stream_p(s) && (TheStream(s)->strmtype == strmtype_twoway))

LISPFUNNF(two_way_stream_p,1)
{ /* (SYS::TWO-WAY-STREAM-P stream) == (TYPEP stream 'TWO-WAY-STREAM) */
  var object arg = popSTACK();
  VALUES_IF(stream_twoway_p(arg));
}

LISPFUNNR(two_way_stream_input_stream,1)
{ /* (TWO-WAY-STREAM-INPUT-STREAM stream), CLtL2 p. 507 */
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(two_way_stream),stream_twoway_p(stream));
  VALUES1(TheStream(stream)->strm_twoway_input);
}

LISPFUNNR(two_way_stream_output_stream,1)
{ /* (TWO-WAY-STREAM-OUTPUT-STREAM stream), CLtL2 p. 507 */
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(two_way_stream),stream_twoway_p(stream));
  VALUES1(TheStream(stream)->strm_twoway_output);
}


/* Echo-Stream
   ===========

 READ-BYTE - Pseudo-Function for Echo-Streams: */
local maygc object rd_by_echo (object stream) {
  check_SP(); check_STACK();
  pushSTACK(stream);
  var object obj = read_byte(TheStream(stream)->strm_twoway_input);
  stream = popSTACK();
  if (!eq(obj,eof_value)) {
    pushSTACK(obj);
    write_byte(TheStream(stream)->strm_twoway_output,obj);
    obj = popSTACK();
  }
  return obj;
}

/* READ-BYTE-ARRAY - Pseudo-Function for Echo-Streams: */
local maygc uintL rd_by_array_echo (const gcv_object_t* stream_,
                                    const gcv_object_t* bytearray_,
                                    uintL start, uintL len,
                                    perseverance_t persev) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_input);
  var uintL result = read_byte_array(&STACK_0,bytearray_,start,len,persev);
  STACK_0 = TheStream(*stream_)->strm_twoway_output;
  write_byte_array(&STACK_0,bytearray_,start,result,persev_full);
  skipSTACK(1);
  return result;
}

/* READ-CHAR - Pseudo-Function for Echo-Streams: */
local maygc object rd_ch_echo (const gcv_object_t* stream_) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_input);
  var object obj = read_char(&STACK_0);
  if (!eq(obj,eof_value)) {
    STACK_0 = TheStream(*stream_)->strm_twoway_output;
    pushSTACK(obj);
    write_char(&STACK_1,obj);
    obj = popSTACK();
  }
  skipSTACK(1);
  return obj;
}

/* READ-CHAR-ARRAY - Pseudo-Function for Echo-Streams: */
local maygc uintL rd_ch_array_echo (const gcv_object_t* stream_,
                                    const gcv_object_t* chararray_,
                                    uintL start, uintL len) {
  check_SP(); check_STACK();
  pushSTACK(TheStream(*stream_)->strm_twoway_input);
  var uintL result = read_char_array(&STACK_0,chararray_,start,len);
  STACK_0 = TheStream(*stream_)->strm_twoway_output;
  write_char_array(&STACK_0,chararray_,start,result);
  skipSTACK(1);
  return result;
}

/* returns an Echo-Stream for an Input-Stream and an Output-Stream.
 make_echo_stream(input_stream,output_stream)
 > input_stream : Input-Stream
 > output_stream : Output-Stream
 < result : Echo-Stream
 can trigger GC */
local maygc object make_echo_stream (object input_stream, object output_stream)
{
  pushSTACK(input_stream); pushSTACK(output_stream); /* save Streams */
  var uintB flags = strmflags_rdwr_B
    | (TheStream(input_stream)->strmflags & strmflags_immut_B);
  var object stream = /* new Stream, all Operations allowed */
    allocate_stream(flags,strmtype_echo,strm_len+2,0);
  TheStream(stream)->strm_rd_by = P(rd_by_echo);
  TheStream(stream)->strm_rd_by_array = P(rd_by_array_echo);
  TheStream(stream)->strm_wr_by = P(wr_by_twoway);
  TheStream(stream)->strm_wr_by_array = P(wr_by_array_twoway);
  TheStream(stream)->strm_rd_ch = P(rd_ch_echo);
  TheStream(stream)->strm_pk_ch = P(pk_ch_twoway);
  TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_echo);
  TheStream(stream)->strm_rd_ch_last = NIL;
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_twoway);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_twoway);
  output_stream = popSTACK(); input_stream = popSTACK(); /* put back Streams */
  TheStream(stream)->strm_wr_ch_lpos =
    TheStream(output_stream)->strm_wr_ch_lpos;
  TheStream(stream)->strm_twoway_input = input_stream;
  TheStream(stream)->strm_twoway_output = output_stream;
  return stream;
}

LISPFUNNR(make_echo_stream,2)
{ /* (MAKE-ECHO-STREAM input-stream output-stream), CLTL p. 330 */
  /* check that both are Streams: */
  check_stream_args(args_end_pointer STACKop 2, 2);
  var object output_stream = popSTACK();
  var object input_stream = popSTACK();
  test_input_stream(input_stream);
  test_output_stream(output_stream);
  /* build Stream: */
  VALUES1(make_echo_stream(input_stream,output_stream));
}

/* check whether the stream S is a two-way-stream */
#define stream_echo_p(s)                                                 \
  (builtin_stream_p(s) && (TheStream(s)->strmtype == strmtype_echo))

LISPFUNNF(echo_stream_p,1)
{ /* (SYS::ECHO-STREAM-P stream) == (TYPEP stream 'ECHO-STREAM) */
  var object arg = popSTACK();
  VALUES_IF(stream_echo_p(arg));
}

LISPFUNNR(echo_stream_input_stream,1)
{ /* (ECHO-STREAM-INPUT-STREAM stream), CLtL2 p. 507 */
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(echo_stream),stream_echo_p(stream));
  VALUES1(TheStream(stream)->strm_twoway_input);
}

LISPFUNNR(echo_stream_output_stream,1)
{ /* (ECHO-STREAM-OUTPUT-STREAM stream), CLtL2 p. 507 */
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(echo_stream),stream_echo_p(stream));
  VALUES1(TheStream(stream)->strm_twoway_output);
}


/* String-Input-Stream
   ===================

 Additional Components: */
#define strm_str_in_string   strm_other[0] /* String for Input */
#define strm_str_in_index    strm_other[1] /* Index in the String (Fixnum>=0)*/
#define strm_str_in_begindex strm_other[2] /* Begindex (Fixnum >= index >=0) */
#define strm_str_in_endindex strm_other[3] /* Endindex (Fixnum >= index >=0) */

/* error-message, if index >= length(string):
 error_str_in_adjusted(stream);
 > stream: problematic String-Input-Stream */
local _Noreturn void error_str_in_adjusted (object stream) {
  pushSTACK(stream); /* STREAM-ERROR slot STREAM */
  pushSTACK(TheStream(stream)->strm_str_in_string);
  pushSTACK(stream);
  error(stream_error,GETTEXT("~S is beyond the end because the string ~S has been adjusted"));
}

/* READ-CHAR - Pseudo-Function for String-Input-Streams: */
local maygc object rd_ch_str_in (const gcv_object_t* stream_) {
  var object stream = *stream_;
  var uintV index = posfixnum_to_V(TheStream(stream)->strm_str_in_index);
  var uintV endindex = posfixnum_to_V(TheStream(stream)->strm_str_in_endindex);
  if (index >= endindex) {
    return eof_value; /* EOF reached */
  } else { /* index < endvalid */
    var uintL len;
    var uintL offset;
    var object string =
      unpack_string_ro(TheStream(stream)->strm_str_in_string,&len,&offset);
    if (index >= len) /* Index too big? */
      error_str_in_adjusted(stream);
    /* fetch character from String */
    var object ch = code_char(schar(string,offset+index));
    /* increase Index: */
    TheStream(stream)->strm_str_in_index =
      fixnum_inc(TheStream(stream)->strm_str_in_index,1);
    return ch;
  }
}

/* READ-CHAR-ARRAY - Pseudo-Function for String-Input-Streams: */
local maygc uintL rd_ch_array_str_in (const gcv_object_t* stream_,
                                      const gcv_object_t* chararray_,
                                      uintL start, uintL len) {
  var object stream = *stream_;
  var uintV index = posfixnum_to_V(TheStream(stream)->strm_str_in_index);
  var uintV endindex = posfixnum_to_V(TheStream(stream)->strm_str_in_endindex);
  if (index < endindex) {
    var uintL srclen;
    var uintL srcoffset;
    var object string = unpack_string_ro(TheStream(stream)->strm_str_in_string,
                                         &srclen,&srcoffset);
    if (srclen < endindex)
      error_str_in_adjusted(stream);
    var uintL count = endindex - index;
    if (count > len)
      count = len;
    /* count = min(len,endindex-index) > 0. */
    var object chararray = *chararray_;
    sstring_un_realloc(chararray);
    elt_copy(string,srcoffset+index,chararray,start,count);
    stream = *stream_;
    TheStream(stream)->strm_str_in_index =
      fixnum_inc(TheStream(stream)->strm_str_in_index,count);
    return count;
  } else {
    return 0;
  }
}

/* Closes a String-Input-Stream.
 close_str_in(stream, abort);
 > stream : String-Input-Stream */
local maygc void close_str_in (object stream) {
  TheStream(stream)->strm_str_in_string = NIL; /* String := NIL */
}

/* Determines, if a character is available on a String-Input-Stream.
 listen_char_str_in(stream)
 > stream : String-Input-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_char_str_in (object stream) {
  var uintV index = posfixnum_to_V(TheStream(stream)->strm_str_in_index);
  var uintV endindex = posfixnum_to_V(TheStream(stream)->strm_str_in_endindex);
  if (index >= endindex)
    return LISTEN_EOF; /* EOF reached */
  else
    return LISTEN_AVAIL;
}

LISPFUN(make_string_input_stream,seclass_read,1,2,norest,nokey,0,NIL)
{ /* (MAKE-STRING-INPUT-STREAM string [start [end]]), CLTL p. 330 */
  /* fetch String and check range: */
  var stringarg arg;
  var object string = test_string_limits_ro(&arg);
  var object start_arg = fixnum(arg.index); /* start-Argument (Fixnum >=0) */
  var object end_arg = fixnum_inc(start_arg,arg.len); /* end-Argument (Fixnum >=0) */
  pushSTACK(string); /* save String */
  var object stream = /* new Stream, only READ-CHAR allowed */
    allocate_stream(strmflags_rd_ch_B,strmtype_str_in,strm_len+4,0);
  stream_dummy_fill(stream);
  TheStream(stream)->strm_rd_ch = P(rd_ch_str_in);
  TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_str_in);
  TheStream(stream)->strm_str_in_string = popSTACK();
  TheStream(stream)->strm_str_in_index = /* (Beg)Index := start-Argument */
    TheStream(stream)->strm_str_in_begindex = start_arg;
  TheStream(stream)->strm_str_in_endindex = end_arg; /* Endindex := end-Argument */
  VALUES1(stream); /* stream as value */
}

local _Noreturn void error_string_stream (object stream, const char *message) {
  pushSTACK(stream);           /* TYPE-ERROR slot DATUM */
  pushSTACK(S(string_stream)); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(stream);
  pushSTACK(TheSubr(subr_self)->name);
  error(type_error,message);
}

LISPFUNNR(string_input_stream_index,1)
{ /* (SYSTEM::STRING-INPUT-STREAM-INDEX string-input-stream) ==> Index */
  var object stream = popSTACK(); /* Argument */
  /* must be a String-Input-Stream: */
  if (!(builtin_stream_p(stream)
        && (TheStream(stream)->strmtype == strmtype_str_in)))
    error_string_stream(stream,GETTEXT("~S: ~S is not a string input stream"));
  var object index = TheStream(stream)->strm_str_in_index;
  /* if a Character was pushed back with UNREAD-CHAR,
   use (1- index), a Fixnum >=0, as value: */
  if (TheStream(stream)->strmflags & strmflags_unread_B)
    index = fixnum_inc(index,-1);
  VALUES1(index);
}


/* String-Output-Stream
   ====================

 Additional Components: */
#define strm_str_out_string  strm_other[0]  /* Semi-Simple-String for Output */

/* WRITE-CHAR - Pseudo-Function for String-Output-Streams: */
local maygc void wr_ch_str_out (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  check_wr_char(stream,ch);
  /* push Character in the String: */
  ssstring_push_extend(TheStream(stream)->strm_str_out_string,char_code(ch));
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for String-Output-Streams: */
local maygc void wr_ch_array_str_out (const gcv_object_t* stream_,
                                      const gcv_object_t* chararray_,
                                      uintL start, uintL len) {
  var object ssstring = TheStream(*stream_)->strm_str_out_string; /* Semi-Simple-String */
  ssstring = ssstring_append_extend(ssstring,*chararray_,start,len);
  wr_ss_lpos(*stream_,&TheSnstring(TheIarray(ssstring)->data)->data[TheIarray(ssstring)->dims[1]],len); /* update Line-Position */
}

/* Returns a String-Output-Stream.
 make_string_output_stream()
 can trigger GC */
global maygc object make_string_output_stream (void) {
  pushSTACK(make_ssstring(SEMI_SIMPLE_DEFAULT_SIZE));
  var object stream = /* new Stream, only WRITE-CHAR allowed */
    allocate_stream(strmflags_wr_ch_B,strmtype_str_out,strm_len+1,0);
  stream_dummy_fill(stream);
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_str_out);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_str_out);
  TheStream(stream)->strm_str_out_string = popSTACK(); /* enter the String */
  return stream;
}

LISPFUN(make_string_output_stream,seclass_read,0,0,norest,key,2,
        (kw(element_type),kw(line_position)))
{ /* (MAKE-STRING-OUTPUT-STREAM [:element-type] [:line-position]) */
  /* check line-position: */
  if (missingp(STACK_0)) {
    STACK_0 = Fixnum_0;         /* Default value 0 */
  } else /* line-position specified, should be a Fixnum >=0 : */
    STACK_0 = check_posfixnum(STACK_0);
  /* check element-type: */
  if (boundp(STACK_1) && !nullp(STACK_1) && !eq(STACK_1,S(character))) {
    var object eltype = STACK_1;
   restart_check_eltype:
    /* Verify (SUBTYPEP eltype 'CHARACTER): */
    pushSTACK(eltype); pushSTACK(S(character)); funcall(S(subtypep),2);
    if (nullp(value1)) {
      pushSTACK(NIL);           /* no PLACE */
      pushSTACK(STACK_2);       /* TYPE-ERROR slot DATUM - eltype */
      pushSTACK(S(character));  /* TYPE-ERROR slot EXPECTED-TYPE */
      pushSTACK(STACK_1);       /* eltype */
      pushSTACK(S(character));  /* CHARACTER */
      pushSTACK(S(Kelement_type)); /* :ELEMENT-TYPE */
      pushSTACK(S(make_string_output_stream));
      check_value(type_error,
                  GETTEXT("~S: ~S argument must be a subtype of ~S, not ~S"));
      eltype = STACK_1 = value1;
      goto restart_check_eltype;
    }
  }
  var object stream;
  if (nullp(STACK_1)) {
    /* A string-output-stream with element type NIL is a handicapped guy:
       You cannot feed him with any character... */
    /* Call (MAKE-ARRAY 0 :ELEMENT-TYPE NIL :FILL-POINTER 0): */
    pushSTACK(fixnum(0));
    pushSTACK(S(Kelement_type)); pushSTACK(NIL);
    pushSTACK(S(Kfill_pointer)); pushSTACK(Fixnum_0);
    funcall(L(make_array),5); pushSTACK(value1);
    stream = allocate_stream(strmflags_wr_ch_B,strmtype_str_out,strm_len+1,0);
    stream_dummy_fill(stream);
    TheStream(stream)->strm_wr_ch =
      TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_forbidden);
    TheStream(stream)->strm_wr_ch_array =
      TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_forbidden);
    TheStream(stream)->strm_str_out_string = popSTACK();
  } else
    stream = make_string_output_stream(); /* normal String-Output-Stream */
  TheStream(stream)->strm_wr_ch_lpos = popSTACK(); /* enter Line Position */
  VALUES1(stream); /* return stream */
  skipSTACK(1);
}

/* UP: Returns the collected stuff from a String-Output-Stream.
 get_output_stream_string(&stream)
 > stream: String-Output-Stream
 < stream: emptied Stream
 < result: collected stuff, a Simple-String
 can trigger GC */
global maygc object get_output_stream_string (const gcv_object_t* stream_) {
  harden_elastic_newline(stream_);
  var object string = TheStream(*stream_)->strm_str_out_string; /* old String */
  if ((Iarray_flags(string) & arrayflags_atype_mask) == Atype_NIL) {
    /* Return the encapsulated (VECTOR NIL). It is an immutable object, since
       it is not adjustable and its fill-pointer is constrained to remain 0.
       Therefore no need to copy it into a string without fill-pointer. */
  } else {
    string = coerce_ss(string); /* convert to Simple-String (enforces copying) */
    /* empty old String by Fill-Pointer:=0 : */
    TheIarray(TheStream(*stream_)->strm_str_out_string)->dims[1] = 0;
  }
  return string;
}

LISPFUNN(get_output_stream_string,1)
{ /* (GET-OUTPUT-STREAM-STRING string-output-stream), CLTL p. 330 */
  var object stream = STACK_0;  /* Argument */
  /* must be a String-Output-Stream: */
  if (!(builtin_stream_p(stream)
        && (TheStream(stream)->strmtype == strmtype_str_out)))
    error_string_stream(stream,GETTEXT("~S: ~S is not a string output stream"));
  /* the collected stuff is the value */
  VALUES1(get_output_stream_string(&STACK_0));
  skipSTACK(1);
}


/* String-Push-Stream
   ==================

 Additional Components: */
#define strm_str_push_string  strm_other[0]  /* String with Fill-Pointer for Output */

/* WRITE-CHAR - Pseudo-Function for String-Push-Streams: */
local maygc void wr_ch_str_push (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  check_wr_char(stream,ch);
  /* push Character in the String: */
  pushSTACK(ch); pushSTACK(TheStream(stream)->strm_str_push_string);
  funcall(L(vector_push_extend),2); /* (VECTOR-PUSH-EXTEND ch string) */
}

/* (SYSTEM::MAKE-STRING-PUSH-STREAM string) returns a Stream, whose
 WRITE-CHAR operation is equivalent to a VECTOR-PUSH-EXTEND
 on the given String. */
LISPFUNNR(make_string_push_stream,1) {
  {
    var object arg = STACK_0; /* Argument */
    /* must be a String with Fill-Pointer: */
    if (!(stringp(arg) && array_has_fill_pointer_p(arg))) {
      pushSTACK(arg);                              /* TYPE-ERROR slot DATUM */
      pushSTACK(O(type_string_with_fill_pointer)); /* TYPE-ERROR slot EXPECTED-TYPE */
      pushSTACK(arg); pushSTACK(S(with_output_to_string));
      error(type_error,
            GETTEXT("~S: argument ~S should be a string with fill pointer"));
    }
  }
  var object stream = /* new Stream, only WRITE-CHAR allowed */
    allocate_stream(strmflags_wr_ch_B,strmtype_str_push,strm_len+1,0);
  stream_dummy_fill(stream);
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_str_push);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_dummy);
  TheStream(stream)->strm_str_push_string = popSTACK(); /* enter String */
  VALUES1(stream); /* return stream */
}


/* String-Stream in general
   ======================= */

LISPFUNNF(string_stream_p,1)
{ /* (SYS::STRING-STREAM-P stream) == (TYPEP stream 'STRING-STREAM) */
  var object arg = popSTACK();
  if (builtin_stream_p(arg)) {
    switch (TheStream(arg)->strmtype) {
      case strmtype_str_in:   /* String-Input-Stream */
      case strmtype_str_out:  /* String-Output-Stream */
      case strmtype_str_push: /* String-Push-Stream */
        VALUES1(T); break;
      default:
        VALUES1(NIL); break;
    }
  } else
    VALUES1(NIL);
}

LISPFUNNR(string_stream_string,1)
{ /* (SYSTEM::STRING-STREAM-STRING string-stream) ==> String [beg end] */
  var object stream = popSTACK();
  if (builtin_stream_p(stream))
    switch (TheStream(stream)->strmtype) {
      case strmtype_str_in:   /* String-Input-Stream */
        VALUES3(TheStream(stream)->strm_str_in_string,
                TheStream(stream)->strm_str_in_begindex,
                TheStream(stream)->strm_str_in_endindex);
        return;
      case strmtype_str_out:  /* String-Output-Stream */
        VALUES1(TheStream(stream)->strm_str_out_string);
        return;
      case strmtype_str_push: /* String-Push-Stream */
        VALUES1(TheStream(stream)->strm_str_push_string);
        return;
    }
  error_string_stream(stream,GETTEXT("~S: ~S is not a string stream"));
}


/* Pretty-Printer-Help-Stream
   ==========================

 Additional Components:
 define strm_pphelp_strings  strm_other[0]   - Semi-Simple-Strings for Output
 define strm_pphelp_modus    strm_other[1]   - Mode (NIL=single-liner, T=multi-liner)

 WRITE-CHAR - Pseudo-Function for Pretty-Printer-Auxiliary-Streams: */
local maygc void wr_ch_pphelp (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  check_wr_char(stream,ch);
  var chart c = char_code(ch); /* Character */
  /* At NL: Now  Mode := Multi-liner */
  if (chareq(c,ascii(NL))) {
    TheStream(stream)->strm_pphelp_modus = T;
    cons_ssstring(stream_,NIL);
  } else if ((chareq(c,ascii(' ')) || chareq(c,ascii('\t')))
             && !nullpSv(print_pretty_fill)) {
    var object list = TheStream(stream)->strm_pphelp_strings;
    if (!(vector_length(Car(list)) == 0 && mconsp(Cdr(list))
          && mconsp(Car(Cdr(list))) && eq(S(Kfill),Car(Car(Cdr(list)))))) {
      ssstring_push_extend(Car(list),c);
      /* spaces right after a :FILL newline or multiple spaces are ignored */
      cons_ssstring(stream_,S(Kfill));
    }
  } else
    /* push Character in the first String: */
    ssstring_push_extend(Car(TheStream(stream)->strm_pphelp_strings),c);
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for Pretty-Printer-Auxiliary-Streams: */
local maygc void wr_ch_array_pphelp (const gcv_object_t* stream_,
                                     const gcv_object_t* chararray_,
                                     uintL start, uintL len) {
  var bool filling = !nullpSv(print_pretty_fill);
  var uintL beg = start;
  DEBUG_OUT(("s=%d l=%d",start,len));
  while (1) {
    var uintL end = beg;
    var object nl_type = NIL;
    DEBUG_OUT((" [%d/",beg));
    while (end < start+len) {
      var chart ch = schar(*chararray_,end);
      if (chareq(ch,ascii(NL))) { DEBUG_OUT(("%d=NL",end)); break; }
      if (filling && (chareq(ch,ascii(' ')) || chareq(ch,ascii('\t')))) {
        DEBUG_OUT(("%d=SPC",end));
        end++; /* include the space */
        nl_type = S(Kfill);
        break;
      }
      end++;
    }
    DEBUG_OUT(("/%d]",end));
    if (beg != end) {
      var uintL count = end-beg;
      var object ssstring = Car(TheStream(*stream_)->strm_pphelp_strings); /* Semi-Simple-String */
      ssstring = ssstring_append_extend(ssstring,*chararray_,beg,count);
      if (wr_ss_lpos(*stream_,&TheSnstring(TheIarray(ssstring)->data)->data[TheIarray(ssstring)->dims[1]],count)) /* update Line-Position */
        TheStream(*stream_)->strm_pphelp_modus = T; /* After NL: Mode := multi-liner */
    }
    if (end == start+len)
      break;
    if (nullp(nl_type))
      TheStream(*stream_)->strm_pphelp_modus = T;
    cons_ssstring(stream_,nl_type);
    beg = end;
    if (nullp(nl_type))
      beg++; /* skip the newline */
  }
  DEBUG_OUT(("\n"));
}

/* UP: Returns a Pretty-Printer-Auxiliary-Stream.
 make_pphelp_stream()
 can trigger GC */
global maygc object make_pphelp_stream (void) {
  pushSTACK(cons_ssstring(NULL,NIL));
  var object stream = /* new Stream, only WRITE-CHAR allowed */
    allocate_stream(strmflags_wr_ch_B,strmtype_pphelp,strm_len+2,0);
  stream_dummy_fill(stream);
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_pphelp);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_pphelp);
  TheStream(stream)->strm_pphelp_strings = popSTACK(); /* enter String-List */
  TheStream(stream)->strm_pphelp_modus = NIL; /* Mode := single-liner */
  return stream;
}


/* Buffered-Input-Stream
   =====================

 Element-Type: character
 Directions: only input
 (make-buffered-input-stream fun mode) returns a Buffered-Input-Stream.
   fun is a Function of 0 Arguments, that returns upon call
   either NIL (stands for EOF) or up to three values string, start, end.
   Functionality: (read-char ...) returns one after another the characters
   of the current String; if it is consumed, fun is called, and if the returning
   value is a String, the new current String is given by
     (multiple-value-bind (str start end) (funcall fun)
       (subseq str (or start 0) (or end 'NIL))
     )
   The String returned by fun should not be changed.
   (Otherwise fun should copy the String with COPY-SEQ beforehand.)
   mode determines, how the Stream acts regarding to LISTEN.
   mode = NIL: Stream acts like a File-Stream, i.e. on LISTEN
               and empty current String fun is called.
   mode = T: Stream acts like an interactive Stream without EOF,
             i.e. one can assume, that always further characters will
             arrive, without calling fun.
   mode a Function: This Function tells, upon call, if
             further non-empty Strings are to be expected.
   (clear-input ...) finishes the processing of the current String.

 Additional Components:
  define strm_buff_in_fun     strm_other[0]  - Read-Function */
#define strm_buff_in_mode     strm_other[1] /* Mode or Listen-Function */
#define strm_buff_in_string   strm_other[2] /* current String for Input */
#define strm_buff_in_index    strm_other[3] /* Index in the String (Fixnum >=0) */
#define strm_buff_in_endindex strm_other[4] /* Endindex (Fixnum >= index >=0) */

/* READ-CHAR - Pseudo-Function for Buffered-Input-Streams: */
local maygc object rd_ch_buff_in (const gcv_object_t* stream_) {
  var object stream = *stream_;
  var uintV index = posfixnum_to_V(TheStream(stream)->strm_buff_in_index);
  var uintV endindex =
    posfixnum_to_V(TheStream(stream)->strm_buff_in_endindex);
  while (index >= endindex) { /* string end reached */
    /* call fun: */
    funcall(TheStream(stream)->strm_buff_in_fun,0);
    if (!stringp(value1))
      return eof_value; /* EOF reached */
    /* fetch new String and check ranges: */
    pushSTACK(value1); /* String */
    pushSTACK(mv_count >= 2 ? value2 : unbound); /* start */
    pushSTACK(mv_count >= 3 ? value3 : unbound); /* end */
    var stringarg val;
    var object string = test_string_limits_ro(&val);
    stream = *stream_;
    index = val.index; /* val.offset==0 since the buffer is simple! */
    endindex = index+val.len;
    TheStream(stream)->strm_buff_in_string = string;
    TheStream(stream)->strm_buff_in_index = fixnum(index);
    TheStream(stream)->strm_buff_in_endindex = fixnum(endindex);
  }
  /* index < endvalid */
  var uintL len;
  var uintL offset;
  var object string = unpack_string_ro(TheStream(stream)->strm_buff_in_string,&len,&offset);
  if (index >= len) { /* Index too big ? */
    pushSTACK(stream); /* STREAM-ERROR slot STREAM */
    pushSTACK(TheStream(stream)->strm_buff_in_string);
    pushSTACK(stream);
    error(stream_error,GETTEXT("~S is beyond the end because the string ~S has been adjusted"));
  }
  /* fetch character from String */
  var object ch = code_char(schar(string,offset+index));
  /* increase Index: */
  TheStream(stream)->strm_buff_in_index = fixnum_inc(TheStream(stream)->strm_buff_in_index,1);
  return ch;
}

/* Closes a Buffered-Input-Stream.
 close_buff_in(stream, abort);
 > stream : Buffered-Input-Stream */
local maygc void close_buff_in (object stream) {
  TheStream(stream)->strm_buff_in_fun = NIL; /* Function := NIL */
  TheStream(stream)->strm_buff_in_mode = NIL; /* Mode := NIL */
  TheStream(stream)->strm_buff_in_string = NIL; /* String := NIL */
}

/* Determines, if a character is available on a Buffered-Input-Stream.
 listen_char_buff_in(stream)
 > stream : Buffered-Input-Stream
 < result: input availability
 can trigger GC */
local maygc listen_t listen_char_buff_in (object stream) {
  var uintV index = posfixnum_to_V(TheStream(stream)->strm_buff_in_index);
  var uintV endindex = posfixnum_to_V(TheStream(stream)->strm_buff_in_endindex);
  if (index < endindex)
    return LISTEN_AVAIL;
  var object mode = TheStream(stream)->strm_buff_in_mode;
  if (eq(mode,S(nil))) {
    pushSTACK(stream);
    mode = peek_char(&STACK_0); /* peek_char makes read_char, calls fun */
    skipSTACK(1);
    if (eq(mode,eof_value))
      return LISTEN_EOF; /* EOF reached */
    else
      return LISTEN_AVAIL;
  } else if (eq(mode,S(t))) {
    return LISTEN_AVAIL;
  } else {
    funcall(mode,0); /* call mode */
    if (nullp(value1)) /* no more Strings to be expected? */
      return LISTEN_EOF; /* yes -> EOF reached */
    else
      return LISTEN_AVAIL;
  }
}

/* UP: Deletes already entered interactive Input from a Buffered-Input-Stream.
 clear_input_buff_in(stream)
 > stream: Buffered-Input-Stream
 < result: true if Input was deleted
 can trigger GC */
local maygc bool clear_input_buff_in (object stream) {
  /* end processing of the current String: */
  var object index = TheStream(stream)->strm_buff_in_index;
  var object endindex = TheStream(stream)->strm_buff_in_endindex;
  TheStream(stream)->strm_buff_in_index = endindex; /* index := endindex */
  if (eq(index,endindex))
    return false;
  else
    return true;
}

LISPFUNNR(make_buffered_input_stream,2)
{ /* (MAKE-BUFFERED-INPUT-STREAM fun mode) */
  var object stream = /* new Stream, only READ-CHAR allowed */
    allocate_stream(strmflags_rd_ch_B,strmtype_buff_in,strm_len+5,0);
  stream_dummy_fill(stream);
  TheStream(stream)->strm_rd_ch = P(rd_ch_buff_in);
  TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_dummy);
  TheStream(stream)->strm_buff_in_mode = popSTACK();
  TheStream(stream)->strm_buff_in_fun = popSTACK();
  TheStream(stream)->strm_buff_in_string = O(empty_string); /* String := "" */
  TheStream(stream)->strm_buff_in_index = Fixnum_0; /* Index := 0 */
  TheStream(stream)->strm_buff_in_endindex = Fixnum_0; /* Endindex := 0 */
  VALUES1(stream); /* return stream */
}

LISPFUNNR(buffered_input_stream_index,1)
{ /* (SYS::BUFFERED-INPUT-STREAM-INDEX buffered-input-stream)
     returns the Index */
  var object stream = popSTACK(); /* Argument */
  /* must be a Buffered-Input-Stream: */
  if (!(builtin_stream_p(stream)
        && (TheStream(stream)->strmtype == strmtype_buff_in))) {
    pushSTACK(stream);
    pushSTACK(TheSubr(subr_self)->name);
    error(error_condition,GETTEXT("~S: ~S is not a buffered input stream"));
  }
  var object index = TheStream(stream)->strm_buff_in_index;
  /* if a Character was pushed back with UNREAD-CHAR,
   use (1- index), a Fixnum >=0, as value: */
  if (TheStream(stream)->strmflags & strmflags_unread_B)
    index = fixnum_inc(index,-1);
  VALUES1(index);
}

/* handling of (close :abort): ignore the error and proceed to close FDs */
#if !defined(MULTITHREAD)
/* should be per thread - moved to clisp_thread_t in MT */
local bool running_handle_close_errors = false;
#endif
local void handle_close_errors (void* sp, gcv_object_t* frame, object label,
                                object condition) {
  unused(sp); unused(label); unused(condition);
  if (running_handle_close_errors) return;
  else running_handle_close_errors = true;
  unwind_upto(frame);
}
#define MAYBE_IGNORE_ERRORS(abort,code)                                     \
  { var sp_jmp_buf returner; /* return point */                             \
    if (abort) {                                                            \
      running_handle_close_errors = false;                                  \
      make_C_HANDLER_entry_frame(O(handler_for_error), handle_close_errors, \
                                 returner, goto end_ignore_errors; );       \
    }                                                                       \
    code;                                                                   \
    if (abort) running_handle_close_errors = false;                         \
   end_ignore_errors:                                                       \
    if (abort) { unwind_C_HANDLER_frame(); }                                \
  }


/* Buffered-Output-Stream
   ======================

 Element-Type: character
 Directions: only output
 (make-buffered-output-stream fun) returns a Buffered-Output-Stream.
   fun is a Function expecting one Argument, a Simple-String.
   Functionality: (write-char ...) gathers the written characters in
   a String, until a #\Newline or a FORCE-/FINISH-OUTPUT-
   request arrives. Then it calls fun with a Simple-String as Argument,
   that contains the so far collected stuff.
   (clear-output ...) dicards the so far collected characters.

 Additional Components:
 define strm_buff_out_fun    strm_other[0]  - Output-Function */
#define strm_buff_out_string strm_other[1] /* Semi-Simple-String for Output */

/* UP: Moves the pending Output of a Buffered-Output-Stream to the destination.
 finish_output_buff_out(stream);
 > stream: Buffered-Output-Stream
 can trigger GC */
local maygc void finish_output_buff_out (object stream) {
  pushSTACK(stream);
  var object string = TheStream(stream)->strm_buff_out_string; /* String */
  string = coerce_ss(string); /* convert to Simple-String (enforces copying) */
  stream = STACK_0; STACK_0 = string;
  /* empty String by Fill-Pointer:=0 : */
  TheIarray(TheStream(stream)->strm_buff_out_string)->dims[1] = 0;
  funcall(TheStream(stream)->strm_buff_out_fun,1); /* call Function */
}

/* UP: Moves the pending Output of a Buffered-Output-Stream to the destination.
 force_output_buff_out(stream);
 > stream: Buffered-Output-Stream
 can trigger GC */
#define force_output_buff_out  finish_output_buff_out

/* UP: Deletes the pending Output of a Buffered-Output-Stream.
 clear_output_buff_out(stream);
 > stream: Buffered-Output-Stream
 can trigger GC */
local maygc void clear_output_buff_out (object stream) {
  /* empty String by Fill-Pointer:=0 : */
  TheIarray(TheStream(stream)->strm_buff_out_string)->dims[1] = 0;
  /* leave Line-Position unchanged?? */
}

/* WRITE-CHAR - Pseudo-Function for Buffered-Output-Streams: */
local maygc void wr_ch_buff_out (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  check_wr_char(stream,ch);
  /* push Character in the String: */
  ssstring_push_extend(TheStream(stream)->strm_buff_out_string,char_code(ch));
  /* After #\Newline pass on Buffer: */
  if (chareq(char_code(ch),ascii(NL)))
    force_output_buff_out(*stream_);
}

/* Closes a Buffered-Output-Stream.
 close_buff_out(stream, abort);
 > stream : Buffered-Output-Stream
 > abort: flag: non-0 => ignore errors
 can trigger GC */
local maygc void close_buff_out (object stream, uintB abort) {
  pushSTACK(stream); /* save stream */
  MAYBE_IGNORE_ERRORS(abort,finish_output_buff_out(stream));
  stream = popSTACK(); /* restore stream */
  TheStream(stream)->strm_buff_out_fun = NIL; /* Function := NIL */
  TheStream(stream)->strm_buff_out_string = NIL; /* String := NIL */
}

/* (MAKE-BUFFERED-OUTPUT-STREAM fun [line-position]) */
LISPFUN(make_buffered_output_stream,seclass_read,1,1,norest,nokey,0,NIL) {
  /* check line-position: */
  if (!boundp(STACK_0)) {
    STACK_0 = Fixnum_0; /* default value 0 */
  } else { /* line-position specified, should be a Fixnum >=0 : */
    if (!posfixnump(STACK_0))
      error_posfixnum(STACK_0);
  }
  /* allocate small Semi-Simple-String of Length 50 : */
  pushSTACK(make_ssstring(SEMI_SIMPLE_DEFAULT_SIZE));
  var object stream = /* new Stream, only WRITE-CHAR allowed */
    allocate_stream(strmflags_wr_ch_B,strmtype_buff_out,strm_len+2,0);
  stream_dummy_fill(stream);
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_buff_out);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_dummy);
  TheStream(stream)->strm_buff_out_string = popSTACK(); /* enter String */
  TheStream(stream)->strm_wr_ch_lpos = popSTACK(); /* enter Line Position */
  TheStream(stream)->strm_buff_out_fun = popSTACK(); /* enter Function */
  VALUES1(stream); /* return stream */
}


#ifdef GENERIC_STREAMS

/* Generic Streams
   ===============

 Contains a "controller object".
 define strm_controller_object  strm_other[0]  - see lispbibl.d

 The function GENERIC-STREAM-CONTROLLER will return some
 object c associated with the stream s.

     (GENERIC-STREAM-READ-CHAR c)                      --> character or NIL
     (GENERIC-STREAM-PEEK-CHAR c)                      --> character or NIL
     (GENERIC-STREAM-READ-CHAR-WILL-HANG-P c)          --> {T,NIL}
     (GENERIC-STREAM-CLEAR-INPUT c)                    --> {T,NIL}
     (GENERIC-STREAM-WRITE-CHAR c ch)                  -->
     (GENERIC-STREAM-WRITE-STRING c string start len)  -->
     (GENERIC-STREAM-FINISH-OUTPUT c)                  -->
     (GENERIC-STREAM-FORCE-OUTPUT c)                   -->
     (GENERIC-STREAM-CLEAR-OUTPUT c)                   -->
     (GENERIC-STREAM-READ-BYTE c)                      --> integer or NIL
     (GENERIC-STREAM-WRITE-BYTE c i)                   -->
     (GENERIC-STREAM-CLOSE c)                          -->

 (READ-CHAR s) == (GENERIC-STREAM-READ-CHAR c) */
local maygc object rd_ch_generic (const gcv_object_t* stream_) {
  pushSTACK(*stream_); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_rdch),1);
  return nullp(value1) ? eof_value : value1;
}

/* (PEEK-CHAR s) == (GENERIC-STREAM-PEEK-CHAR c) */
local maygc object pk_ch_generic (const gcv_object_t* stream_) {
  pushSTACK(*stream_); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_pkch),1);
  if (nullp(value1))
    value1 = eof_value;
  if ((mv_count >= 2) && !nullp(value2)) {
    /* READ-CHAR already executed -> must execute an implicit UNREAD-CHAR
     (i.e. save the result for the next READ-CHAR/PEEK-CHAR). */
    TheStream(*stream_)->strm_rd_ch_last = value1;
    if (!eq(value1,eof_value))
      TheStream(*stream_)->strmflags |= strmflags_unread_B;
  }
  return value1;
}

/* (LISTEN s) ==
 (IF (GENERIC-STREAM-READ-CHAR-WILL-HANG-P c)
   :WAIT
   (IF (GENERIC-STREAM-PEEK-CHAR c)
     :INPUT-AVAILABLE
     :EOF)) */
local maygc listen_t listen_char_generic (object stream) {
  pushSTACK(stream);
  pushSTACK(stream); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_read_char_will_hang_p),1);
  if (!nullp(value1)) {
    skipSTACK(1); return LISTEN_WAIT;
  }
  var object nextchar = pk_ch_generic(&STACK_0);
  skipSTACK(1);
  if (eq(nextchar,eof_value))
    return LISTEN_EOF;
  else
    return LISTEN_AVAIL;
}

/* (CLEAR-INPUT s) == (GENERIC-STREAM-CLEAR-INPUT c) */
local maygc bool clear_input_generic (object stream) {
  pushSTACK(stream); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_clear_input),1);
  return !nullp(value1);
}

/* (WRITE-CHAR ch s) == (GENERIC-STREAM-WRITE-CHAR c ch) */
local maygc void wr_ch_generic (const gcv_object_t* stream_, object ch) {
  /* ch is a character, need not save it */
  pushSTACK(*stream_); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); pushSTACK(ch); funcall(S(generic_stream_wrch),2);
}

/* (WRITE-CHAR-ARRAY s string start len) ==
 (GENERIC-STREAM-WRITE-STRING c string start len) */
local maygc void wr_ch_array_generic (const gcv_object_t* stream_,
                                      const gcv_object_t* chararray_,
                                      uintL start, uintL len) {
  pushSTACK(*stream_); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); pushSTACK(*chararray_);
  pushSTACK(UL_to_I(start)); pushSTACK(UL_to_I(len));
  funcall(S(generic_stream_wrss),4);
  var const chart* charptr;
  unpack_sstring_alloca(*chararray_,len,start, charptr=);
  wr_ss_lpos(*stream_,&charptr[len],len);
}

/* (FINISH-OUTPUT s) == (GENERIC-STREAM-FINISH-OUTPUT c) */
local maygc void finish_output_generic (object stream) {
  pushSTACK(stream); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_finish_output),1);
}

/* (FORCE-OUTPUT s) == (GENERIC-STREAM-FORCE-OUTPUT c) */
local maygc void force_output_generic (object stream) {
  pushSTACK(stream); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_force_output),1);
}

/* (CLEAR-OUTPUT s) == (GENERIC-STREAM-CLEAR-OUTPUT c) */
local maygc void clear_output_generic (object stream) {
  pushSTACK(stream); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_clear_output),1);
}

/* (READ-BYTE s) == (GENERIC-STREAM-READ-BYTE c) */
local maygc object rd_by_generic (object stream) {
  pushSTACK(stream); funcall(L(generic_stream_controller),1);
  pushSTACK(value1); funcall(S(generic_stream_rdby),1);
  return (nullp(value1) ? eof_value : value1);
}

/* (WRITE-BYTE s i) == (GENERIC-STREAM-WRITE-BYTE c i) */
local maygc void wr_by_generic (object stream, object obj) {
  pushSTACK(obj); /* save obj */
  pushSTACK(stream); funcall(L(generic_stream_controller),1);
  obj = STACK_0;
  STACK_0 = value1; pushSTACK(obj); funcall(S(generic_stream_wrby),2);
}

/* (CLOSE s) == (GENERIC-STREAM-CLOSE c) */
local maygc void close_generic (object stream, uintB abort) {
  MAYBE_IGNORE_ERRORS(abort, {
    pushSTACK(stream); funcall(L(generic_stream_controller),1);
    pushSTACK(value1); funcall(S(generic_stream_close),1);
  });
}

LISPFUNN(generic_stream_controller,1) {
  var object stream = popSTACK();
  CHECK_streamtype(stream,S(generic_stream),
                   (builtin_stream_p(stream)
                    && eq(TheStream(stream)->strm_rd_by,P(rd_by_generic))
                    && eq(TheStream(stream)->strm_wr_by,P(wr_by_generic))));
  VALUES1(TheStream(stream)->strm_controller_object);
}

LISPFUNN(make_generic_stream,1) {
  var object stream =
    allocate_stream(strmflags_rdwr_B,strmtype_generic,strm_len+1,0);
  TheStream(stream)->strm_rd_by = P(rd_by_generic);
  TheStream(stream)->strm_rd_by_array = P(rd_by_array_dummy);
  TheStream(stream)->strm_wr_by = P(wr_by_generic);
  TheStream(stream)->strm_wr_by_array = P(wr_by_array_dummy);
  TheStream(stream)->strm_rd_ch = P(rd_ch_generic);
  TheStream(stream)->strm_pk_ch = P(pk_ch_generic);
  TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_dummy);
  TheStream(stream)->strm_rd_ch_last = NIL;
  TheStream(stream)->strm_wr_ch =
    TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_generic);
  TheStream(stream)->strm_wr_ch_array =
    TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_generic);
  TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
  TheStream(stream)->strm_controller_object = popSTACK();
  VALUES1(stream); /* return stream */
}

LISPFUNN(generic_stream_p,1) {
  var object stream = check_stream(popSTACK());
  VALUES_IF(builtin_stream_p(stream)
            && eq(TheStream(stream)->strm_rd_by,P(rd_by_generic))
            && eq(TheStream(stream)->strm_wr_by,P(wr_by_generic)));
}

#endif


/* Streams communicating with the exterior world, based on bytes
   =============================================================

 They can be classified in three ways:
 According to strmtype:

                      file  ----  strmtype_file
                    /
             handle
           /        \           /  strmtype_pipe_in
   channel            pipe  -----  strmtype_pipe_out
            \
             socket  -----   strmtype_x11socket
                         \   strmtype_socket

 According to buffering:

             unbuffered
           /
   channel
            \
             buffered

 According to element type:

             CHARACTER or ([UN]SIGNED-BYTE n), n a multiple of 8 (setfable!)
           /
   channel
            \
             ([UN]SIGNED-BYTE n), n not a multiple of 8 (only if buffered)


 UP: Check a :BUFFERED argument.
 test_buffered_arg(arg)
 > object arg: argument
 < buffered_t: +1 for T, -1 for NIL, 0 for :DEFAULT */
typedef enum { BUFFERED_T, BUFFERED_NIL, BUFFERED_DEFAULT } buffered_t;
local buffered_t test_buffered_arg (object arg) {
  if (!boundp(arg) || eq(arg,S(Kdefault)))
    return BUFFERED_DEFAULT;
  if (nullp(arg))
    return BUFFERED_NIL;
  if (eq(arg,T))
    return BUFFERED_T;
  error_illegal_arg(arg,O(type_buffered_arg),S(Kbuffered));
}

/* Classification of possible :ELEMENT-TYPEs. */
typedef enum {
  eltype_ch,    /* CHARACTER */
  eltype_iu,    /* (UNSIGNED-BYTE n) */
  eltype_is     /* (SIGNED-BYTE n) */
} eltype_kind;

/* An analyzed :ELEMENT-TYPE argument. */
typedef struct {
  eltype_kind kind;
  uintL       size; /* the n in ([UN]SIGNED-BYTE n), */
                    /* >0, <intDsize*uintWC_max,
                     but 0 for eltype_ch */
} decoded_el_t;

/* UP: Check a :ELEMENT-TYPE argument.
 test_eltype_arg(&eltype,&decoded);
 > object eltype: argument (in the STACK)
 < decoded: decoded eltype
 can trigger GC */
local maygc void test_eltype_arg (gcv_object_t* eltype_, decoded_el_t* decoded)
{
  var object arg = *eltype_;
  if (!boundp(arg) || eq(arg,S(character)) || eq(arg,S(string_char))
      || eq(arg,S(Kdefault))) { /* CHARACTER, STRING-CHAR, :DEFAULT */
    decoded->kind = eltype_ch; decoded->size = 0; return;
  }
  if (eq(arg,S(bit))) { /* BIT */
    decoded->kind = eltype_iu; decoded->size = 1; return;
  }
  if (eq(arg,S(unsigned_byte))) { /* UNSIGNED-BYTE */
    decoded->kind = eltype_iu; decoded->size = 8; return;
  }
  if (eq(arg,S(signed_byte))) { /* SIGNED-BYTE */
    decoded->kind = eltype_is; decoded->size = 8; return;
  }
  var object eltype_size;
  if (consp(arg) && mconsp(Cdr(arg)) && nullp(Cdr(Cdr(arg)))) { /* two-element List */
    var object h = Car(arg);
    if (eq(h,S(mod))) { /* (MOD n) */
      decoded->kind = eltype_iu;
      h = Car(Cdr(arg)); /* n */
      /* must be an Integer >0 : */
      if (!(integerp(h) && positivep(h) && !eq(h,Fixnum_0)))
        goto bad_eltype;
      /* build eltype_size := (integer-length (1- n)) : */
      pushSTACK(h); funcall(L(minus_one),1); /* (1- n) */
      pushSTACK(value1); funcall(L(integer_length),1); /* (integer-length (1- n)) */
      eltype_size = value1;
      goto eltype_integer;
    }
    if (eq(h,S(unsigned_byte))) { /* (UNSIGNED-BYTE n) */
      decoded->kind = eltype_iu;
      eltype_size = Car(Cdr(arg));
      goto eltype_integer;
    }
    if (eq(h,S(signed_byte))) { /* (SIGNED-BYTE n) */
      decoded->kind = eltype_is;
      eltype_size = Car(Cdr(arg));
      goto eltype_integer;
    }
  }
  { /* First of all canonicalize a little bit (therewith the different
       SUBTYPEP will not have to do the same three times): */
    pushSTACK(arg); funcall(S(canonicalize_type),1); /* (SYS::CANONICALIZE-TYPE arg) */
    pushSTACK(value1); /* save canon-arg */
    pushSTACK(STACK_0); pushSTACK(S(character)); funcall(S(subtypep),2); /* (SUBTYPEP canon-arg 'CHARACTER) */
    if (!nullp(value1)) {
      skipSTACK(1);
      decoded->kind = eltype_ch; decoded->size = 0;
      return;
    }
    funcall(S(subtype_integer),1); /* (SYS::SUBTYPE-INTEGER canon-arg) */
  }
  if (!((mv_count>1) && integerp(value1) && integerp(value2)))
    goto bad_eltype;
  {
    /* arg is a subtype of `(INTEGER ,low ,high) and
     value1 = low, value2 = high. */
    var uintL l;
    if (positivep(value1)) {
      l = I_integer_length(value2); /* (INTEGER-LENGTH high) */
      decoded->kind = eltype_iu;
    } else {
      var uintL l1 = I_integer_length(value1); /* (INTEGER-LENGTH low) */
      var uintL l2 = I_integer_length(value2); /* (INTEGER-LENGTH high) */
      l = (l1>l2 ? l1 : l2) + 1;
      decoded->kind = eltype_is;
    }
    eltype_size = fixnum(l);
  }
 eltype_integer:
  /* check eltype_size: */
  if (!(posfixnump(eltype_size) && !eq(eltype_size,Fixnum_0)
        && ((oint_data_len < log2_intDsize+intWCsize)
           /* [when oint_data_len <= log2(intDsize)+intWCsize-1 always
             eltype_size < 2^oint_data_len < intDsize*(2^intWCsize-1) ] */
            || (as_oint(eltype_size) <
                as_oint(fixnum(intDsize*(uintV)(vbitm(intWCsize)-1)))))))
    goto bad_eltype;
  decoded->size = posfixnum_to_V(eltype_size);
  return;
 bad_eltype:
  error_illegal_arg(*eltype_,nullobj,S(Kelement_type));
}

/* evaluate the appropriate forms */
#define ELTYPE_DISPATCH(decoded,ch,iu,is)                       \
  switch (decoded->kind) {                                      \
    case eltype_ch: /*CHARACTER*/               ch; break;      \
    case eltype_iu: /*(UNSIGNED-BYTE bitsize)*/ iu; break;      \
    case eltype_is: /*(SIGNED-BYTE bitsize)*/   is; break;      \
    default: NOTREACHED;                                        \
  }

/* UP: Returns a canonical representation for a :ELEMENT-TYPE.
 canon_eltype(&decoded)
 > decoded: decoded eltype
 < result: either CHARACTER or ([UN]SIGNED-BYTE n)
 can trigger GC */
local maygc object canon_eltype (const decoded_el_t* decoded) {
  ELTYPE_DISPATCH(decoded,{
    return S(character);
  },{
    pushSTACK(S(unsigned_byte));
    pushSTACK(fixnum(decoded->size));
    return listof(2);
  },{
    pushSTACK(S(signed_byte));
    pushSTACK(fixnum(decoded->size));
    return listof(2);
  });
}

/* UP: Check an :EXTERNAL-FORMAT argument.
 test_external_format_arg(arg)
 > arg: argument
 < result: an encoding
 can trigger GC */
#define test_external_format_arg(arg)                   \
  check_encoding(arg,&O(default_file_encoding),true)

/* Tells whether this process is running in Microsoft WSL
   (Windows Subsystem for Linux). */
#if defined(UNIX_LINUX) && defined(AMD64)
  local bool is_wsl;
#else
  #define is_wsl false
#endif

/* UP: Initializes the OS dependencies for streams.
 init_stream_osdeps(); */
global void init_stream_osdeps (void) {
 #if defined(UNIX_LINUX) && defined(AMD64)
  struct utsname buf;
  is_wsl = (uname(&buf) >= 0
            && (strstr(buf.release,"Microsoft") != NULL
                || strstr(buf.version, "Microsoft") != NULL));
 #endif
}

#ifdef UNIX

/* UP: Deletes already entered interactive Input from a Handle. */
local void clear_tty_input (Handle handle) {
  /* Method: tcflush TCIFLUSH, see TERMIOS(3V) */
  begin_system_call();
 #ifdef UNIX_TERM_TERMIOS
  /* On AIX, when a clisp process is run through 'nohup ... &' and the user
     logs out, the tty device /dev/pts/N is deallocated, that is, becomes owned
     by root, with permissions rw-rw-rw- (as opposed to rw--w--w- when it is
     allocated). The tcflush TCIFLUSH call can then trigger a SIGHUP signal,
     which would make the process terminate. Avoid this. */
  #ifdef UNIX_AIX
  var signal_handler_t prev_handler = install_signal_handler(SIGHUP,SIG_IGN);
  #endif
  var int ret = TCFLUSH(handle,TCIFLUSH);
  #ifdef UNIX_AIX
  var int saved_errno = errno;
  install_signal_handler(SIGHUP,prev_handler);
  errno = saved_errno;
  #endif
  if (!(ret==0)) {
    if (!((errno==ENOTTY)||(errno==EINVAL))) { /* no TTY: OK */
      local bool flag = false;
      /* report other Error, but only once */
      if (!flag) { flag = true; OS_error(); }
    }
  }
 #endif
  end_system_call();
}

#if defined(UNIX_LINUX)
  #define IS_EINVAL_EXTRA  (is_wsl&&(errno==EIO))
#elif defined(UNIX_CYGWIN) /* for Windows95 and xterm/rxvt, and WindowsXP /dev/null */
  #define IS_EINVAL_EXTRA  ((errno==EBADF)||(errno==EACCES)||(errno==EBADRQC))
#elif defined(UNIX_MACOSX) || defined(UNIX_FREEBSD) || defined(UNIX_NETBSD) || defined(UNIX_OPENBSD)
  #if !defined(ENOTSUP)         /* OpenBSD */
    #define ENOTSUP EOPNOTSUPP
  #endif
  #define IS_EINVAL_EXTRA  ((errno==EOPNOTSUPP)||(errno==ENOTSUP)||(errno==ENODEV))
#elif defined(UNIX_SUNOS5)
  #define IS_EINVAL_EXTRA  ((errno==ENXIO))
#elif defined(UNIX_AIX)
  /* ioctl() on /dev/null produces ENODEV. */
  #define IS_EINVAL_EXTRA  ((errno==ENODEV))
#elif defined(UNIX_IRIX)
  /* ioctl() on stdout, when it is a pipe, produces ENOSYS. */
  #define IS_EINVAL_EXTRA  ((errno==ENOSYS))
#elif defined(UNIX_HAIKU)
  /* ioctl() on /dev/null produces EPERM. */
  #define IS_EINVAL_EXTRA  ((errno==EPERM))
#else
  #define IS_EINVAL_EXTRA  0
#endif
#define IS_EINVAL ((errno==EINVAL)||IS_EINVAL_EXTRA)

/* UP: Move the pending Output of a Handle to the destination. */
local void finish_tty_output (Handle handle) {
  /* Method 1: fsync, see fsync(2)
     Method 2: tcdrain, see termios(3V)
     poss. Method 3: ioctl TCGETS/TCSETSW, see termio(4) or tty_ioctl(4)
     or (almost equivalent) ioctl TIOCGETP/TIOCSETP, see TTCOMPAT(4) */
  begin_system_call();
 #if !(defined(UNIX) && !defined(HAVE_FSYNC))
  if (!( fsync(handle) ==0)) {
  #ifndef UNIX_BEOS /* BeOS 5 apparently does not set errno */
    if (!IS_EINVAL)
      { OS_error(); }
  #endif
  } else goto ok;
 #endif
 #ifdef UNIX_TERM_TERMIOS
  if (!( TCDRAIN(handle) ==0)) {
    if (!((errno==ENOTTY)||IS_EINVAL))
      { OS_error(); } /* no TTY: OK, report other Error */
  } else goto ok;
 #endif
 #if defined(UNIX_TERM_TERMIOS) && defined(TCGETS) && defined(TCSETSW)
  {
    var struct termios term_parameters;
    if (!(   ( ioctl(handle,TCGETS,&term_parameters) ==0)
          && ( ioctl(handle,TCSETSW,&term_parameters) ==0))) {
      if (!((errno==ENOTTY)||IS_EINVAL))
        { OS_error(); } /* no TTY: OK, report other Error */
    } else goto ok;
  }
 #endif
 #if 0 /* Caution: This should cause FINISH-OUTPUT and CLEAR-INPUT! */
  {
    var struct sgttyb tty_parameters;
    if (!(   ( ioctl(handle,TIOCGETP,&tty_parameters) ==0)
          && ( ioctl(handle,TIOCSETP,&tty_parameters) ==0))) {
      if (!(errno==ENOTTY)) { OS_error(); }
    } else goto ok;
  }
 #endif
 ok:
  end_system_call();
}

/* UP: Move the pending Output of a Handle to the destination. */
local void force_tty_output (Handle handle);
#if !(defined(UNIX) && !defined(HAVE_FSYNC))
local void force_tty_output (Handle handle) {
  /* Method: fsync, see FSYNC(2) */
  begin_system_call();
  if (!( fsync(handle) ==0)) {
   #ifndef UNIX_BEOS /* BeOS 5 apparently does not set errno */
    if (!IS_EINVAL)
      OS_error();
   #endif
  }
  end_system_call();
}
#else
  #define force_tty_output(handle)
#endif

/* UP: Deletes the pending Output of a Handle. */
local void clear_tty_output (Handle handle) {
  /* Method: tcflush TCOFLUSH, see TERMIOS(3V) */
  begin_system_call();
 #ifdef UNIX_TERM_TERMIOS
  if (!( TCFLUSH(handle,TCOFLUSH) ==0)) {
    if (!((errno==ENOTTY)||IS_EINVAL))
      { OS_error(); } /* no TTY: OK, report other Error */
  }
 #endif
  end_system_call();
}

#endif /* UNIX */

#if defined(WIN32_NATIVE)

/* signal OS_error unless the error is cause by invalid arguments */
local void error_unless_invalid (void) {
  switch (GetLastError()) {
    case ERROR_INVALID_HANDLE: case ERROR_INVALID_PARAMETER:
    case ERROR_INVALID_FUNCTION: break;
    default: OS_error();
  }
}

/* UP: Deletes already entered interactive Input from a Handle. */
local void clear_tty_input (Handle handle) {
  begin_system_call();
  /* Maybe it's a serial communication. */
  if (!PurgeComm(handle,PURGE_RXABORT|PURGE_RXCLEAR))
    error_unless_invalid();
  /* Maybe it's a console. */
  if (!FlushConsoleInputBuffer(handle))
    error_unless_invalid();
  end_system_call();
}

/* UP: Move the pending Output of a Handle to the destination. */
  local void finish_tty_output (Handle handle);
  /* Maybe call WaitCommEvent with argument EV_TXEMPTY ? */
  #define finish_tty_output(handle)

/* UP: Move the pending Output of a Handle to the destination. */
  local void force_tty_output (Handle handle);
  #define force_tty_output(handle)  finish_tty_output(handle)

/* UP: Deletes the pending Output of a Handle. */
local void clear_tty_output (Handle handle) {
  begin_system_call();
  /* Maybe it's a serial communication. */
  if (!PurgeComm(handle,PURGE_TXABORT|PURGE_TXCLEAR))
    error_unless_invalid();
  end_system_call();
}


#endif

/* UP: Return platform-specific file type
 handle_type(handle)
 > handle: open handle (file or pipe)
 < result: an integer, identifying the type */
#if defined(UNIX)
#define handle_type_t mode_t
local handle_type_t handle_type (Handle handle) {
  var struct stat statbuf;
  begin_system_call();
  if (!( fstat(handle,&statbuf) ==0)) {
    #if defined(UNIX_MACOSX)
    /* This happens with stdin_handle of a process launched through nohup,
        on Mac OS X 10.5. */
    if (errno == EBADF) { end_system_call(); return 0; }
    #endif
    OS_error();
  }
  end_system_call();
  return statbuf.st_mode;
}
#elif defined(WIN32_NATIVE)
#define handle_type_t DWORD
local handle_type_t handle_type (Handle handle) {
  var DWORD filetype;
  begin_system_call();
  filetype = GetFileType(handle);
  end_system_call();
  return filetype;
}
#else
#error handle_type() and handle_type_t are not defined
#endif

/* UP: Determines, if a Handle refers to a (static) File.
 regular_handle_p(handle)
 > handle: Handle of the opened File
 < result: true if it is a (static) File */
local inline bool regular_handle_type_p (handle_type_t mode) {
 #if defined(UNIX)
  return S_ISREG(mode) || S_ISBLK(mode);
 #elif defined(WIN32_NATIVE)
  return mode == FILE_TYPE_DISK;
 #endif
}
#define regular_handle_p(h)  regular_handle_type_p(handle_type(h))

/* UP: Determines, if a Handle refers to a pipe or a socket
 pipe_handle_p(handle)
 > handle: Handle of the opened File
 < result: true if it is a socket or a pipe */
local inline bool pipe_handle_type_p (handle_type_t mode) {
 #if defined(UNIX)
  return S_ISFIFO(mode)
   #if defined(S_ISSOCK)
    || S_ISSOCK(mode)
   #endif
    ;
 #elif defined(WIN32_NATIVE)
  return mode == FILE_TYPE_PIPE;
 #endif
}
#define pipe_handle_p(h)  pipe_handle_type_p(handle_type(h))

/* UP: Determines, if a Handle refers to a pipe, socket, file
 regular_or_pipe_handle_p(handle)
 > handle: Handle of the opened File
 < result: true if it is a socket/pipe/file */
local inline bool regular_or_pipe_handle_p (Handle handle) {
  var handle_type_t mode = handle_type(handle);
  DEBUG_OUT(("\nregular_or_pipe_handle_p(%d): 0x%x\n",handle,mode));
  return regular_handle_type_p(mode) || pipe_handle_type_p(mode);
}

/* UP: Determines if two Handle refer to the same file or device.
 same_handle_p(handle1,handle2)
 > handle1: Handle of the first open device
 > handle2: Handle of the second open device
 < result: true if handle1 and handle2 are exchangeable */
local bool same_handle_p (Handle handle1, Handle handle2) {
 #if defined(UNIX)
  var struct stat statbuf1;
  var struct stat statbuf2;
  begin_system_call();
  DEBUG_OUT(("\nsame_handle_p(%d,%d)\n",handle1,handle2));
  if (!( fstat(handle1,&statbuf1) ==0)) { OS_error(); }
  if (!( fstat(handle2,&statbuf2) ==0)) { OS_error(); }
  DEBUG_OUT(("dev: 0x%lx 0x%lx  ino: 0x%lx 0x%lx  mode: 0x%x 0x%x\n",
             statbuf1.st_dev,statbuf2.st_dev,statbuf1.st_ino,statbuf2.st_ino,
             statbuf1.st_mode,statbuf2.st_mode));
  if (statbuf1.st_dev == statbuf2.st_dev
      && statbuf1.st_ino == statbuf2.st_ino) {
    /* handle1 and handle2 point to the same inode. */
    if ((S_ISREG(statbuf1.st_mode) || S_ISBLK(statbuf1.st_mode))
        && (S_ISREG(statbuf2.st_mode) || S_ISBLK(statbuf2.st_mode))) {
      /* handle1 and handle2 are exchangeable only if they are positioned
         at the same file position. */
      var off_t pos1 = lseek(handle1,0,SEEK_CUR);
      DEBUG_OUT(("pos1: %ld\n",pos1));
      if (pos1 >= 0) {
        var off_t pos2 = lseek(handle2,0,SEEK_CUR);
        DEBUG_OUT(("pos2: %ld\n",pos2));
        if (pos2 >= 0) {
          end_system_call();
          return (pos1 == pos2);
        }
      }
    }
    end_system_call();
    return true;
  } else {
    end_system_call();
    return false;
  }
 #endif
 #if defined(WIN32_NATIVE)
  /* Same handle? */
  DEBUG_OUT(("\nsame_handle_p(0x%lx,0x%lx)\n",handle1,handle2));
  if (handle1 == handle2)
    return true;
  /* Same handle type? */
  begin_system_call();
  var DWORD filetype1;
  var DWORD filetype2;
  filetype1 = GetFileType(handle1);
  filetype2 = GetFileType(handle2);
  DEBUG_OUT(("GetFileType: 0x%lx  0x%lx\n",filetype1,filetype2));
  if (filetype1 == filetype2) {
    if (filetype1 == FILE_TYPE_DISK) {
      /* handle1 and handle2 are both files. */
      var BY_HANDLE_FILE_INFORMATION fileinfo1;
      var BY_HANDLE_FILE_INFORMATION fileinfo2;
      if (!GetFileInformationByHandle(handle1,&fileinfo1)) { OS_error(); }
      if (!GetFileInformationByHandle(handle2,&fileinfo2)) { OS_error(); }
      DEBUG_OUT(("GetFileInformationByHandle:\n vol: 0x%lx  0x%lx\n"
                 " index: 0x%x,0x%x  0x%x,0x%x\n attr: 0x%lx  0x%lx\n"
                 " size: 0x%x,0x%x  0x%x,0x%x\n",
                 fileinfo1.dwVolumeSerialNumber,
                 fileinfo2.dwVolumeSerialNumber,
                 fileinfo1.nFileIndexHigh,fileinfo1.nFileIndexLow,
                 fileinfo2.nFileIndexHigh,fileinfo2.nFileIndexLow,
                 fileinfo1.dwFileAttributes,fileinfo2.dwFileAttributes,
                 fileinfo1.nFileSizeHigh,fileinfo1.nFileSizeLow,
                 fileinfo2.nFileSizeHigh,fileinfo2.nFileSizeLow));
      end_system_call();
      #define TIME_EQ(ft1,ft2)  \
        ((ft1).dwLowDateTime == (ft2).dwLowDateTime \
         && (ft1).dwHighDateTime == (ft2).dwHighDateTime)
      return (fileinfo1.dwVolumeSerialNumber == fileinfo2.dwVolumeSerialNumber
              && fileinfo1.nFileIndexLow == fileinfo2.nFileIndexLow
              && fileinfo1.nFileIndexHigh == fileinfo2.nFileIndexHigh
              /* Comparing the other members of the BY_HANDLE_FILE_INFORMATION
                 structure shouldn't be necessary, but doesn't hurt either. */
              && fileinfo1.dwFileAttributes == fileinfo2.dwFileAttributes
              && TIME_EQ(fileinfo1.ftCreationTime,fileinfo2.ftCreationTime)
              && TIME_EQ(fileinfo1.ftLastAccessTime,fileinfo2.ftLastAccessTime)
              && TIME_EQ(fileinfo1.ftLastWriteTime,fileinfo2.ftLastWriteTime)
              && fileinfo1.nFileSizeLow == fileinfo2.nFileSizeLow
              && fileinfo1.nFileSizeHigh == fileinfo2.nFileSizeHigh
              && fileinfo1.nNumberOfLinks == fileinfo2.nNumberOfLinks);
      #undef TIME_EQ
    } else if (filetype1 == FILE_TYPE_CHAR) {
      /* Same console? */
      var DWORD console_mode;
      DEBUG_OUT(("FILE_TYPE_CHAR\n"));
      if (GetConsoleMode(handle1,&console_mode)) {
        DEBUG_OUT(("console_mode1: 0x%lx\n",console_mode));
        if (GetConsoleMode(handle2,&console_mode)) {
          DEBUG_OUT(("console_mode2: 0x%lx\n",console_mode));
          end_system_call();
          return true;
        }
      }
    } else { DEBUG_OUT(("neither FILE_TYPE_CHAR nor FILE_TYPE_DISK\n")); }
    /* Cannot determine equality. Assume they are different. */
  }
  end_system_call();
  return false;
 #endif
}


/* Channel-Streams
   ===============

 Channel streams are a common framework which perform their input/output
 via a channel from the operating system. Encompasses: terminal stream,
 file stream, pipe stream, socket stream.

 Because the input side has some non-GCed fields, all channel streams must
 have the same number of GCed fields.

 Fields used for both the input side and the output side:

 define strm_eltype   strm_other[0] - CHARACTER or ([UN]SIGNED-BYTE n)
 define strm_encoding strm_other[1] - Encoding (used iff eltype = CHARACTER) */

#define strm_bitbuffer strm_other[2] /* (used if eltype /= CHARACTER only) */
#define strm_buffer    strm_other[3] /* (used by buffered streams only) */

/* Fields used for the input side only: */

/* /=NIL or NIL, depending on whether the input channel is a tty
 handle and therefore needs special treatment in the
 low_listen function on some OSes (used by unbuffered streams only) */
#define strm_isatty    strm_other[3]
#define strm_ichannel_position 4     /* ichannel index */

/* the input channel, an encapsulated handle, or, on WIN32_NATIVE,
   an encapsulated SOCKET */
#define strm_ichannel  strm_other[strm_ichannel_position]

/* Fields used for the output side only: */
#define strm_ochannel_position 5    /* ochannel index */
#define strm_ochannel strm_other[strm_ochannel_position] /* the output channel */
/* an encapsulated handle, or, on WIN32_NATIVE, an encapsulated SOCKET */

/* Fields reserved for the specialized stream: */
#define strm_field1    strm_other[6]
#define strm_field2    strm_other[7]

/* Binary fields start here. */
#define strm_channel_extrafields  strm_other[8]
#define strm_channel_len  (strm_len+8)

/* Additional binary (not GCed) fields: */
typedef struct strm_channel_extrafields_t {
  /*bool*/int buffered : 8; /* false for unbuffered streams,
                                  true for buffered streams */
  /*bool*/int regular : 8;  /* whether the handle refers to a regular file */
  uintL bitsize;            /* If the element-type is ([UN]SIGNED-BYTE n):
                               n = number of bits per unit,
                               >0, <intDsize*uintWC_max.
                               If the element-type is CHARACTER: 0. */
  void (* low_close) (object stream, object handle, uintB abort);
  /* Fields used if the element-type is CHARACTER: */
  uintL lineno;                        /* line number during read, >0 */
   /* For general interoperability with Win32 systems, we recognize all possible
    line-terminators: LF, CR/LF and CR, independently of strm_encoding.
    This is because, when confronted with Unix-style text files (eol = LF),
    some Microsoft editors insert new lines with eol = CR/LF,
    while other Microsoft editors insert new lines with eol = CR.
    Java learned the lesson and understands all three line-terminators.
    So do we, see http://clisp.org/impnotes/clhs-newline.html
    See also http://www.unicode.org/reports/tr13/tr13-9.html */
  /*bool*/int  ignore_next_LF : 8;     /* true after reading a CR */
  struct file_id fid;                  /* unique file ID */
  #if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
  iconv_t iconvdesc;        /* input conversion descriptor and state */
  iconv_t oconvdesc;        /* output conversion descriptor and state */
  #endif
} strm_channel_extrafields_t;

/* Accessors. */
#define ChannelStream_eltype(stream)  TheStream(stream)->strm_eltype
#define ChannelStream_isatty(stream)  TheStream(stream)->strm_isatty
#define ChannelStream_ichannel(stream)  TheStream(stream)->strm_ichannel
#define ChannelStream_ochannel(stream)  TheStream(stream)->strm_ochannel
#define ChannelStream_buffered(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->buffered
#define ChannelStream_regular(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->regular
#define ChannelStream_bitsize(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->bitsize
#define ChannelStreamLow_close(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_close
#define ChannelStream_lineno(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->lineno
#define ChannelStream_ignore_next_LF(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->ignore_next_LF
#define ChannelStream_file_id(stream)  ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->fid
#if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
#define ChannelStream_iconvdesc(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->iconvdesc
#define ChannelStream_oconvdesc(stream)   ((strm_channel_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->oconvdesc
#endif

/* Additional binary (not GCed) fields, used by unbuffered streams only: */
typedef struct strm_unbuffered_extrafields_t {
  strm_channel_extrafields_t _parent;
  /* The low_... operations operate on bytes only, and independently of the
   stream's element type. They cannot cause GC.
   Fields used for the input side only: */
  sintL        (* low_read)        (object stream);
  listen_t     (* low_listen)      (object stream);
  bool         (* low_clear_input) (object stream);
  uintB*       (* low_read_array)  (object stream, uintB* byteptr,
                                    uintL len, perseverance_t persev);
  sintL status;                 /* -1 means EOF reached
                                   0  means unknown, bytebuf invalid
                                   >0 means the number of valid bytes in
                                      bytebuf, to be consumed */
  uintB bytebuf[max_bytes_per_chart]; /* the last bytes read but not yet consumed */
  /* Fields used for the output side only: */
  void         (* low_write)         (object stream, uintB b);
  const uintB* (* low_write_array)   (object stream, const uintB* byteptr,
                                      uintL len, perseverance_t persev);
  void         (* low_finish_output) (object stream);
  void         (* low_force_output)  (object stream);
  void         (* low_clear_output)  (object stream);
} strm_unbuffered_extrafields_t;

/* Accessors. */
#define UnbufferedStreamLow_read(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_read
#define UnbufferedStreamLow_listen(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_listen
#define UnbufferedStreamLow_clear_input(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_clear_input
#define UnbufferedStreamLow_read_array(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_read_array
#define UnbufferedStream_status(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->status
#define UnbufferedStream_bytebuf(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->bytebuf
#define UnbufferedStreamLow_write(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_write
#define UnbufferedStreamLow_write_array(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_write_array
#define UnbufferedStreamLow_finish_output(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_finish_output
#define UnbufferedStreamLow_force_output(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_force_output
#define UnbufferedStreamLow_clear_output(stream)  ((strm_unbuffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_clear_output

/* Error message after user interrupt.
 error_interrupt(); */
local _Noreturn void error_interrupt (void) {
  pushSTACK(TheSubr(subr_self)->name);
  error(interrupt_condition,GETTEXT("~S: Ctrl-C: User break"));
}

/* General Subroutines
   ===================

 saving_errno(statement) -- execute a statement, but save the errno during it
 OS_error_saving_errno(statement) -- ... then signal the error */
#ifdef WIN32
  #define saving_errno(statement)  \
    do { var int _olderrno = GetLastError(); statement; SetLastError(_olderrno); } while(0)
  #define OS_error_saving_errno(statement)  \
    do { var int _olderrno = GetLastError(); statement; SetLastError(_olderrno); OS_error(); } while(0)
#else
  #define saving_errno(statement)  \
    do { var int _olderrno = errno; statement; errno = _olderrno; } while(0)
  #define OS_error_saving_errno(statement)  \
    do { var int _olderrno = errno; statement; errno = _olderrno; OS_error(); } while(0)
#endif

/* iconv-based encodings
   ---------------------

 Here enc_charset is a simple-string, not a symbol. The system decides
 which encodings are available, and there is no API for getting them all. */

#if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)

/* Our internal encoding is UCS-4 with platform dependent endianness. */
#ifdef GNU_LIBICONV
  #define CLISP_INTERNAL_CHARSET  "UCS-4-INTERNAL"
#else
  #if (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 2))
    /* glibc >= 2.2 also has UCS-4BE, UCS-4LE but WCHAR_T is more efficient. */
    #define CLISP_INTERNAL_CHARSET  "WCHAR_T"
  #elif defined(UNIX_HPUX) && BIG_ENDIAN_P
    #define CLISP_INTERNAL_CHARSET  "ucs4"
  #else
    #if BIG_ENDIAN_P
      #define CLISP_INTERNAL_CHARSET  "UCS-4"
    #else
      #define CLISP_INTERNAL_CHARSET  "UCS-4"  /* FIXME: This is probably wrong */
    #endif
  #endif
#endif

/* min. bytes per character = 1
 max. bytes per character unknown, assume it's <= max_bytes_per_chart */

global uintL iconv_mblen (object encoding, const uintB* src, const uintB* srcend);
global void iconv_mbstowcs (object encoding, object stream, const uintB* *srcp, const uintB* srcend, chart* *destp, chart* destend);
global uintL iconv_wcslen (object encoding, const chart* src, const chart* srcend);
global void iconv_wcstombs (object encoding, object stream, const chart* *srcp, const chart* srcend, uintB* *destp, uintB* destend);
global object iconv_range (object encoding, uintL start, uintL end, uintL maxintervals);

/* Error, when a character cannot be converted to an encoding.
 error_unencodable(encoding); */
extern _Noreturn void error_unencodable (object encoding, chart ch);

/* Avoid annoying warning caused by a wrongly standardized iconv() prototype. */
#if defined(GNU_LIBICONV) && defined(iconv)
  #undef iconv
  #define iconv(cd,inbuf,inbytesleft,outbuf,outbytesleft) \
    libiconv(cd,(ICONV_CONST char **)(inbuf),inbytesleft,outbuf,outbytesleft)
#else
  #define iconv(cd,inbuf,inbytesleft,outbuf,outbytesleft) \
    (iconv)(cd,(ICONV_CONST char **)(inbuf),inbytesleft,outbuf,outbytesleft)
#endif

/* open the iconv conversion and signal errors when necessary
 skip error when CHARSET is NULLOBJ
 begin_system_call() must be called before this!!!
 end_system_call() must be called after this!!! */
local iconv_t open_iconv (const char * to_code, const char * from_code,
                          object charset) {
  var iconv_t cd = iconv_open(to_code,from_code);
  if ((cd == (iconv_t)(-1)) && (!eq(nullobj,charset))) {
    if (errno == EINVAL) {
      end_system_call();
      pushSTACK(charset);
      error(error_condition,GETTEXT("unknown character set ~S"));
    }
    ANSIC_error();
  }
  return cd;
}

/* check whether the charset is valid
 when CHARSET is NULLOBJ, return false instead of signalling an error */
global bool check_charset (const char * code, object charset) {
  begin_system_call();
  var iconv_t cd = open_iconv(CLISP_INTERNAL_CHARSET,code,charset);
  if (cd == (iconv_t)(-1)) return false;
  if (iconv_close(cd) < 0) {
    if (eq(nullobj,charset)) return false;
    ANSIC_error();
  }
  cd = open_iconv(code,CLISP_INTERNAL_CHARSET,charset);
  if (cd == (iconv_t)(-1)) return false;
  if (iconv_close(cd) < 0) {
    if (eq(nullobj,charset)) return false;
    ANSIC_error();
  }
  end_system_call();
  return true;
}

/* Bytes to characters. */

global uintL iconv_mblen (object encoding, const uintB* src,
                          const uintB* srcend) {
  var uintL count = 0;
  #define tmpbufsize 4096
  var chart tmpbuf[tmpbufsize];
  with_sstring_0(TheEncoding(encoding)->enc_charset,Symbol_value(S(ascii)),
                 charset_asciz, {
    begin_system_call();
    var iconv_t cd = open_iconv(CLISP_INTERNAL_CHARSET,charset_asciz,
                                TheEncoding(encoding)->enc_charset);
    {
      var const char* inptr = (const char*)src;
      var size_t insize = srcend-src;
      while (insize > 0) {
        var char* outptr = (char*)tmpbuf;
        var size_t outsize = tmpbufsize*sizeof(chart);
        var size_t res = iconv(cd,&inptr,&insize,&outptr,&outsize);
        if (res == (size_t)(-1) && errno != E2BIG) {
          /* At the end of a delimited string, we treat
           EINVAL (incomplete input) like EILSEQ (conversion error) */
          if (errno == EILSEQ || errno == EINVAL) {
            ASSERT(insize > 0);
            var object action = TheEncoding(encoding)->enc_towcs_error;
            if (eq(action,S(Kignore))) {
              inptr++; insize--;
            } else if (eq(action,S(Kerror))) {
              iconv_close(cd); errno = EILSEQ; ANSIC_error();
            } else {
              outptr += sizeof(chart);
              inptr++; insize--;
            }
          } else {
            var int saved_errno = errno;
            iconv_close(cd);
            errno = saved_errno;
            ANSIC_error();
          }
        }
        count += (outptr-(char*)tmpbuf);
      }
    }
    if (iconv_close(cd) < 0) { ANSIC_error(); }
    end_system_call();
  });
  #undef tmpbufsize
  return count/sizeof(chart);
}

global void iconv_mbstowcs (object encoding, object stream,
                            const uintB* *srcp, const uintB* srcend,
                            chart* *destp, chart* destend) {
  var const char* inptr = (const char*)*srcp;
  var size_t insize = srcend-*srcp;
  var char* outptr = (char*)*destp;
  var size_t outsize = (char*)destend-(char*)*destp;
  if (eq(stream,nullobj)) {
    /* Standalone call, must be consistent with iconv_mblen: */
    with_sstring_0(TheEncoding(encoding)->enc_charset,Symbol_value(S(ascii)),
                   charset_asciz, {
      begin_system_call();
      var iconv_t cd = open_iconv(CLISP_INTERNAL_CHARSET,charset_asciz,
                                  TheEncoding(encoding)->enc_charset);
      while (insize > 0 && outsize > 0) {
        var size_t res = iconv(cd,&inptr,&insize,&outptr,&outsize);
        if (res == (size_t)(-1)) {
          /* At the end of a delimited string, we treat
           EINVAL (incomplete input) like EILSEQ (conversion error) */
          if (errno == EILSEQ || errno == EINVAL) {
            ASSERT(insize > 0);
            var object action = TheEncoding(encoding)->enc_towcs_error;
            if (eq(action,S(Kignore))) {
              inptr++; insize--;
            } else if (eq(action,S(Kerror))) {
              iconv_close(cd); errno = EILSEQ; ANSIC_error();
            } else {
              if (outsize < sizeof(chart))
                break;
              *(chart*)outptr = char_code(action);
              outptr += sizeof(chart); outsize -= sizeof(chart);
              inptr++; insize--;
            }
          } else {
            var int saved_errno = errno;
            iconv_close(cd);
            errno = saved_errno;
            ANSIC_error();
          }
        }
      }
      if (iconv_close(cd) < 0) { ANSIC_error(); }
      end_system_call();
      ASSERT(insize == 0 && outsize == 0);
    });
  } else {
    /* Called from a channel-stream. */
    var iconv_t cd = ChannelStream_iconvdesc(stream);
    begin_system_call();
    while (insize > 0) {
      var size_t res = iconv(cd,&inptr,&insize,&outptr,&outsize);
      if (res == (size_t)(-1)) {
        if (errno == EINVAL) /* incomplete input? */
          break;
        else if (errno == E2BIG) /* output buffer full? */
          break;
        else if (errno == EILSEQ) {
          ASSERT(insize > 0);
          var object action = TheEncoding(encoding)->enc_towcs_error;
          if (eq(action,S(Kignore))) {
            inptr++; insize--;
          } else if (eq(action,S(Kerror))) {
            if (inptr > (const char*)*srcp)
              break;
            ANSIC_error();
          } else {
            if (outsize < sizeof(chart))
              break;
            *(chart*)outptr = char_code(action);
            outptr += sizeof(chart); outsize -= sizeof(chart);
            inptr++; insize--;
          }
        } else {
          ANSIC_error();
        }
      }
    }
    end_system_call();
  }
  *srcp = (const uintB*)inptr;
  *destp = (chart*)outptr;
}

/* Characters to bytes. */

global uintL iconv_wcslen (object encoding, const chart* src,
                           const chart* srcend) {
  var uintL count = 0;
  #define tmpbufsize 4096
  var uintB tmpbuf[tmpbufsize];
  with_sstring_0(TheEncoding(encoding)->enc_charset,Symbol_value(S(ascii)),
                 charset_asciz, {
    begin_system_call();
    var iconv_t cd = open_iconv(charset_asciz,CLISP_INTERNAL_CHARSET,
                                TheEncoding(encoding)->enc_charset);
    {
      var const char* inptr = (const char*)src;
      var size_t insize = (char*)srcend-(char*)src;
      while (insize > 0) {
        var char* outptr = (char*)tmpbuf;
        var size_t outsize = tmpbufsize;
        var size_t res = iconv(cd,&inptr,&insize,&outptr,&outsize);
        if (res == (size_t)(-1) && errno != E2BIG) {
          if (errno == EILSEQ) { /* invalid input? */
            ASSERT(insize >= sizeof(chart));
            var object action = TheEncoding(encoding)->enc_tombs_error;
            if (eq(action,S(Kignore))) {
              inptr += sizeof(chart); insize -= sizeof(chart);
            } else if (uint8_p(action)) {
              outptr++; outsize--;
              inptr += sizeof(chart); insize -= sizeof(chart);
            } else if (!eq(action,S(Kerror))) {
              var chart c = char_code(action);
              var const char* inptr1 = (const char*)&c;
              var size_t insize1 = sizeof(c);
              if (iconv(cd,&inptr1,&insize1,&outptr,&outsize)
                  != (size_t)(-1)) {
                inptr += sizeof(chart); insize -= sizeof(chart);
              } else {
                if (errno != EILSEQ) {
                  ANSIC_error();
                } else {
                  end_system_call();
                  error_unencodable(encoding,*(const chart*)inptr);
                }
              }
            } else {
              end_system_call();
              error_unencodable(encoding,*(const chart*)inptr);
            }
          } else if (errno == EINVAL) { /* incomplete input? */
            NOTREACHED;
          } else {
            var int saved_errno = errno;
            iconv_close(cd);
            errno = saved_errno;
            ANSIC_error();
          }
        }
        count += (outptr-(char*)tmpbuf);
      }
    }
    {
      var char* outptr = (char*)tmpbuf;
      var size_t outsize = tmpbufsize;
      var size_t res = iconv(cd,NULL,NULL,&outptr,&outsize);
      if (res == (size_t)(-1)) {
        if (errno == E2BIG) { /* output buffer too small? */
          NOTREACHED;
        } else {
          var int saved_errno = errno;
          iconv_close(cd);
          errno = saved_errno;
          ANSIC_error();
        }
      }
      count += (outptr-(char*)tmpbuf);
    }
    if (iconv_close(cd) < 0) { ANSIC_error(); }
    end_system_call();
  });
  #undef tmpbufsize
  return count;
}

global void iconv_wcstombs (object encoding, object stream,
                            const chart* *srcp,const chart* srcend,
                            uintB* *destp, uintB* destend) {
  var const char* inptr = (char*)*srcp;
  var size_t insize = (char*)srcend-(char*)*srcp;
  var char* outptr = (char*)*destp;
  var size_t outsize = destend-*destp;
  if (eq(stream,nullobj)) {
    /* Standalone call, must be consistent with iconv_wcslen: */
    with_sstring_0(TheEncoding(encoding)->enc_charset,Symbol_value(S(ascii)),
                   charset_asciz, {
      begin_system_call();
      var iconv_t cd = open_iconv(charset_asciz,CLISP_INTERNAL_CHARSET,
                                  TheEncoding(encoding)->enc_charset);
      while (insize > 0) {
        var size_t res = iconv(cd,&inptr,&insize,&outptr,&outsize);
        if (res == (size_t)(-1)) {
          if (errno == EILSEQ) { /* invalid input? */
            ASSERT(insize >= sizeof(chart));
            var object action = TheEncoding(encoding)->enc_tombs_error;
            if (eq(action,S(Kignore))) {
              inptr += sizeof(chart); insize -= sizeof(chart);
            } else if (uint8_p(action)) {
              *outptr++ = I_to_uint8(action); outsize--;
              inptr += sizeof(chart); insize -= sizeof(chart);
            } else if (!eq(action,S(Kerror))) {
              var chart c = char_code(action);
              var const char* inptr1 = (const char*)&c;
              var size_t insize1 = sizeof(c);
              if (iconv(cd,&inptr1,&insize1,&outptr,&outsize) != (size_t)(-1)) {
                inptr += sizeof(chart); insize -= sizeof(chart);
              } else {
                if (errno != EILSEQ) {
                  ANSIC_error();
                } else {
                  end_system_call();
                  error_unencodable(encoding,*(const chart*)inptr);
                }
              }
            } else {
              end_system_call();
              error_unencodable(encoding,*(const chart*)inptr);
            }
          } else if (errno == EINVAL) { /* incomplete input? */
            NOTREACHED;
          } else if (errno == E2BIG) { /* output buffer too small? */
            NOTREACHED;
          } else {
            var int saved_errno = errno;
            iconv_close(cd);
            errno = saved_errno;
            ANSIC_error();
          }
        }
      }
      {
        var size_t res = iconv(cd,NULL,NULL,&outptr,&outsize);
        if (res == (size_t)(-1)) {
          if (errno == E2BIG) { /* output buffer too small? */
            NOTREACHED;
          } else {
            var int saved_errno = errno;
            iconv_close(cd);
            errno = saved_errno;
            ANSIC_error();
          }
        }
      }
      if (iconv_close(cd) < 0) { ANSIC_error(); }
      end_system_call();
      /* Now insize == 0, and if iconv_wcslen has been used to determine
       the destination size, then also outsize == 0. */
    });
  } else {
    /* Called from a channel-stream. */
    var iconv_t cd = ChannelStream_oconvdesc(stream);
    begin_system_call();
    while (insize > 0) {
      var size_t res = iconv(cd,&inptr,&insize,&outptr,&outsize);
      if (res == (size_t)(-1)) {
        if (errno == EILSEQ) { /* invalid input? */
          ASSERT(insize >= sizeof(chart));
          var object action = TheEncoding(encoding)->enc_tombs_error;
          if (eq(action,S(Kignore))) {
            inptr += sizeof(chart); insize -= sizeof(chart);
          } else if (uint8_p(action)) {
            if (outsize == 0)
              break;
            *outptr++ = I_to_uint8(action); outsize--;
            inptr += sizeof(chart); insize -= sizeof(chart);
          } else if (!eq(action,S(Kerror))) {
            var chart c = char_code(action);
            var const char* inptr1 = (const char*)&c;
            var size_t insize1 = sizeof(c);
            if (iconv(cd,&inptr1,&insize1,&outptr,&outsize) != (size_t)(-1)) {
              inptr += sizeof(chart); insize -= sizeof(chart);
            } else {
              if (errno == E2BIG)
                break;
              else if (errno != EILSEQ) {
                ANSIC_error();
              } else {
                if (inptr > (char*)*srcp)
                  break;
                end_system_call();
                error_unencodable(encoding,*(const chart*)inptr);
              }
            }
          } else {
            if (inptr > (char*)*srcp)
              break;
            end_system_call();
            error_unencodable(encoding,*(const chart*)inptr);
          }
        } else if (errno == EINVAL) { /* incomplete input? */
          NOTREACHED;
        } else if (errno == E2BIG) { /* output buffer full? */
          break;
        } else {
          ANSIC_error();
        }
      }
    }
    end_system_call();
  }
  *srcp = (const chart*)inptr;
  *destp = (uintB*)outptr;
}

/* Determining the range of encodable characters. */
global object iconv_range (object encoding, uintL start, uintL end,
                           uintL maxintervals) {
  var uintL count = 0; /* number of intervals already on the STACK */
  if (maxintervals > 0) {
    var iconv_t cd;
    with_sstring_0(TheEncoding(encoding)->enc_charset,Symbol_value(S(ascii)),
                   charset_asciz, {
      begin_system_call();
      cd = open_iconv(charset_asciz,CLISP_INTERNAL_CHARSET,
                      TheEncoding(encoding)->enc_charset);
      end_system_call();
    });
    {
      var uintL i1;
      var uintL i2;
      var bool have_i1_i2 = false; /* [i1,i2] = interval being built */
      var uintL i = start;
      while (1) {
        /* Here count < maxintervals. */
        var chart ch = as_chart(i);
        var uintB buf[max_bytes_per_chart];
        var const char* inptr = (const char*)&ch;
        var size_t insize = sizeof(chart);
        var char* outptr = (char*)&buf[0];
        var size_t outsize = max_bytes_per_chart;
        begin_system_call();
        {
          var size_t res = iconv(cd,&inptr,&insize,&outptr,&outsize);
          if (res == (size_t)(-1)) {
            if (errno == EILSEQ) { /* invalid input? */
              end_system_call();
              /* ch not encodable -> finish the interval */
              if (have_i1_i2) {
                pushSTACK(code_char(as_chart(i1)));
                pushSTACK(code_char(as_chart(i2)));
                check_STACK(); count++;
                have_i1_i2 = false;
                /* If we have already produced the maximum number of intervals
                 requested by the caller, it's of no use to search further. */
                if (count == maxintervals)
                  break;
              }
            } else if (errno == EINVAL) { /* incomplete input? */
              NOTREACHED;
            } else if (errno == E2BIG) { /* output buffer too small? */
              NOTREACHED;
            } else {
              var int saved_errno = errno;
              iconv_close(cd);
              errno = saved_errno;
              ANSIC_error();
            }
          } else {
            end_system_call();
            /* ch encodable -> extend the interval */
            if (!have_i1_i2) {
              have_i1_i2 = true;
              i1 = i;
            }
            i2 = i;
          }
        }
        if (i == end)
          break;
        i++;
      }
      if (have_i1_i2) {
        pushSTACK(code_char(as_chart(i1)));
        pushSTACK(code_char(as_chart(i2)));
        check_STACK(); count++;
      }
    }
    begin_system_call();
    if (iconv_close(cd) < 0) { ANSIC_error(); }
    end_system_call();
  };
  return stringof(2*count);
}

#endif /* ENABLE_UNICODE && HAVE_GOOD_ICONV */

/* Initializes some ChannelStream fields.
 ChannelStream_init(stream);
 > stream: channel-stream with encoding */
#if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
local void ChannelStream_init (object stream) {
  var object encoding = TheStream(stream)->strm_encoding;
  if (simple_string_p(TheEncoding(encoding)->enc_charset)) {
    with_sstring_0(TheEncoding(encoding)->enc_charset,Symbol_value(S(ascii)),
                   charset_asciz, {
      var uintB flags = TheStream(stream)->strmflags;
      if (flags & strmflags_rd_B) {
        begin_system_call();
        ChannelStream_iconvdesc(stream) =
          open_iconv(CLISP_INTERNAL_CHARSET,charset_asciz,
                     TheEncoding(encoding)->enc_charset);
        end_system_call();
      } else {
        ChannelStream_iconvdesc(stream) = (iconv_t)0;
      }
      if (flags & strmflags_wr_B) {
        begin_system_call();
        ChannelStream_oconvdesc(stream) =
          open_iconv(charset_asciz,CLISP_INTERNAL_CHARSET,
                     TheEncoding(encoding)->enc_charset);
        end_system_call();
      } else {
        ChannelStream_oconvdesc(stream) = (iconv_t)0;
      }
    });
  } else {
    ChannelStream_iconvdesc(stream) = (iconv_t)0;
    ChannelStream_oconvdesc(stream) = (iconv_t)0;
  }
}
#else
  #define ChannelStream_init(stream)
#endif

/* Cleans up some ChannelStream fields.
 ChannelStream_fini(stream,abort); */
#if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
local void ChannelStream_fini (object stream, uintB abort) {
  if (ChannelStream_iconvdesc(stream) != (iconv_t)0) {
    begin_system_call();
    if (iconv_close(ChannelStream_iconvdesc(stream)) < 0 && !abort)
      { ANSIC_error(); }
    end_system_call();
    ChannelStream_iconvdesc(stream) = (iconv_t)0;
  }
  if (ChannelStream_oconvdesc(stream) != (iconv_t)0) {
    begin_system_call();
    if (iconv_close(ChannelStream_oconvdesc(stream)) < 0 && !abort)
      { ANSIC_error(); }
    end_system_call();
    ChannelStream_oconvdesc(stream) = (iconv_t)0;
  }
}
#else
#define ChannelStream_fini(stream,abort)
#endif

/* Closes a handle. */
local maygc void low_close_handle (object stream, object handle, uintB abort) {
  var Handle fd = TheHandle(handle);
  pushSTACK(stream);
  begin_blocking_system_call();
 #ifdef UNIX
  if (!( CLOSE(fd) ==0) && !abort)
    { end_blocking_system_call(); OS_filestream_error(popSTACK()); }
 #endif
 #ifdef WIN32_NATIVE
  if (!CloseHandle(fd) && !abort)
    { end_blocking_system_call(); OS_filestream_error(popSTACK()); }
 #endif
  end_blocking_system_call();
  skipSTACK(1);
}

/* Subroutines for Integer-Streams
   ===============================

 For file streams with element type INTEGER ("byte files") every integer
 uses the same amount of bits. The bits and bytes are stored in little-endian
 order, because big-endian order would lead to madness. So the bit number i
 of element number j is = bit number (i+j*bitsize) of the entire bit stream
 = bit number ((i+j*bitsize) mod 8) in byte number floor((i+j*bitsize)/8).

 strm_bitbuffer is a simple-bit-vector with ceiling(bitsize/8)*8 bits,
 filled in little-endian order.

 All subroutines below get passed as arguments: bitsize (size per unit, it is
 also stored in the stream), bytesize = ceiling(bitsize/8) = number of bytes
 the bitbuffer can hold.

 Note that unbuffered file-streams cannot be of type ib or ic (too
 complicated for the moment), only type ia is supported for them.

 Subroutines for the Input side
 ------------------------------ */

local maygc object bitbuff_iu_I (object bitbuffer, uintL bitsize,
                                 uintL bytesize) {
  var uintB* bitbufferptr = &TheSbvector(bitbuffer)->data[bytesize-1];
  *bitbufferptr &= (bit(((bitsize-1)%8)+1)-1); /* mask High byte */
  pushSTACK(bitbuffer);
  var object result = LESbvector_to_UI(bytesize,&STACK_0);
  skipSTACK(1);
  return result;
}

/* UP for READ-BYTE on File-Streams of Integers, Type u :
 Returns the bytesize Bytes contained in the Bitbuffer as Integer >=0.
 can trigger GC */
local maygc object rd_by_iu_I (object stream, uintL bitsize, uintL bytesize) {
  return bitbuff_iu_I(TheStream(stream)->strm_bitbuffer,bitsize,bytesize);
}

local maygc object bitbuff_is_I (object bitbuffer, uintL bitsize,
                                 uintL bytesize) {
  var uintB* bitbufferptr = &TheSbvector(bitbuffer)->data[bytesize-1];
  var uintL signbitnr = (bitsize-1)%8;
  if (!(*bitbufferptr & bit(signbitnr))) {
    *bitbufferptr &= (bitm(signbitnr+1)-1); /* sign-extend High byte */
  } else {
    *bitbufferptr |= minus_bitm(signbitnr+1); /* sign-extend High byte */
  }
  pushSTACK(bitbuffer);
  var object result = LESbvector_to_I(bytesize,&STACK_0);
  skipSTACK(1);
  return result;
}

/* UP for READ-BYTE on File-Streams of Integers, Type s :
 Returns the bytesize Bytes contained in the Bitbuffer as Integer.
 can trigger GC */
local maygc object rd_by_is_I (object stream, uintL bitsize, uintL bytesize) {
  return bitbuff_is_I(TheStream(stream)->strm_bitbuffer,bitsize,bytesize);
}

/* Typ rd_by_ix_I: one of these two Subroutines: */
typedef maygc object rd_by_ix_I (object stream, uintL bitsize, uintL bytesize);

/* Subroutines for the Output side
   -------------------------------

 Function type of a subroutine which writes the bitbuffer contents to the
 stream. */
typedef void wr_by_aux_ix (object stream, uintL bitsize, uintL bytesize);

local inline void bitbuff_ixu_sub (object stream, object bitbuffer,
                                   uintL bitsize, object obj) {
  if (UI_to_LEbytes(obj,bitsize,TheSbvector(bitbuffer)->data))
    error_bad_integer(stream,obj);
}

/* UP for WRITE-BYTE on File-Streams of Integers, Type u :
 Store the Object (an Integer >=0) as bytesize Bytes in the Bitbuffer.
 > stream : File-Stream for Integers, Type u
 > obj : Object to be written
 > finisher : Routine for Finalization */
local maygc void wr_by_ixu_sub (object stream, object obj,
                                wr_by_aux_ix* finisher) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  var uintL bytesize = ceiling(bitsize,8);
  ASSERT_wr_int(stream,obj);
  bitbuff_ixu_sub(stream,TheStream(stream)->strm_bitbuffer,bitsize,obj);
  (*finisher)(stream,bitsize,bytesize);
}

local inline void bitbuff_ixs_sub (object stream, object bitbuffer,
                                   uintL bitsize, object obj) {
  if (I_to_LEbytes(obj,bitsize,TheSbvector(bitbuffer)->data))
    error_bad_integer(stream,obj);
}

/* UP for WRITE-BYTE on File-Streams of Integers, Type s :
 Stores the Object (an Integer) as bytesize Bytes in the Bitbuffer.
 > stream : File-Stream for Integers, Type s
 > obj : Object to be written
 > finisher : Routine for Finalization */
local maygc void wr_by_ixs_sub (object stream, object obj,
                                wr_by_aux_ix* finisher) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  var uintL bytesize = ceiling(bitsize,8);
  ASSERT_wr_int(stream,obj);
  bitbuff_ixs_sub(stream,TheStream(stream)->strm_bitbuffer,bitsize,obj);
  (*finisher)(stream,bitsize,bytesize);
}

/* Handle-Streams, Input side
   ==========================

 Low-level
 ---------

 Push a byte into bytebuf.
 UnbufferedStreamLow_push_byte(stream,b);
 Assumes 0 <= UnbufferedStream_status(stream) < max_bytes_per_chart. */
#if (max_bytes_per_chart > 1) /* i.e. defined(ENABLE_UNICODE) */
  #define UnbufferedStreamLow_push_byte(stream,b)  \
     ASSERT((uintL)UnbufferedStream_status(stream) < max_bytes_per_chart);    \
     UnbufferedStream_bytebuf(stream)[UnbufferedStream_status(stream)++] = b;
#else
  #define UnbufferedStreamLow_push_byte(stream,b)  \
     UnbufferedStream_bytebuf(stream)[0] = b; \
     UnbufferedStream_status(stream) = 1;
#endif

/* Push a byte to the front of bytebuf.
 UnbufferedStreamLow_pushfront_byte(stream,b);
 Assumes 0 <= UnbufferedStream_status(stream) < max_bytes_per_chart. */
#if (max_bytes_per_chart > 1) /* i.e. defined(ENABLE_UNICODE) */
  #define UnbufferedStreamLow_pushfront_byte(stream,b)  \
      ASSERT((uintL)UnbufferedStream_status(stream) < max_bytes_per_chart); \
      { var uintL _count = UnbufferedStream_status(stream)++;               \
        var uintB* _ptr = &UnbufferedStream_bytebuf(stream)[_count];        \
        if (_count > 0)                                                     \
          { do { _ptr[0] = _ptr[-1]; _ptr--; } while (--_count > 0); }      \
        _ptr[0] = b;                                                        \
      }
#else
  #define UnbufferedStreamLow_pushfront_byte(stream,b)  \
      UnbufferedStream_bytebuf(stream)[0] = b; \
      UnbufferedStream_status(stream) = 1;
#endif

#ifdef ENABLE_UNICODE
/* Push a number of bytes to the front of bytebuf.
 UnbufferedStreamLow_pushfront_bytes(stream,byteptr,bytecount); */
#define UnbufferedStreamLow_pushfront_bytes(stream,byteptr,bytecount)        \
  { var uintL _push = (bytecount);                                           \
    if (_push > 0) {                                                         \
      var uintL _count = UnbufferedStream_status(stream);                    \
      ASSERT(_push + _count <= max_bytes_per_chart);                         \
      UnbufferedStream_status(stream) = _push + _count;                      \
      { var const uintB* _ptr1 = (byteptr);                                  \
        var uintB* _ptr2 = &UnbufferedStream_bytebuf(stream)[_count];        \
        if (_count > 0)                                                      \
          { do { _ptr2--; _ptr2[_push] = _ptr2[0]; } while (--_count > 0); } \
        do { *_ptr2++ = *_ptr1++; } while (--_push > 0);                     \
      }}                                                                     \
  }
#endif

/* Pop a byte from bytebuf.
 UnbufferedStreamLow_pop_byte(stream,b);
 declares and assigns a value to b.
 Assumes UnbufferedStream_status(stream) > 0. */
#if (max_bytes_per_chart > 1) /* i.e. defined(ENABLE_UNICODE) */
  #define UnbufferedStreamLow_pop_byte(stream,b)  \
      var uintB b = UnbufferedStream_bytebuf(stream)[0];            \
      { var uintL _count = --UnbufferedStream_status(stream);       \
        if (_count > 0)                                             \
          { var uintB* _ptr = &UnbufferedStream_bytebuf(stream)[0]; \
            do { _ptr[0] = _ptr[1]; _ptr++; } while (--_count > 0); \
      }   }
#else
  #define UnbufferedStreamLow_pop_byte(stream,b)  \
      var uintB b;                             \
      UnbufferedStream_status(stream) = 0;     \
      b = UnbufferedStream_bytebuf(stream)[0];
#endif

/* Pop at most *len bytes from stream's bytebuf and store them at byteptr.
   Returns the increased byteptr and decrements *len accordingly. */
local inline uintB* UnbufferedStream_pop_all (object stream,
                                              uintB* byteptr, uintL *len)
{ /* pop bytebuf into byteptr */
  while (UnbufferedStream_status(stream) > 0) { /* have valid bytes? */
    UnbufferedStreamLow_pop_byte(stream,b);
    *byteptr++ = b;
    if (--*len == 0)
      break;
  }
  return byteptr;
}

local maygc sintL low_read_unbuffered_handle (object stream) {
  if (UnbufferedStream_status(stream) < 0) { /* already EOF? */
    return -1;
  }
  if (UnbufferedStream_status(stream) > 0) { /* bytebuf contains valid bytes? */
    UnbufferedStreamLow_pop_byte(stream,b); return b;
  }
  var Handle handle = TheHandle(TheStream(stream)->strm_ichannel);
  var uintB b;
  pushSTACK(stream);
  /*restart_it:*/
  /* try to read a byte */
  var ssize_t result;
  GC_SAFE_SYSTEM_CALL(result = full_read(handle,&b,1));
  stream=popSTACK();
  if (result<0) {
    #ifdef WIN32_NATIVE
    begin_system_call();
    if (GetLastError()==ERROR_SIGINT) { /* Interrupt by Ctrl-C ? */
      end_system_call();
      error_interrupt();
    }
    end_system_call();
    #endif
    if (errno == EIO && TheStream(stream)->strmtype==strmtype_terminal) {
      /* An EIO error is seen when the clisp process escapes into
         background execution, when started under gdb and gdb reports a
         "problem internal to GDB". We need to silence this, otherwise it
         runs into an infinite recursion. */
      result = 0;
    } else
      OS_error();
  }
  if (result==0) { /* no byte available -> must be EOF */
    UnbufferedStream_status(stream) = -1; return -1;
  } else {
    return b;
  }
}

local listen_t listen_handle (Handle handle, bool tty_p, int *byte) {
/* Method 1: poll, see POLL(2)
   Method 2: select, see SELECT(2)
   Method 3: ioctl FIONREAD, see FILIO(4)
   Method 4: switch temporarily to non-blocking I/O and try read(),
             see READ(2V), FILIO(4), or
             see READ(2V), FCNTL(2V), FCNTL(5) */
  #if !defined(WIN32_NATIVE)
  #if defined(HAVE_POLL) && (defined(HAVE_RELIABLE_POLL) || !defined(HAVE_RELIABLE_SELECT))
  {
    /* Use poll() with a single handle and timeout = zero interval. */
    var struct pollfd pollfd_bag[1];
    pollfd_bag[0].fd = handle;
    pollfd_bag[0].events = POLLIN;
    pollfd_bag[0].revents = 0;
    begin_system_call();
   restart_poll:
    var int result = poll(&pollfd_bag[0],1,0);
    if (result<0) {
      if (errno==EINTR)
        goto restart_poll;
      OS_error();
    } else {
      end_system_call();
      /* revents has POLLIN or some other bits set if read() would return
       without blocking. */
      if (pollfd_bag[0].revents == 0)
        return LISTEN_WAIT;
      /* When read() returns a result without blocking, this can also be
       EOF! (Example: Linux and pipes.) We therefore refrain from simply
       doing  { return LISTEN_AVAIL; }  and instead try methods 3 and 4. */
    }
  }
  #elif defined(HAVE_SELECT) && !defined(UNIX_BEOS)
  {
    /* Use select() with readfds = singleton set {handle}
     and timeout = zero interval. */
    var fd_set handle_set; /* set of handles := {handle} */
    var struct timeval zero_time; /* time interval := 0 */
    begin_system_call();
    FD_ZERO(&handle_set); FD_SET(handle,&handle_set);
  restart_select:
    zero_time.tv_sec = 0; zero_time.tv_usec = 0;
    var int result = select(FD_SETSIZE,&handle_set,NULL,NULL,&zero_time);
    if (result<0) {
      if (errno==EINTR)
        goto restart_select;
      if (!(errno==EBADF)) { OS_error(); } /* UNIX_LINUX returns EBADF for files! */
      end_system_call();
    } else {
      end_system_call();
      /* result = number of handles in handle_set for which read() would
       return without blocking. */
      if (result==0)
        return LISTEN_WAIT;
      /* result=1
       When read() returns a result without blocking, this can also be
       EOF! (Example: Linux and pipes.) We therefore refrain from simply
       doing  { return LISTEN_AVAIL; }  and instead try methods 3 and 4. */
    }
  }
  #endif
  begin_system_call();
  #ifdef HAVE_FIONREAD
  /* Try to enquire the number of available bytes: */
  {
    var unsigned long bytes_ready;
    /* Clear bytes_ready before use. Some kernels (such as Linux-2.4.18 on ia64)
     apparently expect an 'int *', not a 'long *', as argument of this ioctl,
     and thus fill only part of the bytes_ready variable. Fortunately,
     endianness is not a problem here, because we only check whether
     bytes_ready is == 0 or != 0. */
    bytes_ready = 0;
    if ( ioctl(handle,FIONREAD,&bytes_ready) <0) {
      /* Enquiry failed, probably wasn't a file */
      if (!((errno == ENOTTY)||IS_EINVAL))
        { OS_error(); }
    } else {
      /* Enquiry succeeded, so it was a file */
      end_system_call();
      if (bytes_ready > 0)
        return LISTEN_AVAIL;
      #ifdef HAVE_RELIABLE_FIONREAD
      /* else we have reached the file's EOF: */
      return LISTEN_EOF;
      #endif
    }
  }
  #endif
  #if !((defined(HAVE_POLL) && (defined(HAVE_RELIABLE_POLL) || !defined(HAVE_RELIABLE_SELECT))) || (defined(HAVE_SELECT) && !defined(UNIX_BEOS)))
  if (tty_p) { /* Terminal */
    /* switch to non-blocking mode, then try read(): */
    var uintB b;
    var int result;
   restart_read_tty:
    { NO_BLOCK_DECL();
      START_NO_BLOCK(handle, OS_error());
      result = read(handle,&b,1);
      var int saved_errno = errno;
      END_NO_BLOCK(handle, OS_error());
      errno = saved_errno;
    }
    if (result < 0) {
      if (errno==EINTR)
        goto restart_read_tty;
      if
       #ifdef FIONBIO
        (errno==EWOULDBLOCK) /* BSD 4.2 Error-Code */
       #else
        ((errno==EAGAIN) /* Posix Error-Code */
        #ifdef EWOULDBLOCK
         || (errno==EWOULDBLOCK)
         #endif
         )
       #endif
          return LISTEN_WAIT;
      OS_error();
    }
    end_system_call();
    if (result==0) {
      return LISTEN_WAIT;
    } else {
      *byte = b;
      return LISTEN_AVAIL;
    }
    /* If this doesn't work, should use a timer 0.1 sec ?? */
  } else
    #endif
    /* file (or pipe) */
  restart_read_other: { /* try to read a byte: */
    var uintB b;
    var int result = read(handle,&b,1);
    if (result<0) {
      if (errno==EINTR)
        goto restart_read_other;
      OS_error();
    }
    end_system_call();
    if (result==0) {
      return LISTEN_EOF;
    } else {
      *byte = b;
      return LISTEN_AVAIL;
    }
  }
  #elif defined(WIN32_NATIVE)
  begin_system_call();
  var int wont_hang = fd_read_wont_hang_p(handle);
  if (wont_hang == 0) {
    end_system_call(); return LISTEN_WAIT;
  }
  if (wont_hang == 2) {
    end_system_call(); return LISTEN_EOF;
  }
  if (wont_hang == 3) {
    end_system_call(); return LISTEN_AVAIL;
  }
  /* try to read a byte */
  var uintB b;
  var ssize_t result = full_read(handle,&b,1);
  if (result<0) {
    OS_error();
  }
  end_system_call();
  if (result==0) {
    return LISTEN_EOF;
  } else {
    if (byte) *byte = b;
    return LISTEN_AVAIL;
  }
  #endif
}

local listen_t low_listen_unbuffered_handle (object stream) {
  if (UnbufferedStream_status(stream) < 0) /* already EOF? */
    return LISTEN_EOF;
  if (UnbufferedStream_status(stream) > 0) /* bytebuf contains valid bytes? */
    return LISTEN_AVAIL;
  var int byte = -1;
  var listen_t ret =
    listen_handle(TheHandle(TheStream(stream)->strm_ichannel),
                  !nullp(TheStream(stream)->strm_isatty),&byte);
  if (ret == LISTEN_EOF) UnbufferedStream_status(stream) = -1;
  /* Stuff the read byte into the buffer, for next low_read call. */
  if (byte >= 0) { UnbufferedStreamLow_push_byte(stream,byte); }
  return ret;
}

local maygc bool low_clear_input_unbuffered_handle (object stream) {
  if (nullp(TheStream(stream)->strm_isatty))
    return false; /* it's a file -> nothing to do */
  UnbufferedStream_status(stream) = 0; /* forget about past EOF */
  /* Terminal. */
  clear_tty_input(TheHandle(TheStream(stream)->strm_ichannel));
  /* In case this didn't work, and as a general method for platforms on
   which clear_tty_input() does nothing: read a byte, as long as listen
   says that a byte is available. */

  /* low_read_unbuffered_handle is not going to block - we are sure there is
     character waiting. May be call directly full_read() without defining
     safe gc region ???*/
  pushSTACK(stream);
  while (LISTEN_AVAIL == low_listen_unbuffered_handle(stream)) {
    #ifdef WIN32_NATIVE
    /* Our low_listen_unbuffered_handle function, when applied to a WinNT
     console, cannot tell when there is an LF pending after the
     preceding CR has been eaten. Therefore be careful to set
     ChannelStream_ignore_next_LF to true when we read a LF. */
    var sintL c = low_read_unbuffered_handle(stream);
    stream=STACK_0;
    if (c >= 0)
      ChannelStream_ignore_next_LF(stream) = (c == CR);
    #else
    low_read_unbuffered_handle(stream);
    stream=STACK_0;
    #endif
  }
  skipSTACK(1);
  return true;
}

/* Return true if the last error from fd_read()/fd_write() indicates an EOF. */
local bool fd_error_eof_p (void) {
  var bool ret = false;
  begin_system_call();
 #if defined(WIN32_NATIVE)
  var DWORD err = GetLastError();
  if (err==ERROR_HANDLE_EOF)
    ret = true;
 #else
  if (errno==ENOENT) /* indicates EOF */
    ret = true;
 #endif
  end_system_call();
  return ret;
}

local maygc uintB* low_read_array_unbuffered_handle
(object stream, uintB* byteptr, uintL len, perseverance_t persev) {
  if (UnbufferedStream_status(stream) < 0) /* already EOF? */
    return byteptr;
  byteptr = UnbufferedStream_pop_all(stream,byteptr,&len);
  if (len == 0) return byteptr;
  var Handle handle = TheHandle(TheStream(stream)->strm_ichannel);
  /* On regular file handles, persev_immediate and persev_bonus are effectively
   equivalent to persev_partial. Transforming persev_immediate, persev_bonus
   here 1) avoids useless system calls for poll(), select() or non-blocking
   I/O and 2) improves EOF detection. */
  if ((persev == persev_immediate || persev == persev_bonus)
      && ChannelStream_regular(stream))
    persev = persev_partial;
  pushSTACK(stream);
  var ssize_t result;
  GC_SAFE_SYSTEM_CALL(result = fd_read(handle,byteptr,len,persev));
  stream = popSTACK();
  if (result<0) {
   #if !defined(WIN32_NATIVE)
    begin_system_call();
    if (errno==EINTR) /* Interrupt (poss. by Ctrl-C) ? */
      { interruptp({ end_system_call(); error_interrupt(); }) };
   #endif
   #ifdef WIN32_NATIVE
    begin_system_call();
    if (GetLastError()==ERROR_SIGINT) { /* Interrupt by Ctrl-C ? */
      end_system_call(); error_interrupt();
    }
   #endif
    OS_error();
  }
  if (result==0 && fd_error_eof_p())
    UnbufferedStream_status(stream) = -1;
  return byteptr+result;
}

/* Integer streams
   ---------------

 UP for READ-BYTE on File-Streams of Integers, Type a :
 Fills the Bitbuffer with the next bitsize Bits.
 > stream : File-Stream for Integers, Type a
 > finisher : Routine for Finalization
 < result : read Integer or eof_value */
local maygc object rd_by_aux_iax_unbuffered (object stream, rd_by_ix_I* finisher) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  var uintL bytesize = bitsize/8;
  /* transfer sufficiently many bytes into the bitbuffer */
  var uintB* bitbufferptr =
    &TheSbvector(TheStream(stream)->strm_bitbuffer)->data[0];
  pin_unprotect_varobject(TheStream(stream)->strm_bitbuffer,PROT_READ_WRITE);
  pushSTACK(stream);
  if (UnbufferedStreamLow_read_array(stream)(stream,bitbufferptr,bytesize,
                                             persev_full)
      != bitbufferptr+bytesize)
    goto eof;
  stream = popSTACK();
  unpin_varobject(TheStream(stream)->strm_bitbuffer);
  /* convert to number: */
  return (*finisher)(stream,bitsize,bytesize);
 eof: /* EOF reached */
  stream = popSTACK();
  unpin_varobject(TheStream(stream)->strm_bitbuffer);
  return eof_value;
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type au : */
local maygc object rd_by_iau_unbuffered (object stream) {
  return rd_by_aux_iax_unbuffered(stream,&rd_by_iu_I);
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type as : */
local maygc object rd_by_ias_unbuffered (object stream) {
  return rd_by_aux_iax_unbuffered(stream,&rd_by_is_I);
}

/* READ-BYTE - Pseudo-Function for Handle-Streams, Type au, bitsize = 8 : */
local maygc object rd_by_iau8_unbuffered (object stream) {
 rd_by_iau8_unbuffered_retry:
  var sintL b = UnbufferedStreamLow_read(stream)(stream);
  if (b < 0)
    return eof_value;
  if (b == LF && ChannelStream_ignore_next_LF(stream)) {
    /* see comment in rd_by_array_iau8_unbuffered */
    ChannelStream_ignore_next_LF(stream) = false;
    goto rd_by_iau8_unbuffered_retry;
  }
  return fixnum((uintB)b);
}

/* READ-BYTE-ARRAY - Pseudo-Function for Handle-Streams, Type au, bitsize = 8 : */
local maygc uintL rd_by_array_iau8_unbuffered
(const gcv_object_t* stream_, const gcv_object_t* bytearray_,
 uintL start, uintL len, perseverance_t persev) {
  var uintB* startptr = &TheSbvector(*bytearray_)->data[start];
  pin_unprotect_varobject(*bytearray_,PROT_READ_WRITE);
  var uintB* endptr =
    UnbufferedStreamLow_read_array(*stream_)(*stream_,startptr,len,persev);
  unpin_varobject(*bytearray_);
  var object stream = *stream_;
  if (startptr < endptr && *startptr == LF
      && ChannelStream_ignore_next_LF(stream)) {
    /* if we switch from character to byte input after a NL,
       we need to drop the next CR
       https://sourceforge.net/p/clisp/bugs/490/ */
    var uintL len = endptr-startptr-1;
    /* shift the whole array down by one, dropping CR */
    var uintL count = len;
    for (; count--; startptr++) startptr[0] = startptr[1];
    ChannelStream_ignore_next_LF(stream) = false;
    endptr = UnbufferedStreamLow_read_array(stream)(stream,startptr,1,persev);
    return len + (endptr - startptr);
  } else return endptr-startptr;
}

/* Determines, if  a Byte is available on an Unbuffered-Channel-Stream.
 listen_byte_ia8_unbuffered(stream)
 > stream: Unbuffered-Channel-Stream, Type a, bitsize = 8
 < result: input availability */
local listen_t listen_byte_ia8_unbuffered (object stream) {
  return UnbufferedStreamLow_listen(stream)(stream);
}

/* Character streams
   -----------------

 READ-CHAR - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc object rd_ch_unbuffered (const gcv_object_t* stream_) {
  var object stream = *stream_;
  if (eq(TheStream(stream)->strm_rd_ch_last,eof_value)) /* already EOF? */
    return eof_value;
 retry: {
    var chart c;
   #ifdef ENABLE_UNICODE
    var uintB buf[max_bytes_per_chart];
    var uintL buflen = 0;
    while (1) {
      var sintL b = UnbufferedStreamLow_read(stream)(stream);
      if (b < 0)
        return eof_value;
      stream=*stream_;
      ASSERT(buflen < max_bytes_per_chart);
      buf[buflen++] = (uintB)b;
      var const uintB* bptr = &buf[0];
      var chart* cptr = &c;
      var object encoding = TheStream(stream)->strm_encoding;
      Encoding_mbstowcs(encoding)
        (encoding,stream,&bptr,&buf[buflen],&cptr,cptr+1);
      if (cptr == &c) { /* Not a complete character. */
        /* Shift the buffer */
        if (bptr != &buf[0]) {
          var const uintB* ptr1 = bptr;
          var uintB* ptr2 = &buf[0];
          while (ptr1 != &buf[buflen]) { *ptr2++ = *ptr1++; }
          buflen = ptr2 - &buf[0];
        }
      } else { /* Read a complete character. */
        /* Move the remainder of the buffer into bytebuf. */
        UnbufferedStreamLow_pushfront_bytes(stream,bptr,&buf[buflen]-bptr);
        break;
      }
    }
   #else
    {
      var sintL b = UnbufferedStreamLow_read(stream)(stream);
      if (b < 0)
        return eof_value;
      stream=*stream_;
      c = as_chart((uintB)b);
    }
   #endif
    if (chareq(c,ascii(NL))) {
      if (ChannelStream_ignore_next_LF(stream)) {
        ChannelStream_ignore_next_LF(stream) = false;
        goto retry;
      }
      /* increment lineno: */
      ChannelStream_lineno(stream) += 1;
    } else if (chareq(c,ascii(CR))) {
      ChannelStream_ignore_next_LF(stream) = true;
      c = ascii(NL);
      /* increment lineno: */
      ChannelStream_lineno(stream) += 1;
    } else {
      ChannelStream_ignore_next_LF(stream) = false;
    }
    return code_char(c);
  }
}

/* Determines, if a character is available on an Unbuffered-Channel-Stream.
 listen_char_unbuffered(stream)
 > stream: Unbuffered-Channel-Stream
 < result: input availability */
local maygc listen_t listen_char_unbuffered (object stream) {
  if (eq(TheStream(stream)->strm_rd_ch_last,eof_value)) /* already EOF ? */
    return LISTEN_EOF;
  var listen_t result;
  pushSTACK(stream); /* save it */
  #ifdef ENABLE_UNICODE
  var chart c;
  var uintB buf[max_bytes_per_chart];
  var uintL buflen = 0;
  while (1) {
    result = UnbufferedStreamLow_listen(stream)(stream);
    if (result == LISTEN_EOF)
      break;
    if (result != LISTEN_AVAIL) {
      /* Stop reading.
       Move the buffer into bytebuf. */
      UnbufferedStreamLow_pushfront_bytes(stream,&buf[0],buflen);
      break;
    }
    /* this call is not going to block since we are sure that there is
       character waiting to be read. However since low_read_unbuffered_handle
       may trigger GC (full_read) so this function also maygc.
       Another option is to call full_read() here without surrounding it
       in safe for GC ??? */
    var sintL b = UnbufferedStreamLow_read(stream)(stream);
    if (b < 0) {
      result = LISTEN_EOF; break;
    }
    stream=STACK_0;
    ASSERT(buflen < max_bytes_per_chart);
    buf[buflen++] = (uintB)b;
    var const uintB* bptr = &buf[0];
    var chart* cptr = &c;
    var object encoding = TheStream(stream)->strm_encoding;
    Encoding_mbstowcs(encoding)
      (encoding,stream,&bptr,&buf[buflen],&cptr,cptr+1);
    if (cptr == &c) {
      /* Not a complete character.
       Shift the buffer */
      if (!(bptr == &buf[0])) {
        var const uintB* ptr1 = bptr;
        var uintB* ptr2 = &buf[0];
        while (ptr1 != &buf[buflen]) { *ptr2++ = *ptr1++; }
        buflen = ptr2 - &buf[0];
      }
    } else {
      /* Read a complete character. */
      if (ChannelStream_ignore_next_LF(stream) && chareq(c,ascii(NL))) {
        /* Move the remainder of the buffer into bytebuf. */
        UnbufferedStreamLow_pushfront_bytes(stream,bptr,&buf[buflen]-bptr);
        buflen--; /* discard the NL from buf */
        ChannelStream_ignore_next_LF(stream) = false;
      } else {
        /* Move the buffer into bytebuf. */
        UnbufferedStreamLow_pushfront_bytes(stream,&buf[0],buflen);
        ChannelStream_ignore_next_LF(stream) = false;
        result = LISTEN_AVAIL;
        break;
      }
    }
  }
  #else
 retry:
  result = UnbufferedStreamLow_listen(stream)(stream);
  if (result == LISTEN_AVAIL && ChannelStream_ignore_next_LF(stream)) {
    var sintL b = UnbufferedStreamLow_read(stream)(stream);
    stream=STACK_0;
    if (b < 0)
      return LISTEN_EOF;
    ChannelStream_ignore_next_LF(stream) = false;
    if (b == NL)
      goto retry;
    UnbufferedStreamLow_pushfront_byte(stream,b);
  }
  #endif
  skipSTACK(1); /* discard the stream */
  return result;
}

/* UP: Deletes already entered interactive Input from a
 Unbuffered-Channel-Stream.
 clear_input_unbuffered(stream);
 > stream: Unbuffered-Channel-Stream
 < result: true if Input was deleted, else false */
local maygc bool clear_input_unbuffered (object stream) {
  UnbufferedStream_status(stream) = 0; /* forget about past EOF & bytebuf */
  TheStream(stream)->strm_rd_ch_last = NIL; /* forget last char */
  if (nullp(TheStream(stream)->strm_isatty))
    return false; /* it's a file -> nothing to do */
  #ifdef WIN32_NATIVE
  /* Our low_listen_unbuffered_handle function, when applied to a WinNT
   console, cannot tell when there is an LF pending after the
   preceding CR has been eaten. Therefore be careful not to reset
   ChannelStream_ignore_next_LF. */
  #else
  ChannelStream_ignore_next_LF(stream) = false;
  #endif
  UnbufferedStreamLow_clear_input(stream)(stream);
  return true;
}

/* READ-CHAR-ARRAY - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc uintL rd_ch_array_unbuffered (const gcv_object_t* stream_,
                                          const gcv_object_t* chararray_,
                                          uintL start, uintL len) {
  /* Need a temporary buffer for CR/LF->NL translation. */
  #define tmpbufsize 4096
  var chart tmpbuf[tmpbufsize];
  var object stream = *stream_;
  var uintL end = start+len;
  var uintL currindex = start;
  while (1) {
    var uintL remaining = end - currindex;
    if (remaining == 0)
      break;
    if (remaining > tmpbufsize)
      remaining = tmpbufsize;
    var uintL count;
    #ifdef ENABLE_UNICODE
    /* In order to read n characters, we read n bytes. (Fewer than n bytes
     will not suffice.) If these aren't enough bytes, the next round
     will provide them.
     FIXME: Could use TheEncoding(encoding)->min_bytes_per_char here. */
    pushSTACK(TheStream(stream)->strm_encoding);
    {
      var uintB tmptmpbuf[tmpbufsize];
      var uintB* tmptmpendptr =
        UnbufferedStreamLow_read_array(stream)(stream,tmptmpbuf,remaining,
                                               persev_full);
      stream=*stream_; /* restore stream */
      var object encoding = STACK_0; /* restore the encoding */
      var const uintB* tmptmpptr = &tmptmpbuf[0];
      var chart* tmpptr = &tmpbuf[0];
      Encoding_mbstowcs(encoding)
        (encoding,stream,&tmptmpptr,tmptmpendptr,&tmpptr,&tmpbuf[tmpbufsize]);
      count = tmpptr - &tmpbuf[0];
      ASSERT(tmptmpendptr-tmptmpptr < max_bytes_per_chart);
      /* Move the remainder of tmptmpbuf into bytebuf. */
      UnbufferedStreamLow_pushfront_bytes(stream,tmptmpptr,
                                          tmptmpendptr-tmptmpptr);
    }
    skipSTACK(1); /* the encoding */
    if (count == 0) {
      /* Filling the last few characters must be done one by one, in
       order not to overrun the goal. */
      do {
        var object ch = rd_ch_unbuffered(stream_);
        if (eq(ch,eof_value))
          break;
        tmpbuf[count++] = char_code(ch);
        remaining--;
      } while (remaining > 0);
    }
    #else
    count = (chart*)UnbufferedStreamLow_read_array(stream)(stream,(uintB*)tmpbuf,remaining,persev_full) - &tmpbuf[0];
    #endif
    stream=*stream_; /* rd_ch_unbuffered or read_array maygc */
    if (count == 0)
      break;
    var const chart* tmpptr = &tmpbuf[0];
    do {
      var chart c = *tmpptr++;
      count--;
      if (chareq(c,ascii(NL))) {
        if (ChannelStream_ignore_next_LF(stream)) {
          ChannelStream_ignore_next_LF(stream) = false;
        } else {
          ChannelStream_lineno(stream) += 1;
          sstring_store(*chararray_,currindex++,ascii(NL));
        }
      } else if (chareq(c,ascii(CR))) {
        if (count > 0) {
          if (chareq(*tmpptr,ascii(NL))) {
            tmpptr++; count--;
          }
          ChannelStream_ignore_next_LF(stream) = false;
        } else {
          ChannelStream_ignore_next_LF(stream) = true;
        }
        ChannelStream_lineno(stream) += 1;
        sstring_store(*chararray_,currindex++,ascii(NL));
      } else {
        ChannelStream_ignore_next_LF(stream) = false;
        sstring_store(*chararray_,currindex++,c);
      }
    } while (count > 0);
  }
  return currindex - start;
  #undef tmpbufsize
}

/* Initializes the input side fields of an unbuffered stream.
 UnbufferedHandleStream_input_init(stream); */
#define UnbufferedHandleStream_input_init(stream)   do {                \
  UnbufferedStreamLow_read(stream) = &low_read_unbuffered_handle;       \
  UnbufferedStreamLow_listen(stream) = &low_listen_unbuffered_handle;   \
  UnbufferedStreamLow_clear_input(stream) =                             \
    &low_clear_input_unbuffered_handle;                                 \
  UnbufferedStreamLow_read_array(stream) =                              \
    &low_read_array_unbuffered_handle;                                  \
  UnbufferedHandleStream_input_init_data(stream);                       \
 } while(0)
#define UnbufferedHandleStream_input_init_data(stream)  \
    UnbufferedStream_status(stream) = 0

/* Closes a Channel-Stream.
 close_ichannel(stream, abort);
 > stream : Channel-Stream
 > abort: flag: non-0 => ignore errors */
local maygc void close_ichannel (object stream, uintB abort) {
  pushSTACK(stream);
  ChannelStreamLow_close(stream)(stream,TheStream(stream)->strm_ichannel,abort);
  stream = popSTACK();
  ChannelStream_fini(stream,abort);
  if (ChannelStream_bitsize(stream) > 0) {
    ChannelStream_bitsize(stream) = 0; /* delete bitsize */
    TheStream(stream)->strm_bitbuffer = NIL; /* free Bitbuffer */
  }
}

/* Handle-Streams, Output side
   ===========================

 Low-level
 --------- */

local maygc void low_write_unbuffered_handle (object stream, uintB b) {
  var Handle handle = TheHandle(TheStream(stream)->strm_ochannel);
 restart_it:
  /* Try to output the byte. */
  pushSTACK(stream);
  var ssize_t result;
  GC_SAFE_SYSTEM_CALL(result = full_write(handle,&b,1));
  stream = popSTACK();
  if (result<0) { OS_error(); }
  if (result==0) /* not successful? */
    error_unwritable(TheSubr(subr_self)->name,stream);
}

local maygc const uintB* low_write_array_unbuffered_handle
(object stream, const uintB* byteptr, uintL len, perseverance_t persev) {
  var Handle handle = TheHandle(TheStream(stream)->strm_ochannel);
  /* On regular file handles, persev_immediate and persev_bonus are effectively
   equivalent to persev_partial. Transforming persev_immediate, persev_bonus
   here 1) avoids useless system calls for poll(), select() or non-blocking
   I/O and 2) improves EOWF detection. */
  if ((persev == persev_immediate || persev == persev_bonus)
      && ChannelStream_regular(stream))
    persev = persev_partial;
  pushSTACK(stream);
  var ssize_t result;
  GC_SAFE_SYSTEM_CALL(result = fd_write(handle,byteptr,len,persev));
  stream = popSTACK();
  if (result<0) { OS_error(); }
  /* Safety check whether persev argument was respected or EOWF was reached: */
  if ((persev == persev_full && !(result==(sintL)len))
      || (persev == persev_partial && !(result>0)))
    error_unwritable(TheSubr(subr_self)->name,stream);
  return byteptr+result;
}

local void low_finish_output_unbuffered_handle (object stream) {
  finish_tty_output(TheHandle(TheStream(stream)->strm_ochannel));
}

local void low_force_output_unbuffered_handle (object stream) {
  force_tty_output(TheHandle(TheStream(stream)->strm_ochannel));
}

local void low_clear_output_unbuffered_handle (object stream) {
  clear_tty_output(TheHandle(TheStream(stream)->strm_ochannel));
}

/* Integer streams
   ---------------

 UP for WRITE-BYTE on File-Streams of Integers, Type a :
 Writes the Bitbuffer-Content to the File. */
local maygc void wr_by_aux_ia_unbuffered (object stream, uintL bitsize,
                                          uintL bytesize) {
  unused(bitsize);
  var uintB* bitbufferptr = TheSbvector(TheStream(stream)->strm_bitbuffer)->data;
  pin_unprotect_varobject(TheStream(stream)->strm_bitbuffer,PROT_READ);
  UnbufferedStreamLow_write_array(stream)(stream,bitbufferptr,bytesize,
                                          persev_full);
  unpin_varobject(TheStream(stream)->strm_bitbuffer);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type au : */
local maygc void wr_by_iau_unbuffered (object stream, object obj) {
  wr_by_ixu_sub(stream,obj,&wr_by_aux_ia_unbuffered);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type as : */
local maygc void wr_by_ias_unbuffered (object stream, object obj) {
  wr_by_ixs_sub(stream,obj,&wr_by_aux_ia_unbuffered);
}

/* WRITE-BYTE - Pseudo-Function for Handle-Streams, Type au, bitsize = 8 : */
local maygc void wr_by_iau8_unbuffered (object stream, object obj) {
  ASSERT_wr_int(stream,obj);
  if (!(posfixnump(obj) && (posfixnum_to_V(obj) < bit(8))))
    error_bad_integer(stream,obj);
  UnbufferedStreamLow_write(stream)(stream,(uintB)posfixnum_to_V(obj));
}

/* WRITE-BYTE-ARRAY - Pseudo-Function for Handle-Streams, Type au, bitsize = 8 : */
local maygc uintL wr_by_array_iau8_unbuffered
(const gcv_object_t* stream_, const gcv_object_t* bytearray_,
 uintL start, uintL len, perseverance_t persev) {
  var object stream = *stream_;
  var uintB* startp = &TheSbvector(*bytearray_)->data[start];
  pin_unprotect_varobject(*bytearray_,PROT_READ);
  var const uintB* endp =
    UnbufferedStreamLow_write_array(stream)(stream,startp,len,persev);
  unpin_varobject(*bytearray_);
  return (endp - startp);
}

/* Character streams
   -----------------

 Three versions, one for each kind of line-terminator: :unix, :mac, :dos.

 WRITE-CHAR - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc void wr_ch_unbuffered_unix (const gcv_object_t* stream_, object ch)
{
  var object stream = *stream_;
  check_wr_char(stream,ch);
  var chart c = char_code(ch); /* Code of the character */
  #ifdef ENABLE_UNICODE
  var uintB buf[max_bytes_per_chart];
  var object encoding = TheStream(stream)->strm_encoding;
  var const chart* cptr = &c;
  var uintB* bptr = &buf[0];
  Encoding_wcstombs(encoding)
    (encoding,stream,&cptr,cptr+1,&bptr,&buf[max_bytes_per_chart]);
  ASSERT(cptr == &c+1);
  var uintL buflen = bptr-&buf[0];
  if (buflen > 0)
    UnbufferedStreamLow_write_array(stream)(stream,&buf[0],buflen,persev_full);
  #else
  UnbufferedStreamLow_write(stream)(stream,as_cint(c));
  #endif
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc void wr_ch_array_unbuffered_unix (const gcv_object_t* stream_,
                                              const gcv_object_t* chararray_,
                                              uintL start, uintL len) {
  var object stream = *stream_;
  var const chart* charptr;
  unpack_sstring_alloca(*chararray_,len,start, charptr=);
  pin_unprotect_varobject(*chararray_,PROT_READ); /*charptr may point to heap*/
  #ifdef ENABLE_UNICODE
  #define tmpbufsize 4096
  var const chart* endptr = charptr + len;
  var uintB tmptmpbuf[tmpbufsize*max_bytes_per_chart];
  do {
    var uintB* bptr = &tmptmpbuf[0];
    var object encoding = TheStream(stream)->strm_encoding;
    Encoding_wcstombs(encoding)(encoding,stream,&charptr,endptr,&bptr,
                                &tmptmpbuf[tmpbufsize*max_bytes_per_chart]);
    var uintL tmptmpbuflen = bptr-&tmptmpbuf[0];
    if (tmptmpbuflen > 0)
      UnbufferedStreamLow_write_array(stream)(stream,&tmptmpbuf[0],
                                              tmptmpbuflen,persev_full);
    stream=*stream_; /* write_array maygc */
  } while (charptr != endptr);
  #undef tmpbufsize
  #else
  var const chart* endptr = (const chart*)UnbufferedStreamLow_write_array(stream)(stream,(const uintB*)charptr,len,persev_full);
  stream=*stream_; /* write_array maygc */
  #endif
  unpin_varobject(*chararray_);
  wr_ss_lpos(stream,endptr,len); /* update Line-Position */
}

/* WRITE-CHAR - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc void wr_ch_unbuffered_mac (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  check_wr_char(stream,ch);
  var chart c = char_code(ch); /* Code of the character */
  if (chareq(c,ascii(NL)))
    c = ascii(CR);
  #ifdef ENABLE_UNICODE
  var uintB buf[max_bytes_per_chart];
  var object encoding = TheStream(stream)->strm_encoding;
  var const chart* cptr = &c;
  var uintB* bptr = &buf[0];
  Encoding_wcstombs(encoding)(encoding,stream,&cptr,cptr+1,&bptr,
                              &buf[max_bytes_per_chart]);
  ASSERT(cptr == &c+1);
  var uintL buflen = bptr-&buf[0];
  if (buflen > 0)
    UnbufferedStreamLow_write_array(stream)(stream,&buf[0],buflen,persev_full);
  #else
  UnbufferedStreamLow_write(stream)(stream,as_cint(c));
  #endif
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc void wr_ch_array_unbuffered_mac (const gcv_object_t* stream_,
                                             const gcv_object_t* chararray_,
                                             uintL start, uintL len) {
  var object stream = *stream_;
  var const chart* charptr;
  unpack_sstring_alloca(*chararray_,len,start, charptr=);
  pin_unprotect_varobject(*chararray_,PROT_READ);
  /* Need a temporary buffer for NL->CR translation. */
  #define tmpbufsize 4096
  var chart tmpbuf[tmpbufsize];
  #ifdef ENABLE_UNICODE
  var uintB tmptmpbuf[tmpbufsize*max_bytes_per_chart];
  var object encoding;
  pushSTACK(TheStream(stream)->strm_encoding);
  #endif
  var uintL remaining = len;
  do {
    var uintL n = remaining;
    if (n > tmpbufsize)
      n = tmpbufsize;
    {
      var chart* tmpptr = &tmpbuf[0];
      var uintL count;
      dotimespL(count,n, {
        var chart c = *charptr++;
        if (chareq(c,ascii(NL)))
          c = ascii(CR);
        *tmpptr++ = c;
      });
      #ifdef ENABLE_UNICODE
      var const chart* cptr = tmpbuf;
      var uintB* bptr = &tmptmpbuf[0];
      encoding = STACK_0;
      Encoding_wcstombs(encoding)(encoding,stream,&cptr,tmpptr,&bptr,
                                  &tmptmpbuf[tmpbufsize*max_bytes_per_chart]);
      ASSERT(cptr == tmpptr);
      var uintL tmptmpbuflen = bptr-&tmptmpbuf[0];
      if (tmptmpbuflen > 0)
        UnbufferedStreamLow_write_array(stream)(stream,&tmptmpbuf[0],
                                                tmptmpbuflen,persev_full);
      #else
      UnbufferedStreamLow_write_array(stream)(stream,(const uintB*)tmpbuf,n,
                                              persev_full);
      #endif
      stream=*stream_; /* write_array maygc */
    }
    remaining -= n;
  } while (remaining > 0);
  #undef tmpbufsize
  #ifdef ENABLE_UNICODE
  skipSTACK(1); /* the encoding */
  #endif
  unpin_varobject(*chararray_);
  wr_ss_lpos(stream,charptr,len); /* update Line-Position */
}

/* WRITE-CHAR - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc void wr_ch_unbuffered_dos (const gcv_object_t* stream_, object ch) {
  var object stream = *stream_;
  check_wr_char(stream,ch);
  var chart c = char_code(ch); /* Code of the character */
  static chart const crlf[2] = { ascii(CR), ascii(LF) };
  #ifdef ENABLE_UNICODE
  var uintB buf[2*max_bytes_per_chart];
  var object encoding = TheStream(stream)->strm_encoding;
  var const chart* cp;
  var uintL n;
  if (chareq(c,ascii(NL))) {
    cp = crlf; n = 2;
  } else {
    cp = &c; n = 1;
  }
  var const chart* cptr = cp;
  var uintB* bptr = &buf[0];
  Encoding_wcstombs(encoding)(encoding,stream,&cptr,cp+n,&bptr,
                              &buf[2*max_bytes_per_chart]);
  ASSERT(cptr == cp+n);
  var uintL buflen = bptr-&buf[0];
  if (buflen > 0)
    UnbufferedStreamLow_write_array(stream)(stream,&buf[0],buflen,persev_full);
  #else
  if (chareq(c,ascii(NL))) {
    UnbufferedStreamLow_write_array(stream)(stream,(const uintB*)crlf,2,persev_full);
  } else {
    UnbufferedStreamLow_write(stream)(stream,as_cint(c));
  }
  #endif
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for Unbuffered-Channel-Streams: */
local maygc void wr_ch_array_unbuffered_dos (const gcv_object_t* stream_,
                                             const gcv_object_t* chararray_,
                                             uintL start, uintL len) {
  var object stream = *stream_;
  var const chart* charptr;
  unpack_sstring_alloca(*chararray_,len,start, charptr=);
  pin_unprotect_varobject(*chararray_,PROT_READ);
  /* Need a temporary buffer for NL->CR/LF translation. */
  #define tmpbufsize 4096
  var chart tmpbuf[2*tmpbufsize];
  #ifdef ENABLE_UNICODE
  var uintB tmptmpbuf[2*tmpbufsize*max_bytes_per_chart];
  var object encoding;
  pushSTACK(TheStream(stream)->strm_encoding);
  #endif
  var uintL remaining = len;
  do {
    var uintL n = remaining;
    if (n > tmpbufsize)
      n = tmpbufsize;
    {
      var chart* tmpptr = &tmpbuf[0];
      var uintL count;
      dotimespL(count,n, {
        var chart c = *charptr++;
        if (chareq(c,ascii(NL))) {
          *tmpptr++ = ascii(CR); *tmpptr++ = ascii(LF);
        } else {
          *tmpptr++ = c;
        }
      });
      #ifdef ENABLE_UNICODE
      var const chart* cptr = tmpbuf;
      var uintB* bptr = &tmptmpbuf[0];
      encoding=STACK_0;
      Encoding_wcstombs(encoding)(encoding,stream,&cptr,tmpptr,&bptr,&tmptmpbuf[2*tmpbufsize*max_bytes_per_chart]);
      ASSERT(cptr == tmpptr);
      var uintL tmptmpbuflen = bptr-&tmptmpbuf[0];
      if (tmptmpbuflen > 0)
        UnbufferedStreamLow_write_array(stream)(stream,&tmptmpbuf[0],
                                                tmptmpbuflen,persev_full);
      #else
      UnbufferedStreamLow_write_array(stream)(stream,(const uintB*)tmpbuf,
                                              tmpptr-&tmpbuf[0],persev_full);
      #endif
      stream=*stream_;
    }
    remaining -= n;
  } while (remaining > 0);
  #undef tmpbufsize
  #ifdef ENABLE_UNICODE
  skipSTACK(1); /* encoding */
  #endif
  unpin_varobject(*chararray_);
  wr_ss_lpos(stream,charptr,len); /* update Line-Position */
}

/* Macro: Emits a shift sequence to let the output conversion descriptor of an
 Unbuffered-Channel-Stream return to the initial state.
 oconv_unshift_output_unbuffered(stream);
 > stream: Unbuffered-Channel-Stream */
#if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
 #define oconv_unshift_output_unbuffered(stream)               \
     if (ChannelStream_oconvdesc(stream) != (iconv_t)0) {      \
       oconv_unshift_output_unbuffered_(stream);               \
     }
local maygc void oconv_unshift_output_unbuffered_ (object stream) {
 #define tmpbufsize 4096
  var uintB tmpbuf[tmpbufsize];
  var char* outptr = (char*)tmpbuf;
  var size_t outsize = tmpbufsize;
  begin_system_call();
  var size_t res =
    iconv(ChannelStream_oconvdesc(stream),NULL,NULL,&outptr,&outsize);
  if (res == (size_t)(-1)) {
    /* BUG: On Windows, after iconv(), we must use errno, not GetLastError(). */
    if (OS_errno == E2BIG) {    /* output buffer too small? */
      NOTREACHED;
    } else {
      OS_error();
    }
  }
  end_system_call();
  var uintL outcount = outptr-(char*)tmpbuf;
  if (outcount > 0)
    UnbufferedStreamLow_write_array(stream)(stream,&tmpbuf[0],
                                            outcount,persev_full);
 #undef tmpbufsize
}
#else
 #define oconv_unshift_output_unbuffered(stream)
#endif

/* UP: Move the pending Output of a Unbuffered-Channel-Stream to the destination.
 finish_output_unbuffered(stream);
 > stream: Handle-Stream
 can trigger GC */
local maygc void finish_output_unbuffered (object stream) {
  pushSTACK(stream);
  oconv_unshift_output_unbuffered(stream);
  stream = popSTACK();
  UnbufferedStreamLow_finish_output(stream)(stream);
}

/* UP: Move the pending Output of a Unbuffered-Channel-Stream to the destination.
 force_output_unbuffered(stream);
 > stream: Handle-Stream
 can trigger GC */
local maygc void force_output_unbuffered (object stream) {
  pushSTACK(stream);
  oconv_unshift_output_unbuffered(stream);
  stream = popSTACK();
  UnbufferedStreamLow_force_output(stream)(stream);
}

/* UP: Delete the pending Output of a Unbuffered-Channel-Stream.
 clear_output_unbuffered(stream);
 > stream: Handle-Stream
 can trigger GC */
local maygc void clear_output_unbuffered (object stream) {
  UnbufferedStreamLow_clear_output(stream)(stream);
}

/* Initializes the output side fields of an unbuffered handle stream.
 UnbufferedHandleStream_output_init(stream); */
#define UnbufferedHandleStream_output_init(stream)     do {             \
  UnbufferedStreamLow_write(stream) = &low_write_unbuffered_handle;     \
  UnbufferedStreamLow_write_array(stream) =                             \
    &low_write_array_unbuffered_handle;                                 \
  UnbufferedStreamLow_finish_output(stream) =                           \
    &low_finish_output_unbuffered_handle;                               \
  UnbufferedStreamLow_force_output(stream) =                            \
    &low_force_output_unbuffered_handle;                                \
  UnbufferedStreamLow_clear_output(stream) =                            \
    &low_clear_output_unbuffered_handle;                                \
 } while (0)

/* Closes a Channel-Stream.
 close_ochannel(stream, abort);
 > stream : Channel-Stream
 > abort: flag: non-0 => ignore errors */
local maygc void close_ochannel (object stream, uintB abort) {
  pushSTACK(stream);
  MAYBE_IGNORE_ERRORS(abort,oconv_unshift_output_unbuffered(stream));
  stream = STACK_0;
  ChannelStreamLow_close(stream)(stream,TheStream(stream)->strm_ochannel,abort);
  stream = popSTACK();
  ChannelStream_fini(stream,abort);
  if (ChannelStream_bitsize(stream) > 0) {
    ChannelStream_bitsize(stream) = 0; /* delete bitsize */
    TheStream(stream)->strm_bitbuffer = NIL; /* free Bitbuffer */
  }
}


/* Unbuffered File-Stream
   ====================== */

/* check if the eltype specifies a binary stream which element size which is
   not a whole multiple of a byte, i.e., a stream which must be buffered */
#define NON_WHOLE_BYTE_P(eltype)                                \
  ((eltype->kind != eltype_ch) && ((eltype->size % 8) != 0))

/* UP: Checks an Element-Type for an Unbuffered-Stream
 check_unbuffered_eltype(&eltype);
 > eltype: Element-Type in decoded form */
local void check_unbuffered_eltype (const decoded_el_t* eltype) {
  if (NON_WHOLE_BYTE_P(eltype)) {
    pushSTACK(canon_eltype(eltype));
    pushSTACK(S(Kelement_type));
    error(error_condition,GETTEXT("Unbuffered streams need an ~S with a bit size being a multiple of 8, not ~S"));
  }
}
#define CHECK_UNBUFFERED_ELTYPE(buffered,direction,eltype)              \
  if ((direction == DIRECTION_INPUT && buffered == BUFFERED_NIL)        \
      || (direction == DIRECTION_OUTPUT && buffered != BUFFERED_T))     \
    check_unbuffered_eltype(&eltype)

/* UP: Fills in the pseudofunctions for an unbuffered stream.
 fill_pseudofuns_unbuffered(stream,&eltype);
 > stream: stream being built up, with correct strmflags and encoding
 > eltype: Element-Type in decoded form */
local void fill_pseudofuns_unbuffered (object stream,
                                       const decoded_el_t* eltype) {
  var uintB flags = TheStream(stream)->strmflags;
  stream_dummy_fill(stream);
  if (flags & strmflags_rd_B) {
    if (eltype->kind==eltype_ch) {
      TheStream(stream)->strm_rd_ch = P(rd_ch_unbuffered);
      TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_unbuffered);
    } else {
      TheStream(stream)->strm_rd_by =
        (eltype->kind == eltype_iu
         ? (eltype->size == 8
            ? P(rd_by_iau8_unbuffered)
            : P(rd_by_iau_unbuffered))
         : P(rd_by_ias_unbuffered));
      TheStream(stream)->strm_rd_by_array =
        ((eltype->kind == eltype_iu) && (eltype->size == 8)
         ? P(rd_by_array_iau8_unbuffered)
         : P(rd_by_array_dummy));
    }
  }
  if (flags & strmflags_wr_B) {
    if (eltype->kind == eltype_ch) {
      var object eol = TheEncoding(TheStream(stream)->strm_encoding)->enc_eol;
      if (eq(eol,S(Kunix))) {
        TheStream(stream)->strm_wr_ch =
          TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_unbuffered_unix);
        TheStream(stream)->strm_wr_ch_array =
          TheStream(stream)->strm_wr_ch_array_npnl =
          P(wr_ch_array_unbuffered_unix);
      } else if (eq(eol,S(Kmac))) {
        TheStream(stream)->strm_wr_ch =
          TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_unbuffered_mac);
        TheStream(stream)->strm_wr_ch_array =
          TheStream(stream)->strm_wr_ch_array_npnl =
          P(wr_ch_array_unbuffered_mac);
      } else if (eq(eol,S(Kdos))) {
        TheStream(stream)->strm_wr_ch =
          TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_unbuffered_dos);
        TheStream(stream)->strm_wr_ch_array =
          TheStream(stream)->strm_wr_ch_array_npnl =
          P(wr_ch_array_unbuffered_dos);
      } else
        NOTREACHED;
    } else {
      TheStream(stream)->strm_wr_by =
        (eltype->kind == eltype_iu
         ? (eltype->size == 8
            ? P(wr_by_iau8_unbuffered)
            : P(wr_by_iau_unbuffered))
         : P(wr_by_ias_unbuffered));
      TheStream(stream)->strm_wr_by_array =
        ((eltype->kind == eltype_iu) && (eltype->size == 8)
         ? P(wr_by_array_iau8_unbuffered)
         : P(wr_by_array_dummy));
      TheStream(stream)->strm_wr_ch =
        TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_error);
      TheStream(stream)->strm_wr_ch_array =
        TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_error);
    }
  }
}

#define READ_P(dir)  ((dir) & bit(0)) /* readable */
#define RO_P(dir)    ((dir) & bit(1)) /* immutable */
#define WRITE_P(dir) ((dir) & bit(2)) /* writable */
#define DIRECTION_FLAGS(dir)                                                \
  ((READ_P(dir) ? strmflags_rd_B : 0)  /* permits READ-CHAR, READ-BYTE */ \
 | (WRITE_P(dir) ? strmflags_wr_B : 0) /* permits WRITE-CHAR, WRITE-BYTE */ \
 | (RO_P(dir) ? strmflags_immut_B : 0)) /* immutable object */

#define ELTYPE_FLAFS(eltype)                                    \
  (strmflags_immut_B | (eltype->kind == eltype_ch               \
                        ? strmflags_ch_B : strmflags_by_B))


/* UP: creates an Unbuffered-Channel-Stream
 make_unbuffered_stream(type,direction,&eltype,handle_regular,handle_tty)
 > STACK_2: Encoding
 > STACK_1: Element-Type
 > STACK_0: Handle of the opened File
 > type: stream type
 > direction: direction_t (see lispbibl.d)
 > eltype: Element-Type in decoded form
 > handle_regular: whether the handle refers to a regular file
 > handle_tty: if the Handle is a tty (only necessary if direction & bit(0))
 < result: File-Handle-Stream, Handle_{input,output}_init still needs to be called
 < STACK: cleaned up
 can trigger GC */
local maygc object make_unbuffered_stream
(uintB type, direction_t direction, const decoded_el_t* eltype,
 bool handle_regular, bool handle_tty) {
  var uintB flags = DIRECTION_FLAGS(direction) & ELTYPE_FLAFS(eltype);
  /* allocate Stream: */
  var object stream = allocate_stream(flags,type,strm_channel_len,
                                      sizeof(strm_unbuffered_extrafields_t));
  /* and fill: */
  TheStream(stream)->strm_encoding = STACK_2;
  fill_pseudofuns_unbuffered(stream,eltype);
  ChannelStream_ignore_next_LF(stream) = false;
  TheStream(stream)->strm_wr_ch_lpos = Fixnum_0; /* Line Position := 0 */
  {
    var object handle = popSTACK();
    if (READ_P(direction))
      TheStream(stream)->strm_ichannel = handle; /* enter Handle */
    if (WRITE_P(direction))
      TheStream(stream)->strm_ochannel = handle; /* enter Handle */
    if (type == strmtype_file)
      TheStream(stream)->strm_buffered_channel = handle; /* enter Handle */
  }
  /* enter Flag isatty = (handle_tty ? T : NIL) : */
  TheStream(stream)->strm_isatty = (handle_tty ? T : NIL);
  TheStream(stream)->strm_eltype = popSTACK();
  ChannelStream_buffered(stream) = false;
  ChannelStream_regular(stream) = handle_regular;
  ChannelStream_init(stream);
  /* element-type dependent initializations: */
  ChannelStream_bitsize(stream) = eltype->size;
  ChannelStream_lineno(stream) = 1; /* initialize always (cf. set-stream-element-type) */
  if (!(eltype->kind == eltype_ch)) {
  /* File-Stream for Integers
   allocate Bitbuffer: */
    pushSTACK(stream);
    var object bitbuffer = allocate_bit_vector(Atype_Bit,eltype->size);
    stream = popSTACK();
    TheStream(stream)->strm_bitbuffer = bitbuffer;
  }
  skipSTACK(1);
  return stream;
}


/* File-Stream
   ===========

 In order to not have to bestir the UNIX for each Character,
 our own Buffer is maintained.
 (This caused e.g. for the Consumption of a 408 KByte- File on an Atari
 an acceleration by a Factor of 2.7 from 500 sec to 180 sec.)

 Additional fields:
  define strm_file_name        strm_field1   - Filename, a pathname or NIL
  define strm_file_truename    strm_field2   - Truename, a non-logical pathname or NIL
  define strm_buffered_channel strm_ochannel - a wrapped Handle
  define strm_buffered_bufflen 4096 - buffer length, a power of 2, <2^16
 our own buffer, a simple-bit-vector with strm_buffered_bufflen bytes: */
#define strm_buffered_buffer strm_buffer

/* Additional binary (not GCed) fields: */
typedef struct strm_buffered_extrafields_t {
  strm_channel_extrafields_t _parent;
  uintL (* low_fill)  (object stream, perseverance_t persev);
  void  (* low_flush) (object stream, uintL bufflen);
  uoff_t buffstart _attribute_in_misaligned_varobjects_; /* start position of buffer */
  uintL endvalid;      /* index up to which the data is known to be valid */
  uintL index;         /* index into buffer (>=0, <=endvalid) */
  /*bool*/int have_eof_p : 8; /* indicates that eof is right after endvalid */
  /*bool*/int modified : 8;   /* true if the buffer contains modified data,
    else false */
  /*bool*/int blockpositioning : 8; /* whether the handle refers to a regular
                                   file and permits to position the buffer at
                           buffstart = (sector number) * strm_buffered_bufflen
   endvalid always indicates how much of the buffer contains data
   have_eof_p = true indicates that the EOF is known to be at the
      endvalid position.  It could be there without have_eof_p being true,
      but it will be discovered by the next buffered_nextbyte() then
   buffstart = (sector number) * strm_buffered_bufflen,
               if blockpositioning permitted.
   The position of handle, known to the OS, set via lseek, is normally
   (but not always!) the end of the current buffer.  More importantly,
   before flushing the buffer to disk, the handle is lseek()ed to
   buffstart, which ensures data is written where it should be.  This
   then leaves the position at the correct point for subsequent reads.
 Up to now a file is considered built from bytes of 8 bits.
 Logically, it is built up from other units: */
  uoff_t position _attribute_in_misaligned_varobjects_; /* position in logical units */
} strm_buffered_extrafields_t;

/* More fields in file streams with element type INTEGER, type ib or ic. */
typedef struct strm_i_buffered_extrafields_t {
  strm_buffered_extrafields_t _parent;
  /* If bitsize is not a multiple of 8: */
  uintL bitindex;               /* index in the current byte, >=0, <=8 */
  /* The buffer contains 8*index+bitindex bits. The bits are ordered in the
   order bit0,....,bit7. If bitsize<8, the length of the file (measured in
   bits) is stored in the first 4 bytes of the files [in little-endian order]
   when the file is closed. The actual data then begins in the 5th byte. */
  uoff_t eofposition _attribute_in_misaligned_varobjects_; /* position of logical EOF */
} strm_i_buffered_extrafields_t;

/* In closed file streams only the fields `name' and `truename' are relevant. */

/* Accessors. */
#define FileStream_name(stream)  TheStream(stream)->strm_file_name
#define FileStream_truename(stream)  TheStream(stream)->strm_file_truename
#define BufferedStream_channel(stream) TheStream(stream)->strm_buffered_channel
#define BufferedStream_buffer(stream)  TheStream(stream)->strm_buffered_buffer
#define BufferedStream_buffer_address(stream,shift) \
  (&TheSbvector(BufferedStream_buffer(stream))->data[shift])
#define BufferedStreamLow_fill(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_fill
#define BufferedStreamLow_flush(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->low_flush
#define BufferedStream_buffstart(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->buffstart
#define BufferedStream_endvalid(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->endvalid
#define BufferedStream_index(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->index
#define BufferedStream_have_eof_p(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->have_eof_p
#define BufferedStream_modified(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->modified
#define BufferedStream_blockpositioning(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->blockpositioning
#define BufferedStream_position(stream)  \
  ((strm_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->position
#define BufferedStream_bitindex(stream)  \
  ((strm_i_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->bitindex
#define BufferedStream_eofposition(stream)  \
  ((strm_i_buffered_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)->eofposition

#define Truename_or_Self(stream)                                  \
 (nullp(TheStream(stream)->strm_file_truename) ? (object)stream : \
  (object)TheStream(stream)->strm_file_truename)

#define ChannelStream_ihandle(obj)                                      \
  TheHandle(ChannelStream_buffered(obj) ? BufferedStream_channel(obj)   \
            : ChannelStream_ichannel(obj))
#define ChannelStream_ohandle(obj)                                      \
  TheHandle(ChannelStream_buffered(obj) ? BufferedStream_channel(obj)   \
            : ChannelStream_ochannel(obj))

/* File-Stream in general
   ====================== */

#ifdef UNIX
/* Assumption: All File-Descriptors delivered by OPEN(2)  (called Handles
 here) fit in an uintW.
 Substantiation: as is generally known: 0 <= fd < getdtablesize() . */
#endif

/* Note about regular and non-regular files:
 - For regular files that were opened with O_RDONLY or O_RDWR but not O_WRONLY,
   we assume that it makes sense to read a block, modify it, reposition the
   handle back to the beginning of the block and write it back.
 - For regular files opened with O_WRONLY, we use a simple output buffer.
 - For non-regular files, we don't call handle_lseek. Therefore mixed I/O is
   not possible. Only input-only and output-only modes are possible.

 position the Handle:
 handle_lseek(stream,handle,offset,mode,result_assignment);
 stream_ should be pointer to GC safe location (since the call itself is
 surrounded by GC safe region - multithreading).
 > mode: Positioning-Mode:
         SEEK_SET  "absolute"
         SEEK_CUR  "relative"
         SEEK_END  "at the end"
 < result: new Position */
#if defined(UNIX) || defined(WIN32_NATIVE)
  #define fd_lseek(stream_,fd,offset,mode,result_assignment)    \
    { var off_t result = lseek(fd,offset,mode);                \
      if (result<0) /* error occurred? */                      \
        { end_blocking_system_call(); OS_filestream_error(*stream_); }    \
      unused (result_assignment result);                       \
    }
  #define handle_lseek(stream_,fd,offset,mode,result_assignment) \
    fd_lseek(stream_,fd,offset,mode,result_assignment)
#endif

/* UP: Fills the buffer, up to strm_buffered_bufflen bytes.
 low_fill_buffered_handle(stream,persev)
 > stream: (open) byte-based file stream
 > persev: one of persev_partial, persev_immediate, persev_bonus
 < result: number of bytes read */
local maygc uintL low_fill_buffered_handle (object stream, perseverance_t persev) {
  var Handle handle = TheHandle(BufferedStream_channel(stream));
  var uintB* buff = BufferedStream_buffer_address(stream,0);
  /* On regular file handles, persev_immediate and persev_bonus are effectively
   equivalent to persev_partial. Transforming persev_immediate, persev_bonus
   here 1) avoids useless system calls for poll(), select() or non-blocking
   I/O and 2) improves EOF detection. */
  if ((persev == persev_immediate || persev == persev_bonus)
      && ChannelStream_regular(stream))
    persev = persev_partial;
  if ((TheStream(stream)->strmflags & strmflags_rd_B) == 0
      && !ChannelStream_regular(stream))
    return 0; /* wronly stream to a special device, handle is O_WRONLY */
  pin_unprotect_varobject(BufferedStream_buffer(stream),PROT_READ_WRITE);
  pushSTACK(stream);
  var ssize_t result;
  GC_SAFE_SYSTEM_CALL(result = fd_read(handle,buff,strm_buffered_bufflen,persev));
  stream = popSTACK();
  unpin_varobject(BufferedStream_buffer(stream));
  if (result<0)               /* error occurred? */
    OS_filestream_error(stream);
  if (result==0 && fd_error_eof_p())
    BufferedStream_have_eof_p(stream) = true;
  return result;
}

/* Functions for writing the buffer.
 low_flush_buffered_handle(stream,bufflen);
 buffered_flush(stream);
 These are called only if the buffer is modified.
 Of course, the buffer is modified only by the WRITE-BYTE/WRITE-CHAR
 operations. */

/* UP: Finishes the Writing-Back of the Buffers.
 low_flush_buffered_handle(stream,bufflen);
 > stream : (open) Byte-based File-Stream.
 > bufflen : Number of Bytes to be written
 < modified_flag of stream : deleted
 changed in stream: index */
local maygc void low_flush_buffered_handle (object stream, uintL bufflen) {
  var Handle handle = TheHandle(BufferedStream_channel(stream));
  var uintB* buff = BufferedStream_buffer_address(stream,0);
  pin_unprotect_varobject(BufferedStream_buffer(stream),PROT_READ);
  pushSTACK(stream);
  var ssize_t result;
  GC_SAFE_SYSTEM_CALL(result = full_write(handle,buff,bufflen));
  stream = popSTACK();
  unpin_varobject(BufferedStream_buffer(stream));
  if (result==bufflen) { /* everything written correctly */
    BufferedStream_modified(stream) = false;
  } else { /* not everything written */
    #ifdef UNIX
    if (result<0) /* error occurred? */
      #ifdef ENOSPC
      if (!(errno == ENOSPC))
      #endif
        #ifdef EDQUOT
        if (!(errno == EDQUOT))
        #endif
          { OS_filestream_error(stream); }
    #endif
    #if defined(WIN32_NATIVE)
    if (result<0) { /* error occurred? */
      OS_filestream_error(stream);
    }
    #endif
    /* Not everything was written, probably because of full disk.
     In order to avoid inconsistencies, must close the file. */
    BufferedStream_modified(stream) = false; /* data is lost! */
    pushSTACK(stream);
    builtin_stream_close(&STACK_0,0); /* file close */
    clr_break_sem_4(); /* no more UNIX operations are active */
    /* Report the error. */
    pushSTACK(Truename_or_Self(STACK_0)); /* FILE-ERROR slot PATHNAME */
    pushSTACK(STACK_(0+1)); /* stream */
    error(file_error,GETTEXT("Closed ~S because disk is full."));
  }
}

#define BufferedHandleStream_init(stream)  \
  { BufferedStreamLow_fill(stream) = &low_fill_buffered_handle;   \
    BufferedStreamLow_flush(stream) = &low_flush_buffered_handle; \
  }

/* UP: Writes the modified Buffer back.
 buffered_flush(stream);
 > stream : (open) Byte-based File-Stream.
 < modified_flag of stream : deleted
 changed in stream: index */
local maygc void buffered_flush (object stream) {
  if (BufferedStream_blockpositioning(stream)) {
    var Handle handle = TheHandle(BufferedStream_channel(stream));
    var uoff_t buffstart = BufferedStream_buffstart(stream);
    pushSTACK(stream);
    begin_blocking_system_call();
    handle_lseek(&STACK_0,handle,buffstart,SEEK_SET,); /* positioning back */
    end_blocking_system_call();
    stream = popSTACK();
  }
  BufferedStreamLow_flush(stream)(stream,BufferedStream_endvalid(stream));
}

/* UP: Positions a Byte-based File-Stream, so the next Byte can be
 read or overwritten.
 buffered_nextbyte(stream,persev)
 > stream : (open) Byte-based File-Stream.
 > persev: one of persev_partial, persev_immediate, persev_bonus
 < result : 0 = EOF (the next byte can be written, not read)
            -1 = would block (only if not persev_partial, next byte cannot yet
                 be read or written)
            else Pointer to the next Byte (can be read or written)
 changed in stream: index, endvalid, have_eof_p, buffstart */
local maygc uintB* buffered_nextbyte (object stream, perseverance_t persev) {
  var sintL endvalid = BufferedStream_endvalid(stream);
  var uintL index = BufferedStream_index(stream);
  if ((endvalid == index) && !BufferedStream_have_eof_p(stream)) {
    pushSTACK(stream);
    /* Buffer must be newly filled. */
    if (BufferedStream_modified(stream)) {
      /* First, the Buffer must be flushed out: */
      buffered_flush(stream); /* FIXME: buffered_flush() may hang! */
      stream = STACK_0; /* flush maygc */
    }
    BufferedStream_buffstart(stream) += endvalid;
    var uintL result;
    if (BufferedStream_blockpositioning(stream)
        || (TheStream(stream)->strmflags & strmflags_rd_B)) {
      result = BufferedStreamLow_fill(stream)(stream,persev);
      stream = popSTACK(); /* fill maygc */
      if (result == 0 && !BufferedStream_have_eof_p(stream)
          && persev != persev_partial)
        return (uintB*)-1; /* would hang */
    } else {
      skipSTACK(1); /* saved stream */
      result = 0;
    }
    BufferedStream_index(stream) = index = 0;
    BufferedStream_modified(stream) = false;
    BufferedStream_endvalid(stream) = endvalid = result;
    if (result == 0)
      BufferedStream_have_eof_p(stream) = true;
  }
  if (index < endvalid)
    return BufferedStream_buffer_address(stream,index);
  else if (BufferedStream_have_eof_p(stream))
    return (uintB*)NULL; /* EOF reached */
  else
    NOTREACHED;
}

/* UP: Prepares the writing of a Byte at EOF.
 buffered_eofbyte(stream);
 > stream : (open) Byte-based File-Stream, for which
            currently  buffered_nextbyte(stream)==NULL  is true.
 < result : Pointer to the next (free) Byte
 changed in stream: index, endvalid, buffstart */
local maygc uintB* buffered_eofbyte (object stream) {
  /* EOF.  endvalid=index. */
  ASSERT(BufferedStream_have_eof_p(stream));
  if (BufferedStream_endvalid(stream) == strm_buffered_bufflen) {
    /* Buffer must be filled newly. Because after that EOF will occur anyway,
     it is sufficient, to flush the Buffer out: */
    if (BufferedStream_modified(stream)) {
      pushSTACK(stream);
      buffered_flush(stream);
      stream = popSTACK();
    }
    BufferedStream_buffstart(stream) += strm_buffered_bufflen;
    BufferedStream_endvalid(stream) = 0;
    BufferedStream_index(stream) = 0; /* index := 0 */
    BufferedStream_modified(stream) = false; /* unmodified */
  }
  /* increase endvalid: */
  BufferedStream_endvalid(stream) += 1;
  return BufferedStream_buffer_address(stream,BufferedStream_index(stream));
}

/* UP: Writes a Byte to a Byte-based File-Stream.
 buffered_writebyte(stream,b);
 > stream : (open) Byteblock-based File-Stream.
 > b : Byte to be written
 changed in stream: index, endvalid, buffstart */
local maygc void buffered_writebyte (object stream, uintB b) {
  pushSTACK(stream);
  var uintB* ptr = buffered_nextbyte(stream,persev_partial);
  stream = STACK_0;
  if (!(ptr == (uintB*)NULL)) {
    if (*ptr == b) /* no real Modification? */
      goto no_modification;
  } else {
    ptr = buffered_eofbyte(stream); /* EOF -> make room for 1 Byte */
    stream = STACK_0;
  }
  /* write next Byte in the Buffer: */
  *ptr = b; BufferedStream_modified(stream) = true;
 no_modification:
  skipSTACK(1);
  /* increment index */
  BufferedStream_index(stream) += 1;
}

/* File-Stream, Byte-based (b_file)
   ===========  ==========

 error-message because of positioning behind EOF.
 error_position_beyond_EOF(stream); */
local _Noreturn void error_position_beyond_EOF (object stream) {
  pushSTACK(Truename_or_Self(stream)); /* FILE-ERROR slot PATHNAME */
  pushSTACK(stream);
  error(file_error,GETTEXT("cannot position ~S beyond EOF"));
}

/* UP: Positions an (open) Byte-based File-Stream to a
 specified Position.
 position_file_buffered(stream,position);
 > stream : (open) Byte-based File-Stream.
 > position : new Position
 changed in stream: index, endvalid, buffstart */
local maygc void position_file_buffered (object stream, uoff_t position) {
  /* Is the new Position in the same Sector? */
  {
    var uintL endvalid = BufferedStream_endvalid(stream);
    var uoff_t newindex = position - BufferedStream_buffstart(stream);
    if (newindex <= endvalid) { /* yes -> only index has to be changed: */
      BufferedStream_index(stream) = newindex;
      return;
    }
  }
  pushSTACK(stream);
  /* poss. flush Buffer: */
  if (BufferedStream_modified(stream)) {
    buffered_flush(stream);
    stream = STACK_0; /* restore stream in case of GC during blocking*/
  }
  var Handle handle = TheHandle(BufferedStream_channel(stream));
  /* Now modified_flag is deleted. */
  if (!BufferedStream_blockpositioning(stream)) { /* Positioning: */
    begin_blocking_system_call();
    handle_lseek(&STACK_0,handle,position,SEEK_SET,);
    end_blocking_system_call();
    stream = STACK_0;
    BufferedStream_buffstart(stream) = position;
    BufferedStream_endvalid(stream) = 0;
    BufferedStream_index(stream) = 0; /* index := 0 */
    BufferedStream_modified(stream) = false; /* unmodified */
    BufferedStream_have_eof_p(stream) = false;
  } else {
    var uoff_t oldposition = BufferedStream_buffstart(stream) + BufferedStream_index(stream);
    /* Positioning: */
    {
      var uoff_t newposition;
      begin_blocking_system_call();
      handle_lseek(&STACK_0,handle,
                   floor(position,strm_buffered_bufflen)*strm_buffered_bufflen,
                   SEEK_SET,newposition=);
      end_blocking_system_call();
      stream = STACK_0;
      BufferedStream_buffstart(stream) = newposition;
    }
    /* read Sector: */
    BufferedStream_endvalid(stream) = 0;
    BufferedStream_index(stream) = 0; /* index := 0 */
    BufferedStream_modified(stream) = false; /* unmodified */
    BufferedStream_have_eof_p(stream) = false;
    var uintL newindex = position % strm_buffered_bufflen; /* desired Index in the Sector */
    if (newindex!=0) { /* Position between Sectors -> nothing needs to be read */
      buffered_nextbyte(stream,persev_partial);
      stream = STACK_0;
      /* index=0; set index to (position mod bufflen), but check first: */
      var uintL endvalid = BufferedStream_endvalid(stream);
      /* newindex must be in the valid range */
      if (newindex > endvalid) {
        /* Error. But first position back to the old Position: */
        check_SP();
        position_file_buffered(stream,oldposition); /* position back */
        stream = popSTACK(); /* error will not return */
        error_position_beyond_EOF(stream);
      }
      BufferedStream_index(stream) = newindex;
    }
  }
  skipSTACK(1);
}

/* UP: flushes pending write (if any), moves OS file pointer so
 that there's no more preread data in the buffer to use the handle.
 sync_file_buffered(stream,position);
 > stream : (open) Byte-based File-Stream.
 changed in stream: index, endvalid, buffstart */
local maygc void sync_file_buffered (object stream) {
  var uoff_t position = BufferedStream_buffstart(stream)+BufferedStream_index(stream);
  var Handle handle = TheHandle(BufferedStream_channel(stream));
  pushSTACK(stream);
  /* poss. flush Buffer: */
  if (BufferedStream_modified(stream)) {
    buffered_flush(stream);
    stream = STACK_0;
  }
  /* Now modified_flag is deleted. */
  begin_blocking_system_call();
  handle_lseek(&STACK_0,handle,position,SEEK_SET,);
  end_blocking_system_call();
  stream = popSTACK();
  /* ampy: don't respect blockpositioning, acceptable ? */
  BufferedStream_buffstart(stream) = position;
  BufferedStream_endvalid(stream) = 0;
  BufferedStream_index(stream) = 0; /* index == endvalid, next read will refill the buffer */
  BufferedStream_modified(stream) = false; /* unmodified */
  BufferedStream_have_eof_p(stream) = false;
}

/* UP: Reads an Array of Bytes from an (open) Byte-based
 File-Stream.
 read_byte_array_buffered(stream,byteptr,len,persev)
 > stream : (open) Byte-based File-Stream.
 > byteptr[0..len-1] : place
 > len : > 0
 > persev: how to react on incomplete I/O
 < byteptr[0..count-1] : read Bytes.
 < result: &byteptr[count] (with count = len, or count < len if EOF reached)
 changed in stream: index, endvalid, buffstart */
local maygc uintB* read_byte_array_buffered
(object stream, uintB* byteptr, uintL len, perseverance_t persev) {
  pushSTACK(stream);
  for (;;) {
    var uintB* ptr = buffered_nextbyte(stream, persev == persev_full ? persev_partial : persev);
    if (ptr == (uintB*)NULL || ptr == (uintB*)-1)
      break;
    stream = STACK_0; /* restore stream */
    var uintL endvalid = BufferedStream_endvalid(stream);
    var uintL available = endvalid - BufferedStream_index(stream);
    if (available > len)
      available = len;
    /* copy all available bytes: */
    copy_mem_b(byteptr,ptr,available);
    byteptr += available;
    /* increment index: */
    BufferedStream_index(stream) += available;
    len -= available;
    if (len == 0)
      break;
    if (available > 0) {
      if (persev == persev_partial)
        persev = persev_bonus;
      #if defined(UNIX) || defined(WIN32_NATIVE)
      if (persev == persev_immediate || persev == persev_bonus)
        /* There's no need to continue the loop, with persev_immediate or
         persev_bonus, because if read() has returned a partial result, it
         means that nothing more is immediately available. (The OS doesn't
         gratuitously return less bytes to read() than available. Except when
         the system call was interrupted by a signal; but this can't happen
         because install_signal_handler() is careful to ensure restartable
         system calls.) */
        break;
      #endif
    }
  }
  skipSTACK(1);
  return byteptr;
}

/* UP: Writes an Array of Bytes to an (open) Byte-based
 File-Stream.
 write_byte_array_buffered(stream,byteptr,len,persev)
 > stream : (open) Byte-based File-Stream.
 > byteptr[0..len-1] : Bytes to be written.
 > len : > 0
 > persev: how to react on incomplete I/O
 < result: &byteptr[len]
 changed in stream: index, endvalid, buffstart */
local maygc const uintB* write_byte_array_buffered
(object stream, const uintB* byteptr, uintL len, perseverance_t persev) {
  var uintL remaining = len;
  var uintB* ptr;
  pushSTACK(stream);
  for (;;) { /* still remaining>0 Bytes to be filled. */
    ptr = buffered_nextbyte(stream, persev == persev_full ? persev_partial : persev);
    stream = STACK_0;
    if (ptr == (uintB*)NULL)
      goto eof_reached;
    if (ptr == (uintB*)-1) return byteptr;
    var uintL endvalid = BufferedStream_endvalid(stream);
    var uintL next = /* as many as still fit in the Buffer or until EOF */
      endvalid - BufferedStream_index(stream); /* > 0 ! */
    if (next > remaining)
      next = remaining;
    { /* copy next Bytes in the Buffer: */
      var uintL count;
      dotimespL(count,next, {
        var uintB b = *byteptr++; /* next Byte */
        if (!(*ptr == b)) {
          *ptr = b; BufferedStream_modified(stream) = true; /* in the Buffer */
        }
        ptr++;
      });
    }
    remaining = remaining - next;
    /* increment index */
    BufferedStream_index(stream) += next;
    if (remaining == 0)
      break;
    if (next > 0) {
      if (persev == persev_partial)
        persev = persev_bonus;
      #if defined(UNIX) || defined(WIN32_NATIVE)
      if (persev == persev_immediate || persev == persev_bonus)
        /* There's no need to continue the loop, with persev_immediate or
         persev_bonus, because if write() has returned a partial result, it
         means that nothing more is immediately accepted. (The OS doesn't
         gratuitously return less bytes to write() than it can. Except when
         the system call was interrupted by a signal; but this can't happen
         because install_signal_handler() is careful to ensure restartable
         system calls.) */
        break;
      #endif
    }
  }
  if (false) {
  eof_reached: /* Write at EOF, endvalid = index */
    do { /* Still remaining>0 Bytes to file. */
      var uintL next = /* as many as there is still room in the Buffer */
        strm_buffered_bufflen - BufferedStream_index(stream);
      if (next==0) {
        /* Buffer must be filled newly. After that, EOF arrives anyway,
         so it is sufficient to flush the buffer: */
        if (BufferedStream_modified(stream)) {
          buffered_flush(stream);
          stream = STACK_0;
        }
        BufferedStream_buffstart(stream) += strm_buffered_bufflen;
        BufferedStream_endvalid(stream) = 0;
        BufferedStream_index(stream) = 0; /* index := 0 */
        BufferedStream_modified(stream) = false; /* unmodified */
        /* Then try again: */
        next = strm_buffered_bufflen;
      }
      if (next > remaining)
        next = remaining;
      /* copy the next bytes in the buffer: */
      copy_mem_b(BufferedStream_buffer_address(stream,BufferedStream_index(stream)),
                 byteptr,next);
      byteptr += next;
      BufferedStream_modified(stream) = true;
      remaining = remaining - next;
      /* increment index and endvalid */
      BufferedStream_index(stream) += next;
      BufferedStream_endvalid(stream) += next;
    } while (remaining != 0);
  }
  skipSTACK(1);
  return byteptr;
}

/* File-Stream of Characters
   ==========================

 Input side
 ----------

 READ-CHAR - Pseudo-Function for File-Streams of Characters */
local maygc object rd_ch_buffered (const gcv_object_t* stream_) {
 rd_ch_buffered_retry:
  var uintB* bufferptr = buffered_nextbyte(*stream_,persev_partial);
  var object stream = *stream_;
  if (bufferptr == (uintB*)NULL) /* EOF ? */
    return eof_value;
  /* fetch next character: */
  var chart c;
  #ifdef ENABLE_UNICODE
  var object encoding = TheStream(stream)->strm_encoding;
  { /* Does the buffer contain a complete character? */
    var uintL endvalid = BufferedStream_endvalid(stream);
    var uintL available = endvalid - BufferedStream_index(stream);
    var const uintB* bptr = bufferptr;
    var chart* cptr = &c;
    Encoding_mbstowcs(encoding)
      (encoding,stream,&bptr,bufferptr+available,&cptr,&c+1);
    if (cptr == &c+1) {
      var uintL n = bptr-bufferptr;
      /* increment index and position */
      BufferedStream_index(stream) += n;
      BufferedStream_position(stream) += n;
    } else {
      var uintB buf[max_bytes_per_chart];
      var uintL buflen = 0;
      pushSTACK(encoding);
      while (1) {
        ASSERT(buflen < max_bytes_per_chart);
        buf[buflen++] = *bufferptr;
        /* increment index and position */
        BufferedStream_index(stream) += 1;
        BufferedStream_position(stream) += 1;
        var const uintB* bptr = &buf[0];
        var chart* cptr = &c;
        Encoding_mbstowcs(encoding)(encoding,stream,&bptr,&buf[buflen],&cptr,cptr+1);
        if (cptr == &c) {
          /* Not a complete character.
           Shift the buffer */
          if (!(bptr == &buf[0])) {
            var const uintB* ptr1 = bptr;
            var uintB* ptr2 = &buf[0];
            while (ptr1 != &buf[buflen]) { *ptr2++ = *ptr1++; }
            buflen = ptr2 - &buf[0];
          }
        } else {
          /* Read a complete character. */
          if (!(bptr == &buf[buflen])) {
            /* At most one lookahead byte. Make it unread. */
            ASSERT(bptr == &buf[buflen-1]);
            /* decrement index and position again: */
            BufferedStream_index(stream) -= 1;
            BufferedStream_position(stream) -= 1;
          }
          break;
        }
        bufferptr = buffered_nextbyte(stream,persev_partial);
        if (bufferptr == (uintB*)NULL)
          return eof_value;
        stream = *stream_; /* restore stream */
        encoding = STACK_0;
      }
      skipSTACK(1);
    }
  }
  #else
  c = as_chart(*bufferptr); /* Character from the Buffer */
  /* increment index and position */
  BufferedStream_index(stream) += 1;
  BufferedStream_position(stream) += 1;
  #endif
  if (chareq(c,ascii(NL))) {
    if (ChannelStream_ignore_next_LF(stream)) {
      ChannelStream_ignore_next_LF(stream) = false;
      goto rd_ch_buffered_retry;
    }
    ChannelStream_lineno(stream) += 1;
  } else if (chareq(c,ascii(CR))) {
    ChannelStream_ignore_next_LF(stream) = true;
    c = ascii(NL);
    ChannelStream_lineno(stream) += 1;
  }
  return code_char(c);
}

/* Determines, if a character is available on a File-Stream.
 listen_char_buffered(stream)
 > stream: File-Stream of Characters
 < result: input availability */
local maygc listen_t listen_char_buffered (object stream) {
 listen_char_buffered_retry:
  pushSTACK(stream);
  var uintB* buf = buffered_nextbyte(stream,persev_immediate);
  stream = popSTACK();
  if (buf == (uintB*)NULL) return LISTEN_EOF; /* EOF */
  if (buf == (uintB*)-1)   return LISTEN_WAIT; /* will hang */
  if (*buf == '\n' && ChannelStream_ignore_next_LF(stream)) { /* discard LF */
    /* assume that '\n' is LF in all encodings */
    BufferedStream_index(stream) += 1;
    BufferedStream_position(stream) += 1;
    ChannelStream_ignore_next_LF(stream) = false;
    goto listen_char_buffered_retry;
    /* we might extract rd_ch_buffered_low from above instead,
       but it seems too much work for little gain */
  }
  /* In case of ENABLE_UNICODE, the presence of a byte does not guarantee the
   presence of a multi-byte character. Returning LISTEN_AVAIL here is
   therefore not correct. But this doesn't matter since programs seeing
   LISTEN_AVAIL will call read-char, and this will do the right thing anyway. */
  return LISTEN_AVAIL;
}

/* UP: discard already entered input from a Buffered Stream.
 clear_input_buffered(stream);
 > stream: Buffered Stream
 < result: true if Input was deleted, else false */
local maygc bool clear_input_buffered (object stream) {
  var bool ret = BufferedStream_have_eof_p(stream);
  BufferedStream_have_eof_p(stream) = false;
  return ret;
}

/* READ-CHAR-ARRAY - Pseudo-Function for File-Streams of Characters: */
local maygc uintL rd_ch_array_buffered (const gcv_object_t* stream_,
                                        const gcv_object_t* chararray_,
                                        uintL start, uintL len) {
  var object stream = *stream_;
  #ifdef ENABLE_UNICODE
  #define tmpbufsize 4096
  var uintL end = start+len;
  var uintL currindex = start;
  var object encoding = TheStream(stream)->strm_encoding;
  pushSTACK(encoding);
  while (1) {
    var uintL startindex = currindex;
    var uintB* bufferptr = buffered_nextbyte(stream,persev_partial);
    stream = *stream_; /* restore */
    encoding = STACK_0;
    if (bufferptr == (uintB*)NULL) /* EOF -> finished */
      break;
    { /* Read as many complete characters from the buffer as possible. */
      var uintL endvalid = BufferedStream_endvalid(stream);
      var uintL available = endvalid - BufferedStream_index(stream);
      var const uintB* bptr = bufferptr;
      var chart tmpbuf[tmpbufsize];
      var chart* cptr = &tmpbuf[0];
      Encoding_mbstowcs(encoding)
        (encoding,stream,&bptr,bufferptr+available,&cptr,
         &tmpbuf[end-currindex < tmpbufsize ? end-currindex : tmpbufsize]);
      if (!(cptr == &tmpbuf[0])) {
        var uintL n = bptr-bufferptr;
        /* increment index and position */
        BufferedStream_index(stream) += n;
        BufferedStream_position(stream) += n;
        /* store the read characters */
        sstring_store_array(*chararray_,currindex,tmpbuf,cptr-&tmpbuf[0]);
        currindex += cptr-&tmpbuf[0];
        stream = *stream_;
        encoding = STACK_0;
      } else {
        var uintB buf[max_bytes_per_chart];
        var uintL buflen = 0;
        while (1) {
          ASSERT(buflen < max_bytes_per_chart);
          buf[buflen++] = *bufferptr;
          /* increment index and position */
          BufferedStream_index(stream) += 1;
          BufferedStream_position(stream) += 1;
          var const uintB* bptr = &buf[0];
          var chart* cptr = &tmpbuf[0];
          Encoding_mbstowcs(encoding)(encoding,stream,&bptr,&buf[buflen],&cptr,cptr+1);
          if (cptr == &tmpbuf[0]) { /* Not a complete character. */
            /* Shift the buffer */
            if (!(bptr == &buf[0])) {
              var const uintB* ptr1 = bptr;
              var uintB* ptr2 = &buf[0];
              while (ptr1 != &buf[buflen]) { *ptr2++ = *ptr1++; }
              buflen = ptr2 - &buf[0];
            }
          } else { /* Read a complete character. */
            if (!(bptr == &buf[buflen])) {
              /* At most one lookahead byte. Make it unread. */
              ASSERT(bptr == &buf[buflen-1]);
              /* decrement index and position again: */
              BufferedStream_index(stream) -= 1;
              BufferedStream_position(stream) -= 1;
            }
            /* store the read character */
            sstring_store(*chararray_,currindex++,tmpbuf[0]);
            stream = *stream_;
            break;
          }
          bufferptr = buffered_nextbyte(stream,persev_partial);
          stream = *stream_;
          encoding = STACK_0;
          if (bufferptr == (uintB*)NULL) /* EOF -> finished */
            break;
        }
        if (currindex == startindex) /* EOF -> finished */
          break;
      }
    }

    /* Now apply CR/LF->NL and CR->NL conversion to the characters
     [startindex..currindex). */
    {
      var object chararray = *chararray_;
      sstring_un_realloc(chararray);
      SstringDispatch(chararray,X, {
        var cintX* startptr = &((SstringX)TheVarobject(chararray))->data[startindex];
        var cintX* currptr = &((SstringX)TheVarobject(chararray))->data[currindex];
        var const cintX* ptr1 = startptr;
        var cintX* ptr2 = startptr;
        do {
          var cintX c = *ptr1++;
          if (chareq(as_chart(c),ascii(NL))) {
            if (ChannelStream_ignore_next_LF(stream)) {
              ChannelStream_ignore_next_LF(stream) = false;
              if (ptr1 == currptr) break; else continue;
            }
            ChannelStream_lineno(stream) += 1;
          } else if (chareq(as_chart(c),ascii(CR))) {
            /* check next character for LF */
            if (ptr1 == currptr) {
              /* cannot check in this buffer; mark for next. */
              ChannelStream_ignore_next_LF(stream) = true;
            } else {
              if (chareq(as_chart(*ptr1),ascii(LF)))
                ptr1++;
            }
            c = NL;
            ChannelStream_lineno(stream) += 1;
          }
          *ptr2++ = c;
        } while (ptr1 != currptr);
        currindex = ptr2 - &((SstringX)TheVarobject(chararray))->data[0];
      });
    }
    if (currindex == end)
      break;
  }
  skipSTACK(1); /* encoding */
  return currindex - start;
  #else
  var chart* startptr = &TheSnstring(*chararray_)->data[start];
  var chart* charptr = startptr;
  do {
    var uintB* ptr = buffered_nextbyte(stream,persev_partial);
    if (ptr == (uintB*)NULL) /* EOF -> finished */
      break;
    stream = *stream_;
    var chart ch = as_chart(*ptr);
    /* increment index and position */
    BufferedStream_index(stream) += 1;
    BufferedStream_position(stream) += 1;
    if (chareq(ch,ascii(NL))) {
      ChannelStream_lineno(stream) += 1;
    } else if (chareq(ch,ascii(CR))) {
      /* check next character for LF */
      ptr = buffered_nextbyte(stream,persev_partial);
      stream = *stream_;
      if (!(ptr == (uintB*)NULL) && chareq(as_chart(*ptr),ascii(LF))) {
        /* increment index and position */
        BufferedStream_index(stream) += 1;
        BufferedStream_position(stream) += 1;
      }
      ch = ascii(NL);
      ChannelStream_lineno(stream) += 1;
    }
    *charptr++ = ch; len--;
  } while (len > 0);
  return charptr - startptr;
  #endif
}

/* Output side
   -----------

 UP: Writes a Byte to a Byte-based File-Stream.
 write_byte_buffered(stream,b);
 > stream : (open) Byte-based File-Stream.
 > b : Byte to be written
 changed in stream: index, endvalid, buffstart, position */
local maygc void write_byte_buffered (object stream, uintB b) {
  pushSTACK(stream);
  buffered_writebyte(stream,b);
  stream = popSTACK();
  /* increment position */
  BufferedStream_position(stream) += 1;
}

/* WRITE-CHAR - Pseudo-Function for File-Streams of Characters */
local maygc void wr_ch_buffered_unix (const gcv_object_t* stream_, object obj) {
  var object stream = *stream_;
  check_wr_char(stream,obj);
  var chart c = char_code(obj);
 #ifdef ENABLE_UNICODE
  var uintB buf[max_bytes_per_chart];
  var object encoding = TheStream(stream)->strm_encoding;
  var const chart* cptr = &c;
  var uintB* bptr = &buf[0];
  Encoding_wcstombs(encoding)(encoding,stream,&cptr,cptr+1,&bptr,
                              &buf[max_bytes_per_chart]);
  ASSERT(cptr == &c+1);
  var uintL buflen = bptr-&buf[0];
  if (buflen > 0) {
    write_byte_array_buffered(stream,&buf[0],buflen,persev_full);
    stream = *stream_;
    /* increment position */
    BufferedStream_position(stream) += buflen;
  }
 #else
  write_byte_buffered(stream,as_cint(c)); /* write unchanged */
 #endif
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for File-Streams of Characters: */
local maygc void wr_ch_array_buffered_unix (const gcv_object_t* stream_,
                                            const gcv_object_t* chararray_,
                                            uintL start, uintL len) {
  var object stream = *stream_;
  var const chart* charptr;
  unpack_sstring_alloca(*chararray_,len,start, charptr=);
  var const chart* endptr = charptr + len;
  pin_unprotect_varobject(*chararray_,PROT_READ);
 #ifdef ENABLE_UNICODE
  #define tmpbufsize 4096
  var uintB tmptmpbuf[tmpbufsize*max_bytes_per_chart];
  do {
    var uintB* bptr = &tmptmpbuf[0];
    var object encoding = TheStream(stream)->strm_encoding;
    Encoding_wcstombs(encoding)(encoding,stream,&charptr,endptr,&bptr,
                                &tmptmpbuf[tmpbufsize*max_bytes_per_chart]);
    var uintL tmptmpbuflen = bptr-&tmptmpbuf[0];
    if (tmptmpbuflen > 0) {
      write_byte_array_buffered(stream,&tmptmpbuf[0],tmptmpbuflen,persev_full);
      stream=*stream_;
      /* increment position */
      BufferedStream_position(stream) += tmptmpbuflen;
    }
  } while (charptr != endptr);
  #undef tmpbufsize
 #else
  write_byte_array_buffered(stream,(const uintB*)charptr,len,persev_full);
  stream=*stream_;
  /* increment position */
  BufferedStream_position(stream) += len;
 #endif
  unpin_varobject(*chararray_);
  wr_ss_lpos(stream,endptr,len); /* update Line-Position */
}

/* WRITE-CHAR - Pseudo-Function for File-Streams of Characters */
local maygc void wr_ch_buffered_mac (const gcv_object_t* stream_, object obj) {
  var object stream = *stream_;
  check_wr_char(stream,obj);
  var chart c = char_code(obj);
  if (chareq(c,ascii(NL)))
    c = ascii(CR);
 #ifdef ENABLE_UNICODE
  var uintB buf[max_bytes_per_chart];
  var object encoding = TheStream(stream)->strm_encoding;
  var const chart* cptr = &c;
  var uintB* bptr = &buf[0];
  Encoding_wcstombs(encoding)(encoding,stream,&cptr,cptr+1,&bptr,&buf[max_bytes_per_chart]);
  ASSERT(cptr == &c+1);
  var uintL buflen = bptr-&buf[0];
  if (buflen > 0) {
    write_byte_array_buffered(stream,&buf[0],buflen,persev_full);
    /* increment position */
    BufferedStream_position(*stream_) += buflen;
  }
 #else
  write_byte_buffered(stream,as_cint(c));
 #endif
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for File-Streams of Characters: */
local maygc void wr_ch_array_buffered_mac (const gcv_object_t* stream_,
                                           const gcv_object_t* chararray_,
                                           uintL start, uintL len) {
  var object stream = *stream_;
  var const chart* charptr;
  unpack_sstring_alloca(*chararray_,len,start, charptr=);
  pin_unprotect_varobject(*chararray_,PROT_READ);
 #ifdef ENABLE_UNICODE
  /* Need a temporary buffer for NL->CR translation. */
  #define tmpbufsize 4096
  var chart tmpbuf[tmpbufsize];
  var uintB tmptmpbuf[tmpbufsize*max_bytes_per_chart];
  var uintL remaining = len;
  do {
    var uintL n = remaining;
    if (n > tmpbufsize)
      n = tmpbufsize;
    {
      var chart* tmpptr = &tmpbuf[0];
      var uintL count;
      dotimespL(count,n, {
        var chart c = *charptr++;
        if (chareq(c,ascii(NL)))
          c = ascii(CR);
        *tmpptr++ = c;
      });
      var const chart* cptr = tmpbuf;
      var uintB* bptr = &tmptmpbuf[0];
      var object encoding = TheStream(stream)->strm_encoding;
      Encoding_wcstombs(encoding)(encoding,stream,&cptr,tmpptr,&bptr,
                                  &tmptmpbuf[tmpbufsize*max_bytes_per_chart]);
      ASSERT(cptr == tmpptr);
      var uintL tmptmpbuflen = bptr-&tmptmpbuf[0];
      if (tmptmpbuflen > 0) {
        write_byte_array_buffered(stream,&tmptmpbuf[0],tmptmpbuflen,persev_full);
        stream = *stream_;
        /* increment position */
        BufferedStream_position(stream) += tmptmpbuflen;
      }
    }
    remaining -= n;
  } while (remaining > 0);
  #undef tmpbufsize
 #else
  var uintL remaining = len;
  do {
    var chart c = *charptr++;
    if (chareq(c,ascii(NL)))
      c = ascii(CR);
    write_byte_buffered(*stream_,as_cint(c));
    remaining--;
  } while (remaining != 0);
 #endif
  unpin_varobject(*chararray_);
  wr_ss_lpos(*stream_,charptr,len); /* update Line-Position */
}

/* WRITE-CHAR - Pseudo-Function for File-Streams of Characters */
local maygc void wr_ch_buffered_dos (const gcv_object_t* stream_, object obj) {
  var object stream = *stream_;
  check_wr_char(stream,obj);
  var chart c = char_code(obj);
#ifdef ENABLE_UNICODE
  static chart const crlf[2] = { ascii(CR), ascii(LF) };
  var uintB buf[2*max_bytes_per_chart];
  var object encoding = TheStream(stream)->strm_encoding;
  var const chart* cp;
  var uintL n;
  if (chareq(c,ascii(NL))) {
    cp = crlf; n = 2;
  } else {
    cp = &c; n = 1;
  }
  var const chart* cptr = cp;
  var uintB* bptr = &buf[0];
  Encoding_wcstombs(encoding)(encoding,stream,&cptr,cp+n,&bptr,
                              &buf[2*max_bytes_per_chart]);
  ASSERT(cptr == cp+n);
  var uintL buflen = bptr-&buf[0];
  if (buflen > 0) {
    write_byte_array_buffered(stream,&buf[0],buflen,persev_full);
    /* increment position */
    BufferedStream_position(*stream_) += buflen;
  }
 #else
  if (chareq(c,ascii(NL))) {
    write_byte_buffered(stream,CR); write_byte_buffered(*stream_,LF);
  } else {
    write_byte_buffered(stream,as_cint(c));
  }
 #endif
}

/* WRITE-CHAR-ARRAY - Pseudo-Function for File-Streams of Characters: */
local maygc void wr_ch_array_buffered_dos (const gcv_object_t* stream_,
                                           const gcv_object_t* chararray_,
                                           uintL start, uintL len) {
  var object stream = *stream_;
  var const chart* charptr;
  unpack_sstring_alloca(*chararray_,len,start, charptr=);
  pin_unprotect_varobject(*chararray_,PROT_READ);
 #ifdef ENABLE_UNICODE
  /* Need a temporary buffer for NL->CR translation. */
  #define tmpbufsize 4096
  var chart tmpbuf[2*tmpbufsize];
  var uintB tmptmpbuf[2*tmpbufsize*max_bytes_per_chart];
  var uintL remaining = len;
  do {
    var uintL n = remaining;
    if (n > tmpbufsize)
      n = tmpbufsize;
    {
      var chart* tmpptr = &tmpbuf[0];
      var uintL count;
      dotimespL(count,n, {
        var chart c = *charptr++;
        if (chareq(c,ascii(NL))) {
          *tmpptr++ = ascii(CR); *tmpptr++ = ascii(LF);
        } else {
          *tmpptr++ = c;
        }
      });
      var const chart* cptr = tmpbuf;
      var uintB* bptr = &tmptmpbuf[0];
      var object encoding = TheStream(stream)->strm_encoding;
      Encoding_wcstombs(encoding)(encoding,stream,&cptr,tmpptr,&bptr,&tmptmpbuf[2*tmpbufsize*max_bytes_per_chart]);
      ASSERT(cptr == tmpptr);
      var uintL tmptmpbuflen = bptr-&tmptmpbuf[0];
      if (tmptmpbuflen > 0) {
        write_byte_array_buffered(stream,&tmptmpbuf[0],tmptmpbuflen,persev_full);
        stream = *stream_;
        /* increment position */
        BufferedStream_position(stream) += tmptmpbuflen;
      }
    }
    remaining -= n;
  } while (remaining > 0);
  #undef tmpbufsize
 #else
  var uintL remaining = len;
  do {
    var chart c = *charptr++;
    if (chareq(c,ascii(NL))) {
      write_byte_buffered(stream,CR); write_byte_buffered(*stream_,LF);
    } else {
      write_byte_buffered(stream,as_cint(c));
    }
    stream = *stream_;
    remaining--;
  } while (remaining != 0);
 #endif
  unpin_varobject(*chararray_);
  wr_ss_lpos(stream,charptr,len); /* update Line-Position */
}

/* Macro: Emits a shift sequence to let the output conversion descriptor of an
 Buffered-Channel-Stream return to the initial state.
 oconv_unshift_output_buffered(stream);
 > stream: Buffered-Channel-Stream */
#if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
  #define oconv_unshift_output_buffered(stream,abort)   \
    ((ChannelStream_oconvdesc(stream) != (iconv_t)0)    \
     ? oconv_unshift_output_buffered_(stream,abort) : 0)
local maygc uintB oconv_unshift_output_buffered_ (object stream, uintB abort) {
 #define tmpbufsize 4096
  var uintB tmpbuf[tmpbufsize];
  var char* outptr = (char*)tmpbuf;
  var size_t outsize = tmpbufsize;
  begin_system_call();
  var size_t res =
    iconv(ChannelStream_oconvdesc(stream),NULL,NULL,&outptr,&outsize);
  if (res == (size_t)(-1)) {
    if (abort) return 1;
    /* BUG: On Windows, after iconv(), we must use errno, not GetLastError(). */
    if (OS_errno == E2BIG) {    /* output buffer too small? */
      NOTREACHED;
    } else {
      OS_error();
    }
  }
  end_system_call();
  var uintL outcount = outptr-(char*)tmpbuf;
  if (outcount > 0) {
    pushSTACK(stream);
    write_byte_array_buffered(stream,&tmpbuf[0],outcount,persev_full);
    stream = popSTACK();
    /* increment position */
    BufferedStream_position(stream) += outcount;
  }
  return 0;
 #undef tmpbufsize
}
#else
 #define oconv_unshift_output_buffered(stream,abort)  0
#endif

/* File-Stream, Bit-based
   ========================

 There are 6 types, altogether:
 Three Cases
   a - bitsize divisible by 8,
   b - bitsize < 8,
   c - bitsize not divisible by 8 and >= 8,
 distinguished by
   s - Element-Type (signed-byte bitsize),
       including signed-byte = (signed-byte 8)
   u - Element-Type (unsigned-byte bitsize),
       including unsigned-byte = (unsigned-byte 8)
       and bit = (unsigned-byte 1)
       and (mod n) = (unsigned-byte (integer-length n))

 UP: Positions an (open) Bit-based File-Stream to a
 specified Position.
 position_file_i_buffered(stream,position);
 > stream : (open) Byte-based File-Stream.
 > position : new (logical) Position
 changed in stream: index, endvalid, buffstart, bitindex */
local maygc void position_file_i_buffered (object stream, uoff_t position) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  var uoff_t position_bits = position * bitsize;
  pushSTACK(stream);
  if (bitsize < 8)
    position_bits += sizeof(uintL)*8; /* consider Header */
  /* position at Bit Number position_bits. */
  position_file_buffered(stream,floor(position_bits,8)); /* position to the Byte */
  stream = STACK_0;
  if ((bitsize % 8) == 0) /* For Type a that's all. */
    return;
  if (/* Is the addressed position situated in the first byte after EOF ? */
      ((!((position_bits%8)==0))
       && (buffered_nextbyte(stream,persev_partial) == (uintB*)NULL))
       /* Is the addressed position situated in the last byte too far? */
      || ((bitsize < 8)
          && (position > BufferedStream_eofposition(STACK_0/*stream*/)))) {
    /* Error. But first position back to the old Position: */
    stream = popSTACK();
    var uoff_t oldposition = BufferedStream_position(stream);
    check_SP();
    position_file_i_buffered(stream,oldposition); /* positioning back */
    error_position_beyond_EOF(stream);
  }
  stream = popSTACK();
  BufferedStream_bitindex(stream) = position_bits%8;
}

/* Input side
   ----------

 UP for READ-BYTE on File-Streams of Integers, Type a :
 Fills the Bitbuffer with the next bitsize Bits.
 > stream : File-Stream of Integers, Type a
 > finisher : Routine for Finalization
 < result : read Integer or eof_value */
local object rd_by_aux_iax_buffered (object stream, rd_by_ix_I* finisher) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  var uintL bytesize = bitsize/8;
  /* transfer sufficiently many bytes into the bitbuffer */
  var uintB* bitbufferptr =
    &TheSbvector(TheStream(stream)->strm_bitbuffer)->data[0];
  pin_unprotect_varobject(TheStream(stream)->strm_bitbuffer,PROT_READ_WRITE);
  pushSTACK(stream);
  #if 0 /* equivalent, but slower */
  var uintL count;
  dotimespL(count,bytesize, {
    var uintB* ptr = buffered_nextbyte(stream,persev_partial);
    if (ptr == (uintB*)NULL)
      goto eof;
    stream = STACK_0;
    /* fetch next Byte: */
    *bitbufferptr++ = *ptr;
    /* increment index */
    BufferedStream_index(stream) += 1;
  });
  #else
  if (read_byte_array_buffered(stream,bitbufferptr,bytesize,persev_full)
      != bitbufferptr+bytesize)
    goto eof;
  #endif
  stream = popSTACK();
  unpin_varobject(TheStream(stream)->strm_bitbuffer);
  /* increment position */
  BufferedStream_position(stream) += 1;
  /* convert to number: */
  return (*finisher)(stream,bitsize,bytesize);
  eof: /* EOF reached */
  stream = popSTACK();
  unpin_varobject(TheStream(stream)->strm_bitbuffer);
  position_file_buffered(stream,BufferedStream_position(stream)*bytesize);
  return eof_value;
}

/* UP for READ-BYTE on File-Streams of Integers, Type b :
 Fills the Bitbuffer with the next bitsize Bits.
 > stream : File-Stream of Integers, Type b
 > finisher : Routine for Finalization
 < result : read Integer or eof_value */
local maygc object rd_by_aux_ibx_buffered(object stream, rd_by_ix_I* finisher) {
  /* Only for position < eofposition there's something to read: */
  if (BufferedStream_position(stream) == BufferedStream_eofposition(stream))
    goto eof;
  pushSTACK(stream);
  {
    var uintL bitsize = ChannelStream_bitsize(stream); /* bitsize (>0, <8) */
    /* transfer sufficient many bits into the bitbuffer */
    var uintL bitindex = BufferedStream_bitindex(stream);
    var uintL count = bitindex + bitsize;
    var uint8 bit_akku;
    var uintB* ptr = buffered_nextbyte(stream,persev_partial);
    if (ptr == (uintB*)NULL)
      goto eof;
    stream = STACK_0;
    /* Get first partial byte: */
    bit_akku = (*ptr)>>bitindex;
    /* bitshift := 8-bitindex
     For bit_akku the Bits (bitshift-1)..0 are valid. */
    if (count > 8) {
      /* increment index, because *ptr is processed: */
      BufferedStream_index(stream) += 1;
      count -= 8; /* still count (>0) Bits to fetch. */
      var uintB* ptr = buffered_nextbyte(stream,persev_partial);
      stream = STACK_0;
      if (ptr == (uintB*)NULL)
        goto eof1;
      /* fetch next Byte:
       (8-bitindex < 8, because else count = 0+bitsize < 8 !) */
      bit_akku |= (*ptr)<<(8-bitindex);
    }
    /* For bit_akku all 8 Bits are valid.
     save 8 Bits: */
    TheSbvector(TheStream(stream)->strm_bitbuffer)->data[0] = bit_akku;
    BufferedStream_bitindex(stream) = count;
    /* increment position */
    BufferedStream_position(stream) += 1;
    skipSTACK(1);
    /* convert to number: */
    return (*finisher)(stream,bitsize,1);
  eof1:
    /* position back again: */
    position_file_i_buffered(stream,BufferedStream_position(stream));
  }
 eof: /* EOF was reached */
  skipSTACK(1);
  return eof_value;
}

/* UP for READ-BYTE on File-Streams of Integers, Type c :
 Fills the Bitbuffer with the next bitsize Bits.
 > stream : File-Stream of Integers, Type c
 > finisher : Routine for Finalization
 < result : read Integer or eof_value */
local maygc object rd_by_aux_icx_buffered (object stream,
                                           rd_by_ix_I* finisher) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  var uintL bytesize = ceiling(bitsize,8);
  /* transfer sufficiently many bits into the bitbuffer */
  var uintB* bitbufferptr =
    &TheSbvector(TheStream(stream)->strm_bitbuffer)->data[0];
  pin_unprotect_varobject(TheStream(stream)->strm_bitbuffer,PROT_READ_WRITE);
  pushSTACK(stream);
  var uintL count = bitsize;
  var uintL bitshift = BufferedStream_bitindex(stream);
  var uintB* ptr = buffered_nextbyte(stream,persev_partial);
  stream = STACK_0;
  if (ptr != (uintB*)NULL) {
    if (bitshift==0) {
      /* Optimized loop, without shifting. */
      while (1) {
        *bitbufferptr++ = *ptr; /* store 8 bits */
        /* After digesting *ptr, increment index: */
        BufferedStream_index(stream) += 1;
        count -= 8;
        /* have to get count (>0) bits. */
        ptr = buffered_nextbyte(stream,persev_partial);
        stream = STACK_0;
        if (ptr == (uintB*)NULL)
          goto eof;
        if (count<=8) /* are count bits finished? */
          break;
      }
      /* Still need count = bitsize%8 (>0,<8) bits. */
      *bitbufferptr++ = *ptr; /* store 8 bits */
    } else {
      /* start getting bytes: */
      var uint16 bit_akku = (*ptr)>>bitshift;
      bitshift = 8-bitshift; /* bitshift := 8-bitindex (>0, <8) */
      count -= bitshift;
      while (1) {
        BufferedStream_index(stream) += 1;
        /* bit_akku: bits (bitshift-1)..0 are valid.
         have to get count (>0) bits. */
        {
          var uintB* ptr = buffered_nextbyte(stream,persev_partial);
          stream = STACK_0;
          if (ptr == (uintB*)NULL)
            goto eof;
          /* get next byte: */
          bit_akku |= (uint16)(*ptr)<<bitshift;
        }
        /* bit_akku: bits (7+bitshift)..0 are valid. */
        *bitbufferptr++ = (uint8)bit_akku; /* store 8 bits */
        bit_akku >>= 8;
        if (count<=8) /* are count bits finished? */
          break;
        count -= 8;
      }
      if (count == 8) {
        count = 0;
        BufferedStream_index(stream) += 1;
      }
      if ((bitsize%8) <= bitshift)
        *bitbufferptr++ = (uint8)bit_akku; /* store bitshift bits */
      /* Now bitbufferptr has been incremented
         ceiling(bitsize-bitshift,8) + ((bitsize%8) <= bitshift ? 1 : 0)
         = ceiling(bitsize,8) = bytesize
       times. */
    }
    skipSTACK(1);
    unpin_varobject(TheStream(stream)->strm_bitbuffer);
    ASSERT(bitbufferptr == &TheSbvector(TheStream(stream)->strm_bitbuffer)->data[bytesize]);
    BufferedStream_bitindex(stream) = count;
    BufferedStream_position(stream) += 1; /* increment position */
    return (*finisher)(stream,bitsize,bytesize); /* convert to a number */
  }
 eof:
  unpin_varobject(TheStream(stream)->strm_bitbuffer);
  position_file_i_buffered(stream,BufferedStream_position(stream));
  return eof_value;
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type au : */
local maygc object rd_by_iau_buffered (object stream) {
  return rd_by_aux_iax_buffered(stream,&rd_by_iu_I);
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type as : */
local maygc object rd_by_ias_buffered (object stream) {
  return rd_by_aux_iax_buffered(stream,&rd_by_is_I);
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type bu : */
local maygc object rd_by_ibu_buffered (object stream) {
  return rd_by_aux_ibx_buffered(stream,&rd_by_iu_I);
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type bs : */
local maygc object rd_by_ibs_buffered (object stream) {
  return rd_by_aux_ibx_buffered(stream,&rd_by_is_I);
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type cu : */
local maygc object rd_by_icu_buffered (object stream) {
  return rd_by_aux_icx_buffered(stream,&rd_by_iu_I);
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type cs : */
local maygc object rd_by_ics_buffered (object stream) {
  return rd_by_aux_icx_buffered(stream,&rd_by_is_I);
}

/* READ-BYTE - Pseudo-Function for File-Streams of Integers, Type au, bitsize = 8 : */
local maygc object rd_by_iau8_buffered (object stream) {
  pushSTACK(stream);
 rd_by_iau8_buffered_retry:
  var uintB* ptr = buffered_nextbyte(stream,persev_partial);
  stream = STACK_0;
  if (!(ptr == (uintB*)NULL)) {
    BufferedStream_index(stream) += 1;
    if (*ptr == LF && ChannelStream_ignore_next_LF(stream)) {
      /* see comment in rd_by_array_iau8_unbuffered */
      ChannelStream_ignore_next_LF(stream) = false;
      goto rd_by_iau8_buffered_retry;
    }
    skipSTACK(1);
    var object obj = fixnum(*ptr);
    BufferedStream_position(stream) += 1;
    return obj;
  } else {
    skipSTACK(1);
    return eof_value;
  }
}

/* READ-BYTE-SEQUENCE for File-Streams of Integers, Type au, bitsize = 8 : */
local maygc uintL rd_by_array_iau8_buffered
(const gcv_object_t* stream_, const gcv_object_t* bytearray_,
 uintL start, uintL len, perseverance_t persev) {
  pin_unprotect_varobject(*bytearray_,PROT_READ_WRITE);
  var uintB* startptr = &TheSbvector(*bytearray_)->data[start];
  var uintB* endptr = read_byte_array_buffered(*stream_,startptr,len,persev);
  var uintL result = endptr-startptr;
  if (result && *startptr == LF && ChannelStream_ignore_next_LF(*stream_)) {
    /* see comment in rd_by_array_iau8_unbuffered */
    var uintL count = --result;
    for (; count--; startptr++) startptr[0] = startptr[1];
    ChannelStream_ignore_next_LF(*stream_) = false;
    endptr = read_byte_array_buffered(*stream_,startptr,1,persev);
    result += endptr - startptr;  /* 0 or 1 */
  }
  unpin_varobject(*bytearray_);
  /* increment position: */
  BufferedStream_position(*stream_) += result;
  return result;
}

/* Determines, if a Byte is available on a File-Stream.
 listen_byte_ia8_buffered(stream)
 > stream: File-Stream of Integers, Type a, bitsize = 8
 < result: input availability
 can trigger GC */
local maygc listen_t listen_byte_ia8_buffered (object stream) {
  var uintB* buf = buffered_nextbyte(stream,persev_immediate);
  if (buf == (uintB*)NULL) return LISTEN_EOF; /* EOF */
  if (buf == (uintB*)-1)   return LISTEN_WAIT; /* will hang */
  return LISTEN_AVAIL;
}

/* Output side
   -----------

 UP for WRITE-BYTE on File-Streams of Integers, Type a :
 Writes the Bitbuffer-Content to the File. */
local maygc void wr_by_aux_ia_buffered (object stream, uintL bitsize,
                                        uintL bytesize)
{
  unused(bitsize);
  pin_unprotect_varobject(TheStream(stream)->strm_bitbuffer,PROT_READ);
  pushSTACK(stream);
  var uintB* bitbufferptr = &TheSbvector(TheStream(stream)->strm_bitbuffer)->data[0];
  #if 0 /* equivalent, but slow */
  var uintL count;
  dotimespL(count,bytesize, {
    buffered_writebyte(stream,*bitbufferptr++);
    stream = STACK_0;
  });
  skipSTACK(0);
  #else
  write_byte_array_buffered(stream,bitbufferptr,bytesize,persev_full);
  stream = popSTACK();
  #endif
  /* increment position: */
  BufferedStream_position(stream) += 1;
  unpin_varobject(TheStream(stream)->strm_bitbuffer);
}

/* write last byte (count bits): */
#define WRITE_LAST_BYTE                                                 \
 if (count!=0) {                                                        \
   ptr = buffered_nextbyte(stream,persev_partial);                      \
   stream = STACK_0;                                                    \
   if (ptr == (uintB*)NULL) { /* EOF */                                 \
     ptr = buffered_eofbyte(stream); /* 1 Byte */                       \
     stream = STACK_0;                                                  \
     *ptr = (uint8)bit_akku; /* write byte */                           \
   } else { /* overwrite the last byte only partially: */               \
     var uint8 diff = (*ptr ^ (uint8)bit_akku) & (uint8)(bit(count)-1); \
     if (diff == 0)                                                     \
       goto no_modification;                                            \
     *ptr ^= diff;                                                      \
   }                                                                    \
   BufferedStream_modified(stream) = true;                              \
 no_modification: ;                                                     \
 }

/* UP for WRITE-BYTE on File-Streams of Integers, Type b :
 Writes the Bitbuffer-Content to the File. */
local maygc void wr_by_aux_ib_buffered (object stream, uintL bitsize,
                                        uintL bytesize)
{
  unused(bytesize);
  pin_unprotect_varobject(TheStream(stream)->strm_bitbuffer,PROT_READ);
  pushSTACK(stream);
  var uintL bitshift = BufferedStream_bitindex(stream);
  var uint16 bit_akku = (uint16)(TheSbvector(TheStream(stream)->strm_bitbuffer)->data[0])<<bitshift;
  var uintL count = bitsize;
  var uintB* ptr = buffered_nextbyte(stream,persev_partial);
  stream = STACK_0;
  /* start getting bytes: */
  if (!(ptr == (uintB*)NULL))
    bit_akku |= (*ptr)&(bit(bitshift)-1);
  count += bitshift;
  /* poss. write single Byte: */
  if (count>=8) {
    buffered_writebyte(stream,(uint8)bit_akku);
    stream = STACK_0;
    bit_akku = bit_akku>>8;
    count -= 8;
  }
  WRITE_LAST_BYTE;
  BufferedStream_bitindex(stream) = count;
  /* increment position and poss. eofposition: */
  if (BufferedStream_eofposition(stream) == BufferedStream_position(stream))
    BufferedStream_eofposition(stream) += 1;
  BufferedStream_position(stream) += 1;
  skipSTACK(1); unpin_varobject(TheStream(stream)->strm_bitbuffer);
}

/* UP for WRITE-BYTE on File-Streams of Integers, Type c :
 Writes the Bitbuffer-Content to the File. */
local maygc void wr_by_aux_ic_buffered (object stream, uintL bitsize,
                                        uintL bytesize) {
  unused(bytesize);
  pin_unprotect_varobject(TheStream(stream)->strm_bitbuffer,PROT_READ);
  pushSTACK(stream);
  var uintB* bitbufferptr=TheSbvector(TheStream(stream)->strm_bitbuffer)->data;
  var uintL bitshift = BufferedStream_bitindex(stream);
  var uintL count = bitsize;
  var uint16 bit_akku;
  var uintB* ptr = buffered_nextbyte(stream,persev_partial);
  stream = STACK_0;
  /* start getting bytes: */
  bit_akku = (ptr==(uintB*)NULL ? 0 : (*ptr)&(bit(bitshift)-1) );
  count += bitshift;
  /* write individual bytes: */
  while (1) {
    bit_akku |= (uint16)(*bitbufferptr++)<<bitshift;
    if (count<8)
      break;
    buffered_writebyte(stream,(uint8)bit_akku);
    stream = STACK_0;
    bit_akku = bit_akku>>8;
    count -= 8;
    if (count<=bitshift)
      break;
  }
  WRITE_LAST_BYTE;
  BufferedStream_bitindex(stream) = count;
  BufferedStream_position(stream) += 1;
  skipSTACK(1); unpin_varobject(TheStream(stream)->strm_bitbuffer);
}
#undef WRITE_LAST_BYTE

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type au : */
local maygc void wr_by_iau_buffered (object stream, object obj) {
  wr_by_ixu_sub(stream,obj,&wr_by_aux_ia_buffered);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type as : */
local maygc void wr_by_ias_buffered (object stream, object obj) {
  wr_by_ixs_sub(stream,obj,&wr_by_aux_ia_buffered);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type bu : */
local maygc void wr_by_ibu_buffered (object stream, object obj) {
  wr_by_ixu_sub(stream,obj,&wr_by_aux_ib_buffered);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type bs : */
local maygc void wr_by_ibs_buffered (object stream, object obj) {
  wr_by_ixs_sub(stream,obj,&wr_by_aux_ib_buffered);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type cu : */
local maygc void wr_by_icu_buffered (object stream, object obj) {
  wr_by_ixu_sub(stream,obj,&wr_by_aux_ic_buffered);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type cs : */
local maygc void wr_by_ics_buffered (object stream, object obj) {
  wr_by_ixs_sub(stream,obj,&wr_by_aux_ic_buffered);
}

/* WRITE-BYTE - Pseudo-Function for File-Streams of Integers, Type au, bitsize = 8 : */
local maygc void wr_by_iau8_buffered (object stream, object obj) {
  ASSERT_wr_int(stream,obj);
  if (!(posfixnump(obj) && (posfixnum_to_V(obj) < bit(8))))
    error_bad_integer(stream,obj);
  write_byte_buffered(stream,(uintB)posfixnum_to_V(obj));
}

/* WRITE-BYTE-SEQUENCE for File-Streams of Integers, Type au, bitsize = 8 : */
local maygc uintL wr_by_array_iau8_buffered
(const gcv_object_t* stream_, const gcv_object_t* bytearray_,
 uintL start, uintL len, perseverance_t persev) {
  pin_unprotect_varobject(*bytearray_,PROT_READ);
  write_byte_array_buffered(*stream_,TheSbvector(*bytearray_)->data+start,len,persev);
  unpin_varobject(*bytearray_);
  /* increment position: */
  BufferedStream_position(*stream_) += len;
  return len;
}

/* File-Stream in general
   ======================

 UP: Positions an (open) File-Stream to the start.
 logical_position_file_start(stream);
 > stream : (open) File-Stream.
 changed in stream: index, endvalid, buffstart, ..., position, rd_ch_last */
local maygc uoff_t logical_position_file_start (object stream) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  pushSTACK(stream);
  position_file_buffered
    (stream,
     bitsize > 0 && bitsize < 8 /* Integer-Stream of Type b ? */
     ? sizeof(uintL) : 0); /* yes -> Position 4, else Position 0 */
  stream = popSTACK();
  if (!((bitsize % 8) == 0))
    /* Integer-Stream of Type b,c */
    BufferedStream_bitindex(stream) = 0; /* bitindex := 0 */
  TheStream(stream)->strm_rd_ch_last = NIL; /* Lastchar := NIL */
  TheStream(stream)->strmflags &= ~strmflags_unread_B;
  return BufferedStream_position(stream) = 0; /* position := 0 */
}

/* UP: Positions an (open) File-Stream to a given Position.
 logical_position_file(stream,position);
 > stream : (open) File-Stream.
 > position : new (logical) Position
 changed in stream: index, endvalid, buffstart, ..., position, rd_ch_last */
local maygc uoff_t logical_position_file (object stream, uoff_t position) {
  var uintL bitsize = ChannelStream_bitsize(stream);
  pushSTACK(stream);
  if (bitsize > 0) { /* Integer-Stream ? */
    if ((bitsize % 8) == 0) { /* Type a */
      position_file_buffered(stream,position*(bitsize/8));
    } else { /* Type b,c */
      position_file_i_buffered(stream,position);
    }
    stream = popSTACK();
  } else { /* Character-Stream */
    position_file_buffered(stream,position);
    stream = popSTACK();
    TheStream(stream)->strm_rd_ch_last = NIL; /* Lastchar := NIL */
    TheStream(stream)->strmflags &= ~strmflags_unread_B;
  }
  return BufferedStream_position(stream) = position;
}

/* UP: Positions an (open) File-Stream to the end.
 logical_position_file_end(stream);
 > stream : (open) File-Stream.
 changed in stream: index, endvalid, buffstart, ..., position, rd_ch_last */
local maygc uoff_t logical_position_file_end (object stream) {
  pushSTACK(stream);
  /* poss. flush Buffer: */
  if (BufferedStream_modified(stream)) {
    buffered_flush(stream);
    stream = STACK_0;
  }
  var Handle handle = TheHandle(BufferedStream_channel(stream));
  var uoff_t eofbytes; /* EOF-Position, measured in Bytes */
  /* position to the End: */
  begin_blocking_system_call();
  handle_lseek(&STACK_0,handle,0,SEEK_END,eofbytes=);
  end_blocking_system_call();
  stream = STACK_0;
  /* calculate logical Position and correct eofbytes: */
  var uoff_t position; /* logical Position */
  var uintL eofbits = 0; /* Bit-Complement for eofbytes */
  var uintL bitsize = ChannelStream_bitsize(stream);
  if (bitsize > 0) { /* Integer-Stream ? */
    if ((bitsize % 8) == 0) { /* Type a */
      var uintL bytesize = bitsize/8;
      position = floor(eofbytes,bytesize);
      eofbytes = position*bytesize;
    } else if (bitsize < 8) { /* Type b */
      eofbytes -= sizeof(uintL); /* consider Header */
      /* Is the memorized EOF-Position plausible? */
      position = BufferedStream_eofposition(stream);
      if (!(ceiling(position*bitsize,8)==eofbytes)) /* yes -> use it */
        position = floor(eofbytes*8,bitsize); /* no -> recalculate it */
      /* recalculate eofbytes and eofbits: */
      eofbytes = floor(position*bitsize,8);
      eofbits = (position*bitsize)%8;
      eofbytes += sizeof(uintL); /* consider Header */
    } else { /* Type c */
      position = floor(eofbytes*8,bitsize);
      eofbytes = floor(position*bitsize,8);
      eofbits = (position*bitsize)%8;
    }
  } else { /* Character-Stream */
    position = eofbytes;
  }
  if (!BufferedStream_blockpositioning(stream)) {
    /* Now position at the End: */
    BufferedStream_buffstart(stream) = eofbytes;
    BufferedStream_endvalid(stream) = 0;
    BufferedStream_index(stream) = 0; /* index := 0 */
    BufferedStream_modified(stream) = false; /* unmodified */
    BufferedStream_have_eof_p(stream) = true;
  } else { /* position to the start of the last Sector: */
    {
      var uoff_t buffstart;
      begin_blocking_system_call();
      handle_lseek(&STACK_0,handle,
                   floor(eofbytes,strm_buffered_bufflen)*strm_buffered_bufflen,
                   SEEK_SET,buffstart=);
      end_blocking_system_call();
      stream = STACK_0;
      BufferedStream_buffstart(stream) = buffstart;
    }
    /* read Sector: */
    BufferedStream_endvalid(stream) = 0;
    BufferedStream_index(stream) = 0; /* index := 0 */
    BufferedStream_modified(stream) = false; /* unmodified */
    BufferedStream_have_eof_p(stream) = false;
    var uintL endvalid = eofbytes % strm_buffered_bufflen;
    if (!((endvalid==0) && (eofbits==0))) {
      /* EOF at end of Sector -> nothing to read */
      buffered_nextbyte(stream,persev_partial);
      stream = STACK_0;
      /* Now index=0. set index and endvalid: */
      BufferedStream_index(stream) = endvalid;
      if (eofbits != 0)
        endvalid += 1;
      BufferedStream_endvalid(stream) = endvalid;
    }
  }
  if (!((bitsize % 8) == 0)) { /* Integer-Stream of type b,c */
    BufferedStream_bitindex(stream) = eofbits;
  }
  TheStream(stream)->strm_rd_ch_last = NIL; /* Lastchar := NIL */
  TheStream(stream)->strmflags &= ~strmflags_unread_B;
  skipSTACK(1);
  return BufferedStream_position(stream) = position; /* set position */
}

/* UP: Fills in the pseudofunctions for a buffered stream.
 fill_pseudofuns_buffered(stream,&eltype);
 > stream: stream being built up, with correct strmflags and encoding
 > eltype: Element-Type in decoded form */
local void fill_pseudofuns_buffered (object stream,
                                     const decoded_el_t* eltype) {
  var uintB flags = TheStream(stream)->strmflags;
  stream_dummy_fill(stream);
  if (flags & strmflags_rd_by_B) {
    ELTYPE_DISPATCH(eltype,{},{
      TheStream(stream)->strm_rd_by =
        ((eltype->size % 8) == 0
         ? (eltype->size == 8 ? P(rd_by_iau8_buffered) : P(rd_by_iau_buffered))
         : eltype->size < 8 ? P(rd_by_ibu_buffered) : P(rd_by_icu_buffered));
      TheStream(stream)->strm_rd_by_array =
        (eltype->size == 8
         ? P(rd_by_array_iau8_buffered) : P(rd_by_array_dummy));
    },{
      TheStream(stream)->strm_rd_by =
        ((eltype->size % 8) == 0 ? P(rd_by_ias_buffered) :
         eltype->size < 8 ? P(rd_by_ibs_buffered) : P(rd_by_ics_buffered));
      TheStream(stream)->strm_rd_by_array = P(rd_by_array_dummy);
    });
  }
  if (flags & strmflags_wr_by_B) {
    ELTYPE_DISPATCH(eltype,{},{
      TheStream(stream)->strm_wr_by =
        ((eltype->size % 8) == 0
         ? (eltype->size == 8 ? P(wr_by_iau8_buffered) : P(wr_by_iau_buffered))
         : eltype->size < 8 ? P(wr_by_ibu_buffered) : P(wr_by_icu_buffered));
      TheStream(stream)->strm_wr_by_array =
        (eltype->size == 8
         ? P(wr_by_array_iau8_buffered) : P(wr_by_array_dummy));
    },{
      TheStream(stream)->strm_wr_by =
        ((eltype->size % 8) == 0 ? P(wr_by_ias_buffered) :
         eltype->size < 8 ? P(wr_by_ibs_buffered) : P(wr_by_ics_buffered));
      TheStream(stream)->strm_wr_by_array = P(wr_by_array_dummy);
    });
  }
  if (eltype->kind == eltype_ch) {
    if (flags & strmflags_rd_ch_B) {
      TheStream(stream)->strm_rd_ch = P(rd_ch_buffered);
      TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_buffered);
    }
    if (flags & strmflags_wr_ch_B) {
      var object eol=TheEncoding(TheStream(stream)->strm_encoding)->enc_eol;
      if (eq(eol,S(Kunix))) {
        TheStream(stream)->strm_wr_ch =
          TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_buffered_unix);
        TheStream(stream)->strm_wr_ch_array =
          TheStream(stream)->strm_wr_ch_array_npnl =
          P(wr_ch_array_buffered_unix);
      } else if (eq(eol,S(Kmac))) {
        TheStream(stream)->strm_wr_ch =
          TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_buffered_mac);
        TheStream(stream)->strm_wr_ch_array =
          TheStream(stream)->strm_wr_ch_array_npnl =
          P(wr_ch_array_buffered_mac);
      } else if (eq(eol,S(Kdos))) {
        TheStream(stream)->strm_wr_ch =
          TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_buffered_dos);
        TheStream(stream)->strm_wr_ch_array =
          TheStream(stream)->strm_wr_ch_array_npnl =
          P(wr_ch_array_buffered_dos);
      } else
        NOTREACHED;
    }
  }
}


/* UP: creates a buffered file stream
 make_buffered_stream(type,direction,&eltype,handle_regular,handle_blockpositioning)
 > STACK_2: Encoding
 > STACK_1: Element-Type
 > STACK_0: open file handle
 > type: stream type
 > direction: direction_t (see lispbibl.d)
 > eltype: Element-Type in decoded form
 > handle_regular: whether the handle refers to a regular file
 > handle_blockpositioning: whether the handle refers to a regular file which
                            can be positioned at n*strm_buffered_bufflen
 If direction==DIRECTION_IO(5), handle_blockpositioning must be true.
 < result: buffered file stream, Handle_{input,output}_init still to be called,
           for eltype.size<8 also eofposition still to be to determined
 < STACK: cleaned up
 can trigger GC */
local maygc object make_buffered_stream
(uintB type, direction_t direction, const decoded_el_t* eltype,
 bool handle_regular, bool handle_blockpositioning) {
  var uintB flags = DIRECTION_FLAGS(direction) & ELTYPE_FLAFS(eltype);
  var uintC xlen = NON_WHOLE_BYTE_P(eltype)
    ? sizeof(strm_i_buffered_extrafields_t) /* integer file-streams */
    : sizeof(strm_buffered_extrafields_t); /* all other file-streams */
  /* allocate Stream: */
  var object stream = allocate_stream(flags,type,strm_channel_len,xlen);
  /* and fill: */
  TheStream(stream)->strm_encoding = STACK_2;
  fill_pseudofuns_buffered(stream,eltype);
  TheStream(stream)->strm_rd_ch_last = NIL; /* Lastchar := NIL */
  TheStream(stream)->strm_wr_ch_lpos = Fixnum_0; /* Line Position := 0 */
  /* Components of File-Streams: */
  {
    var object handle = popSTACK(); /* restore Handle */
    TheStream(stream)->strm_eltype = popSTACK(); /* enter Element-Type */
    ChannelStream_buffered(stream) = true;
    ChannelStream_regular(stream) = handle_regular;
    ChannelStream_init(stream);
    if (!nullp(handle)) { /* Handle=NIL -> Rest already initialized with NIL, finished */
      BufferedStream_channel(stream) = handle; /* enter Handle */
      BufferedStream_blockpositioning(stream) = handle_blockpositioning;
      BufferedStream_buffstart(stream) = 0; /* buffstart := 0 */
      /* allocate Buffer: */
      pushSTACK(stream);
      {
        var object buffer =
          allocate_bit_vector(Atype_8Bit,strm_buffered_bufflen);
        stream = popSTACK();
        BufferedStream_buffer(stream) = buffer;
      }
      BufferedStream_endvalid(stream) = 0;
      BufferedStream_index(stream) = 0; /* index := 0 */
      BufferedStream_modified(stream) = false; /* Buffer unmodified */
      BufferedStream_have_eof_p(stream) = false;
      BufferedStream_position(stream) = 0; /* position := 0 */
      ChannelStream_bitsize(stream) = eltype->size;
      ChannelStream_lineno(stream) = 1; /* initialize always (cf. set-stream-element-type) */
      if (!(eltype->kind == eltype_ch)) {
        /* File-Stream of Integers
         allocate Bitbuffer: */
        pushSTACK(stream);
        {
          var object bitbuffer =
            allocate_bit_vector(Atype_Bit,ceiling(eltype->size,8)*8);
          stream = popSTACK();
          TheStream(stream)->strm_bitbuffer = bitbuffer;
        }
        if (!((eltype->size % 8) == 0)) { /* Types b,c */
          BufferedStream_bitindex(stream) = 0; /* bitindex := 0 */
        }
      }
    }
  }
  if (direction == DIRECTION_PROBE) { /* close stream right away */
    STACK_0 = stream; builtin_stream_close(&STACK_0,0); stream = STACK_0;
  }
  skipSTACK(1);
  return stream;
}

#if defined(MULTITHREAD)
/* O(open_files) is guarded by a global lock */
global xmutex_t open_files_lock;
#endif

/* UP: add a stream to the list of open streams O(open_files)
 add_to_open_streams()
 <> stream
 can trigger GC */
local maygc object add_to_open_streams (object stream) {
  pushSTACK(stream);
  var gcv_object_t *stream_ = &STACK_0;
  WITH_OS_MUTEX_LOCK(0,&open_files_lock, {
    var object new_cons = allocate_cons();
    Car(new_cons) = *stream_;
    Cdr(new_cons) = O(open_files);
    O(open_files) = new_cons;
  });
  return popSTACK();
}

/* UP: removes a stream from the list of open streams O(open_files)
 > stream
 maygc GC in MT builds */
local maygc void remove_from_open_streams(object stream)
{
  pushSTACK(stream);
  var gcv_object_t *stream_ = &STACK_0;
  WITH_OS_MUTEX_LOCK(0,&open_files_lock, {
    O(open_files) = deleteq(O(open_files),*stream_);
  });
  skipSTACK(1);
}

/* Find an open file that matches the given file ID
 > struct file_id fid = file ID to match
 > uintB flags = open flags to filter
 < pointer to the stream saved on STACK or NULL
   i.e., on success, adds 1 element to STACK */
global maygc void* find_open_file (struct file_id *fid, uintB flags);
global maygc void* find_open_file (struct file_id *fid, uintB flags) {
  pushSTACK(NIL); /* return value if file is found */
  var gcv_object_t *stream_ = &STACK_0;
  WITH_OS_MUTEX_LOCK(0, &open_files_lock, {
    var object tail = O(open_files);
    while (nullp(*stream_) && consp(tail)) {
      var object stream = Car(tail); tail = Cdr(tail);
      if (TheStream(stream)->strmtype == strmtype_file
          && TheStream(stream)->strmflags & flags
          && file_id_eq(fid,&ChannelStream_file_id(stream))) {
        *stream_ = stream;
      }
    }
  });
  return nullp(*stream_) ? (skipSTACK(1),(void*)NULL) : (void*)stream_;
}

/* UP: creates a File-Stream
 make_file_stream(direction,append_flag,handle_fresh)
 > STACK_5: Filename, a Pathname or NIL
 > STACK_4: Truename, a Pathname or NIL
 > STACK_3: :BUFFERED argument
 > STACK_2: :EXTERNAL-FORMAT argument
 > STACK_1: :ELEMENT-TYPE argument
 > STACK_0: Handle of the opened File
 > direction: direction_t (see lispbibl.d)
 > append_flag: true if the Stream is to be positioned to the End at the
         first go, else false
 > handle_fresh: whether the handle is freshly created.
         This means 1. that it is currently positioned at position 0,
                    2. if (direction & bit(2)), it is opened for read/write,
                       not only for write.
         If the handle refers to a regular file, this together means that it
         supports handle_lseek, reading/repositioning/writing and close/reopen.
   If direction==DIRECTION_IO(5), handle_fresh must be true.
 < result: File-Stream (or poss. File-Handle-Stream)
 < STACK: cleaned up
 can trigger GC */
modexp maygc object make_file_stream
(direction_t direction, bool append_flag, bool handle_fresh) {
  var decoded_el_t eltype;
  var buffered_t buffered;
  /* Check and canonicalize the :ELEMENT-TYPE argument: */
  test_eltype_arg(&STACK_1,&eltype);
  STACK_1 = canon_eltype(&eltype);
  /* Check and canonicalize the :EXTERNAL-FORMAT argument: */
  STACK_2 = test_external_format_arg(STACK_2);
  /* Stack Layout: filename, truename, buffered, encoding, eltype, handle. */
  var object stream;
  var object handle = STACK_0;
  var Handle file_des = INVALID_HANDLE;
  var bool handle_regular = true;
  if (!nullp(handle))
    handle_regular = regular_handle_p(file_des = TheHandle(handle));
  /* Check and canonicalize the :BUFFERED argument:
   Default is T for regular files, NIL for non-regular files because they
   probably don't support lseek(). */
  buffered = test_buffered_arg(STACK_3);
 #if defined(UNIX)
  /* /proc files are unbuffered by default */
  if ((buffered == BUFFERED_DEFAULT) && !nullp(STACK_4)) { /* truename */
    var object dir = ThePathname(STACK_4)->pathname_directory;
    if (consp(dir) && consp(Cdr(dir)))
      with_sstring_0(Car(Cdr(dir)),O(pathname_encoding),top_dir,
                     { if (asciz_equal(top_dir,"proc"))
                         buffered = BUFFERED_NIL; });
  }
 #endif
  if (buffered == BUFFERED_DEFAULT)
    buffered = (handle_regular ? BUFFERED_T : BUFFERED_NIL);
  if (buffered == BUFFERED_NIL) {
    if (!(eltype.kind == eltype_ch) && !((eltype.size % 8) == 0)) {
      pushSTACK(STACK_4); /* Truename, FILE-ERROR slot PATHNAME */
      pushSTACK(STACK_0);
      pushSTACK(STACK_(1+2));
      pushSTACK(S(Kelement_type));
      pushSTACK(TheSubr(subr_self)->name);
      error(file_error,GETTEXT("~S: argument ~S ~S was specified, but ~S is not a regular file."));
    }
    var bool handle_tty = false;
    if (READ_P(direction)) /* only needed for input handles */
      if (!handle_regular) { /* regular files are certainly not ttys */
        begin_system_call();
        handle_tty = isatty(file_des);
        end_system_call();
      }
    stream = make_unbuffered_stream(strmtype_file,direction,&eltype,
                                    handle_regular,handle_tty);
    /* file-handle-streams are treated for pathname purposes as file-streams
     thus (wrt file_write_date) strm_buffered_channel == strm_ochannel,
     and we have pathnames now: */
    TheStream(stream)->strm_file_truename = STACK_1; /* truename */
    TheStream(stream)->strm_file_name = STACK_2; /* filename */
    if (READ_P(direction))
      UnbufferedHandleStream_input_init(stream);
    if (WRITE_P(direction))
      UnbufferedHandleStream_output_init(stream);
    ChannelStreamLow_close(stream) = &low_close_handle;
  } else {
    if (direction==DIRECTION_IO && !handle_regular) {
      /* FIXME: Instead of signalling an error, we could return some kind
       of two-way-stream (cf. make_socket_stream). */
      pushSTACK(STACK_4); /* Truename, FILE-ERROR slot PATHNAME */
      pushSTACK(STACK_0);
      pushSTACK(T);
      pushSTACK(S(Kbuffered));
      pushSTACK(S(Kio));
      pushSTACK(S(Kdirection));
      pushSTACK(TheSubr(subr_self)->name);
      error(file_error,GETTEXT("~S: arguments ~S ~S and ~S ~S were specified, but ~S is not a regular file."));
    }
    /* Positioning the buffer on block boundaries is possible only if
     1. the handle refers to a regular file (otherwise read() and
        write() on the handle may be unrelated),
     2. if write access is requested, the handle is known to have
        read access as well (O_RDWR vs. O_WRONLY). */
    var bool handle_blockpositioning =
      (handle_regular && (WRITE_P(direction) ? handle_fresh : true));
    /* Now, if direction==DIRECTION_IO(5), handle_blockpositioning is true.
     allocate stream: */
    stream = make_buffered_stream(strmtype_file,direction,&eltype,
                                  handle_regular,handle_blockpositioning);
    TheStream(stream)->strm_file_truename = STACK_1; /* truename */
    TheStream(stream)->strm_file_name = STACK_2; /* filename */
    BufferedHandleStream_init(stream);
    ChannelStreamLow_close(stream) = &low_close_handle;
    pushSTACK(stream); /* STACK_0 = stream */
    if (handle_regular && !handle_fresh) {
      var uoff_t position;
      var Handle fd = TheHandle(BufferedStream_channel(stream));
      begin_blocking_system_call();
      handle_lseek(&STACK_0,fd,0,SEEK_CUR,position=);
      end_blocking_system_call();
      stream = STACK_0;
      position_file_buffered(stream,position);
      stream = STACK_0;
    }
    if (!nullp(BufferedStream_channel(stream))
        && !(eltype.kind == eltype_ch) && (eltype.size < 8)) {
      /* Type b
       read eofposition: */
      var uoff_t eofposition = 0;
      var uintC count;
      for (count = 0; count < 8*sizeof(uintL); count += 8) {
        var uintB* ptr = buffered_nextbyte(stream,persev_partial);
        stream = STACK_0;
        if (ptr == (uintB*)NULL)
          goto too_short;
        eofposition |= ((*ptr) << count);
        /* increment index, because *ptr is processed: */
        BufferedStream_index(stream) += 1;
      }
      if (false) {
       too_short:
        /* File too short (< sizeof(uintL) Bytes) */
        if ((TheStream(stream)->strmflags & strmflags_wr_by_B) == 0) /* Read-Only-Stream? */
          goto bad_eofposition;
        /* File Read/Write -> set eofposition := 0 */
        eofposition = 0;
        position_file_buffered(stream,0); /* move to position 0 */
        stream = STACK_0;
        var uintC count; /* and write eofposition = 0 */
        dotimespC(count,sizeof(uintL), { buffered_writebyte(stream,0); stream = STACK_0; } );
      } else if (eofposition > (uintV)(vbitm(oint_data_len)-1)) {
       bad_eofposition:
        /* No valid EOF-Position.
         close File and report Error: */
        TheStream(stream)->strmflags &= ~strmflags_wr_by_B; /* make Stream Read-Only */
        /* the stream is already on the stack */
        /*pushSTACK(stream);*/
        builtin_stream_close(&STACK_0,0);
        pushSTACK(Truename_or_Self(STACK_0)); /* STREAM-ERROR slot STREAM */
        error(stream_error,GETTEXT("file ~S is not an integer file"));
      }
      /* We rely on the read EOF-Position now! */
      BufferedStream_eofposition(stream) = eofposition;
    }
    skipSTACK(1); /* the stream */
  }
  skipSTACK(3);
  /* extend List of open File-Streams by stream: */
  if (direction != DIRECTION_PROBE) {
    if (handle_regular) { /* init file id */
      begin_system_call();
      if (handle_file_id(file_des,&ChannelStream_file_id(stream)))
        OS_filestream_error(stream);
      end_system_call();
    }
    stream = add_to_open_streams(stream);
  }
  /* treat Mode :APPEND:
   CLHS says that :APPEND implies that "the file pointer is _initially_
   positioned at the end of the file". Note that this is different from
   the Unix O_APPEND semantics. */
  if (append_flag) {
    pushSTACK(stream);
    if (buffered == BUFFERED_NIL) {
      /* position to the End: */
      var Handle output = TheHandle(TheStream(stream)->strm_ochannel);
      begin_blocking_system_call();
      handle_lseek(&STACK_0,output,0,SEEK_END,);
      end_blocking_system_call();
    } else {
      logical_position_file_end(stream);
    }
    stream = popSTACK();
  }
  return stream;
}

/* UP: Prepares the Closing of a File-Stream.
 Thereby the Buffer and poss. eofposition is flushed.
 buffered_flush_everything(stream);
 > stream : (open) File-Stream.
 changed in stream: index, endvalid, buffstart, ... */
local maygc void buffered_flush_everything (object stream) {
  /* For Integer-Streams (Type b) save eofposition: */
  if (ChannelStream_bitsize(stream) > 0 && ChannelStream_bitsize(stream) < 8)
    if (TheStream(stream)->strmflags & strmflags_wr_by_B) { /* only if not read-only */
      pushSTACK(stream);
      position_file_buffered(stream,0); /* move to position 0 */
      stream = STACK_0;
      var uoff_t eofposition = BufferedStream_eofposition(stream);
      /* FIXME: We should give an error if eofposition > ~(uintL)0. */
      var uintC count;
      dotimespC(count,sizeof(uintL), {
        buffered_writebyte(stream,(uintB)eofposition);
        stream = STACK_0;
        eofposition = eofposition>>8;
      });
      stream = popSTACK();
    }
  if (BufferedStream_modified(stream))
    buffered_flush(stream);
  /* Now the modified_flag is deleted. */
}

/* UP: Moves the pending Output of a File-Stream to the destination.
 Writes the Buffer of the File-Stream (also physically) to the File.
 finish_output_buffered(stream);
 > stream : File-Stream.
 changed in stream: handle, index, endvalid, buffstart, ..., rd_ch_last
 can trigger GC */
local maygc void finish_output_buffered (object stream) {
  /* Handle=NIL (Stream already closed) -> finished: */
  if (nullp(BufferedStream_channel(stream)))
    return;
  /* no File with write-access -> nothing to do: */
  if (!(TheStream(stream)->strmflags & strmflags_wr_B))
    return;
  pushSTACK(stream);
  /* flush pending Output in the iconv-Descriptor: */
  (void)oconv_unshift_output_buffered(stream,0);
  stream = STACK_0;
  /* poss. flush Buffer and eofposition: */
  buffered_flush_everything(stream);
  stream = STACK_0;
  /* Now the modified_flag is deleted. */
  if (ChannelStream_regular(stream)) {
   #ifdef UNIX
    #ifdef HAVE_FSYNC
    Handle fd=TheHandle(BufferedStream_channel(stream));
    begin_blocking_system_call();
    if (fsync(fd)) {
      end_blocking_system_call(); OS_filestream_error(popSTACK());
    }
    end_blocking_system_call();
    stream = STACK_0;
    #endif
   #endif
  }
  skipSTACK(1);
  /* and reposition: */
  var uoff_t position = BufferedStream_buffstart(stream) + BufferedStream_index(stream);
  BufferedStream_index(stream) = 0; /* index := 0 */
  BufferedStream_endvalid(stream) = 0;
  if (!BufferedStream_blockpositioning(stream)) {
    BufferedStream_buffstart(stream) = position;
  } else {
    BufferedStream_buffstart(stream) = 0; /* buffstart := 0 */
    position_file_buffered(stream,position);
  }
  /* Components position, ..., lastchar remain unchanged */
}

/* UP: Moves the pending Output of a File-Stream to the destination.
 Writes the Buffer of the File-Stream (also physically) to the File.
 force_output_buffered(stream);
 > stream : File-Stream.
 changed in stream: handle, index, endvalid, buffstart, ..., rd_ch_last
 can trigger GC */
  #define force_output_buffered  finish_output_buffered

/* UP: Declares a File-Stream as closed.
 closed_buffered(stream);
 > stream : (open) File-Stream.
 changed in stream: all Components except name and truename */
local void closed_buffered (object stream) {
  BufferedStream_channel(stream) = NIL; /* Handle becomes invalid */
  BufferedStream_buffer(stream) = NIL; /* free Buffer */
  BufferedStream_buffstart(stream) = 0; /* delete buffstart (unnecessary) */
  BufferedStream_endvalid(stream) = 0; /* delete endvalid (unnecessary) */
  BufferedStream_index(stream) = 0; /* delete index (unnecessary) */
  BufferedStream_modified(stream) = false; /* delete modified_flag (unnecessary) */
  BufferedStream_position(stream) = 0; /* delete position (unnecessary) */
  BufferedStream_have_eof_p(stream) = false; /* delete have_eof_p (unnecessary) */
  if (ChannelStream_bitsize(stream) > 0) {
    ChannelStream_bitsize(stream) = 0; /* delete bitsize */
    TheStream(stream)->strm_bitbuffer = NIL; /* free Bitbuffer */
  }
  #if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
  ChannelStream_iconvdesc(stream) = (iconv_t)0; /* delete iconvdesc */
  ChannelStream_oconvdesc(stream) = (iconv_t)0; /* delete oconvdesc */
  #endif
}

/* UP: Closes a File-Stream.
 close_buffered(stream, abort);
 > stream : File-Stream.
 > abort: flag: non-0 => ignore errors
 changed in stream: all Components except name and truename */
local maygc void close_buffered (object stream, uintB abort) {
  /* Handle=NIL (Stream already closed) -> finished: */
  if (nullp(BufferedStream_channel(stream)))
    return;
  pushSTACK(stream);
  /* Flush pending Output in the iconv-Descriptor: */
  if (!oconv_unshift_output_buffered(stream,abort)) { /* success */
    stream = STACK_0;
    /* poss. flush Buffer and eofposition: */
    MAYBE_IGNORE_ERRORS(abort,buffered_flush_everything(stream));
  }
  stream = STACK_0;
  /* Now the modified_flag is deleted (unless aborted!)
   close File: */
  ChannelStreamLow_close(stream)(stream,BufferedStream_channel(stream),abort);
  stream = popSTACK();
  ChannelStream_fini(stream,abort);
  /* make Components invalid (close_dummys comes later): */
  closed_buffered(stream);
  /* remove stream from the List of all open File-Streams: */
  remove_from_open_streams(stream);
}

LISPFUNNF(file_stream_p,1)
{ /* (SYS::FILE-STREAM-P stream) == (TYPEP stream 'FILE-STREAM) */
  var object arg = popSTACK();
  VALUES_IF(builtin_stream_p(arg)
            && (TheStream(arg)->strmtype == strmtype_file));
}


#ifdef KEYBOARD

/* Keyboard-Stream
   ===============

 Functionality:
 Reads a character from the keyboard.
 Returns a Character with Font=0 and following Bits:
   HYPER      if special key.
              Among the special keys are the Non-Standard-Tasten.
   CHAR-CODE  For normal keys the Ascii-Code,
   SUPER      if pressed with Shift-Key(s) and another Code had been the result
                without Shift,
   CONTROL    if pressed with Control-Key,
   META       if pressed with Alternate-Key. */

#if defined(UNIX)
  /* Additional Components: */
  #define strm_keyboard_isatty  strm_isatty   /* Flag, if stdin is a Terminal */
  #define strm_keyboard_handle  strm_ichannel /* Handle for listen_char_unbuffered() */
  #define strm_keyboard_buffer  strm_field1   /* List of still to be delivered characters */
  #define strm_keyboard_keytab  strm_field2   /* List of all key bindings */
                                              /* always (char1 ... charn . result) */
  #define strm_keyboard_len  strm_channel_len
  #define strm_keyboard_xlen  sizeof(strm_unbuffered_extrafields_t)
#elif defined(WIN32_NATIVE)
  /* Additional Components: */
  #define strm_keyboard_isatty  strm_isatty   /* Flag, if stdin is a Terminal */
  #define strm_keyboard_handle  strm_ichannel /* Handle for listen_char_unbuffered() */
  #define strm_keyboard_len  strm_channel_len
  #define strm_keyboard_xlen  sizeof(strm_unbuffered_extrafields_t)
#else
  /* No Additional Components: */
  #define strm_keyboard_len  strm_len
  #define strm_keyboard_xlen  0
#endif

/* The keyboard events are instances of INPUT-CHARACTER. We create them by
 calling MAKE-INPUT-CHARACTER or MAKE-CHAR. The following structure describes
 the arguments to MAKE-INPUT-CHARACTER. */
typedef struct {
  const char * key;
  chart code;
  uintB bits;
} key_event_t;

/* Initializers for the two most common kinds of keyboard events. */
  #define key_ascii(asc)  { NULL, ascii(asc), 0 }
  #define key_special(name)  { name, ascii(0), char_hyper_c }

/* Creates a keyboard event. */
local object make_key_event (const key_event_t* event) {
  if ((event->key == NULL) && (event->bits == 0)) {
    pushSTACK(S(Kchar)); pushSTACK(code_char(event->code));
    funcall(S(make_input_character),2);
  } else {
    pushSTACK(S(Kkey));
    if (event->key == NULL)
      pushSTACK(code_char(event->code));
    else
      pushSTACK(intern_keyword(ascii_to_string(event->key)));
    pushSTACK(S(Kbits)); pushSTACK(fixnum(event->bits));
    funcall(S(make_input_character),4);
  }
  return value1;
}

/* Values for the bits, must agree with xcharin.lisp. */
  #define char_control_c  1
  #define char_meta_c     2
  #define char_super_c    4
  #define char_hyper_c    8

/* Determines, if a Character is available on the Keyboard-Stream.
 listen_char_keyboard(stream)
 > stream: Stream
 < result: input availability */
#ifdef WIN32_NATIVE
local listen_t listen_char_keyboard (object stream) {
  var Handle handle = TheHandle(TheStream(stream)->strm_keyboard_handle);
  /* See the implementation of listen_char_unbuffered() for consoles. */
  var DWORD nevents;
  begin_system_call();
  if (!GetNumberOfConsoleInputEvents(handle,&nevents)) {
    OS_error();
  }
  /* It's a console. */
  if (nevents==0) { /* no character available */
    end_system_call(); return LISTEN_WAIT;
  }
  var DYNAMIC_ARRAY(events,INPUT_RECORD,nevents);
  var DWORD nevents_read;
  if (!PeekConsoleInput(handle,events,nevents,&nevents_read)) {
    OS_error();
  }
  if (nevents_read==0) { /* no character available */
    FREE_DYNAMIC_ARRAY(events);
    end_system_call(); return LISTEN_WAIT;
  }
  { /* Look out for any Key-Down event. */
    var DWORD i;
    for (i = 0; i < nevents_read; i++) {
      if (events[i].EventType == KEY_EVENT
          && events[i].Event.KeyEvent.bKeyDown
          && events[i].Event.KeyEvent.uAsciiChar != 0) {
        /* character available */
        FREE_DYNAMIC_ARRAY(events);
        end_system_call(); return LISTEN_AVAIL;
      }
    }
  }
  /* no character available */
  FREE_DYNAMIC_ARRAY(events);
  end_system_call(); return LISTEN_WAIT;
}
#endif
#if defined(UNIX)
  #define listen_char_keyboard  listen_char_unbuffered
#endif

/* UP: Deletes already entered interactive Input from a Keyboard-Stream.
 clear_input_keyboard(stream);
 > stream: Stream
 < result: true if Input was deleted, else false */
local bool clear_input_keyboard (object stream) {
 #ifdef WIN32_NATIVE
  clear_tty_input(TheHandle(TheStream(stream)->strm_keyboard_handle));
  pushSTACK(stream);
  while (LISTEN_AVAIL == listen_char_keyboard(STACK_0))
    read_char(&STACK_0);
  skipSTACK(1);
 #endif
 #if defined(UNIX)
  if (nullp(TheStream(stream)->strm_keyboard_isatty)) /* File -> do nothing */
    return false;
  /* Terminal */
  TheStream(stream)->strm_rd_ch_last = NIL; /* EOF forgotten */
  clear_tty_input(stdin_handle);
  pushSTACK(stream);
  while (LISTEN_AVAIL == listen_char_keyboard(STACK_0))
    read_char(&STACK_0);
  skipSTACK(1);
 #endif
  return true;
}

/* Read a character from Keyboard: */
#ifdef WIN32_NATIVE
local object rd_ch_keyboard (const gcv_object_t* stream_) {
  var INPUT_RECORD event;
  var DWORD nevents_read;
  var Handle handle;
 restart_it:
  handle = TheHandle(TheStream(*stream_)->strm_keyboard_handle);
  begin_system_call();
  while (1) {
    if (!ReadConsoleInput1(handle,&event,&nevents_read)) {
      if (GetLastError()==ERROR_SIGINT) { /* Break by Ctrl-C ? */
        end_system_call();
        pushSTACK(S(read_char)); tast_break(); /* call Break-Loop */
        goto restart_it;
      }
      OS_error();
    }
    ASSERT(nevents_read==1);
    if (event.EventType == KEY_EVENT && event.Event.KeyEvent.bKeyDown) {
      var key_event_t ev;
      if (event.Event.KeyEvent.wRepeatCount > 1) {
        var DWORD nevents_written;
        event.Event.KeyEvent.wRepeatCount--;
        if (!WriteConsoleInput(handle,&event,1,&nevents_written)) {
          OS_error();
        }
      }
      if ((uintB)event.Event.KeyEvent.uAsciiChar <= ' ') {
        /* Translate Virtual Keycode. */
        local const struct { WORD vkcode; key_event_t myevent; } vktable[] = {
          VK_BACK,    { NULL,  BS, 0 },               /* #\Backspace */
          VK_TAB,     { NULL, TAB, 0 },               /* #\Tab */
          VK_CLEAR,   { NULL, PG, 0 },                /* #\Page */
          VK_RETURN,  { NULL,  CR, 0 },               /* #\Return */
          VK_ESCAPE,  { NULL, ESC, 0 },               /* #\Escape */
          VK_SHIFT,   { "SHIFT", 0, 0 },
          VK_CONTROL, { "CONTROL", 0, 0 },
          VK_MENU,    { "MENU", 0, 0 },
          VK_PAUSE,   { "PAUSE", 0, 0 },
          VK_CAPITAL, { "CAPITAL", 0, 0 },
          VK_LEFT,    { "LEFT", 0, char_hyper_c },    /* #\Left */
          VK_RIGHT,   { "RIGHT", 0, char_hyper_c },   /* #\Right */
          VK_UP,      { "UP", 0, char_hyper_c },      /* #\Up */
          VK_DOWN,    { "DOWN", 0, char_hyper_c },    /* #\Down */
          VK_PRIOR,   { "PGUP", 0, char_hyper_c },    /* #\PgUp */
          VK_NEXT,    { "PGDN", 0, char_hyper_c },    /* #\PgDn */
          VK_HOME,    { "HOME", 0, char_hyper_c },    /* #\Home */
          VK_END,     { "END", 0, char_hyper_c },     /* #\End */
          VK_INSERT,  { "INSERT", 0, char_hyper_c },  /* #\Insert */
          VK_DELETE,  { "DELETE", 0, char_hyper_c },  /* #\Delete */
          12,         { "CENTER", 0, char_hyper_c },  /* #\Center */
          VK_F1,      { "F1", 0, char_hyper_c },      /* #\F1 */
          VK_F2,      { "F2", 0, char_hyper_c },      /* #\F2 */
          VK_F3,      { "F3", 0, char_hyper_c },      /* #\F3 */
          VK_F4,      { "F4", 0, char_hyper_c },      /* #\F4 */
          VK_F5,      { "F5", 0, char_hyper_c },      /* #\F5 */
          VK_F6,      { "F6", 0, char_hyper_c },      /* #\F6 */
          VK_F7,      { "F7", 0, char_hyper_c },      /* #\F7 */
          VK_F8,      { "F8", 0, char_hyper_c },      /* #\F8 */
          VK_F9,      { "F9", 0, char_hyper_c },      /* #\F9 */
          VK_F10,     { "F10", 0, char_hyper_c },     /* #\F10 */
          VK_F11,     { "F11", 0, char_hyper_c },     /* #\F11 */
          VK_F12,     { "F12", 0, char_hyper_c },     /* #\F12 */
          VK_LWIN,    { "WIN", 0, char_hyper_c },     /* Win key */
          VK_RWIN,    { "WIN", 0, char_hyper_c },     /* Same */
          VK_APPS,    { "APPS", 0, char_hyper_c },    /* App key */
          VK_SELECT,  { "SELECT", 0, char_hyper_c },
          VK_PRINT,   { "PRINT", 0, char_hyper_c },
          VK_EXECUTE, { "EXECUTE", 0, char_hyper_c },
          VK_SNAPSHOT,{ "SNAPSHOT", 0, char_hyper_c },
          VK_ADD,     { "ADD", 0, char_hyper_c },
          VK_SEPARATOR,{ "SEPARATOR", 0, char_hyper_c },
          VK_SUBTRACT,{ "SUBTRACT", 0, char_hyper_c },
          VK_DECIMAL, { "DECIMAL", 0, char_hyper_c },
          VK_DIVIDE,  { "DIVIDE", 0, char_hyper_c },
          VK_NUMLOCK, { "NUMLOCK", 0, char_hyper_c },
          VK_SCROLL,  { "SCROLL", 0, char_hyper_c },
          VK_LSHIFT,  { "LSHIFT", 0, char_hyper_c },
          VK_RSHIFT,  { "RSHIFT", 0, char_hyper_c },
          VK_LCONTROL,{ "LCONTROL", 0, char_hyper_c },
          VK_RCONTROL,{ "RCONTROL", 0, char_hyper_c },
          VK_LMENU,   { "LMENU", 0, char_hyper_c },
          VK_RMENU,   { "RMENU", 0, char_hyper_c },
         #if (_WIN32_WINNT >= 0x0500)
          VK_BROWSER_BACK, { "BROWSER_BACK", 0, char_hyper_c },
          VK_BROWSER_FORWARD, { "BROWSER_FORWARD", 0, char_hyper_c },
          VK_BROWSER_REFRESH, { "BROWSER_REFRESH", 0, char_hyper_c },
          VK_BROWSER_STOP, { "BROWSER_STOP", 0, char_hyper_c },
          VK_BROWSER_SEARCH, { "BROWSER_SEARCH", 0, char_hyper_c },
          VK_BROWSER_FAVORITES, { "BROWSER_FAVORITES", 0, char_hyper_c },
          VK_BROWSER_HOME, { "BROWSER_HOME", 0, char_hyper_c },
          VK_VOLUME_MUTE, { "VOLUME_MUTE", 0, char_hyper_c },
          VK_VOLUME_DOWN, { "VOLUME_DOWN", 0, char_hyper_c },
          VK_VOLUME_UP, { "VOLUME_UP", 0, char_hyper_c },
          VK_MEDIA_NEXT_TRACK, { "MEDIA_NEXT_TRACK", 0, char_hyper_c },
          VK_MEDIA_PREV_TRACK, { "MEDIA_PREV_TRACK", 0, char_hyper_c },
          VK_MEDIA_STOP, { "MEDIA_STOP", 0, char_hyper_c },
          VK_MEDIA_PLAY_PAUSE, { "MEDIA_PLAY_PAUSE", 0, char_hyper_c },
          VK_LAUNCH_MAIL, { "LAUNCH_MAIL", 0, char_hyper_c },
          VK_LAUNCH_MEDIA_SELECT, { "LAUNCH_MEDIA_SELECT", 0, char_hyper_c },
          VK_LAUNCH_APP1, { "LAUNCH_APP1", 0, char_hyper_c },
          VK_LAUNCH_APP2, { "LAUNCH_APP2", 0, char_hyper_c },
         #endif
          ' ',        { NULL, ' ', 0 },               /* #\Space */
          '0',        { NULL, '0', 0 },               /* #\0 */
          '1',        { NULL, '1', 0 },               /* #\1 */
          '2',        { NULL, '2', 0 },               /* #\2 */
          '3',        { NULL, '3', 0 },               /* #\3 */
          '4',        { NULL, '4', 0 },               /* #\4 */
          '5',        { NULL, '5', 0 },               /* #\5 */
          '6',        { NULL, '6', 0 },               /* #\6 */
          '7',        { NULL, '7', 0 },               /* #\7 */
          '8',        { NULL, '8', 0 },               /* #\8 */
          '9',        { NULL, '9', 0 },               /* #\9 */
          'A',        { NULL, 'A', 0 },               /* #\A */
          'B',        { NULL, 'B', 0 },               /* #\B */
          'C',        { NULL, 'C', 0 },               /* #\C */
          'D',        { NULL, 'D', 0 },               /* #\D */
          'E',        { NULL, 'E', 0 },               /* #\E */
          'F',        { NULL, 'F', 0 },               /* #\F */
          'G',        { NULL, 'G', 0 },               /* #\G */
          'H',        { NULL, 'H', 0 },               /* #\H */
          'I',        { NULL, 'I', 0 },               /* #\I */
          'J',        { NULL, 'J', 0 },               /* #\J */
          'K',        { NULL, 'K', 0 },               /* #\K */
          'L',        { NULL, 'L', 0 },               /* #\L */
          'M',        { NULL, 'M', 0 },               /* #\M */
          'N',        { NULL, 'N', 0 },               /* #\N */
          'O',        { NULL, 'O', 0 },               /* #\O */
          'P',        { NULL, 'P', 0 },               /* #\P */
          'Q',        { NULL, 'Q', 0 },               /* #\Q */
          'R',        { NULL, 'R', 0 },               /* #\R */
          'S',        { NULL, 'S', 0 },               /* #\S */
          'T',        { NULL, 'T', 0 },               /* #\T */
          'U',        { NULL, 'U', 0 },               /* #\U */
          'V',        { NULL, 'V', 0 },               /* #\V */
          'W',        { NULL, 'W', 0 },               /* #\W */
          'X',        { NULL, 'X', 0 },               /* #\X */
          'Y',        { NULL, 'Y', 0 },               /* #\Y */
          'Z',        { NULL, 'Z', 0 },               /* #\Z */
          107,        { NULL, '+', char_hyper_c },    /* #\HYPER-+ */
          109,        { NULL, '-', char_hyper_c },    /* #\HYPER-- */
          106,        { NULL, '*', char_hyper_c },    /* #\HYPER-* */
          111,        { NULL, '/', char_hyper_c },    /* #\HYPER-/ */
          186,        { NULL, ';', 0 },               /* #\; */
          187,        { NULL, '=', 0 },               /* #\= */
          188,        { NULL, ',', 0 },               /* #\, */
          189,        { NULL, '-', 0 },               /* #\- */
          190,        { NULL, '.', 0 },               /* #\. */
          191,        { NULL, '/', 0 },               /* #\/ */
          192,        { NULL, '`', 0 },               /* #\` */
          219,        { NULL, '[', 0 },               /* #\[ */
          220,        { NULL, '\\', 0 },              /* #\ */\
          221,        { NULL, ']', 0 },               /* #\] */
          222,        { NULL, '\'', 0 },              /* #\' */
        };
        var int i;
        for (i = 0; i < sizeof(vktable)/sizeof(vktable[0]); i++) {
          if (event.Event.KeyEvent.wVirtualKeyCode == vktable[i].vkcode) {
            ev = vktable[i].myevent; goto found_keycode;
          }
        }
        switch (event.Event.KeyEvent.wVirtualKeyCode) {
          case VK_SHIFT:
          case VK_CONTROL:
          case 18: case 20:
            break;
          default:
            fprintf(stderr,"["STRINGIFY(_WIN32_WINNT)"] Unknown keyboard event, VKeyCode = %d, VScanCode = %d, AsciiChar = %d\n",event.Event.KeyEvent.wVirtualKeyCode,event.Event.KeyEvent.wVirtualScanCode,event.Event.KeyEvent.uAsciiChar);
        }
        continue;
      found_keycode:
        if (event.Event.KeyEvent.dwControlKeyState & SHIFT_PRESSED)
          ev.bits |= char_super_c;
        if (event.Event.KeyEvent.dwControlKeyState
            & (LEFT_CTRL_PRESSED | RIGHT_CTRL_PRESSED))
          ev.bits |= char_control_c;
        if (event.Event.KeyEvent.dwControlKeyState
            & (LEFT_ALT_PRESSED | RIGHT_ALT_PRESSED))
          ev.bits |= char_meta_c;
      } else {
       #ifdef ENABLE_UNICODE
        var object encoding = TheStream(*stream_)->strm_encoding;
        var chart c = as_chart(0);
        var uintB buf[max_bytes_per_chart];
        var chart* cptr  = &c;
        var const uintB* bptr  = buf;
        memset(buf,0,max_bytes_per_chart);
        buf[0] = (uintB) event.Event.KeyEvent.uAsciiChar;
        Encoding_mbstowcs(encoding)
          (encoding,*stream_,&bptr,bptr+max_bytes_per_chart,&cptr,cptr+1);
       #else
        var cint ci = event.Event.KeyEvent.uAsciiChar;
        var chart c = as_chart(ci);
        OemToCharBuff((char *)&ci,(char *)&ci,1);
        c = as_chart(ci);
       #endif
        ev.key = NULL;
        ev.code = c;
        ev.bits = 0;
        if (event.Event.KeyEvent.dwControlKeyState &
            (LEFT_ALT_PRESSED | RIGHT_ALT_PRESSED)) {
          /* c = 'a'..'z' -> translate to 'A'..'Z'
           c = 'A'..'Z' -> add "Shift"
           c = '<','>' etc. -> don't add "Shift" */
          ev.code = up_case(ev.code);
          if (!chareq(ev.code,down_case(ev.code))) {
            if (event.Event.KeyEvent.dwControlKeyState & SHIFT_PRESSED)
              ev.bits |= char_super_c;
          }
          ev.bits |= char_meta_c;
        }
      }
      end_system_call();
      return make_key_event(&ev);
    }
    /* Other events are silently thrown away. */
  }
}
#endif

#if defined(UNIX)
local inline gcv_object_t* kbd_last_buf (const object stream) {
  var gcv_object_t* last_ = &TheStream(stream)->strm_keyboard_buffer;
  while (mconsp(*last_)) { last_ = &Cdr(*last_); }
  return last_;
}

/* cf. rd_ch_unbuffered() : */
local object rd_ch_keyboard (const gcv_object_t* stream_) {
 restart_it: {
  var object stream = *stream_;
  if (eq(TheStream(stream)->strm_rd_ch_last,eof_value)) /* EOF already? */
    return eof_value;
  /* Still something in the Buffer? */
  if (UnbufferedStream_status(stream) > 0) {
    var uintL num_bytes = UnbufferedStream_status(stream);
    var uintB *bytes = UnbufferedStream_bytebuf(stream);
    var uintL count;
    UnbufferedStream_status(stream) = 0;
    dotimespL(count,num_bytes,{ pushSTACK(code_char(as_chart(*bytes++))); }); /* FIXME: This should take into account the encoding. */
    var object new_list = listof(num_bytes);
    *kbd_last_buf(stream = *stream_) = new_list;
  }
  if (mconsp(TheStream(stream)->strm_keyboard_buffer))
    goto empty_buffer;
  { /* read a character: */
    var uintB c;
   read_next_char: {
      begin_system_call();
      var int result = read(stdin_handle,&c,1); /* try to read a byte */
      end_system_call();
      if (result<0) {
        begin_system_call();
        if (errno==EINTR) { /* break (poss. by Ctrl-C) ? */
          end_system_call();
          interruptp({ pushSTACK(S(read_char)); tast_break(); }); /* call Break-Loop */
          goto restart_it;
        }
        OS_error();
      }
      if (result==0) { /* no character available -> recognize EOF */
        TheStream(stream)->strm_rd_ch_last = eof_value; return eof_value;
      }
    }
   next_char_is_read: { /* increase the buffer: */
      var object new_cons = allocate_cons();
      Car(new_cons) = code_char(as_chart(c)); /* FIXME: This should take into account the encoding. */
      *kbd_last_buf(stream = *stream_) = new_cons;
    }
    /* Is the buffer a complete sequence of characters for a key,
     so we will return this key. Is the buffer a genuine starting piece
     of a sequence of characters for a key, so we will wait a little bit.
     Otherwise we start to empty the buffer character for character. */
    {
      var object keytab = TheStream(stream)->strm_keyboard_keytab;
      while (consp(keytab)) {
        var object L1 = Car(keytab);
        keytab = Cdr(keytab);
        var object L2 = TheStream(stream)->strm_keyboard_buffer;
        while (consp(L1) && consp(L2) && eq(Car(L1),Car(L2))) {
          L1 = Cdr(L1); L2 = Cdr(L2);
        }
        if (atomp(L2)) {
          if (atomp(L1)) {
            /* complete sequence of characters */
            TheStream(stream)->strm_keyboard_buffer = NIL;
            return L1;
          }
        }
      }
    }
    {
      var object keytab = TheStream(stream)->strm_keyboard_keytab;
      while (consp(keytab)) {
        var object L1 = Car(keytab);
        keytab = Cdr(keytab);
        var object L2 = TheStream(stream)->strm_keyboard_buffer;
        while (consp(L1) && consp(L2) && eq(Car(L1),Car(L2))) {
          L1 = Cdr(L1); L2 = Cdr(L2);
        }
        if (atomp(L2))
          /* As consp(L1), the starting piece of a sequence of characters is there. */
          goto wait_for_another;
      }
    }
    goto empty_buffer;
  wait_for_another:
  #if defined(HAVE_POLL)
    {
      /* Use poll() with a single handle {stdin_handle}
       and timeout = zero interval. */
      var struct pollfd pollfd_bag[1];
      pollfd_bag[0].fd = stdin_handle;
      pollfd_bag[0].events = POLLIN;
      pollfd_bag[0].revents = 0;
     restart_poll:
      begin_system_call();
      var int result = poll(&pollfd_bag[0],1,100); /* 1/10 sec */
      end_system_call();
      if (result<0) {
        begin_system_call();
        if (errno==EINTR) {
          end_system_call(); goto restart_poll;
        }
        OS_error();
      } else {
        /* revents has POLLIN or some other bits set if read() would return
         without blocking. */
        if (pollfd_bag[0].revents == 0)
          goto empty_buffer; /* no character available */
      }
    }
  #elif defined(HAVE_SELECT) && !defined(UNIX_BEOS)
    {
      /* Use select with readfds = one-element set {stdin_handle}
       and timeout = small time-interval. */
      var fd_set handle_set; /* set of handles := {stdin_handle} */
      var struct timeval small_time; /* time-interval := 0 */
      FD_ZERO(&handle_set); FD_SET(stdin_handle,&handle_set);
    restart_select:
      small_time.tv_sec = 0; small_time.tv_usec = 1000000/10; /* 1/10 sec */
      begin_system_call();
      var int result;
      result = select(FD_SETSIZE,&handle_set,NULL,NULL,&small_time);
      end_system_call();
      if (result<0) {
        begin_system_call();
        if (errno==EINTR) {
          end_system_call(); goto restart_select;
        }
        if (!(errno == EBADF)) {
          OS_error();
        }
        end_system_call();
      } else {
        /* result = number of Handles in handle_set, for which read
         would return a result immediately. */
        if (result==0)
          goto empty_buffer; /* no character available */
        /* result=1 -> character available */
      }
    }
  #else
   #ifdef UNIX_TERM_TERMIOS
    {
      /* Use the Termio-Elements VMIN and VTIME. */
      var struct termios oldtermio;
      var struct termios newtermio;
      begin_system_call();
      if (!( tcgetattr(stdin_handle,&oldtermio) ==0)) {
        if (!(errno==ENOTTY)) { OS_error(); }
      }
      /* We assume now, that oldtermio is now identical with the newtermio
       from term_raw() (see below). This is ensured, if
       1. (SYS::TERMINAL-RAW T) was called and
       2. stdin_handle and stdout_handle both are the same Terminal. ?? */
      newtermio = oldtermio;
      newtermio.c_cc[VMIN] = 0;
      newtermio.c_cc[VTIME] = 1; /* 1/10 second timeout */
      if (!( TCSETATTR(stdin_handle,TCSANOW,&newtermio) ==0)) {
        if (!(errno==ENOTTY)) { OS_error(); }
      }
      var int result = read(stdin_handle,&c,1); /* try to read a byte, with timeout */
      if (!( TCSETATTR(stdin_handle,TCSANOW,&oldtermio) ==0)) {
        if (!(errno==ENOTTY)) { OS_error(); }
      }
      end_system_call();
      if (result<0) {
        begin_system_call();
        if (errno==EINTR) { /* break (poss. by Ctrl-C) ? */
          end_system_call();
          interruptp({ pushSTACK(S(read_char)); tast_break(); }); /* call Break-Loop */
          goto restart_it;
        }
        OS_error();
      }
      if (result==0)
        goto empty_buffer; /* no character available */
      goto next_char_is_read; /* result=1 -> character available */
    }
   #else
    /* One could use fcntl(stdin_handle,F_SETFL,...|FASYNC) here
     and wait for the Signal SIGIO. But this works only on so
     few Systems (see Emacs), that it does not pay off. */
   #endif
  #endif
    goto read_next_char;
  }
   empty_buffer: { /* return buffer character for character: */
    var object l = TheStream(stream)->strm_keyboard_buffer;
    TheStream(stream)->strm_keyboard_buffer = Cdr(l);
    var cint c = as_cint(char_code(Car(l)));
    if ((c >= ' ') || (c == ESC) || (c == TAB) || (c == CR) || (c == BS)) {
      /* FIXME: This should take into account the encoding. */
      pushSTACK(code_char(as_chart(c))); funcall(S(make_char),1);
      return value1;
    } else {
      /* key presumably pressed with Ctrl */
      var key_event_t event;
      event.key = NULL;
      event.code = ascii(c == 0 ? ' ' : (c | bit(6)));
      event.bits = char_control_c;
      return make_key_event(&event);
    }
  }
 }
}


/* UP: extends the List STACK_0 by one key-assignment.
 can trigger GC */
local maygc void add_keybinding (const char* cap, const key_event_t* event) {
  var const uintB* ptr = (const uintB*)cap;
  if (*ptr=='\0') /* avoid empty key-sequence */
    return;
  /* FIXME: This should take into account the encoding. */
  pushSTACK(allocate_cons());
  /* create List (char1 ... charn . key) : */
  {
    var uintC count = 0;
    do { pushSTACK(code_char(as_chart(*ptr))); ptr++; count++;
    } while (*ptr != '\0');
    pushSTACK(make_key_event(event)); count++;
    funcall(L(liststar),count);
  }
  /* and push on STACK_0: */
  {
    var object l = popSTACK();
    Car(l) = value1; Cdr(l) = STACK_0; STACK_0 = l;
  }
}
#define keybinding(cap,initializer)  \
  do { key_event_t event = initializer; add_keybinding(cap,&event); } while(0)
#endif

/* returns a Keyboard-Stream.
 make_keyboard_stream()
 can trigger GC */
local maygc object make_keyboard_stream (void) {
 #if defined(UNIX)
  {
    /* build Table of all assignments character-sequence -> Key : */
    pushSTACK(NIL);
    /* query Terminal-Type: */
    begin_system_call();
    var const char* s = getenv("TERM");
    if (s==NULL) {
      end_system_call();
    } else {
      var char tbuf[4096]; /* internal Buffer for the Termcap-Routines */
      if (tgetent(tbuf,s) !=1) {
        end_system_call();
      } else {
        var char tentry[4096]; /* Buffer for the Capabilities that I need */
        var char* tp = &tentry[0];
        var const char* cap;
        end_system_call();
        /* Backspace: */
        begin_system_call(); cap = tgetstr("kb",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_ascii(BS)); /* #\Backspace */
        /* Insert, Delete: */
        begin_system_call(); cap = tgetstr("kI",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("INSERT")); /* #\Insert */
        begin_system_call(); cap = tgetstr("kD",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("DELETE")); /* #\Delete */
        /* arrow keys: */
        begin_system_call(); cap = tgetstr("ku",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("UP")); /* #\Up */
        if (cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'A') && (cap[3] == '\0'))
          keybinding(ESCstring"[A", key_special("UP")); /* #\Up */
        begin_system_call(); cap = tgetstr("kd",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("DOWN")); /* #\Down */
        if (cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'B') && (cap[3] == '\0'))
          keybinding(ESCstring"[B", key_special("DOWN")); /* #\Down */
        begin_system_call(); cap = tgetstr("kr",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("RIGHT")); /* #\Right */
        if (cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'C') && (cap[3] == '\0'))
          keybinding(ESCstring"[C", key_special("RIGHT")); /* #\Right */
        begin_system_call(); cap = tgetstr("kl",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("LEFT")); /* #\Left */
        if (cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'D') && (cap[3] == '\0'))
          keybinding(ESCstring"[D", key_special("LEFT")); /* #\Left */
        /* other cursorblock-keys: */
        begin_system_call(); cap = tgetstr("kh",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("HOME")); /* #\Home */
        begin_system_call(); cap = tgetstr("K1",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("HOME")); /* #\Home */
        begin_system_call(); cap = tgetstr("KH",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("END")); /* #\End */
        begin_system_call(); cap = tgetstr("K4",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("END")); /* #\End */
        begin_system_call(); cap = tgetstr("kP",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("PGUP")); /* #\PgUp */
        begin_system_call(); cap = tgetstr("K3",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("PGUP")); /* #\PgUp */
        begin_system_call(); cap = tgetstr("kN",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("PGDN")); /* #\PgDn */
        begin_system_call(); cap = tgetstr("K5",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("PGDN")); /* #\PgDn */
        begin_system_call(); cap = tgetstr("K2",&tp); end_system_call();
        if (cap)
          keybinding(cap, key_special("CENTER")); /* #\Center */
        /* Function Keys: */
        {
          typedef struct { const char* capname; key_event_t key; } funkey;
          local var const funkey funkey_tab[] = {
            { "k1", key_special("F1") }, /* #\F1 */
            { "k2", key_special("F2") }, /* #\F2 */
            { "k3", key_special("F3") }, /* #\F3 */
            { "k4", key_special("F4") }, /* #\F4 */
            { "k5", key_special("F5") }, /* #\F5 */
            { "k6", key_special("F6") }, /* #\F6 */
            { "k7", key_special("F7") }, /* #\F7 */
            { "k8", key_special("F8") }, /* #\F8 */
            { "k9", key_special("F9") }, /* #\F9 */
            { "k0", key_special("F10") }, /* #\F10 */
            { "k;", key_special("F10") }, /* #\F10 */
            { "F1", key_special("F11") }, /* #\F11 */
            { "F2", key_special("F12") }, /* #\F12 */
          };
          var uintL i;
          for (i=0; i < sizeof(funkey_tab)/sizeof(funkey); i++) {
            begin_system_call();
            cap = tgetstr(funkey_tab[i].capname,&tp);
            end_system_call();
            if (cap)
              add_keybinding(cap,&funkey_tab[i].key);
          }
        }
        /* Special Linux console handling: */
        begin_system_call();
        cap = tgetstr("kh",&tp); /* Home */
        if (!(cap && (cap[0] == ESC) && (cap[1] == '[') && (cap[2] == '1') && (cap[3] == '~') && (cap[4] == '\0')))
          goto not_linux;
        cap = tgetstr("kI",&tp); /* Insert */
        if (!(cap && (cap[0] == ESC) && (cap[1] == '[') && (cap[2] == '2') && (cap[3] == '~') && (cap[4] == '\0')))
          goto not_linux;
        cap = tgetstr("kD",&tp); /* Delete */
        if (!(cap && (cap[0] == ESC) && (cap[1] == '[') && (cap[2] == '3') && (cap[3] == '~') && (cap[4] == '\0')))
          goto not_linux;
        end_system_call();
        keybinding(ESCstring"[4~", key_special("END")); /* #\End */
        if (false) {
        not_linux:
          end_system_call();
        }
        /* Special xterm handling: */
        begin_system_call();
        cap = tgetstr("ku",&tp);
        if (!(cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'A') && (cap[3] == '\0')))
          goto not_xterm;
        cap = tgetstr("kd",&tp);
        if (!(cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'B') && (cap[3] == '\0')))
          goto not_xterm;
        cap = tgetstr("kr",&tp);
        if (!(cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'C') && (cap[3] == '\0')))
          goto not_xterm;
        cap = tgetstr("kl",&tp);
        if (!(cap && (cap[0] == ESC) && (cap[1] == 'O') && (cap[2] == 'D') && (cap[3] == '\0')))
          goto not_xterm;
        end_system_call();
        /* Insert, Delete: */
        keybinding(ESCstring"[2~", key_special("INSERT")); /* #\Insert */
        keybinding(ESCstring"[3~", key_special("DELETE")); /* #\Delete */
        {
          /* Application Keypad: ESC O M -> Return,
           ESC O k -> +, ESC O m -> -, ESC O j -> *, ESC O o -> /
           (without Hyper-Bit, because that is too terminal-specific)
           ESC O x -> Up, ESC O r -> Down,
           ESC O v -> Right, ESC O t -> Left,
           ESC O p -> Insert, ESC O l -> Delete. */
          var char cap[4];
          cap[0] = ESC; cap[1] = 'O'; cap[3] = '\0';
          cap[2] = 'M'; keybinding(cap, key_ascii('M'-64));
          cap[2] = '+'+64; keybinding(cap, key_ascii('+'));
          cap[2] = '-'+64; keybinding(cap, key_ascii('-'));
          cap[2] = '*'+64; keybinding(cap, key_ascii('*'));
          cap[2] = '/'+64; keybinding(cap, key_ascii('/'));
          cap[2] = '8'+64; keybinding(cap, key_special("UP")); /* #\Up */
          cap[2] = '2'+64; keybinding(cap, key_special("DOWN")); /* #\Down */
          cap[2] = '6'+64; keybinding(cap, key_special("RIGHT")); /* #\Right */
          cap[2] = '4'+64; keybinding(cap, key_special("LEFT")); /* #\Left */
          cap[2] = '0'+64; keybinding(cap, key_special("INSERT")); /* #\Insert */
          cap[2] = '.'+64; keybinding(cap, key_special("DELETE")); /* #\Delete */
          cap[2] = ','+64; keybinding(cap, key_special("DELETE")); /* #\Delete */
          /* "7" -> #\Home, "1" -> #\End, "9" -> #\PgUp, "3" -> #\PgDn,
           "5" -> #\Center are already handled above. */
        }
      xterm:
        /* arrow keys (see above)
         other cursorblock-keys: */
        keybinding(ESCstring"[5~", key_special("PGUP")); /* #\PgUp */
        keybinding(ESCstring"[6~", key_special("PGDN")); /* #\PgDn */
        keybinding(ESCstring"[7~", key_special("HOME")); /* #\Home */
        keybinding(ESCstring"[8~", key_special("END")); /* #\End */
        keybinding(ESCstring"OH", key_special("HOME")); /* #\Home */
        keybinding(ESCstring"[H", key_special("HOME")); /* #\Home */
        keybinding(ESCstring"OF", key_special("END")); /* #\End */
        keybinding(ESCstring"[F", key_special("END")); /* #\End */
        /* function-keys: */
        keybinding(ESCstring"[11~", key_special("F1")); /* #\F1 */
        keybinding(ESCstring"[12~", key_special("F2")); /* #\F2 */
        keybinding(ESCstring"[13~", key_special("F3")); /* #\F3 */
        keybinding(ESCstring"[14~", key_special("F4")); /* #\F4 */
        keybinding(ESCstring"[15~", key_special("F5")); /* #\F5 */
        keybinding(ESCstring"[17~", key_special("F6")); /* #\F6 */
        keybinding(ESCstring"[18~", key_special("F7")); /* #\F7 */
        keybinding(ESCstring"[19~", key_special("F8")); /* #\F8 */
        keybinding(ESCstring"[20~", key_special("F9")); /* #\F9 */
        keybinding(ESCstring"[21~", key_special("F10")); /* #\F10 */
        keybinding(ESCstring"[23~", key_special("F11")); /* #\F11 */
        keybinding(ESCstring"[24~", key_special("F12")); /* #\F12 */
        if (false) {
         not_xterm:
          end_system_call();
        }
      }
    }
  }
  pushSTACK(allocate_handle(stdin_handle));
 #endif
 #ifdef WIN32_NATIVE
  /* build Console-Handle:
   Maybe use CREATE_ALWAYS ?? Maybe use AllocConsole() ?? */
  {
    begin_system_call();
    var Handle handle = CreateFile("CONIN$", GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
    if (handle==INVALID_HANDLE_VALUE) {
      OS_error();
    }
    end_system_call();
    pushSTACK(allocate_handle(handle));
  }
 #endif
  /* allocate new Stream: */
  var object stream = /* Flags: only READ-CHAR allowed */
    allocate_stream(strmflags_rd_ch_B,strmtype_keyboard,strm_keyboard_len,strm_keyboard_xlen);
  /* and fill: */
  stream_dummy_fill(stream);
  var Stream s = TheStream(stream);
  s->strm_encoding = O(terminal_encoding);
  s->strm_rd_ch = P(rd_ch_keyboard); /* READ-CHAR-Pseudofunction */
  s->strm_rd_ch_array = P(rd_ch_array_dummy); /* READ-CHAR-SEQUENCE-Pseudofunction */
 #if defined(UNIX)
  /* determine Flag isatty = (stdin_tty ? T : NIL) : */
  begin_system_call();
  s->strm_keyboard_isatty = (isatty(stdin_handle) ? T : NIL);
  end_system_call();
  s->strm_keyboard_handle = popSTACK();
  s->strm_keyboard_buffer = NIL;
  s->strm_keyboard_keytab = popSTACK();
  ChannelStream_buffered(stream) = false;
  ChannelStream_regular(stream) = false;
  ChannelStream_init(stream);
  UnbufferedHandleStream_input_init(stream);
 #endif
 #ifdef WIN32_NATIVE
  s->strm_keyboard_isatty = T;
  s->strm_keyboard_handle = popSTACK();
  ChannelStream_buffered(stream) = false;
  ChannelStream_regular(stream) = false;
  ChannelStream_init(stream);
  UnbufferedHandleStream_input_init(stream);
 #endif
  return stream;
}

/* (SYSTEM::MAKE-KEYBOARD-STREAM) creates a new keyboard stream.
 Should be called once only, and the result assigned to *KEYBOARD-INPUT*. */
LISPFUNN(make_keyboard_stream,0) {
  VALUES1(make_keyboard_stream());
}

#endif /* KEYBOARD */


/* Interactive Terminal Stream
   =========================== */

#if defined(GNU_READLINE)

#define begin_rl_callback() end_blocking_call(); begin_callback()
#define end_rl_callback() end_callback(); begin_blocking_call()

/* Function to ignore unconvertible symbols. */
local void lisp_completion_ignore (void* sp, gcv_object_t* frame, object label,
                                   object condition) {
  unused(sp); unused(frame); unused(label); unused(condition);
  /* (THROW 'SYS::CONVERSION-FAILURE NIL): */
  VALUES1(NIL);
  throw_to(S(conversion_failure));
}
/* Completion of Lisp-Symbols */
local maygc char** lisp_completion (char* text, int start, int end) {
  /* text[start..end-1] = thing to complete within line of text
   This is a Callback-Function, we must set the Stack correctly again: */
  begin_rl_callback();
 #ifdef ENABLE_UNICODE
  { var object encoding = O(terminal_encoding);
    start = Encoding_mblen(encoding)(encoding,(const uintB*)text,
                                     (const uintB*)text+start);
    end   = Encoding_mblen(encoding)(encoding,(const uintB*)text,
                                     (const uintB*)text+end);
  }
 #endif
  var object mlist = NIL; /* List of the possibilities */
  if (!nullpSv(completion)) { /* (funcall CUSTOM:*COMPLETION* text start end) */
  pushSTACK(asciz_to_string(text,O(terminal_encoding)));
  pushSTACK(fixnum((uintL)start));
  pushSTACK(fixnum((uintL)end));
    funcall(Symbol_value(S(completion)),3);
    mlist = value1;
  }
  /* reconstruct List of Simple-Strings in malloc-ed Array from malloc-ed
   Asciz-Strings: */
  if (nullp(mlist)) {
    end_rl_callback();
    return NULL;
  } else if (eq(mlist,Fixnum_0)) { /* complete called describe => redraw */
    end_rl_callback();
    rl_refresh_line(0,0);
    return NULL;
  } else if (!consp(mlist)) {
    /* This error message is self-defense against people who fiddle
     around with sys::completion. */
    pushSTACK(mlist);   /* slot DATUM of TYPE-ERROR */
    pushSTACK(S(list)); /* slot EXPECTED-TYPE of TYPE-ERROR */
    pushSTACK(S(completion));
    pushSTACK(mlist);
    error(type_error,GETTEXT("Return value ~S of call to ~S is not a list."));
  }
  begin_system_call();
  var char** array = (char**) malloc((llength(mlist)+1)*sizeof(char*));
  end_system_call();
  if (array==NULL) {
    end_rl_callback();
    return NULL;
  }
  {
    var char** ptr = array;
    pushSTACK(mlist);
    while (mconsp(STACK_0)) {
      var object m = Car(STACK_0);
      if (!simple_string_p(m)) {
        pushSTACK(m);                /* slot DATUM of TYPE-ERROR */
        pushSTACK(S(simple_string)); /* slot EXPECTED-TYPE of TYPE-ERROR */
        pushSTACK(S(simple_string));
        pushSTACK(m);
        pushSTACK(S(completion));
        pushSTACK(mlist);
        error(type_error,GETTEXT("Return value ~S of call to ~S contains ~S which is not a ~S."));
      }
      sstring_un_realloc(m);
      var uintL charcount = Sstring_length(m);
      var const chart* ptr1;
      unpack_sstring_alloca(m,charcount,0, ptr1=);
      { /* (CATCH 'SYS::CONVERSION-FAILURE ...) */
        var gcv_object_t* top_of_frame = STACK;
        pushSTACK(S(conversion_failure));
        var sp_jmp_buf returner;
        finish_entry_frame(CATCH,returner,, goto catch_return; );
        /* Upon charset_type_error, call lisp_completion_ignore. */
        make_C_HANDLER_frame(O(handler_for_charset_type_error),
                             &lisp_completion_ignore,NULL);
        { /* Convert ptr1 to *TERMINAL-ENCODING*: */
          var uintL bytecount = cslen(O(terminal_encoding),ptr1,charcount);
          begin_system_call();
          var char* ptr2 = (char*) malloc((bytecount+1)*sizeof(char));
          if (ptr2==NULL) { /* malloc fails -> return everything */
            while (ptr != array) { free(*--ptr); }
            free(array);
            end_system_call();
            unwind_C_HANDLER_frame();
            skipSTACK(3+1); /* unwind CATCH frame, pop mlist */
            end_rl_callback();
            return NULL;
          }
          end_system_call();
          cstombs(O(terminal_encoding),ptr1,charcount,(uintB*)ptr2,bytecount);
          ptr2[bytecount] = '\0';
          *ptr++ = ptr2;
        }
        unwind_C_HANDLER_frame();
      catch_return:
        /* Here we need the values of array and ptr. Avoid gcc warnings. */
        unused &array; /* avoid "'array' might be clobbered by 'longjmp'" */
        unused &ptr;   /* avoid "'ptr' might be clobbered by 'longjmp'" */
        skipSTACK(3); /* unwind CATCH frame */
        STACK_0 = Cdr(STACK_0);
      }
    }
    skipSTACK(1); /* pop mlist */
    *ptr = NULL;
  }
  if (*array == NULL) {
    begin_system_call();
    free(array);
    end_system_call();
    array = NULL;
  }
  end_rl_callback();
  return array;
}
#endif

#if defined(UNIX) || defined(WIN32_NATIVE)

/* Functionality:
 Standard-Input and Standard-Output are accessed.
 Because of the possibility of Redirection some Functions have to determine, if
 Standard-Input is a Terminal or not.
 If Standard-Output is a Terminal or not, is irrelevant in this context.
 However, it is relevant, if Standard-Input and Standard-Output are the same
 Terminal; in this case we assume, that after completion of an input line
 (by NL) of Standard-Input the Cursor of Standard-Output is situated in
 column 0, and in this case we can also use the
 GNU readline()-Library.

 There are three possible Variants of the Terminal-Streams:
 When Standard-Input and Standard-Output are not the same Terminal:
   * terminal1 normally,
   * terminal2 with per-line-buffering of the input,
 When Standard-Input and Standard-Output are the same Terminal:
   * terminal3 uses the readline()-Library, with per-line-buffering of
     Input and Output. */

#define HAVE_TERMINAL1
/* define TERMINAL_LINEBUFFERED  0
   define TERMINAL_OUTBUFFERED   0 */

#ifdef GNU_READLINE
/* We use the GNU Readline-Library. It returns the Input line-by-line,
   with possibility for editing, completion and History. unfortunately we
   have to save the Output intermediately line-by-line in order to be able to
   use the last commenced line as "Prompt". */
#define HAVE_TERMINAL3
/* define TERMINAL_LINEBUFFERED  1
   define TERMINAL_OUTBUFFERED   1 */
#endif

/* Additional Components:
 ISATTY : Flag, if stdin is a TTY and if stdin and stdout are identical:
            NIL: stdin is a File or similar.
            T, EQUAL: stdin is a Terminal
            EQUAL: stdin and stdout are the same Terminal */
#define strm_terminal_isatty   strm_isatty
#define strm_terminal_ihandle  strm_ichannel
#define strm_terminal_ohandle  strm_ochannel
#if defined(HAVE_TERMINAL2) || defined(HAVE_TERMINAL3)
  /* Components because of TERMINAL_LINEBUFFERED:
   INBUFF : input-buffer, a Semi-Simple-String */
  #define strm_terminal_inbuff  strm_field1
  /* COUNT = its Fill-Pointer : number of characters in the input-buffer
   INDEX : number of already consumed characters */
  #define strm_terminal_index   strm_other[2]  /* FIXME: this is ugly */
#endif
#ifdef HAVE_TERMINAL3
  /* Components because of TERMINAL_OUTBUFFERED:
   OUTBUFF : output-buffer, a Semi-Simple-String */
  #define strm_terminal_outbuff strm_field2
#endif
#define strm_terminal_len  strm_channel_len

/* distinction according to type of Terminal-Streams:
 terminalcase(stream, statement1,statement2,statement3); */
#if defined(HAVE_TERMINAL2) && defined(HAVE_TERMINAL3)
  #define terminalcase(stream,statement1,statement2,statement3) \
    if (nullp(TheStream(stream)->strm_field2)) {                \
      if (nullp(TheStream(stream)->strm_field1)) { statement1 } \
      else { statement2 }                                       \
    } else { statement3 }
#elif defined(HAVE_TERMINAL2)
  #define terminalcase(stream,statement1,statement2,statement3) \
    if (nullp(TheStream(stream)->strm_field1)) { statement1 }   \
    else { statement2 }
#elif defined(HAVE_TERMINAL3)
  #define terminalcase(stream,statement1,statement2,statement3) \
    if (nullp(TheStream(stream)->strm_field2)) { statement1 }   \
    else { statement3 }
#else
  #define terminalcase(stream,statement1,statement2,statement3) statement1
#endif

#ifdef HAVE_TERMINAL1

/* read a character from a terminal-stream. */
local maygc object rd_ch_terminal1 (const gcv_object_t* stream_) {
  var object ch = rd_ch_unbuffered(stream_);
  /* If both stdin and stdout are the same Terminal,
   and we read a NL, we can assume, that afterwards
   the cursor is situated in column 0. */
  if (eq(ch,ascii_char(NL))) {
    var object stream = *stream_;
    if (eq(TheStream(stream)->strm_terminal_isatty,S(equal)))
      TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
  }
  return ch;
}

/* Determines, if a character is available on a Terminal-Stream.
 listen_char_terminal1(stream)
 > stream: Terminal-Stream
 < result: input availability */
#define listen_char_terminal1  listen_char_unbuffered

/* UP: Deletes already entered interactive Input from a Terminal-Stream.
 clear_input_terminal1(stream);
 > stream: Terminal-Stream
 < result: true if Input was deleted, else false */
#define clear_input_terminal1  clear_input_unbuffered

/* UP: write a character to a Terminal-Stream.
 wr_ch_terminal1(&stream,ch);
 > stream: Terminal-Stream
 > ch: character to be written */
#define wr_ch_terminal1  wr_ch_unbuffered_unix

/* UP: write several characters on a Terminal-Stream.
 wr_ch_array_terminal1(&stream,&chararray,start,len);
 > stream: Terminal-Stream
 > chararray: not-reallocated Simple-String
 > start: Startindex
 > len: number of characters to be written */
#define wr_ch_array_terminal1  wr_ch_array_unbuffered_unix

/* UP: Deletes the pending Output of a Terminal-Stream.
 clear_output_terminal1(stream);
 > stream: Terminal-Stream
 can trigger GC */
#define clear_output_terminal1  clear_output_unbuffered

#endif /* HAVE_TERMINAL1 */

#ifdef HAVE_TERMINAL2

#define TERMINAL_LINEBUFFERED  true

/* read a character from a terminal-stream. */
local maygc object rd_ch_terminal2 (const gcv_object_t* stream_) {
  var object stream = *stream_;
  if (eq(TheStream(stream)->strm_rd_ch_last,eof_value)) /* EOF already? */
    return eof_value;
  if (!(posfixnum_to_V(TheStream(stream)->strm_terminal_index)
        < TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1])) {
    /* index=count -> must read a whole line from the keyboard: */
    TheStream(stream)->strm_terminal_index = Fixnum_0; /* index := 0 */
    TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1] = 0; /* count := 0 */
    while (1) {
      var object ch = rd_ch_unbuffered(stream_);
      if (eq(ch,eof_value)) {
        if (TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1] > 0)
          break; /* deliver character of the Buffer, only then return eof_value */
        else
          return eof_value;
      }
      /* add character ch to the input-line, poss. enlarge the line: */
      ssstring_push_extend(TheStream(stream)->strm_terminal_inbuff,char_code(ch));
      stream = *stream_;
      /* If both stdin and stdout are the same Terminal,
       and we read a NL, we can assume, that afterwards the
       Cursor is situated in column 0. */
      if (chareq(char_code(ch),ascii(NL))) {
        if (eq(TheStream(stream)->strm_terminal_isatty,S(equal)))
          TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
        break; /* deliver character of the Buffer */
      }
    }
    ASSERT(posfixnum_to_V(TheStream(stream)->strm_terminal_index)
           < TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1]);
  }
  /* index<count -> there are still characters in the buffer */
  var uintV index =
    posfixnum_to_V(TheStream(stream)->strm_terminal_index); /* Index */
  TheStream(stream)->strm_terminal_index =
    fixnum_inc(TheStream(stream)->strm_terminal_index,1); /* increase Index */
  return code_char(TheSnstring(TheIarray(TheStream(stream)->strm_terminal_inbuff)->data)->data[index]); /* next Character */
}

/* Determines, if a character is available on a Terminal-Stream.
 listen_char_terminal2(stream)
 > stream: Terminal-Stream
 < result: input availability */
local maygc listen_t listen_char_terminal2 (object stream) {
  if (eq(TheStream(stream)->strm_rd_ch_last,eof_value)) /* EOF already? */
    return LISTEN_EOF;
  if (posfixnum_to_V(TheStream(stream)->strm_terminal_index)
      < TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1])
    /* index<count -> there are still characters in the buffer */
    return LISTEN_AVAIL;
  return listen_char_unbuffered(stream);
}

/* UP: Deletes already entered interactive Input from a Terminal-Stream.
 clear_input_terminal2(stream);
 > stream: Terminal-Stream
 < result: true if Input was deleted, else false
 can trigger GC */
local maygc bool clear_input_terminal2 (object stream) {
  if (nullp(TheStream(stream)->strm_terminal_isatty)) /* File -> do nothing */
    return false;
  /* Terminal */
  pushSTACK(stream);              /* save */
  clear_input_unbuffered(stream); /* forget about past EOF, call clear_tty_input */
 #if TERMINAL_LINEBUFFERED
  TheStream(STACK_0)->strm_terminal_index = Fixnum_0; /* index := 0 */
  TheIarray(TheStream(STACK_0)->strm_terminal_inbuff)->dims[1] = 0; /* count := 0 */
 #endif
  while (LISTEN_AVAIL == listen_char_terminal2(STACK_0))
    read_char(&STACK_0);
  skipSTACK(1);                 /* drop */
  return true;
}

/* UP: Write a character to a Terminal-Stream.
 wr_ch_terminal2(&stream,ch);
 > stream: Terminal-Stream
 > ch: character to be written */
#define wr_ch_terminal2  wr_ch_unbuffered_dos

/* UP: Write several characters to a Terminal-Stream.
 wr_ch_array_terminal2(&stream,&chararray,start,len);
 > stream: Terminal-Stream
 > chararray: not-reallocated Simple-String
 > start: Startindex
 > len: number of characters to be written */
#define wr_ch_array_terminal2  wr_ch_array_unbuffered_dos

/* UP: Deletes the pending Output of a Terminal-Stream.
 clear_output_terminal2(stream);
 > stream: Terminal-Stream
 can trigger GC */
#define clear_output_terminal2  clear_output_unbuffered

#endif /* HAVE_TERMINAL2 */

#ifdef HAVE_TERMINAL3

#define TERMINAL_LINEBUFFERED  true
#define TERMINAL_OUTBUFFERED   true

local bool want_filename_completion;
local char** lisp_completion_matches (READLINE_CONST char* text,
                                      int start, int end)
{ /* text[0..end-start-1] = the_line[start..end-1] */
  unused(text);
  if (((start>=2)
       && (rl_line_buffer[start-2]=='#')
       && (rl_line_buffer[start-1]== '\"'))
      || ((start>=3)
          && (rl_line_buffer[start-3]=='#')
          && (rl_line_buffer[start-2]=='P' || rl_line_buffer[start-2]=='p')
          && (rl_line_buffer[start-1]== '\"'))) {
    /* Completion after #" or #P" relates to file names: */
    want_filename_completion = true; return NULL;
  }
  var char** result = lisp_completion(rl_line_buffer,start,end);
  want_filename_completion = false;
  return result;
}

/* If the function above returns NULL (no Matches), the following
 function is called until it returns NULL on its part. */
local char* lisp_completion_more (READLINE_CONST char* text, int state) {
  if (want_filename_completion)
    return READLINE_FILE_COMPLETE(text,state);
  else
    return NULL;
}

/* Strip trailing '\r' from the end of STRING.
 Returns STRING.
 Borrowed from BASH 2.05
 we do not strip the initial whitespace
 since it is needed for indentation.
 we do not strip the trailing whitespace since this would break
 READ-LINE on terminal streams: it must not strip whitespace. */
local char * strip_white (char *string) {
  char *end, *beg=string;
  if (beg == NULL) return NULL;
  /* while (ch_blank_p(*beg)) beg++; */
  if (*beg == 0) return beg;
  for (end = beg + strlen (beg) - 1; end > beg && (*end == '\r'); end--) ;
  *++end = '\0';
  return beg;
}

#ifdef GNU_READLINE
/* prototype here for rd_ch_terminal3()
 cannot have the whole thing here since they need rl_memory_abort()
 which calls make_terminal_stream() which is not yet defined */
local char* xmalloc (int count);
#endif

/* In the implementation of rd_ch_terminal3 and listen_char_terminal3, we
 should not use the corresponding rd_ch_unbuffered and listen_char_unbuffered
 functions, because they store intermediately read bytes in
 UnbufferedStream_bytebuf(stream), where readline() will not see them.
 As a workaround, we use rl_stuff_char() before calling readline().

 However, there is a deeper problem with the rd_ch_terminal3/
 listen_char_terminal3 implementation: readline() terminates when `rl_done'
 gets set to 1, whereas listen_char_unbuffered normally returns LISTEN_AVAIL when
 the user has entered a line of characters followed by #\Newline. Normally
 this is the same condition, but if the user modifies his readline key
 bindings so that newline does not always cause `rl_done' to become 1, then
 rd_ch_terminal3() might block although listen_char_terminal3() returned
 LISTEN_AVAIL. One possible fix would be to use the READLINE_CALLBACK functions,
 see readline.dvi p. 29, but in order to get this right, RUN-PROGRAM and
 MAKE-PIPE-INPUT-STREAM might need to be modified to temporarily turn off
 readline. */

local HIST_ENTRY * history_last (void)
{ /* get the last history entry and its offset */
  HIST_ENTRY ** all = history_list();
  if (all == NULL) return NULL;
  while (*all) all++;
  return *(all-1);
}

/* read a character from a terminal-stream.
 cp. rd_ch_unbuffered() : */
local object rd_ch_terminal3 (const gcv_object_t* stream_) {
  var object stream = *stream_;
  if (eq(TheStream(stream)->strm_rd_ch_last,eof_value)) /* EOF already? */
    return eof_value;
  if (!(posfixnum_to_V(TheStream(stream)->strm_terminal_index)
        < TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1])) {
    /* index=count -> must read a whole line from the keyboard: */
    TheStream(stream)->strm_terminal_index = Fixnum_0; /* index := 0 */
    TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1] = 0; /* count := 0 */
    /* Pass bytes that we have already read down into readline's buffer. */
    while (UnbufferedStream_status(stream) > 0) {
      UnbufferedStreamLow_pop_byte(stream,b);
      begin_system_call(); rl_stuff_char(b); end_system_call();
    }
    {
      var object lastline = string_to_asciz(TheStream(stream)->strm_terminal_outbuff,TheStream(stream)->strm_encoding);
      var DYNAMIC_ARRAY(prompt,char,Sbvector_length(lastline)+1); /* Prompt: last output line */
      if (prompt!=NULL) {
        begin_system_call();
        strcpy(prompt,TheAsciz(lastline));
        end_system_call();
      }
      /* lexema-separating characters: with syntax code whsp,tmac,nmac
       (see IO.D, actually depends on the current *READTABLE*): */
      rl_basic_word_break_characters = "\t\n \"#'(),;`";
      rl_basic_quote_characters = "\"|";
      rl_completer_quote_characters = "\\|";
      begin_blocking_system_call();
      rl_already_prompted = true;
      var char* line = strip_white(readline(prompt==NULL ? "" : prompt));
      end_blocking_system_call();
      FREE_DYNAMIC_ARRAY(prompt);
      if (line==NULL)
        /* detect EOF (at the start of line) */
        return eof_value;
      /* add read line to the input line: */
     #ifdef ENABLE_UNICODE
      {
        var object inbuff = TheStream(*stream_)->strm_terminal_inbuff;
        var object encoding = TheStream(*stream_)->strm_encoding;
        var const uintB* bptr = (uintB*)line;
        var const uintB* bendptr = bptr + asciz_length((const char*)bptr);
        var uintL clen = Encoding_mblen(encoding)(encoding,bptr,bendptr);
        ssstring_extend(inbuff,TheIarray(inbuff)->dims[1]+clen);
        inbuff = TheStream(*stream_)->strm_terminal_inbuff;
        encoding = TheStream(*stream_)->strm_encoding;
        var chart* cptr = &TheSnstring(TheIarray(inbuff)->data)->data[TheIarray(inbuff)->dims[1]];
        var chart* cendptr = cptr+clen;
        Encoding_mbstowcs(encoding)(encoding,nullobj,&bptr,bendptr,&cptr,cendptr);
        ASSERT(cptr == cendptr);
        TheIarray(inbuff)->dims[1] += clen;
      }
     #else
      {
        var const uintB* ptr = (uintB*)line;
        while (*ptr != '\0') {
          ssstring_push_extend(TheStream(*stream_)->strm_terminal_inbuff,
                               as_chart(*ptr++));
        }
      }
     #endif
      ssstring_push_extend(TheStream(*stream_)->strm_terminal_inbuff,
                           ascii(NL));
      /* put into the history if non-empty */
      begin_system_call();
      if (line[0] != '\0') {
        var HIST_ENTRY *last = history_last();
        if (boundp(Symbol_value(S(terminal_read_open_object)))) {
          /* append this line to the previous history entry */
          ASSERT(last); /* in the middle of something => history non-empty */
          var char *new_line =
            (char*)xmalloc(2 + strlen(line) + strlen(last->line));
          /* strcpy(new_line,last->line[0]=='\n' ? "" : "\n"); */
          strcpy(new_line,last->line);
          strcat(new_line,"\n");
          strcat(new_line,line);
          free(last->line);
          last->line = new_line;
        } else if (last==NULL || !asciz_equal(line,last->line))
          /* this is different from the last one, save it */
          add_history(line);
      }
      free(line); /* must release the original line */
      end_system_call();
    }
    stream = *stream_;
    /* If both stdin and stdout are the same Terminal, we can assume,
     that the Cursor is situated in column 0. */
    if (eq(TheStream(stream)->strm_terminal_isatty,S(equal))) {
      TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
      TheIarray(TheStream(stream)->strm_terminal_outbuff)->dims[1] = 0; /* Fill-Pointer := 0 */
    }
    ASSERT(posfixnum_to_V(TheStream(stream)->strm_terminal_index)
           < TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1]);
  }
  /* index<count -> there are still characters in the buffer */
  var uintV index =
    posfixnum_to_V(TheStream(stream)->strm_terminal_index); /* Index */
  TheStream(stream)->strm_terminal_index =
    fixnum_inc(TheStream(stream)->strm_terminal_index,1); /* increase Index */
  return code_char(TheSnstring(TheIarray(TheStream(stream)->strm_terminal_inbuff)->data)->data[index]); /* next Character */
}

/* Determines, if a character is available on a Terminal-Stream.
 listen_char_terminal3(stream)
 > stream: Terminal-Stream
 < result: input availability */
local listen_t listen_char_terminal3 (object stream) {
  if (eq(TheStream(stream)->strm_rd_ch_last,eof_value)) /* EOF already? */
    return LISTEN_EOF;
  if (posfixnum_to_V(TheStream(stream)->strm_terminal_index)
      < TheIarray(TheStream(stream)->strm_terminal_inbuff)->dims[1])
    /* index<count -> there are still characters in the buffer */
    return LISTEN_AVAIL;
  return listen_char_unbuffered(stream);
}

/* UP: Deletes already entered interactive Input from a Terminal-Stream.
 clear_input_terminal3(stream);
 > stream: Terminal-Stream
 < result: true if Input was deleted, else false
 can trigger GC */
local maygc bool clear_input_terminal3 (object stream) {
  if (nullp(TheStream(stream)->strm_terminal_isatty)) /* File -> do nothing */
    return false;
  /* Terminal */
  pushSTACK(stream);              /* save */
  clear_input_unbuffered(stream); /* forget about past EOF, call clear_tty_input */
 #if TERMINAL_LINEBUFFERED
  TheStream(STACK_0)->strm_terminal_index = Fixnum_0; /* index := 0 */
  TheIarray(TheStream(STACK_0)->strm_terminal_inbuff)->dims[1] = 0; /* count := 0 */
 #endif
  while (LISTEN_AVAIL == listen_char_terminal3(STACK_0))
    read_char(&STACK_0);
  skipSTACK(1);                 /* drop */
  return true;
}

/* UP: Write a character to a Terminal-Stream.
 wr_ch_terminal3(&stream,ch);
 > stream: Terminal-Stream
 > ch: character to be written */
local maygc void wr_ch_terminal3 (const gcv_object_t* stream_, object ch) {
  check_wr_char(*stream_,ch);
 #if TERMINAL_OUTBUFFERED
  {
    var chart c = char_code(ch); /* Code of the character */
    if (chareq(c,ascii(NL)))
      TheIarray(TheStream(*stream_)->strm_terminal_outbuff)->dims[1] = 0; /* Fill-Pointer := 0 */
    else
      ssstring_push_extend(TheStream(*stream_)->strm_terminal_outbuff,c);
  }
 #endif
  { var object eol = TheEncoding(TheStream(*stream_)->strm_encoding)->enc_eol;
    if (eq(eol,S(Kunix)))
      wr_ch_unbuffered_unix(stream_,ch);
    else if (eq(eol,S(Kmac)))
      wr_ch_unbuffered_mac(stream_,ch);
    else if (eq(eol,S(Kdos)))
      wr_ch_unbuffered_dos(stream_,ch);
    else
      NOTREACHED;
  }
}

/* UP: Write several characters to a Terminal-Stream.
 wr_ch_array_terminal3(&stream,&chararray,start,len);
 > stream: Terminal-Stream
 > chararray: not-reallocated Simple-String
 > start: Startindex
 > len: number of characters to be written */
local maygc void wr_ch_array_terminal3 (const gcv_object_t* stream_,
                                        const gcv_object_t* chararray_,
                                        uintL start, uintL len) {
  { var object eol = TheEncoding(TheStream(*stream_)->strm_encoding)->enc_eol;
    if (eq(eol,S(Kunix)))
      wr_ch_array_unbuffered_unix(stream_,chararray_,start,len);
    else if (eq(eol,S(Kmac)))
      wr_ch_array_unbuffered_mac(stream_,chararray_,start,len);
    else if (eq(eol,S(Kdos)))
      wr_ch_array_unbuffered_dos(stream_,chararray_,start,len);
    else
      NOTREACHED;
  }
 #if TERMINAL_OUTBUFFERED
  {
    var object string = *chararray_;
    var const chart* ptr;
    unpack_sstring_alloca(string,len,start, ptr =);
    /* characters since the last NL in the Buffer: */
    var uintL pos = 0; /* count the number of characters since the last NL */
    var uintL count;
    ptr += len;
    dotimespL(count,len, {
      if (chareq(*--ptr,ascii(NL)))
        goto found_NL;
      pos++;
    });
    if (false) {
    found_NL: /* pos characters since the last NL */
      ptr++;
      TheIarray(TheStream(*stream_)->strm_terminal_outbuff)->dims[1] = 0; /* Fill-Pointer := 0 */
    }
    if (pos > 0) {
      SstringCase(string, {
        /* ptr points into the stack, not the string, so it's GC-safe. */
        dotimespL(count,pos, {
          ssstring_push_extend(TheStream(*stream_)->strm_terminal_outbuff,
                               *ptr++);
        });
      },{
        /* ptr points into the stack, not the string, so it's GC-safe. */
        dotimespL(count,pos, {
          ssstring_push_extend(TheStream(*stream_)->strm_terminal_outbuff,
                               *ptr++);
        });
      },{
        /* ptr points into the string, not GC-safe. */
        var uintL index = start + len - pos;
        dotimespL(count,pos, {
          ssstring_push_extend(TheStream(*stream_)->strm_terminal_outbuff,
                               TheSnstring(*chararray_)->data[index]);
          index++;
        });
      },{
        NOTREACHED;
      });
    }
  }
 #endif
}

/* UP: Deletes the pending Output of a Terminal-Stream.
 clear_output_terminal3(stream);
 > stream: Terminal-Stream
 can trigger GC */
local maygc void clear_output_terminal3 (object stream) {
 #if TERMINAL_OUTBUFFERED
  pushSTACK(stream);            /* save */
 #endif
  clear_output_unbuffered(stream);
 #if TERMINAL_OUTBUFFERED
  stream = popSTACK();          /* restore */
  TheIarray(TheStream(stream)->strm_terminal_outbuff)->dims[1] = 0; /* Fill-Pointer := 0 */
 #endif
}

#endif /* HAVE_TERMINAL3 */

/* UP: Moves the pending Output of a Terminal-Stream to the destination.
 finish_output_terminal(stream);
 > stream: Terminal-Stream
 can trigger GC */
#define finish_output_terminal  finish_output_unbuffered

/* UP: Moves the pending Output of a Terminal-Stream to the destination.
 force_output_terminal(stream);
 > stream: Terminal-Stream
 can trigger GC */
#define force_output_terminal  force_output_unbuffered

local bool stdio_same_tty_p (void)
{ /* check that STDIN and STDOUT point to the same TTY */
#ifdef UNIX
 #if defined(UNIX_CYGWIN)
  /* st_ino does not make sense on Cygwin: they are based on
     filenames, and stdin is CONIN$ while stdout is CONOUT$ */
  var char* res = ttyname(stdin_handle);
  if (strcmp(res,"/dev/conin")) { /* not a windows console, maybe X? */
    var char tmp[MAXPATHLEN];
    strcpy(tmp,res);
    return !strcmp(tmp,ttyname(stdout_handle));
  } else
    return !strcmp("/dev/conout",ttyname(stdout_handle));
 #else  /* ttyname() is rather slow, fstat() is faster. */
  var struct stat stdin_stat;
  var struct stat stdout_stat;
  return (fstat(stdin_handle,&stdin_stat) >= 0)
    && (fstat(stdout_handle,&stdout_stat) >= 0)
    && (stdin_stat.st_dev == stdout_stat.st_dev)
    && (stdin_stat.st_ino == stdout_stat.st_ino);
 #endif
#endif
#ifdef WIN32_NATIVE
  var DWORD console_mode;
  return GetConsoleMode(stdin_handle,&console_mode)
    && GetConsoleMode(stdout_handle,&console_mode);
#endif
}

/* Returns an interactive Terminal-Stream.
 can trigger GC */
local maygc object make_terminal_stream_ (void) {
  begin_system_call();
  var bool stdin_tty = isatty(stdin_handle); /* stdin a Terminal? */
  var bool stdout_tty = isatty(stdout_handle); /* stdout a Terminal? */
  var bool same_tty = stdin_tty && stdout_tty && stdio_same_tty_p();
  end_system_call();
 #ifdef HAVE_TERMINAL3
  /* we handle all signals ourselves */
  rl_catch_signals = 0;
  if (rl_gnu_readline_p && same_tty && !disable_readline) { /* Build a TERMINAL3-Stream: */
    pushSTACK(make_ssstring(80)); /* allocate line-buffer */
    pushSTACK(make_ssstring(80)); /* allocate line-buffer */
    pushSTACK(allocate_handle(stdout_handle));
    pushSTACK(allocate_handle(stdin_handle));
    /* allocate new Stream: */
    var object stream = /* Flags: only READ-CHAR and WRITE-CHAR allowed */
      allocate_stream(strmflags_ch_B,strmtype_terminal,strm_terminal_len,
                      sizeof(strm_unbuffered_extrafields_t));
    /* and fill: */
    stream_dummy_fill(stream);
    var Stream s = TheStream(stream);
    s->strm_encoding = O(terminal_encoding);
    s->strm_rd_ch = P(rd_ch_terminal3); /* READ-CHAR-Pseudofunction */
    s->strm_rd_ch_array = P(rd_ch_array_dummy); /* READ-CHAR-SEQUENCE-Pseudofunction */
    s->strm_wr_ch = s->strm_wr_ch_npnl = P(wr_ch_terminal3); /* WRITE-CHAR-Pseudofunction */
    s->strm_wr_ch_array = s->strm_wr_ch_array_npnl = P(wr_ch_array_terminal3); /* WRITE-CHAR-SEQUENCE-Pseudofunction */
    s->strm_terminal_isatty = S(equal); /* stdout=stdin */
    s->strm_terminal_ihandle = popSTACK(); /* Handle for listen_char_unbuffered() */
    s->strm_terminal_ohandle = popSTACK(); /* Handle for Output */
   #if 1 /* TERMINAL_LINEBUFFERED */
    s->strm_terminal_inbuff = popSTACK(); /* register line buffer, count := 0 */
    s->strm_terminal_index = Fixnum_0; /* index := 0 */
   #endif
   #if 1 /* TERMINAL_OUTBUFFERED */
    s->strm_terminal_outbuff = popSTACK(); /* register line buffer */
   #endif
    ChannelStream_buffered(stream) = false;
    ChannelStream_regular(stream) = false;
    ChannelStream_init(stream);
    UnbufferedHandleStream_input_init(stream);
    UnbufferedHandleStream_output_init(stream);
    return stream;
  }
 #endif
 #ifdef HAVE_TERMINAL2
  if (stdin_tty) { /* Build a TERMINAL2-Stream: */
    pushSTACK(make_ssstring(80)); /* allocate line-buffer */
    pushSTACK(allocate_handle(stdout_handle));
    pushSTACK(allocate_handle(stdin_handle));
    /* allocate new Stream: */
    var object stream = /* Flags: only READ-CHAR and WRITE-CHAR allowed */
      allocate_stream(strmflags_ch_B,strmtype_terminal,strm_terminal_len,
                      sizeof(strm_unbuffered_extrafields_t));
    /* and fill: */
    stream_dummy_fill(stream);
    var Stream s = TheStream(stream);
    s->strm_encoding = O(terminal_encoding);
    s->strm_rd_ch = P(rd_ch_terminal2); /* READ-CHAR-Pseudofunction */
    s->strm_rd_ch_array = P(rd_ch_array_dummy); /* READ-CHAR-SEQUENCE-Pseudofunction */
    s->strm_wr_ch = s->strm_wr_ch_npnl = P(wr_ch_terminal2); /* WRITE-CHAR-Pseudofunction */
    s->strm_wr_ch_array = s->strm_wr_ch_array_npnl = P(wr_ch_array_terminal2); /* WRITE-CHAR-SEQUENCE-Pseudofunction */
    s->strm_terminal_isatty = (stdin_tty ? (same_tty ? S(equal) : T) : NIL);
    s->strm_terminal_ihandle = popSTACK(); /* Handle for listen_char_unbuffered() */
    s->strm_terminal_ohandle = popSTACK(); /* Handle for Output */
   #if 1 /* TERMINAL_LINEBUFFERED */
    s->strm_terminal_inbuff = popSTACK(); /* register line buffer, count := 0 */
    s->strm_terminal_index = Fixnum_0; /* index := 0 */
   #endif
    ChannelStream_buffered(stream) = false;
    ChannelStream_regular(stream) = false;
    ChannelStream_init(stream);
    UnbufferedHandleStream_input_init(stream);
    UnbufferedHandleStream_output_init(stream);
    return stream;
  }
 #endif
  /* Build a TERMINAL1-Stream: */
  {
    pushSTACK(allocate_handle(stdout_handle));
    pushSTACK(allocate_handle(stdin_handle));
    /* allocate new Stream: */
    var object stream = /* Flags: only READ-CHAR and WRITE-CHAR allowed */
      allocate_stream(strmflags_ch_B,strmtype_terminal,strm_terminal_len,
                      sizeof(strm_unbuffered_extrafields_t));
    /* and fill: */
    stream_dummy_fill(stream);
    var Stream s = TheStream(stream);
    s->strm_encoding = O(terminal_encoding);
    s->strm_rd_ch = P(rd_ch_terminal1); /* READ-CHAR-Pseudofunction */
    s->strm_rd_ch_array = P(rd_ch_array_dummy); /* READ-CHAR-SEQUENCE-Pseudofunction */
    s->strm_wr_ch = s->strm_wr_ch_npnl = P(wr_ch_terminal1); /* WRITE-CHAR-Pseudofunction */
    s->strm_wr_ch_array = s->strm_wr_ch_array_npnl = P(wr_ch_array_terminal1); /* WRITE-CHAR-SEQUENCE-Pseudofunction */
    s->strm_terminal_isatty = (stdin_tty ? (same_tty ? S(equal) : T) : NIL);
    s->strm_terminal_ihandle = popSTACK(); /* Handle for listen_char_unbuffered() */
    s->strm_terminal_ohandle = popSTACK(); /* Handle for Output */
    ChannelStream_buffered(stream) = false;
    ChannelStream_regular(stream) = false;
    ChannelStream_init(stream);
    UnbufferedHandleStream_input_init(stream);
    UnbufferedHandleStream_output_init(stream);
    return stream;
  }
}

#ifdef UNIX

/* (SYS::TERMINAL-RAW *terminal-io* flag [errorp])
 flag /= NIL: sets the Terminal in cbreak/noecho-Mode,
 flag = NIL: sets the Terminal back in nocbreak/echo-Mode.
 If it is not possible and errorp is specified and is /= NIL, Error is reported.
 Returns the old Mode. */

/* (SYS::TERMINAL-RAW *terminal-io* t) is essentially
 (progn
   ; no possibilities for editing, no Echo, no CR<-->NL-conversions:
   (shell "stty -icanon -echo -icrnl -inlcr")
   ; don't catch anything:
   ;              C-S   C-Q      Del     C-U       C-W      C-R      C-O      C-V     C-Y     C-C     C-\      C-Q     C-S    C-D
   (shell "stty -ixon -ixoff erase ^- kill ^- werase ^- rprnt ^- flush ^- lnext ^- susp ^- intr ^- quit ^- start ^- stop ^- eof ^-")
   ; demand 1 character at a time (not 4!):
   (shell "stty min 1") ; this has to come at the end, paradoxically...
 )
 (SYS::TERMINAL-RAW *terminal-io* nil) is essentially
 (shell "stty sane") */

local void term_raw (void);
local void term_unraw (void);

local bool oldterm_initialized = false;

#ifdef UNIX_TERM_TERMIOS
  local struct termios oldtermio; /* original TTY-Mode */
local void term_raw() {
  if (!oldterm_initialized) {
    if (!( tcgetattr(stdout_handle,&oldtermio) ==0)) {
      if (!(errno==ENOTTY)) { OS_error(); }
    }
    oldterm_initialized = true;
  }
  var struct termios newtermio;
  newtermio = oldtermio;
  newtermio.c_iflag &= ( /* IXON|IXOFF|IXANY| */ ISTRIP|IGNBRK);
  /* newtermio.c_oflag &= ~OPOST; */ /* Curses is deranged by this! */
  newtermio.c_lflag &= ISIG;
  {
    var uintC i;
    for (i=0; i<NCCS; i++)
      newtermio.c_cc[i] = 0;
  }
  newtermio.c_cc[VMIN] = 1;
  newtermio.c_cc[VTIME] = 0;
  if (!( TCSETATTR(stdout_handle,TCSAFLUSH,&newtermio) ==0)) {
    if (!(errno==ENOTTY)) { OS_error(); }
  }
}
local void term_unraw() {
  if (oldterm_initialized) {
    if (!( TCSETATTR(stdout_handle,TCSAFLUSH,&oldtermio) ==0)) {
      if (!(errno==ENOTTY)) { OS_error(); }
    }
  }
}
/* Some do it like this:
 define crmode()    (_tty.c_lflag &=~ICANON,_tty.c_cc[VMIN]=1,tcsetattr(_tty_ch, TCSAFLUSH, &_tty))
 define nocrmode()  (_tty.c_lflag |= ICANON,_tty.c_cc[VEOF] = CEOF,tcsetattr(_tty_ch, TCSAFLUSH,&_tty))
 define echo()      (_tty.c_lflag |= ECHO, tcsetattr(_tty_ch, TCSAFLUSH, &_tty))
 define noecho()    (_tty.c_lflag &=~ECHO, tcsetattr(_tty_ch, TCSAFLUSH, &_tty))
 define nl()        (_tty.c_iflag |= ICRNL,_tty.c_oflag |= ONLCR,tcsetattr(_tty_ch, TCSAFLUSH, &_tty))
 define nonl()      (_tty.c_iflag &=~ICRNL,_tty.c_oflag &=~ONLCR,tcsetattr(_tty_ch, TCSAFLUSH, &_tty))
 define savetty()   (tcgetattr(_tty_ch, &_oldtty),tcgetattr(_tty_ch, &_tty))
 define resetty()   (tcsetattr(_tty_ch, TCSAFLUSH, &_oldtty)) */
#endif

/* We store, if term_raw() or term_unraw() was executed lastly,
 therewith we can switch back on program-exit. */
local bool terminal_raw = false;

global void terminal_sane (void) {
  if (terminal_raw) {
    term_unraw();
    terminal_raw = false;
  }
}

LISPFUN(terminal_raw,seclass_default,2,1,norest,nokey,0,NIL) {
  skipSTACK(1); /* ignore errorp */
  var object flag = popSTACK();
  var object stream = check_stream(popSTACK());
  stream = resolve_synonym_stream(stream);
  value1 = NIL;
  if (builtin_stream_p(stream)) {
    if (((TheStream(stream)->strmtype == strmtype_terminal)  /* Terminal-Stream */
         && !nullp(TheStream(stream)->strm_terminal_isatty)) /* Terminal */
   #ifdef KEYBOARD
        || ((TheStream(stream)->strmtype == strmtype_keyboard)  /* Keyboard-Stream */
            && !nullp(TheStream(stream)->strm_keyboard_isatty))
   #endif
        ) {
      value1 = (terminal_raw ? T : NIL);
      begin_system_call();
      if (!nullp(flag)) { /* switch to cbreak/noecho-Mode: */
        term_raw(); terminal_raw = true;
      } else { /* switch to nocbreak/echo-Mode: */
        term_unraw(); terminal_raw = false;
      }
      end_system_call();
    }
  }
  mv_count=1;
}

#endif  /* UNIX */

#endif  /* UNIX || WIN32_NATIVE */

#if !defined(UNIX)
LISPFUN(terminal_raw,seclass_default,2,1,norest,nokey,0,NIL) {
  VALUES1(NIL); skipSTACK(3); /* do nothing */
}
#endif

/* Returns an interactive Terminal-Stream.
 can trigger GC */
local maygc object make_terminal_stream (void) {
  return add_to_open_streams(make_terminal_stream_());
}


/* Window-Stream
   ============= */

#ifdef SCREEN

/* Editor-Support:
 CURSES: A Window-Stream is essentially a Curses-WINDOW.

 (SCREEN:MAKE-WINDOW)
   returns a Window-Stream. Until it is closed again,
   the Terminal is in cbreak-noecho-Mode; further In-/Output via
   *terminal-io* should not happen during this period of time.

 (SCREEN:WINDOW-SIZE window-stream)
   returns the size of the Window,
   as 2 values: Height (= Ymax+1), Width (= Xmax+1).

 (SCREEN:WINDOW-CURSOR-POSITION window-stream)
   returns the Position of the Cursor in the Window
   as 2 values: row (>=0, <=Ymax, 0=oben), column (>=0, <=Xmax, 0=links).

 (SCREEN:SET-WINDOW-CURSOR-POSITION window-stream line column)
   sets the Position of the Cursor in the Window.

 (SCREEN:CLEAR-WINDOW window-stream)
   deletes the content of the Window and
   positions the Cursor to the upper left corner

 (SCREEN:CLEAR-WINDOW-TO-EOT window-stream)
   deletes the content of the Window from Cursor-Position to end of screen

 (SCREEN:CLEAR-WINDOW-TO-EOL window-stream)
   deletes the content of the Window from Cursor-Position to end of line

 (SCREEN:DELETE-WINDOW-LINE window-stream)
   deletes the cursor-line, shifts the lines below up one row
   and deletes the last line of the screen.

 (SCREEN:INSERT-WINDOW-LINE window-stream)
   inserts a new line at the line of the cursor and thereby shifts down
   all lines starting at the cursor by 1.

 (SCREEN:HIGHLIGHT-ON window-stream)
   switches on "highlighted" output.

 (SCREEN:HIGHLIGHT-OFF window-stream)
   switches off "highlighted" output again.

 (SCREEN:WINDOW-CURSOR-ON window-stream)
   turns the Cursor(block) visible.

 (SCREEN:WINDOW-CURSOR-OFF window-stream)
   turns the Cursor(block) invisible again.

 check that the argument is a window-stream. */
local object check_window_stream (object stream) {
  if (!(builtin_stream_p(stream)
        && (TheStream(stream)->strmtype == strmtype_window))) {
    pushSTACK(stream);
    pushSTACK(TheSubr(subr_self)->name);
    error(error_condition,GETTEXT("~S: argument ~S should be a window stream"));
  }
  return stream;
}

#ifdef WIN32_NATIVE

global void resize_screen (int rows, int columns) {}

/* Implementation on top of the Win32 console.
 Contributed by Arseny Slobodjuck <ampy@crosswinds.net>, 2001-02-14
 modified on 2001-07-31

 The API is documented at
 http://www.msdn.microsoft.com/library/psdk/winbase/conchar_4svm.htm
 (Platform SDK documentation -> Base Services -> Files and I/O ->
  Consoles and Character-Mode Support -> About Character Mode Support ->
  Consoles)

 console is a kind of channel stream

 accessor that can be used at the Right Side */
#define ConsoleHandleR(stream) TheHandle(TheStream(stream)->strm_ochannel)

typedef struct win32_console_extrafields_t {
  strm_channel_extrafields_t channel_fields;
  COORD cursor_position;
  COORD console_size;
  WORD  attribute;
  bool  handle_reused;
} win32_console_extrafields_t;

#define ConsoleData(stream) ((win32_console_extrafields_t*)&TheStream(stream)->strm_channel_extrafields)

/* The following attribute constants are defined in the <wincon.h> header file:
 FOREGROUND_BLUE
 FOREGROUND_GREEN
 FOREGROUND_RED
 FOREGROUND_INTENSITY
 BACKGROUND_BLUE
 BACKGROUND_GREEN
 BACKGROUND_RED
 BACKGROUND_INTENSITY */

local const WORD attr_table[5] = {
  /* no standout   */
  BACKGROUND_BLUE
  | FOREGROUND_BLUE | FOREGROUND_GREEN | FOREGROUND_RED,
  /* standout      */
  BACKGROUND_BLUE
  | FOREGROUND_INTENSITY | FOREGROUND_BLUE | FOREGROUND_GREEN | FOREGROUND_RED,
  /* visible bell  */
  BACKGROUND_BLUE
  | FOREGROUND_INTENSITY | FOREGROUND_RED,
  /* underline     */
  BACKGROUND_BLUE
  | FOREGROUND_INTENSITY | FOREGROUND_GREEN,
  /* alt. char set */
  BACKGROUND_BLUE
  | FOREGROUND_INTENSITY | FOREGROUND_GREEN | FOREGROUND_RED
};

local void move_ccp_by(COORD *pos,COORD sz,int by) {
  var int linear_ccp = pos->Y * sz.X + pos->X;
  var int new_linear = linear_ccp + by;
  pos->X = new_linear % sz.X;
  pos->Y = ( new_linear % ( sz.X * sz.Y )) / sz.X;
}

local void v_move(HANDLE handle,uintW y,uintW x) {
  /* set cursor */
  var COORD pos;
  pos.X = x; pos.Y = y;
  SetConsoleCursorPosition(handle,pos);
}

local void v_emit_spaces(HANDLE handle,COORD *pos,int nspaces,uintW attr) {
  var DWORD i;
  FillConsoleOutputAttribute(handle,attr,nspaces,*pos,&i);
  FillConsoleOutputCharacter(handle,' ',nspaces,*pos,&i);
}

local void v_cb (HANDLE handle) {
  /* cursor have 50 percent fill and visibility */
  var CONSOLE_CURSOR_INFO ci = { 50, 1 };
  SetConsoleCursorInfo(handle,&ci);
}

local void v_cs (HANDLE handle) {
  /* cursor have 10 percent fill and 0 visibility */
  var CONSOLE_CURSOR_INFO ci = { 10, 0 };
  SetConsoleCursorInfo(handle,&ci);
}

local void v_ce (HANDLE handle,COORD *pos,COORD sz,uintW attr) {
  /* clear to end: get cursor position and emit the appropriate number
   of spaces, without moving cursor. attr of spaces set to default. */
  var int nspaces = sz.X - pos->X;
  v_emit_spaces(handle,pos,nspaces,attr);
}

local void v_cl (HANDLE handle,COORD *pos,COORD sz,uintW attr) {
  var int nspaces = sz.X * sz.Y;
  v_emit_spaces(handle,pos,nspaces,attr);
  v_move(handle,0,0);
}

local void v_cd (HANDLE handle,COORD *pos,COORD sz,uintW attr) {
  /* clear to bottom: get position, clear to eol, clear next line to end */
  var int nspaces = (sz.Y - pos->Y) * sz.X - pos->X;
  v_emit_spaces(handle,pos,nspaces,attr);
}

local void v_scroll (HANDLE handle,int ax,int ay,int bx,int by,
                     int n,uintW attr) {
  var CHAR_INFO c;
  var SMALL_RECT r1;
  var SMALL_RECT r2;
  var COORD p;
  c.Char.AsciiChar = ' '; c.Attributes = attr;
  r1.Left = ax; r1.Top = ay; r1.Right = bx; r1.Bottom = by;
  r2 = r1;
  p.X = ax; p.Y = ay + n;
  ScrollConsoleScreenBuffer(handle,&r1,&r2,p,&c);
}

local void v_al (HANDLE handle,COORD *pos,COORD sz,uintW attr) {
  /* add line: scroll rest of screen down */
  v_scroll(handle,0,pos->Y+1,sz.X-1,sz.Y-1,1,attr);
}

local void v_dl (HANDLE handle,COORD *pos,COORD sz,uintW attr) {
  /* delete line: scroll rest up */
  v_scroll(handle,0,pos->Y,sz.X-1,sz.Y-1,-1,attr);
}

local void v_su (HANDLE handle,COORD *pos,COORD sz,uintW attr) {
  /* not used. why is it here ?
   scroll up: scroll whole screen */
  v_scroll(handle,0,0,sz.X-1,sz.Y-1,-1,attr);
}

local uintW v_put(HANDLE handle,uintW ch,COORD *pos,COORD sz,uintW attr) {
  /* put character:
   put attribute and char (no scroll!), then update cursor position. */
  ch &= 0xff;
  if (ch==NL) {
    pos->Y += 1;
    pos->Y %= sz.Y;
    pos->X = 0;
  } else {
    CHAR_INFO c;
    SMALL_RECT rto;
    COORD p0;
    COORD p1;
    c.Char.AsciiChar = ch;
    c.Attributes = attr;
    rto.Left = pos->X; rto.Top = pos->Y;
    rto.Right = pos->X+1; rto.Bottom = pos->Y+1;
    p0.X = 0; p0.Y = 0;
    p1.X = 1; p1.Y = 1;
    WriteConsoleOutput(handle,&c,p1,p0,&rto);
    move_ccp_by(pos,sz,1);
  }
  return ch;
}

local void v_puts(HANDLE handle,char *s,COORD *pos,COORD sz,uintW attr) {
  var char * cp    = s;           /* cp = current position */
  var char * start = s;           /* start of current piece of string */
  var char terminator = 0;        /* judgement day */
  do {
    /* move cp to end of line or newline char or right screen border
     set terminator accordingly */
    while (1) {
      if (!(*cp) || *cp == NL) {
        terminator = *cp;
        break;              }
      cp++;
      if ((cp - start) >= (sz.X - pos->X)) {
        terminator = CR;
        break;                                  }
    }
    if (cp > start) {
      var CHAR_INFO * ac = (CHAR_INFO *)malloc((cp - start) * sizeof(CHAR_INFO));
      var SMALL_RECT rto;
      var COORD zp;
      var COORD p;
      var int i;
      zp.X = 0; zp.Y = 0;
      if (!ac) return;
      for (i=0;i<(cp - start);i++) {
        ac[i].Char.AsciiChar = start[i];
        ac[i].Attributes = attr;
      }
      rto.Left = pos->X;
      rto.Top = pos->Y;
      rto.Right = pos->X + (cp - start) - 1;
      rto.Bottom = pos->Y;
      p.X = cp - start;
      p.Y = 1;
      WriteConsoleOutput(handle,ac,p,zp,&rto);
      pos->X+=cp - start;
      if (terminator == NL || terminator == CR) {
        pos->X = 0;
        if (pos->Y >= sz.Y - 1)
          pos->Y = 0;
        else pos->Y++;
      }
      free(ac);
    }
    if (terminator == NL) cp++;
    start = cp;
  } while (terminator == NL || terminator == CR);
}

/* Lisp functions: */

local maygc void wr_ch_array_window (const gcv_object_t* stream_,
                                     const gcv_object_t* chararray_,
                                     uintL start, uintL len) {
  var Handle handle = ConsoleHandleR(*stream_);
  var COORD  pos    = ConsoleData(*stream_)->cursor_position;
  var COORD  sz     = ConsoleData(*stream_)->console_size;
  var uintW  attr   = attr_table[ConsoleData(*stream_)->attribute];
  var uintL end = start + len;
  var uintL index = start;
  var uintL strindex = 0;
  var uintL mbpos = 0;
  var chart * chart_str = (chart *)malloc((len + 1)*sizeof(chart));
  var char  * char_str = (char *)chart_str;
  if (!chart_str) return;
  SstringDispatch(*chararray_,X, {
    do {
      chart_str[strindex] = as_chart(((SstringX)TheVarobject(*chararray_))->data[index]);
      index++; strindex++;
    } while (index < end);
    chart_str[strindex] = as_chart(0);
  });
 #ifdef ENABLE_UNICODE
  var uintB *mb_str = (uintB*)malloc((len + 1)*sizeof(char)*max_bytes_per_chart);
  if (mb_str) {
    var object encoding = TheStream(*stream_)->strm_encoding;
    var const chart* cptr = chart_str;
    var uintB * bptr      = mb_str;
    memset(mb_str, 0, (len + 1)*sizeof(char)*max_bytes_per_chart);
    Encoding_wcstombs(encoding)
      (encoding,*stream_,&cptr,chart_str+strindex,
       &bptr,mb_str + len * max_bytes_per_chart);
    v_puts(handle,(char*)mb_str,&pos,sz,attr); /* will work only when multi == 1 in multibytes */
    free(mb_str);
  }
 #else
  for (mbpos=0; as_cint(chart_str[mbpos]); mbpos++)
    char_str[mbpos] = as_cint(chart_str[mbpos]);
  char_str[mbpos] = 0;
  CharToOem(char_str,char_str);
  v_puts(handle,char_str,&pos,sz,attr);
 #endif
  free(chart_str);
  SetConsoleCursorPosition(handle,pos);
  ConsoleData(*stream_)->cursor_position = pos;
}

/* UP: write a character to a Window-Stream.
 wr_ch_window(&stream,ch);
 > stream: Window-Stream
 > ch: character to be written */
local maygc void wr_ch_window (const gcv_object_t* stream_, object ch) {
  var Handle handle = ConsoleHandleR(*stream_);
  var COORD  pos    = ConsoleData(*stream_)->cursor_position;
  var COORD  sz     = ConsoleData(*stream_)->console_size;
  var uintW  attr   = attr_table[ConsoleData(*stream_)->attribute];
  check_wr_char(*stream_,ch);
  var chart c = char_code(ch);
 #ifdef ENABLE_UNICODE
  var uintB buf[max_bytes_per_chart];
  var object encoding = TheStream(*stream_)->strm_encoding;
  var const chart* cptr = &c;
  var uintB* bptr = buf;
  Encoding_wcstombs(encoding)
    (encoding,*stream_,&cptr,cptr+1,&bptr,buf+max_bytes_per_chart);
  c = as_chart((uintB)*buf);
 #else
  CharToOemBuff((char *)&c,(char *)&c,1);
 #endif
  v_put(handle,(uintW)as_cint(c),&pos,sz,attr);
  SetConsoleCursorPosition(handle,pos);
  ConsoleData(*stream_)->cursor_position = pos;
}

local void low_close_console (object stream, object handle, uintB abort) {
  if (!ConsoleData(stream)->handle_reused) {
    begin_system_call();
    if (!CloseHandle(TheHandle(handle)) && !abort)
      { end_system_call(); OS_filestream_error(stream); }
    end_system_call();
  }
}

LISPFUNN(make_window,0) {
  var object stream =
    allocate_stream(strmflags_wr_ch_B,strmtype_window,strm_channel_len,
                    sizeof(win32_console_extrafields_t));
  /* try to reuse handle on win 95/98
   make new handle on NT */
  var int nt_systemp = 0;
  var bool handle_reused = 1;
  var OSVERSIONINFO osvers;
  osvers.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
  if (GetVersionEx(&osvers) && osvers.dwPlatformId == VER_PLATFORM_WIN32_NT)
    nt_systemp = 1;

  var HANDLE handle = (nt_systemp ? INVALID_HANDLE_VALUE
                       : GetStdHandle(STD_OUTPUT_HANDLE));
  if (handle==INVALID_HANDLE_VALUE) {
    handle = CreateConsoleScreenBuffer(GENERIC_READ|GENERIC_WRITE,
                                       0,
                                       NULL,
                                       CONSOLE_TEXTMODE_BUFFER,
                                       NULL);
    if (handle == INVALID_HANDLE_VALUE)
      error_unwritable(S(make_window),stream);
    SetConsoleActiveScreenBuffer(handle);
    handle_reused = 0;
  }
  var COORD console_size;
  var COORD console_pos;
  var CONSOLE_SCREEN_BUFFER_INFO info;
  if (GetConsoleScreenBufferInfo(handle,&info))
    console_size = info.dwSize;
  else {
    console_size.X = 80; console_size.Y = 25;
  }
  console_pos.X = 0;console_pos.Y = 0;
  pushSTACK(stream);            /* save */
  var object handle_object = allocate_handle(handle);
  stream = popSTACK();          /* restore */
  stream_dummy_fill(stream);
  var Stream s = TheStream(stream);
  s->strm_wr_ch       = s->strm_wr_ch_npnl       = P(wr_ch_window);       /* WRITE-CHAR Pseudofunction */
  s->strm_wr_ch_array = s->strm_wr_ch_array_npnl = P(wr_ch_array_window); /* WRITE-CHAR-SEQUENCE Pseudofunction */
  s->strm_encoding    = O(terminal_encoding);
  s->strm_isatty      = NIL;
  s->strm_ichannel    = NIL;
  TheStream(stream)->strm_ochannel = handle_object;
  /* non GC-ed fields */
  ConsoleData(stream)->console_size = console_size;
  ConsoleData(stream)->cursor_position = console_pos;
  ConsoleData(stream)->attribute = 0;
  ConsoleData(stream)->handle_reused = handle_reused;
  ChannelStream_init(stream);  /* iconv extrafields init */
  ChannelStream_lineno(stream) = 1;
  ChannelStream_buffered(stream) = false;
  ChannelStream_regular(stream) = false;
  ChannelStream_bitsize(stream) = 0;
  ChannelStreamLow_close(stream) = &low_close_console;
  v_move(handle,0,0);
  v_cl(handle,&console_pos,console_size,attr_table[0]);
  v_cs(handle);
  VALUES1(stream);
}

/* close a window stream. */
local void close_window (object stream, uintB abort) {
  close_ochannel(stream,abort);
}

LISPFUNN(window_size,1) {
  var object stream = check_window_stream(popSTACK());
  var COORD  sz     = ConsoleData(stream)->console_size;
  VALUES2(fixnum(sz.Y),
          fixnum(sz.X));
}

LISPFUNN(window_cursor_position,1) {
  var object stream = check_window_stream(popSTACK());
  var COORD  pos    = ConsoleData(stream)->cursor_position;
  VALUES2(fixnum(pos.Y),
          fixnum(pos.X));
}

LISPFUNN(set_window_cursor_position,3) {
  var object stream = check_window_stream(STACK_2);
  var Handle handle = ConsoleHandleR(stream);
  var COORD  sz     = ConsoleData(stream)->console_size;
  var COORD pos;
  pos.Y = posfixnum_to_V(STACK_1);
  pos.X = posfixnum_to_V(STACK_0);
  if ((pos.Y < sz.Y) && (pos.X < sz.X)
      && (pos.Y >= 0) && (pos.X >= 0)) {
    v_move(handle,pos.Y,pos.X);
    ConsoleData(stream)->cursor_position = pos;
  }
  VALUES2(STACK_1, STACK_0); skipSTACK(3);
}

LISPFUNN(clear_window,1) {
  var object stream = check_window_stream(popSTACK());
  var Handle handle = ConsoleHandleR(stream);
  var COORD  pos    = ConsoleData(stream)->cursor_position;
  var COORD  sz     = ConsoleData(stream)->console_size;
  var uintW  attr   = attr_table[ConsoleData(stream)->attribute];
  v_cl(handle,&pos,sz,attr);
  ConsoleData(stream)->cursor_position = pos;
  VALUES0;
}

LISPFUNN(clear_window_to_eot,1) {
  var object stream = check_window_stream(popSTACK());
  var Handle handle = ConsoleHandleR(stream);
  var COORD  pos    = ConsoleData(stream)->cursor_position;
  var COORD  sz     = ConsoleData(stream)->console_size;
  var uintW  attr   = attr_table[ConsoleData(stream)->attribute];
  v_cd(handle,&pos,sz,attr);
  VALUES0;
}

LISPFUNN(clear_window_to_eol,1) {
  var object stream = check_window_stream(popSTACK());
  var Handle handle = ConsoleHandleR(stream);
  var COORD  pos    = ConsoleData(stream)->cursor_position;
  var COORD  sz     = ConsoleData(stream)->console_size;
  var uintW  attr   = attr_table[ConsoleData(stream)->attribute];
  v_ce(handle,&pos,sz,attr);
  VALUES0;
}

LISPFUNN(delete_window_line,1) {
  var object stream = check_window_stream(popSTACK());
  var Handle handle = ConsoleHandleR(stream);
  var COORD  pos    = ConsoleData(stream)->cursor_position;
  var COORD  sz     = ConsoleData(stream)->console_size;
  var uintW  attr   = attr_table[ConsoleData(stream)->attribute];
  v_dl(handle,&pos,sz,attr);
  VALUES0;
}

LISPFUNN(insert_window_line,1) {
  var object stream = check_window_stream(popSTACK());
  var Handle handle = ConsoleHandleR(stream);
  var COORD  pos    = ConsoleData(stream)->cursor_position;
  var COORD  sz     = ConsoleData(stream)->console_size;
  var uintW  attr   = attr_table[ConsoleData(stream)->attribute];
  v_al(handle,&pos,sz,attr);
  VALUES0;
}

LISPFUNN(highlight_on,1) {
  var object stream = check_window_stream(popSTACK());
  ConsoleData(stream)->attribute = 1;
  VALUES0;
}

LISPFUNN(highlight_off,1) {
  var object stream = check_window_stream(popSTACK());
  ConsoleData(stream)->attribute = 0;
  VALUES0;
}

LISPFUNN(window_cursor_on,1) {
  var object stream = check_window_stream(popSTACK());
  v_cb(ConsoleHandleR(stream));
  VALUES0;
}

LISPFUNN(window_cursor_off,1) {
  var object stream = check_window_stream(popSTACK());
  v_cs(ConsoleHandleR(stream));
  VALUES0;
}


#endif /* WIN32_NATIVE */

#if defined(UNIX)

/* -------------------------------------------------------------------------

 Routines for the Emulation of all VT100-Features on normal Terminals.
 Idea: Oliver Laumann 1987
 Bruno Haible, Tue, 25 Feb 2003 22:23:11 +0100 (CET):
 libtermcap is a permanent security problem. Better remove it from your
 system, and use libncurses instead.
 See also m4/termcap.m4: we look for these routines in libncurses first.

 Uses the TERMCAP Library:
  Gets the Capability-Informations for Terminal-Type name.
   result: 1 if OK, 0 if name unknown, -1 on other error. */
extern_C int tgetent (const char* bp, const char* name);
/* gets the value of a numerical Capability (-1 if not available). */
extern_C int tgetnum (const char* id);
/* gets the value of a boolean Capability (1 if available, else 0). */
extern_C int tgetflag (const char* id);
/* gets the value of a String-significant Capability and (if area/=NULL)
   copies it to *area and further advances *area. */
extern_C const char* tgetstr (const char* id, char** area);
/* gets the String, that causes a Cursor-Positioning to (destcol,destline).
   (Necessary, because tgetstr("cm") has a special Format!) */
extern_C const char* tgoto (const char* cm, int destcol, int destline);
/* Performs a String-Capability. Thereto the output-function *outcharfun
   is called for each Character. (Necessary, because String-Capabilities
   can contain Padding-Commands!) */
#ifdef __cplusplus
typedef void (*outcharfun_t) (...);
#else
typedef void (*outcharfun_t) ();
#endif
extern_C const char* tputs (const char* cp, int affcnt, outcharfun_t outcharfun);

/* Adjustable settings: */
  #define WANT_INSERT  false  /* Insert-Mode */
  #define WANT_SAVE    false  /* Save/Restore for the Cursor-Position */
  #define WANT_ATTR    true   /* Attributes (bold, reverse etc.) */
  #define WANT_CHARSET false  /* Fonts = Charsets */
  /* Functions to be defined: */
  #define WANT_CURSOR_MOVE         false
  #define WANT_CURSOR_BACKSPACE    false
  #define WANT_CURSOR_RETURN       true
  #define WANT_CURSOR_LINEFEED     true
  #define WANT_CURSOR_REVLINEFEED  false
  #define WANT_CLEAR_SCREEN        true
  #define WANT_CLEAR_FROM_BOS      false
  #define WANT_CLEAR_TO_EOS        true
  #define WANT_CLEAR_LINE          false
  #define WANT_CLEAR_FROM_BOL      false
  #define WANT_CLEAR_TO_EOL        true
  #define WANT_INSERT_1CHAR        false
  #define WANT_INSERT_CHAR         false
  #define WANT_INSERT_LINE         true
  #define WANT_DELETE_CHAR         false
  #define WANT_DELETE_LINE         true
  #define WANT_OUTPUT_1CHAR        true
  /* small corrections: */
  #define WANT_CLEAR_SCREEN        true
  #if WANT_OUTPUT_1CHAR && WANT_INSERT
  #define WANT_INSERT_1CHAR        true
  #endif

/* output of a character, directly. */
local void out_char (uintB c) {
 restart_it: {
  var int result = write(stdout_handle,&c,1); /* try to write character */
  if (result<0) {
    if (errno==EINTR)
      goto restart_it;
    OS_error();
  }
  if (result==0) { /* not successful? */
    pushSTACK(var_stream(S(terminal_io),0)); /* FILE-ERROR slot PATHNAME */
    error(file_error,GETTEXT("cannot output to standard output"));
  }
 }
}

/* output of a Capability-String. */
local void out_capstring (const char* s) {
  if (!(s==NULL)) /* protection against non-existing Capability */
    tputs(s,1,(outcharfun_t) &out_char);
}

/* output of a Capability-String with an Argument. */
local void out_cap1string (const char* s, int arg) {
  if (!(s==NULL)) /* protection against non-existing Capability */
    tputs(tgoto(s,0,arg),1,(outcharfun_t) &out_char);
}

/* costs of execution of a Capability: */
  #define EXPENSIVE 1000
  local uintC cost_counter; /* counter */
/* Function, that does not write, but only counts: */
local void count_char (char c) {
  unused(c);
  cost_counter++;
}

/* calculates the costs of the writing of a Capability: */
local uintC cap_cost (const char* s) {
  if (s==NULL) {
    return EXPENSIVE; /* Capability non-existing */
  } else {
    cost_counter = 0;
    tputs(s,1,(outcharfun_t) &count_char);
    return cost_counter;
  }
}

/* Buffer for Capabilities that I need and Pointer to it: */
local char tentry[4096];
local char* tp = &tentry[0];
/* some chosen Capabilities (NULL or Pointer into tentry): */
/* Insert-Mode: */
local const char* IMcap; /* Enter Insert Mode */
local uintC IMcost;
local const char* EIcap; /* End Insert Mode */
local uintC EIcost;
#if WANT_ATTR
/* Attributes: */
local const char* SOcap; /* Enter standout mode */
local const char* SEcap; /* End standout mode */
local const char* UScap; /* Enter underline mode */
local const char* UEcap; /* End underline mode */
local const char* MBcap; /* Turn on blinking */
local const char* MDcap; /* Turn on bold (extra-bright) mode */
local const char* MHcap; /* Turn on half-bright mode */
local const char* MRcap; /* Turn on reverse mode */
local const char* MEcap; /* Turn off all attributes */
#endif
#if WANT_CHARSET
/* charsets: */
local bool ISO2022; /* if charset change according to ISO2022 is supported */
#endif
/* Cursor-Motion: */
local const char* CMcap; /* Cursor motion, common Cursor-Positioning */
local const char* TIcap; /* Initialize mode where CM is usable */
local const char* TEcap; /* Exit mode where CM is usable */
local const char* BCcap; /* Backspace Cursor */
local uintC BCcost;
local const char* NDcap; /* cursor right */
local uintC NDcost;
local const char* DOcap; /* cursor down */
local uintC DOcost;
local const char* UPcap; /* cursor up */
local uintC UPcost;
local const char* NLcap; /* Newline */
local const char* CRcap; /* Carriage Return */
local uintC CRcost;
/* Scrolling: */
local const char* CScap; /* change scroll region */
#if WANT_DELETE_LINE
local const char* SFcap; /* Scroll (text up) */
#endif
#if WANT_CURSOR_REVLINEFEED || WANT_INSERT_LINE
local const char* SRcap; /* Scroll reverse (text down) */
#endif
/* Others: */
local const char* IScap; /* Terminal Initialization 2 */
/*  local const char* BLcap; - Bell
    local const char* VBcap; - Visible Bell (Flash) */
local const char* CLcap; /* clear screen, cursor home */
#if WANT_CLEAR_FROM_BOS || WANT_CLEAR_TO_EOS || WANT_CLEAR_LINE || WANT_CLEAR_FROM_BOL || WANT_CLEAR_TO_EOL
local const char* CEcap; /* clear to end of line */
#endif
#if WANT_CLEAR_TO_EOS
local const char* CDcap; /* clear to end of screen */
#endif
#if WANT_CURSOR_REVLINEFEED || WANT_INSERT_LINE
local const char* ALcap; /* add new blank line */
#endif
#if WANT_DELETE_LINE
local const char* DLcap; /* delete line */
#endif
#if WANT_DELETE_CHAR
local const char* DCcap; /* delete character */
#endif
#if WANT_INSERT_1CHAR || WANT_INSERT_CHAR
local const char* ICcap; /* insert character */
#endif
#if WANT_INSERT_CHAR
local const char* CICcap; /* insert count characters */
#endif
#if WANT_INSERT_LINE
local const char* CALcap; /* add count blank lines */
#endif
#if WANT_DELETE_CHAR
local const char* CDCcap; /* delete count chars */
#endif
#if WANT_DELETE_LINE
local const char* CDLcap; /* delete count lines */
#endif
local bool AM; /* automatic margins, if scrolling on right bottom corner (??) */
local int rows; /* number of rows of the screen, >0 */
local int cols; /* number of columns of the screen, >0 */
/* top row is row 0, bottom row is row rows-1.
   left-most column is column 0, right-most column is column cols-1. */
#if WANT_ATTR || WANT_CHARSET
local uintB* null; /* Pointer to cols Zeros */
#endif
local uintB* blank; /* Pointer to cols Blanks */

/* Description of a Terminal-Output-Unit: */
typedef struct {
  uintB** image; /* image[y][x] is the character at Position (x,y) */
  #if WANT_ATTR
  uintB** attr;  /* attr[y][x] is its Attribute */
  uintB curr_attr; /* which Attribut is now the current one */
  #endif
  #if WANT_CHARSET
  uintB** font;  /* font[y][x] is its Font (Charset) */
  #define charset_count 4
  uintB charsets[charset_count]; /* Table of charsets */
  uintC curr_charset; /* which of the charsets is the current one */
                      /* (>=0, <charset_count) */
  #endif
  int x; /* Cursorposition (>=0, <=cols) */
  int y; /* Cursorposition (>=0, <rows) */
         /* (At x=cols the Cursor is displayed in column cols-1.) */
  int top, bot; /* Scroll-Region = rows y with top <= y <= bot, */
                /* It applies: 0 <= top <= bot <= rows-1. */
  #if WANT_INSERT
  bool insert; /* if the Output-Unit works in Insert-Mode */
                  /* (then the Terminal is mostly in Insert-Mode) */
  #endif
  #if WANT_SAVE
  bool saved;
  #if WANT_ATTR
  uintB saved_curr_attr;
  #endif
  #if WANT_CHARSET
  uintB saved_charsets[charset_count];
  uintC saved_curr_charset;
  #endif
  int saved_x, saved_y;
  #endif
} win;

/* current Output-Unit: */
local win currwin; /* there is only one! */
#define curr (&currwin)

#if WANT_INSERT

/* switch on/of Insert-Mode:
 Flag, if the Terminal is in Insert-Mode (if there is one): */
local bool insert;
local void set_insert_mode (bool flag) {
  if (flag) { /* switch on */
    if (!insert)
      out_capstring(IMcap);
  } else { /* switch off */
    if (insert)
      out_capstring(EIcap);
  }
  insert = flag;
}

#endif

#if WANT_ATTR

/* toggle the Output-Attributes of the Terminal: */
local uintB term_attr; /* current Attributes of the Terminal */
/* possible Attributes are on ODER off: */
#define A_SO    bit(0)  /* Standout mode */
#define A_US    bit(1)  /* Underscore mode */
#define A_BL    bit(2)  /* Blinking */
#define A_BD    bit(3)  /* Bold mode */
#define A_DI    bit(4)  /* Dim mode */
#define A_RV    bit(5)  /* Reverse mode */
local void change_attr (uintB new_attr) {
  var uintB old_attr = term_attr;
  if (old_attr == new_attr)
    return;
  if (((old_attr & A_SO) && !(new_attr & A_SO))
      || ((old_attr & A_US) && !(new_attr & A_US))
      || ((old_attr & A_BL) && !(new_attr & A_BL))
      || ((old_attr & A_BD) && !(new_attr & A_BD))
      || ((old_attr & A_DI) && !(new_attr & A_DI))
      || ((old_attr & A_RV) && !(new_attr & A_RV))) {
    /* Must switch of Attributes. */
    out_capstring(UEcap); /* all are off */
    out_capstring(SEcap);
    out_capstring(MEcap);
    if (new_attr & A_SO) out_capstring(SOcap); /* and switch on selectively */
    if (new_attr & A_US) out_capstring(UScap);
    if (new_attr & A_BL) out_capstring(MBcap);
    if (new_attr & A_BD) out_capstring(MDcap);
    if (new_attr & A_DI) out_capstring(MHcap);
    if (new_attr & A_RV) out_capstring(MRcap);
  } else {
    /* switch on selectively: */
    if ((new_attr & A_SO) && !(old_attr & A_SO)) out_capstring(SOcap);
    if ((new_attr & A_US) && !(old_attr & A_US)) out_capstring(UScap);
    if ((new_attr & A_BL) && !(old_attr & A_BL)) out_capstring(MBcap);
    if ((new_attr & A_BD) && !(old_attr & A_BD)) out_capstring(MDcap);
    if ((new_attr & A_DI) && !(old_attr & A_DI)) out_capstring(MHcap);
    if ((new_attr & A_RV) && !(old_attr & A_RV)) out_capstring(MRcap);
  }
  term_attr = new_attr;
}

#endif

#if WANT_CHARSET

/* change Output-Charset of the Terminal: */
local uintB term_charset; /* current charset of the Terminal */
/* = curr->charsets[curr->curr_charset] */
#define ASCII 0  /* abbreviation for the charset 'B' */
local void change_charset (uintB new) {
  if (term_charset==new)
    return;
  if (ISO2022) {
    out_char(ESC); out_char('('); out_char(new==ASCII ? 'B' : new);
  }
  term_charset = new;
}
/* change Charset Nr. n to c: */
local void choose_charset (uintB c, uintC n) {
  if (c=='B')
    c = ASCII;
  if (curr->charsets[n] == c)
    return;
  curr->charsets[n] = c;
  if (curr->curr_charset == n) /* the current one? */
    change_charset(c);
}
/* make Charset Nr. n the current one: */
local void set_curr_charset (uintC n) {
  if (curr->curr_charset == n)
    return;
  curr->curr_charset = n;
  change_charset(curr->charsets[n]);
}

#endif

/* calculate the costs of Redisplay of row y, characters x1..x2-1:
 (0 <= y < rows, 0 <= x1 <= x2 <= cols) */
local uintC rewrite_cost (int y, int x1, int x2) {
  if (AM && (y==rows-1) && (x2==cols)) /* right bottom corner can scroll? */
    return EXPENSIVE;
  var int dx = x2-x1;
  if (dx==0)
    return 0;
 #if WANT_ATTR
  {
    var uintB* p = &curr->attr[y][x1];
    var uintC count;
    dotimespC(count,dx, {
      if (!(*p++ == term_attr)) /* Attribut-Change necessary? */
        return EXPENSIVE;
    });
  }
 #endif
 #if WANT_CHARSET
  {
    var uintB* p = &curr->font[y][x1];
    var uintC count;
    dotimespC(count,dx, {
      if (!(*p++ == term_charset)) /* Font-Change necessary? */
        return EXPENSIVE;
    });
  }
 #endif
  var uintC cost = dx;
 #if WANT_INSERT
  if (curr->insert)
    cost += EIcost + IMcost;
 #endif
  return cost;
}

/* Moves the Cursor from Position (y1,x1) to Position (y2,x2).
 (x1,y1) = (-1,-1) if the current Position is unknown. */
local void gofromto (int y1, int x1, int y2, int x2) {
  if (x2==cols) { /* Cursor to the right border? */
    x2--; out_capstring(tgoto(CMcap,x2,y2)); return; /* remains in last column */
  }
  if (x1==cols) { /* Cursor is at the right border? */
    out_capstring(tgoto(CMcap,x2,y2)); return; /* address in absolute coords */
  }
  var int dy = y2-y1;
  var int dx = x2-x1;
  if ((dy==0) && (dx==0))
    return;
  if ((y1==-1) || (x1==-1) || (y2 > curr->bot) || (y2 < curr->top)) {
    out_capstring(tgoto(CMcap,x2,y2)); return;
  }
  var enum { MX_NONE, MX_LE, MX_RI, MX_RW, MX_CR } mx = MX_NONE;
  var enum { MY_NONE, MY_UP, MY_DO } my = MY_NONE;
  /* Option 1: with CMcap */
  var uintC CMcost = cap_cost(tgoto(CMcap,x2,y2));
  /* Option 2: with separate x- and y-movements: */
  var uintC xycost = 0;
  if (dx > 0) {
    var uintC cost1 = rewrite_cost(y1,x1,x2);
    var uintC cost2 = dx * NDcost;
    if (cost1 < cost2) {
      mx = MX_RW; xycost += cost1;
    } else {
      mx = MX_RI; xycost += cost2;
    }
  } else if (dx < 0) {
    mx = MX_LE; xycost += (-dx) * BCcost;
  }
  if (!(dx==0)) {
    var uintC cost1 = CRcost + rewrite_cost(y1,0,x2);
    if (cost1 < xycost) {
      mx = MX_CR; xycost = cost1;
    }
  }
  if (dy > 0) {
    my = MY_DO; xycost += dy * DOcost;
  } else if (dy < 0) {
    my = MY_UP; xycost += (-dy) * UPcost;
  }
  if (xycost >= CMcost) {
    out_capstring(tgoto(CMcap,x2,y2)); return;
  }
  if (!(mx==MX_NONE)) {
    if ((mx==MX_LE) || (mx==MX_RI)) {
      var const char* s;
      if (mx==MX_LE) {
        dx = -dx; s = BCcap;
      } else {
        s = NDcap;
      }
      do {
        out_capstring(s);
      } while (--dx != 0);
    } else {
      if (mx==MX_CR) {
        out_capstring(CRcap); x1=0;
      }
      /* hereof the costs were calculated with rewrite_cost: */
      if (x1<x2) {
       #if WANT_INSERT
        if (curr->insert)
          set_insert_mode(false);
       #endif
        {
          var uintB* ptr = &curr->image[y1][x1];
          var uintC count;
          dotimespC(count,x2-x1, { out_char(*ptr++); });
        }
       #if WANT_INSERT
        if (curr->insert)
          set_insert_mode(true);
       #endif
      }
    }
  }
  if (!(my==MY_NONE)) {
    var const char* s;
    if (my==MY_UP) {
      dy = -dy; s = UPcap;
    } else {
      s = DOcap;
    }
    do {
      out_capstring(s);
    } while (--dy != 0);
  }
}

/* Redisplay
 local Variables: */
local int last_x;
local int last_y;
/* Redisplay a line, that might have changed:
 pass only Parameters that are really needed: */
#if WANT_ATTR && WANT_CHARSET
  #define RHargs(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,oap,ofp,nsp,nap,nfp,y,x1,x2)
  #define RHparms(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,oap,ofp,nsp,nap,nfp,y,x1,x2)
#endif
#if !WANT_ATTR && WANT_CHARSET
  #define RHargs(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,ofp,nsp,nfp,y,x1,x2)
  #define RHparms(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,ofp,nsp,nfp,y,x1,x2,oap,nap)
#endif
#if WANT_ATTR && !WANT_CHARSET
  #define RHargs(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,oap,nsp,nap,y,x1,x2)
  #define RHparms(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,oap,nsp,nap,y,x1,x2,ofp,nfp)
#endif
#if !WANT_ATTR && !WANT_CHARSET
  #define RHargs(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,nsp,y,x1,x2)
  #define RHparms(osp,oap,ofp,nsp,nap,nfp,y,x1,x2) (osp,nsp,y,x1,x2,oap,ofp,nap,nfp)
#endif
#undef RHparms
#define RHparms  RHargs  /* declare correctly */
local void redisplay_help RHparms (uintB* osp, uintB* oap, uintB* ofp, /* old */
                                   uintB* nsp, uintB* nap, uintB* nfp, /* new */
                                   /* line y, from x1 to x2-1 */
                                   int y, int x1, int x2) {
  if (AM && (y == rows-1) && (x2 == cols))
    x2--;
 #if WANT_ATTR
  var uintB a = term_attr; /* last Attribute */
 #endif
 #if WANT_CHARSET
  var uintB f = term_charset; /* last Font */
 #endif
  var int x = x1;
  osp = &osp[x1]; nsp = &nsp[x1];
 #if WANT_ATTR
  oap = &oap[x1]; nap = &nap[x1];
 #endif
 #if WANT_CHARSET
  ofp = &ofp[x1]; nfp = &nfp[x1];
 #endif
  while (x < x2) {
    if (!((*nsp==*osp)
        #if WANT_ATTR
          && (*nap==*oap) && (*nap==a)
        #endif
        #if WANT_CHARSET
          && (*nfp==*nap) && (*nfp==f)
        #endif
          )) {
      gofromto(last_y,last_x,y,x);
     #if WANT_ATTR
      a = *nap;
      if (!(a==term_attr))
        change_attr(a);
     #endif
     #if WANT_CHARSET
      f = *nfp;
      if (!(f==term_charset))
        change_charset(f);
     #endif
      out_char(*nsp);
      last_y = y; last_x = x+1;
    }
    x++;
    osp++; nsp++;
   #if WANT_ATTR
    oap++; nap++;
   #endif
   #if WANT_CHARSET
    ofp++; nfp++;
   #endif
  }
}
#if WANT_INSERT_1CHAR || WANT_INSERT_CHAR || WANT_DELETE_CHAR
/* Redisplay a line:
 pass only Parameters that are really needed: */
#if WANT_ATTR && WANT_CHARSET
  #define RLargs(osp,oap,ofp,y,x1,x2) (osp,oap,ofp,y,x1,x2)
  #define RLparms(osp,oap,ofp,y,x1,x2) (osp,oap,ofp,y,x1,x2)
#endif
#if !WANT_ATTR && WANT_CHARSET
  #define RLargs(osp,oap,ofp,y,x1,x2) (osp,ofp,y,x1,x2)
  #define RLparms(osp,oap,ofp,y,x1,x2) (osp,ofp,y,x1,x2,oap)
#endif
#if WANT_ATTR && !WANT_CHARSET
  #define RLargs(osp,oap,ofp,y,x1,x2) (osp,oap,y,x1,x2)
  #define RLparms(osp,oap,ofp,y,x1,x2) (osp,oap,y,x1,x2,ofp)
#endif
#if !WANT_ATTR && !WANT_CHARSET
  #define RLargs(osp,oap,ofp,y,x1,x2) (osp,y,x1,x2)
  #define RLparms(osp,oap,ofp,y,x1,x2) (osp,y,x1,x2,oap,ofp)
#endif
#undef RHparms
#define RHparms  RHargs  /* declare correctly */
local void redisplay_line RLparms (uintB* osp, uintB* oap, uintB* ofp, /* old */
                                   /* line y, from x1 to x2-1 */
                                   int y, int x1, int x2) {
 #if WANT_INSERT
  if (curr->insert)
    set_insert_mode(false);
 #endif
 #if WANT_ATTR
  var uintB saved_attr = term_attr;
  change_attr(0);
 #endif
 #if WANT_CHARSET
  var uintB saved_charset = term_charset;
  change_charset(ASCII);
 #endif
  last_y = y; last_x = x1;
  redisplay_help RHargs(osp,           oap,          ofp,
                        curr->image[y],curr->attr[y],curr->font[y],
                        y, x1,x2);
 #if WANT_CHARSET
  change_charset(saved_charset);
 #endif
 #if WANT_ATTR
  change_attr(saved_attr);
 #endif
 #if WANT_INSERT
  if (curr->insert)
    set_insert_mode(true);
 #endif
}
#endif
/* Redisplay the whole screen: */
local void redisplay (void) {
 #if WANT_INSERT
  set_insert_mode(false);
 #endif
 #if WANT_ATTR
  var uintB saved_attr = term_attr;
  change_attr(0);
 #endif
 #if WANT_CHARSET
  var uintB saved_charset = term_charset;
  change_charset(ASCII);
 #endif
  out_capstring(CLcap); last_x = 0; last_y = 0;
  {
    var uintC y = 0;
    while (y<rows) {
      redisplay_help
        RHargs(blank,         null,         null,          /* old */
               curr->image[y],curr->attr[y],curr->font[y], /* new */
               y,                                          /* line y */
               0,cols);                                    /* all columns */
      y++;
    }
  }
 #if WANT_CHARSET
  change_charset(saved_charset);
 #endif
 #if WANT_ATTR
  change_attr(saved_attr);
 #endif
 #if WANT_INSERT
  if (curr->insert)
    set_insert_mode(true);
 #endif
  gofromto(last_y,last_x,curr->y,curr->x);
}

global void resize_screen (int lines, int columns) {
  rows = lines; cols = columns;
  if (curr->image) redisplay();
}

/* Further Cursor-Movements: */
#if WANT_CURSOR_MOVE

local void cursor_right (int n) {
  var int x = curr->x;
  if (x==cols)
    return;
  var int new_x = x + n;
  if (new_x > cols)
    new_x = cols;
  gofromto(curr->y,x,curr->y,curr->x = new_x);
}

local void cursor_left (int n) {
  var int x = curr->x;
  var int new_x = x - n;
  if (new_x < 0)
    new_x = 0;
  gofromto(curr->y,x,curr->y,curr->x = new_x);
}

local void cursor_up (int n) {
  var int y = curr->y;
  var int new_y = y - n;
  if (new_y < 0)
    new_y = 0;
  gofromto(y,curr->x,curr->y = new_y,curr->x);
}

local void cursor_down (int n) {
  var int y = curr->y;
  var int new_y = y + n;
  if (new_y >= rows)
    new_y = rows-1;
  gofromto(y,curr->x,curr->y = new_y,curr->x);
}

#endif

/* Backspace (Cursor to the left by 1, within a line) */
#if WANT_CURSOR_BACKSPACE
local void cursor_backspace (void) {
  if (curr->x > 0) {
    if (curr->x < cols) {
      if (BCcap)
        out_capstring(BCcap);
      else
        gofromto(curr->y,curr->x,curr->y,curr->x - 1);
    }
    curr->x = curr->x - 1;
  }
}
#endif

/* Return (Cursor to the beginning of a line) */
#if WANT_CURSOR_RETURN
local void cursor_return (void) {
  if (curr->x > 0) {
    out_capstring(CRcap); curr->x = 0;
  }
}
#endif

/* auxiliary routines for scrolling: */
#if WANT_CURSOR_LINEFEED || WANT_DELETE_LINE
local void scroll_up_help (uintB** pp, uintB filler) {
  /* shift pp[top..bot] by one to the left,
   take out pp[top], delete and insert again as pp[bot]: */
  pp = &pp[curr->top];
  var uintC count;
  var uintB* tmp = *pp;
  dotimesC(count,curr->bot - curr->top, { pp[0] = pp[1]; pp++; } );
  memset(tmp,filler,cols);
  *pp = tmp;
}
local void scroll_up (void) {
  scroll_up_help(curr->image,' ');
 #if WANT_ATTR
  scroll_up_help(curr->attr,0);
 #endif
 #if WANT_CHARSET
  scroll_up_help(curr->font,0);
 #endif
}
#endif
#if WANT_CURSOR_REVLINEFEED || WANT_INSERT_LINE
local void scroll_down_help (uintB** pp, uintB filler) {
  /* shift pp[top..bot] by one to the right,
   take out pp[top], delete and insert again as pp[bot]: */
  pp = &pp[curr->bot];
  var uintC count;
  var uintB* tmp = *pp;
  dotimesC(count,curr->bot - curr->top, { pp[0] = pp[-1]; pp--; } );
  memset(tmp,filler,cols);
  *pp = tmp;
}
local void scroll_down (void) {
  scroll_down_help(curr->image,' ');
 #if WANT_ATTR
  scroll_down_help(curr->attr,0);
 #endif
 #if WANT_CHARSET
  scroll_down_help(curr->font,0);
 #endif
}
#endif

/* Linefeed (Cursor down by 1): */
#if WANT_CURSOR_LINEFEED
local void cursor_linefeed (void) {
  if (curr->y == curr->bot)
    scroll_up();
  else if (curr->y < rows-1)
    curr->y++;
  out_capstring(NLcap);
}
#endif

/* Reverse Linefeed (Cursor up by 1): */
#if WANT_CURSOR_REVLINEFEED
local void cursor_revlinefeed (void) {
  if (curr->y == curr->top) {
    scroll_down();
    if (SRcap) {
      out_capstring(SRcap);
    } else if (ALcap) {
      gofromto(curr->top,curr->x,curr->top,0); /* Cursor to the left */
      out_capstring(ALcap);
      gofromto(curr->top,0,curr->top,curr->x); /* Cursor back again */
    } else {
      redisplay();
    }
  } else if (curr->y > 0) {
    cursor_up(1);
  }
}
#endif

/* Deletion-Operations: */

/* delete part of a line: */
#if WANT_CLEAR_SCREEN || WANT_CLEAR_FROM_BOS
local void cleared_linepart (int y, int x1, int x2) {
  var int n = x2-x1;
  if (n>0) {
    memset(&curr->image[y][x1],' ',n);
   #if WANT_ATTR
    memset(&curr->attr[y][x1],0,n);
   #endif
   #if WANT_CHARSET
    memset(&curr->font[y][x1],0,n);
   #endif
  }
}
#endif

/* delete screen: */
#if WANT_CLEAR_SCREEN
local void clear_screen (void) {
  out_capstring(CLcap);
  var uintC y = 0;
  while (y<rows) { cleared_linepart(y,0,cols); y++; }
}
#endif

/* delete part of a line: */
#if WANT_CLEAR_FROM_BOS || WANT_CLEAR_TO_EOS || WANT_CLEAR_LINE || WANT_CLEAR_FROM_BOL || WANT_CLEAR_TO_EOL
local void clear_linepart (int y, int x1, int x2) {
  var int n = x2-x1;
  if (n>0) {
    memset(&curr->image[y][x1],' ',n);
   #if WANT_ATTR
    memset(&curr->attr[y][x1],0,n);
   #endif
   #if WANT_CHARSET
    memset(&curr->font[y][x1],0,n);
   #endif
    if ((x2==cols) && CEcap) {
      gofromto(curr->y,curr->x,y,x1); curr->y = y; curr->x = x1;
      out_capstring(CEcap);
    } else {
      if ((x2==cols) && (y==rows-1) && AM)
        n--;
      if (n>0) {
       #if WANT_ATTR
        var uintB saved_attr = term_attr;
        change_attr(0);
       #endif
       #if WANT_CHARSET
        var uintB saved_charset = term_charset;
        change_charset(ASCII);
       #endif
       #if WANT_INSERT
        if (curr->insert)
          set_insert_mode(false);
          #endif
        gofromto(curr->y,curr->x,y,x1);
        {
          var uintC count;
          dotimespC(count,n, { out_char(' '); } );
        }
        curr->y = y; curr->x = x1+n;
       #if WANT_CHARSET
        change_charset(saved_charset);
       #endif
       #if WANT_ATTR
        change_attr(saved_attr);
       #endif
       #if WANT_INSERT
        if (curr->insert)
          set_insert_mode(true);
       #endif
      }
    }
  }
}
#endif

/* delete screen up to the Cursor (exclusive): */
#if WANT_CLEAR_FROM_BOS
local void clear_from_BOS (void) {
  var int y0 = curr->y;
  var int x0 = curr->x;
  var int y = 0;
  while (y<y0) { clear_linepart(y,0,cols); y++; }
  clear_linepart(y0,0,x0);
  gofromto(curr->y,curr->x,y0,x0); curr->y = y0; curr->x = x0;
}
#endif

/* delete screen starting at cursor (inclusive): */
#if WANT_CLEAR_TO_EOS
local void clear_to_EOS (void) {
  var int y0 = curr->y;
  var int x0 = curr->x;
  if (CDcap) {
    out_capstring(CDcap);
    cleared_linepart(y0,x0,cols);
    var int y = y0;
    while (++y < rows) { cleared_linepart(y,0,cols); }
  } else {
    clear_linepart(y0,x0,cols);
    var int y = y0;
    while (++y < rows) { clear_linepart(y,0,cols); }
  }
  gofromto(curr->y,curr->x,y0,x0); curr->y = y0; curr->x = x0;
}
#endif

/* delete cursor-line: */
#if WANT_CLEAR_LINE
local void clear_line (void) {
  var int y0 = curr->y;
  var int x0 = curr->x;
  clear_linepart(y0,0,cols);
  gofromto(curr->y,curr->x,y0,x0); curr->y = y0; curr->x = x0;
}
#endif

/* delete cursor-line up to cursor (exclusive): */
#if WANT_CLEAR_FROM_BOL
local void clear_from_BOL (void) {
  var int y0 = curr->y;
  var int x0 = curr->x;
  clear_linepart(y0,0,x0);
  gofromto(curr->y,curr->x,y0,x0); curr->y = y0; curr->x = x0;
}
#endif

/* delete cursor-line starting at cursor (inclusive): */
#if WANT_CLEAR_TO_EOL
local void clear_to_EOL (void) {
  var int y0 = curr->y;
  var int x0 = curr->x;
  clear_linepart(y0,x0,cols);
  gofromto(curr->y,curr->x,y0,x0); curr->y = y0; curr->x = x0;
}
#endif

/* Insertion-Operations: */

/* old content of line: */
#if WANT_INSERT_1CHAR || WANT_INSERT_CHAR || WANT_DELETE_CHAR
  local uintB* old_image_y;
  #if WANT_ATTR
  local uintB* old_attr_y;
  #endif
  #if WANT_CHARSET
  local uintB* old_font_y;
  #endif
local void save_line_old (int y) {
  if (cols > 0) {
    memcpy(&old_image_y[0],&curr->image[y][0],cols);
   #if WANT_ATTR
    memcpy(&old_attr_y[0],&curr->attr[y][0],cols);
   #endif
   #if WANT_CHARSET
    memcpy(&old_font_y[0],&curr->font[y][0],cols);
   #endif
  }
}
#endif

/* insert a character: */
#if WANT_INSERT_1CHAR
local void insert_1char (uintB c) {
  var int y = curr->y;
  var int x = curr->x;
  if (x==cols)
    x--; /* do not write beyond right border! */
  if (ICcap || IMcap) {
    curr->image[y][x] = c;
   #if WANT_ATTR
    curr->attr[y][x] = curr->curr_attr;
   #endif
   #if WANT_CHARSET
    curr->font[y][x] = curr->charsets[curr->curr_charset]; /* = term_charset */
   #endif
   #if WANT_INSERT
    if (!curr->insert)
   #endif
      set_insert_mode(true);
    out_capstring(ICcap); out_char(c);
   #if WANT_INSERT
    if (!curr->insert)
   #endif
      set_insert_mode(false);
    curr->x = x+1;
  } else {
    /* save old line-content: */
    save_line_old(y);
    /* build new line-content: */
    {
      var uintB* p1 = &curr->image[y][x];
      *p1++ = c;
      memcpy(p1,&old_image[x],cols-1-x);
    }
   #if WANT_ATTR
    {
      var uintB* p1 = &curr->attr[y][x];
      *p1++ = curr->curr_attr;
      memcpy(p1,&old_attr[x],cols-1-x);
    }
   #endif
   #if WANT_CHARSET
    {
      var uintB* p1 = &curr->font[y][x];
      *p1++ = term_charset; /* = curr->charsets[curr->curr_charset] */
      memcpy(p1,&old_font[x],cols-1-x);
    }
   #endif
    /* display line: */
    redisplay_line RLargs(old_image,old_attr,old_font,y,x,cols);
    x++;
    gofromto(last_y,last_x,y,x); curr->x = x;
  }
}
#endif

/* create room for n characters: */
#if WANT_INSERT_CHAR
local void insert_char (uintC n) {
  var int y = curr->y;
  var int x = curr->x;
  if (n > cols-x)
    n = cols-x;
  if (n==0)
    return;
  /* save old line-content: */
  save_line_old(y);
  /* build new line-content: */
  {
    var uintB* p1 = &curr->image[y][x];
    memset(p1,' ',n);
    memcpy(p1+n,&old_image[x],cols-x-n);
  }
 #if WANT_ATTR
  {
    var uintB* p1 = &curr->attr[y][x];
    memset(p1,0,n);
    memcpy(p1+n,&old_attr[x],cols-x-n);
  }
 #endif
 #if WANT_CHARSET
  {
    var uintB* p1 = &curr->font[y][x];
    memset(p1,0,n);
    memcpy(p1+n,&old_font[x],cols-x-n);
  }
 #endif
  if (CICcap && (n > 1)) {
   #if WANT_INSERT
    if (curr->insert)
      set_insert_mode(false);
   #endif
    out_cap1string(CICcap,n);
    {
      var uintC count;
      dotimespC(count,n, { out_char(' '); } );
    }
   #if WANT_INSERT
    if (curr->insert)
      set_insert_mode(true);
   #endif
    gofromto(y,x+n,y,x);
  } else if (ICcap || IMcap) {
   #if WANT_INSERT
    if (!curr->insert)
   #endif
      set_insert_mode(true);
    {
      var uintC count;
      dotimespC(count,n, { out_capstring(ICcap); out_char(' '); } );
    }
   #if WANT_INSERT
    if (!curr->insert)
   #endif
      set_insert_mode(false);
    gofromto(y,x+n,y,x);
  } else {
    redisplay_line RLargs(old_image,old_attr,old_font,y,x,cols);
    gofromto(last_y,last_x,y,x);
  }
}
#endif

/* insert lines: */
#if WANT_INSERT_LINE
local void insert_line (uintC n) {
  if (n > curr->bot - curr->y + 1)
    n = curr->bot - curr->y + 1;
  if (n==0)
    return;
  var int oldtop = curr->top;
  curr->top = curr->y;
  {
    var uintC count;
    dotimespC(count,n, { scroll_down(); } );
  }
  if (ALcap || CALcap) {
    gofromto(curr->y,curr->x,curr->y,0); /* to the beginning of the line */
    if ((CALcap && (n>1)) || !ALcap) {
      out_cap1string(CALcap,n);
    } else {
      var uintC count;
      dotimespC(count,n, { out_capstring(ALcap); } );
    }
    gofromto(curr->y,0,curr->y,curr->x);
  } else if (CScap && SRcap) {
    out_capstring(tgoto(CScap,curr->bot,curr->top));
    gofromto(-1,-1,curr->top,0);
    {
      var uintC count;
      dotimespC(count,n, { out_capstring(SRcap); } );
    }
    out_capstring(tgoto(CScap,curr->bot,oldtop));
    gofromto(-1,-1,curr->y,curr->x);
  } else {
    redisplay();
  }
  curr->top = oldtop;
}
#endif

/* Deletion-Operations: */

/* delete Characters: */
#if WANT_DELETE_CHAR
local void delete_char (uintC n) {
  var int y = curr->y;
  var int x = curr->x;
  if (n > cols-x)
    n = cols-x;
  if (n==0)
    return;
  /* save old line-content: */
  save_line_old(y);
  /* build new line-content: */
  {
    var uintB* p1 = &curr->image[y][x];
    memcpy(p1,&old_image[x],cols-x-n);
    memset(p1+cols-x-n,' ',n);
  }
 #if WANT_ATTR
  {
    var uintB* p1 = &curr->attr[y][x];
    memcpy(p1,&old_attr[x],cols-x-n);
    memset(p1+cols-x-n,0,n);
  }
 #endif
 #if WANT_CHARSET
  {
    var uintB* p1 = &curr->font[y][x];
    memcpy(p1,&old_font[x],cols-x-n);
    memset(p1+cols-x-n,0,n);
  }
 #endif
  if (CDCcap && ((n>1) || !DCcap)) {
    out_cap1string(CDCcap,n);
  } else if (DCcap) {
    var uintC count;
    dotimespC(count,n, { out_capstring(DCcap); } );
  } else {
    redisplay_line RLargs(old_image,old_attr,old_font,y,x,cols);
    gofromto(last_y,last_x,y,x);
  }
}

#endif

/* delete lines: */
#if WANT_DELETE_LINE
local void delete_line (uintC n) {
  if (n > curr->bot - curr->y + 1)
    n = curr->bot - curr->y + 1;
  if (n==0)
    return;
  var int oldtop = curr->top;
  curr->top = curr->y;
  {
    var uintC count;
    dotimespC(count,n, { scroll_up(); } );
  }
  if (DLcap || CDLcap) {
    gofromto(curr->y,curr->x,curr->y,0); /* to the beginning of the line */
    if ((CDLcap && (n>1)) || !DLcap) {
      out_cap1string(CDLcap,n);
    } else {
      var uintC count;
      dotimespC(count,n, { out_capstring(DLcap); } );
    }
    gofromto(curr->y,0,curr->y,curr->x);
  } else if (CScap) {
    out_capstring(tgoto(CScap,curr->bot,curr->top));
    gofromto(-1,-1,curr->bot,0);
    {
      var uintC count;
      dotimespC(count,n, { out_capstring(SFcap); } );
    }
    out_capstring(tgoto(CScap,curr->bot,oldtop));
    gofromto(-1,-1,curr->y,curr->x);
  } else {
    redisplay();
  }
  curr->top = oldtop;
}
#endif

/* write a character: */
#if WANT_OUTPUT_1CHAR
local void output_1char (uintB c) {
 #if WANT_INSERT
  if (curr->insert) {
    insert_1char(c);
    return;
  }
 #endif
  var int y = curr->y;
  var int x = curr->x;
  if (x==cols)
    x--; /* do not write beyond right border! */
  curr->image[y][x] = c;
 #if WANT_ATTR
  curr->attr[y][x] = curr->curr_attr;
 #endif
 #if WANT_CHARSET
  curr->font[y][x] = curr->charsets[curr->curr_charset]; /* = term_charset */
 #endif
  x++;
  if (!(AM && (x==cols) && (curr->y==curr->bot))) /* poss. spare right lower corner */
    out_char(c); /* write character */
  curr->x = x; /* Cursor is advanced by one */
  if (x==cols) /* except it was already located rightmost */
    gofromto(-1,-1,curr->y,curr->x);
}
#endif

#if WANT_SAVE

/* stored Cursor-Position: */
local void save_cursor (void) {
  curr->saved_x = curr->x;
  curr->saved_y = curr->y;
 #if WANT_ATTR
  curr->saved_curr_attr = curr->curr_attr;
 #endif
 #if WANT_CHARSET
  curr->saved_curr_charset = curr->curr_charset;
  {
    var uintC i = 0;
    while (i<charset_count)
      { curr->saved_charsets[i] = curr->charsets[i]; i++; }
  }
 #endif
  curr->saved = true;
}
local void restore_cursor (void) {
  if (curr->saved) {
    gofromto(curr->y,curr->x,curr->saved_y,curr->saved_x);
    curr->y = curr->saved_y; curr->x = curr->saved_x;
   #if WANT_ATTR
    curr->curr_attr = curr->saved_curr_attr;
    change_attr(curr->curr_attr);
   #endif
   #if WANT_CHARSET
    curr->curr_charset = curr->saved_curr_charset;
    {
      var uintC i = 0;
      while (i<charset_count)
        { curr->charsets[i] = curr->saved_charsets[i]; i++; }
    }
    change_charset(curr->charsets[curr->curr_charset]);
   #endif
  }
}

#endif

/* Initializes the Terminal.
 Returns NULL if OK, else returns an error-string. */
local bool term_initialized = false;
local const char * init_term (void) {
  var char tbuf[4096]; /* internal Buffer for the Termcap-Routines */
  if (term_initialized)
    return NULL; /* already initialized -> OK */
  /* query Terminal-Type: */
  begin_system_call();
  {
    var const char* s = getenv("TERM");
    if (s==NULL) {
      end_system_call();
      return GETTEXT("environment has no TERM variable");
    }
    if (!(tgetent(tbuf,s)==1)) {
      end_system_call();
      pushSTACK(asciz_to_string(s,O(misc_encoding)));
      return GETTEXT("terminal type ~S unknown to termcap");
    }
  }
  {
    var int i = tgetnum("co");
    cols = (i>0 ? i : 80);
  }
  {
    var int i = tgetnum("li");
    rows = (i>0 ? i : 24);
  }
  if (tgetflag("hc")) {
    end_system_call();
    return GETTEXT("insufficient terminal: hardcopy terminal");
  }
  if (tgetflag("os")) {
    end_system_call();
    return GETTEXT("insufficient terminal: overstrikes, cannot clear output");
  }
  if (tgetflag("ns")) {
    end_system_call();
    return GETTEXT("insufficient terminal: cannot scroll");
  }
  if (!(CLcap = tgetstr("cl",&tp))) {
    /* Could use CLcap = "\n\n\n\n"; as Default ('weird HPs') */
    end_system_call();
    return GETTEXT("insufficient terminal: cannot clear screen");
  }
  if (!(CMcap = tgetstr("cm",&tp))) {
    end_system_call();
    return GETTEXT("insufficient terminal: cannot position cursor randomly");
  }
  /* initialize Capabilities: */
  AM = tgetflag("am"); if (tgetflag("LP")) AM = false;
  TIcap = tgetstr("ti",&tp);
  TEcap = tgetstr("te",&tp);
  /* BLcap = tgetstr("bl",&tp); if (!BLcap) BLcap = "\007";
   VBcap = tgetstr("vb",&tp); */
  BCcap = tgetstr("bc",&tp); if (!BCcap) BCcap = (tgetflag("bs") ? "\b" : tgetstr("le",&tp));
  CRcap = tgetstr("cr",&tp); if (!CRcap) CRcap = "\r";
  NLcap = tgetstr("nl",&tp); if (!NLcap) NLcap = "\n";
  DOcap = tgetstr("do",&tp); if (!DOcap) DOcap = NLcap;
  UPcap = tgetstr("up",&tp);
  NDcap = tgetstr("nd",&tp);
  IScap = tgetstr("is",&tp);
 #if WANT_ATTR
  if ((tgetnum("sg") > 0) || (tgetnum("ug") > 0)) {
    /* switching to Standout-Mode or switching to
     Underline-Mode yields blankspace -> unusable! */
    SOcap = NULL; SEcap = NULL; UScap = NULL; UEcap = NULL;
    MBcap = NULL; MDcap = NULL; MHcap = NULL; MRcap = NULL; MEcap = NULL;
  } else {
    SOcap = tgetstr("so",&tp);
    SEcap = tgetstr("se",&tp);
    UScap = tgetstr("us",&tp);
    UEcap = tgetstr("ue",&tp);
    if (!UScap && !UEcap) { /* no Underline? */
      UScap = SOcap; UEcap = SEcap; /* use Standout as replacement */
    }
    MBcap = tgetstr("mb",&tp);
    MDcap = tgetstr("md",&tp);
    MHcap = tgetstr("mh",&tp);
    MRcap = tgetstr("mr",&tp);
    MEcap = tgetstr("me",&tp);
    /* Does ME also reverse the effect of SO and/or US?  This is not
     clearly specified by the termcap manual.
     Anyway, we should at least look whether ME/SE/UE are equal: */
    if (UEcap && SEcap && asciz_equal(UEcap,SEcap)) UEcap = NULL;
    if (UEcap && MEcap && asciz_equal(UEcap,MEcap)) UEcap = NULL;
    if (SEcap && MEcap && asciz_equal(SEcap,MEcap)) SEcap = NULL;
    /* tgetstr("uc",&tp) returns an underline-character. Then execute
     backspace() and out_capstring(UCcap) at a time in redisplay_help()
     and output_1char() after out_char().
     For which Terminals is this worthwhile?? */
  }
 #endif
 #if WANT_CHARSET
  ISO2022 = tgetflag("G0");
 #endif
  CScap = tgetstr("cs",&tp);
 #if WANT_DELETE_LINE
  SFcap = tgetstr("sf",&tp); if (!SFcap) SFcap = NLcap;
 #endif
 #if WANT_CURSOR_REVLINEFEED || WANT_INSERT_LINE
  SRcap = tgetstr("sr",&tp);
 #endif
 #if WANT_CLEAR_FROM_BOS || WANT_CLEAR_TO_EOS || WANT_CLEAR_LINE || WANT_CLEAR_FROM_BOL || WANT_CLEAR_TO_EOL
  CEcap = tgetstr("ce",&tp);
 #endif
 #if WANT_CLEAR_TO_EOS
  CDcap = tgetstr("cd",&tp);
 #endif
 #if WANT_CURSOR_REVLINEFEED || WANT_INSERT_LINE
  ALcap = tgetstr("al",&tp);
 #endif
 #if WANT_DELETE_LINE
  DLcap = tgetstr("dl",&tp);
 #endif
 #if WANT_DELETE_CHAR
  DCcap = tgetstr("dc",&tp);
 #endif
 #if WANT_INSERT_1CHAR || WANT_INSERT_CHAR
  ICcap = tgetstr("ic",&tp);
 #endif
 #if WANT_INSERT_CHAR
  CICcap = tgetstr("IC",&tp);
 #endif
 #if WANT_INSERT_LINE
  CALcap = tgetstr("AL",&tp);
 #endif
 #if WANT_DELETE_CHAR
  CDCcap = tgetstr("DC",&tp);
 #endif
 #if WANT_DELETE_LINE
  CDLcap = tgetstr("DL",&tp);
 #endif
  IMcap = tgetstr("im",&tp);
  EIcap = tgetstr("ei",&tp);
  if (tgetflag ("in")) { /* Insert-Mode unusable? */
    IMcap = NULL; EIcap = NULL;
   #if WANT_INSERT_1CHAR || WANT_INSERT_CHAR
    ICcap = NULL;
   #endif
   #if WANT_INSERT_CHAR
    CICcap = NULL;
   #endif
  }
  if (IMcap && (IMcap[0]==0)) IMcap = NULL; /* IMcap empty? */
  if (EIcap && (EIcap[0]==0)) EIcap = NULL; /* EIcap empty? */
 #if WANT_INSERT_1CHAR || WANT_INSERT_CHAR
  if (ICcap && (ICcap[0]==0)) ICcap = NULL; /* ICcap empty? */
 #endif
  /* calculate the costs of the Capabilities: */
  IMcost = cap_cost(IMcap);
  EIcost = cap_cost(EIcap);
  BCcost = cap_cost(BCcap);
  NDcost = cap_cost(NDcap);
  DOcost = cap_cost(DOcap);
 #ifndef NL_HACK
  /* If DOcap writes a LF, it is not sure, if this arrives
   at the Terminal as such (and not as CR/LF). In this case we
   declare DOcap as unusable. This spares us the NL_HACK. */
  if (DOcap[0]=='\n')
    DOcost = EXPENSIVE;
 #endif
  UPcost = cap_cost(UPcap);
  CRcost = cap_cost(CRcap);
  /* provide Auxiliary-Data-Structures: */
  blank = (uintB*) malloc(cols*sizeof(uintB));
   memset(blank,' ',cols);
#if WANT_ATTR || WANT_CHARSET
  {
    var uintB* ptr = (uintB*) malloc(cols*sizeof(uintB));
    null = ptr;
    memset(ptr,0,cols);
  }
 #endif
 #if WANT_INSERT_1CHAR || WANT_INSERT_CHAR || WANT_DELETE_CHAR
  old_image_y = (uintB*) malloc(cols*sizeof(uintB));
 #if WANT_ATTR
  old_attr_y = (uintB*) malloc(cols*sizeof(uintB));
 #endif
 #if WANT_CHARSET
  old_font_y = (uintB*) malloc(cols*sizeof(uintB));
 #endif
 #endif
  end_system_call();
  term_initialized = true;
  return NULL;
}


#ifdef NL_HACK

/* If NLcap = "\n" , we must execute an "stty -onlcr", because otherwise
 the NL is converted to CR by the Terminal-Driver, before it
 arrives at the Terminal. */
  local void term_nlraw (void);
  local void term_nlunraw (uintB abort);
#ifdef UNIX_TERM_TERMIOS
  static unsigned long old_c_oflag = 0;
local void term_nlraw() {
  var struct termios oldtermio;
  if (!( tcgetattr(stdout_handle,&oldtermio) ==0)) {
    if (!(errno==ENOTTY)) { OS_error(); }
  }
  old_c_oflag = oldtermio.c_oflag;
  oldtermio.c_oflag &= ~ONLCR;
  if (!( TCSETATTR(stdout_handle,TCSAFLUSH,&oldtermio) ==0)) {
    if (!(errno==ENOTTY)) { OS_error(); }
  }
}
local void term_nlunraw (uintB abort) {
  if (old_c_oflag & ONLCR) {
    var struct termios oldtermio;
    if (!( tcgetattr(stdout_handle,&oldtermio) ==0)) {
      if (!abort && errno!=ENOTTY) { OS_error(); }
    }
    oldtermio.c_oflag |= ONLCR;
    if (!( TCSETATTR(stdout_handle,TCSAFLUSH,&oldtermio) ==0)) {
      if (!abort && errno!=ENOTTY) { OS_error(); }
    }
  }
}
#endif

#endif /* NL_HACK */

/* Begin of Processing this Packet: */
local void start_term (void) {
 #ifdef NL_HACK
  if (NLcap[0] == '\n')
    term_nlraw();
 #endif
  out_capstring (IScap);
  out_capstring (TIcap);
}

/* End of Processing this Packet: */
local void end_term (uintB abort) {
  out_capstring (TEcap);
  out_capstring (IScap);
 #if 0
  /* On ANSI-Terminals with several colors: TEcap resets the colors. */
  out_capstring(CLcap); /* delete screen, this time with the normal color */
 #endif
 #ifdef NL_HACK
  if (NLcap[0] == '\n')
    term_nlunraw(abort);
 #else
  unused(abort);
 #endif
}

/* Initializes the Window curr. */
local void init_curr (void) {
  {
    var uintB** ptr = (uintB**) malloc(rows*sizeof(uintB*));
    var uintC count;
    curr->image = ptr;
    dotimespC(count,rows, { *ptr++ = (uintB*) malloc(cols*sizeof(uintB)); } );
  }
 #if WANT_ATTR
  {
    var uintB** ptr = (uintB**) malloc(rows*sizeof(uintB*));
    var uintC count;
    curr->attr = ptr;
    dotimespC(count,rows, { *ptr++ = (uintB*) malloc(cols*sizeof(uintB)); } );
  }
  /* deactivate Attribute: */
  out_capstring(UEcap); /* all deactivated */
  out_capstring(SEcap);
  out_capstring(MEcap);
  term_attr = curr->curr_attr = 0;
 #endif
 #if WANT_CHARSET
  {
    var uintB** ptr = (uintB**) malloc(rows*sizeof(uintB*));
    var uintC count;
    curr->font = ptr;
    dotimespC(count,rows, { *ptr++ = (uintB*) malloc(cols*sizeof(uintB)); } );
  }
  {
    var uintC i = 0;
    while (i<charset_count) { curr->charsets[i] = ASCII; i++; }
  }
  curr->curr_charset = 0;
  if (ISO2022) {
    out_char(ESC); out_char('('); out_char('B'); /*)*/
  }
  term_charset = ASCII;
 #endif
  curr->x = 0; curr->y = 0;
  curr->top = 0; curr->bot = rows-1;
 #if WANT_INSERT
  curr->insert = false;
 #endif
 #if WANT_SAVE
  curr->saved = false;
 #endif
  if (CScap)
    out_capstring(tgoto(CScap,curr->bot,curr->top));
  clear_screen();
}

/* ------------------------------------------------------------------------

 UP: Write character to a Window-Stream.
 wr_ch_window(&stream,ch);
 > stream: Window-Stream
 > ch: character to be written */
local maygc void wr_ch_window (const gcv_object_t* stream_, object ch) {
  check_wr_char(*stream_,ch);
  var uintB c = as_cint(char_code(ch)); /* FIXME: This should take into account the encoding. */
  begin_system_call();
  if (graphic_char_p(as_chart(c))) {
    if (curr->x == cols) {
      cursor_return(); cursor_linefeed(); /* Wrap! */
    }
    output_1char(c);
  } else if (c == NL) {
    cursor_return(); cursor_linefeed();
  } else if (c == BS) {
    var int x0 = curr->x;
    if (x0>0) {
      var int y0 = curr->y;
      clear_linepart(y0,x0-1,x0);
      gofromto(curr->y,curr->x,y0,x0-1); curr->y = y0; curr->x = x0-1;
    }
  }
  end_system_call();
}

LISPFUNN(make_window,0) {
  var object stream = /* Flags: only WRITE-CHAR allowed */
    allocate_stream(strmflags_wr_ch_B,strmtype_window,strm_len+1,0);
  /* and fill: */
  stream_dummy_fill(stream);
  var Stream s = TheStream(stream);
  s->strm_wr_ch = s->strm_wr_ch_npnl = P(wr_ch_window); /* WRITE-CHAR-Pseudofunction */
  s->strm_wr_ch_array = s->strm_wr_ch_array_npnl = P(wr_ch_array_dummy); /* WRITE-CHAR-SEQUENCE-Pseudofunction */
  /* Initialize: */
  begin_system_call();
  {
    var const char * result = init_term();
    if (!(result==NULL))
      error(error_condition,result);
  }
  start_term();
  init_curr();
  end_system_call();
  VALUES1(stream);
}

/* Closes a Window-Stream. */
local void close_window (object stream, uintB abort) {
  unused(stream);
  begin_system_call();
  end_term(abort);
  end_system_call();
}

LISPFUNN(window_size,1) {
  check_window_stream(popSTACK());
  VALUES2(fixnum(rows), /* query Variables rows,cols */
          fixnum(cols));
}

LISPFUNN(window_cursor_position,1) {
  check_window_stream(popSTACK());
  VALUES2(fixnum(curr->y),
          fixnum(curr->x));
}

LISPFUNN(set_window_cursor_position,3) {
  check_window_stream(STACK_2);
  var uintV line = posfixnum_to_V(STACK_1);
  var uintV column = posfixnum_to_V(STACK_0);
  if ((line < rows) && (column < cols)) {
    begin_system_call();
    gofromto(curr->y,curr->x,line,column); /* position Cursor */
    curr->y = line; curr->x = column;
    end_system_call();
  }
  VALUES2(STACK_1, STACK_0); skipSTACK(3);
}

LISPFUNN(clear_window,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  clear_screen();
  end_system_call();
  VALUES0;
}

LISPFUNN(clear_window_to_eot,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  clear_to_EOS();
  end_system_call();
  VALUES0;
}

LISPFUNN(clear_window_to_eol,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  clear_to_EOL();
  end_system_call();
  VALUES0;
}

LISPFUNN(delete_window_line,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  delete_line(1);
  end_system_call();
  VALUES0;
}

LISPFUNN(insert_window_line,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  insert_line(1);
  end_system_call();
  VALUES0;
}

LISPFUNN(highlight_on,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  change_attr(curr->curr_attr |= A_US);
  end_system_call();
  VALUES0;
}

LISPFUNN(highlight_off,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  change_attr(curr->curr_attr &= ~A_US);
  end_system_call();
  VALUES0;
}

LISPFUNN(window_cursor_on,1) {
  check_window_stream(popSTACK());
  /* Cursor is permanently activated! */
  VALUES0;
}

LISPFUNN(window_cursor_off,1) {
  check_window_stream(popSTACK());
  /* not possible, because Cursor is activated permanently! */
  VALUES0;
}

#endif  /* UNIX */

#if defined(UNIX) && 0

/* Normal CURSES-Package, we use only stdscr. */

#undef BS
#undef CR
#undef NL
#include <curses.h>
#undef OK
#define CR  13
#define NL  10

/* UP: Write character to Window-Stream.
 wr_ch_window(&stream,ch);
 > stream: Window-Stream
 > ch: character to be written */
local maygc void wr_ch_window (const gcv_object_t* stream_, object ch) {
  check_wr_char(*stream_,ch);
  var uintB c = as_cint(char_code(ch)); /* FIXME: This should take into account the encoding. */
  begin_system_call();
  if (graphic_char_p(as_chart(c))) { /* let only printable characters pass to the screen */
    addch(c);
  } else if (c == NL) { /* convert NL to CR/LF */
    addch(CR); addch(LF);
  } else { /* write something, for the Cursor-Position to be correct */
    addch('?');
  }
  end_system_call();
}

LISPFUNN(make_window,0) {
  var object stream = /* Flags: only WRITE-CHAR allowed */
    allocate_stream(strmflags_wr_ch_B,strmtype_window,strm_len+1,0);
  /* and fill: */
  stream_dummy_fill(stream);
  var Stream s = TheStream(stream);
  s->strm_wr_ch = s->strm_wr_ch_npnl = P(wr_ch_window); /* WRITE-CHAR-Pseudofunction */
  s->strm_wr_ch_array = s->strm_wr_ch_array_npnl = P(wr_ch_array_dummy); /* WRITE-CHAR-SEQUENCE-Pseudofunction */
  begin_system_call();
  initscr(); /* initialize Curses - What, if this crashes?? use newterm()?? */
  cbreak(); noecho(); /* Input not line-buffered, without Echo */
 #ifdef SUN4
  keypad(stdscr,true); /* activate Function-Key-Detection */
 #endif
  end_system_call();
  VALUES1(stream);
}

/* Closes a Window-Stream. */
local void close_window (object stream, uintB abort) {
  begin_system_call();
  nocbreak(); echo(); /* Input is line-buffered again, with Echo */
 #ifdef SUN4
  keypad(stdscr,false); /* deactivate Function-Key-Detection again */
 #endif
  endwin(); /* deactivate Curses */
  end_system_call();
}

LISPFUNN(window_size,1) {
  check_window_stream(popSTACK());
  VALUES2(fixnum(LINES), /* query Curses-Variables LINES, COLS */
          fixnum(COLS));
}

LISPFUNN(window_cursor_position,1) {
  check_window_stream(popSTACK());
  var int y;
  var int x;
  begin_system_call();
  getyx(stdscr,y,x); /* (y,x) := cursor position */
  end_system_call();
  VALUES2(fixnum(y),
          fixnum(x));
}

LISPFUNN(set_window_cursor_position,3) {
  check_window_stream(STACK_2);
  var uintV line = posfixnum_to_V(STACK_1);
  var uintV column = posfixnum_to_V(STACK_0);
  if ((line < LINES) && (column < COLS)) {
    begin_system_call();
    move(line,column); refresh(); /* position Cursor */
    end_system_call();
  }
  VALUES2(STACK_1, STACK_0); skipSTACK(3);
}

LISPFUNN(clear_window,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  clear(); refresh();
  end_system_call();
  VALUES0;
}

LISPFUNN(clear_window_to_eot,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  clrtobot(); refresh();
  end_system_call();
  VALUES0;
}

LISPFUNN(clear_window_to_eol,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  clrtoeol(); refresh();
  end_system_call();
  VALUES0;
}

LISPFUNN(delete_window_line,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  deleteln(); refresh();
  end_system_call();
  VALUES0;
}

LISPFUNN(insert_window_line,1) {
  check_window_stream(popSTACK());
  begin_system_call();
  insertln(); refresh();
  end_system_call();
  VALUES0;
}

LISPFUNN(highlight_on,1) {
  check_window_stream(popSTACK());
#ifdef A_STANDOUT /* only works, if Curses manages the Attributes */
  begin_system_call();
  attron(A_STANDOUT); /* add Attribut A_STANDOUT with OR at addch() */
  end_system_call();
#endif
  VALUES0;
}

LISPFUNN(highlight_off,1) {
  check_window_stream(popSTACK());
 #ifdef A_STANDOUT /* only works, if Curses manages the Attributes */
  begin_system_call();
  attroff(A_STANDOUT); /* don't add Attribute with OR at addch() */
  end_system_call();
 #endif
  VALUES0;
}

LISPFUNN(window_cursor_on,1) {
  check_window_stream(popSTACK());
  /* Cursor is permanently activated! */
  VALUES0;
}

LISPFUNN(window_cursor_off,1) {
  check_window_stream(popSTACK());
  /* not possible, because Cursor is activated permanently! */
  VALUES0;
}

#endif /* UNIX */

#endif /* SCREEN */


#ifdef PIPES

/* Pipe-Input-Stream, Pipe-Output-Stream
   =====================================

 Additional Components:
 define strm_pipe_pid  strm_field1   - Process-Id, a Fixnum >=0 */

#if defined(UNIX) || defined(WIN32_NATIVE)
  #define low_close_pipe  low_close_handle
#endif

#if defined(HAVE_SIGNALS) && defined(SIGPIPE)

/* Be careful to disable SIGPIPE during write() to a subprocess. */

local maygc void low_flush_buffered_pipe (object stream, uintL bufflen) {
  begin_system_call();
  var Handle fd = TheHandle(BufferedStream_channel(stream));
  var uintB* buff = BufferedStream_buffer_address(stream,0);
  pin_unprotect_varobject(BufferedStream_buffer(stream),PROT_READ);
  pushSTACK(stream);
  START_WRITING_TO_SUBPROCESS;
  var ssize_t result;
  GC_SAFE_CALL(result = full_write(fd,buff,bufflen));
  STOP_WRITING_TO_SUBPROCESS;
  stream = popSTACK();
  unpin_varobject(BufferedStream_buffer(stream));
  if (result == bufflen) { /* everything was written correctly */
    end_system_call(); BufferedStream_modified(stream) = false;
  } else { /* not everything was written */
    if (result<0) { /* Error? */
      end_system_call(); OS_filestream_error(stream);
    }
    end_system_call();
    error_unwritable(TheSubr(subr_self)->name,stream);
  }
}

#else

  #define low_flush_buffered_pipe  low_flush_buffered_handle

#endif

#define BufferedPipeStream_init(stream)  \
  { BufferedStreamLow_fill(stream) = &low_fill_buffered_handle; \
    BufferedStreamLow_flush(stream) = &low_flush_buffered_pipe; \
  }

/* Pipe-Input-Stream
   =================

 Low-level. */

  #define UnbufferedPipeStream_input_init(stream)  UnbufferedHandleStream_input_init(stream)

local inline void create_input_pipe (const char* command) {
  var int child;
 #ifdef UNIX
  var int handles[2]; /* two Handles for the pipe */
  {
    /* As shell we always use the Command-Shell.
     copy command to Stack: */
    var uintL command_length = asciz_length(command)+1;
    var DYNAMIC_ARRAY(command_data,char,command_length);
    begin_system_call();
    memcpy(command_data,command,command_length);
    begin_want_sigcld();
    /* build pipe: */
    if (!( pipe(handles) ==0)) {
      FREE_DYNAMIC_ARRAY(command_data);
      end_want_sigcld(); OS_error();
    }
    /* Everything, that is stuffed in handles[1], resurfaces at handles[0]
     again. We will utilize this as follows:
           write            system            read
     child  ->   handles[1]   ->   handles[0]  ->  parent
     start a new process: */
    if ((child = vfork()) ==0) {
      /* this piece of code is executed by the child-process: */
      if ( dup2(handles[1],stdout_handle) >=0) /* redirect standard-output */
        if ( CLOSE(handles[1]) ==0) /* we want to write only via stdout_handle */
          if ( CLOSE(handles[0]) ==0) { /* we do not want to read from the pipe */
            /* (I have to tell this the operating system. Then - if the Child
             has filled the pipe - the parent-process is called
             in order to empty the pipe (and not the child-process).)
             turn child-process into a background process: */
            SETSID(); /* it receives its own process group */
            close_all_fd();
            execl(SHELL,            /* call shell */
                  SHELL,            /* =: argv[0] */
                  "-c",             /* =: argv[1] */
                  &command_data[0], /* =: argv[2] */
                  NULL);
          }
      _exit(-1); /* if this fails, finish child-process */
    }
    /* This piece of code is again executed by the caller: */
    end_want_sigcld();
    if (child==-1)
      /* Something failed, either on vfork or on execl.
       In both cases errno was set. */
      OS_error_saving_errno({
        CLOSE(handles[1]); CLOSE(handles[0]);
        FREE_DYNAMIC_ARRAY(command_data);
      });
    /* We only want to read from the pipe, not write: */
    if (!( CLOSE(handles[1]) ==0))
      OS_error_saving_errno({
        CLOSE(handles[0]);
        FREE_DYNAMIC_ARRAY(command_data);
      });
    /* (I have to tell this the operating system. Then - if the parent-process
     has emptied the pipe - the child-process is called in order to fill the
     pipe again (and not the parent-process).) */
    end_system_call();
    FREE_DYNAMIC_ARRAY(command_data);
  }
 #endif
 #ifdef WIN32_NATIVE
  var Handle handles[2]; /* two Handles for the pipe */
  {
    begin_system_call();
    var Handle child_write_handle;
    /* Create a pipe and make one of the two handles inheritable. */
    if (!CreatePipe(&handles[0],&handles[1],NULL,0)) { OS_error(); }
    if (!DuplicateHandle(GetCurrentProcess(),handles[1],
                         GetCurrentProcess(),&child_write_handle,
                         0, true, DUPLICATE_SAME_ACCESS)) {
      OS_error();
    }
    if (!CloseHandle(handles[1])) { OS_error(); }
    var HANDLE stdinput,stderror;
    var PROCESS_INFORMATION pinfo;
    stdinput = GetStdHandle(STD_INPUT_HANDLE);
    if (stdinput == INVALID_HANDLE_VALUE) { OS_error(); }
    stderror = GetStdHandle(STD_ERROR_HANDLE);
    if (stderror == INVALID_HANDLE_VALUE) { OS_error(); }
    if (!MyCreateProcess((TCHAR*)command,stdinput,child_write_handle,
                         stderror,&pinfo))
      { OS_error(); }
    /* Close our copy of the child's handle, so that the OS knows
     that we won't write on it. */
    if (!CloseHandle(child_write_handle)) { OS_error(); }
    if (!CloseHandle(pinfo.hThread)) { OS_error(); }
    if (!CloseHandle(pinfo.hProcess)) { OS_error(); }
    child = pinfo.dwProcessId;
    end_system_call();
  }
 #endif
  pushSTACK(UL_to_I(child));
  pushSTACK(STACK_(1+1));
  pushSTACK(STACK_(2+2));
  pushSTACK(allocate_handle(handles[0]));
}

/* forward declaration */
local maygc object make_pipe (buffered_t, direction_t, decoded_el_t*);

/* UP: The common part of MAKE-PIPE-INPUT-STREAM & MAKE-PIPE-OUTPUT-STREAM
 > STACK_0: :buffered
 > STACK_1: :external-format
 > STACK_2: :element-type
 > STACK_3: command line
 < value1: pipe stream
 cleans up the STACK
 can trigger GC */
local maygc Values make_pipe_stream (direction_t direction,
                                     void create_pipe (const char*)) {
  var decoded_el_t eltype;
  var buffered_t buffered;
  STACK_3 = check_string(STACK_3); /* check command */
  /* Check and canonicalize the :BUFFERED argument: */
  buffered = test_buffered_arg(STACK_0);
  /* Check and canonicalize the :ELEMENT-TYPE argument: */
  test_eltype_arg(&STACK_2,&eltype);
  STACK_2 = canon_eltype(&eltype);
  CHECK_UNBUFFERED_ELTYPE(buffered,direction,eltype);
  /* Check and canonicalize the :EXTERNAL-FORMAT argument: */
  STACK_1 = test_external_format_arg(STACK_1);
  /* Now create the pipe. */
  with_string_0(STACK_3,O(misc_encoding),command_asciz,
                { create_pipe(command_asciz); });
  /* allocate Stream: */
  var object stream = make_pipe(buffered,direction,&eltype);
  TheStream(stream)->strm_pipe_pid = popSTACK(); /* Child-Pid */
  skipSTACK(4);
  VALUES1(stream); /* return stream */
}

/* (MAKE-PIPE-INPUT-STREAM command [:element-type] [:external-format] [:buffered])
 calls a shell, that executes command, whereby its Standard-Output
 is directed into our pipe. */
LISPFUN(make_pipe_input_stream,seclass_default,1,0,norest,key,3,
        (kw(element_type),kw(external_format),kw(buffered)) )
{ make_pipe_stream(DIRECTION_INPUT,create_input_pipe); }

/* Pipe-Output-Stream
 ================== */

/* Low-level. */

#if defined(HAVE_SIGNALS) && defined(SIGPIPE)

  /* Be careful to disable SIGPIPE during write() to a subprocess. */

local maygc void low_write_unbuffered_pipe (object stream, uintB b) {
  var Handle handle = TheHandle(TheStream(stream)->strm_ochannel);
 restart_it:
  begin_system_call();
  /* Try to output the byte. */
  pushSTACK(stream);
  START_WRITING_TO_SUBPROCESS;
  var int result;
  GC_SAFE_CALL(result = write(handle,&b,1));
  STOP_WRITING_TO_SUBPROCESS;
  stream = popSTACK();
  if (result<0) {
    if (errno==EINTR) { /* Break (poss. by Ctrl-C) ? */
      end_system_call();
      interruptp({ error_interrupt(); });
      goto restart_it;
    }
    OS_error();
  }
  end_system_call();
  if (result==0) /* not successful? */
    error_unwritable(TheSubr(subr_self)->name,stream);
}

local maygc const uintB* low_write_array_unbuffered_pipe
(object stream, const uintB* byteptr, uintL len, perseverance_t persev) {
  var Handle handle = TheHandle(TheStream(stream)->strm_ochannel);
  begin_system_call();
  pushSTACK(stream);
  START_WRITING_TO_SUBPROCESS;
  var ssize_t result;
  GC_SAFE_CALL(result = fd_write(handle,byteptr,len,persev));
  STOP_WRITING_TO_SUBPROCESS;
  stream = popSTACK();
  if (result<0) { OS_error(); }
  end_system_call();
  /* Safety check whether persev argument was respected or EOWF was reached: */
  if ((persev == persev_full && !(result==(sintL)len))
      || (persev == persev_partial && !(result>0)))
    error_unwritable(TheSubr(subr_self)->name,stream);
  return byteptr+result;
}

#else

  #define low_write_unbuffered_pipe  low_write_unbuffered_handle
  #define low_write_array_unbuffered_pipe  low_write_array_unbuffered_handle

#endif

local void low_finish_output_unbuffered_pipe (object stream) /* do nothing */
{ unused(stream); }
local void low_force_output_unbuffered_pipe (object stream) /* do nothing */
{ unused(stream); }
local void low_clear_output_unbuffered_pipe (object stream) /* do nothing */
{ unused(stream); }

/* make, init, and register pipe stream object
 > buffered
 > direction
 > eltype
 < stream object
 can trigger GC */
local maygc object make_pipe (buffered_t buffered, direction_t direction,
                              decoded_el_t *eltype) {
  var object stream;
  var uintB type = (direction == DIRECTION_INPUT
                    ? strmtype_pipe_in : strmtype_pipe_out);
  if (buffered == BUFFERED_NIL) {
    stream = make_unbuffered_stream(type,direction,eltype,false,false);
    if (READ_P(direction)) UnbufferedPipeStream_input_init(stream);
    if (WRITE_P(direction)) { /*UnbufferedPipeStream_output_init(stream);*/
      UnbufferedStreamLow_write(stream) = &low_write_unbuffered_pipe;
      UnbufferedStreamLow_write_array(stream) =
        &low_write_array_unbuffered_pipe;
      UnbufferedStreamLow_finish_output(stream) =
        &low_finish_output_unbuffered_pipe;
      UnbufferedStreamLow_force_output(stream) =
        &low_force_output_unbuffered_pipe;
      UnbufferedStreamLow_clear_output(stream) =
        &low_clear_output_unbuffered_pipe;
    }
  } else {
    stream = make_buffered_stream(type,direction,eltype,false,false);
    BufferedPipeStream_init(stream);
  }
  ChannelStreamLow_close(stream) = &low_close_pipe;
  return add_to_open_streams(stream);
}

local inline void create_output_pipe (const char* command) {
  var int child;
 #ifdef UNIX
  var int handles[2]; /* two Handles for the pipe */
  {
    /* As shell we always use the Command-Shell.
     copy command to Stack: */
    var uintL command_length = asciz_length(command)+1;
    var DYNAMIC_ARRAY(command_data,char,command_length);
    begin_system_call();
    memcpy(command_data,command,command_length);
    begin_want_sigcld();
    if (!( pipe(handles) ==0)) {
      FREE_DYNAMIC_ARRAY(command_data);
      end_want_sigcld(); OS_error();
    }
    /* Everything, that is stuffed in handles[1], resurfaces at handles[0]
     again. We will utilize this as follows:
            write            system            read
     parent  ->   handles[1]   ->   handles[0]  ->  child
     start a new process: */
    if ((child = vfork()) ==0) {
      /* this piece of code is executed by the child-process: */
      if ( dup2(handles[0],stdin_handle) >=0) /* redirect standard-input */
        if ( CLOSE(handles[0]) ==0) /* we want to read only via stdin_handle */
          if ( CLOSE(handles[1]) ==0) { /* we do not want to write to the pipe */
            /* (I have to tell this the operating system, so that - when the
             Child has emptied the pipe - the parent-process and not the
             child-process is called, in order to fill the pipe again.)
             turn child-process into a background process: */
            SETSID(); /* it receives its own process group */
            close_all_fd();
            execl(SHELL,            /* call shell */
                  SHELL,            /* =: argv[0] */
                  "-c",             /* =: argv[1] */
                  &command_data[0], /* =: argv[2] */
                  NULL);
          }
      _exit(-1); /* if this fails, finish child-process */
    }
    /* This piece of code is again executed by the caller: */
    end_want_sigcld();
    if (child==-1)
      /* Something failed, either on vfork or on execl.
       In both cases errno was set. */
      OS_error_saving_errno({
        CLOSE(handles[1]); CLOSE(handles[0]);
        FREE_DYNAMIC_ARRAY(command_data);
      });
    /* We only want to write to the pipe, not read: */
    if (!( CLOSE(handles[0]) ==0))
      OS_error_saving_errno({
        CLOSE(handles[1]);
        FREE_DYNAMIC_ARRAY(command_data);
      });
    /* (I have to tell this the operating system, so that - when the
     parent-process has filled the pipe - the child-process and not the
     parent-process is called, in order to empty the pipe again.) */
    end_system_call();
    FREE_DYNAMIC_ARRAY(command_data);
  }
 #endif
 #ifdef WIN32_NATIVE
  var Handle handles[2]; /* two Handles for the Pipe */
  {
    begin_system_call();
    var Handle child_read_handle;
    /* Create a pipe and make one of the two handles inheritable. */
    if (!CreatePipe(&handles[0],&handles[1],NULL,0)) { OS_error(); }
    if (!DuplicateHandle(GetCurrentProcess(),handles[0],
                         GetCurrentProcess(),&child_read_handle,
                         0, true, DUPLICATE_SAME_ACCESS)) {
      OS_error();
    }
    if (!CloseHandle(handles[0])) { OS_error(); }
    var HANDLE stdoutput,stderror;
    var PROCESS_INFORMATION pinfo;
    stdoutput = GetStdHandle(STD_OUTPUT_HANDLE);
    if (stdoutput == INVALID_HANDLE_VALUE) { OS_error(); }
    stderror = GetStdHandle(STD_ERROR_HANDLE);
    if (stderror == INVALID_HANDLE_VALUE) { OS_error(); }
    if (!MyCreateProcess((TCHAR*)command,child_read_handle,stdoutput,
                         stderror,&pinfo))
      { OS_error(); }
    /* Close our copy of the child's handle, so that the OS knows
     that we won't read from it. */
    if (!CloseHandle(child_read_handle)) { OS_error(); }
    if (!CloseHandle(pinfo.hThread)) { OS_error(); }
    if (!CloseHandle(pinfo.hProcess)) { OS_error(); }
    child = pinfo.dwProcessId;
    end_system_call();
  }
 #endif
  pushSTACK(UL_to_I(child));
  pushSTACK(STACK_(1+1));
  pushSTACK(STACK_(2+2));
  pushSTACK(allocate_handle(handles[1]));
}

/* (MAKE-PIPE-OUTPUT-STREAM command [:element-type] [:external-format] [:buffered])
 calls a shell, that executes command, whereby our Pipe is redirected
 into the standard-input of the command. */
LISPFUN(make_pipe_output_stream,seclass_default,1,0,norest,key,3,
        (kw(element_type),kw(external_format),kw(buffered)) )
{ make_pipe_stream(DIRECTION_OUTPUT,create_output_pipe); }

/* mk_pipe_from_handle(pipe,process_id,dir)
 Make a PIPE-OUTPUT-STREAM from pipe handle and a process-id
 > STACK_0: buffered
 > STACK_1: element-type
 > STACK_2: encoding
 > pipe: input or output pipe, depending on direction
 > process_id: PID of the underlying process
 > direction: pipe stream direction
 < result - a PIPE-OUTPUT-STREAM
 Used in LAUNCH
 can trigger GC */
extern maygc object mk_pipe_from_handle (Handle pipe, int process_id,
                                         direction_t direction) {
  var decoded_el_t eltype;
  var buffered_t buffered;
  /* Check and canonicalize the :BUFFERED argument: */
  buffered = test_buffered_arg(STACK_0);
  /* Check and canonicalize the :ELEMENT-TYPE argument: */
  test_eltype_arg(&STACK_1,&eltype);
  STACK_1 = canon_eltype(&eltype);
  CHECK_UNBUFFERED_ELTYPE(buffered,direction,eltype);
  /* Check and canonicalize the :EXTERNAL-FORMAT argument: */
  STACK_2 = test_external_format_arg(STACK_2);
  STACK_0 = allocate_handle(pipe);
  var object stream = make_pipe(buffered,direction,&eltype);
  pushSTACK(stream);
  var object pid = UL_to_I(process_id);
  TheStream(STACK_0)->strm_pipe_pid = pid;
  return popSTACK(); /* return stream */
}


#ifdef PIPES2

/* Bidirectional Pipes
 ==================== */

local inline void create_io_pipe (const char* command) {
  var int child;
 #ifdef UNIX
  var int in_handles[2]; /* two Handles for the Pipe to the Input-Stream */
  var int out_handles[2]; /* two Handles for the Pipe to the Output-Stream */
  {
    /* As shell we always use the Command-Shell.
     copy command to Stack: */
    var uintL command_length = asciz_length(command)+1;
    var DYNAMIC_ARRAY(command_data,char,command_length);
    begin_system_call();
    memcpy(command_data,command,command_length);
    begin_want_sigcld();
    /* build Pipes: */
    if (pipe(in_handles))
      OS_error_saving_errno({
        FREE_DYNAMIC_ARRAY(command_data);
        end_want_sigcld();
      });
    if (pipe(out_handles))
      OS_error_saving_errno({
        FREE_DYNAMIC_ARRAY(command_data);
        end_want_sigcld();
        CLOSE(in_handles[1]); CLOSE(in_handles[0]);
      });
    /* Everything, that is stuffed in handles[1], resurfaces at handles[0]
     again. We will utilize this as follows:
            write                system                read
     parent  ->   out_handles[1]   ->   out_handles[0]  ->   child
     parent  <-   in_handles[0]    <-   in_handles[1]   <-   child
            read                 system                write
     start a new process: */
    if ((child = vfork()) ==0) {
      /* this piece of code is executed by the child-process: */
      if ( dup2(out_handles[0],stdin_handle) >=0) /* redirect Standard-Input */
        if ( dup2(in_handles[1],stdout_handle) >=0) /* redirect Standard-Output */
          if ( CLOSE(out_handles[0]) ==0) /* read only via stdin_handle */
            if ( CLOSE(in_handles[1]) ==0) /* write only via stdout_handle */
              if ( CLOSE(out_handles[1]) ==0) /* do not write to the pipe */
                /* (I have to tell this the operating system, so that -
                 when the child-process has emptied the pipe -
                 the parent-process and not the child-process is called,
                 in order to fill the pipe again.) */
                if ( CLOSE(in_handles[0]) ==0) { /* do not to read from the pipe */
                  /* (I have to tell this the operating system, so that -
                   when the child-process has filled the pipe -
                   the parent-process and not the child-process is called,
                   in order to empty the pipe.)
                   turn child-process into a background process: */
                  SETSID(); /* it receives its own process group */
                  close_all_fd();
                  execl(SHELL,            /* call shell */
                        SHELL,            /* =: argv[0] */
                        "-c",             /* =: argv[1] */
                        &command_data[0], /* =: argv[2] */
                        NULL);
                }
      _exit(-1); /* if this fails, finish child-process */
    }
    /* This piece of code is again executed by the caller: */
    end_want_sigcld();
    if (child==-1)
      /* Something failed, either on vfork or on execl.
       In both cases errno was set. */
      OS_error_saving_errno({
        CLOSE(in_handles[1]); CLOSE(in_handles[0]);
        CLOSE(out_handles[1]); CLOSE(out_handles[0]);
        FREE_DYNAMIC_ARRAY(command_data);
      });
    /* We only want to write to the pipe, not read: */
    if (!( CLOSE(out_handles[0]) ==0))
      OS_error_saving_errno({
        CLOSE(in_handles[1]); CLOSE(in_handles[0]);
        CLOSE(out_handles[1]);
        FREE_DYNAMIC_ARRAY(command_data);
      });
    /* (I have to tell this the operating system, so that - when the
     parent-process has filled the pipe - the child-process and not the
     parent-process is called, in order to empty the pipe again.)
     We only want to read from the pipe, not write: */
    if (!( CLOSE(in_handles[1]) ==0))
      OS_error_saving_errno({
        CLOSE(in_handles[0]); CLOSE(out_handles[1]);
        FREE_DYNAMIC_ARRAY(command_data);
      });
    /* (I have to tell this the operating system, so that - when the
     parent-process has emptied the pipe - the child-process and not the
     parent-process is called, in order to fill the pipe again.) */
    end_system_call();
    FREE_DYNAMIC_ARRAY(command_data);
  }
 #endif
 #ifdef WIN32_NATIVE
  var Handle in_handles[2]; /* two Handles for the Pipe to the Input-Stream */
  var Handle out_handles[2]; /* two Handles for the Pipe to the Output-Stream */
  {
    begin_system_call();
    var Handle child_read_handle;
    var Handle child_write_handle;
    var Handle stderror;
    /* Create two pipes and make two of the four handles inheritable. */
    if (!CreatePipe(&in_handles[0],&in_handles[1],NULL,0)) { OS_error(); }
    if (!DuplicateHandle(GetCurrentProcess(),in_handles[1],
                         GetCurrentProcess(),&child_write_handle,
                         0, true, DUPLICATE_SAME_ACCESS))
      { OS_error(); }
    if (!CloseHandle(in_handles[1])) { OS_error(); }
    if (!CreatePipe(&out_handles[0],&out_handles[1],NULL,0)) { OS_error(); }
    if (!DuplicateHandle(GetCurrentProcess(),out_handles[0],
                         GetCurrentProcess(),&child_read_handle,
                         0, true, DUPLICATE_SAME_ACCESS))
      { OS_error(); }
    if (!CloseHandle(out_handles[0])) { OS_error(); }
    stderror = GetStdHandle(STD_ERROR_HANDLE);
    if (stderror == INVALID_HANDLE_VALUE) { OS_error(); }
    var PROCESS_INFORMATION pinfo;
    if (!MyCreateProcess((TCHAR*)command,child_read_handle,child_write_handle,
                         stderror,&pinfo))
      { OS_error(); }
    /* Close our copies of the child's handles, so that the OS knows
     that we won't use them. */
    if (!CloseHandle(child_read_handle)) { OS_error(); }
    if (!CloseHandle(child_write_handle)) { OS_error(); }
    if (!CloseHandle(pinfo.hThread)) { OS_error(); }
    if (!CloseHandle(pinfo.hProcess)) { OS_error(); }
    child = pinfo.dwProcessId;
    end_system_call();
  }
 #endif
  pushSTACK(UL_to_I(child));
  pushSTACK(allocate_handle(in_handles[0]));
  pushSTACK(allocate_handle(out_handles[1]));
}

/* (MAKE-PIPE-IO-STREAM command [:element-type] [:external-format] [:buffered])
 calls a shell, that executes command, whereby the output of our pipe
 is redirected into the standard-input of command and its standard-output
 is redirected into our pipe. */
LISPFUN(make_pipe_io_stream,seclass_default,1,0,norest,key,3,
        (kw(element_type),kw(external_format),kw(buffered)) ) {
  var decoded_el_t eltype;
  var buffered_t buffered;
  /* check command: */
  pushSTACK(STACK_3); funcall(L(string),1); /* (STRING command) */
  STACK_3 = value1;
  /* Check and canonicalize the :BUFFERED argument: */
  buffered = test_buffered_arg(STACK_0);
  /* Check and canonicalize the :ELEMENT-TYPE argument: */
  test_eltype_arg(&STACK_2,&eltype);
  STACK_2 = canon_eltype(&eltype);
  if (buffered <= 0) { check_unbuffered_eltype(&eltype); }
  /* Check and canonicalize the :EXTERNAL-FORMAT argument: */
  STACK_1 = test_external_format_arg(STACK_1);
  /* Now create the pipe. */
  with_string_0(STACK_3,O(misc_encoding),command_asciz, {
    create_io_pipe(command_asciz);
  });
  /* allocate Input-Stream: */
  {
    pushSTACK(STACK_(1+3)); /* encoding */
    pushSTACK(STACK_(2+3+1)); /* eltype */
    pushSTACK(STACK_(1+2));
    var object stream = make_pipe(buffered,DIRECTION_INPUT,&eltype);
    TheStream(stream)->strm_pipe_pid = STACK_2; /* Child-Pid */
    STACK_1 = stream;
  }
  /* allocate Output-Stream: */
  {
    pushSTACK(STACK_(1+3)); /* encoding */
    pushSTACK(STACK_(2+3+1)); /* eltype */
    pushSTACK(STACK_(0+2));
    var object stream = make_pipe(buffered,DIRECTION_OUTPUT,&eltype);
    TheStream(stream)->strm_pipe_pid = STACK_2; /* Child-Pid */
    STACK_0 = stream;
  }
  /* 3 values:
   (make-two-way-stream input-stream output-stream), input-stream, output-stream. */
  STACK_2 = make_twoway_stream(STACK_1,STACK_0);
  STACK_to_mv(3);
  skipSTACK(4);
}

#endif /* PIPES2 */

#endif /* PIPES */


#if defined(X11SOCKETS) || defined(SOCKET_STREAMS)

/* X11-Socket-Stream, Socket-Stream
   ================================

 Socket streams are just like handle streams (unbuffered file streams),
 except that on UNIX_BEOS and WIN32_NATIVE, the low-level functions are
 different.

 Both sides
 ----------

 Closes a socket handle. */
#if defined(UNIX_BEOS) || defined(WIN32_NATIVE)
local void low_close_socket (object stream, object handle, uintB abort) {
  begin_system_call();
  var int closed;
  var SOCKET socket = TheSocket(handle);
  GC_SAFE_CALL(closed = close(socket));
  if (!(closed == 0) && !abort)
    { ANSIC_error(); }
  end_system_call();
}
#else
  #define low_close_socket  low_close_handle
#endif

#if defined(UNIX_BEOS) || defined(WIN32_NATIVE)

#ifdef WIN32_NATIVE
  #define CHECK_INTERRUPT                       \
    if (errno==EINTR) /* Break by Ctrl-C ?*/    \
      { end_system_call(); error_interrupt(); }
#else
  #define CHECK_INTERRUPT
#endif

#define SYSCALL(result,call)                          \
  do {                                                \
    begin_system_call();                              \
    begin_blocking_call();                            \
    result = (call);                                  \
    end_blocking_call();                              \
    if (result<0) { CHECK_INTERRUPT; ANSIC_error(); } \
    end_system_call();                                \
  } while(0)

#endif

/* Return true if the last error from sock_read()/sock_write() indicates an EOF. */
local bool sock_error_eof_p (void) {
  var bool ret = false;
  begin_system_call();
 #if defined(WIN32_NATIVE)
  if (errno==ENOENT || errno==WSAESHUTDOWN) /* indicates EOF */
    ret = true;
 #else
  if (errno==ENOENT) /* indicates EOF */
    ret = true;
 #endif
  end_system_call();
  return ret;
}

/* Input side
 ---------- */

#if defined(UNIX_BEOS) || defined(WIN32_NATIVE)

local maygc sintL low_read_unbuffered_socket (object stream) {
  if (UnbufferedStream_status(stream) < 0) /* already EOF? */
    return -1;
  if (UnbufferedStream_status(stream) > 0) { /* bytebuf contains valid bytes? */
    UnbufferedStreamLow_pop_byte(stream,b); return b;
  }
  var SOCKET handle = TheSocket(TheStream(stream)->strm_ichannel);
  var uintB b;
  var ssize_t result;
  pushSTACK(stream);
  SYSCALL(result,sock_read(handle,&b,1,persev_full)); /* try to read a byte */
  stream = popSTACK();
  if (result==0) {
    ASSERT(sock_error_eof_p()); /* no byte available -> must be EOF */
    UnbufferedStream_status(stream) = -1; return -1;
  } else {
    return b;
  }
}

local listen_t low_listen_unbuffered_socket (object stream) {
  if (UnbufferedStream_status(stream) < 0) /* already EOF? */
    return LISTEN_EOF;
  if (UnbufferedStream_status(stream) > 0) /* bytebuf contains valid bytes? */
    return LISTEN_AVAIL;
  var SOCKET handle = TheSocket(TheStream(stream)->strm_ichannel);
  /* Use select() with readfds = singleton set {handle}
   and timeout = zero interval. */
  var fd_set handle_set; /* set of handles := {handle} */
  var struct timeval zero_time; /* time interval := 0 */
  begin_system_call();
  FD_ZERO(&handle_set); FD_SET(handle,&handle_set);
 restart_select:
  zero_time.tv_sec = 0; zero_time.tv_usec = 0;
  var int result = select(FD_SETSIZE,&handle_set,NULL,NULL,&zero_time);
  if (result<0) {
    CHECK_INTERRUPT;
   #ifdef UNIX_BEOS
    if (errno==EINTR)
      goto restart_select;
   #endif
    ANSIC_error();
  } else {
    /* result = number of handles in handle_set for which read() would
     return without blocking. */
    if (result==0) {
      end_system_call(); return LISTEN_WAIT;
    }
    /* result=1
     When read() returns a result without blocking, this can also be EOF!
     try to read a byte: */
    var uintB b;
    /* read will not block */
    var ssize_t result = sock_read(handle,&b,1,persev_full);
    if (result<0) {
      CHECK_INTERRUPT;
      ANSIC_error();
    }
    end_system_call();
    if (result==0) {
      ASSERT(sock_error_eof_p());
      UnbufferedStream_status(stream) = -1; return LISTEN_EOF;
    } else {
      /* Stuff the read byte into the buffer, for next low_read call. */
      UnbufferedStreamLow_push_byte(stream,b);
      return LISTEN_AVAIL;
    }
  }
}

local bool low_clear_input_unbuffered_socket (object stream) {
  /* This is not called anyway, because TheStream(stream)->strm_isatty = NIL. */
  return false; /* Not sure whether this is the correct behaviour?? */
}

local maygc uintB* low_read_array_unbuffered_socket
(object stream, uintB* byteptr, uintL len, perseverance_t persev) {
  if (UnbufferedStream_status(stream) < 0) /* already EOF? */
    return byteptr;
  byteptr = UnbufferedStream_pop_all(stream,byteptr,&len);
  if (len == 0) return byteptr;
  var SOCKET handle = TheSocket(TheStream(stream)->strm_ichannel);
  var ssize_t result;
  pushSTACK(stream);
  SYSCALL(result,sock_read(handle,byteptr,len,persev));
  stream = popSTACK();
  if (result==0 && sock_error_eof_p())
    UnbufferedStream_status(stream) = -1;
  return byteptr+result;
}

/* Initializes the input side fields of a socket stream.
 UnbufferedSocketStream_input_init(stream); */
#define UnbufferedSocketStream_input_init(stream)   do {                \
  UnbufferedStreamLow_read(stream) = &low_read_unbuffered_socket;       \
  UnbufferedStreamLow_listen(stream) = &low_listen_unbuffered_socket;   \
  UnbufferedStreamLow_clear_input(stream) =                             \
    &low_clear_input_unbuffered_socket;                                 \
  UnbufferedStreamLow_read_array(stream) =                              \
    &low_read_array_unbuffered_socket;                                  \
  UnbufferedHandleStream_input_init_data(stream);                       \
 } while (0)

#else

  #define UnbufferedSocketStream_input_init(stream)  \
    UnbufferedHandleStream_input_init(stream)

#endif /* UNIX_BEOS || WIN32_NATIVE */

/* Output side
   ----------- */

#if defined(UNIX_BEOS) || defined(WIN32_NATIVE)

local maygc void low_write_unbuffered_socket (object stream, uintB b) {
  var SOCKET handle = TheSocket(TheStream(stream)->strm_ochannel);
  var ssize_t result;
  pushSTACK(stream);
  SYSCALL(result,sock_write(handle,&b,1,persev_full)); /* Try to output the byte. */
  stream = popSTACK();
  if (result==0) /* not successful? */
    error_unwritable(TheSubr(subr_self)->name,stream);
}

local maygc const uintB* low_write_array_unbuffered_socket
(object stream, const uintB* byteptr, uintL len, perseverance_t persev) {
  var SOCKET handle = TheSocket(TheStream(stream)->strm_ochannel);
  var ssize_t result;
  pushSTACK(stream);
  SYSCALL(result,sock_write(handle,byteptr,len,persev));
  stream = popSTACK();
  /* Safety check whether persev argument was respected or EOWF was reached: */
  if ((persev == persev_full && !(result==(sintL)len))
      || (persev == persev_partial && !(result>0)))
    error_unwritable(TheSubr(subr_self)->name,stream);
  return byteptr+result;
}

#endif /* UNIX_BEOS || WIN32_NATIVE */

/* Initializes the output side fields of a socket stream.
 UnbufferedSocketStream_output_init(stream); */
#if defined(UNIX_BEOS) || defined(WIN32_NATIVE)
  #define UnbufferedSocketStream_output_init(stream)                    \
    { UnbufferedStreamLow_write(stream) = &low_write_unbuffered_socket; \
      UnbufferedStreamLow_write_array(stream) =                         \
        &low_write_array_unbuffered_socket;                             \
      UnbufferedStreamLow_finish_output(stream) =                       \
        &low_finish_output_unbuffered_pipe;                             \
      UnbufferedStreamLow_force_output(stream) =                        \
        &low_force_output_unbuffered_pipe;                              \
      UnbufferedStreamLow_clear_output(stream) =                        \
        &low_clear_output_unbuffered_pipe;                              \
    }
#else
/* Use low_write_unbuffered_pipe, not low_write_unbuffered_handle, here because
 writing to a closed socket generates a SIGPIPE signal, just like for pipes. */
  #define UnbufferedSocketStream_output_init(stream)  \
    { UnbufferedStreamLow_write(stream) = &low_write_unbuffered_pipe;   \
      UnbufferedStreamLow_write_array(stream) =                         \
        &low_write_array_unbuffered_pipe;                               \
      UnbufferedStreamLow_finish_output(stream) =                       \
        &low_finish_output_unbuffered_pipe;                             \
      UnbufferedStreamLow_force_output(stream) =                        \
        &low_force_output_unbuffered_pipe;                              \
      UnbufferedStreamLow_clear_output(stream) =                        \
        &low_clear_output_unbuffered_pipe;                              \
    }
#endif /* UNIX_BEOS || WIN32_NATIVE */

#endif /* X11SOCKETS || SOCKET_STREAMS */


#ifdef X11SOCKETS

/* X11-Socket-Stream
   =================

 usage: for X-Windows.

 Additional Components:
 define strm_x11socket_connect strm_field1 - List (host display) */

extern SOCKET connect_to_x_server (const char* host, int display); /* a piece X-Source... */

/* (SYS::MAKE-SOCKET-STREAM host display)
 returns an X11-Socket-Stream for X-Windows or NIL. */
LISPFUNN(make_x11socket_stream,2) {
  if (!stringp(STACK_1)) {
    pushSTACK(STACK_1);   /* TYPE-ERROR slot DATUM */
    pushSTACK(S(string)); /* TYPE-ERROR slot EXPECTED-TYPE */
    pushSTACK(STACK_(1+2));
    error(type_error,GETTEXT("host should be string, not ~S"));
  }
  if (!uint16_p(STACK_0)) {
    pushSTACK(STACK_0);        /* TYPE-ERROR slot DATUM */
    pushSTACK(O(type_uint16)); /* TYPE-ERROR slot EXPECTED-TYPE */
    pushSTACK(STACK_(0+2));
    error(type_error,
          GETTEXT("display should be a small nonnegative integer, not ~S"));
  }
  var int display = I_to_uint16(STACK_0);
  var SOCKET handle;
  with_string_0(STACK_1,O(misc_encoding),host, {
    GC_SAFE_SYSTEM_CALL(handle = connect_to_x_server(host,display));
  });
  if (handle == INVALID_SOCKET) { ANSIC_error(); }
  /* build list: */
  { var object list = listof(2); pushSTACK(list); }
  pushSTACK(test_external_format_arg(S(Kunix)));
  pushSTACK(O(strmtype_ubyte8));
  pushSTACK(allocate_socket(handle));
  /* allocate Stream: */
  var decoded_el_t eltype = { eltype_iu, 8 };
  var object stream = make_unbuffered_stream(strmtype_x11socket,DIRECTION_IO,
                                             &eltype,false,false);
  UnbufferedSocketStream_input_init(stream);
  UnbufferedSocketStream_output_init(stream);
  ChannelStreamLow_close(stream) = &low_close_socket;
  TheStream(stream)->strm_x11socket_connect = popSTACK(); /* two-element list */
  VALUES1(add_to_open_streams(stream)); /* return stream */
}

/* The two following functions should
 1. not only work for Handle- and Socket-Streams, but also for Synonym-
    and Concatenated-Streams, ideally for File-Streams, too.
 2. also accept non-simple Byte-Vectors.
 For CLX this implementation is sufficient.

 (SYS::READ-N-BYTES stream vector start count)
 reads n Bytes at once.
 Source:
   stream: Handle- or Socket-Stream
 Destination: (aref vector start), ..., (aref vector (+ start (- count 1))),
  whereby
   vector: semi-simple 8Bit-Byte-Vector
   start: Start-Index in the Vector
   count: Number of bytes

 (SYS::WRITE-N-BYTES stream vector start count)
 writes n Bytes at once.
 Source: (aref vector start), ..., (aref vector (+ start (- count 1))),
  whereby
   vector: semi-simple 8Bit-Byte-Vector
   start: Start-Index in the Vector
   count: Number of Bytes
 Destination:
   stream: Handle- or Socket-Stream

 Argument-Checks:
 Returns the Index in *index_, the count in *count_, the data-vector in the
 Stack instead of the vector, and cleans up the Stack by 2.
 can trigger GC */
local maygc void test_n_bytes_args (uintL* index_, uintL* count_) {
  CHECK_streamtype(STACK_3,S(x11_socket_stream),
                   (builtin_stream_p(STACK_3)
                    && eq(TheStream(STACK_3)->strm_rd_by,
                          P(rd_by_iau8_unbuffered))
                    && eq(TheStream(STACK_3)->strm_wr_by,
                          P(wr_by_iau8_unbuffered))));
  *count_ = I_to_UL(check_uint32(popSTACK()));
  *index_ = I_to_UL(check_uint32(popSTACK()));
  STACK_0 = array_displace_check(check_byte_vector(STACK_0),*count_,index_);
}

/* UP: report END-OF-FILE error
 > stream: the stream that has reached EOS */
local _Noreturn void error_eos (object stream) {
  pushSTACK(stream);            /* STREAM-ERROR slot STREAM */
  pushSTACK(stream); pushSTACK(TheSubr(subr_self)->name);
  error(end_of_file,GETTEXT("~S: input stream ~S has reached its end"));
}
#define HANDLE_EOF(eof_e_p,eofval,skip_stack)                           \
  if (nullp(eof_e_p)) { /* handle EOF: */                               \
    value1 = eofval;                                                    \
    if (!boundp(value1)) value1 = NIL; /* Default is NIL */             \
    mv_count = 1; skipSTACK(skip_stack); /* return eofval */            \
  } else               /* eof-error-p /= NIL (e.g. = #<UNBOUND>) ? */   \
    error_eos(STACK_2);

LISPFUNN(read_n_bytes,4) {
  var uintL startindex;
  var uintL totalcount;
  test_n_bytes_args(&startindex,&totalcount);
  if (totalcount !=0
      && (read_byte_array(&STACK_1,&STACK_0,startindex,totalcount,persev_full)
          != totalcount))
    error_eos(STACK_1);
  skipSTACK(2);
  VALUES1(T);
}

LISPFUNN(write_n_bytes,4) {
  var uintL startindex;
  var uintL totalcount;
  test_n_bytes_args(&startindex,&totalcount);
  if (!(totalcount==0)) {
    write_byte_array(&STACK_1,&STACK_0,startindex,totalcount,persev_full);
  }
  skipSTACK(2);
  VALUES1(T);
}

#endif /* X11SOCKETS */


#ifdef SOCKET_STREAMS

/* Socket-Streams
   ==============

   define strm_socket_port strm_field1 - port, a fixnum >=0
   define strm_socket_host strm_field2 - host, NIL or a string */

#define SocketChannel(stream)                                              \
 TheSocket(ChannelStream_buffered(stream) ? BufferedStream_channel(stream) \
           : ChannelStream_ichannel(stream))

/* Low-level functions for buffered socket streams. */

#if defined(UNIX_BEOS) || defined(WIN32_NATIVE)

/* UP: Fills the buffer, up to strm_buffered_bufflen bytes.
 low_fill_buffered_socket(stream,persev)
 > stream: (open) byte-based socket stream
 > persev: one of persev_partial, persev_immediate, persev_bonus
 < result: number of bytes read */
local maygc uintL low_fill_buffered_socket (object stream,
                                            perseverance_t persev) {
  var SOCKET handle=TheSocket(BufferedStream_channel(stream));
  var uintB *buff=BufferedStream_buffer_address(stream,0);
  pin_unprotect_varobject(BufferedStream_buffer(stream),PROT_READ_WRITE);
  pushSTACK(stream);
  var ssize_t result;
  SYSCALL(result,sock_read(handle,buff,strm_buffered_bufflen,persev));
  stream = popSTACK();
  unpin_varobject(BufferedStream_buffer(stream));
  if (result==0 && sock_error_eof_p())
    BufferedStream_have_eof_p(stream) = true;
  return result;
}

/* UP: Finshes the Write-Back of the Buffer.
 low_flush_buffered_socket(stream,bufflen);
 > stream : (open) Byte-based File-Stream.
 > bufflen : number of bytes to be written
 < modified_flag von stream : deleted
 changed in stream: index */
local maygc void low_flush_buffered_socket (object stream, uintL bufflen) {
  begin_system_call();
  START_WRITING_TO_SUBPROCESS;
  var SOCKET handle=TheSocket(BufferedStream_channel(stream));
  var uintB *buff=BufferedStream_buffer_address(stream,0);
  pin_unprotect_varobject(BufferedStream_buffer(stream),PROT_READ);
  pushSTACK(stream);
  var ssize_t result;        /* flush Buffer */
  GC_SAFE_CALL(result = sock_write(handle,buff,bufflen,persev_full));
  stream = popSTACK();
  unpin_varobject(BufferedStream_buffer(stream));
  STOP_WRITING_TO_SUBPROCESS;
  if (result==bufflen) {
    /* everything written correctly */
    end_system_call(); BufferedStream_modified(stream) = false;
  } else { /* not everything written */
    if (result<0) {
      CHECK_INTERRUPT;
      ANSIC_error();
    }
    end_system_call();
    error_unwritable(TheSubr(subr_self)->name,stream);
  }
}

#else

/* Use low_flush_buffered_pipe, not low_flush_buffered_handle, here because
 writing to a closed socket generates a SIGPIPE signal, just like for pipes. */
  #define low_fill_buffered_socket  low_fill_buffered_handle
  #define low_flush_buffered_socket  low_flush_buffered_pipe

#endif

#define BufferedSocketStream_init(stream)  \
  { BufferedStreamLow_fill(stream) = &low_fill_buffered_socket;   \
    BufferedStreamLow_flush(stream) = &low_flush_buffered_socket; \
  }

/* Twoway-Socket-Streams are twoway streams with both input and output side
 being socket streams. (They are needed because the input and output side
 need different buffers. Sockets are not regular files.)
 define strm_twoway_socket_input  strm_twoway_input  - input side, a socket stream */
#define strm_twoway_socket_output  strm_twoway_output /* output side, a socket stream */

/* Hack for avoiding that the handle is closed twice. */
local void low_close_socket_nop (object stream, object handle, uintB abort) {
  unused(stream); unused(handle); unused(abort);
}

/* Creates a socket stream.
 > STACK_2: element-type
 > STACK_1: encoding */
local object make_socket_stream (SOCKET handle, decoded_el_t* eltype,
                                 buffered_t buffered, object host, object port)
{
  pushSTACK(host);
  pushSTACK(STACK_(1+1)); /* encoding */
  pushSTACK(STACK_(2+2)); /* eltype */
  pushSTACK(allocate_socket(handle));
  /* allocate stream: */
  var object stream;
  if (buffered == BUFFERED_NIL) {
    stream = make_unbuffered_stream(strmtype_socket,DIRECTION_IO,
                                    eltype,false,false);
    UnbufferedSocketStream_input_init(stream);
    UnbufferedSocketStream_output_init(stream);
    ChannelStreamLow_close(stream) = &low_close_socket;
    TheStream(stream)->strm_socket_port = port;
    TheStream(stream)->strm_socket_host = popSTACK();
  } else {
    /* allocate Input-Stream: */
    pushSTACK(STACK_2); pushSTACK(STACK_(1+1)); pushSTACK(STACK_(0+2));
    stream = make_buffered_stream(strmtype_socket,DIRECTION_INPUT,
                                  eltype,false,false);
    BufferedSocketStream_init(stream);
    ChannelStreamLow_close(stream) = &low_close_socket;
    TheStream(stream)->strm_socket_port = port;
    TheStream(stream)->strm_socket_host = STACK_3;
    pushSTACK(stream);
    /* allocate Output-Stream: */
    pushSTACK(STACK_(2+1)); pushSTACK(STACK_(1+2)); pushSTACK(STACK_(0+3));
    if (buffered != BUFFERED_T) {
      stream = make_unbuffered_stream(strmtype_socket,DIRECTION_OUTPUT,
                                      eltype,false,false);
      UnbufferedSocketStream_output_init(stream);
    } else {
      stream = make_buffered_stream(strmtype_socket,DIRECTION_OUTPUT,
                                    eltype,false,false);
      BufferedSocketStream_init(stream);
    }
    ChannelStreamLow_close(stream) = &low_close_socket;
    TheStream(stream)->strm_socket_port = port;
    TheStream(stream)->strm_socket_host = STACK_(3+1);
    pushSTACK(stream);
    /* Allocate a Two-Way-Socket-Stream: */
    stream = allocate_stream(strmflags_rdwr_B,strmtype_twoway_socket,
                             strm_len+2,0);
    TheStream(stream)->strm_rd_by = P(rd_by_twoway);
    TheStream(stream)->strm_rd_by_array = P(rd_by_array_twoway);
    TheStream(stream)->strm_wr_by = P(wr_by_twoway);
    TheStream(stream)->strm_wr_by_array = P(wr_by_array_twoway);
    TheStream(stream)->strm_rd_ch = P(rd_ch_twoway);
    TheStream(stream)->strm_pk_ch = P(pk_ch_twoway);
    TheStream(stream)->strm_rd_ch_array = P(rd_ch_array_twoway);
    TheStream(stream)->strm_rd_ch_last = NIL;
    TheStream(stream)->strm_wr_ch =
      TheStream(stream)->strm_wr_ch_npnl = P(wr_ch_twoway);
    TheStream(stream)->strm_wr_ch_array =
      TheStream(stream)->strm_wr_ch_array_npnl = P(wr_ch_array_twoway);
    TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
    TheStream(stream)->strm_twoway_socket_input = STACK_1;
    TheStream(stream)->strm_twoway_socket_output = STACK_0;
    skipSTACK(6);
  }
  return stream;
}

local void test_socket_server (object obj, bool check_open) {
  if (!socket_server_p(obj)) {
    pushSTACK(obj);              /* TYPE-ERROR slot DATUM */
    pushSTACK(S(socket_server)); /* TYPE-ERROR slot EXPECTED-TYPE */
    pushSTACK(S(socket_server)); pushSTACK(obj);
    pushSTACK(TheSubr(subr_self)->name);
    error(type_error,GETTEXT("~S: ~S is not a ~S"));
  }
  if (check_open && nullp(TheSocketServer(obj)->socket_handle)) {
    pushSTACK(obj);
    pushSTACK(TheSubr(subr_self)->name);
    error(error_condition,GETTEXT("~S on ~S is illegal"));
  }
}

/* Called when some socket server dies. */
LISPFUNN(socket_server_close,1) {
  test_socket_server(STACK_0,false);
  var object ss = STACK_0;
  if (!nullp(TheSocketServer(ss)->socket_handle)) {
    var SOCKET s = TheSocket(TheSocketServer(ss)->socket_handle);
    begin_system_call();
    while (1) {
      var int closed;
      GC_SAFE_CALL(closed = close(s));
      if (closed >= 0) break;
      if (errno != EINTR) { ANSIC_error(); }
    }
    end_system_call();
    ss = STACK_0;
    TheSocketServer(ss)->socket_handle = NIL;
  }
  skipSTACK(1);
  VALUES1(NIL);
}

extern SOCKET create_server_socket_by_string
(host_data_t *hd, const char *ip_interface, unsigned int port, int backlog);
extern SOCKET create_server_socket_by_socket
(host_data_t *hd, SOCKET sock, unsigned int port, int backlog);

local object test_socket_stream (object obj, bool check_open) {
  if (builtin_stream_p(obj)) {
    switch (TheStream(obj)->strmtype) {
      case strmtype_twoway_socket:
        obj = TheStream(obj)->strm_twoway_socket_input;
        /*FALLTHROUGH*/
      case strmtype_socket:
        if (check_open
            && ((TheStream(obj)->strmflags & strmflags_open_B) == 0)) {
          pushSTACK(obj);       /* TYPE-ERROR slot DATUM */
          pushSTACK(S(stream)); /* TYPE-ERROR slot EXPECTED-TYPE */
          pushSTACK(obj);
          pushSTACK(TheSubr(subr_self)->name);
          error(type_error,
                GETTEXT("~S: argument ~S is not an open SOCKET-STREAM"));
        }
        return obj;
      default:
        break;
    }
  }
  pushSTACK(obj);               /* TYPE-ERROR slot DATUM */
  pushSTACK(S(stream));         /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(obj);
  pushSTACK(TheSubr(subr_self)->name);
  error(type_error,GETTEXT("~S: argument ~S is not a SOCKET-STREAM"));
}

/* (SOCKET-SERVER &optional port &key backlog interface)
 * old version (SOCKET-SERVER socket) allowed, but deprecated. */
LISPFUN(socket_server,seclass_default,0,1,norest,key,2,
         (kw(backlog),kw(interface)) ) {
  var unsigned int port=0;              /* port to be used */
  var int backlog=1;                    /* parameter for listen(2) */
  var SOCKET sock = INVALID_SOCKET;     /* interface to be bound, as peer */
  if (!missingp (STACK_1))              /* backlog */
    backlog = I_to_sint32(check_sint32(STACK_1));
  if (!missingp(STACK_2)) {     /* port */
    if (builtin_stream_p(STACK_2)) {
      pushSTACK(CLSTEXT("WARNING: (socket-server <socket>) is deprecated, use (socket-server <port> :interface <socket>)"));
      funcall(S(warn),1);
      stream_handles(test_socket_stream(STACK_2,true),true,NULL,&sock,NULL);
    } else /* Leave this last, so that type error talks about integer */
      port = I_to_uint16(check_uint16(STACK_2));
  }
  {
    var SOCKET sk = INVALID_SOCKET;
    var host_data_t myname;
    if (!missingp(STACK_0)) {   /* interface */
      if (builtin_stream_p(STACK_0)) {
        stream_handles(test_socket_stream(STACK_0,true),true,NULL,&sock,NULL);
      } else { /* Leave this last, so that type error talks about string */
        with_string_0(check_string(STACK_0),O(misc_encoding),interfacez, {
          begin_blocking_system_call();
          sk = create_server_socket_by_string(&myname,interfacez,port,backlog);
          end_blocking_system_call();
        });
        goto got_sk;
      }
    }
    begin_blocking_system_call();
    if (sock != INVALID_SOCKET)
      sk = create_server_socket_by_socket(&myname,sock,port,backlog);
    else
      sk = create_server_socket_by_string(&myname,"0.0.0.0",port,backlog);
    end_blocking_system_call();
   got_sk:
    if (sk == INVALID_SOCKET) { ANSIC_error(); }
    pushSTACK(allocate_socket(sk));
    pushSTACK(allocate_socket_server());
    TheSocketServer(STACK_0)->socket_handle = STACK_1;
    TheSocketServer(STACK_0)->port = fixnum(myname.port);
    { /* for GC-safety: */
      var object host = asciz_to_string(myname.hostname,O(misc_encoding));
      TheSocketServer(STACK_0)->host = host;
    }
    pushSTACK(STACK_4);
    pushSTACK(L(socket_server_close));
    funcall(L(finalize),2); /* (FINALIZE socket-server #'socket-server-close) */
    VALUES1(popSTACK());
    skipSTACK(4);
  }
}

/* (SOCKET-SERVER-PORT socket-server) */
LISPFUNN(socket_server_port,1) {
  test_socket_server(STACK_0,false);
  VALUES1(TheSocketServer(STACK_0)->port);
  skipSTACK(1);
}

/* (SOCKET-SERVER-HOST socket-server) */
LISPFUNN(socket_server_host,1) {
  test_socket_server(STACK_0,false);
  VALUES1(TheSocketServer(STACK_0)->host);
  skipSTACK(1);
}

/* parse timeout argument
 sec = posfixnum or (SEC . USEC) or (SEC USEC) or float or ratio or nil/unbound
 usec = posfixnum or nil/unbound
 can trigger GC */
modexp maygc struct timeval * sec_usec
(object sec, object usec, struct timeval *tv) {
  if (missingp(sec)) {
    return NULL;
  } else if (consp(sec)) {
    if (!nullp(Cdr(sec)) && !boundp(usec))
      usec = (consp(Cdr(sec)) ? Car(Cdr(sec)) : Cdr(sec));
    sec = Car(sec);
  } else if (floatp(sec) || ratiop(sec)) {
    /* Compute (floor sec 1). */
    pushSTACK(sec); funcall(L(floor),1);
    sec = value1;
    if (!boundp(usec)) { /* usec = round(sec*1000000) */
      pushSTACK(value2); pushSTACK(fixnum(1000000)); funcall(L(star),2);
      pushSTACK(value1); funcall(L(round),1);
      usec = value1;
    }
  }
#if defined(SIZEOF_STRUCT_TIMEVAL) && SIZEOF_STRUCT_TIMEVAL == 16
 #define TV_SEC(s)  I_to_uint64(check_uint64(s))
#else
 #define TV_SEC(s)  I_to_uint32(check_uint32(s))
#endif
  tv->tv_sec = TV_SEC(sec);
  tv->tv_usec = (missingp(usec) ? 0 : TV_SEC(usec));
#undef TV_SEC
  return tv;
}

/* Convert C sec/usec (struct timeval et al) pair into Lisp number (of seconds)
 if abs_p is true, add UNIX_LISP_TIME_DIFF
 can trigger GC */
#if defined(SIZEOF_STRUCT_TIMEVAL) && SIZEOF_STRUCT_TIMEVAL == 16
#define TO_INT(x)  uint64_to_I(x)
modexp maygc object sec_usec_number (uint64 sec, uint64 usec, bool abs_p)
#else
#define TO_INT(x)  uint32_to_I(x)
modexp maygc object sec_usec_number (uint32 sec, uint32 usec, bool abs_p)
#endif
{
  pushSTACK(TO_INT((abs_p ? UNIX_LISP_TIME_DIFF : 0) + sec));
  if (usec) {
    /* this is likely to end up as a ratio... */
    pushSTACK(TO_INT(usec)); pushSTACK(fixnum(1000000)); funcall(L(slash),2);
    pushSTACK(value1); funcall(L(plus),2);
    return value1;
  } else
    return popSTACK();
}
#undef TO_INT

#if defined(HAVE_SELECT) || defined(WIN32_NATIVE)
/* wait for the socket server to have a connection ready
 returns true if socket_accept will return immediately */
local maygc bool socket_server_wait (gcv_object_t *sose_, struct timeval *tvp) {
  var SOCKET handle = TheSocket(TheSocketServer(*sose_)->socket_handle);
 #if defined(WIN32_NATIVE)
  return interruptible_socket_wait(handle,socket_wait_read,tvp);
 #else
 restart_select:
  begin_system_call();
  var int ret;
  var fd_set handle_set;
  FD_ZERO(&handle_set); FD_SET(handle,&handle_set);
  GC_SAFE_CALL(ret = select(FD_SETSIZE,&handle_set,NULL,NULL,tvp));
  if (ret < 0) {
    if (errno == EINTR) {
      end_system_call(); goto restart_select;
    }
    ANSIC_error();
  }
  end_system_call();
  return (ret != 0);
 #endif /* WIN32_NATIVE */
}
#endif

/* (SOCKET-ACCEPT socket-server [:element-type] [:external-format] [:buffered]
                [:timeout]) */
LISPFUN(socket_accept,seclass_default,1,0,norest,key,4,
        (kw(element_type),kw(external_format),kw(buffered),kw(timeout)) ) {
  var struct timeval tv;
  var struct timeval *tvp = sec_usec(popSTACK(),unbound,&tv);

  test_socket_server(STACK_3,true);

  /* Check and canonicalize the :BUFFERED argument: */
  var buffered_t buffered = test_buffered_arg(STACK_0);

  /* Check and canonicalize the :ELEMENT-TYPE argument: */
  var decoded_el_t eltype;
  test_eltype_arg(&STACK_2,&eltype);
  STACK_2 = canon_eltype(&eltype);
  if (buffered != BUFFERED_T) { check_unbuffered_eltype(&eltype); }

  /* Check and canonicalize the :EXTERNAL-FORMAT argument: */
  STACK_1 = test_external_format_arg(STACK_1);

 #if defined(HAVE_SELECT) || defined(WIN32_NATIVE)
  if (tvp && !socket_server_wait(&STACK_3,tvp)) { /* handle :TIMEOUT */
    skipSTACK(4); errno = ETIMEDOUT; OS_error();
  }
 #endif

  var SOCKET sock = TheSocket(TheSocketServer(STACK_3)->socket_handle);
  begin_blocking_system_call();
  var SOCKET handle = accept_connection (sock);
  end_blocking_system_call();
  if (handle == INVALID_SOCKET) { ANSIC_error(); }
  value1 = make_socket_stream(handle,&eltype,buffered,
                              TheSocketServer(STACK_3)->host,
                              TheSocketServer(STACK_3)->port);
  VALUES1(add_to_open_streams(value1));
  skipSTACK(4);
}

/* (SOCKET-WAIT socket-server [seconds [microseconds]]) */
LISPFUN(socket_wait,seclass_default,1,2,norest,nokey,0,NIL) {
  test_socket_server(STACK_2,true);
 #if defined(HAVE_SELECT) || defined(WIN32_NATIVE)
  var struct timeval timeout;
  var struct timeval * timeout_ptr = sec_usec(STACK_1,STACK_0,&timeout);
  VALUES_IF(socket_server_wait(&STACK_2,timeout_ptr));
 #else
  VALUES1(NIL);
 #endif
  skipSTACK(3);
}

/* (SOCKET-CONNECT port [host] [:element-type] [:external-format] [:buffered]
                 [:timeout]) */
LISPFUN(socket_connect,seclass_default,1,1,norest,key,4,
        (kw(element_type),kw(external_format),kw(buffered),kw(timeout)) ) {
  var struct timeval tv;
  var struct timeval *tvp = sec_usec(popSTACK(),unbound,&tv);
  /* On Linux, with a timeout of 0, even a local connection would fail with
     error EINPROGRESS. This is undesired. Use a timeout of 1 ms instead. */
  if (tvp != NULL && tvp->tv_sec == 0 && tvp->tv_usec == 0) {
    tvp->tv_usec = 1000;
  }

  STACK_4 = check_uint16(STACK_4);

  /* Check and canonicalize the :BUFFERED argument: */
  var buffered_t buffered = test_buffered_arg(STACK_0);

  /* Check and canonicalize the :ELEMENT-TYPE argument: */
  var decoded_el_t eltype;
  test_eltype_arg(&STACK_2,&eltype);
  STACK_2 = canon_eltype(&eltype);
  if (buffered != BUFFERED_T) { check_unbuffered_eltype(&eltype); }

  /* Check and canonicalize the :EXTERNAL-FORMAT argument: */
  STACK_1 = test_external_format_arg(STACK_1);

  /* ensure that we have host name*/
  if (missingp(STACK_3))
    STACK_3 = asciz_to_string("localhost",O(misc_encoding));

  var SOCKET handle;
  begin_blocking_system_call();
  /* instead to pin the host name object in the heap - let's allocate it
     on the stack.*/
  with_string_0(STACK_3,O(misc_encoding),hostname, {
    handle = create_client_socket(hostname,I_to_uint16(STACK_4),tvp);
  });
  end_blocking_system_call();
  if (handle == INVALID_SOCKET) { ANSIC_error(); }

  value1 = make_socket_stream(handle,&eltype,buffered,STACK_3,STACK_4);
  VALUES1(add_to_open_streams(value1));
  skipSTACK(5);
}

/* check whether the object is a handle stream or a socket-server
 and return its socket-like handle(s) */
modexp void stream_handles (object obj, bool check_open, bool* char_p,
                            SOCKET* in_sock, SOCKET* out_sock) {
  if (uint_p(obj)) {
    if (in_sock)   *in_sock = (SOCKET)I_to_uint(obj);
    if (out_sock) *out_sock = (SOCKET)I_to_uint(obj);
    if (char_p) *char_p = false;
    return;
  }
  if (socket_server_p(obj)) {
    if (check_open) test_socket_server(obj,true);
    if (in_sock) *in_sock = TheSocket(TheSocketServer(obj)->socket_handle);
    return;
  }
  if (!(streamp(obj)
        && (!check_open || TheStream(obj)->strmflags & strmflags_open_B))) {
    pushSTACK(obj);             /* TYPE-ERROR slot DATUM */
    pushSTACK(S(stream));       /* TYPE-ERROR slot EXPECTED-TYPE */
    pushSTACK(obj);
    pushSTACK(TheSubr(subr_self)->name);
    error(type_error,GETTEXT("~S: argument ~S is not an open stream"));
  }
 restart_stream_handles:
  switch (TheStream(obj)->strmtype) {
    case strmtype_synonym:
      obj = resolve_synonym_stream(obj);
      goto restart_stream_handles;
    case strmtype_terminal:
      if (in_sock)  *in_sock  = (SOCKET)stdin_handle;
      if (out_sock) *out_sock = (SOCKET)stdout_handle;
      if (char_p) *char_p = true;
      return;
   #ifdef KEYBOARD
    case strmtype_keyboard:
      if (in_sock)
        *in_sock = TheSocket(TheStream(obj)->strm_keyboard_handle);
      if (char_p) *char_p = true;
      return;
   #endif
   #ifdef X11SOCKETS
    case strmtype_x11socket:
      if (in_sock && input_stream_p(obj))
        *in_sock = TheSocket(TheStream(obj)->strm_ichannel);
      if (out_sock && output_stream_p(obj))
        *out_sock = TheSocket(TheStream(obj)->strm_ochannel);
      if (char_p) *char_p = false;
      return;
   #endif
    case strmtype_twoway_socket:
      obj = TheStream(obj)->strm_twoway_socket_input;
      if (in_sock)  *in_sock  = SocketChannel(obj);
      if (out_sock) *out_sock = SocketChannel(obj);
      if (char_p) *char_p = eq(TheStream(obj)->strm_eltype,S(character));
      return;
    case strmtype_socket:
      if (in_sock  && input_stream_p(obj))  *in_sock  = SocketChannel(obj);
      if (out_sock && output_stream_p(obj)) *out_sock = SocketChannel(obj);
      if (char_p) *char_p = eq(TheStream(obj)->strm_eltype,S(character));
      return;
    case strmtype_echo:
    case strmtype_twoway:
      stream_handles(TheStream(obj)->strm_twoway_input,
                     check_open,char_p,in_sock,NULL);
      stream_handles(TheStream(obj)->strm_twoway_output,
                     check_open,NULL,NULL,out_sock);
      return;
   #ifdef PIPES
    case strmtype_pipe_in:
      if (in_sock) *in_sock  = (SOCKET)ChannelStream_ihandle(obj);
      if (char_p) *char_p = eq(TheStream(obj)->strm_eltype,S(character));
      return;
    case strmtype_pipe_out:
      if (out_sock) *out_sock = (SOCKET)ChannelStream_ohandle(obj);
      return;
   #endif
    case strmtype_file: {
      var Handle handle = ChannelStream_ihandle(obj);
      if (in_sock  && input_stream_p(obj))  *in_sock  = (SOCKET)handle;
      if (out_sock && output_stream_p(obj)) *out_sock = (SOCKET)handle;
      if (char_p) *char_p = eq(TheStream(obj)->strm_eltype,S(character));
      return;
    }
    default: error_illegal_streamop(TheSubr(subr_self)->name,obj);
  }
}

/* extract socket, direction and status place from the SOCKET-STATUS
   argument. returns the cons which cdr should be changed with the status */
local object parse_sock_list (object obj,object *sock,direction_t *dir)
{
  if (consp(obj)) { /* (sock ...) */
    *sock = (object)Car(obj);
    if (nullp(Cdr(obj))) { /* (sock) */
      *dir = DIRECTION_IO;
      return obj;
    } else if (consp(Cdr(obj))) { /* (sock dir . place) */
      *dir = check_direction(Car(Cdr(obj)));
      return Cdr(obj);
    } else { /* (sock . dir) or (server . place) */
      if (socket_server_p(*sock)) { /* (server . place) */
        *dir = DIRECTION_INPUT;
        return obj;
      } else {                  /* (sock . dir) */
        *dir = check_direction(Cdr(obj));
        return NIL;
      }
    }
  } else { /* sock */
    *sock = obj;
    *dir = DIRECTION_IO;
    return NIL;
  }
}

/* set the appropriate fd_sets for the socket,
 either a socket-server, a socket-stream or a (socket . direction)
 if the socket is a buffered stream with non-empty input buffer,
    reset non_empty_buffers_p to true
 see socket_status() for details
 return the number of handles set */
local uintB stream_isbuffered_low (object stream, uintL *avail);
local uintL handle_set (object socket, fd_set *readfds, fd_set *writefds,
                        fd_set *errorfds, bool *need_new_list,
                        bool *non_empty_buffers_p) {
  var object sock;
  var direction_t dir;
  var SOCKET in_sock = INVALID_SOCKET;
  var SOCKET out_sock = INVALID_SOCKET;
  var uintL ret = 0, avail = 0;
  if (nullp(parse_sock_list(socket,&sock,&dir)) && need_new_list)
    *need_new_list = true;
  stream_handles(sock,true,NULL,
                 READ_P(dir)  ? &in_sock  : NULL,
                 WRITE_P(dir) ? &out_sock : NULL);
  if (READ_P(dir) && streamp(sock) /* read from stream - check buffer */
      && (bit(1) & stream_isbuffered_low(sock,&avail)) && avail)
    *non_empty_buffers_p = true;
  if (in_sock != INVALID_SOCKET) {
    ret++;
    FD_SET(in_sock,errorfds);
    FD_SET(in_sock,readfds);
  }
  if (out_sock != INVALID_SOCKET) {
    ret++;
    FD_SET(out_sock,errorfds);
    FD_SET(out_sock,writefds);
  }
  return ret;
}

/* check the appropriate fd_sets for the socket,
 either a socket-server, a socket-stream or a (socket . direction)
 see socket_status() for details
 can trigger GC */
local maygc object handle_isset (object socket, fd_set *readfds,
                                 fd_set *writefds, fd_set *errorfds) {
  var object sock, ret;
  var direction_t dir;
  var object status_cons = parse_sock_list(socket,&sock,&dir);
  var SOCKET in_sock = INVALID_SOCKET;
  var SOCKET out_sock = INVALID_SOCKET;
  var bool char_p = true, wr = false;
  var listen_t rd = LISTEN_WAIT;
  stream_handles(sock,true,&char_p,
                 READ_P(dir)  ? &in_sock  : NULL,
                 WRITE_P(dir) ? &out_sock : NULL);
  if (in_sock != INVALID_SOCKET) {
    if (FD_ISSET(in_sock,errorfds)) return S(Kerror);
    if (socket_server_p(sock)) {
      ret = FD_ISSET(in_sock,readfds) ? T : NIL;
      if (!nullp(status_cons)) Cdr(status_cons) = ret;
      return ret;
    } else if (uint_p(sock)) {
      if (FD_ISSET(in_sock,readfds)) rd = LISTEN_AVAIL;
    } else {                    /* stream */
      if (FD_ISSET(in_sock,readfds) || (stream_isbuffered(sock) & bit(1))) {
        pushSTACK(status_cons);
        rd = (char_p ? listen_char(sock) : listen_byte(sock));
        status_cons = popSTACK();
      }
    }
  }
  if (out_sock != INVALID_SOCKET) {
    if (FD_ISSET(out_sock,errorfds)) return S(Kerror);
    wr = FD_ISSET(out_sock,writefds);
  }
  switch (rd) {
    case LISTEN_AVAIL: ret = wr ? S(Kio)     : S(Kinput); break;
    case LISTEN_EOF:   ret = wr ? S(Kappend) : S(Keof); break;
    case LISTEN_WAIT:  ret = wr ? S(Koutput) : NIL; break;
    case LISTEN_ERROR: ret = S(Kerror); break;
  }
  if (!nullp(status_cons)) Cdr(status_cons) = ret;
  return ret;
}

/* (SOCKET-STATUS socket-or-list [seconds [microseconds]])
 socket-or-list should be either
   -- socket [socket-stream or socket-server]
   -- (socket . direction) [direction is :input or :output or :io (default)]
   -- (socket direction . ???) [??? is replaced with the status, no consing]
   -- non-empty list of the above
 NIL signals an error because (SOCKET-STATUS X NIL) returning means that
   some operation is available (the second value is non-0)
 returns either a single symbol :ERROR/:INPUT/:OUTPUT/:IO/:EOF/:APPEND/NIL
   (for streams) or T/NIL (for socket-servers) - when a single object was
   given - or a list of such symbols:
  we can distinguish between 3 states for input:
    <i1> available
    <i2> EOF
    <i3> no info/will block/did not request information
  and 2 states for output:
    <o1> available
    <o2> no info/will block/did not request information/EOF
  the return values are:
       <i1>   <i2>     <i3>
  <o1> :IO    :APPEND  :OUTPUT
  <o2> :INPUT :EOF     NIL
 The second value is the number of "actionable" objects, i.e.,
  the number of arguments for which non-NIL is returned (or set).
 May cons the list (and thus can trigger GC) if the list does not
  provide space for the return values. */
LISPFUN(socket_status,seclass_default,1,2,norest,nokey,0,NIL) {
 #if defined(HAVE_SELECT) || defined(WIN32_NATIVE)
  var struct timeval timeout;
  var struct timeval * timeout_ptr = sec_usec(STACK_1,STACK_0,&timeout);

 restart_select:
  begin_system_call();
  { var fd_set readfds, writefds, errorfds;
    var object all = STACK_2;
    var bool non_empty_buffers_p = false;
    FD_ZERO(&readfds); FD_ZERO(&writefds); FD_ZERO(&errorfds);
    var bool many_sockets_p =
      (consp(all) && !(symbolp(Cdr(all)) && keywordp(Cdr(all))));
    var bool need_new_list = false;
    if (many_sockets_p) {
      var object list = all;
      var int index = 0;
      for(; !nullp(list); list = Cdr(list)) {
        if (!listp(list)) error_list(list);
        index += handle_set(Car(list),&readfds,&writefds,&errorfds,
                            &need_new_list,&non_empty_buffers_p);
        if (index > FD_SETSIZE) {
          pushSTACK(fixnum(FD_SETSIZE));
          pushSTACK(all);
          pushSTACK(S(socket_status));
          error(error_condition,GETTEXT("~S: list ~S is too long (~S maximum)"));
        }
      }
    } else
      handle_set(all,&readfds,&writefds,&errorfds,NULL,&non_empty_buffers_p);
    if (non_empty_buffers_p) {
      /* reset timeout to 0 because we should return immediately even if
         the user specified waiting forever: the socket may not be ready
         because the buffer contains everything it has got */
      timeout_ptr = &timeout;
      timeout.tv_sec = timeout.tv_usec = 0;
    }
    var int selectret;
    GC_SAFE_CALL(selectret = select(FD_SETSIZE,&readfds,&writefds,&errorfds,timeout_ptr));
    if (selectret < 0) {
      if (errno == EINTR) { end_system_call(); goto restart_select; }
      if (errno != EBADF) { ANSIC_error(); }
    }
    all=STACK_2; /* reload */
    if (many_sockets_p) {
      var object list = all;
      var uintL index = 0, count = 0;
      while(!nullp(list)) {
        index++; pushSTACK(list); /* save list */
        var object tmp = handle_isset(Car(list),&readfds,&writefds,&errorfds);
        if (need_new_list) {
          list = Cdr(STACK_0); /* (POP list) */
          STACK_0 = tmp;
        } else
          list = Cdr(popSTACK()); /* (POP list) */
        if (!nullp(tmp)) count ++;
      }
      if (need_new_list)
        VALUES2(listof(index),fixnum(count));
      else VALUES2(STACK_2,fixnum(count));
    } else {
      value1 = handle_isset(all,&readfds,&writefds,&errorfds);
      value2 = nullp(value1) ? Fixnum_0 : Fixnum_1;
      mv_count = 2;
    }
    end_system_call();
  }
 #else
  VALUES2(NIL,Fixnum_0);
 #endif
  skipSTACK(3);
}

/* the next three functions handle getsockopt()/setsockopt() calls
   for boolean, integer and timeval options respectively.
   each pushes one result on STACK */
#if defined(SO_DEBUG) || defined(SO_ACCEPTCONN) || defined(SO_BROADCAST) || defined(SO_REUSEADDR) || defined(SO_DONTROUTE) || defined(SO_KEEPALIVE) || defined(SO_ERROR) || defined(SO_OOBINLINE) || defined(SO_TYPE)
local void sock_opt_bool (SOCKET handle, int option, object value)
{
  var int val;
  var socklen_t len = sizeof(val);
  #ifdef HAVE_GETSOCKOPT
  if (-1 == getsockopt(handle,SOL_SOCKET,option,(char*)&val,&len))
    OS_error();
  pushSTACK(val ? T : NIL);
  if (!(eq(value,nullobj)))
  #endif
  {
    val = !nullp(value);
    if (-1 == setsockopt(handle,SOL_SOCKET,option,(char*)&val,len))
      OS_error();
  }
}
#endif
#if defined(SO_RCVBUF) || defined(SO_SNDBUF) || defined(SO_RCVLOWAT) || defined(SO_SNDLOWAT)
/* can trigger GC */
local maygc void sock_opt_int (SOCKET handle, int option, object value)
{
  var unsigned int val;
  var socklen_t len = sizeof(val);
  #ifdef HAVE_GETSOCKOPT
  if (-1 == getsockopt(handle,SOL_SOCKET,option,(char*)&val,&len))
    OS_error();
  pushSTACK(uint_to_I(val));
  if (!(eq(value,nullobj)))
  #endif
  {
    val = I_to_uint(check_uint(value));
    if (-1 == setsockopt(handle,SOL_SOCKET,option,(char*)&val,len))
      OS_error();
  }
}
#endif
#if defined(SO_RCVTIMEO) || defined(SO_SNDTIMEO)
/* can trigger GC */
local maygc void sock_opt_time (SOCKET handle, int option, object value)
{
  var struct timeval val;
  var socklen_t len = sizeof(val);
  #ifdef HAVE_GETSOCKOPT
  if (-1 == getsockopt(handle,SOL_SOCKET,option,(char *)&val,&len)) OS_error();
  if (val.tv_usec) {
    var double x = val.tv_sec + val.tv_sec*0.000001;
    var dfloatjanus t = *(dfloatjanus*)&x;
    pushSTACK(c_double_to_DF(&t));
  } else
    pushSTACK(fixnum(val.tv_sec));
  if (!(eq(value,nullobj)))
  #endif
  {
    sec_usec(value,unbound,&val);
    if (-1 == setsockopt(handle,SOL_SOCKET,option,(char*)&val,len))
      OS_error();
  }
}
#endif


/* (SOCKET-OPTIONS socket-stream &rest options)
   queries and sets socket options.
   returns the old value for each option:
   (SOCKET-OPTIONS s :so-keepalive :so-rcvlowat 10)
   will set :so-rcvlowat to 10 and return the current
   value of :so-keepalive and the old value of :so-rcvlowat */
LISPFUN(socket_options,seclass_default,1,0,rest,nokey,0,NIL) {
  var object socket = *(rest_args_pointer STACKop 1);
  var gcv_object_t *arg_p = rest_args_pointer;
  var int count = argcount;
  var SOCKET handle;
  stream_handles(socket,true,NULL,&handle,NULL);
  var gcv_object_t *old_STACK = STACK;
  while (count-->0) {
    check_STACK();
    var object kwd = NEXT(arg_p);
    var object arg = Next(arg_p);
    if (count && !(symbolp(arg) && keywordp(arg))) {
      (void)NEXT(arg_p);
      count--;
    } else
      arg = nullobj;
    begin_system_call();
    if (false)
      ;
   #ifdef SO_DEBUG
    else if (eq(kwd,S(Kso_debug)))
      sock_opt_bool(handle,SO_DEBUG,arg);
   #endif
   #ifdef SO_ACCEPTCONN
    else if (eq(kwd,S(Kso_acceptconn)))
      sock_opt_bool(handle,SO_ACCEPTCONN,arg);
   #endif
   #ifdef SO_BROADCAST
    else if (eq(kwd,S(Kso_broadcast)))
      sock_opt_bool(handle,SO_BROADCAST,arg);
   #endif
   #ifdef SO_REUSEADDR
    else if (eq(kwd,S(Kso_reuseaddr)))
      sock_opt_bool(handle,SO_REUSEADDR,arg);
   #endif
   #ifdef SO_DONTROUTE
    else if (eq(kwd,S(Kso_dontroute)))
      sock_opt_bool(handle,SO_DONTROUTE,arg);
   #endif
   #ifdef SO_KEEPALIVE
    else if (eq(kwd,S(Kso_keepalive)))
      sock_opt_bool(handle,SO_KEEPALIVE,arg);
   #endif
   #ifdef SO_ERROR
    else if (eq(kwd,S(Kso_error)))
      sock_opt_bool(handle,SO_ERROR,arg);
   #endif
   #ifdef SO_LINGER
    else if (eq(kwd,S(Kso_linger))) {
      struct linger val;
      var socklen_t len = sizeof(val);
      #ifdef HAVE_GETSOCKOPT
      if (-1 == getsockopt(handle,SOL_SOCKET,SO_LINGER,(char*)&val,&len))
        OS_error();
      if (val.l_onoff)
        pushSTACK(fixnum(val.l_linger));
      else
        pushSTACK(NIL);
      if (!(eq(arg,nullobj)))
      #endif
      { /* arg points to STACK so it is safe */
        if (eq(T,arg)) {
          val.l_onoff = 1;
        } else if (nullp(arg)) {
          val.l_onoff = 0;
        } else {
          val.l_onoff = 1;
          val.l_linger = I_to_uint(check_uint(arg));
        }
        if (-1 == setsockopt(handle,SOL_SOCKET,SO_LINGER,(char*)&val,len))
          OS_error();
      }
    }
   #endif
   #ifdef SO_OOBINLINE
    else if (eq(kwd,S(Kso_oobinline)))
      sock_opt_bool(handle,SO_OOBINLINE,arg);
   #endif
   #ifdef SO_TYPE
    else if (eq(kwd,S(Kso_type)))
      sock_opt_bool(handle,SO_TYPE,arg);
   #endif
   #ifdef SO_RCVBUF
    else if (eq(kwd,S(Kso_rcvbuf)))
      sock_opt_int(handle,SO_RCVBUF,arg);
   #endif
   #ifdef SO_SNDBUF
    else if (eq(kwd,S(Kso_sndbuf)))
      sock_opt_int(handle,SO_SNDBUF,arg);
   #endif
   #ifdef SO_RCVLOWAT
    else if (eq(kwd,S(Kso_rcvlowat)))
      sock_opt_int(handle,SO_RCVLOWAT,arg);
   #endif
   #ifdef SO_SNDLOWAT
    else if (eq(kwd,S(Kso_sndlowat)))
      sock_opt_int(handle,SO_SNDLOWAT,arg);
   #endif
   #ifdef SO_RCVTIMEO
    else if (eq(kwd,S(Kso_rcvtimeo)))
      sock_opt_time(handle,SO_RCVTIMEO,arg);
   #endif
   #ifdef SO_SNDTIMEO
    else if (eq(kwd,S(Kso_sndtimeo)))
      sock_opt_time(handle,SO_SNDTIMEO,arg);
   #endif
    else {
      pushSTACK(kwd);                   /* TYPE-ERROR slot DATUM */
      pushSTACK(O(type_socket_option)); /* TYPE-ERROR slot EXPECTED-TYPE */
      pushSTACK(O(type_socket_option));
      pushSTACK(kwd); pushSTACK(S(socket_options));
      error(type_error,GETTEXT("~S: argument ~S should be of type ~S."));
    }
    end_system_call();
  }
  #ifdef STACK_DOWN
  var uintL retval_count = old_STACK - STACK;
  #endif
  #ifdef STACK_UP
  var uintL retval_count = STACK - old_STACK;
  #endif
  STACK_to_mv(retval_count);
  skipSTACK(argcount+1);
}

LISPFUNN(socket_stream_port,1)
{ /* (SOCKET-STREAM-PORT socket-stream) */
  var object stream = test_socket_stream(STACK_0,false);
  VALUES1(TheStream(stream)->strm_socket_port);
  skipSTACK(1);
}

LISPFUNN(socket_stream_host,1)
{ /* (SOCKET-STREAM-HOST socket-stream) */
  var object stream = test_socket_stream(STACK_0,false);
  VALUES1(TheStream(stream)->strm_socket_host);
  skipSTACK(1);
}

typedef host_data_t * host_data_fetcher_t (SOCKET, host_data_t *, bool);
extern host_data_fetcher_t socket_getpeername, socket_getlocalname;

local maygc void publish_host_data (host_data_fetcher_t* func) {
  var bool resolve_p = missingp(STACK_0);
  var SOCKET sk;
  var host_data_t hd;
  var object hostname;
  if (uint_p(STACK_1)) sk = I_to_uint(STACK_1);
  else {
    STACK_1 = test_socket_stream(STACK_1,true);
    sk = SocketChannel(STACK_1);
  }
  skipSTACK(2);                 /* drop the arguments */
  begin_system_call();
  begin_blocking_call();
  if ((*func)(sk,&hd,resolve_p) == NULL) { end_blocking_call();ANSIC_error(); }
  end_blocking_call();
  end_system_call();
  if (hd.truename[0] == '\0') {
    hostname = asciz_to_string(hd.hostname,O(misc_encoding));
  } else {
    var DYNAMIC_ARRAY(tmp_str,char,strlen(hd.truename)+2+strlen(hd.hostname)+1+1);
    strcpy(tmp_str, hd.hostname);
    strcat(tmp_str, " (");
    strcat(tmp_str, hd.truename);
    strcat(tmp_str, ")");
    hostname = asciz_to_string(tmp_str,O(misc_encoding));
    FREE_DYNAMIC_ARRAY(tmp_str);
  }
  VALUES2(hostname, fixnum(hd.port));
}

LISPFUN(socket_stream_peer,seclass_default,1,1,norest,nokey,0,NIL)
{ /* (SOCKET-STREAM-PEER socket-stream [do-not-resolve-p]) */
  publish_host_data (&socket_getpeername);
}

LISPFUN(socket_stream_local,seclass_default,1,1,norest,nokey,0,NIL)
{ /* (SOCKET-STREAM-LOCAL socket-stream [do-not-resolve-p]) */
  publish_host_data (&socket_getlocalname);
}

#ifdef HAVE_SHUTDOWN

/* close a socket stream using shutdown(2)
 (SOCKET-STREAM-SHUTDOWN socket direction) */
local SOCKET get_handle_and_mark (object stream, uintB flag, int channel) {
  TheStream(stream)->strmflags &= ~flag;
  if (ChannelStream_buffered(stream)) {
    buffered_flush_everything(stream);
    return TheSocket(BufferedStream_channel(stream));
  } else
    return TheSocket(TheStream(stream)->strm_other[channel]);
}
LISPFUNN(socket_stream_shutdown,2) {
  var direction_t dir = check_direction(popSTACK());
  var int shutdown_how = -1;
  var bool rd_p = true;
  var bool wr_p = true;
  var uintB flag = 0;
  var SOCKET handle = -1;
  if (!integerp(STACK_0)) {
    test_socket_stream(STACK_0,false);
    rd_p = ((TheStream(STACK_0)->strmflags & strmflags_rd_B) != 0);
    wr_p = ((TheStream(STACK_0)->strmflags & strmflags_wr_B) != 0);
  } else /* raw socket */
    handle = (SOCKET)(I_to_uint(check_uint(STACK_0)));
  switch (dir) {
    case DIRECTION_PROBE:       /* INPUT/OUTPUT/IO */
      if (rd_p) {
        if (wr_p) value1 = S(Kio);
        else value1 = S(Kinput);
      } else {
        if (wr_p) value1 = S(Koutput);
        else value1 = NIL;
      }
      goto done;
    case DIRECTION_INPUT_IMMUTABLE: case DIRECTION_INPUT:
      if (!rd_p) {              /* not readable => done */
        value1 = NIL; goto done;
      } else {
        shutdown_how = SHUT_RD;
        flag = strmflags_rd_B;
      }
      break;
    case DIRECTION_OUTPUT:
      if (!wr_p) {              /* not writable => done */
        value1 = NIL; goto done;
      } else {
        shutdown_how = SHUT_WR;
        flag = strmflags_wr_B;
      }
      break;
    case DIRECTION_IO:
      shutdown_how = SHUT_RDWR;
      flag = strmflags_wr_B | strmflags_rd_B;
      break;
    default: NOTREACHED;
  }
  if (streamp(STACK_0)) {
    switch (TheStream(STACK_0)->strmtype) {
      case strmtype_twoway_socket:
        switch (dir) {
          case DIRECTION_OUTPUT:
            TheStream(STACK_0)->strmflags &= ~strmflags_wr_B;
            handle =
              get_handle_and_mark(TheStream(STACK_0)->strm_twoway_socket_output,
                                  strmflags_wr_B,strm_ochannel_position);
            break;
          case DIRECTION_IO:
            TheStream(STACK_0)->strmflags &= ~strmflags_wr_B;
            get_handle_and_mark(TheStream(STACK_0)->strm_twoway_socket_output,
                                strmflags_wr_B,strm_ochannel_position);
            /*FALLTHROUGH*/
          case DIRECTION_INPUT: case DIRECTION_INPUT_IMMUTABLE:
            TheStream(STACK_0)->strmflags &= ~strmflags_rd_B;
            handle =
              get_handle_and_mark(TheStream(STACK_0)->strm_twoway_socket_input,
                                  strmflags_rd_B,strm_ichannel_position);
            break;
          default: NOTREACHED;
        }
        break;
      case strmtype_socket:
        handle = get_handle_and_mark(STACK_0,flag,strm_ichannel_position);
      break;
      default: NOTREACHED;
    }
  }
  begin_system_call();
  begin_blocking_call();
  if (shutdown(handle,shutdown_how)) {
    end_blocking_call();
    ANSIC_error();
  }
  end_blocking_call();
  end_system_call();
  { value1 = NIL; }
 done:
  skipSTACK(1);
  mv_count = 1;
}
#endif

#endif  /* SOCKET_STREAMS */


/* Streams in general
   ================== */

#if defined(WIN32_NATIVE)
/* http://msdn.microsoft.com/en-us/library/ms804359.aspx */
typedef NTSTATUS (__stdcall *QueryInformationFile_t)
(IN HANDLE FileHandle, OUT PIO_STATUS_BLOCK IoStatusBlock,
 OUT PVOID FileInformation, IN ULONG Length,
 IN FILE_INFORMATION_CLASS FileInformationClass);
static QueryInformationFile_t qif = (QueryInformationFile_t) -1;
static QueryInformationFile_t get_qif (void) {
  if (qif == NULL) return qif;
  var HMODULE ntdll = LoadLibrary("ntdll.dll");
  if (ntdll == NULL) return (qif = NULL);
  return (qif = (QueryInformationFile_t)
          GetProcAddress(ntdll, "NtQueryInformationFile"));
}
#endif

/* UP: find out whether the direction is compatible with the handle
 > fd: file handle
 > dir: direction
 > true is the direction is compatible with the handle */
local bool handle_direction_compatible (Handle fd, direction_t dir) {
 #if defined(UNIX)
  begin_blocking_system_call();
  var int fcntl_flags = fcntl(fd,F_GETFL,0);
  end_blocking_system_call();
  if (fcntl_flags < 0)
    return false;           /* closed handle? errno is probably EBADF */
  var bool ret =
    !(    (READ_P(dir) && ((fcntl_flags & O_ACCMODE) == O_WRONLY))
      || (WRITE_P(dir) && ((fcntl_flags & O_ACCMODE) == O_RDONLY)));
  DEBUG_OUT(("\nhandle_direction_compatible(%d,%d): 0x%x => %d\n",
             fd,dir,fcntl_flags,ret));
  return ret;
 #elif defined(WIN32_NATIVE)
  var bool ret = true;          /* assume compatibility */
  /* http://groups.google.com/group/microsoft.public.win32.programmer.kernel/browse_thread/thread/a446be4fb332aeba */
  begin_blocking_system_call();
  switch (GetFileType(fd)) {
    case FILE_TYPE_DISK: {
      var QueryInformationFile_t qif = get_qif();
      if (qif != NULL) {
        var IO_STATUS_BLOCK iosb;
        var FILE_ACCESS_INFORMATION fai;
        var NTSTATUS s = qif(fd,&iosb,(void*)&fai,sizeof(fai),
                             FileAccessInformation);
        ret = (s == STATUS_SUCCESS
               && (!READ_P(dir) || fai.AccessFlags & FILE_READ_DATA)
               && (!WRITE_P(dir) || fai.AccessFlags & FILE_WRITE_DATA));
        DEBUG_OUT(("\nhandle_direction_compatible(%d,%d)D: 0x%x 0x%x => %d\n",
                   fd,dir,s,fai.AccessFlags,ret));
      }
    } break;
    case FILE_TYPE_CHAR: if (READ_P(dir)) {
      var DWORD nevents = -1, nr = 0;
      if (GetNumberOfConsoleInputEvents(fd,&nevents)) { /* It's a console. */
        var INPUT_RECORD ir;
        ret = PeekConsoleInput(fd,&ir,1,&nr);
      } else switch (GetLastError()) {
          case ERROR_INVALID_HANDLE: case ERROR_ACCESS_DENIED:
          case ERROR_INVALID_FUNCTION: ret = false;
      }
      DEBUG_OUT(("\nhandle_direction_compatible(%d,%d)C: %d %d => %d (%d)\n",
                 fd,dir,nevents,nr,ret,GetLastError()));
    } break;
    case FILE_TYPE_PIPE: if (READ_P(dir)) {
      var DWORD nbytes;
      ret = PeekNamedPipe(fd,NULL,0,NULL,&nbytes,NULL);
      DEBUG_OUT(("\nhandle_direction_compatible(%d,%d)P: %d => %d (%d)\n",
                 fd,dir,nbytes,ret,GetLastError()));
    } break;
    case FILE_TYPE_REMOTE:
      break;                    /* assume compatibility */
    case FILE_TYPE_UNKNOWN:
      /* GetFileType failed => handle was invalid */
      if (GetLastError() != NO_ERROR) ret = false;
  }
  end_blocking_system_call();
  return ret;
 #else
  return true;                  /* assume compatibility */
 #endif
}

/* UP: find the pathname corresponding to the given handle
 > fd: file handle
 < pathname or NIL
 can trigger GC */
local maygc object handle_pathname (Handle fd) {
  /* Most UNIX platforms have /dev/fd/[012] pseudo-files. */
  /* AIX has /proc/<pid>/fd/[012] pseudo-files but they have zero permissions
     and are therefore not usable for any purpose. */
 #if defined(UNIX) && !(defined(UNIX_AIX) || defined(UNIX_HPUX) || defined(UNIX_BEOS) || defined(UNIX_HAIKU) || defined(UNIX_MINIX))
  var char buf[20];
  begin_system_call();
  sprintf(buf,"/dev/fd/%d",fd);
  end_system_call();
  pushSTACK(ascii_to_string(buf)); funcall(L(pathname),1);
  return value1;
 #elif defined(WIN32_NATIVE)
  var NTSTATUS s = ~STATUS_SUCCESS;
  var char wbuf[MAXPATHLEN*sizeof(WCHAR) + sizeof(ULONG)];
  begin_blocking_system_call();
  switch (GetFileType(fd)) {
    case FILE_TYPE_DISK: {
      var QueryInformationFile_t qif = get_qif();
      if (qif != NULL) {
        var IO_STATUS_BLOCK iosb;
        s = qif(fd,&iosb,(void*)wbuf,sizeof(wbuf),FileNameInformation);
      }
    } break;
    case FILE_TYPE_CHAR: case FILE_TYPE_PIPE: case FILE_TYPE_REMOTE:
    case FILE_TYPE_UNKNOWN: break;
  }
  end_blocking_system_call();
  if (s == STATUS_SUCCESS) {
    var FILE_NAME_INFORMATION *fni = (FILE_NAME_INFORMATION*)&wbuf;
    var char abuf[2 * MAXPATHLEN];
    var int n = WideCharToMultiByte(CP_ACP,0,fni->FileName,
                                    fni->FileNameLength/sizeof(WCHAR),
                                    abuf,2 * MAXPATHLEN,NULL,NULL);
    pushSTACK(n_char_to_string(abuf,n,O(pathname_encoding)));
    funcall(L(pathname),1);
    return value1;
  } else return NIL;
 #else
  return NIL;
 #endif
}

/* Create a stream based on a handle
 can trigger GC */
local maygc object handle_to_stream (Handle fd, object direction, object buff_p,
                                     object ext_fmt, object eltype) {
  var direction_t dir;
  pushSTACK(NIL); /* Filename */
  pushSTACK(NIL); /* Truename */
  pushSTACK(buff_p);
  pushSTACK(ext_fmt);
  pushSTACK(eltype);
  pushSTACK(allocate_handle(handle_dup(fd)));
  dir = check_direction(direction);
  STACK_5 = handle_pathname(fd);
  if (!handle_direction_compatible(fd,dir)) {
    var condition_t errortype = nullp(STACK_5)
      ? (pushSTACK(STACK_0), error_condition)
      : (pushSTACK(STACK_5), /* FILE-ERROR slot PATHNAME */
         pushSTACK(STACK_0), file_error);
    pushSTACK(direction);
    error(errortype,GETTEXT("Invalid direction ~S for accessing ~S"));
  }
  return make_file_stream(dir,false,dir == DIRECTION_IO);
}

LISPFUNN(stream_handles,1)
{ /* (STREAM-HANDLES stream) */
  var SOCKET in_sock=INVALID_SOCKET, out_sock=INVALID_SOCKET;
  stream_handles(popSTACK(),false,NULL,&in_sock,&out_sock);
  VALUES2(in_sock  == INVALID_SOCKET ? NIL : fixnum(in_sock),
          out_sock == INVALID_SOCKET ? NIL : fixnum(out_sock));
}

LISPFUN(make_stream,seclass_default,1,0,norest,key,4,
        (kw(direction),kw(element_type),kw(external_format),kw(buffered)) )
{
  var Handle fd;
 restart_make_stream:
  if (uint_p(STACK_4)) {
    fd = (Handle)I_to_uint(STACK_4);
  } else if (eq(STACK_4,S(Kinput))) {
    fd = stdin_handle;
    if (missingp(STACK_3)) STACK_3 = S(Kinput);
  } else if (eq(STACK_4,S(Koutput))) {
    fd = stdout_handle;
    if (missingp(STACK_3)) STACK_3 = S(Koutput);
  } else if (eq(STACK_4,S(Kerror))) {
    fd = stderr_handle;
    if (missingp(STACK_3)) STACK_3 = S(Koutput);
  } else if (streamp(STACK_4)) {
    var direction_t dir = check_direction(STACK_3);
    fd = stream_lend_handle(&STACK_4,READ_P(dir),NULL);
  } else {
    pushSTACK(NIL); /* no PLACE */
    pushSTACK(S(Kerror)); pushSTACK(S(Koutput)); pushSTACK(S(Kinput));
    pushSTACK(STACK_(4+4)); pushSTACK(TheSubr(subr_self)->name);
    check_value(error_condition,GETTEXT("~S: ~S should be a handle, handle stream, or one of ~S, ~S, ~S"));
    STACK_4 = value1;
    goto restart_make_stream;
  }
  VALUES1(handle_to_stream(fd,STACK_3,STACK_0,STACK_1,STACK_2));
  skipSTACK(5);
}

#undef READ_P
#undef WRITE_P

/* Allocates the equivalent of the C stream stdin.
 can trigger GC */
local inline maygc object make_standard_input_file_stream (void) {
  if (!handle_direction_compatible(stdin_handle,DIRECTION_INPUT))
    /* no stdin: nohup or embedded */
    return make_concatenated_stream(NIL); /* empty stream */
  /* This uses the external-format :default, not O(terminal_encoding),
     because this stream is used when *terminal-io* is not interactive. */
  return handle_to_stream(stdin_handle,S(Kinput),S(Kdefault),S(Kdefault),
                          S(character));
}

/* Allocates the equivalent of the C stream stdout/stderr.
 > handle : file descriptor (stdout_handle or stderr_handle)
 can trigger GC */
local inline maygc object make_standard_output_file_stream (Handle handle) {
  if (!handle_direction_compatible(handle,DIRECTION_OUTPUT))
    /* no stdout/stderr: nohup or embedded */
    return make_broadcast_stream(NIL); /* empty stream */
  /* This uses the external-format :default, not O(terminal_encoding),
     because this stream is used when *terminal-io* is not interactive. */
  return handle_to_stream(handle,S(Koutput),S(Kdefault),S(Kdefault),
                          S(character));
}

/* It is important to allocate each of the standard_output_file_stream,
   standard_error_file_stream only _once_, because otherwise FRESH-LINE on one
   of these streams would not see that some output has been sent to another
   of these streams and would therefore not print a newline when it should.
   (FRESH-LINE is only allowed to err in the other direction: It may output
   a newline although it is not needed.)

 Returns the equivalent of the C stream stdin.
 can trigger GC */
local maygc object get_standard_input_file_stream (void) {
  if (nullp(O(standard_input_file_stream)))
    O(standard_input_file_stream) = make_standard_input_file_stream();
  return O(standard_input_file_stream);
}

/* Returns the equivalent of the C stream stdout.
 can trigger GC */
local maygc object get_standard_output_file_stream (void) {
  #if defined(UNIX) || defined(WIN32_NATIVE)
  /* On these systems make_terminal_stream() uses stdout_handle. */
  var object terminal_stream = Symbol_value(S(terminal_io)); /* *TERMINAL-IO* */
  if (builtin_stream_p(terminal_stream)
      && (TheStream(terminal_stream)->strmflags & strmflags_open_B)
      && (TheStream(terminal_stream)->strmflags & strmflags_wr_ch_B)
      && TheStream(terminal_stream)->strmtype == strmtype_terminal) {
    /* For FRESH-LINE to work correctly, we must avoid that *TERMINAL-IO* and
     the stream returned by this function have a different wr_ch_lpos field.
     Therefore we just return (MAKE-SYNONYM-STREAM (QUOTE *TERMINAL-IO*)). */
    return make_synonym_stream(S(terminal_io));
  }
  #endif
  if (nullp(O(standard_output_file_stream)))
    O(standard_output_file_stream) =
      make_standard_output_file_stream(stdout_handle);
  return O(standard_output_file_stream);
}

/* Returns the equivalent of the C stream stderr.
 can trigger GC */
local maygc object get_standard_error_file_stream (void) {
  #if 0
  /* On these systems make_terminal_stream() uses stderr_handle. */
  var object terminal_stream = Symbol_value(S(terminal_io)); /* *TERMINAL-IO* */
  if (builtin_stream_p(terminal_stream)
      && (TheStream(terminal_stream)->strmflags & strmflags_open_B)
      && (TheStream(terminal_stream)->strmflags & strmflags_wr_ch_B)
      && TheStream(terminal_stream)->strmtype == strmtype_terminal) {
    /* For FRESH-LINE to work correctly, we must avoid that *TERMINAL-IO* and
     the stream returned by this function have a different wr_ch_lpos field.
     Therefore we just return (MAKE-SYNONYM-STREAM (QUOTE *TERMINAL-IO*)). */
    return make_synonym_stream(S(terminal_io));
  }
  #endif
  if (nullp(O(standard_error_file_stream)))
    O(standard_error_file_stream) =
      (same_handle_p(stderr_handle,stdout_handle)
       ? get_standard_output_file_stream()
       : make_standard_output_file_stream(stderr_handle));
  return O(standard_error_file_stream);
}

/* UP: Returns the default value for *terminal-io*.
 can trigger GC */
local maygc object make_terminal_io (void) {
  /* If stdin or stdout is a file, use a buffered stream instead of an
   unbuffered terminal stream. For the ud2cd program used as filter,
   this reduces the runtime on Solaris from 165 sec to 47 sec. */
  var bool stdin_terminal =
    handle_direction_compatible(stdin_handle,DIRECTION_INPUT)
    && !regular_or_pipe_handle_p(stdin_handle);
  var bool stdout_terminal =
    handle_direction_compatible(stdout_handle,DIRECTION_OUTPUT)
    && !regular_or_pipe_handle_p(stdout_handle);
  DEBUG_OUT(("\nmake_terminal_io: %d %d\n",stdin_terminal,stdout_terminal));
  /* note that if a stream is incompatible, handle_direction_compatible
     will be called again by get_standard_*_file_stream;
     this is an extra system call on startup; should not be a big deal */
  if (!stdin_terminal || !stdout_terminal) {
    var object istream = stdin_terminal ? /* Input side */
      make_terminal_stream() : get_standard_input_file_stream();
    pushSTACK(istream);
    var object ostream = stdout_terminal ? /* Output side */
      make_terminal_stream() : get_standard_output_file_stream();
    /* Build a two-way-stream: */
    return make_twoway_stream(popSTACK(),ostream);
  }
  return make_terminal_stream();
}

/* UP: Returns the input side of *TERMINAL-IO*.
 Defaults to a (make-synonym-stream '*terminal-io*).
 > preallocated_default: (make-synonym-stream '*terminal-io*) or unbound
 < result: a stream that can be used for *STANDARD-INPUT*
 can trigger GC - if preallocated_default is unbound */
local /*maygc*/ object terminal_io_input_stream (object preallocated_default) {
  GCTRIGGER_IF(!boundp(preallocated_default), GCTRIGGER());
  var object terminal_io = Symbol_value(S(terminal_io));
  /* Optimization: Extract the input side if possible. */
  if (stream_twoway_p(terminal_io))
    return TheStream(terminal_io)->strm_twoway_input;
  /* General case: Use a synonym stream. */
  return (boundp(preallocated_default) ? preallocated_default :
          make_synonym_stream(S(terminal_io)));
}

/* UP: Returns the output side of *TERMINAL-IO*.
 Defaults to a (make-synonym-stream '*terminal-io*).
 > preallocated_default: (make-synonym-stream '*terminal-io*) or unbound
 < result: a stream that can be used for *STANDARD-OUTPUT*
 can trigger GC - if preallocated_default is unbound */
local /*maygc*/ object terminal_io_output_stream (object preallocated_default) {
  GCTRIGGER_IF(!boundp(preallocated_default), GCTRIGGER());
  var object terminal_io = Symbol_value(S(terminal_io));
  /* Optimization: Extract the output side if possible. */
  if (stream_twoway_p(terminal_io))
    return TheStream(terminal_io)->strm_twoway_output;
  /* General case: Use a synonym stream. */
  return (boundp(preallocated_default) ? preallocated_default :
          make_synonym_stream(S(terminal_io)));
}

#ifdef GNU_READLINE
local int next_line_virtual(int,int);
local int previous_line_virtual(int,int);
local int get_col (void) {
  var int col = rl_point;
  while(col && rl_line_buffer[col]!='\n') col--;
  return rl_point - col;
}
local int next_line_virtual (int count, int key) {
  if (count > 0) {
    var int col = get_col();
    var int len = strlen(rl_line_buffer);
    while (count--) {
      while (rl_point<len && rl_line_buffer[rl_point]!='\n') rl_point++;
      if (rl_point<len) rl_point++;
    }
    rl_point += col-1;
    if (rl_point>=len) rl_point = len-1;
  } else if (count < 0)
    return previous_line_virtual(-count,key);
  /* else rl_variable_dumper(1); */
  return 0;
}
local int previous_line_virtual (int count, int key) {
  if (count > 0) {
    var int col = get_col();
    do {
      while(rl_point && rl_line_buffer[rl_point]!='\n') rl_point--;
      if (rl_point) rl_point--;
      else return 0;
    } while (count--);
    rl_point += col+1;
  } else if (count < 0)
    return next_line_virtual(-count,key);
  /* else rl_variable_dumper(1); */
  return 0;
}
#endif

/* UP: Initializes the stream-variables.
 init_streamvars(batch_p);
 > batch_p: Flag, whether *standard-input*, *standard-output*, *error-output*
            should be initialized to the C stdio handle-streams
            (deviates from the standard)
 can trigger GC */
global maygc void init_streamvars (bool batch_p) {
 #ifdef GNU_READLINE
  begin_call();
  #if HAVE_DECL_RL_READLINE_NAME
  { /* we could have used a string literal, but then readline:readline-name
       would have to be read-only because one cannot free() a string literal */
    var char* name = (char*)malloc(6); strcpy(name,"CLISP");
    rl_readline_name = name;
  }
  #endif
  if (ilisp_mode) {
    /* Simulate the following instruction in .inputrc:
       Control-i: self-insert */
    rl_bind_key(CTRL('I'),rl_named_function("self-insert"));
  }
  rl_attempted_completion_function = &lisp_completion_matches;
  rl_completion_entry_function = &lisp_completion_more;
  rl_variable_bind("comment-begin",";");
  rl_variable_bind("blink-matching-paren","on");
  /* rl_set_paren_blink_timeout(1000000);  == 1 sec [default 0.5 sec] */
  rl_add_defun("next-line-virtual",&next_line_virtual,META('n'));
  rl_add_defun("previous-line-virtual",&previous_line_virtual,META('p'));
  end_call();
 #endif  /* GNU_READLINE */
 #ifdef MULTITHREAD
  /* clear per thread binding */
  #define def_var(sym,val) do {                                         \
    define_variable(sym,val);                                           \
    current_thread()->_ptr_symvalues[TheSymbol(sym)->tls_index]=SYMVALUE_EMPTY;\
  } while(0)
  #else
  #define def_var(sym,val) define_variable(sym,val)
  #endif
  {
    var object stream = make_terminal_io();
    def_var(S(terminal_io),stream);  /* *TERMINAL-IO* */
  }
  {
    var object stream = make_synonym_stream(S(terminal_io));
    def_var(S(query_io),stream);         /* *QUERY-IO* */
    def_var(S(debug_io),stream);         /* *DEBUG-IO* */
    def_var(S(trace_output),stream);     /* *TRACE-OUTPUT* */
    def_var(S(standard_input),           /* *STANDARD-INPUT* */
                    batch_p ? get_standard_input_file_stream()
                    : terminal_io_input_stream(stream));
    def_var(S(standard_output),          /* *STANDARD-OUTPUT* */
                    batch_p ? get_standard_output_file_stream()
                    : terminal_io_output_stream(stream));
    def_var(S(error_output),             /* *ERROR-OUTPUT* */
                    batch_p ? get_standard_error_file_stream()
                    : (object)Symbol_value(S(standard_output)));
  }
  #ifdef KEYBOARD
  /* Initialize the *KEYBOARD-INPUT* stream. This can fail in some cases,
   therefore we do it after the standard streams are in place, so that
   the user will get a reasonable error message. */
  #ifdef UNIX
  /* Building the keyboard stream is a costly operation. Delay it
   until we really need it. */
  def_var(S(keyboard_input),NIL);     /* *KEYBOARD-INPUT* */
  #else
  {
    var object stream = make_keyboard_stream();
    def_var(S(keyboard_input),stream); /* *KEYBOARD-INPUT* */
  }
  #endif
  #endif
  #undef def_var
}

/* Returns error-message, if the value of the symbol sym is not a stream. */
local void error_value_stream (object sym) {
  /* Possibly repair before the error-message
   (initialized as in init_streamvars resp. init_pathnames): */
  var object stream;
  pushSTACK(sym); /* save sym */
  #ifdef KEYBOARD
  if (eq(sym,S(keyboard_input))) { /* Keyboard-Stream as Default */
    stream = make_keyboard_stream();
  } else
  #endif
  if (eq(sym,S(terminal_io))) {
    /* Terminal-Stream as Default
     (Use make_terminal_stream() here, not make_terminal_io(), because
     that might have been a file stream and got closed when the disk
     became full.) */
    stream = make_terminal_stream();
  } else if (eq(sym,S(query_io)) || eq(sym,S(debug_io))
             || eq(sym,S(error_output)) || eq(sym,S(trace_output))) {
    /* Synonym-Stream to *TERMINAL-IO* as Default */
    stream = make_synonym_stream(S(terminal_io));
  } else if (eq(sym,S(standard_input))) {
    stream = terminal_io_input_stream(unbound);
  } else if (eq(sym,S(standard_output))) {
    stream = terminal_io_output_stream(unbound);
  } else {
    /* other Symbol, not fixable -> instant error-message: */
    pushSTACK(Symbol_value(sym)); /* TYPE-ERROR slot DATUM */
    pushSTACK(S(stream));         /* TYPE-ERROR slot EXPECTED-TYPE */
    pushSTACK(Symbol_value(sym)); /* variable value */
    pushSTACK(sym); /* variable */
    pushSTACK(TheSubr(subr_self)->name);
    if (!streamp(Symbol_value(sym))) {
      error(type_error,GETTEXT("~S: The value of ~S is not a stream: ~S"));
    } else {
      error(type_error,GETTEXT("~S: The value of ~S is not an appropriate stream: ~S"));
    }
  }
  sym = popSTACK();
  /* repair finished: stream is the new value of sym. */
  var object oldvalue = Symbol_value(sym);
  Symbol_value(sym) = stream;
  pushSTACK(oldvalue);  /* TYPE-ERROR slot DATUM */
  pushSTACK(S(stream)); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(stream); /* new variable value */
  pushSTACK(oldvalue); /* old variable value */
  pushSTACK(sym); /* Variable */
  pushSTACK(TheSubr(subr_self)->name);
  error(type_error,GETTEXT("~S: The value of ~S was not an appropriate stream: ~S. It has been changed to ~S."));
}

#ifdef GNU_READLINE
/* Auxiliary functions for the GNU ReadLine Library: */
local _Noreturn void rl_memory_abort (void) {
  /* when there is no more memory for the ReadLine
   drop it and replace the *TERMINAL-IO* with another
   terminal-stream without ReadLine */
  rl_deprep_terminal(); /* cancel all ioctl()s */
  begin_rl_callback(); /* reset STACK to a reasonable value */
  rl_gnu_readline_p = false;
  Symbol_value(S(terminal_io)) = make_terminal_stream();
  error(storage_condition,GETTEXT("readline library: out of memory."));
}

local char* xmalloc (int count) {
  var char* tmp = (char*)malloc(count);
  if (tmp) return tmp;
  else     rl_memory_abort();
}
#endif

LISPFUNNR(built_in_stream_open_p,1)
{ /* (SYS::BUILT-IN-STREAM-OPEN-P stream) */
  var object stream = popSTACK();
  CHECK_builtin_stream(stream);
  VALUES_IF(TheStream(stream)->strmflags & strmflags_open_B); /* open? */
}

LISPFUNNR(input_stream_p,1)
{ /* (INPUT-STREAM-P stream), CLTL p. 332, CLtL2 p. 505 */
  var object stream = check_stream(popSTACK());
  VALUES_IF(input_stream_p(stream));
}

LISPFUNNR(output_stream_p,1)
{ /* (OUTPUT-STREAM-P stream), CLTL p. 332, CLtL2 p. 505 */
  var object stream = check_stream(popSTACK());
  VALUES_IF(output_stream_p(stream));
}

/* (SYS::STREAM-ELEMENT-TYPE-EQ T0 T1)
 this function is used for `stream-element-type' type merging
 it does not handle types not seen as stream element types
 it should be reasonably fast, so we are not using `canonicalize-type'
 (defun stream-element-type-eq (t0 t1)
   (or (eq t0 t1)
       (and (consp t0) (consp t1)
            (eq (car t0) (car t1))
            (member (car t0) '(unsigned-byte signed-byte))
            (eql (cadr t0) (cadr t1))))) */
LISPFUNN(stream_element_type_eq,2) {
  var object t0 = popSTACK();
  var object t1 = popSTACK();
  VALUES_IF(eq(t0,t1)
            || (consp(t0) && consp(t1) && eq(Car(t0),Car(t1))
                && (eq(Car(t0),S(unsigned_byte)) || eq(Car(t0),S(signed_byte)))
                && consp(Cdr(t0)) && consp(Cdr(t1))
                && eql(Car(Cdr(t0)),Car(Cdr(t1)))));
}

/* combine several stream-element-type into one, using OR
 types are on the STACK (numarg or them)
 remove numarg elements from STACK
 can trigger GC */
local maygc object combine_stream_element_types (uintL numarg) {
  var uintL count = numarg;
  var gcv_object_t *arg_ptr = &STACK_0;
  do { /* remove OR / listify */
    if (consp(*arg_ptr) && eq(Car(*arg_ptr),S(or)))
      *arg_ptr = Cdr(*arg_ptr);
    else if (!nullp(*arg_ptr)) {
      var object tmp = allocate_cons();
      Car(tmp) = *arg_ptr;
      *arg_ptr = tmp;
    }
    (void)BEFORE(arg_ptr);
  } while (--count);
  funcall(L(append),numarg);
  pushSTACK(value1); pushSTACK(S(Ktest));
  pushSTACK(L(stream_element_type_eq));
  funcall(L(remove_duplicates),3);
  if (consp(value1)) {
    if (!nullp(Cdr(value1))) {  /* (PUSH 'OR LIST) */
      pushSTACK(value1);
      var object tmp = allocate_cons();
      Car(tmp) = S(or); Cdr(tmp) = popSTACK();
      return tmp;
    } else return Car(value1); /* single type, no OR */
  } else return value1; /* NIL */
}

/* (SYS::BUILT-IN-STREAM-ELEMENT-TYPE stream)
 returns CHARACTER or INTEGER or T
 or (more specific) (UNSIGNED-BYTE n) or (SIGNED-BYTE n). */
LISPFUNNR(built_in_stream_element_type,1) {
  var object stream = popSTACK();
  var object eltype;
  CHECK_builtin_stream(stream);
 start:
  switch (TheStream(stream)->strmtype) {
    case strmtype_synonym: /* Synonym-Stream: follow further */
      resolve_as_synonym(stream);
      if (builtin_stream_p(stream))
        goto start;
      else { /* Call (STREAM-ELEMENT-TYPE stream): */
        pushSTACK(stream); funcall(S(stream_element_type),1);
        return;
      }
    case strmtype_broad: /* issue 021 */
      stream = broadcast_stream_last(stream);
      if (streamp(stream)) {
        pushSTACK(stream); funcall(S(stream_element_type),1);
        return;
      } else eltype = T; /* empty stream list */
      break;
    /* first the stream-types with restricted element-types: */
    case strmtype_str_out: {    /* could be (VECTOR NIL) */
      eltype = (((Iarray_flags(TheStream(stream)->strm_str_out_string)
                  & arrayflags_atype_mask) == Atype_NIL)
                ? NIL : S(character));
    } break;
    case strmtype_str_in:
    case strmtype_str_push:
    case strmtype_pphelp:
    case strmtype_buff_in:
    case strmtype_buff_out:
      /* CHARACTER */
      { eltype = S(character); } break;
   #ifdef KEYBOARD
    case strmtype_keyboard:
      { eltype = T; } break;
   #endif
    case strmtype_terminal:
   #ifdef SCREEN
    case strmtype_window:
   #endif
   #ifdef PRINTER
    case strmtype_printer:
   #endif
      /* CHARACTER */
      { eltype = S(character); } break;
    case strmtype_file:
   #ifdef PIPES
    case strmtype_pipe_in:
    case strmtype_pipe_out:
   #endif
   #ifdef X11SOCKETS
    case strmtype_x11socket:
   #endif
   #ifdef SOCKET_STREAMS
    case strmtype_socket:
   #endif
      /* CHARACTER or ([UN]SIGNED-BYTE n) */
      eltype = TheStream(stream)->strm_eltype; break;
   #ifdef SOCKET_STREAMS
    case strmtype_twoway_socket:
      /* CHARACTER or ([UN]SIGNED-BYTE n) */
      stream = TheStream(stream)->strm_twoway_socket_input;
      eltype = TheStream(stream)->strm_eltype; break;
   #endif
    case strmtype_twoway:
    case strmtype_echo: {
      /* (let ((itype (stream-element-type (two-way-input-stream stream)))
             (otype (stream-element-type (two-way-output-stream stream))))
         ; Simplify `(OR ,itype ,otype)
         (cond ((eq itype 'NIL) otype)
               ((eq otype 'NIL) itype)
               ((eq itype otype) itype)
               (t
                 (cons 'OR
                   (remove-duplicates
                     (append
                       (if (and (consp itype) (eq (car itype) 'OR))
                         (cdr itype)
                         (list itype))
                       (if (and (consp otype) (eq (car otype) 'OR))
                         (cdr otype)
                         (list otype))))))))) */
        pushSTACK(TheStream(stream)->strm_twoway_input);
        pushSTACK(TheStream(stream)->strm_twoway_output);
        pushSTACK(STACK_1); funcall(S(stream_element_type),1);
        STACK_1 = value1; funcall(S(stream_element_type),1);
        pushSTACK(value1);
        var object itype = STACK_1;
        var object otype = STACK_0;
        if (nullp(itype)) {
          eltype = otype;
          skipSTACK(2);
        } else if (nullp(otype) || eq(itype,otype)) {
          eltype = itype;
          skipSTACK(2);
        } else
          eltype = combine_stream_element_types(2);
    } break;
    case strmtype_concat: {
      var uintL count = 0;
      var gcv_object_t *stream_list_;
      pushSTACK(TheStream(stream)->strm_concat_list);
      stream_list_ = &STACK_0;
      while (consp(*stream_list_)) {
        pushSTACK(Car(*stream_list_)); funcall(S(stream_element_type),1);
        pushSTACK(value1); count++;
        *stream_list_ = Cdr(*stream_list_);
      }
      switch (count) {
        case 0: { eltype = NIL; skipSTACK(1); } break; /* no streams */
        case 1: { eltype = STACK_0; skipSTACK(2); } break;
        default: eltype = combine_stream_element_types(count); skipSTACK(1);
      }
    } break;
      /* then the general streams: */
   #ifdef GENERIC_STREAMS
    case strmtype_generic:
   #endif
    default: {
      var uintB flags = TheStream(stream)->strmflags;
      if (flags & strmflags_by_B) {
        if (flags & strmflags_ch_B) { /* (OR CHARACTER INTEGER) */
          pushSTACK(S(or)); pushSTACK(S(character)); pushSTACK(S(integer));
          eltype = listof(3);
        } else eltype = S(integer);
      } else
        if (flags & strmflags_ch_B) eltype = S(character);
        else eltype = NIL;
    }
      break;
  }
  VALUES1(eltype);
}

/* UP: reset the stream for the eltype and flush out the missing LF.
 IF the stream is unbuffered, AND ignore_next_LF is true, THEN
 this can block (we will try to read the next LF) and trigger GC
 > stream: a channel-stream
 < result: the same stream
 can trigger GC */
local maygc object stream_reset_eltype (object stream, decoded_el_t* eltype_) {
  if (ChannelStream_buffered(stream)) {
    fill_pseudofuns_buffered(stream,eltype_);
  } else {
    if (ChannelStream_ignore_next_LF(stream)
        && eq(TheStream(stream)->strm_eltype,S(character))) {
      pushSTACK(stream);
      ChannelStream_ignore_next_LF(stream) = false; /* do not skip LF! */
      var object ch = read_char(&STACK_0);
      if (!eq(ch,eof_value) && !chareq(char_code(ch),ascii(LF)))
        unread_char(&STACK_0,ch);
      stream = popSTACK();
    }
    fill_pseudofuns_unbuffered(stream,eltype_);
  }
  return stream;
}

/* (SYSTEM::BUILT-IN-STREAM-SET-ELEMENT-TYPE stream element-type) */
LISPFUNN(built_in_stream_set_element_type,2) {
  var object stream = STACK_1;
  var decoded_el_t eltype;
  CHECK_builtin_stream(stream);
  test_eltype_arg(&STACK_0,&eltype);
  pushSTACK(canon_eltype(&eltype));
  /* Stack contents: stream, element-type, canon-element-type. */
  stream = STACK_2;
 start:
  switch (TheStream(stream)->strmtype) {
    case strmtype_synonym: /* Synonym-Stream: follow further */
      resolve_as_synonym(stream);
      if (builtin_stream_p(stream))
        goto start;
      else { /* Call ((SETF STREAM-ELEMENT-TYPE) element-type stream): */
        pushSTACK(STACK_1); pushSTACK(stream);
        funcall(O(setf_stream_element_type),2);
        return;
      }
    case strmtype_broad:        /* Recurse. */
      check_SP(); check_STACK();
      pushSTACK(TheStream(stream)->strm_broad_list);
      while (consp(STACK_0)) {
        pushSTACK(Car(STACK_0)); pushSTACK(STACK_(1+2));
        C_built_in_stream_set_element_type();
        STACK_0 = Cdr(STACK_0);
      }
      skipSTACK(1);
      break;
    case strmtype_concat:       /* Recurse. */
      check_SP(); check_STACK();
      pushSTACK(TheStream(stream)->strm_concat_totallist);
      while (consp(STACK_0)) {
        pushSTACK(Car(STACK_0)); pushSTACK(STACK_(1+2));
        C_built_in_stream_set_element_type();
        STACK_0 = Cdr(STACK_0);
      }
      skipSTACK(1);
      break;
    case strmtype_file:
   #ifdef PIPES
    case strmtype_pipe_in:
    case strmtype_pipe_out:
   #endif
   #ifdef SOCKET_STREAMS
    case strmtype_socket:
   #endif
      if (!equal(STACK_0,TheStream(stream)->strm_eltype)) {/* nothing to change? */
        /* Check eltype. */
        if (!ChannelStream_buffered(stream))
          check_unbuffered_eltype(&eltype);
        /* The FILE-POSITION return value is constrained by CLHS to
           - be an integer,
           - represent a position into the file (and therefore be
             independent of the stream's current element type),
           - increment by 1 when READ-BYTE or WRITE-BYTE is called.
         In order to achieve these constraints altogether, we allow
         switching only (UNSIGNED-BYTE n) and (SIGNED-BYTE n) with
         the same n, and between ([UN]SIGNED-BYTE 8) and CHARACTER.
         Reading (UNSIGNED-BYTE 8) and (UNSIGNED-BYTE 16) and
         (UNSIGNED-BYTE 32) values from the same stream in succession
         can be achieved through READ-INTEGER and WRITE-INTEGER. */
        if ((ChannelStream_bitsize(stream) > 0 ?
             ChannelStream_bitsize(stream) : 8)
            != (eltype.size > 0 ? eltype.size : 8)) {
          /* canon-element-type in STACK_0. */
          pushSTACK(TheStream(stream)->strm_eltype);
          pushSTACK(stream);
          pushSTACK(S(Kelement_type));
          pushSTACK(O(setf_stream_element_type));
          error(error_condition,
                GETTEXT("~S: The ~S of ~S cannot be changed from ~S to ~S."));
        }
        /* Transform the lastchar back, if possible. */
        if (TheStream(stream)->strmflags & strmflags_open_B) /* stream open? */
          if (eltype.size > 0)
            /* New element type is an integer type. */
            if (ChannelStream_bitsize(stream) == 0) {
              /* Old element type was CHARACTER.
               Transform the lastchar back to bytes. */
              if (charp(TheStream(stream)->strm_rd_ch_last)
                  && (TheStream(stream)->strmflags & strmflags_unread_B)) {
                /* FIXME: This should take into account the encoding. */
                var uintB b = as_cint(char_code(TheStream(stream)->strm_rd_ch_last));
                if (ChannelStream_buffered(stream)) {
                  if ((BufferedStream_index(stream) > 0)
                      && (BufferedStream_position(stream) > 0)
                      && (*BufferedStream_buffer_address(stream,BufferedStream_index(stream)-1)
                          == b)) {
                    /* decrement index and position: */
                    BufferedStream_index(stream) -= 1;
                    BufferedStream_position(stream) -= 1;
                    TheStream(stream)->strm_rd_ch_last = NIL;
                    TheStream(stream)->strmflags &= ~strmflags_unread_B;
                  }
                } else {
                  if (UnbufferedStream_status(stream) == 0) {
                    UnbufferedStreamLow_push_byte(stream,b);
                    ChannelStream_ignore_next_LF(stream) = false;
                    TheStream(stream)->strm_rd_ch_last = NIL;
                    TheStream(stream)->strmflags &= ~strmflags_unread_B;
                  }
                }
              }
            }
        { /* Actually change the stream's element type. */
          var uintB flags = TheStream(stream)->strmflags;
          flags = (flags & ~strmflags_rdwr_B)
            | (flags & strmflags_rd_B ? strmflags_rd_B : 0)
            | (flags & strmflags_wr_B ? strmflags_wr_B : 0);
          ChannelStream_bitsize(stream) = eltype.size;
          if (eltype.kind == eltype_ch) {
            /* New element type is CHARACTER. */
            flags &= ~(strmflags_rdwr_B & ~strmflags_ch_B);
          } else {
            /* New element type is an integer type.
             allocate Bitbuffer: */
            pushSTACK(stream);
            var object bitbuffer = allocate_bit_vector(Atype_Bit,eltype.size);
            stream = popSTACK();
            TheStream(stream)->strm_bitbuffer = bitbuffer;
            flags &= ~(strmflags_rdwr_B & ~strmflags_by_B);
          }
          TheStream(stream)->strmflags = flags;
        }
        stream = stream_reset_eltype(stream,&eltype);
        TheStream(stream)->strm_eltype = STACK_0;
      }
      break;
   #ifdef SOCKET_STREAMS
    case strmtype_twoway_socket: {
      /* Apply to the input and output side individually. */
      pushSTACK(TheStream(STACK_2)->strm_twoway_socket_input); /* stream */
      pushSTACK(STACK_(0+1));
      funcall(L(built_in_stream_set_element_type),2);
      pushSTACK(TheStream(STACK_2)->strm_twoway_socket_output); /* stream */
      pushSTACK(STACK_(0+1));
      funcall(L(built_in_stream_set_element_type),2);
    } break;
   #endif
    default:
      error_illegal_streamop(O(setf_stream_element_type),stream);
  }
  VALUES1(STACK_1);
  skipSTACK(3);
}

LISPFUNNR(stream_external_format,1)
{ /* (STREAM-EXTERNAL-FORMAT stream) */
  var object stream = check_stream(popSTACK());
 start:
  if (builtin_stream_p(stream))
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym: /* Synonym-Stream: follow further */
        resolve_as_synonym(stream);
        goto start;
     #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
        pushSTACK(TheStream(stream)->strm_twoway_socket_input);
        pushSTACK(TheStream(stream)->strm_twoway_socket_output);
        goto stream_external_format_strmtype_twoway;
     #endif
      case strmtype_twoway:
      case strmtype_echo:
        pushSTACK(TheStream(stream)->strm_twoway_input);
        pushSTACK(TheStream(stream)->strm_twoway_output);
      stream_external_format_strmtype_twoway:
        C_stream_external_format();
        if (eq(value1,S(Kdefault))) {
          skipSTACK(1);         /* drop input stream */
          return;               /* return :DEFAULT */
        }
        pushSTACK(STACK_0);     /* input stream */
        STACK_1 = value1;       /* save output external format */
        C_stream_external_format();
        { object output_ex_fmt = popSTACK();
          if (equalp(value1,output_ex_fmt)) /* same ex fmt for input & output */
            return;             /* return this same ex fmt */
          VALUES1(S(Kdefault));
        }
        break;
      case strmtype_file:
     #ifdef PIPES
      case strmtype_pipe_in:
      case strmtype_pipe_out:
     #endif
     #ifdef X11SOCKETS
      case strmtype_x11socket:
     #endif
     #ifdef SOCKET_STREAMS
      case strmtype_socket:
     #endif
     #if (defined(UNIX) || defined(WIN32_NATIVE)) && defined(ENABLE_UNICODE)
      case strmtype_terminal:
     #endif
        VALUES1(TheStream(stream)->strm_encoding); break;
      case strmtype_concat:
        stream = TheStream(stream)->strm_concat_list;
        if (consp(stream)) {
          pushSTACK(Car(stream)); funcall(L(stream_external_format),1);
          return;
        }
        VALUES1(S(Kdefault)); break;
      case strmtype_broad:
        stream = broadcast_stream_last(stream);
        if (streamp(stream)) {
          pushSTACK(stream); funcall(L(stream_external_format),1);
          return;
        } /* empty => FALLTHROUGH*/
      default:
        VALUES1(S(Kdefault)); break;
    }
  else
    VALUES1(S(Kdefault));
}

/* (SYSTEM::SET-STREAM-EXTERNAL-FORMAT stream external-format [direction])
 direction can be :INPUT or :OUTPUT or NIL.
 If no direction is given, the operation is nonrecursive. */
LISPFUN(set_stream_external_format,seclass_default,2,1,norest,nokey,0,NIL) {
  STACK_2 = check_stream(STACK_2);
  var object encoding = STACK_1 =
    check_encoding(STACK_1,&O(default_file_encoding),false);
  var object stream = STACK_2;
  var object direction = STACK_0;
 start:
  if (builtin_stream_p(stream))
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym: /* Synonym-Stream: follow further */
        resolve_as_synonym(stream);
        goto start;
      case strmtype_broad:
        if (eq(direction,S(Kinput)))
          goto done;
        if (eq(direction,S(Koutput))) { /* Recurse. */
          check_SP(); check_STACK();
          pushSTACK(TheStream(stream)->strm_broad_list);
          while (consp(STACK_0)) {
            pushSTACK(Car(STACK_0)); pushSTACK(STACK_(1+2));
            pushSTACK(STACK_(0+3)); C_set_stream_external_format();
            STACK_0 = Cdr(STACK_0);
          }
          skipSTACK(1);
          encoding = STACK_1;
          goto done;
        }
        goto unchangeable_external_format;
      case strmtype_concat:
        if (eq(direction,S(Kinput))) { /* Recurse. */
          check_SP(); check_STACK();
          pushSTACK(TheStream(stream)->strm_concat_totallist);
          while (consp(STACK_0)) {
            pushSTACK(Car(STACK_0)); pushSTACK(STACK_(1+2));
            pushSTACK(STACK_(0+3)); C_set_stream_external_format();
            STACK_0 = Cdr(STACK_0);
          }
          skipSTACK(1);
          encoding = STACK_1;
          goto done;
        }
        if (eq(direction,S(Koutput)))
          goto done;
        goto unchangeable_external_format;
      case strmtype_str_in:
      case strmtype_str_out:
      case strmtype_str_push:
      case strmtype_pphelp:
      case strmtype_buff_in:
      case strmtype_buff_out:
     #ifdef GENERIC_STREAMS
      case strmtype_generic:
     #endif
        if (eq(direction,S(Kinput)) || eq(direction,S(Koutput)))
          goto done;
        goto unchangeable_external_format;
      case strmtype_file:
     #ifdef PIPES
      case strmtype_pipe_in:
      case strmtype_pipe_out:
     #endif
     #ifdef X11SOCKETS
      case strmtype_x11socket:
     #endif
     #ifdef SOCKET_STREAMS
      case strmtype_socket:
     #endif
        {
          var decoded_el_t eltype;
          STACK_2 = stream; /* save stream */
          test_eltype_arg(&TheStream(stream)->strm_eltype,&eltype);
          stream = STACK_2; /* restore stream */
          ChannelStream_fini(stream,0);
          stream = stream_reset_eltype(stream,&eltype);
          encoding = STACK_1; /* restore encoding */
          TheStream(stream)->strm_encoding = encoding;
          /* reset pseudofunctions in case line terminator changed */
          stream_reset_eltype(stream,&eltype);
          stream = STACK_2;     /* restore stream */
          ChannelStream_init(stream);
          VALUES1(TheStream(stream)->strm_encoding);
        }
        break;
     #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
     #endif
      case strmtype_twoway:
      case strmtype_echo:
        if (eq(direction,S(Kinput))) { /* Recurse. */
          stream = TheStream(stream)->strm_twoway_input; goto start;
        }
        if (eq(direction,S(Koutput))) { /* Recurse. */
          stream = TheStream(stream)->strm_twoway_output; goto start;
        }
        /* Recurse twice. */
        pushSTACK(TheStream(stream)->strm_twoway_output);
        pushSTACK(STACK_(1+1)); pushSTACK(STACK_(0+2));
        pushSTACK(TheStream(stream)->strm_twoway_input);
        pushSTACK(STACK_(1+4)); pushSTACK(STACK_(0+5));
        C_set_stream_external_format();
        C_set_stream_external_format();
        encoding = STACK_1;
        goto done;
      default:
        if (eq(direction,S(Kinput)))
          if ((TheStream(stream)->strmflags & strmflags_rd_B) == 0)
            goto done;
        if (eq(direction,S(Koutput)))
          if ((TheStream(stream)->strmflags & strmflags_wr_B) == 0)
            goto done;
    unchangeable_external_format:
        if (!eq(encoding,S(Kdefault)))
          error_illegal_streamop(S(set_stream_external_format),stream);
    done:
        VALUES1(encoding); break;
    }
  else {
    if (eq(direction,S(Kinput)))
      if (!instanceof(stream,O(class_fundamental_input_stream)))
        goto done2;
    if (eq(direction,S(Koutput)))
      if (!instanceof(stream,O(class_fundamental_output_stream)))
        goto done2;
    if (!eq(encoding,S(Kdefault)))
      error_illegal_streamop(S(set_stream_external_format),stream);
  done2:
    VALUES1(encoding);
  }
  skipSTACK(3);
}

#ifdef ENABLE_UNICODE

/* Changes a terminal stream's external format.
 > stream: a stream
 > encoding: an encoding
 can trigger GC */
global maygc void set_terminalstream_external_format (object stream,
                                                      object encoding) {
  if (builtin_stream_p(stream)
      && TheStream(stream)->strmtype == strmtype_terminal
      && eq(TheStream(stream)->strm_encoding,O(terminal_encoding))) {
    /* This is the only place which is allowed to modify the terminal
     stream's encoding.
     The terminal stream's end-of-line coding is hardwired, therefore we
     don't need to do the equivalent of fill_pseudofuns_unbuffered here. */
    ChannelStream_fini(stream,0);
    TheStream(stream)->strm_encoding = encoding;
    ChannelStream_init(stream);
  } else {
    pushSTACK(stream); pushSTACK(encoding);
    funcall(L(set_stream_external_format),2);
  }
}

#endif

/* UP: Determines, if a Stream is "interactive", i.e. if Input of Stream
 will presumably depend on a previously printed prompt.
 interactive_stream_p(stream)
 > stream: Stream
 NB: Relation between clear_input, listen, interactive_stream_p:
   If LISTEN_WAIT==listen_char(stream) after clear_input(stream)
   (i.e. no more character available and no EOF), then
   interactive_stream_p(stream) is true.
   (Because then stream is effectively a Keyboard-Stream, Terminal-Stream,
   Handle-Stream with !regular_handle_p(ihandle), Pipe-Input-Stream,
   X11-Socket-Stream, Socket-Stream or Generic-Stream.)
   (For a Concatenated-Stream, which is at the end of a non-interactive
   Sub-Stream and where the next Sub-Stream is non-interactive, this is
   possibly not valid. But this can be caught by inserting a
   listen_char(stream) before the query.)
   But not vice-versa: For Streams of type strmtype_pipe_in,
   strmtype_x11socket, strmtype_socket (that comply with
   interactive_stream_p(stream)) clear_input(stream) does nothing,
   and listen_char(stream) can return LISTEN_AVAIL. */
global bool interactive_stream_p (object stream) {
 start:
  if (!builtin_stream_p(stream)) /* Assume the worst. */
    return true;
  if ((TheStream(stream)->strmflags & strmflags_rd_B) == 0)
    /* Stream is closed for Input */
    return false;
  /* Stream open */
  switch (TheStream(stream)->strmtype) {
    case strmtype_synonym: /* Synonym-Stream: follow further */
      resolve_as_synonym(stream);
      goto start;
    case strmtype_concat:
      /* Here one could call listen_char(stream) in order to ignore Streams,
       that arrived at EOF. But it is no good for
       interactive_stream_p to do system-calls and I/O.??
       Query the first of the streams: */
      {
        var object streamlist = TheStream(stream)->strm_concat_list;
        if (consp(streamlist)) {
          stream = Car(streamlist);
          goto start;
        } else
          return false;
      }
    case strmtype_twoway:
    case strmtype_echo:
      /* Two-Way-Stream or Echo-Stream: look at Input-Stream */
      stream = TheStream(stream)->strm_twoway_input;
      goto start;
    case strmtype_str_in:
      return false;
    case strmtype_buff_in:
    #ifdef GENERIC_STREAMS
    case strmtype_generic:
    #endif
      return true;
    case strmtype_terminal:
    case strmtype_file:
      if (ChannelStream_buffered(stream))
        /* Buffered file streams are not considered to be interactive. */
        return false;
      if (nullp(TheStream(stream)->strm_isatty))
        /* regular files are for sure not interactive. */
        if (regular_handle_p(TheHandle(TheStream(stream)->strm_ichannel)))
          return false;
    #ifdef KEYBOARD
    case strmtype_keyboard:
    #endif
    #ifdef PIPES
    case strmtype_pipe_in:
    #endif
    #ifdef X11SOCKETS
    case strmtype_x11socket:
    #endif
    #ifdef SOCKET_STREAMS
    case strmtype_socket:
    case strmtype_twoway_socket:
    #endif
      return true;
    default:
      return false;
  }
}

/* (INTERACTIVE-STREAM-P stream), CLTL2 p. 507/508
 determines, if stream is interactive. */
LISPFUNN(interactive_stream_p,1) {
  var object arg = check_stream(popSTACK());
  VALUES_IF(interactive_stream_p(arg));
}

/* UP: Closes a Stream.
 builtin_stream_close(&stream, abort);
 > stream: Builtin-Stream
 > abort: flag: non-0 => ignore errors: may be called from GC & quit()
    -- if abort is non-0, we end up calling close(2) on the underlying object
       no matter what else might have failed (iconv, buffer flushing &c)
    -- even if abort is non-0, we do try to flush buffers et al, but we do that
       under IGNORE-ERRORS, i.e., some output might be silently lost
 < stream: Builtin-Stream
 can trigger GC */
modexp maygc void builtin_stream_close
(const gcv_object_t* stream_, uintB abort) {
  if ((TheStream(*stream_)->strmflags & strmflags_open_B) == 0) /* Stream already closed? */
    return;
  if (!abort) harden_elastic_newline(stream_);
  var object stream = *stream_;
  /* call type-specific routine (can trigger GC): */
  switch (TheStream(stream)->strmtype) {
    case strmtype_synonym:
      close_synonym(stream,abort); break; /* X3J13_014 says: non-recursive */
    case strmtype_broad:  break; /* non-recursive */
    case strmtype_concat: break; /* non-recursive */
    case strmtype_twoway: break; /* non-recursive */
    case strmtype_echo:   break; /* non-recursive */
    case strmtype_str_in:  close_str_in(stream); break;
    case strmtype_str_out:  break;
    case strmtype_str_push: break;
    case strmtype_pphelp:   break;
    case strmtype_buff_in:  close_buff_in(stream);  break;
    case strmtype_buff_out: close_buff_out(stream,abort); break;
    #ifdef GENERIC_STREAMS
    case strmtype_generic: close_generic(stream,abort); break;
    #endif
    case strmtype_file:
    #ifdef PIPES
    case strmtype_pipe_in:
    case strmtype_pipe_out:
    #endif
    #ifdef X11SOCKETS
    case strmtype_x11socket:
    #endif
    #ifdef SOCKET_STREAMS
    case strmtype_socket:
    #endif
      if (ChannelStream_buffered(stream)) {
        close_buffered(stream,abort);
      } else {
        if (!nullp(TheStream(stream)->strm_ochannel))
          close_ochannel(stream,abort);
        else
          close_ichannel(stream,abort);
        /* remove stream from the List of all open File-Streams: */
        remove_from_open_streams(*stream_);
      }
      break;
    #ifdef SOCKET_STREAMS
    case strmtype_twoway_socket:
      /* Close the two substreams, but close the handle once only. */
      ChannelStreamLow_close(TheStream(stream)->strm_twoway_socket_input) =
        &low_close_socket_nop;
      pushSTACK(TheStream(stream)->strm_twoway_socket_input);
      pushSTACK(TheStream(stream)->strm_twoway_socket_output);
      builtin_stream_close(&STACK_1,abort);
      builtin_stream_close(&STACK_0,abort);
      skipSTACK(2);
      break;
    #endif
    #ifdef KEYBOARD
    case strmtype_keyboard: break;
    #endif
    case strmtype_terminal: break;
    #ifdef SCREEN
    case strmtype_window: close_window(stream,abort); break;
    #endif
    default: NOTREACHED;
  }
  /* enter dummys: */
  close_dummys(*stream_);
}

/* UP: Closes a list of open files - no errors!
 close_some_files(list);
 > list: list of open Builtin-Streams
 can trigger GC */
global maygc void close_some_files (object list) {
  pushSTACK(NIL); /* dummy */
  pushSTACK(list); /* list */
  while (mconsp(STACK_0)) {
    var object streamlist = STACK_0;
    STACK_0 = Cdr(streamlist); /* remaining streams */
    STACK_1 = Car(streamlist); /* a stream from the list */
    builtin_stream_close(&STACK_1,1); /* close -- no errors! */
  }
  skipSTACK(2);
}

/* UP: Closes all open files.
 close_all_files();
 can trigger GC */
global maygc void close_all_files (void) {
  /* NB: no locking on O(open_files). it is used only when exitting process.*/
  close_some_files(O(open_files)); /* list of all open File-Streams */
}

/* UP: Declares all open File-Streams as closed.
 closed_all_files(); */
global void closed_all_files (void) {
  /* NB: no locking on O(open_files). it is used only during runtime
     initialization (loadmem()). */
  var object streamlist = O(open_files); /* list of all open File-Streams */
  while (consp(streamlist)) {
    var object stream = Car(streamlist); /* a Stream from the list */
    if (TheStream(stream)->strmtype == strmtype_file) { /* File-Stream ? */
      if (!nullp(BufferedStream_channel(stream))) /* with Handle /= NIL ? */
        /* yes: Stream still open */
        closed_buffered(stream);
    }
    close_dummys(stream);
    streamlist = Cdr(streamlist); /* remaining Streams */
  }
  O(open_files) = NIL; /* no more open Files */
}

/* (SYS::BUILT-IN-STREAM-CLOSE stream :abort) */
LISPFUN(built_in_stream_close,seclass_default,1,0,norest,key,1, (kw(abort)) ) {
  var uintB abort = !missingp(STACK_0); skipSTACK(1);
  var object stream = STACK_0; /* Argument */
  CHECK_builtin_stream(stream); /* must be a Stream */
  builtin_stream_close(&STACK_0,abort);
  skipSTACK(1);
  VALUES1(T); /* T as result */
}

/* Reads a line of characters from a stream.
 read_line(&stream,&buffer)
 > stream: stream
 > buffer: a semi-simple string
 < stream: stream
 < buffer: contains the read characters, excluding the terminating #\Newline
 < result: true if EOF was seen before newline, else false
 can trigger GC */
local inline maygc bool push_ch (object ch, object buffer) {
  if (!charp(ch)) {
    if (eq(subr_self,L(read_line))) error_char(ch);
    else with_saved_back_trace_subr(L(read_line),STACK STACKop -4,-1,
                                    error_char(ch));
  }
  if (eq(ch,ascii_char(NL)))
    return false;
  ssstring_push_extend(buffer,char_code(ch));
  return true;
}
global maygc bool read_line (const gcv_object_t* stream_,
                             const gcv_object_t* buffer_) {
  var object stream = *stream_;
  if (builtin_stream_p(stream)) {
    if (TheStream(stream)->strmflags & strmflags_unread_B) { /* Char after UNREAD ? */
      /* yes -> delete Flagbit and fetch last character: */
      TheStream(stream)->strmflags &= ~strmflags_unread_B;
      if (!push_ch(TheStream(stream)->strm_rd_ch_last,*buffer_))
        return false;
    }
    var bool eofp;
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym:
        eofp = read_line_synonym(stream,buffer_);
        break;
      case strmtype_twoway:
     #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
     #endif
        eofp = read_line_twoway(stream,buffer_);
        break;
        /* No special-casing of strmtype_echo, because the echo-stream may
         be interactive, and delaying the echo in this case is undesirable. */
      default:
        do {
          var object ch = rd_ch(*stream_)(stream_); /* read next character */
          if (eq(ch,eof_value)) { /* EOF ? */
            eofp = true; break;
          }
          eofp = push_ch(ch,*buffer_);
        } while (eofp);
        break;
    }
    stream = *stream_;
    TheStream(stream)->strm_rd_ch_last = (eofp ? eof_value : ascii_char(NL));
    TheStream(stream)->strmflags &= ~strmflags_unread_B;
    return eofp;
  } else {
    pushSTACK(stream);
    /* Call the generic function (STREAM-READ-LINE stream): */
    pushSTACK(stream); funcall(S(stream_read_line),1);
    if (!stringp(value1)) {
      pushSTACK(value1);    /* TYPE-ERROR slot DATUM */
      pushSTACK(S(string)); /* TYPE-ERROR slot EXPECTED-TYPE */
      pushSTACK(S(stream_read_line));
      pushSTACK(value1);
      error(type_error,GETTEXT("Return value ~S of call to ~S is not a string."));
    }
    var bool eofp = (mv_count >= 2 && !nullp(value2));
    /* Add the line to the buffer: */
    var uintL len;
    var uintL offset;
    var object srcstring = unpack_string_ro(value1,&len,&offset);
    if (len > 0) {
      if (simple_nilarray_p(srcstring)) error_nilarray_retrieve();
      ssstring_append_extend(*buffer_,srcstring,offset,len);
    }
    /* Set the stream's $lastchar := #\Newline or #<EOF>: */
    stream_set_lastchar(popSTACK(), eofp ? eof_value : ascii_char(NL));
    return eofp;
  }
}

/* UP: Determines, if a character is instantly available in the Stream stream.
 listen_char(stream)
 > stream: Stream
 < result: input availability
 can trigger GC */
global maygc listen_t listen_char (object stream) {
  if (builtin_stream_p(stream)) {
    check_SP(); check_STACK();
    if (TheStream(stream)->strmflags & strmflags_unread_B) { /* Char after UNREAD ? */
      return LISTEN_AVAIL; /* yes -> available */
    } else {
      /* else branch according to Streamtype.
       Each single routine can trigger GC. Except for Keyboard-Stream
       or Terminal-Stream this is a pure EOF-Test. */
      switch (TheStream(stream)->strmtype) {
        case strmtype_synonym:  return listen_char_synonym(stream);
        case strmtype_broad:    return LISTEN_EOF; /* no READ-CHAR */
        case strmtype_concat:   return listen_char_concat(stream);
        case strmtype_twoway:
        case strmtype_echo:
        #ifdef SOCKET_STREAMS
        case strmtype_twoway_socket:
        #endif
          return listen_char_twoway(stream);
        case strmtype_str_in:   return listen_char_str_in(stream);
        case strmtype_str_out:  return LISTEN_EOF; /* no READ-CHAR */
        case strmtype_str_push: return LISTEN_EOF; /* no READ-CHAR */
        case strmtype_pphelp:   return LISTEN_EOF; /* no READ-CHAR */
        case strmtype_buff_in:  return listen_char_buff_in(stream);
        case strmtype_buff_out: return LISTEN_EOF; /* no READ-CHAR */
        #ifdef GENERIC_STREAMS
        case strmtype_generic:  return listen_char_generic(stream);
        #endif
        case strmtype_file:
        #ifdef PIPES
        case strmtype_pipe_in:
        case strmtype_pipe_out:
        #endif
        #ifdef X11SOCKETS
        case strmtype_x11socket:
        #endif
        #ifdef SOCKET_STREAMS
        case strmtype_socket:
        #endif
          if (TheStream(stream)->strmflags & strmflags_rd_ch_B) {
            if (ChannelStream_buffered(stream))
              return listen_char_buffered(stream);
            else
              return listen_char_unbuffered(stream);
          } else {
            return LISTEN_EOF; /* no READ-CHAR */
          }
        #ifdef KEYBOARD
        case strmtype_keyboard: return listen_char_keyboard(stream);
        #endif
        case strmtype_terminal:
        #if defined(UNIX) || defined(WIN32_NATIVE)
          terminalcase(stream,
          { return listen_char_terminal1(stream); },
          { return listen_char_terminal2(stream); },
          { return listen_char_terminal3(stream); });
        #endif
          NOTREACHED;
        #ifdef SCREEN
        case strmtype_window:   return LISTEN_EOF; /* no READ-CHAR */
        #endif
        #ifdef PRINTER
        case strmtype_printer:  return LISTEN_EOF; /* no READ-CHAR */
        #endif
        default: /* in general: query only for EOF */
          if (TheStream(stream)->strmflags & strmflags_rd_ch_B) {
            pushSTACK(stream);
            var object nextchar = peek_char(&STACK_0);
            skipSTACK(1);
            if (eq(nextchar,eof_value))
              return LISTEN_EOF; /* EOF reached */
            else
              return LISTEN_AVAIL;
          } else {
            return LISTEN_EOF; /* no READ-CHAR */
          }
      }
    }
  } else {
    /* Call the generic function (STREAM-READ-CHAR-WILL-HANG-P stream),
     then call (PEEK-CHAR NIL STREAM): */
    pushSTACK(stream);
    pushSTACK(stream); funcall(S(stream_read_char_will_hang_p),1);
    if (!nullp(value1)) {
      skipSTACK(1); return LISTEN_WAIT;
    }
    var object nextchar = peek_char(&STACK_0);
    skipSTACK(1);
    if (eq(nextchar,eof_value))
      return LISTEN_EOF;
    else
      return LISTEN_AVAIL;
  }
}

/* UP: Deletes already entered interactive Input from a Stream stream.
 clear_input(stream)
 > stream: Stream
 < result: true if Input was deleted
 can trigger GC */
global maygc bool clear_input (object stream) {
  check_SP(); check_STACK();
  pushSTACK(stream); /* save Stream */
  /* call type-specific Routine (can trigger GC). */
  if (builtin_stream_p(stream)) {
    /* Only for Keyboard-Stream and Terminal-Stream something is done. */
    var bool result;
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym:
        result = clear_input_synonym(stream); break;
      case strmtype_concat:
        result = clear_input_concat(stream); break;
      case strmtype_twoway:
      case strmtype_echo:
      #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
      #endif
        result = clear_input_twoway(stream); break;
      case strmtype_buff_in:
        result = clear_input_buff_in(stream); break;
      #ifdef GENERIC_STREAMS
      case strmtype_generic:
        result = clear_input_generic(stream); break;
      #endif
      case strmtype_file:
      #ifdef PIPES
      case strmtype_pipe_in:
      case strmtype_pipe_out:
      #endif
      #ifdef X11SOCKETS
      case strmtype_x11socket:
      #endif
      #ifdef SOCKET_STREAMS
      case strmtype_socket:
      #endif
        if (TheStream(stream)->strmflags & strmflags_rd_ch_B
            && !ChannelStream_buffered(stream))
          result = clear_input_unbuffered(stream);
        else
          result = clear_input_buffered(stream);
        break;
      #ifdef KEYBOARD
      case strmtype_keyboard:
        result = clear_input_keyboard(stream); break;
      #endif
      case strmtype_terminal:
      #if defined(UNIX) || defined(WIN32_NATIVE)
        terminalcase(stream,
        { result = clear_input_terminal1(stream); },
        { result = clear_input_terminal2(stream); },
        { result = clear_input_terminal3(stream); });
      #endif
        break;
      default:
        result = false; break;
    }
    stream = popSTACK();
    if (result) {
      /* Input was deleted -> also the Lastchar has to be deleted.
       An already seen EOF will be forgotten thereby. */
      TheStream(stream)->strm_rd_ch_last = NIL;
      TheStream(stream)->strmflags &= ~strmflags_unread_B;
    }
    return result;
  } else {
    /* Call the generic function (STREAM-CLEAR-INPUT stream): */
    funcall(S(stream_clear_input),1);
    return !nullp(value1);
  }
}

/* UP: Determines whether a stream has a byte immediately available.
 listen_byte(stream)
 > stream: a stream with element-type ([UN]SIGNED-BYTE 8)
 < result: input availability
 can trigger GC */
global maygc listen_t listen_byte (object stream) {
  if (builtin_stream_p(stream)) {
    if (TheStream(stream)->strmflags & strmflags_rd_B) { /* Input-Stream? */
      check_SP(); check_STACK();
      /* branch according to Streamtype.
       Each single routine can trigger GC. Except for Sockets
       this is a pure EOF-Test. */
      switch (TheStream(stream)->strmtype) {
        case strmtype_synonym:  return listen_byte_synonym(stream);
        case strmtype_broad:    return LISTEN_EOF; /* no READ-BYTE */
        case strmtype_concat:   return listen_byte_concat(stream);
        case strmtype_twoway:
        case strmtype_echo:
        #ifdef SOCKET_STREAMS
        case strmtype_twoway_socket:
        #endif
          return listen_byte_twoway(stream);
        case strmtype_str_in:
        case strmtype_str_out:
        case strmtype_str_push:
        case strmtype_pphelp:
        case strmtype_buff_in:
        case strmtype_buff_out:
        #ifdef GENERIC_STREAMS
        case strmtype_generic: /* unsupported functionality */
        #endif
        #ifdef KEYBOARD
        case strmtype_keyboard:
        #endif
        case strmtype_terminal:
        #ifdef SCREEN
        case strmtype_window:
        #endif
        #ifdef PRINTER
        case strmtype_printer:
        #endif
          return LISTEN_EOF; /* no READ-BYTE */
        case strmtype_file:
        #ifdef PIPES
        case strmtype_pipe_in:
        case strmtype_pipe_out:
        #endif
        #ifdef X11SOCKETS
        case strmtype_x11socket:
        #endif
        #ifdef SOCKET_STREAMS
        case strmtype_socket:
        #endif
          if (TheStream(stream)->strmflags & strmflags_rd_by_B) {
            /* Only 8-bit element types. A general LISTEN-BYTE function
             would be hairy (at least the case where you want to know
             whether a multibyte integer is pending, and the stream is
             unbuffered). For CLX and most applications, it is sufficient
             to deal with a socket stream with 8-bit element types. */
            if (ChannelStream_buffered(stream))
              return listen_byte_ia8_buffered(stream);
            else
              return listen_byte_ia8_unbuffered(stream);
          } else {
            return LISTEN_EOF; /* no READ-BYTE */
          }
        default: NOTREACHED;
      }
    } else {
      return LISTEN_EOF; /* no READ-BYTE */
    }
  } else { /* Call the generic function (STREAM-READ-BYTE-LOOKAHEAD stream): */
    pushSTACK(stream); funcall(S(stream_read_byte_lookahead),1);
    if (nullp(value1))
      return LISTEN_WAIT;
    else if (eq(value1,S(Keof)))
      return LISTEN_EOF;
    else
      return LISTEN_AVAIL;
  }
}

/* UP: Move the pending Output of a Stream to the destination.
 finish_output(stream);
 > stream: Stream
 can trigger GC */
global maygc void finish_output (object stream) {
  pushSTACK(stream);
  harden_elastic_newline(&STACK_0);
  stream = popSTACK();
  if (builtin_stream_p(stream)) {
    if (TheStream(stream)->strmflags & strmflags_wr_B) { /* Output-Stream? */
      /* no -> finished, yes -> branch according to Stream-Type: */
      switch (TheStream(stream)->strmtype) {
        case strmtype_synonym:
          finish_output_synonym(stream); break;
        case strmtype_broad:
          finish_output_broad(stream); break;
        case strmtype_twoway:
        case strmtype_echo:
        #ifdef SOCKET_STREAMS
        case strmtype_twoway_socket:
        #endif
          finish_output_twoway(stream); break;
        case strmtype_buff_out:
          finish_output_buff_out(stream); break;
        #ifdef GENERIC_STREAMS
        case strmtype_generic:
          finish_output_generic(stream); break;
        #endif
        case strmtype_file:
        #ifdef PIPES
        case strmtype_pipe_in:
        case strmtype_pipe_out:
        #endif
        #ifdef X11SOCKETS
        case strmtype_x11socket:
        #endif
        #ifdef SOCKET_STREAMS
        case strmtype_socket:
        #endif
          if (ChannelStream_buffered(stream))
            finish_output_buffered(stream);
          else
            finish_output_unbuffered(stream);
          break;
        case strmtype_terminal:
          finish_output_terminal(stream); break;
        default: /* do nothing */
          break;
      }
    }
  } else { /* Call the generic function (STREAM-FINISH-OUTPUT stream): */
    pushSTACK(stream); funcall(S(stream_finish_output),1);
  }
}

/* UP: Move the pending Output of a Stream to the destination.
 force_output(stream);
 > stream: Stream
 can trigger GC */
global maygc void force_output (object stream) {
  pushSTACK(stream);
  harden_elastic_newline(&STACK_0);
  stream = popSTACK();
  if (builtin_stream_p(stream)) {
    if (TheStream(stream)->strmflags & strmflags_wr_B) { /* Output-Stream? */
      /* no -> finished, yes -> branch according to Stream-Type: */
      switch (TheStream(stream)->strmtype) {
        case strmtype_synonym:
          force_output_synonym(stream); break;
        case strmtype_broad:
          force_output_broad(stream); break;
        case strmtype_twoway:
        case strmtype_echo:
        #ifdef SOCKET_STREAMS
        case strmtype_twoway_socket:
        #endif
          force_output_twoway(stream); break;
        case strmtype_buff_out:
          force_output_buff_out(stream); break;
        #ifdef GENERIC_STREAMS
        case strmtype_generic:
          force_output_generic(stream); break;
        #endif
        case strmtype_file:
        #ifdef PIPES
        case strmtype_pipe_in:
        case strmtype_pipe_out:
        #endif
        #ifdef X11SOCKETS
        case strmtype_x11socket:
        #endif
        #ifdef SOCKET_STREAMS
        case strmtype_socket:
        #endif
          if (ChannelStream_buffered(stream))
            force_output_buffered(stream);
          else
            force_output_unbuffered(stream);
          break;
        case strmtype_terminal:
          force_output_terminal(stream); break;
        default: /* do nothing */
          break;
      }
    }
  } else { /* Call the generic function (STREAM-FORCE-OUTPUT stream): */
    pushSTACK(stream); funcall(S(stream_force_output),1);
  }
}

/* UP: Delete pending Output of a Stream.
 clear_output(stream);
 > stream: Stream
 can trigger GC */
global maygc void clear_output (object stream) {
  /* On DOS nothing actually has to be done for File- or Terminal-Streams,
   but we cannot take advantage of that, because clear_output on
   Buffered-Output-Streams always works. */
  if (builtin_stream_p(stream)) {
    if (TheStream(stream)->strmflags & strmflags_wr_B) { /* Output-Stream? */
      /* no -> finished, yes -> branch according to Stream-Type: */
      switch (TheStream(stream)->strmtype) {
        case strmtype_synonym:
          clear_output_synonym(stream); break;
        case strmtype_broad:
          clear_output_broad(stream); break;
        case strmtype_twoway:
        case strmtype_echo:
        #ifdef SOCKET_STREAMS
        case strmtype_twoway_socket:
        #endif
          clear_output_twoway(stream); break;
        case strmtype_buff_out:
          clear_output_buff_out(stream); break;
        #ifdef GENERIC_STREAMS
        case strmtype_generic:
          clear_output_generic(stream); break;
        #endif
        case strmtype_file:
        #ifdef PIPES
        case strmtype_pipe_in:
        case strmtype_pipe_out:
        #endif
        #ifdef X11SOCKETS
        case strmtype_x11socket:
        #endif
        #ifdef SOCKET_STREAMS
        case strmtype_socket:
        #endif
          if (ChannelStream_buffered(stream)) {
            /* File: do nothing (would disturb the File-Management) */
          } else {
            clear_output_unbuffered(stream);
          }
          break;
        case strmtype_terminal:
          #if defined(UNIX) || defined(WIN32_NATIVE)
          terminalcase(stream,
          { clear_output_terminal1(stream); },
          { clear_output_terminal2(stream); },
          { clear_output_terminal3(stream); });
          #endif
          break;
        default: /* do nothing */
          break;
      }
    }
  } else { /* Call the generic function (STREAM-CLEAR-OUTPUT stream): */
    pushSTACK(stream); funcall(S(stream_clear_output),1);
  }
}

/* UP: Returns the Line-Position of a Stream.
 get_line_position(stream)
 > stream: Stream
 < result: Line-Position (Fixnum >=0 or NIL)
 can trigger GC */
global maygc object get_line_position (object stream) {
  check_SP();
 start:
  if (builtin_stream_p(stream))
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym: /* Synonym-Stream: follow further */
        resolve_as_synonym(stream);
        goto start;
      case strmtype_broad: /* Broadcast-Stream: */
        /* Maximum of Line-Positions of the single Streams */
        {
          pushSTACK(TheStream(stream)->strm_broad_list);
          var uintV maximum = 0; /* previous Maximum := 0 */
          while (consp(STACK_0)) {
            var object next = /* Line-Position of the next substream */
              get_line_position(Car(STACK_0));
            if (nullp(next)) {
              skipSTACK(1); return NIL;
            }
            if (posfixnum_to_V(next) > maximum)
              maximum = posfixnum_to_V(next); /* take Maximum */
            STACK_0 = Cdr(STACK_0);
          }
          skipSTACK(1); return fixnum(maximum); /* Maximum as result */
        }
      case strmtype_twoway:
      case strmtype_echo:
      #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
      #endif
        /* Two-Way-Stream or Echo-Stream: look at Output-Stream */
        stream = TheStream(stream)->strm_twoway_output;
        /* return get_line_position(stream); */ /* without recursion: */
        goto start;
      default: /* normal Stream */
        return TheStream(stream)->strm_wr_ch_lpos;
    }
  else {
    pushSTACK(stream);
    /* Test (SLOT-VALUE stream '$penl): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(penl),TheClass(clas)->slot_location_table,false);
    if (!nullp(TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)])) {
      /* A newline is pending. The line position is already 0. */
      skipSTACK(1);
      return Fixnum_0;
    } else {
      /* Call the generic function (STREAM-LINE-COLUMN stream): */
      funcall(S(stream_line_column),1);
      if (!(posfixnump(value1) || nullp(value1))) {
        pushSTACK(S(stream_line_column));
        pushSTACK(value1);
        error(error_condition,GETTEXT("Return value ~S of call to ~S is not a fixnum >= 0 or NIL."));
      }
      return value1;
    }
  }
}

/* do the actual legwork of fresh_line
 fresh_line_low(stream)
 > stream: Stream
 < result: true if a newline has been output
 can trigger GC */
local maygc bool fresh_line_low (const gcv_object_t* stream_) {
  /* Test whether an elastic newline is pending, so that
   (ELASTIC-NEWLINE stream) followed by (FRESH-LINE stream) always leads
   to exactly one newline being output. */
 #define TERPRI_IF(cond) return cond ? (terpri(stream_), true) : false
  var object stream = *stream_;
  check_SP();
 start:
  if (builtin_stream_p(stream))
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym: /* Synonym-Stream: follow further */
        resolve_as_synonym(stream);
        goto start;
      case strmtype_broad: { /* Broadcast-Stream: */
        /* FRESH-LINE is a "control", not an "output" operation,
           so do it one by one on the individual constituent streams. */
        var bool ret = false;
        pushSTACK(TheStream(stream)->strm_broad_list);
        while (consp(STACK_0)) {
          pushSTACK(Car(STACK_0));
          ret = fresh_line_low(&STACK_0);
          skipSTACK(1);
          STACK_0 = Cdr(STACK_0);
        }
        skipSTACK(1);
        return ret;
      }
      case strmtype_twoway:
      case strmtype_echo:
      #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
      #endif
        /* Two-Way-Stream or Echo-Stream: look at Output-Stream */
        stream = TheStream(stream)->strm_twoway_output;
        goto start;
      default: /* normal stream */
        TERPRI_IF(eq(TheStream(stream)->strm_wr_ch,P(wr_ch_pending_newline))
                  || !eq(get_line_position(*stream_),Fixnum_0));
    }
  else { /* Test (SLOT-VALUE stream '$penl): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(penl),TheClass(clas)->slot_location_table,false);
    TERPRI_IF(!nullp(TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)])
              || !eq(get_line_position(stream_forwarded),Fixnum_0));
  }
 #undef TERPRI_IF
}

/* Writes a newline on a stream, if it is not already positioned at column 0.
 fresh_line(&stream);
 > stream: Stream
 < stream: Stream
 < result: true if did output a newline
 can trigger GC */
global maygc bool fresh_line (const gcv_object_t* stream_) {
  { /* Special hack that acknowledges the fact that sometimes *standard-output* */
    /* and *error-output* go to the same device, although they are different.
     For example, in batch mode
       $ ./clisp -x '(progn (format *standard-output* "~&line1~.") (format *error-output* "~&line2~."))' | cat
     or on Cygwin in Windows2000, when clisp is launched from the "cmd" shell,
     the same_handle_p function fails to recognize the two outputs as
     identical.
     (unless (eq *standard-output* *error-output*)
       (cond ((eq stream *standard-output*) (finish-output *error-output*))
             ((eq stream *error-output*) (finish-output *standard-output*)))) */
    var object stream1 = Symbol_value(S(standard_output));
    var object stream2 = Symbol_value(S(error_output));
    if (!eq(stream1,stream2)) {
      if (eq(*stream_,stream1)) {
        if (output_stream_p(stream2)
            && (!builtin_stream_p(stream2)
                || (TheStream(stream2)->strmflags & strmflags_open_B) != 0))
          finish_output(stream2);
      } else if (eq(*stream_,stream2)) {
        if (output_stream_p(stream1)
            && (!builtin_stream_p(stream1)
                || (TheStream(stream1)->strmflags & strmflags_open_B) != 0))
          finish_output(stream1);
      }
    }
  }
  return fresh_line_low(stream_);
}

/* Writes a newline on a stream, delayed and nullified if the next character
 written would be a newline anyway.
 elastic_newline(&stream);
 > stream: Stream
 < stream: Stream
 can trigger GC */
global maygc void elastic_newline (const gcv_object_t* stream_) {
  check_SP();
  var object stream = *stream_;
 start:
  if (builtin_stream_p(stream))
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym: /* Synonym-Stream: follow further */
        resolve_as_synonym(stream);
        goto start;
      case strmtype_broad: /* Broadcast-Stream: dispatch */
        {
          pushSTACK(TheStream(stream)->strm_broad_list);
          pushSTACK(NIL);
          while (consp(STACK_1)) {
            STACK_0 = Car(STACK_1);
            elastic_newline(&STACK_0);
            STACK_1 = Cdr(STACK_1);
          }
          skipSTACK(2);
          break;
        }
      case strmtype_twoway:
      case strmtype_echo:
      #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
      #endif
        /* Two-Way-Stream or Echo-Stream: look at Output-Stream */
        stream = TheStream(stream)->strm_twoway_output;
        goto start;
      default: /* normal stream */
        TheStream(stream)->strm_wr_ch = P(wr_ch_pending_newline);
        TheStream(stream)->strm_wr_ch_array = P(wr_ch_array_pending_newline);
        TheStream(stream)->strm_wr_ch_lpos = Fixnum_0;
        break;
    }
  else {
    /* (SETF (SLOT-VALUE stream '$penl) T): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(penl),TheClass(clas)->slot_location_table,false);
    TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)] = T;
  }
}

/* UP: Check an element-type for READ-INTEGER/WRITE-INTEGER.
 check_multiple8_eltype(&eltype);
 > eltype: Element-Type in decoded form */
local void check_multiple8_eltype (const decoded_el_t* eltype) {
  if (!((eltype->size > 0) && ((eltype->size % 8) == 0))) {
    pushSTACK(canon_eltype(eltype));
    pushSTACK(S(Kelement_type));
    pushSTACK(TheSubr(subr_self)->name);
    error(error_condition,GETTEXT("~S needs an ~S with a bit size being a multiple of 8, not ~S"));
  }
}

/* UP: Check an element-type for READ-FLOAT/WRITE-FLOAT.
 check_float_eltype(&eltype)
 > object eltype: argument (in the STACK)
 < result: sizeof(ffloatjanus) or sizeof(dfloatjanus) */
local uintL check_float_eltype (gcv_object_t* eltype_) {
  var object arg = *eltype_;
  if (eq(arg,S(single_float)))
    return sizeof(ffloatjanus);
  if (eq(arg,S(double_float)))
    return sizeof(dfloatjanus);
  var bool is_ffloat_subtype;
  var bool is_dfloat_subtype;
  /* First of all, make it a little more canonical (so then the different
   SUBTYPEP do not have to do the same thing twice): */
  pushSTACK(arg); funcall(S(canonicalize_type),1); /* (SYS::CANONICALIZE-TYPE arg) */
  pushSTACK(value1); /* save canon-arg */
  pushSTACK(STACK_0); pushSTACK(S(single_float)); funcall(S(subtypep),2); /* (SUBTYPEP canon-arg 'SINGLE-FLOAT) */
  is_ffloat_subtype = !nullp(value1);
  pushSTACK(S(double_float)); funcall(S(subtypep),2); /* (SUBTYPEP canon-arg 'DOUBLE-FLOAT) */
  is_dfloat_subtype = !nullp(value1);
  if (is_ffloat_subtype) {
    if (!is_dfloat_subtype)
      return sizeof(ffloatjanus);
  } else {
    if (is_dfloat_subtype)
      return sizeof(dfloatjanus);
  }
  error_illegal_arg(*eltype_,nullobj,S(Kelement_type));
}

/* UP: Check an endianness argument.
 check_endianness_arg(arg)
 > arg: the argument
 < bool result: endianness (BIG = true, LITTLE = false)
 can trigger GC */
local bool maygc check_endianness_arg (object arg) {
 restart_check_endianness_arg:
  if (!boundp(arg) || eq(arg,S(Klittle)) || eq(arg,S(Kdefault)))
    return false;
  if (eq(arg,S(Kbig)))
    return true;
  pushSTACK(arg);                /* TYPE-ERROR slot DATUM */
  pushSTACK(O(type_endianness)); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(arg); pushSTACK(TheSubr(subr_self)->name);
  check_value(type_error,GETTEXT("~S: illegal endianness argument ~S"));
  arg = value1;
  goto restart_check_endianness_arg;
}


/* UP: give away corresponding underlying handle
 making sure buffers were flushed. One can then use the
 handle outside of stream object as far as the latter
 is not used and not GCed.
 stream_lend_handle(stream, inputp, handletype)
 > stream_: stream for handle to extract
 > inputp: whether its input or output side is requested.
 < stream_: corrected stream (if the original argument was not a handle stream)
 < int * handletype 0:reserved, 1:file, 2:socket
 < Handle result - extracted handle
 can trigger GC */
modexp maygc Handle stream_lend_handle
(gcv_object_t *stream_, bool inputp, int * handletype) {
  var int errkind = 0;
  var object stream = *stream_;
 restart_stream_lend_handle:
  /* TODO: use finish-output ? */
  if (builtin_stream_p(stream)) {
    switch (TheStream(stream)->strmtype) {
     #ifdef X11SOCKETS
      case strmtype_x11socket:
     #endif
     #ifdef SOCKET_STREAMS
      case strmtype_socket:
     #endif
       #if defined(X11SOCKETS) || defined(SOCKET_STREAMS)
        if (handletype) *handletype = 2;
        /* it is not clear that buffered sockets should be supported,
           cf strmtype_pipe_in below */
        if (ChannelStream_buffered(stream))
          return TheHandle(TheStream(stream)->strm_buffered_channel);
        else if (inputp) return TheHandle(TheStream(stream)->strm_ichannel);
        else return TheHandle(TheStream(stream)->strm_ochannel);
       #endif
      case strmtype_file:
        if (handletype) *handletype = 1;
        if (inputp && TheStream(stream)->strmflags & strmflags_rd_B) {
          if (ChannelStream_buffered(stream)) {
            sync_file_buffered(stream);
            return TheHandle(TheStream(*stream_)->strm_buffered_channel);
          }
          return TheHandle(TheStream(stream)->strm_ichannel);
        } else if (!inputp && TheStream(stream)->strmflags & strmflags_wr_B) {
          if (ChannelStream_buffered(stream)) {
            /* reposition index back to not yet read position */
            sync_file_buffered(stream);
            return TheHandle(TheStream(*stream_)->strm_buffered_channel);
          }
          return TheHandle(TheStream(stream)->strm_ochannel);
        } else {
          errkind = 2; /* wrong direction */
          goto show_error;
        }
     #ifdef SOCKET_STREAMS
      case strmtype_twoway_socket:
        stream = inputp ? TheStream(stream)->strm_twoway_socket_input
          : TheStream(stream)->strm_twoway_socket_output;
        goto restart_stream_lend_handle;
     #endif
      case strmtype_twoway:
      case strmtype_echo:
        stream = TheStream(stream)->strm_twoway_input;
        goto restart_stream_lend_handle;
      case strmtype_synonym:
        stream = resolve_synonym_stream(stream);
        goto restart_stream_lend_handle;
      #ifdef KEYBOARD
      case strmtype_keyboard:
       #if defined(UNIX) || defined(WIN32_NATIVE)
        if (inputp) {
          if (handletype) *handletype = 1;
          return TheHandle(TheStream(stream)->strm_keyboard_handle);
        } else {
          errkind = 2; /* wrong direction */
          goto show_error;
        }
       #endif
        break;
      #endif
      case strmtype_terminal:
        /* FIXME: no actual need to flush */
        if (handletype) *handletype = 1;
        return TheHandle(inputp?TheStream(stream)->strm_terminal_ihandle:
                         TheStream(stream)->strm_terminal_ohandle);
     #ifdef PIPES
      case strmtype_pipe_in:
        if (inputp) {
          if (ChannelStream_buffered(stream)) {
            /* pipes doesn't support OS level repositioning so I see no way how
            to make interleaved input and lend to work correctly */
            errkind = 1; /* buffered pipe-input-stream is unsupported */
            goto show_error;
          } else {
            if (handletype) *handletype = 1;
            return TheHandle(TheStream(stream)->strm_ichannel);
          }
        } else {
          errkind = 2; /* wrong direction */
          goto show_error;
        }
        break;
      case strmtype_pipe_out:
        if (!inputp) {
          if (handletype) *handletype = 1;
          if (ChannelStream_buffered(stream)) {
            if (BufferedStream_modified(stream))
              buffered_flush(stream);
            return TheHandle(TheStream(stream)->strm_buffered_channel);
          } else
            return TheHandle(TheStream(stream)->strm_ochannel);
        } else {
          errkind = 2; /* wrong direction */
          goto show_error;
        }
        break;
     #endif
      default:
        break;
    }
  }
 show_error:
  pushSTACK(NIL);                      /* no PLACE */
  pushSTACK(stream);                   /* TYPE-ERROR slot DATUM */
  pushSTACK(O(type_open_file_stream)); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(stream);
  pushSTACK(TheSubr(subr_self)->name);
  check_value(type_error,
    (errkind==0)?GETTEXT("~S: argument ~S does not contain a valid OS stream handle")
    :(errkind==1)?GETTEXT("~S: ~S: buffered pipe-input-streams are not supported")
    :GETTEXT("~S: ~S: stream of wrong direction"));
  *stream_ = stream = value1;
  goto restart_stream_lend_handle;
}

/* (READ-BYTE stream [eof-error-p [eof-value]]), CLTL p. 382 */
LISPFUN(read_byte,seclass_default,1,2,norest,nokey,0,NIL) {
  var object stream = check_stream(STACK_2);
  /* read Integer: */
  var object obj = read_byte(stream);
  if (eq(obj,eof_value)) { /* EOF-treatment */
    HANDLE_EOF(STACK_1, STACK_0, 3);
  } else {
    VALUES1(obj); skipSTACK(3); /* return obj */
  }
}

/* (READ-BYTE-LOOKAHEAD stream) */
LISPFUNN(read_byte_lookahead,1) {
  var object stream = check_stream(popSTACK());
  /* Query the status: */
  switch (listen_byte(stream)) {
    case LISTEN_WAIT: value1 = NIL; break;
    case LISTEN_EOF: value1 = S(Keof); break;
    case LISTEN_AVAIL: value1 = T; break;
    case LISTEN_ERROR: OS_filestream_error(stream);
  }
  mv_count=1;
}

/* (READ-BYTE-WILL-HANG-P stream) */
LISPFUNN(read_byte_will_hang_p,1) {
  var object stream = check_stream(popSTACK());
  /* Query the status: */
  VALUES_IF(LISTEN_WAIT == listen_byte(stream));
}

/* (READ-BYTE-NO-HANG stream [eof-error-p [eof-value]]) */
LISPFUN(read_byte_no_hang,seclass_default,1,2,norest,nokey,0,NIL) {
  var object stream = STACK_2 = check_stream(STACK_2);
  /* Query the status: */
  switch (listen_byte(stream)) {
    case LISTEN_WAIT: /* Return NIL. */
      VALUES1(NIL); skipSTACK(3);
      return;
    case LISTEN_EOF: HANDLE_EOF(STACK_1, STACK_0, 3); break;
    case LISTEN_AVAIL: { /* Read a byte: */
      var object obj = read_byte(stream);
      if (!eq(obj,eof_value)) {
        /* Return the read integer. */
        VALUES1(obj); skipSTACK(3);
        return;
      }
    }
    case LISTEN_ERROR: OS_filestream_error(STACK_2);
  }
}

/* (READ-INTEGER stream element-type [endianness [eof-error-p [eof-value]]])
 is a generalized READ-BYTE. */
LISPFUN(read_integer,seclass_default,2,3,norest,nokey,0,NIL) {
  /* check Element-Type */
  var decoded_el_t eltype;
  test_eltype_arg(&STACK_3,&eltype);
  check_multiple8_eltype(&eltype);
  var bool endianness = check_endianness_arg(STACK_2); /* check Endianness */
  STACK_4 = check_stream(STACK_4);
  var uintL bitsize = eltype.size;
  var uintL bytesize = bitsize/8;
  var DYNAMIC_8BIT_VECTOR(bitbuffer,bytesize);
  pushSTACK(bitbuffer);
  /* Stack layout: stream, element-type, endianness, eof-error-p, eof-value, bitbuffer.
   Read the data. */
  if (read_byte_array(&STACK_5,&STACK_0,0,bytesize,persev_full) != bytesize)
    goto eof;
  bitbuffer = STACK_0;
  if (endianness) /* byte swap */
    elt_nreverse(bitbuffer,0,bytesize);
  { /* The data is now in little-endian order. Convert it to an integer. */
    var object result;
    switch (eltype.kind) {
      case eltype_iu:
        result = bitbuff_iu_I(bitbuffer,bitsize,bytesize);
        break;
      case eltype_is:
        result = bitbuff_is_I(bitbuffer,bitsize,bytesize);
        break;
      default: NOTREACHED;
    }
    bitbuffer = STACK_0;
    FREE_DYNAMIC_8BIT_VECTOR(bitbuffer);
    VALUES1(result);
    skipSTACK(6);
    return;
  }
 eof: /* EOF-Treatment */
  HANDLE_EOF(STACK_2, STACK_1, 6);
}

/* (READ-FLOAT stream element-type [endianness [eof-error-p [eof-value]]])
 reads a float in IEEE binary representation. */
LISPFUN(read_float,seclass_default,2,3,norest,nokey,0,NIL) {
  var uintL bytesize = check_float_eltype(&STACK_3); /* check Element-Type */
  var bool endianness = check_endianness_arg(STACK_2); /* check Endianness */
  STACK_4 = check_stream(STACK_4);
  var DYNAMIC_8BIT_VECTOR(bitbuffer,bytesize);
  pushSTACK(bitbuffer);
  /* Stack layout: stream, element-type, endianness, eof-error-p, eof-value, bitbuffer.
   Read the data. */
  if (read_byte_array(&STACK_5,&STACK_0,0,bytesize,persev_full) != bytesize)
    goto eof;
  bitbuffer = STACK_0;
  if (BIG_ENDIAN_P ? !endianness : endianness) /* byte swap */
    elt_nreverse(bitbuffer,0,bytesize);
  /* The data is now in machine-dependent order. Convert it to a float. */
  switch (bytesize) {
    case sizeof(ffloatjanus):
      if (((varobject_alignment % alignof(ffloatjanus)) == 0)
          && ((offsetofa(sbvector_,data) % alignof(ffloatjanus)) == 0)) {
        value1 = c_float_to_FF((ffloatjanus*)&TheSbvector(bitbuffer)->data[0]);
      } else {
        var ffloatjanus tmp;
        copy_mem_b(&tmp,&TheSbvector(bitbuffer)->data[0],sizeof(ffloatjanus));
        value1 = c_float_to_FF(&tmp);
      }
      break;
    case sizeof(dfloatjanus):
      if (((varobject_alignment % alignof(dfloatjanus)) == 0)
          && ((offsetofa(sbvector_,data) % alignof(dfloatjanus)) == 0)) {
        value1 = c_double_to_DF((dfloatjanus*)&TheSbvector(bitbuffer)->data[0]);
      } else {
        var dfloatjanus tmp;
        copy_mem_b(&tmp,&TheSbvector(bitbuffer)->data[0],sizeof(dfloatjanus));
        value1 = c_double_to_DF(&tmp);
      }
      break;
    default: NOTREACHED;
  }
  bitbuffer = STACK_0;
  FREE_DYNAMIC_8BIT_VECTOR(bitbuffer);
  mv_count=1;
  skipSTACK(6);
  return;
 eof: /* EOF-Treatment */
  HANDLE_EOF(STACK_2, STACK_1, 6);
}

/* (WRITE-BYTE integer stream), CLTL p. 385 */
LISPFUNN(write_byte,2) {
  var object stream = check_stream(STACK_0);
  var object obj = STACK_1;
  ASSERT_wr_int(stream,obj);
  /* write Integer: */
  write_byte(stream,obj);
  VALUES1(STACK_1); skipSTACK(2); /* return obj */
}

/* (WRITE-INTEGER integer stream element-type [endianness])
 is a generalized WRITE-BYTE. */
LISPFUN(write_integer,seclass_default,3,1,norest,nokey,0,NIL) {
  /* check Element-Type */
  var decoded_el_t eltype;
  test_eltype_arg(&STACK_1,&eltype);
  check_multiple8_eltype(&eltype);
  var bool endianness = check_endianness_arg(STACK_0); /* check Endianness */
  STACK_2 = check_stream(STACK_2);
  /* check Integer: */
  var uintL bitsize = eltype.size;
  var uintL bytesize = bitsize/8;
  ASSERT_wr_int(STACK_2,STACK_3);
  var DYNAMIC_8BIT_VECTOR(bitbuffer,bytesize);
  pushSTACK(bitbuffer);
  /* Stack layout: obj, stream, element-type, endianness, bitbuffer. */
  /* Copy the integer's data into the buffer. */
  switch (eltype.kind) {
    case eltype_iu:
      bitbuff_ixu_sub(STACK_3,STACK_0,bitsize,STACK_4);
      break;
    case eltype_is:
      bitbuff_ixs_sub(STACK_3,STACK_0,bitsize,STACK_4);
      break;
    default: NOTREACHED;
  }
  /* The data is now in little-endian order. */
  if (endianness) /* byte swap */
    elt_nreverse(STACK_0,0,bytesize);
  /* Write the data. */
  write_byte_array(&STACK_3,&STACK_0,0,bytesize,persev_full);
  bitbuffer = STACK_0;
  FREE_DYNAMIC_8BIT_VECTOR(bitbuffer);
  VALUES1(STACK_4); /* return obj */
  skipSTACK(5);
}

/* (WRITE-FLOAT float stream element-type [endianness])
 writes a float in IEEE binary representation. */
LISPFUN(write_float,seclass_default,3,1,norest,nokey,0,NIL) {
  var uintL bytesize = check_float_eltype(&STACK_1); /* check Element-Type */
  var bool endianness = check_endianness_arg(STACK_0); /* check Endianness */
  STACK_2 = check_stream(STACK_2);
  /* check Float: */
  var object obj = STACK_3;
  switch (bytesize) {
    case sizeof(ffloatjanus):
      if (!single_float_p(obj)) {
        pushSTACK(obj);             /* TYPE-ERROR slot DATUM */
        pushSTACK(S(single_float)); /* TYPE-ERROR slot EXPECTED-TYPE */
        pushSTACK(STACK_(2+2));
        pushSTACK(S(single_float));
        pushSTACK(obj);
        error(type_error,GETTEXT("~S is not a ~S, cannot be output onto ~S"));
      }
      break;
    case sizeof(dfloatjanus):
      if (!double_float_p(obj)) {
        pushSTACK(obj);             /* TYPE-ERROR slot DATUM */
        pushSTACK(S(double_float)); /* TYPE-ERROR slot EXPECTED-TYPE */
        pushSTACK(STACK_(2+2));
        pushSTACK(S(double_float));
        pushSTACK(obj);
        error(type_error,GETTEXT("~S is not a ~S, cannot be output onto ~S"));
      }
      break;
    default: NOTREACHED;
  }
  var DYNAMIC_8BIT_VECTOR(bitbuffer,bytesize);
  pushSTACK(bitbuffer);
  /* Stack layout: obj, stream, element-type, endianness, bitbuffer. */
  obj = STACK_4;
  /* Copy the float's data into the buffer. */
  switch (bytesize) {
    case sizeof(ffloatjanus):
      if (((varobject_alignment % alignof(ffloatjanus)) == 0)
          && ((offsetofa(sbvector_,data) % alignof(ffloatjanus)) == 0)) {
        FF_to_c_float(obj,(ffloatjanus*)&TheSbvector(bitbuffer)->data[0]);
      } else {
        var ffloatjanus tmp;
        FF_to_c_float(obj,&tmp);
        memcpy(&TheSbvector(bitbuffer)->data[0],&tmp,sizeof(ffloatjanus));
      }
      break;
    case sizeof(dfloatjanus):
      if (((varobject_alignment % alignof(dfloatjanus)) == 0)
          && ((offsetofa(sbvector_,data) % alignof(dfloatjanus)) == 0)) {
        DF_to_c_double(obj,(dfloatjanus*)&TheSbvector(bitbuffer)->data[0]);
      } else {
        var dfloatjanus tmp;
        DF_to_c_double(obj,&tmp);
        copy_mem_b(&TheSbvector(bitbuffer)->data[0],&tmp,sizeof(dfloatjanus));
      }
      break;
    default: NOTREACHED;
  }
  /* The data is now in machine-dependent order. */
  if (BIG_ENDIAN_P ? !endianness : endianness) /* byte swap */
    elt_nreverse(bitbuffer,0,bytesize);
  /* Write the data. */
  write_byte_array(&STACK_3,&STACK_0,0,bytesize,persev_full);
  bitbuffer = STACK_0;
  FREE_DYNAMIC_8BIT_VECTOR(bitbuffer);
  VALUES1(STACK_4); /* return obj */
  skipSTACK(5);
}

/* UP: Checks, if an Argument is an open File-Stream.
 check_open_file_stream(obj);
 > obj: Argument
 > permissive_p: return nullobj instead of signaling an error
 < result: open File-Stream (or maybe nullobj if permissive_p was true) */
local object check_open_file_stream (object obj, bool permissive_p) {
 check_open_file_stream_restart:
  obj = resolve_synonym_stream(obj);
  if (streamp(obj) && TheStream(obj)->strmtype == strmtype_broad) {
    var object last_stream = broadcast_stream_last(obj);
    if (eq(last_stream,nullobj)) {
      if (permissive_p) return nullobj;
      else return last_stream;
    } else obj = last_stream;
    goto check_open_file_stream_restart;
  }
  if (!builtin_stream_p(obj)) /* Stream ? */
    goto error_bad_obj;
  if (!(TheStream(obj)->strmtype == strmtype_file)) /* Streamtyp File-Stream ? */
    goto error_bad_obj;
  if ((TheStream(obj)->strmflags & strmflags_open_B) == 0) /* Stream open ? */
    goto error_bad_obj;
  if (nullp(BufferedStream_channel(obj))) /* and Handle /= NIL ? */
    goto error_bad_obj;
  return obj; /* yes -> OK */
 error_bad_obj:
  if (permissive_p) return nullobj;
  pushSTACK(obj);                      /* TYPE-ERROR slot DATUM */
  pushSTACK(O(type_open_file_stream)); /* TYPE-ERROR slot EXPECTED-TYPE */
  pushSTACK(obj);
  pushSTACK(TheSubr(subr_self)->name);
  error(type_error,GETTEXT("~S: argument ~S is not an open file stream"));
}

/* extract the OS file handle from the file stream
 > stream: open Lisp file stream
 < fd: OS file handle
 > permissive_p: return nullobj instead of signaling an error
 < result: either stream, or a corrected stream in case stream was invalid
           or nullobj if permissive_p was true and the stream was invalid
 for syscall module
 can trigger GC */
modexp maygc object open_file_stream_handle
(object stream, Handle *fd, bool permissive_p) {
  stream = check_open_file_stream(stream,permissive_p);
  if (!eq(stream,nullobj))
    *fd = ChannelStream_ihandle(stream);
  return stream;
}

/* return the OS's idea of the stream length for the file stream
 > stream_: for error reporting - point to GC safe location
 > fd: OS file handle
 < result: the length of the stream
 should be wrapped in begin_blocking_system_call()/end_blocking_system_call()
 for gdbm module */
modexp maygc off_t handle_length (gcv_object_t *stream_, Handle fd) {
  off_t len, pos;
  fd_lseek(stream_,fd,0,SEEK_CUR,pos=); /* save current location */
  fd_lseek(stream_,fd,0,SEEK_END,len=); /* get EOF location */
  /* if the above call fails, we may be screwed now:
     the file position was modified but not restored.
     However, this would indicate a bug in the underlying lseek()
     implementation, see the list of ERRORS in
     http://opengroup.org/onlinepubs/9699919799/functions/lseek.html */
  fd_lseek(stream_,fd,pos,SEEK_SET,); /* restore the original location */
  return len;
}

typedef enum { POS_QUERY, POS_SET_START, POS_SET_END, POS_SET_OFF } pos_arg_t;
LISPFUN(file_position,seclass_default,1,1,norest,nokey,0,NIL)
{ /* (FILE-POSITION stream [position]), CLTL p. 425 */
  var object position = STACK_0;
  var object stream = STACK_1;
  var uoff_t pos_off = 0;
  var pos_arg_t pos_type = POS_QUERY;
  if (boundp(position)) {
    if (eq(position,S(Kstart))) { /* set position to start: */
      pos_type = POS_SET_START;
    } else if (eq(position,S(Kend))) { /* set position to end: */
      pos_type = POS_SET_END;
    } else if (uoff_t_p(position)) { /* set position as specified: */
      pos_type = POS_SET_OFF;
      pos_off = I_to_uoff_t(position);
    } else { /* illegal Position-Argument */
      pushSTACK(position);         /* TYPE-ERROR slot DATUM */
      pushSTACK(O(type_position)); /* TYPE-ERROR slot EXPECTED-TYPE */
      pushSTACK(position); pushSTACK(S(Kend)); pushSTACK(S(Kstart));
      pushSTACK(TheSubr(subr_self)->name);
      error(type_error,GETTEXT("~S: position argument should be ~S or ~S or a nonnegative integer, not ~S"));
    }
  }
 restart_file_position:
  if (builtin_stream_p(stream)) {
    switch (TheStream(stream)->strmtype) {
      case strmtype_synonym:    /* Synonym-Stream: follow further */
        resolve_as_synonym(stream);
        goto restart_file_position;
      case strmtype_broad:      /* Broadcast-Stream: */
        stream = broadcast_stream_last(stream);
        if (eq(stream,nullobj)) { /* empty BROADCAST-STREAM? */
          /* http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/syscla_broadcast-stream.html */
          VALUES1(Fixnum_0); break;
        }
        goto restart_file_position;
      case strmtype_str_in: {
        STACK_1 = stream;
        var stringarg arg;
        pushSTACK(TheStream(stream)->strm_str_in_string);
        switch (pos_type) {
          case POS_SET_END: {   /* :END */
            pushSTACK(TheStream(stream)->strm_str_in_begindex);
            pushSTACK(TheStream(stream)->strm_str_in_endindex);
            test_string_limits_ro(&arg);
            stream = STACK_1; /* restore */
            TheStream(stream)->strm_str_in_index =
              TheStream(stream)->strm_str_in_endindex;
            value1 = fixnum(arg.len);
          } break;
          case POS_SET_START: { /* :START */
            TheStream(stream)->strm_str_in_index =
              TheStream(stream)->strm_str_in_begindex;
            value1 = Fixnum_0;
            skipSTACK(1);
          } break;
          case POS_SET_OFF: {   /* OFFSET */
            pushSTACK(TheStream(stream)->strm_str_in_begindex);
            pushSTACK(fixnum_inc(STACK_0,pos_off));
            test_string_limits_ro(&arg);
            stream = STACK_1; /* restore */
            TheStream(stream)->strm_str_in_index = fixnum(arg.index+arg.len);
            value1 = fixnum(arg.len); /* == pos */
          } break;
          case POS_QUERY: {     /* ask for position */
            pushSTACK(TheStream(stream)->strm_str_in_begindex);
            pushSTACK(TheStream(stream)->strm_str_in_index);
            test_string_limits_ro(&arg);
            stream = STACK_1; /* restore */
            pos_off = arg.len;
          } goto get_position_common;
          default: NOTREACHED;
        }
       set_position_common:   /* value1 is pre-set! */
        TheStream(stream)->strm_rd_ch_last = NIL; /* Lastchar := NIL */
        TheStream(stream)->strmflags &= ~strmflags_unread_B;
        mv_count = 1;
      } break;
      case strmtype_str_out: {
        var object ssstring = TheStream(stream)->strm_str_out_string;
        switch (pos_type) {
          case POS_SET_END:     /* :END */
            break;              /* do nothing */
          case POS_SET_START:   /* :START */
            TheIarray(ssstring)->dims[1] = 0; /* fill-pointer := 0 */
            break;
          case POS_SET_OFF:     /* OFFSET */
            if (pos_off <= TheIarray(ssstring)->dims[1]) {
              TheIarray(ssstring)->dims[1] = pos_off;
            } else {
              pushSTACK(fixnum(pos_off));
              error_index_range(ssstring,TheIarray(ssstring)->dims[1]);
            }
            break;
          case POS_QUERY:
            pos_off = TheIarray(ssstring)->dims[1];
            goto get_position_common;
          default: NOTREACHED;
        }
        value1 = fixnum(TheIarray(ssstring)->dims[1]);
        goto set_position_common;
      } break;
      case strmtype_str_push: {
        var object string = TheStream(stream)->strm_str_push_string;
        switch (pos_type) {
          case POS_SET_END: {   /* :END */
            /* Pretend that the "end" of the stream corresponds to the current
               fill-pointer. The array-dimension 0 wouldn't be the right choice
               because it depends on how the implementation increases the size
               during vector-push-extend. A slightly better choice would be
               the maximum value of the fill-pointer during the lifetime of the
               stream, but since the user can modify the fill-pointer directly,
               this is hairy to implement correctly. */
            value1 = fixnum(vector_length(string));
            /* No need to call set-fill-pointer because it would be a nop. */
          } break;
          case POS_SET_START:        /* :START, pos_off==0 already */
          case POS_SET_OFF: {        /* OFFSET */
            pushSTACK(string); pushSTACK(fixnum(pos_off)); C_set_fill_pointer();
          } break;
          case POS_QUERY: {
            pos_off = vector_length(string);
          } goto get_position_common;
          default: NOTREACHED;
        }
        goto set_position_common;
      } break;
      case strmtype_file:
        stream = check_open_file_stream(stream,false); /* check open */
        if (!ChannelStream_buffered(stream)) {
          var Handle fd = TheHandle(TheStream(stream)->strmflags & strmflags_wr_B
                                    ? ChannelStream_ochannel(stream)
                                    : ChannelStream_ichannel(stream));
          pushSTACK(stream);
          switch (pos_type) {
            case POS_SET_END:   /* :END */
              begin_blocking_system_call();
              handle_lseek(&STACK_0,fd,0,SEEK_END,pos_off=);
              stream = popSTACK();
              end_blocking_system_call();
              goto get_position_pos_off;
            case POS_SET_START: /* :START */
              begin_blocking_system_call();
              handle_lseek(&STACK_0,fd,0,SEEK_SET,pos_off=);
              stream = popSTACK();
              end_blocking_system_call();
              goto get_position_pos_off;
            case POS_SET_OFF:   /* OFFSET */
              begin_blocking_system_call();
              handle_lseek(&STACK_0,fd,pos_off,SEEK_SET,pos_off=);
              stream = popSTACK();
              end_blocking_system_call();
            get_position_pos_off:
              VALUES1(uoff_to_I(pos_off)); break;
            case POS_QUERY:
              begin_blocking_system_call();
              handle_lseek(&STACK_0,fd,0,SEEK_CUR,pos_off=);
              stream = popSTACK();
              end_blocking_system_call();
              goto get_position_common;
            default: NOTREACHED;
          }
        } else {
          pushSTACK(stream);
          switch (pos_type) {
            case POS_SET_END:   /* :END */
              VALUES1(uoff_to_I(logical_position_file_end(stream)));
              stream = popSTACK();
              break;
            case POS_SET_START: /* :START */
              VALUES1(uoff_to_I(logical_position_file_start(stream)));
              stream = popSTACK();
              break;
            case POS_SET_OFF:   /* OFFSET */
              VALUES1(uoff_to_I(logical_position_file(stream,pos_off)));
              stream = popSTACK();
              break;
            case POS_QUERY:
              pos_off = BufferedStream_position(stream);
              stream = popSTACK();
              /* if a character has been unread, decrement position
                 so that PEEK-CHAR does not modify FILE-POSITION */
            get_position_common:
              VALUES1(uoff_to_I(pos_off - (TheStream(stream)->strmflags
                                           & strmflags_unread_B ? 1 : 0)));
              break;
            default: NOTREACHED;
          }
        }
        break;
      default: /* do not know what to do ==> NIL */
        VALUES1(NIL); break;
    }
    skipSTACK(2);
  } else { /* (GRAY:STREAM-POSITION stream position) */
    if (!boundp(STACK_0)) STACK_0 = NIL;
    funcall(S(stream_position),2);
  }
}

LISPFUNNR(file_length,1)
{ /* (FILE-LENGTH file-stream), CLTL p. 425 */
  var object stream = STACK_0;
  stream = check_open_file_stream(stream,false); /* check stream */
  if (eq(stream,nullobj)) { /* empty BROADCAST-STREAM */
    /* http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/syscla_broadcast-stream.html */
    skipSTACK(1);
    VALUES1(Fixnum_0); return;
  }
  if (!ChannelStream_buffered(stream)) {
    off_t len;
    Handle fd=ChannelStream_ihandle(stream);
    begin_blocking_system_call();
    len = handle_length(&STACK_0,fd);
    end_blocking_system_call();
    VALUES1(off_to_I(len));
  } else {
    /* memorize Position: */
    var uoff_t position = BufferedStream_position(stream);
    /* set position to end and memorize End-Position: */
    var uoff_t endposition = logical_position_file_end(stream);
    stream = STACK_0;
    /* set back to old position: */
    logical_position_file(stream,position);
    VALUES1(uoff_to_I(endposition)); /* return End-Position */
  }
  skipSTACK(1);
}

LISPFUNN(file_string_length,2)
{ /* (FILE-STRING-LENGTH stream object) */
  var object stream = check_open_file_stream(STACK_1,false); /* check stream */
  var object obj = STACK_0;
  skipSTACK(2);
  if (eq(stream,nullobj)) { /* empty BROADCAST-STREAM */
    /* http://www.ai.mit.edu/projects/iiip/doc/CommonLISP/HyperSpec/Body/syscla_broadcast-stream.html */
    VALUES1(Fixnum_1); return;
  }
  if (!(TheStream(stream)->strmflags & strmflags_wr_ch_B))
    error_illegal_streamop(S(file_string_length),stream);
  var object encoding = TheStream(stream)->strm_encoding;
 #if defined(ENABLE_UNICODE) && defined(HAVE_GOOD_ICONV)
  if (simple_string_p(TheEncoding(encoding)->enc_charset)) {
    /* iconv-based encodings have state. Since we cannot duplicate an iconv_t
     we have no way to know for sure how many bytes the string will span. */
    if (stringp(obj)) {
      VALUES1(vector_length(obj) == 0 ? Fixnum_0 : NIL);
    } else if (charp(obj)) {
      VALUES1(NIL);
    } else
      error_write(stream,obj,S(character));
    return;
  }
 #endif
 #ifdef ENABLE_UNICODE
  if (TheEncoding(encoding)->min_bytes_per_char !=
      TheEncoding(encoding)->max_bytes_per_char) {
    /* Have to look at each character individually. */
    var const chart* charptr;
    var uintL len;
    var chart auxch;
    if (stringp(obj)) {
      var uintL offset;
      var object string = unpack_string_ro(obj,&len,&offset);
      unpack_sstring_alloca(string,len,offset, charptr=);
    } else if (charp(obj)) {
      auxch = char_code(obj); charptr = &auxch; len = 1;
    } else
      error_write(stream,obj,S(character));
    if (eq(TheEncoding(encoding)->enc_eol,S(Kunix))) {
      /* Treat all the characters all at once. */
      var uintL result = cslen(encoding,charptr,len);
      VALUES1(UL_to_I(result)); return;
    } else {
      /* Treat line-by-line. */
      var const chart* eol_charptr;
      var uintL eol_len;
      if (eq(TheEncoding(encoding)->enc_eol,S(Kmac))) {
        static const chart eol_mac[1] = { ascii(CR) };
        eol_charptr = &eol_mac[0]; eol_len = 1;
      } else if (eq(TheEncoding(encoding)->enc_eol,S(Kdos))) {
        static const chart eol_dos[2] = { ascii(CR), ascii(LF) };
        eol_charptr = &eol_dos[0]; eol_len = 2;
      } else {
        NOTREACHED;
      }
      var const chart* endptr = charptr+len;
      var uintL result = 0;
      while (charptr < endptr) {
        /* Search the next NL. */
        var const chart* ptr = charptr;
        while (!chareq(*ptr,ascii(NL))) {
          ptr++;
          if (ptr == endptr)
            break;
        }
        /* Count the bytes needed for the characters before the NL. */
        if (!(ptr == charptr))
          result += cslen(encoding,charptr,ptr-charptr);
        charptr = ptr;
        /* Count the bytes needed for the NL. */
        if (charptr < endptr) {
          /* *charptr is ascii(NL). */
          result += cslen(encoding,eol_charptr,eol_len);
          charptr++;
        }
      }
      VALUES1(UL_to_I(result)); return;
    }
  }
  /* Now the easy case: a fixed number of bytes per character. */
  var uintL bytes_per_char = TheEncoding(encoding)->min_bytes_per_char;
 #else
  #define bytes_per_char  1
 #endif
  if (eq(TheEncoding(encoding)->enc_eol,S(Kunix))
      || eq(TheEncoding(encoding)->enc_eol,S(Kmac))) {
    if (stringp(obj)) {
      var uintL result = vector_length(obj);
      VALUES1(UL_to_I(result*bytes_per_char)); return;
    } else if (charp(obj)) {
      VALUES1(fixnum(bytes_per_char)); return;
    } else
      error_write(stream,obj,S(character));
  }
  if (eq(TheEncoding(encoding)->enc_eol,S(Kdos))) {
    /* Take into account the NL -> CR/LF translation. */
    if (stringp(obj)) {
      var uintL len;
      var uintL offset;
      var object string = unpack_string_ro(obj,&len,&offset);
      var uintL result = len;
      if (len > 0) {
        SstringDispatch(string,X, {
          var const cintX* charptr = &((SstringX)TheVarobject(string))->data[offset];
          var uintL count;
          dotimespL(count,len, {
            if (chareq(as_chart(*charptr++),ascii(NL)))
              result++;
          });
        });
      }
      VALUES1(UL_to_I(result*bytes_per_char)); return;
    } else if (charp(obj)) {
      var uintL result = 1;
      if (chareq(char_code(obj),ascii(NL)))
        result++;
      VALUES1(fixnum(result*bytes_per_char)); return;
    } else
      error_write(stream,obj,S(character));
  }
  NOTREACHED;
  #undef bytes_per_char
}

/* UP: Tells whether a stream is buffered.
 stream_isbuffered(stream)
 > stream: a channel or socket stream
 < avail: the number of bytes available in the input buffer
 < result: bit(1) set if input side is buffered,
           bit(0) set if output side is buffered */
local uintB stream_isbuffered_low (object stream, uintL *avail) {
  switch (TheStream(stream)->strmtype) {
    case strmtype_file:
    #ifdef PIPES
    case strmtype_pipe_in:
    case strmtype_pipe_out:
    #endif
    #ifdef X11SOCKETS
    case strmtype_x11socket:
    #endif
    #ifdef SOCKET_STREAMS
    case strmtype_socket:
    #endif
      if (ChannelStream_buffered(stream)) {
        if (avail) *avail = BufferedStream_endvalid(stream)
          - BufferedStream_index(stream);
        return bit(1)|bit(0);
      } else return 0;
    #ifdef SOCKET_STREAMS
    case strmtype_twoway_socket:
    #endif
    case strmtype_twoway: {
      var object input = TheStream(stream)->strm_twoway_socket_input;
      var uintB input_b = 0;
      if (ChannelStream_buffered(input)) {
        input_b = bit(1);
        if (avail) *avail = BufferedStream_endvalid(input)
          - BufferedStream_index(input);
      }
      return input_b | (ChannelStream_buffered(TheStream(stream)->strm_twoway_socket_output) ? bit(0) : 0);
    }
    default:
      return 0;
  }
}
global uintB stream_isbuffered (object stream)
{ return stream_isbuffered_low(stream,NULL); }

/* UP: Returns the current line number of a stream.
 stream_line_number(stream)
 > stream: a stream
 < result: an integer or NIL
 can trigger GC */
global maygc object stream_line_number (object stream) {
  return (builtin_stream_p(stream)
          && TheStream(stream)->strmtype == strmtype_file
          && eq(TheStream(stream)->strm_eltype,S(character))
          ? UL_to_I(ChannelStream_lineno(stream)) /* current line-number */
          : NIL);                                 /* NIL if unknown */
}

/* (SYS::LINE-NUMBER stream) returns the current line-number (if stream
 is a Character-File-Input-Stream, which was only used for reading). */
LISPFUNN(line_number,1) {
  var object stream = check_stream(popSTACK());
  VALUES1(stream_line_number(stream));
}

/* Function: Returns true if a stream is a FASL stream:
   "i/o consistency is more important than ANSI compliance"
 == read-eval is allowed regardless of *READ-EVAL*
 == #\Return in strings and symbols is printed as \r
 == #\Newline in strings and symbols is printed as \n
 == literal newline inside strings is ignored on input
 stream_get_read_eval(stream)
 > stream: a stream
 < result: true if read-eval is allowed from the stream, else false
 can trigger GC */
global maygc bool stream_get_fasl (object stream) {
  if (builtin_stream_p(stream)) {
    return ((TheStream(stream)->strmflags & strmflags_fasl_B) != 0);
  } else {
    /* (SLOT-VALUE stream '$fasl): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(fasl),TheClass(clas)->slot_location_table,false);
    var object value = TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)];
    return !nullp(value);
  }
}

/* Function: Changes the FASL state of a stream.
 stream_set_read_eval(stream,value);
 > stream: a stream
 > value: true if the stream should be a FASL stream, else false
 can trigger GC */
global maygc void stream_set_fasl (object stream, bool value) {
  if (builtin_stream_p(stream)) {
    if (value)
      TheStream(stream)->strmflags |= strmflags_fasl_B;
    else
      TheStream(stream)->strmflags &= ~strmflags_fasl_B;
  } else {
    /* (SETF (SLOT-VALUE stream '$fasl) value): */
    var object stream_forwarded = stream;
    instance_un_realloc(stream_forwarded);
    instance_update(stream,stream_forwarded);
    var object cv = TheInstance(stream_forwarded)->inst_class_version;
    var object clas = TheClassVersion(cv)->cv_class;
    var object slotinfo = gethash(S(fasl),TheClass(clas)->slot_location_table,false);
    TheSrecord(stream_forwarded)->recdata[posfixnum_to_V(slotinfo)] = (value ? T : NIL);
  }
}

/* (SYS::STREAM-FASL-P stream) returns the stream's FASL flag.
 (SYS::STREAM-FASL-P stream flag) sets the stream's FASL flag. */
LISPFUN(stream_fasl_p,seclass_default,1,1,norest,nokey,0,NIL) {
  var object stream = check_stream(STACK_1);
  var object flag = STACK_0;
  if (!boundp(flag)) {
    value1 = (stream_get_fasl(stream) ? T : NIL);
  } else {
    if (nullp(flag)) {
      stream_set_fasl(stream,false); value1 = NIL;
    } else {
      stream_set_fasl(stream,true); value1 = T;
    }
  }
  skipSTACK(2); mv_count=1;
}

/* (SYS::%DEFGRAY fundamental-stream-classes)
 Initializes O(class_fundamental*_stream). */
LISPFUNN(defgray,1) {
  copy_mem_o(&O(class_fundamental_stream),&TheSvector(STACK_0)->data[0],
             Svector_length(STACK_0));
  VALUES0; skipSTACK(1);
}

/* ====================================================================== */

/* table of all pseudo-functions */
global struct pseudocode_tab_ pseudocode_tab = {
  #define PSEUDO  PSEUDO_D
  #include "pseudofun.c"
  #undef PSEUDO
};
global struct pseudodata_tab_ pseudodata_tab = {
  #define PSEUDO  PSEUDO_E
  #include "pseudofun.c"
  #undef PSEUDO
  #if defined(MICROSOFT) && !defined(ENABLE_UNICODE)
   (Pseudofun) NULL
  #endif
};

/* ====================================================================== */

/* protect filestatus/if_file_exists, file_datetime by break_sem_4??
 Signal-Handling on EXECUTE, SHELL, MAKE-PIPE-INPUT-STREAM, MAKE-PIPE-OUTPUT-STREAM, MAKE-PIPE-IO-STREAM ??
 naming of file/handle/buffered/b_file/unbuffered stuff
 do not access strm_file_truename on pipe and socket streams
 implement FILE-POSITION for unbuffered file-streams (regular handle, direction != 5)
 LISTEN on unbuffered (non-regular) file and socket streams can cause the process to block */
