/****************************************
*  Computer Algebra System SINGULAR     *
****************************************/

//**************************************************************************/
//
//
//**************************************************************************/
// 'ndbm.cc' containes all low-level functions to manipulate dbm-files
// for the original Copyright of this file and 'ndbm.h' see below .
//
// some minor change where needed to compile and run under MacOS/MPW
//
//**************************************************************************/


#include "kernel/mod2.h"

#ifdef HAVE_DBM
#include "reporter/si_signals.h"
#include "Singular/links/ndbm.h"
#ifndef HPUX_9
#include <strings.h>
#endif
/*
 * Copyright (c) 1983 Regents of the University of California.
 * All rights reserved.  The Berkeley software License Agreement
 * specifies the terms and conditions for redistribution.
 * for details see ndbm.h
 */

//**************************************************************************/

/* alternative:
* #   define EPERM 1
* #   define ENOMEM 23
* #   define ENOSPC 28
*/
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#ifndef HAVE_BCOPY
#   define bcopy(a,b,c) memmove(b,a,c)
#endif /* not HAVE_BCOPY */

#define BYTESIZ 8
#undef setbit

static  void dbm_access(DBM *db, long hash);
static  int getbit(DBM *db);
static  void setbit(DBM *db);
static  datum makdatum(char buf[PBLKSIZ], int n);
static  int finddatum(char buf[PBLKSIZ], datum item);
static  long dcalchash(datum item);
static  int delitem(char buf[PBLKSIZ], int n);
static  int additem(char buf[PBLKSIZ], datum item, datum item1);
extern "C" int singular_fstat(int fd, struct stat *buf);

DBM * dbm_open(char *file, int flags, int mode)
{
  struct stat statb;
  DBM *db;

  if ((db = (DBM *)malloc(sizeof *db)) == 0)
  {
    errno = ENOMEM;
    return ((DBM *)0);
  }
#ifdef MSDOS
  // default mode of open is ascii, we need binary mode.
  flags |= O_BINARY;
#endif
  db->dbm_flags = (flags & 03) == O_RDONLY ? _DBM_RDONLY : 0;
  if ((flags & 03) == O_WRONLY)
    flags = (flags & ~03) | O_RDWR;
  strcpy(db->dbm_pagbuf, file);
  strcat(db->dbm_pagbuf, ".pag");
  db->dbm_pagf = si_open(db->dbm_pagbuf, flags, mode);
  if (db->dbm_pagf < 0)
    goto bad;
  strcpy(db->dbm_pagbuf, file);
  strcat(db->dbm_pagbuf, ".dir");
  db->dbm_dirf = si_open(db->dbm_pagbuf, flags, mode);
  if (db->dbm_dirf < 0)
    goto bad1;
  singular_fstat(db->dbm_dirf, &statb);
  db->dbm_maxbno = statb.st_size*BYTESIZ-1;
  db->dbm_pagbno = db->dbm_dirbno = -1;
  return (db);
bad1:
  (void) si_close(db->dbm_pagf);
bad:
  free((char *)db);
  return ((DBM *)0);
}

void dbm_close(DBM *db)
{
  (void) si_close(db->dbm_dirf);
  (void) si_close(db->dbm_pagf);
  free((char *)db);
}

long dbm_forder(DBM *db, datum key)
{
  long hash;

  hash = dcalchash(key);
  for (db->dbm_hmask=0;; db->dbm_hmask=(db->dbm_hmask<<1)+1)
  {
    db->dbm_blkno = hash & db->dbm_hmask;
    db->dbm_bitno = db->dbm_blkno + db->dbm_hmask;
    if (getbit(db) == 0)
      break;
  }
  return (db->dbm_blkno);
}

datum dbm_fetch(DBM *db, datum key)
{
  int i;
  datum item;

  if (dbm_error(db))
    goto err;
  dbm_access(db, dcalchash(key));
  if ((i = finddatum(db->dbm_pagbuf, key)) >= 0)
  {
    item = makdatum(db->dbm_pagbuf, i+1);
    if (item.dptr != NULL)
      return (item);
  }
err:
  item.dptr = NULL;
  item.dsize = 0;
  return (item);
}

int dbm_delete(DBM *db, datum key)
{
  int i;
  // datum item;

  if (dbm_error(db))
    return (-1);
  if (dbm_rdonly(db))
  {
    errno = EPERM;
    return (-1);
  }
  dbm_access(db, dcalchash(key));
  if ((i = finddatum(db->dbm_pagbuf, key)) < 0)
    return (-1);
  if (!delitem(db->dbm_pagbuf, i))
    goto err;
  db->dbm_pagbno = db->dbm_blkno;
  (void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, SEEK_SET);
  if (si_write(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ)
  {
  err:
    db->dbm_flags |= _DBM_IOERR;
    return (-1);
  }
  return (0);
}

int dbm_store(DBM *db, datum key, datum dat, int replace)
{
  int i;
  int ret;
  datum item, item1;
  char ovfbuf[PBLKSIZ];

  if (dbm_error(db))
    return (-1);
  if (dbm_rdonly(db))
  {
    errno = EPERM;
    return (-1);
  }

_loop:
  dbm_access(db, dcalchash(key));
  if ((i = finddatum(db->dbm_pagbuf, key)) >= 0)
  {
    if (!replace)
      return (1);
    if (!delitem(db->dbm_pagbuf, i))
    {
      db->dbm_flags |= _DBM_IOERR;
      return (-1);
    }
  }
  if (!additem(db->dbm_pagbuf, key, dat))
    goto split;
  db->dbm_pagbno = db->dbm_blkno;
  (void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, SEEK_SET);
  if ( (ret=si_write(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ)) != PBLKSIZ)
  {
    db->dbm_flags |= _DBM_IOERR;
    return (-1);
  }
  return (0);

split:
  if (key.dsize+dat.dsize+3*sizeof(short) >= PBLKSIZ)
  {
    db->dbm_flags |= _DBM_IOERR;
    errno = ENOSPC;
    return (-1);
  }
  memset(ovfbuf, 0, PBLKSIZ);
  for (i=0;;) {
    item = makdatum(db->dbm_pagbuf, i);
    if (item.dptr == NULL)
      break;
    if (dcalchash(item) & (db->dbm_hmask+1))
    {
      item1 = makdatum(db->dbm_pagbuf, i+1);
      if (item1.dptr == NULL) {
        fprintf(stderr, "ndbm: split not paired\n");
        db->dbm_flags |= _DBM_IOERR;
        break;
      }
      if (!additem(ovfbuf, item, item1) ||
          !delitem(db->dbm_pagbuf, i))
      {
        db->dbm_flags |= _DBM_IOERR;
        return (-1);
      }
      continue;
    }
    i += 2;
  }
  db->dbm_pagbno = db->dbm_blkno;
  (void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, SEEK_SET);
  if (si_write(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ)
  {
    db->dbm_flags |= _DBM_IOERR;
    return (-1);
  }
  (void) lseek(db->dbm_pagf, (db->dbm_blkno+db->dbm_hmask+1)*PBLKSIZ, SEEK_SET);
  if (si_write(db->dbm_pagf, ovfbuf, PBLKSIZ) != PBLKSIZ)
  {
    db->dbm_flags |= _DBM_IOERR;
    return (-1);
  }
  setbit(db);
  goto _loop;
}

datum dbm_firstkey(DBM *db)
{

  db->dbm_blkptr = 0L;
  db->dbm_keyptr = 0;
  return (dbm_nextkey(db));
}

datum dbm_nextkey(DBM *db)
{
  struct stat statb;
  datum item;

  if (dbm_error(db)
       || singular_fstat(db->dbm_pagf, &statb) < 0
  )
                goto err;
  statb.st_size /= PBLKSIZ;
  for (;;)
  {
    if (db->dbm_blkptr != db->dbm_pagbno)
    {
      db->dbm_pagbno = db->dbm_blkptr;
      (void) lseek(db->dbm_pagf, db->dbm_blkptr*PBLKSIZ, SEEK_SET);
      if (si_read(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ)
        memset(db->dbm_pagbuf, 0, PBLKSIZ);
#ifdef DEBUG
      else if (chkblk(db->dbm_pagbuf) < 0)
        db->dbm_flags |= _DBM_IOERR;
#endif
    }
    if (((short *)db->dbm_pagbuf)[0] != 0)
    {
      item = makdatum(db->dbm_pagbuf, db->dbm_keyptr);
      if (item.dptr != NULL)
      {
        db->dbm_keyptr += 2;
        return (item);
      }
      db->dbm_keyptr = 0;
    }
    if (++db->dbm_blkptr >= statb.st_size)
      break;
  }
err:
  item.dptr = NULL;
  item.dsize = 0;
  return (item);
}

static void dbm_access(DBM *db, long hash)
{
  for (db->dbm_hmask=0;; db->dbm_hmask=(db->dbm_hmask<<1)+1)
  {
    db->dbm_blkno = hash & db->dbm_hmask;
    db->dbm_bitno = db->dbm_blkno + db->dbm_hmask;
    if (getbit(db) == 0)
      break;
  }
  if (db->dbm_blkno != db->dbm_pagbno)
  {
    db->dbm_pagbno = db->dbm_blkno;
    (void) lseek(db->dbm_pagf, db->dbm_blkno*PBLKSIZ, SEEK_SET);
    if (si_read(db->dbm_pagf, db->dbm_pagbuf, PBLKSIZ) != PBLKSIZ)
      memset(db->dbm_pagbuf, 0, PBLKSIZ);
#ifdef DEBUG
    else if (chkblk(db->dbm_pagbuf) < 0)
      db->dbm_flags |= _DBM_IOERR;
#endif
  }
}

static int getbit(DBM *db)
{
  long bn;
  int b, i, n;


  if (db->dbm_bitno > db->dbm_maxbno)
    return (0);
  n = db->dbm_bitno % BYTESIZ;
  bn = db->dbm_bitno / BYTESIZ;
  i = bn % DBLKSIZ;
  b = bn / DBLKSIZ;
  if (b != db->dbm_dirbno)
  {
    db->dbm_dirbno = b;
    (void) lseek(db->dbm_dirf, (long)b*DBLKSIZ, SEEK_SET);
    if (si_read(db->dbm_dirf, db->dbm_dirbuf, DBLKSIZ) != DBLKSIZ)
      memset(db->dbm_dirbuf, 0, DBLKSIZ);
  }
  return (db->dbm_dirbuf[i] & (1<<n));
}

static void setbit(DBM *db)
{
  long bn;
  int i, n, b;

  if (db->dbm_bitno > db->dbm_maxbno)
    db->dbm_maxbno = db->dbm_bitno;
  n = db->dbm_bitno % BYTESIZ;
  bn = db->dbm_bitno / BYTESIZ;
  i = bn % DBLKSIZ;
  b = bn / DBLKSIZ;
  if (b != db->dbm_dirbno)
  {
    db->dbm_dirbno = b;
    (void) lseek(db->dbm_dirf, (long)b*DBLKSIZ, SEEK_SET);
    if (si_read(db->dbm_dirf, db->dbm_dirbuf, DBLKSIZ) != DBLKSIZ)
      memset(db->dbm_dirbuf, 0, DBLKSIZ);
  }
  db->dbm_dirbuf[i] |= 1<<n;
  db->dbm_dirbno = b;
  (void) lseek(db->dbm_dirf, (long)b*DBLKSIZ, SEEK_SET);
  if (si_write(db->dbm_dirf, db->dbm_dirbuf, DBLKSIZ) != DBLKSIZ)
    db->dbm_flags |= _DBM_IOERR;
}

static datum makdatum(char buf[PBLKSIZ], int n)
{
  short *sp;
  int t;
  datum item;

  sp = (short *)buf;
  if ((unsigned)n >= (unsigned)sp[0])
  {
    item.dptr = NULL;
    item.dsize = 0;
    return (item);
  }
  t = PBLKSIZ;
  if (n > 0)
    t = sp[n];
  item.dptr = buf+sp[n+1];
  item.dsize = t - sp[n+1];
  return (item);
}

static int finddatum(char buf[PBLKSIZ], datum item)
{
  short *sp;
  int i, n, j;

  sp = (short *)buf;
  n = PBLKSIZ;
  for (i=0, j=sp[0]; i<j; i+=2, n = sp[i])
  {
    n -= sp[i+1];
    if (n != item.dsize)
      continue;
    if (n == 0 || memcmp(&buf[sp[i+1]], item.dptr, n) == 0)
      return (i);
  }
  return (-1);
}

static  int hitab[16]
/* ken's
{
        055,043,036,054,063,014,004,005,
        010,064,077,000,035,027,025,071,
};
*/
 = {    61, 57, 53, 49, 45, 41, 37, 33,
        29, 25, 21, 17, 13,  9,  5,  1,
};
static  long hltab[64]
 = {
        06100151277L,06106161736L,06452611562L,05001724107L,
        02614772546L,04120731531L,04665262210L,07347467531L,
        06735253126L,06042345173L,03072226605L,01464164730L,
        03247435524L,07652510057L,01546775256L,05714532133L,
        06173260402L,07517101630L,02431460343L,01743245566L,
        00261675137L,02433103631L,03421772437L,04447707466L,
        04435620103L,03757017115L,03641531772L,06767633246L,
        02673230344L,00260612216L,04133454451L,00615531516L,
        06137717526L,02574116560L,02304023373L,07061702261L,
        05153031405L,05322056705L,07401116734L,06552375715L,
        06165233473L,05311063631L,01212221723L,01052267235L,
        06000615237L,01075222665L,06330216006L,04402355630L,
        01451177262L,02000133436L,06025467062L,07121076461L,
        03123433522L,01010635225L,01716177066L,05161746527L,
        01736635071L,06243505026L,03637211610L,01756474365L,
        04723077174L,03642763134L,05750130273L,03655541561L,
};

static long dcalchash(datum item)
{
  int s, c, j;
  char *cp;
  unsigned long hashl;
  unsigned int hashi;

  hashl = 0;
  hashi = 0;
  for (cp = item.dptr, s=item.dsize; --s >= 0; )
  {
    c = *cp++;
    for (j=0; j<BYTESIZ; j+=4)
    {
      hashi += hitab[c&017];
      hashl += hltab[hashi&63];
      c >>= 4;
    }
  }
  return (long)(hashl);
}

/*
 * Delete pairs of items (n & n+1).
 */
static int delitem(char buf[PBLKSIZ], int n)
{
  short *sp, *sp1;
  int i1, i2;

  sp = (short *)buf;
  i2 = sp[0];
  if ((unsigned)n >= (unsigned)i2 || (n & 1))
    return (0);
  if (n == i2-2)
  {
    sp[0] -= 2;
    return (1);
  }
  i1 = PBLKSIZ;
  if (n > 0)
    i1 = sp[n];
  i1 -= sp[n+2];
  if (i1 > 0)
  {
    i2 = sp[i2];
    bcopy(&buf[i2], &buf[i2 + i1], sp[n+2] - i2);
  }
  sp[0] -= 2;
  for (sp1 = sp + sp[0], sp += n+1; sp <= sp1; sp++)
    sp[0] = sp[2] + i1;
  return (1);
}

/*
 * Add pairs of items (item & item1).
 */
static int additem(char buf[PBLKSIZ], datum item, datum item1)
{
  short *sp;
  int i1, i2, tmp;

  sp = (short *)buf;
  i1 = PBLKSIZ;
  i2 = sp[0];
  if (i2 > 0)
    i1 = sp[i2];
  i1 -= item.dsize + item1.dsize;
  tmp = (i2+3) * sizeof(short);
  if (i1 <= tmp) return (0);
  sp[0] += 2;
  sp[++i2] = i1 + item1.dsize;
  bcopy(item.dptr, &buf[i1 + item1.dsize], item.dsize);
  sp[++i2] = i1;
  bcopy(item1.dptr, &buf[i1], item1.dsize);
  return (1);
}

#ifdef DEBUG
static chkblk(char buf[PBLKSIZ])
{
  short *sp;
  int t, i;

  sp = (short *)buf;
  t = PBLKSIZ;
  for (i=0; i<sp[0]; i++)
  {
    if (sp[i+1] > t)
      return (-1);
    t = sp[i+1];
  }
  if (t < (sp[0]+1)*sizeof(short))
    return (-1);
  return (0);
}
#endif

#endif /* HAVE_DBM */
