/**********************************************************************
 * cbf_nibble_offset -- nibble-offset compression                     *
 *                                                                    *
 * Version 0.9.8 6 December 2012                                      *
 *                                                                    *
 *                          Paul Ellis and                            *
 *         Herbert J. Bernstein (yaya@bernstein-plus-sons.com)        *
 *                                                                    *
 * (C) Copyright 2006, 2007 Herbert J. Bernstein                      *
 *                                                                    *
 **********************************************************************/

/**********************************************************************
 *                                                                    *
 * YOU MAY REDISTRIBUTE THE CBFLIB PACKAGE UNDER THE TERMS OF THE GPL *
 *                                                                    *
 * ALTERNATIVELY YOU MAY REDISTRIBUTE THE CBFLIB API UNDER THE TERMS  *
 * OF THE LGPL                                                        *
 *                                                                    *
 **********************************************************************/

/*************************** GPL NOTICES ******************************
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/************************* LGPL NOTICES *******************************
 *                                                                    *
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 **********************************************************************/

/**********************************************************************
 *                                                                    *
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#ifdef __cplusplus

extern "C" {

#endif

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <ctype.h>

#include "cbf.h"
#include "cbf_file.h"
#include "cbf_nibble_offset.h"
    
/*  The nibble offset algorithm is a variant on 
    A. P. Hammersley's byte offset algorithm.  The
    major differences are that the compression modes
    are "sticky", the compression can be reset at
    any point to allow for block parallelism, and
    the basic unit of compression is the nibble,
    but for very clean data, the dibit is also supported.
 
    This versions is set up to fully support parallel
    operations by also allowing the specification of the start address
    in the image for each block after a reset.  Therefore
    the blocks do not have to be in order.
 
    The data stream starts with and in general uses
    a mode-setting octet presented in one if three
    forms, a single dibit a0, two dibits a0, a1, or
    two dibits and a nibble a0, a1, b:
 
    a0 a1 b    octet     meaning
    00 00 0000 0x00 --   reset to zero
    01         0x01 --   up 1 mode
    10         0x02 --   dibit mode
    11         0x03 --   up n modes
    00 01      0x04 --   nibble mode
    00 11      0x0C --   6-bit mode
    00 10      0x08 --   byte mode
    00 00 0011 0x30 --   12-bit word mode
    00 00 0001 0x10 --   16-bit word mode
    00 00 0010 0x20 --   32-bit word mode
    00 00 0100 0x40 --   64-bit word mode
    00 00 1100 0xC0 --   specify starting address
 
    The reset to zero is followed by a new mode octet
    A reset to zero resets the prior value for delta to zero
 
    The up n modes code is followed immediately
    by a dibit specifying 2 less than the number of modes 
    by which to change, and then by a delta in the mode.
 
    Note that up n modes has no effect until
    an actual mode has been set and can be used immediately
    after a reset to pad to nibble, octet or double-word
    boundaries.
 
    Once a mode is established, it is followed by a stream 
    of deltas of that size (for modes 2 or 4-64) or by one delta
    of that size and then a stream of deltas of the size that
    was in effect before an up or down giving little-endian 
    offsets from the currently accumulated value.  If the 
    offset is one of the following in the indicated mode
 
       dibit mode:       0x2
       nibble mode:      0x8
       6-bit mode:       0x20
       byte mode:        0x80
       12-bit word mode  0x800
       16-bit word mode  0x8000
       32-bit word mode  0x8000 0000
       64-bit word mode  0x8000 0000 0000 0000
 
     it is followed by the new mode as 1 or 2 dibits or
     2 dibits and a nibble a1 a1 b.  If a1 is 1 or 2 or 3,
     that is the new mode.  If a1 is zero and a2 is 1 or 2
     the new mode is a2*4.  If a2 is 3 the new mode is
     a2*2.  If both a1 and a2 are zero, the new mode is 
     b*16 unless b is 3.  If b is 3 the new mode is b*4
 
     The 0xC0 flag is followed by a second mode giving
     the number of bytes of image starting offset address
     followed by the image offset address followed by the
     mode of that data.   0xC0 also acts as a reset.
     Use of the 0xC0 flag is not required.  Addresses
     default to sequential starting from 0, but is
     provided to faciliate parallel compression.
 
     The array succs is indexed by mode (not mode-1) and
     returns the next larger mode, so succs[2] = 4,
     succs[4] = 6, succs[6] = 8, succs[8] = 12, etc.

    */
    
#define CBF_NIBBLE_RUN      8
#define CBF_NIBBLE_RUN_MASK 7
#define CBF_NIBBLE_UPONE    1
#define CBF_NIBBLE_UPN      3
#define CBF_NIBBLE_SET_ADDR 0xC0
 
    static size_t histogram[65];
    static size_t runs[65];
    static size_t currun[65];
    static size_t succs[65]={ 0, 2, 4, 4, 6, 6, 8, 8,12,12,    /*0 - 9*/
                      12,12,16,16,16,16,32,32,32,32,    /*10-19*/
                      32,32,32,32,32,32,32,32,32,32,    /*20-29*/
                      32,32,64,64,64,64,64,64,64,64,    /*30-39*/
                      64,64,64,64,64,64,64,64,64,64,    /*40-49*/
                      64,64,64,64,64,64,64,64,64,64,    /*50-59*/
                      64,64,64,64,128};                 /*60-64*/
    
    static long int validrange[33] =
                     /* 0   1   2   3   4    5    6    7     8     9*/
                     { 0L, 0L, 1L, 3L, 7L, 15L, 31L, 63L, 127L, 255L,
                     /*  10     11     12     13     14 */
                       511L, 1023L, 2047L, 4095L, 8191L, 
                     /*    15      16      17       18       19 */
                       16383L, 32767L, 65535L, 131071L, 262143L, 
                     /*     20        21        22        23        24*/
                       524287L, 1048575L, 2097151L, 4194303L, 8388608L, 
                     /*       25         26         27          28          29*/
                       16777215L, 33554431L, 67108863L, 134217727L, 268435455L, 
                     /*       30           31           32*/
                      536870911L, 1073741823L, 2147483647L};
    
    static unsigned long int masks[33] =
                     /*   0     1     2     3      4     5      6    7     8     9 */
                     { 0x0L, 0x1L, 0x3L, 0x7L, 0xFL, 0x1FL, 0x3FL, 0x7FL, 0xFFL, 0x1FFL,
                     /*    10      11      12       13       14 */
                       0x3FFL, 0x7FFL, 0xFFFL, 0x1FFFL, 0x3FFFL,
                     /*     15       16        17        18        19 */
                       0x7FFFL, 0xFFFFL, 0x1FFFFL, 0x3FFFFL, 0x7FFFFL,  
                     /*      20         21         22        23         24 */
                       0xFFFFFL, 0x1FFFFFL, 0x3FFFFFL, 0x7FFFFFL, 0xFFFFFFL,
                     /*       25          26          27          28           29 */
                       0x1FFFFFFL, 0x3FFFFFFL, 0x7FFFFFFL, 0xFFFFFFFL, 0x1FFFFFFFL,
                     /*       30           31           32*/
                         0x3FFFFFFFL, 0x7FFFFFFFL, 0xFFFFFFFFL};
    int numints;
    
    unsigned int bits;
    
#define setcurmode(newmode) \
{   int a0, a1, b, md;      \
    md = (newmode);         \
    if ((newmode) == 6) md = 12;      \
        if ((newmode) == 12) md = 48; \
            a0 = md&0x3;              \
            a1 = (md&0xC)>>2;         \
            b = (md&0xF0)>>4;         \
            cbf_failnez(cbf_put_bits(file,&a0,2)) \
            if ((newmode) == 0 || b != 0) {         \
                cbf_failnez(cbf_put_bits(file,&a1,2)) \
                cbf_failnez(cbf_put_bits(file,&b,4))  \
                bsize += 8;                          \
            } else if (a1 != 0) {                     \
                cbf_failnez(cbf_put_bits(file,&a1,2)) \
                bsize += 4;                           \
            } else {                                  \
                bsize += 2;                           \
            }                                         \
}

    
    static int getcurmode ( cbf_file * file, size_t * bitsread){
        int a0, a1, b;
        cbf_failnez(cbf_get_bits(file,&a0,2))
        a0 &= 3;
        if (a0 != 0) {
            *bitsread += 2;
            return a0;
        }
        cbf_failnez(cbf_get_bits(file,&a1,2))
        a1 &= 3;
        if (a1 != 0) {
            *bitsread += 4;
            if (a1==3) return 6;
            return a1*4;
        }
        cbf_failnez(cbf_get_bits(file,&b,4))
        b &= 0xF;
        *bitsread += 8;
        if (b==3) return 12;
        return b*16;
    }
    
    static int testmode(int *delta,int kint) {
        if (kint == 0) {
            if (delta[0] >= -validrange[8] && delta[0] <=validrange[8] ) {
                if (delta[0] >= -validrange[2] && delta[0] <=validrange[2] ) return 2;
                if (delta[0] >= -validrange[4] && delta[0] <=validrange[4] ) return 4;
                if (delta[0] >= -validrange[6] && delta[0] <=validrange[6] ) return 6;
                return 8;
            }
            if (delta[0] >= -validrange[12] && delta[0] <=validrange[12] ) return 12;
            if (delta[0] >= -validrange[16] && delta[0] <=validrange[16] ) return 16;
            if (sizeof(int) >3 ) {
              if (delta[0] >= -validrange[32] &&
                      delta[0] <= validrange[32]) return 32;
              return 64;
            } else {
              return 32;
            }
        } else {
            if ((kint+1)*sizeof(int) < 5) {
                return 32;
            } else
                return 64;
        }
    }


#define changemode    \
{                     \
    int prevmode;     \
    int termmode;     \
    int xzero = 0;    \
    int iint, jsize;  \
    int jrun;         \
    int succnt = 0;   \
    if (numints==1 || curmode <= (int)(sizeof(int)*CHAR_BIT)) { \
      termmode = 1<<(curmode-1);  \
      cbf_failnez(cbf_put_bits(file,&termmode,curmode)) \
    } else { \
      jsize = 0; \
      for (iint=0; (int)(iint*sizeof(int)) < curmode; iint++) { \
        cbf_failnez(cbf_put_bits(file,&xzero,sizeof(int))) \
        jsize += sizeof(int); \
      } \
      termmode = 1<<(curmode-jsize);  \
      cbf_failnez(cbf_put_bits(file,&termmode,curmode-jsize)) \
    } \
    bsize += curmode; \
    if (bsize > 7) {  \
        csize += (bsize/8);  \
        bsize %= 8;   \
    }                 \
    jrun = (inrun+CBF_NIBBLE_RUN-lagby+1)&CBF_NIBBLE_RUN_MASK; \
    prevmode = curmode; \
    curmode = usedmode = newmode; \
    if ( tempmode==CBF_NIBBLE_UPN  && prevmode <= 32) { \
        if (curmode == (int)succs[prevmode]) { \
            succnt = 1; \
        } else if (prevmode <= 16 && curmode == (int)succs[succs[prevmode]]) { \
            succnt = 2; \
        } else if (prevmode <= 12 && curmode == (int)succs[succs[succs[prevmode]]]) { \
            succnt = 3; \
        } else if (prevmode <= 8 && curmode == (int)succs[succs[succs[succs[prevmode]]]]) { \
            succnt = 4; \
        } else if (prevmode <= 6 && curmode == (int)succs[succs[succs[succs[succs[prevmode]]]]]) { \
            succnt = 5; \
        } else { tempmode = curmode;} \
    } \
    if (tempmode==CBF_NIBBLE_UPN && succnt > 0 ) { \
        if (succnt==1) { \
          setcurmode(CBF_NIBBLE_UPONE); \
        } else { \
          setcurmode(CBF_NIBBLE_UPN);  \
          succnt-=2; \
          cbf_failnez(cbf_put_bits(file,&succnt,2)) \
          bsize += 2; \
        } \
        if (kint[jrun] == 0) {    \
            cbf_failnez(cbf_put_bits(file,delta[jrun],curmode))  \
            bsize += curmode; \
        } else {            \
            for (iint = 0; iint < (kint[jrun]+1); iint++) { \
                \
                cbf_failnez (cbf_put_integer (file, delta[jrun][iint], \
                                              iint==numints-1?1:0,\
                                              iint<(numints-1)?(CHAR_BIT*sizeof (int)): \
                                              curmode-(CHAR_BIT*sizeof (int))*iint ))\
            } \
            bsize += curmode; \
        } \
        curmode = prevmode; \
    } else {                                              \
        setcurmode(curmode);                              \
        if (kint[jrun] == 0) {                                  \
            cbf_failnez(cbf_put_bits(file,delta[jrun],curmode)) \
            bsize += curmode; \
        } else {                                          \
            for (iint = 0; iint < (kint[jrun]+1); iint++) {       \
                                                          \
                cbf_failnez (cbf_put_integer (file, delta[jrun][iint],                        \
                                              iint==numints-1?1:0,                      \
                                              iint<(numints-1)?(CHAR_BIT*sizeof (int)): \
                                              curmode-(CHAR_BIT*sizeof (int))*iint ))      \
            }               \
            bsize += curmode; \
        }                   \
    }                       \
    if (bsize > 7) {        \
        csize += (bsize/8); \
        bsize %= 8;         \
    }                       \
}


  /* Compress and array with the nibble-offset algorithm */

int cbf_compress_nibble_offset (void         *source,
                              size_t        elsize,
                              int           elsign,
                              size_t        nelem,
                              unsigned int  compression,
                              cbf_file     *file,
                              size_t       *compressedsize,
                              int          *storedbits,
                              int           realarray,
                              const char   *byteorder,
                              size_t        dimfast,
                              size_t        dimmid,
                              size_t        dimslow,
                              size_t        padding)
    {
        unsigned int count, borrow, element[4], prevelement[4], 
        
        unsign, sign, limit;
        
        unsigned char *unsigned_char_data;
        
        size_t csize, bsize;
                
        int delta[CBF_NIBBLE_RUN][4];
        
        int dmode[CBF_NIBBLE_RUN],maxmode,minmode,newmode,nextmaxmode,tempmode;
        
        int iint, ii, kint[CBF_NIBBLE_RUN], inrun=0, lagby;
        
        char * border;
        
        char * rformat;
        
        int curmode = 0;
                
        int zerobyte = 0;
        
        int dflag=0x2;
        
        int nflag=0x8;
        
        int sixflag = 0x20;
        
        int byteflag = 0x80;
        
        int shortflag = 0x8000;
                        
        int usedmode;
        
        int *termflag[17];

        CBF_UNUSED( termflag );

        CBF_UNUSED( borrow );
        
        CBF_UNUSED( compression );
        
        CBF_UNUSED( byteorder );
        
        CBF_UNUSED( dimfast );
        
        CBF_UNUSED( dimmid );
        
        CBF_UNUSED( dimslow );
        
        CBF_UNUSED( padding );
        
        termflag[2] = &dflag;
        
        termflag[4] = &nflag;
        
        termflag[6] = &sixflag;
        
        termflag[8] = &byteflag;
        
        termflag[16] = &shortflag;
        
        for (iint = 0; iint < 65; iint++) {
            histogram[iint] = 0;
            runs[iint] = 0;
            currun[iint] = 0;
        }
        
        /* Is the element size valid? */
        
        if (elsize != sizeof (int) &&
            elsize != 2* sizeof (int) &&
            elsize != 4* sizeof (int) &&
            elsize != sizeof (short) &&
            elsize != sizeof (char))
            
            return CBF_ARGUMENT;
        
        /* check for compatible real format */
        
        if ( realarray ) {
            
            cbf_failnez (cbf_get_local_real_format(&rformat) )
            
            if ( strncmp(rformat,"ieee",4) ) return CBF_ARGUMENT;
            
        }
        
        bits = elsize * CHAR_BIT;
        
        if (bits < 1 || bits > 64)
            
            return CBF_ARGUMENT;
        
        if (bits != 8 && bits != 16 && bits != 32 && bits != 64)
            
            return CBF_ARGUMENT;
        
        numints = (bits + CHAR_BIT*sizeof (int) -1)/(CHAR_BIT*sizeof (int));
        
        
        /* Maximum limits */
        
        sign = 1 << ((elsize-(numints-1)*sizeof(int))* CHAR_BIT - 1);
        
        if (elsize == sizeof (int) || elsize == numints*sizeof(int) )
            
            limit = ~0;
        
        else
            
            if (numints == 1) {
                
                limit = ~-(1 << (elsize * CHAR_BIT));
                
            } else {
                
                limit = ~-(1 << ((elsize-(numints-1)*sizeof(int)) * CHAR_BIT));
                
            }
        
        
        if (storedbits)
            
            *storedbits = bits;
        
        
        /* Offset to make the value unsigned */
        
        if (elsign)
            
            unsign = sign;
        
        else
            
            unsign = 0;
        
        /* Get the local byte order */
        
        if (realarray) {
            
            cbf_get_local_real_byte_order(&border);
            
        } else {
            
            cbf_get_local_integer_byte_order(&border);
            
        }
    
        
        /* Initialise the pointer */
        
        unsigned_char_data = (unsigned char *) source;
        
        
        /* Set up the previous element for comparison */
        
        prevelement[0] = prevelement[1] = prevelement[2] = prevelement[3] = 0;
        
        prevelement[numints-1] = unsign;
        
        
        /* Write the elements */
        
        
        csize = 0;
        
        bsize = 0;
        
        curmode  = 0;
        
        lagby = 0;
        
        
        for (count = 0; count < nelem; count++) {
            
            inrun = count&CBF_NIBBLE_RUN_MASK;
            
            /* Get the next element */
            
            if (numints > 1) {
                
                if (border[0] == 'b') {
                    
                    for (iint = numints; iint; iint--) {
                        
                        element[iint-1] = *((unsigned int *) unsigned_char_data);
                        
                        unsigned_char_data += sizeof (int);
                        
                    }
                    
                } else {
                    
                    for (iint = 0; iint < numints; iint++) {
                        
                        element[iint] = *((unsigned int *) unsigned_char_data);
                        
                        unsigned_char_data += sizeof (int);
                    }
                }
                
            } else {
                
                if (elsize == sizeof (int))
                    
                    element[0] = *((unsigned int *) unsigned_char_data);
                
                else
                    
                    if (elsize == sizeof (short))
                        
                        element[0] = *((unsigned short *) unsigned_char_data);
                
                    else
                        
                        element[0] = *unsigned_char_data;
                
                unsigned_char_data += elsize;
                
            }
            
            
            /* Make the element unsigned */
            
            element[numints-1] += unsign;
            
            element[numints-1] &= limit;
                        
            /* Compute the delta */
            
            borrow = 0;
            
            kint[inrun] = 0;
            
            if (numints > 1) {
                
                for (iint = 0; iint < numints; iint++) delta[inrun][iint] = prevelement[iint];
                
                cbf_failnez(cbf_mpint_negate_acc((unsigned int *)delta[inrun],numints));
                
                cbf_failnez(cbf_mpint_add_acc((unsigned int *)delta[inrun], numints, element, numints))
                
                delta[inrun][numints-1] &=limit;
                
                if (delta[inrun][numints-1] & sign) delta[inrun][numints-1] |= (~limit);
                                
            } else  {
                
                delta[inrun][0] = element[0] - prevelement[0];
                
                delta[inrun][0] &=limit;
                
                if (delta[inrun][0] & sign) delta[inrun][0] |= (~limit);
                
            }
            
            
            prevelement[0] = element[0];
            
            for (iint = 1; iint < numints; iint++) {
                
                prevelement[iint] = element[iint];
                
                if ((delta[inrun][0] >= 0 && delta[inrun][iint] != 0 )
                    || (delta[inrun][0] < 0 && (delta[inrun][iint]+1)!=0) ) kint[inrun] = iint;
                
            }

            dmode[inrun] = testmode(delta[inrun],kint[inrun]);
            currun[dmode[inrun]]++;
            if (count > 0 && dmode[inrun] != dmode[(inrun+CBF_NIBBLE_RUN-1)&CBF_NIBBLE_RUN_MASK]) runs[dmode[(inrun+CBF_NIBBLE_RUN-1)&CBF_NIBBLE_RUN_MASK]]++;
            
            lagby++;
 
            if (lagby < CBF_NIBBLE_RUN) continue;
            
            if (curmode == 0) {
                
                curmode = dmode[inrun];
                for (ii=1;ii<lagby;ii++) {
                    if (dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]>curmode) {
                        curmode=dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK];
                    }
                }
                histogram[curmode]+=lagby;
                setcurmode(curmode);
                for (ii=lagby-1;ii>=0;ii--){
                    if (kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]==0) {
                        cbf_failnez(cbf_put_bits(file,delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK],curmode))
                    } else {
                        for (iint = 0; iint < kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]+1; iint++) {
                            cbf_failnez (cbf_put_integer (file, delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK][iint],
                                                          iint==numints-1?1:0, iint<(numints-1)?(CHAR_BIT*sizeof (int)): curmode-(CHAR_BIT*sizeof (int))*iint ))
                        }
                    }
                }
                
                bsize += (curmode*lagby);
                if (bsize > 7) {
                    csize += (bsize/8);
                    bsize %= 8;
                }
                lagby = 0;
                continue;
            }
            
            /* we are already in a workable mode,
               stay with it if possible, unless we can drop
               to a smaller value for at least CBF_NIBBLE_RUN values*/
            
            
            maxmode = minmode = nextmaxmode = dmode[inrun];
            for (ii=1;ii<lagby;ii++) {
                if (dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]>maxmode) {
                    maxmode = dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK];
                    if (ii < lagby-1) nextmaxmode= dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK];
                }
                if (dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]<minmode) {
                    minmode = dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK];
                }
            }
            ii = lagby-1;
            if (dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]<=curmode
                && maxmode>= curmode) {
                histogram[curmode]++;
                if (kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]==0) {
                    cbf_failnez(cbf_put_bits(file,delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK],curmode))
                } else {
                    for (iint = 0; iint < kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]+1; iint++) {
                        cbf_failnez (cbf_put_integer (file, delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK][iint],
                                                      iint==numints-1?1:0, iint<(numints-1)?(CHAR_BIT*sizeof (int)): curmode-(CHAR_BIT*sizeof (int))*iint ))
                    }
                }
                bsize += curmode;
                if (bsize > 7) {
                    csize += (bsize/8);
                    bsize %= 8;
                }
                lagby--;
                continue;
            }
            
            /* we need to change --  see if we need to go up */
            
            if (dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]> curmode) {
                newmode = dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK];
                tempmode = CBF_NIBBLE_UPN;
                if (nextmaxmode > curmode){
                    tempmode = newmode = maxmode;
                }
                changemode;
                lagby--;
                continue;
            }
            
            /* that leaves going up or down to whatever is in the next run */
            
            tempmode = newmode = maxmode;
            changemode;
            lagby--;
            continue;
            
        }
        
        if (curmode == 0) {
            
            curmode = dmode[inrun];
            for (ii=1;ii<lagby;ii++) {
                if (dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]>curmode) {
                    curmode=dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK];
                }
            }
            histogram[curmode]+=lagby;
            setcurmode(curmode);
            for (ii=lagby-1;ii>=0;ii--){
                if (kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]==0) {
                    cbf_failnez(cbf_put_bits(file,delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK],curmode))
                } else {
                    for (iint = 0; iint < kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]+1; iint++) {
                        cbf_failnez (cbf_put_integer (file, delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK][iint],
                                                      iint==numints-1?1:0, iint<(numints-1)?(CHAR_BIT*sizeof (int)): curmode-(CHAR_BIT*sizeof (int))*iint ))

                    }
                }
            }
            
            bsize += (curmode*lagby);
            if (bsize > 7) {
                csize += (bsize/8);
                bsize %= 8;
            }
            lagby = 0;
        } else {
            maxmode = dmode[inrun];
            for (ii=1;ii<lagby;ii++) {
                if (dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]>maxmode) {
                    maxmode = dmode[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK];
                }
            }
            if (maxmode > curmode ) {
                tempmode=newmode=maxmode;
                changemode;
                lagby--;
            }
            if (lagby > 0) {
                histogram[curmode]+= lagby;
                for (ii=lagby-1;ii>=0; ii--) {
                    if (kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]==0) {
                        cbf_failnez(cbf_put_bits(file,delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK],curmode))
                    } else {
                        for (iint = 0; iint < kint[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK]+1; iint++) {
                            cbf_failnez (cbf_put_integer (file, delta[(CBF_NIBBLE_RUN+inrun-ii)&CBF_NIBBLE_RUN_MASK][iint],
                                                          iint==numints-1?1:0, iint<(numints-1)?(CHAR_BIT*sizeof (int)): curmode-(CHAR_BIT*sizeof (int))*iint ))
                        }
                    }
                }
                bsize += (curmode*lagby);
                if (bsize > 7) {
                    csize += (bsize/8);
                    bsize %= 8;
                }
                lagby=0;
            }
        }
        
        bsize %= 8;
        if (bsize !=0) {
            cbf_failnez(cbf_put_bits(file,&zerobyte,8-bsize))
            csize++;
            bsize = 0;
        }
        /* Return the number of characters written */
        
        if (compressedsize)
            
            *compressedsize = csize;
        
/*      fprintf(stderr," nibble offset compressed size %ld elements %ld\n",(long)csize,(long)nelem);
        for (ii=1;ii<65;ii++) {
            if (histogram[ii]) fprintf(stderr,"histogram[%d] %d\n",ii,(int)histogram[ii]);
            if (runs[ii]) fprintf(stderr,"avgrun[%d] %g\n",ii,((double)currun[ii])/((double)runs[ii]));
        }
*/
        
        
        /* Success */
        
        return 0;
    }


  /* Decompress an array with the nibble-offset algorithm */

int cbf_decompress_nibble_offset (void         *destination,
                                size_t        elsize,
                                int           elsign,
                                size_t        nelem,
                                size_t       *nelem_read,
                                size_t        compressedsize,
                                unsigned int  compression,
                                int           data_bits,
                                int           data_sign,
                                cbf_file     *file,
                                int           realarray,
                                const char   *byteorder,
                                size_t        dimover,
                                size_t        dimfast,
                                size_t        dimmid,
                                size_t        dimslow,
                                size_t        padding)
    {
        unsigned int element[4], prevelement[4], sign, unsign, limit;
        
        unsigned int data_unsign;
        
        unsigned char *unsigned_char_data;
        
        int errorcode, overflow, numints, iint;
        
        int delta[4];
        
        int curmode, prevmode, nextmode;
        
        char * border;
        
        char * rformat;
        
        size_t numread,bitsread;
        
        int succnt, sucmode;

        CBF_UNUSED( errorcode );
        
        CBF_UNUSED( compressedsize );
        
        CBF_UNUSED( compression );
        
        CBF_UNUSED( byteorder );
        
        CBF_UNUSED( dimover );
        
        CBF_UNUSED( dimfast );
        
        CBF_UNUSED( dimmid );
        
        CBF_UNUSED( dimslow );
        
        CBF_UNUSED( padding );
        
        /* prepare the errorcode */
        
        errorcode = 0;
        
        /* Is the element size valid? */
        
        if (elsize != sizeof (int) &&
            elsize != 2* sizeof (int) &&
            elsize != 4* sizeof (int) &&
            elsize != sizeof (short) &&
            elsize != sizeof (char))
            
            return CBF_ARGUMENT;
        
        /* check for compatible real format */
        
        if ( realarray ) {
            
            cbf_failnez (cbf_get_local_real_format(&rformat) )
            
            if ( strncmp(rformat,"ieee",4) ) return CBF_ARGUMENT;
            
        }
        
        /* Check the stored element size */
        
        if (data_bits < 1 || data_bits > 64)
            
            return CBF_ARGUMENT;
        
        numints = (data_bits + CHAR_BIT*sizeof (int) -1)/(CHAR_BIT*sizeof (int));
        
        
        /* Initialise the pointer */
        
        unsigned_char_data = (unsigned char *) destination;
        
        
        /* Maximum limits */
        
        sign = 1 << ((elsize-(numints-1)*sizeof(int))* CHAR_BIT - 1);
        
        if (elsize == sizeof (int) || elsize == numints*sizeof(int))
            
            limit = ~0;
        
        else
            
            if (numints == 1 ) {
                
                limit = ~(-(1 << (elsize * CHAR_BIT)));
                
            } else {
                
                limit = ~(-(1 << ((elsize-(numints-1)*sizeof(int)) * CHAR_BIT)));
                
            }
        
        
        /* Offsets to make the value unsigned */
        
        if (data_sign)
            
            data_unsign = sign;
        
        else
            
            data_unsign = 0;
        
        if (elsign)
            
            unsign = sign;
        
        else
            
            unsign = 0;
        
        /* Get the local byte order */
        
        if (realarray) {
            
            cbf_get_local_real_byte_order(&border);
            
        } else {
            
            cbf_get_local_integer_byte_order(&border);
            
        }
        
        
        /* Set up the previous element for increments */
        
        prevelement[0] = prevelement[1] = prevelement[2] = prevelement[3] = 0;
        
        prevelement[numints-1] = data_unsign;
        
        
        /* Read the elements */
        
        overflow = 0;
        
        numread = 0;
        
        bitsread = 0;
        
        curmode = 0;
        
        prevmode = 0;
        
        nextmode = 0;
        
        prevelement[0] = prevelement[1] = prevelement[2] = prevelement[3] = 0;
        prevelement[numints-1] = data_unsign;

        while (numread < nelem)
        {
            
            while (curmode==0) {
                curmode = getcurmode(file,&bitsread);
                if (curmode==0 && prevmode==0) {
                    prevelement[0] = prevelement[1] = prevelement[2] = prevelement[3] = 0;
                    prevelement[numints-1] = data_unsign;                    
                }
                if (prevmode==0 && (curmode==CBF_NIBBLE_UPN||curmode==CBF_NIBBLE_UPONE)) {
                    curmode = 0;
                    prevmode=0;
                }
            }
            
            for (iint=0; iint < numints; iint++){
                
                element[iint] = prevelement[iint];
                
                delta[iint] = 0;
                
            }
            
            switch (curmode) {
                case(CBF_NIBBLE_UPN):
                    cbf_failnez(cbf_get_bits(file,&succnt,2))
                    succnt &= 3;
                    sucmode = (succnt==0)?succs[succs[prevmode]]:
                      ((succnt==1)?succs[succs[succs[prevmode]]]:
                       ((succnt==2)?succs[succs[succs[succs[prevmode]]]]:
                        succs[succs[succs[succs[succs[prevmode]]]]]));
                    cbf_failnez(cbf_get_bits(file,delta,sucmode))
                    if (succs[prevmode] < sizeof(int))
                        delta[0] &= masks[sucmode];
                    bitsread += sucmode;
                    nextmode = prevmode;
                    curmode = sucmode;
                    break;
                case(CBF_NIBBLE_UPONE):
                    succnt &= 3;
                    sucmode = succs[prevmode];
                    cbf_failnez(cbf_get_bits(file,delta,sucmode))
                    if (succs[prevmode] < sizeof(int))
                        delta[0] &= masks[sucmode];
                    bitsread += sucmode;
                    nextmode = prevmode;
                    curmode = sucmode;
                    break;
                 case(CBF_NIBBLE_SET_ADDR):
                    fprintf(stderr,"CBFLIB:  cbf-nibble_offset CBF_NIBBLE_SET_ADDR not implemented yet\n");
                    cbf_failnez(CBF_FORMAT);
                    break;

                 default:
                    cbf_failnez(cbf_get_bits(file,delta,curmode))
                    if (curmode < (int)sizeof(int))
                        delta[0] &= masks[curmode];
                    bitsread += curmode;
                    nextmode = curmode;
                    break;
            }
            
            bitsread %= 8;
            
            switch (curmode) {
                    
                case(2):
                    if ((delta[0]&0x3) == 0x2) {
                        prevmode=curmode;
                        nextmode = 0;
                    } else {
                        if ((delta[0]&0x2) == 0x2) {
                            delta[0] = -1;
                            for (iint = 1; iint < numints; iint++) {
                                delta[iint] = ~0;                            
                            }   
                        }
                    }
                    break;
                    
                case(4):
                    if ((delta[0]&0xF) == 0x8) {
                        prevmode=curmode;
                        nextmode = 0;
                    } else {
                        if ((delta[0]&0x8) == 0x8) {
                            delta[0] |= ~0xF;
                            for (iint = 1; iint < numints; iint++) {
                                delta[iint] = ~0;                            
                            } 
                        }
                    }
                    break;
                    
                case(6):
                    if ((delta[0]&0x3F) == 0x20) {
                        prevmode=curmode;
                        nextmode = 0;
                    } else {
                        if ((delta[0]&0x20) == 0x20) {
                            delta[0] |= ~0x3F;
                            for (iint = 1; iint < numints; iint++) {
                                delta[iint] = ~0;                            
                            } 
                        }
                    }
                    break;
                    
                case(8):
                    if ((delta[0]&0xFF) == 0x80) {
                        prevmode=curmode;
                        nextmode = 0;
                    } else {
                        if ((delta[0]&0x80) == 0x80) {
                            delta[0] |= ~0xFF;
                            for (iint = 1; iint < numints; iint++) {
                                delta[iint] = ~0;                            
                            }  
                        }
                    }
                    break;
                    
                case(12):
                    if ((delta[0]&0xFFF) == 0x800) {
                        prevmode=curmode;
                        nextmode = 0;
                    } else {
                        if ((delta[0]&0x800) == 0x800) {
                            delta[0] |= ~0xFFF;
                            for (iint = 1; iint < numints; iint++) {
                                delta[iint] = ~0;                            
                            }  
                        }
                    }
                    break;
                    
                case(16):
                    if ((delta[0]&0xFFFF) == 0x8000){
                        prevmode=curmode;
                        nextmode = 0;
                    } else {
                        if ((delta[0]&0x8000) == 0x8000) {
                            delta[0] |= ~0xFFFF;
                            for (iint = 1; iint < numints; iint++) {
                                delta[iint] = ~0;                            
                            }
                        }
                    }
                    break;
                    
                case(32):
                    if (sizeof(int) == 2) {
                        if ((delta[1]&0xFFFF) == 0x8000
                            && (delta[0]&0xFFFF) == 0) {
                            prevmode=curmode;
                            nextmode = 0;
                        } else {
                            if ((delta[1]&0x8000) == 0x8000) {
                                for (iint = 2; iint < numints; iint++) delta[iint] = ~0;
                            }
                        }
                        
                    } else {
                        if ((delta[0]&0xFFFFFFFF) == 0x80000000) {
                            prevmode=curmode;
                            nextmode = 0;
                        } else {
                            if ((delta[0]&0x80000000) == 0x80000000) {
                                delta[0] |= ~0xFFFFFFFFFF;
                                for (iint = 1; iint < numints; iint++) {
                                    delta[iint] = ~0;                            
                                }
                            }
                        }
                    } 
                    break;

                case(64):
                    if (sizeof(int) == 2) {
                        if ((delta[3]&0xFFFF) == 0x8000
                            && (delta[2]&0xFFFF) == 0
                            && (delta[1]&0xFFFF) == 0
                            && (delta[0]&0xFFFF) == 0) {
                            prevmode=curmode;
                            nextmode = 0;
                        } else {
                            if ((delta[3]&0x8000) == 0x8000) {
                                for (iint = 4; iint < numints; iint++) delta[iint] = ~0;
                            }
                        }

                    } else if (sizeof(int) == 4) {
                        if ((delta[1]&0xFFFFFFFF) == 0x80000000L
                            && (delta[0]&0xFFFFFFFF) == 0x00000000L) {
                            prevmode=curmode;
                            nextmode = 0;
                        } else {
                            if ((delta[1]&0x80000000L) == 0x80000000L) {
                                for (iint = 2; iint < numints; iint++) delta[iint] = ~(0L);
                            }
                        }
                        
                    } else {
                        if ((((long)delta[0]>>32)&0xFFFFFFFFL)==0x80000000L&&(((long)delta[0]&0xFFFFFFFFl)==0L)) {
                            prevmode=curmode;
                            nextmode = 0;
                        } else {
                            if ((((long)delta[0]>>32)&0x80000000L) == 0x80000000L) {
                                delta[0] |= ~(-1L);
                                for (iint = 1; iint < numints; iint++) {
                                    delta[iint] = ~(0L);
                                }
                            }
                        }
                    } 
                    break;

            }
            
            prevmode = curmode;
            
            curmode = nextmode;
            
            if (curmode == 0) continue;
            
            if (numints > 1) {
                
                for (iint = 0; iint < numints; iint++) element[iint] = prevelement[iint];
                
                cbf_failnez(cbf_mpint_add_acc(element,numints, (unsigned int *)delta,numints))
                
            } else {
                
                element[0] = prevelement[0] + delta[0];
                
                element[0] &= limit;
                
            }
            
            for (iint = 0; iint < numints; iint++)   {
                
                prevelement[iint] = element[iint];
                
            }
            
            /* Make the element signed? */
            
            element[numints-1] -= unsign;
            
                        
            /* Save the element */
            
            if (numints > 1) {
                
                if (border[0] == 'b') {
                    
                    for (iint = numints; iint; iint--) {
                        
                        *((unsigned int *) unsigned_char_data) = element[iint-1];
                        
                        unsigned_char_data += sizeof (int);
                        
                    }
                    
                } else {
                    
                    for (iint = 0; iint < numints; iint++) {
                        
                        *((unsigned int *) unsigned_char_data) = element[iint];
                        
                        unsigned_char_data += sizeof (int);
                    }
                }
                
            } else {
                
                if (elsize == sizeof (int))
                    
                    *((unsigned int *) unsigned_char_data) = element[0];
                
                else
                    
                    if (elsize == sizeof (short))
                        
                        *((unsigned short *) unsigned_char_data) = element[0];
                
                    else
                        
                        *unsigned_char_data = element[0];
                
                unsigned_char_data += elsize;
                
            }
            
            numread++;
            
        }
        
        /* Number read */
        
        if (nelem_read)
            
            *nelem_read = numread;
        
        
        /* Success */
        
        return overflow;
    }



#ifdef __cplusplus

}

#endif
