src/huffman.c

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/* {{{
 * CalcRogue, a roguelike game for PCs, calculators and PDAs
 * Copyright (C) 2003 Jim Babcock
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 * }}} */
// huffman.c

#ifdef TARGET // Compiling CalcRogue (not a tool)
#include "crogue.h"
#endif

#include "hufftable.h"
#include "huffman.h"
#include "substdio.h"

#ifdef DISABLE_COMPRESSION
#define DISABLE_HUFFMAN
#endif

static unsigned long _hp_pending=0;
static unsigned short _hp_pending_length=0;

void fhuffmaninit_write(void)
{
    _hp_pending = 0;
    _hp_pending_length = 0;
}

void fhuffmanputc(unsigned char c, FILE *f)
{
#ifdef DISABLE_HUFFMAN
    fputc(c, f);
#else
    
    _hp_pending_length += huff_compress.replen[c];
    _hp_pending |= (long)huff_compress.rep[c] << (32L - _hp_pending_length);
    if(_hp_pending_length >= 16)
        fhuffmanflush(f);
#endif
}

void fhuffmanflush(FILE *f)
{
#ifndef DISABLE_HUFFMAN
    fputc((char)(_hp_pending>>24L), f);
    fputc((char)(_hp_pending>>16L), f);
    _hp_pending <<= 16;
    if(_hp_pending_length >= 16)
        _hp_pending_length -= 16;
    else
        _hp_pending_length = 0;
#endif
}

static unsigned long _hg_pending=0;
static unsigned short _hg_pending_length=0;

void fhuffmaninit_read(void)
{
    _hg_pending = 0;
    _hg_pending_length = 0;
}

char fhuffmangetc(FILE *f)
{
#ifdef DISABLE_HUFFMAN
    return fgetc(f);
#else
    short high, low, mid;
    unsigned short searchtarget;
    
    while(_hg_pending_length < 24)
    {
        _hg_pending <<= 8;
        _hg_pending_length += 8;
        if(!feof(f))
            _hg_pending |= fgetc(f);
    }
    searchtarget = _hg_pending >> (_hg_pending_length - 16UL);
    low = 0;
    high = 255;
    
    do
    {
        mid = (low+high+1)/2;
        if(huff_decompress.entries[mid].binrep > searchtarget)
            high = mid-1;
        else
            low = mid;
    } while(high>low);
    
    
    _hg_pending <<= (32L + huff_decompress.entries[low].binreplen - _hg_pending_length);
    _hg_pending_length -= huff_decompress.entries[low].binreplen;
    _hg_pending >>= (32L - _hg_pending_length);
    
    return huff_decompress.entries[low].byterep;
#endif
}

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