/*
* Copyright (C) 2001, 2002, and 2003 Roy Keene
*
* 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, see <http://www.gnu.org/licenses/>.
*
* email: dact@rkeene.org
*/
#include "dact.h"
#include "comp_rle.h"
#include <stdio.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
/*
mode - DACT_MODE_COMPR or DACT_MODE_DECMP
Determine whether to compress or decompress.
prev_block - Previous (uncompressed) block.
curr_block - The data to be compressed.
out_block - Where to put data after compression.
blk_size - Size of prev_block and curr_block.
*/
#if defined(AS_MODULE) && defined(USE_MODULES)
#include "module.h"
uint32_t DACT_MOD_NUM=1;
uint32_t DACT_MOD_TYPE=DACT_MOD_TYPE_COMP;
void *DACT_MOD_ALGO=comp_rle_algo;
char *DACT_MOD_NAME="RLE Compression (MOD)";
char *DACT_MOD_SIGN="RGlnaXRhbFNpZ25hdHVyZQ==";
char *DACT_MOD_URL_GET="http://www.rkeene.org/projects/compression/dact/@@OSNM@@-@@ARCH@@/comp_rle.dll";
char *DACT_MOD_URL_VER="http://www.rkeene.org/projects/compression/dact/@@OSNM@@-@@ARCH@@/comp_rle.ver";
uint32_t DACT_MOD_VER=0x00080d;
uint32_t DACT_MOD_REQUIRE=DACT_MOD_REQ_ATLEAST|(0x00080d);
#endif
int comp_rle_algo(int mode, unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) {
switch(mode) {
case DACT_MODE_COMPR:
return(comp_rle_compress(prev_block, curr_block, out_block, blk_size, bufsize));
break; /* Heh */
case DACT_MODE_DECMP:
return(comp_rle_decompress(prev_block, curr_block, out_block, blk_size, bufsize));
break;
default:
printf("Unsupported mode: %i\n", mode);
return(-1);
}
}
int comp_rle_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) {
int i,x=0,m;
unsigned char sentinel=0xff;
unsigned char currchar=0, prevchar;
unsigned char charcnt=0;
unsigned int lowestcnt=0xffff;
unsigned int count[256];
for (i=0;i<256;i++) count[i]=0;
for (i=0;i<blk_size;i++) count[curr_block[i]]++;
for (i=0;i<256;i++) {
if (count[i]<lowestcnt) {
sentinel=i;
lowestcnt=count[i];
}
}
out_block[x++]=sentinel;
prevchar=curr_block[0];
for (i=0;i<(blk_size+1);i++) {
if (i!=blk_size) { currchar=curr_block[i]; } else { currchar++; }
if (prevchar!=currchar || charcnt==255 || i>=(blk_size)) {
if (charcnt<=2 && prevchar!=sentinel) {
for (m=0;m<charcnt;m++) out_block[x++]=prevchar;
} else {
out_block[x++]=sentinel;
out_block[x++]=prevchar;
out_block[x++]=charcnt;
}
charcnt=0;
}
charcnt++;
prevchar=currchar;
}
return(x);
}
int comp_rle_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) {
int i,x=0,m;
unsigned char sentinel=curr_block[0];
unsigned char currchar;
unsigned char charcnt;
for (i=1;i<blk_size;i++) {
currchar=curr_block[i];
if (currchar==sentinel) {
currchar=curr_block[++i];
charcnt=curr_block[++i];
if ((x+charcnt)>bufsize) {
printf("Error in RLE compression!\n");
return(0);
}
for (m=0;m<charcnt;m++) out_block[x++]=currchar;
} else {
out_block[x++]=currchar;
}
}
return(x);
}