/*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* email: dact@rkeene.org
*/
#include "dact.h"
#include "comp_text.h"
#include "buffer.h"
#include <stdio.h>
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
#ifdef HAVE_STDLIB_H
#include <stdlib.h>
#endif
#ifdef HAVE_STRING_H
#include <string.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(USE_MODULES) && defined(AS_MODULE)
#include "module.h"
uint32_t DC_NUM=3;
uint32_t DC_TYPE=DACT_MOD_TYPE_COMP;
void *DC_ALGO=comp_text_algo;
char *DC_NAME="Text Compression (MOD)";
#endif
int comp_text_algo(int mode, unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size) {
switch(mode) {
case DACT_MODE_COMPR:
return(comp_text_compress(prev_block,curr_block,out_block,blk_size));
break; /* Heh */
case DACT_MODE_DECMP:
return(comp_text_decompress(prev_block,curr_block,out_block,blk_size));
break;
default:
printf("Unsupported mode: %i\n", mode);
return(-1);
}
}
int comp_text_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size) {
unsigned char low_byte=255, high_byte=0;
unsigned char byte_buf;
unsigned int range;
int i,x=0,y;
bit_buffer_purge();
for (i=0;i<blk_size;i++) {
if (((unsigned char) curr_block[i])<low_byte) low_byte=curr_block[i];
if (((unsigned char) curr_block[i])>high_byte) high_byte=curr_block[i];
}
range=(unsigned int) (high_byte-low_byte);
out_block[x++]=low_byte;
out_block[x++]=high_byte;
if (range==0)
return(2);
for (y=1;y<=8;y++)
if ((range>>y)==0) break;
if (y==8) return(-1);
for (i=0;i<blk_size;i++) {
byte_buf=(unsigned char) (curr_block[i]-low_byte);
/*
if ((byte_buf>>y)==1) {
return(-1);
}
*/
bit_buffer_write(byte_buf,y);
while (bit_buffer_size()>=8) {
out_block[x++]=bit_buffer_read(8);
}
}
/* Remove any less-than-one-byte data */
if ((i=bit_buffer_size())!=0) {
out_block[x++]=(bit_buffer_read(i)<<(8-i));
}
return(x);
}
int comp_text_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size) {
unsigned char high_byte, low_byte;
unsigned int range;
int i=0,x=0,y;
low_byte=curr_block[x++];
high_byte=curr_block[x++];
range=(unsigned int) (high_byte-low_byte);
if (range==0) {
memset(out_block,low_byte,DACT_BLK_SIZE);
return(DACT_BLK_SIZE);
}
for (y=1;y<=8;y++)
if ((range>>y)==0) break;
bit_buffer_purge();
while (1) {
if (bit_buffer_size()<y) bit_buffer_write((unsigned char) curr_block[x++],8);
out_block[i++]=(bit_buffer_read(y)+low_byte);
if ((x==blk_size) && (bit_buffer_size()<y)) break;
if (i>=(DACT_BLK_SIZE)) break;
}
return(i);
}