/*
* 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_delta.h"
#include "buffer.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(USE_MODULES) && defined(AS_MODULE)
#include "module.h"
uint32_t DC_NUM=2;
uint32_t DC_TYPE=DACT_MOD_TYPE_COMP;
void *DC_ALGO=comp_delta_algo;
char *DC_NAME="Delta Compression (MOD)";
#endif
int comp_delta_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_delta_compress(prev_block, curr_block, out_block, blk_size, bufsize));
break; /* Heh */
case DACT_MODE_DECMP:
return(comp_delta_decompress(prev_block, curr_block, out_block, blk_size, bufsize));
break;
default:
printf("Unsupported mode: %i\n", mode);
return(-1);
}
}
int comp_delta_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) {
int i,x=0,y=0;
char Val;
unsigned char CurrByte, PrevByte;
signed char DeltaByte;
bit_buffer_purge();
CurrByte=curr_block[0];
out_block[x]=CurrByte;
for (i=1;i<blk_size;i++) {
PrevByte=CurrByte;
CurrByte=curr_block[i];
DeltaByte=(CurrByte-PrevByte);
if (abs(DeltaByte)<32) {
Val=(((1<<6) | (( ( DeltaByte<0 ))<<5) | (abs(DeltaByte)&33)));
bit_buffer_write(Val,7);
} else {
bit_buffer_write(CurrByte,9);
}
y=bit_buffer_size();
while (y>=8 && y!=16) {
out_block[++x]=bit_buffer_read(8);
if (x>=blk_size*2) return(-1);
y=bit_buffer_size();
}
}
y=bit_buffer_size();
if (y!=0) {
out_block[++x]=(bit_buffer_read(y)<<(8-y));
}
return(x+1);
}
int comp_delta_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) {
int i=0,x=0;
unsigned char CurrByte;
unsigned char DeltaByte;
char CompBit;
char Neg;
char Val;
CurrByte=curr_block[0];
bit_buffer_purge();
while (1) {
if ((bit_buffer_size()<=8) && i==blk_size) break;
if ((bit_buffer_size()<=8) && i!=blk_size)
bit_buffer_write((unsigned char) curr_block[++i],8);
CompBit=bit_buffer_read(1);
if ((bit_buffer_size()<=8) && i!=blk_size)
bit_buffer_write((unsigned char) curr_block[++i],8);
if (CompBit==1) {
Neg=bit_buffer_read(1);
DeltaByte=bit_buffer_read(5);
Val=CurrByte+(((-2*Neg)+1)*DeltaByte);
} else {
Val=bit_buffer_read(8);
}
out_block[x++]=CurrByte;
CurrByte=Val;
}
return(x);
}