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/*
* 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
*/
/*
Example block compression routine for interfacing with DACT.
Seminibble Compression (Actually, a 2bit Huffman Implementation)
*/
#include "dact.h"
#include "comp_snibble.h"
#include "buffer.h"
#include "sort.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=6;
uint32_t DC_TYPE=DACT_MOD_TYPE_COMP;
void *DC_ALGO=comp_snibble_algo;
char *DC_NAME="Seminibble Encoding (MOD)";
#endif
int comp_snibble_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_snibble_compress(prev_block, curr_block, out_block, blk_size, bufsize));
break; /* Heh */
case DACT_MODE_DECMP:
return(comp_snibble_decompress(prev_block, curr_block, out_block, blk_size, bufsize));
break;
default:
printf("Unsupported mode: %i\n", mode);
return(-1);
}
}
int comp_snibble_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) {
const unsigned char hash_table[4]={0, 2, 6, 7};
const unsigned char hash_len[8]= {1, 0, 2, 0, 0, 0, 3, 3};
unsigned char lookup_table[4]={0, 0, 0, 0};
uint32_t freq[4]={0, 0, 0, 0};
char *curr_cpy;
int i,x,m,g=0;
if ((curr_cpy=malloc(blk_size))==NULL) {
return(-1);
}
memcpy(curr_cpy,curr_block,blk_size);
bit_buffer_purge();
for (i=0;i<blk_size;i++) {
freq[(int) ((curr_cpy[i]&0xc0)>>6)]++;
freq[(int) ((curr_cpy[i]&0x30)>>4)]++;
freq[(int) ((curr_cpy[i]&0x0c)>>2)]++;
freq[(int) ((curr_cpy[i]&0x03))]++;
}
int_sort(freq,4,1);
for (i=0;i<4;i++) lookup_table[freq[i]]=hash_table[i];
bit_buffer_write(freq[0],2);
bit_buffer_write(freq[1],2);
bit_buffer_write(freq[2],2);
/*
outsize=((int) ((((((float) (freq[0]&0xffff))/2)+(freq[1]&0xffff)+(((float) (freq[2]&0xffff)+(freq[3]&0xffff))*1.5))/4.0)+0.99));
*/
for (i=0;i<blk_size;i++) {
for (x=0;x<4;x++) {
m=((curr_cpy[i]&(3<<(x*2)))>>( x*2 )) ;
bit_buffer_write(lookup_table[m],hash_len[lookup_table[m]]);
while (bit_buffer_size()>=8) out_block[g++]=((unsigned char) (bit_buffer_read(8)));
}
}
i=bit_buffer_size();
if (i!=0) out_block[g++]=bit_buffer_read(i)<<(8-i);
free(curr_cpy);
return(g);
}
int comp_snibble_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) {
const unsigned char lookup_table[8]={0, 0, 1, 0, 0, 0, 2, 3};
unsigned int freq[4];
unsigned int x, m=0;
unsigned int i, cnt=0, f=0, j=0;
int32_t g=0;
freq[0]=(curr_block[0]&0xc0)>>6; /* 0 */
freq[1]=(curr_block[0]&0x30)>>4; /* 2 */
freq[2]=(curr_block[0]&0x0c)>>2; /* 6 */
for (i=0;i<4;i++) {
if (freq[0]!=i && freq[1]!=i && freq[2]!=i) freq[3]=i;
}
out_block[0]=0;
bit_buffer_purge();
bit_buffer_write(curr_block[g++]&0x03,2);
while (1) {
while (((bit_buffer_size()+8)<=16) && g<=blk_size) bit_buffer_write(curr_block[g++],8);
x=bit_buffer_read(1);
m=(m<<1)+x;
cnt++;
if (x==0 || cnt==3) {
out_block[f]|=(freq[lookup_table[m]]<<( j )) ;
j+=2;
/* Obsficated comes to mind ... */
if (j==8) out_block[++f]=(j=0);
m=0;
cnt=0;
}
if (bit_buffer_size()==0 || f==bufsize) break;
}
return(f);
}
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