2674529 [rkeene@sledge /home/rkeene/devel/dact]$ cat -n comp_textrle.c
  1 /*
  2  * Copyright (C) 2001, 2002, and 2003  Roy Keene
  3  *
  4  * This program is free software; you can redistribute it and/or
  5  * modify it under the terms of the GNU General Public License
  6  * as published by the Free Software Foundation; either version 2
  7  * of the License, or (at your option) any later version.
  8  *
  9  * This program is distributed in the hope that it will be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, write to the Free Software
 16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 17  *
 18  *      email: dact@rkeene.org
 19  */
 20 
 21 
 22 #include "dact.h"
 23 #include "comp_textrle.h"
 24 #include <stdio.h>
 25 #ifdef HAVE_UNISTD_H
 26 #include <unistd.h>
 27 #endif
 28 #ifdef HAVE_STDLIB_H
 29 #include <stdlib.h>
 30 #endif
 31 
 32 
 33 /*
 34     mode        - DACT_MODE_COMPR or DACT_MODE_DECMP
 35                 Determine whether to compress or decompress.
 36     prev_block  - Previous (uncompressed) block.
 37     curr_block  - The data to be compressed.
 38     out_block   - Where to put data after compression.
 39     blk_size    - Size of prev_block and curr_block.
 40 */
 41 
 42 #if defined(AS_MODULE) && defined(USE_MODULES)
 43 #include "module.h"
 44 uint32_t DC_NUM=12;
 45 uint32_t DC_TYPE=DACT_MOD_TYPE_COMP;
 46 void *DC_ALGO=comp_textrle_algo;
 47 char *DC_NAME="Text RLE Compression (MOD)";
 48 #endif
 49 
 50 int comp_textrle_algo(int mode, unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int
	bufsize) {
 51     switch(mode) {
 52         case DACT_MODE_COMPR:
 53             return(comp_textrle_compress(prev_block, curr_block, out_block, blk_size, bufsize));
 54             break; /* Heh */
 55         case DACT_MODE_DECMP:
 56             return(comp_textrle_decompress(prev_block, curr_block, out_block, blk_size, bufsize));
 57             break;
 58         default:
 59             printf("Unsupported mode: %i\n", mode);
 60             return(-1);
 61     }
 62 }
 63 
 64 int comp_textrle_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int
	bufsize) {
 65     int i,x=0,m;
 66     unsigned char sentinel=0xff;
 67     unsigned char currchar=0, prevchar;
 68     unsigned char charcnt=0;
 69     unsigned int lowestcnt=0xffff;
 70     unsigned int count[256];
 71 
 72     for (i=0;i<256;i++) count[i]=0;
 73 
 74     for (i=0;i<blk_size;i++) count[curr_block[i]]++;
 75 
 76     for (i=0;i<256;i++) {
 77         if (count[i]<lowestcnt) {
 78             sentinel=i;
 79             lowestcnt=count[i];
 80         }
 81     }
 82 
 83     out_block[x++]=sentinel;
 84 
 85     
 86 
 87     return(x);
 88 }
 89 
 90 int comp_textrle_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int
	bufsize) {
 91     int i,x=0,m;
 92     unsigned char sentinel=curr_block[0];
 93     unsigned char currchar;
 94     unsigned char charcnt;
 95 
 96     for (i=1;i<blk_size;i++) {
 97         currchar=curr_block[i];
 98         if (currchar==sentinel) {
 99             currchar=curr_block[++i];
100             charcnt=curr_block[++i];
101             if ((x+charcnt)>bufsize) {
102                 printf("Error in RLE compression!\n");
103                 return(0);
104             }
105             for (m=0;m<charcnt;m++) out_block[x++]=currchar;
106         } else {
107             out_block[x++]=currchar;
108         }
109     }
110     return(x);
111 }
2674530 [rkeene@sledge /home/rkeene/devel/dact]$

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last modified: 2004-04-04 01:01:50