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
comp_textrle_algo(int mode,unsigned char * prev_block,unsigned char * curr_block,char * out_block,int blk_size,int bufsize)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
comp_textrle_compress(unsigned char * prev_block,unsigned char * curr_block,char * out_block,int blk_size,int bufsize)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
comp_textrle_decompress(unsigned char * prev_block,unsigned char * curr_block,char * out_block,int blk_size,int bufsize)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 }
112