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_rle.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=1; 45 uint32_t DC_TYPE=DACT_MOD_TYPE_COMP; 46 void *DC_ALGO=comp_rle_algo; 47 char *DC_NAME="RLE Compression (MOD)"; 48 char *DC_SIGN="RGlnaXRhbFNpZ25hdHVyZQ=="; 49 char *DC_URL_GET="http://www.rkeene.org/projects/compression/dact/@@OSNM@@-@@ARCH@@/comp_rle.dll"; 50 char *DC_URL_VER="http://www.rkeene.org/projects/compression/dact/@@OSNM@@-@@ARCH@@/comp_rle.ver"; 51 uint32_t DC_VER=0x00080d; 52 uint32_t DC_REQUIRE=DACT_MOD_REQ_ATLEAST|(0x00080d); 53 #endif 54 55 int comp_rle_algo(int mode, unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) { 56 switch(mode) { 57 case DACT_MODE_COMPR: 58 return(comp_rle_compress(prev_block, curr_block, out_block, blk_size, bufsize)); 59 break; /* Heh */ 60 case DACT_MODE_DECMP: 61 return(comp_rle_decompress(prev_block, curr_block, out_block, blk_size, bufsize)); 62 break; 63 default: 64 printf("Unsupported mode: %i\n", mode); 65 return(-1); 66 } 67 } 68 69 int comp_rle_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) { 70 int i,x=0,m; 71 unsigned char sentinel=0xff; 72 unsigned char currchar=0, prevchar; 73 unsigned char charcnt=0; 74 unsigned int lowestcnt=0xffff; 75 unsigned int count[256]; 76 77 for (i=0;i<256;i++) count[i]=0; 78 79 for (i=0;i<blk_size;i++) count[curr_block[i]]++; 80 81 for (i=0;i<256;i++) { 82 if (count[i]<lowestcnt) { 83 sentinel=i; 84 lowestcnt=count[i]; 85 } 86 } 87 88 out_block[x++]=sentinel; 89 90 prevchar=curr_block[0]; 91 for (i=0;i<(blk_size+1);i++) { 92 if (i!=blk_size) { currchar=curr_block[i]; } else { currchar++; } 93 if (prevchar!=currchar || charcnt==255 || i>=(blk_size)) { 94 if (charcnt<=2 && prevchar!=sentinel) { 95 for (m=0;m<charcnt;m++) out_block[x++]=prevchar; 96 } else { 97 out_block[x++]=sentinel; 98 out_block[x++]=prevchar; 99 out_block[x++]=charcnt; 100 } 101 charcnt=0; 102 } 103 charcnt++; 104 prevchar=currchar; 105 } 106 return(x); 107 } 108 109 int comp_rle_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) { 110 int i,x=0,m; 111 unsigned char sentinel=curr_block[0]; 112 unsigned char currchar; 113 unsigned char charcnt; 114 115 for (i=1;i<blk_size;i++) { 116 currchar=curr_block[i]; 117 if (currchar==sentinel) { 118 currchar=curr_block[++i]; 119 charcnt=curr_block[++i]; 120 if ((x+charcnt)>bufsize) { 121 printf("Error in RLE compression!\n"); 122 return(0); 123 } 124 for (m=0;m<charcnt;m++) out_block[x++]=currchar; 125 } else { 126 out_block[x++]=currchar; 127 } 128 } 129 return(x); 130 } |