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_text.h" 24 #include "buffer.h" 25 #include <stdio.h> 26 #ifdef HAVE_UNISTD_H 27 #include <unistd.h> 28 #endif 29 #ifdef HAVE_STDLIB_H 30 #include <stdlib.h> 31 #endif 32 #ifdef HAVE_STRING_H 33 #include <string.h> 34 #endif 35 36 37 /* 38 mode - DACT_MODE_COMPR or DACT_MODE_DECMP 39 Determine whether to compress or decompress. 40 prev_block - Previous (uncompressed) block. 41 curr_block - The data to be compressed. 42 out_block - Where to put data after compression. 43 blk_size - Size of prev_block and curr_block. 44 */ 45 46 #if defined(USE_MODULES) && defined(AS_MODULE) 47 #include "module.h" 48 uint32_t DC_NUM=3; 49 uint32_t DC_TYPE=DACT_MOD_TYPE_COMP; 50 void *DC_ALGO=comp_text_algo; 51 char *DC_NAME="Text Compression (MOD)"; 52 #endif 53 54 int comp_text_algo(int mode, unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) { 55 switch(mode) { 56 case DACT_MODE_COMPR: 57 return(comp_text_compress(prev_block, curr_block, out_block, blk_size, bufsize)); 58 break; /* Heh */ 59 case DACT_MODE_DECMP: 60 return(comp_text_decompress(prev_block, curr_block, out_block, blk_size, bufsize)); 61 break; 62 default: 63 printf("Unsupported mode: %i\n", mode); 64 return(-1); 65 } 66 } 67 68 int comp_text_compress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) { 69 unsigned char low_byte=255, high_byte=0; 70 unsigned char byte_buf; 71 unsigned int range; 72 int i,x=0,y; 73 74 75 bit_buffer_purge(); 76 77 for (i=0;i<blk_size;i++) { 78 if (((unsigned char) curr_block[i])<low_byte) low_byte=curr_block[i]; 79 if (((unsigned char) curr_block[i])>high_byte) high_byte=curr_block[i]; 80 } 81 82 range=(unsigned int) (high_byte-low_byte); 83 84 out_block[x++]=low_byte; 85 out_block[x++]=high_byte; 86 87 if (range==0) 88 return(2); 89 90 for (y=1;y<=8;y++) 91 if ((range>>y)==0) break; 92 if (y==8) return(-1); 93 94 for (i=0;i<blk_size;i++) { 95 byte_buf=(unsigned char) (curr_block[i]-low_byte); 96 /* 97 if ((byte_buf>>y)==1) { 98 return(-1); 99 } 100 */ 101 bit_buffer_write(byte_buf,y); 102 103 while (bit_buffer_size()>=8) { 104 out_block[x++]=bit_buffer_read(8); 105 } 106 } 107 /* Remove any less-than-one-byte data */ 108 if ((i=bit_buffer_size())!=0) { 109 out_block[x++]=(bit_buffer_read(i)<<(8-i)); 110 } 111 112 return(x); 113 } 114 115 int comp_text_decompress(unsigned char *prev_block, unsigned char *curr_block, char *out_block, int blk_size, int bufsize) { 116 unsigned char high_byte, low_byte; 117 unsigned int range; 118 int i=0,x=0,y; 119 120 low_byte=curr_block[x++]; 121 high_byte=curr_block[x++]; 122 range=(unsigned int) (high_byte-low_byte); 123 124 if (range==0) { 125 memset(out_block, low_byte, bufsize); 126 return(bufsize); 127 } 128 for (y=1;y<=8;y++) 129 if ((range>>y)==0) break; 130 131 bit_buffer_purge(); 132 133 while (1) { 134 if (bit_buffer_size()<y) bit_buffer_write((unsigned char) curr_block[x++],8); 135 out_block[i++]=(bit_buffer_read(y)+low_byte); 136 if ((x==blk_size) && (bit_buffer_size()<y)) break; 137 if (i>=(bufsize)) break; 138 } 139 140 return(i); 141 } |