1/* ************************************************************************** 2 3 This program creates a CRC checksum and encodes the file that is named 4 in the command line. 5 6 Compile with: gcc encode_crc.c -Wall -o encode_crc 7 8 Author: Michael Margraf (michael.margraf@freecom.com) 9 Copyright: Freecom Technology GmbH, Berlin, 2004 10 www.freecom.com 11 12 This program is free software; you can redistribute it and/or modify 13 it under the terms of the GNU General Public License as published by 14 the Free Software Foundation; either version 2 of the License, or 15 (at your option) any later version. 16 17 This program is distributed in the hope that it will be useful, 18 but WITHOUT ANY WARRANTY; without even the implied warranty of 19 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 20 General Public License for more details. 21 22 You should have received a copy of the GNU General Public License 23 along with this program; if not, write to the Free Software 24 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 25 26 ************************************************************************* */ 27 28 29#include <stdio.h> 30#include <stdlib.h> 31#include <string.h> 32#include <sys/stat.h> 33 34// ******************************************************************* 35// CCITT polynom G(x)=x^16+x^12+x^5+1 36#define POLYNOM 0x1021 37 38// CRC algorithm with MSB first 39int make_crc16(int crc, char new) 40{ 41 int i; 42 crc = crc ^ (((int)new) << 8); 43 44 for(i=0; i<8; i++) { // work on 8 bits in "new" 45 crc <<= 1; // MSBs first 46 if(crc & 0x10000) crc ^= POLYNOM; 47 } 48 return crc & 0xFFFF; 49} 50 51// ******************************************************************* 52// Reads the file "filename" into memory and returns pointer to the buffer. 53static char *readfile(char *filename, int *size) 54{ 55 FILE *fp; 56 char *buffer; 57 struct stat info; 58 59 if (stat(filename,&info)!=0) 60 return NULL; 61 62 if ((fp=fopen(filename,"r"))==NULL) 63 return NULL; 64 65 buffer=NULL; 66 for (;;) 67 { 68 if ((buffer=(char *)malloc(info.st_size+1))==NULL) 69 break; 70 71 if (fread(buffer,1,info.st_size,fp)!=info.st_size) 72 { 73 free(buffer); 74 buffer=NULL; 75 break; 76 } 77 78 buffer[info.st_size]='\0'; 79 if(size) *size = info.st_size; 80 81 break; 82 } 83 84 (void)fclose(fp); 85 86 return buffer; 87} 88 89 90// ******************************************************************* 91int main(int argc, char** argv) 92{ 93 if(argc < 3) { 94 printf("ERROR: Argument missing!\n\n"); 95 return 1; 96 } 97 98 int count; // size of file in bytes 99 char *p, *master = readfile(argv[1], &count); 100 if(!master) { 101 printf("ERROR: File not found!\n"); 102 return 1; 103 } 104 105 int crc = 0xFFFF, z; 106 107 p = master; 108 for(z=0; z<count; z++) 109 crc = make_crc16(crc, *(p++)); // calculate CRC 110 short crc16 = (short)crc; 111 112 /* 113 if(argc > 2) { // with flag for device recognition ? 114 p = argv[2]; 115 for(z=strlen(p); z>0; z--) { 116 crc ^= (int)(*p); 117 *(p++) = (char)crc; // encode device flag 118 } 119 } 120 */ 121 122 p = master; 123 for(z=0; z<count; z++) { 124 crc ^= (int)(*p); 125 *(p++) = (char)crc; // encode file 126 } 127 128 129 // write encoded file... 130 FILE *fp = fopen(argv[2], "w"); 131 if(!fp) { 132 printf("ERROR: File not writeable!\n"); 133 return 1; 134 } 135 136 if(argc > 3) { // add flag for device recognition ? 137 fwrite(argv[3], strlen(argv[3]), sizeof(char), fp); 138 } 139 else { 140 // Device is an FSG, so byte swap (IXP4xx is big endian) 141 crc16 = ((crc16 >> 8) & 0xFF) | ((crc16 << 8) & 0xFF00); 142 } 143 144 fwrite(&crc16, 1, sizeof(short), fp); // first write CRC 145 146 fwrite(master, count, sizeof(char), fp); // write content 147 fclose(fp); 148 149 free(master); 150 return 0; 151} 152