| 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 |
| 39 | int 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. |
| 53 | static 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 | // ******************************************************************* |
| 91 | int 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 | |
