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152 lines
3.6 KiB
C
152 lines
3.6 KiB
C
/* **************************************************************************
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This program creates a CRC checksum and encodes the file that is named
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in the command line.
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Compile with: gcc encode_crc.c -Wall -o encode_crc
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Author: Michael Margraf (michael.margraf@freecom.com)
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Copyright: Freecom Technology GmbH, Berlin, 2004
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www.freecom.com
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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************************************************************************* */
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/stat.h>
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// *******************************************************************
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// CCITT polynom G(x)=x^16+x^12+x^5+1
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#define POLYNOM 0x1021
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// CRC algorithm with MSB first
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int make_crc16(int crc, char new)
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{
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int i;
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crc = crc ^ (((int)new) << 8);
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for(i=0; i<8; i++) { // work on 8 bits in "new"
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crc <<= 1; // MSBs first
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if(crc & 0x10000) crc ^= POLYNOM;
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}
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return crc & 0xFFFF;
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}
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// *******************************************************************
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// Reads the file "filename" into memory and returns pointer to the buffer.
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static char *readfile(char *filename, int *size)
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{
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FILE *fp;
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char *buffer;
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struct stat info;
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if (stat(filename,&info)!=0)
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return NULL;
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if ((fp=fopen(filename,"r"))==NULL)
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return NULL;
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buffer=NULL;
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for (;;)
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{
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if ((buffer=(char *)malloc(info.st_size+1))==NULL)
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break;
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if (fread(buffer,1,info.st_size,fp)!=info.st_size)
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{
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free(buffer);
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buffer=NULL;
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break;
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}
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buffer[info.st_size]='\0';
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if(size) *size = info.st_size;
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break;
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}
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(void)fclose(fp);
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return buffer;
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}
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// *******************************************************************
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int main(int argc, char** argv)
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{
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if(argc < 3) {
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printf("ERROR: Argument missing!\n\n");
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return 1;
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}
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int count; // size of file in bytes
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char *p, *master = readfile(argv[1], &count);
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if(!master) {
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printf("ERROR: File not found!\n");
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return 1;
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}
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int crc = 0xFFFF, z;
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p = master;
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for(z=0; z<count; z++)
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crc = make_crc16(crc, *(p++)); // calculate CRC
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short crc16 = (short)crc;
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/*
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if(argc > 2) { // with flag for device recognition ?
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p = argv[2];
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for(z=strlen(p); z>0; z--) {
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crc ^= (int)(*p);
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*(p++) = (char)crc; // encode device flag
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}
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}
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*/
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p = master;
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for(z=0; z<count; z++) {
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crc ^= (int)(*p);
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*(p++) = (char)crc; // encode file
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}
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// write encoded file...
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FILE *fp = fopen(argv[2], "w");
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if(!fp) {
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printf("ERROR: File not writeable!\n");
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return 1;
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}
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if(argc > 3) { // add flag for device recognition ?
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fwrite(argv[3], strlen(argv[3]), sizeof(char), fp);
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}
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else {
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// Device is an FSG, so byte swap (IXP4xx is big endian)
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crc16 = ((crc16 >> 8) & 0xFF) | ((crc16 << 8) & 0xFF00);
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}
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fwrite(&crc16, 1, sizeof(short), fp); // first write CRC
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fwrite(master, count, sizeof(char), fp); // write content
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fclose(fp);
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free(master);
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return 0;
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}
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