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