1 /* **************************************************************************
3 This program creates a CRC checksum and encodes the file that is named
6 Compile with: gcc encode_crc.c -Wall -o encode_crc
8 Author: Michael Margraf (michael.margraf@freecom.com)
9 Copyright: Freecom Technology GmbH, Berlin, 2004
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.
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.
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
26 ************************************************************************* */
34 // *******************************************************************
35 // CCITT polynom G(x)=x^16+x^12+x^5+1
36 #define POLYNOM 0x1021
38 // CRC algorithm with MSB first
39 int make_crc16(int crc
, char new)
42 crc
= crc
^ (((int)new) << 8);
44 for(i
=0; i
<8; i
++) { // work on 8 bits in "new"
45 crc
<<= 1; // MSBs first
46 if(crc
& 0x10000) crc
^= POLYNOM
;
51 // *******************************************************************
52 // Reads the file "filename" into memory and returns pointer to the buffer.
53 static char *readfile(char *filename
, int *size
)
59 if (stat(filename
,&info
)!=0)
62 if ((fp
=fopen(filename
,"r"))==NULL
)
68 if ((buffer
=(char *)malloc(info
.st_size
+1))==NULL
)
71 if (fread(buffer
,1,info
.st_size
,fp
)!=info
.st_size
)
78 buffer
[info
.st_size
]='\0';
79 if(size
) *size
= info
.st_size
;
90 // *******************************************************************
91 int main(int argc
, char** argv
)
94 printf("ERROR: Argument missing!\n\n");
98 int count
; // size of file in bytes
99 char *p
, *master
= readfile(argv
[1], &count
);
101 printf("ERROR: File not found!\n");
108 for(z
=0; z
<count
; z
++)
109 crc
= make_crc16(crc
, *(p
++)); // calculate CRC
110 short crc16
= (short)crc
;
113 if(argc > 2) { // with flag for device recognition ?
115 for(z=strlen(p); z>0; z--) {
117 *(p++) = (char)crc; // encode device flag
123 for(z
=0; z
<count
; z
++) {
125 *(p
++) = (char)crc
; // encode file
129 // write encoded file...
130 FILE *fp
= fopen(argv
[2], "w");
132 printf("ERROR: File not writeable!\n");
136 if(argc
> 3) { // add flag for device recognition ?
137 fwrite(argv
[3], strlen(argv
[3]), sizeof(char), fp
);
140 // Device is an FSG, so byte swap (IXP4xx is big endian)
141 crc16
= ((crc16
>> 8) & 0xFF) | ((crc16
<< 8) & 0xFF00);
144 fwrite(&crc16
, 1, sizeof(short), fp
); // first write CRC
146 fwrite(master
, count
, sizeof(char), fp
); // write content
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