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 | |