2 * xorimage.c - partially based on OpenWrt's addpattern.c
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
27 static char default_pattern[] = "12345678";
30 int xor_data(uint8_t *data, size_t len, const uint8_t *pattern, int p_len, int p_off)
34 *data ^= pattern[offset];
36 offset = (offset + 1) % p_len;
42 void usage(void) __attribute__ (( __noreturn__ ));
46 fprintf(stderr, "Usage: xorimage [-i infile] [-o outfile] [-p <pattern>]\n");
51 int main(int argc, char **argv)
53 char buf[1024]; /* keep this at 1k or adjust garbage calc below */
58 const char *pattern = default_pattern;
64 while ((c = getopt(argc, argv, "i:o:p:h")) != -1) {
81 if (optind != argc || optind == 1) {
82 fprintf(stderr, "illegal arg \"%s\"\n", argv[optind]);
86 if (ifn && !(in = fopen(ifn, "r"))) {
87 fprintf(stderr, "can not open \"%s\" for reading\n", ifn);
91 if (ofn && !(out = fopen(ofn, "w"))) {
92 fprintf(stderr, "can not open \"%s\" for writing\n", ofn);
96 p_len = strlen(pattern);
99 fprintf(stderr, "pattern cannot be empty\n");
104 while ((n = fread(buf, 1, sizeof(buf), in)) > 0) {
105 if (n < sizeof(buf)) {
108 fprintf(stderr, "fread error\n");
113 p_off = xor_data(buf, n, pattern, p_len, p_off);
115 if (!fwrite(buf, n, 1, out)) {
117 fprintf(stderr, "fwrite error\n");