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- /*
- * xorimage.c - partially based on OpenWrt's addpattern.c
- *
- * 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 <stdint.h>
- #include <time.h>
- #include <unistd.h>
- #include <sys/stat.h>
- static char default_pattern[] = "12345678";
- int xor_data(uint8_t *data, size_t len, const uint8_t *pattern, int p_len, int p_off)
- {
- int offset = p_off;
- while (len--) {
- *data ^= pattern[offset];
- data++;
- offset = (offset + 1) % p_len;
- }
- return offset;
- }
- void usage(void) __attribute__ (( __noreturn__ ));
- void usage(void)
- {
- fprintf(stderr, "Usage: xorimage [-i infile] [-o outfile] [-p <pattern>]\n");
- exit(EXIT_FAILURE);
- }
- int main(int argc, char **argv)
- {
- char buf[1024]; /* keep this at 1k or adjust garbage calc below */
- FILE *in = stdin;
- FILE *out = stdout;
- char *ifn = NULL;
- char *ofn = NULL;
- const char *pattern = default_pattern;
- int c;
- int v0, v1, v2;
- size_t n;
- int p_len, p_off = 0;
- while ((c = getopt(argc, argv, "i:o:p:h")) != -1) {
- switch (c) {
- case 'i':
- ifn = optarg;
- break;
- case 'o':
- ofn = optarg;
- break;
- case 'p':
- pattern = optarg;
- break;
- case 'h':
- default:
- usage();
- }
- }
- if (optind != argc || optind == 1) {
- fprintf(stderr, "illegal arg \"%s\"\n", argv[optind]);
- usage();
- }
- if (ifn && !(in = fopen(ifn, "r"))) {
- fprintf(stderr, "can not open \"%s\" for reading\n", ifn);
- usage();
- }
- if (ofn && !(out = fopen(ofn, "w"))) {
- fprintf(stderr, "can not open \"%s\" for writing\n", ofn);
- usage();
- }
- p_len = strlen(pattern);
- if (p_len == 0) {
- fprintf(stderr, "pattern cannot be empty\n");
- usage();
- }
- while ((n = fread(buf, 1, sizeof(buf), in)) > 0) {
- if (n < sizeof(buf)) {
- if (ferror(in)) {
- FREAD_ERROR:
- fprintf(stderr, "fread error\n");
- return EXIT_FAILURE;
- }
- }
- p_off = xor_data(buf, n, pattern, p_len, p_off);
- if (!fwrite(buf, n, 1, out)) {
- FWRITE_ERROR:
- fprintf(stderr, "fwrite error\n");
- return EXIT_FAILURE;
- }
- }
- if (ferror(in)) {
- goto FREAD_ERROR;
- }
- if (fflush(out)) {
- goto FWRITE_ERROR;
- }
- fclose(in);
- fclose(out);
- return EXIT_SUCCESS;
- }
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