135 lines
2.8 KiB
C
135 lines
2.8 KiB
C
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/*
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* xorimage.c - partially based on OpenWrt's addpattern.c
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdint.h>
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#include <unistd.h>
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#include <sys/stat.h>
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static char default_pattern[] = "12345678";
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int xor_data(uint8_t *data, size_t len, const uint8_t *pattern, int p_len, int p_off)
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{
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int offset = p_off;
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while (len--) {
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*data ^= pattern[offset];
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data++;
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offset = (offset + 1) % p_len;
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}
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return offset;
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}
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void usage(void) __attribute__ (( __noreturn__ ));
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void usage(void)
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{
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fprintf(stderr, "Usage: xorimage [-i infile] [-o outfile] [-p <pattern>]\n");
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exit(EXIT_FAILURE);
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}
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int main(int argc, char **argv)
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{
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char buf[1024]; /* keep this at 1k or adjust garbage calc below */
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FILE *in = stdin;
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FILE *out = stdout;
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char *ifn = NULL;
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char *ofn = NULL;
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const char *pattern = default_pattern;
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int c;
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int v0, v1, v2;
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size_t n;
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int p_len, p_off = 0;
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while ((c = getopt(argc, argv, "i:o:p:h")) != -1) {
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switch (c) {
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case 'i':
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ifn = optarg;
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break;
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case 'o':
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ofn = optarg;
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break;
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case 'p':
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pattern = optarg;
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break;
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case 'h':
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default:
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usage();
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}
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}
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if (optind != argc || optind == 1) {
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fprintf(stderr, "illegal arg \"%s\"\n", argv[optind]);
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usage();
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}
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if (ifn && !(in = fopen(ifn, "r"))) {
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fprintf(stderr, "can not open \"%s\" for reading\n", ifn);
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usage();
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}
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if (ofn && !(out = fopen(ofn, "w"))) {
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fprintf(stderr, "can not open \"%s\" for writing\n", ofn);
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usage();
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}
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p_len = strlen(pattern);
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if (p_len == 0) {
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fprintf(stderr, "pattern cannot be empty\n");
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usage();
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}
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while ((n = fread(buf, 1, sizeof(buf), in)) > 0) {
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if (n < sizeof(buf)) {
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if (ferror(in)) {
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FREAD_ERROR:
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fprintf(stderr, "fread error\n");
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return EXIT_FAILURE;
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}
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}
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p_off = xor_data(buf, n, pattern, p_len, p_off);
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if (!fwrite(buf, n, 1, out)) {
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FWRITE_ERROR:
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fprintf(stderr, "fwrite error\n");
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return EXIT_FAILURE;
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}
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}
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if (ferror(in)) {
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goto FREAD_ERROR;
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}
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if (fflush(out)) {
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goto FWRITE_ERROR;
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}
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fclose(in);
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fclose(out);
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return EXIT_SUCCESS;
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}
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