/* bin_patch.c */
/* Based on sourcecode by Tomek Malesinski. */
/* Patchfile can be created with `cmp -l'. */

#include <stdio.h>
#include <stdlib.h>


void
next_patch_line(unsigned int *offset, unsigned int *old_v, unsigned int *new_v)
{
	if (scanf(" %u %o %o", offset, old_v, new_v) != 3) *offset = -1;
	*offset -= 1;
}

int
main(int argc, char *argv[])
{
	FILE *fp1, *fp2;
	unsigned int i, c;
	unsigned int offset, old_v, new_v;

	if (argc < 3) {
		fprintf(stderr, "Usage: %s INFILE OUTFILE < PATCHFILE\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	fp1 = fopen(argv[1], "rb");
	if (!fp1) {
		fprintf(stderr, "Cannot open the input file.\n");
		exit(EXIT_FAILURE);
	}

	fp2 = fopen(argv[2], "wb");
	if (!fp2) {
		fprintf(stderr, "Cannot open the output file.\n");
		exit(EXIT_FAILURE);
	}

	i = 0;
	next_patch_line(&offset, &old_v, &new_v);

	while ((c = fgetc(fp1)) != EOF) {
		if (i == offset) {
			if (c != old_v) {
				fprintf(stderr, "Wrong input file.\n");
				exit(EXIT_FAILURE);
			}

			c = new_v;
			next_patch_line(&offset, &old_v, &new_v);
		}
		fputc(c, fp2);
		i++;
	}

	return EXIT_SUCCESS;
}