Program to apply IPS patches.

ips_patch.c

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

#if 0
#define DBG_LOG(...) fprintf(stderr, __VA_ARGS__)
#else
#define DBG_LOG(...) (void)0
#endif

int main(int argc, char **argv) {
	FILE *fo = NULL, *fi = stdin;
	const char *err; unsigned n;
	uint8_t buf[256];

	err = "Usage: ips_patch dest.bin [patch.ips]\n";
	if (argc < 2 || argc > 3) goto end;
	if (argc > 2) {
		fi = fopen(argv[2], "rb");
		err = "!!! can't open patch file\n";
		if (!fi) goto end;
	}
	err = "!!! fread failed\n";
	n = fread(buf, 1, 5, fi);
	if (!n && fi == stdin)
		err = "!!! expected patch in stdin\n";
	if (n != 5) goto end;
	err = "!!! wrong patch header\n";
	if (memcmp(buf, "PATCH", 5)) goto end;
	err = "!!! can't open dest file\n";
	fo = fopen(argv[1], "rb+");
	if (!fo) goto end;
	for (;;) {
		unsigned offset, size, rep = 0;
		n = fread(buf, 1, 5, fi);
		if (n != 5) {
			err = "!!! fread failed\n";
			if (n == 3 && !memcmp(buf, "EOF", 3)) err = NULL;
			break;
		}
		offset = buf[0] << 16 | buf[1] << 8 | buf[2];
		size = buf[3] << 8 | buf[4];
		if (!size) {
			err = "!!! fread failed\n";
			if (fread(buf, 1, 3, fi) != 3) break;
			size = rep = buf[0] << 8 | buf[1];
			DBG_LOG("rle: 0x%x, 0x%x, 0x%02x\n", offset, size, buf[2]);
			err = "!!! empty rle record\n";
			if (!rep) goto end;
			n = sizeof(buf);
			if (n > size) n = size;
			memset(buf, buf[2], n);
		} else {
			DBG_LOG("copy: 0x%x, 0x%x\n", offset, size);
		}
		err = "!!! fseek failed\n";
		if (fseek(fo, offset, SEEK_SET)) break;
		do {
			n = sizeof(buf);
			if (n > size) n = size;
			if (!rep) {
				err = "!!! fread failed\n";
				if (fread(buf, 1, n, fi) != n) goto end;
			}
			err = "!!! fwrite failed\n";
			if (fwrite(buf, 1, n, fo) != n) goto end;
		} while ((size -= n));
	}
end:
	if (fo) fclose(fo);
	if (fi != stdin) fclose(fi);
	if (err) fputs(err, stderr);
	return !!err;
}