Function check_collision

object-file.c:345–397

#define CHECK_COLLISION_DEST_VANISHED -2

static int check_collision(const char *source, const char *dest)
{
	char buf_source[4096], buf_dest[4096];
	int fd_source = -1, fd_dest = -1;
	int ret = 0;

	fd_source = open(source, O_RDONLY);
	if (fd_source < 0) {
		ret = error_errno(_("unable to open %s"), source);
		goto out;
	}

	fd_dest = open(dest, O_RDONLY);
	if (fd_dest < 0) {
		if (errno != ENOENT)
			ret = error_errno(_("unable to open %s"), dest);
		else
			ret = CHECK_COLLISION_DEST_VANISHED;
		goto out;
	}

	while (1) {
		ssize_t sz_a, sz_b;

		sz_a = read_in_full(fd_source, buf_source, sizeof(buf_source));
		if (sz_a < 0) {
			ret = error_errno(_("unable to read %s"), source);
			goto out;
		}

		sz_b = read_in_full(fd_dest, buf_dest, sizeof(buf_dest));
		if (sz_b < 0) {
			ret = error_errno(_("unable to read %s"), dest);
			goto out;
		}

		if (sz_a != sz_b || memcmp(buf_source, buf_dest, sz_a)) {
			ret = error(_("files '%s' and '%s' differ in contents"),
				    source, dest);
			goto out;
		}

		if ((size_t) sz_a < sizeof(buf_source))
			break;
	}

out:
	if (fd_source > -1)
		close(fd_source);
	if (fd_dest > -1)
		close(fd_dest);
	return ret;
}

/*
 * Move the just written object into its final resting place.