static int diff_get_patch_id(struct diff_options *options, unsigned char *sha1)
{
	struct diff_queue_struct *q = &diff_queued_diff;
	int i;
	SHA_CTX ctx;
	struct patch_id_t data;
	char buffer[PATH_MAX * 4 + 20];

	SHA1_Init(&ctx);
	memset(&data, 0, sizeof(struct patch_id_t));
	data.ctx = &ctx;
	data.xm.consume = patch_id_consume;

	for (i = 0; i < q->nr; i++) {
		xpparam_t xpp;
		xdemitconf_t xecfg;
		xdemitcb_t ecb;
		mmfile_t mf1, mf2;
		struct diff_filepair *p = q->queue[i];
		int len1, len2;

		memset(&xecfg, 0, sizeof(xecfg));
		if (p->status == 0)
			return error("internal diff status error");
		if (p->status == DIFF_STATUS_UNKNOWN)
			continue;
		if (diff_unmodified_pair(p))
			continue;
		if ((DIFF_FILE_VALID(p->one) && S_ISDIR(p->one->mode)) ||
		    (DIFF_FILE_VALID(p->two) && S_ISDIR(p->two->mode)))
			continue;
		if (DIFF_PAIR_UNMERGED(p))
			continue;

		diff_fill_sha1_info(p->one);
		diff_fill_sha1_info(p->two);
		if (fill_mmfile(&mf1, p->one) < 0 ||
				fill_mmfile(&mf2, p->two) < 0)
			return error("unable to read files to diff");

		len1 = remove_space(p->one->path, strlen(p->one->path));
		len2 = remove_space(p->two->path, strlen(p->two->path));
		if (p->one->mode == 0)
			len1 = snprintf(buffer, sizeof(buffer),
					"diff--gita/%.*sb/%.*s"
					"newfilemode%06o"
					"---/dev/null"
					"+++b/%.*s",
					len1, p->one->path,
					len2, p->two->path,
					p->two->mode,
					len2, p->two->path);
		else if (p->two->mode == 0)
			len1 = snprintf(buffer, sizeof(buffer),
					"diff--gita/%.*sb/%.*s"
					"deletedfilemode%06o"
					"---a/%.*s"
					"+++/dev/null",
					len1, p->one->path,
					len2, p->two->path,
					p->one->mode,
					len1, p->one->path);
		else
			len1 = snprintf(buffer, sizeof(buffer),
					"diff--gita/%.*sb/%.*s"
					"---a/%.*s"
					"+++b/%.*s",
					len1, p->one->path,
					len2, p->two->path,
					len1, p->one->path,
					len2, p->two->path);
		SHA1_Update(&ctx, buffer, len1);

		xpp.flags = XDF_NEED_MINIMAL;
		xecfg.ctxlen = 3;
		xecfg.flags = XDL_EMIT_FUNCNAMES;
		ecb.outf = xdiff_outf;
		ecb.priv = &data;
		xdi_diff(&mf1, &mf2, &xpp, &xecfg, &ecb);
	}

	SHA1_Final(sha1, &ctx);
	return 0;
}
Unknown