const char *
purple_util_get_image_extension(gconstpointer data, size_t len)
{
	g_return_val_if_fail(data != NULL, NULL);
	g_return_val_if_fail(len   > 0,    NULL);

	if (len >= 4)
	{
		if (!strncmp((char *)data, "GIF8", 4))
			return "gif";
		else if (!strncmp((char *)data, "\xff\xd8\xff", 3)) /* 4th may be e0 through ef */
			return "jpg";
		else if (!strncmp((char *)data, "\x89PNG", 4))
			return "png";
		else if (!strncmp((char *)data, "MM", 2) ||
				 !strncmp((char *)data, "II", 2))
			return "tif";
		else if (!strncmp((char *)data, "BM", 2))
			return "bmp";
	}

	return "icon";
}