static gint
stream_null_reset (CamelStream *stream,
                   GError **error)
{
	CAMEL_STREAM_NULL (stream)->written = 0;

	return 0;
}
static gssize
stream_null_write (CamelStream *stream,
                   const gchar *buffer,
                   gsize n,
                   GCancellable *cancellable,
                   GError **error)
{
	CAMEL_STREAM_NULL (stream)->written += n;

	return n;
}
static guint32
get_message_size (CamelMimeMessage *message,
                  GCancellable *cancellable)
{
	CamelStream *null;
	guint32 size;

	null = camel_stream_null_new ();
	camel_data_wrapper_write_to_stream_sync (
		CAMEL_DATA_WRAPPER (message), null, cancellable, NULL);
	size = CAMEL_STREAM_NULL (null)->written;
	g_object_unref (null);

	return size;
}
static gboolean
empe_mp_alternative_parse (EMailParserExtension *extension,
                           EMailParser *parser,
                           CamelMimePart *part,
                           GString *part_id,
                           GCancellable *cancellable,
                           GQueue *out_mail_parts)
{
	CamelMultipart *mp;
	gint i, nparts, bestid = 0;
	CamelMimePart *best = NULL;
	EMailExtensionRegistry *reg;

	reg = e_mail_parser_get_extension_registry (parser);

	mp = (CamelMultipart *) camel_medium_get_content ((CamelMedium *) part);

	if (!CAMEL_IS_MULTIPART (mp))
		return e_mail_parser_parse_part_as (
			parser, part, part_id,
			"application/vnd.evolution.source",
			cancellable, out_mail_parts);

	/* as per rfc, find the last part we know how to display */
	nparts = camel_multipart_get_number (mp);
	for (i = 0; i < nparts; i++) {
		CamelMimePart *mpart;
		CamelDataWrapper *data_wrapper;
		CamelContentType *type;
		CamelStream *null_stream;
		gchar *mime_type;
		gsize content_size;

		if (g_cancellable_is_cancelled (cancellable))
			return TRUE;

		/* is it correct to use the passed in *part here? */
		mpart = camel_multipart_get_part (mp, i);

		if (mpart == NULL)
			continue;

		/* This may block even though the stream does not.
		 * XXX Pretty inefficient way to test if the MIME part
		 *     is empty.  Surely there's a quicker way? */
		null_stream = camel_stream_null_new ();
		data_wrapper = camel_medium_get_content (CAMEL_MEDIUM (mpart));
		camel_data_wrapper_decode_to_stream_sync (
			data_wrapper, null_stream, cancellable, NULL);
		content_size = CAMEL_STREAM_NULL (null_stream)->written;
		g_object_unref (null_stream);

		if (content_size == 0)
			continue;

		type = camel_mime_part_get_content_type (mpart);
		mime_type = camel_content_type_simple (type);

		camel_strdown (mime_type);

		if (!e_mail_part_is_attachment (mpart) &&
			 ((camel_content_type_is (type, "multipart", "related") == 0) ||
			  !related_display_part_is_attachment (mpart)) &&
		    (e_mail_extension_registry_get_for_mime_type (reg, mime_type) ||
			((best == NULL) &&
			 (e_mail_extension_registry_get_fallback (reg, mime_type)))))
		{
			best = mpart;
			bestid = i;
		}

		g_free (mime_type);
	}

	if (best) {
		gint len = part_id->len;

		g_string_append_printf (part_id, ".alternative.%d", bestid);

		e_mail_parser_parse_part (
			parser, best, part_id,
			cancellable, out_mail_parts);

		g_string_truncate (part_id, len);
	} else {
		e_mail_parser_parse_part_as (
			parser, part, part_id, "multipart/mixed",
			cancellable, out_mail_parts);
	}

	return TRUE;
}