+
+const char* bus_message_get_arg(sd_bus_message *m, unsigned i);
+
+int bus_message_append_ap(sd_bus_message *m, const char *types, va_list ap);
+
+int bus_message_parse_fields(sd_bus_message *m);
+
+int bus_header_size(struct bus_header *h, size_t *sum);