dbus: New helper function: pa_dbus_get_error_message().

src/pulsecore/dbus-util.c

@@ -452,6 +452,20 @@ void pa_dbus_free_pending_list(pa_dbus_pending **p) {
     }
 }
 
+const char *pa_dbus_get_error_message(DBusMessage *m) {
+    const char *message;
+
+    pa_assert(m);
+    pa_assert(dbus_message_get_type(m) == DBUS_MESSAGE_TYPE_ERROR);
+
+    if (dbus_message_get_signature(m)[0] != 's')
+        return "<no explanation>";
+
+    pa_assert_se(dbus_message_get_args(m, NULL, DBUS_TYPE_STRING, &message, DBUS_TYPE_INVALID));
+
+    return message;
+}
+
 void pa_dbus_send_error(DBusConnection *c, DBusMessage *in_reply_to, const char *name, const char *format, ...) {
     va_list ap;
     char *message;

src/pulsecore/dbus-util.h

@@ -67,6 +67,14 @@ void pa_dbus_sync_pending_list(pa_dbus_pending **p);
 /* Free up a list of pa_dbus_pending_call objects */
 void pa_dbus_free_pending_list(pa_dbus_pending **p);
 
+/* When receiving a DBusMessage with type DBUS_MESSAGE_TYPE_ERROR, the
+ * DBusMessage may or may not contain an error message (a human-readable
+ * explanation of what went wrong). Extracting the error message from the
+ * DBusMessage object is a bit tedious, so here's a helper function that does
+ * that. If the DBusMessage doesn't contain any error message,
+ * "<no explanation>" is returned. */
+const char *pa_dbus_get_error_message(DBusMessage *m);
+
 /* Sends an error message as the reply to the given message. */
 void pa_dbus_send_error(
         DBusConnection *c,