registry: API: Add gst_{default,}_registry_get_feature_list_cookie()

This returns the internal feature list cookie, which changes every
time a feature is added or removed. This can be used by elements
to check if they should update their cached feature lists.

docs/gst/gstreamer-sections.txt

@@ -1945,6 +1945,7 @@ gst_buffering_mode_get_type
 GstRegistry
 gst_registry_get_default
 gst_registry_get_feature_list
+gst_registry_get_feature_list_cookie
 gst_registry_get_feature_list_by_plugin
 gst_registry_get_path_list
 gst_registry_get_plugin_list
@@ -1972,6 +1973,7 @@ gst_default_registry_add_path
 gst_default_registry_find_plugin
 gst_default_registry_find_feature
 gst_default_registry_get_plugin_list
+gst_default_registry_get_feature_list_cookie
 gst_default_registry_feature_filter
 <SUBSECTION Standard>
 GstRegistryClass

gst/gstregistry.c

@@ -1653,3 +1653,21 @@ gst_update_registry (void)
 
   return res;
 }
+
+/**
+ * gst_registry_get_feature_list_cookie:
+ *
+ * Returns the registrys feature list cookie. This changes
+ * every time a feature is added or removed from the registry.
+ *
+ * Returns: the feature list cookie.
+ *
+ * Since: 0.10.26
+ */
+guint32
+gst_registry_get_feature_list_cookie (GstRegistry * registry)
+{
+  g_return_val_if_fail (GST_IS_REGISTRY (registry), 0);
+
+  return registry->priv->cookie;
+}

gst/gstregistry.h

@@ -107,6 +107,7 @@ GList*			gst_registry_feature_filter	(GstRegistry *registry,
 GList *                 gst_registry_get_feature_list   (GstRegistry *registry,
                                                          GType type);
 GList *                 gst_registry_get_feature_list_by_plugin (GstRegistry *registry, const gchar *name);
+guint32                 gst_registry_get_feature_list_cookie (GstRegistry *registry);
 
 GstPlugin*		gst_registry_find_plugin	(GstRegistry *registry, const gchar *name);
 GstPluginFeature*	gst_registry_find_feature	(GstRegistry *registry, const gchar *name, GType type);
@@ -204,6 +205,19 @@ gboolean 		gst_registry_xml_write_cache 	(GstRegistry * registry, const char *lo
 #define gst_default_registry_feature_filter(filter,first,user_data) \
   gst_registry_feature_filter (gst_registry_get_default(),filter,first,user_data)
 
+/**
+ * gst_default_registry_get_feature_list_cookie:
+ *
+ * Returns the default registrys feature list cookie. This changes
+ * every time a feature is added or removed from the registry.
+ *
+ * Returns: the feature list cookie.
+ *
+ * Since: 0.10.26
+ */
+#define gst_default_registry_get_feature_list_cookie() \
+  gst_registry_get_feature_list_cookie (gst_registry_get_default())
+
 gboolean                gst_default_registry_check_feature_version (const gchar *feature_name,
                                                                     guint        min_major,
                                                                     guint        min_minor,

win32/common/libgstreamer.def

@@ -827,6 +827,7 @@ EXPORTS
 	gst_registry_get_default
 	gst_registry_get_feature_list
 	gst_registry_get_feature_list_by_plugin
+	gst_registry_get_feature_list_cookie
 	gst_registry_get_path_list
 	gst_registry_get_plugin_list
 	gst_registry_get_type