+static void
+g_io_extension_point_free (GIOExtensionPoint *ep)
+{
+ g_free (ep->name);
+ g_free (ep);
+}
+
+/**
+ * g_io_extension_point_register:
+ * @name: The name of the extension point
+ *
+ * Registers an extension point.
+ *
+ * Returns: (transfer none): the new #GIOExtensionPoint. This object is
+ * owned by GIO and should not be freed.
+ */
+GIOExtensionPoint *
+g_io_extension_point_register (const char *name)
+{
+ GIOExtensionPoint *ep;
+
+ G_LOCK (extension_points);
+ if (extension_points == NULL)
+ extension_points = g_hash_table_new_full (g_str_hash,
+ g_str_equal,
+ NULL,
+ (GDestroyNotify)g_io_extension_point_free);
+
+ ep = g_hash_table_lookup (extension_points, name);
+ if (ep != NULL)
+ {
+ G_UNLOCK (extension_points);
+ return ep;
+ }
+
+ ep = g_new0 (GIOExtensionPoint, 1);
+ ep->name = g_strdup (name);
+
+ g_hash_table_insert (extension_points, ep->name, ep);
+
+ G_UNLOCK (extension_points);
+
+ return ep;
+}
+
+/**
+ * g_io_extension_point_lookup:
+ * @name: the name of the extension point
+ *
+ * Looks up an existing extension point.
+ *
+ * Returns: (transfer none): the #GIOExtensionPoint, or %NULL if there
+ * is no registered extension point with the given name.
+ */
+GIOExtensionPoint *
+g_io_extension_point_lookup (const char *name)
+{
+ GIOExtensionPoint *ep;
+
+ G_LOCK (extension_points);
+ ep = NULL;
+ if (extension_points != NULL)
+ ep = g_hash_table_lookup (extension_points, name);
+
+ G_UNLOCK (extension_points);
+
+ return ep;
+
+}
+
+/**
+ * g_io_extension_point_set_required_type:
+ * @extension_point: a #GIOExtensionPoint
+ * @type: the #GType to require
+ *
+ * Sets the required type for @extension_point to @type.
+ * All implementations must henceforth have this type.
+ */
+void
+g_io_extension_point_set_required_type (GIOExtensionPoint *extension_point,
+ GType type)
+{
+ extension_point->required_type = type;
+}
+
+/**
+ * g_io_extension_point_get_required_type:
+ * @extension_point: a #GIOExtensionPoint
+ *
+ * Gets the required type for @extension_point.
+ *
+ * Returns: the #GType that all implementations must have,
+ * or #G_TYPE_INVALID if the extension point has no required type
+ */
+GType
+g_io_extension_point_get_required_type (GIOExtensionPoint *extension_point)
+{
+ return extension_point->required_type;
+}
+
+static void
+lazy_load_modules (GIOExtensionPoint *extension_point)
+{
+ GIOModule *module;
+ GList *l;
+
+ for (l = extension_point->lazy_load_modules; l != NULL; l = l->next)
+ {
+ module = l->data;
+
+ if (!module->initialized)
+ {
+ if (g_type_module_use (G_TYPE_MODULE (module)))
+ g_type_module_unuse (G_TYPE_MODULE (module)); /* Unload */
+ else
+ g_printerr ("Failed to load module: %s\n",
+ module->filename);
+ }
+ }
+}
+
+/**
+ * g_io_extension_point_get_extensions:
+ * @extension_point: a #GIOExtensionPoint
+ *
+ * Gets a list of all extensions that implement this extension point.
+ * The list is sorted by priority, beginning with the highest priority.
+ *
+ * Returns: (element-type GIOExtension) (transfer none): a #GList of
+ * #GIOExtensions. The list is owned by GIO and should not be
+ * modified.
+ */
+GList *
+g_io_extension_point_get_extensions (GIOExtensionPoint *extension_point)
+{
+ lazy_load_modules (extension_point);
+ return extension_point->extensions;
+}
+
+/**
+ * g_io_extension_point_get_extension_by_name:
+ * @extension_point: a #GIOExtensionPoint
+ * @name: the name of the extension to get
+ *
+ * Finds a #GIOExtension for an extension point by name.
+ *
+ * Returns: (transfer none): the #GIOExtension for @extension_point that has the
+ * given name, or %NULL if there is no extension with that name
+ */
+GIOExtension *
+g_io_extension_point_get_extension_by_name (GIOExtensionPoint *extension_point,
+ const char *name)
+{
+ GList *l;
+
+ g_return_val_if_fail (name != NULL, NULL);
+
+ lazy_load_modules (extension_point);
+ for (l = extension_point->extensions; l != NULL; l = l->next)
+ {
+ GIOExtension *e = l->data;
+
+ if (e->name != NULL &&
+ strcmp (e->name, name) == 0)
+ return e;
+ }
+
+ return NULL;
+}
+
+static gint
+extension_prio_compare (gconstpointer a,
+ gconstpointer b)
+{
+ const GIOExtension *extension_a = a, *extension_b = b;
+
+ if (extension_a->priority > extension_b->priority)
+ return -1;
+
+ if (extension_b->priority > extension_a->priority)
+ return 1;
+
+ return 0;
+}
+
+/**
+ * g_io_extension_point_implement:
+ * @extension_point_name: the name of the extension point
+ * @type: the #GType to register as extension
+ * @extension_name: the name for the extension
+ * @priority: the priority for the extension
+ *
+ * Registers @type as extension for the extension point with name
+ * @extension_point_name.
+ *
+ * If @type has already been registered as an extension for this
+ * extension point, the existing #GIOExtension object is returned.
+ *
+ * Returns: (transfer none): a #GIOExtension object for #GType
+ */
+GIOExtension *
+g_io_extension_point_implement (const char *extension_point_name,
+ GType type,
+ const char *extension_name,
+ gint priority)
+{
+ GIOExtensionPoint *extension_point;
+ GIOExtension *extension;
+ GList *l;
+
+ g_return_val_if_fail (extension_point_name != NULL, NULL);
+
+ extension_point = g_io_extension_point_lookup (extension_point_name);
+ if (extension_point == NULL)
+ {
+ g_warning ("Tried to implement non-registered extension point %s", extension_point_name);
+ return NULL;
+ }
+
+ if (extension_point->required_type != 0 &&
+ !g_type_is_a (type, extension_point->required_type))
+ {
+ g_warning ("Tried to register an extension of the type %s to extension point %s. "
+ "Expected type is %s.",
+ g_type_name (type),
+ extension_point_name,
+ g_type_name (extension_point->required_type));
+ return NULL;
+ }
+
+ /* It's safe to register the same type multiple times */
+ for (l = extension_point->extensions; l != NULL; l = l->next)
+ {
+ extension = l->data;
+ if (extension->type == type)
+ return extension;
+ }
+
+ extension = g_slice_new0 (GIOExtension);
+ extension->type = type;
+ extension->name = g_strdup (extension_name);
+ extension->priority = priority;
+
+ extension_point->extensions = g_list_insert_sorted (extension_point->extensions,
+ extension, extension_prio_compare);
+
+ return extension;
+}
+
+/**
+ * g_io_extension_ref_class:
+ * @extension: a #GIOExtension
+ *
+ * Gets a reference to the class for the type that is
+ * associated with @extension.
+ *
+ * Returns: (transfer full): the #GTypeClass for the type of @extension
+ */
+GTypeClass *
+g_io_extension_ref_class (GIOExtension *extension)
+{
+ return g_type_class_ref (extension->type);
+}
+
+/**
+ * g_io_extension_get_type:
+ * @extension: a #GIOExtension
+ *
+ * Gets the type associated with @extension.
+ *
+ * Returns: the type of @extension
+ */
+GType
+g_io_extension_get_type (GIOExtension *extension)
+{
+ return extension->type;
+}
+
+/**
+ * g_io_extension_get_name:
+ * @extension: a #GIOExtension
+ *
+ * Gets the name under which @extension was registered.
+ *
+ * Note that the same type may be registered as extension
+ * for multiple extension points, under different names.
+ *
+ * Returns: the name of @extension.
+ */
+const char *
+g_io_extension_get_name (GIOExtension *extension)
+{
+ return extension->name;
+}
+
+/**
+ * g_io_extension_get_priority:
+ * @extension: a #GIOExtension
+ *
+ * Gets the priority with which @extension was registered.
+ *
+ * Returns: the priority of @extension
+ */
+gint
+g_io_extension_get_priority (GIOExtension *extension)
+{
+ return extension->priority;
+}