+struct _GIOExtension {
+ char *name;
+ GType type;
+ gint priority;
+};
+
+struct _GIOExtensionPoint {
+ GType required_type;
+ char *name;
+ GList *extensions;
+};
+
+static GHashTable *extension_points = NULL;
+G_LOCK_DEFINE_STATIC(extension_points);
+
+
+static void
+g_io_extension_point_free (GIOExtensionPoint *ep)
+{
+ g_free (ep->name);
+ g_free (ep);
+}
+
+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);
+
+ if (g_hash_table_lookup (extension_points, name) != NULL)
+ {
+ g_warning ("Extension point %s registered multiple times", name);
+ G_UNLOCK (extension_points);
+ return NULL;
+ }
+
+ 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;
+}
+
+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;
+
+}
+
+void
+g_io_extension_point_set_required_type (GIOExtensionPoint *extension_point,
+ GType type)
+{
+ extension_point->required_type = type;
+}
+
+GType
+g_io_extension_point_get_required_type (GIOExtensionPoint *extension_point)
+{
+ return extension_point->required_type;
+}
+
+GList *
+g_io_extension_point_get_extensions (GIOExtensionPoint *extension_point)
+{
+ return extension_point->extensions;
+}
+
+GIOExtension *
+g_io_extension_point_get_extension_by_name (GIOExtensionPoint *extension_point,
+ const char *name)
+{
+ GList *l;
+
+ 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;
+
+ return extension_b->priority - extension_a->priority;
+}
+
+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;
+ }
+
+ /* Its 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;
+}
+
+GTypeClass *
+g_io_extension_ref_class (GIOExtension *extension)
+{
+ return g_type_class_ref (extension->type);
+}
+
+
+GType
+g_io_extension_get_type (GIOExtension *extension)
+{
+ return extension->type;
+}
+
+const char *
+g_io_extension_get_name (GIOExtension *extension)
+{
+ return extension->name;
+}
+
+gint
+g_io_extension_get_priority (GIOExtension *extension)
+{
+ return extension->priority;
+}
+