Collect useless graph's connections

[babeltrace.git] / include / babeltrace / object-internal.h

diff --git a/include/babeltrace/object-internal.h b/include/babeltrace/object-internal.h
index e130a81e883d620cba525cffc28a4ffba2f90fcd..545a20aadd21a7f9f9bd3b78971f9e64b0c5182b 100644 (file)
--- a/include/babeltrace/object-internal.h
+++ b/include/babeltrace/object-internal.h
@@ -38,8 +38,10 @@
  */
 struct bt_object {
        struct bt_ref ref_count;
-       /* Class-specific release function. */
+       /* Class-specific, optional release function. */
        bt_object_release_func release;
+       /* Class-specific, optional "parent is owner" notification listener. */
+       bt_object_release_func parent_is_owner_listener;
        /* @see doc/ref-counting.md */
        struct bt_object *parent;
 };
@@ -66,8 +68,20 @@ static inline
 void generic_release(struct bt_object *obj)
 {
        if (obj->parent) {
+               void *parent = obj->parent;
+
+               if (obj->parent_is_owner_listener) {
+                       /*
+                        * Object has a chance to destroy itself here
+                        * under certain conditions and notify its
+                        * parent. At this point the parent is
+                        * guaranteed to exist because it's not put yet.
+                        */
+                       obj->parent_is_owner_listener(obj);
+               }
+
                /* The release function will be invoked by the parent. */
-               bt_put(obj->parent);
+               bt_put(parent);
        } else {
                bt_object_release(obj);
        }
@@ -116,4 +130,12 @@ void bt_object_init(void *ptr, bt_object_release_func release)
        bt_ref_init(&obj->ref_count, generic_release);
 }
 
+static inline
+void bt_object_set_parent_is_owner_listener(void *obj,
+               bt_object_release_func cb)
+{
+       assert(obj);
+       ((struct bt_object *) obj)->parent_is_owner_listener = cb;
+}
+
 #endif /* BABELTRACE_OBJECT_INTERNAL_H */