+Unit* unit_ref_set(UnitRef *ref, Unit *u) {
+ assert(ref);
+ assert(u);
+
+ if (ref->unit)
+ unit_ref_unset(ref);
+
+ ref->unit = u;
+ LIST_PREPEND(UnitRef, refs, u->meta.refs, ref);
+ return u;
+}
+
+void unit_ref_unset(UnitRef *ref) {
+ assert(ref);
+
+ if (!ref->unit)
+ return;
+
+ LIST_REMOVE(UnitRef, refs, ref->unit->meta.refs, ref);
+ ref->unit = NULL;
+}
+