Everywhere: Hoist the Libraries folder to the top-level

Libraries/LibJS/Runtime/WeakRef.cpp

@@ -0,0 +1,60 @@
+/*
+ * Copyright (c) 2021-2022, Idan Horowitz <idan.horowitz@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibJS/Runtime/WeakRef.h>
+
+namespace JS {
+
+JS_DEFINE_ALLOCATOR(WeakRef);
+
+NonnullGCPtr<WeakRef> WeakRef::create(Realm& realm, Object& value)
+{
+    return realm.heap().allocate<WeakRef>(realm, value, realm.intrinsics().weak_ref_prototype());
+}
+
+NonnullGCPtr<WeakRef> WeakRef::create(Realm& realm, Symbol& value)
+{
+    return realm.heap().allocate<WeakRef>(realm, value, realm.intrinsics().weak_ref_prototype());
+}
+
+WeakRef::WeakRef(Object& value, Object& prototype)
+    : Object(ConstructWithPrototypeTag::Tag, prototype)
+    , WeakContainer(heap())
+    , m_value(&value)
+    , m_last_execution_generation(vm().execution_generation())
+{
+}
+
+WeakRef::WeakRef(Symbol& value, Object& prototype)
+    : Object(ConstructWithPrototypeTag::Tag, prototype)
+    , WeakContainer(heap())
+    , m_value(&value)
+    , m_last_execution_generation(vm().execution_generation())
+{
+}
+
+void WeakRef::remove_dead_cells(Badge<Heap>)
+{
+    if (m_value.visit([](Cell* cell) -> bool { return cell->state() == Cell::State::Live; }, [](Empty) -> bool { VERIFY_NOT_REACHED(); }))
+        return;
+
+    m_value = Empty {};
+    // This is an optimization, we deregister from the garbage collector early (even if we were not garbage collected ourself yet)
+    // to reduce the garbage collection overhead, which we can do because a cleared weak ref cannot be reused.
+    WeakContainer::deregister();
+}
+
+void WeakRef::visit_edges(Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+
+    if (vm().execution_generation() == m_last_execution_generation) {
+        auto* cell = m_value.visit([](Cell* cell) -> Cell* { return cell; }, [](Empty) -> Cell* { return nullptr; });
+        visitor.visit(cell);
+    }
+}
+
+}