1/*
2 * Copyright (C) 2019 Apple, Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#include "JSObject.h"
29
30namespace JSC {
31
32class JSWeakObjectRef final : public JSNonFinalObject {
33public:
34 using Base = JSNonFinalObject;
35
36 DECLARE_EXPORT_INFO;
37
38 static Structure* createStructure(VM& vm, JSGlobalObject* globalObject, JSValue prototype)
39 {
40 return Structure::create(vm, globalObject, prototype, TypeInfo(ObjectType, StructureFlags), info());
41 }
42
43 static JSWeakObjectRef* create(VM& vm, Structure* structure, JSObject* target)
44 {
45 JSWeakObjectRef* instance = new (NotNull, allocateCell<JSWeakObjectRef>(vm.heap)) JSWeakObjectRef(vm, structure);
46 instance->finishCreation(vm, target);
47 return instance;
48 }
49
50 JSObject* deref(VM& vm)
51 {
52 if (m_value && vm.currentWeakRefVersion() != m_lastAccessVersion) {
53 m_lastAccessVersion = vm.currentWeakRefVersion();
54 // Perform a GC barrier here so we rescan this object and keep the object alive if we wouldn't otherwise.
55 vm.heap.writeBarrier(this);
56 }
57
58 return m_value.get();
59 }
60
61 template<typename CellType, SubspaceAccess mode>
62 static IsoSubspace* subspaceFor(VM& vm)
63 {
64 return vm.weakObjectRefSpace<mode>();
65 }
66
67 void finalizeUnconditionally(VM&);
68 static void visitChildren(JSCell*, SlotVisitor&);
69
70private:
71 JSWeakObjectRef(VM& vm, Structure* structure)
72 : Base(vm, structure)
73 {
74 }
75
76 JS_EXPORT_PRIVATE void finishCreation(VM&, JSObject* value);
77
78 static String toStringName(const JSObject*, JSGlobalObject*);
79
80 uintptr_t m_lastAccessVersion;
81 WriteBarrier<JSObject> m_value;
82};
83
84} // namespace JSC
85
86