1/*
2 * Copyright (C) 2009-2019 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. AND ITS CONTRIBUTORS ``AS IS''
14 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
15 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
17 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
18 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
19 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
20 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
21 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
22 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
23 * THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#pragma once
27
28#include "JSExportMacros.h"
29#include <cstddef>
30#include <wtf/HashTraits.h>
31#include <wtf/Noncopyable.h>
32#include <wtf/VectorTraits.h>
33
34namespace JSC {
35
36class WeakImpl;
37class WeakHandleOwner;
38
39// This is a free function rather than a Weak<T> member function so we can put it in Weak.cpp.
40JS_EXPORT_PRIVATE void weakClearSlowCase(WeakImpl*&);
41
42template<typename T> class Weak {
43 WTF_MAKE_NONCOPYABLE(Weak);
44public:
45 Weak()
46 : m_impl(0)
47 {
48 }
49
50 Weak(std::nullptr_t)
51 : m_impl(0)
52 {
53 }
54
55 inline Weak(T*, WeakHandleOwner* = 0, void* context = 0);
56
57 enum HashTableDeletedValueTag { HashTableDeletedValue };
58 inline bool isHashTableDeletedValue() const;
59 inline Weak(HashTableDeletedValueTag);
60
61 inline Weak(Weak&&);
62
63 ~Weak()
64 {
65 clear();
66 }
67
68 inline void swap(Weak&);
69
70 inline Weak& operator=(Weak&&);
71
72 inline bool operator!() const;
73 inline T* operator->() const;
74 inline T& operator*() const;
75 inline T* get() const;
76
77 inline bool was(T*) const;
78
79 inline explicit operator bool() const;
80
81 inline WeakImpl* leakImpl() WARN_UNUSED_RETURN;
82 void clear()
83 {
84 if (!m_impl)
85 return;
86 weakClearSlowCase(m_impl);
87 }
88
89private:
90 static inline WeakImpl* hashTableDeletedValue();
91
92 WeakImpl* m_impl;
93};
94
95} // namespace JSC
96
97namespace WTF {
98
99template<typename T> struct VectorTraits<JSC::Weak<T>> : SimpleClassVectorTraits {
100 static constexpr bool canCompareWithMemcmp = false;
101};
102
103template<typename T> struct HashTraits<JSC::Weak<T>> : SimpleClassHashTraits<JSC::Weak<T>> {
104 typedef JSC::Weak<T> StorageType;
105
106 typedef std::nullptr_t EmptyValueType;
107 static EmptyValueType emptyValue() { return nullptr; }
108
109 typedef T* PeekType;
110 static PeekType peek(const StorageType& value) { return value.get(); }
111 static PeekType peek(EmptyValueType) { return PeekType(); }
112};
113
114} // namespace WTF
115