1/*
2 * Copyright (C) 2009, 2012, 2013 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#ifndef Weak_h
27#define Weak_h
28
29#include <cstddef>
30#include <wtf/Noncopyable.h>
31
32namespace JSC {
33
34class WeakImpl;
35class WeakHandleOwner;
36
37// This is a free function rather than a Weak<T> member function so we can put it in Weak.cpp.
38JS_EXPORT_PRIVATE void weakClearSlowCase(WeakImpl*&);
39
40template<typename T> class Weak {
41    WTF_MAKE_NONCOPYABLE(Weak);
42public:
43    Weak()
44        : m_impl(0)
45    {
46    }
47
48    Weak(std::nullptr_t)
49        : m_impl(0)
50    {
51    }
52
53    Weak(T*, WeakHandleOwner* = 0, void* context = 0);
54
55    enum HashTableDeletedValueTag { HashTableDeletedValue };
56    bool isHashTableDeletedValue() const;
57    Weak(HashTableDeletedValueTag);
58
59    Weak(Weak&&);
60
61    ~Weak()
62    {
63        clear();
64    }
65
66    void swap(Weak&);
67
68    Weak& operator=(Weak&&);
69
70    bool operator!() const;
71    T* operator->() const;
72    T& operator*() const;
73    T* get() const;
74
75    bool was(T*) const;
76
77    // This conversion operator allows implicit conversion to bool but not to other integer types.
78    typedef void* (Weak::*UnspecifiedBoolType);
79    operator UnspecifiedBoolType*() const;
80
81    WeakImpl* leakImpl() WARN_UNUSED_RETURN;
82    void clear()
83    {
84        if (!m_impl)
85            return;
86        weakClearSlowCase(m_impl);
87    }
88
89private:
90    static WeakImpl* hashTableDeletedValue();
91
92    WeakImpl* m_impl;
93};
94
95} // namespace JSC
96
97#endif // Weak_h
98