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 <wtf/Noncopyable.h>
30#include <wtf/NullPtr.h>
31
32namespace JSC {
33
34template<typename T> class PassWeak;
35class WeakImpl;
36class WeakHandleOwner;
37
38// This is a free function rather than a Weak<T> member function so we can put it in Weak.cpp.
39JS_EXPORT_PRIVATE void weakClearSlowCase(WeakImpl*&);
40
41template<typename T> class Weak {
42    WTF_MAKE_NONCOPYABLE(Weak);
43public:
44    Weak()
45        : m_impl(0)
46    {
47    }
48
49    explicit Weak(std::nullptr_t)
50        : m_impl(0)
51    {
52    }
53
54    explicit Weak(T*, WeakHandleOwner* = 0, void* context = 0);
55
56    enum HashTableDeletedValueTag { HashTableDeletedValue };
57    bool isHashTableDeletedValue() const;
58    Weak(HashTableDeletedValueTag);
59
60    template<typename U> Weak(const PassWeak<U>&);
61
62    ~Weak()
63    {
64        clear();
65    }
66
67    void swap(Weak&);
68    Weak& operator=(const PassWeak<T>&);
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    PassWeak<T> release();
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