1/*
2 * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
3 * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com)
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * 1.  Redistributions of source code must retain the above copyright
10 *     notice, this list of conditions and the following disclaimer.
11 * 2.  Redistributions in binary form must reproduce the above copyright
12 *     notice, this list of conditions and the following disclaimer in the
13 *     documentation and/or other materials provided with the distribution.
14 * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
15 *     its contributors may be used to endorse or promote products derived
16 *     from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 *
30 * Note: The implementations of InterlockedIncrement and InterlockedDecrement are based
31 * on atomic_increment and atomic_exchange_and_add from the Boost C++ Library. The license
32 * is virtually identical to the Apple license above but is included here for completeness.
33 *
34 * Boost Software License - Version 1.0 - August 17th, 2003
35 *
36 * Permission is hereby granted, free of charge, to any person or organization
37 * obtaining a copy of the software and accompanying documentation covered by
38 * this license (the "Software") to use, reproduce, display, distribute,
39 * execute, and transmit the Software, and to prepare derivative works of the
40 * Software, and to permit third-parties to whom the Software is furnished to
41 * do so, all subject to the following:
42 *
43 * The copyright notices in the Software and this entire statement, including
44 * the above license grant, this restriction and the following disclaimer,
45 * must be included in all copies of the Software, in whole or in part, and
46 * all derivative works of the Software, unless such copies or derivative
47 * works are solely in the form of machine-executable object code generated by
48 * a source language processor.
49 *
50 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
51 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
52 * FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
53 * SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
54 * FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
55 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
56 * DEALINGS IN THE SOFTWARE.
57 */
58
59#ifndef ThreadSafeRefCounted_h
60#define ThreadSafeRefCounted_h
61
62#include <atomic>
63#include <wtf/FastMalloc.h>
64#include <wtf/Noncopyable.h>
65
66namespace WTF {
67
68class ThreadSafeRefCountedBase {
69    WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
70    WTF_MAKE_FAST_ALLOCATED;
71public:
72    ThreadSafeRefCountedBase(int initialRefCount = 1)
73        : m_refCount(initialRefCount)
74    {
75    }
76
77    void ref()
78    {
79        ++m_refCount;
80    }
81
82    bool hasOneRef()
83    {
84        return refCount() == 1;
85    }
86
87    int refCount() const
88    {
89        return m_refCount;
90    }
91
92protected:
93    // Returns whether the pointer should be freed or not.
94    bool derefBase()
95    {
96        if (--m_refCount <= 0) {
97            return true;
98        }
99
100        return false;
101    }
102
103private:
104    std::atomic<int> m_refCount;
105};
106
107template<class T> class ThreadSafeRefCounted : public ThreadSafeRefCountedBase {
108public:
109    void deref()
110    {
111        if (derefBase())
112            delete static_cast<T*>(this);
113    }
114
115protected:
116    ThreadSafeRefCounted()
117    {
118    }
119};
120
121} // namespace WTF
122
123using WTF::ThreadSafeRefCounted;
124
125#endif // ThreadSafeRefCounted_h
126