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 Computer, 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 "Platform.h"
63
64#include <wtf/Atomics.h>
65#include <wtf/DynamicAnnotations.h>
66#include <wtf/ThreadingPrimitives.h>
67
68namespace WTF {
69
70class ThreadSafeRefCountedBase {
71    WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
72    WTF_MAKE_FAST_ALLOCATED;
73public:
74    ThreadSafeRefCountedBase(int initialRefCount = 1)
75        : m_refCount(initialRefCount)
76    {
77    }
78
79    void ref()
80    {
81#if USE(LOCKFREE_THREADSAFEREFCOUNTED)
82        atomicIncrement(&m_refCount);
83#else
84        MutexLocker locker(m_mutex);
85        ++m_refCount;
86#endif
87    }
88
89    bool hasOneRef()
90    {
91        return refCount() == 1;
92    }
93
94    int refCount() const
95    {
96#if !USE(LOCKFREE_THREADSAFEREFCOUNTED)
97        MutexLocker locker(m_mutex);
98#endif
99        return static_cast<int const volatile &>(m_refCount);
100    }
101
102protected:
103    // Returns whether the pointer should be freed or not.
104    bool derefBase()
105    {
106#if USE(LOCKFREE_THREADSAFEREFCOUNTED)
107        WTF_ANNOTATE_HAPPENS_BEFORE(&m_refCount);
108        if (atomicDecrement(&m_refCount) <= 0) {
109            WTF_ANNOTATE_HAPPENS_AFTER(&m_refCount);
110            return true;
111        }
112#else
113        int refCount;
114        {
115            MutexLocker locker(m_mutex);
116            --m_refCount;
117            refCount = m_refCount;
118        }
119        if (refCount <= 0)
120            return true;
121#endif
122        return false;
123    }
124
125private:
126    template<class T>
127    friend class CrossThreadRefCounted;
128
129    int m_refCount;
130#if !USE(LOCKFREE_THREADSAFEREFCOUNTED)
131    mutable Mutex m_mutex;
132#endif
133};
134
135template<class T> class ThreadSafeRefCounted : public ThreadSafeRefCountedBase {
136public:
137    void deref()
138    {
139        if (derefBase())
140            delete static_cast<T*>(this);
141    }
142
143protected:
144    ThreadSafeRefCounted()
145    {
146    }
147};
148
149} // namespace WTF
150
151using WTF::ThreadSafeRefCounted;
152
153#endif // ThreadSafeRefCounted_h
154