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#ifndef ThreadSafeRefCounted_h
31#define ThreadSafeRefCounted_h
32
33#include "wtf/Atomics.h"
34#include "wtf/DynamicAnnotations.h"
35#include "wtf/FastAllocBase.h"
36#include "wtf/Noncopyable.h"
37#include "wtf/WTFExport.h"
38
39namespace WTF {
40
41class WTF_EXPORT ThreadSafeRefCountedBase {
42    WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
43    WTF_MAKE_FAST_ALLOCATED;
44public:
45    ThreadSafeRefCountedBase(int initialRefCount = 1)
46        : m_refCount(initialRefCount)
47    {
48    }
49
50    void ref()
51    {
52        atomicIncrement(&m_refCount);
53    }
54
55    bool hasOneRef()
56    {
57        return refCount() == 1;
58    }
59
60    int refCount() const
61    {
62        return static_cast<int const volatile &>(m_refCount);
63    }
64
65protected:
66    // Returns whether the pointer should be freed or not.
67    bool derefBase()
68    {
69        WTF_ANNOTATE_HAPPENS_BEFORE(&m_refCount);
70        if (atomicDecrement(&m_refCount) <= 0) {
71            WTF_ANNOTATE_HAPPENS_AFTER(&m_refCount);
72            return true;
73        }
74        return false;
75    }
76
77private:
78    int m_refCount;
79};
80
81template<class T> class ThreadSafeRefCounted : public ThreadSafeRefCountedBase {
82public:
83    void deref()
84    {
85        if (derefBase())
86            delete static_cast<T*>(this);
87    }
88
89protected:
90    ThreadSafeRefCounted()
91    {
92    }
93};
94
95} // namespace WTF
96
97using WTF::ThreadSafeRefCounted;
98
99#endif // ThreadSafeRefCounted_h
100