wtf/ThreadSafeRefCounted.h

   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
  68 namespace WTF {
  69
  70 class ThreadSafeRefCountedBase {
  71     WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase);
  72     WTF_MAKE_FAST_ALLOCATED;
  73 public:
  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
 102 protected:
 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
 125 private:
 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
 135 template<class T> class ThreadSafeRefCounted : public ThreadSafeRefCountedBase {
 136 public:
 137     void deref()
 138     {
 139         if (derefBase())
 140             delete static_cast<T*>(this);
 141     }
 142
 143 protected:
 144     ThreadSafeRefCounted()
 145     {
 146     }
 147 };
 148
 149 } // namespace WTF
 150
 151 using WTF::ThreadSafeRefCounted;
 152
 153 #endif // ThreadSafeRefCounted_h