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) m_refCount(initialRefCount)75 : m_refCount(initialRefCount) 76 { 77 } 78 ref()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 hasOneRef()89 bool hasOneRef() 90 { 91 return refCount() == 1; 92 } 93 refCount()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. derefBase()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: deref()137 void deref() 138 { 139 if (derefBase()) 140 delete static_cast<T*>(this); 141 } 142 143 protected: ThreadSafeRefCounted()144 ThreadSafeRefCounted() 145 { 146 } 147 }; 148 149 } // namespace WTF 150 151 using WTF::ThreadSafeRefCounted; 152 153 #endif // ThreadSafeRefCounted_h 154