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