1 /* 2 * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved. 3 * Copyright (C) 2007 Justin Haygood (jhaygood (at) 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/Platform.h" 38 #include "wtf/WTFExport.h" 39 40 namespace WTF { 41 42 class WTF_EXPORT ThreadSafeRefCountedBase { 43 WTF_MAKE_NONCOPYABLE(ThreadSafeRefCountedBase); 44 WTF_MAKE_FAST_ALLOCATED; 45 public: 46 ThreadSafeRefCountedBase(int initialRefCount = 1) 47 : m_refCount(initialRefCount) 48 { 49 } 50 51 void ref() 52 { 53 atomicIncrement(&m_refCount); 54 } 55 56 bool hasOneRef() 57 { 58 return refCount() == 1; 59 } 60 61 int refCount() const 62 { 63 return static_cast<int const volatile &>(m_refCount); 64 } 65 66 protected: 67 // Returns whether the pointer should be freed or not. 68 bool derefBase() 69 { 70 WTF_ANNOTATE_HAPPENS_BEFORE(&m_refCount); 71 if (atomicDecrement(&m_refCount) <= 0) { 72 WTF_ANNOTATE_HAPPENS_AFTER(&m_refCount); 73 return true; 74 } 75 return false; 76 } 77 78 private: 79 int m_refCount; 80 }; 81 82 template<class T> class ThreadSafeRefCounted : public ThreadSafeRefCountedBase { 83 public: 84 void deref() 85 { 86 if (derefBase()) 87 delete static_cast<T*>(this); 88 } 89 90 protected: 91 ThreadSafeRefCounted() 92 { 93 } 94 }; 95 96 } // namespace WTF 97 98 using WTF::ThreadSafeRefCounted; 99 100 #endif // ThreadSafeRefCounted_h 101