1/* 2 * Copyright (C) 2013 Google, Inc. All Rights Reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY 14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 16 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR 17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, 19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY 21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26#ifndef WTF_WeakPtr_h 27#define WTF_WeakPtr_h 28 29#include "wtf/Noncopyable.h" 30#include "wtf/PassRefPtr.h" 31#include "wtf/RefPtr.h" 32#include "wtf/ThreadSafeRefCounted.h" 33#include "wtf/Threading.h" 34 35namespace WTF { 36 37template<typename T> 38class WeakReference : public ThreadSafeRefCounted<WeakReference<T> > { 39 WTF_MAKE_NONCOPYABLE(WeakReference<T>); 40 WTF_MAKE_FAST_ALLOCATED; 41public: 42 static PassRefPtr<WeakReference<T> > create(T* ptr) { return adoptRef(new WeakReference(ptr)); } 43 static PassRefPtr<WeakReference<T> > createUnbound() { return adoptRef(new WeakReference()); } 44 45 T* get() const 46 { 47 ASSERT(m_boundThread == currentThread()); 48 return m_ptr; 49 } 50 51 void clear() 52 { 53 ASSERT(m_boundThread == currentThread()); 54 m_ptr = 0; 55 } 56 57 void bindTo(T* ptr) 58 { 59 ASSERT(!m_ptr); 60#ifndef NDEBUG 61 m_boundThread = currentThread(); 62#endif 63 m_ptr = ptr; 64 } 65 66private: 67 WeakReference() : m_ptr(0) { } 68 69 explicit WeakReference(T* ptr) 70 : m_ptr(ptr) 71#ifndef NDEBUG 72 , m_boundThread(currentThread()) 73#endif 74 { 75 } 76 77 T* m_ptr; 78#ifndef NDEBUG 79 ThreadIdentifier m_boundThread; 80#endif 81}; 82 83template<typename T> 84class WeakPtr { 85 WTF_MAKE_FAST_ALLOCATED; 86public: 87 WeakPtr() { } 88 WeakPtr(std::nullptr_t) { } 89 WeakPtr(PassRefPtr<WeakReference<T> > ref) : m_ref(ref) { } 90 91 T* get() const { return m_ref ? m_ref->get() : 0; } 92 void clear() { m_ref.clear(); } 93 94 T* operator->() const 95 { 96 ASSERT(get()); 97 return get(); 98 } 99 100 typedef RefPtr<WeakReference<T> > (WeakPtr::*UnspecifiedBoolType); 101 operator UnspecifiedBoolType() const { return get() ? &WeakPtr::m_ref : 0; } 102 103private: 104 RefPtr<WeakReference<T> > m_ref; 105}; 106 107template<typename T, typename U> inline bool operator==(const WeakPtr<T>& a, const WeakPtr<U>& b) 108{ 109 return a.get() == b.get(); 110} 111 112template<typename T, typename U> inline bool operator!=(const WeakPtr<T>& a, const WeakPtr<U>& b) 113{ 114 return a.get() != b.get(); 115} 116 117template<typename T> 118class WeakPtrFactory { 119 WTF_MAKE_NONCOPYABLE(WeakPtrFactory<T>); 120 WTF_MAKE_FAST_ALLOCATED; 121public: 122 explicit WeakPtrFactory(T* ptr) : m_ref(WeakReference<T>::create(ptr)) { } 123 124 WeakPtrFactory(PassRefPtr<WeakReference<T> > ref, T* ptr) 125 : m_ref(ref) 126 { 127 m_ref->bindTo(ptr); 128 } 129 130 ~WeakPtrFactory() { m_ref->clear(); } 131 132 // We should consider having createWeakPtr populate m_ref the first time createWeakPtr is called. 133 WeakPtr<T> createWeakPtr() { return WeakPtr<T>(m_ref); } 134 135 void revokeAll() 136 { 137 T* ptr = m_ref->get(); 138 m_ref->clear(); 139 // We create a new WeakReference so that future calls to createWeakPtr() create nonzero WeakPtrs. 140 m_ref = WeakReference<T>::create(ptr); 141 } 142 143private: 144 RefPtr<WeakReference<T> > m_ref; 145}; 146 147} // namespace WTF 148 149using WTF::WeakPtr; 150using WTF::WeakPtrFactory; 151using WTF::WeakReference; 152 153#endif 154