1 /* 2 * Copyright (C) 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved. 3 * 4 * This library is free software; you can redistribute it and/or 5 * modify it under the terms of the GNU Library General Public 6 * License as published by the Free Software Foundation; either 7 * version 2 of the License, or (at your option) any later version. 8 * 9 * This library is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 12 * Library General Public License for more details. 13 * 14 * You should have received a copy of the GNU Library General Public License 15 * along with this library; see the file COPYING.LIB. If not, write to 16 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 17 * Boston, MA 02110-1301, USA. 18 * 19 */ 20 21 #ifndef RefCounted_h 22 #define RefCounted_h 23 24 #include "wtf/FastAllocBase.h" 25 #include "wtf/InstanceCounter.h" 26 #include "wtf/Noncopyable.h" 27 #include "wtf/WTFExport.h" 28 29 #ifdef NDEBUG 30 #define CHECK_REF_COUNTED_LIFECYCLE 0 31 #else 32 #define CHECK_REF_COUNTED_LIFECYCLE 1 33 #include "wtf/Assertions.h" 34 #include "wtf/ThreadRestrictionVerifier.h" 35 #endif 36 37 namespace WTF { 38 39 // This base class holds the non-template methods and attributes. 40 // The RefCounted class inherits from it reducing the template bloat 41 // generated by the compiler (technique called template hoisting). 42 class WTF_EXPORT RefCountedBase { 43 public: 44 void ref() 45 { 46 #if CHECK_REF_COUNTED_LIFECYCLE 47 // Start thread verification as soon as the ref count gets to 2. This 48 // heuristic reflects the fact that items are often created on one thread 49 // and then given to another thread to be used. 50 // FIXME: Make this restriction tigher. Especially as we move to more 51 // common methods for sharing items across threads like CrossThreadCopier.h 52 // We should be able to add a "detachFromThread" method to make this explicit. 53 if (m_refCount == 1) 54 m_verifier.setShared(true); 55 // If this assert fires, it either indicates a thread safety issue or 56 // that the verification needs to change. See ThreadRestrictionVerifier for 57 // the different modes. 58 ASSERT(m_verifier.isSafeToUse()); 59 ASSERT(!m_adoptionIsRequired); 60 #endif 61 ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun); 62 ++m_refCount; 63 } 64 65 bool hasOneRef() const 66 { 67 ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun); 68 #if CHECK_REF_COUNTED_LIFECYCLE 69 ASSERT(m_verifier.isSafeToUse()); 70 #endif 71 return m_refCount == 1; 72 } 73 74 int refCount() const 75 { 76 #if CHECK_REF_COUNTED_LIFECYCLE 77 ASSERT(m_verifier.isSafeToUse()); 78 #endif 79 return m_refCount; 80 } 81 82 void relaxAdoptionRequirement() 83 { 84 ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun); 85 #if CHECK_REF_COUNTED_LIFECYCLE 86 ASSERT(m_adoptionIsRequired); 87 m_adoptionIsRequired = false; 88 #endif 89 } 90 91 protected: 92 RefCountedBase() 93 : m_refCount(1) 94 #if SECURITY_ASSERT_ENABLED 95 , m_deletionHasBegun(false) 96 #endif 97 #if CHECK_REF_COUNTED_LIFECYCLE 98 , m_adoptionIsRequired(true) 99 #endif 100 { 101 } 102 103 ~RefCountedBase() 104 { 105 ASSERT_WITH_SECURITY_IMPLICATION(m_deletionHasBegun); 106 #if CHECK_REF_COUNTED_LIFECYCLE 107 ASSERT(!m_adoptionIsRequired); 108 #endif 109 } 110 111 // Returns whether the pointer should be freed or not. 112 bool derefBase() 113 { 114 ASSERT_WITH_SECURITY_IMPLICATION(!m_deletionHasBegun); 115 #if CHECK_REF_COUNTED_LIFECYCLE 116 ASSERT(m_verifier.isSafeToUse()); 117 ASSERT(!m_adoptionIsRequired); 118 #endif 119 120 ASSERT(m_refCount > 0); 121 if (m_refCount == 1) { 122 #if SECURITY_ASSERT_ENABLED 123 m_deletionHasBegun = true; 124 #endif 125 return true; 126 } 127 128 --m_refCount; 129 #if CHECK_REF_COUNTED_LIFECYCLE 130 // Stop thread verification when the ref goes to 1 because it 131 // is safe to be passed to another thread at this point. 132 if (m_refCount == 1) 133 m_verifier.setShared(false); 134 #endif 135 return false; 136 } 137 138 #if CHECK_REF_COUNTED_LIFECYCLE 139 bool deletionHasBegun() const 140 { 141 return m_deletionHasBegun; 142 } 143 #endif 144 145 private: 146 147 #if CHECK_REF_COUNTED_LIFECYCLE || SECURITY_ASSERT_ENABLED 148 friend void adopted(RefCountedBase*); 149 #endif 150 151 int m_refCount; 152 #if SECURITY_ASSERT_ENABLED 153 bool m_deletionHasBegun; 154 #endif 155 #if CHECK_REF_COUNTED_LIFECYCLE 156 bool m_adoptionIsRequired; 157 ThreadRestrictionVerifier m_verifier; 158 #endif 159 }; 160 161 #if CHECK_REF_COUNTED_LIFECYCLE || SECURITY_ASSERT_ENABLED 162 inline void adopted(RefCountedBase* object) 163 { 164 if (!object) 165 return; 166 ASSERT_WITH_SECURITY_IMPLICATION(!object->m_deletionHasBegun); 167 #if CHECK_REF_COUNTED_LIFECYCLE 168 object->m_adoptionIsRequired = false; 169 #endif 170 } 171 #endif 172 173 template<typename T> class RefCounted : public RefCountedBase { 174 WTF_MAKE_NONCOPYABLE(RefCounted); 175 WTF_MAKE_FAST_ALLOCATED; 176 177 public: 178 void deref() 179 { 180 if (derefBase()) 181 delete static_cast<T*>(this); 182 } 183 184 protected: 185 #ifdef ENABLE_INSTANCE_COUNTER 186 RefCounted() 187 { 188 incrementInstanceCount<T>(static_cast<T*>(this)); 189 } 190 191 ~RefCounted() 192 { 193 decrementInstanceCount<T>(static_cast<T*>(this)); 194 } 195 #else 196 RefCounted() 197 { 198 } 199 #endif 200 }; 201 202 } // namespace WTF 203 204 using WTF::RefCounted; 205 206 #endif // RefCounted_h 207
