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1 /* |
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2 * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved. |
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3 * Copyright (C) 2007 Justin Haygood (jhaygood@reaktix.com) |
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4 * |
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5 * Redistribution and use in source and binary forms, with or without |
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6 * modification, are permitted provided that the following conditions |
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7 * are met: |
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8 * |
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9 * 1. Redistributions of source code must retain the above copyright |
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10 * notice, this list of conditions and the following disclaimer. |
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11 * 2. Redistributions in binary form must reproduce the above copyright |
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12 * notice, this list of conditions and the following disclaimer in the |
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13 * documentation and/or other materials provided with the distribution. |
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14 * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of |
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15 * its contributors may be used to endorse or promote products derived |
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16 * from this software without specific prior written permission. |
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17 * |
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18 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY |
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19 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
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20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
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21 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY |
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22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
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23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
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24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
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25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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28 * |
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29 * |
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30 * Note: The implementations of InterlockedIncrement and InterlockedDecrement are based |
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31 * on atomic_increment and atomic_exchange_and_add from the Boost C++ Library. The license |
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32 * is virtually identical to the Apple license above but is included here for completeness. |
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33 * |
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34 * Boost Software License - Version 1.0 - August 17th, 2003 |
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35 * |
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36 * Permission is hereby granted, free of charge, to any person or organization |
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37 * obtaining a copy of the software and accompanying documentation covered by |
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38 * this license (the "Software") to use, reproduce, display, distribute, |
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39 * execute, and transmit the Software, and to prepare derivative works of the |
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40 * Software, and to permit third-parties to whom the Software is furnished to |
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41 * do so, all subject to the following: |
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42 * |
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43 * The copyright notices in the Software and this entire statement, including |
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44 * the above license grant, this restriction and the following disclaimer, |
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45 * must be included in all copies of the Software, in whole or in part, and |
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46 * all derivative works of the Software, unless such copies or derivative |
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47 * works are solely in the form of machine-executable object code generated by |
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48 * a source language processor. |
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49 * |
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50 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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51 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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52 * FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT |
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53 * SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE |
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54 * FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, |
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55 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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56 * DEALINGS IN THE SOFTWARE. |
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57 */ |
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58 |
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59 #ifndef ThreadSafeShared_h |
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60 #define ThreadSafeShared_h |
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61 |
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62 #include "Platform.h" |
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63 |
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64 #include <wtf/Atomics.h> |
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65 #include <wtf/Noncopyable.h> |
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66 #include <wtf/ThreadingPrimitives.h> |
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67 |
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68 namespace WTF { |
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69 |
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70 class ThreadSafeSharedBase : public Noncopyable { |
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71 public: |
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72 ThreadSafeSharedBase(int initialRefCount = 1) |
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73 : m_refCount(initialRefCount) |
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74 { |
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75 } |
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76 |
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77 void ref() |
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78 { |
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79 #if USE(LOCKFREE_THREADSAFESHARED) |
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80 atomicIncrement(&m_refCount); |
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81 #else |
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82 MutexLocker locker(m_mutex); |
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83 ++m_refCount; |
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84 #endif |
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85 } |
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86 |
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87 bool hasOneRef() |
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88 { |
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89 return refCount() == 1; |
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90 } |
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91 |
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92 int refCount() const |
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93 { |
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94 #if !USE(LOCKFREE_THREADSAFESHARED) |
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95 MutexLocker locker(m_mutex); |
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96 #endif |
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97 return static_cast<int const volatile &>(m_refCount); |
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98 } |
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99 |
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100 protected: |
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101 // Returns whether the pointer should be freed or not. |
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102 bool derefBase() |
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103 { |
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104 #if USE(LOCKFREE_THREADSAFESHARED) |
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105 if (atomicDecrement(&m_refCount) <= 0) |
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106 return true; |
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107 #else |
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108 int refCount; |
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109 { |
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110 MutexLocker locker(m_mutex); |
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111 --m_refCount; |
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112 refCount = m_refCount; |
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113 } |
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114 if (refCount <= 0) |
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115 return true; |
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116 #endif |
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117 return false; |
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118 } |
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119 |
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120 private: |
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121 template<class T> |
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122 friend class CrossThreadRefCounted; |
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123 |
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124 int m_refCount; |
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125 #if !USE(LOCKFREE_THREADSAFESHARED) |
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126 mutable Mutex m_mutex; |
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127 #endif |
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128 }; |
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129 |
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130 template<class T> class ThreadSafeShared : public ThreadSafeSharedBase { |
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131 public: |
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132 void deref() |
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133 { |
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134 if (derefBase()) |
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135 delete static_cast<T*>(this); |
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136 } |
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137 |
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138 protected: |
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139 ThreadSafeShared() |
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140 { |
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141 } |
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142 }; |
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143 |
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144 } // namespace WTF |
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145 |
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146 using WTF::ThreadSafeShared; |
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147 |
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148 #endif // ThreadSafeShared_h |