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5564 | serge | 1 | // Copyright 2003 Google Inc. |
2 | // All rights reserved. |
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3 | // |
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4 | // Redistribution and use in source and binary forms, with or without |
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5 | // modification, are permitted provided that the following conditions are |
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6 | // met: |
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7 | // |
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8 | // * Redistributions of source code must retain the above copyright |
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9 | // notice, this list of conditions and the following disclaimer. |
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10 | // * Redistributions in binary form must reproduce the above |
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11 | // copyright notice, this list of conditions and the following disclaimer |
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12 | // in the documentation and/or other materials provided with the |
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13 | // distribution. |
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14 | // * Neither the name of Google Inc. nor the names of its |
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15 | // contributors may be used to endorse or promote products derived from |
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16 | // this software without specific prior written permission. |
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17 | // |
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18 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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19 | // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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20 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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21 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
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22 | // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
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23 | // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
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24 | // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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25 | // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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26 | // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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27 | // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
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28 | // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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29 | // |
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30 | // Authors: Dan Egnor (egnor@google.com) |
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31 | // |
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32 | // A "smart" pointer type with reference tracking. Every pointer to a |
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33 | // particular object is kept on a circular linked list. When the last pointer |
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34 | // to an object is destroyed or reassigned, the object is deleted. |
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35 | // |
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36 | // Used properly, this deletes the object when the last reference goes away. |
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37 | // There are several caveats: |
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38 | // - Like all reference counting schemes, cycles lead to leaks. |
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39 | // - Each smart pointer is actually two pointers (8 bytes instead of 4). |
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40 | // - Every time a pointer is assigned, the entire list of pointers to that |
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41 | // object is traversed. This class is therefore NOT SUITABLE when there |
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42 | // will often be more than two or three pointers to a particular object. |
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43 | // - References are only tracked as long as linked_ptr<> objects are copied. |
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44 | // If a linked_ptr<> is converted to a raw pointer and back, BAD THINGS |
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45 | // will happen (double deletion). |
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46 | // |
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47 | // A good use of this class is storing object references in STL containers. |
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48 | // You can safely put linked_ptr<> in a vector<>. |
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49 | // Other uses may not be as good. |
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50 | // |
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51 | // Note: If you use an incomplete type with linked_ptr<>, the class |
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52 | // *containing* linked_ptr<> must have a constructor and destructor (even |
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53 | // if they do nothing!). |
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54 | // |
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55 | // Bill Gibbons suggested we use something like this. |
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56 | // |
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57 | // Thread Safety: |
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58 | // Unlike other linked_ptr implementations, in this implementation |
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59 | // a linked_ptr object is thread-safe in the sense that: |
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60 | // - it's safe to copy linked_ptr objects concurrently, |
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61 | // - it's safe to copy *from* a linked_ptr and read its underlying |
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62 | // raw pointer (e.g. via get()) concurrently, and |
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63 | // - it's safe to write to two linked_ptrs that point to the same |
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64 | // shared object concurrently. |
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65 | // TODO(wan@google.com): rename this to safe_linked_ptr to avoid |
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66 | // confusion with normal linked_ptr. |
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67 | |||
68 | #ifndef GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ |
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69 | #define GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ |
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70 | |||
71 | #include |
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72 | #include |
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73 | |||
74 | #include "gtest/internal/gtest-port.h" |
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75 | |||
76 | namespace testing { |
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77 | namespace internal { |
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78 | |||
79 | // Protects copying of all linked_ptr objects. |
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80 | GTEST_API_ GTEST_DECLARE_STATIC_MUTEX_(g_linked_ptr_mutex); |
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81 | |||
82 | // This is used internally by all instances of linked_ptr<>. It needs to be |
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83 | // a non-template class because different types of linked_ptr<> can refer to |
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84 | // the same object (linked_ptr |
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85 | // So, it needs to be possible for different types of linked_ptr to participate |
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86 | // in the same circular linked list, so we need a single class type here. |
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87 | // |
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88 | // DO NOT USE THIS CLASS DIRECTLY YOURSELF. Use linked_ptr |
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89 | class linked_ptr_internal { |
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90 | public: |
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91 | // Create a new circle that includes only this instance. |
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92 | void join_new() { |
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93 | next_ = this; |
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94 | } |
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95 | |||
96 | // Many linked_ptr operations may change p.link_ for some linked_ptr |
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97 | // variable p in the same circle as this object. Therefore we need |
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98 | // to prevent two such operations from occurring concurrently. |
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99 | // |
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100 | // Note that different types of linked_ptr objects can coexist in a |
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101 | // circle (e.g. linked_ptr |
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102 | // linked_ptr |
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103 | // protect all linked_ptr objects. This can create serious |
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104 | // contention in production code, but is acceptable in a testing |
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105 | // framework. |
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106 | |||
107 | // Join an existing circle. |
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108 | void join(linked_ptr_internal const* ptr) |
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109 | GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) { |
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110 | MutexLock lock(&g_linked_ptr_mutex); |
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111 | |||
112 | linked_ptr_internal const* p = ptr; |
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113 | while (p->next_ != ptr) p = p->next_; |
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114 | p->next_ = this; |
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115 | next_ = ptr; |
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116 | } |
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117 | |||
118 | // Leave whatever circle we're part of. Returns true if we were the |
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119 | // last member of the circle. Once this is done, you can join() another. |
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120 | bool depart() |
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121 | GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) { |
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122 | MutexLock lock(&g_linked_ptr_mutex); |
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123 | |||
124 | if (next_ == this) return true; |
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125 | linked_ptr_internal const* p = next_; |
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126 | while (p->next_ != this) p = p->next_; |
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127 | p->next_ = next_; |
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128 | return false; |
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129 | } |
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130 | |||
131 | private: |
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132 | mutable linked_ptr_internal const* next_; |
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133 | }; |
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134 | |||
135 | template |
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136 | class linked_ptr { |
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137 | public: |
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138 | typedef T element_type; |
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139 | |||
140 | // Take over ownership of a raw pointer. This should happen as soon as |
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141 | // possible after the object is created. |
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142 | explicit linked_ptr(T* ptr = NULL) { capture(ptr); } |
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143 | ~linked_ptr() { depart(); } |
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144 | |||
145 | // Copy an existing linked_ptr<>, adding ourselves to the list of references. |
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146 | template |
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147 | linked_ptr(linked_ptr const& ptr) { // NOLINT |
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148 | assert(&ptr != this); |
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149 | copy(&ptr); |
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150 | } |
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151 | |||
152 | // Assignment releases the old value and acquires the new. |
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153 | template |
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154 | depart(); |
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155 | copy(&ptr); |
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156 | return *this; |
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157 | } |
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158 | |||
159 | linked_ptr& operator=(linked_ptr const& ptr) { |
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160 | if (&ptr != this) { |
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161 | depart(); |
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162 | copy(&ptr); |
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163 | } |
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164 | return *this; |
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165 | } |
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166 | |||
167 | // Smart pointer members. |
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168 | void reset(T* ptr = NULL) { |
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169 | depart(); |
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170 | capture(ptr); |
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171 | } |
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172 | T* get() const { return value_; } |
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173 | T* operator->() const { return value_; } |
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174 | T& operator*() const { return *value_; } |
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175 | |||
176 | bool operator==(T* p) const { return value_ == p; } |
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177 | bool operator!=(T* p) const { return value_ != p; } |
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178 | template |
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179 | bool operator==(linked_ptr const& ptr) const { |
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180 | return value_ == ptr.get(); |
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181 | } |
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182 | template |
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183 | bool operator!=(linked_ptr const& ptr) const { |
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184 | return value_ != ptr.get(); |
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185 | } |
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186 | |||
187 | private: |
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188 | template |
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189 | friend class linked_ptr; |
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190 | |||
191 | T* value_; |
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192 | linked_ptr_internal link_; |
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193 | |||
194 | void depart() { |
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195 | if (link_.depart()) delete value_; |
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196 | } |
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197 | |||
198 | void capture(T* ptr) { |
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199 | value_ = ptr; |
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200 | link_.join_new(); |
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201 | } |
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202 | |||
203 | template |
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204 | value_ = ptr->get(); |
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205 | if (value_) |
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206 | link_.join(&ptr->link_); |
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207 | else |
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208 | link_.join_new(); |
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209 | } |
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210 | }; |
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211 | |||
212 | template |
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213 | bool operator==(T* ptr, const linked_ptr |
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214 | return ptr == x.get(); |
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215 | } |
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216 | |||
217 | template |
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218 | bool operator!=(T* ptr, const linked_ptr |
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219 | return ptr != x.get(); |
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220 | } |
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221 | |||
222 | // A function to convert T* into linked_ptr |
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223 | // Doing e.g. make_linked_ptr(new FooBarBaz |
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224 | // for linked_ptr |
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225 | template |
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226 | linked_ptr |
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227 | return linked_ptr |
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228 | } |
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229 | |||
230 | } // namespace internal |
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231 | } // namespace testing |
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232 | |||
233 | #endif // GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_>>>>>>>>> |