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comparison gtest/include/gtest/internal/gtest-linked_ptr.h @ 4:34a7a99dbcfa
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author | David Demelier <markand@malikania.fr> |
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date | Fri, 01 Dec 2017 16:46:31 +0100 |
parents | d9d3406c1250 |
children | ebcc8c9c8831 |
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1 // Copyright 2003 Google Inc. | |
2 // 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 are | |
6 // met: | |
7 // | |
8 // * Redistributions of source code must retain the above copyright | |
9 // notice, this list of conditions and the following disclaimer. | |
10 // * Redistributions in binary form must reproduce the above | |
11 // copyright notice, this list of conditions and the following disclaimer | |
12 // in the documentation and/or other materials provided with the | |
13 // distribution. | |
14 // * Neither the name of Google Inc. nor the names of its | |
15 // contributors may be used to endorse or promote products derived from | |
16 // this software without specific prior written permission. | |
17 // | |
18 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
19 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
20 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
21 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
22 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
23 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
24 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
25 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
26 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
27 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
28 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
29 // | |
30 // Authors: Dan Egnor (egnor@google.com) | |
31 // | |
32 // A "smart" pointer type with reference tracking. Every pointer to a | |
33 // particular object is kept on a circular linked list. When the last pointer | |
34 // to an object is destroyed or reassigned, the object is deleted. | |
35 // | |
36 // Used properly, this deletes the object when the last reference goes away. | |
37 // There are several caveats: | |
38 // - Like all reference counting schemes, cycles lead to leaks. | |
39 // - Each smart pointer is actually two pointers (8 bytes instead of 4). | |
40 // - Every time a pointer is assigned, the entire list of pointers to that | |
41 // object is traversed. This class is therefore NOT SUITABLE when there | |
42 // will often be more than two or three pointers to a particular object. | |
43 // - References are only tracked as long as linked_ptr<> objects are copied. | |
44 // If a linked_ptr<> is converted to a raw pointer and back, BAD THINGS | |
45 // will happen (double deletion). | |
46 // | |
47 // A good use of this class is storing object references in STL containers. | |
48 // You can safely put linked_ptr<> in a vector<>. | |
49 // Other uses may not be as good. | |
50 // | |
51 // Note: If you use an incomplete type with linked_ptr<>, the class | |
52 // *containing* linked_ptr<> must have a constructor and destructor (even | |
53 // if they do nothing!). | |
54 // | |
55 // Bill Gibbons suggested we use something like this. | |
56 // | |
57 // Thread Safety: | |
58 // Unlike other linked_ptr implementations, in this implementation | |
59 // a linked_ptr object is thread-safe in the sense that: | |
60 // - it's safe to copy linked_ptr objects concurrently, | |
61 // - it's safe to copy *from* a linked_ptr and read its underlying | |
62 // raw pointer (e.g. via get()) concurrently, and | |
63 // - it's safe to write to two linked_ptrs that point to the same | |
64 // shared object concurrently. | |
65 // TODO(wan@google.com): rename this to safe_linked_ptr to avoid | |
66 // confusion with normal linked_ptr. | |
67 | |
68 #ifndef GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ | |
69 #define GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ | |
70 | |
71 #include <stdlib.h> | |
72 #include <assert.h> | |
73 | |
74 #include "gtest/internal/gtest-port.h" | |
75 | |
76 namespace testing { | |
77 namespace internal { | |
78 | |
79 // Protects copying of all linked_ptr objects. | |
80 GTEST_API_ GTEST_DECLARE_STATIC_MUTEX_(g_linked_ptr_mutex); | |
81 | |
82 // This is used internally by all instances of linked_ptr<>. It needs to be | |
83 // a non-template class because different types of linked_ptr<> can refer to | |
84 // the same object (linked_ptr<Superclass>(obj) vs linked_ptr<Subclass>(obj)). | |
85 // So, it needs to be possible for different types of linked_ptr to participate | |
86 // in the same circular linked list, so we need a single class type here. | |
87 // | |
88 // DO NOT USE THIS CLASS DIRECTLY YOURSELF. Use linked_ptr<T>. | |
89 class linked_ptr_internal { | |
90 public: | |
91 // Create a new circle that includes only this instance. | |
92 void join_new() { | |
93 next_ = this; | |
94 } | |
95 | |
96 // Many linked_ptr operations may change p.link_ for some linked_ptr | |
97 // variable p in the same circle as this object. Therefore we need | |
98 // to prevent two such operations from occurring concurrently. | |
99 // | |
100 // Note that different types of linked_ptr objects can coexist in a | |
101 // circle (e.g. linked_ptr<Base>, linked_ptr<Derived1>, and | |
102 // linked_ptr<Derived2>). Therefore we must use a single mutex to | |
103 // protect all linked_ptr objects. This can create serious | |
104 // contention in production code, but is acceptable in a testing | |
105 // framework. | |
106 | |
107 // Join an existing circle. | |
108 void join(linked_ptr_internal const* ptr) | |
109 GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) { | |
110 MutexLock lock(&g_linked_ptr_mutex); | |
111 | |
112 linked_ptr_internal const* p = ptr; | |
113 while (p->next_ != ptr) p = p->next_; | |
114 p->next_ = this; | |
115 next_ = ptr; | |
116 } | |
117 | |
118 // Leave whatever circle we're part of. Returns true if we were the | |
119 // last member of the circle. Once this is done, you can join() another. | |
120 bool depart() | |
121 GTEST_LOCK_EXCLUDED_(g_linked_ptr_mutex) { | |
122 MutexLock lock(&g_linked_ptr_mutex); | |
123 | |
124 if (next_ == this) return true; | |
125 linked_ptr_internal const* p = next_; | |
126 while (p->next_ != this) p = p->next_; | |
127 p->next_ = next_; | |
128 return false; | |
129 } | |
130 | |
131 private: | |
132 mutable linked_ptr_internal const* next_; | |
133 }; | |
134 | |
135 template <typename T> | |
136 class linked_ptr { | |
137 public: | |
138 typedef T element_type; | |
139 | |
140 // Take over ownership of a raw pointer. This should happen as soon as | |
141 // possible after the object is created. | |
142 explicit linked_ptr(T* ptr = NULL) { capture(ptr); } | |
143 ~linked_ptr() { depart(); } | |
144 | |
145 // Copy an existing linked_ptr<>, adding ourselves to the list of references. | |
146 template <typename U> linked_ptr(linked_ptr<U> const& ptr) { copy(&ptr); } | |
147 linked_ptr(linked_ptr const& ptr) { // NOLINT | |
148 assert(&ptr != this); | |
149 copy(&ptr); | |
150 } | |
151 | |
152 // Assignment releases the old value and acquires the new. | |
153 template <typename U> linked_ptr& operator=(linked_ptr<U> const& ptr) { | |
154 depart(); | |
155 copy(&ptr); | |
156 return *this; | |
157 } | |
158 | |
159 linked_ptr& operator=(linked_ptr const& ptr) { | |
160 if (&ptr != this) { | |
161 depart(); | |
162 copy(&ptr); | |
163 } | |
164 return *this; | |
165 } | |
166 | |
167 // Smart pointer members. | |
168 void reset(T* ptr = NULL) { | |
169 depart(); | |
170 capture(ptr); | |
171 } | |
172 T* get() const { return value_; } | |
173 T* operator->() const { return value_; } | |
174 T& operator*() const { return *value_; } | |
175 | |
176 bool operator==(T* p) const { return value_ == p; } | |
177 bool operator!=(T* p) const { return value_ != p; } | |
178 template <typename U> | |
179 bool operator==(linked_ptr<U> const& ptr) const { | |
180 return value_ == ptr.get(); | |
181 } | |
182 template <typename U> | |
183 bool operator!=(linked_ptr<U> const& ptr) const { | |
184 return value_ != ptr.get(); | |
185 } | |
186 | |
187 private: | |
188 template <typename U> | |
189 friend class linked_ptr; | |
190 | |
191 T* value_; | |
192 linked_ptr_internal link_; | |
193 | |
194 void depart() { | |
195 if (link_.depart()) delete value_; | |
196 } | |
197 | |
198 void capture(T* ptr) { | |
199 value_ = ptr; | |
200 link_.join_new(); | |
201 } | |
202 | |
203 template <typename U> void copy(linked_ptr<U> const* ptr) { | |
204 value_ = ptr->get(); | |
205 if (value_) | |
206 link_.join(&ptr->link_); | |
207 else | |
208 link_.join_new(); | |
209 } | |
210 }; | |
211 | |
212 template<typename T> inline | |
213 bool operator==(T* ptr, const linked_ptr<T>& x) { | |
214 return ptr == x.get(); | |
215 } | |
216 | |
217 template<typename T> inline | |
218 bool operator!=(T* ptr, const linked_ptr<T>& x) { | |
219 return ptr != x.get(); | |
220 } | |
221 | |
222 // A function to convert T* into linked_ptr<T> | |
223 // Doing e.g. make_linked_ptr(new FooBarBaz<type>(arg)) is a shorter notation | |
224 // for linked_ptr<FooBarBaz<type> >(new FooBarBaz<type>(arg)) | |
225 template <typename T> | |
226 linked_ptr<T> make_linked_ptr(T* ptr) { | |
227 return linked_ptr<T>(ptr); | |
228 } | |
229 | |
230 } // namespace internal | |
231 } // namespace testing | |
232 | |
233 #endif // GTEST_INCLUDE_GTEST_INTERNAL_GTEST_LINKED_PTR_H_ |