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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // The LazyInstance<Type, Traits> class manages a single instance of Type, | 5 // The LazyInstance<Type, Traits> class manages a single instance of Type, |
6 // which will be lazily created on the first time it's accessed. This class is | 6 // which will be lazily created on the first time it's accessed. This class is |
7 // useful for places you would normally use a function-level static, but you | 7 // useful for places you would normally use a function-level static, but you |
8 // need to have guaranteed thread-safety. The Type constructor will only ever | 8 // need to have guaranteed thread-safety. The Type constructor will only ever |
9 // be called once, even if two threads are racing to create the object. Get() | 9 // be called once, even if two threads are racing to create the object. Get() |
10 // and Pointer() will always return the same, completely initialized instance. | 10 // and Pointer() will always return the same, completely initialized instance. |
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32 // ptr->DoDoDo(); // MyClass::DoDoDo | 32 // ptr->DoDoDo(); // MyClass::DoDoDo |
33 // } | 33 // } |
34 | 34 |
35 #ifndef BASE_LAZY_INSTANCE_H_ | 35 #ifndef BASE_LAZY_INSTANCE_H_ |
36 #define BASE_LAZY_INSTANCE_H_ | 36 #define BASE_LAZY_INSTANCE_H_ |
37 | 37 |
38 #include <new> // For placement new. | 38 #include <new> // For placement new. |
39 | 39 |
40 #include "base/atomicops.h" | 40 #include "base/atomicops.h" |
41 #include "base/base_export.h" | 41 #include "base/base_export.h" |
42 #include "base/basictypes.h" | |
43 #include "base/debug/leak_annotations.h" | 42 #include "base/debug/leak_annotations.h" |
44 #include "base/logging.h" | 43 #include "base/logging.h" |
45 #include "base/memory/aligned_memory.h" | 44 #include "base/memory/aligned_memory.h" |
46 #include "base/threading/thread_restrictions.h" | 45 #include "base/threading/thread_restrictions.h" |
47 | 46 |
48 // LazyInstance uses its own struct initializer-list style static | 47 // LazyInstance uses its own struct initializer-list style static |
49 // initialization, as base's LINKER_INITIALIZED requires a constructor and on | 48 // initialization, as base's LINKER_INITIALIZED requires a constructor and on |
50 // some compilers (notably gcc 4.4) this still ends up needing runtime | 49 // some compilers (notably gcc 4.4) this still ends up needing runtime |
51 // initialization. | 50 // initialization. |
52 #define LAZY_INSTANCE_INITIALIZER {0} | 51 #define LAZY_INSTANCE_INITIALIZER {0} |
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199 LazyInstance<Type, Traits>* me = | 198 LazyInstance<Type, Traits>* me = |
200 reinterpret_cast<LazyInstance<Type, Traits>*>(lazy_instance); | 199 reinterpret_cast<LazyInstance<Type, Traits>*>(lazy_instance); |
201 Traits::Delete(me->instance()); | 200 Traits::Delete(me->instance()); |
202 subtle::NoBarrier_Store(&me->private_instance_, 0); | 201 subtle::NoBarrier_Store(&me->private_instance_, 0); |
203 } | 202 } |
204 }; | 203 }; |
205 | 204 |
206 } // namespace base | 205 } // namespace base |
207 | 206 |
208 #endif // BASE_LAZY_INSTANCE_H_ | 207 #endif // BASE_LAZY_INSTANCE_H_ |
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