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Side by Side Diff: base/memory/weak_ptr.h

Issue 11564003: Make WeakPtr use SequenceChecker instead of ThreadChecker (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Sync to head Created 7 years, 10 months ago
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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 // Weak pointers help in cases where you have many objects referring back to a 5 // Weak pointers help in cases where you have many objects referring back to a
6 // shared object and you wish for the lifetime of the shared object to not be 6 // shared object and you wish for the lifetime of the shared object to not be
7 // bound to the lifetime of the referrers. In other words, this is useful when 7 // bound to the lifetime of the referrers. In other words, this is useful when
8 // reference counting is not a good fit. 8 // reference counting is not a good fit.
9 // 9 //
10 // A common alternative to weak pointers is to have the shared object hold a 10 // A common alternative to weak pointers is to have the shared object hold a
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67 // may only be dereferenced on the thread that the original WeakPtr was bound 67 // may only be dereferenced on the thread that the original WeakPtr was bound
68 // to. 68 // to.
69 69
70 #ifndef BASE_MEMORY_WEAK_PTR_H_ 70 #ifndef BASE_MEMORY_WEAK_PTR_H_
71 #define BASE_MEMORY_WEAK_PTR_H_ 71 #define BASE_MEMORY_WEAK_PTR_H_
72 72
73 #include "base/basictypes.h" 73 #include "base/basictypes.h"
74 #include "base/base_export.h" 74 #include "base/base_export.h"
75 #include "base/logging.h" 75 #include "base/logging.h"
76 #include "base/memory/ref_counted.h" 76 #include "base/memory/ref_counted.h"
77 #include "base/sequence_checker.h"
77 #include "base/template_util.h" 78 #include "base/template_util.h"
78 #include "base/threading/thread_checker.h"
79 79
80 namespace base { 80 namespace base {
81 81
82 template <typename T> class SupportsWeakPtr; 82 template <typename T> class SupportsWeakPtr;
83 template <typename T> class WeakPtr; 83 template <typename T> class WeakPtr;
84 84
85 namespace internal { 85 namespace internal {
86 // These classes are part of the WeakPtr implementation. 86 // These classes are part of the WeakPtr implementation.
87 // DO NOT USE THESE CLASSES DIRECTLY YOURSELF. 87 // DO NOT USE THESE CLASSES DIRECTLY YOURSELF.
88 88
89 class BASE_EXPORT WeakReference { 89 class BASE_EXPORT WeakReference {
90 public: 90 public:
91 // While Flag is bound to a specific thread, it may be deleted from another 91 // While Flag is bound to a specific thread, it may be deleted from another
92 // via base::WeakPtr::~WeakPtr(). 92 // via base::WeakPtr::~WeakPtr().
93 class Flag : public RefCountedThreadSafe<Flag> { 93 class Flag : public RefCountedThreadSafe<Flag> {
94 public: 94 public:
95 Flag(); 95 Flag();
96 96
97 void Invalidate(); 97 void Invalidate();
98 bool IsValid() const; 98 bool IsValid() const;
99 99
100 void DetachFromThread() { thread_checker_.DetachFromThread(); } 100 void DetachFromThread();
101 101
102 private: 102 private:
103 friend class base::RefCountedThreadSafe<Flag>; 103 friend class base::RefCountedThreadSafe<Flag>;
104 104
105 ~Flag(); 105 ~Flag();
106 106
107 ThreadChecker thread_checker_; 107 SequenceChecker sequence_checker_;
108 bool is_valid_; 108 bool is_valid_;
109 }; 109 };
110 110
111 WeakReference(); 111 WeakReference();
112 explicit WeakReference(const Flag* flag); 112 explicit WeakReference(const Flag* flag);
113 ~WeakReference(); 113 ~WeakReference();
114 114
115 bool is_valid() const; 115 bool is_valid() const;
116 116
117 private: 117 private:
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238 WeakPtr(const internal::WeakReference& ref, T* ptr) 238 WeakPtr(const internal::WeakReference& ref, T* ptr)
239 : WeakPtrBase(ref), 239 : WeakPtrBase(ref),
240 ptr_(ptr) { 240 ptr_(ptr) {
241 } 241 }
242 242
243 // This pointer is only valid when ref_.is_valid() is true. Otherwise, its 243 // This pointer is only valid when ref_.is_valid() is true. Otherwise, its
244 // value is undefined (as opposed to NULL). 244 // value is undefined (as opposed to NULL).
245 T* ptr_; 245 T* ptr_;
246 }; 246 };
247 247
248 // TODO(akalin): Make WeakPtrFactory and SupportsWeakPtr support
jar (doing other things) 2013/02/16 02:37:27 nit: Can you add a bug number.
249 // binding to a SequencedTaskRunner instead of just a single thread.
250
248 // A class may extend from SupportsWeakPtr to expose weak pointers to itself. 251 // A class may extend from SupportsWeakPtr to expose weak pointers to itself.
249 // This is useful in cases where you want others to be able to get a weak 252 // This is useful in cases where you want others to be able to get a weak
250 // pointer to your class. It also has the property that you don't need to 253 // pointer to your class. It also has the property that you don't need to
251 // initialize it from your constructor. 254 // initialize it from your constructor.
252 template <class T> 255 template <class T>
253 class SupportsWeakPtr : public internal::SupportsWeakPtrBase { 256 class SupportsWeakPtr : public internal::SupportsWeakPtrBase {
254 public: 257 public:
255 SupportsWeakPtr() {} 258 SupportsWeakPtr() {}
256 259
257 WeakPtr<T> AsWeakPtr() { 260 WeakPtr<T> AsWeakPtr() {
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334 337
335 private: 338 private:
336 internal::WeakReferenceOwner weak_reference_owner_; 339 internal::WeakReferenceOwner weak_reference_owner_;
337 T* ptr_; 340 T* ptr_;
338 DISALLOW_IMPLICIT_CONSTRUCTORS(WeakPtrFactory); 341 DISALLOW_IMPLICIT_CONSTRUCTORS(WeakPtrFactory);
339 }; 342 };
340 343
341 } // namespace base 344 } // namespace base
342 345
343 #endif // BASE_MEMORY_WEAK_PTR_H_ 346 #endif // BASE_MEMORY_WEAK_PTR_H_
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