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| 1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_SHARED_DATA_H_ | |
| 6 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_SHARED_DATA_H_ | |
| 7 | |
| 8 #include "base/logging.h" | |
| 9 #include "base/macros.h" | |
| 10 #include "base/threading/thread_checker.h" | |
| 11 | |
| 12 namespace mojo { | |
| 13 namespace internal { | |
| 14 | |
| 15 // Used to allocate an instance of T that can be shared via reference counting. | |
| 16 // | |
| 17 // A default constructed SharedData does not have a Holder until it is set, | |
| 18 // either by assignment, or by accessing the value. As a result, it is not tied | |
| 19 // to any thread. The Holder is lazily allocated on first access. The complexity | |
| 20 // is due to the behaviour around copying. If a default constructed SharedData | |
| 21 // is copied into another, the two share the same empty state, and changing the | |
| 22 // value of one will affect the other. | |
| 23 template <typename T> | |
| 24 class SharedData { | |
| 25 public: | |
| 26 ~SharedData() { | |
| 27 if (holder_) | |
| 28 holder_->Release(); | |
| 29 } | |
| 30 | |
| 31 SharedData() : holder_(nullptr) {} | |
| 32 | |
| 33 explicit SharedData(const T& value) : holder_(new Holder(value)) {} | |
| 34 | |
| 35 SharedData(const SharedData<T>& other) { | |
| 36 other.LazyInit(); | |
| 37 holder_ = other.holder_; | |
| 38 holder_->Retain(); | |
| 39 } | |
| 40 | |
| 41 SharedData<T>& operator=(const SharedData<T>& other) { | |
| 42 other.LazyInit(); | |
| 43 if (other.holder_ == holder_) | |
| 44 return *this; | |
| 45 if (holder_) | |
| 46 holder_->Release(); | |
| 47 holder_ = other.holder_; | |
| 48 holder_->Retain(); | |
| 49 return *this; | |
| 50 } | |
| 51 | |
| 52 void reset() { | |
| 53 if (holder_) | |
| 54 holder_->Release(); | |
| 55 holder_ = nullptr; | |
| 56 } | |
| 57 | |
| 58 void reset(const T& value) { | |
| 59 if (holder_) | |
| 60 holder_->Release(); | |
| 61 holder_ = new Holder(value); | |
| 62 } | |
| 63 | |
| 64 void set_value(const T& value) { | |
| 65 LazyInit(); | |
| 66 holder_->value = value; | |
| 67 } | |
| 68 T* mutable_value() { | |
| 69 LazyInit(); | |
| 70 return &holder_->value; | |
| 71 } | |
| 72 const T& value() const { | |
| 73 LazyInit(); | |
| 74 return holder_->value; | |
| 75 } | |
| 76 | |
| 77 private: | |
| 78 class Holder { | |
| 79 public: | |
| 80 Holder() : value(), ref_count_(1) {} | |
| 81 Holder(const T& value) : value(value), ref_count_(1) {} | |
| 82 | |
| 83 void Retain() { | |
| 84 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 85 ++ref_count_; | |
| 86 } | |
| 87 void Release() { | |
| 88 DCHECK(thread_checker_.CalledOnValidThread()); | |
| 89 if (--ref_count_ == 0) | |
| 90 delete this; | |
| 91 } | |
| 92 | |
| 93 T value; | |
| 94 | |
| 95 private: | |
| 96 int ref_count_; | |
| 97 base::ThreadChecker thread_checker_; | |
| 98 DISALLOW_COPY_AND_ASSIGN(Holder); | |
| 99 }; | |
| 100 | |
| 101 void LazyInit() const { | |
| 102 if (!holder_) | |
| 103 holder_ = new Holder(); | |
| 104 } | |
| 105 | |
| 106 mutable Holder* holder_; | |
| 107 }; | |
| 108 | |
| 109 } // namespace internal | |
| 110 } // namespace mojo | |
| 111 | |
| 112 #endif // MOJO_PUBLIC_CPP_BINDINGS_LIB_SHARED_DATA_H_ | |
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Chromium Code Reviews
Issue 2062333002:
mojo::Callback -> base::Callback (Closed)
Base URL: https://chromium.googlesource.com/chromium/src.git@master