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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 #ifndef BASE_CALLBACK_H_ | 5 #ifndef BASE_CALLBACK_H_ |
6 #define BASE_CALLBACK_H_ | 6 #define BASE_CALLBACK_H_ |
7 | 7 |
8 #include "base/callback_forward.h" | 8 #include "base/callback_forward.h" |
9 #include "base/callback_internal.h" | 9 #include "base/callback_internal.h" |
10 | 10 |
11 // NOTE: Header files that do not require the full definition of Callback or | 11 // NOTE: Header files that do not require the full definition of Callback or |
12 // Closure should #include "base/callback_forward.h" instead of this file. | 12 // Closure should #include "base/callback_forward.h" instead of this file. |
13 | 13 |
14 // ----------------------------------------------------------------------------- | 14 // ----------------------------------------------------------------------------- |
15 // Usage documentation | 15 // Usage documentation |
16 // ----------------------------------------------------------------------------- | 16 // ----------------------------------------------------------------------------- |
17 // | 17 // |
18 // See //docs/callback.md for documentation. | 18 // See //docs/callback.md for documentation. |
19 | 19 |
20 namespace base { | 20 namespace base { |
21 | 21 |
22 template <typename R, typename... Args, internal::CopyMode copy_mode> | 22 namespace internal { |
23 class Callback<R(Args...), copy_mode> | 23 |
24 : public internal::CallbackBase<copy_mode> { | 24 // RunMixin provides different variants of `Run()` function to `Callback<>` |
| 25 // based on the type of callback. |
| 26 template <typename CallbackType> |
| 27 class RunMixin; |
| 28 |
| 29 // Specialization for OnceCallback. |
| 30 template <typename R, typename... Args> |
| 31 class RunMixin<Callback<R(Args...), CopyMode::MoveOnly, RepeatMode::Once>> { |
| 32 private: |
| 33 using CallbackType = |
| 34 Callback<R(Args...), CopyMode::MoveOnly, RepeatMode::Once>; |
| 35 |
25 public: | 36 public: |
26 using PolymorphicInvoke = R (*)(internal::BindStateBase*, Args&&...); | 37 using PolymorphicInvoke = R(*)(internal::BindStateBase*, Args&&...); |
27 | 38 |
28 // MSVC 2013 doesn't support Type Alias of function types. | 39 R Run(Args... args) && { |
29 // Revisit this after we update it to newer version. | 40 // Move the callback instance into a local variable before the invocation, |
30 typedef R RunType(Args...); | 41 // that ensures the internal state is cleared after the invocation. |
| 42 // It's not safe to touch |this| after the invocation, since running the |
| 43 // bound function may destroy |this|. |
| 44 CallbackType cb = static_cast<CallbackType&&>(*this); |
| 45 PolymorphicInvoke f = |
| 46 reinterpret_cast<PolymorphicInvoke>(cb.polymorphic_invoke()); |
| 47 return f(cb.bind_state_.get(), std::forward<Args>(args)...); |
| 48 } |
| 49 }; |
| 50 |
| 51 // Specialization for RepeatingCallback. |
| 52 template <typename R, typename... Args, CopyMode copy_mode> |
| 53 class RunMixin<Callback<R(Args...), copy_mode, RepeatMode::Repeating>> { |
| 54 private: |
| 55 using CallbackType = Callback<R(Args...), copy_mode, RepeatMode::Repeating>; |
| 56 |
| 57 public: |
| 58 using PolymorphicInvoke = R(*)(internal::BindStateBase*, Args&&...); |
| 59 |
| 60 R Run(Args... args) const { |
| 61 const CallbackType& cb = static_cast<const CallbackType&>(*this); |
| 62 PolymorphicInvoke f = |
| 63 reinterpret_cast<PolymorphicInvoke>(cb.polymorphic_invoke()); |
| 64 return f(cb.bind_state_.get(), std::forward<Args>(args)...); |
| 65 } |
| 66 }; |
| 67 |
| 68 template <typename From, typename To> |
| 69 struct IsCallbackConvertible : std::false_type {}; |
| 70 |
| 71 template <typename Signature> |
| 72 struct IsCallbackConvertible< |
| 73 Callback<Signature, CopyMode::Copyable, RepeatMode::Repeating>, |
| 74 Callback<Signature, CopyMode::MoveOnly, RepeatMode::Once>> : std::true_type { |
| 75 }; |
| 76 |
| 77 } // namespace internal |
| 78 |
| 79 template <typename R, |
| 80 typename... Args, |
| 81 internal::CopyMode copy_mode, |
| 82 internal::RepeatMode repeat_mode> |
| 83 class Callback<R(Args...), copy_mode, repeat_mode> |
| 84 : public internal::CallbackBase<copy_mode>, |
| 85 public internal::RunMixin<Callback<R(Args...), copy_mode, repeat_mode>> { |
| 86 public: |
| 87 static_assert(repeat_mode != internal::RepeatMode::Once || |
| 88 copy_mode == internal::CopyMode::MoveOnly, |
| 89 "OnceCallback must be MoveOnly."); |
| 90 |
| 91 using RunType = R(Args...); |
31 | 92 |
32 Callback() : internal::CallbackBase<copy_mode>(nullptr) {} | 93 Callback() : internal::CallbackBase<copy_mode>(nullptr) {} |
33 | 94 |
34 explicit Callback(internal::BindStateBase* bind_state) | 95 explicit Callback(internal::BindStateBase* bind_state) |
35 : internal::CallbackBase<copy_mode>(bind_state) { | 96 : internal::CallbackBase<copy_mode>(bind_state) { |
36 } | 97 } |
37 | 98 |
| 99 template <typename OtherCallback, |
| 100 typename = typename std::enable_if< |
| 101 internal::IsCallbackConvertible<OtherCallback, Callback>::value |
| 102 >::type> |
| 103 Callback(OtherCallback other) |
| 104 : internal::CallbackBase<copy_mode>(std::move(other)) {} |
| 105 |
| 106 template <typename OtherCallback, |
| 107 typename = typename std::enable_if< |
| 108 internal::IsCallbackConvertible<OtherCallback, Callback>::value |
| 109 >::type> |
| 110 Callback& operator=(OtherCallback other) { |
| 111 static_cast<internal::CallbackBase<copy_mode>&>(*this) = std::move(other); |
| 112 return *this; |
| 113 } |
| 114 |
38 bool Equals(const Callback& other) const { | 115 bool Equals(const Callback& other) const { |
39 return this->EqualsInternal(other); | 116 return this->EqualsInternal(other); |
40 } | 117 } |
41 | 118 |
42 // Run() makes an extra copy compared to directly calling the bound function | 119 friend class internal::RunMixin<Callback>; |
43 // if an argument is passed-by-value and is copyable-but-not-movable: | |
44 // i.e. below copies CopyableNonMovableType twice. | |
45 // void F(CopyableNonMovableType) {} | |
46 // Bind(&F).Run(CopyableNonMovableType()); | |
47 // | |
48 // We can not fully apply Perfect Forwarding idiom to the callchain from | |
49 // Callback::Run() to the target function. Perfect Forwarding requires | |
50 // knowing how the caller will pass the arguments. However, the signature of | |
51 // InvokerType::Run() needs to be fixed in the callback constructor, so Run() | |
52 // cannot template its arguments based on how it's called. | |
53 R Run(Args... args) const { | |
54 PolymorphicInvoke f = | |
55 reinterpret_cast<PolymorphicInvoke>(this->polymorphic_invoke()); | |
56 return f(this->bind_state_.get(), std::forward<Args>(args)...); | |
57 } | |
58 }; | 120 }; |
59 | 121 |
60 } // namespace base | 122 } // namespace base |
61 | 123 |
62 #endif // BASE_CALLBACK_H_ | 124 #endif // BASE_CALLBACK_H_ |
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