1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
|
// Copyright 2011 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// CancelableOnceCallback is a wrapper around OnceCallback that allows
// cancellation of the callback. CanacelableRepeatingCallback is the same sort
// of wrapper around RepeatingCallback. The wrapper takes a reference on the
// wrapped callback until this object is destroyed or Reset()/Cancel() are
// called.
//
// NOTE:
//
// Calling Cancel() brings the object back to its natural, default-constructed
// state, i.e., callback() will return a null callback.
//
// THREAD-SAFETY:
//
// Cancelable callback objects must be created on, posted to, cancelled on, and
// destroyed on the same SequencedTaskRunner.
//
//
// EXAMPLE USAGE:
//
// In the following example, the test is verifying that RunIntensiveTest()
// Quit()s the message loop within 4 seconds. The cancelable callback is posted
// to the message loop, the intensive test runs, the message loop is run,
// then the callback is cancelled.
//
// RunLoop run_loop;
//
// void TimeoutCallback(const std::string& timeout_message) {
// FAIL() << timeout_message;
// run_loop.QuitWhenIdle();
// }
//
// CancelableOnceClosure timeout(
// base::BindOnce(&TimeoutCallback, "Test timed out."));
// SingleThreadTaskRunner::GetCurrentDefault()->PostDelayedTask(
// FROM_HERE, timeout.callback(), Seconds(4));
// RunIntensiveTest();
// run_loop.Run();
// timeout.Cancel(); // Hopefully this is hit before the timeout callback runs.
//
#ifndef BASE_CANCELABLE_CALLBACK_H_
#define BASE_CANCELABLE_CALLBACK_H_
#include <utility>
#include "base/check.h"
#include "base/compiler_specific.h"
#include "base/functional/bind.h"
#include "base/functional/callback.h"
#include "base/functional/callback_internal.h"
#include "base/memory/weak_ptr.h"
namespace base {
namespace internal {
template <typename CallbackType>
class CancelableCallbackImpl {
public:
CancelableCallbackImpl() = default;
CancelableCallbackImpl(const CancelableCallbackImpl&) = delete;
CancelableCallbackImpl& operator=(const CancelableCallbackImpl&) = delete;
// |callback| must not be null.
explicit CancelableCallbackImpl(CallbackType callback)
: callback_(std::move(callback)) {
DCHECK(callback_);
}
~CancelableCallbackImpl() = default;
// Cancels and drops the reference to the wrapped callback.
void Cancel() {
weak_ptr_factory_.InvalidateWeakPtrs();
callback_.Reset();
}
// Returns true if the wrapped callback has been cancelled.
bool IsCancelled() const {
return callback_.is_null();
}
// Sets |callback| as the closure that may be cancelled. |callback| may not
// be null. Outstanding and any previously wrapped callbacks are cancelled.
void Reset(CallbackType callback) {
DCHECK(callback);
// Outstanding tasks (e.g., posted to a message loop) must not be called.
Cancel();
callback_ = std::move(callback);
}
// Returns a callback that can be disabled by calling Cancel().
CallbackType callback() const {
if (!callback_)
return CallbackType();
CallbackType forwarder;
MakeForwarder(&forwarder);
return forwarder;
}
private:
template <typename... Args>
void MakeForwarder(RepeatingCallback<void(Args...)>* out) const {
using ForwarderType = void (CancelableCallbackImpl::*)(Args...);
ForwarderType forwarder = &CancelableCallbackImpl::ForwardRepeating;
*out = BindRepeating(forwarder, weak_ptr_factory_.GetWeakPtr());
}
template <typename... Args>
void MakeForwarder(OnceCallback<void(Args...)>* out) const {
using ForwarderType = void (CancelableCallbackImpl::*)(Args...);
ForwarderType forwarder = &CancelableCallbackImpl::ForwardOnce;
*out = BindOnce(forwarder, weak_ptr_factory_.GetWeakPtr());
}
template <typename... Args>
void ForwardRepeating(Args... args) {
callback_.Run(std::forward<Args>(args)...);
}
template <typename... Args>
void ForwardOnce(Args... args) {
weak_ptr_factory_.InvalidateWeakPtrs();
std::move(callback_).Run(std::forward<Args>(args)...);
}
// The stored closure that may be cancelled.
CallbackType callback_;
mutable base::WeakPtrFactory<CancelableCallbackImpl> weak_ptr_factory_{this};
};
} // namespace internal
// Consider using base::WeakPtr directly instead of base::CancelableOnceCallback
// for task cancellation.
template <typename Signature>
using CancelableOnceCallback =
internal::CancelableCallbackImpl<OnceCallback<Signature>>;
using CancelableOnceClosure = CancelableOnceCallback<void()>;
template <typename Signature>
using CancelableRepeatingCallback =
internal::CancelableCallbackImpl<RepeatingCallback<Signature>>;
using CancelableRepeatingClosure = CancelableRepeatingCallback<void()>;
} // namespace base
#endif // BASE_CANCELABLE_CALLBACK_H_
|
