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
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
|
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/timer/timer.h"
#include <stddef.h>
#include "base/logging.h"
#include "base/memory/ref_counted.h"
#include "base/single_thread_task_runner.h"
#include "base/thread_task_runner_handle.h"
#include "base/threading/platform_thread.h"
namespace base {
// BaseTimerTaskInternal is a simple delegate for scheduling a callback to
// Timer in the thread's default task runner. It also handles the following
// edge cases:
// - deleted by the task runner.
// - abandoned (orphaned) by Timer.
class BaseTimerTaskInternal {
public:
explicit BaseTimerTaskInternal(Timer* timer)
: timer_(timer) {
}
~BaseTimerTaskInternal() {
// This task may be getting cleared because the task runner has been
// destructed. If so, don't leave Timer with a dangling pointer
// to this.
if (timer_)
timer_->StopAndAbandon();
}
void Run() {
// timer_ is NULL if we were abandoned.
if (!timer_)
return;
// *this will be deleted by the task runner, so Timer needs to
// forget us:
timer_->scheduled_task_ = NULL;
// Although Timer should not call back into *this, let's clear
// the timer_ member first to be pedantic.
Timer* timer = timer_;
timer_ = NULL;
timer->RunScheduledTask();
}
// The task remains in the MessageLoop queue, but nothing will happen when it
// runs.
void Abandon() {
timer_ = NULL;
}
private:
Timer* timer_;
};
Timer::Timer(bool retain_user_task, bool is_repeating)
: scheduled_task_(NULL),
thread_id_(0),
is_repeating_(is_repeating),
retain_user_task_(retain_user_task),
is_running_(false) {
}
Timer::Timer(const tracked_objects::Location& posted_from,
TimeDelta delay,
const base::Closure& user_task,
bool is_repeating)
: scheduled_task_(NULL),
posted_from_(posted_from),
delay_(delay),
user_task_(user_task),
thread_id_(0),
is_repeating_(is_repeating),
retain_user_task_(true),
is_running_(false) {
}
Timer::~Timer() {
StopAndAbandon();
}
void Timer::Start(const tracked_objects::Location& posted_from,
TimeDelta delay,
const base::Closure& user_task) {
SetTaskInfo(posted_from, delay, user_task);
Reset();
}
void Timer::Stop() {
is_running_ = false;
if (!retain_user_task_)
user_task_.Reset();
}
void Timer::Reset() {
DCHECK(!user_task_.is_null());
// If there's no pending task, start one up and return.
if (!scheduled_task_) {
PostNewScheduledTask(delay_);
return;
}
// Set the new desired_run_time_.
if (delay_ > TimeDelta::FromMicroseconds(0))
desired_run_time_ = TimeTicks::Now() + delay_;
else
desired_run_time_ = TimeTicks();
// We can use the existing scheduled task if it arrives before the new
// desired_run_time_.
if (desired_run_time_ >= scheduled_run_time_) {
is_running_ = true;
return;
}
// We can't reuse the scheduled_task_, so abandon it and post a new one.
AbandonScheduledTask();
PostNewScheduledTask(delay_);
}
void Timer::SetTaskInfo(const tracked_objects::Location& posted_from,
TimeDelta delay,
const base::Closure& user_task) {
posted_from_ = posted_from;
delay_ = delay;
user_task_ = user_task;
}
void Timer::PostNewScheduledTask(TimeDelta delay) {
DCHECK(scheduled_task_ == NULL);
is_running_ = true;
scheduled_task_ = new BaseTimerTaskInternal(this);
if (delay > TimeDelta::FromMicroseconds(0)) {
ThreadTaskRunnerHandle::Get()->PostDelayedTask(posted_from_,
base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_)),
delay);
scheduled_run_time_ = desired_run_time_ = TimeTicks::Now() + delay;
} else {
ThreadTaskRunnerHandle::Get()->PostTask(posted_from_,
base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_)));
scheduled_run_time_ = desired_run_time_ = TimeTicks();
}
// Remember the thread ID that posts the first task -- this will be verified
// later when the task is abandoned to detect misuse from multiple threads.
if (!thread_id_)
thread_id_ = static_cast<int>(PlatformThread::CurrentId());
}
void Timer::AbandonScheduledTask() {
DCHECK(thread_id_ == 0 ||
thread_id_ == static_cast<int>(PlatformThread::CurrentId()));
if (scheduled_task_) {
scheduled_task_->Abandon();
scheduled_task_ = NULL;
}
}
void Timer::RunScheduledTask() {
// Task may have been disabled.
if (!is_running_)
return;
// First check if we need to delay the task because of a new target time.
if (desired_run_time_ > scheduled_run_time_) {
// TimeTicks::Now() can be expensive, so only call it if we know the user
// has changed the desired_run_time_.
TimeTicks now = TimeTicks::Now();
// Task runner may have called us late anyway, so only post a continuation
// task if the desired_run_time_ is in the future.
if (desired_run_time_ > now) {
// Post a new task to span the remaining time.
PostNewScheduledTask(desired_run_time_ - now);
return;
}
}
// Make a local copy of the task to run. The Stop method will reset the
// user_task_ member if retain_user_task_ is false.
base::Closure task = user_task_;
if (is_repeating_)
PostNewScheduledTask(delay_);
else
Stop();
task.Run();
// No more member accesses here: *this could be deleted at this point.
}
} // namespace base
|
