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| 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 | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "base/timer/timer.h" | |
| 6 | |
| 7 #include <stddef.h> | |
| 8 | |
| 9 #include "base/logging.h" | |
| 10 #include "base/memory/ref_counted.h" | |
| 11 #include "base/single_thread_task_runner.h" | |
| 12 #include "base/thread_task_runner_handle.h" | |
| 13 #include "base/threading/platform_thread.h" | |
| 14 | |
| 15 namespace base { | |
| 16 | |
| 17 // BaseTimerTaskInternal is a simple delegate for scheduling a callback to | |
| 18 // Timer in the thread's default task runner. It also handles the following | |
| 19 // edge cases: | |
| 20 // - deleted by the task runner. | |
| 21 // - abandoned (orphaned) by Timer. | |
| 22 class BaseTimerTaskInternal { | |
| 23 public: | |
| 24 explicit BaseTimerTaskInternal(Timer* timer) | |
| 25 : timer_(timer) { | |
| 26 } | |
| 27 | |
| 28 ~BaseTimerTaskInternal() { | |
| 29 // This task may be getting cleared because the task runner has been | |
| 30 // destructed. If so, don't leave Timer with a dangling pointer | |
| 31 // to this. | |
| 32 if (timer_) | |
| 33 timer_->StopAndAbandon(); | |
| 34 } | |
| 35 | |
| 36 void Run() { | |
| 37 // timer_ is NULL if we were abandoned. | |
| 38 if (!timer_) | |
| 39 return; | |
| 40 | |
| 41 // *this will be deleted by the task runner, so Timer needs to | |
| 42 // forget us: | |
| 43 timer_->scheduled_task_ = NULL; | |
| 44 | |
| 45 // Although Timer should not call back into *this, let's clear | |
| 46 // the timer_ member first to be pedantic. | |
| 47 Timer* timer = timer_; | |
| 48 timer_ = NULL; | |
| 49 timer->RunScheduledTask(); | |
| 50 } | |
| 51 | |
| 52 // The task remains in the MessageLoop queue, but nothing will happen when it | |
| 53 // runs. | |
| 54 void Abandon() { | |
| 55 timer_ = NULL; | |
| 56 } | |
| 57 | |
| 58 private: | |
| 59 Timer* timer_; | |
| 60 }; | |
| 61 | |
| 62 Timer::Timer(bool retain_user_task, bool is_repeating) | |
| 63 : scheduled_task_(NULL), | |
| 64 thread_id_(0), | |
| 65 is_repeating_(is_repeating), | |
| 66 retain_user_task_(retain_user_task), | |
| 67 is_running_(false) { | |
| 68 } | |
| 69 | |
| 70 Timer::Timer(const tracked_objects::Location& posted_from, | |
| 71 TimeDelta delay, | |
| 72 const base::Closure& user_task, | |
| 73 bool is_repeating) | |
| 74 : scheduled_task_(NULL), | |
| 75 posted_from_(posted_from), | |
| 76 delay_(delay), | |
| 77 user_task_(user_task), | |
| 78 thread_id_(0), | |
| 79 is_repeating_(is_repeating), | |
| 80 retain_user_task_(true), | |
| 81 is_running_(false) { | |
| 82 } | |
| 83 | |
| 84 Timer::~Timer() { | |
| 85 StopAndAbandon(); | |
| 86 } | |
| 87 | |
| 88 bool Timer::IsRunning() const { | |
| 89 return is_running_; | |
| 90 } | |
| 91 | |
| 92 TimeDelta Timer::GetCurrentDelay() const { | |
| 93 return delay_; | |
| 94 } | |
| 95 | |
| 96 void Timer::SetTaskRunner(scoped_refptr<SingleThreadTaskRunner> task_runner) { | |
| 97 // Do not allow changing the task runner once something has been scheduled. | |
| 98 DCHECK_EQ(thread_id_, 0); | |
| 99 task_runner_.swap(task_runner); | |
| 100 } | |
| 101 | |
| 102 void Timer::Start(const tracked_objects::Location& posted_from, | |
| 103 TimeDelta delay, | |
| 104 const base::Closure& user_task) { | |
| 105 SetTaskInfo(posted_from, delay, user_task); | |
| 106 Reset(); | |
| 107 } | |
| 108 | |
| 109 void Timer::Stop() { | |
| 110 is_running_ = false; | |
| 111 if (!retain_user_task_) | |
| 112 user_task_.Reset(); | |
| 113 } | |
| 114 | |
| 115 void Timer::Reset() { | |
| 116 DCHECK(!user_task_.is_null()); | |
| 117 | |
| 118 // If there's no pending task, start one up and return. | |
| 119 if (!scheduled_task_) { | |
| 120 PostNewScheduledTask(delay_); | |
| 121 return; | |
| 122 } | |
| 123 | |
| 124 // Set the new desired_run_time_. | |
| 125 if (delay_ > TimeDelta::FromMicroseconds(0)) | |
| 126 desired_run_time_ = TimeTicks::Now() + delay_; | |
| 127 else | |
| 128 desired_run_time_ = TimeTicks(); | |
| 129 | |
| 130 // We can use the existing scheduled task if it arrives before the new | |
| 131 // desired_run_time_. | |
| 132 if (desired_run_time_ >= scheduled_run_time_) { | |
| 133 is_running_ = true; | |
| 134 return; | |
| 135 } | |
| 136 | |
| 137 // We can't reuse the scheduled_task_, so abandon it and post a new one. | |
| 138 AbandonScheduledTask(); | |
| 139 PostNewScheduledTask(delay_); | |
| 140 } | |
| 141 | |
| 142 void Timer::SetTaskInfo(const tracked_objects::Location& posted_from, | |
| 143 TimeDelta delay, | |
| 144 const base::Closure& user_task) { | |
| 145 posted_from_ = posted_from; | |
| 146 delay_ = delay; | |
| 147 user_task_ = user_task; | |
| 148 } | |
| 149 | |
| 150 void Timer::PostNewScheduledTask(TimeDelta delay) { | |
| 151 DCHECK(scheduled_task_ == NULL); | |
| 152 is_running_ = true; | |
| 153 scheduled_task_ = new BaseTimerTaskInternal(this); | |
| 154 if (delay > TimeDelta::FromMicroseconds(0)) { | |
| 155 GetTaskRunner()->PostDelayedTask(posted_from_, | |
| 156 base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_)), | |
| 157 delay); | |
| 158 scheduled_run_time_ = desired_run_time_ = TimeTicks::Now() + delay; | |
| 159 } else { | |
| 160 GetTaskRunner()->PostTask(posted_from_, | |
| 161 base::Bind(&BaseTimerTaskInternal::Run, base::Owned(scheduled_task_))); | |
| 162 scheduled_run_time_ = desired_run_time_ = TimeTicks(); | |
| 163 } | |
| 164 // Remember the thread ID that posts the first task -- this will be verified | |
| 165 // later when the task is abandoned to detect misuse from multiple threads. | |
| 166 if (!thread_id_) { | |
| 167 DCHECK(GetTaskRunner()->BelongsToCurrentThread()); | |
| 168 thread_id_ = static_cast<int>(PlatformThread::CurrentId()); | |
| 169 } | |
| 170 } | |
| 171 | |
| 172 scoped_refptr<SingleThreadTaskRunner> Timer::GetTaskRunner() { | |
| 173 return task_runner_.get() ? task_runner_ : ThreadTaskRunnerHandle::Get(); | |
| 174 } | |
| 175 | |
| 176 void Timer::AbandonScheduledTask() { | |
| 177 DCHECK(thread_id_ == 0 || | |
| 178 thread_id_ == static_cast<int>(PlatformThread::CurrentId())); | |
| 179 if (scheduled_task_) { | |
| 180 scheduled_task_->Abandon(); | |
| 181 scheduled_task_ = NULL; | |
| 182 } | |
| 183 } | |
| 184 | |
| 185 void Timer::RunScheduledTask() { | |
| 186 // Task may have been disabled. | |
| 187 if (!is_running_) | |
| 188 return; | |
| 189 | |
| 190 // First check if we need to delay the task because of a new target time. | |
| 191 if (desired_run_time_ > scheduled_run_time_) { | |
| 192 // TimeTicks::Now() can be expensive, so only call it if we know the user | |
| 193 // has changed the desired_run_time_. | |
| 194 TimeTicks now = TimeTicks::Now(); | |
| 195 // Task runner may have called us late anyway, so only post a continuation | |
| 196 // task if the desired_run_time_ is in the future. | |
| 197 if (desired_run_time_ > now) { | |
| 198 // Post a new task to span the remaining time. | |
| 199 PostNewScheduledTask(desired_run_time_ - now); | |
| 200 return; | |
| 201 } | |
| 202 } | |
| 203 | |
| 204 // Make a local copy of the task to run. The Stop method will reset the | |
| 205 // user_task_ member if retain_user_task_ is false. | |
| 206 base::Closure task = user_task_; | |
| 207 | |
| 208 if (is_repeating_) | |
| 209 PostNewScheduledTask(delay_); | |
| 210 else | |
| 211 Stop(); | |
| 212 | |
| 213 task.Run(); | |
| 214 | |
| 215 // No more member accesses here: *this could be deleted at this point. | |
| 216 } | |
| 217 | |
| 218 } // namespace base | |
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