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331 lines
13 KiB
331 lines
13 KiB
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// OneShotTimer and RepeatingTimer provide a simple timer API. As the names
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// suggest, OneShotTimer calls you back once after a time delay expires.
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// RepeatingTimer on the other hand calls you back periodically with the
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// prescribed time interval.
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//
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// OneShotTimer and RepeatingTimer both cancel the timer when they go out of
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// scope, which makes it easy to ensure that you do not get called when your
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// object has gone out of scope. Just instantiate a OneShotTimer or
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// RepeatingTimer as a member variable of the class for which you wish to
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// receive timer events.
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//
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// Sample RepeatingTimer usage:
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//
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// class MyClass {
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// public:
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// void StartDoingStuff() {
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// timer_.Start(FROM_HERE, TimeDelta::FromSeconds(1),
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// this, &MyClass::DoStuff);
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// }
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// void StopDoingStuff() {
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// timer_.Stop();
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// }
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// private:
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// void DoStuff() {
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// // This method is called every second to do stuff.
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// ...
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// }
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// base::RepeatingTimer timer_;
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// };
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//
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// Both OneShotTimer and RepeatingTimer also support a Reset method, which
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// allows you to easily defer the timer event until the timer delay passes once
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// again. So, in the above example, if 0.5 seconds have already passed,
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// calling Reset on |timer_| would postpone DoStuff by another 1 second. In
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// other words, Reset is shorthand for calling Stop and then Start again with
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// the same arguments.
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//
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// These APIs are not thread safe. All methods must be called from the same
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// sequence (not necessarily the construction sequence), except for the
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// destructor and SetTaskRunner().
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// - The destructor may be called from any sequence when the timer is not
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// running and there is no scheduled task active, i.e. when Start() has never
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// been called or after AbandonAndStop() has been called.
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// - SetTaskRunner() may be called from any sequence when the timer is not
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// running, i.e. when Start() has never been called or Stop() has been called
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// since the last Start().
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//
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// By default, the scheduled tasks will be run on the same sequence that the
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// Timer was *started on*, but this can be changed *prior* to Start() via
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// SetTaskRunner().
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#ifndef BASE_TIMER_TIMER_H_
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#define BASE_TIMER_TIMER_H_
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// IMPORTANT: If you change timer code, make sure that all tests (including
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// disabled ones) from timer_unittests.cc pass locally. Some are disabled
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// because they're flaky on the buildbot, but when you run them locally you
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// should be able to tell the difference.
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#include <memory>
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#include "base/base_export.h"
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#include "base/bind.h"
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#include "base/bind_helpers.h"
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#include "base/callback.h"
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#include "base/location.h"
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#include "base/macros.h"
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#include "base/sequence_checker_impl.h"
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#include "base/sequenced_task_runner.h"
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#include "base/time/time.h"
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namespace base {
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class BaseTimerTaskInternal;
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class TickClock;
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//-----------------------------------------------------------------------------
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// This class wraps TaskRunner::PostDelayedTask to manage delayed and repeating
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// tasks. See meta comment above for thread-safety requirements.
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//
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class BASE_EXPORT Timer {
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public:
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// Construct a timer in repeating or one-shot mode. Start must be called later
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// to set task info. |retain_user_task| determines whether the user_task is
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// retained or reset when it runs or stops. If |tick_clock| is provided, it is
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// used instead of TimeTicks::Now() to get TimeTicks when scheduling tasks.
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Timer(bool retain_user_task, bool is_repeating);
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Timer(bool retain_user_task, bool is_repeating, const TickClock* tick_clock);
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// Construct a timer with retained task info. If |tick_clock| is provided, it
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// is used instead of TimeTicks::Now() to get TimeTicks when scheduling tasks.
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Timer(const Location& posted_from,
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TimeDelta delay,
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const base::Closure& user_task,
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bool is_repeating);
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Timer(const Location& posted_from,
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TimeDelta delay,
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const base::Closure& user_task,
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bool is_repeating,
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const TickClock* tick_clock);
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virtual ~Timer();
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// Returns true if the timer is running (i.e., not stopped).
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bool IsRunning() const;
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// Returns the current delay for this timer.
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TimeDelta GetCurrentDelay() const;
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// Set the task runner on which the task should be scheduled. This method can
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// only be called before any tasks have been scheduled. If |task_runner| runs
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// tasks on a different sequence than the sequence owning this Timer,
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// |user_task_| will be posted to it when the Timer fires (note that this
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// means |user_task_| can run after ~Timer() and should support that).
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virtual void SetTaskRunner(scoped_refptr<SequencedTaskRunner> task_runner);
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// Start the timer to run at the given |delay| from now. If the timer is
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// already running, it will be replaced to call the given |user_task|.
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virtual void Start(const Location& posted_from,
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TimeDelta delay,
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const base::Closure& user_task);
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// Start the timer to run at the given |delay| from now. If the timer is
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// already running, it will be replaced to call a task formed from
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// |reviewer->*method|.
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template <class Receiver>
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void Start(const Location& posted_from,
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TimeDelta delay,
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Receiver* receiver,
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void (Receiver::*method)()) {
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Start(posted_from, delay,
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base::BindRepeating(method, base::Unretained(receiver)));
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}
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// Call this method to stop and cancel the timer. It is a no-op if the timer
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// is not running.
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virtual void Stop();
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// Stop running task (if any) and abandon scheduled task (if any).
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void AbandonAndStop() {
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AbandonScheduledTask();
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Stop();
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// No more member accesses here: |this| could be deleted at this point.
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}
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// Call this method to reset the timer delay. The |user_task_| must be set. If
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// the timer is not running, this will start it by posting a task.
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virtual void Reset();
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const base::Closure& user_task() const { return user_task_; }
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const TimeTicks& desired_run_time() const { return desired_run_time_; }
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protected:
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// Returns the current tick count.
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TimeTicks Now() const;
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void set_user_task(const Closure& task) { user_task_ = task; }
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void set_desired_run_time(TimeTicks desired) { desired_run_time_ = desired; }
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void set_is_running(bool running) { is_running_ = running; }
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const Location& posted_from() const { return posted_from_; }
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// The task runner on which the task should be scheduled. If it is null, the
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// task runner for the current sequence will be used.
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scoped_refptr<SequencedTaskRunner> task_runner_;
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// Timer isn't thread-safe and must only be used on its origin sequence
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// (sequence on which it was started). Once fully Stop()'ed it may be
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// destroyed or restarted on another sequence.
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SequenceChecker origin_sequence_checker_;
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private:
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friend class BaseTimerTaskInternal;
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// Allocates a new |scheduled_task_| and posts it on the current sequence with
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// the given |delay|. |scheduled_task_| must be null. |scheduled_run_time_|
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// and |desired_run_time_| are reset to Now() + delay.
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void PostNewScheduledTask(TimeDelta delay);
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// Returns the task runner on which the task should be scheduled. If the
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// corresponding |task_runner_| field is null, the task runner for the current
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// sequence is returned.
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scoped_refptr<SequencedTaskRunner> GetTaskRunner();
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// Disable |scheduled_task_| and abandon it so that it no longer refers back
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// to this object.
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void AbandonScheduledTask();
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// Called by BaseTimerTaskInternal when the delayed task fires.
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void RunScheduledTask();
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// When non-null, the |scheduled_task_| was posted to call RunScheduledTask()
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// at |scheduled_run_time_|.
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BaseTimerTaskInternal* scheduled_task_;
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// Location in user code.
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Location posted_from_;
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// Delay requested by user.
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TimeDelta delay_;
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// |user_task_| is what the user wants to be run at |desired_run_time_|.
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base::Closure user_task_;
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// The time at which |scheduled_task_| is expected to fire. This time can be a
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// "zero" TimeTicks if the task must be run immediately.
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TimeTicks scheduled_run_time_;
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// The desired run time of |user_task_|. The user may update this at any time,
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// even if their previous request has not run yet. If |desired_run_time_| is
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// greater than |scheduled_run_time_|, a continuation task will be posted to
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// wait for the remaining time. This allows us to reuse the pending task so as
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// not to flood the delayed queues with orphaned tasks when the user code
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// excessively Stops and Starts the timer. This time can be a "zero" TimeTicks
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// if the task must be run immediately.
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TimeTicks desired_run_time_;
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// Repeating timers automatically post the task again before calling the task
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// callback.
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const bool is_repeating_;
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// If true, hold on to the |user_task_| closure object for reuse.
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const bool retain_user_task_;
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// The tick clock used to calculate the run time for scheduled tasks.
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const TickClock* const tick_clock_;
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// If true, |user_task_| is scheduled to run sometime in the future.
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bool is_running_;
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DISALLOW_COPY_AND_ASSIGN(Timer);
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};
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//-----------------------------------------------------------------------------
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// A simple, one-shot timer. See usage notes at the top of the file.
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class BASE_EXPORT OneShotTimer : public Timer {
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public:
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OneShotTimer() : OneShotTimer(nullptr) {}
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explicit OneShotTimer(const TickClock* tick_clock)
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: Timer(false, false, tick_clock) {}
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// Run the scheduled task immediately, and stop the timer. The timer needs to
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// be running.
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void FireNow();
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};
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//-----------------------------------------------------------------------------
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// A simple, repeating timer. See usage notes at the top of the file.
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class RepeatingTimer : public Timer {
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public:
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RepeatingTimer() : RepeatingTimer(nullptr) {}
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explicit RepeatingTimer(const TickClock* tick_clock)
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: Timer(true, true, tick_clock) {}
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RepeatingTimer(const Location& posted_from,
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TimeDelta delay,
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RepeatingClosure user_task)
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: Timer(posted_from, delay, std::move(user_task), true) {}
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RepeatingTimer(const Location& posted_from,
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TimeDelta delay,
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RepeatingClosure user_task,
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const TickClock* tick_clock)
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: Timer(posted_from, delay, std::move(user_task), true, tick_clock) {}
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};
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//-----------------------------------------------------------------------------
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// A simple, one-shot timer with the retained user task. See usage notes at the
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// top of the file.
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class RetainingOneShotTimer : public Timer {
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public:
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RetainingOneShotTimer() : RetainingOneShotTimer(nullptr) {}
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explicit RetainingOneShotTimer(const TickClock* tick_clock)
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: Timer(true, false, tick_clock) {}
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RetainingOneShotTimer(const Location& posted_from,
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TimeDelta delay,
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RepeatingClosure user_task)
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: Timer(posted_from, delay, std::move(user_task), false) {}
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RetainingOneShotTimer(const Location& posted_from,
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TimeDelta delay,
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RepeatingClosure user_task,
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const TickClock* tick_clock)
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: Timer(posted_from, delay, std::move(user_task), false, tick_clock) {}
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};
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//-----------------------------------------------------------------------------
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// A Delay timer is like The Button from Lost. Once started, you have to keep
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// calling Reset otherwise it will call the given method on the sequence it was
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// initially Reset() from.
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//
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// Once created, it is inactive until Reset is called. Once |delay| seconds have
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// passed since the last call to Reset, the callback is made. Once the callback
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// has been made, it's inactive until Reset is called again.
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//
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// If destroyed, the timeout is canceled and will not occur even if already
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// inflight.
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class DelayTimer {
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public:
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template <class Receiver>
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DelayTimer(const Location& posted_from,
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TimeDelta delay,
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Receiver* receiver,
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void (Receiver::*method)())
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: DelayTimer(posted_from, delay, receiver, method, nullptr) {}
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template <class Receiver>
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DelayTimer(const Location& posted_from,
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TimeDelta delay,
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Receiver* receiver,
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void (Receiver::*method)(),
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const TickClock* tick_clock)
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: timer_(posted_from,
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delay,
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BindRepeating(method, Unretained(receiver)),
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tick_clock) {}
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void Reset() { timer_.Reset(); }
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private:
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RetainingOneShotTimer timer_;
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DISALLOW_COPY_AND_ASSIGN(DelayTimer);
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};
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} // namespace base
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#endif // BASE_TIMER_TIMER_H_
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