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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_TIMER_WALL_CLOCK_TIMER_H_
#define BASE_TIMER_WALL_CLOCK_TIMER_H_
#include "base/base_export.h"
#include "base/bind.h"
#include "base/callback.h"
#include "base/location.h"
#include "base/memory/raw_ptr.h"
#include "base/power_monitor/power_observer.h"
#include "base/time/default_clock.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
namespace base {
class Clock;
class TickClock;
// WallClockTimer is based on OneShotTimer and provides a simple timer API
// which is mostly similar to OneShotTimer's API. The main difference is that
// WallClockTimer is using Time (which is system-dependent) to schedule task.
// WallClockTimer calls you back once scheduled time has come.
//
// Comparison with OneShotTimer: WallClockTimer runs |user_task_| after |delay_|
// expires according to usual time, while OneShotTimer runs |user_task_| after
// |delay_| expires according to TimeTicks which may freeze on some platforms
// when power suspends (desktop falls asleep). On platforms where TimeTicks
// don't freeze, the WallClockTimer has the same behavior as OneShotTimer.
//
// The API is not thread safe. All methods must be called from the same
// sequence (not necessarily the construction sequence), except for the
// destructor.
// - The destructor may be called from any sequence when the timer is not
// running and there is no scheduled task active.
class BASE_EXPORT WallClockTimer : public PowerSuspendObserver {
public:
// Constructs a timer. Start() must be called later to start the timer.
// If |clock| is provided, it's used instead of
// DefaultClock::GetInstance() to calulate timer's delay. If |tick_clock|
// is provided, it's used instead of TimeTicks::Now() to get TimeTicks when
// scheduling tasks.
WallClockTimer();
WallClockTimer(const Clock* clock, const TickClock* tick_clock);
WallClockTimer(const WallClockTimer&) = delete;
WallClockTimer& operator=(const WallClockTimer&) = delete;
~WallClockTimer() override;
// Starts the timer to run at the given |desired_run_time|. If the timer is
// already running, it will be replaced to call the given |user_task|.
virtual void Start(const Location& posted_from,
Time desired_run_time,
OnceClosure user_task);
// Starts the timer to run at the given |desired_run_time|. If the timer is
// already running, it will be replaced to call a task formed from
// |receiver|->*|method|.
template <class Receiver>
void Start(const Location& posted_from,
Time desired_run_time,
Receiver* receiver,
void (Receiver::*method)()) {
Start(posted_from, desired_run_time,
BindOnce(method, Unretained(receiver)));
}
// Stops the timer. It is a no-op if the timer is not running.
void Stop();
// Returns true if the timer is running.
bool IsRunning() const;
// PowerSuspendObserver:
void OnResume() override;
Time desired_run_time() const { return desired_run_time_; }
private:
void AddObserver();
void RemoveObserver();
// Actually run scheduled task
void RunUserTask();
// Returns the current time count.
Time Now() const;
bool observer_added_ = false;
// Location in user code.
Location posted_from_;
// The desired run time of |user_task_|.
Time desired_run_time_;
OnceClosure user_task_;
// Timer which should notify to run task in the period while system awake
OneShotTimer timer_;
// The clock used to calculate the run time for scheduled tasks.
const raw_ptr<const Clock> clock_ = DefaultClock::GetInstance();
};
} // namespace base
#endif // BASE_TIMER_WALL_CLOCK_TIMER_H_
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