components/timers/alarm_timer.h

   1 // Copyright 2014 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 #ifndef COMPONENTS_TIMER_ALARM_TIMER_H_
   6 #define COMPONENTS_TIMER_ALARM_TIMER_H_
   7
   8 #include "base/callback.h"
   9 #include "base/macros.h"
  10 #include "base/memory/ref_counted.h"
  11 #include "base/memory/weak_ptr.h"
  12 #include "base/message_loop/message_loop.h"
  13 #include "base/time/time.h"
  14 #include "base/timer/timer.h"
  15
  16 namespace base {
  17 struct PendingTask;
  18 }
  19
  20 namespace timers {
  21 // The class implements a timer that is capable of waking the system up from a
  22 // suspended state.  For example, this is useful for running tasks that are
  23 // needed for maintaining network connectivity, like sending heartbeat messages.
  24 // Currently, this feature is only available on Chrome OS systems running linux
  25 // version 3.11 or higher.  On all other platforms, the AlarmTimer behaves
  26 // exactly the same way as a regular Timer.
  27 class AlarmTimer : public base::Timer,
  28                    public base::MessageLoop::DestructionObserver {
  29  public:
  30   // The delegate is responsible for managing the system level details for
  31   // actually setting up and monitoring a timer that is capable of waking the
  32   // system from suspend.  This class is reference counted because it may need
  33   // to outlive the timer in order to clean up after itself.
  34   class Delegate : public base::RefCountedThreadSafe<Delegate> {
  35    public:
  36     // Initializes the timer.  Should return true iff the system has timers that
  37     // can wake it up from suspend.  Will only be called once.
  38     virtual bool Init(base::WeakPtr<AlarmTimer> timer) = 0;
  39
  40     // Stops the currently running timer.  It should be safe to call this more
  41     // than once.
  42     virtual void Stop() = 0;
  43
  44     // Resets the timer to fire after |delay| has passed.  Cancels any
  45     // pre-existing delay.
  46     virtual void Reset(base::TimeDelta delay) = 0;
  47
  48    protected:
  49     virtual ~Delegate() {}
  50
  51    private:
  52     friend class base::RefCountedThreadSafe<Delegate>;
  53   };
  54
  55   AlarmTimer(bool retain_user_task, bool is_repeating);
  56
  57   AlarmTimer(const tracked_objects::Location& posted_from,
  58              base::TimeDelta delay,
  59              const base::Closure& user_task,
  60              bool is_repeating);
  61
  62   ~AlarmTimer() override;
  63
  64   bool can_wake_from_suspend() { return can_wake_from_suspend_; }
  65
  66   // Timer overrides.
  67   void Stop() override;
  68   void Reset() override;
  69
  70   // MessageLoop::DestructionObserver overrides.
  71   void WillDestroyCurrentMessageLoop() override;
  72
  73   // Must be called by the delegate to indicate that the timer has fired and
  74   // that the user task should be run.
  75   void OnTimerFired();
  76
  77  private:
  78   // Initializes the timer with the appropriate delegate.
  79   void Init();
  80
  81   // Delegate that will manage actually setting the timer.
  82   scoped_refptr<Delegate> delegate_;
  83
  84   // Keeps track of the user task we want to run.  A new one is constructed
  85   // every time Reset() is called.
  86   scoped_ptr<base::PendingTask> pending_task_;
  87
  88   // Tracks whether the timer has the ability to wake the system up from
  89   // suspend.  This is a runtime check because we won't know if the system
  90   // supports being woken up from suspend until the delegate actually tries to
  91   // set it up.
  92   bool can_wake_from_suspend_;
  93
  94   // Pointer to the message loop that started the timer.  Used to track the
  95   // destruction of that message loop.
  96   base::MessageLoop* origin_message_loop_;
  97
  98   base::WeakPtrFactory<AlarmTimer> weak_factory_;
  99
 100   DISALLOW_COPY_AND_ASSIGN(AlarmTimer);
 101 };
 102
 103 }  // namespace timers
 104
 105 #endif  // COMPONENTS_TIMER_ALARM_TIMER_H_