chromecast/base/system_time_change_notifier.h

   1 // Copyright 2015 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 CHROMECAST_BASE_SYSTEM_TIME_CHANGE_NOTIFIER_H_
   6 #define CHROMECAST_BASE_SYSTEM_TIME_CHANGE_NOTIFIER_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/observer_list_threadsafe.h"
  13 #include "base/time/time.h"
  14
  15 namespace base {
  16 class SequencedTaskRunner;
  17 }
  18
  19 namespace chromecast {
  20
  21 // Abstract class to notify system time changes.
  22 class SystemTimeChangeNotifier {
  23  public:
  24   class Observer {
  25    public:
  26     // Called when current system time has changed.
  27     virtual void OnSystemTimeChanged() = 0;
  28
  29    protected:
  30     virtual ~Observer() {}
  31   };
  32
  33   virtual ~SystemTimeChangeNotifier();
  34
  35   virtual void Initialize() = 0;
  36   virtual void Finalize() = 0;
  37
  38   void AddObserver(Observer* observer);
  39   void RemoveObserver(Observer* observer);
  40
  41  protected:
  42   SystemTimeChangeNotifier();
  43
  44   // Implementations are expected to call this to notify system time changes.
  45   void NotifySystemTimeChanged();
  46
  47  private:
  48   scoped_refptr<base::ObserverListThreadSafe<Observer>> observer_list_;
  49
  50   DISALLOW_COPY_AND_ASSIGN(SystemTimeChangeNotifier);
  51 };
  52
  53 // Default implementation of SystemTimeChangeNotifier for most platform.
  54 // It monitors system time changes periodically and notifies if the current
  55 // system time is different from the expected one by more than 10 seconds.
  56 // After reboot or system time has changed, it checks for time changes every
  57 // second for first 1 minute. Then, checks every 10 seconds for next 10 minutes.
  58 // Then, checks every 10 minutes.
  59 class SystemTimeChangeNotifierPeriodicMonitor
  60     : public SystemTimeChangeNotifier {
  61  public:
  62   explicit SystemTimeChangeNotifierPeriodicMonitor(
  63       const scoped_refptr<base::SequencedTaskRunner>& task_runner);
  64   ~SystemTimeChangeNotifierPeriodicMonitor() override;
  65
  66   // SystemTimeChangeNotifier implementation:
  67   void Initialize() override;
  68   void Finalize() override;
  69
  70   // For unittests.
  71   void set_fake_now_for_testing(base::Time now) { fake_now_ = now; }
  72
  73  private:
  74   // Helper functions to monitor system time changes.
  75   void ResetTimeAndLimits(base::Time now);
  76   void ScheduleNextMonitor(base::Time now);
  77   void CheckSystemTime();
  78
  79   // Returns base::Time::Now() unless fake_now is set.
  80   base::Time Now() const;
  81
  82   const scoped_refptr<base::SequencedTaskRunner> task_runner_;
  83
  84   base::Time expected_system_time_;
  85   base::Time monitoring_limit_time_1sec_;
  86   base::Time monitoring_limit_time_10sec_;
  87
  88   base::Time fake_now_;
  89
  90   base::WeakPtrFactory<SystemTimeChangeNotifierPeriodicMonitor> weak_factory_;
  91
  92   DISALLOW_COPY_AND_ASSIGN(SystemTimeChangeNotifierPeriodicMonitor);
  93 };
  94
  95 }  // namespace chromecast
  96
  97 #endif  // CHROMECAST_BASE_SYSTEM_TIME_CHANGE_NOTIFIER_H_