| // Copyright 2015 The Chromium Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include "chromecast/base/system_time_change_notifier.h" |
| |
| #include "base/location.h" |
| #include "base/sequenced_task_runner.h" |
| |
| namespace chromecast { |
| |
| namespace { |
| |
| // Limits for periodic system time monitoring. |
| const int kLimitForMonitorPer1Sec = 60; // 1 minute |
| const int kLimitForMonitorPer10Sec = 600; // 10 minutes |
| |
| } // namespace |
| |
| SystemTimeChangeNotifier::SystemTimeChangeNotifier() |
| : observer_list_(new base::ObserverListThreadSafe<Observer>()) { |
| } |
| |
| SystemTimeChangeNotifier::~SystemTimeChangeNotifier() { |
| } |
| |
| void SystemTimeChangeNotifier::AddObserver(Observer* observer) { |
| observer_list_->AddObserver(observer); |
| } |
| |
| void SystemTimeChangeNotifier::RemoveObserver(Observer* observer) { |
| observer_list_->RemoveObserver(observer); |
| } |
| |
| void SystemTimeChangeNotifier::NotifySystemTimeChanged() { |
| observer_list_->Notify(FROM_HERE, &Observer::OnSystemTimeChanged); |
| } |
| |
| SystemTimeChangeNotifierPeriodicMonitor:: |
| SystemTimeChangeNotifierPeriodicMonitor( |
| const scoped_refptr<base::SequencedTaskRunner>& task_runner) |
| : task_runner_(task_runner), |
| weak_factory_(this) { |
| DCHECK(task_runner_); |
| } |
| |
| SystemTimeChangeNotifierPeriodicMonitor:: |
| ~SystemTimeChangeNotifierPeriodicMonitor() { |
| } |
| |
| void SystemTimeChangeNotifierPeriodicMonitor::Initialize() { |
| base::Time now = Now(); |
| ResetTimeAndLimits(now); |
| ScheduleNextMonitor(now); |
| } |
| |
| void SystemTimeChangeNotifierPeriodicMonitor::Finalize() { |
| } |
| |
| void SystemTimeChangeNotifierPeriodicMonitor::ResetTimeAndLimits( |
| base::Time now) { |
| // ScheduleNextMonitor() will adjust actual expected_system_time. |
| expected_system_time_ = now; |
| monitoring_limit_time_1sec_ = |
| now + base::TimeDelta::FromSeconds(kLimitForMonitorPer1Sec); |
| monitoring_limit_time_10sec_ = |
| monitoring_limit_time_1sec_ + |
| base::TimeDelta::FromSeconds(kLimitForMonitorPer10Sec); |
| } |
| |
| void SystemTimeChangeNotifierPeriodicMonitor::ScheduleNextMonitor( |
| base::Time now) { |
| base::TimeDelta next_checking_interval = |
| now <= monitoring_limit_time_1sec_ ? base::TimeDelta::FromSeconds(1) : |
| now <= monitoring_limit_time_10sec_ ? base::TimeDelta::FromSeconds(10) : |
| base::TimeDelta::FromMinutes(10); |
| // Adjusting expected_system_time based on now cannot detect continuous system |
| // time drift (false negative), but tolerates task delay (false positive). |
| // Task delay is expected more than system time drift. |
| expected_system_time_ = now + next_checking_interval; |
| task_runner_->PostDelayedTask( |
| FROM_HERE, |
| base::Bind(&SystemTimeChangeNotifierPeriodicMonitor::CheckSystemTime, |
| weak_factory_.GetWeakPtr()), |
| next_checking_interval); |
| } |
| |
| void SystemTimeChangeNotifierPeriodicMonitor::CheckSystemTime() { |
| base::Time now = Now(); |
| const base::TimeDelta kInterval10Seconds(base::TimeDelta::FromSeconds(10)); |
| if (now < expected_system_time_ - kInterval10Seconds || |
| now > expected_system_time_ + kInterval10Seconds) { // Time changed! |
| ResetTimeAndLimits(now); |
| NotifySystemTimeChanged(); |
| } |
| ScheduleNextMonitor(now); |
| } |
| |
| base::Time SystemTimeChangeNotifierPeriodicMonitor::Now() const { |
| if (!fake_now_.is_null()) |
| return fake_now_; |
| return base::Time::Now(); |
| } |
| |
| } // namespace chromecast |