[Chromecast] Add an alarm manager for firing events on wall clock time.

chromecast/base/alarm_manager.cc

+// Copyright 2017 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/alarm_manager.h"
+
+#include "base/memory/ptr_util.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "base/time/default_clock.h"
+
+namespace chromecast {
+
+namespace {
+// How often to poll the clock.
+int kClockPollInterval = 5;
+}  // namespace
+
+// AlarmInfo is for recording the time and task runner for the alarm.
+AlarmManager::AlarmInfo::AlarmInfo(
+    base::Time time,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
+  time_ = time;
+  task_runner_ = task_runner;
+}
+
+AlarmManager::AlarmInfo::~AlarmInfo() {}
+
+AlarmManager::AlarmManager(std::unique_ptr<base::Clock> clock)
+    : clock_(std::move(clock)), weak_factory_(this) {
+  Start();
+}
+
+AlarmManager::AlarmManager()
+    : clock_(new base::DefaultClock()), weak_factory_(this) {
+  Start();
+}
+
+AlarmManager::~AlarmManager() {
+  Stop();
+}
+
+void AlarmManager::Start() {
+  clock_tick_timer_.reset(new base::RepeatingTimer());
+  base::TimeDelta polling_frequency =
+      base::TimeDelta::FromSeconds(kClockPollInterval);
+  clock_tick_timer_->Start(
+      FROM_HERE, polling_frequency,
+      base::Bind(&AlarmManager::CheckAlarm, weak_factory_.GetWeakPtr()));
+}
+
+void AlarmManager::Stop() {
+  clock_tick_timer_.reset(nullptr);
+}
+
+void AlarmManager::AddAlarm(AlarmDelegate* delegate, base::Time time) {
+  base::AutoLock lock(alarms_lock_);
+  next_alarm_.push(time);
+  std::unique_ptr<AlarmInfo> info =
+      base::MakeUnique<AlarmInfo>(time, base::ThreadTaskRunnerHandle::Get());
+  alarms_[delegate] = std::move(info);
+}
+void AlarmManager::RemoveAlarm(AlarmDelegate* delegate) {
+  base::AutoLock lock(alarms_lock_);
+  alarms_.erase(delegate);
+}
+
+void AlarmManager::CheckAlarm() {
+  base::AutoLock lock(alarms_lock_);
+  base::Time now = clock_->Now();
+  if (next_alarm_.empty() || now < next_alarm_.top()) {
+    return;
+  }
+
+  // An alarm should fire.
+  while ((!next_alarm_.empty()) && now >= next_alarm_.top()) {
+    // Clear all the elapsed dates.
+    next_alarm_.pop();
+  }
+
+  // Fire appropriate alarms.
+  for (auto alarm = alarms_.begin(); alarm != alarms_.end();) {
+    if (now >= alarm->second->time_) {
+      alarm->second->task_runner_->PostTask(
+          FROM_HERE, base::Bind(&AlarmDelegate::OnAlarmFire,
+                                base::Unretained(alarm->first)));
+      alarm = alarms_.erase(alarm);
+    } else {
+      ++alarm;
+    }
+  }
+}
+
+}  // chromecast