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// Copyright 2014 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 <memory>
#include "base/files/file_descriptor_watcher_posix.h"
#include "base/macros.h"
#include "base/memory/scoped_refptr.h"
#include "base/memory/weak_ptr.h"
#include "base/threading/sequenced_task_runner_handle.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
namespace base {
struct PendingTask;
namespace timers {
// The class implements a timer that is capable of waking the system up from a
// suspended state. For example, this is useful for running tasks that are
// needed for maintaining network connectivity, like sending heartbeat messages.
// Currently, this feature is only available on Chrome OS systems running linux
// version 3.11 or higher. On all other platforms, the SimpleAlarmTimer behaves
// exactly the same way as a regular Timer.
// A SimpleAlarmTimer instance can only be used from the sequence on which it
// was instantiated. Start() and Stop() must be called from a thread that
// supports FileDescriptorWatcher.
// A SimpleAlarmTimer only fires once but remembers the task that it was given
// even after it has fired. Useful if you want to run the same task multiple
// times but not at a regular interval.
class SimpleAlarmTimer : public base::RetainingOneShotTimer {
~SimpleAlarmTimer() override;
// Timer overrides.
void Stop() override;
void Reset() override;
// Called when |alarm_fd_| is readable without blocking. Reads data from
// |alarm_fd_| and calls OnTimerFired().
void OnAlarmFdReadableWithoutBlocking();
// Called when the timer fires. Runs the callback.
void OnTimerFired();
// Tracks whether the timer has the ability to wake the system up from
// suspend. This is a runtime check because we won't know if the system
// supports being woken up from suspend until the constructor actually tries
// to set it up.
bool CanWakeFromSuspend() const;
// Timer file descriptor.
const int alarm_fd_;
// Watches |alarm_fd_|.
std::unique_ptr<base::FileDescriptorWatcher::Controller> alarm_fd_watcher_;
// Posts tasks to the sequence on which this AlarmTimer was instantiated.
const scoped_refptr<base::SequencedTaskRunner> origin_task_runner_ =
// Keeps track of the user task we want to run. A new one is constructed every
// time Reset() is called.
std::unique_ptr<base::PendingTask> pending_task_;
// Used to invalidate pending callbacks.
base::WeakPtrFactory<SimpleAlarmTimer> weak_factory_;
} // namespace timers