chromium/media/audio/alive_checker.h

// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_AUDIO_ALIVE_CHECKER_H_
#define MEDIA_AUDIO_ALIVE_CHECKER_H_

#include <memory>

#include "base/functional/callback_forward.h"
#include "base/memory/scoped_refptr.h"
#include "base/memory/weak_ptr.h"
#include "base/task/sequenced_task_runner.h"
#include "base/task/single_thread_task_runner.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "media/audio/power_observer_helper.h"
#include "media/base/media_export.h"

namespace media {

// A class that checks if a client that is expected to have regular activity
// is alive. For example, audio streams expect regular callbacks from the
// operating system. The client informs regularly that it's alive by calling
// NotifyAlive(). At a certain interval the AliveChecker checks that it has been
// notified within a timeout period. If not, it runs a callback to inform about
// detecting dead. The callback is run once and further checking is stopped at
// detection. Checking can be restarted if desired.
//
// The AliveChecker can pause checking when the machine is suspending, i.e.
// between suspend and resume notification from base::PowerMonitor. Checking
// during this period can cause false positives. Shorter timeout gives higher
// risk of false positives.
//
// It lives on the task runner it's created on; all functions except
// NotifyAlive() must be called on it. NotifyAlive() can be called on any task
// runner.
//
// It stops at the first NotifyAlive() call if
// |stop_at_first_alive_notification| is specified at construction time. This
// can be useful for example if the platform doesn't support suspend/resume
// notifications, as Linux.
class MEDIA_EXPORT AliveChecker { … };

}  // namespace media

#endif  // MEDIA_AUDIO_ALIVE_CHECKER_H_