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/*
* Copyright 2018 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <chrono>
#include <condition_variable>
#include <thread>
#include <android-base/thread_annotations.h>
namespace android {
namespace scheduler {
/*
* Class that sets off a timer for a given interval, and fires a callback when the
* interval expires.
*/
class OneShotTimer {
public:
using Interval = std::chrono::milliseconds;
using ResetCallback = std::function<void()>;
using TimeoutCallback = std::function<void()>;
OneShotTimer(const Interval& interval, const ResetCallback& resetCallback,
const TimeoutCallback& timeoutCallback);
~OneShotTimer();
// Initializes and turns on the idle timer.
void start();
// Stops the idle timer and any held resources.
void stop();
// Resets the wakeup time and fires the reset callback.
void reset();
std::string dump() const;
private:
// Enum to track in what state is the timer.
enum class TimerState {
// The internal timer thread has been destroyed, and no state is
// tracked.
// Possible state transitions: RESET
STOPPED = 0,
// An external thread has just reset this timer.
// If there is a reset callback, then that callback is fired.
// Possible state transitions: STOPPED, WAITING
RESET = 1,
// This timer is waiting for the timeout interval to expire.
// Possible state transaitions: STOPPED, RESET, IDLE
WAITING = 2,
// The timeout interval has expired, so we are sleeping now.
// Possible state transaitions: STOPPED, RESET
IDLE = 3
};
// Function that loops until the condition for stopping is met.
void loop();
// Thread waiting for timer to expire.
std::thread mThread;
// Condition used to notify mThread.
std::condition_variable_any mCondition;
// Lock used for synchronizing the waiting thread with the application thread.
std::mutex mMutex;
// Current timer state
TimerState mState GUARDED_BY(mMutex) = TimerState::RESET;
// Interval after which timer expires.
const Interval mInterval;
// Callback that happens when timer resets.
const ResetCallback mResetCallback;
// Callback that happens when timer expires.
const TimeoutCallback mTimeoutCallback;
};
} // namespace scheduler
} // namespace android
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