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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 <semaphore.h>
#include <chrono>
#include <condition_variable>
#include <thread>
#include "../Clock.h"
#include <android-base/thread_annotations.h>
#include <scheduler/Time.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(std::string name, const Interval& interval, const ResetCallback& resetCallback,
const TimeoutCallback& timeoutCallback,
std::unique_ptr<android::Clock> clock = std::make_unique<SteadyClock>());
~OneShotTimer();
Duration interval() const { return mInterval; }
// 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();
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();
// Checks whether mResetTriggered and mStopTriggered were set and updates
// mState if so.
TimerState checkForResetAndStop(TimerState state);
// Thread waiting for timer to expire.
std::thread mThread;
// Clock object for the timer. Mocked in unit tests.
std::unique_ptr<android::Clock> mClock;
// Semaphore to keep mThread synchronized.
sem_t mSemaphore;
// Timer's name.
std::string mName;
// 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;
// After removing lock guarding mState, the state can be now accessed at
// any time. Keep a bool if the reset or stop were requested, and occasionally
// check in the main loop if they were.
std::atomic<bool> mResetTriggered = false;
std::atomic<bool> mStopTriggered = false;
std::atomic<bool> mWaiting = false;
std::atomic<std::chrono::steady_clock::time_point> mLastResetTime;
};
} // namespace scheduler
} // namespace android
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