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/*
* Copyright (C) 2020 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.
*/
#ifndef ANDROID_VIBRATOR_CALLBACK_SCHEDULER_H
#define ANDROID_VIBRATOR_CALLBACK_SCHEDULER_H
#include <android-base/thread_annotations.h>
#include <chrono>
#include <condition_variable>
#include <queue>
#include <thread>
namespace android {
namespace vibrator {
// Wrapper for a callback to be executed after a delay.
class DelayedCallback {
public:
using Timestamp = std::chrono::time_point<std::chrono::steady_clock>;
DelayedCallback(std::function<void()> callback, std::chrono::milliseconds delay)
: mCallback(callback), mExpiration(std::chrono::steady_clock::now() + delay) {}
~DelayedCallback() = default;
void run() const;
bool isExpired() const;
Timestamp getExpiration() const;
// Compare by expiration time, where A < B when A expires first.
bool operator<(const DelayedCallback& other) const;
bool operator>(const DelayedCallback& other) const;
private:
std::function<void()> mCallback;
Timestamp mExpiration;
};
// Schedules callbacks to be executed after a delay.
class CallbackScheduler {
public:
CallbackScheduler() : mCallbackThread(nullptr), mFinished(false) {}
virtual ~CallbackScheduler();
virtual void schedule(std::function<void()> callback, std::chrono::milliseconds delay);
private:
std::condition_variable_any mCondition;
std::mutex mMutex;
// Lazily instantiated only at the first time this scheduler is used.
std::unique_ptr<std::thread> mCallbackThread;
// Used to quit the callback thread when this instance is being destroyed.
bool mFinished GUARDED_BY(mMutex);
// Priority queue with reverse comparator, so tasks that expire first will be on top.
std::priority_queue<DelayedCallback, std::vector<DelayedCallback>,
std::greater<DelayedCallback>>
mQueue GUARDED_BY(mMutex);
void loop();
};
}; // namespace vibrator
}; // namespace android
#endif // ANDROID_VIBRATOR_CALLBACK_SCHEDULER_H
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