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/*
* Copyright 2021 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 <Tracing/LocklessStack.h>
#include <android-base/thread_annotations.h>
#include <ftl/small_vector.h>
#include <semaphore.h>
#include <utils/Singleton.h>
#include <mutex>
#include <queue>
#include <thread>
namespace android {
// Executes tasks off the main thread.
class BackgroundExecutor : public Singleton<BackgroundExecutor> {
public:
BackgroundExecutor();
~BackgroundExecutor();
using Callbacks = ftl::SmallVector<std::function<void()>, 10>;
// Queues callbacks onto a work queue to be executed by a background thread.
// Note that this is not thread-safe - a single producer is assumed.
void sendCallbacks(Callbacks&& tasks);
private:
sem_t mSemaphore;
std::atomic_bool mDone = false;
// Sequence number for work items.
// Work items are batched by sequence number. Work items for earlier sequence numbers are
// executed first. Work items with the same sequence number are executed in the same order they
// were added to the stack (meaning the stack must reverse the order after popping from the
// queue)
int32_t mSequence = 0;
struct Work {
int32_t sequence = 0;
Callbacks tasks;
};
LocklessStack<Work> mWorks;
std::thread mThread;
};
} // namespace android
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