| /* |
| * 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 |