| // Copyright 2017 The Abseil Authors. |
| // |
| // 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 |
| // |
| // https://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 ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_ |
| #define ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_ |
| |
| #include <cassert> |
| #include <cstddef> |
| #include <functional> |
| #include <queue> |
| #include <thread> // NOLINT(build/c++11) |
| #include <vector> |
| |
| #include "absl/base/thread_annotations.h" |
| #include "absl/synchronization/mutex.h" |
| |
| namespace absl { |
| namespace synchronization_internal { |
| |
| // A simple ThreadPool implementation for tests. |
| class ThreadPool { |
| public: |
| explicit ThreadPool(int num_threads) { |
| for (int i = 0; i < num_threads; ++i) { |
| threads_.push_back(std::thread(&ThreadPool::WorkLoop, this)); |
| } |
| } |
| |
| ThreadPool(const ThreadPool &) = delete; |
| ThreadPool &operator=(const ThreadPool &) = delete; |
| |
| ~ThreadPool() { |
| { |
| absl::MutexLock l(&mu_); |
| for (size_t i = 0; i < threads_.size(); i++) { |
| queue_.push(nullptr); // Shutdown signal. |
| } |
| } |
| for (auto &t : threads_) { |
| t.join(); |
| } |
| } |
| |
| // Schedule a function to be run on a ThreadPool thread immediately. |
| void Schedule(std::function<void()> func) { |
| assert(func != nullptr); |
| absl::MutexLock l(&mu_); |
| queue_.push(std::move(func)); |
| } |
| |
| private: |
| bool WorkAvailable() const ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) { |
| return !queue_.empty(); |
| } |
| |
| void WorkLoop() { |
| while (true) { |
| std::function<void()> func; |
| { |
| absl::MutexLock l(&mu_); |
| mu_.Await(absl::Condition(this, &ThreadPool::WorkAvailable)); |
| func = std::move(queue_.front()); |
| queue_.pop(); |
| } |
| if (func == nullptr) { // Shutdown signal. |
| break; |
| } |
| func(); |
| } |
| } |
| |
| absl::Mutex mu_; |
| std::queue<std::function<void()>> queue_ ABSL_GUARDED_BY(mu_); |
| std::vector<std::thread> threads_; |
| }; |
| |
| } // namespace synchronization_internal |
| } // namespace absl |
| |
| #endif // ABSL_SYNCHRONIZATION_INTERNAL_THREAD_POOL_H_ |