57 lines
1.5 KiB
C++
57 lines
1.5 KiB
C++
// Copyright 2022 Google LLC. All rights reserved.
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//
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file or at
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// https://developers.google.com/open-source/licenses/bsd
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#ifndef PACKAGER_FILE_THREAD_POOL_H_
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#define PACKAGER_FILE_THREAD_POOL_H_
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#include <functional>
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#include <queue>
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#include <absl/base/thread_annotations.h>
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#include <absl/synchronization/mutex.h>
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#include <packager/macros.h>
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namespace shaka {
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/// A simple thread pool. We used to get this from Chromium base::, but there
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/// is no replacement in the C++ standard library nor in absl.
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/// (As of June 2022.) The pool will grow when there are no threads available
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/// to handle a task, and it will shrink when a thread is idle for too long.
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class ThreadPool {
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public:
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typedef std::function<void()> Task;
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ThreadPool();
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~ThreadPool();
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/// Find or spawn a worker thread to handle |task|.
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/// @param task A potentially long-running task to be handled by the pool.
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void PostTask(const Task& task);
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static ThreadPool instance;
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private:
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/// Stop handing out tasks to workers, wake up all threads, and make them
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/// exit.
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void Terminate();
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Task WaitForTask();
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void ThreadMain();
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absl::Mutex mutex_;
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absl::CondVar tasks_available_ ABSL_GUARDED_BY(mutex_);
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std::queue<Task> tasks_ ABSL_GUARDED_BY(mutex_);
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size_t num_idle_threads_ ABSL_GUARDED_BY(mutex_);
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bool terminated_ ABSL_GUARDED_BY(mutex_);
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DISALLOW_COPY_AND_ASSIGN(ThreadPool);
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};
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} // namespace shaka
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#endif // PACKAGER_FILE_THREAD_POOL_H_
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