Import roar11's thread pool
See https://roar11.com/2016/01/a-platform-independent-thread-pool-using-c14/
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239
src/roar11/ThreadPool.hpp
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239
src/roar11/ThreadPool.hpp
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/**
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* The ThreadPool class.
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* Keeps a set of threads constantly waiting to execute incoming jobs.
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*/
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#pragma once
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#ifndef THREADPOOL_HPP
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#define THREADPOOL_HPP
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#include "ThreadSafeQueue.hpp"
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#include <algorithm>
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#include <atomic>
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#include <cstdint>
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#include <functional>
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#include <future>
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#include <memory>
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#include <thread>
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#include <type_traits>
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#include <utility>
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#include <vector>
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namespace roar11
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{
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class ThreadPool
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{
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private:
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class IThreadTask
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{
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public:
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IThreadTask(void) = default;
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virtual ~IThreadTask(void) = default;
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IThreadTask(const IThreadTask& rhs) = delete;
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IThreadTask& operator=(const IThreadTask& rhs) = delete;
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IThreadTask(IThreadTask&& other) = default;
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IThreadTask& operator=(IThreadTask&& other) = default;
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/**
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* Run the task.
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*/
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virtual void execute() = 0;
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};
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template <typename Func>
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class ThreadTask: public IThreadTask
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{
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public:
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ThreadTask(Func&& func)
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:m_func{std::move(func)}
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{
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}
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~ThreadTask(void) override = default;
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ThreadTask(const ThreadTask& rhs) = delete;
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ThreadTask& operator=(const ThreadTask& rhs) = delete;
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ThreadTask(ThreadTask&& other) = default;
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ThreadTask& operator=(ThreadTask&& other) = default;
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/**
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* Run the task.
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*/
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void execute() override
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{
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m_func();
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}
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private:
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Func m_func;
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};
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public:
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/**
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* A wrapper around a std::future that adds the behavior of futures returned from std::async.
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* Specifically, this object will block and wait for execution to finish before going out of scope.
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*/
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template <typename T>
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class TaskFuture
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{
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public:
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TaskFuture(std::future<T>&& future)
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:m_future{std::move(future)}
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{
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}
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TaskFuture(const TaskFuture& rhs) = delete;
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TaskFuture& operator=(const TaskFuture& rhs) = delete;
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TaskFuture(TaskFuture&& other) = default;
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TaskFuture& operator=(TaskFuture&& other) = default;
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~TaskFuture(void)
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{
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if(m_future.valid())
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{
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m_future.get();
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}
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}
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auto get(void)
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{
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return m_future.get();
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}
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private:
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std::future<T> m_future;
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};
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public:
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/**
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* Constructor.
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*/
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ThreadPool(void)
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:ThreadPool{std::max(std::thread::hardware_concurrency(), 2u) - 1u}
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{
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/*
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* Always create at least one thread. If hardware_concurrency() returns 0,
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* subtracting one would turn it to UINT_MAX, so get the maximum of
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* hardware_concurrency() and 2 before subtracting 1.
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*/
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}
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/**
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* Constructor.
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*/
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explicit ThreadPool(const std::uint32_t numThreads)
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:m_done{false},
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m_workQueue{},
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m_threads{}
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{
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try
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{
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for(std::uint32_t i = 0u; i < numThreads; ++i)
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{
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m_threads.emplace_back(&ThreadPool::worker, this);
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}
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}
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catch(...)
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{
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destroy();
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throw;
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}
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}
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/**
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* Non-copyable.
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*/
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ThreadPool(const ThreadPool& rhs) = delete;
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/**
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* Non-assignable.
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*/
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ThreadPool& operator=(const ThreadPool& rhs) = delete;
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/**
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* Destructor.
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*/
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~ThreadPool(void)
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{
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destroy();
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}
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/**
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* Submit a job to be run by the thread pool.
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*/
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template <typename Func, typename... Args>
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auto submit(Func&& func, Args&&... args)
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{
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auto boundTask = std::bind(std::forward<Func>(func), std::forward<Args>(args)...);
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using ResultType = std::result_of_t<decltype(boundTask)()>;
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using PackagedTask = std::packaged_task<ResultType()>;
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using TaskType = ThreadTask<PackagedTask>;
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PackagedTask task{std::move(boundTask)};
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TaskFuture<ResultType> result{task.get_future()};
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m_workQueue.push(std::make_unique<TaskType>(std::move(task)));
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return result;
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}
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private:
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/**
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* Constantly running function each thread uses to acquire work items from the queue.
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*/
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void worker(void)
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{
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while(!m_done)
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{
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std::unique_ptr<IThreadTask> pTask{nullptr};
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if(m_workQueue.waitPop(pTask))
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{
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pTask->execute();
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}
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}
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}
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/**
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* Invalidates the queue and joins all running threads.
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*/
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void destroy(void)
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{
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m_done = true;
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m_workQueue.invalidate();
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for(auto& thread : m_threads)
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{
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if(thread.joinable())
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{
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thread.join();
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}
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}
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}
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private:
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std::atomic_bool m_done;
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ThreadSafeQueue<std::unique_ptr<IThreadTask>> m_workQueue;
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std::vector<std::thread> m_threads;
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};
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namespace DefaultThreadPool
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{
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/**
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* Get the default thread pool for the application.
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* This pool is created with std::thread::hardware_concurrency() - 1 threads.
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*/
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inline ThreadPool& getThreadPool(void)
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{
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static ThreadPool defaultPool;
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return defaultPool;
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}
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/**
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* Submit a job to the default thread pool.
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*/
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template <typename Func, typename... Args>
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inline auto submitJob(Func&& func, Args&&... args)
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{
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return getThreadPool().submit(std::forward<Func>(func), std::forward<Args>(args)...);
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}
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}
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}
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#endif
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134
src/roar11/ThreadSafeQueue.hpp
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134
src/roar11/ThreadSafeQueue.hpp
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@ -0,0 +1,134 @@
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/**
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* The ThreadSafeQueue class.
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* Provides a wrapper around a basic queue to provide thread safety.
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*/
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#pragma once
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#ifndef THREADSAFEQUEUE_HPP
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#define THREADSAFEQUEUE_HPP
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#include <atomic>
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#include <condition_variable>
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#include <mutex>
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#include <queue>
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#include <utility>
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namespace roar11
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{
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template <typename T>
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class ThreadSafeQueue
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{
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public:
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/**
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* Destructor.
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*/
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~ThreadSafeQueue(void)
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{
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invalidate();
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}
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/**
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* Attempt to get the first value in the queue.
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* Returns true if a value was successfully written to the out parameter, false otherwise.
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*/
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bool tryPop(T& out)
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{
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std::lock_guard<std::mutex> lock{m_mutex};
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if(m_queue.empty() || !m_valid)
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{
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return false;
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}
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out = std::move(m_queue.front());
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m_queue.pop();
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return true;
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}
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/**
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* Get the first value in the queue.
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* Will block until a value is available unless clear is called or the instance is destructed.
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* Returns true if a value was successfully written to the out parameter, false otherwise.
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*/
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bool waitPop(T& out)
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{
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std::unique_lock<std::mutex> lock{m_mutex};
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m_condition.wait(lock, [this]()
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{
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return !m_queue.empty() || !m_valid;
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});
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/*
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* Using the condition in the predicate ensures that spurious wakeups with a valid
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* but empty queue will not proceed, so only need to check for validity before proceeding.
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*/
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if(!m_valid)
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{
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return false;
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}
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out = std::move(m_queue.front());
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m_queue.pop();
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return true;
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}
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/**
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* Push a new value onto the queue.
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*/
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void push(T value)
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{
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std::lock_guard<std::mutex> lock{m_mutex};
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m_queue.push(std::move(value));
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m_condition.notify_one();
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}
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/**
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* Check whether or not the queue is empty.
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*/
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bool empty(void) const
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{
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std::lock_guard<std::mutex> lock{m_mutex};
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return m_queue.empty();
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}
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/**
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* Clear all items from the queue.
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*/
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void clear(void)
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{
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std::lock_guard<std::mutex> lock{m_mutex};
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while(!m_queue.empty())
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{
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m_queue.pop();
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}
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m_condition.notify_all();
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}
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/**
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* Invalidate the queue.
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* Used to ensure no conditions are being waited on in waitPop when
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* a thread or the application is trying to exit.
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* The queue is invalid after calling this method and it is an error
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* to continue using a queue after this method has been called.
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*/
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void invalidate(void)
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{
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std::lock_guard<std::mutex> lock{m_mutex};
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m_valid = false;
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m_condition.notify_all();
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}
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/**
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* Returns whether or not this queue is valid.
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*/
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bool isValid(void) const
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{
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std::lock_guard<std::mutex> lock{m_mutex};
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return m_valid;
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}
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private:
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std::atomic_bool m_valid{true};
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mutable std::mutex m_mutex;
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std::queue<T> m_queue;
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std::condition_variable m_condition;
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};
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}
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#endif
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