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https://github.com/YACReader/yacreader
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ConcurrentQueue is currently used only by two classes and a test, but modifying concurrent_queue.h requires recompiling 30 source files. None of the member functions is so lightweight as to make it worth inlining. An alternative to `@note ConcurrentQueue is unable to execute jobs if @p threadCount == 0.` is `assert(threadCount != 0);`. But this would force classes that contain a ConcurrentQueue data member to always start a thread, even if they detect at runtime that they are never going to enqueue a job. Add Job type alias to avoid repeating the type. Use default member initializers instead of the member initializer list to make it clear [to the reader of the header] that no data member is left uninitialized.
56 lines
1.6 KiB
C++
56 lines
1.6 KiB
C++
#ifndef CONCURRENT_QUEUE_H
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#define CONCURRENT_QUEUE_H
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#include <thread>
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#include <mutex>
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#include <functional>
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#include <condition_variable>
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#include <queue>
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#include <vector>
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namespace YACReader {
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//! All functions in this class are thread-safe in the Qt documentation sense.
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class ConcurrentQueue
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{
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public:
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//! @brief Creates and starts executing @p threadCount worker threads.
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//! @note ConcurrentQueue is unable to execute jobs if @p threadCount == 0.
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explicit ConcurrentQueue(std::size_t threadCount);
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//! Cancels all jobs that have not been picked up by worker threads yet,
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//! waits for all worker threads to complete their jobs and joins them.
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~ConcurrentQueue();
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using Job = std::function<void()>;
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//! @brief Adds @p job to the queue.
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//! @note A worker thread may start executing @p job immediately if it is idle.
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//! Worker threads start executing jobs in the same order as they are enqueued.
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void enqueue(Job job);
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//! @brief Cancels all jobs that have not been picked up by worker threads yet.
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//! @return The number of jobs that were canceled.
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std::size_t cancelPending();
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//! @brief Blocks the current thread until all enqueued jobs are completed.
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void waitAll();
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private:
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std::vector<std::thread> threads;
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std::queue<Job> _queue;
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std::size_t jobsLeft = 0; //!< @invariant jobsLeft >= _queue.size()
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bool bailout = false;
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std::condition_variable jobAvailableVar;
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std::condition_variable _waitVar;
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std::mutex jobsLeftMutex;
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std::mutex queueMutex;
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void nextJob();
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void finalizeJobs(std::size_t count);
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void joinAll();
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};
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}
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#endif // CONCURRENT_QUEUE_H
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