cpl_worker_thread_pool.h

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/**********************************************************************
 *
 * Project:  CPL - Common Portability Library
 * Purpose:  CPL worker thread pool
 * Author:   Even Rouault, <even dot rouault at spatialys dot com>
 *
 **********************************************************************
 * Copyright (c) 2015, Even Rouault, <even dot rouault at spatialys dot com>
 *
 * SPDX-License-Identifier: MIT
 ****************************************************************************/
 
#ifndef CPL_WORKER_THREAD_POOL_H_INCLUDED_
#define CPL_WORKER_THREAD_POOL_H_INCLUDED_
 
#include "cpl_multiproc.h"
#include "cpl_list.h"
 
#include <condition_variable>
#include <functional>
#include <memory>
#include <mutex>
#include <queue>
#include <vector>

 
#ifndef DOXYGEN_SKIP
class CPLWorkerThreadPool;
 
struct CPLWorkerThread
{
    CPL_DISALLOW_COPY_ASSIGN(CPLWorkerThread)
    CPLWorkerThread() = default;
 
    CPLThreadFunc pfnInitFunc = nullptr;
    void *pInitData = nullptr;
    CPLWorkerThreadPool *poTP = nullptr;
    CPLJoinableThread *hThread = nullptr;
    bool bMarkedAsWaiting = false;
 
    std::mutex m_mutex{};
    std::condition_variable m_cv{};
};
 
typedef enum
{
    CPLWTS_OK,
    CPLWTS_STOP,
    CPLWTS_ERROR
} CPLWorkerThreadState;
#endif  // ndef DOXYGEN_SKIP
 
class CPLJobQueue;
using CPLJobQueuePtr = std::unique_ptr<CPLJobQueue>;

class CPL_DLL CPLWorkerThreadPool
{
    CPL_DISALLOW_COPY_ASSIGN(CPLWorkerThreadPool)
 
    std::vector<std::unique_ptr<CPLWorkerThread>> aWT{};
    mutable std::mutex m_mutex{};
    std::condition_variable m_cv{};
    volatile CPLWorkerThreadState eState = CPLWTS_OK;
    std::queue<std::function<void()>> jobQueue;
    int nPendingJobs = 0;
    bool m_bNotifyEvent = false;
 
    CPLList *psWaitingWorkerThreadsList = nullptr;
    int nWaitingWorkerThreads = 0;
 
    int m_nMaxThreads = 0;
 
    static void WorkerThreadFunction(void *user_data);
 
    void DeclareJobFinished();
    std::function<void()> GetNextJob(CPLWorkerThread *psWorkerThread);
 
  public:
    CPLWorkerThreadPool();
    explicit CPLWorkerThreadPool(int nThreads);
    ~CPLWorkerThreadPool();
 
    bool Setup(int nThreads, CPLThreadFunc pfnInitFunc, void **pasInitData);
    bool Setup(int nThreads, CPLThreadFunc pfnInitFunc, void **pasInitData,
               bool bWaitallStarted);
 
    CPLJobQueuePtr CreateJobQueue();
 
    bool SubmitJob(std::function<void()> task);
    bool SubmitJob(CPLThreadFunc pfnFunc, void *pData);
    bool SubmitJobs(CPLThreadFunc pfnFunc, const std::vector<void *> &apData);
    void WaitCompletion(int nMaxRemainingJobs = 0);
    void WaitEvent();
    void WakeUpWaitEvent();

    int GetThreadCount() const;
};

class CPL_DLL CPLJobQueue
{
    CPL_DISALLOW_COPY_ASSIGN(CPLJobQueue)
    CPLWorkerThreadPool *m_poPool = nullptr;
    std::mutex m_mutex{};
    std::condition_variable m_cv{};
    int m_nPendingJobs = 0;
 
    void DeclareJobFinished();

  protected:
    friend class CPLWorkerThreadPool;
    explicit CPLJobQueue(CPLWorkerThreadPool *poPool);
 
  public:
    ~CPLJobQueue();

    CPLWorkerThreadPool *GetPool()
    {
        return m_poPool;
    }
 
    bool SubmitJob(CPLThreadFunc pfnFunc, void *pData);
    bool SubmitJob(std::function<void()> task);
    void WaitCompletion(int nMaxRemainingJobs = 0);
    bool WaitEvent();
};
 
#endif  // CPL_WORKER_THREAD_POOL_H_INCLUDED_