thread_pool.h

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/*
 * Copyright (C) 2019-2024 Norbert Schlia (nschlia@oblivion-software.de)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * On Debian systems, the complete text of the GNU General Public License
 * Version 3 can be found in `/usr/share/common-licenses/GPL-3'.
 */
 
#ifndef THREAD_POOL_H
#define THREAD_POOL_H
 
#pragma once
 
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <iostream>
#include <thread>
#include <vector>
#include <queue>
#include <mutex>
#include <condition_variable>
#include <unistd.h>
#include <atomic>
#include <functional>
 
class thread_pool
{
public:
    typedef std::function<int(void)> FunctionPointer; 
public:
    explicit thread_pool(unsigned int num_threads = std::thread::hardware_concurrency() * 4);
    virtual ~thread_pool();
 
    int init(unsigned int num_threads = 0);
    void            tear_down(bool silent = false);
    bool            schedule_thread(FunctionPointer && func);
    unsigned int    current_running() const;
    unsigned int    current_queued();
    unsigned int    pool_size() const;
 
private:
    static void     loop_function_starter(thread_pool &tp);
    void            loop_function();
 
protected:
    std::vector<std::thread>    m_thread_pool;      
    std::mutex                  m_queue_mutex;      
    std::condition_variable     m_queue_cond;       
    std::queue<FunctionPointer> m_thread_queue;     
    std::atomic_bool            m_queue_shutdown;   
    unsigned int                m_num_threads;      
    unsigned int                m_cur_threads;      
    std::atomic_uint32_t        m_threads_running;  
};
 
#endif // THREAD_POOL_H