threadpool.h

/*
 * Copyright 2021 Amitesh Singh <singh.amitesh@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and 
 * associated documentation files (the "Software"), to deal in the Software without restriction, including without 
 * limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 
 * IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/


#ifndef _THREAD_POOL_H__
#define _THREAD_POOL_H__

#include <thread>
#include <mutex>
#include <condition_variable>
#include <vector>
#include <functional>
#include <queue>
#include <atomic>

namespace nonstd
{
   class result
     {
        std::mutex m;
        std::condition_variable cond;
        bool waitEnabled = true;
        std::atomic<bool> workdone = false;

       public:
        void get();

        friend class thread_pool;
     };

   class thread_pool
     {
        struct job_info
          {
             std::function<void()> f;
             result *fobject;
             job_info(std::function<void()> &_f, result *_fobject): f(_f), fobject(_fobject) {}
          };

        std::mutex m;
        std::condition_variable cond;
        std::vector<std::thread *> thread_list;
        std::queue<job_info *> jobs;
        bool terminate = false;
        int MAX_THREADS;

        void worker(int id);

       public:
        thread_pool(int n = 1);

        void start();

        void stop();

        void addJob(std::function<void()> f, result &fobject);

        void addJob(std::function<void()> f);
     };
}
#endif