thread_tasks.h

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/*
* MIT License
* 
* Copyright (c) 2025 Open Media Transport Contributors
* 
* 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.
* 
*/
 
#pragma once
#include <thread>
#include <queue>
#include <mutex>
#include <condition_variable>
#include <functional>
 
struct ThreadTask
{
    std::thread thread;
    std::queue<std::function<void()>> queue;
    std::mutex mtx;
    std::condition_variable cv;
    std::condition_variable complete;
    bool running = false;
 
    void Join()
    {
        std::unique_lock<std::mutex> lock(mtx);
        if (queue.size() > 0)
        {
            complete.wait(lock);
        }
    }
 
    void TaskLoop()
    {
        while (running)
        {           
            std::unique_lock<std::mutex> lock(mtx);
            if (queue.size() == 0)
            {
                complete.notify_all();
                cv.wait(lock);
            }
            if (!running) break;
            std::function<void()> func = NULL;
            if (queue.size() > 0)
            {
                func = queue.front();
                queue.pop();
            }
            if (func)
            {
                func();
            }
 
        }
    }
    void Initialize()
    {
        running = true;
        queue = std::queue<std::function<void()>>();
        thread = std::thread(&ThreadTask::TaskLoop, this);
    }
    void Push(std::function<void()> task)
    {
        {
            std::lock_guard<std::mutex> lock(mtx);
            queue.push(task);
        }
        cv.notify_all();
    }
    void Destroy()
    {
        {
            std::lock_guard<std::mutex> lock(mtx);
            running = false;
        }
        cv.notify_all();
        thread.join();
    }
};
 
struct ThreadTasks
{
    int numThreads;
    ThreadTask** tasks;
};
 
static ThreadTasks* CreateTasks(int numThreads)
{
    ThreadTasks* th = new ThreadTasks();
    th->numThreads = numThreads;
    th->tasks = new ThreadTask*[numThreads];
    for (int i = 0; i < numThreads; i++)
    {
        ThreadTask* task = new ThreadTask();
        th->tasks[i] = task;
        task->Initialize();
    }
    return th;
}
 
static void DestroyTasks(ThreadTasks* tasks)
{
    if (tasks)
    {
        for (int i = 0; i < tasks->numThreads; i++)
        {
            tasks->tasks[i]->Destroy();
            ThreadTask* task = tasks->tasks[i];
            delete task;
        }
        delete tasks;
    }
}