/*
 * Copyright (c) 2016 The ZLToolKit project authors. All Rights Reserved.
 *
 * This file is part of ZLToolKit(https://github.com/xia-chu/ZLToolKit).
 *
 * Use of this source code is governed by MIT license that can be found in the
 * LICENSE file in the root of the source tree. All contributing project authors
 * may be found in the AUTHORS file in the root of the source tree.
 */

#ifndef TASKQUEUE_H_
#define TASKQUEUE_H_

#include <list>
#include <deque>
#include <atomic>
#include <mutex>
#include <functional>
#include "Util/List.h"
#include "semaphore.h"
using namespace std;

namespace toolkit {

//实现了一个基于函数对象的任务列队，该列队是线程安全的，任务列队任务数由信号量控制
template<typename T>
class TaskQueue {
public:
    //打入任务至列队
    template<typename C>
    void push_task(C &&task_func) {
        {
            lock_guard<decltype(_mutex)> lock(_mutex);
            _queue.emplace_back(std::forward<C>(task_func));
        }
        _sem.post();
    }
    template<typename C>
    void push_task_first(C &&task_func) {
        {
            lock_guard<decltype(_mutex)> lock(_mutex);
            _queue.emplace_front(std::forward<C>(task_func));
        }
        _sem.post();
    }
    //清空任务列队
    void push_exit(size_t n) {
        _sem.post(n);
    }
    //从列队获取一个任务，由执行线程执行
    bool get_task(T &tsk) {
        _sem.wait();
        lock_guard<decltype(_mutex)> lock(_mutex);
        if (_queue.size() == 0) {
            return false;
        }
        //改成右值引用后性能提升了1倍多！
        tsk = std::move(_queue.front());
        _queue.pop_front();
        return true;
    }
    size_t size() const{
        lock_guard<decltype(_mutex)> lock(_mutex);
        return _queue.size();
    }
private:
    //经过对比List,std::list,std::deque三种容器发现，
    //在i5-6200U单线程环境下，执行1000万个任务时，分别耗时1.3，2.4，1.8秒左右
    //所以此处我们替换成性能最好的List模板
    List<T> _queue;
    mutable mutex _mutex;
    semaphore _sem;
};

} /* namespace toolkit */
#endif /* TASKQUEUE_H_ */