15-3-threadpool.h

#ifndef THREADPOOL_H_
#define THREADPOOL_H_

#include <list>
#include <cstdio>
#include <exception>
#include <pthread.h>

/*引入第14章的线程同步机制的包装类*/
#include "14-2-locker.h"

/*线程池类，将它定义为模板类是为了代码复用。模板参数T是任务类*/
template <typename T>
class threadpool
{
public:
    //参数thread_number是线程池中线程的数量，max_requests是请求队列中最多允许的、等待处理的请求的数量
    threadpool(int thread_number = 8, int max_requests = 10000);
    ~threadpool();

    //往请求队列中添加任务

    bool append(T* request);

private:
    //工作线程运行的函数，它不断从工作队列中取出任务并执行之
    static void *worker(void *arg);
    void run();

private:
    int m_thread_number; //线程池中的线程数
    int m_max_requests;  //请求队列中允许的最大请求数
    pthread_t * m_threads; //描述线程池的数组，其大小为m_thread_number
    std::list<T*>m_workqueue; //请求队列
    locker m_queuelocker;  //保护请求队列的互斥锁
    sem m_queuestat;   //是否有任务需要处理
    bool m_stop;   //是否结束线程
};

template<typename T>
threadpool<T>::threadpool(int thread_number, int max_requests):
    m_thread_number(thread_number), m_max_requests(max_requests),
    m_stop(false), m_threads(NULL)
{
    if ((thread_number <= 0) || (max_requests <= 0))
    {
        throw std::exception();
    }

    m_threads = new pthread_t[m_thread_number];
    if (!m_threads) 
    {
        throw std::exception();
    }

    //创建thread_number个线程，并将他们都设置为脱离线程
    for(int i = 0; i < thread_number; i++) 
    {
        printf("create the %dth thread\n", i);
        if (pthread_create(m_threads + i, NULL, worker, this) != 0)
        {
            delete [] m_threads;
            throw std::exception();
        }
        if (pthread_detach(m_threads[i]))
        {
            delete [] m_threads;
            throw std::exception();
        }
    }
}

template<typename T>
threadpool<T>::~threadpool()
{
    delete [] m_threads;
    m_stop = true;
}

template<typename T>
bool threadpool<T>::append(T *request)
{
    //操作工作队列时一定要加锁，因为它被所有线程共享
    m_queuelocker.lock();
    if (m_workqueue.size() > m_max_requests) 
    {
        m_queuelocker.unlock();
        return false;
    }
    m_workqueue.push_back(request);
    m_queuelocker.unlock();
    m_queuestat.post();
    return true;
}

template<typename T>
void *threadpool<T>::worker(void *arg)
{
    threadpool *pool = (threadpool *)arg;
    pool->run();
    return pool;
}

template<typename T>
void threadpool<T>::run()
{
    while(!m_stop)
    {
        m_queuestat.wait();
        m_queuelocker.lock();
        if (m_workqueue.empty())
        {
            m_queuelocker.unlock();
            continue;
        }

        T *request = m_workqueue.front();
        m_workqueue.pop_front();
        m_queuelocker.unlock();
        if (!request) 
        {
            continue;
        }
        request->process();
    }
}

#endif