线程池的原理及意义，请移步这篇博文：

　　下面，介绍的这个线程池与上面提到的那个线程池有一部分相似的地方。

　　主要区别为：

　　　　1、线程池中的每个线程都有自己的互斥量和条件变量，而不是线程池共享一个。

　　　　2、线程池中的线程在程序结束时，等待线程池中线程停止的机制不同。

　　该程序主要由两个文件构成，分别为ThreadPool.h和ThreadPool.cpp文件。

　　ThreadPool.h文件：

#define MAXT_IN_POOL 200#define BUSY_THRESHOlD 0.5#define MANAGE_INTREVAL 2class ThreadPool;typedef void (*dispatch_fn)(void*);    //线程函数参数typedef struct tagThread           {    pthread_t thread_id;           //线程ID    pthread_mutex_t thread_mutex;  //信号量    pthread_cond_t thread_cond;    //条件变量    dispatch_fn do_job;            //调用的函数，任务    void* args;                    //函数参数    ThreadPool *parent;            //线程池指针}_thread;//线程池class ThreadPool{    public:    //================================================================================================    //函数名：                  ThreadPool    //函数描述：                构造函数    //输入：                    [in] max_threads_in_pool 线程池最大线程数    //输入：                    [in] min_threads_in_pool 线程池最小问题数    //输出：                    无    //返回：                    无    //================================================================================================    ThreadPool(unsigned int max_threads_in_pool, unsigned int min_threads_in_pool = 2);    ~ThreadPool();        //================================================================================================    //函数名：                  dispatch_threadpool    //函数描述：                将任务加入线程池，由线程池进行分发    //输入：                    [in] dispatch_me 调用的函数地址    //输入：                    [in] dispatch_me 函数参数    //输出：                    无    //返回：                    无    //================================================================================================    void dispatch_threadpool(dispatch_fn dispatch_me, void* dispatch_me);private:    pthread_mutex_t tp_mutex;  //信号量    pthread_cond_t tp_idle;    //线程池中线程有空闲线程的条件变量    pthread_cond_t tp_full;    //线程池中线程为满的条件变量     pthread_cond_t tp_empty;   //线程池中线程为空的条件变量    int tp_min;                //线程池的最小线程数    int tp_max;                //线程池的最大线程数    int tp_avail;              //线程池中空闲的线程数    int tp_total;              //线程池中已创建的线程数    _thread** tp_list;         //指向线程池中所有空闲线程的参数的指针    bool tp_stop;              //线程池是否已停止        //================================================================================================    //函数名：                  add_avail    //函数描述：                加入空闲线程    //输入：                    [in] avail 线程的参数    //输出：                    无    //返回：                    成功：true，失败：false    //================================================================================================    bool add_avail(_thread* avail);        //================================================================================================    //函数名：                  work_thread    //函数描述：                线程函数    //输入：                    [in] args 参数    //输出：                    无    //返回：                    无    //================================================================================================    static void* work_thread(void* args);        //================================================================================================    //函数名：                  add_thread    //函数描述：                添加一个线程    //输入：                    [in] dispatch_me 函数指针    //输入：                    [in] args        函数参数    //输出：                    无    //返回：                    无    //================================================================================================    bool add_thread(dispatch_fn dispatch_me, void* args);        //================================================================================================    //函数名：                  syn_all    //函数描述：                等待线程池中所有线程空闲    //输入：                    无    //输出：                    无    //返回：                    无    //================================================================================================    void syn_all();    };

　　ThreadPool.cpp文件：

ThreadPool::ThreadPool(unsigned int max_threads_in_pool, unsigned int min_threads_in_pool){    pthread_t manage_id;    if (min_threads_in_pool <= 0 || max_threads_in_pool < 0 || min_threads_in_pool > max_threads_in_pool || max_threads_in_pool > MAXT_IN_POOL)    {        return ;    }    tp_avail = 0;      //初始化线程池    tp_total = 0;    tp_min = min_threads_in_pool;    tp_max = max_threads_in_pool;    tp_stop = false;    tp_list = (_thread * *)    malloc(sizeof(void *) * max_threads_in_pool);        if (NULL == tp_list)    {        return;    }    memset(tp_list, 0, sizeof(void *) * max_threads_in_pool);        pthread_mutex_init(&tp_mutex, NULL);    pthread_cond_init(&tp_idle, NULL);    pthread_cond_init(&tp_full, NULL);    pthread_cond_init(&tp_empty, NULL);}bool ThreadPool::add_avail(_thread* avail){    bool ret = false;    pthread_mutex_lock(&tp_mutex);    if (tp_avail < tp_max)    {        tp_list[tp_avail] = avail;        tp_avail++;                pthread_cond_signal(&tp_idle);  //线程池中有线程为空闲        if (tp_avail >= tp_total)        {            pthread_cond_signal(&tp_full); //线程池中所有线程都为为空闲        }        ret = true;    }    pthread_mutex_unlock(&tp_mutex);        return ret;}void* ThreadPool::work_thread(void* args){    _thread* thread = (_thread*) args;    ThreadPool *pool = thread->parent;    while (pool->tp_stop == false)     {        thread->do_job(thread->args);        pthread_mutex_lock(&thread->thread_mutex); //执行完任务之后，添加到空闲线程队列中        if (pool->add_avail(thread))        {                pthread_cond_wait(&thread->thread_cond, &thread->thread_mutex);            pthread_mutex_unlock(&thread->thread_mutex);        }        else        {            pthread_mutex_unlock(&thread->thread_mutex);            pthread_mutex_destroy(&thread->thread_mutex);            pthread_cond_destroy(&thread->thread_cond);            free(thread);            break;        }    }    pthread_mutex_lock(&pool->tp_mutex);    pool->tp_total--;    if (pool->tp_total <= 0)    {        pthread_cond_signal(&pool->tp_empty);    }    pthread_mutex_unlock(&pool->tp_mutex);    return NULL;}bool ThreadPool::add_thread(dispatch_fn dispatch_me, void* args)  //添加一个线程{    _thread* thread = NULL;    pthread_attr_t attr;        thread = (_thread *) malloc(sizeof(_thread));    if (NULL == thread)    {        return false;    }    pthread_mutex_init(&thread->thread_mutex, NULL);    pthread_cond_init(&thread->thread_cond, NULL);    thread->do_job = dispatch_me;    thread->args = args;    thread->parent = this;    pthread_attr_init(&attr);    pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);    if (pthread_create(&thread->thread_id, &attr, work_thread, (void *) thread) != 0)    {        pthread_mutex_destroy(&thread->thread_mutex);        pthread_cond_destroy(&thread->thread_cond);        pthread_attr_destroy(&attr);        free(thread);        return false;    }                    tp_total++;    return true;}void ThreadPool::dispatch_threadpool(dispatch_fn dispatch_me, void* args){    _thread* thread = NULL;    pthread_mutex_lock(&tp_mutex);        if (tp_avail <= 0 && tp_total >= tp_max) //无可用线程，而且线程数已达最大值，等待空闲线程    {        pthread_cond_wait(&tp_idle, &tp_mutex);    }    if (tp_avail <= 0)  //无可用线程，而且线程数未达最大值，添加线程    {        if (!add_thread(dispatch_me, args))        {            return;        }    }    else   //有可用线程    {        tp_avail--;        thread = tp_list[tp_avail];        tp_list[tp_avail] = NULL;                thread->do_job = dispatch_me;        thread->args = args;        pthread_mutex_lock(&thread->thread_mutex);        pthread_cond_signal(&thread->thread_cond);        pthread_mutex_unlock(&thread->thread_mutex);    }    pthread_mutex_unlock(&tp_mutex);}void ThreadPool::syn_all(){        if (tp_avail < tp_total)   //等待线程池中所有线程都为空闲状态    {        pthread_cond_wait(&tp_full, &tp_mutex);    }            tp_stop = true;        int i = 0;        for (i = 0; i < tp_avail; i++)  //唤醒线程池中所有线程    {        _thread *thread = tp_list[i];                pthread_mutex_lock(&thread->thread_mutex);        pthread_cond_signal(&thread->thread_cond);        pthread_mutex_unlock(&thread->thread_mutex);    }        if (tp_total > 0)    {        pthread_cond_wait(&tp_empty, &tp_mutex);  //等待线程池中所有线程都结束    }}ThreadPool::~ThreadPool(){    sleep(MANAGE_INTREVAL);    pthread_mutex_lock(&tp_mutex);    syn_all();                        //等待线程池为空    int i = 0;    for (i = 0; i < tp_total; i++)  //资源释放    {        free(tp_list[i]);        tp_list[i] = NULL;    }    pthread_mutex_unlock(&tp_mutex);    pthread_mutex_destroy(&tp_mutex);    pthread_cond_destroy(&tp_idle);    pthread_cond_destroy(&tp_full);    pthread_cond_destroy(&tp_empty);    free(tp_list);}