#include <pthread.h>#include <cstdlib>#include <ctime>#include <iostream>using namespace std;class RWLock {private :    pthread_mutex_t cnt_mutex;    pthread_cond_t rw_cond;    int rd_cnt, wr_cnt;    RWLock(const RWLock&);    RWLock& operator= (const RWLock&);public :    RWLock(): rd_cnt(0),wr_cnt(0)        {            pthread_mutex_init(&cnt_mutex, NULL);            pthread_cond_init(&rw_cond, NULL);        }    void get_shared_lock()        {            pthread_mutex_lock(&cnt_mutex);            while (wr_cnt >0)                {                    pthread_cond_wait(&rw_cond,&cnt_mutex);                }            rd_cnt++;            pthread_mutex_unlock(&cnt_mutex);        }    void release_shared_lock()        {            pthread_mutex_lock(&cnt_mutex);            rd_cnt--;            if (0 == rd_cnt)                {                    pthread_cond_signal(&rw_cond);                }            pthread_mutex_unlock(&cnt_mutex);        }    void get_exclusive_lock()        {            pthread_mutex_lock(&cnt_mutex);            while (rd_cnt+wr_cnt>0)                {                    pthread_cond_wait(&rw_cond,&cnt_mutex);                }            wr_cnt++;            pthread_mutex_unlock(&cnt_mutex);        }    void release_exclusive_lock()        {            pthread_mutex_lock(&cnt_mutex);            wr_cnt--;            pthread_cond_broadcast(&rw_cond);            pthread_mutex_unlock(&cnt_mutex);        }    ~RWLock()        {            pthread_mutex_destroy(&cnt_mutex);            pthread_cond_destroy(&rw_cond);        }};class Test{private :        RWLock lock;        static void* shared_task_handler(void* arg)        {            Test* testptr = static_cast<Test*>(arg);            testptr->lock.get_shared_lock();//得到共享锁            //do the shared task here            testptr->lock.release_shared_lock();        }    static void * exclusive_task_handler(void * arg)        {            Test* testptr = static_cast<Test*>(arg);            testptr->lock.get_exclusive_lock();            //do the exclusive task here            testptr->lock.release_exclusive_lock();        }public :    typedef void* (*ThreadFunc) (void*);    void start()        {            srand(time(NULL));            const int THREADS_NO=rand()%100;            pthread_t* threads = new pthread_t[THREADS_NO];            for(int i=0; i<THREADS_NO; i++)                {                    ThreadFunc tmpfunc = rand()%2? shared_task_handler : exclusive_task_handler;                    if (pthread_create(threads+i,NULL,tmpfunc,this))                        {                            cerr << "pthread_create fails" << endl;                            exit(1);                        }                }            for(int i=0; i<THREADS_NO; i++)                {                    pthread_join(threads[i],NULL);                }            delete[] threads;        }};int main(){    Test tmptest;    tmptest.start();}static_cast < type-id > ( expression )int i;float f = 166.71;i = static_cast<int>(f);此时结果，i的值为166。cstdlib是C++里面的一个常用函数库， 等价于C中的<stdlib.h>。http://blog.chinaunix.net/uid-52437-id-2108727.html