Posix信号量实例

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/************************************Date：Thu Apr 10 17:51:36 CST 2014*有名信号量在多线程中的使用************************************/#include <iostream>extern "C"{    #include <sys/types.h>    #include <fcntl.h>    #include <errno.h>    #include <semaphore.h>    #include <pthread.h>}using namespace std;#define SEM_MUTEX    "sem_mutex"#define SEM_NEMPTY   "sem_empty"#define SEM_NSTORED  "sem_stored"#define NDATABUF     10int data_buf[NDATABUF];sem_t* sem_mutex = NULL;//锁sem_t* sem_nempty = NULL;//是否空sem_t* sem_nstored = NULL;//是否可以存int init(){    sem_mutex = sem_open(SEM_MUTEX,O_CREAT|O_RDWR,0666,1);    if(sem_mutex == SEM_FAILED){        cerr << "failed to open mutex sem,error:" << strerror(errno) << endl;        return -1;    }    sem_nempty = sem_open(SEM_NEMPTY,O_CREAT|O_RDWR,0666,NDATABUF);//初始化，数组是空的，均未存数据    if(sem_nempty == SEM_FAILED){        cerr << "failed to open empty sem,error:" << strerror(errno) << endl;        return -1;    }    sem_nstored = sem_open(SEM_NSTORED,O_CREAT|O_RDWR,0666,0);    if(sem_nstored == SEM_FAILED){        cerr << "failed to open stored sem,error:" << strerror(errno) << endl;        return -1;    }    return 0;}void destroy(){    sem_unlink(SEM_MUTEX);    sem_unlink(SEM_NEMPTY);    sem_unlink(SEM_NSTORED);}//生产者线程void* produce(void* arg){    int iNempty,iNstored,iMutex;    for(int i = 0;i < NDATABUF;i++){        sem_wait(sem_nempty);//有空间存数据        sem_wait(sem_mutex);//锁住临界区        data_buf[i] = i+1;        #ifdef _DEBUG        sem_getvalue(sem_nempty,&iNempty);        sem_getvalue(sem_nstored,&iNstored);        sem_getvalue(sem_mutex,&iMutex);        cout << "produce->nempty:" << iNempty << ",nstored:" << iNstored << ",mutex:" << iMutex << endl;        #endif        sem_post(sem_mutex);//解锁        sem_post(sem_nstored);//唤醒线程有数据可取    }    return NULL;}//消费者线程void* consume(void* arg){    int iNempty,iNstored,iMutex;    for(int i = 0;i < NDATABUF;i++){        sem_wait(sem_nstored);//有数据可取        sem_wait(sem_mutex);//锁住临界区        #ifdef _DEBUG        sem_getvalue(sem_nempty,&iNempty);        sem_getvalue(sem_nstored,&iNstored);        sem_getvalue(sem_mutex,&iMutex);        cout << "consume->nempty:" << iNempty << ",nstored:" << iNstored << ",mutex:" << iMutex << endl;        #endif        cout << data_buf[i] << endl;        sem_post(sem_mutex);//解锁        sem_post(sem_nempty);//通知有空间可以存    }    return NULL;}int main(int argc,char* argv[]){    int res = init();    if(res == -1){        cerr << "failed to initialize semaphore" << endl;        destroy();        return -1;    }    pthread_t p1,p2;    res = pthread_create(&p1,NULL,produce,NULL);    if(res == -1){        cerr << "failed to create thread 1" << endl;        destroy();        return -1;    }    res = pthread_create(&p2,NULL,consume,NULL);    if(res == -1){        cerr << "failed to create thread 2" << endl;        destroy();        return -1;    }    //等待线程结束    pthread_join(p1,NULL);    pthread_join(p2,NULL);    destroy();    return 0;}
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