POSIX 线程(一)

一. POSIX线程先关函数

返回值: 成功返回0, 失败返回错误码

案例代码:

pthread.c

#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define ERR_EXIT(m) 	do 	{ 		perror(m); 		exit(EXIT_FAILURE); 	}while(0)

void* thread_routine(void *arg)
{
	int i;
	for(i=0;i<20;i++)
	{
		printf(" B ");
		fflush(stdout);
		usleep(20);

		if(i==3)
			pthread_exit("when i==3, pthread exit ");
	}
	sleep(3);  //延迟子线程的结束
	return 0;
}

int main()
{
	pthread_t tid;
	int ret;
	// 错误信息通过函数返回
	if ( (ret = pthread_create(&tid,NULL,thread_routine,NULL)) !=0 )
	{
	 	fprintf(stderr,"pthread_create:%s\n",strerror(ret));
	 	exit(EXIT_FAILURE);
	}
	int i;   /// 为主线程,打印字母 A
	for(i=0;i<20;++i)
	{
		printf(" A ");
		fflush(stdout);	// 刷新输出缓冲区
		usleep(20);
	}

	// 等待子线程的结束
	void *value;
	if( (ret = pthread_join(tid,&value)) != 0)
	{
		fprintf(stderr,"pthread_create:%s\n",strerror(ret));
		exit(EXIT_FAILURE);
	}
	printf("\n");
	printf("return message: %s\n",(char*)value);
	return 0;
}

二. 用线程实现回射客户/服务器程序

#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>

#define ERR_EXIT(m)         do         {                 perror(m);                 exit(EXIT_FAILURE);         } while(0)

void echo_srv(int conn)
{
    char recvbuf[1024];
    while (1)
    {
        memset(recvbuf, 0, sizeof(recvbuf));
        int ret = read(conn, recvbuf, sizeof(recvbuf));
        if (ret == 0)
        {
            printf("client close\n");
            break;
        }
        else if (ret == -1)
            ERR_EXIT("read");
        fputs(recvbuf, stdout);
        write(conn, recvbuf, ret);
    }
   close(conn);
}

void *thread_routine(void *arg)
{
     // 主线程没有调用pthread_join等待线程退出
     //剥离线程，避免产生僵线程    int conn = (int)arg;
     // pthread_self 返回线程ID
     // pthread_detach 分离线程
    pthread_detach(pthread_self());
    int conn = *((int *)arg);  // 将无类型指针强制转换成int* 指针
    free(arg); // 取完值,free掉
    echo_srv(conn); //每个线程处理一个连接,同一个进程没有可监听套接字
    printf("exiting thread ...\n");
    return NULL;
}

int main(void)
{
    int listenfd;
    if ((listenfd = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0)
        ERR_EXIT("socket");

    struct sockaddr_in servaddr;
    memset(&servaddr, 0, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(5188);
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);

    int on = 1;
    if (setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
        ERR_EXIT("setsockopt");

    if (bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)
        ERR_EXIT("bind");
    if (listen(listenfd, SOMAXCONN) < 0)
        ERR_EXIT("listen");

    struct sockaddr_in peeraddr;
    socklen_t peerlen = sizeof(peeraddr);
    int conn;

    while (1)
    {
        if ((conn = accept(listenfd, (struct sockaddr *)&peeraddr, &peerlen)) < 0)
            ERR_EXIT("accept");

        printf("ip=%s port=%d\n", inet_ntoa(peeraddr.sin_addr), ntohs(peeraddr.sin_port));

        pthread_t tid;
        //int ret;  /*pthread_create(&tid, NULL, thread_routine, (void*)&conn);*/
        // race condition问题，竟态问题
        int *p = malloc(sizeof(int));
        *p = conn;
        int ret;
        if ((ret = pthread_create(&tid, NULL, thread_routine,p)) != 0)
        //64位系统时指针不是4个字节，不可移植 , 所有使用malloc,
        {
        	fprintf(stderr, "pthread_create:%s\n", strerror(ret));
            exit(EXIT_FAILURE);
        }
    }
}