多个缓冲区

版权声明： https://blog.csdn.net/dashoumeixi/article/details/84670375

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <semaphore.h>
#include <pthread.h>
#include <unistd.h>

#define BUFFSIZE 8192
#define NBUFF 10
struct {
    struct{
        ssize_t readbytes;   //读取的字节 。 如果是0 则读完
        char data[BUFFSIZE]; //缓冲区
    }buf[NBUFF];             //N个缓冲区
    sem_t nempty , nstored;  //生产者/消费者信号量
}share;
static void * producer(void*p)
{
    int readfd = *(int*)p;
    int nindex = 0; // buff index;
    while(1){
        sem_wait(&share.nempty);
        share.buf[nindex].readbytes = read(readfd,share.buf[nindex].data,BUFFSIZE);
        if(share.buf[nindex].readbytes <= 0){
            sem_post(&share.nstored);
            break;
        }
        if(++nindex >= NBUFF)
            nindex = 0;
        sem_post(&share.nstored);
    }
    return 0;
}
static void * consumer(void*p)
{
    int writefd = *(int*)p;
    int nindex = 0;
    int bytes = 0;
    while(1){
        sem_wait(&share.nstored);
        //检查是否读完了或者出错了
        bytes = share.buf[nindex].readbytes;
        if(bytes <= 0){
            break;
        }
        bytes = write(writefd,share.buf[nindex].data,bytes);
        printf("write bytes:%d\n" , bytes);
        if(++nindex >= NBUFF)
            nindex = 0;
        sem_post(&share.nempty);
    }
    return 0;
}

int main(int argc ,char **argv)
{
    if(argc < 3){
        puts("srcfile destfile");
        return 0;
    }
    int readfd = open(argv[1],O_RDONLY);
    int writefd = open(argv[2],O_CREAT|O_WRONLY|O_TRUNC,0644);
    if(readfd < 0 || writefd < 0){
        perror("open failed");
        exit(0);
    }
    sem_init(&share.nempty,0,NBUFF);
    sem_init(&share.nstored,0,0);
    pthread_t  tid_producer , tid_consumer;
    pthread_create(&tid_producer,NULL,producer,(void*)&readfd);
    pthread_create(&tid_consumer,NULL,consumer,(void*)&writefd);
    pthread_join(tid_producer,NULL);
    pthread_join(tid_consumer,NULL);

    return 0;
}