RIO包 健壮的I/O函数代码

下面是关于

#include <stdio.h>

#include <string.h>

#include <errno.h>

#include <sys/types.h>

#include <fcntl.h>

#include <sys/stat.h>



#define MAXLINE 1024



/*unbuffer input/output function*/



ssize_t rio_readn(int fd,void *usrbuf,size_t n)

{

    size_t nleft = n;

    ssize_t nread;

    char *bufp = usrbuf;



    while(nleft > 0){

        if((nread = read(fd,bufp,nleft)) < 0){

            if(errno == EINTR){/*interrupted by sig handler return*/

                nread = 0;

            }else{

                return -1;/*error*/

            }

        }else if(nread == 0){

            break;  /*EOF*/

        }else{/*read content*/

            nleft -= nread;

            bufp += nread;

        }

    }

    return (n - nleft);

}



ssize_t rio_writen(int fd,void *usrbuf,size_t n)

{

    size_t nleft = n;

    ssize_t nwritten;

    char *bufp = usrbuf;



    while(nwritten = write(fd,bufp,nleft) <= 0){

        if(errno == EINTR){

            nwritten = 0;

        }else{

            return -1;

        }

        nleft -= nwritten;

        bufp += nwritten;

    }

    return n;

}

/******************************************************************************/

#define RIO_BUFSIZE 8192

typedef struct{

    int rio_fd; /*To operate the file descriptor*/

    int rio_cnt;/*unread bytes in internal buf*/

    char *rio_bufptr;/*next unread byte int internal buf*/

    char rio_buf[RIO_BUFSIZE];/*internal buf*/

}rio_t;

void rio_readinitb(rio_t *rp,int fd)

{

    rp->rio_fd = fd;

    rp->rio_cnt = 0;

    rp->rio_bufptr = rp->rio_buf;

}

static ssize_t rio_read(rio_t *rp,char *usrbuf,size_t n)

{

    int cnt;

    while(rp->rio_cnt <= 0){/*Read the file content if buf is empty*/

        rp->rio_cnt = read(rp->rio_fd, rp->rio_buf,sizeof(rp->rio_buf));

        if(rp->rio_cnt < 0){

            if(errno != EINTR){

                return -1;

            }

        }else if(rp->rio_cnt == 0){/*EOF*/

            return 0;

        }else {/*reset buf ptr*/

            rp->rio_bufptr = rp->rio_buf;

        }

    }

    /*when n < rp->rio_cnt, need copy some times */

    cnt = n;

    if(rp->rio_cnt < n){/*one time copy end*/

        cnt = rp->rio_cnt;

    }

    memcpy(usrbuf,rp->rio_bufptr,cnt);

    rp->rio_bufptr += cnt;

    rp->rio_cnt -= cnt;

    return cnt;

}

ssize_t rio_readlineb(rio_t *rp, void *usrbuf,size_t maxlen)

{

    int n,rc;

    char c,*bufp = usrbuf;

    for(n = 1; n < maxlen; n++){

        if (( rc = rio_read(rp,&c,1)) == 1){

            *bufp++ = c;

            if(c == '\n'){

                break;

            }

        }else if (rc == 0){

            if(n == 1){/*EOF no data read*/

                return 0;

            }else{/*EOF some data read*/

                break;

            }

        }else{/*ERROR*/

            return -1;

        }

    }

    *bufp = 0;/*string end sign :'\0'*/

    return n;

}



ssize_t rio_readnb(rio_t *rp,void *usrbuf,size_t n)

{

    size_t nleft = n;

    ssize_t nread;

    char *bufp = usrbuf;



    while(nleft > 0){

        if((nread = rio_read(rp,bufp, nleft)) < 0){

            if(errno == EINTR){/*interrupted by sig handler return*/

                nread =0;

            }else{/*errno set by read() */

                return -1;

            }

        }else if(nread == 0){/*EOF*/

            break;

        }

        nleft -= nread;

        bufp += nread;

    }

    return (n-nleft);/*return >=0*/

}



int main()

{

    int n;

    rio_t rio;

    char buf[MAXLINE];



    int fd = open("1.txt",O_RDONLY,755);

    if(fd <=0){

        printf("error\n");

    }

    rio_readinitb(&rio,fd);

    while ((n = rio_readlineb(&rio,buf,MAXLINE)) != 0){

           rio_writen(1,buf,n);

    }

    close(fd);

    return 0;

}

上面的函数式ＲＩＯ包提供的两类不同的函数：

１、不带缓冲的输入输出函数

2、带缓冲的输入函数

这里主要针对文件Io，因为标准Io本身就是带缓冲的，我们在对文件进行读写操作时，一般会优先使用标准的Io函数，但是在网络编程中，只能使用文件Io的函数，这里可能就用到我们上面的函数编写，有兴趣的可以多了解下上面的机制。在网络通信中，这种机制方法运用还是比较多的！