RIO package robust I/O function code_PHP tutorial

[php]
The following is about

下面是关于[php] 
#include  
#include  
#include  
#include  
#include  
#include  
 
#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))             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)         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         rp->rio_cnt = read(rp->rio_fd, rp->rio_buf,sizeof(rp->rio_buf)); 
        if(rp->rio_cnt             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 rio_cnt, need copy some times */ 
    cnt = n; 
    if(rp->rio_cnt         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         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 :'