robust_io.cpp

#include "robust_io.h"
#include <unistd.h>
#include <errno.h>


ssize_t rio_readn(int fd, void *usrbuf, size_t n)
{
    size_t nleft = n;
    ssize_t nread;
    char *bufp = (char *)usrbuf;

    while (nleft > 0)
    {
        if ((nread = read(fd, bufp, nleft)) < 0)
        {
            /* interrupted by sig handler return */
            if (errno == EINTR)
                nread = 0;      /* and call read() again */
            else
                return -1;      /* errno set by read() */
        }
        else if (nread == 0)
            break;              /* EOF */
        nleft -= nread;
        bufp += nread;
    }
    return (n - nleft);         /* return >= 0 */
}

ssize_t rio_writen(int fd, void *usrbuf, size_t n)
{
    size_t nleft = n;
    ssize_t nwritten;
    char *bufp = (char *)usrbuf;

    while (nleft > 0)
    {
        if ((nwritten = write(fd, bufp, nleft)) <= 0)
        {
            if (errno == EINTR)  /* interrupted by sig handler return */
                nwritten = 0;    /* and call write() again */
            else
            {
                return -1;       /* errorno set by write() */
            }
        }
        nleft -= nwritten;
        bufp += nwritten;
    }

    return n;
}