readn和writen函数

int readn(int connfd, void *pbuf, int nums)
{
    int nleft = 0;
    int nread = 0;
    char *pread_buf = NULL;
    struct timeval select_timeout;
    fd_set rset;
    int ret = 0;

    memset(&select_timeout, 0, sizeof(select_timeout));

    if ((connfd <= 0) || (NULL == pbuf) || (nums <= 0))
    {
        printf("readn: param err.
");
        return -1;
    }

    pread_buf = (char *)pbuf;
    nleft = nums;

    while (nleft > 0)
    {
        select_timeout.tv_sec = 10;
        select_timeout.tv_usec = 0;

        FD_ZERO(&rset);
        FD_SET((unsigned int)connfd, &rset);
        ret = select(connfd + 1, &rset, NULL, NULL, &select_timeout);        
        if (ret < 0)
        {
            printf("readn: select failed, %s
", strerror(errno));
            return -1;
        }
        else if (ret == 0)
        {
            break;
        }
        else
        {
            if (FD_ISSET(connfd, &rset))
            {
                nread = recv(connfd, pread_buf, nleft, 0);
                if (nread < 0)
                {
                    perror("recv");
                    if (EINTR == errno)
                    {
                        nread = 0;
                    }
                    else
                    {
                        printf("recv, %s
", strerror(errno));
                        return -1;
                    }
                }
                else if (0 == nread)
                {
                    break;
                }
                else
                {
                    nleft -= nread;
                    pread_buf += nread;
                }
            }
            else
                return -1;
        }
    }

    return(nums - nleft);
}

int writen(int connfd, void *pbuf, int nums)
{
    int nleft = 0;
    int nwritten = 0;
    char *pwrite_buf = NULL;
    struct timeval select_timeout;
    fd_set rset;

    memset(&select_timeout, 0, sizeof(select_timeout));

    if ((connfd <= 0) || (NULL == pbuf) || (nums < 0))
    {
        printf("writen: param err.
");
        return -1;
    }

    pwrite_buf = (char *)pbuf;
    nleft = nums;

    while(nleft > 0)
    {

        select_timeout.tv_sec = 10;
        select_timeout.tv_usec = 0;

        FD_ZERO(&rset);
        FD_SET((unsigned int)connfd, &rset);
        if (select(connfd + 1, NULL, &rset, NULL, &select_timeout) <= 0)
        {    
            printf("writen: select failed, %s
", strerror(errno));
            return -1;
        }

        if (-1 == (nwritten = send(connfd, pwrite_buf, nleft, MSG_NOSIGNAL)))
        {
            if (EINTR == errno)
            {
                printf("EINTR
");
                nwritten = 0;
            }
            else 
            {
                printf("Send() error, 0x%x
", errno);
                return -1;
            }
        }
        nleft -= nwritten;
        pwrite_buf += nwritten;
    }

    return(nums);
}