loop.c

unix环境高级编程的源代码

#include    "call.h"
#include    <poll.h>
#include    <stropts.h>

/* Copy everything from stdin to "remfd",
 * and everything from "remfd" to stdout. */

#define    BUFFSIZE    512

void
loop(int remfd)
{
    int                bol, n, nread;
    char            c, buff[BUFFSIZE];
    struct pollfd    fds[2];

    setbuf(stdout, NULL);        /* set stdout unbuffered */
                                /* (for printfs in take() and put() */
    fds[0].fd = STDIN_FILENO;    /* user's terminal input */
    fds[0].events = POLLIN;
    fds[1].fd = remfd;            /* input from remote (modem) */
    fds[1].events = POLLIN;

    for ( ; ; ) {
        if (poll(fds, 2, INFTIM) <= 0)
            err_sys("poll error");

        if (fds[0].revents & POLLIN) {    /* data to read on stdin */
            if (read(STDIN_FILENO, &c, 1) != 1)
                err_sys("read error from stdin");

            if (c == escapec && bol) {
                if ( (n = doescape(remfd)) < 0)
                    break;        /* user wants to terminate */
                else if (n == 0)
                    continue;    /* escape seq has been processed */

                /* else, char following escape was not special,
                   so it's returned and echoed below */
                c = n;
            }
            if (c == '\r' || c == '\n')
                bol = 1;
            else
                bol = 0;

            if (write(remfd, &c, 1) != 1)
                err_sys("write error");
        }
        if (fds[0].revents & POLLHUP)
            break;        /* stdin hangup -> done */

        if (fds[1].revents & POLLIN) {    /* data to read from remote */
            if ( (nread = read(remfd, buff, BUFFSIZE)) <= 0)
                break;        /* error or EOF, terminate */

            if (writen(STDOUT_FILENO, buff, nread) != nread)
                err_sys("writen error to stdout");
        }
        if (fds[1].revents & POLLHUP)
            break;        /* modem hangup -> done */
    }
}