Function ttydisc_write

components/lwp/terminal/freebsd/tty_ttydisc.c:475–618

* Just like the old TTY implementation, we need to copy data in chunks * into a temporary buffer. One of the reasons why we need to do this, * is because output processing (only TAB3 though) may allow the buffer * to grow eight times. */

 * to grow eight times.
 */
int ttydisc_write(struct lwp_tty *tp, struct uio *uio, int ioflag)
{
    char ob[TTY_STACKBUF];
    char *obstart;
    int error = 0;
    unsigned int oblen = 0;

    tty_assert_locked(tp);

    if (tp->t_flags & TF_ZOMBIE)
        return -EIO;

    /*
     * We don't need to check whether the process is the foreground
     * process group or if we have a carrier. This is already done
     * in ttydev_write().
     */

    while (uio->uio_resid > 0)
    {
        unsigned int nlen;

        MPASS(oblen == 0);

        if (CMP_FLAG(l, FLUSHO))
        {
            uio->uio_offset += uio->uio_resid;
            uio->uio_resid = 0;
            return 0;
        }

        /* Step 1: read data. */
        obstart = ob;
        nlen = MIN(uio->uio_resid, sizeof ob);
        tty_unlock(tp);
        error = uiomove(ob, nlen, uio);
        tty_lock(tp);
        if (error != 0)
            break;
        oblen = nlen;

        if (tty_gone(tp))
        {
            error = -ENXIO;
            break;
        }

        MPASS(oblen > 0);

        /* Step 2: process data. */
        do
        {
            unsigned int plen, wlen;

            if (CMP_FLAG(l, FLUSHO))
            {
                uio->uio_offset += uio->uio_resid;
                uio->uio_resid = 0;