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Annotation of xinu/sys/ttywrite.c, revision 1.1

1.1     ! root        1: /* ttywrite.c - ttywrite, writcopy */
        !             2: 
        !             3: #include <conf.h>
        !             4: #include <kernel.h>
        !             5: #include <tty.h>
        !             6: #include <io.h>
        !             7: #include <slu.h>
        !             8: 
        !             9: /*------------------------------------------------------------------------
        !            10:  *  ttywrite - write one or more characters to a tty device
        !            11:  *------------------------------------------------------------------------
        !            12:  */
        !            13: ttywrite(devptr, buff, count)
        !            14: struct devsw   *devptr;
        !            15: char   *buff;
        !            16: int    count;
        !            17: {
        !            18:        register struct tty *ttyp;
        !            19:        int ncopied;
        !            20:        PStype ps;
        !            21: 
        !            22:        if (count < 0)
        !            23:                return(SYSERR);
        !            24:        if (count == 0)
        !            25:                return(OK);
        !            26:        disable(ps);
        !            27:        ttyp = &tty[devptr->dvminor];
        !            28:        count -= (ncopied = writcopy(buff, ttyp, count));
        !            29:        buff += ncopied;
        !            30:        for ( ; count>0 ; count--)
        !            31:                ttyputc(devptr, *buff++);
        !            32:        restore(ps);
        !            33:        return(OK);
        !            34: }
        !            35: 
        !            36: /*------------------------------------------------------------------------
        !            37:  *  writcopy - high-speed copy from user's buffer into system buffer
        !            38:  *------------------------------------------------------------------------
        !            39:  */
        !            40: LOCAL writcopy(buff, ttyp, count)
        !            41: char   *buff;
        !            42: struct tty *ttyp;
        !            43: int    count;
        !            44: {
        !            45:        register int    avail;
        !            46:        register char   *cp, *qhead, *qend, *uend;
        !            47: 
        !            48:        avail = scount(ttyp->osem);
        !            49:        qhead = &ttyp->obuff[ttyp->ohead];
        !            50:        qend  = &ttyp->obuff[OBUFLEN];
        !            51:        cp    = buff;
        !            52:        uend  = buff + count;
        !            53:        while (avail-- > 1 && cp < uend) {
        !            54:                if (*cp == NEWLINE && ttyp->ocrlf) {
        !            55:                        *qhead++ = RETURN;
        !            56:                        --avail;
        !            57:                        if ( qhead >= qend )
        !            58:                                qhead = ttyp->obuff;
        !            59:                }
        !            60:                *qhead++ = *cp++;
        !            61:                if ( qhead >= qend )
        !            62:                        qhead = ttyp->obuff;
        !            63:        }                                       /* avail decremented one*/
        !            64:        ttyp->ohead = qhead - ttyp->obuff;      /* extra time when loop */
        !            65:        sreset(ttyp->osem, ++avail);            /* condition fails.     */
        !            66:        (ttyp->ioaddr)->ctstat = SLUENABLE;
        !            67:        return(cp - buff);
        !            68: }

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