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Annotation of xinu/sys/ttyread.c, revision 1.1.1.2

1.1       root        1: /* ttyread.c - ttyread, readcopy */
                      2: 
                      3: #include <conf.h>
                      4: #include <kernel.h>
                      5: #include <tty.h>
                      6: #include <io.h>
                      7: 
                      8: /*------------------------------------------------------------------------
                      9:  *  ttyread - read one or more characters from a tty device
                     10:  *------------------------------------------------------------------------
                     11:  */
                     12: ttyread(devptr, buff, count)
1.1.1.2 ! root       13:        struct  devsw   *devptr;
        !            14:        int count;
        !            15:        char *buff;
1.1       root       16: {
1.1.1.2 ! root       17:        register struct tty     *ttyp;
        !            18:        int     avail, numread;
1.1       root       19: 
1.1.1.2 ! root       20: #ifdef DEBUG
        !            21:        dotrace("ttyread", &devptr, 3);
        !            22: #endif
1.1       root       23:        if (count < 0)
                     24:                return(SYSERR);
1.1.1.2 ! root       25:        disable();
        !            26: 
        !            27:        avail = scount( (ttyp= &tty[devptr->dvminor])->isem );
        !            28:        if ( (count = (count==0 ? avail : count)) == 0) {
        !            29:                restore();
        !            30:                return(0);
1.1       root       31:        }
1.1.1.2 ! root       32:        numread = count;
        !            33:        if (avail >= count) {
        !            34:                readcopy(buff, ttyp, count);
        !            35:                restore();
        !            36:                return(numread);
1.1       root       37:        }
1.1.1.2 ! root       38:        if (avail > 0) {
        !            39:                readcopy(buff, ttyp, avail);
        !            40:                buff += avail;
        !            41:                count -= avail;
1.1       root       42:        }
1.1.1.2 ! root       43:        restore();
        !            44:        for ( ; count>0 ; count--)
        !            45:                *buff++ = ttygetc(devptr);
        !            46:        return(numread);
        !            47: }
        !            48: 
        !            49: /*------------------------------------------------------------------------
        !            50:  *  readcopy - high speed copy procedure used by ttyread
        !            51:  *------------------------------------------------------------------------
        !            52:  */
        !            53: LOCAL readcopy(buff,ttyp,count)
        !            54: register char *buff;
        !            55: struct tty *ttyp;
        !            56: int count;
        !            57: {
        !            58:        register char *qtail, *qend, *uend;     /* copy loop variables  */
        !            59: 
        !            60:        qtail = &ttyp->ibuff[ttyp->itail];
        !            61:        qend  = &ttyp->ibuff[IBUFLEN];
        !            62:        uend = buff + count;
        !            63:        while ( buff < uend ) {
        !            64:                *buff++ = *qtail++;
        !            65:                if ( qtail >= qend )
        !            66:                        qtail = ttyp->ibuff;
1.1       root       67:        }
1.1.1.2 ! root       68:        ttyp->itail = qtail-ttyp->ibuff;
        !            69:        sreset(ttyp->isem, scount(ttyp->isem)-count);
1.1       root       70: }

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