/* ttyread.c - ttyread */

#include 

/*------------------------------------------------------------------------
 *  ttyread  -  Read character(s) from a tty device (interrupts disabled)
 *------------------------------------------------------------------------
 */
devcall ttyread(
          struct dentry *devptr,        /* Entry in device switch table */
          char  *buff,                  /* Buffer of characters         */
          int32 count                   /* Count of character to read   */
        )
{
        struct  ttycblk *typtr;         /* Pointer to tty control block */
        int32   avail;                  /* Characters available in buff.*/
        int32   nread;                  /* Number of characters read    */
        int32   firstch;                /* First input character on line*/
        char    ch;                     /* Next input character         */

        if (count < 0) {
                return SYSERR;
        }
        typtr= &ttytab[devptr->dvminor];

        if (typtr->tyimode != TY_IMCOOKED) {

                /* For count of zero, return all available characters */

                if (count == 0) {
                        avail = semcount(typtr->tyisem);
                        if (avail == 0) {
                                return 0;
                        } else {
                                count = avail;
                        }
                }
                for (nread = 0; nread < count; nread++) {
                        *buff++ = (char) ttygetc(devptr);
                }
                return nread;
        }

        /* Block until input arrives */

        firstch = ttygetc(devptr);

        /* Check for End-Of-File */

        if (firstch == EOF) {
                return EOF;
        }

        /* Read up to a line */

        ch = (char) firstch;
        *buff++ = ch;
        nread = 1;
        while ( (nread < count) && (ch != TY_NEWLINE) &&
                        (ch != TY_RETURN) ) {
                ch = ttygetc(devptr);
                *buff++ = ch;
                nread++;
        }
        return nread;
}