/* lflgetc.c - lfgetc */

#include 

/*------------------------------------------------------------------------
 * lflgetc  -  Read the next byte from an open local file
 *------------------------------------------------------------------------
 */
devcall lflgetc (
          struct dentry *devptr         /* Entry in device switch table */
        )
{
        struct  lflcblk *lfptr;         /* Ptr to open file table entry */
        struct  ldentry *ldptr;         /* Ptr to file's entry in the   */
                                        /*   in-memory directory        */
        int32   onebyte;                /* Next data byte in the file   */

        /* Obtain exclusive use of the file */

        lfptr = &lfltab[devptr->dvminor];
        wait(lfptr->lfmutex);

        /* If file is not open, return an error */

        if (lfptr->lfstate != LF_USED) {
                signal(lfptr->lfmutex);
                return SYSERR;
        }

        /* Return EOF for any attempt to read beyond the end-of-file */

        ldptr = lfptr->lfdirptr;
        if (lfptr->lfpos >= ldptr->ld_size) {
                signal(lfptr->lfmutex);
                return EOF;
        }

        /* If byte pointer is beyond the current data block, set up     */
        /*      a new data block                                        */

        if (lfptr->lfbyte >= &lfptr->lfdblock[LF_BLKSIZ]) {
                lfsetup(lfptr);
        }

        /* Extract the next byte from block, update file position, and  */
        /*      return the byte to the caller                           */

        onebyte = 0xff & *lfptr->lfbyte++;
        lfptr->lfpos++;
        signal(lfptr->lfmutex);
        return onebyte;
}