/* lflputc.c - lfputc */

#include 

/*------------------------------------------------------------------------
 * lflputc  -  Write a single byte to an open local file
 *------------------------------------------------------------------------
 */
devcall lflputc (
          struct dentry *devptr,        /* Entry in device switch table */
          char          ch              /* Character (byte) to write    */
        )
{
        struct  lflcblk *lfptr;         /* Ptr to open file table entry */
        struct  ldentry *ldptr;         /* Ptr to file's entry in the   */
                                        /*  in-memory directory         */

        /* 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 SYSERR for an attempt to skip bytes beyond the byte   */
        /*      that is currently the end of the file                   */

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

        /* If pointer is outside current block, set up new block */

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

                /* Set up block for current file position */

                lfsetup(lfptr);
        }

        /* If appending a byte to the file, increment the file size.    */
        /*   Note: comparison might be equal, but should not be greater.*/

        if (lfptr->lfpos >= ldptr->ld_size) {
                ldptr->ld_size++;
                Lf_data.lf_dirdirty = TRUE;
        }

        /* Place byte in buffer and mark buffer "dirty" */

        *lfptr->lfbyte++ = ch;
        lfptr->lfpos++;
        lfptr->lfdbdirty = TRUE;

        signal(lfptr->lfmutex);
        return OK;
}