ptcount.c

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#include <xinu.h>

int32 ptcount(int32 portid)
{
    intmask mask;          /* Saved interrupt mask      */
    int32 count;           /* Count of messages available   */
    int32 sndcnt;          /* Count of sender semaphore */
    struct ptentry *ptptr; /* Pointer to port table entry   */

    mask = disable();
    if (isbadport(portid) ||
        (ptptr = &porttab[portid])->ptstate != PT_ALLOC)
    {
        restore(mask);
        return SYSERR;
    }

    /* Get count of messages available */

    count = semcount(ptptr->ptrsem);

    /* If messages are waiting, check for blocked senders */

    if (count >= 0)
    {
        sndcnt = semcount(ptptr->ptssem);
        if (sndcnt < 0)
        { /* -sndcnt senders blocked */
            count += -sndcnt;
        }
    }
    restore(mask);
    return count;
}