ptcreate.c

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#include <xinu.h>

syscall ptcreate(int32 count)
{
    intmask mask;          /* Saved interrupt mask      */
    int32 i;               /* Counts all possible ports */
    int32 ptnum;           /* Candidate port number to try  */
    struct ptentry *ptptr; /* Pointer to port table entry   */

    mask = disable();
    if (count < 0)
    {
        restore(mask);
        return SYSERR;
    }

    for (i = 0; i < NPORTS; i++)
    {                     /* Count all table entries    */
        ptnum = ptnextid; /* Get an entry to check  */
        if (++ptnextid >= NPORTS)
        {
            ptnextid = 0; /* Reset for next iteration   */
        }

        /* Check table entry that corresponds to ID ptnum */

        ptptr = &porttab[ptnum];
        if (ptptr->ptstate == PT_FREE)
        {
            ptptr->ptstate = PT_ALLOC;
            ptptr->ptssem = semcreate(count);
            ptptr->ptrsem = semcreate(0);
            ptptr->pthead = ptptr->pttail = NULL;
            ptptr->ptseq++;
            ptptr->ptmaxcnt = count;
            restore(mask);
            return ptnum;
        }
    }
    restore(mask);
    return SYSERR;
}