semcreate.c

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#include <xinu.h>

local sid32 newsem(void);

sid32 semcreate(int32 count)
{
    intmask mask; /* Saved interrupt mask       */
    sid32 sem;    /* Semaphore ID to return */

    mask = disable();

    if (count < 0 || ((sem = newsem()) == SYSERR))
    {
        restore(mask);
        return SYSERR;
    }
    semtab[sem].scount = count; /* Initialize table entry   */

    restore(mask);
    return sem;
}

local sid32 newsem(void)
{
    static sid32 nextsem = 0; /* Next semaphore index to try    */
    sid32 sem;                /* Semaphore ID to return */
    int32 i;                  /* Iterate through # entries  */

    for (i = 0; i < NSEM; i++)
    {
        sem = nextsem++;
        if (nextsem >= NSEM)
            nextsem = 0;
        if (semtab[sem].sstate == S_FREE)
        {
            semtab[sem].sstate = S_USED;
            return sem;
        }
    }
    return SYSERR;
}