/* queue.h - firstid, firstkey, isempty, lastkey, nonempty              */

/* Queue structure declarations, constants, and inline functions        */

/* Default # of queue entries: 1 per process plus 2 for ready list plus */
/*                      2 for sleep list plus 2 per semaphore           */
#ifndef NQENT
#define NQENT   (NPROC + 4 + NSEM + NSEM)
#endif

#define EMPTY   (-1)            /* Null value for qnext or qprev index  */
#define MAXKEY  0x7FFFFFFF      /* Max key that can be stored in queue  */
#define MINKEY  0x80000000      /* Min key that can be stored in queue  */

struct  qentry  {               /* One per process plus two per list    */
        int32   qkey;           /* Key on which the queue is ordered    */
        qid16   qnext;          /* Index of next process or tail        */
        qid16   qprev;          /* Index of previous process or head    */
};

extern  struct qentry   queuetab[];

/* Inline queue manipulation functions */

#define queuehead(q)    (q)
#define queuetail(q)    ((q) + 1)
#define firstid(q)      (queuetab[queuehead(q)].qnext)
#define lastid(q)       (queuetab[queuetail(q)].qprev)
#define isempty(q)      (firstid(q) >= NPROC)
#define nonempty(q)     (firstid(q) <  NPROC)
#define firstkey(q)     (queuetab[firstid(q)].qkey)
#define lastkey(q)      (queuetab[ lastid(q)].qkey)

/* Inline to check queue id assumes interrupts are disabled */

#define isbadqid(x)     (((int32)(x) < NPROC) || (int32)(x) >= NQENT-1)