Function SHMQueueNext

src/backend/storage/ipc/shmqueue.c:144–155

-------------------- * SHMQueueNext -- Get the next element from a queue * * To start the iteration, pass the queue head as both queue and curElem. * Returns NULL if no more elements. * * Next element is at curElem->next. If SHMQueue is part of * a larger structure, we want to return a pointer to the * whole structure rather than a pointer to its SHMQueue field. * For example, * struct

 *--------------------
 */
Pointer
SHMQueueNext(const SHM_QUEUE *queue, const SHM_QUEUE *curElem, Size linkOffset)
{
	SHM_QUEUE  *elemPtr = curElem->next;

	Assert(ShmemAddrIsValid(curElem));

	if (elemPtr == queue)		/* back to the queue head? */
		return NULL;

	return (Pointer) (((char *) elemPtr) - linkOffset);
}

/*--------------------
 * SHMQueuePrev -- Get the previous element from a queue