diff options
Diffstat (limited to 'src/backend/storage/ipc/shmqueue.c')
| -rw-r--r-- | src/backend/storage/ipc/shmqueue.c | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/src/backend/storage/ipc/shmqueue.c b/src/backend/storage/ipc/shmqueue.c index 1cf69a09c83..5d684b2b85f 100644 --- a/src/backend/storage/ipc/shmqueue.c +++ b/src/backend/storage/ipc/shmqueue.c @@ -104,7 +104,6 @@ SHMQueueInsertBefore(SHM_QUEUE *queue, SHM_QUEUE *elem) * element. Inserting "after" the queue head puts the elem * at the head of the queue. */ -#ifdef NOT_USED void SHMQueueInsertAfter(SHM_QUEUE *queue, SHM_QUEUE *elem) { @@ -118,7 +117,6 @@ SHMQueueInsertAfter(SHM_QUEUE *queue, SHM_QUEUE *elem) queue->next = elem; nextPtr->prev = elem; } -#endif /* NOT_USED */ /*-------------------- * SHMQueueNext -- Get the next element from a queue @@ -156,6 +154,25 @@ SHMQueueNext(const SHM_QUEUE *queue, const SHM_QUEUE *curElem, Size linkOffset) return (Pointer) (((char *) elemPtr) - linkOffset); } +/*-------------------- + * SHMQueuePrev -- Get the previous element from a queue + * + * Same as SHMQueueNext, just starting at tail and moving towards head + * All other comments and usage applies. + */ +Pointer +SHMQueuePrev(const SHM_QUEUE *queue, const SHM_QUEUE *curElem, Size linkOffset) +{ + SHM_QUEUE *elemPtr = curElem->prev; + + Assert(ShmemAddrIsValid(curElem)); + + if (elemPtr == queue) /* back to the queue head? */ + return NULL; + + return (Pointer) (((char *) elemPtr) - linkOffset); +} + /* * SHMQueueEmpty -- TRUE if queue head is only element, FALSE otherwise */ |