Hi all, just got a couple of questions about Semaphores.
Here's a brief summary of what I am trying to achieve:
I am writing a thread-safe FIFO queue.
The Queue Class has a Semaphore to notify any relevant Threads that an item
is available in the queue.
The Semaphore is created with an initial value of 0 as follows:
FNotifySemaphore := CreateSemaphore( nil, 0, MAXINT, nil );
After enque(ing) an Item I basically increment the Semaphore counter:
ReleaseSemaphore( FNotifySemaphore, 1, nil );
Before dequeue(ing) I block the Thread until an item is available:
if ( WaitForSingleObject( FNotifySemaphore, INFINITE) = WAIT_OBJECT_0 ) then
...
The Queue Class has a Clear function that simply empties the Queue.
Within the Clear function, I need to reset the Semaphore counter back to 0
(since there are now no items in the Queue).
This has raised the following questions:
1. There does not appear to be any mechanism for resetting the count value
of a Semaphore.
Can this only be done by releasing the Semaphore handle and then
recreating the Semaphore ?
ie.
CloseHandle( FNotifySemaphore );
FNotifySemaphore := CreateSemaphore( nil, 0, MAXINT, nil );
2. What happens if the handle of a Semaphore is released while a Thread is
waiting on a WaitForSingleObject call for that particular Semaphore handle ?
thanks for any help
Dale McKay
