/**
* Cancellation handlers
*/
/**
* Try to cancel an async take request.
*/
private void TakeCancellationHandler(object _takeNode, bool canceling)
{
LinkedListNode <AsyncTake> takeNode = (LinkedListNode <AsyncTake>)_takeNode;
AsyncTake take = null;
// Acquire the lock to access the shared mutable state
lock (theLock) {
/**
* Here, the async take request can be completed or canceled
*/
if (!takeNode.Value.done)
{
// Remove the async take from the queue and mark it as canceled
asyncTakes.Remove(takeNode);
take = takeNode.Value;
take.done = true;
}
}
if (take != null)
{
// Dispose resources associated with this async take request.
take.Dispose(canceling);
// Complete the underlying task properly.
if (canceling)
{
take.SetCanceled();
}
else
{
take.SetResult(null);
}
}
}
/**
* Put a message on the queue asynchronously enabling, optionally,
* a timeout and/or cancellation.
*/
public Task <bool> PutAsync(T sentMessage, int timeout = Timeout.Infinite,
CancellationToken cToken = default(CancellationToken))
{
Task <bool> putTask = null;
AsyncTake take = null;
lock (theLock) {
if (state != OPERATING)
{
throw new InvalidOperationException();
}
if ((putIdx - takeIdx) < capacity)
{
// Do an immediate put
messageRoom[putIdx++ & mask] = sentMessage;
putTask = trueTask;
// Try to satisfy a pending async take request.
if (asyncTakes.Count > 0)
{
take = asyncTakes.First.Value;
asyncTakes.RemoveFirst();
take.receivedMessage = messageRoom[takeIdx++ & mask];
take.done = true;
}
}
else
{
// The current thread must block, so we check for immediate cancelers
if (timeout == 0)
{
return(falseTask);
}
// If a cancellation was requested return a task in the Canceled state
if (cToken.IsCancellationRequested)
{
return(Task.FromCanceled <bool>(cToken));
}
// Create a waiter node and insert it in the wait queue
AsyncPut put = new AsyncPut(sentMessage, cToken);
LinkedListNode <AsyncPut> putNode = asyncPuts.AddLast(put);
/**
* Activate the specified cancelers owning the lock.
* Since the timeout handler acquires the lock before use the "put.timer" and
* "put.cTokenRegistration" the assignements will be visible.
*/
if (timeout != Timeout.Infinite)
{
put.timer = new Timer(putTimeoutHandler, putNode, timeout, Timeout.Infinite);
}
/**
* If the cancellation token is already in the canceled state, the cancellation
* will run immediately and synchronously, which causes no damage because the
* implicit locks can be acquired recursively and this is a terminal processing.
*/
if (cToken.CanBeCanceled)
{
put.cTokenRegistration = cToken.Register(putCancellationHandler, putNode);
}
// Set the result task that represents the asynchronous operation
putTask = put.Task;
}
}
// If we released any putter, cancel its cancellers and complete its tasks.
if (take != null)
{
take.Dispose();
take.SetResult(take.receivedMessage);
}
return(putTask);
}
