/**
* Try to cancel an async put request.
*/
private void PutCancellationHandler(object _putNode, bool canceling)
{
LinkedListNode <AsyncPut> putNode = (LinkedListNode <AsyncPut>)_putNode;
AsyncPut put = null;
lock (theLock) {
if (!putNode.Value.done)
{
asyncPuts.Remove(putNode);
put = putNode.Value;
put.done = true;
}
}
if (put != null)
{
// Dispose resources associated with this async put request.
put.Dispose(canceling);
// Complete the underlying task properly.
if (canceling)
{
put.SetCanceled();
}
else
{
put.SetResult(false);
}
}
}
/**
* Asynchronous TAP interface
*/
/**
* Take a message from the queue asynchronously enabling, optionally,
* timeout and/or cancellation.
*/
public Task <T> TakeAsync(int timeout = Timeout.Infinite,
CancellationToken cToken = default(CancellationToken))
{
Task <T> takeTask = null;
AsyncPut put = null;
lock (theLock) {
if (putIdx - takeIdx > 0)
{
// Immediate take
takeTask = Task.FromResult <T>(messageRoom[takeIdx++ & mask]);
// Try to satisfy a pending async put request
if (asyncPuts.Count > 0)
{
put = asyncPuts.First.Value;
asyncPuts.RemoveFirst();
messageRoom[putIdx++ & mask] = put.sentMessage;
put.done = true;
}
/**
* If the queue is in the COMPLETING state, the message queue is empty and
* we released the last pending put, then transition the queue to the
* COMPLETED state.
*/
if (putIdx == takeIdx && state == COMPLETING && asyncPuts.Count == 0)
{
state = COMPLETED;
}
}
else
{
// If the queue was already completed or an immediate take was spedified
// return failure.
if (state != OPERATING)
{
throw new InvalidOperationException();
}
if (timeout == 0)
{
return(nullTask);
}
// If a cancellation was requested return a task in the Canceled state
if (cToken.IsCancellationRequested)
{
return(Task.FromCanceled <T>(cToken));
}
// Create a waiter node and insert it in the wait queue
AsyncTake take = new AsyncTake(cToken);
LinkedListNode <AsyncTake> takeNode = asyncTakes.AddLast(take);
/**
* Activate the specified cancellers owning the lock.
* Since the timeout handler acquires the lock before use the "take.timer" and
* "take.cTokenRegistration" the assignements will be visible.
*/
if (timeout != Timeout.Infinite)
{
take.timer = new Timer(takeTimeoutHandler, takeNode, timeout, Timeout.Infinite);
}
/**
* If the cancellation token is already in the cancelled 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)
{
take.cTokenRegistration = cToken.Register(takeCancellationHandler, takeNode);
}
// Set the result task that represents the asynchronous operation
takeTask = take.Task;
}
}
// If we released any putter, cancel its cancellers and complete its task.
if (put != null)
{
put.Dispose();
put.SetResult(true);
}
return(takeTask);
}