public Task <IDisposable> EnterAsync(CancellationToken ct)
{
// The item may have been already dequeued by the previous since it was set as '_next',
// If so, return sync (note: the '_count' was already incremented)
if (_state == State.Waiting)
{
_enterAsync = new FastTaskCompletionSource <IDisposable>();
if (ct.CanBeCanceled)
{
_enterAsync.OnCompleted(ct.Register(Abort).Dispose);
void Abort()
{
if (Interlocked.CompareExchange(ref _state, State.Aborted, State.Waiting) == State.Waiting)
{
_enterAsync.SetCanceled();
}
}
}
// This instance may have been dequeued by previous while we where initiazing the async hanlde,
// so make sure to not wait a task that will never complete.
if (_state == State.Waiting)
{
return(_enterAsync.Task);
}
}
return(Task.FromResult <IDisposable>(new Handle(this)));
}
private bool DequeueWaiter(out FastTaskCompletionSource <bool> result)
{
#if HAS_NO_CONCURRENT_DICT
lock (_queue)
{
if (_queue.Count == 0)
{
result = null;
return(false);
}
result = _queue.Dequeue();
return(true);
}
#else
return(_queue.TryDequeue(out result));
#endif
}
public Task <bool> Wait(CancellationToken cancellationToken)
{
var src = new FastTaskCompletionSource <bool>();
bool shouldWait;
int result;
do
{
if (cancellationToken.IsCancellationRequested)
{
src.TrySetResult(false);
return(src.Task);
}
shouldWait = true;
result = _currentCount;
if (result > 0)
{
shouldWait = false;
}
else
{
break;
}
} while (Interlocked.CompareExchange(ref _currentCount, result - 1, result) != result);
if (!shouldWait)
{
src.TrySetResult(true);
}
else
{
#if HAS_NO_CONCURRENT_DICT
lock (_queue)
#endif
{
_queue.Enqueue(src);
}
}
return(src.Task);
}
