public async Task <(T result, bool success)> TryDequeueAsync(CancellationToken token)
{
WaitQueueReader reader = null;
Item item = new Item();
lock (ThisLock)
{
if (_queueState == QueueState.Open)
{
if (_itemQueue.HasAvailableItem)
{
item = _itemQueue.DequeueAvailableItem();
}
else
{
reader = new WaitQueueReader(this);
_readerQueue.Enqueue(reader);
}
}
else if (_queueState == QueueState.Shutdown)
{
if (_itemQueue.HasAvailableItem)
{
item = _itemQueue.DequeueAvailableItem();
}
else if (_itemQueue.HasAnyItem)
{
reader = new WaitQueueReader(this);
_readerQueue.Enqueue(reader);
}
else
{
return(default(T), true);
}
}
else // queueState == QueueState.Closed
{
return(default(T), true);
}
}
if (reader != null)
{
return(await reader.WaitAsync(token));
}
else
{
InvokeDequeuedCallback(item.DequeuedCallback);
return(item.GetValue(), true);
}
}