/// <summary>Dequeues an item, and then fixes up our state around writers and completion.</summary>
/// <returns>The dequeued item.</returns>
private T DequeueItemAndPostProcess()
{
BoundedChannel <T> parent = _parent;
Debug.Assert(Monitor.IsEntered(parent.SyncObj));
// Dequeue an item.
T item = parent._items.DequeueHead();
// If we're now empty and we're done writing, complete the channel.
if (parent._doneWriting != null && parent._items.IsEmpty)
{
ChannelUtilities.Complete(parent._completion, parent._doneWriting);
}
// If there are any writers blocked, there's now room for at least one
// to be promoted to have its item moved into the items queue. We need
// to loop while trying to complete the writer in order to find one that
// hasn't yet been canceled (canceled writers transition to canceled but
// remain in the physical queue).
while (!parent._blockedWriters.IsEmpty)
{
WriterInteractor <T> w = parent._blockedWriters.DequeueHead();
if (w.Success(default(VoidResult)))
{
parent._items.EnqueueTail(w.Item);
return(item);
}
}
// There was no blocked writer, so see if there's a WaitToWriteAsync
// we should wake up.
ChannelUtilities.WakeUpWaiters(ref parent._waitingWriters, result: true);
// Return the item
return(item);
}
public override bool TryRead(out T item)
{
UnbufferedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// Try to find a writer to pair with
while (!parent._blockedWriters.IsEmpty)
{
WriterInteractor <T> w = parent._blockedWriters.DequeueHead();
if (w.Success(default(VoidResult)))
{
item = w.Item;
return(true);
}
}
}
// None found
item = default;
return(false);
}