public override bool TryRead(out T item)
{
SingleConsumerUnboundedChannel <T> parent = _parent;
if (parent._items.TryDequeue(out item))
{
if (parent._doneWriting != null && parent._items.IsEmpty)
{
ChannelUtilities.Complete(parent._completion, parent._doneWriting);
}
return(true);
}
return(false);
}
public override Task <bool> WaitToReadAsync(CancellationToken cancellationToken)
{
// Outside of the lock, check if there are any items waiting to be read. If there are, we're done.
return(!_parent._items.IsEmpty ?
ChannelUtilities.s_trueTask :
WaitToReadAsyncCore(cancellationToken));
Task <bool> WaitToReadAsyncCore(CancellationToken ct)
{
// Now check for cancellation.
if (ct.IsCancellationRequested)
{
return(Task.FromCanceled <bool>(ct));
}
SingleConsumerUnboundedChannel <T> parent = _parent;
ReaderInteractor <bool> oldWaiter = null, newWaiter;
lock (parent.SyncObj)
{
// Again while holding the lock, check to see if there are any items available.
if (!parent._items.IsEmpty)
{
return(ChannelUtilities.s_trueTask);
}
// There aren't any items; if we're done writing, there never will be more items.
if (parent._doneWriting != null)
{
return(parent._doneWriting != ChannelUtilities.s_doneWritingSentinel ?
Task.FromException <bool>(parent._doneWriting) :
ChannelUtilities.s_falseTask);
}
// Create the new waiter. We're a bit more tolerant of a stray waiting reader
// than we are of a blocked reader, as with usage patterns it's easier to leave one
// behind, so we just cancel any that may have been waiting around.
oldWaiter = parent._waitingReader;
parent._waitingReader = newWaiter = ReaderInteractor <bool> .Create(parent._runContinuationsAsynchronously, ct);
}
oldWaiter?.TrySetCanceled();
return(newWaiter.Task);
}
}
internal UnboundedChannelReader(SingleConsumerUnboundedChannel <T> parent) => _parent = parent;