public override ValueTask <bool> WaitToReadAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
return(new ValueTask <bool>(Task.FromCanceled <bool>(cancellationToken)));
}
BoundedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// If there are any items available, a read is possible.
if (!parent._items.IsEmpty)
{
return(new ValueTask <bool>(true));
}
// There were no items available, so if we're done writing, a read will never be possible.
if (parent._doneWriting != null)
{
return(parent._doneWriting != ChannelUtilities.s_doneWritingSentinel ?
new ValueTask <bool>(Task.FromException <bool>(parent._doneWriting)) :
new ValueTask <bool>(false));
}
// There were no items available, but there could be in the future, so ensure
// there's a blocked reader task and return it.
var waiter = new AsyncOperation <bool>(parent._runContinuationsAsynchronously, cancellationToken);
ChannelUtilities.QueueWaiter(ref _parent._waitingReadersTail, waiter);
return(waiter.ValueTaskOfT);
}
}
public override ValueTask <bool> WaitToReadAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
return(new ValueTask <bool>(Task.FromCanceled <bool>(cancellationToken)));
}
if (!_parent._items.IsEmpty)
{
return(new ValueTask <bool>(true));
}
UnboundedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// Try again to read now that we're synchronized with writers.
if (!parent._items.IsEmpty)
{
return(new ValueTask <bool>(true));
}
// There are no items, so if we're done writing, there's never going to be data available.
if (parent._doneWriting != null)
{
return(parent._doneWriting != ChannelUtilities.s_doneWritingSentinel ?
new ValueTask <bool>(Task.FromException <bool>(parent._doneWriting)) :
new ValueTask <bool>(false));
}
// If we're able to use the singleton waiter, do so.
if (!cancellationToken.CanBeCanceled)
{
AsyncOperation <bool> singleton = _waiterSingleton;
if (singleton.TryOwnAndReset())
{
ChannelUtilities.QueueWaiter(ref parent._waitingReadersTail, singleton);
return(singleton.ValueTaskOfT);
}
}
// Otherwise, create and queue a waiter.
var waiter = new AsyncOperation <bool>(parent._runContinuationsAsynchronously, cancellationToken);
ChannelUtilities.QueueWaiter(ref parent._waitingReadersTail, waiter);
return(waiter.ValueTaskOfT);
}
}
