public override Task <bool> WaitToReadAsync(CancellationToken cancellationToken)
{
// If there are any items, readers can try to get them.
return(!_parent._items.IsEmpty ?
ChannelUtilities.s_trueTask :
WaitToReadAsyncCore(cancellationToken));
Task <bool> WaitToReadAsyncCore(CancellationToken ct)
{
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(ChannelUtilities.s_trueTask);
}
// 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 ?
Task.FromException <bool>(parent._doneWriting) :
ChannelUtilities.s_falseTask);
}
// Queue the waiter
return(ChannelUtilities.GetOrCreateWaiter(ref parent._waitingReaders, parent._runContinuationsAsynchronously, ct));
}
}
}
public override Task <bool> WaitToReadAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
return(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(ChannelUtilities.s_trueTask);
}
// 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 ?
Task.FromException <bool>(parent._doneWriting) :
ChannelUtilities.s_falseTask);
}
// There were no items available, but there could be in the future, so ensure
// there's a blocked reader task and return it.
return(ChannelUtilities.GetOrCreateWaiter(ref parent._waitingReaders, parent._runContinuationsAsynchronously, cancellationToken));
}
}
public override Task <bool> WaitToReadAsync(CancellationToken cancellationToken)
{
UnbufferedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
// If we're done writing, fail.
if (parent._completion.Task.IsCompleted)
{
return(parent._completion.Task.IsFaulted ?
Task.FromException <bool>(parent._completion.Task.Exception.InnerException) :
ChannelUtilities.s_falseTask);
}
// If there's a blocked writer, we can read.
if (!parent._blockedWriters.IsEmpty)
{
return(ChannelUtilities.s_trueTask);
}
// Otherwise, queue the waiter.
return(ChannelUtilities.GetOrCreateWaiter(ref parent._waitingReaders, true, cancellationToken));
}
}
