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 ValueTask <T> ReadAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
return(new ValueTask <T>(Task.FromCanceled <T>(cancellationToken)));
}
BoundedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// If there are any items, hand one back.
if (!parent._items.IsEmpty)
{
return(new ValueTask <T>(DequeueItemAndPostProcess()));
}
// There weren't any items. If we're done writing so that there
// will never be more items, fail.
if (parent._doneWriting != null)
{
return(ChannelUtilities.GetInvalidCompletionValueTask <T>(parent._doneWriting));
}
// Otherwise, queue the reader.
var reader = ReaderInteractor <T> .Create(parent._runContinuationsAsynchronously, cancellationToken);
parent._blockedReaders.EnqueueTail(reader);
return(new ValueTask <T>(reader.Task));
}
}
public override ValueTask <T> ReadAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
return(new ValueTask <T>(Task.FromCanceled <T>(cancellationToken)));
}
BoundedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// If there are any items, hand one back.
if (!parent._items.IsEmpty)
{
return(new ValueTask <T>(DequeueItemAndPostProcess()));
}
// There weren't any items. If we're done writing so that there
// will never be more items, fail.
if (parent._doneWriting != null)
{
return(ChannelUtilities.GetInvalidCompletionValueTask <T>(parent._doneWriting));
}
// If we're able to use the singleton reader, do so.
if (!cancellationToken.CanBeCanceled)
{
AsyncOperation <T> singleton = _readerSingleton;
if (singleton.TryOwnAndReset())
{
parent._blockedReaders.EnqueueTail(singleton);
return(singleton.ValueTaskOfT);
}
}
// Otherwise, queue a reader. Note that in addition to checking whether synchronous continuations were requested,
// we also check whether the supplied cancellation token can be canceled. The writer calls UnregisterCancellation
// while holding the lock, and if a callback needs to be unregistered and is currently running, it needs to wait
// for that callback to complete so that the subsequent code knows it won't be contending with another thread
// trying to complete the operation. However, if we allowed a synchronous continuation from this operation, that
// cancellation callback could end up running arbitrary code, including code that called back into the reader or
// writer and tried to take the same lock held by the thread running UnregisterCancellation... deadlock. As such,
// we only allow synchronous continuations here if both a) the caller requested it and the token isn't cancelable.
var reader = new AsyncOperation <T>(parent._runContinuationsAsynchronously | cancellationToken.CanBeCanceled, cancellationToken);
parent._blockedReaders.EnqueueTail(reader);
return(reader.ValueTaskOfT);
}
}
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.
// 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, queue a reader.
var waiter = new AsyncOperation <bool>(parent._runContinuationsAsynchronously, cancellationToken);
ChannelUtilities.QueueWaiter(ref _parent._waitingReadersTail, waiter);
return(waiter.ValueTaskOfT);
}
}
public override bool TryRead([MaybeNullWhen(false)] out T item)
{
BoundedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// Get an item if there is one.
if (!parent._items.IsEmpty)
{
item = DequeueItemAndPostProcess();
return(true);
}
}
item = default !;
public override ValueTask <T> ReadAsync(CancellationToken cancellationToken)
{
if (cancellationToken.IsCancellationRequested)
{
return(new ValueTask <T>(Task.FromCanceled <T>(cancellationToken)));
}
BoundedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// If there are any items, hand one back.
if (!parent._items.IsEmpty)
{
return(new ValueTask <T>(DequeueItemAndPostProcess()));
}
// There weren't any items. If we're done writing so that there
// will never be more items, fail.
if (parent._doneWriting != null)
{
return(ChannelUtilities.GetInvalidCompletionValueTask <T>(parent._doneWriting));
}
// If we're able to use the singleton reader, do so.
if (!cancellationToken.CanBeCanceled)
{
AsyncOperation <T> singleton = _readerSingleton;
if (singleton.TryOwnAndReset())
{
parent._blockedReaders.EnqueueTail(singleton);
return(singleton.ValueTaskOfT);
}
}
// Otherwise, queue the reader.
var reader = new AsyncOperation <T>(parent._runContinuationsAsynchronously, cancellationToken);
parent._blockedReaders.EnqueueTail(reader);
return(reader.ValueTaskOfT);
}
}
public override bool TryPeek([MaybeNullWhen(false)] out T item)
{
BoundedChannel <T> parent = _parent;
lock (parent.SyncObj)
{
parent.AssertInvariants();
// Peek at an item if there is one.
if (!parent._items.IsEmpty)
{
item = parent._items.PeekHead();
return(true);
}
}
item = default;
return(false);
}
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)) :