public AsyncReaderWriterLock()
{
_readerTail = new ReaderLockSource(this);
_writerTail = new WriterLockSource(this);
_readerTail.CompleteTasks();
_writerTail.TryCompleteTask();
_writerTail.Task.Result.Dispose();
}
public bool TrySetNext(out WriterLockSource next)
{
if (_nextWriter != null)
{
next = null;
return(false);
}
next = new WriterLockSource(_host);
return(Interlocked.CompareExchange(ref _nextWriter, next, null) == null);
}
private void CompleteReaderTasksIfRequired(WriterLockSource writer)
{
var reader = _readerTail;
while (writer != null && writer.IsCompleted)
{
writer = writer.NextWriter;
}
// No writer source left - complete reader source tasks
if (writer == null)
{
reader.CompleteTasks();
}
}
private void CompleteNextTask(WriterLockSource writer)
{
var reader = _readerTail;
while (writer != null && !writer.TryCompleteTask())
{
writer = writer.NextWriter;
}
// No writer source left - complete reader source tasks
if (writer == null)
{
reader.CompleteTasks();
}
}
public Task <IAsyncReaderWriterLockToken> WriterLockAsync(CancellationToken cancellationToken = default(CancellationToken), ReentrancyToken reentrancyToken = default(ReentrancyToken))
{
Task <IAsyncReaderWriterLockToken> task;
var writerFromToken = WriterLockTokenFactory.GetSource(reentrancyToken);
if (writerFromToken != null && writerFromToken.TryReenter(out task))
{
return(task);
}
while (true)
{
if (cancellationToken.IsCancellationRequested)
{
return(Task.FromCanceled <IAsyncReaderWriterLockToken>(cancellationToken));
}
WriterLockSource oldWriter = _writerTail;
WriterLockSource newWriter;
if (!oldWriter.TrySetNext(out newWriter))
{
continue;
}
var reader = oldWriter.IsCompleted && _lastAcquiredWriter == oldWriter
? Interlocked.Exchange(ref _readerTail, new ReaderLockSource(this))
: null;
if (Interlocked.CompareExchange(ref _writerTail, newWriter, oldWriter) != oldWriter)
{
throw new InvalidOperationException();
}
if (reader != null) // oldWriter.IsCompleted
{
reader.RegisterWait(newWriter, cancellationToken);
}
else
{
oldWriter.RegisterWait(cancellationToken);
}
return(newWriter.Task);
}
}
public void RegisterWait(WriterLockSource writer, CancellationToken cancellationToken)
{
Interlocked.Exchange(ref _writer, writer);
CompleteTasks();
if (cancellationToken.IsCancellationRequested)
{
CancelWaitReaders(cancellationToken);
}
else if (_count == 0)
{
writer.TryCompleteTask();
}
else if (cancellationToken.CanBeCanceled)
{
cancellationToken.Register(CancelWaitReaders, cancellationToken, false);
}
}
public Token(Action dispose, WriterLockSource reentrancySource)
{
_dispose = dispose;
Reentrancy = WriterLockTokenFactory.Create(reentrancySource);
}
