public Task <IAsyncReaderWriterLockToken> WriterLockAsync(CancellationToken cancellationToken = default(CancellationToken), ReentrancyToken reentrancyToken = default(ReentrancyToken))
{
TaskUtilities.AssertIsOnBackgroundThread();
var task = ReentrantOrCanceled(true, cancellationToken, reentrancyToken);
if (task != null)
{
return(task);
}
var source = new LockSource(this, true);
_queue.AddWriter(source, out var isFirstWriter);
if (isFirstWriter)
{
source.Release();
}
else
{
source.RegisterCancellation(cancellationToken);
}
return(source.Task);
}
static AsyncReaderWriterLock()
{
LockTokenFactory = ReentrancyToken.CreateFactory <LockSource>();
}
private static Task <IAsyncReaderWriterLockToken> ReentrantOrCanceled(bool writerOnly, CancellationToken cancellationToken, ReentrancyToken reentrancyToken)
{
var source = LockTokenFactory.GetSource(reentrancyToken);
if (source != null && source.TryReenter(writerOnly, out var task))
{
return(task);
}
return(cancellationToken.IsCancellationRequested ? Task.FromCanceled <IAsyncReaderWriterLockToken>(cancellationToken) : null);
}
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 Task <IAsyncReaderWriterLockToken> ReaderLockAsync(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);
}
var readerFromToken = ReaderLockTokenFactory.GetSource(reentrancyToken);
if (readerFromToken != null && readerFromToken.TryReenter(out task))
{
return(task);
}
while (true)
{
if (cancellationToken.IsCancellationRequested)
{
return(Task.FromCanceled <IAsyncReaderWriterLockToken>(cancellationToken));
}
task = _readerTail.WaitAsync(cancellationToken);
if (task != null)
{
return(task);
}
}
}
public Token(Action dispose, ReaderLockSource reentrancySource)
{
_dispose = dispose;
Reentrancy = ReaderLockTokenFactory.Create(reentrancySource);
}