/// <summary>
/// Adds a reader from exclusive reader lock
/// </summary>
/// <remarks>
/// 1. _wTail erlTail
/// ↓ ↓
/// R−→R−→R ―► R−→R−→R−→E
/// ↑ ↑
/// _tail _tail
///
///
/// 2. _wTail _wTail erlTail
/// ↓ ↓ ↓
/// R−→R−→W ―► R−→R−→W−→E
/// ↑ ↑
/// _tail _tail
///
///
/// 3. _wTail _wTail erlTail
/// ↓ ↓ ↓
/// R−→W−→W−→R−→R ―► R−→W−→W−→R−→R−→E
/// ↑ ↑
/// _tail _tail
///
///
/// 4. _wTail _tail _wTail _tail
/// ↓ ↓ ↓ ↓
/// R−→W−→W−→E−→R ―► R−→W−→W−→E−→E−→R
/// ↑ ↑
/// erlTail erlTail
/// </remarks>
public void AddExclusiveReader(ExclusiveReaderLockSource item, out bool isAddedAfterWriterOrExclusiveReader) {
lock (this) {
var erlTail = item.ExclusiveReaderLock.Tail;
if (erlTail?.Next == null) {
UpdateTail(item);
isAddedAfterWriterOrExclusiveReader = _wTail != null || erlTail != null;
} else {
Link(item, erlTail.Next);
Link(erlTail, item);
isAddedAfterWriterOrExclusiveReader = true;
}
Interlocked.Exchange(ref item.ExclusiveReaderLock.Tail, item);
}
}
/// <summary>
/// Adds a reader from exclusive reader lock
/// </summary>
/// <remarks>
/// 1. _wTail erlTail
/// ↓ ↓
/// R−→R−→R ―► R−→R−→R−→E
/// ↑ ↑
/// _tail _tail
///
///
/// 2. _wTail _wTail erlTail
/// ↓ ↓ ↓
/// R−→R−→W ―► R−→R−→W−→E
/// ↑ ↑
/// _tail _tail
///
///
/// 3. _wTail _wTail erlTail
/// ↓ ↓ ↓
/// R−→W−→W−→R−→R ―► R−→W−→W−→R−→R−→E
/// ↑ ↑
/// _tail _tail
///
///
/// 4. _wTail _tail _wTail _tail
/// ↓ ↓ ↓ ↓
/// R−→W−→W−→E−→R ―► R−→W−→W−→E−→E−→R
/// ↑ ↑
/// erlTail erlTail
/// </remarks>
public void AddExclusiveReader(ExclusiveReaderLockSource item, out bool isAddedAfterWriterOrExclusiveReader)
{
lock (this) {
var erlTail = item.ExclusiveReaderLock.Tail;
if (erlTail?.Next == null)
{
UpdateTail(item);
isAddedAfterWriterOrExclusiveReader = _wTail != null || erlTail != null;
}
else
{
Link(item, erlTail.Next);
Link(erlTail, item);
isAddedAfterWriterOrExclusiveReader = true;
}
Interlocked.Exchange(ref item.ExclusiveReaderLock.Tail, item);
}
}
private Task <IAsyncReaderWriterLockToken> ExclusiveReaderLockAsync(ExclusiveReaderLock erLock, CancellationToken cancellationToken = default(CancellationToken))
{
TaskUtilities.AssertIsOnBackgroundThread();
if (cancellationToken.IsCancellationRequested)
{
return(Task.FromCanceled <IAsyncReaderWriterLockToken>(cancellationToken));
}
var source = new ExclusiveReaderLockSource(this, erLock);
_queue.AddExclusiveReader(source, out var isAddedAfterWriterOrExclusiveReader);
if (isAddedAfterWriterOrExclusiveReader)
{
source.RegisterCancellation(cancellationToken);
}
else
{
source.Release();
}
return(source.Task);
}
