1 files changed, 98 insertions, 0 deletions
diff --git a/qpid/dotnet/Qpid.Client/Client/Util/FlowControlQueue.cs b/qpid/dotnet/Qpid.Client/Client/Util/FlowControlQueue.cs
new file mode 100644
index 0000000000..a06de9eac8
--- /dev/null
+++ b/qpid/dotnet/Qpid.Client/Client/Util/FlowControlQueue.cs
@@ -0,0 +1,98 @@
+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ * 
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ *
+ */
+using System;
+using System.Collections;
+using System.Text;
+using System.Threading;
+using Apache.Qpid.Collections;
+using Apache.Qpid.Common;
+
+namespace Apache.Qpid.Client.Util
+{
+   internal delegate void ThresholdMethod(int currentCount);
+
+   /// <summary>
+   /// Basic bounded queue used to implement prefetching.
+   /// Notice we do the callbacks here asynchronously to
+   /// avoid adding more complexity to the channel impl.
+   /// </summary>
+   internal class FlowControlQueue
+   {
+      private BlockingQueue _queue = new LinkedBlockingQueue();
+      private int _itemCount;
+      private int _lowerBound;
+      private int _upperBound;
+      private ThresholdMethod _underThreshold;
+      private ThresholdMethod _overThreshold;
+
+      public FlowControlQueue(
+         int lowerBound, 
+         int upperBound,
+         ThresholdMethod underThreshold,
+         ThresholdMethod overThreshold
+         )
+      {
+         _lowerBound = lowerBound;
+         _upperBound = upperBound;
+         _underThreshold = underThreshold;
+         _overThreshold = overThreshold;
+      }
+
+      public void Enqueue(object item)
+      {
+         _queue.EnqueueBlocking(item);
+         int count = Interlocked.Increment(ref _itemCount);
+         if ( _overThreshold != null )
+         {
+            if ( count == _upperBound )
+            {
+               _overThreshold.BeginInvoke(
+                  count, new AsyncCallback(OnAsyncCallEnd), 
+                  _overThreshold
+                  );
+            }
+         }
+      }
+
+      public object Dequeue()
+      {
+         object item = _queue.DequeueBlocking();
+         int count = Interlocked.Decrement(ref _itemCount);
+         if ( _underThreshold != null )
+         {
+            if ( count == _lowerBound )
+            {
+               _underThreshold.BeginInvoke(
+                  count, new AsyncCallback(OnAsyncCallEnd),
+                  _underThreshold
+                  );
+            }
+         }
+         return item;
+      }
+
+      private void OnAsyncCallEnd(IAsyncResult res)
+      {
+         ThresholdMethod method = (ThresholdMethod)res.AsyncState;
+         method.EndInvoke(res);
+      }
+   }
+}