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/*
*
* 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);
}
}
}
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