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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.Threading;
namespace Apache.Qpid.Collections
{
/// <summary>
/// Simple FIFO queue to support multi-threaded consumer
/// and producers. It supports timeouts in dequeue operations.
/// </summary>
public sealed class ConsumerProducerQueue
{
private Queue _queue = new Queue();
private WaitSemaphore _semaphore = new WaitSemaphore();
/// <summary>
/// Put an item into the tail of the queue
/// </summary>
/// <param name="item"></param>
public void Enqueue(object item)
{
lock ( _queue.SyncRoot )
{
_queue.Enqueue(item);
_semaphore.Increment();
}
}
/// <summary>
/// Wait indefinitely for an item to be available
/// on the queue.
/// </summary>
/// <returns>The object at the head of the queue</returns>
public object Dequeue()
{
return Dequeue(Timeout.Infinite);
}
/// <summary>
/// Wait up to the number of milliseconds specified
/// for an item to be available on the queue
/// </summary>
/// <param name="timeout">Number of milliseconds to wait</param>
/// <returns>The object at the head of the queue, or null
/// if the timeout expires</returns>
public object Dequeue(long timeout)
{
if ( _semaphore.Decrement(timeout) )
{
lock ( _queue.SyncRoot )
{
return _queue.Dequeue();
}
}
return null;
}
#region Simple Semaphore
//
// Simple Semaphore
//
class WaitSemaphore
{
private int _count;
private AutoResetEvent _event = new AutoResetEvent(false);
public void Increment()
{
Interlocked.Increment(ref _count);
_event.Set();
}
public bool Decrement(long timeout)
{
if ( timeout > int.MaxValue )
throw new ArgumentOutOfRangeException("timeout", timeout, "Must be <= Int32.MaxValue");
int millis = (int) (timeout & 0x7FFFFFFF);
if ( Interlocked.Decrement(ref _count) > 0 )
{
// there are messages in queue, so no need to wait
return true;
} else
{
return _event.WaitOne(millis, false);
}
}
}
#endregion // Simple Semaphore
}
}
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