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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
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
namespace Org.Apache.REEF.Network.Utilities
public static class BlockingCollectionExtensions
/// <summary>
/// Removes the given item from the BlockingCollection if it is present.
/// If it is not present, it blocks until any item is available in the
/// BlockingCollection. It then removes and returns that first available
/// item.
/// </summary>
/// <typeparam name="T">The type of BlockingCollection</typeparam>
/// <param name="collection">The BlockingCollection to remove the specified item</param>
/// <param name="item">The item to remove from the BlockingCollection, if it exists</param>
/// <returns>The specified item, or the first available item if the specified item is
/// not present in the BlockingCollection</returns>
public static T Take<T>(this BlockingCollection<T> collection, T item)
T ret = default(T);
bool foundItem = false;
List<T> removedItems = new List<T>();
// Empty the collection
for (int i = 0; i < collection.Count; i++)
T removed;
if (collection.TryTake(out removed))
// Add them back to the collection minus the specified item
foreach (T removedItem in removedItems)
if (removedItem.Equals(item))
ret = removedItem;
foundItem = true;
if (!foundItem)
// Error: the element wasn't in the collection
throw new InvalidOperationException(item + " not found in blocking collection");
return ret;