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/***********************************************************************************************************************
 * Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
 *
 * Licensed 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.
 **********************************************************************************************************************/

package eu.stratosphere.pact.runtime.task.util;

import java.io.IOException;

import eu.stratosphere.api.common.typeutils.TypeSerializer;
import eu.stratosphere.runtime.io.api.MutableReader;
import eu.stratosphere.pact.runtime.plugable.DeserializationDelegate;
import eu.stratosphere.util.MutableObjectIterator;


/**
 * A {@link MutableObjectIterator} that wraps a Nephele Reader producing records of a certain type.
 */
public final class ReaderIterator implements MutableObjectIterator {
	
	private final MutableReader> reader;		// the source
	
	private final DeserializationDelegate delegate;

	/**
	 * Creates a new iterator, wrapping the given reader.
	 * 
	 * @param reader The reader to wrap.
	 */
	public ReaderIterator(MutableReader> reader, TypeSerializer serializer) {
		this.reader = reader;
		this.delegate = new DeserializationDelegate(serializer);
	}

	@Override
	public T next(T target) throws IOException {
		this.delegate.setInstance(target);
		try {
			if (this.reader.next(this.delegate)) {
				return this.delegate.getInstance();
			} else {
				return null;
			}

		}
		catch (InterruptedException e) {
			throw new IOException("Reader interrupted.", e);
		}
	}
}