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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.runtime.io.api;

import eu.stratosphere.core.io.IOReadableWritable;

/**
 * Objects implementing this interface are passed to an {@link eu.stratosphere.runtime.io.gates.OutputGate}. When a record is sent through the output
 * gate, the channel selector object is called to determine to which {@link eu.stratosphere.runtime.io.channels.OutputChannel} objects the record
 * shall be passed on.
 * 
 * @param 
 *        the type of record which is sent through the attached output gate
 */
public interface ChannelSelector {

	/**
	 * Called to determine to which attached {@link eu.stratosphere.runtime.io.channels.OutputChannel} objects the given record shall be forwarded.
	 * 
	 * @param record
	 *        the record to the determine the output channels for
	 * @param numberOfOutputChannels
	 *        the total number of output channels which are attached to respective output gate
	 * @return a (possibly empty) array of integer numbers which indicate the indices of the output channels through
	 *         which the record shall be forwarded
	 */
	int[] selectChannels(T record, int numberOfOutputChannels);
}