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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.
 */
package org.apache.hadoop.mapred;

import java.io.IOException;

import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
import org.apache.hadoop.io.DataInputBuffer;
import org.apache.hadoop.util.Progress;

/**
 * RawKeyValueIterator is an iterator used to iterate over
 * the raw keys and values during sort/merge of intermediate data. 
 */
@InterfaceAudience.Private
@InterfaceStability.Unstable
public interface RawKeyValueIterator {
  /** 
   * Gets the current raw key.
   * 
   * @return Gets the current raw key as a DataInputBuffer
   * @throws IOException
   */
  DataInputBuffer getKey() throws IOException;
  
  /** 
   * Gets the current raw value.
   * 
   * @return Gets the current raw value as a DataInputBuffer 
   * @throws IOException
   */
  DataInputBuffer getValue() throws IOException;
  
  /** 
   * Sets up the current key and value (for getKey and getValue).
   * 
   * @return true if there exists a key/value, 
   *         false otherwise. 
   * @throws IOException
   */
  boolean next() throws IOException;
  
  /** 
   * Closes the iterator so that the underlying streams can be closed.
   * 
   * @throws IOException
   */
  void close() throws IOException;
  
  /** Gets the Progress object; this has a float (0.0 - 1.0) 
   * indicating the bytes processed by the iterator so far
   */
  Progress getProgress();
}