001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.mapred.lib;
020
021import java.io.IOException;
022
023import org.apache.hadoop.classification.InterfaceAudience;
024import org.apache.hadoop.classification.InterfaceStability;
025import org.apache.hadoop.conf.Configuration;
026import org.apache.hadoop.mapred.FileInputFormat;
027import org.apache.hadoop.mapred.FileSplit;
028import org.apache.hadoop.mapred.JobConf;
029import org.apache.hadoop.mapred.RecordReader;
030import org.apache.hadoop.mapred.Reporter;
031
032/**
033 * A wrapper class for a record reader that handles a single file split. It
034 * delegates most of the methods to the wrapped instance. A concrete subclass
035 * needs to provide a constructor that calls this parent constructor with the
036 * appropriate input format. The subclass constructor must satisfy the specific
037 * constructor signature that is required by
038 * <code>CombineFileRecordReader</code>.
039 *
040 * Subclassing is needed to get a concrete record reader wrapper because of the
041 * constructor requirement.
042 *
043 * @see CombineFileRecordReader
044 * @see CombineFileInputFormat
045 */
046@InterfaceAudience.Public
047@InterfaceStability.Stable
048public abstract class CombineFileRecordReaderWrapper<K,V>
049  implements RecordReader<K,V> {
050  private final RecordReader<K,V> delegate;
051
052  protected CombineFileRecordReaderWrapper(FileInputFormat<K,V> inputFormat,
053    CombineFileSplit split, Configuration conf, Reporter reporter, Integer idx)
054    throws IOException {
055    FileSplit fileSplit = new FileSplit(split.getPath(idx),
056      split.getOffset(idx),
057      split.getLength(idx),
058      split.getLocations());
059
060    delegate = inputFormat.getRecordReader(fileSplit, (JobConf)conf, reporter);
061  }
062
063  public boolean next(K key, V value) throws IOException {
064    return delegate.next(key, value);
065  }
066
067  public K createKey() {
068    return delegate.createKey();
069  }
070
071  public V createValue() {
072    return delegate.createValue();
073  }
074
075  public long getPos() throws IOException {
076    return delegate.getPos();
077  }
078
079  public void close() throws IOException {
080    delegate.close();
081  }
082
083  public float getProgress() throws IOException {
084    return delegate.getProgress();
085  }
086}