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    
019    package org.apache.hadoop.mapred.lib;
020    
021    import java.io.IOException;
022    
023    import org.apache.hadoop.classification.InterfaceAudience;
024    import org.apache.hadoop.classification.InterfaceStability;
025    import org.apache.hadoop.conf.Configuration;
026    import org.apache.hadoop.mapred.FileInputFormat;
027    import org.apache.hadoop.mapred.FileSplit;
028    import org.apache.hadoop.mapred.JobConf;
029    import org.apache.hadoop.mapred.RecordReader;
030    import 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
048    public 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    }