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;
020
021import java.io.IOException;
022
023
024import org.apache.hadoop.classification.InterfaceAudience;
025import org.apache.hadoop.classification.InterfaceStability;
026import org.apache.hadoop.conf.Configuration;
027import org.apache.hadoop.fs.FileSystem;
028import org.apache.hadoop.fs.Path;
029import org.apache.hadoop.io.*;
030import org.apache.hadoop.util.ReflectionUtils;
031
032/** 
033 * An {@link RecordReader} for {@link SequenceFile}s. 
034 */
035@InterfaceAudience.Public
036@InterfaceStability.Stable
037public class SequenceFileRecordReader<K, V> implements RecordReader<K, V> {
038  
039  private SequenceFile.Reader in;
040  private long start;
041  private long end;
042  private boolean more = true;
043  protected Configuration conf;
044
045  public SequenceFileRecordReader(Configuration conf, FileSplit split)
046    throws IOException {
047    Path path = split.getPath();
048    FileSystem fs = path.getFileSystem(conf);
049    this.in = new SequenceFile.Reader(fs, path, conf);
050    this.end = split.getStart() + split.getLength();
051    this.conf = conf;
052
053    if (split.getStart() > in.getPosition())
054      in.sync(split.getStart());                  // sync to start
055
056    this.start = in.getPosition();
057    more = start < end;
058  }
059
060
061  /** The class of key that must be passed to {@link
062   * #next(Object, Object)}.. */
063  public Class getKeyClass() { return in.getKeyClass(); }
064
065  /** The class of value that must be passed to {@link
066   * #next(Object, Object)}.. */
067  public Class getValueClass() { return in.getValueClass(); }
068  
069  @SuppressWarnings("unchecked")
070  public K createKey() {
071    return (K) ReflectionUtils.newInstance(getKeyClass(), conf);
072  }
073  
074  @SuppressWarnings("unchecked")
075  public V createValue() {
076    return (V) ReflectionUtils.newInstance(getValueClass(), conf);
077  }
078    
079  public synchronized boolean next(K key, V value) throws IOException {
080    if (!more) return false;
081    long pos = in.getPosition();
082    boolean remaining = (in.next(key) != null);
083    if (remaining) {
084      getCurrentValue(value);
085    }
086    if (pos >= end && in.syncSeen()) {
087      more = false;
088    } else {
089      more = remaining;
090    }
091    return more;
092  }
093  
094  protected synchronized boolean next(K key)
095    throws IOException {
096    if (!more) return false;
097    long pos = in.getPosition();
098    boolean remaining = (in.next(key) != null);
099    if (pos >= end && in.syncSeen()) {
100      more = false;
101    } else {
102      more = remaining;
103    }
104    return more;
105  }
106  
107  protected synchronized void getCurrentValue(V value)
108    throws IOException {
109    in.getCurrentValue(value);
110  }
111  
112  /**
113   * Return the progress within the input split
114   * @return 0.0 to 1.0 of the input byte range
115   */
116  public float getProgress() throws IOException {
117    if (end == start) {
118      return 0.0f;
119    } else {
120      return Math.min(1.0f, (in.getPosition() - start) / (float)(end - start));
121    }
122  }
123  
124  public synchronized long getPos() throws IOException {
125    return in.getPosition();
126  }
127  
128  protected synchronized void seek(long pos) throws IOException {
129    in.seek(pos);
130  }
131  public synchronized void close() throws IOException { in.close(); }
132  
133}
134