org.apache.hadoop.mapred.SequenceFileRecordReader.java Source code

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Here is the source code for org.apache.hadoop.mapred.SequenceFileRecordReader.java

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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.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.*;
import org.apache.hadoop.util.ReflectionUtils;

/** 
 * An {@link RecordReader} for {@link SequenceFile}s. 
 */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class SequenceFileRecordReader<K, V> implements RecordReader<K, V> {

    private SequenceFile.Reader in;
    private long start;
    private long end;
    private boolean more = true;
    protected Configuration conf;

    public SequenceFileRecordReader(Configuration conf, FileSplit split) throws IOException {
        Path path = split.getPath();
        FileSystem fs = path.getFileSystem(conf);
        this.in = new SequenceFile.Reader(fs, path, conf);
        this.end = split.getStart() + split.getLength();
        this.conf = conf;

        if (split.getStart() > in.getPosition())
            in.sync(split.getStart()); // sync to start

        this.start = in.getPosition();
        more = start < end;
    }

    /** The class of key that must be passed to {@link
     * #next(Object, Object)}.. */
    public Class getKeyClass() {
        return in.getKeyClass();
    }

    /** The class of value that must be passed to {@link
     * #next(Object, Object)}.. */
    public Class getValueClass() {
        return in.getValueClass();
    }

    @SuppressWarnings("unchecked")
    public K createKey() {
        return (K) ReflectionUtils.newInstance(getKeyClass(), conf);
    }

    @SuppressWarnings("unchecked")
    public V createValue() {
        return (V) ReflectionUtils.newInstance(getValueClass(), conf);
    }

    public synchronized boolean next(K key, V value) throws IOException {
        if (!more)
            return false;
        long pos = in.getPosition();
        boolean remaining = (in.next(key) != null);
        if (remaining) {
            getCurrentValue(value);
        }
        if (pos >= end && in.syncSeen()) {
            more = false;
        } else {
            more = remaining;
        }
        return more;
    }

    protected synchronized boolean next(K key) throws IOException {
        if (!more)
            return false;
        long pos = in.getPosition();
        boolean remaining = (in.next(key) != null);
        if (pos >= end && in.syncSeen()) {
            more = false;
        } else {
            more = remaining;
        }
        return more;
    }

    protected synchronized void getCurrentValue(V value) throws IOException {
        in.getCurrentValue(value);
    }

    /**
     * Return the progress within the input split
     * @return 0.0 to 1.0 of the input byte range
     */
    public float getProgress() throws IOException {
        if (end == start) {
            return 0.0f;
        } else {
            return Math.min(1.0f, (in.getPosition() - start) / (float) (end - start));
        }
    }

    public synchronized long getPos() throws IOException {
        return in.getPosition();
    }

    protected synchronized void seek(long pos) throws IOException {
        in.seek(pos);
    }

    public synchronized void close() throws IOException {
        in.close();
    }

}