org.apache.hadoop.mapreduce.lib.input.SequenceFileRecordReader.java Source code

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Here is the source code for org.apache.hadoop.mapreduce.lib.input.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.mapreduce.lib.input;

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.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

/** An {@link RecordReader} for {@link SequenceFile}s. */
@InterfaceAudience.Public
@InterfaceStability.Stable
public class SequenceFileRecordReader<K, V> extends RecordReader<K, V> {
    private SequenceFile.Reader in;
    private long start;
    private long end;
    private boolean more = true;
    private K key = null;
    private V value = null;
    protected Configuration conf;

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        FileSplit fileSplit = (FileSplit) split;
        conf = context.getConfiguration();
        Path path = fileSplit.getPath();
        FileSystem fs = path.getFileSystem(conf);
        this.in = new SequenceFile.Reader(fs, path, conf);
        this.end = fileSplit.getStart() + fileSplit.getLength();

        if (fileSplit.getStart() > in.getPosition()) {
            in.sync(fileSplit.getStart()); // sync to start
        }

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

    @Override
    @SuppressWarnings("unchecked")
    public boolean nextKeyValue() throws IOException, InterruptedException {
        if (!more) {
            return false;
        }
        long pos = in.getPosition();
        key = (K) in.next(key);
        if (key == null || (pos >= end && in.syncSeen())) {
            more = false;
            key = null;
            value = null;
        } else {
            value = (V) in.getCurrentValue(value);
        }
        return more;
    }

    @Override
    public K getCurrentKey() {
        return key;
    }

    @Override
    public V getCurrentValue() {
        return 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 void close() throws IOException {
        in.close();
    }

}