org.kitesdk.data.spi.filesystem.AbstractCombineFileRecordReader.java Source code

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Here is the source code for org.kitesdk.data.spi.filesystem.AbstractCombineFileRecordReader.java

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/*
 * Licensed 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.kitesdk.data.spi.filesystem;

import java.io.IOException;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.mapreduce.lib.input.CombineFileSplit;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.FileSplit;
import org.kitesdk.data.DatasetOperationException;

/**
 * Base class for wrapping file-based record readers with CombineFileInputFormat functionality. This allows multiple
 * files to be combined into a single InputSplit, with the main pre-requisite being that the InputFormat being wrapped
 * must make use of FileInputSplits.
 * <p/>
 * Sub-classes need only implement the method to instantiate an instance of their owning InputFormat class.
 */
abstract class AbstractCombineFileRecordReader<K, V> extends RecordReader<K, V> {

    private int idx;
    private RecordReader<K, V> delegate;

    public AbstractCombineFileRecordReader(CombineFileSplit split, TaskAttemptContext context, Integer idx) {
        this.idx = idx;
    }

    /**
     * Single extension point. Returns an instance of the underlying InputFormat being used.
     *
     * @return an instance of the underlying FileInputFormat
     */
    abstract FileInputFormat<K, V> getInputFormat();

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException, InterruptedException {
        if (delegate != null) {
            delegate.close();
        }
        if (split instanceof CombineFileSplit) {
            CombineFileSplit combineSplit = (CombineFileSplit) split;
            FileSplit fileSplit = new FileSplit(combineSplit.getPath(idx), combineSplit.getOffset(idx),
                    combineSplit.getLength(idx), combineSplit.getLocations());
            delegate = getInputFormat().createRecordReader(fileSplit, context);
            delegate.initialize(fileSplit, context);
        } else {
            throw new DatasetOperationException("Split is not a CombineFileSplit: %s:%s",
                    split.getClass().getCanonicalName(), split);
        }
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        return delegate.nextKeyValue();
    }

    @Override
    public K getCurrentKey() throws IOException, InterruptedException {
        return delegate.getCurrentKey();
    }

    @Override
    public V getCurrentValue() throws IOException, InterruptedException {
        return delegate.getCurrentValue();
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        return delegate.getProgress();
    }

    @Override
    public void close() throws IOException {
        if (delegate != null) {
            delegate.close();
            delegate = null;
        }
    }
}