com.google.appengine.tools.mapreduce.RangeRecordReader.java Source code

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Here is the source code for com.google.appengine.tools.mapreduce.RangeRecordReader.java

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/*
 * Copyright 2010 Google Inc.
 *
 * 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 com.google.appengine.tools.mapreduce;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;

import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;

/**
 * The record reader class for {@link RangeInputFormat}.
 *
 */
public class RangeRecordReader extends RecordReader<Long, NullWritable> implements Writable {

    private RangeInputSplit split;
    private long currentKey;

    public RangeRecordReader() {
        currentKey = -1;
    }

    @Override
    public void close() throws IOException {
    }

    @Override
    public Long getCurrentKey() throws IOException, InterruptedException {
        if (split == null) {
            throw new RuntimeException("Attempted to read from RangeRecordReader without a RangeInputSplit");
        }
        if (currentKey < 0 || currentKey >= split.getSplitEnd()) {
            return null;
        }
        return currentKey;
    }

    @Override
    public NullWritable getCurrentValue() throws IOException, InterruptedException {
        return null;
    }

    @Override
    public float getProgress() throws IOException, InterruptedException {
        if (currentKey < 0) {
            return 0;
        }

        return ((float) currentKey - split.getSplitStart()) / (split.getSplitEnd() - split.getSplitStart());
    }

    @Override
    public void initialize(InputSplit split, TaskAttemptContext context) throws IOException {
        this.split = (RangeInputSplit) split;
    }

    @Override
    public boolean nextKeyValue() throws IOException, InterruptedException {
        if (currentKey < 0) {
            currentKey = split.getSplitStart();
        } else {
            currentKey++;
        }

        if (currentKey >= split.getSplitEnd()) {
            return false;
        }

        return true;
    }

    @Override
    public void readFields(DataInput input) throws IOException {
        currentKey = input.readLong();
    }

    @Override
    public void write(DataOutput output) throws IOException {
        output.writeLong(currentKey);
    }

}