org.opencloudengine.flamingo.mapreduce.util.WritableUtils.java Source code

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Here is the source code for org.opencloudengine.flamingo.mapreduce.util.WritableUtils.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.opencloudengine.flamingo.mapreduce.util;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.ReflectionUtils;

import java.io.*;
import java.util.ArrayList;
import java.util.List;

/**
 * Helper static methods for working with Writable objects.
 */
public class WritableUtils {

    /**
     * Read fields from byteArray to a Writeable object.
     *
     * @param byteArray      Byte array to find the fields in.
     * @param writableObject Object to fill in the fields.
     */
    public static void readFieldsFromByteArray(byte[] byteArray, Writable writableObject) {
        DataInputStream inputStream = new DataInputStream(new ByteArrayInputStream(byteArray));
        try {
            writableObject.readFields(inputStream);
        } catch (IOException e) {
            throw new IllegalStateException("readFieldsFromByteArray: IOException", e);
        }
    }

    /**
     * Write object to a byte array.
     *
     * @param writableObject Object to write from.
     * @return Byte array with serialized object.
     */
    public static byte[] writeToByteArray(Writable writableObject) {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        DataOutput output = new DataOutputStream(outputStream);
        try {
            writableObject.write(output);
        } catch (IOException e) {
            throw new IllegalStateException("writeToByteArray: IOStateException", e);
        }
        return outputStream.toByteArray();
    }

    /**
     * Write list of object to a byte array.
     *
     * @param writableList List of object to write from.
     * @return Byte array with serialized objects.
     */
    public static byte[] writeListToByteArray(List<? extends Writable> writableList) {
        ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
        DataOutput output = new DataOutputStream(outputStream);
        try {
            output.writeInt(writableList.size());
            for (Writable writable : writableList) {
                writable.write(output);
            }
        } catch (IOException e) {
            throw new IllegalStateException("writeListToByteArray: IOException", e);
        }
        return outputStream.toByteArray();
    }

    /**
     * Read fields from byteArray to a list of Writeable objects.
     *
     * @param byteArray     Byte array to find the fields in.
     * @param writableClass Class of the objects to instantiate.
     * @param conf          Configuration used for instantiation (i.e Configurable)
     * @return List of writable objects.
     */
    public static List<? extends Writable> readListFieldsFromByteArray(byte[] byteArray,
            Class<? extends Writable> writableClass, Configuration conf) {
        try {
            DataInputStream inputStream = new DataInputStream(new ByteArrayInputStream(byteArray));
            int size = inputStream.readInt();
            List<Writable> writableList = new ArrayList<Writable>(size);
            for (int i = 0; i < size; ++i) {
                Writable writable = ReflectionUtils.newInstance(writableClass, conf);
                writable.readFields(inputStream);
                writableList.add(writable);
            }
            return writableList;
        } catch (IOException e) {
            throw new IllegalStateException("readListFieldsFromZnode: IOException", e);
        }
    }
}