eu.stratosphere.pact.runtime.task.util.SerializationCopier.java Source code

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Here is the source code for eu.stratosphere.pact.runtime.task.util.SerializationCopier.java

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/***********************************************************************************************************************
 *
 * Copyright (C) 2010 by the Stratosphere project (http://stratosphere.eu)
 *
 * 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 eu.stratosphere.pact.runtime.task.util;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import eu.stratosphere.nephele.io.IOReadableWritable;

/**
 * Creates deep copies of {@link IOReadableWritable} objects.
 * Objects are serialized into a byte array and later deserialized from there.
 * 
 * @author Fabian Hueske (fabian.hueske@tu-berlin.de)
 * @param <T>
 */
public class SerializationCopier<T extends IOReadableWritable> {

    private byte[] serializedCopy;

    // streams for reading and writing to byte array
    private ByteArrayOutputStream baos;

    private DataOutputStream dos;

    private ByteArrayInputStream bais;

    private DataInputStream dis;

    private static final Log LOG = LogFactory.getLog(SerializationCopier.class);

    /**
     * Creates a SerializationCopier with an byte array of initial size 1024 byte.
     */
    public SerializationCopier() {
        serializedCopy = new byte[1024];
        baos = new ByteArrayOutputStream();
        dos = new DataOutputStream(baos);
        bais = new ByteArrayInputStream(serializedCopy);
        dis = new DataInputStream(bais);
    }

    /**
     * Creates a SerializationCopier with an byte array of specified size.
     * 
     * @param initialCopySize
     *        Initial size of the byte array that stores the serialized copy.
     */
    public SerializationCopier(int initialCopySize) {
        serializedCopy = new byte[initialCopySize];
        baos = new ByteArrayOutputStream();
        dos = new DataOutputStream(baos);
        bais = new ByteArrayInputStream(serializedCopy);
        dis = new DataInputStream(bais);
    }

    /**
     * Resets the array and write a serialized copy to the array.
     * If the array is not sufficiently large, a new array is created.
     * The new size is double of the required size for the current copy.
     * 
     * @param copy
     *        Object from which a serialized copy is created.
     */
    public void setCopy(T copy) {

        try {
            copy.write(dos);
            dos.flush();
            baos.flush();
        } catch (IOException e) {
            LOG.error(e);
        }

        if (baos.size() <= serializedCopy.length) {
            // copy
            System.arraycopy(baos.toByteArray(), 0, serializedCopy, 0, baos.size());
        } else {
            // allocate larger array
            serializedCopy = new byte[baos.size() * 2];
            System.arraycopy(baos.toByteArray(), 0, serializedCopy, 0, baos.size());
            // create new input streams
            bais = new ByteArrayInputStream(serializedCopy);
            dis = new DataInputStream(bais);
        }
        baos.reset();
    }

    /**
     * Deserializes the copy into the provided instance.
     * 
     * @param newCopy
     *        Instance in which the copy is deserialized.
     */
    public void getCopy(T newCopy) {

        try {
            newCopy.read(dis);
        } catch (IOException e) {
            LOG.error(e);
        }

        bais.reset();

    }

}