trunk/core-avl/src/main/java/org/apache/directory/server/core/avltree/ArrayMarshaller.java

/*
 *   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.directory.server.core.avltree;


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

import org.apache.directory.api.util.Strings;
import org.apache.directory.server.i18n.I18n;


/**
 * Class to serialize the Array data.
 *
 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
 */
@SuppressWarnings("unchecked")
public class ArrayMarshaller<E> implements Marshaller<ArrayTree<E>>
{
    /** used for serialized form of an empty AvlTree */
    private static final byte[] EMPTY_TREE = new byte[1];

    /** marshaller to be used for marshalling the keys */
    private Marshaller<E> keyMarshaller;

    /** key Comparator for the AvlTree */
    private Comparator<E> comparator;


    /**
     * Creates a new instance of AvlTreeMarshaller with a custom key
     * Marshaller.
     *
     * @param comparator Comparator to be used for key comparision
     * @param keyMarshaller marshaller for keys
     */
    public ArrayMarshaller( Comparator<E> comparator, Marshaller<E> keyMarshaller )
    {
        this.comparator = comparator;
        this.keyMarshaller = keyMarshaller;
    }


    /**
     * Creates a new instance of AvlTreeMarshaller with the default key
     * Marshaller which uses Java Serialization.
     *
     * @param comparator Comparator to be used for key comparision
     */
    public ArrayMarshaller( Comparator<E> comparator )
    {
        this.comparator = comparator;
        this.keyMarshaller = ( Marshaller<E> ) DefaultMarshaller.INSTANCE;
    }


    /**
     * Marshals the given tree to bytes
     * @param tree the tree to be marshalled
     */
    public byte[] serialize( ArrayTree<E> tree )
    {
        if ( ( tree == null ) || ( tree.size() == 0 ) )
        {
            return EMPTY_TREE;
        }

        ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
        DataOutputStream out = new DataOutputStream( byteStream );
        byte[] data = null;

        try
        {
            out.writeByte( 0 ); // represents the start of an Array byte stream
            out.writeInt( tree.size() );

            for ( int position = 0; position < tree.size(); position++ )
            {
                E value = tree.get( position );
                byte[] bytes = keyMarshaller.serialize( value );

                // Write the key length
                out.writeInt( bytes.length );

                // Write the key if its length is not null
                if ( bytes.length != 0 )
                {
                    out.write( bytes );
                }
            }

            out.flush();
            data = byteStream.toByteArray();

            // Try to deserialize, just to see
            /*
            try
            {
                deserialize( data );
            }
            catch ( NullPointerException npe )
            {
                System.out.println( I18n.err( I18n.ERR_438, Strings.dumpBytes( data ) ) );
                throw npe;
            }
            */

            out.close();
        }
        catch ( IOException e )
        {
            e.printStackTrace();
        }

        return data;
    }


    /**
     * Creates an Array from given bytes of data.
     * 
     * @param data byte array to be converted into an array  
     */
    public ArrayTree<E> deserialize( byte[] data ) throws IOException
    {
        //LOG.debug( "Deserializing the tree, called by {}", Reflection.getCallerClass( 2 ).getSimpleName() );

        try
        {
            if ( ( data == null ) || ( data.length == 0 ) )
            {
                throw new IOException( I18n.err( I18n.ERR_439 ) );
            }

            if ( ( data.length == 1 ) && ( data[0] == 0 ) )
            {
                E[] array = ( E[] ) new Object[]
                    {};
                ArrayTree<E> tree = new ArrayTree<E>( comparator, array );
                return tree;
            }

            ByteArrayInputStream bin = new ByteArrayInputStream( data );
            DataInputStream din = new DataInputStream( bin );

            byte startByte = din.readByte();

            if ( startByte != 0 )
            {
                throw new IOException( I18n.err( I18n.ERR_440 ) );
            }

            int size = din.readInt();
            E[] nodes = ( E[] ) new Object[size];

            for ( int i = 0; i < size; i++ )
            {
                // Read the object's size
                int dataSize = din.readInt();

                if ( dataSize != 0 )
                {
                    byte[] bytes = new byte[dataSize];

                    din.readFully( bytes );
                    E key = keyMarshaller.deserialize( bytes );
                    nodes[i] = key;
                }
            }

            ArrayTree<E> arrayTree = new ArrayTree<E>( comparator, nodes );

            return arrayTree;
        }
        catch ( NullPointerException npe )
        {
            System.out.println( I18n.err( I18n.ERR_441, Strings.dumpBytes( data ) ) );
            throw npe;
        }
    }
}