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Neo4j kernel is a lightweight, embedded Java database designed to store data structured as graphs rather than tables. For more information, see http://neo4j.org.

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/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [http://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.dbms.identity;

import java.io.IOException;
import java.util.UUID;

import org.neo4j.io.fs.ReadableChannel;
import org.neo4j.io.fs.WritableChannel;
import org.neo4j.io.marshal.SafeStateMarshal;
import org.neo4j.util.Id;

/**
 * ServerId is used for identifying a Neo4J instance.
 * It is persisted in the root of the data directory.
 */
public final class ServerId extends Id
{
    public ServerId( UUID uuid )
    {
        super( uuid );
    }

    @Override
    public String toString()
    {
        return "ServerId{" + shortName() + '}';
    }

    public static class Marshal extends SafeStateMarshal
    {
        public static final Marshal INSTANCE = new Marshal();

        private Marshal()
        {
            // use INSTANCE
        }

        @Override
        public void marshal( ServerId serverId, WritableChannel channel ) throws IOException
        {
            if ( serverId == null )
            {
                channel.put( (byte) 0 );
            }
            else
            {
                channel.put( (byte) 1 );
                channel.putLong( serverId.uuid().getMostSignificantBits() );
                channel.putLong( serverId.uuid().getLeastSignificantBits() );
            }
        }

        @Override
        public ServerId unmarshal0( ReadableChannel channel ) throws IOException
        {
            byte nullMarker = channel.get();
            if ( nullMarker == 0 )
            {
                return null;
            }
            else
            {
                long mostSigBits = channel.getLong();
                long leastSigBits = channel.getLong();
                return new ServerId( new UUID( mostSigBits, leastSigBits ) );
            }
        }

        @Override
        public ServerId startState()
        {
            return null;
        }

        @Override
        public long ordinal( ServerId serverId )
        {
            return serverId == null ? 0 : 1;
        }
    }
}