/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008, Red Hat Middleware LLC or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Middleware LLC.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 */
package org.hibernate.id;
import java.net.InetAddress;

import org.hibernate.internal.util.BytesHelper;

The base class for identifier generators that use a UUID algorithm. This
class implements the algorithm, subclasses define the identifier
format.
Author:
Gavin King
See Also:
UUIDHexGenerator/**
 * The base class for identifier generators that use a UUID algorithm. This
 * class implements the algorithm, subclasses define the identifier
 * format.
 *
 * @see UUIDHexGenerator
 * @author Gavin King
 */

public abstract class AbstractUUIDGenerator implements IdentifierGenerator {

	private static final int IP;
	static {
		int ipadd;
		try {
			ipadd = BytesHelper.toInt( InetAddress.getLocalHost().getAddress() );
		}
		catch (Exception e) {
			ipadd = 0;
		}
		IP = ipadd;
	}
	private static short counter = (short) 0;
	private static final int JVM = (int) ( System.currentTimeMillis() >>> 8 );

	public AbstractUUIDGenerator() {
	}

	
Unique across JVMs on this machine (unless they load this class
in the same quater second - very unlikely)
/**
	 * Unique across JVMs on this machine (unless they load this class
	 * in the same quater second - very unlikely)
	 */
	protected int getJVM() {
		return JVM;
	}

	
Unique in a millisecond for this JVM instance (unless there
are > Short.MAX_VALUE instances created in a millisecond)
/**
	 * Unique in a millisecond for this JVM instance (unless there
	 * are > Short.MAX_VALUE instances created in a millisecond)
	 */
	protected short getCount() {
		synchronized(AbstractUUIDGenerator.class) {
			if (counter<0) counter=0;
			return counter++;
		}
	}

	
Unique in a local network
/**
	 * Unique in a local network
	 */
	protected int getIP() {
		return IP;
	}

	
Unique down to millisecond
/**
	 * Unique down to millisecond
	 */
	protected short getHiTime() {
		return (short) ( System.currentTimeMillis() >>> 32 );
	}
	protected int getLoTime() {
		return (int) System.currentTimeMillis();
	}


}