uuidutil.java

sea是一个基于seda模式的实现。这个设计模式将系统分为很多stage。每个stage分布不同的任务（基于线程池）。通过任务流的方式提高系统的效率。

/*
 * Copyright (c) 2003, The Regents of the University of California, through
 * Lawrence Berkeley National Laboratory (subject to receipt of any required
 * approvals from the U.S. Dept. of Energy). All rights reserved.
 */
package gov.lbl.dsd.sea.nio.util;

import java.security.SecureRandom;
import java.util.Random;

/**
 * Utilities to create Universally Unique Identifiers as defined by IETF standards.
 * 
 * @author [e-mail]
 * @author $Author: hoschek3 $
 * @version $Revision: 1.2 $, $Date: 2004/07/27 00:18:19 $ 
 */
public class UUIDUtil {

	private static Random randomGenerator;

	/**
	 * Make non-instantiable  
	 */
	protected UUIDUtil() {}

	/**
	 * Returns a type 4 (pseudo randomly generated) Universally Unique Identifier 
	 * as defined by IETF standards. Example UUID: <code>e96d0caf-76f4-44a9-904e-cad4c0f93b22</code>.
	 * The returned UUID consists of 36 characters. Note that this method is thread-safe.
	 * <p>
	 * See <a href="http://www1.ics.uci.edu/~ejw/authoring/uuid-guid/draft-leach-uuids-guids-01.txt">draft-leach-uuids-guids-01.txt</a> 
	 * for details.
	 * 
	 * @param generator -
	 *            the (pseudo) random number generator used to generate random
	 *            bytes. Set this parameter to <code>null</code> to use a
	 *            built-in default secure random number generator.
	 * 
	 * @return a randomly generated UUID.
	 */
	public static String createRandomUUID(Random generator) {
		if (generator == null) {
			if (randomGenerator == null) randomGenerator = new SecureRandom();
			generator = randomGenerator;
		}
		
		byte[] data = new byte[16];
		generator.nextBytes(data);
		data[6] &= 0x0f;
		data[6] |= 0x40;
		data[8] &= 0x3f;
		data[8] |= 0x80;
		
		String chars = "0123456789abcdefABCDEF";
		StringBuffer buf = new StringBuffer(36);
		for (int i = 0; i < 16; i++) {
			if (i==4 || i==6 || i==8 || i==10) buf.append('-');
			int val = data[i] & 0xFF;
			buf.append(chars.charAt(val >> 4));
			buf.append(chars.charAt(val & 0x0f));
		}
		return buf.toString();
	}
    
}