001 /*
002 * Copyright (c) 2003, The Regents of the University of California, through
003 * Lawrence Berkeley National Laboratory (subject to receipt of any required
004 * approvals from the U.S. Dept. of Energy). All rights reserved.
005 */
006 package gov.lbl.dsd.sea.nio.util;
007
008 import java.security.SecureRandom;
009 import java.util.Random;
010
011 /**
012 * Utilities to create Universally Unique Identifiers as defined by IETF standards.
013 *
014 * @author whoschek@lbl.gov
015 * @author $Author: hoschek3 $
016 * @version $Revision: 1.2 $, $Date: 2004/07/27 00:18:19 $
017 */
018 public class UUIDUtil {
019
020 private static Random randomGenerator;
021
022 /**
023 * Make non-instantiable
024 */
025 protected UUIDUtil() {}
026
027 /**
028 * Returns a type 4 (pseudo randomly generated) Universally Unique Identifier
029 * as defined by IETF standards. Example UUID: <code>e96d0caf-76f4-44a9-904e-cad4c0f93b22</code>.
030 * The returned UUID consists of 36 characters. Note that this method is thread-safe.
031 * <p>
032 * 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>
033 * for details.
034 *
035 * @param generator -
036 * the (pseudo) random number generator used to generate random
037 * bytes. Set this parameter to <code>null</code> to use a
038 * built-in default secure random number generator.
039 *
040 * @return a randomly generated UUID.
041 */
042 public static String createRandomUUID(Random generator) {
043 if (generator == null) {
044 if (randomGenerator == null) randomGenerator = new SecureRandom();
045 generator = randomGenerator;
046 }
047
048 byte[] data = new byte[16];
049 generator.nextBytes(data);
050 data[6] &= 0x0f;
051 data[6] |= 0x40;
052 data[8] &= 0x3f;
053 data[8] |= 0x80;
054
055 String chars = "0123456789abcdefABCDEF";
056 StringBuffer buf = new StringBuffer(36);
057 for (int i = 0; i < 16; i++) {
058 if (i==4 || i==6 || i==8 || i==10) buf.append('-');
059 int val = data[i] & 0xFF;
060 buf.append(chars.charAt(val >> 4));
061 buf.append(chars.charAt(val & 0x0f));
062 }
063 return buf.toString();
064 }
065
066 }