UUID.java

/*
 *  Copyright (c) 2008, Robert Kieffer
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are
 *  met:
 *
 *  * Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *  * Neither the name of Robert Kieffer nor the names of its contributors may
 *    be used to endorse or promote products derived from this software without
 *    specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 *  POSSIBILITY OF SUCH DAMAGE.
 *
 *  http://www.pst.ifi.lmu.de/~rauschma/download/UUID.java
 */

package rpc.shared;

public class UUID {
    private static final char[] CHARS =
        ("0123456789" +
         "abcdefghijklmnopqrstuvwxyz" +
         "ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();

    public static String uuid(int len) {
        return uuid(len, CHARS.length);
    }

    public static String uuid(int len, int radix) {
        if (radix > CHARS.length) {
            throw new IllegalArgumentException();
        }

        char[] uuid = new char[len];

        for (int i = 0; i < len; i++) {
            uuid[i] = CHARS[(int)(Math.random() * radix)];
        }

        return new String(uuid);
    }

    public static String uuid() {
        char[] uuid = new char[36];
        int r;

        // rfc4122 requires these characters
        uuid[8] = uuid[13] = uuid[18] = uuid[23] = '-';
        uuid[14] = '4';

        // Fill in random data. At i==19 set the high bits of clock sequence
        // as per rfc4122, sec. 4.1.5
        for (int i = 0; i < 36; i++) {
            if (uuid[i] == 0) {
                r = (int) (Math.random() * 16);
                uuid[i] = CHARS[(i == 19) ? (r & 0x3) | 0x8 : r & 0xf];
            }
        }

        return new String(uuid);
    }
}