Guid.java

/*
 * Copyright 2014-2016 CyberVision, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.kaaproject.kaa.server.admin.client.util;

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

  /**
   * Generate a random uuid of the specified length. Example: uuid(15) returns
   * "VcydxgltxrVZSTV"
   *
   * @param len the desired number of characters
   * @return the string
   */
  public static String get(int len) {
    return get(len, CHARS.length);
  }

  /**
   * Generate a random uuid of the specified length, and radix. Examples:
   * <ul>
   * <li>uuid(8, 2) returns "01001010" (8 character ID, base=2)
   * <li>uuid(8, 10) returns "47473046" (8 character ID, base=10)
   * <li>uuid(8, 16) returns "098F4D35" (8 character ID, base=16)
   * </ul>
   *
   * @param len   the desired number of characters
   * @param radix the number of allowable values for each character
   *              (must be equals or grater than 62)
   * @return the string
   */
  public static String get(int len, int radix) {
    if (radix > CHARS.length) {
      throw new IllegalArgumentException();
    }
    char[] uuid = new char[len];
    // Compact form
    for (int i = 0; i < len; i++) {
      uuid[i] = CHARS[(int) (Math.random() * radix)];
    }
    return new String(uuid);
  }

  /**
   * Generate a RFC4122, version 4 ID. Example:
   * "92329D39-6F5C-4520-ABFC-AAB64544E172"
   *
   * @return the string
   */
  public static String get() {
    char[] uuid = new char[36];
    int num;

    // 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) {
        num = (int) (Math.random() * 16);
        uuid[i] = CHARS[(i == 19) ? (num & 0x3) | 0x8 : num & 0xf];
      }
    }
    return new String(uuid);
  }
}