1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.apache.myfaces.util;
20
21 /**
22 * A simple XORShift Random generator.
23 * This class is NOT synchronized, you need to do that yourself if needed!
24 */
25 public class XorShiftRandom
26 {
27 private long value;
28
29 public XorShiftRandom( long initialSeed )
30 {
31 value = initialSeed;
32 }
33
34 /**
35 * Calculate a random value based on the previous value stored in this instance.
36 * If you use this method in a concurring way, you need to synchronize the access!
37 * @return
38 */
39 public long random()
40 {
41 value = random(value);
42 return value;
43 }
44
45 /**
46 * Calculate a random value based on the given start Value.
47 * @param randomStart the start value. Usually the result of the previous invocation
48 * @return the new random value.
49 */
50 public static long random(final long randomStart)
51 {
52 long randomValue = randomStart;
53 randomValue ^= (randomValue << 21);
54 randomValue ^= (randomValue >>> 35);
55 randomValue ^= (randomValue << 4);
56
57 return randomValue;
58 }
59 }