1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.rng.core.source64;
18
19 import org.apache.commons.rng.core.util.NumberFactory;
20
21 /**
22 * Implement Bob Jenkins's small fast (JSF) 64-bit generator.
23 *
24 * <p>The state size is 256-bits.</p>
25 *
26 * @see <a href="https://burtleburtle.net/bob/rand/smallprng.html">A small noncryptographic PRNG</a>
27 * @since 1.3
28 */
29 public class JenkinsSmallFast64 extends LongProvider {
30 /** State a. */
31 private long a;
32 /** State b. */
33 private long b;
34 /** State c. */
35 private long c;
36 /** Statd d. */
37 private long d;
38
39 /**
40 * Creates an instance with the given seed.
41 *
42 * @param seed Initial seed.
43 */
44 public JenkinsSmallFast64(Long seed) {
45 setSeedInternal(seed);
46 }
47
48 /**
49 * Seeds the RNG.
50 *
51 * @param seed Seed.
52 */
53 private void setSeedInternal(long seed) {
54 a = 0xf1ea5eedL;
55 b = c = d = seed;
56 for (int i = 0; i < 20; i++) {
57 next();
58 }
59 }
60
61 /** {@inheritDoc} */
62 @Override
63 public final long next() {
64 final long e = a - Long.rotateLeft(b, 7);
65 a = b ^ Long.rotateLeft(c, 13);
66 b = c + Long.rotateLeft(d, 37);
67 c = d + e;
68 d = e + a;
69 return d;
70 }
71
72 /** {@inheritDoc} */
73 @Override
74 protected byte[] getStateInternal() {
75 return composeStateInternal(NumberFactory.makeByteArray(new long[] {a, b, c, d}),
76 super.getStateInternal());
77 }
78
79 /** {@inheritDoc} */
80 @Override
81 protected void setStateInternal(byte[] s) {
82 final byte[][] parts = splitStateInternal(s, 4 * 8);
83
84 final long[] tmp = NumberFactory.makeLongArray(parts[0]);
85 a = tmp[0];
86 b = tmp[1];
87 c = tmp[2];
88 d = tmp[3];
89
90 super.setStateInternal(parts[1]);
91 }
92 }