1 /*
2 * Copyright (C) 2008-2010, Google Inc. and others
3 *
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Distribution License v. 1.0 which is available at
6 * https://www.eclipse.org/org/documents/edl-v10.php.
7 *
8 * SPDX-License-Identifier: BSD-3-Clause
9 */
10
11 package org.eclipse.jgit.junit;
12
13 /**
14 * Toy RNG to ensure we get predictable numbers during unit tests.
15 */
16 public class TestRng {
17 private int next;
18
19 /**
20 * Create a new random number generator, seeded by a string.
21 *
22 * @param seed
23 * seed to bootstrap, usually this is the test method name.
24 */
25 public TestRng(String seed) {
26 next = 0;
27 for (int i = 0; i < seed.length(); i++)
28 next = next * 11 + seed.charAt(i);
29 }
30
31 /**
32 * Get the next {@code cnt} bytes of random data.
33 *
34 * @param cnt
35 * number of random bytes to produce.
36 * @return array of {@code cnt} randomly generated bytes.
37 */
38 public byte[] nextBytes(int cnt) {
39 final byte[] r = new byte[cnt];
40 for (int i = 0; i < cnt; i++)
41 r[i] = (byte) nextInt();
42 return r;
43 }
44
45 /**
46 * Next int
47 *
48 * @return the next random integer.
49 */
50 public int nextInt() {
51 next = next * 1103515245 + 12345;
52 return next;
53 }
54 }