/*
 * Copyright (C) 2008-2010, Google Inc.
 * and other copyright owners as documented in the project's IP log.
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
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 * without modification, are permitted provided that the following
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 * - Redistributions of source code must retain the above copyright
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 *
 * - Redistributions in binary form must reproduce the above
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 *   with the distribution.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 */

package org.eclipse.jgit.junit;

/**
 * Toy RNG to ensure we get predictable numbers during unit tests.
 */
public class TestRng {
	private int next;

	/**
	 * Create a new random number generator, seeded by a string.
	 *
	 * @param seed
	 *            seed to bootstrap, usually this is the test method name.
	 */
	public TestRng(String seed) {
		next = 0;
		for (int i = 0; i < seed.length(); i++)
			next = next * 11 + seed.charAt(i);
	}

	/**
	 * Get the next {@code cnt} bytes of random data.
	 *
	 * @param cnt
	 *            number of random bytes to produce.
	 * @return array of {@code cnt} randomly generated bytes.
	 */
	public byte[] nextBytes(int cnt) {
		final byte[] r = new byte[cnt];
		for (int i = 0; i < cnt; i++)
			r[i] = (byte) nextInt();
		return r;
	}

	/**
	 * Next int
	 *
	 * @return the next random integer.
	 */
	public int nextInt() {
		next = next * 1103515245 + 12345;
		return next;
	}
}