Move TestRng to our JUnit helper package

Other test suites may find this useful, especially when trying
to defeat the pack file compression with random data files.

Change-Id: Ic00a4ac626af7a1c94d18ee99305e295b267b1a3
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

1 files changed, 83 insertions, 0 deletions

diff --git a/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRng.java b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRng.java
new file mode 100644
index 0000000000..93facc3777
--- /dev/null
+++ b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/TestRng.java
@@ -0,0 +1,83 @@
+/*
+ * 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.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ *
+ * - Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following
+ *   disclaimer in the documentation and/or other materials provided
+ *   with the distribution.
+ *
+ * - Neither the name of the Eclipse Foundation, Inc. nor the
+ *   names of its contributors may be used to endorse or promote
+ *   products derived from this software without specific prior
+ *   written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
+ * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
+ * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+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(final 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(final int cnt) {
+		final byte[] r = new byte[cnt];
+		for (int i = 0; i < cnt; i++)
+			r[i] = (byte) nextInt();
+		return r;
+	}
+
+	/**
+	 * @return the next random integer.
+	 */
+	public int nextInt() {
+		next = next * 1103515245 + 12345;
+		return next;
+	}
+}