+ * This default implementation is copied from Apache Harmony + * java.util.Random (r929253). + *
+ * + *Implementation notes: + *
+ * The array is filled with bytes extracted from random integers generated + * using {@link #nextInt()}. + * This implies that the number of random bytes generated may be larger than + * the length of the byte array. + *
+ * + * @param bytes Array in which to put the generated bytes. Cannot be {@code null}. + */ + @Override + public void nextBytes(byte[] bytes) { + nextBytesFill(bytes, 0, bytes.length); + } + + /** + * Generates random bytes and places them into a user-supplied array. + * + *+ * The array is filled with bytes extracted from random integers generated + * using {@link #nextInt()}. + * This implies that the number of random bytes generated may be larger than + * the length of the byte array. + *
+ * + * @param bytes Array in which to put the generated bytes. Cannot be {@code null}. + * @param start Index at which to start inserting the generated bytes. + * @param len Number of bytes to insert. + * @throws OutOfRangeException if {@code start < 0} or {@code start >= bytes.length}. + * @throws OutOfRangeException if {@code len <= 0} or {@code len > bytes.length - start}. + */ + public void nextBytes(byte[] bytes, + int start, + int len) { + if (start < 0 || + start >= bytes.length) { + throw new OutOfRangeException(start, 0, bytes.length); + } + final int max = bytes.length - start; + if (len <= 0 || + len > max) { + throw new OutOfRangeException(len, 0, max); + } + + nextBytesFill(bytes, start, len); + } + + /** + * Generates random bytes and places them into a user-supplied array. + * + *+ * The array is filled with bytes extracted from random integers generated + * using {@link #nextInt()}. + * This implies that the number of random bytes generated may be larger than + * the length of the byte array. + *
+ * + * @param bytes Array in which to put the generated bytes. Cannot be {@code null}. + * @param position Index at which to start inserting the generated bytes. + * @param length Number of bytes to insert. + */ + private void nextBytesFill(byte[] bytes, + int position, + int length) { + int index = position; // Index of first insertion. + + // Index of first insertion plus multiple 4 part of length (i.e. length + // with two least significant bits unset). + final int indexLoopLimit = index + (length & 0x7ffffffc); + + // Start filling in the byte array, 4 bytes at a time. + while (index < indexLoopLimit) { + final int random = nextInt(); + bytes[index++] = (byte) random; + bytes[index++] = (byte) (random >>> 8); + bytes[index++] = (byte) (random >>> 16); + bytes[index++] = (byte) (random >>> 24); + } + + final int indexLimit = position + length; // Index of last insertion + 1. + + // Fill in the remaining bytes. + if (index < indexLimit) { + int random = nextInt(); + while (true) { + bytes[index++] = (byte) random; + if (index < indexLimit) { + random >>>= 8; + } else { + break; + } + } + } + } +} diff --git a/src/test/java/org/apache/commons/math4/random/BaseRandomGeneratorTest.java b/src/test/java/org/apache/commons/math4/random/BaseRandomGeneratorTest.java new file mode 100644 index 000000000..40ab9b54f --- /dev/null +++ b/src/test/java/org/apache/commons/math4/random/BaseRandomGeneratorTest.java @@ -0,0 +1,129 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ +package org.apache.commons.math4.random; + +import java.util.Random; + +import org.apache.commons.math4.exception.OutOfRangeException; + +import org.junit.Assert; +import org.junit.Before; +import org.junit.Test; + +/** + * Tests for the generic implementations of the methods defined in the + * {@link BaseRandomGenerator} class, using the standard {@link Random} + * class as the source of randomness. + */ +public class BaseRandomGeneratorTest extends RandomGeneratorAbstractTest { + /** To simplify testing of additional utility methods. */ + protected BaseRandomGenerator baseRandomGenerator; + + @Before + public void setUp() { + baseRandomGenerator = (BaseRandomGenerator) generator; + } + + @Override + protected RandomGenerator makeGenerator() { + final RandomGenerator generator = new TestGenerator(); + generator.setSeed(1000); + return generator; + } + + @Test(expected=OutOfRangeException.class) + public void testNextBytesPrecondition1() { + final int len = 3; + final byte[] b = new byte[len]; + baseRandomGenerator.nextBytes(b, -1, 1); + } + + @Test(expected=OutOfRangeException.class) + public void testNextBytesPrecondition2() { + final int len = 3; + final byte[] b = new byte[len]; + baseRandomGenerator.nextBytes(b, len, 0); + } + + @Test(expected=OutOfRangeException.class) + public void testNextBytesPrecondition3() { + final int len = 3; + final byte[] b = new byte[len]; + baseRandomGenerator.nextBytes(b, 0, 0); + } + + @Test(expected=OutOfRangeException.class) + public void testNextBytesPrecondition4() { + final int len = 3; + final byte[] b = new byte[len]; + baseRandomGenerator.nextBytes(b, 0, len + 1); + } + + @Test + public void testNextBytesSubArray() { + final int size = 123; + final int insert = 72; + final int len = 37; + + final byte[] buffer = new byte[size]; + baseRandomGenerator.nextBytes(buffer, insert, len); + + final byte[] bufferCopy = buffer.clone(); + baseRandomGenerator.nextBytes(buffer, insert, len); + + for (int i = 0; i < insert; i++) { + Assert.assertEquals(bufferCopy[i], buffer[i]); + } + final int maxInsert = insert + len; + for (int i = insert; i < maxInsert; i++) { + Assert.assertNotEquals(bufferCopy[i], buffer[i]); + } + for (int i = maxInsert; i < size; i++) { + Assert.assertEquals(bufferCopy[i], buffer[i]); + } + } + + /** + * Test RNG delegating to {@link Random}. + */ + private static class TestGenerator extends BaseRandomGenerator { + /** Delegate. */ + private Random random = new Random(); + + @Override + public void setSeed(int seed) { + random.setSeed(seed); + clear(); + } + + @Override + public void setSeed(int[] seed) { + random.setSeed(seed[0]); + } + + @Override + public void setSeed(long seed) { + random.setSeed((int) seed); + } + + @Override + public int nextInt() { + // Delegate. + return random.nextInt(); + } + } +}