| /* |
| * 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.rng.core.source64; |
| |
| import org.apache.commons.rng.core.util.NumberFactory; |
| import org.apache.commons.rng.core.BaseProvider; |
| |
| /** |
| * Base class for all implementations that provide a {@code long}-based |
| * source randomness. |
| */ |
| public abstract class LongProvider |
| extends BaseProvider |
| implements RandomLongSource { |
| |
| /** |
| * Provides a bit source for booleans. |
| * |
| * <p>A cached value from a call to {@link #nextLong()}. |
| */ |
| private long booleanSource; // Initialised as 0 |
| |
| /** |
| * The bit mask of the boolean source to obtain the boolean bit. |
| * |
| * <p>The bit mask contains a single bit set. This begins at the least |
| * significant bit and is gradually shifted upwards until overflow to zero. |
| * |
| * <p>When zero a new boolean source should be created and the mask set to the |
| * least significant bit (i.e. 1). |
| */ |
| private long booleanBitMask; // Initialised as 0 |
| |
| /** |
| * Provides a source for ints. |
| * |
| * <p>A cached value from a call to {@link #nextLong()}. |
| */ |
| private long intSource; |
| |
| /** Flag to indicate an int source has been cached. */ |
| private boolean cachedIntSource; // Initialised as false |
| |
| /** |
| * Creates a new instance. |
| */ |
| public LongProvider() { |
| super(); |
| } |
| |
| /** |
| * Creates a new instance copying the state from the source. |
| * |
| * <p>This provides base functionality to allow a generator to create a copy, for example |
| * for use in the {@link org.apache.commons.rng.JumpableUniformRandomProvider |
| * JumpableUniformRandomProvider} interface. |
| * |
| * @param source Source to copy. |
| * @since 1.3 |
| */ |
| protected LongProvider(LongProvider source) { |
| booleanSource = source.booleanSource; |
| booleanBitMask = source.booleanBitMask; |
| intSource = source.intSource; |
| cachedIntSource = source.cachedIntSource; |
| } |
| |
| /** |
| * Reset the cached state used in the default implementation of {@link #nextBoolean()} |
| * and {@link #nextInt()}. |
| * |
| * <p>This should be used when the state is no longer valid, for example after a jump |
| * performed for the {@link org.apache.commons.rng.JumpableUniformRandomProvider |
| * JumpableUniformRandomProvider} interface.</p> |
| * |
| * @since 1.3 |
| */ |
| protected void resetCachedState() { |
| booleanSource = 0L; |
| booleanBitMask = 0L; |
| intSource = 0L; |
| cachedIntSource = false; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected byte[] getStateInternal() { |
| // Pack the boolean inefficiently as a long |
| final long[] state = new long[] {booleanSource, |
| booleanBitMask, |
| intSource, |
| cachedIntSource ? 1 : 0 }; |
| return composeStateInternal(NumberFactory.makeByteArray(state), |
| super.getStateInternal()); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| protected void setStateInternal(byte[] s) { |
| final byte[][] c = splitStateInternal(s, 32); |
| final long[] state = NumberFactory.makeLongArray(c[0]); |
| booleanSource = state[0]; |
| booleanBitMask = state[1]; |
| intSource = state[2]; |
| // Non-zero is true |
| cachedIntSource = state[3] != 0; |
| super.setStateInternal(c[1]); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public long nextLong() { |
| return next(); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public int nextInt() { |
| // Directly store and use the long value as a source for ints |
| if (cachedIntSource) { |
| // Consume the cache value |
| cachedIntSource = false; |
| // Return the lower 32 bits |
| return NumberFactory.extractLo(intSource); |
| } |
| // Fill the cache |
| cachedIntSource = true; |
| intSource = nextLong(); |
| // Return the upper 32 bits |
| return NumberFactory.extractHi(intSource); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public double nextDouble() { |
| return NumberFactory.makeDouble(nextLong()); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public boolean nextBoolean() { |
| // Shift up. This will eventually overflow and become zero. |
| booleanBitMask <<= 1; |
| // The mask will either contain a single bit or none. |
| if (booleanBitMask == 0) { |
| // Set the least significant bit |
| booleanBitMask = 1; |
| // Get the next value |
| booleanSource = nextLong(); |
| } |
| // Return if the bit is set |
| return (booleanSource & booleanBitMask) != 0; |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public float nextFloat() { |
| return NumberFactory.makeFloat(nextInt()); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public void nextBytes(byte[] bytes) { |
| nextBytesFill(this, bytes, 0, bytes.length); |
| } |
| |
| /** {@inheritDoc} */ |
| @Override |
| public void nextBytes(byte[] bytes, |
| int start, |
| int len) { |
| checkIndex(0, bytes.length - 1, start); |
| checkIndex(0, bytes.length - start, len); |
| |
| nextBytesFill(this, bytes, start, len); |
| } |
| |
| /** |
| * Generates random bytes and places them into a user-supplied array. |
| * |
| * <p> |
| * The array is filled with bytes extracted from random {@code long} values. |
| * This implies that the number of random bytes generated may be larger than |
| * the length of the byte array. |
| * </p> |
| * |
| * @param source Source of randomness. |
| * @param bytes Array in which to put the generated bytes. Cannot be null. |
| * @param start Index at which to start inserting the generated bytes. |
| * @param len Number of bytes to insert. |
| */ |
| static void nextBytesFill(RandomLongSource source, |
| byte[] bytes, |
| int start, |
| int len) { |
| int index = start; // Index of first insertion. |
| |
| // Index of first insertion plus multiple of 8 part of length |
| // (i.e. length with 3 least significant bits unset). |
| final int indexLoopLimit = index + (len & 0x7ffffff8); |
| |
| // Start filling in the byte array, 8 bytes at a time. |
| while (index < indexLoopLimit) { |
| final long random = source.next(); |
| bytes[index++] = (byte) random; |
| bytes[index++] = (byte) (random >>> 8); |
| bytes[index++] = (byte) (random >>> 16); |
| bytes[index++] = (byte) (random >>> 24); |
| bytes[index++] = (byte) (random >>> 32); |
| bytes[index++] = (byte) (random >>> 40); |
| bytes[index++] = (byte) (random >>> 48); |
| bytes[index++] = (byte) (random >>> 56); |
| } |
| |
| final int indexLimit = start + len; // Index of last insertion + 1. |
| |
| // Fill in the remaining bytes. |
| if (index < indexLimit) { |
| long random = source.next(); |
| while (true) { |
| bytes[index++] = (byte) random; |
| if (index < indexLimit) { |
| random >>>= 8; |
| } else { |
| break; |
| } |
| } |
| } |
| } |
| } |