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 * Copyright (c) 2013, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.util;

import java.util.Spliterator;

import java.util.function.Consumer;

import java.util.function.IntConsumer;

import java.util.function.LongConsumer;

import java.util.function.DoubleConsumer;

import java.util.stream.StreamSupport;

import java.util.stream.Stream;

/**

 * This class provides much of the implementation of the {@code Rng}

 * interface, to minimize the effort required to implement that interface.

 *

 * To implement a pseudorandom number generator, the programmer needs

 * only to extend this class and provide implementations for the

 * {@code nextInt()} and {@code nextLong()} methods.  In order for

 * the implementations of other methods in this class to operate

 * correctly, it must be safe for multiple threads to call these

 * methods on that same object.  The principal purpose of this class

 * is to support the implementations of {@code java.util.Random}

 * and {@code java.util.concurrent.ThreadLocalRandom}, but it could

 * in principle be used to implement others as well.

 *

 * (If the pseudorandom number generator has the ability to split or

 * jump, then the programmer may wish to consider instead extending

 * another abstract class, such as {@code AbstractSplittableRng},

 * {@code AbstractJumpableRng}, {@code AbstractArbitrarilyJumpableRng},

 * {@code AbstractSplittableJumpableRng}, or

 * {@code AbstractSplittableArbitrarilyJumpableRng}.)

 *

 * The programmer should generally provide at least three constructors:

 * one that takes no arguments, one that accepts a {@code long}

 * seed value, and one that accepts an array of seed {@code byte} values.

 * This class provides a public {@code initialSeed()} method that may

 * be useful in initializing some static state from which to derive

 * defaults seeds for use by the no-argument constructor.

 *

 * For the stream methods (such as {@code ints()} and {@code splits()}),

 * this class provides {@code Spliterator}-based implementations that

 * allow parallel execution when appropriate.

 *

 * The documentation for each non-abstract method in this class

 * describes its implementation in detail. Each of these methods may

 * be overridden if the pseudorandom number generator being

 * implemented admits a more efficient implementation.

 *

 * @author  Guy Steele

 * @author  Doug Lea

 * @since   1.9

 */

public abstract class AbstractSharedRng extends AbstractSpliteratorRng {

    /*

     * Implementation Overview.

     *

     * This class provides most of the "user API" methods needed to

     * satisfy the interface java.util.Rng.  Most of these methods

     * are in turn inherited from AbstractRng and the non-public class

     * AbstractSpliteratorRng; this file implements methods and spliterators

     * necessary to support the latter.

     *

     * File organization: First some non-public methods, followed by

     * some custom spliterator classes needed for stream methods.

     */

    // Methods required by class AbstractSpliteratorRng

    Spliterator.OfInt makeIntsSpliterator(long index, long fence, int origin, int bound) {

	return new RandomIntsSpliterator(this, index, fence, origin, bound);

    }

    Spliterator.OfLong makeLongsSpliterator(long index, long fence, long origin, long bound) {

	return new RandomLongsSpliterator(this, index, fence, origin, bound);

    }

    Spliterator.OfDouble makeDoublesSpliterator(long index, long fence, double origin, double bound) {

	return new RandomDoublesSpliterator(this, index, fence, origin, bound);

    }

    // Spliterators for producing streams. These are based on abstract

    // spliterator classes provided by class AbstractSpliteratorRng.

    // Each one needs to define only a constructor and two methods.

    static class RandomIntsSpliterator extends RngSupport.RandomSpliterator implements Spliterator.OfInt {

	final AbstractSharedRng generatingRng;

        final int origin;

        final int bound;

        RandomIntsSpliterator(AbstractSharedRng generatingRng, long index, long fence, int origin, int bound) {

	    super(index, fence);

	    this.generatingRng = generatingRng;

            this.origin = origin; this.bound = bound;

        }

        public Spliterator.OfInt trySplit() {

            long i = index, m = (i + fence) >>> 1;

	    if (m <= i) return null;

	    index = m;

	    // The same generatingRng is used, with no splitting or copying.

	    return new RandomIntsSpliterator(generatingRng, i, m, origin, bound);

        }

        public boolean tryAdvance(IntConsumer consumer) {

            if (consumer == null) throw new NullPointerException();

            long i = index, f = fence;

            if (i < f) {

                consumer.accept(RngSupport.boundedNextInt(generatingRng, origin, bound));

                index = i + 1;

                return true;

            }

            else return false;

        }

        public void forEachRemaining(IntConsumer consumer) {

            if (consumer == null) throw new NullPointerException();

            long i = index, f = fence;

            if (i < f) {

                index = f;

                Rng r = generatingRng;

                int o = origin, b = bound;

                do {

                    consumer.accept(RngSupport.boundedNextInt(r, o, b));

                } while (++i < f);

            }

        }

    }

    /**

     * Spliterator for long streams.

     */

    static class RandomLongsSpliterator extends RngSupport.RandomSpliterator implements Spliterator.OfLong {

	final AbstractSharedRng generatingRng;

        final long origin;

        final long bound;

        RandomLongsSpliterator(AbstractSharedRng generatingRng, long index, long fence, long origin, long bound) {

	    super(index, fence);

	    this.generatingRng = generatingRng;

            this.origin = origin; this.bound = bound;

        }

        public Spliterator.OfLong trySplit() {

            long i = index, m = (i + fence) >>> 1;

	    if (m <= i) return null;

	    index = m;

	    // The same generatingRng is used, with no splitting or copying.

	    return new RandomLongsSpliterator(generatingRng, i, m, origin, bound);

        }

        public boolean tryAdvance(LongConsumer consumer) {

            if (consumer == null) throw new NullPointerException();

            long i = index, f = fence;

            if (i < f) {

                consumer.accept(RngSupport.boundedNextLong(generatingRng, origin, bound));

                index = i + 1;

                return true;

            }

            else return false;

        }

        public void forEachRemaining(LongConsumer consumer) {

            if (consumer == null) throw new NullPointerException();

            long i = index, f = fence;

            if (i < f) {

                index = f;

                Rng r = generatingRng;

                long o = origin, b = bound;

                do {

                    consumer.accept(RngSupport.boundedNextLong(r, o, b));

                } while (++i < f);

            }

        }

    }

    /**

     * Spliterator for double streams.

     */

    static class RandomDoublesSpliterator extends RngSupport.RandomSpliterator implements Spliterator.OfDouble {

	final AbstractSharedRng generatingRng;

        final double origin;

        final double bound;

        RandomDoublesSpliterator(AbstractSharedRng generatingRng, long index, long fence, double origin, double bound) {

	    super(index, fence);

	    this.generatingRng = generatingRng;

            this.origin = origin; this.bound = bound;

        }

        public Spliterator.OfDouble trySplit() {

            long i = index, m = (i + fence) >>> 1;

	    if (m <= i) return null;

	    index = m;

	    // The same generatingRng is used, with no splitting or copying.

	    return new RandomDoublesSpliterator(generatingRng, i, m, origin, bound);

        }

        public boolean tryAdvance(DoubleConsumer consumer) {

            if (consumer == null) throw new NullPointerException();

            long i = index, f = fence;

            if (i < f) {

                consumer.accept(RngSupport.boundedNextDouble(generatingRng, origin, bound));

                index = i + 1;

                return true;

            }

            else return false;

        }

        public void forEachRemaining(DoubleConsumer consumer) {

            if (consumer == null) throw new NullPointerException();

            long i = index, f = fence;

            if (i < f) {

                index = f;

                Rng r = generatingRng;

                double o = origin, b = bound;

                do {

                    consumer.accept(RngSupport.boundedNextDouble(r, o, b));

                } while (++i < f);

            }

        }

    }

}