1 /*

     2  * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.

     3  * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

     4  *

     5  *

     6  *

     7  *

     8  *

     9  *

    10  *

    11  *

    12  *

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    16  *

    17  *

    18  *

    19  *

    20  *

    21  *

    22  *

    23  *

    24  */

    25 

    26 // package java.util;

    27 

    28 import java.util.Spliterator;

    29 import java.util.function.Consumer;

    30 import java.util.function.IntConsumer;

    31 import java.util.function.LongConsumer;

    32 import java.util.function.DoubleConsumer;

    33 import java.util.stream.StreamSupport;

    34 import java.util.stream.Stream;

    35 

    36 /**

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

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

    39  *

    40  * To implement a pseudorandom number generator, the programmer needs

    41  * only to extend this class and provide implementations for the

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

    43  * the implementations of other methods in this class to operate

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

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

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

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

    48  * in principle be used to implement others as well.

    49  *

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

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

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

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

    54  * {@code AbstractSplittableJumpableRng}, or

    55  * {@code AbstractSplittableArbitrarilyJumpableRng}.)

    56  *

    57  * The programmer should generally provide at least three constructors:

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

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

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

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

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

    63  *

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

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

    66  * allow parallel execution when appropriate.

    67  *

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

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

    70  * be overridden if the pseudorandom number generator being

    71  * implemented admits a more efficient implementation.

    72  *

    73  * @author  Guy Steele

    74  * @author  Doug Lea

    75  * @since   1.9

    76  */

    77 public abstract class AbstractSharedRng extends AbstractSpliteratorRng {

    78 

    79     /*

    80      * Implementation Overview.

    81      *

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

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

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

    85      * AbstractSpliteratorRng; this file implements methods and spliterators

    86      * necessary to support the latter.

    87      *

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

    89      * some custom spliterator classes needed for stream methods.

    90      */

    91 

    92     // Methods required by class AbstractSpliteratorRng

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

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

    95     }

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

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

    98     }

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

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

   101     }

   102 

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

   104     // spliterator classes provided by class AbstractSpliteratorRng.

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

   106 

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

   108 	final AbstractSharedRng generatingRng;

   109         final int origin;

   110         final int bound;

   111 

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

   113 	    super(index, fence);

   114 	    this.generatingRng = generatingRng;

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

   116         }

   117 	

   118         public Spliterator.OfInt trySplit() {

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

   120 	    if (m <= i) return null;

   121 	    index = m;

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

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

   124         }

   125 

   126         public boolean tryAdvance(IntConsumer consumer) {

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

   128             long i = index, f = fence;

   129             if (i < f) {

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

   131                 index = i + 1;

   132                 return true;

   133             }

   134             else return false;

   135         }

   136 

   137         public void forEachRemaining(IntConsumer consumer) {

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

   139             long i = index, f = fence;

   140             if (i < f) {

   141                 index = f;

   142                 Rng r = generatingRng;

   143                 int o = origin, b = bound;

   144                 do {

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

   146                 } while (++i < f);

   147             }

   148         }

   149     }

   150 

   151     /**

   152      * Spliterator for long streams.

   153      */

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

   155 	final AbstractSharedRng generatingRng;

   156         final long origin;

   157         final long bound;

   158 

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

   160 	    super(index, fence);

   161 	    this.generatingRng = generatingRng;

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

   163         }

   164 	

   165         public Spliterator.OfLong trySplit() {

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

   167 	    if (m <= i) return null;

   168 	    index = m;

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

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

   171         }

   172 

   173         public boolean tryAdvance(LongConsumer consumer) {

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

   175             long i = index, f = fence;

   176             if (i < f) {

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

   178                 index = i + 1;

   179                 return true;

   180             }

   181             else return false;

   182         }

   183 

   184         public void forEachRemaining(LongConsumer consumer) {

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

   186             long i = index, f = fence;

   187             if (i < f) {

   188                 index = f;

   189                 Rng r = generatingRng;

   190                 long o = origin, b = bound;

   191                 do {

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

   193                 } while (++i < f);

   194             }

   195         }

   196     }

   197 

   198     /**

   199      * Spliterator for double streams.

   200      */

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

   202 	final AbstractSharedRng generatingRng;

   203         final double origin;

   204         final double bound;

   205 

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

   207 	    super(index, fence);

   208 	    this.generatingRng = generatingRng;

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

   210         }

   211 	

   212         public Spliterator.OfDouble trySplit() {

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

   214 	    if (m <= i) return null;

   215 	    index = m;

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

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

   218         }

   219 

   220         public boolean tryAdvance(DoubleConsumer consumer) {

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

   222             long i = index, f = fence;

   223             if (i < f) {

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

   225                 index = i + 1;

   226                 return true;

   227             }

   228             else return false;

   229         }

   230 

   231         public void forEachRemaining(DoubleConsumer consumer) {

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

   233             long i = index, f = fence;

   234             if (i < f) {

   235                 index = f;

   236                 Rng r = generatingRng;

   237                 double o = origin, b = bound;

   238                 do {

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

   240                 } while (++i < f);

   241             }

   242         }

   243     }

   244 

   245 }