1 /*

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

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

     4  *

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

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

     7  * published by the Free Software Foundation.  Oracle designates this

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

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

    10  *

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

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

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

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

    15  * accompanied this code).

    16  *

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

    18  * 2 along with this work; if not, write to the Free Software Foundation,

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

    20  *

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

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 package java.util;

    26 

    27 import java.util.Spliterator;

    28 import java.util.function.Consumer;

    29 import java.util.function.IntConsumer;

    30 import java.util.function.LongConsumer;

    31 import java.util.function.DoubleConsumer;

    32 import java.util.stream.StreamSupport;

    33 import java.util.stream.Stream;

    34 

    35 /**

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

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

    38  *

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

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

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

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

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

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

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

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

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

    48  *

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

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

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

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

    53  * {@code AbstractSplittableJumpableRng}, or

    54  * {@code AbstractSplittableArbitrarilyJumpableRng}.)

    55  *

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

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

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

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

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

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

    62  *

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

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

    65  * allow parallel execution when appropriate.

    66  *

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

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

    69  * be overridden if the pseudorandom number generator being

    70  * implemented admits a more efficient implementation.

    71  *

    72  * @author  Guy Steele

    73  * @author  Doug Lea

    74  * @since   1.9

    75  */

    76 public abstract class AbstractSharedRng extends AbstractSpliteratorRng {

    77 

    78     /*

    79      * Implementation Overview.

    80      *

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

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

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

    84      * AbstractSpliteratorRng; this file implements methods and spliterators

    85      * necessary to support the latter.

    86      *

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

    88      * some custom spliterator classes needed for stream methods.

    89      */

    90 

    91     // Methods required by class AbstractSpliteratorRng

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

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

    94     }

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

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

    97     }

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

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

   100     }

   101 

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

   103     // spliterator classes provided by class AbstractSpliteratorRng.

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

   105 

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

   107 	final AbstractSharedRng generatingRng;

   108         final int origin;

   109         final int bound;

   110 

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

   112 	    super(index, fence);

   113 	    this.generatingRng = generatingRng;

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

   115         }

   116 	

   117         public Spliterator.OfInt trySplit() {

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

   119 	    if (m <= i) return null;

   120 	    index = m;

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

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

   123         }

   124 

   125         public boolean tryAdvance(IntConsumer consumer) {

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

   127             long i = index, f = fence;

   128             if (i < f) {

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

   130                 index = i + 1;

   131                 return true;

   132             }

   133             else return false;

   134         }

   135 

   136         public void forEachRemaining(IntConsumer consumer) {

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

   138             long i = index, f = fence;

   139             if (i < f) {

   140                 index = f;

   141                 Rng r = generatingRng;

   142                 int o = origin, b = bound;

   143                 do {

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

   145                 } while (++i < f);

   146             }

   147         }

   148     }

   149 

   150     /**

   151      * Spliterator for long streams.

   152      */

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

   154 	final AbstractSharedRng generatingRng;

   155         final long origin;

   156         final long bound;

   157 

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

   159 	    super(index, fence);

   160 	    this.generatingRng = generatingRng;

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

   162         }

   163 	

   164         public Spliterator.OfLong trySplit() {

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

   166 	    if (m <= i) return null;

   167 	    index = m;

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

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

   170         }

   171 

   172         public boolean tryAdvance(LongConsumer consumer) {

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

   174             long i = index, f = fence;

   175             if (i < f) {

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

   177                 index = i + 1;

   178                 return true;

   179             }

   180             else return false;

   181         }

   182 

   183         public void forEachRemaining(LongConsumer consumer) {

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

   185             long i = index, f = fence;

   186             if (i < f) {

   187                 index = f;

   188                 Rng r = generatingRng;

   189                 long o = origin, b = bound;

   190                 do {

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

   192                 } while (++i < f);

   193             }

   194         }

   195     }

   196 

   197     /**

   198      * Spliterator for double streams.

   199      */

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

   201 	final AbstractSharedRng generatingRng;

   202         final double origin;

   203         final double bound;

   204 

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

   206 	    super(index, fence);

   207 	    this.generatingRng = generatingRng;

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

   209         }

   210 	

   211         public Spliterator.OfDouble trySplit() {

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

   213 	    if (m <= i) return null;

   214 	    index = m;

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

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

   217         }

   218 

   219         public boolean tryAdvance(DoubleConsumer consumer) {

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

   221             long i = index, f = fence;

   222             if (i < f) {

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

   224                 index = i + 1;

   225                 return true;

   226             }

   227             else return false;

   228         }

   229 

   230         public void forEachRemaining(DoubleConsumer consumer) {

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

   232             long i = index, f = fence;

   233             if (i < f) {

   234                 index = f;

   235                 Rng r = generatingRng;

   236                 double o = origin, b = bound;

   237                 do {

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

   239                 } while (++i < f);

   240             }

   241         }

   242     }

   243 

   244 }