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* Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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// package java.util;
import java.util.function.Consumer;
import java.util.function.IntConsumer;
import java.util.function.LongConsumer;
import java.util.function.DoubleConsumer;
import java.util.Spliterator;
import java.util.stream.StreamSupport;
import java.util.stream.Stream;
/**
* This class provides much of the implementation of the {@code SplittableRng}
* interface, to minimize the effort required to implement this interface.
*
* To implement a pseudorandom number generator, the programmer needs
* only to extend this class and provide implementations for the
* methods {@code nextInt()}, {@code nextLong()}, {@code period()},
* and {@code split(SplittableRng)}.
*
* (If the pseudorandom number generator also has the ability to jump,
* then the programmer may wish to consider instead extending
* the class {@code AbstractSplittableJumpableRng} or (if it can also leap)
* {@code AbstractSplittableLeapableRng}. But if the pseudorandom number
* generator furthermore has the ability to jump an arbitrary specified
* distance, then the programmer may wish to consider instead extending
* the class {@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 AbstractSplittableRng extends AbstractSpliteratorRng implements SplittableRng {
/*
* Implementation Overview.
*
* This class provides most of the "user API" methods needed to
* satisfy the interface java.util.JumpableRng. Most of these methods
* are in turn inherited from AbstractRng and the non-public class
* AbstractSpliteratorRng; this file implements two versions of the
* splits method and defines the spliterators necessary to support
* them.
*
* The abstract split() method from interface SplittableRng is redeclared
* here so as to narrow the return type to AbstractSplittableRng.
*
* File organization: First the non-public methods needed by the class
* AbstractSpliteratorRng, then the main public methods, followed by some
* custom spliterator classes.
*/
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);
}
Spliterator<SplittableRng> makeSplitsSpliterator(long index, long fence, SplittableRng source) {
return new RandomSplitsSpliterator(source, index, fence, this);
}
/* ---------------- public methods ---------------- */
/**
* Implements the @code{split()} method as {@code this.split(this) }.
*
* @return the new {@code AbstractSplittableRng} instance
*/
public SplittableRng split() { return this.split(this); }
// Stream methods for splittings
/**
* Returns an effectively unlimited stream of new pseudorandom
* number generators, each of which implements the {@code SplittableRng}
* interface.
*
* This pseudorandom number generator provides the
* entropy used to seed the new ones.
*
* @implNote This method is implemented to be equivalent to
* {@code splits(Long.MAX_VALUE)}.
*
* @return a stream of {@code SplittableRng} objects
*/
public Stream<SplittableRng> splits() {
return this.splits(Long.MAX_VALUE, this);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* new pseudorandom number generators, each of which implements the
* {@code SplittableRng} interface.
*
* This pseudorandom number generator provides the
* entropy used to seed the new ones.
*
* @param streamSize the number of values to generate
* @return a stream of {@code SplittableRng} objects
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public Stream<SplittableRng> splits(long streamSize) {
return this.splits(streamSize, this);
}
/**
* Returns an effectively unlimited stream of new pseudorandom
* number generators, each of which implements the {@code SplittableRng}
* interface.
*
* @implNote This method is implemented to be equivalent to
* {@code splits(Long.MAX_VALUE)}.
*
* @param source a {@code SplittableRng} instance to be used instead
* of this one as a source of pseudorandom bits used to
* initialize the state of the new ones.
* @return a stream of {@code SplittableRng} objects
*/
public Stream<SplittableRng> splits(SplittableRng source) {
return this.splits(Long.MAX_VALUE, source);
}
/**
* Returns a stream producing the given {@code streamSize} number of
* new pseudorandom number generators, each of which implements the
* {@code SplittableRng} interface.
*
* @param streamSize the number of values to generate
* @param source a {@code SplittableRng} instance to be used instead
* of this one as a source of pseudorandom bits used to
* initialize the state of the new ones.
* @return a stream of {@code SplittableRng} objects
* @throws IllegalArgumentException if {@code streamSize} is
* less than zero
*/
public Stream<SplittableRng> splits(long streamSize, SplittableRng source) {
RngSupport.checkStreamSize(streamSize);
return StreamSupport.stream(makeSplitsSpliterator(0L, streamSize, source), false);
}
/**
* Spliterator for int streams. We multiplex the four int
* versions into one class by treating a bound less than origin as
* unbounded, and also by treating "infinite" as equivalent to
* Long.MAX_VALUE. For splits, it uses the standard divide-by-two
* approach. The long and double versions of this class are
* identical except for types.
*/
static class RandomIntsSpliterator extends RngSupport.RandomSpliterator implements Spliterator.OfInt {
final SplittableRng generatingRng;
final int origin;
final int bound;
RandomIntsSpliterator(SplittableRng 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;
return new RandomIntsSpliterator(generatingRng.split(), 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 SplittableRng generatingRng;
final long origin;
final long bound;
RandomLongsSpliterator(SplittableRng 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;
return new RandomLongsSpliterator(generatingRng.split(), 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 SplittableRng generatingRng;
final double origin;
final double bound;
RandomDoublesSpliterator(SplittableRng 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;
return new RandomDoublesSpliterator(generatingRng.split(), 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);
}
}
}
/**
* Spliterator for stream of generators of type SplittableRng. We multiplex the two
* versions into one class by treating "infinite" as equivalent to Long.MAX_VALUE.
* For splits, it uses the standard divide-by-two approach.
*/
static class RandomSplitsSpliterator extends RngSupport.RandomSpliterator implements Spliterator<SplittableRng> {
final SplittableRng generatingRng;
final SplittableRng constructingRng;
RandomSplitsSpliterator(SplittableRng generatingRng, long index, long fence, SplittableRng constructingRng) {
super(index, fence);
this.generatingRng = generatingRng;
this.constructingRng = constructingRng;
}
public Spliterator<SplittableRng> trySplit() {
long i = index, m = (i + fence) >>> 1;
if (m <= i) return null;
index = m;
return new RandomSplitsSpliterator(generatingRng.split(), i, m, constructingRng);
}
public boolean tryAdvance(Consumer<? super SplittableRng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
consumer.accept(constructingRng.split(generatingRng));
index = i + 1;
return true;
}
else return false;
}
public void forEachRemaining(Consumer<? super SplittableRng> consumer) {
if (consumer == null) throw new NullPointerException();
long i = index, f = fence;
if (i < f) {
index = f;
SplittableRng c = constructingRng;
SplittableRng r = generatingRng;
do {
consumer.accept(c.split(r));
} while (++i < f);
}
}
}
}