--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/newrandom/JumpableRng.java Thu May 23 16:45:56 2019 -0400
@@ -0,0 +1,176 @@
+/*
+ * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
+ * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ *
+ */
+// package java.util;
+
+import java.math.BigInteger;
+import java.util.stream.Stream;
+
+/**
+ * This interface is designed to provide a common protocol for objects
+ * that generate pseudorandom sequences of numbers (or Boolean values)
+ * and furthermore can easily <it>jump</it> forward (by a fixed amount)
+ * to a distant point in the state cycle.
+ *
+ * <p>Ideally, all {@code JumpableRng} objects produced by iterative
+ * jumping from a single original {@code JumpableRng} object are
+ * statistically independent of one another and individually uniform.
+ * In practice, one must settle for some approximation to independence
+ * and uniformity. In particular, a specific implementation may
+ * assume that each generator in a stream produced by the {@code jumps}
+ * method is used to produce a number of values no larger than either
+ * 2<sup>64</sup> or the square root of its period. Implementors are
+ * advised to use algorithms whose period is at least 2<sup>127</sup>.
+ *
+ * <p>Methods are provided to perform a single jump operation and also
+ * to produce a stream of generators produced from the original by
+ * iterative copying and jumping of internal state. A typical
+ * strategy for a multithreaded application is to create a single
+ * {@code JumpableRng} object, calls its {@code jumps} method exactly
+ * once, and then parcel out generators from the resulting stream, one
+ * to each thread. It is generally not a good idea to call {@code jump}
+ * on a generator that was itself produced by the {@code jumps} method,
+ * because the result may be a generator identical to another
+ * generator already produce by that call to the {@code jumps} method.
+ * For this reason, the return type of the {@code jumps} method is
+ * {@code Stream<Rng>} rather than {@code Stream<JumpableRng>}, even
+ * though the actual generator objects in that stream likely do also
+ * implement the {@code JumpableRng} interface.
+ *
+ * <p>An implementation of the {@code JumpableRng} interface must provide
+ * concrete definitions for the methods {@code nextInt()}, {@code nextLong},
+ * {@code period()}, {@code copy()}, {@code jump()}, and {@code defaultJumpDistance()}.
+ * Default implementations are provided for all other methods.
+ *
+ * <p>Objects that implement {@code java.util.JumpableRng} are
+ * typically not cryptographically secure. Consider instead using
+ * {@link java.security.SecureRandom} to get a cryptographically
+ * secure pseudo-random number generator for use by
+ * security-sensitive applications.
+ *
+ * @author Guy Steele
+ * @since 1.9
+ */
+interface JumpableRng extends StreamableRng {
+ /**
+ * Returns a new generator whose internal state is an exact copy
+ * of this generator (therefore their future behavior should be
+ * identical if subjected to the same series of operations).
+ *
+ * @return a new object that is a copy of this generator
+ */
+ JumpableRng copy();
+
+ /**
+ * Alter the state of this pseudorandom number generator so as to
+ * jump forward a large, fixed distance (typically 2<sup>64</sup>
+ * or more) within its state cycle.
+ */
+ void jump();
+
+ /**
+ * Returns the distance by which the {@code jump()} method will jump
+ * forward within the state cycle of this generator object.
+ *
+ * @return the default jump distance (as a {@code double} value)
+ */
+ double defaultJumpDistance();
+
+ /**
+ * Returns an effectively unlimited stream of new pseudorandom
+ * number generators, each of which implements the {@code Rng}
+ * interface.
+ *
+ * @implNote It is permitted to implement this method in a manner
+ * equivalent to {@code jumps(Long.MAX_VALUE)}.
+ *
+ * @implNote The default implementation produces a sequential stream
+ * that repeatedly calls {@code copy()} and {@code jump()} on this generator,
+ * and the copies become the generators produced by the stream.
+ *
+ * @return a stream of objects that implement the {@code Rng} interface
+ */
+ default Stream<Rng> jumps() {
+ return Stream.generate(this::copyAndJump).sequential();
+ }
+
+ /**
+ * Returns a stream producing the given {@code streamSize} number of
+ * new pseudorandom number generators, each of which implements the
+ * {@code Rng} interface.
+ *
+ * @implNote The default implementation produces a sequential stream
+ * that repeatedly calls {@code copy()} and {@code jump()} on this generator,
+ * and the copies become the generators produced by the stream.
+ *
+ * @param streamSize the number of generators to generate
+ * @return a stream of objects that implement the {@code Rng} interface
+ * @throws IllegalArgumentException if {@code streamSize} is
+ * less than zero
+ */
+ default Stream<Rng> jumps(long streamSize) {
+ return jumps().limit(streamSize);
+ }
+
+ /**
+ * Returns an effectively unlimited stream of new pseudorandom
+ * number generators, each of which implements the {@code Rng}
+ * interface. Ideally the generators in the stream will appear
+ * to be statistically independent.
+ *
+ * @implNote The default implementation calls {@code jumps()}.
+ *
+ * @return a stream of objects that implement the {@code Rng} interface
+ */
+ default Stream<Rng> rngs() {
+ return this.jumps();
+ }
+
+ /**
+ * Returns a stream producing the given {@code streamSize} number of
+ * new pseudorandom number generators, each of which implements the
+ * {@code Rng} interface. Ideally the generators in the stream will
+ * appear to be statistically independent.
+ *
+ * @implNote The default implementation calls {@code jumps(streamSize)}.
+ *
+ * @param streamSize the number of generators to generate
+ * @return a stream of objects that implement the {@code Rng} interface
+ * @throws IllegalArgumentException if {@code streamSize} is
+ * less than zero
+ */
+ default Stream<Rng> rngs(long streamSize) {
+ return this.jumps(streamSize);
+ }
+
+ /**
+ * Copy this generator, jump this generator forward, then return the copy.
+ */
+ default Rng copyAndJump() {
+ Rng result = copy();
+ jump();
+ return result;
+ }
+
+}