mirror of https://github.com/apache/cassandra
113 lines
3.5 KiB
Java
113 lines
3.5 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one
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* or more contributor license agreements. See the NOTICE file
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* distributed with this work for additional information
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* regarding copyright ownership. The ASF licenses this file
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* to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.quicktheories.impl;
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import java.util.Objects;
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import java.util.Random;
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import org.quicktheories.core.DetatchedRandomnessSource;
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import org.quicktheories.core.RandomnessSource;
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/**
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* The {@link Constraint} class does not expose {@link Constraint#min()} or {@link Constraint#max()} outside the package, so
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* the only way to build a {@link RandomnessSource} is to define it in the package "org.quicktheories.impl"
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*/
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public class JavaRandom implements RandomnessSource, DetatchedRandomnessSource
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{
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private final Random random;
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public JavaRandom(long seed)
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{
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this.random = new Random(seed);
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}
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public JavaRandom(Random random)
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{
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this.random = Objects.requireNonNull(random);
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}
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public void setSeed(long seed)
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{
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this.random.setSeed(seed);
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}
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public static JavaRandom wrap(RandomnessSource rnd)
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{
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if (rnd instanceof JavaRandom)
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return (JavaRandom) rnd;
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return new JavaRandom(rnd.next(Constraint.none().withNoShrinkPoint()));
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}
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@Override
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public long next(Constraint constraint)
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{
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long max = constraint.max();
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return nextLong(constraint.min(), max == Long.MAX_VALUE ? max : max + 1);
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}
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private long nextLong(long minInclusive, long maxExclusive)
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{
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// pulled from accord.utils.RandomSource#nextLong(long, long)...
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// long term it will be great to unify the two and drop QuickTheories classes all together
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// this is diff behavior than ThreadLocalRandom, which returns nextLong
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if (minInclusive >= maxExclusive)
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throw new IllegalArgumentException(String.format("Min (%s) should be less than max (%d).", minInclusive, maxExclusive));
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long result = random.nextLong();
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long delta = maxExclusive - minInclusive;
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long mask = delta - 1;
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if ((delta & mask) == 0L) // power of two
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result = (result & mask) + minInclusive;
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else if (delta > 0L)
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{
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// reject over-represented candidates
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for (long u = result >>> 1; // ensure nonnegative
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u + mask - (result = u % delta) < 0L; // rejection check
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u = random.nextLong() >>> 1) // retry
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;
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result += minInclusive;
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}
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else
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{
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// range not representable as long
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while (result < minInclusive || result >= maxExclusive)
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result = random.nextLong();
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}
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return result;
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}
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@Override
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public DetatchedRandomnessSource detach()
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{
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return this;
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}
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@Override
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public void registerFailedAssumption()
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{
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}
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@Override
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public void commit()
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{
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// no-op
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}
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}
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