minecraft-src/net/minecraft/world/level/levelgen/XoroshiroRandomSource.java

package net.minecraft.world.level.levelgen;

import com.google.common.annotations.VisibleForTesting;
import com.mojang.serialization.Codec;
import net.minecraft.util.Mth;
import net.minecraft.util.RandomSource;
import net.minecraft.world.level.levelgen.RandomSupport.Seed128bit;

public class XoroshiroRandomSource implements RandomSource {
	private static final float FLOAT_UNIT = 5.9604645E-8F;
	private static final double DOUBLE_UNIT = 1.110223E-16F;
	public static final Codec<XoroshiroRandomSource> CODEC = Xoroshiro128PlusPlus.CODEC
		.xmap(xoroshiro128PlusPlus -> new XoroshiroRandomSource(xoroshiro128PlusPlus), xoroshiroRandomSource -> xoroshiroRandomSource.randomNumberGenerator);
	private Xoroshiro128PlusPlus randomNumberGenerator;
	private final MarsagliaPolarGaussian gaussianSource = new MarsagliaPolarGaussian(this);

	public XoroshiroRandomSource(long seed) {
		this.randomNumberGenerator = new Xoroshiro128PlusPlus(RandomSupport.upgradeSeedTo128bit(seed));
	}

	public XoroshiroRandomSource(Seed128bit seed) {
		this.randomNumberGenerator = new Xoroshiro128PlusPlus(seed);
	}

	public XoroshiroRandomSource(long seedLo, long seedHi) {
		this.randomNumberGenerator = new Xoroshiro128PlusPlus(seedLo, seedHi);
	}

	private XoroshiroRandomSource(Xoroshiro128PlusPlus randomNumberGenerator) {
		this.randomNumberGenerator = randomNumberGenerator;
	}

	@Override
	public RandomSource fork() {
		return new XoroshiroRandomSource(this.randomNumberGenerator.nextLong(), this.randomNumberGenerator.nextLong());
	}

	@Override
	public PositionalRandomFactory forkPositional() {
		return new XoroshiroRandomSource.XoroshiroPositionalRandomFactory(this.randomNumberGenerator.nextLong(), this.randomNumberGenerator.nextLong());
	}

	@Override
	public void setSeed(long seed) {
		this.randomNumberGenerator = new Xoroshiro128PlusPlus(RandomSupport.upgradeSeedTo128bit(seed));
		this.gaussianSource.reset();
	}

	@Override
	public int nextInt() {
		return (int)this.randomNumberGenerator.nextLong();
	}

	@Override
	public int nextInt(int bound) {
		if (bound <= 0) {
			throw new IllegalArgumentException("Bound must be positive");
		} else {
			long l = Integer.toUnsignedLong(this.nextInt());
			long m = l * bound;
			long n = m & 4294967295L;
			if (n < bound) {
				for (int i = Integer.remainderUnsigned(~bound + 1, bound); n < i; n = m & 4294967295L) {
					l = Integer.toUnsignedLong(this.nextInt());
					m = l * bound;
				}
			}

			long o = m >> 32;
			return (int)o;
		}
	}

	@Override
	public long nextLong() {
		return this.randomNumberGenerator.nextLong();
	}

	@Override
	public boolean nextBoolean() {
		return (this.randomNumberGenerator.nextLong() & 1L) != 0L;
	}

	@Override
	public float nextFloat() {
		return (float)this.nextBits(24) * 5.9604645E-8F;
	}

	@Override
	public double nextDouble() {
		return this.nextBits(53) * 1.110223E-16F;
	}

	@Override
	public double nextGaussian() {
		return this.gaussianSource.nextGaussian();
	}

	@Override
	public void consumeCount(int count) {
		for (int i = 0; i < count; i++) {
			this.randomNumberGenerator.nextLong();
		}
	}

	private long nextBits(int bits) {
		return this.randomNumberGenerator.nextLong() >>> 64 - bits;
	}

	public static class XoroshiroPositionalRandomFactory implements PositionalRandomFactory {
		private final long seedLo;
		private final long seedHi;

		public XoroshiroPositionalRandomFactory(long seedLo, long seedHi) {
			this.seedLo = seedLo;
			this.seedHi = seedHi;
		}

		@Override
		public RandomSource at(int x, int y, int z) {
			long l = Mth.getSeed(x, y, z);
			long m = l ^ this.seedLo;
			return new XoroshiroRandomSource(m, this.seedHi);
		}

		@Override
		public RandomSource fromHashOf(String name) {
			Seed128bit seed128bit = RandomSupport.seedFromHashOf(name);
			return new XoroshiroRandomSource(seed128bit.xor(this.seedLo, this.seedHi));
		}

		@Override
		public RandomSource fromSeed(long seed) {
			return new XoroshiroRandomSource(seed ^ this.seedLo, seed ^ this.seedHi);
		}

		@VisibleForTesting
		@Override
		public void parityConfigString(StringBuilder builder) {
			builder.append("seedLo: ").append(this.seedLo).append(", seedHi: ").append(this.seedHi);
		}
	}
}