From 32ef2911fa8a7186d1143054c0b5c849257fafb8 Mon Sep 17 00:00:00 2001
From: DBotThePony <dbotthepony@yandex.ru>
Date: Mon, 3 Mar 2025 12:02:42 +0700
Subject: [PATCH] Implement Complementary Multiply-With-Curry Random

---
 .../mc/otm/core/util/CMWCRandom.kt            | 115 ++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 src/main/kotlin/ru/dbotthepony/mc/otm/core/util/CMWCRandom.kt

diff --git a/src/main/kotlin/ru/dbotthepony/mc/otm/core/util/CMWCRandom.kt b/src/main/kotlin/ru/dbotthepony/mc/otm/core/util/CMWCRandom.kt
new file mode 100644
index 000000000..aec7fc452
--- /dev/null
+++ b/src/main/kotlin/ru/dbotthepony/mc/otm/core/util/CMWCRandom.kt
@@ -0,0 +1,115 @@
+package ru.dbotthepony.mc.otm.core.util
+
+import net.minecraft.util.Mth
+import net.minecraft.util.RandomSource
+import net.minecraft.world.level.levelgen.MarsagliaPolarGaussian
+import net.minecraft.world.level.levelgen.PositionalRandomFactory
+import java.lang.StringBuilder
+import java.util.random.RandomGenerator
+
+class CMWCRandom(seed: Long = System.nanoTime(), private val stateSize: Int = CMWC_DEFAULT_STATE_SIZE) : RandomGenerator, RandomSource {
+	private val state = IntArray(stateSize)
+	private var carry = 0
+	private var stateIndex = 0
+	private val gaussian = MarsagliaPolarGaussian(this)
+
+	var seed: Long = seed
+		private set
+
+	init {
+		setSeed(seed)
+	}
+
+	override fun setSeed(seed: Long) {
+		this.seed = seed
+		carry = Integer.remainderUnsigned(seed.toInt(), CMWC_CARRY_MAX)
+
+		// init state with regular LCG produced values
+		state[0] = seed.toInt()
+		state[1] = seed.shr(32).toInt()
+
+		for (i in 2 until state.size) {
+			state[i] = 69069 * state[i - 2] + 362437
+		}
+
+		stateIndex = state.size - 1
+		gaussian.reset()
+	}
+
+	override fun nextInt(): Int {
+		stateIndex = (stateIndex + 1) % state.size
+		val t = 18782L * state[stateIndex] + carry
+
+		carry = t.ushr(32).toInt()
+		var x = t.toInt() + carry
+
+		if (x < carry) {
+			x++
+			carry++
+		}
+
+		state[stateIndex] = 0xfffffffe.toInt() - x
+		return state[stateIndex]
+	}
+
+	override fun nextLong(): Long {
+		val a = nextInt().toLong() and 0xFFFFFFFFL
+		val b = nextInt().toLong() and 0xFFFFFFFFL
+		return a.shl(32) or b
+	}
+
+	override fun nextInt(bound: Int): Int {
+		return super<RandomGenerator>.nextInt(bound)
+	}
+
+	override fun nextInt(origin: Int, bound: Int): Int {
+		return super<RandomGenerator>.nextInt(origin, bound)
+	}
+
+	override fun nextBoolean(): Boolean {
+		return super.nextBoolean()
+	}
+
+	override fun nextFloat(): Float {
+		return super.nextFloat()
+	}
+
+	override fun nextDouble(): Double {
+		return super.nextDouble()
+	}
+
+	override fun nextGaussian(): Double {
+		return gaussian.nextGaussian()
+	}
+
+	override fun fork(): RandomSource {
+		return CMWCRandom(nextLong(), stateSize)
+	}
+
+	override fun forkPositional(): PositionalRandomFactory {
+		return Positional(nextLong(), stateSize)
+	}
+
+	class Positional(val seed: Long, val stateSize: Int = CMWC_DEFAULT_STATE_SIZE) : PositionalRandomFactory {
+		override fun at(x: Int, y: Int, z: Int): RandomSource {
+			return CMWCRandom(Mth.getSeed(x, y, z).xor(seed), stateSize)
+		}
+
+		override fun fromHashOf(name: String): RandomSource {
+			return CMWCRandom(name.hashCode().toLong().xor(seed), stateSize)
+		}
+
+		override fun fromSeed(seed: Long): RandomSource {
+			return CMWCRandom(seed, stateSize)
+		}
+
+		override fun parityConfigString(builder: StringBuilder) {
+			throw UnsupportedOperationException()
+		}
+	}
+
+	companion object {
+		const val CMWC_DEFAULT_STATE_SIZE = 256 // 4096
+		const val CMWC_CARRY_MAX = 809430660
+	}
+}