Provide LCG64 implementation as separate class

src/main/kotlin/ru/dbotthepony/mc/otm/core/util/CMWCRandom.kt

@@ -22,17 +22,15 @@ class CMWCRandom(seed: Long = System.nanoTime()) : RandomGenerator, RandomSource
 
 	override fun setSeed(seed: Long) {
 		this.seed = seed
-		var lcg = seed
+		val rng = LCG64Random(seed)
 
 		// init state with regular LCG produced values
 		for (i in 1 until state.size) {
-			lcg = lcg * 6364136223846793005 + 1442695040888963407
+			state[i] = rng.nextInt()
-			state[i] = lcg.ushr(32).toInt()
 		}
 
 		do {
-			lcg = lcg * 6364136223846793005 + 1442695040888963407
+			carry = rng.nextInt()
-			carry = lcg.ushr(32).toInt()
 		} while(carry !in 0 until CMWC_CARRY_MAX)
 
 		stateIndex = state.size - 1

src/main/kotlin/ru/dbotthepony/mc/otm/core/util/LCG64Random.kt

@@ -0,0 +1,86 @@
+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
+
+// different from LegacyRandomSource minecraft uses in meaning that this class use different constants
+// and always use upper 32 bits instead of implementing BitRandomSource
+// AND it uses all bits from provided seed
+class LCG64Random(private var seed: Long = System.nanoTime()) : RandomGenerator, RandomSource {
+	private val gaussian = MarsagliaPolarGaussian(this)
+
+	override fun setSeed(seed: Long) {
+		this.seed = seed
+		gaussian.reset()
+	}
+
+	override fun nextInt(): Int {
+		this.seed = MULTIPLIER * this.seed + INCREMENT
+		return this.seed.ushr(32).toInt()
+	}
+
+	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 LCG64Random(nextLong())
+	}
+
+	override fun forkPositional(): PositionalRandomFactory {
+		return Positional(nextLong())
+	}
+
+	class Positional(val seed: Long) : PositionalRandomFactory {
+		override fun at(x: Int, y: Int, z: Int): RandomSource {
+			return LCG64Random(Mth.getSeed(x, y, z).xor(seed))
+		}
+
+		override fun fromHashOf(name: String): RandomSource {
+			return LCG64Random(name.hashCode().toLong().xor(seed))
+		}
+
+		override fun fromSeed(seed: Long): RandomSource {
+			return LCG64Random(seed)
+		}
+
+		override fun parityConfigString(builder: StringBuilder) {
+			throw UnsupportedOperationException()
+		}
+	}
+
+	companion object {
+		const val MULTIPLIER = 6364136223846793005
+		const val INCREMENT = 1442695040888963407
+	}
+}