Barebone c2me integration code

build.gradle

@@ -133,6 +133,8 @@ dependencies {
     // For more info:
     // http://www.gradle.org/docs/current/userguide/artifact_dependencies_tutorial.html
     // http://www.gradle.org/docs/current/userguide/dependency_management.html
+
+    // compileOnly(project(":c2me"))
 }
 
 // This block of code expands all declared replace properties in the specified resource targets.

settings.gradle

@@ -9,3 +9,5 @@ pluginManagement {
 plugins {
     id 'org.gradle.toolchains.foojay-resolver-convention' version '0.8.0'
 }
+
+// include("c2me")

src/main/java/ru/dbotthepony/mc/prng/BetterRandom.java

@@ -1,9 +1,24 @@
 package ru.dbotthepony.mc.prng;
 
+import net.minecraft.util.RandomSource;
+import net.neoforged.fml.ModList;
 import net.neoforged.fml.common.Mod;
 
+import java.util.function.Supplier;
+
 @Mod(BetterRandom.MOD_ID)
 public final class BetterRandom {
 	public static final String MOD_ID = "better_random";
 	public static final String SAVEDATA_LOCATION = "better_random_sequences";
+
+	private static RandomSource createWorldRandomC2ME(Supplier<Thread> thread) {
+		return new SynchronizedGJRAND64RandomSource();
+	}
+
+	public static RandomSource createWorldRandom(Supplier<Thread> thread) {
+		if (ModList.get().isLoaded("c2me"))
+			return createWorldRandomC2ME(thread);
+
+		return new GJRAND64RandomSource();
+	}
 }

src/main/java/ru/dbotthepony/mc/prng/GJRAND64RandomSource.java

@@ -11,7 +11,7 @@ import org.jetbrains.annotations.NotNull;
 
 import java.util.random.RandomGenerator;
 
-public final class GJRAND64RandomSource implements RandomGenerator, RandomSource {
+public class GJRAND64RandomSource implements RandomGenerator, RandomSource {
 	public static final Codec<GJRAND64RandomSource> CODEC = RecordCodecBuilder.create(it -> {
 		return it.group(
 			Codec.LONG.fieldOf("s0").forGetter(o -> o.s0),

src/main/java/ru/dbotthepony/mc/prng/SynchronizedGJRAND64RandomSource.java

@@ -0,0 +1,95 @@
+package ru.dbotthepony.mc.prng;
+
+import it.unimi.dsi.fastutil.HashCommon;
+import net.minecraft.util.Mth;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.levelgen.PositionalRandomFactory;
+import net.minecraft.world.level.levelgen.RandomSupport;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.concurrent.locks.ReentrantLock;
+
+public class SynchronizedGJRAND64RandomSource extends GJRAND64RandomSource {
+	private final ReentrantLock lock = new ReentrantLock();
+
+	public SynchronizedGJRAND64RandomSource() {
+		super();
+	}
+
+	public SynchronizedGJRAND64RandomSource(long seed) {
+		super(seed);
+	}
+
+	public SynchronizedGJRAND64RandomSource(long seed0, long seed1) {
+		super(seed0, seed1);
+	}
+
+	public SynchronizedGJRAND64RandomSource(RandomSupport.Seed128bit seed) {
+		super(seed);
+	}
+
+	@Override
+	public long nextLong() {
+		lock.lock();
+		long result = super.nextLong();
+		lock.unlock();
+		return result;
+	}
+
+	@Override
+	public void setSeed(long l) {
+		lock.lock();
+		super.setSeed(l);
+		lock.unlock();
+	}
+
+	@Override
+	public double nextGaussian() {
+		lock.lock();
+		double value = super.nextGaussian();
+		lock.unlock();
+		return value;
+	}
+
+	@Override
+	public @NotNull RandomSource fork() {
+		return new SynchronizedGJRAND64RandomSource(nextLong(), nextLong());
+	}
+
+	@Override
+	public @NotNull PositionalRandomFactory forkPositional() {
+		return new Positional(nextLong(), nextLong());
+	}
+
+	public static class Positional implements PositionalRandomFactory {
+		private final long seed0;
+		private final long seed1;
+
+		public Positional(long seed0, long seed1) {
+			this.seed0 = seed0;
+			this.seed1 = seed1;
+		}
+
+		@Override
+		public @NotNull RandomSource fromHashOf(@NotNull String s) {
+			long seed = HashCommon.murmurHash3((long) s.hashCode() & 0xFFFFFFFFL);
+			return new SynchronizedGJRAND64RandomSource(seed0 ^ Long.rotateLeft(seed, 32), seed1 ^ seed);
+		}
+
+		@Override
+		public @NotNull RandomSource fromSeed(long l) {
+			return new SynchronizedGJRAND64RandomSource(l);
+		}
+
+		@Override
+		public @NotNull RandomSource at(int x, int y, int z) {
+			long seed = Mth.getSeed(x, y, z);
+			return new SynchronizedGJRAND64RandomSource(seed0 ^ Long.rotateLeft(seed, 32), seed1 ^ seed);
+		}
+
+		@Override
+		public void parityConfigString(@NotNull StringBuilder stringBuilder) {
+			throw new UnsupportedOperationException();
+		}
+	}
+}

src/main/java/ru/dbotthepony/mc/prng/mixin/LevelMixin.java

@@ -1,12 +1,34 @@
 package ru.dbotthepony.mc.prng.mixin;
 
 import net.minecraft.core.BlockPos;
+import net.minecraft.util.RandomSource;
 import net.minecraft.world.level.Level;
+import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Redirect;
+import ru.dbotthepony.mc.prng.BetterRandom;
 
 @Mixin(Level.class)
 public abstract class LevelMixin {
+	@Shadow
+	@Final
+	private Thread thread;
+
+	@Final // ensure it is on top-level
+	@Redirect(
+		method = "<init>",
+		at = @At(
+			value = "INVOKE",
+			target = "Lnet/minecraft/util/RandomSource;create()Lnet/minecraft/util/RandomSource;"
+		)
+	)
+	public RandomSource ensureBetterRandom() {
+		return BetterRandom.createWorldRandom(() -> thread);
+	}
+
 	@Overwrite
 	public BlockPos getBlockRandomPos(int x, int y, int z, int yMask) {
 		long value = ((Level) (Object) this).random.nextLong();