Optimize Vec3i hashing (#573)

Author: HaHaWTH

leaf-server/minecraft-patches/features/0305-Optimize-Vec3i-hashing.patch

@@ -0,0 +1,22 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: HaHaWTH <[email protected]>
+Date: Tue, 9 Nov 2077 00:00:00 +0800
+Subject: [PATCH] Optimize Vec3i hashing
+
+Replaces the default hashCode calculation with a high-quality spatial hasher.
+This implementation utilizes large prime coefficients and Phi mixing (for avalanche effect) to significantly reduce hash collisions,
+thereby improving lookup performance and mitigating worst-case hash distribution scenarios.
+
+diff --git a/net/minecraft/core/Vec3i.java b/net/minecraft/core/Vec3i.java
+index 8334e92013722bf2fc7b4c26e38f7ca1e75b6191..886da8b99e344eb352405de421aa77fe2c73b22b 100644
+--- a/net/minecraft/core/Vec3i.java
++++ b/net/minecraft/core/Vec3i.java
+@@ -47,7 +47,7 @@ public class Vec3i implements Comparable<Vec3i> {
+ 
+     @Override
+     public final int hashCode() { // Paper - Perf: Final for inline
+-        return (this.getY() + this.getZ() * 31) * 31 + this.getX();
++        return org.dreeam.leaf.util.Vec3iHasher.hash(this.x, this.y, this.z); // Leaf - Optimize Vec3i hashing
+     }
+ 
+     @Override

leaf-server/src/main/java/org/dreeam/leaf/util/Vec3iHasher.java

@@ -0,0 +1,24 @@
+package org.dreeam.leaf.util;
+
+/**
+ * A high-quality 3D coordinate hasher that prioritizes distribution over raw instruction count.
+ * <p>
+ * This implementation trades a marginal amount of calculation speed for extremely low hash collision rates,
+ * significantly improving the performance of large HashMaps.
+ */
+public final class Vec3iHasher {
+
+    // See https://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm
+    // 2^32 * (sqrt(5) - 1) / 2
+    private static final int INT_PHI = 0x9E3779B9;
+
+    private Vec3iHasher() {
+    }
+
+    public static int hash(int x, int y, int z) {
+        final int h = x * 31337 + y * 961 + z;
+
+        final int hash = h * INT_PHI;
+        return hash ^ (hash >>> 16);
+    }
+}