From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: HaHaWTH <102713261+HaHaWTH@users.noreply.github.com>
Date: Fri, 14 Jun 2024 23:19:55 +0800
Subject: [PATCH] Reduce-worldgen-allocations

This change optimizes the way SurfaceRules update their biome supplier,avoiding unnecessary object creations and thus reducing memory allocations
during world generation. The update method now reuses the existing PositionalBiomeGetter object if it's already present, otherwise it
initializes a new one.
Additionally, the tryApply method in SurfaceRules now avoids iterator
allocation by directly accessing the rules list, which further contributes
to reducing garbage collection pressure during world generation.

diff --git a/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java b/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java
index 9df053ddff459d4aab478106c6e66a5fc3cda8f6..7a9b36b93032fbbfd439b8d95c82c7515616cbbd 100644
--- a/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java
+++ b/src/main/java/net/minecraft/world/level/levelgen/SurfaceRules.java
@@ -314,8 +314,14 @@ public class SurfaceRules {
         }
 
         protected void updateY(int stoneDepthAbove, int stoneDepthBelow, int fluidHeight, int blockX, int blockY, int blockZ) {
-            this.lastUpdateY++;
-            this.biome = Suppliers.memoize(() -> this.biomeGetter.apply(this.pos.set(blockX, blockY, blockZ)));
+            // Leaf start - Reuse supplier object instead of creating new ones every time
+            ++this.lastUpdateY;
+            var getter = this.biome;
+            if (getter == null) {
+                this.biome = getter = new org.dreeam.leaf.util.biome.PositionalBiomeGetter(this.biomeGetter, this.pos);
+            }
+            ((org.dreeam.leaf.util.biome.PositionalBiomeGetter)getter).update(blockX, blockY, blockZ);
+            // Leaf end
             this.blockY = blockY;
             this.waterHeight = fluidHeight;
             this.stoneDepthBelow = stoneDepthBelow;
@@ -577,8 +583,12 @@ public class SurfaceRules {
         @Nullable
         @Override
         public BlockState tryApply(int x, int y, int z) {
-            for (SurfaceRules.SurfaceRule surfaceRule : this.rules) {
-                BlockState blockState = surfaceRule.tryApply(x, y, z);
+            // Leaf start - Avoid iterator allocation
+            int size = this.rules.size();
+            //noinspection ForLoopReplaceableByForEach
+            for (int i = 0; i < size; i++) {
+                BlockState blockState = this.rules.get(i).tryApply(x, y, z);
+                // Leaf end
                 if (blockState != null) {
                     return blockState;
                 }
diff --git a/src/main/java/org/dreeam/leaf/util/biome/PositionalBiomeGetter.java b/src/main/java/org/dreeam/leaf/util/biome/PositionalBiomeGetter.java
new file mode 100644
index 0000000000000000000000000000000000000000..2385f09404274aa650d082e2928deab847b570a0
--- /dev/null
+++ b/src/main/java/org/dreeam/leaf/util/biome/PositionalBiomeGetter.java
@@ -0,0 +1,36 @@
+package org.dreeam.leaf.util.biome;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.world.level.biome.Biome;
+
+import java.util.function.Function;
+import java.util.function.Supplier;
+
+public class PositionalBiomeGetter implements Supplier<Holder<Biome>> {
+    private final Function<BlockPos, Holder<Biome>> biomeGetter;
+    private final BlockPos.MutableBlockPos pos;
+    private int nextX, nextY, nextZ;
+    private volatile Holder<Biome> curBiome;
+
+    public PositionalBiomeGetter(Function<BlockPos, Holder<Biome>> biomeGetter, BlockPos.MutableBlockPos pos) {
+        this.biomeGetter = biomeGetter;
+        this.pos = pos;
+    }
+
+    public void update(int nextX, int nextY, int nextZ) {
+        this.nextX = nextX;
+        this.nextY = nextY;
+        this.nextZ = nextZ;
+        this.curBiome = null;
+    }
+
+    @Override
+    public Holder<Biome> get() {
+        var biome = curBiome;
+        if(biome == null) {
+            curBiome = biome = biomeGetter.apply(pos.set(nextX, nextY, nextZ));
+        }
+        return biome;
+    }
+}