From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: violetc <58360096+s-yh-china@users.noreply.github.com>
Date: Tue, 18 Jul 2023 13:36:25 +0800
Subject: [PATCH] Optimize world generation chunk and block access

This patch is Powered by Gale(https://github.com/GaleMC/Gale)

diff --git a/src/main/java/net/minecraft/server/level/WorldGenRegion.java b/src/main/java/net/minecraft/server/level/WorldGenRegion.java
index 877498729c66de9aa6a27c9148f7494d7895615c..28386146cada17442d3b3f1517512b95ddcc6a9f 100644
--- a/src/main/java/net/minecraft/server/level/WorldGenRegion.java
+++ b/src/main/java/net/minecraft/server/level/WorldGenRegion.java
@@ -83,6 +83,10 @@ public class WorldGenRegion implements WorldGenLevel {
     private Supplier<String> currentlyGenerating;
     private final AtomicLong subTickCount = new AtomicLong();
     private static final ResourceLocation WORLDGEN_REGION_RANDOM = new ResourceLocation("worldgen_region_random");
+    // Leaves start - optimize world generation chunk and block access
+    private ChunkAccess[] chunksArr;
+    private int minChunkX, minChunkZ;
+    // Leaves end - optimize world generation chunk and block access
 
     public WorldGenRegion(ServerLevel world, List<ChunkAccess> chunks, ChunkStatus status, int placementRadius) {
         this.generatingStatus = status;
@@ -105,6 +109,11 @@ public class WorldGenRegion implements WorldGenLevel {
             this.lastPos = ((ChunkAccess) chunks.get(chunks.size() - 1)).getPos();
             this.structureManager = world.structureManager().forWorldGenRegion(this);
         }
+        // Leaves start - optimize world generation chunk and block access
+        this.minChunkX = this.firstPos.x;
+        this.minChunkZ = this.firstPos.z;
+        this.chunksArr = chunks.toArray(new ChunkAccess[0]);
+        // Leaves end - optimize world generation chunk and block access
     }
 
     public boolean isOldChunkAround(ChunkPos chunkPos, int checkRadius) {
@@ -122,8 +131,29 @@ public class WorldGenRegion implements WorldGenLevel {
 
     @Override
     public ChunkAccess getChunk(int chunkX, int chunkZ) {
-        return this.getChunk(chunkX, chunkZ, ChunkStatus.EMPTY);
+        // Leaves start - optimize world generation chunk and block access
+        if (!top.leavesmc.leaves.LeavesConfig.optimizeWorldGenerationAccess) {
+            return this.getChunk(chunkX, chunkZ, ChunkStatus.EMPTY);
+        } else {
+            int x = chunkX - this.minChunkX;
+            int z = chunkZ - this.minChunkZ;
+            int w = this.size;
+
+            if (x >= 0 && z >= 0 && x < w && z < w) {
+                return this.chunksArr[x + z * w];
+            } else {
+                throw new NullPointerException("No chunk exists at " + new ChunkPos(chunkX, chunkZ));
+            }
+        }
+        // Leaves end - optimize world generation chunk and block access
+    }
+
+    // Leaves start - optimize world generation chunk and block access
+    public ChunkAccess getChunk(BlockPos pos) {
+        // Skip checking chunk.getStatus().isAtLeast(ChunkStatus.EMPTY) here, because it is always true
+        return this.getChunk(SectionPos.blockToSectionCoord(pos.getX()), SectionPos.blockToSectionCoord(pos.getZ()));
     }
+    // Leaves end - optimize world generation chunk and block access
 
     @Nullable
     @Override
@@ -182,7 +212,21 @@ public class WorldGenRegion implements WorldGenLevel {
 
     @Override
     public BlockState getBlockState(BlockPos pos) {
-        return this.getChunk(SectionPos.blockToSectionCoord(pos.getX()), SectionPos.blockToSectionCoord(pos.getZ())).getBlockState(pos);
+        // Leaves start - optimize world generation chunk and block access
+        if (!top.leavesmc.leaves.LeavesConfig.optimizeWorldGenerationAccess) {
+            return this.getChunk(SectionPos.blockToSectionCoord(pos.getX()), SectionPos.blockToSectionCoord(pos.getZ())).getBlockState(pos);
+        } else {
+            int x = SectionPos.blockToSectionCoord(pos.getX()) - this.minChunkX;
+            int z = SectionPos.blockToSectionCoord(pos.getZ()) - this.minChunkZ;
+            int w = this.size;
+
+            if (x >= 0 && z >= 0 && x < w && z < w) {
+                return this.chunksArr[x + z * w].getBlockState(pos);
+            } else {
+                throw new NullPointerException("No chunk exists at " + new ChunkPos(pos));
+            }
+        }
+        // Leaves end - optimize world generation chunk and block access
     }
 
     @Override
diff --git a/src/main/java/top/leavesmc/leaves/lithium/common/util/Pos.java b/src/main/java/top/leavesmc/leaves/lithium/common/util/Pos.java
new file mode 100644
index 0000000000000000000000000000000000000000..f1650846d080ab743aa324a3fe94447e2b3d7ece
--- /dev/null
+++ b/src/main/java/top/leavesmc/leaves/lithium/common/util/Pos.java
@@ -0,0 +1,104 @@
+
+package top.leavesmc.leaves.lithium.common.util;
+
+import net.minecraft.core.SectionPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+
+public class Pos {
+
+    public static class BlockCoord {
+        public static int getYSize(LevelHeightAccessor view) {
+            return view.getHeight();
+        }
+
+        public static int getMinY(LevelHeightAccessor view) {
+            return view.getMinBuildHeight();
+        }
+
+        public static int getMaxYInclusive(LevelHeightAccessor view) {
+            return view.getMaxBuildHeight() - 1;
+        }
+
+        public static int getMaxYExclusive(LevelHeightAccessor view) {
+            return view.getMaxBuildHeight();
+        }
+
+        public static int getMaxInSectionCoord(int sectionCoord) {
+            return 15 + getMinInSectionCoord(sectionCoord);
+        }
+
+        public static int getMaxYInSectionIndex(LevelHeightAccessor view, int sectionIndex) {
+            return getMaxInSectionCoord(SectionYCoord.fromSectionIndex(view, sectionIndex));
+        }
+
+        public static int getMinInSectionCoord(int sectionCoord) {
+            return SectionPos.sectionToBlockCoord(sectionCoord);
+        }
+
+        public static int getMinYInSectionIndex(LevelHeightAccessor view, int sectionIndex) {
+            return getMinInSectionCoord(SectionYCoord.fromSectionIndex(view, sectionIndex));
+        }
+    }
+
+    public static class ChunkCoord {
+        public static int fromBlockCoord(int blockCoord) {
+            return SectionPos.blockToSectionCoord(blockCoord);
+        }
+
+        public static int fromBlockSize(int i) {
+            return i >> 4; //same method as fromBlockCoord, just be clear about coord/size semantic difference
+        }
+    }
+
+    public static class SectionYCoord {
+        public static int getNumYSections(LevelHeightAccessor view) {
+            return view.getSectionsCount();
+        }
+
+        public static int getMinYSection(LevelHeightAccessor view) {
+            return view.getMinSection();
+        }
+
+        public static int getMaxYSectionInclusive(LevelHeightAccessor view) {
+            return view.getMaxSection() - 1;
+        }
+
+        public static int getMaxYSectionExclusive(LevelHeightAccessor view) {
+            return view.getMaxSection();
+        }
+
+        public static int fromSectionIndex(LevelHeightAccessor view, int sectionCoord) {
+            return sectionCoord + SectionYCoord.getMinYSection(view);
+        }
+
+        public static int fromBlockCoord(int blockCoord) {
+            return SectionPos.blockToSectionCoord(blockCoord);
+        }
+    }
+
+    public static class SectionYIndex {
+        public static int getNumYSections(LevelHeightAccessor view) {
+            return view.getSectionsCount();
+        }
+
+        public static int getMinYSectionIndex(LevelHeightAccessor view) {
+            return 0;
+        }
+
+        public static int getMaxYSectionIndexInclusive(LevelHeightAccessor view) {
+            return view.getSectionsCount() - 1;
+        }
+
+        public static int getMaxYSectionIndexExclusive(LevelHeightAccessor view) {
+            return view.getSectionsCount();
+        }
+
+        public static int fromSectionCoord(LevelHeightAccessor view, int sectionCoord) {
+            return sectionCoord - SectionYCoord.getMinYSection(view);
+        }
+
+        public static int fromBlockCoord(LevelHeightAccessor view, int blockCoord) {
+            return fromSectionCoord(view, SectionPos.blockToSectionCoord(blockCoord));
+        }
+    }
+}