From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Wed, 6 May 2020 23:30:30 -0400
Subject: [PATCH] Optimize NibbleArray to use pooled buffers

Massively reduces memory allocation of 2048 byte buffers by using
an object pool for these.

diff --git a/src/main/java/net/minecraft/server/ChunkRegionLoader.java b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/ChunkRegionLoader.java
+++ b/src/main/java/net/minecraft/server/ChunkRegionLoader.java
@@ -0,0 +0,0 @@ public class ChunkRegionLoader {
                 }
 
                 if (nibblearray != null && !nibblearray.c()) {
-                    nbttagcompound2.setByteArray("BlockLight", nibblearray.asBytes());
+                    nbttagcompound2.setByteArray("BlockLight", nibblearray.getIfSet()); // Paper
                 }
 
                 if (nibblearray1 != null && !nibblearray1.c()) {
-                    nbttagcompound2.setByteArray("SkyLight", nibblearray1.asBytes());
+                    nbttagcompound2.setByteArray("SkyLight", nibblearray1.getIfSet()); // Paper
                 }
 
                 nbttaglist.add(nbttagcompound2);
diff --git a/src/main/java/net/minecraft/server/LightEngineStorageSky.java b/src/main/java/net/minecraft/server/LightEngineStorageSky.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/LightEngineStorageSky.java
+++ b/src/main/java/net/minecraft/server/LightEngineStorageSky.java
@@ -0,0 +0,0 @@ public class LightEngineStorageSky extends LightEngineStorage<LightEngineStorage
                     j = SectionPosition.a(j, EnumDirection.UP);
                 }
 
-                return new NibbleArray((new NibbleArrayFlat(nibblearray1, 0)).asBytes());
+                return new NibbleArray((new NibbleArrayFlat(nibblearray1, 0)).asBytes(), true); // Paper - mark buffer as safe
             } else {
                 return new NibbleArray();
             }
diff --git a/src/main/java/net/minecraft/server/NibbleArray.java b/src/main/java/net/minecraft/server/NibbleArray.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/NibbleArray.java
+++ b/src/main/java/net/minecraft/server/NibbleArray.java
@@ -0,0 +0,0 @@
 package net.minecraft.server;
 
+import com.destroystokyo.paper.util.pooled.PooledObjects;
+
 import javax.annotation.Nullable;
 
 public class NibbleArray {
 
-    @Nullable
-    protected byte[] a;
+    // Paper start
+    public static byte[] EMPTY_NIBBLE = new byte[2048];
+    public static final PooledObjects<byte[]> BYTE_2048 = new PooledObjects<>(() -> new byte[2048], 16384, 1);
+    public static void releaseBytes(byte[] bytes) {
+        if (bytes != EMPTY_NIBBLE) {
+            System.arraycopy(EMPTY_NIBBLE, 0, bytes, 0, 2048);
+            BYTE_2048.release(bytes);
+        }
+    }
+
+    public byte[] getIfSet() {
+        return this.a != null ? this.a : EMPTY_NIBBLE;
+    }
+    public byte[] getCloneIfSet() {
+        if (a == null) {
+            return EMPTY_NIBBLE;
+        }
+        byte[] ret = BYTE_2048.acquire();
+        System.arraycopy(getIfSet(), 0, ret, 0, 2048);
+        return ret;
+    }
+
+    @Override
+    protected void finalize() throws Throwable {
+        try {
+            if (this.a != null) {
+                releaseBytes(this.a);
+                this.a = null;
+            }
+        } finally {
+            super.finalize();
+        }
+    }
+    // Paper end
+    @Nullable protected byte[] a;
+
 
     public NibbleArray() {}
 
     public NibbleArray(byte[] abyte) {
+        // Paper start
+        this(abyte, false);
+    }
+    public NibbleArray(byte[] abyte, boolean isSafe) {
         this.a = abyte;
+        if (!isSafe) this.a = getCloneIfSet(); // Paper - clone for safety
+        // Paper end
         if (abyte.length != 2048) {
             throw (IllegalArgumentException) SystemUtils.c(new IllegalArgumentException("ChunkNibbleArrays should be 2048 bytes not: " + abyte.length));
         }
@@ -0,0 +0,0 @@ public class NibbleArray {
 
     public void a(int i, int j) { // PAIL: private -> public
         if (this.a == null) {
-            this.a = new byte[2048];
+            this.a = BYTE_2048.acquire(); // Paper
         }
 
         int k = this.d(i);
@@ -0,0 +0,0 @@ public class NibbleArray {
 
     public byte[] asBytes() {
         if (this.a == null) {
-            this.a = new byte[2048];
+            this.a = BYTE_2048.acquire(); // Paper
         }
 
         return this.a;
@@ -0,0 +0,0 @@ public class NibbleArray {
 
     public NibbleArray copy() { return this.b(); } // Paper - OBFHELPER
     public NibbleArray b() {
-        return this.a == null ? new NibbleArray() : new NibbleArray((byte[]) this.a.clone());
+        return this.a == null ? new NibbleArray() : new NibbleArray(this.a); // Paper - clone in ctor
     }
 
     public String toString() {
diff --git a/src/main/java/net/minecraft/server/NibbleArrayFlat.java b/src/main/java/net/minecraft/server/NibbleArrayFlat.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/NibbleArrayFlat.java
+++ b/src/main/java/net/minecraft/server/NibbleArrayFlat.java
@@ -0,0 +0,0 @@ public class NibbleArrayFlat extends NibbleArray {
 
     @Override
     public byte[] asBytes() {
-        byte[] abyte = new byte[2048];
+        byte[] abyte = BYTE_2048.acquire(); // Paper
 
         for (int i = 0; i < 16; ++i) {
             System.arraycopy(this.a, 0, abyte, i * 128, 128);
diff --git a/src/main/java/net/minecraft/server/PacketPlayOutLightUpdate.java b/src/main/java/net/minecraft/server/PacketPlayOutLightUpdate.java
index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
--- a/src/main/java/net/minecraft/server/PacketPlayOutLightUpdate.java
+++ b/src/main/java/net/minecraft/server/PacketPlayOutLightUpdate.java
@@ -0,0 +0,0 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
     private List<byte[]> h;
 
     public PacketPlayOutLightUpdate() {}
+    // Paper start
+    private java.util.List<byte[]> usedBytes = new java.util.ArrayList<>();
+
+    @Override
+    public void finalize() throws Throwable {
+        try {
+            usedBytes.forEach(NibbleArray::releaseBytes);
+            usedBytes.clear();
+        } finally {
+            super.finalize();
+        }
+    }
+    // Paper end
 
     public PacketPlayOutLightUpdate(ChunkCoordIntPair chunkcoordintpair, LightEngine lightengine) {
         this.a = chunkcoordintpair.x;
@@ -0,0 +0,0 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
         this.g = Lists.newArrayList();
         this.h = Lists.newArrayList();
 
+        byte[] lastBytes; // Paper
         for (int i = 0; i < 18; ++i) {
             NibbleArray nibblearray = lightengine.a(EnumSkyBlock.SKY).a(SectionPosition.a(chunkcoordintpair, -1 + i));
             NibbleArray nibblearray1 = lightengine.a(EnumSkyBlock.BLOCK).a(SectionPosition.a(chunkcoordintpair, -1 + i));
@@ -0,0 +0,0 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
                     this.e |= 1 << i;
                 } else {
                     this.c |= 1 << i;
-                    this.g.add(nibblearray.asBytes().clone());
+                    this.g.add(lastBytes = nibblearray.getCloneIfSet()); usedBytes.add(lastBytes); // Paper
                 }
             }
 
@@ -0,0 +0,0 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
                     this.f |= 1 << i;
                 } else {
                     this.d |= 1 << i;
-                    this.h.add(nibblearray1.asBytes().clone());
+                    this.h.add(lastBytes = nibblearray1.getCloneIfSet()); usedBytes.add(lastBytes); // Paper
                 }
             }
         }
@@ -0,0 +0,0 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
         this.g = Lists.newArrayList();
         this.h = Lists.newArrayList();
 
+        byte[] lastBytes; // Paper
         for (int k = 0; k < 18; ++k) {
             NibbleArray nibblearray;
 
             if ((this.c & 1 << k) != 0) {
                 nibblearray = lightengine.a(EnumSkyBlock.SKY).a(SectionPosition.a(chunkcoordintpair, -1 + k));
                 if (nibblearray != null && !nibblearray.c()) {
-                    this.g.add(nibblearray.asBytes().clone());
+                    this.g.add(lastBytes = nibblearray.getCloneIfSet()); usedBytes.add(lastBytes); // Paper
                 } else {
                     this.c &= ~(1 << k);
                     if (nibblearray != null) {
@@ -0,0 +0,0 @@ public class PacketPlayOutLightUpdate implements Packet<PacketListenerPlayOut> {
             if ((this.d & 1 << k) != 0) {
                 nibblearray = lightengine.a(EnumSkyBlock.BLOCK).a(SectionPosition.a(chunkcoordintpair, -1 + k));
                 if (nibblearray != null && !nibblearray.c()) {
-                    this.h.add(nibblearray.asBytes().clone());
+                    this.h.add(lastBytes = nibblearray.getCloneIfSet()); usedBytes.add(lastBytes); // Paper
                 } else {
                     this.d &= ~(1 << k);
                     if (nibblearray != null) {