From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Ivan Pekov <ivan@mrivanplays.com>
Date: Tue, 29 Sep 2020 19:25:49 +0300
Subject: [PATCH] Fix IndexOutOfBoundsException when sending too many changes


diff --git a/src/main/java/net/minecraft/server/PacketDataSerializer.java b/src/main/java/net/minecraft/server/PacketDataSerializer.java
index f43193c1090238f2241b878120247d1b3d0d4e57..a7783944e8e4ee2a164aa19b3cc342252bc84ee2 100644
--- a/src/main/java/net/minecraft/server/PacketDataSerializer.java
+++ b/src/main/java/net/minecraft/server/PacketDataSerializer.java
@@ -182,6 +182,7 @@ public class PacketDataSerializer extends ByteBuf {
         return i;
     }
 
+    public final long readVarLong() { return j(); } // Yatopia - OBFHELPER
     public long j() {
         long i = 0L;
         int j = 0;
diff --git a/src/main/java/net/minecraft/server/PacketPlayOutMultiBlockChange.java b/src/main/java/net/minecraft/server/PacketPlayOutMultiBlockChange.java
index f260459d70053ffd17952aebf3e0410666f9bcd0..cae074a9a29fe5ddab74ec983a07c05d1439283d 100644
--- a/src/main/java/net/minecraft/server/PacketPlayOutMultiBlockChange.java
+++ b/src/main/java/net/minecraft/server/PacketPlayOutMultiBlockChange.java
@@ -8,8 +8,8 @@ import java.util.function.BiConsumer;
 public class PacketPlayOutMultiBlockChange implements Packet<PacketListenerPlayOut> {
 
     private SectionPosition a;
-    private short[] b;
-    private IBlockData[] c;
+    private java.util.List<Short> b; // Yatopia - change to list
+    private java.util.List<IBlockData> c; // Yatopia - change to list
     private boolean d;
 
     public PacketPlayOutMultiBlockChange() {}
@@ -17,6 +17,8 @@ public class PacketPlayOutMultiBlockChange implements Packet<PacketListenerPlayO
     public PacketPlayOutMultiBlockChange(SectionPosition sectionposition, ShortSet shortset, ChunkSection chunksection, boolean flag) {
         this.a = sectionposition;
         this.d = flag;
+        // Yatopia start - replace logic
+        /*
         this.a(shortset.size());
         int i = 0;
 
@@ -26,12 +28,27 @@ public class PacketPlayOutMultiBlockChange implements Packet<PacketListenerPlayO
             this.b[i] = short0;
             this.c[i] = (chunksection != null) ? chunksection.getType(SectionPosition.a(short0), SectionPosition.b(short0), SectionPosition.c(short0)) : Blocks.AIR.getBlockData(); // CraftBukkit - SPIGOT-6076, Mojang bug when empty chunk section notified
         }
+         */
+        b = new java.util.ArrayList<>();
+        c = new java.util.ArrayList<>();
+        for (short s : shortset) {
+            b.add(s);
+            if (chunksection != null) {
+                c.add(chunksection.getType(SectionPosition.a(s), SectionPosition.b(s), SectionPosition.c(s)));
+            } else {
+                c.add(Blocks.AIR.getBlockData());
+            }
+        }
+        // Yatopia end
 
     }
 
+
     private void a(int i) {
+        /* // Yatopia start
         this.b = new short[i];
         this.c = new IBlockData[i];
+         */ // Yatopia end
     }
 
     @Override
@@ -40,6 +57,8 @@ public class PacketPlayOutMultiBlockChange implements Packet<PacketListenerPlayO
         this.d = packetdataserializer.readBoolean();
         int i = packetdataserializer.i();
 
+        // Yatopia start - replaced logic
+        /*
         this.a(i);
 
         for (int j = 0; j < this.b.length; ++j) {
@@ -48,6 +67,15 @@ public class PacketPlayOutMultiBlockChange implements Packet<PacketListenerPlayO
             this.b[j] = (short) ((int) (k & 4095L));
             this.c[j] = (IBlockData) Block.REGISTRY_ID.fromId((int) (k >>> 12));
         }
+         */
+        b = new java.util.ArrayList<>();
+        c = new java.util.ArrayList<>();
+        for (int j = 0; j < i; j++) {
+            long k = packetdataserializer.readVarLong();
+            b.add((short) ((int) (k & 4095L)));
+            c.add(Block.REGISTRY_ID.fromId((int) (k >>> 12)));
+        }
+        // Yatopia end
 
     }
 
@@ -55,10 +83,10 @@ public class PacketPlayOutMultiBlockChange implements Packet<PacketListenerPlayO
     public void b(PacketDataSerializer packetdataserializer) throws IOException {
         packetdataserializer.writeLong(this.a.s());
         packetdataserializer.writeBoolean(this.d);
-        packetdataserializer.d(this.b.length);
+        packetdataserializer.d(this.b.size()); // Yatopia
 
-        for (int i = 0; i < this.b.length; ++i) {
-            packetdataserializer.b((long) (Block.getCombinedId(this.c[i]) << 12 | this.b[i]));
+        for (int i = 0; i < this.b.size(); ++i) { // Yatopia
+            packetdataserializer.b((long) (Block.getCombinedId(this.c.get(i)) << 12 | this.b.get(i))); // Yatopia
         }
 
     }
@@ -70,11 +98,11 @@ public class PacketPlayOutMultiBlockChange implements Packet<PacketListenerPlayO
     public void a(BiConsumer<BlockPosition, IBlockData> biconsumer) {
         BlockPosition.MutableBlockPosition blockposition_mutableblockposition = new BlockPosition.MutableBlockPosition();
 
-        for (int i = 0; i < this.b.length; ++i) {
-            short short0 = this.b[i];
+        for (int i = 0; i < this.b.size(); ++i) { // Yatopia
+            short short0 = this.b.get(i); // Yatopia
 
             blockposition_mutableblockposition.d(this.a.d(short0), this.a.e(short0), this.a.f(short0));
-            biconsumer.accept(blockposition_mutableblockposition, this.c[i]);
+            biconsumer.accept(blockposition_mutableblockposition, this.c.get(i)); // Yatopia
         }
 
     }