Fix long NBT tag encoding for >32768 bytes

src/main/java/com/mitchej123/hodgepodge/mixins/early/minecraft/MixinPacketBuffer.java

@@ -1,20 +1,67 @@
 package com.mitchej123.hodgepodge.mixins.early.minecraft;
 
+import java.io.IOException;
+
+import net.minecraft.nbt.CompressedStreamTools;
+import net.minecraft.nbt.NBTSizeTracker;
+import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.network.PacketBuffer;
 
 import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.injection.At;
-import org.spongepowered.asm.mixin.injection.ModifyArg;
+import org.spongepowered.asm.mixin.Overwrite;
+import org.spongepowered.asm.mixin.Unique;
 
 import com.mitchej123.hodgepodge.Common;
 
 @Mixin(PacketBuffer.class)
 public class MixinPacketBuffer {
 
-    @ModifyArg(
-            method = "Lnet/minecraft/network/PacketBuffer;readNBTTagCompoundFromBuffer()Lnet/minecraft/nbt/NBTTagCompound;",
-            at = @At(value = "INVOKE", target = "Lnet/minecraft/nbt/NBTSizeTracker;<init>(J)V"))
-    private long hodgepodge$modifyMaxNetworkNBTSizeLimit(long original) {
-        return Common.config.maxNetworkNbtSizeLimit;
+    // A magic value that means the real length of the packet is encoded in a following int.
+    @Unique
+    private static final short MAGIC_LENGTH_IS_INT = Short.MAX_VALUE;
+
+    /**
+     * @author eigenraven
+     * @reason Change the length encoding to support values longer than a short, requires changing of local variable
+     *         types.
+     */
+    @Overwrite
+    public NBTTagCompound readNBTTagCompoundFromBuffer() throws IOException {
+        final PacketBuffer self = (PacketBuffer) (Object) this;
+        short shortLength = self.readShort();
+        final int realLength;
+        if (shortLength < 0) {
+            return null;
+        } else if (shortLength == MAGIC_LENGTH_IS_INT) {
+            realLength = self.readInt();
+        } else {
+            realLength = shortLength;
+        }
+        byte[] buffer = new byte[shortLength];
+        self.readBytes(buffer);
+        return CompressedStreamTools.func_152457_a(buffer, new NBTSizeTracker(Common.config.maxNetworkNbtSizeLimit));
     }
+
+    /**
+     * @author eigenraven
+     * @reason Change the length encoding to support values longer than a short, requires changing of local variable
+     *         types.
+     */
+    @Overwrite
+    public void writeNBTTagCompoundToBuffer(NBTTagCompound nbt) throws IOException {
+        final PacketBuffer self = (PacketBuffer) (Object) this;
+        if (nbt == null) {
+            self.writeShort(-1);
+        } else {
+            byte[] buffer = CompressedStreamTools.compress(nbt);
+            if (buffer.length >= MAGIC_LENGTH_IS_INT) {
+                self.writeShort(MAGIC_LENGTH_IS_INT);
+                self.writeInt(buffer.length);
+            } else {
+                self.writeShort(buffer.length);
+            }
+            self.writeBytes(buffer);
+        }
+    }
+
 }