[Experimental] Remove PacketWrapper objects

In both Velocity and BungeeCord, the most commonly created object is an
object that encapsulates a Minecraft packet and a its associated byte
data.

At first, I considered trying to recycle these objects, but then I
discovered that this object has no reason to exist, and actually somewhat
complicates the implementation. Thus, this commit removes these objects,
making Velocity more more GC-friendly by not allocating frequently-created
objects.

This is still an experimental change, but it's a fairly safe one to make.

proxy/src/main/java/com/velocitypowered/proxy/connection/MinecraftConnection.java

@@ -5,12 +5,12 @@ import com.velocitypowered.natives.compression.VelocityCompressor;
 import com.velocitypowered.natives.encryption.VelocityCipherFactory;
 import com.velocitypowered.natives.util.Natives;
 import com.velocitypowered.proxy.VelocityServer;
-import com.velocitypowered.proxy.protocol.PacketWrapper;
+import com.velocitypowered.proxy.protocol.MinecraftPacket;
 import com.velocitypowered.proxy.protocol.ProtocolConstants;
 import com.velocitypowered.proxy.protocol.StateRegistry;
-import com.velocitypowered.natives.encryption.JavaVelocityCipher;
 import com.velocitypowered.natives.encryption.VelocityCipher;
 import com.velocitypowered.proxy.protocol.netty.*;
+import io.netty.buffer.ByteBuf;
 import io.netty.channel.Channel;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandlerContext;
@@ -79,18 +79,13 @@ public class MinecraftConnection extends ChannelInboundHandlerAdapter {
 
     @Override
     public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
-        if (msg instanceof PacketWrapper) {
-            PacketWrapper pw = (PacketWrapper) msg;
+        if (msg instanceof MinecraftPacket) {
+            sessionHandler.handle((MinecraftPacket) msg);
+        } else if (msg instanceof ByteBuf) {
             try {
-                if (sessionHandler != null) {
-                    if (pw.getPacket() == null) {
-                        sessionHandler.handleUnknown(pw.getBuffer());
-                    } else {
-                        sessionHandler.handle(pw.getPacket());
-                    }
-                }
+                sessionHandler.handleUnknown((ByteBuf) msg);
             } finally {
-                ReferenceCountUtil.release(pw.getBuffer());
+                ReferenceCountUtil.release(msg);
             }
         }
     }

proxy/src/main/java/com/velocitypowered/proxy/protocol/PacketWrapper.java

@@ -1,30 +0,0 @@
-package com.velocitypowered.proxy.protocol;
-
-import io.netty.buffer.ByteBuf;
-import io.netty.buffer.ByteBufUtil;
-
-public class PacketWrapper {
-    private final MinecraftPacket packet;
-    private final ByteBuf buffer;
-
-    public PacketWrapper(MinecraftPacket packet, ByteBuf buffer) {
-        this.packet = packet;
-        this.buffer = buffer;
-    }
-
-    public MinecraftPacket getPacket() {
-        return packet;
-    }
-
-    public ByteBuf getBuffer() {
-        return buffer;
-    }
-
-    @Override
-    public String toString() {
-        return "PacketWrapper{" +
-                "packet=" + packet +
-                ", buffer=" + ByteBufUtil.hexDump(buffer) +
-                '}';
-    }
-}

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/LegacyPingDecoder.java

@@ -1,10 +1,8 @@
 package com.velocitypowered.proxy.protocol.netty;
 
-import com.velocitypowered.proxy.protocol.PacketWrapper;
 import com.velocitypowered.proxy.protocol.packet.LegacyHandshake;
 import com.velocitypowered.proxy.protocol.packet.LegacyPing;
 import io.netty.buffer.ByteBuf;
-import io.netty.buffer.Unpooled;
 import io.netty.channel.ChannelHandlerContext;
 import io.netty.handler.codec.ByteToMessageDecoder;
 
@@ -21,10 +19,10 @@ public class LegacyPingDecoder extends ByteToMessageDecoder {
         short second = in.getUnsignedByte(in.readerIndex() + 1);
         if (first == 0xfe && second == 0x01) {
             in.skipBytes(in.readableBytes());
-            out.add(new PacketWrapper(new LegacyPing(), Unpooled.EMPTY_BUFFER));
+            out.add(new LegacyPing());
         } else if (first == 0x02) {
             in.skipBytes(in.readableBytes());
-            out.add(new PacketWrapper(new LegacyHandshake(), Unpooled.EMPTY_BUFFER));
+            out.add(new LegacyHandshake());
         } else {
             ctx.pipeline().remove(this);
         }

proxy/src/main/java/com/velocitypowered/proxy/protocol/netty/MinecraftDecoder.java

@@ -26,13 +26,13 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf> {
             return;
         }
 
-        ByteBuf slice = msg.retainedSlice();
+        ByteBuf slice = msg.slice();
 
         int packetId = ProtocolUtils.readVarInt(msg);
         MinecraftPacket packet = this.protocolVersion.createPacket(packetId);
         if (packet == null) {
             msg.skipBytes(msg.readableBytes());
-            out.add(new PacketWrapper(null, slice));
+            out.add(slice.retain());
         } else {
             try {
                 packet.decode(msg, direction, protocolVersion.id);
@@ -40,7 +40,7 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf> {
                 throw new CorruptedFrameException("Error decoding " + packet.getClass() + " Direction " + direction
                         + " Protocol " + protocolVersion + " State " + state + " ID " + Integer.toHexString(packetId), e);
             }
-            out.add(new PacketWrapper(packet, slice));
+            out.add(packet);
         }
     }