Convert Packet into an interface

And moves / adds typical serialisation static functions to the Packet interface.

mod/common/src/main/java/gjum/minecraft/mapsync/common/Utils.java

@@ -1,16 +1,12 @@
 package gjum.minecraft.mapsync.common;
 
-import io.netty.buffer.ByteBuf;
 import net.minecraft.client.Minecraft;
 import net.minecraft.core.Registry;
 import net.minecraft.world.level.biome.Biome;
 import org.jetbrains.annotations.NotNull;
-import org.jetbrains.annotations.Nullable;
 
 import java.util.HashMap;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
-
 public class Utils {
 	public static final Minecraft mc = Minecraft.getInstance();
 
@@ -31,21 +27,4 @@ public static void printErrorRateLimited(@NotNull Throwable e) {
 			e2.printStackTrace();
 		}
 	}
-
-	public static void writeStringToBuf(@NotNull ByteBuf buf, @Nullable String string) {
-		if (string == null || string.isEmpty()) {
-			buf.writeInt(0);
-			return;
-		}
-		final byte[] bytes = string.getBytes(UTF_8);
-		buf.writeInt(bytes.length);
-		buf.writeBytes(bytes);
-	}
-
-	public static @NotNull String readStringFromBuf(@NotNull ByteBuf buf) {
-		int length = buf.readInt();
-		final byte[] bytes = new byte[length];
-		buf.readBytes(bytes);
-		return new String(bytes, UTF_8);
-	}
 }

mod/common/src/main/java/gjum/minecraft/mapsync/common/data/ChunkTile.java

@@ -1,18 +1,15 @@
 package gjum.minecraft.mapsync.common.data;
 
+import gjum.minecraft.mapsync.common.net.Packet;
 import io.netty.buffer.ByteBuf;
 import net.minecraft.core.Registry;
 import net.minecraft.resources.ResourceKey;
-import net.minecraft.resources.ResourceLocation;
 import net.minecraft.world.level.ChunkPos;
 import net.minecraft.world.level.Level;
 
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
 
-import static gjum.minecraft.mapsync.common.Utils.readStringFromBuf;
-import static gjum.minecraft.mapsync.common.Utils.writeStringToBuf;
-
 public record ChunkTile(
 		ResourceKey<Level> dimension,
 		int x, int z,
@@ -34,7 +31,7 @@ public void write(ByteBuf buf) {
 	 * without columns
 	 */
 	public void writeMetadata(ByteBuf buf) {
-		writeStringToBuf(buf, dimension.location().toString());
+		Packet.writeResourceKey(buf, dimension);
 		buf.writeInt(x);
 		buf.writeInt(z);
 		buf.writeLong(timestamp);
@@ -51,8 +48,7 @@ public static void writeColumns(BlockColumn[] columns, ByteBuf buf) {
 	}
 
 	public static ChunkTile fromBuf(ByteBuf buf) {
-		String dimensionStr = readStringFromBuf(buf);
-		var dimension = ResourceKey.create(Registry.DIMENSION_REGISTRY, new ResourceLocation(dimensionStr));
+		var dimension = Packet.readResourceKey(buf, Registry.DIMENSION_REGISTRY);
 		int x = buf.readInt();
 		int z = buf.readInt();
 		long timestamp = buf.readLong();

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/Packet.java

@@ -1,19 +1,77 @@
 package gjum.minecraft.mapsync.common.net;
 
 import io.netty.buffer.ByteBuf;
+import java.nio.charset.StandardCharsets;
+import net.minecraft.core.Registry;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.ResourceLocation;
+import org.apache.commons.lang3.NotImplementedException;
+import org.jetbrains.annotations.NotNull;
 
-public abstract class Packet {
-	public abstract void write(ByteBuf buf);
+public interface Packet {
+	default void write(@NotNull ByteBuf out) {
+		throw new NotImplementedException();
+	}
 
-	protected static byte[] readByteArray(ByteBuf in) {
-		int length = in.readInt();
-		byte[] array = new byte[length];
-		in.readBytes(array);
+	static byte @NotNull [] readIntLengthByteArray(
+			final @NotNull ByteBuf in
+	) {
+		final var array = new byte[in.readInt()];
+		if (array.length > 0) {
+			in.readBytes(array);
+		}
 		return array;
 	}
 
-	protected static void writeByteArray(ByteBuf out, byte[] array) {
-		out.writeInt(array.length);
-		out.writeBytes(array);
+	static void writeIntLengthByteArray(
+			final @NotNull ByteBuf out,
+			final byte @NotNull [] array
+	) {
+		if (array.length > 0) {
+			out.writeInt(array.length);
+			out.writeBytes(array);
+		}
+		else {
+			out.writeInt(0);
+		}
+	}
+
+	static @NotNull String readUtf8String(
+			final @NotNull ByteBuf in
+	) {
+		return new String(
+				readIntLengthByteArray(in),
+				StandardCharsets.UTF_8
+		);
+	}
+
+	static void writeUtf8String(
+			final @NotNull ByteBuf out,
+			final @NotNull String string
+	) {
+		writeIntLengthByteArray(
+				out,
+				string.getBytes(StandardCharsets.UTF_8)
+		);
+	}
+
+	static <T, R extends ResourceKey<Registry<T>>> @NotNull ResourceKey<T> readResourceKey(
+			final @NotNull ByteBuf in,
+			final @NotNull R registry
+	) {
+		return ResourceKey.create(
+				registry,
+				new ResourceLocation(readUtf8String(in))
+		);
+	}
+
+	static void writeResourceKey(
+			final @NotNull ByteBuf out,
+			final @NotNull ResourceKey<?> resourceKey
+	) {
+		writeUtf8String(
+				out,
+				resourceKey.location().toString()
+		);
 	}
 }

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/packet/ChunkTilePacket.java

@@ -3,6 +3,7 @@
 import gjum.minecraft.mapsync.common.data.ChunkTile;
 import gjum.minecraft.mapsync.common.net.Packet;
 import io.netty.buffer.ByteBuf;
+import org.jetbrains.annotations.NotNull;
 
 import javax.annotation.Nonnull;
 
@@ -13,7 +14,7 @@
  *
  * 2. You have requested synchronisation via {@link ServerboundCatchupRequestPacket}.
  */
-public class ChunkTilePacket extends Packet {
+public class ChunkTilePacket implements Packet {
 	public static final int PACKET_ID = 4;
 
 	public final ChunkTile chunkTile;
@@ -28,7 +29,7 @@ public static Packet read(ByteBuf buf) {
 	}
 
 	@Override
-	public void write(ByteBuf buf) {
+	public void write(@NotNull ByteBuf buf) {
 		chunkTile.write(buf);
 	}
 }

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/packet/ClientboundChunkTimestampsResponsePacket.java

@@ -4,21 +4,17 @@
 import gjum.minecraft.mapsync.common.net.Packet;
 import io.netty.buffer.ByteBuf;
 import net.minecraft.core.Registry;
-import net.minecraft.resources.ResourceKey;
-import net.minecraft.resources.ResourceLocation;
 
 import javax.annotation.Nonnull;
 import java.util.ArrayList;
 import java.util.List;
 
-import static gjum.minecraft.mapsync.common.Utils.readStringFromBuf;
-
 /**
  * You'll receive this in response to a sent {@link ServerboundChunkTimestampsRequestPacket},
  * containing an elaboration of chunk timestamps of all the regions you listed.
  * You should respond with a {@link ServerboundCatchupRequestPacket}.
  */
-public class ClientboundChunkTimestampsResponsePacket extends Packet {
+public class ClientboundChunkTimestampsResponsePacket implements Packet {
 	public static final int PACKET_ID = 5;
 
 	/**
@@ -31,8 +27,7 @@ public ClientboundChunkTimestampsResponsePacket(@Nonnull List<CatchupChunk> chun
 	}
 
 	public static Packet read(ByteBuf buf) {
-		String dimensionStr = readStringFromBuf(buf);
-		var dimension = ResourceKey.create(Registry.DIMENSION_REGISTRY, new ResourceLocation(dimensionStr));
+		var dimension = Packet.readResourceKey(buf, Registry.DIMENSION_REGISTRY);
 
 		int length = buf.readInt();
 		List<CatchupChunk> chunks = new ArrayList<>(length);
@@ -46,9 +41,4 @@ public static Packet read(ByteBuf buf) {
 		}
 		return new ClientboundChunkTimestampsResponsePacket(chunks);
 	}
-
-	@Override
-	public void write(ByteBuf buf) {
-		throw new Error("Can't be sent from client");
-	}
 }

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/packet/ClientboundEncryptionRequestPacket.java

@@ -12,7 +12,7 @@
  * You will receive this in response to {@link ServerboundHandshakePacket}, and
  * will expect a {@link ServerboundEncryptionResponsePacket} in response.
  */
-public class ClientboundEncryptionRequestPacket extends Packet {
+public class ClientboundEncryptionRequestPacket implements Packet {
 	public static final int PACKET_ID = 2;
 
 	@Nonnull
@@ -28,18 +28,12 @@ public ClientboundEncryptionRequestPacket(@Nonnull PublicKey publicKey, @Nonnull
 	public static Packet read(ByteBuf buf) {
 		return new ClientboundEncryptionRequestPacket(
 				readKey(buf),
-				readByteArray(buf));
-	}
-
-	@Override
-	public void write(ByteBuf buf) {
-		writeByteArray(buf, publicKey.getEncoded());
-		writeByteArray(buf, verifyToken);
+				Packet.readIntLengthByteArray(buf));
 	}
 
 	protected static PublicKey readKey(ByteBuf in) {
 		try {
-			byte[] encodedKey = readByteArray(in);
+			byte[] encodedKey = Packet.readIntLengthByteArray(in);
 			X509EncodedKeySpec keySpec = new X509EncodedKeySpec(encodedKey);
 			KeyFactory keyFactory = KeyFactory.getInstance("RSA");
 			return keyFactory.generatePublic(keySpec);

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/packet/ClientboundRegionTimestampsPacket.java

@@ -1,6 +1,5 @@
 package gjum.minecraft.mapsync.common.net.packet;
 
-import gjum.minecraft.mapsync.common.Utils;
 import gjum.minecraft.mapsync.common.data.RegionTimestamp;
 import gjum.minecraft.mapsync.common.net.Packet;
 import io.netty.buffer.ByteBuf;
@@ -10,7 +9,7 @@
  * sent immediately after you've been authenticated. You should respond with a
  * {@link ServerboundChunkTimestampsRequestPacket}.
  */
-public class ClientboundRegionTimestampsPacket extends Packet {
+public class ClientboundRegionTimestampsPacket implements Packet {
   public static final int PACKET_ID = 7;
 
   private final String dimension;
@@ -31,7 +30,7 @@ public RegionTimestamp[] getTimestamps() {
   }
 
   public static Packet read(ByteBuf buf) {
-    String dimension = Utils.readStringFromBuf(buf);
+    String dimension = Packet.readUtf8String(buf);
 
     short totalRegions = buf.readShort();
     RegionTimestamp[] timestamps = new RegionTimestamp[totalRegions];
@@ -46,9 +45,4 @@ public static Packet read(ByteBuf buf) {
 
     return new ClientboundRegionTimestampsPacket(dimension, timestamps);
   }
-
-  @Override
-  public void write(ByteBuf buf) {
-    throw new IllegalStateException();
-  }
 }

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/packet/ServerboundCatchupRequestPacket.java

@@ -5,19 +5,18 @@
 import io.netty.buffer.ByteBuf;
 import net.minecraft.resources.ResourceKey;
 import net.minecraft.world.level.Level;
+import org.jetbrains.annotations.NotNull;
 
 import javax.annotation.Nonnull;
 import java.util.List;
 
-import static gjum.minecraft.mapsync.common.Utils.writeStringToBuf;
-
 /**
  * This is the final stage in the synchronisation process, sent in response to
  * a received {@link ClientboundChunkTimestampsResponsePacket}. Here you list
  * what chunks you'd like to receive from the server, who'll then respond with
  * a bunch of {@link ChunkTilePacket}.
  */
-public class ServerboundCatchupRequestPacket extends Packet {
+public class ServerboundCatchupRequestPacket implements Packet {
 	public static final int PACKET_ID = 6;
 
 	/**
@@ -41,8 +40,8 @@ else if (!dim.equals(chunk.dimension())) {
 	}
 
 	@Override
-	public void write(ByteBuf buf) {
-		writeStringToBuf(buf, chunks.get(0).dimension().location().toString());
+	public void write(@NotNull ByteBuf buf) {
+		Packet.writeResourceKey(buf, chunks.get(0).dimension());
 		buf.writeInt(chunks.size());
 		for (CatchupChunk chunk : chunks) {
 			buf.writeInt(chunk.chunk_x());

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/packet/ServerboundChunkTimestampsRequestPacket.java

@@ -1,9 +1,9 @@
 package gjum.minecraft.mapsync.common.net.packet;
 
-import gjum.minecraft.mapsync.common.Utils;
 import gjum.minecraft.mapsync.common.data.RegionPos;
 import gjum.minecraft.mapsync.common.net.Packet;
 import io.netty.buffer.ByteBuf;
+import org.jetbrains.annotations.NotNull;
 
 import java.util.List;
 
@@ -12,7 +12,7 @@
  * listing all the regions you'd like the server to elaborate on. You should
  * expect a {@link ClientboundChunkTimestampsResponsePacket}.
  */
-public class ServerboundChunkTimestampsRequestPacket extends Packet {
+public class ServerboundChunkTimestampsRequestPacket implements Packet {
   public static final int PACKET_ID = 8;
 
   private final String dimension;
@@ -24,8 +24,8 @@ public ServerboundChunkTimestampsRequestPacket(String dimension, List<RegionPos>
   }
 
   @Override
-  public void write(ByteBuf buf) {
-    Utils.writeStringToBuf(buf, dimension);
+  public void write(@NotNull ByteBuf buf) {
+    Packet.writeUtf8String(buf, dimension);
     buf.writeShort(regions.size());
     for (var region : regions) {
       buf.writeShort(region.x());

mod/common/src/main/java/gjum/minecraft/mapsync/common/net/packet/ServerboundEncryptionResponsePacket.java

@@ -2,13 +2,14 @@
 
 import gjum.minecraft.mapsync.common.net.Packet;
 import io.netty.buffer.ByteBuf;
+import org.jetbrains.annotations.NotNull;
 
 /**
  * This is sent to the server in response to a {@link ClientboundEncryptionRequestPacket},
  * after which, if the connection persists, you are considered authenticated
  * with the server. You should then receive a {@link ClientboundRegionTimestampsPacket}.
  */
-public class ServerboundEncryptionResponsePacket extends Packet {
+public class ServerboundEncryptionResponsePacket implements Packet {
 	public static final int PACKET_ID = 3;
 
 	/**
@@ -25,13 +26,9 @@ public ServerboundEncryptionResponsePacket(byte[] sharedSecret, byte[] verifyTok
 		this.verifyToken = verifyToken;
 	}
 
-	public static Packet read(ByteBuf buf) {
-		return new ServerboundEncryptionResponsePacket(readByteArray(buf), readByteArray(buf));
-	}
-
 	@Override
-	public void write(ByteBuf out) {
-		writeByteArray(out, sharedSecret);
-		writeByteArray(out, verifyToken);
+	public void write(@NotNull ByteBuf out) {
+		Packet.writeIntLengthByteArray(out, sharedSecret);
+		Packet.writeIntLengthByteArray(out, verifyToken);
 	}
 }