What should i do if i want to read and change entity_identifiers.dat

guaiMiao · 4 January 2021 21:21

i have tried to use NBTIO.read() but it doesnt work

joserobjr · 4 January 2021 21:26

Hello,

Sorry for the late reply, I was taking some time off in December.

Why would you need to modify that resource?

We extract that file from the connection between a bedrock client (usually Windows 10 Edition) and BDS.

TL;DR

Read: (CompoundTag) NBTIO.readTag(stream, ByteOrder.LITTLE_ENDIAN, true);
Write: NBTIO.write(tags, ByteOrder.LITTLE_ENDIAN, true);

It is used in PowerNukkit directly in the AvailableEntityIdentifiersPacket:

github.com

PowerNukkit/PowerNukkit/blob/6b67441d7e57f6010b6f679d753cf21342a65d00/src/main/java/cn/nukkit/network/protocol/AvailableEntityIdentifiersPacket.java#L17


import java.io.InputStream;

@ToString(exclude = {"tag"})
public class AvailableEntityIdentifiersPacket extends DataPacket {
    public static final byte NETWORK_ID = ProtocolInfo.AVAILABLE_ENTITY_IDENTIFIERS_PACKET;

    private static final byte[] TAG;

    static {
        try {
            InputStream inputStream = Nukkit.class.getClassLoader().getResourceAsStream("entity_identifiers.dat");
            if (inputStream == null) {
                throw new AssertionError("Could not find entity_identifiers.dat");
            }
            //noinspection UnstableApiUsage
            TAG = ByteStreams.toByteArray(inputStream);
        } catch (Exception e) {
            throw new AssertionError("Error whilst loading entity_identifiers.dat", e);
        }
    }

We get the content using ProxyPass:

github.com

PowerNukkit/Bedrock-ProxyPass/blob/a336e4c320ba1ad06f68dfa85420c8a9c12728df/src/main/java/com/nukkitx/proxypass/network/bedrock/session/DownstreamPacketHandler.java#L64



    ClientToServerHandshakePacket clientToServerHandshake = new ClientToServerHandshakePacket();
    session.sendPacketImmediately(clientToServerHandshake);
    return true;
}

public boolean handle(AvailableEntityIdentifiersPacket packet) {
    if (!proxy.getConfiguration().isExportData()) {
        return false;
    }
    proxy.saveNBT("entity_identifiers", packet.getIdentifiers());
    return false;
}

public boolean handle(BiomeDefinitionListPacket packet) {
    if (!proxy.getConfiguration().isExportData()) {
        return false;
    }
    proxy.saveNBT("biome_definitions", packet.getDefinitions());
    return false;
}

Here is how you could read it directly from the file:

public class EntityIdentifiersDumper {
    public static void main(String[] args)  {
        CompoundTag tags;
        try (InputStream stream = Server.class.getClassLoader().getResourceAsStream("entity_identifiers.dat")) {
            if (stream == null) {
                throw new AssertionError("Unable to locate entity_identifiers.dat");
            }

            tags = (CompoundTag) NBTIO.readTag(stream, ByteOrder.LITTLE_ENDIAN, true);
        } catch (IOException e) {
            throw new AssertionError(e);
        }
        System.out.println(tags);
    }
}

And how you could use the cache from the packet:

public class EntityIdentifiersDumper {
    public static void main(String[] args) {
        CompoundTag tags;
        try (InputStream stream = new ByteArrayInputStream(new AvailableEntityIdentifiersPacket().tag)) {
            tags = (CompoundTag) NBTIO.readTag(stream, ByteOrder.LITTLE_ENDIAN, true);
        } catch (IOException e) {
            throw new AssertionError(e);
        }
        System.out.println(tags);
    }
}

To write in the same format:

NBTIO.write(tags, ByteOrder.LITTLE_ENDIAN, true)

Example output:

CompoundTag '' (1 entries) {
	'idlist' : ListTag 'idlist' (111 entries of type TAG_Compound) {
		CompoundTag '' (6 entries) {
			'hasspawnegg' : ByteTag hasspawnegg (data: 0x01),
			'experimental' : ByteTag experimental (data: 0x00),
			'summonable' : ByteTag summonable (data: 0x00),
			'id' : StringTag id (data: minecraft:villager_v2),
			'bid' : StringTag bid (data: ),
			'rid' : IntTag rid(data: 115)
		},
		CompoundTag '' (6 entries) {
			'hasspawnegg' : ByteTag hasspawnegg (data: 0x01),
			'experimental' : ByteTag experimental (data: 0x00),
			'summonable' : ByteTag summonable (data: 0x01),
			'id' : StringTag id (data: minecraft:cat),
			'bid' : StringTag bid (data: ),
			'rid' : IntTag rid(data: 75)
		},
		CompoundTag '' (6 entries) {
			'hasspawnegg' : ByteTag hasspawnegg (data: 0x01),
			'experimental' : ByteTag experimental (data: 0x00),
			'summonable' : ByteTag summonable (data: 0x01),
			'id' : StringTag id (data: minecraft:turtle),
			'bid' : StringTag bid (data: ),
			'rid' : IntTag rid(data: 74)
		},

guaiMiao · 5 January 2021 04:48

thanks. i’m going to create a server like Decimation in JE so i need to register entities. you really helps me a lot.