SpecMC Protocol

A library for parsing Minecraft protocol specification.

Default types

Primitives:

• bool: Boolean.
• u8, u16, u32, u64: Unsigned integers of size 8, 16, 32 and 64 bits respectively.
• i8, i16, i32, i64: Signed integers of size 8, 16, 32 and 64 bits respectively.
• VarInt, VarLong: Regular signed integers of size 32 and 64 bits respectively, but encoded in the LEB128 format.
• f32, f64: Floating point numbers of size 32 and 64 bits respectively.

Other types:

• String: UTF-8 encoded string prefixed with its size in bytes as VarInt. The maximum length is 32767. Use String[n] to explicitly specify the length.
• List[type; n]: A list, where type is the type of the elements and n is the number of elements. n can also be an identifier, in which case the number of elements is to be determined at runtime.
• Nbt: NBT encoded data.

Enums

An enum definition consists of an enum name, followed by its representation type, and a list of variants. Variants will be implicitly assigned a value of the previous variant plus one. The first variant will be implicitly assigned the value 0. You can explicitly assign a value to an enum variant. An enum State is necessary and is used for packet definitions.

Example:

enum ABC(i32) {
    A = 1
    B // implicitly assigned 2
    C // implicitly assigned 3
}

Packets

A packet definition consists of a packet name, followed by its direction, state and id, and a list of fields. Enums will be represented as the type specified in the enum definition. if statements can be used to define conditional fields. Fields of primitive types can be set to equal a literal or another field or constant.

Example:

packet SomePacket(serverbound, Play, 0x42) {
    u32 length
    List[u8; length] data
    if (length > 0) {
        String message
    }
}

Types

A custom type can be defined using the type keyword. Fields are equivalent to fields in a packet.

Constants

Constants can be defined using the const keyword. A constant PVN is automatically defined.

Examples

use specmc_base::{parse::Parse, tokenize::tokenize};
use specmc_protocol::Protocol;

const INPUT: &str = "
enum TestEnum(i32) {}
type TestType {
    String message
}
packet TestPacket(serverbound, Play, 0x42) {
    u32 length
    List[u8; length] data
    if (length > 0) {
        TestType message
    }
}";

let mut tokens: Vec<String> = tokenize(INPUT);
tokens.reverse();
println!("{:#?}", Protocol::parse(&mut tokens));