vtx-format

vtx-format defines the proprietary binary container format (.vtx) used by the VTX plugin system.

It is responsible for encapsulating standard WebAssembly Components (.wasm) into VTX plugin packages equipped with a Magic Header and version control. This ensures that the runtime loads only valid and version-compatible plugins.

Specification

Currently, only the V1 format is supported. All multibyte integers are stored in Big-Endian (Note: The current version only involves a single-byte version number, so endianness handling is not yet required).

V1 Structure Layout

The file header is fixed at 4 bytes, immediately followed by the raw Wasm Component byte stream.

Offset	Length (Bytes)	Field	Value / Description
0x00	3	Magic Prefix	`0x56 0x54 0x58` (ASCII: "VTX")
0x03	1	Version	`0x01` (Current Version)
0x04	N	Payload	Raw WebAssembly Component binary data

Installation

Add the following to your Cargo.toml:

[dependencies]
vtx-format = "0.1"

Usage

Encoding

Encapsulate raw Wasm bytes into the .vtx format:

use vtx_format::encode_v1;

fn main() {
    let wasm_bytes = std::fs::read("plugin.wasm").unwrap();
    
    // Automatically adds the "VTX\x01" header
    let vtx_data = encode_v1(&wasm_bytes);
    
    std::fs::write("plugin.vtx", vtx_data).unwrap();
}

Decoding

Parse a .vtx file and verify the header:

use vtx_format::{decode, VtxFormatError};

fn main() -> Result<(), VtxFormatError> {
    let data = std::fs::read("plugin.vtx").unwrap();

    // Returns (version, raw payload slice)
    let (version, payload) = decode(&data)?;

    println!("Detected VTX version: {}", version);
    println!("Payload size: {} bytes", payload.len());
    
    Ok(())
}

Error Handling

The library provides the VtxFormatError enum to handle parsing errors:

TooShort: Data length is less than 4 bytes.
InvalidPrefix: Header is not "VTX".
UnsupportedVersion(u8): Encountered an unknown version number.

License

MIT License

vtx-format 0.1.1