#lz4 #writer #minecraft #format #region #access #streaming

lz4-java-wrc

A fork of lz4jb to ensure it gives back access to the underlying writer (wrc = “write continue”) lz4jb is a Rust implementation of the LZ4BlockOutputStream format from https://github.com/lz4/lz4-java. This is not compatible with the standard LZ4 Block format, and is useful for reading Minecraft region files

1 unstable release

0.2.0 Feb 16, 2024

#559 in Compression


Used in mca

MIT license

58KB
1.5K SLoC

lz4-java-wrc

Crate API

This is a fork of lz4jb that accepts the writer as a pointer instead of consuming it.

A streaming compression/decompression library which implements the LZ4BlockOutputStream format from lz4-java.

Beware: this format is not compatible with the standard LZ4 Block format. The Minecraft 1.20.5 lz4 chunk compression format is an example of a place this is used.

This repository contains:

  • lz4_java_wrc: a library which implements the Read and Write traits,

Usage

Add this to your Cargo.toml:

[dependencies]
lz4-java-wrc = "0.2.0"

Compression

Lz4BlockOutput is a wrapper around a type which implements the Write trait.

use lz4_java_wrc::Lz4BlockOutput;
use std::io::Write;

fn main() -> std::io::Result<()> {
    let mut output = Vec::new(); // Vec<u8> implements the Write trait
    Lz4BlockOutput::new(&mut output, 64)?
        .write_all("...".as_bytes())?;
    println!("{:?}", output);
    Ok(())
}

Decompression

Lz4BlockInput is a wrapper around a type which implements the Read trait.

use lz4_java_wrc::Lz4BlockInput;
use std::io::Read;

const D: [u8; 24] = [
    76, 90, 52, 66, 108, 111, 99, 107, 16, 3, 0, 0, 0, 3, 0, 0, 0, 82, 228, 119, 6, 46, 46, 46,
];

fn main() -> std::io::Result<()> {
    let mut output = String::new();
    Lz4BlockInput::new(&D[..]) // &[u8] implements the Read trait
        .read_to_string(&mut output)?;
    println!("{}", output);
    Ok(())
}

License

See the LICENCE file.

Dependencies

~150–500KB