refpack-rs

A very overengineered rust crate for compressing and decompressing data in the RefPack format utilized by many EA games of the early 2000s

RefPack

RefPack, also known as QFS, is a semi-standardized compression format utilized by many games published by Electronic Arts from the 90s to the late 2000s. In many cases, it was deployed with a custom header format.

Structure

RefPack shares many similarities with lz77 compression; it is a lossless compression format which relies on length-distance pairs to existing bytes within the decompression buffer. Where it differs from lz77 is that rather than a single format for "Literal" control codes and "Pointer" control codes, RefPack uses 4 distinct control codes for different sizes of pointers and literal blocks. A fifth control code is also present to indicate end of stream rather than requiring a size to be specified before decompression.

Codes

RefPack utilizes one "Literal" bytes-only control code similar to lz77, but with limited precision to multiples of 4. The remaining three control codes are varying sizes of "Pointer" control codes, for small, medium, and large back-references and lengths. The limited precision of the "Literal" control code is compensated for via "Pointer" control codes also having the ability to write up to 3 literal bytes to the stream

See Command for further details.

Decompression

Decompression simply requires reading from a stream of RefPack data until a stopcode is reached.

See decompression for further details

Compression

Compressing via RefPack is largely similar to lz77 compression algorithms, and involves a sliding window over the data to search for repeating blocks, and then writing to the stream as the previously specified codes.

See compression for further details

Headers

While the actual data block of RefPack has only one known implementation, multiple types of headers for the library have been identified.

Other Implementations

RefPack has been implemented in various other languages and for various games:

• RefPack.cpp (download): Original canonical implementation of RefPack by Frank Barchard for Origin Software. Utilized by some early Origin Software games.
• JDBPF: Early Simcity 4 Java Library for reading DBPF files which utilize RefPack
• JDBPFX: Later currently maintained fork of JDBPF
• DBPFSharp: Simcity 4 DBPF Library written in C#
• Sims2Tools: Sims 2 DBPF Library written in C#

This Crate

This crate is a rust implementation designed to compress and decompress refpack data with any header format. It uses generics to support arbitrary header formats to allow pure usage of this library without having to write "glue" code to parse header info.

Put simply, this means that you get the benefit of being able to use any format however you like without any performance overhead from dynamic dispatch, as well as being able to implement your own arbitrary formats that are still compatible with the same compression algorithms.

Usage

refpack-rs exposes two functions: compress and decompress, along with easy variants with easier but less flexible of usage.

compress and decompress take mutable references to a buffer to read and write from, that implements std::io::Read and std::io::Write, respectively.

decompress will read from the buffer until it encounters a stopcode (byte within (0xFC..=0xFF)), while compress will read in the provided length.

all compression and decompression functions accept one generic argument constrained to the Format trait. Implementations be "unconstructable" types, with the recommended type being an empty enum.

Implementations

Example

use std::io::{Cursor, Seek};

use refpack::format::Reference;

let mut source_reader = Cursor::new(b"Hello World!".to_vec());
let mut out_buf = Cursor::new(vec![]);
refpack::compress::<Reference>(
    source_reader.get_ref().len(),
    &mut source_reader,
    &mut out_buf,
)
.unwrap();

The easy variants are compress_easy and decompress_easy, which take a &[u8] and return a Result<Vec<u8>, RefPackError>.

Internally they simply call compress and decompress with a Cursor to the input and output buffers, however they are more convenient to use in many cases.

License

This repository is licensed under the terms of the Mozilla Public License Version 2.0

The MPL is a weak copyleft license, in simple, non-legally binding language:

You can

1. Use this software privately
2. Use this software commercially
3. Modify this software
4. Redistribute this software

As long as

1. You disclose the license and copyright of this library
2. You disclose the source of this library
3. You disclose the source changes made to this library's files
4. You use the same license for your changes made to the library's files

In even simpler terms, you can use this for pretty much anything as long as you credit and link to it, but if you change any files from this library you must also share the source code of your changes. Again, non-legally binding, see actual license text, etc.