szs

Lightweight crate for SZS ("Yaz0") compression/decompression used in the Nintendo GameCube/Wii games. The library provides C, C++ and C# bindings. YAY0 ("SZP") is supported, too.

Rust

The following snippet demonstrates how to compress a file as a SZS format using Rust:

// Sample source bytes to be encoded.
let src_data: Vec<u8> = "Hello, World!".as_bytes().to_vec();

match szs::encode(&src_data, szs::EncodeAlgo::Nintendo) {
    Ok(encoded_data) => {
        println!("Encoded into {} bytes", encoded_data.len());
    }
    Err(szs::EncodeAlgoError::Error(err_msg)) => {
        println!("Encoding failed: {}", err_msg);
    }
}

And similarly, to decompress:

match szs::decode(&encoded_data) {
    Ok(decoded_data) => {
        println!("Decoded {} bytes", decoded_data.len());
    }
    Err(szs::EncodeAlgoError::Error(err_msg)) => {
        println!("Decoding failed: {}", err_msg);
    }
}

C# Bindings

The following C# bindings are provided:

using System;

public class SZSExample
{
    public static void Main(string[] args)
    {
        byte[] data = ...; // Initialize your data here

        szs.CompressionAlgorithm algorithm = szs.CompressionAlgorithm.Nintendo;
        byte[] encodedData = szs.Encode(data, algorithm);

        if (encodedData == null || encodedData.Length == 0)
        {
            Console.WriteLine("Failed to compress.");
            return;
        }

        Console.WriteLine($"Encoded {encodedData.Length} bytes.");
    }
}

Warning: These algorithms are currently implemented in the C programming language, and not in Rust. While they have been rigorously validated, please use at your own risk. A Rust rewrite is planned.

Algorithms

Generally, the mk8 algorithm gets acceptable compression the fastest. For cases where filesize matters, lib-yaz0 ties wszst ultra for the smallest filesizes, while being ~25% faster.

Large file comparison

NSMBU 8-43 (63.9 MB decompressed)

* Average of 3 runs; x64 Clang (15, 16) build tested on an Intel i7-9750H on Windows 11

Generally, the mk8 algorithm gets acceptable compression the fastest. For cases where filesize matters, lib-yaz0 ties wszst ultra for the smallest filesizes, while being ~25% faster.

Small file comparison

Task: Compress N64 Bowser Castle (Source filesize: 2,574,368)

* Average of 3 runs; x64 Clang (15, 16) build tested on an Intel i7-9750H on Windows 11

Example (C Bindings)

#include `szs.h`

// Calculate the upper bound for encoding.
u32 max_size = riiszs_encoded_upper_bound(sizeof(data));

// Allocate a buffer based on the calculated upper bound.
void* encoded_buf = malloc(max_size);
if (!buf) {
	fprintf(stderr, "Failed to allocate %u bytes.\n", max_size);
	return -1;
}

// Boyer-Moore-horspool variant
u32 algorithm = RII_SZS_ENCODE_ALGO_NINTENDO;

u32 actual_len = 0;
const char* ec = riiszs_encode_algo_fast(encoded_buf, max_size, data, sizeof(data), &actual_len, algorithm);
if (ec != NULL) {
	fprintf(stderr, "Failed to compress: %s\n", ec);
	riiszs_free_error_message(ec);
	return -1;
}
printf("Encoded %u bytes.\n", actual_len);
// Optionally: shrink the dst_data to the actual size.
encoded_buf = realloc(encoded_buf, actual_len);

C++ Wrapper on top of C Bindings

A CMake example is provided, too.

#include `szs.h`

// Boyer-Moore-horspool variant
szs::Algo algorithm = szs::Algo::Nintendo;
auto encoded = szs::encode(data, algorithm);
if (!encoded)
	std::println(stderr, "Failed to compress: {}.", encoded.error()); {
	return -1;
}
std::vector<u8> szs_data = *encoded;
std::println("Encoded {} bytes.", szs_data.size());

License

This library is published under the MIT license.