rosu-map

Library to de- and encode .osu files from osu!.

What

At it's core, rosu-map provides the DecodeBeatmap trait. The trait is responsible for decoding the file itself, error handling, and section parsing. All that's left to do for implementators of the trait is to keep a state of parsed data and, given a section and a line of text, to modify that state.

rosu-map also provides multiple types that already implement this trait, namely one for each section (see Editor, TimingPoints, ...) and one for the (almost) full content, Beatmap.

Why

Exposing functionality through the trait allows for flexibility when deciding which content to parse and thus make it more efficient when not all data is needed.

If only the difficulty attributes are required, parsing via the Difficulty struct will discard everything except for the few lines within the [Difficulty] section of the .osu file. Similarly, if only the artist, title, and version is of interest, the Metadata struct can be used.

Additionally, it's worth noting that Beatmap parses (almost) everything which might be overkill for many use-cases. The work-around would be to define a new custom type, copy-paste Beatmap's DecodeBeatmap implementation, and then throw out everything that's not needed.

How

The simplest way to make use of a type's DecodeBeatmap implementation is by using rosu-maps functions from_bytes, from_path, and from_str.

use rosu_map::section::difficulty::Difficulty;

let content = "[Difficulty]
ApproachRate: 9.2
SliderMultiplier: 1.9

[Metadata]
Creator: peppy";

let difficulty = rosu_map::from_str::<Difficulty>(content).unwrap();
assert_eq!(difficulty.approach_rate, 9.2);

let path = "./resources/Soleily - Renatus (Gamu) [Insane].osu";
let map = rosu_map::from_path::<Beatmap>(path).unwrap();
assert_eq!(map.audio_file, "03. Renatus - Soleily 192kbps.mp3");

For information on implementing the DecodeBeatmap trait on a new type, check out the trait's documentation. For examples, check how types like General or HitObjects implement the trait.

Encoding

The Beatmap struct provides a built-in way to turn itself into the content of a .osu file through its encode* methods.

let path = "./resources/Within Temptation - The Unforgiving (Armin) [Marathon].osu";
let mut map: Beatmap = rosu_map::from_path(path).unwrap();

map.approach_rate = 10.0;

map.encode_to_path("./new_file.osu").unwrap();

let metadata = rosu_map::section::metadata::Metadata {
    title: "song title".to_string(),
    artist: "artist name".to_string(),
    ..Default::default()
};

let content = Beatmap::from(metadata).encode_to_string().unwrap();
assert!(content.contains("Title: song title"));

Features

Misc

Internals

A sizable section of rosu-map is a port of osu!lazer's beatmap {de/en}coding. Not only does its functionality mirror osu!, but many test cases were translated too, providing a solid degree of correctness even on fringe edge cases.

Lazer commit on last port: 8bd65d9938a10fc42e6409501b0282f0fa4a25ef

Async

After some testing and benchmarking, it turns out that async IO does not provide any improvements or performance gains even in a concurrent context. In fact, regular sequential IO consistently outperformed its async counterpart. As such rosu-map does not provide an async interface.

Storyboard

rosu-map does not provide types that parse storyboards, but the crate rosu-storyboard does.