osu-db is an osu! binary file format encoder/decoder, providing support for loading, modifying and saving the following osu! file formats:

• osu!.db: The main beatmap information cache osu! uses.
• collection.db: A list of collections and the beatmaps they contain.
• scores.db: Overview of all user scores.
• .osr files: Individual in-depth score data of a single replay.

To use, simply add this line to your Cargo.toml:

osu-db = "*"

After that you will want to use the different load/save functions on the Listing (cached beatmap database), ScoreList (summary of all player scores), CollectionList (in-game beatmap collections) or Replay (a single in-depth standalone replay file).

For example, to change all your osu!mania grades to SS+:

use osu_db::listing::{Listing, Grade};

// Load the listing to memory
let mut listing=Listing::from_file("osu!.db").unwrap();

// Modify listing in-place
for beatmap in listing.beatmaps.iter_mut() {
    beatmap.mania_grade = Grade::SSPlus;
}

// Save back to disk
listing.save("osu!.db").unwrap();

More details in the crate documentation.