BTree leaderboard

BTreeStore leaderboard

Focus: one persistent leaderboard contract that stores score keys in order and reads the highest scores.

leaderboard.slx


const BOARD_NS: bytes = "leaderboard".to_bytes()
 
fn score_key(score: u64, player: Address) -> bytes {
    let key: bytes = score.to_be_bytes()
    key.extend(player.to_bytes())
    return key
}
 
entry submit_score(player: Address, score: u64) {
    let board: BTreeStore = BTreeStore::new(BOARD_NS)
 
    board.insert(score_key(score, player), [player, score])
    return 0
}
 
entry top(limit: u32) -> any[] {
    let board: BTreeStore = BTreeStore::new(BOARD_NS)
    let (cursor, first): (BTreeCursor, optional<Entry>) = board.seek(
        u64::MAX.to_be_bytes(),
        BTreeSeekBias::LessOrEqual,
        false
    )
 
    let results: any[] = []
    let entry: optional<Entry> = first
    let count: u32 = 0
 
    while count < limit && entry != null {
        let item: Entry = entry.unwrap()
        results.push(item.value)
        entry = cursor.next()
        count += 1
    }
 
    return results
}

How it works

BOARD_NS gives this contract a dedicated persistent tree namespace.
score_key(score, player) encodes the score first, then the player address, so keys sort by score.
submit_score(player, score) stores one [player, score] value and returns the default success exit code.
top(limit) seeks near the maximum possible score and walks backward by passing false for ascending order.
top(limit) returns the selected leaderboard entries directly.