Stateful tree index. Or well, stateful flat-tree. It's what happens when you combine a flat-tree with a sparse-bitfield - which ends up being pretty cool!
Adapted from mafintosh/hypercore/lib/tree-index.js.
extern crate sparse_bitfield as bitfield;
extern crate tree_index;
use tree_index::TreeIndex;
use self::bitfield::{Bitfield, Change};
let bitfield = Bitfield::new(1024);
let mut tree = TreeIndex::new(bitfield);
assert_eq!(tree.set(0), Change::Changed);
assert_eq!(tree.set(0), Change::Unchanged);
assert_eq!(tree.get(0), true);
assert_eq!(tree.get(1), false);$ cargo add tree-indexMIT OR Apache-2.0