pmtree

Persistent Merkle Tree (optimized & sparse & fixed-size) in Rust

## How to use ```toml [dependencies] pmtree = { git = "https://github.com/Rate-Limiting-Nullifier/pmtree" } ``` ## Example In-Memory DB (HashMap) + Keccak ```rust struct MemoryDB(HashMap); struct MyKeccak(Keccak); impl Database for MemoryDB { fn new(_dbpath: &str) -> Result { Ok(MemoryDB(HashMap::new())) } fn load(_dbpath: &str) -> Result { Err(Error("Cannot load in-memory DB".to_string())) } fn get(&self, key: DBKey) -> Result> { Ok(self.0.get(&key).cloned()) } fn put(&mut self, key: DBKey, value: Value) -> Result<()> { self.0.insert(key, value); Ok(()) } fn put_batch(&mut self, subtree: HashMap) -> Result<()> { self.0.extend(subtree.into_iter()); Ok(()) } } impl Hasher for MyKeccak { type Fr = [u8; 32]; fn default_leaf() -> Self::Fr { [0; 32] } fn serialize(value: Self::Fr) -> Value { value.to_vec() } fn deserialize(value: Value) -> Self::Fr { value.try_into().unwrap() } fn hash(input: &[Self::Fr]) -> Self::Fr { let mut output = [0; 32]; let mut hasher = Keccak::v256(); for element in input { hasher.update(element); } hasher.finalize(&mut output); output } } fn main() { let mut mt = MerkleTree::::new(2, "abacaba").unwrap(); assert_eq!(mt.capacity(), 4); assert_eq!(mt.depth(), 2); mt.update_next(hex!( "c1ba1812ff680ce84c1d5b4f1087eeb08147a4d510f3496b2849df3a73f5af95" )) .unwrap(); } ```