hash array mapped table immutable overlay node

gistfile1.txt

enum HAMTOverlay<K, V, Hash> {
  Empty(),
  FullTable(&[Self; 32]),
  SingleKey(Hash::Hash, K, V, Rc<Self>),
  SingleSubtree(Hash::Hash, Rc<Self>, Rc<Self>),
}


impl ... for SingleKey {
  fn lookupWithHash(&self, k: K, h: Hash::Hash) -> Option<V> {
    if h == self.0 && k == self.1 {
      Some(self.2)
    } else {
      self.3.lookupWithHash(k, h)
    }
  }
}

impl ... for SingleSubtree {
  fn lookupWithHash(&self, k: K, h: Hash::Hash) -> Option<V> {
    if hashPrefixMatches(self.0, h) {
      self.1.lookupWithHash(k, removeHashPrefix(h))
    } else {
      self.2.lookupWithHash(k, h)
    }
  }
}

impl ... for FullTable {
  fn lookupWithHash(&self, k: K, h: hash::Hash) -> Option<V> {
    self.0[getHashPrefix(h)].lookupWithHash(k, removeHashPrefix(h))
  }
}

impl ... for Empty {
  fn lookupWithHash(&self, k: K, h: hash::Hash) -> Option<V> {
    None
  }
}