#[cfg(test)]
mod test;
use serde::{ser::SerializeSeq, Serialize, Serializer};
use serde_bytes::Bytes;
use sha2::{Digest, Sha256};
use std::borrow::Cow;
pub type Hash = [u8; 32];
#[derive(Debug, Clone, Default)]
pub enum HashTree<'a> {
#[default]
Empty,
Fork(Box<(HashTree<'a>, HashTree<'a>)>),
Labeled(&'a [u8], Box<HashTree<'a>>),
Leaf(Cow<'a, [u8]>),
Pruned(Hash),
}
pub fn fork<'a>(l: HashTree<'a>, r: HashTree<'a>) -> HashTree<'a> {
HashTree::Fork(Box::new((l, r)))
}
pub fn labeled<'a>(l: &'a [u8], t: HashTree<'a>) -> HashTree<'a> {
HashTree::Labeled(l, Box::new(t))
}
pub fn fork_hash(l: &Hash, r: &Hash) -> Hash {
let mut h = domain_sep("ic-hashtree-fork");
h.update(&l[..]);
h.update(&r[..]);
h.finalize().into()
}
pub fn leaf_hash(data: &[u8]) -> Hash {
let mut h = domain_sep("ic-hashtree-leaf");
h.update(data);
h.finalize().into()
}
pub fn labeled_hash(label: &[u8], content_hash: &Hash) -> Hash {
let mut h = domain_sep("ic-hashtree-labeled");
h.update(label);
h.update(&content_hash[..]);
h.finalize().into()
}
impl HashTree<'_> {
pub fn reconstruct(&self) -> Hash {
match self {
Self::Empty => domain_sep("ic-hashtree-empty").finalize().into(),
Self::Fork(f) => fork_hash(&f.0.reconstruct(), &f.1.reconstruct()),
Self::Labeled(l, t) => {
let thash = t.reconstruct();
labeled_hash(l, &thash)
}
Self::Leaf(data) => leaf_hash(data),
Self::Pruned(h) => *h,
}
}
}
impl Serialize for HashTree<'_> {
fn serialize<S>(&self, serializer: S) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>
where
S: Serializer,
{
match self {
HashTree::Empty => {
let mut seq = serializer.serialize_seq(Some(1))?;
seq.serialize_element(&0u8)?;
seq.end()
}
HashTree::Fork(p) => {
let mut seq = serializer.serialize_seq(Some(3))?;
seq.serialize_element(&1u8)?;
seq.serialize_element(&p.0)?;
seq.serialize_element(&p.1)?;
seq.end()
}
HashTree::Labeled(label, tree) => {
let mut seq = serializer.serialize_seq(Some(3))?;
seq.serialize_element(&2u8)?;
seq.serialize_element(Bytes::new(label))?;
seq.serialize_element(&tree)?;
seq.end()
}
HashTree::Leaf(leaf_bytes) => {
let mut seq = serializer.serialize_seq(Some(2))?;
seq.serialize_element(&3u8)?;
seq.serialize_element(Bytes::new(leaf_bytes.as_ref()))?;
seq.end()
}
HashTree::Pruned(digest) => {
let mut seq = serializer.serialize_seq(Some(2))?;
seq.serialize_element(&4u8)?;
seq.serialize_element(Bytes::new(&digest[..]))?;
seq.end()
}
}
}
}
fn domain_sep(s: &str) -> sha2::Sha256 {
let buf: [u8; 1] = [s.len() as u8];
let mut h = Sha256::new();
h.update(&buf[..]);
h.update(s.as_bytes());
h
}