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use super::{vec, InnerNodeInfo, MerkleError, NodeIndex, Rpo256, RpoDigest, Vec};
use core::ops::{Deref, DerefMut};
// MERKLE PATH
// ================================================================================================
/// A merkle path container, composed of a sequence of nodes of a Merkle tree.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub struct MerklePath {
nodes: Vec<RpoDigest>,
}
impl MerklePath {
// CONSTRUCTORS
// --------------------------------------------------------------------------------------------
/// Creates a new Merkle path from a list of nodes.
pub fn new(nodes: Vec<RpoDigest>) -> Self {
Self { nodes }
}
// PROVIDERS
// --------------------------------------------------------------------------------------------
/// Returns the depth in which this Merkle path proof is valid.
pub fn depth(&self) -> u8 {
self.nodes.len() as u8
}
/// Computes the merkle root for this opening.
pub fn compute_root(&self, index: u64, node: RpoDigest) -> Result<RpoDigest, MerkleError> {
let mut index = NodeIndex::new(self.depth(), index)?;
let root = self.nodes.iter().copied().fold(node, |node, sibling| {
// compute the node and move to the next iteration.
let input = index.build_node(node, sibling);
index.move_up();
Rpo256::merge(&input)
});
Ok(root)
}
/// Verifies the Merkle opening proof towards the provided root.
///
/// Returns `true` if `node` exists at `index` in a Merkle tree with `root`.
pub fn verify(&self, index: u64, node: RpoDigest, root: &RpoDigest) -> bool {
match self.compute_root(index, node) {
Ok(computed_root) => root == &computed_root,
Err(_) => false,
}
}
/// Returns an iterator over every inner node of this [MerklePath].
///
/// The iteration order is unspecified.
///
/// # Errors
/// Returns an error if the specified index is not valid for this path.
pub fn inner_nodes(
&self,
index: u64,
node: RpoDigest,
) -> Result<InnerNodeIterator, MerkleError> {
Ok(InnerNodeIterator {
nodes: &self.nodes,
index: NodeIndex::new(self.depth(), index)?,
value: node,
})
}
}
impl From<MerklePath> for Vec<RpoDigest> {
fn from(path: MerklePath) -> Self {
path.nodes
}
}
impl From<Vec<RpoDigest>> for MerklePath {
fn from(path: Vec<RpoDigest>) -> Self {
Self::new(path)
}
}
impl Deref for MerklePath {
// we use `Vec` here instead of slice so we can call vector mutation methods directly from the
// merkle path (example: `Vec::remove`).
type Target = Vec<RpoDigest>;
fn deref(&self) -> &Self::Target {
&self.nodes
}
}
impl DerefMut for MerklePath {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.nodes
}
}
// ITERATORS
// ================================================================================================
impl FromIterator<RpoDigest> for MerklePath {
fn from_iter<T: IntoIterator<Item = RpoDigest>>(iter: T) -> Self {
Self::new(iter.into_iter().collect())
}
}
impl IntoIterator for MerklePath {
type Item = RpoDigest;
type IntoIter = vec::IntoIter<RpoDigest>;
fn into_iter(self) -> Self::IntoIter {
self.nodes.into_iter()
}
}
/// An iterator over internal nodes of a [MerklePath].
pub struct InnerNodeIterator<'a> {
nodes: &'a Vec<RpoDigest>,
index: NodeIndex,
value: RpoDigest,
}
impl<'a> Iterator for InnerNodeIterator<'a> {
type Item = InnerNodeInfo;
fn next(&mut self) -> Option<Self::Item> {
if !self.index.is_root() {
let sibling_pos = self.nodes.len() - self.index.depth() as usize;
let (left, right) = if self.index.is_value_odd() {
(self.nodes[sibling_pos], self.value)
} else {
(self.value, self.nodes[sibling_pos])
};
self.value = Rpo256::merge(&[left, right]);
self.index.move_up();
Some(InnerNodeInfo { value: self.value, left, right })
} else {
None
}
}
}
// MERKLE PATH CONTAINERS
// ================================================================================================
/// A container for a [Word] value and its [MerklePath] opening.
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct ValuePath {
/// The node value opening for `path`.
pub value: RpoDigest,
/// The path from `value` to `root` (exclusive).
pub path: MerklePath,
}
impl ValuePath {
/// Returns a new [ValuePath] instantiated from the specified value and path.
pub fn new(value: RpoDigest, path: Vec<RpoDigest>) -> Self {
Self { value, path: MerklePath::new(path) }
}
}
/// A container for a [MerklePath] and its [Word] root.
///
/// This structure does not provide any guarantees regarding the correctness of the path to the
/// root. For more information, check [MerklePath::verify].
#[derive(Clone, Debug, Default, PartialEq, Eq)]
pub struct RootPath {
/// The node value opening for `path`.
pub root: RpoDigest,
/// The path from `value` to `root` (exclusive).
pub path: MerklePath,
}
// TESTS
// ================================================================================================
#[cfg(test)]
mod tests {
use crate::merkle::{int_to_node, MerklePath};
#[test]
fn test_inner_nodes() {
let nodes = vec![int_to_node(1), int_to_node(2), int_to_node(3), int_to_node(4)];
let merkle_path = MerklePath::new(nodes);
let index = 6;
let node = int_to_node(5);
let root = merkle_path.compute_root(index, node).unwrap();
let inner_root = merkle_path.inner_nodes(index, node).unwrap().last().unwrap().value;
assert_eq!(root, inner_root);
}
}