Expose `MerklePath` type without a feature flag.
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@ -464,6 +464,53 @@ impl<'a> From<&'a Address> for Option<Position> {
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}
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}
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/// A path from a position in a particular commitment tree to the root of that tree.
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct MerklePath<H, const DEPTH: u8> {
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path_elems: Vec<H>,
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position: Position,
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}
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impl<H, const DEPTH: u8> MerklePath<H, DEPTH> {
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/// Constructs a Merkle path directly from a path and position.
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#[allow(clippy::result_unit_err)]
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pub fn from_parts(path_elems: Vec<H>, position: Position) -> Result<Self, ()> {
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if path_elems.len() == usize::from(DEPTH) {
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Ok(MerklePath {
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path_elems,
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position,
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})
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} else {
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Err(())
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}
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}
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pub fn path_elems(&self) -> &[H] {
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&self.path_elems
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}
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pub fn position(&self) -> Position {
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self.position
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}
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}
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impl<H: Hashable, const DEPTH: u8> MerklePath<H, DEPTH> {
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/// Returns the root of the tree corresponding to this path applied to `leaf`.
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pub fn root(&self, leaf: H) -> H {
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self.path_elems
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.iter()
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.enumerate()
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.fold(leaf, |root, (i, h)| {
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let level = Level(i as u8);
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if self.position.0 >> i & 0x1 == 0 {
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H::combine(level, &root, h)
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} else {
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H::combine(level, h, &root)
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}
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})
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}
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}
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/// A trait describing the operations that make a type suitable for use as
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/// a leaf or node value in a merkle tree.
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pub trait Hashable: Sized + core::fmt::Debug {
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@ -480,6 +527,8 @@ pub trait Hashable: Sized + core::fmt::Debug {
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#[cfg(test)]
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pub(crate) mod tests {
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use crate::MerklePath;
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use super::{Address, Level, Position, Source};
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use core::ops::Range;
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use either::Either;
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@ -663,4 +712,23 @@ pub(crate) mod tests {
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Either::Left(Address::from_parts(Level(5), 1))
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);
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}
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#[test]
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fn merkle_path_root() {
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let path: MerklePath<String, 3> = MerklePath::from_parts(
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vec!["a".to_string(), "cd".to_string(), "efgh".to_string()],
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Position(1),
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)
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.unwrap();
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assert_eq!(path.root("b".to_string()), "abcdefgh".to_string());
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let path: MerklePath<String, 3> = MerklePath::from_parts(
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vec!["d".to_string(), "ab".to_string(), "efgh".to_string()],
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Position(2),
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)
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.unwrap();
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assert_eq!(path.root("c".to_string()), "abcdefgh".to_string());
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}
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}
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@ -3,57 +3,9 @@ use std::iter::repeat;
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use crate::{
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frontier::{CommitmentTree, PathFiller},
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Hashable, Level,
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Hashable, Level, MerklePath, Position,
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};
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/// A path from a position in a particular commitment tree to the root of that tree.
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct MerklePath<H, const DEPTH: u8> {
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auth_path: Vec<(H, bool)>,
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position: u64,
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}
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impl<H, const DEPTH: u8> MerklePath<H, DEPTH> {
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/// Constructs a Merkle path directly from a path and position.
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#[allow(clippy::result_unit_err)]
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pub fn from_parts(auth_path: Vec<(H, bool)>, position: u64) -> Result<Self, ()> {
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if auth_path.len() == usize::from(DEPTH) {
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Ok(MerklePath {
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auth_path,
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position,
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})
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} else {
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Err(())
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}
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}
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pub fn auth_path(&self) -> &[(H, bool)] {
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&self.auth_path
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}
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pub fn position(&self) -> u64 {
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self.position
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}
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}
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impl<H: Hashable, const DEPTH: u8> MerklePath<H, DEPTH> {
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/// Returns the root of the tree corresponding to this path applied to `leaf`.
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pub fn root(&self, leaf: H) -> H {
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self.auth_path
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.iter()
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.enumerate()
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.fold(leaf, |root, (i, (p, leaf_is_on_right))| {
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let level = u8::try_from(i)
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.expect("Parents list length may not exceed what is representable by an u8")
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.into();
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match leaf_is_on_right {
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false => H::combine(level, &root, p),
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true => H::combine(level, p, &root),
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}
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})
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}
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}
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/// An updatable witness to a path from a position in a particular [`CommitmentTree`].
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///
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/// Appending the same commitments in the same order to both the original
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@ -131,8 +83,8 @@ impl<H, const DEPTH: u8> IncrementalWitness<H, DEPTH> {
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}
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/// Returns the position of the witnessed leaf node in the commitment tree.
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pub fn position(&self) -> usize {
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self.tree.size() - 1
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pub fn position(&self) -> Position {
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Position::from(self.tree.size() - 1)
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}
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/// Finds the next "depth" of an unfilled subtree.
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@ -233,9 +185,9 @@ impl<H: Hashable + Clone, const DEPTH: u8> IncrementalWitness<H, DEPTH> {
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if let Some(node) = &self.tree.left {
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if self.tree.right.is_some() {
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auth_path.push((node.clone(), true));
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auth_path.push(node.clone());
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} else {
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auth_path.push((filler.next(0.into()), false));
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auth_path.push(filler.next(0.into()));
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}
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} else {
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// Can't create an authentication path for the beginning of the tree
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@ -251,13 +203,13 @@ impl<H: Hashable + Clone, const DEPTH: u8> IncrementalWitness<H, DEPTH> {
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.enumerate()
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{
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auth_path.push(match p {
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Some(node) => (node.clone(), true),
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None => (filler.next(Level::from((i + 1) as u8)), false),
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Some(node) => node.clone(),
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None => filler.next(Level::from((i + 1) as u8)),
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});
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}
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assert_eq!(auth_path.len(), usize::from(depth));
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MerklePath::from_parts(auth_path, self.position() as u64).ok()
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MerklePath::from_parts(auth_path, self.position()).ok()
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}
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}
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