Move frontier types from `bridgetree` to `incrementalmerkletree`
These types are reusable outside of the context of the `bridgetree` crate.
This commit is contained in:
Kris Nuttycombe
parent
ff8095b7ed
commit
4e3c6a6378
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@ -14,6 +14,8 @@ and this project adheres to Rust's notion of
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### Removed
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- The `NonEmptyFrontier`, `Frontier`, and `FrontierError` types have
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been moved to the `incrementalmerkletree` crate.
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- The `testing` module has been removed in favor of depending on
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`incrementalmerkletree::testing`.
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- `serde` serialization and parsing are no longer supported.
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@ -30,27 +30,14 @@
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//! reset the state to.
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//!
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//! In this module, the term "ommer" is used as for the sibling of a parent node in a binary tree.
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pub use incrementalmerkletree::{
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frontier::{Frontier, NonEmptyFrontier},
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Address, Hashable, Level, Position, Retention, Source,
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};
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use std::collections::{BTreeMap, BTreeSet, VecDeque};
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use std::convert::TryFrom;
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use std::fmt::Debug;
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use std::mem::size_of;
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use std::ops::Range;
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pub use incrementalmerkletree::{Address, Hashable, Level, Position, Retention};
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/// Validation errors that can occur during reconstruction of a Merkle frontier from
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/// its constituent parts.
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub enum FrontierError {
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/// An error representing that the number of ommers provided in frontier construction does not
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/// the expected length of the ommers list given the position.
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PositionMismatch { expected_ommers: usize },
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/// An error representing that the position and/or list of ommers provided to frontier
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/// construction would result in a frontier that exceeds the maximum statically allowed depth
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/// of the tree.
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MaxDepthExceeded { depth: u8 },
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}
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/// Errors that can be discovered during checks that verify the compatibility of adjacent bridges.
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub enum ContinuityError {
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@ -73,284 +60,6 @@ pub enum WitnessingError {
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BridgeAddressInvalid(Address),
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}
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#[derive(Copy, Clone, Debug, PartialEq, Eq)]
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enum Source {
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/// The sibling to the address can be derived from the incremental frontier
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/// at the contained ommer index
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Past(usize),
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/// The sibling to the address must be obtained from values discovered by
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/// the addition of more nodes to the tree
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Future,
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}
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#[must_use = "iterators are lazy and do nothing unless consumed"]
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struct WitnessAddrsIter {
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root_level: Level,
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current: Address,
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ommer_count: usize,
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}
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/// Returns an iterator over the addresses of nodes required to create a witness for this
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/// position, beginning with the sibling of the leaf at this position and ending with the
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/// sibling of the ancestor of the leaf at this position that is required to compute a root at
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/// the specified level.
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fn witness_addrs(position: Position, root_level: Level) -> impl Iterator<Item = (Address, Source)> {
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WitnessAddrsIter {
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root_level,
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current: Address::from(position),
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ommer_count: 0,
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}
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}
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impl Iterator for WitnessAddrsIter {
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type Item = (Address, Source);
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fn next(&mut self) -> Option<(Address, Source)> {
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if self.current.level() < self.root_level {
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let current = self.current;
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let source = if current.is_right_child() {
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Source::Past(self.ommer_count)
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} else {
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Source::Future
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};
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self.current = current.parent();
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if matches!(source, Source::Past(_)) {
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self.ommer_count += 1;
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}
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Some((current.sibling(), source))
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} else {
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None
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}
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}
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}
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/// A [`NonEmptyFrontier`] is a reduced representation of a Merkle tree, containing a single leaf
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/// value, along with the vector of hashes produced by the reduction of previously appended leaf
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/// values that will be required when producing a witness for the current leaf.
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#[derive(Clone, Debug, PartialEq, Eq)]
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pub struct NonEmptyFrontier<H> {
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position: Position,
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leaf: H,
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ommers: Vec<H>,
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}
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impl<H> NonEmptyFrontier<H> {
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/// Constructs a new frontier with the specified value at position 0.
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pub fn new(leaf: H) -> Self {
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Self {
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position: 0.into(),
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leaf,
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ommers: vec![],
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}
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}
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/// Constructs a new frontier from its constituent parts
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pub fn from_parts(position: Position, leaf: H, ommers: Vec<H>) -> Result<Self, FrontierError> {
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let expected_ommers = position.past_ommer_count();
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if ommers.len() == expected_ommers {
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Ok(Self {
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position,
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leaf,
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ommers,
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})
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} else {
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Err(FrontierError::PositionMismatch { expected_ommers })
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}
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}
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/// Returns the position of the most recently appended leaf.
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pub fn position(&self) -> Position {
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self.position
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}
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/// Returns the leaf most recently appended to the frontier
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pub fn leaf(&self) -> &H {
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&self.leaf
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}
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/// Returns the list of past hashes required to construct a witness for the
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/// leaf most recently appended to the frontier.
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pub fn ommers(&self) -> &[H] {
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&self.ommers
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}
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}
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impl<H: Hashable + Clone> NonEmptyFrontier<H> {
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/// Append a new leaf to the frontier, and recompute recompute ommers by hashing together full
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/// subtrees until an empty ommer slot is found.
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pub fn append(&mut self, leaf: H) {
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let prior_position = self.position;
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let prior_leaf = self.leaf.clone();
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self.position += 1;
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self.leaf = leaf;
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if self.position.is_odd() {
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// if the new position is odd, the current leaf will directly become
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// an ommer at level 0, and there is no other mutation made to the tree.
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self.ommers.insert(0, prior_leaf);
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} else {
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// if the new position is even, then the current leaf will be hashed
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// with the first ommer, and so forth up the tree.
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let new_root_level = self.position.root_level();
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let mut carry = Some((prior_leaf, 0.into()));
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let mut new_ommers = Vec::with_capacity(self.position.past_ommer_count());
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for (addr, source) in witness_addrs(prior_position, new_root_level) {
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if let Source::Past(i) = source {
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if let Some((carry_ommer, carry_lvl)) = carry.as_ref() {
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if *carry_lvl == addr.level() {
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carry = Some((
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H::combine(addr.level(), &self.ommers[i], carry_ommer),
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addr.level() + 1,
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))
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} else {
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// insert the carry at the first empty slot; then the rest of the
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// ommers will remain unchanged
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new_ommers.push(carry_ommer.clone());
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new_ommers.push(self.ommers[i].clone());
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carry = None;
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}
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} else {
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// when there's no carry, just push on the ommer value
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new_ommers.push(self.ommers[i].clone());
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}
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}
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}
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// we carried value out, so we need to push on one more ommer.
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if let Some((carry_ommer, _)) = carry {
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new_ommers.push(carry_ommer);
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}
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self.ommers = new_ommers;
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}
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}
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/// Generate the root of the Merkle tree by hashing against empty subtree roots.
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pub fn root(&self, root_level: Option<Level>) -> H {
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let max_level = root_level.unwrap_or_else(|| self.position.root_level());
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witness_addrs(self.position, max_level)
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.fold(
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(self.leaf.clone(), Level::from(0)),
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|(digest, complete_lvl), (addr, source)| {
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// fold up from complete_lvl to addr.level() pairing with empty roots; if
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// complete_lvl == addr.level() this is just the complete digest to this point
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let digest = complete_lvl
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.iter_to(addr.level())
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.fold(digest, |d, l| H::combine(l, &d, &H::empty_root(l)));
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let res_digest = match source {
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Source::Past(i) => H::combine(addr.level(), &self.ommers[i], &digest),
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Source::Future => {
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H::combine(addr.level(), &digest, &H::empty_root(addr.level()))
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}
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};
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(res_digest, addr.level() + 1)
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},
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)
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.0
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}
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/// Constructs a witness for the leaf at the tip of this
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/// frontier, given a source of node values that complement this frontier.
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pub fn witness<F>(&self, depth: u8, bridge_value_at: F) -> Result<Vec<H>, WitnessingError>
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where
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F: Fn(Address) -> Option<H>,
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{
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// construct a complete trailing edge that includes the data from
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// the following frontier not yet included in the trailing edge.
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witness_addrs(self.position(), depth.into())
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.map(|(addr, source)| match source {
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Source::Past(i) => Ok(self.ommers[i].clone()),
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Source::Future => {
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bridge_value_at(addr).ok_or(WitnessingError::BridgeAddressInvalid(addr))
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}
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})
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.collect::<Result<Vec<_>, _>>()
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}
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}
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/// A possibly-empty Merkle frontier.
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct Frontier<H, const DEPTH: u8> {
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frontier: Option<NonEmptyFrontier<H>>,
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}
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impl<H, const DEPTH: u8> TryFrom<NonEmptyFrontier<H>> for Frontier<H, DEPTH> {
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type Error = FrontierError;
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fn try_from(f: NonEmptyFrontier<H>) -> Result<Self, FrontierError> {
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if f.position.root_level() <= Level::from(DEPTH) {
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Ok(Frontier { frontier: Some(f) })
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} else {
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Err(FrontierError::MaxDepthExceeded {
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depth: f.position.root_level().into(),
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})
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}
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}
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}
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impl<H, const DEPTH: u8> Frontier<H, DEPTH> {
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/// Constructs a new empty frontier.
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pub fn empty() -> Self {
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Self { frontier: None }
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}
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/// Constructs a new frontier from its constituent parts.
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///
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/// Returns `None` if the new frontier would exceed the maximum
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/// allowed depth or if the list of ommers provided is not consistent
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/// with the position of the leaf.
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pub fn from_parts(position: Position, leaf: H, ommers: Vec<H>) -> Result<Self, FrontierError> {
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NonEmptyFrontier::from_parts(position, leaf, ommers).and_then(Self::try_from)
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}
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/// Return the wrapped NonEmptyFrontier reference, or None if
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/// the frontier is empty.
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pub fn value(&self) -> Option<&NonEmptyFrontier<H>> {
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self.frontier.as_ref()
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}
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/// Returns the amount of memory dynamically allocated for ommer
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/// values within the frontier.
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pub fn dynamic_memory_usage(&self) -> usize {
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self.frontier.as_ref().map_or(0, |f| {
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size_of::<usize>() + (f.ommers.capacity() + 1) * size_of::<H>()
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})
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}
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}
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impl<H: Hashable + Clone, const DEPTH: u8> Frontier<H, DEPTH> {
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/// Appends a new value to the frontier at the next available slot.
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/// Returns true if successful and false if the frontier would exceed
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/// the maximum allowed depth.
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pub fn append(&mut self, value: H) -> bool {
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if let Some(frontier) = self.frontier.as_mut() {
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if frontier.position().is_complete_subtree(DEPTH.into()) {
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false
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} else {
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frontier.append(value);
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true
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}
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} else {
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self.frontier = Some(NonEmptyFrontier::new(value));
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true
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}
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}
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/// Obtains the current root of this Merkle frontier by hashing
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/// against empty nodes up to the maximum height of the pruned
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/// tree that the frontier represents.
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pub fn root(&self) -> H {
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self.frontier
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.as_ref()
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.map_or(H::empty_root(DEPTH.into()), |frontier| {
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frontier.root(Some(DEPTH.into()))
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})
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}
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}
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/// The information required to "update" witnesses from one state of a Merkle tree to another.
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///
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/// The witness for a particular leaf of a Merkle tree consists of the siblings of that leaf, plus
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@ -581,19 +290,21 @@ impl<'a, H: Hashable + Ord + Clone + 'a> MerkleBridge<H> {
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) -> Result<Vec<H>, WitnessingError> {
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assert!(Some(prior_frontier.position()) == self.prior_position);
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prior_frontier.witness(depth, |addr| {
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let r = addr.position_range();
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if self.frontier.position() < r.start {
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Some(H::empty_root(addr.level()))
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} else if r.contains(&self.frontier.position()) {
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Some(self.frontier.root(Some(addr.level())))
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} else {
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// the frontier's position is after the end of the requested
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// range, so the requested value should exist in a stored
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// fragment
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self.ommers.get(&addr).cloned()
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}
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})
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prior_frontier
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.witness(depth, |addr| {
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let r = addr.position_range();
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if self.frontier.position() < r.start {
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Some(H::empty_root(addr.level()))
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} else if r.contains(&self.frontier.position()) {
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Some(self.frontier.root(Some(addr.level())))
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} else {
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// the frontier's position is after the end of the requested
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// range, so the requested value should exist in a stored
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// fragment
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self.ommers.get(&addr).cloned()
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}
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})
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.map_err(WitnessingError::BridgeAddressInvalid)
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}
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fn retain(&mut self, ommer_addrs: &BTreeSet<Address>) {
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@ -1229,8 +940,10 @@ impl<H: Hashable + Ord + Clone, const DEPTH: u8> BridgeTree<H, DEPTH> {
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// Add the elements of the auth path to the set of addresses we should
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// continue to track and retain information for
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for (addr, source) in
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witness_addrs(cur_bridge.frontier.position(), Level::from(DEPTH))
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for (addr, source) in cur_bridge
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.frontier
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.position()
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.witness_addrs(Level::from(DEPTH))
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{
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if source == Source::Future {
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ommer_addrs.insert(addr);
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@ -1283,24 +996,14 @@ mod tests {
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use super::*;
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use incrementalmerkletree::{
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testing::{
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apply_operation, arb_operation, check_checkpoint_rewind, check_operations,
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self, apply_operation, arb_operation, check_checkpoint_rewind, check_operations,
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check_remove_mark, check_rewind_remove_mark, check_root_hashes, check_witnesses,
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complete_tree::CompleteTree, CombinedTree, Frontier, SipHashable, Tree,
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complete_tree::CompleteTree, CombinedTree, SipHashable,
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},
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Hashable,
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};
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impl<H: Hashable + Clone, const DEPTH: u8> Frontier<H> for super::Frontier<H, DEPTH> {
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fn append(&mut self, value: H) -> bool {
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super::Frontier::append(self, value)
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}
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fn root(&self) -> H {
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super::Frontier::root(self)
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}
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}
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impl<H: Hashable + Ord + Clone, const DEPTH: u8> Tree<H, usize> for BridgeTree<H, DEPTH> {
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impl<H: Hashable + Ord + Clone, const DEPTH: u8> testing::Tree<H, usize> for BridgeTree<H, DEPTH> {
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fn append(&mut self, value: H, retention: Retention<usize>) -> bool {
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let appended = BridgeTree::append(self, value);
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if appended {
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@ -1351,101 +1054,6 @@ mod tests {
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}
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}
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#[test]
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fn position_witness_addrs() {
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use Source::*;
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let path_elem = |l, i, s| (Address::from_parts(Level::from(l), i), s);
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assert_eq!(
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vec![path_elem(0, 1, Future), path_elem(1, 1, Future)],
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witness_addrs(Position::from(0), Level::from(2)).collect::<Vec<_>>()
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);
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assert_eq!(
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vec![path_elem(0, 3, Future), path_elem(1, 0, Past(0))],
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witness_addrs(Position::from(2), Level::from(2)).collect::<Vec<_>>()
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);
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assert_eq!(
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vec![
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path_elem(0, 2, Past(0)),
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path_elem(1, 0, Past(1)),
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path_elem(2, 1, Future)
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],
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witness_addrs(Position::from(3), Level::from(3)).collect::<Vec<_>>()
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);
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assert_eq!(
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vec![
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path_elem(0, 5, Future),
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path_elem(1, 3, Future),
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path_elem(2, 0, Past(0)),
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path_elem(3, 1, Future)
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],
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witness_addrs(Position::from(4), Level::from(4)).collect::<Vec<_>>()
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);
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assert_eq!(
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vec![
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path_elem(0, 7, Future),
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path_elem(1, 2, Past(0)),
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path_elem(2, 0, Past(1)),
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path_elem(3, 1, Future)
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],
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witness_addrs(Position::from(6), Level::from(4)).collect::<Vec<_>>()
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);
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}
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#[test]
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fn nonempty_frontier_root() {
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let mut frontier = NonEmptyFrontier::new("a".to_string());
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assert_eq!(frontier.root(None), "a");
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|
||||
frontier.append("b".to_string());
|
||||
assert_eq!(frontier.root(None), "ab");
|
||||
|
||||
frontier.append("c".to_string());
|
||||
assert_eq!(frontier.root(None), "abc_");
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn frontier_from_parts() {
|
||||
assert!(super::Frontier::<(), 1>::from_parts(0.into(), (), vec![]).is_ok());
|
||||
assert!(super::Frontier::<(), 1>::from_parts(1.into(), (), vec![()]).is_ok());
|
||||
assert!(super::Frontier::<(), 1>::from_parts(0.into(), (), vec![()]).is_err());
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn frontier_root() {
|
||||
let mut frontier: super::Frontier<String, 4> = super::Frontier::empty();
|
||||
assert_eq!(frontier.root().len(), 16);
|
||||
assert_eq!(frontier.root(), "________________");
|
||||
|
||||
frontier.append("a".to_string());
|
||||
assert_eq!(frontier.root(), "a_______________");
|
||||
|
||||
frontier.append("b".to_string());
|
||||
assert_eq!(frontier.root(), "ab______________");
|
||||
|
||||
frontier.append("c".to_string());
|
||||
assert_eq!(frontier.root(), "abc_____________");
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn frontier_witness() {
|
||||
let mut frontier = NonEmptyFrontier::<String>::new("a".to_string());
|
||||
for c in 'b'..'h' {
|
||||
frontier.append(c.to_string());
|
||||
}
|
||||
let bridge_value_at = |addr: Address| match <u8>::from(addr.level()) {
|
||||
0 => Some("h".to_string()),
|
||||
3 => Some("xxxxxxxx".to_string()),
|
||||
_ => None,
|
||||
};
|
||||
|
||||
assert_eq!(
|
||||
Ok(["h", "ef", "abcd", "xxxxxxxx"]
|
||||
.map(|v| v.to_string())
|
||||
.to_vec()),
|
||||
frontier.witness(4, bridge_value_at)
|
||||
);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn tree_depth() {
|
||||
let mut tree = BridgeTree::<String, 3>::new(100, 0);
|
||||
|
|
|
|||
|
|
@ -7,6 +7,12 @@ and this project adheres to Rust's notion of
|
|||
|
||||
## [Unreleased]
|
||||
|
||||
### Added
|
||||
- `incrementalmerkletree::frontier` Types that model the state at the rightmost
|
||||
node of a Merkle tree that is filled sequentially from the left. These have
|
||||
been migrated here from the `bridgetree` crate as they are useful outside
|
||||
of the context of the `bridgetree` data structures.
|
||||
|
||||
## [0.3.1] - 2023-02-28
|
||||
|
||||
### Fixed
|
||||
|
|
|
|||
|
|
@ -0,0 +1,322 @@
|
|||
use std::convert::TryFrom;
|
||||
use std::mem::size_of;
|
||||
|
||||
use crate::{Address, Hashable, Level, Position, Source};
|
||||
|
||||
/// Validation errors that can occur during reconstruction of a Merkle frontier from
|
||||
/// its constituent parts.
|
||||
#[derive(Clone, Debug, PartialEq, Eq)]
|
||||
pub enum FrontierError {
|
||||
/// An error representing that the number of ommers provided in frontier construction does not
|
||||
/// the expected length of the ommers list given the position.
|
||||
PositionMismatch { expected_ommers: usize },
|
||||
/// An error representing that the position and/or list of ommers provided to frontier
|
||||
/// construction would result in a frontier that exceeds the maximum statically allowed depth
|
||||
/// of the tree.
|
||||
MaxDepthExceeded { depth: u8 },
|
||||
}
|
||||
|
||||
/// A [`NonEmptyFrontier`] is a reduced representation of a Merkle tree, containing a single leaf
|
||||
/// value, along with the vector of hashes produced by the reduction of previously appended leaf
|
||||
/// values that will be required when producing a witness for the current leaf.
|
||||
#[derive(Clone, Debug, PartialEq, Eq)]
|
||||
pub struct NonEmptyFrontier<H> {
|
||||
position: Position,
|
||||
leaf: H,
|
||||
ommers: Vec<H>,
|
||||
}
|
||||
|
||||
impl<H> NonEmptyFrontier<H> {
|
||||
/// Constructs a new frontier with the specified value at position 0.
|
||||
pub fn new(leaf: H) -> Self {
|
||||
Self {
|
||||
position: 0.into(),
|
||||
leaf,
|
||||
ommers: vec![],
|
||||
}
|
||||
}
|
||||
|
||||
/// Constructs a new frontier from its constituent parts
|
||||
pub fn from_parts(position: Position, leaf: H, ommers: Vec<H>) -> Result<Self, FrontierError> {
|
||||
let expected_ommers = position.past_ommer_count();
|
||||
if ommers.len() == expected_ommers {
|
||||
Ok(Self {
|
||||
position,
|
||||
leaf,
|
||||
ommers,
|
||||
})
|
||||
} else {
|
||||
Err(FrontierError::PositionMismatch { expected_ommers })
|
||||
}
|
||||
}
|
||||
|
||||
/// Returns the position of the most recently appended leaf.
|
||||
pub fn position(&self) -> Position {
|
||||
self.position
|
||||
}
|
||||
|
||||
/// Returns the leaf most recently appended to the frontier
|
||||
pub fn leaf(&self) -> &H {
|
||||
&self.leaf
|
||||
}
|
||||
|
||||
/// Returns the list of past hashes required to construct a witness for the
|
||||
/// leaf most recently appended to the frontier.
|
||||
pub fn ommers(&self) -> &[H] {
|
||||
&self.ommers
|
||||
}
|
||||
}
|
||||
|
||||
impl<H: Hashable + Clone> NonEmptyFrontier<H> {
|
||||
/// Append a new leaf to the frontier, and recompute recompute ommers by hashing together full
|
||||
/// subtrees until an empty ommer slot is found.
|
||||
pub fn append(&mut self, leaf: H) {
|
||||
let prior_position = self.position;
|
||||
let prior_leaf = self.leaf.clone();
|
||||
self.position += 1;
|
||||
self.leaf = leaf;
|
||||
if self.position.is_odd() {
|
||||
// if the new position is odd, the current leaf will directly become
|
||||
// an ommer at level 0, and there is no other mutation made to the tree.
|
||||
self.ommers.insert(0, prior_leaf);
|
||||
} else {
|
||||
// if the new position is even, then the current leaf will be hashed
|
||||
// with the first ommer, and so forth up the tree.
|
||||
let new_root_level = self.position.root_level();
|
||||
|
||||
let mut carry = Some((prior_leaf, 0.into()));
|
||||
let mut new_ommers = Vec::with_capacity(self.position.past_ommer_count());
|
||||
for (addr, source) in prior_position.witness_addrs(new_root_level) {
|
||||
if let Source::Past(i) = source {
|
||||
if let Some((carry_ommer, carry_lvl)) = carry.as_ref() {
|
||||
if *carry_lvl == addr.level() {
|
||||
carry = Some((
|
||||
H::combine(addr.level(), &self.ommers[i], carry_ommer),
|
||||
addr.level() + 1,
|
||||
))
|
||||
} else {
|
||||
// insert the carry at the first empty slot; then the rest of the
|
||||
// ommers will remain unchanged
|
||||
new_ommers.push(carry_ommer.clone());
|
||||
new_ommers.push(self.ommers[i].clone());
|
||||
carry = None;
|
||||
}
|
||||
} else {
|
||||
// when there's no carry, just push on the ommer value
|
||||
new_ommers.push(self.ommers[i].clone());
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// we carried value out, so we need to push on one more ommer.
|
||||
if let Some((carry_ommer, _)) = carry {
|
||||
new_ommers.push(carry_ommer);
|
||||
}
|
||||
|
||||
self.ommers = new_ommers;
|
||||
}
|
||||
}
|
||||
|
||||
/// Generate the root of the Merkle tree by hashing against empty subtree roots.
|
||||
pub fn root(&self, root_level: Option<Level>) -> H {
|
||||
let max_level = root_level.unwrap_or_else(|| self.position.root_level());
|
||||
self.position
|
||||
.witness_addrs(max_level)
|
||||
.fold(
|
||||
(self.leaf.clone(), Level::from(0)),
|
||||
|(digest, complete_lvl), (addr, source)| {
|
||||
// fold up from complete_lvl to addr.level() pairing with empty roots; if
|
||||
// complete_lvl == addr.level() this is just the complete digest to this point
|
||||
let digest = complete_lvl
|
||||
.iter_to(addr.level())
|
||||
.fold(digest, |d, l| H::combine(l, &d, &H::empty_root(l)));
|
||||
|
||||
let res_digest = match source {
|
||||
Source::Past(i) => H::combine(addr.level(), &self.ommers[i], &digest),
|
||||
Source::Future => {
|
||||
H::combine(addr.level(), &digest, &H::empty_root(addr.level()))
|
||||
}
|
||||
};
|
||||
|
||||
(res_digest, addr.level() + 1)
|
||||
},
|
||||
)
|
||||
.0
|
||||
}
|
||||
|
||||
/// Constructs a witness for the leaf at the tip of this frontier, given a source of node
|
||||
/// values that complement this frontier.
|
||||
///
|
||||
/// If the `complement_nodes` function returns `None` when the value is requested at a given
|
||||
/// tree address, the address at which the failure occurs will be returned as an error.
|
||||
pub fn witness<F>(&self, depth: u8, complement_nodes: F) -> Result<Vec<H>, Address>
|
||||
where
|
||||
F: Fn(Address) -> Option<H>,
|
||||
{
|
||||
// construct a complete trailing edge that includes the data from
|
||||
// the following frontier not yet included in the trailing edge.
|
||||
self.position()
|
||||
.witness_addrs(depth.into())
|
||||
.map(|(addr, source)| match source {
|
||||
Source::Past(i) => Ok(self.ommers[i].clone()),
|
||||
Source::Future => complement_nodes(addr).ok_or(addr),
|
||||
})
|
||||
.collect::<Result<Vec<_>, _>>()
|
||||
}
|
||||
}
|
||||
|
||||
/// A possibly-empty Merkle frontier.
|
||||
#[derive(Debug, Clone, PartialEq, Eq)]
|
||||
pub struct Frontier<H, const DEPTH: u8> {
|
||||
frontier: Option<NonEmptyFrontier<H>>,
|
||||
}
|
||||
|
||||
impl<H, const DEPTH: u8> TryFrom<NonEmptyFrontier<H>> for Frontier<H, DEPTH> {
|
||||
type Error = FrontierError;
|
||||
fn try_from(f: NonEmptyFrontier<H>) -> Result<Self, FrontierError> {
|
||||
if f.position.root_level() <= Level::from(DEPTH) {
|
||||
Ok(Frontier { frontier: Some(f) })
|
||||
} else {
|
||||
Err(FrontierError::MaxDepthExceeded {
|
||||
depth: f.position.root_level().into(),
|
||||
})
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl<H, const DEPTH: u8> Frontier<H, DEPTH> {
|
||||
/// Constructs a new empty frontier.
|
||||
pub fn empty() -> Self {
|
||||
Self { frontier: None }
|
||||
}
|
||||
|
||||
/// Constructs a new frontier from its constituent parts.
|
||||
///
|
||||
/// Returns `None` if the new frontier would exceed the maximum
|
||||
/// allowed depth or if the list of ommers provided is not consistent
|
||||
/// with the position of the leaf.
|
||||
pub fn from_parts(position: Position, leaf: H, ommers: Vec<H>) -> Result<Self, FrontierError> {
|
||||
NonEmptyFrontier::from_parts(position, leaf, ommers).and_then(Self::try_from)
|
||||
}
|
||||
|
||||
/// Return the wrapped NonEmptyFrontier reference, or None if
|
||||
/// the frontier is empty.
|
||||
pub fn value(&self) -> Option<&NonEmptyFrontier<H>> {
|
||||
self.frontier.as_ref()
|
||||
}
|
||||
|
||||
/// Returns the amount of memory dynamically allocated for ommer
|
||||
/// values within the frontier.
|
||||
pub fn dynamic_memory_usage(&self) -> usize {
|
||||
self.frontier.as_ref().map_or(0, |f| {
|
||||
size_of::<usize>() + (f.ommers.capacity() + 1) * size_of::<H>()
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
impl<H: Hashable + Clone, const DEPTH: u8> Frontier<H, DEPTH> {
|
||||
/// Appends a new value to the frontier at the next available slot.
|
||||
/// Returns true if successful and false if the frontier would exceed
|
||||
/// the maximum allowed depth.
|
||||
pub fn append(&mut self, value: H) -> bool {
|
||||
if let Some(frontier) = self.frontier.as_mut() {
|
||||
if frontier.position().is_complete_subtree(DEPTH.into()) {
|
||||
false
|
||||
} else {
|
||||
frontier.append(value);
|
||||
true
|
||||
}
|
||||
} else {
|
||||
self.frontier = Some(NonEmptyFrontier::new(value));
|
||||
true
|
||||
}
|
||||
}
|
||||
|
||||
/// Obtains the current root of this Merkle frontier by hashing
|
||||
/// against empty nodes up to the maximum height of the pruned
|
||||
/// tree that the frontier represents.
|
||||
pub fn root(&self) -> H {
|
||||
self.frontier
|
||||
.as_ref()
|
||||
.map_or(H::empty_root(DEPTH.into()), |frontier| {
|
||||
frontier.root(Some(DEPTH.into()))
|
||||
})
|
||||
}
|
||||
}
|
||||
|
||||
#[cfg(feature = "test-dependencies")]
|
||||
pub mod testing {
|
||||
use crate::Hashable;
|
||||
|
||||
impl<H: Hashable + Clone, const DEPTH: u8> crate::testing::Frontier<H>
|
||||
for super::Frontier<H, DEPTH>
|
||||
{
|
||||
fn append(&mut self, value: H) -> bool {
|
||||
super::Frontier::append(self, value)
|
||||
}
|
||||
|
||||
fn root(&self) -> H {
|
||||
super::Frontier::root(self)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
#[cfg(test)]
|
||||
mod tests {
|
||||
use super::*;
|
||||
|
||||
#[test]
|
||||
fn nonempty_frontier_root() {
|
||||
let mut frontier = NonEmptyFrontier::new("a".to_string());
|
||||
assert_eq!(frontier.root(None), "a");
|
||||
|
||||
frontier.append("b".to_string());
|
||||
assert_eq!(frontier.root(None), "ab");
|
||||
|
||||
frontier.append("c".to_string());
|
||||
assert_eq!(frontier.root(None), "abc_");
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn frontier_from_parts() {
|
||||
assert!(super::Frontier::<(), 1>::from_parts(0.into(), (), vec![]).is_ok());
|
||||
assert!(super::Frontier::<(), 1>::from_parts(1.into(), (), vec![()]).is_ok());
|
||||
assert!(super::Frontier::<(), 1>::from_parts(0.into(), (), vec![()]).is_err());
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn frontier_root() {
|
||||
let mut frontier: super::Frontier<String, 4> = super::Frontier::empty();
|
||||
assert_eq!(frontier.root().len(), 16);
|
||||
assert_eq!(frontier.root(), "________________");
|
||||
|
||||
frontier.append("a".to_string());
|
||||
assert_eq!(frontier.root(), "a_______________");
|
||||
|
||||
frontier.append("b".to_string());
|
||||
assert_eq!(frontier.root(), "ab______________");
|
||||
|
||||
frontier.append("c".to_string());
|
||||
assert_eq!(frontier.root(), "abc_____________");
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn frontier_witness() {
|
||||
let mut frontier = NonEmptyFrontier::<String>::new("a".to_string());
|
||||
for c in 'b'..'h' {
|
||||
frontier.append(c.to_string());
|
||||
}
|
||||
let bridge_value_at = |addr: Address| match <u8>::from(addr.level()) {
|
||||
0 => Some("h".to_string()),
|
||||
3 => Some("xxxxxxxx".to_string()),
|
||||
_ => None,
|
||||
};
|
||||
|
||||
assert_eq!(
|
||||
Ok(["h", "ef", "abcd", "xxxxxxxx"]
|
||||
.map(|v| v.to_string())
|
||||
.to_vec()),
|
||||
frontier.witness(4, bridge_value_at)
|
||||
);
|
||||
}
|
||||
}
|
||||
|
|
@ -6,6 +6,8 @@ use std::convert::{TryFrom, TryInto};
|
|||
use std::num::TryFromIntError;
|
||||
use std::ops::{Add, AddAssign, Range, Sub};
|
||||
|
||||
pub mod frontier;
|
||||
|
||||
#[cfg(feature = "test-dependencies")]
|
||||
pub mod testing;
|
||||
|
||||
|
|
@ -42,6 +44,47 @@ impl<C> Retention<C> {
|
|||
}
|
||||
}
|
||||
|
||||
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
|
||||
pub enum Source {
|
||||
/// The sibling to the address can be derived from the incremental frontier
|
||||
/// at the contained ommer index
|
||||
Past(usize),
|
||||
/// The sibling to the address must be obtained from values discovered by
|
||||
/// the addition of more nodes to the tree
|
||||
Future,
|
||||
}
|
||||
|
||||
#[must_use = "iterators are lazy and do nothing unless consumed"]
|
||||
struct WitnessAddrsIter {
|
||||
root_level: Level,
|
||||
current: Address,
|
||||
ommer_count: usize,
|
||||
}
|
||||
|
||||
impl Iterator for WitnessAddrsIter {
|
||||
type Item = (Address, Source);
|
||||
|
||||
fn next(&mut self) -> Option<(Address, Source)> {
|
||||
if self.current.level() < self.root_level {
|
||||
let current = self.current;
|
||||
let source = if current.is_right_child() {
|
||||
Source::Past(self.ommer_count)
|
||||
} else {
|
||||
Source::Future
|
||||
};
|
||||
|
||||
self.current = current.parent();
|
||||
if matches!(source, Source::Past(_)) {
|
||||
self.ommer_count += 1;
|
||||
}
|
||||
|
||||
Some((current.sibling(), source))
|
||||
} else {
|
||||
None
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
/// A type representing the position of a leaf in a Merkle tree.
|
||||
#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
|
||||
#[repr(transparent)]
|
||||
|
|
@ -73,6 +116,18 @@ impl Position {
|
|||
pub fn is_complete_subtree(&self, root_level: Level) -> bool {
|
||||
!(0..(root_level.0)).any(|l| self.0 & (1 << l) == 0)
|
||||
}
|
||||
|
||||
/// Returns an iterator over the addresses of nodes required to create a witness for this
|
||||
/// position, beginning with the sibling of the leaf at this position and ending with the
|
||||
/// sibling of the ancestor of the leaf at this position that is required to compute a root at
|
||||
/// the specified level.
|
||||
pub fn witness_addrs(&self, root_level: Level) -> impl Iterator<Item = (Address, Source)> {
|
||||
WitnessAddrsIter {
|
||||
root_level,
|
||||
current: Address::from(*self),
|
||||
ommer_count: 0,
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl From<Position> for usize {
|
||||
|
|
@ -419,7 +474,7 @@ pub trait Hashable: Sized + core::fmt::Debug {
|
|||
|
||||
#[cfg(test)]
|
||||
pub(crate) mod tests {
|
||||
use super::{Address, Level, Position};
|
||||
use super::{Address, Level, Position, Source};
|
||||
use core::ops::Range;
|
||||
use either::Either;
|
||||
|
||||
|
|
@ -458,7 +513,57 @@ pub(crate) mod tests {
|
|||
}
|
||||
|
||||
#[test]
|
||||
fn current_incomplete() {
|
||||
fn position_witness_addrs() {
|
||||
use Source::*;
|
||||
let path_elem = |l, i, s| (Address::from_parts(Level::from(l), i), s);
|
||||
assert_eq!(
|
||||
vec![path_elem(0, 1, Future), path_elem(1, 1, Future)],
|
||||
Position::from(0)
|
||||
.witness_addrs(Level::from(2))
|
||||
.collect::<Vec<_>>()
|
||||
);
|
||||
assert_eq!(
|
||||
vec![path_elem(0, 3, Future), path_elem(1, 0, Past(0))],
|
||||
Position::from(2)
|
||||
.witness_addrs(Level::from(2))
|
||||
.collect::<Vec<_>>()
|
||||
);
|
||||
assert_eq!(
|
||||
vec![
|
||||
path_elem(0, 2, Past(0)),
|
||||
path_elem(1, 0, Past(1)),
|
||||
path_elem(2, 1, Future)
|
||||
],
|
||||
Position::from(3)
|
||||
.witness_addrs(Level::from(3))
|
||||
.collect::<Vec<_>>()
|
||||
);
|
||||
assert_eq!(
|
||||
vec![
|
||||
path_elem(0, 5, Future),
|
||||
path_elem(1, 3, Future),
|
||||
path_elem(2, 0, Past(0)),
|
||||
path_elem(3, 1, Future)
|
||||
],
|
||||
Position::from(4)
|
||||
.witness_addrs(Level::from(4))
|
||||
.collect::<Vec<_>>()
|
||||
);
|
||||
assert_eq!(
|
||||
vec![
|
||||
path_elem(0, 7, Future),
|
||||
path_elem(1, 2, Past(0)),
|
||||
path_elem(2, 0, Past(1)),
|
||||
path_elem(3, 1, Future)
|
||||
],
|
||||
Position::from(6)
|
||||
.witness_addrs(Level::from(4))
|
||||
.collect::<Vec<_>>()
|
||||
);
|
||||
}
|
||||
|
||||
#[test]
|
||||
fn address_current_incomplete() {
|
||||
let addr = |l, i| Address::from_parts(Level(l), i);
|
||||
assert_eq!(addr(0, 0), addr(0, 0).current_incomplete());
|
||||
assert_eq!(addr(1, 0), addr(0, 1).current_incomplete());
|
||||
|
|
@ -467,7 +572,7 @@ pub(crate) mod tests {
|
|||
}
|
||||
|
||||
#[test]
|
||||
fn next_incomplete_parent() {
|
||||
fn address_next_incomplete_parent() {
|
||||
let addr = |l, i| Address::from_parts(Level(l), i);
|
||||
assert_eq!(addr(1, 0), addr(0, 0).next_incomplete_parent());
|
||||
assert_eq!(addr(1, 0), addr(0, 1).next_incomplete_parent());
|
||||
|
|
|
|||
Loading…
Reference in New Issue