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use super::{
mmr::Mmr, BTreeMap, EmptySubtreeRoots, InnerNodeInfo, KvMap, MerkleError, MerklePath,
MerkleStoreDelta, MerkleTree, NodeIndex, PartialMerkleTree, RecordingMap, RootPath, Rpo256,
RpoDigest, SimpleSmt, TieredSmt, TryApplyDiff, ValuePath, Vec, EMPTY_WORD,
};
use crate::utils::{ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable};
use core::borrow::Borrow;
#[cfg(test)]
mod tests;
// MERKLE STORE
// ================================================================================================
/// A default [MerkleStore] which uses a simple [BTreeMap] as the backing storage.
pub type DefaultMerkleStore = MerkleStore<BTreeMap<RpoDigest, StoreNode>>;
/// A [MerkleStore] with recording capabilities which uses [RecordingMap] as the backing storage.
pub type RecordingMerkleStore = MerkleStore<RecordingMap<RpoDigest, StoreNode>>;
#[derive(Debug, Default, Copy, Clone, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub struct StoreNode {
left: RpoDigest,
right: RpoDigest,
}
/// An in-memory data store for Merkelized data.
///
/// This is a in memory data store for Merkle trees, this store allows all the nodes of multiple
/// trees to live as long as necessary and without duplication, this allows the implementation of
/// space efficient persistent data structures.
///
/// Example usage:
///
/// ```rust
/// # use miden_crypto::{ZERO, Felt, Word};
/// # use miden_crypto::merkle::{NodeIndex, MerkleStore, MerkleTree};
/// # use miden_crypto::hash::rpo::Rpo256;
/// # const fn int_to_node(value: u64) -> Word {
/// # [Felt::new(value), ZERO, ZERO, ZERO]
/// # }
/// # let A = int_to_node(1);
/// # let B = int_to_node(2);
/// # let C = int_to_node(3);
/// # let D = int_to_node(4);
/// # let E = int_to_node(5);
/// # let F = int_to_node(6);
/// # let G = int_to_node(7);
/// # let H0 = int_to_node(8);
/// # let H1 = int_to_node(9);
/// # let T0 = MerkleTree::new([A, B, C, D, E, F, G, H0].to_vec()).expect("even number of leaves provided");
/// # let T1 = MerkleTree::new([A, B, C, D, E, F, G, H1].to_vec()).expect("even number of leaves provided");
/// # let ROOT0 = T0.root();
/// # let ROOT1 = T1.root();
/// let mut store: MerkleStore = MerkleStore::new();
///
/// // the store is initialized with the SMT empty nodes
/// assert_eq!(store.num_internal_nodes(), 255);
///
/// let tree1 = MerkleTree::new(vec![A, B, C, D, E, F, G, H0]).unwrap();
/// let tree2 = MerkleTree::new(vec![A, B, C, D, E, F, G, H1]).unwrap();
///
/// // populates the store with two merkle trees, common nodes are shared
/// store.extend(tree1.inner_nodes());
/// store.extend(tree2.inner_nodes());
///
/// // every leaf except the last are the same
/// for i in 0..7 {
/// let idx0 = NodeIndex::new(3, i).unwrap();
/// let d0 = store.get_node(ROOT0, idx0).unwrap();
/// let idx1 = NodeIndex::new(3, i).unwrap();
/// let d1 = store.get_node(ROOT1, idx1).unwrap();
/// assert_eq!(d0, d1, "Both trees have the same leaf at pos {i}");
/// }
///
/// // The leafs A-B-C-D are the same for both trees, so are their 2 immediate parents
/// for i in 0..4 {
/// let idx0 = NodeIndex::new(3, i).unwrap();
/// let d0 = store.get_path(ROOT0, idx0).unwrap();
/// let idx1 = NodeIndex::new(3, i).unwrap();
/// let d1 = store.get_path(ROOT1, idx1).unwrap();
/// assert_eq!(d0.path[0..2], d1.path[0..2], "Both sub-trees are equal up to two levels");
/// }
///
/// // Common internal nodes are shared, the two added trees have a total of 30, but the store has
/// // only 10 new entries, corresponding to the 10 unique internal nodes of these trees.
/// assert_eq!(store.num_internal_nodes() - 255, 10);
/// ```
#[derive(Debug, Clone, Eq, PartialEq)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
pub struct MerkleStore<T: KvMap<RpoDigest, StoreNode> = BTreeMap<RpoDigest, StoreNode>> {
nodes: T,
}
impl<T: KvMap<RpoDigest, StoreNode>> Default for MerkleStore<T> {
fn default() -> Self {
Self::new()
}
}
impl<T: KvMap<RpoDigest, StoreNode>> MerkleStore<T> {
// CONSTRUCTORS
// --------------------------------------------------------------------------------------------
/// Creates an empty `MerkleStore` instance.
pub fn new() -> MerkleStore<T> {
// pre-populate the store with the empty hashes
let nodes = empty_hashes().into_iter().collect();
MerkleStore { nodes }
}
// PUBLIC ACCESSORS
// --------------------------------------------------------------------------------------------
/// Return a count of the non-leaf nodes in the store.
pub fn num_internal_nodes(&self) -> usize {
self.nodes.len()
}
/// Returns the node at `index` rooted on the tree `root`.
///
/// # Errors
/// This method can return the following errors:
/// - `RootNotInStore` if the `root` is not present in the store.
/// - `NodeNotInStore` if a node needed to traverse from `root` to `index` is not present in
/// the store.
pub fn get_node(&self, root: RpoDigest, index: NodeIndex) -> Result<RpoDigest, MerkleError> {
let mut hash = root;
// corner case: check the root is in the store when called with index `NodeIndex::root()`
self.nodes.get(&hash).ok_or(MerkleError::RootNotInStore(hash))?;
for i in (0..index.depth()).rev() {
let node = self.nodes.get(&hash).ok_or(MerkleError::NodeNotInStore(hash, index))?;
let bit = (index.value() >> i) & 1;
hash = if bit == 0 { node.left } else { node.right }
}
Ok(hash)
}
/// Returns the node at the specified `index` and its opening to the `root`.
///
/// The path starts at the sibling of the target leaf.
///
/// # Errors
/// This method can return the following errors:
/// - `RootNotInStore` if the `root` is not present in the store.
/// - `NodeNotInStore` if a node needed to traverse from `root` to `index` is not present in
/// the store.
pub fn get_path(&self, root: RpoDigest, index: NodeIndex) -> Result<ValuePath, MerkleError> {
let mut hash = root;
let mut path = Vec::with_capacity(index.depth().into());
// corner case: check the root is in the store when called with index `NodeIndex::root()`
self.nodes.get(&hash).ok_or(MerkleError::RootNotInStore(hash))?;
for i in (0..index.depth()).rev() {
let node = self.nodes.get(&hash).ok_or(MerkleError::NodeNotInStore(hash, index))?;
let bit = (index.value() >> i) & 1;
hash = if bit == 0 {
path.push(node.right);
node.left
} else {
path.push(node.left);
node.right
}
}
// the path is computed from root to leaf, so it must be reversed
path.reverse();
Ok(ValuePath::new(hash, path))
}
// LEAF TRAVERSAL
// --------------------------------------------------------------------------------------------
/// Returns the depth of the first leaf or an empty node encountered while traversing the tree
/// from the specified root down according to the provided index.
///
/// The `tree_depth` parameter specifies the depth of the tree rooted at `root`. The
/// maximum value the argument accepts is [u64::BITS].
///
/// # Errors
/// Will return an error if:
/// - The provided root is not found.
/// - The provided `tree_depth` is greater than 64.
/// - The provided `index` is not valid for a depth equivalent to `tree_depth`.
/// - No leaf or an empty node was found while traversing the tree down to `tree_depth`.
pub fn get_leaf_depth(
&self,
root: RpoDigest,
tree_depth: u8,
index: u64,
) -> Result<u8, MerkleError> {
// validate depth and index
if tree_depth > 64 {
return Err(MerkleError::DepthTooBig(tree_depth as u64));
}
NodeIndex::new(tree_depth, index)?;
// check if the root exists, providing the proper error report if it doesn't
let empty = EmptySubtreeRoots::empty_hashes(tree_depth);
let mut hash = root;
if !self.nodes.contains_key(&hash) {
return Err(MerkleError::RootNotInStore(hash));
}
// we traverse from root to leaf, so the path is reversed
let mut path = (index << (64 - tree_depth)).reverse_bits();
// iterate every depth and reconstruct the path from root to leaf
for depth in 0..=tree_depth {
// we short-circuit if an empty node has been found
if hash == empty[depth as usize] {
return Ok(depth);
}
// fetch the children pair, mapped by its parent hash
let children = match self.nodes.get(&hash) {
Some(node) => node,
None => return Ok(depth),
};
// traverse down
hash = if path & 1 == 0 { children.left } else { children.right };
path >>= 1;
}
// return an error because we exhausted the index but didn't find either a leaf or an
// empty node
Err(MerkleError::DepthTooBig(tree_depth as u64 + 1))
}
/// Returns index and value of a leaf node which is the only leaf node in a subtree defined by
/// the provided root. If the subtree contains zero or more than one leaf nodes None is
/// returned.
///
/// The `tree_depth` parameter specifies the depth of the parent tree such that `root` is
/// located in this tree at `root_index`. The maximum value the argument accepts is
/// [u64::BITS].
///
/// # Errors
/// Will return an error if:
/// - The provided root is not found.
/// - The provided `tree_depth` is greater than 64.
/// - The provided `root_index` has depth greater than `tree_depth`.
/// - A lone node at depth `tree_depth` is not a leaf node.
pub fn find_lone_leaf(
&self,
root: RpoDigest,
root_index: NodeIndex,
tree_depth: u8,
) -> Result<Option<(NodeIndex, RpoDigest)>, MerkleError> {
// we set max depth at u64::BITS as this is the largest meaningful value for a 64-bit index
const MAX_DEPTH: u8 = u64::BITS as u8;
if tree_depth > MAX_DEPTH {
return Err(MerkleError::DepthTooBig(tree_depth as u64));
}
let empty = EmptySubtreeRoots::empty_hashes(MAX_DEPTH);
let mut node = root;
if !self.nodes.contains_key(&node) {
return Err(MerkleError::RootNotInStore(node));
}
let mut index = root_index;
if index.depth() > tree_depth {
return Err(MerkleError::DepthTooBig(index.depth() as u64));
}
// traverse down following the path of single non-empty nodes; this works because if a
// node has two empty children it cannot contain a lone leaf. similarly if a node has
// two non-empty children it must contain at least two leaves.
for depth in index.depth()..tree_depth {
// if the node is a leaf, return; otherwise, examine the node's children
let children = match self.nodes.get(&node) {
Some(node) => node,
None => return Ok(Some((index, node))),
};
let empty_node = empty[depth as usize + 1];
node = if children.left != empty_node && children.right == empty_node {
index = index.left_child();
children.left
} else if children.left == empty_node && children.right != empty_node {
index = index.right_child();
children.right
} else {
return Ok(None);
};
}
// if we are here, we got to `tree_depth`; thus, either the current node is a leaf node,
// and so we return it, or it is an internal node, and then we return an error
if self.nodes.contains_key(&node) {
Err(MerkleError::DepthTooBig(tree_depth as u64 + 1))
} else {
Ok(Some((index, node)))
}
}
// DATA EXTRACTORS
// --------------------------------------------------------------------------------------------
/// Returns a subset of this Merkle store such that the returned Merkle store contains all
/// nodes which are descendants of the specified roots.
///
/// The roots for which no descendants exist in this Merkle store are ignored.
pub fn subset<I, R>(&self, roots: I) -> MerkleStore<T>
where
I: Iterator<Item = R>,
R: Borrow<RpoDigest>,
{
let mut store = MerkleStore::new();
for root in roots {
let root = *root.borrow();
store.clone_tree_from(root, self);
}
store
}
/// Iterator over the inner nodes of the [MerkleStore].
pub fn inner_nodes(&self) -> impl Iterator<Item = InnerNodeInfo> + '_ {
self.nodes
.iter()
.map(|(r, n)| InnerNodeInfo { value: *r, left: n.left, right: n.right })
}
/// Iterator over the non-empty leaves of the Merkle tree associated with the specified `root`
/// and `max_depth`.
pub fn non_empty_leaves(
&self,
root: RpoDigest,
max_depth: u8,
) -> impl Iterator<Item = (NodeIndex, RpoDigest)> + '_ {
let empty_roots = EmptySubtreeRoots::empty_hashes(max_depth);
let mut stack = Vec::new();
stack.push((NodeIndex::new_unchecked(0, 0), root));
core::iter::from_fn(move || {
while let Some((index, node_hash)) = stack.pop() {
// if we are at the max depth then we have reached a leaf
if index.depth() == max_depth {
return Some((index, node_hash));
}
// fetch the nodes children and push them onto the stack if they are not the roots
// of empty subtrees
if let Some(node) = self.nodes.get(&node_hash) {
if !empty_roots.contains(&node.left) {
stack.push((index.left_child(), node.left));
}
if !empty_roots.contains(&node.right) {
stack.push((index.right_child(), node.right));
}
// if the node is not in the store assume it is a leaf
} else {
// assert that if we have a leaf that is not at the max depth then it must be
// at the depth of one of the tiers of an TSMT.
debug_assert!(TieredSmt::TIER_DEPTHS[..3].contains(&index.depth()));
return Some((index, node_hash));
}
}
None
})
}
// STATE MUTATORS
// --------------------------------------------------------------------------------------------
/// Adds all the nodes of a Merkle path represented by `path`, opening to `node`. Returns the
/// new root.
///
/// This will compute the sibling elements determined by the Merkle `path` and `node`, and
/// include all the nodes into the store.
pub fn add_merkle_path(
&mut self,
index: u64,
node: RpoDigest,
path: MerklePath,
) -> Result<RpoDigest, MerkleError> {
let root = path.inner_nodes(index, node)?.fold(RpoDigest::default(), |_, node| {
let value: RpoDigest = node.value;
let left: RpoDigest = node.left;
let right: RpoDigest = node.right;
debug_assert_eq!(Rpo256::merge(&[left, right]), value);
self.nodes.insert(value, StoreNode { left, right });
node.value
});
Ok(root)
}
/// Adds all the nodes of multiple Merkle paths into the store.
///
/// This will compute the sibling elements for each Merkle `path` and include all the nodes
/// into the store.
///
/// For further reference, check [MerkleStore::add_merkle_path].
pub fn add_merkle_paths<I>(&mut self, paths: I) -> Result<(), MerkleError>
where
I: IntoIterator<Item = (u64, RpoDigest, MerklePath)>,
{
for (index_value, node, path) in paths.into_iter() {
self.add_merkle_path(index_value, node, path)?;
}
Ok(())
}
/// Sets a node to `value`.
///
/// # Errors
/// This method can return the following errors:
/// - `RootNotInStore` if the `root` is not present in the store.
/// - `NodeNotInStore` if a node needed to traverse from `root` to `index` is not present in
/// the store.
pub fn set_node(
&mut self,
mut root: RpoDigest,
index: NodeIndex,
value: RpoDigest,
) -> Result<RootPath, MerkleError> {
let node = value;
let ValuePath { value, path } = self.get_path(root, index)?;
// performs the update only if the node value differs from the opening
if node != value {
root = self.add_merkle_path(index.value(), node, path.clone())?;
}
Ok(RootPath { root, path })
}
/// Merges two elements and adds the resulting node into the store.
///
/// Merges arbitrary values. They may be leafs, nodes, or a mixture of both.
pub fn merge_roots(
&mut self,
left_root: RpoDigest,
right_root: RpoDigest,
) -> Result<RpoDigest, MerkleError> {
let parent = Rpo256::merge(&[left_root, right_root]);
self.nodes.insert(parent, StoreNode { left: left_root, right: right_root });
Ok(parent)
}
// DESTRUCTURING
// --------------------------------------------------------------------------------------------
/// Returns the inner storage of this MerkleStore while consuming `self`.
pub fn into_inner(self) -> T {
self.nodes
}
// HELPER METHODS
// --------------------------------------------------------------------------------------------
/// Recursively clones a tree with the specified root from the specified source into self.
///
/// If the source store does not contain a tree with the specified root, this is a noop.
fn clone_tree_from(&mut self, root: RpoDigest, source: &Self) {
// process the node only if it is in the source
if let Some(node) = source.nodes.get(&root) {
// if the node has already been inserted, no need to process it further as all of its
// descendants should be already cloned from the source store
if self.nodes.insert(root, *node).is_none() {
self.clone_tree_from(node.left, source);
self.clone_tree_from(node.right, source);
}
}
}
}
// CONVERSIONS
// ================================================================================================
impl<T: KvMap<RpoDigest, StoreNode>> From<&MerkleTree> for MerkleStore<T> {
fn from(value: &MerkleTree) -> Self {
let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
Self { nodes }
}
}
impl<T: KvMap<RpoDigest, StoreNode>> From<&SimpleSmt> for MerkleStore<T> {
fn from(value: &SimpleSmt) -> Self {
let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
Self { nodes }
}
}
impl<T: KvMap<RpoDigest, StoreNode>> From<&Mmr> for MerkleStore<T> {
fn from(value: &Mmr) -> Self {
let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
Self { nodes }
}
}
impl<T: KvMap<RpoDigest, StoreNode>> From<&TieredSmt> for MerkleStore<T> {
fn from(value: &TieredSmt) -> Self {
let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
Self { nodes }
}
}
impl<T: KvMap<RpoDigest, StoreNode>> From<&PartialMerkleTree> for MerkleStore<T> {
fn from(value: &PartialMerkleTree) -> Self {
let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
Self { nodes }
}
}
impl<T: KvMap<RpoDigest, StoreNode>> From<T> for MerkleStore<T> {
fn from(values: T) -> Self {
let nodes = values.into_iter().chain(empty_hashes()).collect();
Self { nodes }
}
}
impl<T: KvMap<RpoDigest, StoreNode>> FromIterator<InnerNodeInfo> for MerkleStore<T> {
fn from_iter<I: IntoIterator<Item = InnerNodeInfo>>(iter: I) -> Self {
let nodes = combine_nodes_with_empty_hashes(iter).collect();
Self { nodes }
}
}
impl<T: KvMap<RpoDigest, StoreNode>> FromIterator<(RpoDigest, StoreNode)> for MerkleStore<T> {
fn from_iter<I: IntoIterator<Item = (RpoDigest, StoreNode)>>(iter: I) -> Self {
let nodes = iter.into_iter().chain(empty_hashes()).collect();
Self { nodes }
}
}
// ITERATORS
// ================================================================================================
impl<T: KvMap<RpoDigest, StoreNode>> Extend<InnerNodeInfo> for MerkleStore<T> {
fn extend<I: IntoIterator<Item = InnerNodeInfo>>(&mut self, iter: I) {
self.nodes.extend(
iter.into_iter()
.map(|info| (info.value, StoreNode { left: info.left, right: info.right })),
);
}
}
// DiffT & ApplyDiffT TRAIT IMPLEMENTATION
// ================================================================================================
impl<T: KvMap<RpoDigest, StoreNode>> TryApplyDiff<RpoDigest, StoreNode> for MerkleStore<T> {
type Error = MerkleError;
type DiffType = MerkleStoreDelta;
fn try_apply(&mut self, diff: Self::DiffType) -> Result<(), MerkleError> {
for (root, delta) in diff.0 {
let mut root = root;
for cleared_slot in delta.cleared_slots() {
root = self
.set_node(
root,
NodeIndex::new(delta.depth(), *cleared_slot)?,
EMPTY_WORD.into(),
)?
.root;
}
for (updated_slot, updated_value) in delta.updated_slots() {
root = self
.set_node(
root,
NodeIndex::new(delta.depth(), *updated_slot)?,
(*updated_value).into(),
)?
.root;
}
}
Ok(())
}
}
// SERIALIZATION
// ================================================================================================
impl Serializable for StoreNode {
fn write_into<W: ByteWriter>(&self, target: &mut W) {
self.left.write_into(target);
self.right.write_into(target);
}
}
impl Deserializable for StoreNode {
fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
let left = RpoDigest::read_from(source)?;
let right = RpoDigest::read_from(source)?;
Ok(StoreNode { left, right })
}
}
impl<T: KvMap<RpoDigest, StoreNode>> Serializable for MerkleStore<T> {
fn write_into<W: ByteWriter>(&self, target: &mut W) {
target.write_u64(self.nodes.len() as u64);
for (k, v) in self.nodes.iter() {
k.write_into(target);
v.write_into(target);
}
}
}
impl<T: KvMap<RpoDigest, StoreNode>> Deserializable for MerkleStore<T> {
fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
let len = source.read_u64()?;
let mut nodes: Vec<(RpoDigest, StoreNode)> = Vec::with_capacity(len as usize);
for _ in 0..len {
let key = RpoDigest::read_from(source)?;
let value = StoreNode::read_from(source)?;
nodes.push((key, value));
}
Ok(nodes.into_iter().collect())
}
}
// HELPER FUNCTIONS
// ================================================================================================
/// Creates empty hashes for all the subtrees of a tree with a max depth of 255.
fn empty_hashes() -> impl IntoIterator<Item = (RpoDigest, StoreNode)> {
let subtrees = EmptySubtreeRoots::empty_hashes(255);
subtrees
.iter()
.rev()
.copied()
.zip(subtrees.iter().rev().skip(1).copied())
.map(|(child, parent)| (parent, StoreNode { left: child, right: child }))
}
/// Consumes an iterator of [InnerNodeInfo] and returns an iterator of `(value, node)` tuples
/// which includes the nodes associate with roots of empty subtrees up to a depth of 255.
fn combine_nodes_with_empty_hashes(
nodes: impl IntoIterator<Item = InnerNodeInfo>,
) -> impl Iterator<Item = (RpoDigest, StoreNode)> {
nodes
.into_iter()
.map(|info| (info.value, StoreNode { left: info.left, right: info.right }))
.chain(empty_hashes())
}