miden-crypto/src/merkle/store/mod.rs
src/merkle/store/mod.rsRaw
1use super::{
2 mmr::Mmr, BTreeMap, EmptySubtreeRoots, InnerNodeInfo, KvMap, MerkleError, MerklePath,
3 MerkleTree, NodeIndex, PartialMerkleTree, RecordingMap, RootPath, Rpo256, RpoDigest, SimpleSmt,
4 Smt, ValuePath, Vec,
5};
6use crate::utils::{ByteReader, ByteWriter, Deserializable, DeserializationError, Serializable};
7use core::borrow::Borrow;
8
9#[cfg(test)]
10mod tests;
11
12// MERKLE STORE
13// ================================================================================================
14
15/// A default [MerkleStore] which uses a simple [BTreeMap] as the backing storage.
16pub type DefaultMerkleStore = MerkleStore<BTreeMap<RpoDigest, StoreNode>>;
17
18/// A [MerkleStore] with recording capabilities which uses [RecordingMap] as the backing storage.
19pub type RecordingMerkleStore = MerkleStore<RecordingMap<RpoDigest, StoreNode>>;
20
21#[derive(Debug, Default, Copy, Clone, Eq, PartialEq)]
22#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
23pub struct StoreNode {
24 left: RpoDigest,
25 right: RpoDigest,
26}
27
28/// An in-memory data store for Merkelized data.
29///
30/// This is a in memory data store for Merkle trees, this store allows all the nodes of multiple
31/// trees to live as long as necessary and without duplication, this allows the implementation of
32/// space efficient persistent data structures.
33///
34/// Example usage:
35///
36/// ```rust
37/// # use miden_crypto::{ZERO, Felt, Word};
38/// # use miden_crypto::merkle::{NodeIndex, MerkleStore, MerkleTree};
39/// # use miden_crypto::hash::rpo::Rpo256;
40/// # const fn int_to_node(value: u64) -> Word {
41/// # [Felt::new(value), ZERO, ZERO, ZERO]
42/// # }
43/// # let A = int_to_node(1);
44/// # let B = int_to_node(2);
45/// # let C = int_to_node(3);
46/// # let D = int_to_node(4);
47/// # let E = int_to_node(5);
48/// # let F = int_to_node(6);
49/// # let G = int_to_node(7);
50/// # let H0 = int_to_node(8);
51/// # let H1 = int_to_node(9);
52/// # let T0 = MerkleTree::new([A, B, C, D, E, F, G, H0].to_vec()).expect("even number of leaves provided");
53/// # let T1 = MerkleTree::new([A, B, C, D, E, F, G, H1].to_vec()).expect("even number of leaves provided");
54/// # let ROOT0 = T0.root();
55/// # let ROOT1 = T1.root();
56/// let mut store: MerkleStore = MerkleStore::new();
57///
58/// // the store is initialized with the SMT empty nodes
59/// assert_eq!(store.num_internal_nodes(), 255);
60///
61/// let tree1 = MerkleTree::new(vec![A, B, C, D, E, F, G, H0]).unwrap();
62/// let tree2 = MerkleTree::new(vec![A, B, C, D, E, F, G, H1]).unwrap();
63///
64/// // populates the store with two merkle trees, common nodes are shared
65/// store.extend(tree1.inner_nodes());
66/// store.extend(tree2.inner_nodes());
67///
68/// // every leaf except the last are the same
69/// for i in 0..7 {
70/// let idx0 = NodeIndex::new(3, i).unwrap();
71/// let d0 = store.get_node(ROOT0, idx0).unwrap();
72/// let idx1 = NodeIndex::new(3, i).unwrap();
73/// let d1 = store.get_node(ROOT1, idx1).unwrap();
74/// assert_eq!(d0, d1, "Both trees have the same leaf at pos {i}");
75/// }
76///
77/// // The leafs A-B-C-D are the same for both trees, so are their 2 immediate parents
78/// for i in 0..4 {
79/// let idx0 = NodeIndex::new(3, i).unwrap();
80/// let d0 = store.get_path(ROOT0, idx0).unwrap();
81/// let idx1 = NodeIndex::new(3, i).unwrap();
82/// let d1 = store.get_path(ROOT1, idx1).unwrap();
83/// assert_eq!(d0.path[0..2], d1.path[0..2], "Both sub-trees are equal up to two levels");
84/// }
85///
86/// // Common internal nodes are shared, the two added trees have a total of 30, but the store has
87/// // only 10 new entries, corresponding to the 10 unique internal nodes of these trees.
88/// assert_eq!(store.num_internal_nodes() - 255, 10);
89/// ```
90#[derive(Debug, Clone, Eq, PartialEq)]
91#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
92pub struct MerkleStore<T: KvMap<RpoDigest, StoreNode> = BTreeMap<RpoDigest, StoreNode>> {
93 nodes: T,
94}
95
96impl<T: KvMap<RpoDigest, StoreNode>> Default for MerkleStore<T> {
97 fn default() -> Self {
98 Self::new()
99 }
100}
101
102impl<T: KvMap<RpoDigest, StoreNode>> MerkleStore<T> {
103 // CONSTRUCTORS
104 // --------------------------------------------------------------------------------------------
105
106 /// Creates an empty `MerkleStore` instance.
107 pub fn new() -> MerkleStore<T> {
108 // pre-populate the store with the empty hashes
109 let nodes = empty_hashes().into_iter().collect();
110 MerkleStore { nodes }
111 }
112
113 // PUBLIC ACCESSORS
114 // --------------------------------------------------------------------------------------------
115
116 /// Return a count of the non-leaf nodes in the store.
117 pub fn num_internal_nodes(&self) -> usize {
118 self.nodes.len()
119 }
120
121 /// Returns the node at `index` rooted on the tree `root`.
122 ///
123 /// # Errors
124 /// This method can return the following errors:
125 /// - `RootNotInStore` if the `root` is not present in the store.
126 /// - `NodeNotInStore` if a node needed to traverse from `root` to `index` is not present in
127 /// the store.
128 pub fn get_node(&self, root: RpoDigest, index: NodeIndex) -> Result<RpoDigest, MerkleError> {
129 let mut hash = root;
130
131 // corner case: check the root is in the store when called with index `NodeIndex::root()`
132 self.nodes.get(&hash).ok_or(MerkleError::RootNotInStore(hash))?;
133
134 for i in (0..index.depth()).rev() {
135 let node = self.nodes.get(&hash).ok_or(MerkleError::NodeNotInStore(hash, index))?;
136
137 let bit = (index.value() >> i) & 1;
138 hash = if bit == 0 { node.left } else { node.right }
139 }
140
141 Ok(hash)
142 }
143
144 /// Returns the node at the specified `index` and its opening to the `root`.
145 ///
146 /// The path starts at the sibling of the target leaf.
147 ///
148 /// # Errors
149 /// This method can return the following errors:
150 /// - `RootNotInStore` if the `root` is not present in the store.
151 /// - `NodeNotInStore` if a node needed to traverse from `root` to `index` is not present in
152 /// the store.
153 pub fn get_path(&self, root: RpoDigest, index: NodeIndex) -> Result<ValuePath, MerkleError> {
154 let mut hash = root;
155 let mut path = Vec::with_capacity(index.depth().into());
156
157 // corner case: check the root is in the store when called with index `NodeIndex::root()`
158 self.nodes.get(&hash).ok_or(MerkleError::RootNotInStore(hash))?;
159
160 for i in (0..index.depth()).rev() {
161 let node = self.nodes.get(&hash).ok_or(MerkleError::NodeNotInStore(hash, index))?;
162
163 let bit = (index.value() >> i) & 1;
164 hash = if bit == 0 {
165 path.push(node.right);
166 node.left
167 } else {
168 path.push(node.left);
169 node.right
170 }
171 }
172
173 // the path is computed from root to leaf, so it must be reversed
174 path.reverse();
175
176 Ok(ValuePath::new(hash, MerklePath::new(path)))
177 }
178
179 // LEAF TRAVERSAL
180 // --------------------------------------------------------------------------------------------
181
182 /// Returns the depth of the first leaf or an empty node encountered while traversing the tree
183 /// from the specified root down according to the provided index.
184 ///
185 /// The `tree_depth` parameter specifies the depth of the tree rooted at `root`. The
186 /// maximum value the argument accepts is [u64::BITS].
187 ///
188 /// # Errors
189 /// Will return an error if:
190 /// - The provided root is not found.
191 /// - The provided `tree_depth` is greater than 64.
192 /// - The provided `index` is not valid for a depth equivalent to `tree_depth`.
193 /// - No leaf or an empty node was found while traversing the tree down to `tree_depth`.
194 pub fn get_leaf_depth(
195 &self,
196 root: RpoDigest,
197 tree_depth: u8,
198 index: u64,
199 ) -> Result<u8, MerkleError> {
200 // validate depth and index
201 if tree_depth > 64 {
202 return Err(MerkleError::DepthTooBig(tree_depth as u64));
203 }
204 NodeIndex::new(tree_depth, index)?;
205
206 // check if the root exists, providing the proper error report if it doesn't
207 let empty = EmptySubtreeRoots::empty_hashes(tree_depth);
208 let mut hash = root;
209 if !self.nodes.contains_key(&hash) {
210 return Err(MerkleError::RootNotInStore(hash));
211 }
212
213 // we traverse from root to leaf, so the path is reversed
214 let mut path = (index << (64 - tree_depth)).reverse_bits();
215
216 // iterate every depth and reconstruct the path from root to leaf
217 for depth in 0..=tree_depth {
218 // we short-circuit if an empty node has been found
219 if hash == empty[depth as usize] {
220 return Ok(depth);
221 }
222
223 // fetch the children pair, mapped by its parent hash
224 let children = match self.nodes.get(&hash) {
225 Some(node) => node,
226 None => return Ok(depth),
227 };
228
229 // traverse down
230 hash = if path & 1 == 0 { children.left } else { children.right };
231 path >>= 1;
232 }
233
234 // return an error because we exhausted the index but didn't find either a leaf or an
235 // empty node
236 Err(MerkleError::DepthTooBig(tree_depth as u64 + 1))
237 }
238
239 /// Returns index and value of a leaf node which is the only leaf node in a subtree defined by
240 /// the provided root. If the subtree contains zero or more than one leaf nodes None is
241 /// returned.
242 ///
243 /// The `tree_depth` parameter specifies the depth of the parent tree such that `root` is
244 /// located in this tree at `root_index`. The maximum value the argument accepts is
245 /// [u64::BITS].
246 ///
247 /// # Errors
248 /// Will return an error if:
249 /// - The provided root is not found.
250 /// - The provided `tree_depth` is greater than 64.
251 /// - The provided `root_index` has depth greater than `tree_depth`.
252 /// - A lone node at depth `tree_depth` is not a leaf node.
253 pub fn find_lone_leaf(
254 &self,
255 root: RpoDigest,
256 root_index: NodeIndex,
257 tree_depth: u8,
258 ) -> Result<Option<(NodeIndex, RpoDigest)>, MerkleError> {
259 // we set max depth at u64::BITS as this is the largest meaningful value for a 64-bit index
260 const MAX_DEPTH: u8 = u64::BITS as u8;
261 if tree_depth > MAX_DEPTH {
262 return Err(MerkleError::DepthTooBig(tree_depth as u64));
263 }
264 let empty = EmptySubtreeRoots::empty_hashes(MAX_DEPTH);
265
266 let mut node = root;
267 if !self.nodes.contains_key(&node) {
268 return Err(MerkleError::RootNotInStore(node));
269 }
270
271 let mut index = root_index;
272 if index.depth() > tree_depth {
273 return Err(MerkleError::DepthTooBig(index.depth() as u64));
274 }
275
276 // traverse down following the path of single non-empty nodes; this works because if a
277 // node has two empty children it cannot contain a lone leaf. similarly if a node has
278 // two non-empty children it must contain at least two leaves.
279 for depth in index.depth()..tree_depth {
280 // if the node is a leaf, return; otherwise, examine the node's children
281 let children = match self.nodes.get(&node) {
282 Some(node) => node,
283 None => return Ok(Some((index, node))),
284 };
285
286 let empty_node = empty[depth as usize + 1];
287 node = if children.left != empty_node && children.right == empty_node {
288 index = index.left_child();
289 children.left
290 } else if children.left == empty_node && children.right != empty_node {
291 index = index.right_child();
292 children.right
293 } else {
294 return Ok(None);
295 };
296 }
297
298 // if we are here, we got to `tree_depth`; thus, either the current node is a leaf node,
299 // and so we return it, or it is an internal node, and then we return an error
300 if self.nodes.contains_key(&node) {
301 Err(MerkleError::DepthTooBig(tree_depth as u64 + 1))
302 } else {
303 Ok(Some((index, node)))
304 }
305 }
306
307 // DATA EXTRACTORS
308 // --------------------------------------------------------------------------------------------
309
310 /// Returns a subset of this Merkle store such that the returned Merkle store contains all
311 /// nodes which are descendants of the specified roots.
312 ///
313 /// The roots for which no descendants exist in this Merkle store are ignored.
314 pub fn subset<I, R>(&self, roots: I) -> MerkleStore<T>
315 where
316 I: Iterator<Item = R>,
317 R: Borrow<RpoDigest>,
318 {
319 let mut store = MerkleStore::new();
320 for root in roots {
321 let root = *root.borrow();
322 store.clone_tree_from(root, self);
323 }
324 store
325 }
326
327 /// Iterator over the inner nodes of the [MerkleStore].
328 pub fn inner_nodes(&self) -> impl Iterator<Item = InnerNodeInfo> + '_ {
329 self.nodes
330 .iter()
331 .map(|(r, n)| InnerNodeInfo { value: *r, left: n.left, right: n.right })
332 }
333
334 /// Iterator over the non-empty leaves of the Merkle tree associated with the specified `root`
335 /// and `max_depth`.
336 pub fn non_empty_leaves(
337 &self,
338 root: RpoDigest,
339 max_depth: u8,
340 ) -> impl Iterator<Item = (NodeIndex, RpoDigest)> + '_ {
341 let empty_roots = EmptySubtreeRoots::empty_hashes(max_depth);
342 let mut stack = Vec::new();
343 stack.push((NodeIndex::new_unchecked(0, 0), root));
344
345 core::iter::from_fn(move || {
346 while let Some((index, node_hash)) = stack.pop() {
347 // if we are at the max depth then we have reached a leaf
348 if index.depth() == max_depth {
349 return Some((index, node_hash));
350 }
351
352 // fetch the nodes children and push them onto the stack if they are not the roots
353 // of empty subtrees
354 if let Some(node) = self.nodes.get(&node_hash) {
355 if !empty_roots.contains(&node.left) {
356 stack.push((index.left_child(), node.left));
357 }
358 if !empty_roots.contains(&node.right) {
359 stack.push((index.right_child(), node.right));
360 }
361
362 // if the node is not in the store assume it is a leaf
363 } else {
364 return Some((index, node_hash));
365 }
366 }
367
368 None
369 })
370 }
371
372 // STATE MUTATORS
373 // --------------------------------------------------------------------------------------------
374
375 /// Adds all the nodes of a Merkle path represented by `path`, opening to `node`. Returns the
376 /// new root.
377 ///
378 /// This will compute the sibling elements determined by the Merkle `path` and `node`, and
379 /// include all the nodes into the store.
380 pub fn add_merkle_path(
381 &mut self,
382 index: u64,
383 node: RpoDigest,
384 path: MerklePath,
385 ) -> Result<RpoDigest, MerkleError> {
386 let root = path.inner_nodes(index, node)?.fold(RpoDigest::default(), |_, node| {
387 let value: RpoDigest = node.value;
388 let left: RpoDigest = node.left;
389 let right: RpoDigest = node.right;
390
391 debug_assert_eq!(Rpo256::merge(&[left, right]), value);
392 self.nodes.insert(value, StoreNode { left, right });
393
394 node.value
395 });
396 Ok(root)
397 }
398
399 /// Adds all the nodes of multiple Merkle paths into the store.
400 ///
401 /// This will compute the sibling elements for each Merkle `path` and include all the nodes
402 /// into the store.
403 ///
404 /// For further reference, check [MerkleStore::add_merkle_path].
405 pub fn add_merkle_paths<I>(&mut self, paths: I) -> Result<(), MerkleError>
406 where
407 I: IntoIterator<Item = (u64, RpoDigest, MerklePath)>,
408 {
409 for (index_value, node, path) in paths.into_iter() {
410 self.add_merkle_path(index_value, node, path)?;
411 }
412 Ok(())
413 }
414
415 /// Sets a node to `value`.
416 ///
417 /// # Errors
418 /// This method can return the following errors:
419 /// - `RootNotInStore` if the `root` is not present in the store.
420 /// - `NodeNotInStore` if a node needed to traverse from `root` to `index` is not present in
421 /// the store.
422 pub fn set_node(
423 &mut self,
424 mut root: RpoDigest,
425 index: NodeIndex,
426 value: RpoDigest,
427 ) -> Result<RootPath, MerkleError> {
428 let node = value;
429 let ValuePath { value, path } = self.get_path(root, index)?;
430
431 // performs the update only if the node value differs from the opening
432 if node != value {
433 root = self.add_merkle_path(index.value(), node, path.clone())?;
434 }
435
436 Ok(RootPath { root, path })
437 }
438
439 /// Merges two elements and adds the resulting node into the store.
440 ///
441 /// Merges arbitrary values. They may be leafs, nodes, or a mixture of both.
442 pub fn merge_roots(
443 &mut self,
444 left_root: RpoDigest,
445 right_root: RpoDigest,
446 ) -> Result<RpoDigest, MerkleError> {
447 let parent = Rpo256::merge(&[left_root, right_root]);
448 self.nodes.insert(parent, StoreNode { left: left_root, right: right_root });
449
450 Ok(parent)
451 }
452
453 // DESTRUCTURING
454 // --------------------------------------------------------------------------------------------
455
456 /// Returns the inner storage of this MerkleStore while consuming `self`.
457 pub fn into_inner(self) -> T {
458 self.nodes
459 }
460
461 // HELPER METHODS
462 // --------------------------------------------------------------------------------------------
463
464 /// Recursively clones a tree with the specified root from the specified source into self.
465 ///
466 /// If the source store does not contain a tree with the specified root, this is a noop.
467 fn clone_tree_from(&mut self, root: RpoDigest, source: &Self) {
468 // process the node only if it is in the source
469 if let Some(node) = source.nodes.get(&root) {
470 // if the node has already been inserted, no need to process it further as all of its
471 // descendants should be already cloned from the source store
472 if self.nodes.insert(root, *node).is_none() {
473 self.clone_tree_from(node.left, source);
474 self.clone_tree_from(node.right, source);
475 }
476 }
477 }
478}
479
480// CONVERSIONS
481// ================================================================================================
482
483impl<T: KvMap<RpoDigest, StoreNode>> From<&MerkleTree> for MerkleStore<T> {
484 fn from(value: &MerkleTree) -> Self {
485 let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
486 Self { nodes }
487 }
488}
489
490impl<T: KvMap<RpoDigest, StoreNode>, const DEPTH: u8> From<&SimpleSmt<DEPTH>> for MerkleStore<T> {
491 fn from(value: &SimpleSmt<DEPTH>) -> Self {
492 let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
493 Self { nodes }
494 }
495}
496
497impl<T: KvMap<RpoDigest, StoreNode>> From<&Smt> for MerkleStore<T> {
498 fn from(value: &Smt) -> Self {
499 let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
500 Self { nodes }
501 }
502}
503
504impl<T: KvMap<RpoDigest, StoreNode>> From<&Mmr> for MerkleStore<T> {
505 fn from(value: &Mmr) -> Self {
506 let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
507 Self { nodes }
508 }
509}
510
511impl<T: KvMap<RpoDigest, StoreNode>> From<&PartialMerkleTree> for MerkleStore<T> {
512 fn from(value: &PartialMerkleTree) -> Self {
513 let nodes = combine_nodes_with_empty_hashes(value.inner_nodes()).collect();
514 Self { nodes }
515 }
516}
517
518impl<T: KvMap<RpoDigest, StoreNode>> From<T> for MerkleStore<T> {
519 fn from(values: T) -> Self {
520 let nodes = values.into_iter().chain(empty_hashes()).collect();
521 Self { nodes }
522 }
523}
524
525impl<T: KvMap<RpoDigest, StoreNode>> FromIterator<InnerNodeInfo> for MerkleStore<T> {
526 fn from_iter<I: IntoIterator<Item = InnerNodeInfo>>(iter: I) -> Self {
527 let nodes = combine_nodes_with_empty_hashes(iter).collect();
528 Self { nodes }
529 }
530}
531
532impl<T: KvMap<RpoDigest, StoreNode>> FromIterator<(RpoDigest, StoreNode)> for MerkleStore<T> {
533 fn from_iter<I: IntoIterator<Item = (RpoDigest, StoreNode)>>(iter: I) -> Self {
534 let nodes = iter.into_iter().chain(empty_hashes()).collect();
535 Self { nodes }
536 }
537}
538
539// ITERATORS
540// ================================================================================================
541impl<T: KvMap<RpoDigest, StoreNode>> Extend<InnerNodeInfo> for MerkleStore<T> {
542 fn extend<I: IntoIterator<Item = InnerNodeInfo>>(&mut self, iter: I) {
543 self.nodes.extend(
544 iter.into_iter()
545 .map(|info| (info.value, StoreNode { left: info.left, right: info.right })),
546 );
547 }
548}
549
550// SERIALIZATION
551// ================================================================================================
552
553impl Serializable for StoreNode {
554 fn write_into<W: ByteWriter>(&self, target: &mut W) {
555 self.left.write_into(target);
556 self.right.write_into(target);
557 }
558}
559
560impl Deserializable for StoreNode {
561 fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
562 let left = RpoDigest::read_from(source)?;
563 let right = RpoDigest::read_from(source)?;
564 Ok(StoreNode { left, right })
565 }
566}
567
568impl<T: KvMap<RpoDigest, StoreNode>> Serializable for MerkleStore<T> {
569 fn write_into<W: ByteWriter>(&self, target: &mut W) {
570 target.write_u64(self.nodes.len() as u64);
571
572 for (k, v) in self.nodes.iter() {
573 k.write_into(target);
574 v.write_into(target);
575 }
576 }
577}
578
579impl<T: KvMap<RpoDigest, StoreNode>> Deserializable for MerkleStore<T> {
580 fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
581 let len = source.read_u64()?;
582 let mut nodes: Vec<(RpoDigest, StoreNode)> = Vec::with_capacity(len as usize);
583
584 for _ in 0..len {
585 let key = RpoDigest::read_from(source)?;
586 let value = StoreNode::read_from(source)?;
587 nodes.push((key, value));
588 }
589
590 Ok(nodes.into_iter().collect())
591 }
592}
593
594// HELPER FUNCTIONS
595// ================================================================================================
596
597/// Creates empty hashes for all the subtrees of a tree with a max depth of 255.
598fn empty_hashes() -> impl IntoIterator<Item = (RpoDigest, StoreNode)> {
599 let subtrees = EmptySubtreeRoots::empty_hashes(255);
600 subtrees
601 .iter()
602 .rev()
603 .copied()
604 .zip(subtrees.iter().rev().skip(1).copied())
605 .map(|(child, parent)| (parent, StoreNode { left: child, right: child }))
606}
607
608/// Consumes an iterator of [InnerNodeInfo] and returns an iterator of `(value, node)` tuples
609/// which includes the nodes associate with roots of empty subtrees up to a depth of 255.
610fn combine_nodes_with_empty_hashes(
611 nodes: impl IntoIterator<Item = InnerNodeInfo>,
612) -> impl Iterator<Item = (RpoDigest, StoreNode)> {
613 nodes
614 .into_iter()
615 .map(|info| (info.value, StoreNode { left: info.left, right: info.right }))
616 .chain(empty_hashes())
617}