feat: add inner node iterator to MerklePath

src/merkle/merkle_tree.rs

@@ -150,9 +150,11 @@ impl MerkleTree {
         Ok(())
     }
 
-    /// An iterator over every inner node in the tree. The iterator order is unspecified.
-    pub fn inner_nodes(&self) -> MerkleTreeNodes<'_> {
-        MerkleTreeNodes {
+    /// Returns n iterator over every inner node of this [MerkleTree].
+    ///
+    /// The iterator order is unspecified.
+    pub fn inner_nodes(&self) -> InnerNodeIterator<'_> {
+        InnerNodeIterator {
             nodes: &self.nodes,
             index: 1, // index 0 is just padding, start at 1
         }
@@ -165,12 +167,12 @@ impl MerkleTree {
 /// An iterator over every inner node of the [MerkleTree].
 ///
 /// Use this to extract the data of the tree, there is no guarantee on the order of the elements.
-pub struct MerkleTreeNodes<'a> {
+pub struct InnerNodeIterator<'a> {
     nodes: &'a Vec<Word>,
     index: usize,
 }
 
-impl<'a> Iterator for MerkleTreeNodes<'a> {
+impl<'a> Iterator for InnerNodeIterator<'a> {
     type Item = InnerNodeInfo;
 
     fn next(&mut self) -> Option<Self::Item> {

src/merkle/path.rs

@@ -1,4 +1,4 @@
-use super::{vec, MerkleError, NodeIndex, Rpo256, Vec, Word};
+use super::{vec, InnerNodeInfo, MerkleError, NodeIndex, Rpo256, Vec, Word};
 use core::ops::{Deref, DerefMut};
 
 // MERKLE PATH
@@ -22,6 +22,11 @@ impl MerklePath {
     // PROVIDERS
     // --------------------------------------------------------------------------------------------
 
+    /// Returns the depth in which this Merkle path proof is valid.
+    pub fn depth(&self) -> u8 {
+        self.nodes.len() as u8
+    }
+
     /// Computes the merkle root for this opening.
     pub fn compute_root(&self, index: u64, node: Word) -> Result<Word, MerkleError> {
         let mut index = NodeIndex::new(self.depth(), index)?;
@@ -34,11 +39,6 @@ impl MerklePath {
         Ok(root)
     }
 
-    /// Returns the depth in which this Merkle path proof is valid.
-    pub fn depth(&self) -> u8 {
-        self.nodes.len() as u8
-    }
-
     /// Verifies the Merkle opening proof towards the provided root.
     ///
     /// Returns `true` if `node` exists at `index` in a Merkle tree with `root`.
@@ -48,6 +48,20 @@ impl MerklePath {
             Err(_) => false,
         }
     }
+
+    /// Returns an iterator over every inner node of this [MerklePath].
+    ///
+    /// The iteration order is unspecified.
+    ///
+    /// # Errors
+    /// Returns an error if the specified index is not valid for this path.
+    pub fn inner_nodes(&self, index: u64, node: Word) -> Result<InnerNodeIterator, MerkleError> {
+        Ok(InnerNodeIterator {
+            nodes: &self.nodes,
+            index: NodeIndex::new(self.depth(), index)?,
+            value: node,
+        })
+    }
 }
 
 impl From<Vec<Word>> for MerklePath {
@@ -72,6 +86,9 @@ impl DerefMut for MerklePath {
     }
 }
 
+// ITERATORS
+// ================================================================================================
+
 impl FromIterator<Word> for MerklePath {
     fn from_iter<T: IntoIterator<Item = Word>>(iter: T) -> Self {
         Self::new(iter.into_iter().collect())
@@ -87,6 +104,39 @@ impl IntoIterator for MerklePath {
     }
 }
 
+/// An iterator over internal nodes of a [MerklePath].
+pub struct InnerNodeIterator<'a> {
+    nodes: &'a Vec<Word>,
+    index: NodeIndex,
+    value: Word,
+}
+
+impl<'a> Iterator for InnerNodeIterator<'a> {
+    type Item = InnerNodeInfo;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if !self.index.is_root() {
+            let sibling_pos = self.nodes.len() - self.index.depth() as usize;
+            let (left, right) = if self.index.is_value_odd() {
+                (self.nodes[sibling_pos], self.value)
+            } else {
+                (self.value, self.nodes[sibling_pos])
+            };
+
+            self.value = Rpo256::merge(&[left.into(), right.into()]).into();
+            self.index.move_up();
+
+            Some(InnerNodeInfo {
+                value: self.value,
+                left,
+                right,
+            })
+        } else {
+            None
+        }
+    }
+}
+
 // MERKLE PATH CONTAINERS
 // ================================================================================================
 
@@ -110,3 +160,25 @@ pub struct RootPath {
     /// The path from `value` to `root` (exclusive).
     pub path: MerklePath,
 }
+
+// TESTS
+// ================================================================================================
+
+#[cfg(test)]
+mod tests {
+    use crate::merkle::{int_to_node, MerklePath};
+
+    #[test]
+    fn test_inner_nodes() {
+        let nodes = vec![int_to_node(1), int_to_node(2), int_to_node(3), int_to_node(4)];
+        let merkle_path = MerklePath::new(nodes);
+
+        let index = 6;
+        let node = int_to_node(5);
+        let root = merkle_path.compute_root(index, node).unwrap();
+
+        let inner_root = merkle_path.inner_nodes(index, node).unwrap().last().unwrap().value;
+
+        assert_eq!(root, inner_root);
+    }
+}

src/merkle/store/mod.rs

@@ -115,26 +115,6 @@ impl MerkleStore {
         MerkleStore { nodes }
     }
 
-    /// Appends the provided merkle path set.
-    pub fn with_merkle_path(
-        mut self,
-        index_value: u64,
-        node: Word,
-        path: MerklePath,
-    ) -> Result<Self, MerkleError> {
-        self.add_merkle_path(index_value, node, path)?;
-        Ok(self)
-    }
-
-    /// Appends the provided merkle path set.
-    pub fn with_merkle_paths<I>(mut self, paths: I) -> Result<Self, MerkleError>
-    where
-        I: IntoIterator<Item = (u64, Word, MerklePath)>,
-    {
-        self.add_merkle_paths(paths)?;
-        Ok(self)
-    }
-
     // PUBLIC ACCESSORS
     // --------------------------------------------------------------------------------------------
 
@@ -280,8 +260,11 @@ impl MerkleStore {
     // STATE MUTATORS
     // --------------------------------------------------------------------------------------------
 
-    /// Adds a new [InnerNodeInfo] into the store.
-    pub fn extend(&mut self, iter: impl Iterator<Item = InnerNodeInfo>) -> &mut MerkleStore {
+    /// Adds a sequence of nodes yielded by the provided iterator into the store.
+    pub fn extend<I>(&mut self, iter: I) -> &mut MerkleStore
+    where
+        I: Iterator<Item = InnerNodeInfo>,
+    {
         for node in iter {
             let value: RpoDigest = node.value.into();
             let left: RpoDigest = node.left.into();
@@ -301,31 +284,21 @@ impl MerkleStore {
     /// include all the nodes into the store.
     pub fn add_merkle_path(
         &mut self,
-        index_value: u64,
-        mut node: Word,
+        index: u64,
+        node: Word,
         path: MerklePath,
     ) -> Result<Word, MerkleError> {
-        let mut index = NodeIndex::new(path.len() as u8, index_value)?;
+        let root = path.inner_nodes(index, node)?.fold(Word::default(), |_, node| {
+            let value: RpoDigest = node.value.into();
+            let left: RpoDigest = node.left.into();
+            let right: RpoDigest = node.right.into();
 
-        for sibling in path {
-            let (left, right) = match index.is_value_odd() {
-                true => (sibling, node),
-                false => (node, sibling),
-            };
-            let parent = Rpo256::merge(&[left.into(), right.into()]);
-            self.nodes.insert(
-                parent,
-                Node {
-                    left: left.into(),
-                    right: right.into(),
-                },
-            );
-
-            index.move_up();
-            node = parent.into();
-        }
+            debug_assert_eq!(Rpo256::merge(&[left, right]), value);
+            self.nodes.insert(value, Node { left, right });
 
-        Ok(node)
+            node.value
+        });
+        Ok(root)
     }
 
     /// Adds all the nodes of multiple Merkle paths into the store.

src/merkle/store/tests.rs

@@ -547,12 +547,14 @@ fn test_constructors() -> Result<(), MerkleError> {
         (3, LEAVES4[3], mtree.get_path(NodeIndex::make(d, 3)).unwrap()),
     ];
 
-    let store1 = MerkleStore::default().with_merkle_paths(paths.clone())?;
-    let store2 = MerkleStore::default()
-        .with_merkle_path(0, LEAVES4[0], mtree.get_path(NodeIndex::make(d, 0))?)?
-        .with_merkle_path(1, LEAVES4[1], mtree.get_path(NodeIndex::make(d, 1))?)?
-        .with_merkle_path(2, LEAVES4[2], mtree.get_path(NodeIndex::make(d, 2))?)?
-        .with_merkle_path(3, LEAVES4[3], mtree.get_path(NodeIndex::make(d, 3))?)?;
+    let mut store1 = MerkleStore::default();
+    store1.add_merkle_paths(paths.clone())?;
+
+    let mut store2 = MerkleStore::default();
+    store2.add_merkle_path(0, LEAVES4[0], mtree.get_path(NodeIndex::make(d, 0))?)?;
+    store2.add_merkle_path(1, LEAVES4[1], mtree.get_path(NodeIndex::make(d, 1))?)?;
+    store2.add_merkle_path(2, LEAVES4[2], mtree.get_path(NodeIndex::make(d, 2))?)?;
+    store2.add_merkle_path(3, LEAVES4[3], mtree.get_path(NodeIndex::make(d, 3))?)?;
     let set = MerklePathSet::new(d).with_paths(paths).unwrap();
 
     for key in [0, 1, 2, 3] {