Merge pull request #195 from 0xPolygonMiden/hacka-partial-mmr2

mmr: added partial mmr

CHANGELOG.md

@@ -12,6 +12,7 @@
 * Implemented benchmarking for `TieredSmt` (#182).
 * Added more leaf traversal methods for `MerkleStore` (#185).
 * Added SVE acceleration for RPO hash function (#189).
+* Implemented the `PartialMmr` datastructure (#195).
 
 ## 0.6.0 (2023-06-25)
 

src/merkle/merkle_tree.rs

@@ -20,7 +20,11 @@ impl MerkleTree {
     ///
     /// # Errors
     /// Returns an error if the number of leaves is smaller than two or is not a power of two.
-    pub fn new(leaves: Vec<Word>) -> Result<Self, MerkleError> {
+    pub fn new<T>(leaves: T) -> Result<Self, MerkleError>
+    where
+        T: AsRef<[Word]>,
+    {
+        let leaves = leaves.as_ref();
         let n = leaves.len();
         if n <= 1 {
             return Err(MerkleError::DepthTooSmall(n as u8));
@@ -34,7 +38,7 @@ impl MerkleTree {
 
         // copy leaves into the second part of the nodes vector
         nodes[n..].iter_mut().zip(leaves).for_each(|(node, leaf)| {
-            *node = RpoDigest::from(leaf);
+            *node = RpoDigest::from(*leaf);
         });
 
         // re-interpret nodes as an array of two nodes fused together
@@ -175,6 +179,26 @@ impl MerkleTree {
     }
 }
 
+// CONVERSIONS
+// ================================================================================================
+
+impl TryFrom<&[Word]> for MerkleTree {
+    type Error = MerkleError;
+
+    fn try_from(value: &[Word]) -> Result<Self, Self::Error> {
+        MerkleTree::new(value)
+    }
+}
+
+impl TryFrom<&[RpoDigest]> for MerkleTree {
+    type Error = MerkleError;
+
+    fn try_from(value: &[RpoDigest]) -> Result<Self, Self::Error> {
+        let value: Vec<Word> = value.iter().map(|v| *v.deref()).collect();
+        MerkleTree::new(value)
+    }
+}
+
 // ITERATORS
 // ================================================================================================
 

src/merkle/mmr/delta.rs

@@ -0,0 +1,16 @@
+use super::super::{RpoDigest, Vec};
+
+/// Container for the update data of a [PartialMmr]
+#[derive(Debug)]
+pub struct MmrDelta {
+    /// The new version of the [Mmr]
+    pub forest: usize,
+
+    /// Update data.
+    ///
+    /// The data is packed as follows:
+    /// 1. All the elements needed to perform authentication path updates. These are the right
+    ///    siblings required to perform tree merges on the [PartialMmr].
+    /// 2. The new peaks.
+    pub data: Vec<RpoDigest>,
+}

src/merkle/mmr/error.rs

@@ -0,0 +1,35 @@
+use crate::merkle::MerkleError;
+use core::fmt::{Display, Formatter};
+
+#[cfg(feature = "std")]
+use std::error::Error;
+
+#[derive(Debug, PartialEq, Eq, Clone)]
+pub enum MmrError {
+    InvalidPosition(usize),
+    InvalidPeaks,
+    InvalidPeak,
+    InvalidUpdate,
+    UnknownPeak,
+    MerkleError(MerkleError),
+}
+
+impl Display for MmrError {
+    fn fmt(&self, fmt: &mut Formatter<'_>) -> Result<(), core::fmt::Error> {
+        match self {
+            MmrError::InvalidPosition(pos) => write!(fmt, "Mmr does not contain position {pos}"),
+            MmrError::InvalidPeaks => write!(fmt, "Invalid peaks count"),
+            MmrError::InvalidPeak => {
+                write!(fmt, "Peak values does not match merkle path computed root")
+            }
+            MmrError::InvalidUpdate => write!(fmt, "Invalid mmr update"),
+            MmrError::UnknownPeak => {
+                write!(fmt, "Peak not in Mmr")
+            }
+            MmrError::MerkleError(err) => write!(fmt, "{}", err),
+        }
+    }
+}
+
+#[cfg(feature = "std")]
+impl Error for MmrError {}