chore: backport LargeSmtForest to 0.19.x branch

.github/workflows/msrv.yml

@@ -25,7 +25,7 @@ jobs:
       - uses: dtolnay/rust-toolchain@stable
       - uses: Swatinem/rust-cache@v2
       - name: Install cargo-msrv
-        run: cargo install cargo-msrv
+        run: cargo install --locked cargo-msrv
       - name: Cache rustup toolchains
         run: rustup update
       - name: Check MSRV for each workspace member

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.19.4 (unreleased)
+
+- Backport `LargeSmtForest` with its `InMemory` backend ([#834](https://github.com/0xMiden/crypto/pull/834)).
+
 ## 0.19.3 (2026-01-21)
 
 - Fix: don't disable WAL during subtree construction in `LargeSmt`'s RocksDB backend ([#792](https://github.com/0xMiden/crypto/pull/792)).

miden-crypto/src/lib.rs

@@ -2,7 +2,6 @@
 
 #[macro_use]
 extern crate alloc;
-
 #[cfg(feature = "std")]
 extern crate std;
 
@@ -38,6 +37,8 @@ pub type Map<K, V> = hashbrown::HashMap<K, V>;
 
 #[cfg(feature = "hashmaps")]
 pub use hashbrown::hash_map::Entry as MapEntry;
+#[cfg(feature = "hashmaps")]
+pub use hashbrown::hash_map::IntoIter as MapIntoIter;
 
 /// An alias for a key-value map.
 ///
@@ -48,6 +49,22 @@ pub type Map<K, V> = alloc::collections::BTreeMap<K, V>;
 
 #[cfg(not(feature = "hashmaps"))]
 pub use alloc::collections::btree_map::Entry as MapEntry;
+#[cfg(not(feature = "hashmaps"))]
+pub use alloc::collections::btree_map::IntoIter as MapIntoIter;
+
+/// An alias for a simple set.
+///
+/// By default, this is an alias for the [`alloc::collections::BTreeSet`]. However, when the
+/// `hashmaps` feature is enabled, this becomes an alias for hashbrown's HashSet.
+#[cfg(feature = "hashmaps")]
+pub type Set<V> = hashbrown::HashSet<V>;
+
+/// An alias for a simple set.
+///
+/// By default, this is an alias for the [`alloc::collections::BTreeSet`]. However, when the
+/// `hashmaps` feature is enabled, this becomes an alias for hashbrown's HashSet.
+#[cfg(not(feature = "hashmaps"))]
+pub type Set<V> = alloc::collections::BTreeSet<V>;
 
 // CONSTANTS
 // ================================================================================================

miden-crypto/src/merkle/smt/full/leaf.rs

@@ -175,6 +175,10 @@ impl SmtLeaf {
         self.clone().into_elements()
     }
 
+    pub fn to_entries(&self) -> impl Iterator<Item = (&Word, &Word)> {
+        self.entries().iter().map(|(k, v)| (k, v))
+    }
+
     /// Converts a leaf to a list of field elements
     pub fn into_elements(self) -> Vec<Felt> {
         self.into_entries().into_iter().flat_map(kv_to_elements).collect()

miden-crypto/src/merkle/smt/full/mod.rs

@@ -259,6 +259,11 @@ impl Smt {
         <Self as SparseMerkleTree<SMT_DEPTH>>::get_leaf(self, key)
     }
 
+    /// Returns the leaf corresponding to the provided `index`.
+    pub fn get_leaf_by_index(&self, index: LeafIndex<SMT_DEPTH>) -> Option<SmtLeaf> {
+        self.leaves.get(&index.position()).cloned()
+    }
+
     /// Returns the value associated with `key`
     pub fn get_value(&self, key: &Word) -> Word {
         <Self as SparseMerkleTree<SMT_DEPTH>>::get_value(self, key)