From ce4697aca54e655729a772ae729de804bd155504 Mon Sep 17 00:00:00 2001
From: Kris Nuttycombe <kris@electriccoin.co>
Date: Thu, 17 Jun 2021 08:34:09 -0600
Subject: [PATCH] Add construction of OrchardIncrementalTreeDigest

---
 src/lib.rs  |  2 +-
 src/tree.rs | 18 ++++++++++++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index 3b46ae84..3bc712e8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -26,7 +26,7 @@ pub mod note;
 mod note_encryption;
 pub mod primitives;
 mod spec;
-mod tree;
+pub mod tree;
 pub mod value;
 
 #[cfg(test)]
diff --git a/src/tree.rs b/src/tree.rs
index f4a18ee0..ace8906b 100644
--- a/src/tree.rs
+++ b/src/tree.rs
@@ -1,3 +1,5 @@
+//! Types related to Orchard note commitment trees and anchors.
+
 use crate::{
     constants::{
         util::gen_const_array, L_ORCHARD_MERKLE, MERKLE_CRH_PERSONALIZATION, MERKLE_DEPTH_ORCHARD,
@@ -35,6 +37,8 @@ impl Anchor {
     }
 }
 
+/// The Merkle path from a leaf of the note commitment tree
+/// to its anchor.
 #[derive(Debug)]
 pub struct MerklePath {
     position: u32,
@@ -132,8 +136,18 @@ fn hash_layer(l_star: usize, pair: Pair) -> CtOption<pallas::Base> {
     )
 }
 
-#[derive(Clone)]
-struct OrchardIncrementalTreeDigest(CtOption<pallas::Base>);
+/// A newtype wrapper for leaves and internal nodes in the Orchard
+/// incremental note commitment tree.
+#[derive(Clone, Debug)]
+pub struct OrchardIncrementalTreeDigest(CtOption<pallas::Base>);
+
+impl OrchardIncrementalTreeDigest {
+    /// Parses a incremental tree leaf digest from the bytes of
+    /// a note commitment.
+    pub fn from_bytes(bytes: &[u8; 32]) -> Self {
+        OrchardIncrementalTreeDigest(pallas::Base::from_bytes(bytes))
+    }
+}
 
 impl Hashable for OrchardIncrementalTreeDigest {
     fn empty_leaf() -> Self {