From 4758e0672f91a5fbf0d8cd63735cabfff69bdf69 Mon Sep 17 00:00:00 2001
From: "Augusto F. Hack" <hack.augusto@gmail.com>
Date: Mon, 4 Dec 2023 14:50:05 +0100
Subject: [PATCH] serde: for MerklePath, ValuePath, and RootPath

---
 src/merkle/path.rs | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/src/merkle/path.rs b/src/merkle/path.rs
index 745931c..16a092f 100644
--- a/src/merkle/path.rs
+++ b/src/merkle/path.rs
@@ -1,5 +1,6 @@
 use super::{vec, InnerNodeInfo, MerkleError, NodeIndex, Rpo256, RpoDigest, Vec};
 use core::ops::{Deref, DerefMut};
+use winter_utils::{ByteReader, Deserializable, DeserializationError, Serializable};
 
 // MERKLE PATH
 // ================================================================================================
@@ -17,6 +18,7 @@ impl MerklePath {
 
     /// Creates a new Merkle path from a list of nodes.
     pub fn new(nodes: Vec<RpoDigest>) -> Self {
+        assert!(nodes.len() <= u8::MAX.into(), "MerklePath may have at most 256 items");
         Self { nodes }
     }
 
@@ -189,6 +191,54 @@ pub struct RootPath {
     pub path: MerklePath,
 }
 
+// SERILIZATION
+// ================================================================================================
+impl Serializable for MerklePath {
+    fn write_into<W: winter_utils::ByteWriter>(&self, target: &mut W) {
+        assert!(self.nodes.len() <= u8::MAX.into(), "Length enforced in the construtor");
+        target.write_u8(self.nodes.len() as u8);
+        self.nodes.write_into(target);
+    }
+}
+
+impl Deserializable for MerklePath {
+    fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
+        let count = source.read_u8()?.into();
+        let nodes = RpoDigest::read_batch_from(source, count)?;
+        Ok(Self { nodes })
+    }
+}
+
+impl Serializable for ValuePath {
+    fn write_into<W: winter_utils::ByteWriter>(&self, target: &mut W) {
+        self.value.write_into(target);
+        self.path.write_into(target);
+    }
+}
+
+impl Deserializable for ValuePath {
+    fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
+        let value = RpoDigest::read_from(source)?;
+        let path = MerklePath::read_from(source)?;
+        Ok(Self { value, path })
+    }
+}
+
+impl Serializable for RootPath {
+    fn write_into<W: winter_utils::ByteWriter>(&self, target: &mut W) {
+        self.root.write_into(target);
+        self.path.write_into(target);
+    }
+}
+
+impl Deserializable for RootPath {
+    fn read_from<R: ByteReader>(source: &mut R) -> Result<Self, DeserializationError> {
+        let root = RpoDigest::read_from(source)?;
+        let path = MerklePath::read_from(source)?;
+        Ok(Self { root, path })
+    }
+}
+
 // TESTS
 // ================================================================================================