Refine JoinSplit::anchor to be a sprout::NoteTreeRootHash type

zebra-chain/src/transaction/joinsplit.rs

@@ -4,6 +4,7 @@ use crate::{
     ed25519_zebra,
     notes::sprout,
     proofs::ZkSnarkProof,
+    treestate,
     types::amount::{Amount, NonNegative},
 };
 
@@ -22,9 +23,7 @@ pub struct JoinSplit<P: ZkSnarkProof> {
     /// A root of the Sprout note commitment tree at some block height in the
     /// past, or the root produced by a previous JoinSplit transfer in this
     /// transaction.
-    ///
-    /// XXX refine type
-    pub anchor: [u8; 32],
+    pub anchor: treestate::sprout::NoteTreeRootHash,
     /// A nullifier for the input notes.
     pub nullifiers: [crate::notes::sprout::Nullifier; 2],
     /// A note commitment for this output note.

zebra-chain/src/transaction/serialize.rs

@@ -14,7 +14,7 @@ use crate::{
     serialization::{
         ReadZcashExt, SerializationError, WriteZcashExt, ZcashDeserialize, ZcashSerialize,
     },
-    types,
+    treestate, types,
 };
 
 use super::*;
@@ -241,7 +241,7 @@ impl<P: ZkSnarkProof> ZcashSerialize for JoinSplit<P> {
     fn zcash_serialize<W: io::Write>(&self, mut writer: W) -> Result<(), io::Error> {
         writer.write_u64::<LittleEndian>(self.vpub_old.into())?;
         writer.write_u64::<LittleEndian>(self.vpub_new.into())?;
-        writer.write_all(&self.anchor[..])?;
+        writer.write_32_bytes(&self.anchor.into())?;
         writer.write_32_bytes(&self.nullifiers[0].into())?;
         writer.write_32_bytes(&self.nullifiers[1].into())?;
         writer.write_32_bytes(&self.commitments[0].into())?;
@@ -262,7 +262,7 @@ impl<P: ZkSnarkProof> ZcashDeserialize for JoinSplit<P> {
         Ok(JoinSplit::<P> {
             vpub_old: reader.read_u64::<LittleEndian>()?.try_into()?,
             vpub_new: reader.read_u64::<LittleEndian>()?.try_into()?,
-            anchor: reader.read_32_bytes()?,
+            anchor: treestate::sprout::NoteTreeRootHash::from(reader.read_32_bytes()?),
             nullifiers: [
                 reader.read_32_bytes()?.into(),
                 reader.read_32_bytes()?.into(),

zebra-chain/src/transaction/tests/arbitrary.rs

@@ -6,7 +6,7 @@ use crate::{
         CoinbaseData, JoinSplit, JoinSplitData, OutPoint, Output, ShieldedData, Spend, Transaction,
         TransparentInput,
     },
-    treestate::note_commitment_tree::SaplingNoteTreeRootHash,
+    treestate::{self, note_commitment_tree::SaplingNoteTreeRootHash},
     types::{
         amount::{Amount, NonNegative},
         BlockHeight, Script,
@@ -22,7 +22,7 @@ impl<P: ZkSnarkProof + Arbitrary + 'static> Arbitrary for JoinSplit<P> {
         (
             any::<Amount<NonNegative>>(),
             any::<Amount<NonNegative>>(),
-            array::uniform32(any::<u8>()),
+            any::<treestate::sprout::NoteTreeRootHash>(),
             array::uniform2(any::<sprout::Nullifier>()),
             array::uniform2(any::<commitments::sprout::NoteCommitment>()),
             array::uniform32(any::<u8>()),

zebra-chain/src/treestate.rs

@@ -2,3 +2,4 @@
 
 pub mod note_commitment_tree;
 // mod nullifier_set;
+pub mod sprout;