Add ShieldedOutput::cmstar

CHANGELOG.md

@@ -6,6 +6,10 @@ and this library adheres to Rust's notion of
 [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- A blanket `impl<D, O, const CIPHERTEXT_SIZE: usize> ShieldedOutput<D, CIPHERTEXT_SIZE> for &O`
+    where `D: Domain, O: ShieldedOutput<D, CIPHERTEXT_SIZE>`
+
 ### Changed
 - **Breaking change:** removed the constants `COMPACT_NOTE_SIZE`,
   `NOTE_PLAINTEXT_SIZE`, and `ENC_CIPHERTEXT_SIZE` as they are now
@@ -27,14 +31,18 @@ and this library adheres to Rust's notion of
   `Option` of a reference instead of a copy.
 - Added a new `note_bytes` module with helper trait and struct to deal with note
   bytes data with abstracted underlying array size.
+- `ShieldedOutput` has added method `cmstar`, which exposes the
+  `ExtractedCommitment` of the shielded output directly, in addition to the
+  byte encoding exposed by `ShieldedOutput::cmstar_bytes`. This is useful for
+  further generalizing scanning code.
 
 ## [0.4.1] - 2024-12-06
 ### Added
 - `zcash_note_encryption::try_output_recovery_with_pkd_esk`
 
 ## [0.4.0] - 2023-06-06
 ### Changed
-- The `esk` and `ephemeral_key` arguments have been removed from 
+- The `esk` and `ephemeral_key` arguments have been removed from
   `Domain::parse_note_plaintext_without_memo_ovk`. It is therefore no longer
   necessary (or possible) to ensure that `ephemeral_key` is derived from `esk`
   and the diversifier within the note plaintext. We have analyzed the safety of
@@ -46,7 +54,7 @@ and this library adheres to Rust's notion of
 ## [0.3.0] - 2023-03-22
 ### Changed
 - The `recipient` parameter has been removed from `Domain::note_plaintext_bytes`.
-- The `recipient` parameter has been removed from `NoteEncryption::new`. Since 
+- The `recipient` parameter has been removed from `NoteEncryption::new`. Since
   the `Domain::Note` type is now expected to contain information about the
   recipient of the note, there is no longer any need to pass this information
   in via the encryption context.

src/lib.rs

@@ -356,8 +356,13 @@ pub trait ShieldedOutput<D: Domain> {
     /// Exposes the `ephemeral_key` field of the output.
     fn ephemeral_key(&self) -> EphemeralKeyBytes;
 
-    /// Exposes the `cmu_bytes` or `cmx_bytes` field of the output.
-    fn cmstar_bytes(&self) -> D::ExtractedCommitmentBytes;
+    /// Exposes the `cmu` or `cmx` field of the output.
+    fn cmstar(&self) -> &D::ExtractedCommitment;
+
+    /// Exposes the `cmu_bytes` or `cmx_bytes` representation of the output.
+    fn cmstar_bytes(&self) -> D::ExtractedCommitmentBytes {
+        D::ExtractedCommitmentBytes::from(self.cmstar())
+    }
 
     /// Exposes the note ciphertext of the output. Returns `None` if the output is compact.
     fn enc_ciphertext(&self) -> Option<&D::NoteCiphertextBytes>;
@@ -389,6 +394,28 @@ pub trait ShieldedOutput<D: Domain> {
     }
 }
 
+impl<D, O> ShieldedOutput<D> for &O
+where
+    D: Domain,
+    O: ShieldedOutput<D>,
+{
+    fn ephemeral_key(&self) -> EphemeralKeyBytes {
+        (*self).ephemeral_key()
+    }
+
+    fn cmstar(&self) -> &<D as Domain>::ExtractedCommitment {
+        (*self).cmstar()
+    }
+
+    fn enc_ciphertext(&self) -> Option<&<D as Domain>::NoteCiphertextBytes> {
+        (*self).enc_ciphertext()
+    }
+
+    fn enc_ciphertext_compact(&self) -> <D as Domain>::CompactNoteCiphertextBytes {
+        (*self).enc_ciphertext_compact()
+    }
+}
+
 /// A struct containing context required for encrypting Sapling and Orchard notes.
 ///
 /// This struct provides a safe API for encrypting Sapling and Orchard notes. In particular, it