Add identity `MapAuth` implementations

zcash_primitives/CHANGELOG.md

@@ -31,8 +31,13 @@ and this library adheres to Rust's notion of
     fee rule.
   - `zip317`, a new module containing an implementation of the ZIP 317 fee
     rules.
-- Added to `zcash_primitives::transaction::components::sapling::builder`
-  - `SaplingBuilder::{inputs, outputs}`: accessors for Sapling builder state.
+- Added to `zcash_primitives::transaction::components::orchard`:
+  - `impl MapAuth<orchard::bundle::Authorized, orchard::bundle::Authorized> for ()`
+    (the identity map).
+- Added to `zcash_primitives::transaction::components::sapling`:
+  - `impl MapAuth<Authorized, Authorized> for ()` (the identity map).
+  - `builder::SaplingBuilder::{inputs, outputs}`: accessors for Sapling builder
+    state.
 - `zcash_primitives::transaction::components::sapling::fees`
 - Added to `zcash_primitives::transaction::components::transparent::builder`
   - `TransparentBuilder::{inputs, outputs}`: accessors for transparent builder state.

zcash_primitives/src/transaction/components/orchard.rs

@@ -33,6 +33,25 @@ pub trait MapAuth<A: Authorization, B: Authorization> {
     fn map_authorization(&self, a: A) -> B;
 }
 
+/// The identity map.
+///
+/// This can be used with [`TransactionData::map_authorization`] when you want to map the
+/// authorization of a subset of the transaction's bundles.
+///
+/// [`TransactionData::map_authorization`]: crate::transaction::TransactionData::map_authorization
+impl MapAuth<Authorized, Authorized> for () {
+    fn map_spend_auth(
+        &self,
+        s: <Authorized as Authorization>::SpendAuth,
+    ) -> <Authorized as Authorization>::SpendAuth {
+        s
+    }
+
+    fn map_authorization(&self, a: Authorized) -> Authorized {
+        a
+    }
+}
+
 /// Reads an [`orchard::Bundle`] from a v5 transaction format.
 pub fn read_v5_bundle<R: Read>(
     mut reader: R,

zcash_primitives/src/transaction/components/sapling.rs

@@ -55,6 +55,32 @@ pub trait MapAuth<A: Authorization, B: Authorization> {
     fn map_authorization(&self, a: A) -> B;
 }
 
+/// The identity map.
+///
+/// This can be used with [`TransactionData::map_authorization`] when you want to map the
+/// authorization of a subset of the transaction's bundles.
+///
+/// [`TransactionData::map_authorization`]: crate::transaction::TransactionData::map_authorization
+impl MapAuth<Authorized, Authorized> for () {
+    fn map_proof(
+        &self,
+        p: <Authorized as Authorization>::Proof,
+    ) -> <Authorized as Authorization>::Proof {
+        p
+    }
+
+    fn map_auth_sig(
+        &self,
+        s: <Authorized as Authorization>::AuthSig,
+    ) -> <Authorized as Authorization>::AuthSig {
+        s
+    }
+
+    fn map_authorization(&self, a: Authorized) -> Authorized {
+        a
+    }
+}
+
 #[derive(Debug, Clone)]
 pub struct Bundle<A: Authorization> {
     pub shielded_spends: Vec<SpendDescription<A>>,