librustzcash-wrapper/src/lib.rs

@@ -738,6 +738,26 @@ impl<RW> FromHaskell<RW> for Htree {
     }
 }
 
+#[derive(BorshSerialize, BorshDeserialize)]
+pub struct Hpath {
+    position: u32,
+    path: Vec<Hhex>
+}
+
+impl<RW> ToHaskell<RW> for Hpath {
+    fn to_haskell<W: Write>(&self, writer: &mut W, _tag: PhantomData<RW>) -> Result<()> {
+        self.serialize(writer)?;
+        Ok(())
+    }
+}
+
+impl<RW> FromHaskell<RW> for Hpath {
+    fn from_haskell(buf: &mut &[u8], _tag: PhantomData<RW>) -> Result<Self> {
+        let x = Hpath::deserialize(buf)?;
+        Ok(x)
+    }
+}
+
 fn to_array<T, const N: usize>(v: Vec<T>) -> [T; N] {
     v.try_into().unwrap_or_else(|v: Vec<T>| panic!("Expected a Vec of length {} but it was {}", N, v.len()))
 }
@@ -1659,6 +1679,29 @@ pub extern "C" fn rust_wrapper_read_orchard_node(
     }
 }
 
+#[no_mangle]
+pub extern "C" fn rust_wrapper_read_orchard_path_anchor(
+    path: *const u8,
+    path_len: usize,
+    cmx: *const u8,
+    cmx_len: usize,
+    out: *mut u8,
+    out_len: &mut usize
+    ){
+    let path_in: Hpath = marshall_from_haskell_var(path, path_len, RW);
+    let cmx_in: Vec<u8> = marshall_from_haskell_var(cmx, cmx_len, RW);
+    let mk_path = orchard::tree::MerklePath::from_parts(path_in.position, to_array(path_in.path.iter().map(|x| MerkleHashOrchard::from_bytes(&to_array(x.bytes.clone())).unwrap()).collect()));
+    let nc = ExtractedNoteCommitment::from_bytes(&to_array(cmx_in));
+    if nc.is_some().into() {
+        let anchor = mk_path.root(nc.unwrap());
+        let h = Hhex { bytes: anchor.to_bytes().to_vec() };
+        marshall_to_haskell_var(&h, out, out_len, RW);
+    } else {
+        let h0 = Hhex { bytes: vec![0] };
+        marshall_to_haskell_var(&h0, out, out_len, RW);
+    }
+}
+
 #[no_mangle]
 pub extern "C" fn rust_wrapper_combine_orchard_nodes(
     level: u8,

src/C/Zcash.chs

@@ -276,6 +276,14 @@ import ZcashHaskell.Types
   -> `()'
 #} 
 
+{# fun unsafe rust_wrapper_read_orchard_path_anchor as rustWrapperReadOrchardPathAnchor
+     { toBorshVar* `MerklePath'&
+     , toBorshVar* `BS.ByteString'&
+     , getVarBuffer `Buffer HexString'&
+     }
+  -> `()'
+#}
+
 {# fun unsafe rust_wrapper_get_orchard_root as rustWrapperGetOrchardRootTest
      { `Int8'
      , getVarBuffer `Buffer HexString'&

src/ZcashHaskell/Orchard.hs

@@ -29,6 +29,7 @@ import C.Zcash
   , rustWrapperReadOrchardCommitmentTree
   , rustWrapperReadOrchardFrontier
   , rustWrapperReadOrchardNode
+  , rustWrapperReadOrchardPathAnchor
   , rustWrapperReadOrchardPosition
   , rustWrapperReadOrchardTreeAnchor
   , rustWrapperReadOrchardTreeParts
@@ -249,6 +250,10 @@ getOrchardTreeParts h =
       withPureBorshVarBuffer $
       rustWrapperReadOrchardTreeParts $ toBytes $ orchTree h
 
+getOrchardPathAnchor :: HexString -> MerklePath -> HexString
+getOrchardPathAnchor hex p =
+  withPureBorshVarBuffer $ rustWrapperReadOrchardPathAnchor p (hexBytes hex)
+
 -- | Update a Orchard commitment tree
 updateOrchardCommitmentTree ::
      OrchardFrontier -- ^ the base tree