Add memo type with Debug impl and some test cases

zebra-chain/src/lib.rs

@@ -7,6 +7,7 @@ mod sha256d_writer;
 pub mod block;
 pub mod equihash_solution;
 pub mod note_commitment_tree;
+pub mod note_encryption;
 pub mod proofs;
 pub mod serialization;
 pub mod transaction;

zebra-chain/src/note_encryption.rs

@@ -0,0 +1,47 @@
+//! Note encryption types.
+
+use std::fmt;
+
+/// A 512-byte _Memo_ field associated with a note, as described in
+/// [protocol specification §5.5][ps].
+///
+/// The usage of the memo field is by agreement between the sender and
+/// recipient of the note.
+///
+/// [ps]: https://zips.z.cash/protocol/protocol.pdf#spendencoding
+#[derive(Clone, Copy)]
+pub struct Memo([u8; 512]);
+
+impl Memo {}
+
+impl fmt::Debug for Memo {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let output: String;
+
+        match String::from_utf8(self.0.to_vec()) {
+            Ok(memo) => output = memo,
+            _ => output = hex::encode(&self.0[..]),
+        }
+
+        f.debug_tuple("Memo").field(&output).finish()
+    }
+}
+
+#[test]
+fn memo_fmt() {
+    let memo = Memo([0u8; 512]);
+
+    println!("{:?}", memo);
+
+    let memo2 = Memo(
+        *b"thiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis \
+                 iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis \
+                 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \
+                 veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeryyyyyyyyyyyyyyyyyyyyyyyyyy \
+                 looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong \
+                 meeeeeeeeeeeeeeeeeeemooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo \
+                 but it's just short enough",
+    );
+
+    println!("{:?}", memo2);
+}