Move memo to its own module under note_encryption, turn try_from into a match cmp

zebra-chain/src/note_encryption.rs

@@ -1,92 +1,5 @@
 //! Note encryption types.
 
-use std::{
+pub mod memo;
-    convert::{AsRef, From},
-    fmt,
-};
-
 mod sapling;
 mod sprout;
-
-/// A 512-byte _Memo_ field associated with a note, as described in
-/// [protocol specification §5.5][ps].
-///
-/// The _Memo- field of a note is a plaintext type; the parent note is
-/// what is encrypted and stored on the blockchain. The underlying
-/// usage of the memo field is by agreement between the sender and
-/// recipient of the note.
-///
-/// [ps]: https://zips.z.cash/protocol/protocol.pdf#notept
-#[derive(Clone, Copy)]
-pub struct Memo([u8; 512]);
-
-impl<T: AsRef<[u8]>> From<T> for Memo {
-    fn from(input: T) -> Self {
-        let input_bytes: &[u8] = input.as_ref();
-
-        let mut full_bytes = [0; 512];
-
-        if input_bytes.len() < 512 {
-            full_bytes[0..input_bytes.len()].copy_from_slice(input_bytes);
-            Memo(full_bytes)
-        } else if input_bytes.len() == 512 {
-            full_bytes[..].copy_from_slice(input_bytes);
-            Memo(full_bytes)
-        } else {
-            // Because this is a From impl, we truncate your input
-            // rather than return any Memo at all.
-            full_bytes.copy_from_slice(&input_bytes[0..512]);
-            Memo(full_bytes)
-        }
-    }
-}
-
-impl fmt::Debug for Memo {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let output: String;
-
-        // This saves work but if the 'valid utf8 string' is just a
-        // bunch of numbers, it prints them out like
-        // 'Memo("\u{0}\u{0}..")', so. ¯\_(ツ)_/¯
-        match std::str::from_utf8(&self.0[..]) {
-            Ok(memo) => output = String::from(memo),
-            _ => output = hex::encode(&self.0[..]),
-        }
-
-        f.debug_tuple("Memo").field(&output).finish()
-    }
-}
-
-#[test]
-fn memo_fmt() {
-    let memo = Memo(
-        *b"thiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis \
-           iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis \
-           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \
-           veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeryyyyyyyyyyyyyyyyyyyyyyyyyy \
-           looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong \
-           meeeeeeeeeeeeeeeeeeemooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo \
-           but it's just short enough",
-    );
-
-    assert_eq!(format!("{:?}", memo),
-               "Memo(\"thiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeryyyyyyyyyyyyyyyyyyyyyyyyyy looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong meeeeeeeeeeeeeeeeeeemooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo but it\\\'s just short enough\")"
-    );
-
-    let mut some_bytes = [0u8; 512];
-    some_bytes[0] = 0xF6;
-
-    assert_eq!(format!("{:?}", Memo(some_bytes)),
-               "Memo(\"f600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000\")"
-    );
-}
-
-#[test]
-fn memo_from_string() {
-    let memo = Memo::from("foo bar baz");
-
-    let mut bytes = [0; 512];
-    bytes[0..11].copy_from_slice(&[102, 111, 111, 32, 98, 97, 114, 32, 98, 97, 122]);
-
-    assert!(memo.0.iter().eq(bytes.iter()));
-}

zebra-chain/src/note_encryption/memo.rs

@@ -0,0 +1,83 @@
+use std::{cmp, convert::TryFrom, fmt};
+
+/// A 512-byte _Memo_ field associated with a note, as described in
+/// [protocol specification §5.5][ps].
+///
+/// The _Memo_ field of a note is a plaintext type; the parent note is
+/// what is encrypted and stored on the blockchain. The underlying
+/// usage of the memo field is by agreement between the sender and
+/// recipient of the note.
+///
+/// [ps]: https://zips.z.cash/protocol/protocol.pdf#notept
+#[derive(Clone, Copy)]
+pub struct Memo([u8; 512]);
+
+impl<'a> TryFrom<&'a [u8]> for Memo {
+    type Error = &'static str;
+
+    fn try_from(input: &'a [u8]) -> Result<Self, Self::Error> {
+        let mut full_bytes = [0; 512];
+
+        match input.len().cmp(&512) {
+            cmp::Ordering::Less => {
+                full_bytes[0..input.len()].copy_from_slice(input);
+                Ok(Memo(full_bytes))
+            }
+            cmp::Ordering::Equal => {
+                full_bytes[..].copy_from_slice(input);
+                Ok(Memo(full_bytes))
+            }
+            cmp::Ordering::Greater => Err("Memos have a max length of 512 bytes."),
+        }
+    }
+}
+
+impl fmt::Debug for Memo {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let output: String;
+
+        // This saves work but if the 'valid utf8 string' is just a
+        // bunch of numbers, it prints them out like
+        // 'Memo("\u{0}\u{0}..")', so. ¯\_(ツ)_/¯
+        match std::str::from_utf8(&self.0[..]) {
+            Ok(memo) => output = String::from(memo),
+            _ => output = hex::encode(&self.0[..]),
+        }
+
+        f.debug_tuple("Memo").field(&output).finish()
+    }
+}
+
+#[test]
+fn memo_fmt() {
+    let memo = Memo(
+        *b"thiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis \
+           iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis \
+           aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa \
+           veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeryyyyyyyyyyyyyyyyyyyyyyyyyy \
+           looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong \
+           meeeeeeeeeeeeeeeeeeemooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo \
+           but it's just short enough",
+    );
+
+    assert_eq!(format!("{:?}", memo),
+               "Memo(\"thiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiis aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa veeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeryyyyyyyyyyyyyyyyyyyyyyyyyy looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong meeeeeeeeeeeeeeeeeeemooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo but it\\\'s just short enough\")"
+    );
+
+    let mut some_bytes = [0u8; 512];
+    some_bytes[0] = 0xF6;
+
+    assert_eq!(format!("{:?}", Memo(some_bytes)),
+               "Memo(\"f600000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000\")"
+    );
+}
+
+#[test]
+fn memo_from_string() {
+    let memo = Memo::try_from("foo bar baz".as_ref()).unwrap();
+
+    let mut bytes = [0; 512];
+    bytes[0..11].copy_from_slice(&[102, 111, 111, 32, 98, 97, 114, 32, 98, 97, 122]);
+
+    assert!(memo.0.iter().eq(bytes.iter()));
+}