Add a new `zcash_serialize_bytes` utility function (#2150)

zebra-chain/src/serialization/zcash_serialize.rs

@@ -40,6 +40,22 @@ impl<T: ZcashSerialize> ZcashSerialize for Vec<T> {
     }
 }
 
+/// Serialize a byte vector as a compactsize number of items, then the items.
+///
+/// # Correctness
+///
+/// Most Zcash types have specific rules about serialization of `Vec<u8>`s.
+/// Check the spec and consensus rules before using this function.
+///
+/// See `zcash_serialize_bytes_external_count` for more details, and usage information.
+//
+// we specifically want to serialize `Vec`s here, rather than generic slices
+#[allow(clippy::ptr_arg)]
+pub fn zcash_serialize_bytes<W: io::Write>(vec: &Vec<u8>, mut writer: W) -> Result<(), io::Error> {
+    writer.write_compactsize(vec.len() as u64)?;
+    zcash_serialize_bytes_external_count(vec, writer)
+}
+
 /// Serialize an `AtLeastOne` vector as a compactsize number of items, then the
 /// items. This is the most common format in Zcash.
 impl<T: ZcashSerialize> ZcashSerialize for AtLeastOne<T> {
@@ -101,10 +117,9 @@ pub fn zcash_serialize_bytes_external_count<W: io::Write>(
 
 /// Write a Bitcoin-encoded UTF-8 `&str`.
 impl ZcashSerialize for &str {
-    fn zcash_serialize<W: io::Write>(&self, mut writer: W) -> Result<(), io::Error> {
-        let str_bytes = self.as_bytes();
-        writer.write_compactsize(str_bytes.len() as u64)?;
-        writer.write_all(str_bytes)
+    fn zcash_serialize<W: io::Write>(&self, writer: W) -> Result<(), io::Error> {
+        let str_bytes = self.as_bytes().to_vec();
+        zcash_serialize_bytes(&str_bytes, writer)
     }
 }