codec: implement Encoder<BytesMut> for BytesCodec (#4465)

tokio-util/src/codec/bytes_codec.rs

@@ -74,3 +74,13 @@ impl Encoder<Bytes> for BytesCodec {
         Ok(())
     }
 }
+
+impl Encoder<BytesMut> for BytesCodec {
+    type Error = io::Error;
+
+    fn encode(&mut self, data: BytesMut, buf: &mut BytesMut) -> Result<(), io::Error> {
+        buf.reserve(data.len());
+        buf.put(data);
+        Ok(())
+    }
+}

tokio-util/tests/codecs.rs

@@ -38,6 +38,9 @@ fn bytes_encoder() {
     codec
         .encode(Bytes::from_static(&[0; INITIAL_CAPACITY + 1]), &mut buf)
         .unwrap();
+    codec
+        .encode(BytesMut::from(&b"hello"[..]), &mut buf)
+        .unwrap();
 }
 
 #[test]