Rust Programming By Example

Decoding data bytes

Then, we implement the Decoder trait like we did for the FtpCodec:

impl Decoder for BytesCodec {
    type Item = Vec<u8>;
    type Error = io::Error;

    fn decode(&mut self, buf: &mut BytesMut) -> io::Result<Option<Vec<u8>>> {
        if buf.len() == 0 {
            return Ok(None);
        }
        let data = buf.to_vec();
        buf.clear();
        Ok(Some(data))
    }
}

Since the data of a transmitted file can be binary, we cannot use an Item of type String. We instead use Vec<u8>, which we can contain every possible byte. If the buffer is empty, we return Ok(None) to indicate to tokio that we need more data. Otherwise, we convert it to a vector, clear the buffer and return the vector.