Function encode_bytes_data 

pub fn encode_bytes_data(
    buf: &mut [u8],
    offset: usize,
    data: &[u8],
) -> Result<usize, ZError>

Encode raw bytes (dynamic).

Use this when constructing the data part of bytes/string. Does NOT write length prefix or offset (that’s for higher level logic). Just pads the data to 32-byte boundary if needed? Actually, ABI encoding of bytes is: [offset] [length] [data + padding] This helper writes [data + padding] given a destination. Returns number of bytes written (including padding).