send.rs

enum Error<T> {
  ..
  Again(T),
}
  

  fn send<T: AsRef<[u8]>>(buf: T, ...) -> Result<(), Error<T>> { ... }
  
  let mut buf = ...;
  
  loop {
    match send(buf, ...) {
      Ok(()) => buf = get_new_buf(),
      Err(Error::Again(b)) => buf = b,
      Err(e) => return Err(e),
  }