code: func (s *Sum32) Write(data []byte) (int, error) {
  	hash := *s
  	for _, b := range data {
  		hash += Sum32(b)
  		hash += hash << 10
  		hash ^= hash >> 6
  	}
  	*s = hash
  	return len(data), nil
  }
docs: // Write adds more data to the running hash.
  //
  // It never returns an error.