code: def feed(self, char, char_len):
          
          if char_len == 2:
              # we only care about 2-bytes character in our distribution analysis
              order = self.get_order(char)
          else:
              order = -1
          if order >= 0:
              self._total_chars += 1
              # order is valid
              if order < self._table_size:
                  if 512 > self._char_to_freq_order[order]:
                      self._freq_chars += 1
docs: feed a character with known length