feed a character with known length

def feed(self, char, char_len):
        """feed a character with known length"""
        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