code: def feed(self, aBuf, aCharLen):
          
          if aCharLen == 2:
              # we only care about 2-bytes character in our distribution analysis
              order = self.get_order(aBuf)
          else:
              order = -1
          if order >= 0:
              self._mTotalChars += 1
              # order is valid
              if order < self._mTableSize:
                  if 512 > self._mCharToFreqOrder[order]:
                      self._mFreqChars += 1
docs: feed a character with known length