code: public NewChunk asciiLength(NewChunk nc) {
      //pre-allocate since size is known
      nc.alloc_mantissa(_len);
      nc.alloc_exponent(_len); // sadly, a waste
      // fill in lengths
      for(int i=0; i < _len; i++) {
        int off = UnsafeUtils.get4(_mem,idx(i));
        int len = 0;
        if (off != NA) {
          while (_mem[_valstart + off + len] != 0) len++;
          nc.addNum(len, 0);
        } else nc.addNA();
      }
      return nc;
    }
docs: Optimized length() method for a buffer of only ASCII characters.
  This is a straight byte count for each word in the chunk. The presence
  of UTF-8 multi-byte characters would give incorrect results.
  
  @param nc NewChunk to be filled with lengths of strings in this chunk
  @return Filled NewChunk