[]

# File lib/csv.rb, line 803
    def [](idx, n = nil) 
      if idx < 0
        return nil
      end
      if (idx_is_eos?(idx))
        if n and (@offset + idx == buf_size(@cur_buf))
          # Like a String, 'abc'[4, 1] returns nil and
          # 'abc'[3, 1] returns '' not nil.
          return ''
        else
          return nil
        end
      end
      my_buf = @cur_buf
      my_offset = @offset
      next_idx = idx
      while (my_offset + next_idx >= buf_size(my_buf))
        if (my_buf == @buf_tail_idx)
          unless add_buf
            break
          end
        end
        next_idx = my_offset + next_idx - buf_size(my_buf)
        my_buf += 1
        my_offset = 0
      end
      loc = my_offset + next_idx
      if !n
        return @buf_list[my_buf][loc]           # Fixnum of char code.
      elsif (loc + n - 1 < buf_size(my_buf))
        return @buf_list[my_buf][loc, n]        # String.
      else # should do loop insted of (tail) recursive call...
        res = @buf_list[my_buf][loc, BufSize]
        size_added = buf_size(my_buf) - loc
        if size_added > 0
          idx += size_added
          n -= size_added
          ret = self[idx, n]
          if ret
            res << ret
          end
        end
        return res
      end
    end