code: private function readBIFF8CellAddress($cellAddressStructure)
      {
          // offset: 0; size: 2; index to row (0... 65535) (or offset (-32768... 32767))
          $row = self::getUInt2d($cellAddressStructure, 0) + 1;
  
          // offset: 2; size: 2; index to column or column offset + relative flags
          // bit: 7-0; mask 0x00FF; column index
          $column = Coordinate::stringFromColumnIndex((0x00FF & self::getUInt2d($cellAddressStructure, 2)) + 1);
  
          // bit: 14; mask 0x4000; (1 = relative column index, 0 = absolute column index)
          if (!(0x4000 & self::getUInt2d($cellAddressStructure, 2))) {
              $column = '$' . $column;
          }
          // bit: 15; mask 0x8000; (1 = relative row index, 0 = absolute row index)
          if (!(0x8000 & self::getUInt2d($cellAddressStructure, 2))) {
              $row = '$' . $row;
          }
  
          return $column . $row;
      }
docs: Reads a cell address in BIFF8 e.g. 'A2' or '$A$2'
  section 3.3.4.
  
  @param string $cellAddressStructure
  
  @return string