code: private function readCodepage()
      {
          $length = self::getUInt2d($this->data, $this->pos + 2);
          $recordData = $this->readRecordData($this->data, $this->pos + 4, $length);
  
          // move stream pointer to next record
          $this->pos += 4 + $length;
  
          // offset: 0; size: 2; code page identifier
          $codepage = self::getUInt2d($recordData, 0);
  
          $this->codepage = CodePage::numberToName($codepage);
      }
docs: CODEPAGE.
  
  This record stores the text encoding used to write byte
  strings, stored as MS Windows code page identifier.
  
  --    "OpenOffice.org's Documentation of the Microsoft
  Excel File Format"