Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/Reader/Xls.php
private function readStyle()
    {
        $length = self::getUInt2d($this->data, $this->pos + 2);
        $recordData = $this->readRecordData($this->data, $this->pos + 4, $length);

        // move stream pointer to next record
        $this->pos += 4 + $length;

        if (!$this->readDataOnly) {
            // offset: 0; size: 2; index to XF record and flag for built-in style
            $ixfe = self::getUInt2d($recordData, 0);

            // bit: 11-0; mask 0x0FFF; index to XF record
            $xfIndex = (0x0FFF & $ixfe) >> 0;

            // bit: 15; mask 0x8000; 0 = user-defined style, 1 = built-in style
            $isBuiltIn = (bool) ((0x8000 & $ixfe) >> 15);

            if ($isBuiltIn) {
                // offset: 2; size: 1; identifier for built-in style
                $builtInId = ord($recordData[2]);

                switch ($builtInId) {
                    case 0x00:
                        // currently, we are not using this for anything
                        break;
                    default:
                        break;
                }
            }
            // user-defined; not supported by PhpSpreadsheet
        }
    }
private function readStyle()
    {
        $length = self::getUInt2d($this->data, $this->pos + 2);
        $recordData = $this->readRecordData($this->data, $this->pos + 4, $length);

        // move stream pointer to next record
        $this->pos += 4 + $length;

        if (!$this->readDataOnly) {
            // offset: 0; size: 2; index to XF record and flag for built-in style
            $ixfe = self::getUInt2d($recordData, 0);

            // bit: 11-0; mask 0x0FFF; index to XF record
            $xfIndex = (0x0FFF & $ixfe) >> 0;

            // bit: 15; mask 0x8000; 0 = user-defined style, 1 = built-in style
            $isBuiltIn = (bool) ((0x8000 & $ixfe) >> 15);

            if ($isBuiltIn) {
                // offset: 2; size: 1; identifier for built-in style
                $builtInId = ord($recordData[2]);

                switch ($builtInId) {
                    case 0x00:
                        // currently, we are not using this for anything
                        break;
                    default:
                        break;
                }
            }
            // user-defined; not supported by PhpSpreadsheet
        }
    }
Read STYLE record.