PHPOffice / PhpSpreadsheet

        // Read rest of Master Block Allocation Table (if any is left)

        $pos = $this->_getBlockOffset($mbatFirstBlockId);

        for ($i = 0; $i < $mbbatBlockCount; ++$i) {

            fseek($fh, $pos);

            for ($j = 0; $j < $this->bigBlockSize / 4 - 1; ++$j) {

                $mbatBlocks[] = self::_readInt4($fh);

            }

            // Last block id in each block points to next block

            $pos = $this->_getBlockOffset(self::_readInt4($fh));

        }

        // Read Big Block Allocation Table according to chain specified by $mbatBlocks

        for ($i = 0; $i < $bbatBlockCount; ++$i) {

        }

        // Read Big Block Allocation Table according to chain specified by $mbatBlocks

        for ($i = 0; $i < $bbatBlockCount; ++$i) {

            $pos = $this->_getBlockOffset($mbatBlocks[$i]);

            fseek($fh, $pos);

            for ($j = 0; $j < $this->bigBlockSize / 4; ++$j) {

                $this->bbat[] = self::_readInt4($fh);

            }

        }

        // Read short block allocation table (SBAT)

        $this->sbat = [];