biffwriter.php

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<?php
/*
*  Module written/ported by Xavier Noguer <[e-mail]>
*
*  The majority of this is _NOT_ my code.  I simply ported it from the
*  PERL Spreadsheet::WriteExcel module.
*
*  The author of the Spreadsheet::WriteExcel module is John McNamara
*  <[e-mail]>
*
*  I _DO_ maintain this code, and John McNamara has nothing to do with the
*  porting of this code to PHP.  Any questions directly related to this
*  class library should be directed to me.
*
*  License Information:
*
*    Spreadsheet_Excel_Writer:  A library for generating Excel Spreadsheets
*    Copyright (c) 2002-2003 Xavier Noguer [e-mail]
*
*    This library is free software; you can redistribute it and/or
*    modify it under the terms of the GNU Lesser General Public
*    License as published by the Free Software Foundation; either
*    version 2.1 of the License, or (at your option) any later version.
*
*    This library is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
*    Lesser General Public License for more details.
*
*    You should have received a copy of the GNU Lesser General Public
*    License along with this library; if not, write to the Free Software
*    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

require_once 'PEAR.php';

/**
* Class for writing Excel BIFF records.
*
* From "MICROSOFT EXCEL BINARY FILE FORMAT" by Mark O'Brien (Microsoft Corporation):
*
* BIFF (BInary File Format) is the file format in which Excel documents are
* saved on disk.  A BIFF file is a complete description of an Excel document.
* BIFF files consist of sequences of variable-length records. There are many
* different types of BIFF records.  For example, one record type describes a
* formula entered into a cell; one describes the size and location of a
* window into a document; another describes a picture format.
*
* @author   Xavier Noguer <[e-mail]>
* @category FileFormats
* @package  Spreadsheet_Excel_Writer
*/

class Spreadsheet_Excel_Writer_BIFFwriter extends PEAR
{
    /**
    * The BIFF/Excel version (5).
    * @var integer
    */
    var $_BIFF_version = 0x0500;

    /**
    * The byte order of this architecture. 0 => little endian, 1 => big endian
    * @var integer
    */
    var $_byte_order;

    /**
    * The string containing the data of the BIFF stream
    * @var string
    */
    var $_data;

    /**
    * The size of the data in bytes. Should be the same as strlen($this->_data)
    * @var integer
    */
    var $_datasize;

    /**
    * The maximun length for a BIFF record. See _addContinue()
    * @var integer
    * @see _addContinue()
    */
    var $_limit;

    /**
    * Constructor
    *
    * @access public
    */
    function Spreadsheet_Excel_Writer_BIFFwriter()
    {
        $this->_byte_order = '';
        $this->_data       = '';
        $this->_datasize   = 0;
        $this->_limit      = 2080;
        // Set the byte order
        $this->_setByteOrder();
    }

    /**
    * Determine the byte order and store it as class data to avoid
    * recalculating it for each call to new().
    *
    * @access private
    */
    function _setByteOrder()
    {
        // Check if "pack" gives the required IEEE 64bit float
        $teststr = pack("d", 1.2345);
        $number  = pack("C8", 0x8D, 0x97, 0x6E, 0x12, 0x83, 0xC0, 0xF3, 0x3F);
        if ($number == $teststr) {
            $byte_order = 0;    // Little Endian
        } elseif ($number == strrev($teststr)){
            $byte_order = 1;    // Big Endian
        } else {
            // Give up. I'll fix this in a later version.
            return $this->raiseError("Required floating point format ".
                                     "not supported on this platform.");
        }
        $this->_byte_order = $byte_order;
    }

    /**
    * General storage function
    *
    * @param string $data binary data to prepend
    * @access private
    */
    function _prepend($data)
    {
        if (strlen($data) > $this->_limit) {
            $data = $this->_addContinue($data);
        }
        $this->_data      = $data.$this->_data;
        $this->_datasize += strlen($data);
    }

    /**
    * General storage function
    *
    * @param string $data binary data to append
    * @access private
    */
    function _append($data)
    {
        if (strlen($data) > $this->_limit) {
            $data = $this->_addContinue($data);
        }
        $this->_data      = $this->_data.$data;
        $this->_datasize += strlen($data);
    }

    /**
    * Writes Excel BOF record to indicate the beginning of a stream or
    * sub-stream in the BIFF file.
    *
    * @param  integer $type Type of BIFF file to write: 0x0005 Workbook,
    *                       0x0010 Worksheet.
    * @access private
    */
    function _storeBof($type)
    {
        $record  = 0x0809;        // Record identifier

        // According to the SDK $build and $year should be set to zero.
        // However, this throws a warning in Excel 5. So, use magic numbers.
        if ($this->_BIFF_version == 0x0500) {
            $length  = 0x0008;
            $unknown = '';
            $build   = 0x096C;
            $year    = 0x07C9;
        } elseif ($this->_BIFF_version == 0x0600) {
            $length  = 0x0010;
            $unknown = pack("VV", 0x00000041, 0x00000006); //unknown last 8 bytes for BIFF8
            $build   = 0x0DBB;
            $year    = 0x07CC;
        }
        $version = $this->_BIFF_version;

        $header  = pack("vv",   $record, $length);
        $data    = pack("vvvv", $version, $type, $build, $year);
        $this->_prepend($header . $data . $unknown);
    }

    /**
    * Writes Excel EOF record to indicate the end of a BIFF stream.
    *
    * @access private
    */
    function _storeEof()
    {
        $record    = 0x000A;   // Record identifier
        $length    = 0x0000;   // Number of bytes to follow
        $header    = pack("vv", $record, $length);
        $this->_append($header);
    }

    /**
    * Excel limits the size of BIFF records. In Excel 5 the limit is 2084 bytes. In
    * Excel 97 the limit is 8228 bytes. Records that are longer than these limits
    * must be split up into CONTINUE blocks.
    *
    * This function takes a long BIFF record and inserts CONTINUE records as
    * necessary.
    *
    * @param  string  $data The original binary data to be written
    * @return string        A very convenient string of continue blocks
    * @access private
    */
    function _addContinue($data)
    {
        $limit  = $this->_limit;
        $record = 0x003C;         // Record identifier

        // The first 2080/8224 bytes remain intact. However, we have to change
        // the length field of the record.
        $tmp = substr($data, 0, 2).pack("v", $limit-4).substr($data, 4, $limit - 4);

        $header = pack("vv", $record, $limit);  // Headers for continue records

        // Retrieve chunks of 2080/8224 bytes +4 for the header.
        $data_length = strlen($data);
        for ($i = $limit; $i <  ($data_length - $limit); $i += $limit) {
            $tmp .= $header;
            $tmp .= substr($data, $i, $limit);
        }

        // Retrieve the last chunk of data
        $header  = pack("vv", $record, strlen($data) - $i);
        $tmp    .= $header;
        $tmp    .= substr($data, $i, strlen($data) - $i);

        return $tmp;
    }
}
?>