<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<META http-equiv="Content-Type" content="text/html; charset=UTF-8">
<!--*** This is a generated file. Do not edit. ***-->
<link rel="stylesheet" href="../skin/tigris.css" type="text/css">
<link rel="stylesheet" href="../skin/mysite.css" type="text/css">
<link rel="stylesheet" href="../skin/site.css" type="text/css">
<link media="print" rel="stylesheet" href="../skin/print.css" type="text/css">
<title>POIFS File System Internals</title>
</head>
<body bgcolor="white" class="composite">
<!--================= start Banner ==================-->
<div id="banner">
<table width="100%" cellpadding="8" cellspacing="0" summary="banner" border="0">
<tbody>
<tr>
<!--================= start Group Logo ==================-->
<td width="50%" align="left">
<div class="groupLogo">
<a href="http://poi.apache.org"><img border="0" class="logoImage" alt="Apache POI" src="../resources/images/group-logo.jpg"></a>
</div>
</td>
<!--================= end Group Logo ==================-->
<!--================= start Project Logo ==================--><td width="50%" align="right">
<div align="right" class="projectLogo">
<a href="http://poi.apache.org/"><img border="0" class="logoImage" alt="POI" src="../resources/images/project-logo.jpg"></a>
</div>
</td>
<!--================= end Project Logo ==================-->
</tr>
</tbody>
</table>
</div>
<!--================= end Banner ==================-->
<!--================= start Main ==================-->
<table width="100%" cellpadding="0" cellspacing="0" border="0" summary="nav" id="breadcrumbs">
<tbody>
<!--================= start Status ==================-->
<tr class="status">
<td>
<!--================= start BreadCrumb ==================--><a href="http://www.apache.org/">Apache</a> | <a href="http://poi.apache.org/">POI</a><a href=""></a>
<!--================= end BreadCrumb ==================--></td><td id="tabs">
<!--================= start Tabs ==================-->
<div class="tab">
<span class="selectedTab"><a class="base-selected" href="../index.html">Home</a></span> | <script language="Javascript" type="text/javascript">
function printit() {
if (window.print) {
window.print() ;
} else {
var WebBrowser = '<OBJECT ID="WebBrowser1" WIDTH="0" HEIGHT="0" CLASSID="CLSID:8856F961-340A-11D0-A96B-00C04FD705A2"></OBJECT>';
document.body.insertAdjacentHTML('beforeEnd', WebBrowser);
WebBrowser1.ExecWB(6, 2);//Use a 1 vs. a 2 for a prompting dialog box WebBrowser1.outerHTML = "";
}
}
</script><script language="Javascript" type="text/javascript">
var NS = (navigator.appName == "Netscape");
var VERSION = parseInt(navigator.appVersion);
if (VERSION > 3) {
document.write(' <a title="PRINT this page OUT" href="javascript:printit()">PRINT</a>');
}
</script> | <a title="PDF file of this page" href="fileformat.pdf">PDF</a>
</div>
<!--================= end Tabs ==================-->
</td>
</tr>
</tbody>
</table>
<!--================= end Status ==================-->
<table id="main" width="100%" cellpadding="8" cellspacing="0" summary="" border="0">
<tbody>
<tr valign="top">
<!--================= start Menu ==================-->
<td id="leftcol">
<div id="navcolumn">
<div class="menuBar">
<div class="menu">
<span class="menuLabel">Apache POI</span>
<div class="menuItem">
<a href="../index.html">Top</a>
</div>
</div>
<div class="menu">
<span class="menuLabel">POIFS</span>
<div class="menuItem">
<a href="index.html">Overview</a>
</div>
<div class="menuItem">
<a href="how-to.html">How To</a>
</div>
<div class="menuItem">
<a href="embeded.html">Embeded Documents</a>
</div>
<div class="menuItem">
<span class="menuSelected">File System Documentation</span>
</div>
<div class="menuItem">
<a href="usecases.html">Use Cases</a>
</div>
</div>
</div>
</div>
<form target="_blank" action="http://www.google.com/search" method="get">
<table summary="search" border="0" cellspacing="0" cellpadding="0">
<tr>
<td><img height="1" width="1" alt="" src="../skin/images/spacer.gif" class="spacer"></td><td nowrap="nowrap">
Search Apache POI<br>
<input value="poi.apache.org" name="sitesearch" type="hidden"><input size="10" name="q" id="query" type="text"><img height="1" width="5" alt="" src="../skin/images/spacer.gif" class="spacer"><input name="Search" value="GO" type="submit"></td><td><img height="1" width="1" alt="" src="../skin/images/spacer.gif" class="spacer"></td>
</tr>
<tr>
<td colspan="3"><img height="7" width="1" alt="" src="../skin/images/spacer.gif" class="spacer"></td>
</tr>
<tr>
<td class="bottom-left-thick"></td><td bgcolor="#a5b6c6"><img height="1" width="1" alt="" src="../skin/images/spacer.gif" class="spacer"></td><td class="bottom-right-thick"></td>
</tr>
</table>
</form>
</td>
<!--================= end Menu ==================-->
<!--================= start Content ==================--><td>
<div id="bodycol">
<div class="app">
<div align="center">
<h1>POIFS File System Internals</h1>
</div>
<div class="h3">
<a name="POIFS+File+System+Internals"></a>
<div class="h3">
<h3>POIFS File System Internals</h3>
</div>
<a name="Introduction"></a>
<div class="h4">
<h4>Introduction</h4>
</div>
<p>POIFS file systems are essentially normal files stored on a
Java-compatible platform's native file system. They are
typically identified by names ending in a four character
extension noting what type of data they contain. For
example, a file ending in ".xls" would likely
contain spreadsheet data, and a file ending in
".doc" would probably contain a word processing
document. POIFS file systems are called "file
system", because they contain multiple embedded files
in a manner similar to traditional file systems. Along
functional lines, it would be more accurate to call these
POIFS archives. For the remainder of this document it is
referred to as a file system in order to avoid confusion
with the "files" it contains.</p>
<p>POIFS file systems are compatible with those document
formats used by a well-known software company's popular
office productivity suite and programs outputting
compatible data. Because the POIFS file system does not
provide compression, encryption or any other worthwhile
feature, its not a good choice unless you require
interoperability with these programs.</p>
<p>The POIFS file system does not encode the documents
themselves. For example, if you had a word processor file
with the extension ".doc", you would actually
have a POIFS file system with a document file archived
inside of that file system.</p>
<p>Note - this document is a good overview and explanation of
the file format, but for the very nitty-gritty details,
you should refer to
<a href="http://msdn.microsoft.com/en-us/library/dd942138%28v=prot.13%29.aspx">[MS-CFB].pdf</a>
in the (now public) Microsoft Documentation.</p>
<a name="Document+Conventions"></a>
<div class="h4">
<h4>Document Conventions</h4>
</div>
<p>This document utilizes the numeric types as described by
the Java Language Specification, which can be found at
<a href="http://java.sun.com">http://java.sun.com</a>. In
short:</p>
<ul>
<li>A <em>byte</em> is an 8 bit signed integer ranging from
-128 to 127.</li>
<li>A <em>short</em> is a 16 bit signed integer ranging from
-32768 to 32767</li>
<li>An <em>int</em> is a 32 bit signed integer ranging from
-2147483648 to 2147483647</li>
<li>A <em>long</em> is a 64 bit signed integer ranging from
-9.22E18 to 9.22E18.</li>
</ul>
<p>The Java Language Specification spells out a number of
other types that are not referred to by this document.</p>
<p>Where this document makes references to "endian
conversion" it is referring to the byte order of
stored numbers. Numbers in "little-endian order"
are stored with the <em>least</em> significant byte first. In
order to properly read a short, for example, you'd read two
bytes and then shift the second byte 8 bits to the left
before performing an <span class="codefrag">or</span> operation to it
against the first byte. The following code illustrates this
method:</p>
<pre class="code">
public int getShort (byte[] rec)
{
return ((rec[1] << 8) | (rec[0] & 0x00ff));
}</pre>
<a name="File+System+Walkthrough"></a>
<div class="h4">
<h4>File System Walkthrough</h4>
</div>
<p>This is a walkthrough of a POIFS file system and how it is
put together. It is not intended to give a concise
description but to give a "big picture" of the
general structure and how it's interpreted.</p>
<p>A POIFS file system begins with a header. This header
identifies locations in the file by function and provides a
sanity check identifying a file as a POIFS file system.</p>
<p>The first 64 bits of the header compose a <em>magic number
identifier.</em> This identifier tells the client software
that this is indeed a POIFS file system and that it should
be treated as such. This is a "sanity check" to
make sure this is a POIFS file system and not some other
format. The header also contains an <em>array of block
numbers</em>. These block numbers refer to blocks in the
file. When these blocks are read together they form the
<em>Block Allocation Table</em>. The header also contains a
pointer to the first element in the <em>property table</em>,
also known as the <em>root element</em>, and a pointer to the
<em>small Block Allocation Table (SBAT)</em>.</p>
<p>The <em>block allocation table</em> or <em>BAT</em>, along with
the <em>property table</em>, specify which blocks in the file
system belong to which files. After the header block, the
file system is divided into identically sized blocks of
data, numbered from 0 to however many blocks there are in
the file system. For each file in the file system, its
entry in the property table includes the index of the first
block in the array of blocks. Each block's index into the
array of blocks is also its index into the BAT, and the
integer value stored at that index in the BAT gives the
index of the next block in the array (and thus the index of
the next BAT value). A special value is stored in the BAT
to indicate "end of file".</p>
<p>The <em>property table</em> is essentially the directory
storage for the file system. It consists of the name of the
file or directory, its <em>start block</em> in both the file
system and <em>BAT</em>, and its actual size. The first
property in the property table is the <em>root
element</em>. It has two purposes: to be a directory entry
(the root of the directory tree, to be specific), and to
hold the start block for the <em>small block data</em>.</p>
<p>Small block data is a special file that contains the data
for small files (less than 4K bytes). It subdivides its
blocks into smaller blocks and there is a special small
block allocation table that, like the main BAT for larger
files, is used to map a small file to its small blocks.</p>
<a name="Header+Block"></a>
<div class="h4">
<h4>Header Block</h4>
</div>
<p>The POIFS file system begins with a <em>header
block</em>. The first 64 bits of the header form a long
<em>file type id</em> or <em>magic number identifier</em> of
<span class="codefrag">0xE11AB1A1E011CFD0L</span>. This is basically a
sanity check. If this isn't the first thing in the header
(and consequently the file system) then this is not a
POIFS file system and should be read with some other
library.</p>
<p>It's important to know the most important parts of the
header. These are discussed in the rest of this
section.</p>
<a name="BATs"></a>
<div class="h2">
<h2>BATs</h2>
</div>
<p>At offset <em>0x2C</em> is an int specifying the number
of elements in the <em>BAT array</em>. The array at
<em>0x4C</em> an array of ints. This array contains the
indices of every block in the Block Allocation
Table.</p>
<a name="XBATs"></a>
<div class="h2">
<h2>XBATs</h2>
</div>
<p>Very large POIFS archives may have more blocks than can
be addressed by the BAT blocks enumerated in the header
block. How large? Well, the BAT array in the header can
contain up to 109 BAT block indices; each BAT block
references up to 128 blocks, and each block is 512
bytes, so we're talking about 109 * 128 * 512 =
6.8MB. That's a pretty respectable document! But, you
could have much more data than that, and in today's
world of cheap gigabyte drives, why not? So, the BAT
may be extended in that event. The integer value at
offset <em>0x44</em> of the header is the index of the
first <em>extended BAT (XBAT) block</em>. At offset
<em>0x48</em> of the header, there is an int value that
specifies how many XBAT blocks there are. The XBAT
blocks begin at the specified index into the array of
blocks making up the POIFS file system, and are chained
for the specified count of XBAT blocks.</p>
<p>Each XBAT block contains the indices of up to 127 BAT
blocks, so the document size can be expanded by another
~8MB for each XBAT block. The BAT blocks indexed by an
XBAT block are appended to the end of the list of BAT
blocks enumerated in the header block. Thus the BAT
blocks enumerated in the header block are BAT blocks 0
through 108, the BAT blocks enumerated in the first
XBAT block are BAT blocks 109 through 235, the BAT
blocks enumerated in the second XBAT block are BAT
blocks 236 through 362, and so on.</p>
<p>While a normal BAT block holds 128 entries, each XBAT
only references 127 BAT blocks. The last, 128th entry
in an XBAT is the offset to the next XBAT block in the
chain (or -1 if this is the last XBAT).</p>
<p>Through the use of XBAT blocks, the limit on the
overall document size is that imposed by the 4-byte
block indices; if the indices are unsigned ints, the
maximum file size is 2 terabytes, 1 terabyte if the
indices are treated as signed ints. Either way, I have
yet to see a disk drive large enough to accommodate
such a file on the shelves at the local office supply
stores.</p>
<a name="SBATs"></a>
<div class="h2">
<h2>SBATs</h2>
</div>
<p>If a file contained in a POIFS archive is smaller than
4096 bytes, it is stored in small blocks. Small blocks
are 64 bytes in length and are contained within big
blocks, up to 8 to a big block. As the main BAT is used
to navigate the array of big blocks, so the <em>small
block allocation table</em> is used to navigate the
array of small blocks. The SBAT's start block index is
found at offset <em>0x3C</em> of the header block, and
remaining blocks constituting the SBAT are found by
walking the main BAT as if it were an ordinary file in
the POIFS file system (this process is described
below).</p>
<a name="Property+Table+Start+Index"></a>
<div class="h2">
<h2>Property Table Start Index</h2>
</div>
<p>An integer at address <em>0x30</em> specifies the start
index of the property table. This integer is specified
as a <em>"block index"</em>. The Property Table
is stored, as is almost everything in a POIFS file
system, in big blocks and walked via the BAT. The
Property Table is described below.</p>
<a name="Property+Table"></a>
<div class="h4">
<h4>Property Table</h4>
</div>
<p>The property table is essentially nothing more than the
directory system. Properties are 128 byte records
contained within the 512 byte blocks. The first property
is always the Root Entry. The following applies to
individual properties within a property table:</p>
<ul>
<li>At offset <em>0x00</em> in the property is the
"<em>name</em>". This is stored as an
uncompressed 16 bit unicode string. In short every
other byte corresponds to an "ASCII"
character. The size of this string is stored at offset
<em>0x40</em> (<em>string size</em>) as a short.</li>
<li>At offset <em>0x42</em> is the <em>property type</em>
(byte). The type is 1 for directory, 2 for file or 5
for the Root Entry.</li>
<li>At offset <em>0x43</em> is the <em>node color</em>
(byte). The color is either 1, (black), or 0,
(red). Properties are apparently meant to be arranged
in a red-black binary tree, subject to the following
rules:
<ol>
<li>The root of the tree is always black</li>
<li>Two consecutive nodes cannot both be red</li>
<li>A property is less than another property if its
name length is less than the other property's name
length</li>
<li>If two properties have the same name length, the
sort order is determined by the sort order of the
properties' names.</li>
</ol>
</li>
<li>At offset <em>0x44</em> is the index (int) of the
<em>previous property</em>.</li>
<li>At offset <em>0x48</em> is the index (int) of the
<em>next property</em>.</li>
<li>At offset <em>0x4C</em> is the index (int) of the
<em>first directory entry</em>. This is used by
directory entries.</li>
<li>At offset <em>0x74</em> is an integer giving the
<em>start block</em> for the file described by this
property. This index corresponds to an index in the
array of indices that is the Block Allocation Table
(or the Small Block Allocation Table) as well as the
index of the first block in the file. This is used by
files and the root entry.</li>
<li>At offset <em>0x78</em> is an integer giving the total
<em>actual size</em> of the file pointed at by this
property. If the file size is less than 4096, the file
is stored in small blocks and the SBAT is used to walk
the small blocks making up the file. If the file size
is 4096 or larger, the file is stored in big blocks
and the main BAT is used to walk the big blocks making
up the file. The exception to this rule is the <em>Root
Entry</em>, which, regardless of its size, is
<em>always</em> stored in big blocks and the main BAT is
used to walk the big blocks making up this special
file.</li>
</ul>
<a name="Root+Entry"></a>
<div class="h4">
<h4>Root Entry</h4>
</div>
<p>The <em>Root Entry</em> in the <em>Property Table</em>
contains the information necessary to read and write
small files, which are files less than 4096 bytes
long. The start block field of the Root Entry is the
start index of the <em>Small Block Array</em>, which is
read like any other file in the POIFS file system. Since
the SBAT cannot be used without the Small Block Array,
the Root Entry MUST be read or written using the <em>Block
Allocation Table</em>. The blocks making up the Small
Block Array are divided into 64-byte small blocks, up to
the size indicated in the Root Entry (which should always
be a multiple of 64).</p>
<a name="Walking+the+Nodes+of+the+Property+Table"></a>
<div class="h4">
<h4>Walking the Nodes of the Property Table</h4>
</div>
<p>The individual properties form a directory tree, with the
<em>Root Entry</em> as the directory tree's root, as shown
in the accompanying drawing. Note the numbers in
parentheses in each node; they represent the node's index
in the array of properties. The <em>NEXT_PROP</em>,
<em>PREVIOUS_PROP</em>, and <em>CHILD_PROP</em> fields hold
these indices, and are used to navigate the tree.</p>
<p>
<img alt="property set" src="images/PropertySet.jpg"></p>
<p>Each directory entry (i.e., a property whose type is
<em>directory</em> or <em>root entry</em>) uses its
<em>CHILD_PROP</em> field to point to one of its
subordinate (child) properties. It doesn't seem to matter
which of its children it points to. Thus in the previous
drawing, the Root Entry's CHILD_PROP field may contain 1,
4, or the index of one of its other children. Similarly,
the directory node (index 1) may have, in its CHILD_PROP
field, 2, 3, or the index of one of its other
children.</p>
<p>The children of a given directory property point to each
other in a similar fashion by using their
<em>NEXT_PROP</em> and <em>PREVIOUS_PROP</em> fields.</p>
<p>Unused <em>NEXT_PROP</em>, <em>PREVIOUS_PROP</em>, and
<em>CHILD_PROP</em> fields contain the marker value of
-1. All file properties have a value of -1 for their
CHILD_PROP fields for example.</p>
<a name="Block+Allocation+Table"></a>
<div class="h4">
<h4>Block Allocation Table</h4>
</div>
<p>The <em>BAT blocks</em> are pointed at by the bat array
contained in the header and supplemented, if necessary,
by the <em>XBAT blocks</em>. These blocks form a large
table of integers. These integers are block numbers. The
<em>Block Allocation Table</em> holds chains of integers.
These chains are terminated with -2. The elements in
these chains refer to blocks in the files. The starting
block of a file is NOT specified in the BAT. It is
specified by the <em>property</em> for a given file. The
elements in this BAT are both the block number (within
the file minus the header) <em>and</em> the number of the
next BAT element in the chain. This can be thought of as
a linked list of blocks. The BAT array contains the links
from one block to the next, including the end of chain
marker.</p>
<p>Here's an example: Let's assume that the BAT begins as
follows:</p>
<p>
<span class="codefrag">BAT[ 0 ] = 2</span>
</p>
<p>
<span class="codefrag">BAT[ 1 ] = 5</span>
</p>
<p>
<span class="codefrag">BAT[ 2 ] = 3</span>
</p>
<p>
<span class="codefrag">BAT[ 3 ] = 4</span>
</p>
<p>
<span class="codefrag">BAT[ 4 ] = 6</span>
</p>
<p>
<span class="codefrag">BAT[ 5 ] = -2</span>
</p>
<p>
<span class="codefrag">BAT[ 6 ] = 7</span>
</p>
<p>
<span class="codefrag">BAT[ 7 ] = -2</span>
</p>
<p>
<span class="codefrag">...</span>
</p>
<p>Now, if we have a file whose Property Table entry says it
begins with index 0, we walk the BAT array and see that
the file consists of blocks 0 (because the start block is
0), 2 (because BAT[ 0 ] is 2), 3 (BAT[ 2 ] is 3), 4 (BAT[
3 ] is 4), 6 (BAT[ 4 ] is 6), and 7 (BAT[ 6 ] is 7). It
ends at block 7 because BAT[ 7 ] is -2, which is the end
of chain marker.</p>
<p>Similarly, a file beginning at index 1 consists of
blocks 1 and 5.</p>
<p>Other special numbers in a BAT array are:</p>
<ul>
<li>-1, which indicates an unused block</li>
<li>-3, which indicates a "special" block, such
as a block used to make up the Small Block Array, the
Property Table, the main BAT, or the SBAT</li>
</ul>
<a name="File+System+Structures"></a>
<div class="h4">
<h4>File System Structures</h4>
</div>
<p>The following outlines the basic file system structures.</p>
<a name="Header+%28block+1%29+--+512+%280x200%29+bytes"></a>
<div class="h2">
<h2>Header (block 1) -- 512 (0x200) bytes</h2>
</div>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<td colspan="1" rowspan="1"><em>Field</em></td>
<td colspan="1" rowspan="1"><em>Description</em></td>
<td colspan="1" rowspan="1"><em>Offset</em></td>
<td colspan="1" rowspan="1"><em>Length</em></td>
<td colspan="1" rowspan="1"><em>Default value or const</em></td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">FILETYPE</td>
<td colspan="1" rowspan="1">Magic number identifying this as a POIFS file
system.</td>
<td colspan="1" rowspan="1">0x0000</td>
<td colspan="1" rowspan="1">Long</td>
<td colspan="1" rowspan="1">0xE11AB1A1E011CFD0</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">UK1</td>
<td colspan="1" rowspan="1">Unknown constant</td>
<td colspan="1" rowspan="1">0x0008</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">UK2</td>
<td colspan="1" rowspan="1">Unknown Constant</td>
<td colspan="1" rowspan="1">0x000C</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">UK3</td>
<td colspan="1" rowspan="1">Unknown Constant</td>
<td colspan="1" rowspan="1">0x0014</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">UK4</td>
<td colspan="1" rowspan="1">Unknown Constant (revision?)</td>
<td colspan="1" rowspan="1">0x0018</td>
<td colspan="1" rowspan="1">Short</td>
<td colspan="1" rowspan="1">0x003B</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">UK5</td>
<td colspan="1" rowspan="1">Unknown Constant (version?)</td>
<td colspan="1" rowspan="1">0x001A</td>
<td colspan="1" rowspan="1">Short</td>
<td colspan="1" rowspan="1">0x0003</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">UK6</td>
<td colspan="1" rowspan="1">Unknown Constant</td>
<td colspan="1" rowspan="1">0x001C</td>
<td colspan="1" rowspan="1">Short</td>
<td colspan="1" rowspan="1">-2</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">LOG_2_BIG_BLOCK_SIZE</td>
<td colspan="1" rowspan="1">Log, base 2, of the big block size</td>
<td colspan="1" rowspan="1">0x001E</td>
<td colspan="1" rowspan="1">Short</td>
<td colspan="1" rowspan="1">9 (2 ^ 9 = 512 bytes)</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">LOG_2_SMALL_BLOCK_SIZE</td>
<td colspan="1" rowspan="1">Log, base 2, of the small block size</td>
<td colspan="1" rowspan="1">0x0020</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">6 (2 ^ 6 = 64 bytes)</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">UK7</td>
<td colspan="1" rowspan="1">Unknown Constant</td>
<td colspan="1" rowspan="1">0x0024</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">UK8</td>
<td colspan="1" rowspan="1">Unknown Constant</td>
<td colspan="1" rowspan="1">0x0028</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">BAT_COUNT</td>
<td colspan="1" rowspan="1">Number of elements in the BAT array</td>
<td colspan="1" rowspan="1">0x002C</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">required</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">PROPERTIES_START</td>
<td colspan="1" rowspan="1">Block index of the first block of the property
table</td>
<td colspan="1" rowspan="1">0x0030</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">required</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">UK9</td>
<td colspan="1" rowspan="1">Unknown Constant</td>
<td colspan="1" rowspan="1">0x0034</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">UK10</td>
<td colspan="1" rowspan="1">Unknown Constant</td>
<td colspan="1" rowspan="1">0x0038</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0x00001000</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">SBAT_START</td>
<td colspan="1" rowspan="1">Block index of first big block containing the small
block allocation table (SBAT)</td>
<td colspan="1" rowspan="1">0x003C</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">-2</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">SBAT_Block_Count</td>
<td colspan="1" rowspan="1">Number of big blocks holding the SBAT</td>
<td colspan="1" rowspan="1">0x0040</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">1</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">XBAT_START</td>
<td colspan="1" rowspan="1">Block index of the first block in the Extended Block
Allocation Table (XBAT)</td>
<td colspan="1" rowspan="1">0x0044</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">-2</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">XBAT_COUNT</td>
<td colspan="1" rowspan="1">Number of elements in the Extended Block Allocation
Table (to be added to the BAT)</td>
<td colspan="1" rowspan="1">0x0048</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">BAT_ARRAY</td>
<td colspan="1" rowspan="1">Array of block indices constituting the Block
Allocation Table (BAT)</td>
<td colspan="1" rowspan="1">0x004C, 0x0050, 0x0054 ... 0x01FC</td>
<td colspan="1" rowspan="1">Integer[]</td>
<td colspan="1" rowspan="1">-1 for unused elements, at least first element must
be filled.</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">N/A</td>
<td colspan="1" rowspan="1">Header block data not otherwise described in this
table</td>
<td colspan="1" rowspan="1">N/A</td>
<td colspan="1" rowspan="1">N/A</td>
<td colspan="1" rowspan="1">-1</td>
</tr>
</table>
<a name="Block+Allocation+Table+Block+--+512+%280x200%29+bytes"></a>
<div class="h2">
<h2>Block Allocation Table Block -- 512 (0x200) bytes</h2>
</div>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<td colspan="1" rowspan="1">
<em>Field</em>
</td>
<td colspan="1" rowspan="1">
<em>Description</em>
</td>
<td colspan="1" rowspan="1">
<em>Offset</em>
</td>
<td colspan="1" rowspan="1">
<em>Length</em>
</td>
<td colspan="1" rowspan="1">
<em>Default value or const</em>
</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">BAT_ELEMENT</td>
<td colspan="1" rowspan="1">Any given element in the BAT block</td>
<td colspan="1" rowspan="1">0x0000, 0x0004, 0x0008, ... 0x01FC</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">
-1 = unused<br>
-2 = end of chain<br>
-3 = special (e.g., BAT block)<br>
All other values point to the next element in the
chain and the next index of a block composing the
file.
</td>
</tr>
</table>
<a name="Property+Block+--+512+%280x200%29+byte+block"></a>
<div class="h2">
<h2>Property Block -- 512 (0x200) byte block</h2>
</div>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<td colspan="1" rowspan="1"><em>Field</em></td>
<td colspan="1" rowspan="1"><em>Description</em></td>
<td colspan="1" rowspan="1"><em>Offset</em></td>
<td colspan="1" rowspan="1"><em>Length</em></td>
<td colspan="1" rowspan="1"><em>Default value or const</em></td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">Properties[]</td>
<td colspan="1" rowspan="1">This block contains the properties.</td>
<td colspan="1" rowspan="1">0x0000, 0x0080, 0x0100, 0x0180</td>
<td colspan="1" rowspan="1">128 bytes</td>
<td colspan="1" rowspan="1">All unused space is set to -1.</td>
</tr>
</table>
<a name="Property+--+128+%280x80%29+byte+block"></a>
<div class="h2">
<h2>Property -- 128 (0x80) byte block</h2>
</div>
<table class="ForrestTable" cellspacing="1" cellpadding="4">
<tr class="b">
<td colspan="1" rowspan="1"><em>Field</em></td>
<td colspan="1" rowspan="1"><em>Description</em></td>
<td colspan="1" rowspan="1"><em>Offset</em></td>
<td colspan="1" rowspan="1"><em>Length</em></td>
<td colspan="1" rowspan="1"><em>Default value or const</em></td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">NAME</td>
<td colspan="1" rowspan="1">A unicode null-terminated uncompressed 16bit string
(lose the high bytes) containing the name of the
property.</td>
<td colspan="1" rowspan="1">0x00, 0x02, 0x04, ... 0x3E</td>
<td colspan="1" rowspan="1">Short[]</td>
<td colspan="1" rowspan="1">0x0000 for unused elements, field required, 32
(0x40) element max</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">NAME_SIZE</td>
<td colspan="1" rowspan="1">Number of characters in the NAME field</td>
<td colspan="1" rowspan="1">0x40</td>
<td colspan="1" rowspan="1">Short</td>
<td colspan="1" rowspan="1">Required</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">PROPERTY_TYPE</td>
<td colspan="1" rowspan="1">Property type (directory, file, or root)</td>
<td colspan="1" rowspan="1">0x42</td>
<td colspan="1" rowspan="1">Byte</td>
<td colspan="1" rowspan="1">1 (directory), 2 (file), or 5 (root entry)</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">NODE_COLOR</td>
<td colspan="1" rowspan="1">Node color</td>
<td colspan="1" rowspan="1">0x43</td>
<td colspan="1" rowspan="1">Byte</td>
<td colspan="1" rowspan="1">0 (red) or 1 (black)</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">PREVIOUS_PROP</td>
<td colspan="1" rowspan="1">Previous property index</td>
<td colspan="1" rowspan="1">0x44</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">-1</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">NEXT_PROP</td>
<td colspan="1" rowspan="1">Next property index</td>
<td colspan="1" rowspan="1">0x48</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">-1</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">CHILD_PROP</td>
<td colspan="1" rowspan="1">First child property index</td>
<td colspan="1" rowspan="1">0x4c</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">-1</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">SECONDS_1</td>
<td colspan="1" rowspan="1">Seconds component of the created timestamp?</td>
<td colspan="1" rowspan="1">0x64</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">DAYS_1</td>
<td colspan="1" rowspan="1">Days component of the created timestamp?</td>
<td colspan="1" rowspan="1">0x68</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">SECONDS_2</td>
<td colspan="1" rowspan="1">Seconds component of the modified timestamp?</td>
<td colspan="1" rowspan="1">0x6C</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">DAYS_2</td>
<td colspan="1" rowspan="1">Days component of the modified timestamp?</td>
<td colspan="1" rowspan="1">0x70</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
<tr class="b">
<td colspan="1" rowspan="1">START_BLOCK</td>
<td colspan="1" rowspan="1">Starting block of the file, used as the first block
in the file and the pointer to the next block from
the BAT</td>
<td colspan="1" rowspan="1">0x74</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">Required</td>
</tr>
<tr class="a">
<td colspan="1" rowspan="1">SIZE</td>
<td colspan="1" rowspan="1">Actual size of the file this property points
to. (used to truncate the blocks to the real
size).</td>
<td colspan="1" rowspan="1">0x78</td>
<td colspan="1" rowspan="1">Integer</td>
<td colspan="1" rowspan="1">0</td>
</tr>
</table>
<div id="authors" align="right">by Marc Johnson</div>
</div>
</div>
</div>
</td>
<!--================= end Content ==================-->
</tr>
</tbody>
</table>
<!--================= end Main ==================-->
<!--================= start Footer ==================-->
<div id="footer">
<table summary="footer" cellspacing="0" cellpadding="4" width="100%" border="0">
<tbody>
<tr>
<!--================= start Copyright ==================-->
<td colspan="2">
<div align="center">
<div class="copyright">
Copyright © 2002-2011 The Apache Software Foundation. All rights reserved.<br>
Apache POI, POI, Apache, the Apache feather logo, and the Apache
POI project logo are trademarks of The Apache Software Foundation.
</div>
</div>
</td>
<!--================= end Copyright ==================-->
</tr>
<tr>
<td align="left">
<!--================= start Host ==================-->
<!--================= end Host ==================--></td><td align="right">
<!--================= start Credits ==================-->
<div align="right">
<div class="credit"></div>
</div>
<!--================= end Credits ==================-->
</td>
</tr>
</tbody>
</table>
</div>
<!--================= end Footer ==================-->
</body>
</html>
