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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.1//EN" "../dtd/document-v11.dtd">
<document>
<header>
<title>Hacking HSSF</title>
<authors>
<person email="poi-user@jakarta.apache.org" name="Glen Stampoultzis" id="GJS"/>
<person email="acoliver@apache.org" name="Andrew Oliver" id="AO"/>
</authors>
</header>
<body>
<section><title>Where Can I Find Documentation on Feature X</title>
<p>
You might find the
'Excel 97 Developer's Kit' (out of print, Microsoft Press, no
restrictive covenants, available on Amazon.com) helpful for
understanding the file format.
</p>
<p>
Also useful is the <link href="http://sc.openoffice.org/excelfileformat.pdf">open office XLS spec</link>. We
are collaborating with the maintainer of the spec so if you think you can add something to their
document just send through your changes.
</p>
</section>
<section><title>Help, I Can't Find Feature X Documented Anywhere</title>
<ol>
<li>
Look at OpenOffice.org or Gnumeric sources if its implemented there.
</li>
<li>
Use org.apache.poi.hssf.dev.BiffViewer to view the structure of the
file. Experiment by adding one criteria entry at a time. See what it
does to the structure, infer behavior and structure from it. Using the
unix diff command (or get cygwin from www.cygwin.com for windows) you
can figure out a lot very quickly. Unimplemented records show up as
'UNKNOWN' and prints a hex dump.
</li>
</ol>
</section>
<section><title>Low-level Record Generation</title>
<p>
Low level records can be time consuming to created. We created a record
generator to help generate some of the simpler tasks.
</p>
<p>
We use XML
descriptors to generate the Java code (which sure beats the heck out of
the PERL scripts originally used ;-) for low level records. The
generator is kinda alpha-ish right now and could use some enhancement,
so you may find that to be about 1/2 of the work. Notice this is in
org.apache.poi.hssf.record.definitions.
</p>
</section>
<section><title>Important Notice</title>
<p>One thing to note: If you are making a large code contribution we need to ensure
any participants in this process have never
signed a "Non Disclosure Agreement" with Microsoft, and have not
received any information covered by such an agreement. If they have
they'll not be able to participate in the POI project. For large contributions we
may ask you to sign an agreement.</p>
</section>
<section><title>What Can I Work On?</title>
<p>Check our <link href="../todo.html">todo list</link> or simply look for missing functionality. Start small
and work your way up.</p>
</section>
<section><title>What Else Should I Know?</title>
<p>Make sure you <link href="http://jakarta.apache.org/poi/contrib.html">read the contributing section</link>
as it contains more generation information about contributing to POI in general.</p>
</section>
</body>
</document>
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