Olivier Mengué – Code & rando

I'm currently playing with XSLT to improve my XMLTV grabbing solution. Much fun playing with a functionnal language available in most web browsers.

I had the need to handle timezone with daylight savings to display date/times in my timezone, Europe/Paris (same as most of western Europe), which has currently the following definition (I'm not interested in history for this project):

• Winter is UTC + 01:00
• Summer is UTC + 02:00
• Transition from winter to summer occurs on the last sunday of March at 01:00 UTC
• Transition from summer to winter occurs on the last sunday of October at 01:00 UTC

So I wrote the following template date-time-Paris which is very specialized as it handles only one specific timezone, but it is very fast. I'm using only two extensions from EXSLT: date:day-in-week() and date:add().

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:tap="test:tap"
  xmlns:date="http://exslt.org/dates-and-times"
  extension-element-prefixes="date"
  >

  <!-- Transformation de l'heure UTC en heure de Paris -->
  <!-- Copyright (c) 2008 Olivier Mengué -->
  <xsl:template name="date-time-Paris">
    <!--
      Daylight savings transitions:
      - last sunday of March at 1:00 UTC
      - last sunday of October at 1:00 UTC
      Time offsets:
      - winter: +01:00
      - summer: +02:00
    -->
    <xsl:param name="date-time-Z"/><!-- UTC -->
    <xsl:variable name="len" select="string-length($date-time-Z)"/>
    <xsl:variable name="seps" select="translate($date-time-Z, '0123456789', '')"/>
    <xsl:if test="$len &lt; 11 or substring($date-time-Z, $len, 1) != 'Z' or ($seps != '--T::Z' and $seps != '--T::.Z' and $seps != '--Z' and $seps != '--TZ' and $seps != '--T:Z')">
      <xsl:message terminate="yes">date-time-Paris: date '<xsl:value-of select="$date-time-Z"/>' invalide.</xsl:message>
    </xsl:if>
    <xsl:variable name="month" select="number(substring($date-time-Z, 6, 2))"/>
    <xsl:variable name="offset">
      <xsl:choose>
        <xsl:when test="$month &lt; 3 or $month &gt; 10">1</xsl:when>
        <xsl:when test="$month &gt; 3 and $month &lt; 10">2</xsl:when>
        <xsl:otherwise>
          <xsl:variable name="transition-day" select="32 - date:day-in-week(concat(substring($date-time-Z, 1, 7), '-31Z'))"/>
          <xsl:variable name="less" select="translate(substring($date-time-Z, 8), '-T:Z', '') &lt; $transition-day*1000000+10000"/>
          <xsl:value-of select="1+number(($less and $month = 10) or (not($less) and $month = 3))"/>
        </xsl:otherwise>
      </xsl:choose>
    </xsl:variable>
    <xsl:value-of select="concat(translate(date:add($date-time-Z, concat('PT', $offset, 'H')), 'Z', ''), '+0', $offset, ':00')"/>
  </xsl:template>

The implementation is really short, however it is quite complex as XSLT 1.0 requires to uses many tricks to workaround languages limitations (no native date type, no string order, no xor operator). Here are some tips to follow the code:

• (a xor b) is equivalent to ((a and not(b) ) and (not(a) and b)).
• number(true()) is 1, number(false()) is 0.
• March and October have the same number of days: 31.
• $transition-day*10000000+10000 for october 2008 (26010000) is an number representation of 2008-10-26T01:00:00Z.
• the second argument to date:add() is a ISO 8601 duration. Ex: PT2H (2 hours).

In fact I present here the fourth version of the code, the first one was much longer (5x) as I was using intermediate templates for computations (last-sunday-of-month, previous-sunday). Of course the key to debug, and then optimise and refactor the implementation was to start with a good test suite. The test suite is of course written in XML and embedded in the stylesheet so it can evolve with the code.

  <tap:suite name="date-time-Paris" xmlns:t="test:date-time-Paris">
    <t:t dt="2008-09-24T21:37:52Z"     r="2008-09-24T23:37:52+02:00"/>
    <t:t dt="2008-09-24T23:37:52Z"     r="2008-09-25T01:37:52+02:00"/>
    <t:t dt="2008-09-24T23:37:52.325Z" r="2008-09-25T01:37:52.325+02:00"/>
    <t:t dt="2008-10-01T00:00:00Z"     r="2008-10-01T02:00:00+02:00"/>
    <t:t dt="2008-10-26T00:59:59Z"     r="2008-10-26T02:59:59+02:00"/>
    <t:t dt="2008-10-26T01:00:00Z"     r="2008-10-26T02:00:00+01:00"/>
    <t:t dt="2008-10-31T12:00:00Z"     r="2008-10-31T13:00:00+01:00"/>
    <t:t dt="2008-11-24T21:37:52Z"     r="2008-11-24T22:37:52+01:00"/>
    <t:t dt="2008-12-31T23:30:00Z"     r="2009-01-01T00:30:00+01:00"/>
    <t:t dt="2009-01-01T00:00:00Z"     r="2009-01-01T01:00:00+01:00"/>
    <t:t dt="2009-03-01T12:00:00Z"     r="2009-03-01T13:00:00+01:00"/>
    <t:t dt="2009-03-29T00:59:59Z"     r="2009-03-29T01:59:59+01:00"/>
    <t:t dt="2009-03-29T01:00:00Z"     r="2009-03-29T03:00:00+02:00"/>
    <t:t dt="2009-03-30T12:00:00Z"     r="2009-03-30T14:00:00+02:00"/>
    <t:t dt="2009-07-01T00:00:00Z"     r="2009-07-01T02:00:00+02:00"/>
  </tap:suite>

A more complete testsuite can be generated from a local dump of the zoneinfo database (directly works on Ubuntu Hardy, however the zdump tool is missing on RHEL/CentOS):

zdump -v Europe/Paris | perl -ne 'm/ (Mar|Oct) (\d{2}) (\d{2}:\d{2}:\d{2}) (20[0-5]\d) UTC = ... (?:Oct|Mar) (\d{2}) (\d{2}:\d{2}:\d{2}) / && do { my $mm = sprintf "%02d", 3+7*($1 eq 'Oct'); print "    <t:t dt=\"$4-$mm-$2T$3\" r=\"$4-$mm-$5T$6\"/>\n"; }'

Now, we need is a way to run the test suite. In XSLT terms, we say: "to apply a template to the test data". This template will just apply a date-time-Paris call to each of the tests.

  <xsl:template match="t:t" xmlns:t="test:date-time-Paris">
    <xsl:call-template name="tap:is">
      <xsl:with-param name="got">
        <xsl:call-template name="date-time-Paris">
          <xsl:with-param name="date-time-Z" select="@dt"/>
        </xsl:call-template>
      </xsl:with-param>
      <xsl:with-param name="expected" select="@r"/>
      <xsl:with-param name="name" select="@dt"/>
    </xsl:call-template>
  </xsl:template>

</xsl:stylesheet>

We now have a complete stylesheet that can be used as a library in other stylesheet. But we have not yet run the tests. Also you probably wonder what are this XML namespace test:tap and the template called tap:is.

test:tap is just a small XSLT test framework that I wrote and the report test results following the Test Anything Protocol that is well known by Perl programmers. tap:is is part of the test:tap API and just check for equality and reports in the TAP format.

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:tap="test:tap"
  >

  <!-- Run all the tests in the test suite -->
  <xsl:template match="tap:suite">
    <xsl:message>1..<xsl:value-of select="count(node()[name()!=''])"/></xsl:message>
    <xsl:message># Suite: <xsl:value-of select="@name"/></xsl:message>
    <!-- TODO fix this expression -->
    <xsl:apply-templates select="node()[name()!='']"/>
  </xsl:template>

  <!-- Test Anything Protocol style reporting of tests -->
  <xsl:template name="tap:is">
    <xsl:param name="got"/>
    <xsl:param name="expected"/>
    <xsl:param name="name"/>
    <xsl:choose>
      <xsl:when test="$got = $expected">
        <xsl:message>ok <xsl:value-of select="position()"/> - <xsl:value-of select="concat($name, ' -&gt; ', $got)"/></xsl:message>
      </xsl:when>
      <xsl:otherwise>
        <xsl:message>not ok <xsl:value-of select="position()"/> - <xsl:value-of select="$name"/></xsl:message>
        <xsl:message>#          got: <xsl:value-of select="$got"/></xsl:message>
        <xsl:message>#     expected: <xsl:value-of select="$expected"/></xsl:message>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:template>

</xsl:stylesheet>

We now have two libraries. Let's add a bit more XSLT to glue them together. The main stylesheet applies tap:suite templates to all tap:suite from all imported stylesheets.

<?xml version="1.0" encoding="UTF-8"?>
<xsl:transform version="1.0"
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  >

  <!-- Test framework -->
  <xsl:import href="tap.xslt"/>

  <!-- All stylesheets to test -->
  <xsl:import href="date-time-Paris.xslt"/>

  <!-- Launch the tests embedded in libraires, whatever the input is -->
  <xsl:template match="/">
    <xsl:for-each select="document('')/xsl:transform/xsl:import/@href">
      <xsl:apply-templates select="document(.)//tap:suite" xmlns:tap="test:tap"/>
    </xsl:for-each>
  </xsl:template>

</xsl:transform>

We now have everything to run the test suite:

$ echo '<x/>' | xsltproc tap-run.xslt -
1..15
# Suite: date-time-Paris
ok 1 - 2008-09-24T21:37:52Z -> 2008-09-24T23:37:52+02:00
ok 2 - 2008-09-24T23:37:52Z -> 2008-09-25T01:37:52+02:00
not ok 3 - 2008-09-24T23:37:52.325Z
#          got: 2008-09-25T01:37:52.3249999999998+02:00
#     expected: 2008-09-25T01:37:52.325+02:00
ok 4 - 2008-10-01T00:00:00Z -> 2008-10-01T02:00:00+02:00
ok 5 - 2008-10-26T00:59:59Z -> 2008-10-26T02:59:59+02:00
ok 6 - 2008-10-26T01:00:00Z -> 2008-10-26T02:00:00+01:00
ok 7 - 2008-10-31T12:00:00Z -> 2008-10-31T13:00:00+01:00
ok 8 - 2008-11-24T21:37:52Z -> 2008-11-24T22:37:52+01:00
ok 9 - 2008-12-31T23:30:00Z -> 2009-01-01T00:30:00+01:00
ok 10 - 2009-01-01T00:00:00Z -> 2009-01-01T01:00:00+01:00
ok 11 - 2009-03-01T12:00:00Z -> 2009-03-01T13:00:00+01:00
ok 12 - 2009-03-29T00:59:59Z -> 2009-03-29T01:59:59+01:00
ok 13 - 2009-03-29T01:00:00Z -> 2009-03-29T03:00:00+02:00
ok 14 - 2009-03-30T12:00:00Z -> 2009-03-30T14:00:00+02:00
ok 15 - 2009-07-01T00:00:00Z -> 2009-07-01T02:00:00+02:00

So now I know that I have a failing test due to rounding occuring. For my XMLTV project it is not important as I will not have to handle decimal seconds.

TiddlyWiki is a standalone wiki that is fully interactive and fully contained in a single HTML file. Here is a tip to add a favicon to your wiki.

To enable saving you have to give to the browser some special permissions allowing the JavaScript code to write to your disk. When using it with Microsoft Internet Explorer, the easy way to enable saving is to just rename your wiki as .hta to transform it into an "HTML Application", as Microsoft calls it.

But you can do better with HTML Applications than just decreasing the security level. I was particularly interested in a better integration with Windows. I wanted in particular to change the icon of the window that appears in the taskbar (I commonly have about 30-40 windows opened on my desktop). This is quite easy: you just have to add an <HTA:APPLICATION ICON="myfile.ico"> tag the <head> section of the HTML file.

Here is how to do it the TiddlyWiki way:

1. Get an icon and save it as tiddlywiki.ico in the same directory as your wiki.hta file. For example: http://www.tiddlywiki.org/favicon.ico. You can also create you own icon here or here.
2. Edit the built-in tiddler MarkupPreHead
3. Insert the following text just after <!--{{{-->:

   <!--[if IE]>
   <HTA:APPLICATION ID="oHTA" APPLICATIONNAME="My wiki" ICON='tiddlywiki.ico'/>
   <![endif]-->
   <link rel='shortcut icon' href='tiddlywiki.ico' type='image/vnd.microsoft.icon '/>
   

4. Reload your wiki.hta. That's it!

I now have to explore how to convert this to a plugin...

I found in the svn source code of Maemo Mapper that the new default map provider for Maemo Mapper is now OpenStreetMap, a free map database that you can contribute to. You can already manually add the OpenStreetMap repository with the following URI: http://tile.openstreetmap.org/%0d/%d/%d.png

I uploaded two Vim syntax scripts for Polyhedra :

• polycfg.vim : a new script for Polyhedra configuration files
• polycl.vim : a new release of this script

See my post about the previous release.

I uploaded this afternoon on vim.org a syntax highlighting script for Polyhedra CL.

Polyhedra is a memory based database engine. It can be used in for embedded development, but also in high performance application where more classiscal disk-based engines are too slow. CL is the programming language used for stored procedures.

For my post of this morning that included a video I did use DailyMotion services. When you upload a video, they provide HTML code to embed it on your site. OK, that seems fine. But it's not. Here is the code:

<div>
  <object width="425" height="335">
    <param name="movie" value="http://www.dailymotion.com/swf/2JarEXHqOuOxZ4psf"></param>
    <param name="allowfullscreen" value="true"></param>
    <embed src="http://www.dailymotion.com/swf/2JarEXHqOuOxZ4psf" type="application/x-shockwave-flash" width="425" height="334" allowfullscreen="true"></embed>
  </object><br />
  <b><a href="http://www.dailymotion.com/video/xmj2z_rallye-de-vence-2006-speciale-3-96">Rallye de Vence 2006 - Spéciale 3 - 96</a></b>
</div>

Here are my grievances:

• This code uses <embed> tags, which have never been part of any W3C HTML specifications. <embed> is, AFAIK, a Netscape-only tag. Firefox/Mozilla now recognizes the standard <object> tag, so <embed> is only required for compatiblity with Netscape 4.x which, at web2.0 time, nobody uses anymore.
• They do not provide alternative strictly validating XHTML code. Most blog and CMS software are now XHTML strict compliant. Embedding this code breaks strict validation and could cause the page to not display at all.
• The code is not working with old Flash versions and does not tells why or proposes to upgrade. My parents have Flashplayer 6, and the display is weired. Even worse, when clicking on the link below the video to go to DailyMotion site, it crashes IE6 (with latest security patches).

So, here is my own code:

<div class="video dailymotion">
  <object width="425" height="335" classid="clsid:D27CDB6E-AE6D-11CF-96B8-444553540000" codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=8,0,0,0">
    <param name="movie" value="http://www.dailymotion.com/swf/2JarEXHqOuOxZ4psf"></param>
    <param name="FlashVars" value="playerMode=embedded"></param>
    <!--[if !IE]>-->
      <object width="425" height="335" data="http://www.dailymotion.com/swf/2JarEXHqOuOxZ4psf" type="application/x-shockwave-flash"></object>
    <!--<![endif]-->
  </object><br />
  <b><a href="http://www.dailymotion.com/video/xmj2z_rallye-de-vence-2006-speciale-3-96">Rallye de Vence 2006 - Spéciale 3 - 96</a></b>
</div>

Tested with Firefox 1.5.0.8 and Internet Explorer 6. I just hope it works with Opera/Safari/Konqueror…

Some reference documentation from Netscape/Mozilla and Ado be were useful.