<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE book
  PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<book>
<bookinfo>
<title>XSL Library Template Reference</title>
<releaseinfo role="cvs">$Id$
</releaseinfo>
<corpauthor>DocBook Open Repository Team</corpauthor>
<copyright>
  <year>1999</year>
  <year>2000</year>
  <year>2001</year>
  <year>2002</year>
  <holder>Norman Walsh</holder>
</copyright>
</bookinfo>

<preface><title>Introduction</title>

<para>This is technical reference documentation for the DocBook XSL
Stylesheets; it documents (some of) the parameters, templates, and
other elements of the stylesheets.</para>

<para>This is not intended to be <quote>user</quote> documentation.
It is provided for developers writing customization layers for the
stylesheets, and for anyone who's interested in <quote>how it
works</quote>.</para>

<para>Although I am trying to be thorough, this documentation is known
to be incomplete. Don't forget to read the source, too :-)</para>

</preface>

<reference>
<title>General Library Templates</title>

<refentry id="dot.count">
<refnamediv>
<refname>dot.count</refname>
<refpurpose>Returns the number of <quote>.</quote> characters in a string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<programlisting format="linespecific"><programlisting id="dot.count.frag">
&lt;xsl:template name="dot.count"&gt;
  &lt;!-- Returns the number of "." characters in a string --&gt;
  &lt;xsl:param name="string"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="count" select="0"&gt;&lt;/xsl:param&gt;
  &lt;xsl:choose&gt;
    &lt;xsl:when test="contains($string, '.')"&gt;
      &lt;xsl:call-template name="dot.count"&gt;
        &lt;xsl:with-param name="string" select="substring-after($string, '.')"&gt;&lt;/xsl:with-param&gt;
        &lt;xsl:with-param name="count" select="$count+1"&gt;&lt;/xsl:with-param&gt;
      &lt;/xsl:call-template&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:value-of select="$count"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="copy-string">
<refnamediv>
<refname>copy-string</refname>
<refpurpose>Returns <quote>count</quote> copies of a string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<programlisting format="linespecific"><programlisting id="copy-string.frag">
&lt;xsl:template name="copy-string"&gt;
  &lt;!-- returns 'count' copies of 'string' --&gt;
  &lt;xsl:param name="string"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="count" select="0"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="result"&gt;&lt;/xsl:param&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="$count&gt;0"&gt;
      &lt;xsl:call-template name="copy-string"&gt;
        &lt;xsl:with-param name="string" select="$string"&gt;&lt;/xsl:with-param&gt;
        &lt;xsl:with-param name="count" select="$count - 1"&gt;&lt;/xsl:with-param&gt;
        &lt;xsl:with-param name="result"&gt;
          &lt;xsl:value-of select="$result"&gt;&lt;/xsl:value-of&gt;
          &lt;xsl:value-of select="$string"&gt;&lt;/xsl:value-of&gt;
        &lt;/xsl:with-param&gt;
      &lt;/xsl:call-template&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:value-of select="$result"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="string.subst">
<refnamediv>
<refname>string.subst</refname>
<refpurpose>Substitute one text string for another in a string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">string.subst</function> template replaces all
occurances of <parameter moreinfo="none">target</parameter> in <parameter moreinfo="none">string</parameter>
with <parameter moreinfo="none">replacement</parameter> and returns the result.
</para>

<programlisting format="linespecific"><programlisting id="string.subst.frag">
&lt;xsl:template name="string.subst"&gt;
  &lt;xsl:param name="string"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="target"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="replacement"&gt;&lt;/xsl:param&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="contains($string, $target)"&gt;
      &lt;xsl:variable name="rest"&gt;
        &lt;xsl:call-template name="string.subst"&gt;
          &lt;xsl:with-param name="string" select="substring-after($string, $target)"&gt;&lt;/xsl:with-param&gt;
          &lt;xsl:with-param name="target" select="$target"&gt;&lt;/xsl:with-param&gt;
          &lt;xsl:with-param name="replacement" select="$replacement"&gt;&lt;/xsl:with-param&gt;
        &lt;/xsl:call-template&gt;
      &lt;/xsl:variable&gt;
      &lt;xsl:value-of select="concat(substring-before($string, $target),                                    $replacement,                                    $rest)"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:value-of select="$string"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="xpointer.idref">
<refnamediv>
<refname>xpointer.idref</refname>
<refpurpose>Extract IDREF from an XPointer</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">xpointer.idref</function> template returns the
ID portion of an XPointer which is a pointer to an ID within the current
document, or the empty string if it is not.</para>
<para>In other words, <function moreinfo="none">xpointer.idref</function> returns
<quote>foo</quote> when passed either <literal moreinfo="none">#foo</literal>
or <literal moreinfo="none">#xpointer(id('foo'))</literal>, otherwise it returns
the empty string.</para>

<programlisting format="linespecific"><programlisting id="xpointer.idref.frag">
&lt;xsl:template name="xpointer.idref"&gt;
  &lt;xsl:param name="xpointer"&gt;http://...&lt;/xsl:param&gt;
  &lt;xsl:choose&gt;
    &lt;xsl:when test="starts-with($xpointer, '#xpointer(id(')"&gt;
      &lt;xsl:variable name="rest" select="substring-after($xpointer, '#xpointer(id(')"&gt;&lt;/xsl:variable&gt;
      &lt;xsl:variable name="quote" select="substring($rest, 1, 1)"&gt;&lt;/xsl:variable&gt;
      &lt;xsl:value-of select="substring-before(substring-after($xpointer, $quote), $quote)"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="starts-with($xpointer, '#')"&gt;
      &lt;xsl:value-of select="substring-after($xpointer, '#')"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;!-- otherwise it's a pointer to some other document --&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>




<refentry id="length-magnitude">
<refnamediv>
<refname>length-magnitude</refname>
<refpurpose>Return the unqualified dimension from a length specification</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">length-magnitude</function> template returns the
unqualified length ("20" for "20pt") from a dimension.
</para>

<programlisting format="linespecific"><programlisting id="length-magnitude.frag">
&lt;xsl:template name="length-magnitude"&gt;
  &lt;xsl:param name="length" select="'0pt'"&gt;&lt;/xsl:param&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="string-length($length) = 0"&gt;&lt;/xsl:when&gt;
    &lt;xsl:when test="substring($length,1,1) = '0'                     or substring($length,1,1) = '1'                     or substring($length,1,1) = '2'                     or substring($length,1,1) = '3'                     or substring($length,1,1) = '4'                     or substring($length,1,1) = '5'                     or substring($length,1,1) = '6'                     or substring($length,1,1) = '7'                     or substring($length,1,1) = '8'                     or substring($length,1,1) = '9'                     or substring($length,1,1) = '.'"&gt;
      &lt;xsl:value-of select="substring($length,1,1)"&gt;&lt;/xsl:value-of&gt;
      &lt;xsl:call-template name="length-magnitude"&gt;
        &lt;xsl:with-param name="length" select="substring($length,2)"&gt;&lt;/xsl:with-param&gt;
      &lt;/xsl:call-template&gt;
    &lt;/xsl:when&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="length-units">
<refnamediv>
<refname>length-units</refname>
<refpurpose>Return the units from a length specification</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">length-units</function> template returns the
units ("pt" for "20pt") from a length. If no units are supplied on the
length, the <parameter moreinfo="none">defauilt.units</parameter> are returned.</para>

<programlisting format="linespecific"><programlisting id="length-units.frag">
&lt;xsl:template name="length-units"&gt;
  &lt;xsl:param name="length" select="'0pt'"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="default.units" select="'px'"&gt;&lt;/xsl:param&gt;
  &lt;xsl:variable name="magnitude"&gt;
    &lt;xsl:call-template name="length-magnitude"&gt;
      &lt;xsl:with-param name="length" select="$length"&gt;&lt;/xsl:with-param&gt;
    &lt;/xsl:call-template&gt;
  &lt;/xsl:variable&gt;

  &lt;xsl:variable name="units"&gt;
    &lt;xsl:value-of select="substring($length, string-length($magnitude)+1)"&gt;&lt;/xsl:value-of&gt;
  &lt;/xsl:variable&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="$units = ''"&gt;
      &lt;xsl:value-of select="$default.units"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:value-of select="$units"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="length-spec">
<refnamediv>
<refname>length-spec</refname>
<refpurpose>Return a fully qualified length specification</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">length-spec</function> template returns the
qualified length from a dimension. If an unqualified length is given,
the <parameter moreinfo="none">default.units</parameter> will be added to it.
</para>

<programlisting format="linespecific"><programlisting id="length-spec.frag">
&lt;xsl:template name="length-spec"&gt;
  &lt;xsl:param name="length" select="'0pt'"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="default.units" select="'px'"&gt;&lt;/xsl:param&gt;

  &lt;xsl:variable name="magnitude"&gt;
    &lt;xsl:call-template name="length-magnitude"&gt;
      &lt;xsl:with-param name="length" select="$length"&gt;&lt;/xsl:with-param&gt;
    &lt;/xsl:call-template&gt;
  &lt;/xsl:variable&gt;

  &lt;xsl:variable name="units"&gt;
    &lt;xsl:value-of select="substring($length, string-length($magnitude)+1)"&gt;&lt;/xsl:value-of&gt;
  &lt;/xsl:variable&gt;

  &lt;xsl:value-of select="$magnitude"&gt;&lt;/xsl:value-of&gt;
  &lt;xsl:choose&gt;
    &lt;xsl:when test="$units='cm'                     or $units='mm'                     or $units='in'                     or $units='pt'                     or $units='pc'                     or $units='px'                     or $units='em'"&gt;
      &lt;xsl:value-of select="$units"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="$units = ''"&gt;
      &lt;xsl:value-of select="$default.units"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:message&gt;
        &lt;xsl:text&gt;Unrecognized unit of measure: &lt;/xsl:text&gt;
        &lt;xsl:value-of select="$units"&gt;&lt;/xsl:value-of&gt;
        &lt;xsl:text&gt;.&lt;/xsl:text&gt;
      &lt;/xsl:message&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="length-in-points">
<refnamediv>
<refname>length-in-points</refname>
<refpurpose>Returns the size, in points, of a specified length</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">length-in-points</function> template converts a length
specification to points and returns that value as an unqualified
number.
</para>

<caution>
<para>There is no way for the template to infer the size of an
<literal moreinfo="none">em</literal>. It relies on the default <parameter moreinfo="none">em.size</parameter>
which is initially <literal moreinfo="none">10</literal> (for 10pt).</para>

<para>Similarly, converting pixesl to points relies on the
<parameter moreinfo="none">pixels.per.inch</parameter> parameter which is initially
<literal moreinfo="none">90</literal>.
</para>
</caution>

<programlisting format="linespecific"><programlisting id="length-in-points.frag">
&lt;xsl:template name="length-in-points"&gt;
  &lt;xsl:param name="length" select="'0pt'"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="em.size" select="10"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="pixels.per.inch" select="90"&gt;&lt;/xsl:param&gt;

  &lt;xsl:variable name="magnitude"&gt;
    &lt;xsl:call-template name="length-magnitude"&gt;
      &lt;xsl:with-param name="length" select="$length"&gt;&lt;/xsl:with-param&gt;
    &lt;/xsl:call-template&gt;
  &lt;/xsl:variable&gt;

  &lt;xsl:variable name="units"&gt;
    &lt;xsl:value-of select="substring($length, string-length($magnitude)+1)"&gt;&lt;/xsl:value-of&gt;
  &lt;/xsl:variable&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="$units = 'pt'"&gt;
      &lt;xsl:value-of select="$magnitude"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="$units = 'cm'"&gt;
      &lt;xsl:value-of select="$magnitude div 2.54 * 72.0"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="$units = 'mm'"&gt;
      &lt;xsl:value-of select="$magnitude div 25.4 * 72.0"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="$units = 'in'"&gt;
      &lt;xsl:value-of select="$magnitude * 72.0"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="$units = 'pc'"&gt;
      &lt;xsl:value-of select="$magnitude * 12.0"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="$units = 'px'"&gt;
      &lt;xsl:value-of select="$magnitude div $pixels.per.inch * 72.0"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:when test="$units = 'em'"&gt;
      &lt;xsl:value-of select="$magnitude * $em.size"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:message&gt;
        &lt;xsl:text&gt;Unrecognized unit of measure: &lt;/xsl:text&gt;
        &lt;xsl:value-of select="$units"&gt;&lt;/xsl:value-of&gt;
        &lt;xsl:text&gt;.&lt;/xsl:text&gt;
      &lt;/xsl:message&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="pi-attribute">
<refnamediv>
<refname>pi-attribute</refname>
<refpurpose>Extract a pseudo-attribute from a PI</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">pi-attribute</function> template extracts a pseudo-attribute
from a processing instruction. For example, given the PI
<quote><literal moreinfo="none">&lt;?foo bar="1" baz='red'?&gt;</literal></quote>,</para>
<programlisting format="linespecific">&lt;xsl:call-template name="pi-attribute"&gt;
  &lt;xsl:with-param name="pis" select="processing-instruction('foo')"/&gt;
  &lt;xsl:with-param name="attribute" select="'baz'"/&gt;
&lt;/xsl:call-template&gt;</programlisting>
<para>will return <quote>red</quote>. This template returns the first matching
attribute that it finds. Presented with processing instructions that
contain badly formed pseudo-attributes (missing or unbalanced quotes,
for example), the template may silently return erroneous results.</para>

<programlisting format="linespecific"><programlisting id="pi-attribute.frag">
&lt;xsl:template name="pi-attribute"&gt;
  &lt;xsl:param name="pis" select="processing-instruction('BOGUS_PI')"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="attribute"&gt;filename&lt;/xsl:param&gt;
  &lt;xsl:param name="count"&gt;1&lt;/xsl:param&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="$count&gt;count($pis)"&gt;
      &lt;!-- not found --&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:variable name="pi"&gt;
        &lt;xsl:value-of select="$pis[$count]"&gt;&lt;/xsl:value-of&gt;
      &lt;/xsl:variable&gt;
      &lt;xsl:variable name="pivalue"&gt;
        &lt;xsl:value-of select="concat(' ', normalize-space($pi))"&gt;&lt;/xsl:value-of&gt;
      &lt;/xsl:variable&gt;
      &lt;xsl:choose&gt;
        &lt;xsl:when test="contains($pivalue,concat(' ', $attribute, '='))"&gt;
          &lt;xsl:variable name="rest" select="substring-after($pivalue,concat(' ', $attribute,'='))"&gt;&lt;/xsl:variable&gt;
          &lt;xsl:variable name="quote" select="substring($rest,1,1)"&gt;&lt;/xsl:variable&gt;
          &lt;xsl:value-of select="substring-before(substring($rest,2),$quote)"&gt;&lt;/xsl:value-of&gt;
        &lt;/xsl:when&gt;
        &lt;xsl:otherwise&gt;
          &lt;xsl:call-template name="pi-attribute"&gt;
            &lt;xsl:with-param name="pis" select="$pis"&gt;&lt;/xsl:with-param&gt;
            &lt;xsl:with-param name="attribute" select="$attribute"&gt;&lt;/xsl:with-param&gt;
            &lt;xsl:with-param name="count" select="$count + 1"&gt;&lt;/xsl:with-param&gt;
          &lt;/xsl:call-template&gt;
        &lt;/xsl:otherwise&gt;
      &lt;/xsl:choose&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="lookup.key">
<refnamediv>
<refname>lookup.key</refname>
<refpurpose>Retrieve the value associated with a particular key in a table</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>Given a table of space-delimited key/value pairs,
the <function moreinfo="none">lookup.key</function> template extracts the value associated
with a particular key.</para>

<programlisting format="linespecific"><programlisting id="lookup.key.frag">
&lt;xsl:template name="lookup.key"&gt;
  &lt;xsl:param name="key" select="''"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="table" select="''"&gt;&lt;/xsl:param&gt;

  &lt;xsl:if test="contains($table, ' ')"&gt;
    &lt;xsl:choose&gt;
      &lt;xsl:when test="substring-before($table, ' ') = $key"&gt;
        &lt;xsl:variable name="rest" select="substring-after($table, ' ')"&gt;&lt;/xsl:variable&gt;
        &lt;xsl:choose&gt;
          &lt;xsl:when test="contains($rest, ' ')"&gt;
            &lt;xsl:value-of select="substring-before($rest, ' ')"&gt;&lt;/xsl:value-of&gt;
          &lt;/xsl:when&gt;
          &lt;xsl:otherwise&gt;
            &lt;xsl:value-of select="$rest"&gt;&lt;/xsl:value-of&gt;
          &lt;/xsl:otherwise&gt;
        &lt;/xsl:choose&gt;
      &lt;/xsl:when&gt;
      &lt;xsl:otherwise&gt;
        &lt;xsl:call-template name="lookup.key"&gt;
          &lt;xsl:with-param name="key" select="$key"&gt;&lt;/xsl:with-param&gt;
          &lt;xsl:with-param name="table" select="substring-after(substring-after($table,' '), ' ')"&gt;&lt;/xsl:with-param&gt;
        &lt;/xsl:call-template&gt;
      &lt;/xsl:otherwise&gt;
    &lt;/xsl:choose&gt;
  &lt;/xsl:if&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="xpath.location">
<refnamediv>
<refname>xpath.location</refname>
<refpurpose>Calculate the XPath child-sequence to the current node</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">xpath.location</function> template calculates the
absolute path from the root of the tree to the current element node.
</para>

<programlisting format="linespecific"><programlisting id="xpath.location.frag">
&lt;xsl:template name="xpath.location"&gt;
  &lt;xsl:param name="node" select="."&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="path" select="''"&gt;&lt;/xsl:param&gt;

  &lt;xsl:variable name="next.path"&gt;
    &lt;xsl:value-of select="local-name($node)"&gt;&lt;/xsl:value-of&gt;
    &lt;xsl:if test="$path != ''"&gt;/&lt;/xsl:if&gt;
    &lt;xsl:value-of select="$path"&gt;&lt;/xsl:value-of&gt;
  &lt;/xsl:variable&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="$node/parent::*"&gt;
      &lt;xsl:call-template name="xpath.location"&gt;
        &lt;xsl:with-param name="node" select="$node/parent::*"&gt;&lt;/xsl:with-param&gt;
        &lt;xsl:with-param name="path" select="$next.path"&gt;&lt;/xsl:with-param&gt;
      &lt;/xsl:call-template&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:text&gt;/&lt;/xsl:text&gt;
      &lt;xsl:value-of select="$next.path"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>



<refentry id="comment-escape-string">
<refnamediv>
<refname>comment-escape-string</refname>
<refpurpose>Prepare a string for inclusion in an XML comment</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">comment-escape-string</function> template returns a string
that has been transformed so that it can safely be output as an XML comment.
Internal occurrences of "--" will be replaced with "- -" and a leading and/or
trailing space will be added to the string, if necessary.</para>

<programlisting format="linespecific"><programlisting id="comment-escape-string">
&lt;xsl:template name="comment-escape-string"&gt;
  &lt;xsl:param name="string" select="''"&gt;&lt;/xsl:param&gt;

  &lt;xsl:if test="starts-with($string, '-')"&gt;
    &lt;xsl:text&gt; &lt;/xsl:text&gt;
  &lt;/xsl:if&gt;

  &lt;xsl:call-template name="comment-escape-string.recursive"&gt;
    &lt;xsl:with-param name="string" select="$string"&gt;&lt;/xsl:with-param&gt;
  &lt;/xsl:call-template&gt;

  &lt;xsl:if test="substring($string, string-length($string), 1) = '-'"&gt;
    &lt;xsl:text&gt; &lt;/xsl:text&gt;
  &lt;/xsl:if&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>

<refentry id="comment-escape-string.recursive">
<refnamediv>
<refname>comment-escape-string.recursive</refname>
<refpurpose>Internal function used by comment-escape-string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function moreinfo="none">comment-escape-string.recursive</function> template is used
by <function moreinfo="none">comment-escape-string</function>.</para>

<programlisting format="linespecific"><programlisting id="comment-escape-string.recursive">
&lt;xsl:template name="comment-escape-string.recursive"&gt;
  &lt;xsl:param name="string" select="''"&gt;&lt;/xsl:param&gt;
  &lt;xsl:choose&gt;
    &lt;xsl:when test="contains($string, '--')"&gt;
      &lt;xsl:value-of select="substring-before($string, '--')"&gt;&lt;/xsl:value-of&gt;
      &lt;xsl:value-of select="'- -'"&gt;&lt;/xsl:value-of&gt;
      &lt;xsl:call-template name="comment-escape-string.recursive"&gt;
        &lt;xsl:with-param name="string" select="substring-after($string, '--')"&gt;&lt;/xsl:with-param&gt;
      &lt;/xsl:call-template&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:value-of select="$string"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>
</refsect1>
</refentry>

</reference>

<reference>
<title>Relative URI Functions</title>

<partintro><title>Introduction</title>

<para>These functions manipulate relative URI references.</para>

<para>The following assumptions must hold true:</para>

<orderedlist inheritnum="ignore" continuation="restarts">
<listitem>
<para>All URIs are relative.</para>
</listitem>
<listitem>
<para>No URI contains the <quote><literal moreinfo="none">../</literal></quote> sequence
which would effectively move <quote>up</quote> the hierarchy.</para>
</listitem>
</orderedlist>

<para>If these assumptions do not hold, the results are unpredictable.</para>

</partintro>

<refentry id="count.uri.path.depth">
<refnamediv>
<refname>count.uri.path.depth</refname>
<refpurpose>Count the number of path components in a relative URI</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>This function counts the number of path components in a relative URI.</para>

<programlisting format="linespecific"><programlisting id="count.uri.path.depth.frag">
&lt;xsl:template name="count.uri.path.depth"&gt;
  &lt;xsl:param name="filename" select="''"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="count" select="0"&gt;&lt;/xsl:param&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="contains($filename, '/')"&gt;
      &lt;xsl:call-template name="count.uri.path.depth"&gt;
        &lt;xsl:with-param name="filename" select="substring-after($filename, '/')"&gt;&lt;/xsl:with-param&gt;
        &lt;xsl:with-param name="count" select="$count + 1"&gt;&lt;/xsl:with-param&gt;
      &lt;/xsl:call-template&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:value-of select="$count"&gt;&lt;/xsl:value-of&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>

<refentry id="trim.common.uri.paths">
<refnamediv>
<refname>trim.common.uri.paths</refname>
<refpurpose>Trim common leading path components from a relative URI</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>This function trims common leading path components from a relative URI.</para>

<programlisting format="linespecific"><programlisting id="trim.common.uri.paths.frag">
&lt;xsl:template name="trim.common.uri.paths"&gt;
  &lt;xsl:param name="uriA" select="''"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="uriB" select="''"&gt;&lt;/xsl:param&gt;
  &lt;xsl:param name="return" select="'A'"&gt;&lt;/xsl:param&gt;

  &lt;xsl:choose&gt;
    &lt;xsl:when test="contains($uriA, '/') and contains($uriB, '/')                     and substring-before($uriA, '/') = substring-before($uriB, '/')"&gt;
      &lt;xsl:call-template name="trim.common.uri.paths"&gt;
        &lt;xsl:with-param name="uriA" select="substring-after($uriA, '/')"&gt;&lt;/xsl:with-param&gt;
        &lt;xsl:with-param name="uriB" select="substring-after($uriB, '/')"&gt;&lt;/xsl:with-param&gt;
        &lt;xsl:with-param name="return" select="$return"&gt;&lt;/xsl:with-param&gt;
      &lt;/xsl:call-template&gt;
    &lt;/xsl:when&gt;
    &lt;xsl:otherwise&gt;
      &lt;xsl:choose&gt;
        &lt;xsl:when test="$return = 'A'"&gt;
          &lt;xsl:value-of select="$uriA"&gt;&lt;/xsl:value-of&gt;
        &lt;/xsl:when&gt;
        &lt;xsl:otherwise&gt;
          &lt;xsl:value-of select="$uriB"&gt;&lt;/xsl:value-of&gt;
        &lt;/xsl:otherwise&gt;
      &lt;/xsl:choose&gt;
    &lt;/xsl:otherwise&gt;
  &lt;/xsl:choose&gt;
&lt;/xsl:template&gt;
</programlisting></programlisting>

</refsect1>
</refentry>

</reference>

<appendix><title>The Stylesheet</title>

<para>The <filename moreinfo="none">lib.xsl</filename> stylesheet is just a wrapper
around these functions.</para>

<programlisting id="top">

&lt;!-- ********************************************************************
     $Id$
     ********************************************************************

     This file is part of the XSL DocBook Stylesheet distribution.
     See ../README or http://nwalsh.com/docbook/xsl/ for copyright
     and other information.

     This module implements DTD-independent functions

     ******************************************************************** --&gt;

&lt;xsl:stylesheet exclude-result-prefixes="src" version="1.0"&gt;

&lt;src:fragref linkend="dot.count.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="copy-string.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="string.subst.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="xpointer.idref.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="length-magnitude.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="length-units.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="length-spec.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="length-in-points.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="pi-attribute.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="lookup.key.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="xpath.location.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="comment-escape-string"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="comment-escape-string.recursive"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="count.uri.path.depth.frag"&gt;&lt;/src:fragref&gt;
&lt;src:fragref linkend="trim.common.uri.paths.frag"&gt;&lt;/src:fragref&gt;

&lt;/xsl:stylesheet&gt;
</programlisting>

</appendix>
</book>