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   <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Contents</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10">&nbsp;</TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif">
   <UL>
     <LI><A href="#functionality">Functionality</A></LI>
     <LI><A href="#implementation">Implementation</A></LI>
   </UL>
   </FONT></TD></TR></TABLE><BR>

   <A name="functionality"><!--anchor--></A>
   <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Functionality</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10">&nbsp;</TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif">

   <P>The <CODE><FONT face="courier, monospaced">&lt;xsl:key&gt;</FONT></CODE> element is a top-level element that can be
   used to define a named index of nodes from the source XML tree(s). The
   element has three attributes:</P>

   <UL>
     <LI>
       <CODE><FONT face="courier, monospaced">name</FONT></CODE> - the name of the index
     </LI>
     <LI>
       <CODE><FONT face="courier, monospaced">match</FONT></CODE> - a pattern that defines the nodeset we want
       indexed
     </LI>
     <LI>
       <CODE><FONT face="courier, monospaced">use</FONT></CODE> - an expression that defines the value to be used
       as the index key value.
     </LI>
   </UL>

   <P>A named index can be accessed using either the <CODE><FONT face="courier, monospaced">key()</FONT></CODE> function
   or a KeyPattern. Both these methods address the index using its defined name
   (the &quot;name&quot; attribute above) and a parameter defining one or more lookup
   values for the index. The function or pattern returns a node set containing
   all nodes in the index whose key value match the parameter's value(s):</P>

   <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE>
     &lt;xsl:key name=&quot;book-author&quot; match=&quot;book&quot; use=&quot;author&quot;/&gt;
         :
         :
     &lt;xsl:for-each select=&quot;key('book-author', 'Mikhail Bulgakov')&quot;&gt;
       &lt;xsl:value-of select=&quot;author&quot;/&gt;
       &lt;xsl:text&gt;: &lt;/xsl:text&gt;
       &lt;xsl:value-of select=&quot;author&quot;/&gt;
       &lt;xsl:text&gt;&amp;#xa;&lt;/xsl:text&gt;
     &lt;/xsl:for-each&gt;</PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV>

   <P>The KeyPattern can be used within an index definition to create unions
   and intersections of node sets:</P><DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE>
     &lt;xsl:key name=&quot;cultcies&quot; match=&quot;farmer | fisherman&quot; use=&quot;name&quot;/&gt;</PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV>

   <P>This could have been done using regular <CODE><FONT face="courier, monospaced">&lt;xsl:for-each&gt;</FONT></CODE>
   and <CODE><FONT face="courier, monospaced">&lt;xsl:select&gt;</FONT></CODE> elements. However, if your stylesheet
   accesses the same selection of nodes over and over again, the transformation
   will be much more efficient using pre-indexed keys as shown above.</P>

   </FONT></TD></TR></TABLE><BR>

   <A name="implementation"><!--anchor--></A>
   <TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="666699" colspan="2" width="494"><TABLE border="0" cellpadding="0" cellspacing="0" width="494"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="492"><FONT color="#ffffff" face="arial,helvetica,sanserif" size="+1"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Implementation</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="492"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="492"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10">&nbsp;</TD><TD width="484"><FONT color="#000000" face="arial,helvetica,sanserif">

     <A name="indexing"><!--anchor--></A>
     <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Indexing</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10">&nbsp;</TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1">

     <P>The <CODE><FONT face="courier, monospaced">AbstractTranslet</FONT></CODE> class has a global hashtable that holds
     an index for each named key in the stylesheet (hashing on the &quot;name&quot;
     attribute of <CODE><FONT face="courier, monospaced">&lt;xsl:key&gt;</FONT></CODE>). <CODE><FONT face="courier, monospaced">AbstractTranslet</FONT></CODE>
     has a couple of public methods for inserting and retrieving data from this
     hashtable:</P><DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE>
     public void buildKeyIndex(String keyName, int nodeID, String value);
     public KeyIndex KeyIndex getKeyIndex(String keyName);</PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV>

     <P>The <CODE><FONT face="courier, monospaced">Key</FONT></CODE> class compiles code that traverses the input DOM and
     extracts nodes that match some given parameters (the <CODE><FONT face="courier, monospaced">&quot;match&quot;</FONT></CODE>
     attribute of the <CODE><FONT face="courier, monospaced">&lt;xsl:key&gt;</FONT></CODE> element). A new element is
     inserted into the named key's index. The nodes' DOM index and the value
     translated from the <CODE><FONT face="courier, monospaced">&quot;use&quot;</FONT></CODE> attribute of the
     <CODE><FONT face="courier, monospaced">&lt;xsl:key&gt;</FONT></CODE> element are stored in the new entry in the
     index.</P>

     <P>Something similar is done for indexing IDs. This index is generated from
     the <CODE><FONT face="courier, monospaced">ID</FONT></CODE> and <CODE><FONT face="courier, monospaced">IDREF</FONT></CODE> fields in the input document's
     DTD. This means that the code for generating this index cannot be generated
     at compile-time, which again means that the code has to be generic enough
     to handle all DTDs. The class that handles this is the
     <CODE><FONT face="courier, monospaced">org.apache.xalan.xsltc.dom.DTDMonitor</FONT></CODE> class. This class
     implements the <CODE><FONT face="courier, monospaced">org.xml.sax.XMLReader</FONT></CODE> and
     <CODE><FONT face="courier, monospaced">org.xml.sax.DTDHandler</FONT></CODE> interfaces. A client application using
     the native API must instanciate a <CODE><FONT face="courier, monospaced">DTDMonitor</FONT></CODE> and pass it to the
     translet code - if, and only if, it wants IDs indexed (one can improve
     performance by omitting this step). This is descrived in the
     <A href="xsltc_native_api.html">XSLTC Native API reference</A>. The
     <CODE><FONT face="courier, monospaced">DTDMonitor</FONT></CODE> class will use the same indexing as the code
     generated by the <CODE><FONT face="courier, monospaced">Key</FONT></CODE> class. The index for ID's is called
     &quot;##id&quot;. We assume that no stylesheets will contain a key with this name.</P>

     <P>The index itself is implemented in the
     <CODE><FONT face="courier, monospaced">org.apache.xalan.xsltc.dom.KeyIndex</FONT></CODE> class. The index has an
     hashtable with all the values from the matching nodes (the part of the node
     used to generate this value is the one specified in the <CODE><FONT face="courier, monospaced">&quot;use&quot;</FONT></CODE>
     attribute). For every matching value there is a bit-array (implemented in
     the <CODE><FONT face="courier, monospaced">org.apache.xalan.xsltc.BitArray</FONT></CODE> class), holding a list of
     all node indexes for which this value gives a match:</P>
     <P><IMG align="right" alt="key_relations.gif" border="0" hspace="4" src="images/key_relations.gif" vspace="4"><BR clear="all"></P>
     <P><I>Figure 1: Indexing tables</I></P>

     <P>The <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> class implements the <CODE><FONT face="courier, monospaced">NodeIterator</FONT></CODE>
     interface, so that it can be returned directly by the implementation of the
     <CODE><FONT face="courier, monospaced">key()</FONT></CODE> function. This is how the index generated by
     <CODE><FONT face="courier, monospaced">&lt;xsl:key&gt;</FONT></CODE> and the node-set returned by the
     <CODE><FONT face="courier, monospaced">key()</FONT></CODE> and KeyPattern are tied together. You can see how this is
     done in the <CODE><FONT face="courier, monospaced">translate()</FONT></CODE> method of the <CODE><FONT face="courier, monospaced">KeyCall</FONT></CODE>
     class.</P>

     <P>The <CODE><FONT face="courier, monospaced">key()</FONT></CODE> function can be called in two ways:</P><DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE>
     key('key-name','value')
     key('key-name','node-set')</PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV>

     <P>The first parameter is always the name of the key. We use this value to
     lookup our index from the _keyIndexes hashtable in AbstractTranslet:</P>
     <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE>
     il.append(classGen.aloadThis());
     _name.translate(classGen, methodGen);
     il.append(new INVOKEVIRTUAL(getKeyIndex));</PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV>

     <P>This compiles into a call to
     <CODE><FONT face="courier, monospaced">AbstractTranslet.getKeyIndex(String name)</FONT></CODE>, and it leaves a
     <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> object on the stack. What we then need to do it to
     initialise the <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> to give us nodes with the requested
     value. This is done by leaving the <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> object on the stack
     and pushing the <CODE><FONT face="courier, monospaced">&quot;value&quot;</FONT></CODE> parameter to <CODE><FONT face="courier, monospaced">key()</FONT></CODE>, before
     calling <CODE><FONT face="courier, monospaced">lookup()</FONT></CODE> on the index:</P><DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE>
     il.append(DUP);  // duplicate the KeyIndex obejct before return
     _value.translate(classGen, methodGen);
     il.append(new INVOKEVIRTUAL(lookup));</PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV>

     <P>This compiles into a call to <CODE><FONT face="courier, monospaced">KeyIndex.lookup(String value)</FONT></CODE>.
     This will initialise the <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> object to return nodes that
     match the given value, so the <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> object can be left on
     the stack when we return. This because the <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> object
     implements the <CODE><FONT face="courier, monospaced">NodeIterator</FONT></CODE> interface.</P>

     <P>This matter is a bit more complex when the second parameter of
     <CODE><FONT face="courier, monospaced">key()</FONT></CODE> is a node-set. In this case we need to traverse the nodes
     in the set and do a lookup for each node in the set. What I do is this:</P>

     <UL>
       <LI>
         construct a <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> object that will hold the
         return node-set
       </LI>
       <LI>
         find the named <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> object from the hashtable in
         AbstractTranslet
       </LI>
       <LI>
         get an iterator for the node-set and do the folowing loop:</LI>
         <UL>
           <LI>get string value for current node</LI>
           <LI>do lookup in KeyIndex object for the named index</LI>
           <LI>merge the resulting node-set into the return node-set</LI>
         </UL>
       <LI>
         leave the return node-set on stack when done
       </LI>
     </UL>

     </FONT></TD></TR></TABLE><BR>

     <A name="improvements"><!--anchor--></A>
     <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Possible indexing improvements</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10">&nbsp;</TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1">

     <P>The indexing implementation can be very, very memeory exhaustive as there
     is one <CODE><FONT face="courier, monospaced">BitArray</FONT></CODE> allocated for each value for every index. This
     is particulary bad for the index used for IDs ('##id'), where a single value
     should only map to one, single node. This means that a whole
     <CODE><FONT face="courier, monospaced">BitArray</FONT></CODE> is used just to contain one node. The
     <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> class should be updated to hold the first node for a
     value in an <CODE><FONT face="courier, monospaced">Integer</FONT></CODE> object, and then replace that with a
     <CODE><FONT face="courier, monospaced">BitArray</FONT></CODE> or a <CODE><FONT face="courier, monospaced">Vector</FONT></CODE> only is a second node is
     added to the value. Here is an outline for <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE>:</P>
     <DIV align="right"><TABLE border="0" cellpadding="0" cellspacing="4" width="464"><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#ffffff" width="462"><FONT size="-1"><PRE>

     public void add(Object value, int node) {
         Object container;
 	if ((container = (BitArray)_index.get(value)) == null) {
             _index.put(value, new Integer(node));
 	}
 	else {
             // Check if there is _one_ node for this value
             if (container instanceof Integer) {
                 int first = ((Integer)container
                 _nodes = new BitArray(_arraySize);
                 _nodes.setMask(node &amp; 0xff000000);
                 _nodes.setBit(first &amp; 0x00ffffff);
                 _nodes.setBit(node &amp; 0x00ffffff);
                 _index.put(value, _nodes);
             }
             // Otherwise add node to axisting bit array
             else {
                 _nodex = (BitArray)container;
                 _nodes.setBit(node &amp; 0x00ffffff);
             }
         }
     }</PRE></FONT></TD><TD bgcolor="#0086b2" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" height="1" width="462"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="462"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></DIV>

     <P>Other methods inside the <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> should be updated to
     reflect this.</P>

     </FONT></TD></TR></TABLE><BR>

     <A name="patterns"><!--anchor--></A>
     <TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="666699" colspan="2" width="484"><TABLE border="0" cellpadding="0" cellspacing="0" width="484"><TR><TD bgcolor="#039acc" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#039acc" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#039acc" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#0086b2" width="482"><FONT color="#ffffff" face="arial,helvetica,sanserif"><IMG alt="" border="0" height="2" hspace="0" src="resources/void.gif" vspace="0" width="2"><B>Id and Key patterns</B></FONT></TD><TD bgcolor="#017299" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR><TR><TD bgcolor="#0086b2" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD><TD bgcolor="#017299" height="1" width="482"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="482"></TD><TD bgcolor="#017299" height="1" width="1"><IMG alt="" border="0" height="1" hspace="0" src="resources/void.gif" vspace="0" width="1"></TD></TR></TABLE></TD></TR><TR><TD width="10">&nbsp;</TD><TD width="474"><FONT color="#000000" face="arial,helvetica,sanserif" size="-1">

     <P>As already mentioned, the challenge with the <CODE><FONT face="courier, monospaced">id()</FONT></CODE> and
     <CODE><FONT face="courier, monospaced">key()</FONT></CODE> patterns is that they have no specific node type.
     Patterns are normally grouped based on their pattern's &quot;kernel&quot; node type.
     This is done in the <CODE><FONT face="courier, monospaced">org.apache.xalan.xsltc.compiler.Mode</FONT></CODE> class.
     The <CODE><FONT face="courier, monospaced">Mode</FONT></CODE> class has a method, <CODE><FONT face="courier, monospaced">flatternAlaternative</FONT></CODE>,
     that does this grouping, and all templates with a common kernel node type
     will be inserted into a &quot;test sequence&quot;. A test sequence is a set templates
     with the same kernel node type. The <CODE><FONT face="courier, monospaced">TestSeq</FONT></CODE> class generates
     code that will figure out which pattern, amongst several patterns with the
     same kernel node type, that matches a certain node. This is used by the
     <CODE><FONT face="courier, monospaced">Mode</FONT></CODE> class when generating the <CODE><FONT face="courier, monospaced">applyTemplates</FONT></CODE>
     method in the translet. A test sequence is also generated for all templates
     whose pattern does not have a kernel node type. This is the case for all
     Id and KeyPatterns. This test sequence, if necessary, is put before the
     big <CODE><FONT face="courier, monospaced">switch()</FONT></CODE> in the <CODE><FONT face="courier, monospaced">applyTemplates()</FONT></CODE> mehtod. This
     test has to be done for every single node that is traversed, causing the
     transformation to slow down siginificantly. This is why we do <B>not</B>
     recommend using this type of patterns with XSLTC.</P>

     </FONT></TD></TR></TABLE><BR>

   </FONT></TD></TR></TABLE><BR>

 </TD></TR></TABLE></TD></TR></TABLE><BR><TABLE border="0" cellpadding="0" cellspacing="0" width="620"><TR><TD bgcolor="#0086b2"><IMG alt="dot" height="1" src="resources/dot.gif" width="1"></TD></TR><TR><TD align="center"><FONT color="#0086b2" size="-1"><I>
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