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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">
<P>This document describes the function of XSLTC's node iterators. It also
describes the <CODE><FONT face="courier, monospaced">NodeIterator</FONT></CODE> interface and some implementations of
this interface are described in detail:</P>
<UL>
<LI><A href="#purpose">Node iterator function</A></LI>
<LI><A href="#interface">NodeIterator interface</A></LI>
<LI><A href="#baseclass">Node iterator base class</A></LI>
<LI><A href="#details">Implementation details</A></LI>
</UL>
</FONT></TD></TR></TABLE><BR>
<A name="purpose"><!--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>Node Iterator Function</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>Node iterators have several functions in XSLTC. The most obvious is
acting as a placeholder for node-sets. Node iterators also act as a link
between the translet and the DOM(s), they can act as filters (implementing
predicates), they contain the functionality necessary to cover all XPath
axes and they even serve as a front-end to XSLTC's node-indexing mechanism
(for the <CODE><FONT face="courier, monospaced">id()</FONT></CODE> and <CODE><FONT face="courier, monospaced">key()</FONT></CODE> functions).</P>
</FONT></TD></TR></TABLE><BR>
<A name="interface"><!--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>Node Iterator Interface</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 node iterator interface is defined in
<CODE><FONT face="courier, monospaced">org.apache.xalan.xsltc.NodeIterator</FONT></CODE>.</P>
<P>The most basic operations in the <CODE><FONT face="courier, monospaced">NodeIterator</FONT></CODE> interface are
for setting the iterators start-node. The &quot;start-node&quot; is
an index into the DOM. This index, and the axis of the iterator, determine
the node-set that the iterator contains. The axis is programmed into the
various node iterator implementations, while the start-node can be set by
calling:</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 NodeIterator setStartNode(int node);</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>Once the start node is set the node-set can be traversed by a sequence of
calls to:</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 int next();</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 method will return the constant <CODE><FONT face="courier, monospaced">NodeIterator.END</FONT></CODE> when
the whole node-set has been returned. The iterator can be reset to the start
of the node-set by calling:</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 NodeIterator reset();</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>Two additional methods are provided to set the position within the
node-set. The first method below will mark the current node in the
node-set, while the second will (at any point) set the iterators position
back to that node.</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 setMark();
public void gotoMark();</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>Every node iterator implements two functions that make up the
functionality behind XPath's <CODE><FONT face="courier, monospaced">getPosition()</FONT></CODE> and
<CODE><FONT face="courier, monospaced">getLast()</FONT></CODE> functions.</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 int getPosition();
public int getLast();</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">getLast()</FONT></CODE> function returns the number of nodes in the
set, while the <CODE><FONT face="courier, monospaced">getPosition()</FONT></CODE> returns the current position
within the node-set. The value returned by <CODE><FONT face="courier, monospaced">getPosition()</FONT></CODE> for
the first node in the set is always 1 (one), and the value returned for the
last node in the set is always the same value as is returned by
<CODE><FONT face="courier, monospaced">getLast()</FONT></CODE>.</P>
<P>All node iterators that implement an XPath axis will return the node-set
in the natural order of the axis. For example, the iterator implementing the
ancestor axis will return nodes in reverse document order (bottom to
top), while the iterator implementing the descendant will return
nodes in document order. The node iterator interface has a method that can
be used to determine if an iterator returns nodes in reverse document order:
</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 boolean isReverse();</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>Two methods are provided for when node iterators are encapsulated inside
a variable or parameter. To understand the purpose behind these two methods
we should have a look at a sample XML document and stylesheet first:</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;?xml version=&quot;1.0&quot;?&gt;
&lt;foo&gt;
&lt;bar&gt;
&lt;baz&gt;A&lt;/baz&gt;
&lt;baz&gt;B&lt;/baz&gt;
&lt;/bar&gt;
&lt;bar&gt;
&lt;baz&gt;C&lt;/baz&gt;
&lt;baz&gt;D&lt;/baz&gt;
&lt;/bar&gt;
&lt;/foo&gt;
&lt;xsl:stylesheet version=&quot;1.0&quot; xmlns:xsl=&quot;http://www.w3.org/1999/XSL/Transform&quot;&gt;
&lt;xsl:template match=&quot;foo&quot;&gt;
&lt;xsl:variable name=&quot;my-nodes&quot; select=&quot;//foo/bar/baz&quot;/&gt;
&lt;xsl:for-each select=&quot;bar&quot;&gt;
&lt;xsl:for-each select=&quot;baz&quot;&gt;
&lt;xsl:value-of select=&quot;.&quot;/&gt;
&lt;/xsl:for-each&gt;
&lt;xsl:for-each select=&quot;$my-nodes&quot;&gt;
&lt;xsl:value-of select=&quot;.&quot;/&gt;
&lt;/xsl:for-each&gt;
&lt;/xsl:for-each&gt;
&lt;/xsl:template&gt;
&lt;/xsl:stylesheet&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>Now, there are three iterators at work here. The first iterator is the
one that is wrapped inside the variable <CODE><FONT face="courier, monospaced">my-nodes</FONT></CODE> - this
iterator contains all <CODE><FONT face="courier, monospaced">&lt;baz/&gt;</FONT></CODE> elements in the
document. The second iterator contains all <CODE><FONT face="courier, monospaced">&lt;bar&gt;</FONT></CODE>
elements under the current element (this is the iterator used by the
outer <CODE><FONT face="courier, monospaced">for-each</FONT></CODE> loop). The third and last iterator is the one
used by the first of the inner <CODE><FONT face="courier, monospaced">for-each</FONT></CODE> loops. When the outer
loop is run the first time, this third iterator will be initialized to
contain the first two <CODE><FONT face="courier, monospaced">&lt;baz&gt;</FONT></CODE> elements under the context
node (the first <CODE><FONT face="courier, monospaced">&lt;bar&gt;</FONT></CODE> element). Iterators are by default
restarted from the current node when used inside a <CODE><FONT face="courier, monospaced">for-each</FONT></CODE>
loop like this. But what about the iterator inside the variable
<CODE><FONT face="courier, monospaced">my-nodes</FONT></CODE>? The variable should keep its assigned value, no
matter what the context node is. In able to prevent the iterator from being
reset, we must use a mechanism to block calls to the
<CODE><FONT face="courier, monospaced">setStartNode()</FONT></CODE> method. This is done in three steps:</P>
<UL>
<LI>The iterator is created and initialized when the variable gets
assigned its value (node-set).</LI>
<LI>When the variable is read, the iterator is copied (cloned). The
original iterator inside the variable is never used directly. This is
to make sure that the iterator inside the variable is always in its
original state when read.</LI>
<LI>The iterator clone is marked as not restartable to prevent it from
being restarted when used to iterate the <CODE><FONT face="courier, monospaced">&lt;xsl:for-each&gt;</FONT></CODE>
element loop.</LI>
</UL>
<P>These are the two methods used for the three steps above:</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 NodeIterator cloneIterator();
public void setRestartable(boolean isRestartable);</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>Special care must be taken when implementing these methods in some
iterators. The <CODE><FONT face="courier, monospaced">StepIterator</FONT></CODE> class is the best example of this.
This iterator wraps two other iterators; one of which is used to generate
start-nodes for the other - so one of the encapsulated node iterators must
always remain restartable - even when used inside variables. The
<CODE><FONT face="courier, monospaced">StepIterator</FONT></CODE> class is described in detail later in this
document.</P>
</FONT></TD></TR></TABLE><BR>
<A name="baseclass"><!--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>Node Iterator Base Class</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>A node iterator base class is provided to contain some common
functionality. The base class implements the node iterator interface, and
has a few additional methods:</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 NodeIterator includeSelf();
protected final int returnNode(final int node);
protected final NodeIterator resetPosition();</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">includeSelf()</FONT></CODE> is used with certain axis iterators that
implement both the <CODE><FONT face="courier, monospaced">ancestor</FONT></CODE> and <CODE><FONT face="courier, monospaced">ancestor-or-self</FONT></CODE>
axis and similar. One common implementation is used for these axes and
this method is used to signal that the &quot;self&quot; node should
also be included in the node-set.</P>
<P>The <CODE><FONT face="courier, monospaced">returnNode()</FONT></CODE> method is called by the implementation of
the <CODE><FONT face="courier, monospaced">next()</FONT></CODE> method. <CODE><FONT face="courier, monospaced">returnNode()</FONT></CODE> increments an
internal node counter/cursor that keeps track of the current position within
the node set. This counter/cursor is then used by the
<CODE><FONT face="courier, monospaced">getPosition()</FONT></CODE> implementation to return the current position.
The node cursor can be reset by calling <CODE><FONT face="courier, monospaced">resetPosition()</FONT></CODE>. This
method is normally called by an iterator's <CODE><FONT face="courier, monospaced">reset()</FONT></CODE> method.</P>
</FONT></TD></TR></TABLE><BR>
<A name="details"><!--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>Node Iterator Implementation Details</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">
<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>Axis iterators</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>All axis iterators are implemented as inner classes of the internal
DOM implementation <CODE><FONT face="courier, monospaced">org.apache.xalan.xsltc.dom.DOMImpl</FONT></CODE>. In this
way all axis iterator classes have direct access to the internal node
type- and navigation arrays of the DOM:</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>
private short[] _type; // Node types
private short[] _namespace; // Namespace URI types
private short[] _prefix; // Namespace prefix types
private int[] _parent; // Index of a node's parent
private int[] _nextSibling; // Index of a node's next sibling node
private int[] _offsetOrChild; // Index of an elements first child node
private int[] _lengthOrAttr; // Index of an elements first attribute node</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 axis iterators can be instanciated by calling either of these two
methods of the DOM:</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 NodeIterator getAxisIterator(final int axis);
public NodeIterator getTypedAxisIterator(final int axis, final int type);</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>
</FONT></TD></TR></TABLE><BR>
<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>StepIterator</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">StepIterator</FONT></CODE> is used to chain other iterators. A
very basic example is this XPath expression:</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:for-each select=&quot;foo/bar&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>To generate the appropriate node-set for this loop we need three
iterators. The compiler will generate code that first creates a typed axis
iterator; the axis will be child and the type will be that assigned
to <CODE><FONT face="courier, monospaced">&lt;foo&gt;</FONT></CODE> elements. Then a second typed axis iterator will
be created; this also a child -iterator, but this one with the type
assigned to <CODE><FONT face="courier, monospaced">&lt;bar&gt;</FONT></CODE> elements. The third iterator is a
step iterator that encapsulates the two axis iterators. The step iterator is
the initialized with the context node.</P>
<P>The step iterator will use the first axis iterator to generate
start-nodes for the second axis iterator. In plain english this means that
the step iterator will scan all <CODE><FONT face="courier, monospaced">foo</FONT></CODE> elements for any
<CODE><FONT face="courier, monospaced">bar</FONT></CODE> child elements. When a <CODE><FONT face="courier, monospaced">StepIterator</FONT></CODE> is
initialized with a start-node it passes the start node to the
<CODE><FONT face="courier, monospaced">setStartNode()</FONT></CODE> method of its source -iterator (left).
It then calls <CODE><FONT face="courier, monospaced">next()</FONT></CODE> on that iterator to get the start-node
for the iterator iterator (right):</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>
// Set start node for left-hand iterator...
_source.setStartNode(_startNode);
// ... and get start node for right-hand iterator from left-hand,
_iterator.setStartNode(_source.next());</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 step iterator will keep returning nodes from its right iterator until
it runs out of nodes. Then a new start-node is retrieved by again calling
<CODE><FONT face="courier, monospaced">next()</FONT></CODE> on the source -iterator. This is why the
right-hand iterator always has to be restartable - even if the step iterator
is placed inside a variable or parameter. This becomes even more complicated
for step iterators that encapsulate other step iterators. We'll make our
previous example a bit more interesting:</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:for-each select=&quot;foo/bar[@name='cat and cage']/baz&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 will result in an iterator-tree similar to this:</P>
<P><IMG align="right" alt="iterator_stack.gif" border="0" hspace="4" src="images/iterator_stack.gif" vspace="4"><BR clear="all"></P>
<P><I>Figure 1: Stacked step iterators</I></P>
<P>The &quot;foo&quot; iterator is used to supply the second step
iterator with start nodes. The second step iterator will pass these start
nodes to the &quot;bar&quot; iterator, which will be used to get the
start nodes for the third step iterator, and so on....</P>
</FONT></TD></TR></TABLE><BR>
<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>Iterators for Filtering/Predicates</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">org.apache.xalan.xsltc.dom</FONT></CODE> package contains a few
iterators that are used to implement predicates and filters. Such iterators
are normally placed on top of another iterator, and return only those nodes
that match a specific node value, position, etc.
These iterators include:</P>
<UL>
<LI>NthIterator</LI>
<LI>NodeValueIterator</LI>
<LI>FilteredStepIterator</LI>
<LI>CurrentNodeListIterator</LI>
</UL>
<P>The last one is the most interesting. This iterator is used to implement
chained predicates, such as:</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:value-of select=&quot;foo[@blob='boo'][2]&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>The first predicate reduces the node set from containing all
<CODE><FONT face="courier, monospaced">&lt;foo&gt;</FONT></CODE> elements, to containing only those elements that
have a &quot;blob&quot; attribute with the value 'boo'. The
<CODE><FONT face="courier, monospaced">CurrentNodeListIterator</FONT></CODE> is used to contain this reduced
node-set. The iterator is constructed by passing it a source iterator (in
this case an iterator that contains all <CODE><FONT face="courier, monospaced">&lt;foo&gt;</FONT></CODE> elements)
and a filter that implements the predicate (<CODE><FONT face="courier, monospaced">@blob = 'boo'</FONT></CODE>).</P>
</FONT></TD></TR></TABLE><BR>
<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>SortingIterator</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 sorting iterator is one of the main functional components behind the
implementation of the <CODE><FONT face="courier, monospaced">&lt;xsl:sort&gt;</FONT></CODE> element. This element,
including the sorting iterator, is described in detail in the
<CODE><FONT face="courier, monospaced">&lt;xsl:sort&gt;</FONT></CODE>
<A href="xsl_sort_design.html">design document</A>.</P>
</FONT></TD></TR></TABLE><BR>
<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>SingletonIterator</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"></FONT></TD></TR></TABLE><BR>
<P>The singleton iterator is a wrapper for a single node. The node passed
in to the <CODE><FONT face="courier, monospaced">setStartNode()</FONT></CODE> method is the only node that will be
returned by the <CODE><FONT face="courier, monospaced">next()</FONT></CODE> method. The singleton iterator is used
mainly for node to node-set type conversions.</P>
<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>UnionIterator</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 union iterator is used to contain unions of node-sets contained in
other iterators. Some of the methods in this iterator are unnecessary
comlicated. The <CODE><FONT face="courier, monospaced">next()</FONT></CODE> method contains an algorithm for
ensuring that the union node-set is returned in document order. We might be
better off by simply wrapping the union iterator inside a duplicate filter
iterator, but there could be some performance implications. Worth checking.
</P>
</FONT></TD></TR></TABLE><BR>
<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>KeyIndex</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>This is not just an node iterator. An index used for keys and ids will
return a set of nodes that are contained within the named index and that
share a certain property. The <CODE><FONT face="courier, monospaced">KeyIndex</FONT></CODE> implements the node
iterator interface, so that these nodes can be returned and handled just
like any other node set. See the
<A href="xsl_key_design.html">design document</A> for
<CODE><FONT face="courier, monospaced">&lt;xsl:key&gt;</FONT></CODE>, <CODE><FONT face="courier, monospaced">key()</FONT></CODE> and <CODE><FONT face="courier, monospaced">id()</FONT></CODE>
for further details.</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>
Copyright &copy; 2004 The Apache Software Foundation.
All Rights Reserved.
</I></FONT></TD></TR></TABLE></BODY></HTML>