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113 lines
4.9 KiB
113 lines
4.9 KiB
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
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<HTML>
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<HEAD>
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<TITLE>Mini-XML Programmers Manual, Version 2.2.1</TITLE>
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<META NAME="author" CONTENT="Michael Sweet">
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<META NAME="copyright" CONTENT="Copyright 2003-2005">
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; CHARSET=iso-iso-8859-1">
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<LINK REL="Start" HREF="index.html">
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<LINK REL="Contents" HREF="toc.html">
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<LINK REL="Prev" HREF="FormattedText.html">
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<LINK REL="Next" HREF="4UsingthemxmldocUtility.html">
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<STYLE TYPE="text/css"><!--
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BODY { font-family: serif }
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H1 { font-family: sans-serif }
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H2 { font-family: sans-serif }
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H3 { font-family: sans-serif }
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H4 { font-family: sans-serif }
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H5 { font-family: sans-serif }
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H6 { font-family: sans-serif }
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SUB { font-size: smaller }
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SUP { font-size: smaller }
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PRE { font-family: monospace }
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--></STYLE>
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</HEAD>
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<BODY>
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<A HREF="toc.html">Contents</A>
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<A HREF="FormattedText.html">Previous</A>
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<A HREF="4UsingthemxmldocUtility.html">Next</A>
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<HR NOSHADE>
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<H2><A NAME="4_6">Indexing</A></H2>
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<P>Mini-XML provides functions for managing indices of nodes. The
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current implementation provides the same functionality as the <A href="mxmlFindElement.html#mxmlFindElement">
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<TT>mxmlFindElement()</TT></A>. The advantage of using an index is that
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searching and enumeration of elements is significantly faster. The only
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disadvantage is that each index is a static snapshot of the XML
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document, so indices are not well suited to XML data that is updated
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more often than it is searched. The overhead of creating an index is
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approximately equal to walking the XML document tree. Nodes in the
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index are sorted by element name and attribute value.</P>
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<P>Indices are stored in <A href="mxmlindext.html#mxml_index_t"><TT>
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mxml_index_t</TT></A> structures. The <A href="mxmlIndexNew.html#mxmlIndexNew">
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<TT>mxmlIndexNew()</TT></A> function creates a new index:</P>
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<PRE>
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<A href="mxmlnodet.html#mxml_node_t">mxml_node_t</A> *tree;
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<A href="mxmlindext.html#mxml_index_t">mxml_index_t</A> *ind;
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ind = <A href="mxmlIndexNew.html#mxmlIndexNew">mxmlIndexNew</A>(tree, "element", "attribute");
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</PRE>
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<P>The first argument is the XML node tree to index. Normally this will
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be a pointer to the <TT>?xml</TT> element.</P>
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<P>The second argument contains the element to index; passing <TT>NULL</TT>
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indexes all element nodes alphabetically.</P>
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<P>The third argument contains the attribute to index; passing <TT>NULL</TT>
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causes only the element name to be indexed.</P>
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<P>Once the index is created, the <A href="mxmlIndexEnum.html#mxmlIndexEnum">
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<TT>mxmlIndexEnum()</TT></A>, <A href="mxmlIndexFind.html#mxmlIndexFind">
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<TT>mxmlIndexFind()</TT></A>, and <A href="mxmlIndexReset.html#mxmlIndexReset">
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<TT>mxmlIndexReset()</TT></A> functions are used to access the nodes in
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the index. The <A href="mxmlIndexReset.html#mxmlIndexReset"><TT>
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mxmlIndexReset()</TT></A> function resets the "current" node pointer in
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the index, allowing you to do new searches and enumerations on the same
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index. Typically you will call this function prior to your calls to <A href="mxmlIndexEnum.html#mxmlIndexEnum">
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<TT>mxmlIndexEnum()</TT></A> and <A href="mxmlIndexFind.html#mxmlIndexFind">
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<TT>mxmlIndexFind()</TT></A>.</P>
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<P>The <A href="mxmlIndexEnum.html#mxmlIndexEnum"><TT>mxmlIndexEnum()</TT>
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</A> function enumerates each of the nodes in the index and can be used
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in a loop as follows:</P>
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<PRE>
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<A href="mxmlnodet.html#mxml_node_t">mxml_node_t</A> *node;
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<A href="mxmlindext.html#mxml_index_t">mxml_index_t</A> *ind;
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mxmlIndexReset(ind);
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while ((node = mxmlIndexEnum(ind)) != NULL)
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{
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// do something with node
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}
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</PRE>
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<P>The <A href="mxmlIndexFind.html#mxmlIndexFind"><TT>mxmlIndexFind()</TT>
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</A> function locates the next occurrence of the named element and
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attribute value in the index. It can be used to find all matching
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elements in an index, as follows:</P>
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<PRE>
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<A href="mxmlnodet.html#mxml_node_t">mxml_node_t</A> *node;
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<A href="mxmlindext.html#mxml_index_t">mxml_index_t</A> *ind;
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mxmlIndexReset(ind);
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while ((node = mxmlIndexFind(ind, "element", "attr-value")) != NULL)
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{
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// do something with node
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}
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</PRE>
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<P>The second and third arguments represent the element name and
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attribute value, respectively. A <TT>NULL</TT> pointer is used to
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return all elements or attributes in the index. Passing <TT>NULL</TT>
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for both the element name and attribute value is equivalent to calling <TT>
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mxmlIndexEnum</TT>.</P>
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<!-- NEED 2in -->
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<P>When you are done using the index, delete it using the <A href="#mxmlIndexDelete()">
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<TT>mxmlIndexDelete()</TT></A> function:</P>
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<PRE>
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<A href="mxmlindext.html#mxml_index_t">mxml_index_t</A> *ind;
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mxmlIndexDelete(ind);
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</PRE>
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<HR NOSHADE>
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<A HREF="toc.html">Contents</A>
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<A HREF="FormattedText.html">Previous</A>
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