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</style><title>The parser interfaces</title></head><bodybgcolor="#8b7765"text="#000000"link="#a06060"vlink="#000000"><tableborder="0"width="100%"cellpadding="5"cellspacing="0"align="center"><tr><tdwidth="120"><ahref="http://swpat.ffii.org/"><imgsrc="epatents.png"alt="Action against software patents"/></a></td><tdwidth="180"><ahref="http://www.gnome.org/"><imgsrc="gnome2.png"alt="Gnome2 Logo"/></a><ahref="http://www.w3.org/Status"><imgsrc="w3c.png"alt="W3C Logo"/></a><ahref="http://www.redhat.com/"><imgsrc="redhat.gif"alt="Red Hat Logo"/></a><divalign="left"><ahref="http://xmlsoft.org/"><imgsrc="Libxml2-Logo-180x168.gif"alt="Made with Libxml2 Logo"/></a></div></td><td><tableborder="0"width="90%"cellpadding="2"cellspacing="0"align="center"bgcolor="#000000"><tr><td><tablewidth="100%"border="0"cellspacing="1"cellpadding="3"bgcolor="#fffacd"><tr><tdalign="center"><h1>The XML C parser and toolkit of Gnome</h1><h2>The parser interfaces</h2></td></tr></table></td></tr></table></td></tr></table><tableborder="0"cellpadding="4"cellspacing="0"width="100%"align="center"><tr><tdbgcolor="#8b7765"><tableborder="0"cellspacing="0"cellpadding="2"width="100%"><tr><tdvalign="top"width="200"bgcolor="#8b7765"><tableborder="0"cellspacing="0"cellpadding="1"width="100%"bgcolor="#000000"><tr><td><tablewidth="100%"border="0"cellspacing="1"cellpadding="3"><tr><tdcolspan="1"bgcolor="#eecfa1"align="center"><center><b>Developer Menu</b></center></td></tr><tr><tdbgcolor="#fffacd"><formaction="search.php"enctype="application/x-www-form-urlencoded"method="get"><inputname="query"type="text"size="20"value=""/><inputname="submit"type="submit"value="Search ..."/></form><ul><li><ahref="index.html"style="font-weight:bold">Main Menu</a></li><li><ahref="html/index.html"style="font-weight:bold">Reference Manual</a></li><li><ahref="examples/index.html"style="font-weight:bold">Code Examples</a></li><li><ahref="guidelines.html">XML Guidelines</a></li><li><ahref="tutorial/index.html">Tutorial</a></li><li><ahref="xmlreader.html">The Reader Interface</a></li><li><ahref="ChangeLog.html">ChangeLog</a></li><li><ahref="XSLT.html">XSLT</a></li><li><ahref="python.html">Python and bindings</a></li><li><ahref="architecture.html">libxml2 architecture</a></li><li><ahref="tree.html">The tree output</a></li><li><ahref="interface.html">The SAX interface</a></li><li><ahref="xmlmem.html">Memory Management</a></li><li><ahref="xmlio.html">I/O Interfaces</a></li><li><ahref="library.html">The parser interfaces</a></li><li><ahref="entities.html">Entities or no entities</a></li><li><ahref="namespaces.html">Namespaces</a></li><li><ahref="upgrade.html">Upgrading 1.x code</a></li><li><ahref="threads.html">Thread safety</a></li><li><ahref="DOM.html">DOM Principles</a></li><li><ahref="example.html">A real example</a></li><li><ahref="xml.html">flat page</a>, <ahref="site.xsl">stylesheet</a></li></ul></td></tr></table><tablewidth="100%"border="0"cellspacing="1"cellpadding="3"><tr><tdcolspan="1"bgcolor="#eecfa1"align="center"><center><b>API Indexes</b></center></td></tr><tr><tdbgcolor="#fffacd"><ul><li><ahref="APIchunk0.html">Alphabetic</a></li><li><ahref="APIconstructors.html">Constructors</a></li><li><ahref="APIfunctions.html">Functions/Types</a></li><li><ahref="APIfiles.html">Modules</a></li><li><ahref="APIsymbols.html">Symbols</a></li></ul></td></tr></table><tablewidth="100%"border="0"cellspacing="1"cellpadding="3"><tr><tdcolspan="1"bgcolor="#eecfa1"align="center"><center><b>Related links</b></center></td></tr><tr><tdbgcolor="#fffacd"><ul><li><ahref="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><ahref="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><ahref="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><ahref="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><ahref="ftp://xmlsoft.org/">FTP</a></li><li><ahref="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><ahref="http://opencsw.org/packages/libxm
using the XML tollkit from the C language. It is not intended to be
extensive. I hope the automatically generated documents will provide the
completeness required, but as a separate set of documents. The interfaces of
the XML parser are by principle low level, Those interested in a higher level
API should <ahref="#DOM">look at DOM</a>.</p><p>The <ahref="html/libxml-parser.html">parser interfaces for XML</a> are
separated from the <ahref="html/libxml-htmlparser.html">HTML parser
interfaces</a>. Let's have a look at how the XML parser can be called:</p><h3><aname="Invoking"id="Invoking">Invoking the parser : the pull method</a></h3><p>Usually, the first thing to do is to read an XML input. The parser accepts
documents either from in-memory strings or from files. The functions are
defined in "parser.h":</p><dl><dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
}</pre><p>The HTML parser embedded into libxml2 also has a push interface; the
functions are just prefixed by "html" rather than "xml".</p><h3id="Invoking2">Invoking the parser: the SAX interface</h3><p>The tree-building interface makes the parser memory-hungry, first loading
the document in memory and then building the tree itself. Reading a document
without building the tree is possible using the SAX interfaces (see SAX.h and
Henstridge's documentation</a>). Note also that the push interface can be
limited to SAX: just use the two first arguments of
<code>xmlCreatePushParserCtxt()</code>.</p><h3><aname="Building"id="Building">Building a tree from scratch</a></h3><p>The other way to get an XML tree in memory is by building it. Basically
there is a set of functions dedicated to building new elements. (These are
also described in <libxml/tree.h>.) For example, here is a piece of
code that produces the XML document used in the previous examples:</p><pre> #include <libxml/tree.h>
xmlSetProp(subtree, "href", "linus.gif");</pre><p>Not really rocket science ...</p><h3><aname="Traversing"id="Traversing">Traversing the tree</a></h3><p>Basically by <ahref="html/libxml-tree.html">including "tree.h"</a> your
code has access to the internal structure of all the elements of the tree.
The names should be somewhat simple like <strong>parent</strong>,
<strong>properties</strong>, etc... For example, still with the previous
example:</p><pre><code>doc->children->children->children</code></pre><p>points to the title element,</p><pre>doc->children->children->next->children->children</pre><p>points to the text node containing the chapter title "The Linux
adventure".</p><p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
present before the document root, so <code>doc->children</code> may point
to an element which is not the document Root Element; a function
<code>xmlDocGetRootElement()</code> was added for this purpose.</p><h3><aname="Modifying"id="Modifying">Modifying the tree</a></h3><p>Functions are provided for reading and writing the document content. Here
is an excerpt from the <ahref="html/libxml-tree.html">tree API</a>:</p><dl><dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
xmlChar *value);</code></dt>
<dd><p>This sets (or changes) an attribute carried by an ELEMENT node.
</dl><h3><aname="Saving"id="Saving">Saving a tree</a></h3><p>Basically 3 options are possible:</p><dl><dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int