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<?xml version="1.0" encoding="ISO-8859-1"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css">TD {font-family: Verdana,Arial,Helvetica}BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}H1 {font-family: Verdana,Arial,Helvetica}H2 {font-family: Verdana,Arial,Helvetica}H3 {font-family: Verdana,Arial,Helvetica}A:link, A:visited, A:active { text-decoration: underline }</style><title>The parser interfaces</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="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><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Developer Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html" style="font-weight:bold">Main Menu</a></li><li><a href="html/index.html" style="font-weight:bold">Reference Manual</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="tutorial/index.html">Tutorial</a></li><li><a href="xmlreader.html">The Reader Interface</a></li><li><a href="ChangeLog.html">ChangeLog</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="python.html">Python and bindings</a></li><li><a href="architecture.html">libxml2 architecture</a></li><li><a href="tree.html">The tree output</a></li><li><a href="interface.html">The SAX interface</a></li><li><a href="xmlmem.html">Memory Management</a></li><li><a href="xmlio.html">I/O Interfaces</a></li><li><a href="library.html">The parser interfaces</a></li><li><a href="entities.html">Entities or no entities</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="upgrade.html">Upgrading 1.x code</a></li><li><a href="threads.html">Thread safety</a></li><li><a href="DOM.html">DOM Principles</a></li><li><a href="example.html">A real example</a></li><li><a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="APIchunk0.html">Alphabetic</a></li><li><a href="APIconstructors.html">Constructors</a></li><li><a href="APIfunctions.html">Functions/Types</a></li><li><a href="APIfiles.html">Modules</a></li><li><a href="APIsymbols.html">Symbols</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://www.blastwave.org/packages.php/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://libxmlplusplus.sourceforge.net/">C++ bindings</a></li><li><a href="http://www.zend.com/php5/articles/php5-xmlphp.php#Heading4">PHP bindings</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://libxml.rubyforge.org/">Ruby bindings</a></li><li><a href="http://tclxml.sourceforge.net/">Tcl bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><p>This section is directly intended to help programmers getting bootstrappedusing the XML tollkit from the C language. It is not intended to beextensive. I hope the automatically generated documents will provide thecompleteness required, but as a separate set of documents. The interfaces ofthe XML parser are by principle low level, Those interested in a higher levelAPI should <a href="#DOM">look at DOM</a>.</p><p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> areseparated from the <a href="html/libxml-htmlparser.html">HTML parserinterfaces</a>. Let's have a look at how the XML parser can be called:</p><h3><a name="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 acceptsdocuments either from in-memory strings or from files. The functions aredefined in "parser.h":</p><dl><dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> <dd><p>Parse a null-terminated string containing the document.</p> </dd></dl><dl><dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> <dd><p>Parse an XML document contained in a (possibly compressed) file.</p> </dd></dl><p>The parser returns a pointer to the document structure (or NULL in case offailure).</p><h3 id="Invoking1">Invoking the parser: the push method</h3><p>In order for the application to keep the control when the document isbeing fetched (which is common for GUI based programs) libxml2 provides apush interface, too, as of version 1.8.3. Here are the interfacefunctions:</p><pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, void *user_data, const char *chunk, int size, const char *filename);int xmlParseChunk (xmlParserCtxtPtr ctxt, const char *chunk, int size, int terminate);</pre><p>and here is a simple example showing how to use the interface:</p><pre> FILE *f; f = fopen(filename, "r"); if (f != NULL) { int res, size = 1024; char chars[1024]; xmlParserCtxtPtr ctxt; res = fread(chars, 1, 4, f); if (res > 0) { ctxt = xmlCreatePushParserCtxt(NULL, NULL, chars, res, filename); while ((res = fread(chars, 1, size, f)) > 0) { xmlParseChunk(ctxt, chars, res, 0); } xmlParseChunk(ctxt, chars, 0, 1); doc = ctxt->myDoc; xmlFreeParserCtxt(ctxt); } }</pre><p>The HTML parser embedded into libxml2 also has a push interface; thefunctions are just prefixed by "html" rather than "xml".</p><h3 id="Invoking2">Invoking the parser: the SAX interface</h3><p>The tree-building interface makes the parser memory-hungry, first loadingthe document in memory and then building the tree itself. Reading a documentwithout building the tree is possible using the SAX interfaces (see SAX.h and<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">JamesHenstridge's documentation</a>). Note also that the push interface can belimited to SAX: just use the two first arguments of<code>xmlCreatePushParserCtxt()</code>.</p><h3><a name="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. Basicallythere is a set of functions dedicated to building new elements. (These arealso described in <libxml/tree.h>.) For example, here is a piece ofcode that produces the XML document used in the previous examples:</p><pre> #include <libxml/tree.h> xmlDocPtr doc; xmlNodePtr tree, subtree; doc = xmlNewDoc("1.0"); doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); xmlSetProp(doc->children, "prop1", "gnome is great"); xmlSetProp(doc->children, "prop2", "& linux too"); tree = xmlNewChild(doc->children, NULL, "head", NULL); subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); tree = xmlNewChild(doc->children, NULL, "chapter", NULL); subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); subtree = xmlNewChild(tree, NULL, "image", NULL); xmlSetProp(subtree, "href", "linus.gif");</pre><p>Not really rocket science ...</p><h3><a name="Traversing" id="Traversing">Traversing the tree</a></h3><p>Basically by <a href="html/libxml-tree.html">including "tree.h"</a> yourcode has access to the internal structure of all the elements of the tree.The names should be somewhat simple like <strong>parent</strong>,<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>,<strong>properties</strong>, etc... For example, still with the previousexample:</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 Linuxadventure".</p><p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to bepresent before the document root, so <code>doc->children</code> may pointto an element which is not the document Root Element; a function<code>xmlDocGetRootElement()</code> was added for this purpose.</p><h3><a name="Modifying" id="Modifying">Modifying the tree</a></h3><p>Functions are provided for reading and writing the document content. Hereis an excerpt from the <a href="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. The value can be NULL.</p> </dd></dl><dl><dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar *name);</code></dt> <dd><p>This function returns a pointer to new copy of the property content. Note that the user must deallocate the result.</p> </dd></dl><p>Two functions are provided for reading and writing the text associatedwith elements:</p><dl><dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar *value);</code></dt> <dd><p>This function takes an "external" string and converts it to one text node or possibly to a list of entity and text nodes. All non-predefined entity references like &Gnome; will be stored internally as entity nodes, hence the result of the function may not be a single node.</p> </dd></dl><dl><dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int inLine);</code></dt> <dd><p>This function is the inverse of <code>xmlStringGetNodeList()</code>. It generates a new string containing the content of the text and entity nodes. Note the extra argument inLine. If this argument is set to 1, the function will expand entity references. For example, instead of returning the &Gnome; XML encoding in the string, it will substitute it with its value (say, "GNU Network Object Model Environment").</p> </dd></dl><h3><a name="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 *size);</code></dt> <dd><p>Returns a buffer into which the document has been saved.</p> </dd></dl><dl><dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> <dd><p>Dumps a document to an open file descriptor.</p> </dd></dl><dl><dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> <dd><p>Saves the document to a file. In this case, the compression interface is triggered if it has been turned on.</p> </dd></dl><h3><a name="Compressio" id="Compressio">Compression</a></h3><p>The library transparently handles compression when doing file-basedaccesses. The level of compression on saves can be turned on either globallyor individually for one file:</p><dl><dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> <dd><p>Gets the document compression ratio (0-9).</p> </dd></dl><dl><dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> <dd><p>Sets the document compression ratio.</p> </dd></dl><dl><dt><code>int xmlGetCompressMode(void);</code></dt> <dd><p>Gets the default compression ratio.</p> </dd></dl><dl><dt><code>void xmlSetCompressMode(int mode);</code></dt> <dd><p>Sets the default compression ratio.</p> </dd></dl><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>⌨️ 快捷键说明
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