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Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]1<?xml version="1.0" encoding="ISO-8859-1"?>
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Daniel Veillarde8ba84e2003-11-18 13:54:15 +0000[diff] [blame]10</style><title>The parser interfaces</title></head><body bgcolor="#8b7765" text="#000000" link="#000000" 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="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="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://garypennington.net/libxml2/">Solaris binaries</a></li><li><a href="http://www.zveno.com/open_source/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal 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 bootstrapped
Daniel Veillard8a469172003-06-12 16:05:07 +0000[diff] [blame]11using the XML tollkit from the C language. It is not intended to be
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]12extensive. I hope the automatically generated documents will provide the
13completeness required, but as a separate set of documents. The interfaces of
Daniel Veillard95c09d92003-07-07 12:11:06 +0000[diff] [blame]14the XML parser are by principle low level, Those interested in a higher level
15API should <a href="#DOM">look at DOM</a>.</p><p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]16separated from the <a href="html/libxml-htmlparser.html">HTML parser
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]17interfaces</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 accepts
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]18documents either from in-memory strings or from files. The functions are
Daniel Veillard024f1992003-12-10 16:43:49 +0000[diff] [blame]19defined in "parser.h":</p><dl><dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]20 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]21 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]22</dl><dl><dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
23 <dd><p>Parse an XML document contained in a (possibly compressed)
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]24 file.</p>
25 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]26</dl><p>The parser returns a pointer to the document structure (or NULL in case of
27failure).</p><h3 id="Invoking1">Invoking the parser: the push method</h3><p>In order for the application to keep the control when the document is
Daniel Veillard95c09d92003-07-07 12:11:06 +0000[diff] [blame]28being fetched (which is common for GUI based programs) libxml2 provides a
29push interface, too, as of version 1.8.3. Here are the interface
30functions:</p><pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]31 void *user_data,
32 const char *chunk,
33 int size,
34 const char *filename);
35int xmlParseChunk (xmlParserCtxtPtr ctxt,
36 const char *chunk,
37 int size,
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]38 int terminate);</pre><p>and here is a simple example showing how to use the interface:</p><pre> FILE *f;
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]39
Daniel Veillard024f1992003-12-10 16:43:49 +0000[diff] [blame]40 f = fopen(filename, "r");
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]41 if (f != NULL) {
42 int res, size = 1024;
43 char chars[1024];
44 xmlParserCtxtPtr ctxt;
45
46 res = fread(chars, 1, 4, f);
47 if (res &gt; 0) {
48 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
49 chars, res, filename);
50 while ((res = fread(chars, 1, size, f)) &gt; 0) {
51 xmlParseChunk(ctxt, chars, res, 0);
52 }
53 xmlParseChunk(ctxt, chars, 0, 1);
54 doc = ctxt-&gt;myDoc;
55 xmlFreeParserCtxt(ctxt);
56 }
Daniel Veillard8a469172003-06-12 16:05:07 +0000[diff] [blame]57 }</pre><p>The HTML parser embedded into libxml2 also has a push interface; the
Daniel Veillard024f1992003-12-10 16:43:49 +0000[diff] [blame]58functions 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 loading
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]59the document in memory and then building the tree itself. Reading a document
60without building the tree is possible using the SAX interfaces (see SAX.h and
61<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
62Henstridge's documentation</a>). Note also that the push interface can be
63limited to SAX: just use the two first arguments of
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]64<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. Basically
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]65there is a set of functions dedicated to building new elements. (These are
66also described in &lt;libxml/tree.h&gt;.) For example, here is a piece of
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]67code that produces the XML document used in the previous examples:</p><pre> #include &lt;libxml/tree.h&gt;
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]68 xmlDocPtr doc;
69 xmlNodePtr tree, subtree;
70
Daniel Veillard024f1992003-12-10 16:43:49 +0000[diff] [blame]71 doc = xmlNewDoc("1.0");
72 doc-&gt;children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
73 xmlSetProp(doc-&gt;children, "prop1", "gnome is great");
74 xmlSetProp(doc-&gt;children, "prop2", "&amp; linux too");
75 tree = xmlNewChild(doc-&gt;children, NULL, "head", NULL);
76 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
77 tree = xmlNewChild(doc-&gt;children, NULL, "chapter", NULL);
78 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
79 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
80 subtree = xmlNewChild(tree, NULL, "image", NULL);
81 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> your
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]82code has access to the internal structure of all the elements of the tree.
83The names should be somewhat simple like <strong>parent</strong>,
84<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>,
85<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard024f1992003-12-10 16:43:49 +0000[diff] [blame]86example:</p><pre><code>doc-&gt;children-&gt;children-&gt;children</code></pre><p>points to the title element,</p><pre>doc-&gt;children-&gt;children-&gt;next-&gt;children-&gt;children</pre><p>points to the text node containing the chapter title "The Linux
87adventure".</p><p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]88present before the document root, so <code>doc-&gt;children</code> may point
89to an element which is not the document Root Element; a function
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]90<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. Here
91is 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
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]92 xmlChar *value);</code></dt>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]93 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node.
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]94 The value can be NULL.</p>
95 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]96</dl><dl><dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]97 *name);</code></dt>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]98 <dd><p>This function returns a pointer to new copy of the property
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]99 content. Note that the user must deallocate the result.</p>
100 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]101</dl><p>Two functions are provided for reading and writing the text associated
102with elements:</p><dl><dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]103 *value);</code></dt>
Daniel Veillard024f1992003-12-10 16:43:49 +0000[diff] [blame]104 <dd><p>This function takes an "external" string and converts it to one
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]105 text node or possibly to a list of entity and text nodes. All
106 non-predefined entity references like &amp;Gnome; will be stored
107 internally as entity nodes, hence the result of the function may not be
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]108 a single node.</p>
109 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]110</dl><dl><dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]111 inLine);</code></dt>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]112 <dd><p>This function is the inverse of
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]113 <code>xmlStringGetNodeList()</code>. It generates a new string
114 containing the content of the text and entity nodes. Note the extra
115 argument inLine. If this argument is set to 1, the function will expand
116 entity references. For example, instead of returning the &amp;Gnome;
117 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard024f1992003-12-10 16:43:49 +0000[diff] [blame]118 "GNU Network Object Model Environment").</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]119 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]120</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
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]121 *size);</code></dt>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]122 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]123 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]124</dl><dl><dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
125 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]126 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]127</dl><dl><dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
128 <dd><p>Saves the document to a file. In this case, the compression
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]129 interface is triggered if it has been turned on.</p>
130 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]131</dl><h3><a name="Compressio" id="Compressio">Compression</a></h3><p>The library transparently handles compression when doing file-based
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]132accesses. The level of compression on saves can be turned on either globally
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]133or individually for one file:</p><dl><dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
134 <dd><p>Gets the document compression ratio (0-9).</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]135 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]136</dl><dl><dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
137 <dd><p>Sets the document compression ratio.</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]138 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]139</dl><dl><dt><code>int xmlGetCompressMode(void);</code></dt>
140 <dd><p>Gets the default compression ratio.</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]141 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]142</dl><dl><dt><code>void xmlSetCompressMode(int mode);</code></dt>
143 <dd><p>Sets the default compression ratio.</p>
Daniel Veillard0b28e882002-07-24 23:47:05 +0000[diff] [blame]144 </dd>
Daniel Veillard1177ca42003-04-26 22:29:54 +0000[diff] [blame]145</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>