Gitiles
Code Review Sign In
gerrit-public.fairphone.software / platform / external / libxml2 / c6271d208e0dc8768aac1dd7c162ddef121fbaa3 / . / doc / library.html
blob: 99a0a9d8abe30e9a1a63b1d8bcabcc5164b7701e [file] [log] [blame]
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
2<html>
3<head>
4<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type">
5<style type="text/css"><!--
6TD {font-size: 10pt; font-family: Verdana,Arial,Helvetica}
7BODY {font-size: 10pt; font-family: Verdana,Arial,Helvetica; margin-top: 5pt; margin-left: 0pt; margin-right: 0pt}
8H1 {font-size: 16pt; font-family: Verdana,Arial,Helvetica}
9H2 {font-size: 14pt; font-family: Verdana,Arial,Helvetica}
10H3 {font-size: 12pt; font-family: Verdana,Arial,Helvetica}
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]11A:link, A:visited, A:active { text-decoration: underline }
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]12--></style>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]13<title>The parser interfaces</title>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]14</head>
15<body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000">
16<table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr>
17<td width="180">
18<a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome 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>
19</td>
20<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">
21<h1>The XML C library for Gnome</h1>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]22<h2>The parser interfaces</h2>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]23</td></tr></table></td></tr></table></td>
24</tr></table>
25<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>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]26<td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td>
27<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]28<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr>
29<tr><td bgcolor="#fffacd"><ul style="margin-left: -2pt">
30<li><a href="index.html">Home</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]31<li><a href="intro.html">Introduction</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]32<li><a href="FAQ.html">FAQ</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]33<li><a href="docs.html">Documentation</a></li>
34<li><a href="bugs.html">Reporting bugs and getting help</a></li>
35<li><a href="help.html">How to help</a></li>
36<li><a href="downloads.html">Downloads</a></li>
37<li><a href="news.html">News</a></li>
38<li><a href="XML.html">XML</a></li>
39<li><a href="XSLT.html">XSLT</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]40<li><a href="architecture.html">libxml architecture</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]41<li><a href="tree.html">The tree output</a></li>
42<li><a href="interface.html">The SAX interface</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]43<li><a href="xmldtd.html">Validation &amp; DTDs</a></li>
44<li><a href="xmlmem.html">Memory Management</a></li>
45<li><a href="encoding.html">Encodings support</a></li>
46<li><a href="xmlio.html">I/O Interfaces</a></li>
47<li><a href="catalog.html">Catalog support</a></li>
48<li><a href="library.html">The parser interfaces</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]49<li><a href="entities.html">Entities or no entities</a></li>
50<li><a href="namespaces.html">Namespaces</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]51<li><a href="upgrade.html">Upgrading 1.x code</a></li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]52<li><a href="DOM.html">DOM Principles</a></li>
53<li><a href="example.html">A real example</a></li>
54<li><a href="contribs.html">Contributions</a></li>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]55<li>
56<a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a>
57</li>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]58</ul></td></tr>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]59</table>
60<table width="100%" border="0" cellspacing="1" cellpadding="3">
61<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
62<tr><td bgcolor="#fffacd"><ul style="margin-left: -2pt">
63<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
64<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
65<li><a href="http://www.cs.unibo.it/~casarini/gdome2/">DOM gdome2</a></li>
66<li><a href="ftp://xmlsoft.org/">FTP</a></li>
67<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
68<li><a href="http://pages.eidosnet.co.uk/~garypen/libxml/">Solaris binaries</a></li>
Daniel Veillardc6271d22001-10-27 07:50:58 +0000[diff] [blame^]69<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Bug Tracker</a></li>
Daniel Veillard594cf0b2001-10-25 08:09:12 +0000[diff] [blame]70</ul></td></tr>
71</table>
72</td></tr></table></td>
Daniel Veillardc9484202001-10-24 12:35:52 +0000[diff] [blame]73<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">
74<p>This section is directly intended to help programmers getting bootstrapped
75using the XML library from the C language. It is not intended to be
76extensive. I hope the automatically generated documents will provide the
77completeness required, but as a separate set of documents. The interfaces of
78the XML library are by principle low level, there is nearly zero abstraction.
79Those interested in a higher level API should <a href="#DOM">look at
80DOM</a>.</p>
81<p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are
82separated from the <a href="html/libxml-htmlparser.html">HTML parser
83interfaces</a>. Let's have a look at how the XML parser can be called:</p>
84<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
85<p>Usually, the first thing to do is to read an XML input. The parser accepts
86documents either from in-memory strings or from files. The functions are
87defined in &quot;parser.h&quot;:</p>
88<dl>
89<dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
90<dd><p>Parse a null-terminated string containing the document.</p></dd>
91</dl>
92<dl>
93<dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
94<dd><p>Parse an XML document contained in a (possibly compressed)
95 file.</p></dd>
96</dl>
97<p>The parser returns a pointer to the document structure (or NULL in case of
98failure).</p>
99<h3 id="Invoking1">Invoking the parser: the push method</h3>
100<p>In order for the application to keep the control when the document is
101being fetched (which is common for GUI based programs) libxml provides a push
102interface, too, as of version 1.8.3. Here are the interface functions:</p>
103<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
104 void *user_data,
105 const char *chunk,
106 int size,
107 const char *filename);
108int xmlParseChunk (xmlParserCtxtPtr ctxt,
109 const char *chunk,
110 int size,
111 int terminate);</pre>
112<p>and here is a simple example showing how to use the interface:</p>
113<pre> FILE *f;
114
115 f = fopen(filename, &quot;r&quot;);
116 if (f != NULL) {
117 int res, size = 1024;
118 char chars[1024];
119 xmlParserCtxtPtr ctxt;
120
121 res = fread(chars, 1, 4, f);
122 if (res &gt; 0) {
123 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
124 chars, res, filename);
125 while ((res = fread(chars, 1, size, f)) &gt; 0) {
126 xmlParseChunk(ctxt, chars, res, 0);
127 }
128 xmlParseChunk(ctxt, chars, 0, 1);
129 doc = ctxt-&gt;myDoc;
130 xmlFreeParserCtxt(ctxt);
131 }
132 }</pre>
133<p>The HTML parser embedded into libxml also has a push interface; the
134functions are just prefixed by &quot;html&quot; rather than &quot;xml&quot;.</p>
135<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
136<p>The tree-building interface makes the parser memory-hungry, first loading
137the document in memory and then building the tree itself. Reading a document
138without building the tree is possible using the SAX interfaces (see SAX.h and
139<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
140Henstridge's documentation</a>). Note also that the push interface can be
141limited to SAX: just use the two first arguments of
142<code>xmlCreatePushParserCtxt()</code>.</p>
143<h3><a name="Building">Building a tree from scratch</a></h3>
144<p>The other way to get an XML tree in memory is by building it. Basically
145there is a set of functions dedicated to building new elements. (These are
146also described in &lt;libxml/tree.h&gt;.) For example, here is a piece of
147code that produces the XML document used in the previous examples:</p>
148<pre> #include &lt;libxml/tree.h&gt;
149 xmlDocPtr doc;
150 xmlNodePtr tree, subtree;
151
152 doc = xmlNewDoc(&quot;1.0&quot;);
153 doc-&gt;children = xmlNewDocNode(doc, NULL, &quot;EXAMPLE&quot;, NULL);
154 xmlSetProp(doc-&gt;children, &quot;prop1&quot;, &quot;gnome is great&quot;);
155 xmlSetProp(doc-&gt;children, &quot;prop2&quot;, &quot;&amp; linux too&quot;);
156 tree = xmlNewChild(doc-&gt;children, NULL, &quot;head&quot;, NULL);
157 subtree = xmlNewChild(tree, NULL, &quot;title&quot;, &quot;Welcome to Gnome&quot;);
158 tree = xmlNewChild(doc-&gt;children, NULL, &quot;chapter&quot;, NULL);
159 subtree = xmlNewChild(tree, NULL, &quot;title&quot;, &quot;The Linux adventure&quot;);
160 subtree = xmlNewChild(tree, NULL, &quot;p&quot;, &quot;bla bla bla ...&quot;);
161 subtree = xmlNewChild(tree, NULL, &quot;image&quot;, NULL);
162 xmlSetProp(subtree, &quot;href&quot;, &quot;linus.gif&quot;);</pre>
163<p>Not really rocket science ...</p>
164<h3><a name="Traversing">Traversing the tree</a></h3>
165<p>Basically by <a href="html/libxml-tree.html">including &quot;tree.h&quot;</a> your
166code has access to the internal structure of all the elements of the tree.
167The names should be somewhat simple like <strong>parent</strong>,
168<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>,
169<strong>properties</strong>, etc... For example, still with the previous
170example:</p>
171<pre><code>doc-&gt;children-&gt;children-&gt;children</code></pre>
172<p>points to the title element,</p>
173<pre>doc-&gt;children-&gt;children-&gt;next-&gt;children-&gt;children</pre>
174<p>points to the text node containing the chapter title &quot;The Linux
175adventure&quot;.</p>
176<p>
177<strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
178present before the document root, so <code>doc-&gt;children</code> may point
179to an element which is not the document Root Element; a function
180<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
181<h3><a name="Modifying">Modifying the tree</a></h3>
182<p>Functions are provided for reading and writing the document content. Here
183is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p>
184<dl>
185<dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
186 xmlChar *value);</code></dt>
187<dd><p>This sets (or changes) an attribute carried by an ELEMENT node.
188 The value can be NULL.</p></dd>
189</dl>
190<dl>
191<dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
192 *name);</code></dt>
193<dd><p>This function returns a pointer to new copy of the property
194 content. Note that the user must deallocate the result.</p></dd>
195</dl>
196<p>Two functions are provided for reading and writing the text associated
197with elements:</p>
198<dl>
199<dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
200 *value);</code></dt>
201<dd><p>This function takes an &quot;external&quot; string and converts it to one
202 text node or possibly to a list of entity and text nodes. All
203 non-predefined entity references like &amp;Gnome; will be stored
204 internally as entity nodes, hence the result of the function may not be
205 a single node.</p></dd>
206</dl>
207<dl>
208<dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
209 inLine);</code></dt>
210<dd><p>This function is the inverse of
211 <code>xmlStringGetNodeList()</code>. It generates a new string
212 containing the content of the text and entity nodes. Note the extra
213 argument inLine. If this argument is set to 1, the function will expand
214 entity references. For example, instead of returning the &amp;Gnome;
215 XML encoding in the string, it will substitute it with its value (say,
216 &quot;GNU Network Object Model Environment&quot;).</p></dd>
217</dl>
218<h3><a name="Saving">Saving a tree</a></h3>
219<p>Basically 3 options are possible:</p>
220<dl>
221<dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
222 *size);</code></dt>
223<dd><p>Returns a buffer into which the document has been saved.</p></dd>
224</dl>
225<dl>
226<dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
227<dd><p>Dumps a document to an open file descriptor.</p></dd>
228</dl>
229<dl>
230<dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
231<dd><p>Saves the document to a file. In this case, the compression
232 interface is triggered if it has been turned on.</p></dd>
233</dl>
234<h3><a name="Compressio">Compression</a></h3>
235<p>The library transparently handles compression when doing file-based
236accesses. The level of compression on saves can be turned on either globally
237or individually for one file:</p>
238<dl>
239<dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
240<dd><p>Gets the document compression ratio (0-9).</p></dd>
241</dl>
242<dl>
243<dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
244<dd><p>Sets the document compression ratio.</p></dd>
245</dl>
246<dl>
247<dt><code>int xmlGetCompressMode(void);</code></dt>
248<dd><p>Gets the default compression ratio.</p></dd>
249</dl>
250<dl>
251<dt><code>void xmlSetCompressMode(int mode);</code></dt>
252<dd><p>Sets the default compression ratio.</p></dd>
253</dl>
254<p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p>
255</td></tr></table></td></tr></table></td></tr></table></td>
256</tr></table></td></tr></table>
257</body>
258</html>