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4<head>
Daniel Veillardb05deb71999-08-10 19:04:08 +00005 <title>The XML library for Gnome</title>
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Daniel Veillardccb09631998-10-27 06:21:04 +00009
Daniel Veillardb05deb71999-08-10 19:04:08 +000010<body bgcolor="#ffffff">
Daniel Veillard60979bd2000-07-10 12:17:33 +000011<p><a href="http://www.gnome.org/"><img src="smallfootonly.gif"
12alt="Gnome Logo"></a><a href="http://www.w3.org/Status"><img src="w3c.png"
13alt="W3C Logo"></a></p>
Daniel Veillardec303412000-03-24 13:41:54 +000014
Daniel Veillardccb09631998-10-27 06:21:04 +000015<h1 align="center">The XML library for Gnome</h1>
Daniel Veillardb05deb71999-08-10 19:04:08 +000016
Daniel Veillardc8eab3a1999-09-04 18:27:23 +000017<h2 style="text-align: center">libxml, a.k.a. gnome-xml</h2>
18
19<p></p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +000020<ul>
21 <li><a href="#Introducti">Introduction</a></li>
22 <li><a href="#Documentat">Documentation</a></li>
Daniel Veillard10a2c651999-12-12 13:03:50 +000023 <li><a href="#Downloads">Downloads</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +000024 <li><a href="#News">News</a></li>
25 <li><a href="#XML">XML</a></li>
26 <li><a href="#tree">The tree output</a></li>
27 <li><a href="#interface">The SAX interface</a></li>
28 <li><a href="#library">The XML library interfaces</a>
29 <ul>
Daniel Veillard0142b842000-01-14 14:45:24 +000030 <li><a href="#Invoking">Invoking the parser: the pull way</a></li>
31 <li><a href="#Invoking">Invoking the parser: the push way</a></li>
32 <li><a href="#Invoking2">Invoking the parser: the SAX interface</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +000033 <li><a href="#Building">Building a tree from scratch</a></li>
34 <li><a href="#Traversing">Traversing the tree</a></li>
35 <li><a href="#Modifying">Modifying the tree</a></li>
36 <li><a href="#Saving">Saving the tree</a></li>
37 <li><a href="#Compressio">Compression</a></li>
38 </ul>
39 </li>
40 <li><a href="#Entities">Entities or no entities</a></li>
41 <li><a href="#Namespaces">Namespaces</a></li>
42 <li><a href="#Validation">Validation</a></li>
43 <li><a href="#Principles">DOM principles</a></li>
44 <li><a href="#real">A real example</a></li>
Daniel Veillardc310d562000-06-23 18:32:15 +000045 <li><a href="#Contributi">Contribution</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +000046</ul>
47
48<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +000049
Daniel Veillardf13e1ed2000-03-06 07:41:49 +000050<p>This document describes libxml, the <a
51href="http://www.w3.org/XML/">XML</a> library provided in the <a
52href="http://www.gnome.org/">Gnome</a> framework. XML is a standard for
53building tag-based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +000054
Daniel Veillard0142b842000-01-14 14:45:24 +000055<p>Here are some key points about libxml:</p>
56<ul>
Daniel Veillard6f0adb52000-07-03 11:41:26 +000057 <li>It is written in plain C, making as few assumptions as possible and
58 sticking closely to ANSI C for easy embedding.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +000059 <li>The internal document repesentation is as close as possible to the <a
60 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li>
61 <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX
Daniel Veillard402e8c82000-02-29 22:57:47 +000062 like interface</a>; the interface is designed to be compatible with <a
63 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li>
Daniel Veillard88f00ae2000-03-02 00:15:55 +000064 <li>Libxml now includes a nearly complete <a
Daniel Veillard0142b842000-01-14 14:45:24 +000065 href="http://www.w3.org/TR/xpath">XPath</a> implementation.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +000066 <li>Libxml exports Push and Pull type parser interfaces for both XML and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +000067 HTML.</li>
Daniel Veillardec303412000-03-24 13:41:54 +000068 <li>This library is released both under the <a
69 href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
70 IPR</a> and the GNU LGPL. Use either at your convenience, basically this
71 should make everybody happy, if not, drop me a mail.</li>
Daniel Veillardc310d562000-06-23 18:32:15 +000072 <li>There is <a href="upgrade.html">a first set of instructions</a>
Daniel Veillardedfb29b2000-03-14 19:59:05 +000073 concerning upgrade from libxml-1.x to libxml-2.x</li>
Daniel Veillard0142b842000-01-14 14:45:24 +000074</ul>
Daniel Veillardccb09631998-10-27 06:21:04 +000075
Daniel Veillard2f4dfc41999-09-24 14:03:48 +000076<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +000077
Daniel Veillard402e8c82000-02-29 22:57:47 +000078<p>There are some on-line resources about using libxml:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +000079<ol>
Daniel Veillard365e13b2000-07-02 07:56:37 +000080 <li>Check the <a href="FAQ.html">FAQ</a></li>
Daniel Veillardc19fccc2000-07-03 11:52:01 +000081 <li>Check the <a href="http://xmlsoft.org/html/libxml-lib.html">extensive
Daniel Veillard365e13b2000-07-02 07:56:37 +000082 documentation</a> automatically extracted from code comments.</li>
Daniel Veillard8d869642000-07-14 12:12:59 +000083 <li>Look at the documentation about <a href="encoding.html">libxml
84 internationalization support</a></li>
Daniel Veillard0142b842000-01-14 14:45:24 +000085 <li>This page provides a global overview and <a href="#real">some
Daniel Veillard402e8c82000-02-29 22:57:47 +000086 examples</a> on how to use libxml.</li>
87 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a
88 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
89 documentation</a> explaining how to use the libxml SAX interface.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +000090 <li>George Lebl wrote <a
91 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article
Daniel Veillard402e8c82000-02-29 22:57:47 +000092 for IBM developerWorks</a> about using libxml.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +000093 <li>It is also a good idea to check to <a href="mailto:raph@levien.com">Raph
94 Levien</a> <a href="http://levien.com/gnome/">web site</a> since he is
95 building the <a href="http://levien.com/gnome/gdome.html">DOM interface
Daniel Veillard402e8c82000-02-29 22:57:47 +000096 gdome</a> on top of libxml result tree and an implementation of <a
Daniel Veillard0142b842000-01-14 14:45:24 +000097 href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
98 href="http://www.levien.com/svg/">gill</a>. Check his <a
99 href="http://www.levien.com/gnome/domination.html">DOMination
100 paper</a>.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000101 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO
102 file</a></li>
103 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a>. If you are
104 starting a new project using libxml you should really use the 2.x
105 version.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000106 <li>And don't forget to look at the <a href="/messages/">mailing-list
Daniel Veillardc310d562000-06-23 18:32:15 +0000107 archive</a>.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000108</ol>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000109
Daniel Veillard0142b842000-01-14 14:45:24 +0000110<h3>Reporting bugs and getting help</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000111
Daniel Veillard402e8c82000-02-29 22:57:47 +0000112<p>Well, bugs or missing features are always possible, and I will make a point
113of fixing them in a timely fashion. The best way to report a bug is to <a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000114href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
Daniel Veillard402e8c82000-02-29 22:57:47 +0000115database</a>. I look at reports there regularly and it's good to have a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000116reminder when a bug is still open. Check the <a
117href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000118and be sure to specify that the bug is for the package gnome-xml.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000119
Daniel Veillard0142b842000-01-14 14:45:24 +0000120<p>There is also a mailing-list <a
121href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
122href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
Daniel Veillard402e8c82000-02-29 22:57:47 +0000123majordomo based list, send a mail message to <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000124href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
125"subscribe xml" in the <strong>content</strong> of the message.</p>
126
Daniel Veillard402e8c82000-02-29 22:57:47 +0000127<p>Alternatively, you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000128href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000129
Daniel Veillardec303412000-03-24 13:41:54 +0000130<p>Of course, bugs reports with a suggested patch for fixing them will
131probably be processed faster.</p>
132
133<p>If you're looking for help, a quick look at <a
134href="http://xmlsoft.org/messages/#407">the list archive</a> may actually
135provide the answer, I usually send source samples when answering libxml usage
Daniel Veillard6f0adb52000-07-03 11:41:26 +0000136questions. The <a href="http://xmlsoft.org/html/book1.html">auto-generated
Daniel Veillardec303412000-03-24 13:41:54 +0000137documentantion</a> is not as polished as I would like (i need to learn more
138about Docbook), but it's a good starting point.</p>
139
Daniel Veillard10a2c651999-12-12 13:03:50 +0000140<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000141
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000142<p>The latest versions of libxml can be found on <a
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000143href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or on the <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000144href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000145as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillard306be992000-07-03 12:38:45 +0000146archive</a> or <a
147href="ftp://ftp.gnome.org/pub/GNOME/contrib/redhat/SRPMS/">RPM packages</a>.
148(NOTE that you need both the <a
Daniel Veillardc19fccc2000-07-03 11:52:01 +0000149href="http://rpmfind.net/linux/RPM/libxml2.html">libxml(2)</a> and <a
150href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml(2)-devel</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000151packages installed to compile applications using libxml.)</p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000152
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000153<p><a name="Snapshot">Snapshot:</a></p>
154<ul>
155 <li>Code from the W3C cvs base libxml <a
156 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li>
157 <li>Docs, content of the web site, the list archive included <a
158 href="ftp://rpmfind.net/pub/libxml/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li>
159</ul>
160
161<p><a name="Contribs">Contribs:</a></p>
162
163<p>I do accept external contributions, especially if compiling on another
164platform, get in touch with me to upload the package. I will keep them in the
165<a href="ftp://rpmfind.net/pub/libxml/contribs/">contrib directory</a></p>
166
Daniel Veillardc310d562000-06-23 18:32:15 +0000167<p>Libxml is also available from 2 CVS bases:</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000168<ul>
169 <li><p>The <a href="http://dev.w3.org/cvsweb/XML/">W3C CVS base</a>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000170 available read-only using the CVS pserver authentification (I tend to use
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000171 this base for my own development, so it's updated more regularly, but the
172 content may not be as stable):</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000173 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
Daniel Veillard365e13b2000-07-02 07:56:37 +0000174 password: anonymous
175 module: XML</pre>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000176 </li>
177 <li><p>The <a
178 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&amp;dir=gnome-xml">Gnome
Daniel Veillard402e8c82000-02-29 22:57:47 +0000179 CVS base</a>. Check the <a
180 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page;
181 the CVS module is <b>gnome-xml</b>.</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000182 </li>
183</ul>
184
185<h2><a name="News">News</a></h2>
186
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000187<h3>CVS only : check the <a
188href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
189for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000190<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000191 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000192 if you want to test those.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000193</ul>
194
Daniel Veillarda2679fa2000-07-22 02:38:15 +0000195<h2>2.2.1: July 21 2000</h2>
196<ul>
197 <li>a purely bug fixes release</li>
198 <li>fixed an encoding support problem when parsing from a memory block</li>
199 <li>fixed a DOCTYPE parsing problem</li>
200 <li>removed a bug in the function allowing to override the memory allocation
201 routines</li>
202</ul>
203
Daniel Veillard94e90602000-07-17 14:38:19 +0000204<h2>2.2.0: July 14 2000</h2>
205<ul>
206 <li>applied a lot of portability fixes</li>
207 <li>better encoding support/cleanup and saving (content is now always
208 encoded in UTF-8)</li>
209 <li>the HTML parser now correctly handles encodings</li>
210 <li>added xmlHasProp()</li>
211 <li>fixed a serious problem with &amp;#38;</li>
212 <li>propagated the fix to FTP client</li>
213 <li>cleanup, bugfixes, etc ...</li>
214 <li>Added a page about <a href="encoding.html">libxml Internationalization
215 support</a></li>
216</ul>
217
Daniel Veillard60979bd2000-07-10 12:17:33 +0000218<h3>1.8.9: July 9 2000</h3>
219<ul>
220 <li>fixed the spec the RPMs should be better</li>
221 <li>fixed a serious bug in the FTP implementation, released 1.8.9 to solve
222 rpmfind users problem</li>
223</ul>
224
Daniel Veillard6388e172000-07-03 16:07:19 +0000225<h3>2.1.1: July 1 2000</h3>
226<ul>
227 <li>fixes a couple of bugs in the 2.1.0 packaging</li>
228 <li>improvements on the HTML parser</li>
229</ul>
230
Daniel Veillard3f6f7f62000-06-30 17:58:25 +0000231<h3>2.1.0 and 1.8.8: June 29 2000</h3>
232<ul>
233 <li>1.8.8 is mostly a comodity package for upgrading to libxml2 accoding to
234 <a href="upgrade.html">new instructions</a>. It fixes a nasty problem
235 about &amp;#38; charref parsing</li>
236 <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it
237 also contains numerous fixes and enhancements:
238 <ul>
239 <li>added xmlStopParser() to stop parsing</li>
240 <li>improved a lot parsing speed when there is large CDATA blocs</li>
241 <li>includes XPath patches provided by Picdar Technology</li>
242 <li>tried to fix as much as possible DtD validation and namespace
243 related problems</li>
244 <li>output to a given encoding has been added/tested</li>
245 <li>lot of various fixes</li>
246 </ul>
247 </li>
248</ul>
249
Daniel Veillarde0aed302000-04-16 08:52:20 +0000250<h3>2.0.0: Apr 12 2000</h3>
Daniel Veillard361d8452000-04-03 19:48:13 +0000251<ul>
252 <li>First public release of libxml2. If you are using libxml, it's a good
Daniel Veillarde0aed302000-04-16 08:52:20 +0000253 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initally
254 scheduled for Apr 3 the relase occured only on Apr 12 due to massive
255 workload.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000256 <li>The include are now located under $prefix/include/libxml (instead of
Daniel Veillarde0aed302000-04-16 08:52:20 +0000257 $prefix/include/gnome-xml), they also are referenced by
Daniel Veillard60979bd2000-07-10 12:17:33 +0000258 <pre>#include &lt;libxml/xxx.h&gt;</pre>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000259 <p>instead of</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000260 <pre>#include "xxx.h"</pre>
261 </li>
Daniel Veillard8f621982000-03-20 13:07:15 +0000262 <li>a new URI module for parsing URIs and following strictly RFC 2396</li>
263 <li>the memory allocation routines used by libxml can now be overloaded
264 dynamically by using xmlMemSetup()</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000265 <li>The previously CVS only tool tester has been renamed
266 <strong>xmllint</strong> and is now installed as part of the libxml2
267 package</li>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000268 <li>The I/O interface has been revamped. There is now ways to plug in
269 specific I/O modules, either at the URI scheme detection level using
270 xmlRegisterInputCallbacks() or by passing I/O functions when creating a
271 parser context using xmlCreateIOParserCtxt()</li>
272 <li>there is a C preprocessor macro LIBXML_VERSION providing the version
273 number of the libxml module in use</li>
274 <li>a number of optional features of libxml can now be excluded at configure
275 time (FTP/HTTP/HTML/XPath/Debug)</li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000276</ul>
277
278<h3>2.0.0beta: Mar 14 2000</h3>
279<ul>
280 <li>This is a first Beta release of libxml version 2</li>
281 <li>It's available only from<a href="ftp://rpmfind.net/pub/libxml/">
282 rpmfind.net FTP</a>, it's packaged as libxml2-2.0.0beta and available as
283 tar and RPMs</li>
284 <li>This version is now the head in the Gnome CVS base, the old one is
285 available under the tag LIB_XML_1_X</li>
286 <li>This includes a very large set of changes. Froma programmatic point of
287 view applications should not have to be modified too much, check the <a
288 href="upgrade.html">upgrade page</a></li>
289 <li>Some interfaces may changes (especially a bit about encoding).</li>
290 <li>the updates includes:
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000291 <ul>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000292 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly
293 handled now</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000294 <li>Better handling of entities, especially well formedness checking and
295 proper PEref extensions in external subsets</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000296 <li>DTD conditional sections</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000297 <li>Validation now correcly handle entities content</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000298 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
299 structures to accomodate DOM</a></li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000300 </ul>
301 </li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000302 <li>Serious progress were made toward compliance, <a
303 href="conf/result.html">here are the result of the test</a> against the
304 OASIS testsuite (except the japanese tests since I don't support that
305 encoding yet). This URL is rebuilt every couple of hours using the CVS
306 head version.</li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000307</ul>
308
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000309<h3>1.8.7: Mar 6 2000</h3>
310<ul>
311 <li>This is a bug fix release:</li>
312 <li>It is possible to disable the ignorable blanks heuristic used by
313 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note
314 that for adherence to XML spec, this behaviour will be disabled by default
315 in 2.x . The same function will allow to keep compatibility for old
316 code.</li>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000317 <li>Blanks in &lt;a&gt; &lt;/a&gt; constructs are not ignored anymore,
318 avoiding heuristic is really the Right Way :-\</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000319 <li>The unchecked use of snprintf which was breaking libxml-1.8.6
320 compilation on some platforms has been fixed</li>
321 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing
322 URIs</li>
323</ul>
324
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000325<h3>1.8.6: Jan 31 2000</h3>
326<ul>
327 <li>added a nanoFTP transport module, debugged until the new version of <a
328 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
329 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000330</ul>
331
332<h3>1.8.5: Jan 21 2000</h3>
333<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000334 <li>adding APIs to parse a well balanced chunk of XML (production <a
335 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
336 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000337 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000338 <li>Jody Goldberg &lt;jgoldberg@home.com&gt; provided another patch trying
339 to solve the zlib checks problems</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000340 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
341 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000342</ul>
343
344<h3>1.8.4: Jan 13 2000</h3>
345<ul>
346 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
347 <li>all exit() call should have been removed from libxml</li>
348 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
349 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000350</ul>
351
352<h3>1.8.3: Jan 5 2000</h3>
353<ul>
354 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000355 <li>a shell-like interface to the document tree (try tester --shell :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000356 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000357 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000358 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
359 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000360 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000361 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000362 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000363</ul>
364
365<h3>1.8.2: Dec 21 1999</h3>
366<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000367 <li>I got another problem with includes and C++, I hope this issue is fixed
368 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000369 <li>Added a few tree modification functions: xmlReplaceNode,
370 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
371 xmlDocSetRootElement</li>
372 <li>Tried to improve the HTML output with help from <a
373 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000374</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000375
Daniel Veillarde4e51311999-12-18 15:32:46 +0000376<h3>1.8.1: Dec 18 1999</h3>
377<ul>
378 <li>various patches to avoid troubles when using libxml with C++ compilers
379 the "namespace" keyword and C escaping in include files</li>
380 <li>a problem in one of the core macros IS_CHAR was corrected</li>
381 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
382 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000383 <li>fixed a posteriori validation (validation after parsing, or by using a
384 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000385 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000386</ul>
387
388<h3>1.8.0: Dec 12 1999</h3>
389<ul>
390 <li>cleanup, especially memory wise</li>
391 <li>the parser should be more reliable, especially the HTML one, it should
392 not crash, whatever the input !</li>
393 <li>Integrated various patches, especially a speedup improvement for large
394 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
395 configure with --with-buffers to enable them.</li>
396 <li>attribute normalization, oops should have been added long ago !</li>
397 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
398 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000399</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000400
401<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000402<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000403 <li>Lots of HTML improvement</li>
404 <li>Fixed some errors when saving both XML and HTML</li>
405 <li>More examples, the regression tests should now look clean</li>
406 <li>Fixed a bug with contiguous charref</li>
407</ul>
408
409<h3>1.7.3: Sep 29 1999</h3>
410<ul>
411 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000412 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000413 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000414</ul>
415
416<h3>1.7.1: Sep 24 1999</h3>
417<ul>
418 <li>The basic type for strings manipulated by libxml has been renamed in
419 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
420 is that CHAR was conflicting with a predefined type on Windows. However on
421 non WIN32 environment, compatibility is provided by the way of a
422 <strong>#define </strong>.</li>
423 <li>Changed another error : the use of a structure field called errno, and
424 leading to troubles on platforms where it's a macro</li>
425</ul>
426
427<h3>1.7.0: sep 23 1999</h3>
428<ul>
429 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
Daniel Veillardc19fccc2000-07-03 11:52:01 +0000430 href="html/gnome-xml-nanohttp.html">nanohttp</a> module.</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000431 <li>Added an errno to report errors by another mean than a simple printf
432 like callback</li>
433 <li>Finished ID/IDREF support and checking when validation</li>
434 <li>Serious memory leaks fixed (there is now a <a
Daniel Veillardc19fccc2000-07-03 11:52:01 +0000435 href="html/gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000436 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
437 implementation</li>
438 <li>Added an HTML parser front-end</li>
439</ul>
440
441<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000442
Daniel Veillard402e8c82000-02-29 22:57:47 +0000443<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000444markup-based structured documents. Here is <a name="example">an example XML
445document</a>:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000446<pre>&lt;?xml version="1.0"?&gt;
447&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too"&gt;
448 &lt;head&gt;
449 &lt;title&gt;Welcome to Gnome&lt;/title&gt;
450 &lt;/head&gt;
451 &lt;chapter&gt;
452 &lt;title&gt;The Linux adventure&lt;/title&gt;
453 &lt;p&gt;bla bla bla ...&lt;/p&gt;
454 &lt;image href="linus.gif"/&gt;
455 &lt;p&gt;...&lt;/p&gt;
456 &lt;/chapter&gt;
457&lt;/EXAMPLE&gt;</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000458
Daniel Veillard402e8c82000-02-29 22:57:47 +0000459<p>The first line specifies that it's an XML document and gives useful
460information about its encoding. Then the document is a text format whose
461structure is specified by tags between brackets. <strong>Each tag opened has
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000462to be closed</strong>. XML is pedantic about this. However, if a tag is empty
463(no content), a single tag can serve as both the opening and closing tag if it
Daniel Veillard60979bd2000-07-10 12:17:33 +0000464ends with <code>/&gt;</code> rather than with <code>&gt;</code>. Note that,
465for example, the image tag has no content (just an attribute) and is closed by
466ending the tag with <code>/&gt;</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000467
Daniel Veillard402e8c82000-02-29 22:57:47 +0000468<p>XML can be applied sucessfully to a wide range of uses, from long term
469structured document maintenance (where it follows the steps of SGML) to simple
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000470data encoding mechanisms like configuration file formatting (glade),
471spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where
472it is used to encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000473
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000474<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000475
476<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000477returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000478<strong>xmlDoc</strong> structure). This structure contains information such
Daniel Veillard306be992000-07-03 12:38:45 +0000479as the file name, the document type, and a <strong>children</strong> pointer
480which is the root of the document (or more exactly the first child under the
481root which is the document). The tree is made of <strong>xmlNode</strong>s,
Daniel Veillard60979bd2000-07-10 12:17:33 +0000482chained in double-linked lists of siblings and with children&lt;-&gt;parent
Daniel Veillard306be992000-07-03 12:38:45 +0000483relationship. An xmlNode can also carry properties (a chain of xmlAttr
484structures). An attribute may have a value which is a list of TEXT or
485ENTITY_REF nodes.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000486
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000487<p>Here is an example (erroneous with respect to the XML spec since there
488should be only one ELEMENT under the root):</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000489
490<p><img src="structure.gif" alt=" structure.gif "></p>
491
492<p>In the source package there is a small program (not installed by default)
Daniel Veillard361d8452000-04-03 19:48:13 +0000493called <strong>xmllint</strong> which parses XML files given as argument and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000494prints them back as parsed. This is useful for detecting errors both in XML
495code and in the XML parser itself. It has an option <strong>--debug</strong>
496which prints the actual in-memory structure of the document, here is the
497result with the <a href="#example">example</a> given before:</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000498<pre>DOCUMENT
499version=1.0
500standalone=true
501 ELEMENT EXAMPLE
502 ATTRIBUTE prop1
503 TEXT
504 content=gnome is great
505 ATTRIBUTE prop2
506 ENTITY_REF
507 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000508 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000509 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000510 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000511 TEXT
512 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000513 ELEMENT chapter
514 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000515 TEXT
516 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000517 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000518 TEXT
519 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000520 ELEMENT image
521 ATTRIBUTE href
522 TEXT
523 content=linus.gif
524 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000525 TEXT
526 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000527
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000528<p>This should be useful for learning the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000529
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000530<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000531
Daniel Veillard402e8c82000-02-29 22:57:47 +0000532<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000533memory. In that case (and if you don't expect to save back the XML document
534loaded using libxml), it's better to use the SAX interface of libxml. SAX is a
Daniel Veillard402e8c82000-02-29 22:57:47 +0000535<strong>callback-based interface</strong> to the parser. Before parsing, the
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000536application layer registers a customized set of callbacks which are called by
537the library as it progresses through the XML input.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000538
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000539<p>To get more detailed step-by-step guidance on using the SAX interface of
540libxml, see the
Daniel Veillard60979bd2000-07-10 12:17:33 +0000541href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html"&gt;nice
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000542documentation.written by <a href="mailto:james@daa.com.au">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000543Henstridge</a>.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000544
545<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
546program located in the gnome-xml module (it's usually not shipped in the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000547binary packages of libxml, but you can find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000548distribution). Here is the sequence of callbacks that would be reported by
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000549testSAX when parsing the example XML document shown earlier:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000550<pre>SAX.setDocumentLocator()
551SAX.startDocument()
552SAX.getEntity(amp)
553SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
554SAX.characters( , 3)
555SAX.startElement(head)
556SAX.characters( , 4)
557SAX.startElement(title)
558SAX.characters(Welcome to Gnome, 16)
559SAX.endElement(title)
560SAX.characters( , 3)
561SAX.endElement(head)
562SAX.characters( , 3)
563SAX.startElement(chapter)
564SAX.characters( , 4)
565SAX.startElement(title)
566SAX.characters(The Linux adventure, 19)
567SAX.endElement(title)
568SAX.characters( , 4)
569SAX.startElement(p)
570SAX.characters(bla bla bla ..., 15)
571SAX.endElement(p)
572SAX.characters( , 4)
573SAX.startElement(image, href='linus.gif')
574SAX.endElement(image)
575SAX.characters( , 4)
576SAX.startElement(p)
577SAX.characters(..., 3)
578SAX.endElement(p)
579SAX.characters( , 3)
580SAX.endElement(chapter)
581SAX.characters( , 1)
582SAX.endElement(EXAMPLE)
583SAX.endDocument()</pre>
584
Daniel Veillard402e8c82000-02-29 22:57:47 +0000585<p>Most of the other functionalities of libxml are based on the DOM
586tree-building facility, so nearly everything up to the end of this document
587presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000588itself is built by a set of registered default callbacks, without internal
589specific interface.</p>
590
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000591<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000592
593<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000594using the XML library from the C language. It is not intended to be extensive.
595I hope the automatically generated documents will provide the completeness
596required, but as a separate set of documents. The interfaces of the XML
597library are by principle low level, there is nearly zero abstraction. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000598interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000599
Daniel Veillardc19fccc2000-07-03 11:52:01 +0000600<p>The <a href="html/gnome-xml-parser.html">parser interfaces for XML</a> are
601separated from the <a href="html/gnome-xml-htmlparser.html">HTML parser
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000602interfaces</a>. Let's have a look at how the XML parser can be called:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000603
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000604<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000605
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000606<p>Usually, the first thing to do is to read an XML input. The parser accepts
607documents either from in-memory strings or from files. The functions are
Daniel Veillardb05deb71999-08-10 19:04:08 +0000608defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000609<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000610 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000611 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000612 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000613</dl>
614<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000615 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000616 <dd><p>Parse an XML document contained in a (possibly compressed)
617 file.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000618 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000619</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000620
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000621<p>The parser returns a pointer to the document structure (or NULL in case of
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000622failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000623
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000624<h3 id="Invoking1">Invoking the parser: the push method</h3>
Daniel Veillard0142b842000-01-14 14:45:24 +0000625
626<p>In order for the application to keep the control when the document is been
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000627fetched (which is common for GUI based programs) libxml provides a push
628interface, too, as of version 1.8.3. Here are the interface functions:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000629<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
630 void *user_data,
631 const char *chunk,
632 int size,
633 const char *filename);
634int xmlParseChunk (xmlParserCtxtPtr ctxt,
635 const char *chunk,
636 int size,
637 int terminate);</pre>
638
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000639<p>and here is a simple example showing how to use the interface:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000640<pre> FILE *f;
641
642 f = fopen(filename, "r");
643 if (f != NULL) {
644 int res, size = 1024;
645 char chars[1024];
646 xmlParserCtxtPtr ctxt;
647
648 res = fread(chars, 1, 4, f);
Daniel Veillard60979bd2000-07-10 12:17:33 +0000649 if (res &gt; 0) {
Daniel Veillard0142b842000-01-14 14:45:24 +0000650 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
651 chars, res, filename);
Daniel Veillard60979bd2000-07-10 12:17:33 +0000652 while ((res = fread(chars, 1, size, f)) &gt; 0) {
Daniel Veillard0142b842000-01-14 14:45:24 +0000653 xmlParseChunk(ctxt, chars, res, 0);
654 }
655 xmlParseChunk(ctxt, chars, 0, 1);
Daniel Veillard60979bd2000-07-10 12:17:33 +0000656 doc = ctxt-&gt;myDoc;
Daniel Veillard0142b842000-01-14 14:45:24 +0000657 xmlFreeParserCtxt(ctxt);
658 }
659 }</pre>
660
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000661<p>Also note that the HTML parser embedded into libxml also has a push
662interface; the functions are just prefixed by "html" rather than "xml"</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000663
664<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
665
Daniel Veillardb05deb71999-08-10 19:04:08 +0000666<p>A couple of comments can be made, first this mean that the parser is
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000667memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000668Reading a document without building the tree is possible using the SAX
669interfaces (see SAX.h and <a
670href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000671Henstridge's documentation</a>). Note also that the push interface can be
672limited to SAX. Just use the two first arguments of
Daniel Veillard0142b842000-01-14 14:45:24 +0000673<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000674
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000675<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000676
677<p>The other way to get an XML tree in memory is by building it. Basically
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000678there is a set of functions dedicated to building new elements. (These are
Daniel Veillard60979bd2000-07-10 12:17:33 +0000679also described in &lt;libxml/tree.h&gt;.) For example, here is a piece of code
Daniel Veillard361d8452000-04-03 19:48:13 +0000680that produces the XML document used in the previous examples:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000681<pre> #include &lt;libxml/tree.h&gt;
Daniel Veillard361d8452000-04-03 19:48:13 +0000682 xmlDocPtr doc;
Daniel Veillard25940b71998-10-29 05:51:30 +0000683 xmlNodePtr tree, subtree;
684
685 doc = xmlNewDoc("1.0");
Daniel Veillard60979bd2000-07-10 12:17:33 +0000686 doc-&gt;children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
687 xmlSetProp(doc-&gt;children, "prop1", "gnome is great");
688 xmlSetProp(doc-&gt;children, "prop2", "&amp; linux too");
689 tree = xmlNewChild(doc-&gt;children, NULL, "head", NULL);
Daniel Veillard25940b71998-10-29 05:51:30 +0000690 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
Daniel Veillard60979bd2000-07-10 12:17:33 +0000691 tree = xmlNewChild(doc-&gt;children, NULL, "chapter", NULL);
Daniel Veillard25940b71998-10-29 05:51:30 +0000692 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
693 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
694 subtree = xmlNewChild(tree, NULL, "image", NULL);
695 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000696
697<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000698
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000699<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000700
Daniel Veillard306be992000-07-03 12:38:45 +0000701<p>Basically by <a href="html/gnome-xml-tree.html">including "tree.h"</a> your
702code has access to the internal structure of all the elements of the tree. The
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000703names should be somewhat simple like <strong>parent</strong>,
Daniel Veillard306be992000-07-03 12:38:45 +0000704<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000705<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard0142b842000-01-14 14:45:24 +0000706example:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000707<pre><code>doc-&gt;children-&gt;children-&gt;children</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000708
709<p>points to the title element,</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000710<pre>doc-&gt;children-&gt;children-&gt;next-&gt;child-&gt;child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000711
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000712<p>points to the text node containing the chapter title "The Linux
713adventure".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000714
Daniel Veillardb24054a1999-12-18 15:32:46 +0000715<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
Daniel Veillard60979bd2000-07-10 12:17:33 +0000716present before the document root, so <code>doc-&gt;children</code> may point
717to an element which is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000718<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000719
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000720<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000721
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000722<p>Functions are provided for reading and writing the document content. Here
Daniel Veillardc19fccc2000-07-03 11:52:01 +0000723is an excerpt from the <a href="html/gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000724<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000725 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
726 xmlChar *value);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000727 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. The
728 value can be NULL.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000729 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000730</dl>
731<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000732 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000733 *name);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000734 <dd><p>This function returns a pointer to the property content. Note that
735 no extra copy is made.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000736 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000737</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000738
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000739<p>Two functions are provided for reading and writing the text associated with
Daniel Veillard25940b71998-10-29 05:51:30 +0000740elements:</p>
741<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000742 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000743 *value);</code></dt>
744 <dd><p>This function takes an "external" string and convert it to one text
745 node or possibly to a list of entity and text nodes. All non-predefined
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000746 entity references like &amp;Gnome; will be stored internally as entity
747 nodes, hence the result of the function may not be a single node.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000748 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000749</dl>
750<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000751 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000752 inLine);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000753 <dd><p>This function is the inverse of
754 <code>xmlStringGetNodeList()</code>. It generates a new string
755 containing the content of the text and entity nodes. Note the extra
756 argument inLine. If this argument is set to 1, the function will expand
757 entity references. For example, instead of returning the &amp;Gnome;
758 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000759 "GNU Network Object Model Environment"). Set this argument if you want
760 to use the string for non-XML usage like User Interface.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000761 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000762</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000763
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000764<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000765
766<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000767<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000768 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000769 *size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000770 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000771 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000772</dl>
773<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000774 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000775 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000776 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000777</dl>
778<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000779 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000780 <dd><p>Saves the document to a file. In this case, the compression
781 interface is triggered if it has been turned on.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000782 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000783</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000784
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000785<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000786
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000787<p>The library transparently handles compression when doing file-based
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000788accesses. The level of compression on saves can be turned on either globally
789or individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000790<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000791 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000792 <dd><p>Gets the document compression ratio (0-9).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000793 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000794</dl>
795<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000796 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000797 <dd><p>Sets the document compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000798 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000799</dl>
800<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000801 <dt><code>int xmlGetCompressMode(void);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000802 <dd><p>Gets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000803 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000804</dl>
805<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000806 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000807 <dd><p>Sets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000808 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000809</dl>
810
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000811<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000812
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000813<p>Entities in principle are similar to simple C macros. An entity defines an
814abbreviation for a given string that you can reuse many times throughout the
815content of your document. Entities are especially useful when a given string
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000816may occur frequently within a document, or to confine the change needed to a
817document to a restricted area in the internal subset of the document (at the
818beginning). Example:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000819<pre>1 &lt;?xml version="1.0"?&gt;
Daniel Veillardc8eab3a1999-09-04 18:27:23 +00008202 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
Daniel Veillard60979bd2000-07-10 12:17:33 +00008213 &lt;!ENTITY xml "Extensible Markup Language"&gt;
8224 ]&gt;
8235 &lt;EXAMPLE&gt;
Daniel Veillardc8eab3a1999-09-04 18:27:23 +00008246 &amp;xml;
Daniel Veillard60979bd2000-07-10 12:17:33 +00008257 &lt;/EXAMPLE&gt;</pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000826
827<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000828it's name with '&amp;' and following it by ';' without any spaces added. There
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000829are 5 predefined entities in libxml allowing you to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000830predefined meaning in some parts of the xml document content:
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000831<strong>&amp;lt;</strong> for the character '&lt;', <strong>&amp;gt;</strong>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000832for the character '&gt;', <strong>&amp;apos;</strong> for the character ''',
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000833<strong>&amp;quot;</strong> for the character '"', and
834<strong>&amp;amp;</strong> for the character '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000835
836<p>One of the problems related to entities is that you may want the parser to
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000837substitute an entity's content so that you can see the replacement text in
838your application. Or you may prefer to keep entity references as such in the
839content to be able to save the document back without losing this usually
840precious information (if the user went through the pain of explicitly defining
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000841entities, he may have a a rather negative attitude if you blindly susbtitute
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000842them as saving time). The <a
Daniel Veillardc19fccc2000-07-03 11:52:01 +0000843href="html/gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000844function allows you to check and change the behaviour, which is to not
845substitute entities by default.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000846
847<p>Here is the DOM tree built by libxml for the previous document in the
848default case:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000849<pre>/gnome/src/gnome-xml -&gt; ./xmllint --debug test/ent1
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000850DOCUMENT
851version=1.0
852 ELEMENT EXAMPLE
853 TEXT
854 content=
855 ENTITY_REF
856 INTERNAL_GENERAL_ENTITY xml
857 content=Extensible Markup Language
858 TEXT
859 content=</pre>
860
861<p>And here is the result when substituting entities:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000862<pre>/gnome/src/gnome-xml -&gt; ./tester --debug --noent test/ent1
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000863DOCUMENT
864version=1.0
865 ELEMENT EXAMPLE
866 TEXT
867 content= Extensible Markup Language</pre>
868
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000869<p>So, entities or no entities? Basically, it depends on your use case. I
870suggest that you keep the non-substituting default behaviour and avoid using
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000871entities in your XML document or data if you are not willing to handle the
872entity references elements in the DOM tree.</p>
873
874<p>Note that at save time libxml enforce the conversion of the predefined
875entities where necessary to prevent well-formedness problems, and will also
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000876transparently replace those with chars (i.e., it will not generate entity
877reference elements in the DOM tree or call the reference() SAX callback when
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000878finding them in the input).</p>
879
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000880<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000881
Daniel Veillardec303412000-03-24 13:41:54 +0000882<p>The libxml library implements <a
883href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by
884recognizing namespace contructs in the input, and does namespace lookup
885automatically when building the DOM tree. A namespace declaration is
886associated with an in-memory structure and all elements or attributes within
887that namespace point to it. Hence testing the namespace is a simple and fast
888equality operation at the user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000889
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000890<p>I suggest that people using libxml use a namespace, and declare it in the
891root element of their document as the default namespace. Then they don't need
892to use the prefix in the content but we will have a basis for future semantic
893refinement and merging of data from different sources. This doesn't augment
894significantly the size of the XML output, but significantly increase its value
Daniel Veillardec303412000-03-24 13:41:54 +0000895in the long-term. Example:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +0000896<pre>&lt;mydoc xmlns="http://mydoc.example.org/schemas/"&gt;
897 &lt;elem1&gt;...&lt;/elem1&gt;
898 &lt;elem2&gt;...&lt;/elem2&gt;
899&lt;/mydoc&gt;</pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000900
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000901<p>Concerning the namespace value, this has to be an URL, but the URL doesn't
Daniel Veillardec303412000-03-24 13:41:54 +0000902have to point to any existing resource on the Web. It will bind all the
903element and atributes with that URL. I suggest to use an URL within a domain
904you control, and that the URL should contain some kind of version information
905if possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is
Daniel Veillard361d8452000-04-03 19:48:13 +0000906a good namespace scheme.</p>
Daniel Veillardec303412000-03-24 13:41:54 +0000907
908<p>Then when you load a file, make sure that a namespace carrying the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000909version-independent prefix is installed on the root element of your document,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000910and if the version information don't match something you know, warn the user
911and be liberal in what you accept as the input. Also do *not* try to base
Daniel Veillard60979bd2000-07-10 12:17:33 +0000912namespace checking on the prefix value. &lt;foo:text&gt; may be exactly the
913same as &lt;bar:text&gt; in another document. What really matter is the URI
914associated with the element or the attribute, not the prefix string (which is
915just a shortcut for the full URI). In libxml element and attributes have a
Daniel Veillardec303412000-03-24 13:41:54 +0000916<code>ns</code> field pointing to an xmlNs structure detailing the namespace
917prefix and it's URI.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000918
919<p>@@Interfaces@@</p>
920
921<p>@@Examples@@</p>
922
923<p>Usually people object using namespace in the case of validation, I object
924this and will make sure that using namespaces won't break validity checking,
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000925so even is you plan to use or currently are using validation I strongly
926suggest adding namespaces to your document. A default namespace scheme
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000927<code>xmlns="http://...."</code> should not break validity even on less
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000928flexible parsers. Now using namespace to mix and differentiate content coming
929from multiple DTDs will certainly break current validation schemes. I will try
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000930to provide ways to do this, but this may not be portable or standardized.</p>
931
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000932<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000933
934<p>Well what is validation and what is a DTD ?</p>
935
936<p>Validation is the process of checking a document against a set of
937construction rules, a <strong>DTD</strong> (Document Type Definition) is such
938a set of rules.</p>
939
940<p>The validation process and building DTDs are the two most difficult parts
941of XML life cycle. Briefly a DTD defines all the possibles element to be
942found within your document, what is the formal shape of your document tree (by
943defining the allowed content of an element, either text, a regular expression
Daniel Veillard306be992000-07-03 12:38:45 +0000944for the allowed list of children, or mixed content i.e. both text and
945children). The DTD also defines the allowed attributes for all elements and
946the types of the attributes. For more detailed informations, I suggest to read
947the related parts of the XML specification, the examples found under
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000948gnome-xml/test/valid/dtd and the large amount of books available on XML. The
949dia example in gnome-xml/test/valid should be both simple and complete enough
950to allow you to build your own.</p>
951
952<p>A word of warning, building a good DTD which will fit your needs of your
953application in the long-term is far from trivial, however the extra level of
954quality it can insure is well worth the price for some sets of applications or
955if you already have already a DTD defined for your application field.</p>
956
957<p>The validation is not completely finished but in a (very IMHO) usable
958state. Until a real validation interface is defined the way to do it is to
959define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
960variable to 1, this will of course be changed at some point:</p>
961
962<p>extern int xmlDoValidityCheckingDefaultValue;</p>
963
964<p>...</p>
965
966<p>xmlDoValidityCheckingDefaultValue = 1;</p>
967
968<p></p>
969
970<p>To handle external entities, use the function
971<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
972link in you HTTP/FTP/Entities database library to the standard libxml
973core.</p>
974
975<p>@@interfaces@@</p>
976
Daniel Veillard35008381999-10-25 13:15:52 +0000977<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000978
979<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document Object
Daniel Veillardccb09631998-10-27 06:21:04 +0000980Model</em> this is an API for accessing XML or HTML structured documents.
981Native support for DOM in Gnome is on the way (module gnome-dom), and it will
Daniel Veillard25940b71998-10-29 05:51:30 +0000982be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000983files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000984set of IDL (or Java) interfaces allowing to traverse and manipulate a
985document. The DOM library will allow accessing and modifying "live" documents
986presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000987
988<p><img src="DOM.gif" alt=" DOM.gif "></p>
989
990<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000991embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000992
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000993<p>The current DOM implementation on top of libxml is the <a
994href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
995a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
996Levien</a>.</p>
997
998<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
999
Daniel Veillard35008381999-10-25 13:15:52 +00001000<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +00001001
1002<p>Here is a real size example, where the actual content of the application
1003data is not kept in the DOM tree but uses internal structures. It is based on
Daniel Veillard14fff061999-06-22 21:49:07 +00001004a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +00001005storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
1006base</a>:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +00001007<pre>&lt;?xml version="1.0"?&gt;
1008&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"&gt;
1009 &lt;gjob:Jobs&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001010
Daniel Veillard60979bd2000-07-10 12:17:33 +00001011 &lt;gjob:Job&gt;
1012 &lt;gjob:Project ID="3"/&gt;
1013 &lt;gjob:Application&gt;GBackup&lt;/gjob:Application&gt;
1014 &lt;gjob:Category&gt;Development&lt;/gjob:Category&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001015
Daniel Veillard60979bd2000-07-10 12:17:33 +00001016 &lt;gjob:Update&gt;
1017 &lt;gjob:Status&gt;Open&lt;/gjob:Status&gt;
1018 &lt;gjob:Modified&gt;Mon, 07 Jun 1999 20:27:45 -0400 MET DST&lt;/gjob:Modified&gt;
1019 &lt;gjob:Salary&gt;USD 0.00&lt;/gjob:Salary&gt;
1020 &lt;/gjob:Update&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001021
Daniel Veillard60979bd2000-07-10 12:17:33 +00001022 &lt;gjob:Developers&gt;
1023 &lt;gjob:Developer&gt;
1024 &lt;/gjob:Developer&gt;
1025 &lt;/gjob:Developers&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001026
Daniel Veillard60979bd2000-07-10 12:17:33 +00001027 &lt;gjob:Contact&gt;
1028 &lt;gjob:Person&gt;Nathan Clemons&lt;/gjob:Person&gt;
1029 &lt;gjob:Email&gt;nathan@windsofstorm.net&lt;/gjob:Email&gt;
1030 &lt;gjob:Company&gt;
1031 &lt;/gjob:Company&gt;
1032 &lt;gjob:Organisation&gt;
1033 &lt;/gjob:Organisation&gt;
1034 &lt;gjob:Webpage&gt;
1035 &lt;/gjob:Webpage&gt;
1036 &lt;gjob:Snailmail&gt;
1037 &lt;/gjob:Snailmail&gt;
1038 &lt;gjob:Phone&gt;
1039 &lt;/gjob:Phone&gt;
1040 &lt;/gjob:Contact&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001041
Daniel Veillard60979bd2000-07-10 12:17:33 +00001042 &lt;gjob:Requirements&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001043 The program should be released as free software, under the GPL.
Daniel Veillard60979bd2000-07-10 12:17:33 +00001044 &lt;/gjob:Requirements&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001045
Daniel Veillard60979bd2000-07-10 12:17:33 +00001046 &lt;gjob:Skills&gt;
1047 &lt;/gjob:Skills&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001048
Daniel Veillard60979bd2000-07-10 12:17:33 +00001049 &lt;gjob:Details&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001050 A GNOME based system that will allow a superuser to configure
1051 compressed and uncompressed files and/or file systems to be backed
1052 up with a supported media in the system. This should be able to
1053 perform via find commands generating a list of files that are passed
1054 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
1055 or via operations performed on the filesystem itself. Email
1056 notification and GUI status display very important.
Daniel Veillard60979bd2000-07-10 12:17:33 +00001057 &lt;/gjob:Details&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001058
Daniel Veillard60979bd2000-07-10 12:17:33 +00001059 &lt;/gjob:Job&gt;
Daniel Veillard14fff061999-06-22 21:49:07 +00001060
Daniel Veillard60979bd2000-07-10 12:17:33 +00001061 &lt;/gjob:Jobs&gt;
1062&lt;/gjob:Helping&gt;</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +00001063
1064<p>While loading the XML file into an internal DOM tree is a matter of calling
1065only a couple of functions, browsing the tree to gather the informations and
1066generate the internals structures is harder, and more error prone.</p>
1067
1068<p>The suggested principle is to be tolerant with respect to the input
Daniel Veillardf13e1ed2000-03-06 07:41:49 +00001069structure. For example, the ordering of the attributes is not significant,
1070Cthe XML specification is clear about it. It's also usually a good idea to not
Daniel Veillard306be992000-07-03 12:38:45 +00001071be dependent of the orders of the children of a given node, unless it really
Daniel Veillardf13e1ed2000-03-06 07:41:49 +00001072makes things harder. Here is some code to parse the informations for a
1073person:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +00001074<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +00001075 * A person record
1076 */
1077typedef struct person {
1078 char *name;
1079 char *email;
1080 char *company;
1081 char *organisation;
1082 char *smail;
1083 char *webPage;
1084 char *phone;
1085} person, *personPtr;
1086
1087/*
1088 * And the code needed to parse it
1089 */
1090personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1091 personPtr ret = NULL;
1092
1093DEBUG("parsePerson\n");
1094 /*
1095 * allocate the struct
1096 */
1097 ret = (personPtr) malloc(sizeof(person));
1098 if (ret == NULL) {
1099 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +00001100 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +00001101 }
1102 memset(ret, 0, sizeof(person));
1103
1104 /* We don't care what the top level element name is */
Daniel Veillard60979bd2000-07-10 12:17:33 +00001105 cur = cur-&gt;xmlChildrenNode;
Daniel Veillard14fff061999-06-22 21:49:07 +00001106 while (cur != NULL) {
Daniel Veillard60979bd2000-07-10 12:17:33 +00001107 if ((!strcmp(cur-&gt;name, "Person")) &amp;&amp; (cur-&gt;ns == ns))
1108 ret-&gt;name = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
1109 if ((!strcmp(cur-&gt;name, "Email")) &amp;&amp; (cur-&gt;ns == ns))
1110 ret-&gt;email = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
1111 cur = cur-&gt;next;
Daniel Veillard14fff061999-06-22 21:49:07 +00001112 }
1113
1114 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +00001115}</pre>
1116
1117<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +00001118<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +00001119 <li>Usually a recursive parsing style is the more convenient one, XML data
1120 being by nature subject to repetitive constructs and usualy exibit highly
1121 stuctured patterns.</li>
1122 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
1123 the pointer to the global XML document and the namespace reserved to the
1124 application. Document wide information are needed for example to decode
1125 entities and it's a good coding practice to define a namespace for your
1126 application set of data and test that the element and attributes you're
1127 analyzing actually pertains to your application space. This is done by a
Daniel Veillard60979bd2000-07-10 12:17:33 +00001128 simple equality test (cur-&gt;ns == ns).</li>
Daniel Veillardb05deb71999-08-10 19:04:08 +00001129 <li>To retrieve text and attributes value, it is suggested to use the
1130 function <em>xmlNodeListGetString</em> to gather all the text and entity
1131 reference nodes generated by the DOM output and produce an single text
1132 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +00001133</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +00001134
1135<p>Here is another piece of code used to parse another level of the
1136structure:</p>
Daniel Veillard60979bd2000-07-10 12:17:33 +00001137<pre>#include &lt;libxml/tree.h&gt;
Daniel Veillard361d8452000-04-03 19:48:13 +00001138/*
Daniel Veillard14fff061999-06-22 21:49:07 +00001139 * a Description for a Job
1140 */
1141typedef struct job {
1142 char *projectID;
1143 char *application;
1144 char *category;
1145 personPtr contact;
1146 int nbDevelopers;
1147 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
1148} job, *jobPtr;
1149
1150/*
1151 * And the code needed to parse it
1152 */
1153jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1154 jobPtr ret = NULL;
1155
1156DEBUG("parseJob\n");
1157 /*
1158 * allocate the struct
1159 */
1160 ret = (jobPtr) malloc(sizeof(job));
1161 if (ret == NULL) {
1162 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +00001163 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +00001164 }
1165 memset(ret, 0, sizeof(job));
1166
1167 /* We don't care what the top level element name is */
Daniel Veillard60979bd2000-07-10 12:17:33 +00001168 cur = cur-&gt;xmlChildrenNode;
Daniel Veillard14fff061999-06-22 21:49:07 +00001169 while (cur != NULL) {
1170
Daniel Veillard60979bd2000-07-10 12:17:33 +00001171 if ((!strcmp(cur-&gt;name, "Project")) &amp;&amp; (cur-&gt;ns == ns)) {
1172 ret-&gt;projectID = xmlGetProp(cur, "ID");
1173 if (ret-&gt;projectID == NULL) {
Daniel Veillardb05deb71999-08-10 19:04:08 +00001174 fprintf(stderr, "Project has no ID\n");
1175 }
1176 }
Daniel Veillard60979bd2000-07-10 12:17:33 +00001177 if ((!strcmp(cur-&gt;name, "Application")) &amp;&amp; (cur-&gt;ns == ns))
1178 ret-&gt;application = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
1179 if ((!strcmp(cur-&gt;name, "Category")) &amp;&amp; (cur-&gt;ns == ns))
1180 ret-&gt;category = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
1181 if ((!strcmp(cur-&gt;name, "Contact")) &amp;&amp; (cur-&gt;ns == ns))
1182 ret-&gt;contact = parsePerson(doc, ns, cur);
1183 cur = cur-&gt;next;
Daniel Veillard14fff061999-06-22 21:49:07 +00001184 }
1185
1186 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +00001187}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +00001188
Daniel Veillardb05deb71999-08-10 19:04:08 +00001189<p>One can notice that once used to it, writing this kind of code is quite
1190simple, but boring. Ultimately, it could be possble to write stubbers taking
1191either C data structure definitions, a set of XML examples or an XML DTD and
1192produce the code needed to import and export the content between C data and
1193XML storage. This is left as an exercise to the reader :-)</p>
1194
Daniel Veillard6f0adb52000-07-03 11:41:26 +00001195<p>Feel free to use <a href="example/gjobread.c">the code for the full C
1196parsing example</a> as a template, it is also available with Makefile in the
1197Gnome CVS base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +00001198
Daniel Veillardc310d562000-06-23 18:32:15 +00001199<h2><a name="Contributi">Contributions</a></h2>
1200<ul>
1201 <li><a href="mailto:ari@btigate.com">Ari Johnson</a> provides a C++ wrapper
1202 for libxml:
1203 <p>Website: <a
1204 href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p>
1205 <p>Download: <a
1206 href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p>
1207 </li>
1208 <li><a href="mailto:doolin@cs.utk.edu">David Doolin</a> provides a
1209 precompiled Windows version
1210 <p><a
1211 href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p>
1212 </li>
Daniel Veillard3f6f7f62000-06-30 17:58:25 +00001213 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> provided <a
1214 href="libxml-doc.el">an emacs module</a> to lookup libxml functions
1215 documentation</li>
Daniel Veillardc310d562000-06-23 18:32:15 +00001216 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a
1217 href="http://xmlsoft.org/messages/0488.html">man pages</a> (not yet
1218 integrated in the distribution)</li>
1219</ul>
1220
Daniel Veillardc8eab3a1999-09-04 18:27:23 +00001221<p></p>
1222
1223<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1224
Daniel Veillarda2679fa2000-07-22 02:38:15 +00001225<p>$Id: xml.html,v 1.43 2000/07/17 14:38:19 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +00001226</body>
1227</html>