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Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]2 "http://www.w3.org/TR/REC-html40/loose.dtd">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]3<html>
4<head>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]5 <title>The XML library for Gnome</title>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]6 <meta name="GENERATOR" content="amaya V2.4">
7 <meta http-equiv="Content-Type" content="text/html">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]8</head>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]9
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]10<body bgcolor="#ffffff">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]11<h1 align="center">The XML library for Gnome</h1>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]12
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]13<h2 style="text-align: center">libxml, a.k.a. gnome-xml</h2>
14
15<p></p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]16<ul>
17 <li><a href="#Introducti">Introduction</a></li>
18 <li><a href="#Documentat">Documentation</a></li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]19 <li><a href="#Downloads">Downloads</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]20 <li><a href="#News">News</a></li>
21 <li><a href="#XML">XML</a></li>
22 <li><a href="#tree">The tree output</a></li>
23 <li><a href="#interface">The SAX interface</a></li>
24 <li><a href="#library">The XML library interfaces</a>
25 <ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]26 <li><a href="#Invoking">Invoking the parser: the pull way</a></li>
27 <li><a href="#Invoking">Invoking the parser: the push way</a></li>
28 <li><a href="#Invoking2">Invoking the parser: the SAX interface</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]29 <li><a href="#Building">Building a tree from scratch</a></li>
30 <li><a href="#Traversing">Traversing the tree</a></li>
31 <li><a href="#Modifying">Modifying the tree</a></li>
32 <li><a href="#Saving">Saving the tree</a></li>
33 <li><a href="#Compressio">Compression</a></li>
34 </ul>
35 </li>
36 <li><a href="#Entities">Entities or no entities</a></li>
37 <li><a href="#Namespaces">Namespaces</a></li>
38 <li><a href="#Validation">Validation</a></li>
39 <li><a href="#Principles">DOM principles</a></li>
40 <li><a href="#real">A real example</a></li>
41</ul>
42
43<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]44
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]45<p>This document describes libxml, the <a href="http://www.w3.org/XML/">XML</a>
46library provided in the <a href="http://www.gnome.org/">Gnome</a> framework.
47XML is a standard for building tag-based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]48
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]49<p>Here are some key points about libxml:</p>
50<ul>
51 <li>The internal document repesentation is as close as possible to the <a
52 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li>
53 <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]54 like interface</a>; the interface is designed to be compatible with <a
55 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]56 <li>Libxml now include a nearly complete <a
57 href="http://www.w3.org/TR/xpath">XPath</a> implementation.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]58 <li>Libxml exports Push and Pull type parser interfaces for both XML and
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]59 HTML.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]60 <li>This library is released both under the W3C Copyright and the GNU LGPL.
61 Basically, everybody should be happy; if not, drop me a mail.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]62</ul>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]63
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]64<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]65
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]66<p>There are some on-line resources about using libxml:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]67<ol>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]68 <li>The code is commented in a way which allows <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]69 href="http://xmlsoft.org/libxml.html">extensive documentation</a> to be
70 automatically extracted.</li>
71 <li>This page provides a global overview and <a href="#real">some
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]72 examples</a> on how to use libxml.</li>
73 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a
74 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
75 documentation</a> explaining how to use the libxml SAX interface.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]76 <li>George Lebl wrote <a
77 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]78 for IBM developerWorks</a> about using libxml.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]79 <li>It is also a good idea to check to <a href="mailto:raph@levien.com">Raph
80 Levien</a> <a href="http://levien.com/gnome/">web site</a> since he is
81 building the <a href="http://levien.com/gnome/gdome.html">DOM interface
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]82 gdome</a> on top of libxml result tree and an implementation of <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]83 href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
84 href="http://www.levien.com/svg/">gill</a>. Check his <a
85 href="http://www.levien.com/gnome/domination.html">DOMination
86 paper</a>.</li>
87 <li>And don't forget to look at the <a href="/messages/">mailing-list
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]88 archive</a>, too.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]89</ol>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]90
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]91<h3>Reporting bugs and getting help</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]92
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]93<p>Well, bugs or missing features are always possible, and I will make a point
94of fixing them in a timely fashion. The best way to report a bug is to <a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]95href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]96database</a>. I look at reports there regularly and it's good to have a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]97reminder when a bug is still open. Check the <a
98href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]99and be sure to specify that the bug is for the package gnome-xml.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]100
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]101<p>There is also a mailing-list <a
102href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
103href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]104majordomo based list, send a mail message to <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]105href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
106"subscribe xml" in the <strong>content</strong> of the message.</p>
107
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]108<p>Alternatively, you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]109href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]110
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]111<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]112
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]113<p>Latest versions can be found on <a
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame^]114href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or on the <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]115href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]116as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]117archive</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/contrib/rpms/">RPMs
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]118packages</a> (NOTE that you need both the <a
119href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a
120href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
121packages installed to compile applications using libxml).</p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]122
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame^]123<p><a name="Snapshot">Snapshot:</a></p>
124<ul>
125 <li>Code from the W3C cvs base libxml <a
126 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li>
127 <li>Docs, content of the web site, the list archive included <a
128 href="ftp://rpmfind.net/pub/libxml/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li>
129</ul>
130
131<p><a name="Contribs">Contribs:</a></p>
132
133<p>I do accept external contributions, especially if compiling on another
134platform, get in touch with me to upload the package. I will keep them in the
135<a href="ftp://rpmfind.net/pub/libxml/contribs/">contrib directory</a></p>
136
137<p>Libxml is also available from 2 CVs bases:</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]138<ul>
139 <li><p>The <a href="http://dev.w3.org/cvsweb/XML/">W3C CVS base</a>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]140 available read-only using the CVS pserver authentification (I tend to use
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]141 this base for my own development, so it's updated more regularly, but
142 the content may not be as stable):</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]143 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
144password: anonymous
145module: XML</pre>
146 </li>
147 <li><p>The <a
148 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&amp;dir=gnome-xml">Gnome
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]149 CVS base</a>. Check the <a
150 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page;
151 the CVS module is <b>gnome-xml</b>.</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]152 </li>
153</ul>
154
155<h2><a name="News">News</a></h2>
156
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]157<h3>CVS only : check the <a
158href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
159for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]160<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]161 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]162 if you want to test those.</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame^]163 <li>huge work toward libxml-2.0: This work is available only in W3C CVs base
164 for the moment. You get the <a
165 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">snapshot</a> for
166 the updated version:
167 <ul>
168 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 seems correctly handled
169 now</li>
170 <li>Better handling of entities</li>
171 <li>DTD conditional sections</li>
172 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
173 structures to accomodate DOM</a></li>
174 <li>Lot of work toward a better compliance. I'm now running and
175 debugging regression tests agains the <a
176 href="http://www.oasis-open.org/committees/xmlconf-pub.html">OASIS
177 testsuite</a></li>
178 </ul>
179 </li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]180</ul>
181
182<h3>1.8.6: Jan 31 2000</h3>
183<ul>
184 <li>added a nanoFTP transport module, debugged until the new version of <a
185 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
186 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000[diff] [blame]187</ul>
188
189<h3>1.8.5: Jan 21 2000</h3>
190<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]191 <li>adding APIs to parse a well balanced chunk of XML (production <a
192 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
193 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000[diff] [blame]194 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
195 <li>Jody Goldberg &lt;jgoldberg@home.com> provided another patch trying to
196 solve the zlib checks problems</li>
197 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
198 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]199</ul>
200
201<h3>1.8.4: Jan 13 2000</h3>
202<ul>
203 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
204 <li>all exit() call should have been removed from libxml</li>
205 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
206 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]207</ul>
208
209<h3>1.8.3: Jan 5 2000</h3>
210<ul>
211 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]212 <li>an shell like interface to the document tree (try tester --shell
213 :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame]214 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]215 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]216 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
217 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]218 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]219 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]220 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]221</ul>
222
223<h3>1.8.2: Dec 21 1999</h3>
224<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]225 <li>I got another problem with includes and C++, I hope this issue is fixed
226 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]227 <li>Added a few tree modification functions: xmlReplaceNode,
228 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
229 xmlDocSetRootElement</li>
230 <li>Tried to improve the HTML output with help from <a
231 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]232</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]233
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]234<h3>1.8.1: Dec 18 1999</h3>
235<ul>
236 <li>various patches to avoid troubles when using libxml with C++ compilers
237 the "namespace" keyword and C escaping in include files</li>
238 <li>a problem in one of the core macros IS_CHAR was corrected</li>
239 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
240 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]241 <li>fixed a posteriori validation (validation after parsing, or by using a
242 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]243 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]244</ul>
245
246<h3>1.8.0: Dec 12 1999</h3>
247<ul>
248 <li>cleanup, especially memory wise</li>
249 <li>the parser should be more reliable, especially the HTML one, it should
250 not crash, whatever the input !</li>
251 <li>Integrated various patches, especially a speedup improvement for large
252 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
253 configure with --with-buffers to enable them.</li>
254 <li>attribute normalization, oops should have been added long ago !</li>
255 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
256 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]257</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]258
259<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]260<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]261 <li>Lots of HTML improvement</li>
262 <li>Fixed some errors when saving both XML and HTML</li>
263 <li>More examples, the regression tests should now look clean</li>
264 <li>Fixed a bug with contiguous charref</li>
265</ul>
266
267<h3>1.7.3: Sep 29 1999</h3>
268<ul>
269 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]270 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]271 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]272</ul>
273
274<h3>1.7.1: Sep 24 1999</h3>
275<ul>
276 <li>The basic type for strings manipulated by libxml has been renamed in
277 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
278 is that CHAR was conflicting with a predefined type on Windows. However on
279 non WIN32 environment, compatibility is provided by the way of a
280 <strong>#define </strong>.</li>
281 <li>Changed another error : the use of a structure field called errno, and
282 leading to troubles on platforms where it's a macro</li>
283</ul>
284
285<h3>1.7.0: sep 23 1999</h3>
286<ul>
287 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
288 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
289 <li>Added an errno to report errors by another mean than a simple printf
290 like callback</li>
291 <li>Finished ID/IDREF support and checking when validation</li>
292 <li>Serious memory leaks fixed (there is now a <a
293 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
294 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
295 implementation</li>
296 <li>Added an HTML parser front-end</li>
297</ul>
298
299<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]300
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]301<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for
302markup-based structured documents. Here is <a name="example">an example
303XML document</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]304<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]305&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]306 &lt;head>
307 &lt;title>Welcome to Gnome&lt;/title>
308 &lt;/head>
309 &lt;chapter>
310 &lt;title>The Linux adventure&lt;/title>
311 &lt;p>bla bla bla ...&lt;/p>
312 &lt;image href="linus.gif"/>
313 &lt;p>...&lt;/p>
314 &lt;/chapter>
315&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]316
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]317<p>The first line specifies that it's an XML document and gives useful
318information about its encoding. Then the document is a text format whose
319structure is specified by tags between brackets. <strong>Each tag opened has
320to be closed</strong>. XML is pedantic about this. However, if a tag is
321empty (no content), a single tag can serve as both the opening and closing
322tag if it ends with <code>/></code> rather than with <code>></code>.
323Note that, for example, the
324image tag has no content (just an attribute) and is closed by ending the
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]325tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]326
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]327<p>XML can be applied sucessfully to a wide range of uses, from long term
328structured document maintenance (where it follows the steps of SGML) to simple
329data encoding mechanisms like configuration file formatting (glade), spreadsheets
330(gnumeric), or even shorter lived documents such as WebDAV where it is used to
331encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]332
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]333<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]334
335<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]336returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
337<strong>xmlDoc</strong> structure). This structure contains information such as
338the file name, the document type, and a <strong>root</strong> pointer which
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]339is the root of the document (or more exactly the first child under the root
340which is the document). The tree is made of <strong>xmlNode</strong>s, chained
341in double linked lists of siblings and with childs&lt;->parent relationship.
342An xmlNode can also carry properties (a chain of xmlAttr structures). An
343attribute may have a value which is a list of TEXT or ENTITY_REF nodes.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]344
345<p>Here is an example (erroneous w.r.t. the XML spec since there should be
346only one ELEMENT under the root):</p>
347
348<p><img src="structure.gif" alt=" structure.gif "></p>
349
350<p>In the source package there is a small program (not installed by default)
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]351called <strong>tester</strong> which parses XML files given as argument and
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]352prints them back as parsed. This is useful to detect errors both in XML code
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]353and in the XML parser itself. It has an option <strong>--debug</strong> which
354prints the actual in-memory structure of the document, here is the result with
355the <a href="#example">example</a> given before:</p>
356<pre>DOCUMENT
357version=1.0
358standalone=true
359 ELEMENT EXAMPLE
360 ATTRIBUTE prop1
361 TEXT
362 content=gnome is great
363 ATTRIBUTE prop2
364 ENTITY_REF
365 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]366 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]367 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]368 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]369 TEXT
370 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]371 ELEMENT chapter
372 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]373 TEXT
374 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]375 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]376 TEXT
377 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]378 ELEMENT image
379 ATTRIBUTE href
380 TEXT
381 content=linus.gif
382 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]383 TEXT
384 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]385
386<p>This should be useful to learn the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]387
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]388<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]389
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]390<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]391memory. In that case and if you don't expect to save back the XML document
392loaded using libxml, it's better to use the SAX interface of libxml. SAX is a
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]393<strong>callback-based interface</strong> to the parser. Before parsing, the
394application layer registers a customized set of callbacks which are called
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]395by the library as it progresses through the XML input.</p>
396
397<p>To get a more detailed step-by-step guidance on using the SAX interface of
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]398libxml, <a href="mailto:james@daa.com.au">James Henstridge</a> has written <a
399href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]400documentation.</a></p>
401
402<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
403program located in the gnome-xml module (it's usually not shipped in the
404binary packages of libxml, but you can also find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]405distribution). Here is the sequence of callbacks that would be reported by
406testSAX when parsing the example given before:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]407<pre>SAX.setDocumentLocator()
408SAX.startDocument()
409SAX.getEntity(amp)
410SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
411SAX.characters( , 3)
412SAX.startElement(head)
413SAX.characters( , 4)
414SAX.startElement(title)
415SAX.characters(Welcome to Gnome, 16)
416SAX.endElement(title)
417SAX.characters( , 3)
418SAX.endElement(head)
419SAX.characters( , 3)
420SAX.startElement(chapter)
421SAX.characters( , 4)
422SAX.startElement(title)
423SAX.characters(The Linux adventure, 19)
424SAX.endElement(title)
425SAX.characters( , 4)
426SAX.startElement(p)
427SAX.characters(bla bla bla ..., 15)
428SAX.endElement(p)
429SAX.characters( , 4)
430SAX.startElement(image, href='linus.gif')
431SAX.endElement(image)
432SAX.characters( , 4)
433SAX.startElement(p)
434SAX.characters(..., 3)
435SAX.endElement(p)
436SAX.characters( , 3)
437SAX.endElement(chapter)
438SAX.characters( , 1)
439SAX.endElement(EXAMPLE)
440SAX.endDocument()</pre>
441
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]442<p>Most of the other functionalities of libxml are based on the DOM
443tree-building facility, so nearly everything up to the end of this document
444presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]445itself is built by a set of registered default callbacks, without internal
446specific interface.</p>
447
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]448<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]449
450<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]451using the XML library from the C language. It doesn't intent to be extensive,
452I hope the automatically generated docs will provide the completeness
453required, but as a separated set of documents. The interfaces of the XML
454library are by principle low level, there is nearly zero abstration. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]455interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]456
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]457<p>The <a href="gnome-xml-parser.html">parser interfaces for XML</a> are
458separated from the <a href="gnome-xml-htmlparser.html">HTML parser ones</a>,
459let's have a look at how it can be called:</p>
460
461<h3><a name="Invoking">Invoking the parser : the pull way</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]462
463<p>Usually, the first thing to do is to read an XML input, the parser accepts
464to parse both memory mapped documents or direct files. The functions are
465defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]466<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]467 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
468 <dd><p>parse a zero terminated string containing the document</p>
469 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]470</dl>
471<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]472 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
473 <dd><p>parse an XML document contained in a file (possibly compressed)</p>
474 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]475</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]476
477<p>This returns a pointer to the document structure (or NULL in case of
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]478failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]479
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]480<h3 id="Invoking1">Invoking the parser: the push way</h3>
481
482<p>In order for the application to keep the control when the document is been
483fetched (common for GUI based programs) the libxml, as of version 1.8.3
484provides a push interface too, here are the interfaces:</p>
485<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
486 void *user_data,
487 const char *chunk,
488 int size,
489 const char *filename);
490int xmlParseChunk (xmlParserCtxtPtr ctxt,
491 const char *chunk,
492 int size,
493 int terminate);</pre>
494
495<p>and here is a simple use example:</p>
496<pre> FILE *f;
497
498 f = fopen(filename, "r");
499 if (f != NULL) {
500 int res, size = 1024;
501 char chars[1024];
502 xmlParserCtxtPtr ctxt;
503
504 res = fread(chars, 1, 4, f);
505 if (res > 0) {
506 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
507 chars, res, filename);
508 while ((res = fread(chars, 1, size, f)) > 0) {
509 xmlParseChunk(ctxt, chars, res, 0);
510 }
511 xmlParseChunk(ctxt, chars, 0, 1);
512 doc = ctxt->myDoc;
513 xmlFreeParserCtxt(ctxt);
514 }
515 }</pre>
516
517<p>Also note that the HTML parser embedded into libxml also have a push
518interface they are just prefixed by "html" instead of "xml"</p>
519
520<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
521
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]522<p>A couple of comments can be made, first this mean that the parser is
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]523memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]524Reading a document without building the tree is possible using the SAX
525interfaces (see SAX.h and <a
526href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
527Henstridge documentation</a>), not also that the push interface can be limited
528to SAX, just use the two first arguments of
529<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]530
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]531<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]532
533<p>The other way to get an XML tree in memory is by building it. Basically
534there is a set of functions dedicated to building new elements, those are also
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]535described in "tree.h", here is for example the piece of code producing the
536example used before:</p>
537<pre> xmlDocPtr doc;
538 xmlNodePtr tree, subtree;
539
540 doc = xmlNewDoc("1.0");
541 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
542 xmlSetProp(doc->root, "prop1", "gnome is great");
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]543 xmlSetProp(doc->root, "prop2", "&amp; linux too");
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]544 tree = xmlNewChild(doc->root, NULL, "head", NULL);
545 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
546 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
547 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
548 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
549 subtree = xmlNewChild(tree, NULL, "image", NULL);
550 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]551
552<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]553
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]554<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]555
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]556<p>Basically by <a href="gnome-xml-tree.html">including "tree.h"</a> your code
557has access to the internal structure of all the element of the tree. The names
558should be somewhat simple like <strong>parent</strong>,
559<strong>childs</strong>, <strong>next</strong>, <strong>prev</strong>,
560<strong>properties</strong>, etc... For example still with the previous
561example:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]562<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]563
564<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]565<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]566
567<p>points to the text node containing the chapter titlle "The Linux adventure"
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]568and</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]569
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]570<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
571present before the document root, so doc->root may point to an element which
572is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]573<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]574
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]575<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]576
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]577<p>functions are provided to read and write the document content, here is an
578excerpt from the <a href="gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]579<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]580 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
581 xmlChar *value);</code></dt>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]582 <dd><p>This set (or change) an attribute carried by an ELEMENT node the
583 value can be NULL</p>
584 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]585</dl>
586<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]587 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]588 *name);</code></dt>
589 <dd><p>This function returns a pointer to the property content, note that
590 no extra copy is made</p>
591 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]592</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]593
594<p>Two functions must be used to read an write the text associated to
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]595elements:</p>
596<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]597 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]598 *value);</code></dt>
599 <dd><p>This function takes an "external" string and convert it to one text
600 node or possibly to a list of entity and text nodes. All non-predefined
601 entity references like &amp;Gnome; will be stored internally as an
602 entity node, hence the result of the function may not be a single
603 node.</p>
604 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]605</dl>
606<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]607 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]608 inLine);</code></dt>
609 <dd><p>this is the dual function, which generate a new string containing
610 the content of the text and entity nodes. Note the extra argument
611 inLine, if set to 1 instead of returning the &amp;Gnome; XML encoding in
612 the string it will substitute it with it's value say "GNU Network Object
613 Model Environment". Set it if you want to use the string for non XML
614 usage like User Interface.</p>
615 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]616</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]617
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]618<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]619
620<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]621<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]622 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]623 *size);</code></dt>
624 <dd><p>returns a buffer where the document has been saved</p>
625 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]626</dl>
627<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]628 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
629 <dd><p>dumps a buffer to an open file descriptor</p>
630 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]631</dl>
632<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]633 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
634 <dd><p>save the document ot a file. In that case the compression interface
635 is triggered if turned on</p>
636 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]637</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]638
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]639<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]640
641<p>The library handle transparently compression when doing file based
642accesses, the level of compression on saves can be tuned either globally or
643individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]644<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]645 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
646 <dd><p>Get the document compression ratio (0-9)</p>
647 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]648</dl>
649<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]650 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
651 <dd><p>Set the document compression ratio</p>
652 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]653</dl>
654<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]655 <dt><code>int xmlGetCompressMode(void);</code></dt>
656 <dd><p>Get the default compression ratio</p>
657 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]658</dl>
659<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]660 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
661 <dd><p>set the default compression ratio</p>
662 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]663</dl>
664
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]665<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]666
667<p>Entities principle is similar to simple C macros. They define an
668abbreviation for a given string that you can reuse many time through the
669content of your document. They are especially useful when frequent occurrences
670of a given string may occur within a document or to confine the change needed
671to a document to a restricted area in the internal subset of the document (at
672the beginning). Example:</p>
673<pre>1 &lt;?xml version="1.0"?>
6742 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
6753 &lt;!ENTITY xml "Extensible Markup Language">
6764 ]>
6775 &lt;EXAMPLE>
6786 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]6797 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]680
681<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]682it's name with '&amp;' and following it by ';' without any spaces added. There
683are 5 predefined entities in libxml allowing to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]684predefined meaning in some parts of the xml document content:
685<strong>&amp;lt;</strong> for the letter '&lt;', <strong>&amp;gt;</strong> for
686the letter '>', <strong>&amp;apos;</strong> for the letter ''',
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]687<strong>&amp;quot;</strong> for the letter '"', and <strong>&amp;amp;</strong>
688for the letter '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]689
690<p>One of the problems related to entities is that you may want the parser to
691substitute entities content to see the replacement text in your application,
692or you may prefer keeping entities references as such in the content to be
693able to save the document back without loosing this usually precious
694information (if the user went through the pain of explicitley defining
695entities, he may have a a rather negative attitude if you blindly susbtitute
696them as saving time). The function <a
697href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
698allows to check and change the behaviour, which is to not substitute entities
699by default.</p>
700
701<p>Here is the DOM tree built by libxml for the previous document in the
702default case:</p>
703<pre>/gnome/src/gnome-xml -> ./tester --debug test/ent1
704DOCUMENT
705version=1.0
706 ELEMENT EXAMPLE
707 TEXT
708 content=
709 ENTITY_REF
710 INTERNAL_GENERAL_ENTITY xml
711 content=Extensible Markup Language
712 TEXT
713 content=</pre>
714
715<p>And here is the result when substituting entities:</p>
716<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
717DOCUMENT
718version=1.0
719 ELEMENT EXAMPLE
720 TEXT
721 content= Extensible Markup Language</pre>
722
723<p>So entities or no entities ? Basically it depends on your use case, I
724suggest to keep the non-substituting default behaviour and avoid using
725entities in your XML document or data if you are not willing to handle the
726entity references elements in the DOM tree.</p>
727
728<p>Note that at save time libxml enforce the conversion of the predefined
729entities where necessary to prevent well-formedness problems, and will also
730transparently replace those with chars (i.e. will not generate entity
731reference elements in the DOM tree nor call the reference() SAX callback when
732finding them in the input).</p>
733
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]734<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]735
736<p>The libxml library implement namespace @@ support by recognizing namespace
737contructs in the input, and does namespace lookup automatically when building
738the DOM tree. A namespace declaration is associated with an in-memory
739structure and all elements or attributes within that namespace point to it.
740Hence testing the namespace is a simple and fast equality operation at the
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]741user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]742
743<p>I suggest it that people using libxml use a namespace, and declare it on
744the root element of their document as the default namespace. Then they dont
745need to happend the prefix in the content but we will have a basis for future
746semantic refinement and merging of data from different sources. This doesn't
747augment significantly the size of the XML output, but significantly increase
748it's value in the long-term.</p>
749
750<p>Concerning the namespace value, this has to be an URL, but this doesn't
751have to point to any existing resource on the Web. I suggest using an URL
752within a domain you control, which makes sense and if possible holding some
753kind of versionning informations. For example
754<code>"http://www.gnome.org/gnumeric/1.0"</code> is a good namespace scheme.
755Then when you load a file, make sure that a namespace carrying the
756version-independant prefix is installed on the root element of your document,
757and if the version information don't match something you know, warn the user
758and be liberal in what you accept as the input. Also do *not* try to base
759namespace checking on the prefix value &lt;foo:text> may be exactly the same
760as &lt;bar:text> in another document, what really matter is the URI
761associated with the element or the attribute, not the prefix string which is
762just a shortcut for the full URI.</p>
763
764<p>@@Interfaces@@</p>
765
766<p>@@Examples@@</p>
767
768<p>Usually people object using namespace in the case of validation, I object
769this and will make sure that using namespaces won't break validity checking,
770so even is you plan or are using validation I strongly suggest to add
771namespaces to your document. A default namespace scheme
772<code>xmlns="http://...."</code> should not break validity even on less
773flexible parsers. Now using namespace to mix and differenciate content coming
774from mutliple Dtd will certainly break current validation schemes, I will try
775to provide ways to do this, but this may not be portable or standardized.</p>
776
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]777<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]778
779<p>Well what is validation and what is a DTD ?</p>
780
781<p>Validation is the process of checking a document against a set of
782construction rules, a <strong>DTD</strong> (Document Type Definition) is such
783a set of rules.</p>
784
785<p>The validation process and building DTDs are the two most difficult parts
786of XML life cycle. Briefly a DTD defines all the possibles element to be
787found within your document, what is the formal shape of your document tree (by
788defining the allowed content of an element, either text, a regular expression
789for the allowed list of children, or mixed content i.e. both text and childs).
790The DTD also defines the allowed attributes for all elements and the types of
791the attributes. For more detailed informations, I suggest to read the related
792parts of the XML specification, the examples found under
793gnome-xml/test/valid/dtd and the large amount of books available on XML. The
794dia example in gnome-xml/test/valid should be both simple and complete enough
795to allow you to build your own.</p>
796
797<p>A word of warning, building a good DTD which will fit your needs of your
798application in the long-term is far from trivial, however the extra level of
799quality it can insure is well worth the price for some sets of applications or
800if you already have already a DTD defined for your application field.</p>
801
802<p>The validation is not completely finished but in a (very IMHO) usable
803state. Until a real validation interface is defined the way to do it is to
804define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
805variable to 1, this will of course be changed at some point:</p>
806
807<p>extern int xmlDoValidityCheckingDefaultValue;</p>
808
809<p>...</p>
810
811<p>xmlDoValidityCheckingDefaultValue = 1;</p>
812
813<p></p>
814
815<p>To handle external entities, use the function
816<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
817link in you HTTP/FTP/Entities database library to the standard libxml
818core.</p>
819
820<p>@@interfaces@@</p>
821
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]822<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]823
824<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document Object
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]825Model</em> this is an API for accessing XML or HTML structured documents.
826Native support for DOM in Gnome is on the way (module gnome-dom), and it will
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]827be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]828files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]829set of IDL (or Java) interfaces allowing to traverse and manipulate a
830document. The DOM library will allow accessing and modifying "live" documents
831presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]832
833<p><img src="DOM.gif" alt=" DOM.gif "></p>
834
835<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]836embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]837
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]838<p>The current DOM implementation on top of libxml is the <a
839href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
840a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
841Levien</a>.</p>
842
843<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
844
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]845<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]846
847<p>Here is a real size example, where the actual content of the application
848data is not kept in the DOM tree but uses internal structures. It is based on
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]849a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]850storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
851base</a>:</p>
852<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]853&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
854 &lt;gjob:Jobs>
855
856 &lt;gjob:Job>
857 &lt;gjob:Project ID="3"/>
858 &lt;gjob:Application>GBackup&lt;/gjob:Application>
859 &lt;gjob:Category>Development&lt;/gjob:Category>
860
861 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]862 &lt;gjob:Status>Open&lt;/gjob:Status>
863 &lt;gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST&lt;/gjob:Modified>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]864 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
865 &lt;/gjob:Update>
866
867 &lt;gjob:Developers>
868 &lt;gjob:Developer>
869 &lt;/gjob:Developer>
870 &lt;/gjob:Developers>
871
872 &lt;gjob:Contact>
873 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]874 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]875 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]876 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]877 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]878 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]879 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]880 &lt;/gjob:Webpage>
881 &lt;gjob:Snailmail>
882 &lt;/gjob:Snailmail>
883 &lt;gjob:Phone>
884 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]885 &lt;/gjob:Contact>
886
887 &lt;gjob:Requirements>
888 The program should be released as free software, under the GPL.
889 &lt;/gjob:Requirements>
890
891 &lt;gjob:Skills>
892 &lt;/gjob:Skills>
893
894 &lt;gjob:Details>
895 A GNOME based system that will allow a superuser to configure
896 compressed and uncompressed files and/or file systems to be backed
897 up with a supported media in the system. This should be able to
898 perform via find commands generating a list of files that are passed
899 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
900 or via operations performed on the filesystem itself. Email
901 notification and GUI status display very important.
902 &lt;/gjob:Details>
903
904 &lt;/gjob:Job>
905
906 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]907&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]908
909<p>While loading the XML file into an internal DOM tree is a matter of calling
910only a couple of functions, browsing the tree to gather the informations and
911generate the internals structures is harder, and more error prone.</p>
912
913<p>The suggested principle is to be tolerant with respect to the input
914structure. For example the ordering of the attributes is not significant, Cthe
915XML specification is clear about it. It's also usually a good idea to not be
916dependant of the orders of the childs of a given node, unless it really makes
917things harder. Here is some code to parse the informations for a person:</p>
918<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]919 * A person record
920 */
921typedef struct person {
922 char *name;
923 char *email;
924 char *company;
925 char *organisation;
926 char *smail;
927 char *webPage;
928 char *phone;
929} person, *personPtr;
930
931/*
932 * And the code needed to parse it
933 */
934personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
935 personPtr ret = NULL;
936
937DEBUG("parsePerson\n");
938 /*
939 * allocate the struct
940 */
941 ret = (personPtr) malloc(sizeof(person));
942 if (ret == NULL) {
943 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]944 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]945 }
946 memset(ret, 0, sizeof(person));
947
948 /* We don't care what the top level element name is */
949 cur = cur->childs;
950 while (cur != NULL) {
951 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]952 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]953 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]954 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
955 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]956 }
957
958 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]959}</pre>
960
961<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]962<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]963 <li>Usually a recursive parsing style is the more convenient one, XML data
964 being by nature subject to repetitive constructs and usualy exibit highly
965 stuctured patterns.</li>
966 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
967 the pointer to the global XML document and the namespace reserved to the
968 application. Document wide information are needed for example to decode
969 entities and it's a good coding practice to define a namespace for your
970 application set of data and test that the element and attributes you're
971 analyzing actually pertains to your application space. This is done by a
972 simple equality test (cur->ns == ns).</li>
973 <li>To retrieve text and attributes value, it is suggested to use the
974 function <em>xmlNodeListGetString</em> to gather all the text and entity
975 reference nodes generated by the DOM output and produce an single text
976 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]977</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]978
979<p>Here is another piece of code used to parse another level of the
980structure:</p>
981<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]982 * a Description for a Job
983 */
984typedef struct job {
985 char *projectID;
986 char *application;
987 char *category;
988 personPtr contact;
989 int nbDevelopers;
990 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
991} job, *jobPtr;
992
993/*
994 * And the code needed to parse it
995 */
996jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
997 jobPtr ret = NULL;
998
999DEBUG("parseJob\n");
1000 /*
1001 * allocate the struct
1002 */
1003 ret = (jobPtr) malloc(sizeof(job));
1004 if (ret == NULL) {
1005 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1006 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1007 }
1008 memset(ret, 0, sizeof(job));
1009
1010 /* We don't care what the top level element name is */
1011 cur = cur->childs;
1012 while (cur != NULL) {
1013
1014 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1015 ret->projectID = xmlGetProp(cur, "ID");
1016 if (ret->projectID == NULL) {
1017 fprintf(stderr, "Project has no ID\n");
1018 }
1019 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1020 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1021 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1022 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1023 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1024 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1025 ret->contact = parsePerson(doc, ns, cur);
1026 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1027 }
1028
1029 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1030}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1031
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1032<p>One can notice that once used to it, writing this kind of code is quite
1033simple, but boring. Ultimately, it could be possble to write stubbers taking
1034either C data structure definitions, a set of XML examples or an XML DTD and
1035produce the code needed to import and export the content between C data and
1036XML storage. This is left as an exercise to the reader :-)</p>
1037
1038<p>Feel free to use <a href="gjobread.c">the code for the full C parsing
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1039example</a> as a template, it is also available with Makefile in the Gnome CVS
1040base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1041
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1042<p></p>
1043
1044<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1045
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame^]1046<p>$Id: xml.html,v 1.25 2000/02/29 22:57:47 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1047</body>
1048</html>