Gitiles
Code Review Sign In
gerrit-public.fairphone.software / platform / external / libxml2 / e0aed304b1d326d7481e50d14e6ed0967f5ce4f0 / . / doc / xml.html
blob: c867e011bbfe28b2aaa396482f41edd9e3110c23 [file] [log] [blame]
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 Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame^]6 <meta name="GENERATOR" content="amaya V3.0">
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]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 Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]11<p><a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome
12Logo"></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C
13Logo"></a></p>
14
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]15<h1 align="center">The XML library for Gnome</h1>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]16
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]17<h2 style="text-align: center">libxml, a.k.a. gnome-xml</h2>
18
19<p></p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]20<ul>
21 <li><a href="#Introducti">Introduction</a></li>
22 <li><a href="#Documentat">Documentation</a></li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]23 <li><a href="#Downloads">Downloads</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]24 <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 +0000[diff] [blame]30 <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 +0000[diff] [blame]33 <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>
45</ul>
46
47<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]48
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]49<p>This document describes libxml, the <a
50href="http://www.w3.org/XML/">XML</a> library provided in the <a
51href="http://www.gnome.org/">Gnome</a> framework. XML is a standard for
52building tag-based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]53
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]54<p>Here are some key points about libxml:</p>
55<ul>
56 <li>The internal document repesentation is as close as possible to the <a
57 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li>
58 <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]59 like interface</a>; the interface is designed to be compatible with <a
60 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]61 <li>Libxml now includes a nearly complete <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]62 href="http://www.w3.org/TR/xpath">XPath</a> implementation.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]63 <li>Libxml exports Push and Pull type parser interfaces for both XML and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]64 HTML.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]65 <li>This library is released both under the <a
66 href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
67 IPR</a> and the GNU LGPL. Use either at your convenience, basically this
68 should make everybody happy, if not, drop me a mail.</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]69 <li>There is <a href="upgrade.html">a first set of instruction</a>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]70 concerning upgrade from libxml-1.x to libxml-2.x</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]71</ul>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]72
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]73<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]74
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]75<p>There are some on-line resources about using libxml:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]76<ol>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]77 <li>The code is commented in a way which allows <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]78 href="http://xmlsoft.org/libxml.html">extensive documentation</a> to be
79 automatically extracted.</li>
80 <li>This page provides a global overview and <a href="#real">some
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]81 examples</a> on how to use libxml.</li>
82 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a
83 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
84 documentation</a> explaining how to use the libxml SAX interface.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]85 <li>George Lebl wrote <a
86 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]87 for IBM developerWorks</a> about using libxml.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]88 <li>It is also a good idea to check to <a href="mailto:raph@levien.com">Raph
89 Levien</a> <a href="http://levien.com/gnome/">web site</a> since he is
90 building the <a href="http://levien.com/gnome/gdome.html">DOM interface
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]91 gdome</a> on top of libxml result tree and an implementation of <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]92 href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
93 href="http://www.levien.com/svg/">gill</a>. Check his <a
94 href="http://www.levien.com/gnome/domination.html">DOMination
95 paper</a>.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]96 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO
97 file</a></li>
98 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a>. If you are
99 starting a new project using libxml you should really use the 2.x
100 version.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]101 <li>And don't forget to look at the <a href="/messages/">mailing-list
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]102 archive</a>, too.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]103</ol>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]104
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]105<h3>Reporting bugs and getting help</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]106
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]107<p>Well, bugs or missing features are always possible, and I will make a point
108of 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]109href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]110database</a>. I look at reports there regularly and it's good to have a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]111reminder when a bug is still open. Check the <a
112href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]113and be sure to specify that the bug is for the package gnome-xml.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]114
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]115<p>There is also a mailing-list <a
116href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
117href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]118majordomo based list, send a mail message to <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]119href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
120"subscribe xml" in the <strong>content</strong> of the message.</p>
121
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]122<p>Alternatively, you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]123href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]124
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]125<p>Of course, bugs reports with a suggested patch for fixing them will
126probably be processed faster.</p>
127
128<p>If you're looking for help, a quick look at <a
129href="http://xmlsoft.org/messages/#407">the list archive</a> may actually
130provide the answer, I usually send source samples when answering libxml usage
131questions. The <a href="http://xmlsoft.org/book1.html">auto-generated
132documentantion</a> is not as polished as I would like (i need to learn more
133about Docbook), but it's a good starting point.</p>
134
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]135<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]136
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]137<p>The latest versions of libxml can be found on <a
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]138href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or on the <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]139href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]140as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]141archive</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/contrib/rpms/">RPMs
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]142packages</a>. (NOTE that you need both the <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]143href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a
144href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]145packages installed to compile applications using libxml.)</p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]146
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]147<p><a name="Snapshot">Snapshot:</a></p>
148<ul>
149 <li>Code from the W3C cvs base libxml <a
150 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li>
151 <li>Docs, content of the web site, the list archive included <a
152 href="ftp://rpmfind.net/pub/libxml/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li>
153</ul>
154
155<p><a name="Contribs">Contribs:</a></p>
156
157<p>I do accept external contributions, especially if compiling on another
158platform, get in touch with me to upload the package. I will keep them in the
159<a href="ftp://rpmfind.net/pub/libxml/contribs/">contrib directory</a></p>
160
161<p>Libxml is also available from 2 CVs bases:</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]162<ul>
163 <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]164 available read-only using the CVS pserver authentification (I tend to use
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]165 this base for my own development, so it's updated more regularly, but the
166 content may not be as stable):</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]167 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]168 password: anonymous
169 module: XML</pre>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]170 </li>
171 <li><p>The <a
172 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]173 CVS base</a>. Check the <a
174 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page;
175 the CVS module is <b>gnome-xml</b>.</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]176 </li>
177</ul>
178
179<h2><a name="News">News</a></h2>
180
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]181<h3>CVS only : check the <a
182href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
183for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]184<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]185 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]186 if you want to test those.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]187</ul>
188
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame^]189<h3>2.0.0: Apr 12 2000</h3>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]190<ul>
191 <li>First public release of libxml2. If you are using libxml, it's a good
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame^]192 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initally
193 scheduled for Apr 3 the relase occured only on Apr 12 due to massive
194 workload.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]195 <li>The include are now located under $prefix/include/libxml (instead of
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame^]196 $prefix/include/gnome-xml), they also are referenced by
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]197 <pre>#include &lt;libxml/xxx.h></pre>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame^]198 <p>instead of</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]199 <pre>#include "xxx.h"</pre>
200 </li>
Daniel Veillard8f621982000-03-20 13:07:15 +0000[diff] [blame]201 <li>a new URI module for parsing URIs and following strictly RFC 2396</li>
202 <li>the memory allocation routines used by libxml can now be overloaded
203 dynamically by using xmlMemSetup()</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]204 <li>The previously CVS only tool tester has been renamed
205 <strong>xmllint</strong> and is now installed as part of the libxml2
206 package</li>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame^]207 <li>The I/O interface has been revamped. There is now ways to plug in
208 specific I/O modules, either at the URI scheme detection level using
209 xmlRegisterInputCallbacks() or by passing I/O functions when creating a
210 parser context using xmlCreateIOParserCtxt()</li>
211 <li>there is a C preprocessor macro LIBXML_VERSION providing the version
212 number of the libxml module in use</li>
213 <li>a number of optional features of libxml can now be excluded at configure
214 time (FTP/HTTP/HTML/XPath/Debug)</li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]215</ul>
216
217<h3>2.0.0beta: Mar 14 2000</h3>
218<ul>
219 <li>This is a first Beta release of libxml version 2</li>
220 <li>It's available only from<a href="ftp://rpmfind.net/pub/libxml/">
221 rpmfind.net FTP</a>, it's packaged as libxml2-2.0.0beta and available as
222 tar and RPMs</li>
223 <li>This version is now the head in the Gnome CVS base, the old one is
224 available under the tag LIB_XML_1_X</li>
225 <li>This includes a very large set of changes. Froma programmatic point of
226 view applications should not have to be modified too much, check the <a
227 href="upgrade.html">upgrade page</a></li>
228 <li>Some interfaces may changes (especially a bit about encoding).</li>
229 <li>the updates includes:
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]230 <ul>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]231 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly
232 handled now</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]233 <li>Better handling of entities, especially well formedness checking and
234 proper PEref extensions in external subsets</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]235 <li>DTD conditional sections</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]236 <li>Validation now correcly handle entities content</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]237 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
238 structures to accomodate DOM</a></li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]239 </ul>
240 </li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]241 <li>Serious progress were made toward compliance, <a
242 href="conf/result.html">here are the result of the test</a> against the
243 OASIS testsuite (except the japanese tests since I don't support that
244 encoding yet). This URL is rebuilt every couple of hours using the CVS
245 head version.</li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]246</ul>
247
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]248<h3>1.8.7: Mar 6 2000</h3>
249<ul>
250 <li>This is a bug fix release:</li>
251 <li>It is possible to disable the ignorable blanks heuristic used by
252 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note
253 that for adherence to XML spec, this behaviour will be disabled by default
254 in 2.x . The same function will allow to keep compatibility for old
255 code.</li>
256 <li>Blanks in &lt;a> &lt;/a> constructs are not ignored anymore, avoiding
257 heuristic is really the Right Way :-\</li>
258 <li>The unchecked use of snprintf which was breaking libxml-1.8.6
259 compilation on some platforms has been fixed</li>
260 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing
261 URIs</li>
262</ul>
263
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]264<h3>1.8.6: Jan 31 2000</h3>
265<ul>
266 <li>added a nanoFTP transport module, debugged until the new version of <a
267 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
268 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000[diff] [blame]269</ul>
270
271<h3>1.8.5: Jan 21 2000</h3>
272<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]273 <li>adding APIs to parse a well balanced chunk of XML (production <a
274 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
275 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000[diff] [blame]276 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
277 <li>Jody Goldberg &lt;jgoldberg@home.com> provided another patch trying to
278 solve the zlib checks problems</li>
279 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
280 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]281</ul>
282
283<h3>1.8.4: Jan 13 2000</h3>
284<ul>
285 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
286 <li>all exit() call should have been removed from libxml</li>
287 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
288 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]289</ul>
290
291<h3>1.8.3: Jan 5 2000</h3>
292<ul>
293 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]294 <li>a shell-like interface to the document tree (try tester --shell :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame]295 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]296 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]297 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
298 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]299 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]300 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]301 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]302</ul>
303
304<h3>1.8.2: Dec 21 1999</h3>
305<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]306 <li>I got another problem with includes and C++, I hope this issue is fixed
307 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]308 <li>Added a few tree modification functions: xmlReplaceNode,
309 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
310 xmlDocSetRootElement</li>
311 <li>Tried to improve the HTML output with help from <a
312 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]313</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]314
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]315<h3>1.8.1: Dec 18 1999</h3>
316<ul>
317 <li>various patches to avoid troubles when using libxml with C++ compilers
318 the "namespace" keyword and C escaping in include files</li>
319 <li>a problem in one of the core macros IS_CHAR was corrected</li>
320 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
321 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]322 <li>fixed a posteriori validation (validation after parsing, or by using a
323 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]324 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]325</ul>
326
327<h3>1.8.0: Dec 12 1999</h3>
328<ul>
329 <li>cleanup, especially memory wise</li>
330 <li>the parser should be more reliable, especially the HTML one, it should
331 not crash, whatever the input !</li>
332 <li>Integrated various patches, especially a speedup improvement for large
333 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
334 configure with --with-buffers to enable them.</li>
335 <li>attribute normalization, oops should have been added long ago !</li>
336 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
337 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]338</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]339
340<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]341<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]342 <li>Lots of HTML improvement</li>
343 <li>Fixed some errors when saving both XML and HTML</li>
344 <li>More examples, the regression tests should now look clean</li>
345 <li>Fixed a bug with contiguous charref</li>
346</ul>
347
348<h3>1.7.3: Sep 29 1999</h3>
349<ul>
350 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]351 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]352 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]353</ul>
354
355<h3>1.7.1: Sep 24 1999</h3>
356<ul>
357 <li>The basic type for strings manipulated by libxml has been renamed in
358 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
359 is that CHAR was conflicting with a predefined type on Windows. However on
360 non WIN32 environment, compatibility is provided by the way of a
361 <strong>#define </strong>.</li>
362 <li>Changed another error : the use of a structure field called errno, and
363 leading to troubles on platforms where it's a macro</li>
364</ul>
365
366<h3>1.7.0: sep 23 1999</h3>
367<ul>
368 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
369 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
370 <li>Added an errno to report errors by another mean than a simple printf
371 like callback</li>
372 <li>Finished ID/IDREF support and checking when validation</li>
373 <li>Serious memory leaks fixed (there is now a <a
374 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
375 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
376 implementation</li>
377 <li>Added an HTML parser front-end</li>
378</ul>
379
380<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]381
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]382<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]383markup-based structured documents. Here is <a name="example">an example XML
384document</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]385<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]386&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]387 &lt;head>
388 &lt;title>Welcome to Gnome&lt;/title>
389 &lt;/head>
390 &lt;chapter>
391 &lt;title>The Linux adventure&lt;/title>
392 &lt;p>bla bla bla ...&lt;/p>
393 &lt;image href="linus.gif"/>
394 &lt;p>...&lt;/p>
395 &lt;/chapter>
396&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]397
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]398<p>The first line specifies that it's an XML document and gives useful
399information about its encoding. Then the document is a text format whose
400structure is specified by tags between brackets. <strong>Each tag opened has
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]401to be closed</strong>. XML is pedantic about this. However, if a tag is empty
402(no content), a single tag can serve as both the opening and closing tag if it
403ends with <code>/></code> rather than with <code>></code>. Note that, for
404example, the image tag has no content (just an attribute) and is closed by
405ending the tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]406
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]407<p>XML can be applied sucessfully to a wide range of uses, from long term
408structured document maintenance (where it follows the steps of SGML) to simple
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]409data encoding mechanisms like configuration file formatting (glade),
410spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where
411it is used to encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]412
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]413<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]414
415<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]416returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]417<strong>xmlDoc</strong> structure). This structure contains information such
418as the file name, the document type, and a <strong>root</strong> pointer which
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]419is the root of the document (or more exactly the first child under the root
420which is the document). The tree is made of <strong>xmlNode</strong>s, chained
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]421in double-linked lists of siblings and with childs&lt;->parent relationship.
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]422An xmlNode can also carry properties (a chain of xmlAttr structures). An
423attribute 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]424
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]425<p>Here is an example (erroneous with respect to the XML spec since there
426should be only one ELEMENT under the root):</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]427
428<p><img src="structure.gif" alt=" structure.gif "></p>
429
430<p>In the source package there is a small program (not installed by default)
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]431called <strong>xmllint</strong> which parses XML files given as argument and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]432prints them back as parsed. This is useful for detecting errors both in XML
433code and in the XML parser itself. It has an option <strong>--debug</strong>
434which prints the actual in-memory structure of the document, here is the
435result with the <a href="#example">example</a> given before:</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]436<pre>DOCUMENT
437version=1.0
438standalone=true
439 ELEMENT EXAMPLE
440 ATTRIBUTE prop1
441 TEXT
442 content=gnome is great
443 ATTRIBUTE prop2
444 ENTITY_REF
445 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]446 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]447 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]448 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]449 TEXT
450 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]451 ELEMENT chapter
452 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]453 TEXT
454 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]455 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]456 TEXT
457 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]458 ELEMENT image
459 ATTRIBUTE href
460 TEXT
461 content=linus.gif
462 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]463 TEXT
464 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]465
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]466<p>This should be useful for learning the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]467
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]468<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]469
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]470<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]471memory. In that case (and if you don't expect to save back the XML document
472loaded 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]473<strong>callback-based interface</strong> to the parser. Before parsing, the
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]474application layer registers a customized set of callbacks which are called by
475the library as it progresses through the XML input.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]476
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]477<p>To get more detailed step-by-step guidance on using the SAX interface of
478libxml, see the
479href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]480documentation.written by <a href="mailto:james@daa.com.au">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]481Henstridge</a>.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]482
483<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
484program located in the gnome-xml module (it's usually not shipped in the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]485binary packages of libxml, but you can find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]486distribution). Here is the sequence of callbacks that would be reported by
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]487testSAX when parsing the example XML document shown earlier:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]488<pre>SAX.setDocumentLocator()
489SAX.startDocument()
490SAX.getEntity(amp)
491SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
492SAX.characters( , 3)
493SAX.startElement(head)
494SAX.characters( , 4)
495SAX.startElement(title)
496SAX.characters(Welcome to Gnome, 16)
497SAX.endElement(title)
498SAX.characters( , 3)
499SAX.endElement(head)
500SAX.characters( , 3)
501SAX.startElement(chapter)
502SAX.characters( , 4)
503SAX.startElement(title)
504SAX.characters(The Linux adventure, 19)
505SAX.endElement(title)
506SAX.characters( , 4)
507SAX.startElement(p)
508SAX.characters(bla bla bla ..., 15)
509SAX.endElement(p)
510SAX.characters( , 4)
511SAX.startElement(image, href='linus.gif')
512SAX.endElement(image)
513SAX.characters( , 4)
514SAX.startElement(p)
515SAX.characters(..., 3)
516SAX.endElement(p)
517SAX.characters( , 3)
518SAX.endElement(chapter)
519SAX.characters( , 1)
520SAX.endElement(EXAMPLE)
521SAX.endDocument()</pre>
522
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]523<p>Most of the other functionalities of libxml are based on the DOM
524tree-building facility, so nearly everything up to the end of this document
525presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]526itself is built by a set of registered default callbacks, without internal
527specific interface.</p>
528
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]529<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]530
531<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]532using the XML library from the C language. It is not intended to be extensive.
533I hope the automatically generated documents will provide the completeness
534required, but as a separate set of documents. The interfaces of the XML
535library are by principle low level, there is nearly zero abstraction. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]536interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]537
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]538<p>The <a href="gnome-xml-parser.html">parser interfaces for XML</a> are
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]539separated from the <a href="gnome-xml-htmlparser.html">HTML parser
540interfaces</a>. Let's have a look at how the XML parser can be called:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]541
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]542<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]543
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]544<p>Usually, the first thing to do is to read an XML input. The parser accepts
545documents either from in-memory strings or from files. The functions are
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]546defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]547<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]548 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]549 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]550 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]551</dl>
552<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]553 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]554 <dd><p>Parse an XML document contained in a (possibly compressed)
555 file.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]556 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]557</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]558
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]559<p>The parser returns a pointer to the document structure (or NULL in case of
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]560failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]561
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]562<h3 id="Invoking1">Invoking the parser: the push method</h3>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]563
564<p>In order for the application to keep the control when the document is been
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]565fetched (which is common for GUI based programs) libxml provides a push
566interface, too, as of version 1.8.3. Here are the interface functions:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]567<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
568 void *user_data,
569 const char *chunk,
570 int size,
571 const char *filename);
572int xmlParseChunk (xmlParserCtxtPtr ctxt,
573 const char *chunk,
574 int size,
575 int terminate);</pre>
576
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]577<p>and here is a simple example showing how to use the interface:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]578<pre> FILE *f;
579
580 f = fopen(filename, "r");
581 if (f != NULL) {
582 int res, size = 1024;
583 char chars[1024];
584 xmlParserCtxtPtr ctxt;
585
586 res = fread(chars, 1, 4, f);
587 if (res > 0) {
588 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
589 chars, res, filename);
590 while ((res = fread(chars, 1, size, f)) > 0) {
591 xmlParseChunk(ctxt, chars, res, 0);
592 }
593 xmlParseChunk(ctxt, chars, 0, 1);
594 doc = ctxt->myDoc;
595 xmlFreeParserCtxt(ctxt);
596 }
597 }</pre>
598
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]599<p>Also note that the HTML parser embedded into libxml also has a push
600interface; the functions are just prefixed by "html" rather than "xml"</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]601
602<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
603
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]604<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]605memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]606Reading a document without building the tree is possible using the SAX
607interfaces (see SAX.h and <a
608href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]609Henstridge's documentation</a>). Note also that the push interface can be
610limited to SAX. Just use the two first arguments of
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]611<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]612
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]613<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]614
615<p>The other way to get an XML tree in memory is by building it. Basically
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]616there is a set of functions dedicated to building new elements. (These are
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]617also described in &lt;libxml/tree.h>.) For example, here is a piece of code
618that produces the XML document used in the previous examples:</p>
619<pre> #include &lt;libxml/tree.h>
620 xmlDocPtr doc;
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]621 xmlNodePtr tree, subtree;
622
623 doc = xmlNewDoc("1.0");
624 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
625 xmlSetProp(doc->root, "prop1", "gnome is great");
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]626 xmlSetProp(doc->root, "prop2", "&amp; linux too");
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]627 tree = xmlNewChild(doc->root, NULL, "head", NULL);
628 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
629 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
630 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
631 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
632 subtree = xmlNewChild(tree, NULL, "image", NULL);
633 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]634
635<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]636
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]637<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]638
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]639<p>Basically by <a href="gnome-xml-tree.html">including "tree.h"</a> your code
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]640has access to the internal structure of all the elements of the tree. The
641names should be somewhat simple like <strong>parent</strong>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]642<strong>childs</strong>, <strong>next</strong>, <strong>prev</strong>,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]643<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]644example:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]645<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]646
647<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]648<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]649
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]650<p>points to the text node containing the chapter title "The Linux
651adventure".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]652
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]653<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]654present before the document root, so <code>doc->root</code> may point to an
655element which is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]656<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]657
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]658<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]659
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]660<p>Functions are provided for reading and writing the document content. Here
661is an excerpt from the <a href="gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]662<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]663 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
664 xmlChar *value);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]665 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. The
666 value can be NULL.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]667 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]668</dl>
669<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]670 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]671 *name);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]672 <dd><p>This function returns a pointer to the property content. Note that
673 no extra copy is made.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]674 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]675</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]676
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]677<p>Two functions are provided for reading and writing the text associated with
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]678elements:</p>
679<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]680 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]681 *value);</code></dt>
682 <dd><p>This function takes an "external" string and convert it to one text
683 node or possibly to a list of entity and text nodes. All non-predefined
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]684 entity references like &amp;Gnome; will be stored internally as entity
685 nodes, hence the result of the function may not be a single node.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]686 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]687</dl>
688<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]689 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]690 inLine);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]691 <dd><p>This function is the inverse of
692 <code>xmlStringGetNodeList()</code>. It generates a new string
693 containing the content of the text and entity nodes. Note the extra
694 argument inLine. If this argument is set to 1, the function will expand
695 entity references. For example, instead of returning the &amp;Gnome;
696 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]697 "GNU Network Object Model Environment"). Set this argument if you want
698 to use the string for non-XML usage like User Interface.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]699 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]700</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]701
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]702<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]703
704<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]705<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]706 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]707 *size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]708 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]709 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]710</dl>
711<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]712 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]713 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]714 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]715</dl>
716<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]717 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]718 <dd><p>Saves the document to a file. In this case, the compression
719 interface is triggered if it has been turned on.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]720 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]721</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]722
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]723<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]724
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]725<p>The library transparently handles compression when doing file-based
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]726accesses. The level of compression on saves can be turned on either globally
727or individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]728<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]729 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]730 <dd><p>Gets the document compression ratio (0-9).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]731 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]732</dl>
733<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]734 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]735 <dd><p>Sets the document compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]736 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]737</dl>
738<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]739 <dt><code>int xmlGetCompressMode(void);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]740 <dd><p>Gets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]741 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]742</dl>
743<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]744 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]745 <dd><p>Sets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]746 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]747</dl>
748
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]749<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]750
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]751<p>Entities in principle are similar to simple C macros. An entity defines an
752abbreviation for a given string that you can reuse many times throughout the
753content of your document. Entities are especially useful when a given string
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]754may occur frequently within a document, or to confine the change needed to a
755document to a restricted area in the internal subset of the document (at the
756beginning). Example:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]757<pre>1 &lt;?xml version="1.0"?>
7582 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
7593 &lt;!ENTITY xml "Extensible Markup Language">
7604 ]>
7615 &lt;EXAMPLE>
7626 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]7637 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]764
765<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]766it's name with '&amp;' and following it by ';' without any spaces added. There
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]767are 5 predefined entities in libxml allowing you to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]768predefined meaning in some parts of the xml document content:
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]769<strong>&amp;lt;</strong> for the character '&lt;', <strong>&amp;gt;</strong>
770for the character '>', <strong>&amp;apos;</strong> for the character ''',
771<strong>&amp;quot;</strong> for the character '"', and
772<strong>&amp;amp;</strong> for the character '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]773
774<p>One of the problems related to entities is that you may want the parser to
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]775substitute an entity's content so that you can see the replacement text in
776your application. Or you may prefer to keep entity references as such in the
777content to be able to save the document back without losing this usually
778precious information (if the user went through the pain of explicitly defining
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]779entities, he may have a a rather negative attitude if you blindly susbtitute
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]780them as saving time). The <a
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]781href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]782function allows you to check and change the behaviour, which is to not
783substitute entities by default.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]784
785<p>Here is the DOM tree built by libxml for the previous document in the
786default case:</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]787<pre>/gnome/src/gnome-xml -> ./xmllint --debug test/ent1
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]788DOCUMENT
789version=1.0
790 ELEMENT EXAMPLE
791 TEXT
792 content=
793 ENTITY_REF
794 INTERNAL_GENERAL_ENTITY xml
795 content=Extensible Markup Language
796 TEXT
797 content=</pre>
798
799<p>And here is the result when substituting entities:</p>
800<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
801DOCUMENT
802version=1.0
803 ELEMENT EXAMPLE
804 TEXT
805 content= Extensible Markup Language</pre>
806
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]807<p>So, entities or no entities? Basically, it depends on your use case. I
808suggest that you keep the non-substituting default behaviour and avoid using
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]809entities in your XML document or data if you are not willing to handle the
810entity references elements in the DOM tree.</p>
811
812<p>Note that at save time libxml enforce the conversion of the predefined
813entities where necessary to prevent well-formedness problems, and will also
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]814transparently replace those with chars (i.e., it will not generate entity
815reference elements in the DOM tree or call the reference() SAX callback when
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]816finding them in the input).</p>
817
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]818<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]819
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]820<p>The libxml library implements <a
821href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by
822recognizing namespace contructs in the input, and does namespace lookup
823automatically when building the DOM tree. A namespace declaration is
824associated with an in-memory structure and all elements or attributes within
825that namespace point to it. Hence testing the namespace is a simple and fast
826equality operation at the user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]827
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]828<p>I suggest that people using libxml use a namespace, and declare it in the
829root element of their document as the default namespace. Then they don't need
830to use the prefix in the content but we will have a basis for future semantic
831refinement and merging of data from different sources. This doesn't augment
832significantly the size of the XML output, but significantly increase its value
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]833in the long-term. Example:</p>
834<pre>&lt;mydoc xmlns="http://mydoc.example.org/schemas/">
835 &lt;elem1>...&lt;/elem1>
836 &lt;elem2>...&lt;/elem2>
837&lt;/mydoc></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]838
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]839<p>Concerning the namespace value, this has to be an URL, but the URL doesn't
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]840have to point to any existing resource on the Web. It will bind all the
841element and atributes with that URL. I suggest to use an URL within a domain
842you control, and that the URL should contain some kind of version information
843if possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]844a good namespace scheme.</p>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]845
846<p>Then when you load a file, make sure that a namespace carrying the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]847version-independent prefix is installed on the root element of your document,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]848and if the version information don't match something you know, warn the user
849and be liberal in what you accept as the input. Also do *not* try to base
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]850namespace checking on the prefix value. &lt;foo:text> may be exactly the same
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]851as &lt;bar:text> in another document. What really matter is the URI associated
852with the element or the attribute, not the prefix string (which is just a
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]853shortcut for the full URI). In libxml element and attributes have a
854<code>ns</code> field pointing to an xmlNs structure detailing the namespace
855prefix and it's URI.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]856
857<p>@@Interfaces@@</p>
858
859<p>@@Examples@@</p>
860
861<p>Usually people object using namespace in the case of validation, I object
862this and will make sure that using namespaces won't break validity checking,
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]863so even is you plan to use or currently are using validation I strongly
864suggest adding namespaces to your document. A default namespace scheme
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]865<code>xmlns="http://...."</code> should not break validity even on less
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]866flexible parsers. Now using namespace to mix and differentiate content coming
867from multiple DTDs will certainly break current validation schemes. I will try
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]868to provide ways to do this, but this may not be portable or standardized.</p>
869
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]870<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]871
872<p>Well what is validation and what is a DTD ?</p>
873
874<p>Validation is the process of checking a document against a set of
875construction rules, a <strong>DTD</strong> (Document Type Definition) is such
876a set of rules.</p>
877
878<p>The validation process and building DTDs are the two most difficult parts
879of XML life cycle. Briefly a DTD defines all the possibles element to be
880found within your document, what is the formal shape of your document tree (by
881defining the allowed content of an element, either text, a regular expression
882for the allowed list of children, or mixed content i.e. both text and childs).
883The DTD also defines the allowed attributes for all elements and the types of
884the attributes. For more detailed informations, I suggest to read the related
885parts of the XML specification, the examples found under
886gnome-xml/test/valid/dtd and the large amount of books available on XML. The
887dia example in gnome-xml/test/valid should be both simple and complete enough
888to allow you to build your own.</p>
889
890<p>A word of warning, building a good DTD which will fit your needs of your
891application in the long-term is far from trivial, however the extra level of
892quality it can insure is well worth the price for some sets of applications or
893if you already have already a DTD defined for your application field.</p>
894
895<p>The validation is not completely finished but in a (very IMHO) usable
896state. Until a real validation interface is defined the way to do it is to
897define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
898variable to 1, this will of course be changed at some point:</p>
899
900<p>extern int xmlDoValidityCheckingDefaultValue;</p>
901
902<p>...</p>
903
904<p>xmlDoValidityCheckingDefaultValue = 1;</p>
905
906<p></p>
907
908<p>To handle external entities, use the function
909<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
910link in you HTTP/FTP/Entities database library to the standard libxml
911core.</p>
912
913<p>@@interfaces@@</p>
914
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]915<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]916
917<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]918Model</em> this is an API for accessing XML or HTML structured documents.
919Native 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]920be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]921files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]922set of IDL (or Java) interfaces allowing to traverse and manipulate a
923document. The DOM library will allow accessing and modifying "live" documents
924presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]925
926<p><img src="DOM.gif" alt=" DOM.gif "></p>
927
928<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]929embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]930
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]931<p>The current DOM implementation on top of libxml is the <a
932href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
933a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
934Levien</a>.</p>
935
936<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
937
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]938<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]939
940<p>Here is a real size example, where the actual content of the application
941data 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]942a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]943storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
944base</a>:</p>
945<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]946&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
947 &lt;gjob:Jobs>
948
949 &lt;gjob:Job>
950 &lt;gjob:Project ID="3"/>
951 &lt;gjob:Application>GBackup&lt;/gjob:Application>
952 &lt;gjob:Category>Development&lt;/gjob:Category>
953
954 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]955 &lt;gjob:Status>Open&lt;/gjob:Status>
956 &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]957 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
958 &lt;/gjob:Update>
959
960 &lt;gjob:Developers>
961 &lt;gjob:Developer>
962 &lt;/gjob:Developer>
963 &lt;/gjob:Developers>
964
965 &lt;gjob:Contact>
966 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]967 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]968 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]969 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]970 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]971 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]972 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]973 &lt;/gjob:Webpage>
974 &lt;gjob:Snailmail>
975 &lt;/gjob:Snailmail>
976 &lt;gjob:Phone>
977 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]978 &lt;/gjob:Contact>
979
980 &lt;gjob:Requirements>
981 The program should be released as free software, under the GPL.
982 &lt;/gjob:Requirements>
983
984 &lt;gjob:Skills>
985 &lt;/gjob:Skills>
986
987 &lt;gjob:Details>
988 A GNOME based system that will allow a superuser to configure
989 compressed and uncompressed files and/or file systems to be backed
990 up with a supported media in the system. This should be able to
991 perform via find commands generating a list of files that are passed
992 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
993 or via operations performed on the filesystem itself. Email
994 notification and GUI status display very important.
995 &lt;/gjob:Details>
996
997 &lt;/gjob:Job>
998
999 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1000&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1001
1002<p>While loading the XML file into an internal DOM tree is a matter of calling
1003only a couple of functions, browsing the tree to gather the informations and
1004generate the internals structures is harder, and more error prone.</p>
1005
1006<p>The suggested principle is to be tolerant with respect to the input
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]1007structure. For example, the ordering of the attributes is not significant,
1008Cthe XML specification is clear about it. It's also usually a good idea to not
1009be dependent of the orders of the childs of a given node, unless it really
1010makes things harder. Here is some code to parse the informations for a
1011person:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1012<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1013 * A person record
1014 */
1015typedef struct person {
1016 char *name;
1017 char *email;
1018 char *company;
1019 char *organisation;
1020 char *smail;
1021 char *webPage;
1022 char *phone;
1023} person, *personPtr;
1024
1025/*
1026 * And the code needed to parse it
1027 */
1028personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1029 personPtr ret = NULL;
1030
1031DEBUG("parsePerson\n");
1032 /*
1033 * allocate the struct
1034 */
1035 ret = (personPtr) malloc(sizeof(person));
1036 if (ret == NULL) {
1037 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1038 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1039 }
1040 memset(ret, 0, sizeof(person));
1041
1042 /* We don't care what the top level element name is */
1043 cur = cur->childs;
1044 while (cur != NULL) {
1045 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1046 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1047 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1048 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
1049 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1050 }
1051
1052 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1053}</pre>
1054
1055<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1056<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1057 <li>Usually a recursive parsing style is the more convenient one, XML data
1058 being by nature subject to repetitive constructs and usualy exibit highly
1059 stuctured patterns.</li>
1060 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
1061 the pointer to the global XML document and the namespace reserved to the
1062 application. Document wide information are needed for example to decode
1063 entities and it's a good coding practice to define a namespace for your
1064 application set of data and test that the element and attributes you're
1065 analyzing actually pertains to your application space. This is done by a
1066 simple equality test (cur->ns == ns).</li>
1067 <li>To retrieve text and attributes value, it is suggested to use the
1068 function <em>xmlNodeListGetString</em> to gather all the text and entity
1069 reference nodes generated by the DOM output and produce an single text
1070 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1071</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1072
1073<p>Here is another piece of code used to parse another level of the
1074structure:</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]1075<pre>#include &lt;libxml/tree.h>
1076/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1077 * a Description for a Job
1078 */
1079typedef struct job {
1080 char *projectID;
1081 char *application;
1082 char *category;
1083 personPtr contact;
1084 int nbDevelopers;
1085 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
1086} job, *jobPtr;
1087
1088/*
1089 * And the code needed to parse it
1090 */
1091jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1092 jobPtr ret = NULL;
1093
1094DEBUG("parseJob\n");
1095 /*
1096 * allocate the struct
1097 */
1098 ret = (jobPtr) malloc(sizeof(job));
1099 if (ret == NULL) {
1100 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1101 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1102 }
1103 memset(ret, 0, sizeof(job));
1104
1105 /* We don't care what the top level element name is */
1106 cur = cur->childs;
1107 while (cur != NULL) {
1108
1109 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1110 ret->projectID = xmlGetProp(cur, "ID");
1111 if (ret->projectID == NULL) {
1112 fprintf(stderr, "Project has no ID\n");
1113 }
1114 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1115 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1116 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1117 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1118 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1119 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1120 ret->contact = parsePerson(doc, ns, cur);
1121 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1122 }
1123
1124 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1125}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1126
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1127<p>One can notice that once used to it, writing this kind of code is quite
1128simple, but boring. Ultimately, it could be possble to write stubbers taking
1129either C data structure definitions, a set of XML examples or an XML DTD and
1130produce the code needed to import and export the content between C data and
1131XML storage. This is left as an exercise to the reader :-)</p>
1132
1133<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]1134example</a> as a template, it is also available with Makefile in the Gnome CVS
1135base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1136
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1137<p></p>
1138
1139<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1140
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame^]1141<p>$Id: xml.html,v 1.32 2000/04/03 19:48:13 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1142</body>
1143</html>