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blob: 84a6aaf1dad651fac555c8cd32852f9679dfee88 [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 Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]6 <meta name="GENERATOR" content="amaya V3.1">
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>
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]45 <li><a href="#Contributi">Contribution</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]46</ul>
47
48<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]49
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]50<p>This document describes libxml, the <a
51href="http://www.w3.org/XML/">XML</a> library provided in the <a
52href="http://www.gnome.org/">Gnome</a> framework. XML is a standard for
53building tag-based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]54
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]55<p>Here are some key points about libxml:</p>
56<ul>
57 <li>The internal document repesentation is as close as possible to the <a
58 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li>
59 <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]60 like interface</a>; the interface is designed to be compatible with <a
61 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]62 <li>Libxml now includes a nearly complete <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]63 href="http://www.w3.org/TR/xpath">XPath</a> implementation.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]64 <li>Libxml exports Push and Pull type parser interfaces for both XML and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]65 HTML.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]66 <li>This library is released both under the <a
67 href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
68 IPR</a> and the GNU LGPL. Use either at your convenience, basically this
69 should make everybody happy, if not, drop me a mail.</li>
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]70 <li>There is <a href="upgrade.html">a first set of instructions</a>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]71 concerning upgrade from libxml-1.x to libxml-2.x</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]72</ul>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]73
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]74<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]75
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]76<p>There are some on-line resources about using libxml:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]77<ol>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]78 <li>The code is commented in a way which allows <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]79 href="http://xmlsoft.org/libxml.html">extensive documentation</a> to be
80 automatically extracted.</li>
81 <li>This page provides a global overview and <a href="#real">some
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]82 examples</a> on how to use libxml.</li>
83 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a
84 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
85 documentation</a> explaining how to use the libxml SAX interface.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]86 <li>George Lebl wrote <a
87 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]88 for IBM developerWorks</a> about using libxml.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]89 <li>It is also a good idea to check to <a href="mailto:raph@levien.com">Raph
90 Levien</a> <a href="http://levien.com/gnome/">web site</a> since he is
91 building the <a href="http://levien.com/gnome/gdome.html">DOM interface
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]92 gdome</a> on top of libxml result tree and an implementation of <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]93 href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
94 href="http://www.levien.com/svg/">gill</a>. Check his <a
95 href="http://www.levien.com/gnome/domination.html">DOMination
96 paper</a>.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]97 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO
98 file</a></li>
99 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a>. If you are
100 starting a new project using libxml you should really use the 2.x
101 version.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]102 <li>And don't forget to look at the <a href="/messages/">mailing-list
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]103 archive</a>.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]104</ol>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]105
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]106<h3>Reporting bugs and getting help</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]107
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]108<p>Well, bugs or missing features are always possible, and I will make a point
109of 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]110href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]111database</a>. I look at reports there regularly and it's good to have a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]112reminder when a bug is still open. Check the <a
113href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]114and be sure to specify that the bug is for the package gnome-xml.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]115
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]116<p>There is also a mailing-list <a
117href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
118href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]119majordomo based list, send a mail message to <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]120href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
121"subscribe xml" in the <strong>content</strong> of the message.</p>
122
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]123<p>Alternatively, you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]124href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]125
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]126<p>Of course, bugs reports with a suggested patch for fixing them will
127probably be processed faster.</p>
128
129<p>If you're looking for help, a quick look at <a
130href="http://xmlsoft.org/messages/#407">the list archive</a> may actually
131provide the answer, I usually send source samples when answering libxml usage
132questions. The <a href="http://xmlsoft.org/book1.html">auto-generated
133documentantion</a> is not as polished as I would like (i need to learn more
134about Docbook), but it's a good starting point.</p>
135
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]136<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]137
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]138<p>The latest versions of libxml can be found on <a
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]139href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or on the <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]140href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]141as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]142archive</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/contrib/rpms/">RPM
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]143packages</a>. (NOTE that you need both the <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]144href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a
145href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]146packages installed to compile applications using libxml.)</p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]147
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]148<p><a name="Snapshot">Snapshot:</a></p>
149<ul>
150 <li>Code from the W3C cvs base libxml <a
151 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li>
152 <li>Docs, content of the web site, the list archive included <a
153 href="ftp://rpmfind.net/pub/libxml/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li>
154</ul>
155
156<p><a name="Contribs">Contribs:</a></p>
157
158<p>I do accept external contributions, especially if compiling on another
159platform, get in touch with me to upload the package. I will keep them in the
160<a href="ftp://rpmfind.net/pub/libxml/contribs/">contrib directory</a></p>
161
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]162<p>Libxml is also available from 2 CVS bases:</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]163<ul>
164 <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]165 available read-only using the CVS pserver authentification (I tend to use
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]166 this base for my own development, so it's updated more regularly, but the
167 content may not be as stable):</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]168 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]169 password: anonymous
170 module: XML</pre>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]171 </li>
172 <li><p>The <a
173 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]174 CVS base</a>. Check the <a
175 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page;
176 the CVS module is <b>gnome-xml</b>.</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]177 </li>
178</ul>
179
180<h2><a name="News">News</a></h2>
181
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]182<h3>CVS only : check the <a
183href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
184for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]185<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]186 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]187 if you want to test those.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]188</ul>
189
Daniel Veillard3f6f7f62000-06-30 17:58:25 +0000[diff] [blame^]190<h3>2.1.0 and 1.8.8: June 29 2000</h3>
191<ul>
192 <li>1.8.8 is mostly a comodity package for upgrading to libxml2 accoding to
193 <a href="upgrade.html">new instructions</a>. It fixes a nasty problem
194 about &amp;#38; charref parsing</li>
195 <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it
196 also contains numerous fixes and enhancements:
197 <ul>
198 <li>added xmlStopParser() to stop parsing</li>
199 <li>improved a lot parsing speed when there is large CDATA blocs</li>
200 <li>includes XPath patches provided by Picdar Technology</li>
201 <li>tried to fix as much as possible DtD validation and namespace
202 related problems</li>
203 <li>output to a given encoding has been added/tested</li>
204 <li>lot of various fixes</li>
205 </ul>
206 </li>
207</ul>
208
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]209<h3>2.0.0: Apr 12 2000</h3>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]210<ul>
211 <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]212 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initally
213 scheduled for Apr 3 the relase occured only on Apr 12 due to massive
214 workload.</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]215 <li>The include are now located under $prefix/include/libxml (instead of
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]216 $prefix/include/gnome-xml), they also are referenced by
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]217 <pre>#include &lt;libxml/xxx.h></pre>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]218 <p>instead of</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]219 <pre>#include "xxx.h"</pre>
220 </li>
Daniel Veillard8f621982000-03-20 13:07:15 +0000[diff] [blame]221 <li>a new URI module for parsing URIs and following strictly RFC 2396</li>
222 <li>the memory allocation routines used by libxml can now be overloaded
223 dynamically by using xmlMemSetup()</li>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]224 <li>The previously CVS only tool tester has been renamed
225 <strong>xmllint</strong> and is now installed as part of the libxml2
226 package</li>
Daniel Veillarde0aed302000-04-16 08:52:20 +0000[diff] [blame]227 <li>The I/O interface has been revamped. There is now ways to plug in
228 specific I/O modules, either at the URI scheme detection level using
229 xmlRegisterInputCallbacks() or by passing I/O functions when creating a
230 parser context using xmlCreateIOParserCtxt()</li>
231 <li>there is a C preprocessor macro LIBXML_VERSION providing the version
232 number of the libxml module in use</li>
233 <li>a number of optional features of libxml can now be excluded at configure
234 time (FTP/HTTP/HTML/XPath/Debug)</li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]235</ul>
236
237<h3>2.0.0beta: Mar 14 2000</h3>
238<ul>
239 <li>This is a first Beta release of libxml version 2</li>
240 <li>It's available only from<a href="ftp://rpmfind.net/pub/libxml/">
241 rpmfind.net FTP</a>, it's packaged as libxml2-2.0.0beta and available as
242 tar and RPMs</li>
243 <li>This version is now the head in the Gnome CVS base, the old one is
244 available under the tag LIB_XML_1_X</li>
245 <li>This includes a very large set of changes. Froma programmatic point of
246 view applications should not have to be modified too much, check the <a
247 href="upgrade.html">upgrade page</a></li>
248 <li>Some interfaces may changes (especially a bit about encoding).</li>
249 <li>the updates includes:
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]250 <ul>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]251 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly
252 handled now</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]253 <li>Better handling of entities, especially well formedness checking and
254 proper PEref extensions in external subsets</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]255 <li>DTD conditional sections</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]256 <li>Validation now correcly handle entities content</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]257 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
258 structures to accomodate DOM</a></li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]259 </ul>
260 </li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]261 <li>Serious progress were made toward compliance, <a
262 href="conf/result.html">here are the result of the test</a> against the
263 OASIS testsuite (except the japanese tests since I don't support that
264 encoding yet). This URL is rebuilt every couple of hours using the CVS
265 head version.</li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]266</ul>
267
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]268<h3>1.8.7: Mar 6 2000</h3>
269<ul>
270 <li>This is a bug fix release:</li>
271 <li>It is possible to disable the ignorable blanks heuristic used by
272 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note
273 that for adherence to XML spec, this behaviour will be disabled by default
274 in 2.x . The same function will allow to keep compatibility for old
275 code.</li>
276 <li>Blanks in &lt;a> &lt;/a> constructs are not ignored anymore, avoiding
277 heuristic is really the Right Way :-\</li>
278 <li>The unchecked use of snprintf which was breaking libxml-1.8.6
279 compilation on some platforms has been fixed</li>
280 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing
281 URIs</li>
282</ul>
283
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]284<h3>1.8.6: Jan 31 2000</h3>
285<ul>
286 <li>added a nanoFTP transport module, debugged until the new version of <a
287 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
288 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000[diff] [blame]289</ul>
290
291<h3>1.8.5: Jan 21 2000</h3>
292<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]293 <li>adding APIs to parse a well balanced chunk of XML (production <a
294 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
295 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000[diff] [blame]296 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
297 <li>Jody Goldberg &lt;jgoldberg@home.com> provided another patch trying to
298 solve the zlib checks problems</li>
299 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
300 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]301</ul>
302
303<h3>1.8.4: Jan 13 2000</h3>
304<ul>
305 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
306 <li>all exit() call should have been removed from libxml</li>
307 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
308 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]309</ul>
310
311<h3>1.8.3: Jan 5 2000</h3>
312<ul>
313 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]314 <li>a shell-like interface to the document tree (try tester --shell :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame]315 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]316 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]317 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
318 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]319 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]320 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]321 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]322</ul>
323
324<h3>1.8.2: Dec 21 1999</h3>
325<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]326 <li>I got another problem with includes and C++, I hope this issue is fixed
327 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]328 <li>Added a few tree modification functions: xmlReplaceNode,
329 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
330 xmlDocSetRootElement</li>
331 <li>Tried to improve the HTML output with help from <a
332 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]333</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]334
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]335<h3>1.8.1: Dec 18 1999</h3>
336<ul>
337 <li>various patches to avoid troubles when using libxml with C++ compilers
338 the "namespace" keyword and C escaping in include files</li>
339 <li>a problem in one of the core macros IS_CHAR was corrected</li>
340 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
341 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]342 <li>fixed a posteriori validation (validation after parsing, or by using a
343 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]344 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]345</ul>
346
347<h3>1.8.0: Dec 12 1999</h3>
348<ul>
349 <li>cleanup, especially memory wise</li>
350 <li>the parser should be more reliable, especially the HTML one, it should
351 not crash, whatever the input !</li>
352 <li>Integrated various patches, especially a speedup improvement for large
353 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
354 configure with --with-buffers to enable them.</li>
355 <li>attribute normalization, oops should have been added long ago !</li>
356 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
357 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]358</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]359
360<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]361<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]362 <li>Lots of HTML improvement</li>
363 <li>Fixed some errors when saving both XML and HTML</li>
364 <li>More examples, the regression tests should now look clean</li>
365 <li>Fixed a bug with contiguous charref</li>
366</ul>
367
368<h3>1.7.3: Sep 29 1999</h3>
369<ul>
370 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]371 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]372 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]373</ul>
374
375<h3>1.7.1: Sep 24 1999</h3>
376<ul>
377 <li>The basic type for strings manipulated by libxml has been renamed in
378 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
379 is that CHAR was conflicting with a predefined type on Windows. However on
380 non WIN32 environment, compatibility is provided by the way of a
381 <strong>#define </strong>.</li>
382 <li>Changed another error : the use of a structure field called errno, and
383 leading to troubles on platforms where it's a macro</li>
384</ul>
385
386<h3>1.7.0: sep 23 1999</h3>
387<ul>
388 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
389 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
390 <li>Added an errno to report errors by another mean than a simple printf
391 like callback</li>
392 <li>Finished ID/IDREF support and checking when validation</li>
393 <li>Serious memory leaks fixed (there is now a <a
394 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
395 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
396 implementation</li>
397 <li>Added an HTML parser front-end</li>
398</ul>
399
400<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]401
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]402<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]403markup-based structured documents. Here is <a name="example">an example XML
404document</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]405<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]406&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]407 &lt;head>
408 &lt;title>Welcome to Gnome&lt;/title>
409 &lt;/head>
410 &lt;chapter>
411 &lt;title>The Linux adventure&lt;/title>
412 &lt;p>bla bla bla ...&lt;/p>
413 &lt;image href="linus.gif"/>
414 &lt;p>...&lt;/p>
415 &lt;/chapter>
416&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]417
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]418<p>The first line specifies that it's an XML document and gives useful
419information about its encoding. Then the document is a text format whose
420structure is specified by tags between brackets. <strong>Each tag opened has
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]421to be closed</strong>. XML is pedantic about this. However, if a tag is empty
422(no content), a single tag can serve as both the opening and closing tag if it
423ends with <code>/></code> rather than with <code>></code>. Note that, for
424example, the image tag has no content (just an attribute) and is closed by
425ending the tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]426
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]427<p>XML can be applied sucessfully to a wide range of uses, from long term
428structured document maintenance (where it follows the steps of SGML) to simple
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]429data encoding mechanisms like configuration file formatting (glade),
430spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where
431it is used to encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]432
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]433<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]434
435<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]436returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]437<strong>xmlDoc</strong> structure). This structure contains information such
438as the file name, the document type, and a <strong>root</strong> pointer which
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]439is the root of the document (or more exactly the first child under the root
440which is the document). The tree is made of <strong>xmlNode</strong>s, chained
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]441in double-linked lists of siblings and with childs&lt;->parent relationship.
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]442An xmlNode can also carry properties (a chain of xmlAttr structures). An
443attribute 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]444
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]445<p>Here is an example (erroneous with respect to the XML spec since there
446should be only one ELEMENT under the root):</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]447
448<p><img src="structure.gif" alt=" structure.gif "></p>
449
450<p>In the source package there is a small program (not installed by default)
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]451called <strong>xmllint</strong> which parses XML files given as argument and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]452prints them back as parsed. This is useful for detecting errors both in XML
453code and in the XML parser itself. It has an option <strong>--debug</strong>
454which prints the actual in-memory structure of the document, here is the
455result with the <a href="#example">example</a> given before:</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]456<pre>DOCUMENT
457version=1.0
458standalone=true
459 ELEMENT EXAMPLE
460 ATTRIBUTE prop1
461 TEXT
462 content=gnome is great
463 ATTRIBUTE prop2
464 ENTITY_REF
465 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]466 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]467 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]468 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]469 TEXT
470 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]471 ELEMENT chapter
472 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]473 TEXT
474 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]475 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]476 TEXT
477 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]478 ELEMENT image
479 ATTRIBUTE href
480 TEXT
481 content=linus.gif
482 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]483 TEXT
484 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]485
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]486<p>This should be useful for learning the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]487
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]488<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]489
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]490<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]491memory. In that case (and if you don't expect to save back the XML document
492loaded 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]493<strong>callback-based interface</strong> to the parser. Before parsing, the
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]494application layer registers a customized set of callbacks which are called by
495the library as it progresses through the XML input.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]496
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]497<p>To get more detailed step-by-step guidance on using the SAX interface of
498libxml, see the
499href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]500documentation.written by <a href="mailto:james@daa.com.au">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]501Henstridge</a>.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]502
503<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
504program located in the gnome-xml module (it's usually not shipped in the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]505binary packages of libxml, but you can find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]506distribution). Here is the sequence of callbacks that would be reported by
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]507testSAX when parsing the example XML document shown earlier:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]508<pre>SAX.setDocumentLocator()
509SAX.startDocument()
510SAX.getEntity(amp)
511SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
512SAX.characters( , 3)
513SAX.startElement(head)
514SAX.characters( , 4)
515SAX.startElement(title)
516SAX.characters(Welcome to Gnome, 16)
517SAX.endElement(title)
518SAX.characters( , 3)
519SAX.endElement(head)
520SAX.characters( , 3)
521SAX.startElement(chapter)
522SAX.characters( , 4)
523SAX.startElement(title)
524SAX.characters(The Linux adventure, 19)
525SAX.endElement(title)
526SAX.characters( , 4)
527SAX.startElement(p)
528SAX.characters(bla bla bla ..., 15)
529SAX.endElement(p)
530SAX.characters( , 4)
531SAX.startElement(image, href='linus.gif')
532SAX.endElement(image)
533SAX.characters( , 4)
534SAX.startElement(p)
535SAX.characters(..., 3)
536SAX.endElement(p)
537SAX.characters( , 3)
538SAX.endElement(chapter)
539SAX.characters( , 1)
540SAX.endElement(EXAMPLE)
541SAX.endDocument()</pre>
542
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]543<p>Most of the other functionalities of libxml are based on the DOM
544tree-building facility, so nearly everything up to the end of this document
545presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]546itself is built by a set of registered default callbacks, without internal
547specific interface.</p>
548
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]549<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]550
551<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]552using the XML library from the C language. It is not intended to be extensive.
553I hope the automatically generated documents will provide the completeness
554required, but as a separate set of documents. The interfaces of the XML
555library are by principle low level, there is nearly zero abstraction. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]556interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]557
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]558<p>The <a href="gnome-xml-parser.html">parser interfaces for XML</a> are
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]559separated from the <a href="gnome-xml-htmlparser.html">HTML parser
560interfaces</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]561
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]562<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]563
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]564<p>Usually, the first thing to do is to read an XML input. The parser accepts
565documents either from in-memory strings or from files. The functions are
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]566defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]567<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]568 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]569 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]570 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]571</dl>
572<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]573 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]574 <dd><p>Parse an XML document contained in a (possibly compressed)
575 file.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]576 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]577</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]578
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]579<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]580failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]581
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]582<h3 id="Invoking1">Invoking the parser: the push method</h3>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]583
584<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]585fetched (which is common for GUI based programs) libxml provides a push
586interface, too, as of version 1.8.3. Here are the interface functions:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]587<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
588 void *user_data,
589 const char *chunk,
590 int size,
591 const char *filename);
592int xmlParseChunk (xmlParserCtxtPtr ctxt,
593 const char *chunk,
594 int size,
595 int terminate);</pre>
596
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]597<p>and here is a simple example showing how to use the interface:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]598<pre> FILE *f;
599
600 f = fopen(filename, "r");
601 if (f != NULL) {
602 int res, size = 1024;
603 char chars[1024];
604 xmlParserCtxtPtr ctxt;
605
606 res = fread(chars, 1, 4, f);
607 if (res > 0) {
608 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
609 chars, res, filename);
610 while ((res = fread(chars, 1, size, f)) > 0) {
611 xmlParseChunk(ctxt, chars, res, 0);
612 }
613 xmlParseChunk(ctxt, chars, 0, 1);
614 doc = ctxt->myDoc;
615 xmlFreeParserCtxt(ctxt);
616 }
617 }</pre>
618
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]619<p>Also note that the HTML parser embedded into libxml also has a push
620interface; the functions are just prefixed by "html" rather than "xml"</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]621
622<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
623
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]624<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]625memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]626Reading a document without building the tree is possible using the SAX
627interfaces (see SAX.h and <a
628href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]629Henstridge's documentation</a>). Note also that the push interface can be
630limited to SAX. Just use the two first arguments of
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]631<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]632
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]633<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]634
635<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]636there is a set of functions dedicated to building new elements. (These are
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]637also described in &lt;libxml/tree.h>.) For example, here is a piece of code
638that produces the XML document used in the previous examples:</p>
639<pre> #include &lt;libxml/tree.h>
640 xmlDocPtr doc;
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]641 xmlNodePtr tree, subtree;
642
643 doc = xmlNewDoc("1.0");
644 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
645 xmlSetProp(doc->root, "prop1", "gnome is great");
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]646 xmlSetProp(doc->root, "prop2", "&amp; linux too");
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]647 tree = xmlNewChild(doc->root, NULL, "head", NULL);
648 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
649 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
650 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
651 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
652 subtree = xmlNewChild(tree, NULL, "image", NULL);
653 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]654
655<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]656
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]657<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]658
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]659<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]660has access to the internal structure of all the elements of the tree. The
661names should be somewhat simple like <strong>parent</strong>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]662<strong>childs</strong>, <strong>next</strong>, <strong>prev</strong>,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]663<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]664example:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]665<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]666
667<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]668<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]669
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]670<p>points to the text node containing the chapter title "The Linux
671adventure".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]672
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]673<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]674present before the document root, so <code>doc->root</code> may point to an
675element which is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]676<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]677
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]678<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]679
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]680<p>Functions are provided for reading and writing the document content. Here
681is an excerpt from the <a href="gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]682<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]683 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
684 xmlChar *value);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]685 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. The
686 value can be NULL.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]687 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]688</dl>
689<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]690 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]691 *name);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]692 <dd><p>This function returns a pointer to the property content. Note that
693 no extra copy is made.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]694 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]695</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]696
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]697<p>Two functions are provided for reading and writing the text associated with
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]698elements:</p>
699<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]700 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]701 *value);</code></dt>
702 <dd><p>This function takes an "external" string and convert it to one text
703 node or possibly to a list of entity and text nodes. All non-predefined
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]704 entity references like &amp;Gnome; will be stored internally as entity
705 nodes, hence the result of the function may not be a single node.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]706 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]707</dl>
708<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]709 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]710 inLine);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]711 <dd><p>This function is the inverse of
712 <code>xmlStringGetNodeList()</code>. It generates a new string
713 containing the content of the text and entity nodes. Note the extra
714 argument inLine. If this argument is set to 1, the function will expand
715 entity references. For example, instead of returning the &amp;Gnome;
716 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]717 "GNU Network Object Model Environment"). Set this argument if you want
718 to use the string for non-XML usage like User Interface.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]719 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]720</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]721
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]722<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]723
724<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]725<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]726 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]727 *size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]728 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]729 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]730</dl>
731<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]732 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]733 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]734 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]735</dl>
736<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]737 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]738 <dd><p>Saves the document to a file. In this case, the compression
739 interface is triggered if it has been turned on.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]740 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]741</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]742
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]743<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]744
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]745<p>The library transparently handles compression when doing file-based
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]746accesses. The level of compression on saves can be turned on either globally
747or individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]748<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]749 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]750 <dd><p>Gets the document compression ratio (0-9).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]751 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]752</dl>
753<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]754 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]755 <dd><p>Sets the document compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]756 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]757</dl>
758<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]759 <dt><code>int xmlGetCompressMode(void);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]760 <dd><p>Gets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]761 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]762</dl>
763<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]764 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]765 <dd><p>Sets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]766 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]767</dl>
768
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]769<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]770
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]771<p>Entities in principle are similar to simple C macros. An entity defines an
772abbreviation for a given string that you can reuse many times throughout the
773content of your document. Entities are especially useful when a given string
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]774may occur frequently within a document, or to confine the change needed to a
775document to a restricted area in the internal subset of the document (at the
776beginning). Example:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]777<pre>1 &lt;?xml version="1.0"?>
7782 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
7793 &lt;!ENTITY xml "Extensible Markup Language">
7804 ]>
7815 &lt;EXAMPLE>
7826 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]7837 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]784
785<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]786it's name with '&amp;' and following it by ';' without any spaces added. There
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]787are 5 predefined entities in libxml allowing you to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]788predefined meaning in some parts of the xml document content:
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]789<strong>&amp;lt;</strong> for the character '&lt;', <strong>&amp;gt;</strong>
790for the character '>', <strong>&amp;apos;</strong> for the character ''',
791<strong>&amp;quot;</strong> for the character '"', and
792<strong>&amp;amp;</strong> for the character '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]793
794<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]795substitute an entity's content so that you can see the replacement text in
796your application. Or you may prefer to keep entity references as such in the
797content to be able to save the document back without losing this usually
798precious information (if the user went through the pain of explicitly defining
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]799entities, he may have a a rather negative attitude if you blindly susbtitute
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]800them as saving time). The <a
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]801href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]802function allows you to check and change the behaviour, which is to not
803substitute entities by default.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]804
805<p>Here is the DOM tree built by libxml for the previous document in the
806default case:</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]807<pre>/gnome/src/gnome-xml -> ./xmllint --debug test/ent1
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]808DOCUMENT
809version=1.0
810 ELEMENT EXAMPLE
811 TEXT
812 content=
813 ENTITY_REF
814 INTERNAL_GENERAL_ENTITY xml
815 content=Extensible Markup Language
816 TEXT
817 content=</pre>
818
819<p>And here is the result when substituting entities:</p>
820<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
821DOCUMENT
822version=1.0
823 ELEMENT EXAMPLE
824 TEXT
825 content= Extensible Markup Language</pre>
826
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]827<p>So, entities or no entities? Basically, it depends on your use case. I
828suggest that you keep the non-substituting default behaviour and avoid using
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]829entities in your XML document or data if you are not willing to handle the
830entity references elements in the DOM tree.</p>
831
832<p>Note that at save time libxml enforce the conversion of the predefined
833entities where necessary to prevent well-formedness problems, and will also
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]834transparently replace those with chars (i.e., it will not generate entity
835reference elements in the DOM tree or call the reference() SAX callback when
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]836finding them in the input).</p>
837
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]838<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]839
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]840<p>The libxml library implements <a
841href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by
842recognizing namespace contructs in the input, and does namespace lookup
843automatically when building the DOM tree. A namespace declaration is
844associated with an in-memory structure and all elements or attributes within
845that namespace point to it. Hence testing the namespace is a simple and fast
846equality operation at the user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]847
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]848<p>I suggest that people using libxml use a namespace, and declare it in the
849root element of their document as the default namespace. Then they don't need
850to use the prefix in the content but we will have a basis for future semantic
851refinement and merging of data from different sources. This doesn't augment
852significantly the size of the XML output, but significantly increase its value
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]853in the long-term. Example:</p>
854<pre>&lt;mydoc xmlns="http://mydoc.example.org/schemas/">
855 &lt;elem1>...&lt;/elem1>
856 &lt;elem2>...&lt;/elem2>
857&lt;/mydoc></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]858
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]859<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]860have to point to any existing resource on the Web. It will bind all the
861element and atributes with that URL. I suggest to use an URL within a domain
862you control, and that the URL should contain some kind of version information
863if possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]864a good namespace scheme.</p>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]865
866<p>Then when you load a file, make sure that a namespace carrying the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]867version-independent prefix is installed on the root element of your document,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]868and if the version information don't match something you know, warn the user
869and 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]870namespace checking on the prefix value. &lt;foo:text> may be exactly the same
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]871as &lt;bar:text> in another document. What really matter is the URI associated
872with the element or the attribute, not the prefix string (which is just a
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame]873shortcut for the full URI). In libxml element and attributes have a
874<code>ns</code> field pointing to an xmlNs structure detailing the namespace
875prefix and it's URI.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]876
877<p>@@Interfaces@@</p>
878
879<p>@@Examples@@</p>
880
881<p>Usually people object using namespace in the case of validation, I object
882this and will make sure that using namespaces won't break validity checking,
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]883so even is you plan to use or currently are using validation I strongly
884suggest adding namespaces to your document. A default namespace scheme
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]885<code>xmlns="http://...."</code> should not break validity even on less
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]886flexible parsers. Now using namespace to mix and differentiate content coming
887from multiple DTDs will certainly break current validation schemes. I will try
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]888to provide ways to do this, but this may not be portable or standardized.</p>
889
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]890<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]891
892<p>Well what is validation and what is a DTD ?</p>
893
894<p>Validation is the process of checking a document against a set of
895construction rules, a <strong>DTD</strong> (Document Type Definition) is such
896a set of rules.</p>
897
898<p>The validation process and building DTDs are the two most difficult parts
899of XML life cycle. Briefly a DTD defines all the possibles element to be
900found within your document, what is the formal shape of your document tree (by
901defining the allowed content of an element, either text, a regular expression
902for the allowed list of children, or mixed content i.e. both text and childs).
903The DTD also defines the allowed attributes for all elements and the types of
904the attributes. For more detailed informations, I suggest to read the related
905parts of the XML specification, the examples found under
906gnome-xml/test/valid/dtd and the large amount of books available on XML. The
907dia example in gnome-xml/test/valid should be both simple and complete enough
908to allow you to build your own.</p>
909
910<p>A word of warning, building a good DTD which will fit your needs of your
911application in the long-term is far from trivial, however the extra level of
912quality it can insure is well worth the price for some sets of applications or
913if you already have already a DTD defined for your application field.</p>
914
915<p>The validation is not completely finished but in a (very IMHO) usable
916state. Until a real validation interface is defined the way to do it is to
917define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
918variable to 1, this will of course be changed at some point:</p>
919
920<p>extern int xmlDoValidityCheckingDefaultValue;</p>
921
922<p>...</p>
923
924<p>xmlDoValidityCheckingDefaultValue = 1;</p>
925
926<p></p>
927
928<p>To handle external entities, use the function
929<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
930link in you HTTP/FTP/Entities database library to the standard libxml
931core.</p>
932
933<p>@@interfaces@@</p>
934
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]935<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]936
937<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]938Model</em> this is an API for accessing XML or HTML structured documents.
939Native 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]940be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]941files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]942set of IDL (or Java) interfaces allowing to traverse and manipulate a
943document. The DOM library will allow accessing and modifying "live" documents
944presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]945
946<p><img src="DOM.gif" alt=" DOM.gif "></p>
947
948<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]949embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]950
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]951<p>The current DOM implementation on top of libxml is the <a
952href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
953a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
954Levien</a>.</p>
955
956<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
957
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]958<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]959
960<p>Here is a real size example, where the actual content of the application
961data 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]962a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]963storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
964base</a>:</p>
965<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]966&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
967 &lt;gjob:Jobs>
968
969 &lt;gjob:Job>
970 &lt;gjob:Project ID="3"/>
971 &lt;gjob:Application>GBackup&lt;/gjob:Application>
972 &lt;gjob:Category>Development&lt;/gjob:Category>
973
974 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]975 &lt;gjob:Status>Open&lt;/gjob:Status>
976 &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]977 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
978 &lt;/gjob:Update>
979
980 &lt;gjob:Developers>
981 &lt;gjob:Developer>
982 &lt;/gjob:Developer>
983 &lt;/gjob:Developers>
984
985 &lt;gjob:Contact>
986 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]987 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]988 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]989 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]990 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]991 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]992 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]993 &lt;/gjob:Webpage>
994 &lt;gjob:Snailmail>
995 &lt;/gjob:Snailmail>
996 &lt;gjob:Phone>
997 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]998 &lt;/gjob:Contact>
999
1000 &lt;gjob:Requirements>
1001 The program should be released as free software, under the GPL.
1002 &lt;/gjob:Requirements>
1003
1004 &lt;gjob:Skills>
1005 &lt;/gjob:Skills>
1006
1007 &lt;gjob:Details>
1008 A GNOME based system that will allow a superuser to configure
1009 compressed and uncompressed files and/or file systems to be backed
1010 up with a supported media in the system. This should be able to
1011 perform via find commands generating a list of files that are passed
1012 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
1013 or via operations performed on the filesystem itself. Email
1014 notification and GUI status display very important.
1015 &lt;/gjob:Details>
1016
1017 &lt;/gjob:Job>
1018
1019 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1020&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1021
1022<p>While loading the XML file into an internal DOM tree is a matter of calling
1023only a couple of functions, browsing the tree to gather the informations and
1024generate the internals structures is harder, and more error prone.</p>
1025
1026<p>The suggested principle is to be tolerant with respect to the input
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]1027structure. For example, the ordering of the attributes is not significant,
1028Cthe XML specification is clear about it. It's also usually a good idea to not
1029be dependent of the orders of the childs of a given node, unless it really
1030makes things harder. Here is some code to parse the informations for a
1031person:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1032<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1033 * A person record
1034 */
1035typedef struct person {
1036 char *name;
1037 char *email;
1038 char *company;
1039 char *organisation;
1040 char *smail;
1041 char *webPage;
1042 char *phone;
1043} person, *personPtr;
1044
1045/*
1046 * And the code needed to parse it
1047 */
1048personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1049 personPtr ret = NULL;
1050
1051DEBUG("parsePerson\n");
1052 /*
1053 * allocate the struct
1054 */
1055 ret = (personPtr) malloc(sizeof(person));
1056 if (ret == NULL) {
1057 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1058 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1059 }
1060 memset(ret, 0, sizeof(person));
1061
1062 /* We don't care what the top level element name is */
1063 cur = cur->childs;
1064 while (cur != NULL) {
1065 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1066 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1067 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1068 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
1069 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1070 }
1071
1072 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1073}</pre>
1074
1075<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1076<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1077 <li>Usually a recursive parsing style is the more convenient one, XML data
1078 being by nature subject to repetitive constructs and usualy exibit highly
1079 stuctured patterns.</li>
1080 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
1081 the pointer to the global XML document and the namespace reserved to the
1082 application. Document wide information are needed for example to decode
1083 entities and it's a good coding practice to define a namespace for your
1084 application set of data and test that the element and attributes you're
1085 analyzing actually pertains to your application space. This is done by a
1086 simple equality test (cur->ns == ns).</li>
1087 <li>To retrieve text and attributes value, it is suggested to use the
1088 function <em>xmlNodeListGetString</em> to gather all the text and entity
1089 reference nodes generated by the DOM output and produce an single text
1090 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1091</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1092
1093<p>Here is another piece of code used to parse another level of the
1094structure:</p>
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]1095<pre>#include &lt;libxml/tree.h>
1096/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1097 * a Description for a Job
1098 */
1099typedef struct job {
1100 char *projectID;
1101 char *application;
1102 char *category;
1103 personPtr contact;
1104 int nbDevelopers;
1105 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
1106} job, *jobPtr;
1107
1108/*
1109 * And the code needed to parse it
1110 */
1111jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1112 jobPtr ret = NULL;
1113
1114DEBUG("parseJob\n");
1115 /*
1116 * allocate the struct
1117 */
1118 ret = (jobPtr) malloc(sizeof(job));
1119 if (ret == NULL) {
1120 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1121 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1122 }
1123 memset(ret, 0, sizeof(job));
1124
1125 /* We don't care what the top level element name is */
1126 cur = cur->childs;
1127 while (cur != NULL) {
1128
1129 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1130 ret->projectID = xmlGetProp(cur, "ID");
1131 if (ret->projectID == NULL) {
1132 fprintf(stderr, "Project has no ID\n");
1133 }
1134 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1135 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1136 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1137 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1138 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1139 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1140 ret->contact = parsePerson(doc, ns, cur);
1141 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1142 }
1143
1144 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1145}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1146
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1147<p>One can notice that once used to it, writing this kind of code is quite
1148simple, but boring. Ultimately, it could be possble to write stubbers taking
1149either C data structure definitions, a set of XML examples or an XML DTD and
1150produce the code needed to import and export the content between C data and
1151XML storage. This is left as an exercise to the reader :-)</p>
1152
1153<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]1154example</a> as a template, it is also available with Makefile in the Gnome CVS
1155base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1156
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]1157<h2><a name="Contributi">Contributions</a></h2>
1158<ul>
1159 <li><a href="mailto:ari@btigate.com">Ari Johnson</a> provides a C++ wrapper
1160 for libxml:
1161 <p>Website: <a
1162 href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p>
1163 <p>Download: <a
1164 href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p>
1165 </li>
1166 <li><a href="mailto:doolin@cs.utk.edu">David Doolin</a> provides a
1167 precompiled Windows version
1168 <p><a
1169 href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p>
1170 </li>
Daniel Veillard3f6f7f62000-06-30 17:58:25 +0000[diff] [blame^]1171 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> provided <a
1172 href="libxml-doc.el">an emacs module</a> to lookup libxml functions
1173 documentation</li>
Daniel Veillardc310d562000-06-23 18:32:15 +0000[diff] [blame]1174 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a
1175 href="http://xmlsoft.org/messages/0488.html">man pages</a> (not yet
1176 integrated in the distribution)</li>
1177</ul>
1178
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1179<p></p>
1180
1181<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1182
Daniel Veillard3f6f7f62000-06-30 17:58:25 +0000[diff] [blame^]1183<p>$Id: xml.html,v 1.34 2000/06/23 18:32:15 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1184</body>
1185</html>