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blob: e0403f30345f16cf7a80bc81facc49ef5f1f4479 [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 Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame^]6 <meta name="GENERATOR" content="amaya V2.4">
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 Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]11<h1 align="center">The XML library for Gnome</h1>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]12
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]13<h2 style="text-align: center">libxml, a.k.a. gnome-xml</h2>
14
15<p></p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]16<ul>
17 <li><a href="#Introducti">Introduction</a></li>
18 <li><a href="#Documentat">Documentation</a></li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]19 <li><a href="#Downloads">Downloads</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]20 <li><a href="#News">News</a></li>
21 <li><a href="#XML">XML</a></li>
22 <li><a href="#tree">The tree output</a></li>
23 <li><a href="#interface">The SAX interface</a></li>
24 <li><a href="#library">The XML library interfaces</a>
25 <ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]26 <li><a href="#Invoking">Invoking the parser: the pull way</a></li>
27 <li><a href="#Invoking">Invoking the parser: the push way</a></li>
28 <li><a href="#Invoking2">Invoking the parser: the SAX interface</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]29 <li><a href="#Building">Building a tree from scratch</a></li>
30 <li><a href="#Traversing">Traversing the tree</a></li>
31 <li><a href="#Modifying">Modifying the tree</a></li>
32 <li><a href="#Saving">Saving the tree</a></li>
33 <li><a href="#Compressio">Compression</a></li>
34 </ul>
35 </li>
36 <li><a href="#Entities">Entities or no entities</a></li>
37 <li><a href="#Namespaces">Namespaces</a></li>
38 <li><a href="#Validation">Validation</a></li>
39 <li><a href="#Principles">DOM principles</a></li>
40 <li><a href="#real">A real example</a></li>
41</ul>
42
43<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]44
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]45<p>This document describes libxml, the <a
46href="http://www.w3.org/XML/">XML</a> library provided in the <a
47href="http://www.gnome.org/">Gnome</a> framework. XML is a standard for
48building tag-based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]49
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]50<p>Here are some key points about libxml:</p>
51<ul>
52 <li>The internal document repesentation is as close as possible to the <a
53 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li>
54 <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]55 like interface</a>; the interface is designed to be compatible with <a
56 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]57 <li>Libxml now includes a nearly complete <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]58 href="http://www.w3.org/TR/xpath">XPath</a> implementation.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]59 <li>Libxml exports Push and Pull type parser interfaces for both XML and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]60 HTML.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]61 <li>This library is released both under the W3C Copyright and the GNU LGPL.
62 Basically, everybody should be happy; if not, drop me a mail.</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]63 <li>There is <a href="upgrade.html">a first set of instruction</a>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame^]64 concerning upgrade from libxml-1.x to libxml-2.x</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]65</ul>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]66
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]67<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]68
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]69<p>There are some on-line resources about using libxml:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]70<ol>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]71 <li>The code is commented in a way which allows <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]72 href="http://xmlsoft.org/libxml.html">extensive documentation</a> to be
73 automatically extracted.</li>
74 <li>This page provides a global overview and <a href="#real">some
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]75 examples</a> on how to use libxml.</li>
76 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a
77 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
78 documentation</a> explaining how to use the libxml SAX interface.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]79 <li>George Lebl wrote <a
80 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]81 for IBM developerWorks</a> about using libxml.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]82 <li>It is also a good idea to check to <a href="mailto:raph@levien.com">Raph
83 Levien</a> <a href="http://levien.com/gnome/">web site</a> since he is
84 building the <a href="http://levien.com/gnome/gdome.html">DOM interface
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]85 gdome</a> on top of libxml result tree and an implementation of <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]86 href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
87 href="http://www.levien.com/svg/">gill</a>. Check his <a
88 href="http://www.levien.com/gnome/domination.html">DOMination
89 paper</a>.</li>
90 <li>And don't forget to look at the <a href="/messages/">mailing-list
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]91 archive</a>, too.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]92</ol>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]93
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]94<h3>Reporting bugs and getting help</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]95
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]96<p>Well, bugs or missing features are always possible, and I will make a point
97of 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]98href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]99database</a>. I look at reports there regularly and it's good to have a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]100reminder when a bug is still open. Check the <a
101href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]102and be sure to specify that the bug is for the package gnome-xml.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]103
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]104<p>There is also a mailing-list <a
105href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
106href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]107majordomo based list, send a mail message to <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]108href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
109"subscribe xml" in the <strong>content</strong> of the message.</p>
110
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]111<p>Alternatively, you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]112href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]113
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]114<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]115
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]116<p>The latest versions of libxml can be found on <a
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]117href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or on the <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]118href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]119as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]120archive</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/contrib/rpms/">RPMs
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]121packages</a>. (NOTE that you need both the <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]122href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a
123href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]124packages installed to compile applications using libxml.)</p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]125
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]126<p><a name="Snapshot">Snapshot:</a></p>
127<ul>
128 <li>Code from the W3C cvs base libxml <a
129 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li>
130 <li>Docs, content of the web site, the list archive included <a
131 href="ftp://rpmfind.net/pub/libxml/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li>
132</ul>
133
134<p><a name="Contribs">Contribs:</a></p>
135
136<p>I do accept external contributions, especially if compiling on another
137platform, get in touch with me to upload the package. I will keep them in the
138<a href="ftp://rpmfind.net/pub/libxml/contribs/">contrib directory</a></p>
139
140<p>Libxml is also available from 2 CVs bases:</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]141<ul>
142 <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]143 available read-only using the CVS pserver authentification (I tend to use
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]144 this base for my own development, so it's updated more regularly, but the
145 content may not be as stable):</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]146 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]147 password: anonymous
148 module: XML</pre>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]149 </li>
150 <li><p>The <a
151 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]152 CVS base</a>. Check the <a
153 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page;
154 the CVS module is <b>gnome-xml</b>.</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]155 </li>
156</ul>
157
158<h2><a name="News">News</a></h2>
159
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]160<h3>CVS only : check the <a
161href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
162for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]163<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]164 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]165 if you want to test those.</li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame^]166</ul>
167
168<h3>2.0.0beta: Mar 14 2000</h3>
169<ul>
170 <li>This is a first Beta release of libxml version 2</li>
171 <li>It's available only from<a href="ftp://rpmfind.net/pub/libxml/">
172 rpmfind.net FTP</a>, it's packaged as libxml2-2.0.0beta and available as
173 tar and RPMs</li>
174 <li>This version is now the head in the Gnome CVS base, the old one is
175 available under the tag LIB_XML_1_X</li>
176 <li>This includes a very large set of changes. Froma programmatic point of
177 view applications should not have to be modified too much, check the <a
178 href="upgrade.html">upgrade page</a></li>
179 <li>Some interfaces may changes (especially a bit about encoding).</li>
180 <li>the updates includes:
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]181 <ul>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame^]182 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly
183 handled now</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]184 <li>Better handling of entities, especially well formedness checking and
185 proper PEref extensions in external subsets</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]186 <li>DTD conditional sections</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]187 <li>Validation now correcly handle entities content</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]188 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
189 structures to accomodate DOM</a></li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]190 </ul>
191 </li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame^]192 <li>Serious progress were made toward compliance, <a
193 href="conf/result.html">here are the result of the test</a> against the
194 OASIS testsuite (except the japanese tests since I don't support that
195 encoding yet). This URL is rebuilt every couple of hours using the CVS
196 head version.</li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]197</ul>
198
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]199<h3>1.8.7: Mar 6 2000</h3>
200<ul>
201 <li>This is a bug fix release:</li>
202 <li>It is possible to disable the ignorable blanks heuristic used by
203 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note
204 that for adherence to XML spec, this behaviour will be disabled by default
205 in 2.x . The same function will allow to keep compatibility for old
206 code.</li>
207 <li>Blanks in &lt;a> &lt;/a> constructs are not ignored anymore, avoiding
208 heuristic is really the Right Way :-\</li>
209 <li>The unchecked use of snprintf which was breaking libxml-1.8.6
210 compilation on some platforms has been fixed</li>
211 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing
212 URIs</li>
213</ul>
214
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]215<h3>1.8.6: Jan 31 2000</h3>
216<ul>
217 <li>added a nanoFTP transport module, debugged until the new version of <a
218 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
219 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000[diff] [blame]220</ul>
221
222<h3>1.8.5: Jan 21 2000</h3>
223<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]224 <li>adding APIs to parse a well balanced chunk of XML (production <a
225 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
226 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000[diff] [blame]227 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
228 <li>Jody Goldberg &lt;jgoldberg@home.com> provided another patch trying to
229 solve the zlib checks problems</li>
230 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
231 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]232</ul>
233
234<h3>1.8.4: Jan 13 2000</h3>
235<ul>
236 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
237 <li>all exit() call should have been removed from libxml</li>
238 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
239 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]240</ul>
241
242<h3>1.8.3: Jan 5 2000</h3>
243<ul>
244 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]245 <li>a shell-like interface to the document tree (try tester --shell :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame]246 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]247 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]248 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
249 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]250 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]251 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]252 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]253</ul>
254
255<h3>1.8.2: Dec 21 1999</h3>
256<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]257 <li>I got another problem with includes and C++, I hope this issue is fixed
258 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]259 <li>Added a few tree modification functions: xmlReplaceNode,
260 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
261 xmlDocSetRootElement</li>
262 <li>Tried to improve the HTML output with help from <a
263 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]264</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]265
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]266<h3>1.8.1: Dec 18 1999</h3>
267<ul>
268 <li>various patches to avoid troubles when using libxml with C++ compilers
269 the "namespace" keyword and C escaping in include files</li>
270 <li>a problem in one of the core macros IS_CHAR was corrected</li>
271 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
272 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]273 <li>fixed a posteriori validation (validation after parsing, or by using a
274 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]275 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]276</ul>
277
278<h3>1.8.0: Dec 12 1999</h3>
279<ul>
280 <li>cleanup, especially memory wise</li>
281 <li>the parser should be more reliable, especially the HTML one, it should
282 not crash, whatever the input !</li>
283 <li>Integrated various patches, especially a speedup improvement for large
284 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
285 configure with --with-buffers to enable them.</li>
286 <li>attribute normalization, oops should have been added long ago !</li>
287 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
288 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]289</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]290
291<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]292<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]293 <li>Lots of HTML improvement</li>
294 <li>Fixed some errors when saving both XML and HTML</li>
295 <li>More examples, the regression tests should now look clean</li>
296 <li>Fixed a bug with contiguous charref</li>
297</ul>
298
299<h3>1.7.3: Sep 29 1999</h3>
300<ul>
301 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]302 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]303 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]304</ul>
305
306<h3>1.7.1: Sep 24 1999</h3>
307<ul>
308 <li>The basic type for strings manipulated by libxml has been renamed in
309 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
310 is that CHAR was conflicting with a predefined type on Windows. However on
311 non WIN32 environment, compatibility is provided by the way of a
312 <strong>#define </strong>.</li>
313 <li>Changed another error : the use of a structure field called errno, and
314 leading to troubles on platforms where it's a macro</li>
315</ul>
316
317<h3>1.7.0: sep 23 1999</h3>
318<ul>
319 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
320 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
321 <li>Added an errno to report errors by another mean than a simple printf
322 like callback</li>
323 <li>Finished ID/IDREF support and checking when validation</li>
324 <li>Serious memory leaks fixed (there is now a <a
325 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
326 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
327 implementation</li>
328 <li>Added an HTML parser front-end</li>
329</ul>
330
331<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]332
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]333<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]334markup-based structured documents. Here is <a name="example">an example XML
335document</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]336<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]337&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]338 &lt;head>
339 &lt;title>Welcome to Gnome&lt;/title>
340 &lt;/head>
341 &lt;chapter>
342 &lt;title>The Linux adventure&lt;/title>
343 &lt;p>bla bla bla ...&lt;/p>
344 &lt;image href="linus.gif"/>
345 &lt;p>...&lt;/p>
346 &lt;/chapter>
347&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]348
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]349<p>The first line specifies that it's an XML document and gives useful
350information about its encoding. Then the document is a text format whose
351structure is specified by tags between brackets. <strong>Each tag opened has
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]352to be closed</strong>. XML is pedantic about this. However, if a tag is empty
353(no content), a single tag can serve as both the opening and closing tag if it
354ends with <code>/></code> rather than with <code>></code>. Note that, for
355example, the image tag has no content (just an attribute) and is closed by
356ending the tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]357
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]358<p>XML can be applied sucessfully to a wide range of uses, from long term
359structured document maintenance (where it follows the steps of SGML) to simple
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]360data encoding mechanisms like configuration file formatting (glade),
361spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where
362it is used to encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]363
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]364<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]365
366<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]367returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]368<strong>xmlDoc</strong> structure). This structure contains information such
369as the file name, the document type, and a <strong>root</strong> pointer which
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]370is the root of the document (or more exactly the first child under the root
371which is the document). The tree is made of <strong>xmlNode</strong>s, chained
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]372in double-linked lists of siblings and with childs&lt;->parent relationship.
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]373An xmlNode can also carry properties (a chain of xmlAttr structures). An
374attribute 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]375
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]376<p>Here is an example (erroneous with respect to the XML spec since there
377should be only one ELEMENT under the root):</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]378
379<p><img src="structure.gif" alt=" structure.gif "></p>
380
381<p>In the source package there is a small program (not installed by default)
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]382called <strong>tester</strong> which parses XML files given as argument and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]383prints them back as parsed. This is useful for detecting errors both in XML
384code and in the XML parser itself. It has an option <strong>--debug</strong>
385which prints the actual in-memory structure of the document, here is the
386result with the <a href="#example">example</a> given before:</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]387<pre>DOCUMENT
388version=1.0
389standalone=true
390 ELEMENT EXAMPLE
391 ATTRIBUTE prop1
392 TEXT
393 content=gnome is great
394 ATTRIBUTE prop2
395 ENTITY_REF
396 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]397 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]398 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]399 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]400 TEXT
401 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]402 ELEMENT chapter
403 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]404 TEXT
405 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]406 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]407 TEXT
408 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]409 ELEMENT image
410 ATTRIBUTE href
411 TEXT
412 content=linus.gif
413 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]414 TEXT
415 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]416
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]417<p>This should be useful for learning the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]418
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]419<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]420
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]421<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]422memory. In that case (and if you don't expect to save back the XML document
423loaded 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]424<strong>callback-based interface</strong> to the parser. Before parsing, the
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]425application layer registers a customized set of callbacks which are called by
426the library as it progresses through the XML input.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]427
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]428<p>To get more detailed step-by-step guidance on using the SAX interface of
429libxml, see the
430href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]431documentation.written by <a href="mailto:james@daa.com.au">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]432Henstridge</a>.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]433
434<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
435program located in the gnome-xml module (it's usually not shipped in the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]436binary packages of libxml, but you can find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]437distribution). Here is the sequence of callbacks that would be reported by
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]438testSAX when parsing the example XML document shown earlier:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]439<pre>SAX.setDocumentLocator()
440SAX.startDocument()
441SAX.getEntity(amp)
442SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
443SAX.characters( , 3)
444SAX.startElement(head)
445SAX.characters( , 4)
446SAX.startElement(title)
447SAX.characters(Welcome to Gnome, 16)
448SAX.endElement(title)
449SAX.characters( , 3)
450SAX.endElement(head)
451SAX.characters( , 3)
452SAX.startElement(chapter)
453SAX.characters( , 4)
454SAX.startElement(title)
455SAX.characters(The Linux adventure, 19)
456SAX.endElement(title)
457SAX.characters( , 4)
458SAX.startElement(p)
459SAX.characters(bla bla bla ..., 15)
460SAX.endElement(p)
461SAX.characters( , 4)
462SAX.startElement(image, href='linus.gif')
463SAX.endElement(image)
464SAX.characters( , 4)
465SAX.startElement(p)
466SAX.characters(..., 3)
467SAX.endElement(p)
468SAX.characters( , 3)
469SAX.endElement(chapter)
470SAX.characters( , 1)
471SAX.endElement(EXAMPLE)
472SAX.endDocument()</pre>
473
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]474<p>Most of the other functionalities of libxml are based on the DOM
475tree-building facility, so nearly everything up to the end of this document
476presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]477itself is built by a set of registered default callbacks, without internal
478specific interface.</p>
479
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]480<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]481
482<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]483using the XML library from the C language. It is not intended to be extensive.
484I hope the automatically generated documents will provide the completeness
485required, but as a separate set of documents. The interfaces of the XML
486library are by principle low level, there is nearly zero abstraction. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]487interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]488
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]489<p>The <a href="gnome-xml-parser.html">parser interfaces for XML</a> are
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]490separated from the <a href="gnome-xml-htmlparser.html">HTML parser
491interfaces</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]492
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]493<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]494
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]495<p>Usually, the first thing to do is to read an XML input. The parser accepts
496documents either from in-memory strings or from files. The functions are
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]497defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]498<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]499 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]500 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]501 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]502</dl>
503<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]504 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]505 <dd><p>Parse an XML document contained in a (possibly compressed)
506 file.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]507 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]508</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]509
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]510<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]511failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]512
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]513<h3 id="Invoking1">Invoking the parser: the push method</h3>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]514
515<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]516fetched (which is common for GUI based programs) libxml provides a push
517interface, too, as of version 1.8.3. Here are the interface functions:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]518<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
519 void *user_data,
520 const char *chunk,
521 int size,
522 const char *filename);
523int xmlParseChunk (xmlParserCtxtPtr ctxt,
524 const char *chunk,
525 int size,
526 int terminate);</pre>
527
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]528<p>and here is a simple example showing how to use the interface:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]529<pre> FILE *f;
530
531 f = fopen(filename, "r");
532 if (f != NULL) {
533 int res, size = 1024;
534 char chars[1024];
535 xmlParserCtxtPtr ctxt;
536
537 res = fread(chars, 1, 4, f);
538 if (res > 0) {
539 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
540 chars, res, filename);
541 while ((res = fread(chars, 1, size, f)) > 0) {
542 xmlParseChunk(ctxt, chars, res, 0);
543 }
544 xmlParseChunk(ctxt, chars, 0, 1);
545 doc = ctxt->myDoc;
546 xmlFreeParserCtxt(ctxt);
547 }
548 }</pre>
549
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]550<p>Also note that the HTML parser embedded into libxml also has a push
551interface; the functions are just prefixed by "html" rather than "xml"</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]552
553<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
554
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]555<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]556memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]557Reading a document without building the tree is possible using the SAX
558interfaces (see SAX.h and <a
559href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]560Henstridge's documentation</a>). Note also that the push interface can be
561limited to SAX. Just use the two first arguments of
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]562<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]563
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]564<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]565
566<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]567there is a set of functions dedicated to building new elements. (These are
568also described in "tree.h".) For example, here is a piece of code that
569produces the XML document used in the previous examples:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]570<pre> xmlDocPtr doc;
571 xmlNodePtr tree, subtree;
572
573 doc = xmlNewDoc("1.0");
574 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
575 xmlSetProp(doc->root, "prop1", "gnome is great");
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]576 xmlSetProp(doc->root, "prop2", "&amp; linux too");
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]577 tree = xmlNewChild(doc->root, NULL, "head", NULL);
578 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
579 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
580 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
581 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
582 subtree = xmlNewChild(tree, NULL, "image", NULL);
583 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]584
585<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]586
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]587<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]588
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]589<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]590has access to the internal structure of all the elements of the tree. The
591names should be somewhat simple like <strong>parent</strong>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]592<strong>childs</strong>, <strong>next</strong>, <strong>prev</strong>,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]593<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]594example:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]595<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]596
597<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]598<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]599
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]600<p>points to the text node containing the chapter title "The Linux
601adventure".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]602
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]603<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]604present before the document root, so <code>doc->root</code> may point to an
605element which is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]606<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]607
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]608<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]609
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]610<p>Functions are provided for reading and writing the document content. Here
611is an excerpt from the <a href="gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]612<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]613 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
614 xmlChar *value);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]615 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. The
616 value can be NULL.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]617 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]618</dl>
619<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]620 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]621 *name);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]622 <dd><p>This function returns a pointer to the property content. Note that
623 no extra copy is made.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]624 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]625</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]626
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]627<p>Two functions are provided for reading and writing the text associated with
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]628elements:</p>
629<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]630 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]631 *value);</code></dt>
632 <dd><p>This function takes an "external" string and convert it to one text
633 node or possibly to a list of entity and text nodes. All non-predefined
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]634 entity references like &amp;Gnome; will be stored internally as entity
635 nodes, hence the result of the function may not be a single node.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]636 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]637</dl>
638<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]639 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]640 inLine);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]641 <dd><p>This function is the inverse of
642 <code>xmlStringGetNodeList()</code>. It generates a new string
643 containing the content of the text and entity nodes. Note the extra
644 argument inLine. If this argument is set to 1, the function will expand
645 entity references. For example, instead of returning the &amp;Gnome;
646 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]647 "GNU Network Object Model Environment"). Set this argument if you want
648 to use the string for non-XML usage like User Interface.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]649 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]650</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]651
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]652<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]653
654<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]655<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]656 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]657 *size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]658 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]659 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]660</dl>
661<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]662 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]663 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]664 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]665</dl>
666<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]667 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]668 <dd><p>Saves the document to a file. In this case, the compression
669 interface is triggered if it has been turned on.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]670 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]671</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]672
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]673<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]674
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]675<p>The library transparently handles compression when doing file-based
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]676accesses. The level of compression on saves can be turned on either globally
677or individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]678<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]679 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]680 <dd><p>Gets the document compression ratio (0-9).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]681 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]682</dl>
683<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]684 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]685 <dd><p>Sets the document compression ratio.</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 Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]689 <dt><code>int xmlGetCompressMode(void);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]690 <dd><p>Gets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]691 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]692</dl>
693<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]694 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]695 <dd><p>Sets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]696 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]697</dl>
698
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]699<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]700
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]701<p>Entities in principle are similar to simple C macros. An entity defines an
702abbreviation for a given string that you can reuse many times throughout the
703content of your document. Entities are especially useful when a given string
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]704may occur frequently within a document, or to confine the change needed to a
705document to a restricted area in the internal subset of the document (at the
706beginning). Example:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]707<pre>1 &lt;?xml version="1.0"?>
7082 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
7093 &lt;!ENTITY xml "Extensible Markup Language">
7104 ]>
7115 &lt;EXAMPLE>
7126 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]7137 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]714
715<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]716it's name with '&amp;' and following it by ';' without any spaces added. There
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]717are 5 predefined entities in libxml allowing you to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]718predefined meaning in some parts of the xml document content:
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]719<strong>&amp;lt;</strong> for the character '&lt;', <strong>&amp;gt;</strong>
720for the character '>', <strong>&amp;apos;</strong> for the character ''',
721<strong>&amp;quot;</strong> for the character '"', and
722<strong>&amp;amp;</strong> for the character '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]723
724<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]725substitute an entity's content so that you can see the replacement text in
726your application. Or you may prefer to keep entity references as such in the
727content to be able to save the document back without losing this usually
728precious information (if the user went through the pain of explicitly defining
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]729entities, he may have a a rather negative attitude if you blindly susbtitute
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]730them as saving time). The <a
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]731href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]732function allows you to check and change the behaviour, which is to not
733substitute entities by default.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]734
735<p>Here is the DOM tree built by libxml for the previous document in the
736default case:</p>
737<pre>/gnome/src/gnome-xml -> ./tester --debug test/ent1
738DOCUMENT
739version=1.0
740 ELEMENT EXAMPLE
741 TEXT
742 content=
743 ENTITY_REF
744 INTERNAL_GENERAL_ENTITY xml
745 content=Extensible Markup Language
746 TEXT
747 content=</pre>
748
749<p>And here is the result when substituting entities:</p>
750<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
751DOCUMENT
752version=1.0
753 ELEMENT EXAMPLE
754 TEXT
755 content= Extensible Markup Language</pre>
756
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]757<p>So, entities or no entities? Basically, it depends on your use case. I
758suggest that you keep the non-substituting default behaviour and avoid using
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]759entities in your XML document or data if you are not willing to handle the
760entity references elements in the DOM tree.</p>
761
762<p>Note that at save time libxml enforce the conversion of the predefined
763entities where necessary to prevent well-formedness problems, and will also
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]764transparently replace those with chars (i.e., it will not generate entity
765reference elements in the DOM tree or call the reference() SAX callback when
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]766finding them in the input).</p>
767
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]768<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]769
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]770<p>The libxml library implements namespace @@ support by recognizing namespace
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]771contructs in the input, and does namespace lookup automatically when building
772the DOM tree. A namespace declaration is associated with an in-memory
773structure and all elements or attributes within that namespace point to it.
774Hence testing the namespace is a simple and fast equality operation at the
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]775user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]776
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]777<p>I suggest that people using libxml use a namespace, and declare it in the
778root element of their document as the default namespace. Then they don't need
779to use the prefix in the content but we will have a basis for future semantic
780refinement and merging of data from different sources. This doesn't augment
781significantly the size of the XML output, but significantly increase its value
782in the long-term.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]783
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]784<p>Concerning the namespace value, this has to be an URL, but the URL doesn't
785have to point to any existing resource on the Web. I suggest that it makes
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]786sense to use an URL within a domain you control, and that the URL should
787contain some kind of version information if possible. For example,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]788<code>"http://www.gnome.org/gnumeric/1.0"</code> is a good namespace scheme.
789Then when you load a file, make sure that a namespace carrying the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]790version-independent prefix is installed on the root element of your document,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]791and if the version information don't match something you know, warn the user
792and 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]793namespace checking on the prefix value. &lt;foo:text> may be exactly the same
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]794as &lt;bar:text> in another document. What really matter is the URI associated
795with the element or the attribute, not the prefix string (which is just a
796shortcut for the full URI).</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]797
798<p>@@Interfaces@@</p>
799
800<p>@@Examples@@</p>
801
802<p>Usually people object using namespace in the case of validation, I object
803this and will make sure that using namespaces won't break validity checking,
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]804so even is you plan to use or currently are using validation I strongly
805suggest adding namespaces to your document. A default namespace scheme
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]806<code>xmlns="http://...."</code> should not break validity even on less
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]807flexible parsers. Now using namespace to mix and differentiate content coming
808from multiple DTDs will certainly break current validation schemes. I will try
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]809to provide ways to do this, but this may not be portable or standardized.</p>
810
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]811<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]812
813<p>Well what is validation and what is a DTD ?</p>
814
815<p>Validation is the process of checking a document against a set of
816construction rules, a <strong>DTD</strong> (Document Type Definition) is such
817a set of rules.</p>
818
819<p>The validation process and building DTDs are the two most difficult parts
820of XML life cycle. Briefly a DTD defines all the possibles element to be
821found within your document, what is the formal shape of your document tree (by
822defining the allowed content of an element, either text, a regular expression
823for the allowed list of children, or mixed content i.e. both text and childs).
824The DTD also defines the allowed attributes for all elements and the types of
825the attributes. For more detailed informations, I suggest to read the related
826parts of the XML specification, the examples found under
827gnome-xml/test/valid/dtd and the large amount of books available on XML. The
828dia example in gnome-xml/test/valid should be both simple and complete enough
829to allow you to build your own.</p>
830
831<p>A word of warning, building a good DTD which will fit your needs of your
832application in the long-term is far from trivial, however the extra level of
833quality it can insure is well worth the price for some sets of applications or
834if you already have already a DTD defined for your application field.</p>
835
836<p>The validation is not completely finished but in a (very IMHO) usable
837state. Until a real validation interface is defined the way to do it is to
838define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
839variable to 1, this will of course be changed at some point:</p>
840
841<p>extern int xmlDoValidityCheckingDefaultValue;</p>
842
843<p>...</p>
844
845<p>xmlDoValidityCheckingDefaultValue = 1;</p>
846
847<p></p>
848
849<p>To handle external entities, use the function
850<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
851link in you HTTP/FTP/Entities database library to the standard libxml
852core.</p>
853
854<p>@@interfaces@@</p>
855
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]856<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]857
858<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]859Model</em> this is an API for accessing XML or HTML structured documents.
860Native 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]861be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]862files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]863set of IDL (or Java) interfaces allowing to traverse and manipulate a
864document. The DOM library will allow accessing and modifying "live" documents
865presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]866
867<p><img src="DOM.gif" alt=" DOM.gif "></p>
868
869<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]870embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]871
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]872<p>The current DOM implementation on top of libxml is the <a
873href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
874a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
875Levien</a>.</p>
876
877<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
878
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]879<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]880
881<p>Here is a real size example, where the actual content of the application
882data 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]883a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]884storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
885base</a>:</p>
886<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]887&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
888 &lt;gjob:Jobs>
889
890 &lt;gjob:Job>
891 &lt;gjob:Project ID="3"/>
892 &lt;gjob:Application>GBackup&lt;/gjob:Application>
893 &lt;gjob:Category>Development&lt;/gjob:Category>
894
895 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]896 &lt;gjob:Status>Open&lt;/gjob:Status>
897 &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]898 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
899 &lt;/gjob:Update>
900
901 &lt;gjob:Developers>
902 &lt;gjob:Developer>
903 &lt;/gjob:Developer>
904 &lt;/gjob:Developers>
905
906 &lt;gjob:Contact>
907 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]908 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]909 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]910 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]911 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]912 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]913 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]914 &lt;/gjob:Webpage>
915 &lt;gjob:Snailmail>
916 &lt;/gjob:Snailmail>
917 &lt;gjob:Phone>
918 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]919 &lt;/gjob:Contact>
920
921 &lt;gjob:Requirements>
922 The program should be released as free software, under the GPL.
923 &lt;/gjob:Requirements>
924
925 &lt;gjob:Skills>
926 &lt;/gjob:Skills>
927
928 &lt;gjob:Details>
929 A GNOME based system that will allow a superuser to configure
930 compressed and uncompressed files and/or file systems to be backed
931 up with a supported media in the system. This should be able to
932 perform via find commands generating a list of files that are passed
933 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
934 or via operations performed on the filesystem itself. Email
935 notification and GUI status display very important.
936 &lt;/gjob:Details>
937
938 &lt;/gjob:Job>
939
940 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]941&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]942
943<p>While loading the XML file into an internal DOM tree is a matter of calling
944only a couple of functions, browsing the tree to gather the informations and
945generate the internals structures is harder, and more error prone.</p>
946
947<p>The suggested principle is to be tolerant with respect to the input
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]948structure. For example, the ordering of the attributes is not significant,
949Cthe XML specification is clear about it. It's also usually a good idea to not
950be dependent of the orders of the childs of a given node, unless it really
951makes things harder. Here is some code to parse the informations for a
952person:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]953<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]954 * A person record
955 */
956typedef struct person {
957 char *name;
958 char *email;
959 char *company;
960 char *organisation;
961 char *smail;
962 char *webPage;
963 char *phone;
964} person, *personPtr;
965
966/*
967 * And the code needed to parse it
968 */
969personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
970 personPtr ret = NULL;
971
972DEBUG("parsePerson\n");
973 /*
974 * allocate the struct
975 */
976 ret = (personPtr) malloc(sizeof(person));
977 if (ret == NULL) {
978 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]979 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]980 }
981 memset(ret, 0, sizeof(person));
982
983 /* We don't care what the top level element name is */
984 cur = cur->childs;
985 while (cur != NULL) {
986 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]987 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]988 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]989 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
990 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]991 }
992
993 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]994}</pre>
995
996<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]997<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]998 <li>Usually a recursive parsing style is the more convenient one, XML data
999 being by nature subject to repetitive constructs and usualy exibit highly
1000 stuctured patterns.</li>
1001 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
1002 the pointer to the global XML document and the namespace reserved to the
1003 application. Document wide information are needed for example to decode
1004 entities and it's a good coding practice to define a namespace for your
1005 application set of data and test that the element and attributes you're
1006 analyzing actually pertains to your application space. This is done by a
1007 simple equality test (cur->ns == ns).</li>
1008 <li>To retrieve text and attributes value, it is suggested to use the
1009 function <em>xmlNodeListGetString</em> to gather all the text and entity
1010 reference nodes generated by the DOM output and produce an single text
1011 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1012</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1013
1014<p>Here is another piece of code used to parse another level of the
1015structure:</p>
1016<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1017 * a Description for a Job
1018 */
1019typedef struct job {
1020 char *projectID;
1021 char *application;
1022 char *category;
1023 personPtr contact;
1024 int nbDevelopers;
1025 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
1026} job, *jobPtr;
1027
1028/*
1029 * And the code needed to parse it
1030 */
1031jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1032 jobPtr ret = NULL;
1033
1034DEBUG("parseJob\n");
1035 /*
1036 * allocate the struct
1037 */
1038 ret = (jobPtr) malloc(sizeof(job));
1039 if (ret == NULL) {
1040 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1041 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1042 }
1043 memset(ret, 0, sizeof(job));
1044
1045 /* We don't care what the top level element name is */
1046 cur = cur->childs;
1047 while (cur != NULL) {
1048
1049 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1050 ret->projectID = xmlGetProp(cur, "ID");
1051 if (ret->projectID == NULL) {
1052 fprintf(stderr, "Project has no ID\n");
1053 }
1054 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1055 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1056 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1057 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1058 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1059 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1060 ret->contact = parsePerson(doc, ns, cur);
1061 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1062 }
1063
1064 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1065}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1066
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1067<p>One can notice that once used to it, writing this kind of code is quite
1068simple, but boring. Ultimately, it could be possble to write stubbers taking
1069either C data structure definitions, a set of XML examples or an XML DTD and
1070produce the code needed to import and export the content between C data and
1071XML storage. This is left as an exercise to the reader :-)</p>
1072
1073<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]1074example</a> as a template, it is also available with Makefile in the Gnome CVS
1075base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1076
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1077<p></p>
1078
1079<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1080
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame^]1081<p>$Id: xml.html,v 1.28 2000/03/06 07:41:49 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1082</body>
1083</html>