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blob: 6504b94901d08dcf9eb0298e3d9e6a29a18b98ff [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 Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]11<p><a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome
12Logo"></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C
13Logo"></a></p>
14
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]15<h1 align="center">The XML library for Gnome</h1>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]16
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]17<h2 style="text-align: center">libxml, a.k.a. gnome-xml</h2>
18
19<p></p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]20<ul>
21 <li><a href="#Introducti">Introduction</a></li>
22 <li><a href="#Documentat">Documentation</a></li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]23 <li><a href="#Downloads">Downloads</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]24 <li><a href="#News">News</a></li>
25 <li><a href="#XML">XML</a></li>
26 <li><a href="#tree">The tree output</a></li>
27 <li><a href="#interface">The SAX interface</a></li>
28 <li><a href="#library">The XML library interfaces</a>
29 <ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]30 <li><a href="#Invoking">Invoking the parser: the pull way</a></li>
31 <li><a href="#Invoking">Invoking the parser: the push way</a></li>
32 <li><a href="#Invoking2">Invoking the parser: the SAX interface</a></li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]33 <li><a href="#Building">Building a tree from scratch</a></li>
34 <li><a href="#Traversing">Traversing the tree</a></li>
35 <li><a href="#Modifying">Modifying the tree</a></li>
36 <li><a href="#Saving">Saving the tree</a></li>
37 <li><a href="#Compressio">Compression</a></li>
38 </ul>
39 </li>
40 <li><a href="#Entities">Entities or no entities</a></li>
41 <li><a href="#Namespaces">Namespaces</a></li>
42 <li><a href="#Validation">Validation</a></li>
43 <li><a href="#Principles">DOM principles</a></li>
44 <li><a href="#real">A real example</a></li>
45</ul>
46
47<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]48
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]49<p>This document describes libxml, the <a
50href="http://www.w3.org/XML/">XML</a> library provided in the <a
51href="http://www.gnome.org/">Gnome</a> framework. XML is a standard for
52building tag-based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]53
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]54<p>Here are some key points about libxml:</p>
55<ul>
56 <li>The internal document repesentation is as close as possible to the <a
57 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li>
58 <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]59 like interface</a>; the interface is designed to be compatible with <a
60 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]61 <li>Libxml now includes a nearly complete <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]62 href="http://www.w3.org/TR/xpath">XPath</a> implementation.</li>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]63 <li>Libxml exports Push and Pull type parser interfaces for both XML and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]64 HTML.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]65 <li>This library is released both under the <a
66 href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
67 IPR</a> and the GNU LGPL. Use either at your convenience, basically this
68 should make everybody happy, if not, drop me a mail.</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]69 <li>There is <a href="upgrade.html">a first set of instruction</a>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]70 concerning upgrade from libxml-1.x to libxml-2.x</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]71</ul>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]72
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]73<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]74
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]75<p>There are some on-line resources about using libxml:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]76<ol>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]77 <li>The code is commented in a way which allows <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]78 href="http://xmlsoft.org/libxml.html">extensive documentation</a> to be
79 automatically extracted.</li>
80 <li>This page provides a global overview and <a href="#real">some
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]81 examples</a> on how to use libxml.</li>
82 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a
83 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice
84 documentation</a> explaining how to use the libxml SAX interface.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]85 <li>George Lebl wrote <a
86 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]87 for IBM developerWorks</a> about using libxml.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]88 <li>It is also a good idea to check to <a href="mailto:raph@levien.com">Raph
89 Levien</a> <a href="http://levien.com/gnome/">web site</a> since he is
90 building the <a href="http://levien.com/gnome/gdome.html">DOM interface
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]91 gdome</a> on top of libxml result tree and an implementation of <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]92 href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
93 href="http://www.levien.com/svg/">gill</a>. Check his <a
94 href="http://www.levien.com/gnome/domination.html">DOMination
95 paper</a>.</li>
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]96 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO
97 file</a></li>
98 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a>. If you are
99 starting a new project using libxml you should really use the 2.x
100 version.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]101 <li>And don't forget to look at the <a href="/messages/">mailing-list
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]102 archive</a>, too.</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]103</ol>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]104
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]105<h3>Reporting bugs and getting help</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]106
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]107<p>Well, bugs or missing features are always possible, and I will make a point
108of fixing them in a timely fashion. The best way to report a bug is to <a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]109href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]110database</a>. I look at reports there regularly and it's good to have a
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]111reminder when a bug is still open. Check the <a
112href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]113and be sure to specify that the bug is for the package gnome-xml.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]114
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]115<p>There is also a mailing-list <a
116href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
117href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]118majordomo based list, send a mail message to <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]119href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
120"subscribe xml" in the <strong>content</strong> of the message.</p>
121
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]122<p>Alternatively, you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]123href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]124
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]125<p>Of course, bugs reports with a suggested patch for fixing them will
126probably be processed faster.</p>
127
128<p>If you're looking for help, a quick look at <a
129href="http://xmlsoft.org/messages/#407">the list archive</a> may actually
130provide the answer, I usually send source samples when answering libxml usage
131questions. The <a href="http://xmlsoft.org/book1.html">auto-generated
132documentantion</a> is not as polished as I would like (i need to learn more
133about Docbook), but it's a good starting point.</p>
134
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]135<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]136
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]137<p>The latest versions of libxml can be found on <a
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]138href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or on the <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]139href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]140as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]141archive</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/contrib/rpms/">RPMs
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]142packages</a>. (NOTE that you need both the <a
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]143href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a
144href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]145packages installed to compile applications using libxml.)</p>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]146
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]147<p><a name="Snapshot">Snapshot:</a></p>
148<ul>
149 <li>Code from the W3C cvs base libxml <a
150 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li>
151 <li>Docs, content of the web site, the list archive included <a
152 href="ftp://rpmfind.net/pub/libxml/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li>
153</ul>
154
155<p><a name="Contribs">Contribs:</a></p>
156
157<p>I do accept external contributions, especially if compiling on another
158platform, get in touch with me to upload the package. I will keep them in the
159<a href="ftp://rpmfind.net/pub/libxml/contribs/">contrib directory</a></p>
160
161<p>Libxml is also available from 2 CVs bases:</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]162<ul>
163 <li><p>The <a href="http://dev.w3.org/cvsweb/XML/">W3C CVS base</a>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]164 available read-only using the CVS pserver authentification (I tend to use
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]165 this base for my own development, so it's updated more regularly, but the
166 content may not be as stable):</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]167 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]168 password: anonymous
169 module: XML</pre>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]170 </li>
171 <li><p>The <a
172 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&amp;dir=gnome-xml">Gnome
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]173 CVS base</a>. Check the <a
174 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page;
175 the CVS module is <b>gnome-xml</b>.</p>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]176 </li>
177</ul>
178
179<h2><a name="News">News</a></h2>
180
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]181<h3>CVS only : check the <a
182href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
183for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]184<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]185 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]186 if you want to test those.</li>
Daniel Veillard8f621982000-03-20 13:07:15 +0000[diff] [blame]187 <li>a new URI module for parsing URIs and following strictly RFC 2396</li>
188 <li>the memory allocation routines used by libxml can now be overloaded
189 dynamically by using xmlMemSetup()</li>
190 <li>So far the feedback on the libxml2 beta is positive</li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]191</ul>
192
193<h3>2.0.0beta: Mar 14 2000</h3>
194<ul>
195 <li>This is a first Beta release of libxml version 2</li>
196 <li>It's available only from<a href="ftp://rpmfind.net/pub/libxml/">
197 rpmfind.net FTP</a>, it's packaged as libxml2-2.0.0beta and available as
198 tar and RPMs</li>
199 <li>This version is now the head in the Gnome CVS base, the old one is
200 available under the tag LIB_XML_1_X</li>
201 <li>This includes a very large set of changes. Froma programmatic point of
202 view applications should not have to be modified too much, check the <a
203 href="upgrade.html">upgrade page</a></li>
204 <li>Some interfaces may changes (especially a bit about encoding).</li>
205 <li>the updates includes:
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]206 <ul>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]207 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly
208 handled now</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]209 <li>Better handling of entities, especially well formedness checking and
210 proper PEref extensions in external subsets</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]211 <li>DTD conditional sections</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]212 <li>Validation now correcly handle entities content</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]213 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
214 structures to accomodate DOM</a></li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]215 </ul>
216 </li>
Daniel Veillardedfb29b2000-03-14 19:59:05 +0000[diff] [blame]217 <li>Serious progress were made toward compliance, <a
218 href="conf/result.html">here are the result of the test</a> against the
219 OASIS testsuite (except the japanese tests since I don't support that
220 encoding yet). This URL is rebuilt every couple of hours using the CVS
221 head version.</li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]222</ul>
223
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]224<h3>1.8.7: Mar 6 2000</h3>
225<ul>
226 <li>This is a bug fix release:</li>
227 <li>It is possible to disable the ignorable blanks heuristic used by
228 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note
229 that for adherence to XML spec, this behaviour will be disabled by default
230 in 2.x . The same function will allow to keep compatibility for old
231 code.</li>
232 <li>Blanks in &lt;a> &lt;/a> constructs are not ignored anymore, avoiding
233 heuristic is really the Right Way :-\</li>
234 <li>The unchecked use of snprintf which was breaking libxml-1.8.6
235 compilation on some platforms has been fixed</li>
236 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing
237 URIs</li>
238</ul>
239
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]240<h3>1.8.6: Jan 31 2000</h3>
241<ul>
242 <li>added a nanoFTP transport module, debugged until the new version of <a
243 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
244 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000[diff] [blame]245</ul>
246
247<h3>1.8.5: Jan 21 2000</h3>
248<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]249 <li>adding APIs to parse a well balanced chunk of XML (production <a
250 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
251 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000[diff] [blame]252 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
253 <li>Jody Goldberg &lt;jgoldberg@home.com> provided another patch trying to
254 solve the zlib checks problems</li>
255 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
256 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]257</ul>
258
259<h3>1.8.4: Jan 13 2000</h3>
260<ul>
261 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
262 <li>all exit() call should have been removed from libxml</li>
263 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
264 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]265</ul>
266
267<h3>1.8.3: Jan 5 2000</h3>
268<ul>
269 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]270 <li>a shell-like interface to the document tree (try tester --shell :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame]271 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]272 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]273 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
274 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]275 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]276 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]277 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]278</ul>
279
280<h3>1.8.2: Dec 21 1999</h3>
281<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]282 <li>I got another problem with includes and C++, I hope this issue is fixed
283 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]284 <li>Added a few tree modification functions: xmlReplaceNode,
285 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
286 xmlDocSetRootElement</li>
287 <li>Tried to improve the HTML output with help from <a
288 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]289</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]290
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]291<h3>1.8.1: Dec 18 1999</h3>
292<ul>
293 <li>various patches to avoid troubles when using libxml with C++ compilers
294 the "namespace" keyword and C escaping in include files</li>
295 <li>a problem in one of the core macros IS_CHAR was corrected</li>
296 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
297 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]298 <li>fixed a posteriori validation (validation after parsing, or by using a
299 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]300 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]301</ul>
302
303<h3>1.8.0: Dec 12 1999</h3>
304<ul>
305 <li>cleanup, especially memory wise</li>
306 <li>the parser should be more reliable, especially the HTML one, it should
307 not crash, whatever the input !</li>
308 <li>Integrated various patches, especially a speedup improvement for large
309 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
310 configure with --with-buffers to enable them.</li>
311 <li>attribute normalization, oops should have been added long ago !</li>
312 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
313 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]314</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]315
316<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]317<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]318 <li>Lots of HTML improvement</li>
319 <li>Fixed some errors when saving both XML and HTML</li>
320 <li>More examples, the regression tests should now look clean</li>
321 <li>Fixed a bug with contiguous charref</li>
322</ul>
323
324<h3>1.7.3: Sep 29 1999</h3>
325<ul>
326 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]327 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]328 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]329</ul>
330
331<h3>1.7.1: Sep 24 1999</h3>
332<ul>
333 <li>The basic type for strings manipulated by libxml has been renamed in
334 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
335 is that CHAR was conflicting with a predefined type on Windows. However on
336 non WIN32 environment, compatibility is provided by the way of a
337 <strong>#define </strong>.</li>
338 <li>Changed another error : the use of a structure field called errno, and
339 leading to troubles on platforms where it's a macro</li>
340</ul>
341
342<h3>1.7.0: sep 23 1999</h3>
343<ul>
344 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
345 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
346 <li>Added an errno to report errors by another mean than a simple printf
347 like callback</li>
348 <li>Finished ID/IDREF support and checking when validation</li>
349 <li>Serious memory leaks fixed (there is now a <a
350 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
351 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
352 implementation</li>
353 <li>Added an HTML parser front-end</li>
354</ul>
355
356<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]357
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]358<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]359markup-based structured documents. Here is <a name="example">an example XML
360document</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]361<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]362&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]363 &lt;head>
364 &lt;title>Welcome to Gnome&lt;/title>
365 &lt;/head>
366 &lt;chapter>
367 &lt;title>The Linux adventure&lt;/title>
368 &lt;p>bla bla bla ...&lt;/p>
369 &lt;image href="linus.gif"/>
370 &lt;p>...&lt;/p>
371 &lt;/chapter>
372&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]373
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]374<p>The first line specifies that it's an XML document and gives useful
375information about its encoding. Then the document is a text format whose
376structure is specified by tags between brackets. <strong>Each tag opened has
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]377to be closed</strong>. XML is pedantic about this. However, if a tag is empty
378(no content), a single tag can serve as both the opening and closing tag if it
379ends with <code>/></code> rather than with <code>></code>. Note that, for
380example, the image tag has no content (just an attribute) and is closed by
381ending the tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]382
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]383<p>XML can be applied sucessfully to a wide range of uses, from long term
384structured document maintenance (where it follows the steps of SGML) to simple
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]385data encoding mechanisms like configuration file formatting (glade),
386spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where
387it is used to encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]388
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]389<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]390
391<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]392returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]393<strong>xmlDoc</strong> structure). This structure contains information such
394as the file name, the document type, and a <strong>root</strong> pointer which
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]395is the root of the document (or more exactly the first child under the root
396which is the document). The tree is made of <strong>xmlNode</strong>s, chained
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]397in double-linked lists of siblings and with childs&lt;->parent relationship.
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]398An xmlNode can also carry properties (a chain of xmlAttr structures). An
399attribute 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]400
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]401<p>Here is an example (erroneous with respect to the XML spec since there
402should be only one ELEMENT under the root):</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]403
404<p><img src="structure.gif" alt=" structure.gif "></p>
405
406<p>In the source package there is a small program (not installed by default)
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]407called <strong>tester</strong> which parses XML files given as argument and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]408prints them back as parsed. This is useful for detecting errors both in XML
409code and in the XML parser itself. It has an option <strong>--debug</strong>
410which prints the actual in-memory structure of the document, here is the
411result with the <a href="#example">example</a> given before:</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]412<pre>DOCUMENT
413version=1.0
414standalone=true
415 ELEMENT EXAMPLE
416 ATTRIBUTE prop1
417 TEXT
418 content=gnome is great
419 ATTRIBUTE prop2
420 ENTITY_REF
421 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]422 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]423 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]424 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]425 TEXT
426 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]427 ELEMENT chapter
428 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]429 TEXT
430 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]431 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]432 TEXT
433 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]434 ELEMENT image
435 ATTRIBUTE href
436 TEXT
437 content=linus.gif
438 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]439 TEXT
440 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]441
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]442<p>This should be useful for learning the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]443
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]444<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]445
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]446<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]447memory. In that case (and if you don't expect to save back the XML document
448loaded 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]449<strong>callback-based interface</strong> to the parser. Before parsing, the
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]450application layer registers a customized set of callbacks which are called by
451the library as it progresses through the XML input.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]452
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]453<p>To get more detailed step-by-step guidance on using the SAX interface of
454libxml, see the
455href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]456documentation.written by <a href="mailto:james@daa.com.au">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]457Henstridge</a>.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]458
459<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
460program located in the gnome-xml module (it's usually not shipped in the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]461binary packages of libxml, but you can find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]462distribution). Here is the sequence of callbacks that would be reported by
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]463testSAX when parsing the example XML document shown earlier:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]464<pre>SAX.setDocumentLocator()
465SAX.startDocument()
466SAX.getEntity(amp)
467SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
468SAX.characters( , 3)
469SAX.startElement(head)
470SAX.characters( , 4)
471SAX.startElement(title)
472SAX.characters(Welcome to Gnome, 16)
473SAX.endElement(title)
474SAX.characters( , 3)
475SAX.endElement(head)
476SAX.characters( , 3)
477SAX.startElement(chapter)
478SAX.characters( , 4)
479SAX.startElement(title)
480SAX.characters(The Linux adventure, 19)
481SAX.endElement(title)
482SAX.characters( , 4)
483SAX.startElement(p)
484SAX.characters(bla bla bla ..., 15)
485SAX.endElement(p)
486SAX.characters( , 4)
487SAX.startElement(image, href='linus.gif')
488SAX.endElement(image)
489SAX.characters( , 4)
490SAX.startElement(p)
491SAX.characters(..., 3)
492SAX.endElement(p)
493SAX.characters( , 3)
494SAX.endElement(chapter)
495SAX.characters( , 1)
496SAX.endElement(EXAMPLE)
497SAX.endDocument()</pre>
498
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]499<p>Most of the other functionalities of libxml are based on the DOM
500tree-building facility, so nearly everything up to the end of this document
501presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]502itself is built by a set of registered default callbacks, without internal
503specific interface.</p>
504
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]505<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]506
507<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]508using the XML library from the C language. It is not intended to be extensive.
509I hope the automatically generated documents will provide the completeness
510required, but as a separate set of documents. The interfaces of the XML
511library are by principle low level, there is nearly zero abstraction. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]512interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]513
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]514<p>The <a href="gnome-xml-parser.html">parser interfaces for XML</a> are
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]515separated from the <a href="gnome-xml-htmlparser.html">HTML parser
516interfaces</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]517
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]518<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]519
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]520<p>Usually, the first thing to do is to read an XML input. The parser accepts
521documents either from in-memory strings or from files. The functions are
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]522defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]523<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]524 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]525 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]526 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]527</dl>
528<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]529 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]530 <dd><p>Parse an XML document contained in a (possibly compressed)
531 file.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]532 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]533</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]534
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]535<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]536failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]537
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]538<h3 id="Invoking1">Invoking the parser: the push method</h3>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]539
540<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]541fetched (which is common for GUI based programs) libxml provides a push
542interface, too, as of version 1.8.3. Here are the interface functions:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]543<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
544 void *user_data,
545 const char *chunk,
546 int size,
547 const char *filename);
548int xmlParseChunk (xmlParserCtxtPtr ctxt,
549 const char *chunk,
550 int size,
551 int terminate);</pre>
552
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]553<p>and here is a simple example showing how to use the interface:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]554<pre> FILE *f;
555
556 f = fopen(filename, "r");
557 if (f != NULL) {
558 int res, size = 1024;
559 char chars[1024];
560 xmlParserCtxtPtr ctxt;
561
562 res = fread(chars, 1, 4, f);
563 if (res > 0) {
564 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
565 chars, res, filename);
566 while ((res = fread(chars, 1, size, f)) > 0) {
567 xmlParseChunk(ctxt, chars, res, 0);
568 }
569 xmlParseChunk(ctxt, chars, 0, 1);
570 doc = ctxt->myDoc;
571 xmlFreeParserCtxt(ctxt);
572 }
573 }</pre>
574
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]575<p>Also note that the HTML parser embedded into libxml also has a push
576interface; the functions are just prefixed by "html" rather than "xml"</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]577
578<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
579
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]580<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]581memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]582Reading a document without building the tree is possible using the SAX
583interfaces (see SAX.h and <a
584href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]585Henstridge's documentation</a>). Note also that the push interface can be
586limited to SAX. Just use the two first arguments of
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]587<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]588
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]589<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]590
591<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]592there is a set of functions dedicated to building new elements. (These are
593also described in "tree.h".) For example, here is a piece of code that
594produces the XML document used in the previous examples:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]595<pre> xmlDocPtr doc;
596 xmlNodePtr tree, subtree;
597
598 doc = xmlNewDoc("1.0");
599 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
600 xmlSetProp(doc->root, "prop1", "gnome is great");
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]601 xmlSetProp(doc->root, "prop2", "&amp; linux too");
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]602 tree = xmlNewChild(doc->root, NULL, "head", NULL);
603 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
604 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
605 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
606 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
607 subtree = xmlNewChild(tree, NULL, "image", NULL);
608 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]609
610<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]611
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]612<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]613
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]614<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]615has access to the internal structure of all the elements of the tree. The
616names should be somewhat simple like <strong>parent</strong>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]617<strong>childs</strong>, <strong>next</strong>, <strong>prev</strong>,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]618<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]619example:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]620<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]621
622<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]623<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]624
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]625<p>points to the text node containing the chapter title "The Linux
626adventure".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]627
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]628<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]629present before the document root, so <code>doc->root</code> may point to an
630element which is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]631<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]632
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]633<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]634
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]635<p>Functions are provided for reading and writing the document content. Here
636is an excerpt from the <a href="gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]637<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]638 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
639 xmlChar *value);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]640 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. The
641 value can be NULL.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]642 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]643</dl>
644<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]645 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]646 *name);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]647 <dd><p>This function returns a pointer to the property content. Note that
648 no extra copy is made.</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 Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]651
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]652<p>Two functions are provided for reading and writing the text associated with
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]653elements:</p>
654<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]655 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]656 *value);</code></dt>
657 <dd><p>This function takes an "external" string and convert it to one text
658 node or possibly to a list of entity and text nodes. All non-predefined
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]659 entity references like &amp;Gnome; will be stored internally as entity
660 nodes, hence the result of the function may not be a single node.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]661 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]662</dl>
663<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]664 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]665 inLine);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]666 <dd><p>This function is the inverse of
667 <code>xmlStringGetNodeList()</code>. It generates a new string
668 containing the content of the text and entity nodes. Note the extra
669 argument inLine. If this argument is set to 1, the function will expand
670 entity references. For example, instead of returning the &amp;Gnome;
671 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]672 "GNU Network Object Model Environment"). Set this argument if you want
673 to use the string for non-XML usage like User Interface.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]674 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]675</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]676
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]677<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]678
679<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]680<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]681 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]682 *size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]683 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]684 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]685</dl>
686<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]687 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]688 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]689 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]690</dl>
691<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]692 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]693 <dd><p>Saves the document to a file. In this case, the compression
694 interface is triggered if it has been turned on.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]695 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]696</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]697
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]698<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]699
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]700<p>The library transparently handles compression when doing file-based
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]701accesses. The level of compression on saves can be turned on either globally
702or individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]703<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]704 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]705 <dd><p>Gets the document compression ratio (0-9).</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 Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]709 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]710 <dd><p>Sets the document compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]711 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]712</dl>
713<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]714 <dt><code>int xmlGetCompressMode(void);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]715 <dd><p>Gets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]716 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]717</dl>
718<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]719 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]720 <dd><p>Sets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]721 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]722</dl>
723
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]724<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]725
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]726<p>Entities in principle are similar to simple C macros. An entity defines an
727abbreviation for a given string that you can reuse many times throughout the
728content of your document. Entities are especially useful when a given string
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]729may occur frequently within a document, or to confine the change needed to a
730document to a restricted area in the internal subset of the document (at the
731beginning). Example:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]732<pre>1 &lt;?xml version="1.0"?>
7332 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
7343 &lt;!ENTITY xml "Extensible Markup Language">
7354 ]>
7365 &lt;EXAMPLE>
7376 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]7387 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]739
740<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]741it's name with '&amp;' and following it by ';' without any spaces added. There
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]742are 5 predefined entities in libxml allowing you to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]743predefined meaning in some parts of the xml document content:
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]744<strong>&amp;lt;</strong> for the character '&lt;', <strong>&amp;gt;</strong>
745for the character '>', <strong>&amp;apos;</strong> for the character ''',
746<strong>&amp;quot;</strong> for the character '"', and
747<strong>&amp;amp;</strong> for the character '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]748
749<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]750substitute an entity's content so that you can see the replacement text in
751your application. Or you may prefer to keep entity references as such in the
752content to be able to save the document back without losing this usually
753precious information (if the user went through the pain of explicitly defining
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]754entities, he may have a a rather negative attitude if you blindly susbtitute
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]755them as saving time). The <a
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]756href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]757function allows you to check and change the behaviour, which is to not
758substitute entities by default.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]759
760<p>Here is the DOM tree built by libxml for the previous document in the
761default case:</p>
762<pre>/gnome/src/gnome-xml -> ./tester --debug test/ent1
763DOCUMENT
764version=1.0
765 ELEMENT EXAMPLE
766 TEXT
767 content=
768 ENTITY_REF
769 INTERNAL_GENERAL_ENTITY xml
770 content=Extensible Markup Language
771 TEXT
772 content=</pre>
773
774<p>And here is the result when substituting entities:</p>
775<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
776DOCUMENT
777version=1.0
778 ELEMENT EXAMPLE
779 TEXT
780 content= Extensible Markup Language</pre>
781
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]782<p>So, entities or no entities? Basically, it depends on your use case. I
783suggest that you keep the non-substituting default behaviour and avoid using
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]784entities in your XML document or data if you are not willing to handle the
785entity references elements in the DOM tree.</p>
786
787<p>Note that at save time libxml enforce the conversion of the predefined
788entities where necessary to prevent well-formedness problems, and will also
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]789transparently replace those with chars (i.e., it will not generate entity
790reference elements in the DOM tree or call the reference() SAX callback when
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]791finding them in the input).</p>
792
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]793<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]794
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]795<p>The libxml library implements <a
796href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by
797recognizing namespace contructs in the input, and does namespace lookup
798automatically when building the DOM tree. A namespace declaration is
799associated with an in-memory structure and all elements or attributes within
800that namespace point to it. Hence testing the namespace is a simple and fast
801equality operation at the user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]802
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]803<p>I suggest that people using libxml use a namespace, and declare it in the
804root element of their document as the default namespace. Then they don't need
805to use the prefix in the content but we will have a basis for future semantic
806refinement and merging of data from different sources. This doesn't augment
807significantly the size of the XML output, but significantly increase its value
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]808in the long-term. Example:</p>
809<pre>&lt;mydoc xmlns="http://mydoc.example.org/schemas/">
810 &lt;elem1>...&lt;/elem1>
811 &lt;elem2>...&lt;/elem2>
812&lt;/mydoc></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]813
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]814<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^]815have to point to any existing resource on the Web. It will bind all the
816element and atributes with that URL. I suggest to use an URL within a domain
817you control, and that the URL should contain some kind of version information
818if possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is
819a good namespace scheme. </p>
820
821<p>Then when you load a file, make sure that a namespace carrying the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]822version-independent prefix is installed on the root element of your document,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]823and if the version information don't match something you know, warn the user
824and 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]825namespace checking on the prefix value. &lt;foo:text> may be exactly the same
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]826as &lt;bar:text> in another document. What really matter is the URI associated
827with the element or the attribute, not the prefix string (which is just a
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]828shortcut for the full URI). In libxml element and attributes have a
829<code>ns</code> field pointing to an xmlNs structure detailing the namespace
830prefix and it's URI.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]831
832<p>@@Interfaces@@</p>
833
834<p>@@Examples@@</p>
835
836<p>Usually people object using namespace in the case of validation, I object
837this and will make sure that using namespaces won't break validity checking,
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]838so even is you plan to use or currently are using validation I strongly
839suggest adding namespaces to your document. A default namespace scheme
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]840<code>xmlns="http://...."</code> should not break validity even on less
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]841flexible parsers. Now using namespace to mix and differentiate content coming
842from multiple DTDs will certainly break current validation schemes. I will try
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]843to provide ways to do this, but this may not be portable or standardized.</p>
844
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]845<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]846
847<p>Well what is validation and what is a DTD ?</p>
848
849<p>Validation is the process of checking a document against a set of
850construction rules, a <strong>DTD</strong> (Document Type Definition) is such
851a set of rules.</p>
852
853<p>The validation process and building DTDs are the two most difficult parts
854of XML life cycle. Briefly a DTD defines all the possibles element to be
855found within your document, what is the formal shape of your document tree (by
856defining the allowed content of an element, either text, a regular expression
857for the allowed list of children, or mixed content i.e. both text and childs).
858The DTD also defines the allowed attributes for all elements and the types of
859the attributes. For more detailed informations, I suggest to read the related
860parts of the XML specification, the examples found under
861gnome-xml/test/valid/dtd and the large amount of books available on XML. The
862dia example in gnome-xml/test/valid should be both simple and complete enough
863to allow you to build your own.</p>
864
865<p>A word of warning, building a good DTD which will fit your needs of your
866application in the long-term is far from trivial, however the extra level of
867quality it can insure is well worth the price for some sets of applications or
868if you already have already a DTD defined for your application field.</p>
869
870<p>The validation is not completely finished but in a (very IMHO) usable
871state. Until a real validation interface is defined the way to do it is to
872define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
873variable to 1, this will of course be changed at some point:</p>
874
875<p>extern int xmlDoValidityCheckingDefaultValue;</p>
876
877<p>...</p>
878
879<p>xmlDoValidityCheckingDefaultValue = 1;</p>
880
881<p></p>
882
883<p>To handle external entities, use the function
884<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
885link in you HTTP/FTP/Entities database library to the standard libxml
886core.</p>
887
888<p>@@interfaces@@</p>
889
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]890<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]891
892<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]893Model</em> this is an API for accessing XML or HTML structured documents.
894Native 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]895be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]896files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]897set of IDL (or Java) interfaces allowing to traverse and manipulate a
898document. The DOM library will allow accessing and modifying "live" documents
899presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]900
901<p><img src="DOM.gif" alt=" DOM.gif "></p>
902
903<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]904embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]905
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]906<p>The current DOM implementation on top of libxml is the <a
907href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
908a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
909Levien</a>.</p>
910
911<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
912
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]913<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]914
915<p>Here is a real size example, where the actual content of the application
916data 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]917a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]918storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
919base</a>:</p>
920<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]921&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
922 &lt;gjob:Jobs>
923
924 &lt;gjob:Job>
925 &lt;gjob:Project ID="3"/>
926 &lt;gjob:Application>GBackup&lt;/gjob:Application>
927 &lt;gjob:Category>Development&lt;/gjob:Category>
928
929 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]930 &lt;gjob:Status>Open&lt;/gjob:Status>
931 &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]932 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
933 &lt;/gjob:Update>
934
935 &lt;gjob:Developers>
936 &lt;gjob:Developer>
937 &lt;/gjob:Developer>
938 &lt;/gjob:Developers>
939
940 &lt;gjob:Contact>
941 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]942 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]943 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]944 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]945 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]946 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]947 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]948 &lt;/gjob:Webpage>
949 &lt;gjob:Snailmail>
950 &lt;/gjob:Snailmail>
951 &lt;gjob:Phone>
952 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]953 &lt;/gjob:Contact>
954
955 &lt;gjob:Requirements>
956 The program should be released as free software, under the GPL.
957 &lt;/gjob:Requirements>
958
959 &lt;gjob:Skills>
960 &lt;/gjob:Skills>
961
962 &lt;gjob:Details>
963 A GNOME based system that will allow a superuser to configure
964 compressed and uncompressed files and/or file systems to be backed
965 up with a supported media in the system. This should be able to
966 perform via find commands generating a list of files that are passed
967 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
968 or via operations performed on the filesystem itself. Email
969 notification and GUI status display very important.
970 &lt;/gjob:Details>
971
972 &lt;/gjob:Job>
973
974 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]975&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]976
977<p>While loading the XML file into an internal DOM tree is a matter of calling
978only a couple of functions, browsing the tree to gather the informations and
979generate the internals structures is harder, and more error prone.</p>
980
981<p>The suggested principle is to be tolerant with respect to the input
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame]982structure. For example, the ordering of the attributes is not significant,
983Cthe XML specification is clear about it. It's also usually a good idea to not
984be dependent of the orders of the childs of a given node, unless it really
985makes things harder. Here is some code to parse the informations for a
986person:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]987<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]988 * A person record
989 */
990typedef struct person {
991 char *name;
992 char *email;
993 char *company;
994 char *organisation;
995 char *smail;
996 char *webPage;
997 char *phone;
998} person, *personPtr;
999
1000/*
1001 * And the code needed to parse it
1002 */
1003personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1004 personPtr ret = NULL;
1005
1006DEBUG("parsePerson\n");
1007 /*
1008 * allocate the struct
1009 */
1010 ret = (personPtr) malloc(sizeof(person));
1011 if (ret == NULL) {
1012 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1013 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1014 }
1015 memset(ret, 0, sizeof(person));
1016
1017 /* We don't care what the top level element name is */
1018 cur = cur->childs;
1019 while (cur != NULL) {
1020 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1021 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1022 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1023 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
1024 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1025 }
1026
1027 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1028}</pre>
1029
1030<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1031<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1032 <li>Usually a recursive parsing style is the more convenient one, XML data
1033 being by nature subject to repetitive constructs and usualy exibit highly
1034 stuctured patterns.</li>
1035 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
1036 the pointer to the global XML document and the namespace reserved to the
1037 application. Document wide information are needed for example to decode
1038 entities and it's a good coding practice to define a namespace for your
1039 application set of data and test that the element and attributes you're
1040 analyzing actually pertains to your application space. This is done by a
1041 simple equality test (cur->ns == ns).</li>
1042 <li>To retrieve text and attributes value, it is suggested to use the
1043 function <em>xmlNodeListGetString</em> to gather all the text and entity
1044 reference nodes generated by the DOM output and produce an single text
1045 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1046</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1047
1048<p>Here is another piece of code used to parse another level of the
1049structure:</p>
1050<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1051 * a Description for a Job
1052 */
1053typedef struct job {
1054 char *projectID;
1055 char *application;
1056 char *category;
1057 personPtr contact;
1058 int nbDevelopers;
1059 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
1060} job, *jobPtr;
1061
1062/*
1063 * And the code needed to parse it
1064 */
1065jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1066 jobPtr ret = NULL;
1067
1068DEBUG("parseJob\n");
1069 /*
1070 * allocate the struct
1071 */
1072 ret = (jobPtr) malloc(sizeof(job));
1073 if (ret == NULL) {
1074 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1075 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1076 }
1077 memset(ret, 0, sizeof(job));
1078
1079 /* We don't care what the top level element name is */
1080 cur = cur->childs;
1081 while (cur != NULL) {
1082
1083 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1084 ret->projectID = xmlGetProp(cur, "ID");
1085 if (ret->projectID == NULL) {
1086 fprintf(stderr, "Project has no ID\n");
1087 }
1088 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1089 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1090 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1091 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1092 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1093 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1094 ret->contact = parsePerson(doc, ns, cur);
1095 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1096 }
1097
1098 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1099}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1100
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1101<p>One can notice that once used to it, writing this kind of code is quite
1102simple, but boring. Ultimately, it could be possble to write stubbers taking
1103either C data structure definitions, a set of XML examples or an XML DTD and
1104produce the code needed to import and export the content between C data and
1105XML storage. This is left as an exercise to the reader :-)</p>
1106
1107<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]1108example</a> as a template, it is also available with Makefile in the Gnome CVS
1109base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1110
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1111<p></p>
1112
1113<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1114
Daniel Veillardec303412000-03-24 13:41:54 +0000[diff] [blame^]1115<p>$Id: xml.html,v 1.30 2000/03/20 13:07:14 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1116</body>
1117</html>