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gerrit-public.fairphone.software / platform / external / libxml2 / f13e1ed19c0df67a738be2b581a547a0d5cc3d39 / . / doc / xml.html
blob: 28cf5ea562206cd2aaeffb35187b04aa74d98e9a [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 Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]6 <meta name="GENERATOR" content="amaya V2.1">
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]7 <meta http-equiv="Content-Type" content="text/html">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]8</head>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]9
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]10<body bgcolor="#ffffff">
Daniel 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>
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 Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]166 <li>huge work toward libxml-2.0: This work is available only in W3C CVs base
167 for the moment. You get the <a
168 href="ftp://rpmfind.net/pub/libxml/cvs-snapshot.tar.gz">snapshot</a> for
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]169 the updated version:
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]170 <ul>
171 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 seems correctly handled
172 now</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]173 <li>Better handling of entities, especially well formedness checking and
174 proper PEref extensions in external subsets</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]175 <li>DTD conditional sections</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]176 <li>Validation now correcly handle entities content</li>
Daniel Veillard6c8b1172000-03-01 00:40:41 +0000[diff] [blame]177 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change
178 structures to accomodate DOM</a></li>
179 <li>Lot of work toward a better compliance. I'm now running and
180 debugging regression tests agains the <a
181 href="http://www.oasis-open.org/committees/xmlconf-pub.html">OASIS
182 testsuite</a></li>
183 </ul>
184 </li>
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]185</ul>
186
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]187<h3>1.8.7: Mar 6 2000</h3>
188<ul>
189 <li>This is a bug fix release:</li>
190 <li>It is possible to disable the ignorable blanks heuristic used by
191 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note
192 that for adherence to XML spec, this behaviour will be disabled by default
193 in 2.x . The same function will allow to keep compatibility for old
194 code.</li>
195 <li>Blanks in &lt;a> &lt;/a> constructs are not ignored anymore, avoiding
196 heuristic is really the Right Way :-\</li>
197 <li>The unchecked use of snprintf which was breaking libxml-1.8.6
198 compilation on some platforms has been fixed</li>
199 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing
200 URIs</li>
201</ul>
202
Daniel Veillarde41f2b72000-01-30 20:00:07 +0000[diff] [blame]203<h3>1.8.6: Jan 31 2000</h3>
204<ul>
205 <li>added a nanoFTP transport module, debugged until the new version of <a
206 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use
207 it without troubles</li>
Daniel Veillardda07c342000-01-25 18:31:22 +0000[diff] [blame]208</ul>
209
210<h3>1.8.5: Jan 21 2000</h3>
211<ul>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]212 <li>adding APIs to parse a well balanced chunk of XML (production <a
213 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the XML
214 spec)</li>
Daniel Veillard461a66c2000-01-18 18:01:01 +0000[diff] [blame]215 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li>
216 <li>Jody Goldberg &lt;jgoldberg@home.com> provided another patch trying to
217 solve the zlib checks problems</li>
218 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with
219 gnumeric soon</li>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]220</ul>
221
222<h3>1.8.4: Jan 13 2000</h3>
223<ul>
224 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li>
225 <li>all exit() call should have been removed from libxml</li>
226 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li>
227 <li>added newDocFragment()</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]228</ul>
229
230<h3>1.8.3: Jan 5 2000</h3>
231<ul>
232 <li>a Push interface for the XML and HTML parsers</li>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]233 <li>a shell-like interface to the document tree (try tester --shell :-)</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame]234 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]235 <li>fixed the DTD parsing code to work with the xhtml DTD</li>
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]236 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li>
237 <li>Fixed bugs in xmlNewNs()</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]238 <li>External entity loading code has been revamped, now it uses
Daniel Veillardf84f71f2000-01-05 19:54:23 +0000[diff] [blame]239 xmlLoadExternalEntity(), some fix on entities processing were added</li>
Daniel Veillard437b87b2000-01-03 17:30:46 +0000[diff] [blame]240 <li>cleaned up WIN32 includes of socket stuff</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]241</ul>
242
243<h3>1.8.2: Dec 21 1999</h3>
244<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]245 <li>I got another problem with includes and C++, I hope this issue is fixed
246 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]247 <li>Added a few tree modification functions: xmlReplaceNode,
248 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
249 xmlDocSetRootElement</li>
250 <li>Tried to improve the HTML output with help from <a
251 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]252</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]253
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]254<h3>1.8.1: Dec 18 1999</h3>
255<ul>
256 <li>various patches to avoid troubles when using libxml with C++ compilers
257 the "namespace" keyword and C escaping in include files</li>
258 <li>a problem in one of the core macros IS_CHAR was corrected</li>
259 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
260 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]261 <li>fixed a posteriori validation (validation after parsing, or by using a
262 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]263 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]264</ul>
265
266<h3>1.8.0: Dec 12 1999</h3>
267<ul>
268 <li>cleanup, especially memory wise</li>
269 <li>the parser should be more reliable, especially the HTML one, it should
270 not crash, whatever the input !</li>
271 <li>Integrated various patches, especially a speedup improvement for large
272 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
273 configure with --with-buffers to enable them.</li>
274 <li>attribute normalization, oops should have been added long ago !</li>
275 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
276 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]277</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]278
279<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]280<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]281 <li>Lots of HTML improvement</li>
282 <li>Fixed some errors when saving both XML and HTML</li>
283 <li>More examples, the regression tests should now look clean</li>
284 <li>Fixed a bug with contiguous charref</li>
285</ul>
286
287<h3>1.7.3: Sep 29 1999</h3>
288<ul>
289 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]290 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]291 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]292</ul>
293
294<h3>1.7.1: Sep 24 1999</h3>
295<ul>
296 <li>The basic type for strings manipulated by libxml has been renamed in
297 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
298 is that CHAR was conflicting with a predefined type on Windows. However on
299 non WIN32 environment, compatibility is provided by the way of a
300 <strong>#define </strong>.</li>
301 <li>Changed another error : the use of a structure field called errno, and
302 leading to troubles on platforms where it's a macro</li>
303</ul>
304
305<h3>1.7.0: sep 23 1999</h3>
306<ul>
307 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
308 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
309 <li>Added an errno to report errors by another mean than a simple printf
310 like callback</li>
311 <li>Finished ID/IDREF support and checking when validation</li>
312 <li>Serious memory leaks fixed (there is now a <a
313 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
314 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
315 implementation</li>
316 <li>Added an HTML parser front-end</li>
317</ul>
318
319<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]320
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]321<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^]322markup-based structured documents. Here is <a name="example">an example XML
323document</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]324<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]325&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]326 &lt;head>
327 &lt;title>Welcome to Gnome&lt;/title>
328 &lt;/head>
329 &lt;chapter>
330 &lt;title>The Linux adventure&lt;/title>
331 &lt;p>bla bla bla ...&lt;/p>
332 &lt;image href="linus.gif"/>
333 &lt;p>...&lt;/p>
334 &lt;/chapter>
335&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]336
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]337<p>The first line specifies that it's an XML document and gives useful
338information about its encoding. Then the document is a text format whose
339structure is specified by tags between brackets. <strong>Each tag opened has
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]340to be closed</strong>. XML is pedantic about this. However, if a tag is empty
341(no content), a single tag can serve as both the opening and closing tag if it
342ends with <code>/></code> rather than with <code>></code>. Note that, for
343example, the image tag has no content (just an attribute) and is closed by
344ending the tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]345
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]346<p>XML can be applied sucessfully to a wide range of uses, from long term
347structured document maintenance (where it follows the steps of SGML) to simple
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]348data encoding mechanisms like configuration file formatting (glade),
349spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where
350it is used to encode remote calls between a client and a server.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]351
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]352<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]353
354<p>The parser returns a tree built during the document analysis. The value
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]355returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]356<strong>xmlDoc</strong> structure). This structure contains information such
357as the file name, the document type, and a <strong>root</strong> pointer which
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]358is the root of the document (or more exactly the first child under the root
359which is the document). The tree is made of <strong>xmlNode</strong>s, chained
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]360in double-linked lists of siblings and with childs&lt;->parent relationship.
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]361An xmlNode can also carry properties (a chain of xmlAttr structures). An
362attribute 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]363
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]364<p>Here is an example (erroneous with respect to the XML spec since there
365should be only one ELEMENT under the root):</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]366
367<p><img src="structure.gif" alt=" structure.gif "></p>
368
369<p>In the source package there is a small program (not installed by default)
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]370called <strong>tester</strong> which parses XML files given as argument and
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]371prints them back as parsed. This is useful for detecting errors both in XML
372code and in the XML parser itself. It has an option <strong>--debug</strong>
373which prints the actual in-memory structure of the document, here is the
374result with the <a href="#example">example</a> given before:</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]375<pre>DOCUMENT
376version=1.0
377standalone=true
378 ELEMENT EXAMPLE
379 ATTRIBUTE prop1
380 TEXT
381 content=gnome is great
382 ATTRIBUTE prop2
383 ENTITY_REF
384 TEXT
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]385 content= linux too
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]386 ELEMENT head
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]387 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]388 TEXT
389 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]390 ELEMENT chapter
391 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]392 TEXT
393 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]394 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]395 TEXT
396 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]397 ELEMENT image
398 ATTRIBUTE href
399 TEXT
400 content=linus.gif
401 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]402 TEXT
403 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]404
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]405<p>This should be useful for learning the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]406
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]407<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]408
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]409<p>Sometimes the DOM tree output is just too large to fit reasonably into
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]410memory. In that case (and if you don't expect to save back the XML document
411loaded 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]412<strong>callback-based interface</strong> to the parser. Before parsing, the
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]413application layer registers a customized set of callbacks which are called by
414the library as it progresses through the XML input.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]415
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]416<p>To get more detailed step-by-step guidance on using the SAX interface of
417libxml, see the
418href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]419documentation.written by <a href="mailto:james@daa.com.au">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]420Henstridge</a>.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]421
422<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
423program located in the gnome-xml module (it's usually not shipped in the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]424binary packages of libxml, but you can find it in the tar source
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]425distribution). Here is the sequence of callbacks that would be reported by
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]426testSAX when parsing the example XML document shown earlier:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]427<pre>SAX.setDocumentLocator()
428SAX.startDocument()
429SAX.getEntity(amp)
430SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
431SAX.characters( , 3)
432SAX.startElement(head)
433SAX.characters( , 4)
434SAX.startElement(title)
435SAX.characters(Welcome to Gnome, 16)
436SAX.endElement(title)
437SAX.characters( , 3)
438SAX.endElement(head)
439SAX.characters( , 3)
440SAX.startElement(chapter)
441SAX.characters( , 4)
442SAX.startElement(title)
443SAX.characters(The Linux adventure, 19)
444SAX.endElement(title)
445SAX.characters( , 4)
446SAX.startElement(p)
447SAX.characters(bla bla bla ..., 15)
448SAX.endElement(p)
449SAX.characters( , 4)
450SAX.startElement(image, href='linus.gif')
451SAX.endElement(image)
452SAX.characters( , 4)
453SAX.startElement(p)
454SAX.characters(..., 3)
455SAX.endElement(p)
456SAX.characters( , 3)
457SAX.endElement(chapter)
458SAX.characters( , 1)
459SAX.endElement(EXAMPLE)
460SAX.endDocument()</pre>
461
Daniel Veillard402e8c82000-02-29 22:57:47 +0000[diff] [blame]462<p>Most of the other functionalities of libxml are based on the DOM
463tree-building facility, so nearly everything up to the end of this document
464presupposes the use of the standard DOM tree build. Note that the DOM tree
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]465itself is built by a set of registered default callbacks, without internal
466specific interface.</p>
467
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]468<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]469
470<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]471using the XML library from the C language. It is not intended to be extensive.
472I hope the automatically generated documents will provide the completeness
473required, but as a separate set of documents. The interfaces of the XML
474library are by principle low level, there is nearly zero abstraction. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]475interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]476
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]477<p>The <a href="gnome-xml-parser.html">parser interfaces for XML</a> are
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]478separated from the <a href="gnome-xml-htmlparser.html">HTML parser
479interfaces</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]480
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]481<h3><a name="Invoking">Invoking the parser : the pull method</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]482
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]483<p>Usually, the first thing to do is to read an XML input. The parser accepts
484documents either from in-memory strings or from files. The functions are
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]485defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]486<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]487 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]488 <dd><p>Parse a null-terminated string containing the document.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]489 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]490</dl>
491<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]492 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]493 <dd><p>Parse an XML document contained in a (possibly compressed)
494 file.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]495 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]496</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]497
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]498<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]499failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]500
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]501<h3 id="Invoking1">Invoking the parser: the push method</h3>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]502
503<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]504fetched (which is common for GUI based programs) libxml provides a push
505interface, too, as of version 1.8.3. Here are the interface functions:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]506<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax,
507 void *user_data,
508 const char *chunk,
509 int size,
510 const char *filename);
511int xmlParseChunk (xmlParserCtxtPtr ctxt,
512 const char *chunk,
513 int size,
514 int terminate);</pre>
515
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]516<p>and here is a simple example showing how to use the interface:</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]517<pre> FILE *f;
518
519 f = fopen(filename, "r");
520 if (f != NULL) {
521 int res, size = 1024;
522 char chars[1024];
523 xmlParserCtxtPtr ctxt;
524
525 res = fread(chars, 1, 4, f);
526 if (res > 0) {
527 ctxt = xmlCreatePushParserCtxt(NULL, NULL,
528 chars, res, filename);
529 while ((res = fread(chars, 1, size, f)) > 0) {
530 xmlParseChunk(ctxt, chars, res, 0);
531 }
532 xmlParseChunk(ctxt, chars, 0, 1);
533 doc = ctxt->myDoc;
534 xmlFreeParserCtxt(ctxt);
535 }
536 }</pre>
537
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]538<p>Also note that the HTML parser embedded into libxml also has a push
539interface; the functions are just prefixed by "html" rather than "xml"</p>
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]540
541<h3 id="Invoking2">Invoking the parser: the SAX interface</h3>
542
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]543<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]544memory-hungry, first to load the document in memory, second to build the tree.
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]545Reading a document without building the tree is possible using the SAX
546interfaces (see SAX.h and <a
547href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]548Henstridge's documentation</a>). Note also that the push interface can be
549limited to SAX. Just use the two first arguments of
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]550<code>xmlCreatePushParserCtxt()</code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]551
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]552<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]553
554<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^]555there is a set of functions dedicated to building new elements. (These are
556also described in "tree.h".) For example, here is a piece of code that
557produces the XML document used in the previous examples:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]558<pre> xmlDocPtr doc;
559 xmlNodePtr tree, subtree;
560
561 doc = xmlNewDoc("1.0");
562 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
563 xmlSetProp(doc->root, "prop1", "gnome is great");
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]564 xmlSetProp(doc->root, "prop2", "&amp; linux too");
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]565 tree = xmlNewChild(doc->root, NULL, "head", NULL);
566 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
567 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
568 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
569 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
570 subtree = xmlNewChild(tree, NULL, "image", NULL);
571 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]572
573<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]574
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]575<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]576
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]577<p>Basically by <a href="gnome-xml-tree.html">including "tree.h"</a> your code
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]578has access to the internal structure of all the elements of the tree. The
579names should be somewhat simple like <strong>parent</strong>,
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]580<strong>childs</strong>, <strong>next</strong>, <strong>prev</strong>,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]581<strong>properties</strong>, etc... For example, still with the previous
Daniel Veillard0142b842000-01-14 14:45:24 +0000[diff] [blame]582example:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]583<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]584
585<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]586<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]587
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]588<p>points to the text node containing the chapter title "The Linux
589adventure".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]590
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]591<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]592present before the document root, so <code>doc->root</code> may point to an
593element which is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]594<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]595
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]596<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]597
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]598<p>Functions are provided for reading and writing the document content. Here
599is an excerpt from the <a href="gnome-xml-tree.html">tree API</a>:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]600<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]601 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
602 xmlChar *value);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]603 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. The
604 value can be NULL.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]605 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]606</dl>
607<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]608 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]609 *name);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]610 <dd><p>This function returns a pointer to the property content. Note that
611 no extra copy is made.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]612 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]613</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]614
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]615<p>Two functions are provided for reading and writing the text associated with
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]616elements:</p>
617<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]618 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]619 *value);</code></dt>
620 <dd><p>This function takes an "external" string and convert it to one text
621 node or possibly to a list of entity and text nodes. All non-predefined
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]622 entity references like &amp;Gnome; will be stored internally as entity
623 nodes, hence the result of the function may not be a single node.</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>
626<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]627 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]628 inLine);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]629 <dd><p>This function is the inverse of
630 <code>xmlStringGetNodeList()</code>. It generates a new string
631 containing the content of the text and entity nodes. Note the extra
632 argument inLine. If this argument is set to 1, the function will expand
633 entity references. For example, instead of returning the &amp;Gnome;
634 XML encoding in the string, it will substitute it with its value (say,
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]635 "GNU Network Object Model Environment"). Set this argument if you want
636 to use the string for non-XML usage like User Interface.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]637 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]638</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]639
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]640<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]641
642<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]643<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]644 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]645 *size);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]646 <dd><p>Returns a buffer into which the document has been saved.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]647 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]648</dl>
649<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]650 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]651 <dd><p>Dumps a document to an open file descriptor.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]652 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]653</dl>
654<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]655 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]656 <dd><p>Saves the document to a file. In this case, the compression
657 interface is triggered if it has been turned on.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]658 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]659</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]660
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]661<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]662
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]663<p>The library transparently handles compression when doing file-based
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]664accesses. The level of compression on saves can be turned on either globally
665or individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]666<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]667 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]668 <dd><p>Gets the document compression ratio (0-9).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]669 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]670</dl>
671<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]672 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]673 <dd><p>Sets the document compression ratio.</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>
676<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]677 <dt><code>int xmlGetCompressMode(void);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]678 <dd><p>Gets the default compression ratio.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]679 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]680</dl>
681<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]682 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]683 <dd><p>Sets the default compression ratio.</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
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]687<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]688
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]689<p>Entities in principle are similar to simple C macros. An entity defines an
690abbreviation for a given string that you can reuse many times throughout the
691content of your document. Entities are especially useful when a given string
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]692may occur frequently within a document, or to confine the change needed to a
693document to a restricted area in the internal subset of the document (at the
694beginning). Example:</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]695<pre>1 &lt;?xml version="1.0"?>
6962 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
6973 &lt;!ENTITY xml "Extensible Markup Language">
6984 ]>
6995 &lt;EXAMPLE>
7006 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]7017 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]702
703<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]704it's name with '&amp;' and following it by ';' without any spaces added. There
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]705are 5 predefined entities in libxml allowing you to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]706predefined meaning in some parts of the xml document content:
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]707<strong>&amp;lt;</strong> for the character '&lt;', <strong>&amp;gt;</strong>
708for the character '>', <strong>&amp;apos;</strong> for the character ''',
709<strong>&amp;quot;</strong> for the character '"', and
710<strong>&amp;amp;</strong> for the character '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]711
712<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^]713substitute an entity's content so that you can see the replacement text in
714your application. Or you may prefer to keep entity references as such in the
715content to be able to save the document back without losing this usually
716precious information (if the user went through the pain of explicitly defining
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]717entities, he may have a a rather negative attitude if you blindly susbtitute
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]718them as saving time). The <a
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]719href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]720function allows you to check and change the behaviour, which is to not
721substitute entities by default.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]722
723<p>Here is the DOM tree built by libxml for the previous document in the
724default case:</p>
725<pre>/gnome/src/gnome-xml -> ./tester --debug test/ent1
726DOCUMENT
727version=1.0
728 ELEMENT EXAMPLE
729 TEXT
730 content=
731 ENTITY_REF
732 INTERNAL_GENERAL_ENTITY xml
733 content=Extensible Markup Language
734 TEXT
735 content=</pre>
736
737<p>And here is the result when substituting entities:</p>
738<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
739DOCUMENT
740version=1.0
741 ELEMENT EXAMPLE
742 TEXT
743 content= Extensible Markup Language</pre>
744
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]745<p>So, entities or no entities? Basically, it depends on your use case. I
746suggest that you keep the non-substituting default behaviour and avoid using
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]747entities in your XML document or data if you are not willing to handle the
748entity references elements in the DOM tree.</p>
749
750<p>Note that at save time libxml enforce the conversion of the predefined
751entities where necessary to prevent well-formedness problems, and will also
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]752transparently replace those with chars (i.e., it will not generate entity
753reference elements in the DOM tree or call the reference() SAX callback when
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]754finding them in the input).</p>
755
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]756<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]757
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]758<p>The libxml library implements namespace @@ support by recognizing namespace
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]759contructs in the input, and does namespace lookup automatically when building
760the DOM tree. A namespace declaration is associated with an in-memory
761structure and all elements or attributes within that namespace point to it.
762Hence testing the namespace is a simple and fast equality operation at the
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]763user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]764
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]765<p>I suggest that people using libxml use a namespace, and declare it in the
766root element of their document as the default namespace. Then they don't need
767to use the prefix in the content but we will have a basis for future semantic
768refinement and merging of data from different sources. This doesn't augment
769significantly the size of the XML output, but significantly increase its value
770in the long-term.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]771
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]772<p>Concerning the namespace value, this has to be an URL, but the URL doesn't
773have to point to any existing resource on the Web. I suggest that it makes
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]774sense to use an URL within a domain you control, and that the URL should
775contain some kind of version information if possible. For example,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]776<code>"http://www.gnome.org/gnumeric/1.0"</code> is a good namespace scheme.
777Then when you load a file, make sure that a namespace carrying the
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]778version-independent prefix is installed on the root element of your document,
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]779and if the version information don't match something you know, warn the user
780and 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]781namespace checking on the prefix value. &lt;foo:text> may be exactly the same
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]782as &lt;bar:text> in another document. What really matter is the URI associated
783with the element or the attribute, not the prefix string (which is just a
784shortcut for the full URI).</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]785
786<p>@@Interfaces@@</p>
787
788<p>@@Examples@@</p>
789
790<p>Usually people object using namespace in the case of validation, I object
791this and will make sure that using namespaces won't break validity checking,
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]792so even is you plan to use or currently are using validation I strongly
793suggest adding namespaces to your document. A default namespace scheme
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]794<code>xmlns="http://...."</code> should not break validity even on less
Daniel Veillard88f00ae2000-03-02 00:15:55 +0000[diff] [blame]795flexible parsers. Now using namespace to mix and differentiate content coming
796from multiple DTDs will certainly break current validation schemes. I will try
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]797to provide ways to do this, but this may not be portable or standardized.</p>
798
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]799<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]800
801<p>Well what is validation and what is a DTD ?</p>
802
803<p>Validation is the process of checking a document against a set of
804construction rules, a <strong>DTD</strong> (Document Type Definition) is such
805a set of rules.</p>
806
807<p>The validation process and building DTDs are the two most difficult parts
808of XML life cycle. Briefly a DTD defines all the possibles element to be
809found within your document, what is the formal shape of your document tree (by
810defining the allowed content of an element, either text, a regular expression
811for the allowed list of children, or mixed content i.e. both text and childs).
812The DTD also defines the allowed attributes for all elements and the types of
813the attributes. For more detailed informations, I suggest to read the related
814parts of the XML specification, the examples found under
815gnome-xml/test/valid/dtd and the large amount of books available on XML. The
816dia example in gnome-xml/test/valid should be both simple and complete enough
817to allow you to build your own.</p>
818
819<p>A word of warning, building a good DTD which will fit your needs of your
820application in the long-term is far from trivial, however the extra level of
821quality it can insure is well worth the price for some sets of applications or
822if you already have already a DTD defined for your application field.</p>
823
824<p>The validation is not completely finished but in a (very IMHO) usable
825state. Until a real validation interface is defined the way to do it is to
826define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
827variable to 1, this will of course be changed at some point:</p>
828
829<p>extern int xmlDoValidityCheckingDefaultValue;</p>
830
831<p>...</p>
832
833<p>xmlDoValidityCheckingDefaultValue = 1;</p>
834
835<p></p>
836
837<p>To handle external entities, use the function
838<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
839link in you HTTP/FTP/Entities database library to the standard libxml
840core.</p>
841
842<p>@@interfaces@@</p>
843
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]844<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]845
846<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]847Model</em> this is an API for accessing XML or HTML structured documents.
848Native 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]849be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]850files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]851set of IDL (or Java) interfaces allowing to traverse and manipulate a
852document. The DOM library will allow accessing and modifying "live" documents
853presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]854
855<p><img src="DOM.gif" alt=" DOM.gif "></p>
856
857<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]858embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]859
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]860<p>The current DOM implementation on top of libxml is the <a
861href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
862a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
863Levien</a>.</p>
864
865<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
866
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]867<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]868
869<p>Here is a real size example, where the actual content of the application
870data 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]871a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]872storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
873base</a>:</p>
874<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]875&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
876 &lt;gjob:Jobs>
877
878 &lt;gjob:Job>
879 &lt;gjob:Project ID="3"/>
880 &lt;gjob:Application>GBackup&lt;/gjob:Application>
881 &lt;gjob:Category>Development&lt;/gjob:Category>
882
883 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]884 &lt;gjob:Status>Open&lt;/gjob:Status>
885 &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]886 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
887 &lt;/gjob:Update>
888
889 &lt;gjob:Developers>
890 &lt;gjob:Developer>
891 &lt;/gjob:Developer>
892 &lt;/gjob:Developers>
893
894 &lt;gjob:Contact>
895 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]896 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]897 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]898 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]899 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]900 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]901 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]902 &lt;/gjob:Webpage>
903 &lt;gjob:Snailmail>
904 &lt;/gjob:Snailmail>
905 &lt;gjob:Phone>
906 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]907 &lt;/gjob:Contact>
908
909 &lt;gjob:Requirements>
910 The program should be released as free software, under the GPL.
911 &lt;/gjob:Requirements>
912
913 &lt;gjob:Skills>
914 &lt;/gjob:Skills>
915
916 &lt;gjob:Details>
917 A GNOME based system that will allow a superuser to configure
918 compressed and uncompressed files and/or file systems to be backed
919 up with a supported media in the system. This should be able to
920 perform via find commands generating a list of files that are passed
921 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
922 or via operations performed on the filesystem itself. Email
923 notification and GUI status display very important.
924 &lt;/gjob:Details>
925
926 &lt;/gjob:Job>
927
928 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]929&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]930
931<p>While loading the XML file into an internal DOM tree is a matter of calling
932only a couple of functions, browsing the tree to gather the informations and
933generate the internals structures is harder, and more error prone.</p>
934
935<p>The suggested principle is to be tolerant with respect to the input
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]936structure. For example, the ordering of the attributes is not significant,
937Cthe XML specification is clear about it. It's also usually a good idea to not
938be dependent of the orders of the childs of a given node, unless it really
939makes things harder. Here is some code to parse the informations for a
940person:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]941<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]942 * A person record
943 */
944typedef struct person {
945 char *name;
946 char *email;
947 char *company;
948 char *organisation;
949 char *smail;
950 char *webPage;
951 char *phone;
952} person, *personPtr;
953
954/*
955 * And the code needed to parse it
956 */
957personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
958 personPtr ret = NULL;
959
960DEBUG("parsePerson\n");
961 /*
962 * allocate the struct
963 */
964 ret = (personPtr) malloc(sizeof(person));
965 if (ret == NULL) {
966 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]967 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]968 }
969 memset(ret, 0, sizeof(person));
970
971 /* We don't care what the top level element name is */
972 cur = cur->childs;
973 while (cur != NULL) {
974 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]975 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]976 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]977 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
978 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]979 }
980
981 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]982}</pre>
983
984<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]985<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]986 <li>Usually a recursive parsing style is the more convenient one, XML data
987 being by nature subject to repetitive constructs and usualy exibit highly
988 stuctured patterns.</li>
989 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
990 the pointer to the global XML document and the namespace reserved to the
991 application. Document wide information are needed for example to decode
992 entities and it's a good coding practice to define a namespace for your
993 application set of data and test that the element and attributes you're
994 analyzing actually pertains to your application space. This is done by a
995 simple equality test (cur->ns == ns).</li>
996 <li>To retrieve text and attributes value, it is suggested to use the
997 function <em>xmlNodeListGetString</em> to gather all the text and entity
998 reference nodes generated by the DOM output and produce an single text
999 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1000</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1001
1002<p>Here is another piece of code used to parse another level of the
1003structure:</p>
1004<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1005 * a Description for a Job
1006 */
1007typedef struct job {
1008 char *projectID;
1009 char *application;
1010 char *category;
1011 personPtr contact;
1012 int nbDevelopers;
1013 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
1014} job, *jobPtr;
1015
1016/*
1017 * And the code needed to parse it
1018 */
1019jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
1020 jobPtr ret = NULL;
1021
1022DEBUG("parseJob\n");
1023 /*
1024 * allocate the struct
1025 */
1026 ret = (jobPtr) malloc(sizeof(job));
1027 if (ret == NULL) {
1028 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1029 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1030 }
1031 memset(ret, 0, sizeof(job));
1032
1033 /* We don't care what the top level element name is */
1034 cur = cur->childs;
1035 while (cur != NULL) {
1036
1037 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1038 ret->projectID = xmlGetProp(cur, "ID");
1039 if (ret->projectID == NULL) {
1040 fprintf(stderr, "Project has no ID\n");
1041 }
1042 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1043 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1044 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1045 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1046 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1047 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1048 ret->contact = parsePerson(doc, ns, cur);
1049 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1050 }
1051
1052 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1053}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]1054
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1055<p>One can notice that once used to it, writing this kind of code is quite
1056simple, but boring. Ultimately, it could be possble to write stubbers taking
1057either C data structure definitions, a set of XML examples or an XML DTD and
1058produce the code needed to import and export the content between C data and
1059XML storage. This is left as an exercise to the reader :-)</p>
1060
1061<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]1062example</a> as a template, it is also available with Makefile in the Gnome CVS
1063base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]1064
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]1065<p></p>
1066
1067<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
1068
Daniel Veillardf13e1ed2000-03-06 07:41:49 +0000[diff] [blame^]1069<p>$Id: xml.html,v 1.27 2000/03/02 00:15:55 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]1070</body>
1071</html>