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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 Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]6 <meta name="GENERATOR" content="amaya V2.4">
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>
26 <li><a href="#Invoking">Invoking the parser</a></li>
27 <li><a href="#Building">Building a tree from scratch</a></li>
28 <li><a href="#Traversing">Traversing the tree</a></li>
29 <li><a href="#Modifying">Modifying the tree</a></li>
30 <li><a href="#Saving">Saving the tree</a></li>
31 <li><a href="#Compressio">Compression</a></li>
32 </ul>
33 </li>
34 <li><a href="#Entities">Entities or no entities</a></li>
35 <li><a href="#Namespaces">Namespaces</a></li>
36 <li><a href="#Validation">Validation</a></li>
37 <li><a href="#Principles">DOM principles</a></li>
38 <li><a href="#real">A real example</a></li>
39</ul>
40
41<h2><a name="Introducti">Introduction</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]42
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]43<p>This document describes the <a href="http://www.w3.org/XML/">XML</a>
44library provideed in the <a href="http://www.gnome.org/">Gnome</a> framework.
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]45XML is a standard to build tag based structured documents/data.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]46
47<p>The internal document repesentation is as close as possible to the <a
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]48href="http://www.w3.org/DOM/">DOM</a> interfaces.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]49
50<p>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX
51interface</a>, <a href="mailto:james@daa.com.au">James Henstridge</a> made <a
52href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">a nice
53documentation</a> expaining how to use it. The interface is as compatible as
54possible with <a href="http://www.jclark.com/xml/expat.html">Expat</a>
55one.</p>
56
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]57<p>There is also a mailing-list <a
Daniel Veillard6bd26dc1999-09-03 14:28:40 +0000[diff] [blame]58href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> for libxml, with an <a
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]59href="http://xmlsoft.org/messages">on-line archive</a>. To subscribe to this
60majordomo based list, send a mail to <a
Daniel Veillard6bd26dc1999-09-03 14:28:40 +0000[diff] [blame]61href="mailto:majordomo@rufus.w3.org">majordomo@rufus.w3.org</a> with
62"subscribe xml" in the <strong>content</strong> of the message.</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]63
64<p>This library is released both under the W3C Copyright and the GNU LGP,
65basically everybody should be happy, if not, drop me a mail.</p>
66
67<p>People are invited to use the <a
68href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module to</a> get a
69full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
70Levien</a>, check his <a
71href="http://www.levien.com/gnome/domination.html">DOMination paper</a>. He
72uses it for his implementation of <a
73href="http://www.w3.org/Graphics/SVG/">SVG</a> called <a
74href="http://www.levien.com/svg/">gill</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]75
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]76<h2><a name="Documentat">Documentation</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]77
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]78<p>The code is commented in a <a href=""></a>way which allow <a
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]79href="http://xmlsoft.org/libxml.html">extensive documentation</a> to be
80automatically extracted.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]81
82<p>At some point I will change the back-end to produce XML documentation in
83addition to SGML Docbook and HTML.</p>
84
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]85<h3>Reporting bugs</h3>
86
87<p>Well bugs or missing features are always possible, and I will make a point
88of fixing them in a timely fashion. The best way it to <a
89href="http://bugs.gnome.org/db/pa/lgnome-xml.html">use the Gnome bug tracking
90database</a>. I look at reports there regulary and it's good to have a
91reminder when a bug is still open. Check the <a
92href="http://bugs.gnome.org/Reporting.html">instructions on reporting bugs</a>
93and be sure to specify thatthe bug is for the package gnome-xml.</p>
94
95<p>Alternately you can just send the bug to the <a
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]96href="mailto:xml@rufus.w3.org">xml@rufus.w3.org</a> list.</p>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]97
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]98<h2><a name="Downloads">Downloads</a></h2>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]99
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]100<p>Latest version is 1.8.1, you can find it on <a
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]101href="ftp://rpmfind.net/pub/veillard/">rpmfind.net</a> or on the <a
102href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]103as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]104archive</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/contrib/rpms/">RPMs
105packages</a>.</p>
106
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]107<p>Libxml is also available from 2 CVs bases:</p>
108<ul>
109 <li><p>The <a href="http://dev.w3.org/cvsweb/XML/">W3C CVS base</a>,
110 available read-only using the CVS pserver authentification:</p>
111 <pre>CVSROOT=:pserver:anonymous@dev.w3.org:/sources/public
112password: anonymous
113module: XML</pre>
114 </li>
115 <li><p>The <a
116 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&amp;dir=gnome-xml">Gnome
117 CVS base</a>, Check the <a
118 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> page,
119 the CVS module is <b>gnome-xml</b></p>
120 </li>
121</ul>
122
123<h2><a name="News">News</a></h2>
124
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]125<h3>CVS only : check the <a
126href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file
127for really accurate description</h3>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]128<ul>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]129 <li>working on HTML and XML links recognition layers, get in touch with me
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]130 if you want to test those.</li>
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame^]131 <li>a Push interface for the XML parser</li>
132 <li>an shell like interface to the document tree (try tester --shell :-)</li>
133 <li>lots of bug fixes and improvement added over XMas hollidays</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]134</ul>
135
136<h3>1.8.2: Dec 21 1999</h3>
137<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]138 <li>I got another problem with includes and C++, I hope this issue is fixed
139 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]140 <li>Added a few tree modification functions: xmlReplaceNode,
141 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
142 xmlDocSetRootElement</li>
143 <li>Tried to improve the HTML output with help from <a
144 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]145</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]146
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]147<h3>1.8.1: Dec 18 1999</h3>
148<ul>
149 <li>various patches to avoid troubles when using libxml with C++ compilers
150 the "namespace" keyword and C escaping in include files</li>
151 <li>a problem in one of the core macros IS_CHAR was corrected</li>
152 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
153 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]154 <li>fixed a posteriori validation (validation after parsing, or by using a
155 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]156 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]157</ul>
158
159<h3>1.8.0: Dec 12 1999</h3>
160<ul>
161 <li>cleanup, especially memory wise</li>
162 <li>the parser should be more reliable, especially the HTML one, it should
163 not crash, whatever the input !</li>
164 <li>Integrated various patches, especially a speedup improvement for large
165 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
166 configure with --with-buffers to enable them.</li>
167 <li>attribute normalization, oops should have been added long ago !</li>
168 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
169 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]170</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]171
172<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]173<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]174 <li>Lots of HTML improvement</li>
175 <li>Fixed some errors when saving both XML and HTML</li>
176 <li>More examples, the regression tests should now look clean</li>
177 <li>Fixed a bug with contiguous charref</li>
178</ul>
179
180<h3>1.7.3: Sep 29 1999</h3>
181<ul>
182 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]183 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]184 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]185</ul>
186
187<h3>1.7.1: Sep 24 1999</h3>
188<ul>
189 <li>The basic type for strings manipulated by libxml has been renamed in
190 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
191 is that CHAR was conflicting with a predefined type on Windows. However on
192 non WIN32 environment, compatibility is provided by the way of a
193 <strong>#define </strong>.</li>
194 <li>Changed another error : the use of a structure field called errno, and
195 leading to troubles on platforms where it's a macro</li>
196</ul>
197
198<h3>1.7.0: sep 23 1999</h3>
199<ul>
200 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
201 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
202 <li>Added an errno to report errors by another mean than a simple printf
203 like callback</li>
204 <li>Finished ID/IDREF support and checking when validation</li>
205 <li>Serious memory leaks fixed (there is now a <a
206 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
207 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
208 implementation</li>
209 <li>Added an HTML parser front-end</li>
210</ul>
211
212<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]213
214<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for markup
215based structured documents, here is <a name="example">an example</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]216<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]217&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]218 &lt;head>
219 &lt;title>Welcome to Gnome&lt;/title>
220 &lt;/head>
221 &lt;chapter>
222 &lt;title>The Linux adventure&lt;/title>
223 &lt;p>bla bla bla ...&lt;/p>
224 &lt;image href="linus.gif"/>
225 &lt;p>...&lt;/p>
226 &lt;/chapter>
227&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]228
229<p>The first line specify that it's an XML document and gives useful
230informations about it's encoding. Then the document is a text format whose
231structure is specified by tags between brackets. <strong>Each tag opened have
232to be closed</strong> XML is pedantic about this, not that for example the
233image tag has no content (just an attribute) and is closed by ending up the
234tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]235
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]236<p>XML can be applied sucessfully to a wide range or usage from long term
237structured document maintenance where it follows the steps of SGML to simple
238data encoding mechanism like configuration file format (glade), spreadsheets
239(gnumeric), or even shorter lived document like in WebDAV where it is used to
240encode remote call between a client and a server.</p>
241
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]242<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]243
244<p>The parser returns a tree built during the document analysis. The value
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]245returned is an <strong>xmlDocPtr</strong> (i.e. a pointer to an
246<strong>xmlDoc</strong> structure). This structure contains informations like
247the file name, the document type, and a <strong>root</strong> pointer which
248is the root of the document (or more exactly the first child under the root
249which is the document). The tree is made of <strong>xmlNode</strong>s, chained
250in double linked lists of siblings and with childs&lt;->parent relationship.
251An xmlNode can also carry properties (a chain of xmlAttr structures). An
252attribute 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]253
254<p>Here is an example (erroneous w.r.t. the XML spec since there should be
255only one ELEMENT under the root):</p>
256
257<p><img src="structure.gif" alt=" structure.gif "></p>
258
259<p>In the source package there is a small program (not installed by default)
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]260called <strong>tester</strong> which parses XML files given as argument and
261prints them back as parsed, this is useful to detect errors both in XML code
262and in the XML parser itself. It has an option <strong>--debug</strong> which
263prints the actual in-memory structure of the document, here is the result with
264the <a href="#example">example</a> given before:</p>
265<pre>DOCUMENT
266version=1.0
267standalone=true
268 ELEMENT EXAMPLE
269 ATTRIBUTE prop1
270 TEXT
271 content=gnome is great
272 ATTRIBUTE prop2
273 ENTITY_REF
274 TEXT
275 content= too
276 ELEMENT head
277 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]278 TEXT
279 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]280 ELEMENT chapter
281 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]282 TEXT
283 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]284 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]285 TEXT
286 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]287 ELEMENT image
288 ATTRIBUTE href
289 TEXT
290 content=linus.gif
291 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]292 TEXT
293 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]294
295<p>This should be useful to learn the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]296
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]297<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]298
299<p>Sometimes the DOM tree output is just to large to fit reasonably into
300memory. In that case and if you don't expect to save back the XML document
301loaded using libxml, it's better to use the SAX interface of libxml. SAX is a
302<strong>callback based interface</strong> to the parser. Before parsing, the
303application layer register a customized set of callbacks which will be called
304by the library as it progresses through the XML input.</p>
305
306<p>To get a more detailed step-by-step guidance on using the SAX interface of
307libxml, <a href="mailto:james@daa.com.au">James Henstridge</a> made <a
308href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">a nice
309documentation.</a></p>
310
311<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
312program located in the gnome-xml module (it's usually not shipped in the
313binary packages of libxml, but you can also find it in the tar source
314distribution). Here is the sequence of callback that would be generated when
315parsing the example given before as reported by testSAX:</p>
316<pre>SAX.setDocumentLocator()
317SAX.startDocument()
318SAX.getEntity(amp)
319SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
320SAX.characters( , 3)
321SAX.startElement(head)
322SAX.characters( , 4)
323SAX.startElement(title)
324SAX.characters(Welcome to Gnome, 16)
325SAX.endElement(title)
326SAX.characters( , 3)
327SAX.endElement(head)
328SAX.characters( , 3)
329SAX.startElement(chapter)
330SAX.characters( , 4)
331SAX.startElement(title)
332SAX.characters(The Linux adventure, 19)
333SAX.endElement(title)
334SAX.characters( , 4)
335SAX.startElement(p)
336SAX.characters(bla bla bla ..., 15)
337SAX.endElement(p)
338SAX.characters( , 4)
339SAX.startElement(image, href='linus.gif')
340SAX.endElement(image)
341SAX.characters( , 4)
342SAX.startElement(p)
343SAX.characters(..., 3)
344SAX.endElement(p)
345SAX.characters( , 3)
346SAX.endElement(chapter)
347SAX.characters( , 1)
348SAX.endElement(EXAMPLE)
349SAX.endDocument()</pre>
350
351<p>Most of the other functionnalities of libxml are based on the DOM tree
352building facility, so nearly everything up to the end of this document
353presuppose the use of the standard DOM tree build. Note that the DOM tree
354itself is built by a set of registered default callbacks, without internal
355specific interface.</p>
356
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]357<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]358
359<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]360using the XML library from the C language. It doesn't intent to be extensive,
361I hope the automatically generated docs will provide the completeness
362required, but as a separated set of documents. The interfaces of the XML
363library are by principle low level, there is nearly zero abstration. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]364interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]365
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]366<h3><a name="Invoking">Invoking the parser</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]367
368<p>Usually, the first thing to do is to read an XML input, the parser accepts
369to parse both memory mapped documents or direct files. The functions are
370defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]371<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]372 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
373 <dd><p>parse a zero terminated string containing the document</p>
374 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]375</dl>
376<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]377 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
378 <dd><p>parse an XML document contained in a file (possibly compressed)</p>
379 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]380</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]381
382<p>This returns a pointer to the document structure (or NULL in case of
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]383failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]384
385<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]386memory-hungry, first to load the document in memory, second to build the tree.
387Reading a document without building the tree will be possible in the future by
388pluggin the code to the SAX interface (see SAX.c).</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]389
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]390<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]391
392<p>The other way to get an XML tree in memory is by building it. Basically
393there is a set of functions dedicated to building new elements, those are also
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]394described in "tree.h", here is for example the piece of code producing the
395example used before:</p>
396<pre> xmlDocPtr doc;
397 xmlNodePtr tree, subtree;
398
399 doc = xmlNewDoc("1.0");
400 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
401 xmlSetProp(doc->root, "prop1", "gnome is great");
402 xmlSetProp(doc->root, "prop2", "&amp;linux; too");
403 tree = xmlNewChild(doc->root, NULL, "head", NULL);
404 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
405 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
406 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
407 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
408 subtree = xmlNewChild(tree, NULL, "image", NULL);
409 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]410
411<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]412
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]413<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]414
415<p>Basically by including "tree.h" your code has access to the internal
416structure of all the element of the tree. The names should be somewhat simple
417like <strong>parent</strong>, <strong>childs</strong>, <strong>next</strong>,
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]418<strong>prev</strong>, <strong>properties</strong>, etc... For example still
419with the previous example:</p>
420<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]421
422<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]423<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]424
425<p>points to the text node containing the chapter titlle "The Linux adventure"
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]426and</p>
427<pre>doc->root->properties->next->val</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]428
429<p>points to the entity reference containing the value of "&amp;linux" at the
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]430beginning of the second attribute of the root element "EXAMPLE".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]431
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]432<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
433present before the document root, so doc->root may point to an element which
434is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame]435<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]436
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]437<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]438
439<p>functions are provided to read and write the document content:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]440<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]441 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
442 xmlChar *value);</code></dt>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]443 <dd><p>This set (or change) an attribute carried by an ELEMENT node the
444 value can be NULL</p>
445 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]446</dl>
447<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]448 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]449 *name);</code></dt>
450 <dd><p>This function returns a pointer to the property content, note that
451 no extra copy is made</p>
452 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]453</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]454
455<p>Two functions must be used to read an write the text associated to
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]456elements:</p>
457<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]458 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]459 *value);</code></dt>
460 <dd><p>This function takes an "external" string and convert it to one text
461 node or possibly to a list of entity and text nodes. All non-predefined
462 entity references like &amp;Gnome; will be stored internally as an
463 entity node, hence the result of the function may not be a single
464 node.</p>
465 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]466</dl>
467<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]468 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]469 inLine);</code></dt>
470 <dd><p>this is the dual function, which generate a new string containing
471 the content of the text and entity nodes. Note the extra argument
472 inLine, if set to 1 instead of returning the &amp;Gnome; XML encoding in
473 the string it will substitute it with it's value say "GNU Network Object
474 Model Environment". Set it if you want to use the string for non XML
475 usage like User Interface.</p>
476 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]477</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]478
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]479<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]480
481<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]482<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]483 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]484 *size);</code></dt>
485 <dd><p>returns a buffer where the document has been saved</p>
486 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]487</dl>
488<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]489 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
490 <dd><p>dumps a buffer to an open file descriptor</p>
491 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]492</dl>
493<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]494 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
495 <dd><p>save the document ot a file. In that case the compression interface
496 is triggered if turned on</p>
497 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]498</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]499
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]500<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]501
502<p>The library handle transparently compression when doing file based
503accesses, the level of compression on saves can be tuned either globally or
504individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]505<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]506 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
507 <dd><p>Get the document compression ratio (0-9)</p>
508 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]509</dl>
510<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]511 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
512 <dd><p>Set the document compression ratio</p>
513 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]514</dl>
515<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]516 <dt><code>int xmlGetCompressMode(void);</code></dt>
517 <dd><p>Get the default compression ratio</p>
518 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]519</dl>
520<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]521 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
522 <dd><p>set the default compression ratio</p>
523 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]524</dl>
525
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]526<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]527
528<p>Entities principle is similar to simple C macros. They define an
529abbreviation for a given string that you can reuse many time through the
530content of your document. They are especially useful when frequent occurrences
531of a given string may occur within a document or to confine the change needed
532to a document to a restricted area in the internal subset of the document (at
533the beginning). Example:</p>
534<pre>1 &lt;?xml version="1.0"?>
5352 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
5363 &lt;!ENTITY xml "Extensible Markup Language">
5374 ]>
5385 &lt;EXAMPLE>
5396 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]5407 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]541
542<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]543it's name with '&amp;' and following it by ';' without any spaces added. There
544are 5 predefined entities in libxml allowing to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]545predefined meaning in some parts of the xml document content:
546<strong>&amp;lt;</strong> for the letter '&lt;', <strong>&amp;gt;</strong> for
547the letter '>', <strong>&amp;apos;</strong> for the letter ''',
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]548<strong>&amp;quot;</strong> for the letter '"', and <strong>&amp;amp;</strong>
549for the letter '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]550
551<p>One of the problems related to entities is that you may want the parser to
552substitute entities content to see the replacement text in your application,
553or you may prefer keeping entities references as such in the content to be
554able to save the document back without loosing this usually precious
555information (if the user went through the pain of explicitley defining
556entities, he may have a a rather negative attitude if you blindly susbtitute
557them as saving time). The function <a
558href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
559allows to check and change the behaviour, which is to not substitute entities
560by default.</p>
561
562<p>Here is the DOM tree built by libxml for the previous document in the
563default case:</p>
564<pre>/gnome/src/gnome-xml -> ./tester --debug test/ent1
565DOCUMENT
566version=1.0
567 ELEMENT EXAMPLE
568 TEXT
569 content=
570 ENTITY_REF
571 INTERNAL_GENERAL_ENTITY xml
572 content=Extensible Markup Language
573 TEXT
574 content=</pre>
575
576<p>And here is the result when substituting entities:</p>
577<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
578DOCUMENT
579version=1.0
580 ELEMENT EXAMPLE
581 TEXT
582 content= Extensible Markup Language</pre>
583
584<p>So entities or no entities ? Basically it depends on your use case, I
585suggest to keep the non-substituting default behaviour and avoid using
586entities in your XML document or data if you are not willing to handle the
587entity references elements in the DOM tree.</p>
588
589<p>Note that at save time libxml enforce the conversion of the predefined
590entities where necessary to prevent well-formedness problems, and will also
591transparently replace those with chars (i.e. will not generate entity
592reference elements in the DOM tree nor call the reference() SAX callback when
593finding them in the input).</p>
594
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]595<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]596
597<p>The libxml library implement namespace @@ support by recognizing namespace
598contructs in the input, and does namespace lookup automatically when building
599the DOM tree. A namespace declaration is associated with an in-memory
600structure and all elements or attributes within that namespace point to it.
601Hence testing the namespace is a simple and fast equality operation at the
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]602user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]603
604<p>I suggest it that people using libxml use a namespace, and declare it on
605the root element of their document as the default namespace. Then they dont
606need to happend the prefix in the content but we will have a basis for future
607semantic refinement and merging of data from different sources. This doesn't
608augment significantly the size of the XML output, but significantly increase
609it's value in the long-term.</p>
610
611<p>Concerning the namespace value, this has to be an URL, but this doesn't
612have to point to any existing resource on the Web. I suggest using an URL
613within a domain you control, which makes sense and if possible holding some
614kind of versionning informations. For example
615<code>"http://www.gnome.org/gnumeric/1.0"</code> is a good namespace scheme.
616Then when you load a file, make sure that a namespace carrying the
617version-independant prefix is installed on the root element of your document,
618and if the version information don't match something you know, warn the user
619and be liberal in what you accept as the input. Also do *not* try to base
620namespace checking on the prefix value &lt;foo:text> may be exactly the same
621as &lt;bar:text> in another document, what really matter is the URI
622associated with the element or the attribute, not the prefix string which is
623just a shortcut for the full URI.</p>
624
625<p>@@Interfaces@@</p>
626
627<p>@@Examples@@</p>
628
629<p>Usually people object using namespace in the case of validation, I object
630this and will make sure that using namespaces won't break validity checking,
631so even is you plan or are using validation I strongly suggest to add
632namespaces to your document. A default namespace scheme
633<code>xmlns="http://...."</code> should not break validity even on less
634flexible parsers. Now using namespace to mix and differenciate content coming
635from mutliple Dtd will certainly break current validation schemes, I will try
636to provide ways to do this, but this may not be portable or standardized.</p>
637
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]638<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]639
640<p>Well what is validation and what is a DTD ?</p>
641
642<p>Validation is the process of checking a document against a set of
643construction rules, a <strong>DTD</strong> (Document Type Definition) is such
644a set of rules.</p>
645
646<p>The validation process and building DTDs are the two most difficult parts
647of XML life cycle. Briefly a DTD defines all the possibles element to be
648found within your document, what is the formal shape of your document tree (by
649defining the allowed content of an element, either text, a regular expression
650for the allowed list of children, or mixed content i.e. both text and childs).
651The DTD also defines the allowed attributes for all elements and the types of
652the attributes. For more detailed informations, I suggest to read the related
653parts of the XML specification, the examples found under
654gnome-xml/test/valid/dtd and the large amount of books available on XML. The
655dia example in gnome-xml/test/valid should be both simple and complete enough
656to allow you to build your own.</p>
657
658<p>A word of warning, building a good DTD which will fit your needs of your
659application in the long-term is far from trivial, however the extra level of
660quality it can insure is well worth the price for some sets of applications or
661if you already have already a DTD defined for your application field.</p>
662
663<p>The validation is not completely finished but in a (very IMHO) usable
664state. Until a real validation interface is defined the way to do it is to
665define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
666variable to 1, this will of course be changed at some point:</p>
667
668<p>extern int xmlDoValidityCheckingDefaultValue;</p>
669
670<p>...</p>
671
672<p>xmlDoValidityCheckingDefaultValue = 1;</p>
673
674<p></p>
675
676<p>To handle external entities, use the function
677<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
678link in you HTTP/FTP/Entities database library to the standard libxml
679core.</p>
680
681<p>@@interfaces@@</p>
682
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]683<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]684
685<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]686Model</em> this is an API for accessing XML or HTML structured documents.
687Native 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]688be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]689files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]690set of IDL (or Java) interfaces allowing to traverse and manipulate a
691document. The DOM library will allow accessing and modifying "live" documents
692presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]693
694<p><img src="DOM.gif" alt=" DOM.gif "></p>
695
696<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]697embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]698
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]699<p>The current DOM implementation on top of libxml is the <a
700href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
701a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
702Levien</a>.</p>
703
704<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
705
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]706<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]707
708<p>Here is a real size example, where the actual content of the application
709data 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]710a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]711storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
712base</a>:</p>
713<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]714&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
715 &lt;gjob:Jobs>
716
717 &lt;gjob:Job>
718 &lt;gjob:Project ID="3"/>
719 &lt;gjob:Application>GBackup&lt;/gjob:Application>
720 &lt;gjob:Category>Development&lt;/gjob:Category>
721
722 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]723 &lt;gjob:Status>Open&lt;/gjob:Status>
724 &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]725 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
726 &lt;/gjob:Update>
727
728 &lt;gjob:Developers>
729 &lt;gjob:Developer>
730 &lt;/gjob:Developer>
731 &lt;/gjob:Developers>
732
733 &lt;gjob:Contact>
734 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]735 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]736 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]737 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]738 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]739 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]740 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]741 &lt;/gjob:Webpage>
742 &lt;gjob:Snailmail>
743 &lt;/gjob:Snailmail>
744 &lt;gjob:Phone>
745 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]746 &lt;/gjob:Contact>
747
748 &lt;gjob:Requirements>
749 The program should be released as free software, under the GPL.
750 &lt;/gjob:Requirements>
751
752 &lt;gjob:Skills>
753 &lt;/gjob:Skills>
754
755 &lt;gjob:Details>
756 A GNOME based system that will allow a superuser to configure
757 compressed and uncompressed files and/or file systems to be backed
758 up with a supported media in the system. This should be able to
759 perform via find commands generating a list of files that are passed
760 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
761 or via operations performed on the filesystem itself. Email
762 notification and GUI status display very important.
763 &lt;/gjob:Details>
764
765 &lt;/gjob:Job>
766
767 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]768&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]769
770<p>While loading the XML file into an internal DOM tree is a matter of calling
771only a couple of functions, browsing the tree to gather the informations and
772generate the internals structures is harder, and more error prone.</p>
773
774<p>The suggested principle is to be tolerant with respect to the input
775structure. For example the ordering of the attributes is not significant, Cthe
776XML specification is clear about it. It's also usually a good idea to not be
777dependant of the orders of the childs of a given node, unless it really makes
778things harder. Here is some code to parse the informations for a person:</p>
779<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]780 * A person record
781 */
782typedef struct person {
783 char *name;
784 char *email;
785 char *company;
786 char *organisation;
787 char *smail;
788 char *webPage;
789 char *phone;
790} person, *personPtr;
791
792/*
793 * And the code needed to parse it
794 */
795personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
796 personPtr ret = NULL;
797
798DEBUG("parsePerson\n");
799 /*
800 * allocate the struct
801 */
802 ret = (personPtr) malloc(sizeof(person));
803 if (ret == NULL) {
804 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]805 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]806 }
807 memset(ret, 0, sizeof(person));
808
809 /* We don't care what the top level element name is */
810 cur = cur->childs;
811 while (cur != NULL) {
812 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]813 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]814 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]815 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
816 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]817 }
818
819 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]820}</pre>
821
822<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]823<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]824 <li>Usually a recursive parsing style is the more convenient one, XML data
825 being by nature subject to repetitive constructs and usualy exibit highly
826 stuctured patterns.</li>
827 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
828 the pointer to the global XML document and the namespace reserved to the
829 application. Document wide information are needed for example to decode
830 entities and it's a good coding practice to define a namespace for your
831 application set of data and test that the element and attributes you're
832 analyzing actually pertains to your application space. This is done by a
833 simple equality test (cur->ns == ns).</li>
834 <li>To retrieve text and attributes value, it is suggested to use the
835 function <em>xmlNodeListGetString</em> to gather all the text and entity
836 reference nodes generated by the DOM output and produce an single text
837 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]838</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]839
840<p>Here is another piece of code used to parse another level of the
841structure:</p>
842<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]843 * a Description for a Job
844 */
845typedef struct job {
846 char *projectID;
847 char *application;
848 char *category;
849 personPtr contact;
850 int nbDevelopers;
851 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
852} job, *jobPtr;
853
854/*
855 * And the code needed to parse it
856 */
857jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
858 jobPtr ret = NULL;
859
860DEBUG("parseJob\n");
861 /*
862 * allocate the struct
863 */
864 ret = (jobPtr) malloc(sizeof(job));
865 if (ret == NULL) {
866 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]867 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]868 }
869 memset(ret, 0, sizeof(job));
870
871 /* We don't care what the top level element name is */
872 cur = cur->childs;
873 while (cur != NULL) {
874
875 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]876 ret->projectID = xmlGetProp(cur, "ID");
877 if (ret->projectID == NULL) {
878 fprintf(stderr, "Project has no ID\n");
879 }
880 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]881 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]882 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]883 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]884 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]885 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]886 ret->contact = parsePerson(doc, ns, cur);
887 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]888 }
889
890 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]891}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]892
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]893<p>One can notice that once used to it, writing this kind of code is quite
894simple, but boring. Ultimately, it could be possble to write stubbers taking
895either C data structure definitions, a set of XML examples or an XML DTD and
896produce the code needed to import and export the content between C data and
897XML storage. This is left as an exercise to the reader :-)</p>
898
899<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]900example</a> as a template, it is also available with Makefile in the Gnome CVS
901base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]902
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]903<p></p>
904
905<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
906
Daniel Veillarddbfd6411999-12-28 16:35:14 +0000[diff] [blame^]907<p>$Id: xml.html,v 1.17 1999/12/21 15:35:27 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]908</body>
909</html>