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gerrit-public.fairphone.software / platform / external / libxml2 / 5cb5ab8d94a0715ba600b01377cf57531cc97f73 / . / doc / xml.html
blob: 40d6e0c366bfb5cd1360dedc5f72fc263378ee98 [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 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 Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame^]131</ul>
132
133<h3>1.8.2: Dec 21 1999</h3>
134<ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]135 <li>I got another problem with includes and C++, I hope this issue is fixed
136 for good this time</li>
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame^]137 <li>Added a few tree modification functions: xmlReplaceNode,
138 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and
139 xmlDocSetRootElement</li>
140 <li>Tried to improve the HTML output with help from <a
141 href="mailto:clahey@umich.edu">Chris Lahey</a></li>
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]142</ul>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]143
Daniel Veillarde4e51311999-12-18 15:32:46 +0000[diff] [blame]144<h3>1.8.1: Dec 18 1999</h3>
145<ul>
146 <li>various patches to avoid troubles when using libxml with C++ compilers
147 the "namespace" keyword and C escaping in include files</li>
148 <li>a problem in one of the core macros IS_CHAR was corrected</li>
149 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing,
150 and more specifically the Dia application</li>
Daniel Veillard944b5ff1999-12-15 19:08:24 +0000[diff] [blame]151 <li>fixed a posteriori validation (validation after parsing, or by using a
152 Dtd not specified in the original document)</li>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]153 <li>fixed a bug in</li>
Daniel Veillard10a2c651999-12-12 13:03:50 +0000[diff] [blame]154</ul>
155
156<h3>1.8.0: Dec 12 1999</h3>
157<ul>
158 <li>cleanup, especially memory wise</li>
159 <li>the parser should be more reliable, especially the HTML one, it should
160 not crash, whatever the input !</li>
161 <li>Integrated various patches, especially a speedup improvement for large
162 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>,
163 configure with --with-buffers to enable them.</li>
164 <li>attribute normalization, oops should have been added long ago !</li>
165 <li>attributes defaulted from Dtds should be available, xmlSetProp() now
166 does entities escapting by default.</li>
Daniel Veillard4c3a2031999-11-19 17:46:26 +0000[diff] [blame]167</ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]168
169<h3>1.7.4: Oct 25 1999</h3>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]170<ul>
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]171 <li>Lots of HTML improvement</li>
172 <li>Fixed some errors when saving both XML and HTML</li>
173 <li>More examples, the regression tests should now look clean</li>
174 <li>Fixed a bug with contiguous charref</li>
175</ul>
176
177<h3>1.7.3: Sep 29 1999</h3>
178<ul>
179 <li>portability problems fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]180 <li>snprintf was used unconditionnally, leading to link problems on system
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]181 were it's not available, fixed</li>
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]182</ul>
183
184<h3>1.7.1: Sep 24 1999</h3>
185<ul>
186 <li>The basic type for strings manipulated by libxml has been renamed in
187 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason
188 is that CHAR was conflicting with a predefined type on Windows. However on
189 non WIN32 environment, compatibility is provided by the way of a
190 <strong>#define </strong>.</li>
191 <li>Changed another error : the use of a structure field called errno, and
192 leading to troubles on platforms where it's a macro</li>
193</ul>
194
195<h3>1.7.0: sep 23 1999</h3>
196<ul>
197 <li>Added the ability to fetch remote DTD or parsed entities, see the <a
198 href="gnome-xml-nanohttp.html">nanohttp</a> module.</li>
199 <li>Added an errno to report errors by another mean than a simple printf
200 like callback</li>
201 <li>Finished ID/IDREF support and checking when validation</li>
202 <li>Serious memory leaks fixed (there is now a <a
203 href="gnome-xml-xmlmemory.html">memory wrapper</a> module)</li>
204 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a>
205 implementation</li>
206 <li>Added an HTML parser front-end</li>
207</ul>
208
209<h2><a name="XML">XML</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]210
211<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for markup
212based structured documents, here is <a name="example">an example</a>:</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]213<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]214&lt;EXAMPLE prop1="gnome is great" prop2="&amp;amp; linux too">
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]215 &lt;head>
216 &lt;title>Welcome to Gnome&lt;/title>
217 &lt;/head>
218 &lt;chapter>
219 &lt;title>The Linux adventure&lt;/title>
220 &lt;p>bla bla bla ...&lt;/p>
221 &lt;image href="linus.gif"/>
222 &lt;p>...&lt;/p>
223 &lt;/chapter>
224&lt;/EXAMPLE></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]225
226<p>The first line specify that it's an XML document and gives useful
227informations about it's encoding. Then the document is a text format whose
228structure is specified by tags between brackets. <strong>Each tag opened have
229to be closed</strong> XML is pedantic about this, not that for example the
230image tag has no content (just an attribute) and is closed by ending up the
231tag with <code>/></code>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]232
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]233<p>XML can be applied sucessfully to a wide range or usage from long term
234structured document maintenance where it follows the steps of SGML to simple
235data encoding mechanism like configuration file format (glade), spreadsheets
236(gnumeric), or even shorter lived document like in WebDAV where it is used to
237encode remote call between a client and a server.</p>
238
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]239<h2><a name="tree">The tree output</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]240
241<p>The parser returns a tree built during the document analysis. The value
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]242returned is an <strong>xmlDocPtr</strong> (i.e. a pointer to an
243<strong>xmlDoc</strong> structure). This structure contains informations like
244the file name, the document type, and a <strong>root</strong> pointer which
245is the root of the document (or more exactly the first child under the root
246which is the document). The tree is made of <strong>xmlNode</strong>s, chained
247in double linked lists of siblings and with childs&lt;->parent relationship.
248An xmlNode can also carry properties (a chain of xmlAttr structures). An
249attribute 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]250
251<p>Here is an example (erroneous w.r.t. the XML spec since there should be
252only one ELEMENT under the root):</p>
253
254<p><img src="structure.gif" alt=" structure.gif "></p>
255
256<p>In the source package there is a small program (not installed by default)
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]257called <strong>tester</strong> which parses XML files given as argument and
258prints them back as parsed, this is useful to detect errors both in XML code
259and in the XML parser itself. It has an option <strong>--debug</strong> which
260prints the actual in-memory structure of the document, here is the result with
261the <a href="#example">example</a> given before:</p>
262<pre>DOCUMENT
263version=1.0
264standalone=true
265 ELEMENT EXAMPLE
266 ATTRIBUTE prop1
267 TEXT
268 content=gnome is great
269 ATTRIBUTE prop2
270 ENTITY_REF
271 TEXT
272 content= too
273 ELEMENT head
274 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]275 TEXT
276 content=Welcome to Gnome
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]277 ELEMENT chapter
278 ELEMENT title
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]279 TEXT
280 content=The Linux adventure
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]281 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]282 TEXT
283 content=bla bla bla ...
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]284 ELEMENT image
285 ATTRIBUTE href
286 TEXT
287 content=linus.gif
288 ELEMENT p
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]289 TEXT
290 content=...</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]291
292<p>This should be useful to learn the internal representation model.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]293
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]294<h2><a name="interface">The SAX interface</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]295
296<p>Sometimes the DOM tree output is just to large to fit reasonably into
297memory. In that case and if you don't expect to save back the XML document
298loaded using libxml, it's better to use the SAX interface of libxml. SAX is a
299<strong>callback based interface</strong> to the parser. Before parsing, the
300application layer register a customized set of callbacks which will be called
301by the library as it progresses through the XML input.</p>
302
303<p>To get a more detailed step-by-step guidance on using the SAX interface of
304libxml, <a href="mailto:james@daa.com.au">James Henstridge</a> made <a
305href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">a nice
306documentation.</a></p>
307
308<p>You can debug the SAX behaviour by using the <strong>testSAX</strong>
309program located in the gnome-xml module (it's usually not shipped in the
310binary packages of libxml, but you can also find it in the tar source
311distribution). Here is the sequence of callback that would be generated when
312parsing the example given before as reported by testSAX:</p>
313<pre>SAX.setDocumentLocator()
314SAX.startDocument()
315SAX.getEntity(amp)
316SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp;amp; linux too')
317SAX.characters( , 3)
318SAX.startElement(head)
319SAX.characters( , 4)
320SAX.startElement(title)
321SAX.characters(Welcome to Gnome, 16)
322SAX.endElement(title)
323SAX.characters( , 3)
324SAX.endElement(head)
325SAX.characters( , 3)
326SAX.startElement(chapter)
327SAX.characters( , 4)
328SAX.startElement(title)
329SAX.characters(The Linux adventure, 19)
330SAX.endElement(title)
331SAX.characters( , 4)
332SAX.startElement(p)
333SAX.characters(bla bla bla ..., 15)
334SAX.endElement(p)
335SAX.characters( , 4)
336SAX.startElement(image, href='linus.gif')
337SAX.endElement(image)
338SAX.characters( , 4)
339SAX.startElement(p)
340SAX.characters(..., 3)
341SAX.endElement(p)
342SAX.characters( , 3)
343SAX.endElement(chapter)
344SAX.characters( , 1)
345SAX.endElement(EXAMPLE)
346SAX.endDocument()</pre>
347
348<p>Most of the other functionnalities of libxml are based on the DOM tree
349building facility, so nearly everything up to the end of this document
350presuppose the use of the standard DOM tree build. Note that the DOM tree
351itself is built by a set of registered default callbacks, without internal
352specific interface.</p>
353
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]354<h2><a name="library">The XML library interfaces</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]355
356<p>This section is directly intended to help programmers getting bootstrapped
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]357using the XML library from the C language. It doesn't intent to be extensive,
358I hope the automatically generated docs will provide the completeness
359required, but as a separated set of documents. The interfaces of the XML
360library are by principle low level, there is nearly zero abstration. Those
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]361interested in a higher level API should <a href="#DOM">look at DOM</a>.</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]362
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]363<h3><a name="Invoking">Invoking the parser</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]364
365<p>Usually, the first thing to do is to read an XML input, the parser accepts
366to parse both memory mapped documents or direct files. The functions are
367defined in "parser.h":</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]368<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]369 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt>
370 <dd><p>parse a zero terminated string containing the document</p>
371 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]372</dl>
373<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]374 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt>
375 <dd><p>parse an XML document contained in a file (possibly compressed)</p>
376 </dd>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]377</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]378
379<p>This returns a pointer to the document structure (or NULL in case of
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]380failure).</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]381
382<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]383memory-hungry, first to load the document in memory, second to build the tree.
384Reading a document without building the tree will be possible in the future by
385pluggin the code to the SAX interface (see SAX.c).</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]386
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]387<h3><a name="Building">Building a tree from scratch</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]388
389<p>The other way to get an XML tree in memory is by building it. Basically
390there is a set of functions dedicated to building new elements, those are also
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]391described in "tree.h", here is for example the piece of code producing the
392example used before:</p>
393<pre> xmlDocPtr doc;
394 xmlNodePtr tree, subtree;
395
396 doc = xmlNewDoc("1.0");
397 doc->root = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL);
398 xmlSetProp(doc->root, "prop1", "gnome is great");
399 xmlSetProp(doc->root, "prop2", "&amp;linux; too");
400 tree = xmlNewChild(doc->root, NULL, "head", NULL);
401 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome");
402 tree = xmlNewChild(doc->root, NULL, "chapter", NULL);
403 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure");
404 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ...");
405 subtree = xmlNewChild(tree, NULL, "image", NULL);
406 xmlSetProp(subtree, "href", "linus.gif");</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]407
408<p>Not really rocket science ...</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]409
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]410<h3><a name="Traversing">Traversing the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]411
412<p>Basically by including "tree.h" your code has access to the internal
413structure of all the element of the tree. The names should be somewhat simple
414like <strong>parent</strong>, <strong>childs</strong>, <strong>next</strong>,
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]415<strong>prev</strong>, <strong>properties</strong>, etc... For example still
416with the previous example:</p>
417<pre><code>doc->root->childs->childs</code></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]418
419<p>points to the title element,</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]420<pre>doc->root->childs->next->child->child</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]421
422<p>points to the text node containing the chapter titlle "The Linux adventure"
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]423and</p>
424<pre>doc->root->properties->next->val</pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]425
426<p>points to the entity reference containing the value of "&amp;linux" at the
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]427beginning of the second attribute of the root element "EXAMPLE".</p>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]428
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]429<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be
430present before the document root, so doc->root may point to an element which
431is not the document Root Element, a function
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame^]432<code>xmlDocGetRootElement()</code> was added for this purpose.</p>
Daniel Veillardb24054a1999-12-18 15:32:46 +0000[diff] [blame]433
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]434<h3><a name="Modifying">Modifying the tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]435
436<p>functions are provided to read and write the document content:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]437<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]438 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const
439 xmlChar *value);</code></dt>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]440 <dd><p>This set (or change) an attribute carried by an ELEMENT node the
441 value can be NULL</p>
442 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]443</dl>
444<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]445 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]446 *name);</code></dt>
447 <dd><p>This function returns a pointer to the property content, note that
448 no extra copy is made</p>
449 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]450</dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]451
452<p>Two functions must be used to read an write the text associated to
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]453elements:</p>
454<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]455 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]456 *value);</code></dt>
457 <dd><p>This function takes an "external" string and convert it to one text
458 node or possibly to a list of entity and text nodes. All non-predefined
459 entity references like &amp;Gnome; will be stored internally as an
460 entity node, hence the result of the function may not be a single
461 node.</p>
462 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]463</dl>
464<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]465 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]466 inLine);</code></dt>
467 <dd><p>this is the dual function, which generate a new string containing
468 the content of the text and entity nodes. Note the extra argument
469 inLine, if set to 1 instead of returning the &amp;Gnome; XML encoding in
470 the string it will substitute it with it's value say "GNU Network Object
471 Model Environment". Set it if you want to use the string for non XML
472 usage like User Interface.</p>
473 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]474</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]475
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]476<h3><a name="Saving">Saving a tree</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]477
478<p>Basically 3 options are possible:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]479<dl>
Daniel Veillarddd6b3671999-09-23 22:19:22 +0000[diff] [blame]480 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]481 *size);</code></dt>
482 <dd><p>returns a buffer where the document has been saved</p>
483 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]484</dl>
485<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]486 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt>
487 <dd><p>dumps a buffer to an open file descriptor</p>
488 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]489</dl>
490<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]491 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt>
492 <dd><p>save the document ot a file. In that case the compression interface
493 is triggered if turned on</p>
494 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]495</dl>
Daniel Veillard10c6a8f1998-10-28 01:00:12 +0000[diff] [blame]496
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]497<h3><a name="Compressio">Compression</a></h3>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]498
499<p>The library handle transparently compression when doing file based
500accesses, the level of compression on saves can be tuned either globally or
501individually for one file:</p>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]502<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]503 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt>
504 <dd><p>Get the document compression ratio (0-9)</p>
505 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]506</dl>
507<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]508 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt>
509 <dd><p>Set the document compression ratio</p>
510 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]511</dl>
512<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]513 <dt><code>int xmlGetCompressMode(void);</code></dt>
514 <dd><p>Get the default compression ratio</p>
515 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]516</dl>
517<dl>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]518 <dt><code>void xmlSetCompressMode(int mode);</code></dt>
519 <dd><p>set the default compression ratio</p>
520 </dd>
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]521</dl>
522
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]523<h2><a name="Entities">Entities or no entities</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]524
525<p>Entities principle is similar to simple C macros. They define an
526abbreviation for a given string that you can reuse many time through the
527content of your document. They are especially useful when frequent occurrences
528of a given string may occur within a document or to confine the change needed
529to a document to a restricted area in the internal subset of the document (at
530the beginning). Example:</p>
531<pre>1 &lt;?xml version="1.0"?>
5322 &lt;!DOCTYPE EXAMPLE SYSTEM "example.dtd" [
5333 &lt;!ENTITY xml "Extensible Markup Language">
5344 ]>
5355 &lt;EXAMPLE>
5366 &amp;xml;
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]5377 &lt;/EXAMPLE></pre>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]538
539<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]540it's name with '&amp;' and following it by ';' without any spaces added. There
541are 5 predefined entities in libxml allowing to escape charaters with
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]542predefined meaning in some parts of the xml document content:
543<strong>&amp;lt;</strong> for the letter '&lt;', <strong>&amp;gt;</strong> for
544the letter '>', <strong>&amp;apos;</strong> for the letter ''',
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]545<strong>&amp;quot;</strong> for the letter '"', and <strong>&amp;amp;</strong>
546for the letter '&amp;'.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]547
548<p>One of the problems related to entities is that you may want the parser to
549substitute entities content to see the replacement text in your application,
550or you may prefer keeping entities references as such in the content to be
551able to save the document back without loosing this usually precious
552information (if the user went through the pain of explicitley defining
553entities, he may have a a rather negative attitude if you blindly susbtitute
554them as saving time). The function <a
555href="gnome-xml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a>
556allows to check and change the behaviour, which is to not substitute entities
557by default.</p>
558
559<p>Here is the DOM tree built by libxml for the previous document in the
560default case:</p>
561<pre>/gnome/src/gnome-xml -> ./tester --debug test/ent1
562DOCUMENT
563version=1.0
564 ELEMENT EXAMPLE
565 TEXT
566 content=
567 ENTITY_REF
568 INTERNAL_GENERAL_ENTITY xml
569 content=Extensible Markup Language
570 TEXT
571 content=</pre>
572
573<p>And here is the result when substituting entities:</p>
574<pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1
575DOCUMENT
576version=1.0
577 ELEMENT EXAMPLE
578 TEXT
579 content= Extensible Markup Language</pre>
580
581<p>So entities or no entities ? Basically it depends on your use case, I
582suggest to keep the non-substituting default behaviour and avoid using
583entities in your XML document or data if you are not willing to handle the
584entity references elements in the DOM tree.</p>
585
586<p>Note that at save time libxml enforce the conversion of the predefined
587entities where necessary to prevent well-formedness problems, and will also
588transparently replace those with chars (i.e. will not generate entity
589reference elements in the DOM tree nor call the reference() SAX callback when
590finding them in the input).</p>
591
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]592<h2><a name="Namespaces">Namespaces</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]593
594<p>The libxml library implement namespace @@ support by recognizing namespace
595contructs in the input, and does namespace lookup automatically when building
596the DOM tree. A namespace declaration is associated with an in-memory
597structure and all elements or attributes within that namespace point to it.
598Hence testing the namespace is a simple and fast equality operation at the
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]599user level.</p>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]600
601<p>I suggest it that people using libxml use a namespace, and declare it on
602the root element of their document as the default namespace. Then they dont
603need to happend the prefix in the content but we will have a basis for future
604semantic refinement and merging of data from different sources. This doesn't
605augment significantly the size of the XML output, but significantly increase
606it's value in the long-term.</p>
607
608<p>Concerning the namespace value, this has to be an URL, but this doesn't
609have to point to any existing resource on the Web. I suggest using an URL
610within a domain you control, which makes sense and if possible holding some
611kind of versionning informations. For example
612<code>"http://www.gnome.org/gnumeric/1.0"</code> is a good namespace scheme.
613Then when you load a file, make sure that a namespace carrying the
614version-independant prefix is installed on the root element of your document,
615and if the version information don't match something you know, warn the user
616and be liberal in what you accept as the input. Also do *not* try to base
617namespace checking on the prefix value &lt;foo:text> may be exactly the same
618as &lt;bar:text> in another document, what really matter is the URI
619associated with the element or the attribute, not the prefix string which is
620just a shortcut for the full URI.</p>
621
622<p>@@Interfaces@@</p>
623
624<p>@@Examples@@</p>
625
626<p>Usually people object using namespace in the case of validation, I object
627this and will make sure that using namespaces won't break validity checking,
628so even is you plan or are using validation I strongly suggest to add
629namespaces to your document. A default namespace scheme
630<code>xmlns="http://...."</code> should not break validity even on less
631flexible parsers. Now using namespace to mix and differenciate content coming
632from mutliple Dtd will certainly break current validation schemes, I will try
633to provide ways to do this, but this may not be portable or standardized.</p>
634
Daniel Veillard2f4dfc41999-09-24 14:03:48 +0000[diff] [blame]635<h2><a name="Validation">Validation, or are you afraid of DTDs ?</a></h2>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]636
637<p>Well what is validation and what is a DTD ?</p>
638
639<p>Validation is the process of checking a document against a set of
640construction rules, a <strong>DTD</strong> (Document Type Definition) is such
641a set of rules.</p>
642
643<p>The validation process and building DTDs are the two most difficult parts
644of XML life cycle. Briefly a DTD defines all the possibles element to be
645found within your document, what is the formal shape of your document tree (by
646defining the allowed content of an element, either text, a regular expression
647for the allowed list of children, or mixed content i.e. both text and childs).
648The DTD also defines the allowed attributes for all elements and the types of
649the attributes. For more detailed informations, I suggest to read the related
650parts of the XML specification, the examples found under
651gnome-xml/test/valid/dtd and the large amount of books available on XML. The
652dia example in gnome-xml/test/valid should be both simple and complete enough
653to allow you to build your own.</p>
654
655<p>A word of warning, building a good DTD which will fit your needs of your
656application in the long-term is far from trivial, however the extra level of
657quality it can insure is well worth the price for some sets of applications or
658if you already have already a DTD defined for your application field.</p>
659
660<p>The validation is not completely finished but in a (very IMHO) usable
661state. Until a real validation interface is defined the way to do it is to
662define and set the <strong>xmlDoValidityCheckingDefaultValue</strong> external
663variable to 1, this will of course be changed at some point:</p>
664
665<p>extern int xmlDoValidityCheckingDefaultValue;</p>
666
667<p>...</p>
668
669<p>xmlDoValidityCheckingDefaultValue = 1;</p>
670
671<p></p>
672
673<p>To handle external entities, use the function
674<strong>xmlSetExternalEntityLoader</strong>(xmlExternalEntityLoader f); to
675link in you HTTP/FTP/Entities database library to the standard libxml
676core.</p>
677
678<p>@@interfaces@@</p>
679
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]680<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]681
682<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]683Model</em> this is an API for accessing XML or HTML structured documents.
684Native 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]685be based on gnome-xml. This will be a far cleaner interface to manipulate XML
Daniel Veillardc08a2c61999-09-08 21:35:25 +0000[diff] [blame]686files within Gnome since it won't expose the internal structure. DOM defines a
Daniel Veillard25940b71998-10-29 05:51:30 +0000[diff] [blame]687set of IDL (or Java) interfaces allowing to traverse and manipulate a
688document. The DOM library will allow accessing and modifying "live" documents
689presents on other programs like this:</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]690
691<p><img src="DOM.gif" alt=" DOM.gif "></p>
692
693<p>This should help greatly doing things like modifying a gnumeric spreadsheet
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]694embedded in a GWP document for example.</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]695
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]696<p>The current DOM implementation on top of libxml is the <a
697href="http://cvs.gnome.org/lxr/source/gdome/">gdome Gnome module</a>, this is
698a full DOM interface, thanks to <a href="mailto:raph@levien.com">Raph
699Levien</a>.</p>
700
701<p>The gnome-dom module in the Gnome CVS base is obsolete</p>
702
Daniel Veillard35008381999-10-25 13:15:52 +0000[diff] [blame]703<h2><a name="Example"></a><a name="real">A real example</a></h2>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]704
705<p>Here is a real size example, where the actual content of the application
706data 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]707a proposal to keep a database of jobs related to Gnome, with an XML based
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]708storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
709base</a>:</p>
710<pre>&lt;?xml version="1.0"?>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]711&lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
712 &lt;gjob:Jobs>
713
714 &lt;gjob:Job>
715 &lt;gjob:Project ID="3"/>
716 &lt;gjob:Application>GBackup&lt;/gjob:Application>
717 &lt;gjob:Category>Development&lt;/gjob:Category>
718
719 &lt;gjob:Update>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]720 &lt;gjob:Status>Open&lt;/gjob:Status>
721 &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]722 &lt;gjob:Salary>USD 0.00&lt;/gjob:Salary>
723 &lt;/gjob:Update>
724
725 &lt;gjob:Developers>
726 &lt;gjob:Developer>
727 &lt;/gjob:Developer>
728 &lt;/gjob:Developers>
729
730 &lt;gjob:Contact>
731 &lt;gjob:Person>Nathan Clemons&lt;/gjob:Person>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]732 &lt;gjob:Email>nathan@windsofstorm.net&lt;/gjob:Email>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]733 &lt;gjob:Company>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]734 &lt;/gjob:Company>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]735 &lt;gjob:Organisation>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]736 &lt;/gjob:Organisation>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]737 &lt;gjob:Webpage>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]738 &lt;/gjob:Webpage>
739 &lt;gjob:Snailmail>
740 &lt;/gjob:Snailmail>
741 &lt;gjob:Phone>
742 &lt;/gjob:Phone>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]743 &lt;/gjob:Contact>
744
745 &lt;gjob:Requirements>
746 The program should be released as free software, under the GPL.
747 &lt;/gjob:Requirements>
748
749 &lt;gjob:Skills>
750 &lt;/gjob:Skills>
751
752 &lt;gjob:Details>
753 A GNOME based system that will allow a superuser to configure
754 compressed and uncompressed files and/or file systems to be backed
755 up with a supported media in the system. This should be able to
756 perform via find commands generating a list of files that are passed
757 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
758 or via operations performed on the filesystem itself. Email
759 notification and GUI status display very important.
760 &lt;/gjob:Details>
761
762 &lt;/gjob:Job>
763
764 &lt;/gjob:Jobs>
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]765&lt;/gjob:Helping></pre>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]766
767<p>While loading the XML file into an internal DOM tree is a matter of calling
768only a couple of functions, browsing the tree to gather the informations and
769generate the internals structures is harder, and more error prone.</p>
770
771<p>The suggested principle is to be tolerant with respect to the input
772structure. For example the ordering of the attributes is not significant, Cthe
773XML specification is clear about it. It's also usually a good idea to not be
774dependant of the orders of the childs of a given node, unless it really makes
775things harder. Here is some code to parse the informations for a person:</p>
776<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]777 * A person record
778 */
779typedef struct person {
780 char *name;
781 char *email;
782 char *company;
783 char *organisation;
784 char *smail;
785 char *webPage;
786 char *phone;
787} person, *personPtr;
788
789/*
790 * And the code needed to parse it
791 */
792personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
793 personPtr ret = NULL;
794
795DEBUG("parsePerson\n");
796 /*
797 * allocate the struct
798 */
799 ret = (personPtr) malloc(sizeof(person));
800 if (ret == NULL) {
801 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]802 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]803 }
804 memset(ret, 0, sizeof(person));
805
806 /* We don't care what the top level element name is */
807 cur = cur->childs;
808 while (cur != NULL) {
809 if ((!strcmp(cur->name, "Person")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]810 ret->name = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]811 if ((!strcmp(cur->name, "Email")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]812 ret->email = xmlNodeListGetString(doc, cur->childs, 1);
813 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]814 }
815
816 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]817}</pre>
818
819<p>Here is a couple of things to notice:</p>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]820<ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]821 <li>Usually a recursive parsing style is the more convenient one, XML data
822 being by nature subject to repetitive constructs and usualy exibit highly
823 stuctured patterns.</li>
824 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, i.e.
825 the pointer to the global XML document and the namespace reserved to the
826 application. Document wide information are needed for example to decode
827 entities and it's a good coding practice to define a namespace for your
828 application set of data and test that the element and attributes you're
829 analyzing actually pertains to your application space. This is done by a
830 simple equality test (cur->ns == ns).</li>
831 <li>To retrieve text and attributes value, it is suggested to use the
832 function <em>xmlNodeListGetString</em> to gather all the text and entity
833 reference nodes generated by the DOM output and produce an single text
834 string.</li>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]835</ul>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]836
837<p>Here is another piece of code used to parse another level of the
838structure:</p>
839<pre>/*
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]840 * a Description for a Job
841 */
842typedef struct job {
843 char *projectID;
844 char *application;
845 char *category;
846 personPtr contact;
847 int nbDevelopers;
848 personPtr developers[100]; /* using dynamic alloc is left as an exercise */
849} job, *jobPtr;
850
851/*
852 * And the code needed to parse it
853 */
854jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
855 jobPtr ret = NULL;
856
857DEBUG("parseJob\n");
858 /*
859 * allocate the struct
860 */
861 ret = (jobPtr) malloc(sizeof(job));
862 if (ret == NULL) {
863 fprintf(stderr,"out of memory\n");
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]864 return(NULL);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]865 }
866 memset(ret, 0, sizeof(job));
867
868 /* We don't care what the top level element name is */
869 cur = cur->childs;
870 while (cur != NULL) {
871
872 if ((!strcmp(cur->name, "Project")) &amp;&amp; (cur->ns == ns)) {
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]873 ret->projectID = xmlGetProp(cur, "ID");
874 if (ret->projectID == NULL) {
875 fprintf(stderr, "Project has no ID\n");
876 }
877 }
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]878 if ((!strcmp(cur->name, "Application")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]879 ret->application = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]880 if ((!strcmp(cur->name, "Category")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]881 ret->category = xmlNodeListGetString(doc, cur->childs, 1);
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]882 if ((!strcmp(cur->name, "Contact")) &amp;&amp; (cur->ns == ns))
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]883 ret->contact = parsePerson(doc, ns, cur);
884 cur = cur->next;
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]885 }
886
887 return(ret);
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]888}</pre>
Daniel Veillard14fff061999-06-22 21:49:07 +0000[diff] [blame]889
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]890<p>One can notice that once used to it, writing this kind of code is quite
891simple, but boring. Ultimately, it could be possble to write stubbers taking
892either C data structure definitions, a set of XML examples or an XML DTD and
893produce the code needed to import and export the content between C data and
894XML storage. This is left as an exercise to the reader :-)</p>
895
896<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]897example</a> as a template, it is also available with Makefile in the Gnome CVS
898base under gnome-xml/example</p>
Daniel Veillardb05deb71999-08-10 19:04:08 +0000[diff] [blame]899
Daniel Veillardc8eab3a1999-09-04 18:27:23 +0000[diff] [blame]900<p></p>
901
902<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
903
Daniel Veillard5cb5ab81999-12-21 15:35:29 +0000[diff] [blame^]904<p>$Id: xml.html,v 1.16 1997/01/04 02:49:42 veillard Exp $</p>
Daniel Veillardccb09631998-10-27 06:21:04 +0000[diff] [blame]905</body>
906</html>