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Daniel Veillard	43d3f61	2001-11-10 11:57:23 +0000	[diff] [blame]	1	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	2	<html>
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Daniel Veillard	e166254	2002-08-28 11:50:59 +0000	[diff] [blame]	4	<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
Daniel Veillard	c332dab	2002-03-29 14:08:27 +0000	[diff] [blame]	5	<link rel="SHORTCUT ICON" href="/favicon.ico">
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Daniel Veillard	373a475	2002-02-21 14:46:29 +0000	[diff] [blame]	7	TD {font-family: Verdana,Arial,Helvetica}
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Daniel Veillard	b8cfbd1	2001-10-25 10:53:28 +0000	[diff] [blame]	12	A:link, A:visited, A:active { text-decoration: underline }
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				14	<title>A real example</title>
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				16	<body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000">
				17	<table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr>
				18	<td width="180">
Daniel Veillard	8f40f1e	2002-08-28 21:18:45 +0000	[diff] [blame]	19	<a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo"></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo"></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo"></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo"></a></div>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	20	</td>
				21	<td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center">
				22	<h1>The XML C library for Gnome</h1>
				23	<h2>A real example</h2>
				24	</td></tr></table></td></tr></table></td>
				25	</tr></table>
				26	<table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr>
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	27	<td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td>
				28	<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	29	<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Main Menu</b></center></td></tr>
Daniel Veillard	8acca11	2002-01-21 09:52:27 +0000	[diff] [blame]	30	<tr><td bgcolor="#fffacd"><ul>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	31	<li><a href="index.html">Home</a></li>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	32	<li><a href="intro.html">Introduction</a></li>
Daniel Veillard	b8cfbd1	2001-10-25 10:53:28 +0000	[diff] [blame]	33	<li><a href="FAQ.html">FAQ</a></li>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	34	<li><a href="docs.html">Documentation</a></li>
				35	<li><a href="bugs.html">Reporting bugs and getting help</a></li>
				36	<li><a href="help.html">How to help</a></li>
				37	<li><a href="downloads.html">Downloads</a></li>
				38	<li><a href="news.html">News</a></li>
Daniel Veillard	7b602b4	2002-01-08 13:26:00 +0000	[diff] [blame]	39	<li><a href="XMLinfo.html">XML</a></li>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	40	<li><a href="XSLT.html">XSLT</a></li>
Daniel Veillard	6dbcaf8	2002-02-20 14:37:47 +0000	[diff] [blame]	41	<li><a href="python.html">Python and bindings</a></li>
Daniel Veillard	b8cfbd1	2001-10-25 10:53:28 +0000	[diff] [blame]	42	<li><a href="architecture.html">libxml architecture</a></li>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	43	<li><a href="tree.html">The tree output</a></li>
				44	<li><a href="interface.html">The SAX interface</a></li>
Daniel Veillard	b8cfbd1	2001-10-25 10:53:28 +0000	[diff] [blame]	45	<li><a href="xmldtd.html">Validation & DTDs</a></li>
				46	<li><a href="xmlmem.html">Memory Management</a></li>
				47	<li><a href="encoding.html">Encodings support</a></li>
				48	<li><a href="xmlio.html">I/O Interfaces</a></li>
				49	<li><a href="catalog.html">Catalog support</a></li>
				50	<li><a href="library.html">The parser interfaces</a></li>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	51	<li><a href="entities.html">Entities or no entities</a></li>
				52	<li><a href="namespaces.html">Namespaces</a></li>
Daniel Veillard	b8cfbd1	2001-10-25 10:53:28 +0000	[diff] [blame]	53	<li><a href="upgrade.html">Upgrading 1.x code</a></li>
Daniel Veillard	52dcab3	2001-10-30 12:51:17 +0000	[diff] [blame]	54	<li><a href="threads.html">Thread safety</a></li>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	55	<li><a href="DOM.html">DOM Principles</a></li>
				56	<li><a href="example.html">A real example</a></li>
				57	<li><a href="contribs.html">Contributions</a></li>
Daniel Veillard	fc59c09	2002-06-05 14:48:26 +0000	[diff] [blame]	58	<li><a href="tutorial/index.html">Tutorial</a></li>
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	59	<li>
				60	<a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a>
				61	</li>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	62	</ul></td></tr>
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	63	</table>
				64	<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillard	3bf65be	2002-01-23 12:36:34 +0000	[diff] [blame]	65	<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr>
				66	<tr><td bgcolor="#fffacd"><ul>
Daniel Veillard	f859256	2002-01-23 17:58:17 +0000	[diff] [blame]	67	<li><a href="APIchunk0.html">Alphabetic</a></li>
Daniel Veillard	3bf65be	2002-01-23 12:36:34 +0000	[diff] [blame]	68	<li><a href="APIconstructors.html">Constructors</a></li>
				69	<li><a href="APIfunctions.html">Functions/Types</a></li>
				70	<li><a href="APIfiles.html">Modules</a></li>
				71	<li><a href="APIsymbols.html">Symbols</a></li>
				72	</ul></td></tr>
				73	</table>
				74	<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	75	<tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr>
Daniel Veillard	8acca11	2002-01-21 09:52:27 +0000	[diff] [blame]	76	<tr><td bgcolor="#fffacd"><ul>
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	77	<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
				78	<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
Daniel Veillard	4a85920	2002-01-08 11:49:22 +0000	[diff] [blame]	79	<li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li>
Daniel Veillard	2d347fa	2002-03-17 10:34:11 +0000	[diff] [blame]	80	<li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li>
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	81	<li><a href="ftp://xmlsoft.org/">FTP</a></li>
				82	<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
Daniel Veillard	db9dfd9	2001-11-26 17:25:02 +0000	[diff] [blame]	83	<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
Daniel Veillard	cb7543b	2002-09-09 10:54:06 +0000	[diff] [blame^]	84	<li><a href="http://www.zveno.com/open_source/libxml2xslt.html">MacOsX binaries</a></li>
Daniel Veillard	e6d8e20	2002-05-02 06:11:10 +0000	[diff] [blame]	85	<li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li>
Daniel Veillard	2d347fa	2002-03-17 10:34:11 +0000	[diff] [blame]	86	<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml&product=libxml2">Bug Tracker</a></li>
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	87	</ul></td></tr>
				88	</table>
				89	</td></tr></table></td>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	90	<td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd">
				91	<p>Here is a real size example, where the actual content of the application
				92	data is not kept in the DOM tree but uses internal structures. It is based on
				93	a proposal to keep a database of jobs related to Gnome, with an XML based
				94	storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
				95	base</a>:</p>
				96	<pre><?xml version="1.0"?>
				97	<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
				98	<gjob:Jobs>
				99
				100	<gjob:Job>
				101	<gjob:Project ID="3"/>
				102	<gjob:Application>GBackup</gjob:Application>
				103	<gjob:Category>Development</gjob:Category>
				104
				105	<gjob:Update>
				106	<gjob:Status>Open</gjob:Status>
				107	<gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified>
				108	<gjob:Salary>USD 0.00</gjob:Salary>
				109	</gjob:Update>
				110
				111	<gjob:Developers>
				112	<gjob:Developer>
				113	</gjob:Developer>
				114	</gjob:Developers>
				115
				116	<gjob:Contact>
				117	<gjob:Person>Nathan Clemons</gjob:Person>
				118	<gjob:Email>nathan@windsofstorm.net</gjob:Email>
				119	<gjob:Company>
				120	</gjob:Company>
				121	<gjob:Organisation>
				122	</gjob:Organisation>
				123	<gjob:Webpage>
				124	</gjob:Webpage>
				125	<gjob:Snailmail>
				126	</gjob:Snailmail>
				127	<gjob:Phone>
				128	</gjob:Phone>
				129	</gjob:Contact>
				130
				131	<gjob:Requirements>
				132	The program should be released as free software, under the GPL.
				133	</gjob:Requirements>
				134
				135	<gjob:Skills>
				136	</gjob:Skills>
				137
				138	<gjob:Details>
				139	A GNOME based system that will allow a superuser to configure
				140	compressed and uncompressed files and/or file systems to be backed
				141	up with a supported media in the system. This should be able to
				142	perform via find commands generating a list of files that are passed
				143	to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
				144	or via operations performed on the filesystem itself. Email
				145	notification and GUI status display very important.
				146	</gjob:Details>
				147
				148	</gjob:Job>
				149
				150	</gjob:Jobs>
				151	</gjob:Helping></pre>
				152	<p>While loading the XML file into an internal DOM tree is a matter of
Daniel Veillard	63d8314	2002-05-20 06:51:05 +0000	[diff] [blame]	153	calling only a couple of functions, browsing the tree to gather the data and
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	154	generate the internal structures is harder, and more error prone.</p>
				155	<p>The suggested principle is to be tolerant with respect to the input
				156	structure. For example, the ordering of the attributes is not significant,
				157	the XML specification is clear about it. It's also usually a good idea not to
				158	depend on the order of the children of a given node, unless it really makes
				159	things harder. Here is some code to parse the information for a person:</p>
				160	<pre>/*
				161	* A person record
				162	*/
				163	typedef struct person {
				164	char *name;
				165	char *email;
				166	char *company;
				167	char *organisation;
				168	char *smail;
				169	char *webPage;
				170	char *phone;
				171	} person, *personPtr;
				172
				173	/*
				174	* And the code needed to parse it
				175	*/
				176	personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				177	personPtr ret = NULL;
				178
				179	DEBUG("parsePerson\n");
				180	/*
				181	* allocate the struct
				182	*/
				183	ret = (personPtr) malloc(sizeof(person));
				184	if (ret == NULL) {
				185	fprintf(stderr,"out of memory\n");
				186	return(NULL);
				187	}
				188	memset(ret, 0, sizeof(person));
				189
				190	/* We don't care what the top level element name is */
				191	cur = cur->xmlChildrenNode;
				192	while (cur != NULL) {
				193	if ((!strcmp(cur->name, "Person")) && (cur->ns == ns))
				194	ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				195	if ((!strcmp(cur->name, "Email")) && (cur->ns == ns))
				196	ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				197	cur = cur->next;
				198	}
				199
				200	return(ret);
				201	}</pre>
				202	<p>Here are a couple of things to notice:</p>
				203	<ul>
				204	<li>Usually a recursive parsing style is the more convenient one: XML data
Daniel Veillard	63d8314	2002-05-20 06:51:05 +0000	[diff] [blame]	205	is by nature subject to repetitive constructs and usually exhibits highly
				206	structured patterns.</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame]	207	<li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>,
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	208	i.e. the pointer to the global XML document and the namespace reserved to
				209	the application. Document wide information are needed for example to
				210	decode entities and it's a good coding practice to define a namespace for
				211	your application set of data and test that the element and attributes
				212	you're analyzing actually pertains to your application space. This is
				213	done by a simple equality test (cur->ns == ns).</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame]	214	<li>To retrieve text and attributes value, you can use the function
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	215	<em>xmlNodeListGetString</em> to gather all the text and entity reference
				216	nodes generated by the DOM output and produce an single text string.</li>
				217	</ul>
				218	<p>Here is another piece of code used to parse another level of the
				219	structure:</p>
				220	<pre>#include <libxml/tree.h>
				221	/*
				222	* a Description for a Job
				223	*/
				224	typedef struct job {
				225	char *projectID;
				226	char *application;
				227	char *category;
				228	personPtr contact;
				229	int nbDevelopers;
				230	personPtr developers[100]; /* using dynamic alloc is left as an exercise */
				231	} job, *jobPtr;
				232
				233	/*
				234	* And the code needed to parse it
				235	*/
				236	jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				237	jobPtr ret = NULL;
				238
				239	DEBUG("parseJob\n");
				240	/*
				241	* allocate the struct
				242	*/
				243	ret = (jobPtr) malloc(sizeof(job));
				244	if (ret == NULL) {
				245	fprintf(stderr,"out of memory\n");
				246	return(NULL);
				247	}
				248	memset(ret, 0, sizeof(job));
				249
				250	/* We don't care what the top level element name is */
				251	cur = cur->xmlChildrenNode;
				252	while (cur != NULL) {
				253
				254	if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) {
				255	ret->projectID = xmlGetProp(cur, "ID");
				256	if (ret->projectID == NULL) {
				257	fprintf(stderr, "Project has no ID\n");
				258	}
				259	}
				260	if ((!strcmp(cur->name, "Application")) && (cur->ns == ns))
				261	ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				262	if ((!strcmp(cur->name, "Category")) && (cur->ns == ns))
				263	ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				264	if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns))
				265	ret->contact = parsePerson(doc, ns, cur);
				266	cur = cur->next;
				267	}
				268
				269	return(ret);
				270	}</pre>
				271	<p>Once you are used to it, writing this kind of code is quite simple, but
Daniel Veillard	63d8314	2002-05-20 06:51:05 +0000	[diff] [blame]	272	boring. Ultimately, it could be possible to write stubbers taking either C
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	273	data structure definitions, a set of XML examples or an XML DTD and produce
				274	the code needed to import and export the content between C data and XML
				275	storage. This is left as an exercise to the reader :-)</p>
				276	<p>Feel free to use <a href="example/gjobread.c">the code for the full C
				277	parsing example</a> as a template, it is also available with Makefile in the
				278	Gnome CVS base under gnome-xml/example</p>
Daniel Veillard	3f4c40f	2002-02-13 09:19:28 +0000	[diff] [blame]	279	<p><a href="bugs.html">Daniel Veillard</a></p>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	280	</td></tr></table></td></tr></table></td></tr></table></td>
				281	</tr></table></td></tr></table>
				282	</body>
				283	</html>