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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">
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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 }
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	13	--></style>
				14	<title>A real example</title>
				15	</head>
				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>
Daniel Veillard	5ede35e	2002-10-01 11:37:35 +0000	[diff] [blame^]	66	<tr><td bgcolor="#fffacd">
				67	<form action="http://xmlsoft.org/search.php" enctype="application/x-www-form-urlencoded" method="GET">
				68	<input name="query" type="TEXT" size="20" value=""><input name="submit" type="submit" value="Search ...">
				69	</form>
				70	<ul>
Daniel Veillard	f859256	2002-01-23 17:58:17 +0000	[diff] [blame]	71	<li><a href="APIchunk0.html">Alphabetic</a></li>
Daniel Veillard	3bf65be	2002-01-23 12:36:34 +0000	[diff] [blame]	72	<li><a href="APIconstructors.html">Constructors</a></li>
				73	<li><a href="APIfunctions.html">Functions/Types</a></li>
				74	<li><a href="APIfiles.html">Modules</a></li>
				75	<li><a href="APIsymbols.html">Symbols</a></li>
Daniel Veillard	5ede35e	2002-10-01 11:37:35 +0000	[diff] [blame^]	76	</ul>
				77	</td></tr>
Daniel Veillard	3bf65be	2002-01-23 12:36:34 +0000	[diff] [blame]	78	</table>
				79	<table width="100%" border="0" cellspacing="1" cellpadding="3">
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	80	<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]	81	<tr><td bgcolor="#fffacd"><ul>
Daniel Veillard	594cf0b	2001-10-25 08:09:12 +0000	[diff] [blame]	82	<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
				83	<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
Daniel Veillard	4a85920	2002-01-08 11:49:22 +0000	[diff] [blame]	84	<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]	85	<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]	86	<li><a href="ftp://xmlsoft.org/">FTP</a></li>
				87	<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]	88	<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
Daniel Veillard	cb7543b	2002-09-09 10:54:06 +0000	[diff] [blame]	89	<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]	90	<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]	91	<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]	92	</ul></td></tr>
				93	</table>
				94	</td></tr></table></td>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	95	<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">
				96	<p>Here is a real size example, where the actual content of the application
				97	data is not kept in the DOM tree but uses internal structures. It is based on
				98	a proposal to keep a database of jobs related to Gnome, with an XML based
				99	storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
				100	base</a>:</p>
				101	<pre><?xml version="1.0"?>
				102	<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
				103	<gjob:Jobs>
				104
				105	<gjob:Job>
				106	<gjob:Project ID="3"/>
				107	<gjob:Application>GBackup</gjob:Application>
				108	<gjob:Category>Development</gjob:Category>
				109
				110	<gjob:Update>
				111	<gjob:Status>Open</gjob:Status>
				112	<gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified>
				113	<gjob:Salary>USD 0.00</gjob:Salary>
				114	</gjob:Update>
				115
				116	<gjob:Developers>
				117	<gjob:Developer>
				118	</gjob:Developer>
				119	</gjob:Developers>
				120
				121	<gjob:Contact>
				122	<gjob:Person>Nathan Clemons</gjob:Person>
				123	<gjob:Email>nathan@windsofstorm.net</gjob:Email>
				124	<gjob:Company>
				125	</gjob:Company>
				126	<gjob:Organisation>
				127	</gjob:Organisation>
				128	<gjob:Webpage>
				129	</gjob:Webpage>
				130	<gjob:Snailmail>
				131	</gjob:Snailmail>
				132	<gjob:Phone>
				133	</gjob:Phone>
				134	</gjob:Contact>
				135
				136	<gjob:Requirements>
				137	The program should be released as free software, under the GPL.
				138	</gjob:Requirements>
				139
				140	<gjob:Skills>
				141	</gjob:Skills>
				142
				143	<gjob:Details>
				144	A GNOME based system that will allow a superuser to configure
				145	compressed and uncompressed files and/or file systems to be backed
				146	up with a supported media in the system. This should be able to
				147	perform via find commands generating a list of files that are passed
				148	to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
				149	or via operations performed on the filesystem itself. Email
				150	notification and GUI status display very important.
				151	</gjob:Details>
				152
				153	</gjob:Job>
				154
				155	</gjob:Jobs>
				156	</gjob:Helping></pre>
				157	<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]	158	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]	159	generate the internal structures is harder, and more error prone.</p>
				160	<p>The suggested principle is to be tolerant with respect to the input
				161	structure. For example, the ordering of the attributes is not significant,
				162	the XML specification is clear about it. It's also usually a good idea not to
				163	depend on the order of the children of a given node, unless it really makes
				164	things harder. Here is some code to parse the information for a person:</p>
				165	<pre>/*
				166	* A person record
				167	*/
				168	typedef struct person {
				169	char *name;
				170	char *email;
				171	char *company;
				172	char *organisation;
				173	char *smail;
				174	char *webPage;
				175	char *phone;
				176	} person, *personPtr;
				177
				178	/*
				179	* And the code needed to parse it
				180	*/
				181	personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				182	personPtr ret = NULL;
				183
				184	DEBUG("parsePerson\n");
				185	/*
				186	* allocate the struct
				187	*/
				188	ret = (personPtr) malloc(sizeof(person));
				189	if (ret == NULL) {
				190	fprintf(stderr,"out of memory\n");
				191	return(NULL);
				192	}
				193	memset(ret, 0, sizeof(person));
				194
				195	/* We don't care what the top level element name is */
				196	cur = cur->xmlChildrenNode;
				197	while (cur != NULL) {
				198	if ((!strcmp(cur->name, "Person")) && (cur->ns == ns))
				199	ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				200	if ((!strcmp(cur->name, "Email")) && (cur->ns == ns))
				201	ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				202	cur = cur->next;
				203	}
				204
				205	return(ret);
				206	}</pre>
				207	<p>Here are a couple of things to notice:</p>
				208	<ul>
				209	<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]	210	is by nature subject to repetitive constructs and usually exhibits highly
				211	structured patterns.</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame]	212	<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]	213	i.e. the pointer to the global XML document and the namespace reserved to
				214	the application. Document wide information are needed for example to
				215	decode entities and it's a good coding practice to define a namespace for
				216	your application set of data and test that the element and attributes
				217	you're analyzing actually pertains to your application space. This is
				218	done by a simple equality test (cur->ns == ns).</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame]	219	<li>To retrieve text and attributes value, you can use the function
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	220	<em>xmlNodeListGetString</em> to gather all the text and entity reference
				221	nodes generated by the DOM output and produce an single text string.</li>
				222	</ul>
				223	<p>Here is another piece of code used to parse another level of the
				224	structure:</p>
				225	<pre>#include <libxml/tree.h>
				226	/*
				227	* a Description for a Job
				228	*/
				229	typedef struct job {
				230	char *projectID;
				231	char *application;
				232	char *category;
				233	personPtr contact;
				234	int nbDevelopers;
				235	personPtr developers[100]; /* using dynamic alloc is left as an exercise */
				236	} job, *jobPtr;
				237
				238	/*
				239	* And the code needed to parse it
				240	*/
				241	jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				242	jobPtr ret = NULL;
				243
				244	DEBUG("parseJob\n");
				245	/*
				246	* allocate the struct
				247	*/
				248	ret = (jobPtr) malloc(sizeof(job));
				249	if (ret == NULL) {
				250	fprintf(stderr,"out of memory\n");
				251	return(NULL);
				252	}
				253	memset(ret, 0, sizeof(job));
				254
				255	/* We don't care what the top level element name is */
				256	cur = cur->xmlChildrenNode;
				257	while (cur != NULL) {
				258
				259	if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) {
				260	ret->projectID = xmlGetProp(cur, "ID");
				261	if (ret->projectID == NULL) {
				262	fprintf(stderr, "Project has no ID\n");
				263	}
				264	}
				265	if ((!strcmp(cur->name, "Application")) && (cur->ns == ns))
				266	ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				267	if ((!strcmp(cur->name, "Category")) && (cur->ns == ns))
				268	ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				269	if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns))
				270	ret->contact = parsePerson(doc, ns, cur);
				271	cur = cur->next;
				272	}
				273
				274	return(ret);
				275	}</pre>
				276	<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]	277	boring. Ultimately, it could be possible to write stubbers taking either C
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	278	data structure definitions, a set of XML examples or an XML DTD and produce
				279	the code needed to import and export the content between C data and XML
				280	storage. This is left as an exercise to the reader :-)</p>
				281	<p>Feel free to use <a href="example/gjobread.c">the code for the full C
				282	parsing example</a> as a template, it is also available with Makefile in the
				283	Gnome CVS base under gnome-xml/example</p>
Daniel Veillard	3f4c40f	2002-02-13 09:19:28 +0000	[diff] [blame]	284	<p><a href="bugs.html">Daniel Veillard</a></p>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	285	</td></tr></table></td></tr></table></td></tr></table></td>
				286	</tr></table></td></tr></table>
				287	</body>
				288	</html>