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				14	<title>A real example</title>
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				19	<a href="http://www.gnome.org/"><img src="smallfootonly.gif" alt="Gnome 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>
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				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>
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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>
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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	e6d8e20	2002-05-02 06:11:10 +0000	[diff] [blame]	84	<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]	85	<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]	86	</ul></td></tr>
				87	</table>
				88	</td></tr></table></td>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	89	<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">
				90	<p>Here is a real size example, where the actual content of the application
				91	data is not kept in the DOM tree but uses internal structures. It is based on
				92	a proposal to keep a database of jobs related to Gnome, with an XML based
				93	storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
				94	base</a>:</p>
				95	<pre><?xml version="1.0"?>
				96	<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
				97	<gjob:Jobs>
				98
				99	<gjob:Job>
				100	<gjob:Project ID="3"/>
				101	<gjob:Application>GBackup</gjob:Application>
				102	<gjob:Category>Development</gjob:Category>
				103
				104	<gjob:Update>
				105	<gjob:Status>Open</gjob:Status>
				106	<gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified>
				107	<gjob:Salary>USD 0.00</gjob:Salary>
				108	</gjob:Update>
				109
				110	<gjob:Developers>
				111	<gjob:Developer>
				112	</gjob:Developer>
				113	</gjob:Developers>
				114
				115	<gjob:Contact>
				116	<gjob:Person>Nathan Clemons</gjob:Person>
				117	<gjob:Email>nathan@windsofstorm.net</gjob:Email>
				118	<gjob:Company>
				119	</gjob:Company>
				120	<gjob:Organisation>
				121	</gjob:Organisation>
				122	<gjob:Webpage>
				123	</gjob:Webpage>
				124	<gjob:Snailmail>
				125	</gjob:Snailmail>
				126	<gjob:Phone>
				127	</gjob:Phone>
				128	</gjob:Contact>
				129
				130	<gjob:Requirements>
				131	The program should be released as free software, under the GPL.
				132	</gjob:Requirements>
				133
				134	<gjob:Skills>
				135	</gjob:Skills>
				136
				137	<gjob:Details>
				138	A GNOME based system that will allow a superuser to configure
				139	compressed and uncompressed files and/or file systems to be backed
				140	up with a supported media in the system. This should be able to
				141	perform via find commands generating a list of files that are passed
				142	to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
				143	or via operations performed on the filesystem itself. Email
				144	notification and GUI status display very important.
				145	</gjob:Details>
				146
				147	</gjob:Job>
				148
				149	</gjob:Jobs>
				150	</gjob:Helping></pre>
				151	<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]	152	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]	153	generate the internal structures is harder, and more error prone.</p>
				154	<p>The suggested principle is to be tolerant with respect to the input
				155	structure. For example, the ordering of the attributes is not significant,
				156	the XML specification is clear about it. It's also usually a good idea not to
				157	depend on the order of the children of a given node, unless it really makes
				158	things harder. Here is some code to parse the information for a person:</p>
				159	<pre>/*
				160	* A person record
				161	*/
				162	typedef struct person {
				163	char *name;
				164	char *email;
				165	char *company;
				166	char *organisation;
				167	char *smail;
				168	char *webPage;
				169	char *phone;
				170	} person, *personPtr;
				171
				172	/*
				173	* And the code needed to parse it
				174	*/
				175	personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				176	personPtr ret = NULL;
				177
				178	DEBUG("parsePerson\n");
				179	/*
				180	* allocate the struct
				181	*/
				182	ret = (personPtr) malloc(sizeof(person));
				183	if (ret == NULL) {
				184	fprintf(stderr,"out of memory\n");
				185	return(NULL);
				186	}
				187	memset(ret, 0, sizeof(person));
				188
				189	/* We don't care what the top level element name is */
				190	cur = cur->xmlChildrenNode;
				191	while (cur != NULL) {
				192	if ((!strcmp(cur->name, "Person")) && (cur->ns == ns))
				193	ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				194	if ((!strcmp(cur->name, "Email")) && (cur->ns == ns))
				195	ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				196	cur = cur->next;
				197	}
				198
				199	return(ret);
				200	}</pre>
				201	<p>Here are a couple of things to notice:</p>
				202	<ul>
				203	<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]	204	is by nature subject to repetitive constructs and usually exhibits highly
				205	structured patterns.</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame^]	206	<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]	207	i.e. the pointer to the global XML document and the namespace reserved to
				208	the application. Document wide information are needed for example to
				209	decode entities and it's a good coding practice to define a namespace for
				210	your application set of data and test that the element and attributes
				211	you're analyzing actually pertains to your application space. This is
				212	done by a simple equality test (cur->ns == ns).</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame^]	213	<li>To retrieve text and attributes value, you can use the function
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	214	<em>xmlNodeListGetString</em> to gather all the text and entity reference
				215	nodes generated by the DOM output and produce an single text string.</li>
				216	</ul>
				217	<p>Here is another piece of code used to parse another level of the
				218	structure:</p>
				219	<pre>#include <libxml/tree.h>
				220	/*
				221	* a Description for a Job
				222	*/
				223	typedef struct job {
				224	char *projectID;
				225	char *application;
				226	char *category;
				227	personPtr contact;
				228	int nbDevelopers;
				229	personPtr developers[100]; /* using dynamic alloc is left as an exercise */
				230	} job, *jobPtr;
				231
				232	/*
				233	* And the code needed to parse it
				234	*/
				235	jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				236	jobPtr ret = NULL;
				237
				238	DEBUG("parseJob\n");
				239	/*
				240	* allocate the struct
				241	*/
				242	ret = (jobPtr) malloc(sizeof(job));
				243	if (ret == NULL) {
				244	fprintf(stderr,"out of memory\n");
				245	return(NULL);
				246	}
				247	memset(ret, 0, sizeof(job));
				248
				249	/* We don't care what the top level element name is */
				250	cur = cur->xmlChildrenNode;
				251	while (cur != NULL) {
				252
				253	if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) {
				254	ret->projectID = xmlGetProp(cur, "ID");
				255	if (ret->projectID == NULL) {
				256	fprintf(stderr, "Project has no ID\n");
				257	}
				258	}
				259	if ((!strcmp(cur->name, "Application")) && (cur->ns == ns))
				260	ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				261	if ((!strcmp(cur->name, "Category")) && (cur->ns == ns))
				262	ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				263	if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns))
				264	ret->contact = parsePerson(doc, ns, cur);
				265	cur = cur->next;
				266	}
				267
				268	return(ret);
				269	}</pre>
				270	<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]	271	boring. Ultimately, it could be possible to write stubbers taking either C
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	272	data structure definitions, a set of XML examples or an XML DTD and produce
				273	the code needed to import and export the content between C data and XML
				274	storage. This is left as an exercise to the reader :-)</p>
				275	<p>Feel free to use <a href="example/gjobread.c">the code for the full C
				276	parsing example</a> as a template, it is also available with Makefile in the
				277	Gnome CVS base under gnome-xml/example</p>
Daniel Veillard	3f4c40f	2002-02-13 09:19:28 +0000	[diff] [blame]	278	<p><a href="bugs.html">Daniel Veillard</a></p>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	279	</td></tr></table></td></tr></table></td></tr></table></td>
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