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