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Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	1	<?xml version="1.0" encoding="ISO-8859-1"?>
				2	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
				3	<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css">
Daniel Veillard	373a475	2002-02-21 14:46:29 +0000	[diff] [blame]	4	TD {font-family: Verdana,Arial,Helvetica}
				5	BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em}
				6	H1 {font-family: Verdana,Arial,Helvetica}
				7	H2 {font-family: Verdana,Arial,Helvetica}
				8	H3 {font-family: Verdana,Arial,Helvetica}
Daniel Veillard	b8cfbd1	2001-10-25 10:53:28 +0000	[diff] [blame]	9	A:link, A:visited, A:active { text-decoration: underline }
Daniel Veillard	598bec3	2003-07-06 10:02:03 +0000	[diff] [blame^]	10	</style><title>A real example</title></head><body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="180"><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></td><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"><h1>The XML C parser and toolkit of Gnome</h1><h2>A real example</h2></td></tr></table></td></tr></table></td></tr></table><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><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Developer Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html">Home</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="tutorial/index.html">Tutorial</a></li><li><a href="xmlreader.html">The Reader Interface</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="python.html">Python and bindings</a></li><li><a href="architecture.html">libxml2 architecture</a></li><li><a href="tree.html">The tree output</a></li><li><a href="interface.html">The SAX interface</a></li><li><a href="xmlmem.html">Memory Management</a></li><li><a href="xmlio.html">I/O Interfaces</a></li><li><a href="library.html">The parser interfaces</a></li><li><a href="entities.html">Entities or no entities</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="upgrade.html">Upgrading 1.x code</a></li><li><a href="threads.html">Thread safety</a></li><li><a href="DOM.html">DOM Principles</a></li><li><a href="example.html">A real example</a></li><li><a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="APIchunk0.html">Alphabetic</a></li><li><a href="APIconstructors.html">Constructors</a></li><li><a href="APIfunctions.html">Functions/Types</a></li><li><a href="APIfiles.html">Modules</a></li><li><a href="APIsymbols.html">Symbols</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li><li><a href="http://www.zveno.com/open_source/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml&product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><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"><p>Here is a real size example, where the actual content of the application
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	11	data is not kept in the DOM tree but uses internal structures. It is based on
				12	a proposal to keep a database of jobs related to Gnome, with an XML based
				13	storage structure. Here is an <a href="gjobs.xml">XML encoded jobs
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	14	base</a>:</p><pre><?xml version="1.0"?>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	15	<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
				16	<gjob:Jobs>
				17
				18	<gjob:Job>
				19	<gjob:Project ID="3"/>
				20	<gjob:Application>GBackup</gjob:Application>
				21	<gjob:Category>Development</gjob:Category>
				22
				23	<gjob:Update>
				24	<gjob:Status>Open</gjob:Status>
				25	<gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified>
				26	<gjob:Salary>USD 0.00</gjob:Salary>
				27	</gjob:Update>
				28
				29	<gjob:Developers>
				30	<gjob:Developer>
				31	</gjob:Developer>
				32	</gjob:Developers>
				33
				34	<gjob:Contact>
				35	<gjob:Person>Nathan Clemons</gjob:Person>
				36	<gjob:Email>nathan@windsofstorm.net</gjob:Email>
				37	<gjob:Company>
				38	</gjob:Company>
				39	<gjob:Organisation>
				40	</gjob:Organisation>
				41	<gjob:Webpage>
				42	</gjob:Webpage>
				43	<gjob:Snailmail>
				44	</gjob:Snailmail>
				45	<gjob:Phone>
				46	</gjob:Phone>
				47	</gjob:Contact>
				48
				49	<gjob:Requirements>
				50	The program should be released as free software, under the GPL.
				51	</gjob:Requirements>
				52
				53	<gjob:Skills>
				54	</gjob:Skills>
				55
				56	<gjob:Details>
				57	A GNOME based system that will allow a superuser to configure
				58	compressed and uncompressed files and/or file systems to be backed
				59	up with a supported media in the system. This should be able to
				60	perform via find commands generating a list of files that are passed
				61	to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine
				62	or via operations performed on the filesystem itself. Email
				63	notification and GUI status display very important.
				64	</gjob:Details>
				65
				66	</gjob:Job>
				67
				68	</gjob:Jobs>
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	69	</gjob:Helping></pre><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]	70	calling only a couple of functions, browsing the tree to gather the data and
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	71	generate the internal structures is harder, and more error prone.</p><p>The suggested principle is to be tolerant with respect to the input
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	72	structure. For example, the ordering of the attributes is not significant,
				73	the XML specification is clear about it. It's also usually a good idea not to
				74	depend on the order of the children of a given node, unless it really makes
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	75	things harder. Here is some code to parse the information for a person:</p><pre>/*
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	76	* A person record
				77	*/
				78	typedef struct person {
				79	char *name;
				80	char *email;
				81	char *company;
				82	char *organisation;
				83	char *smail;
				84	char *webPage;
				85	char *phone;
				86	} person, *personPtr;
				87
				88	/*
				89	* And the code needed to parse it
				90	*/
				91	personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				92	personPtr ret = NULL;
				93
				94	DEBUG("parsePerson\n");
				95	/*
				96	* allocate the struct
				97	*/
				98	ret = (personPtr) malloc(sizeof(person));
				99	if (ret == NULL) {
				100	fprintf(stderr,"out of memory\n");
				101	return(NULL);
				102	}
				103	memset(ret, 0, sizeof(person));
				104
				105	/* We don't care what the top level element name is */
				106	cur = cur->xmlChildrenNode;
				107	while (cur != NULL) {
				108	if ((!strcmp(cur->name, "Person")) && (cur->ns == ns))
				109	ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				110	if ((!strcmp(cur->name, "Email")) && (cur->ns == ns))
				111	ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				112	cur = cur->next;
				113	}
				114
				115	return(ret);
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	116	}</pre><p>Here are a couple of things to notice:</p><ul><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]	117	is by nature subject to repetitive constructs and usually exhibits highly
				118	structured patterns.</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame]	119	<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]	120	i.e. the pointer to the global XML document and the namespace reserved to
				121	the application. Document wide information are needed for example to
				122	decode entities and it's a good coding practice to define a namespace for
				123	your application set of data and test that the element and attributes
				124	you're analyzing actually pertains to your application space. This is
				125	done by a simple equality test (cur->ns == ns).</li>
Daniel Veillard	0b28e88	2002-07-24 23:47:05 +0000	[diff] [blame]	126	<li>To retrieve text and attributes value, you can use the function
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	127	<em>xmlNodeListGetString</em> to gather all the text and entity reference
				128	nodes generated by the DOM output and produce an single text string.</li>
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	129	</ul><p>Here is another piece of code used to parse another level of the
				130	structure:</p><pre>#include <libxml/tree.h>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	131	/*
				132	* a Description for a Job
				133	*/
				134	typedef struct job {
				135	char *projectID;
				136	char *application;
				137	char *category;
				138	personPtr contact;
				139	int nbDevelopers;
				140	personPtr developers[100]; /* using dynamic alloc is left as an exercise */
				141	} job, *jobPtr;
				142
				143	/*
				144	* And the code needed to parse it
				145	*/
				146	jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				147	jobPtr ret = NULL;
				148
				149	DEBUG("parseJob\n");
				150	/*
				151	* allocate the struct
				152	*/
				153	ret = (jobPtr) malloc(sizeof(job));
				154	if (ret == NULL) {
				155	fprintf(stderr,"out of memory\n");
				156	return(NULL);
				157	}
				158	memset(ret, 0, sizeof(job));
				159
				160	/* We don't care what the top level element name is */
				161	cur = cur->xmlChildrenNode;
				162	while (cur != NULL) {
				163
				164	if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) {
				165	ret->projectID = xmlGetProp(cur, "ID");
				166	if (ret->projectID == NULL) {
				167	fprintf(stderr, "Project has no ID\n");
				168	}
				169	}
				170	if ((!strcmp(cur->name, "Application")) && (cur->ns == ns))
				171	ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				172	if ((!strcmp(cur->name, "Category")) && (cur->ns == ns))
				173	ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				174	if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns))
				175	ret->contact = parsePerson(doc, ns, cur);
				176	cur = cur->next;
				177	}
				178
				179	return(ret);
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	180	}</pre><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]	181	boring. Ultimately, it could be possible to write stubbers taking either C
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	182	data structure definitions, a set of XML examples or an XML DTD and produce
				183	the code needed to import and export the content between C data and XML
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	184	storage. This is left as an exercise to the reader :-)</p><p>Feel free to use <a href="example/gjobread.c">the code for the full C
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	185	parsing example</a> as a template, it is also available with Makefile in the
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	186	Gnome CVS base under gnome-xml/example</p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>