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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	fabafd5	2006-06-08 08:16:33 +0000	[diff] [blame^]	10	</style><title>A real example</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><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" style="font-weight:bold">Main Menu</a></li><li><a href="html/index.html" style="font-weight:bold">Reference Manual</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</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="ChangeLog.html">ChangeLog</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://www.blastwave.org/packages.php/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://libxmlplusplus.sourceforge.net/">C++ bindings</a></li><li><a href="http://www.zend.com/php5/articles/php5-xmlphp.php#Heading4">PHP bindings</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://libxml.rubyforge.org/">Ruby bindings</a></li><li><a href="http://tclxml.sourceforge.net/">Tcl bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?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
				11	theapplicationdata is not kept in the DOM tree but uses internal structures.
				12	Itis based ona proposal to keep a database of jobs related to Gnome, with
				13	anXML basedstorage structure. Here is an <a href="gjobs.xml">XML
				14	encodedjobsbase</a>:</p><pre><?xml version="1.0"?>
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	15	<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location">
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	16	<gjob:Jobs>
				17
				18	<gjob:Job>
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	19	<gjob:Project ID="3"/>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	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	fabafd5	2006-06-08 08:16:33 +0000	[diff] [blame^]	69	</gjob:Helping></pre><p>While loading the XML file into an internal DOM tree is a matter
				70	ofcallingonly a couple of functions, browsing the tree to gather the data
				71	andgeneratethe internal structures is harder, and more error prone.</p><p>The suggested principle is to be tolerant with respect to
				72	theinputstructure. For example, the ordering of the attributes is
				73	notsignificant,the XML specification is clear about it. It's also usually a
				74	goodidea not todepend on the order of the children of a given node, unless
				75	itreally makesthings harder. Here is some code to parse the information for
				76	aperson:</p><pre>/*
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	77	* A person record
				78	*/
				79	typedef struct person {
				80	char *name;
				81	char *email;
				82	char *company;
				83	char *organisation;
				84	char *smail;
				85	char *webPage;
				86	char *phone;
				87	} person, *personPtr;
				88
				89	/*
				90	* And the code needed to parse it
				91	*/
				92	personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				93	personPtr ret = NULL;
				94
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	95	DEBUG("parsePerson\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	96	/*
				97	* allocate the struct
				98	*/
				99	ret = (personPtr) malloc(sizeof(person));
				100	if (ret == NULL) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	101	fprintf(stderr,"out of memory\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	102	return(NULL);
				103	}
				104	memset(ret, 0, sizeof(person));
				105
				106	/* We don't care what the top level element name is */
				107	cur = cur->xmlChildrenNode;
				108	while (cur != NULL) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	109	if ((!strcmp(cur->name, "Person")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	110	ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	111	if ((!strcmp(cur->name, "Email")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	112	ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				113	cur = cur->next;
				114	}
				115
				116	return(ret);
Daniel Veillard	fabafd5	2006-06-08 08:16:33 +0000	[diff] [blame^]	117	}</pre><p>Here are a couple of things to notice:</p><ul><li>Usually a recursive parsing style is the more convenient one: XMLdatais
				118	by nature subject to repetitive constructs and usually
				119	exhibitshighlystructured patterns.</li>
				120	<li>The two arguments of type <em>xmlDocPtr</em>and
				121	<em>xmlNsPtr</em>,i.e.the pointer to the global XML document and the
				122	namespace reserved totheapplication. Document wide information are needed
				123	for example todecodeentities and it's a good coding practice to define a
				124	namespace foryourapplication set of data and test that the element and
				125	attributesyou'reanalyzing actually pertains to your application space.
				126	This isdone by asimple equality test (cur->ns == ns).</li>
				127	<li>To retrieve text and attributes value, you can use
				128	thefunction<em>xmlNodeListGetString</em>to gather all the text and
				129	entityreferencenodes generated by the DOM output and produce an single
				130	textstring.</li>
				131	</ul><p>Here is another piece of code used to parse another level
				132	ofthestructure:</p><pre>#include <libxml/tree.h>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	133	/*
				134	* a Description for a Job
				135	*/
				136	typedef struct job {
				137	char *projectID;
				138	char *application;
				139	char *category;
				140	personPtr contact;
				141	int nbDevelopers;
				142	personPtr developers[100]; /* using dynamic alloc is left as an exercise */
				143	} job, *jobPtr;
				144
				145	/*
				146	* And the code needed to parse it
				147	*/
				148	jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				149	jobPtr ret = NULL;
				150
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	151	DEBUG("parseJob\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	152	/*
				153	* allocate the struct
				154	*/
				155	ret = (jobPtr) malloc(sizeof(job));
				156	if (ret == NULL) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	157	fprintf(stderr,"out of memory\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	158	return(NULL);
				159	}
				160	memset(ret, 0, sizeof(job));
				161
				162	/* We don't care what the top level element name is */
				163	cur = cur->xmlChildrenNode;
				164	while (cur != NULL) {
				165
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	166	if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) {
				167	ret->projectID = xmlGetProp(cur, "ID");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	168	if (ret->projectID == NULL) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	169	fprintf(stderr, "Project has no ID\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	170	}
				171	}
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	172	if ((!strcmp(cur->name, "Application")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	173	ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	174	if ((!strcmp(cur->name, "Category")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	175	ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	176	if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	177	ret->contact = parsePerson(doc, ns, cur);
				178	cur = cur->next;
				179	}
				180
				181	return(ret);
Daniel Veillard	fabafd5	2006-06-08 08:16:33 +0000	[diff] [blame^]	182	}</pre><p>Once you are used to it, writing this kind of code is quite
				183	simple,butboring. Ultimately, it could be possible to write stubbers taking
				184	eitherCdata structure definitions, a set of XML examples or an XML DTD
				185	andproducethe code needed to import and export the content between C data
				186	andXMLstorage. This is left as an exercise to the reader :-)</p><p>Feel free to use <a href="example/gjobread.c">the code for the
				187	fullCparsing example</a>as a template, it is also available with Makefile
				188	intheGnome 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>