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Daniel Veillard	d2190fa	2010-09-30 13:58:22 +0200	[diff] [blame]	1	<?xml version="1.0" encoding="UTF-8"?>
Daniel Veillard	1177ca4	2003-04-26 22:29:54 +0000	[diff] [blame]	2	<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
Daniel Veillard	d2190fa	2010-09-30 13:58:22 +0200	[diff] [blame]	3	<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><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	28fdf8b	2011-03-07 08:12:39 +0800	[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://opencsw.org/packages/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://lxml.de/">lxml Python bindings</a></li><li><a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl bindings</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 the application
Daniel Veillard	f781dba	2006-06-09 13:34:49 +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
				14	base</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	f781dba	2006-06-09 13:34:49 +0000	[diff] [blame]	69	</gjob:Helping></pre><p>While loading the XML file into an internal DOM tree is a matter of
				70	calling only a couple of functions, browsing the tree to gather the data and
				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
				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
				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
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	94	DEBUG("parsePerson\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	95	/*
				96	* allocate the struct
				97	*/
				98	ret = (personPtr) malloc(sizeof(person));
				99	if (ret == NULL) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	100	fprintf(stderr,"out of memory\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	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) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	108	if ((!strcmp(cur->name, "Person")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	109	ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	110	if ((!strcmp(cur->name, "Email")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	111	ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
				112	cur = cur->next;
				113	}
				114
				115	return(ret);
Daniel Veillard	e38217a	2013-05-10 15:40:13 +0800	[diff] [blame]	116	}</pre><p>Here are a couple of things to notice:</p><ul>
				117	<li>Usually a recursive parsing style is the more convenient one: XML data
Daniel Veillard	f781dba	2006-06-09 13:34:49 +0000	[diff] [blame]	118	is by nature subject to repetitive constructs and usually exhibits highly
				119	structured patterns.</li>
				120	<li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>,
				121	i.e. the pointer to the global XML document and the namespace reserved to
				122	the application. Document wide information are needed for example to
				123	decode entities and it's a good coding practice to define a namespace for
				124	your application set of data and test that the element and attributes
				125	you're analyzing actually pertains to your application space. This is
				126	done by a simple equality test (cur->ns == ns).</li>
				127	<li>To retrieve text and attributes value, you can use the function
				128	<em>xmlNodeListGetString</em> to gather all the text and entity reference
				129	nodes generated by the DOM output and produce an single text string.</li>
				130	</ul><p>Here is another piece of code used to parse another level of the
				131	structure:</p><pre>#include <libxml/tree.h>
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	132	/*
				133	* a Description for a Job
				134	*/
				135	typedef struct job {
				136	char *projectID;
				137	char *application;
				138	char *category;
				139	personPtr contact;
				140	int nbDevelopers;
				141	personPtr developers[100]; /* using dynamic alloc is left as an exercise */
				142	} job, *jobPtr;
				143
				144	/*
				145	* And the code needed to parse it
				146	*/
				147	jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) {
				148	jobPtr ret = NULL;
				149
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	150	DEBUG("parseJob\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	151	/*
				152	* allocate the struct
				153	*/
				154	ret = (jobPtr) malloc(sizeof(job));
				155	if (ret == NULL) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	156	fprintf(stderr,"out of memory\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	157	return(NULL);
				158	}
				159	memset(ret, 0, sizeof(job));
				160
				161	/* We don't care what the top level element name is */
				162	cur = cur->xmlChildrenNode;
				163	while (cur != NULL) {
				164
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	165	if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) {
				166	ret->projectID = xmlGetProp(cur, "ID");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	167	if (ret->projectID == NULL) {
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	168	fprintf(stderr, "Project has no ID\n");
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	169	}
				170	}
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	171	if ((!strcmp(cur->name, "Application")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	172	ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	173	if ((!strcmp(cur->name, "Category")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	174	ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1);
Daniel Veillard	024f199	2003-12-10 16:43:49 +0000	[diff] [blame]	175	if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns))
Daniel Veillard	c948420	2001-10-24 12:35:52 +0000	[diff] [blame]	176	ret->contact = parsePerson(doc, ns, cur);
				177	cur = cur->next;
				178	}
				179
				180	return(ret);
Daniel Veillard	f781dba	2006-06-09 13:34:49 +0000	[diff] [blame]	181	}</pre><p>Once you are used to it, writing this kind of code is quite simple, but
				182	boring. Ultimately, it could be possible to write stubbers taking either C
				183	data structure definitions, a set of XML examples or an XML DTD and produce
				184	the code needed to import and export the content between C data and XML
				185	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
				186	parsing example</a> as a template, it is also available with Makefile in the
William M. Brack	43a8729	2007-02-15 20:41:02 +0000	[diff] [blame]	187	Gnome SVN base under libxml2/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>