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                     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://codespeak.net/lxml/">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
                     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>&lt;?xml version="1.0"?&gt;
                     15: &lt;gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"&gt;
                     16:   &lt;gjob:Jobs&gt;
                     17: 
                     18:     &lt;gjob:Job&gt;
                     19:       &lt;gjob:Project ID="3"/&gt;
                     20:       &lt;gjob:Application&gt;GBackup&lt;/gjob:Application&gt;
                     21:       &lt;gjob:Category&gt;Development&lt;/gjob:Category&gt;
                     22: 
                     23:       &lt;gjob:Update&gt;
                     24:         &lt;gjob:Status&gt;Open&lt;/gjob:Status&gt;
                     25:         &lt;gjob:Modified&gt;Mon, 07 Jun 1999 20:27:45 -0400 MET DST&lt;/gjob:Modified&gt;
                     26:         &lt;gjob:Salary&gt;USD 0.00&lt;/gjob:Salary&gt;
                     27:       &lt;/gjob:Update&gt;
                     28: 
                     29:       &lt;gjob:Developers&gt;
                     30:         &lt;gjob:Developer&gt;
                     31:         &lt;/gjob:Developer&gt;
                     32:       &lt;/gjob:Developers&gt;
                     33: 
                     34:       &lt;gjob:Contact&gt;
                     35:         &lt;gjob:Person&gt;Nathan Clemons&lt;/gjob:Person&gt;
                     36:         &lt;gjob:Email&gt;nathan@windsofstorm.net&lt;/gjob:Email&gt;
                     37:         &lt;gjob:Company&gt;
                     38:         &lt;/gjob:Company&gt;
                     39:         &lt;gjob:Organisation&gt;
                     40:         &lt;/gjob:Organisation&gt;
                     41:         &lt;gjob:Webpage&gt;
                     42:         &lt;/gjob:Webpage&gt;
                     43:         &lt;gjob:Snailmail&gt;
                     44:         &lt;/gjob:Snailmail&gt;
                     45:         &lt;gjob:Phone&gt;
                     46:         &lt;/gjob:Phone&gt;
                     47:       &lt;/gjob:Contact&gt;
                     48: 
                     49:       &lt;gjob:Requirements&gt;
                     50:       The program should be released as free software, under the GPL.
                     51:       &lt;/gjob:Requirements&gt;
                     52: 
                     53:       &lt;gjob:Skills&gt;
                     54:       &lt;/gjob:Skills&gt;
                     55: 
                     56:       &lt;gjob:Details&gt;
                     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:       &lt;/gjob:Details&gt;
                     65: 
                     66:     &lt;/gjob:Job&gt;
                     67: 
                     68:   &lt;/gjob:Jobs&gt;
                     69: &lt;/gjob:Helping&gt;</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>/*
                     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-&gt;xmlChildrenNode;
                    107:     while (cur != NULL) {
                    108:         if ((!strcmp(cur-&gt;name, "Person")) &amp;&amp; (cur-&gt;ns == ns))
                    109:             ret-&gt;name = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
                    110:         if ((!strcmp(cur-&gt;name, "Email")) &amp;&amp; (cur-&gt;ns == ns))
                    111:             ret-&gt;email = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
                    112:         cur = cur-&gt;next;
                    113:     }
                    114: 
                    115:     return(ret);
                    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
                    117:     is by nature subject to repetitive constructs and usually exhibits highly
                    118:     structured patterns.</li>
                    119:   <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>,
                    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-&gt;ns == ns).</li>
                    126:   <li>To retrieve text and attributes value, you can use the function
                    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>
                    129: </ul><p>Here is another piece of code used to parse another level of the
                    130: structure:</p><pre>#include &lt;libxml/tree.h&gt;
                    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-&gt;xmlChildrenNode;
                    162:     while (cur != NULL) {
                    163:         
                    164:         if ((!strcmp(cur-&gt;name, "Project")) &amp;&amp; (cur-&gt;ns == ns)) {
                    165:             ret-&gt;projectID = xmlGetProp(cur, "ID");
                    166:             if (ret-&gt;projectID == NULL) {
                    167:                 fprintf(stderr, "Project has no ID\n");
                    168:             }
                    169:         }
                    170:         if ((!strcmp(cur-&gt;name, "Application")) &amp;&amp; (cur-&gt;ns == ns))
                    171:             ret-&gt;application = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
                    172:         if ((!strcmp(cur-&gt;name, "Category")) &amp;&amp; (cur-&gt;ns == ns))
                    173:             ret-&gt;category = xmlNodeListGetString(doc, cur-&gt;xmlChildrenNode, 1);
                    174:         if ((!strcmp(cur-&gt;name, "Contact")) &amp;&amp; (cur-&gt;ns == ns))
                    175:             ret-&gt;contact = parsePerson(doc, ns, cur);
                    176:         cur = cur-&gt;next;
                    177:     }
                    178: 
                    179:     return(ret);
                    180: }</pre><p>Once you are used to it, writing this kind of code is quite simple, but
                    181: boring. Ultimately, it could be possible to write stubbers taking either C
                    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
                    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
                    185: parsing example</a> as a template, it is also available with Makefile in the
                    186: 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>

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