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21<h1>The XML C library for Gnome</h1>
22<h2>Python and bindings</h2>
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74<tr><td bgcolor="#fffacd"><ul>
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>
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78<li><a href="ftp://xmlsoft.org/">FTP</a></li>
79<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
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86<p>There is a number of language bindings and wrappers available for libxml2,
87the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>
88(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
89order to get updates to this list or to discuss the specific topic of libxml2
90or libxslt wrappers or bindings:</p>
91<ul>
92<li>
93<a href="mailto:ari@lusis.org">Ari Johnson</a>
94 provides a C++ wrapper for libxml:<br>
95 Website: <a href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a><br>
96 Download: <a href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a>
97</li>
98<li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper
99 based on the gdome2 </a>bindings maintained by Tobias Peters.</li>
100<li>
101<a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
102 Sergeant</a>
103 developped <a href="http://axkit.org/download/">XML::LibXSLT</a>, a perl
104 wrapper for libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML application server</a>
105</li>
106<li>
107<a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a>
108 provides and earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>
109</li>
110<li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
111 libxml2</a> with Kylix, Delphi and other Pascal compilers</li>
112<li>Wai-Sun &quot;Squidster&quot; Chia provides <a href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and
113 libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
114 maintained by Tobias Peters.</li>
Daniel Veillardb9e469a2002-02-21 12:08:42 +0000[diff] [blame]115<li>Steve Ball and contributors maintains
116 <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
117 Tcl</a>
118</li>
119<li>There is support for libxml2 in the DOM module of PHP.
120</li>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]121</ul>
122<p>The distribution includes a set of Python bindings, which are garanteed to
123be maintained as part of the library in the future, though the Python
124interface have not yet reached the maturity of the C API. The distribution
125includes a set of examples and regression tests for the python bindings in
126the <code>python/tests</code> directory. Here are some excepts from those
127tests:</p>
128<h3>tst.py:</h3>
129<p>This is a basic test of the file interface and DOM navigation:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]130<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]131
132doc = libxml2.parseFile(&quot;tst.xml&quot;)
133if doc.name != &quot;tst.xml&quot;:
134 print &quot;doc.name failed&quot;
135 sys.exit(1)
136root = doc.children
137if root.name != &quot;doc&quot;:
138 print &quot;root.name failed&quot;
139 sys.exit(1)
140child = root.children
141if child.name != &quot;foo&quot;:
142 print &quot;child.name failed&quot;
143 sys.exit(1)
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]144doc.freeDoc()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]145<p>The Python module is called libxml2, parseFile is the equivalent of
146xmlParseFile (most of the bindings are automatically generated, and the xml
147prefix is removed and the casing convention are kept). All node seen at the
148binding level share the same subset of accesors:</p>
149<ul>
150<li>
151<code>name</code>
152 : returns the node name</li>
153<li>
154<code>type</code>
155 : returns a string indicating the node typ<code>e</code>
156</li>
157<li>
158<code>content</code>
159 : returns the content of the node, it is based on xmlNodeGetContent() and
160 hence is recursive.</li>
161<li>
162<code>parent</code>
163 , <code>children</code>, <code>last</code>, <code>next</code>,
164 <code>prev</code>, <code>doc</code>, <code>properties</code>: pointing to
165 the associated element in the tree, those may return None in case no such
166 link exists.</li>
167</ul>
168<p>Also note the need to explicitely deallocate documents with freeDoc() .
169Reference counting for libxml2 trees would need quite a lot of work to
170function properly, and rather than risk memory leaks if not implemented
171correctly it sounds safer to have an explicit function to free a tree. The
172wrapper python objects like doc, root or child are them automatically garbage
173collected.</p>
174<h3>validate.py:</h3>
175<p>This test check the validation interfaces and redirection of error
176messages:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]177<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]178
179#desactivate error messages from the validation
180def noerr(ctx, str):
181 pass
182
183libxml2.registerErrorHandler(noerr, None)
184
185ctxt = libxml2.createFileParserCtxt(&quot;invalid.xml&quot;)
186ctxt.validate(1)
187ctxt.parseDocument()
188doc = ctxt.doc()
189valid = ctxt.isValid()
190doc.freeDoc()
191if valid != 0:
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]192 print &quot;validity chec failed&quot;</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]193<p>The first thing to notice is the call to registerErrorHandler(), it
194defines a new error handler global to the library. It is used to avoid seeing
195the error messages when trying to validate the invalid document.</p>
196<p>The main interest of that test is the creation of a parser context with
197createFileParserCtxt() and how the behaviour can be changed before calling
198parseDocument() . Similary the informations resulting from the parsing phase
199are also available using context methods.</p>
200<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the
201C function interfaces in terms of objects method as much as possible. The
202best to get a complete view of what methods are supported is to look at the
203libxml2.py module containing all the wrappers.</p>
204<h3>push.py:</h3>
205<p>This test show how to activate the push parser interface:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]206<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]207
208ctxt = libxml2.createPushParser(None, &quot;&lt;foo&quot;, 4, &quot;test.xml&quot;)
209ctxt.parseChunk(&quot;/&gt;&quot;, 2, 1)
210doc = ctxt.doc()
211
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]212doc.freeDoc()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]213<p>The context is created with a speciall call based on the
214xmlCreatePushParser() from the C library. The first argument is an optional
215SAX callback object, then the initial set of data, the lenght and the name of
216the resource in case URI-References need to be computed by the parser.</p>
217<p>Then the data are pushed using the parseChunk() method, the last call
218setting the thrird argument terminate to 1.</p>
219<h3>pushSAX.py:</h3>
220<p>this test show the use of the event based parsing interfaces. In this case
221the parser does not build a document, but provides callback information as
222the parser makes progresses analyzing the data being provided:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]223<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]224log = &quot;&quot;
225
226class callback:
227 def startDocument(self):
228 global log
229 log = log + &quot;startDocument:&quot;
230
231 def endDocument(self):
232 global log
233 log = log + &quot;endDocument:&quot;
234
235 def startElement(self, tag, attrs):
236 global log
237 log = log + &quot;startElement %s %s:&quot; % (tag, attrs)
238
239 def endElement(self, tag):
240 global log
241 log = log + &quot;endElement %s:&quot; % (tag)
242
243 def characters(self, data):
244 global log
245 log = log + &quot;characters: %s:&quot; % (data)
246
247 def warning(self, msg):
248 global log
249 log = log + &quot;warning: %s:&quot; % (msg)
250
251 def error(self, msg):
252 global log
253 log = log + &quot;error: %s:&quot; % (msg)
254
255 def fatalError(self, msg):
256 global log
257 log = log + &quot;fatalError: %s:&quot; % (msg)
258
259handler = callback()
260
261ctxt = libxml2.createPushParser(handler, &quot;&lt;foo&quot;, 4, &quot;test.xml&quot;)
262chunk = &quot; url='tst'&gt;b&quot;
263ctxt.parseChunk(chunk, len(chunk), 0)
264chunk = &quot;ar&lt;/foo&gt;&quot;
265ctxt.parseChunk(chunk, len(chunk), 1)
266
Daniel Veillardfcbfa2d2002-02-21 17:54:27 +0000[diff] [blame^]267reference = &quot;startDocument:startElement foo {'url': 'tst'}:&quot; + \
268 &quot;characters: bar:endElement foo:endDocument:&quot;
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]269if log != reference:
270 print &quot;Error got: %s&quot; % log
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]271 print &quot;Exprected: %s&quot; % reference</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]272<p>The key object in that test is the handler, it provides a number of entry
273points which can be called by the parser as it makes progresses to indicate
274the information set obtained. The full set of callback is larger than what
275the callback class in that specific example implements (see the SAX
276definition for a complete list). The wrapper will only call those supplied by
277the object when activated. The startElement receives the names of the element
278and a dictionnary containing the attributes carried by this element.</p>
279<p>Also note that the reference string generated from the callback shows a
280single character call even though the string &quot;bar&quot; is passed to the parser
281from 2 different call to parseChunk()</p>
282<h3>xpath.py:</h3>
283<p>This is a basic test of XPath warppers support</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]284<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]285
286doc = libxml2.parseFile(&quot;tst.xml&quot;)
287ctxt = doc.xpathNewContext()
288res = ctxt.xpathEval(&quot;//*&quot;)
289if len(res) != 2:
290 print &quot;xpath query: wrong node set size&quot;
291 sys.exit(1)
292if res[0].name != &quot;doc&quot; or res[1].name != &quot;foo&quot;:
293 print &quot;xpath query: wrong node set value&quot;
294 sys.exit(1)
295doc.freeDoc()
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]296ctxt.xpathFreeContext()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]297<p>This test parses a file, then create an XPath context to evaluate XPath
298expression on it. The xpathEval() method execute an XPath query and returns
299the result mapped in a Python way. String and numbers are natively converted,
300and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like
301the document, the XPath context need to be freed explicitely, also not that
302the result of the XPath query may point back to the document tree and hence
303the document must be freed after the result of the query is used.</p>
304<h3>xpathext.py:</h3>
305<p>This test shows how to extend the XPath engine with functions written in
306python:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]307<pre>import libxml2
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]308
309def foo(ctx, x):
310 return x + 1
311
312doc = libxml2.parseFile(&quot;tst.xml&quot;)
313ctxt = doc.xpathNewContext()
314libxml2.registerXPathFunction(ctxt._o, &quot;foo&quot;, None, foo)
315res = ctxt.xpathEval(&quot;foo(1)&quot;)
316if res != 2:
317 print &quot;xpath extension failure&quot;
318doc.freeDoc()
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]319ctxt.xpathFreeContext()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]320<p>Note how the extension function is registered with the context (but that
321part is not yet finalized, ths may change slightly in the future).</p>
322<h3>tstxpath.py:</h3>
323<p>This test is similar to the previousone but shows how the extension
324function can access the XPath evaluation context:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]325<pre>def foo(ctx, x):
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]326 global called
327
328 #
329 # test that access to the XPath evaluation contexts
330 #
331 pctxt = libxml2.xpathParserContext(_obj=ctx)
332 ctxt = pctxt.context()
333 called = ctxt.function()
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]334 return x + 1</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]335<p>All the interfaces around the XPath parser(or rather evaluation) context
336are not finalized, but it should be sufficient to do contextual work at the
337evaluation point.</p>
338<h3>Memory debugging:</h3>
339<p>last but not least, all tests starts with the following prologue:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]340<pre>#memory debug specific
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]341libxml2.debugMemory(1)
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]342</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]343<p>and ends with the following epilogue:</p>
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]344<pre>#memory debug specific
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]345libxml2.cleanupParser()
346if libxml2.debugMemory(1) == 0:
347 print &quot;OK&quot;
348else:
349 print &quot;Memory leak %d bytes&quot; % (libxml2.debugMemory(1))
Daniel Veillard9eb146b2002-02-21 16:04:51 +0000[diff] [blame]350 libxml2.dumpMemory()</pre>
Daniel Veillard6dbcaf82002-02-20 14:37:47 +0000[diff] [blame]351<p>Those activate the memory debugging interface of libxml2 where all
352alloacted block in the library are tracked. The prologue then cleans up the
353library state and checks that all allocated memory has been freed. If not it
354calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p>
355<p><a href="bugs.html">Daniel Veillard</a></p>
356</td></tr></table></td></tr></table></td></tr></table></td>
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