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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>Python and bindings</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 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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=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>There are a number of language bindings and wrappers available for 11libxml2, the list below is not exhaustive. Please contact the <a href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a> 12(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in 13order to get updates to this list or to discuss the specific topic of libxml2 14or libxslt wrappers or bindings:</p><ul><li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the 15 most up-to-date C++ bindings for libxml2, check the <a href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> 16 and the <a href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> 17 <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper 18 based on the gdome2 bindings</a> maintained by Tobias Peters.</li> 19 <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> 20 <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 21 </li> 22 <li><a href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 23 Sergeant</a> developed <a href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 24 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 25 application server</a>.</li> 26 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an 27 earlier version of the libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> 28 <li>Gopal.V and Peter Minten develop <a href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of 29 C# libxml2 bindings.</li> 30 <li>Petr Kozelka provides <a href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 31 libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> 32 <li>Uwe Fechner also provides <a href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 33 implementation for Kylix2/D5/D6 from Borland.</li> 34 <li>Wai-Sun "Squidster" Chia provides <a href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and 35 libxml2 bindings are also available in Ruby through the <a href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module 36 maintained by Tobias Peters.</li> 37 <li>Steve Ball and contributors maintains <a href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for 38 Tcl</a>.</li> 39 <li>There is support for libxml2 in the DOM module of PHP.</li> 40 <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is 41 an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and 42 libxslt as part of GNU ClasspathX project.</li> 43</ul><p>The distribution includes a set of Python bindings, which are guaranteed 44to be maintained as part of the library in the future, though the Python 45interface have not yet reached the completeness of the C API.</p><p><a href="mailto:stephane.bidoul@softwareag.com">St�phane Bidoul</a> 46maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port 47of the Python bindings</a>.</p><p>Note to people interested in building bindings, the API is formalized as 48<a href="libxml2-api.xml">an XML API description file</a> which allows to 49automate a large part of the Python bindings, this includes function 50descriptions, enums, structures, typedefs, etc... The Python script used to 51build the bindings is python/generator.py in the source distribution.</p><p>To install the Python bindings there are 2 options:</p><ul><li>If you use an RPM based distribution, simply install the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python 52 RPM</a> (and if needed the <a href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python 53 RPM</a>).</li> 54 <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python 55 module distribution</a> corresponding to your installed version of 56 libxml2 and libxslt. Note that to install it you will need both libxml2 57 and libxslt installed and run "python setup.py build install" in the 58 module tree.</li> 59</ul><p>The distribution includes a set of examples and regression tests for the 60python bindings in the <code>python/tests</code> directory. Here are some 61excerpts from those tests:</p><h3>tst.py:</h3><p>This is a basic test of the file interface and DOM navigation:</p><pre>import libxml2 62 63doc = libxml2.parseFile("tst.xml") 64if doc.name != "tst.xml": 65 print "doc.name failed" 66 sys.exit(1) 67root = doc.children 68if root.name != "doc": 69 print "root.name failed" 70 sys.exit(1) 71child = root.children 72if child.name != "foo": 73 print "child.name failed" 74 sys.exit(1) 75doc.freeDoc()</pre><p>The Python module is called libxml2; parseFile is the equivalent of 76xmlParseFile (most of the bindings are automatically generated, and the xml 77prefix is removed and the casing convention are kept). All node seen at the 78binding level share the same subset of accessors:</p><ul><li><code>name</code> : returns the node name</li> 79 <li><code>type</code> : returns a string indicating the node type</li> 80 <li><code>content</code> : returns the content of the node, it is based on 81 xmlNodeGetContent() and hence is recursive.</li> 82 <li><code>parent</code> , <code>children</code>, <code>last</code>, 83 <code>next</code>, <code>prev</code>, <code>doc</code>, 84 <code>properties</code>: pointing to the associated element in the tree, 85 those may return None in case no such link exists.</li> 86</ul><p>Also note the need to explicitly deallocate documents with freeDoc() . 87Reference counting for libxml2 trees would need quite a lot of work to 88function properly, and rather than risk memory leaks if not implemented 89correctly it sounds safer to have an explicit function to free a tree. The 90wrapper python objects like doc, root or child are them automatically garbage 91collected.</p><h3>validate.py:</h3><p>This test check the validation interfaces and redirection of error 92messages:</p><pre>import libxml2 93 94#deactivate error messages from the validation 95def noerr(ctx, str): 96 pass 97 98libxml2.registerErrorHandler(noerr, None) 99 100ctxt = libxml2.createFileParserCtxt("invalid.xml") 101ctxt.validate(1) 102ctxt.parseDocument() 103doc = ctxt.doc() 104valid = ctxt.isValid() 105doc.freeDoc() 106if valid != 0: 107 print "validity check failed"</pre><p>The first thing to notice is the call to registerErrorHandler(), it 108defines a new error handler global to the library. It is used to avoid seeing 109the error messages when trying to validate the invalid document.</p><p>The main interest of that test is the creation of a parser context with 110createFileParserCtxt() and how the behaviour can be changed before calling 111parseDocument() . Similarly the informations resulting from the parsing phase 112are also available using context methods.</p><p>Contexts like nodes are defined as class and the libxml2 wrappers maps the 113C function interfaces in terms of objects method as much as possible. The 114best to get a complete view of what methods are supported is to look at the 115libxml2.py module containing all the wrappers.</p><h3>push.py:</h3><p>This test show how to activate the push parser interface:</p><pre>import libxml2 116 117ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") 118ctxt.parseChunk("/>", 2, 1) 119doc = ctxt.doc() 120 121doc.freeDoc()</pre><p>The context is created with a special call based on the 122xmlCreatePushParser() from the C library. The first argument is an optional 123SAX callback object, then the initial set of data, the length and the name of 124the resource in case URI-References need to be computed by the parser.</p><p>Then the data are pushed using the parseChunk() method, the last call 125setting the third argument terminate to 1.</p><h3>pushSAX.py:</h3><p>this test show the use of the event based parsing interfaces. In this case 126the parser does not build a document, but provides callback information as 127the parser makes progresses analyzing the data being provided:</p><pre>import libxml2 128log = "" 129 130class callback: 131 def startDocument(self): 132 global log 133 log = log + "startDocument:" 134 135 def endDocument(self): 136 global log 137 log = log + "endDocument:" 138 139 def startElement(self, tag, attrs): 140 global log 141 log = log + "startElement %s %s:" % (tag, attrs) 142 143 def endElement(self, tag): 144 global log 145 log = log + "endElement %s:" % (tag) 146 147 def characters(self, data): 148 global log 149 log = log + "characters: %s:" % (data) 150 151 def warning(self, msg): 152 global log 153 log = log + "warning: %s:" % (msg) 154 155 def error(self, msg): 156 global log 157 log = log + "error: %s:" % (msg) 158 159 def fatalError(self, msg): 160 global log 161 log = log + "fatalError: %s:" % (msg) 162 163handler = callback() 164 165ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") 166chunk = " url='tst'>b" 167ctxt.parseChunk(chunk, len(chunk), 0) 168chunk = "ar</foo>" 169ctxt.parseChunk(chunk, len(chunk), 1) 170 171reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 172 "characters: bar:endElement foo:endDocument:" 173if log != reference: 174 print "Error got: %s" % log 175 print "Expected: %s" % reference</pre><p>The key object in that test is the handler, it provides a number of entry 176points which can be called by the parser as it makes progresses to indicate 177the information set obtained. The full set of callback is larger than what 178the callback class in that specific example implements (see the SAX 179definition for a complete list). The wrapper will only call those supplied by 180the object when activated. The startElement receives the names of the element 181and a dictionary containing the attributes carried by this element.</p><p>Also note that the reference string generated from the callback shows a 182single character call even though the string "bar" is passed to the parser 183from 2 different call to parseChunk()</p><h3>xpath.py:</h3><p>This is a basic test of XPath wrappers support</p><pre>import libxml2 184 185doc = libxml2.parseFile("tst.xml") 186ctxt = doc.xpathNewContext() 187res = ctxt.xpathEval("//*") 188if len(res) != 2: 189 print "xpath query: wrong node set size" 190 sys.exit(1) 191if res[0].name != "doc" or res[1].name != "foo": 192 print "xpath query: wrong node set value" 193 sys.exit(1) 194doc.freeDoc() 195ctxt.xpathFreeContext()</pre><p>This test parses a file, then create an XPath context to evaluate XPath 196expression on it. The xpathEval() method execute an XPath query and returns 197the result mapped in a Python way. String and numbers are natively converted, 198and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like 199the document, the XPath context need to be freed explicitly, also not that 200the result of the XPath query may point back to the document tree and hence 201the document must be freed after the result of the query is used.</p><h3>xpathext.py:</h3><p>This test shows how to extend the XPath engine with functions written in 202python:</p><pre>import libxml2 203 204def foo(ctx, x): 205 return x + 1 206 207doc = libxml2.parseFile("tst.xml") 208ctxt = doc.xpathNewContext() 209libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) 210res = ctxt.xpathEval("foo(1)") 211if res != 2: 212 print "xpath extension failure" 213doc.freeDoc() 214ctxt.xpathFreeContext()</pre><p>Note how the extension function is registered with the context (but that 215part is not yet finalized, this may change slightly in the future).</p><h3>tstxpath.py:</h3><p>This test is similar to the previous one but shows how the extension 216function can access the XPath evaluation context:</p><pre>def foo(ctx, x): 217 global called 218 219 # 220 # test that access to the XPath evaluation contexts 221 # 222 pctxt = libxml2.xpathParserContext(_obj=ctx) 223 ctxt = pctxt.context() 224 called = ctxt.function() 225 return x + 1</pre><p>All the interfaces around the XPath parser(or rather evaluation) context 226are not finalized, but it should be sufficient to do contextual work at the 227evaluation point.</p><h3>Memory debugging:</h3><p>last but not least, all tests starts with the following prologue:</p><pre>#memory debug specific 228libxml2.debugMemory(1)</pre><p>and ends with the following epilogue:</p><pre>#memory debug specific 229libxml2.cleanupParser() 230if libxml2.debugMemory(1) == 0: 231 print "OK" 232else: 233 print "Memory leak %d bytes" % (libxml2.debugMemory(1)) 234 libxml2.dumpMemory()</pre><p>Those activate the memory debugging interface of libxml2 where all 235allocated block in the library are tracked. The prologue then cleans up the 236library state and checks that all allocated memory has been freed. If not it 237calls dumpMemory() which saves that list in a <code>.memdump</code> file.</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> 238
