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10: </style><title>Upgrading 1.x code</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>Upgrading 1.x code</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>Incompatible changes:</p><p>Version 2 of libxml2 is the first version introducing serious backward
11: incompatible changes. The main goals were:</p><ul><li>a general cleanup. A number of mistakes inherited from the very early
12: versions couldn't be changed due to compatibility constraints. Example
13: the "childs" element in the nodes.</li>
14: <li>Uniformization of the various nodes, at least for their header and link
15: parts (doc, parent, children, prev, next), the goal is a simpler
16: programming model and simplifying the task of the DOM implementors.</li>
17: <li>better conformances to the XML specification, for example version 1.x
18: had an heuristic to try to detect ignorable white spaces. As a result the
19: SAX event generated were ignorableWhitespace() while the spec requires
20: character() in that case. This also mean that a number of DOM node
21: containing blank text may populate the DOM tree which were not present
22: before.</li>
23: </ul><h3>How to fix libxml-1.x code:</h3><p>So client code of libxml designed to run with version 1.x may have to be
24: changed to compile against version 2.x of libxml. Here is a list of changes
25: that I have collected, they may not be sufficient, so in case you find other
26: change which are required, <a href="mailto:Daniel.Veillard@w3.org">drop me a
27: mail</a>:</p><ol><li>The package name have changed from libxml to libxml2, the library name
28: is now -lxml2 . There is a new xml2-config script which should be used to
29: select the right parameters libxml2</li>
30: <li>Node <strong>childs</strong> field has been renamed
31: <strong>children</strong> so s/childs/children/g should be applied
32: (probability of having "childs" anywhere else is close to 0+</li>
33: <li>The document don't have anymore a <strong>root</strong> element it has
34: been replaced by <strong>children</strong> and usually you will get a
35: list of element here. For example a Dtd element for the internal subset
36: and it's declaration may be found in that list, as well as processing
37: instructions or comments found before or after the document root element.
38: Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of
39: a document. Alternatively if you are sure to not reference DTDs nor have
40: PIs or comments before or after the root element
41: s/->root/->children/g will probably do it.</li>
42: <li>The white space issue, this one is more complex, unless special case of
43: validating parsing, the line breaks and spaces usually used for indenting
44: and formatting the document content becomes significant. So they are
45: reported by SAX and if your using the DOM tree, corresponding nodes are
46: generated. Too approach can be taken:
47: <ol><li>lazy one, use the compatibility call
48: <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are
49: relying on a special (and possibly broken) set of heuristics of
50: libxml to detect ignorable blanks. Don't complain if it breaks or
51: make your application not 100% clean w.r.t. to it's input.</li>
52: <li>the Right Way: change you code to accept possibly insignificant
53: blanks characters, or have your tree populated with weird blank text
54: nodes. You can spot them using the commodity function
55: <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank
56: nodes.</li>
57: </ol><p>Note also that with the new default the output functions don't add any
58: extra indentation when saving a tree in order to be able to round trip
59: (read and save) without inflating the document with extra formatting
60: chars.</p>
61: </li>
62: <li>The include path has changed to $prefix/libxml/ and the includes
63: themselves uses this new prefix in includes instructions... If you are
64: using (as expected) the
65: <pre>xml2-config --cflags</pre>
66: <p>output to generate you compile commands this will probably work out of
67: the box</p>
68: </li>
69: <li>xmlDetectCharEncoding takes an extra argument indicating the length in
70: byte of the head of the document available for character detection.</li>
71: </ol><h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3><p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released
72: to allow smooth upgrade of existing libxml v1code while retaining
73: compatibility. They offers the following:</p><ol><li>similar include naming, one should use
74: <strong>#include<libxml/...></strong> in both cases.</li>
75: <li>similar identifiers defined via macros for the child and root fields:
76: respectively <strong>xmlChildrenNode</strong> and
77: <strong>xmlRootNode</strong></li>
78: <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be
79: inserted once in the client code</li>
80: </ol><p>So the roadmap to upgrade your existing libxml applications is the
81: following:</p><ol><li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li>
82: <li>find all occurrences where the xmlDoc <strong>root</strong> field is
83: used and change it to <strong>xmlRootNode</strong></li>
84: <li>similarly find all occurrences where the xmlNode
85: <strong>childs</strong> field is used and change it to
86: <strong>xmlChildrenNode</strong></li>
87: <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your
88: <strong>main()</strong> or in the library init entry point</li>
89: <li>Recompile, check compatibility, it should still work</li>
90: <li>Change your configure script to look first for xml2-config and fall
91: back using xml-config . Use the --cflags and --libs output of the command
92: as the Include and Linking parameters needed to use libxml.</li>
93: <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and
94: libxml-devel-1.8.y can be kept simultaneously)</li>
95: <li>remove your config.cache, relaunch your configuration mechanism, and
96: recompile, if steps 2 and 3 were done right it should compile as-is</li>
97: <li>Test that your application is still running correctly, if not this may
98: be due to extra empty nodes due to formating spaces being kept in libxml2
99: contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your
100: code before calling the parser (next to
101: <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li>
102: </ol><p>Following those steps should work. It worked for some of my own code.</p><p>Let me put some emphasis on the fact that there is far more changes from
103: libxml 1.x to 2.x than the ones you may have to patch for. The overall code
104: has been considerably cleaned up and the conformance to the XML specification
105: has been drastically improved too. Don't take those changes as an excuse to
106: not upgrade, it may cost a lot on the long term ...</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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