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| </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 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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>Incompatible changes:</p><p>Version 2 of libxml2 is the first version introducing serious backward |
| incompatible changes. The main goals were:</p><ul><li>a general cleanup. A number of mistakes inherited from the very early |
| versions couldn't be changed due to compatibility constraints. Example |
| the "childs" element in the nodes.</li> |
| <li>Uniformization of the various nodes, at least for their header and link |
| parts (doc, parent, children, prev, next), the goal is a simpler |
| programming model and simplifying the task of the DOM implementors.</li> |
| <li>better conformances to the XML specification, for example version 1.x |
| had an heuristic to try to detect ignorable white spaces. As a result the |
| SAX event generated were ignorableWhitespace() while the spec requires |
| character() in that case. This also mean that a number of DOM node |
| containing blank text may populate the DOM tree which were not present |
| before.</li> |
| </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 |
| changed to compile against version 2.x of libxml. Here is a list of changes |
| that I have collected, they may not be sufficient, so in case you find other |
| change which are required, <a href="mailto:Daniel.Veillard@w3.org">drop me a |
| mail</a>:</p><ol><li>The package name have changed from libxml to libxml2, the library name |
| is now -lxml2 . There is a new xml2-config script which should be used to |
| select the right parameters libxml2</li> |
| <li>Node <strong>childs</strong> field has been renamed |
| <strong>children</strong> so s/childs/children/g should be applied |
| (probability of having "childs" anywhere else is close to 0+</li> |
| <li>The document don't have anymore a <strong>root</strong> element it has |
| been replaced by <strong>children</strong> and usually you will get a |
| list of element here. For example a Dtd element for the internal subset |
| and it's declaration may be found in that list, as well as processing |
| instructions or comments found before or after the document root element. |
| Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of |
| a document. Alternatively if you are sure to not reference DTDs nor have |
| PIs or comments before or after the root element |
| s/->root/->children/g will probably do it.</li> |
| <li>The white space issue, this one is more complex, unless special case of |
| validating parsing, the line breaks and spaces usually used for indenting |
| and formatting the document content becomes significant. So they are |
| reported by SAX and if your using the DOM tree, corresponding nodes are |
| generated. Too approach can be taken: |
| <ol><li>lazy one, use the compatibility call |
| <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are |
| relying on a special (and possibly broken) set of heuristics of |
| libxml to detect ignorable blanks. Don't complain if it breaks or |
| make your application not 100% clean w.r.t. to it's input.</li> |
| <li>the Right Way: change you code to accept possibly insignificant |
| blanks characters, or have your tree populated with weird blank text |
| nodes. You can spot them using the commodity function |
| <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank |
| nodes.</li> |
| </ol><p>Note also that with the new default the output functions don't add any |
| extra indentation when saving a tree in order to be able to round trip |
| (read and save) without inflating the document with extra formatting |
| chars.</p> |
| </li> |
| <li>The include path has changed to $prefix/libxml/ and the includes |
| themselves uses this new prefix in includes instructions... If you are |
| using (as expected) the |
| <pre>xml2-config --cflags</pre> |
| <p>output to generate you compile commands this will probably work out of |
| the box</p> |
| </li> |
| <li>xmlDetectCharEncoding takes an extra argument indicating the length in |
| byte of the head of the document available for character detection.</li> |
| </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 |
| to allow smooth upgrade of existing libxml v1code while retaining |
| compatibility. They offers the following:</p><ol><li>similar include naming, one should use |
| <strong>#include<libxml/...></strong> in both cases.</li> |
| <li>similar identifiers defined via macros for the child and root fields: |
| respectively <strong>xmlChildrenNode</strong> and |
| <strong>xmlRootNode</strong></li> |
| <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be |
| inserted once in the client code</li> |
| </ol><p>So the roadmap to upgrade your existing libxml applications is the |
| following:</p><ol><li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> |
| <li>find all occurrences where the xmlDoc <strong>root</strong> field is |
| used and change it to <strong>xmlRootNode</strong></li> |
| <li>similarly find all occurrences where the xmlNode |
| <strong>childs</strong> field is used and change it to |
| <strong>xmlChildrenNode</strong></li> |
| <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your |
| <strong>main()</strong> or in the library init entry point</li> |
| <li>Recompile, check compatibility, it should still work</li> |
| <li>Change your configure script to look first for xml2-config and fall |
| back using xml-config . Use the --cflags and --libs output of the command |
| as the Include and Linking parameters needed to use libxml.</li> |
| <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and |
| libxml-devel-1.8.y can be kept simultaneously)</li> |
| <li>remove your config.cache, relaunch your configuration mechanism, and |
| recompile, if steps 2 and 3 were done right it should compile as-is</li> |
| <li>Test that your application is still running correctly, if not this may |
| be due to extra empty nodes due to formating spaces being kept in libxml2 |
| contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your |
| code before calling the parser (next to |
| <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li> |
| </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 |
| libxml 1.x to 2.x than the ones you may have to patch for. The overall code |
| has been considerably cleaned up and the conformance to the XML specification |
| has been drastically improved too. Don't take those changes as an excuse to |
| 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> |