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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 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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
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| 11 | incompatible changes. The main goals were:</p><ul>
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| 12 | <li>a general cleanup. A number of mistakes inherited from the very early
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| 13 | versions couldn't be changed due to compatibility constraints. Example
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| 14 | the "childs" element in the nodes.</li>
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| 15 | <li>Uniformization of the various nodes, at least for their header and link
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| 16 | parts (doc, parent, children, prev, next), the goal is a simpler
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| 17 | programming model and simplifying the task of the DOM implementors.</li>
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| 18 | <li>better conformances to the XML specification, for example version 1.x
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| 19 | had an heuristic to try to detect ignorable white spaces. As a result the
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| 20 | SAX event generated were ignorableWhitespace() while the spec requires
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| 21 | character() in that case. This also mean that a number of DOM node
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| 22 | containing blank text may populate the DOM tree which were not present
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| 23 | before.</li>
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| 24 | </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
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| 25 | changed to compile against version 2.x of libxml. Here is a list of changes
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| 26 | that I have collected, they may not be sufficient, so in case you find other
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| 27 | change which are required, <a href="mailto:[email protected]">drop me a
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| 28 | mail</a>:</p><ol>
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| 29 | <li>The package name have changed from libxml to libxml2, the library name
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| 30 | is now -lxml2 . There is a new xml2-config script which should be used to
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| 31 | select the right parameters libxml2</li>
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| 32 | <li>Node <strong>childs</strong> field has been renamed
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| 33 | <strong>children</strong> so s/childs/children/g should be applied
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| 34 | (probability of having "childs" anywhere else is close to 0+</li>
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| 35 | <li>The document don't have anymore a <strong>root</strong> element it has
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| 36 | been replaced by <strong>children</strong> and usually you will get a
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| 37 | list of element here. For example a Dtd element for the internal subset
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| 38 | and it's declaration may be found in that list, as well as processing
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| 39 | instructions or comments found before or after the document root element.
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| 40 | Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of
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| 41 | a document. Alternatively if you are sure to not reference DTDs nor have
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| 42 | PIs or comments before or after the root element
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| 43 | s/->root/->children/g will probably do it.</li>
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| 44 | <li>The white space issue, this one is more complex, unless special case of
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| 45 | validating parsing, the line breaks and spaces usually used for indenting
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| 46 | and formatting the document content becomes significant. So they are
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| 47 | reported by SAX and if your using the DOM tree, corresponding nodes are
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| 48 | generated. Too approach can be taken:
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| 49 | <ol>
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| 50 | <li>lazy one, use the compatibility call
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| 51 | <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are
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| 52 | relying on a special (and possibly broken) set of heuristics of
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| 53 | libxml to detect ignorable blanks. Don't complain if it breaks or
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| 54 | make your application not 100% clean w.r.t. to it's input.</li>
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| 55 | <li>the Right Way: change you code to accept possibly insignificant
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| 56 | blanks characters, or have your tree populated with weird blank text
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| 57 | nodes. You can spot them using the commodity function
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| 58 | <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank
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| 59 | nodes.</li>
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| 60 | </ol>
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| 61 | <p>Note also that with the new default the output functions don't add any
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| 62 | extra indentation when saving a tree in order to be able to round trip
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| 63 | (read and save) without inflating the document with extra formatting
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| 64 | chars.</p>
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| 65 | </li>
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| 66 | <li>The include path has changed to $prefix/libxml/ and the includes
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| 67 | themselves uses this new prefix in includes instructions... If you are
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| 68 | using (as expected) the
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| 69 | <pre>xml2-config --cflags</pre>
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| 70 | <p>output to generate you compile commands this will probably work out of
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| 71 | the box</p>
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| 72 | </li>
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| 73 | <li>xmlDetectCharEncoding takes an extra argument indicating the length in
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| 74 | byte of the head of the document available for character detection.</li>
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| 75 | </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
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| 76 | to allow smooth upgrade of existing libxml v1code while retaining
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| 77 | compatibility. They offers the following:</p><ol>
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| 78 | <li>similar include naming, one should use
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| 79 | <strong>#include<libxml/...></strong> in both cases.</li>
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| 80 | <li>similar identifiers defined via macros for the child and root fields:
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| 81 | respectively <strong>xmlChildrenNode</strong> and
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| 82 | <strong>xmlRootNode</strong></li>
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| 83 | <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be
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| 84 | inserted once in the client code</li>
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| 85 | </ol><p>So the roadmap to upgrade your existing libxml applications is the
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| 86 | following:</p><ol>
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| 87 | <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li>
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| 88 | <li>find all occurrences where the xmlDoc <strong>root</strong> field is
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| 89 | used and change it to <strong>xmlRootNode</strong></li>
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| 90 | <li>similarly find all occurrences where the xmlNode
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| 91 | <strong>childs</strong> field is used and change it to
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| 92 | <strong>xmlChildrenNode</strong></li>
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| 93 | <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your
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| 94 | <strong>main()</strong> or in the library init entry point</li>
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| 95 | <li>Recompile, check compatibility, it should still work</li>
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| 96 | <li>Change your configure script to look first for xml2-config and fall
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| 97 | back using xml-config . Use the --cflags and --libs output of the command
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| 98 | as the Include and Linking parameters needed to use libxml.</li>
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| 99 | <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and
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| 100 | libxml-devel-1.8.y can be kept simultaneously)</li>
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| 101 | <li>remove your config.cache, relaunch your configuration mechanism, and
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| 102 | recompile, if steps 2 and 3 were done right it should compile as-is</li>
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| 103 | <li>Test that your application is still running correctly, if not this may
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| 104 | be due to extra empty nodes due to formating spaces being kept in libxml2
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| 105 | contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your
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| 106 | code before calling the parser (next to
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| 107 | <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li>
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| 108 | </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
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| 109 | libxml 1.x to 2.x than the ones you may have to patch for. The overall code
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| 110 | has been considerably cleaned up and the conformance to the XML specification
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| 111 | has been drastically improved too. Don't take those changes as an excuse to
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| 112 | 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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