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2.1.0 test release for good, updated doc and example, Daniel.
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Daniel Veillard
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@ -3,7 +3,7 @@
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<html>
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<head>
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<title>Upgrading libxml client code from 1.x to 2.x</title>
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<meta name="GENERATOR" content="amaya V3.1">
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<meta name="GENERATOR" content="amaya V2.1">
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<meta http-equiv="Content-Type" content="text/html">
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</head>
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@ -48,17 +48,7 @@ mail</a>:</p>
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Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of
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a document. Alternatively if you are sure to not reference Dtds nor have
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PIs or comments before or after the root element s/->root/->children/g
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will probably do it.
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<p><strong>Note</strong>: libxml2 final version now export a version
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number as the LIBXML_VERSION preprocessor token. In most case the changes
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required for 1/ and 2/ can be dealt with using the following construct (if
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you don't use root identifier for other purposes):</p>
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<pre>#if defined(LIBXML_VERSION) && LIBXML_VERSION >= 20000
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#define root children
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#define childs children
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#endif
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</pre>
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</li>
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will probably do it. </li>
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<li>The white space issue, this one is more complex, unless special case of
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validating parsing, the line breaks and spaces usually used for indenting
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and formatting the document content becomes significant. So they are
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@ -90,49 +80,45 @@ mail</a>:</p>
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</li>
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</ol>
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<h2>Keeping both libxml-1.x and libxml-2.x compatibility:</h2>
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<h2>Ensuring both libxml-1.x and libxml-2.x compatibility</h2>
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<p>Here is the steps i applied successfully to a couple of gnome project
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dependant on libxml to allow compilation under both environments:</p>
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<p>Two new version of libxml (1.8.8) and libxml2 (2.1.0) have been released to
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allow smoth upgrade of existing libxml v1code while retaining compatibility.
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They offers the following:</p>
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<ol>
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<li>make sure your configure adds the output of "xml-config --cflags" to
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the compiler command line</li>
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<li>in your C files including libxml includes do the following
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<pre>#include <xmlmemory.h>
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#if defined(LIBXML_VERSION) && LIBXML_VERSION >= 20000
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#include <libxml/parser.h>
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#include <libxml/tree.h>
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#define root children
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#define childs children
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#else
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#include <gnome-xml/parser.h>
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#include <gnome-xml/tree.h>
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#endif</pre>
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<p>the first include name is really specific to libxml and won't clash
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with other installed softare includes. Once included we can tell
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the version used and use prefixed path for the includes to safely
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include headers like tree.h .</p>
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<p>Second the two #defines allows to handle changes dones in the names of
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public structures. Just make sure that you don't use the "root" name for
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other structure in your module. Using xmlDocGetRootElement(doc) is the
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proper way to access the root node now but is not available on old libxml
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version (but present in 1.8.7).</p>
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</li>
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<li>libxml-2 generates "empty" text nodes for "formatting spaces" found in
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the XML input. The proper way to handle this change is to check them (and
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ignore them) when scanning an XML tree produced after libxml parsing. The
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quick and dirty solution is to force libxml to the old behaviour of
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ignoring those formatting spaces by adding the following code before any
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call to the XML parser:
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<pre>#if defined(LIBXML_VERSION) && LIBXML_VERSION >= 20000
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xmlKeepBlanksDefault(0);
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#endif</pre>
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</li>
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<li>similar include naming, one should use
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<strong>#include<libxml/...></strong> in both cases.</li>
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<li>similar identifiers defined via macros for the child and root fields:
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respectively <strong>xmlChildrenNode</strong> and
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<strong>xmlRootNode</strong> </li>
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<li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be
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inserted once in the client code</li>
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</ol>
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<p>Following those 3 steps should work. It worked for some of my own code and
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for the gnome-print module. Other modules (including bonobo/gconf/nautilus)
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will have to be patched in the same way. </p>
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<p>So the roadmap to upgrade your existing libxml applications is the
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following:</p>
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<ol>
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<li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li>
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<li>find all occurences where the xmlDoc <strong>root</strong> field is used
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and change it to <strong>xmlRootNode</strong></li>
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<li>similary find all occurences where the xmlNode <strong>childs</strong>
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field is used and change it to <strong>xmlChildrenNode</strong></li>
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<li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your
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<strong>main()</strong> or in the library init entry point</li>
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<li>Recompile, check compatibility, it should still work</li>
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<li>install libxml2-2.1.0, remove libxml-devel-1.8.8 and install
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libxml2-devel-2.1.0 (libxml-1.8.8 can be kept installed for legacy
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stuff)</li>
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<li>remove your config.cache, relaunch your configuration mechanism, and
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recompile, if steps 2 and 3 were done right it should compile as-is</li>
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<li>Test that your application is still running correctly, if not this may
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be due to extra empty nodes due to formating spaces being kept in libxml2
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contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your
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code before calling the parser (next to
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<strong>LIBXML_TEST_VERSION</strong> is a fine place).</li>
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</ol>
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<p>Following those 3 steps should work. It worked for some of my own code.</p>
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<p>Let me put some emphasis on the fact that there is far more changes from
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libxml 1.x to 2.x than the ones you may have to patch for. The overall code
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@ -142,6 +128,6 @@ upgrade, it may cost a lot on the long term ...</p>
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<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>
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<p>$Id: upgrade.html,v 1.4 2000/04/12 13:27:38 veillard Exp $</p>
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<p>$Id: upgrade.html,v 1.5 2000/05/06 08:11:18 veillard Exp $</p>
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</body>
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</html>
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@ -262,6 +262,7 @@ int main(int argc, char **argv) {
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gJobPtr cur;
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/* COMPAT: Do not genrate nodes for formatting spaces */
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LIBXML_TEST_VERSION
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xmlKeepBlanksDefault(0);
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for (i = 1; i < argc ; i++) {
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