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13<title>Upgrading 1.x code</title>
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]14</head>
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21<h1>The XML C library for Gnome</h1>
22<h2>Upgrading 1.x code</h2>
23</td></tr></table></td></tr></table></td>
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Daniel Veillard8acca112002-01-21 09:52:27 +0000[diff] [blame^]29<tr><td bgcolor="#fffacd"><ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]30<li><a href="index.html">Home</a></li>
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Daniel Veillard7b602b42002-01-08 13:26:00 +0000[diff] [blame]38<li><a href="XMLinfo.html">XML</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]39<li><a href="XSLT.html">XSLT</a></li>
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51<li><a href="upgrade.html">Upgrading 1.x code</a></li>
Daniel Veillard52dcab32001-10-30 12:51:17 +0000[diff] [blame]52<li><a href="threads.html">Thread safety</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]53<li><a href="DOM.html">DOM Principles</a></li>
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Daniel Veillard8acca112002-01-21 09:52:27 +0000[diff] [blame^]63<tr><td bgcolor="#fffacd"><ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]64<li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li>
65<li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li>
Daniel Veillard4a859202002-01-08 11:49:22 +0000[diff] [blame]66<li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]67<li><a href="ftp://xmlsoft.org/">FTP</a></li>
68<li><a href="http://www.fh-frankfurt.de/~igor/projects/libxml/">Windows binaries</a></li>
Daniel Veillarddb9dfd92001-11-26 17:25:02 +0000[diff] [blame]69<li><a href="http://garypennington.net/libxml2/">Solaris binaries</a></li>
Daniel Veillardc6271d22001-10-27 07:50:58 +0000[diff] [blame]70<li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Bug Tracker</a></li>
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75<p>Incompatible changes:</p>
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]76<p>Version 2 of libxml is the first version introducing serious backward
77incompatible changes. The main goals were:</p>
78<ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]79<li>a general cleanup. A number of mistakes inherited from the very early
Daniel Veillard585b4ea2001-10-24 07:26:23 +0000[diff] [blame]80 versions couldn't be changed due to compatibility constraints. Example
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]81 the &quot;childs&quot; element in the nodes.</li>
82<li>Uniformization of the various nodes, at least for their header and link
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]83 parts (doc, parent, children, prev, next), the goal is a simpler
84 programming model and simplifying the task of the DOM implementors.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]85<li>better conformances to the XML specification, for example version 1.x
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]86 had an heuristic to try to detect ignorable white spaces. As a result the
87 SAX event generated were ignorableWhitespace() while the spec requires
88 character() in that case. This also mean that a number of DOM node
89 containing blank text may populate the DOM tree which were not present
90 before.</li>
91</ul>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]92<h3>How to fix libxml-1.x code:</h3>
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]93<p>So client code of libxml designed to run with version 1.x may have to be
94changed to compile against version 2.x of libxml. Here is a list of changes
95that I have collected, they may not be sufficient, so in case you find other
96change which are required, <a href="mailto:Daniel.Ïeillardw3.org">drop me a
97mail</a>:</p>
98<ol>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]99<li>The package name have changed from libxml to libxml2, the library name
Daniel Veillard480363b2001-03-16 22:04:15 +0000[diff] [blame]100 is now -lxml2 . There is a new xml2-config script which should be used to
101 select the right parameters libxml2</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]102<li>Node <strong>childs</strong> field has been renamed
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]103 <strong>children</strong> so s/childs/children/g should be applied
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]104 (probablility of having &quot;childs&quot; anywere else is close to 0+</li>
105<li>The document don't have anymore a <strong>root</strong> element it has
Daniel Veillard585b4ea2001-10-24 07:26:23 +0000[diff] [blame]106 been replaced by <strong>children</strong> and usually you will get a
107 list of element here. For example a Dtd element for the internal subset
108 and it's declaration may be found in that list, as well as processing
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]109 instructions or comments found before or after the document root element.
110 Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of
111 a document. Alternatively if you are sure to not reference Dtds nor have
Daniel Veillard480363b2001-03-16 22:04:15 +0000[diff] [blame]112 PIs or comments before or after the root element
113 s/-&gt;root/-&gt;children/g will probably do it.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]114<li>The white space issue, this one is more complex, unless special case of
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]115 validating parsing, the line breaks and spaces usually used for indenting
116 and formatting the document content becomes significant. So they are
117 reported by SAX and if your using the DOM tree, corresponding nodes are
118 generated. Too approach can be taken:
119 <ol>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]120<li>lazy one, use the compatibility call
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]121 <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are
Daniel Veillard585b4ea2001-10-24 07:26:23 +0000[diff] [blame]122 relying on a special (and possibly broken) set of heuristics of
123 libxml to detect ignorable blanks. Don't complain if it breaks or
124 make your application not 100% clean w.r.t. to it's input.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]125<li>the Right Way: change you code to accept possibly unsignificant
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]126 blanks characters, or have your tree populated with weird blank text
127 nodes. You can spot them using the comodity function
128 <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank
129 nodes.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]130</ol>
131<p>Note also that with the new default the output functions don't add any
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]132 extra indentation when saving a tree in order to be able to round trip
133 (read and save) without inflating the document with extra formatting
134 chars.</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]135</li>
136<li>The include path has changed to $prefix/libxml/ and the includes
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]137 themselves uses this new prefix in includes instructions... If you are
Daniel Veillard5e873c42000-04-12 13:27:38 +0000[diff] [blame]138 using (as expected) the
Daniel Veillard480363b2001-03-16 22:04:15 +0000[diff] [blame]139 <pre>xml2-config --cflags</pre>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]140<p>output to generate you compile commands this will probably work out of
Daniel Veillard361d8452000-04-03 19:48:13 +0000[diff] [blame]141 the box</p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]142</li>
143<li>xmlDetectCharEncoding takes an extra argument indicating the lenght in
Daniel Veillard585b4ea2001-10-24 07:26:23 +0000[diff] [blame]144 byte of the head of the document available for character detection.</li>
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]145</ol>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]146<h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3>
Daniel Veillard480363b2001-03-16 22:04:15 +0000[diff] [blame]147<p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released
148to allow smoth upgrade of existing libxml v1code while retaining
149compatibility. They offers the following:</p>
Daniel Veillardf3029822000-05-06 08:11:19 +0000[diff] [blame]150<ol>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]151<li>similar include naming, one should use
Daniel Veillard480363b2001-03-16 22:04:15 +0000[diff] [blame]152 <strong>#include&lt;libxml/...&gt;</strong> in both cases.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]153<li>similar identifiers defined via macros for the child and root fields:
Daniel Veillardc2304102000-06-29 00:43:27 +0000[diff] [blame]154 respectively <strong>xmlChildrenNode</strong> and
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]155 <strong>xmlRootNode</strong>
156</li>
157<li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be
Daniel Veillardc2304102000-06-29 00:43:27 +0000[diff] [blame]158 inserted once in the client code</li>
Daniel Veillardf3029822000-05-06 08:11:19 +0000[diff] [blame]159</ol>
Daniel Veillardc2304102000-06-29 00:43:27 +0000[diff] [blame]160<p>So the roadmap to upgrade your existing libxml applications is the
161following:</p>
162<ol>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]163<li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li>
164<li>find all occurences where the xmlDoc <strong>root</strong> field is
165 used and change it to <strong>xmlRootNode</strong>
166</li>
167<li>similary find all occurences where the xmlNode <strong>childs</strong>
168 field is used and change it to <strong>xmlChildrenNode</strong>
169</li>
170<li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your
Daniel Veillardc2304102000-06-29 00:43:27 +0000[diff] [blame]171 <strong>main()</strong> or in the library init entry point</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]172<li>Recompile, check compatibility, it should still work</li>
173<li>Change your configure script to look first for xml2-config and fallback
Daniel Veillard480363b2001-03-16 22:04:15 +0000[diff] [blame]174 using xml-config . Use the --cflags and --libs ouptut of the command as
175 the Include and Linking parameters needed to use libxml.</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]176<li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and
Daniel Veillard480363b2001-03-16 22:04:15 +0000[diff] [blame]177 libxml-devel-1.8.y can be kept simultaneously)</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]178<li>remove your config.cache, relaunch your configuration mechanism, and
Daniel Veillardc2304102000-06-29 00:43:27 +0000[diff] [blame]179 recompile, if steps 2 and 3 were done right it should compile as-is</li>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]180<li>Test that your application is still running correctly, if not this may
Daniel Veillardc2304102000-06-29 00:43:27 +0000[diff] [blame]181 be due to extra empty nodes due to formating spaces being kept in libxml2
182 contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your
183 code before calling the parser (next to
184 <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li>
185</ol>
Daniel Veillardd83eb822000-06-30 18:39:56 +0000[diff] [blame]186<p>Following those steps should work. It worked for some of my own code.</p>
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]187<p>Let me put some emphasis on the fact that there is far more changes from
Daniel Veillardf3029822000-05-06 08:11:19 +0000[diff] [blame]188libxml 1.x to 2.x than the ones you may have to patch for. The overall code
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]189has been considerably cleaned up and the conformance to the XML specification
190has been drastically improved too. Don't take those changes as an excuse to
191not upgrade, it may cost a lot on the long term ...</p>
Daniel Veillardc5d64342001-06-24 12:13:24 +0000[diff] [blame]192<p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p>
Daniel Veillardb8cfbd12001-10-25 10:53:28 +0000[diff] [blame]193</td></tr></table></td></tr></table></td></tr></table></td>
194</tr></table></td></tr></table>
Daniel Veillard3e6d2372000-03-04 11:39:43 +0000[diff] [blame]195</body>
196</html>