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| 13 | <title>Upgrading 1.x code</title> |
Daniel Veillard | 3e6d237 | 2000-03-04 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> |
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| 75 | <p>Incompatible changes:</p> |
Daniel Veillard | 3e6d237 | 2000-03-04 11:39:43 +0000 | [diff] [blame] | 76 | <p>Version 2 of libxml is the first version introducing serious backward |
| 77 | incompatible changes. The main goals were:</p> |
| 78 | <ul> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 79 | <li>a general cleanup. A number of mistakes inherited from the very early |
Daniel Veillard | 585b4ea | 2001-10-24 07:26:23 +0000 | [diff] [blame] | 80 | versions couldn't be changed due to compatibility constraints. Example |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 81 | the "childs" element in the nodes.</li> |
| 82 | <li>Uniformization of the various nodes, at least for their header and link |
Daniel Veillard | 3e6d237 | 2000-03-04 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 Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 85 | <li>better conformances to the XML specification, for example version 1.x |
Daniel Veillard | 3e6d237 | 2000-03-04 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 Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 92 | <h3>How to fix libxml-1.x code:</h3> |
Daniel Veillard | 3e6d237 | 2000-03-04 11:39:43 +0000 | [diff] [blame] | 93 | <p>So client code of libxml designed to run with version 1.x may have to be |
| 94 | changed to compile against version 2.x of libxml. Here is a list of changes |
| 95 | that I have collected, they may not be sufficient, so in case you find other |
| 96 | change which are required, <a href="mailto:Daniel.Ïeillardw3.org">drop me a |
| 97 | mail</a>:</p> |
| 98 | <ol> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 99 | <li>The package name have changed from libxml to libxml2, the library name |
Daniel Veillard | 480363b | 2001-03-16 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 Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 102 | <li>Node <strong>childs</strong> field has been renamed |
Daniel Veillard | 3e6d237 | 2000-03-04 11:39:43 +0000 | [diff] [blame] | 103 | <strong>children</strong> so s/childs/children/g should be applied |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 104 | (probablility of having "childs" anywere else is close to 0+</li> |
| 105 | <li>The document don't have anymore a <strong>root</strong> element it has |
Daniel Veillard | 585b4ea | 2001-10-24 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 Veillard | 3e6d237 | 2000-03-04 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 Veillard | 480363b | 2001-03-16 22:04:15 +0000 | [diff] [blame] | 112 | PIs or comments before or after the root element |
| 113 | s/->root/->children/g will probably do it.</li> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 114 | <li>The white space issue, this one is more complex, unless special case of |
Daniel Veillard | 3e6d237 | 2000-03-04 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 Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 120 | <li>lazy one, use the compatibility call |
Daniel Veillard | 3e6d237 | 2000-03-04 11:39:43 +0000 | [diff] [blame] | 121 | <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are |
Daniel Veillard | 585b4ea | 2001-10-24 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 Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 125 | <li>the Right Way: change you code to accept possibly unsignificant |
Daniel Veillard | 3e6d237 | 2000-03-04 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 Veillard | b8cfbd1 | 2001-10-25 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 Veillard | 3e6d237 | 2000-03-04 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 Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 135 | </li> |
| 136 | <li>The include path has changed to $prefix/libxml/ and the includes |
Daniel Veillard | 361d845 | 2000-04-03 19:48:13 +0000 | [diff] [blame] | 137 | themselves uses this new prefix in includes instructions... If you are |
Daniel Veillard | 5e873c4 | 2000-04-12 13:27:38 +0000 | [diff] [blame] | 138 | using (as expected) the |
Daniel Veillard | 480363b | 2001-03-16 22:04:15 +0000 | [diff] [blame] | 139 | <pre>xml2-config --cflags</pre> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 140 | <p>output to generate you compile commands this will probably work out of |
Daniel Veillard | 361d845 | 2000-04-03 19:48:13 +0000 | [diff] [blame] | 141 | the box</p> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 142 | </li> |
| 143 | <li>xmlDetectCharEncoding takes an extra argument indicating the lenght in |
Daniel Veillard | 585b4ea | 2001-10-24 07:26:23 +0000 | [diff] [blame] | 144 | byte of the head of the document available for character detection.</li> |
Daniel Veillard | 3e6d237 | 2000-03-04 11:39:43 +0000 | [diff] [blame] | 145 | </ol> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 146 | <h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3> |
Daniel Veillard | 480363b | 2001-03-16 22:04:15 +0000 | [diff] [blame] | 147 | <p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released |
| 148 | to allow smoth upgrade of existing libxml v1code while retaining |
| 149 | compatibility. They offers the following:</p> |
Daniel Veillard | f302982 | 2000-05-06 08:11:19 +0000 | [diff] [blame] | 150 | <ol> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 151 | <li>similar include naming, one should use |
Daniel Veillard | 480363b | 2001-03-16 22:04:15 +0000 | [diff] [blame] | 152 | <strong>#include<libxml/...></strong> in both cases.</li> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 153 | <li>similar identifiers defined via macros for the child and root fields: |
Daniel Veillard | c230410 | 2000-06-29 00:43:27 +0000 | [diff] [blame] | 154 | respectively <strong>xmlChildrenNode</strong> and |
Daniel Veillard | b8cfbd1 | 2001-10-25 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 Veillard | c230410 | 2000-06-29 00:43:27 +0000 | [diff] [blame] | 158 | inserted once in the client code</li> |
Daniel Veillard | f302982 | 2000-05-06 08:11:19 +0000 | [diff] [blame] | 159 | </ol> |
Daniel Veillard | c230410 | 2000-06-29 00:43:27 +0000 | [diff] [blame] | 160 | <p>So the roadmap to upgrade your existing libxml applications is the |
| 161 | following:</p> |
| 162 | <ol> |
Daniel Veillard | b8cfbd1 | 2001-10-25 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 Veillard | c230410 | 2000-06-29 00:43:27 +0000 | [diff] [blame] | 171 | <strong>main()</strong> or in the library init entry point</li> |
Daniel Veillard | b8cfbd1 | 2001-10-25 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 Veillard | 480363b | 2001-03-16 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 Veillard | b8cfbd1 | 2001-10-25 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 Veillard | 480363b | 2001-03-16 22:04:15 +0000 | [diff] [blame] | 177 | libxml-devel-1.8.y can be kept simultaneously)</li> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 178 | <li>remove your config.cache, relaunch your configuration mechanism, and |
Daniel Veillard | c230410 | 2000-06-29 00:43:27 +0000 | [diff] [blame] | 179 | recompile, if steps 2 and 3 were done right it should compile as-is</li> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 180 | <li>Test that your application is still running correctly, if not this may |
Daniel Veillard | c230410 | 2000-06-29 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 Veillard | d83eb82 | 2000-06-30 18:39:56 +0000 | [diff] [blame] | 186 | <p>Following those steps should work. It worked for some of my own code.</p> |
Daniel Veillard | 3e6d237 | 2000-03-04 11:39:43 +0000 | [diff] [blame] | 187 | <p>Let me put some emphasis on the fact that there is far more changes from |
Daniel Veillard | f302982 | 2000-05-06 08:11:19 +0000 | [diff] [blame] | 188 | libxml 1.x to 2.x than the ones you may have to patch for. The overall code |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 189 | has been considerably cleaned up and the conformance to the XML specification |
| 190 | has been drastically improved too. Don't take those changes as an excuse to |
| 191 | not upgrade, it may cost a lot on the long term ...</p> |
Daniel Veillard | c5d6434 | 2001-06-24 12:13:24 +0000 | [diff] [blame] | 192 | <p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p> |
Daniel Veillard | b8cfbd1 | 2001-10-25 10:53:28 +0000 | [diff] [blame] | 193 | </td></tr></table></td></tr></table></td></tr></table></td> |
| 194 | </tr></table></td></tr></table> |
Daniel Veillard | 3e6d237 | 2000-03-04 11:39:43 +0000 | [diff] [blame] | 195 | </body> |
| 196 | </html> |