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11 <h1 align="center">The XSLT C library for GNOME</h1>
13 <h1 style="text-align: center">libxslt</h1>
15 <p>Libxslt is the <a href="http://www.w3.org/TR/xslt">XSLT</a> C library
16 developed for the GNOME project. XSLT itself is a an XML language to define
17 transformation for XML. Libxslt is based on <a
18 href="http://xmlsoft.org/">libxml2</a> the XML C library developed for the
19 GNOME project. It also implements most of the <a
20 href="http://www.exslt.org/">EXSLT</a> set of processor-portable extensions
21 functions and some of Saxon's evaluate and expressions extensions.</p>
23 <p>People can either embed the library in their application or use xsltproc
24 the command line processing tool. This library is free software and can be
25 reused in commercial applications (see the <a href="intro.html">intro</a>)</p>
27 <p>External documents:</p>
29 <li>John Fleck wrote <a href="tutorial/libxslttutorial.html">a tutorial for
31 <li><a href="xsltproc.html">xsltproc user manual</a></li>
32 <li><a href="http://xmlsoft.org/">the libxml documentation</a></li>
37 <p>Logo designed by <a href="mailto:liyanage@access.ch">Marc Liyanage</a>.</p>
39 <h2><a name="Introducti">Introduction</a></h2>
41 <p>This document describes <a href="http://xmlsoft.org/XSLT/">libxslt</a>,
42 the <a href="http://www.w3.org/TR/xslt">XSLT</a> C library developed for the
43 <a href="http://www.gnome.org/">GNOME</a> project.</p>
45 <p>Here are some key points about libxslt:</p>
47 <li>Libxslt is a C implementation</li>
48 <li>Libxslt is based on libxml for XML parsing, tree manipulation and XPath
50 <li>It is written in plain C, making as few assumptions as possible, and
51 sticking closely to ANSI C/POSIX for easy embedding. Should works on
52 Linux/Unix/Windows.</li>
53 <li>This library is released under the <a
54 href="http://www.opensource.org/licenses/mit-license.html">MIT
56 <li>Though not designed primarily with performances in mind, libxslt seems
57 to be a relatively fast processor.</li>
60 <h2><a name="Documentat">Documentation</a></h2>
62 <p>There are some on-line resources about using libxslt:</p>
64 <li>Check the <a href="html/libxslt-lib.html#LIBXSLT-LIB">API
65 documentation</a> automatically extracted from code comments (using the
66 program apibuild.py, developed for libxml, together with the xsl script
67 'newapi.xsl' and the libxslt xsltproc program).</li>
68 <li>Look at the <a href="http://mail.gnome.org/archives/xslt/">mailing-list
70 <li>Of course since libxslt is based on libxml, it's a good idea to at
71 least read <a href="http://xmlsoft.org/">libxml description</a></li>
74 <h2><a name="Reporting">Reporting bugs and getting help</a></h2>
76 <p>If you need help with the XSLT language itself, here are a number of
79 <li>I strongly suggest to subscribe to <a
80 href="http://www.mulberrytech.com/xsl/xsl-list">XSL-list</a>, check <a
81 href="http://www.biglist.com/lists/xsl-list/archives/">the XSL-list
83 <li>The <a href="http://www.dpawson.co.uk/xsl/xslfaq.html">XSL FAQ</a>.</li>
85 href="http://www.nwalsh.com/docs/tutorials/xsl/xsl/slides.html">tutorial</a>
86 written by Paul Grosso and Norman Walsh is a very good on-line
87 introdution to the language.</li>
89 href="http://www.zvon.org/xxl/XSLTutorial/Books/Book1/index.html">only
90 Zvon XSLT tutorial</a> details a lot of constructs with examples.</li>
91 <li><a href="http://www.jenitennison.com/xslt/index.html">Jeni Tennison's
92 XSLT</a> pages provide links to a lot of answers</li>
93 <li>the <a href="http://incrementaldevelopment.com/xsltrick/">Gallery of
94 XSLT Tricks</a> provides non-standard use case of XSLT</li>
95 <li>And I suggest to buy Michael Kay "XSLT Programmer's Reference" book
96 published by <a href="http://www.wrox.com/">Wrox</a> if you plan to work
97 seriously with XSLT in the future.</li>
100 <p>Well, bugs or missing features are always possible, and I will make a
101 point of fixing them in a timely fashion. The best way to report a bug is to
103 href="http://bugzilla.gnome.org/enter_bug.cgi?product=libxslt">GNOME bug
104 tracking database</a> (make sure to use the "libxslt" module name). Before
105 filing a bug, check the <a
106 href="http://bugzilla.gnome.org/buglist.cgi?product=libxslt">list of existing
107 libxslt bugs</a> to make sure it hasn't already been filed. I look at reports
108 there regularly and it's good to have a reminder when a bug is still open. Be
109 sure to specify that the bug is for the package libxslt.</p>
111 <p>For small problems you can try to get help on IRC, the #xml channel on
112 irc.gnome.org (port 6667) usually have a few person subscribed which may help
113 (but there is no guarantee and if a real issue is raised it should go on the
114 mailing-list for archival).</p>
116 <p>There is also a mailing-list <a
117 href="mailto:xslt@gnome.org">xslt@gnome.org</a> for libxslt, with an <a
118 href="http://mail.gnome.org/archives/xslt/">on-line archive</a>. To subscribe
119 to this list, please visit the <a
120 href="http://mail.gnome.org/mailman/listinfo/xslt">associated Web</a> page
121 and follow the instructions.</p>
123 <p>Alternatively, you can just send the bug to the <a
124 href="mailto:xslt@gnome.org">xslt@gnome.org</a> list, if it's really libxslt
125 related I will approve it.. Please do not send me mail directly especially
126 for portability problem, it makes things really harder to track and in some
127 cases I'm not the best person to answer a given question, ask the list
128 instead. <strong>Do not send code, I won't debug it</strong> (but patches are
129 really appreciated!).</p>
131 <p>Please note that with the current amount of virus and SPAM, sending mail
132 to the list without being subscribed won't work. There is *far too many
133 bounces* (in the order of a thousand a day !) I cannot approve them manually
134 anymore. If your mail to the list bounced waiting for administrator approval,
135 it is LOST ! Repost it and fix the problem triggering the error. Also please
136 note that <span style="color: #FF0000; background-color: #FFFFFF">emails with
137 a legal warning asking to not copy or redistribute freely the information
138 they contain</span> are <strong>NOT</strong> acceptable for the mailing-list,
139 such mail will as much as possible be discarded automatically, and are less
140 likely to be answered if they made it to the list, <strong>DO NOT</strong>
141 post to the list from an email address where such legal requirements are
142 automatically added, get private paying support if you can't share
145 <p>Check the following too <span style="color: #E50000">before
148 <li><a href="search.php">use the search engine</a> to get information
149 related to your problem.</li>
150 <li>make sure you are <a href="ftp://xmlsoft.org/libxslt/">using a recent
151 version</a>, and that the problem still shows up in those</li>
152 <li>check the <a href="http://mail.gnome.org/archives/xslt/">list
153 archives</a> to see if the problem was reported already, in this case
154 there is probably a fix available, similarly check the <a
155 href="http://bugzilla.gnome.org/buglist.cgi?product=libxslt">registered
157 <li>make sure you can reproduce the bug with xsltproc, a very useful thing
158 to do is run the transformation with -v argument and redirect the
159 standard error to a file, then search in this file for the transformation
160 logs just preceding the possible problem</li>
161 <li>Please send the command showing the error as well as the input and
162 stylesheet (as an attachment)</li>
165 <p>Then send the bug with associated information to reproduce it to the <a
166 href="mailto:xslt@gnome.org">xslt@gnome.org</a> list; if it's really libxslt
167 related I will approve it. Please do not send mail to me directly, it makes
168 things really hard to track and in some cases I am not the best person to
169 answer a given question, ask on the list.</p>
171 <p>To <span style="color: #E50000">be really clear about support</span>:</p>
173 <li>Support or help <span style="color: #E50000">request MUST be sent to
174 the list or on bugzilla</span> in case of problems, so that the Question
175 and Answers can be shared publicly. Failing to do so carries the implicit
176 message "I want free support but I don't want to share the benefits with
177 others" and is not welcome. I will automatically Carbon-Copy the
178 xslt@gnome.org mailing list for any technical reply made about libxml2 or
180 <li>There is <span style="color: #E50000">no guarantee for support</span>,
181 if your question remains unanswered after a week, repost it, making sure
182 you gave all the detail needed and the information requested.</li>
183 <li>Failing to provide information as requested or double checking first
184 for prior feedback also carries the implicit message "the time of the
185 library maintainers is less valuable than my time" and might not be
189 <p>Of course, bugs reports with a suggested patch for fixing them will
190 probably be processed faster.</p>
192 <p>If you're looking for help, a quick look at <a
193 href="http://mail.gnome.org/archives/xslt/">the list archive</a> may actually
194 provide the answer, I usually send source samples when answering libxslt
195 usage questions. The <a
196 href="html/libxslt-lib.html#LIBXSLT-LIB">auto-generated documentation</a> is
197 not as polished as I would like (I need to learn more about Docbook), but
198 it's a good starting point.</p>
200 <h2><a name="help">How to help</a></h2>
202 <p>You can help the project in various ways, the best thing to do first is to
203 subscribe to the mailing-list as explained before, check the <a
204 href="http://mail.gnome.org/archives/xslt/">archives </a>and the <a
205 href="http://bugzilla.gnome.org/buglist.cgi?product=libxslt">GNOME bug
208 <li>provide patches when you find problems</li>
209 <li>provide the diffs when you port libxslt to a new platform. They may not
210 be integrated in all cases but help pinpointing portability problems
212 <li>provide documentation fixes (either as patches to the code comments or
214 <li>provide new documentations pieces (translations, examples, etc ...)</li>
215 <li>Check the TODO file and try to close one of the items</li>
216 <li>take one of the points raised in the archive or the bug database and
217 provide a fix. <a href="mailto:daniel@veillard.com">Get in touch with me
218 </a>before to avoid synchronization problems and check that the suggested
219 fix will fit in nicely :-)</li>
222 <h2><a name="Downloads">Downloads</a></h2>
224 <p>The latest versions of libxslt can be found on the <a
225 href="ftp://xmlsoft.org/libxslt/">xmlsoft.org</a> server and on mirrors (<a
226 href="ftp://fr.rpmfind.net/pub/libxml/">France</a>) or on the <a
227 href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">GNOME FTP server</a> as a
228 <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxslt/1.1/">source
229 archive</a>, Antonin Sprinzl also provides <a
230 href="ftp://gd.tuwien.ac.at/pub/libxml/">a mirror in Austria</a>. (NOTE that
231 you need the <a href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a>,
232 <a href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a>,
233 <a href="http://rpmfind.net/linux/RPM/libxslt.html">libxslt</a> and <a
234 href="http://rpmfind.net/linux/RPM/libxslt-devel.html">libxslt-devel</a>
235 packages installed to compile applications using libxslt.) <a
236 href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the maintainer of
238 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides
239 binaries</a>. <a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a>
240 provides <a href="http://garypennington.net/libxml2/">Solaris binaries</a>.
241 <a href="mailto:Steve.Ball@explain.com.au">Steve Ball</a> provides <a
242 href="http://www.explain.com.au/oss/libxml2xslt.html">Mac Os X
245 <p><a name="Contribs">Contribs:</a></p>
247 <p>I do accept external contributions, especially if compiling on another
248 platform, get in touch with me to upload the package. I will keep them in the
249 <a href="ftp://xmlsoft.org/libxml2/contribs/">contrib directory</a></p>
251 <p>Libxslt is also available from SVN:</p>
253 <li><p>The <a href="http://svn.gnome.org/viewcvs/libxslt/trunk/">GNOME SVN
254 base</a>. Check the <a
255 href="http://developer.gnome.org/tools/svn.html">GNOME SVN Tools</a>
256 page; the SVN module is <b>libxslt</b>.</p>
258 <li><a href="ftp://xmlsoft.org/libxml2/libxslt-cvs-snapshot.tar.gz">snapshots from
259 SVN</a> updated every hour are also provided</li>
262 <h2><a name="FAQ">FAQ</a></h2>
264 <li><em>Troubles compiling or linking programs using libxslt</em>
265 <p>Usually the problem comes from the fact that the compiler doesn't get
266 the right compilation or linking flags. There is a small shell script
267 <code>xslt-config</code> which is installed as part of libxslt usual
268 install process which provides those flags. Use</p>
269 <p><code>xslt-config --cflags</code></p>
270 <p>to get the compilation flags and</p>
271 <p><code>xslt-config --libs</code></p>
272 <p>to get the linker flags. Usually this is done directly from the
274 <p><code>CFLAGS=`xslt-config --cflags`</code></p>
275 <p><code>LIBS=`xslt-config --libs`</code></p>
276 <p>Note also that if you use the EXSLT extensions from the program then
277 you should prepend <code>-lexslt</code> to the LIBS options</p>
279 <li><em>passing parameters on the xsltproc command line doesn't work</em>
280 <p><em>xsltproc --param test alpha foo.xsl foo.xml</em></p>
281 <p><em>the param does not get passed and ends up as ""</em></p>
282 <p>In a nutshell do a double escaping at the shell prompt:</p>
283 <p>xsltproc --param test "'alpha'" foo.xsl foo.xml</p>
284 <p>i.e. the string value is surrounded by " and ' then terminated by '
285 and ". Libxslt interpret the parameter values as XPath expressions, so
286 the string -><code>alpha</code><- is intepreted as the node set
287 matching this string. You really want -><code>'alpha'</code><- to
288 be passed to the processor. And to allow this you need to escape the
289 quotes at the shell level using -><code>"'alpha'"</code><- .</p>
291 <p>xsltproc --stringparam test alpha foo.xsl foo.xml</p>
293 <li><em>Is there C++ bindings ?</em>
294 <p>Yes for example <a
295 href="http://pmade.org/pjones/software/xmlwrapp/">xmlwrapp</a> , see <a
296 href="python.html">the related pages about bindings</a></p>
300 <h2><a name="News">News</a></h2>
302 <p>The <a href="ChangeLog.html">change log</a> describes the recents commits
303 to the <a href="http://svn.gnome.org/viewcvs/libxslt/trunk/">SVN</a> code base.</p>
305 <p>Those are the public releases made:</p>
307 <h3>1.1.21: Jun 12 2007</h3>
309 <li>Bug fixes: out of memory allocation errors (William Brack),
310 namespace problem on compound predicates (William Brack),
311 python space/tab inconsistencies (Andreas Hanke), hook xsl:message
312 to per transformation error callbacks (Shaun McCance),
313 cached RVT problem (William Brack), XPath context maintainance
314 on choose (William Brack), memory leaks in the math module (William
315 Brack), exclude-result-prefix induced namespace problem (William
317 <li>Build: configure setup for TRIO_REPLACE_STDIO (William Brack)
318 <li>Documentation: updated after change from CVs to SVN (William Brack)</li>
320 <h3>1.1.20: Jan 17 2007</h3>
322 <li>Portability fixes: strict aliasing fix (Marcus Meissner), BSD portability
323 patches (Roland Illig)</li>
324 <li>Bug fixes: Result Value Tree handling fix (William Brack), function
325 parameters fix (William), uninitialized variable (Kjartan Maraas),
326 empty text node handling (William), plugin support and test fixes (William),
327 fragment support fixes (William)</li>
328 <li>Improvements: python stylesheet compare and transform context
329 access (Nic Ferrier), EXSLT string replace support (Joel Reed),
330 xsltproc better low level error handling (Mike Hommey and William)</li>
332 <h3>1.1.19: Nov 29 2006</h3>
334 <li>Bug fixes: entities within attributes (William Brack), Python detection
335 problem (Joseph Sacco), in-scope namespace bug (Mike Hommey), Result
336 value tree caching bug (William Brack)</li>
338 <h3>1.1.18: Oct 26 2006</h3>
340 <li>portability and build fixes: DESTDIR problem, build paths in python
341 shared lib, compile when libxml2 doesn't support XInclude (Gary Coady).</li>
342 <li>bug fixes: a number of namespace related bugs (Kasimier Buchcik),
343 parameters bugs (Kasimier Buchcik), proximity position in predicates
344 of match patterns (Kasimier), exslt-node-set troubles with strings
345 (Kasimier), CDATA serialization, Python floats and booleans XPath
346 conversions, XInclude support fixes, RVT cleanup problem (William Brack
347 and Kasimier), attribute checking in stylesheets (Kasimier), xsltForEach
348 context problem (Kasimier), security check should pass full URLs (Shane
349 Corgatelli), security cleanup patch (Mikhail Zabaluev), some python
350 accessor for stylesheet were broken, memory errors when compiling
351 stylesheets (Mike Hommey), EXSLT current date end-of-month problem
352 (William Brack).</li>
353 <li>improvements: refactoring of namespace handling, value-of impleemntation
354 and template internal processing (Kasimier Buchcik), new xsltproc
355 flag to apply Xinclude to stylesheets.</li>
356 <li>documentation: xsltproc man pages (Daniel Leidert), tests updates
357 (William Brack), various typo fixes (Daniel Leidert), comments on
358 versions macros (Peter Breitenlohner).</li>
360 <h3>1.1.17: Jun 6 2006</h3>
362 <li>portability fixes: python detection</li>
363 <li>bug fixes: some regression tests, attribute/namespaces output (Kasimier
364 Buchcik), problem in mixed xsl:value-of and xsl:text uses (Kasimier)</li>
365 <li>improvements: internal refactoring (Kasimier Buchcik), use of the XPath
366 object cache in libxml2-2.6.25 (Kasimier)</li>
369 <h3>1.1.16: May 01 2006</h3>
371 <li>portability fixes: EXSLT date/time on Solaris and IRIX (Albert Chin),
372 HP-UX build (Albert Chin),
373 <li>build fixes: Python detection(Joseph Sacco), plugin configurei
375 <li>bug fixes: pattern compilation fix(William Brack), EXSLT date/time
376 fix (Thomas Broyer), EXSLT function bug, potential loop on variable
377 eval, startup race (Christopher Palmer), debug statement left in python
378 (Nic Ferrier), various cleanup based on Coverity reports), error on
379 Out of memory condition (Charles Hardin), various namespace prefixes
380 fixes (Kasimier Buchcik), </li>
381 <li>improvement: speed up sortingi, start of internals refactoring (Kasimier
383 <li>documentation: man page fixes and updates (Daniel Leidert)
386 <h3>1.1.15: Sep 04 2005</h3>
388 <li>build fixes: Windows build cleanups and updates (Igor Zlatkovic),
389 remove jhbuild warnings</li>
390 <li>bug fixes: negative number formatting (William Brack), number
391 formatting per mille definition (William Brack), XInclude default values
392 (William), text copy bugs (William), bug related to xmlXPathContext size,
393 reuse libxml2 memory management for text nodes, dictionary text bug,
394 forbid variables in match (needs libxml2-2.6.21)</li>
395 <li>improvements: EXSLT dyn:map (Mark Vakoc),</li>
396 <li>documentation: EXSLT date and time functions namespace in man (Jonathan
400 <h3>1.1.14: Apr 02 2005</h3>
402 <li>bug fixes: text node on stylesheet document without a dictionary
403 (William Brack), more checking of XSLT syntax, calling xsltInit()
404 multiple times, mode values interning raised by Mark Vakoc, bug in
405 pattern matching with ancestors, bug in patterna matching with cascading
406 select, xinclude and document() problem, build outside of source tree
408 <li>improvement: added a --nodict mode to xsltproc to check problems for
409 docuemtns without dictionaries</li>
412 <h3>1.1.13: Mar 13 2005</h3>
414 <li>build fixes: 64bits cleanup (William Brack), python 2.4 test (William),
415 LIBXSLT_VERSION_EXTRA on Windows (William), Windows makefiles fixes (Joel
416 Reed), libgcrypt-devel requires for RPM spec.</li>
417 <li>bug fixes: exslt day-of-week-in-month (Sal Paradise), xsl:call-template
418 should not change the current template rule (William Brack), evaluation
419 of global variables (William Brack), RVT's in XPath predicates (William),
420 namespace URI on template names (Mark Vakoc), stat() for Windows patch
421 (Aleksey Gurtovoy), pattern expression fixes (William Brack), out of
422 memory detection misses (William), parserOptions propagation (William),
423 exclude-result-prefixes fix (William), // patten fix (William).</li>
424 <li>extensions: module support (Joel Reed), dictionary based speedups
425 trying to get rid of xmlStrEqual as much as possible.</li>
426 <li>documentation: added Wiki (Joel Reed)</li>
429 <h3>1.1.12: Oct 29 2004</h3>
431 <li>build fixes: warnings removal (William).</li>
432 <li>bug fixes: attribute document pointer fix (Mark Vakoc), exslt date
433 negative periods (William Brack), generated tree structure fixes,
434 namespace lookup fix, use reentrant gmtime_r (William Brack),
435 exslt:funtion namespace fix (William), potential NULL pointer reference
436 (Dennis Dams, William), force string interning on generated
438 <li>documentation: update of the second tutorial (Panagiotis Louridas), add
439 exslt doc in rpm packages, fix the xsltproc man page.</li>
442 <h3>1.1.11: Sep 29 2004</h3>
444 <li>bug fixes: xsl:include problems (William Brack), UTF8 number pattern
445 (William), date-time validation (William), namespace fix (William),
446 various Exslt date fixes (William), error callback fixes, leak with
447 namespaced global variable, attempt to fix a weird problem #153137</li>
448 <li>improvements: exslt:date-sum tests (Derek Poon)</li>
449 <li>documentation: second tutorial by Panagiotis Lourida</li>
452 <h3>1.1.10: Aug 31 2004</h3>
454 <li>build fix: NUL in c file blocking compilation on Solaris, Windows build
455 (Igor Zlatkovic)</li>
456 <li>fix: key initialization problem (William Brack)</li>
457 <li>documentation: fixed missing man page description for --path</li>
460 <h3>1.1.9: Aug 22 2004</h3>
462 <li>build fixes: missing tests (William Brack), Python dependancies, Python
463 on 64bits boxes, --with-crypto flag (Rob Richards),</li>
464 <li>fixes: RVT key handling (William), Python binding (William and Sitsofe
465 Wheeler), key and XPath troubles (William), template priority on imports
466 (William), str:tokenize with empty strings (William), #default namespace
467 alias behaviour (William), doc ordering missing for main document
468 (William), 64bit bug (Andreas Schwab)</li>
469 <li>improvements: EXSLT date:sum added (Joel Reed), hook for document
470 loading for David Hyatt, xsltproc --nodtdattr to avoid defaulting DTD
471 attributes, extend xsltproc --version with CVS stamp (William).</li>
472 <li>Documentation: web page problem reported by Oliver Stoeneberg</li>
475 <h3>1.1.8: July 5 2004</h3>
477 <li>build fixes: Windows runtime options (Oliver Stoeneberg), Windows
478 binary package layout (Igor Zlatkovic), libgcrypt version test and link
480 <li>documentation: fix libxslt namespace name in doc (William)</li>
481 <li>bug fixes: undefined namespace message (William Brack), search engine
482 (William), multiple namespace fixups (William), namespace fix for key
483 evaluation (William), Python memory debug bindings,</li>
484 <li>improvements: crypto extensions for exslt (Joel Reed, William)</li>
487 <h3>1.1.7: May 17 2004</h3>
489 <li>build fix: warning about localtime_r on Solaris</li>
490 <li>bug fix: UTF8 string tokenize (William Brack), subtle memory
491 corruption, linefeed after comment at document level (William),
492 disable-output-escaping problem (William), pattern compilation in deep
493 imported stylesheets (William), namespace extension prefix bug,
494 libxslt.m4 bug (Edward Rudd), namespace lookup for attribute, namespaced
498 <h3>1.1.6: Apr 18 2004</h3>
500 <li>2 bug fixes about keys fixed one by Mark Vakoc</li>
503 <h3>1.1.5: Mar 23 2004</h3>
505 <li>performance: use dictionary lookup for variables</li>
506 <li>remove use of _private from source documents</li>
507 <li>cleanup of "make tests" output</li>
508 <li>bugfixes: AVT in local variables, use localtime_r to avoid thread
509 troubles (William), dictionary handling bug (William), limited number of
510 stubstitutions in AVT (William), tokenize fix for UTF-8 (William),
511 superfluous namespace (William), xsltproc error code on
512 <xsl:message> halt, OpenVMS fix, dictionary reference counting
516 <h3>1.1.4: Feb 23 2004</h3>
518 <li>bugfixes: attributes without doc (Mariano Suárez-Alvarez), problem with
519 Yelp, extension problem</li>
520 <li>display extension modules (Steve Little)</li>
521 <li>Windows compilation patch (Mark Vadoc), Mingw (Mikhail Grushinskiy)</li>
524 <h3>1.1.3: Feb 16 2004</h3>
526 <li>Rewrote the Attribute Value Template code, new XPath compilation
527 interfaces, dictionary reuses for XSLT with potential for serious
528 performance improvements.</li>
529 <li>bug fixes: portability (William Brack), key() in node-set() results
530 (William), comment before doctype (William), math and node-set() problems
531 (William), cdata element and default namespace (William), behaviour on
532 unknown XSLT elements (Stefan Kost), priority of "//foo" patterns
533 (William), xsl:element and xsl:attribute QName check (William), comments
534 with -- (William), attribute namespace (William), check for ?> in PI
536 <li>Documentations: cleanup (John Fleck and William)</li>
537 <li>Python: patch for OS-X (Gianni Ceccarelli), enums export (Stephane
541 <h3>1.1.2: Dec 24 2003</h3>
543 <li>Documentation fixes (John Fleck, William Brack), EXSLT documentation
545 <li>Windows compilation fixes for MSVC and Mingw (Igor Zlatkovic)</li>
546 <li>Bug fixes: exslt:date returning NULL strings (William Brack),
547 namespaces output (William Brack), key and namespace definition problem,
548 passing options down to the document() parser, xsl:number fixes (William
552 <h3>1.1.1: Dec 10 2003</h3>
554 <li>code cleanup (William Brack)</li>
555 <li>Windows: Makefile improvements (Igor Zlatkovic)</li>
556 <li>documentation improvements: William Brack, libexslt man page (Jonathan
558 <li>param in EXSLT functions (Shaun McCance)</li>
559 <li>XSLT debugging improvements (Mark Vakoc)</li>
560 <li>bug fixes: number formatting (Bjorn Reese), exslt:tokenize (William
561 Brack), key selector parsing with | reported by Oleg Paraschenko,
562 xsl:element with computed namespaces (William Brack), xslt:import/include
563 recursion detection (William Brack), exslt:function used in keys (William
564 Brack), bug when CDATA_SECTION are foun in the tree (William Brack),
565 entities handling when using XInclude.</li>
568 <h3>1.1.0: Nov 4 2003</h3>
570 <li>Removed DocBook SGML broken support</li>
571 <li>fix xsl:key to work with PIs</li>
572 <li>Makefile and build improvement (Graham Wilson), build cleanup (William
573 Brack), macro fix (Justin Fletcher), build outside of source tree (Roumen
575 <li>xsltproc option display fix (Alexey Efimov), --load-trace (Crutcher
577 <li>Python: never use stdout for error</li>
578 <li>extension memory error fix (Karl Eichwalder)</li>
579 <li>header path fixes (Steve Ball)</li>
580 <li>added saxon:line-number() to libexslt (Brett Kail)</li>
581 <li>Fix some tortuous template problems when using predicates (William
583 <li>Debugger status patch (Kasimier Buchcik)</li>
584 <li>Use new libxml2-2.6.x APIs for faster processing</li>
585 <li>Make sure xsl:sort is empty</li>
586 <li>Fixed a bug in default processing of attributes</li>
587 <li>Removes the deprecated breakpoint library</li>
588 <li>detect invalid names on templates (William Brack)</li>
589 <li>fix exslt:document (and similar) base handling problem</li>
592 <h3>1.0.33: Sep 12 2003</h3>
594 <p>This is a bugfix only release</p>
596 <li>error message missing argument (William Brack)</li>
597 <li>mode not cascaded in template fallbacks (William Brack)</li>
598 <li>catch redefinition of parameter/variables (William Brack)</li>
599 <li>multiple keys with same namespace name (William Brack)</li>
600 <li>patch for compilation using MingW on Windows (Mikhail Grushinskiy)</li>
601 <li>header export macros for Windows (Igor Zlatkovic)</li>
602 <li>cdata-section-elements handling of namespaced names</li>
603 <li>compilation without libxml2 XPointer support (Mark Vadoc)</li>
604 <li>apply-templates crash (William Brack)</li>
605 <li>bug with imported templates (William Brack)</li>
606 <li>imported attribute-sets merging bug (DocBook) (William Brack)</li>
609 <h3>1.0.32: Aug 9 2003</h3>
611 <li>bugfixes: xsltSaveResultToFile() python binding (Chris Jaeger), EXSLT
612 function (William Brack), RVT for globals (William Brack), EXSLT date
614 <p>speed of large text output, xsl:copy with attributes, strip-space and
615 namespaces prefix, fix for --path xsltproc option, EXST:tokenize (Shaun
616 McCance), EXSLT:seconds (William Brack), sort with multiple keys (William
617 Brack), checking of { and } for attribute value templates (William
620 <li>Python bindings for extension elements (Sean Treadway)</li>
621 <li>EXSLT:split added (Shaun McCance)</li>
622 <li>portability fixes for HP-UX/Solaris/IRIX (William Brack)</li>
626 <h3>1.0.31: Jul 6 2003</h3>
628 <li>bugfixes: xsl:copy on namespace nodes, AVT for xsl:sort order, fix for
629 the debugger (Keith Isdale), output filename limitation, trio.h and
630 triodef.h added (Albert Chin), EXSLT node-set (Peter Breitenlohner),
631 xsltChoose and whitespace (Igor Zlatkovic),
632 <p>stylesheet compilation (Igor Zlatkovic), NaN and sort (William Brack),
633 RVT bug introduced in 1.0.30</p>
635 <li>avoid generating &quot; (fix in libxml2-2.5.8)</li>
636 <li>fix 64bit cleaness problem and compilation troubles introduced in
638 <li>Windows makefile generation (Igor Zlatkovic)</li>
639 <li>HP-UX portability fix</li>
642 <h3>1.0.30: May 4 2003</h3>
644 <li>Fixes and new APIs to handle Result Value Trees and avoid leaks</li>
645 <li>Fixes for: EXSLT math pow() function (Charles Bozeman), global
646 parameter and global variables mismatch, a segfault on pattern
647 compilation errors, namespace copy in xsl:copy-of, python generator
648 problem, OpenVMS trio update, premature call to xsltFreeStackElem (Igor),
649 current node when templates applies to attributes</li>
652 <h3>1.0.29: Apr 1 2003</h3>
654 <li>performance improvements especially for large flat documents</li>
655 <li>bug fixes: Result Value Tree handling, XML IDs, keys(), extra namespace
656 declarations with xsl:elements.</li>
657 <li>portability: python and trio fixes (Albert Chin), python on Solaris
661 <h3>1.0.28: Mar 24 2003</h3>
663 <li>fixed node() in patterns semantic.</li>
664 <li>fixed a memory access problem in format-number()</li>
665 <li>fixed stack overflow in recursive global variable or params</li>
666 <li>cleaned up Result Value Tree handling, and fixed a couple of old bugs
670 <h3>1.0.27: Feb 24 2003</h3>
672 <li>bug fixes: spurious xmlns:nsX="" generation, serialization bug (in
673 libxml2), a namespace copy problem, errors in the RPM spec prereqs</li>
674 <li>Windows path canonicalization and document cache fix (Igor)</li>
677 <h3>1.0.26: Feb 10 2003</h3>
679 <li>Fixed 3 serious bugs in document() and stylesheet compilation which
680 could lead to a crash</li>
683 <h3>1.0.25: Feb 5 2003</h3>
685 <li>Bug fix: double-free for standalone stylesheets introduced in 1.0.24, C
686 syntax pbm, 3 bugs reported by Eric van der Vlist</li>
687 <li>Some XPath and XInclude related problems were actually fixed in
689 <li>Documentation: emphasize taht --docbook is not for XML docs.</li>
692 <h3>1.0.24: Jan 14 2003</h3>
694 <li>bug fixes: imported global varables, python bindings (Stéphane Bidoul),
695 EXSLT memory leak (Charles Bozeman), namespace generation on
696 xsl:attribute, space handling with imports (Daniel Stodden),
697 extension-element-prefixes (Josh Parsons), comments within xsl:text (Matt
698 Sergeant), superfluous xmlns generation, XInclude related bug for
699 numbering, EXSLT strings (Alexey Efimov), attribute-sets computation on
700 imports, extension module init and shutdown callbacks not called</li>
701 <li>HP-UX portability (Alexey Efimov), Windows makefiles (Igor and Stephane
702 Bidoul), VMS makefile updates (Craig A. Berry)</li>
703 <li>adds xsltGetProfileInformation() (Michael Rothwell)</li>
704 <li>fix the API generation scripts</li>
705 <li>API to provide the sorting routines (Richard Jinks)</li>
706 <li>added XML description of the EXSLT API</li>
707 <li>added ESXLT URI (un)escaping (Jörg Walter)</li>
708 <li>Some memory leaks have been found and fixed</li>
709 <li>document() now support fragment identifiers in URIs</li>
712 <h3>1.0.23: Nov 17 2002</h3>
714 <li>Windows build cleanup (Igor)</li>
715 <li>Unix build and RPM packaging cleanup</li>
716 <li>Improvement of the python bindings: extension functions and activating
718 <li>various bug fixes: number formatting, portability for bounded string
719 functions, CData nodes, key(), @*[...] patterns</li>
720 <li>Documentation improvements (John Fleck)</li>
721 <li>added libxslt.m4 (Thomas Schraitle)</li>
724 <h3>1.0.22: Oct 18 2002</h3>
726 <li>Updates on the Windows Makefiles</li>
727 <li>Added a security module, and a related set of new options to
729 <li>Allowed per transformation error handler.</li>
730 <li>Fixed a few bugs: node() semantic, URI escaping, media-type, attribute
734 <h3>1.0.21: Sep 26 2002</h3>
736 <li>Bug fixes: match="node()", date:difference() (Igor and Charlie
737 Bozeman), disable-output-escaping</li>
738 <li>Python bindings: style.saveResultToString() from Ralf Mattes</li>
739 <li>Logos from Marc Liyanage</li>
740 <li>Mem leak fix from Nathan Myers</li>
741 <li>Makefile: DESTDIR fix from Christophe Merlet, AMD x86_64 (Mandrake),
742 Windows (Igor), Python detection</li>
743 <li>Documentation improvements: John Fleck</li>
746 <h3>1.0.20: Aug 23 2002</h3>
748 <li>Windows makefile updates (Igor) and x86-64 (Frederic Crozat)</li>
749 <li>fixed HTML meta tag saving for Mac/IE users</li>
750 <li>possible leak patches from Nathan Myers</li>
751 <li>try to handle document('') as best as possible depending in the
753 <li>Fixed the DocBook stylesheets handling problem</li>
754 <li>Fixed a few XSLT reported errors</li>
757 <h3>1.0.19: July 6 2002</h3>
759 <li>EXSLT: dynamic functions and date support bug fixes (Mark Vakoc)</li>
760 <li>xsl:number fix: Richard Jinks</li>
761 <li>xsl:format-numbers fix: Ken Neighbors</li>
762 <li>document('') fix: bug pointed by Eric van der Vlist</li>
763 <li>xsl:message with terminate="yes" fixes: William Brack</li>
764 <li>xsl:sort order support added: Ken Neighbors</li>
765 <li>a few other bug fixes, some of them requiring the latest version of
769 <h3>1.0.18: May 27 2002</h3>
771 <li>a number of bug fixes: attributes, extra namespace declarations
772 (DocBook), xsl:include crash (Igor), documentation (Christian Cornelssen,
773 Charles Bozeman and Geert Kloosterman), element-available (Richard
775 <li>xsltproc can now list teh registered extensions thanks to Mark
777 <li>there is a new API to save directly to a string
778 xsltSaveResultToString() by Morus Walter</li>
779 <li>specific error registration function for the python API</li>
782 <h3>1.0.17: April 29 2002</h3>
784 <li>cleanup in code, XSLT debugger support and Makefiles for Windows by
786 <li>a C++ portability fix by Mark Vakoc</li>
787 <li>EXSLT date improvement and regression tests by Charles Bozeman</li>
788 <li>attempt to fix a bug in xsltProcessUserParamInternal</li>
791 <h3>1.0.16: April 15 2002</h3>
793 <li>Bug fixes: strip-space, URL in HTML output, error when xsltproc can't
795 <li>portability fixes: OSF/1, IEEE on alphas, Windows, Python bindings</li>
798 <h3>1.0.15: Mar 25 2002</h3>
800 <li>Bugfixes: XPath, python Makefile, recursive attribute sets, @foo[..]
802 <li>Debug of memory alocation with valgind</li>
803 <li>serious profiling leading to significant improvement for DocBook
805 <li>revamp of the Windows build</li>
808 <h3>1.0.14: Mar 18 2002</h3>
810 <li>Improvement in the XPath engine (libxml2-2.4.18)</li>
811 <li>Nasty bug fix related to exslt:node-set</li>
812 <li>Fixed the python Makefiles, cleanup of doc comments, Windows
813 portability fixes</li>
816 <h3>1.0.13: Mar 8 2002</h3>
818 <li>a number of bug fixes including "namespace node have no parents"</li>
819 <li>Improvement of the Python bindings</li>
820 <li>Charles Bozeman provided fixes and regression tests for exslt date
824 <h3>1.0.12: Feb 11 2002</h3>
826 <li>Fixed the makefiles especially the python module ones</li>
827 <li>half a dozen bugs fixes including 2 old ones</li>
830 <h3>1.0.11: Feb 8 2002</h3>
832 <li>Change of Licence to the <a
833 href="http://www.opensource.org/licenses/mit-license.html">MIT
835 <li>Added a beta version of the Python bindings, including support to
836 extend the engine with functions written in Python</li>
837 <li>A number of bug fixes</li>
838 <li>Charlie Bozeman provided more EXSLT functions</li>
839 <li>Portability fixes</li>
842 <h3>1.0.10: Jan 14 2002</h3>
844 <li>Windows fixes for Win32 from Igor</li>
845 <li>Fixed the Solaris compilation trouble (Albert)</li>
846 <li>Documentation changes and updates: John Fleck</li>
847 <li>Added a stringparam option to avoid escaping hell at the shell
849 <li>A few bug fixes</li>
852 <h3>1.0.9: Dec 7 2001</h3>
854 <li>Makefile patches from Peter Williams</li>
855 <li>attempt to fix the compilation problem associated to prelinking</li>
856 <li>obsoleted libxsltbreakpoint now deprecated and frozen to 1.0.8 API</li>
857 <li>xsltproc return codes are now significant, John Fleck updated the
859 <li>patch to allow as much as 40 steps in patterns (Marc Tardif), should be
860 made dynamic really</li>
861 <li>fixed a bug raised by Nik Clayton when using doctypes with HTML
863 <li>patches from Keith Isdale to interface with xsltdebugger</li>
866 <h3>1.0.8: Nov 26 2001</h3>
868 <li>fixed an annoying header problem, removed a few bugs and some code
870 <li>patches for Windows and update of Windows Makefiles by Igor</li>
871 <li>OpenVMS port instructions from John A Fotheringham</li>
872 <li>fixed some Makefiles annoyance and libraries prelinking
876 <h3>1.0.7: Nov 10 2001</h3>
878 <li>remove a compilation problem with LIBXSLT_PUBLIC</li>
879 <li>Finishing the integration steps for Keith Isdale debugger</li>
880 <li>fixes the handling of indent="no" on HTML output</li>
881 <li>fixes on the configure script and RPM spec file</li>
884 <h3>1.0.6: Oct 30 2001</h3>
886 <li>bug fixes on number formatting (Thomas), date/time functions (Bruce
888 <li>update of the Windows Makefiles (Igor)</li>
889 <li>fixed DOCTYPE generation rules for HTML output (me)</li>
892 <h3>1.0.5: Oct 10 2001</h3>
894 <li>some portability fixes, including Windows makefile updates from
896 <li>fixed a dozen bugs on XSLT and EXSLT (me and Thomas Broyer)</li>
897 <li>support for Saxon's evaluate and expressions extensions added (initial
898 contribution from Darren Graves)</li>
899 <li>better handling of XPath evaluation errors</li>
902 <h3>1.0.4: Sep 12 2001</h3>
904 <li>Documentation updates from John fleck</li>
905 <li>bug fixes (DocBook FO generation should be fixed) and portability
907 <li>Thomas Broyer improved the existing EXSLT support and added String,
908 Time and Date core functions support</li>
911 <h3>1.0.3: Aug 23 2001</h3>
913 <li>XML Catalog support see the doc</li>
914 <li>New NaN/Infinity floating point code</li>
915 <li>A few bug fixes</li>
918 <h3>1.0.2: Aug 15 2001</h3>
920 <li>lot of bug fixes, increased the testsuite</li>
921 <li>a large chunk of EXSLT is implemented</li>
922 <li>improvements on the extension framework</li>
923 <li>documentation improvements</li>
924 <li>Windows MSC projects files should be up-to-date</li>
925 <li>handle attributes inherited from the DTD by default</li>
928 <h3>1.0.1: July 24 2001</h3>
930 <li>initial EXSLT framework</li>
931 <li>better error reporting</li>
932 <li>fixed the profiler on Windows</li>
936 <h3>1.0.0: July 10 2001</h3>
938 <li>a lot of cleanup, a lot of regression tests added or fixed</li>
939 <li>added a documentation for <a href="extensions.html">writing
941 <li>fixed some variable evaluation problems (with William)</li>
942 <li>added profiling of stylesheet execution accessible as the xsltproc
943 --profile option</li>
944 <li>fixed element-available() and the implementation of the various
945 chunking methods present, Norm Walsh provided a lot of feedback</li>
946 <li>exclude-result-prefixes and namespaces output should now work as
948 <li>added support of embedded stylesheet as described in section 2.7 of the
952 <h3>0.14.0: July 5 2001</h3>
954 <li>lot of bug fixes, and code cleanup</li>
955 <li>completion of the little XSLT-1.0 features left unimplemented</li>
956 <li>Added and implemented the extension API suggested by Thomas Broyer</li>
957 <li>the Windows MSC environment should be complete</li>
958 <li>tested and optimized with a really large document (DocBook Definitive
959 Guide) libxml/libxslt should really be faster on serious workloads</li>
962 <h3>0.13.0: June 26 2001</h3>
964 <li>lots of cleanups</li>
965 <li>fixed a C++ compilation problem</li>
966 <li>couple of fixes to xsltSaveTo()</li>
967 <li>try to fix Docbook-xslt-1.4 and chunking, updated the regression test
969 <li>fixed pattern compilation and priorities problems</li>
970 <li>Patches for Windows and MSC project mostly contributed by Yon Derek</li>
971 <li>update to the Tutorial by John Fleck</li>
972 <li>William fixed bugs in templates and for-each functions</li>
973 <li>added a new interface xsltRunStylesheet() for a more flexible output
974 (incomplete), added -o option to xsltproc</li>
977 <h3>0.12.0: June 18 2001</h3>
979 <li>fixed a dozen of bugs reported</li>
980 <li>HTML generation should be quite better (requires libxml-2.3.11 upgrade
982 <li>William fixed some problems with document()</li>
983 <li>Fix namespace nodes selection and copy (requires libxml-2.3.11 upgrade
985 <li>John Fleck added a<a href="tutorial/libxslttutorial.html">
987 <li>Fixes for namespace handling when evaluating variables</li>
988 <li>XInclude global flag added to process XInclude on document() if
990 <li>made xsltproc --version more detailed</li>
993 <h3>0.11.0: June 1 2001</h3>
995 <p>Mostly a bug fix release.</p>
997 <li>integration of catalogs from xsltproc</li>
998 <li>added --version to xsltproc for bug reporting</li>
999 <li>fixed errors when handling ID in external parsed entities</li>
1000 <li>document() should hopefully work correctly but ...</li>
1001 <li>fixed bug with PI and comments processing</li>
1002 <li>William fixed the XPath string functions when using unicode</li>
1005 <h3>0.10.0: May 19 2001</h3>
1007 <li>cleanups to make stylesheet read-only (not 100% complete)</li>
1008 <li>fixed URI resolution in document()</li>
1009 <li>force all XPath expression to be compiled at stylesheet parsing time,
1010 even if unused ...</li>
1011 <li>Fixed HTML default output detection</li>
1012 <li>Fixed double attribute generation #54446</li>
1013 <li>Fixed {{ handling in attributes #54451</li>
1014 <li>More tests and speedups for DocBook document transformations</li>
1015 <li>Fixed a really bad race like bug in xsltCopyTreeList()</li>
1016 <li>added a documentation on the libxslt internals</li>
1017 <li>William Brack and Bjorn Reese improved format-number()</li>
1018 <li>Fixed multiple sort, it should really work now</li>
1019 <li>added a --docbook option for SGML DocBook input (hackish)</li>
1020 <li>a number of other bug fixes and regression test added as people were
1021 submitting them</li>
1024 <h3>0.9.0: May 3 2001</h3>
1026 <li>lot of various bugfixes, extended the regression suite</li>
1027 <li>xsltproc should work with multiple params</li>
1028 <li>added an option to use xsltproc with HTML input</li>
1029 <li>improved the stylesheet compilation, processing of complex stylesheets
1030 should be faster</li>
1031 <li>using the same stylesheet for concurrent processing on multithreaded
1032 programs should work now</li>
1033 <li>fixed another batch of namespace handling problems</li>
1034 <li>Implemented multiple level of sorting</li>
1037 <h3>0.8.0: Apr 22 2001</h3>
1039 <li>fixed ansidecl.h problem</li>
1040 <li>fixed unparsed-entity-uri() and generate-id()</li>
1041 <li>sort semantic fixes and priority prob from William M. Brack</li>
1042 <li>fixed namespace handling problems in XPath expression computations
1043 (requires libxml-2.3.7)</li>
1044 <li>fixes to current() and key()</li>
1045 <li>other, smaller fixes, lots of testing with N Walsh DocBook HTML
1049 <h3>0.7.0: Apr 10 2001</h3>
1051 <li>cleanup using stricter compiler flags</li>
1052 <li>command line parameter passing</li>
1053 <li>fix to xsltApplyTemplates from William M. Brack</li>
1054 <li>added the XSLTMark in the regression tests as well as document()</li>
1057 <h3>0.6.0: Mar 22 2001</h3>
1059 <li>another beta</li>
1060 <li>requires 2.3.5, which provide XPath expression compilation support</li>
1061 <li>document() extension should function properly</li>
1062 <li>fixed a number or reported bugs</li>
1065 <h3>0.5.0: Mar 10 2001</h3>
1068 <li>some optimization work, for the moment 2 XSLT transform cannot use the
1069 same stylesheet at the same time (to be fixed)</li>
1070 <li>fixed problems with handling of tree results</li>
1071 <li>fixed a reported strip-spaces problem</li>
1072 <li>added more reported/fixed bugs to the test suite</li>
1073 <li>incorporated William M. Brack fix for imports and global variables as
1074 well as patch for with-param support in apply-templates</li>
1075 <li>a bug fix on for-each</li>
1078 <h3>0.4.0: Mar 1 2001</h3>
1080 <li>fourth beta test, released at the same time of libxml2-2.3.3</li>
1082 <li>some optimization</li>
1083 <li>started implement extension support, not finished</li>
1084 <li>implemented but not tested multiple file output</li>
1087 <h3>0.3.0: Feb 24 2001</h3>
1089 <li>third beta test, released at the same time of libxml2-2.3.2</li>
1090 <li>lot of bug fixes</li>
1091 <li>some optimization</li>
1092 <li>added DocBook XSL based testsuite</li>
1095 <h3>0.2.0: Feb 15 2001</h3>
1097 <li>second beta version, released at the same time as libxml2-2.3.1</li>
1098 <li>getting close to feature completion, lot of bug fixes, some in the HTML
1099 and XPath support of libxml</li>
1100 <li>start becoming usable for real work. This version can now regenerate
1101 the XML 2e HTML from the original XML sources and the associated
1103 href="http://www.w3.org/TR/REC-xml#b4d250b6c21">section I of the XML
1105 <li>Still misses extension element/function/prefixes support. Support of
1106 key() and document() is not complete</li>
1109 <h3>0.1.0: Feb 8 2001</h3>
1111 <li>first beta version, released at the same time as libxml2-2.3.0</li>
1112 <li>lots of bug fixes, first "testing" version, but incomplete</li>
1115 <h3>0.0.1: Jan 25 2001</h3>
1117 <li>first alpha version released at the same time as libxml2-2.2.12</li>
1118 <li>Framework in place, should work on simple examples, but far from being
1119 feature complete</li>
1122 <h2><a name="xsltproc">The xsltproc tool</a></h2>
1124 <p>This program is the simplest way to use libxslt: from the command line. It
1125 is also used for doing the regression tests of the library.</p>
1127 <p>It takes as first argument the path or URL to an XSLT stylesheet, the next
1128 arguments are filenames or URIs of the inputs to be processed. The output of
1129 the processing is redirected on the standard output. There is actually a few
1130 more options available:</p>
1131 <pre>orchis:~ -> xsltproc
1132 Usage: xsltproc [options] stylesheet file [file ...]
1134 --version or -V: show the version of libxml and libxslt used
1135 --verbose or -v: show logs of what's happening
1136 --output file or -o file: save to a given file
1137 --timing: display the time used
1138 --repeat: run the transformation 20 times
1139 --debug: dump the tree of the result instead
1140 --novalid: skip the Dtd loading phase
1141 --noout: do not dump the result
1142 --maxdepth val : increase the maximum depth
1143 --html: the input document is(are) an HTML file(s)
1144 --docbook: the input document is SGML docbook
1145 --param name value : pass a (parameter,value) pair
1146 --nonet refuse to fetch DTDs or entities over network
1147 --warnnet warn against fetching over the network
1148 --catalogs : use the catalogs from $SGML_CATALOG_FILES
1149 --xinclude : do XInclude processing on document input
1150 --profile or --norman : dump profiling information
1151 orchis:~ -></pre>
1153 <h2><a name="DocBook">DocBook</a></h2>
1155 <p><img src="duck.png" align="right" alt="The duck picture"></p>
1157 <p><a href="http://www.oasis-open.org/committees/docbook/">DocBook</a> is an
1158 XML/SGML vocabulary particularly well suited to books and papers about
1159 computer hardware and software.</p>
1161 <p>xsltproc and libxslt are not specifically dependant on DocBook, but since
1162 a lot of people use xsltproc and libxml2 for DocBook formatting, here are a
1163 few pointers and information which may be helpful:</p>
1165 <li>The <a href="http://www.oasis-open.org/committees/docbook/">DocBook
1166 homepage at Oasis</a> you should find pointers there on all the lastest
1167 versions of the DTDs and XSLT stylesheets</li>
1168 <li><a href="http://www.docbook.org/">DocBook: The Definitive Guide</a> is
1169 the official reference documentation for DocBook.</li>
1171 href="https://sourceforge.net/docman/index.php?group_id=21935">DocBook
1172 Open Repository</a> contains a lot of information about DocBook</li>
1173 <li>Bob Stayton provides a <a href="http://www.sagehill.net/">lot of
1174 resources</a> and consulting services around DocBook.</li>
1175 <li>Here is a <a href="/buildDocBookCatalog">shell script</a> to generate
1176 XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/
1177 directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on
1178 the resources found on the system. Otherwise it will just create
1179 ~/xmlcatalog and ~/dbkxmlcatalog and doing:
1180 <p><code>export XMLCATALOG=$HOME/xmlcatalog</code></p>
1181 <p>should allow to process DocBook documentations without requiring
1182 network accesses for the DTd or stylesheets</p>
1184 <li>I have uploaded <a href="ftp://xmlsoft.org/libxml2/test/dbk412catalog.tar.gz">a
1185 small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems
1186 to work fine for me too</li>
1187 <li>Informations on installing a <a
1188 href="http://ourworld.compuserve.com/homepages/hoenicka_markus/ntsgml.html">Windows
1189 DocBook processing setup</a> based on Cygwin (using the binaries from the
1190 official Windows port should be possible too)</li>
1191 <li>Alexander Kirillov's page on <a
1192 href="http://www.math.sunysb.edu/~kirillov/dbxml/">Using DocBook XML
1193 4.1.2</a> (RPM packages)</li>
1194 <li>Tim Waugh's <a href="http://cyberelk.net/tim/xmlto/">xmlto front-end
1195 conversion script</a></li>
1196 <li>Linux Documentation Project <a
1197 href="http://www.linuxdoc.org/HOWTO/mini/DocBook-Install/">
1198 DocBook-Install-mini-HOWTO</a></li>
1199 <li>ScrollKeeper the open documentation cataloging project has a <a
1200 href="http://scrollkeeper.sourceforge.net/docbook.shtml">DocBook
1202 <li>Dan York presentation on <a
1203 href="http://www.lodestar2.com/people/dyork/talks/2001/xugo/docbook/index.html">Publishing
1204 using DocBook XML</a></li>
1207 <p>Do not use the --docbook option of xsltproc to process XML DocBook
1208 documents, this option is only intended to provide some (limited) support of
1209 the SGML version of DocBook.</p>
1211 <p>Points which are not DocBook specific but still worth mentionning
1214 <li>if you think DocBook processing time is too slow, make sure you have
1215 XML Catalogs pointing to a local installation of the DTD of DocBook.
1216 Check the <a href="http://xmlsoft.org/catalog.html">XML Catalog page</a>
1217 to understand more on this subject.</li>
1218 <li>before processing a new document, use the command
1219 <p><code>xmllint --valid --noout path_to_document</code></p>
1220 <p>to make sure that your input is valid DocBook. And fixes the errors
1221 before processing further. Note that XSLT processing may work correctly
1222 with some forms of validity errors left, but in general it can give
1223 troubles on output.</p>
1227 <h2><a name="API">The programming API</a></h2>
1229 <p>Okay this section is clearly incomplete. But integrating libxslt into your
1230 application should be relatively easy. First check the few steps described
1231 below, then for more detailed information, look at the<a
1232 href="html/libxslt-lib.html"> generated pages</a> for the API and the source
1233 of libxslt/xsltproc.c and the <a
1234 href="tutorial/libxslttutorial.html">tutorial</a>.</p>
1236 <p>Basically doing an XSLT transformation can be done in a few steps:</p>
1238 <li>configure the parser for XSLT:
1239 <p>xmlSubstituteEntitiesDefault(1);</p>
1240 <p>xmlLoadExtDtdDefaultValue = 1;</p>
1242 <li>parse the stylesheet with xsltParseStylesheetFile()</li>
1243 <li>parse the document with xmlParseFile()</li>
1244 <li>apply the stylesheet using xsltApplyStylesheet()</li>
1245 <li>save the result using xsltSaveResultToFile() if needed set
1246 xmlIndentTreeOutput to 1</li>
1249 <p>Steps 2,3, and 5 will probably need to be changed depending on you
1250 processing needs and environment for example if reading/saving from/to
1251 memory, or if you want to apply XInclude processing to the stylesheet or
1252 input documents.</p>
1254 <h2><a name="Python">Python and bindings</a></h2>
1256 <p>There is a number of language bindings and wrappers available for libxml2,
1257 the list below is not exhaustive. Please contact the <a
1258 href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a>
1259 (<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in
1260 order to get updates to this list or to discuss the specific topic of libxml2
1261 or libxslt wrappers or bindings:</p>
1264 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
1265 Sergeant</a> developped <a href="http://axkit.org/download/">XML::LibXML
1266 and XML::LibXSLT</a>, Perl wrappers for libxml2/libxslt as part of the <a
1267 href="http://axkit.com/">AxKit XML application server</a></li>
1268 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides and
1269 earlier version of the libxml/libxslt <a
1270 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li>
1271 <li>Petr Kozelka provides <a
1272 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue
1273 libxml2</a> with Kylix, Delphi and other Pascal compilers</li>
1274 <li>Wai-Sun "Squidster" Chia provides <a
1275 href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and
1276 libxml2 bindings are also available in Ruby through the <a
1277 href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module
1278 maintained by Tobias Peters.</li>
1279 <li>Steve Ball and contributors maintains <a
1280 href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for
1282 <li><a href="mailto:xmlwrapp@pmade.org">Peter Jones</a> maintains C++
1283 bindings for libxslt within <a
1284 href="http://pmade.org/pjones/software/xmlwrapp/">xmlwrapp</a></li>
1285 <li><a href="phillim2@comcast.net">Mike Phillips</a> provides a module
1286 using <a href="http://siasl.dyndns.org/projects/projects.html">libxslt
1288 <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is
1289 an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and
1290 libxslt as part of GNU ClasspathX project.</li>
1291 <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for
1292 <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li>
1294 href="http://www.satimage.fr/software/en/xml_suite.html">Satimage</a>
1296 href="http://www.satimage.fr/software/en/downloads_osaxen.html">XMLLib
1297 osax</a>. This is an osax for Mac OS X with a set of commands to
1298 implement in AppleScript the XML DOM, XPATH and XSLT.</li>
1301 <p>The libxslt Python module depends on the <a
1302 href="http://xmlsoft.org/python.html">libxml2 Python</a> module.</p>
1304 <p>The distribution includes a set of Python bindings, which are guaranteed to
1305 be maintained as part of the library in the future, though the Python
1306 interface have not yet reached the completeness of the C API.</p>
1308 <p><a href="mailto:stephane.bidoul@softwareag.com">Stéphane Bidoul</a>
1309 maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port
1310 of the Python bindings</a>.</p>
1312 <p>Note to people interested in building bindings, the API is formalized as
1313 <a href="libxslt-api.xml">an XML API description file</a> which allows to
1314 automate a large part of the Python bindings, this includes function
1315 descriptions, enums, structures, typedefs, etc... The Python script used to
1316 build the bindings is python/generator.py in the source distribution.</p>
1318 <p>To install the Python bindings there are 2 options:</p>
1320 <li>If you use an RPM based distribution, simply install the <a
1321 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python
1323 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python
1325 <li>Otherwise use the <a href="ftp://xmlsoft.org/libxml2/python/">libxml2-python
1326 module distribution</a> corresponding to your installed version of
1327 libxml2 and libxslt. Note that to install it you will need both libxml2
1328 and libxslt installed and run "python setup.py build install" in the
1332 <p>The distribution includes a set of examples and regression tests for the
1333 python bindings in the <code>python/tests</code> directory. Here are some
1334 excepts from those tests:</p>
1338 <p>This is a basic test of XSLT interfaces: loading a stylesheet and a
1339 document, transforming the document and saving the result.</p>
1343 styledoc = libxml2.parseFile("test.xsl")
1344 style = libxslt.parseStylesheetDoc(styledoc)
1345 doc = libxml2.parseFile("test.xml")
1346 result = style.applyStylesheet(doc, None)
1347 style.saveResultToFilename("foo", result, 0)
1348 style.freeStylesheet()
1350 result.freeDoc()</pre>
1352 <p>The Python module is called libxslt, you will also need the libxml2 module
1353 for the operations on XML trees. Let's have a look at the objects manipulated
1354 in that example and how is the processing done:</p>
1356 <li><code>styledoc</code> : is a libxml2 document tree. It is obtained by
1357 parsing the XML file "test.xsl" containing the stylesheet.</li>
1358 <li><code>style</code> : this is a precompiled stylesheet ready to be used
1359 by the following transformations (note the plural form, multiple
1360 transformations can resuse the same stylesheet).</li>
1361 <li><code>doc</code> : this is the document to apply the transformation to.
1362 In this case it is simply generated by parsing it from a file but any
1363 other processing is possible as long as one get a libxml2 Doc. Note that
1364 HTML tree are suitable for XSLT processing in libxslt. This is actually
1365 how this page is generated !</li>
1366 <li><code>result</code> : this is a document generated by applying the
1367 stylesheet to the document. Note that some of the stylesheet information
1368 may be related to the serialization of that document and as in this
1369 example a specific saveResultToFilename() method of the stylesheet should
1370 be used to save it to a file (in that case to "foo").</li>
1373 <p>Also note the need to explicitely deallocate documents with freeDoc()
1374 except for the stylesheet document which is freed when its compiled form is
1375 garbage collected.</p>
1377 <h3>extfunc.py:</h3>
1379 <p>This one is a far more complex test. It shows how to modify the behaviour
1380 of an XSLT transformation by passing parameters and how to extend the XSLT
1381 engine with functions defined in python:</p>
1391 # Small check to verify the context is correcly accessed
1394 pctxt = libxslt.xpathParserContext(_obj=ctx)
1395 ctxt = pctxt.context()
1396 tctxt = ctxt.transformContext()
1397 nodeName = tctxt.insertNode().name
1401 return string.upper(str)
1403 libxslt.registerExtModuleFunction("foo", "http://example.com/foo", f)</pre>
1405 <p>This code defines and register an extension function. Note that the
1406 function can be bound to any name (foo) and how the binding is also
1407 associated to a namespace name "http://example.com/foo". From an XSLT point
1408 of view the function just returns an upper case version of the string passed
1409 as a parameter. But the first part of the function also read some contextual
1410 information from the current XSLT processing environement, in that case it
1411 looks for the current insertion node in the resulting output (either the
1412 resulting document or the Result Value Tree being generated), and saves it to
1413 a global variable for checking that the access actually worked.</p>
1415 <p>For more information on the xpathParserContext and transformContext
1416 objects check the <a href="internals.html">libray internals description</a>.
1417 The pctxt is actually an object from a class derived from the
1418 libxml2.xpathParserContext() with just a couple more properties including the
1419 possibility to look up the XSLT transformation context from the XPath
1421 <pre>styledoc = libxml2.parseDoc("""
1422 <xsl:stylesheet version='1.0'
1423 xmlns:xsl='http://www.w3.org/1999/XSL/Transform'
1424 xmlns:foo='http://example.com/foo'
1425 xsl:exclude-result-prefixes='foo'>
1427 <xsl:param name='bar'>failure</xsl:param>
1428 <xsl:template match='/'>
1429 <article><xsl:value-of select='foo:foo($bar)'/></article>
1430 </xsl:template>
1431 </xsl:stylesheet>
1434 <p>Here is a simple example of how to read an XML document from a python
1435 string with libxml2. Note how this stylesheet:</p>
1437 <li>Uses a global parameter <code>bar</code></li>
1438 <li>Reference the extension function f</li>
1439 <li>how the Namespace name "http://example.com/foo" has to be bound to a
1441 <li>how that prefix is excluded from the output</li>
1442 <li>how the function is called from the select</li>
1444 <pre>style = libxslt.parseStylesheetDoc(styledoc)
1445 doc = libxml2.parseDoc("<doc/>")
1446 result = style.applyStylesheet(doc, { "bar": "'success'" })
1447 style.freeStylesheet()
1450 <p>that part is identical, to the basic example except that the
1451 transformation is passed a dictionary of parameters. Note that the string
1452 passed "success" had to be quoted, otherwise it is interpreted as an XPath
1453 query for the childs of root named "success".</p>
1454 <pre>root = result.children
1455 if root.name != "article":
1456 print "Unexpected root node name"
1458 if root.content != "SUCCESS":
1459 print "Unexpected root node content, extension function failed"
1461 if nodeName != 'article':
1462 print "The function callback failed to access its context"
1465 result.freeDoc()</pre>
1467 <p>That part just verifies that the transformation worked, that the parameter
1468 got properly passed to the engine, that the function f() got called and that
1469 it properly accessed the context to find the name of the insertion node.</p>
1471 <h3>pyxsltproc.py:</h3>
1473 <p>this module is a bit too long to be described there but it is basically a
1474 rewrite of the xsltproc command line interface of libxslt in Python. It
1475 provides nearly all the functionalities of xsltproc and can be used as a base
1476 module to write Python customized XSLT processors. One of the thing to notice
1478 <pre>libxml2.lineNumbersDefault(1)
1479 libxml2.substituteEntitiesDefault(1)</pre>
1481 <p>those two calls in the main() function are needed to force the libxml2
1482 processor to generate DOM trees compliant with the XPath data model.</p>
1484 <h2><a name="Internals">Library internals</a></h2>
1486 <h3>Table of contents</h3>
1488 <li><a href="internals.html#Introducti">Introduction</a></li>
1489 <li><a href="internals.html#Basics">Basics</a></li>
1490 <li><a href="internals.html#Keep">Keep it simple stupid</a></li>
1491 <li><a href="internals.html#libxml">The libxml nodes</a></li>
1492 <li><a href="internals.html#XSLT">The XSLT processing steps</a></li>
1493 <li><a href="internals.html#XSLT1">The XSLT stylesheet compilation</a></li>
1494 <li><a href="internals.html#XSLT2">The XSLT template compilation</a></li>
1495 <li><a href="internals.html#processing">The processing itself</a></li>
1496 <li><a href="internals.html#XPath">XPath expressions compilation</a></li>
1497 <li><a href="internals.html#XPath1">XPath interpretation</a></li>
1498 <li><a href="internals.html#Descriptio">Description of XPath
1500 <li><a href="internals.html#XPath3">XPath functions</a></li>
1501 <li><a href="internals.html#stack">The variables stack frame</a></li>
1502 <li><a href="internals.html#Extension">Extension support</a></li>
1503 <li><a href="internals.html#Futher">Further reading</a></li>
1504 <li><a href="internals.html#TODOs">TODOs</a></li>
1507 <h3><a name="Introducti2">Introduction</a></h3>
1509 <p>This document describes the processing of <a
1510 href="http://xmlsoft.org/XSLT/">libxslt</a>, the <a
1511 href="http://www.w3.org/TR/xslt">XSLT</a> C library developed for the <a
1512 href="http://www.gnome.org/">GNOME</a> project.</p>
1514 <p>Note: this documentation is by definition incomplete and I am not good at
1515 spelling, grammar, so patches and suggestions are <a
1516 href="mailto:veillard@redhat.com">really welcome</a>.</p>
1518 <h3><a name="Basics1">Basics</a></h3>
1520 <p>XSLT is a transformation language. It takes an input document and a
1521 stylesheet document and generates an output document:</p>
1523 <p align="center"><img src="processing.gif"
1524 alt="the XSLT processing model"></p>
1526 <p>Libxslt is written in C. It relies on <a
1527 href="http://www.xmlsoft.org/">libxml</a>, the XML C library for GNOME, for
1528 the following operations:</p>
1530 <li>parsing files</li>
1531 <li>building the in-memory DOM structure associated with the documents
1533 <li>the XPath implementation</li>
1534 <li>serializing back the result document to XML and HTML. (Text is handled
1538 <h3><a name="Keep1">Keep it simple stupid</a></h3>
1540 <p>Libxslt is not very specialized. It is built under the assumption that all
1541 nodes from the source and output document can fit in the virtual memory of
1542 the system. There is a big trade-off there. It is fine for reasonably sized
1543 documents but may not be suitable for large sets of data. The gain is that it
1544 can be used in a relatively versatile way. The input or output may never be
1545 serialized, but the size of documents it can handle are limited by the size
1546 of the memory available.</p>
1548 <p>More specialized memory handling approaches are possible, like building
1549 the input tree from a serialization progressively as it is consumed,
1550 factoring repetitive patterns, or even on-the-fly generation of the output as
1551 the input is parsed but it is possible only for a limited subset of the
1552 stylesheets. In general the implementation of libxslt follows the following
1555 <li>KISS (keep it simple stupid)</li>
1556 <li>when there is a clear bottleneck optimize on top of this simple
1557 framework and refine only as much as is needed to reach the expected
1561 <p>The result is not that bad, clearly one can do a better job but more
1562 specialized too. Most optimization like building the tree on-demand would
1563 need serious changes to the libxml XPath framework. An easy step would be to
1564 serialize the output directly (or call a set of SAX-like output handler to
1565 keep this a flexible interface) and hence avoid the memory consumption of the
1568 <h3><a name="libxml">The libxml nodes</a></h3>
1570 <p>DOM-like trees, as used and generated by libxml and libxslt, are
1571 relatively complex. Most node types follow the given structure except a few
1572 variations depending on the node type:</p>
1574 <p align="center"><img src="node.gif" alt="description of a libxml node"></p>
1576 <p>Nodes carry a <strong>name</strong> and the node <strong>type</strong>
1577 indicates the kind of node it represents, the most common ones are:</p>
1579 <li>document nodes</li>
1580 <li>element nodes</li>
1584 <p>For the XSLT processing, entity nodes should not be generated (i.e. they
1585 should be replaced by their content). Most nodes also contains the following
1586 "navigation" information:</p>
1588 <li>the containing <strong>doc</strong>ument</li>
1589 <li>the <strong>parent</strong> node</li>
1590 <li>the first <strong>children</strong> node</li>
1591 <li>the <strong>last</strong> children node</li>
1592 <li>the <strong>prev</strong>ious sibling</li>
1593 <li>the following sibling (<strong>next</strong>)</li>
1596 <p>Elements nodes carries the list of attributes in the properties, an
1597 attribute itself holds the navigation pointers and the children list (the
1598 attribute value is not represented as a simple string to allow usage of
1599 entities references).</p>
1601 <p>The <strong>ns</strong> points to the namespace declaration for the
1602 namespace associated to the node, <strong>nsDef</strong> is the linked list
1603 of namespace declaration present on element nodes.</p>
1605 <p>Most nodes also carry an <strong>_private</strong> pointer which can be
1606 used by the application to hold specific data on this node.</p>
1608 <h3><a name="XSLT">The XSLT processing steps</a></h3>
1610 <p>There are a few steps which are clearly decoupled at the interface
1613 <li>parse the stylesheet and generate a DOM tree</li>
1614 <li>take the stylesheet tree and build a compiled version of it (the
1615 compilation phase)</li>
1616 <li>take the input and generate a DOM tree</li>
1617 <li>process the stylesheet against the input tree and generate an output
1619 <li>serialize the output tree</li>
1622 <p>A few things should be noted here:</p>
1624 <li>the steps 1/ 3/ and 5/ are optional</li>
1625 <li>the stylesheet obtained at 2/ can be reused by multiple processing 4/
1626 (and this should also work in threaded programs)</li>
1627 <li>the tree provided in 2/ should never be freed using xmlFreeDoc, but by
1628 freeing the stylesheet.</li>
1629 <li>the input tree 4/ is not modified except the _private field which may
1630 be used for labelling keys if used by the stylesheet</li>
1633 <h3><a name="XSLT1">The XSLT stylesheet compilation</a></h3>
1635 <p>This is the second step described. It takes a stylesheet tree, and
1636 "compiles" it. This associates to each node a structure stored in the
1637 _private field and containing information computed in the stylesheet:</p>
1639 <p align="center"><img src="stylesheet.gif"
1640 alt="a compiled XSLT stylesheet"></p>
1642 <p>One xsltStylesheet structure is generated per document parsed for the
1643 stylesheet. XSLT documents allow includes and imports of other documents,
1644 imports are stored in the <strong>imports</strong> list (hence keeping the
1645 tree hierarchy of includes which is very important for a proper XSLT
1646 processing model) and includes are stored in the <strong>doclist</strong>
1647 list. An imported stylesheet has a parent link to allow browsing of the
1650 <p>The DOM tree associated to the document is stored in <strong>doc</strong>.
1651 It is preprocessed to remove ignorable empty nodes and all the nodes in the
1652 XSLT namespace are subject to precomputing. This usually consist of
1653 extracting all the context information from the context tree (attributes,
1654 namespaces, XPath expressions), and storing them in an xsltStylePreComp
1655 structure associated to the <strong>_private</strong> field of the node.</p>
1657 <p>A couple of notable exceptions to this are XSLT template nodes (more on
1658 this later) and attribute value templates. If they are actually templates,
1659 the value cannot be computed at compilation time. (Some preprocessing could
1660 be done like isolation and preparsing of the XPath subexpressions but it's
1663 <p>The xsltStylePreComp structure also allows storing of the precompiled form
1664 of an XPath expression that can be associated to an XSLT element (more on
1667 <h3><a name="XSLT2">The XSLT template compilation</a></h3>
1669 <p>A proper handling of templates lookup is one of the keys of fast XSLT
1670 processing. (Given a node in the source document this is the process of
1671 finding which templates should be applied to this node.) Libxslt follows the
1672 hint suggested in the <a href="http://www.w3.org/TR/xslt#patterns">5.2
1673 Patterns</a> section of the XSLT Recommendation, i.e. it doesn't evaluate it
1674 as an XPath expression but tokenizes it and compiles it as a set of rules to
1675 be evaluated on a candidate node. There usually is an indication of the node
1676 name in the last step of this evaluation and this is used as a key check for
1677 the match. As a result libxslt builds a relatively more complex set of
1678 structures for the templates:</p>
1680 <p align="center"><img src="templates.gif"
1681 alt="The templates related structure"></p>
1683 <p>Let's describe a bit more closely what is built. First the xsltStylesheet
1684 structure holds a pointer to the template hash table. All the XSLT patterns
1685 compiled in this stylesheet are indexed by the value of the the target
1686 element (or attribute, pi ...) name, so when a element or an attribute "foo"
1687 needs to be processed the lookup is done using the name as a key.</p>
1689 <p>Each of the patterns is compiled into an xsltCompMatch structure. It holds
1690 the set of rules based on the tokenization of the pattern stored in reverse
1691 order (matching is easier this way). It also holds some information about the
1692 previous matches used to speed up the process when one iterates over a set of
1693 siblings. (This optimization may be defeated by trashing when running
1694 threaded computation, it's unclear that this is a big deal in practice.)
1695 Predicate expressions are not compiled at this stage, they may be at run-time
1696 if needed, but in this case they are compiled as full XPath expressions (the
1697 use of some fixed predicate can probably be optimized, they are not yet).</p>
1699 <p>The xsltCompMatch are then stored in the hash table, the clash list is
1700 itself sorted by priority of the template to implement "naturally" the XSLT
1703 <p>Associated to the compiled pattern is the xsltTemplate itself containing
1704 the information required for the processing of the pattern including, of
1705 course, a pointer to the list of elements used for building the pattern
1708 <p>Last but not least a number of patterns do not fit in the hash table
1709 because they are not associated to a name, this is the case for patterns
1710 applying to the root, any element, any attributes, text nodes, pi nodes, keys
1711 etc. Those are stored independently in the stylesheet structure as separate
1712 linked lists of xsltCompMatch.</p>
1714 <h3><a name="processing">The processing itself</a></h3>
1716 <p>The processing is defined by the XSLT specification (the basis of the
1717 algorithm is explained in <a
1718 href="http://www.w3.org/TR/xslt#section-Introduction">the Introduction</a>
1719 section). Basically it works by taking the root of the input document and
1720 applying the following algorithm:</p>
1722 <li>Finding the template applying to it. This is a lookup in the template
1723 hash table, walking the hash list until the node satisfies all the steps
1724 of the pattern, then checking the appropriate(s) global templates to see
1725 if there isn't a higher priority rule to apply</li>
1726 <li>If there is no template, apply the default rule (recurse on the
1728 <li>else walk the content list of the selected templates, for each of them:
1730 <li>if the node is in the XSLT namespace then the node has a _private
1731 field pointing to the preprocessed values, jump to the specific
1733 <li>if the node is in an extension namespace, look up the associated
1735 <li>otherwise copy the node.</li>
1737 <p>The closure is usually done through the XSLT
1738 <strong>apply-templates</strong> construct recursing by applying the
1739 adequate template on the input node children or on the result of an
1740 associated XPath selection lookup.</p>
1744 <p>Note that large parts of the input tree may not be processed by a given
1745 stylesheet and that on the opposite some may be processed multiple times.
1746 (This often is the case when a Table of Contents is built).</p>
1748 <p>The module <code>transform.c</code> is the one implementing most of this
1749 logic. <strong>xsltApplyStylesheet()</strong> is the entry point, it
1750 allocates an xsltTransformContext containing the following:</p>
1752 <li>a pointer to the stylesheet being processed</li>
1753 <li>a stack of templates</li>
1754 <li>a stack of variables and parameters</li>
1755 <li>an XPath context</li>
1756 <li>the template mode</li>
1757 <li>current document</li>
1758 <li>current input node</li>
1759 <li>current selected node list</li>
1760 <li>the current insertion points in the output document</li>
1761 <li>a couple of hash tables for extension elements and functions</li>
1764 <p>Then a new document gets allocated (HTML or XML depending on the type of
1765 output), the user parameters and global variables and parameters are
1766 evaluated. Then <strong>xsltProcessOneNode()</strong> which implements the
1767 1-2-3 algorithm is called on the root element of the input. Step 1/ is
1768 implemented by calling <strong>xsltGetTemplate()</strong>, step 2/ is
1769 implemented by <strong>xsltDefaultProcessOneNode()</strong> and step 3/ is
1770 implemented by <strong>xsltApplyOneTemplate()</strong>.</p>
1772 <h3><a name="XPath">XPath expression compilation</a></h3>
1774 <p>The XPath support is actually implemented in the libxml module (where it
1775 is reused by the XPointer implementation). XPath is a relatively classic
1776 expression language. The only uncommon feature is that it is working on XML
1777 trees and hence has specific syntax and types to handle them.</p>
1779 <p>XPath expressions are compiled using <strong>xmlXPathCompile()</strong>.
1780 It will take an expression string in input and generate a structure
1781 containing the parsed expression tree, for example the expression:</p>
1782 <pre>/doc/chapter[title='Introduction']</pre>
1784 <p>will be compiled as</p>
1785 <pre>Compiled Expression : 10 elements
1787 COLLECT 'child' 'name' 'node' chapter
1788 COLLECT 'child' 'name' 'node' doc
1793 COLLECT 'child' 'name' 'node' title
1795 ELEM Object is a string : Introduction
1796 COLLECT 'child' 'name' 'node' title
1799 <p>This can be tested using the <code>testXPath</code> command (in the
1800 libxml codebase) using the <code>--tree</code> option.</p>
1802 <p>Again, the KISS approach is used. No optimization is done. This could be
1803 an interesting thing to add. <a
1804 href="http://www-106.ibm.com/developerworks/library/x-xslt2/?dwzone=x?open&l=132%2ct=gr%2c+p=saxon">Michael
1805 Kay describes</a> a lot of possible and interesting optimizations done in
1806 Saxon which would be possible at this level. I'm unsure they would provide
1807 much gain since the expressions tends to be relatively simple in general and
1808 stylesheets are still hand generated. Optimizations at the interpretation
1809 sounds likely to be more efficient.</p>
1811 <h3><a name="XPath1">XPath interpretation</a></h3>
1813 <p>The interpreter is implemented by <strong>xmlXPathCompiledEval()</strong>
1814 which is the front-end to <strong>xmlXPathCompOpEval()</strong> the function
1815 implementing the evaluation of the expression tree. This evaluation follows
1816 the KISS approach again. It's recursive and calls
1817 <strong>xmlXPathNodeCollectAndTest()</strong> to collect nodes set when
1818 evaluating a <code>COLLECT</code> node.</p>
1820 <p>An evaluation is done within the framework of an XPath context stored in
1821 an <strong>xmlXPathContext</strong> structure, in the framework of a
1822 transformation the context is maintained within the XSLT context. Its content
1823 follows the requirements from the XPath specification:</p>
1825 <li>the current document</li>
1826 <li>the current node</li>
1827 <li>a hash table of defined variables (but not used by XSLT)</li>
1828 <li>a hash table of defined functions</li>
1829 <li>the proximity position (the place of the node in the current node
1831 <li>the context size (the size of the current node list)</li>
1832 <li>the array of namespace declarations in scope (there also is a namespace
1833 hash table but it is not used in the XSLT transformation).</li>
1836 <p>For the purpose of XSLT an <strong>extra</strong> pointer has been added
1837 allowing to retrieve the XSLT transformation context. When an XPath
1838 evaluation is about to be performed, an XPath parser context is allocated
1839 containing and XPath object stack (this is actually an XPath evaluation
1840 context, this is a remain of the time where there was no separate parsing and
1841 evaluation phase in the XPath implementation). Here is an overview of the set
1842 of contexts associated to an XPath evaluation within an XSLT
1845 <p align="center"><img src="contexts.gif"
1846 alt="The set of contexts associated "></p>
1848 <p>Clearly this is a bit too complex and confusing and should be refactored
1849 at the next set of binary incompatible releases of libxml. For example the
1850 xmlXPathCtxt has a lot of unused parts and should probably be merged with
1851 xmlXPathParserCtxt.</p>
1853 <h3><a name="Descriptio">Description of XPath Objects</a></h3>
1855 <p>An XPath expression manipulates XPath objects. XPath defines the default
1856 types boolean, numbers, strings and node sets. XSLT adds the result tree
1857 fragment type which is basically an unmodifiable node set.</p>
1859 <p>Implementation-wise, libxml follows again a KISS approach, the
1860 xmlXPathObject is a structure containing a type description and the various
1861 possibilities. (Using an enum could have gained some bytes.) In the case of
1862 node sets (or result tree fragments), it points to a separate xmlNodeSet
1863 object which contains the list of pointers to the document nodes:</p>
1865 <p align="center"><img src="object.gif"
1866 alt="An Node set object pointing to "></p>
1868 <p>The <a href="http://xmlsoft.org/html/libxml-xpath.html">XPath API</a> (and
1869 its <a href="http://xmlsoft.org/html/libxml-xpathinternals.html">'internal'
1870 part</a>) includes a number of functions to create, copy, compare, convert or
1871 free XPath objects.</p>
1873 <h3><a name="XPath3">XPath functions</a></h3>
1875 <p>All the XPath functions available to the interpreter are registered in the
1876 function hash table linked from the XPath context. They all share the same
1878 <pre>void xmlXPathFunc (xmlXPathParserContextPtr ctxt, int nargs);</pre>
1880 <p>The first argument is the XPath interpretation context, holding the
1881 interpretation stack. The second argument defines the number of objects
1882 passed on the stack for the function to consume (last argument is on top of
1885 <p>Basically an XPath function does the following:</p>
1887 <li>check <code>nargs</code> for proper handling of errors or functions
1888 with variable numbers of parameters</li>
1889 <li>pop the parameters from the stack using <code>obj =
1890 valuePop(ctxt);</code></li>
1891 <li>do the function specific computation</li>
1892 <li>push the result parameter on the stack using <code>valuePush(ctxt,
1894 <li>free up the input parameters with
1895 <code>xmlXPathFreeObject(obj);</code></li>
1899 <p>Sometime the work can be done directly by modifying in-situ the top object
1900 on the stack <code>ctxt->value</code>.</p>
1902 <h3><a name="stack">The XSLT variables stack frame</a></h3>
1904 <p>Not to be confused with XPath object stack, this stack holds the XSLT
1905 variables and parameters as they are defined through the recursive calls of
1906 call-template, apply-templates and default templates. This is used to define
1907 the scope of variables being called.</p>
1909 <p>This part seems to be the most urgent attention right now, first it is
1910 done in a very inefficient way since the location of the variables and
1911 parameters within the stylesheet tree is still done at run time (it really
1912 should be done statically at compile time), and I am still unsure that my
1913 understanding of the template variables and parameter scope is actually
1916 <p>This part of the documentation is still to be written once this part of
1917 the code will be stable. <span
1918 style="background-color: #FF0000">TODO</span></p>
1920 <h3><a name="Extension">Extension support</a></h3>
1922 <p>There is a separate document explaining <a href="extensions.html">how the
1923 extension support works</a>.</p>
1925 <h3><a name="Futher">Further reading</a></h3>
1927 <p>Michael Kay wrote <a
1928 href="http://www-106.ibm.com/developerworks/library/x-xslt2/?dwzone=x?open&l=132%2ct=gr%2c+p=saxon">a
1929 really interesting article on Saxon internals</a> and the work he did on
1930 performance issues. I wishes I had read it before starting libxslt design (I
1931 would probably have avoided a few mistakes and progressed faster). A lot of
1932 the ideas in his papers should be implemented or at least tried in
1935 <p>The <a href="http://xmlsoft.org/">libxml documentation</a>, especially <a
1936 href="http://xmlsoft.org/xmlio.html">the I/O interfaces</a> and the <a
1937 href="http://xmlsoft.org/xmlmem.html">memory management</a>.</p>
1939 <h3><a name="TODOs">TODOs</a></h3>
1941 <p>redesign the XSLT stack frame handling. Far too much work is done at
1942 execution time. Similarly for the attribute value templates handling, at
1943 least the embedded subexpressions ought to be precompiled.</p>
1945 <p>Allow output to be saved to a SAX like output (this notion of SAX like API
1946 for output should be added directly to libxml).</p>
1948 <p>Implement and test some of the optimization explained by Michael Kay
1951 <li>static slot allocation on the stack frame</li>
1952 <li>specific boolean interpretation of an XPath expression</li>
1953 <li>some of the sorting optimization</li>
1954 <li>Lazy evaluation of location path. (this may require more changes but
1955 sounds really interesting. XT does this too.)</li>
1956 <li>Optimization of an expression tree (This could be done as a completely
1957 independent module.)</li>
1962 <p>Error reporting, there is a lot of case where the XSLT specification
1963 specify that a given construct is an error are not checked adequately by
1964 libxslt. Basically one should do a complete pass on the XSLT spec again and
1965 add all tests to the stylesheet compilation. Using the DTD provided in the
1966 appendix and making direct checks using the libxml validation API sounds a
1967 good idea too (though one should take care of not raising errors for
1968 elements/attributes in different namespaces).</p>
1970 <p>Double check all the places where the stylesheet compiled form might be
1971 modified at run time (extra removal of blanks nodes, hint on the
1976 <h2><a name="Extensions">Writing extensions</a></h2>
1978 <h3>Table of content</h3>
1980 <li><a href="extensions.html#Introducti">Introduction</a></li>
1981 <li><a href="extensions.html#Basics">Basics</a></li>
1982 <li><a href="extensions.html#Keep">Extension modules</a></li>
1983 <li><a href="extensions.html#Registerin">Registering a module</a></li>
1984 <li><a href="extensions.html#module">Loading a module</a></li>
1985 <li><a href="extensions.html#Registerin1">Registering an extension
1987 <li><a href="extensions.html#Implementi">Implementing an extension
1989 <li><a href="extensions.html#Examples">Examples for extension
1991 <li><a href="extensions.html#Registerin2">Registering an extension
1993 <li><a href="extensions.html#Implementi1">Implementing an extension
1995 <li><a href="extensions.html#Example">Example for extension
1997 <li><a href="extensions.html#shutdown">The shutdown of a module</a></li>
1998 <li><a href="extensions.html#Future">Future work</a></li>
2001 <h3><a name="Introducti1">Introduction</a></h3>
2003 <p>This document describes the work needed to write extensions to the
2004 standard XSLT library for use with <a
2005 href="http://xmlsoft.org/XSLT/">libxslt</a>, the <a
2006 href="http://www.w3.org/TR/xslt">XSLT</a> C library developed for the <a
2007 href="http://www.gnome.org/">GNOME</a> project.</p>
2009 <p>Before starting reading this document it is highly recommended to get
2010 familiar with <a href="internals.html">the libxslt internals</a>.</p>
2012 <p>Note: this documentation is by definition incomplete and I am not good at
2013 spelling, grammar, so patches and suggestions are <a
2014 href="mailto:veillard@redhat.com">really welcome</a>.</p>
2016 <h3><a name="Basics">Basics</a></h3>
2018 <p>The <a href="http://www.w3.org/TR/xslt">XSLT specification</a> provides
2019 two <a href="http://www.w3.org/TR/xslt">ways to extend an XSLT engine</a>:</p>
2021 <li>providing <a href="http://www.w3.org/TR/xslt">new extension
2022 functions</a> which can be called from XPath expressions</li>
2023 <li>providing <a href="http://www.w3.org/TR/xslt">new extension
2024 elements</a> which can be inserted in stylesheets</li>
2027 <p>In both cases the extensions need to be associated to a new namespace,
2028 i.e. an URI used as the name for the extension's namespace (there is no need
2029 to have a resource there for this to work).</p>
2031 <p>libxslt provides a few extensions itself, either in the libxslt namespace
2032 "http://xmlsoft.org/XSLT/namespace" or in namespaces for other well known
2033 extensions provided by other XSLT processors like Saxon, Xalan or XT.</p>
2035 <h3><a name="Keep">Extension modules</a></h3>
2037 <p>Since extensions are bound to a namespace name, usually sets of extensions
2038 coming from a given source are using the same namespace name defining in
2039 practice a group of extensions providing elements, functions or both. From
2040 the libxslt point of view those are considered as an "extension module", and
2041 most of the APIs work at a module point of view.</p>
2043 <p>Registration of new functions or elements are bound to the activation of
2044 the module. This is currently done by declaring the namespace as an extension
2045 by using the attribute <code>extension-element-prefixes</code> on the
2046 <code><a href="http://www.w3.org/TR/xslt">xsl:stylesheet</a></code>
2049 <p>An extension module is defined by 3 objects:</p>
2051 <li>the namespace name associated</li>
2052 <li>an initialization function</li>
2053 <li>a shutdown function</li>
2056 <h3><a name="Registerin">Registering a module</a></h3>
2058 <p>Currently a libxslt module has to be compiled within the application using
2059 libxslt. There is no code to load dynamically shared libraries associated to
2060 a namespace (this may be added but is likely to become a portability
2063 <p>The current way to register a module is to link the code implementing it
2064 with the application and to call a registration function:</p>
2065 <pre>int xsltRegisterExtModule(const xmlChar *URI,
2066 xsltExtInitFunction initFunc,
2067 xsltExtShutdownFunction shutdownFunc);</pre>
2069 <p>The associated header is read by:</p>
2070 <pre>#include<libxslt/extensions.h></pre>
2072 <p>which also defines the type for the initialization and shutdown
2075 <h3><a name="module">Loading a module</a></h3>
2077 <p>Once the module URI has been registered and if the XSLT processor detects
2078 that a given stylesheet needs the functionalities of an extended module, this
2079 one is initialized.</p>
2081 <p>The xsltExtInitFunction type defines the interface for an initialization
2084 * xsltExtInitFunction:
2085 * @ctxt: an XSLT transformation context
2086 * @URI: the namespace URI for the extension
2088 * A function called at initialization time of an XSLT
2091 * Returns a pointer to the module specific data for this
2094 typedef void *(*xsltExtInitFunction)(xsltTransformContextPtr ctxt,
2095 const xmlChar *URI);</pre>
2097 <p>There are 3 things to notice:</p>
2099 <li>The function gets passed the namespace name URI as an argument. This
2100 allows a single function to provide the initialization for multiple
2101 logical modules.</li>
2102 <li>It also gets passed a transformation context. The initialization is
2103 done at run time before any processing occurs on the stylesheet but it
2104 will be invoked separately each time for each transformation.</li>
2105 <li>It returns a pointer. This can be used to store module specific
2106 information which can be retrieved later when a function or an element
2107 from the extension is used. An obvious example is a connection to a
2108 database which should be kept and reused along with the transformation.
2109 NULL is a perfectly valid return; there is no way to indicate a failure
2113 <p>What this function is expected to do is:</p>
2115 <li>prepare the context for this module (like opening the database
2117 <li>register the extensions specific to this module</li>
2120 <h3><a name="Registerin1">Registering an extension function</a></h3>
2122 <p>There is a single call to do this registration:</p>
2123 <pre>int xsltRegisterExtFunction(xsltTransformContextPtr ctxt,
2124 const xmlChar *name,
2126 xmlXPathEvalFunc function);</pre>
2128 <p>The registration is bound to a single transformation instance referred by
2129 ctxt, name is the UTF8 encoded name for the NCName of the function, and URI
2130 is the namespace name for the extension (no checking is done, a module could
2131 register functions or elements from a different namespace, but it is not
2134 <h3><a name="Implementi">Implementing an extension function</a></h3>
2136 <p>The implementation of the function must have the signature of a libxml
2140 * @ctxt: an XPath parser context
2141 * @nargs: the number of arguments passed to the function
2143 * an XPath evaluation function, the parameters are on the
2144 * XPath context stack
2147 typedef void (*xmlXPathEvalFunc)(xmlXPathParserContextPtr ctxt,
2150 <p>The context passed to an XPath function is not an XSLT context but an <a
2151 href="internals.html#XPath1">XPath context</a>. However it is possible to
2152 find one from the other:</p>
2154 <li>The function xsltXPathGetTransformContext provides this lookup facility:
2155 <pre>xsltTransformContextPtr
2156 xsltXPathGetTransformContext
2157 (xmlXPathParserContextPtr ctxt);</pre>
2159 <li>The <code>xmlXPathContextPtr</code> associated to an
2160 <code>xsltTransformContext</code> is stored in the <code>xpathCtxt</code>
2164 <p>The first thing an extension function may want to do is to check the
2165 arguments passed on the stack, the <code>nargs</code> parameter will tell how
2166 many of them were provided on the XPath expression. The macro valuePop will
2167 extract them from the XPath stack:</p>
2168 <pre>#include <libxml/xpath.h>
2169 #include <libxml/xpathInternals.h>
2171 xmlXPathObjectPtr obj = valuePop(ctxt); </pre>
2173 <p>Note that <code>ctxt</code> is the XPath context not the XSLT one. It is
2174 then possible to examine the content of the value. Check <a
2175 href="internals.html#Descriptio">the description of XPath objects</a> if
2176 necessary. The following is a common sequence checking whether the argument
2177 passed is a string and converting it using the built-in XPath
2178 <code>string()</code> function if this is not the case:</p>
2179 <pre>if (obj->type != XPATH_STRING) {
2180 valuePush(ctxt, obj);
2181 xmlXPathStringFunction(ctxt, 1);
2182 obj = valuePop(ctxt);
2185 <p>Most common XPath functions are available directly at the C level and are
2186 exported either in <code><libxml/xpath.h></code> or in
2187 <code><libxml/xpathInternals.h></code>.</p>
2189 <p>The extension function may also need to retrieve the data associated to
2190 this module instance (the database connection in the previous example) this
2191 can be done using the xsltGetExtData:</p>
2192 <pre>void * xsltGetExtData(xsltTransformContextPtr ctxt,
2193 const xmlChar *URI);</pre>
2195 <p>Again the URI to be provided is the one which was used when registering
2198 <p>Once the function finishes, don't forget to:</p>
2200 <li>push the return value on the stack using <code>valuePush(ctxt,
2202 <li>deallocate the parameters passed to the function using
2203 <code>xmlXPathFreeObject(obj)</code></li>
2206 <h3><a name="Examples">Examples for extension functions</a></h3>
2208 <p>The module libxslt/functions.c contains the sources of the XSLT built-in
2209 functions, including document(), key(), generate-id(), etc. as well as a full
2210 example module at the end. Here is the test function implementation for the
2211 libxslt:test function:</p>
2213 * xsltExtFunctionTest:
2214 * @ctxt: the XPath Parser context
2215 * @nargs: the number of arguments
2217 * function libxslt:test() for testing the extensions support.
2220 xsltExtFunctionTest(xmlXPathParserContextPtr ctxt, int nargs)
2222 xsltTransformContextPtr tctxt;
2225 tctxt = xsltXPathGetTransformContext(ctxt);
2226 if (tctxt == NULL) {
2227 xsltGenericError(xsltGenericErrorContext,
2228 "xsltExtFunctionTest: failed to get the transformation context\n");
2231 data = xsltGetExtData(tctxt, (const xmlChar *) XSLT_DEFAULT_URL);
2233 xsltGenericError(xsltGenericErrorContext,
2234 "xsltExtFunctionTest: failed to get module data\n");
2237 #ifdef WITH_XSLT_DEBUG_FUNCTION
2238 xsltGenericDebug(xsltGenericDebugContext,
2239 "libxslt:test() called with %d args\n", nargs);
2243 <h3><a name="Registerin2">Registering an extension element</a></h3>
2245 <p>There is a single call to do this registration:</p>
2246 <pre>int xsltRegisterExtElement(xsltTransformContextPtr ctxt,
2247 const xmlChar *name,
2249 xsltTransformFunction function);</pre>
2251 <p>It is similar to the mechanism used to register an extension function,
2252 except that the signature of an extension element implementation is
2255 <p>The registration is bound to a single transformation instance referred to
2256 by ctxt, name is the UTF8 encoded name for the NCName of the element, and URI
2257 is the namespace name for the extension (no checking is done, a module could
2258 register elements for a different namespace, but it is not recommended).</p>
2260 <h3><a name="Implementi1">Implementing an extension element</a></h3>
2262 <p>The implementation of the element must have the signature of an XSLT
2263 transformation function:</p>
2265 * xsltTransformFunction:
2266 * @ctxt: the XSLT transformation context
2267 * @node: the input node
2268 * @inst: the stylesheet node
2269 * @comp: the compiled information from the stylesheet
2271 * signature of the function associated to elements part of the
2272 * stylesheet language like xsl:if or xsl:apply-templates.
2274 typedef void (*xsltTransformFunction)
2275 (xsltTransformContextPtr ctxt,
2278 xsltStylePreCompPtr comp);</pre>
2280 <p>The first argument is the XSLT transformation context. The second and
2281 third arguments are xmlNodePtr i.e. internal memory <a
2282 href="internals.html#libxml">representation of XML nodes</a>. They are
2283 respectively <code>node</code> from the the input document being transformed
2284 by the stylesheet and <code>inst</code> the extension element in the
2285 stylesheet. The last argument is <code>comp</code> a pointer to a precompiled
2286 representation of <code>inst</code> but usually for an extension function
2287 this value is <code>NULL</code> by default (it could be added and associated
2288 to the instruction in <code>inst->_private</code>).</p>
2290 <p>The same functions are available from a function implementing an extension
2291 element as in an extension function, including
2292 <code>xsltGetExtData()</code>.</p>
2294 <p>The goal of an extension element being usually to enrich the generated
2295 output, it is expected that they will grow the currently generated output
2296 tree. This can be done by grabbing ctxt->insert which is the current
2297 libxml node being generated (Note this can also be the intermediate value
2298 tree being built for example to initialize a variable, the processing should
2299 be similar). The functions for libxml tree manipulation from <a
2300 href="http://xmlsoft.org/html/libxml-tree.html"><libxml/tree.h></a> can
2301 be employed to extend or modify the tree, but it is required to preserve the
2302 insertion node and its ancestors since there are existing pointers to those
2303 elements still in use in the XSLT template execution stack.</p>
2305 <h3><a name="Example">Example for extension elements</a></h3>
2307 <p>The module libxslt/transform.c contains the sources of the XSLT built-in
2308 elements, including xsl:element, xsl:attribute, xsl:if, etc. There is a small
2309 but full example in functions.c providing the implementation for the
2310 libxslt:test element, it will output a comment in the result tree:</p>
2312 * xsltExtElementTest:
2313 * @ctxt: an XSLT processing context
2314 * @node: The current node
2315 * @inst: the instruction in the stylesheet
2316 * @comp: precomputed information
2318 * Process a libxslt:test node
2321 xsltExtElementTest(xsltTransformContextPtr ctxt, xmlNodePtr node,
2323 xsltStylePreCompPtr comp)
2328 xsltGenericError(xsltGenericErrorContext,
2329 "xsltExtElementTest: no transformation context\n");
2333 xsltGenericError(xsltGenericErrorContext,
2334 "xsltExtElementTest: no current node\n");
2338 xsltGenericError(xsltGenericErrorContext,
2339 "xsltExtElementTest: no instruction\n");
2342 if (ctxt->insert == NULL) {
2343 xsltGenericError(xsltGenericErrorContext,
2344 "xsltExtElementTest: no insertion point\n");
2348 xmlNewComment((const xmlChar *)
2349 "libxslt:test element test worked");
2350 xmlAddChild(ctxt->insert, comment);
2353 <h3><a name="shutdown">The shutdown of a module</a></h3>
2355 <p>When the XSLT processor ends a transformation, the shutdown function (if
2356 it exists) for each of the modules initialized is called. The
2357 xsltExtShutdownFunction type defines the interface for a shutdown
2360 * xsltExtShutdownFunction:
2361 * @ctxt: an XSLT transformation context
2362 * @URI: the namespace URI for the extension
2363 * @data: the data associated to this module
2365 * A function called at shutdown time of an XSLT extension module
2367 typedef void (*xsltExtShutdownFunction) (xsltTransformContextPtr ctxt,
2371 <p>This is really similar to a module initialization function except a third
2372 argument is passed, it's the value that was returned by the initialization
2373 function. This allows the routine to deallocate resources from the module for
2374 example close the connection to the database to keep the same example.</p>
2376 <h3><a name="Future">Future work</a></h3>
2378 <p>Well, some of the pieces missing:</p>
2380 <li>a way to load shared libraries to instantiate new modules</li>
2381 <li>a better detection of extension functions usage and their registration
2382 without having to use the extension prefix which ought to be reserved to
2383 element extensions.</li>
2384 <li>more examples</li>
2385 <li>implementations of the <a href="http://www.exslt.org/">EXSLT</a> common
2386 extension libraries, Thomas Broyer nearly finished implementing them.</li>
2391 <h2><a name="Contributi">Contributions</a></h2>
2393 <li>Bjorn Reese is the author of the number support and worked on the
2394 XSLTMark support</li>
2395 <li>William Brack was an early adopted, contributed a number of patches and
2396 spent quite some time debugging non-trivial problems in early versions of
2398 <li><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the
2399 maintainer of the Windows port, <a
2400 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides
2402 <li>Thomas Broyer provided a lot of suggestions, and drafted most of the
2404 <li>John Fleck maintains <a href="tutorial/libxslttutorial.html">a tutorial
2405 for libxslt</a></li>
2407 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt
2408 Sergeant</a> developed <a
2409 href="http://axkit.org/download/">XML::LibXSLT</a>, a perl wrapper for
2410 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML
2411 application server</a></li>
2412 <li>there is a module for <a
2413 href="http://acs-misc.sourceforge.net/nsxml.html">libxml/libxslt support
2414 in OpenNSD/AOLServer</a></li>
2415 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides
2416 libxml/libxslt <a href="http://www.rexx.com/~dkuhlman">wrappers for
2418 <li><a href="mailto:Steve.Ball@explain.com.au">Steve Ball</a>, and
2419 contributors maintain <a href="http://tclxml.sourceforge.net/">tcl
2420 bindings for libxml2 and libxslt</a>, as well as <a
2421 href="http://tclxml.sf.net/tkxmllint.html">tkxmllint</a> a GUI for
2422 xmllint and <a href="http://tclxml.sf.net/tkxsltproc.html">tkxsltproc</a>
2423 a GUI for xsltproc.</li>
2424 <li>If you want to use libxslt in a Mac OS X/Cocoa or Objective-C
2425 framework, Marc Liyanage provides <a
2426 href="http://www.entropy.ch/software/macosx/#testxslt">an application
2427 TestXSLT for XSLT and XML editing</a> including wrapper classes for the
2428 XML parser and XSLT processor.</li>
2433 <p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p>