xml.html revision 10ee8b38fb5d1a69a3a73b43aef2fb6352d07244
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 2 "http://www.w3.org/TR/html4/loose.dtd"> 3<html> 4<head> 5 <title>The XML C library for Gnome</title> 6 <meta name="GENERATOR" content="amaya 5.1"> 7 <meta http-equiv="Content-Type" content="text/html"> 8</head> 9 10<body bgcolor="#ffffff"> 11<h1 align="center">The XML C library for Gnome</h1> 12 13<h1>Note: this is the flat content of the <a href="index.html">web 14site</a></h1> 15 16<h1 style="text-align: center">libxml, a.k.a. gnome-xml</h1> 17 18<p></p> 19 20<p>Libxml is the XML C library developed for the Gnome project. XML itself 21is a metalanguage to design markup languages, i.e. text language where 22semantic and structure are added to the content using extra "markup" 23information enclosed between angle brackets. HTML is the most well-known 24markup language. Though the library is written in C <a href="python.html">a 25variety of language bindings</a> make it available in other environments.</p> 26 27<p>Libxml2 implements a number of existing standards related to markup 28languages:</p> 29<ul> 30 <li>the XML standard: <a 31 href="http://www.w3.org/TR/REC-xml">http://www.w3.org/TR/REC-xml</a></li> 32 <li>Namespaces in XML: <a 33 href="http://www.w3.org/TR/REC-xml-names/">http://www.w3.org/TR/REC-xml-names/</a></li> 34 <li>XML Base: <a 35 href="http://www.w3.org/TR/xmlbase/">http://www.w3.org/TR/xmlbase/</a></li> 36 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc2396.txt">RFC 2396</a> : 37 Uniform Resource Identifiers <a 38 href="http://www.ietf.org/rfc/rfc2396.txt">http://www.ietf.org/rfc/rfc2396.txt</a></li> 39 <li>XML Path Language (XPath) 1.0: <a 40 href="http://www.w3.org/TR/xpath">http://www.w3.org/TR/xpath</a></li> 41 <li>HTML4 parser: <a 42 href="http://www.w3.org/TR/html401/">http://www.w3.org/TR/html401/</a></li> 43 <li>most of XML Pointer Language (XPointer) Version 1.0: <a 44 href="http://www.w3.org/TR/xptr">http://www.w3.org/TR/xptr</a></li> 45 <li>XML Inclusions (XInclude) Version 1.0: <a 46 href="http://www.w3.org/TR/xinclude/">http://www.w3.org/TR/xinclude/</a></li> 47 <li>[ISO-8859-1], <a 48 href="http://www.cis.ohio-state.edu/rfc/rfc2044.txt">rfc2044</a> [UTF-8] 49 and <a href="http://www.cis.ohio-state.edu/rfc/rfc2781.txt">rfc2781</a> 50 [UTF-16] core encodings</li> 51 <li>part of SGML Open Technical Resolution TR9401:1997</li> 52 <li>XML Catalogs Working Draft 06 August 2001: <a 53 href="http://www.oasis-open.org/committees/entity/spec-2001-08-06.html">http://www.oasis-open.org/committees/entity/spec-2001-08-06.html</a></li> 54 <li>Canonical XML Version 1.0: <a 55 href="http://www.w3.org/TR/xml-c14n">http://www.w3.org/TR/xml-c14n</a> 56 and the Exclusive XML Canonicalization CR draft <a 57 href="http://www.w3.org/TR/xml-exc-c14n">http://www.w3.org/TR/xml-exc-c14n</a></li> 58</ul> 59 60<p>In most cases libxml tries to implement the specifications in a relatively 61strictly compliant way. As of release 2.4.16, libxml2 passes all 1800+ tests 62from the <a 63href="http://www.oasis-open.org/committees/xml-conformance/">OASIS XML Tests 64Suite</a>.</p> 65 66<p>To some extent libxml2 provides support for the following additional 67specifications but doesn't claim to implement them completely:</p> 68<ul> 69 <li>Document Object Model (DOM) <a 70 href="http://www.w3.org/TR/DOM-Level-2-Core/">http://www.w3.org/TR/DOM-Level-2-Core/</a> 71 it doesn't implement the API itself, gdome2 does this on top of 72 libxml2</li> 73 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc959.txt">RFC 959</a> : 74 libxml implements a basic FTP client code</li> 75 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc1945.txt">RFC 1945</a> : 76 HTTP/1.0, again a basic HTTP client code</li> 77 <li>SAX: a minimal SAX implementation compatible with early expat 78 versions</li> 79 <li>DocBook SGML v4: libxml2 includes a hackish parser to transition to 80 XML</li> 81</ul> 82 83<p>A first implementation of RelaxNG is available as of libxml2-2.5.2, it 84should cover most of the specification, feedback welcome.</p> 85 86<p>A partial implementation of XML Schemas is being worked on but it would be 87far too early to make any conformance statement about it at the moment.</p> 88 89<p>Libxml2 is known to be very portable, the library should build and work 90without serious troubles on a variety of systems (Linux, Unix, Windows, 91CygWin, MacOS, MacOS X, RISC Os, OS/2, VMS, QNX, MVS, ...)</p> 92 93<p>Separate documents:</p> 94<ul> 95 <li><a href="http://xmlsoft.org/XSLT/">the libxslt page</a> providing an 96 implementation of XSLT 1.0 and common extensions like EXSLT for 97 libxml2</li> 98 <li><a href="http://www.cs.unibo.it/~casarini/gdome2/">the gdome2 page</a> 99 : a standard DOM2 implementation for libxml2</li> 100 <li><a href="http://www.aleksey.com/xmlsec/">the XMLSec page</a>: an 101 implementation of <a href="http://www.w3.org/TR/xmldsig-core/">W3C XML 102 Digital Signature</a> for libxml2</li> 103 <li>also check the related links section below for more related and active 104 projects.</li> 105</ul> 106 107<p>Logo designed by <a href="mailto:liyanage@access.ch">Marc Liyanage</a>.</p> 108 109<h2><a name="Introducti">Introduction</a></h2> 110 111<p>This document describes libxml, the <a 112href="http://www.w3.org/XML/">XML</a> C library developed for the <a 113href="http://www.gnome.org/">Gnome</a> project. <a 114href="http://www.w3.org/XML/">XML is a standard</a> for building tag-based 115structured documents/data.</p> 116 117<p>Here are some key points about libxml:</p> 118<ul> 119 <li>Libxml exports Push (progressive) and Pull (blocking) type parser 120 interfaces for both XML and HTML.</li> 121 <li>Libxml can do DTD validation at parse time, using a parsed document 122 instance, or with an arbitrary DTD.</li> 123 <li>Libxml includes complete <a 124 href="http://www.w3.org/TR/xpath">XPath</a>, <a 125 href="http://www.w3.org/TR/xptr">XPointer</a> and <a 126 href="http://www.w3.org/TR/xinclude">XInclude</a> implementations.</li> 127 <li>It is written in plain C, making as few assumptions as possible, and 128 sticking closely to ANSI C/POSIX for easy embedding. Works on 129 Linux/Unix/Windows, ported to a number of other platforms.</li> 130 <li>Basic support for HTTP and FTP client allowing applications to fetch 131 remote resources.</li> 132 <li>The design is modular, most of the extensions can be compiled out.</li> 133 <li>The internal document representation is as close as possible to the <a 134 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li> 135 <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX 136 like interface</a>; the interface is designed to be compatible with <a 137 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li> 138 <li>This library is released under the <a 139 href="http://www.opensource.org/licenses/mit-license.html">MIT 140 License</a>. See the Copyright file in the distribution for the precise 141 wording.</li> 142</ul> 143 144<p>Warning: unless you are forced to because your application links with a 145Gnome-1.X library requiring it, <strong><span 146style="background-color: #FF0000">Do Not Use libxml1</span></strong>, use 147libxml2</p> 148 149<h2><a name="FAQ">FAQ</a></h2> 150 151<p>Table of Contents:</p> 152<ul> 153 <li><a href="FAQ.html#License">License(s)</a></li> 154 <li><a href="FAQ.html#Installati">Installation</a></li> 155 <li><a href="FAQ.html#Compilatio">Compilation</a></li> 156 <li><a href="FAQ.html#Developer">Developer corner</a></li> 157</ul> 158 159<h3><a name="License">License</a>(s)</h3> 160<ol> 161 <li><em>Licensing Terms for libxml</em> 162 <p>libxml is released under the <a 163 href="http://www.opensource.org/licenses/mit-license.html">MIT 164 License</a>; see the file Copyright in the distribution for the precise 165 wording</p> 166 </li> 167 <li><em>Can I embed libxml in a proprietary application ?</em> 168 <p>Yes. The MIT License allows you to keep proprietary the changes you 169 made to libxml, but it would be graceful to send-back bug fixes and 170 improvements as patches for possible incorporation in the main 171 development tree.</p> 172 </li> 173</ol> 174 175<h3><a name="Installati">Installation</a></h3> 176<ol> 177 <li>Unless you are forced to because your application links with a Gnome 178 library requiring it, <strong><span style="background-color: #FF0000">Do 179 Not Use libxml1</span></strong>, use libxml2</li> 180 <li><em>Where can I get libxml</em> ? 181 <p>The original distribution comes from <a 182 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a 183 href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">gnome.org</a></p> 184 <p>Most Linux and BSD distributions include libxml, this is probably the 185 safer way for end-users to use libxml.</p> 186 <p>David Doolin provides precompiled Windows versions at <a 187 href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p> 188 </li> 189 <li><em>I see libxml and libxml2 releases, which one should I install ?</em> 190 <ul> 191 <li>If you are not constrained by backward compatibility issues with 192 existing applications, install libxml2 only</li> 193 <li>If you are not doing development, you can safely install both. 194 Usually the packages <a 195 href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a 196 href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are 197 compatible (this is not the case for development packages).</li> 198 <li>If you are a developer and your system provides separate packaging 199 for shared libraries and the development components, it is possible 200 to install libxml and libxml2, and also <a 201 href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> 202 and <a 203 href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> 204 too for libxml2 >= 2.3.0</li> 205 <li>If you are developing a new application, please develop against 206 libxml2(-devel)</li> 207 </ul> 208 </li> 209 <li><em>I can't install the libxml package, it conflicts with libxml0</em> 210 <p>You probably have an old libxml0 package used to provide the shared 211 library for libxml.so.0, you can probably safely remove it. The libxml 212 packages provided on <a 213 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provide 214 libxml.so.0</p> 215 </li> 216 <li><em>I can't install the libxml(2) RPM package due to failed 217 dependencies</em> 218 <p>The most generic solution is to re-fetch the latest src.rpm , and 219 rebuild it locally with</p> 220 <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> 221 <p>If everything goes well it will generate two binary rpm packages (one 222 providing the shared libs and xmllint, and the other one, the -devel 223 package, providing includes, static libraries and scripts needed to build 224 applications with libxml(2)) that you can install locally.</p> 225 </li> 226</ol> 227 228<h3><a name="Compilatio">Compilation</a></h3> 229<ol> 230 <li><em>What is the process to compile libxml ?</em> 231 <p>As most UNIX libraries libxml follows the "standard":</p> 232 <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> 233 <p><code>cd libxml-xxxx</code></p> 234 <p><code>/configure --help</code></p> 235 <p>to see the options, then the compilation/installation proper</p> 236 <p><code>/configure [possible options]</code></p> 237 <p><code>make</code></p> 238 <p><code>make install</code></p> 239 <p>At that point you may have to rerun ldconfig or a similar utility to 240 update your list of installed shared libs.</p> 241 </li> 242 <li><em>What other libraries are needed to compile/install libxml ?</em> 243 <p>Libxml does not require any other library, the normal C ANSI API 244 should be sufficient (please report any violation to this rule you may 245 find).</p> 246 <p>However if found at configuration time libxml will detect and use the 247 following libs:</p> 248 <ul> 249 <li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a 250 highly portable and available widely compression library.</li> 251 <li>iconv: a powerful character encoding conversion library. It is 252 included by default in recent glibc libraries, so it doesn't need to 253 be installed specifically on Linux. It now seems a <a 254 href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part 255 of the official UNIX</a> specification. Here is one <a 256 href="http://www.gnu.org/software/libiconv/">implementation of the 257 library</a> which source can be found <a 258 href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> 259 </ul> 260 </li> 261 <li><em>Make check fails on some platforms</em> 262 <p>Sometimes the regression tests' results don't completely match the 263 value produced by the parser, and the makefile uses diff to print the 264 delta. On some platforms the diff return breaks the compilation process; 265 if the diff is small this is probably not a serious problem.</p> 266 <p>Sometimes (especially on Solaris) make checks fail due to limitations 267 in make. Try using GNU-make instead.</p> 268 </li> 269 <li><em>I use the CVS version and there is no configure script</em> 270 <p>The configure script (and other Makefiles) are generated. Use the 271 autogen.sh script to regenerate the configure script and Makefiles, 272 like:</p> 273 <p><code>/autogen.sh --prefix=/usr --disable-shared</code></p> 274 </li> 275 <li><em>I have troubles when running make tests with gcc-3.0</em> 276 <p>It seems the initial release of gcc-3.0 has a problem with the 277 optimizer which miscompiles the URI module. Please use another 278 compiler.</p> 279 </li> 280</ol> 281 282<h3><a name="Developer">Developer</a> corner</h3> 283<ol> 284 <li><em>xmlDocDump() generates output on one line.</em> 285 <p>Libxml will not <strong>invent</strong> spaces in the content of a 286 document since <strong>all spaces in the content of a document are 287 significant</strong>. If you build a tree from the API and want 288 indentation:</p> 289 <ol> 290 <li>the correct way is to generate those yourself too.</li> 291 <li>the dangerous way is to ask libxml to add those blanks to your 292 content <strong>modifying the content of your document in the 293 process</strong>. The result may not be what you expect. There is 294 <strong>NO</strong> way to guarantee that such a modification won't 295 affect other parts of the content of your document. See <a 296 href="http://xmlsoft.org/html/libxml-parser.html#XMLKEEPBLANKSDEFAULT">xmlKeepBlanksDefault 297 ()</a> and <a 298 href="http://xmlsoft.org/html/libxml-tree.html#XMLSAVEFORMATFILE">xmlSaveFormatFile 299 ()</a></li> 300 </ol> 301 </li> 302 <li>Extra nodes in the document: 303 <p><em>For a XML file as below:</em></p> 304 <pre><?xml version="1.0"?> 305<PLAN xmlns="http://www.argus.ca/autotest/1.0/"> 306<NODE CommFlag="0"/> 307<NODE CommFlag="1"/> 308</PLAN></pre> 309 <p><em>after parsing it with the function 310 pxmlDoc=xmlParseFile(...);</em></p> 311 <p><em>I want to the get the content of the first node (node with the 312 CommFlag="0")</em></p> 313 <p><em>so I did it as following;</em></p> 314 <pre>xmlNodePtr pnode; 315pnode=pxmlDoc->children->children;</pre> 316 <p><em>but it does not work. If I change it to</em></p> 317 <pre>pnode=pxmlDoc->children->children->next;</pre> 318 <p><em>then it works. Can someone explain it to me.</em></p> 319 <p></p> 320 <p>In XML all characters in the content of the document are significant 321 <strong>including blanks and formatting line breaks</strong>.</p> 322 <p>The extra nodes you are wondering about are just that, text nodes with 323 the formatting spaces which are part of the document but that people tend 324 to forget. There is a function <a 325 href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault 326 ()</a> to remove those at parse time, but that's an heuristic, and its 327 use should be limited to cases where you are certain there is no 328 mixed-content in the document.</p> 329 </li> 330 <li><em>I get compilation errors of existing code like when accessing 331 <strong>root</strong> or <strong>child fields</strong> of nodes.</em> 332 <p>You are compiling code developed for libxml version 1 and using a 333 libxml2 development environment. Either switch back to libxml v1 devel or 334 even better fix the code to compile with libxml2 (or both) by <a 335 href="upgrade.html">following the instructions</a>.</p> 336 </li> 337 <li><em>I get compilation errors about non existing 338 <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> 339 fields.</em> 340 <p>The source code you are using has been <a 341 href="upgrade.html">upgraded</a> to be able to compile with both libxml 342 and libxml2, but you need to install a more recent version: 343 libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> 344 </li> 345 <li><em>XPath implementation looks seriously broken</em> 346 <p>XPath implementation prior to 2.3.0 was really incomplete. Upgrade to 347 a recent version, there are no known bugs in the current version.</p> 348 </li> 349 <li><em>The example provided in the web page does not compile.</em> 350 <p>It's hard to maintain the documentation in sync with the code 351 <grin/> ...</p> 352 <p>Check the previous points 1/ and 2/ raised before, and please send 353 patches.</p> 354 </li> 355 <li><em>Where can I get more examples and information than privoded on the 356 web page?</em> 357 <p>Ideally a libxml book would be nice. I have no such plan ... But you 358 can:</p> 359 <ul> 360 <li>check more deeply the <a href="html/libxml-lib.html">existing 361 generated doc</a></li> 362 <li>look for examples of use for libxml function using the Gnome code. 363 For example the following will query the full Gnome CVS base for the 364 use of the <strong>xmlAddChild()</strong> function: 365 <p><a 366 href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> 367 <p>This may be slow, a large hardware donation to the gnome project 368 could cure this :-)</p> 369 </li> 370 <li><a 371 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse 372 the libxml source</a> , I try to write code as clean and documented 373 as possible, so looking at it may be helpful. In particular the code 374 of xmllint.c and of the various testXXX.c test programs should 375 provide good examples of how to do things with the library.</li> 376 </ul> 377 </li> 378 <li>What about C++ ? 379 <p>libxml is written in pure C in order to allow easy reuse on a number 380 of platforms, including embedded systems. I don't intend to convert to 381 C++.</p> 382 <p>There are however a few C++ wrappers which may fulfill your needs:</p> 383 <ul> 384 <li>by Ari Johnson <ari@btigate.com>: 385 <p>Website: <a 386 href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p> 387 <p>Download: <a 388 href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p> 389 </li> 390 <li>by Peter Jones <pjones@pmade.org> 391 <p>Website: <a 392 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 393 </li> 394 </ul> 395 </li> 396 <li>How to validate a document a posteriori ? 397 <p>It is possible to validate documents which had not been validated at 398 initial parsing time or documents which have been built from scratch 399 using the API. Use the <a 400 href="http://xmlsoft.org/html/libxml-valid.html#XMLVALIDATEDTD">xmlValidateDtd()</a> 401 function. It is also possible to simply add a DTD to an existing 402 document:</p> 403 <pre>xmlDocPtr doc; /* your existing document */ 404xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 405 406 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 407 408 doc->intSubset = dtd; 409 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 410 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 411 </pre> 412 </li> 413 <li>So what is this funky "xmlChar" used all the time? 414 <p>It is a null terminated sequence of utf-8 characters. And only utf-8! 415 You need to convert strings encoded in different ways to utf-8 before 416 passing them to the API. This can be accomplished with the iconv library 417 for instance.</p> 418 </li> 419 <li>etc ...</li> 420</ol> 421 422<p></p> 423 424<h2><a name="Documentat">Documentation</a></h2> 425 426<p>There are several on-line resources related to using libxml:</p> 427<ol> 428 <li>Use the <a href="search.php">search engine</a> to lookup 429 informations.</li> 430 <li>Check the <a href="FAQ.html">FAQ.</a></li> 431 <li>Check the <a href="http://xmlsoft.org/html/libxml-lib.html">extensive 432 documentation</a> automatically extracted from code comments (using <a 433 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gtk-doc">gtk 434 doc</a>).</li> 435 <li>Look at the documentation about <a href="encoding.html">libxml 436 internationalization support</a>.</li> 437 <li>This page provides a global overview and <a href="example.html">some 438 examples</a> on how to use libxml.</li> 439 <li>John Fleck's libxml tutorial: <a href="tutorial/index.html">html</a> or 440 <a href="tutorial/xmltutorial.pdf">pdf</a>.</li> 441 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a 442 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice 443 documentation</a> explaining how to use the libxml SAX interface.</li> 444 <li>George Lebl wrote <a 445 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article 446 for IBM developerWorks</a> about using libxml.</li> 447 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO 448 file</a>.</li> 449 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a> 450 description. If you are starting a new project using libxml you should 451 really use the 2.x version.</li> 452 <li>And don't forget to look at the <a 453 href="http://mail.gnome.org/archives/xml/">mailing-list archive</a>.</li> 454</ol> 455 456<h2><a name="Reporting">Reporting bugs and getting help</a></h2> 457 458<p>Well, bugs or missing features are always possible, and I will make a 459point of fixing them in a timely fashion. The best way to report a bug is to 460use the <a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome 461bug tracking database</a> (make sure to use the "libxml2" module name). I 462look at reports there regularly and it's good to have a reminder when a bug 463is still open. Be sure to specify that the bug is for the package libxml2.</p> 464 465<p>There is also a mailing-list <a 466href="mailto:xml@gnome.org">xml@gnome.org</a> for libxml, with an <a 467href="http://mail.gnome.org/archives/xml/">on-line archive</a> (<a 468href="http://xmlsoft.org/messages">old</a>). To subscribe to this list, 469please visit the <a 470href="http://mail.gnome.org/mailman/listinfo/xml">associated Web</a> page and 471follow the instructions. <strong>Do not send code, I won't debug it</strong> 472(but patches are really appreciated!).</p> 473 474<p>Check the following <strong><span style="color: #FF0000">before 475posting</span></strong>:</p> 476<ul> 477 <li>Read the <a href="FAQ.html">FAQ</a> and <a href="search.php">use the 478 search engine</a> to get informations related to your problem.</li> 479 <li>Make sure you are <a href="ftp://xmlsoft.org/">using a recent 480 version</a>, and that the problem still shows up in a recent version.</li> 481 <li>Check the <a href="http://mail.gnome.org/archives/xml/">list 482 archives</a> to see if the problem was reported already. In this case 483 there is probably a fix available, similarly check the <a 484 href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">registered 485 open bugs</a>.</li> 486 <li>Make sure you can reproduce the bug with xmllint or one of the test 487 programs found in source in the distribution.</li> 488 <li>Please send the command showing the error as well as the input (as an 489 attachment)</li> 490</ul> 491 492<p>Then send the bug with associated informations to reproduce it to the <a 493href="mailto:xml@gnome.org">xml@gnome.org</a> list; if it's really libxml 494related I will approve it. Please do not send mail to me directly, it makes 495things really hard to track and in some cases I am not the best person to 496answer a given question, ask on the list.</p> 497 498<p>To <span style="color: #E50000">be really clear about support</span>:</p> 499<ul> 500 <li>Support or help <span style="color: #E50000">request MUST be sent to 501 the list or on bugzilla</span> in case of problems, so that the Question 502 and Answers can be shared publicly. Failing to do so carries the implicit 503 message "I want free support but I don't want to share the benefits with 504 others" and is not welcome. I will automatically Carbon-Copy the 505 xml@gnome.org mailing list for any technical reply made about libxml2 or 506 libxslt.</li> 507 <li>There is <span style="color: #E50000">no garantee for support</span>, 508 if your question remains unanswered after a week, repost it, making sure 509 you gave all the detail needed and the informations requested.</li> 510 <li>Failing to provide informations as requested or double checking first 511 for prior feedback also carries the implicit message "the time of the 512 library maintainers is less valuable than my time" and might not be 513 welcome.</li> 514</ul> 515 516<p>Of course, bugs reported with a suggested patch for fixing them will 517probably be processed faster than those without.</p> 518 519<p>If you're looking for help, a quick look at <a 520href="http://mail.gnome.org/archives/xml/">the list archive</a> may actually 521provide the answer. I usually send source samples when answering libxml usage 522questions. The <a href="http://xmlsoft.org/html/book1.html">auto-generated 523documentation</a> is not as polished as I would like (i need to learn more 524about DocBook), but it's a good starting point.</p> 525 526<h2><a name="help">How to help</a></h2> 527 528<p>You can help the project in various ways, the best thing to do first is to 529subscribe to the mailing-list as explained before, check the <a 530href="http://mail.gnome.org/archives/xml/">archives </a>and the <a 531href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome bug 532database</a>:</p> 533<ol> 534 <li>Provide patches when you find problems.</li> 535 <li>Provide the diffs when you port libxml to a new platform. They may not 536 be integrated in all cases but help pinpointing portability problems 537 and</li> 538 <li>Provide documentation fixes (either as patches to the code comments or 539 as HTML diffs).</li> 540 <li>Provide new documentations pieces (translations, examples, etc 541 ...).</li> 542 <li>Check the TODO file and try to close one of the items.</li> 543 <li>Take one of the points raised in the archive or the bug database and 544 provide a fix. <a href="mailto:daniel@veillard.com">Get in touch with me 545 </a>before to avoid synchronization problems and check that the suggested 546 fix will fit in nicely :-)</li> 547</ol> 548 549<h2><a name="Downloads">Downloads</a></h2> 550 551<p>The latest versions of libxml can be found on <a 552href="ftp://xmlsoft.org/">xmlsoft.org</a> (<a 553href="ftp://speakeasy.rpmfind.net/pub/libxml/">Seattle</a>, <a 554href="ftp://fr.rpmfind.net/pub/libxml/">France</a>) or on the <a 555href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either 556as a <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">source 557archive</a><!-- commenting this out because they seem to have disappeared or <a 558href="ftp://ftp.gnome.org/pub/GNOME/stable/redhat/i386/libxml/">RPM 559packages</a> --> 560 , Antonin Sprinzl also provide <a href="ftp://gd.tuwien.ac.at/pub/libxml/">a 561mirror in Austria</a>. (NOTE that you need both the <a 562href="http://rpmfind.net/linux/RPM/libxml2.html">libxml(2)</a> and <a 563href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml(2)-devel</a> 564packages installed to compile applications using libxml.) <a 565href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the maintainer of 566the Windows port, <a 567href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 568binaries</a>. <a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> 569provides <a href="http://garypennington.net/libxml2/">Solaris binaries</a>. 570<a href="mailto:Steve.Ball@zveno.com">Steve Ball</a> provides <a 571href="http://www.zveno.com/open_source/libxml2xslt.html">Mac Os X 572binaries</a>.</p> 573 574<p><a name="Snapshot">Snapshot:</a></p> 575<ul> 576 <li>Code from the W3C cvs base libxml <a 577 href="ftp://xmlsoft.org/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a>.</li> 578 <li>Docs, content of the web site, the list archive included <a 579 href="ftp://xmlsoft.org/libxml-docs.tar.gz">libxml-docs.tar.gz</a>.</li> 580</ul> 581 582<p><a name="Contribs">Contributions:</a></p> 583 584<p>I do accept external contributions, especially if compiling on another 585platform, get in touch with me to upload the package, wrappers for various 586languages have been provided, and can be found in the <a 587href="contribs.html">contrib section</a></p> 588 589<p>Libxml is also available from CVS:</p> 590<ul> 591 <li><p>The <a 592 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Gnome 593 CVS base</a>. Check the <a 594 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> 595 page; the CVS module is <b>gnome-xml</b>.</p> 596 </li> 597 <li>The <strong>libxslt</strong> module is also present there</li> 598</ul> 599 600<h2><a name="News">News</a></h2> 601 602<h3>CVS only : check the <a 603href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file 604for a really accurate description</h3> 605 606<p>Items not finished and worked on, get in touch with the list if you want 607to test those</p> 608<ul> 609 <li>More testing on RelaxNG</li> 610 <li>Finishing up <a href="http://www.w3.org/TR/xmlschema-1/">XML 611 Schemas</a></li> 612</ul> 613 614<h3>2.5.3: Feb 10 2003</h3> 615<ul> 616 <li>RelaxNG and XML Schemas datatypes improvements, and added a first 617 version of RelaxNG Python bindings</li> 618 <li>Fixes: XLink (Sean Chittenden), XInclude (Sean Chittenden), API fix for 619 serializing namespace nodes, encoding conversion bug, XHTML1 620 serialization</li> 621 <li>Portability fixes: Windows (Igor), AMD 64bits RPM spec file</li> 622</ul> 623 624<h3>2.5.2: Feb 5 2003</h3> 625<ul> 626 <li>First implementation of RelaxNG, added --relaxng flag to xmllint</li> 627 <li>Schemas support now compiled in by default.</li> 628 <li>Bug fixes: DTD validation, namespace checking, XInclude and entities, 629 delegateURI in XML Catalogs, HTML parser, XML reader (St�phane Bidoul), 630 XPath parser and evaluation, UTF8ToUTF8 serialization, XML reader memory 631 consumption, HTML parser, HTML serialization in the presence of 632 namespaces</li> 633 <li>added an HTML API to check elements and attributes.</li> 634 <li>Documentation improvement, PDF for the tutorial (John Fleck), doc 635 patches (Stefan Kost)</li> 636 <li>Portability fixes: NetBSD (Julio Merino), Windows (Igor Zlatkovic)</li> 637 <li>Added python bindings for XPointer, contextual error reporting 638 (St�phane Bidoul)</li> 639 <li>URI/file escaping problems (Stefano Zacchiroli)</li> 640</ul> 641 642<h3>2.5.1: Jan 8 2003</h3> 643<ul> 644 <li>Fixes a memory leak and configuration/compilation problems in 2.5.0</li> 645 <li>documentation updates (John)</li> 646 <li>a couple of XmlTextReader fixes</li> 647</ul> 648 649<h3>2.5.0: Jan 6 2003</h3> 650<ul> 651 <li>New <a href="xmlreader.html">XmltextReader interface</a> based on C# 652 API (with help of St�phane Bidoul)</li> 653 <li>Windows: more exports, including the new API (Igor)</li> 654 <li>XInclude fallback fix</li> 655 <li>Python: bindings for the new API, packaging (St�phane Bidoul), 656 drv_libxml2.py Python xml.sax driver (St�phane Bidoul), fixes, speedup 657 and iterators for Python-2.2 (Hannu Krosing)</li> 658 <li>Tutorial fixes (john Fleck and Niraj Tolia) xmllint man update 659 (John)</li> 660 <li>Fix an XML parser bug raised by Vyacheslav Pindyura</li> 661 <li>Fix for VMS serialization (Nigel Hall) and config (Craig A. Berry)</li> 662 <li>Entities handling fixes</li> 663 <li>new API to optionally track node creation and deletion (Lukas 664 Schroeder)</li> 665 <li>Added documentation for the XmltextReader interface and some <a 666 href="guidelines.html">XML guidelines</a></li> 667</ul> 668 669<h3>2.4.30: Dec 12 2002</h3> 670<ul> 671 <li>2.4.29 broke the python bindings, rereleasing</li> 672 <li>Improvement/fixes of the XML API generator, and couple of minor code 673 fixes.</li> 674</ul> 675 676<h3>2.4.29: Dec 11 2002</h3> 677<ul> 678 <li>Windows fixes (Igor): Windows CE port, pthread linking, python bindings 679 (St�phane Bidoul), Mingw (Magnus Henoch), and export list updates</li> 680 <li>Fix for prev in python bindings (ERDI Gergo)</li> 681 <li>Fix for entities handling (Marcus Clarke)</li> 682 <li>Refactored the XML and HTML dumps to a single code path, fixed XHTML1 683 dump</li> 684 <li>Fix for URI parsing when handling URNs with fragment identifiers</li> 685 <li>Fix for HTTP URL escaping problem</li> 686 <li>added an TextXmlReader (C#) like API (work in progress)</li> 687 <li>Rewrote the API in XML generation script, includes a C parser and saves 688 more informations needed for C# bindings</li> 689</ul> 690 691<h3>2.4.28: Nov 22 2002</h3> 692<ul> 693 <li>a couple of python binding fixes</li> 694 <li>2 bug fixes in the XML push parser</li> 695 <li>potential memory leak removed (Martin Stoilov)</li> 696 <li>fix to the configure script for Unix (Dimitri Papadopoulos)</li> 697 <li>added encoding support for XInclude parse="text"</li> 698 <li>autodetection of XHTML1 and specific serialization rules added</li> 699 <li>nasty threading bug fixed (William Brack)</li> 700</ul> 701 702<h3>2.4.27: Nov 17 2002</h3> 703<ul> 704 <li>fixes for the Python bindings</li> 705 <li>a number of bug fixes: SGML catalogs, xmlParseBalancedChunkMemory(), 706 HTML parser, Schemas (Charles Bozeman), document fragment support 707 (Christian Glahn), xmlReconciliateNs (Brian Stafford), XPointer, 708 xmlFreeNode(), xmlSAXParseMemory (Peter Jones), xmlGetNodePath (Petr 709 Pajas), entities processing</li> 710 <li>added grep to xmllint --shell</li> 711 <li>VMS update patch from Craig A. Berry</li> 712 <li>cleanup of the Windows build with support for more compilers (Igor), 713 better thread support on Windows</li> 714 <li>cleanup of Unix Makefiles and spec file</li> 715 <li>Improvements to the documentation (John Fleck)</li> 716</ul> 717 718<h3>2.4.26: Oct 18 2002</h3> 719<ul> 720 <li>Patches for Windows CE port, improvements on Windows paths handling</li> 721 <li>Fixes to the validation code (DTD and Schemas), xmlNodeGetPath() , 722 HTML serialization, Namespace compliance, and a number of small 723 problems</li> 724</ul> 725 726<h3>2.4.25: Sep 26 2002</h3> 727<ul> 728 <li>A number of bug fixes: XPath, validation, Python bindings, DOM and 729 tree, xmlI/O, Html</li> 730 <li>Serious rewrite of XInclude</li> 731 <li>Made XML Schemas regexp part of the default build and APIs, small fix 732 and improvement of the regexp core</li> 733 <li>Changed the validation code to reuse XML Schemas regexp APIs</li> 734 <li>Better handling of Windows file paths, improvement of Makefiles (Igor, 735 Daniel Gehriger, Mark Vakoc)</li> 736 <li>Improved the python I/O bindings, the tests, added resolver and regexp 737 APIs</li> 738 <li>New logos from Marc Liyanage</li> 739 <li>Tutorial improvements: John Fleck, Christopher Harris</li> 740 <li>Makefile: Fixes for AMD x86_64 (Mandrake), DESTDIR (Christophe 741 Merlet)</li> 742 <li>removal of all stderr/perror use for error reporting</li> 743 <li>Better error reporting: XPath and DTD validation</li> 744 <li>update of the trio portability layer (Bjorn Reese)</li> 745</ul> 746 747<p><strong>2.4.24: Aug 22 2002</strong></p> 748<ul> 749 <li>XPath fixes (William), xf:escape-uri() (Wesley Terpstra)</li> 750 <li>Python binding fixes: makefiles (William), generator, rpm build, x86-64 751 (fcrozat)</li> 752 <li>HTML <style> and boolean attributes serializer fixes</li> 753 <li>C14N improvements by Aleksey</li> 754 <li>doc cleanups: Rick Jones</li> 755 <li>Windows compiler makefile updates: Igor and Elizabeth Barham</li> 756 <li>XInclude: implementation of fallback and xml:base fixup added</li> 757</ul> 758 759<h3>2.4.23: July 6 2002</h3> 760<ul> 761 <li>performances patches: Peter Jacobi</li> 762 <li>c14n fixes, testsuite and performances: Aleksey Sanin</li> 763 <li>added xmlDocFormatDump: Chema Celorio</li> 764 <li>new tutorial: John Fleck</li> 765 <li>new hash functions and performances: Sander Vesik, portability fix from 766 Peter Jacobi</li> 767 <li>a number of bug fixes: XPath (William Brack, Richard Jinks), XML and 768 HTML parsers, ID lookup function</li> 769 <li>removal of all remaining sprintf: Aleksey Sanin</li> 770</ul> 771 772<h3>2.4.22: May 27 2002</h3> 773<ul> 774 <li>a number of bug fixes: configure scripts, base handling, parser, memory 775 usage, HTML parser, XPath, documentation (Christian Cornelssen), 776 indentation, URI parsing</li> 777 <li>Optimizations for XMLSec, fixing and making public some of the network 778 protocol handlers (Aleksey)</li> 779 <li>performance patch from Gary Pennington</li> 780 <li>Charles Bozeman provided date and time support for XML Schemas 781 datatypes</li> 782</ul> 783 784<h3>2.4.21: Apr 29 2002</h3> 785 786<p>This release is both a bug fix release and also contains the early XML 787Schemas <a href="http://www.w3.org/TR/xmlschema-1/">structures</a> and <a 788href="http://www.w3.org/TR/xmlschema-2/">datatypes</a> code, beware, all 789interfaces are likely to change, there is huge holes, it is clearly a work in 790progress and don't even think of putting this code in a production system, 791it's actually not compiled in by default. The real fixes are:</p> 792<ul> 793 <li>a couple of bugs or limitations introduced in 2.4.20</li> 794 <li>patches for Borland C++ and MSC by Igor</li> 795 <li>some fixes on XPath strings and conformance patches by Richard 796 Jinks</li> 797 <li>patch from Aleksey for the ExcC14N specification</li> 798 <li>OSF/1 bug fix by Bjorn</li> 799</ul> 800 801<h3>2.4.20: Apr 15 2002</h3> 802<ul> 803 <li>bug fixes: file descriptor leak, XPath, HTML output, DTD validation</li> 804 <li>XPath conformance testing by Richard Jinks</li> 805 <li>Portability fixes: Solaris, MPE/iX, Windows, OSF/1, python bindings, 806 libxml.m4</li> 807</ul> 808 809<h3>2.4.19: Mar 25 2002</h3> 810<ul> 811 <li>bug fixes: half a dozen XPath bugs, Validation, ISO-Latin to UTF8 812 encoder</li> 813 <li>portability fixes in the HTTP code</li> 814 <li>memory allocation checks using valgrind, and profiling tests</li> 815 <li>revamp of the Windows build and Makefiles</li> 816</ul> 817 818<h3>2.4.18: Mar 18 2002</h3> 819<ul> 820 <li>bug fixes: tree, SAX, canonicalization, validation, portability, 821 XPath</li> 822 <li>removed the --with-buffer option it was becoming unmaintainable</li> 823 <li>serious cleanup of the Python makefiles</li> 824 <li>speedup patch to XPath very effective for DocBook stylesheets</li> 825 <li>Fixes for Windows build, cleanup of the documentation</li> 826</ul> 827 828<h3>2.4.17: Mar 8 2002</h3> 829<ul> 830 <li>a lot of bug fixes, including "namespace nodes have no parents in 831 XPath"</li> 832 <li>fixed/improved the Python wrappers, added more examples and more 833 regression tests, XPath extension functions can now return node-sets</li> 834 <li>added the XML Canonicalization support from Aleksey Sanin</li> 835</ul> 836 837<h3>2.4.16: Feb 20 2002</h3> 838<ul> 839 <li>a lot of bug fixes, most of them were triggered by the XML Testsuite 840 from OASIS and W3C. Compliance has been significantly improved.</li> 841 <li>a couple of portability fixes too.</li> 842</ul> 843 844<h3>2.4.15: Feb 11 2002</h3> 845<ul> 846 <li>Fixed the Makefiles, especially the python module ones</li> 847 <li>A few bug fixes and cleanup</li> 848 <li>Includes cleanup</li> 849</ul> 850 851<h3>2.4.14: Feb 8 2002</h3> 852<ul> 853 <li>Change of License to the <a 854 href="http://www.opensource.org/licenses/mit-license.html">MIT 855 License</a> basically for integration in XFree86 codebase, and removing 856 confusion around the previous dual-licensing</li> 857 <li>added Python bindings, beta software but should already be quite 858 complete</li> 859 <li>a large number of fixes and cleanups, especially for all tree 860 manipulations</li> 861 <li>cleanup of the headers, generation of a reference API definition in 862 XML</li> 863</ul> 864 865<h3>2.4.13: Jan 14 2002</h3> 866<ul> 867 <li>update of the documentation: John Fleck and Charlie Bozeman</li> 868 <li>cleanup of timing code from Justin Fletcher</li> 869 <li>fixes for Windows and initial thread support on Win32: Igor and Serguei 870 Narojnyi</li> 871 <li>Cygwin patch from Robert Collins</li> 872 <li>added xmlSetEntityReferenceFunc() for Keith Isdale work on xsldbg</li> 873</ul> 874 875<h3>2.4.12: Dec 7 2001</h3> 876<ul> 877 <li>a few bug fixes: thread (Gary Pennington), xmllint (Geert Kloosterman), 878 XML parser (Robin Berjon), XPointer (Danny Jamshy), I/O cleanups 879 (robert)</li> 880 <li>Eric Lavigne contributed project files for MacOS</li> 881 <li>some makefiles cleanups</li> 882</ul> 883 884<h3>2.4.11: Nov 26 2001</h3> 885<ul> 886 <li>fixed a couple of errors in the includes, fixed a few bugs, some code 887 cleanups</li> 888 <li>xmllint man pages improvement by Heiko Rupp</li> 889 <li>updated VMS build instructions from John A Fotheringham</li> 890 <li>Windows Makefiles updates from Igor</li> 891</ul> 892 893<h3>2.4.10: Nov 10 2001</h3> 894<ul> 895 <li>URI escaping fix (Joel Young)</li> 896 <li>added xmlGetNodePath() (for paths or XPointers generation)</li> 897 <li>Fixes namespace handling problems when using DTD and validation</li> 898 <li>improvements on xmllint: Morus Walter patches for --format and 899 --encode, Stefan Kost and Heiko Rupp improvements on the --shell</li> 900 <li>fixes for xmlcatalog linking pointed by Weiqi Gao</li> 901 <li>fixes to the HTML parser</li> 902</ul> 903 904<h3>2.4.9: Nov 6 2001</h3> 905<ul> 906 <li>fixes more catalog bugs</li> 907 <li>avoid a compilation problem, improve xmlGetLineNo()</li> 908</ul> 909 910<h3>2.4.8: Nov 4 2001</h3> 911<ul> 912 <li>fixed SGML catalogs broken in previous release, updated xmlcatalog 913 tool</li> 914 <li>fixed a compile errors and some includes troubles.</li> 915</ul> 916 917<h3>2.4.7: Oct 30 2001</h3> 918<ul> 919 <li>exported some debugging interfaces</li> 920 <li>serious rewrite of the catalog code</li> 921 <li>integrated Gary Pennington thread safety patch, added configure option 922 and regression tests</li> 923 <li>removed an HTML parser bug</li> 924 <li>fixed a couple of potentially serious validation bugs</li> 925 <li>integrated the SGML DocBook support in xmllint</li> 926 <li>changed the nanoftp anonymous login passwd</li> 927 <li>some I/O cleanup and a couple of interfaces for Perl wrapper</li> 928 <li>general bug fixes</li> 929 <li>updated xmllint man page by John Fleck</li> 930 <li>some VMS and Windows updates</li> 931</ul> 932 933<h3>2.4.6: Oct 10 2001</h3> 934<ul> 935 <li>added an updated man pages by John Fleck</li> 936 <li>portability and configure fixes</li> 937 <li>an infinite loop on the HTML parser was removed (William)</li> 938 <li>Windows makefile patches from Igor</li> 939 <li>fixed half a dozen bugs reported for libxml or libxslt</li> 940 <li>updated xmlcatalog to be able to modify SGML super catalogs</li> 941</ul> 942 943<h3>2.4.5: Sep 14 2001</h3> 944<ul> 945 <li>Remove a few annoying bugs in 2.4.4</li> 946 <li>forces the HTML serializer to output decimal charrefs since some 947 version of Netscape can't handle hexadecimal ones</li> 948</ul> 949 950<h3>1.8.16: Sep 14 2001</h3> 951<ul> 952 <li>maintenance release of the old libxml1 branch, couple of bug and 953 portability fixes</li> 954</ul> 955 956<h3>2.4.4: Sep 12 2001</h3> 957<ul> 958 <li>added --convert to xmlcatalog, bug fixes and cleanups of XML 959 Catalog</li> 960 <li>a few bug fixes and some portability changes</li> 961 <li>some documentation cleanups</li> 962</ul> 963 964<h3>2.4.3: Aug 23 2001</h3> 965<ul> 966 <li>XML Catalog support see the doc</li> 967 <li>New NaN/Infinity floating point code</li> 968 <li>A few bug fixes</li> 969</ul> 970 971<h3>2.4.2: Aug 15 2001</h3> 972<ul> 973 <li>adds xmlLineNumbersDefault() to control line number generation</li> 974 <li>lot of bug fixes</li> 975 <li>the Microsoft MSC projects files should now be up to date</li> 976 <li>inheritance of namespaces from DTD defaulted attributes</li> 977 <li>fixes a serious potential security bug</li> 978 <li>added a --format option to xmllint</li> 979</ul> 980 981<h3>2.4.1: July 24 2001</h3> 982<ul> 983 <li>possibility to keep line numbers in the tree</li> 984 <li>some computation NaN fixes</li> 985 <li>extension of the XPath API</li> 986 <li>cleanup for alpha and ia64 targets</li> 987 <li>patch to allow saving through HTTP PUT or POST</li> 988</ul> 989 990<h3>2.4.0: July 10 2001</h3> 991<ul> 992 <li>Fixed a few bugs in XPath, validation, and tree handling.</li> 993 <li>Fixed XML Base implementation, added a couple of examples to the 994 regression tests</li> 995 <li>A bit of cleanup</li> 996</ul> 997 998<h3>2.3.14: July 5 2001</h3> 999<ul> 1000 <li>fixed some entities problems and reduce memory requirement when 1001 substituting them</li> 1002 <li>lots of improvements in the XPath queries interpreter can be 1003 substantially faster</li> 1004 <li>Makefiles and configure cleanups</li> 1005 <li>Fixes to XPath variable eval, and compare on empty node set</li> 1006 <li>HTML tag closing bug fixed</li> 1007 <li>Fixed an URI reference computation problem when validating</li> 1008</ul> 1009 1010<h3>2.3.13: June 28 2001</h3> 1011<ul> 1012 <li>2.3.12 configure.in was broken as well as the push mode XML parser</li> 1013 <li>a few more fixes for compilation on Windows MSC by Yon Derek</li> 1014</ul> 1015 1016<h3>1.8.14: June 28 2001</h3> 1017<ul> 1018 <li>Zbigniew Chyla gave a patch to use the old XML parser in push mode</li> 1019 <li>Small Makefile fix</li> 1020</ul> 1021 1022<h3>2.3.12: June 26 2001</h3> 1023<ul> 1024 <li>lots of cleanup</li> 1025 <li>a couple of validation fix</li> 1026 <li>fixed line number counting</li> 1027 <li>fixed serious problems in the XInclude processing</li> 1028 <li>added support for UTF8 BOM at beginning of entities</li> 1029 <li>fixed a strange gcc optimizer bugs in xpath handling of float, gcc-3.0 1030 miscompile uri.c (William), Thomas Leitner provided a fix for the 1031 optimizer on Tru64</li> 1032 <li>incorporated Yon Derek and Igor Zlatkovic fixes and improvements for 1033 compilation on Windows MSC</li> 1034 <li>update of libxml-doc.el (Felix Natter)</li> 1035 <li>fixed 2 bugs in URI normalization code</li> 1036</ul> 1037 1038<h3>2.3.11: June 17 2001</h3> 1039<ul> 1040 <li>updates to trio, Makefiles and configure should fix some portability 1041 problems (alpha)</li> 1042 <li>fixed some HTML serialization problems (pre, script, and block/inline 1043 handling), added encoding aware APIs, cleanup of this code</li> 1044 <li>added xmlHasNsProp()</li> 1045 <li>implemented a specific PI for encoding support in the DocBook SGML 1046 parser</li> 1047 <li>some XPath fixes (-Infinity, / as a function parameter and namespaces 1048 node selection)</li> 1049 <li>fixed a performance problem and an error in the validation code</li> 1050 <li>fixed XInclude routine to implement the recursive behaviour</li> 1051 <li>fixed xmlFreeNode problem when libxml is included statically twice</li> 1052 <li>added --version to xmllint for bug reports</li> 1053</ul> 1054 1055<h3>2.3.10: June 1 2001</h3> 1056<ul> 1057 <li>fixed the SGML catalog support</li> 1058 <li>a number of reported bugs got fixed, in XPath, iconv detection, 1059 XInclude processing</li> 1060 <li>XPath string function should now handle unicode correctly</li> 1061</ul> 1062 1063<h3>2.3.9: May 19 2001</h3> 1064 1065<p>Lots of bugfixes, and added a basic SGML catalog support:</p> 1066<ul> 1067 <li>HTML push bugfix #54891 and another patch from Jonas Borgstr�m</li> 1068 <li>some serious speed optimization again</li> 1069 <li>some documentation cleanups</li> 1070 <li>trying to get better linking on Solaris (-R)</li> 1071 <li>XPath API cleanup from Thomas Broyer</li> 1072 <li>Validation bug fixed #54631, added a patch from Gary Pennington, fixed 1073 xmlValidGetValidElements()</li> 1074 <li>Added an INSTALL file</li> 1075 <li>Attribute removal added to API: #54433</li> 1076 <li>added a basic support for SGML catalogs</li> 1077 <li>fixed xmlKeepBlanksDefault(0) API</li> 1078 <li>bugfix in xmlNodeGetLang()</li> 1079 <li>fixed a small configure portability problem</li> 1080 <li>fixed an inversion of SYSTEM and PUBLIC identifier in HTML document</li> 1081</ul> 1082 1083<h3>1.8.13: May 14 2001</h3> 1084<ul> 1085 <li>bugfixes release of the old libxml1 branch used by Gnome</li> 1086</ul> 1087 1088<h3>2.3.8: May 3 2001</h3> 1089<ul> 1090 <li>Integrated an SGML DocBook parser for the Gnome project</li> 1091 <li>Fixed a few things in the HTML parser</li> 1092 <li>Fixed some XPath bugs raised by XSLT use, tried to fix the floating 1093 point portability issue</li> 1094 <li>Speed improvement (8M/s for SAX, 3M/s for DOM, 1.5M/s for 1095 DOM+validation using the XML REC as input and a 700MHz celeron).</li> 1096 <li>incorporated more Windows cleanup</li> 1097 <li>added xmlSaveFormatFile()</li> 1098 <li>fixed problems in copying nodes with entities references (gdome)</li> 1099 <li>removed some troubles surrounding the new validation module</li> 1100</ul> 1101 1102<h3>2.3.7: April 22 2001</h3> 1103<ul> 1104 <li>lots of small bug fixes, corrected XPointer</li> 1105 <li>Non deterministic content model validation support</li> 1106 <li>added xmlDocCopyNode for gdome2</li> 1107 <li>revamped the way the HTML parser handles end of tags</li> 1108 <li>XPath: corrections of namespaces support and number formatting</li> 1109 <li>Windows: Igor Zlatkovic patches for MSC compilation</li> 1110 <li>HTML output fixes from P C Chow and William M. Brack</li> 1111 <li>Improved validation speed sensible for DocBook</li> 1112 <li>fixed a big bug with ID declared in external parsed entities</li> 1113 <li>portability fixes, update of Trio from Bjorn Reese</li> 1114</ul> 1115 1116<h3>2.3.6: April 8 2001</h3> 1117<ul> 1118 <li>Code cleanup using extreme gcc compiler warning options, found and 1119 cleared half a dozen potential problem</li> 1120 <li>the Eazel team found an XML parser bug</li> 1121 <li>cleaned up the user of some of the string formatting function. used the 1122 trio library code to provide the one needed when the platform is missing 1123 them</li> 1124 <li>xpath: removed a memory leak and fixed the predicate evaluation 1125 problem, extended the testsuite and cleaned up the result. XPointer seems 1126 broken ...</li> 1127</ul> 1128 1129<h3>2.3.5: Mar 23 2001</h3> 1130<ul> 1131 <li>Biggest change is separate parsing and evaluation of XPath expressions, 1132 there is some new APIs for this too</li> 1133 <li>included a number of bug fixes(XML push parser, 51876, notations, 1134 52299)</li> 1135 <li>Fixed some portability issues</li> 1136</ul> 1137 1138<h3>2.3.4: Mar 10 2001</h3> 1139<ul> 1140 <li>Fixed bugs #51860 and #51861</li> 1141 <li>Added a global variable xmlDefaultBufferSize to allow default buffer 1142 size to be application tunable.</li> 1143 <li>Some cleanup in the validation code, still a bug left and this part 1144 should probably be rewritten to support ambiguous content model :-\</li> 1145 <li>Fix a couple of serious bugs introduced or raised by changes in 2.3.3 1146 parser</li> 1147 <li>Fixed another bug in xmlNodeGetContent()</li> 1148 <li>Bjorn fixed XPath node collection and Number formatting</li> 1149 <li>Fixed a loop reported in the HTML parsing</li> 1150 <li>blank space are reported even if the Dtd content model proves that they 1151 are formatting spaces, this is for XML conformance</li> 1152</ul> 1153 1154<h3>2.3.3: Mar 1 2001</h3> 1155<ul> 1156 <li>small change in XPath for XSLT</li> 1157 <li>documentation cleanups</li> 1158 <li>fix in validation by Gary Pennington</li> 1159 <li>serious parsing performances improvements</li> 1160</ul> 1161 1162<h3>2.3.2: Feb 24 2001</h3> 1163<ul> 1164 <li>chasing XPath bugs, found a bunch, completed some TODO</li> 1165 <li>fixed a Dtd parsing bug</li> 1166 <li>fixed a bug in xmlNodeGetContent</li> 1167 <li>ID/IDREF support partly rewritten by Gary Pennington</li> 1168</ul> 1169 1170<h3>2.3.1: Feb 15 2001</h3> 1171<ul> 1172 <li>some XPath and HTML bug fixes for XSLT</li> 1173 <li>small extension of the hash table interfaces for DOM gdome2 1174 implementation</li> 1175 <li>A few bug fixes</li> 1176</ul> 1177 1178<h3>2.3.0: Feb 8 2001 (2.2.12 was on 25 Jan but I didn't kept track)</h3> 1179<ul> 1180 <li>Lots of XPath bug fixes</li> 1181 <li>Add a mode with Dtd lookup but without validation error reporting for 1182 XSLT</li> 1183 <li>Add support for text node without escaping (XSLT)</li> 1184 <li>bug fixes for xmlCheckFilename</li> 1185 <li>validation code bug fixes from Gary Pennington</li> 1186 <li>Patch from Paul D. Smith correcting URI path normalization</li> 1187 <li>Patch to allow simultaneous install of libxml-devel and 1188 libxml2-devel</li> 1189 <li>the example Makefile is now fixed</li> 1190 <li>added HTML to the RPM packages</li> 1191 <li>tree copying bugfixes</li> 1192 <li>updates to Windows makefiles</li> 1193 <li>optimization patch from Bjorn Reese</li> 1194</ul> 1195 1196<h3>2.2.11: Jan 4 2001</h3> 1197<ul> 1198 <li>bunch of bug fixes (memory I/O, xpath, ftp/http, ...)</li> 1199 <li>added htmlHandleOmittedElem()</li> 1200 <li>Applied Bjorn Reese's IPV6 first patch</li> 1201 <li>Applied Paul D. Smith patches for validation of XInclude results</li> 1202 <li>added XPointer xmlns() new scheme support</li> 1203</ul> 1204 1205<h3>2.2.10: Nov 25 2000</h3> 1206<ul> 1207 <li>Fix the Windows problems of 2.2.8</li> 1208 <li>integrate OpenVMS patches</li> 1209 <li>better handling of some nasty HTML input</li> 1210 <li>Improved the XPointer implementation</li> 1211 <li>integrate a number of provided patches</li> 1212</ul> 1213 1214<h3>2.2.9: Nov 25 2000</h3> 1215<ul> 1216 <li>erroneous release :-(</li> 1217</ul> 1218 1219<h3>2.2.8: Nov 13 2000</h3> 1220<ul> 1221 <li>First version of <a href="http://www.w3.org/TR/xinclude">XInclude</a> 1222 support</li> 1223 <li>Patch in conditional section handling</li> 1224 <li>updated MS compiler project</li> 1225 <li>fixed some XPath problems</li> 1226 <li>added an URI escaping function</li> 1227 <li>some other bug fixes</li> 1228</ul> 1229 1230<h3>2.2.7: Oct 31 2000</h3> 1231<ul> 1232 <li>added message redirection</li> 1233 <li>XPath improvements (thanks TOM !)</li> 1234 <li>xmlIOParseDTD() added</li> 1235 <li>various small fixes in the HTML, URI, HTTP and XPointer support</li> 1236 <li>some cleanup of the Makefile, autoconf and the distribution content</li> 1237</ul> 1238 1239<h3>2.2.6: Oct 25 2000:</h3> 1240<ul> 1241 <li>Added an hash table module, migrated a number of internal structure to 1242 those</li> 1243 <li>Fixed a posteriori validation problems</li> 1244 <li>HTTP module cleanups</li> 1245 <li>HTML parser improvements (tag errors, script/style handling, attribute 1246 normalization)</li> 1247 <li>coalescing of adjacent text nodes</li> 1248 <li>couple of XPath bug fixes, exported the internal API</li> 1249</ul> 1250 1251<h3>2.2.5: Oct 15 2000:</h3> 1252<ul> 1253 <li>XPointer implementation and testsuite</li> 1254 <li>Lot of XPath fixes, added variable and functions registration, more 1255 tests</li> 1256 <li>Portability fixes, lots of enhancements toward an easy Windows build 1257 and release</li> 1258 <li>Late validation fixes</li> 1259 <li>Integrated a lot of contributed patches</li> 1260 <li>added memory management docs</li> 1261 <li>a performance problem when using large buffer seems fixed</li> 1262</ul> 1263 1264<h3>2.2.4: Oct 1 2000:</h3> 1265<ul> 1266 <li>main XPath problem fixed</li> 1267 <li>Integrated portability patches for Windows</li> 1268 <li>Serious bug fixes on the URI and HTML code</li> 1269</ul> 1270 1271<h3>2.2.3: Sep 17 2000</h3> 1272<ul> 1273 <li>bug fixes</li> 1274 <li>cleanup of entity handling code</li> 1275 <li>overall review of all loops in the parsers, all sprintf usage has been 1276 checked too</li> 1277 <li>Far better handling of larges Dtd. Validating against DocBook XML Dtd 1278 works smoothly now.</li> 1279</ul> 1280 1281<h3>1.8.10: Sep 6 2000</h3> 1282<ul> 1283 <li>bug fix release for some Gnome projects</li> 1284</ul> 1285 1286<h3>2.2.2: August 12 2000</h3> 1287<ul> 1288 <li>mostly bug fixes</li> 1289 <li>started adding routines to access xml parser context options</li> 1290</ul> 1291 1292<h3>2.2.1: July 21 2000</h3> 1293<ul> 1294 <li>a purely bug fixes release</li> 1295 <li>fixed an encoding support problem when parsing from a memory block</li> 1296 <li>fixed a DOCTYPE parsing problem</li> 1297 <li>removed a bug in the function allowing to override the memory 1298 allocation routines</li> 1299</ul> 1300 1301<h3>2.2.0: July 14 2000</h3> 1302<ul> 1303 <li>applied a lot of portability fixes</li> 1304 <li>better encoding support/cleanup and saving (content is now always 1305 encoded in UTF-8)</li> 1306 <li>the HTML parser now correctly handles encodings</li> 1307 <li>added xmlHasProp()</li> 1308 <li>fixed a serious problem with &#38;</li> 1309 <li>propagated the fix to FTP client</li> 1310 <li>cleanup, bugfixes, etc ...</li> 1311 <li>Added a page about <a href="encoding.html">libxml Internationalization 1312 support</a></li> 1313</ul> 1314 1315<h3>1.8.9: July 9 2000</h3> 1316<ul> 1317 <li>fixed the spec the RPMs should be better</li> 1318 <li>fixed a serious bug in the FTP implementation, released 1.8.9 to solve 1319 rpmfind users problem</li> 1320</ul> 1321 1322<h3>2.1.1: July 1 2000</h3> 1323<ul> 1324 <li>fixes a couple of bugs in the 2.1.0 packaging</li> 1325 <li>improvements on the HTML parser</li> 1326</ul> 1327 1328<h3>2.1.0 and 1.8.8: June 29 2000</h3> 1329<ul> 1330 <li>1.8.8 is mostly a commodity package for upgrading to libxml2 according 1331 to <a href="upgrade.html">new instructions</a>. It fixes a nasty problem 1332 about &#38; charref parsing</li> 1333 <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it 1334 also contains numerous fixes and enhancements: 1335 <ul> 1336 <li>added xmlStopParser() to stop parsing</li> 1337 <li>improved a lot parsing speed when there is large CDATA blocs</li> 1338 <li>includes XPath patches provided by Picdar Technology</li> 1339 <li>tried to fix as much as possible DTD validation and namespace 1340 related problems</li> 1341 <li>output to a given encoding has been added/tested</li> 1342 <li>lot of various fixes</li> 1343 </ul> 1344 </li> 1345</ul> 1346 1347<h3>2.0.0: Apr 12 2000</h3> 1348<ul> 1349 <li>First public release of libxml2. If you are using libxml, it's a good 1350 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initially 1351 scheduled for Apr 3 the release occurred only on Apr 12 due to massive 1352 workload.</li> 1353 <li>The include are now located under $prefix/include/libxml (instead of 1354 $prefix/include/gnome-xml), they also are referenced by 1355 <pre>#include <libxml/xxx.h></pre> 1356 <p>instead of</p> 1357 <pre>#include "xxx.h"</pre> 1358 </li> 1359 <li>a new URI module for parsing URIs and following strictly RFC 2396</li> 1360 <li>the memory allocation routines used by libxml can now be overloaded 1361 dynamically by using xmlMemSetup()</li> 1362 <li>The previously CVS only tool tester has been renamed 1363 <strong>xmllint</strong> and is now installed as part of the libxml2 1364 package</li> 1365 <li>The I/O interface has been revamped. There is now ways to plug in 1366 specific I/O modules, either at the URI scheme detection level using 1367 xmlRegisterInputCallbacks() or by passing I/O functions when creating a 1368 parser context using xmlCreateIOParserCtxt()</li> 1369 <li>there is a C preprocessor macro LIBXML_VERSION providing the version 1370 number of the libxml module in use</li> 1371 <li>a number of optional features of libxml can now be excluded at 1372 configure time (FTP/HTTP/HTML/XPath/Debug)</li> 1373</ul> 1374 1375<h3>2.0.0beta: Mar 14 2000</h3> 1376<ul> 1377 <li>This is a first Beta release of libxml version 2</li> 1378 <li>It's available only from<a href="ftp://xmlsoft.org/">xmlsoft.org 1379 FTP</a>, it's packaged as libxml2-2.0.0beta and available as tar and 1380 RPMs</li> 1381 <li>This version is now the head in the Gnome CVS base, the old one is 1382 available under the tag LIB_XML_1_X</li> 1383 <li>This includes a very large set of changes. From a programmatic point 1384 of view applications should not have to be modified too much, check the 1385 <a href="upgrade.html">upgrade page</a></li> 1386 <li>Some interfaces may changes (especially a bit about encoding).</li> 1387 <li>the updates includes: 1388 <ul> 1389 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly 1390 handled now</li> 1391 <li>Better handling of entities, especially well-formedness checking 1392 and proper PEref extensions in external subsets</li> 1393 <li>DTD conditional sections</li> 1394 <li>Validation now correctly handle entities content</li> 1395 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change 1396 structures to accommodate DOM</a></li> 1397 </ul> 1398 </li> 1399 <li>Serious progress were made toward compliance, <a 1400 href="conf/result.html">here are the result of the test</a> against the 1401 OASIS testsuite (except the Japanese tests since I don't support that 1402 encoding yet). This URL is rebuilt every couple of hours using the CVS 1403 head version.</li> 1404</ul> 1405 1406<h3>1.8.7: Mar 6 2000</h3> 1407<ul> 1408 <li>This is a bug fix release:</li> 1409 <li>It is possible to disable the ignorable blanks heuristic used by 1410 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note 1411 that for adherence to XML spec, this behaviour will be disabled by 1412 default in 2.x . The same function will allow to keep compatibility for 1413 old code.</li> 1414 <li>Blanks in <a> </a> constructs are not ignored anymore, 1415 avoiding heuristic is really the Right Way :-\</li> 1416 <li>The unchecked use of snprintf which was breaking libxml-1.8.6 1417 compilation on some platforms has been fixed</li> 1418 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing 1419 URIs</li> 1420</ul> 1421 1422<h3>1.8.6: Jan 31 2000</h3> 1423<ul> 1424 <li>added a nanoFTP transport module, debugged until the new version of <a 1425 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use 1426 it without troubles</li> 1427</ul> 1428 1429<h3>1.8.5: Jan 21 2000</h3> 1430<ul> 1431 <li>adding APIs to parse a well balanced chunk of XML (production <a 1432 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the 1433 XML spec)</li> 1434 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li> 1435 <li>Jody Goldberg <jgoldberg@home.com> provided another patch trying 1436 to solve the zlib checks problems</li> 1437 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with 1438 gnumeric soon</li> 1439</ul> 1440 1441<h3>1.8.4: Jan 13 2000</h3> 1442<ul> 1443 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li> 1444 <li>all exit() call should have been removed from libxml</li> 1445 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li> 1446 <li>added newDocFragment()</li> 1447</ul> 1448 1449<h3>1.8.3: Jan 5 2000</h3> 1450<ul> 1451 <li>a Push interface for the XML and HTML parsers</li> 1452 <li>a shell-like interface to the document tree (try tester --shell :-)</li> 1453 <li>lots of bug fixes and improvement added over XMas holidays</li> 1454 <li>fixed the DTD parsing code to work with the xhtml DTD</li> 1455 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li> 1456 <li>Fixed bugs in xmlNewNs()</li> 1457 <li>External entity loading code has been revamped, now it uses 1458 xmlLoadExternalEntity(), some fix on entities processing were added</li> 1459 <li>cleaned up WIN32 includes of socket stuff</li> 1460</ul> 1461 1462<h3>1.8.2: Dec 21 1999</h3> 1463<ul> 1464 <li>I got another problem with includes and C++, I hope this issue is fixed 1465 for good this time</li> 1466 <li>Added a few tree modification functions: xmlReplaceNode, 1467 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and 1468 xmlDocSetRootElement</li> 1469 <li>Tried to improve the HTML output with help from <a 1470 href="mailto:clahey@umich.edu">Chris Lahey</a></li> 1471</ul> 1472 1473<h3>1.8.1: Dec 18 1999</h3> 1474<ul> 1475 <li>various patches to avoid troubles when using libxml with C++ compilers 1476 the "namespace" keyword and C escaping in include files</li> 1477 <li>a problem in one of the core macros IS_CHAR was corrected</li> 1478 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing, 1479 and more specifically the Dia application</li> 1480 <li>fixed a posteriori validation (validation after parsing, or by using a 1481 Dtd not specified in the original document)</li> 1482 <li>fixed a bug in</li> 1483</ul> 1484 1485<h3>1.8.0: Dec 12 1999</h3> 1486<ul> 1487 <li>cleanup, especially memory wise</li> 1488 <li>the parser should be more reliable, especially the HTML one, it should 1489 not crash, whatever the input !</li> 1490 <li>Integrated various patches, especially a speedup improvement for large 1491 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>, 1492 configure with --with-buffers to enable them.</li> 1493 <li>attribute normalization, oops should have been added long ago !</li> 1494 <li>attributes defaulted from DTDs should be available, xmlSetProp() now 1495 does entities escaping by default.</li> 1496</ul> 1497 1498<h3>1.7.4: Oct 25 1999</h3> 1499<ul> 1500 <li>Lots of HTML improvement</li> 1501 <li>Fixed some errors when saving both XML and HTML</li> 1502 <li>More examples, the regression tests should now look clean</li> 1503 <li>Fixed a bug with contiguous charref</li> 1504</ul> 1505 1506<h3>1.7.3: Sep 29 1999</h3> 1507<ul> 1508 <li>portability problems fixed</li> 1509 <li>snprintf was used unconditionally, leading to link problems on system 1510 were it's not available, fixed</li> 1511</ul> 1512 1513<h3>1.7.1: Sep 24 1999</h3> 1514<ul> 1515 <li>The basic type for strings manipulated by libxml has been renamed in 1516 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason 1517 is that CHAR was conflicting with a predefined type on Windows. However 1518 on non WIN32 environment, compatibility is provided by the way of a 1519 <strong>#define </strong>.</li> 1520 <li>Changed another error : the use of a structure field called errno, and 1521 leading to troubles on platforms where it's a macro</li> 1522</ul> 1523 1524<h3>1.7.0: Sep 23 1999</h3> 1525<ul> 1526 <li>Added the ability to fetch remote DTD or parsed entities, see the <a 1527 href="html/libxml-nanohttp.html">nanohttp</a> module.</li> 1528 <li>Added an errno to report errors by another mean than a simple printf 1529 like callback</li> 1530 <li>Finished ID/IDREF support and checking when validation</li> 1531 <li>Serious memory leaks fixed (there is now a <a 1532 href="html/libxml-xmlmemory.html">memory wrapper</a> module)</li> 1533 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a> 1534 implementation</li> 1535 <li>Added an HTML parser front-end</li> 1536</ul> 1537 1538<h2><a name="XML">XML</a></h2> 1539 1540<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for 1541markup-based structured documents. Here is <a name="example">an example XML 1542document</a>:</p> 1543<pre><?xml version="1.0"?> 1544<EXAMPLE prop1="gnome is great" prop2="&amp; linux too"> 1545 <head> 1546 <title>Welcome to Gnome</title> 1547 </head> 1548 <chapter> 1549 <title>The Linux adventure</title> 1550 <p>bla bla bla ...</p> 1551 <image href="linus.gif"/> 1552 <p>...</p> 1553 </chapter> 1554</EXAMPLE></pre> 1555 1556<p>The first line specifies that it is an XML document and gives useful 1557information about its encoding. Then the rest of the document is a text 1558format whose structure is specified by tags between brackets. <strong>Each 1559tag opened has to be closed</strong>. XML is pedantic about this. However, if 1560a tag is empty (no content), a single tag can serve as both the opening and 1561closing tag if it ends with <code>/></code> rather than with 1562<code>></code>. Note that, for example, the image tag has no content (just 1563an attribute) and is closed by ending the tag with <code>/></code>.</p> 1564 1565<p>XML can be applied successfully to a wide range of tasks, ranging from 1566long term structured document maintenance (where it follows the steps of 1567SGML) to simple data encoding mechanisms like configuration file formatting 1568(glade), spreadsheets (gnumeric), or even shorter lived documents such as 1569WebDAV where it is used to encode remote calls between a client and a 1570server.</p> 1571 1572<h2><a name="XSLT">XSLT</a></h2> 1573 1574<p>Check <a href="http://xmlsoft.org/XSLT">the separate libxslt page</a></p> 1575 1576<p><a href="http://www.w3.org/TR/xslt">XSL Transformations</a>, is a 1577language for transforming XML documents into other XML documents (or 1578HTML/textual output).</p> 1579 1580<p>A separate library called libxslt is being developed on top of libxml2. 1581This module "libxslt" too can be found in the Gnome CVS base.</p> 1582 1583<p>You can check the <a 1584href="http://cvs.gnome.org/lxr/source/libxslt/FEATURES">features</a> 1585supported and the progresses on the <a 1586href="http://cvs.gnome.org/lxr/source/libxslt/ChangeLog" 1587name="Changelog">Changelog</a>.</p> 1588 1589<h2><a name="Python">Python and bindings</a></h2> 1590 1591<p>There are a number of language bindings and wrappers available for 1592libxml2, the list below is not exhaustive. Please contact the <a 1593href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a> 1594(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in 1595order to get updates to this list or to discuss the specific topic of libxml2 1596or libxslt wrappers or bindings:</p> 1597<ul> 1598 <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the 1599 most up-to-date C++ bindings for libxml2, check the <a 1600 href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> 1601 and the <a 1602 href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> 1603 <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper 1604 based on the gdome2 bindings</a> maintained by Tobias Peters.</li> 1605 <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> 1606 <p>Website: <a 1607 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 1608 </li> 1609 <li><a 1610 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 1611 Sergeant</a> developed <a 1612 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 1613 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 1614 application server</a>.</li> 1615 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an 1616 earlier version of the libxml/libxslt <a 1617 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> 1618 <li>Gopal.V and Peter Minten develop <a 1619 href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of 1620 C# libxml2 bindings.</li> 1621 <li>Petr Kozelka provides <a 1622 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 1623 libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> 1624 <li>Uwe Fechner also provides <a 1625 href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 1626 implementation for Kylix2/D5/D6 from Borland.</li> 1627 <li>Wai-Sun "Squidster" Chia provides <a 1628 href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and 1629 libxml2 bindings are also available in Ruby through the <a 1630 href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module 1631 maintained by Tobias Peters.</li> 1632 <li>Steve Ball and contributors maintains <a 1633 href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for 1634 Tcl</a>.</li> 1635 <li>There is support for libxml2 in the DOM module of PHP.</li> 1636</ul> 1637 1638<p>The distribution includes a set of Python bindings, which are guaranteed 1639to be maintained as part of the library in the future, though the Python 1640interface have not yet reached the maturity of the C API.</p> 1641 1642<p><a href="mailto:stephane.bidoul@softwareag.com">St�phane Bidoul</a> 1643maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port 1644of the Python bindings</a>.</p> 1645 1646<p>Note to people interested in building bindings, the API is formalized as 1647<a href="libxml2-api.xml">an XML API description file</a> which allows to 1648automate a large part of the Python bindings, this includes function 1649descriptions, enums, structures, typedefs, etc... The Python script used to 1650build the bindings is python/generator.py in the source distribution.</p> 1651 1652<p>To install the Python bindings there are 2 options:</p> 1653<ul> 1654 <li>If you use an RPM based distribution, simply install the <a 1655 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python 1656 RPM</a> (and if needed the <a 1657 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python 1658 RPM</a>).</li> 1659 <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python 1660 module distribution</a> corresponding to your installed version of 1661 libxml2 and libxslt. Note that to install it you will need both libxml2 1662 and libxslt installed and run "python setup.py build install" in the 1663 module tree.</li> 1664</ul> 1665 1666<p>The distribution includes a set of examples and regression tests for the 1667python bindings in the <code>python/tests</code> directory. Here are some 1668excerpts from those tests:</p> 1669 1670<h3>tst.py:</h3> 1671 1672<p>This is a basic test of the file interface and DOM navigation:</p> 1673<pre>import libxml2 1674 1675doc = libxml2.parseFile("tst.xml") 1676if doc.name != "tst.xml": 1677 print "doc.name failed" 1678 sys.exit(1) 1679root = doc.children 1680if root.name != "doc": 1681 print "root.name failed" 1682 sys.exit(1) 1683child = root.children 1684if child.name != "foo": 1685 print "child.name failed" 1686 sys.exit(1) 1687doc.freeDoc()</pre> 1688 1689<p>The Python module is called libxml2; parseFile is the equivalent of 1690xmlParseFile (most of the bindings are automatically generated, and the xml 1691prefix is removed and the casing convention are kept). All node seen at the 1692binding level share the same subset of accessors:</p> 1693<ul> 1694 <li><code>name</code> : returns the node name</li> 1695 <li><code>type</code> : returns a string indicating the node type</li> 1696 <li><code>content</code> : returns the content of the node, it is based on 1697 xmlNodeGetContent() and hence is recursive.</li> 1698 <li><code>parent</code> , <code>children</code>, <code>last</code>, 1699 <code>next</code>, <code>prev</code>, <code>doc</code>, 1700 <code>properties</code>: pointing to the associated element in the tree, 1701 those may return None in case no such link exists.</li> 1702</ul> 1703 1704<p>Also note the need to explicitly deallocate documents with freeDoc() . 1705Reference counting for libxml2 trees would need quite a lot of work to 1706function properly, and rather than risk memory leaks if not implemented 1707correctly it sounds safer to have an explicit function to free a tree. The 1708wrapper python objects like doc, root or child are them automatically garbage 1709collected.</p> 1710 1711<h3>validate.py:</h3> 1712 1713<p>This test check the validation interfaces and redirection of error 1714messages:</p> 1715<pre>import libxml2 1716 1717#deactivate error messages from the validation 1718def noerr(ctx, str): 1719 pass 1720 1721libxml2.registerErrorHandler(noerr, None) 1722 1723ctxt = libxml2.createFileParserCtxt("invalid.xml") 1724ctxt.validate(1) 1725ctxt.parseDocument() 1726doc = ctxt.doc() 1727valid = ctxt.isValid() 1728doc.freeDoc() 1729if valid != 0: 1730 print "validity check failed"</pre> 1731 1732<p>The first thing to notice is the call to registerErrorHandler(), it 1733defines a new error handler global to the library. It is used to avoid seeing 1734the error messages when trying to validate the invalid document.</p> 1735 1736<p>The main interest of that test is the creation of a parser context with 1737createFileParserCtxt() and how the behaviour can be changed before calling 1738parseDocument() . Similarly the informations resulting from the parsing phase 1739are also available using context methods.</p> 1740 1741<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the 1742C function interfaces in terms of objects method as much as possible. The 1743best to get a complete view of what methods are supported is to look at the 1744libxml2.py module containing all the wrappers.</p> 1745 1746<h3>push.py:</h3> 1747 1748<p>This test show how to activate the push parser interface:</p> 1749<pre>import libxml2 1750 1751ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") 1752ctxt.parseChunk("/>", 2, 1) 1753doc = ctxt.doc() 1754 1755doc.freeDoc()</pre> 1756 1757<p>The context is created with a special call based on the 1758xmlCreatePushParser() from the C library. The first argument is an optional 1759SAX callback object, then the initial set of data, the length and the name of 1760the resource in case URI-References need to be computed by the parser.</p> 1761 1762<p>Then the data are pushed using the parseChunk() method, the last call 1763setting the third argument terminate to 1.</p> 1764 1765<h3>pushSAX.py:</h3> 1766 1767<p>this test show the use of the event based parsing interfaces. In this case 1768the parser does not build a document, but provides callback information as 1769the parser makes progresses analyzing the data being provided:</p> 1770<pre>import libxml2 1771log = "" 1772 1773class callback: 1774 def startDocument(self): 1775 global log 1776 log = log + "startDocument:" 1777 1778 def endDocument(self): 1779 global log 1780 log = log + "endDocument:" 1781 1782 def startElement(self, tag, attrs): 1783 global log 1784 log = log + "startElement %s %s:" % (tag, attrs) 1785 1786 def endElement(self, tag): 1787 global log 1788 log = log + "endElement %s:" % (tag) 1789 1790 def characters(self, data): 1791 global log 1792 log = log + "characters: %s:" % (data) 1793 1794 def warning(self, msg): 1795 global log 1796 log = log + "warning: %s:" % (msg) 1797 1798 def error(self, msg): 1799 global log 1800 log = log + "error: %s:" % (msg) 1801 1802 def fatalError(self, msg): 1803 global log 1804 log = log + "fatalError: %s:" % (msg) 1805 1806handler = callback() 1807 1808ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") 1809chunk = " url='tst'>b" 1810ctxt.parseChunk(chunk, len(chunk), 0) 1811chunk = "ar</foo>" 1812ctxt.parseChunk(chunk, len(chunk), 1) 1813 1814reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 1815 "characters: bar:endElement foo:endDocument:" 1816if log != reference: 1817 print "Error got: %s" % log 1818 print "Expected: %s" % reference</pre> 1819 1820<p>The key object in that test is the handler, it provides a number of entry 1821points which can be called by the parser as it makes progresses to indicate 1822the information set obtained. The full set of callback is larger than what 1823the callback class in that specific example implements (see the SAX 1824definition for a complete list). The wrapper will only call those supplied by 1825the object when activated. The startElement receives the names of the element 1826and a dictionary containing the attributes carried by this element.</p> 1827 1828<p>Also note that the reference string generated from the callback shows a 1829single character call even though the string "bar" is passed to the parser 1830from 2 different call to parseChunk()</p> 1831 1832<h3>xpath.py:</h3> 1833 1834<p>This is a basic test of XPath wrappers support</p> 1835<pre>import libxml2 1836 1837doc = libxml2.parseFile("tst.xml") 1838ctxt = doc.xpathNewContext() 1839res = ctxt.xpathEval("//*") 1840if len(res) != 2: 1841 print "xpath query: wrong node set size" 1842 sys.exit(1) 1843if res[0].name != "doc" or res[1].name != "foo": 1844 print "xpath query: wrong node set value" 1845 sys.exit(1) 1846doc.freeDoc() 1847ctxt.xpathFreeContext()</pre> 1848 1849<p>This test parses a file, then create an XPath context to evaluate XPath 1850expression on it. The xpathEval() method execute an XPath query and returns 1851the result mapped in a Python way. String and numbers are natively converted, 1852and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like 1853the document, the XPath context need to be freed explicitly, also not that 1854the result of the XPath query may point back to the document tree and hence 1855the document must be freed after the result of the query is used.</p> 1856 1857<h3>xpathext.py:</h3> 1858 1859<p>This test shows how to extend the XPath engine with functions written in 1860python:</p> 1861<pre>import libxml2 1862 1863def foo(ctx, x): 1864 return x + 1 1865 1866doc = libxml2.parseFile("tst.xml") 1867ctxt = doc.xpathNewContext() 1868libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) 1869res = ctxt.xpathEval("foo(1)") 1870if res != 2: 1871 print "xpath extension failure" 1872doc.freeDoc() 1873ctxt.xpathFreeContext()</pre> 1874 1875<p>Note how the extension function is registered with the context (but that 1876part is not yet finalized, this may change slightly in the future).</p> 1877 1878<h3>tstxpath.py:</h3> 1879 1880<p>This test is similar to the previous one but shows how the extension 1881function can access the XPath evaluation context:</p> 1882<pre>def foo(ctx, x): 1883 global called 1884 1885 # 1886 # test that access to the XPath evaluation contexts 1887 # 1888 pctxt = libxml2.xpathParserContext(_obj=ctx) 1889 ctxt = pctxt.context() 1890 called = ctxt.function() 1891 return x + 1</pre> 1892 1893<p>All the interfaces around the XPath parser(or rather evaluation) context 1894are not finalized, but it should be sufficient to do contextual work at the 1895evaluation point.</p> 1896 1897<h3>Memory debugging:</h3> 1898 1899<p>last but not least, all tests starts with the following prologue:</p> 1900<pre>#memory debug specific 1901libxml2.debugMemory(1)</pre> 1902 1903<p>and ends with the following epilogue:</p> 1904<pre>#memory debug specific 1905libxml2.cleanupParser() 1906if libxml2.debugMemory(1) == 0: 1907 print "OK" 1908else: 1909 print "Memory leak %d bytes" % (libxml2.debugMemory(1)) 1910 libxml2.dumpMemory()</pre> 1911 1912<p>Those activate the memory debugging interface of libxml2 where all 1913allocated block in the library are tracked. The prologue then cleans up the 1914library state and checks that all allocated memory has been freed. If not it 1915calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p> 1916 1917<h2><a name="architecture">libxml architecture</a></h2> 1918 1919<p>Libxml is made of multiple components; some of them are optional, and most 1920of the block interfaces are public. The main components are:</p> 1921<ul> 1922 <li>an Input/Output layer</li> 1923 <li>FTP and HTTP client layers (optional)</li> 1924 <li>an Internationalization layer managing the encodings support</li> 1925 <li>a URI module</li> 1926 <li>the XML parser and its basic SAX interface</li> 1927 <li>an HTML parser using the same SAX interface (optional)</li> 1928 <li>a SAX tree module to build an in-memory DOM representation</li> 1929 <li>a tree module to manipulate the DOM representation</li> 1930 <li>a validation module using the DOM representation (optional)</li> 1931 <li>an XPath module for global lookup in a DOM representation 1932 (optional)</li> 1933 <li>a debug module (optional)</li> 1934</ul> 1935 1936<p>Graphically this gives the following:</p> 1937 1938<p><img src="libxml.gif" alt="a graphical view of the various"></p> 1939 1940<p></p> 1941 1942<h2><a name="tree">The tree output</a></h2> 1943 1944<p>The parser returns a tree built during the document analysis. The value 1945returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an 1946<strong>xmlDoc</strong> structure). This structure contains information such 1947as the file name, the document type, and a <strong>children</strong> pointer 1948which is the root of the document (or more exactly the first child under the 1949root which is the document). The tree is made of <strong>xmlNode</strong>s, 1950chained in double-linked lists of siblings and with a children<->parent 1951relationship. An xmlNode can also carry properties (a chain of xmlAttr 1952structures). An attribute may have a value which is a list of TEXT or 1953ENTITY_REF nodes.</p> 1954 1955<p>Here is an example (erroneous with respect to the XML spec since there 1956should be only one ELEMENT under the root):</p> 1957 1958<p><img src="structure.gif" alt=" structure.gif "></p> 1959 1960<p>In the source package there is a small program (not installed by default) 1961called <strong>xmllint</strong> which parses XML files given as argument and 1962prints them back as parsed. This is useful for detecting errors both in XML 1963code and in the XML parser itself. It has an option <strong>--debug</strong> 1964which prints the actual in-memory structure of the document; here is the 1965result with the <a href="#example">example</a> given before:</p> 1966<pre>DOCUMENT 1967version=1.0 1968standalone=true 1969 ELEMENT EXAMPLE 1970 ATTRIBUTE prop1 1971 TEXT 1972 content=gnome is great 1973 ATTRIBUTE prop2 1974 ENTITY_REF 1975 TEXT 1976 content= linux too 1977 ELEMENT head 1978 ELEMENT title 1979 TEXT 1980 content=Welcome to Gnome 1981 ELEMENT chapter 1982 ELEMENT title 1983 TEXT 1984 content=The Linux adventure 1985 ELEMENT p 1986 TEXT 1987 content=bla bla bla ... 1988 ELEMENT image 1989 ATTRIBUTE href 1990 TEXT 1991 content=linus.gif 1992 ELEMENT p 1993 TEXT 1994 content=...</pre> 1995 1996<p>This should be useful for learning the internal representation model.</p> 1997 1998<h2><a name="interface">The SAX interface</a></h2> 1999 2000<p>Sometimes the DOM tree output is just too large to fit reasonably into 2001memory. In that case (and if you don't expect to save back the XML document 2002loaded using libxml), it's better to use the SAX interface of libxml. SAX is 2003a <strong>callback-based interface</strong> to the parser. Before parsing, 2004the application layer registers a customized set of callbacks which are 2005called by the library as it progresses through the XML input.</p> 2006 2007<p>To get more detailed step-by-step guidance on using the SAX interface of 2008libxml, see the <a 2009href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice 2010documentation</a>.written by <a href="mailto:james@daa.com.au">James 2011Henstridge</a>.</p> 2012 2013<p>You can debug the SAX behaviour by using the <strong>testSAX</strong> 2014program located in the gnome-xml module (it's usually not shipped in the 2015binary packages of libxml, but you can find it in the tar source 2016distribution). Here is the sequence of callbacks that would be reported by 2017testSAX when parsing the example XML document shown earlier:</p> 2018<pre>SAX.setDocumentLocator() 2019SAX.startDocument() 2020SAX.getEntity(amp) 2021SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too') 2022SAX.characters( , 3) 2023SAX.startElement(head) 2024SAX.characters( , 4) 2025SAX.startElement(title) 2026SAX.characters(Welcome to Gnome, 16) 2027SAX.endElement(title) 2028SAX.characters( , 3) 2029SAX.endElement(head) 2030SAX.characters( , 3) 2031SAX.startElement(chapter) 2032SAX.characters( , 4) 2033SAX.startElement(title) 2034SAX.characters(The Linux adventure, 19) 2035SAX.endElement(title) 2036SAX.characters( , 4) 2037SAX.startElement(p) 2038SAX.characters(bla bla bla ..., 15) 2039SAX.endElement(p) 2040SAX.characters( , 4) 2041SAX.startElement(image, href='linus.gif') 2042SAX.endElement(image) 2043SAX.characters( , 4) 2044SAX.startElement(p) 2045SAX.characters(..., 3) 2046SAX.endElement(p) 2047SAX.characters( , 3) 2048SAX.endElement(chapter) 2049SAX.characters( , 1) 2050SAX.endElement(EXAMPLE) 2051SAX.endDocument()</pre> 2052 2053<p>Most of the other interfaces of libxml are based on the DOM tree-building 2054facility, so nearly everything up to the end of this document presupposes the 2055use of the standard DOM tree build. Note that the DOM tree itself is built by 2056a set of registered default callbacks, without internal specific 2057interface.</p> 2058 2059<h2><a name="Validation">Validation & DTDs</a></h2> 2060 2061<p>Table of Content:</p> 2062<ol> 2063 <li><a href="#General5">General overview</a></li> 2064 <li><a href="#definition">The definition</a></li> 2065 <li><a href="#Simple">Simple rules</a> 2066 <ol> 2067 <li><a href="#reference">How to reference a DTD from a document</a></li> 2068 <li><a href="#Declaring">Declaring elements</a></li> 2069 <li><a href="#Declaring1">Declaring attributes</a></li> 2070 </ol> 2071 </li> 2072 <li><a href="#Some">Some examples</a></li> 2073 <li><a href="#validate">How to validate</a></li> 2074 <li><a href="#Other">Other resources</a></li> 2075</ol> 2076 2077<h3><a name="General5">General overview</a></h3> 2078 2079<p>Well what is validation and what is a DTD ?</p> 2080 2081<p>DTD is the acronym for Document Type Definition. This is a description of 2082the content for a family of XML files. This is part of the XML 1.0 2083specification, and allows one to describe and verify that a given document 2084instance conforms to the set of rules detailing its structure and content.</p> 2085 2086<p>Validation is the process of checking a document against a DTD (more 2087generally against a set of construction rules).</p> 2088 2089<p>The validation process and building DTDs are the two most difficult parts 2090of the XML life cycle. Briefly a DTD defines all the possible elements to be 2091found within your document, what is the formal shape of your document tree 2092(by defining the allowed content of an element; either text, a regular 2093expression for the allowed list of children, or mixed content i.e. both text 2094and children). The DTD also defines the valid attributes for all elements and 2095the types of those attributes.</p> 2096 2097<h3><a name="definition1">The definition</a></h3> 2098 2099<p>The <a href="http://www.w3.org/TR/REC-xml">W3C XML Recommendation</a> (<a 2100href="http://www.xml.com/axml/axml.html">Tim Bray's annotated version of 2101Rev1</a>):</p> 2102<ul> 2103 <li><a href="http://www.w3.org/TR/REC-xml#elemdecls">Declaring 2104 elements</a></li> 2105 <li><a href="http://www.w3.org/TR/REC-xml#attdecls">Declaring 2106 attributes</a></li> 2107</ul> 2108 2109<p>(unfortunately) all this is inherited from the SGML world, the syntax is 2110ancient...</p> 2111 2112<h3><a name="Simple1">Simple rules</a></h3> 2113 2114<p>Writing DTDs can be done in many ways. The rules to build them if you need 2115something permanent or something which can evolve over time can be radically 2116different. Really complex DTDs like DocBook ones are flexible but quite 2117harder to design. I will just focus on DTDs for a formats with a fixed simple 2118structure. It is just a set of basic rules, and definitely not exhaustive nor 2119usable for complex DTD design.</p> 2120 2121<h4><a name="reference1">How to reference a DTD from a document</a>:</h4> 2122 2123<p>Assuming the top element of the document is <code>spec</code> and the dtd 2124is placed in the file <code>mydtd</code> in the subdirectory 2125<code>dtds</code> of the directory from where the document were loaded:</p> 2126 2127<p><code><!DOCTYPE spec SYSTEM "dtds/mydtd"></code></p> 2128 2129<p>Notes:</p> 2130<ul> 2131 <li>The system string is actually an URI-Reference (as defined in <a 2132 href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>) so you can use a 2133 full URL string indicating the location of your DTD on the Web. This is a 2134 really good thing to do if you want others to validate your document.</li> 2135 <li>It is also possible to associate a <code>PUBLIC</code> identifier (a 2136 magic string) so that the DTD is looked up in catalogs on the client side 2137 without having to locate it on the web.</li> 2138 <li>A DTD contains a set of element and attribute declarations, but they 2139 don't define what the root of the document should be. This is explicitly 2140 told to the parser/validator as the first element of the 2141 <code>DOCTYPE</code> declaration.</li> 2142</ul> 2143 2144<h4><a name="Declaring2">Declaring elements</a>:</h4> 2145 2146<p>The following declares an element <code>spec</code>:</p> 2147 2148<p><code><!ELEMENT spec (front, body, back?)></code></p> 2149 2150<p>It also expresses that the spec element contains one <code>front</code>, 2151one <code>body</code> and one optional <code>back</code> children elements in 2152this order. The declaration of one element of the structure and its content 2153are done in a single declaration. Similarly the following declares 2154<code>div1</code> elements:</p> 2155 2156<p><code><!ELEMENT div1 (head, (p | list | note)*, div2?)></code></p> 2157 2158<p>which means div1 contains one <code>head</code> then a series of optional 2159<code>p</code>, <code>list</code>s and <code>note</code>s and then an 2160optional <code>div2</code>. And last but not least an element can contain 2161text:</p> 2162 2163<p><code><!ELEMENT b (#PCDATA)></code></p> 2164 2165<p><code>b</code> contains text or being of mixed content (text and elements 2166in no particular order):</p> 2167 2168<p><code><!ELEMENT p (#PCDATA|a|ul|b|i|em)*></code></p> 2169 2170<p><code>p </code>can contain text or <code>a</code>, <code>ul</code>, 2171<code>b</code>, <code>i </code>or <code>em</code> elements in no particular 2172order.</p> 2173 2174<h4><a name="Declaring1">Declaring attributes</a>:</h4> 2175 2176<p>Again the attributes declaration includes their content definition:</p> 2177 2178<p><code><!ATTLIST termdef name CDATA #IMPLIED></code></p> 2179 2180<p>means that the element <code>termdef</code> can have a <code>name</code> 2181attribute containing text (<code>CDATA</code>) and which is optional 2182(<code>#IMPLIED</code>). The attribute value can also be defined within a 2183set:</p> 2184 2185<p><code><!ATTLIST list type (bullets|ordered|glossary) 2186"ordered"></code></p> 2187 2188<p>means <code>list</code> element have a <code>type</code> attribute with 3 2189allowed values "bullets", "ordered" or "glossary" and which default to 2190"ordered" if the attribute is not explicitly specified.</p> 2191 2192<p>The content type of an attribute can be text (<code>CDATA</code>), 2193anchor/reference/references 2194(<code>ID</code>/<code>IDREF</code>/<code>IDREFS</code>), entity(ies) 2195(<code>ENTITY</code>/<code>ENTITIES</code>) or name(s) 2196(<code>NMTOKEN</code>/<code>NMTOKENS</code>). The following defines that a 2197<code>chapter</code> element can have an optional <code>id</code> attribute 2198of type <code>ID</code>, usable for reference from attribute of type 2199IDREF:</p> 2200 2201<p><code><!ATTLIST chapter id ID #IMPLIED></code></p> 2202 2203<p>The last value of an attribute definition can be <code>#REQUIRED 2204</code>meaning that the attribute has to be given, <code>#IMPLIED</code> 2205meaning that it is optional, or the default value (possibly prefixed by 2206<code>#FIXED</code> if it is the only allowed).</p> 2207 2208<p>Notes:</p> 2209<ul> 2210 <li>Usually the attributes pertaining to a given element are declared in a 2211 single expression, but it is just a convention adopted by a lot of DTD 2212 writers: 2213 <pre><!ATTLIST termdef 2214 id ID #REQUIRED 2215 name CDATA #IMPLIED></pre> 2216 <p>The previous construct defines both <code>id</code> and 2217 <code>name</code> attributes for the element <code>termdef</code>.</p> 2218 </li> 2219</ul> 2220 2221<h3><a name="Some1">Some examples</a></h3> 2222 2223<p>The directory <code>test/valid/dtds/</code> in the libxml distribution 2224contains some complex DTD examples. The example in the file 2225<code>test/valid/dia.xml</code> shows an XML file where the simple DTD is 2226directly included within the document.</p> 2227 2228<h3><a name="validate1">How to validate</a></h3> 2229 2230<p>The simplest way is to use the xmllint program included with libxml. The 2231<code>--valid</code> option turns-on validation of the files given as input. 2232For example the following validates a copy of the first revision of the XML 22331.0 specification:</p> 2234 2235<p><code>xmllint --valid --noout test/valid/REC-xml-19980210.xml</code></p> 2236 2237<p>the -- noout is used to disable output of the resulting tree.</p> 2238 2239<p>The <code>--dtdvalid dtd</code> allows validation of the document(s) 2240against a given DTD.</p> 2241 2242<p>Libxml exports an API to handle DTDs and validation, check the <a 2243href="http://xmlsoft.org/html/libxml-valid.html">associated 2244description</a>.</p> 2245 2246<h3><a name="Other1">Other resources</a></h3> 2247 2248<p>DTDs are as old as SGML. So there may be a number of examples on-line, I 2249will just list one for now, others pointers welcome:</p> 2250<ul> 2251 <li><a href="http://www.xml101.com:8081/dtd/">XML-101 DTD</a></li> 2252</ul> 2253 2254<p>I suggest looking at the examples found under test/valid/dtd and any of 2255the large number of books available on XML. The dia example in test/valid 2256should be both simple and complete enough to allow you to build your own.</p> 2257 2258<p></p> 2259 2260<h2><a name="Memory">Memory Management</a></h2> 2261 2262<p>Table of Content:</p> 2263<ol> 2264 <li><a href="#General3">General overview</a></li> 2265 <li><a href="#setting">Setting libxml set of memory routines</a></li> 2266 <li><a href="#cleanup">Cleaning up after parsing</a></li> 2267 <li><a href="#Debugging">Debugging routines</a></li> 2268 <li><a href="#General4">General memory requirements</a></li> 2269</ol> 2270 2271<h3><a name="General3">General overview</a></h3> 2272 2273<p>The module <code><a 2274href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlmemory.h</a></code> 2275provides the interfaces to the libxml memory system:</p> 2276<ul> 2277 <li>libxml does not use the libc memory allocator directly but xmlFree(), 2278 xmlMalloc() and xmlRealloc()</li> 2279 <li>those routines can be reallocated to a specific set of routine, by 2280 default the libc ones i.e. free(), malloc() and realloc()</li> 2281 <li>the xmlmemory.c module includes a set of debugging routine</li> 2282</ul> 2283 2284<h3><a name="setting">Setting libxml set of memory routines</a></h3> 2285 2286<p>It is sometimes useful to not use the default memory allocator, either for 2287debugging, analysis or to implement a specific behaviour on memory management 2288(like on embedded systems). Two function calls are available to do so:</p> 2289<ul> 2290 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemGet 2291 ()</a> which return the current set of functions in use by the parser</li> 2292 <li><a 2293 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemSetup()</a> 2294 which allow to set up a new set of memory allocation functions</li> 2295</ul> 2296 2297<p>Of course a call to xmlMemSetup() should probably be done before calling 2298any other libxml routines (unless you are sure your allocations routines are 2299compatibles).</p> 2300 2301<h3><a name="cleanup">Cleaning up after parsing</a></h3> 2302 2303<p>Libxml is not stateless, there is a few set of memory structures needing 2304allocation before the parser is fully functional (some encoding structures 2305for example). This also mean that once parsing is finished there is a tiny 2306amount of memory (a few hundred bytes) which can be recollected if you don't 2307reuse the parser immediately:</p> 2308<ul> 2309 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlCleanupParser 2310 ()</a> is a centralized routine to free the parsing states. Note that it 2311 won't deallocate any produced tree if any (use the xmlFreeDoc() and 2312 related routines for this).</li> 2313 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlInitParser 2314 ()</a> is the dual routine allowing to preallocate the parsing state 2315 which can be useful for example to avoid initialization reentrancy 2316 problems when using libxml in multithreaded applications</li> 2317</ul> 2318 2319<p>Generally xmlCleanupParser() is safe, if needed the state will be rebuild 2320at the next invocation of parser routines, but be careful of the consequences 2321in multithreaded applications.</p> 2322 2323<h3><a name="Debugging">Debugging routines</a></h3> 2324 2325<p>When configured using --with-mem-debug flag (off by default), libxml uses 2326a set of memory allocation debugging routines keeping track of all allocated 2327blocks and the location in the code where the routine was called. A couple of 2328other debugging routines allow to dump the memory allocated infos to a file 2329or call a specific routine when a given block number is allocated:</p> 2330<ul> 2331 <li><a 2332 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMallocLoc()</a> 2333 <a 2334 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlReallocLoc()</a> 2335 and <a 2336 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemStrdupLoc()</a> 2337 are the memory debugging replacement allocation routines</li> 2338 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemoryDump 2339 ()</a> dumps all the informations about the allocated memory block lefts 2340 in the <code>.memdump</code> file</li> 2341</ul> 2342 2343<p>When developing libxml memory debug is enabled, the tests programs call 2344xmlMemoryDump () and the "make test" regression tests will check for any 2345memory leak during the full regression test sequence, this helps a lot 2346ensuring that libxml does not leak memory and bullet proof memory 2347allocations use (some libc implementations are known to be far too permissive 2348resulting in major portability problems!).</p> 2349 2350<p>If the .memdump reports a leak, it displays the allocation function and 2351also tries to give some informations about the content and structure of the 2352allocated blocks left. This is sufficient in most cases to find the culprit, 2353but not always. Assuming the allocation problem is reproducible, it is 2354possible to find more easily:</p> 2355<ol> 2356 <li>write down the block number xxxx not allocated</li> 2357 <li>export the environment variable XML_MEM_BREAKPOINT=xxxx , the easiest 2358 when using GDB is to simply give the command 2359 <p><code>set environment XML_MEM_BREAKPOINT xxxx</code></p> 2360 <p>before running the program.</p> 2361 </li> 2362 <li>run the program under a debugger and set a breakpoint on 2363 xmlMallocBreakpoint() a specific function called when this precise block 2364 is allocated</li> 2365 <li>when the breakpoint is reached you can then do a fine analysis of the 2366 allocation an step to see the condition resulting in the missing 2367 deallocation.</li> 2368</ol> 2369 2370<p>I used to use a commercial tool to debug libxml memory problems but after 2371noticing that it was not detecting memory leaks that simple mechanism was 2372used and proved extremely efficient until now. Lately I have also used <a 2373href="http://developer.kde.org/~sewardj/">valgrind</a> with quite some 2374success, it is tied to the i386 architecture since it works by emulating the 2375processor and instruction set, it is slow but extremely efficient, i.e. it 2376spot memory usage errors in a very precise way.</p> 2377 2378<h3><a name="General4">General memory requirements</a></h3> 2379 2380<p>How much libxml memory require ? It's hard to tell in average it depends 2381of a number of things:</p> 2382<ul> 2383 <li>the parser itself should work in a fixed amount of memory, except for 2384 information maintained about the stacks of names and entities locations. 2385 The I/O and encoding handlers will probably account for a few KBytes. 2386 This is true for both the XML and HTML parser (though the HTML parser 2387 need more state).</li> 2388 <li>If you are generating the DOM tree then memory requirements will grow 2389 nearly linear with the size of the data. In general for a balanced 2390 textual document the internal memory requirement is about 4 times the 2391 size of the UTF8 serialization of this document (example the XML-1.0 2392 recommendation is a bit more of 150KBytes and takes 650KBytes of main 2393 memory when parsed). Validation will add a amount of memory required for 2394 maintaining the external Dtd state which should be linear with the 2395 complexity of the content model defined by the Dtd</li> 2396 <li>If you don't care about the advanced features of libxml like 2397 validation, DOM, XPath or XPointer, but really need to work fixed memory 2398 requirements, then the SAX interface should be used.</li> 2399</ul> 2400 2401<p></p> 2402 2403<h2><a name="Encodings">Encodings support</a></h2> 2404 2405<p>Table of Content:</p> 2406<ol> 2407 <li><a href="encoding.html#What">What does internationalization support 2408 mean ?</a></li> 2409 <li><a href="encoding.html#internal">The internal encoding, how and 2410 why</a></li> 2411 <li><a href="encoding.html#implemente">How is it implemented ?</a></li> 2412 <li><a href="encoding.html#Default">Default supported encodings</a></li> 2413 <li><a href="encoding.html#extend">How to extend the existing 2414 support</a></li> 2415</ol> 2416 2417<h3><a name="What">What does internationalization support mean ?</a></h3> 2418 2419<p>XML was designed from the start to allow the support of any character set 2420by using Unicode. Any conformant XML parser has to support the UTF-8 and 2421UTF-16 default encodings which can both express the full unicode ranges. UTF8 2422is a variable length encoding whose greatest points are to reuse the same 2423encoding for ASCII and to save space for Western encodings, but it is a bit 2424more complex to handle in practice. UTF-16 use 2 bytes per characters (and 2425sometimes combines two pairs), it makes implementation easier, but looks a 2426bit overkill for Western languages encoding. Moreover the XML specification 2427allows document to be encoded in other encodings at the condition that they 2428are clearly labeled as such. For example the following is a wellformed XML 2429document encoded in ISO-8859 1 and using accentuated letter that we French 2430likes for both markup and content:</p> 2431<pre><?xml version="1.0" encoding="ISO-8859-1"?> 2432<tr�s>l�</tr�s></pre> 2433 2434<p>Having internationalization support in libxml means the following:</p> 2435<ul> 2436 <li>the document is properly parsed</li> 2437 <li>informations about it's encoding are saved</li> 2438 <li>it can be modified</li> 2439 <li>it can be saved in its original encoding</li> 2440 <li>it can also be saved in another encoding supported by libxml (for 2441 example straight UTF8 or even an ASCII form)</li> 2442</ul> 2443 2444<p>Another very important point is that the whole libxml API, with the 2445exception of a few routines to read with a specific encoding or save to a 2446specific encoding, is completely agnostic about the original encoding of the 2447document.</p> 2448 2449<p>It should be noted too that the HTML parser embedded in libxml now obey 2450the same rules too, the following document will be (as of 2.2.2) handled in 2451an internationalized fashion by libxml too:</p> 2452<pre><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" 2453 "http://www.w3.org/TR/REC-html40/loose.dtd"> 2454<html lang="fr"> 2455<head> 2456 <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"> 2457</head> 2458<body> 2459<p>W3C cr�e des standards pour le Web.</body> 2460</html></pre> 2461 2462<h3><a name="internal">The internal encoding, how and why</a></h3> 2463 2464<p>One of the core decision was to force all documents to be converted to a 2465default internal encoding, and that encoding to be UTF-8, here are the 2466rationale for those choices:</p> 2467<ul> 2468 <li>keeping the native encoding in the internal form would force the libxml 2469 users (or the code associated) to be fully aware of the encoding of the 2470 original document, for examples when adding a text node to a document, 2471 the content would have to be provided in the document encoding, i.e. the 2472 client code would have to check it before hand, make sure it's conformant 2473 to the encoding, etc ... Very hard in practice, though in some specific 2474 cases this may make sense.</li> 2475 <li>the second decision was which encoding. From the XML spec only UTF8 and 2476 UTF16 really makes sense as being the two only encodings for which there 2477 is mandatory support. UCS-4 (32 bits fixed size encoding) could be 2478 considered an intelligent choice too since it's a direct Unicode mapping 2479 support. I selected UTF-8 on the basis of efficiency and compatibility 2480 with surrounding software: 2481 <ul> 2482 <li>UTF-8 while a bit more complex to convert from/to (i.e. slightly 2483 more costly to import and export CPU wise) is also far more compact 2484 than UTF-16 (and UCS-4) for a majority of the documents I see it used 2485 for right now (RPM RDF catalogs, advogato data, various configuration 2486 file formats, etc.) and the key point for today's computer 2487 architecture is efficient uses of caches. If one nearly double the 2488 memory requirement to store the same amount of data, this will trash 2489 caches (main memory/external caches/internal caches) and my take is 2490 that this harms the system far more than the CPU requirements needed 2491 for the conversion to UTF-8</li> 2492 <li>Most of libxml version 1 users were using it with straight ASCII 2493 most of the time, doing the conversion with an internal encoding 2494 requiring all their code to be rewritten was a serious show-stopper 2495 for using UTF-16 or UCS-4.</li> 2496 <li>UTF-8 is being used as the de-facto internal encoding standard for 2497 related code like the <a href="http://www.pango.org/">pango</a> 2498 upcoming Gnome text widget, and a lot of Unix code (yep another place 2499 where Unix programmer base takes a different approach from Microsoft 2500 - they are using UTF-16)</li> 2501 </ul> 2502 </li> 2503</ul> 2504 2505<p>What does this mean in practice for the libxml user:</p> 2506<ul> 2507 <li>xmlChar, the libxml data type is a byte, those bytes must be assembled 2508 as UTF-8 valid strings. The proper way to terminate an xmlChar * string 2509 is simply to append 0 byte, as usual.</li> 2510 <li>One just need to make sure that when using chars outside the ASCII set, 2511 the values has been properly converted to UTF-8</li> 2512</ul> 2513 2514<h3><a name="implemente">How is it implemented ?</a></h3> 2515 2516<p>Let's describe how all this works within libxml, basically the I18N 2517(internationalization) support get triggered only during I/O operation, i.e. 2518when reading a document or saving one. Let's look first at the reading 2519sequence:</p> 2520<ol> 2521 <li>when a document is processed, we usually don't know the encoding, a 2522 simple heuristic allows to detect UTF-18 and UCS-4 from whose where the 2523 ASCII range (0-0x7F) maps with ASCII</li> 2524 <li>the xml declaration if available is parsed, including the encoding 2525 declaration. At that point, if the autodetected encoding is different 2526 from the one declared a call to xmlSwitchEncoding() is issued.</li> 2527 <li>If there is no encoding declaration, then the input has to be in either 2528 UTF-8 or UTF-16, if it is not then at some point when processing the 2529 input, the converter/checker of UTF-8 form will raise an encoding error. 2530 You may end-up with a garbled document, or no document at all ! Example: 2531 <pre>~/XML -> /xmllint err.xml 2532err.xml:1: error: Input is not proper UTF-8, indicate encoding ! 2533<tr�s>l�</tr�s> 2534 ^ 2535err.xml:1: error: Bytes: 0xE8 0x73 0x3E 0x6C 2536<tr�s>l�</tr�s> 2537 ^</pre> 2538 </li> 2539 <li>xmlSwitchEncoding() does an encoding name lookup, canonicalize it, and 2540 then search the default registered encoding converters for that encoding. 2541 If it's not within the default set and iconv() support has been compiled 2542 it, it will ask iconv for such an encoder. If this fails then the parser 2543 will report an error and stops processing: 2544 <pre>~/XML -> /xmllint err2.xml 2545err2.xml:1: error: Unsupported encoding UnsupportedEnc 2546<?xml version="1.0" encoding="UnsupportedEnc"?> 2547 ^</pre> 2548 </li> 2549 <li>From that point the encoder processes progressively the input (it is 2550 plugged as a front-end to the I/O module) for that entity. It captures 2551 and convert on-the-fly the document to be parsed to UTF-8. The parser 2552 itself just does UTF-8 checking of this input and process it 2553 transparently. The only difference is that the encoding information has 2554 been added to the parsing context (more precisely to the input 2555 corresponding to this entity).</li> 2556 <li>The result (when using DOM) is an internal form completely in UTF-8 2557 with just an encoding information on the document node.</li> 2558</ol> 2559 2560<p>Ok then what happens when saving the document (assuming you 2561collected/built an xmlDoc DOM like structure) ? It depends on the function 2562called, xmlSaveFile() will just try to save in the original encoding, while 2563xmlSaveFileTo() and xmlSaveFileEnc() can optionally save to a given 2564encoding:</p> 2565<ol> 2566 <li>if no encoding is given, libxml will look for an encoding value 2567 associated to the document and if it exists will try to save to that 2568 encoding, 2569 <p>otherwise everything is written in the internal form, i.e. UTF-8</p> 2570 </li> 2571 <li>so if an encoding was specified, either at the API level or on the 2572 document, libxml will again canonicalize the encoding name, lookup for a 2573 converter in the registered set or through iconv. If not found the 2574 function will return an error code</li> 2575 <li>the converter is placed before the I/O buffer layer, as another kind of 2576 buffer, then libxml will simply push the UTF-8 serialization to through 2577 that buffer, which will then progressively be converted and pushed onto 2578 the I/O layer.</li> 2579 <li>It is possible that the converter code fails on some input, for example 2580 trying to push an UTF-8 encoded Chinese character through the UTF-8 to 2581 ISO-8859-1 converter won't work. Since the encoders are progressive they 2582 will just report the error and the number of bytes converted, at that 2583 point libxml will decode the offending character, remove it from the 2584 buffer and replace it with the associated charRef encoding &#123; and 2585 resume the conversion. This guarantees that any document will be saved 2586 without losses (except for markup names where this is not legal, this is 2587 a problem in the current version, in practice avoid using non-ascii 2588 characters for tags or attributes names @@). A special "ascii" encoding 2589 name is used to save documents to a pure ascii form can be used when 2590 portability is really crucial</li> 2591</ol> 2592 2593<p>Here is a few examples based on the same test document:</p> 2594<pre>~/XML -> /xmllint isolat1 2595<?xml version="1.0" encoding="ISO-8859-1"?> 2596<tr�s>l�</tr�s> 2597~/XML -> /xmllint --encode UTF-8 isolat1 2598<?xml version="1.0" encoding="UTF-8"?> 2599<très>l� �</très> 2600~/XML -> </pre> 2601 2602<p>The same processing is applied (and reuse most of the code) for HTML I18N 2603processing. Looking up and modifying the content encoding is a bit more 2604difficult since it is located in a <meta> tag under the <head>, 2605so a couple of functions htmlGetMetaEncoding() and htmlSetMetaEncoding() have 2606been provided. The parser also attempts to switch encoding on the fly when 2607detecting such a tag on input. Except for that the processing is the same 2608(and again reuses the same code).</p> 2609 2610<h3><a name="Default">Default supported encodings</a></h3> 2611 2612<p>libxml has a set of default converters for the following encodings 2613(located in encoding.c):</p> 2614<ol> 2615 <li>UTF-8 is supported by default (null handlers)</li> 2616 <li>UTF-16, both little and big endian</li> 2617 <li>ISO-Latin-1 (ISO-8859-1) covering most western languages</li> 2618 <li>ASCII, useful mostly for saving</li> 2619 <li>HTML, a specific handler for the conversion of UTF-8 to ASCII with HTML 2620 predefined entities like &copy; for the Copyright sign.</li> 2621</ol> 2622 2623<p>More over when compiled on an Unix platform with iconv support the full 2624set of encodings supported by iconv can be instantly be used by libxml. On a 2625linux machine with glibc-2.1 the list of supported encodings and aliases fill 26263 full pages, and include UCS-4, the full set of ISO-Latin encodings, and the 2627various Japanese ones.</p> 2628 2629<h4>Encoding aliases</h4> 2630 2631<p>From 2.2.3, libxml has support to register encoding names aliases. The 2632goal is to be able to parse document whose encoding is supported but where 2633the name differs (for example from the default set of names accepted by 2634iconv). The following functions allow to register and handle new aliases for 2635existing encodings. Once registered libxml will automatically lookup the 2636aliases when handling a document:</p> 2637<ul> 2638 <li>int xmlAddEncodingAlias(const char *name, const char *alias);</li> 2639 <li>int xmlDelEncodingAlias(const char *alias);</li> 2640 <li>const char * xmlGetEncodingAlias(const char *alias);</li> 2641 <li>void xmlCleanupEncodingAliases(void);</li> 2642</ul> 2643 2644<h3><a name="extend">How to extend the existing support</a></h3> 2645 2646<p>Well adding support for new encoding, or overriding one of the encoders 2647(assuming it is buggy) should not be hard, just write an input and output 2648conversion routines to/from UTF-8, and register them using 2649xmlNewCharEncodingHandler(name, xxxToUTF8, UTF8Toxxx), and they will be 2650called automatically if the parser(s) encounter such an encoding name 2651(register it uppercase, this will help). The description of the encoders, 2652their arguments and expected return values are described in the encoding.h 2653header.</p> 2654 2655<p>A quick note on the topic of subverting the parser to use a different 2656internal encoding than UTF-8, in some case people will absolutely want to 2657keep the internal encoding different, I think it's still possible (but the 2658encoding must be compliant with ASCII on the same subrange) though I didn't 2659tried it. The key is to override the default conversion routines (by 2660registering null encoders/decoders for your charsets), and bypass the UTF-8 2661checking of the parser by setting the parser context charset 2662(ctxt->charset) to something different than XML_CHAR_ENCODING_UTF8, but 2663there is no guarantee that this will work. You may also have some troubles 2664saving back.</p> 2665 2666<p>Basically proper I18N support is important, this requires at least 2667libxml-2.0.0, but a lot of features and corrections are really available only 2668starting 2.2.</p> 2669 2670<h2><a name="IO">I/O Interfaces</a></h2> 2671 2672<p>Table of Content:</p> 2673<ol> 2674 <li><a href="#General1">General overview</a></li> 2675 <li><a href="#basic">The basic buffer type</a></li> 2676 <li><a href="#Input">Input I/O handlers</a></li> 2677 <li><a href="#Output">Output I/O handlers</a></li> 2678 <li><a href="#entities">The entities loader</a></li> 2679 <li><a href="#Example2">Example of customized I/O</a></li> 2680</ol> 2681 2682<h3><a name="General1">General overview</a></h3> 2683 2684<p>The module <code><a 2685href="http://xmlsoft.org/html/libxml-xmlio.html">xmlIO.h</a></code> provides 2686the interfaces to the libxml I/O system. This consists of 4 main parts:</p> 2687<ul> 2688 <li>Entities loader, this is a routine which tries to fetch the entities 2689 (files) based on their PUBLIC and SYSTEM identifiers. The default loader 2690 don't look at the public identifier since libxml do not maintain a 2691 catalog. You can redefine you own entity loader by using 2692 <code>xmlGetExternalEntityLoader()</code> and 2693 <code>xmlSetExternalEntityLoader()</code>. <a href="#entities">Check the 2694 example</a>.</li> 2695 <li>Input I/O buffers which are a commodity structure used by the parser(s) 2696 input layer to handle fetching the informations to feed the parser. This 2697 provides buffering and is also a placeholder where the encoding 2698 converters to UTF8 are piggy-backed.</li> 2699 <li>Output I/O buffers are similar to the Input ones and fulfill similar 2700 task but when generating a serialization from a tree.</li> 2701 <li>A mechanism to register sets of I/O callbacks and associate them with 2702 specific naming schemes like the protocol part of the URIs. 2703 <p>This affect the default I/O operations and allows to use specific I/O 2704 handlers for certain names.</p> 2705 </li> 2706</ul> 2707 2708<p>The general mechanism used when loading http://rpmfind.net/xml.html for 2709example in the HTML parser is the following:</p> 2710<ol> 2711 <li>The default entity loader calls <code>xmlNewInputFromFile()</code> with 2712 the parsing context and the URI string.</li> 2713 <li>the URI string is checked against the existing registered handlers 2714 using their match() callback function, if the HTTP module was compiled 2715 in, it is registered and its match() function will succeeds</li> 2716 <li>the open() function of the handler is called and if successful will 2717 return an I/O Input buffer</li> 2718 <li>the parser will the start reading from this buffer and progressively 2719 fetch information from the resource, calling the read() function of the 2720 handler until the resource is exhausted</li> 2721 <li>if an encoding change is detected it will be installed on the input 2722 buffer, providing buffering and efficient use of the conversion 2723 routines</li> 2724 <li>once the parser has finished, the close() function of the handler is 2725 called once and the Input buffer and associated resources are 2726 deallocated.</li> 2727</ol> 2728 2729<p>The user defined callbacks are checked first to allow overriding of the 2730default libxml I/O routines.</p> 2731 2732<h3><a name="basic">The basic buffer type</a></h3> 2733 2734<p>All the buffer manipulation handling is done using the 2735<code>xmlBuffer</code> type define in <code><a 2736href="http://xmlsoft.org/html/libxml-tree.html">tree.h</a> </code>which is a 2737resizable memory buffer. The buffer allocation strategy can be selected to be 2738either best-fit or use an exponential doubling one (CPU vs. memory use 2739trade-off). The values are <code>XML_BUFFER_ALLOC_EXACT</code> and 2740<code>XML_BUFFER_ALLOC_DOUBLEIT</code>, and can be set individually or on a 2741system wide basis using <code>xmlBufferSetAllocationScheme()</code>. A number 2742of functions allows to manipulate buffers with names starting with the 2743<code>xmlBuffer...</code> prefix.</p> 2744 2745<h3><a name="Input">Input I/O handlers</a></h3> 2746 2747<p>An Input I/O handler is a simple structure 2748<code>xmlParserInputBuffer</code> containing a context associated to the 2749resource (file descriptor, or pointer to a protocol handler), the read() and 2750close() callbacks to use and an xmlBuffer. And extra xmlBuffer and a charset 2751encoding handler are also present to support charset conversion when 2752needed.</p> 2753 2754<h3><a name="Output">Output I/O handlers</a></h3> 2755 2756<p>An Output handler <code>xmlOutputBuffer</code> is completely similar to an 2757Input one except the callbacks are write() and close().</p> 2758 2759<h3><a name="entities">The entities loader</a></h3> 2760 2761<p>The entity loader resolves requests for new entities and create inputs for 2762the parser. Creating an input from a filename or an URI string is done 2763through the xmlNewInputFromFile() routine. The default entity loader do not 2764handle the PUBLIC identifier associated with an entity (if any). So it just 2765calls xmlNewInputFromFile() with the SYSTEM identifier (which is mandatory in 2766XML).</p> 2767 2768<p>If you want to hook up a catalog mechanism then you simply need to 2769override the default entity loader, here is an example:</p> 2770<pre>#include <libxml/xmlIO.h> 2771 2772xmlExternalEntityLoader defaultLoader = NULL; 2773 2774xmlParserInputPtr 2775xmlMyExternalEntityLoader(const char *URL, const char *ID, 2776 xmlParserCtxtPtr ctxt) { 2777 xmlParserInputPtr ret; 2778 const char *fileID = NULL; 2779 /* lookup for the fileID depending on ID */ 2780 2781 ret = xmlNewInputFromFile(ctxt, fileID); 2782 if (ret != NULL) 2783 return(ret); 2784 if (defaultLoader != NULL) 2785 ret = defaultLoader(URL, ID, ctxt); 2786 return(ret); 2787} 2788 2789int main(..) { 2790 ... 2791 2792 /* 2793 * Install our own entity loader 2794 */ 2795 defaultLoader = xmlGetExternalEntityLoader(); 2796 xmlSetExternalEntityLoader(xmlMyExternalEntityLoader); 2797 2798 ... 2799}</pre> 2800 2801<h3><a name="Example2">Example of customized I/O</a></h3> 2802 2803<p>This example come from <a href="http://xmlsoft.org/messages/0708.html">a 2804real use case</a>, xmlDocDump() closes the FILE * passed by the application 2805and this was a problem. The <a 2806href="http://xmlsoft.org/messages/0711.html">solution</a> was to redefine a 2807new output handler with the closing call deactivated:</p> 2808<ol> 2809 <li>First define a new I/O output allocator where the output don't close 2810 the file: 2811 <pre>xmlOutputBufferPtr 2812xmlOutputBufferCreateOwn(FILE *file, xmlCharEncodingHandlerPtr encoder) { 2813����xmlOutputBufferPtr ret; 2814���� 2815����if (xmlOutputCallbackInitialized == 0) 2816��������xmlRegisterDefaultOutputCallbacks(); 2817 2818����if (file == NULL) return(NULL); 2819����ret = xmlAllocOutputBuffer(encoder); 2820����if (ret != NULL) { 2821��������ret->context = file; 2822��������ret->writecallback = xmlFileWrite; 2823��������ret->closecallback = NULL; /* No close callback */ 2824����} 2825����return(ret); <br> 2826 2827 2828 2829 2830 2831 2832 2833 2834 2835 2836 2837 2838 2839 2840 2841 2842 2843 2844 2845 2846 2847 2848 2849 2850 2851 2852 2853 2854 2855 2856 2857 2858 2859 2860} </pre> 2861 </li> 2862 <li>And then use it to save the document: 2863 <pre>FILE *f; 2864xmlOutputBufferPtr output; 2865xmlDocPtr doc; 2866int res; 2867 2868f = ... 2869doc = .... 2870 2871output = xmlOutputBufferCreateOwn(f, NULL); 2872res = xmlSaveFileTo(output, doc, NULL); 2873 </pre> 2874 </li> 2875</ol> 2876 2877<h2><a name="Catalog">Catalog support</a></h2> 2878 2879<p>Table of Content:</p> 2880<ol> 2881 <li><a href="General2">General overview</a></li> 2882 <li><a href="#definition">The definition</a></li> 2883 <li><a href="#Simple">Using catalogs</a></li> 2884 <li><a href="#Some">Some examples</a></li> 2885 <li><a href="#reference">How to tune catalog usage</a></li> 2886 <li><a href="#validate">How to debug catalog processing</a></li> 2887 <li><a href="#Declaring">How to create and maintain catalogs</a></li> 2888 <li><a href="#implemento">The implementor corner quick review of the 2889 API</a></li> 2890 <li><a href="#Other">Other resources</a></li> 2891</ol> 2892 2893<h3><a name="General2">General overview</a></h3> 2894 2895<p>What is a catalog? Basically it's a lookup mechanism used when an entity 2896(a file or a remote resource) references another entity. The catalog lookup 2897is inserted between the moment the reference is recognized by the software 2898(XML parser, stylesheet processing, or even images referenced for inclusion 2899in a rendering) and the time where loading that resource is actually 2900started.</p> 2901 2902<p>It is basically used for 3 things:</p> 2903<ul> 2904 <li>mapping from "logical" names, the public identifiers and a more 2905 concrete name usable for download (and URI). For example it can associate 2906 the logical name 2907 <p>"-//OASIS//DTD DocBook XML V4.1.2//EN"</p> 2908 <p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be 2909 downloaded</p> 2910 <p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p> 2911 </li> 2912 <li>remapping from a given URL to another one, like an HTTP indirection 2913 saying that 2914 <p>"http://www.oasis-open.org/committes/tr.xsl"</p> 2915 <p>should really be looked at</p> 2916 <p>"http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"</p> 2917 </li> 2918 <li>providing a local cache mechanism allowing to load the entities 2919 associated to public identifiers or remote resources, this is a really 2920 important feature for any significant deployment of XML or SGML since it 2921 allows to avoid the aleas and delays associated to fetching remote 2922 resources.</li> 2923</ul> 2924 2925<h3><a name="definition">The definitions</a></h3> 2926 2927<p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p> 2928<ul> 2929 <li>the older SGML catalogs, the official spec is SGML Open Technical 2930 Resolution TR9401:1997, but is better understood by reading <a 2931 href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from 2932 James Clark. This is relatively old and not the preferred mode of 2933 operation of libxml.</li> 2934 <li><a href="http://www.oasis-open.org/committees/entity/spec.html">XML 2935 Catalogs</a> is far more flexible, more recent, uses an XML syntax and 2936 should scale quite better. This is the default option of libxml.</li> 2937</ul> 2938 2939<p></p> 2940 2941<h3><a name="Simple">Using catalog</a></h3> 2942 2943<p>In a normal environment libxml will by default check the presence of a 2944catalog in /etc/xml/catalog, and assuming it has been correctly populated, 2945the processing is completely transparent to the document user. To take a 2946concrete example, suppose you are authoring a DocBook document, this one 2947starts with the following DOCTYPE definition:</p> 2948<pre><?xml version='1.0'?> 2949<!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN" 2950 "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd"></pre> 2951 2952<p>When validating the document with libxml, the catalog will be 2953automatically consulted to lookup the public identifier "-//Norman Walsh//DTD 2954DocBk XML V3.1.4//EN" and the system identifier 2955"http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if these entities have 2956been installed on your system and the catalogs actually point to them, libxml 2957will fetch them from the local disk.</p> 2958 2959<p style="font-size: 10pt"><strong>Note</strong>: Really don't use this 2960DOCTYPE example it's a really old version, but is fine as an example.</p> 2961 2962<p>Libxml will check the catalog each time that it is requested to load an 2963entity, this includes DTD, external parsed entities, stylesheets, etc ... If 2964your system is correctly configured all the authoring phase and processing 2965should use only local files, even if your document stays portable because it 2966uses the canonical public and system ID, referencing the remote document.</p> 2967 2968<h3><a name="Some">Some examples:</a></h3> 2969 2970<p>Here is a couple of fragments from XML Catalogs used in libxml early 2971regression tests in <code>test/catalogs</code> :</p> 2972<pre><?xml version="1.0"?> 2973<!DOCTYPE catalog PUBLIC 2974 "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 2975 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 2976<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 2977 <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 2978 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 2979...</pre> 2980 2981<p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are 2982written in XML, there is a specific namespace for catalog elements 2983"urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry in this 2984catalog is a <code>public</code> mapping it allows to associate a Public 2985Identifier with an URI.</p> 2986<pre>... 2987 <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/" 2988 rewritePrefix="file:///usr/share/xml/docbook/"/> 2989...</pre> 2990 2991<p>A <code>rewriteSystem</code> is a very powerful instruction, it says that 2992any URI starting with a given prefix should be looked at another URI 2993constructed by replacing the prefix with an new one. In effect this acts like 2994a cache system for a full area of the Web. In practice it is extremely useful 2995with a file prefix if you have installed a copy of those resources on your 2996local system.</p> 2997<pre>... 2998<delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //" 2999 catalog="file:///usr/share/xml/docbook.xml"/> 3000<delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML" 3001 catalog="file:///usr/share/xml/docbook.xml"/> 3002<delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML" 3003 catalog="file:///usr/share/xml/docbook.xml"/> 3004<delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/" 3005 catalog="file:///usr/share/xml/docbook.xml"/> 3006<delegateURI uriStartString="http://www.oasis-open.org/docbook/" 3007 catalog="file:///usr/share/xml/docbook.xml"/> 3008...</pre> 3009 3010<p>Delegation is the core features which allows to build a tree of catalogs, 3011easier to maintain than a single catalog, based on Public Identifier, System 3012Identifier or URI prefixes it instructs the catalog software to look up 3013entries in another resource. This feature allow to build hierarchies of 3014catalogs, the set of entries presented should be sufficient to redirect the 3015resolution of all DocBook references to the specific catalog in 3016<code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all 3017references for DocBook 4.2.1 to a specific catalog installed at the same time 3018as the DocBook resources on the local machine.</p> 3019 3020<h3><a name="reference">How to tune catalog usage:</a></h3> 3021 3022<p>The user can change the default catalog behaviour by redirecting queries 3023to its own set of catalogs, this can be done by setting the 3024<code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an 3025empty one should deactivate loading the default <code>/etc/xml/catalog</code> 3026default catalog</p> 3027 3028<h3><a name="validate">How to debug catalog processing:</a></h3> 3029 3030<p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will 3031make libxml output debugging informations for each catalog operations, for 3032example:</p> 3033<pre>orchis:~/XML -> xmllint --memory --noout test/ent2 3034warning: failed to load external entity "title.xml" 3035orchis:~/XML -> export XML_DEBUG_CATALOG= 3036orchis:~/XML -> xmllint --memory --noout test/ent2 3037Failed to parse catalog /etc/xml/catalog 3038Failed to parse catalog /etc/xml/catalog 3039warning: failed to load external entity "title.xml" 3040Catalogs cleanup 3041orchis:~/XML -> </pre> 3042 3043<p>The test/ent2 references an entity, running the parser from memory makes 3044the base URI unavailable and the the "title.xml" entity cannot be loaded. 3045Setting up the debug environment variable allows to detect that an attempt is 3046made to load the <code>/etc/xml/catalog</code> but since it's not present the 3047resolution fails.</p> 3048 3049<p>But the most advanced way to debug XML catalog processing is to use the 3050<strong>xmlcatalog</strong> command shipped with libxml2, it allows to load 3051catalogs and make resolution queries to see what is going on. This is also 3052used for the regression tests:</p> 3053<pre>orchis:~/XML -> /xmlcatalog test/catalogs/docbook.xml \ 3054 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3055http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3056orchis:~/XML -> </pre> 3057 3058<p>For debugging what is going on, adding one -v flags increase the verbosity 3059level to indicate the processing done (adding a second flag also indicate 3060what elements are recognized at parsing):</p> 3061<pre>orchis:~/XML -> /xmlcatalog -v test/catalogs/docbook.xml \ 3062 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3063Parsing catalog test/catalogs/docbook.xml's content 3064Found public match -//OASIS//DTD DocBook XML V4.1.2//EN 3065http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3066Catalogs cleanup 3067orchis:~/XML -> </pre> 3068 3069<p>A shell interface is also available to debug and process multiple queries 3070(and for regression tests):</p> 3071<pre>orchis:~/XML -> /xmlcatalog -shell test/catalogs/docbook.xml \ 3072 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3073> help 3074Commands available: 3075public PublicID: make a PUBLIC identifier lookup 3076system SystemID: make a SYSTEM identifier lookup 3077resolve PublicID SystemID: do a full resolver lookup 3078add 'type' 'orig' 'replace' : add an entry 3079del 'values' : remove values 3080dump: print the current catalog state 3081debug: increase the verbosity level 3082quiet: decrease the verbosity level 3083exit: quit the shell 3084> public "-//OASIS//DTD DocBook XML V4.1.2//EN" 3085http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3086> quit 3087orchis:~/XML -> </pre> 3088 3089<p>This should be sufficient for most debugging purpose, this was actually 3090used heavily to debug the XML Catalog implementation itself.</p> 3091 3092<h3><a name="Declaring">How to create and maintain</a> catalogs:</h3> 3093 3094<p>Basically XML Catalogs are XML files, you can either use XML tools to 3095manage them or use <strong>xmlcatalog</strong> for this. The basic step is 3096to create a catalog the -create option provide this facility:</p> 3097<pre>orchis:~/XML -> /xmlcatalog --create tst.xml 3098<?xml version="1.0"?> 3099<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3100 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3101<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3102orchis:~/XML -> </pre> 3103 3104<p>By default xmlcatalog does not overwrite the original catalog and save the 3105result on the standard output, this can be overridden using the -noout 3106option. The <code>-add</code> command allows to add entries in the 3107catalog:</p> 3108<pre>orchis:~/XML -> /xmlcatalog --noout --create --add "public" \ 3109 "-//OASIS//DTD DocBook XML V4.1.2//EN" \ 3110 http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml 3111orchis:~/XML -> cat tst.xml 3112<?xml version="1.0"?> 3113<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \ 3114 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3115<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 3116<public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 3117 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 3118</catalog> 3119orchis:~/XML -> </pre> 3120 3121<p>The <code>-add</code> option will always take 3 parameters even if some of 3122the XML Catalog constructs (like nextCatalog) will have only a single 3123argument, just pass a third empty string, it will be ignored.</p> 3124 3125<p>Similarly the <code>-del</code> option remove matching entries from the 3126catalog:</p> 3127<pre>orchis:~/XML -> /xmlcatalog --del \ 3128 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml 3129<?xml version="1.0"?> 3130<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3131 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3132<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3133orchis:~/XML -> </pre> 3134 3135<p>The catalog is now empty. Note that the matching of <code>-del</code> is 3136exact and would have worked in a similar fashion with the Public ID 3137string.</p> 3138 3139<p>This is rudimentary but should be sufficient to manage a not too complex 3140catalog tree of resources.</p> 3141 3142<h3><a name="implemento">The implementor corner quick review of the 3143API:</a></h3> 3144 3145<p>First, and like for every other module of libxml, there is an 3146automatically generated <a href="html/libxml-catalog.html">API page for 3147catalog support</a>.</p> 3148 3149<p>The header for the catalog interfaces should be included as:</p> 3150<pre>#include <libxml/catalog.h></pre> 3151 3152<p>The API is voluntarily kept very simple. First it is not obvious that 3153applications really need access to it since it is the default behaviour of 3154libxml (Note: it is possible to completely override libxml default catalog by 3155using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to 3156plug an application specific resolver).</p> 3157 3158<p>Basically libxml support 2 catalog lists:</p> 3159<ul> 3160 <li>the default one, global shared by all the application</li> 3161 <li>a per-document catalog, this one is built if the document uses the 3162 <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is 3163 associated to the parser context and destroyed when the parsing context 3164 is destroyed.</li> 3165</ul> 3166 3167<p>the document one will be used first if it exists.</p> 3168 3169<h4>Initialization routines:</h4> 3170 3171<p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be 3172used at startup to initialize the catalog, if the catalog should be 3173initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs() 3174should be called before xmlInitializeCatalog() which would otherwise do a 3175default initialization first.</p> 3176 3177<p>The xmlCatalogAddLocal() call is used by the parser to grow the document 3178own catalog list if needed.</p> 3179 3180<h4>Preferences setup:</h4> 3181 3182<p>The XML Catalog spec requires the possibility to select default 3183preferences between public and system delegation, 3184xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and 3185xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should 3186be forbidden, allowed for global catalog, for document catalog or both, the 3187default is to allow both.</p> 3188 3189<p>And of course xmlCatalogSetDebug() allows to generate debug messages 3190(through the xmlGenericError() mechanism).</p> 3191 3192<h4>Querying routines:</h4> 3193 3194<p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic() 3195and xmlCatalogResolveURI() are relatively explicit if you read the XML 3196Catalog specification they correspond to section 7 algorithms, they should 3197also work if you have loaded an SGML catalog with a simplified semantic.</p> 3198 3199<p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but 3200operate on the document catalog list</p> 3201 3202<h4>Cleanup and Miscellaneous:</h4> 3203 3204<p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is 3205the per-document equivalent.</p> 3206 3207<p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the 3208first catalog in the global list, and xmlCatalogDump() allows to dump a 3209catalog state, those routines are primarily designed for xmlcatalog, I'm not 3210sure that exposing more complex interfaces (like navigation ones) would be 3211really useful.</p> 3212 3213<p>The xmlParseCatalogFile() is a function used to load XML Catalog files, 3214it's similar as xmlParseFile() except it bypass all catalog lookups, it's 3215provided because this functionality may be useful for client tools.</p> 3216 3217<h4>threaded environments:</h4> 3218 3219<p>Since the catalog tree is built progressively, some care has been taken to 3220try to avoid troubles in multithreaded environments. The code is now thread 3221safe assuming that the libxml library has been compiled with threads 3222support.</p> 3223 3224<p></p> 3225 3226<h3><a name="Other">Other resources</a></h3> 3227 3228<p>The XML Catalog specification is relatively recent so there isn't much 3229literature to point at:</p> 3230<ul> 3231 <li>You can find a good rant from Norm Walsh about <a 3232 href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the 3233 need for catalogs</a>, it provides a lot of context informations even if 3234 I don't agree with everything presented. Norm also wrote a more recent 3235 article <a 3236 href="http://wwws.sun.com/software/xml/developers/resolver/article/">XML 3237 entities and URI resolvers</a> describing them.</li> 3238 <li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML 3239 catalog proposal</a> from John Cowan</li> 3240 <li>The <a href="http://www.rddl.org/">Resource Directory Description 3241 Language</a> (RDDL) another catalog system but more oriented toward 3242 providing metadata for XML namespaces.</li> 3243 <li>the page from the OASIS Technical <a 3244 href="http://www.oasis-open.org/committees/entity/">Committee on Entity 3245 Resolution</a> who maintains XML Catalog, you will find pointers to the 3246 specification update, some background and pointers to others tools 3247 providing XML Catalog support</li> 3248 <li>Here is a <a href="buildDocBookCatalog">shell script</a> to generate 3249 XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/ 3250 directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on 3251 the resources found on the system. Otherwise it will just create 3252 ~/xmlcatalog and ~/dbkxmlcatalog and doing: 3253 <p><code>export XMLCATALOG=$HOME/xmlcatalog</code></p> 3254 <p>should allow to process DocBook documentations without requiring 3255 network accesses for the DTD or stylesheets</p> 3256 </li> 3257 <li>I have uploaded <a href="ftp://xmlsoft.org/test/dbk412catalog.tar.gz">a 3258 small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems 3259 to work fine for me too</li> 3260 <li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog 3261 manual page</a></li> 3262</ul> 3263 3264<p>If you have suggestions for corrections or additions, simply contact 3265me:</p> 3266 3267<h2><a name="library">The parser interfaces</a></h2> 3268 3269<p>This section is directly intended to help programmers getting bootstrapped 3270using the XML library from the C language. It is not intended to be 3271extensive. I hope the automatically generated documents will provide the 3272completeness required, but as a separate set of documents. The interfaces of 3273the XML library are by principle low level, there is nearly zero abstraction. 3274Those interested in a higher level API should <a href="#DOM">look at 3275DOM</a>.</p> 3276 3277<p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are 3278separated from the <a href="html/libxml-htmlparser.html">HTML parser 3279interfaces</a>. Let's have a look at how the XML parser can be called:</p> 3280 3281<h3><a name="Invoking">Invoking the parser : the pull method</a></h3> 3282 3283<p>Usually, the first thing to do is to read an XML input. The parser accepts 3284documents either from in-memory strings or from files. The functions are 3285defined in "parser.h":</p> 3286<dl> 3287 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> 3288 <dd><p>Parse a null-terminated string containing the document.</p> 3289 </dd> 3290</dl> 3291<dl> 3292 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> 3293 <dd><p>Parse an XML document contained in a (possibly compressed) 3294 file.</p> 3295 </dd> 3296</dl> 3297 3298<p>The parser returns a pointer to the document structure (or NULL in case of 3299failure).</p> 3300 3301<h3 id="Invoking1">Invoking the parser: the push method</h3> 3302 3303<p>In order for the application to keep the control when the document is 3304being fetched (which is common for GUI based programs) libxml provides a push 3305interface, too, as of version 1.8.3. Here are the interface functions:</p> 3306<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, 3307 void *user_data, 3308 const char *chunk, 3309 int size, 3310 const char *filename); 3311int xmlParseChunk (xmlParserCtxtPtr ctxt, 3312 const char *chunk, 3313 int size, 3314 int terminate);</pre> 3315 3316<p>and here is a simple example showing how to use the interface:</p> 3317<pre> FILE *f; 3318 3319 f = fopen(filename, "r"); 3320 if (f != NULL) { 3321 int res, size = 1024; 3322 char chars[1024]; 3323 xmlParserCtxtPtr ctxt; 3324 3325 res = fread(chars, 1, 4, f); 3326 if (res > 0) { 3327 ctxt = xmlCreatePushParserCtxt(NULL, NULL, 3328 chars, res, filename); 3329 while ((res = fread(chars, 1, size, f)) > 0) { 3330 xmlParseChunk(ctxt, chars, res, 0); 3331 } 3332 xmlParseChunk(ctxt, chars, 0, 1); 3333 doc = ctxt->myDoc; 3334 xmlFreeParserCtxt(ctxt); 3335 } 3336 }</pre> 3337 3338<p>The HTML parser embedded into libxml also has a push interface; the 3339functions are just prefixed by "html" rather than "xml".</p> 3340 3341<h3 id="Invoking2">Invoking the parser: the SAX interface</h3> 3342 3343<p>The tree-building interface makes the parser memory-hungry, first loading 3344the document in memory and then building the tree itself. Reading a document 3345without building the tree is possible using the SAX interfaces (see SAX.h and 3346<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James 3347Henstridge's documentation</a>). Note also that the push interface can be 3348limited to SAX: just use the two first arguments of 3349<code>xmlCreatePushParserCtxt()</code>.</p> 3350 3351<h3><a name="Building">Building a tree from scratch</a></h3> 3352 3353<p>The other way to get an XML tree in memory is by building it. Basically 3354there is a set of functions dedicated to building new elements. (These are 3355also described in <libxml/tree.h>.) For example, here is a piece of 3356code that produces the XML document used in the previous examples:</p> 3357<pre> #include <libxml/tree.h> 3358 xmlDocPtr doc; 3359 xmlNodePtr tree, subtree; 3360 3361 doc = xmlNewDoc("1.0"); 3362 doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); 3363 xmlSetProp(doc->children, "prop1", "gnome is great"); 3364 xmlSetProp(doc->children, "prop2", "& linux too"); 3365 tree = xmlNewChild(doc->children, NULL, "head", NULL); 3366 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); 3367 tree = xmlNewChild(doc->children, NULL, "chapter", NULL); 3368 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); 3369 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); 3370 subtree = xmlNewChild(tree, NULL, "image", NULL); 3371 xmlSetProp(subtree, "href", "linus.gif");</pre> 3372 3373<p>Not really rocket science ...</p> 3374 3375<h3><a name="Traversing">Traversing the tree</a></h3> 3376 3377<p>Basically by <a href="html/libxml-tree.html">including "tree.h"</a> your 3378code has access to the internal structure of all the elements of the tree. 3379The names should be somewhat simple like <strong>parent</strong>, 3380<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>, 3381<strong>properties</strong>, etc... For example, still with the previous 3382example:</p> 3383<pre><code>doc->children->children->children</code></pre> 3384 3385<p>points to the title element,</p> 3386<pre>doc->children->children->next->children->children</pre> 3387 3388<p>points to the text node containing the chapter title "The Linux 3389adventure".</p> 3390 3391<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be 3392present before the document root, so <code>doc->children</code> may point 3393to an element which is not the document Root Element; a function 3394<code>xmlDocGetRootElement()</code> was added for this purpose.</p> 3395 3396<h3><a name="Modifying">Modifying the tree</a></h3> 3397 3398<p>Functions are provided for reading and writing the document content. Here 3399is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p> 3400<dl> 3401 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const 3402 xmlChar *value);</code></dt> 3403 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. 3404 The value can be NULL.</p> 3405 </dd> 3406</dl> 3407<dl> 3408 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar 3409 *name);</code></dt> 3410 <dd><p>This function returns a pointer to new copy of the property 3411 content. Note that the user must deallocate the result.</p> 3412 </dd> 3413</dl> 3414 3415<p>Two functions are provided for reading and writing the text associated 3416with elements:</p> 3417<dl> 3418 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar 3419 *value);</code></dt> 3420 <dd><p>This function takes an "external" string and converts it to one 3421 text node or possibly to a list of entity and text nodes. All 3422 non-predefined entity references like &Gnome; will be stored 3423 internally as entity nodes, hence the result of the function may not be 3424 a single node.</p> 3425 </dd> 3426</dl> 3427<dl> 3428 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int 3429 inLine);</code></dt> 3430 <dd><p>This function is the inverse of 3431 <code>xmlStringGetNodeList()</code>. It generates a new string 3432 containing the content of the text and entity nodes. Note the extra 3433 argument inLine. If this argument is set to 1, the function will expand 3434 entity references. For example, instead of returning the &Gnome; 3435 XML encoding in the string, it will substitute it with its value (say, 3436 "GNU Network Object Model Environment").</p> 3437 </dd> 3438</dl> 3439 3440<h3><a name="Saving">Saving a tree</a></h3> 3441 3442<p>Basically 3 options are possible:</p> 3443<dl> 3444 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int 3445 *size);</code></dt> 3446 <dd><p>Returns a buffer into which the document has been saved.</p> 3447 </dd> 3448</dl> 3449<dl> 3450 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> 3451 <dd><p>Dumps a document to an open file descriptor.</p> 3452 </dd> 3453</dl> 3454<dl> 3455 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> 3456 <dd><p>Saves the document to a file. In this case, the compression 3457 interface is triggered if it has been turned on.</p> 3458 </dd> 3459</dl> 3460 3461<h3><a name="Compressio">Compression</a></h3> 3462 3463<p>The library transparently handles compression when doing file-based 3464accesses. The level of compression on saves can be turned on either globally 3465or individually for one file:</p> 3466<dl> 3467 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> 3468 <dd><p>Gets the document compression ratio (0-9).</p> 3469 </dd> 3470</dl> 3471<dl> 3472 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> 3473 <dd><p>Sets the document compression ratio.</p> 3474 </dd> 3475</dl> 3476<dl> 3477 <dt><code>int xmlGetCompressMode(void);</code></dt> 3478 <dd><p>Gets the default compression ratio.</p> 3479 </dd> 3480</dl> 3481<dl> 3482 <dt><code>void xmlSetCompressMode(int mode);</code></dt> 3483 <dd><p>Sets the default compression ratio.</p> 3484 </dd> 3485</dl> 3486 3487<h2><a name="Entities">Entities or no entities</a></h2> 3488 3489<p>Entities in principle are similar to simple C macros. An entity defines an 3490abbreviation for a given string that you can reuse many times throughout the 3491content of your document. Entities are especially useful when a given string 3492may occur frequently within a document, or to confine the change needed to a 3493document to a restricted area in the internal subset of the document (at the 3494beginning). Example:</p> 3495<pre>1 <?xml version="1.0"?> 34962 <!DOCTYPE EXAMPLE SYSTEM "example.dtd" [ 34973 <!ENTITY xml "Extensible Markup Language"> 34984 ]> 34995 <EXAMPLE> 35006 &xml; 35017 </EXAMPLE></pre> 3502 3503<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing 3504its name with '&' and following it by ';' without any spaces added. There 3505are 5 predefined entities in libxml allowing you to escape characters with 3506predefined meaning in some parts of the xml document content: 3507<strong>&lt;</strong> for the character '<', <strong>&gt;</strong> 3508for the character '>', <strong>&apos;</strong> for the character ''', 3509<strong>&quot;</strong> for the character '"', and 3510<strong>&amp;</strong> for the character '&'.</p> 3511 3512<p>One of the problems related to entities is that you may want the parser to 3513substitute an entity's content so that you can see the replacement text in 3514your application. Or you may prefer to keep entity references as such in the 3515content to be able to save the document back without losing this usually 3516precious information (if the user went through the pain of explicitly 3517defining entities, he may have a a rather negative attitude if you blindly 3518substitute them as saving time). The <a 3519href="html/libxml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a> 3520function allows you to check and change the behaviour, which is to not 3521substitute entities by default.</p> 3522 3523<p>Here is the DOM tree built by libxml for the previous document in the 3524default case:</p> 3525<pre>/gnome/src/gnome-xml -> /xmllint --debug test/ent1 3526DOCUMENT 3527version=1.0 3528 ELEMENT EXAMPLE 3529 TEXT 3530 content= 3531 ENTITY_REF 3532 INTERNAL_GENERAL_ENTITY xml 3533 content=Extensible Markup Language 3534 TEXT 3535 content=</pre> 3536 3537<p>And here is the result when substituting entities:</p> 3538<pre>/gnome/src/gnome-xml -> /tester --debug --noent test/ent1 3539DOCUMENT 3540version=1.0 3541 ELEMENT EXAMPLE 3542 TEXT 3543 content= Extensible Markup Language</pre> 3544 3545<p>So, entities or no entities? Basically, it depends on your use case. I 3546suggest that you keep the non-substituting default behaviour and avoid using 3547entities in your XML document or data if you are not willing to handle the 3548entity references elements in the DOM tree.</p> 3549 3550<p>Note that at save time libxml enforces the conversion of the predefined 3551entities where necessary to prevent well-formedness problems, and will also 3552transparently replace those with chars (i.e. it will not generate entity 3553reference elements in the DOM tree or call the reference() SAX callback when 3554finding them in the input).</p> 3555 3556<p><span style="background-color: #FF0000">WARNING</span>: handling entities 3557on top of the libxml SAX interface is difficult!!! If you plan to use 3558non-predefined entities in your documents, then the learning curve to handle 3559then using the SAX API may be long. If you plan to use complex documents, I 3560strongly suggest you consider using the DOM interface instead and let libxml 3561deal with the complexity rather than trying to do it yourself.</p> 3562 3563<h2><a name="Namespaces">Namespaces</a></h2> 3564 3565<p>The libxml library implements <a 3566href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by 3567recognizing namespace constructs in the input, and does namespace lookup 3568automatically when building the DOM tree. A namespace declaration is 3569associated with an in-memory structure and all elements or attributes within 3570that namespace point to it. Hence testing the namespace is a simple and fast 3571equality operation at the user level.</p> 3572 3573<p>I suggest that people using libxml use a namespace, and declare it in the 3574root element of their document as the default namespace. Then they don't need 3575to use the prefix in the content but we will have a basis for future semantic 3576refinement and merging of data from different sources. This doesn't increase 3577the size of the XML output significantly, but significantly increases its 3578value in the long-term. Example:</p> 3579<pre><mydoc xmlns="http://mydoc.example.org/schemas/"> 3580 <elem1>...</elem1> 3581 <elem2>...</elem2> 3582</mydoc></pre> 3583 3584<p>The namespace value has to be an absolute URL, but the URL doesn't have to 3585point to any existing resource on the Web. It will bind all the element and 3586attributes with that URL. I suggest to use an URL within a domain you 3587control, and that the URL should contain some kind of version information if 3588possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a 3589good namespace scheme.</p> 3590 3591<p>Then when you load a file, make sure that a namespace carrying the 3592version-independent prefix is installed on the root element of your document, 3593and if the version information don't match something you know, warn the user 3594and be liberal in what you accept as the input. Also do *not* try to base 3595namespace checking on the prefix value. <foo:text> may be exactly the 3596same as <bar:text> in another document. What really matters is the URI 3597associated with the element or the attribute, not the prefix string (which is 3598just a shortcut for the full URI). In libxml, element and attributes have an 3599<code>ns</code> field pointing to an xmlNs structure detailing the namespace 3600prefix and its URI.</p> 3601 3602<p>@@Interfaces@@</p> 3603 3604<p>@@Examples@@</p> 3605 3606<p>Usually people object to using namespaces together with validity checking. 3607I will try to make sure that using namespaces won't break validity checking, 3608so even if you plan to use or currently are using validation I strongly 3609suggest adding namespaces to your document. A default namespace scheme 3610<code>xmlns="http://...."</code> should not break validity even on less 3611flexible parsers. Using namespaces to mix and differentiate content coming 3612from multiple DTDs will certainly break current validation schemes. I will 3613try to provide ways to do this, but this may not be portable or 3614standardized.</p> 3615 3616<h2><a name="Upgrading">Upgrading 1.x code</a></h2> 3617 3618<p>Incompatible changes:</p> 3619 3620<p>Version 2 of libxml is the first version introducing serious backward 3621incompatible changes. The main goals were:</p> 3622<ul> 3623 <li>a general cleanup. A number of mistakes inherited from the very early 3624 versions couldn't be changed due to compatibility constraints. Example 3625 the "childs" element in the nodes.</li> 3626 <li>Uniformization of the various nodes, at least for their header and link 3627 parts (doc, parent, children, prev, next), the goal is a simpler 3628 programming model and simplifying the task of the DOM implementors.</li> 3629 <li>better conformances to the XML specification, for example version 1.x 3630 had an heuristic to try to detect ignorable white spaces. As a result the 3631 SAX event generated were ignorableWhitespace() while the spec requires 3632 character() in that case. This also mean that a number of DOM node 3633 containing blank text may populate the DOM tree which were not present 3634 before.</li> 3635</ul> 3636 3637<h3>How to fix libxml-1.x code:</h3> 3638 3639<p>So client code of libxml designed to run with version 1.x may have to be 3640changed to compile against version 2.x of libxml. Here is a list of changes 3641that I have collected, they may not be sufficient, so in case you find other 3642change which are required, <a href="mailto:Daniel.�eillardw3.org">drop me a 3643mail</a>:</p> 3644<ol> 3645 <li>The package name have changed from libxml to libxml2, the library name 3646 is now -lxml2 . There is a new xml2-config script which should be used to 3647 select the right parameters libxml2</li> 3648 <li>Node <strong>childs</strong> field has been renamed 3649 <strong>children</strong> so s/childs/children/g should be applied 3650 (probability of having "childs" anywhere else is close to 0+</li> 3651 <li>The document don't have anymore a <strong>root</strong> element it has 3652 been replaced by <strong>children</strong> and usually you will get a 3653 list of element here. For example a Dtd element for the internal subset 3654 and it's declaration may be found in that list, as well as processing 3655 instructions or comments found before or after the document root element. 3656 Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of 3657 a document. Alternatively if you are sure to not reference DTDs nor have 3658 PIs or comments before or after the root element 3659 s/->root/->children/g will probably do it.</li> 3660 <li>The white space issue, this one is more complex, unless special case of 3661 validating parsing, the line breaks and spaces usually used for indenting 3662 and formatting the document content becomes significant. So they are 3663 reported by SAX and if your using the DOM tree, corresponding nodes are 3664 generated. Too approach can be taken: 3665 <ol> 3666 <li>lazy one, use the compatibility call 3667 <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are 3668 relying on a special (and possibly broken) set of heuristics of 3669 libxml to detect ignorable blanks. Don't complain if it breaks or 3670 make your application not 100% clean w.r.t. to it's input.</li> 3671 <li>the Right Way: change you code to accept possibly insignificant 3672 blanks characters, or have your tree populated with weird blank text 3673 nodes. You can spot them using the commodity function 3674 <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank 3675 nodes.</li> 3676 </ol> 3677 <p>Note also that with the new default the output functions don't add any 3678 extra indentation when saving a tree in order to be able to round trip 3679 (read and save) without inflating the document with extra formatting 3680 chars.</p> 3681 </li> 3682 <li>The include path has changed to $prefix/libxml/ and the includes 3683 themselves uses this new prefix in includes instructions... If you are 3684 using (as expected) the 3685 <pre>xml2-config --cflags</pre> 3686 <p>output to generate you compile commands this will probably work out of 3687 the box</p> 3688 </li> 3689 <li>xmlDetectCharEncoding takes an extra argument indicating the length in 3690 byte of the head of the document available for character detection.</li> 3691</ol> 3692 3693<h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3> 3694 3695<p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released 3696to allow smooth upgrade of existing libxml v1code while retaining 3697compatibility. They offers the following:</p> 3698<ol> 3699 <li>similar include naming, one should use 3700 <strong>#include<libxml/...></strong> in both cases.</li> 3701 <li>similar identifiers defined via macros for the child and root fields: 3702 respectively <strong>xmlChildrenNode</strong> and 3703 <strong>xmlRootNode</strong></li> 3704 <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be 3705 inserted once in the client code</li> 3706</ol> 3707 3708<p>So the roadmap to upgrade your existing libxml applications is the 3709following:</p> 3710<ol> 3711 <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> 3712 <li>find all occurrences where the xmlDoc <strong>root</strong> field is 3713 used and change it to <strong>xmlRootNode</strong></li> 3714 <li>similarly find all occurrences where the xmlNode 3715 <strong>childs</strong> field is used and change it to 3716 <strong>xmlChildrenNode</strong></li> 3717 <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your 3718 <strong>main()</strong> or in the library init entry point</li> 3719 <li>Recompile, check compatibility, it should still work</li> 3720 <li>Change your configure script to look first for xml2-config and fall 3721 back using xml-config . Use the --cflags and --libs output of the command 3722 as the Include and Linking parameters needed to use libxml.</li> 3723 <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and 3724 libxml-devel-1.8.y can be kept simultaneously)</li> 3725 <li>remove your config.cache, relaunch your configuration mechanism, and 3726 recompile, if steps 2 and 3 were done right it should compile as-is</li> 3727 <li>Test that your application is still running correctly, if not this may 3728 be due to extra empty nodes due to formating spaces being kept in libxml2 3729 contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your 3730 code before calling the parser (next to 3731 <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li> 3732</ol> 3733 3734<p>Following those steps should work. It worked for some of my own code.</p> 3735 3736<p>Let me put some emphasis on the fact that there is far more changes from 3737libxml 1.x to 2.x than the ones you may have to patch for. The overall code 3738has been considerably cleaned up and the conformance to the XML specification 3739has been drastically improved too. Don't take those changes as an excuse to 3740not upgrade, it may cost a lot on the long term ...</p> 3741 3742<h2><a name="Thread">Thread safety</a></h2> 3743 3744<p>Starting with 2.4.7, libxml makes provisions to ensure that concurrent 3745threads can safely work in parallel parsing different documents. There is 3746however a couple of things to do to ensure it:</p> 3747<ul> 3748 <li>configure the library accordingly using the --with-threads options</li> 3749 <li>call xmlInitParser() in the "main" thread before using any of the 3750 libxml API (except possibly selecting a different memory allocator)</li> 3751</ul> 3752 3753<p>Note that the thread safety cannot be ensured for multiple threads sharing 3754the same document, the locking must be done at the application level, libxml 3755exports a basic mutex and reentrant mutexes API in <libxml/threads.h>. 3756The parts of the library checked for thread safety are:</p> 3757<ul> 3758 <li>concurrent loading</li> 3759 <li>file access resolution</li> 3760 <li>catalog access</li> 3761 <li>catalog building</li> 3762 <li>entities lookup/accesses</li> 3763 <li>validation</li> 3764 <li>global variables per-thread override</li> 3765 <li>memory handling</li> 3766</ul> 3767 3768<p>XPath is supposed to be thread safe now, but this wasn't tested 3769seriously.</p> 3770 3771<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2> 3772 3773<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document 3774Object Model</em>; this is an API for accessing XML or HTML structured 3775documents. Native support for DOM in Gnome is on the way (module gnome-dom), 3776and will be based on gnome-xml. This will be a far cleaner interface to 3777manipulate XML files within Gnome since it won't expose the internal 3778structure.</p> 3779 3780<p>The current DOM implementation on top of libxml is the <a 3781href="http://cvs.gnome.org/lxr/source/gdome2/">gdome2 Gnome module</a>, this 3782is a full DOM interface, thanks to Paolo Casarini, check the <a 3783href="http://www.cs.unibo.it/~casarini/gdome2/">Gdome2 homepage</a> for more 3784informations.</p> 3785 3786<h2><a name="Example"></a><a name="real">A real example</a></h2> 3787 3788<p>Here is a real size example, where the actual content of the application 3789data is not kept in the DOM tree but uses internal structures. It is based on 3790a proposal to keep a database of jobs related to Gnome, with an XML based 3791storage structure. Here is an <a href="gjobs.xml">XML encoded jobs 3792base</a>:</p> 3793<pre><?xml version="1.0"?> 3794<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"> 3795 <gjob:Jobs> 3796 3797 <gjob:Job> 3798 <gjob:Project ID="3"/> 3799 <gjob:Application>GBackup</gjob:Application> 3800 <gjob:Category>Development</gjob:Category> 3801 3802 <gjob:Update> 3803 <gjob:Status>Open</gjob:Status> 3804 <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified> 3805 <gjob:Salary>USD 0.00</gjob:Salary> 3806 </gjob:Update> 3807 3808 <gjob:Developers> 3809 <gjob:Developer> 3810 </gjob:Developer> 3811 </gjob:Developers> 3812 3813 <gjob:Contact> 3814 <gjob:Person>Nathan Clemons</gjob:Person> 3815 <gjob:Email>nathan@windsofstorm.net</gjob:Email> 3816 <gjob:Company> 3817 </gjob:Company> 3818 <gjob:Organisation> 3819 </gjob:Organisation> 3820 <gjob:Webpage> 3821 </gjob:Webpage> 3822 <gjob:Snailmail> 3823 </gjob:Snailmail> 3824 <gjob:Phone> 3825 </gjob:Phone> 3826 </gjob:Contact> 3827 3828 <gjob:Requirements> 3829 The program should be released as free software, under the GPL. 3830 </gjob:Requirements> 3831 3832 <gjob:Skills> 3833 </gjob:Skills> 3834 3835 <gjob:Details> 3836 A GNOME based system that will allow a superuser to configure 3837 compressed and uncompressed files and/or file systems to be backed 3838 up with a supported media in the system. This should be able to 3839 perform via find commands generating a list of files that are passed 3840 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine 3841 or via operations performed on the filesystem itself. Email 3842 notification and GUI status display very important. 3843 </gjob:Details> 3844 3845 </gjob:Job> 3846 3847 </gjob:Jobs> 3848</gjob:Helping></pre> 3849 3850<p>While loading the XML file into an internal DOM tree is a matter of 3851calling only a couple of functions, browsing the tree to gather the data and 3852generate the internal structures is harder, and more error prone.</p> 3853 3854<p>The suggested principle is to be tolerant with respect to the input 3855structure. For example, the ordering of the attributes is not significant, 3856the XML specification is clear about it. It's also usually a good idea not to 3857depend on the order of the children of a given node, unless it really makes 3858things harder. Here is some code to parse the information for a person:</p> 3859<pre>/* 3860 * A person record 3861 */ 3862typedef struct person { 3863 char *name; 3864 char *email; 3865 char *company; 3866 char *organisation; 3867 char *smail; 3868 char *webPage; 3869 char *phone; 3870} person, *personPtr; 3871 3872/* 3873 * And the code needed to parse it 3874 */ 3875personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 3876 personPtr ret = NULL; 3877 3878DEBUG("parsePerson\n"); 3879 /* 3880 * allocate the struct 3881 */ 3882 ret = (personPtr) malloc(sizeof(person)); 3883 if (ret == NULL) { 3884 fprintf(stderr,"out of memory\n"); 3885 return(NULL); 3886 } 3887 memset(ret, 0, sizeof(person)); 3888 3889 /* We don't care what the top level element name is */ 3890 cur = cur->xmlChildrenNode; 3891 while (cur != NULL) { 3892 if ((!strcmp(cur->name, "Person")) && (cur->ns == ns)) 3893 ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3894 if ((!strcmp(cur->name, "Email")) && (cur->ns == ns)) 3895 ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3896 cur = cur->next; 3897 } 3898 3899 return(ret); 3900}</pre> 3901 3902<p>Here are a couple of things to notice:</p> 3903<ul> 3904 <li>Usually a recursive parsing style is the more convenient one: XML data 3905 is by nature subject to repetitive constructs and usually exhibits highly 3906 structured patterns.</li> 3907 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, 3908 i.e. the pointer to the global XML document and the namespace reserved to 3909 the application. Document wide information are needed for example to 3910 decode entities and it's a good coding practice to define a namespace for 3911 your application set of data and test that the element and attributes 3912 you're analyzing actually pertains to your application space. This is 3913 done by a simple equality test (cur->ns == ns).</li> 3914 <li>To retrieve text and attributes value, you can use the function 3915 <em>xmlNodeListGetString</em> to gather all the text and entity reference 3916 nodes generated by the DOM output and produce an single text string.</li> 3917</ul> 3918 3919<p>Here is another piece of code used to parse another level of the 3920structure:</p> 3921<pre>#include <libxml/tree.h> 3922/* 3923 * a Description for a Job 3924 */ 3925typedef struct job { 3926 char *projectID; 3927 char *application; 3928 char *category; 3929 personPtr contact; 3930 int nbDevelopers; 3931 personPtr developers[100]; /* using dynamic alloc is left as an exercise */ 3932} job, *jobPtr; 3933 3934/* 3935 * And the code needed to parse it 3936 */ 3937jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 3938 jobPtr ret = NULL; 3939 3940DEBUG("parseJob\n"); 3941 /* 3942 * allocate the struct 3943 */ 3944 ret = (jobPtr) malloc(sizeof(job)); 3945 if (ret == NULL) { 3946 fprintf(stderr,"out of memory\n"); 3947 return(NULL); 3948 } 3949 memset(ret, 0, sizeof(job)); 3950 3951 /* We don't care what the top level element name is */ 3952 cur = cur->xmlChildrenNode; 3953 while (cur != NULL) { 3954 3955 if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) { 3956 ret->projectID = xmlGetProp(cur, "ID"); 3957 if (ret->projectID == NULL) { 3958 fprintf(stderr, "Project has no ID\n"); 3959 } 3960 } 3961 if ((!strcmp(cur->name, "Application")) && (cur->ns == ns)) 3962 ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3963 if ((!strcmp(cur->name, "Category")) && (cur->ns == ns)) 3964 ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3965 if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns)) 3966 ret->contact = parsePerson(doc, ns, cur); 3967 cur = cur->next; 3968 } 3969 3970 return(ret); 3971}</pre> 3972 3973<p>Once you are used to it, writing this kind of code is quite simple, but 3974boring. Ultimately, it could be possible to write stubbers taking either C 3975data structure definitions, a set of XML examples or an XML DTD and produce 3976the code needed to import and export the content between C data and XML 3977storage. This is left as an exercise to the reader :-)</p> 3978 3979<p>Feel free to use <a href="example/gjobread.c">the code for the full C 3980parsing example</a> as a template, it is also available with Makefile in the 3981Gnome CVS base under gnome-xml/example</p> 3982 3983<h2><a name="Contributi">Contributions</a></h2> 3984<ul> 3985 <li>Bjorn Reese, William Brack and Thomas Broyer have provided a number of 3986 patches, Gary Pennington worked on the validation API, threading support 3987 and Solaris port.</li> 3988 <li>John Fleck helps maintaining the documentation and man pages.</li> 3989 <li><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the 3990 maintainer of the Windows port, <a 3991 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 3992 binaries</a></li> 3993 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 3994 <a href="http://garypennington.net/libxml2/">Solaris binaries</a></li> 3995 <li><a 3996 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 3997 Sergeant</a> developed <a 3998 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 3999 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 4000 application server</a></li> 4001 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> and <a 4002 href="mailto:geertk@ai.rug.nl">Geert Kloosterman</a> provide <a 4003 href="libxml-doc.el">an emacs module</a> to lookup libxml(2) functions 4004 documentation</li> 4005 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a 4006 href="http://xmlsoft.org/messages/0488.html">man pages</a></li> 4007 <li>there is a module for <a 4008 href="http://acs-misc.sourceforge.net/nsxml.html">libxml/libxslt support 4009 in OpenNSD/AOLServer</a></li> 4010 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provided the 4011 first version of libxml/libxslt <a 4012 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li> 4013 <li>Petr Kozelka provides <a 4014 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 4015 libxml2</a> with Kylix and Delphi and other Pascal compilers</li> 4016 <li><a href="mailto:aleksey@aleksey.com">Aleksey Sanin</a> implemented the 4017 <a href="http://www.w3.org/Signature/">XML Canonicalization and XML 4018 Digital Signature</a> <a 4019 href="http://www.aleksey.com/xmlsec/">implementations for libxml2</a></li> 4020 <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a>, 4021 <a href="http://www.zveno.com/">Zveno</a> and contributors maintain 4022 <a href="http://tclxml.sourceforge.net/">tcl bindings for libxml2 and libxslt</a>, as well as 4023 <a href="http://tclxml.sf.net/tkxmllint.html">tkxmllint</a> a GUI for 4024 xmllint and 4025 <a href="http://tclxml.sf.net/tkxsltproc.html">tkxsltproc</a> a GUI for 4026 xsltproc. 4027</ul> 4028 4029<p></p> 4030</body> 4031</html> 4032
