xml.html revision 31ae462a4d0d8e10137b0f5be11d1f7fbbf8d704
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 parser and toolkit of 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 parser and toolkit of 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>Libxml2 is the XML C parser and toolkit developed for the Gnome project 21(but usable outside of the Gnome platform), it is free software available 22under the <a href="http://www.opensource.org/licenses/mit-license.html">MIT 23License</a>. XML itself is a metalanguage to design markup languages, i.e. 24text language where semantic and structure are added to the content using 25extra "markup" information enclosed between angle brackets. HTML is the most 26well-known markup language. Though the library is written in C <a 27href="python.html">a variety of language bindings</a> make it available in 28other environments.</p> 29 30<p>Libxml2 is known to be very portable, the library should build and work 31without serious troubles on a variety of systems (Linux, Unix, Windows, 32CygWin, MacOS, MacOS X, RISC Os, OS/2, VMS, QNX, MVS, ...)</p> 33 34<p>Libxml2 implements a number of existing standards related to markup 35languages:</p> 36<ul> 37 <li>the XML standard: <a 38 href="http://www.w3.org/TR/REC-xml">http://www.w3.org/TR/REC-xml</a></li> 39 <li>Namespaces in XML: <a 40 href="http://www.w3.org/TR/REC-xml-names/">http://www.w3.org/TR/REC-xml-names/</a></li> 41 <li>XML Base: <a 42 href="http://www.w3.org/TR/xmlbase/">http://www.w3.org/TR/xmlbase/</a></li> 43 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc2396.txt">RFC 2396</a> : 44 Uniform Resource Identifiers <a 45 href="http://www.ietf.org/rfc/rfc2396.txt">http://www.ietf.org/rfc/rfc2396.txt</a></li> 46 <li>XML Path Language (XPath) 1.0: <a 47 href="http://www.w3.org/TR/xpath">http://www.w3.org/TR/xpath</a></li> 48 <li>HTML4 parser: <a 49 href="http://www.w3.org/TR/html401/">http://www.w3.org/TR/html401/</a></li> 50 <li>XML Pointer Language (XPointer) Version 1.0: <a 51 href="http://www.w3.org/TR/xptr">http://www.w3.org/TR/xptr</a></li> 52 <li>XML Inclusions (XInclude) Version 1.0: <a 53 href="http://www.w3.org/TR/xinclude/">http://www.w3.org/TR/xinclude/</a></li> 54 <li>ISO-8859-x encodings, as well as <a 55 href="http://www.cis.ohio-state.edu/rfc/rfc2044.txt">rfc2044</a> [UTF-8] 56 and <a href="http://www.cis.ohio-state.edu/rfc/rfc2781.txt">rfc2781</a> 57 [UTF-16] Unicode encodings, and more if using iconv support</li> 58 <li>part of SGML Open Technical Resolution TR9401:1997</li> 59 <li>XML Catalogs Working Draft 06 August 2001: <a 60 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> 61 <li>Canonical XML Version 1.0: <a 62 href="http://www.w3.org/TR/xml-c14n">http://www.w3.org/TR/xml-c14n</a> 63 and the Exclusive XML Canonicalization CR draft <a 64 href="http://www.w3.org/TR/xml-exc-c14n">http://www.w3.org/TR/xml-exc-c14n</a></li> 65 <li>Relax NG, ISO/IEC 19757-2:2003, <a 66 href="http://www.oasis-open.org/committees/relax-ng/spec-20011203.html">http://www.oasis-open.org/committees/relax-ng/spec-20011203.html</a></li> 67 <li>W3C XML Schemas Part 2: Datatypes <a 68 href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/">REC 02 May 69 2001</a></li> 70</ul> 71 72<p>In most cases libxml2 tries to implement the specifications in a 73relatively strictly compliant way. As of release 2.4.16, libxml2 passes all 741800+ tests from the <a 75href="http://www.oasis-open.org/committees/xml-conformance/">OASIS XML Tests 76Suite</a>.</p> 77 78<p>To some extent libxml2 provides support for the following additional 79specifications but doesn't claim to implement them completely:</p> 80<ul> 81 <li>Document Object Model (DOM) <a 82 href="http://www.w3.org/TR/DOM-Level-2-Core/">http://www.w3.org/TR/DOM-Level-2-Core/</a> 83 it doesn't implement the API itself, gdome2 does this on top of 84 libxml2</li> 85 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc959.txt">RFC 959</a> : 86 libxml2 implements a basic FTP client code</li> 87 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc1945.txt">RFC 1945</a> : 88 HTTP/1.0, again a basic HTTP client code</li> 89 <li>SAX: a minimal SAX implementation compatible with early expat 90 versions</li> 91 <li>DocBook SGML v4: libxml2 includes a hackish parser to transition to 92 XML</li> 93</ul> 94 95<p>A partial implementation of <a 96href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/">XML Schemas Part 971: Structure</a> is being worked on but it would be far too early to make any 98conformance statement about it at the moment.</p> 99 100<p>Separate documents:</p> 101<ul> 102 <li><a href="http://xmlsoft.org/XSLT/">the libxslt page</a> providing an 103 implementation of XSLT 1.0 and common extensions like EXSLT for 104 libxml2</li> 105 <li><a href="http://www.cs.unibo.it/~casarini/gdome2/">the gdome2 page</a> 106 : a standard DOM2 implementation for libxml2</li> 107 <li><a href="http://www.aleksey.com/xmlsec/">the XMLSec page</a>: an 108 implementation of <a href="http://www.w3.org/TR/xmldsig-core/">W3C XML 109 Digital Signature</a> for libxml2</li> 110 <li>also check the related links section below for more related and active 111 projects.</li> 112</ul> 113 114<p>Results of the <a 115href="http://xmlbench.sourceforge.net/results/benchmark/index.html">xmlbench 116benchmark</a> on sourceforge February 2004 (smaller is better):</p> 117 118<p align="center"><img src="benchmark.png" 119alt="benchmark results for Expat Xerces libxml2 Oracle and Sun toolkits"></p> 120 121<p>Logo designed by <a href="mailto:liyanage@access.ch">Marc Liyanage</a>.</p> 122 123<h2><a name="Introducti">Introduction</a></h2> 124 125<p>This document describes libxml, the <a 126href="http://www.w3.org/XML/">XML</a> C parser and toolkit developed for the 127<a href="http://www.gnome.org/">Gnome</a> project. <a 128href="http://www.w3.org/XML/">XML is a standard</a> for building tag-based 129structured documents/data.</p> 130 131<p>Here are some key points about libxml:</p> 132<ul> 133 <li>Libxml2 exports Push (progressive) and Pull (blocking) type parser 134 interfaces for both XML and HTML.</li> 135 <li>Libxml2 can do DTD validation at parse time, using a parsed document 136 instance, or with an arbitrary DTD.</li> 137 <li>Libxml2 includes complete <a 138 href="http://www.w3.org/TR/xpath">XPath</a>, <a 139 href="http://www.w3.org/TR/xptr">XPointer</a> and <a 140 href="http://www.w3.org/TR/xinclude">XInclude</a> implementations.</li> 141 <li>It is written in plain C, making as few assumptions as possible, and 142 sticking closely to ANSI C/POSIX for easy embedding. Works on 143 Linux/Unix/Windows, ported to a number of other platforms.</li> 144 <li>Basic support for HTTP and FTP client allowing applications to fetch 145 remote resources.</li> 146 <li>The design is modular, most of the extensions can be compiled out.</li> 147 <li>The internal document representation is as close as possible to the <a 148 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li> 149 <li>Libxml2 also has a <a 150 href="http://www.megginson.com/SAX/index.html">SAX like interface</a>; 151 the interface is designed to be compatible with <a 152 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li> 153 <li>This library is released under the <a 154 href="http://www.opensource.org/licenses/mit-license.html">MIT 155 License</a>. See the Copyright file in the distribution for the precise 156 wording.</li> 157</ul> 158 159<p>Warning: unless you are forced to because your application links with a 160Gnome-1.X library requiring it, <strong><span 161style="background-color: #FF0000">Do Not Use libxml1</span></strong>, use 162libxml2</p> 163 164<h2><a name="FAQ">FAQ</a></h2> 165 166<p>Table of Contents:</p> 167<ul> 168 <li><a href="FAQ.html#License">License(s)</a></li> 169 <li><a href="FAQ.html#Installati">Installation</a></li> 170 <li><a href="FAQ.html#Compilatio">Compilation</a></li> 171 <li><a href="FAQ.html#Developer">Developer corner</a></li> 172</ul> 173 174<h3><a name="License">License</a>(s)</h3> 175<ol> 176 <li><em>Licensing Terms for libxml</em> 177 <p>libxml2 is released under the <a 178 href="http://www.opensource.org/licenses/mit-license.html">MIT 179 License</a>; see the file Copyright in the distribution for the precise 180 wording</p> 181 </li> 182 <li><em>Can I embed libxml2 in a proprietary application ?</em> 183 <p>Yes. The MIT License allows you to keep proprietary the changes you 184 made to libxml, but it would be graceful to send-back bug fixes and 185 improvements as patches for possible incorporation in the main 186 development tree.</p> 187 </li> 188</ol> 189 190<h3><a name="Installati">Installation</a></h3> 191<ol> 192 <li><strong><span style="background-color: #FF0000">Do Not Use 193 libxml1</span></strong>, use libxml2</li> 194 <li><em>Where can I get libxml</em> ? 195 <p>The original distribution comes from <a 196 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a 197 href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.6/">gnome.org</a></p> 198 <p>Most Linux and BSD distributions include libxml, this is probably the 199 safer way for end-users to use libxml.</p> 200 <p>David Doolin provides precompiled Windows versions at <a 201 href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p> 202 </li> 203 <li><em>I see libxml and libxml2 releases, which one should I install ?</em> 204 <ul> 205 <li>If you are not constrained by backward compatibility issues with 206 existing applications, install libxml2 only</li> 207 <li>If you are not doing development, you can safely install both. 208 Usually the packages <a 209 href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a 210 href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are 211 compatible (this is not the case for development packages).</li> 212 <li>If you are a developer and your system provides separate packaging 213 for shared libraries and the development components, it is possible 214 to install libxml and libxml2, and also <a 215 href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> 216 and <a 217 href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> 218 too for libxml2 >= 2.3.0</li> 219 <li>If you are developing a new application, please develop against 220 libxml2(-devel)</li> 221 </ul> 222 </li> 223 <li><em>I can't install the libxml package, it conflicts with libxml0</em> 224 <p>You probably have an old libxml0 package used to provide the shared 225 library for libxml.so.0, you can probably safely remove it. The libxml 226 packages provided on <a 227 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provide 228 libxml.so.0</p> 229 </li> 230 <li><em>I can't install the libxml(2) RPM package due to failed 231 dependencies</em> 232 <p>The most generic solution is to re-fetch the latest src.rpm , and 233 rebuild it locally with</p> 234 <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> 235 <p>If everything goes well it will generate two binary rpm packages (one 236 providing the shared libs and xmllint, and the other one, the -devel 237 package, providing includes, static libraries and scripts needed to build 238 applications with libxml(2)) that you can install locally.</p> 239 </li> 240</ol> 241 242<h3><a name="Compilatio">Compilation</a></h3> 243<ol> 244 <li><em>What is the process to compile libxml2 ?</em> 245 <p>As most UNIX libraries libxml2 follows the "standard":</p> 246 <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> 247 <p><code>cd libxml-xxxx</code></p> 248 <p><code>/configure --help</code></p> 249 <p>to see the options, then the compilation/installation proper</p> 250 <p><code>/configure [possible options]</code></p> 251 <p><code>make</code></p> 252 <p><code>make install</code></p> 253 <p>At that point you may have to rerun ldconfig or a similar utility to 254 update your list of installed shared libs.</p> 255 </li> 256 <li><em>What other libraries are needed to compile/install libxml2 ?</em> 257 <p>Libxml2 does not require any other library, the normal C ANSI API 258 should be sufficient (please report any violation to this rule you may 259 find).</p> 260 <p>However if found at configuration time libxml2 will detect and use the 261 following libs:</p> 262 <ul> 263 <li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a 264 highly portable and available widely compression library.</li> 265 <li>iconv: a powerful character encoding conversion library. It is 266 included by default in recent glibc libraries, so it doesn't need to 267 be installed specifically on Linux. It now seems a <a 268 href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part 269 of the official UNIX</a> specification. Here is one <a 270 href="http://www.gnu.org/software/libiconv/">implementation of the 271 library</a> which source can be found <a 272 href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> 273 </ul> 274 </li> 275 <li><em>Make check fails on some platforms</em> 276 <p>Sometimes the regression tests' results don't completely match the 277 value produced by the parser, and the makefile uses diff to print the 278 delta. On some platforms the diff return breaks the compilation process; 279 if the diff is small this is probably not a serious problem.</p> 280 <p>Sometimes (especially on Solaris) make checks fail due to limitations 281 in make. Try using GNU-make instead.</p> 282 </li> 283 <li><em>I use the CVS version and there is no configure script</em> 284 <p>The configure script (and other Makefiles) are generated. Use the 285 autogen.sh script to regenerate the configure script and Makefiles, 286 like:</p> 287 <p><code>/autogen.sh --prefix=/usr --disable-shared</code></p> 288 </li> 289 <li><em>I have troubles when running make tests with gcc-3.0</em> 290 <p>It seems the initial release of gcc-3.0 has a problem with the 291 optimizer which miscompiles the URI module. Please use another 292 compiler.</p> 293 </li> 294</ol> 295 296<h3><a name="Developer">Developer</a> corner</h3> 297<ol> 298 <li><em>Troubles compiling or linking programs using libxml2</em> 299 <p>Usually the problem comes from the fact that the compiler doesn't get 300 the right compilation or linking flags. There is a small shell script 301 <code>xml2-config</code> which is installed as part of libxml2 usual 302 install process which provides those flags. Use</p> 303 <p><code>xml2-config --cflags</code></p> 304 <p>to get the compilation flags and</p> 305 <p><code>xml2-config --libs</code></p> 306 <p>to get the linker flags. Usually this is done directly from the 307 Makefile as:</p> 308 <p><code>CFLAGS=`xml2-config --cflags`</code></p> 309 <p><code>LIBS=`xml2-config --libs`</code></p> 310 </li> 311 <li><em>xmlDocDump() generates output on one line.</em> 312 <p>Libxml2 will not <strong>invent</strong> spaces in the content of a 313 document since <strong>all spaces in the content of a document are 314 significant</strong>. If you build a tree from the API and want 315 indentation:</p> 316 <ol> 317 <li>the correct way is to generate those yourself too.</li> 318 <li>the dangerous way is to ask libxml2 to add those blanks to your 319 content <strong>modifying the content of your document in the 320 process</strong>. The result may not be what you expect. There is 321 <strong>NO</strong> way to guarantee that such a modification won't 322 affect other parts of the content of your document. See <a 323 href="http://xmlsoft.org/html/libxml-parser.html#xmlKeepBlanksDefault">xmlKeepBlanksDefault 324 ()</a> and <a 325 href="http://xmlsoft.org/html/libxml-tree.html#xmlSaveFormatFile">xmlSaveFormatFile 326 ()</a></li> 327 </ol> 328 </li> 329 <li>Extra nodes in the document: 330 <p><em>For a XML file as below:</em></p> 331 <pre><?xml version="1.0"?> 332<PLAN xmlns="http://www.argus.ca/autotest/1.0/"> 333<NODE CommFlag="0"/> 334<NODE CommFlag="1"/> 335</PLAN></pre> 336 <p><em>after parsing it with the function 337 pxmlDoc=xmlParseFile(...);</em></p> 338 <p><em>I want to the get the content of the first node (node with the 339 CommFlag="0")</em></p> 340 <p><em>so I did it as following;</em></p> 341 <pre>xmlNodePtr pnode; 342pnode=pxmlDoc->children->children;</pre> 343 <p><em>but it does not work. If I change it to</em></p> 344 <pre>pnode=pxmlDoc->children->children->next;</pre> 345 <p><em>then it works. Can someone explain it to me.</em></p> 346 <p></p> 347 <p>In XML all characters in the content of the document are significant 348 <strong>including blanks and formatting line breaks</strong>.</p> 349 <p>The extra nodes you are wondering about are just that, text nodes with 350 the formatting spaces which are part of the document but that people tend 351 to forget. There is a function <a 352 href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault 353 ()</a> to remove those at parse time, but that's an heuristic, and its 354 use should be limited to cases where you are certain there is no 355 mixed-content in the document.</p> 356 </li> 357 <li><em>I get compilation errors of existing code like when accessing 358 <strong>root</strong> or <strong>child fields</strong> of nodes.</em> 359 <p>You are compiling code developed for libxml version 1 and using a 360 libxml2 development environment. Either switch back to libxml v1 devel or 361 even better fix the code to compile with libxml2 (or both) by <a 362 href="upgrade.html">following the instructions</a>.</p> 363 </li> 364 <li><em>I get compilation errors about non existing 365 <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> 366 fields.</em> 367 <p>The source code you are using has been <a 368 href="upgrade.html">upgraded</a> to be able to compile with both libxml 369 and libxml2, but you need to install a more recent version: 370 libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> 371 </li> 372 <li><em>XPath implementation looks seriously broken</em> 373 <p>XPath implementation prior to 2.3.0 was really incomplete. Upgrade to 374 a recent version, there are no known bugs in the current version.</p> 375 </li> 376 <li><em>The example provided in the web page does not compile.</em> 377 <p>It's hard to maintain the documentation in sync with the code 378 <grin/> ...</p> 379 <p>Check the previous points 1/ and 2/ raised before, and please send 380 patches.</p> 381 </li> 382 <li><em>Where can I get more examples and information than provided on the 383 web page?</em> 384 <p>Ideally a libxml2 book would be nice. I have no such plan ... But you 385 can:</p> 386 <ul> 387 <li>check more deeply the <a href="html/libxml-lib.html">existing 388 generated doc</a></li> 389 <li>have a look at <a href="examples/index.html">the set of 390 examples</a>.</li> 391 <li>look for examples of use for libxml2 function using the Gnome code. 392 For example the following will query the full Gnome CVS base for the 393 use of the <strong>xmlAddChild()</strong> function: 394 <p><a 395 href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> 396 <p>This may be slow, a large hardware donation to the gnome project 397 could cure this :-)</p> 398 </li> 399 <li><a 400 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse 401 the libxml2 source</a> , I try to write code as clean and documented 402 as possible, so looking at it may be helpful. In particular the code 403 of xmllint.c and of the various testXXX.c test programs should 404 provide good examples of how to do things with the library.</li> 405 </ul> 406 </li> 407 <li>What about C++ ? 408 <p>libxml2 is written in pure C in order to allow easy reuse on a number 409 of platforms, including embedded systems. I don't intend to convert to 410 C++.</p> 411 <p>There is however a C++ wrapper which may fulfill your needs:</p> 412 <ul> 413 <li>by Ari Johnson <ari@btigate.com>: 414 <p>Website: <a 415 href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a></p> 416 <p>Download: <a 417 href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a></p> 418 </li> 419 <!-- Website is currently unavailable as of 2003-08-02 420 <li>by Peter Jones <pjones@pmade.org> 421 <p>Website: <a 422 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 423 </li> 424 --> 425 </ul> 426 </li> 427 <li>How to validate a document a posteriori ? 428 <p>It is possible to validate documents which had not been validated at 429 initial parsing time or documents which have been built from scratch 430 using the API. Use the <a 431 href="http://xmlsoft.org/html/libxml-valid.html#xmlValidateDtd">xmlValidateDtd()</a> 432 function. It is also possible to simply add a DTD to an existing 433 document:</p> 434 <pre>xmlDocPtr doc; /* your existing document */ 435xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 436 437 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 438 439 doc->intSubset = dtd; 440 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 441 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 442 </pre> 443 </li> 444 <li>So what is this funky "xmlChar" used all the time? 445 <p>It is a null terminated sequence of utf-8 characters. And only utf-8! 446 You need to convert strings encoded in different ways to utf-8 before 447 passing them to the API. This can be accomplished with the iconv library 448 for instance.</p> 449 </li> 450 <li>etc ...</li> 451</ol> 452 453<p></p> 454 455<h2><a name="Documentat">Developer Menu</a></h2> 456 457<p>There are several on-line resources related to using libxml:</p> 458<ol> 459 <li>Use the <a href="search.php">search engine</a> to look up 460 information.</li> 461 <li>Check the <a href="FAQ.html">FAQ.</a></li> 462 <li>Check the <a href="http://xmlsoft.org/html/libxml-lib.html">extensive 463 documentation</a> automatically extracted from code comments.</li> 464 <li>Look at the documentation about <a href="encoding.html">libxml 465 internationalization support</a>.</li> 466 <li>This page provides a global overview and <a href="example.html">some 467 examples</a> on how to use libxml.</li> 468 <li><a href="examples/index.html">Code examples</a></li> 469 <li>John Fleck's libxml2 tutorial: <a href="tutorial/index.html">html</a> 470 or <a href="tutorial/xmltutorial.pdf">pdf</a>.</li> 471 <li>If you need to parse large files, check the <a 472 href="xmlreader.html">xmlReader</a> API tutorial</li> 473 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a 474 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice 475 documentation</a> explaining how to use the libxml SAX interface.</li> 476 <li>George Lebl wrote <a 477 href="http://www-106.ibm.com/developerworks/library/l-gnome3/">an article 478 for IBM developerWorks</a> about using libxml.</li> 479 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO 480 file</a>.</li> 481 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a> 482 description. If you are starting a new project using libxml you should 483 really use the 2.x version.</li> 484 <li>And don't forget to look at the <a 485 href="http://mail.gnome.org/archives/xml/">mailing-list archive</a>.</li> 486</ol> 487 488<h2><a name="Reporting">Reporting bugs and getting help</a></h2> 489 490<p>Well, bugs or missing features are always possible, and I will make a 491point of fixing them in a timely fashion. The best way to report a bug is to 492use the <a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Gnome 493bug tracking database</a> (make sure to use the "libxml2" module name). I 494look at reports there regularly and it's good to have a reminder when a bug 495is still open. Be sure to specify that the bug is for the package libxml2.</p> 496 497<p>For small problems you can try to get help on IRC, the #xml channel on 498irc.gnome.org (port 6667) usually have a few person subscribed which may help 499(but there is no garantee and if a real issue is raised it should go on the 500mailing-list for archival).</p> 501 502<p>There is also a mailing-list <a 503href="mailto:xml@gnome.org">xml@gnome.org</a> for libxml, with an <a 504href="http://mail.gnome.org/archives/xml/">on-line archive</a> (<a 505href="http://xmlsoft.org/messages">old</a>). To subscribe to this list, 506please visit the <a 507href="http://mail.gnome.org/mailman/listinfo/xml">associated Web</a> page and 508follow the instructions. <strong>Do not send code, I won't debug it</strong> 509(but patches are really appreciated!).</p> 510 511<p>Check the following <strong><span style="color: #FF0000">before 512posting</span></strong>:</p> 513<ul> 514 <li>Read the <a href="FAQ.html">FAQ</a> and <a href="search.php">use the 515 search engine</a> to get information related to your problem.</li> 516 <li>Make sure you are <a href="ftp://xmlsoft.org/">using a recent 517 version</a>, and that the problem still shows up in a recent version.</li> 518 <li>Check the <a href="http://mail.gnome.org/archives/xml/">list 519 archives</a> to see if the problem was reported already. In this case 520 there is probably a fix available, similarly check the <a 521 href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">registered 522 open bugs</a>.</li> 523 <li>Make sure you can reproduce the bug with xmllint or one of the test 524 programs found in source in the distribution.</li> 525 <li>Please send the command showing the error as well as the input (as an 526 attachment)</li> 527</ul> 528 529<p>Then send the bug with associated information to reproduce it to the <a 530href="mailto:xml@gnome.org">xml@gnome.org</a> list; if it's really libxml 531related I will approve it. Please do not send mail to me directly, it makes 532things really hard to track and in some cases I am not the best person to 533answer a given question, ask on the list.</p> 534 535<p>To <span style="color: #E50000">be really clear about support</span>:</p> 536<ul> 537 <li>Support or help <span style="color: #E50000">requests MUST be sent to 538 the list or on bugzilla</span> in case of problems, so that the Question 539 and Answers can be shared publicly. Failing to do so carries the implicit 540 message "I want free support but I don't want to share the benefits with 541 others" and is not welcome. I will automatically Carbon-Copy the 542 xml@gnome.org mailing list for any technical reply made about libxml2 or 543 libxslt.</li> 544 <li>There is <span style="color: #E50000">no garantee of support</span>, if 545 your question remains unanswered after a week, repost it, making sure you 546 gave all the detail needed and the information requested.</li> 547 <li>Failing to provide information as requested or double checking first 548 for prior feedback also carries the implicit message "the time of the 549 library maintainers is less valuable than my time" and might not be 550 welcome.</li> 551</ul> 552 553<p>Of course, bugs reported with a suggested patch for fixing them will 554probably be processed faster than those without.</p> 555 556<p>If you're looking for help, a quick look at <a 557href="http://mail.gnome.org/archives/xml/">the list archive</a> may actually 558provide the answer. I usually send source samples when answering libxml2 559usage questions. The <a 560href="http://xmlsoft.org/html/book1.html">auto-generated documentation</a> is 561not as polished as I would like (i need to learn more about DocBook), but 562it's a good starting point.</p> 563 564<h2><a name="help">How to help</a></h2> 565 566<p>You can help the project in various ways, the best thing to do first is to 567subscribe to the mailing-list as explained before, check the <a 568href="http://mail.gnome.org/archives/xml/">archives </a>and the <a 569href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Gnome bug 570database</a>:</p> 571<ol> 572 <li>Provide patches when you find problems.</li> 573 <li>Provide the diffs when you port libxml2 to a new platform. They may not 574 be integrated in all cases but help pinpointing portability problems 575 and</li> 576 <li>Provide documentation fixes (either as patches to the code comments or 577 as HTML diffs).</li> 578 <li>Provide new documentations pieces (translations, examples, etc 579 ...).</li> 580 <li>Check the TODO file and try to close one of the items.</li> 581 <li>Take one of the points raised in the archive or the bug database and 582 provide a fix. <a href="mailto:daniel@veillard.com">Get in touch with me 583 </a>before to avoid synchronization problems and check that the suggested 584 fix will fit in nicely :-)</li> 585</ol> 586 587<h2><a name="Downloads">Downloads</a></h2> 588 589<p>The latest versions of libxml2 can be found on <a 590href="ftp://xmlsoft.org/">xmlsoft.org</a> (<a 591href="ftp://speakeasy.rpmfind.net/pub/libxml/">Seattle</a>, <a 592href="ftp://fr.rpmfind.net/pub/libxml/">France</a>) or on the <a 593href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either 594as a <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.6/">source 595archive</a><!-- commenting this out because they seem to have disappeared or <a 596href="ftp://ftp.gnome.org/pub/GNOME/stable/redhat/i386/libxml/">RPM 597packages</a> --> 598 , Antonin Sprinzl also provide <a href="ftp://gd.tuwien.ac.at/pub/libxml/">a 599mirror in Austria</a>. (NOTE that you need both the <a 600href="http://rpmfind.net/linux/RPM/libxml2.html">libxml(2)</a> and <a 601href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml(2)-devel</a> 602packages installed to compile applications using libxml.)</p> 603 604<p>Binary ports:</p> 605<ul> 606 <li>Red Hat RPMs for i386 are available directly on <a 607 href="ftp://xmlsoft.org/">xmlsoft.org</a>, the source RPM will compile on 608 any architecture supported by Red Hat.</li> 609 <li><p><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a></p> 610 is now the maintainer of the Windows port, <a 611 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 612 binaries</a>.</li> 613 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 614 <a href="http://garypennington.net/libxml2/">Solaris binaries</a>.</li> 615 <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a> provides <a 616 href="http://www.zveno.com/open_source/libxml2xslt.html">Mac Os X 617 binaries</a>.</li> 618 <li>The HP-UX porting center provides <a 619 href="http://hpux.connect.org.uk/hppd/hpux/Gnome/">HP-UX binaries</a></li> 620</ul> 621 622<p>If you know other supported binary ports, please <a 623href="http://veillard.com/">contact me</a>.</p> 624 625<p><a name="Snapshot">Snapshot:</a></p> 626<ul> 627 <li>Code from the W3C cvs base gnome-xml <a 628 href="ftp://xmlsoft.org/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a>.</li> 629 <li>Docs, content of the web site, the list archive included <a 630 href="ftp://xmlsoft.org/libxml-docs.tar.gz">libxml-docs.tar.gz</a>.</li> 631</ul> 632 633<p><a name="Contribs">Contributions:</a></p> 634 635<p>I do accept external contributions, especially if compiling on another 636platform, get in touch with me to upload the package, wrappers for various 637languages have been provided, and can be found in the <a 638href="contribs.html">contrib section</a></p> 639 640<p>Libxml2 is also available from CVS:</p> 641<ul> 642 <li><p>The <a 643 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Gnome 644 CVS base</a>. Check the <a 645 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> 646 page; the CVS module is <b>gnome-xml</b>.</p> 647 </li> 648 <li>The <strong>libxslt</strong> module is also present there</li> 649</ul> 650 651<h2><a name="News">News</a></h2> 652 653<h3>CVS only : check the <a 654href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file 655for a really accurate description</h3> 656 657<p>Items not finished and worked on, get in touch with the list if you want 658to test those</p> 659<ul> 660 <li>More testing on RelaxNG</li> 661 <li>Finishing up <a href="http://www.w3.org/TR/xmlschema-1/">XML 662 Schemas</a></li> 663</ul> 664 665<h3>2.6.6: Feb 12 2004</h3> 666<ul> 667 <li>nanohttp and nanoftp: buffer overflow error on URI parsing (Igor and 668 William) reported by Yuuichi Teranishi</li> 669 <li>bugfixes: make test and path issues, xmlWriter attribute serialization 670 (William Brack), xmlWriter indentation (William), schemas validation 671 (Eric Haszlakiewicz), XInclude dictionnaries issues (William and Oleg 672 Paraschenko), XInclude empty fallback (William), HTML warnings (William), 673 XPointer in XInclude (William), Python namespace serialization, 674 isolat1ToUTF8 bound error (Alfred Mickautsch), output of parameter 675 entities in internal subset (William), internal subset bug in push mode, 676 <xs:all> fix (Alexey Sarytchev)</li> 677 <li>Build: fix for automake-1.8 (Alexander Winston), warnings removal 678 (Philip Ludlam), SOCKLEN_T detection fixes (Daniel Richard), fix 679 --with-minimum configuration.</li> 680 <li>XInclude: allow the 2001 namespace without warning.</li> 681 <li>Documentation: missing example/index.html (John Fleck), version 682 dependancies (John Fleck)</li> 683 <li>reader API: structured error reporting (Steve Ball)</li> 684 <li>Windows compilation: mingw, msys (Mikhail Grushinskiy), function 685 prototype (Cameron Johnson), MSVC6 compiler warnings, _WINSOCKAPI_ 686 patch</li> 687 <li>Parsers: added xmlByteConsumed(ctxt) API to get the byte offest in 688 input.</li> 689</ul> 690 691<h3>2.6.5: Jan 25 2004</h3> 692<ul> 693 <li>Bugfixes: dictionnaries for schemas (William Brack), regexp segfault 694 (William), xs:all problem (William), a number of XPointer bugfixes 695 (William), xmllint error go to stderr, DTD validation problem with 696 namespace, memory leak (William), SAX1 cleanup and minimal options fixes 697 (Mark Vadoc), parser context reset on error (Shaun McCance), XPath union 698 evaluation problem (William) , xmlReallocLoc with NULL (Aleksey Sanin), 699 XML Schemas double free (Steve Ball), XInclude with no href, argument 700 callbacks order for XPath callbacks (Frederic Peters)</li> 701 <li>Documentation: python scripts (William Brack), xslt stylesheets (John 702 Fleck), doc (Sven Zimmerman), I/O example.</li> 703 <li>Python bindings: fixes (William), enum support (St�phane Bidoul), 704 structured error reporting (St�phane Bidoul)</li> 705 <li>XInclude: various fixes for conformance, problem related to dictionnary 706 references (William & me), recursion (William)</li> 707 <li>xmlWriter: indentation (Lucas Brasilino), memory leaks (Alfred 708 Mickautsch),</li> 709 <li>xmlSchemas: normalizedString datatype (John Belmonte)</li> 710 <li>code cleanup for strings functions (William)</li> 711 <li>Windows: compiler patches (Mark Vakoc)</li> 712 <li>Parser optimizations, a few new XPath and dictionnary APIs for future 713 XSLT optimizations.</li> 714</ul> 715 716<h3>2.6.4: Dec 24 2003</h3> 717<ul> 718 <li>Windows build fixes (Igor Zlatkovic)</li> 719 <li>Some serious XInclude problems reported by Oleg Paraschenko and</li> 720 <li>Unix and Makefile packaging fixes (me, William Brack,</li> 721 <li>Documentation improvements (John Fleck, William Brack), example fix 722 (Lucas Brasilino)</li> 723 <li>bugfixes: xmlTextReaderExpand() with xmlReaderWalker, XPath handling of 724 NULL strings (William Brack) , API building reader or parser from 725 filedescriptor should not close it, changed XPath sorting to be stable 726 again (William Brack), xmlGetNodePath() generating '(null)' (William 727 Brack), DTD validation and namespace bug (William Brack), XML Schemas 728 double inclusion behaviour</li> 729</ul> 730 731<h3>2.6.3: Dec 10 2003</h3> 732<ul> 733 <li>documentation updates and cleanup (DV, William Brack, John Fleck)</li> 734 <li>added a repository of examples, examples from Aleksey Sanin, Dodji 735 Seketeli, Alfred Mickautsch</li> 736 <li>Windows updates: Mark Vakoc, Igor Zlatkovic, Eric Zurcher, Mingw 737 (Kenneth Haley)</li> 738 <li>Unicode range checking (William Brack)</li> 739 <li>code cleanup (William Brack)</li> 740 <li>Python bindings: doc (John Fleck), bug fixes</li> 741 <li>UTF-16 cleanup and BOM issues (William Brack)</li> 742 <li>bug fixes: ID and xmlReader validation, XPath (William Brack), 743 xmlWriter (Alfred Mickautsch), hash.h inclusion problem, HTML parser 744 (James Bursa), attribute defaulting and validation, some serialization 745 cleanups, XML_GET_LINE macro, memory debug when using threads (William 746 Brack), serialization of attributes and entities content, xmlWriter 747 (Daniel Schulman)</li> 748 <li>XInclude bugfix, new APIs and update to the last version including the 749 namespace change.</li> 750 <li>XML Schemas improvements: include (Robert Stepanek), import and 751 namespace handling, fixed the regression tests troubles, added examples 752 based on Eric van der Vlist book, regexp fixes</li> 753 <li>preliminary pattern support for streaming (needed for schemas 754 constraints), added xmlTextReaderPreservePattern() to collect subdocument 755 when streaming.</li> 756 <li>various fixes in the structured error handling</li> 757</ul> 758 759<h3>2.6.2: Nov 4 2003</h3> 760<ul> 761 <li>XPath context unregistration fixes</li> 762 <li>text node coalescing fixes (Mark Lilback)</li> 763 <li>API to screate a W3C Schemas from an existing document (Steve Ball)</li> 764 <li>BeOS patches (Marcin 'Shard' Konicki)</li> 765 <li>xmlStrVPrintf function added (Aleksey Sanin)</li> 766 <li>compilation fixes (Mark Vakoc)</li> 767 <li>stdin parsing fix (William Brack)</li> 768 <li>a posteriori DTD validation fixes</li> 769 <li>xmlReader bug fixes: Walker fixes, python bindings</li> 770 <li>fixed xmlStopParser() to really stop the parser and errors</li> 771 <li>always generate line numbers when using the new xmlReadxxx 772 functions</li> 773 <li>added XInclude support to the xmlReader interface</li> 774 <li>implemented XML_PARSE_NONET parser option</li> 775 <li>DocBook XSLT processing bug fixed</li> 776 <li>HTML serialization for <p> elements (William Brack and me)</li> 777 <li>XPointer failure in XInclude are now handled as resource errors</li> 778 <li>fixed xmllint --html to use the HTML serializer on output (added 779 --xmlout to implement the previous behaviour of saving it using the XML 780 serializer)</li> 781</ul> 782 783<h3>2.6.1: Oct 28 2003</h3> 784<ul> 785 <li>Mostly bugfixes after the big 2.6.0 changes</li> 786 <li>Unix compilation patches: libxml.m4 (Patrick Welche), warnings cleanup 787 (William Brack)</li> 788 <li>Windows compilation patches (Joachim Bauch, Stephane Bidoul, Igor 789 Zlatkovic)</li> 790 <li>xmlWriter bugfix (Alfred Mickautsch)</li> 791 <li>chvalid.[ch]: couple of fixes from Stephane Bidoul</li> 792 <li>context reset: error state reset, push parser reset (Graham 793 Bennett)</li> 794 <li>context reuse: generate errors if file is not readable</li> 795 <li>defaulted attributes for element coming from internal entities 796 (Stephane Bidoul)</li> 797 <li>Python: tab and spaces mix (William Brack)</li> 798 <li>Error handler could crash in DTD validation in 2.6.0</li> 799 <li>xmlReader: do not use the document or element _private field</li> 800 <li>testSAX.c: avoid a problem with some PIs (Massimo Morara)</li> 801 <li>general bug fixes: mandatory encoding in text decl, serializing 802 Document Fragment nodes, xmlSearchNs 2.6.0 problem (Kasimier Buchcik), 803 XPath errors not reported, slow HTML parsing of large documents.</li> 804</ul> 805 806<h3>2.6.0: Oct 20 2003</h3> 807<ul> 808 <li>Major revision release: should be API and ABI compatible but got a lot 809 of change</li> 810 <li>Increased the library modularity, far more options can be stripped out, 811 a --with-minimum configuration will weight around 160KBytes</li> 812 <li>Use per parser and per document dictionnary, allocate names and small 813 text nodes from the dictionnary</li> 814 <li>Switch to a SAX2 like parser rewrote most of the XML parser core, 815 provides namespace resolution and defaulted attributes, minimize memory 816 allocations and copies, namespace checking and specific error handling, 817 immutable buffers, make predefined entities static structures, etc...</li> 818 <li>rewrote all the error handling in the library, all errors can be 819 intercepted at a structured level, with precise information 820 available.</li> 821 <li>New simpler and more generic XML and HTML parser APIs, allowing to 822 easilly modify the parsing options and reuse parser context for multiple 823 consecutive documents.</li> 824 <li>Similar new APIs for the xmlReader, for options and reuse, provided new 825 functions to access content as const strings, use them for Python 826 bindings</li> 827 <li>a lot of other smaller API improvements: xmlStrPrintf (Aleksey Sanin), 828 Walker i.e. reader on a document tree based on Alfred Mickautsch code, 829 make room in nodes for line numbers, reference counting and future PSVI 830 extensions, generation of character ranges to be checked with faster 831 algorithm (William), xmlParserMaxDepth (Crutcher Dunnavant), buffer 832 access</li> 833 <li>New xmlWriter API provided by Alfred Mickautsch</li> 834 <li>Schemas: base64 support by Anthony Carrico</li> 835 <li>Parser<->HTTP integration fix, proper processing of the Mime-Type 836 and charset informations if available.</li> 837 <li>Relax-NG: bug fixes including the one reported by Martijn Faassen and 838 zeroOrMore, better error reporting.</li> 839 <li>Python bindings (St�phane Bidoul), never use stdout for errors 840 output</li> 841 <li>Portability: all the headers have macros for export and calling 842 convention definitions (Igor Zlatkovic), VMS update (Craig A. Berry), 843 Windows: threads (Jesse Pelton), Borland compiler (Eric Zurcher, Igor), 844 Mingw (Igor), typos (Mark Vakoc), beta version (Stephane Bidoul), 845 warning cleanups on AIX and MIPS compilers (William Brack), BeOS (Marcin 846 'Shard' Konicki)</li> 847 <li>Documentation fixes and README (William Brack), search fix (William), 848 tutorial updates (John Fleck), namespace docs (Stefan Kost)</li> 849 <li>Bug fixes: xmlCleanupParser (Dave Beckett), threading uninitialized 850 mutexes, HTML doctype lowercase, SAX/IO (William), compression detection 851 and restore (William), attribute declaration in DTDs (William), namespace 852 on attribute in HTML output (William), input filename (Rob Richards), 853 namespace DTD validation, xmlReplaceNode (Chris Ryland), I/O callbacks 854 (Markus Keim), CDATA serialization (Shaun McCance), xmlReader (Peter 855 Derr), high codepoint charref like &#x10FFFF;, buffer access in push 856 mode (Justin Fletcher), TLS threads on Windows (Jesse Pelton), XPath bug 857 (William), xmlCleanupParser (Marc Liyanage), CDATA output (William), HTTP 858 error handling.</li> 859 <li>xmllint options: --dtdvalidfpi for Tobias Reif, --sax1 for compat 860 testing, --nodict for building without tree dictionnary, --nocdata to 861 replace CDATA by text, --nsclean to remove surperfluous namespace 862 declarations</li> 863 <li>added xml2-config --libtool-libs option from Kevin P. Fleming</li> 864 <li>a lot of profiling and tuning of the code, speedup patch for 865 xmlSearchNs() by Luca Padovani. The xmlReader should do far less 866 allocation and it speed should get closer to SAX. Chris Anderson worked 867 on speeding and cleaning up repetitive checking code.</li> 868 <li>cleanup of "make tests"</li> 869 <li>libxml-2.0-uninstalled.pc from Malcolm Tredinnick</li> 870 <li>deactivated the broken docBook SGML parser code and plugged the XML 871 parser instead.</li> 872</ul> 873 874<h3>2.5.11: Sep 9 2003</h3> 875 876<p>A bugfix only release:</p> 877<ul> 878 <li>risk of crash in Relax-NG</li> 879 <li>risk of crash when using multithreaded programs</li> 880</ul> 881 882<h3>2.5.10: Aug 15 2003</h3> 883 884<p>A bugfixes only release</p> 885<ul> 886 <li>Windows Makefiles (William Brack)</li> 887 <li>UTF-16 support fixes (Mark Itzcovitz)</li> 888 <li>Makefile and portability (William Brack) automake, Linux alpha, Mingw 889 on Windows (Mikhail Grushinskiy)</li> 890 <li>HTML parser (Oliver Stoeneberg)</li> 891 <li>XInclude performance problem reported by Kevin Ruscoe</li> 892 <li>XML parser performance problem reported by Grant Goodale</li> 893 <li>xmlSAXParseDTD() bug fix from Malcolm Tredinnick</li> 894 <li>and a couple other cleanup</li> 895</ul> 896 897<h3>2.5.9: Aug 9 2003</h3> 898<ul> 899 <li>bugfixes: IPv6 portability, xmlHasNsProp (Markus Keim), Windows build 900 (Wiliam Brake, Jesse Pelton, Igor), Schemas (Peter Sobisch), threading 901 (Rob Richards), hexBinary type (), UTF-16 BOM (Dodji Seketeli), 902 xmlReader, Relax-NG schemas compilation, namespace handling, EXSLT (Sean 903 Griffin), HTML parsing problem (William Brack), DTD validation for mixed 904 content + namespaces, HTML serialization, library initialization, 905 progressive HTML parser</li> 906 <li>better interfaces for Relax-NG error handling (Joachim Bauch, )</li> 907 <li>adding xmlXIncludeProcessTree() for XInclud'ing in a subtree</li> 908 <li>doc fixes and improvements (John Fleck)</li> 909 <li>configure flag for -with-fexceptions when embedding in C++</li> 910 <li>couple of new UTF-8 helper functions (William Brack)</li> 911 <li>general encoding cleanup + ISO-8859-x without iconv (Peter Jacobi)</li> 912 <li>xmlTextReader cleanup + enum for node types (Bjorn Reese)</li> 913 <li>general compilation/warning cleanup Solaris/HP-UX/... (William 914 Brack)</li> 915</ul> 916 917<h3>2.5.8: Jul 6 2003</h3> 918<ul> 919 <li>bugfixes: XPath, XInclude, file/URI mapping, UTF-16 save (Mark 920 Itzcovitz), UTF-8 checking, URI saving, error printing (William Brack), 921 PI related memleak, compilation without schemas or without xpath (Joerg 922 Schmitz-Linneweber/Garry Pennington), xmlUnlinkNode problem with DTDs, 923 rpm problem on , i86_64, removed a few compilation problems from 2.5.7, 924 xmlIOParseDTD, and xmlSAXParseDTD (Malcolm Tredinnick)</li> 925 <li>portability: DJGPP (MsDos) , OpenVMS (Craig A. Berry)</li> 926 <li>William Brack fixed multithreading lock problems</li> 927 <li>IPv6 patch for FTP and HTTP accesses (Archana Shah/Wipro)</li> 928 <li>Windows fixes (Igor Zlatkovic, Eric Zurcher), threading (St�phane 929 Bidoul)</li> 930 <li>A few W3C Schemas Structure improvements</li> 931 <li>W3C Schemas Datatype improvements (Charlie Bozeman)</li> 932 <li>Python bindings for thread globals (St�phane Bidoul), and method/class 933 generator</li> 934 <li>added --nonet option to xmllint</li> 935 <li>documentation improvements (John Fleck)</li> 936</ul> 937 938<h3>2.5.7: Apr 25 2003</h3> 939<ul> 940 <li>Relax-NG: Compiling to regexp and streaming validation on top of the 941 xmlReader interface, added to xmllint --stream</li> 942 <li>xmlReader: Expand(), Next() and DOM access glue, bug fixes</li> 943 <li>Support for large files: RGN validated a 4.5GB instance</li> 944 <li>Thread support is now configured in by default</li> 945 <li>Fixes: update of the Trio code (Bjorn), WXS Date and Duration fixes 946 (Charles Bozeman), DTD and namespaces (Brent Hendricks), HTML push parser 947 and zero bytes handling, some missing Windows file path conversions, 948 behaviour of the parser and validator in the presence of "out of memory" 949 error conditions</li> 950 <li>extended the API to be able to plug a garbage collecting memory 951 allocator, added xmlMallocAtomic() and modified the allocations 952 accordingly.</li> 953 <li>Performances: removed excessive malloc() calls, speedup of the push and 954 xmlReader interfaces, removed excessive thread locking</li> 955 <li>Documentation: man page (John Fleck), xmlReader documentation</li> 956 <li>Python: adding binding for xmlCatalogAddLocal (Brent M Hendricks)</li> 957</ul> 958 959<h3>2.5.6: Apr 1 2003</h3> 960<ul> 961 <li>Fixed W3C XML Schemas datatype, should be compliant now except for 962 binHex and base64 which are not supported yet.</li> 963 <li>bug fixes: non-ASCII IDs, HTML output, XInclude on large docs and 964 XInclude entities handling, encoding detection on external subsets, XML 965 Schemas bugs and memory leaks, HTML parser (James Bursa)</li> 966 <li>portability: python/trio (Albert Chin), Sun compiler warnings</li> 967 <li>documentation: added --relaxng option to xmllint man page (John)</li> 968 <li>improved error reporting: xml:space, start/end tag mismatches, Relax NG 969 errors</li> 970</ul> 971 972<h3>2.5.5: Mar 24 2003</h3> 973<ul> 974 <li>Lot of fixes on the Relax NG implementation. More testing including 975 DocBook and TEI examples.</li> 976 <li>Increased the support for W3C XML Schemas datatype</li> 977 <li>Several bug fixes in the URI handling layer</li> 978 <li>Bug fixes: HTML parser, xmlReader, DTD validation, XPath, encoding 979 conversion, line counting in the parser.</li> 980 <li>Added support for $XMLLINT_INDENT environment variable, FTP delete</li> 981 <li>Fixed the RPM spec file name</li> 982</ul> 983 984<h3>2.5.4: Feb 20 2003</h3> 985<ul> 986 <li>Conformance testing and lot of fixes on Relax NG and XInclude 987 implementation</li> 988 <li>Implementation of XPointer element() scheme</li> 989 <li>Bug fixes: XML parser, XInclude entities merge, validity checking on 990 namespaces, 991 <p>2 serialization bugs, node info generation problems, a DTD regexp 992 generation problem.</p> 993 </li> 994 <li>Portability: windows updates and path canonicalization (Igor)</li> 995 <li>A few typo fixes (Kjartan Maraas)</li> 996 <li>Python bindings generator fixes (Stephane Bidoul)</li> 997</ul> 998 999<h3>2.5.3: Feb 10 2003</h3> 1000<ul> 1001 <li>RelaxNG and XML Schemas datatypes improvements, and added a first 1002 version of RelaxNG Python bindings</li> 1003 <li>Fixes: XLink (Sean Chittenden), XInclude (Sean Chittenden), API fix for 1004 serializing namespace nodes, encoding conversion bug, XHTML1 1005 serialization</li> 1006 <li>Portability fixes: Windows (Igor), AMD 64bits RPM spec file</li> 1007</ul> 1008 1009<h3>2.5.2: Feb 5 2003</h3> 1010<ul> 1011 <li>First implementation of RelaxNG, added --relaxng flag to xmllint</li> 1012 <li>Schemas support now compiled in by default.</li> 1013 <li>Bug fixes: DTD validation, namespace checking, XInclude and entities, 1014 delegateURI in XML Catalogs, HTML parser, XML reader (St�phane Bidoul), 1015 XPath parser and evaluation, UTF8ToUTF8 serialization, XML reader memory 1016 consumption, HTML parser, HTML serialization in the presence of 1017 namespaces</li> 1018 <li>added an HTML API to check elements and attributes.</li> 1019 <li>Documentation improvement, PDF for the tutorial (John Fleck), doc 1020 patches (Stefan Kost)</li> 1021 <li>Portability fixes: NetBSD (Julio Merino), Windows (Igor Zlatkovic)</li> 1022 <li>Added python bindings for XPointer, contextual error reporting 1023 (St�phane Bidoul)</li> 1024 <li>URI/file escaping problems (Stefano Zacchiroli)</li> 1025</ul> 1026 1027<h3>2.5.1: Jan 8 2003</h3> 1028<ul> 1029 <li>Fixes a memory leak and configuration/compilation problems in 2.5.0</li> 1030 <li>documentation updates (John)</li> 1031 <li>a couple of XmlTextReader fixes</li> 1032</ul> 1033 1034<h3>2.5.0: Jan 6 2003</h3> 1035<ul> 1036 <li>New <a href="xmlreader.html">XmltextReader interface</a> based on C# 1037 API (with help of St�phane Bidoul)</li> 1038 <li>Windows: more exports, including the new API (Igor)</li> 1039 <li>XInclude fallback fix</li> 1040 <li>Python: bindings for the new API, packaging (St�phane Bidoul), 1041 drv_libxml2.py Python xml.sax driver (St�phane Bidoul), fixes, speedup 1042 and iterators for Python-2.2 (Hannu Krosing)</li> 1043 <li>Tutorial fixes (john Fleck and Niraj Tolia) xmllint man update 1044 (John)</li> 1045 <li>Fix an XML parser bug raised by Vyacheslav Pindyura</li> 1046 <li>Fix for VMS serialization (Nigel Hall) and config (Craig A. Berry)</li> 1047 <li>Entities handling fixes</li> 1048 <li>new API to optionally track node creation and deletion (Lukas 1049 Schroeder)</li> 1050 <li>Added documentation for the XmltextReader interface and some <a 1051 href="guidelines.html">XML guidelines</a></li> 1052</ul> 1053 1054<h3>2.4.30: Dec 12 2002</h3> 1055<ul> 1056 <li>2.4.29 broke the python bindings, rereleasing</li> 1057 <li>Improvement/fixes of the XML API generator, and couple of minor code 1058 fixes.</li> 1059</ul> 1060 1061<h3>2.4.29: Dec 11 2002</h3> 1062<ul> 1063 <li>Windows fixes (Igor): Windows CE port, pthread linking, python bindings 1064 (St�phane Bidoul), Mingw (Magnus Henoch), and export list updates</li> 1065 <li>Fix for prev in python bindings (ERDI Gergo)</li> 1066 <li>Fix for entities handling (Marcus Clarke)</li> 1067 <li>Refactored the XML and HTML dumps to a single code path, fixed XHTML1 1068 dump</li> 1069 <li>Fix for URI parsing when handling URNs with fragment identifiers</li> 1070 <li>Fix for HTTP URL escaping problem</li> 1071 <li>added an TextXmlReader (C#) like API (work in progress)</li> 1072 <li>Rewrote the API in XML generation script, includes a C parser and saves 1073 more informations needed for C# bindings</li> 1074</ul> 1075 1076<h3>2.4.28: Nov 22 2002</h3> 1077<ul> 1078 <li>a couple of python binding fixes</li> 1079 <li>2 bug fixes in the XML push parser</li> 1080 <li>potential memory leak removed (Martin Stoilov)</li> 1081 <li>fix to the configure script for Unix (Dimitri Papadopoulos)</li> 1082 <li>added encoding support for XInclude parse="text"</li> 1083 <li>autodetection of XHTML1 and specific serialization rules added</li> 1084 <li>nasty threading bug fixed (William Brack)</li> 1085</ul> 1086 1087<h3>2.4.27: Nov 17 2002</h3> 1088<ul> 1089 <li>fixes for the Python bindings</li> 1090 <li>a number of bug fixes: SGML catalogs, xmlParseBalancedChunkMemory(), 1091 HTML parser, Schemas (Charles Bozeman), document fragment support 1092 (Christian Glahn), xmlReconciliateNs (Brian Stafford), XPointer, 1093 xmlFreeNode(), xmlSAXParseMemory (Peter Jones), xmlGetNodePath (Petr 1094 Pajas), entities processing</li> 1095 <li>added grep to xmllint --shell</li> 1096 <li>VMS update patch from Craig A. Berry</li> 1097 <li>cleanup of the Windows build with support for more compilers (Igor), 1098 better thread support on Windows</li> 1099 <li>cleanup of Unix Makefiles and spec file</li> 1100 <li>Improvements to the documentation (John Fleck)</li> 1101</ul> 1102 1103<h3>2.4.26: Oct 18 2002</h3> 1104<ul> 1105 <li>Patches for Windows CE port, improvements on Windows paths handling</li> 1106 <li>Fixes to the validation code (DTD and Schemas), xmlNodeGetPath() , 1107 HTML serialization, Namespace compliance, and a number of small 1108 problems</li> 1109</ul> 1110 1111<h3>2.4.25: Sep 26 2002</h3> 1112<ul> 1113 <li>A number of bug fixes: XPath, validation, Python bindings, DOM and 1114 tree, xmlI/O, Html</li> 1115 <li>Serious rewrite of XInclude</li> 1116 <li>Made XML Schemas regexp part of the default build and APIs, small fix 1117 and improvement of the regexp core</li> 1118 <li>Changed the validation code to reuse XML Schemas regexp APIs</li> 1119 <li>Better handling of Windows file paths, improvement of Makefiles (Igor, 1120 Daniel Gehriger, Mark Vakoc)</li> 1121 <li>Improved the python I/O bindings, the tests, added resolver and regexp 1122 APIs</li> 1123 <li>New logos from Marc Liyanage</li> 1124 <li>Tutorial improvements: John Fleck, Christopher Harris</li> 1125 <li>Makefile: Fixes for AMD x86_64 (Mandrake), DESTDIR (Christophe 1126 Merlet)</li> 1127 <li>removal of all stderr/perror use for error reporting</li> 1128 <li>Better error reporting: XPath and DTD validation</li> 1129 <li>update of the trio portability layer (Bjorn Reese)</li> 1130</ul> 1131 1132<p><strong>2.4.24: Aug 22 2002</strong></p> 1133<ul> 1134 <li>XPath fixes (William), xf:escape-uri() (Wesley Terpstra)</li> 1135 <li>Python binding fixes: makefiles (William), generator, rpm build, x86-64 1136 (fcrozat)</li> 1137 <li>HTML <style> and boolean attributes serializer fixes</li> 1138 <li>C14N improvements by Aleksey</li> 1139 <li>doc cleanups: Rick Jones</li> 1140 <li>Windows compiler makefile updates: Igor and Elizabeth Barham</li> 1141 <li>XInclude: implementation of fallback and xml:base fixup added</li> 1142</ul> 1143 1144<h3>2.4.23: July 6 2002</h3> 1145<ul> 1146 <li>performances patches: Peter Jacobi</li> 1147 <li>c14n fixes, testsuite and performances: Aleksey Sanin</li> 1148 <li>added xmlDocFormatDump: Chema Celorio</li> 1149 <li>new tutorial: John Fleck</li> 1150 <li>new hash functions and performances: Sander Vesik, portability fix from 1151 Peter Jacobi</li> 1152 <li>a number of bug fixes: XPath (William Brack, Richard Jinks), XML and 1153 HTML parsers, ID lookup function</li> 1154 <li>removal of all remaining sprintf: Aleksey Sanin</li> 1155</ul> 1156 1157<h3>2.4.22: May 27 2002</h3> 1158<ul> 1159 <li>a number of bug fixes: configure scripts, base handling, parser, memory 1160 usage, HTML parser, XPath, documentation (Christian Cornelssen), 1161 indentation, URI parsing</li> 1162 <li>Optimizations for XMLSec, fixing and making public some of the network 1163 protocol handlers (Aleksey)</li> 1164 <li>performance patch from Gary Pennington</li> 1165 <li>Charles Bozeman provided date and time support for XML Schemas 1166 datatypes</li> 1167</ul> 1168 1169<h3>2.4.21: Apr 29 2002</h3> 1170 1171<p>This release is both a bug fix release and also contains the early XML 1172Schemas <a href="http://www.w3.org/TR/xmlschema-1/">structures</a> and <a 1173href="http://www.w3.org/TR/xmlschema-2/">datatypes</a> code, beware, all 1174interfaces are likely to change, there is huge holes, it is clearly a work in 1175progress and don't even think of putting this code in a production system, 1176it's actually not compiled in by default. The real fixes are:</p> 1177<ul> 1178 <li>a couple of bugs or limitations introduced in 2.4.20</li> 1179 <li>patches for Borland C++ and MSC by Igor</li> 1180 <li>some fixes on XPath strings and conformance patches by Richard 1181 Jinks</li> 1182 <li>patch from Aleksey for the ExcC14N specification</li> 1183 <li>OSF/1 bug fix by Bjorn</li> 1184</ul> 1185 1186<h3>2.4.20: Apr 15 2002</h3> 1187<ul> 1188 <li>bug fixes: file descriptor leak, XPath, HTML output, DTD validation</li> 1189 <li>XPath conformance testing by Richard Jinks</li> 1190 <li>Portability fixes: Solaris, MPE/iX, Windows, OSF/1, python bindings, 1191 libxml.m4</li> 1192</ul> 1193 1194<h3>2.4.19: Mar 25 2002</h3> 1195<ul> 1196 <li>bug fixes: half a dozen XPath bugs, Validation, ISO-Latin to UTF8 1197 encoder</li> 1198 <li>portability fixes in the HTTP code</li> 1199 <li>memory allocation checks using valgrind, and profiling tests</li> 1200 <li>revamp of the Windows build and Makefiles</li> 1201</ul> 1202 1203<h3>2.4.18: Mar 18 2002</h3> 1204<ul> 1205 <li>bug fixes: tree, SAX, canonicalization, validation, portability, 1206 XPath</li> 1207 <li>removed the --with-buffer option it was becoming unmaintainable</li> 1208 <li>serious cleanup of the Python makefiles</li> 1209 <li>speedup patch to XPath very effective for DocBook stylesheets</li> 1210 <li>Fixes for Windows build, cleanup of the documentation</li> 1211</ul> 1212 1213<h3>2.4.17: Mar 8 2002</h3> 1214<ul> 1215 <li>a lot of bug fixes, including "namespace nodes have no parents in 1216 XPath"</li> 1217 <li>fixed/improved the Python wrappers, added more examples and more 1218 regression tests, XPath extension functions can now return node-sets</li> 1219 <li>added the XML Canonicalization support from Aleksey Sanin</li> 1220</ul> 1221 1222<h3>2.4.16: Feb 20 2002</h3> 1223<ul> 1224 <li>a lot of bug fixes, most of them were triggered by the XML Testsuite 1225 from OASIS and W3C. Compliance has been significantly improved.</li> 1226 <li>a couple of portability fixes too.</li> 1227</ul> 1228 1229<h3>2.4.15: Feb 11 2002</h3> 1230<ul> 1231 <li>Fixed the Makefiles, especially the python module ones</li> 1232 <li>A few bug fixes and cleanup</li> 1233 <li>Includes cleanup</li> 1234</ul> 1235 1236<h3>2.4.14: Feb 8 2002</h3> 1237<ul> 1238 <li>Change of License to the <a 1239 href="http://www.opensource.org/licenses/mit-license.html">MIT 1240 License</a> basically for integration in XFree86 codebase, and removing 1241 confusion around the previous dual-licensing</li> 1242 <li>added Python bindings, beta software but should already be quite 1243 complete</li> 1244 <li>a large number of fixes and cleanups, especially for all tree 1245 manipulations</li> 1246 <li>cleanup of the headers, generation of a reference API definition in 1247 XML</li> 1248</ul> 1249 1250<h3>2.4.13: Jan 14 2002</h3> 1251<ul> 1252 <li>update of the documentation: John Fleck and Charlie Bozeman</li> 1253 <li>cleanup of timing code from Justin Fletcher</li> 1254 <li>fixes for Windows and initial thread support on Win32: Igor and Serguei 1255 Narojnyi</li> 1256 <li>Cygwin patch from Robert Collins</li> 1257 <li>added xmlSetEntityReferenceFunc() for Keith Isdale work on xsldbg</li> 1258</ul> 1259 1260<h3>2.4.12: Dec 7 2001</h3> 1261<ul> 1262 <li>a few bug fixes: thread (Gary Pennington), xmllint (Geert Kloosterman), 1263 XML parser (Robin Berjon), XPointer (Danny Jamshy), I/O cleanups 1264 (robert)</li> 1265 <li>Eric Lavigne contributed project files for MacOS</li> 1266 <li>some makefiles cleanups</li> 1267</ul> 1268 1269<h3>2.4.11: Nov 26 2001</h3> 1270<ul> 1271 <li>fixed a couple of errors in the includes, fixed a few bugs, some code 1272 cleanups</li> 1273 <li>xmllint man pages improvement by Heiko Rupp</li> 1274 <li>updated VMS build instructions from John A Fotheringham</li> 1275 <li>Windows Makefiles updates from Igor</li> 1276</ul> 1277 1278<h3>2.4.10: Nov 10 2001</h3> 1279<ul> 1280 <li>URI escaping fix (Joel Young)</li> 1281 <li>added xmlGetNodePath() (for paths or XPointers generation)</li> 1282 <li>Fixes namespace handling problems when using DTD and validation</li> 1283 <li>improvements on xmllint: Morus Walter patches for --format and 1284 --encode, Stefan Kost and Heiko Rupp improvements on the --shell</li> 1285 <li>fixes for xmlcatalog linking pointed by Weiqi Gao</li> 1286 <li>fixes to the HTML parser</li> 1287</ul> 1288 1289<h3>2.4.9: Nov 6 2001</h3> 1290<ul> 1291 <li>fixes more catalog bugs</li> 1292 <li>avoid a compilation problem, improve xmlGetLineNo()</li> 1293</ul> 1294 1295<h3>2.4.8: Nov 4 2001</h3> 1296<ul> 1297 <li>fixed SGML catalogs broken in previous release, updated xmlcatalog 1298 tool</li> 1299 <li>fixed a compile errors and some includes troubles.</li> 1300</ul> 1301 1302<h3>2.4.7: Oct 30 2001</h3> 1303<ul> 1304 <li>exported some debugging interfaces</li> 1305 <li>serious rewrite of the catalog code</li> 1306 <li>integrated Gary Pennington thread safety patch, added configure option 1307 and regression tests</li> 1308 <li>removed an HTML parser bug</li> 1309 <li>fixed a couple of potentially serious validation bugs</li> 1310 <li>integrated the SGML DocBook support in xmllint</li> 1311 <li>changed the nanoftp anonymous login passwd</li> 1312 <li>some I/O cleanup and a couple of interfaces for Perl wrapper</li> 1313 <li>general bug fixes</li> 1314 <li>updated xmllint man page by John Fleck</li> 1315 <li>some VMS and Windows updates</li> 1316</ul> 1317 1318<h3>2.4.6: Oct 10 2001</h3> 1319<ul> 1320 <li>added an updated man pages by John Fleck</li> 1321 <li>portability and configure fixes</li> 1322 <li>an infinite loop on the HTML parser was removed (William)</li> 1323 <li>Windows makefile patches from Igor</li> 1324 <li>fixed half a dozen bugs reported for libxml or libxslt</li> 1325 <li>updated xmlcatalog to be able to modify SGML super catalogs</li> 1326</ul> 1327 1328<h3>2.4.5: Sep 14 2001</h3> 1329<ul> 1330 <li>Remove a few annoying bugs in 2.4.4</li> 1331 <li>forces the HTML serializer to output decimal charrefs since some 1332 version of Netscape can't handle hexadecimal ones</li> 1333</ul> 1334 1335<h3>1.8.16: Sep 14 2001</h3> 1336<ul> 1337 <li>maintenance release of the old libxml1 branch, couple of bug and 1338 portability fixes</li> 1339</ul> 1340 1341<h3>2.4.4: Sep 12 2001</h3> 1342<ul> 1343 <li>added --convert to xmlcatalog, bug fixes and cleanups of XML 1344 Catalog</li> 1345 <li>a few bug fixes and some portability changes</li> 1346 <li>some documentation cleanups</li> 1347</ul> 1348 1349<h3>2.4.3: Aug 23 2001</h3> 1350<ul> 1351 <li>XML Catalog support see the doc</li> 1352 <li>New NaN/Infinity floating point code</li> 1353 <li>A few bug fixes</li> 1354</ul> 1355 1356<h3>2.4.2: Aug 15 2001</h3> 1357<ul> 1358 <li>adds xmlLineNumbersDefault() to control line number generation</li> 1359 <li>lot of bug fixes</li> 1360 <li>the Microsoft MSC projects files should now be up to date</li> 1361 <li>inheritance of namespaces from DTD defaulted attributes</li> 1362 <li>fixes a serious potential security bug</li> 1363 <li>added a --format option to xmllint</li> 1364</ul> 1365 1366<h3>2.4.1: July 24 2001</h3> 1367<ul> 1368 <li>possibility to keep line numbers in the tree</li> 1369 <li>some computation NaN fixes</li> 1370 <li>extension of the XPath API</li> 1371 <li>cleanup for alpha and ia64 targets</li> 1372 <li>patch to allow saving through HTTP PUT or POST</li> 1373</ul> 1374 1375<h3>2.4.0: July 10 2001</h3> 1376<ul> 1377 <li>Fixed a few bugs in XPath, validation, and tree handling.</li> 1378 <li>Fixed XML Base implementation, added a couple of examples to the 1379 regression tests</li> 1380 <li>A bit of cleanup</li> 1381</ul> 1382 1383<h3>2.3.14: July 5 2001</h3> 1384<ul> 1385 <li>fixed some entities problems and reduce memory requirement when 1386 substituting them</li> 1387 <li>lots of improvements in the XPath queries interpreter can be 1388 substantially faster</li> 1389 <li>Makefiles and configure cleanups</li> 1390 <li>Fixes to XPath variable eval, and compare on empty node set</li> 1391 <li>HTML tag closing bug fixed</li> 1392 <li>Fixed an URI reference computation problem when validating</li> 1393</ul> 1394 1395<h3>2.3.13: June 28 2001</h3> 1396<ul> 1397 <li>2.3.12 configure.in was broken as well as the push mode XML parser</li> 1398 <li>a few more fixes for compilation on Windows MSC by Yon Derek</li> 1399</ul> 1400 1401<h3>1.8.14: June 28 2001</h3> 1402<ul> 1403 <li>Zbigniew Chyla gave a patch to use the old XML parser in push mode</li> 1404 <li>Small Makefile fix</li> 1405</ul> 1406 1407<h3>2.3.12: June 26 2001</h3> 1408<ul> 1409 <li>lots of cleanup</li> 1410 <li>a couple of validation fix</li> 1411 <li>fixed line number counting</li> 1412 <li>fixed serious problems in the XInclude processing</li> 1413 <li>added support for UTF8 BOM at beginning of entities</li> 1414 <li>fixed a strange gcc optimizer bugs in xpath handling of float, gcc-3.0 1415 miscompile uri.c (William), Thomas Leitner provided a fix for the 1416 optimizer on Tru64</li> 1417 <li>incorporated Yon Derek and Igor Zlatkovic fixes and improvements for 1418 compilation on Windows MSC</li> 1419 <li>update of libxml-doc.el (Felix Natter)</li> 1420 <li>fixed 2 bugs in URI normalization code</li> 1421</ul> 1422 1423<h3>2.3.11: June 17 2001</h3> 1424<ul> 1425 <li>updates to trio, Makefiles and configure should fix some portability 1426 problems (alpha)</li> 1427 <li>fixed some HTML serialization problems (pre, script, and block/inline 1428 handling), added encoding aware APIs, cleanup of this code</li> 1429 <li>added xmlHasNsProp()</li> 1430 <li>implemented a specific PI for encoding support in the DocBook SGML 1431 parser</li> 1432 <li>some XPath fixes (-Infinity, / as a function parameter and namespaces 1433 node selection)</li> 1434 <li>fixed a performance problem and an error in the validation code</li> 1435 <li>fixed XInclude routine to implement the recursive behaviour</li> 1436 <li>fixed xmlFreeNode problem when libxml is included statically twice</li> 1437 <li>added --version to xmllint for bug reports</li> 1438</ul> 1439 1440<h3>2.3.10: June 1 2001</h3> 1441<ul> 1442 <li>fixed the SGML catalog support</li> 1443 <li>a number of reported bugs got fixed, in XPath, iconv detection, 1444 XInclude processing</li> 1445 <li>XPath string function should now handle unicode correctly</li> 1446</ul> 1447 1448<h3>2.3.9: May 19 2001</h3> 1449 1450<p>Lots of bugfixes, and added a basic SGML catalog support:</p> 1451<ul> 1452 <li>HTML push bugfix #54891 and another patch from Jonas Borgstr�m</li> 1453 <li>some serious speed optimization again</li> 1454 <li>some documentation cleanups</li> 1455 <li>trying to get better linking on Solaris (-R)</li> 1456 <li>XPath API cleanup from Thomas Broyer</li> 1457 <li>Validation bug fixed #54631, added a patch from Gary Pennington, fixed 1458 xmlValidGetValidElements()</li> 1459 <li>Added an INSTALL file</li> 1460 <li>Attribute removal added to API: #54433</li> 1461 <li>added a basic support for SGML catalogs</li> 1462 <li>fixed xmlKeepBlanksDefault(0) API</li> 1463 <li>bugfix in xmlNodeGetLang()</li> 1464 <li>fixed a small configure portability problem</li> 1465 <li>fixed an inversion of SYSTEM and PUBLIC identifier in HTML document</li> 1466</ul> 1467 1468<h3>1.8.13: May 14 2001</h3> 1469<ul> 1470 <li>bugfixes release of the old libxml1 branch used by Gnome</li> 1471</ul> 1472 1473<h3>2.3.8: May 3 2001</h3> 1474<ul> 1475 <li>Integrated an SGML DocBook parser for the Gnome project</li> 1476 <li>Fixed a few things in the HTML parser</li> 1477 <li>Fixed some XPath bugs raised by XSLT use, tried to fix the floating 1478 point portability issue</li> 1479 <li>Speed improvement (8M/s for SAX, 3M/s for DOM, 1.5M/s for 1480 DOM+validation using the XML REC as input and a 700MHz celeron).</li> 1481 <li>incorporated more Windows cleanup</li> 1482 <li>added xmlSaveFormatFile()</li> 1483 <li>fixed problems in copying nodes with entities references (gdome)</li> 1484 <li>removed some troubles surrounding the new validation module</li> 1485</ul> 1486 1487<h3>2.3.7: April 22 2001</h3> 1488<ul> 1489 <li>lots of small bug fixes, corrected XPointer</li> 1490 <li>Non deterministic content model validation support</li> 1491 <li>added xmlDocCopyNode for gdome2</li> 1492 <li>revamped the way the HTML parser handles end of tags</li> 1493 <li>XPath: corrections of namespaces support and number formatting</li> 1494 <li>Windows: Igor Zlatkovic patches for MSC compilation</li> 1495 <li>HTML output fixes from P C Chow and William M. Brack</li> 1496 <li>Improved validation speed sensible for DocBook</li> 1497 <li>fixed a big bug with ID declared in external parsed entities</li> 1498 <li>portability fixes, update of Trio from Bjorn Reese</li> 1499</ul> 1500 1501<h3>2.3.6: April 8 2001</h3> 1502<ul> 1503 <li>Code cleanup using extreme gcc compiler warning options, found and 1504 cleared half a dozen potential problem</li> 1505 <li>the Eazel team found an XML parser bug</li> 1506 <li>cleaned up the user of some of the string formatting function. used the 1507 trio library code to provide the one needed when the platform is missing 1508 them</li> 1509 <li>xpath: removed a memory leak and fixed the predicate evaluation 1510 problem, extended the testsuite and cleaned up the result. XPointer seems 1511 broken ...</li> 1512</ul> 1513 1514<h3>2.3.5: Mar 23 2001</h3> 1515<ul> 1516 <li>Biggest change is separate parsing and evaluation of XPath expressions, 1517 there is some new APIs for this too</li> 1518 <li>included a number of bug fixes(XML push parser, 51876, notations, 1519 52299)</li> 1520 <li>Fixed some portability issues</li> 1521</ul> 1522 1523<h3>2.3.4: Mar 10 2001</h3> 1524<ul> 1525 <li>Fixed bugs #51860 and #51861</li> 1526 <li>Added a global variable xmlDefaultBufferSize to allow default buffer 1527 size to be application tunable.</li> 1528 <li>Some cleanup in the validation code, still a bug left and this part 1529 should probably be rewritten to support ambiguous content model :-\</li> 1530 <li>Fix a couple of serious bugs introduced or raised by changes in 2.3.3 1531 parser</li> 1532 <li>Fixed another bug in xmlNodeGetContent()</li> 1533 <li>Bjorn fixed XPath node collection and Number formatting</li> 1534 <li>Fixed a loop reported in the HTML parsing</li> 1535 <li>blank space are reported even if the Dtd content model proves that they 1536 are formatting spaces, this is for XML conformance</li> 1537</ul> 1538 1539<h3>2.3.3: Mar 1 2001</h3> 1540<ul> 1541 <li>small change in XPath for XSLT</li> 1542 <li>documentation cleanups</li> 1543 <li>fix in validation by Gary Pennington</li> 1544 <li>serious parsing performances improvements</li> 1545</ul> 1546 1547<h3>2.3.2: Feb 24 2001</h3> 1548<ul> 1549 <li>chasing XPath bugs, found a bunch, completed some TODO</li> 1550 <li>fixed a Dtd parsing bug</li> 1551 <li>fixed a bug in xmlNodeGetContent</li> 1552 <li>ID/IDREF support partly rewritten by Gary Pennington</li> 1553</ul> 1554 1555<h3>2.3.1: Feb 15 2001</h3> 1556<ul> 1557 <li>some XPath and HTML bug fixes for XSLT</li> 1558 <li>small extension of the hash table interfaces for DOM gdome2 1559 implementation</li> 1560 <li>A few bug fixes</li> 1561</ul> 1562 1563<h3>2.3.0: Feb 8 2001 (2.2.12 was on 25 Jan but I didn't kept track)</h3> 1564<ul> 1565 <li>Lots of XPath bug fixes</li> 1566 <li>Add a mode with Dtd lookup but without validation error reporting for 1567 XSLT</li> 1568 <li>Add support for text node without escaping (XSLT)</li> 1569 <li>bug fixes for xmlCheckFilename</li> 1570 <li>validation code bug fixes from Gary Pennington</li> 1571 <li>Patch from Paul D. Smith correcting URI path normalization</li> 1572 <li>Patch to allow simultaneous install of libxml-devel and 1573 libxml2-devel</li> 1574 <li>the example Makefile is now fixed</li> 1575 <li>added HTML to the RPM packages</li> 1576 <li>tree copying bugfixes</li> 1577 <li>updates to Windows makefiles</li> 1578 <li>optimization patch from Bjorn Reese</li> 1579</ul> 1580 1581<h3>2.2.11: Jan 4 2001</h3> 1582<ul> 1583 <li>bunch of bug fixes (memory I/O, xpath, ftp/http, ...)</li> 1584 <li>added htmlHandleOmittedElem()</li> 1585 <li>Applied Bjorn Reese's IPV6 first patch</li> 1586 <li>Applied Paul D. Smith patches for validation of XInclude results</li> 1587 <li>added XPointer xmlns() new scheme support</li> 1588</ul> 1589 1590<h3>2.2.10: Nov 25 2000</h3> 1591<ul> 1592 <li>Fix the Windows problems of 2.2.8</li> 1593 <li>integrate OpenVMS patches</li> 1594 <li>better handling of some nasty HTML input</li> 1595 <li>Improved the XPointer implementation</li> 1596 <li>integrate a number of provided patches</li> 1597</ul> 1598 1599<h3>2.2.9: Nov 25 2000</h3> 1600<ul> 1601 <li>erroneous release :-(</li> 1602</ul> 1603 1604<h3>2.2.8: Nov 13 2000</h3> 1605<ul> 1606 <li>First version of <a href="http://www.w3.org/TR/xinclude">XInclude</a> 1607 support</li> 1608 <li>Patch in conditional section handling</li> 1609 <li>updated MS compiler project</li> 1610 <li>fixed some XPath problems</li> 1611 <li>added an URI escaping function</li> 1612 <li>some other bug fixes</li> 1613</ul> 1614 1615<h3>2.2.7: Oct 31 2000</h3> 1616<ul> 1617 <li>added message redirection</li> 1618 <li>XPath improvements (thanks TOM !)</li> 1619 <li>xmlIOParseDTD() added</li> 1620 <li>various small fixes in the HTML, URI, HTTP and XPointer support</li> 1621 <li>some cleanup of the Makefile, autoconf and the distribution content</li> 1622</ul> 1623 1624<h3>2.2.6: Oct 25 2000:</h3> 1625<ul> 1626 <li>Added an hash table module, migrated a number of internal structure to 1627 those</li> 1628 <li>Fixed a posteriori validation problems</li> 1629 <li>HTTP module cleanups</li> 1630 <li>HTML parser improvements (tag errors, script/style handling, attribute 1631 normalization)</li> 1632 <li>coalescing of adjacent text nodes</li> 1633 <li>couple of XPath bug fixes, exported the internal API</li> 1634</ul> 1635 1636<h3>2.2.5: Oct 15 2000:</h3> 1637<ul> 1638 <li>XPointer implementation and testsuite</li> 1639 <li>Lot of XPath fixes, added variable and functions registration, more 1640 tests</li> 1641 <li>Portability fixes, lots of enhancements toward an easy Windows build 1642 and release</li> 1643 <li>Late validation fixes</li> 1644 <li>Integrated a lot of contributed patches</li> 1645 <li>added memory management docs</li> 1646 <li>a performance problem when using large buffer seems fixed</li> 1647</ul> 1648 1649<h3>2.2.4: Oct 1 2000:</h3> 1650<ul> 1651 <li>main XPath problem fixed</li> 1652 <li>Integrated portability patches for Windows</li> 1653 <li>Serious bug fixes on the URI and HTML code</li> 1654</ul> 1655 1656<h3>2.2.3: Sep 17 2000</h3> 1657<ul> 1658 <li>bug fixes</li> 1659 <li>cleanup of entity handling code</li> 1660 <li>overall review of all loops in the parsers, all sprintf usage has been 1661 checked too</li> 1662 <li>Far better handling of larges Dtd. Validating against DocBook XML Dtd 1663 works smoothly now.</li> 1664</ul> 1665 1666<h3>1.8.10: Sep 6 2000</h3> 1667<ul> 1668 <li>bug fix release for some Gnome projects</li> 1669</ul> 1670 1671<h3>2.2.2: August 12 2000</h3> 1672<ul> 1673 <li>mostly bug fixes</li> 1674 <li>started adding routines to access xml parser context options</li> 1675</ul> 1676 1677<h3>2.2.1: July 21 2000</h3> 1678<ul> 1679 <li>a purely bug fixes release</li> 1680 <li>fixed an encoding support problem when parsing from a memory block</li> 1681 <li>fixed a DOCTYPE parsing problem</li> 1682 <li>removed a bug in the function allowing to override the memory 1683 allocation routines</li> 1684</ul> 1685 1686<h3>2.2.0: July 14 2000</h3> 1687<ul> 1688 <li>applied a lot of portability fixes</li> 1689 <li>better encoding support/cleanup and saving (content is now always 1690 encoded in UTF-8)</li> 1691 <li>the HTML parser now correctly handles encodings</li> 1692 <li>added xmlHasProp()</li> 1693 <li>fixed a serious problem with &#38;</li> 1694 <li>propagated the fix to FTP client</li> 1695 <li>cleanup, bugfixes, etc ...</li> 1696 <li>Added a page about <a href="encoding.html">libxml Internationalization 1697 support</a></li> 1698</ul> 1699 1700<h3>1.8.9: July 9 2000</h3> 1701<ul> 1702 <li>fixed the spec the RPMs should be better</li> 1703 <li>fixed a serious bug in the FTP implementation, released 1.8.9 to solve 1704 rpmfind users problem</li> 1705</ul> 1706 1707<h3>2.1.1: July 1 2000</h3> 1708<ul> 1709 <li>fixes a couple of bugs in the 2.1.0 packaging</li> 1710 <li>improvements on the HTML parser</li> 1711</ul> 1712 1713<h3>2.1.0 and 1.8.8: June 29 2000</h3> 1714<ul> 1715 <li>1.8.8 is mostly a commodity package for upgrading to libxml2 according 1716 to <a href="upgrade.html">new instructions</a>. It fixes a nasty problem 1717 about &#38; charref parsing</li> 1718 <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it 1719 also contains numerous fixes and enhancements: 1720 <ul> 1721 <li>added xmlStopParser() to stop parsing</li> 1722 <li>improved a lot parsing speed when there is large CDATA blocs</li> 1723 <li>includes XPath patches provided by Picdar Technology</li> 1724 <li>tried to fix as much as possible DTD validation and namespace 1725 related problems</li> 1726 <li>output to a given encoding has been added/tested</li> 1727 <li>lot of various fixes</li> 1728 </ul> 1729 </li> 1730</ul> 1731 1732<h3>2.0.0: Apr 12 2000</h3> 1733<ul> 1734 <li>First public release of libxml2. If you are using libxml, it's a good 1735 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initially 1736 scheduled for Apr 3 the release occurred only on Apr 12 due to massive 1737 workload.</li> 1738 <li>The include are now located under $prefix/include/libxml (instead of 1739 $prefix/include/gnome-xml), they also are referenced by 1740 <pre>#include <libxml/xxx.h></pre> 1741 <p>instead of</p> 1742 <pre>#include "xxx.h"</pre> 1743 </li> 1744 <li>a new URI module for parsing URIs and following strictly RFC 2396</li> 1745 <li>the memory allocation routines used by libxml can now be overloaded 1746 dynamically by using xmlMemSetup()</li> 1747 <li>The previously CVS only tool tester has been renamed 1748 <strong>xmllint</strong> and is now installed as part of the libxml2 1749 package</li> 1750 <li>The I/O interface has been revamped. There is now ways to plug in 1751 specific I/O modules, either at the URI scheme detection level using 1752 xmlRegisterInputCallbacks() or by passing I/O functions when creating a 1753 parser context using xmlCreateIOParserCtxt()</li> 1754 <li>there is a C preprocessor macro LIBXML_VERSION providing the version 1755 number of the libxml module in use</li> 1756 <li>a number of optional features of libxml can now be excluded at 1757 configure time (FTP/HTTP/HTML/XPath/Debug)</li> 1758</ul> 1759 1760<h3>2.0.0beta: Mar 14 2000</h3> 1761<ul> 1762 <li>This is a first Beta release of libxml version 2</li> 1763 <li>It's available only from<a href="ftp://xmlsoft.org/">xmlsoft.org 1764 FTP</a>, it's packaged as libxml2-2.0.0beta and available as tar and 1765 RPMs</li> 1766 <li>This version is now the head in the Gnome CVS base, the old one is 1767 available under the tag LIB_XML_1_X</li> 1768 <li>This includes a very large set of changes. From a programmatic point 1769 of view applications should not have to be modified too much, check the 1770 <a href="upgrade.html">upgrade page</a></li> 1771 <li>Some interfaces may changes (especially a bit about encoding).</li> 1772 <li>the updates includes: 1773 <ul> 1774 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly 1775 handled now</li> 1776 <li>Better handling of entities, especially well-formedness checking 1777 and proper PEref extensions in external subsets</li> 1778 <li>DTD conditional sections</li> 1779 <li>Validation now correctly handle entities content</li> 1780 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change 1781 structures to accommodate DOM</a></li> 1782 </ul> 1783 </li> 1784 <li>Serious progress were made toward compliance, <a 1785 href="conf/result.html">here are the result of the test</a> against the 1786 OASIS testsuite (except the Japanese tests since I don't support that 1787 encoding yet). This URL is rebuilt every couple of hours using the CVS 1788 head version.</li> 1789</ul> 1790 1791<h3>1.8.7: Mar 6 2000</h3> 1792<ul> 1793 <li>This is a bug fix release:</li> 1794 <li>It is possible to disable the ignorable blanks heuristic used by 1795 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note 1796 that for adherence to XML spec, this behaviour will be disabled by 1797 default in 2.x . The same function will allow to keep compatibility for 1798 old code.</li> 1799 <li>Blanks in <a> </a> constructs are not ignored anymore, 1800 avoiding heuristic is really the Right Way :-\</li> 1801 <li>The unchecked use of snprintf which was breaking libxml-1.8.6 1802 compilation on some platforms has been fixed</li> 1803 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing 1804 URIs</li> 1805</ul> 1806 1807<h3>1.8.6: Jan 31 2000</h3> 1808<ul> 1809 <li>added a nanoFTP transport module, debugged until the new version of <a 1810 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use 1811 it without troubles</li> 1812</ul> 1813 1814<h3>1.8.5: Jan 21 2000</h3> 1815<ul> 1816 <li>adding APIs to parse a well balanced chunk of XML (production <a 1817 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the 1818 XML spec)</li> 1819 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li> 1820 <li>Jody Goldberg <jgoldberg@home.com> provided another patch trying 1821 to solve the zlib checks problems</li> 1822 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with 1823 gnumeric soon</li> 1824</ul> 1825 1826<h3>1.8.4: Jan 13 2000</h3> 1827<ul> 1828 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li> 1829 <li>all exit() call should have been removed from libxml</li> 1830 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li> 1831 <li>added newDocFragment()</li> 1832</ul> 1833 1834<h3>1.8.3: Jan 5 2000</h3> 1835<ul> 1836 <li>a Push interface for the XML and HTML parsers</li> 1837 <li>a shell-like interface to the document tree (try tester --shell :-)</li> 1838 <li>lots of bug fixes and improvement added over XMas holidays</li> 1839 <li>fixed the DTD parsing code to work with the xhtml DTD</li> 1840 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li> 1841 <li>Fixed bugs in xmlNewNs()</li> 1842 <li>External entity loading code has been revamped, now it uses 1843 xmlLoadExternalEntity(), some fix on entities processing were added</li> 1844 <li>cleaned up WIN32 includes of socket stuff</li> 1845</ul> 1846 1847<h3>1.8.2: Dec 21 1999</h3> 1848<ul> 1849 <li>I got another problem with includes and C++, I hope this issue is fixed 1850 for good this time</li> 1851 <li>Added a few tree modification functions: xmlReplaceNode, 1852 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and 1853 xmlDocSetRootElement</li> 1854 <li>Tried to improve the HTML output with help from <a 1855 href="mailto:clahey@umich.edu">Chris Lahey</a></li> 1856</ul> 1857 1858<h3>1.8.1: Dec 18 1999</h3> 1859<ul> 1860 <li>various patches to avoid troubles when using libxml with C++ compilers 1861 the "namespace" keyword and C escaping in include files</li> 1862 <li>a problem in one of the core macros IS_CHAR was corrected</li> 1863 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing, 1864 and more specifically the Dia application</li> 1865 <li>fixed a posteriori validation (validation after parsing, or by using a 1866 Dtd not specified in the original document)</li> 1867 <li>fixed a bug in</li> 1868</ul> 1869 1870<h3>1.8.0: Dec 12 1999</h3> 1871<ul> 1872 <li>cleanup, especially memory wise</li> 1873 <li>the parser should be more reliable, especially the HTML one, it should 1874 not crash, whatever the input !</li> 1875 <li>Integrated various patches, especially a speedup improvement for large 1876 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>, 1877 configure with --with-buffers to enable them.</li> 1878 <li>attribute normalization, oops should have been added long ago !</li> 1879 <li>attributes defaulted from DTDs should be available, xmlSetProp() now 1880 does entities escaping by default.</li> 1881</ul> 1882 1883<h3>1.7.4: Oct 25 1999</h3> 1884<ul> 1885 <li>Lots of HTML improvement</li> 1886 <li>Fixed some errors when saving both XML and HTML</li> 1887 <li>More examples, the regression tests should now look clean</li> 1888 <li>Fixed a bug with contiguous charref</li> 1889</ul> 1890 1891<h3>1.7.3: Sep 29 1999</h3> 1892<ul> 1893 <li>portability problems fixed</li> 1894 <li>snprintf was used unconditionally, leading to link problems on system 1895 were it's not available, fixed</li> 1896</ul> 1897 1898<h3>1.7.1: Sep 24 1999</h3> 1899<ul> 1900 <li>The basic type for strings manipulated by libxml has been renamed in 1901 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason 1902 is that CHAR was conflicting with a predefined type on Windows. However 1903 on non WIN32 environment, compatibility is provided by the way of a 1904 <strong>#define </strong>.</li> 1905 <li>Changed another error : the use of a structure field called errno, and 1906 leading to troubles on platforms where it's a macro</li> 1907</ul> 1908 1909<h3>1.7.0: Sep 23 1999</h3> 1910<ul> 1911 <li>Added the ability to fetch remote DTD or parsed entities, see the <a 1912 href="html/libxml-nanohttp.html">nanohttp</a> module.</li> 1913 <li>Added an errno to report errors by another mean than a simple printf 1914 like callback</li> 1915 <li>Finished ID/IDREF support and checking when validation</li> 1916 <li>Serious memory leaks fixed (there is now a <a 1917 href="html/libxml-xmlmemory.html">memory wrapper</a> module)</li> 1918 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a> 1919 implementation</li> 1920 <li>Added an HTML parser front-end</li> 1921</ul> 1922 1923<h2><a name="XML">XML</a></h2> 1924 1925<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for 1926markup-based structured documents. Here is <a name="example">an example XML 1927document</a>:</p> 1928<pre><?xml version="1.0"?> 1929<EXAMPLE prop1="gnome is great" prop2="&amp; linux too"> 1930 <head> 1931 <title>Welcome to Gnome</title> 1932 </head> 1933 <chapter> 1934 <title>The Linux adventure</title> 1935 <p>bla bla bla ...</p> 1936 <image href="linus.gif"/> 1937 <p>...</p> 1938 </chapter> 1939</EXAMPLE></pre> 1940 1941<p>The first line specifies that it is an XML document and gives useful 1942information about its encoding. Then the rest of the document is a text 1943format whose structure is specified by tags between brackets. <strong>Each 1944tag opened has to be closed</strong>. XML is pedantic about this. However, if 1945a tag is empty (no content), a single tag can serve as both the opening and 1946closing tag if it ends with <code>/></code> rather than with 1947<code>></code>. Note that, for example, the image tag has no content (just 1948an attribute) and is closed by ending the tag with <code>/></code>.</p> 1949 1950<p>XML can be applied successfully to a wide range of tasks, ranging from 1951long term structured document maintenance (where it follows the steps of 1952SGML) to simple data encoding mechanisms like configuration file formatting 1953(glade), spreadsheets (gnumeric), or even shorter lived documents such as 1954WebDAV where it is used to encode remote calls between a client and a 1955server.</p> 1956 1957<h2><a name="XSLT">XSLT</a></h2> 1958 1959<p>Check <a href="http://xmlsoft.org/XSLT">the separate libxslt page</a></p> 1960 1961<p><a href="http://www.w3.org/TR/xslt">XSL Transformations</a>, is a 1962language for transforming XML documents into other XML documents (or 1963HTML/textual output).</p> 1964 1965<p>A separate library called libxslt is available implementing XSLT-1.0 for 1966libxml2. This module "libxslt" too can be found in the Gnome CVS base.</p> 1967 1968<p>You can check the <a 1969href="http://cvs.gnome.org/lxr/source/libxslt/FEATURES">features</a> 1970supported and the progresses on the <a 1971href="http://cvs.gnome.org/lxr/source/libxslt/ChangeLog" 1972name="Changelog">Changelog</a>.</p> 1973 1974<h2><a name="Python">Python and bindings</a></h2> 1975 1976<p>There are a number of language bindings and wrappers available for 1977libxml2, the list below is not exhaustive. Please contact the <a 1978href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a> 1979(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in 1980order to get updates to this list or to discuss the specific topic of libxml2 1981or libxslt wrappers or bindings:</p> 1982<ul> 1983 <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the 1984 most up-to-date C++ bindings for libxml2, check the <a 1985 href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> 1986 and the <a 1987 href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> 1988 <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper 1989 based on the gdome2 bindings</a> maintained by Tobias Peters.</li> 1990 <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> 1991 <p>Website: <a 1992 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 1993 </li> 1994 <li><a 1995 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 1996 Sergeant</a> developed <a 1997 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 1998 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 1999 application server</a>.</li> 2000 <li>If you're interested into scripting XML processing, have a look at <a 2001 href="http://xsh.sourceforge.net/">XSH</a> an XML editing shell based on 2002 Libxml2 Perl bindings.</li> 2003 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an 2004 earlier version of the libxml/libxslt <a 2005 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> 2006 <li>Gopal.V and Peter Minten develop <a 2007 href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of 2008 C# libxml2 bindings.</li> 2009 <li>Petr Kozelka provides <a 2010 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 2011 libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> 2012 <li>Uwe Fechner also provides <a 2013 href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 2014 implementation for Kylix2/D5/D6 from Borland.</li> 2015 <li>Wai-Sun "Squidster" Chia provides <a 2016 href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and 2017 libxml2 bindings are also available in Ruby through the <a 2018 href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module 2019 maintained by Tobias Peters.</li> 2020 <li>Steve Ball and contributors maintains <a 2021 href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for 2022 Tcl</a>.</li> 2023 <li>There is support for libxml2 in the DOM module of PHP.</li> 2024 <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is 2025 an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and 2026 libxslt as part of GNU ClasspathX project.</li> 2027 <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for 2028 <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li> 2029</ul> 2030 2031<p>The distribution includes a set of Python bindings, which are guaranteed 2032to be maintained as part of the library in the future, though the Python 2033interface have not yet reached the completeness of the C API.</p> 2034 2035<p><a href="mailto:stephane.bidoul@softwareag.com">St�phane Bidoul</a> 2036maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port 2037of the Python bindings</a>.</p> 2038 2039<p>Note to people interested in building bindings, the API is formalized as 2040<a href="libxml2-api.xml">an XML API description file</a> which allows to 2041automate a large part of the Python bindings, this includes function 2042descriptions, enums, structures, typedefs, etc... The Python script used to 2043build the bindings is python/generator.py in the source distribution.</p> 2044 2045<p>To install the Python bindings there are 2 options:</p> 2046<ul> 2047 <li>If you use an RPM based distribution, simply install the <a 2048 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python 2049 RPM</a> (and if needed the <a 2050 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python 2051 RPM</a>).</li> 2052 <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python 2053 module distribution</a> corresponding to your installed version of 2054 libxml2 and libxslt. Note that to install it you will need both libxml2 2055 and libxslt installed and run "python setup.py build install" in the 2056 module tree.</li> 2057</ul> 2058 2059<p>The distribution includes a set of examples and regression tests for the 2060python bindings in the <code>python/tests</code> directory. Here are some 2061excerpts from those tests:</p> 2062 2063<h3>tst.py:</h3> 2064 2065<p>This is a basic test of the file interface and DOM navigation:</p> 2066<pre>import libxml2, sys 2067 2068doc = libxml2.parseFile("tst.xml") 2069if doc.name != "tst.xml": 2070 print "doc.name failed" 2071 sys.exit(1) 2072root = doc.children 2073if root.name != "doc": 2074 print "root.name failed" 2075 sys.exit(1) 2076child = root.children 2077if child.name != "foo": 2078 print "child.name failed" 2079 sys.exit(1) 2080doc.freeDoc()</pre> 2081 2082<p>The Python module is called libxml2; parseFile is the equivalent of 2083xmlParseFile (most of the bindings are automatically generated, and the xml 2084prefix is removed and the casing convention are kept). All node seen at the 2085binding level share the same subset of accessors:</p> 2086<ul> 2087 <li><code>name</code> : returns the node name</li> 2088 <li><code>type</code> : returns a string indicating the node type</li> 2089 <li><code>content</code> : returns the content of the node, it is based on 2090 xmlNodeGetContent() and hence is recursive.</li> 2091 <li><code>parent</code> , <code>children</code>, <code>last</code>, 2092 <code>next</code>, <code>prev</code>, <code>doc</code>, 2093 <code>properties</code>: pointing to the associated element in the tree, 2094 those may return None in case no such link exists.</li> 2095</ul> 2096 2097<p>Also note the need to explicitly deallocate documents with freeDoc() . 2098Reference counting for libxml2 trees would need quite a lot of work to 2099function properly, and rather than risk memory leaks if not implemented 2100correctly it sounds safer to have an explicit function to free a tree. The 2101wrapper python objects like doc, root or child are them automatically garbage 2102collected.</p> 2103 2104<h3>validate.py:</h3> 2105 2106<p>This test check the validation interfaces and redirection of error 2107messages:</p> 2108<pre>import libxml2 2109 2110#deactivate error messages from the validation 2111def noerr(ctx, str): 2112 pass 2113 2114libxml2.registerErrorHandler(noerr, None) 2115 2116ctxt = libxml2.createFileParserCtxt("invalid.xml") 2117ctxt.validate(1) 2118ctxt.parseDocument() 2119doc = ctxt.doc() 2120valid = ctxt.isValid() 2121doc.freeDoc() 2122if valid != 0: 2123 print "validity check failed"</pre> 2124 2125<p>The first thing to notice is the call to registerErrorHandler(), it 2126defines a new error handler global to the library. It is used to avoid seeing 2127the error messages when trying to validate the invalid document.</p> 2128 2129<p>The main interest of that test is the creation of a parser context with 2130createFileParserCtxt() and how the behaviour can be changed before calling 2131parseDocument() . Similarly the informations resulting from the parsing phase 2132are also available using context methods.</p> 2133 2134<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the 2135C function interfaces in terms of objects method as much as possible. The 2136best to get a complete view of what methods are supported is to look at the 2137libxml2.py module containing all the wrappers.</p> 2138 2139<h3>push.py:</h3> 2140 2141<p>This test show how to activate the push parser interface:</p> 2142<pre>import libxml2 2143 2144ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") 2145ctxt.parseChunk("/>", 2, 1) 2146doc = ctxt.doc() 2147 2148doc.freeDoc()</pre> 2149 2150<p>The context is created with a special call based on the 2151xmlCreatePushParser() from the C library. The first argument is an optional 2152SAX callback object, then the initial set of data, the length and the name of 2153the resource in case URI-References need to be computed by the parser.</p> 2154 2155<p>Then the data are pushed using the parseChunk() method, the last call 2156setting the third argument terminate to 1.</p> 2157 2158<h3>pushSAX.py:</h3> 2159 2160<p>this test show the use of the event based parsing interfaces. In this case 2161the parser does not build a document, but provides callback information as 2162the parser makes progresses analyzing the data being provided:</p> 2163<pre>import libxml2 2164log = "" 2165 2166class callback: 2167 def startDocument(self): 2168 global log 2169 log = log + "startDocument:" 2170 2171 def endDocument(self): 2172 global log 2173 log = log + "endDocument:" 2174 2175 def startElement(self, tag, attrs): 2176 global log 2177 log = log + "startElement %s %s:" % (tag, attrs) 2178 2179 def endElement(self, tag): 2180 global log 2181 log = log + "endElement %s:" % (tag) 2182 2183 def characters(self, data): 2184 global log 2185 log = log + "characters: %s:" % (data) 2186 2187 def warning(self, msg): 2188 global log 2189 log = log + "warning: %s:" % (msg) 2190 2191 def error(self, msg): 2192 global log 2193 log = log + "error: %s:" % (msg) 2194 2195 def fatalError(self, msg): 2196 global log 2197 log = log + "fatalError: %s:" % (msg) 2198 2199handler = callback() 2200 2201ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") 2202chunk = " url='tst'>b" 2203ctxt.parseChunk(chunk, len(chunk), 0) 2204chunk = "ar</foo>" 2205ctxt.parseChunk(chunk, len(chunk), 1) 2206 2207reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 2208 "characters: bar:endElement foo:endDocument:" 2209if log != reference: 2210 print "Error got: %s" % log 2211 print "Expected: %s" % reference</pre> 2212 2213<p>The key object in that test is the handler, it provides a number of entry 2214points which can be called by the parser as it makes progresses to indicate 2215the information set obtained. The full set of callback is larger than what 2216the callback class in that specific example implements (see the SAX 2217definition for a complete list). The wrapper will only call those supplied by 2218the object when activated. The startElement receives the names of the element 2219and a dictionary containing the attributes carried by this element.</p> 2220 2221<p>Also note that the reference string generated from the callback shows a 2222single character call even though the string "bar" is passed to the parser 2223from 2 different call to parseChunk()</p> 2224 2225<h3>xpath.py:</h3> 2226 2227<p>This is a basic test of XPath wrappers support</p> 2228<pre>import libxml2 2229 2230doc = libxml2.parseFile("tst.xml") 2231ctxt = doc.xpathNewContext() 2232res = ctxt.xpathEval("//*") 2233if len(res) != 2: 2234 print "xpath query: wrong node set size" 2235 sys.exit(1) 2236if res[0].name != "doc" or res[1].name != "foo": 2237 print "xpath query: wrong node set value" 2238 sys.exit(1) 2239doc.freeDoc() 2240ctxt.xpathFreeContext()</pre> 2241 2242<p>This test parses a file, then create an XPath context to evaluate XPath 2243expression on it. The xpathEval() method execute an XPath query and returns 2244the result mapped in a Python way. String and numbers are natively converted, 2245and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like 2246the document, the XPath context need to be freed explicitly, also not that 2247the result of the XPath query may point back to the document tree and hence 2248the document must be freed after the result of the query is used.</p> 2249 2250<h3>xpathext.py:</h3> 2251 2252<p>This test shows how to extend the XPath engine with functions written in 2253python:</p> 2254<pre>import libxml2 2255 2256def foo(ctx, x): 2257 return x + 1 2258 2259doc = libxml2.parseFile("tst.xml") 2260ctxt = doc.xpathNewContext() 2261libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) 2262res = ctxt.xpathEval("foo(1)") 2263if res != 2: 2264 print "xpath extension failure" 2265doc.freeDoc() 2266ctxt.xpathFreeContext()</pre> 2267 2268<p>Note how the extension function is registered with the context (but that 2269part is not yet finalized, this may change slightly in the future).</p> 2270 2271<h3>tstxpath.py:</h3> 2272 2273<p>This test is similar to the previous one but shows how the extension 2274function can access the XPath evaluation context:</p> 2275<pre>def foo(ctx, x): 2276 global called 2277 2278 # 2279 # test that access to the XPath evaluation contexts 2280 # 2281 pctxt = libxml2.xpathParserContext(_obj=ctx) 2282 ctxt = pctxt.context() 2283 called = ctxt.function() 2284 return x + 1</pre> 2285 2286<p>All the interfaces around the XPath parser(or rather evaluation) context 2287are not finalized, but it should be sufficient to do contextual work at the 2288evaluation point.</p> 2289 2290<h3>Memory debugging:</h3> 2291 2292<p>last but not least, all tests starts with the following prologue:</p> 2293<pre>#memory debug specific 2294libxml2.debugMemory(1)</pre> 2295 2296<p>and ends with the following epilogue:</p> 2297<pre>#memory debug specific 2298libxml2.cleanupParser() 2299if libxml2.debugMemory(1) == 0: 2300 print "OK" 2301else: 2302 print "Memory leak %d bytes" % (libxml2.debugMemory(1)) 2303 libxml2.dumpMemory()</pre> 2304 2305<p>Those activate the memory debugging interface of libxml2 where all 2306allocated block in the library are tracked. The prologue then cleans up the 2307library state and checks that all allocated memory has been freed. If not it 2308calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p> 2309 2310<h2><a name="architecture">libxml2 architecture</a></h2> 2311 2312<p>Libxml2 is made of multiple components; some of them are optional, and 2313most of the block interfaces are public. The main components are:</p> 2314<ul> 2315 <li>an Input/Output layer</li> 2316 <li>FTP and HTTP client layers (optional)</li> 2317 <li>an Internationalization layer managing the encodings support</li> 2318 <li>a URI module</li> 2319 <li>the XML parser and its basic SAX interface</li> 2320 <li>an HTML parser using the same SAX interface (optional)</li> 2321 <li>a SAX tree module to build an in-memory DOM representation</li> 2322 <li>a tree module to manipulate the DOM representation</li> 2323 <li>a validation module using the DOM representation (optional)</li> 2324 <li>an XPath module for global lookup in a DOM representation 2325 (optional)</li> 2326 <li>a debug module (optional)</li> 2327</ul> 2328 2329<p>Graphically this gives the following:</p> 2330 2331<p><img src="libxml.gif" alt="a graphical view of the various"></p> 2332 2333<p></p> 2334 2335<h2><a name="tree">The tree output</a></h2> 2336 2337<p>The parser returns a tree built during the document analysis. The value 2338returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an 2339<strong>xmlDoc</strong> structure). This structure contains information such 2340as the file name, the document type, and a <strong>children</strong> pointer 2341which is the root of the document (or more exactly the first child under the 2342root which is the document). The tree is made of <strong>xmlNode</strong>s, 2343chained in double-linked lists of siblings and with a children<->parent 2344relationship. An xmlNode can also carry properties (a chain of xmlAttr 2345structures). An attribute may have a value which is a list of TEXT or 2346ENTITY_REF nodes.</p> 2347 2348<p>Here is an example (erroneous with respect to the XML spec since there 2349should be only one ELEMENT under the root):</p> 2350 2351<p><img src="structure.gif" alt=" structure.gif "></p> 2352 2353<p>In the source package there is a small program (not installed by default) 2354called <strong>xmllint</strong> which parses XML files given as argument and 2355prints them back as parsed. This is useful for detecting errors both in XML 2356code and in the XML parser itself. It has an option <strong>--debug</strong> 2357which prints the actual in-memory structure of the document; here is the 2358result with the <a href="#example">example</a> given before:</p> 2359<pre>DOCUMENT 2360version=1.0 2361standalone=true 2362 ELEMENT EXAMPLE 2363 ATTRIBUTE prop1 2364 TEXT 2365 content=gnome is great 2366 ATTRIBUTE prop2 2367 ENTITY_REF 2368 TEXT 2369 content= linux too 2370 ELEMENT head 2371 ELEMENT title 2372 TEXT 2373 content=Welcome to Gnome 2374 ELEMENT chapter 2375 ELEMENT title 2376 TEXT 2377 content=The Linux adventure 2378 ELEMENT p 2379 TEXT 2380 content=bla bla bla ... 2381 ELEMENT image 2382 ATTRIBUTE href 2383 TEXT 2384 content=linus.gif 2385 ELEMENT p 2386 TEXT 2387 content=...</pre> 2388 2389<p>This should be useful for learning the internal representation model.</p> 2390 2391<h2><a name="interface">The SAX interface</a></h2> 2392 2393<p>Sometimes the DOM tree output is just too large to fit reasonably into 2394memory. In that case (and if you don't expect to save back the XML document 2395loaded using libxml), it's better to use the SAX interface of libxml. SAX is 2396a <strong>callback-based interface</strong> to the parser. Before parsing, 2397the application layer registers a customized set of callbacks which are 2398called by the library as it progresses through the XML input.</p> 2399 2400<p>To get more detailed step-by-step guidance on using the SAX interface of 2401libxml, see the <a 2402href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice 2403documentation</a>.written by <a href="mailto:james@daa.com.au">James 2404Henstridge</a>.</p> 2405 2406<p>You can debug the SAX behaviour by using the <strong>testSAX</strong> 2407program located in the gnome-xml module (it's usually not shipped in the 2408binary packages of libxml, but you can find it in the tar source 2409distribution). Here is the sequence of callbacks that would be reported by 2410testSAX when parsing the example XML document shown earlier:</p> 2411<pre>SAX.setDocumentLocator() 2412SAX.startDocument() 2413SAX.getEntity(amp) 2414SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too') 2415SAX.characters( , 3) 2416SAX.startElement(head) 2417SAX.characters( , 4) 2418SAX.startElement(title) 2419SAX.characters(Welcome to Gnome, 16) 2420SAX.endElement(title) 2421SAX.characters( , 3) 2422SAX.endElement(head) 2423SAX.characters( , 3) 2424SAX.startElement(chapter) 2425SAX.characters( , 4) 2426SAX.startElement(title) 2427SAX.characters(The Linux adventure, 19) 2428SAX.endElement(title) 2429SAX.characters( , 4) 2430SAX.startElement(p) 2431SAX.characters(bla bla bla ..., 15) 2432SAX.endElement(p) 2433SAX.characters( , 4) 2434SAX.startElement(image, href='linus.gif') 2435SAX.endElement(image) 2436SAX.characters( , 4) 2437SAX.startElement(p) 2438SAX.characters(..., 3) 2439SAX.endElement(p) 2440SAX.characters( , 3) 2441SAX.endElement(chapter) 2442SAX.characters( , 1) 2443SAX.endElement(EXAMPLE) 2444SAX.endDocument()</pre> 2445 2446<p>Most of the other interfaces of libxml2 are based on the DOM tree-building 2447facility, so nearly everything up to the end of this document presupposes the 2448use of the standard DOM tree build. Note that the DOM tree itself is built by 2449a set of registered default callbacks, without internal specific 2450interface.</p> 2451 2452<h2><a name="Validation">Validation & DTDs</a></h2> 2453 2454<p>Table of Content:</p> 2455<ol> 2456 <li><a href="#General5">General overview</a></li> 2457 <li><a href="#definition">The definition</a></li> 2458 <li><a href="#Simple">Simple rules</a> 2459 <ol> 2460 <li><a href="#reference">How to reference a DTD from a document</a></li> 2461 <li><a href="#Declaring">Declaring elements</a></li> 2462 <li><a href="#Declaring1">Declaring attributes</a></li> 2463 </ol> 2464 </li> 2465 <li><a href="#Some">Some examples</a></li> 2466 <li><a href="#validate">How to validate</a></li> 2467 <li><a href="#Other">Other resources</a></li> 2468</ol> 2469 2470<h3><a name="General5">General overview</a></h3> 2471 2472<p>Well what is validation and what is a DTD ?</p> 2473 2474<p>DTD is the acronym for Document Type Definition. This is a description of 2475the content for a family of XML files. This is part of the XML 1.0 2476specification, and allows one to describe and verify that a given document 2477instance conforms to the set of rules detailing its structure and content.</p> 2478 2479<p>Validation is the process of checking a document against a DTD (more 2480generally against a set of construction rules).</p> 2481 2482<p>The validation process and building DTDs are the two most difficult parts 2483of the XML life cycle. Briefly a DTD defines all the possible elements to be 2484found within your document, what is the formal shape of your document tree 2485(by defining the allowed content of an element; either text, a regular 2486expression for the allowed list of children, or mixed content i.e. both text 2487and children). The DTD also defines the valid attributes for all elements and 2488the types of those attributes.</p> 2489 2490<h3><a name="definition1">The definition</a></h3> 2491 2492<p>The <a href="http://www.w3.org/TR/REC-xml">W3C XML Recommendation</a> (<a 2493href="http://www.xml.com/axml/axml.html">Tim Bray's annotated version of 2494Rev1</a>):</p> 2495<ul> 2496 <li><a href="http://www.w3.org/TR/REC-xml#elemdecls">Declaring 2497 elements</a></li> 2498 <li><a href="http://www.w3.org/TR/REC-xml#attdecls">Declaring 2499 attributes</a></li> 2500</ul> 2501 2502<p>(unfortunately) all this is inherited from the SGML world, the syntax is 2503ancient...</p> 2504 2505<h3><a name="Simple1">Simple rules</a></h3> 2506 2507<p>Writing DTDs can be done in many ways. The rules to build them if you need 2508something permanent or something which can evolve over time can be radically 2509different. Really complex DTDs like DocBook ones are flexible but quite 2510harder to design. I will just focus on DTDs for a formats with a fixed simple 2511structure. It is just a set of basic rules, and definitely not exhaustive nor 2512usable for complex DTD design.</p> 2513 2514<h4><a name="reference1">How to reference a DTD from a document</a>:</h4> 2515 2516<p>Assuming the top element of the document is <code>spec</code> and the dtd 2517is placed in the file <code>mydtd</code> in the subdirectory 2518<code>dtds</code> of the directory from where the document were loaded:</p> 2519 2520<p><code><!DOCTYPE spec SYSTEM "dtds/mydtd"></code></p> 2521 2522<p>Notes:</p> 2523<ul> 2524 <li>The system string is actually an URI-Reference (as defined in <a 2525 href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>) so you can use a 2526 full URL string indicating the location of your DTD on the Web. This is a 2527 really good thing to do if you want others to validate your document.</li> 2528 <li>It is also possible to associate a <code>PUBLIC</code> identifier (a 2529 magic string) so that the DTD is looked up in catalogs on the client side 2530 without having to locate it on the web.</li> 2531 <li>A DTD contains a set of element and attribute declarations, but they 2532 don't define what the root of the document should be. This is explicitly 2533 told to the parser/validator as the first element of the 2534 <code>DOCTYPE</code> declaration.</li> 2535</ul> 2536 2537<h4><a name="Declaring2">Declaring elements</a>:</h4> 2538 2539<p>The following declares an element <code>spec</code>:</p> 2540 2541<p><code><!ELEMENT spec (front, body, back?)></code></p> 2542 2543<p>It also expresses that the spec element contains one <code>front</code>, 2544one <code>body</code> and one optional <code>back</code> children elements in 2545this order. The declaration of one element of the structure and its content 2546are done in a single declaration. Similarly the following declares 2547<code>div1</code> elements:</p> 2548 2549<p><code><!ELEMENT div1 (head, (p | list | note)*, div2?)></code></p> 2550 2551<p>which means div1 contains one <code>head</code> then a series of optional 2552<code>p</code>, <code>list</code>s and <code>note</code>s and then an 2553optional <code>div2</code>. And last but not least an element can contain 2554text:</p> 2555 2556<p><code><!ELEMENT b (#PCDATA)></code></p> 2557 2558<p><code>b</code> contains text or being of mixed content (text and elements 2559in no particular order):</p> 2560 2561<p><code><!ELEMENT p (#PCDATA|a|ul|b|i|em)*></code></p> 2562 2563<p><code>p </code>can contain text or <code>a</code>, <code>ul</code>, 2564<code>b</code>, <code>i </code>or <code>em</code> elements in no particular 2565order.</p> 2566 2567<h4><a name="Declaring1">Declaring attributes</a>:</h4> 2568 2569<p>Again the attributes declaration includes their content definition:</p> 2570 2571<p><code><!ATTLIST termdef name CDATA #IMPLIED></code></p> 2572 2573<p>means that the element <code>termdef</code> can have a <code>name</code> 2574attribute containing text (<code>CDATA</code>) and which is optional 2575(<code>#IMPLIED</code>). The attribute value can also be defined within a 2576set:</p> 2577 2578<p><code><!ATTLIST list type (bullets|ordered|glossary) 2579"ordered"></code></p> 2580 2581<p>means <code>list</code> element have a <code>type</code> attribute with 3 2582allowed values "bullets", "ordered" or "glossary" and which default to 2583"ordered" if the attribute is not explicitly specified.</p> 2584 2585<p>The content type of an attribute can be text (<code>CDATA</code>), 2586anchor/reference/references 2587(<code>ID</code>/<code>IDREF</code>/<code>IDREFS</code>), entity(ies) 2588(<code>ENTITY</code>/<code>ENTITIES</code>) or name(s) 2589(<code>NMTOKEN</code>/<code>NMTOKENS</code>). The following defines that a 2590<code>chapter</code> element can have an optional <code>id</code> attribute 2591of type <code>ID</code>, usable for reference from attribute of type 2592IDREF:</p> 2593 2594<p><code><!ATTLIST chapter id ID #IMPLIED></code></p> 2595 2596<p>The last value of an attribute definition can be <code>#REQUIRED 2597</code>meaning that the attribute has to be given, <code>#IMPLIED</code> 2598meaning that it is optional, or the default value (possibly prefixed by 2599<code>#FIXED</code> if it is the only allowed).</p> 2600 2601<p>Notes:</p> 2602<ul> 2603 <li>Usually the attributes pertaining to a given element are declared in a 2604 single expression, but it is just a convention adopted by a lot of DTD 2605 writers: 2606 <pre><!ATTLIST termdef 2607 id ID #REQUIRED 2608 name CDATA #IMPLIED></pre> 2609 <p>The previous construct defines both <code>id</code> and 2610 <code>name</code> attributes for the element <code>termdef</code>.</p> 2611 </li> 2612</ul> 2613 2614<h3><a name="Some1">Some examples</a></h3> 2615 2616<p>The directory <code>test/valid/dtds/</code> in the libxml2 distribution 2617contains some complex DTD examples. The example in the file 2618<code>test/valid/dia.xml</code> shows an XML file where the simple DTD is 2619directly included within the document.</p> 2620 2621<h3><a name="validate1">How to validate</a></h3> 2622 2623<p>The simplest way is to use the xmllint program included with libxml. The 2624<code>--valid</code> option turns-on validation of the files given as input. 2625For example the following validates a copy of the first revision of the XML 26261.0 specification:</p> 2627 2628<p><code>xmllint --valid --noout test/valid/REC-xml-19980210.xml</code></p> 2629 2630<p>the -- noout is used to disable output of the resulting tree.</p> 2631 2632<p>The <code>--dtdvalid dtd</code> allows validation of the document(s) 2633against a given DTD.</p> 2634 2635<p>Libxml2 exports an API to handle DTDs and validation, check the <a 2636href="http://xmlsoft.org/html/libxml-valid.html">associated 2637description</a>.</p> 2638 2639<h3><a name="Other1">Other resources</a></h3> 2640 2641<p>DTDs are as old as SGML. So there may be a number of examples on-line, I 2642will just list one for now, others pointers welcome:</p> 2643<ul> 2644 <li><a href="http://www.xml101.com:8081/dtd/">XML-101 DTD</a></li> 2645</ul> 2646 2647<p>I suggest looking at the examples found under test/valid/dtd and any of 2648the large number of books available on XML. The dia example in test/valid 2649should be both simple and complete enough to allow you to build your own.</p> 2650 2651<p></p> 2652 2653<h2><a name="Memory">Memory Management</a></h2> 2654 2655<p>Table of Content:</p> 2656<ol> 2657 <li><a href="#General3">General overview</a></li> 2658 <li><a href="#setting">Setting libxml2 set of memory routines</a></li> 2659 <li><a href="#cleanup">Cleaning up after parsing</a></li> 2660 <li><a href="#Debugging">Debugging routines</a></li> 2661 <li><a href="#General4">General memory requirements</a></li> 2662</ol> 2663 2664<h3><a name="General3">General overview</a></h3> 2665 2666<p>The module <code><a 2667href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlmemory.h</a></code> 2668provides the interfaces to the libxml2 memory system:</p> 2669<ul> 2670 <li>libxml2 does not use the libc memory allocator directly but xmlFree(), 2671 xmlMalloc() and xmlRealloc()</li> 2672 <li>those routines can be reallocated to a specific set of routine, by 2673 default the libc ones i.e. free(), malloc() and realloc()</li> 2674 <li>the xmlmemory.c module includes a set of debugging routine</li> 2675</ul> 2676 2677<h3><a name="setting">Setting libxml2 set of memory routines</a></h3> 2678 2679<p>It is sometimes useful to not use the default memory allocator, either for 2680debugging, analysis or to implement a specific behaviour on memory management 2681(like on embedded systems). Two function calls are available to do so:</p> 2682<ul> 2683 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemGet 2684 ()</a> which return the current set of functions in use by the parser</li> 2685 <li><a 2686 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemSetup()</a> 2687 which allow to set up a new set of memory allocation functions</li> 2688</ul> 2689 2690<p>Of course a call to xmlMemSetup() should probably be done before calling 2691any other libxml2 routines (unless you are sure your allocations routines are 2692compatibles).</p> 2693 2694<h3><a name="cleanup">Cleaning up after parsing</a></h3> 2695 2696<p>Libxml2 is not stateless, there is a few set of memory structures needing 2697allocation before the parser is fully functional (some encoding structures 2698for example). This also mean that once parsing is finished there is a tiny 2699amount of memory (a few hundred bytes) which can be recollected if you don't 2700reuse the parser immediately:</p> 2701<ul> 2702 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlCleanupParser 2703 ()</a> is a centralized routine to free the parsing states. Note that it 2704 won't deallocate any produced tree if any (use the xmlFreeDoc() and 2705 related routines for this).</li> 2706 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlInitParser 2707 ()</a> is the dual routine allowing to preallocate the parsing state 2708 which can be useful for example to avoid initialization reentrancy 2709 problems when using libxml2 in multithreaded applications</li> 2710</ul> 2711 2712<p>Generally xmlCleanupParser() is safe, if needed the state will be rebuild 2713at the next invocation of parser routines, but be careful of the consequences 2714in multithreaded applications.</p> 2715 2716<h3><a name="Debugging">Debugging routines</a></h3> 2717 2718<p>When configured using --with-mem-debug flag (off by default), libxml2 uses 2719a set of memory allocation debugging routines keeping track of all allocated 2720blocks and the location in the code where the routine was called. A couple of 2721other debugging routines allow to dump the memory allocated infos to a file 2722or call a specific routine when a given block number is allocated:</p> 2723<ul> 2724 <li><a 2725 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMallocLoc()</a> 2726 <a 2727 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlReallocLoc()</a> 2728 and <a 2729 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemStrdupLoc()</a> 2730 are the memory debugging replacement allocation routines</li> 2731 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemoryDump 2732 ()</a> dumps all the informations about the allocated memory block lefts 2733 in the <code>.memdump</code> file</li> 2734</ul> 2735 2736<p>When developing libxml2 memory debug is enabled, the tests programs call 2737xmlMemoryDump () and the "make test" regression tests will check for any 2738memory leak during the full regression test sequence, this helps a lot 2739ensuring that libxml2 does not leak memory and bullet proof memory 2740allocations use (some libc implementations are known to be far too permissive 2741resulting in major portability problems!).</p> 2742 2743<p>If the .memdump reports a leak, it displays the allocation function and 2744also tries to give some informations about the content and structure of the 2745allocated blocks left. This is sufficient in most cases to find the culprit, 2746but not always. Assuming the allocation problem is reproducible, it is 2747possible to find more easily:</p> 2748<ol> 2749 <li>write down the block number xxxx not allocated</li> 2750 <li>export the environment variable XML_MEM_BREAKPOINT=xxxx , the easiest 2751 when using GDB is to simply give the command 2752 <p><code>set environment XML_MEM_BREAKPOINT xxxx</code></p> 2753 <p>before running the program.</p> 2754 </li> 2755 <li>run the program under a debugger and set a breakpoint on 2756 xmlMallocBreakpoint() a specific function called when this precise block 2757 is allocated</li> 2758 <li>when the breakpoint is reached you can then do a fine analysis of the 2759 allocation an step to see the condition resulting in the missing 2760 deallocation.</li> 2761</ol> 2762 2763<p>I used to use a commercial tool to debug libxml2 memory problems but after 2764noticing that it was not detecting memory leaks that simple mechanism was 2765used and proved extremely efficient until now. Lately I have also used <a 2766href="http://developer.kde.org/~sewardj/">valgrind</a> with quite some 2767success, it is tied to the i386 architecture since it works by emulating the 2768processor and instruction set, it is slow but extremely efficient, i.e. it 2769spot memory usage errors in a very precise way.</p> 2770 2771<h3><a name="General4">General memory requirements</a></h3> 2772 2773<p>How much libxml2 memory require ? It's hard to tell in average it depends 2774of a number of things:</p> 2775<ul> 2776 <li>the parser itself should work in a fixed amount of memory, except for 2777 information maintained about the stacks of names and entities locations. 2778 The I/O and encoding handlers will probably account for a few KBytes. 2779 This is true for both the XML and HTML parser (though the HTML parser 2780 need more state).</li> 2781 <li>If you are generating the DOM tree then memory requirements will grow 2782 nearly linear with the size of the data. In general for a balanced 2783 textual document the internal memory requirement is about 4 times the 2784 size of the UTF8 serialization of this document (example the XML-1.0 2785 recommendation is a bit more of 150KBytes and takes 650KBytes of main 2786 memory when parsed). Validation will add a amount of memory required for 2787 maintaining the external Dtd state which should be linear with the 2788 complexity of the content model defined by the Dtd</li> 2789 <li>If you need to work with fixed memory requirements or don't need the 2790 full DOM tree then using the <a href="xmlreader.html">xmlReader 2791 interface</a> is probably the best way to proceed, it still allows to 2792 validate or operate on subset of the tree if needed.</li> 2793 <li>If you don't care about the advanced features of libxml2 like 2794 validation, DOM, XPath or XPointer, don't use entities, need to work with 2795 fixed memory requirements, and try to get the fastest parsing possible 2796 then the SAX interface should be used, but it has known restrictions.</li> 2797</ul> 2798 2799<p></p> 2800 2801<h2><a name="Encodings">Encodings support</a></h2> 2802 2803<p>Table of Content:</p> 2804<ol> 2805 <li><a href="encoding.html#What">What does internationalization support 2806 mean ?</a></li> 2807 <li><a href="encoding.html#internal">The internal encoding, how and 2808 why</a></li> 2809 <li><a href="encoding.html#implemente">How is it implemented ?</a></li> 2810 <li><a href="encoding.html#Default">Default supported encodings</a></li> 2811 <li><a href="encoding.html#extend">How to extend the existing 2812 support</a></li> 2813</ol> 2814 2815<h3><a name="What">What does internationalization support mean ?</a></h3> 2816 2817<p>If you are not really familiar with Internationalization (usual shortcut 2818is I18N) , Unicode, characters and glyphs, I suggest you read a <a 2819href="http://www.tbray.org/ongoing/When/200x/2003/04/06/Unicode">presentation</a> 2820by Tim Bray on Unicode and why you should care about it.</p> 2821 2822<p>XML was designed from the start to allow the support of any character set 2823by using Unicode. Any conformant XML parser has to support the UTF-8 and 2824UTF-16 default encodings which can both express the full unicode ranges. UTF8 2825is a variable length encoding whose greatest points are to reuse the same 2826encoding for ASCII and to save space for Western encodings, but it is a bit 2827more complex to handle in practice. UTF-16 use 2 bytes per character (and 2828sometimes combines two pairs), it makes implementation easier, but looks a 2829bit overkill for Western languages encoding. Moreover the XML specification 2830allows the document to be encoded in other encodings at the condition that 2831they are clearly labeled as such. For example the following is a wellformed 2832XML document encoded in ISO-8859-1 and using accentuated letters that we 2833French like for both markup and content:</p> 2834<pre><?xml version="1.0" encoding="ISO-8859-1"?> 2835<tr�s>l�</tr�s></pre> 2836 2837<p>Having internationalization support in libxml2 means the following:</p> 2838<ul> 2839 <li>the document is properly parsed</li> 2840 <li>informations about it's encoding are saved</li> 2841 <li>it can be modified</li> 2842 <li>it can be saved in its original encoding</li> 2843 <li>it can also be saved in another encoding supported by libxml2 (for 2844 example straight UTF8 or even an ASCII form)</li> 2845</ul> 2846 2847<p>Another very important point is that the whole libxml2 API, with the 2848exception of a few routines to read with a specific encoding or save to a 2849specific encoding, is completely agnostic about the original encoding of the 2850document.</p> 2851 2852<p>It should be noted too that the HTML parser embedded in libxml2 now obey 2853the same rules too, the following document will be (as of 2.2.2) handled in 2854an internationalized fashion by libxml2 too:</p> 2855<pre><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" 2856 "http://www.w3.org/TR/REC-html40/loose.dtd"> 2857<html lang="fr"> 2858<head> 2859 <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"> 2860</head> 2861<body> 2862<p>W3C cr�e des standards pour le Web.</body> 2863</html></pre> 2864 2865<h3><a name="internal">The internal encoding, how and why</a></h3> 2866 2867<p>One of the core decisions was to force all documents to be converted to a 2868default internal encoding, and that encoding to be UTF-8, here are the 2869rationales for those choices:</p> 2870<ul> 2871 <li>keeping the native encoding in the internal form would force the libxml 2872 users (or the code associated) to be fully aware of the encoding of the 2873 original document, for examples when adding a text node to a document, 2874 the content would have to be provided in the document encoding, i.e. the 2875 client code would have to check it before hand, make sure it's conformant 2876 to the encoding, etc ... Very hard in practice, though in some specific 2877 cases this may make sense.</li> 2878 <li>the second decision was which encoding. From the XML spec only UTF8 and 2879 UTF16 really makes sense as being the two only encodings for which there 2880 is mandatory support. UCS-4 (32 bits fixed size encoding) could be 2881 considered an intelligent choice too since it's a direct Unicode mapping 2882 support. I selected UTF-8 on the basis of efficiency and compatibility 2883 with surrounding software: 2884 <ul> 2885 <li>UTF-8 while a bit more complex to convert from/to (i.e. slightly 2886 more costly to import and export CPU wise) is also far more compact 2887 than UTF-16 (and UCS-4) for a majority of the documents I see it used 2888 for right now (RPM RDF catalogs, advogato data, various configuration 2889 file formats, etc.) and the key point for today's computer 2890 architecture is efficient uses of caches. If one nearly double the 2891 memory requirement to store the same amount of data, this will trash 2892 caches (main memory/external caches/internal caches) and my take is 2893 that this harms the system far more than the CPU requirements needed 2894 for the conversion to UTF-8</li> 2895 <li>Most of libxml2 version 1 users were using it with straight ASCII 2896 most of the time, doing the conversion with an internal encoding 2897 requiring all their code to be rewritten was a serious show-stopper 2898 for using UTF-16 or UCS-4.</li> 2899 <li>UTF-8 is being used as the de-facto internal encoding standard for 2900 related code like the <a href="http://www.pango.org/">pango</a> 2901 upcoming Gnome text widget, and a lot of Unix code (yet another place 2902 where Unix programmer base takes a different approach from Microsoft 2903 - they are using UTF-16)</li> 2904 </ul> 2905 </li> 2906</ul> 2907 2908<p>What does this mean in practice for the libxml2 user:</p> 2909<ul> 2910 <li>xmlChar, the libxml2 data type is a byte, those bytes must be assembled 2911 as UTF-8 valid strings. The proper way to terminate an xmlChar * string 2912 is simply to append 0 byte, as usual.</li> 2913 <li>One just need to make sure that when using chars outside the ASCII set, 2914 the values has been properly converted to UTF-8</li> 2915</ul> 2916 2917<h3><a name="implemente">How is it implemented ?</a></h3> 2918 2919<p>Let's describe how all this works within libxml, basically the I18N 2920(internationalization) support get triggered only during I/O operation, i.e. 2921when reading a document or saving one. Let's look first at the reading 2922sequence:</p> 2923<ol> 2924 <li>when a document is processed, we usually don't know the encoding, a 2925 simple heuristic allows to detect UTF-16 and UCS-4 from encodings where 2926 the ASCII range (0-0x7F) maps with ASCII</li> 2927 <li>the xml declaration if available is parsed, including the encoding 2928 declaration. At that point, if the autodetected encoding is different 2929 from the one declared a call to xmlSwitchEncoding() is issued.</li> 2930 <li>If there is no encoding declaration, then the input has to be in either 2931 UTF-8 or UTF-16, if it is not then at some point when processing the 2932 input, the converter/checker of UTF-8 form will raise an encoding error. 2933 You may end-up with a garbled document, or no document at all ! Example: 2934 <pre>~/XML -> /xmllint err.xml 2935err.xml:1: error: Input is not proper UTF-8, indicate encoding ! 2936<tr�s>l�</tr�s> 2937 ^ 2938err.xml:1: error: Bytes: 0xE8 0x73 0x3E 0x6C 2939<tr�s>l�</tr�s> 2940 ^</pre> 2941 </li> 2942 <li>xmlSwitchEncoding() does an encoding name lookup, canonicalize it, and 2943 then search the default registered encoding converters for that encoding. 2944 If it's not within the default set and iconv() support has been compiled 2945 it, it will ask iconv for such an encoder. If this fails then the parser 2946 will report an error and stops processing: 2947 <pre>~/XML -> /xmllint err2.xml 2948err2.xml:1: error: Unsupported encoding UnsupportedEnc 2949<?xml version="1.0" encoding="UnsupportedEnc"?> 2950 ^</pre> 2951 </li> 2952 <li>From that point the encoder processes progressively the input (it is 2953 plugged as a front-end to the I/O module) for that entity. It captures 2954 and converts on-the-fly the document to be parsed to UTF-8. The parser 2955 itself just does UTF-8 checking of this input and process it 2956 transparently. The only difference is that the encoding information has 2957 been added to the parsing context (more precisely to the input 2958 corresponding to this entity).</li> 2959 <li>The result (when using DOM) is an internal form completely in UTF-8 2960 with just an encoding information on the document node.</li> 2961</ol> 2962 2963<p>Ok then what happens when saving the document (assuming you 2964collected/built an xmlDoc DOM like structure) ? It depends on the function 2965called, xmlSaveFile() will just try to save in the original encoding, while 2966xmlSaveFileTo() and xmlSaveFileEnc() can optionally save to a given 2967encoding:</p> 2968<ol> 2969 <li>if no encoding is given, libxml2 will look for an encoding value 2970 associated to the document and if it exists will try to save to that 2971 encoding, 2972 <p>otherwise everything is written in the internal form, i.e. UTF-8</p> 2973 </li> 2974 <li>so if an encoding was specified, either at the API level or on the 2975 document, libxml2 will again canonicalize the encoding name, lookup for a 2976 converter in the registered set or through iconv. If not found the 2977 function will return an error code</li> 2978 <li>the converter is placed before the I/O buffer layer, as another kind of 2979 buffer, then libxml2 will simply push the UTF-8 serialization to through 2980 that buffer, which will then progressively be converted and pushed onto 2981 the I/O layer.</li> 2982 <li>It is possible that the converter code fails on some input, for example 2983 trying to push an UTF-8 encoded Chinese character through the UTF-8 to 2984 ISO-8859-1 converter won't work. Since the encoders are progressive they 2985 will just report the error and the number of bytes converted, at that 2986 point libxml2 will decode the offending character, remove it from the 2987 buffer and replace it with the associated charRef encoding &#123; and 2988 resume the conversion. This guarantees that any document will be saved 2989 without losses (except for markup names where this is not legal, this is 2990 a problem in the current version, in practice avoid using non-ascii 2991 characters for tag or attribute names). A special "ascii" encoding name 2992 is used to save documents to a pure ascii form can be used when 2993 portability is really crucial</li> 2994</ol> 2995 2996<p>Here are a few examples based on the same test document:</p> 2997<pre>~/XML -> /xmllint isolat1 2998<?xml version="1.0" encoding="ISO-8859-1"?> 2999<tr�s>l�</tr�s> 3000~/XML -> /xmllint --encode UTF-8 isolat1 3001<?xml version="1.0" encoding="UTF-8"?> 3002<très>l� �</très> 3003~/XML -> </pre> 3004 3005<p>The same processing is applied (and reuse most of the code) for HTML I18N 3006processing. Looking up and modifying the content encoding is a bit more 3007difficult since it is located in a <meta> tag under the <head>, 3008so a couple of functions htmlGetMetaEncoding() and htmlSetMetaEncoding() have 3009been provided. The parser also attempts to switch encoding on the fly when 3010detecting such a tag on input. Except for that the processing is the same 3011(and again reuses the same code).</p> 3012 3013<h3><a name="Default">Default supported encodings</a></h3> 3014 3015<p>libxml2 has a set of default converters for the following encodings 3016(located in encoding.c):</p> 3017<ol> 3018 <li>UTF-8 is supported by default (null handlers)</li> 3019 <li>UTF-16, both little and big endian</li> 3020 <li>ISO-Latin-1 (ISO-8859-1) covering most western languages</li> 3021 <li>ASCII, useful mostly for saving</li> 3022 <li>HTML, a specific handler for the conversion of UTF-8 to ASCII with HTML 3023 predefined entities like &copy; for the Copyright sign.</li> 3024</ol> 3025 3026<p>More over when compiled on an Unix platform with iconv support the full 3027set of encodings supported by iconv can be instantly be used by libxml. On a 3028linux machine with glibc-2.1 the list of supported encodings and aliases fill 30293 full pages, and include UCS-4, the full set of ISO-Latin encodings, and the 3030various Japanese ones.</p> 3031 3032<h4>Encoding aliases</h4> 3033 3034<p>From 2.2.3, libxml2 has support to register encoding names aliases. The 3035goal is to be able to parse document whose encoding is supported but where 3036the name differs (for example from the default set of names accepted by 3037iconv). The following functions allow to register and handle new aliases for 3038existing encodings. Once registered libxml2 will automatically lookup the 3039aliases when handling a document:</p> 3040<ul> 3041 <li>int xmlAddEncodingAlias(const char *name, const char *alias);</li> 3042 <li>int xmlDelEncodingAlias(const char *alias);</li> 3043 <li>const char * xmlGetEncodingAlias(const char *alias);</li> 3044 <li>void xmlCleanupEncodingAliases(void);</li> 3045</ul> 3046 3047<h3><a name="extend">How to extend the existing support</a></h3> 3048 3049<p>Well adding support for new encoding, or overriding one of the encoders 3050(assuming it is buggy) should not be hard, just write input and output 3051conversion routines to/from UTF-8, and register them using 3052xmlNewCharEncodingHandler(name, xxxToUTF8, UTF8Toxxx), and they will be 3053called automatically if the parser(s) encounter such an encoding name 3054(register it uppercase, this will help). The description of the encoders, 3055their arguments and expected return values are described in the encoding.h 3056header.</p> 3057 3058<p>A quick note on the topic of subverting the parser to use a different 3059internal encoding than UTF-8, in some case people will absolutely want to 3060keep the internal encoding different, I think it's still possible (but the 3061encoding must be compliant with ASCII on the same subrange) though I didn't 3062tried it. The key is to override the default conversion routines (by 3063registering null encoders/decoders for your charsets), and bypass the UTF-8 3064checking of the parser by setting the parser context charset 3065(ctxt->charset) to something different than XML_CHAR_ENCODING_UTF8, but 3066there is no guarantee that this will work. You may also have some troubles 3067saving back.</p> 3068 3069<p>Basically proper I18N support is important, this requires at least 3070libxml-2.0.0, but a lot of features and corrections are really available only 3071starting 2.2.</p> 3072 3073<h2><a name="IO">I/O Interfaces</a></h2> 3074 3075<p>Table of Content:</p> 3076<ol> 3077 <li><a href="#General1">General overview</a></li> 3078 <li><a href="#basic">The basic buffer type</a></li> 3079 <li><a href="#Input">Input I/O handlers</a></li> 3080 <li><a href="#Output">Output I/O handlers</a></li> 3081 <li><a href="#entities">The entities loader</a></li> 3082 <li><a href="#Example2">Example of customized I/O</a></li> 3083</ol> 3084 3085<h3><a name="General1">General overview</a></h3> 3086 3087<p>The module <code><a 3088href="http://xmlsoft.org/html/libxml-xmlio.html">xmlIO.h</a></code> provides 3089the interfaces to the libxml2 I/O system. This consists of 4 main parts:</p> 3090<ul> 3091 <li>Entities loader, this is a routine which tries to fetch the entities 3092 (files) based on their PUBLIC and SYSTEM identifiers. The default loader 3093 don't look at the public identifier since libxml2 do not maintain a 3094 catalog. You can redefine you own entity loader by using 3095 <code>xmlGetExternalEntityLoader()</code> and 3096 <code>xmlSetExternalEntityLoader()</code>. <a href="#entities">Check the 3097 example</a>.</li> 3098 <li>Input I/O buffers which are a commodity structure used by the parser(s) 3099 input layer to handle fetching the informations to feed the parser. This 3100 provides buffering and is also a placeholder where the encoding 3101 converters to UTF8 are piggy-backed.</li> 3102 <li>Output I/O buffers are similar to the Input ones and fulfill similar 3103 task but when generating a serialization from a tree.</li> 3104 <li>A mechanism to register sets of I/O callbacks and associate them with 3105 specific naming schemes like the protocol part of the URIs. 3106 <p>This affect the default I/O operations and allows to use specific I/O 3107 handlers for certain names.</p> 3108 </li> 3109</ul> 3110 3111<p>The general mechanism used when loading http://rpmfind.net/xml.html for 3112example in the HTML parser is the following:</p> 3113<ol> 3114 <li>The default entity loader calls <code>xmlNewInputFromFile()</code> with 3115 the parsing context and the URI string.</li> 3116 <li>the URI string is checked against the existing registered handlers 3117 using their match() callback function, if the HTTP module was compiled 3118 in, it is registered and its match() function will succeeds</li> 3119 <li>the open() function of the handler is called and if successful will 3120 return an I/O Input buffer</li> 3121 <li>the parser will the start reading from this buffer and progressively 3122 fetch information from the resource, calling the read() function of the 3123 handler until the resource is exhausted</li> 3124 <li>if an encoding change is detected it will be installed on the input 3125 buffer, providing buffering and efficient use of the conversion 3126 routines</li> 3127 <li>once the parser has finished, the close() function of the handler is 3128 called once and the Input buffer and associated resources are 3129 deallocated.</li> 3130</ol> 3131 3132<p>The user defined callbacks are checked first to allow overriding of the 3133default libxml2 I/O routines.</p> 3134 3135<h3><a name="basic">The basic buffer type</a></h3> 3136 3137<p>All the buffer manipulation handling is done using the 3138<code>xmlBuffer</code> type define in <code><a 3139href="http://xmlsoft.org/html/libxml-tree.html">tree.h</a> </code>which is a 3140resizable memory buffer. The buffer allocation strategy can be selected to be 3141either best-fit or use an exponential doubling one (CPU vs. memory use 3142trade-off). The values are <code>XML_BUFFER_ALLOC_EXACT</code> and 3143<code>XML_BUFFER_ALLOC_DOUBLEIT</code>, and can be set individually or on a 3144system wide basis using <code>xmlBufferSetAllocationScheme()</code>. A number 3145of functions allows to manipulate buffers with names starting with the 3146<code>xmlBuffer...</code> prefix.</p> 3147 3148<h3><a name="Input">Input I/O handlers</a></h3> 3149 3150<p>An Input I/O handler is a simple structure 3151<code>xmlParserInputBuffer</code> containing a context associated to the 3152resource (file descriptor, or pointer to a protocol handler), the read() and 3153close() callbacks to use and an xmlBuffer. And extra xmlBuffer and a charset 3154encoding handler are also present to support charset conversion when 3155needed.</p> 3156 3157<h3><a name="Output">Output I/O handlers</a></h3> 3158 3159<p>An Output handler <code>xmlOutputBuffer</code> is completely similar to an 3160Input one except the callbacks are write() and close().</p> 3161 3162<h3><a name="entities">The entities loader</a></h3> 3163 3164<p>The entity loader resolves requests for new entities and create inputs for 3165the parser. Creating an input from a filename or an URI string is done 3166through the xmlNewInputFromFile() routine. The default entity loader do not 3167handle the PUBLIC identifier associated with an entity (if any). So it just 3168calls xmlNewInputFromFile() with the SYSTEM identifier (which is mandatory in 3169XML).</p> 3170 3171<p>If you want to hook up a catalog mechanism then you simply need to 3172override the default entity loader, here is an example:</p> 3173<pre>#include <libxml/xmlIO.h> 3174 3175xmlExternalEntityLoader defaultLoader = NULL; 3176 3177xmlParserInputPtr 3178xmlMyExternalEntityLoader(const char *URL, const char *ID, 3179 xmlParserCtxtPtr ctxt) { 3180 xmlParserInputPtr ret; 3181 const char *fileID = NULL; 3182 /* lookup for the fileID depending on ID */ 3183 3184 ret = xmlNewInputFromFile(ctxt, fileID); 3185 if (ret != NULL) 3186 return(ret); 3187 if (defaultLoader != NULL) 3188 ret = defaultLoader(URL, ID, ctxt); 3189 return(ret); 3190} 3191 3192int main(..) { 3193 ... 3194 3195 /* 3196 * Install our own entity loader 3197 */ 3198 defaultLoader = xmlGetExternalEntityLoader(); 3199 xmlSetExternalEntityLoader(xmlMyExternalEntityLoader); 3200 3201 ... 3202}</pre> 3203 3204<h3><a name="Example2">Example of customized I/O</a></h3> 3205 3206<p>This example come from <a href="http://xmlsoft.org/messages/0708.html">a 3207real use case</a>, xmlDocDump() closes the FILE * passed by the application 3208and this was a problem. The <a 3209href="http://xmlsoft.org/messages/0711.html">solution</a> was to redefine a 3210new output handler with the closing call deactivated:</p> 3211<ol> 3212 <li>First define a new I/O output allocator where the output don't close 3213 the file: 3214 <pre>xmlOutputBufferPtr 3215xmlOutputBufferCreateOwn(FILE *file, xmlCharEncodingHandlerPtr encoder) { 3216����xmlOutputBufferPtr ret; 3217���� 3218����if (xmlOutputCallbackInitialized == 0) 3219��������xmlRegisterDefaultOutputCallbacks(); 3220 3221����if (file == NULL) return(NULL); 3222����ret = xmlAllocOutputBuffer(encoder); 3223����if (ret != NULL) { 3224��������ret->context = file; 3225��������ret->writecallback = xmlFileWrite; 3226��������ret->closecallback = NULL; /* No close callback */ 3227����} 3228����return(ret); 3229} </pre> 3230 </li> 3231 <li>And then use it to save the document: 3232 <pre>FILE *f; 3233xmlOutputBufferPtr output; 3234xmlDocPtr doc; 3235int res; 3236 3237f = ... 3238doc = .... 3239 3240output = xmlOutputBufferCreateOwn(f, NULL); 3241res = xmlSaveFileTo(output, doc, NULL); 3242 </pre> 3243 </li> 3244</ol> 3245 3246<h2><a name="Catalog">Catalog support</a></h2> 3247 3248<p>Table of Content:</p> 3249<ol> 3250 <li><a href="General2">General overview</a></li> 3251 <li><a href="#definition">The definition</a></li> 3252 <li><a href="#Simple">Using catalogs</a></li> 3253 <li><a href="#Some">Some examples</a></li> 3254 <li><a href="#reference">How to tune catalog usage</a></li> 3255 <li><a href="#validate">How to debug catalog processing</a></li> 3256 <li><a href="#Declaring">How to create and maintain catalogs</a></li> 3257 <li><a href="#implemento">The implementor corner quick review of the 3258 API</a></li> 3259 <li><a href="#Other">Other resources</a></li> 3260</ol> 3261 3262<h3><a name="General2">General overview</a></h3> 3263 3264<p>What is a catalog? Basically it's a lookup mechanism used when an entity 3265(a file or a remote resource) references another entity. The catalog lookup 3266is inserted between the moment the reference is recognized by the software 3267(XML parser, stylesheet processing, or even images referenced for inclusion 3268in a rendering) and the time where loading that resource is actually 3269started.</p> 3270 3271<p>It is basically used for 3 things:</p> 3272<ul> 3273 <li>mapping from "logical" names, the public identifiers and a more 3274 concrete name usable for download (and URI). For example it can associate 3275 the logical name 3276 <p>"-//OASIS//DTD DocBook XML V4.1.2//EN"</p> 3277 <p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be 3278 downloaded</p> 3279 <p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p> 3280 </li> 3281 <li>remapping from a given URL to another one, like an HTTP indirection 3282 saying that 3283 <p>"http://www.oasis-open.org/committes/tr.xsl"</p> 3284 <p>should really be looked at</p> 3285 <p>"http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"</p> 3286 </li> 3287 <li>providing a local cache mechanism allowing to load the entities 3288 associated to public identifiers or remote resources, this is a really 3289 important feature for any significant deployment of XML or SGML since it 3290 allows to avoid the aleas and delays associated to fetching remote 3291 resources.</li> 3292</ul> 3293 3294<h3><a name="definition">The definitions</a></h3> 3295 3296<p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p> 3297<ul> 3298 <li>the older SGML catalogs, the official spec is SGML Open Technical 3299 Resolution TR9401:1997, but is better understood by reading <a 3300 href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from 3301 James Clark. This is relatively old and not the preferred mode of 3302 operation of libxml.</li> 3303 <li><a href="http://www.oasis-open.org/committees/entity/spec.html">XML 3304 Catalogs</a> is far more flexible, more recent, uses an XML syntax and 3305 should scale quite better. This is the default option of libxml.</li> 3306</ul> 3307 3308<p></p> 3309 3310<h3><a name="Simple">Using catalog</a></h3> 3311 3312<p>In a normal environment libxml2 will by default check the presence of a 3313catalog in /etc/xml/catalog, and assuming it has been correctly populated, 3314the processing is completely transparent to the document user. To take a 3315concrete example, suppose you are authoring a DocBook document, this one 3316starts with the following DOCTYPE definition:</p> 3317<pre><?xml version='1.0'?> 3318<!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN" 3319 "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd"></pre> 3320 3321<p>When validating the document with libxml, the catalog will be 3322automatically consulted to lookup the public identifier "-//Norman Walsh//DTD 3323DocBk XML V3.1.4//EN" and the system identifier 3324"http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if these entities have 3325been installed on your system and the catalogs actually point to them, libxml 3326will fetch them from the local disk.</p> 3327 3328<p style="font-size: 10pt"><strong>Note</strong>: Really don't use this 3329DOCTYPE example it's a really old version, but is fine as an example.</p> 3330 3331<p>Libxml2 will check the catalog each time that it is requested to load an 3332entity, this includes DTD, external parsed entities, stylesheets, etc ... If 3333your system is correctly configured all the authoring phase and processing 3334should use only local files, even if your document stays portable because it 3335uses the canonical public and system ID, referencing the remote document.</p> 3336 3337<h3><a name="Some">Some examples:</a></h3> 3338 3339<p>Here is a couple of fragments from XML Catalogs used in libxml2 early 3340regression tests in <code>test/catalogs</code> :</p> 3341<pre><?xml version="1.0"?> 3342<!DOCTYPE catalog PUBLIC 3343 "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3344 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3345<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 3346 <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 3347 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 3348...</pre> 3349 3350<p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are 3351written in XML, there is a specific namespace for catalog elements 3352"urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry in this 3353catalog is a <code>public</code> mapping it allows to associate a Public 3354Identifier with an URI.</p> 3355<pre>... 3356 <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/" 3357 rewritePrefix="file:///usr/share/xml/docbook/"/> 3358...</pre> 3359 3360<p>A <code>rewriteSystem</code> is a very powerful instruction, it says that 3361any URI starting with a given prefix should be looked at another URI 3362constructed by replacing the prefix with an new one. In effect this acts like 3363a cache system for a full area of the Web. In practice it is extremely useful 3364with a file prefix if you have installed a copy of those resources on your 3365local system.</p> 3366<pre>... 3367<delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //" 3368 catalog="file:///usr/share/xml/docbook.xml"/> 3369<delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML" 3370 catalog="file:///usr/share/xml/docbook.xml"/> 3371<delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML" 3372 catalog="file:///usr/share/xml/docbook.xml"/> 3373<delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/" 3374 catalog="file:///usr/share/xml/docbook.xml"/> 3375<delegateURI uriStartString="http://www.oasis-open.org/docbook/" 3376 catalog="file:///usr/share/xml/docbook.xml"/> 3377...</pre> 3378 3379<p>Delegation is the core features which allows to build a tree of catalogs, 3380easier to maintain than a single catalog, based on Public Identifier, System 3381Identifier or URI prefixes it instructs the catalog software to look up 3382entries in another resource. This feature allow to build hierarchies of 3383catalogs, the set of entries presented should be sufficient to redirect the 3384resolution of all DocBook references to the specific catalog in 3385<code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all 3386references for DocBook 4.2.1 to a specific catalog installed at the same time 3387as the DocBook resources on the local machine.</p> 3388 3389<h3><a name="reference">How to tune catalog usage:</a></h3> 3390 3391<p>The user can change the default catalog behaviour by redirecting queries 3392to its own set of catalogs, this can be done by setting the 3393<code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an 3394empty one should deactivate loading the default <code>/etc/xml/catalog</code> 3395default catalog</p> 3396 3397<h3><a name="validate">How to debug catalog processing:</a></h3> 3398 3399<p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will 3400make libxml2 output debugging informations for each catalog operations, for 3401example:</p> 3402<pre>orchis:~/XML -> xmllint --memory --noout test/ent2 3403warning: failed to load external entity "title.xml" 3404orchis:~/XML -> export XML_DEBUG_CATALOG= 3405orchis:~/XML -> xmllint --memory --noout test/ent2 3406Failed to parse catalog /etc/xml/catalog 3407Failed to parse catalog /etc/xml/catalog 3408warning: failed to load external entity "title.xml" 3409Catalogs cleanup 3410orchis:~/XML -> </pre> 3411 3412<p>The test/ent2 references an entity, running the parser from memory makes 3413the base URI unavailable and the the "title.xml" entity cannot be loaded. 3414Setting up the debug environment variable allows to detect that an attempt is 3415made to load the <code>/etc/xml/catalog</code> but since it's not present the 3416resolution fails.</p> 3417 3418<p>But the most advanced way to debug XML catalog processing is to use the 3419<strong>xmlcatalog</strong> command shipped with libxml2, it allows to load 3420catalogs and make resolution queries to see what is going on. This is also 3421used for the regression tests:</p> 3422<pre>orchis:~/XML -> /xmlcatalog test/catalogs/docbook.xml \ 3423 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3424http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3425orchis:~/XML -> </pre> 3426 3427<p>For debugging what is going on, adding one -v flags increase the verbosity 3428level to indicate the processing done (adding a second flag also indicate 3429what elements are recognized at parsing):</p> 3430<pre>orchis:~/XML -> /xmlcatalog -v test/catalogs/docbook.xml \ 3431 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3432Parsing catalog test/catalogs/docbook.xml's content 3433Found public match -//OASIS//DTD DocBook XML V4.1.2//EN 3434http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3435Catalogs cleanup 3436orchis:~/XML -> </pre> 3437 3438<p>A shell interface is also available to debug and process multiple queries 3439(and for regression tests):</p> 3440<pre>orchis:~/XML -> /xmlcatalog -shell test/catalogs/docbook.xml \ 3441 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3442> help 3443Commands available: 3444public PublicID: make a PUBLIC identifier lookup 3445system SystemID: make a SYSTEM identifier lookup 3446resolve PublicID SystemID: do a full resolver lookup 3447add 'type' 'orig' 'replace' : add an entry 3448del 'values' : remove values 3449dump: print the current catalog state 3450debug: increase the verbosity level 3451quiet: decrease the verbosity level 3452exit: quit the shell 3453> public "-//OASIS//DTD DocBook XML V4.1.2//EN" 3454http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3455> quit 3456orchis:~/XML -> </pre> 3457 3458<p>This should be sufficient for most debugging purpose, this was actually 3459used heavily to debug the XML Catalog implementation itself.</p> 3460 3461<h3><a name="Declaring">How to create and maintain</a> catalogs:</h3> 3462 3463<p>Basically XML Catalogs are XML files, you can either use XML tools to 3464manage them or use <strong>xmlcatalog</strong> for this. The basic step is 3465to create a catalog the -create option provide this facility:</p> 3466<pre>orchis:~/XML -> /xmlcatalog --create tst.xml 3467<?xml version="1.0"?> 3468<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3469 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3470<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3471orchis:~/XML -> </pre> 3472 3473<p>By default xmlcatalog does not overwrite the original catalog and save the 3474result on the standard output, this can be overridden using the -noout 3475option. The <code>-add</code> command allows to add entries in the 3476catalog:</p> 3477<pre>orchis:~/XML -> /xmlcatalog --noout --create --add "public" \ 3478 "-//OASIS//DTD DocBook XML V4.1.2//EN" \ 3479 http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml 3480orchis:~/XML -> cat tst.xml 3481<?xml version="1.0"?> 3482<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \ 3483 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3484<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 3485<public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 3486 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 3487</catalog> 3488orchis:~/XML -> </pre> 3489 3490<p>The <code>-add</code> option will always take 3 parameters even if some of 3491the XML Catalog constructs (like nextCatalog) will have only a single 3492argument, just pass a third empty string, it will be ignored.</p> 3493 3494<p>Similarly the <code>-del</code> option remove matching entries from the 3495catalog:</p> 3496<pre>orchis:~/XML -> /xmlcatalog --del \ 3497 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml 3498<?xml version="1.0"?> 3499<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3500 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3501<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3502orchis:~/XML -> </pre> 3503 3504<p>The catalog is now empty. Note that the matching of <code>-del</code> is 3505exact and would have worked in a similar fashion with the Public ID 3506string.</p> 3507 3508<p>This is rudimentary but should be sufficient to manage a not too complex 3509catalog tree of resources.</p> 3510 3511<h3><a name="implemento">The implementor corner quick review of the 3512API:</a></h3> 3513 3514<p>First, and like for every other module of libxml, there is an 3515automatically generated <a href="html/libxml-catalog.html">API page for 3516catalog support</a>.</p> 3517 3518<p>The header for the catalog interfaces should be included as:</p> 3519<pre>#include <libxml/catalog.h></pre> 3520 3521<p>The API is voluntarily kept very simple. First it is not obvious that 3522applications really need access to it since it is the default behaviour of 3523libxml2 (Note: it is possible to completely override libxml2 default catalog 3524by using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to 3525plug an application specific resolver).</p> 3526 3527<p>Basically libxml2 support 2 catalog lists:</p> 3528<ul> 3529 <li>the default one, global shared by all the application</li> 3530 <li>a per-document catalog, this one is built if the document uses the 3531 <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is 3532 associated to the parser context and destroyed when the parsing context 3533 is destroyed.</li> 3534</ul> 3535 3536<p>the document one will be used first if it exists.</p> 3537 3538<h4>Initialization routines:</h4> 3539 3540<p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be 3541used at startup to initialize the catalog, if the catalog should be 3542initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs() 3543should be called before xmlInitializeCatalog() which would otherwise do a 3544default initialization first.</p> 3545 3546<p>The xmlCatalogAddLocal() call is used by the parser to grow the document 3547own catalog list if needed.</p> 3548 3549<h4>Preferences setup:</h4> 3550 3551<p>The XML Catalog spec requires the possibility to select default 3552preferences between public and system delegation, 3553xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and 3554xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should 3555be forbidden, allowed for global catalog, for document catalog or both, the 3556default is to allow both.</p> 3557 3558<p>And of course xmlCatalogSetDebug() allows to generate debug messages 3559(through the xmlGenericError() mechanism).</p> 3560 3561<h4>Querying routines:</h4> 3562 3563<p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic() 3564and xmlCatalogResolveURI() are relatively explicit if you read the XML 3565Catalog specification they correspond to section 7 algorithms, they should 3566also work if you have loaded an SGML catalog with a simplified semantic.</p> 3567 3568<p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but 3569operate on the document catalog list</p> 3570 3571<h4>Cleanup and Miscellaneous:</h4> 3572 3573<p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is 3574the per-document equivalent.</p> 3575 3576<p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the 3577first catalog in the global list, and xmlCatalogDump() allows to dump a 3578catalog state, those routines are primarily designed for xmlcatalog, I'm not 3579sure that exposing more complex interfaces (like navigation ones) would be 3580really useful.</p> 3581 3582<p>The xmlParseCatalogFile() is a function used to load XML Catalog files, 3583it's similar as xmlParseFile() except it bypass all catalog lookups, it's 3584provided because this functionality may be useful for client tools.</p> 3585 3586<h4>threaded environments:</h4> 3587 3588<p>Since the catalog tree is built progressively, some care has been taken to 3589try to avoid troubles in multithreaded environments. The code is now thread 3590safe assuming that the libxml2 library has been compiled with threads 3591support.</p> 3592 3593<p></p> 3594 3595<h3><a name="Other">Other resources</a></h3> 3596 3597<p>The XML Catalog specification is relatively recent so there isn't much 3598literature to point at:</p> 3599<ul> 3600 <li>You can find a good rant from Norm Walsh about <a 3601 href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the 3602 need for catalogs</a>, it provides a lot of context informations even if 3603 I don't agree with everything presented. Norm also wrote a more recent 3604 article <a 3605 href="http://wwws.sun.com/software/xml/developers/resolver/article/">XML 3606 entities and URI resolvers</a> describing them.</li> 3607 <li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML 3608 catalog proposal</a> from John Cowan</li> 3609 <li>The <a href="http://www.rddl.org/">Resource Directory Description 3610 Language</a> (RDDL) another catalog system but more oriented toward 3611 providing metadata for XML namespaces.</li> 3612 <li>the page from the OASIS Technical <a 3613 href="http://www.oasis-open.org/committees/entity/">Committee on Entity 3614 Resolution</a> who maintains XML Catalog, you will find pointers to the 3615 specification update, some background and pointers to others tools 3616 providing XML Catalog support</li> 3617 <li>There is a <a href="buildDocBookCatalog">shell script</a> to generate 3618 XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/ 3619 directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on 3620 the resources found on the system. Otherwise it will just create 3621 ~/xmlcatalog and ~/dbkxmlcatalog and doing: 3622 <p><code>export XML_CATALOG_FILES=$HOME/xmlcatalog</code></p> 3623 <p>should allow to process DocBook documentations without requiring 3624 network accesses for the DTD or stylesheets</p> 3625 </li> 3626 <li>I have uploaded <a href="ftp://xmlsoft.org/test/dbk412catalog.tar.gz">a 3627 small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems 3628 to work fine for me too</li> 3629 <li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog 3630 manual page</a></li> 3631</ul> 3632 3633<p>If you have suggestions for corrections or additions, simply contact 3634me:</p> 3635 3636<h2><a name="library">The parser interfaces</a></h2> 3637 3638<p>This section is directly intended to help programmers getting bootstrapped 3639using the XML tollkit from the C language. It is not intended to be 3640extensive. I hope the automatically generated documents will provide the 3641completeness required, but as a separate set of documents. The interfaces of 3642the XML parser are by principle low level, Those interested in a higher level 3643API should <a href="#DOM">look at DOM</a>.</p> 3644 3645<p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are 3646separated from the <a href="html/libxml-htmlparser.html">HTML parser 3647interfaces</a>. Let's have a look at how the XML parser can be called:</p> 3648 3649<h3><a name="Invoking">Invoking the parser : the pull method</a></h3> 3650 3651<p>Usually, the first thing to do is to read an XML input. The parser accepts 3652documents either from in-memory strings or from files. The functions are 3653defined in "parser.h":</p> 3654<dl> 3655 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> 3656 <dd><p>Parse a null-terminated string containing the document.</p> 3657 </dd> 3658</dl> 3659<dl> 3660 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> 3661 <dd><p>Parse an XML document contained in a (possibly compressed) 3662 file.</p> 3663 </dd> 3664</dl> 3665 3666<p>The parser returns a pointer to the document structure (or NULL in case of 3667failure).</p> 3668 3669<h3 id="Invoking1">Invoking the parser: the push method</h3> 3670 3671<p>In order for the application to keep the control when the document is 3672being fetched (which is common for GUI based programs) libxml2 provides a 3673push interface, too, as of version 1.8.3. Here are the interface 3674functions:</p> 3675<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, 3676 void *user_data, 3677 const char *chunk, 3678 int size, 3679 const char *filename); 3680int xmlParseChunk (xmlParserCtxtPtr ctxt, 3681 const char *chunk, 3682 int size, 3683 int terminate);</pre> 3684 3685<p>and here is a simple example showing how to use the interface:</p> 3686<pre> FILE *f; 3687 3688 f = fopen(filename, "r"); 3689 if (f != NULL) { 3690 int res, size = 1024; 3691 char chars[1024]; 3692 xmlParserCtxtPtr ctxt; 3693 3694 res = fread(chars, 1, 4, f); 3695 if (res > 0) { 3696 ctxt = xmlCreatePushParserCtxt(NULL, NULL, 3697 chars, res, filename); 3698 while ((res = fread(chars, 1, size, f)) > 0) { 3699 xmlParseChunk(ctxt, chars, res, 0); 3700 } 3701 xmlParseChunk(ctxt, chars, 0, 1); 3702 doc = ctxt->myDoc; 3703 xmlFreeParserCtxt(ctxt); 3704 } 3705 }</pre> 3706 3707<p>The HTML parser embedded into libxml2 also has a push interface; the 3708functions are just prefixed by "html" rather than "xml".</p> 3709 3710<h3 id="Invoking2">Invoking the parser: the SAX interface</h3> 3711 3712<p>The tree-building interface makes the parser memory-hungry, first loading 3713the document in memory and then building the tree itself. Reading a document 3714without building the tree is possible using the SAX interfaces (see SAX.h and 3715<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James 3716Henstridge's documentation</a>). Note also that the push interface can be 3717limited to SAX: just use the two first arguments of 3718<code>xmlCreatePushParserCtxt()</code>.</p> 3719 3720<h3><a name="Building">Building a tree from scratch</a></h3> 3721 3722<p>The other way to get an XML tree in memory is by building it. Basically 3723there is a set of functions dedicated to building new elements. (These are 3724also described in <libxml/tree.h>.) For example, here is a piece of 3725code that produces the XML document used in the previous examples:</p> 3726<pre> #include <libxml/tree.h> 3727 xmlDocPtr doc; 3728 xmlNodePtr tree, subtree; 3729 3730 doc = xmlNewDoc("1.0"); 3731 doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); 3732 xmlSetProp(doc->children, "prop1", "gnome is great"); 3733 xmlSetProp(doc->children, "prop2", "& linux too"); 3734 tree = xmlNewChild(doc->children, NULL, "head", NULL); 3735 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); 3736 tree = xmlNewChild(doc->children, NULL, "chapter", NULL); 3737 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); 3738 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); 3739 subtree = xmlNewChild(tree, NULL, "image", NULL); 3740 xmlSetProp(subtree, "href", "linus.gif");</pre> 3741 3742<p>Not really rocket science ...</p> 3743 3744<h3><a name="Traversing">Traversing the tree</a></h3> 3745 3746<p>Basically by <a href="html/libxml-tree.html">including "tree.h"</a> your 3747code has access to the internal structure of all the elements of the tree. 3748The names should be somewhat simple like <strong>parent</strong>, 3749<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>, 3750<strong>properties</strong>, etc... For example, still with the previous 3751example:</p> 3752<pre><code>doc->children->children->children</code></pre> 3753 3754<p>points to the title element,</p> 3755<pre>doc->children->children->next->children->children</pre> 3756 3757<p>points to the text node containing the chapter title "The Linux 3758adventure".</p> 3759 3760<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be 3761present before the document root, so <code>doc->children</code> may point 3762to an element which is not the document Root Element; a function 3763<code>xmlDocGetRootElement()</code> was added for this purpose.</p> 3764 3765<h3><a name="Modifying">Modifying the tree</a></h3> 3766 3767<p>Functions are provided for reading and writing the document content. Here 3768is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p> 3769<dl> 3770 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const 3771 xmlChar *value);</code></dt> 3772 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. 3773 The value can be NULL.</p> 3774 </dd> 3775</dl> 3776<dl> 3777 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar 3778 *name);</code></dt> 3779 <dd><p>This function returns a pointer to new copy of the property 3780 content. Note that the user must deallocate the result.</p> 3781 </dd> 3782</dl> 3783 3784<p>Two functions are provided for reading and writing the text associated 3785with elements:</p> 3786<dl> 3787 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar 3788 *value);</code></dt> 3789 <dd><p>This function takes an "external" string and converts it to one 3790 text node or possibly to a list of entity and text nodes. All 3791 non-predefined entity references like &Gnome; will be stored 3792 internally as entity nodes, hence the result of the function may not be 3793 a single node.</p> 3794 </dd> 3795</dl> 3796<dl> 3797 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int 3798 inLine);</code></dt> 3799 <dd><p>This function is the inverse of 3800 <code>xmlStringGetNodeList()</code>. It generates a new string 3801 containing the content of the text and entity nodes. Note the extra 3802 argument inLine. If this argument is set to 1, the function will expand 3803 entity references. For example, instead of returning the &Gnome; 3804 XML encoding in the string, it will substitute it with its value (say, 3805 "GNU Network Object Model Environment").</p> 3806 </dd> 3807</dl> 3808 3809<h3><a name="Saving">Saving a tree</a></h3> 3810 3811<p>Basically 3 options are possible:</p> 3812<dl> 3813 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int 3814 *size);</code></dt> 3815 <dd><p>Returns a buffer into which the document has been saved.</p> 3816 </dd> 3817</dl> 3818<dl> 3819 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> 3820 <dd><p>Dumps a document to an open file descriptor.</p> 3821 </dd> 3822</dl> 3823<dl> 3824 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> 3825 <dd><p>Saves the document to a file. In this case, the compression 3826 interface is triggered if it has been turned on.</p> 3827 </dd> 3828</dl> 3829 3830<h3><a name="Compressio">Compression</a></h3> 3831 3832<p>The library transparently handles compression when doing file-based 3833accesses. The level of compression on saves can be turned on either globally 3834or individually for one file:</p> 3835<dl> 3836 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> 3837 <dd><p>Gets the document compression ratio (0-9).</p> 3838 </dd> 3839</dl> 3840<dl> 3841 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> 3842 <dd><p>Sets the document compression ratio.</p> 3843 </dd> 3844</dl> 3845<dl> 3846 <dt><code>int xmlGetCompressMode(void);</code></dt> 3847 <dd><p>Gets the default compression ratio.</p> 3848 </dd> 3849</dl> 3850<dl> 3851 <dt><code>void xmlSetCompressMode(int mode);</code></dt> 3852 <dd><p>Sets the default compression ratio.</p> 3853 </dd> 3854</dl> 3855 3856<h2><a name="Entities">Entities or no entities</a></h2> 3857 3858<p>Entities in principle are similar to simple C macros. An entity defines an 3859abbreviation for a given string that you can reuse many times throughout the 3860content of your document. Entities are especially useful when a given string 3861may occur frequently within a document, or to confine the change needed to a 3862document to a restricted area in the internal subset of the document (at the 3863beginning). Example:</p> 3864<pre>1 <?xml version="1.0"?> 38652 <!DOCTYPE EXAMPLE SYSTEM "example.dtd" [ 38663 <!ENTITY xml "Extensible Markup Language"> 38674 ]> 38685 <EXAMPLE> 38696 &xml; 38707 </EXAMPLE></pre> 3871 3872<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing 3873its name with '&' and following it by ';' without any spaces added. There 3874are 5 predefined entities in libxml2 allowing you to escape characters with 3875predefined meaning in some parts of the xml document content: 3876<strong>&lt;</strong> for the character '<', <strong>&gt;</strong> 3877for the character '>', <strong>&apos;</strong> for the character ''', 3878<strong>&quot;</strong> for the character '"', and 3879<strong>&amp;</strong> for the character '&'.</p> 3880 3881<p>One of the problems related to entities is that you may want the parser to 3882substitute an entity's content so that you can see the replacement text in 3883your application. Or you may prefer to keep entity references as such in the 3884content to be able to save the document back without losing this usually 3885precious information (if the user went through the pain of explicitly 3886defining entities, he may have a a rather negative attitude if you blindly 3887substitute them as saving time). The <a 3888href="html/libxml-parser.html#xmlSubstituteEntitiesDefault">xmlSubstituteEntitiesDefault()</a> 3889function allows you to check and change the behaviour, which is to not 3890substitute entities by default.</p> 3891 3892<p>Here is the DOM tree built by libxml2 for the previous document in the 3893default case:</p> 3894<pre>/gnome/src/gnome-xml -> /xmllint --debug test/ent1 3895DOCUMENT 3896version=1.0 3897 ELEMENT EXAMPLE 3898 TEXT 3899 content= 3900 ENTITY_REF 3901 INTERNAL_GENERAL_ENTITY xml 3902 content=Extensible Markup Language 3903 TEXT 3904 content=</pre> 3905 3906<p>And here is the result when substituting entities:</p> 3907<pre>/gnome/src/gnome-xml -> /tester --debug --noent test/ent1 3908DOCUMENT 3909version=1.0 3910 ELEMENT EXAMPLE 3911 TEXT 3912 content= Extensible Markup Language</pre> 3913 3914<p>So, entities or no entities? Basically, it depends on your use case. I 3915suggest that you keep the non-substituting default behaviour and avoid using 3916entities in your XML document or data if you are not willing to handle the 3917entity references elements in the DOM tree.</p> 3918 3919<p>Note that at save time libxml2 enforces the conversion of the predefined 3920entities where necessary to prevent well-formedness problems, and will also 3921transparently replace those with chars (i.e. it will not generate entity 3922reference elements in the DOM tree or call the reference() SAX callback when 3923finding them in the input).</p> 3924 3925<p><span style="background-color: #FF0000">WARNING</span>: handling entities 3926on top of the libxml2 SAX interface is difficult!!! If you plan to use 3927non-predefined entities in your documents, then the learning curve to handle 3928then using the SAX API may be long. If you plan to use complex documents, I 3929strongly suggest you consider using the DOM interface instead and let libxml 3930deal with the complexity rather than trying to do it yourself.</p> 3931 3932<h2><a name="Namespaces">Namespaces</a></h2> 3933 3934<p>The libxml2 library implements <a 3935href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by 3936recognizing namespace constructs in the input, and does namespace lookup 3937automatically when building the DOM tree. A namespace declaration is 3938associated with an in-memory structure and all elements or attributes within 3939that namespace point to it. Hence testing the namespace is a simple and fast 3940equality operation at the user level.</p> 3941 3942<p>I suggest that people using libxml2 use a namespace, and declare it in the 3943root element of their document as the default namespace. Then they don't need 3944to use the prefix in the content but we will have a basis for future semantic 3945refinement and merging of data from different sources. This doesn't increase 3946the size of the XML output significantly, but significantly increases its 3947value in the long-term. Example:</p> 3948<pre><mydoc xmlns="http://mydoc.example.org/schemas/"> 3949 <elem1>...</elem1> 3950 <elem2>...</elem2> 3951</mydoc></pre> 3952 3953<p>The namespace value has to be an absolute URL, but the URL doesn't have to 3954point to any existing resource on the Web. It will bind all the element and 3955attributes with that URL. I suggest to use an URL within a domain you 3956control, and that the URL should contain some kind of version information if 3957possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a 3958good namespace scheme.</p> 3959 3960<p>Then when you load a file, make sure that a namespace carrying the 3961version-independent prefix is installed on the root element of your document, 3962and if the version information don't match something you know, warn the user 3963and be liberal in what you accept as the input. Also do *not* try to base 3964namespace checking on the prefix value. <foo:text> may be exactly the 3965same as <bar:text> in another document. What really matters is the URI 3966associated with the element or the attribute, not the prefix string (which is 3967just a shortcut for the full URI). In libxml, element and attributes have an 3968<code>ns</code> field pointing to an xmlNs structure detailing the namespace 3969prefix and its URI.</p> 3970 3971<p>@@Interfaces@@</p> 3972<pre>xmlNodePtr node; 3973if(!strncmp(node->name,"mytag",5) 3974 && node->ns 3975 && !strcmp(node->ns->href,"http://www.mysite.com/myns/1.0")) { 3976 ... 3977}</pre> 3978 3979<p>Usually people object to using namespaces together with validity checking. 3980I will try to make sure that using namespaces won't break validity checking, 3981so even if you plan to use or currently are using validation I strongly 3982suggest adding namespaces to your document. A default namespace scheme 3983<code>xmlns="http://...."</code> should not break validity even on less 3984flexible parsers. Using namespaces to mix and differentiate content coming 3985from multiple DTDs will certainly break current validation schemes. To check 3986such documents one needs to use schema-validation, which is supported in 3987libxml2 as well. See <a href="http://www.relaxng.org/">relagx-ng</a> and <a 3988href="http://www.w3c.org/XML/Schema">w3c-schema</a>.</p> 3989 3990<h2><a name="Upgrading">Upgrading 1.x code</a></h2> 3991 3992<p>Incompatible changes:</p> 3993 3994<p>Version 2 of libxml2 is the first version introducing serious backward 3995incompatible changes. The main goals were:</p> 3996<ul> 3997 <li>a general cleanup. A number of mistakes inherited from the very early 3998 versions couldn't be changed due to compatibility constraints. Example 3999 the "childs" element in the nodes.</li> 4000 <li>Uniformization of the various nodes, at least for their header and link 4001 parts (doc, parent, children, prev, next), the goal is a simpler 4002 programming model and simplifying the task of the DOM implementors.</li> 4003 <li>better conformances to the XML specification, for example version 1.x 4004 had an heuristic to try to detect ignorable white spaces. As a result the 4005 SAX event generated were ignorableWhitespace() while the spec requires 4006 character() in that case. This also mean that a number of DOM node 4007 containing blank text may populate the DOM tree which were not present 4008 before.</li> 4009</ul> 4010 4011<h3>How to fix libxml-1.x code:</h3> 4012 4013<p>So client code of libxml designed to run with version 1.x may have to be 4014changed to compile against version 2.x of libxml. Here is a list of changes 4015that I have collected, they may not be sufficient, so in case you find other 4016change which are required, <a href="mailto:Daniel.Veillard@w3.org">drop me a 4017mail</a>:</p> 4018<ol> 4019 <li>The package name have changed from libxml to libxml2, the library name 4020 is now -lxml2 . There is a new xml2-config script which should be used to 4021 select the right parameters libxml2</li> 4022 <li>Node <strong>childs</strong> field has been renamed 4023 <strong>children</strong> so s/childs/children/g should be applied 4024 (probability of having "childs" anywhere else is close to 0+</li> 4025 <li>The document don't have anymore a <strong>root</strong> element it has 4026 been replaced by <strong>children</strong> and usually you will get a 4027 list of element here. For example a Dtd element for the internal subset 4028 and it's declaration may be found in that list, as well as processing 4029 instructions or comments found before or after the document root element. 4030 Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of 4031 a document. Alternatively if you are sure to not reference DTDs nor have 4032 PIs or comments before or after the root element 4033 s/->root/->children/g will probably do it.</li> 4034 <li>The white space issue, this one is more complex, unless special case of 4035 validating parsing, the line breaks and spaces usually used for indenting 4036 and formatting the document content becomes significant. So they are 4037 reported by SAX and if your using the DOM tree, corresponding nodes are 4038 generated. Too approach can be taken: 4039 <ol> 4040 <li>lazy one, use the compatibility call 4041 <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are 4042 relying on a special (and possibly broken) set of heuristics of 4043 libxml to detect ignorable blanks. Don't complain if it breaks or 4044 make your application not 100% clean w.r.t. to it's input.</li> 4045 <li>the Right Way: change you code to accept possibly insignificant 4046 blanks characters, or have your tree populated with weird blank text 4047 nodes. You can spot them using the commodity function 4048 <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank 4049 nodes.</li> 4050 </ol> 4051 <p>Note also that with the new default the output functions don't add any 4052 extra indentation when saving a tree in order to be able to round trip 4053 (read and save) without inflating the document with extra formatting 4054 chars.</p> 4055 </li> 4056 <li>The include path has changed to $prefix/libxml/ and the includes 4057 themselves uses this new prefix in includes instructions... If you are 4058 using (as expected) the 4059 <pre>xml2-config --cflags</pre> 4060 <p>output to generate you compile commands this will probably work out of 4061 the box</p> 4062 </li> 4063 <li>xmlDetectCharEncoding takes an extra argument indicating the length in 4064 byte of the head of the document available for character detection.</li> 4065</ol> 4066 4067<h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3> 4068 4069<p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released 4070to allow smooth upgrade of existing libxml v1code while retaining 4071compatibility. They offers the following:</p> 4072<ol> 4073 <li>similar include naming, one should use 4074 <strong>#include<libxml/...></strong> in both cases.</li> 4075 <li>similar identifiers defined via macros for the child and root fields: 4076 respectively <strong>xmlChildrenNode</strong> and 4077 <strong>xmlRootNode</strong></li> 4078 <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be 4079 inserted once in the client code</li> 4080</ol> 4081 4082<p>So the roadmap to upgrade your existing libxml applications is the 4083following:</p> 4084<ol> 4085 <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> 4086 <li>find all occurrences where the xmlDoc <strong>root</strong> field is 4087 used and change it to <strong>xmlRootNode</strong></li> 4088 <li>similarly find all occurrences where the xmlNode 4089 <strong>childs</strong> field is used and change it to 4090 <strong>xmlChildrenNode</strong></li> 4091 <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your 4092 <strong>main()</strong> or in the library init entry point</li> 4093 <li>Recompile, check compatibility, it should still work</li> 4094 <li>Change your configure script to look first for xml2-config and fall 4095 back using xml-config . Use the --cflags and --libs output of the command 4096 as the Include and Linking parameters needed to use libxml.</li> 4097 <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and 4098 libxml-devel-1.8.y can be kept simultaneously)</li> 4099 <li>remove your config.cache, relaunch your configuration mechanism, and 4100 recompile, if steps 2 and 3 were done right it should compile as-is</li> 4101 <li>Test that your application is still running correctly, if not this may 4102 be due to extra empty nodes due to formating spaces being kept in libxml2 4103 contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your 4104 code before calling the parser (next to 4105 <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li> 4106</ol> 4107 4108<p>Following those steps should work. It worked for some of my own code.</p> 4109 4110<p>Let me put some emphasis on the fact that there is far more changes from 4111libxml 1.x to 2.x than the ones you may have to patch for. The overall code 4112has been considerably cleaned up and the conformance to the XML specification 4113has been drastically improved too. Don't take those changes as an excuse to 4114not upgrade, it may cost a lot on the long term ...</p> 4115 4116<h2><a name="Thread">Thread safety</a></h2> 4117 4118<p>Starting with 2.4.7, libxml2 makes provisions to ensure that concurrent 4119threads can safely work in parallel parsing different documents. There is 4120however a couple of things to do to ensure it:</p> 4121<ul> 4122 <li>configure the library accordingly using the --with-threads options</li> 4123 <li>call xmlInitParser() in the "main" thread before using any of the 4124 libxml2 API (except possibly selecting a different memory allocator)</li> 4125</ul> 4126 4127<p>Note that the thread safety cannot be ensured for multiple threads sharing 4128the same document, the locking must be done at the application level, libxml 4129exports a basic mutex and reentrant mutexes API in <libxml/threads.h>. 4130The parts of the library checked for thread safety are:</p> 4131<ul> 4132 <li>concurrent loading</li> 4133 <li>file access resolution</li> 4134 <li>catalog access</li> 4135 <li>catalog building</li> 4136 <li>entities lookup/accesses</li> 4137 <li>validation</li> 4138 <li>global variables per-thread override</li> 4139 <li>memory handling</li> 4140</ul> 4141 4142<p>XPath is supposed to be thread safe now, but this wasn't tested 4143seriously.</p> 4144 4145<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2> 4146 4147<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document 4148Object Model</em>; this is an API for accessing XML or HTML structured 4149documents. Native support for DOM in Gnome is on the way (module gnome-dom), 4150and will be based on gnome-xml. This will be a far cleaner interface to 4151manipulate XML files within Gnome since it won't expose the internal 4152structure.</p> 4153 4154<p>The current DOM implementation on top of libxml2 is the <a 4155href="http://cvs.gnome.org/lxr/source/gdome2/">gdome2 Gnome module</a>, this 4156is a full DOM interface, thanks to Paolo Casarini, check the <a 4157href="http://www.cs.unibo.it/~casarini/gdome2/">Gdome2 homepage</a> for more 4158informations.</p> 4159 4160<h2><a name="Example"></a><a name="real">A real example</a></h2> 4161 4162<p>Here is a real size example, where the actual content of the application 4163data is not kept in the DOM tree but uses internal structures. It is based on 4164a proposal to keep a database of jobs related to Gnome, with an XML based 4165storage structure. Here is an <a href="gjobs.xml">XML encoded jobs 4166base</a>:</p> 4167<pre><?xml version="1.0"?> 4168<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"> 4169 <gjob:Jobs> 4170 4171 <gjob:Job> 4172 <gjob:Project ID="3"/> 4173 <gjob:Application>GBackup</gjob:Application> 4174 <gjob:Category>Development</gjob:Category> 4175 4176 <gjob:Update> 4177 <gjob:Status>Open</gjob:Status> 4178 <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified> 4179 <gjob:Salary>USD 0.00</gjob:Salary> 4180 </gjob:Update> 4181 4182 <gjob:Developers> 4183 <gjob:Developer> 4184 </gjob:Developer> 4185 </gjob:Developers> 4186 4187 <gjob:Contact> 4188 <gjob:Person>Nathan Clemons</gjob:Person> 4189 <gjob:Email>nathan@windsofstorm.net</gjob:Email> 4190 <gjob:Company> 4191 </gjob:Company> 4192 <gjob:Organisation> 4193 </gjob:Organisation> 4194 <gjob:Webpage> 4195 </gjob:Webpage> 4196 <gjob:Snailmail> 4197 </gjob:Snailmail> 4198 <gjob:Phone> 4199 </gjob:Phone> 4200 </gjob:Contact> 4201 4202 <gjob:Requirements> 4203 The program should be released as free software, under the GPL. 4204 </gjob:Requirements> 4205 4206 <gjob:Skills> 4207 </gjob:Skills> 4208 4209 <gjob:Details> 4210 A GNOME based system that will allow a superuser to configure 4211 compressed and uncompressed files and/or file systems to be backed 4212 up with a supported media in the system. This should be able to 4213 perform via find commands generating a list of files that are passed 4214 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine 4215 or via operations performed on the filesystem itself. Email 4216 notification and GUI status display very important. 4217 </gjob:Details> 4218 4219 </gjob:Job> 4220 4221 </gjob:Jobs> 4222</gjob:Helping></pre> 4223 4224<p>While loading the XML file into an internal DOM tree is a matter of 4225calling only a couple of functions, browsing the tree to gather the data and 4226generate the internal structures is harder, and more error prone.</p> 4227 4228<p>The suggested principle is to be tolerant with respect to the input 4229structure. For example, the ordering of the attributes is not significant, 4230the XML specification is clear about it. It's also usually a good idea not to 4231depend on the order of the children of a given node, unless it really makes 4232things harder. Here is some code to parse the information for a person:</p> 4233<pre>/* 4234 * A person record 4235 */ 4236typedef struct person { 4237 char *name; 4238 char *email; 4239 char *company; 4240 char *organisation; 4241 char *smail; 4242 char *webPage; 4243 char *phone; 4244} person, *personPtr; 4245 4246/* 4247 * And the code needed to parse it 4248 */ 4249personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 4250 personPtr ret = NULL; 4251 4252DEBUG("parsePerson\n"); 4253 /* 4254 * allocate the struct 4255 */ 4256 ret = (personPtr) malloc(sizeof(person)); 4257 if (ret == NULL) { 4258 fprintf(stderr,"out of memory\n"); 4259 return(NULL); 4260 } 4261 memset(ret, 0, sizeof(person)); 4262 4263 /* We don't care what the top level element name is */ 4264 cur = cur->xmlChildrenNode; 4265 while (cur != NULL) { 4266 if ((!strcmp(cur->name, "Person")) && (cur->ns == ns)) 4267 ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4268 if ((!strcmp(cur->name, "Email")) && (cur->ns == ns)) 4269 ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4270 cur = cur->next; 4271 } 4272 4273 return(ret); 4274}</pre> 4275 4276<p>Here are a couple of things to notice:</p> 4277<ul> 4278 <li>Usually a recursive parsing style is the more convenient one: XML data 4279 is by nature subject to repetitive constructs and usually exhibits highly 4280 structured patterns.</li> 4281 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, 4282 i.e. the pointer to the global XML document and the namespace reserved to 4283 the application. Document wide information are needed for example to 4284 decode entities and it's a good coding practice to define a namespace for 4285 your application set of data and test that the element and attributes 4286 you're analyzing actually pertains to your application space. This is 4287 done by a simple equality test (cur->ns == ns).</li> 4288 <li>To retrieve text and attributes value, you can use the function 4289 <em>xmlNodeListGetString</em> to gather all the text and entity reference 4290 nodes generated by the DOM output and produce an single text string.</li> 4291</ul> 4292 4293<p>Here is another piece of code used to parse another level of the 4294structure:</p> 4295<pre>#include <libxml/tree.h> 4296/* 4297 * a Description for a Job 4298 */ 4299typedef struct job { 4300 char *projectID; 4301 char *application; 4302 char *category; 4303 personPtr contact; 4304 int nbDevelopers; 4305 personPtr developers[100]; /* using dynamic alloc is left as an exercise */ 4306} job, *jobPtr; 4307 4308/* 4309 * And the code needed to parse it 4310 */ 4311jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 4312 jobPtr ret = NULL; 4313 4314DEBUG("parseJob\n"); 4315 /* 4316 * allocate the struct 4317 */ 4318 ret = (jobPtr) malloc(sizeof(job)); 4319 if (ret == NULL) { 4320 fprintf(stderr,"out of memory\n"); 4321 return(NULL); 4322 } 4323 memset(ret, 0, sizeof(job)); 4324 4325 /* We don't care what the top level element name is */ 4326 cur = cur->xmlChildrenNode; 4327 while (cur != NULL) { 4328 4329 if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) { 4330 ret->projectID = xmlGetProp(cur, "ID"); 4331 if (ret->projectID == NULL) { 4332 fprintf(stderr, "Project has no ID\n"); 4333 } 4334 } 4335 if ((!strcmp(cur->name, "Application")) && (cur->ns == ns)) 4336 ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4337 if ((!strcmp(cur->name, "Category")) && (cur->ns == ns)) 4338 ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4339 if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns)) 4340 ret->contact = parsePerson(doc, ns, cur); 4341 cur = cur->next; 4342 } 4343 4344 return(ret); 4345}</pre> 4346 4347<p>Once you are used to it, writing this kind of code is quite simple, but 4348boring. Ultimately, it could be possible to write stubbers taking either C 4349data structure definitions, a set of XML examples or an XML DTD and produce 4350the code needed to import and export the content between C data and XML 4351storage. This is left as an exercise to the reader :-)</p> 4352 4353<p>Feel free to use <a href="example/gjobread.c">the code for the full C 4354parsing example</a> as a template, it is also available with Makefile in the 4355Gnome CVS base under gnome-xml/example</p> 4356 4357<h2><a name="Contributi">Contributions</a></h2> 4358<ul> 4359 <li>Bjorn Reese, William Brack and Thomas Broyer have provided a number of 4360 patches, Gary Pennington worked on the validation API, threading support 4361 and Solaris port.</li> 4362 <li>John Fleck helps maintaining the documentation and man pages.</li> 4363 <li><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the 4364 maintainer of the Windows port, <a 4365 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 4366 binaries</a></li> 4367 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 4368 <a href="http://garypennington.net/libxml2/">Solaris binaries</a></li> 4369 <li><a 4370 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 4371 Sergeant</a> developed <a 4372 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 4373 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 4374 application server</a></li> 4375 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> and <a 4376 href="mailto:geertk@ai.rug.nl">Geert Kloosterman</a> provide <a 4377 href="libxml-doc.el">an emacs module</a> to lookup libxml(2) functions 4378 documentation</li> 4379 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a 4380 href="http://xmlsoft.org/messages/0488.html">man pages</a></li> 4381 <li>there is a module for <a 4382 href="http://acs-misc.sourceforge.net/nsxml.html">libxml/libxslt support 4383 in OpenNSD/AOLServer</a></li> 4384 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provided the 4385 first version of libxml/libxslt <a 4386 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li> 4387 <li>Petr Kozelka provides <a 4388 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 4389 libxml2</a> with Kylix and Delphi and other Pascal compilers</li> 4390 <li><a href="mailto:aleksey@aleksey.com">Aleksey Sanin</a> implemented the 4391 <a href="http://www.w3.org/Signature/">XML Canonicalization and XML 4392 Digital Signature</a> <a 4393 href="http://www.aleksey.com/xmlsec/">implementations for libxml2</a></li> 4394 <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a>, <a 4395 href="http://www.zveno.com/">Zveno</a> and contributors maintain <a 4396 href="http://tclxml.sourceforge.net/">tcl bindings for libxml2 and 4397 libxslt</a>, as well as <a 4398 href="http://tclxml.sf.net/tkxmllint.html">tkxmllint</a> a GUI for 4399 xmllint and <a href="http://tclxml.sf.net/tkxsltproc.html">tkxsltproc</a> 4400 a GUI for xsltproc.</li> 4401</ul> 4402 4403<p></p> 4404</body> 4405</html> 4406
