xml.html revision 6d373a26fff17281ac1c872adae95b14727ca959
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 Committee Specification 3 December 2001 <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> except the base64Binary type</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 19 March 2003 (smaller is better):</p> 117 118<p align="center"><img src="benchmark.gif" 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/libxml2/2.5/">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 privoded 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>look for examples of use for libxml2 function using the Gnome code. 390 For example the following will query the full Gnome CVS base for the 391 use of the <strong>xmlAddChild()</strong> function: 392 <p><a 393 href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> 394 <p>This may be slow, a large hardware donation to the gnome project 395 could cure this :-)</p> 396 </li> 397 <li><a 398 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse 399 the libxml2 source</a> , I try to write code as clean and documented 400 as possible, so looking at it may be helpful. In particular the code 401 of xmllint.c and of the various testXXX.c test programs should 402 provide good examples of how to do things with the library.</li> 403 </ul> 404 </li> 405 <li>What about C++ ? 406 <p>libxml2 is written in pure C in order to allow easy reuse on a number 407 of platforms, including embedded systems. I don't intend to convert to 408 C++.</p> 409 <p>There is however a C++ wrapper which may fulfill your needs:</p> 410 <ul> 411 <li>by Ari Johnson <ari@btigate.com>: 412 <p>Website: <a 413 href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a></p> 414 <p>Download: <a 415 href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a></p> 416 </li> 417 <!-- Website is currently unavailable as of 2003-08-02 418 <li>by Peter Jones <pjones@pmade.org> 419 <p>Website: <a 420 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 421 </li> 422 --> 423 </ul> 424 </li> 425 <li>How to validate a document a posteriori ? 426 <p>It is possible to validate documents which had not been validated at 427 initial parsing time or documents which have been built from scratch 428 using the API. Use the <a 429 href="http://xmlsoft.org/html/libxml-valid.html#xmlValidateDtd">xmlValidateDtd()</a> 430 function. It is also possible to simply add a DTD to an existing 431 document:</p> 432 <pre>xmlDocPtr doc; /* your existing document */ 433xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 434 435 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 436 437 doc->intSubset = dtd; 438 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 439 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 440 </pre> 441 </li> 442 <li>So what is this funky "xmlChar" used all the time? 443 <p>It is a null terminated sequence of utf-8 characters. And only utf-8! 444 You need to convert strings encoded in different ways to utf-8 before 445 passing them to the API. This can be accomplished with the iconv library 446 for instance.</p> 447 </li> 448 <li>etc ...</li> 449</ol> 450 451<p></p> 452 453<h2><a name="Documentat">Developer Menu</a></h2> 454 455<p>There are several on-line resources related to using libxml:</p> 456<ol> 457 <li>Use the <a href="search.php">search engine</a> to lookup 458 informations.</li> 459 <li>Check the <a href="FAQ.html">FAQ.</a></li> 460 <li>Check the <a href="http://xmlsoft.org/html/libxml-lib.html">extensive 461 documentation</a> automatically extracted from code comments (using <a 462 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gtk-doc">gtk 463 doc</a>).</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>John Fleck's libxml2 tutorial: <a href="tutorial/index.html">html</a> 469 or <a href="tutorial/xmltutorial.pdf">pdf</a>.</li> 470 <li>If you need to parse large files, check the <a 471 href="xmlreader.html">xmlReader</a> API tutorial</li> 472 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a 473 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice 474 documentation</a> explaining how to use the libxml SAX interface.</li> 475 <li>George Lebl wrote <a 476 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article 477 for IBM developerWorks</a> about using libxml.</li> 478 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO 479 file</a>.</li> 480 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a> 481 description. If you are starting a new project using libxml you should 482 really use the 2.x version.</li> 483 <li>And don't forget to look at the <a 484 href="http://mail.gnome.org/archives/xml/">mailing-list archive</a>.</li> 485</ol> 486 487<h2><a name="Reporting">Reporting bugs and getting help</a></h2> 488 489<p>Well, bugs or missing features are always possible, and I will make a 490point of fixing them in a timely fashion. The best way to report a bug is to 491use the <a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Gnome 492bug tracking database</a> (make sure to use the "libxml2" module name). I 493look at reports there regularly and it's good to have a reminder when a bug 494is still open. Be sure to specify that the bug is for the package libxml2.</p> 495 496<p>For small problems you can try to get help on IRC, the #xml channel on 497irc.gnome.org (port 6667) usually have a few person subscribed which may help 498(but there is no garantee and if a real issue is raised it should go on the 499mailing-list for archival).</p> 500 501<p>There is also a mailing-list <a 502href="mailto:xml@gnome.org">xml@gnome.org</a> for libxml, with an <a 503href="http://mail.gnome.org/archives/xml/">on-line archive</a> (<a 504href="http://xmlsoft.org/messages">old</a>). To subscribe to this list, 505please visit the <a 506href="http://mail.gnome.org/mailman/listinfo/xml">associated Web</a> page and 507follow the instructions. <strong>Do not send code, I won't debug it</strong> 508(but patches are really appreciated!).</p> 509 510<p>Check the following <strong><span style="color: #FF0000">before 511posting</span></strong>:</p> 512<ul> 513 <li>Read the <a href="FAQ.html">FAQ</a> and <a href="search.php">use the 514 search engine</a> to get information related to your problem.</li> 515 <li>Make sure you are <a href="ftp://xmlsoft.org/">using a recent 516 version</a>, and that the problem still shows up in a recent version.</li> 517 <li>Check the <a href="http://mail.gnome.org/archives/xml/">list 518 archives</a> to see if the problem was reported already. In this case 519 there is probably a fix available, similarly check the <a 520 href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">registered 521 open bugs</a>.</li> 522 <li>Make sure you can reproduce the bug with xmllint or one of the test 523 programs found in source in the distribution.</li> 524 <li>Please send the command showing the error as well as the input (as an 525 attachment)</li> 526</ul> 527 528<p>Then send the bug with associated information to reproduce it to the <a 529href="mailto:xml@gnome.org">xml@gnome.org</a> list; if it's really libxml 530related I will approve it. Please do not send mail to me directly, it makes 531things really hard to track and in some cases I am not the best person to 532answer a given question, ask on the list.</p> 533 534<p>To <span style="color: #E50000">be really clear about support</span>:</p> 535<ul> 536 <li>Support or help <span style="color: #E50000">requests MUST be sent to 537 the list or on bugzilla</span> in case of problems, so that the Question 538 and Answers can be shared publicly. Failing to do so carries the implicit 539 message "I want free support but I don't want to share the benefits with 540 others" and is not welcome. I will automatically Carbon-Copy the 541 xml@gnome.org mailing list for any technical reply made about libxml2 or 542 libxslt.</li> 543 <li>There is <span style="color: #E50000">no garantee of support</span>, if 544 your question remains unanswered after a week, repost it, making sure you 545 gave all the detail needed and the information requested.</li> 546 <li>Failing to provide information as requested or double checking first 547 for prior feedback also carries the implicit message "the time of the 548 library maintainers is less valuable than my time" and might not be 549 welcome.</li> 550</ul> 551 552<p>Of course, bugs reported with a suggested patch for fixing them will 553probably be processed faster than those without.</p> 554 555<p>If you're looking for help, a quick look at <a 556href="http://mail.gnome.org/archives/xml/">the list archive</a> may actually 557provide the answer. I usually send source samples when answering libxml2 558usage questions. The <a 559href="http://xmlsoft.org/html/book1.html">auto-generated documentation</a> is 560not as polished as I would like (i need to learn more about DocBook), but 561it's a good starting point.</p> 562 563<h2><a name="help">How to help</a></h2> 564 565<p>You can help the project in various ways, the best thing to do first is to 566subscribe to the mailing-list as explained before, check the <a 567href="http://mail.gnome.org/archives/xml/">archives </a>and the <a 568href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Gnome bug 569database</a>:</p> 570<ol> 571 <li>Provide patches when you find problems.</li> 572 <li>Provide the diffs when you port libxml2 to a new platform. They may not 573 be integrated in all cases but help pinpointing portability problems 574 and</li> 575 <li>Provide documentation fixes (either as patches to the code comments or 576 as HTML diffs).</li> 577 <li>Provide new documentations pieces (translations, examples, etc 578 ...).</li> 579 <li>Check the TODO file and try to close one of the items.</li> 580 <li>Take one of the points raised in the archive or the bug database and 581 provide a fix. <a href="mailto:daniel@veillard.com">Get in touch with me 582 </a>before to avoid synchronization problems and check that the suggested 583 fix will fit in nicely :-)</li> 584</ol> 585 586<h2><a name="Downloads">Downloads</a></h2> 587 588<p>The latest versions of libxml2 can be found on <a 589href="ftp://xmlsoft.org/">xmlsoft.org</a> (<a 590href="ftp://speakeasy.rpmfind.net/pub/libxml/">Seattle</a>, <a 591href="ftp://fr.rpmfind.net/pub/libxml/">France</a>) or on the <a 592href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either 593as a <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">source 594archive</a><!-- commenting this out because they seem to have disappeared or <a 595href="ftp://ftp.gnome.org/pub/GNOME/stable/redhat/i386/libxml/">RPM 596packages</a> --> 597 , Antonin Sprinzl also provide <a href="ftp://gd.tuwien.ac.at/pub/libxml/">a 598mirror in Austria</a>. (NOTE that you need both the <a 599href="http://rpmfind.net/linux/RPM/libxml2.html">libxml(2)</a> and <a 600href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml(2)-devel</a> 601packages installed to compile applications using libxml.)</p> 602 603<p>Binary ports:</p> 604<ul> 605 <li>Red Hat RPMs for i386 are available directly on <a 606 href="ftp://xmlsoft.org/">xmlsoft.org</a>, the source RPM will compile on 607 any architecture supported by Red Hat.</li> 608 <li><p><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a></p> 609 is now the maintainer of the Windows port, <a 610 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 611 binaries</a>.</li> 612 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 613 <a href="http://garypennington.net/libxml2/">Solaris binaries</a>.</li> 614 <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a> provides <a 615 href="http://www.zveno.com/open_source/libxml2xslt.html">Mac Os X 616 binaries</a>.</li> 617 <li>The HP-UX porting center provides <a 618 href="http://hpux.connect.org.uk/hppd/hpux/Gnome/">HP-UX binaries</a></li> 619</ul> 620 621<p>If you know other supported binary ports, please <a 622href="http://veillard.com/">contact me</a>.</p> 623 624<p><a name="Snapshot">Snapshot:</a></p> 625<ul> 626 <li>Code from the W3C cvs base gnome-xml <a 627 href="ftp://xmlsoft.org/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a>.</li> 628 <li>Docs, content of the web site, the list archive included <a 629 href="ftp://xmlsoft.org/libxml-docs.tar.gz">libxml-docs.tar.gz</a>.</li> 630</ul> 631 632<p><a name="Contribs">Contributions:</a></p> 633 634<p>I do accept external contributions, especially if compiling on another 635platform, get in touch with me to upload the package, wrappers for various 636languages have been provided, and can be found in the <a 637href="contribs.html">contrib section</a></p> 638 639<p>Libxml2 is also available from CVS:</p> 640<ul> 641 <li><p>The <a 642 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Gnome 643 CVS base</a>. Check the <a 644 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> 645 page; the CVS module is <b>gnome-xml</b>.</p> 646 </li> 647 <li>The <strong>libxslt</strong> module is also present there</li> 648</ul> 649 650<h2><a name="News">News</a></h2> 651 652<h3>CVS only : check the <a 653href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file 654for a really accurate description</h3> 655 656<p>Items not finished and worked on, get in touch with the list if you want 657to test those</p> 658<ul> 659 <li>More testing on RelaxNG</li> 660 <li>Finishing up <a href="http://www.w3.org/TR/xmlschema-1/">XML 661 Schemas</a></li> 662</ul> 663 664<h3>2.6.2: Nov 4 2003</h3> 665<ul> 666 <li>XPath context unregistration fixes</li> 667 <li>text node coalescing fixes (Mark Lilback)</li> 668 <li>API to screate a W3C Schemas from an existing document (Steve Ball)</li> 669 <li>BeOS patches (Marcin 'Shard' Konicki)</li> 670 <li>xmlStrVPrintf function added (Aleksey Sanin)</li> 671 <li>compilation fixes (Mark Vakoc)</li> 672 <li>stdin parsing fix (William Brack)</li> 673 <li>a posteriori DTD validation fixes</li> 674 <li>xmlReader bug fixes: Walker fixes, python bindings </li> 675 <li>fixed xmlStopParser() to really stop the parser and errors</li> 676 <li>always generate line numbers when using the new xmlReadxxx 677 functions</li> 678 <li>added XInclude support to the xmlReader interface</li> 679 <li>implemented XML_PARSE_NONET parser option</li> 680 <li>DocBook XSLT processing bug fixed</li> 681 <li>HTML serialization for <p> elements (William Brack and me)</li> 682 <li>XPointer failure in XInclude are now handled as resource errors</li> 683 <li>fixed xmllint --html to use the HTML serializer on output (added 684 --xmlout to implement the previous behaviour of saving it using the XML 685 serializer)</li> 686</ul> 687 688<h3>2.6.1: Oct 28 2003</h3> 689<ul> 690 <li>Mostly bugfixes after the big 2.6.0 changes</li> 691 <li>Unix compilation patches: libxml.m4 (Patrick Welche), warnings cleanup 692 (William Brack)</li> 693 <li>Windows compilation patches (Joachim Bauch, Stephane Bidoul, Igor 694 Zlatkovic)</li> 695 <li>xmlWriter bugfix (Alfred Mickautsch)</li> 696 <li>chvalid.[ch]: couple of fixes from Stephane Bidoul</li> 697 <li>context reset: error state reset, push parser reset (Graham 698 Bennett)</li> 699 <li>context reuse: generate errors if file is not readable</li> 700 <li>defaulted attributes for element coming from internal entities 701 (Stephane Bidoul)</li> 702 <li>Python: tab and spaces mix (William Brack)</li> 703 <li>Error handler could crash in DTD validation in 2.6.0</li> 704 <li>xmlReader: do not use the document or element _private field</li> 705 <li>testSAX.c: avoid a problem with some PIs (Massimo Morara)</li> 706 <li>general bug fixes: mandatory encoding in text decl, serializing 707 Document Fragment nodes, xmlSearchNs 2.6.0 problem (Kasimier Buchcik), 708 XPath errors not reported, slow HTML parsing of large documents.</li> 709</ul> 710 711<h3>2.6.0: Oct 20 2003</h3> 712<ul> 713 <li>Major revision release: should be API and ABI compatible but got a lot 714 of change</li> 715 <li>Increased the library modularity, far more options can be stripped out, 716 a --with-minimum configuration will weight around 160KBytes</li> 717 <li>Use per parser and per document dictionnary, allocate names and small 718 text nodes from the dictionnary</li> 719 <li>Switch to a SAX2 like parser rewrote most of the XML parser core, 720 provides namespace resolution and defaulted attributes, minimize memory 721 allocations and copies, namespace checking and specific error handling, 722 immutable buffers, make predefined entities static structures, etc...</li> 723 <li>rewrote all the error handling in the library, all errors can be 724 intercepted at a structured level, with precise information 725 available.</li> 726 <li>New simpler and more generic XML and HTML parser APIs, allowing to 727 easilly modify the parsing options and reuse parser context for multiple 728 consecutive documents.</li> 729 <li>Similar new APIs for the xmlReader, for options and reuse, provided new 730 functions to access content as const strings, use them for Python 731 bindings</li> 732 <li>a lot of other smaller API improvements: xmlStrPrintf (Aleksey Sanin), 733 Walker i.e. reader on a document tree based on Alfred Mickautsch code, 734 make room in nodes for line numbers, reference counting and future PSVI 735 extensions, generation of character ranges to be checked with faster 736 algorithm (William), xmlParserMaxDepth (Crutcher Dunnavant), buffer 737 access</li> 738 <li>New xmlWriter API provided by Alfred Mickautsch</li> 739 <li>Schemas: base64 support by Anthony Carrico</li> 740 <li>Parser<->HTTP integration fix, proper processing of the Mime-Type 741 and charset informations if available.</li> 742 <li>Relax-NG: bug fixes including the one reported by Martijn Faassen and 743 zeroOrMore, better error reporting.</li> 744 <li>Python bindings (St�phane Bidoul), never use stdout for errors 745 output</li> 746 <li>Portability: all the headers have macros for export and calling 747 convention definitions (Igor Zlatkovic), VMS update (Craig A. Berry), 748 Windows: threads (Jesse Pelton), Borland compiler (Eric Zurcher, Igor), 749 Mingw (Igor), typos (Mark Vakoc), beta version (Stephane Bidoul), 750 warning cleanups on AIX and MIPS compilers (William Brack), BeOS (Marcin 751 'Shard' Konicki)</li> 752 <li>Documentation fixes and README (William Brack), search fix (William), 753 tutorial updates (John Fleck), namespace docs (Stefan Kost)</li> 754 <li>Bug fixes: xmlCleanupParser (Dave Beckett), threading uninitialized 755 mutexes, HTML doctype lowercase, SAX/IO (William), compression detection 756 and restore (William), attribute declaration in DTDs (William), namespace 757 on attribute in HTML output (William), input filename (Rob Richards), 758 namespace DTD validation, xmlReplaceNode (Chris Ryland), I/O callbacks 759 (Markus Keim), CDATA serialization (Shaun McCance), xmlReader (Peter 760 Derr), high codepoint charref like &#x10FFFF;, buffer access in push 761 mode (Justin Fletcher), TLS threads on Windows (Jesse Pelton), XPath bug 762 (William), xmlCleanupParser (Marc Liyanage), CDATA output (William), HTTP 763 error handling.</li> 764 <li>xmllint options: --dtdvalidfpi for Tobias Reif, --sax1 for compat 765 testing, --nodict for building without tree dictionnary, --nocdata to 766 replace CDATA by text, --nsclean to remove surperfluous namespace 767 declarations</li> 768 <li>added xml2-config --libtool-libs option from Kevin P. Fleming</li> 769 <li>a lot of profiling and tuning of the code, speedup patch for 770 xmlSearchNs() by Luca Padovani. The xmlReader should do far less 771 allocation and it speed should get closer to SAX. Chris Anderson worked 772 on speeding and cleaning up repetitive checking code.</li> 773 <li>cleanup of "make tests"</li> 774 <li>libxml-2.0-uninstalled.pc from Malcolm Tredinnick</li> 775 <li>deactivated the broken docBook SGML parser code and plugged the XML 776 parser instead.</li> 777</ul> 778 779<h3>2.5.11: Sep 9 2003</h3> 780 781<p>A bugfix only release:</p> 782<ul> 783 <li>risk of crash in Relax-NG</li> 784 <li>risk of crash when using multithreaded programs</li> 785</ul> 786 787<h3>2.5.10: Aug 15 2003</h3> 788 789<p>A bugfixes only release</p> 790<ul> 791 <li>Windows Makefiles (William Brack)</li> 792 <li>UTF-16 support fixes (Mark Itzcovitz)</li> 793 <li>Makefile and portability (William Brack) automake, Linux alpha, Mingw 794 on Windows (Mikhail Grushinskiy)</li> 795 <li>HTML parser (Oliver Stoeneberg)</li> 796 <li>XInclude performance problem reported by Kevin Ruscoe</li> 797 <li>XML parser performance problem reported by Grant Goodale</li> 798 <li>xmlSAXParseDTD() bug fix from Malcolm Tredinnick</li> 799 <li>and a couple other cleanup</li> 800</ul> 801 802<h3>2.5.9: Aug 9 2003</h3> 803<ul> 804 <li>bugfixes: IPv6 portability, xmlHasNsProp (Markus Keim), Windows build 805 (Wiliam Brake, Jesse Pelton, Igor), Schemas (Peter Sobisch), threading 806 (Rob Richards), hexBinary type (), UTF-16 BOM (Dodji Seketeli), 807 xmlReader, Relax-NG schemas compilation, namespace handling, EXSLT (Sean 808 Griffin), HTML parsing problem (William Brack), DTD validation for mixed 809 content + namespaces, HTML serialization, library initialization, 810 progressive HTML parser</li> 811 <li>better interfaces for Relax-NG error handling (Joachim Bauch, )</li> 812 <li>adding xmlXIncludeProcessTree() for XInclud'ing in a subtree</li> 813 <li>doc fixes and improvements (John Fleck)</li> 814 <li>configure flag for -with-fexceptions when embedding in C++</li> 815 <li>couple of new UTF-8 helper functions (William Brack)</li> 816 <li>general encoding cleanup + ISO-8859-x without iconv (Peter Jacobi)</li> 817 <li>xmlTextReader cleanup + enum for node types (Bjorn Reese)</li> 818 <li>general compilation/warning cleanup Solaris/HP-UX/... (William 819 Brack)</li> 820</ul> 821 822<h3>2.5.8: Jul 6 2003</h3> 823<ul> 824 <li>bugfixes: XPath, XInclude, file/URI mapping, UTF-16 save (Mark 825 Itzcovitz), UTF-8 checking, URI saving, error printing (William Brack), 826 PI related memleak, compilation without schemas or without xpath (Joerg 827 Schmitz-Linneweber/Garry Pennington), xmlUnlinkNode problem with DTDs, 828 rpm problem on , i86_64, removed a few compilation problems from 2.5.7, 829 xmlIOParseDTD, and xmlSAXParseDTD (Malcolm Tredinnick)</li> 830 <li>portability: DJGPP (MsDos) , OpenVMS (Craig A. Berry)</li> 831 <li>William Brack fixed multithreading lock problems</li> 832 <li>IPv6 patch for FTP and HTTP accesses (Archana Shah/Wipro)</li> 833 <li>Windows fixes (Igor Zlatkovic, Eric Zurcher), threading (St�phane 834 Bidoul)</li> 835 <li>A few W3C Schemas Structure improvements</li> 836 <li>W3C Schemas Datatype improvements (Charlie Bozeman)</li> 837 <li>Python bindings for thread globals (St�phane Bidoul), and method/class 838 generator</li> 839 <li>added --nonet option to xmllint</li> 840 <li>documentation improvements (John Fleck)</li> 841</ul> 842 843<h3>2.5.7: Apr 25 2003</h3> 844<ul> 845 <li>Relax-NG: Compiling to regexp and streaming validation on top of the 846 xmlReader interface, added to xmllint --stream</li> 847 <li>xmlReader: Expand(), Next() and DOM access glue, bug fixes</li> 848 <li>Support for large files: RGN validated a 4.5GB instance</li> 849 <li>Thread support is now configured in by default</li> 850 <li>Fixes: update of the Trio code (Bjorn), WXS Date and Duration fixes 851 (Charles Bozeman), DTD and namespaces (Brent Hendricks), HTML push parser 852 and zero bytes handling, some missing Windows file path conversions, 853 behaviour of the parser and validator in the presence of "out of memory" 854 error conditions</li> 855 <li>extended the API to be able to plug a garbage collecting memory 856 allocator, added xmlMallocAtomic() and modified the allocations 857 accordingly.</li> 858 <li>Performances: removed excessive malloc() calls, speedup of the push and 859 xmlReader interfaces, removed excessive thread locking</li> 860 <li>Documentation: man page (John Fleck), xmlReader documentation</li> 861 <li>Python: adding binding for xmlCatalogAddLocal (Brent M Hendricks)</li> 862</ul> 863 864<h3>2.5.6: Apr 1 2003</h3> 865<ul> 866 <li>Fixed W3C XML Schemas datatype, should be compliant now except for 867 binHex and base64 which are not supported yet.</li> 868 <li>bug fixes: non-ASCII IDs, HTML output, XInclude on large docs and 869 XInclude entities handling, encoding detection on external subsets, XML 870 Schemas bugs and memory leaks, HTML parser (James Bursa)</li> 871 <li>portability: python/trio (Albert Chin), Sun compiler warnings</li> 872 <li>documentation: added --relaxng option to xmllint man page (John)</li> 873 <li>improved error reporting: xml:space, start/end tag mismatches, Relax NG 874 errors</li> 875</ul> 876 877<h3>2.5.5: Mar 24 2003</h3> 878<ul> 879 <li>Lot of fixes on the Relax NG implementation. More testing including 880 DocBook and TEI examples.</li> 881 <li>Increased the support for W3C XML Schemas datatype</li> 882 <li>Several bug fixes in the URI handling layer</li> 883 <li>Bug fixes: HTML parser, xmlReader, DTD validation, XPath, encoding 884 conversion, line counting in the parser.</li> 885 <li>Added support for $XMLLINT_INDENT environment variable, FTP delete</li> 886 <li>Fixed the RPM spec file name</li> 887</ul> 888 889<h3>2.5.4: Feb 20 2003</h3> 890<ul> 891 <li>Conformance testing and lot of fixes on Relax NG and XInclude 892 implementation</li> 893 <li>Implementation of XPointer element() scheme</li> 894 <li>Bug fixes: XML parser, XInclude entities merge, validity checking on 895 namespaces, 896 <p>2 serialization bugs, node info generation problems, a DTD regexp 897 generation problem.</p> 898 </li> 899 <li>Portability: windows updates and path canonicalization (Igor)</li> 900 <li>A few typo fixes (Kjartan Maraas)</li> 901 <li>Python bindings generator fixes (Stephane Bidoul)</li> 902</ul> 903 904<h3>2.5.3: Feb 10 2003</h3> 905<ul> 906 <li>RelaxNG and XML Schemas datatypes improvements, and added a first 907 version of RelaxNG Python bindings</li> 908 <li>Fixes: XLink (Sean Chittenden), XInclude (Sean Chittenden), API fix for 909 serializing namespace nodes, encoding conversion bug, XHTML1 910 serialization</li> 911 <li>Portability fixes: Windows (Igor), AMD 64bits RPM spec file</li> 912</ul> 913 914<h3>2.5.2: Feb 5 2003</h3> 915<ul> 916 <li>First implementation of RelaxNG, added --relaxng flag to xmllint</li> 917 <li>Schemas support now compiled in by default.</li> 918 <li>Bug fixes: DTD validation, namespace checking, XInclude and entities, 919 delegateURI in XML Catalogs, HTML parser, XML reader (St�phane Bidoul), 920 XPath parser and evaluation, UTF8ToUTF8 serialization, XML reader memory 921 consumption, HTML parser, HTML serialization in the presence of 922 namespaces</li> 923 <li>added an HTML API to check elements and attributes.</li> 924 <li>Documentation improvement, PDF for the tutorial (John Fleck), doc 925 patches (Stefan Kost)</li> 926 <li>Portability fixes: NetBSD (Julio Merino), Windows (Igor Zlatkovic)</li> 927 <li>Added python bindings for XPointer, contextual error reporting 928 (St�phane Bidoul)</li> 929 <li>URI/file escaping problems (Stefano Zacchiroli)</li> 930</ul> 931 932<h3>2.5.1: Jan 8 2003</h3> 933<ul> 934 <li>Fixes a memory leak and configuration/compilation problems in 2.5.0</li> 935 <li>documentation updates (John)</li> 936 <li>a couple of XmlTextReader fixes</li> 937</ul> 938 939<h3>2.5.0: Jan 6 2003</h3> 940<ul> 941 <li>New <a href="xmlreader.html">XmltextReader interface</a> based on C# 942 API (with help of St�phane Bidoul)</li> 943 <li>Windows: more exports, including the new API (Igor)</li> 944 <li>XInclude fallback fix</li> 945 <li>Python: bindings for the new API, packaging (St�phane Bidoul), 946 drv_libxml2.py Python xml.sax driver (St�phane Bidoul), fixes, speedup 947 and iterators for Python-2.2 (Hannu Krosing)</li> 948 <li>Tutorial fixes (john Fleck and Niraj Tolia) xmllint man update 949 (John)</li> 950 <li>Fix an XML parser bug raised by Vyacheslav Pindyura</li> 951 <li>Fix for VMS serialization (Nigel Hall) and config (Craig A. Berry)</li> 952 <li>Entities handling fixes</li> 953 <li>new API to optionally track node creation and deletion (Lukas 954 Schroeder)</li> 955 <li>Added documentation for the XmltextReader interface and some <a 956 href="guidelines.html">XML guidelines</a></li> 957</ul> 958 959<h3>2.4.30: Dec 12 2002</h3> 960<ul> 961 <li>2.4.29 broke the python bindings, rereleasing</li> 962 <li>Improvement/fixes of the XML API generator, and couple of minor code 963 fixes.</li> 964</ul> 965 966<h3>2.4.29: Dec 11 2002</h3> 967<ul> 968 <li>Windows fixes (Igor): Windows CE port, pthread linking, python bindings 969 (St�phane Bidoul), Mingw (Magnus Henoch), and export list updates</li> 970 <li>Fix for prev in python bindings (ERDI Gergo)</li> 971 <li>Fix for entities handling (Marcus Clarke)</li> 972 <li>Refactored the XML and HTML dumps to a single code path, fixed XHTML1 973 dump</li> 974 <li>Fix for URI parsing when handling URNs with fragment identifiers</li> 975 <li>Fix for HTTP URL escaping problem</li> 976 <li>added an TextXmlReader (C#) like API (work in progress)</li> 977 <li>Rewrote the API in XML generation script, includes a C parser and saves 978 more informations needed for C# bindings</li> 979</ul> 980 981<h3>2.4.28: Nov 22 2002</h3> 982<ul> 983 <li>a couple of python binding fixes</li> 984 <li>2 bug fixes in the XML push parser</li> 985 <li>potential memory leak removed (Martin Stoilov)</li> 986 <li>fix to the configure script for Unix (Dimitri Papadopoulos)</li> 987 <li>added encoding support for XInclude parse="text"</li> 988 <li>autodetection of XHTML1 and specific serialization rules added</li> 989 <li>nasty threading bug fixed (William Brack)</li> 990</ul> 991 992<h3>2.4.27: Nov 17 2002</h3> 993<ul> 994 <li>fixes for the Python bindings</li> 995 <li>a number of bug fixes: SGML catalogs, xmlParseBalancedChunkMemory(), 996 HTML parser, Schemas (Charles Bozeman), document fragment support 997 (Christian Glahn), xmlReconciliateNs (Brian Stafford), XPointer, 998 xmlFreeNode(), xmlSAXParseMemory (Peter Jones), xmlGetNodePath (Petr 999 Pajas), entities processing</li> 1000 <li>added grep to xmllint --shell</li> 1001 <li>VMS update patch from Craig A. Berry</li> 1002 <li>cleanup of the Windows build with support for more compilers (Igor), 1003 better thread support on Windows</li> 1004 <li>cleanup of Unix Makefiles and spec file</li> 1005 <li>Improvements to the documentation (John Fleck)</li> 1006</ul> 1007 1008<h3>2.4.26: Oct 18 2002</h3> 1009<ul> 1010 <li>Patches for Windows CE port, improvements on Windows paths handling</li> 1011 <li>Fixes to the validation code (DTD and Schemas), xmlNodeGetPath() , 1012 HTML serialization, Namespace compliance, and a number of small 1013 problems</li> 1014</ul> 1015 1016<h3>2.4.25: Sep 26 2002</h3> 1017<ul> 1018 <li>A number of bug fixes: XPath, validation, Python bindings, DOM and 1019 tree, xmlI/O, Html</li> 1020 <li>Serious rewrite of XInclude</li> 1021 <li>Made XML Schemas regexp part of the default build and APIs, small fix 1022 and improvement of the regexp core</li> 1023 <li>Changed the validation code to reuse XML Schemas regexp APIs</li> 1024 <li>Better handling of Windows file paths, improvement of Makefiles (Igor, 1025 Daniel Gehriger, Mark Vakoc)</li> 1026 <li>Improved the python I/O bindings, the tests, added resolver and regexp 1027 APIs</li> 1028 <li>New logos from Marc Liyanage</li> 1029 <li>Tutorial improvements: John Fleck, Christopher Harris</li> 1030 <li>Makefile: Fixes for AMD x86_64 (Mandrake), DESTDIR (Christophe 1031 Merlet)</li> 1032 <li>removal of all stderr/perror use for error reporting</li> 1033 <li>Better error reporting: XPath and DTD validation</li> 1034 <li>update of the trio portability layer (Bjorn Reese)</li> 1035</ul> 1036 1037<p><strong>2.4.24: Aug 22 2002</strong></p> 1038<ul> 1039 <li>XPath fixes (William), xf:escape-uri() (Wesley Terpstra)</li> 1040 <li>Python binding fixes: makefiles (William), generator, rpm build, x86-64 1041 (fcrozat)</li> 1042 <li>HTML <style> and boolean attributes serializer fixes</li> 1043 <li>C14N improvements by Aleksey</li> 1044 <li>doc cleanups: Rick Jones</li> 1045 <li>Windows compiler makefile updates: Igor and Elizabeth Barham</li> 1046 <li>XInclude: implementation of fallback and xml:base fixup added</li> 1047</ul> 1048 1049<h3>2.4.23: July 6 2002</h3> 1050<ul> 1051 <li>performances patches: Peter Jacobi</li> 1052 <li>c14n fixes, testsuite and performances: Aleksey Sanin</li> 1053 <li>added xmlDocFormatDump: Chema Celorio</li> 1054 <li>new tutorial: John Fleck</li> 1055 <li>new hash functions and performances: Sander Vesik, portability fix from 1056 Peter Jacobi</li> 1057 <li>a number of bug fixes: XPath (William Brack, Richard Jinks), XML and 1058 HTML parsers, ID lookup function</li> 1059 <li>removal of all remaining sprintf: Aleksey Sanin</li> 1060</ul> 1061 1062<h3>2.4.22: May 27 2002</h3> 1063<ul> 1064 <li>a number of bug fixes: configure scripts, base handling, parser, memory 1065 usage, HTML parser, XPath, documentation (Christian Cornelssen), 1066 indentation, URI parsing</li> 1067 <li>Optimizations for XMLSec, fixing and making public some of the network 1068 protocol handlers (Aleksey)</li> 1069 <li>performance patch from Gary Pennington</li> 1070 <li>Charles Bozeman provided date and time support for XML Schemas 1071 datatypes</li> 1072</ul> 1073 1074<h3>2.4.21: Apr 29 2002</h3> 1075 1076<p>This release is both a bug fix release and also contains the early XML 1077Schemas <a href="http://www.w3.org/TR/xmlschema-1/">structures</a> and <a 1078href="http://www.w3.org/TR/xmlschema-2/">datatypes</a> code, beware, all 1079interfaces are likely to change, there is huge holes, it is clearly a work in 1080progress and don't even think of putting this code in a production system, 1081it's actually not compiled in by default. The real fixes are:</p> 1082<ul> 1083 <li>a couple of bugs or limitations introduced in 2.4.20</li> 1084 <li>patches for Borland C++ and MSC by Igor</li> 1085 <li>some fixes on XPath strings and conformance patches by Richard 1086 Jinks</li> 1087 <li>patch from Aleksey for the ExcC14N specification</li> 1088 <li>OSF/1 bug fix by Bjorn</li> 1089</ul> 1090 1091<h3>2.4.20: Apr 15 2002</h3> 1092<ul> 1093 <li>bug fixes: file descriptor leak, XPath, HTML output, DTD validation</li> 1094 <li>XPath conformance testing by Richard Jinks</li> 1095 <li>Portability fixes: Solaris, MPE/iX, Windows, OSF/1, python bindings, 1096 libxml.m4</li> 1097</ul> 1098 1099<h3>2.4.19: Mar 25 2002</h3> 1100<ul> 1101 <li>bug fixes: half a dozen XPath bugs, Validation, ISO-Latin to UTF8 1102 encoder</li> 1103 <li>portability fixes in the HTTP code</li> 1104 <li>memory allocation checks using valgrind, and profiling tests</li> 1105 <li>revamp of the Windows build and Makefiles</li> 1106</ul> 1107 1108<h3>2.4.18: Mar 18 2002</h3> 1109<ul> 1110 <li>bug fixes: tree, SAX, canonicalization, validation, portability, 1111 XPath</li> 1112 <li>removed the --with-buffer option it was becoming unmaintainable</li> 1113 <li>serious cleanup of the Python makefiles</li> 1114 <li>speedup patch to XPath very effective for DocBook stylesheets</li> 1115 <li>Fixes for Windows build, cleanup of the documentation</li> 1116</ul> 1117 1118<h3>2.4.17: Mar 8 2002</h3> 1119<ul> 1120 <li>a lot of bug fixes, including "namespace nodes have no parents in 1121 XPath"</li> 1122 <li>fixed/improved the Python wrappers, added more examples and more 1123 regression tests, XPath extension functions can now return node-sets</li> 1124 <li>added the XML Canonicalization support from Aleksey Sanin</li> 1125</ul> 1126 1127<h3>2.4.16: Feb 20 2002</h3> 1128<ul> 1129 <li>a lot of bug fixes, most of them were triggered by the XML Testsuite 1130 from OASIS and W3C. Compliance has been significantly improved.</li> 1131 <li>a couple of portability fixes too.</li> 1132</ul> 1133 1134<h3>2.4.15: Feb 11 2002</h3> 1135<ul> 1136 <li>Fixed the Makefiles, especially the python module ones</li> 1137 <li>A few bug fixes and cleanup</li> 1138 <li>Includes cleanup</li> 1139</ul> 1140 1141<h3>2.4.14: Feb 8 2002</h3> 1142<ul> 1143 <li>Change of License to the <a 1144 href="http://www.opensource.org/licenses/mit-license.html">MIT 1145 License</a> basically for integration in XFree86 codebase, and removing 1146 confusion around the previous dual-licensing</li> 1147 <li>added Python bindings, beta software but should already be quite 1148 complete</li> 1149 <li>a large number of fixes and cleanups, especially for all tree 1150 manipulations</li> 1151 <li>cleanup of the headers, generation of a reference API definition in 1152 XML</li> 1153</ul> 1154 1155<h3>2.4.13: Jan 14 2002</h3> 1156<ul> 1157 <li>update of the documentation: John Fleck and Charlie Bozeman</li> 1158 <li>cleanup of timing code from Justin Fletcher</li> 1159 <li>fixes for Windows and initial thread support on Win32: Igor and Serguei 1160 Narojnyi</li> 1161 <li>Cygwin patch from Robert Collins</li> 1162 <li>added xmlSetEntityReferenceFunc() for Keith Isdale work on xsldbg</li> 1163</ul> 1164 1165<h3>2.4.12: Dec 7 2001</h3> 1166<ul> 1167 <li>a few bug fixes: thread (Gary Pennington), xmllint (Geert Kloosterman), 1168 XML parser (Robin Berjon), XPointer (Danny Jamshy), I/O cleanups 1169 (robert)</li> 1170 <li>Eric Lavigne contributed project files for MacOS</li> 1171 <li>some makefiles cleanups</li> 1172</ul> 1173 1174<h3>2.4.11: Nov 26 2001</h3> 1175<ul> 1176 <li>fixed a couple of errors in the includes, fixed a few bugs, some code 1177 cleanups</li> 1178 <li>xmllint man pages improvement by Heiko Rupp</li> 1179 <li>updated VMS build instructions from John A Fotheringham</li> 1180 <li>Windows Makefiles updates from Igor</li> 1181</ul> 1182 1183<h3>2.4.10: Nov 10 2001</h3> 1184<ul> 1185 <li>URI escaping fix (Joel Young)</li> 1186 <li>added xmlGetNodePath() (for paths or XPointers generation)</li> 1187 <li>Fixes namespace handling problems when using DTD and validation</li> 1188 <li>improvements on xmllint: Morus Walter patches for --format and 1189 --encode, Stefan Kost and Heiko Rupp improvements on the --shell</li> 1190 <li>fixes for xmlcatalog linking pointed by Weiqi Gao</li> 1191 <li>fixes to the HTML parser</li> 1192</ul> 1193 1194<h3>2.4.9: Nov 6 2001</h3> 1195<ul> 1196 <li>fixes more catalog bugs</li> 1197 <li>avoid a compilation problem, improve xmlGetLineNo()</li> 1198</ul> 1199 1200<h3>2.4.8: Nov 4 2001</h3> 1201<ul> 1202 <li>fixed SGML catalogs broken in previous release, updated xmlcatalog 1203 tool</li> 1204 <li>fixed a compile errors and some includes troubles.</li> 1205</ul> 1206 1207<h3>2.4.7: Oct 30 2001</h3> 1208<ul> 1209 <li>exported some debugging interfaces</li> 1210 <li>serious rewrite of the catalog code</li> 1211 <li>integrated Gary Pennington thread safety patch, added configure option 1212 and regression tests</li> 1213 <li>removed an HTML parser bug</li> 1214 <li>fixed a couple of potentially serious validation bugs</li> 1215 <li>integrated the SGML DocBook support in xmllint</li> 1216 <li>changed the nanoftp anonymous login passwd</li> 1217 <li>some I/O cleanup and a couple of interfaces for Perl wrapper</li> 1218 <li>general bug fixes</li> 1219 <li>updated xmllint man page by John Fleck</li> 1220 <li>some VMS and Windows updates</li> 1221</ul> 1222 1223<h3>2.4.6: Oct 10 2001</h3> 1224<ul> 1225 <li>added an updated man pages by John Fleck</li> 1226 <li>portability and configure fixes</li> 1227 <li>an infinite loop on the HTML parser was removed (William)</li> 1228 <li>Windows makefile patches from Igor</li> 1229 <li>fixed half a dozen bugs reported for libxml or libxslt</li> 1230 <li>updated xmlcatalog to be able to modify SGML super catalogs</li> 1231</ul> 1232 1233<h3>2.4.5: Sep 14 2001</h3> 1234<ul> 1235 <li>Remove a few annoying bugs in 2.4.4</li> 1236 <li>forces the HTML serializer to output decimal charrefs since some 1237 version of Netscape can't handle hexadecimal ones</li> 1238</ul> 1239 1240<h3>1.8.16: Sep 14 2001</h3> 1241<ul> 1242 <li>maintenance release of the old libxml1 branch, couple of bug and 1243 portability fixes</li> 1244</ul> 1245 1246<h3>2.4.4: Sep 12 2001</h3> 1247<ul> 1248 <li>added --convert to xmlcatalog, bug fixes and cleanups of XML 1249 Catalog</li> 1250 <li>a few bug fixes and some portability changes</li> 1251 <li>some documentation cleanups</li> 1252</ul> 1253 1254<h3>2.4.3: Aug 23 2001</h3> 1255<ul> 1256 <li>XML Catalog support see the doc</li> 1257 <li>New NaN/Infinity floating point code</li> 1258 <li>A few bug fixes</li> 1259</ul> 1260 1261<h3>2.4.2: Aug 15 2001</h3> 1262<ul> 1263 <li>adds xmlLineNumbersDefault() to control line number generation</li> 1264 <li>lot of bug fixes</li> 1265 <li>the Microsoft MSC projects files should now be up to date</li> 1266 <li>inheritance of namespaces from DTD defaulted attributes</li> 1267 <li>fixes a serious potential security bug</li> 1268 <li>added a --format option to xmllint</li> 1269</ul> 1270 1271<h3>2.4.1: July 24 2001</h3> 1272<ul> 1273 <li>possibility to keep line numbers in the tree</li> 1274 <li>some computation NaN fixes</li> 1275 <li>extension of the XPath API</li> 1276 <li>cleanup for alpha and ia64 targets</li> 1277 <li>patch to allow saving through HTTP PUT or POST</li> 1278</ul> 1279 1280<h3>2.4.0: July 10 2001</h3> 1281<ul> 1282 <li>Fixed a few bugs in XPath, validation, and tree handling.</li> 1283 <li>Fixed XML Base implementation, added a couple of examples to the 1284 regression tests</li> 1285 <li>A bit of cleanup</li> 1286</ul> 1287 1288<h3>2.3.14: July 5 2001</h3> 1289<ul> 1290 <li>fixed some entities problems and reduce memory requirement when 1291 substituting them</li> 1292 <li>lots of improvements in the XPath queries interpreter can be 1293 substantially faster</li> 1294 <li>Makefiles and configure cleanups</li> 1295 <li>Fixes to XPath variable eval, and compare on empty node set</li> 1296 <li>HTML tag closing bug fixed</li> 1297 <li>Fixed an URI reference computation problem when validating</li> 1298</ul> 1299 1300<h3>2.3.13: June 28 2001</h3> 1301<ul> 1302 <li>2.3.12 configure.in was broken as well as the push mode XML parser</li> 1303 <li>a few more fixes for compilation on Windows MSC by Yon Derek</li> 1304</ul> 1305 1306<h3>1.8.14: June 28 2001</h3> 1307<ul> 1308 <li>Zbigniew Chyla gave a patch to use the old XML parser in push mode</li> 1309 <li>Small Makefile fix</li> 1310</ul> 1311 1312<h3>2.3.12: June 26 2001</h3> 1313<ul> 1314 <li>lots of cleanup</li> 1315 <li>a couple of validation fix</li> 1316 <li>fixed line number counting</li> 1317 <li>fixed serious problems in the XInclude processing</li> 1318 <li>added support for UTF8 BOM at beginning of entities</li> 1319 <li>fixed a strange gcc optimizer bugs in xpath handling of float, gcc-3.0 1320 miscompile uri.c (William), Thomas Leitner provided a fix for the 1321 optimizer on Tru64</li> 1322 <li>incorporated Yon Derek and Igor Zlatkovic fixes and improvements for 1323 compilation on Windows MSC</li> 1324 <li>update of libxml-doc.el (Felix Natter)</li> 1325 <li>fixed 2 bugs in URI normalization code</li> 1326</ul> 1327 1328<h3>2.3.11: June 17 2001</h3> 1329<ul> 1330 <li>updates to trio, Makefiles and configure should fix some portability 1331 problems (alpha)</li> 1332 <li>fixed some HTML serialization problems (pre, script, and block/inline 1333 handling), added encoding aware APIs, cleanup of this code</li> 1334 <li>added xmlHasNsProp()</li> 1335 <li>implemented a specific PI for encoding support in the DocBook SGML 1336 parser</li> 1337 <li>some XPath fixes (-Infinity, / as a function parameter and namespaces 1338 node selection)</li> 1339 <li>fixed a performance problem and an error in the validation code</li> 1340 <li>fixed XInclude routine to implement the recursive behaviour</li> 1341 <li>fixed xmlFreeNode problem when libxml is included statically twice</li> 1342 <li>added --version to xmllint for bug reports</li> 1343</ul> 1344 1345<h3>2.3.10: June 1 2001</h3> 1346<ul> 1347 <li>fixed the SGML catalog support</li> 1348 <li>a number of reported bugs got fixed, in XPath, iconv detection, 1349 XInclude processing</li> 1350 <li>XPath string function should now handle unicode correctly</li> 1351</ul> 1352 1353<h3>2.3.9: May 19 2001</h3> 1354 1355<p>Lots of bugfixes, and added a basic SGML catalog support:</p> 1356<ul> 1357 <li>HTML push bugfix #54891 and another patch from Jonas Borgstr�m</li> 1358 <li>some serious speed optimization again</li> 1359 <li>some documentation cleanups</li> 1360 <li>trying to get better linking on Solaris (-R)</li> 1361 <li>XPath API cleanup from Thomas Broyer</li> 1362 <li>Validation bug fixed #54631, added a patch from Gary Pennington, fixed 1363 xmlValidGetValidElements()</li> 1364 <li>Added an INSTALL file</li> 1365 <li>Attribute removal added to API: #54433</li> 1366 <li>added a basic support for SGML catalogs</li> 1367 <li>fixed xmlKeepBlanksDefault(0) API</li> 1368 <li>bugfix in xmlNodeGetLang()</li> 1369 <li>fixed a small configure portability problem</li> 1370 <li>fixed an inversion of SYSTEM and PUBLIC identifier in HTML document</li> 1371</ul> 1372 1373<h3>1.8.13: May 14 2001</h3> 1374<ul> 1375 <li>bugfixes release of the old libxml1 branch used by Gnome</li> 1376</ul> 1377 1378<h3>2.3.8: May 3 2001</h3> 1379<ul> 1380 <li>Integrated an SGML DocBook parser for the Gnome project</li> 1381 <li>Fixed a few things in the HTML parser</li> 1382 <li>Fixed some XPath bugs raised by XSLT use, tried to fix the floating 1383 point portability issue</li> 1384 <li>Speed improvement (8M/s for SAX, 3M/s for DOM, 1.5M/s for 1385 DOM+validation using the XML REC as input and a 700MHz celeron).</li> 1386 <li>incorporated more Windows cleanup</li> 1387 <li>added xmlSaveFormatFile()</li> 1388 <li>fixed problems in copying nodes with entities references (gdome)</li> 1389 <li>removed some troubles surrounding the new validation module</li> 1390</ul> 1391 1392<h3>2.3.7: April 22 2001</h3> 1393<ul> 1394 <li>lots of small bug fixes, corrected XPointer</li> 1395 <li>Non deterministic content model validation support</li> 1396 <li>added xmlDocCopyNode for gdome2</li> 1397 <li>revamped the way the HTML parser handles end of tags</li> 1398 <li>XPath: corrections of namespaces support and number formatting</li> 1399 <li>Windows: Igor Zlatkovic patches for MSC compilation</li> 1400 <li>HTML output fixes from P C Chow and William M. Brack</li> 1401 <li>Improved validation speed sensible for DocBook</li> 1402 <li>fixed a big bug with ID declared in external parsed entities</li> 1403 <li>portability fixes, update of Trio from Bjorn Reese</li> 1404</ul> 1405 1406<h3>2.3.6: April 8 2001</h3> 1407<ul> 1408 <li>Code cleanup using extreme gcc compiler warning options, found and 1409 cleared half a dozen potential problem</li> 1410 <li>the Eazel team found an XML parser bug</li> 1411 <li>cleaned up the user of some of the string formatting function. used the 1412 trio library code to provide the one needed when the platform is missing 1413 them</li> 1414 <li>xpath: removed a memory leak and fixed the predicate evaluation 1415 problem, extended the testsuite and cleaned up the result. XPointer seems 1416 broken ...</li> 1417</ul> 1418 1419<h3>2.3.5: Mar 23 2001</h3> 1420<ul> 1421 <li>Biggest change is separate parsing and evaluation of XPath expressions, 1422 there is some new APIs for this too</li> 1423 <li>included a number of bug fixes(XML push parser, 51876, notations, 1424 52299)</li> 1425 <li>Fixed some portability issues</li> 1426</ul> 1427 1428<h3>2.3.4: Mar 10 2001</h3> 1429<ul> 1430 <li>Fixed bugs #51860 and #51861</li> 1431 <li>Added a global variable xmlDefaultBufferSize to allow default buffer 1432 size to be application tunable.</li> 1433 <li>Some cleanup in the validation code, still a bug left and this part 1434 should probably be rewritten to support ambiguous content model :-\</li> 1435 <li>Fix a couple of serious bugs introduced or raised by changes in 2.3.3 1436 parser</li> 1437 <li>Fixed another bug in xmlNodeGetContent()</li> 1438 <li>Bjorn fixed XPath node collection and Number formatting</li> 1439 <li>Fixed a loop reported in the HTML parsing</li> 1440 <li>blank space are reported even if the Dtd content model proves that they 1441 are formatting spaces, this is for XML conformance</li> 1442</ul> 1443 1444<h3>2.3.3: Mar 1 2001</h3> 1445<ul> 1446 <li>small change in XPath for XSLT</li> 1447 <li>documentation cleanups</li> 1448 <li>fix in validation by Gary Pennington</li> 1449 <li>serious parsing performances improvements</li> 1450</ul> 1451 1452<h3>2.3.2: Feb 24 2001</h3> 1453<ul> 1454 <li>chasing XPath bugs, found a bunch, completed some TODO</li> 1455 <li>fixed a Dtd parsing bug</li> 1456 <li>fixed a bug in xmlNodeGetContent</li> 1457 <li>ID/IDREF support partly rewritten by Gary Pennington</li> 1458</ul> 1459 1460<h3>2.3.1: Feb 15 2001</h3> 1461<ul> 1462 <li>some XPath and HTML bug fixes for XSLT</li> 1463 <li>small extension of the hash table interfaces for DOM gdome2 1464 implementation</li> 1465 <li>A few bug fixes</li> 1466</ul> 1467 1468<h3>2.3.0: Feb 8 2001 (2.2.12 was on 25 Jan but I didn't kept track)</h3> 1469<ul> 1470 <li>Lots of XPath bug fixes</li> 1471 <li>Add a mode with Dtd lookup but without validation error reporting for 1472 XSLT</li> 1473 <li>Add support for text node without escaping (XSLT)</li> 1474 <li>bug fixes for xmlCheckFilename</li> 1475 <li>validation code bug fixes from Gary Pennington</li> 1476 <li>Patch from Paul D. Smith correcting URI path normalization</li> 1477 <li>Patch to allow simultaneous install of libxml-devel and 1478 libxml2-devel</li> 1479 <li>the example Makefile is now fixed</li> 1480 <li>added HTML to the RPM packages</li> 1481 <li>tree copying bugfixes</li> 1482 <li>updates to Windows makefiles</li> 1483 <li>optimization patch from Bjorn Reese</li> 1484</ul> 1485 1486<h3>2.2.11: Jan 4 2001</h3> 1487<ul> 1488 <li>bunch of bug fixes (memory I/O, xpath, ftp/http, ...)</li> 1489 <li>added htmlHandleOmittedElem()</li> 1490 <li>Applied Bjorn Reese's IPV6 first patch</li> 1491 <li>Applied Paul D. Smith patches for validation of XInclude results</li> 1492 <li>added XPointer xmlns() new scheme support</li> 1493</ul> 1494 1495<h3>2.2.10: Nov 25 2000</h3> 1496<ul> 1497 <li>Fix the Windows problems of 2.2.8</li> 1498 <li>integrate OpenVMS patches</li> 1499 <li>better handling of some nasty HTML input</li> 1500 <li>Improved the XPointer implementation</li> 1501 <li>integrate a number of provided patches</li> 1502</ul> 1503 1504<h3>2.2.9: Nov 25 2000</h3> 1505<ul> 1506 <li>erroneous release :-(</li> 1507</ul> 1508 1509<h3>2.2.8: Nov 13 2000</h3> 1510<ul> 1511 <li>First version of <a href="http://www.w3.org/TR/xinclude">XInclude</a> 1512 support</li> 1513 <li>Patch in conditional section handling</li> 1514 <li>updated MS compiler project</li> 1515 <li>fixed some XPath problems</li> 1516 <li>added an URI escaping function</li> 1517 <li>some other bug fixes</li> 1518</ul> 1519 1520<h3>2.2.7: Oct 31 2000</h3> 1521<ul> 1522 <li>added message redirection</li> 1523 <li>XPath improvements (thanks TOM !)</li> 1524 <li>xmlIOParseDTD() added</li> 1525 <li>various small fixes in the HTML, URI, HTTP and XPointer support</li> 1526 <li>some cleanup of the Makefile, autoconf and the distribution content</li> 1527</ul> 1528 1529<h3>2.2.6: Oct 25 2000:</h3> 1530<ul> 1531 <li>Added an hash table module, migrated a number of internal structure to 1532 those</li> 1533 <li>Fixed a posteriori validation problems</li> 1534 <li>HTTP module cleanups</li> 1535 <li>HTML parser improvements (tag errors, script/style handling, attribute 1536 normalization)</li> 1537 <li>coalescing of adjacent text nodes</li> 1538 <li>couple of XPath bug fixes, exported the internal API</li> 1539</ul> 1540 1541<h3>2.2.5: Oct 15 2000:</h3> 1542<ul> 1543 <li>XPointer implementation and testsuite</li> 1544 <li>Lot of XPath fixes, added variable and functions registration, more 1545 tests</li> 1546 <li>Portability fixes, lots of enhancements toward an easy Windows build 1547 and release</li> 1548 <li>Late validation fixes</li> 1549 <li>Integrated a lot of contributed patches</li> 1550 <li>added memory management docs</li> 1551 <li>a performance problem when using large buffer seems fixed</li> 1552</ul> 1553 1554<h3>2.2.4: Oct 1 2000:</h3> 1555<ul> 1556 <li>main XPath problem fixed</li> 1557 <li>Integrated portability patches for Windows</li> 1558 <li>Serious bug fixes on the URI and HTML code</li> 1559</ul> 1560 1561<h3>2.2.3: Sep 17 2000</h3> 1562<ul> 1563 <li>bug fixes</li> 1564 <li>cleanup of entity handling code</li> 1565 <li>overall review of all loops in the parsers, all sprintf usage has been 1566 checked too</li> 1567 <li>Far better handling of larges Dtd. Validating against DocBook XML Dtd 1568 works smoothly now.</li> 1569</ul> 1570 1571<h3>1.8.10: Sep 6 2000</h3> 1572<ul> 1573 <li>bug fix release for some Gnome projects</li> 1574</ul> 1575 1576<h3>2.2.2: August 12 2000</h3> 1577<ul> 1578 <li>mostly bug fixes</li> 1579 <li>started adding routines to access xml parser context options</li> 1580</ul> 1581 1582<h3>2.2.1: July 21 2000</h3> 1583<ul> 1584 <li>a purely bug fixes release</li> 1585 <li>fixed an encoding support problem when parsing from a memory block</li> 1586 <li>fixed a DOCTYPE parsing problem</li> 1587 <li>removed a bug in the function allowing to override the memory 1588 allocation routines</li> 1589</ul> 1590 1591<h3>2.2.0: July 14 2000</h3> 1592<ul> 1593 <li>applied a lot of portability fixes</li> 1594 <li>better encoding support/cleanup and saving (content is now always 1595 encoded in UTF-8)</li> 1596 <li>the HTML parser now correctly handles encodings</li> 1597 <li>added xmlHasProp()</li> 1598 <li>fixed a serious problem with &#38;</li> 1599 <li>propagated the fix to FTP client</li> 1600 <li>cleanup, bugfixes, etc ...</li> 1601 <li>Added a page about <a href="encoding.html">libxml Internationalization 1602 support</a></li> 1603</ul> 1604 1605<h3>1.8.9: July 9 2000</h3> 1606<ul> 1607 <li>fixed the spec the RPMs should be better</li> 1608 <li>fixed a serious bug in the FTP implementation, released 1.8.9 to solve 1609 rpmfind users problem</li> 1610</ul> 1611 1612<h3>2.1.1: July 1 2000</h3> 1613<ul> 1614 <li>fixes a couple of bugs in the 2.1.0 packaging</li> 1615 <li>improvements on the HTML parser</li> 1616</ul> 1617 1618<h3>2.1.0 and 1.8.8: June 29 2000</h3> 1619<ul> 1620 <li>1.8.8 is mostly a commodity package for upgrading to libxml2 according 1621 to <a href="upgrade.html">new instructions</a>. It fixes a nasty problem 1622 about &#38; charref parsing</li> 1623 <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it 1624 also contains numerous fixes and enhancements: 1625 <ul> 1626 <li>added xmlStopParser() to stop parsing</li> 1627 <li>improved a lot parsing speed when there is large CDATA blocs</li> 1628 <li>includes XPath patches provided by Picdar Technology</li> 1629 <li>tried to fix as much as possible DTD validation and namespace 1630 related problems</li> 1631 <li>output to a given encoding has been added/tested</li> 1632 <li>lot of various fixes</li> 1633 </ul> 1634 </li> 1635</ul> 1636 1637<h3>2.0.0: Apr 12 2000</h3> 1638<ul> 1639 <li>First public release of libxml2. If you are using libxml, it's a good 1640 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initially 1641 scheduled for Apr 3 the release occurred only on Apr 12 due to massive 1642 workload.</li> 1643 <li>The include are now located under $prefix/include/libxml (instead of 1644 $prefix/include/gnome-xml), they also are referenced by 1645 <pre>#include <libxml/xxx.h></pre> 1646 <p>instead of</p> 1647 <pre>#include "xxx.h"</pre> 1648 </li> 1649 <li>a new URI module for parsing URIs and following strictly RFC 2396</li> 1650 <li>the memory allocation routines used by libxml can now be overloaded 1651 dynamically by using xmlMemSetup()</li> 1652 <li>The previously CVS only tool tester has been renamed 1653 <strong>xmllint</strong> and is now installed as part of the libxml2 1654 package</li> 1655 <li>The I/O interface has been revamped. There is now ways to plug in 1656 specific I/O modules, either at the URI scheme detection level using 1657 xmlRegisterInputCallbacks() or by passing I/O functions when creating a 1658 parser context using xmlCreateIOParserCtxt()</li> 1659 <li>there is a C preprocessor macro LIBXML_VERSION providing the version 1660 number of the libxml module in use</li> 1661 <li>a number of optional features of libxml can now be excluded at 1662 configure time (FTP/HTTP/HTML/XPath/Debug)</li> 1663</ul> 1664 1665<h3>2.0.0beta: Mar 14 2000</h3> 1666<ul> 1667 <li>This is a first Beta release of libxml version 2</li> 1668 <li>It's available only from<a href="ftp://xmlsoft.org/">xmlsoft.org 1669 FTP</a>, it's packaged as libxml2-2.0.0beta and available as tar and 1670 RPMs</li> 1671 <li>This version is now the head in the Gnome CVS base, the old one is 1672 available under the tag LIB_XML_1_X</li> 1673 <li>This includes a very large set of changes. From a programmatic point 1674 of view applications should not have to be modified too much, check the 1675 <a href="upgrade.html">upgrade page</a></li> 1676 <li>Some interfaces may changes (especially a bit about encoding).</li> 1677 <li>the updates includes: 1678 <ul> 1679 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly 1680 handled now</li> 1681 <li>Better handling of entities, especially well-formedness checking 1682 and proper PEref extensions in external subsets</li> 1683 <li>DTD conditional sections</li> 1684 <li>Validation now correctly handle entities content</li> 1685 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change 1686 structures to accommodate DOM</a></li> 1687 </ul> 1688 </li> 1689 <li>Serious progress were made toward compliance, <a 1690 href="conf/result.html">here are the result of the test</a> against the 1691 OASIS testsuite (except the Japanese tests since I don't support that 1692 encoding yet). This URL is rebuilt every couple of hours using the CVS 1693 head version.</li> 1694</ul> 1695 1696<h3>1.8.7: Mar 6 2000</h3> 1697<ul> 1698 <li>This is a bug fix release:</li> 1699 <li>It is possible to disable the ignorable blanks heuristic used by 1700 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note 1701 that for adherence to XML spec, this behaviour will be disabled by 1702 default in 2.x . The same function will allow to keep compatibility for 1703 old code.</li> 1704 <li>Blanks in <a> </a> constructs are not ignored anymore, 1705 avoiding heuristic is really the Right Way :-\</li> 1706 <li>The unchecked use of snprintf which was breaking libxml-1.8.6 1707 compilation on some platforms has been fixed</li> 1708 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing 1709 URIs</li> 1710</ul> 1711 1712<h3>1.8.6: Jan 31 2000</h3> 1713<ul> 1714 <li>added a nanoFTP transport module, debugged until the new version of <a 1715 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use 1716 it without troubles</li> 1717</ul> 1718 1719<h3>1.8.5: Jan 21 2000</h3> 1720<ul> 1721 <li>adding APIs to parse a well balanced chunk of XML (production <a 1722 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the 1723 XML spec)</li> 1724 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li> 1725 <li>Jody Goldberg <jgoldberg@home.com> provided another patch trying 1726 to solve the zlib checks problems</li> 1727 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with 1728 gnumeric soon</li> 1729</ul> 1730 1731<h3>1.8.4: Jan 13 2000</h3> 1732<ul> 1733 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li> 1734 <li>all exit() call should have been removed from libxml</li> 1735 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li> 1736 <li>added newDocFragment()</li> 1737</ul> 1738 1739<h3>1.8.3: Jan 5 2000</h3> 1740<ul> 1741 <li>a Push interface for the XML and HTML parsers</li> 1742 <li>a shell-like interface to the document tree (try tester --shell :-)</li> 1743 <li>lots of bug fixes and improvement added over XMas holidays</li> 1744 <li>fixed the DTD parsing code to work with the xhtml DTD</li> 1745 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li> 1746 <li>Fixed bugs in xmlNewNs()</li> 1747 <li>External entity loading code has been revamped, now it uses 1748 xmlLoadExternalEntity(), some fix on entities processing were added</li> 1749 <li>cleaned up WIN32 includes of socket stuff</li> 1750</ul> 1751 1752<h3>1.8.2: Dec 21 1999</h3> 1753<ul> 1754 <li>I got another problem with includes and C++, I hope this issue is fixed 1755 for good this time</li> 1756 <li>Added a few tree modification functions: xmlReplaceNode, 1757 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and 1758 xmlDocSetRootElement</li> 1759 <li>Tried to improve the HTML output with help from <a 1760 href="mailto:clahey@umich.edu">Chris Lahey</a></li> 1761</ul> 1762 1763<h3>1.8.1: Dec 18 1999</h3> 1764<ul> 1765 <li>various patches to avoid troubles when using libxml with C++ compilers 1766 the "namespace" keyword and C escaping in include files</li> 1767 <li>a problem in one of the core macros IS_CHAR was corrected</li> 1768 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing, 1769 and more specifically the Dia application</li> 1770 <li>fixed a posteriori validation (validation after parsing, or by using a 1771 Dtd not specified in the original document)</li> 1772 <li>fixed a bug in</li> 1773</ul> 1774 1775<h3>1.8.0: Dec 12 1999</h3> 1776<ul> 1777 <li>cleanup, especially memory wise</li> 1778 <li>the parser should be more reliable, especially the HTML one, it should 1779 not crash, whatever the input !</li> 1780 <li>Integrated various patches, especially a speedup improvement for large 1781 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>, 1782 configure with --with-buffers to enable them.</li> 1783 <li>attribute normalization, oops should have been added long ago !</li> 1784 <li>attributes defaulted from DTDs should be available, xmlSetProp() now 1785 does entities escaping by default.</li> 1786</ul> 1787 1788<h3>1.7.4: Oct 25 1999</h3> 1789<ul> 1790 <li>Lots of HTML improvement</li> 1791 <li>Fixed some errors when saving both XML and HTML</li> 1792 <li>More examples, the regression tests should now look clean</li> 1793 <li>Fixed a bug with contiguous charref</li> 1794</ul> 1795 1796<h3>1.7.3: Sep 29 1999</h3> 1797<ul> 1798 <li>portability problems fixed</li> 1799 <li>snprintf was used unconditionally, leading to link problems on system 1800 were it's not available, fixed</li> 1801</ul> 1802 1803<h3>1.7.1: Sep 24 1999</h3> 1804<ul> 1805 <li>The basic type for strings manipulated by libxml has been renamed in 1806 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason 1807 is that CHAR was conflicting with a predefined type on Windows. However 1808 on non WIN32 environment, compatibility is provided by the way of a 1809 <strong>#define </strong>.</li> 1810 <li>Changed another error : the use of a structure field called errno, and 1811 leading to troubles on platforms where it's a macro</li> 1812</ul> 1813 1814<h3>1.7.0: Sep 23 1999</h3> 1815<ul> 1816 <li>Added the ability to fetch remote DTD or parsed entities, see the <a 1817 href="html/libxml-nanohttp.html">nanohttp</a> module.</li> 1818 <li>Added an errno to report errors by another mean than a simple printf 1819 like callback</li> 1820 <li>Finished ID/IDREF support and checking when validation</li> 1821 <li>Serious memory leaks fixed (there is now a <a 1822 href="html/libxml-xmlmemory.html">memory wrapper</a> module)</li> 1823 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a> 1824 implementation</li> 1825 <li>Added an HTML parser front-end</li> 1826</ul> 1827 1828<h2><a name="XML">XML</a></h2> 1829 1830<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for 1831markup-based structured documents. Here is <a name="example">an example XML 1832document</a>:</p> 1833<pre><?xml version="1.0"?> 1834<EXAMPLE prop1="gnome is great" prop2="&amp; linux too"> 1835 <head> 1836 <title>Welcome to Gnome</title> 1837 </head> 1838 <chapter> 1839 <title>The Linux adventure</title> 1840 <p>bla bla bla ...</p> 1841 <image href="linus.gif"/> 1842 <p>...</p> 1843 </chapter> 1844</EXAMPLE></pre> 1845 1846<p>The first line specifies that it is an XML document and gives useful 1847information about its encoding. Then the rest of the document is a text 1848format whose structure is specified by tags between brackets. <strong>Each 1849tag opened has to be closed</strong>. XML is pedantic about this. However, if 1850a tag is empty (no content), a single tag can serve as both the opening and 1851closing tag if it ends with <code>/></code> rather than with 1852<code>></code>. Note that, for example, the image tag has no content (just 1853an attribute) and is closed by ending the tag with <code>/></code>.</p> 1854 1855<p>XML can be applied successfully to a wide range of tasks, ranging from 1856long term structured document maintenance (where it follows the steps of 1857SGML) to simple data encoding mechanisms like configuration file formatting 1858(glade), spreadsheets (gnumeric), or even shorter lived documents such as 1859WebDAV where it is used to encode remote calls between a client and a 1860server.</p> 1861 1862<h2><a name="XSLT">XSLT</a></h2> 1863 1864<p>Check <a href="http://xmlsoft.org/XSLT">the separate libxslt page</a></p> 1865 1866<p><a href="http://www.w3.org/TR/xslt">XSL Transformations</a>, is a 1867language for transforming XML documents into other XML documents (or 1868HTML/textual output).</p> 1869 1870<p>A separate library called libxslt is available implementing XSLT-1.0 for 1871libxml2. This module "libxslt" too can be found in the Gnome CVS base.</p> 1872 1873<p>You can check the <a 1874href="http://cvs.gnome.org/lxr/source/libxslt/FEATURES">features</a> 1875supported and the progresses on the <a 1876href="http://cvs.gnome.org/lxr/source/libxslt/ChangeLog" 1877name="Changelog">Changelog</a>.</p> 1878 1879<h2><a name="Python">Python and bindings</a></h2> 1880 1881<p>There are a number of language bindings and wrappers available for 1882libxml2, the list below is not exhaustive. Please contact the <a 1883href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a> 1884(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in 1885order to get updates to this list or to discuss the specific topic of libxml2 1886or libxslt wrappers or bindings:</p> 1887<ul> 1888 <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the 1889 most up-to-date C++ bindings for libxml2, check the <a 1890 href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> 1891 and the <a 1892 href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> 1893 <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper 1894 based on the gdome2 bindings</a> maintained by Tobias Peters.</li> 1895 <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> 1896 <p>Website: <a 1897 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 1898 </li> 1899 <li><a 1900 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 1901 Sergeant</a> developed <a 1902 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 1903 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 1904 application server</a>.</li> 1905 <li>If you're interested into scripting XML processing, have a look at <a 1906 href="http://xsh.sourceforge.net/">XSH</a> an XML editing shell based on 1907 Libxml2 Perl bindings.</li> 1908 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an 1909 earlier version of the libxml/libxslt <a 1910 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> 1911 <li>Gopal.V and Peter Minten develop <a 1912 href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of 1913 C# libxml2 bindings.</li> 1914 <li>Petr Kozelka provides <a 1915 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 1916 libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> 1917 <li>Uwe Fechner also provides <a 1918 href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 1919 implementation for Kylix2/D5/D6 from Borland.</li> 1920 <li>Wai-Sun "Squidster" Chia provides <a 1921 href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and 1922 libxml2 bindings are also available in Ruby through the <a 1923 href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module 1924 maintained by Tobias Peters.</li> 1925 <li>Steve Ball and contributors maintains <a 1926 href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for 1927 Tcl</a>.</li> 1928 <li>There is support for libxml2 in the DOM module of PHP.</li> 1929 <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is 1930 an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and 1931 libxslt as part of GNU ClasspathX project.</li> 1932 <li>Patrick McPhee provides Rexx bindings fof libxml2 and libxslt, look for 1933 <a href="http://www.interlog.com/~ptjm/software.html">RexxXML</a>.</li> 1934</ul> 1935 1936<p>The distribution includes a set of Python bindings, which are guaranteed 1937to be maintained as part of the library in the future, though the Python 1938interface have not yet reached the completeness of the C API.</p> 1939 1940<p><a href="mailto:stephane.bidoul@softwareag.com">St�phane Bidoul</a> 1941maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port 1942of the Python bindings</a>.</p> 1943 1944<p>Note to people interested in building bindings, the API is formalized as 1945<a href="libxml2-api.xml">an XML API description file</a> which allows to 1946automate a large part of the Python bindings, this includes function 1947descriptions, enums, structures, typedefs, etc... The Python script used to 1948build the bindings is python/generator.py in the source distribution.</p> 1949 1950<p>To install the Python bindings there are 2 options:</p> 1951<ul> 1952 <li>If you use an RPM based distribution, simply install the <a 1953 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python 1954 RPM</a> (and if needed the <a 1955 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python 1956 RPM</a>).</li> 1957 <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python 1958 module distribution</a> corresponding to your installed version of 1959 libxml2 and libxslt. Note that to install it you will need both libxml2 1960 and libxslt installed and run "python setup.py build install" in the 1961 module tree.</li> 1962</ul> 1963 1964<p>The distribution includes a set of examples and regression tests for the 1965python bindings in the <code>python/tests</code> directory. Here are some 1966excerpts from those tests:</p> 1967 1968<h3>tst.py:</h3> 1969 1970<p>This is a basic test of the file interface and DOM navigation:</p> 1971<pre>import libxml2 1972 1973doc = libxml2.parseFile("tst.xml") 1974if doc.name != "tst.xml": 1975 print "doc.name failed" 1976 sys.exit(1) 1977root = doc.children 1978if root.name != "doc": 1979 print "root.name failed" 1980 sys.exit(1) 1981child = root.children 1982if child.name != "foo": 1983 print "child.name failed" 1984 sys.exit(1) 1985doc.freeDoc()</pre> 1986 1987<p>The Python module is called libxml2; parseFile is the equivalent of 1988xmlParseFile (most of the bindings are automatically generated, and the xml 1989prefix is removed and the casing convention are kept). All node seen at the 1990binding level share the same subset of accessors:</p> 1991<ul> 1992 <li><code>name</code> : returns the node name</li> 1993 <li><code>type</code> : returns a string indicating the node type</li> 1994 <li><code>content</code> : returns the content of the node, it is based on 1995 xmlNodeGetContent() and hence is recursive.</li> 1996 <li><code>parent</code> , <code>children</code>, <code>last</code>, 1997 <code>next</code>, <code>prev</code>, <code>doc</code>, 1998 <code>properties</code>: pointing to the associated element in the tree, 1999 those may return None in case no such link exists.</li> 2000</ul> 2001 2002<p>Also note the need to explicitly deallocate documents with freeDoc() . 2003Reference counting for libxml2 trees would need quite a lot of work to 2004function properly, and rather than risk memory leaks if not implemented 2005correctly it sounds safer to have an explicit function to free a tree. The 2006wrapper python objects like doc, root or child are them automatically garbage 2007collected.</p> 2008 2009<h3>validate.py:</h3> 2010 2011<p>This test check the validation interfaces and redirection of error 2012messages:</p> 2013<pre>import libxml2 2014 2015#deactivate error messages from the validation 2016def noerr(ctx, str): 2017 pass 2018 2019libxml2.registerErrorHandler(noerr, None) 2020 2021ctxt = libxml2.createFileParserCtxt("invalid.xml") 2022ctxt.validate(1) 2023ctxt.parseDocument() 2024doc = ctxt.doc() 2025valid = ctxt.isValid() 2026doc.freeDoc() 2027if valid != 0: 2028 print "validity check failed"</pre> 2029 2030<p>The first thing to notice is the call to registerErrorHandler(), it 2031defines a new error handler global to the library. It is used to avoid seeing 2032the error messages when trying to validate the invalid document.</p> 2033 2034<p>The main interest of that test is the creation of a parser context with 2035createFileParserCtxt() and how the behaviour can be changed before calling 2036parseDocument() . Similarly the informations resulting from the parsing phase 2037are also available using context methods.</p> 2038 2039<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the 2040C function interfaces in terms of objects method as much as possible. The 2041best to get a complete view of what methods are supported is to look at the 2042libxml2.py module containing all the wrappers.</p> 2043 2044<h3>push.py:</h3> 2045 2046<p>This test show how to activate the push parser interface:</p> 2047<pre>import libxml2 2048 2049ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") 2050ctxt.parseChunk("/>", 2, 1) 2051doc = ctxt.doc() 2052 2053doc.freeDoc()</pre> 2054 2055<p>The context is created with a special call based on the 2056xmlCreatePushParser() from the C library. The first argument is an optional 2057SAX callback object, then the initial set of data, the length and the name of 2058the resource in case URI-References need to be computed by the parser.</p> 2059 2060<p>Then the data are pushed using the parseChunk() method, the last call 2061setting the third argument terminate to 1.</p> 2062 2063<h3>pushSAX.py:</h3> 2064 2065<p>this test show the use of the event based parsing interfaces. In this case 2066the parser does not build a document, but provides callback information as 2067the parser makes progresses analyzing the data being provided:</p> 2068<pre>import libxml2 2069log = "" 2070 2071class callback: 2072 def startDocument(self): 2073 global log 2074 log = log + "startDocument:" 2075 2076 def endDocument(self): 2077 global log 2078 log = log + "endDocument:" 2079 2080 def startElement(self, tag, attrs): 2081 global log 2082 log = log + "startElement %s %s:" % (tag, attrs) 2083 2084 def endElement(self, tag): 2085 global log 2086 log = log + "endElement %s:" % (tag) 2087 2088 def characters(self, data): 2089 global log 2090 log = log + "characters: %s:" % (data) 2091 2092 def warning(self, msg): 2093 global log 2094 log = log + "warning: %s:" % (msg) 2095 2096 def error(self, msg): 2097 global log 2098 log = log + "error: %s:" % (msg) 2099 2100 def fatalError(self, msg): 2101 global log 2102 log = log + "fatalError: %s:" % (msg) 2103 2104handler = callback() 2105 2106ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") 2107chunk = " url='tst'>b" 2108ctxt.parseChunk(chunk, len(chunk), 0) 2109chunk = "ar</foo>" 2110ctxt.parseChunk(chunk, len(chunk), 1) 2111 2112reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 2113 "characters: bar:endElement foo:endDocument:" 2114if log != reference: 2115 print "Error got: %s" % log 2116 print "Expected: %s" % reference</pre> 2117 2118<p>The key object in that test is the handler, it provides a number of entry 2119points which can be called by the parser as it makes progresses to indicate 2120the information set obtained. The full set of callback is larger than what 2121the callback class in that specific example implements (see the SAX 2122definition for a complete list). The wrapper will only call those supplied by 2123the object when activated. The startElement receives the names of the element 2124and a dictionary containing the attributes carried by this element.</p> 2125 2126<p>Also note that the reference string generated from the callback shows a 2127single character call even though the string "bar" is passed to the parser 2128from 2 different call to parseChunk()</p> 2129 2130<h3>xpath.py:</h3> 2131 2132<p>This is a basic test of XPath wrappers support</p> 2133<pre>import libxml2 2134 2135doc = libxml2.parseFile("tst.xml") 2136ctxt = doc.xpathNewContext() 2137res = ctxt.xpathEval("//*") 2138if len(res) != 2: 2139 print "xpath query: wrong node set size" 2140 sys.exit(1) 2141if res[0].name != "doc" or res[1].name != "foo": 2142 print "xpath query: wrong node set value" 2143 sys.exit(1) 2144doc.freeDoc() 2145ctxt.xpathFreeContext()</pre> 2146 2147<p>This test parses a file, then create an XPath context to evaluate XPath 2148expression on it. The xpathEval() method execute an XPath query and returns 2149the result mapped in a Python way. String and numbers are natively converted, 2150and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like 2151the document, the XPath context need to be freed explicitly, also not that 2152the result of the XPath query may point back to the document tree and hence 2153the document must be freed after the result of the query is used.</p> 2154 2155<h3>xpathext.py:</h3> 2156 2157<p>This test shows how to extend the XPath engine with functions written in 2158python:</p> 2159<pre>import libxml2 2160 2161def foo(ctx, x): 2162 return x + 1 2163 2164doc = libxml2.parseFile("tst.xml") 2165ctxt = doc.xpathNewContext() 2166libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) 2167res = ctxt.xpathEval("foo(1)") 2168if res != 2: 2169 print "xpath extension failure" 2170doc.freeDoc() 2171ctxt.xpathFreeContext()</pre> 2172 2173<p>Note how the extension function is registered with the context (but that 2174part is not yet finalized, this may change slightly in the future).</p> 2175 2176<h3>tstxpath.py:</h3> 2177 2178<p>This test is similar to the previous one but shows how the extension 2179function can access the XPath evaluation context:</p> 2180<pre>def foo(ctx, x): 2181 global called 2182 2183 # 2184 # test that access to the XPath evaluation contexts 2185 # 2186 pctxt = libxml2.xpathParserContext(_obj=ctx) 2187 ctxt = pctxt.context() 2188 called = ctxt.function() 2189 return x + 1</pre> 2190 2191<p>All the interfaces around the XPath parser(or rather evaluation) context 2192are not finalized, but it should be sufficient to do contextual work at the 2193evaluation point.</p> 2194 2195<h3>Memory debugging:</h3> 2196 2197<p>last but not least, all tests starts with the following prologue:</p> 2198<pre>#memory debug specific 2199libxml2.debugMemory(1)</pre> 2200 2201<p>and ends with the following epilogue:</p> 2202<pre>#memory debug specific 2203libxml2.cleanupParser() 2204if libxml2.debugMemory(1) == 0: 2205 print "OK" 2206else: 2207 print "Memory leak %d bytes" % (libxml2.debugMemory(1)) 2208 libxml2.dumpMemory()</pre> 2209 2210<p>Those activate the memory debugging interface of libxml2 where all 2211allocated block in the library are tracked. The prologue then cleans up the 2212library state and checks that all allocated memory has been freed. If not it 2213calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p> 2214 2215<h2><a name="architecture">libxml2 architecture</a></h2> 2216 2217<p>Libxml2 is made of multiple components; some of them are optional, and 2218most of the block interfaces are public. The main components are:</p> 2219<ul> 2220 <li>an Input/Output layer</li> 2221 <li>FTP and HTTP client layers (optional)</li> 2222 <li>an Internationalization layer managing the encodings support</li> 2223 <li>a URI module</li> 2224 <li>the XML parser and its basic SAX interface</li> 2225 <li>an HTML parser using the same SAX interface (optional)</li> 2226 <li>a SAX tree module to build an in-memory DOM representation</li> 2227 <li>a tree module to manipulate the DOM representation</li> 2228 <li>a validation module using the DOM representation (optional)</li> 2229 <li>an XPath module for global lookup in a DOM representation 2230 (optional)</li> 2231 <li>a debug module (optional)</li> 2232</ul> 2233 2234<p>Graphically this gives the following:</p> 2235 2236<p><img src="libxml.gif" alt="a graphical view of the various"></p> 2237 2238<p></p> 2239 2240<h2><a name="tree">The tree output</a></h2> 2241 2242<p>The parser returns a tree built during the document analysis. The value 2243returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an 2244<strong>xmlDoc</strong> structure). This structure contains information such 2245as the file name, the document type, and a <strong>children</strong> pointer 2246which is the root of the document (or more exactly the first child under the 2247root which is the document). The tree is made of <strong>xmlNode</strong>s, 2248chained in double-linked lists of siblings and with a children<->parent 2249relationship. An xmlNode can also carry properties (a chain of xmlAttr 2250structures). An attribute may have a value which is a list of TEXT or 2251ENTITY_REF nodes.</p> 2252 2253<p>Here is an example (erroneous with respect to the XML spec since there 2254should be only one ELEMENT under the root):</p> 2255 2256<p><img src="structure.gif" alt=" structure.gif "></p> 2257 2258<p>In the source package there is a small program (not installed by default) 2259called <strong>xmllint</strong> which parses XML files given as argument and 2260prints them back as parsed. This is useful for detecting errors both in XML 2261code and in the XML parser itself. It has an option <strong>--debug</strong> 2262which prints the actual in-memory structure of the document; here is the 2263result with the <a href="#example">example</a> given before:</p> 2264<pre>DOCUMENT 2265version=1.0 2266standalone=true 2267 ELEMENT EXAMPLE 2268 ATTRIBUTE prop1 2269 TEXT 2270 content=gnome is great 2271 ATTRIBUTE prop2 2272 ENTITY_REF 2273 TEXT 2274 content= linux too 2275 ELEMENT head 2276 ELEMENT title 2277 TEXT 2278 content=Welcome to Gnome 2279 ELEMENT chapter 2280 ELEMENT title 2281 TEXT 2282 content=The Linux adventure 2283 ELEMENT p 2284 TEXT 2285 content=bla bla bla ... 2286 ELEMENT image 2287 ATTRIBUTE href 2288 TEXT 2289 content=linus.gif 2290 ELEMENT p 2291 TEXT 2292 content=...</pre> 2293 2294<p>This should be useful for learning the internal representation model.</p> 2295 2296<h2><a name="interface">The SAX interface</a></h2> 2297 2298<p>Sometimes the DOM tree output is just too large to fit reasonably into 2299memory. In that case (and if you don't expect to save back the XML document 2300loaded using libxml), it's better to use the SAX interface of libxml. SAX is 2301a <strong>callback-based interface</strong> to the parser. Before parsing, 2302the application layer registers a customized set of callbacks which are 2303called by the library as it progresses through the XML input.</p> 2304 2305<p>To get more detailed step-by-step guidance on using the SAX interface of 2306libxml, see the <a 2307href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice 2308documentation</a>.written by <a href="mailto:james@daa.com.au">James 2309Henstridge</a>.</p> 2310 2311<p>You can debug the SAX behaviour by using the <strong>testSAX</strong> 2312program located in the gnome-xml module (it's usually not shipped in the 2313binary packages of libxml, but you can find it in the tar source 2314distribution). Here is the sequence of callbacks that would be reported by 2315testSAX when parsing the example XML document shown earlier:</p> 2316<pre>SAX.setDocumentLocator() 2317SAX.startDocument() 2318SAX.getEntity(amp) 2319SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too') 2320SAX.characters( , 3) 2321SAX.startElement(head) 2322SAX.characters( , 4) 2323SAX.startElement(title) 2324SAX.characters(Welcome to Gnome, 16) 2325SAX.endElement(title) 2326SAX.characters( , 3) 2327SAX.endElement(head) 2328SAX.characters( , 3) 2329SAX.startElement(chapter) 2330SAX.characters( , 4) 2331SAX.startElement(title) 2332SAX.characters(The Linux adventure, 19) 2333SAX.endElement(title) 2334SAX.characters( , 4) 2335SAX.startElement(p) 2336SAX.characters(bla bla bla ..., 15) 2337SAX.endElement(p) 2338SAX.characters( , 4) 2339SAX.startElement(image, href='linus.gif') 2340SAX.endElement(image) 2341SAX.characters( , 4) 2342SAX.startElement(p) 2343SAX.characters(..., 3) 2344SAX.endElement(p) 2345SAX.characters( , 3) 2346SAX.endElement(chapter) 2347SAX.characters( , 1) 2348SAX.endElement(EXAMPLE) 2349SAX.endDocument()</pre> 2350 2351<p>Most of the other interfaces of libxml2 are based on the DOM tree-building 2352facility, so nearly everything up to the end of this document presupposes the 2353use of the standard DOM tree build. Note that the DOM tree itself is built by 2354a set of registered default callbacks, without internal specific 2355interface.</p> 2356 2357<h2><a name="Validation">Validation & DTDs</a></h2> 2358 2359<p>Table of Content:</p> 2360<ol> 2361 <li><a href="#General5">General overview</a></li> 2362 <li><a href="#definition">The definition</a></li> 2363 <li><a href="#Simple">Simple rules</a> 2364 <ol> 2365 <li><a href="#reference">How to reference a DTD from a document</a></li> 2366 <li><a href="#Declaring">Declaring elements</a></li> 2367 <li><a href="#Declaring1">Declaring attributes</a></li> 2368 </ol> 2369 </li> 2370 <li><a href="#Some">Some examples</a></li> 2371 <li><a href="#validate">How to validate</a></li> 2372 <li><a href="#Other">Other resources</a></li> 2373</ol> 2374 2375<h3><a name="General5">General overview</a></h3> 2376 2377<p>Well what is validation and what is a DTD ?</p> 2378 2379<p>DTD is the acronym for Document Type Definition. This is a description of 2380the content for a family of XML files. This is part of the XML 1.0 2381specification, and allows one to describe and verify that a given document 2382instance conforms to the set of rules detailing its structure and content.</p> 2383 2384<p>Validation is the process of checking a document against a DTD (more 2385generally against a set of construction rules).</p> 2386 2387<p>The validation process and building DTDs are the two most difficult parts 2388of the XML life cycle. Briefly a DTD defines all the possible elements to be 2389found within your document, what is the formal shape of your document tree 2390(by defining the allowed content of an element; either text, a regular 2391expression for the allowed list of children, or mixed content i.e. both text 2392and children). The DTD also defines the valid attributes for all elements and 2393the types of those attributes.</p> 2394 2395<h3><a name="definition1">The definition</a></h3> 2396 2397<p>The <a href="http://www.w3.org/TR/REC-xml">W3C XML Recommendation</a> (<a 2398href="http://www.xml.com/axml/axml.html">Tim Bray's annotated version of 2399Rev1</a>):</p> 2400<ul> 2401 <li><a href="http://www.w3.org/TR/REC-xml#elemdecls">Declaring 2402 elements</a></li> 2403 <li><a href="http://www.w3.org/TR/REC-xml#attdecls">Declaring 2404 attributes</a></li> 2405</ul> 2406 2407<p>(unfortunately) all this is inherited from the SGML world, the syntax is 2408ancient...</p> 2409 2410<h3><a name="Simple1">Simple rules</a></h3> 2411 2412<p>Writing DTDs can be done in many ways. The rules to build them if you need 2413something permanent or something which can evolve over time can be radically 2414different. Really complex DTDs like DocBook ones are flexible but quite 2415harder to design. I will just focus on DTDs for a formats with a fixed simple 2416structure. It is just a set of basic rules, and definitely not exhaustive nor 2417usable for complex DTD design.</p> 2418 2419<h4><a name="reference1">How to reference a DTD from a document</a>:</h4> 2420 2421<p>Assuming the top element of the document is <code>spec</code> and the dtd 2422is placed in the file <code>mydtd</code> in the subdirectory 2423<code>dtds</code> of the directory from where the document were loaded:</p> 2424 2425<p><code><!DOCTYPE spec SYSTEM "dtds/mydtd"></code></p> 2426 2427<p>Notes:</p> 2428<ul> 2429 <li>The system string is actually an URI-Reference (as defined in <a 2430 href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>) so you can use a 2431 full URL string indicating the location of your DTD on the Web. This is a 2432 really good thing to do if you want others to validate your document.</li> 2433 <li>It is also possible to associate a <code>PUBLIC</code> identifier (a 2434 magic string) so that the DTD is looked up in catalogs on the client side 2435 without having to locate it on the web.</li> 2436 <li>A DTD contains a set of element and attribute declarations, but they 2437 don't define what the root of the document should be. This is explicitly 2438 told to the parser/validator as the first element of the 2439 <code>DOCTYPE</code> declaration.</li> 2440</ul> 2441 2442<h4><a name="Declaring2">Declaring elements</a>:</h4> 2443 2444<p>The following declares an element <code>spec</code>:</p> 2445 2446<p><code><!ELEMENT spec (front, body, back?)></code></p> 2447 2448<p>It also expresses that the spec element contains one <code>front</code>, 2449one <code>body</code> and one optional <code>back</code> children elements in 2450this order. The declaration of one element of the structure and its content 2451are done in a single declaration. Similarly the following declares 2452<code>div1</code> elements:</p> 2453 2454<p><code><!ELEMENT div1 (head, (p | list | note)*, div2?)></code></p> 2455 2456<p>which means div1 contains one <code>head</code> then a series of optional 2457<code>p</code>, <code>list</code>s and <code>note</code>s and then an 2458optional <code>div2</code>. And last but not least an element can contain 2459text:</p> 2460 2461<p><code><!ELEMENT b (#PCDATA)></code></p> 2462 2463<p><code>b</code> contains text or being of mixed content (text and elements 2464in no particular order):</p> 2465 2466<p><code><!ELEMENT p (#PCDATA|a|ul|b|i|em)*></code></p> 2467 2468<p><code>p </code>can contain text or <code>a</code>, <code>ul</code>, 2469<code>b</code>, <code>i </code>or <code>em</code> elements in no particular 2470order.</p> 2471 2472<h4><a name="Declaring1">Declaring attributes</a>:</h4> 2473 2474<p>Again the attributes declaration includes their content definition:</p> 2475 2476<p><code><!ATTLIST termdef name CDATA #IMPLIED></code></p> 2477 2478<p>means that the element <code>termdef</code> can have a <code>name</code> 2479attribute containing text (<code>CDATA</code>) and which is optional 2480(<code>#IMPLIED</code>). The attribute value can also be defined within a 2481set:</p> 2482 2483<p><code><!ATTLIST list type (bullets|ordered|glossary) 2484"ordered"></code></p> 2485 2486<p>means <code>list</code> element have a <code>type</code> attribute with 3 2487allowed values "bullets", "ordered" or "glossary" and which default to 2488"ordered" if the attribute is not explicitly specified.</p> 2489 2490<p>The content type of an attribute can be text (<code>CDATA</code>), 2491anchor/reference/references 2492(<code>ID</code>/<code>IDREF</code>/<code>IDREFS</code>), entity(ies) 2493(<code>ENTITY</code>/<code>ENTITIES</code>) or name(s) 2494(<code>NMTOKEN</code>/<code>NMTOKENS</code>). The following defines that a 2495<code>chapter</code> element can have an optional <code>id</code> attribute 2496of type <code>ID</code>, usable for reference from attribute of type 2497IDREF:</p> 2498 2499<p><code><!ATTLIST chapter id ID #IMPLIED></code></p> 2500 2501<p>The last value of an attribute definition can be <code>#REQUIRED 2502</code>meaning that the attribute has to be given, <code>#IMPLIED</code> 2503meaning that it is optional, or the default value (possibly prefixed by 2504<code>#FIXED</code> if it is the only allowed).</p> 2505 2506<p>Notes:</p> 2507<ul> 2508 <li>Usually the attributes pertaining to a given element are declared in a 2509 single expression, but it is just a convention adopted by a lot of DTD 2510 writers: 2511 <pre><!ATTLIST termdef 2512 id ID #REQUIRED 2513 name CDATA #IMPLIED></pre> 2514 <p>The previous construct defines both <code>id</code> and 2515 <code>name</code> attributes for the element <code>termdef</code>.</p> 2516 </li> 2517</ul> 2518 2519<h3><a name="Some1">Some examples</a></h3> 2520 2521<p>The directory <code>test/valid/dtds/</code> in the libxml2 distribution 2522contains some complex DTD examples. The example in the file 2523<code>test/valid/dia.xml</code> shows an XML file where the simple DTD is 2524directly included within the document.</p> 2525 2526<h3><a name="validate1">How to validate</a></h3> 2527 2528<p>The simplest way is to use the xmllint program included with libxml. The 2529<code>--valid</code> option turns-on validation of the files given as input. 2530For example the following validates a copy of the first revision of the XML 25311.0 specification:</p> 2532 2533<p><code>xmllint --valid --noout test/valid/REC-xml-19980210.xml</code></p> 2534 2535<p>the -- noout is used to disable output of the resulting tree.</p> 2536 2537<p>The <code>--dtdvalid dtd</code> allows validation of the document(s) 2538against a given DTD.</p> 2539 2540<p>Libxml2 exports an API to handle DTDs and validation, check the <a 2541href="http://xmlsoft.org/html/libxml-valid.html">associated 2542description</a>.</p> 2543 2544<h3><a name="Other1">Other resources</a></h3> 2545 2546<p>DTDs are as old as SGML. So there may be a number of examples on-line, I 2547will just list one for now, others pointers welcome:</p> 2548<ul> 2549 <li><a href="http://www.xml101.com:8081/dtd/">XML-101 DTD</a></li> 2550</ul> 2551 2552<p>I suggest looking at the examples found under test/valid/dtd and any of 2553the large number of books available on XML. The dia example in test/valid 2554should be both simple and complete enough to allow you to build your own.</p> 2555 2556<p></p> 2557 2558<h2><a name="Memory">Memory Management</a></h2> 2559 2560<p>Table of Content:</p> 2561<ol> 2562 <li><a href="#General3">General overview</a></li> 2563 <li><a href="#setting">Setting libxml2 set of memory routines</a></li> 2564 <li><a href="#cleanup">Cleaning up after parsing</a></li> 2565 <li><a href="#Debugging">Debugging routines</a></li> 2566 <li><a href="#General4">General memory requirements</a></li> 2567</ol> 2568 2569<h3><a name="General3">General overview</a></h3> 2570 2571<p>The module <code><a 2572href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlmemory.h</a></code> 2573provides the interfaces to the libxml2 memory system:</p> 2574<ul> 2575 <li>libxml2 does not use the libc memory allocator directly but xmlFree(), 2576 xmlMalloc() and xmlRealloc()</li> 2577 <li>those routines can be reallocated to a specific set of routine, by 2578 default the libc ones i.e. free(), malloc() and realloc()</li> 2579 <li>the xmlmemory.c module includes a set of debugging routine</li> 2580</ul> 2581 2582<h3><a name="setting">Setting libxml2 set of memory routines</a></h3> 2583 2584<p>It is sometimes useful to not use the default memory allocator, either for 2585debugging, analysis or to implement a specific behaviour on memory management 2586(like on embedded systems). Two function calls are available to do so:</p> 2587<ul> 2588 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemGet 2589 ()</a> which return the current set of functions in use by the parser</li> 2590 <li><a 2591 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemSetup()</a> 2592 which allow to set up a new set of memory allocation functions</li> 2593</ul> 2594 2595<p>Of course a call to xmlMemSetup() should probably be done before calling 2596any other libxml2 routines (unless you are sure your allocations routines are 2597compatibles).</p> 2598 2599<h3><a name="cleanup">Cleaning up after parsing</a></h3> 2600 2601<p>Libxml2 is not stateless, there is a few set of memory structures needing 2602allocation before the parser is fully functional (some encoding structures 2603for example). This also mean that once parsing is finished there is a tiny 2604amount of memory (a few hundred bytes) which can be recollected if you don't 2605reuse the parser immediately:</p> 2606<ul> 2607 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlCleanupParser 2608 ()</a> is a centralized routine to free the parsing states. Note that it 2609 won't deallocate any produced tree if any (use the xmlFreeDoc() and 2610 related routines for this).</li> 2611 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlInitParser 2612 ()</a> is the dual routine allowing to preallocate the parsing state 2613 which can be useful for example to avoid initialization reentrancy 2614 problems when using libxml2 in multithreaded applications</li> 2615</ul> 2616 2617<p>Generally xmlCleanupParser() is safe, if needed the state will be rebuild 2618at the next invocation of parser routines, but be careful of the consequences 2619in multithreaded applications.</p> 2620 2621<h3><a name="Debugging">Debugging routines</a></h3> 2622 2623<p>When configured using --with-mem-debug flag (off by default), libxml2 uses 2624a set of memory allocation debugging routines keeping track of all allocated 2625blocks and the location in the code where the routine was called. A couple of 2626other debugging routines allow to dump the memory allocated infos to a file 2627or call a specific routine when a given block number is allocated:</p> 2628<ul> 2629 <li><a 2630 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMallocLoc()</a> 2631 <a 2632 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlReallocLoc()</a> 2633 and <a 2634 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemStrdupLoc()</a> 2635 are the memory debugging replacement allocation routines</li> 2636 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemoryDump 2637 ()</a> dumps all the informations about the allocated memory block lefts 2638 in the <code>.memdump</code> file</li> 2639</ul> 2640 2641<p>When developing libxml2 memory debug is enabled, the tests programs call 2642xmlMemoryDump () and the "make test" regression tests will check for any 2643memory leak during the full regression test sequence, this helps a lot 2644ensuring that libxml2 does not leak memory and bullet proof memory 2645allocations use (some libc implementations are known to be far too permissive 2646resulting in major portability problems!).</p> 2647 2648<p>If the .memdump reports a leak, it displays the allocation function and 2649also tries to give some informations about the content and structure of the 2650allocated blocks left. This is sufficient in most cases to find the culprit, 2651but not always. Assuming the allocation problem is reproducible, it is 2652possible to find more easily:</p> 2653<ol> 2654 <li>write down the block number xxxx not allocated</li> 2655 <li>export the environment variable XML_MEM_BREAKPOINT=xxxx , the easiest 2656 when using GDB is to simply give the command 2657 <p><code>set environment XML_MEM_BREAKPOINT xxxx</code></p> 2658 <p>before running the program.</p> 2659 </li> 2660 <li>run the program under a debugger and set a breakpoint on 2661 xmlMallocBreakpoint() a specific function called when this precise block 2662 is allocated</li> 2663 <li>when the breakpoint is reached you can then do a fine analysis of the 2664 allocation an step to see the condition resulting in the missing 2665 deallocation.</li> 2666</ol> 2667 2668<p>I used to use a commercial tool to debug libxml2 memory problems but after 2669noticing that it was not detecting memory leaks that simple mechanism was 2670used and proved extremely efficient until now. Lately I have also used <a 2671href="http://developer.kde.org/~sewardj/">valgrind</a> with quite some 2672success, it is tied to the i386 architecture since it works by emulating the 2673processor and instruction set, it is slow but extremely efficient, i.e. it 2674spot memory usage errors in a very precise way.</p> 2675 2676<h3><a name="General4">General memory requirements</a></h3> 2677 2678<p>How much libxml2 memory require ? It's hard to tell in average it depends 2679of a number of things:</p> 2680<ul> 2681 <li>the parser itself should work in a fixed amount of memory, except for 2682 information maintained about the stacks of names and entities locations. 2683 The I/O and encoding handlers will probably account for a few KBytes. 2684 This is true for both the XML and HTML parser (though the HTML parser 2685 need more state).</li> 2686 <li>If you are generating the DOM tree then memory requirements will grow 2687 nearly linear with the size of the data. In general for a balanced 2688 textual document the internal memory requirement is about 4 times the 2689 size of the UTF8 serialization of this document (example the XML-1.0 2690 recommendation is a bit more of 150KBytes and takes 650KBytes of main 2691 memory when parsed). Validation will add a amount of memory required for 2692 maintaining the external Dtd state which should be linear with the 2693 complexity of the content model defined by the Dtd</li> 2694 <li>If you need to work with fixed memory requirements or don't need the 2695 full DOM tree then using the <a href="xmlreader.html">xmlReader 2696 interface</a> is probably the best way to proceed, it still allows to 2697 validate or operate on subset of the tree if needed.</li> 2698 <li>If you don't care about the advanced features of libxml2 like 2699 validation, DOM, XPath or XPointer, don't use entities, need to work with 2700 fixed memory requirements, and try to get the fastest parsing possible 2701 then the SAX interface should be used, but it has known restrictions.</li> 2702</ul> 2703 2704<p></p> 2705 2706<h2><a name="Encodings">Encodings support</a></h2> 2707 2708<p>Table of Content:</p> 2709<ol> 2710 <li><a href="encoding.html#What">What does internationalization support 2711 mean ?</a></li> 2712 <li><a href="encoding.html#internal">The internal encoding, how and 2713 why</a></li> 2714 <li><a href="encoding.html#implemente">How is it implemented ?</a></li> 2715 <li><a href="encoding.html#Default">Default supported encodings</a></li> 2716 <li><a href="encoding.html#extend">How to extend the existing 2717 support</a></li> 2718</ol> 2719 2720<h3><a name="What">What does internationalization support mean ?</a></h3> 2721 2722<p>If you are not really familiar with Internationalization (usual shorcut is 2723I18N) , Unicode, characters and glyphs, I suggest you read a <a 2724href="http://www.tbray.org/ongoing/When/200x/2003/04/06/Unicode">presentation</a> 2725by Tim Bray on Unicode and why you should care about it.</p> 2726 2727<p>XML was designed from the start to allow the support of any character set 2728by using Unicode. Any conformant XML parser has to support the UTF-8 and 2729UTF-16 default encodings which can both express the full unicode ranges. UTF8 2730is a variable length encoding whose greatest points are to reuse the same 2731encoding for ASCII and to save space for Western encodings, but it is a bit 2732more complex to handle in practice. UTF-16 use 2 bytes per characters (and 2733sometimes combines two pairs), it makes implementation easier, but looks a 2734bit overkill for Western languages encoding. Moreover the XML specification 2735allows document to be encoded in other encodings at the condition that they 2736are clearly labeled as such. For example the following is a wellformed XML 2737document encoded in ISO-8859 1 and using accentuated letter that we French 2738likes for both markup and content:</p> 2739<pre><?xml version="1.0" encoding="ISO-8859-1"?> 2740<tr�s>l�</tr�s></pre> 2741 2742<p>Having internationalization support in libxml2 means the following:</p> 2743<ul> 2744 <li>the document is properly parsed</li> 2745 <li>informations about it's encoding are saved</li> 2746 <li>it can be modified</li> 2747 <li>it can be saved in its original encoding</li> 2748 <li>it can also be saved in another encoding supported by libxml2 (for 2749 example straight UTF8 or even an ASCII form)</li> 2750</ul> 2751 2752<p>Another very important point is that the whole libxml2 API, with the 2753exception of a few routines to read with a specific encoding or save to a 2754specific encoding, is completely agnostic about the original encoding of the 2755document.</p> 2756 2757<p>It should be noted too that the HTML parser embedded in libxml2 now obey 2758the same rules too, the following document will be (as of 2.2.2) handled in 2759an internationalized fashion by libxml2 too:</p> 2760<pre><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" 2761 "http://www.w3.org/TR/REC-html40/loose.dtd"> 2762<html lang="fr"> 2763<head> 2764 <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"> 2765</head> 2766<body> 2767<p>W3C cr�e des standards pour le Web.</body> 2768</html></pre> 2769 2770<h3><a name="internal">The internal encoding, how and why</a></h3> 2771 2772<p>One of the core decision was to force all documents to be converted to a 2773default internal encoding, and that encoding to be UTF-8, here are the 2774rationale for those choices:</p> 2775<ul> 2776 <li>keeping the native encoding in the internal form would force the libxml 2777 users (or the code associated) to be fully aware of the encoding of the 2778 original document, for examples when adding a text node to a document, 2779 the content would have to be provided in the document encoding, i.e. the 2780 client code would have to check it before hand, make sure it's conformant 2781 to the encoding, etc ... Very hard in practice, though in some specific 2782 cases this may make sense.</li> 2783 <li>the second decision was which encoding. From the XML spec only UTF8 and 2784 UTF16 really makes sense as being the two only encodings for which there 2785 is mandatory support. UCS-4 (32 bits fixed size encoding) could be 2786 considered an intelligent choice too since it's a direct Unicode mapping 2787 support. I selected UTF-8 on the basis of efficiency and compatibility 2788 with surrounding software: 2789 <ul> 2790 <li>UTF-8 while a bit more complex to convert from/to (i.e. slightly 2791 more costly to import and export CPU wise) is also far more compact 2792 than UTF-16 (and UCS-4) for a majority of the documents I see it used 2793 for right now (RPM RDF catalogs, advogato data, various configuration 2794 file formats, etc.) and the key point for today's computer 2795 architecture is efficient uses of caches. If one nearly double the 2796 memory requirement to store the same amount of data, this will trash 2797 caches (main memory/external caches/internal caches) and my take is 2798 that this harms the system far more than the CPU requirements needed 2799 for the conversion to UTF-8</li> 2800 <li>Most of libxml2 version 1 users were using it with straight ASCII 2801 most of the time, doing the conversion with an internal encoding 2802 requiring all their code to be rewritten was a serious show-stopper 2803 for using UTF-16 or UCS-4.</li> 2804 <li>UTF-8 is being used as the de-facto internal encoding standard for 2805 related code like the <a href="http://www.pango.org/">pango</a> 2806 upcoming Gnome text widget, and a lot of Unix code (yep another place 2807 where Unix programmer base takes a different approach from Microsoft 2808 - they are using UTF-16)</li> 2809 </ul> 2810 </li> 2811</ul> 2812 2813<p>What does this mean in practice for the libxml2 user:</p> 2814<ul> 2815 <li>xmlChar, the libxml2 data type is a byte, those bytes must be assembled 2816 as UTF-8 valid strings. The proper way to terminate an xmlChar * string 2817 is simply to append 0 byte, as usual.</li> 2818 <li>One just need to make sure that when using chars outside the ASCII set, 2819 the values has been properly converted to UTF-8</li> 2820</ul> 2821 2822<h3><a name="implemente">How is it implemented ?</a></h3> 2823 2824<p>Let's describe how all this works within libxml, basically the I18N 2825(internationalization) support get triggered only during I/O operation, i.e. 2826when reading a document or saving one. Let's look first at the reading 2827sequence:</p> 2828<ol> 2829 <li>when a document is processed, we usually don't know the encoding, a 2830 simple heuristic allows to detect UTF-16 and UCS-4 from whose where the 2831 ASCII range (0-0x7F) maps with ASCII</li> 2832 <li>the xml declaration if available is parsed, including the encoding 2833 declaration. At that point, if the autodetected encoding is different 2834 from the one declared a call to xmlSwitchEncoding() is issued.</li> 2835 <li>If there is no encoding declaration, then the input has to be in either 2836 UTF-8 or UTF-16, if it is not then at some point when processing the 2837 input, the converter/checker of UTF-8 form will raise an encoding error. 2838 You may end-up with a garbled document, or no document at all ! Example: 2839 <pre>~/XML -> /xmllint err.xml 2840err.xml:1: error: Input is not proper UTF-8, indicate encoding ! 2841<tr�s>l�</tr�s> 2842 ^ 2843err.xml:1: error: Bytes: 0xE8 0x73 0x3E 0x6C 2844<tr�s>l�</tr�s> 2845 ^</pre> 2846 </li> 2847 <li>xmlSwitchEncoding() does an encoding name lookup, canonicalize it, and 2848 then search the default registered encoding converters for that encoding. 2849 If it's not within the default set and iconv() support has been compiled 2850 it, it will ask iconv for such an encoder. If this fails then the parser 2851 will report an error and stops processing: 2852 <pre>~/XML -> /xmllint err2.xml 2853err2.xml:1: error: Unsupported encoding UnsupportedEnc 2854<?xml version="1.0" encoding="UnsupportedEnc"?> 2855 ^</pre> 2856 </li> 2857 <li>From that point the encoder processes progressively the input (it is 2858 plugged as a front-end to the I/O module) for that entity. It captures 2859 and convert on-the-fly the document to be parsed to UTF-8. The parser 2860 itself just does UTF-8 checking of this input and process it 2861 transparently. The only difference is that the encoding information has 2862 been added to the parsing context (more precisely to the input 2863 corresponding to this entity).</li> 2864 <li>The result (when using DOM) is an internal form completely in UTF-8 2865 with just an encoding information on the document node.</li> 2866</ol> 2867 2868<p>Ok then what happens when saving the document (assuming you 2869collected/built an xmlDoc DOM like structure) ? It depends on the function 2870called, xmlSaveFile() will just try to save in the original encoding, while 2871xmlSaveFileTo() and xmlSaveFileEnc() can optionally save to a given 2872encoding:</p> 2873<ol> 2874 <li>if no encoding is given, libxml2 will look for an encoding value 2875 associated to the document and if it exists will try to save to that 2876 encoding, 2877 <p>otherwise everything is written in the internal form, i.e. UTF-8</p> 2878 </li> 2879 <li>so if an encoding was specified, either at the API level or on the 2880 document, libxml2 will again canonicalize the encoding name, lookup for a 2881 converter in the registered set or through iconv. If not found the 2882 function will return an error code</li> 2883 <li>the converter is placed before the I/O buffer layer, as another kind of 2884 buffer, then libxml2 will simply push the UTF-8 serialization to through 2885 that buffer, which will then progressively be converted and pushed onto 2886 the I/O layer.</li> 2887 <li>It is possible that the converter code fails on some input, for example 2888 trying to push an UTF-8 encoded Chinese character through the UTF-8 to 2889 ISO-8859-1 converter won't work. Since the encoders are progressive they 2890 will just report the error and the number of bytes converted, at that 2891 point libxml2 will decode the offending character, remove it from the 2892 buffer and replace it with the associated charRef encoding &#123; and 2893 resume the conversion. This guarantees that any document will be saved 2894 without losses (except for markup names where this is not legal, this is 2895 a problem in the current version, in practice avoid using non-ascii 2896 characters for tags or attributes names @@). A special "ascii" encoding 2897 name is used to save documents to a pure ascii form can be used when 2898 portability is really crucial</li> 2899</ol> 2900 2901<p>Here is a few examples based on the same test document:</p> 2902<pre>~/XML -> /xmllint isolat1 2903<?xml version="1.0" encoding="ISO-8859-1"?> 2904<tr�s>l�</tr�s> 2905~/XML -> /xmllint --encode UTF-8 isolat1 2906<?xml version="1.0" encoding="UTF-8"?> 2907<très>l� �</très> 2908~/XML -> </pre> 2909 2910<p>The same processing is applied (and reuse most of the code) for HTML I18N 2911processing. Looking up and modifying the content encoding is a bit more 2912difficult since it is located in a <meta> tag under the <head>, 2913so a couple of functions htmlGetMetaEncoding() and htmlSetMetaEncoding() have 2914been provided. The parser also attempts to switch encoding on the fly when 2915detecting such a tag on input. Except for that the processing is the same 2916(and again reuses the same code).</p> 2917 2918<h3><a name="Default">Default supported encodings</a></h3> 2919 2920<p>libxml2 has a set of default converters for the following encodings 2921(located in encoding.c):</p> 2922<ol> 2923 <li>UTF-8 is supported by default (null handlers)</li> 2924 <li>UTF-16, both little and big endian</li> 2925 <li>ISO-Latin-1 (ISO-8859-1) covering most western languages</li> 2926 <li>ASCII, useful mostly for saving</li> 2927 <li>HTML, a specific handler for the conversion of UTF-8 to ASCII with HTML 2928 predefined entities like &copy; for the Copyright sign.</li> 2929</ol> 2930 2931<p>More over when compiled on an Unix platform with iconv support the full 2932set of encodings supported by iconv can be instantly be used by libxml. On a 2933linux machine with glibc-2.1 the list of supported encodings and aliases fill 29343 full pages, and include UCS-4, the full set of ISO-Latin encodings, and the 2935various Japanese ones.</p> 2936 2937<h4>Encoding aliases</h4> 2938 2939<p>From 2.2.3, libxml2 has support to register encoding names aliases. The 2940goal is to be able to parse document whose encoding is supported but where 2941the name differs (for example from the default set of names accepted by 2942iconv). The following functions allow to register and handle new aliases for 2943existing encodings. Once registered libxml2 will automatically lookup the 2944aliases when handling a document:</p> 2945<ul> 2946 <li>int xmlAddEncodingAlias(const char *name, const char *alias);</li> 2947 <li>int xmlDelEncodingAlias(const char *alias);</li> 2948 <li>const char * xmlGetEncodingAlias(const char *alias);</li> 2949 <li>void xmlCleanupEncodingAliases(void);</li> 2950</ul> 2951 2952<h3><a name="extend">How to extend the existing support</a></h3> 2953 2954<p>Well adding support for new encoding, or overriding one of the encoders 2955(assuming it is buggy) should not be hard, just write an input and output 2956conversion routines to/from UTF-8, and register them using 2957xmlNewCharEncodingHandler(name, xxxToUTF8, UTF8Toxxx), and they will be 2958called automatically if the parser(s) encounter such an encoding name 2959(register it uppercase, this will help). The description of the encoders, 2960their arguments and expected return values are described in the encoding.h 2961header.</p> 2962 2963<p>A quick note on the topic of subverting the parser to use a different 2964internal encoding than UTF-8, in some case people will absolutely want to 2965keep the internal encoding different, I think it's still possible (but the 2966encoding must be compliant with ASCII on the same subrange) though I didn't 2967tried it. The key is to override the default conversion routines (by 2968registering null encoders/decoders for your charsets), and bypass the UTF-8 2969checking of the parser by setting the parser context charset 2970(ctxt->charset) to something different than XML_CHAR_ENCODING_UTF8, but 2971there is no guarantee that this will work. You may also have some troubles 2972saving back.</p> 2973 2974<p>Basically proper I18N support is important, this requires at least 2975libxml-2.0.0, but a lot of features and corrections are really available only 2976starting 2.2.</p> 2977 2978<h2><a name="IO">I/O Interfaces</a></h2> 2979 2980<p>Table of Content:</p> 2981<ol> 2982 <li><a href="#General1">General overview</a></li> 2983 <li><a href="#basic">The basic buffer type</a></li> 2984 <li><a href="#Input">Input I/O handlers</a></li> 2985 <li><a href="#Output">Output I/O handlers</a></li> 2986 <li><a href="#entities">The entities loader</a></li> 2987 <li><a href="#Example2">Example of customized I/O</a></li> 2988</ol> 2989 2990<h3><a name="General1">General overview</a></h3> 2991 2992<p>The module <code><a 2993href="http://xmlsoft.org/html/libxml-xmlio.html">xmlIO.h</a></code> provides 2994the interfaces to the libxml2 I/O system. This consists of 4 main parts:</p> 2995<ul> 2996 <li>Entities loader, this is a routine which tries to fetch the entities 2997 (files) based on their PUBLIC and SYSTEM identifiers. The default loader 2998 don't look at the public identifier since libxml2 do not maintain a 2999 catalog. You can redefine you own entity loader by using 3000 <code>xmlGetExternalEntityLoader()</code> and 3001 <code>xmlSetExternalEntityLoader()</code>. <a href="#entities">Check the 3002 example</a>.</li> 3003 <li>Input I/O buffers which are a commodity structure used by the parser(s) 3004 input layer to handle fetching the informations to feed the parser. This 3005 provides buffering and is also a placeholder where the encoding 3006 converters to UTF8 are piggy-backed.</li> 3007 <li>Output I/O buffers are similar to the Input ones and fulfill similar 3008 task but when generating a serialization from a tree.</li> 3009 <li>A mechanism to register sets of I/O callbacks and associate them with 3010 specific naming schemes like the protocol part of the URIs. 3011 <p>This affect the default I/O operations and allows to use specific I/O 3012 handlers for certain names.</p> 3013 </li> 3014</ul> 3015 3016<p>The general mechanism used when loading http://rpmfind.net/xml.html for 3017example in the HTML parser is the following:</p> 3018<ol> 3019 <li>The default entity loader calls <code>xmlNewInputFromFile()</code> with 3020 the parsing context and the URI string.</li> 3021 <li>the URI string is checked against the existing registered handlers 3022 using their match() callback function, if the HTTP module was compiled 3023 in, it is registered and its match() function will succeeds</li> 3024 <li>the open() function of the handler is called and if successful will 3025 return an I/O Input buffer</li> 3026 <li>the parser will the start reading from this buffer and progressively 3027 fetch information from the resource, calling the read() function of the 3028 handler until the resource is exhausted</li> 3029 <li>if an encoding change is detected it will be installed on the input 3030 buffer, providing buffering and efficient use of the conversion 3031 routines</li> 3032 <li>once the parser has finished, the close() function of the handler is 3033 called once and the Input buffer and associated resources are 3034 deallocated.</li> 3035</ol> 3036 3037<p>The user defined callbacks are checked first to allow overriding of the 3038default libxml2 I/O routines.</p> 3039 3040<h3><a name="basic">The basic buffer type</a></h3> 3041 3042<p>All the buffer manipulation handling is done using the 3043<code>xmlBuffer</code> type define in <code><a 3044href="http://xmlsoft.org/html/libxml-tree.html">tree.h</a> </code>which is a 3045resizable memory buffer. The buffer allocation strategy can be selected to be 3046either best-fit or use an exponential doubling one (CPU vs. memory use 3047trade-off). The values are <code>XML_BUFFER_ALLOC_EXACT</code> and 3048<code>XML_BUFFER_ALLOC_DOUBLEIT</code>, and can be set individually or on a 3049system wide basis using <code>xmlBufferSetAllocationScheme()</code>. A number 3050of functions allows to manipulate buffers with names starting with the 3051<code>xmlBuffer...</code> prefix.</p> 3052 3053<h3><a name="Input">Input I/O handlers</a></h3> 3054 3055<p>An Input I/O handler is a simple structure 3056<code>xmlParserInputBuffer</code> containing a context associated to the 3057resource (file descriptor, or pointer to a protocol handler), the read() and 3058close() callbacks to use and an xmlBuffer. And extra xmlBuffer and a charset 3059encoding handler are also present to support charset conversion when 3060needed.</p> 3061 3062<h3><a name="Output">Output I/O handlers</a></h3> 3063 3064<p>An Output handler <code>xmlOutputBuffer</code> is completely similar to an 3065Input one except the callbacks are write() and close().</p> 3066 3067<h3><a name="entities">The entities loader</a></h3> 3068 3069<p>The entity loader resolves requests for new entities and create inputs for 3070the parser. Creating an input from a filename or an URI string is done 3071through the xmlNewInputFromFile() routine. The default entity loader do not 3072handle the PUBLIC identifier associated with an entity (if any). So it just 3073calls xmlNewInputFromFile() with the SYSTEM identifier (which is mandatory in 3074XML).</p> 3075 3076<p>If you want to hook up a catalog mechanism then you simply need to 3077override the default entity loader, here is an example:</p> 3078<pre>#include <libxml/xmlIO.h> 3079 3080xmlExternalEntityLoader defaultLoader = NULL; 3081 3082xmlParserInputPtr 3083xmlMyExternalEntityLoader(const char *URL, const char *ID, 3084 xmlParserCtxtPtr ctxt) { 3085 xmlParserInputPtr ret; 3086 const char *fileID = NULL; 3087 /* lookup for the fileID depending on ID */ 3088 3089 ret = xmlNewInputFromFile(ctxt, fileID); 3090 if (ret != NULL) 3091 return(ret); 3092 if (defaultLoader != NULL) 3093 ret = defaultLoader(URL, ID, ctxt); 3094 return(ret); 3095} 3096 3097int main(..) { 3098 ... 3099 3100 /* 3101 * Install our own entity loader 3102 */ 3103 defaultLoader = xmlGetExternalEntityLoader(); 3104 xmlSetExternalEntityLoader(xmlMyExternalEntityLoader); 3105 3106 ... 3107}</pre> 3108 3109<h3><a name="Example2">Example of customized I/O</a></h3> 3110 3111<p>This example come from <a href="http://xmlsoft.org/messages/0708.html">a 3112real use case</a>, xmlDocDump() closes the FILE * passed by the application 3113and this was a problem. The <a 3114href="http://xmlsoft.org/messages/0711.html">solution</a> was to redefine a 3115new output handler with the closing call deactivated:</p> 3116<ol> 3117 <li>First define a new I/O output allocator where the output don't close 3118 the file: 3119 <pre>xmlOutputBufferPtr 3120xmlOutputBufferCreateOwn(FILE *file, xmlCharEncodingHandlerPtr encoder) { 3121����xmlOutputBufferPtr ret; 3122���� 3123����if (xmlOutputCallbackInitialized == 0) 3124��������xmlRegisterDefaultOutputCallbacks(); 3125 3126����if (file == NULL) return(NULL); 3127����ret = xmlAllocOutputBuffer(encoder); 3128����if (ret != NULL) { 3129��������ret->context = file; 3130��������ret->writecallback = xmlFileWrite; 3131��������ret->closecallback = NULL; /* No close callback */ 3132����} 3133����return(ret); 3134} </pre> 3135 </li> 3136 <li>And then use it to save the document: 3137 <pre>FILE *f; 3138xmlOutputBufferPtr output; 3139xmlDocPtr doc; 3140int res; 3141 3142f = ... 3143doc = .... 3144 3145output = xmlOutputBufferCreateOwn(f, NULL); 3146res = xmlSaveFileTo(output, doc, NULL); 3147 </pre> 3148 </li> 3149</ol> 3150 3151<h2><a name="Catalog">Catalog support</a></h2> 3152 3153<p>Table of Content:</p> 3154<ol> 3155 <li><a href="General2">General overview</a></li> 3156 <li><a href="#definition">The definition</a></li> 3157 <li><a href="#Simple">Using catalogs</a></li> 3158 <li><a href="#Some">Some examples</a></li> 3159 <li><a href="#reference">How to tune catalog usage</a></li> 3160 <li><a href="#validate">How to debug catalog processing</a></li> 3161 <li><a href="#Declaring">How to create and maintain catalogs</a></li> 3162 <li><a href="#implemento">The implementor corner quick review of the 3163 API</a></li> 3164 <li><a href="#Other">Other resources</a></li> 3165</ol> 3166 3167<h3><a name="General2">General overview</a></h3> 3168 3169<p>What is a catalog? Basically it's a lookup mechanism used when an entity 3170(a file or a remote resource) references another entity. The catalog lookup 3171is inserted between the moment the reference is recognized by the software 3172(XML parser, stylesheet processing, or even images referenced for inclusion 3173in a rendering) and the time where loading that resource is actually 3174started.</p> 3175 3176<p>It is basically used for 3 things:</p> 3177<ul> 3178 <li>mapping from "logical" names, the public identifiers and a more 3179 concrete name usable for download (and URI). For example it can associate 3180 the logical name 3181 <p>"-//OASIS//DTD DocBook XML V4.1.2//EN"</p> 3182 <p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be 3183 downloaded</p> 3184 <p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p> 3185 </li> 3186 <li>remapping from a given URL to another one, like an HTTP indirection 3187 saying that 3188 <p>"http://www.oasis-open.org/committes/tr.xsl"</p> 3189 <p>should really be looked at</p> 3190 <p>"http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"</p> 3191 </li> 3192 <li>providing a local cache mechanism allowing to load the entities 3193 associated to public identifiers or remote resources, this is a really 3194 important feature for any significant deployment of XML or SGML since it 3195 allows to avoid the aleas and delays associated to fetching remote 3196 resources.</li> 3197</ul> 3198 3199<h3><a name="definition">The definitions</a></h3> 3200 3201<p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p> 3202<ul> 3203 <li>the older SGML catalogs, the official spec is SGML Open Technical 3204 Resolution TR9401:1997, but is better understood by reading <a 3205 href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from 3206 James Clark. This is relatively old and not the preferred mode of 3207 operation of libxml.</li> 3208 <li><a href="http://www.oasis-open.org/committees/entity/spec.html">XML 3209 Catalogs</a> is far more flexible, more recent, uses an XML syntax and 3210 should scale quite better. This is the default option of libxml.</li> 3211</ul> 3212 3213<p></p> 3214 3215<h3><a name="Simple">Using catalog</a></h3> 3216 3217<p>In a normal environment libxml2 will by default check the presence of a 3218catalog in /etc/xml/catalog, and assuming it has been correctly populated, 3219the processing is completely transparent to the document user. To take a 3220concrete example, suppose you are authoring a DocBook document, this one 3221starts with the following DOCTYPE definition:</p> 3222<pre><?xml version='1.0'?> 3223<!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN" 3224 "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd"></pre> 3225 3226<p>When validating the document with libxml, the catalog will be 3227automatically consulted to lookup the public identifier "-//Norman Walsh//DTD 3228DocBk XML V3.1.4//EN" and the system identifier 3229"http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if these entities have 3230been installed on your system and the catalogs actually point to them, libxml 3231will fetch them from the local disk.</p> 3232 3233<p style="font-size: 10pt"><strong>Note</strong>: Really don't use this 3234DOCTYPE example it's a really old version, but is fine as an example.</p> 3235 3236<p>Libxml2 will check the catalog each time that it is requested to load an 3237entity, this includes DTD, external parsed entities, stylesheets, etc ... If 3238your system is correctly configured all the authoring phase and processing 3239should use only local files, even if your document stays portable because it 3240uses the canonical public and system ID, referencing the remote document.</p> 3241 3242<h3><a name="Some">Some examples:</a></h3> 3243 3244<p>Here is a couple of fragments from XML Catalogs used in libxml2 early 3245regression tests in <code>test/catalogs</code> :</p> 3246<pre><?xml version="1.0"?> 3247<!DOCTYPE catalog PUBLIC 3248 "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3249 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3250<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 3251 <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 3252 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 3253...</pre> 3254 3255<p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are 3256written in XML, there is a specific namespace for catalog elements 3257"urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry in this 3258catalog is a <code>public</code> mapping it allows to associate a Public 3259Identifier with an URI.</p> 3260<pre>... 3261 <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/" 3262 rewritePrefix="file:///usr/share/xml/docbook/"/> 3263...</pre> 3264 3265<p>A <code>rewriteSystem</code> is a very powerful instruction, it says that 3266any URI starting with a given prefix should be looked at another URI 3267constructed by replacing the prefix with an new one. In effect this acts like 3268a cache system for a full area of the Web. In practice it is extremely useful 3269with a file prefix if you have installed a copy of those resources on your 3270local system.</p> 3271<pre>... 3272<delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //" 3273 catalog="file:///usr/share/xml/docbook.xml"/> 3274<delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML" 3275 catalog="file:///usr/share/xml/docbook.xml"/> 3276<delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML" 3277 catalog="file:///usr/share/xml/docbook.xml"/> 3278<delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/" 3279 catalog="file:///usr/share/xml/docbook.xml"/> 3280<delegateURI uriStartString="http://www.oasis-open.org/docbook/" 3281 catalog="file:///usr/share/xml/docbook.xml"/> 3282...</pre> 3283 3284<p>Delegation is the core features which allows to build a tree of catalogs, 3285easier to maintain than a single catalog, based on Public Identifier, System 3286Identifier or URI prefixes it instructs the catalog software to look up 3287entries in another resource. This feature allow to build hierarchies of 3288catalogs, the set of entries presented should be sufficient to redirect the 3289resolution of all DocBook references to the specific catalog in 3290<code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all 3291references for DocBook 4.2.1 to a specific catalog installed at the same time 3292as the DocBook resources on the local machine.</p> 3293 3294<h3><a name="reference">How to tune catalog usage:</a></h3> 3295 3296<p>The user can change the default catalog behaviour by redirecting queries 3297to its own set of catalogs, this can be done by setting the 3298<code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an 3299empty one should deactivate loading the default <code>/etc/xml/catalog</code> 3300default catalog</p> 3301 3302<h3><a name="validate">How to debug catalog processing:</a></h3> 3303 3304<p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will 3305make libxml2 output debugging informations for each catalog operations, for 3306example:</p> 3307<pre>orchis:~/XML -> xmllint --memory --noout test/ent2 3308warning: failed to load external entity "title.xml" 3309orchis:~/XML -> export XML_DEBUG_CATALOG= 3310orchis:~/XML -> xmllint --memory --noout test/ent2 3311Failed to parse catalog /etc/xml/catalog 3312Failed to parse catalog /etc/xml/catalog 3313warning: failed to load external entity "title.xml" 3314Catalogs cleanup 3315orchis:~/XML -> </pre> 3316 3317<p>The test/ent2 references an entity, running the parser from memory makes 3318the base URI unavailable and the the "title.xml" entity cannot be loaded. 3319Setting up the debug environment variable allows to detect that an attempt is 3320made to load the <code>/etc/xml/catalog</code> but since it's not present the 3321resolution fails.</p> 3322 3323<p>But the most advanced way to debug XML catalog processing is to use the 3324<strong>xmlcatalog</strong> command shipped with libxml2, it allows to load 3325catalogs and make resolution queries to see what is going on. This is also 3326used for the regression tests:</p> 3327<pre>orchis:~/XML -> /xmlcatalog test/catalogs/docbook.xml \ 3328 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3329http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3330orchis:~/XML -> </pre> 3331 3332<p>For debugging what is going on, adding one -v flags increase the verbosity 3333level to indicate the processing done (adding a second flag also indicate 3334what elements are recognized at parsing):</p> 3335<pre>orchis:~/XML -> /xmlcatalog -v test/catalogs/docbook.xml \ 3336 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3337Parsing catalog test/catalogs/docbook.xml's content 3338Found public match -//OASIS//DTD DocBook XML V4.1.2//EN 3339http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3340Catalogs cleanup 3341orchis:~/XML -> </pre> 3342 3343<p>A shell interface is also available to debug and process multiple queries 3344(and for regression tests):</p> 3345<pre>orchis:~/XML -> /xmlcatalog -shell test/catalogs/docbook.xml \ 3346 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3347> help 3348Commands available: 3349public PublicID: make a PUBLIC identifier lookup 3350system SystemID: make a SYSTEM identifier lookup 3351resolve PublicID SystemID: do a full resolver lookup 3352add 'type' 'orig' 'replace' : add an entry 3353del 'values' : remove values 3354dump: print the current catalog state 3355debug: increase the verbosity level 3356quiet: decrease the verbosity level 3357exit: quit the shell 3358> public "-//OASIS//DTD DocBook XML V4.1.2//EN" 3359http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3360> quit 3361orchis:~/XML -> </pre> 3362 3363<p>This should be sufficient for most debugging purpose, this was actually 3364used heavily to debug the XML Catalog implementation itself.</p> 3365 3366<h3><a name="Declaring">How to create and maintain</a> catalogs:</h3> 3367 3368<p>Basically XML Catalogs are XML files, you can either use XML tools to 3369manage them or use <strong>xmlcatalog</strong> for this. The basic step is 3370to create a catalog the -create option provide this facility:</p> 3371<pre>orchis:~/XML -> /xmlcatalog --create tst.xml 3372<?xml version="1.0"?> 3373<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3374 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3375<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3376orchis:~/XML -> </pre> 3377 3378<p>By default xmlcatalog does not overwrite the original catalog and save the 3379result on the standard output, this can be overridden using the -noout 3380option. The <code>-add</code> command allows to add entries in the 3381catalog:</p> 3382<pre>orchis:~/XML -> /xmlcatalog --noout --create --add "public" \ 3383 "-//OASIS//DTD DocBook XML V4.1.2//EN" \ 3384 http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml 3385orchis:~/XML -> cat tst.xml 3386<?xml version="1.0"?> 3387<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \ 3388 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3389<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 3390<public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 3391 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 3392</catalog> 3393orchis:~/XML -> </pre> 3394 3395<p>The <code>-add</code> option will always take 3 parameters even if some of 3396the XML Catalog constructs (like nextCatalog) will have only a single 3397argument, just pass a third empty string, it will be ignored.</p> 3398 3399<p>Similarly the <code>-del</code> option remove matching entries from the 3400catalog:</p> 3401<pre>orchis:~/XML -> /xmlcatalog --del \ 3402 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml 3403<?xml version="1.0"?> 3404<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3405 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3406<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3407orchis:~/XML -> </pre> 3408 3409<p>The catalog is now empty. Note that the matching of <code>-del</code> is 3410exact and would have worked in a similar fashion with the Public ID 3411string.</p> 3412 3413<p>This is rudimentary but should be sufficient to manage a not too complex 3414catalog tree of resources.</p> 3415 3416<h3><a name="implemento">The implementor corner quick review of the 3417API:</a></h3> 3418 3419<p>First, and like for every other module of libxml, there is an 3420automatically generated <a href="html/libxml-catalog.html">API page for 3421catalog support</a>.</p> 3422 3423<p>The header for the catalog interfaces should be included as:</p> 3424<pre>#include <libxml/catalog.h></pre> 3425 3426<p>The API is voluntarily kept very simple. First it is not obvious that 3427applications really need access to it since it is the default behaviour of 3428libxml2 (Note: it is possible to completely override libxml2 default catalog 3429by using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to 3430plug an application specific resolver).</p> 3431 3432<p>Basically libxml2 support 2 catalog lists:</p> 3433<ul> 3434 <li>the default one, global shared by all the application</li> 3435 <li>a per-document catalog, this one is built if the document uses the 3436 <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is 3437 associated to the parser context and destroyed when the parsing context 3438 is destroyed.</li> 3439</ul> 3440 3441<p>the document one will be used first if it exists.</p> 3442 3443<h4>Initialization routines:</h4> 3444 3445<p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be 3446used at startup to initialize the catalog, if the catalog should be 3447initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs() 3448should be called before xmlInitializeCatalog() which would otherwise do a 3449default initialization first.</p> 3450 3451<p>The xmlCatalogAddLocal() call is used by the parser to grow the document 3452own catalog list if needed.</p> 3453 3454<h4>Preferences setup:</h4> 3455 3456<p>The XML Catalog spec requires the possibility to select default 3457preferences between public and system delegation, 3458xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and 3459xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should 3460be forbidden, allowed for global catalog, for document catalog or both, the 3461default is to allow both.</p> 3462 3463<p>And of course xmlCatalogSetDebug() allows to generate debug messages 3464(through the xmlGenericError() mechanism).</p> 3465 3466<h4>Querying routines:</h4> 3467 3468<p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic() 3469and xmlCatalogResolveURI() are relatively explicit if you read the XML 3470Catalog specification they correspond to section 7 algorithms, they should 3471also work if you have loaded an SGML catalog with a simplified semantic.</p> 3472 3473<p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but 3474operate on the document catalog list</p> 3475 3476<h4>Cleanup and Miscellaneous:</h4> 3477 3478<p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is 3479the per-document equivalent.</p> 3480 3481<p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the 3482first catalog in the global list, and xmlCatalogDump() allows to dump a 3483catalog state, those routines are primarily designed for xmlcatalog, I'm not 3484sure that exposing more complex interfaces (like navigation ones) would be 3485really useful.</p> 3486 3487<p>The xmlParseCatalogFile() is a function used to load XML Catalog files, 3488it's similar as xmlParseFile() except it bypass all catalog lookups, it's 3489provided because this functionality may be useful for client tools.</p> 3490 3491<h4>threaded environments:</h4> 3492 3493<p>Since the catalog tree is built progressively, some care has been taken to 3494try to avoid troubles in multithreaded environments. The code is now thread 3495safe assuming that the libxml2 library has been compiled with threads 3496support.</p> 3497 3498<p></p> 3499 3500<h3><a name="Other">Other resources</a></h3> 3501 3502<p>The XML Catalog specification is relatively recent so there isn't much 3503literature to point at:</p> 3504<ul> 3505 <li>You can find a good rant from Norm Walsh about <a 3506 href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the 3507 need for catalogs</a>, it provides a lot of context informations even if 3508 I don't agree with everything presented. Norm also wrote a more recent 3509 article <a 3510 href="http://wwws.sun.com/software/xml/developers/resolver/article/">XML 3511 entities and URI resolvers</a> describing them.</li> 3512 <li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML 3513 catalog proposal</a> from John Cowan</li> 3514 <li>The <a href="http://www.rddl.org/">Resource Directory Description 3515 Language</a> (RDDL) another catalog system but more oriented toward 3516 providing metadata for XML namespaces.</li> 3517 <li>the page from the OASIS Technical <a 3518 href="http://www.oasis-open.org/committees/entity/">Committee on Entity 3519 Resolution</a> who maintains XML Catalog, you will find pointers to the 3520 specification update, some background and pointers to others tools 3521 providing XML Catalog support</li> 3522 <li>Here is a <a href="buildDocBookCatalog">shell script</a> to generate 3523 XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/ 3524 directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on 3525 the resources found on the system. Otherwise it will just create 3526 ~/xmlcatalog and ~/dbkxmlcatalog and doing: 3527 <p><code>export XML_CATALOG_FILES=$HOME/xmlcatalog</code></p> 3528 <p>should allow to process DocBook documentations without requiring 3529 network accesses for the DTD or stylesheets</p> 3530 </li> 3531 <li>I have uploaded <a href="ftp://xmlsoft.org/test/dbk412catalog.tar.gz">a 3532 small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems 3533 to work fine for me too</li> 3534 <li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog 3535 manual page</a></li> 3536</ul> 3537 3538<p>If you have suggestions for corrections or additions, simply contact 3539me:</p> 3540 3541<h2><a name="library">The parser interfaces</a></h2> 3542 3543<p>This section is directly intended to help programmers getting bootstrapped 3544using the XML tollkit from the C language. It is not intended to be 3545extensive. I hope the automatically generated documents will provide the 3546completeness required, but as a separate set of documents. The interfaces of 3547the XML parser are by principle low level, Those interested in a higher level 3548API should <a href="#DOM">look at DOM</a>.</p> 3549 3550<p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are 3551separated from the <a href="html/libxml-htmlparser.html">HTML parser 3552interfaces</a>. Let's have a look at how the XML parser can be called:</p> 3553 3554<h3><a name="Invoking">Invoking the parser : the pull method</a></h3> 3555 3556<p>Usually, the first thing to do is to read an XML input. The parser accepts 3557documents either from in-memory strings or from files. The functions are 3558defined in "parser.h":</p> 3559<dl> 3560 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> 3561 <dd><p>Parse a null-terminated string containing the document.</p> 3562 </dd> 3563</dl> 3564<dl> 3565 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> 3566 <dd><p>Parse an XML document contained in a (possibly compressed) 3567 file.</p> 3568 </dd> 3569</dl> 3570 3571<p>The parser returns a pointer to the document structure (or NULL in case of 3572failure).</p> 3573 3574<h3 id="Invoking1">Invoking the parser: the push method</h3> 3575 3576<p>In order for the application to keep the control when the document is 3577being fetched (which is common for GUI based programs) libxml2 provides a 3578push interface, too, as of version 1.8.3. Here are the interface 3579functions:</p> 3580<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, 3581 void *user_data, 3582 const char *chunk, 3583 int size, 3584 const char *filename); 3585int xmlParseChunk (xmlParserCtxtPtr ctxt, 3586 const char *chunk, 3587 int size, 3588 int terminate);</pre> 3589 3590<p>and here is a simple example showing how to use the interface:</p> 3591<pre> FILE *f; 3592 3593 f = fopen(filename, "r"); 3594 if (f != NULL) { 3595 int res, size = 1024; 3596 char chars[1024]; 3597 xmlParserCtxtPtr ctxt; 3598 3599 res = fread(chars, 1, 4, f); 3600 if (res > 0) { 3601 ctxt = xmlCreatePushParserCtxt(NULL, NULL, 3602 chars, res, filename); 3603 while ((res = fread(chars, 1, size, f)) > 0) { 3604 xmlParseChunk(ctxt, chars, res, 0); 3605 } 3606 xmlParseChunk(ctxt, chars, 0, 1); 3607 doc = ctxt->myDoc; 3608 xmlFreeParserCtxt(ctxt); 3609 } 3610 }</pre> 3611 3612<p>The HTML parser embedded into libxml2 also has a push interface; the 3613functions are just prefixed by "html" rather than "xml".</p> 3614 3615<h3 id="Invoking2">Invoking the parser: the SAX interface</h3> 3616 3617<p>The tree-building interface makes the parser memory-hungry, first loading 3618the document in memory and then building the tree itself. Reading a document 3619without building the tree is possible using the SAX interfaces (see SAX.h and 3620<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James 3621Henstridge's documentation</a>). Note also that the push interface can be 3622limited to SAX: just use the two first arguments of 3623<code>xmlCreatePushParserCtxt()</code>.</p> 3624 3625<h3><a name="Building">Building a tree from scratch</a></h3> 3626 3627<p>The other way to get an XML tree in memory is by building it. Basically 3628there is a set of functions dedicated to building new elements. (These are 3629also described in <libxml/tree.h>.) For example, here is a piece of 3630code that produces the XML document used in the previous examples:</p> 3631<pre> #include <libxml/tree.h> 3632 xmlDocPtr doc; 3633 xmlNodePtr tree, subtree; 3634 3635 doc = xmlNewDoc("1.0"); 3636 doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); 3637 xmlSetProp(doc->children, "prop1", "gnome is great"); 3638 xmlSetProp(doc->children, "prop2", "& linux too"); 3639 tree = xmlNewChild(doc->children, NULL, "head", NULL); 3640 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); 3641 tree = xmlNewChild(doc->children, NULL, "chapter", NULL); 3642 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); 3643 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); 3644 subtree = xmlNewChild(tree, NULL, "image", NULL); 3645 xmlSetProp(subtree, "href", "linus.gif");</pre> 3646 3647<p>Not really rocket science ...</p> 3648 3649<h3><a name="Traversing">Traversing the tree</a></h3> 3650 3651<p>Basically by <a href="html/libxml-tree.html">including "tree.h"</a> your 3652code has access to the internal structure of all the elements of the tree. 3653The names should be somewhat simple like <strong>parent</strong>, 3654<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>, 3655<strong>properties</strong>, etc... For example, still with the previous 3656example:</p> 3657<pre><code>doc->children->children->children</code></pre> 3658 3659<p>points to the title element,</p> 3660<pre>doc->children->children->next->children->children</pre> 3661 3662<p>points to the text node containing the chapter title "The Linux 3663adventure".</p> 3664 3665<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be 3666present before the document root, so <code>doc->children</code> may point 3667to an element which is not the document Root Element; a function 3668<code>xmlDocGetRootElement()</code> was added for this purpose.</p> 3669 3670<h3><a name="Modifying">Modifying the tree</a></h3> 3671 3672<p>Functions are provided for reading and writing the document content. Here 3673is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p> 3674<dl> 3675 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const 3676 xmlChar *value);</code></dt> 3677 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. 3678 The value can be NULL.</p> 3679 </dd> 3680</dl> 3681<dl> 3682 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar 3683 *name);</code></dt> 3684 <dd><p>This function returns a pointer to new copy of the property 3685 content. Note that the user must deallocate the result.</p> 3686 </dd> 3687</dl> 3688 3689<p>Two functions are provided for reading and writing the text associated 3690with elements:</p> 3691<dl> 3692 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar 3693 *value);</code></dt> 3694 <dd><p>This function takes an "external" string and converts it to one 3695 text node or possibly to a list of entity and text nodes. All 3696 non-predefined entity references like &Gnome; will be stored 3697 internally as entity nodes, hence the result of the function may not be 3698 a single node.</p> 3699 </dd> 3700</dl> 3701<dl> 3702 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int 3703 inLine);</code></dt> 3704 <dd><p>This function is the inverse of 3705 <code>xmlStringGetNodeList()</code>. It generates a new string 3706 containing the content of the text and entity nodes. Note the extra 3707 argument inLine. If this argument is set to 1, the function will expand 3708 entity references. For example, instead of returning the &Gnome; 3709 XML encoding in the string, it will substitute it with its value (say, 3710 "GNU Network Object Model Environment").</p> 3711 </dd> 3712</dl> 3713 3714<h3><a name="Saving">Saving a tree</a></h3> 3715 3716<p>Basically 3 options are possible:</p> 3717<dl> 3718 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int 3719 *size);</code></dt> 3720 <dd><p>Returns a buffer into which the document has been saved.</p> 3721 </dd> 3722</dl> 3723<dl> 3724 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> 3725 <dd><p>Dumps a document to an open file descriptor.</p> 3726 </dd> 3727</dl> 3728<dl> 3729 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> 3730 <dd><p>Saves the document to a file. In this case, the compression 3731 interface is triggered if it has been turned on.</p> 3732 </dd> 3733</dl> 3734 3735<h3><a name="Compressio">Compression</a></h3> 3736 3737<p>The library transparently handles compression when doing file-based 3738accesses. The level of compression on saves can be turned on either globally 3739or individually for one file:</p> 3740<dl> 3741 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> 3742 <dd><p>Gets the document compression ratio (0-9).</p> 3743 </dd> 3744</dl> 3745<dl> 3746 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> 3747 <dd><p>Sets the document compression ratio.</p> 3748 </dd> 3749</dl> 3750<dl> 3751 <dt><code>int xmlGetCompressMode(void);</code></dt> 3752 <dd><p>Gets the default compression ratio.</p> 3753 </dd> 3754</dl> 3755<dl> 3756 <dt><code>void xmlSetCompressMode(int mode);</code></dt> 3757 <dd><p>Sets the default compression ratio.</p> 3758 </dd> 3759</dl> 3760 3761<h2><a name="Entities">Entities or no entities</a></h2> 3762 3763<p>Entities in principle are similar to simple C macros. An entity defines an 3764abbreviation for a given string that you can reuse many times throughout the 3765content of your document. Entities are especially useful when a given string 3766may occur frequently within a document, or to confine the change needed to a 3767document to a restricted area in the internal subset of the document (at the 3768beginning). Example:</p> 3769<pre>1 <?xml version="1.0"?> 37702 <!DOCTYPE EXAMPLE SYSTEM "example.dtd" [ 37713 <!ENTITY xml "Extensible Markup Language"> 37724 ]> 37735 <EXAMPLE> 37746 &xml; 37757 </EXAMPLE></pre> 3776 3777<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing 3778its name with '&' and following it by ';' without any spaces added. There 3779are 5 predefined entities in libxml2 allowing you to escape characters with 3780predefined meaning in some parts of the xml document content: 3781<strong>&lt;</strong> for the character '<', <strong>&gt;</strong> 3782for the character '>', <strong>&apos;</strong> for the character ''', 3783<strong>&quot;</strong> for the character '"', and 3784<strong>&amp;</strong> for the character '&'.</p> 3785 3786<p>One of the problems related to entities is that you may want the parser to 3787substitute an entity's content so that you can see the replacement text in 3788your application. Or you may prefer to keep entity references as such in the 3789content to be able to save the document back without losing this usually 3790precious information (if the user went through the pain of explicitly 3791defining entities, he may have a a rather negative attitude if you blindly 3792substitute them as saving time). The <a 3793href="html/libxml-parser.html#xmlSubstituteEntitiesDefault">xmlSubstituteEntitiesDefault()</a> 3794function allows you to check and change the behaviour, which is to not 3795substitute entities by default.</p> 3796 3797<p>Here is the DOM tree built by libxml2 for the previous document in the 3798default case:</p> 3799<pre>/gnome/src/gnome-xml -> /xmllint --debug test/ent1 3800DOCUMENT 3801version=1.0 3802 ELEMENT EXAMPLE 3803 TEXT 3804 content= 3805 ENTITY_REF 3806 INTERNAL_GENERAL_ENTITY xml 3807 content=Extensible Markup Language 3808 TEXT 3809 content=</pre> 3810 3811<p>And here is the result when substituting entities:</p> 3812<pre>/gnome/src/gnome-xml -> /tester --debug --noent test/ent1 3813DOCUMENT 3814version=1.0 3815 ELEMENT EXAMPLE 3816 TEXT 3817 content= Extensible Markup Language</pre> 3818 3819<p>So, entities or no entities? Basically, it depends on your use case. I 3820suggest that you keep the non-substituting default behaviour and avoid using 3821entities in your XML document or data if you are not willing to handle the 3822entity references elements in the DOM tree.</p> 3823 3824<p>Note that at save time libxml2 enforces the conversion of the predefined 3825entities where necessary to prevent well-formedness problems, and will also 3826transparently replace those with chars (i.e. it will not generate entity 3827reference elements in the DOM tree or call the reference() SAX callback when 3828finding them in the input).</p> 3829 3830<p><span style="background-color: #FF0000">WARNING</span>: handling entities 3831on top of the libxml2 SAX interface is difficult!!! If you plan to use 3832non-predefined entities in your documents, then the learning curve to handle 3833then using the SAX API may be long. If you plan to use complex documents, I 3834strongly suggest you consider using the DOM interface instead and let libxml 3835deal with the complexity rather than trying to do it yourself.</p> 3836 3837<h2><a name="Namespaces">Namespaces</a></h2> 3838 3839<p>The libxml2 library implements <a 3840href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by 3841recognizing namespace constructs in the input, and does namespace lookup 3842automatically when building the DOM tree. A namespace declaration is 3843associated with an in-memory structure and all elements or attributes within 3844that namespace point to it. Hence testing the namespace is a simple and fast 3845equality operation at the user level.</p> 3846 3847<p>I suggest that people using libxml2 use a namespace, and declare it in the 3848root element of their document as the default namespace. Then they don't need 3849to use the prefix in the content but we will have a basis for future semantic 3850refinement and merging of data from different sources. This doesn't increase 3851the size of the XML output significantly, but significantly increases its 3852value in the long-term. Example:</p> 3853<pre><mydoc xmlns="http://mydoc.example.org/schemas/"> 3854 <elem1>...</elem1> 3855 <elem2>...</elem2> 3856</mydoc></pre> 3857 3858<p>The namespace value has to be an absolute URL, but the URL doesn't have to 3859point to any existing resource on the Web. It will bind all the element and 3860attributes with that URL. I suggest to use an URL within a domain you 3861control, and that the URL should contain some kind of version information if 3862possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a 3863good namespace scheme.</p> 3864 3865<p>Then when you load a file, make sure that a namespace carrying the 3866version-independent prefix is installed on the root element of your document, 3867and if the version information don't match something you know, warn the user 3868and be liberal in what you accept as the input. Also do *not* try to base 3869namespace checking on the prefix value. <foo:text> may be exactly the 3870same as <bar:text> in another document. What really matters is the URI 3871associated with the element or the attribute, not the prefix string (which is 3872just a shortcut for the full URI). In libxml, element and attributes have an 3873<code>ns</code> field pointing to an xmlNs structure detailing the namespace 3874prefix and its URI.</p> 3875 3876<p>@@Interfaces@@</p> 3877<pre>xmlNodePtr node; 3878if(!strncmp(node->name,"mytag",5) 3879 && node->ns 3880 && !strcmp(node->ns->href,"http://www.mysite.com/myns/1.0")) { 3881 ... 3882}</pre> 3883 3884<p>Usually people object to using namespaces together with validity checking. 3885I will try to make sure that using namespaces won't break validity checking, 3886so even if you plan to use or currently are using validation I strongly 3887suggest adding namespaces to your document. A default namespace scheme 3888<code>xmlns="http://...."</code> should not break validity even on less 3889flexible parsers. Using namespaces to mix and differentiate content coming 3890from multiple DTDs will certainly break current validation schemes. To check 3891such documents one needs to use schema-validation, which is supported in 3892libxml2 as well. See <a href="http://www.relaxng.org/">relagx-ng</a> and <a 3893href="http://www.w3c.org/XML/Schema">w3c-schema</a>.</p> 3894 3895<h2><a name="Upgrading">Upgrading 1.x code</a></h2> 3896 3897<p>Incompatible changes:</p> 3898 3899<p>Version 2 of libxml2 is the first version introducing serious backward 3900incompatible changes. The main goals were:</p> 3901<ul> 3902 <li>a general cleanup. A number of mistakes inherited from the very early 3903 versions couldn't be changed due to compatibility constraints. Example 3904 the "childs" element in the nodes.</li> 3905 <li>Uniformization of the various nodes, at least for their header and link 3906 parts (doc, parent, children, prev, next), the goal is a simpler 3907 programming model and simplifying the task of the DOM implementors.</li> 3908 <li>better conformances to the XML specification, for example version 1.x 3909 had an heuristic to try to detect ignorable white spaces. As a result the 3910 SAX event generated were ignorableWhitespace() while the spec requires 3911 character() in that case. This also mean that a number of DOM node 3912 containing blank text may populate the DOM tree which were not present 3913 before.</li> 3914</ul> 3915 3916<h3>How to fix libxml-1.x code:</h3> 3917 3918<p>So client code of libxml designed to run with version 1.x may have to be 3919changed to compile against version 2.x of libxml. Here is a list of changes 3920that I have collected, they may not be sufficient, so in case you find other 3921change which are required, <a href="mailto:Daniel.Veillard@w3.org">drop me a 3922mail</a>:</p> 3923<ol> 3924 <li>The package name have changed from libxml to libxml2, the library name 3925 is now -lxml2 . There is a new xml2-config script which should be used to 3926 select the right parameters libxml2</li> 3927 <li>Node <strong>childs</strong> field has been renamed 3928 <strong>children</strong> so s/childs/children/g should be applied 3929 (probability of having "childs" anywhere else is close to 0+</li> 3930 <li>The document don't have anymore a <strong>root</strong> element it has 3931 been replaced by <strong>children</strong> and usually you will get a 3932 list of element here. For example a Dtd element for the internal subset 3933 and it's declaration may be found in that list, as well as processing 3934 instructions or comments found before or after the document root element. 3935 Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of 3936 a document. Alternatively if you are sure to not reference DTDs nor have 3937 PIs or comments before or after the root element 3938 s/->root/->children/g will probably do it.</li> 3939 <li>The white space issue, this one is more complex, unless special case of 3940 validating parsing, the line breaks and spaces usually used for indenting 3941 and formatting the document content becomes significant. So they are 3942 reported by SAX and if your using the DOM tree, corresponding nodes are 3943 generated. Too approach can be taken: 3944 <ol> 3945 <li>lazy one, use the compatibility call 3946 <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are 3947 relying on a special (and possibly broken) set of heuristics of 3948 libxml to detect ignorable blanks. Don't complain if it breaks or 3949 make your application not 100% clean w.r.t. to it's input.</li> 3950 <li>the Right Way: change you code to accept possibly insignificant 3951 blanks characters, or have your tree populated with weird blank text 3952 nodes. You can spot them using the commodity function 3953 <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank 3954 nodes.</li> 3955 </ol> 3956 <p>Note also that with the new default the output functions don't add any 3957 extra indentation when saving a tree in order to be able to round trip 3958 (read and save) without inflating the document with extra formatting 3959 chars.</p> 3960 </li> 3961 <li>The include path has changed to $prefix/libxml/ and the includes 3962 themselves uses this new prefix in includes instructions... If you are 3963 using (as expected) the 3964 <pre>xml2-config --cflags</pre> 3965 <p>output to generate you compile commands this will probably work out of 3966 the box</p> 3967 </li> 3968 <li>xmlDetectCharEncoding takes an extra argument indicating the length in 3969 byte of the head of the document available for character detection.</li> 3970</ol> 3971 3972<h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3> 3973 3974<p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released 3975to allow smooth upgrade of existing libxml v1code while retaining 3976compatibility. They offers the following:</p> 3977<ol> 3978 <li>similar include naming, one should use 3979 <strong>#include<libxml/...></strong> in both cases.</li> 3980 <li>similar identifiers defined via macros for the child and root fields: 3981 respectively <strong>xmlChildrenNode</strong> and 3982 <strong>xmlRootNode</strong></li> 3983 <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be 3984 inserted once in the client code</li> 3985</ol> 3986 3987<p>So the roadmap to upgrade your existing libxml applications is the 3988following:</p> 3989<ol> 3990 <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> 3991 <li>find all occurrences where the xmlDoc <strong>root</strong> field is 3992 used and change it to <strong>xmlRootNode</strong></li> 3993 <li>similarly find all occurrences where the xmlNode 3994 <strong>childs</strong> field is used and change it to 3995 <strong>xmlChildrenNode</strong></li> 3996 <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your 3997 <strong>main()</strong> or in the library init entry point</li> 3998 <li>Recompile, check compatibility, it should still work</li> 3999 <li>Change your configure script to look first for xml2-config and fall 4000 back using xml-config . Use the --cflags and --libs output of the command 4001 as the Include and Linking parameters needed to use libxml.</li> 4002 <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and 4003 libxml-devel-1.8.y can be kept simultaneously)</li> 4004 <li>remove your config.cache, relaunch your configuration mechanism, and 4005 recompile, if steps 2 and 3 were done right it should compile as-is</li> 4006 <li>Test that your application is still running correctly, if not this may 4007 be due to extra empty nodes due to formating spaces being kept in libxml2 4008 contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your 4009 code before calling the parser (next to 4010 <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li> 4011</ol> 4012 4013<p>Following those steps should work. It worked for some of my own code.</p> 4014 4015<p>Let me put some emphasis on the fact that there is far more changes from 4016libxml 1.x to 2.x than the ones you may have to patch for. The overall code 4017has been considerably cleaned up and the conformance to the XML specification 4018has been drastically improved too. Don't take those changes as an excuse to 4019not upgrade, it may cost a lot on the long term ...</p> 4020 4021<h2><a name="Thread">Thread safety</a></h2> 4022 4023<p>Starting with 2.4.7, libxml2 makes provisions to ensure that concurrent 4024threads can safely work in parallel parsing different documents. There is 4025however a couple of things to do to ensure it:</p> 4026<ul> 4027 <li>configure the library accordingly using the --with-threads options</li> 4028 <li>call xmlInitParser() in the "main" thread before using any of the 4029 libxml2 API (except possibly selecting a different memory allocator)</li> 4030</ul> 4031 4032<p>Note that the thread safety cannot be ensured for multiple threads sharing 4033the same document, the locking must be done at the application level, libxml 4034exports a basic mutex and reentrant mutexes API in <libxml/threads.h>. 4035The parts of the library checked for thread safety are:</p> 4036<ul> 4037 <li>concurrent loading</li> 4038 <li>file access resolution</li> 4039 <li>catalog access</li> 4040 <li>catalog building</li> 4041 <li>entities lookup/accesses</li> 4042 <li>validation</li> 4043 <li>global variables per-thread override</li> 4044 <li>memory handling</li> 4045</ul> 4046 4047<p>XPath is supposed to be thread safe now, but this wasn't tested 4048seriously.</p> 4049 4050<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2> 4051 4052<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document 4053Object Model</em>; this is an API for accessing XML or HTML structured 4054documents. Native support for DOM in Gnome is on the way (module gnome-dom), 4055and will be based on gnome-xml. This will be a far cleaner interface to 4056manipulate XML files within Gnome since it won't expose the internal 4057structure.</p> 4058 4059<p>The current DOM implementation on top of libxml2 is the <a 4060href="http://cvs.gnome.org/lxr/source/gdome2/">gdome2 Gnome module</a>, this 4061is a full DOM interface, thanks to Paolo Casarini, check the <a 4062href="http://www.cs.unibo.it/~casarini/gdome2/">Gdome2 homepage</a> for more 4063informations.</p> 4064 4065<h2><a name="Example"></a><a name="real">A real example</a></h2> 4066 4067<p>Here is a real size example, where the actual content of the application 4068data is not kept in the DOM tree but uses internal structures. It is based on 4069a proposal to keep a database of jobs related to Gnome, with an XML based 4070storage structure. Here is an <a href="gjobs.xml">XML encoded jobs 4071base</a>:</p> 4072<pre><?xml version="1.0"?> 4073<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"> 4074 <gjob:Jobs> 4075 4076 <gjob:Job> 4077 <gjob:Project ID="3"/> 4078 <gjob:Application>GBackup</gjob:Application> 4079 <gjob:Category>Development</gjob:Category> 4080 4081 <gjob:Update> 4082 <gjob:Status>Open</gjob:Status> 4083 <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified> 4084 <gjob:Salary>USD 0.00</gjob:Salary> 4085 </gjob:Update> 4086 4087 <gjob:Developers> 4088 <gjob:Developer> 4089 </gjob:Developer> 4090 </gjob:Developers> 4091 4092 <gjob:Contact> 4093 <gjob:Person>Nathan Clemons</gjob:Person> 4094 <gjob:Email>nathan@windsofstorm.net</gjob:Email> 4095 <gjob:Company> 4096 </gjob:Company> 4097 <gjob:Organisation> 4098 </gjob:Organisation> 4099 <gjob:Webpage> 4100 </gjob:Webpage> 4101 <gjob:Snailmail> 4102 </gjob:Snailmail> 4103 <gjob:Phone> 4104 </gjob:Phone> 4105 </gjob:Contact> 4106 4107 <gjob:Requirements> 4108 The program should be released as free software, under the GPL. 4109 </gjob:Requirements> 4110 4111 <gjob:Skills> 4112 </gjob:Skills> 4113 4114 <gjob:Details> 4115 A GNOME based system that will allow a superuser to configure 4116 compressed and uncompressed files and/or file systems to be backed 4117 up with a supported media in the system. This should be able to 4118 perform via find commands generating a list of files that are passed 4119 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine 4120 or via operations performed on the filesystem itself. Email 4121 notification and GUI status display very important. 4122 </gjob:Details> 4123 4124 </gjob:Job> 4125 4126 </gjob:Jobs> 4127</gjob:Helping></pre> 4128 4129<p>While loading the XML file into an internal DOM tree is a matter of 4130calling only a couple of functions, browsing the tree to gather the data and 4131generate the internal structures is harder, and more error prone.</p> 4132 4133<p>The suggested principle is to be tolerant with respect to the input 4134structure. For example, the ordering of the attributes is not significant, 4135the XML specification is clear about it. It's also usually a good idea not to 4136depend on the order of the children of a given node, unless it really makes 4137things harder. Here is some code to parse the information for a person:</p> 4138<pre>/* 4139 * A person record 4140 */ 4141typedef struct person { 4142 char *name; 4143 char *email; 4144 char *company; 4145 char *organisation; 4146 char *smail; 4147 char *webPage; 4148 char *phone; 4149} person, *personPtr; 4150 4151/* 4152 * And the code needed to parse it 4153 */ 4154personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 4155 personPtr ret = NULL; 4156 4157DEBUG("parsePerson\n"); 4158 /* 4159 * allocate the struct 4160 */ 4161 ret = (personPtr) malloc(sizeof(person)); 4162 if (ret == NULL) { 4163 fprintf(stderr,"out of memory\n"); 4164 return(NULL); 4165 } 4166 memset(ret, 0, sizeof(person)); 4167 4168 /* We don't care what the top level element name is */ 4169 cur = cur->xmlChildrenNode; 4170 while (cur != NULL) { 4171 if ((!strcmp(cur->name, "Person")) && (cur->ns == ns)) 4172 ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4173 if ((!strcmp(cur->name, "Email")) && (cur->ns == ns)) 4174 ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4175 cur = cur->next; 4176 } 4177 4178 return(ret); 4179}</pre> 4180 4181<p>Here are a couple of things to notice:</p> 4182<ul> 4183 <li>Usually a recursive parsing style is the more convenient one: XML data 4184 is by nature subject to repetitive constructs and usually exhibits highly 4185 structured patterns.</li> 4186 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, 4187 i.e. the pointer to the global XML document and the namespace reserved to 4188 the application. Document wide information are needed for example to 4189 decode entities and it's a good coding practice to define a namespace for 4190 your application set of data and test that the element and attributes 4191 you're analyzing actually pertains to your application space. This is 4192 done by a simple equality test (cur->ns == ns).</li> 4193 <li>To retrieve text and attributes value, you can use the function 4194 <em>xmlNodeListGetString</em> to gather all the text and entity reference 4195 nodes generated by the DOM output and produce an single text string.</li> 4196</ul> 4197 4198<p>Here is another piece of code used to parse another level of the 4199structure:</p> 4200<pre>#include <libxml/tree.h> 4201/* 4202 * a Description for a Job 4203 */ 4204typedef struct job { 4205 char *projectID; 4206 char *application; 4207 char *category; 4208 personPtr contact; 4209 int nbDevelopers; 4210 personPtr developers[100]; /* using dynamic alloc is left as an exercise */ 4211} job, *jobPtr; 4212 4213/* 4214 * And the code needed to parse it 4215 */ 4216jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 4217 jobPtr ret = NULL; 4218 4219DEBUG("parseJob\n"); 4220 /* 4221 * allocate the struct 4222 */ 4223 ret = (jobPtr) malloc(sizeof(job)); 4224 if (ret == NULL) { 4225 fprintf(stderr,"out of memory\n"); 4226 return(NULL); 4227 } 4228 memset(ret, 0, sizeof(job)); 4229 4230 /* We don't care what the top level element name is */ 4231 cur = cur->xmlChildrenNode; 4232 while (cur != NULL) { 4233 4234 if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) { 4235 ret->projectID = xmlGetProp(cur, "ID"); 4236 if (ret->projectID == NULL) { 4237 fprintf(stderr, "Project has no ID\n"); 4238 } 4239 } 4240 if ((!strcmp(cur->name, "Application")) && (cur->ns == ns)) 4241 ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4242 if ((!strcmp(cur->name, "Category")) && (cur->ns == ns)) 4243 ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4244 if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns)) 4245 ret->contact = parsePerson(doc, ns, cur); 4246 cur = cur->next; 4247 } 4248 4249 return(ret); 4250}</pre> 4251 4252<p>Once you are used to it, writing this kind of code is quite simple, but 4253boring. Ultimately, it could be possible to write stubbers taking either C 4254data structure definitions, a set of XML examples or an XML DTD and produce 4255the code needed to import and export the content between C data and XML 4256storage. This is left as an exercise to the reader :-)</p> 4257 4258<p>Feel free to use <a href="example/gjobread.c">the code for the full C 4259parsing example</a> as a template, it is also available with Makefile in the 4260Gnome CVS base under gnome-xml/example</p> 4261 4262<h2><a name="Contributi">Contributions</a></h2> 4263<ul> 4264 <li>Bjorn Reese, William Brack and Thomas Broyer have provided a number of 4265 patches, Gary Pennington worked on the validation API, threading support 4266 and Solaris port.</li> 4267 <li>John Fleck helps maintaining the documentation and man pages.</li> 4268 <li><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the 4269 maintainer of the Windows port, <a 4270 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 4271 binaries</a></li> 4272 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 4273 <a href="http://garypennington.net/libxml2/">Solaris binaries</a></li> 4274 <li><a 4275 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 4276 Sergeant</a> developed <a 4277 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 4278 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 4279 application server</a></li> 4280 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> and <a 4281 href="mailto:geertk@ai.rug.nl">Geert Kloosterman</a> provide <a 4282 href="libxml-doc.el">an emacs module</a> to lookup libxml(2) functions 4283 documentation</li> 4284 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a 4285 href="http://xmlsoft.org/messages/0488.html">man pages</a></li> 4286 <li>there is a module for <a 4287 href="http://acs-misc.sourceforge.net/nsxml.html">libxml/libxslt support 4288 in OpenNSD/AOLServer</a></li> 4289 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provided the 4290 first version of libxml/libxslt <a 4291 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li> 4292 <li>Petr Kozelka provides <a 4293 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 4294 libxml2</a> with Kylix and Delphi and other Pascal compilers</li> 4295 <li><a href="mailto:aleksey@aleksey.com">Aleksey Sanin</a> implemented the 4296 <a href="http://www.w3.org/Signature/">XML Canonicalization and XML 4297 Digital Signature</a> <a 4298 href="http://www.aleksey.com/xmlsec/">implementations for libxml2</a></li> 4299 <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a>, <a 4300 href="http://www.zveno.com/">Zveno</a> and contributors maintain <a 4301 href="http://tclxml.sourceforge.net/">tcl bindings for libxml2 and 4302 libxslt</a>, as well as <a 4303 href="http://tclxml.sf.net/tkxmllint.html">tkxmllint</a> a GUI for 4304 xmllint and <a href="http://tclxml.sf.net/tkxsltproc.html">tkxsltproc</a> 4305 a GUI for xsltproc.</li> 4306</ul> 4307 4308<p></p> 4309</body> 4310</html> 4311
