xml.html revision 9b6fd30f6468773edad65a27478daffed60d2a2f
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 2 "http://www.w3.org/TR/html4/loose.dtd"> 3<html> 4<head> 5 <title>The XML C library for Gnome</title> 6 <meta name="GENERATOR" content="amaya 5.1"> 7 <meta http-equiv="Content-Type" content="text/html"> 8</head> 9 10<body bgcolor="#ffffff"> 11<h1 align="center">The XML C library for Gnome</h1> 12 13<h1>Note: this is the flat content of the <a href="index.html">web 14site</a></h1> 15 16<h1 style="text-align: center">libxml, a.k.a. gnome-xml</h1> 17 18<p></p> 19 20<p>Libxml is the XML C library developped for the Gnome project. XML itself 21is a metalanguage to design markup languages, i.e. text language where 22semantic and structure are added to the content using extra "markup" 23information enclosed between angle bracket. HTML is the most well-known 24markup language. Though the library is written in C <a href="python.html">a 25variety of language binding</a> makes it available in other environments.</p> 26 27<p>Libxml2 implements a number of existing standards related to markup 28languages:</p> 29<ul> 30 <li>the XML standard: <a 31 href="http://www.w3.org/TR/REC-xml">http://www.w3.org/TR/REC-xml</a></li> 32 <li>Namespaces in XML: <a 33 href="http://www.w3.org/TR/REC-xml-names/">http://www.w3.org/TR/REC-xml-names/</a></li> 34 <li>XML Base: <a 35 href="http://www.w3.org/TR/xmlbase/">http://www.w3.org/TR/xmlbase/</a></li> 36 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc2396.txt">RFC 2396</a> : 37 Uniform Resource Identifiers <a 38 href="http://www.ietf.org/rfc/rfc2396.txt">http://www.ietf.org/rfc/rfc2396.txt</a></li> 39 <li>XML Path Language (XPath) 1.0: <a 40 href="http://www.w3.org/TR/xpath">http://www.w3.org/TR/xpath</a></li> 41 <li>HTML4 parser: <a 42 href="http://www.w3.org/TR/html401/">http://www.w3.org/TR/html401/</a></li> 43 <li>most of XML Pointer Language (XPointer) Version 1.0: <a 44 href="http://www.w3.org/TR/xptr">http://www.w3.org/TR/xptr</a></li> 45 <li>XML Inclusions (XInclude) Version 1.0: <a 46 href="http://www.w3.org/TR/xinclude/">http://www.w3.org/TR/xinclude/</a></li> 47 <li>[ISO-8859-1], <a 48 href="http://www.cis.ohio-state.edu/rfc/rfc2044.txt">rfc2044</a> [UTF-8] 49 and <a href="http://www.cis.ohio-state.edu/rfc/rfc2781.txt">rfc2781</a> 50 [UTF-16] core encodings</li> 51 <li>part of SGML Open Technical Resolution TR9401:1997</li> 52 <li>XML Catalogs Working Draft 06 August 2001: <a 53 href="http://www.oasis-open.org/committees/entity/spec-2001-08-06.html">http://www.oasis-open.org/committees/entity/spec-2001-08-06.html</a></li> 54 <li>Canonical XML Version 1.0: <a 55 href="http://www.w3.org/TR/xml-c14n">http://www.w3.org/TR/xml-c14n</a> 56 and the Exclusive XML Canonicalization CR draft <a 57 href="http://www.w3.org/TR/xml-exc-c14n">http://www.w3.org/TR/xml-exc-c14n</a></li> 58</ul> 59 60<p>In most cases libxml tries to implement the specifications in a relatively 61strict way. As of release 2.4.16, libxml2 passes all 1800+ tests from the <a 62href="http://www.oasis-open.org/committees/xml-conformance/">OASIS XML Tests 63Suite</a>.</p> 64 65<p>To some extent libxml2 provide some support for the following other 66specification but don't claim to implement them:</p> 67<ul> 68 <li>Document Object Model (DOM) <a 69 href="http://www.w3.org/TR/DOM-Level-2-Core/">http://www.w3.org/TR/DOM-Level-2-Core/</a> 70 it doesn't implement the API itself, gdome2 does this in top of 71 libxml2</li> 72 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc959.txt">RFC 959</a> : 73 libxml implements a basic FTP client code</li> 74 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc1945.txt">RFC 1945</a> : 75 HTTP/1.0, again a basic HTTP client code</li> 76 <li>SAX: a minimal SAX implementation compatible with early expat 77 versions</li> 78 <li>DocBook SGML v4: libxml2 includes a hackish parser to transition to 79 XML</li> 80</ul> 81 82<p>XML Schemas is being worked on but it would be far too early to make any 83conformance statement about it at the moment.</p> 84 85<p>Libxml2 is known to be very portable, the library should build and work 86without serious troubles on a variety of systems (Linux, Unix, Windows, 87CygWin, MacOs, MacOsX, RISC Os, OS/2, VMS, QNX, MVS, ...)</p> 88 89<p>Separate documents:</p> 90<ul> 91 <li><a href="http://xmlsoft.org/XSLT/">the libxslt page</a> providing an 92 implementation of XSLT 1.0 and common extensions like EXSLT for 93 libxml2</li> 94 <li><a href="http://www.cs.unibo.it/~casarini/gdome2/">the gdome2 page</a> 95 : a standard DOM2 implementation for libxml2</li> 96 <li><a href="http://www.aleksey.com/xmlsec/">the XMLSec page</a>: an 97 implementation of <a href="http://www.w3.org/TR/xmldsig-core/">W3C XML 98 Digital Signature</a> for libxml2</li> 99 <li>also check the related links section below for more related and active 100 projects.</li> 101</ul> 102 103<h2><a name="Introducti">Introduction</a></h2> 104 105<p>This document describes libxml, the <a 106href="http://www.w3.org/XML/">XML</a> C library developped for the <a 107href="http://www.gnome.org/">Gnome</a> project. <a 108href="http://www.w3.org/XML/">XML is a standard</a> for building tag-based 109structured documents/data.</p> 110 111<p>Here are some key points about libxml:</p> 112<ul> 113 <li>Libxml exports Push (progressive) and Pull (blocking) type parser 114 interfaces for both XML and HTML.</li> 115 <li>Libxml can do DTD validation at parse time, using a parsed document 116 instance, or with an arbitrary DTD.</li> 117 <li>Libxml includes complete <a 118 href="http://www.w3.org/TR/xpath">XPath</a>, <a 119 href="http://www.w3.org/TR/xptr">XPointer</a> and <a 120 href="http://www.w3.org/TR/xinclude">XInclude</a> implementations.</li> 121 <li>It is written in plain C, making as few assumptions as possible, and 122 sticking closely to ANSI C/POSIX for easy embedding. Works on 123 Linux/Unix/Windows, ported to a number of other platforms.</li> 124 <li>Basic support for HTTP and FTP client allowing aplications to fetch 125 remote resources</li> 126 <li>The design is modular, most of the extensions can be compiled out.</li> 127 <li>The internal document repesentation is as close as possible to the <a 128 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li> 129 <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX 130 like interface</a>; the interface is designed to be compatible with <a 131 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li> 132 <li>This library is released under the <a 133 href="http://www.opensource.org/licenses/mit-license.html">MIT 134 Licence</a> see the Copyright file in the distribution for the precise 135 wording.</li> 136</ul> 137 138<p>Warning: unless you are forced to because your application links with a 139Gnome-1.X library requiring it, <strong><span 140style="background-color: #FF0000">Do Not Use libxml1</span></strong>, use 141libxml2</p> 142 143<h2><a name="FAQ">FAQ</a></h2> 144 145<p>Table of Content:</p> 146<ul> 147 <li><a href="FAQ.html#Licence">Licence(s)</a></li> 148 <li><a href="FAQ.html#Installati">Installation</a></li> 149 <li><a href="FAQ.html#Compilatio">Compilation</a></li> 150 <li><a href="FAQ.html#Developer">Developer corner</a></li> 151</ul> 152 153<h3><a name="Licence">Licence</a>(s)</h3> 154<ol> 155 <li><em>Licensing Terms for libxml</em> 156 <p>libxml is released under the <a 157 href="http://www.opensource.org/licenses/mit-license.html">MIT 158 Licence</a>, see the file Copyright in the distribution for the precise 159 wording</p> 160 </li> 161 <li><em>Can I embed libxml in a proprietary application ?</em> 162 <p>Yes. The MIT Licence allows you to also keep proprietary the changes 163 you made to libxml, but it would be graceful to provide back bugfixes and 164 improvements as patches for possible incorporation in the main 165 development tree</p> 166 </li> 167</ol> 168 169<h3><a name="Installati">Installation</a></h3> 170<ol> 171 <li>Unless you are forced to because your application links with a Gnome 172 library requiring it, <strong><span style="background-color: #FF0000">Do 173 Not Use libxml1</span></strong>, use libxml2</li> 174 <li><em>Where can I get libxml</em> ? 175 <p>The original distribution comes from <a 176 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a 177 href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">gnome.org</a></p> 178 <p>Most linux and Bsd distribution includes libxml, this is probably the 179 safer way for end-users</p> 180 <p>David Doolin provides precompiled Windows versions at <a 181 href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p> 182 </li> 183 <li><em>I see libxml and libxml2 releases, which one should I install ?</em> 184 <ul> 185 <li>If you are not concerned by any existing backward compatibility 186 with existing application, install libxml2 only</li> 187 <li>If you are not doing development, you can safely install both. 188 usually the packages <a 189 href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a 190 href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are 191 compatible (this is not the case for development packages)</li> 192 <li>If you are a developer and your system provides separate packaging 193 for shared libraries and the development components, it is possible 194 to install libxml and libxml2, and also <a 195 href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> 196 and <a 197 href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> 198 too for libxml2 >= 2.3.0</li> 199 <li>If you are developing a new application, please develop against 200 libxml2(-devel)</li> 201 </ul> 202 </li> 203 <li><em>I can't install the libxml package it conflicts with libxml0</em> 204 <p>You probably have an old libxml0 package used to provide the shared 205 library for libxml.so.0, you can probably safely remove it. Anyway the 206 libxml packages provided on <a 207 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provides 208 libxml.so.0</p> 209 </li> 210 <li><em>I can't install the libxml(2) RPM package due to failed 211 dependancies</em> 212 <p>The most generic solution is to refetch the latest src.rpm , and 213 rebuild it locally with</p> 214 <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code></p> 215 <p>if everything goes well it will generate two binary rpm (one providing 216 the shared libs and xmllint, and the other one, the -devel package 217 providing includes, static libraries and scripts needed to build 218 applications with libxml(2)) that you can install locally.</p> 219 </li> 220</ol> 221 222<h3><a name="Compilatio">Compilation</a></h3> 223<ol> 224 <li><em>What is the process to compile libxml ?</em> 225 <p>As most UNIX libraries libxml follows the "standard":</p> 226 <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> 227 <p><code>cd libxml-xxxx</code></p> 228 <p><code>/configure --help</code></p> 229 <p>to see the options, then the compilation/installation proper</p> 230 <p><code>/configure [possible options]</code></p> 231 <p><code>make</code></p> 232 <p><code>make install</code></p> 233 <p>At that point you may have to rerun ldconfig or similar utility to 234 update your list of installed shared libs.</p> 235 </li> 236 <li><em>What other libraries are needed to compile/install libxml ?</em> 237 <p>Libxml does not requires any other library, the normal C ANSI API 238 should be sufficient (please report any violation to this rule you may 239 find).</p> 240 <p>However if found at configuration time libxml will detect and use the 241 following libs:</p> 242 <ul> 243 <li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a 244 highly portable and available widely compression library</li> 245 <li>iconv: a powerful character encoding conversion library. It's 246 included by default on recent glibc libraries, so it doesn't need to 247 be installed specifically on linux. It seems it's now <a 248 href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part 249 of the official UNIX</a> specification. Here is one <a 250 href="http://clisp.cons.org/~haible/packages-libiconv.html">implementation 251 of the library</a> which source can be found <a 252 href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> 253 </ul> 254 </li> 255 <li><em>make check fails on some platforms</em> 256 <p>Sometime the regression tests results don't completely match the value 257 produced by the parser, and the makefile uses diff to print the delta. On 258 some platforms the diff return breaks the compilation process, if the 259 diff is small this is probably not a serious problem.</p> 260 <p>Sometimes (especially on Solaris) make checks fails due to limitations 261 in make. Try using GNU-make instead.</p> 262 </li> 263 <li><em>I use the CVS version and there is no configure script</em> 264 <p>The configure (and other Makefiles) are generated. Use the autogen.sh 265 script to regenerate the configure and Makefiles, like:</p> 266 <p><code>/autogen.sh --prefix=/usr --disable-shared</code></p> 267 </li> 268 <li><em>I have troubles when running make tests with gcc-3.0</em> 269 <p>It seems the initial release of gcc-3.0 has a problem with the 270 optimizer which miscompiles the URI module. Please use another 271 compiler</p> 272 </li> 273</ol> 274 275<h3><a name="Developer">Developer</a> corner</h3> 276<ol> 277 <li><em>xmlDocDump() generates output on one line</em> 278 <p>libxml will not <strong>invent</strong> spaces in the content of a 279 document since <strong>all spaces in the content of a document are 280 significant</strong>. If you build a tree from the API and want 281 indentation:</p> 282 <ol> 283 <li>the correct way is to generate those yourself too</li> 284 <li>the dangerous way is to ask libxml to add those blanks to your 285 content <strong>modifying the content of your document in the 286 process</strong>. The result may not be what you expect. There is 287 <strong>NO</strong> way to guarantee that such a modification won't 288 impact other part of the content of your document. See <a 289 href="http://xmlsoft.org/html/libxml-parser.html#XMLKEEPBLANKSDEFAULT">xmlKeepBlanksDefault 290 ()</a> and <a 291 href="http://xmlsoft.org/html/libxml-tree.html#XMLSAVEFORMATFILE">xmlSaveFormatFile 292 ()</a></li> 293 </ol> 294 </li> 295 <li>Extra nodes in the document: 296 <p><em>For a XML file as below:</em></p> 297 <pre><?xml version="1.0"?> 298<PLAN xmlns="http://www.argus.ca/autotest/1.0/"> 299<NODE CommFlag="0"/> 300<NODE CommFlag="1"/> 301</PLAN></pre> 302 <p><em>after parsing it with the function 303 pxmlDoc=xmlParseFile(...);</em></p> 304 <p><em>I want to the get the content of the first node (node with the 305 CommFlag="0")</em></p> 306 <p><em>so I did it as following;</em></p> 307 <pre>xmlNodePtr pode; 308pnode=pxmlDoc->children->children;</pre> 309 <p><em>but it does not work. If I change it to</em></p> 310 <pre>pnode=pxmlDoc->children->children->next;</pre> 311 <p><em>then it works. Can someone explain it to me.</em></p> 312 <p></p> 313 <p>In XML all characters in the content of the document are significant 314 <strong>including blanks and formatting line breaks</strong>.</p> 315 <p>The extra nodes you are wondering about are just that, text nodes with 316 the formatting spaces wich are part of the document but that people tend 317 to forget. There is a function <a 318 href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault 319 ()</a> to remove those at parse time, but that's an heuristic, and its 320 use should be limited to case where you are sure there is no 321 mixed-content in the document.</p> 322 </li> 323 <li><em>I get compilation errors of existing code like when accessing 324 <strong>root</strong> or <strong>childs fields</strong> of nodes</em> 325 <p>You are compiling code developed for libxml version 1 and using a 326 libxml2 development environment. Either switch back to libxml v1 devel or 327 even better fix the code to compile with libxml2 (or both) by <a 328 href="upgrade.html">following the instructions</a>.</p> 329 </li> 330 <li><em>I get compilation errors about non existing 331 <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> 332 fields</em> 333 <p>The source code you are using has been <a 334 href="upgrade.html">upgraded</a> to be able to compile with both libxml 335 and libxml2, but you need to install a more recent version: 336 libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> 337 </li> 338 <li><em>XPath implementation looks seriously broken</em> 339 <p>XPath implementation prior to 2.3.0 was really incomplete, upgrade to 340 a recent version, there is no known bug in the current version.</p> 341 </li> 342 <li><em>The example provided in the web page does not compile</em> 343 <p>It's hard to maintain the documentation in sync with the code 344 <grin/> ...</p> 345 <p>Check the previous points 1/ and 2/ raised before, and send 346 patches.</p> 347 </li> 348 <li><em>Where can I get more examples and informations than in the web 349 page</em> 350 <p>Ideally a libxml book would be nice. I have no such plan ... But you 351 can:</p> 352 <ul> 353 <li>check more deeply the <a href="html/libxml-lib.html">existing 354 generated doc</a></li> 355 <li>looks for examples of use for libxml function using the Gnome code 356 for example the following will query the full Gnome CVs base for the 357 use of the <strong>xmlAddChild()</strong> function: 358 <p><a 359 href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> 360 <p>This may be slow, a large hardware donation to the gnome project 361 could cure this :-)</p> 362 </li> 363 <li><a 364 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse 365 the libxml source</a> , I try to write code as clean and documented 366 as possible, so looking at it may be helpful. Especially the code of 367 xmllint.c and of the various testXXX.c tests programs should provide 368 good example on how to do things with the library.</li> 369 </ul> 370 </li> 371 <li>What about C++ ? 372 <p>libxml is written in pure C in order to allow easy reuse on a number 373 of platforms, including embedded systems. I don't intend to convert to 374 C++.</p> 375 <p>There is however a few C++ wrappers which may fullfill your needs:</p> 376 <ul> 377 <li>by Ari Johnson <ari@btigate.com>: 378 <p>Website: <a 379 href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p> 380 <p>Download: <a 381 href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p> 382 </li> 383 <li>by Peter Jones <pjones@pmade.org> 384 <p>Website: <a 385 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 386 </li> 387 </ul> 388 </li> 389 <li>How to validate a document a posteriori ? 390 <p>It is possible to validate documents which had not been validated at 391 initial parsing time or documents who have been built from scratch using 392 the API. Use the <a 393 href="http://xmlsoft.org/html/libxml-valid.html#XMLVALIDATEDTD">xmlValidateDtd()</a> 394 function. It is also possible to simply add a Dtd to an existing 395 document:</p> 396 <pre>xmlDocPtr doc; /* your existing document */ 397 xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 398 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 399 400 doc->intSubset = dtd; 401 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 402 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 403 </pre> 404 </li> 405 <li>etc ...</li> 406</ol> 407 408<p></p> 409 410<h2><a name="Documentat">Documentation</a></h2> 411 412<p>There are some on-line resources about using libxml:</p> 413<ol> 414 <li>Check the <a href="FAQ.html">FAQ</a></li> 415 <li>Check the <a href="http://xmlsoft.org/html/libxml-lib.html">extensive 416 documentation</a> automatically extracted from code comments (using <a 417 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gtk-doc">gtk 418 doc</a>).</li> 419 <li>Look at the documentation about <a href="encoding.html">libxml 420 internationalization support</a></li> 421 <li>This page provides a global overview and <a href="example.html">some 422 examples</a> on how to use libxml.</li> 423 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a 424 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice 425 documentation</a> explaining how to use the libxml SAX interface.</li> 426 <li>George Lebl wrote <a 427 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article 428 for IBM developerWorks</a> about using libxml.</li> 429 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO 430 file</a></li> 431 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a>. If you are 432 starting a new project using libxml you should really use the 2.x 433 version.</li> 434 <li>And don't forget to look at the <a 435 href="http://mail.gnome.org/archives/xml/">mailing-list archive</a>.</li> 436</ol> 437 438<h2><a name="Reporting">Reporting bugs and getting help</a></h2> 439 440<p>Well, bugs or missing features are always possible, and I will make a 441point of fixing them in a timely fashion. The best way to report a bug is to 442use the <a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome 443bug tracking database</a> (make sure to use the "libxml" module name). I look 444at reports there regularly and it's good to have a reminder when a bug is 445still open. Be sure to specify that the bug is for the package libxml.</p> 446 447<p>There is also a mailing-list <a 448href="mailto:xml@gnome.org">xml@gnome.org</a> for libxml, with an <a 449href="http://mail.gnome.org/archives/xml/">on-line archive</a> (<a 450href="http://xmlsoft.org/messages">old</a>). To subscribe to this list, 451please visit the <a 452href="http://mail.gnome.org/mailman/listinfo/xml">associated Web</a> page and 453follow the instructions. <strong>Do not send code, I won't debug it</strong> 454(but patches are really appreciated!).</p> 455 456<p>Check the following <strong><span style="color: #FF0000">before 457posting</span></strong>:</p> 458<ul> 459 <li>read the <a href="FAQ.html">FAQ</a></li> 460 <li>make sure you are <a href="ftp://xmlsoft.org/">using a recent 461 version</a>, and that the problem still shows up in those</li> 462 <li>check the <a href="http://mail.gnome.org/archives/xml/">list 463 archives</a> to see if the problem was reported already, in this case 464 there is probably a fix available, similary check the <a 465 href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">registered 466 open bugs</a></li> 467 <li>make sure you can reproduce the bug with xmllint or one of the test 468 programs found in source in the distribution</li> 469 <li>Please send the command showing the error as well as the input (as an 470 attachement)</li> 471</ul> 472 473<p>Then send the bug with associated informations to reproduce it to the <a 474href="mailto:xml@gnome.org">xml@gnome.org</a> list; if it's really libxml 475related I will approve it.. Please do not send me mail directly, it makes 476things really harder to track and in some cases I'm not the best person to 477answer a given question, ask the list instead.</p> 478 479<p>Of course, bugs reported with a suggested patch for fixing them will 480probably be processed faster.</p> 481 482<p>If you're looking for help, a quick look at <a 483href="http://mail.gnome.org/archives/xml/">the list archive</a> may actually 484provide the answer, I usually send source samples when answering libxml usage 485questions. The <a href="http://xmlsoft.org/html/book1.html">auto-generated 486documentantion</a> is not as polished as I would like (i need to learn more 487about Docbook), but it's a good starting point.</p> 488 489<h2><a name="help">How to help</a></h2> 490 491<p>You can help the project in various ways, the best thing to do first is to 492subscribe to the mailing-list as explained before, check the <a 493href="http://mail.gnome.org/archives/xml/">archives </a>and the <a 494href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome bug 495database:</a>:</p> 496<ol> 497 <li>provide patches when you find problems</li> 498 <li>provide the diffs when you port libxml to a new platform. They may not 499 be integrated in all cases but help pinpointing portability problems 500 and</li> 501 <li>provide documentation fixes (either as patches to the code comments or 502 as HTML diffs).</li> 503 <li>provide new documentations pieces (translations, examples, etc ...)</li> 504 <li>Check the TODO file and try to close one of the items</li> 505 <li>take one of the points raised in the archive or the bug database and 506 provide a fix. <a href="mailto:daniel@veillard.com">Get in touch with me 507 </a>before to avoid synchronization problems and check that the suggested 508 fix will fit in nicely :-)</li> 509</ol> 510 511<h2><a name="Downloads">Downloads</a></h2> 512 513<p>The latest versions of libxml can be found on <a 514href="ftp://xmlsoft.org/">xmlsoft.org</a> (<a 515href="ftp://speakeasy.rpmfind.net/pub/libxml/">Seattle</a>, <a 516href="ftp://fr.rpmfind.net/pub/libxml/">France</a>) or on the <a 517href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either 518as a <a href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">source 519archive</a> or <a 520href="ftp://ftp.gnome.org/pub/GNOME/stable/redhat/i386/libxml/">RPM 521packages</a>, Antonin Sprinzl also provide <a 522href="ftp://gd.tuwien.ac.at/pub/libxml/">a mirror in Austria</a>. (NOTE that 523you need both the <a 524href="http://rpmfind.net/linux/RPM/libxml2.html">libxml(2)</a> and <a 525href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml(2)-devel</a> 526packages installed to compile applications using libxml.) <a 527href="mailto:igor@stud.fh-frankfurt.de">Igor Zlatkovic</a> is now the 528maintainer of the Windows port, <a 529href="http://www.fh-frankfurt.de/~igor/projects/libxml/index.html">he 530provides binaries</a>. <a href="mailto:Gary.Pennington@sun.com">Gary 531Pennington</a> provides <a href="http://garypennington.net/libxml2/">Solaris 532binaries</a>.</p> 533 534<p><a name="Snapshot">Snapshot:</a></p> 535<ul> 536 <li>Code from the W3C cvs base libxml <a 537 href="ftp://xmlsoft.org/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a></li> 538 <li>Docs, content of the web site, the list archive included <a 539 href="ftp://xmlsoft.org/libxml-docs.tar.gz">libxml-docs.tar.gz</a></li> 540</ul> 541 542<p><a name="Contribs">Contributions:</a></p> 543 544<p>I do accept external contributions, especially if compiling on another 545platform, get in touch with me to upload the package, wrappers for various 546languages have been provided, and can be found in the <a 547href="contribs.html">contrib section</a></p> 548 549<p>Libxml is also available from CVS:</p> 550<ul> 551 <li><p>The <a 552 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Gnome 553 CVS base</a>. Check the <a 554 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> 555 page; the CVS module is <b>gnome-xml</b>.</p> 556 </li> 557 <li>The <strong>libxslt</strong> module is also present there</li> 558</ul> 559 560<h2><a name="News">News</a></h2> 561 562<h3>CVS only : check the <a 563href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file 564for a really accurate description</h3> 565 566<p>Items not finished and worked on, get in touch with the list if you want 567to test those</p> 568<ul> 569 <li>Finishing up <a href="http://www.w3.org/TR/xmlschema-1/">XML 570 Schemas</a> and <a href="http://www.w3.org/TR/xinclude">XInclude</a></li> 571</ul> 572 573<h3>2.4.21: Apr 29 2002</h3> 574 575<p>This release is both a bug fix release and also contains the early XML 576Schemas <a href="http://www.w3.org/TR/xmlschema-1/">structures</a> and <a 577href="http://www.w3.org/TR/xmlschema-2/">datatypes</a> code, beware, all 578interfaces are likely to change, there is huge holes, it is clearly a work in 579progress and don't even think of putting this code in a production system, 580it's actually not compiled in by default. The real fixes are:</p> 581<ul> 582 <li>a couple of bugs or limitations introduced in 2.4.20</li> 583 <li>patches for Borland C++ and MSC by Igor</li> 584 <li>some fixes on XPath strings and conformance patches by Richard 585 Jinks</li> 586 <li>patch from Aleksey for the ExcC14N specification</li> 587 <li>OSF/1 bug fix by Bjorn</li> 588</ul> 589 590<h3>2.4.20: Apr 15 2002</h3> 591<ul> 592 <li>bug fixes: file descriptor leak, XPath, HTML ouput, DTD validation</li> 593 <li>XPath conformance testing by Richard Jinks</li> 594 <li>Portability fixes: Solaris, MPE/iX, Windows, OSF/1, python bindings, 595 libxml.m4</li> 596</ul> 597 598<h3>2.4.19: Mar 25 2002</h3> 599<ul> 600 <li>bug fixes: half a dozen XPath bugs, Validation, ISO-Latin to UTF8 601 encoder</li> 602 <li>portability fixes in the HTTP code</li> 603 <li>memory allocation checks using valgrind, and profiling tests</li> 604 <li>revamp of the Windows build and Makefiles</li> 605</ul> 606 607<h3>2.4.18: Mar 18 2002</h3> 608<ul> 609 <li>bug fixes: tree, SAX, canonicalization, validation, portability, 610 xpath</li> 611 <li>removed the --with-buffer option it was becoming unmaintainable</li> 612 <li>serious cleanup of the Python makefiles</li> 613 <li>speedup patch to XPath very effective for DocBook stylesheets</li> 614 <li>Fixes for Windows build, cleanup of the documentation</li> 615</ul> 616 617<h3>2.4.17: Mar 8 2002</h3> 618<ul> 619 <li>a lot of bug fixes, including "namespace nodes have no parents in 620 XPath"</li> 621 <li>fixed/improved the Python wrappers, added more examples and more 622 regression tests, XPath extension functions can now return node-sets</li> 623 <li>added the XML Canonalization support from Aleksey Sanin</li> 624</ul> 625 626<h3>2.4.16: Feb 20 2002</h3> 627<ul> 628 <li>a lot of bug fixes, most of them were triggered by the XML Testsuite 629 from OASIS and W3C. Compliance has been significantly improved.</li> 630 <li>a couple of portability fixes too.</li> 631</ul> 632 633<h3>2.4.15: Feb 11 2002</h3> 634<ul> 635 <li>Fixed the Makefiles, especially the python module ones</li> 636 <li>A few bug fixes and cleanup</li> 637 <li>Includes cleanup</li> 638</ul> 639 640<h3>2.4.14: Feb 8 2002</h3> 641<ul> 642 <li>Change of Licence to the <a 643 href="http://www.opensource.org/licenses/mit-license.html">MIT 644 Licence</a> basisally for integration in XFree86 codebase, and removing 645 confusion around the previous dual-licencing</li> 646 <li>added Python bindings, beta software but should already be quite 647 complete</li> 648 <li>a large number of fixes and cleanups, especially for all tree 649 manipulations</li> 650 <li>cleanup of the headers, generation of a reference API definition in 651 XML</li> 652</ul> 653 654<h3>2.4.13: Jan 14 2002</h3> 655<ul> 656 <li>update of the documentation: John Fleck and Charlie Bozeman</li> 657 <li>cleanup of timing code from Justin Fletcher</li> 658 <li>fixes for Windows and initial thread support on Win32: Igor and Serguei 659 Narojnyi</li> 660 <li>Cygwin patch from Robert Collins</li> 661 <li>added xmlSetEntityReferenceFunc() for Keith Isdale work on xsldbg</li> 662</ul> 663 664<h3>2.4.12: Dec 7 2001</h3> 665<ul> 666 <li>a few bug fixes: thread (Gary Pennington), xmllint (Geert Kloosterman), 667 XML parser (Robin Berjon), XPointer (Danny Jamshy), I/O cleanups 668 (robert)</li> 669 <li>Eric Lavigne contributed project files for MacOS</li> 670 <li>some makefiles cleanups</li> 671</ul> 672 673<h3>2.4.11: Nov 26 2001</h3> 674<ul> 675 <li>fixed a couple of errors in the includes, fixed a few bugs, some code 676 cleanups</li> 677 <li>xmllint man pages improvement by Heiko Rupp</li> 678 <li>updated VMS build instructions from John A Fotheringham</li> 679 <li>Windows Makefiles updates from Igor</li> 680</ul> 681 682<h3>2.4.10: Nov 10 2001</h3> 683<ul> 684 <li>URI escaping fix (Joel Young)</li> 685 <li>added xmlGetNodePath() (for paths or XPointers generation)</li> 686 <li>Fixes namespace handling problems when using DTD and validation</li> 687 <li>improvements on xmllint: Morus Walter patches for --format and 688 --encode, Stefan Kost and Heiko Rupp improvements on the --shell</li> 689 <li>fixes for xmlcatalog linking pointed by Weiqi Gao</li> 690 <li>fixes to the HTML parser</li> 691</ul> 692 693<h3>2.4.9: Nov 6 2001</h3> 694<ul> 695 <li>fixes more catalog bugs</li> 696 <li>avoid a compilation problem, improve xmlGetLineNo()</li> 697</ul> 698 699<h3>2.4.8: Nov 4 2001</h3> 700<ul> 701 <li>fixed SGML catalogs broken in previous release, updated xmlcatalog 702 tool</li> 703 <li>fixed a compile errors and some includes troubles.</li> 704</ul> 705 706<h3>2.4.7: Oct 30 2001</h3> 707<ul> 708 <li>exported some debugging interfaces</li> 709 <li>serious rewrite of the catalog code</li> 710 <li>integrated Gary Pennington thread safety patch, added configure option 711 and regression tests</li> 712 <li>removed an HTML parser bug</li> 713 <li>fixed a couple of potentially serious validation bugs</li> 714 <li>integrated the SGML DocBook support in xmllint</li> 715 <li>changed the nanoftp anonymous login passwd</li> 716 <li>some I/O cleanup and a couple of interfaces for Perl wrapper</li> 717 <li>general bug fixes</li> 718 <li>updated xmllint man page by John Fleck</li> 719 <li>some VMS and Windows updates</li> 720</ul> 721 722<h3>2.4.6: Oct 10 2001</h3> 723<ul> 724 <li>added an updated man pages by John Fleck</li> 725 <li>portability and configure fixes</li> 726 <li>an infinite loop on the HTML parser was removed (William)</li> 727 <li>Windows makefile patches from Igor</li> 728 <li>fixed half a dozen bugs reported fof libxml or libxslt</li> 729 <li>updated xmlcatalog to be able to modify SGML super catalogs</li> 730</ul> 731 732<h3>2.4.5: Sep 14 2001</h3> 733<ul> 734 <li>Remove a few annoying bugs in 2.4.4</li> 735 <li>forces the HTML serializer to output decimal charrefs since some 736 version of Netscape can't handle hexadecimal ones</li> 737</ul> 738 739<h3>1.8.16: Sep 14 2001</h3> 740<ul> 741 <li>maintenance release of the old libxml1 branch, couple of bug and 742 portability fixes</li> 743</ul> 744 745<h3>2.4.4: Sep 12 2001</h3> 746<ul> 747 <li>added --convert to xmlcatalog, bug fixes and cleanups of XML 748 Catalog</li> 749 <li>a few bug fixes and some portability changes</li> 750 <li>some documentation cleanups</li> 751</ul> 752 753<h3>2.4.3: Aug 23 2001</h3> 754<ul> 755 <li>XML Catalog support see the doc</li> 756 <li>New NaN/Infinity floating point code</li> 757 <li>A few bug fixes</li> 758</ul> 759 760<h3>2.4.2: Aug 15 2001</h3> 761<ul> 762 <li>adds xmlLineNumbersDefault() to control line number generation</li> 763 <li>lot of bug fixes</li> 764 <li>the Microsoft MSC projects files shuld now be up to date</li> 765 <li>inheritance of namespaces from DTD defaulted attributes</li> 766 <li>fixes a serious potential security bug</li> 767 <li>added a --format option to xmllint</li> 768</ul> 769 770<h3>2.4.1: July 24 2001</h3> 771<ul> 772 <li>possibility to keep line numbers in the tree</li> 773 <li>some computation NaN fixes</li> 774 <li>extension of the XPath API</li> 775 <li>cleanup for alpha and ia64 targets</li> 776 <li>patch to allow saving through HTTP PUT or POST</li> 777</ul> 778 779<h3>2.4.0: July 10 2001</h3> 780<ul> 781 <li>Fixed a few bugs in XPath, validation, and tree handling.</li> 782 <li>Fixed XML Base implementation, added a coupel of examples to the 783 regression tests</li> 784 <li>A bit of cleanup</li> 785</ul> 786 787<h3>2.3.14: July 5 2001</h3> 788<ul> 789 <li>fixed some entities problems and reduce mem requirement when 790 substituing them</li> 791 <li>lots of improvements in the XPath queries interpreter can be 792 substancially faster</li> 793 <li>Makefiles and configure cleanups</li> 794 <li>Fixes to XPath variable eval, and compare on empty node set</li> 795 <li>HTML tag closing bug fixed</li> 796 <li>Fixed an URI reference computating problem when validating</li> 797</ul> 798 799<h3>2.3.13: June 28 2001</h3> 800<ul> 801 <li>2.3.12 configure.in was broken as well as the push mode XML parser</li> 802 <li>a few more fixes for compilation on Windows MSC by Yon Derek</li> 803</ul> 804 805<h3>1.8.14: June 28 2001</h3> 806<ul> 807 <li>Zbigniew Chyla gave a patch to use the old XML parser in push mode</li> 808 <li>Small Makefile fix</li> 809</ul> 810 811<h3>2.3.12: June 26 2001</h3> 812<ul> 813 <li>lots of cleanup</li> 814 <li>a couple of validation fix</li> 815 <li>fixed line number counting</li> 816 <li>fixed serious problems in the XInclude processing</li> 817 <li>added support for UTF8 BOM at beginning of entities</li> 818 <li>fixed a strange gcc optimizer bugs in xpath handling of float, gcc-3.0 819 miscompile uri.c (William), Thomas Leitner provided a fix for the 820 optimizer on Tru64</li> 821 <li>incorporated Yon Derek and Igor Zlatkovic fixes and improvements for 822 compilation on Windows MSC</li> 823 <li>update of libxml-doc.el (Felix Natter)</li> 824 <li>fixed 2 bugs in URI normalization code</li> 825</ul> 826 827<h3>2.3.11: June 17 2001</h3> 828<ul> 829 <li>updates to trio, Makefiles and configure should fix some portability 830 problems (alpha)</li> 831 <li>fixed some HTML serialization problems (pre, script, and block/inline 832 handling), added encoding aware APIs, cleanup of this code</li> 833 <li>added xmlHasNsProp()</li> 834 <li>implemented a specific PI for encoding support in the DocBook SGML 835 parser</li> 836 <li>some XPath fixes (-Infinity, / as a function parameter and namespaces 837 node selection)</li> 838 <li>fixed a performance problem and an error in the validation code</li> 839 <li>fixed XInclude routine to implement the recursive behaviour</li> 840 <li>fixed xmlFreeNode problem when libxml is included statically twice</li> 841 <li>added --version to xmllint for bug reports</li> 842</ul> 843 844<h3>2.3.10: June 1 2001</h3> 845<ul> 846 <li>fixed the SGML catalog support</li> 847 <li>a number of reported bugs got fixed, in XPath, iconv detection, 848 XInclude processing</li> 849 <li>XPath string function should now handle unicode correctly</li> 850</ul> 851 852<h3>2.3.9: May 19 2001</h3> 853 854<p>Lots of bugfixes, and added a basic SGML catalog support:</p> 855<ul> 856 <li>HTML push bugfix #54891 and another patch from Jonas Borgstr�m</li> 857 <li>some serious speed optimisation again</li> 858 <li>some documentation cleanups</li> 859 <li>trying to get better linking on solaris (-R)</li> 860 <li>XPath API cleanup from Thomas Broyer</li> 861 <li>Validation bug fixed #54631, added a patch from Gary Pennington, fixed 862 xmlValidGetValidElements()</li> 863 <li>Added an INSTALL file</li> 864 <li>Attribute removal added to API: #54433</li> 865 <li>added a basic support for SGML catalogs</li> 866 <li>fixed xmlKeepBlanksDefault(0) API</li> 867 <li>bugfix in xmlNodeGetLang()</li> 868 <li>fixed a small configure portability problem</li> 869 <li>fixed an inversion of SYSTEM and PUBLIC identifier in HTML document</li> 870</ul> 871 872<h3>1.8.13: May 14 2001</h3> 873<ul> 874 <li>bugfixes release of the old libxml1 branch used by Gnome</li> 875</ul> 876 877<h3>2.3.8: May 3 2001</h3> 878<ul> 879 <li>Integrated an SGML DocBook parser for the Gnome project</li> 880 <li>Fixed a few things in the HTML parser</li> 881 <li>Fixed some XPath bugs raised by XSLT use, tried to fix the floating 882 point portability issue</li> 883 <li>Speed improvement (8M/s for SAX, 3M/s for DOM, 1.5M/s for 884 DOM+validation using the XML REC as input and a 700MHz celeron).</li> 885 <li>incorporated more Windows cleanup</li> 886 <li>added xmlSaveFormatFile()</li> 887 <li>fixed problems in copying nodes with entities references (gdome)</li> 888 <li>removed some troubles surrounding the new validation module</li> 889</ul> 890 891<h3>2.3.7: April 22 2001</h3> 892<ul> 893 <li>lots of small bug fixes, corrected XPointer</li> 894 <li>Non determinist content model validation support</li> 895 <li>added xmlDocCopyNode for gdome2</li> 896 <li>revamped the way the HTML parser handles end of tags</li> 897 <li>XPath: corrctions of namespacessupport and number formatting</li> 898 <li>Windows: Igor Zlatkovic patches for MSC compilation</li> 899 <li>HTML ouput fixes from P C Chow and William M. Brack</li> 900 <li>Improved validation speed sensible for DocBook</li> 901 <li>fixed a big bug with ID declared in external parsed entities</li> 902 <li>portability fixes, update of Trio from Bjorn Reese</li> 903</ul> 904 905<h3>2.3.6: April 8 2001</h3> 906<ul> 907 <li>Code cleanup using extreme gcc compiler warning options, found and 908 cleared half a dozen potential problem</li> 909 <li>the Eazel team found an XML parser bug</li> 910 <li>cleaned up the user of some of the string formatting function. used the 911 trio library code to provide the one needed when the platform is missing 912 them</li> 913 <li>xpath: removed a memory leak and fixed the predicate evaluation 914 problem, extended the testsuite and cleaned up the result. XPointer seems 915 broken ...</li> 916</ul> 917 918<h3>2.3.5: Mar 23 2001</h3> 919<ul> 920 <li>Biggest change is separate parsing and evaluation of XPath expressions, 921 there is some new APIs for this too</li> 922 <li>included a number of bug fixes(XML push parser, 51876, notations, 923 52299)</li> 924 <li>Fixed some portability issues</li> 925</ul> 926 927<h3>2.3.4: Mar 10 2001</h3> 928<ul> 929 <li>Fixed bugs #51860 and #51861</li> 930 <li>Added a global variable xmlDefaultBufferSize to allow default buffer 931 size to be application tunable.</li> 932 <li>Some cleanup in the validation code, still a bug left and this part 933 should probably be rewritten to support ambiguous content model :-\</li> 934 <li>Fix a couple of serious bugs introduced or raised by changes in 2.3.3 935 parser</li> 936 <li>Fixed another bug in xmlNodeGetContent()</li> 937 <li>Bjorn fixed XPath node collection and Number formatting</li> 938 <li>Fixed a loop reported in the HTML parsing</li> 939 <li>blank space are reported even if the Dtd content model proves that they 940 are formatting spaces, this is for XmL conformance</li> 941</ul> 942 943<h3>2.3.3: Mar 1 2001</h3> 944<ul> 945 <li>small change in XPath for XSLT</li> 946 <li>documentation cleanups</li> 947 <li>fix in validation by Gary Pennington</li> 948 <li>serious parsing performances improvements</li> 949</ul> 950 951<h3>2.3.2: Feb 24 2001</h3> 952<ul> 953 <li>chasing XPath bugs, found a bunch, completed some TODO</li> 954 <li>fixed a Dtd parsing bug</li> 955 <li>fixed a bug in xmlNodeGetContent</li> 956 <li>ID/IDREF support partly rewritten by Gary Pennington</li> 957</ul> 958 959<h3>2.3.1: Feb 15 2001</h3> 960<ul> 961 <li>some XPath and HTML bug fixes for XSLT</li> 962 <li>small extension of the hash table interfaces for DOM gdome2 963 implementation</li> 964 <li>A few bug fixes</li> 965</ul> 966 967<h3>2.3.0: Feb 8 2001 (2.2.12 was on 25 Jan but I didn't kept track)</h3> 968<ul> 969 <li>Lots of XPath bug fixes</li> 970 <li>Add a mode with Dtd lookup but without validation error reporting for 971 XSLT</li> 972 <li>Add support for text node without escaping (XSLT)</li> 973 <li>bug fixes for xmlCheckFilename</li> 974 <li>validation code bug fixes from Gary Pennington</li> 975 <li>Patch from Paul D. Smith correcting URI path normalization</li> 976 <li>Patch to allow simultaneous install of libxml-devel and 977 libxml2-devel</li> 978 <li>the example Makefile is now fixed</li> 979 <li>added HTML to the RPM packages</li> 980 <li>tree copying bugfixes</li> 981 <li>updates to Windows makefiles</li> 982 <li>optimisation patch from Bjorn Reese</li> 983</ul> 984 985<h3>2.2.11: Jan 4 2001</h3> 986<ul> 987 <li>bunch of bug fixes (memory I/O, xpath, ftp/http, ...)</li> 988 <li>added htmlHandleOmittedElem()</li> 989 <li>Applied Bjorn Reese's IPV6 first patch</li> 990 <li>Applied Paul D. Smith patches for validation of XInclude results</li> 991 <li>added XPointer xmlns() new scheme support</li> 992</ul> 993 994<h3>2.2.10: Nov 25 2000</h3> 995<ul> 996 <li>Fix the Windows problems of 2.2.8</li> 997 <li>integrate OpenVMS patches</li> 998 <li>better handling of some nasty HTML input</li> 999 <li>Improved the XPointer implementation</li> 1000 <li>integrate a number of provided patches</li> 1001</ul> 1002 1003<h3>2.2.9: Nov 25 2000</h3> 1004<ul> 1005 <li>erroneous release :-(</li> 1006</ul> 1007 1008<h3>2.2.8: Nov 13 2000</h3> 1009<ul> 1010 <li>First version of <a href="http://www.w3.org/TR/xinclude">XInclude</a> 1011 support</li> 1012 <li>Patch in conditional section handling</li> 1013 <li>updated MS compiler project</li> 1014 <li>fixed some XPath problems</li> 1015 <li>added an URI escaping function</li> 1016 <li>some other bug fixes</li> 1017</ul> 1018 1019<h3>2.2.7: Oct 31 2000</h3> 1020<ul> 1021 <li>added message redirection</li> 1022 <li>XPath improvements (thanks TOM !)</li> 1023 <li>xmlIOParseDTD() added</li> 1024 <li>various small fixes in the HTML, URI, HTTP and XPointer support</li> 1025 <li>some cleanup of the Makefile, autoconf and the distribution content</li> 1026</ul> 1027 1028<h3>2.2.6: Oct 25 2000:</h3> 1029<ul> 1030 <li>Added an hash table module, migrated a number of internal structure to 1031 those</li> 1032 <li>Fixed a posteriori validation problems</li> 1033 <li>HTTP module cleanups</li> 1034 <li>HTML parser improvements (tag errors, script/style handling, attribute 1035 normalization)</li> 1036 <li>coalescing of adjacent text nodes</li> 1037 <li>couple of XPath bug fixes, exported the internal API</li> 1038</ul> 1039 1040<h3>2.2.5: Oct 15 2000:</h3> 1041<ul> 1042 <li>XPointer implementation and testsuite</li> 1043 <li>Lot of XPath fixes, added variable and functions registration, more 1044 tests</li> 1045 <li>Portability fixes, lots of enhancements toward an easy Windows build 1046 and release</li> 1047 <li>Late validation fixes</li> 1048 <li>Integrated a lot of contributed patches</li> 1049 <li>added memory management docs</li> 1050 <li>a performance problem when using large buffer seems fixed</li> 1051</ul> 1052 1053<h3>2.2.4: Oct 1 2000:</h3> 1054<ul> 1055 <li>main XPath problem fixed</li> 1056 <li>Integrated portability patches for Windows</li> 1057 <li>Serious bug fixes on the URI and HTML code</li> 1058</ul> 1059 1060<h3>2.2.3: Sep 17 2000</h3> 1061<ul> 1062 <li>bug fixes</li> 1063 <li>cleanup of entity handling code</li> 1064 <li>overall review of all loops in the parsers, all sprintf usage has been 1065 checked too</li> 1066 <li>Far better handling of larges Dtd. Validating against Docbook XML Dtd 1067 works smoothly now.</li> 1068</ul> 1069 1070<h3>1.8.10: Sep 6 2000</h3> 1071<ul> 1072 <li>bug fix release for some Gnome projects</li> 1073</ul> 1074 1075<h3>2.2.2: August 12 2000</h3> 1076<ul> 1077 <li>mostly bug fixes</li> 1078 <li>started adding routines to access xml parser context options</li> 1079</ul> 1080 1081<h3>2.2.1: July 21 2000</h3> 1082<ul> 1083 <li>a purely bug fixes release</li> 1084 <li>fixed an encoding support problem when parsing from a memory block</li> 1085 <li>fixed a DOCTYPE parsing problem</li> 1086 <li>removed a bug in the function allowing to override the memory 1087 allocation routines</li> 1088</ul> 1089 1090<h3>2.2.0: July 14 2000</h3> 1091<ul> 1092 <li>applied a lot of portability fixes</li> 1093 <li>better encoding support/cleanup and saving (content is now always 1094 encoded in UTF-8)</li> 1095 <li>the HTML parser now correctly handles encodings</li> 1096 <li>added xmlHasProp()</li> 1097 <li>fixed a serious problem with &#38;</li> 1098 <li>propagated the fix to FTP client</li> 1099 <li>cleanup, bugfixes, etc ...</li> 1100 <li>Added a page about <a href="encoding.html">libxml Internationalization 1101 support</a></li> 1102</ul> 1103 1104<h3>1.8.9: July 9 2000</h3> 1105<ul> 1106 <li>fixed the spec the RPMs should be better</li> 1107 <li>fixed a serious bug in the FTP implementation, released 1.8.9 to solve 1108 rpmfind users problem</li> 1109</ul> 1110 1111<h3>2.1.1: July 1 2000</h3> 1112<ul> 1113 <li>fixes a couple of bugs in the 2.1.0 packaging</li> 1114 <li>improvements on the HTML parser</li> 1115</ul> 1116 1117<h3>2.1.0 and 1.8.8: June 29 2000</h3> 1118<ul> 1119 <li>1.8.8 is mostly a comodity package for upgrading to libxml2 accoding to 1120 <a href="upgrade.html">new instructions</a>. It fixes a nasty problem 1121 about &#38; charref parsing</li> 1122 <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it 1123 also contains numerous fixes and enhancements: 1124 <ul> 1125 <li>added xmlStopParser() to stop parsing</li> 1126 <li>improved a lot parsing speed when there is large CDATA blocs</li> 1127 <li>includes XPath patches provided by Picdar Technology</li> 1128 <li>tried to fix as much as possible DtD validation and namespace 1129 related problems</li> 1130 <li>output to a given encoding has been added/tested</li> 1131 <li>lot of various fixes</li> 1132 </ul> 1133 </li> 1134</ul> 1135 1136<h3>2.0.0: Apr 12 2000</h3> 1137<ul> 1138 <li>First public release of libxml2. If you are using libxml, it's a good 1139 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initally 1140 scheduled for Apr 3 the relase occured only on Apr 12 due to massive 1141 workload.</li> 1142 <li>The include are now located under $prefix/include/libxml (instead of 1143 $prefix/include/gnome-xml), they also are referenced by 1144 <pre>#include <libxml/xxx.h></pre> 1145 <p>instead of</p> 1146 <pre>#include "xxx.h"</pre> 1147 </li> 1148 <li>a new URI module for parsing URIs and following strictly RFC 2396</li> 1149 <li>the memory allocation routines used by libxml can now be overloaded 1150 dynamically by using xmlMemSetup()</li> 1151 <li>The previously CVS only tool tester has been renamed 1152 <strong>xmllint</strong> and is now installed as part of the libxml2 1153 package</li> 1154 <li>The I/O interface has been revamped. There is now ways to plug in 1155 specific I/O modules, either at the URI scheme detection level using 1156 xmlRegisterInputCallbacks() or by passing I/O functions when creating a 1157 parser context using xmlCreateIOParserCtxt()</li> 1158 <li>there is a C preprocessor macro LIBXML_VERSION providing the version 1159 number of the libxml module in use</li> 1160 <li>a number of optional features of libxml can now be excluded at 1161 configure time (FTP/HTTP/HTML/XPath/Debug)</li> 1162</ul> 1163 1164<h3>2.0.0beta: Mar 14 2000</h3> 1165<ul> 1166 <li>This is a first Beta release of libxml version 2</li> 1167 <li>It's available only from<a href="ftp://xmlsoft.org/">xmlsoft.org 1168 FTP</a>, it's packaged as libxml2-2.0.0beta and available as tar and 1169 RPMs</li> 1170 <li>This version is now the head in the Gnome CVS base, the old one is 1171 available under the tag LIB_XML_1_X</li> 1172 <li>This includes a very large set of changes. Froma programmatic point of 1173 view applications should not have to be modified too much, check the <a 1174 href="upgrade.html">upgrade page</a></li> 1175 <li>Some interfaces may changes (especially a bit about encoding).</li> 1176 <li>the updates includes: 1177 <ul> 1178 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly 1179 handled now</li> 1180 <li>Better handling of entities, especially well formedness checking 1181 and proper PEref extensions in external subsets</li> 1182 <li>DTD conditional sections</li> 1183 <li>Validation now correcly handle entities content</li> 1184 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change 1185 structures to accomodate DOM</a></li> 1186 </ul> 1187 </li> 1188 <li>Serious progress were made toward compliance, <a 1189 href="conf/result.html">here are the result of the test</a> against the 1190 OASIS testsuite (except the japanese tests since I don't support that 1191 encoding yet). This URL is rebuilt every couple of hours using the CVS 1192 head version.</li> 1193</ul> 1194 1195<h3>1.8.7: Mar 6 2000</h3> 1196<ul> 1197 <li>This is a bug fix release:</li> 1198 <li>It is possible to disable the ignorable blanks heuristic used by 1199 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note 1200 that for adherence to XML spec, this behaviour will be disabled by 1201 default in 2.x . The same function will allow to keep compatibility for 1202 old code.</li> 1203 <li>Blanks in <a> </a> constructs are not ignored anymore, 1204 avoiding heuristic is really the Right Way :-\</li> 1205 <li>The unchecked use of snprintf which was breaking libxml-1.8.6 1206 compilation on some platforms has been fixed</li> 1207 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing 1208 URIs</li> 1209</ul> 1210 1211<h3>1.8.6: Jan 31 2000</h3> 1212<ul> 1213 <li>added a nanoFTP transport module, debugged until the new version of <a 1214 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use 1215 it without troubles</li> 1216</ul> 1217 1218<h3>1.8.5: Jan 21 2000</h3> 1219<ul> 1220 <li>adding APIs to parse a well balanced chunk of XML (production <a 1221 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the 1222 XML spec)</li> 1223 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li> 1224 <li>Jody Goldberg <jgoldberg@home.com> provided another patch trying 1225 to solve the zlib checks problems</li> 1226 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with 1227 gnumeric soon</li> 1228</ul> 1229 1230<h3>1.8.4: Jan 13 2000</h3> 1231<ul> 1232 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li> 1233 <li>all exit() call should have been removed from libxml</li> 1234 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li> 1235 <li>added newDocFragment()</li> 1236</ul> 1237 1238<h3>1.8.3: Jan 5 2000</h3> 1239<ul> 1240 <li>a Push interface for the XML and HTML parsers</li> 1241 <li>a shell-like interface to the document tree (try tester --shell :-)</li> 1242 <li>lots of bug fixes and improvement added over XMas hollidays</li> 1243 <li>fixed the DTD parsing code to work with the xhtml DTD</li> 1244 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li> 1245 <li>Fixed bugs in xmlNewNs()</li> 1246 <li>External entity loading code has been revamped, now it uses 1247 xmlLoadExternalEntity(), some fix on entities processing were added</li> 1248 <li>cleaned up WIN32 includes of socket stuff</li> 1249</ul> 1250 1251<h3>1.8.2: Dec 21 1999</h3> 1252<ul> 1253 <li>I got another problem with includes and C++, I hope this issue is fixed 1254 for good this time</li> 1255 <li>Added a few tree modification functions: xmlReplaceNode, 1256 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and 1257 xmlDocSetRootElement</li> 1258 <li>Tried to improve the HTML output with help from <a 1259 href="mailto:clahey@umich.edu">Chris Lahey</a></li> 1260</ul> 1261 1262<h3>1.8.1: Dec 18 1999</h3> 1263<ul> 1264 <li>various patches to avoid troubles when using libxml with C++ compilers 1265 the "namespace" keyword and C escaping in include files</li> 1266 <li>a problem in one of the core macros IS_CHAR was corrected</li> 1267 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing, 1268 and more specifically the Dia application</li> 1269 <li>fixed a posteriori validation (validation after parsing, or by using a 1270 Dtd not specified in the original document)</li> 1271 <li>fixed a bug in</li> 1272</ul> 1273 1274<h3>1.8.0: Dec 12 1999</h3> 1275<ul> 1276 <li>cleanup, especially memory wise</li> 1277 <li>the parser should be more reliable, especially the HTML one, it should 1278 not crash, whatever the input !</li> 1279 <li>Integrated various patches, especially a speedup improvement for large 1280 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>, 1281 configure with --with-buffers to enable them.</li> 1282 <li>attribute normalization, oops should have been added long ago !</li> 1283 <li>attributes defaulted from Dtds should be available, xmlSetProp() now 1284 does entities escapting by default.</li> 1285</ul> 1286 1287<h3>1.7.4: Oct 25 1999</h3> 1288<ul> 1289 <li>Lots of HTML improvement</li> 1290 <li>Fixed some errors when saving both XML and HTML</li> 1291 <li>More examples, the regression tests should now look clean</li> 1292 <li>Fixed a bug with contiguous charref</li> 1293</ul> 1294 1295<h3>1.7.3: Sep 29 1999</h3> 1296<ul> 1297 <li>portability problems fixed</li> 1298 <li>snprintf was used unconditionnally, leading to link problems on system 1299 were it's not available, fixed</li> 1300</ul> 1301 1302<h3>1.7.1: Sep 24 1999</h3> 1303<ul> 1304 <li>The basic type for strings manipulated by libxml has been renamed in 1305 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason 1306 is that CHAR was conflicting with a predefined type on Windows. However 1307 on non WIN32 environment, compatibility is provided by the way of a 1308 <strong>#define </strong>.</li> 1309 <li>Changed another error : the use of a structure field called errno, and 1310 leading to troubles on platforms where it's a macro</li> 1311</ul> 1312 1313<h3>1.7.0: sep 23 1999</h3> 1314<ul> 1315 <li>Added the ability to fetch remote DTD or parsed entities, see the <a 1316 href="html/libxml-nanohttp.html">nanohttp</a> module.</li> 1317 <li>Added an errno to report errors by another mean than a simple printf 1318 like callback</li> 1319 <li>Finished ID/IDREF support and checking when validation</li> 1320 <li>Serious memory leaks fixed (there is now a <a 1321 href="html/libxml-xmlmemory.html">memory wrapper</a> module)</li> 1322 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a> 1323 implementation</li> 1324 <li>Added an HTML parser front-end</li> 1325</ul> 1326 1327<h2><a name="XML">XML</a></h2> 1328 1329<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for 1330markup-based structured documents. Here is <a name="example">an example XML 1331document</a>:</p> 1332<pre><?xml version="1.0"?> 1333<EXAMPLE prop1="gnome is great" prop2="&amp; linux too"> 1334 <head> 1335 <title>Welcome to Gnome</title> 1336 </head> 1337 <chapter> 1338 <title>The Linux adventure</title> 1339 <p>bla bla bla ...</p> 1340 <image href="linus.gif"/> 1341 <p>...</p> 1342 </chapter> 1343</EXAMPLE></pre> 1344 1345<p>The first line specifies that it's an XML document and gives useful 1346information about its encoding. Then the document is a text format whose 1347structure is specified by tags between brackets. <strong>Each tag opened has 1348to be closed</strong>. XML is pedantic about this. However, if a tag is empty 1349(no content), a single tag can serve as both the opening and closing tag if 1350it ends with <code>/></code> rather than with <code>></code>. Note 1351that, for example, the image tag has no content (just an attribute) and is 1352closed by ending the tag with <code>/></code>.</p> 1353 1354<p>XML can be applied sucessfully to a wide range of uses, from long term 1355structured document maintenance (where it follows the steps of SGML) to 1356simple data encoding mechanisms like configuration file formatting (glade), 1357spreadsheets (gnumeric), or even shorter lived documents such as WebDAV where 1358it is used to encode remote calls between a client and a server.</p> 1359 1360<h2><a name="XSLT">XSLT</a></h2> 1361 1362<p>Check <a href="http://xmlsoft.org/XSLT">the separate libxslt page</a></p> 1363 1364<p><a href="http://www.w3.org/TR/xslt">XSL Transformations</a>, is a 1365language for transforming XML documents into other XML documents (or 1366HTML/textual output).</p> 1367 1368<p>A separate library called libxslt is being built on top of libxml2. This 1369module "libxslt" can be found in the Gnome CVS base too.</p> 1370 1371<p>You can check the <a 1372href="http://cvs.gnome.org/lxr/source/libxslt/FEATURES">features</a> 1373supported and the progresses on the <a 1374href="http://cvs.gnome.org/lxr/source/libxslt/ChangeLog" 1375name="Changelog">Changelog</a></p> 1376 1377<h2><a name="Python">Python and bindings</a></h2> 1378 1379<p>There is a number of language bindings and wrappers available for libxml2, 1380the list below is not exhaustive. Please contact the <a 1381href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a> 1382(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in 1383order to get updates to this list or to discuss the specific topic of libxml2 1384or libxslt wrappers or bindings:</p> 1385<ul> 1386 <li><a href="mailto:ari@lusis.org">Ari Johnson</a> provides a C++ wrapper 1387 for libxml:<br> 1388 Website: <a 1389 href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a><br> 1390 Download: <a 1391 href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></li> 1392 <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper 1393 based on the gdome2 </a>bindings maintained by Tobias Peters.</li> 1394 <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> 1395 <p>Website: <a 1396 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 1397 </li> 1398 <li><a 1399 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 1400 Sergeant</a> developped <a 1401 href="http://axkit.org/download/">XML::LibXSLT</a>, a perl wrapper for 1402 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 1403 application server</a></li> 1404 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides and 1405 earlier version of the libxml/libxslt <a 1406 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li> 1407 <li>Petr Kozelka provides <a 1408 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 1409 libxml2</a> with Kylix, Delphi and other Pascal compilers</li> 1410 <li>Uwe Fechner also provides <a 1411 href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 1412 implementation for Kylix2/D5/D6 from Borland</li> 1413 <li>Wai-Sun "Squidster" Chia provides <a 1414 href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and 1415 libxml2 bindings are also available in Ruby through the <a 1416 href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module 1417 maintained by Tobias Peters.</li> 1418 <li>Steve Ball and contributors maintains <a 1419 href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for 1420 Tcl</a></li> 1421 <li>There is support for libxml2 in the DOM module of PHP.</li> 1422</ul> 1423 1424<p>The distribution includes a set of Python bindings, which are garanteed to 1425be maintained as part of the library in the future, though the Python 1426interface have not yet reached the maturity of the C API.</p> 1427 1428<p>To install the Python bindings there are 2 options:</p> 1429<ul> 1430 <li>If you use an RPM based distribution, simply install the <a 1431 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python 1432 RPM</a> (and if needed the <a 1433 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python 1434 RPM</a>).</li> 1435 <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python 1436 module distribution</a> corresponding to your installed version of 1437 libxml2 and libxslt. Note that to install it you will need both libxml2 1438 and libxslt installed and run "python setup.py build install" in the 1439 module tree.</li> 1440</ul> 1441 1442<p>The distribution includes a set of examples and regression tests for the 1443python bindings in the <code>python/tests</code> directory. Here are some 1444excepts from those tests:</p> 1445 1446<h3>tst.py:</h3> 1447 1448<p>This is a basic test of the file interface and DOM navigation:</p> 1449<pre>import libxml2 1450 1451doc = libxml2.parseFile("tst.xml") 1452if doc.name != "tst.xml": 1453 print "doc.name failed" 1454 sys.exit(1) 1455root = doc.children 1456if root.name != "doc": 1457 print "root.name failed" 1458 sys.exit(1) 1459child = root.children 1460if child.name != "foo": 1461 print "child.name failed" 1462 sys.exit(1) 1463doc.freeDoc()</pre> 1464 1465<p>The Python module is called libxml2, parseFile is the equivalent of 1466xmlParseFile (most of the bindings are automatically generated, and the xml 1467prefix is removed and the casing convention are kept). All node seen at the 1468binding level share the same subset of accesors:</p> 1469<ul> 1470 <li><code>name</code> : returns the node name</li> 1471 <li><code>type</code> : returns a string indicating the node 1472 typ<code>e</code></li> 1473 <li><code>content</code> : returns the content of the node, it is based on 1474 xmlNodeGetContent() and hence is recursive.</li> 1475 <li><code>parent</code> , <code>children</code>, <code>last</code>, 1476 <code>next</code>, <code>prev</code>, <code>doc</code>, 1477 <code>properties</code>: pointing to the associated element in the tree, 1478 those may return None in case no such link exists.</li> 1479</ul> 1480 1481<p>Also note the need to explicitely deallocate documents with freeDoc() . 1482Reference counting for libxml2 trees would need quite a lot of work to 1483function properly, and rather than risk memory leaks if not implemented 1484correctly it sounds safer to have an explicit function to free a tree. The 1485wrapper python objects like doc, root or child are them automatically garbage 1486collected.</p> 1487 1488<h3>validate.py:</h3> 1489 1490<p>This test check the validation interfaces and redirection of error 1491messages:</p> 1492<pre>import libxml2 1493 1494#desactivate error messages from the validation 1495def noerr(ctx, str): 1496 pass 1497 1498libxml2.registerErrorHandler(noerr, None) 1499 1500ctxt = libxml2.createFileParserCtxt("invalid.xml") 1501ctxt.validate(1) 1502ctxt.parseDocument() 1503doc = ctxt.doc() 1504valid = ctxt.isValid() 1505doc.freeDoc() 1506if valid != 0: 1507 print "validity chec failed"</pre> 1508 1509<p>The first thing to notice is the call to registerErrorHandler(), it 1510defines a new error handler global to the library. It is used to avoid seeing 1511the error messages when trying to validate the invalid document.</p> 1512 1513<p>The main interest of that test is the creation of a parser context with 1514createFileParserCtxt() and how the behaviour can be changed before calling 1515parseDocument() . Similary the informations resulting from the parsing phase 1516are also available using context methods.</p> 1517 1518<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the 1519C function interfaces in terms of objects method as much as possible. The 1520best to get a complete view of what methods are supported is to look at the 1521libxml2.py module containing all the wrappers.</p> 1522 1523<h3>push.py:</h3> 1524 1525<p>This test show how to activate the push parser interface:</p> 1526<pre>import libxml2 1527 1528ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") 1529ctxt.parseChunk("/>", 2, 1) 1530doc = ctxt.doc() 1531 1532doc.freeDoc()</pre> 1533 1534<p>The context is created with a speciall call based on the 1535xmlCreatePushParser() from the C library. The first argument is an optional 1536SAX callback object, then the initial set of data, the lenght and the name of 1537the resource in case URI-References need to be computed by the parser.</p> 1538 1539<p>Then the data are pushed using the parseChunk() method, the last call 1540setting the thrird argument terminate to 1.</p> 1541 1542<h3>pushSAX.py:</h3> 1543 1544<p>this test show the use of the event based parsing interfaces. In this case 1545the parser does not build a document, but provides callback information as 1546the parser makes progresses analyzing the data being provided:</p> 1547<pre>import libxml2 1548log = "" 1549 1550class callback: 1551 def startDocument(self): 1552 global log 1553 log = log + "startDocument:" 1554 1555 def endDocument(self): 1556 global log 1557 log = log + "endDocument:" 1558 1559 def startElement(self, tag, attrs): 1560 global log 1561 log = log + "startElement %s %s:" % (tag, attrs) 1562 1563 def endElement(self, tag): 1564 global log 1565 log = log + "endElement %s:" % (tag) 1566 1567 def characters(self, data): 1568 global log 1569 log = log + "characters: %s:" % (data) 1570 1571 def warning(self, msg): 1572 global log 1573 log = log + "warning: %s:" % (msg) 1574 1575 def error(self, msg): 1576 global log 1577 log = log + "error: %s:" % (msg) 1578 1579 def fatalError(self, msg): 1580 global log 1581 log = log + "fatalError: %s:" % (msg) 1582 1583handler = callback() 1584 1585ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") 1586chunk = " url='tst'>b" 1587ctxt.parseChunk(chunk, len(chunk), 0) 1588chunk = "ar</foo>" 1589ctxt.parseChunk(chunk, len(chunk), 1) 1590 1591reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 1592 "characters: bar:endElement foo:endDocument:" 1593if log != reference: 1594 print "Error got: %s" % log 1595 print "Exprected: %s" % reference</pre> 1596 1597<p>The key object in that test is the handler, it provides a number of entry 1598points which can be called by the parser as it makes progresses to indicate 1599the information set obtained. The full set of callback is larger than what 1600the callback class in that specific example implements (see the SAX 1601definition for a complete list). The wrapper will only call those supplied by 1602the object when activated. The startElement receives the names of the element 1603and a dictionnary containing the attributes carried by this element.</p> 1604 1605<p>Also note that the reference string generated from the callback shows a 1606single character call even though the string "bar" is passed to the parser 1607from 2 different call to parseChunk()</p> 1608 1609<h3>xpath.py:</h3> 1610 1611<p>This is a basic test of XPath warppers support</p> 1612<pre>import libxml2 1613 1614doc = libxml2.parseFile("tst.xml") 1615ctxt = doc.xpathNewContext() 1616res = ctxt.xpathEval("//*") 1617if len(res) != 2: 1618 print "xpath query: wrong node set size" 1619 sys.exit(1) 1620if res[0].name != "doc" or res[1].name != "foo": 1621 print "xpath query: wrong node set value" 1622 sys.exit(1) 1623doc.freeDoc() 1624ctxt.xpathFreeContext()</pre> 1625 1626<p>This test parses a file, then create an XPath context to evaluate XPath 1627expression on it. The xpathEval() method execute an XPath query and returns 1628the result mapped in a Python way. String and numbers are natively converted, 1629and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like 1630the document, the XPath context need to be freed explicitely, also not that 1631the result of the XPath query may point back to the document tree and hence 1632the document must be freed after the result of the query is used.</p> 1633 1634<h3>xpathext.py:</h3> 1635 1636<p>This test shows how to extend the XPath engine with functions written in 1637python:</p> 1638<pre>import libxml2 1639 1640def foo(ctx, x): 1641 return x + 1 1642 1643doc = libxml2.parseFile("tst.xml") 1644ctxt = doc.xpathNewContext() 1645libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) 1646res = ctxt.xpathEval("foo(1)") 1647if res != 2: 1648 print "xpath extension failure" 1649doc.freeDoc() 1650ctxt.xpathFreeContext()</pre> 1651 1652<p>Note how the extension function is registered with the context (but that 1653part is not yet finalized, ths may change slightly in the future).</p> 1654 1655<h3>tstxpath.py:</h3> 1656 1657<p>This test is similar to the previousone but shows how the extension 1658function can access the XPath evaluation context:</p> 1659<pre>def foo(ctx, x): 1660 global called 1661 1662 # 1663 # test that access to the XPath evaluation contexts 1664 # 1665 pctxt = libxml2.xpathParserContext(_obj=ctx) 1666 ctxt = pctxt.context() 1667 called = ctxt.function() 1668 return x + 1</pre> 1669 1670<p>All the interfaces around the XPath parser(or rather evaluation) context 1671are not finalized, but it should be sufficient to do contextual work at the 1672evaluation point.</p> 1673 1674<h3>Memory debugging:</h3> 1675 1676<p>last but not least, all tests starts with the following prologue:</p> 1677<pre>#memory debug specific 1678libxml2.debugMemory(1)</pre> 1679 1680<p>and ends with the following epilogue:</p> 1681<pre>#memory debug specific 1682libxml2.cleanupParser() 1683if libxml2.debugMemory(1) == 0: 1684 print "OK" 1685else: 1686 print "Memory leak %d bytes" % (libxml2.debugMemory(1)) 1687 libxml2.dumpMemory()</pre> 1688 1689<p>Those activate the memory debugging interface of libxml2 where all 1690alloacted block in the library are tracked. The prologue then cleans up the 1691library state and checks that all allocated memory has been freed. If not it 1692calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p> 1693 1694<h2><a name="architecture">libxml architecture</a></h2> 1695 1696<p>Libxml is made of multiple components; some of them are optional, and most 1697of the block interfaces are public. The main components are:</p> 1698<ul> 1699 <li>an Input/Output layer</li> 1700 <li>FTP and HTTP client layers (optional)</li> 1701 <li>an Internationalization layer managing the encodings support</li> 1702 <li>a URI module</li> 1703 <li>the XML parser and its basic SAX interface</li> 1704 <li>an HTML parser using the same SAX interface (optional)</li> 1705 <li>a SAX tree module to build an in-memory DOM representation</li> 1706 <li>a tree module to manipulate the DOM representation</li> 1707 <li>a validation module using the DOM representation (optional)</li> 1708 <li>an XPath module for global lookup in a DOM representation 1709 (optional)</li> 1710 <li>a debug module (optional)</li> 1711</ul> 1712 1713<p>Graphically this gives the following:</p> 1714 1715<p><img src="libxml.gif" alt="a graphical view of the various"></p> 1716 1717<p></p> 1718 1719<h2><a name="tree">The tree output</a></h2> 1720 1721<p>The parser returns a tree built during the document analysis. The value 1722returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an 1723<strong>xmlDoc</strong> structure). This structure contains information such 1724as the file name, the document type, and a <strong>children</strong> pointer 1725which is the root of the document (or more exactly the first child under the 1726root which is the document). The tree is made of <strong>xmlNode</strong>s, 1727chained in double-linked lists of siblings and with a children<->parent 1728relationship. An xmlNode can also carry properties (a chain of xmlAttr 1729structures). An attribute may have a value which is a list of TEXT or 1730ENTITY_REF nodes.</p> 1731 1732<p>Here is an example (erroneous with respect to the XML spec since there 1733should be only one ELEMENT under the root):</p> 1734 1735<p><img src="structure.gif" alt=" structure.gif "></p> 1736 1737<p>In the source package there is a small program (not installed by default) 1738called <strong>xmllint</strong> which parses XML files given as argument and 1739prints them back as parsed. This is useful for detecting errors both in XML 1740code and in the XML parser itself. It has an option <strong>--debug</strong> 1741which prints the actual in-memory structure of the document; here is the 1742result with the <a href="#example">example</a> given before:</p> 1743<pre>DOCUMENT 1744version=1.0 1745standalone=true 1746 ELEMENT EXAMPLE 1747 ATTRIBUTE prop1 1748 TEXT 1749 content=gnome is great 1750 ATTRIBUTE prop2 1751 ENTITY_REF 1752 TEXT 1753 content= linux too 1754 ELEMENT head 1755 ELEMENT title 1756 TEXT 1757 content=Welcome to Gnome 1758 ELEMENT chapter 1759 ELEMENT title 1760 TEXT 1761 content=The Linux adventure 1762 ELEMENT p 1763 TEXT 1764 content=bla bla bla ... 1765 ELEMENT image 1766 ATTRIBUTE href 1767 TEXT 1768 content=linus.gif 1769 ELEMENT p 1770 TEXT 1771 content=...</pre> 1772 1773<p>This should be useful for learning the internal representation model.</p> 1774 1775<h2><a name="interface">The SAX interface</a></h2> 1776 1777<p>Sometimes the DOM tree output is just too large to fit reasonably into 1778memory. In that case (and if you don't expect to save back the XML document 1779loaded using libxml), it's better to use the SAX interface of libxml. SAX is 1780a <strong>callback-based interface</strong> to the parser. Before parsing, 1781the application layer registers a customized set of callbacks which are 1782called by the library as it progresses through the XML input.</p> 1783 1784<p>To get more detailed step-by-step guidance on using the SAX interface of 1785libxml, see the <a 1786href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice 1787documentation</a>.written by <a href="mailto:james@daa.com.au">James 1788Henstridge</a>.</p> 1789 1790<p>You can debug the SAX behaviour by using the <strong>testSAX</strong> 1791program located in the gnome-xml module (it's usually not shipped in the 1792binary packages of libxml, but you can find it in the tar source 1793distribution). Here is the sequence of callbacks that would be reported by 1794testSAX when parsing the example XML document shown earlier:</p> 1795<pre>SAX.setDocumentLocator() 1796SAX.startDocument() 1797SAX.getEntity(amp) 1798SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too') 1799SAX.characters( , 3) 1800SAX.startElement(head) 1801SAX.characters( , 4) 1802SAX.startElement(title) 1803SAX.characters(Welcome to Gnome, 16) 1804SAX.endElement(title) 1805SAX.characters( , 3) 1806SAX.endElement(head) 1807SAX.characters( , 3) 1808SAX.startElement(chapter) 1809SAX.characters( , 4) 1810SAX.startElement(title) 1811SAX.characters(The Linux adventure, 19) 1812SAX.endElement(title) 1813SAX.characters( , 4) 1814SAX.startElement(p) 1815SAX.characters(bla bla bla ..., 15) 1816SAX.endElement(p) 1817SAX.characters( , 4) 1818SAX.startElement(image, href='linus.gif') 1819SAX.endElement(image) 1820SAX.characters( , 4) 1821SAX.startElement(p) 1822SAX.characters(..., 3) 1823SAX.endElement(p) 1824SAX.characters( , 3) 1825SAX.endElement(chapter) 1826SAX.characters( , 1) 1827SAX.endElement(EXAMPLE) 1828SAX.endDocument()</pre> 1829 1830<p>Most of the other interfaces of libxml are based on the DOM tree-building 1831facility, so nearly everything up to the end of this document presupposes the 1832use of the standard DOM tree build. Note that the DOM tree itself is built by 1833a set of registered default callbacks, without internal specific 1834interface.</p> 1835 1836<h2><a name="Validation">Validation & DTDs</a></h2> 1837 1838<p>Table of Content:</p> 1839<ol> 1840 <li><a href="#General5">General overview</a></li> 1841 <li><a href="#definition">The definition</a></li> 1842 <li><a href="#Simple">Simple rules</a> 1843 <ol> 1844 <li><a href="#reference">How to reference a DTD from a document</a></li> 1845 <li><a href="#Declaring">Declaring elements</a></li> 1846 <li><a href="#Declaring1">Declaring attributes</a></li> 1847 </ol> 1848 </li> 1849 <li><a href="#Some">Some examples</a></li> 1850 <li><a href="#validate">How to validate</a></li> 1851 <li><a href="#Other">Other resources</a></li> 1852</ol> 1853 1854<h3><a name="General5">General overview</a></h3> 1855 1856<p>Well what is validation and what is a DTD ?</p> 1857 1858<p>DTD is the acronym for Document Type Definition. This is a description of 1859the content for a familly of XML files. This is part of the XML 1.0 1860specification, and alows to describe and check that a given document instance 1861conforms to a set of rules detailing its structure and content.</p> 1862 1863<p>Validation is the process of checking a document against a DTD (more 1864generally against a set of construction rules).</p> 1865 1866<p>The validation process and building DTDs are the two most difficult parts 1867of the XML life cycle. Briefly a DTD defines all the possibles element to be 1868found within your document, what is the formal shape of your document tree 1869(by defining the allowed content of an element, either text, a regular 1870expression for the allowed list of children, or mixed content i.e. both text 1871and children). The DTD also defines the allowed attributes for all elements 1872and the types of the attributes.</p> 1873 1874<h3><a name="definition1">The definition</a></h3> 1875 1876<p>The <a href="http://www.w3.org/TR/REC-xml">W3C XML Recommendation</a> (<a 1877href="http://www.xml.com/axml/axml.html">Tim Bray's annotated version of 1878Rev1</a>):</p> 1879<ul> 1880 <li><a href="http://www.w3.org/TR/REC-xml#elemdecls">Declaring 1881 elements</a></li> 1882 <li><a href="http://www.w3.org/TR/REC-xml#attdecls">Declaring 1883 attributes</a></li> 1884</ul> 1885 1886<p>(unfortunately) all this is inherited from the SGML world, the syntax is 1887ancient...</p> 1888 1889<h3><a name="Simple1">Simple rules</a></h3> 1890 1891<p>Writing DTD can be done in multiple ways, the rules to build them if you 1892need something fixed or something which can evolve over time can be radically 1893different. Really complex DTD like Docbook ones are flexible but quite harder 1894to design. I will just focuse on DTDs for a formats with a fixed simple 1895structure. It is just a set of basic rules, and definitely not exhaustive nor 1896useable for complex DTD design.</p> 1897 1898<h4><a name="reference1">How to reference a DTD from a document</a>:</h4> 1899 1900<p>Assuming the top element of the document is <code>spec</code> and the dtd 1901is placed in the file <code>mydtd</code> in the subdirectory 1902<code>dtds</code> of the directory from where the document were loaded:</p> 1903 1904<p><code><!DOCTYPE spec SYSTEM "dtds/mydtd"></code></p> 1905 1906<p>Notes:</p> 1907<ul> 1908 <li>the system string is actually an URI-Reference (as defined in <a 1909 href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>) so you can use a 1910 full URL string indicating the location of your DTD on the Web, this is a 1911 really good thing to do if you want others to validate your document</li> 1912 <li>it is also possible to associate a <code>PUBLIC</code> identifier (a 1913 magic string) so that the DTd is looked up in catalogs on the client side 1914 without having to locate it on the web</li> 1915 <li>a dtd contains a set of elements and attributes declarations, but they 1916 don't define what the root of the document should be. This is explicitely 1917 told to the parser/validator as the first element of the 1918 <code>DOCTYPE</code> declaration.</li> 1919</ul> 1920 1921<h4><a name="Declaring2">Declaring elements</a>:</h4> 1922 1923<p>The following declares an element <code>spec</code>:</p> 1924 1925<p><code><!ELEMENT spec (front, body, back?)></code></p> 1926 1927<p>it also expresses that the spec element contains one <code>front</code>, 1928one <code>body</code> and one optionnal <code>back</code> children elements 1929in this order. The declaration of one element of the structure and its 1930content are done in a single declaration. Similary the following declares 1931<code>div1</code> elements:</p> 1932 1933<p><code><!ELEMENT div1 (head, (p | list | note)*, div2?)></code></p> 1934 1935<p>means div1 contains one <code>head</code> then a series of optional 1936<code>p</code>, <code>list</code>s and <code>note</code>s and then an 1937optional <code>div2</code>. And last but not least an element can contain 1938text:</p> 1939 1940<p><code><!ELEMENT b (#PCDATA)></code></p> 1941 1942<p><code>b</code> contains text or being of mixed content (text and elements 1943in no particular order):</p> 1944 1945<p><code><!ELEMENT p (#PCDATA|a|ul|b|i|em)*></code></p> 1946 1947<p><code>p </code>can contain text or <code>a</code>, <code>ul</code>, 1948<code>b</code>, <code>i </code>or <code>em</code> elements in no particular 1949order.</p> 1950 1951<h4><a name="Declaring1">Declaring attributes</a>:</h4> 1952 1953<p>again the attributes declaration includes their content definition:</p> 1954 1955<p><code><!ATTLIST termdef name CDATA #IMPLIED></code></p> 1956 1957<p>means that the element <code>termdef</code> can have a <code>name</code> 1958attribute containing text (<code>CDATA</code>) and which is optionnal 1959(<code>#IMPLIED</code>). The attribute value can also be defined within a 1960set:</p> 1961 1962<p><code><!ATTLIST list type (bullets|ordered|glossary) 1963"ordered"></code></p> 1964 1965<p>means <code>list</code> element have a <code>type</code> attribute with 3 1966allowed values "bullets", "ordered" or "glossary" and which default to 1967"ordered" if the attribute is not explicitely specified.</p> 1968 1969<p>The content type of an attribute can be text (<code>CDATA</code>), 1970anchor/reference/references 1971(<code>ID</code>/<code>IDREF</code>/<code>IDREFS</code>), entity(ies) 1972(<code>ENTITY</code>/<code>ENTITIES</code>) or name(s) 1973(<code>NMTOKEN</code>/<code>NMTOKENS</code>). The following defines that a 1974<code>chapter</code> element can have an optional <code>id</code> attribute 1975of type <code>ID</code>, usable for reference from attribute of type 1976IDREF:</p> 1977 1978<p><code><!ATTLIST chapter id ID #IMPLIED></code></p> 1979 1980<p>The last value of an attribute definition can be <code>#REQUIRED 1981</code>meaning that the attribute has to be given, <code>#IMPLIED</code> 1982meaning that it is optional, or the default value (possibly prefixed by 1983<code>#FIXED</code> if it is the only allowed).</p> 1984 1985<p>Notes:</p> 1986<ul> 1987 <li>usually the attributes pertaining to a given element are declared in a 1988 single expression, but it is just a convention adopted by a lot of DTD 1989 writers: 1990 <pre><!ATTLIST termdef 1991 id ID #REQUIRED 1992 name CDATA #IMPLIED></pre> 1993 <p>The previous construct defines both <code>id</code> and 1994 <code>name</code> attributes for the element <code>termdef</code></p> 1995 </li> 1996</ul> 1997 1998<h3><a name="Some1">Some examples</a></h3> 1999 2000<p>The directory <code>test/valid/dtds/</code> in the libxml distribution 2001contains some complex DTD examples. The <code>test/valid/dia.xml</code> 2002example shows an XML file where the simple DTD is directly included within 2003the document.</p> 2004 2005<h3><a name="validate1">How to validate</a></h3> 2006 2007<p>The simplest is to use the xmllint program comming with libxml. The 2008<code>--valid</code> option turn on validation of the files given as input, 2009for example the following validates a copy of the first revision of the XML 20101.0 specification:</p> 2011 2012<p><code>xmllint --valid --noout test/valid/REC-xml-19980210.xml</code></p> 2013 2014<p>the -- noout is used to not output the resulting tree.</p> 2015 2016<p>The <code>--dtdvalid dtd</code> allows to validate the document(s) against 2017a given DTD.</p> 2018 2019<p>Libxml exports an API to handle DTDs and validation, check the <a 2020href="http://xmlsoft.org/html/libxml-valid.html">associated 2021description</a>.</p> 2022 2023<h3><a name="Other1">Other resources</a></h3> 2024 2025<p>DTDs are as old as SGML. So there may be a number of examples on-line, I 2026will just list one for now, others pointers welcome:</p> 2027<ul> 2028 <li><a href="http://www.xml101.com:8081/dtd/">XML-101 DTD</a></li> 2029</ul> 2030 2031<p>I suggest looking at the examples found under test/valid/dtd and any of 2032the large number of books available on XML. The dia example in test/valid 2033should be both simple and complete enough to allow you to build your own.</p> 2034 2035<p></p> 2036 2037<h2><a name="Memory">Memory Management</a></h2> 2038 2039<p>Table of Content:</p> 2040<ol> 2041 <li><a href="#General3">General overview</a></li> 2042 <li><a href="#setting">Setting libxml set of memory routines</a></li> 2043 <li><a href="#cleanup">Cleaning up after parsing</a></li> 2044 <li><a href="#Debugging">Debugging routines</a></li> 2045 <li><a href="#General4">General memory requirements</a></li> 2046</ol> 2047 2048<h3><a name="General3">General overview</a></h3> 2049 2050<p>The module <code><a 2051href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlmemory.h</a></code> 2052provides the interfaces to the libxml memory system:</p> 2053<ul> 2054 <li>libxml does not use the libc memory allocator directly but xmlFree(), 2055 xmlMalloc() and xmlRealloc()</li> 2056 <li>those routines can be reallocated to a specific set of routine, by 2057 default the libc ones i.e. free(), malloc() and realloc()</li> 2058 <li>the xmlmemory.c module includes a set of debugging routine</li> 2059</ul> 2060 2061<h3><a name="setting">Setting libxml set of memory routines</a></h3> 2062 2063<p>It is sometimes useful to not use the default memory allocator, either for 2064debugging, analysis or to implement a specific behaviour on memory management 2065(like on embedded systems). Two function calls are available to do so:</p> 2066<ul> 2067 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemGet 2068 ()</a> which return the current set of functions in use by the parser</li> 2069 <li><a 2070 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemSetup()</a> 2071 which allow to set up a new set of memory allocation functions</li> 2072</ul> 2073 2074<p>Of course a call to xmlMemSetup() should probably be done before calling 2075any other libxml routines (unless you are sure your allocations routines are 2076compatibles).</p> 2077 2078<h3><a name="cleanup">Cleaning up after parsing</a></h3> 2079 2080<p>Libxml is not stateless, there is a few set of memory structures needing 2081allocation before the parser is fully functionnal (some encoding structures 2082for example). This also mean that once parsing is finished there is a tiny 2083amount of memory (a few hundred bytes) which can be recollected if you don't 2084reuse the parser immediately:</p> 2085<ul> 2086 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlCleanupParser 2087 ()</a> is a centralized routine to free the parsing states. Note that it 2088 won't deallocate any produced tree if any (use the xmlFreeDoc() and 2089 related routines for this).</li> 2090 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlInitParser 2091 ()</a> is the dual routine allowing to preallocate the parsing state 2092 which can be useful for example to avoid initialization reentrancy 2093 problems when using libxml in multithreaded applications</li> 2094</ul> 2095 2096<p>Generally xmlCleanupParser() is safe, if needed the state will be rebuild 2097at the next invocation of parser routines, but be careful of the consequences 2098in multithreaded applications.</p> 2099 2100<h3><a name="Debugging">Debugging routines</a></h3> 2101 2102<p>When configured using --with-mem-debug flag (off by default), libxml uses 2103a set of memory allocation debugging routineskeeping track of all allocated 2104blocks and the location in the code where the routine was called. A couple of 2105other debugging routines allow to dump the memory allocated infos to a file 2106or call a specific routine when a given block number is allocated:</p> 2107<ul> 2108 <li><a 2109 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMallocLoc()</a> 2110 <a 2111 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlReallocLoc()</a> 2112 and <a 2113 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemStrdupLoc()</a> 2114 are the memory debugging replacement allocation routines</li> 2115 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemoryDump 2116 ()</a> dumps all the informations about the allocated memory block lefts 2117 in the <code>.memdump</code> file</li> 2118</ul> 2119 2120<p>When developping libxml memory debug is enabled, the tests programs call 2121xmlMemoryDump () and the "make test" regression tests will check for any 2122memory leak during the full regression test sequence, this helps a lot 2123ensuring that libxml does not leak memory and bullet proof memory 2124allocations use (some libc implementations are known to be far too permissive 2125resulting in major portability problems!).</p> 2126 2127<p>If the .memdump reports a leak, it displays the allocation function and 2128also tries to give some informations about the content and structure of the 2129allocated blocks left. This is sufficient in most cases to find the culprit, 2130but not always. Assuming the allocation problem is reproductible, it is 2131possible to find more easilly:</p> 2132<ol> 2133 <li>write down the block number xxxx not allocated</li> 2134 <li>export the environement variable XML_MEM_BREAKPOINT=xxxx , the easiest 2135 when using GDB is to simply give the command 2136 <p><code>set environment XML_MEM_BREAKPOINT xxxx</code></p> 2137 <p>before running the program.</p> 2138 </li> 2139 <li>run the program under a debugger and set a breakpoint on 2140 xmlMallocBreakpoint() a specific function called when this precise block 2141 is allocated</li> 2142 <li>when the breakpoint is reached you can then do a fine analysis of the 2143 allocation an step to see the condition resulting in the missing 2144 deallocation.</li> 2145</ol> 2146 2147<p>I used to use a commercial tool to debug libxml memory problems but after 2148noticing that it was not detecting memory leaks that simple mechanism was 2149used and proved extremely efficient until now. Lately I have also used <a 2150href="http://developer.kde.org/~sewardj/">valgrind</a> with quite some 2151success, it is tied to the i386 architecture since it works by emulating the 2152processor and instruction set, it is slow but extremely efficient, i.e. it 2153spot memory usage errors in a very precise way.</p> 2154 2155<h3><a name="General4">General memory requirements</a></h3> 2156 2157<p>How much libxml memory require ? It's hard to tell in average it depends 2158of a number of things:</p> 2159<ul> 2160 <li>the parser itself should work in a fixed amout of memory, except for 2161 information maintained about the stacks of names and entities locations. 2162 The I/O and encoding handlers will probably account for a few KBytes. 2163 This is true for both the XML and HTML parser (though the HTML parser 2164 need more state).</li> 2165 <li>If you are generating the DOM tree then memory requirements will grow 2166 nearly lineary with the size of the data. In general for a balanced 2167 textual document the internal memory requirement is about 4 times the 2168 size of the UTF8 serialization of this document (exmple the XML-1.0 2169 recommendation is a bit more of 150KBytes and takes 650KBytes of main 2170 memory when parsed). Validation will add a amount of memory required for 2171 maintaining the external Dtd state which should be linear with the 2172 complexity of the content model defined by the Dtd</li> 2173 <li>If you don't care about the advanced features of libxml like 2174 validation, DOM, XPath or XPointer, but really need to work fixed memory 2175 requirements, then the SAX interface should be used.</li> 2176</ul> 2177 2178<p></p> 2179 2180<h2><a name="Encodings">Encodings support</a></h2> 2181 2182<p>Table of Content:</p> 2183<ol> 2184 <li><a href="encoding.html#What">What does internationalization support 2185 mean ?</a></li> 2186 <li><a href="encoding.html#internal">The internal encoding, how and 2187 why</a></li> 2188 <li><a href="encoding.html#implemente">How is it implemented ?</a></li> 2189 <li><a href="encoding.html#Default">Default supported encodings</a></li> 2190 <li><a href="encoding.html#extend">How to extend the existing 2191 support</a></li> 2192</ol> 2193 2194<h3><a name="What">What does internationalization support mean ?</a></h3> 2195 2196<p>XML was designed from the start to allow the support of any character set 2197by using Unicode. Any conformant XML parser has to support the UTF-8 and 2198UTF-16 default encodings which can both express the full unicode ranges. UTF8 2199is a variable length encoding whose greatest point are to resuse the same 2200emcoding for ASCII and to save space for Western encodings, but it is a bit 2201more complex to handle in practice. UTF-16 use 2 bytes per characters (and 2202sometimes combines two pairs), it makes implementation easier, but looks a 2203bit overkill for Western languages encoding. Moreover the XML specification 2204allows document to be encoded in other encodings at the condition that they 2205are clearly labelled as such. For example the following is a wellformed XML 2206document encoded in ISO-8859 1 and using accentuated letter that we French 2207likes for both markup and content:</p> 2208<pre><?xml version="1.0" encoding="ISO-8859-1"?> 2209<tr�s>l�</tr�s></pre> 2210 2211<p>Having internationalization support in libxml means the foolowing:</p> 2212<ul> 2213 <li>the document is properly parsed</li> 2214 <li>informations about it's encoding are saved</li> 2215 <li>it can be modified</li> 2216 <li>it can be saved in its original encoding</li> 2217 <li>it can also be saved in another encoding supported by libxml (for 2218 example straight UTF8 or even an ASCII form)</li> 2219</ul> 2220 2221<p>Another very important point is that the whole libxml API, with the 2222exception of a few routines to read with a specific encoding or save to a 2223specific encoding, is completely agnostic about the original encoding of the 2224document.</p> 2225 2226<p>It should be noted too that the HTML parser embedded in libxml now obbey 2227the same rules too, the following document will be (as of 2.2.2) handled in 2228an internationalized fashion by libxml too:</p> 2229<pre><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" 2230 "http://www.w3.org/TR/REC-html40/loose.dtd"> 2231<html lang="fr"> 2232<head> 2233 <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"> 2234</head> 2235<body> 2236<p>W3C cr�e des standards pour le Web.</body> 2237</html></pre> 2238 2239<h3><a name="internal">The internal encoding, how and why</a></h3> 2240 2241<p>One of the core decision was to force all documents to be converted to a 2242default internal encoding, and that encoding to be UTF-8, here are the 2243rationale for those choices:</p> 2244<ul> 2245 <li>keeping the native encoding in the internal form would force the libxml 2246 users (or the code associated) to be fully aware of the encoding of the 2247 original document, for examples when adding a text node to a document, 2248 the content would have to be provided in the document encoding, i.e. the 2249 client code would have to check it before hand, make sure it's conformant 2250 to the encoding, etc ... Very hard in practice, though in some specific 2251 cases this may make sense.</li> 2252 <li>the second decision was which encoding. From the XML spec only UTF8 and 2253 UTF16 really makes sense as being the two only encodings for which there 2254 is amndatory support. UCS-4 (32 bits fixed size encoding) could be 2255 considered an intelligent choice too since it's a direct Unicode mapping 2256 support. I selected UTF-8 on the basis of efficiency and compatibility 2257 with surrounding software: 2258 <ul> 2259 <li>UTF-8 while a bit more complex to convert from/to (i.e. slightly 2260 more costly to import and export CPU wise) is also far more compact 2261 than UTF-16 (and UCS-4) for a majority of the documents I see it used 2262 for right now (RPM RDF catalogs, advogato data, various configuration 2263 file formats, etc.) and the key point for today's computer 2264 architecture is efficient uses of caches. If one nearly double the 2265 memory requirement to store the same amount of data, this will trash 2266 caches (main memory/external caches/internal caches) and my take is 2267 that this harms the system far more than the CPU requirements needed 2268 for the conversion to UTF-8</li> 2269 <li>Most of libxml version 1 users were using it with straight ASCII 2270 most of the time, doing the conversion with an internal encoding 2271 requiring all their code to be rewritten was a serious show-stopper 2272 for using UTF-16 or UCS-4.</li> 2273 <li>UTF-8 is being used as the de-facto internal encoding standard for 2274 related code like the <a href="http://www.pango.org/">pango</a> 2275 upcoming Gnome text widget, and a lot of Unix code (yep another place 2276 where Unix programmer base takes a different approach from Microsoft 2277 - they are using UTF-16)</li> 2278 </ul> 2279 </li> 2280</ul> 2281 2282<p>What does this mean in practice for the libxml user:</p> 2283<ul> 2284 <li>xmlChar, the libxml data type is a byte, those bytes must be assembled 2285 as UTF-8 valid strings. The proper way to terminate an xmlChar * string 2286 is simply to append 0 byte, as usual.</li> 2287 <li>One just need to make sure that when using chars outside the ASCII set, 2288 the values has been properly converted to UTF-8</li> 2289</ul> 2290 2291<h3><a name="implemente">How is it implemented ?</a></h3> 2292 2293<p>Let's describe how all this works within libxml, basically the I18N 2294(internationalization) support get triggered only during I/O operation, i.e. 2295when reading a document or saving one. Let's look first at the reading 2296sequence:</p> 2297<ol> 2298 <li>when a document is processed, we usually don't know the encoding, a 2299 simple heuristic allows to detect UTF-18 and UCS-4 from whose where the 2300 ASCII range (0-0x7F) maps with ASCII</li> 2301 <li>the xml declaration if available is parsed, including the encoding 2302 declaration. At that point, if the autodetected encoding is different 2303 from the one declared a call to xmlSwitchEncoding() is issued.</li> 2304 <li>If there is no encoding declaration, then the input has to be in either 2305 UTF-8 or UTF-16, if it is not then at some point when processing the 2306 input, the converter/checker of UTF-8 form will raise an encoding error. 2307 You may end-up with a garbled document, or no document at all ! Example: 2308 <pre>~/XML -> /xmllint err.xml 2309err.xml:1: error: Input is not proper UTF-8, indicate encoding ! 2310<tr�s>l�</tr�s> 2311 ^ 2312err.xml:1: error: Bytes: 0xE8 0x73 0x3E 0x6C 2313<tr�s>l�</tr�s> 2314 ^</pre> 2315 </li> 2316 <li>xmlSwitchEncoding() does an encoding name lookup, canonalize it, and 2317 then search the default registered encoding converters for that encoding. 2318 If it's not within the default set and iconv() support has been compiled 2319 it, it will ask iconv for such an encoder. If this fails then the parser 2320 will report an error and stops processing: 2321 <pre>~/XML -> /xmllint err2.xml 2322err2.xml:1: error: Unsupported encoding UnsupportedEnc 2323<?xml version="1.0" encoding="UnsupportedEnc"?> 2324 ^</pre> 2325 </li> 2326 <li>From that point the encoder process progressingly the input (it is 2327 plugged as a front-end to the I/O module) for that entity. It captures 2328 and convert on-the-fly the document to be parsed to UTF-8. The parser 2329 itself just does UTF-8 checking of this input and process it 2330 transparently. The only difference is that the encoding information has 2331 been added to the parsing context (more precisely to the input 2332 corresponding to this entity).</li> 2333 <li>The result (when using DOM) is an internal form completely in UTF-8 2334 with just an encoding information on the document node.</li> 2335</ol> 2336 2337<p>Ok then what's happen when saving the document (assuming you 2338colllected/built an xmlDoc DOM like structure) ? It depends on the function 2339called, xmlSaveFile() will just try to save in the original encoding, while 2340xmlSaveFileTo() and xmlSaveFileEnc() can optionally save to a given 2341encoding:</p> 2342<ol> 2343 <li>if no encoding is given, libxml will look for an encoding value 2344 associated to the document and if it exists will try to save to that 2345 encoding, 2346 <p>otherwise everything is written in the internal form, i.e. UTF-8</p> 2347 </li> 2348 <li>so if an encoding was specified, either at the API level or on the 2349 document, libxml will again canonalize the encoding name, lookup for a 2350 converter in the registered set or through iconv. If not found the 2351 function will return an error code</li> 2352 <li>the converter is placed before the I/O buffer layer, as another kind of 2353 buffer, then libxml will simply push the UTF-8 serialization to through 2354 that buffer, which will then progressively be converted and pushed onto 2355 the I/O layer.</li> 2356 <li>It is possible that the converter code fails on some input, for example 2357 trying to push an UTF-8 encoded chinese character through the UTF-8 to 2358 ISO-8859-1 converter won't work. Since the encoders are progressive they 2359 will just report the error and the number of bytes converted, at that 2360 point libxml will decode the offending character, remove it from the 2361 buffer and replace it with the associated charRef encoding &#123; and 2362 resume the convertion. This guarante that any document will be saved 2363 without losses (except for markup names where this is not legal, this is 2364 a problem in the current version, in pactice avoid using non-ascci 2365 characters for tags or attributes names @@). A special "ascii" encoding 2366 name is used to save documents to a pure ascii form can be used when 2367 portability is really crucial</li> 2368</ol> 2369 2370<p>Here is a few examples based on the same test document:</p> 2371<pre>~/XML -> /xmllint isolat1 2372<?xml version="1.0" encoding="ISO-8859-1"?> 2373<tr�s>l�</tr�s> 2374~/XML -> /xmllint --encode UTF-8 isolat1 2375<?xml version="1.0" encoding="UTF-8"?> 2376<très>l� �</très> 2377~/XML -> </pre> 2378 2379<p>The same processing is applied (and reuse most of the code) for HTML I18N 2380processing. Looking up and modifying the content encoding is a bit more 2381difficult since it is located in a <meta> tag under the <head>, 2382so a couple of functions htmlGetMetaEncoding() and htmlSetMetaEncoding() have 2383been provided. The parser also attempts to switch encoding on the fly when 2384detecting such a tag on input. Except for that the processing is the same 2385(and again reuses the same code).</p> 2386 2387<h3><a name="Default">Default supported encodings</a></h3> 2388 2389<p>libxml has a set of default converters for the following encodings 2390(located in encoding.c):</p> 2391<ol> 2392 <li>UTF-8 is supported by default (null handlers)</li> 2393 <li>UTF-16, both little and big endian</li> 2394 <li>ISO-Latin-1 (ISO-8859-1) covering most western languages</li> 2395 <li>ASCII, useful mostly for saving</li> 2396 <li>HTML, a specific handler for the conversion of UTF-8 to ASCII with HTML 2397 predefined entities like &copy; for the Copyright sign.</li> 2398</ol> 2399 2400<p>More over when compiled on an Unix platfor with iconv support the full set 2401of encodings supported by iconv can be instantly be used by libxml. On a 2402linux machine with glibc-2.1 the list of supported encodings and aliases fill 24033 full pages, and include UCS-4, the full set of ISO-Latin encodings, and the 2404various Japanese ones.</p> 2405 2406<h4>Encoding aliases</h4> 2407 2408<p>From 2.2.3, libxml has support to register encoding names aliases. The 2409goal is to be able to parse document whose encoding is supported but where 2410the name differs (for example from the default set of names accepted by 2411iconv). The following functions allow to register and handle new aliases for 2412existing encodings. Once registered libxml will automatically lookup the 2413aliases when handling a document:</p> 2414<ul> 2415 <li>int xmlAddEncodingAlias(const char *name, const char *alias);</li> 2416 <li>int xmlDelEncodingAlias(const char *alias);</li> 2417 <li>const char * xmlGetEncodingAlias(const char *alias);</li> 2418 <li>void xmlCleanupEncodingAliases(void);</li> 2419</ul> 2420 2421<h3><a name="extend">How to extend the existing support</a></h3> 2422 2423<p>Well adding support for new encoding, or overriding one of the encoders 2424(assuming it is buggy) should not be hard, just write an input and output 2425conversion routines to/from UTF-8, and register them using 2426xmlNewCharEncodingHandler(name, xxxToUTF8, UTF8Toxxx), and they will be 2427called automatically if the parser(s) encounter such an encoding name 2428(register it uppercase, this will help). The description of the encoders, 2429their arguments and expected return values are described in the encoding.h 2430header.</p> 2431 2432<p>A quick note on the topic of subverting the parser to use a different 2433internal encoding than UTF-8, in some case people will absolutely want to 2434keep the internal encoding different, I think it's still possible (but the 2435encoding must be compliant with ASCII on the same subrange) though I didn't 2436tried it. The key is to override the default conversion routines (by 2437registering null encoders/decoders for your charsets), and bypass the UTF-8 2438checking of the parser by setting the parser context charset 2439(ctxt->charset) to something different than XML_CHAR_ENCODING_UTF8, but 2440there is no guarantee taht this will work. You may also have some troubles 2441saving back.</p> 2442 2443<p>Basically proper I18N support is important, this requires at least 2444libxml-2.0.0, but a lot of features and corrections are really available only 2445starting 2.2.</p> 2446 2447<h2><a name="IO">I/O Interfaces</a></h2> 2448 2449<p>Table of Content:</p> 2450<ol> 2451 <li><a href="#General1">General overview</a></li> 2452 <li><a href="#basic">The basic buffer type</a></li> 2453 <li><a href="#Input">Input I/O handlers</a></li> 2454 <li><a href="#Output">Output I/O handlers</a></li> 2455 <li><a href="#entities">The entities loader</a></li> 2456 <li><a href="#Example2">Example of customized I/O</a></li> 2457</ol> 2458 2459<h3><a name="General1">General overview</a></h3> 2460 2461<p>The module <code><a 2462href="http://xmlsoft.org/html/libxml-xmlio.html">xmlIO.h</a></code> provides 2463the interfaces to the libxml I/O system. This consists of 4 main parts:</p> 2464<ul> 2465 <li>Entities loader, this is a routine which tries to fetch the entities 2466 (files) based on their PUBLIC and SYSTEM identifiers. The default loader 2467 don't look at the public identifier since libxml do not maintain a 2468 catalog. You can redefine you own entity loader by using 2469 <code>xmlGetExternalEntityLoader()</code> and 2470 <code>xmlSetExternalEntityLoader()</code>. <a href="#entities">Check the 2471 example</a>.</li> 2472 <li>Input I/O buffers which are a commodity structure used by the parser(s) 2473 input layer to handle fetching the informations to feed the parser. This 2474 provides buffering and is also a placeholder where the encoding 2475 convertors to UTF8 are piggy-backed.</li> 2476 <li>Output I/O buffers are similar to the Input ones and fulfill similar 2477 task but when generating a serialization from a tree.</li> 2478 <li>A mechanism to register sets of I/O callbacks and associate them with 2479 specific naming schemes like the protocol part of the URIs. 2480 <p>This affect the default I/O operations and allows to use specific I/O 2481 handlers for certain names.</p> 2482 </li> 2483</ul> 2484 2485<p>The general mechanism used when loading http://rpmfind.net/xml.html for 2486example in the HTML parser is the following:</p> 2487<ol> 2488 <li>The default entity loader calls <code>xmlNewInputFromFile()</code> with 2489 the parsing context and the URI string.</li> 2490 <li>the URI string is checked against the existing registered handlers 2491 using their match() callback function, if the HTTP module was compiled 2492 in, it is registered and its match() function will succeeds</li> 2493 <li>the open() function of the handler is called and if successful will 2494 return an I/O Input buffer</li> 2495 <li>the parser will the start reading from this buffer and progressively 2496 fetch information from the resource, calling the read() function of the 2497 handler until the resource is exhausted</li> 2498 <li>if an encoding change is detected it will be installed on the input 2499 buffer, providing buffering and efficient use of the conversion 2500 routines</li> 2501 <li>once the parser has finished, the close() function of the handler is 2502 called once and the Input buffer and associed resources are 2503 deallocated.</li> 2504</ol> 2505 2506<p>The user defined callbacks are checked first to allow overriding of the 2507default libxml I/O routines.</p> 2508 2509<h3><a name="basic">The basic buffer type</a></h3> 2510 2511<p>All the buffer manipulation handling is done using the 2512<code>xmlBuffer</code> type define in <code><a 2513href="http://xmlsoft.org/html/libxml-tree.html">tree.h</a> </code>which is a 2514resizable memory buffer. The buffer allocation strategy can be selected to be 2515either best-fit or use an exponential doubling one (CPU vs. memory use 2516tradeoff). The values are <code>XML_BUFFER_ALLOC_EXACT</code> and 2517<code>XML_BUFFER_ALLOC_DOUBLEIT</code>, and can be set individually or on a 2518system wide basis using <code>xmlBufferSetAllocationScheme()</code>. A number 2519of functions allows to manipulate buffers with names starting with the 2520<code>xmlBuffer...</code> prefix.</p> 2521 2522<h3><a name="Input">Input I/O handlers</a></h3> 2523 2524<p>An Input I/O handler is a simple structure 2525<code>xmlParserInputBuffer</code> containing a context associated to the 2526resource (file descriptor, or pointer to a protocol handler), the read() and 2527close() callbacks to use and an xmlBuffer. And extra xmlBuffer and a charset 2528encoding handler are also present to support charset conversion when 2529needed.</p> 2530 2531<h3><a name="Output">Output I/O handlers</a></h3> 2532 2533<p>An Output handler <code>xmlOutputBuffer</code> is completely similar to an 2534Input one except the callbacks are write() and close().</p> 2535 2536<h3><a name="entities">The entities loader</a></h3> 2537 2538<p>The entity loader resolves requests for new entities and create inputs for 2539the parser. Creating an input from a filename or an URI string is done 2540through the xmlNewInputFromFile() routine. The default entity loader do not 2541handle the PUBLIC identifier associated with an entity (if any). So it just 2542calls xmlNewInputFromFile() with the SYSTEM identifier (which is mandatory in 2543XML).</p> 2544 2545<p>If you want to hook up a catalog mechanism then you simply need to 2546override the default entity loader, here is an example:</p> 2547<pre>#include <libxml/xmlIO.h> 2548 2549xmlExternalEntityLoader defaultLoader = NULL; 2550 2551xmlParserInputPtr 2552xmlMyExternalEntityLoader(const char *URL, const char *ID, 2553 xmlParserCtxtPtr ctxt) { 2554 xmlParserInputPtr ret; 2555 const char *fileID = NULL; 2556 /* lookup for the fileID depending on ID */ 2557 2558 ret = xmlNewInputFromFile(ctxt, fileID); 2559 if (ret != NULL) 2560 return(ret); 2561 if (defaultLoader != NULL) 2562 ret = defaultLoader(URL, ID, ctxt); 2563 return(ret); 2564} 2565 2566int main(..) { 2567 ... 2568 2569 /* 2570 * Install our own entity loader 2571 */ 2572 defaultLoader = xmlGetExternalEntityLoader(); 2573 xmlSetExternalEntityLoader(xmlMyExternalEntityLoader); 2574 2575 ... 2576}</pre> 2577 2578<h3><a name="Example2">Example of customized I/O</a></h3> 2579 2580<p>This example come from <a href="http://xmlsoft.org/messages/0708.html">a 2581real use case</a>, xmlDocDump() closes the FILE * passed by the application 2582and this was a problem. The <a 2583href="http://xmlsoft.org/messages/0711.html">solution</a> was to redefine a 2584new output handler with the closing call deactivated:</p> 2585<ol> 2586 <li>First define a new I/O ouput allocator where the output don't close the 2587 file: 2588 <pre>xmlOutputBufferPtr 2589xmlOutputBufferCreateOwn(FILE *file, xmlCharEncodingHandlerPtr encoder) { 2590����xmlOutputBufferPtr ret; 2591���� 2592����if (xmlOutputCallbackInitialized == 0) 2593��������xmlRegisterDefaultOutputCallbacks(); 2594 2595����if (file == NULL) return(NULL); 2596����ret = xmlAllocOutputBuffer(encoder); 2597����if (ret != NULL) { 2598��������ret->context = file; 2599��������ret->writecallback = xmlFileWrite; 2600��������ret->closecallback = NULL; /* No close callback */ 2601����} 2602����return(ret); <br> 2603 2604 2605 2606 2607 2608 2609 2610 2611 2612 2613 2614 2615} </pre> 2616 </li> 2617 <li>And then use it to save the document: 2618 <pre>FILE *f; 2619xmlOutputBufferPtr output; 2620xmlDocPtr doc; 2621int res; 2622 2623f = ... 2624doc = .... 2625 2626output = xmlOutputBufferCreateOwn(f, NULL); 2627res = xmlSaveFileTo(output, doc, NULL); 2628 </pre> 2629 </li> 2630</ol> 2631 2632<h2><a name="Catalog">Catalog support</a></h2> 2633 2634<p>Table of Content:</p> 2635<ol> 2636 <li><a href="General2">General overview</a></li> 2637 <li><a href="#definition">The definition</a></li> 2638 <li><a href="#Simple">Using catalogs</a></li> 2639 <li><a href="#Some">Some examples</a></li> 2640 <li><a href="#reference">How to tune catalog usage</a></li> 2641 <li><a href="#validate">How to debug catalog processing</a></li> 2642 <li><a href="#Declaring">How to create and maintain catalogs</a></li> 2643 <li><a href="#implemento">The implementor corner quick review of the 2644 API</a></li> 2645 <li><a href="#Other">Other resources</a></li> 2646</ol> 2647 2648<h3><a name="General2">General overview</a></h3> 2649 2650<p>What is a catalog? Basically it's a lookup mechanism used when an entity 2651(a file or a remote resource) references another entity. The catalog lookup 2652is inserted between the moment the reference is recognized by the software 2653(XML parser, stylesheet processing, or even images referenced for inclusion 2654in a rendering) and the time where loading that resource is actually 2655started.</p> 2656 2657<p>It is basically used for 3 things:</p> 2658<ul> 2659 <li>mapping from "logical" names, the public identifiers and a more 2660 concrete name usable for download (and URI). For example it can associate 2661 the logical name 2662 <p>"-//OASIS//DTD DocBook XML V4.1.2//EN"</p> 2663 <p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be 2664 downloaded</p> 2665 <p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p> 2666 </li> 2667 <li>remapping from a given URL to another one, like an HTTP indirection 2668 saying that 2669 <p>"http://www.oasis-open.org/committes/tr.xsl"</p> 2670 <p>should really be looked at</p> 2671 <p>"http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"</p> 2672 </li> 2673 <li>providing a local cache mechanism allowing to load the entities 2674 associated to public identifiers or remote resources, this is a really 2675 important feature for any significant deployment of XML or SGML since it 2676 allows to avoid the aleas and delays associated to fetching remote 2677 resources.</li> 2678</ul> 2679 2680<h3><a name="definition">The definitions</a></h3> 2681 2682<p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p> 2683<ul> 2684 <li>the older SGML catalogs, the official spec is SGML Open Technical 2685 Resolution TR9401:1997, but is better understood by reading <a 2686 href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from 2687 James Clark. This is relatively old and not the preferred mode of 2688 operation of libxml.</li> 2689 <li><a href="http://www.oasis-open.org/committees/entity/spec.html">XML 2690 Catalogs</a> is far more flexible, more recent, uses an XML syntax and 2691 should scale quite better. This is the default option of libxml.</li> 2692</ul> 2693 2694<p></p> 2695 2696<h3><a name="Simple">Using catalog</a></h3> 2697 2698<p>In a normal environment libxml will by default check the presence of a 2699catalog in /etc/xml/catalog, and assuming it has been correctly populated, 2700the processing is completely transparent to the document user. To take a 2701concrete example, suppose you are authoring a DocBook document, this one 2702starts with the following DOCTYPE definition:</p> 2703<pre><?xml version='1.0'?> 2704<!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN" 2705 "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd"></pre> 2706 2707<p>When validating the document with libxml, the catalog will be 2708automatically consulted to lookup the public identifier "-//Norman Walsh//DTD 2709DocBk XML V3.1.4//EN" and the system identifier 2710"http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if these entities have 2711been installed on your system and the catalogs actually point to them, libxml 2712will fetch them from the local disk.</p> 2713 2714<p style="font-size: 10pt"><strong>Note</strong>: Really don't use this 2715DOCTYPE example it's a really old version, but is fine as an example.</p> 2716 2717<p>Libxml will check the catalog each time that it is requested to load an 2718entity, this includes DTD, external parsed entities, stylesheets, etc ... If 2719your system is correctly configured all the authoring phase and processing 2720should use only local files, even if your document stays portable because it 2721uses the canonical public and system ID, referencing the remote document.</p> 2722 2723<h3><a name="Some">Some examples:</a></h3> 2724 2725<p>Here is a couple of fragments from XML Catalogs used in libxml early 2726regression tests in <code>test/catalogs</code> :</p> 2727<pre><?xml version="1.0"?> 2728<!DOCTYPE catalog PUBLIC 2729 "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 2730 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 2731<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 2732 <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 2733 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 2734...</pre> 2735 2736<p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are 2737written in XML, there is a specific namespace for catalog elements 2738"urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry in this 2739catalog is a <code>public</code> mapping it allows to associate a Public 2740Identifier with an URI.</p> 2741<pre>... 2742 <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/" 2743 rewritePrefix="file:///usr/share/xml/docbook/"/> 2744...</pre> 2745 2746<p>A <code>rewriteSystem</code> is a very powerful instruction, it says that 2747any URI starting with a given prefix should be looked at another URI 2748constructed by replacing the prefix with an new one. In effect this acts like 2749a cache system for a full area of the Web. In practice it is extremely useful 2750with a file prefix if you have installed a copy of those resources on your 2751local system.</p> 2752<pre>... 2753<delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //" 2754 catalog="file:///usr/share/xml/docbook.xml"/> 2755<delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML" 2756 catalog="file:///usr/share/xml/docbook.xml"/> 2757<delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML" 2758 catalog="file:///usr/share/xml/docbook.xml"/> 2759<delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/" 2760 catalog="file:///usr/share/xml/docbook.xml"/> 2761<delegateURI uriStartString="http://www.oasis-open.org/docbook/" 2762 catalog="file:///usr/share/xml/docbook.xml"/> 2763...</pre> 2764 2765<p>Delegation is the core features which allows to build a tree of catalogs, 2766easier to maintain than a single catalog, based on Public Identifier, System 2767Identifier or URI prefixes it instructs the catalog software to look up 2768entries in another resource. This feature allow to build hierarchies of 2769catalogs, the set of entries presented should be sufficient to redirect the 2770resolution of all DocBook references to the specific catalog in 2771<code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all 2772references for DocBook 4.2.1 to a specific catalog installed at the same time 2773as the DocBook resources on the local machine.</p> 2774 2775<h3><a name="reference">How to tune catalog usage:</a></h3> 2776 2777<p>The user can change the default catalog behaviour by redirecting queries 2778to its own set of catalogs, this can be done by setting the 2779<code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an 2780empty one should deactivate loading the default <code>/etc/xml/catalog</code> 2781default catalog</p> 2782 2783<h3><a name="validate">How to debug catalog processing:</a></h3> 2784 2785<p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will 2786make libxml output debugging informations for each catalog operations, for 2787example:</p> 2788<pre>orchis:~/XML -> xmllint --memory --noout test/ent2 2789warning: failed to load external entity "title.xml" 2790orchis:~/XML -> export XML_DEBUG_CATALOG= 2791orchis:~/XML -> xmllint --memory --noout test/ent2 2792Failed to parse catalog /etc/xml/catalog 2793Failed to parse catalog /etc/xml/catalog 2794warning: failed to load external entity "title.xml" 2795Catalogs cleanup 2796orchis:~/XML -> </pre> 2797 2798<p>The test/ent2 references an entity, running the parser from memory makes 2799the base URI unavailable and the the "title.xml" entity cannot be loaded. 2800Setting up the debug environment variable allows to detect that an attempt is 2801made to load the <code>/etc/xml/catalog</code> but since it's not present the 2802resolution fails.</p> 2803 2804<p>But the most advanced way to debug XML catalog processing is to use the 2805<strong>xmlcatalog</strong> command shipped with libxml2, it allows to load 2806catalogs and make resolution queries to see what is going on. This is also 2807used for the regression tests:</p> 2808<pre>orchis:~/XML -> /xmlcatalog test/catalogs/docbook.xml \ 2809 "-//OASIS//DTD DocBook XML V4.1.2//EN" 2810http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 2811orchis:~/XML -> </pre> 2812 2813<p>For debugging what is going on, adding one -v flags increase the verbosity 2814level to indicate the processing done (adding a second flag also indicate 2815what elements are recognized at parsing):</p> 2816<pre>orchis:~/XML -> /xmlcatalog -v test/catalogs/docbook.xml \ 2817 "-//OASIS//DTD DocBook XML V4.1.2//EN" 2818Parsing catalog test/catalogs/docbook.xml's content 2819Found public match -//OASIS//DTD DocBook XML V4.1.2//EN 2820http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 2821Catalogs cleanup 2822orchis:~/XML -> </pre> 2823 2824<p>A shell interface is also available to debug and process multiple queries 2825(and for regression tests):</p> 2826<pre>orchis:~/XML -> /xmlcatalog -shell test/catalogs/docbook.xml \ 2827 "-//OASIS//DTD DocBook XML V4.1.2//EN" 2828> help 2829Commands available: 2830public PublicID: make a PUBLIC identifier lookup 2831system SystemID: make a SYSTEM identifier lookup 2832resolve PublicID SystemID: do a full resolver lookup 2833add 'type' 'orig' 'replace' : add an entry 2834del 'values' : remove values 2835dump: print the current catalog state 2836debug: increase the verbosity level 2837quiet: decrease the verbosity level 2838exit: quit the shell 2839> public "-//OASIS//DTD DocBook XML V4.1.2//EN" 2840http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 2841> quit 2842orchis:~/XML -> </pre> 2843 2844<p>This should be sufficient for most debugging purpose, this was actually 2845used heavily to debug the XML Catalog implementation itself.</p> 2846 2847<h3><a name="Declaring">How to create and maintain</a> catalogs:</h3> 2848 2849<p>Basically XML Catalogs are XML files, you can either use XML tools to 2850manage them or use <strong>xmlcatalog</strong> for this. The basic step is 2851to create a catalog the -create option provide this facility:</p> 2852<pre>orchis:~/XML -> /xmlcatalog --create tst.xml 2853<?xml version="1.0"?> 2854<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 2855 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 2856<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 2857orchis:~/XML -> </pre> 2858 2859<p>By default xmlcatalog does not overwrite the original catalog and save the 2860result on the standard output, this can be overridden using the -noout 2861option. The <code>-add</code> command allows to add entries in the 2862catalog:</p> 2863<pre>orchis:~/XML -> /xmlcatalog --noout --create --add "public" \ 2864 "-//OASIS//DTD DocBook XML V4.1.2//EN" \ 2865 http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml 2866orchis:~/XML -> cat tst.xml 2867<?xml version="1.0"?> 2868<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \ 2869 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 2870<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 2871<public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 2872 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 2873</catalog> 2874orchis:~/XML -> </pre> 2875 2876<p>The <code>-add</code> option will always take 3 parameters even if some of 2877the XML Catalog constructs (like nextCatalog) will have only a single 2878argument, just pass a third empty string, it will be ignored.</p> 2879 2880<p>Similarly the <code>-del</code> option remove matching entries from the 2881catalog:</p> 2882<pre>orchis:~/XML -> /xmlcatalog --del \ 2883 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml 2884<?xml version="1.0"?> 2885<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 2886 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 2887<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 2888orchis:~/XML -> </pre> 2889 2890<p>The catalog is now empty. Note that the matching of <code>-del</code> is 2891exact and would have worked in a similar fashion with the Public ID 2892string.</p> 2893 2894<p>This is rudimentary but should be sufficient to manage a not too complex 2895catalog tree of resources.</p> 2896 2897<h3><a name="implemento">The implementor corner quick review of the 2898API:</a></h3> 2899 2900<p>First, and like for every other module of libxml, there is an 2901automatically generated <a href="html/libxml-catalog.html">API page for 2902catalog support</a>.</p> 2903 2904<p>The header for the catalog interfaces should be included as:</p> 2905<pre>#include <libxml/catalog.h></pre> 2906 2907<p>The API is voluntarily kept very simple. First it is not obvious that 2908applications really need access to it since it is the default behaviour of 2909libxml (Note: it is possible to completely override libxml default catalog by 2910using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to 2911plug an application specific resolver).</p> 2912 2913<p>Basically libxml support 2 catalog lists:</p> 2914<ul> 2915 <li>the default one, global shared by all the application</li> 2916 <li>a per-document catalog, this one is built if the document uses the 2917 <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is 2918 associated to the parser context and destroyed when the parsing context 2919 is destroyed.</li> 2920</ul> 2921 2922<p>the document one will be used first if it exists.</p> 2923 2924<h4>Initialization routines:</h4> 2925 2926<p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be 2927used at startup to initialize the catalog, if the catalog should be 2928initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs() 2929should be called before xmlInitializeCatalog() which would otherwise do a 2930default initialization first.</p> 2931 2932<p>The xmlCatalogAddLocal() call is used by the parser to grow the document 2933own catalog list if needed.</p> 2934 2935<h4>Preferences setup:</h4> 2936 2937<p>The XML Catalog spec requires the possibility to select default 2938preferences between public and system delegation, 2939xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and 2940xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should 2941be forbidden, allowed for global catalog, for document catalog or both, the 2942default is to allow both.</p> 2943 2944<p>And of course xmlCatalogSetDebug() allows to generate debug messages 2945(through the xmlGenericError() mechanism).</p> 2946 2947<h4>Querying routines:</h4> 2948 2949<p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic() 2950and xmlCatalogResolveURI() are relatively explicit if you read the XML 2951Catalog specification they correspond to section 7 algorithms, they should 2952also work if you have loaded an SGML catalog with a simplified semantic.</p> 2953 2954<p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but 2955operate on the document catalog list</p> 2956 2957<h4>Cleanup and Miscellaneous:</h4> 2958 2959<p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is 2960the per-document equivalent.</p> 2961 2962<p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the 2963first catalog in the global list, and xmlCatalogDump() allows to dump a 2964catalog state, those routines are primarily designed for xmlcatalog, I'm not 2965sure that exposing more complex interfaces (like navigation ones) would be 2966really useful.</p> 2967 2968<p>The xmlParseCatalogFile() is a function used to load XML Catalog files, 2969it's similar as xmlParseFile() except it bypass all catalog lookups, it's 2970provided because this functionality may be useful for client tools.</p> 2971 2972<h4>threaded environments:</h4> 2973 2974<p>Since the catalog tree is built progressively, some care has been taken to 2975try to avoid troubles in multithreaded environments. The code is now thread 2976safe assuming that the libxml library has been compiled with threads 2977support.</p> 2978 2979<p></p> 2980 2981<h3><a name="Other">Other resources</a></h3> 2982 2983<p>The XML Catalog specification is relatively recent so there isn't much 2984literature to point at:</p> 2985<ul> 2986 <li>You can find an good rant from Norm Walsh about <a 2987 href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the 2988 need for catalogs</a>, it provides a lot of context informations even if 2989 I don't agree with everything presented. Norm also wrote a more recent 2990 article <a 2991 href="http://wwws.sun.com/software/xml/developers/resolver/article/">XML 2992 entities and URI resolvers</a> describing them.</li> 2993 <li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML 2994 catalog proposal</a> from John Cowan</li> 2995 <li>The <a href="http://www.rddl.org/">Resource Directory Description 2996 Language</a> (RDDL) another catalog system but more oriented toward 2997 providing metadata for XML namespaces.</li> 2998 <li>the page from the OASIS Technical <a 2999 href="http://www.oasis-open.org/committees/entity/">Committee on Entity 3000 Resolution</a> who maintains XML Catalog, you will find pointers to the 3001 specification update, some background and pointers to others tools 3002 providing XML Catalog support</li> 3003 <li>Here is a <a href="buildDocBookCatalog">shell script</a> to generate 3004 XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/ 3005 directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on 3006 the resources found on the system. Otherwise it will just create 3007 ~/xmlcatalog and ~/dbkxmlcatalog and doing: 3008 <p><code>export XMLCATALOG=$HOME/xmlcatalog</code></p> 3009 <p>should allow to process DocBook documentations without requiring 3010 network accesses for the DTd or stylesheets</p> 3011 </li> 3012 <li>I have uploaded <a href="ftp://xmlsoft.org/test/dbk412catalog.tar.gz">a 3013 small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems 3014 to work fine for me too</li> 3015 <li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog 3016 manual page</a></li> 3017</ul> 3018 3019<p>If you have suggestions for corrections or additions, simply contact 3020me:</p> 3021 3022<h2><a name="library">The parser interfaces</a></h2> 3023 3024<p>This section is directly intended to help programmers getting bootstrapped 3025using the XML library from the C language. It is not intended to be 3026extensive. I hope the automatically generated documents will provide the 3027completeness required, but as a separate set of documents. The interfaces of 3028the XML library are by principle low level, there is nearly zero abstraction. 3029Those interested in a higher level API should <a href="#DOM">look at 3030DOM</a>.</p> 3031 3032<p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are 3033separated from the <a href="html/libxml-htmlparser.html">HTML parser 3034interfaces</a>. Let's have a look at how the XML parser can be called:</p> 3035 3036<h3><a name="Invoking">Invoking the parser : the pull method</a></h3> 3037 3038<p>Usually, the first thing to do is to read an XML input. The parser accepts 3039documents either from in-memory strings or from files. The functions are 3040defined in "parser.h":</p> 3041<dl> 3042 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> 3043 <dd><p>Parse a null-terminated string containing the document.</p> 3044 </dd> 3045</dl> 3046<dl> 3047 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> 3048 <dd><p>Parse an XML document contained in a (possibly compressed) 3049 file.</p> 3050 </dd> 3051</dl> 3052 3053<p>The parser returns a pointer to the document structure (or NULL in case of 3054failure).</p> 3055 3056<h3 id="Invoking1">Invoking the parser: the push method</h3> 3057 3058<p>In order for the application to keep the control when the document is 3059being fetched (which is common for GUI based programs) libxml provides a push 3060interface, too, as of version 1.8.3. Here are the interface functions:</p> 3061<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, 3062 void *user_data, 3063 const char *chunk, 3064 int size, 3065 const char *filename); 3066int xmlParseChunk (xmlParserCtxtPtr ctxt, 3067 const char *chunk, 3068 int size, 3069 int terminate);</pre> 3070 3071<p>and here is a simple example showing how to use the interface:</p> 3072<pre> FILE *f; 3073 3074 f = fopen(filename, "r"); 3075 if (f != NULL) { 3076 int res, size = 1024; 3077 char chars[1024]; 3078 xmlParserCtxtPtr ctxt; 3079 3080 res = fread(chars, 1, 4, f); 3081 if (res > 0) { 3082 ctxt = xmlCreatePushParserCtxt(NULL, NULL, 3083 chars, res, filename); 3084 while ((res = fread(chars, 1, size, f)) > 0) { 3085 xmlParseChunk(ctxt, chars, res, 0); 3086 } 3087 xmlParseChunk(ctxt, chars, 0, 1); 3088 doc = ctxt->myDoc; 3089 xmlFreeParserCtxt(ctxt); 3090 } 3091 }</pre> 3092 3093<p>The HTML parser embedded into libxml also has a push interface; the 3094functions are just prefixed by "html" rather than "xml".</p> 3095 3096<h3 id="Invoking2">Invoking the parser: the SAX interface</h3> 3097 3098<p>The tree-building interface makes the parser memory-hungry, first loading 3099the document in memory and then building the tree itself. Reading a document 3100without building the tree is possible using the SAX interfaces (see SAX.h and 3101<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James 3102Henstridge's documentation</a>). Note also that the push interface can be 3103limited to SAX: just use the two first arguments of 3104<code>xmlCreatePushParserCtxt()</code>.</p> 3105 3106<h3><a name="Building">Building a tree from scratch</a></h3> 3107 3108<p>The other way to get an XML tree in memory is by building it. Basically 3109there is a set of functions dedicated to building new elements. (These are 3110also described in <libxml/tree.h>.) For example, here is a piece of 3111code that produces the XML document used in the previous examples:</p> 3112<pre> #include <libxml/tree.h> 3113 xmlDocPtr doc; 3114 xmlNodePtr tree, subtree; 3115 3116 doc = xmlNewDoc("1.0"); 3117 doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); 3118 xmlSetProp(doc->children, "prop1", "gnome is great"); 3119 xmlSetProp(doc->children, "prop2", "& linux too"); 3120 tree = xmlNewChild(doc->children, NULL, "head", NULL); 3121 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); 3122 tree = xmlNewChild(doc->children, NULL, "chapter", NULL); 3123 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); 3124 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); 3125 subtree = xmlNewChild(tree, NULL, "image", NULL); 3126 xmlSetProp(subtree, "href", "linus.gif");</pre> 3127 3128<p>Not really rocket science ...</p> 3129 3130<h3><a name="Traversing">Traversing the tree</a></h3> 3131 3132<p>Basically by <a href="html/libxml-tree.html">including "tree.h"</a> your 3133code has access to the internal structure of all the elements of the tree. 3134The names should be somewhat simple like <strong>parent</strong>, 3135<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>, 3136<strong>properties</strong>, etc... For example, still with the previous 3137example:</p> 3138<pre><code>doc->children->children->children</code></pre> 3139 3140<p>points to the title element,</p> 3141<pre>doc->children->children->next->children->children</pre> 3142 3143<p>points to the text node containing the chapter title "The Linux 3144adventure".</p> 3145 3146<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be 3147present before the document root, so <code>doc->children</code> may point 3148to an element which is not the document Root Element; a function 3149<code>xmlDocGetRootElement()</code> was added for this purpose.</p> 3150 3151<h3><a name="Modifying">Modifying the tree</a></h3> 3152 3153<p>Functions are provided for reading and writing the document content. Here 3154is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p> 3155<dl> 3156 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const 3157 xmlChar *value);</code></dt> 3158 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. 3159 The value can be NULL.</p> 3160 </dd> 3161</dl> 3162<dl> 3163 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar 3164 *name);</code></dt> 3165 <dd><p>This function returns a pointer to new copy of the property 3166 content. Note that the user must deallocate the result.</p> 3167 </dd> 3168</dl> 3169 3170<p>Two functions are provided for reading and writing the text associated 3171with elements:</p> 3172<dl> 3173 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar 3174 *value);</code></dt> 3175 <dd><p>This function takes an "external" string and converts it to one 3176 text node or possibly to a list of entity and text nodes. All 3177 non-predefined entity references like &Gnome; will be stored 3178 internally as entity nodes, hence the result of the function may not be 3179 a single node.</p> 3180 </dd> 3181</dl> 3182<dl> 3183 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int 3184 inLine);</code></dt> 3185 <dd><p>This function is the inverse of 3186 <code>xmlStringGetNodeList()</code>. It generates a new string 3187 containing the content of the text and entity nodes. Note the extra 3188 argument inLine. If this argument is set to 1, the function will expand 3189 entity references. For example, instead of returning the &Gnome; 3190 XML encoding in the string, it will substitute it with its value (say, 3191 "GNU Network Object Model Environment").</p> 3192 </dd> 3193</dl> 3194 3195<h3><a name="Saving">Saving a tree</a></h3> 3196 3197<p>Basically 3 options are possible:</p> 3198<dl> 3199 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int 3200 *size);</code></dt> 3201 <dd><p>Returns a buffer into which the document has been saved.</p> 3202 </dd> 3203</dl> 3204<dl> 3205 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> 3206 <dd><p>Dumps a document to an open file descriptor.</p> 3207 </dd> 3208</dl> 3209<dl> 3210 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> 3211 <dd><p>Saves the document to a file. In this case, the compression 3212 interface is triggered if it has been turned on.</p> 3213 </dd> 3214</dl> 3215 3216<h3><a name="Compressio">Compression</a></h3> 3217 3218<p>The library transparently handles compression when doing file-based 3219accesses. The level of compression on saves can be turned on either globally 3220or individually for one file:</p> 3221<dl> 3222 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> 3223 <dd><p>Gets the document compression ratio (0-9).</p> 3224 </dd> 3225</dl> 3226<dl> 3227 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> 3228 <dd><p>Sets the document compression ratio.</p> 3229 </dd> 3230</dl> 3231<dl> 3232 <dt><code>int xmlGetCompressMode(void);</code></dt> 3233 <dd><p>Gets the default compression ratio.</p> 3234 </dd> 3235</dl> 3236<dl> 3237 <dt><code>void xmlSetCompressMode(int mode);</code></dt> 3238 <dd><p>Sets the default compression ratio.</p> 3239 </dd> 3240</dl> 3241 3242<h2><a name="Entities">Entities or no entities</a></h2> 3243 3244<p>Entities in principle are similar to simple C macros. An entity defines an 3245abbreviation for a given string that you can reuse many times throughout the 3246content of your document. Entities are especially useful when a given string 3247may occur frequently within a document, or to confine the change needed to a 3248document to a restricted area in the internal subset of the document (at the 3249beginning). Example:</p> 3250<pre>1 <?xml version="1.0"?> 32512 <!DOCTYPE EXAMPLE SYSTEM "example.dtd" [ 32523 <!ENTITY xml "Extensible Markup Language"> 32534 ]> 32545 <EXAMPLE> 32556 &xml; 32567 </EXAMPLE></pre> 3257 3258<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing 3259its name with '&' and following it by ';' without any spaces added. There 3260are 5 predefined entities in libxml allowing you to escape charaters with 3261predefined meaning in some parts of the xml document content: 3262<strong>&lt;</strong> for the character '<', <strong>&gt;</strong> 3263for the character '>', <strong>&apos;</strong> for the character ''', 3264<strong>&quot;</strong> for the character '"', and 3265<strong>&amp;</strong> for the character '&'.</p> 3266 3267<p>One of the problems related to entities is that you may want the parser to 3268substitute an entity's content so that you can see the replacement text in 3269your application. Or you may prefer to keep entity references as such in the 3270content to be able to save the document back without losing this usually 3271precious information (if the user went through the pain of explicitly 3272defining entities, he may have a a rather negative attitude if you blindly 3273susbtitute them as saving time). The <a 3274href="html/libxml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a> 3275function allows you to check and change the behaviour, which is to not 3276substitute entities by default.</p> 3277 3278<p>Here is the DOM tree built by libxml for the previous document in the 3279default case:</p> 3280<pre>/gnome/src/gnome-xml -> /xmllint --debug test/ent1 3281DOCUMENT 3282version=1.0 3283 ELEMENT EXAMPLE 3284 TEXT 3285 content= 3286 ENTITY_REF 3287 INTERNAL_GENERAL_ENTITY xml 3288 content=Extensible Markup Language 3289 TEXT 3290 content=</pre> 3291 3292<p>And here is the result when substituting entities:</p> 3293<pre>/gnome/src/gnome-xml -> /tester --debug --noent test/ent1 3294DOCUMENT 3295version=1.0 3296 ELEMENT EXAMPLE 3297 TEXT 3298 content= Extensible Markup Language</pre> 3299 3300<p>So, entities or no entities? Basically, it depends on your use case. I 3301suggest that you keep the non-substituting default behaviour and avoid using 3302entities in your XML document or data if you are not willing to handle the 3303entity references elements in the DOM tree.</p> 3304 3305<p>Note that at save time libxml enforces the conversion of the predefined 3306entities where necessary to prevent well-formedness problems, and will also 3307transparently replace those with chars (i.e. it will not generate entity 3308reference elements in the DOM tree or call the reference() SAX callback when 3309finding them in the input).</p> 3310 3311<p><span style="background-color: #FF0000">WARNING</span>: handling entities 3312on top of the libxml SAX interface is difficult!!! If you plan to use 3313non-predefined entities in your documents, then the learning cuvre to handle 3314then using the SAX API may be long. If you plan to use complex documents, I 3315strongly suggest you consider using the DOM interface instead and let libxml 3316deal with the complexity rather than trying to do it yourself.</p> 3317 3318<h2><a name="Namespaces">Namespaces</a></h2> 3319 3320<p>The libxml library implements <a 3321href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by 3322recognizing namespace contructs in the input, and does namespace lookup 3323automatically when building the DOM tree. A namespace declaration is 3324associated with an in-memory structure and all elements or attributes within 3325that namespace point to it. Hence testing the namespace is a simple and fast 3326equality operation at the user level.</p> 3327 3328<p>I suggest that people using libxml use a namespace, and declare it in the 3329root element of their document as the default namespace. Then they don't need 3330to use the prefix in the content but we will have a basis for future semantic 3331refinement and merging of data from different sources. This doesn't increase 3332the size of the XML output significantly, but significantly increases its 3333value in the long-term. Example:</p> 3334<pre><mydoc xmlns="http://mydoc.example.org/schemas/"> 3335 <elem1>...</elem1> 3336 <elem2>...</elem2> 3337</mydoc></pre> 3338 3339<p>The namespace value has to be an absolute URL, but the URL doesn't have to 3340point to any existing resource on the Web. It will bind all the element and 3341atributes with that URL. I suggest to use an URL within a domain you control, 3342and that the URL should contain some kind of version information if possible. 3343For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a good 3344namespace scheme.</p> 3345 3346<p>Then when you load a file, make sure that a namespace carrying the 3347version-independent prefix is installed on the root element of your document, 3348and if the version information don't match something you know, warn the user 3349and be liberal in what you accept as the input. Also do *not* try to base 3350namespace checking on the prefix value. <foo:text> may be exactly the 3351same as <bar:text> in another document. What really matters is the URI 3352associated with the element or the attribute, not the prefix string (which is 3353just a shortcut for the full URI). In libxml, element and attributes have an 3354<code>ns</code> field pointing to an xmlNs structure detailing the namespace 3355prefix and its URI.</p> 3356 3357<p>@@Interfaces@@</p> 3358 3359<p>@@Examples@@</p> 3360 3361<p>Usually people object to using namespaces together with validity checking. 3362I will try to make sure that using namespaces won't break validity checking, 3363so even if you plan to use or currently are using validation I strongly 3364suggest adding namespaces to your document. A default namespace scheme 3365<code>xmlns="http://...."</code> should not break validity even on less 3366flexible parsers. Using namespaces to mix and differentiate content coming 3367from multiple DTDs will certainly break current validation schemes. I will 3368try to provide ways to do this, but this may not be portable or 3369standardized.</p> 3370 3371<h2><a name="Upgrading">Upgrading 1.x code</a></h2> 3372 3373<p>Incompatible changes:</p> 3374 3375<p>Version 2 of libxml is the first version introducing serious backward 3376incompatible changes. The main goals were:</p> 3377<ul> 3378 <li>a general cleanup. A number of mistakes inherited from the very early 3379 versions couldn't be changed due to compatibility constraints. Example 3380 the "childs" element in the nodes.</li> 3381 <li>Uniformization of the various nodes, at least for their header and link 3382 parts (doc, parent, children, prev, next), the goal is a simpler 3383 programming model and simplifying the task of the DOM implementors.</li> 3384 <li>better conformances to the XML specification, for example version 1.x 3385 had an heuristic to try to detect ignorable white spaces. As a result the 3386 SAX event generated were ignorableWhitespace() while the spec requires 3387 character() in that case. This also mean that a number of DOM node 3388 containing blank text may populate the DOM tree which were not present 3389 before.</li> 3390</ul> 3391 3392<h3>How to fix libxml-1.x code:</h3> 3393 3394<p>So client code of libxml designed to run with version 1.x may have to be 3395changed to compile against version 2.x of libxml. Here is a list of changes 3396that I have collected, they may not be sufficient, so in case you find other 3397change which are required, <a href="mailto:Daniel.�eillardw3.org">drop me a 3398mail</a>:</p> 3399<ol> 3400 <li>The package name have changed from libxml to libxml2, the library name 3401 is now -lxml2 . There is a new xml2-config script which should be used to 3402 select the right parameters libxml2</li> 3403 <li>Node <strong>childs</strong> field has been renamed 3404 <strong>children</strong> so s/childs/children/g should be applied 3405 (probablility of having "childs" anywere else is close to 0+</li> 3406 <li>The document don't have anymore a <strong>root</strong> element it has 3407 been replaced by <strong>children</strong> and usually you will get a 3408 list of element here. For example a Dtd element for the internal subset 3409 and it's declaration may be found in that list, as well as processing 3410 instructions or comments found before or after the document root element. 3411 Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of 3412 a document. Alternatively if you are sure to not reference Dtds nor have 3413 PIs or comments before or after the root element 3414 s/->root/->children/g will probably do it.</li> 3415 <li>The white space issue, this one is more complex, unless special case of 3416 validating parsing, the line breaks and spaces usually used for indenting 3417 and formatting the document content becomes significant. So they are 3418 reported by SAX and if your using the DOM tree, corresponding nodes are 3419 generated. Too approach can be taken: 3420 <ol> 3421 <li>lazy one, use the compatibility call 3422 <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are 3423 relying on a special (and possibly broken) set of heuristics of 3424 libxml to detect ignorable blanks. Don't complain if it breaks or 3425 make your application not 100% clean w.r.t. to it's input.</li> 3426 <li>the Right Way: change you code to accept possibly unsignificant 3427 blanks characters, or have your tree populated with weird blank text 3428 nodes. You can spot them using the comodity function 3429 <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank 3430 nodes.</li> 3431 </ol> 3432 <p>Note also that with the new default the output functions don't add any 3433 extra indentation when saving a tree in order to be able to round trip 3434 (read and save) without inflating the document with extra formatting 3435 chars.</p> 3436 </li> 3437 <li>The include path has changed to $prefix/libxml/ and the includes 3438 themselves uses this new prefix in includes instructions... If you are 3439 using (as expected) the 3440 <pre>xml2-config --cflags</pre> 3441 <p>output to generate you compile commands this will probably work out of 3442 the box</p> 3443 </li> 3444 <li>xmlDetectCharEncoding takes an extra argument indicating the lenght in 3445 byte of the head of the document available for character detection.</li> 3446</ol> 3447 3448<h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3> 3449 3450<p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released 3451to allow smoth upgrade of existing libxml v1code while retaining 3452compatibility. They offers the following:</p> 3453<ol> 3454 <li>similar include naming, one should use 3455 <strong>#include<libxml/...></strong> in both cases.</li> 3456 <li>similar identifiers defined via macros for the child and root fields: 3457 respectively <strong>xmlChildrenNode</strong> and 3458 <strong>xmlRootNode</strong></li> 3459 <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be 3460 inserted once in the client code</li> 3461</ol> 3462 3463<p>So the roadmap to upgrade your existing libxml applications is the 3464following:</p> 3465<ol> 3466 <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> 3467 <li>find all occurences where the xmlDoc <strong>root</strong> field is 3468 used and change it to <strong>xmlRootNode</strong></li> 3469 <li>similary find all occurences where the xmlNode <strong>childs</strong> 3470 field is used and change it to <strong>xmlChildrenNode</strong></li> 3471 <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your 3472 <strong>main()</strong> or in the library init entry point</li> 3473 <li>Recompile, check compatibility, it should still work</li> 3474 <li>Change your configure script to look first for xml2-config and fallback 3475 using xml-config . Use the --cflags and --libs ouptut of the command as 3476 the Include and Linking parameters needed to use libxml.</li> 3477 <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and 3478 libxml-devel-1.8.y can be kept simultaneously)</li> 3479 <li>remove your config.cache, relaunch your configuration mechanism, and 3480 recompile, if steps 2 and 3 were done right it should compile as-is</li> 3481 <li>Test that your application is still running correctly, if not this may 3482 be due to extra empty nodes due to formating spaces being kept in libxml2 3483 contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your 3484 code before calling the parser (next to 3485 <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li> 3486</ol> 3487 3488<p>Following those steps should work. It worked for some of my own code.</p> 3489 3490<p>Let me put some emphasis on the fact that there is far more changes from 3491libxml 1.x to 2.x than the ones you may have to patch for. The overall code 3492has been considerably cleaned up and the conformance to the XML specification 3493has been drastically improved too. Don't take those changes as an excuse to 3494not upgrade, it may cost a lot on the long term ...</p> 3495 3496<h2><a name="Thread">Thread safety</a></h2> 3497 3498<p>Starting with 2.4.7, libxml makes provisions to ensure that concurent 3499threads can safely work in parallel parsing different documents. There is 3500however a couple of things to do to ensure it:</p> 3501<ul> 3502 <li>configure the library accordingly using the --with-threads options</li> 3503 <li>call xmlInitParser() in the "main" thread before using any of the 3504 libxml API (except possibly selecting a different memory allocator)</li> 3505</ul> 3506 3507<p>Note that the thread safety cannot be ensured for multiple threads sharing 3508the same document, the locking must be done at the application level, libxml 3509exports a basic mutex and reentrant mutexes API in <libxml/threads.h>. 3510The parts of the library checked for thread safety are:</p> 3511<ul> 3512 <li>concurrent loading</li> 3513 <li>file access resolution</li> 3514 <li>catalog access</li> 3515 <li>catalog building</li> 3516 <li>entities lookup/accesses</li> 3517 <li>validation</li> 3518 <li>global variables per-thread override</li> 3519 <li>memory handling</li> 3520</ul> 3521 3522<p>XPath is supposed to be thread safe now, but this wasn't tested 3523seriously.</p> 3524 3525<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2> 3526 3527<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document 3528Object Model</em>; this is an API for accessing XML or HTML structured 3529documents. Native support for DOM in Gnome is on the way (module gnome-dom), 3530and will be based on gnome-xml. This will be a far cleaner interface to 3531manipulate XML files within Gnome since it won't expose the internal 3532structure.</p> 3533 3534<p>The current DOM implementation on top of libxml is the <a 3535href="http://cvs.gnome.org/lxr/source/gdome2/">gdome2 Gnome module</a>, this 3536is a full DOM interface, thanks to Paolo Casarini, check the <a 3537href="http://www.cs.unibo.it/~casarini/gdome2/">Gdome2 homepage</a> for more 3538informations.</p> 3539 3540<h2><a name="Example"></a><a name="real">A real example</a></h2> 3541 3542<p>Here is a real size example, where the actual content of the application 3543data is not kept in the DOM tree but uses internal structures. It is based on 3544a proposal to keep a database of jobs related to Gnome, with an XML based 3545storage structure. Here is an <a href="gjobs.xml">XML encoded jobs 3546base</a>:</p> 3547<pre><?xml version="1.0"?> 3548<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"> 3549 <gjob:Jobs> 3550 3551 <gjob:Job> 3552 <gjob:Project ID="3"/> 3553 <gjob:Application>GBackup</gjob:Application> 3554 <gjob:Category>Development</gjob:Category> 3555 3556 <gjob:Update> 3557 <gjob:Status>Open</gjob:Status> 3558 <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified> 3559 <gjob:Salary>USD 0.00</gjob:Salary> 3560 </gjob:Update> 3561 3562 <gjob:Developers> 3563 <gjob:Developer> 3564 </gjob:Developer> 3565 </gjob:Developers> 3566 3567 <gjob:Contact> 3568 <gjob:Person>Nathan Clemons</gjob:Person> 3569 <gjob:Email>nathan@windsofstorm.net</gjob:Email> 3570 <gjob:Company> 3571 </gjob:Company> 3572 <gjob:Organisation> 3573 </gjob:Organisation> 3574 <gjob:Webpage> 3575 </gjob:Webpage> 3576 <gjob:Snailmail> 3577 </gjob:Snailmail> 3578 <gjob:Phone> 3579 </gjob:Phone> 3580 </gjob:Contact> 3581 3582 <gjob:Requirements> 3583 The program should be released as free software, under the GPL. 3584 </gjob:Requirements> 3585 3586 <gjob:Skills> 3587 </gjob:Skills> 3588 3589 <gjob:Details> 3590 A GNOME based system that will allow a superuser to configure 3591 compressed and uncompressed files and/or file systems to be backed 3592 up with a supported media in the system. This should be able to 3593 perform via find commands generating a list of files that are passed 3594 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine 3595 or via operations performed on the filesystem itself. Email 3596 notification and GUI status display very important. 3597 </gjob:Details> 3598 3599 </gjob:Job> 3600 3601 </gjob:Jobs> 3602</gjob:Helping></pre> 3603 3604<p>While loading the XML file into an internal DOM tree is a matter of 3605calling only a couple of functions, browsing the tree to gather the ata and 3606generate the internal structures is harder, and more error prone.</p> 3607 3608<p>The suggested principle is to be tolerant with respect to the input 3609structure. For example, the ordering of the attributes is not significant, 3610the XML specification is clear about it. It's also usually a good idea not to 3611depend on the order of the children of a given node, unless it really makes 3612things harder. Here is some code to parse the information for a person:</p> 3613<pre>/* 3614 * A person record 3615 */ 3616typedef struct person { 3617 char *name; 3618 char *email; 3619 char *company; 3620 char *organisation; 3621 char *smail; 3622 char *webPage; 3623 char *phone; 3624} person, *personPtr; 3625 3626/* 3627 * And the code needed to parse it 3628 */ 3629personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 3630 personPtr ret = NULL; 3631 3632DEBUG("parsePerson\n"); 3633 /* 3634 * allocate the struct 3635 */ 3636 ret = (personPtr) malloc(sizeof(person)); 3637 if (ret == NULL) { 3638 fprintf(stderr,"out of memory\n"); 3639 return(NULL); 3640 } 3641 memset(ret, 0, sizeof(person)); 3642 3643 /* We don't care what the top level element name is */ 3644 cur = cur->xmlChildrenNode; 3645 while (cur != NULL) { 3646 if ((!strcmp(cur->name, "Person")) && (cur->ns == ns)) 3647 ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3648 if ((!strcmp(cur->name, "Email")) && (cur->ns == ns)) 3649 ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3650 cur = cur->next; 3651 } 3652 3653 return(ret); 3654}</pre> 3655 3656<p>Here are a couple of things to notice:</p> 3657<ul> 3658 <li>Usually a recursive parsing style is the more convenient one: XML data 3659 is by nature subject to repetitive constructs and usually exibits highly 3660 stuctured patterns.</li> 3661 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, 3662 i.e. the pointer to the global XML document and the namespace reserved to 3663 the application. Document wide information are needed for example to 3664 decode entities and it's a good coding practice to define a namespace for 3665 your application set of data and test that the element and attributes 3666 you're analyzing actually pertains to your application space. This is 3667 done by a simple equality test (cur->ns == ns).</li> 3668 <li>To retrieve text and attributes value, you can use the function 3669 <em>xmlNodeListGetString</em> to gather all the text and entity reference 3670 nodes generated by the DOM output and produce an single text string.</li> 3671</ul> 3672 3673<p>Here is another piece of code used to parse another level of the 3674structure:</p> 3675<pre>#include <libxml/tree.h> 3676/* 3677 * a Description for a Job 3678 */ 3679typedef struct job { 3680 char *projectID; 3681 char *application; 3682 char *category; 3683 personPtr contact; 3684 int nbDevelopers; 3685 personPtr developers[100]; /* using dynamic alloc is left as an exercise */ 3686} job, *jobPtr; 3687 3688/* 3689 * And the code needed to parse it 3690 */ 3691jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 3692 jobPtr ret = NULL; 3693 3694DEBUG("parseJob\n"); 3695 /* 3696 * allocate the struct 3697 */ 3698 ret = (jobPtr) malloc(sizeof(job)); 3699 if (ret == NULL) { 3700 fprintf(stderr,"out of memory\n"); 3701 return(NULL); 3702 } 3703 memset(ret, 0, sizeof(job)); 3704 3705 /* We don't care what the top level element name is */ 3706 cur = cur->xmlChildrenNode; 3707 while (cur != NULL) { 3708 3709 if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) { 3710 ret->projectID = xmlGetProp(cur, "ID"); 3711 if (ret->projectID == NULL) { 3712 fprintf(stderr, "Project has no ID\n"); 3713 } 3714 } 3715 if ((!strcmp(cur->name, "Application")) && (cur->ns == ns)) 3716 ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3717 if ((!strcmp(cur->name, "Category")) && (cur->ns == ns)) 3718 ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3719 if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns)) 3720 ret->contact = parsePerson(doc, ns, cur); 3721 cur = cur->next; 3722 } 3723 3724 return(ret); 3725}</pre> 3726 3727<p>Once you are used to it, writing this kind of code is quite simple, but 3728boring. Ultimately, it could be possble to write stubbers taking either C 3729data structure definitions, a set of XML examples or an XML DTD and produce 3730the code needed to import and export the content between C data and XML 3731storage. This is left as an exercise to the reader :-)</p> 3732 3733<p>Feel free to use <a href="example/gjobread.c">the code for the full C 3734parsing example</a> as a template, it is also available with Makefile in the 3735Gnome CVS base under gnome-xml/example</p> 3736 3737<h2><a name="Contributi">Contributions</a></h2> 3738<ul> 3739 <li>Bjorn Reese, William Brack and Thomas Broyer have provided a number of 3740 patches, Gary Pennington worked on the validation API, threading support 3741 and Solaris port.</li> 3742 <li>John Fleck helps maintaining the documentation and man pages.</li> 3743 <li><a href="mailto:igor@stud.fh-frankfurt.de">Igor Zlatkovic</a> is now 3744 the maintainer of the Windows port, <a 3745 href="http://www.fh-frankfurt.de/~igor/projects/libxml/index.html">he 3746 provides binaries</a></li> 3747 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 3748 <a href="http://garypennington.net/libxml2/">Solaris binaries</a></li> 3749 <li><a 3750 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 3751 Sergeant</a> developped <a 3752 href="http://axkit.org/download/">XML::LibXSLT</a>, a perl wrapper for 3753 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 3754 application server</a></li> 3755 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> and <a 3756 href="mailto:geertk@ai.rug.nl">Geert Kloosterman</a> provide <a 3757 href="libxml-doc.el">an emacs module</a> to lookup libxml(2) functions 3758 documentation</li> 3759 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a 3760 href="http://xmlsoft.org/messages/0488.html">man pages</a></li> 3761 <li>there is a module for <a 3762 href="http://acs-misc.sourceforge.net/nsxml.html">libxml/libxslt support 3763 in OpenNSD/AOLServer</a></li> 3764 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provided the 3765 first version of libxml/libxslt <a 3766 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li> 3767 <li>Petr Kozelka provides <a 3768 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 3769 libxml2</a> with Kylix and Delphi and other Pascal compilers</li> 3770 <li><a href="mailto:aleksey@aleksey.com">Aleksey Sanin</a> implemented the 3771 <a href="http://www.w3.org/Signature/">XML Canonicalization and XML 3772 Digital Signature</a> <a 3773 href="http://www.aleksey.com/xmlsec/">implementations for libxml2</a></li> 3774</ul> 3775 3776<p></p> 3777</body> 3778</html> 3779
