xml.html revision f83a2c7ecaae9e7d8f2f61eccacd5dc89968be79
1<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" 2 "http://www.w3.org/TR/html4/loose.dtd"> 3<html> 4<head> 5 <title>The XML C library for Gnome</title> 6 <meta name="GENERATOR" content="amaya 5.1"> 7 <meta http-equiv="Content-Type" content="text/html"> 8</head> 9 10<body bgcolor="#ffffff"> 11<h1 align="center">The XML C library for Gnome</h1> 12 13<h1>Note: this is the flat content of the <a href="index.html">web 14site</a></h1> 15 16<h1 style="text-align: center">libxml, a.k.a. gnome-xml</h1> 17 18<p></p> 19 20<p>Libxml is the XML C library developed for the Gnome project. XML itself 21is a metalanguage to design markup languages, i.e. text language where 22semantic and structure are added to the content using extra "markup" 23information enclosed between angle brackets. HTML is the most well-known 24markup language. Though the library is written in C <a href="python.html">a 25variety of language bindings</a> make it available in other environments.</p> 26 27<p>Libxml2 is known to be very portable, the library should build and work 28without serious troubles on a variety of systems (Linux, Unix, Windows, 29CygWin, MacOS, MacOS X, RISC Os, OS/2, VMS, QNX, MVS, ...)</p> 30 31<p>Libxml2 implements a number of existing standards related to markup 32languages:</p> 33<ul> 34 <li>the XML standard: <a 35 href="http://www.w3.org/TR/REC-xml">http://www.w3.org/TR/REC-xml</a></li> 36 <li>Namespaces in XML: <a 37 href="http://www.w3.org/TR/REC-xml-names/">http://www.w3.org/TR/REC-xml-names/</a></li> 38 <li>XML Base: <a 39 href="http://www.w3.org/TR/xmlbase/">http://www.w3.org/TR/xmlbase/</a></li> 40 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc2396.txt">RFC 2396</a> : 41 Uniform Resource Identifiers <a 42 href="http://www.ietf.org/rfc/rfc2396.txt">http://www.ietf.org/rfc/rfc2396.txt</a></li> 43 <li>XML Path Language (XPath) 1.0: <a 44 href="http://www.w3.org/TR/xpath">http://www.w3.org/TR/xpath</a></li> 45 <li>HTML4 parser: <a 46 href="http://www.w3.org/TR/html401/">http://www.w3.org/TR/html401/</a></li> 47 <li>most of XML Pointer Language (XPointer) Version 1.0: <a 48 href="http://www.w3.org/TR/xptr">http://www.w3.org/TR/xptr</a></li> 49 <li>XML Inclusions (XInclude) Version 1.0: <a 50 href="http://www.w3.org/TR/xinclude/">http://www.w3.org/TR/xinclude/</a></li> 51 <li>[ISO-8859-1], <a 52 href="http://www.cis.ohio-state.edu/rfc/rfc2044.txt">rfc2044</a> [UTF-8] 53 and <a href="http://www.cis.ohio-state.edu/rfc/rfc2781.txt">rfc2781</a> 54 [UTF-16] core encodings</li> 55 <li>part of SGML Open Technical Resolution TR9401:1997</li> 56 <li>XML Catalogs Working Draft 06 August 2001: <a 57 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> 58 <li>Canonical XML Version 1.0: <a 59 href="http://www.w3.org/TR/xml-c14n">http://www.w3.org/TR/xml-c14n</a> 60 and the Exclusive XML Canonicalization CR draft <a 61 href="http://www.w3.org/TR/xml-exc-c14n">http://www.w3.org/TR/xml-exc-c14n</a></li> 62 <li>Relax NG Committee Specification 3 December 2001 <a 63 href="http://www.oasis-open.org/committees/relax-ng/spec-20011203.html">http://www.oasis-open.org/committees/relax-ng/spec-20011203.html</a></li> 64 <li>W3C XML Schemas Part 2: Datatypes <a 65 href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/">REC 02 May 66 2001</a> except the base64Binary and hexBinary types</li> 67</ul> 68 69<p>In most cases libxml tries to implement the specifications in a relatively 70strictly compliant way. As of release 2.4.16, libxml2 passes all 1800+ tests 71from the <a 72href="http://www.oasis-open.org/committees/xml-conformance/">OASIS XML Tests 73Suite</a>.</p> 74 75<p>To some extent libxml2 provides support for the following additional 76specifications but doesn't claim to implement them completely:</p> 77<ul> 78 <li>Document Object Model (DOM) <a 79 href="http://www.w3.org/TR/DOM-Level-2-Core/">http://www.w3.org/TR/DOM-Level-2-Core/</a> 80 it doesn't implement the API itself, gdome2 does this on top of 81 libxml2</li> 82 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc959.txt">RFC 959</a> : 83 libxml implements a basic FTP client code</li> 84 <li><a href="http://www.cis.ohio-state.edu/rfc/rfc1945.txt">RFC 1945</a> : 85 HTTP/1.0, again a basic HTTP client code</li> 86 <li>SAX: a minimal SAX implementation compatible with early expat 87 versions</li> 88 <li>DocBook SGML v4: libxml2 includes a hackish parser to transition to 89 XML</li> 90</ul> 91 92<p>A partial implementation of <a 93href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/">XML Schemas Part 941: Structure</a> is being worked on but it would be far too early to make any 95conformance statement about it at the moment.</p> 96 97<p>Separate documents:</p> 98<ul> 99 <li><a href="http://xmlsoft.org/XSLT/">the libxslt page</a> providing an 100 implementation of XSLT 1.0 and common extensions like EXSLT for 101 libxml2</li> 102 <li><a href="http://www.cs.unibo.it/~casarini/gdome2/">the gdome2 page</a> 103 : a standard DOM2 implementation for libxml2</li> 104 <li><a href="http://www.aleksey.com/xmlsec/">the XMLSec page</a>: an 105 implementation of <a href="http://www.w3.org/TR/xmldsig-core/">W3C XML 106 Digital Signature</a> for libxml2</li> 107 <li>also check the related links section below for more related and active 108 projects.</li> 109</ul> 110 111<p>Results of the <a 112href="http://xmlbench.sourceforge.net/results/benchmark/index.html">xmlbench 113benchmark</a> on sourceforge 19 March 2003 (smaller is better):</p> 114 115<p align="center"><img src="benchmark.gif" 116alt="benchmark results for Expat Xerces libxml2 Oracle and Sun toolkits"></p> 117 118<p>Logo designed by <a href="mailto:liyanage@access.ch">Marc Liyanage</a>.</p> 119 120<h2><a name="Introducti">Introduction</a></h2> 121 122<p>This document describes libxml, the <a 123href="http://www.w3.org/XML/">XML</a> C library developed for the <a 124href="http://www.gnome.org/">Gnome</a> project. <a 125href="http://www.w3.org/XML/">XML is a standard</a> for building tag-based 126structured documents/data.</p> 127 128<p>Here are some key points about libxml:</p> 129<ul> 130 <li>Libxml exports Push (progressive) and Pull (blocking) type parser 131 interfaces for both XML and HTML.</li> 132 <li>Libxml can do DTD validation at parse time, using a parsed document 133 instance, or with an arbitrary DTD.</li> 134 <li>Libxml includes complete <a 135 href="http://www.w3.org/TR/xpath">XPath</a>, <a 136 href="http://www.w3.org/TR/xptr">XPointer</a> and <a 137 href="http://www.w3.org/TR/xinclude">XInclude</a> implementations.</li> 138 <li>It is written in plain C, making as few assumptions as possible, and 139 sticking closely to ANSI C/POSIX for easy embedding. Works on 140 Linux/Unix/Windows, ported to a number of other platforms.</li> 141 <li>Basic support for HTTP and FTP client allowing applications to fetch 142 remote resources.</li> 143 <li>The design is modular, most of the extensions can be compiled out.</li> 144 <li>The internal document representation is as close as possible to the <a 145 href="http://www.w3.org/DOM/">DOM</a> interfaces.</li> 146 <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX 147 like interface</a>; the interface is designed to be compatible with <a 148 href="http://www.jclark.com/xml/expat.html">Expat</a>.</li> 149 <li>This library is released under the <a 150 href="http://www.opensource.org/licenses/mit-license.html">MIT 151 License</a>. See the Copyright file in the distribution for the precise 152 wording.</li> 153</ul> 154 155<p>Warning: unless you are forced to because your application links with a 156Gnome-1.X library requiring it, <strong><span 157style="background-color: #FF0000">Do Not Use libxml1</span></strong>, use 158libxml2</p> 159 160<h2><a name="FAQ">FAQ</a></h2> 161 162<p>Table of Contents:</p> 163<ul> 164 <li><a href="FAQ.html#License">License(s)</a></li> 165 <li><a href="FAQ.html#Installati">Installation</a></li> 166 <li><a href="FAQ.html#Compilatio">Compilation</a></li> 167 <li><a href="FAQ.html#Developer">Developer corner</a></li> 168</ul> 169 170<h3><a name="License">License</a>(s)</h3> 171<ol> 172 <li><em>Licensing Terms for libxml</em> 173 <p>libxml is released under the <a 174 href="http://www.opensource.org/licenses/mit-license.html">MIT 175 License</a>; see the file Copyright in the distribution for the precise 176 wording</p> 177 </li> 178 <li><em>Can I embed libxml in a proprietary application ?</em> 179 <p>Yes. The MIT License allows you to keep proprietary the changes you 180 made to libxml, but it would be graceful to send-back bug fixes and 181 improvements as patches for possible incorporation in the main 182 development tree.</p> 183 </li> 184</ol> 185 186<h3><a name="Installati">Installation</a></h3> 187<ol> 188 <li>Unless you are forced to because your application links with a Gnome 189 library requiring it, <strong><span style="background-color: #FF0000">Do 190 Not Use libxml1</span></strong>, use libxml2</li> 191 <li><em>Where can I get libxml</em> ? 192 <p>The original distribution comes from <a 193 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a 194 href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">gnome.org</a></p> 195 <p>Most Linux and BSD distributions include libxml, this is probably the 196 safer way for end-users to use libxml.</p> 197 <p>David Doolin provides precompiled Windows versions at <a 198 href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p> 199 </li> 200 <li><em>I see libxml and libxml2 releases, which one should I install ?</em> 201 <ul> 202 <li>If you are not constrained by backward compatibility issues with 203 existing applications, install libxml2 only</li> 204 <li>If you are not doing development, you can safely install both. 205 Usually the packages <a 206 href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a 207 href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are 208 compatible (this is not the case for development packages).</li> 209 <li>If you are a developer and your system provides separate packaging 210 for shared libraries and the development components, it is possible 211 to install libxml and libxml2, and also <a 212 href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> 213 and <a 214 href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> 215 too for libxml2 >= 2.3.0</li> 216 <li>If you are developing a new application, please develop against 217 libxml2(-devel)</li> 218 </ul> 219 </li> 220 <li><em>I can't install the libxml package, it conflicts with libxml0</em> 221 <p>You probably have an old libxml0 package used to provide the shared 222 library for libxml.so.0, you can probably safely remove it. The libxml 223 packages provided on <a 224 href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provide 225 libxml.so.0</p> 226 </li> 227 <li><em>I can't install the libxml(2) RPM package due to failed 228 dependencies</em> 229 <p>The most generic solution is to re-fetch the latest src.rpm , and 230 rebuild it locally with</p> 231 <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> 232 <p>If everything goes well it will generate two binary rpm packages (one 233 providing the shared libs and xmllint, and the other one, the -devel 234 package, providing includes, static libraries and scripts needed to build 235 applications with libxml(2)) that you can install locally.</p> 236 </li> 237</ol> 238 239<h3><a name="Compilatio">Compilation</a></h3> 240<ol> 241 <li><em>What is the process to compile libxml ?</em> 242 <p>As most UNIX libraries libxml follows the "standard":</p> 243 <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> 244 <p><code>cd libxml-xxxx</code></p> 245 <p><code>/configure --help</code></p> 246 <p>to see the options, then the compilation/installation proper</p> 247 <p><code>/configure [possible options]</code></p> 248 <p><code>make</code></p> 249 <p><code>make install</code></p> 250 <p>At that point you may have to rerun ldconfig or a similar utility to 251 update your list of installed shared libs.</p> 252 </li> 253 <li><em>What other libraries are needed to compile/install libxml ?</em> 254 <p>Libxml does not require any other library, the normal C ANSI API 255 should be sufficient (please report any violation to this rule you may 256 find).</p> 257 <p>However if found at configuration time libxml will detect and use the 258 following libs:</p> 259 <ul> 260 <li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a 261 highly portable and available widely compression library.</li> 262 <li>iconv: a powerful character encoding conversion library. It is 263 included by default in recent glibc libraries, so it doesn't need to 264 be installed specifically on Linux. It now seems a <a 265 href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part 266 of the official UNIX</a> specification. Here is one <a 267 href="http://www.gnu.org/software/libiconv/">implementation of the 268 library</a> which source can be found <a 269 href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> 270 </ul> 271 </li> 272 <li><em>Make check fails on some platforms</em> 273 <p>Sometimes the regression tests' results don't completely match the 274 value produced by the parser, and the makefile uses diff to print the 275 delta. On some platforms the diff return breaks the compilation process; 276 if the diff is small this is probably not a serious problem.</p> 277 <p>Sometimes (especially on Solaris) make checks fail due to limitations 278 in make. Try using GNU-make instead.</p> 279 </li> 280 <li><em>I use the CVS version and there is no configure script</em> 281 <p>The configure script (and other Makefiles) are generated. Use the 282 autogen.sh script to regenerate the configure script and Makefiles, 283 like:</p> 284 <p><code>/autogen.sh --prefix=/usr --disable-shared</code></p> 285 </li> 286 <li><em>I have troubles when running make tests with gcc-3.0</em> 287 <p>It seems the initial release of gcc-3.0 has a problem with the 288 optimizer which miscompiles the URI module. Please use another 289 compiler.</p> 290 </li> 291</ol> 292 293<h3><a name="Developer">Developer</a> corner</h3> 294<ol> 295 <li><em>xmlDocDump() generates output on one line.</em> 296 <p>Libxml will not <strong>invent</strong> spaces in the content of a 297 document since <strong>all spaces in the content of a document are 298 significant</strong>. If you build a tree from the API and want 299 indentation:</p> 300 <ol> 301 <li>the correct way is to generate those yourself too.</li> 302 <li>the dangerous way is to ask libxml to add those blanks to your 303 content <strong>modifying the content of your document in the 304 process</strong>. The result may not be what you expect. There is 305 <strong>NO</strong> way to guarantee that such a modification won't 306 affect other parts of the content of your document. See <a 307 href="http://xmlsoft.org/html/libxml-parser.html#XMLKEEPBLANKSDEFAULT">xmlKeepBlanksDefault 308 ()</a> and <a 309 href="http://xmlsoft.org/html/libxml-tree.html#XMLSAVEFORMATFILE">xmlSaveFormatFile 310 ()</a></li> 311 </ol> 312 </li> 313 <li>Extra nodes in the document: 314 <p><em>For a XML file as below:</em></p> 315 <pre><?xml version="1.0"?> 316<PLAN xmlns="http://www.argus.ca/autotest/1.0/"> 317<NODE CommFlag="0"/> 318<NODE CommFlag="1"/> 319</PLAN></pre> 320 <p><em>after parsing it with the function 321 pxmlDoc=xmlParseFile(...);</em></p> 322 <p><em>I want to the get the content of the first node (node with the 323 CommFlag="0")</em></p> 324 <p><em>so I did it as following;</em></p> 325 <pre>xmlNodePtr pnode; 326pnode=pxmlDoc->children->children;</pre> 327 <p><em>but it does not work. If I change it to</em></p> 328 <pre>pnode=pxmlDoc->children->children->next;</pre> 329 <p><em>then it works. Can someone explain it to me.</em></p> 330 <p></p> 331 <p>In XML all characters in the content of the document are significant 332 <strong>including blanks and formatting line breaks</strong>.</p> 333 <p>The extra nodes you are wondering about are just that, text nodes with 334 the formatting spaces which are part of the document but that people tend 335 to forget. There is a function <a 336 href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault 337 ()</a> to remove those at parse time, but that's an heuristic, and its 338 use should be limited to cases where you are certain there is no 339 mixed-content in the document.</p> 340 </li> 341 <li><em>I get compilation errors of existing code like when accessing 342 <strong>root</strong> or <strong>child fields</strong> of nodes.</em> 343 <p>You are compiling code developed for libxml version 1 and using a 344 libxml2 development environment. Either switch back to libxml v1 devel or 345 even better fix the code to compile with libxml2 (or both) by <a 346 href="upgrade.html">following the instructions</a>.</p> 347 </li> 348 <li><em>I get compilation errors about non existing 349 <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> 350 fields.</em> 351 <p>The source code you are using has been <a 352 href="upgrade.html">upgraded</a> to be able to compile with both libxml 353 and libxml2, but you need to install a more recent version: 354 libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> 355 </li> 356 <li><em>XPath implementation looks seriously broken</em> 357 <p>XPath implementation prior to 2.3.0 was really incomplete. Upgrade to 358 a recent version, there are no known bugs in the current version.</p> 359 </li> 360 <li><em>The example provided in the web page does not compile.</em> 361 <p>It's hard to maintain the documentation in sync with the code 362 <grin/> ...</p> 363 <p>Check the previous points 1/ and 2/ raised before, and please send 364 patches.</p> 365 </li> 366 <li><em>Where can I get more examples and information than privoded on the 367 web page?</em> 368 <p>Ideally a libxml book would be nice. I have no such plan ... But you 369 can:</p> 370 <ul> 371 <li>check more deeply the <a href="html/libxml-lib.html">existing 372 generated doc</a></li> 373 <li>look for examples of use for libxml function using the Gnome code. 374 For example the following will query the full Gnome CVS base for the 375 use of the <strong>xmlAddChild()</strong> function: 376 <p><a 377 href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> 378 <p>This may be slow, a large hardware donation to the gnome project 379 could cure this :-)</p> 380 </li> 381 <li><a 382 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse 383 the libxml source</a> , I try to write code as clean and documented 384 as possible, so looking at it may be helpful. In particular the code 385 of xmllint.c and of the various testXXX.c test programs should 386 provide good examples of how to do things with the library.</li> 387 </ul> 388 </li> 389 <li>What about C++ ? 390 <p>libxml is written in pure C in order to allow easy reuse on a number 391 of platforms, including embedded systems. I don't intend to convert to 392 C++.</p> 393 <p>There are however a few C++ wrappers which may fulfill your needs:</p> 394 <ul> 395 <li>by Ari Johnson <ari@btigate.com>: 396 <p>Website: <a 397 href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p> 398 <p>Download: <a 399 href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p> 400 </li> 401 <li>by Peter Jones <pjones@pmade.org> 402 <p>Website: <a 403 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 404 </li> 405 </ul> 406 </li> 407 <li>How to validate a document a posteriori ? 408 <p>It is possible to validate documents which had not been validated at 409 initial parsing time or documents which have been built from scratch 410 using the API. Use the <a 411 href="http://xmlsoft.org/html/libxml-valid.html#XMLVALIDATEDTD">xmlValidateDtd()</a> 412 function. It is also possible to simply add a DTD to an existing 413 document:</p> 414 <pre>xmlDocPtr doc; /* your existing document */ 415xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 416 417 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 418 419 doc->intSubset = dtd; 420 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 421 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 422 </pre> 423 </li> 424 <li>So what is this funky "xmlChar" used all the time? 425 <p>It is a null terminated sequence of utf-8 characters. And only utf-8! 426 You need to convert strings encoded in different ways to utf-8 before 427 passing them to the API. This can be accomplished with the iconv library 428 for instance.</p> 429 </li> 430 <li>etc ...</li> 431</ol> 432 433<p></p> 434 435<h2><a name="Documentat">Documentation</a></h2> 436 437<p>There are several on-line resources related to using libxml:</p> 438<ol> 439 <li>Use the <a href="search.php">search engine</a> to lookup 440 informations.</li> 441 <li>Check the <a href="FAQ.html">FAQ.</a></li> 442 <li>Check the <a href="http://xmlsoft.org/html/libxml-lib.html">extensive 443 documentation</a> automatically extracted from code comments (using <a 444 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gtk-doc">gtk 445 doc</a>).</li> 446 <li>Look at the documentation about <a href="encoding.html">libxml 447 internationalization support</a>.</li> 448 <li>This page provides a global overview and <a href="example.html">some 449 examples</a> on how to use libxml.</li> 450 <li>John Fleck's libxml tutorial: <a href="tutorial/index.html">html</a> or 451 <a href="tutorial/xmltutorial.pdf">pdf</a>.</li> 452 <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a 453 href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice 454 documentation</a> explaining how to use the libxml SAX interface.</li> 455 <li>George Lebl wrote <a 456 href="http://www-4.ibm.com/software/developer/library/gnome3/">an article 457 for IBM developerWorks</a> about using libxml.</li> 458 <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO 459 file</a>.</li> 460 <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a> 461 description. If you are starting a new project using libxml you should 462 really use the 2.x version.</li> 463 <li>And don't forget to look at the <a 464 href="http://mail.gnome.org/archives/xml/">mailing-list archive</a>.</li> 465</ol> 466 467<h2><a name="Reporting">Reporting bugs and getting help</a></h2> 468 469<p>Well, bugs or missing features are always possible, and I will make a 470point of fixing them in a timely fashion. The best way to report a bug is to 471use the <a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome 472bug tracking database</a> (make sure to use the "libxml2" module name). I 473look at reports there regularly and it's good to have a reminder when a bug 474is still open. Be sure to specify that the bug is for the package libxml2.</p> 475 476<p>There is also a mailing-list <a 477href="mailto:xml@gnome.org">xml@gnome.org</a> for libxml, with an <a 478href="http://mail.gnome.org/archives/xml/">on-line archive</a> (<a 479href="http://xmlsoft.org/messages">old</a>). To subscribe to this list, 480please visit the <a 481href="http://mail.gnome.org/mailman/listinfo/xml">associated Web</a> page and 482follow the instructions. <strong>Do not send code, I won't debug it</strong> 483(but patches are really appreciated!).</p> 484 485<p>Check the following <strong><span style="color: #FF0000">before 486posting</span></strong>:</p> 487<ul> 488 <li>Read the <a href="FAQ.html">FAQ</a> and <a href="search.php">use the 489 search engine</a> to get informations related to your problem.</li> 490 <li>Make sure you are <a href="ftp://xmlsoft.org/">using a recent 491 version</a>, and that the problem still shows up in a recent version.</li> 492 <li>Check the <a href="http://mail.gnome.org/archives/xml/">list 493 archives</a> to see if the problem was reported already. In this case 494 there is probably a fix available, similarly check the <a 495 href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">registered 496 open bugs</a>.</li> 497 <li>Make sure you can reproduce the bug with xmllint or one of the test 498 programs found in source in the distribution.</li> 499 <li>Please send the command showing the error as well as the input (as an 500 attachment)</li> 501</ul> 502 503<p>Then send the bug with associated informations to reproduce it to the <a 504href="mailto:xml@gnome.org">xml@gnome.org</a> list; if it's really libxml 505related I will approve it. Please do not send mail to me directly, it makes 506things really hard to track and in some cases I am not the best person to 507answer a given question, ask on the list.</p> 508 509<p>To <span style="color: #E50000">be really clear about support</span>:</p> 510<ul> 511 <li>Support or help <span style="color: #E50000">request MUST be sent to 512 the list or on bugzilla</span> in case of problems, so that the Question 513 and Answers can be shared publicly. Failing to do so carries the implicit 514 message "I want free support but I don't want to share the benefits with 515 others" and is not welcome. I will automatically Carbon-Copy the 516 xml@gnome.org mailing list for any technical reply made about libxml2 or 517 libxslt.</li> 518 <li>There is <span style="color: #E50000">no garantee for support</span>, 519 if your question remains unanswered after a week, repost it, making sure 520 you gave all the detail needed and the informations requested.</li> 521 <li>Failing to provide informations as requested or double checking first 522 for prior feedback also carries the implicit message "the time of the 523 library maintainers is less valuable than my time" and might not be 524 welcome.</li> 525</ul> 526 527<p>Of course, bugs reported with a suggested patch for fixing them will 528probably be processed faster than those without.</p> 529 530<p>If you're looking for help, a quick look at <a 531href="http://mail.gnome.org/archives/xml/">the list archive</a> may actually 532provide the answer. I usually send source samples when answering libxml usage 533questions. The <a href="http://xmlsoft.org/html/book1.html">auto-generated 534documentation</a> is not as polished as I would like (i need to learn more 535about DocBook), but it's a good starting point.</p> 536 537<h2><a name="help">How to help</a></h2> 538 539<p>You can help the project in various ways, the best thing to do first is to 540subscribe to the mailing-list as explained before, check the <a 541href="http://mail.gnome.org/archives/xml/">archives </a>and the <a 542href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome bug 543database</a>:</p> 544<ol> 545 <li>Provide patches when you find problems.</li> 546 <li>Provide the diffs when you port libxml to a new platform. They may not 547 be integrated in all cases but help pinpointing portability problems 548 and</li> 549 <li>Provide documentation fixes (either as patches to the code comments or 550 as HTML diffs).</li> 551 <li>Provide new documentations pieces (translations, examples, etc 552 ...).</li> 553 <li>Check the TODO file and try to close one of the items.</li> 554 <li>Take one of the points raised in the archive or the bug database and 555 provide a fix. <a href="mailto:daniel@veillard.com">Get in touch with me 556 </a>before to avoid synchronization problems and check that the suggested 557 fix will fit in nicely :-)</li> 558</ol> 559 560<h2><a name="Downloads">Downloads</a></h2> 561 562<p>The latest versions of libxml can be found on <a 563href="ftp://xmlsoft.org/">xmlsoft.org</a> (<a 564href="ftp://speakeasy.rpmfind.net/pub/libxml/">Seattle</a>, <a 565href="ftp://fr.rpmfind.net/pub/libxml/">France</a>) or on the <a 566href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either 567as a <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">source 568archive</a><!-- commenting this out because they seem to have disappeared or <a 569href="ftp://ftp.gnome.org/pub/GNOME/stable/redhat/i386/libxml/">RPM 570packages</a> --> 571 , Antonin Sprinzl also provide <a href="ftp://gd.tuwien.ac.at/pub/libxml/">a 572mirror in Austria</a>. (NOTE that you need both the <a 573href="http://rpmfind.net/linux/RPM/libxml2.html">libxml(2)</a> and <a 574href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml(2)-devel</a> 575packages installed to compile applications using libxml.)</p> 576 577<p>Binary ports:</p> 578<ul> 579 <li>Red Hat RPMs for i386 are available directly on <a 580 href="ftp://xmlsoft.org/">xmlsoft.org</a>, the source RPM will compile on 581 any architecture supported by Red Hat.</li> 582 <li><p><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a></p> 583 is now the maintainer of the Windows port, <a 584 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 585 binaries</a>.</li> 586 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 587 <a href="http://garypennington.net/libxml2/">Solaris binaries</a>.</li> 588 <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a> provides <a 589 href="http://www.zveno.com/open_source/libxml2xslt.html">Mac Os X 590 binaries</a>.</li> 591 <li>The HP-UX porting center provides <a 592 href="http://hpux.connect.org.uk/hppd/hpux/Gnome/">HP-UX binaries</a></li> 593</ul> 594 595<p>If you know other supported binary ports, please <a 596href="http://veillard.com/">contact me</a>.</p> 597 598<p><a name="Snapshot">Snapshot:</a></p> 599<ul> 600 <li>Code from the W3C cvs base libxml <a 601 href="ftp://xmlsoft.org/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a>.</li> 602 <li>Docs, content of the web site, the list archive included <a 603 href="ftp://xmlsoft.org/libxml-docs.tar.gz">libxml-docs.tar.gz</a>.</li> 604</ul> 605 606<p><a name="Contribs">Contributions:</a></p> 607 608<p>I do accept external contributions, especially if compiling on another 609platform, get in touch with me to upload the package, wrappers for various 610languages have been provided, and can be found in the <a 611href="contribs.html">contrib section</a></p> 612 613<p>Libxml is also available from CVS:</p> 614<ul> 615 <li><p>The <a 616 href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Gnome 617 CVS base</a>. Check the <a 618 href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> 619 page; the CVS module is <b>gnome-xml</b>.</p> 620 </li> 621 <li>The <strong>libxslt</strong> module is also present there</li> 622</ul> 623 624<h2><a name="News">News</a></h2> 625 626<h3>CVS only : check the <a 627href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file 628for a really accurate description</h3> 629 630<p>Items not finished and worked on, get in touch with the list if you want 631to test those</p> 632<ul> 633 <li>More testing on RelaxNG</li> 634 <li>Finishing up <a href="http://www.w3.org/TR/xmlschema-1/">XML 635 Schemas</a></li> 636</ul> 637 638<h3>2.5.6: Apr 1 2003</h3> 639<ul> 640 <li>Fixed W3C XML Schemas datatype, should be compliant now except for 641 binHex and base64 which are not supported yet.</li> 642 <li>bug fixes: non-ASCII IDs, HTML output, XInclude on large docs and 643 XInclude entities handling, encoding detection on external subsets, XML 644 Schemas bugs and memory leaks, HTML parser (James Bursa)</li> 645 <li>portability: python/trio (Albert Chin), Sun compiler warnings</li> 646 <li>documentation: added --relaxng option to xmllint man page (John)</li> 647 <li>improved error reporting: xml:space, start/end tag mismatches, Relax NG 648 errors</li> 649</ul> 650 651<h3>2.5.5: Mar 24 2003</h3> 652<ul> 653 <li>Lot of fixes on the Relax NG implementation. More testing including 654 DocBook and TEI examples.</li> 655 <li>Increased the support for W3C XML Schemas datatype</li> 656 <li>Several bug fixes in the URI handling layer</li> 657 <li>Bug fixes: HTML parser, xmlReader, DTD validation, XPath, encoding 658 conversion, line counting in the parser.</li> 659 <li>Added support for $XMLLINT_INDENT environment variable, FTP delete</li> 660 <li>Fixed the RPM spec file name</li> 661</ul> 662 663<h3>2.5.4: Feb 20 2003</h3> 664<ul> 665 <li>Conformance testing and lot of fixes on Relax NG and XInclude 666 implementation</li> 667 <li>Implementation of XPointer element() scheme</li> 668 <li>Bug fixes: XML parser, XInclude entities merge, validity checking on 669 namespaces, 670 <p>2 serialization bugs, node info generation problems, a DTD regexp 671 generation problem.</p> 672 </li> 673 <li>Portability: windows updates and path canonicalization (Igor)</li> 674 <li>A few typo fixes (Kjartan Maraas)</li> 675 <li>Python bindings generator fixes (Stephane Bidoul)</li> 676</ul> 677 678<h3>2.5.3: Feb 10 2003</h3> 679<ul> 680 <li>RelaxNG and XML Schemas datatypes improvements, and added a first 681 version of RelaxNG Python bindings</li> 682 <li>Fixes: XLink (Sean Chittenden), XInclude (Sean Chittenden), API fix for 683 serializing namespace nodes, encoding conversion bug, XHTML1 684 serialization</li> 685 <li>Portability fixes: Windows (Igor), AMD 64bits RPM spec file</li> 686</ul> 687 688<h3>2.5.2: Feb 5 2003</h3> 689<ul> 690 <li>First implementation of RelaxNG, added --relaxng flag to xmllint</li> 691 <li>Schemas support now compiled in by default.</li> 692 <li>Bug fixes: DTD validation, namespace checking, XInclude and entities, 693 delegateURI in XML Catalogs, HTML parser, XML reader (St�phane Bidoul), 694 XPath parser and evaluation, UTF8ToUTF8 serialization, XML reader memory 695 consumption, HTML parser, HTML serialization in the presence of 696 namespaces</li> 697 <li>added an HTML API to check elements and attributes.</li> 698 <li>Documentation improvement, PDF for the tutorial (John Fleck), doc 699 patches (Stefan Kost)</li> 700 <li>Portability fixes: NetBSD (Julio Merino), Windows (Igor Zlatkovic)</li> 701 <li>Added python bindings for XPointer, contextual error reporting 702 (St�phane Bidoul)</li> 703 <li>URI/file escaping problems (Stefano Zacchiroli)</li> 704</ul> 705 706<h3>2.5.1: Jan 8 2003</h3> 707<ul> 708 <li>Fixes a memory leak and configuration/compilation problems in 2.5.0</li> 709 <li>documentation updates (John)</li> 710 <li>a couple of XmlTextReader fixes</li> 711</ul> 712 713<h3>2.5.0: Jan 6 2003</h3> 714<ul> 715 <li>New <a href="xmlreader.html">XmltextReader interface</a> based on C# 716 API (with help of St�phane Bidoul)</li> 717 <li>Windows: more exports, including the new API (Igor)</li> 718 <li>XInclude fallback fix</li> 719 <li>Python: bindings for the new API, packaging (St�phane Bidoul), 720 drv_libxml2.py Python xml.sax driver (St�phane Bidoul), fixes, speedup 721 and iterators for Python-2.2 (Hannu Krosing)</li> 722 <li>Tutorial fixes (john Fleck and Niraj Tolia) xmllint man update 723 (John)</li> 724 <li>Fix an XML parser bug raised by Vyacheslav Pindyura</li> 725 <li>Fix for VMS serialization (Nigel Hall) and config (Craig A. Berry)</li> 726 <li>Entities handling fixes</li> 727 <li>new API to optionally track node creation and deletion (Lukas 728 Schroeder)</li> 729 <li>Added documentation for the XmltextReader interface and some <a 730 href="guidelines.html">XML guidelines</a></li> 731</ul> 732 733<h3>2.4.30: Dec 12 2002</h3> 734<ul> 735 <li>2.4.29 broke the python bindings, rereleasing</li> 736 <li>Improvement/fixes of the XML API generator, and couple of minor code 737 fixes.</li> 738</ul> 739 740<h3>2.4.29: Dec 11 2002</h3> 741<ul> 742 <li>Windows fixes (Igor): Windows CE port, pthread linking, python bindings 743 (St�phane Bidoul), Mingw (Magnus Henoch), and export list updates</li> 744 <li>Fix for prev in python bindings (ERDI Gergo)</li> 745 <li>Fix for entities handling (Marcus Clarke)</li> 746 <li>Refactored the XML and HTML dumps to a single code path, fixed XHTML1 747 dump</li> 748 <li>Fix for URI parsing when handling URNs with fragment identifiers</li> 749 <li>Fix for HTTP URL escaping problem</li> 750 <li>added an TextXmlReader (C#) like API (work in progress)</li> 751 <li>Rewrote the API in XML generation script, includes a C parser and saves 752 more informations needed for C# bindings</li> 753</ul> 754 755<h3>2.4.28: Nov 22 2002</h3> 756<ul> 757 <li>a couple of python binding fixes</li> 758 <li>2 bug fixes in the XML push parser</li> 759 <li>potential memory leak removed (Martin Stoilov)</li> 760 <li>fix to the configure script for Unix (Dimitri Papadopoulos)</li> 761 <li>added encoding support for XInclude parse="text"</li> 762 <li>autodetection of XHTML1 and specific serialization rules added</li> 763 <li>nasty threading bug fixed (William Brack)</li> 764</ul> 765 766<h3>2.4.27: Nov 17 2002</h3> 767<ul> 768 <li>fixes for the Python bindings</li> 769 <li>a number of bug fixes: SGML catalogs, xmlParseBalancedChunkMemory(), 770 HTML parser, Schemas (Charles Bozeman), document fragment support 771 (Christian Glahn), xmlReconciliateNs (Brian Stafford), XPointer, 772 xmlFreeNode(), xmlSAXParseMemory (Peter Jones), xmlGetNodePath (Petr 773 Pajas), entities processing</li> 774 <li>added grep to xmllint --shell</li> 775 <li>VMS update patch from Craig A. Berry</li> 776 <li>cleanup of the Windows build with support for more compilers (Igor), 777 better thread support on Windows</li> 778 <li>cleanup of Unix Makefiles and spec file</li> 779 <li>Improvements to the documentation (John Fleck)</li> 780</ul> 781 782<h3>2.4.26: Oct 18 2002</h3> 783<ul> 784 <li>Patches for Windows CE port, improvements on Windows paths handling</li> 785 <li>Fixes to the validation code (DTD and Schemas), xmlNodeGetPath() , 786 HTML serialization, Namespace compliance, and a number of small 787 problems</li> 788</ul> 789 790<h3>2.4.25: Sep 26 2002</h3> 791<ul> 792 <li>A number of bug fixes: XPath, validation, Python bindings, DOM and 793 tree, xmlI/O, Html</li> 794 <li>Serious rewrite of XInclude</li> 795 <li>Made XML Schemas regexp part of the default build and APIs, small fix 796 and improvement of the regexp core</li> 797 <li>Changed the validation code to reuse XML Schemas regexp APIs</li> 798 <li>Better handling of Windows file paths, improvement of Makefiles (Igor, 799 Daniel Gehriger, Mark Vakoc)</li> 800 <li>Improved the python I/O bindings, the tests, added resolver and regexp 801 APIs</li> 802 <li>New logos from Marc Liyanage</li> 803 <li>Tutorial improvements: John Fleck, Christopher Harris</li> 804 <li>Makefile: Fixes for AMD x86_64 (Mandrake), DESTDIR (Christophe 805 Merlet)</li> 806 <li>removal of all stderr/perror use for error reporting</li> 807 <li>Better error reporting: XPath and DTD validation</li> 808 <li>update of the trio portability layer (Bjorn Reese)</li> 809</ul> 810 811<p><strong>2.4.24: Aug 22 2002</strong></p> 812<ul> 813 <li>XPath fixes (William), xf:escape-uri() (Wesley Terpstra)</li> 814 <li>Python binding fixes: makefiles (William), generator, rpm build, x86-64 815 (fcrozat)</li> 816 <li>HTML <style> and boolean attributes serializer fixes</li> 817 <li>C14N improvements by Aleksey</li> 818 <li>doc cleanups: Rick Jones</li> 819 <li>Windows compiler makefile updates: Igor and Elizabeth Barham</li> 820 <li>XInclude: implementation of fallback and xml:base fixup added</li> 821</ul> 822 823<h3>2.4.23: July 6 2002</h3> 824<ul> 825 <li>performances patches: Peter Jacobi</li> 826 <li>c14n fixes, testsuite and performances: Aleksey Sanin</li> 827 <li>added xmlDocFormatDump: Chema Celorio</li> 828 <li>new tutorial: John Fleck</li> 829 <li>new hash functions and performances: Sander Vesik, portability fix from 830 Peter Jacobi</li> 831 <li>a number of bug fixes: XPath (William Brack, Richard Jinks), XML and 832 HTML parsers, ID lookup function</li> 833 <li>removal of all remaining sprintf: Aleksey Sanin</li> 834</ul> 835 836<h3>2.4.22: May 27 2002</h3> 837<ul> 838 <li>a number of bug fixes: configure scripts, base handling, parser, memory 839 usage, HTML parser, XPath, documentation (Christian Cornelssen), 840 indentation, URI parsing</li> 841 <li>Optimizations for XMLSec, fixing and making public some of the network 842 protocol handlers (Aleksey)</li> 843 <li>performance patch from Gary Pennington</li> 844 <li>Charles Bozeman provided date and time support for XML Schemas 845 datatypes</li> 846</ul> 847 848<h3>2.4.21: Apr 29 2002</h3> 849 850<p>This release is both a bug fix release and also contains the early XML 851Schemas <a href="http://www.w3.org/TR/xmlschema-1/">structures</a> and <a 852href="http://www.w3.org/TR/xmlschema-2/">datatypes</a> code, beware, all 853interfaces are likely to change, there is huge holes, it is clearly a work in 854progress and don't even think of putting this code in a production system, 855it's actually not compiled in by default. The real fixes are:</p> 856<ul> 857 <li>a couple of bugs or limitations introduced in 2.4.20</li> 858 <li>patches for Borland C++ and MSC by Igor</li> 859 <li>some fixes on XPath strings and conformance patches by Richard 860 Jinks</li> 861 <li>patch from Aleksey for the ExcC14N specification</li> 862 <li>OSF/1 bug fix by Bjorn</li> 863</ul> 864 865<h3>2.4.20: Apr 15 2002</h3> 866<ul> 867 <li>bug fixes: file descriptor leak, XPath, HTML output, DTD validation</li> 868 <li>XPath conformance testing by Richard Jinks</li> 869 <li>Portability fixes: Solaris, MPE/iX, Windows, OSF/1, python bindings, 870 libxml.m4</li> 871</ul> 872 873<h3>2.4.19: Mar 25 2002</h3> 874<ul> 875 <li>bug fixes: half a dozen XPath bugs, Validation, ISO-Latin to UTF8 876 encoder</li> 877 <li>portability fixes in the HTTP code</li> 878 <li>memory allocation checks using valgrind, and profiling tests</li> 879 <li>revamp of the Windows build and Makefiles</li> 880</ul> 881 882<h3>2.4.18: Mar 18 2002</h3> 883<ul> 884 <li>bug fixes: tree, SAX, canonicalization, validation, portability, 885 XPath</li> 886 <li>removed the --with-buffer option it was becoming unmaintainable</li> 887 <li>serious cleanup of the Python makefiles</li> 888 <li>speedup patch to XPath very effective for DocBook stylesheets</li> 889 <li>Fixes for Windows build, cleanup of the documentation</li> 890</ul> 891 892<h3>2.4.17: Mar 8 2002</h3> 893<ul> 894 <li>a lot of bug fixes, including "namespace nodes have no parents in 895 XPath"</li> 896 <li>fixed/improved the Python wrappers, added more examples and more 897 regression tests, XPath extension functions can now return node-sets</li> 898 <li>added the XML Canonicalization support from Aleksey Sanin</li> 899</ul> 900 901<h3>2.4.16: Feb 20 2002</h3> 902<ul> 903 <li>a lot of bug fixes, most of them were triggered by the XML Testsuite 904 from OASIS and W3C. Compliance has been significantly improved.</li> 905 <li>a couple of portability fixes too.</li> 906</ul> 907 908<h3>2.4.15: Feb 11 2002</h3> 909<ul> 910 <li>Fixed the Makefiles, especially the python module ones</li> 911 <li>A few bug fixes and cleanup</li> 912 <li>Includes cleanup</li> 913</ul> 914 915<h3>2.4.14: Feb 8 2002</h3> 916<ul> 917 <li>Change of License to the <a 918 href="http://www.opensource.org/licenses/mit-license.html">MIT 919 License</a> basically for integration in XFree86 codebase, and removing 920 confusion around the previous dual-licensing</li> 921 <li>added Python bindings, beta software but should already be quite 922 complete</li> 923 <li>a large number of fixes and cleanups, especially for all tree 924 manipulations</li> 925 <li>cleanup of the headers, generation of a reference API definition in 926 XML</li> 927</ul> 928 929<h3>2.4.13: Jan 14 2002</h3> 930<ul> 931 <li>update of the documentation: John Fleck and Charlie Bozeman</li> 932 <li>cleanup of timing code from Justin Fletcher</li> 933 <li>fixes for Windows and initial thread support on Win32: Igor and Serguei 934 Narojnyi</li> 935 <li>Cygwin patch from Robert Collins</li> 936 <li>added xmlSetEntityReferenceFunc() for Keith Isdale work on xsldbg</li> 937</ul> 938 939<h3>2.4.12: Dec 7 2001</h3> 940<ul> 941 <li>a few bug fixes: thread (Gary Pennington), xmllint (Geert Kloosterman), 942 XML parser (Robin Berjon), XPointer (Danny Jamshy), I/O cleanups 943 (robert)</li> 944 <li>Eric Lavigne contributed project files for MacOS</li> 945 <li>some makefiles cleanups</li> 946</ul> 947 948<h3>2.4.11: Nov 26 2001</h3> 949<ul> 950 <li>fixed a couple of errors in the includes, fixed a few bugs, some code 951 cleanups</li> 952 <li>xmllint man pages improvement by Heiko Rupp</li> 953 <li>updated VMS build instructions from John A Fotheringham</li> 954 <li>Windows Makefiles updates from Igor</li> 955</ul> 956 957<h3>2.4.10: Nov 10 2001</h3> 958<ul> 959 <li>URI escaping fix (Joel Young)</li> 960 <li>added xmlGetNodePath() (for paths or XPointers generation)</li> 961 <li>Fixes namespace handling problems when using DTD and validation</li> 962 <li>improvements on xmllint: Morus Walter patches for --format and 963 --encode, Stefan Kost and Heiko Rupp improvements on the --shell</li> 964 <li>fixes for xmlcatalog linking pointed by Weiqi Gao</li> 965 <li>fixes to the HTML parser</li> 966</ul> 967 968<h3>2.4.9: Nov 6 2001</h3> 969<ul> 970 <li>fixes more catalog bugs</li> 971 <li>avoid a compilation problem, improve xmlGetLineNo()</li> 972</ul> 973 974<h3>2.4.8: Nov 4 2001</h3> 975<ul> 976 <li>fixed SGML catalogs broken in previous release, updated xmlcatalog 977 tool</li> 978 <li>fixed a compile errors and some includes troubles.</li> 979</ul> 980 981<h3>2.4.7: Oct 30 2001</h3> 982<ul> 983 <li>exported some debugging interfaces</li> 984 <li>serious rewrite of the catalog code</li> 985 <li>integrated Gary Pennington thread safety patch, added configure option 986 and regression tests</li> 987 <li>removed an HTML parser bug</li> 988 <li>fixed a couple of potentially serious validation bugs</li> 989 <li>integrated the SGML DocBook support in xmllint</li> 990 <li>changed the nanoftp anonymous login passwd</li> 991 <li>some I/O cleanup and a couple of interfaces for Perl wrapper</li> 992 <li>general bug fixes</li> 993 <li>updated xmllint man page by John Fleck</li> 994 <li>some VMS and Windows updates</li> 995</ul> 996 997<h3>2.4.6: Oct 10 2001</h3> 998<ul> 999 <li>added an updated man pages by John Fleck</li> 1000 <li>portability and configure fixes</li> 1001 <li>an infinite loop on the HTML parser was removed (William)</li> 1002 <li>Windows makefile patches from Igor</li> 1003 <li>fixed half a dozen bugs reported for libxml or libxslt</li> 1004 <li>updated xmlcatalog to be able to modify SGML super catalogs</li> 1005</ul> 1006 1007<h3>2.4.5: Sep 14 2001</h3> 1008<ul> 1009 <li>Remove a few annoying bugs in 2.4.4</li> 1010 <li>forces the HTML serializer to output decimal charrefs since some 1011 version of Netscape can't handle hexadecimal ones</li> 1012</ul> 1013 1014<h3>1.8.16: Sep 14 2001</h3> 1015<ul> 1016 <li>maintenance release of the old libxml1 branch, couple of bug and 1017 portability fixes</li> 1018</ul> 1019 1020<h3>2.4.4: Sep 12 2001</h3> 1021<ul> 1022 <li>added --convert to xmlcatalog, bug fixes and cleanups of XML 1023 Catalog</li> 1024 <li>a few bug fixes and some portability changes</li> 1025 <li>some documentation cleanups</li> 1026</ul> 1027 1028<h3>2.4.3: Aug 23 2001</h3> 1029<ul> 1030 <li>XML Catalog support see the doc</li> 1031 <li>New NaN/Infinity floating point code</li> 1032 <li>A few bug fixes</li> 1033</ul> 1034 1035<h3>2.4.2: Aug 15 2001</h3> 1036<ul> 1037 <li>adds xmlLineNumbersDefault() to control line number generation</li> 1038 <li>lot of bug fixes</li> 1039 <li>the Microsoft MSC projects files should now be up to date</li> 1040 <li>inheritance of namespaces from DTD defaulted attributes</li> 1041 <li>fixes a serious potential security bug</li> 1042 <li>added a --format option to xmllint</li> 1043</ul> 1044 1045<h3>2.4.1: July 24 2001</h3> 1046<ul> 1047 <li>possibility to keep line numbers in the tree</li> 1048 <li>some computation NaN fixes</li> 1049 <li>extension of the XPath API</li> 1050 <li>cleanup for alpha and ia64 targets</li> 1051 <li>patch to allow saving through HTTP PUT or POST</li> 1052</ul> 1053 1054<h3>2.4.0: July 10 2001</h3> 1055<ul> 1056 <li>Fixed a few bugs in XPath, validation, and tree handling.</li> 1057 <li>Fixed XML Base implementation, added a couple of examples to the 1058 regression tests</li> 1059 <li>A bit of cleanup</li> 1060</ul> 1061 1062<h3>2.3.14: July 5 2001</h3> 1063<ul> 1064 <li>fixed some entities problems and reduce memory requirement when 1065 substituting them</li> 1066 <li>lots of improvements in the XPath queries interpreter can be 1067 substantially faster</li> 1068 <li>Makefiles and configure cleanups</li> 1069 <li>Fixes to XPath variable eval, and compare on empty node set</li> 1070 <li>HTML tag closing bug fixed</li> 1071 <li>Fixed an URI reference computation problem when validating</li> 1072</ul> 1073 1074<h3>2.3.13: June 28 2001</h3> 1075<ul> 1076 <li>2.3.12 configure.in was broken as well as the push mode XML parser</li> 1077 <li>a few more fixes for compilation on Windows MSC by Yon Derek</li> 1078</ul> 1079 1080<h3>1.8.14: June 28 2001</h3> 1081<ul> 1082 <li>Zbigniew Chyla gave a patch to use the old XML parser in push mode</li> 1083 <li>Small Makefile fix</li> 1084</ul> 1085 1086<h3>2.3.12: June 26 2001</h3> 1087<ul> 1088 <li>lots of cleanup</li> 1089 <li>a couple of validation fix</li> 1090 <li>fixed line number counting</li> 1091 <li>fixed serious problems in the XInclude processing</li> 1092 <li>added support for UTF8 BOM at beginning of entities</li> 1093 <li>fixed a strange gcc optimizer bugs in xpath handling of float, gcc-3.0 1094 miscompile uri.c (William), Thomas Leitner provided a fix for the 1095 optimizer on Tru64</li> 1096 <li>incorporated Yon Derek and Igor Zlatkovic fixes and improvements for 1097 compilation on Windows MSC</li> 1098 <li>update of libxml-doc.el (Felix Natter)</li> 1099 <li>fixed 2 bugs in URI normalization code</li> 1100</ul> 1101 1102<h3>2.3.11: June 17 2001</h3> 1103<ul> 1104 <li>updates to trio, Makefiles and configure should fix some portability 1105 problems (alpha)</li> 1106 <li>fixed some HTML serialization problems (pre, script, and block/inline 1107 handling), added encoding aware APIs, cleanup of this code</li> 1108 <li>added xmlHasNsProp()</li> 1109 <li>implemented a specific PI for encoding support in the DocBook SGML 1110 parser</li> 1111 <li>some XPath fixes (-Infinity, / as a function parameter and namespaces 1112 node selection)</li> 1113 <li>fixed a performance problem and an error in the validation code</li> 1114 <li>fixed XInclude routine to implement the recursive behaviour</li> 1115 <li>fixed xmlFreeNode problem when libxml is included statically twice</li> 1116 <li>added --version to xmllint for bug reports</li> 1117</ul> 1118 1119<h3>2.3.10: June 1 2001</h3> 1120<ul> 1121 <li>fixed the SGML catalog support</li> 1122 <li>a number of reported bugs got fixed, in XPath, iconv detection, 1123 XInclude processing</li> 1124 <li>XPath string function should now handle unicode correctly</li> 1125</ul> 1126 1127<h3>2.3.9: May 19 2001</h3> 1128 1129<p>Lots of bugfixes, and added a basic SGML catalog support:</p> 1130<ul> 1131 <li>HTML push bugfix #54891 and another patch from Jonas Borgstr�m</li> 1132 <li>some serious speed optimization again</li> 1133 <li>some documentation cleanups</li> 1134 <li>trying to get better linking on Solaris (-R)</li> 1135 <li>XPath API cleanup from Thomas Broyer</li> 1136 <li>Validation bug fixed #54631, added a patch from Gary Pennington, fixed 1137 xmlValidGetValidElements()</li> 1138 <li>Added an INSTALL file</li> 1139 <li>Attribute removal added to API: #54433</li> 1140 <li>added a basic support for SGML catalogs</li> 1141 <li>fixed xmlKeepBlanksDefault(0) API</li> 1142 <li>bugfix in xmlNodeGetLang()</li> 1143 <li>fixed a small configure portability problem</li> 1144 <li>fixed an inversion of SYSTEM and PUBLIC identifier in HTML document</li> 1145</ul> 1146 1147<h3>1.8.13: May 14 2001</h3> 1148<ul> 1149 <li>bugfixes release of the old libxml1 branch used by Gnome</li> 1150</ul> 1151 1152<h3>2.3.8: May 3 2001</h3> 1153<ul> 1154 <li>Integrated an SGML DocBook parser for the Gnome project</li> 1155 <li>Fixed a few things in the HTML parser</li> 1156 <li>Fixed some XPath bugs raised by XSLT use, tried to fix the floating 1157 point portability issue</li> 1158 <li>Speed improvement (8M/s for SAX, 3M/s for DOM, 1.5M/s for 1159 DOM+validation using the XML REC as input and a 700MHz celeron).</li> 1160 <li>incorporated more Windows cleanup</li> 1161 <li>added xmlSaveFormatFile()</li> 1162 <li>fixed problems in copying nodes with entities references (gdome)</li> 1163 <li>removed some troubles surrounding the new validation module</li> 1164</ul> 1165 1166<h3>2.3.7: April 22 2001</h3> 1167<ul> 1168 <li>lots of small bug fixes, corrected XPointer</li> 1169 <li>Non deterministic content model validation support</li> 1170 <li>added xmlDocCopyNode for gdome2</li> 1171 <li>revamped the way the HTML parser handles end of tags</li> 1172 <li>XPath: corrections of namespaces support and number formatting</li> 1173 <li>Windows: Igor Zlatkovic patches for MSC compilation</li> 1174 <li>HTML output fixes from P C Chow and William M. Brack</li> 1175 <li>Improved validation speed sensible for DocBook</li> 1176 <li>fixed a big bug with ID declared in external parsed entities</li> 1177 <li>portability fixes, update of Trio from Bjorn Reese</li> 1178</ul> 1179 1180<h3>2.3.6: April 8 2001</h3> 1181<ul> 1182 <li>Code cleanup using extreme gcc compiler warning options, found and 1183 cleared half a dozen potential problem</li> 1184 <li>the Eazel team found an XML parser bug</li> 1185 <li>cleaned up the user of some of the string formatting function. used the 1186 trio library code to provide the one needed when the platform is missing 1187 them</li> 1188 <li>xpath: removed a memory leak and fixed the predicate evaluation 1189 problem, extended the testsuite and cleaned up the result. XPointer seems 1190 broken ...</li> 1191</ul> 1192 1193<h3>2.3.5: Mar 23 2001</h3> 1194<ul> 1195 <li>Biggest change is separate parsing and evaluation of XPath expressions, 1196 there is some new APIs for this too</li> 1197 <li>included a number of bug fixes(XML push parser, 51876, notations, 1198 52299)</li> 1199 <li>Fixed some portability issues</li> 1200</ul> 1201 1202<h3>2.3.4: Mar 10 2001</h3> 1203<ul> 1204 <li>Fixed bugs #51860 and #51861</li> 1205 <li>Added a global variable xmlDefaultBufferSize to allow default buffer 1206 size to be application tunable.</li> 1207 <li>Some cleanup in the validation code, still a bug left and this part 1208 should probably be rewritten to support ambiguous content model :-\</li> 1209 <li>Fix a couple of serious bugs introduced or raised by changes in 2.3.3 1210 parser</li> 1211 <li>Fixed another bug in xmlNodeGetContent()</li> 1212 <li>Bjorn fixed XPath node collection and Number formatting</li> 1213 <li>Fixed a loop reported in the HTML parsing</li> 1214 <li>blank space are reported even if the Dtd content model proves that they 1215 are formatting spaces, this is for XML conformance</li> 1216</ul> 1217 1218<h3>2.3.3: Mar 1 2001</h3> 1219<ul> 1220 <li>small change in XPath for XSLT</li> 1221 <li>documentation cleanups</li> 1222 <li>fix in validation by Gary Pennington</li> 1223 <li>serious parsing performances improvements</li> 1224</ul> 1225 1226<h3>2.3.2: Feb 24 2001</h3> 1227<ul> 1228 <li>chasing XPath bugs, found a bunch, completed some TODO</li> 1229 <li>fixed a Dtd parsing bug</li> 1230 <li>fixed a bug in xmlNodeGetContent</li> 1231 <li>ID/IDREF support partly rewritten by Gary Pennington</li> 1232</ul> 1233 1234<h3>2.3.1: Feb 15 2001</h3> 1235<ul> 1236 <li>some XPath and HTML bug fixes for XSLT</li> 1237 <li>small extension of the hash table interfaces for DOM gdome2 1238 implementation</li> 1239 <li>A few bug fixes</li> 1240</ul> 1241 1242<h3>2.3.0: Feb 8 2001 (2.2.12 was on 25 Jan but I didn't kept track)</h3> 1243<ul> 1244 <li>Lots of XPath bug fixes</li> 1245 <li>Add a mode with Dtd lookup but without validation error reporting for 1246 XSLT</li> 1247 <li>Add support for text node without escaping (XSLT)</li> 1248 <li>bug fixes for xmlCheckFilename</li> 1249 <li>validation code bug fixes from Gary Pennington</li> 1250 <li>Patch from Paul D. Smith correcting URI path normalization</li> 1251 <li>Patch to allow simultaneous install of libxml-devel and 1252 libxml2-devel</li> 1253 <li>the example Makefile is now fixed</li> 1254 <li>added HTML to the RPM packages</li> 1255 <li>tree copying bugfixes</li> 1256 <li>updates to Windows makefiles</li> 1257 <li>optimization patch from Bjorn Reese</li> 1258</ul> 1259 1260<h3>2.2.11: Jan 4 2001</h3> 1261<ul> 1262 <li>bunch of bug fixes (memory I/O, xpath, ftp/http, ...)</li> 1263 <li>added htmlHandleOmittedElem()</li> 1264 <li>Applied Bjorn Reese's IPV6 first patch</li> 1265 <li>Applied Paul D. Smith patches for validation of XInclude results</li> 1266 <li>added XPointer xmlns() new scheme support</li> 1267</ul> 1268 1269<h3>2.2.10: Nov 25 2000</h3> 1270<ul> 1271 <li>Fix the Windows problems of 2.2.8</li> 1272 <li>integrate OpenVMS patches</li> 1273 <li>better handling of some nasty HTML input</li> 1274 <li>Improved the XPointer implementation</li> 1275 <li>integrate a number of provided patches</li> 1276</ul> 1277 1278<h3>2.2.9: Nov 25 2000</h3> 1279<ul> 1280 <li>erroneous release :-(</li> 1281</ul> 1282 1283<h3>2.2.8: Nov 13 2000</h3> 1284<ul> 1285 <li>First version of <a href="http://www.w3.org/TR/xinclude">XInclude</a> 1286 support</li> 1287 <li>Patch in conditional section handling</li> 1288 <li>updated MS compiler project</li> 1289 <li>fixed some XPath problems</li> 1290 <li>added an URI escaping function</li> 1291 <li>some other bug fixes</li> 1292</ul> 1293 1294<h3>2.2.7: Oct 31 2000</h3> 1295<ul> 1296 <li>added message redirection</li> 1297 <li>XPath improvements (thanks TOM !)</li> 1298 <li>xmlIOParseDTD() added</li> 1299 <li>various small fixes in the HTML, URI, HTTP and XPointer support</li> 1300 <li>some cleanup of the Makefile, autoconf and the distribution content</li> 1301</ul> 1302 1303<h3>2.2.6: Oct 25 2000:</h3> 1304<ul> 1305 <li>Added an hash table module, migrated a number of internal structure to 1306 those</li> 1307 <li>Fixed a posteriori validation problems</li> 1308 <li>HTTP module cleanups</li> 1309 <li>HTML parser improvements (tag errors, script/style handling, attribute 1310 normalization)</li> 1311 <li>coalescing of adjacent text nodes</li> 1312 <li>couple of XPath bug fixes, exported the internal API</li> 1313</ul> 1314 1315<h3>2.2.5: Oct 15 2000:</h3> 1316<ul> 1317 <li>XPointer implementation and testsuite</li> 1318 <li>Lot of XPath fixes, added variable and functions registration, more 1319 tests</li> 1320 <li>Portability fixes, lots of enhancements toward an easy Windows build 1321 and release</li> 1322 <li>Late validation fixes</li> 1323 <li>Integrated a lot of contributed patches</li> 1324 <li>added memory management docs</li> 1325 <li>a performance problem when using large buffer seems fixed</li> 1326</ul> 1327 1328<h3>2.2.4: Oct 1 2000:</h3> 1329<ul> 1330 <li>main XPath problem fixed</li> 1331 <li>Integrated portability patches for Windows</li> 1332 <li>Serious bug fixes on the URI and HTML code</li> 1333</ul> 1334 1335<h3>2.2.3: Sep 17 2000</h3> 1336<ul> 1337 <li>bug fixes</li> 1338 <li>cleanup of entity handling code</li> 1339 <li>overall review of all loops in the parsers, all sprintf usage has been 1340 checked too</li> 1341 <li>Far better handling of larges Dtd. Validating against DocBook XML Dtd 1342 works smoothly now.</li> 1343</ul> 1344 1345<h3>1.8.10: Sep 6 2000</h3> 1346<ul> 1347 <li>bug fix release for some Gnome projects</li> 1348</ul> 1349 1350<h3>2.2.2: August 12 2000</h3> 1351<ul> 1352 <li>mostly bug fixes</li> 1353 <li>started adding routines to access xml parser context options</li> 1354</ul> 1355 1356<h3>2.2.1: July 21 2000</h3> 1357<ul> 1358 <li>a purely bug fixes release</li> 1359 <li>fixed an encoding support problem when parsing from a memory block</li> 1360 <li>fixed a DOCTYPE parsing problem</li> 1361 <li>removed a bug in the function allowing to override the memory 1362 allocation routines</li> 1363</ul> 1364 1365<h3>2.2.0: July 14 2000</h3> 1366<ul> 1367 <li>applied a lot of portability fixes</li> 1368 <li>better encoding support/cleanup and saving (content is now always 1369 encoded in UTF-8)</li> 1370 <li>the HTML parser now correctly handles encodings</li> 1371 <li>added xmlHasProp()</li> 1372 <li>fixed a serious problem with &#38;</li> 1373 <li>propagated the fix to FTP client</li> 1374 <li>cleanup, bugfixes, etc ...</li> 1375 <li>Added a page about <a href="encoding.html">libxml Internationalization 1376 support</a></li> 1377</ul> 1378 1379<h3>1.8.9: July 9 2000</h3> 1380<ul> 1381 <li>fixed the spec the RPMs should be better</li> 1382 <li>fixed a serious bug in the FTP implementation, released 1.8.9 to solve 1383 rpmfind users problem</li> 1384</ul> 1385 1386<h3>2.1.1: July 1 2000</h3> 1387<ul> 1388 <li>fixes a couple of bugs in the 2.1.0 packaging</li> 1389 <li>improvements on the HTML parser</li> 1390</ul> 1391 1392<h3>2.1.0 and 1.8.8: June 29 2000</h3> 1393<ul> 1394 <li>1.8.8 is mostly a commodity package for upgrading to libxml2 according 1395 to <a href="upgrade.html">new instructions</a>. It fixes a nasty problem 1396 about &#38; charref parsing</li> 1397 <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it 1398 also contains numerous fixes and enhancements: 1399 <ul> 1400 <li>added xmlStopParser() to stop parsing</li> 1401 <li>improved a lot parsing speed when there is large CDATA blocs</li> 1402 <li>includes XPath patches provided by Picdar Technology</li> 1403 <li>tried to fix as much as possible DTD validation and namespace 1404 related problems</li> 1405 <li>output to a given encoding has been added/tested</li> 1406 <li>lot of various fixes</li> 1407 </ul> 1408 </li> 1409</ul> 1410 1411<h3>2.0.0: Apr 12 2000</h3> 1412<ul> 1413 <li>First public release of libxml2. If you are using libxml, it's a good 1414 idea to check the 1.x to 2.x upgrade instructions. NOTE: while initially 1415 scheduled for Apr 3 the release occurred only on Apr 12 due to massive 1416 workload.</li> 1417 <li>The include are now located under $prefix/include/libxml (instead of 1418 $prefix/include/gnome-xml), they also are referenced by 1419 <pre>#include <libxml/xxx.h></pre> 1420 <p>instead of</p> 1421 <pre>#include "xxx.h"</pre> 1422 </li> 1423 <li>a new URI module for parsing URIs and following strictly RFC 2396</li> 1424 <li>the memory allocation routines used by libxml can now be overloaded 1425 dynamically by using xmlMemSetup()</li> 1426 <li>The previously CVS only tool tester has been renamed 1427 <strong>xmllint</strong> and is now installed as part of the libxml2 1428 package</li> 1429 <li>The I/O interface has been revamped. There is now ways to plug in 1430 specific I/O modules, either at the URI scheme detection level using 1431 xmlRegisterInputCallbacks() or by passing I/O functions when creating a 1432 parser context using xmlCreateIOParserCtxt()</li> 1433 <li>there is a C preprocessor macro LIBXML_VERSION providing the version 1434 number of the libxml module in use</li> 1435 <li>a number of optional features of libxml can now be excluded at 1436 configure time (FTP/HTTP/HTML/XPath/Debug)</li> 1437</ul> 1438 1439<h3>2.0.0beta: Mar 14 2000</h3> 1440<ul> 1441 <li>This is a first Beta release of libxml version 2</li> 1442 <li>It's available only from<a href="ftp://xmlsoft.org/">xmlsoft.org 1443 FTP</a>, it's packaged as libxml2-2.0.0beta and available as tar and 1444 RPMs</li> 1445 <li>This version is now the head in the Gnome CVS base, the old one is 1446 available under the tag LIB_XML_1_X</li> 1447 <li>This includes a very large set of changes. From a programmatic point 1448 of view applications should not have to be modified too much, check the 1449 <a href="upgrade.html">upgrade page</a></li> 1450 <li>Some interfaces may changes (especially a bit about encoding).</li> 1451 <li>the updates includes: 1452 <ul> 1453 <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly 1454 handled now</li> 1455 <li>Better handling of entities, especially well-formedness checking 1456 and proper PEref extensions in external subsets</li> 1457 <li>DTD conditional sections</li> 1458 <li>Validation now correctly handle entities content</li> 1459 <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change 1460 structures to accommodate DOM</a></li> 1461 </ul> 1462 </li> 1463 <li>Serious progress were made toward compliance, <a 1464 href="conf/result.html">here are the result of the test</a> against the 1465 OASIS testsuite (except the Japanese tests since I don't support that 1466 encoding yet). This URL is rebuilt every couple of hours using the CVS 1467 head version.</li> 1468</ul> 1469 1470<h3>1.8.7: Mar 6 2000</h3> 1471<ul> 1472 <li>This is a bug fix release:</li> 1473 <li>It is possible to disable the ignorable blanks heuristic used by 1474 libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note 1475 that for adherence to XML spec, this behaviour will be disabled by 1476 default in 2.x . The same function will allow to keep compatibility for 1477 old code.</li> 1478 <li>Blanks in <a> </a> constructs are not ignored anymore, 1479 avoiding heuristic is really the Right Way :-\</li> 1480 <li>The unchecked use of snprintf which was breaking libxml-1.8.6 1481 compilation on some platforms has been fixed</li> 1482 <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing 1483 URIs</li> 1484</ul> 1485 1486<h3>1.8.6: Jan 31 2000</h3> 1487<ul> 1488 <li>added a nanoFTP transport module, debugged until the new version of <a 1489 href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use 1490 it without troubles</li> 1491</ul> 1492 1493<h3>1.8.5: Jan 21 2000</h3> 1494<ul> 1495 <li>adding APIs to parse a well balanced chunk of XML (production <a 1496 href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the 1497 XML spec)</li> 1498 <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li> 1499 <li>Jody Goldberg <jgoldberg@home.com> provided another patch trying 1500 to solve the zlib checks problems</li> 1501 <li>The current state in gnome CVS base is expected to ship as 1.8.5 with 1502 gnumeric soon</li> 1503</ul> 1504 1505<h3>1.8.4: Jan 13 2000</h3> 1506<ul> 1507 <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li> 1508 <li>all exit() call should have been removed from libxml</li> 1509 <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li> 1510 <li>added newDocFragment()</li> 1511</ul> 1512 1513<h3>1.8.3: Jan 5 2000</h3> 1514<ul> 1515 <li>a Push interface for the XML and HTML parsers</li> 1516 <li>a shell-like interface to the document tree (try tester --shell :-)</li> 1517 <li>lots of bug fixes and improvement added over XMas holidays</li> 1518 <li>fixed the DTD parsing code to work with the xhtml DTD</li> 1519 <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li> 1520 <li>Fixed bugs in xmlNewNs()</li> 1521 <li>External entity loading code has been revamped, now it uses 1522 xmlLoadExternalEntity(), some fix on entities processing were added</li> 1523 <li>cleaned up WIN32 includes of socket stuff</li> 1524</ul> 1525 1526<h3>1.8.2: Dec 21 1999</h3> 1527<ul> 1528 <li>I got another problem with includes and C++, I hope this issue is fixed 1529 for good this time</li> 1530 <li>Added a few tree modification functions: xmlReplaceNode, 1531 xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and 1532 xmlDocSetRootElement</li> 1533 <li>Tried to improve the HTML output with help from <a 1534 href="mailto:clahey@umich.edu">Chris Lahey</a></li> 1535</ul> 1536 1537<h3>1.8.1: Dec 18 1999</h3> 1538<ul> 1539 <li>various patches to avoid troubles when using libxml with C++ compilers 1540 the "namespace" keyword and C escaping in include files</li> 1541 <li>a problem in one of the core macros IS_CHAR was corrected</li> 1542 <li>fixed a bug introduced in 1.8.0 breaking default namespace processing, 1543 and more specifically the Dia application</li> 1544 <li>fixed a posteriori validation (validation after parsing, or by using a 1545 Dtd not specified in the original document)</li> 1546 <li>fixed a bug in</li> 1547</ul> 1548 1549<h3>1.8.0: Dec 12 1999</h3> 1550<ul> 1551 <li>cleanup, especially memory wise</li> 1552 <li>the parser should be more reliable, especially the HTML one, it should 1553 not crash, whatever the input !</li> 1554 <li>Integrated various patches, especially a speedup improvement for large 1555 dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>, 1556 configure with --with-buffers to enable them.</li> 1557 <li>attribute normalization, oops should have been added long ago !</li> 1558 <li>attributes defaulted from DTDs should be available, xmlSetProp() now 1559 does entities escaping by default.</li> 1560</ul> 1561 1562<h3>1.7.4: Oct 25 1999</h3> 1563<ul> 1564 <li>Lots of HTML improvement</li> 1565 <li>Fixed some errors when saving both XML and HTML</li> 1566 <li>More examples, the regression tests should now look clean</li> 1567 <li>Fixed a bug with contiguous charref</li> 1568</ul> 1569 1570<h3>1.7.3: Sep 29 1999</h3> 1571<ul> 1572 <li>portability problems fixed</li> 1573 <li>snprintf was used unconditionally, leading to link problems on system 1574 were it's not available, fixed</li> 1575</ul> 1576 1577<h3>1.7.1: Sep 24 1999</h3> 1578<ul> 1579 <li>The basic type for strings manipulated by libxml has been renamed in 1580 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason 1581 is that CHAR was conflicting with a predefined type on Windows. However 1582 on non WIN32 environment, compatibility is provided by the way of a 1583 <strong>#define </strong>.</li> 1584 <li>Changed another error : the use of a structure field called errno, and 1585 leading to troubles on platforms where it's a macro</li> 1586</ul> 1587 1588<h3>1.7.0: Sep 23 1999</h3> 1589<ul> 1590 <li>Added the ability to fetch remote DTD or parsed entities, see the <a 1591 href="html/libxml-nanohttp.html">nanohttp</a> module.</li> 1592 <li>Added an errno to report errors by another mean than a simple printf 1593 like callback</li> 1594 <li>Finished ID/IDREF support and checking when validation</li> 1595 <li>Serious memory leaks fixed (there is now a <a 1596 href="html/libxml-xmlmemory.html">memory wrapper</a> module)</li> 1597 <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a> 1598 implementation</li> 1599 <li>Added an HTML parser front-end</li> 1600</ul> 1601 1602<h2><a name="XML">XML</a></h2> 1603 1604<p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for 1605markup-based structured documents. Here is <a name="example">an example XML 1606document</a>:</p> 1607<pre><?xml version="1.0"?> 1608<EXAMPLE prop1="gnome is great" prop2="&amp; linux too"> 1609 <head> 1610 <title>Welcome to Gnome</title> 1611 </head> 1612 <chapter> 1613 <title>The Linux adventure</title> 1614 <p>bla bla bla ...</p> 1615 <image href="linus.gif"/> 1616 <p>...</p> 1617 </chapter> 1618</EXAMPLE></pre> 1619 1620<p>The first line specifies that it is an XML document and gives useful 1621information about its encoding. Then the rest of the document is a text 1622format whose structure is specified by tags between brackets. <strong>Each 1623tag opened has to be closed</strong>. XML is pedantic about this. However, if 1624a tag is empty (no content), a single tag can serve as both the opening and 1625closing tag if it ends with <code>/></code> rather than with 1626<code>></code>. Note that, for example, the image tag has no content (just 1627an attribute) and is closed by ending the tag with <code>/></code>.</p> 1628 1629<p>XML can be applied successfully to a wide range of tasks, ranging from 1630long term structured document maintenance (where it follows the steps of 1631SGML) to simple data encoding mechanisms like configuration file formatting 1632(glade), spreadsheets (gnumeric), or even shorter lived documents such as 1633WebDAV where it is used to encode remote calls between a client and a 1634server.</p> 1635 1636<h2><a name="XSLT">XSLT</a></h2> 1637 1638<p>Check <a href="http://xmlsoft.org/XSLT">the separate libxslt page</a></p> 1639 1640<p><a href="http://www.w3.org/TR/xslt">XSL Transformations</a>, is a 1641language for transforming XML documents into other XML documents (or 1642HTML/textual output).</p> 1643 1644<p>A separate library called libxslt is being developed on top of libxml2. 1645This module "libxslt" too can be found in the Gnome CVS base.</p> 1646 1647<p>You can check the <a 1648href="http://cvs.gnome.org/lxr/source/libxslt/FEATURES">features</a> 1649supported and the progresses on the <a 1650href="http://cvs.gnome.org/lxr/source/libxslt/ChangeLog" 1651name="Changelog">Changelog</a>.</p> 1652 1653<h2><a name="Python">Python and bindings</a></h2> 1654 1655<p>There are a number of language bindings and wrappers available for 1656libxml2, the list below is not exhaustive. Please contact the <a 1657href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a> 1658(<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in 1659order to get updates to this list or to discuss the specific topic of libxml2 1660or libxslt wrappers or bindings:</p> 1661<ul> 1662 <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the 1663 most up-to-date C++ bindings for libxml2, check the <a 1664 href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> 1665 and the <a 1666 href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> 1667 <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper 1668 based on the gdome2 bindings</a> maintained by Tobias Peters.</li> 1669 <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> 1670 <p>Website: <a 1671 href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 1672 </li> 1673 <li><a 1674 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 1675 Sergeant</a> developed <a 1676 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 1677 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 1678 application server</a>.</li> 1679 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an 1680 earlier version of the libxml/libxslt <a 1681 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> 1682 <li>Gopal.V and Peter Minten develop <a 1683 href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of 1684 C# libxml2 bindings.</li> 1685 <li>Petr Kozelka provides <a 1686 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 1687 libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> 1688 <li>Uwe Fechner also provides <a 1689 href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 1690 implementation for Kylix2/D5/D6 from Borland.</li> 1691 <li>Wai-Sun "Squidster" Chia provides <a 1692 href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and 1693 libxml2 bindings are also available in Ruby through the <a 1694 href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module 1695 maintained by Tobias Peters.</li> 1696 <li>Steve Ball and contributors maintains <a 1697 href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for 1698 Tcl</a>.</li> 1699 <li>There is support for libxml2 in the DOM module of PHP.</li> 1700 <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is 1701 an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and 1702 libxslt as part of GNU ClasspathX project.</li> 1703</ul> 1704 1705<p>The distribution includes a set of Python bindings, which are guaranteed 1706to be maintained as part of the library in the future, though the Python 1707interface have not yet reached the completeness of the C API.</p> 1708 1709<p><a href="mailto:stephane.bidoul@softwareag.com">St�phane Bidoul</a> 1710maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port 1711of the Python bindings</a>.</p> 1712 1713<p>Note to people interested in building bindings, the API is formalized as 1714<a href="libxml2-api.xml">an XML API description file</a> which allows to 1715automate a large part of the Python bindings, this includes function 1716descriptions, enums, structures, typedefs, etc... The Python script used to 1717build the bindings is python/generator.py in the source distribution.</p> 1718 1719<p>To install the Python bindings there are 2 options:</p> 1720<ul> 1721 <li>If you use an RPM based distribution, simply install the <a 1722 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python 1723 RPM</a> (and if needed the <a 1724 href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python 1725 RPM</a>).</li> 1726 <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python 1727 module distribution</a> corresponding to your installed version of 1728 libxml2 and libxslt. Note that to install it you will need both libxml2 1729 and libxslt installed and run "python setup.py build install" in the 1730 module tree.</li> 1731</ul> 1732 1733<p>The distribution includes a set of examples and regression tests for the 1734python bindings in the <code>python/tests</code> directory. Here are some 1735excerpts from those tests:</p> 1736 1737<h3>tst.py:</h3> 1738 1739<p>This is a basic test of the file interface and DOM navigation:</p> 1740<pre>import libxml2 1741 1742doc = libxml2.parseFile("tst.xml") 1743if doc.name != "tst.xml": 1744 print "doc.name failed" 1745 sys.exit(1) 1746root = doc.children 1747if root.name != "doc": 1748 print "root.name failed" 1749 sys.exit(1) 1750child = root.children 1751if child.name != "foo": 1752 print "child.name failed" 1753 sys.exit(1) 1754doc.freeDoc()</pre> 1755 1756<p>The Python module is called libxml2; parseFile is the equivalent of 1757xmlParseFile (most of the bindings are automatically generated, and the xml 1758prefix is removed and the casing convention are kept). All node seen at the 1759binding level share the same subset of accessors:</p> 1760<ul> 1761 <li><code>name</code> : returns the node name</li> 1762 <li><code>type</code> : returns a string indicating the node type</li> 1763 <li><code>content</code> : returns the content of the node, it is based on 1764 xmlNodeGetContent() and hence is recursive.</li> 1765 <li><code>parent</code> , <code>children</code>, <code>last</code>, 1766 <code>next</code>, <code>prev</code>, <code>doc</code>, 1767 <code>properties</code>: pointing to the associated element in the tree, 1768 those may return None in case no such link exists.</li> 1769</ul> 1770 1771<p>Also note the need to explicitly deallocate documents with freeDoc() . 1772Reference counting for libxml2 trees would need quite a lot of work to 1773function properly, and rather than risk memory leaks if not implemented 1774correctly it sounds safer to have an explicit function to free a tree. The 1775wrapper python objects like doc, root or child are them automatically garbage 1776collected.</p> 1777 1778<h3>validate.py:</h3> 1779 1780<p>This test check the validation interfaces and redirection of error 1781messages:</p> 1782<pre>import libxml2 1783 1784#deactivate error messages from the validation 1785def noerr(ctx, str): 1786 pass 1787 1788libxml2.registerErrorHandler(noerr, None) 1789 1790ctxt = libxml2.createFileParserCtxt("invalid.xml") 1791ctxt.validate(1) 1792ctxt.parseDocument() 1793doc = ctxt.doc() 1794valid = ctxt.isValid() 1795doc.freeDoc() 1796if valid != 0: 1797 print "validity check failed"</pre> 1798 1799<p>The first thing to notice is the call to registerErrorHandler(), it 1800defines a new error handler global to the library. It is used to avoid seeing 1801the error messages when trying to validate the invalid document.</p> 1802 1803<p>The main interest of that test is the creation of a parser context with 1804createFileParserCtxt() and how the behaviour can be changed before calling 1805parseDocument() . Similarly the informations resulting from the parsing phase 1806are also available using context methods.</p> 1807 1808<p>Contexts like nodes are defined as class and the libxml2 wrappers maps the 1809C function interfaces in terms of objects method as much as possible. The 1810best to get a complete view of what methods are supported is to look at the 1811libxml2.py module containing all the wrappers.</p> 1812 1813<h3>push.py:</h3> 1814 1815<p>This test show how to activate the push parser interface:</p> 1816<pre>import libxml2 1817 1818ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") 1819ctxt.parseChunk("/>", 2, 1) 1820doc = ctxt.doc() 1821 1822doc.freeDoc()</pre> 1823 1824<p>The context is created with a special call based on the 1825xmlCreatePushParser() from the C library. The first argument is an optional 1826SAX callback object, then the initial set of data, the length and the name of 1827the resource in case URI-References need to be computed by the parser.</p> 1828 1829<p>Then the data are pushed using the parseChunk() method, the last call 1830setting the third argument terminate to 1.</p> 1831 1832<h3>pushSAX.py:</h3> 1833 1834<p>this test show the use of the event based parsing interfaces. In this case 1835the parser does not build a document, but provides callback information as 1836the parser makes progresses analyzing the data being provided:</p> 1837<pre>import libxml2 1838log = "" 1839 1840class callback: 1841 def startDocument(self): 1842 global log 1843 log = log + "startDocument:" 1844 1845 def endDocument(self): 1846 global log 1847 log = log + "endDocument:" 1848 1849 def startElement(self, tag, attrs): 1850 global log 1851 log = log + "startElement %s %s:" % (tag, attrs) 1852 1853 def endElement(self, tag): 1854 global log 1855 log = log + "endElement %s:" % (tag) 1856 1857 def characters(self, data): 1858 global log 1859 log = log + "characters: %s:" % (data) 1860 1861 def warning(self, msg): 1862 global log 1863 log = log + "warning: %s:" % (msg) 1864 1865 def error(self, msg): 1866 global log 1867 log = log + "error: %s:" % (msg) 1868 1869 def fatalError(self, msg): 1870 global log 1871 log = log + "fatalError: %s:" % (msg) 1872 1873handler = callback() 1874 1875ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") 1876chunk = " url='tst'>b" 1877ctxt.parseChunk(chunk, len(chunk), 0) 1878chunk = "ar</foo>" 1879ctxt.parseChunk(chunk, len(chunk), 1) 1880 1881reference = "startDocument:startElement foo {'url': 'tst'}:" + \ 1882 "characters: bar:endElement foo:endDocument:" 1883if log != reference: 1884 print "Error got: %s" % log 1885 print "Expected: %s" % reference</pre> 1886 1887<p>The key object in that test is the handler, it provides a number of entry 1888points which can be called by the parser as it makes progresses to indicate 1889the information set obtained. The full set of callback is larger than what 1890the callback class in that specific example implements (see the SAX 1891definition for a complete list). The wrapper will only call those supplied by 1892the object when activated. The startElement receives the names of the element 1893and a dictionary containing the attributes carried by this element.</p> 1894 1895<p>Also note that the reference string generated from the callback shows a 1896single character call even though the string "bar" is passed to the parser 1897from 2 different call to parseChunk()</p> 1898 1899<h3>xpath.py:</h3> 1900 1901<p>This is a basic test of XPath wrappers support</p> 1902<pre>import libxml2 1903 1904doc = libxml2.parseFile("tst.xml") 1905ctxt = doc.xpathNewContext() 1906res = ctxt.xpathEval("//*") 1907if len(res) != 2: 1908 print "xpath query: wrong node set size" 1909 sys.exit(1) 1910if res[0].name != "doc" or res[1].name != "foo": 1911 print "xpath query: wrong node set value" 1912 sys.exit(1) 1913doc.freeDoc() 1914ctxt.xpathFreeContext()</pre> 1915 1916<p>This test parses a file, then create an XPath context to evaluate XPath 1917expression on it. The xpathEval() method execute an XPath query and returns 1918the result mapped in a Python way. String and numbers are natively converted, 1919and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like 1920the document, the XPath context need to be freed explicitly, also not that 1921the result of the XPath query may point back to the document tree and hence 1922the document must be freed after the result of the query is used.</p> 1923 1924<h3>xpathext.py:</h3> 1925 1926<p>This test shows how to extend the XPath engine with functions written in 1927python:</p> 1928<pre>import libxml2 1929 1930def foo(ctx, x): 1931 return x + 1 1932 1933doc = libxml2.parseFile("tst.xml") 1934ctxt = doc.xpathNewContext() 1935libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) 1936res = ctxt.xpathEval("foo(1)") 1937if res != 2: 1938 print "xpath extension failure" 1939doc.freeDoc() 1940ctxt.xpathFreeContext()</pre> 1941 1942<p>Note how the extension function is registered with the context (but that 1943part is not yet finalized, this may change slightly in the future).</p> 1944 1945<h3>tstxpath.py:</h3> 1946 1947<p>This test is similar to the previous one but shows how the extension 1948function can access the XPath evaluation context:</p> 1949<pre>def foo(ctx, x): 1950 global called 1951 1952 # 1953 # test that access to the XPath evaluation contexts 1954 # 1955 pctxt = libxml2.xpathParserContext(_obj=ctx) 1956 ctxt = pctxt.context() 1957 called = ctxt.function() 1958 return x + 1</pre> 1959 1960<p>All the interfaces around the XPath parser(or rather evaluation) context 1961are not finalized, but it should be sufficient to do contextual work at the 1962evaluation point.</p> 1963 1964<h3>Memory debugging:</h3> 1965 1966<p>last but not least, all tests starts with the following prologue:</p> 1967<pre>#memory debug specific 1968libxml2.debugMemory(1)</pre> 1969 1970<p>and ends with the following epilogue:</p> 1971<pre>#memory debug specific 1972libxml2.cleanupParser() 1973if libxml2.debugMemory(1) == 0: 1974 print "OK" 1975else: 1976 print "Memory leak %d bytes" % (libxml2.debugMemory(1)) 1977 libxml2.dumpMemory()</pre> 1978 1979<p>Those activate the memory debugging interface of libxml2 where all 1980allocated block in the library are tracked. The prologue then cleans up the 1981library state and checks that all allocated memory has been freed. If not it 1982calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p> 1983 1984<h2><a name="architecture">libxml architecture</a></h2> 1985 1986<p>Libxml is made of multiple components; some of them are optional, and most 1987of the block interfaces are public. The main components are:</p> 1988<ul> 1989 <li>an Input/Output layer</li> 1990 <li>FTP and HTTP client layers (optional)</li> 1991 <li>an Internationalization layer managing the encodings support</li> 1992 <li>a URI module</li> 1993 <li>the XML parser and its basic SAX interface</li> 1994 <li>an HTML parser using the same SAX interface (optional)</li> 1995 <li>a SAX tree module to build an in-memory DOM representation</li> 1996 <li>a tree module to manipulate the DOM representation</li> 1997 <li>a validation module using the DOM representation (optional)</li> 1998 <li>an XPath module for global lookup in a DOM representation 1999 (optional)</li> 2000 <li>a debug module (optional)</li> 2001</ul> 2002 2003<p>Graphically this gives the following:</p> 2004 2005<p><img src="libxml.gif" alt="a graphical view of the various"></p> 2006 2007<p></p> 2008 2009<h2><a name="tree">The tree output</a></h2> 2010 2011<p>The parser returns a tree built during the document analysis. The value 2012returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an 2013<strong>xmlDoc</strong> structure). This structure contains information such 2014as the file name, the document type, and a <strong>children</strong> pointer 2015which is the root of the document (or more exactly the first child under the 2016root which is the document). The tree is made of <strong>xmlNode</strong>s, 2017chained in double-linked lists of siblings and with a children<->parent 2018relationship. An xmlNode can also carry properties (a chain of xmlAttr 2019structures). An attribute may have a value which is a list of TEXT or 2020ENTITY_REF nodes.</p> 2021 2022<p>Here is an example (erroneous with respect to the XML spec since there 2023should be only one ELEMENT under the root):</p> 2024 2025<p><img src="structure.gif" alt=" structure.gif "></p> 2026 2027<p>In the source package there is a small program (not installed by default) 2028called <strong>xmllint</strong> which parses XML files given as argument and 2029prints them back as parsed. This is useful for detecting errors both in XML 2030code and in the XML parser itself. It has an option <strong>--debug</strong> 2031which prints the actual in-memory structure of the document; here is the 2032result with the <a href="#example">example</a> given before:</p> 2033<pre>DOCUMENT 2034version=1.0 2035standalone=true 2036 ELEMENT EXAMPLE 2037 ATTRIBUTE prop1 2038 TEXT 2039 content=gnome is great 2040 ATTRIBUTE prop2 2041 ENTITY_REF 2042 TEXT 2043 content= linux too 2044 ELEMENT head 2045 ELEMENT title 2046 TEXT 2047 content=Welcome to Gnome 2048 ELEMENT chapter 2049 ELEMENT title 2050 TEXT 2051 content=The Linux adventure 2052 ELEMENT p 2053 TEXT 2054 content=bla bla bla ... 2055 ELEMENT image 2056 ATTRIBUTE href 2057 TEXT 2058 content=linus.gif 2059 ELEMENT p 2060 TEXT 2061 content=...</pre> 2062 2063<p>This should be useful for learning the internal representation model.</p> 2064 2065<h2><a name="interface">The SAX interface</a></h2> 2066 2067<p>Sometimes the DOM tree output is just too large to fit reasonably into 2068memory. In that case (and if you don't expect to save back the XML document 2069loaded using libxml), it's better to use the SAX interface of libxml. SAX is 2070a <strong>callback-based interface</strong> to the parser. Before parsing, 2071the application layer registers a customized set of callbacks which are 2072called by the library as it progresses through the XML input.</p> 2073 2074<p>To get more detailed step-by-step guidance on using the SAX interface of 2075libxml, see the <a 2076href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice 2077documentation</a>.written by <a href="mailto:james@daa.com.au">James 2078Henstridge</a>.</p> 2079 2080<p>You can debug the SAX behaviour by using the <strong>testSAX</strong> 2081program located in the gnome-xml module (it's usually not shipped in the 2082binary packages of libxml, but you can find it in the tar source 2083distribution). Here is the sequence of callbacks that would be reported by 2084testSAX when parsing the example XML document shown earlier:</p> 2085<pre>SAX.setDocumentLocator() 2086SAX.startDocument() 2087SAX.getEntity(amp) 2088SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too') 2089SAX.characters( , 3) 2090SAX.startElement(head) 2091SAX.characters( , 4) 2092SAX.startElement(title) 2093SAX.characters(Welcome to Gnome, 16) 2094SAX.endElement(title) 2095SAX.characters( , 3) 2096SAX.endElement(head) 2097SAX.characters( , 3) 2098SAX.startElement(chapter) 2099SAX.characters( , 4) 2100SAX.startElement(title) 2101SAX.characters(The Linux adventure, 19) 2102SAX.endElement(title) 2103SAX.characters( , 4) 2104SAX.startElement(p) 2105SAX.characters(bla bla bla ..., 15) 2106SAX.endElement(p) 2107SAX.characters( , 4) 2108SAX.startElement(image, href='linus.gif') 2109SAX.endElement(image) 2110SAX.characters( , 4) 2111SAX.startElement(p) 2112SAX.characters(..., 3) 2113SAX.endElement(p) 2114SAX.characters( , 3) 2115SAX.endElement(chapter) 2116SAX.characters( , 1) 2117SAX.endElement(EXAMPLE) 2118SAX.endDocument()</pre> 2119 2120<p>Most of the other interfaces of libxml are based on the DOM tree-building 2121facility, so nearly everything up to the end of this document presupposes the 2122use of the standard DOM tree build. Note that the DOM tree itself is built by 2123a set of registered default callbacks, without internal specific 2124interface.</p> 2125 2126<h2><a name="Validation">Validation & DTDs</a></h2> 2127 2128<p>Table of Content:</p> 2129<ol> 2130 <li><a href="#General5">General overview</a></li> 2131 <li><a href="#definition">The definition</a></li> 2132 <li><a href="#Simple">Simple rules</a> 2133 <ol> 2134 <li><a href="#reference">How to reference a DTD from a document</a></li> 2135 <li><a href="#Declaring">Declaring elements</a></li> 2136 <li><a href="#Declaring1">Declaring attributes</a></li> 2137 </ol> 2138 </li> 2139 <li><a href="#Some">Some examples</a></li> 2140 <li><a href="#validate">How to validate</a></li> 2141 <li><a href="#Other">Other resources</a></li> 2142</ol> 2143 2144<h3><a name="General5">General overview</a></h3> 2145 2146<p>Well what is validation and what is a DTD ?</p> 2147 2148<p>DTD is the acronym for Document Type Definition. This is a description of 2149the content for a family of XML files. This is part of the XML 1.0 2150specification, and allows one to describe and verify that a given document 2151instance conforms to the set of rules detailing its structure and content.</p> 2152 2153<p>Validation is the process of checking a document against a DTD (more 2154generally against a set of construction rules).</p> 2155 2156<p>The validation process and building DTDs are the two most difficult parts 2157of the XML life cycle. Briefly a DTD defines all the possible elements to be 2158found within your document, what is the formal shape of your document tree 2159(by defining the allowed content of an element; either text, a regular 2160expression for the allowed list of children, or mixed content i.e. both text 2161and children). The DTD also defines the valid attributes for all elements and 2162the types of those attributes.</p> 2163 2164<h3><a name="definition1">The definition</a></h3> 2165 2166<p>The <a href="http://www.w3.org/TR/REC-xml">W3C XML Recommendation</a> (<a 2167href="http://www.xml.com/axml/axml.html">Tim Bray's annotated version of 2168Rev1</a>):</p> 2169<ul> 2170 <li><a href="http://www.w3.org/TR/REC-xml#elemdecls">Declaring 2171 elements</a></li> 2172 <li><a href="http://www.w3.org/TR/REC-xml#attdecls">Declaring 2173 attributes</a></li> 2174</ul> 2175 2176<p>(unfortunately) all this is inherited from the SGML world, the syntax is 2177ancient...</p> 2178 2179<h3><a name="Simple1">Simple rules</a></h3> 2180 2181<p>Writing DTDs can be done in many ways. The rules to build them if you need 2182something permanent or something which can evolve over time can be radically 2183different. Really complex DTDs like DocBook ones are flexible but quite 2184harder to design. I will just focus on DTDs for a formats with a fixed simple 2185structure. It is just a set of basic rules, and definitely not exhaustive nor 2186usable for complex DTD design.</p> 2187 2188<h4><a name="reference1">How to reference a DTD from a document</a>:</h4> 2189 2190<p>Assuming the top element of the document is <code>spec</code> and the dtd 2191is placed in the file <code>mydtd</code> in the subdirectory 2192<code>dtds</code> of the directory from where the document were loaded:</p> 2193 2194<p><code><!DOCTYPE spec SYSTEM "dtds/mydtd"></code></p> 2195 2196<p>Notes:</p> 2197<ul> 2198 <li>The system string is actually an URI-Reference (as defined in <a 2199 href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>) so you can use a 2200 full URL string indicating the location of your DTD on the Web. This is a 2201 really good thing to do if you want others to validate your document.</li> 2202 <li>It is also possible to associate a <code>PUBLIC</code> identifier (a 2203 magic string) so that the DTD is looked up in catalogs on the client side 2204 without having to locate it on the web.</li> 2205 <li>A DTD contains a set of element and attribute declarations, but they 2206 don't define what the root of the document should be. This is explicitly 2207 told to the parser/validator as the first element of the 2208 <code>DOCTYPE</code> declaration.</li> 2209</ul> 2210 2211<h4><a name="Declaring2">Declaring elements</a>:</h4> 2212 2213<p>The following declares an element <code>spec</code>:</p> 2214 2215<p><code><!ELEMENT spec (front, body, back?)></code></p> 2216 2217<p>It also expresses that the spec element contains one <code>front</code>, 2218one <code>body</code> and one optional <code>back</code> children elements in 2219this order. The declaration of one element of the structure and its content 2220are done in a single declaration. Similarly the following declares 2221<code>div1</code> elements:</p> 2222 2223<p><code><!ELEMENT div1 (head, (p | list | note)*, div2?)></code></p> 2224 2225<p>which means div1 contains one <code>head</code> then a series of optional 2226<code>p</code>, <code>list</code>s and <code>note</code>s and then an 2227optional <code>div2</code>. And last but not least an element can contain 2228text:</p> 2229 2230<p><code><!ELEMENT b (#PCDATA)></code></p> 2231 2232<p><code>b</code> contains text or being of mixed content (text and elements 2233in no particular order):</p> 2234 2235<p><code><!ELEMENT p (#PCDATA|a|ul|b|i|em)*></code></p> 2236 2237<p><code>p </code>can contain text or <code>a</code>, <code>ul</code>, 2238<code>b</code>, <code>i </code>or <code>em</code> elements in no particular 2239order.</p> 2240 2241<h4><a name="Declaring1">Declaring attributes</a>:</h4> 2242 2243<p>Again the attributes declaration includes their content definition:</p> 2244 2245<p><code><!ATTLIST termdef name CDATA #IMPLIED></code></p> 2246 2247<p>means that the element <code>termdef</code> can have a <code>name</code> 2248attribute containing text (<code>CDATA</code>) and which is optional 2249(<code>#IMPLIED</code>). The attribute value can also be defined within a 2250set:</p> 2251 2252<p><code><!ATTLIST list type (bullets|ordered|glossary) 2253"ordered"></code></p> 2254 2255<p>means <code>list</code> element have a <code>type</code> attribute with 3 2256allowed values "bullets", "ordered" or "glossary" and which default to 2257"ordered" if the attribute is not explicitly specified.</p> 2258 2259<p>The content type of an attribute can be text (<code>CDATA</code>), 2260anchor/reference/references 2261(<code>ID</code>/<code>IDREF</code>/<code>IDREFS</code>), entity(ies) 2262(<code>ENTITY</code>/<code>ENTITIES</code>) or name(s) 2263(<code>NMTOKEN</code>/<code>NMTOKENS</code>). The following defines that a 2264<code>chapter</code> element can have an optional <code>id</code> attribute 2265of type <code>ID</code>, usable for reference from attribute of type 2266IDREF:</p> 2267 2268<p><code><!ATTLIST chapter id ID #IMPLIED></code></p> 2269 2270<p>The last value of an attribute definition can be <code>#REQUIRED 2271</code>meaning that the attribute has to be given, <code>#IMPLIED</code> 2272meaning that it is optional, or the default value (possibly prefixed by 2273<code>#FIXED</code> if it is the only allowed).</p> 2274 2275<p>Notes:</p> 2276<ul> 2277 <li>Usually the attributes pertaining to a given element are declared in a 2278 single expression, but it is just a convention adopted by a lot of DTD 2279 writers: 2280 <pre><!ATTLIST termdef 2281 id ID #REQUIRED 2282 name CDATA #IMPLIED></pre> 2283 <p>The previous construct defines both <code>id</code> and 2284 <code>name</code> attributes for the element <code>termdef</code>.</p> 2285 </li> 2286</ul> 2287 2288<h3><a name="Some1">Some examples</a></h3> 2289 2290<p>The directory <code>test/valid/dtds/</code> in the libxml distribution 2291contains some complex DTD examples. The example in the file 2292<code>test/valid/dia.xml</code> shows an XML file where the simple DTD is 2293directly included within the document.</p> 2294 2295<h3><a name="validate1">How to validate</a></h3> 2296 2297<p>The simplest way is to use the xmllint program included with libxml. The 2298<code>--valid</code> option turns-on validation of the files given as input. 2299For example the following validates a copy of the first revision of the XML 23001.0 specification:</p> 2301 2302<p><code>xmllint --valid --noout test/valid/REC-xml-19980210.xml</code></p> 2303 2304<p>the -- noout is used to disable output of the resulting tree.</p> 2305 2306<p>The <code>--dtdvalid dtd</code> allows validation of the document(s) 2307against a given DTD.</p> 2308 2309<p>Libxml exports an API to handle DTDs and validation, check the <a 2310href="http://xmlsoft.org/html/libxml-valid.html">associated 2311description</a>.</p> 2312 2313<h3><a name="Other1">Other resources</a></h3> 2314 2315<p>DTDs are as old as SGML. So there may be a number of examples on-line, I 2316will just list one for now, others pointers welcome:</p> 2317<ul> 2318 <li><a href="http://www.xml101.com:8081/dtd/">XML-101 DTD</a></li> 2319</ul> 2320 2321<p>I suggest looking at the examples found under test/valid/dtd and any of 2322the large number of books available on XML. The dia example in test/valid 2323should be both simple and complete enough to allow you to build your own.</p> 2324 2325<p></p> 2326 2327<h2><a name="Memory">Memory Management</a></h2> 2328 2329<p>Table of Content:</p> 2330<ol> 2331 <li><a href="#General3">General overview</a></li> 2332 <li><a href="#setting">Setting libxml set of memory routines</a></li> 2333 <li><a href="#cleanup">Cleaning up after parsing</a></li> 2334 <li><a href="#Debugging">Debugging routines</a></li> 2335 <li><a href="#General4">General memory requirements</a></li> 2336</ol> 2337 2338<h3><a name="General3">General overview</a></h3> 2339 2340<p>The module <code><a 2341href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlmemory.h</a></code> 2342provides the interfaces to the libxml memory system:</p> 2343<ul> 2344 <li>libxml does not use the libc memory allocator directly but xmlFree(), 2345 xmlMalloc() and xmlRealloc()</li> 2346 <li>those routines can be reallocated to a specific set of routine, by 2347 default the libc ones i.e. free(), malloc() and realloc()</li> 2348 <li>the xmlmemory.c module includes a set of debugging routine</li> 2349</ul> 2350 2351<h3><a name="setting">Setting libxml set of memory routines</a></h3> 2352 2353<p>It is sometimes useful to not use the default memory allocator, either for 2354debugging, analysis or to implement a specific behaviour on memory management 2355(like on embedded systems). Two function calls are available to do so:</p> 2356<ul> 2357 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemGet 2358 ()</a> which return the current set of functions in use by the parser</li> 2359 <li><a 2360 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemSetup()</a> 2361 which allow to set up a new set of memory allocation functions</li> 2362</ul> 2363 2364<p>Of course a call to xmlMemSetup() should probably be done before calling 2365any other libxml routines (unless you are sure your allocations routines are 2366compatibles).</p> 2367 2368<h3><a name="cleanup">Cleaning up after parsing</a></h3> 2369 2370<p>Libxml is not stateless, there is a few set of memory structures needing 2371allocation before the parser is fully functional (some encoding structures 2372for example). This also mean that once parsing is finished there is a tiny 2373amount of memory (a few hundred bytes) which can be recollected if you don't 2374reuse the parser immediately:</p> 2375<ul> 2376 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlCleanupParser 2377 ()</a> is a centralized routine to free the parsing states. Note that it 2378 won't deallocate any produced tree if any (use the xmlFreeDoc() and 2379 related routines for this).</li> 2380 <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlInitParser 2381 ()</a> is the dual routine allowing to preallocate the parsing state 2382 which can be useful for example to avoid initialization reentrancy 2383 problems when using libxml in multithreaded applications</li> 2384</ul> 2385 2386<p>Generally xmlCleanupParser() is safe, if needed the state will be rebuild 2387at the next invocation of parser routines, but be careful of the consequences 2388in multithreaded applications.</p> 2389 2390<h3><a name="Debugging">Debugging routines</a></h3> 2391 2392<p>When configured using --with-mem-debug flag (off by default), libxml uses 2393a set of memory allocation debugging routines keeping track of all allocated 2394blocks and the location in the code where the routine was called. A couple of 2395other debugging routines allow to dump the memory allocated infos to a file 2396or call a specific routine when a given block number is allocated:</p> 2397<ul> 2398 <li><a 2399 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMallocLoc()</a> 2400 <a 2401 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlReallocLoc()</a> 2402 and <a 2403 href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemStrdupLoc()</a> 2404 are the memory debugging replacement allocation routines</li> 2405 <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemoryDump 2406 ()</a> dumps all the informations about the allocated memory block lefts 2407 in the <code>.memdump</code> file</li> 2408</ul> 2409 2410<p>When developing libxml memory debug is enabled, the tests programs call 2411xmlMemoryDump () and the "make test" regression tests will check for any 2412memory leak during the full regression test sequence, this helps a lot 2413ensuring that libxml does not leak memory and bullet proof memory 2414allocations use (some libc implementations are known to be far too permissive 2415resulting in major portability problems!).</p> 2416 2417<p>If the .memdump reports a leak, it displays the allocation function and 2418also tries to give some informations about the content and structure of the 2419allocated blocks left. This is sufficient in most cases to find the culprit, 2420but not always. Assuming the allocation problem is reproducible, it is 2421possible to find more easily:</p> 2422<ol> 2423 <li>write down the block number xxxx not allocated</li> 2424 <li>export the environment variable XML_MEM_BREAKPOINT=xxxx , the easiest 2425 when using GDB is to simply give the command 2426 <p><code>set environment XML_MEM_BREAKPOINT xxxx</code></p> 2427 <p>before running the program.</p> 2428 </li> 2429 <li>run the program under a debugger and set a breakpoint on 2430 xmlMallocBreakpoint() a specific function called when this precise block 2431 is allocated</li> 2432 <li>when the breakpoint is reached you can then do a fine analysis of the 2433 allocation an step to see the condition resulting in the missing 2434 deallocation.</li> 2435</ol> 2436 2437<p>I used to use a commercial tool to debug libxml memory problems but after 2438noticing that it was not detecting memory leaks that simple mechanism was 2439used and proved extremely efficient until now. Lately I have also used <a 2440href="http://developer.kde.org/~sewardj/">valgrind</a> with quite some 2441success, it is tied to the i386 architecture since it works by emulating the 2442processor and instruction set, it is slow but extremely efficient, i.e. it 2443spot memory usage errors in a very precise way.</p> 2444 2445<h3><a name="General4">General memory requirements</a></h3> 2446 2447<p>How much libxml memory require ? It's hard to tell in average it depends 2448of a number of things:</p> 2449<ul> 2450 <li>the parser itself should work in a fixed amount of memory, except for 2451 information maintained about the stacks of names and entities locations. 2452 The I/O and encoding handlers will probably account for a few KBytes. 2453 This is true for both the XML and HTML parser (though the HTML parser 2454 need more state).</li> 2455 <li>If you are generating the DOM tree then memory requirements will grow 2456 nearly linear with the size of the data. In general for a balanced 2457 textual document the internal memory requirement is about 4 times the 2458 size of the UTF8 serialization of this document (example the XML-1.0 2459 recommendation is a bit more of 150KBytes and takes 650KBytes of main 2460 memory when parsed). Validation will add a amount of memory required for 2461 maintaining the external Dtd state which should be linear with the 2462 complexity of the content model defined by the Dtd</li> 2463 <li>If you don't care about the advanced features of libxml like 2464 validation, DOM, XPath or XPointer, but really need to work fixed memory 2465 requirements, then the SAX interface should be used.</li> 2466</ul> 2467 2468<p></p> 2469 2470<h2><a name="Encodings">Encodings support</a></h2> 2471 2472<p>Table of Content:</p> 2473<ol> 2474 <li><a href="encoding.html#What">What does internationalization support 2475 mean ?</a></li> 2476 <li><a href="encoding.html#internal">The internal encoding, how and 2477 why</a></li> 2478 <li><a href="encoding.html#implemente">How is it implemented ?</a></li> 2479 <li><a href="encoding.html#Default">Default supported encodings</a></li> 2480 <li><a href="encoding.html#extend">How to extend the existing 2481 support</a></li> 2482</ol> 2483 2484<h3><a name="What">What does internationalization support mean ?</a></h3> 2485 2486<p>If you are not really familiar with Internationalization (usual shorcut is 2487I18N) , Unicode, characters and glyphs, I suggest you read a <a 2488href="http://www.tbray.org/ongoing/When/200x/2003/04/06/Unicode">presentation</a> 2489by Tim Bray on Unicode and why you should care about it.</p> 2490 2491<p>XML was designed from the start to allow the support of any character set 2492by using Unicode. Any conformant XML parser has to support the UTF-8 and 2493UTF-16 default encodings which can both express the full unicode ranges. UTF8 2494is a variable length encoding whose greatest points are to reuse the same 2495encoding for ASCII and to save space for Western encodings, but it is a bit 2496more complex to handle in practice. UTF-16 use 2 bytes per characters (and 2497sometimes combines two pairs), it makes implementation easier, but looks a 2498bit overkill for Western languages encoding. Moreover the XML specification 2499allows document to be encoded in other encodings at the condition that they 2500are clearly labeled as such. For example the following is a wellformed XML 2501document encoded in ISO-8859 1 and using accentuated letter that we French 2502likes for both markup and content:</p> 2503<pre><?xml version="1.0" encoding="ISO-8859-1"?> 2504<tr�s>l�</tr�s></pre> 2505 2506<p>Having internationalization support in libxml means the following:</p> 2507<ul> 2508 <li>the document is properly parsed</li> 2509 <li>informations about it's encoding are saved</li> 2510 <li>it can be modified</li> 2511 <li>it can be saved in its original encoding</li> 2512 <li>it can also be saved in another encoding supported by libxml (for 2513 example straight UTF8 or even an ASCII form)</li> 2514</ul> 2515 2516<p>Another very important point is that the whole libxml API, with the 2517exception of a few routines to read with a specific encoding or save to a 2518specific encoding, is completely agnostic about the original encoding of the 2519document.</p> 2520 2521<p>It should be noted too that the HTML parser embedded in libxml now obey 2522the same rules too, the following document will be (as of 2.2.2) handled in 2523an internationalized fashion by libxml too:</p> 2524<pre><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" 2525 "http://www.w3.org/TR/REC-html40/loose.dtd"> 2526<html lang="fr"> 2527<head> 2528 <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"> 2529</head> 2530<body> 2531<p>W3C cr�e des standards pour le Web.</body> 2532</html></pre> 2533 2534<h3><a name="internal">The internal encoding, how and why</a></h3> 2535 2536<p>One of the core decision was to force all documents to be converted to a 2537default internal encoding, and that encoding to be UTF-8, here are the 2538rationale for those choices:</p> 2539<ul> 2540 <li>keeping the native encoding in the internal form would force the libxml 2541 users (or the code associated) to be fully aware of the encoding of the 2542 original document, for examples when adding a text node to a document, 2543 the content would have to be provided in the document encoding, i.e. the 2544 client code would have to check it before hand, make sure it's conformant 2545 to the encoding, etc ... Very hard in practice, though in some specific 2546 cases this may make sense.</li> 2547 <li>the second decision was which encoding. From the XML spec only UTF8 and 2548 UTF16 really makes sense as being the two only encodings for which there 2549 is mandatory support. UCS-4 (32 bits fixed size encoding) could be 2550 considered an intelligent choice too since it's a direct Unicode mapping 2551 support. I selected UTF-8 on the basis of efficiency and compatibility 2552 with surrounding software: 2553 <ul> 2554 <li>UTF-8 while a bit more complex to convert from/to (i.e. slightly 2555 more costly to import and export CPU wise) is also far more compact 2556 than UTF-16 (and UCS-4) for a majority of the documents I see it used 2557 for right now (RPM RDF catalogs, advogato data, various configuration 2558 file formats, etc.) and the key point for today's computer 2559 architecture is efficient uses of caches. If one nearly double the 2560 memory requirement to store the same amount of data, this will trash 2561 caches (main memory/external caches/internal caches) and my take is 2562 that this harms the system far more than the CPU requirements needed 2563 for the conversion to UTF-8</li> 2564 <li>Most of libxml version 1 users were using it with straight ASCII 2565 most of the time, doing the conversion with an internal encoding 2566 requiring all their code to be rewritten was a serious show-stopper 2567 for using UTF-16 or UCS-4.</li> 2568 <li>UTF-8 is being used as the de-facto internal encoding standard for 2569 related code like the <a href="http://www.pango.org/">pango</a> 2570 upcoming Gnome text widget, and a lot of Unix code (yep another place 2571 where Unix programmer base takes a different approach from Microsoft 2572 - they are using UTF-16)</li> 2573 </ul> 2574 </li> 2575</ul> 2576 2577<p>What does this mean in practice for the libxml user:</p> 2578<ul> 2579 <li>xmlChar, the libxml data type is a byte, those bytes must be assembled 2580 as UTF-8 valid strings. The proper way to terminate an xmlChar * string 2581 is simply to append 0 byte, as usual.</li> 2582 <li>One just need to make sure that when using chars outside the ASCII set, 2583 the values has been properly converted to UTF-8</li> 2584</ul> 2585 2586<h3><a name="implemente">How is it implemented ?</a></h3> 2587 2588<p>Let's describe how all this works within libxml, basically the I18N 2589(internationalization) support get triggered only during I/O operation, i.e. 2590when reading a document or saving one. Let's look first at the reading 2591sequence:</p> 2592<ol> 2593 <li>when a document is processed, we usually don't know the encoding, a 2594 simple heuristic allows to detect UTF-18 and UCS-4 from whose where the 2595 ASCII range (0-0x7F) maps with ASCII</li> 2596 <li>the xml declaration if available is parsed, including the encoding 2597 declaration. At that point, if the autodetected encoding is different 2598 from the one declared a call to xmlSwitchEncoding() is issued.</li> 2599 <li>If there is no encoding declaration, then the input has to be in either 2600 UTF-8 or UTF-16, if it is not then at some point when processing the 2601 input, the converter/checker of UTF-8 form will raise an encoding error. 2602 You may end-up with a garbled document, or no document at all ! Example: 2603 <pre>~/XML -> /xmllint err.xml 2604err.xml:1: error: Input is not proper UTF-8, indicate encoding ! 2605<tr�s>l�</tr�s> 2606 ^ 2607err.xml:1: error: Bytes: 0xE8 0x73 0x3E 0x6C 2608<tr�s>l�</tr�s> 2609 ^</pre> 2610 </li> 2611 <li>xmlSwitchEncoding() does an encoding name lookup, canonicalize it, and 2612 then search the default registered encoding converters for that encoding. 2613 If it's not within the default set and iconv() support has been compiled 2614 it, it will ask iconv for such an encoder. If this fails then the parser 2615 will report an error and stops processing: 2616 <pre>~/XML -> /xmllint err2.xml 2617err2.xml:1: error: Unsupported encoding UnsupportedEnc 2618<?xml version="1.0" encoding="UnsupportedEnc"?> 2619 ^</pre> 2620 </li> 2621 <li>From that point the encoder processes progressively the input (it is 2622 plugged as a front-end to the I/O module) for that entity. It captures 2623 and convert on-the-fly the document to be parsed to UTF-8. The parser 2624 itself just does UTF-8 checking of this input and process it 2625 transparently. The only difference is that the encoding information has 2626 been added to the parsing context (more precisely to the input 2627 corresponding to this entity).</li> 2628 <li>The result (when using DOM) is an internal form completely in UTF-8 2629 with just an encoding information on the document node.</li> 2630</ol> 2631 2632<p>Ok then what happens when saving the document (assuming you 2633collected/built an xmlDoc DOM like structure) ? It depends on the function 2634called, xmlSaveFile() will just try to save in the original encoding, while 2635xmlSaveFileTo() and xmlSaveFileEnc() can optionally save to a given 2636encoding:</p> 2637<ol> 2638 <li>if no encoding is given, libxml will look for an encoding value 2639 associated to the document and if it exists will try to save to that 2640 encoding, 2641 <p>otherwise everything is written in the internal form, i.e. UTF-8</p> 2642 </li> 2643 <li>so if an encoding was specified, either at the API level or on the 2644 document, libxml will again canonicalize the encoding name, lookup for a 2645 converter in the registered set or through iconv. If not found the 2646 function will return an error code</li> 2647 <li>the converter is placed before the I/O buffer layer, as another kind of 2648 buffer, then libxml will simply push the UTF-8 serialization to through 2649 that buffer, which will then progressively be converted and pushed onto 2650 the I/O layer.</li> 2651 <li>It is possible that the converter code fails on some input, for example 2652 trying to push an UTF-8 encoded Chinese character through the UTF-8 to 2653 ISO-8859-1 converter won't work. Since the encoders are progressive they 2654 will just report the error and the number of bytes converted, at that 2655 point libxml will decode the offending character, remove it from the 2656 buffer and replace it with the associated charRef encoding &#123; and 2657 resume the conversion. This guarantees that any document will be saved 2658 without losses (except for markup names where this is not legal, this is 2659 a problem in the current version, in practice avoid using non-ascii 2660 characters for tags or attributes names @@). A special "ascii" encoding 2661 name is used to save documents to a pure ascii form can be used when 2662 portability is really crucial</li> 2663</ol> 2664 2665<p>Here is a few examples based on the same test document:</p> 2666<pre>~/XML -> /xmllint isolat1 2667<?xml version="1.0" encoding="ISO-8859-1"?> 2668<tr�s>l�</tr�s> 2669~/XML -> /xmllint --encode UTF-8 isolat1 2670<?xml version="1.0" encoding="UTF-8"?> 2671<très>l� �</très> 2672~/XML -> </pre> 2673 2674<p>The same processing is applied (and reuse most of the code) for HTML I18N 2675processing. Looking up and modifying the content encoding is a bit more 2676difficult since it is located in a <meta> tag under the <head>, 2677so a couple of functions htmlGetMetaEncoding() and htmlSetMetaEncoding() have 2678been provided. The parser also attempts to switch encoding on the fly when 2679detecting such a tag on input. Except for that the processing is the same 2680(and again reuses the same code).</p> 2681 2682<h3><a name="Default">Default supported encodings</a></h3> 2683 2684<p>libxml has a set of default converters for the following encodings 2685(located in encoding.c):</p> 2686<ol> 2687 <li>UTF-8 is supported by default (null handlers)</li> 2688 <li>UTF-16, both little and big endian</li> 2689 <li>ISO-Latin-1 (ISO-8859-1) covering most western languages</li> 2690 <li>ASCII, useful mostly for saving</li> 2691 <li>HTML, a specific handler for the conversion of UTF-8 to ASCII with HTML 2692 predefined entities like &copy; for the Copyright sign.</li> 2693</ol> 2694 2695<p>More over when compiled on an Unix platform with iconv support the full 2696set of encodings supported by iconv can be instantly be used by libxml. On a 2697linux machine with glibc-2.1 the list of supported encodings and aliases fill 26983 full pages, and include UCS-4, the full set of ISO-Latin encodings, and the 2699various Japanese ones.</p> 2700 2701<h4>Encoding aliases</h4> 2702 2703<p>From 2.2.3, libxml has support to register encoding names aliases. The 2704goal is to be able to parse document whose encoding is supported but where 2705the name differs (for example from the default set of names accepted by 2706iconv). The following functions allow to register and handle new aliases for 2707existing encodings. Once registered libxml will automatically lookup the 2708aliases when handling a document:</p> 2709<ul> 2710 <li>int xmlAddEncodingAlias(const char *name, const char *alias);</li> 2711 <li>int xmlDelEncodingAlias(const char *alias);</li> 2712 <li>const char * xmlGetEncodingAlias(const char *alias);</li> 2713 <li>void xmlCleanupEncodingAliases(void);</li> 2714</ul> 2715 2716<h3><a name="extend">How to extend the existing support</a></h3> 2717 2718<p>Well adding support for new encoding, or overriding one of the encoders 2719(assuming it is buggy) should not be hard, just write an input and output 2720conversion routines to/from UTF-8, and register them using 2721xmlNewCharEncodingHandler(name, xxxToUTF8, UTF8Toxxx), and they will be 2722called automatically if the parser(s) encounter such an encoding name 2723(register it uppercase, this will help). The description of the encoders, 2724their arguments and expected return values are described in the encoding.h 2725header.</p> 2726 2727<p>A quick note on the topic of subverting the parser to use a different 2728internal encoding than UTF-8, in some case people will absolutely want to 2729keep the internal encoding different, I think it's still possible (but the 2730encoding must be compliant with ASCII on the same subrange) though I didn't 2731tried it. The key is to override the default conversion routines (by 2732registering null encoders/decoders for your charsets), and bypass the UTF-8 2733checking of the parser by setting the parser context charset 2734(ctxt->charset) to something different than XML_CHAR_ENCODING_UTF8, but 2735there is no guarantee that this will work. You may also have some troubles 2736saving back.</p> 2737 2738<p>Basically proper I18N support is important, this requires at least 2739libxml-2.0.0, but a lot of features and corrections are really available only 2740starting 2.2.</p> 2741 2742<h2><a name="IO">I/O Interfaces</a></h2> 2743 2744<p>Table of Content:</p> 2745<ol> 2746 <li><a href="#General1">General overview</a></li> 2747 <li><a href="#basic">The basic buffer type</a></li> 2748 <li><a href="#Input">Input I/O handlers</a></li> 2749 <li><a href="#Output">Output I/O handlers</a></li> 2750 <li><a href="#entities">The entities loader</a></li> 2751 <li><a href="#Example2">Example of customized I/O</a></li> 2752</ol> 2753 2754<h3><a name="General1">General overview</a></h3> 2755 2756<p>The module <code><a 2757href="http://xmlsoft.org/html/libxml-xmlio.html">xmlIO.h</a></code> provides 2758the interfaces to the libxml I/O system. This consists of 4 main parts:</p> 2759<ul> 2760 <li>Entities loader, this is a routine which tries to fetch the entities 2761 (files) based on their PUBLIC and SYSTEM identifiers. The default loader 2762 don't look at the public identifier since libxml do not maintain a 2763 catalog. You can redefine you own entity loader by using 2764 <code>xmlGetExternalEntityLoader()</code> and 2765 <code>xmlSetExternalEntityLoader()</code>. <a href="#entities">Check the 2766 example</a>.</li> 2767 <li>Input I/O buffers which are a commodity structure used by the parser(s) 2768 input layer to handle fetching the informations to feed the parser. This 2769 provides buffering and is also a placeholder where the encoding 2770 converters to UTF8 are piggy-backed.</li> 2771 <li>Output I/O buffers are similar to the Input ones and fulfill similar 2772 task but when generating a serialization from a tree.</li> 2773 <li>A mechanism to register sets of I/O callbacks and associate them with 2774 specific naming schemes like the protocol part of the URIs. 2775 <p>This affect the default I/O operations and allows to use specific I/O 2776 handlers for certain names.</p> 2777 </li> 2778</ul> 2779 2780<p>The general mechanism used when loading http://rpmfind.net/xml.html for 2781example in the HTML parser is the following:</p> 2782<ol> 2783 <li>The default entity loader calls <code>xmlNewInputFromFile()</code> with 2784 the parsing context and the URI string.</li> 2785 <li>the URI string is checked against the existing registered handlers 2786 using their match() callback function, if the HTTP module was compiled 2787 in, it is registered and its match() function will succeeds</li> 2788 <li>the open() function of the handler is called and if successful will 2789 return an I/O Input buffer</li> 2790 <li>the parser will the start reading from this buffer and progressively 2791 fetch information from the resource, calling the read() function of the 2792 handler until the resource is exhausted</li> 2793 <li>if an encoding change is detected it will be installed on the input 2794 buffer, providing buffering and efficient use of the conversion 2795 routines</li> 2796 <li>once the parser has finished, the close() function of the handler is 2797 called once and the Input buffer and associated resources are 2798 deallocated.</li> 2799</ol> 2800 2801<p>The user defined callbacks are checked first to allow overriding of the 2802default libxml I/O routines.</p> 2803 2804<h3><a name="basic">The basic buffer type</a></h3> 2805 2806<p>All the buffer manipulation handling is done using the 2807<code>xmlBuffer</code> type define in <code><a 2808href="http://xmlsoft.org/html/libxml-tree.html">tree.h</a> </code>which is a 2809resizable memory buffer. The buffer allocation strategy can be selected to be 2810either best-fit or use an exponential doubling one (CPU vs. memory use 2811trade-off). The values are <code>XML_BUFFER_ALLOC_EXACT</code> and 2812<code>XML_BUFFER_ALLOC_DOUBLEIT</code>, and can be set individually or on a 2813system wide basis using <code>xmlBufferSetAllocationScheme()</code>. A number 2814of functions allows to manipulate buffers with names starting with the 2815<code>xmlBuffer...</code> prefix.</p> 2816 2817<h3><a name="Input">Input I/O handlers</a></h3> 2818 2819<p>An Input I/O handler is a simple structure 2820<code>xmlParserInputBuffer</code> containing a context associated to the 2821resource (file descriptor, or pointer to a protocol handler), the read() and 2822close() callbacks to use and an xmlBuffer. And extra xmlBuffer and a charset 2823encoding handler are also present to support charset conversion when 2824needed.</p> 2825 2826<h3><a name="Output">Output I/O handlers</a></h3> 2827 2828<p>An Output handler <code>xmlOutputBuffer</code> is completely similar to an 2829Input one except the callbacks are write() and close().</p> 2830 2831<h3><a name="entities">The entities loader</a></h3> 2832 2833<p>The entity loader resolves requests for new entities and create inputs for 2834the parser. Creating an input from a filename or an URI string is done 2835through the xmlNewInputFromFile() routine. The default entity loader do not 2836handle the PUBLIC identifier associated with an entity (if any). So it just 2837calls xmlNewInputFromFile() with the SYSTEM identifier (which is mandatory in 2838XML).</p> 2839 2840<p>If you want to hook up a catalog mechanism then you simply need to 2841override the default entity loader, here is an example:</p> 2842<pre>#include <libxml/xmlIO.h> 2843 2844xmlExternalEntityLoader defaultLoader = NULL; 2845 2846xmlParserInputPtr 2847xmlMyExternalEntityLoader(const char *URL, const char *ID, 2848 xmlParserCtxtPtr ctxt) { 2849 xmlParserInputPtr ret; 2850 const char *fileID = NULL; 2851 /* lookup for the fileID depending on ID */ 2852 2853 ret = xmlNewInputFromFile(ctxt, fileID); 2854 if (ret != NULL) 2855 return(ret); 2856 if (defaultLoader != NULL) 2857 ret = defaultLoader(URL, ID, ctxt); 2858 return(ret); 2859} 2860 2861int main(..) { 2862 ... 2863 2864 /* 2865 * Install our own entity loader 2866 */ 2867 defaultLoader = xmlGetExternalEntityLoader(); 2868 xmlSetExternalEntityLoader(xmlMyExternalEntityLoader); 2869 2870 ... 2871}</pre> 2872 2873<h3><a name="Example2">Example of customized I/O</a></h3> 2874 2875<p>This example come from <a href="http://xmlsoft.org/messages/0708.html">a 2876real use case</a>, xmlDocDump() closes the FILE * passed by the application 2877and this was a problem. The <a 2878href="http://xmlsoft.org/messages/0711.html">solution</a> was to redefine a 2879new output handler with the closing call deactivated:</p> 2880<ol> 2881 <li>First define a new I/O output allocator where the output don't close 2882 the file: 2883 <pre>xmlOutputBufferPtr 2884xmlOutputBufferCreateOwn(FILE *file, xmlCharEncodingHandlerPtr encoder) { 2885����xmlOutputBufferPtr ret; 2886���� 2887����if (xmlOutputCallbackInitialized == 0) 2888��������xmlRegisterDefaultOutputCallbacks(); 2889 2890����if (file == NULL) return(NULL); 2891����ret = xmlAllocOutputBuffer(encoder); 2892����if (ret != NULL) { 2893��������ret->context = file; 2894��������ret->writecallback = xmlFileWrite; 2895��������ret->closecallback = NULL; /* No close callback */ 2896����} 2897����return(ret); 2898} </pre> 2899 </li> 2900 <li>And then use it to save the document: 2901 <pre>FILE *f; 2902xmlOutputBufferPtr output; 2903xmlDocPtr doc; 2904int res; 2905 2906f = ... 2907doc = .... 2908 2909output = xmlOutputBufferCreateOwn(f, NULL); 2910res = xmlSaveFileTo(output, doc, NULL); 2911 </pre> 2912 </li> 2913</ol> 2914 2915<h2><a name="Catalog">Catalog support</a></h2> 2916 2917<p>Table of Content:</p> 2918<ol> 2919 <li><a href="General2">General overview</a></li> 2920 <li><a href="#definition">The definition</a></li> 2921 <li><a href="#Simple">Using catalogs</a></li> 2922 <li><a href="#Some">Some examples</a></li> 2923 <li><a href="#reference">How to tune catalog usage</a></li> 2924 <li><a href="#validate">How to debug catalog processing</a></li> 2925 <li><a href="#Declaring">How to create and maintain catalogs</a></li> 2926 <li><a href="#implemento">The implementor corner quick review of the 2927 API</a></li> 2928 <li><a href="#Other">Other resources</a></li> 2929</ol> 2930 2931<h3><a name="General2">General overview</a></h3> 2932 2933<p>What is a catalog? Basically it's a lookup mechanism used when an entity 2934(a file or a remote resource) references another entity. The catalog lookup 2935is inserted between the moment the reference is recognized by the software 2936(XML parser, stylesheet processing, or even images referenced for inclusion 2937in a rendering) and the time where loading that resource is actually 2938started.</p> 2939 2940<p>It is basically used for 3 things:</p> 2941<ul> 2942 <li>mapping from "logical" names, the public identifiers and a more 2943 concrete name usable for download (and URI). For example it can associate 2944 the logical name 2945 <p>"-//OASIS//DTD DocBook XML V4.1.2//EN"</p> 2946 <p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be 2947 downloaded</p> 2948 <p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p> 2949 </li> 2950 <li>remapping from a given URL to another one, like an HTTP indirection 2951 saying that 2952 <p>"http://www.oasis-open.org/committes/tr.xsl"</p> 2953 <p>should really be looked at</p> 2954 <p>"http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"</p> 2955 </li> 2956 <li>providing a local cache mechanism allowing to load the entities 2957 associated to public identifiers or remote resources, this is a really 2958 important feature for any significant deployment of XML or SGML since it 2959 allows to avoid the aleas and delays associated to fetching remote 2960 resources.</li> 2961</ul> 2962 2963<h3><a name="definition">The definitions</a></h3> 2964 2965<p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p> 2966<ul> 2967 <li>the older SGML catalogs, the official spec is SGML Open Technical 2968 Resolution TR9401:1997, but is better understood by reading <a 2969 href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from 2970 James Clark. This is relatively old and not the preferred mode of 2971 operation of libxml.</li> 2972 <li><a href="http://www.oasis-open.org/committees/entity/spec.html">XML 2973 Catalogs</a> is far more flexible, more recent, uses an XML syntax and 2974 should scale quite better. This is the default option of libxml.</li> 2975</ul> 2976 2977<p></p> 2978 2979<h3><a name="Simple">Using catalog</a></h3> 2980 2981<p>In a normal environment libxml will by default check the presence of a 2982catalog in /etc/xml/catalog, and assuming it has been correctly populated, 2983the processing is completely transparent to the document user. To take a 2984concrete example, suppose you are authoring a DocBook document, this one 2985starts with the following DOCTYPE definition:</p> 2986<pre><?xml version='1.0'?> 2987<!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN" 2988 "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd"></pre> 2989 2990<p>When validating the document with libxml, the catalog will be 2991automatically consulted to lookup the public identifier "-//Norman Walsh//DTD 2992DocBk XML V3.1.4//EN" and the system identifier 2993"http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if these entities have 2994been installed on your system and the catalogs actually point to them, libxml 2995will fetch them from the local disk.</p> 2996 2997<p style="font-size: 10pt"><strong>Note</strong>: Really don't use this 2998DOCTYPE example it's a really old version, but is fine as an example.</p> 2999 3000<p>Libxml will check the catalog each time that it is requested to load an 3001entity, this includes DTD, external parsed entities, stylesheets, etc ... If 3002your system is correctly configured all the authoring phase and processing 3003should use only local files, even if your document stays portable because it 3004uses the canonical public and system ID, referencing the remote document.</p> 3005 3006<h3><a name="Some">Some examples:</a></h3> 3007 3008<p>Here is a couple of fragments from XML Catalogs used in libxml early 3009regression tests in <code>test/catalogs</code> :</p> 3010<pre><?xml version="1.0"?> 3011<!DOCTYPE catalog PUBLIC 3012 "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3013 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3014<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 3015 <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 3016 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 3017...</pre> 3018 3019<p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are 3020written in XML, there is a specific namespace for catalog elements 3021"urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry in this 3022catalog is a <code>public</code> mapping it allows to associate a Public 3023Identifier with an URI.</p> 3024<pre>... 3025 <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/" 3026 rewritePrefix="file:///usr/share/xml/docbook/"/> 3027...</pre> 3028 3029<p>A <code>rewriteSystem</code> is a very powerful instruction, it says that 3030any URI starting with a given prefix should be looked at another URI 3031constructed by replacing the prefix with an new one. In effect this acts like 3032a cache system for a full area of the Web. In practice it is extremely useful 3033with a file prefix if you have installed a copy of those resources on your 3034local system.</p> 3035<pre>... 3036<delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //" 3037 catalog="file:///usr/share/xml/docbook.xml"/> 3038<delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML" 3039 catalog="file:///usr/share/xml/docbook.xml"/> 3040<delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML" 3041 catalog="file:///usr/share/xml/docbook.xml"/> 3042<delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/" 3043 catalog="file:///usr/share/xml/docbook.xml"/> 3044<delegateURI uriStartString="http://www.oasis-open.org/docbook/" 3045 catalog="file:///usr/share/xml/docbook.xml"/> 3046...</pre> 3047 3048<p>Delegation is the core features which allows to build a tree of catalogs, 3049easier to maintain than a single catalog, based on Public Identifier, System 3050Identifier or URI prefixes it instructs the catalog software to look up 3051entries in another resource. This feature allow to build hierarchies of 3052catalogs, the set of entries presented should be sufficient to redirect the 3053resolution of all DocBook references to the specific catalog in 3054<code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all 3055references for DocBook 4.2.1 to a specific catalog installed at the same time 3056as the DocBook resources on the local machine.</p> 3057 3058<h3><a name="reference">How to tune catalog usage:</a></h3> 3059 3060<p>The user can change the default catalog behaviour by redirecting queries 3061to its own set of catalogs, this can be done by setting the 3062<code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an 3063empty one should deactivate loading the default <code>/etc/xml/catalog</code> 3064default catalog</p> 3065 3066<h3><a name="validate">How to debug catalog processing:</a></h3> 3067 3068<p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will 3069make libxml output debugging informations for each catalog operations, for 3070example:</p> 3071<pre>orchis:~/XML -> xmllint --memory --noout test/ent2 3072warning: failed to load external entity "title.xml" 3073orchis:~/XML -> export XML_DEBUG_CATALOG= 3074orchis:~/XML -> xmllint --memory --noout test/ent2 3075Failed to parse catalog /etc/xml/catalog 3076Failed to parse catalog /etc/xml/catalog 3077warning: failed to load external entity "title.xml" 3078Catalogs cleanup 3079orchis:~/XML -> </pre> 3080 3081<p>The test/ent2 references an entity, running the parser from memory makes 3082the base URI unavailable and the the "title.xml" entity cannot be loaded. 3083Setting up the debug environment variable allows to detect that an attempt is 3084made to load the <code>/etc/xml/catalog</code> but since it's not present the 3085resolution fails.</p> 3086 3087<p>But the most advanced way to debug XML catalog processing is to use the 3088<strong>xmlcatalog</strong> command shipped with libxml2, it allows to load 3089catalogs and make resolution queries to see what is going on. This is also 3090used for the regression tests:</p> 3091<pre>orchis:~/XML -> /xmlcatalog test/catalogs/docbook.xml \ 3092 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3093http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3094orchis:~/XML -> </pre> 3095 3096<p>For debugging what is going on, adding one -v flags increase the verbosity 3097level to indicate the processing done (adding a second flag also indicate 3098what elements are recognized at parsing):</p> 3099<pre>orchis:~/XML -> /xmlcatalog -v test/catalogs/docbook.xml \ 3100 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3101Parsing catalog test/catalogs/docbook.xml's content 3102Found public match -//OASIS//DTD DocBook XML V4.1.2//EN 3103http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3104Catalogs cleanup 3105orchis:~/XML -> </pre> 3106 3107<p>A shell interface is also available to debug and process multiple queries 3108(and for regression tests):</p> 3109<pre>orchis:~/XML -> /xmlcatalog -shell test/catalogs/docbook.xml \ 3110 "-//OASIS//DTD DocBook XML V4.1.2//EN" 3111> help 3112Commands available: 3113public PublicID: make a PUBLIC identifier lookup 3114system SystemID: make a SYSTEM identifier lookup 3115resolve PublicID SystemID: do a full resolver lookup 3116add 'type' 'orig' 'replace' : add an entry 3117del 'values' : remove values 3118dump: print the current catalog state 3119debug: increase the verbosity level 3120quiet: decrease the verbosity level 3121exit: quit the shell 3122> public "-//OASIS//DTD DocBook XML V4.1.2//EN" 3123http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd 3124> quit 3125orchis:~/XML -> </pre> 3126 3127<p>This should be sufficient for most debugging purpose, this was actually 3128used heavily to debug the XML Catalog implementation itself.</p> 3129 3130<h3><a name="Declaring">How to create and maintain</a> catalogs:</h3> 3131 3132<p>Basically XML Catalogs are XML files, you can either use XML tools to 3133manage them or use <strong>xmlcatalog</strong> for this. The basic step is 3134to create a catalog the -create option provide this facility:</p> 3135<pre>orchis:~/XML -> /xmlcatalog --create tst.xml 3136<?xml version="1.0"?> 3137<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3138 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3139<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3140orchis:~/XML -> </pre> 3141 3142<p>By default xmlcatalog does not overwrite the original catalog and save the 3143result on the standard output, this can be overridden using the -noout 3144option. The <code>-add</code> command allows to add entries in the 3145catalog:</p> 3146<pre>orchis:~/XML -> /xmlcatalog --noout --create --add "public" \ 3147 "-//OASIS//DTD DocBook XML V4.1.2//EN" \ 3148 http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml 3149orchis:~/XML -> cat tst.xml 3150<?xml version="1.0"?> 3151<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \ 3152 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3153<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> 3154<public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" 3155 uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> 3156</catalog> 3157orchis:~/XML -> </pre> 3158 3159<p>The <code>-add</code> option will always take 3 parameters even if some of 3160the XML Catalog constructs (like nextCatalog) will have only a single 3161argument, just pass a third empty string, it will be ignored.</p> 3162 3163<p>Similarly the <code>-del</code> option remove matching entries from the 3164catalog:</p> 3165<pre>orchis:~/XML -> /xmlcatalog --del \ 3166 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml 3167<?xml version="1.0"?> 3168<!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" 3169 "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> 3170<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> 3171orchis:~/XML -> </pre> 3172 3173<p>The catalog is now empty. Note that the matching of <code>-del</code> is 3174exact and would have worked in a similar fashion with the Public ID 3175string.</p> 3176 3177<p>This is rudimentary but should be sufficient to manage a not too complex 3178catalog tree of resources.</p> 3179 3180<h3><a name="implemento">The implementor corner quick review of the 3181API:</a></h3> 3182 3183<p>First, and like for every other module of libxml, there is an 3184automatically generated <a href="html/libxml-catalog.html">API page for 3185catalog support</a>.</p> 3186 3187<p>The header for the catalog interfaces should be included as:</p> 3188<pre>#include <libxml/catalog.h></pre> 3189 3190<p>The API is voluntarily kept very simple. First it is not obvious that 3191applications really need access to it since it is the default behaviour of 3192libxml (Note: it is possible to completely override libxml default catalog by 3193using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to 3194plug an application specific resolver).</p> 3195 3196<p>Basically libxml support 2 catalog lists:</p> 3197<ul> 3198 <li>the default one, global shared by all the application</li> 3199 <li>a per-document catalog, this one is built if the document uses the 3200 <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is 3201 associated to the parser context and destroyed when the parsing context 3202 is destroyed.</li> 3203</ul> 3204 3205<p>the document one will be used first if it exists.</p> 3206 3207<h4>Initialization routines:</h4> 3208 3209<p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be 3210used at startup to initialize the catalog, if the catalog should be 3211initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs() 3212should be called before xmlInitializeCatalog() which would otherwise do a 3213default initialization first.</p> 3214 3215<p>The xmlCatalogAddLocal() call is used by the parser to grow the document 3216own catalog list if needed.</p> 3217 3218<h4>Preferences setup:</h4> 3219 3220<p>The XML Catalog spec requires the possibility to select default 3221preferences between public and system delegation, 3222xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and 3223xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should 3224be forbidden, allowed for global catalog, for document catalog or both, the 3225default is to allow both.</p> 3226 3227<p>And of course xmlCatalogSetDebug() allows to generate debug messages 3228(through the xmlGenericError() mechanism).</p> 3229 3230<h4>Querying routines:</h4> 3231 3232<p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic() 3233and xmlCatalogResolveURI() are relatively explicit if you read the XML 3234Catalog specification they correspond to section 7 algorithms, they should 3235also work if you have loaded an SGML catalog with a simplified semantic.</p> 3236 3237<p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but 3238operate on the document catalog list</p> 3239 3240<h4>Cleanup and Miscellaneous:</h4> 3241 3242<p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is 3243the per-document equivalent.</p> 3244 3245<p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the 3246first catalog in the global list, and xmlCatalogDump() allows to dump a 3247catalog state, those routines are primarily designed for xmlcatalog, I'm not 3248sure that exposing more complex interfaces (like navigation ones) would be 3249really useful.</p> 3250 3251<p>The xmlParseCatalogFile() is a function used to load XML Catalog files, 3252it's similar as xmlParseFile() except it bypass all catalog lookups, it's 3253provided because this functionality may be useful for client tools.</p> 3254 3255<h4>threaded environments:</h4> 3256 3257<p>Since the catalog tree is built progressively, some care has been taken to 3258try to avoid troubles in multithreaded environments. The code is now thread 3259safe assuming that the libxml library has been compiled with threads 3260support.</p> 3261 3262<p></p> 3263 3264<h3><a name="Other">Other resources</a></h3> 3265 3266<p>The XML Catalog specification is relatively recent so there isn't much 3267literature to point at:</p> 3268<ul> 3269 <li>You can find a good rant from Norm Walsh about <a 3270 href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the 3271 need for catalogs</a>, it provides a lot of context informations even if 3272 I don't agree with everything presented. Norm also wrote a more recent 3273 article <a 3274 href="http://wwws.sun.com/software/xml/developers/resolver/article/">XML 3275 entities and URI resolvers</a> describing them.</li> 3276 <li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML 3277 catalog proposal</a> from John Cowan</li> 3278 <li>The <a href="http://www.rddl.org/">Resource Directory Description 3279 Language</a> (RDDL) another catalog system but more oriented toward 3280 providing metadata for XML namespaces.</li> 3281 <li>the page from the OASIS Technical <a 3282 href="http://www.oasis-open.org/committees/entity/">Committee on Entity 3283 Resolution</a> who maintains XML Catalog, you will find pointers to the 3284 specification update, some background and pointers to others tools 3285 providing XML Catalog support</li> 3286 <li>Here is a <a href="buildDocBookCatalog">shell script</a> to generate 3287 XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/ 3288 directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on 3289 the resources found on the system. Otherwise it will just create 3290 ~/xmlcatalog and ~/dbkxmlcatalog and doing: 3291 <p><code>export XMLCATALOG=$HOME/xmlcatalog</code></p> 3292 <p>should allow to process DocBook documentations without requiring 3293 network accesses for the DTD or stylesheets</p> 3294 </li> 3295 <li>I have uploaded <a href="ftp://xmlsoft.org/test/dbk412catalog.tar.gz">a 3296 small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems 3297 to work fine for me too</li> 3298 <li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog 3299 manual page</a></li> 3300</ul> 3301 3302<p>If you have suggestions for corrections or additions, simply contact 3303me:</p> 3304 3305<h2><a name="library">The parser interfaces</a></h2> 3306 3307<p>This section is directly intended to help programmers getting bootstrapped 3308using the XML library from the C language. It is not intended to be 3309extensive. I hope the automatically generated documents will provide the 3310completeness required, but as a separate set of documents. The interfaces of 3311the XML library are by principle low level, there is nearly zero abstraction. 3312Those interested in a higher level API should <a href="#DOM">look at 3313DOM</a>.</p> 3314 3315<p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are 3316separated from the <a href="html/libxml-htmlparser.html">HTML parser 3317interfaces</a>. Let's have a look at how the XML parser can be called:</p> 3318 3319<h3><a name="Invoking">Invoking the parser : the pull method</a></h3> 3320 3321<p>Usually, the first thing to do is to read an XML input. The parser accepts 3322documents either from in-memory strings or from files. The functions are 3323defined in "parser.h":</p> 3324<dl> 3325 <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> 3326 <dd><p>Parse a null-terminated string containing the document.</p> 3327 </dd> 3328</dl> 3329<dl> 3330 <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> 3331 <dd><p>Parse an XML document contained in a (possibly compressed) 3332 file.</p> 3333 </dd> 3334</dl> 3335 3336<p>The parser returns a pointer to the document structure (or NULL in case of 3337failure).</p> 3338 3339<h3 id="Invoking1">Invoking the parser: the push method</h3> 3340 3341<p>In order for the application to keep the control when the document is 3342being fetched (which is common for GUI based programs) libxml provides a push 3343interface, too, as of version 1.8.3. Here are the interface functions:</p> 3344<pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, 3345 void *user_data, 3346 const char *chunk, 3347 int size, 3348 const char *filename); 3349int xmlParseChunk (xmlParserCtxtPtr ctxt, 3350 const char *chunk, 3351 int size, 3352 int terminate);</pre> 3353 3354<p>and here is a simple example showing how to use the interface:</p> 3355<pre> FILE *f; 3356 3357 f = fopen(filename, "r"); 3358 if (f != NULL) { 3359 int res, size = 1024; 3360 char chars[1024]; 3361 xmlParserCtxtPtr ctxt; 3362 3363 res = fread(chars, 1, 4, f); 3364 if (res > 0) { 3365 ctxt = xmlCreatePushParserCtxt(NULL, NULL, 3366 chars, res, filename); 3367 while ((res = fread(chars, 1, size, f)) > 0) { 3368 xmlParseChunk(ctxt, chars, res, 0); 3369 } 3370 xmlParseChunk(ctxt, chars, 0, 1); 3371 doc = ctxt->myDoc; 3372 xmlFreeParserCtxt(ctxt); 3373 } 3374 }</pre> 3375 3376<p>The HTML parser embedded into libxml also has a push interface; the 3377functions are just prefixed by "html" rather than "xml".</p> 3378 3379<h3 id="Invoking2">Invoking the parser: the SAX interface</h3> 3380 3381<p>The tree-building interface makes the parser memory-hungry, first loading 3382the document in memory and then building the tree itself. Reading a document 3383without building the tree is possible using the SAX interfaces (see SAX.h and 3384<a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James 3385Henstridge's documentation</a>). Note also that the push interface can be 3386limited to SAX: just use the two first arguments of 3387<code>xmlCreatePushParserCtxt()</code>.</p> 3388 3389<h3><a name="Building">Building a tree from scratch</a></h3> 3390 3391<p>The other way to get an XML tree in memory is by building it. Basically 3392there is a set of functions dedicated to building new elements. (These are 3393also described in <libxml/tree.h>.) For example, here is a piece of 3394code that produces the XML document used in the previous examples:</p> 3395<pre> #include <libxml/tree.h> 3396 xmlDocPtr doc; 3397 xmlNodePtr tree, subtree; 3398 3399 doc = xmlNewDoc("1.0"); 3400 doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); 3401 xmlSetProp(doc->children, "prop1", "gnome is great"); 3402 xmlSetProp(doc->children, "prop2", "& linux too"); 3403 tree = xmlNewChild(doc->children, NULL, "head", NULL); 3404 subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); 3405 tree = xmlNewChild(doc->children, NULL, "chapter", NULL); 3406 subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); 3407 subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); 3408 subtree = xmlNewChild(tree, NULL, "image", NULL); 3409 xmlSetProp(subtree, "href", "linus.gif");</pre> 3410 3411<p>Not really rocket science ...</p> 3412 3413<h3><a name="Traversing">Traversing the tree</a></h3> 3414 3415<p>Basically by <a href="html/libxml-tree.html">including "tree.h"</a> your 3416code has access to the internal structure of all the elements of the tree. 3417The names should be somewhat simple like <strong>parent</strong>, 3418<strong>children</strong>, <strong>next</strong>, <strong>prev</strong>, 3419<strong>properties</strong>, etc... For example, still with the previous 3420example:</p> 3421<pre><code>doc->children->children->children</code></pre> 3422 3423<p>points to the title element,</p> 3424<pre>doc->children->children->next->children->children</pre> 3425 3426<p>points to the text node containing the chapter title "The Linux 3427adventure".</p> 3428 3429<p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be 3430present before the document root, so <code>doc->children</code> may point 3431to an element which is not the document Root Element; a function 3432<code>xmlDocGetRootElement()</code> was added for this purpose.</p> 3433 3434<h3><a name="Modifying">Modifying the tree</a></h3> 3435 3436<p>Functions are provided for reading and writing the document content. Here 3437is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p> 3438<dl> 3439 <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const 3440 xmlChar *value);</code></dt> 3441 <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. 3442 The value can be NULL.</p> 3443 </dd> 3444</dl> 3445<dl> 3446 <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar 3447 *name);</code></dt> 3448 <dd><p>This function returns a pointer to new copy of the property 3449 content. Note that the user must deallocate the result.</p> 3450 </dd> 3451</dl> 3452 3453<p>Two functions are provided for reading and writing the text associated 3454with elements:</p> 3455<dl> 3456 <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar 3457 *value);</code></dt> 3458 <dd><p>This function takes an "external" string and converts it to one 3459 text node or possibly to a list of entity and text nodes. All 3460 non-predefined entity references like &Gnome; will be stored 3461 internally as entity nodes, hence the result of the function may not be 3462 a single node.</p> 3463 </dd> 3464</dl> 3465<dl> 3466 <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int 3467 inLine);</code></dt> 3468 <dd><p>This function is the inverse of 3469 <code>xmlStringGetNodeList()</code>. It generates a new string 3470 containing the content of the text and entity nodes. Note the extra 3471 argument inLine. If this argument is set to 1, the function will expand 3472 entity references. For example, instead of returning the &Gnome; 3473 XML encoding in the string, it will substitute it with its value (say, 3474 "GNU Network Object Model Environment").</p> 3475 </dd> 3476</dl> 3477 3478<h3><a name="Saving">Saving a tree</a></h3> 3479 3480<p>Basically 3 options are possible:</p> 3481<dl> 3482 <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int 3483 *size);</code></dt> 3484 <dd><p>Returns a buffer into which the document has been saved.</p> 3485 </dd> 3486</dl> 3487<dl> 3488 <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> 3489 <dd><p>Dumps a document to an open file descriptor.</p> 3490 </dd> 3491</dl> 3492<dl> 3493 <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> 3494 <dd><p>Saves the document to a file. In this case, the compression 3495 interface is triggered if it has been turned on.</p> 3496 </dd> 3497</dl> 3498 3499<h3><a name="Compressio">Compression</a></h3> 3500 3501<p>The library transparently handles compression when doing file-based 3502accesses. The level of compression on saves can be turned on either globally 3503or individually for one file:</p> 3504<dl> 3505 <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> 3506 <dd><p>Gets the document compression ratio (0-9).</p> 3507 </dd> 3508</dl> 3509<dl> 3510 <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> 3511 <dd><p>Sets the document compression ratio.</p> 3512 </dd> 3513</dl> 3514<dl> 3515 <dt><code>int xmlGetCompressMode(void);</code></dt> 3516 <dd><p>Gets the default compression ratio.</p> 3517 </dd> 3518</dl> 3519<dl> 3520 <dt><code>void xmlSetCompressMode(int mode);</code></dt> 3521 <dd><p>Sets the default compression ratio.</p> 3522 </dd> 3523</dl> 3524 3525<h2><a name="Entities">Entities or no entities</a></h2> 3526 3527<p>Entities in principle are similar to simple C macros. An entity defines an 3528abbreviation for a given string that you can reuse many times throughout the 3529content of your document. Entities are especially useful when a given string 3530may occur frequently within a document, or to confine the change needed to a 3531document to a restricted area in the internal subset of the document (at the 3532beginning). Example:</p> 3533<pre>1 <?xml version="1.0"?> 35342 <!DOCTYPE EXAMPLE SYSTEM "example.dtd" [ 35353 <!ENTITY xml "Extensible Markup Language"> 35364 ]> 35375 <EXAMPLE> 35386 &xml; 35397 </EXAMPLE></pre> 3540 3541<p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing 3542its name with '&' and following it by ';' without any spaces added. There 3543are 5 predefined entities in libxml allowing you to escape characters with 3544predefined meaning in some parts of the xml document content: 3545<strong>&lt;</strong> for the character '<', <strong>&gt;</strong> 3546for the character '>', <strong>&apos;</strong> for the character ''', 3547<strong>&quot;</strong> for the character '"', and 3548<strong>&amp;</strong> for the character '&'.</p> 3549 3550<p>One of the problems related to entities is that you may want the parser to 3551substitute an entity's content so that you can see the replacement text in 3552your application. Or you may prefer to keep entity references as such in the 3553content to be able to save the document back without losing this usually 3554precious information (if the user went through the pain of explicitly 3555defining entities, he may have a a rather negative attitude if you blindly 3556substitute them as saving time). The <a 3557href="html/libxml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a> 3558function allows you to check and change the behaviour, which is to not 3559substitute entities by default.</p> 3560 3561<p>Here is the DOM tree built by libxml for the previous document in the 3562default case:</p> 3563<pre>/gnome/src/gnome-xml -> /xmllint --debug test/ent1 3564DOCUMENT 3565version=1.0 3566 ELEMENT EXAMPLE 3567 TEXT 3568 content= 3569 ENTITY_REF 3570 INTERNAL_GENERAL_ENTITY xml 3571 content=Extensible Markup Language 3572 TEXT 3573 content=</pre> 3574 3575<p>And here is the result when substituting entities:</p> 3576<pre>/gnome/src/gnome-xml -> /tester --debug --noent test/ent1 3577DOCUMENT 3578version=1.0 3579 ELEMENT EXAMPLE 3580 TEXT 3581 content= Extensible Markup Language</pre> 3582 3583<p>So, entities or no entities? Basically, it depends on your use case. I 3584suggest that you keep the non-substituting default behaviour and avoid using 3585entities in your XML document or data if you are not willing to handle the 3586entity references elements in the DOM tree.</p> 3587 3588<p>Note that at save time libxml enforces the conversion of the predefined 3589entities where necessary to prevent well-formedness problems, and will also 3590transparently replace those with chars (i.e. it will not generate entity 3591reference elements in the DOM tree or call the reference() SAX callback when 3592finding them in the input).</p> 3593 3594<p><span style="background-color: #FF0000">WARNING</span>: handling entities 3595on top of the libxml SAX interface is difficult!!! If you plan to use 3596non-predefined entities in your documents, then the learning curve to handle 3597then using the SAX API may be long. If you plan to use complex documents, I 3598strongly suggest you consider using the DOM interface instead and let libxml 3599deal with the complexity rather than trying to do it yourself.</p> 3600 3601<h2><a name="Namespaces">Namespaces</a></h2> 3602 3603<p>The libxml library implements <a 3604href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by 3605recognizing namespace constructs in the input, and does namespace lookup 3606automatically when building the DOM tree. A namespace declaration is 3607associated with an in-memory structure and all elements or attributes within 3608that namespace point to it. Hence testing the namespace is a simple and fast 3609equality operation at the user level.</p> 3610 3611<p>I suggest that people using libxml use a namespace, and declare it in the 3612root element of their document as the default namespace. Then they don't need 3613to use the prefix in the content but we will have a basis for future semantic 3614refinement and merging of data from different sources. This doesn't increase 3615the size of the XML output significantly, but significantly increases its 3616value in the long-term. Example:</p> 3617<pre><mydoc xmlns="http://mydoc.example.org/schemas/"> 3618 <elem1>...</elem1> 3619 <elem2>...</elem2> 3620</mydoc></pre> 3621 3622<p>The namespace value has to be an absolute URL, but the URL doesn't have to 3623point to any existing resource on the Web. It will bind all the element and 3624attributes with that URL. I suggest to use an URL within a domain you 3625control, and that the URL should contain some kind of version information if 3626possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a 3627good namespace scheme.</p> 3628 3629<p>Then when you load a file, make sure that a namespace carrying the 3630version-independent prefix is installed on the root element of your document, 3631and if the version information don't match something you know, warn the user 3632and be liberal in what you accept as the input. Also do *not* try to base 3633namespace checking on the prefix value. <foo:text> may be exactly the 3634same as <bar:text> in another document. What really matters is the URI 3635associated with the element or the attribute, not the prefix string (which is 3636just a shortcut for the full URI). In libxml, element and attributes have an 3637<code>ns</code> field pointing to an xmlNs structure detailing the namespace 3638prefix and its URI.</p> 3639 3640<p>@@Interfaces@@</p> 3641 3642<p>@@Examples@@</p> 3643 3644<p>Usually people object to using namespaces together with validity checking. 3645I will try to make sure that using namespaces won't break validity checking, 3646so even if you plan to use or currently are using validation I strongly 3647suggest adding namespaces to your document. A default namespace scheme 3648<code>xmlns="http://...."</code> should not break validity even on less 3649flexible parsers. Using namespaces to mix and differentiate content coming 3650from multiple DTDs will certainly break current validation schemes. I will 3651try to provide ways to do this, but this may not be portable or 3652standardized.</p> 3653 3654<h2><a name="Upgrading">Upgrading 1.x code</a></h2> 3655 3656<p>Incompatible changes:</p> 3657 3658<p>Version 2 of libxml is the first version introducing serious backward 3659incompatible changes. The main goals were:</p> 3660<ul> 3661 <li>a general cleanup. A number of mistakes inherited from the very early 3662 versions couldn't be changed due to compatibility constraints. Example 3663 the "childs" element in the nodes.</li> 3664 <li>Uniformization of the various nodes, at least for their header and link 3665 parts (doc, parent, children, prev, next), the goal is a simpler 3666 programming model and simplifying the task of the DOM implementors.</li> 3667 <li>better conformances to the XML specification, for example version 1.x 3668 had an heuristic to try to detect ignorable white spaces. As a result the 3669 SAX event generated were ignorableWhitespace() while the spec requires 3670 character() in that case. This also mean that a number of DOM node 3671 containing blank text may populate the DOM tree which were not present 3672 before.</li> 3673</ul> 3674 3675<h3>How to fix libxml-1.x code:</h3> 3676 3677<p>So client code of libxml designed to run with version 1.x may have to be 3678changed to compile against version 2.x of libxml. Here is a list of changes 3679that I have collected, they may not be sufficient, so in case you find other 3680change which are required, <a href="mailto:Daniel.�eillardw3.org">drop me a 3681mail</a>:</p> 3682<ol> 3683 <li>The package name have changed from libxml to libxml2, the library name 3684 is now -lxml2 . There is a new xml2-config script which should be used to 3685 select the right parameters libxml2</li> 3686 <li>Node <strong>childs</strong> field has been renamed 3687 <strong>children</strong> so s/childs/children/g should be applied 3688 (probability of having "childs" anywhere else is close to 0+</li> 3689 <li>The document don't have anymore a <strong>root</strong> element it has 3690 been replaced by <strong>children</strong> and usually you will get a 3691 list of element here. For example a Dtd element for the internal subset 3692 and it's declaration may be found in that list, as well as processing 3693 instructions or comments found before or after the document root element. 3694 Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of 3695 a document. Alternatively if you are sure to not reference DTDs nor have 3696 PIs or comments before or after the root element 3697 s/->root/->children/g will probably do it.</li> 3698 <li>The white space issue, this one is more complex, unless special case of 3699 validating parsing, the line breaks and spaces usually used for indenting 3700 and formatting the document content becomes significant. So they are 3701 reported by SAX and if your using the DOM tree, corresponding nodes are 3702 generated. Too approach can be taken: 3703 <ol> 3704 <li>lazy one, use the compatibility call 3705 <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are 3706 relying on a special (and possibly broken) set of heuristics of 3707 libxml to detect ignorable blanks. Don't complain if it breaks or 3708 make your application not 100% clean w.r.t. to it's input.</li> 3709 <li>the Right Way: change you code to accept possibly insignificant 3710 blanks characters, or have your tree populated with weird blank text 3711 nodes. You can spot them using the commodity function 3712 <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank 3713 nodes.</li> 3714 </ol> 3715 <p>Note also that with the new default the output functions don't add any 3716 extra indentation when saving a tree in order to be able to round trip 3717 (read and save) without inflating the document with extra formatting 3718 chars.</p> 3719 </li> 3720 <li>The include path has changed to $prefix/libxml/ and the includes 3721 themselves uses this new prefix in includes instructions... If you are 3722 using (as expected) the 3723 <pre>xml2-config --cflags</pre> 3724 <p>output to generate you compile commands this will probably work out of 3725 the box</p> 3726 </li> 3727 <li>xmlDetectCharEncoding takes an extra argument indicating the length in 3728 byte of the head of the document available for character detection.</li> 3729</ol> 3730 3731<h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3> 3732 3733<p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released 3734to allow smooth upgrade of existing libxml v1code while retaining 3735compatibility. They offers the following:</p> 3736<ol> 3737 <li>similar include naming, one should use 3738 <strong>#include<libxml/...></strong> in both cases.</li> 3739 <li>similar identifiers defined via macros for the child and root fields: 3740 respectively <strong>xmlChildrenNode</strong> and 3741 <strong>xmlRootNode</strong></li> 3742 <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be 3743 inserted once in the client code</li> 3744</ol> 3745 3746<p>So the roadmap to upgrade your existing libxml applications is the 3747following:</p> 3748<ol> 3749 <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> 3750 <li>find all occurrences where the xmlDoc <strong>root</strong> field is 3751 used and change it to <strong>xmlRootNode</strong></li> 3752 <li>similarly find all occurrences where the xmlNode 3753 <strong>childs</strong> field is used and change it to 3754 <strong>xmlChildrenNode</strong></li> 3755 <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your 3756 <strong>main()</strong> or in the library init entry point</li> 3757 <li>Recompile, check compatibility, it should still work</li> 3758 <li>Change your configure script to look first for xml2-config and fall 3759 back using xml-config . Use the --cflags and --libs output of the command 3760 as the Include and Linking parameters needed to use libxml.</li> 3761 <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and 3762 libxml-devel-1.8.y can be kept simultaneously)</li> 3763 <li>remove your config.cache, relaunch your configuration mechanism, and 3764 recompile, if steps 2 and 3 were done right it should compile as-is</li> 3765 <li>Test that your application is still running correctly, if not this may 3766 be due to extra empty nodes due to formating spaces being kept in libxml2 3767 contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your 3768 code before calling the parser (next to 3769 <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li> 3770</ol> 3771 3772<p>Following those steps should work. It worked for some of my own code.</p> 3773 3774<p>Let me put some emphasis on the fact that there is far more changes from 3775libxml 1.x to 2.x than the ones you may have to patch for. The overall code 3776has been considerably cleaned up and the conformance to the XML specification 3777has been drastically improved too. Don't take those changes as an excuse to 3778not upgrade, it may cost a lot on the long term ...</p> 3779 3780<h2><a name="Thread">Thread safety</a></h2> 3781 3782<p>Starting with 2.4.7, libxml makes provisions to ensure that concurrent 3783threads can safely work in parallel parsing different documents. There is 3784however a couple of things to do to ensure it:</p> 3785<ul> 3786 <li>configure the library accordingly using the --with-threads options</li> 3787 <li>call xmlInitParser() in the "main" thread before using any of the 3788 libxml API (except possibly selecting a different memory allocator)</li> 3789</ul> 3790 3791<p>Note that the thread safety cannot be ensured for multiple threads sharing 3792the same document, the locking must be done at the application level, libxml 3793exports a basic mutex and reentrant mutexes API in <libxml/threads.h>. 3794The parts of the library checked for thread safety are:</p> 3795<ul> 3796 <li>concurrent loading</li> 3797 <li>file access resolution</li> 3798 <li>catalog access</li> 3799 <li>catalog building</li> 3800 <li>entities lookup/accesses</li> 3801 <li>validation</li> 3802 <li>global variables per-thread override</li> 3803 <li>memory handling</li> 3804</ul> 3805 3806<p>XPath is supposed to be thread safe now, but this wasn't tested 3807seriously.</p> 3808 3809<h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2> 3810 3811<p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document 3812Object Model</em>; this is an API for accessing XML or HTML structured 3813documents. Native support for DOM in Gnome is on the way (module gnome-dom), 3814and will be based on gnome-xml. This will be a far cleaner interface to 3815manipulate XML files within Gnome since it won't expose the internal 3816structure.</p> 3817 3818<p>The current DOM implementation on top of libxml is the <a 3819href="http://cvs.gnome.org/lxr/source/gdome2/">gdome2 Gnome module</a>, this 3820is a full DOM interface, thanks to Paolo Casarini, check the <a 3821href="http://www.cs.unibo.it/~casarini/gdome2/">Gdome2 homepage</a> for more 3822informations.</p> 3823 3824<h2><a name="Example"></a><a name="real">A real example</a></h2> 3825 3826<p>Here is a real size example, where the actual content of the application 3827data is not kept in the DOM tree but uses internal structures. It is based on 3828a proposal to keep a database of jobs related to Gnome, with an XML based 3829storage structure. Here is an <a href="gjobs.xml">XML encoded jobs 3830base</a>:</p> 3831<pre><?xml version="1.0"?> 3832<gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"> 3833 <gjob:Jobs> 3834 3835 <gjob:Job> 3836 <gjob:Project ID="3"/> 3837 <gjob:Application>GBackup</gjob:Application> 3838 <gjob:Category>Development</gjob:Category> 3839 3840 <gjob:Update> 3841 <gjob:Status>Open</gjob:Status> 3842 <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified> 3843 <gjob:Salary>USD 0.00</gjob:Salary> 3844 </gjob:Update> 3845 3846 <gjob:Developers> 3847 <gjob:Developer> 3848 </gjob:Developer> 3849 </gjob:Developers> 3850 3851 <gjob:Contact> 3852 <gjob:Person>Nathan Clemons</gjob:Person> 3853 <gjob:Email>nathan@windsofstorm.net</gjob:Email> 3854 <gjob:Company> 3855 </gjob:Company> 3856 <gjob:Organisation> 3857 </gjob:Organisation> 3858 <gjob:Webpage> 3859 </gjob:Webpage> 3860 <gjob:Snailmail> 3861 </gjob:Snailmail> 3862 <gjob:Phone> 3863 </gjob:Phone> 3864 </gjob:Contact> 3865 3866 <gjob:Requirements> 3867 The program should be released as free software, under the GPL. 3868 </gjob:Requirements> 3869 3870 <gjob:Skills> 3871 </gjob:Skills> 3872 3873 <gjob:Details> 3874 A GNOME based system that will allow a superuser to configure 3875 compressed and uncompressed files and/or file systems to be backed 3876 up with a supported media in the system. This should be able to 3877 perform via find commands generating a list of files that are passed 3878 to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine 3879 or via operations performed on the filesystem itself. Email 3880 notification and GUI status display very important. 3881 </gjob:Details> 3882 3883 </gjob:Job> 3884 3885 </gjob:Jobs> 3886</gjob:Helping></pre> 3887 3888<p>While loading the XML file into an internal DOM tree is a matter of 3889calling only a couple of functions, browsing the tree to gather the data and 3890generate the internal structures is harder, and more error prone.</p> 3891 3892<p>The suggested principle is to be tolerant with respect to the input 3893structure. For example, the ordering of the attributes is not significant, 3894the XML specification is clear about it. It's also usually a good idea not to 3895depend on the order of the children of a given node, unless it really makes 3896things harder. Here is some code to parse the information for a person:</p> 3897<pre>/* 3898 * A person record 3899 */ 3900typedef struct person { 3901 char *name; 3902 char *email; 3903 char *company; 3904 char *organisation; 3905 char *smail; 3906 char *webPage; 3907 char *phone; 3908} person, *personPtr; 3909 3910/* 3911 * And the code needed to parse it 3912 */ 3913personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 3914 personPtr ret = NULL; 3915 3916DEBUG("parsePerson\n"); 3917 /* 3918 * allocate the struct 3919 */ 3920 ret = (personPtr) malloc(sizeof(person)); 3921 if (ret == NULL) { 3922 fprintf(stderr,"out of memory\n"); 3923 return(NULL); 3924 } 3925 memset(ret, 0, sizeof(person)); 3926 3927 /* We don't care what the top level element name is */ 3928 cur = cur->xmlChildrenNode; 3929 while (cur != NULL) { 3930 if ((!strcmp(cur->name, "Person")) && (cur->ns == ns)) 3931 ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3932 if ((!strcmp(cur->name, "Email")) && (cur->ns == ns)) 3933 ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 3934 cur = cur->next; 3935 } 3936 3937 return(ret); 3938}</pre> 3939 3940<p>Here are a couple of things to notice:</p> 3941<ul> 3942 <li>Usually a recursive parsing style is the more convenient one: XML data 3943 is by nature subject to repetitive constructs and usually exhibits highly 3944 structured patterns.</li> 3945 <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, 3946 i.e. the pointer to the global XML document and the namespace reserved to 3947 the application. Document wide information are needed for example to 3948 decode entities and it's a good coding practice to define a namespace for 3949 your application set of data and test that the element and attributes 3950 you're analyzing actually pertains to your application space. This is 3951 done by a simple equality test (cur->ns == ns).</li> 3952 <li>To retrieve text and attributes value, you can use the function 3953 <em>xmlNodeListGetString</em> to gather all the text and entity reference 3954 nodes generated by the DOM output and produce an single text string.</li> 3955</ul> 3956 3957<p>Here is another piece of code used to parse another level of the 3958structure:</p> 3959<pre>#include <libxml/tree.h> 3960/* 3961 * a Description for a Job 3962 */ 3963typedef struct job { 3964 char *projectID; 3965 char *application; 3966 char *category; 3967 personPtr contact; 3968 int nbDevelopers; 3969 personPtr developers[100]; /* using dynamic alloc is left as an exercise */ 3970} job, *jobPtr; 3971 3972/* 3973 * And the code needed to parse it 3974 */ 3975jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { 3976 jobPtr ret = NULL; 3977 3978DEBUG("parseJob\n"); 3979 /* 3980 * allocate the struct 3981 */ 3982 ret = (jobPtr) malloc(sizeof(job)); 3983 if (ret == NULL) { 3984 fprintf(stderr,"out of memory\n"); 3985 return(NULL); 3986 } 3987 memset(ret, 0, sizeof(job)); 3988 3989 /* We don't care what the top level element name is */ 3990 cur = cur->xmlChildrenNode; 3991 while (cur != NULL) { 3992 3993 if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) { 3994 ret->projectID = xmlGetProp(cur, "ID"); 3995 if (ret->projectID == NULL) { 3996 fprintf(stderr, "Project has no ID\n"); 3997 } 3998 } 3999 if ((!strcmp(cur->name, "Application")) && (cur->ns == ns)) 4000 ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4001 if ((!strcmp(cur->name, "Category")) && (cur->ns == ns)) 4002 ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); 4003 if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns)) 4004 ret->contact = parsePerson(doc, ns, cur); 4005 cur = cur->next; 4006 } 4007 4008 return(ret); 4009}</pre> 4010 4011<p>Once you are used to it, writing this kind of code is quite simple, but 4012boring. Ultimately, it could be possible to write stubbers taking either C 4013data structure definitions, a set of XML examples or an XML DTD and produce 4014the code needed to import and export the content between C data and XML 4015storage. This is left as an exercise to the reader :-)</p> 4016 4017<p>Feel free to use <a href="example/gjobread.c">the code for the full C 4018parsing example</a> as a template, it is also available with Makefile in the 4019Gnome CVS base under gnome-xml/example</p> 4020 4021<h2><a name="Contributi">Contributions</a></h2> 4022<ul> 4023 <li>Bjorn Reese, William Brack and Thomas Broyer have provided a number of 4024 patches, Gary Pennington worked on the validation API, threading support 4025 and Solaris port.</li> 4026 <li>John Fleck helps maintaining the documentation and man pages.</li> 4027 <li><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the 4028 maintainer of the Windows port, <a 4029 href="http://www.zlatkovic.com/projects/libxml/index.html">he provides 4030 binaries</a></li> 4031 <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides 4032 <a href="http://garypennington.net/libxml2/">Solaris binaries</a></li> 4033 <li><a 4034 href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt 4035 Sergeant</a> developed <a 4036 href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for 4037 libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML 4038 application server</a></li> 4039 <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> and <a 4040 href="mailto:geertk@ai.rug.nl">Geert Kloosterman</a> provide <a 4041 href="libxml-doc.el">an emacs module</a> to lookup libxml(2) functions 4042 documentation</li> 4043 <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a 4044 href="http://xmlsoft.org/messages/0488.html">man pages</a></li> 4045 <li>there is a module for <a 4046 href="http://acs-misc.sourceforge.net/nsxml.html">libxml/libxslt support 4047 in OpenNSD/AOLServer</a></li> 4048 <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provided the 4049 first version of libxml/libxslt <a 4050 href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li> 4051 <li>Petr Kozelka provides <a 4052 href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue 4053 libxml2</a> with Kylix and Delphi and other Pascal compilers</li> 4054 <li><a href="mailto:aleksey@aleksey.com">Aleksey Sanin</a> implemented the 4055 <a href="http://www.w3.org/Signature/">XML Canonicalization and XML 4056 Digital Signature</a> <a 4057 href="http://www.aleksey.com/xmlsec/">implementations for libxml2</a></li> 4058 <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a>, <a 4059 href="http://www.zveno.com/">Zveno</a> and contributors maintain <a 4060 href="http://tclxml.sourceforge.net/">tcl bindings for libxml2 and 4061 libxslt</a>, as well as <a 4062 href="http://tclxml.sf.net/tkxmllint.html">tkxmllint</a> a GUI for 4063 xmllint and <a href="http://tclxml.sf.net/tkxsltproc.html">tkxsltproc</a> 4064 a GUI for xsltproc.</li> 4065</ul> 4066 4067<p></p> 4068</body> 4069</html> 4070
