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| <h1 align="center">The XML C library for Gnome</h1> |
| |
| <h1>Note: this is the flat content of the <a href="index.html">web |
| site</a></h1> |
| |
| <h1 style="text-align: center">libxml, a.k.a. gnome-xml</h1> |
| |
| <p></p> |
| |
| <p>Libxml is the XML C library developed for the Gnome project. XML itself |
| is a metalanguage to design markup languages, i.e. text language where |
| semantic and structure are added to the content using extra "markup" |
| information enclosed between angle brackets. HTML is the most well-known |
| markup language. Though the library is written in C <a href="python.html">a |
| variety of language bindings</a> make it available in other environments.</p> |
| |
| <p>Libxml2 is known to be very portable, the library should build and work |
| without serious troubles on a variety of systems (Linux, Unix, Windows, |
| CygWin, MacOS, MacOS X, RISC Os, OS/2, VMS, QNX, MVS, ...)</p> |
| |
| <p>Libxml2 implements a number of existing standards related to markup |
| languages:</p> |
| <ul> |
| <li>the XML standard: <a |
| href="http://www.w3.org/TR/REC-xml">http://www.w3.org/TR/REC-xml</a></li> |
| <li>Namespaces in XML: <a |
| href="http://www.w3.org/TR/REC-xml-names/">http://www.w3.org/TR/REC-xml-names/</a></li> |
| <li>XML Base: <a |
| href="http://www.w3.org/TR/xmlbase/">http://www.w3.org/TR/xmlbase/</a></li> |
| <li><a href="http://www.cis.ohio-state.edu/rfc/rfc2396.txt">RFC 2396</a> : |
| Uniform Resource Identifiers <a |
| href="http://www.ietf.org/rfc/rfc2396.txt">http://www.ietf.org/rfc/rfc2396.txt</a></li> |
| <li>XML Path Language (XPath) 1.0: <a |
| href="http://www.w3.org/TR/xpath">http://www.w3.org/TR/xpath</a></li> |
| <li>HTML4 parser: <a |
| href="http://www.w3.org/TR/html401/">http://www.w3.org/TR/html401/</a></li> |
| <li>most of XML Pointer Language (XPointer) Version 1.0: <a |
| href="http://www.w3.org/TR/xptr">http://www.w3.org/TR/xptr</a></li> |
| <li>XML Inclusions (XInclude) Version 1.0: <a |
| href="http://www.w3.org/TR/xinclude/">http://www.w3.org/TR/xinclude/</a></li> |
| <li>[ISO-8859-1], <a |
| href="http://www.cis.ohio-state.edu/rfc/rfc2044.txt">rfc2044</a> [UTF-8] |
| and <a href="http://www.cis.ohio-state.edu/rfc/rfc2781.txt">rfc2781</a> |
| [UTF-16] core encodings</li> |
| <li>part of SGML Open Technical Resolution TR9401:1997</li> |
| <li>XML Catalogs Working Draft 06 August 2001: <a |
| 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> |
| <li>Canonical XML Version 1.0: <a |
| href="http://www.w3.org/TR/xml-c14n">http://www.w3.org/TR/xml-c14n</a> |
| and the Exclusive XML Canonicalization CR draft <a |
| href="http://www.w3.org/TR/xml-exc-c14n">http://www.w3.org/TR/xml-exc-c14n</a></li> |
| <li>Relax NG Committee Specification 3 December 2001 <a |
| 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> |
| <li>W3C XML Schemas Part 2: Datatypes <a |
| href="http://www.w3.org/TR/2001/REC-xmlschema-2-20010502/">REC 02 May |
| 2001</a> except the base64Binary and hexBinary types</li> |
| </ul> |
| |
| <p>In most cases libxml tries to implement the specifications in a relatively |
| strictly compliant way. As of release 2.4.16, libxml2 passes all 1800+ tests |
| from the <a |
| href="http://www.oasis-open.org/committees/xml-conformance/">OASIS XML Tests |
| Suite</a>.</p> |
| |
| <p>To some extent libxml2 provides support for the following additional |
| specifications but doesn't claim to implement them completely:</p> |
| <ul> |
| <li>Document Object Model (DOM) <a |
| href="http://www.w3.org/TR/DOM-Level-2-Core/">http://www.w3.org/TR/DOM-Level-2-Core/</a> |
| it doesn't implement the API itself, gdome2 does this on top of |
| libxml2</li> |
| <li><a href="http://www.cis.ohio-state.edu/rfc/rfc959.txt">RFC 959</a> : |
| libxml implements a basic FTP client code</li> |
| <li><a href="http://www.cis.ohio-state.edu/rfc/rfc1945.txt">RFC 1945</a> : |
| HTTP/1.0, again a basic HTTP client code</li> |
| <li>SAX: a minimal SAX implementation compatible with early expat |
| versions</li> |
| <li>DocBook SGML v4: libxml2 includes a hackish parser to transition to |
| XML</li> |
| </ul> |
| |
| <p>A partial implementation of <a |
| href="http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/">XML Schemas Part |
| 1: Structure</a> is being worked on but it would be far too early to make any |
| conformance statement about it at the moment.</p> |
| |
| <p>Separate documents:</p> |
| <ul> |
| <li><a href="http://xmlsoft.org/XSLT/">the libxslt page</a> providing an |
| implementation of XSLT 1.0 and common extensions like EXSLT for |
| libxml2</li> |
| <li><a href="http://www.cs.unibo.it/~casarini/gdome2/">the gdome2 page</a> |
| : a standard DOM2 implementation for libxml2</li> |
| <li><a href="http://www.aleksey.com/xmlsec/">the XMLSec page</a>: an |
| implementation of <a href="http://www.w3.org/TR/xmldsig-core/">W3C XML |
| Digital Signature</a> for libxml2</li> |
| <li>also check the related links section below for more related and active |
| projects.</li> |
| </ul> |
| |
| <p>Results of the <a |
| href="http://xmlbench.sourceforge.net/results/benchmark/index.html">xmlbench |
| benchmark</a> on sourceforge 19 March 2003 (smaller is better):</p> |
| |
| <p align="center"><img src="benchmark.gif" |
| alt="benchmark results for Expat Xerces libxml2 Oracle and Sun toolkits"></p> |
| |
| <p>Logo designed by <a href="mailto:liyanage@access.ch">Marc Liyanage</a>.</p> |
| |
| <h2><a name="Introducti">Introduction</a></h2> |
| |
| <p>This document describes libxml, the <a |
| href="http://www.w3.org/XML/">XML</a> C library developed for the <a |
| href="http://www.gnome.org/">Gnome</a> project. <a |
| href="http://www.w3.org/XML/">XML is a standard</a> for building tag-based |
| structured documents/data.</p> |
| |
| <p>Here are some key points about libxml:</p> |
| <ul> |
| <li>Libxml exports Push (progressive) and Pull (blocking) type parser |
| interfaces for both XML and HTML.</li> |
| <li>Libxml can do DTD validation at parse time, using a parsed document |
| instance, or with an arbitrary DTD.</li> |
| <li>Libxml includes complete <a |
| href="http://www.w3.org/TR/xpath">XPath</a>, <a |
| href="http://www.w3.org/TR/xptr">XPointer</a> and <a |
| href="http://www.w3.org/TR/xinclude">XInclude</a> implementations.</li> |
| <li>It is written in plain C, making as few assumptions as possible, and |
| sticking closely to ANSI C/POSIX for easy embedding. Works on |
| Linux/Unix/Windows, ported to a number of other platforms.</li> |
| <li>Basic support for HTTP and FTP client allowing applications to fetch |
| remote resources.</li> |
| <li>The design is modular, most of the extensions can be compiled out.</li> |
| <li>The internal document representation is as close as possible to the <a |
| href="http://www.w3.org/DOM/">DOM</a> interfaces.</li> |
| <li>Libxml also has a <a href="http://www.megginson.com/SAX/index.html">SAX |
| like interface</a>; the interface is designed to be compatible with <a |
| href="http://www.jclark.com/xml/expat.html">Expat</a>.</li> |
| <li>This library is released under the <a |
| href="http://www.opensource.org/licenses/mit-license.html">MIT |
| License</a>. See the Copyright file in the distribution for the precise |
| wording.</li> |
| </ul> |
| |
| <p>Warning: unless you are forced to because your application links with a |
| Gnome-1.X library requiring it, <strong><span |
| style="background-color: #FF0000">Do Not Use libxml1</span></strong>, use |
| libxml2</p> |
| |
| <h2><a name="FAQ">FAQ</a></h2> |
| |
| <p>Table of Contents:</p> |
| <ul> |
| <li><a href="FAQ.html#License">License(s)</a></li> |
| <li><a href="FAQ.html#Installati">Installation</a></li> |
| <li><a href="FAQ.html#Compilatio">Compilation</a></li> |
| <li><a href="FAQ.html#Developer">Developer corner</a></li> |
| </ul> |
| |
| <h3><a name="License">License</a>(s)</h3> |
| <ol> |
| <li><em>Licensing Terms for libxml</em> |
| <p>libxml is released under the <a |
| href="http://www.opensource.org/licenses/mit-license.html">MIT |
| License</a>; see the file Copyright in the distribution for the precise |
| wording</p> |
| </li> |
| <li><em>Can I embed libxml in a proprietary application ?</em> |
| <p>Yes. The MIT License allows you to keep proprietary the changes you |
| made to libxml, but it would be graceful to send-back bug fixes and |
| improvements as patches for possible incorporation in the main |
| development tree.</p> |
| </li> |
| </ol> |
| |
| <h3><a name="Installati">Installation</a></h3> |
| <ol> |
| <li>Unless you are forced to because your application links with a Gnome |
| library requiring it, <strong><span style="background-color: #FF0000">Do |
| Not Use libxml1</span></strong>, use libxml2</li> |
| <li><em>Where can I get libxml</em> ? |
| <p>The original distribution comes from <a |
| href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a |
| href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">gnome.org</a></p> |
| <p>Most Linux and BSD distributions include libxml, this is probably the |
| safer way for end-users to use libxml.</p> |
| <p>David Doolin provides precompiled Windows versions at <a |
| href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p> |
| </li> |
| <li><em>I see libxml and libxml2 releases, which one should I install ?</em> |
| <ul> |
| <li>If you are not constrained by backward compatibility issues with |
| existing applications, install libxml2 only</li> |
| <li>If you are not doing development, you can safely install both. |
| Usually the packages <a |
| href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a |
| href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are |
| compatible (this is not the case for development packages).</li> |
| <li>If you are a developer and your system provides separate packaging |
| for shared libraries and the development components, it is possible |
| to install libxml and libxml2, and also <a |
| href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> |
| and <a |
| href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> |
| too for libxml2 >= 2.3.0</li> |
| <li>If you are developing a new application, please develop against |
| libxml2(-devel)</li> |
| </ul> |
| </li> |
| <li><em>I can't install the libxml package, it conflicts with libxml0</em> |
| <p>You probably have an old libxml0 package used to provide the shared |
| library for libxml.so.0, you can probably safely remove it. The libxml |
| packages provided on <a |
| href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provide |
| libxml.so.0</p> |
| </li> |
| <li><em>I can't install the libxml(2) RPM package due to failed |
| dependencies</em> |
| <p>The most generic solution is to re-fetch the latest src.rpm , and |
| rebuild it locally with</p> |
| <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> |
| <p>If everything goes well it will generate two binary rpm packages (one |
| providing the shared libs and xmllint, and the other one, the -devel |
| package, providing includes, static libraries and scripts needed to build |
| applications with libxml(2)) that you can install locally.</p> |
| </li> |
| </ol> |
| |
| <h3><a name="Compilatio">Compilation</a></h3> |
| <ol> |
| <li><em>What is the process to compile libxml ?</em> |
| <p>As most UNIX libraries libxml follows the "standard":</p> |
| <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> |
| <p><code>cd libxml-xxxx</code></p> |
| <p><code>./configure --help</code></p> |
| <p>to see the options, then the compilation/installation proper</p> |
| <p><code>./configure [possible options]</code></p> |
| <p><code>make</code></p> |
| <p><code>make install</code></p> |
| <p>At that point you may have to rerun ldconfig or a similar utility to |
| update your list of installed shared libs.</p> |
| </li> |
| <li><em>What other libraries are needed to compile/install libxml ?</em> |
| <p>Libxml does not require any other library, the normal C ANSI API |
| should be sufficient (please report any violation to this rule you may |
| find).</p> |
| <p>However if found at configuration time libxml will detect and use the |
| following libs:</p> |
| <ul> |
| <li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a |
| highly portable and available widely compression library.</li> |
| <li>iconv: a powerful character encoding conversion library. It is |
| included by default in recent glibc libraries, so it doesn't need to |
| be installed specifically on Linux. It now seems a <a |
| href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part |
| of the official UNIX</a> specification. Here is one <a |
| href="http://www.gnu.org/software/libiconv/">implementation of the |
| library</a> which source can be found <a |
| href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> |
| </ul> |
| </li> |
| <li><em>Make check fails on some platforms</em> |
| <p>Sometimes the regression tests' results don't completely match the |
| value produced by the parser, and the makefile uses diff to print the |
| delta. On some platforms the diff return breaks the compilation process; |
| if the diff is small this is probably not a serious problem.</p> |
| <p>Sometimes (especially on Solaris) make checks fail due to limitations |
| in make. Try using GNU-make instead.</p> |
| </li> |
| <li><em>I use the CVS version and there is no configure script</em> |
| <p>The configure script (and other Makefiles) are generated. Use the |
| autogen.sh script to regenerate the configure script and Makefiles, |
| like:</p> |
| <p><code>./autogen.sh --prefix=/usr --disable-shared</code></p> |
| </li> |
| <li><em>I have troubles when running make tests with gcc-3.0</em> |
| <p>It seems the initial release of gcc-3.0 has a problem with the |
| optimizer which miscompiles the URI module. Please use another |
| compiler.</p> |
| </li> |
| </ol> |
| |
| <h3><a name="Developer">Developer</a> corner</h3> |
| <ol> |
| <li><em>Troubles compiling or linking programs using libxml2</em> |
| <p>Usually the problem comes from the fact that the compiler doesn't get |
| the right compilation or linking flags. There is a small shell script |
| <code>xml2-config</code> which is installed as part of libxml2 usual |
| install process which provides those flags. Use </p> |
| <p><code>xml2-config --cflags</code></p> |
| <p>to get the compilation flags and</p> |
| <p><code>xml2-config --libs</code></p> |
| <p>to get the linker flags. Usually this is done directly from the |
| Makefile as:</p> |
| <p><code>CFLAGS=`xml2-config --cflags`</code></p> |
| <p><code>LIBS=`xml2-config --libs`</code></p> |
| </li> |
| <li><em>xmlDocDump() generates output on one line.</em> |
| <p>Libxml will not <strong>invent</strong> spaces in the content of a |
| document since <strong>all spaces in the content of a document are |
| significant</strong>. If you build a tree from the API and want |
| indentation:</p> |
| <ol> |
| <li>the correct way is to generate those yourself too.</li> |
| <li>the dangerous way is to ask libxml to add those blanks to your |
| content <strong>modifying the content of your document in the |
| process</strong>. The result may not be what you expect. There is |
| <strong>NO</strong> way to guarantee that such a modification won't |
| affect other parts of the content of your document. See <a |
| href="http://xmlsoft.org/html/libxml-parser.html#XMLKEEPBLANKSDEFAULT">xmlKeepBlanksDefault |
| ()</a> and <a |
| href="http://xmlsoft.org/html/libxml-tree.html#XMLSAVEFORMATFILE">xmlSaveFormatFile |
| ()</a></li> |
| </ol> |
| </li> |
| <li>Extra nodes in the document: |
| <p><em>For a XML file as below:</em></p> |
| <pre><?xml version="1.0"?> |
| <PLAN xmlns="http://www.argus.ca/autotest/1.0/"> |
| <NODE CommFlag="0"/> |
| <NODE CommFlag="1"/> |
| </PLAN></pre> |
| <p><em>after parsing it with the function |
| pxmlDoc=xmlParseFile(...);</em></p> |
| <p><em>I want to the get the content of the first node (node with the |
| CommFlag="0")</em></p> |
| <p><em>so I did it as following;</em></p> |
| <pre>xmlNodePtr pnode; |
| pnode=pxmlDoc->children->children;</pre> |
| <p><em>but it does not work. If I change it to</em></p> |
| <pre>pnode=pxmlDoc->children->children->next;</pre> |
| <p><em>then it works. Can someone explain it to me.</em></p> |
| <p></p> |
| <p>In XML all characters in the content of the document are significant |
| <strong>including blanks and formatting line breaks</strong>.</p> |
| <p>The extra nodes you are wondering about are just that, text nodes with |
| the formatting spaces which are part of the document but that people tend |
| to forget. There is a function <a |
| href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault |
| ()</a> to remove those at parse time, but that's an heuristic, and its |
| use should be limited to cases where you are certain there is no |
| mixed-content in the document.</p> |
| </li> |
| <li><em>I get compilation errors of existing code like when accessing |
| <strong>root</strong> or <strong>child fields</strong> of nodes.</em> |
| <p>You are compiling code developed for libxml version 1 and using a |
| libxml2 development environment. Either switch back to libxml v1 devel or |
| even better fix the code to compile with libxml2 (or both) by <a |
| href="upgrade.html">following the instructions</a>.</p> |
| </li> |
| <li><em>I get compilation errors about non existing |
| <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> |
| fields.</em> |
| <p>The source code you are using has been <a |
| href="upgrade.html">upgraded</a> to be able to compile with both libxml |
| and libxml2, but you need to install a more recent version: |
| libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> |
| </li> |
| <li><em>XPath implementation looks seriously broken</em> |
| <p>XPath implementation prior to 2.3.0 was really incomplete. Upgrade to |
| a recent version, there are no known bugs in the current version.</p> |
| </li> |
| <li><em>The example provided in the web page does not compile.</em> |
| <p>It's hard to maintain the documentation in sync with the code |
| <grin/> ...</p> |
| <p>Check the previous points 1/ and 2/ raised before, and please send |
| patches.</p> |
| </li> |
| <li><em>Where can I get more examples and information than privoded on the |
| web page?</em> |
| <p>Ideally a libxml book would be nice. I have no such plan ... But you |
| can:</p> |
| <ul> |
| <li>check more deeply the <a href="html/libxml-lib.html">existing |
| generated doc</a></li> |
| <li>look for examples of use for libxml function using the Gnome code. |
| For example the following will query the full Gnome CVS base for the |
| use of the <strong>xmlAddChild()</strong> function: |
| <p><a |
| href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> |
| <p>This may be slow, a large hardware donation to the gnome project |
| could cure this :-)</p> |
| </li> |
| <li><a |
| href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse |
| the libxml source</a> , I try to write code as clean and documented |
| as possible, so looking at it may be helpful. In particular the code |
| of xmllint.c and of the various testXXX.c test programs should |
| provide good examples of how to do things with the library.</li> |
| </ul> |
| </li> |
| <li>What about C++ ? |
| <p>libxml is written in pure C in order to allow easy reuse on a number |
| of platforms, including embedded systems. I don't intend to convert to |
| C++.</p> |
| <p>There are however a few C++ wrappers which may fulfill your needs:</p> |
| <ul> |
| <li>by Ari Johnson <ari@btigate.com>: |
| <p>Website: <a |
| href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p> |
| <p>Download: <a |
| href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p> |
| </li> |
| <li>by Peter Jones <pjones@pmade.org> |
| <p>Website: <a |
| href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> |
| </li> |
| </ul> |
| </li> |
| <li>How to validate a document a posteriori ? |
| <p>It is possible to validate documents which had not been validated at |
| initial parsing time or documents which have been built from scratch |
| using the API. Use the <a |
| href="http://xmlsoft.org/html/libxml-valid.html#XMLVALIDATEDTD">xmlValidateDtd()</a> |
| function. It is also possible to simply add a DTD to an existing |
| document:</p> |
| <pre>xmlDocPtr doc; /* your existing document */ |
| xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ |
| |
| dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ |
| |
| doc->intSubset = dtd; |
| if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); |
| else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); |
| </pre> |
| </li> |
| <li>So what is this funky "xmlChar" used all the time? |
| <p>It is a null terminated sequence of utf-8 characters. And only utf-8! |
| You need to convert strings encoded in different ways to utf-8 before |
| passing them to the API. This can be accomplished with the iconv library |
| for instance.</p> |
| </li> |
| <li>etc ...</li> |
| </ol> |
| |
| <p></p> |
| |
| <h2><a name="Documentat">Developer Documentation</a></h2> |
| |
| <p>There are several on-line resources related to using libxml:</p> |
| <ol> |
| <li>Use the <a href="search.php">search engine</a> to lookup |
| informations.</li> |
| <li>Check the <a href="FAQ.html">FAQ.</a></li> |
| <li>Check the <a href="http://xmlsoft.org/html/libxml-lib.html">extensive |
| documentation</a> automatically extracted from code comments (using <a |
| href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gtk-doc">gtk |
| doc</a>).</li> |
| <li>Look at the documentation about <a href="encoding.html">libxml |
| internationalization support</a>.</li> |
| <li>This page provides a global overview and <a href="example.html">some |
| examples</a> on how to use libxml.</li> |
| <li>John Fleck's libxml tutorial: <a href="tutorial/index.html">html</a> or |
| <a href="tutorial/xmltutorial.pdf">pdf</a>.</li> |
| <li>If you need to parse large files, check the <a |
| href="xmlreader.html">xmlReader</a> API tutorial</li> |
| <li><a href="mailto:james@daa.com.au">James Henstridge</a> wrote <a |
| href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">some nice |
| documentation</a> explaining how to use the libxml SAX interface.</li> |
| <li>George Lebl wrote <a |
| href="http://www-4.ibm.com/software/developer/library/gnome3/">an article |
| for IBM developerWorks</a> about using libxml.</li> |
| <li>Check <a href="http://cvs.gnome.org/lxr/source/gnome-xml/TODO">the TODO |
| file</a>.</li> |
| <li>Read the <a href="upgrade.html">1.x to 2.x upgrade path</a> |
| description. If you are starting a new project using libxml you should |
| really use the 2.x version.</li> |
| <li>And don't forget to look at the <a |
| href="http://mail.gnome.org/archives/xml/">mailing-list archive</a>.</li> |
| </ol> |
| |
| <h2><a name="Reporting">Reporting bugs and getting help</a></h2> |
| |
| <p>Well, bugs or missing features are always possible, and I will make a |
| point of fixing them in a timely fashion. The best way to report a bug is to |
| use the <a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome |
| bug tracking database</a> (make sure to use the "libxml2" module name). I |
| look at reports there regularly and it's good to have a reminder when a bug |
| is still open. Be sure to specify that the bug is for the package libxml2.</p> |
| |
| <p>There is also a mailing-list <a |
| href="mailto:xml@gnome.org">xml@gnome.org</a> for libxml, with an <a |
| href="http://mail.gnome.org/archives/xml/">on-line archive</a> (<a |
| href="http://xmlsoft.org/messages">old</a>). To subscribe to this list, |
| please visit the <a |
| href="http://mail.gnome.org/mailman/listinfo/xml">associated Web</a> page and |
| follow the instructions. <strong>Do not send code, I won't debug it</strong> |
| (but patches are really appreciated!).</p> |
| |
| <p>Check the following <strong><span style="color: #FF0000">before |
| posting</span></strong>:</p> |
| <ul> |
| <li>Read the <a href="FAQ.html">FAQ</a> and <a href="search.php">use the |
| search engine</a> to get informations related to your problem.</li> |
| <li>Make sure you are <a href="ftp://xmlsoft.org/">using a recent |
| version</a>, and that the problem still shows up in a recent version.</li> |
| <li>Check the <a href="http://mail.gnome.org/archives/xml/">list |
| archives</a> to see if the problem was reported already. In this case |
| there is probably a fix available, similarly check the <a |
| href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">registered |
| open bugs</a>.</li> |
| <li>Make sure you can reproduce the bug with xmllint or one of the test |
| programs found in source in the distribution.</li> |
| <li>Please send the command showing the error as well as the input (as an |
| attachment)</li> |
| </ul> |
| |
| <p>Then send the bug with associated informations to reproduce it to the <a |
| href="mailto:xml@gnome.org">xml@gnome.org</a> list; if it's really libxml |
| related I will approve it. Please do not send mail to me directly, it makes |
| things really hard to track and in some cases I am not the best person to |
| answer a given question, ask on the list.</p> |
| |
| <p>To <span style="color: #E50000">be really clear about support</span>:</p> |
| <ul> |
| <li>Support or help <span style="color: #E50000">request MUST be sent to |
| the list or on bugzilla</span> in case of problems, so that the Question |
| and Answers can be shared publicly. Failing to do so carries the implicit |
| message "I want free support but I don't want to share the benefits with |
| others" and is not welcome. I will automatically Carbon-Copy the |
| xml@gnome.org mailing list for any technical reply made about libxml2 or |
| libxslt.</li> |
| <li>There is <span style="color: #E50000">no garantee for support</span>, |
| if your question remains unanswered after a week, repost it, making sure |
| you gave all the detail needed and the informations requested.</li> |
| <li>Failing to provide informations as requested or double checking first |
| for prior feedback also carries the implicit message "the time of the |
| library maintainers is less valuable than my time" and might not be |
| welcome.</li> |
| </ul> |
| |
| <p>Of course, bugs reported with a suggested patch for fixing them will |
| probably be processed faster than those without.</p> |
| |
| <p>If you're looking for help, a quick look at <a |
| href="http://mail.gnome.org/archives/xml/">the list archive</a> may actually |
| provide the answer. I usually send source samples when answering libxml usage |
| questions. The <a href="http://xmlsoft.org/html/book1.html">auto-generated |
| documentation</a> is not as polished as I would like (i need to learn more |
| about DocBook), but it's a good starting point.</p> |
| |
| <h2><a name="help">How to help</a></h2> |
| |
| <p>You can help the project in various ways, the best thing to do first is to |
| subscribe to the mailing-list as explained before, check the <a |
| href="http://mail.gnome.org/archives/xml/">archives </a>and the <a |
| href="http://bugzilla.gnome.org/buglist.cgi?product=libxml">Gnome bug |
| database</a>:</p> |
| <ol> |
| <li>Provide patches when you find problems.</li> |
| <li>Provide the diffs when you port libxml to a new platform. They may not |
| be integrated in all cases but help pinpointing portability problems |
| and</li> |
| <li>Provide documentation fixes (either as patches to the code comments or |
| as HTML diffs).</li> |
| <li>Provide new documentations pieces (translations, examples, etc |
| ...).</li> |
| <li>Check the TODO file and try to close one of the items.</li> |
| <li>Take one of the points raised in the archive or the bug database and |
| provide a fix. <a href="mailto:daniel@veillard.com">Get in touch with me |
| </a>before to avoid synchronization problems and check that the suggested |
| fix will fit in nicely :-)</li> |
| </ol> |
| |
| <h2><a name="Downloads">Downloads</a></h2> |
| |
| <p>The latest versions of libxml can be found on <a |
| href="ftp://xmlsoft.org/">xmlsoft.org</a> (<a |
| href="ftp://speakeasy.rpmfind.net/pub/libxml/">Seattle</a>, <a |
| href="ftp://fr.rpmfind.net/pub/libxml/">France</a>) or on the <a |
| href="ftp://ftp.gnome.org/pub/GNOME/MIRRORS.html">Gnome FTP server</a> either |
| as a <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">source |
| archive</a><!-- commenting this out because they seem to have disappeared or <a |
| href="ftp://ftp.gnome.org/pub/GNOME/stable/redhat/i386/libxml/">RPM |
| packages</a> --> |
| , Antonin Sprinzl also provide <a href="ftp://gd.tuwien.ac.at/pub/libxml/">a |
| mirror in Austria</a>. (NOTE that you need both the <a |
| href="http://rpmfind.net/linux/RPM/libxml2.html">libxml(2)</a> and <a |
| href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml(2)-devel</a> |
| packages installed to compile applications using libxml.)</p> |
| |
| <p>Binary ports:</p> |
| <ul> |
| <li>Red Hat RPMs for i386 are available directly on <a |
| href="ftp://xmlsoft.org/">xmlsoft.org</a>, the source RPM will compile on |
| any architecture supported by Red Hat.</li> |
| <li><p><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a></p> |
| is now the maintainer of the Windows port, <a |
| href="http://www.zlatkovic.com/projects/libxml/index.html">he provides |
| binaries</a>.</li> |
| <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides |
| <a href="http://garypennington.net/libxml2/">Solaris binaries</a>.</li> |
| <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a> provides <a |
| href="http://www.zveno.com/open_source/libxml2xslt.html">Mac Os X |
| binaries</a>.</li> |
| <li>The HP-UX porting center provides <a |
| href="http://hpux.connect.org.uk/hppd/hpux/Gnome/">HP-UX binaries</a></li> |
| </ul> |
| |
| <p>If you know other supported binary ports, please <a |
| href="http://veillard.com/">contact me</a>.</p> |
| |
| <p><a name="Snapshot">Snapshot:</a></p> |
| <ul> |
| <li>Code from the W3C cvs base libxml <a |
| href="ftp://xmlsoft.org/cvs-snapshot.tar.gz">cvs-snapshot.tar.gz</a>.</li> |
| <li>Docs, content of the web site, the list archive included <a |
| href="ftp://xmlsoft.org/libxml-docs.tar.gz">libxml-docs.tar.gz</a>.</li> |
| </ul> |
| |
| <p><a name="Contribs">Contributions:</a></p> |
| |
| <p>I do accept external contributions, especially if compiling on another |
| platform, get in touch with me to upload the package, wrappers for various |
| languages have been provided, and can be found in the <a |
| href="contribs.html">contrib section</a></p> |
| |
| <p>Libxml is also available from CVS:</p> |
| <ul> |
| <li><p>The <a |
| href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Gnome |
| CVS base</a>. Check the <a |
| href="http://developer.gnome.org/tools/cvs.html">Gnome CVS Tools</a> |
| page; the CVS module is <b>gnome-xml</b>.</p> |
| </li> |
| <li>The <strong>libxslt</strong> module is also present there</li> |
| </ul> |
| |
| <h2><a name="News">News</a></h2> |
| |
| <h3>CVS only : check the <a |
| href="http://cvs.gnome.org/lxr/source/gnome-xml/ChangeLog">Changelog</a> file |
| for a really accurate description</h3> |
| |
| <p>Items not finished and worked on, get in touch with the list if you want |
| to test those</p> |
| <ul> |
| <li>More testing on RelaxNG</li> |
| <li>Finishing up <a href="http://www.w3.org/TR/xmlschema-1/">XML |
| Schemas</a></li> |
| </ul> |
| |
| <h3>2.5.7: Apr 25 2003</h3> |
| <ul> |
| <li>Relax-NG: Compiling to regexp and streaming validation on top of the |
| xmlReader interface, added to xmllint --stream</li> |
| <li>xmlReader: Expand(), Next() and DOM access glue, bug fixes</li> |
| <li>Support for large files: RGN validated a 4.5GB instance</li> |
| <li>Thread support is now configured in by default</li> |
| <li>Fixes: update of the Trio code (Bjorn), WXS Date and Duration fixes |
| (Charles Bozeman), DTD and namespaces (Brent Hendricks), HTML push parser |
| and zero bytes handling, some missing Windows file path conversions, |
| behaviour of the parser and validator in the presence of "out of memory" |
| error conditions</li> |
| <li>extended the API to be able to plug a garbage collecting memory |
| allocator, added xmlMallocAtomic() and modified the allocations |
| accordingly.</li> |
| <li>Performances: removed excessive malloc() calls, speedup of the push and |
| xmlReader interfaces, removed excessive thread locking</li> |
| <li>Documentation: man page (John Fleck), xmlReader documentation</li> |
| <li>Python: adding binding for xmlCatalogAddLocal (Brent M Hendricks)</li> |
| </ul> |
| |
| <h3>2.5.6: Apr 1 2003</h3> |
| <ul> |
| <li>Fixed W3C XML Schemas datatype, should be compliant now except for |
| binHex and base64 which are not supported yet.</li> |
| <li>bug fixes: non-ASCII IDs, HTML output, XInclude on large docs and |
| XInclude entities handling, encoding detection on external subsets, XML |
| Schemas bugs and memory leaks, HTML parser (James Bursa)</li> |
| <li>portability: python/trio (Albert Chin), Sun compiler warnings</li> |
| <li>documentation: added --relaxng option to xmllint man page (John)</li> |
| <li>improved error reporting: xml:space, start/end tag mismatches, Relax NG |
| errors</li> |
| </ul> |
| |
| <h3>2.5.5: Mar 24 2003</h3> |
| <ul> |
| <li>Lot of fixes on the Relax NG implementation. More testing including |
| DocBook and TEI examples.</li> |
| <li>Increased the support for W3C XML Schemas datatype</li> |
| <li>Several bug fixes in the URI handling layer</li> |
| <li>Bug fixes: HTML parser, xmlReader, DTD validation, XPath, encoding |
| conversion, line counting in the parser.</li> |
| <li>Added support for $XMLLINT_INDENT environment variable, FTP delete</li> |
| <li>Fixed the RPM spec file name</li> |
| </ul> |
| |
| <h3>2.5.4: Feb 20 2003</h3> |
| <ul> |
| <li>Conformance testing and lot of fixes on Relax NG and XInclude |
| implementation</li> |
| <li>Implementation of XPointer element() scheme</li> |
| <li>Bug fixes: XML parser, XInclude entities merge, validity checking on |
| namespaces, |
| <p>2 serialization bugs, node info generation problems, a DTD regexp |
| generation problem.</p> |
| </li> |
| <li>Portability: windows updates and path canonicalization (Igor)</li> |
| <li>A few typo fixes (Kjartan Maraas)</li> |
| <li>Python bindings generator fixes (Stephane Bidoul)</li> |
| </ul> |
| |
| <h3>2.5.3: Feb 10 2003</h3> |
| <ul> |
| <li>RelaxNG and XML Schemas datatypes improvements, and added a first |
| version of RelaxNG Python bindings</li> |
| <li>Fixes: XLink (Sean Chittenden), XInclude (Sean Chittenden), API fix for |
| serializing namespace nodes, encoding conversion bug, XHTML1 |
| serialization</li> |
| <li>Portability fixes: Windows (Igor), AMD 64bits RPM spec file</li> |
| </ul> |
| |
| <h3>2.5.2: Feb 5 2003</h3> |
| <ul> |
| <li>First implementation of RelaxNG, added --relaxng flag to xmllint</li> |
| <li>Schemas support now compiled in by default.</li> |
| <li>Bug fixes: DTD validation, namespace checking, XInclude and entities, |
| delegateURI in XML Catalogs, HTML parser, XML reader (Stéphane Bidoul), |
| XPath parser and evaluation, UTF8ToUTF8 serialization, XML reader memory |
| consumption, HTML parser, HTML serialization in the presence of |
| namespaces</li> |
| <li>added an HTML API to check elements and attributes.</li> |
| <li>Documentation improvement, PDF for the tutorial (John Fleck), doc |
| patches (Stefan Kost)</li> |
| <li>Portability fixes: NetBSD (Julio Merino), Windows (Igor Zlatkovic)</li> |
| <li>Added python bindings for XPointer, contextual error reporting |
| (Stéphane Bidoul)</li> |
| <li>URI/file escaping problems (Stefano Zacchiroli)</li> |
| </ul> |
| |
| <h3>2.5.1: Jan 8 2003</h3> |
| <ul> |
| <li>Fixes a memory leak and configuration/compilation problems in 2.5.0</li> |
| <li>documentation updates (John)</li> |
| <li>a couple of XmlTextReader fixes</li> |
| </ul> |
| |
| <h3>2.5.0: Jan 6 2003</h3> |
| <ul> |
| <li>New <a href="xmlreader.html">XmltextReader interface</a> based on C# |
| API (with help of Stéphane Bidoul)</li> |
| <li>Windows: more exports, including the new API (Igor)</li> |
| <li>XInclude fallback fix</li> |
| <li>Python: bindings for the new API, packaging (Stéphane Bidoul), |
| drv_libxml2.py Python xml.sax driver (Stéphane Bidoul), fixes, speedup |
| and iterators for Python-2.2 (Hannu Krosing)</li> |
| <li>Tutorial fixes (john Fleck and Niraj Tolia) xmllint man update |
| (John)</li> |
| <li>Fix an XML parser bug raised by Vyacheslav Pindyura</li> |
| <li>Fix for VMS serialization (Nigel Hall) and config (Craig A. Berry)</li> |
| <li>Entities handling fixes</li> |
| <li>new API to optionally track node creation and deletion (Lukas |
| Schroeder)</li> |
| <li>Added documentation for the XmltextReader interface and some <a |
| href="guidelines.html">XML guidelines</a></li> |
| </ul> |
| |
| <h3>2.4.30: Dec 12 2002</h3> |
| <ul> |
| <li>2.4.29 broke the python bindings, rereleasing</li> |
| <li>Improvement/fixes of the XML API generator, and couple of minor code |
| fixes.</li> |
| </ul> |
| |
| <h3>2.4.29: Dec 11 2002</h3> |
| <ul> |
| <li>Windows fixes (Igor): Windows CE port, pthread linking, python bindings |
| (Stéphane Bidoul), Mingw (Magnus Henoch), and export list updates</li> |
| <li>Fix for prev in python bindings (ERDI Gergo)</li> |
| <li>Fix for entities handling (Marcus Clarke)</li> |
| <li>Refactored the XML and HTML dumps to a single code path, fixed XHTML1 |
| dump</li> |
| <li>Fix for URI parsing when handling URNs with fragment identifiers</li> |
| <li>Fix for HTTP URL escaping problem</li> |
| <li>added an TextXmlReader (C#) like API (work in progress)</li> |
| <li>Rewrote the API in XML generation script, includes a C parser and saves |
| more informations needed for C# bindings</li> |
| </ul> |
| |
| <h3>2.4.28: Nov 22 2002</h3> |
| <ul> |
| <li>a couple of python binding fixes</li> |
| <li>2 bug fixes in the XML push parser</li> |
| <li>potential memory leak removed (Martin Stoilov)</li> |
| <li>fix to the configure script for Unix (Dimitri Papadopoulos)</li> |
| <li>added encoding support for XInclude parse="text"</li> |
| <li>autodetection of XHTML1 and specific serialization rules added</li> |
| <li>nasty threading bug fixed (William Brack)</li> |
| </ul> |
| |
| <h3>2.4.27: Nov 17 2002</h3> |
| <ul> |
| <li>fixes for the Python bindings</li> |
| <li>a number of bug fixes: SGML catalogs, xmlParseBalancedChunkMemory(), |
| HTML parser, Schemas (Charles Bozeman), document fragment support |
| (Christian Glahn), xmlReconciliateNs (Brian Stafford), XPointer, |
| xmlFreeNode(), xmlSAXParseMemory (Peter Jones), xmlGetNodePath (Petr |
| Pajas), entities processing</li> |
| <li>added grep to xmllint --shell</li> |
| <li>VMS update patch from Craig A. Berry</li> |
| <li>cleanup of the Windows build with support for more compilers (Igor), |
| better thread support on Windows</li> |
| <li>cleanup of Unix Makefiles and spec file</li> |
| <li>Improvements to the documentation (John Fleck)</li> |
| </ul> |
| |
| <h3>2.4.26: Oct 18 2002</h3> |
| <ul> |
| <li>Patches for Windows CE port, improvements on Windows paths handling</li> |
| <li>Fixes to the validation code (DTD and Schemas), xmlNodeGetPath() , |
| HTML serialization, Namespace compliance, and a number of small |
| problems</li> |
| </ul> |
| |
| <h3>2.4.25: Sep 26 2002</h3> |
| <ul> |
| <li>A number of bug fixes: XPath, validation, Python bindings, DOM and |
| tree, xmlI/O, Html</li> |
| <li>Serious rewrite of XInclude</li> |
| <li>Made XML Schemas regexp part of the default build and APIs, small fix |
| and improvement of the regexp core</li> |
| <li>Changed the validation code to reuse XML Schemas regexp APIs</li> |
| <li>Better handling of Windows file paths, improvement of Makefiles (Igor, |
| Daniel Gehriger, Mark Vakoc)</li> |
| <li>Improved the python I/O bindings, the tests, added resolver and regexp |
| APIs</li> |
| <li>New logos from Marc Liyanage</li> |
| <li>Tutorial improvements: John Fleck, Christopher Harris</li> |
| <li>Makefile: Fixes for AMD x86_64 (Mandrake), DESTDIR (Christophe |
| Merlet)</li> |
| <li>removal of all stderr/perror use for error reporting</li> |
| <li>Better error reporting: XPath and DTD validation</li> |
| <li>update of the trio portability layer (Bjorn Reese)</li> |
| </ul> |
| |
| <p><strong>2.4.24: Aug 22 2002</strong></p> |
| <ul> |
| <li>XPath fixes (William), xf:escape-uri() (Wesley Terpstra)</li> |
| <li>Python binding fixes: makefiles (William), generator, rpm build, x86-64 |
| (fcrozat)</li> |
| <li>HTML <style> and boolean attributes serializer fixes</li> |
| <li>C14N improvements by Aleksey</li> |
| <li>doc cleanups: Rick Jones</li> |
| <li>Windows compiler makefile updates: Igor and Elizabeth Barham</li> |
| <li>XInclude: implementation of fallback and xml:base fixup added</li> |
| </ul> |
| |
| <h3>2.4.23: July 6 2002</h3> |
| <ul> |
| <li>performances patches: Peter Jacobi</li> |
| <li>c14n fixes, testsuite and performances: Aleksey Sanin</li> |
| <li>added xmlDocFormatDump: Chema Celorio</li> |
| <li>new tutorial: John Fleck</li> |
| <li>new hash functions and performances: Sander Vesik, portability fix from |
| Peter Jacobi</li> |
| <li>a number of bug fixes: XPath (William Brack, Richard Jinks), XML and |
| HTML parsers, ID lookup function</li> |
| <li>removal of all remaining sprintf: Aleksey Sanin</li> |
| </ul> |
| |
| <h3>2.4.22: May 27 2002</h3> |
| <ul> |
| <li>a number of bug fixes: configure scripts, base handling, parser, memory |
| usage, HTML parser, XPath, documentation (Christian Cornelssen), |
| indentation, URI parsing</li> |
| <li>Optimizations for XMLSec, fixing and making public some of the network |
| protocol handlers (Aleksey)</li> |
| <li>performance patch from Gary Pennington</li> |
| <li>Charles Bozeman provided date and time support for XML Schemas |
| datatypes</li> |
| </ul> |
| |
| <h3>2.4.21: Apr 29 2002</h3> |
| |
| <p>This release is both a bug fix release and also contains the early XML |
| Schemas <a href="http://www.w3.org/TR/xmlschema-1/">structures</a> and <a |
| href="http://www.w3.org/TR/xmlschema-2/">datatypes</a> code, beware, all |
| interfaces are likely to change, there is huge holes, it is clearly a work in |
| progress and don't even think of putting this code in a production system, |
| it's actually not compiled in by default. The real fixes are:</p> |
| <ul> |
| <li>a couple of bugs or limitations introduced in 2.4.20</li> |
| <li>patches for Borland C++ and MSC by Igor</li> |
| <li>some fixes on XPath strings and conformance patches by Richard |
| Jinks</li> |
| <li>patch from Aleksey for the ExcC14N specification</li> |
| <li>OSF/1 bug fix by Bjorn</li> |
| </ul> |
| |
| <h3>2.4.20: Apr 15 2002</h3> |
| <ul> |
| <li>bug fixes: file descriptor leak, XPath, HTML output, DTD validation</li> |
| <li>XPath conformance testing by Richard Jinks</li> |
| <li>Portability fixes: Solaris, MPE/iX, Windows, OSF/1, python bindings, |
| libxml.m4</li> |
| </ul> |
| |
| <h3>2.4.19: Mar 25 2002</h3> |
| <ul> |
| <li>bug fixes: half a dozen XPath bugs, Validation, ISO-Latin to UTF8 |
| encoder</li> |
| <li>portability fixes in the HTTP code</li> |
| <li>memory allocation checks using valgrind, and profiling tests</li> |
| <li>revamp of the Windows build and Makefiles</li> |
| </ul> |
| |
| <h3>2.4.18: Mar 18 2002</h3> |
| <ul> |
| <li>bug fixes: tree, SAX, canonicalization, validation, portability, |
| XPath</li> |
| <li>removed the --with-buffer option it was becoming unmaintainable</li> |
| <li>serious cleanup of the Python makefiles</li> |
| <li>speedup patch to XPath very effective for DocBook stylesheets</li> |
| <li>Fixes for Windows build, cleanup of the documentation</li> |
| </ul> |
| |
| <h3>2.4.17: Mar 8 2002</h3> |
| <ul> |
| <li>a lot of bug fixes, including "namespace nodes have no parents in |
| XPath"</li> |
| <li>fixed/improved the Python wrappers, added more examples and more |
| regression tests, XPath extension functions can now return node-sets</li> |
| <li>added the XML Canonicalization support from Aleksey Sanin</li> |
| </ul> |
| |
| <h3>2.4.16: Feb 20 2002</h3> |
| <ul> |
| <li>a lot of bug fixes, most of them were triggered by the XML Testsuite |
| from OASIS and W3C. Compliance has been significantly improved.</li> |
| <li>a couple of portability fixes too.</li> |
| </ul> |
| |
| <h3>2.4.15: Feb 11 2002</h3> |
| <ul> |
| <li>Fixed the Makefiles, especially the python module ones</li> |
| <li>A few bug fixes and cleanup</li> |
| <li>Includes cleanup</li> |
| </ul> |
| |
| <h3>2.4.14: Feb 8 2002</h3> |
| <ul> |
| <li>Change of License to the <a |
| href="http://www.opensource.org/licenses/mit-license.html">MIT |
| License</a> basically for integration in XFree86 codebase, and removing |
| confusion around the previous dual-licensing</li> |
| <li>added Python bindings, beta software but should already be quite |
| complete</li> |
| <li>a large number of fixes and cleanups, especially for all tree |
| manipulations</li> |
| <li>cleanup of the headers, generation of a reference API definition in |
| XML</li> |
| </ul> |
| |
| <h3>2.4.13: Jan 14 2002</h3> |
| <ul> |
| <li>update of the documentation: John Fleck and Charlie Bozeman</li> |
| <li>cleanup of timing code from Justin Fletcher</li> |
| <li>fixes for Windows and initial thread support on Win32: Igor and Serguei |
| Narojnyi</li> |
| <li>Cygwin patch from Robert Collins</li> |
| <li>added xmlSetEntityReferenceFunc() for Keith Isdale work on xsldbg</li> |
| </ul> |
| |
| <h3>2.4.12: Dec 7 2001</h3> |
| <ul> |
| <li>a few bug fixes: thread (Gary Pennington), xmllint (Geert Kloosterman), |
| XML parser (Robin Berjon), XPointer (Danny Jamshy), I/O cleanups |
| (robert)</li> |
| <li>Eric Lavigne contributed project files for MacOS</li> |
| <li>some makefiles cleanups</li> |
| </ul> |
| |
| <h3>2.4.11: Nov 26 2001</h3> |
| <ul> |
| <li>fixed a couple of errors in the includes, fixed a few bugs, some code |
| cleanups</li> |
| <li>xmllint man pages improvement by Heiko Rupp</li> |
| <li>updated VMS build instructions from John A Fotheringham</li> |
| <li>Windows Makefiles updates from Igor</li> |
| </ul> |
| |
| <h3>2.4.10: Nov 10 2001</h3> |
| <ul> |
| <li>URI escaping fix (Joel Young)</li> |
| <li>added xmlGetNodePath() (for paths or XPointers generation)</li> |
| <li>Fixes namespace handling problems when using DTD and validation</li> |
| <li>improvements on xmllint: Morus Walter patches for --format and |
| --encode, Stefan Kost and Heiko Rupp improvements on the --shell</li> |
| <li>fixes for xmlcatalog linking pointed by Weiqi Gao</li> |
| <li>fixes to the HTML parser</li> |
| </ul> |
| |
| <h3>2.4.9: Nov 6 2001</h3> |
| <ul> |
| <li>fixes more catalog bugs</li> |
| <li>avoid a compilation problem, improve xmlGetLineNo()</li> |
| </ul> |
| |
| <h3>2.4.8: Nov 4 2001</h3> |
| <ul> |
| <li>fixed SGML catalogs broken in previous release, updated xmlcatalog |
| tool</li> |
| <li>fixed a compile errors and some includes troubles.</li> |
| </ul> |
| |
| <h3>2.4.7: Oct 30 2001</h3> |
| <ul> |
| <li>exported some debugging interfaces</li> |
| <li>serious rewrite of the catalog code</li> |
| <li>integrated Gary Pennington thread safety patch, added configure option |
| and regression tests</li> |
| <li>removed an HTML parser bug</li> |
| <li>fixed a couple of potentially serious validation bugs</li> |
| <li>integrated the SGML DocBook support in xmllint</li> |
| <li>changed the nanoftp anonymous login passwd</li> |
| <li>some I/O cleanup and a couple of interfaces for Perl wrapper</li> |
| <li>general bug fixes</li> |
| <li>updated xmllint man page by John Fleck</li> |
| <li>some VMS and Windows updates</li> |
| </ul> |
| |
| <h3>2.4.6: Oct 10 2001</h3> |
| <ul> |
| <li>added an updated man pages by John Fleck</li> |
| <li>portability and configure fixes</li> |
| <li>an infinite loop on the HTML parser was removed (William)</li> |
| <li>Windows makefile patches from Igor</li> |
| <li>fixed half a dozen bugs reported for libxml or libxslt</li> |
| <li>updated xmlcatalog to be able to modify SGML super catalogs</li> |
| </ul> |
| |
| <h3>2.4.5: Sep 14 2001</h3> |
| <ul> |
| <li>Remove a few annoying bugs in 2.4.4</li> |
| <li>forces the HTML serializer to output decimal charrefs since some |
| version of Netscape can't handle hexadecimal ones</li> |
| </ul> |
| |
| <h3>1.8.16: Sep 14 2001</h3> |
| <ul> |
| <li>maintenance release of the old libxml1 branch, couple of bug and |
| portability fixes</li> |
| </ul> |
| |
| <h3>2.4.4: Sep 12 2001</h3> |
| <ul> |
| <li>added --convert to xmlcatalog, bug fixes and cleanups of XML |
| Catalog</li> |
| <li>a few bug fixes and some portability changes</li> |
| <li>some documentation cleanups</li> |
| </ul> |
| |
| <h3>2.4.3: Aug 23 2001</h3> |
| <ul> |
| <li>XML Catalog support see the doc</li> |
| <li>New NaN/Infinity floating point code</li> |
| <li>A few bug fixes</li> |
| </ul> |
| |
| <h3>2.4.2: Aug 15 2001</h3> |
| <ul> |
| <li>adds xmlLineNumbersDefault() to control line number generation</li> |
| <li>lot of bug fixes</li> |
| <li>the Microsoft MSC projects files should now be up to date</li> |
| <li>inheritance of namespaces from DTD defaulted attributes</li> |
| <li>fixes a serious potential security bug</li> |
| <li>added a --format option to xmllint</li> |
| </ul> |
| |
| <h3>2.4.1: July 24 2001</h3> |
| <ul> |
| <li>possibility to keep line numbers in the tree</li> |
| <li>some computation NaN fixes</li> |
| <li>extension of the XPath API</li> |
| <li>cleanup for alpha and ia64 targets</li> |
| <li>patch to allow saving through HTTP PUT or POST</li> |
| </ul> |
| |
| <h3>2.4.0: July 10 2001</h3> |
| <ul> |
| <li>Fixed a few bugs in XPath, validation, and tree handling.</li> |
| <li>Fixed XML Base implementation, added a couple of examples to the |
| regression tests</li> |
| <li>A bit of cleanup</li> |
| </ul> |
| |
| <h3>2.3.14: July 5 2001</h3> |
| <ul> |
| <li>fixed some entities problems and reduce memory requirement when |
| substituting them</li> |
| <li>lots of improvements in the XPath queries interpreter can be |
| substantially faster</li> |
| <li>Makefiles and configure cleanups</li> |
| <li>Fixes to XPath variable eval, and compare on empty node set</li> |
| <li>HTML tag closing bug fixed</li> |
| <li>Fixed an URI reference computation problem when validating</li> |
| </ul> |
| |
| <h3>2.3.13: June 28 2001</h3> |
| <ul> |
| <li>2.3.12 configure.in was broken as well as the push mode XML parser</li> |
| <li>a few more fixes for compilation on Windows MSC by Yon Derek</li> |
| </ul> |
| |
| <h3>1.8.14: June 28 2001</h3> |
| <ul> |
| <li>Zbigniew Chyla gave a patch to use the old XML parser in push mode</li> |
| <li>Small Makefile fix</li> |
| </ul> |
| |
| <h3>2.3.12: June 26 2001</h3> |
| <ul> |
| <li>lots of cleanup</li> |
| <li>a couple of validation fix</li> |
| <li>fixed line number counting</li> |
| <li>fixed serious problems in the XInclude processing</li> |
| <li>added support for UTF8 BOM at beginning of entities</li> |
| <li>fixed a strange gcc optimizer bugs in xpath handling of float, gcc-3.0 |
| miscompile uri.c (William), Thomas Leitner provided a fix for the |
| optimizer on Tru64</li> |
| <li>incorporated Yon Derek and Igor Zlatkovic fixes and improvements for |
| compilation on Windows MSC</li> |
| <li>update of libxml-doc.el (Felix Natter)</li> |
| <li>fixed 2 bugs in URI normalization code</li> |
| </ul> |
| |
| <h3>2.3.11: June 17 2001</h3> |
| <ul> |
| <li>updates to trio, Makefiles and configure should fix some portability |
| problems (alpha)</li> |
| <li>fixed some HTML serialization problems (pre, script, and block/inline |
| handling), added encoding aware APIs, cleanup of this code</li> |
| <li>added xmlHasNsProp()</li> |
| <li>implemented a specific PI for encoding support in the DocBook SGML |
| parser</li> |
| <li>some XPath fixes (-Infinity, / as a function parameter and namespaces |
| node selection)</li> |
| <li>fixed a performance problem and an error in the validation code</li> |
| <li>fixed XInclude routine to implement the recursive behaviour</li> |
| <li>fixed xmlFreeNode problem when libxml is included statically twice</li> |
| <li>added --version to xmllint for bug reports</li> |
| </ul> |
| |
| <h3>2.3.10: June 1 2001</h3> |
| <ul> |
| <li>fixed the SGML catalog support</li> |
| <li>a number of reported bugs got fixed, in XPath, iconv detection, |
| XInclude processing</li> |
| <li>XPath string function should now handle unicode correctly</li> |
| </ul> |
| |
| <h3>2.3.9: May 19 2001</h3> |
| |
| <p>Lots of bugfixes, and added a basic SGML catalog support:</p> |
| <ul> |
| <li>HTML push bugfix #54891 and another patch from Jonas Borgström</li> |
| <li>some serious speed optimization again</li> |
| <li>some documentation cleanups</li> |
| <li>trying to get better linking on Solaris (-R)</li> |
| <li>XPath API cleanup from Thomas Broyer</li> |
| <li>Validation bug fixed #54631, added a patch from Gary Pennington, fixed |
| xmlValidGetValidElements()</li> |
| <li>Added an INSTALL file</li> |
| <li>Attribute removal added to API: #54433</li> |
| <li>added a basic support for SGML catalogs</li> |
| <li>fixed xmlKeepBlanksDefault(0) API</li> |
| <li>bugfix in xmlNodeGetLang()</li> |
| <li>fixed a small configure portability problem</li> |
| <li>fixed an inversion of SYSTEM and PUBLIC identifier in HTML document</li> |
| </ul> |
| |
| <h3>1.8.13: May 14 2001</h3> |
| <ul> |
| <li>bugfixes release of the old libxml1 branch used by Gnome</li> |
| </ul> |
| |
| <h3>2.3.8: May 3 2001</h3> |
| <ul> |
| <li>Integrated an SGML DocBook parser for the Gnome project</li> |
| <li>Fixed a few things in the HTML parser</li> |
| <li>Fixed some XPath bugs raised by XSLT use, tried to fix the floating |
| point portability issue</li> |
| <li>Speed improvement (8M/s for SAX, 3M/s for DOM, 1.5M/s for |
| DOM+validation using the XML REC as input and a 700MHz celeron).</li> |
| <li>incorporated more Windows cleanup</li> |
| <li>added xmlSaveFormatFile()</li> |
| <li>fixed problems in copying nodes with entities references (gdome)</li> |
| <li>removed some troubles surrounding the new validation module</li> |
| </ul> |
| |
| <h3>2.3.7: April 22 2001</h3> |
| <ul> |
| <li>lots of small bug fixes, corrected XPointer</li> |
| <li>Non deterministic content model validation support</li> |
| <li>added xmlDocCopyNode for gdome2</li> |
| <li>revamped the way the HTML parser handles end of tags</li> |
| <li>XPath: corrections of namespaces support and number formatting</li> |
| <li>Windows: Igor Zlatkovic patches for MSC compilation</li> |
| <li>HTML output fixes from P C Chow and William M. Brack</li> |
| <li>Improved validation speed sensible for DocBook</li> |
| <li>fixed a big bug with ID declared in external parsed entities</li> |
| <li>portability fixes, update of Trio from Bjorn Reese</li> |
| </ul> |
| |
| <h3>2.3.6: April 8 2001</h3> |
| <ul> |
| <li>Code cleanup using extreme gcc compiler warning options, found and |
| cleared half a dozen potential problem</li> |
| <li>the Eazel team found an XML parser bug</li> |
| <li>cleaned up the user of some of the string formatting function. used the |
| trio library code to provide the one needed when the platform is missing |
| them</li> |
| <li>xpath: removed a memory leak and fixed the predicate evaluation |
| problem, extended the testsuite and cleaned up the result. XPointer seems |
| broken ...</li> |
| </ul> |
| |
| <h3>2.3.5: Mar 23 2001</h3> |
| <ul> |
| <li>Biggest change is separate parsing and evaluation of XPath expressions, |
| there is some new APIs for this too</li> |
| <li>included a number of bug fixes(XML push parser, 51876, notations, |
| 52299)</li> |
| <li>Fixed some portability issues</li> |
| </ul> |
| |
| <h3>2.3.4: Mar 10 2001</h3> |
| <ul> |
| <li>Fixed bugs #51860 and #51861</li> |
| <li>Added a global variable xmlDefaultBufferSize to allow default buffer |
| size to be application tunable.</li> |
| <li>Some cleanup in the validation code, still a bug left and this part |
| should probably be rewritten to support ambiguous content model :-\</li> |
| <li>Fix a couple of serious bugs introduced or raised by changes in 2.3.3 |
| parser</li> |
| <li>Fixed another bug in xmlNodeGetContent()</li> |
| <li>Bjorn fixed XPath node collection and Number formatting</li> |
| <li>Fixed a loop reported in the HTML parsing</li> |
| <li>blank space are reported even if the Dtd content model proves that they |
| are formatting spaces, this is for XML conformance</li> |
| </ul> |
| |
| <h3>2.3.3: Mar 1 2001</h3> |
| <ul> |
| <li>small change in XPath for XSLT</li> |
| <li>documentation cleanups</li> |
| <li>fix in validation by Gary Pennington</li> |
| <li>serious parsing performances improvements</li> |
| </ul> |
| |
| <h3>2.3.2: Feb 24 2001</h3> |
| <ul> |
| <li>chasing XPath bugs, found a bunch, completed some TODO</li> |
| <li>fixed a Dtd parsing bug</li> |
| <li>fixed a bug in xmlNodeGetContent</li> |
| <li>ID/IDREF support partly rewritten by Gary Pennington</li> |
| </ul> |
| |
| <h3>2.3.1: Feb 15 2001</h3> |
| <ul> |
| <li>some XPath and HTML bug fixes for XSLT</li> |
| <li>small extension of the hash table interfaces for DOM gdome2 |
| implementation</li> |
| <li>A few bug fixes</li> |
| </ul> |
| |
| <h3>2.3.0: Feb 8 2001 (2.2.12 was on 25 Jan but I didn't kept track)</h3> |
| <ul> |
| <li>Lots of XPath bug fixes</li> |
| <li>Add a mode with Dtd lookup but without validation error reporting for |
| XSLT</li> |
| <li>Add support for text node without escaping (XSLT)</li> |
| <li>bug fixes for xmlCheckFilename</li> |
| <li>validation code bug fixes from Gary Pennington</li> |
| <li>Patch from Paul D. Smith correcting URI path normalization</li> |
| <li>Patch to allow simultaneous install of libxml-devel and |
| libxml2-devel</li> |
| <li>the example Makefile is now fixed</li> |
| <li>added HTML to the RPM packages</li> |
| <li>tree copying bugfixes</li> |
| <li>updates to Windows makefiles</li> |
| <li>optimization patch from Bjorn Reese</li> |
| </ul> |
| |
| <h3>2.2.11: Jan 4 2001</h3> |
| <ul> |
| <li>bunch of bug fixes (memory I/O, xpath, ftp/http, ...)</li> |
| <li>added htmlHandleOmittedElem()</li> |
| <li>Applied Bjorn Reese's IPV6 first patch</li> |
| <li>Applied Paul D. Smith patches for validation of XInclude results</li> |
| <li>added XPointer xmlns() new scheme support</li> |
| </ul> |
| |
| <h3>2.2.10: Nov 25 2000</h3> |
| <ul> |
| <li>Fix the Windows problems of 2.2.8</li> |
| <li>integrate OpenVMS patches</li> |
| <li>better handling of some nasty HTML input</li> |
| <li>Improved the XPointer implementation</li> |
| <li>integrate a number of provided patches</li> |
| </ul> |
| |
| <h3>2.2.9: Nov 25 2000</h3> |
| <ul> |
| <li>erroneous release :-(</li> |
| </ul> |
| |
| <h3>2.2.8: Nov 13 2000</h3> |
| <ul> |
| <li>First version of <a href="http://www.w3.org/TR/xinclude">XInclude</a> |
| support</li> |
| <li>Patch in conditional section handling</li> |
| <li>updated MS compiler project</li> |
| <li>fixed some XPath problems</li> |
| <li>added an URI escaping function</li> |
| <li>some other bug fixes</li> |
| </ul> |
| |
| <h3>2.2.7: Oct 31 2000</h3> |
| <ul> |
| <li>added message redirection</li> |
| <li>XPath improvements (thanks TOM !)</li> |
| <li>xmlIOParseDTD() added</li> |
| <li>various small fixes in the HTML, URI, HTTP and XPointer support</li> |
| <li>some cleanup of the Makefile, autoconf and the distribution content</li> |
| </ul> |
| |
| <h3>2.2.6: Oct 25 2000:</h3> |
| <ul> |
| <li>Added an hash table module, migrated a number of internal structure to |
| those</li> |
| <li>Fixed a posteriori validation problems</li> |
| <li>HTTP module cleanups</li> |
| <li>HTML parser improvements (tag errors, script/style handling, attribute |
| normalization)</li> |
| <li>coalescing of adjacent text nodes</li> |
| <li>couple of XPath bug fixes, exported the internal API</li> |
| </ul> |
| |
| <h3>2.2.5: Oct 15 2000:</h3> |
| <ul> |
| <li>XPointer implementation and testsuite</li> |
| <li>Lot of XPath fixes, added variable and functions registration, more |
| tests</li> |
| <li>Portability fixes, lots of enhancements toward an easy Windows build |
| and release</li> |
| <li>Late validation fixes</li> |
| <li>Integrated a lot of contributed patches</li> |
| <li>added memory management docs</li> |
| <li>a performance problem when using large buffer seems fixed</li> |
| </ul> |
| |
| <h3>2.2.4: Oct 1 2000:</h3> |
| <ul> |
| <li>main XPath problem fixed</li> |
| <li>Integrated portability patches for Windows</li> |
| <li>Serious bug fixes on the URI and HTML code</li> |
| </ul> |
| |
| <h3>2.2.3: Sep 17 2000</h3> |
| <ul> |
| <li>bug fixes</li> |
| <li>cleanup of entity handling code</li> |
| <li>overall review of all loops in the parsers, all sprintf usage has been |
| checked too</li> |
| <li>Far better handling of larges Dtd. Validating against DocBook XML Dtd |
| works smoothly now.</li> |
| </ul> |
| |
| <h3>1.8.10: Sep 6 2000</h3> |
| <ul> |
| <li>bug fix release for some Gnome projects</li> |
| </ul> |
| |
| <h3>2.2.2: August 12 2000</h3> |
| <ul> |
| <li>mostly bug fixes</li> |
| <li>started adding routines to access xml parser context options</li> |
| </ul> |
| |
| <h3>2.2.1: July 21 2000</h3> |
| <ul> |
| <li>a purely bug fixes release</li> |
| <li>fixed an encoding support problem when parsing from a memory block</li> |
| <li>fixed a DOCTYPE parsing problem</li> |
| <li>removed a bug in the function allowing to override the memory |
| allocation routines</li> |
| </ul> |
| |
| <h3>2.2.0: July 14 2000</h3> |
| <ul> |
| <li>applied a lot of portability fixes</li> |
| <li>better encoding support/cleanup and saving (content is now always |
| encoded in UTF-8)</li> |
| <li>the HTML parser now correctly handles encodings</li> |
| <li>added xmlHasProp()</li> |
| <li>fixed a serious problem with &#38;</li> |
| <li>propagated the fix to FTP client</li> |
| <li>cleanup, bugfixes, etc ...</li> |
| <li>Added a page about <a href="encoding.html">libxml Internationalization |
| support</a></li> |
| </ul> |
| |
| <h3>1.8.9: July 9 2000</h3> |
| <ul> |
| <li>fixed the spec the RPMs should be better</li> |
| <li>fixed a serious bug in the FTP implementation, released 1.8.9 to solve |
| rpmfind users problem</li> |
| </ul> |
| |
| <h3>2.1.1: July 1 2000</h3> |
| <ul> |
| <li>fixes a couple of bugs in the 2.1.0 packaging</li> |
| <li>improvements on the HTML parser</li> |
| </ul> |
| |
| <h3>2.1.0 and 1.8.8: June 29 2000</h3> |
| <ul> |
| <li>1.8.8 is mostly a commodity package for upgrading to libxml2 according |
| to <a href="upgrade.html">new instructions</a>. It fixes a nasty problem |
| about &#38; charref parsing</li> |
| <li>2.1.0 also ease the upgrade from libxml v1 to the recent version. it |
| also contains numerous fixes and enhancements: |
| <ul> |
| <li>added xmlStopParser() to stop parsing</li> |
| <li>improved a lot parsing speed when there is large CDATA blocs</li> |
| <li>includes XPath patches provided by Picdar Technology</li> |
| <li>tried to fix as much as possible DTD validation and namespace |
| related problems</li> |
| <li>output to a given encoding has been added/tested</li> |
| <li>lot of various fixes</li> |
| </ul> |
| </li> |
| </ul> |
| |
| <h3>2.0.0: Apr 12 2000</h3> |
| <ul> |
| <li>First public release of libxml2. If you are using libxml, it's a good |
| idea to check the 1.x to 2.x upgrade instructions. NOTE: while initially |
| scheduled for Apr 3 the release occurred only on Apr 12 due to massive |
| workload.</li> |
| <li>The include are now located under $prefix/include/libxml (instead of |
| $prefix/include/gnome-xml), they also are referenced by |
| <pre>#include <libxml/xxx.h></pre> |
| <p>instead of</p> |
| <pre>#include "xxx.h"</pre> |
| </li> |
| <li>a new URI module for parsing URIs and following strictly RFC 2396</li> |
| <li>the memory allocation routines used by libxml can now be overloaded |
| dynamically by using xmlMemSetup()</li> |
| <li>The previously CVS only tool tester has been renamed |
| <strong>xmllint</strong> and is now installed as part of the libxml2 |
| package</li> |
| <li>The I/O interface has been revamped. There is now ways to plug in |
| specific I/O modules, either at the URI scheme detection level using |
| xmlRegisterInputCallbacks() or by passing I/O functions when creating a |
| parser context using xmlCreateIOParserCtxt()</li> |
| <li>there is a C preprocessor macro LIBXML_VERSION providing the version |
| number of the libxml module in use</li> |
| <li>a number of optional features of libxml can now be excluded at |
| configure time (FTP/HTTP/HTML/XPath/Debug)</li> |
| </ul> |
| |
| <h3>2.0.0beta: Mar 14 2000</h3> |
| <ul> |
| <li>This is a first Beta release of libxml version 2</li> |
| <li>It's available only from<a href="ftp://xmlsoft.org/">xmlsoft.org |
| FTP</a>, it's packaged as libxml2-2.0.0beta and available as tar and |
| RPMs</li> |
| <li>This version is now the head in the Gnome CVS base, the old one is |
| available under the tag LIB_XML_1_X</li> |
| <li>This includes a very large set of changes. From a programmatic point |
| of view applications should not have to be modified too much, check the |
| <a href="upgrade.html">upgrade page</a></li> |
| <li>Some interfaces may changes (especially a bit about encoding).</li> |
| <li>the updates includes: |
| <ul> |
| <li>fix I18N support. ISO-Latin-x/UTF-8/UTF-16 (nearly) seems correctly |
| handled now</li> |
| <li>Better handling of entities, especially well-formedness checking |
| and proper PEref extensions in external subsets</li> |
| <li>DTD conditional sections</li> |
| <li>Validation now correctly handle entities content</li> |
| <li><a href="http://rpmfind.net/tools/gdome/messages/0039.html">change |
| structures to accommodate DOM</a></li> |
| </ul> |
| </li> |
| <li>Serious progress were made toward compliance, <a |
| href="conf/result.html">here are the result of the test</a> against the |
| OASIS testsuite (except the Japanese tests since I don't support that |
| encoding yet). This URL is rebuilt every couple of hours using the CVS |
| head version.</li> |
| </ul> |
| |
| <h3>1.8.7: Mar 6 2000</h3> |
| <ul> |
| <li>This is a bug fix release:</li> |
| <li>It is possible to disable the ignorable blanks heuristic used by |
| libxml-1.x, a new function xmlKeepBlanksDefault(0) will allow this. Note |
| that for adherence to XML spec, this behaviour will be disabled by |
| default in 2.x . The same function will allow to keep compatibility for |
| old code.</li> |
| <li>Blanks in <a> </a> constructs are not ignored anymore, |
| avoiding heuristic is really the Right Way :-\</li> |
| <li>The unchecked use of snprintf which was breaking libxml-1.8.6 |
| compilation on some platforms has been fixed</li> |
| <li>nanoftp.c nanohttp.c: Fixed '#' and '?' stripping when processing |
| URIs</li> |
| </ul> |
| |
| <h3>1.8.6: Jan 31 2000</h3> |
| <ul> |
| <li>added a nanoFTP transport module, debugged until the new version of <a |
| href="http://rpmfind.net/linux/rpm2html/rpmfind.html">rpmfind</a> can use |
| it without troubles</li> |
| </ul> |
| |
| <h3>1.8.5: Jan 21 2000</h3> |
| <ul> |
| <li>adding APIs to parse a well balanced chunk of XML (production <a |
| href="http://www.w3.org/TR/REC-xml#NT-content">[43] content</a> of the |
| XML spec)</li> |
| <li>fixed a hideous bug in xmlGetProp pointed by Rune.Djurhuus@fast.no</li> |
| <li>Jody Goldberg <jgoldberg@home.com> provided another patch trying |
| to solve the zlib checks problems</li> |
| <li>The current state in gnome CVS base is expected to ship as 1.8.5 with |
| gnumeric soon</li> |
| </ul> |
| |
| <h3>1.8.4: Jan 13 2000</h3> |
| <ul> |
| <li>bug fixes, reintroduced xmlNewGlobalNs(), fixed xmlNewNs()</li> |
| <li>all exit() call should have been removed from libxml</li> |
| <li>fixed a problem with INCLUDE_WINSOCK on WIN32 platform</li> |
| <li>added newDocFragment()</li> |
| </ul> |
| |
| <h3>1.8.3: Jan 5 2000</h3> |
| <ul> |
| <li>a Push interface for the XML and HTML parsers</li> |
| <li>a shell-like interface to the document tree (try tester --shell :-)</li> |
| <li>lots of bug fixes and improvement added over XMas holidays</li> |
| <li>fixed the DTD parsing code to work with the xhtml DTD</li> |
| <li>added xmlRemoveProp(), xmlRemoveID() and xmlRemoveRef()</li> |
| <li>Fixed bugs in xmlNewNs()</li> |
| <li>External entity loading code has been revamped, now it uses |
| xmlLoadExternalEntity(), some fix on entities processing were added</li> |
| <li>cleaned up WIN32 includes of socket stuff</li> |
| </ul> |
| |
| <h3>1.8.2: Dec 21 1999</h3> |
| <ul> |
| <li>I got another problem with includes and C++, I hope this issue is fixed |
| for good this time</li> |
| <li>Added a few tree modification functions: xmlReplaceNode, |
| xmlAddPrevSibling, xmlAddNextSibling, xmlNodeSetName and |
| xmlDocSetRootElement</li> |
| <li>Tried to improve the HTML output with help from <a |
| href="mailto:clahey@umich.edu">Chris Lahey</a></li> |
| </ul> |
| |
| <h3>1.8.1: Dec 18 1999</h3> |
| <ul> |
| <li>various patches to avoid troubles when using libxml with C++ compilers |
| the "namespace" keyword and C escaping in include files</li> |
| <li>a problem in one of the core macros IS_CHAR was corrected</li> |
| <li>fixed a bug introduced in 1.8.0 breaking default namespace processing, |
| and more specifically the Dia application</li> |
| <li>fixed a posteriori validation (validation after parsing, or by using a |
| Dtd not specified in the original document)</li> |
| <li>fixed a bug in</li> |
| </ul> |
| |
| <h3>1.8.0: Dec 12 1999</h3> |
| <ul> |
| <li>cleanup, especially memory wise</li> |
| <li>the parser should be more reliable, especially the HTML one, it should |
| not crash, whatever the input !</li> |
| <li>Integrated various patches, especially a speedup improvement for large |
| dataset from <a href="mailto:cnygard@bellatlantic.net">Carl Nygard</a>, |
| configure with --with-buffers to enable them.</li> |
| <li>attribute normalization, oops should have been added long ago !</li> |
| <li>attributes defaulted from DTDs should be available, xmlSetProp() now |
| does entities escaping by default.</li> |
| </ul> |
| |
| <h3>1.7.4: Oct 25 1999</h3> |
| <ul> |
| <li>Lots of HTML improvement</li> |
| <li>Fixed some errors when saving both XML and HTML</li> |
| <li>More examples, the regression tests should now look clean</li> |
| <li>Fixed a bug with contiguous charref</li> |
| </ul> |
| |
| <h3>1.7.3: Sep 29 1999</h3> |
| <ul> |
| <li>portability problems fixed</li> |
| <li>snprintf was used unconditionally, leading to link problems on system |
| were it's not available, fixed</li> |
| </ul> |
| |
| <h3>1.7.1: Sep 24 1999</h3> |
| <ul> |
| <li>The basic type for strings manipulated by libxml has been renamed in |
| 1.7.1 from <strong>CHAR</strong> to <strong>xmlChar</strong>. The reason |
| is that CHAR was conflicting with a predefined type on Windows. However |
| on non WIN32 environment, compatibility is provided by the way of a |
| <strong>#define </strong>.</li> |
| <li>Changed another error : the use of a structure field called errno, and |
| leading to troubles on platforms where it's a macro</li> |
| </ul> |
| |
| <h3>1.7.0: Sep 23 1999</h3> |
| <ul> |
| <li>Added the ability to fetch remote DTD or parsed entities, see the <a |
| href="html/libxml-nanohttp.html">nanohttp</a> module.</li> |
| <li>Added an errno to report errors by another mean than a simple printf |
| like callback</li> |
| <li>Finished ID/IDREF support and checking when validation</li> |
| <li>Serious memory leaks fixed (there is now a <a |
| href="html/libxml-xmlmemory.html">memory wrapper</a> module)</li> |
| <li>Improvement of <a href="http://www.w3.org/TR/xpath">XPath</a> |
| implementation</li> |
| <li>Added an HTML parser front-end</li> |
| </ul> |
| |
| <h2><a name="XML">XML</a></h2> |
| |
| <p><a href="http://www.w3.org/TR/REC-xml">XML is a standard</a> for |
| markup-based structured documents. Here is <a name="example">an example XML |
| document</a>:</p> |
| <pre><?xml version="1.0"?> |
| <EXAMPLE prop1="gnome is great" prop2="&amp; linux too"> |
| <head> |
| <title>Welcome to Gnome</title> |
| </head> |
| <chapter> |
| <title>The Linux adventure</title> |
| <p>bla bla bla ...</p> |
| <image href="linus.gif"/> |
| <p>...</p> |
| </chapter> |
| </EXAMPLE></pre> |
| |
| <p>The first line specifies that it is an XML document and gives useful |
| information about its encoding. Then the rest of the document is a text |
| format whose structure is specified by tags between brackets. <strong>Each |
| tag opened has to be closed</strong>. XML is pedantic about this. However, if |
| a tag is empty (no content), a single tag can serve as both the opening and |
| closing tag if it ends with <code>/></code> rather than with |
| <code>></code>. Note that, for example, the image tag has no content (just |
| an attribute) and is closed by ending the tag with <code>/></code>.</p> |
| |
| <p>XML can be applied successfully to a wide range of tasks, ranging from |
| long term structured document maintenance (where it follows the steps of |
| SGML) to simple data encoding mechanisms like configuration file formatting |
| (glade), spreadsheets (gnumeric), or even shorter lived documents such as |
| WebDAV where it is used to encode remote calls between a client and a |
| server.</p> |
| |
| <h2><a name="XSLT">XSLT</a></h2> |
| |
| <p>Check <a href="http://xmlsoft.org/XSLT">the separate libxslt page</a></p> |
| |
| <p><a href="http://www.w3.org/TR/xslt">XSL Transformations</a>, is a |
| language for transforming XML documents into other XML documents (or |
| HTML/textual output).</p> |
| |
| <p>A separate library called libxslt is being developed on top of libxml2. |
| This module "libxslt" too can be found in the Gnome CVS base.</p> |
| |
| <p>You can check the <a |
| href="http://cvs.gnome.org/lxr/source/libxslt/FEATURES">features</a> |
| supported and the progresses on the <a |
| href="http://cvs.gnome.org/lxr/source/libxslt/ChangeLog" |
| name="Changelog">Changelog</a>.</p> |
| |
| <h2><a name="Python">Python and bindings</a></h2> |
| |
| <p>There are a number of language bindings and wrappers available for |
| libxml2, the list below is not exhaustive. Please contact the <a |
| href="http://mail.gnome.org/mailman/listinfo/xml-bindings">xml-bindings@gnome.org</a> |
| (<a href="http://mail.gnome.org/archives/xml-bindings/">archives</a>) in |
| order to get updates to this list or to discuss the specific topic of libxml2 |
| or libxslt wrappers or bindings:</p> |
| <ul> |
| <li><a href="http://libxmlplusplus.sourceforge.net/">Libxml++</a> seems the |
| most up-to-date C++ bindings for libxml2, check the <a |
| href="http://libxmlplusplus.sourceforge.net/reference/html/hierarchy.html">documentation</a> |
| and the <a |
| href="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/libxmlplusplus/libxml%2b%2b/examples/">examples</a>.</li> |
| <li>There is another <a href="http://libgdome-cpp.berlios.de/">C++ wrapper |
| based on the gdome2 bindings</a> maintained by Tobias Peters.</li> |
| <li>and a third C++ wrapper by Peter Jones <pjones@pmade.org> |
| <p>Website: <a |
| href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> |
| </li> |
| <li><a |
| href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt |
| Sergeant</a> developed <a |
| href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for |
| libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML |
| application server</a>.</li> |
| <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provides an |
| earlier version of the libxml/libxslt <a |
| href="http://www.rexx.com/~dkuhlman">wrappers for Python</a>.</li> |
| <li>Gopal.V and Peter Minten develop <a |
| href="http://savannah.gnu.org/projects/libxmlsharp">libxml#</a>, a set of |
| C# libxml2 bindings.</li> |
| <li>Petr Kozelka provides <a |
| href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue |
| libxml2</a> with Kylix, Delphi and other Pascal compilers.</li> |
| <li>Uwe Fechner also provides <a |
| href="http://sourceforge.net/projects/idom2-pas/">idom2</a>, a DOM2 |
| implementation for Kylix2/D5/D6 from Borland.</li> |
| <li>Wai-Sun "Squidster" Chia provides <a |
| href="http://www.rubycolor.org/arc/redist/">bindings for Ruby</a> and |
| libxml2 bindings are also available in Ruby through the <a |
| href="http://libgdome-ruby.berlios.de/">libgdome-ruby</a> module |
| maintained by Tobias Peters.</li> |
| <li>Steve Ball and contributors maintains <a |
| href="http://tclxml.sourceforge.net/">libxml2 and libxslt bindings for |
| Tcl</a>.</li> |
| <li>There is support for libxml2 in the DOM module of PHP.</li> |
| <li><a href="http://savannah.gnu.org/projects/classpathx/">LibxmlJ</a> is |
| an effort to create a 100% JAXP-compatible Java wrapper for libxml2 and |
| libxslt as part of GNU ClasspathX project.</li> |
| </ul> |
| |
| <p>The distribution includes a set of Python bindings, which are guaranteed |
| to be maintained as part of the library in the future, though the Python |
| interface have not yet reached the completeness of the C API.</p> |
| |
| <p><a href="mailto:stephane.bidoul@softwareag.com">Stéphane Bidoul</a> |
| maintains <a href="http://users.skynet.be/sbi/libxml-python/">a Windows port |
| of the Python bindings</a>.</p> |
| |
| <p>Note to people interested in building bindings, the API is formalized as |
| <a href="libxml2-api.xml">an XML API description file</a> which allows to |
| automate a large part of the Python bindings, this includes function |
| descriptions, enums, structures, typedefs, etc... The Python script used to |
| build the bindings is python/generator.py in the source distribution.</p> |
| |
| <p>To install the Python bindings there are 2 options:</p> |
| <ul> |
| <li>If you use an RPM based distribution, simply install the <a |
| href="http://rpmfind.net/linux/rpm2html/search.php?query=libxml2-python">libxml2-python |
| RPM</a> (and if needed the <a |
| href="http://rpmfind.net/linux/rpm2html/search.php?query=libxslt-python">libxslt-python |
| RPM</a>).</li> |
| <li>Otherwise use the <a href="ftp://xmlsoft.org/python/">libxml2-python |
| module distribution</a> corresponding to your installed version of |
| libxml2 and libxslt. Note that to install it you will need both libxml2 |
| and libxslt installed and run "python setup.py build install" in the |
| module tree.</li> |
| </ul> |
| |
| <p>The distribution includes a set of examples and regression tests for the |
| python bindings in the <code>python/tests</code> directory. Here are some |
| excerpts from those tests:</p> |
| |
| <h3>tst.py:</h3> |
| |
| <p>This is a basic test of the file interface and DOM navigation:</p> |
| <pre>import libxml2 |
| |
| doc = libxml2.parseFile("tst.xml") |
| if doc.name != "tst.xml": |
| print "doc.name failed" |
| sys.exit(1) |
| root = doc.children |
| if root.name != "doc": |
| print "root.name failed" |
| sys.exit(1) |
| child = root.children |
| if child.name != "foo": |
| print "child.name failed" |
| sys.exit(1) |
| doc.freeDoc()</pre> |
| |
| <p>The Python module is called libxml2; parseFile is the equivalent of |
| xmlParseFile (most of the bindings are automatically generated, and the xml |
| prefix is removed and the casing convention are kept). All node seen at the |
| binding level share the same subset of accessors:</p> |
| <ul> |
| <li><code>name</code> : returns the node name</li> |
| <li><code>type</code> : returns a string indicating the node type</li> |
| <li><code>content</code> : returns the content of the node, it is based on |
| xmlNodeGetContent() and hence is recursive.</li> |
| <li><code>parent</code> , <code>children</code>, <code>last</code>, |
| <code>next</code>, <code>prev</code>, <code>doc</code>, |
| <code>properties</code>: pointing to the associated element in the tree, |
| those may return None in case no such link exists.</li> |
| </ul> |
| |
| <p>Also note the need to explicitly deallocate documents with freeDoc() . |
| Reference counting for libxml2 trees would need quite a lot of work to |
| function properly, and rather than risk memory leaks if not implemented |
| correctly it sounds safer to have an explicit function to free a tree. The |
| wrapper python objects like doc, root or child are them automatically garbage |
| collected.</p> |
| |
| <h3>validate.py:</h3> |
| |
| <p>This test check the validation interfaces and redirection of error |
| messages:</p> |
| <pre>import libxml2 |
| |
| #deactivate error messages from the validation |
| def noerr(ctx, str): |
| pass |
| |
| libxml2.registerErrorHandler(noerr, None) |
| |
| ctxt = libxml2.createFileParserCtxt("invalid.xml") |
| ctxt.validate(1) |
| ctxt.parseDocument() |
| doc = ctxt.doc() |
| valid = ctxt.isValid() |
| doc.freeDoc() |
| if valid != 0: |
| print "validity check failed"</pre> |
| |
| <p>The first thing to notice is the call to registerErrorHandler(), it |
| defines a new error handler global to the library. It is used to avoid seeing |
| the error messages when trying to validate the invalid document.</p> |
| |
| <p>The main interest of that test is the creation of a parser context with |
| createFileParserCtxt() and how the behaviour can be changed before calling |
| parseDocument() . Similarly the informations resulting from the parsing phase |
| are also available using context methods.</p> |
| |
| <p>Contexts like nodes are defined as class and the libxml2 wrappers maps the |
| C function interfaces in terms of objects method as much as possible. The |
| best to get a complete view of what methods are supported is to look at the |
| libxml2.py module containing all the wrappers.</p> |
| |
| <h3>push.py:</h3> |
| |
| <p>This test show how to activate the push parser interface:</p> |
| <pre>import libxml2 |
| |
| ctxt = libxml2.createPushParser(None, "<foo", 4, "test.xml") |
| ctxt.parseChunk("/>", 2, 1) |
| doc = ctxt.doc() |
| |
| doc.freeDoc()</pre> |
| |
| <p>The context is created with a special call based on the |
| xmlCreatePushParser() from the C library. The first argument is an optional |
| SAX callback object, then the initial set of data, the length and the name of |
| the resource in case URI-References need to be computed by the parser.</p> |
| |
| <p>Then the data are pushed using the parseChunk() method, the last call |
| setting the third argument terminate to 1.</p> |
| |
| <h3>pushSAX.py:</h3> |
| |
| <p>this test show the use of the event based parsing interfaces. In this case |
| the parser does not build a document, but provides callback information as |
| the parser makes progresses analyzing the data being provided:</p> |
| <pre>import libxml2 |
| log = "" |
| |
| class callback: |
| def startDocument(self): |
| global log |
| log = log + "startDocument:" |
| |
| def endDocument(self): |
| global log |
| log = log + "endDocument:" |
| |
| def startElement(self, tag, attrs): |
| global log |
| log = log + "startElement %s %s:" % (tag, attrs) |
| |
| def endElement(self, tag): |
| global log |
| log = log + "endElement %s:" % (tag) |
| |
| def characters(self, data): |
| global log |
| log = log + "characters: %s:" % (data) |
| |
| def warning(self, msg): |
| global log |
| log = log + "warning: %s:" % (msg) |
| |
| def error(self, msg): |
| global log |
| log = log + "error: %s:" % (msg) |
| |
| def fatalError(self, msg): |
| global log |
| log = log + "fatalError: %s:" % (msg) |
| |
| handler = callback() |
| |
| ctxt = libxml2.createPushParser(handler, "<foo", 4, "test.xml") |
| chunk = " url='tst'>b" |
| ctxt.parseChunk(chunk, len(chunk), 0) |
| chunk = "ar</foo>" |
| ctxt.parseChunk(chunk, len(chunk), 1) |
| |
| reference = "startDocument:startElement foo {'url': 'tst'}:" + \ |
| "characters: bar:endElement foo:endDocument:" |
| if log != reference: |
| print "Error got: %s" % log |
| print "Expected: %s" % reference</pre> |
| |
| <p>The key object in that test is the handler, it provides a number of entry |
| points which can be called by the parser as it makes progresses to indicate |
| the information set obtained. The full set of callback is larger than what |
| the callback class in that specific example implements (see the SAX |
| definition for a complete list). The wrapper will only call those supplied by |
| the object when activated. The startElement receives the names of the element |
| and a dictionary containing the attributes carried by this element.</p> |
| |
| <p>Also note that the reference string generated from the callback shows a |
| single character call even though the string "bar" is passed to the parser |
| from 2 different call to parseChunk()</p> |
| |
| <h3>xpath.py:</h3> |
| |
| <p>This is a basic test of XPath wrappers support</p> |
| <pre>import libxml2 |
| |
| doc = libxml2.parseFile("tst.xml") |
| ctxt = doc.xpathNewContext() |
| res = ctxt.xpathEval("//*") |
| if len(res) != 2: |
| print "xpath query: wrong node set size" |
| sys.exit(1) |
| if res[0].name != "doc" or res[1].name != "foo": |
| print "xpath query: wrong node set value" |
| sys.exit(1) |
| doc.freeDoc() |
| ctxt.xpathFreeContext()</pre> |
| |
| <p>This test parses a file, then create an XPath context to evaluate XPath |
| expression on it. The xpathEval() method execute an XPath query and returns |
| the result mapped in a Python way. String and numbers are natively converted, |
| and node sets are returned as a tuple of libxml2 Python nodes wrappers. Like |
| the document, the XPath context need to be freed explicitly, also not that |
| the result of the XPath query may point back to the document tree and hence |
| the document must be freed after the result of the query is used.</p> |
| |
| <h3>xpathext.py:</h3> |
| |
| <p>This test shows how to extend the XPath engine with functions written in |
| python:</p> |
| <pre>import libxml2 |
| |
| def foo(ctx, x): |
| return x + 1 |
| |
| doc = libxml2.parseFile("tst.xml") |
| ctxt = doc.xpathNewContext() |
| libxml2.registerXPathFunction(ctxt._o, "foo", None, foo) |
| res = ctxt.xpathEval("foo(1)") |
| if res != 2: |
| print "xpath extension failure" |
| doc.freeDoc() |
| ctxt.xpathFreeContext()</pre> |
| |
| <p>Note how the extension function is registered with the context (but that |
| part is not yet finalized, this may change slightly in the future).</p> |
| |
| <h3>tstxpath.py:</h3> |
| |
| <p>This test is similar to the previous one but shows how the extension |
| function can access the XPath evaluation context:</p> |
| <pre>def foo(ctx, x): |
| global called |
| |
| # |
| # test that access to the XPath evaluation contexts |
| # |
| pctxt = libxml2.xpathParserContext(_obj=ctx) |
| ctxt = pctxt.context() |
| called = ctxt.function() |
| return x + 1</pre> |
| |
| <p>All the interfaces around the XPath parser(or rather evaluation) context |
| are not finalized, but it should be sufficient to do contextual work at the |
| evaluation point.</p> |
| |
| <h3>Memory debugging:</h3> |
| |
| <p>last but not least, all tests starts with the following prologue:</p> |
| <pre>#memory debug specific |
| libxml2.debugMemory(1)</pre> |
| |
| <p>and ends with the following epilogue:</p> |
| <pre>#memory debug specific |
| libxml2.cleanupParser() |
| if libxml2.debugMemory(1) == 0: |
| print "OK" |
| else: |
| print "Memory leak %d bytes" % (libxml2.debugMemory(1)) |
| libxml2.dumpMemory()</pre> |
| |
| <p>Those activate the memory debugging interface of libxml2 where all |
| allocated block in the library are tracked. The prologue then cleans up the |
| library state and checks that all allocated memory has been freed. If not it |
| calls dumpMemory() which saves that list in a <code>.memdump</code> file.</p> |
| |
| <h2><a name="architecture">libxml architecture</a></h2> |
| |
| <p>Libxml is made of multiple components; some of them are optional, and most |
| of the block interfaces are public. The main components are:</p> |
| <ul> |
| <li>an Input/Output layer</li> |
| <li>FTP and HTTP client layers (optional)</li> |
| <li>an Internationalization layer managing the encodings support</li> |
| <li>a URI module</li> |
| <li>the XML parser and its basic SAX interface</li> |
| <li>an HTML parser using the same SAX interface (optional)</li> |
| <li>a SAX tree module to build an in-memory DOM representation</li> |
| <li>a tree module to manipulate the DOM representation</li> |
| <li>a validation module using the DOM representation (optional)</li> |
| <li>an XPath module for global lookup in a DOM representation |
| (optional)</li> |
| <li>a debug module (optional)</li> |
| </ul> |
| |
| <p>Graphically this gives the following:</p> |
| |
| <p><img src="libxml.gif" alt="a graphical view of the various"></p> |
| |
| <p></p> |
| |
| <h2><a name="tree">The tree output</a></h2> |
| |
| <p>The parser returns a tree built during the document analysis. The value |
| returned is an <strong>xmlDocPtr</strong> (i.e., a pointer to an |
| <strong>xmlDoc</strong> structure). This structure contains information such |
| as the file name, the document type, and a <strong>children</strong> pointer |
| which is the root of the document (or more exactly the first child under the |
| root which is the document). The tree is made of <strong>xmlNode</strong>s, |
| chained in double-linked lists of siblings and with a children<->parent |
| relationship. An xmlNode can also carry properties (a chain of xmlAttr |
| structures). An attribute may have a value which is a list of TEXT or |
| ENTITY_REF nodes.</p> |
| |
| <p>Here is an example (erroneous with respect to the XML spec since there |
| should be only one ELEMENT under the root):</p> |
| |
| <p><img src="structure.gif" alt=" structure.gif "></p> |
| |
| <p>In the source package there is a small program (not installed by default) |
| called <strong>xmllint</strong> which parses XML files given as argument and |
| prints them back as parsed. This is useful for detecting errors both in XML |
| code and in the XML parser itself. It has an option <strong>--debug</strong> |
| which prints the actual in-memory structure of the document; here is the |
| result with the <a href="#example">example</a> given before:</p> |
| <pre>DOCUMENT |
| version=1.0 |
| standalone=true |
| ELEMENT EXAMPLE |
| ATTRIBUTE prop1 |
| TEXT |
| content=gnome is great |
| ATTRIBUTE prop2 |
| ENTITY_REF |
| TEXT |
| content= linux too |
| ELEMENT head |
| ELEMENT title |
| TEXT |
| content=Welcome to Gnome |
| ELEMENT chapter |
| ELEMENT title |
| TEXT |
| content=The Linux adventure |
| ELEMENT p |
| TEXT |
| content=bla bla bla ... |
| ELEMENT image |
| ATTRIBUTE href |
| TEXT |
| content=linus.gif |
| ELEMENT p |
| TEXT |
| content=...</pre> |
| |
| <p>This should be useful for learning the internal representation model.</p> |
| |
| <h2><a name="interface">The SAX interface</a></h2> |
| |
| <p>Sometimes the DOM tree output is just too large to fit reasonably into |
| memory. In that case (and if you don't expect to save back the XML document |
| loaded using libxml), it's better to use the SAX interface of libxml. SAX is |
| a <strong>callback-based interface</strong> to the parser. Before parsing, |
| the application layer registers a customized set of callbacks which are |
| called by the library as it progresses through the XML input.</p> |
| |
| <p>To get more detailed step-by-step guidance on using the SAX interface of |
| libxml, see the <a |
| href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">nice |
| documentation</a>.written by <a href="mailto:james@daa.com.au">James |
| Henstridge</a>.</p> |
| |
| <p>You can debug the SAX behaviour by using the <strong>testSAX</strong> |
| program located in the gnome-xml module (it's usually not shipped in the |
| binary packages of libxml, but you can find it in the tar source |
| distribution). Here is the sequence of callbacks that would be reported by |
| testSAX when parsing the example XML document shown earlier:</p> |
| <pre>SAX.setDocumentLocator() |
| SAX.startDocument() |
| SAX.getEntity(amp) |
| SAX.startElement(EXAMPLE, prop1='gnome is great', prop2='&amp; linux too') |
| SAX.characters( , 3) |
| SAX.startElement(head) |
| SAX.characters( , 4) |
| SAX.startElement(title) |
| SAX.characters(Welcome to Gnome, 16) |
| SAX.endElement(title) |
| SAX.characters( , 3) |
| SAX.endElement(head) |
| SAX.characters( , 3) |
| SAX.startElement(chapter) |
| SAX.characters( , 4) |
| SAX.startElement(title) |
| SAX.characters(The Linux adventure, 19) |
| SAX.endElement(title) |
| SAX.characters( , 4) |
| SAX.startElement(p) |
| SAX.characters(bla bla bla ..., 15) |
| SAX.endElement(p) |
| SAX.characters( , 4) |
| SAX.startElement(image, href='linus.gif') |
| SAX.endElement(image) |
| SAX.characters( , 4) |
| SAX.startElement(p) |
| SAX.characters(..., 3) |
| SAX.endElement(p) |
| SAX.characters( , 3) |
| SAX.endElement(chapter) |
| SAX.characters( , 1) |
| SAX.endElement(EXAMPLE) |
| SAX.endDocument()</pre> |
| |
| <p>Most of the other interfaces of libxml are based on the DOM tree-building |
| facility, so nearly everything up to the end of this document presupposes the |
| use of the standard DOM tree build. Note that the DOM tree itself is built by |
| a set of registered default callbacks, without internal specific |
| interface.</p> |
| |
| <h2><a name="Validation">Validation & DTDs</a></h2> |
| |
| <p>Table of Content:</p> |
| <ol> |
| <li><a href="#General5">General overview</a></li> |
| <li><a href="#definition">The definition</a></li> |
| <li><a href="#Simple">Simple rules</a> |
| <ol> |
| <li><a href="#reference">How to reference a DTD from a document</a></li> |
| <li><a href="#Declaring">Declaring elements</a></li> |
| <li><a href="#Declaring1">Declaring attributes</a></li> |
| </ol> |
| </li> |
| <li><a href="#Some">Some examples</a></li> |
| <li><a href="#validate">How to validate</a></li> |
| <li><a href="#Other">Other resources</a></li> |
| </ol> |
| |
| <h3><a name="General5">General overview</a></h3> |
| |
| <p>Well what is validation and what is a DTD ?</p> |
| |
| <p>DTD is the acronym for Document Type Definition. This is a description of |
| the content for a family of XML files. This is part of the XML 1.0 |
| specification, and allows one to describe and verify that a given document |
| instance conforms to the set of rules detailing its structure and content.</p> |
| |
| <p>Validation is the process of checking a document against a DTD (more |
| generally against a set of construction rules).</p> |
| |
| <p>The validation process and building DTDs are the two most difficult parts |
| of the XML life cycle. Briefly a DTD defines all the possible elements to be |
| found within your document, what is the formal shape of your document tree |
| (by defining the allowed content of an element; either text, a regular |
| expression for the allowed list of children, or mixed content i.e. both text |
| and children). The DTD also defines the valid attributes for all elements and |
| the types of those attributes.</p> |
| |
| <h3><a name="definition1">The definition</a></h3> |
| |
| <p>The <a href="http://www.w3.org/TR/REC-xml">W3C XML Recommendation</a> (<a |
| href="http://www.xml.com/axml/axml.html">Tim Bray's annotated version of |
| Rev1</a>):</p> |
| <ul> |
| <li><a href="http://www.w3.org/TR/REC-xml#elemdecls">Declaring |
| elements</a></li> |
| <li><a href="http://www.w3.org/TR/REC-xml#attdecls">Declaring |
| attributes</a></li> |
| </ul> |
| |
| <p>(unfortunately) all this is inherited from the SGML world, the syntax is |
| ancient...</p> |
| |
| <h3><a name="Simple1">Simple rules</a></h3> |
| |
| <p>Writing DTDs can be done in many ways. The rules to build them if you need |
| something permanent or something which can evolve over time can be radically |
| different. Really complex DTDs like DocBook ones are flexible but quite |
| harder to design. I will just focus on DTDs for a formats with a fixed simple |
| structure. It is just a set of basic rules, and definitely not exhaustive nor |
| usable for complex DTD design.</p> |
| |
| <h4><a name="reference1">How to reference a DTD from a document</a>:</h4> |
| |
| <p>Assuming the top element of the document is <code>spec</code> and the dtd |
| is placed in the file <code>mydtd</code> in the subdirectory |
| <code>dtds</code> of the directory from where the document were loaded:</p> |
| |
| <p><code><!DOCTYPE spec SYSTEM "dtds/mydtd"></code></p> |
| |
| <p>Notes:</p> |
| <ul> |
| <li>The system string is actually an URI-Reference (as defined in <a |
| href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>) so you can use a |
| full URL string indicating the location of your DTD on the Web. This is a |
| really good thing to do if you want others to validate your document.</li> |
| <li>It is also possible to associate a <code>PUBLIC</code> identifier (a |
| magic string) so that the DTD is looked up in catalogs on the client side |
| without having to locate it on the web.</li> |
| <li>A DTD contains a set of element and attribute declarations, but they |
| don't define what the root of the document should be. This is explicitly |
| told to the parser/validator as the first element of the |
| <code>DOCTYPE</code> declaration.</li> |
| </ul> |
| |
| <h4><a name="Declaring2">Declaring elements</a>:</h4> |
| |
| <p>The following declares an element <code>spec</code>:</p> |
| |
| <p><code><!ELEMENT spec (front, body, back?)></code></p> |
| |
| <p>It also expresses that the spec element contains one <code>front</code>, |
| one <code>body</code> and one optional <code>back</code> children elements in |
| this order. The declaration of one element of the structure and its content |
| are done in a single declaration. Similarly the following declares |
| <code>div1</code> elements:</p> |
| |
| <p><code><!ELEMENT div1 (head, (p | list | note)*, div2?)></code></p> |
| |
| <p>which means div1 contains one <code>head</code> then a series of optional |
| <code>p</code>, <code>list</code>s and <code>note</code>s and then an |
| optional <code>div2</code>. And last but not least an element can contain |
| text:</p> |
| |
| <p><code><!ELEMENT b (#PCDATA)></code></p> |
| |
| <p><code>b</code> contains text or being of mixed content (text and elements |
| in no particular order):</p> |
| |
| <p><code><!ELEMENT p (#PCDATA|a|ul|b|i|em)*></code></p> |
| |
| <p><code>p </code>can contain text or <code>a</code>, <code>ul</code>, |
| <code>b</code>, <code>i </code>or <code>em</code> elements in no particular |
| order.</p> |
| |
| <h4><a name="Declaring1">Declaring attributes</a>:</h4> |
| |
| <p>Again the attributes declaration includes their content definition:</p> |
| |
| <p><code><!ATTLIST termdef name CDATA #IMPLIED></code></p> |
| |
| <p>means that the element <code>termdef</code> can have a <code>name</code> |
| attribute containing text (<code>CDATA</code>) and which is optional |
| (<code>#IMPLIED</code>). The attribute value can also be defined within a |
| set:</p> |
| |
| <p><code><!ATTLIST list type (bullets|ordered|glossary) |
| "ordered"></code></p> |
| |
| <p>means <code>list</code> element have a <code>type</code> attribute with 3 |
| allowed values "bullets", "ordered" or "glossary" and which default to |
| "ordered" if the attribute is not explicitly specified.</p> |
| |
| <p>The content type of an attribute can be text (<code>CDATA</code>), |
| anchor/reference/references |
| (<code>ID</code>/<code>IDREF</code>/<code>IDREFS</code>), entity(ies) |
| (<code>ENTITY</code>/<code>ENTITIES</code>) or name(s) |
| (<code>NMTOKEN</code>/<code>NMTOKENS</code>). The following defines that a |
| <code>chapter</code> element can have an optional <code>id</code> attribute |
| of type <code>ID</code>, usable for reference from attribute of type |
| IDREF:</p> |
| |
| <p><code><!ATTLIST chapter id ID #IMPLIED></code></p> |
| |
| <p>The last value of an attribute definition can be <code>#REQUIRED |
| </code>meaning that the attribute has to be given, <code>#IMPLIED</code> |
| meaning that it is optional, or the default value (possibly prefixed by |
| <code>#FIXED</code> if it is the only allowed).</p> |
| |
| <p>Notes:</p> |
| <ul> |
| <li>Usually the attributes pertaining to a given element are declared in a |
| single expression, but it is just a convention adopted by a lot of DTD |
| writers: |
| <pre><!ATTLIST termdef |
| id ID #REQUIRED |
| name CDATA #IMPLIED></pre> |
| <p>The previous construct defines both <code>id</code> and |
| <code>name</code> attributes for the element <code>termdef</code>.</p> |
| </li> |
| </ul> |
| |
| <h3><a name="Some1">Some examples</a></h3> |
| |
| <p>The directory <code>test/valid/dtds/</code> in the libxml distribution |
| contains some complex DTD examples. The example in the file |
| <code>test/valid/dia.xml</code> shows an XML file where the simple DTD is |
| directly included within the document.</p> |
| |
| <h3><a name="validate1">How to validate</a></h3> |
| |
| <p>The simplest way is to use the xmllint program included with libxml. The |
| <code>--valid</code> option turns-on validation of the files given as input. |
| For example the following validates a copy of the first revision of the XML |
| 1.0 specification:</p> |
| |
| <p><code>xmllint --valid --noout test/valid/REC-xml-19980210.xml</code></p> |
| |
| <p>the -- noout is used to disable output of the resulting tree.</p> |
| |
| <p>The <code>--dtdvalid dtd</code> allows validation of the document(s) |
| against a given DTD.</p> |
| |
| <p>Libxml exports an API to handle DTDs and validation, check the <a |
| href="http://xmlsoft.org/html/libxml-valid.html">associated |
| description</a>.</p> |
| |
| <h3><a name="Other1">Other resources</a></h3> |
| |
| <p>DTDs are as old as SGML. So there may be a number of examples on-line, I |
| will just list one for now, others pointers welcome:</p> |
| <ul> |
| <li><a href="http://www.xml101.com:8081/dtd/">XML-101 DTD</a></li> |
| </ul> |
| |
| <p>I suggest looking at the examples found under test/valid/dtd and any of |
| the large number of books available on XML. The dia example in test/valid |
| should be both simple and complete enough to allow you to build your own.</p> |
| |
| <p></p> |
| |
| <h2><a name="Memory">Memory Management</a></h2> |
| |
| <p>Table of Content:</p> |
| <ol> |
| <li><a href="#General3">General overview</a></li> |
| <li><a href="#setting">Setting libxml set of memory routines</a></li> |
| <li><a href="#cleanup">Cleaning up after parsing</a></li> |
| <li><a href="#Debugging">Debugging routines</a></li> |
| <li><a href="#General4">General memory requirements</a></li> |
| </ol> |
| |
| <h3><a name="General3">General overview</a></h3> |
| |
| <p>The module <code><a |
| href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlmemory.h</a></code> |
| provides the interfaces to the libxml memory system:</p> |
| <ul> |
| <li>libxml does not use the libc memory allocator directly but xmlFree(), |
| xmlMalloc() and xmlRealloc()</li> |
| <li>those routines can be reallocated to a specific set of routine, by |
| default the libc ones i.e. free(), malloc() and realloc()</li> |
| <li>the xmlmemory.c module includes a set of debugging routine</li> |
| </ul> |
| |
| <h3><a name="setting">Setting libxml set of memory routines</a></h3> |
| |
| <p>It is sometimes useful to not use the default memory allocator, either for |
| debugging, analysis or to implement a specific behaviour on memory management |
| (like on embedded systems). Two function calls are available to do so:</p> |
| <ul> |
| <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemGet |
| ()</a> which return the current set of functions in use by the parser</li> |
| <li><a |
| href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemSetup()</a> |
| which allow to set up a new set of memory allocation functions</li> |
| </ul> |
| |
| <p>Of course a call to xmlMemSetup() should probably be done before calling |
| any other libxml routines (unless you are sure your allocations routines are |
| compatibles).</p> |
| |
| <h3><a name="cleanup">Cleaning up after parsing</a></h3> |
| |
| <p>Libxml is not stateless, there is a few set of memory structures needing |
| allocation before the parser is fully functional (some encoding structures |
| for example). This also mean that once parsing is finished there is a tiny |
| amount of memory (a few hundred bytes) which can be recollected if you don't |
| reuse the parser immediately:</p> |
| <ul> |
| <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlCleanupParser |
| ()</a> is a centralized routine to free the parsing states. Note that it |
| won't deallocate any produced tree if any (use the xmlFreeDoc() and |
| related routines for this).</li> |
| <li><a href="http://xmlsoft.org/html/libxml-parser.html">xmlInitParser |
| ()</a> is the dual routine allowing to preallocate the parsing state |
| which can be useful for example to avoid initialization reentrancy |
| problems when using libxml in multithreaded applications</li> |
| </ul> |
| |
| <p>Generally xmlCleanupParser() is safe, if needed the state will be rebuild |
| at the next invocation of parser routines, but be careful of the consequences |
| in multithreaded applications.</p> |
| |
| <h3><a name="Debugging">Debugging routines</a></h3> |
| |
| <p>When configured using --with-mem-debug flag (off by default), libxml uses |
| a set of memory allocation debugging routines keeping track of all allocated |
| blocks and the location in the code where the routine was called. A couple of |
| other debugging routines allow to dump the memory allocated infos to a file |
| or call a specific routine when a given block number is allocated:</p> |
| <ul> |
| <li><a |
| href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMallocLoc()</a> |
| <a |
| href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlReallocLoc()</a> |
| and <a |
| href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemStrdupLoc()</a> |
| are the memory debugging replacement allocation routines</li> |
| <li><a href="http://xmlsoft.org/html/libxml-xmlmemory.html">xmlMemoryDump |
| ()</a> dumps all the informations about the allocated memory block lefts |
| in the <code>.memdump</code> file</li> |
| </ul> |
| |
| <p>When developing libxml memory debug is enabled, the tests programs call |
| xmlMemoryDump () and the "make test" regression tests will check for any |
| memory leak during the full regression test sequence, this helps a lot |
| ensuring that libxml does not leak memory and bullet proof memory |
| allocations use (some libc implementations are known to be far too permissive |
| resulting in major portability problems!).</p> |
| |
| <p>If the .memdump reports a leak, it displays the allocation function and |
| also tries to give some informations about the content and structure of the |
| allocated blocks left. This is sufficient in most cases to find the culprit, |
| but not always. Assuming the allocation problem is reproducible, it is |
| possible to find more easily:</p> |
| <ol> |
| <li>write down the block number xxxx not allocated</li> |
| <li>export the environment variable XML_MEM_BREAKPOINT=xxxx , the easiest |
| when using GDB is to simply give the command |
| <p><code>set environment XML_MEM_BREAKPOINT xxxx</code></p> |
| <p>before running the program.</p> |
| </li> |
| <li>run the program under a debugger and set a breakpoint on |
| xmlMallocBreakpoint() a specific function called when this precise block |
| is allocated</li> |
| <li>when the breakpoint is reached you can then do a fine analysis of the |
| allocation an step to see the condition resulting in the missing |
| deallocation.</li> |
| </ol> |
| |
| <p>I used to use a commercial tool to debug libxml memory problems but after |
| noticing that it was not detecting memory leaks that simple mechanism was |
| used and proved extremely efficient until now. Lately I have also used <a |
| href="http://developer.kde.org/~sewardj/">valgrind</a> with quite some |
| success, it is tied to the i386 architecture since it works by emulating the |
| processor and instruction set, it is slow but extremely efficient, i.e. it |
| spot memory usage errors in a very precise way.</p> |
| |
| <h3><a name="General4">General memory requirements</a></h3> |
| |
| <p>How much libxml memory require ? It's hard to tell in average it depends |
| of a number of things:</p> |
| <ul> |
| <li>the parser itself should work in a fixed amount of memory, except for |
| information maintained about the stacks of names and entities locations. |
| The I/O and encoding handlers will probably account for a few KBytes. |
| This is true for both the XML and HTML parser (though the HTML parser |
| need more state).</li> |
| <li>If you are generating the DOM tree then memory requirements will grow |
| nearly linear with the size of the data. In general for a balanced |
| textual document the internal memory requirement is about 4 times the |
| size of the UTF8 serialization of this document (example the XML-1.0 |
| recommendation is a bit more of 150KBytes and takes 650KBytes of main |
| memory when parsed). Validation will add a amount of memory required for |
| maintaining the external Dtd state which should be linear with the |
| complexity of the content model defined by the Dtd</li> |
| <li>If you need to work with fixed memory requirements or don't need the |
| full DOM tree then using the <a href="xmlreader.html">xmlReader |
| interface</a> is probably the best way to proceed, it still allows to |
| validate or operate on subset of the tree if needed.</li> |
| <li>If you don't care about the advanced features of libxml like |
| validation, DOM, XPath or XPointer, don't use entities, need to work with |
| fixed memory requirements, and try to get the fastest parsing possible |
| then the SAX interface should be used, but it has known restrictions.</li> |
| </ul> |
| |
| <p></p> |
| |
| <h2><a name="Encodings">Encodings support</a></h2> |
| |
| <p>Table of Content:</p> |
| <ol> |
| <li><a href="encoding.html#What">What does internationalization support |
| mean ?</a></li> |
| <li><a href="encoding.html#internal">The internal encoding, how and |
| why</a></li> |
| <li><a href="encoding.html#implemente">How is it implemented ?</a></li> |
| <li><a href="encoding.html#Default">Default supported encodings</a></li> |
| <li><a href="encoding.html#extend">How to extend the existing |
| support</a></li> |
| </ol> |
| |
| <h3><a name="What">What does internationalization support mean ?</a></h3> |
| |
| <p>If you are not really familiar with Internationalization (usual shorcut is |
| I18N) , Unicode, characters and glyphs, I suggest you read a <a |
| href="http://www.tbray.org/ongoing/When/200x/2003/04/06/Unicode">presentation</a> |
| by Tim Bray on Unicode and why you should care about it.</p> |
| |
| <p>XML was designed from the start to allow the support of any character set |
| by using Unicode. Any conformant XML parser has to support the UTF-8 and |
| UTF-16 default encodings which can both express the full unicode ranges. UTF8 |
| is a variable length encoding whose greatest points are to reuse the same |
| encoding for ASCII and to save space for Western encodings, but it is a bit |
| more complex to handle in practice. UTF-16 use 2 bytes per characters (and |
| sometimes combines two pairs), it makes implementation easier, but looks a |
| bit overkill for Western languages encoding. Moreover the XML specification |
| allows document to be encoded in other encodings at the condition that they |
| are clearly labeled as such. For example the following is a wellformed XML |
| document encoded in ISO-8859 1 and using accentuated letter that we French |
| likes for both markup and content:</p> |
| <pre><?xml version="1.0" encoding="ISO-8859-1"?> |
| <très>là</très></pre> |
| |
| <p>Having internationalization support in libxml means the following:</p> |
| <ul> |
| <li>the document is properly parsed</li> |
| <li>informations about it's encoding are saved</li> |
| <li>it can be modified</li> |
| <li>it can be saved in its original encoding</li> |
| <li>it can also be saved in another encoding supported by libxml (for |
| example straight UTF8 or even an ASCII form)</li> |
| </ul> |
| |
| <p>Another very important point is that the whole libxml API, with the |
| exception of a few routines to read with a specific encoding or save to a |
| specific encoding, is completely agnostic about the original encoding of the |
| document.</p> |
| |
| <p>It should be noted too that the HTML parser embedded in libxml now obey |
| the same rules too, the following document will be (as of 2.2.2) handled in |
| an internationalized fashion by libxml too:</p> |
| <pre><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" |
| "http://www.w3.org/TR/REC-html40/loose.dtd"> |
| <html lang="fr"> |
| <head> |
| <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=ISO-8859-1"> |
| </head> |
| <body> |
| <p>W3C crée des standards pour le Web.</body> |
| </html></pre> |
| |
| <h3><a name="internal">The internal encoding, how and why</a></h3> |
| |
| <p>One of the core decision was to force all documents to be converted to a |
| default internal encoding, and that encoding to be UTF-8, here are the |
| rationale for those choices:</p> |
| <ul> |
| <li>keeping the native encoding in the internal form would force the libxml |
| users (or the code associated) to be fully aware of the encoding of the |
| original document, for examples when adding a text node to a document, |
| the content would have to be provided in the document encoding, i.e. the |
| client code would have to check it before hand, make sure it's conformant |
| to the encoding, etc ... Very hard in practice, though in some specific |
| cases this may make sense.</li> |
| <li>the second decision was which encoding. From the XML spec only UTF8 and |
| UTF16 really makes sense as being the two only encodings for which there |
| is mandatory support. UCS-4 (32 bits fixed size encoding) could be |
| considered an intelligent choice too since it's a direct Unicode mapping |
| support. I selected UTF-8 on the basis of efficiency and compatibility |
| with surrounding software: |
| <ul> |
| <li>UTF-8 while a bit more complex to convert from/to (i.e. slightly |
| more costly to import and export CPU wise) is also far more compact |
| than UTF-16 (and UCS-4) for a majority of the documents I see it used |
| for right now (RPM RDF catalogs, advogato data, various configuration |
| file formats, etc.) and the key point for today's computer |
| architecture is efficient uses of caches. If one nearly double the |
| memory requirement to store the same amount of data, this will trash |
| caches (main memory/external caches/internal caches) and my take is |
| that this harms the system far more than the CPU requirements needed |
| for the conversion to UTF-8</li> |
| <li>Most of libxml version 1 users were using it with straight ASCII |
| most of the time, doing the conversion with an internal encoding |
| requiring all their code to be rewritten was a serious show-stopper |
| for using UTF-16 or UCS-4.</li> |
| <li>UTF-8 is being used as the de-facto internal encoding standard for |
| related code like the <a href="http://www.pango.org/">pango</a> |
| upcoming Gnome text widget, and a lot of Unix code (yep another place |
| where Unix programmer base takes a different approach from Microsoft |
| - they are using UTF-16)</li> |
| </ul> |
| </li> |
| </ul> |
| |
| <p>What does this mean in practice for the libxml user:</p> |
| <ul> |
| <li>xmlChar, the libxml data type is a byte, those bytes must be assembled |
| as UTF-8 valid strings. The proper way to terminate an xmlChar * string |
| is simply to append 0 byte, as usual.</li> |
| <li>One just need to make sure that when using chars outside the ASCII set, |
| the values has been properly converted to UTF-8</li> |
| </ul> |
| |
| <h3><a name="implemente">How is it implemented ?</a></h3> |
| |
| <p>Let's describe how all this works within libxml, basically the I18N |
| (internationalization) support get triggered only during I/O operation, i.e. |
| when reading a document or saving one. Let's look first at the reading |
| sequence:</p> |
| <ol> |
| <li>when a document is processed, we usually don't know the encoding, a |
| simple heuristic allows to detect UTF-18 and UCS-4 from whose where the |
| ASCII range (0-0x7F) maps with ASCII</li> |
| <li>the xml declaration if available is parsed, including the encoding |
| declaration. At that point, if the autodetected encoding is different |
| from the one declared a call to xmlSwitchEncoding() is issued.</li> |
| <li>If there is no encoding declaration, then the input has to be in either |
| UTF-8 or UTF-16, if it is not then at some point when processing the |
| input, the converter/checker of UTF-8 form will raise an encoding error. |
| You may end-up with a garbled document, or no document at all ! Example: |
| <pre>~/XML -> ./xmllint err.xml |
| err.xml:1: error: Input is not proper UTF-8, indicate encoding ! |
| <très>là</très> |
| ^ |
| err.xml:1: error: Bytes: 0xE8 0x73 0x3E 0x6C |
| <très>là</très> |
| ^</pre> |
| </li> |
| <li>xmlSwitchEncoding() does an encoding name lookup, canonicalize it, and |
| then search the default registered encoding converters for that encoding. |
| If it's not within the default set and iconv() support has been compiled |
| it, it will ask iconv for such an encoder. If this fails then the parser |
| will report an error and stops processing: |
| <pre>~/XML -> ./xmllint err2.xml |
| err2.xml:1: error: Unsupported encoding UnsupportedEnc |
| <?xml version="1.0" encoding="UnsupportedEnc"?> |
| ^</pre> |
| </li> |
| <li>From that point the encoder processes progressively the input (it is |
| plugged as a front-end to the I/O module) for that entity. It captures |
| and convert on-the-fly the document to be parsed to UTF-8. The parser |
| itself just does UTF-8 checking of this input and process it |
| transparently. The only difference is that the encoding information has |
| been added to the parsing context (more precisely to the input |
| corresponding to this entity).</li> |
| <li>The result (when using DOM) is an internal form completely in UTF-8 |
| with just an encoding information on the document node.</li> |
| </ol> |
| |
| <p>Ok then what happens when saving the document (assuming you |
| collected/built an xmlDoc DOM like structure) ? It depends on the function |
| called, xmlSaveFile() will just try to save in the original encoding, while |
| xmlSaveFileTo() and xmlSaveFileEnc() can optionally save to a given |
| encoding:</p> |
| <ol> |
| <li>if no encoding is given, libxml will look for an encoding value |
| associated to the document and if it exists will try to save to that |
| encoding, |
| <p>otherwise everything is written in the internal form, i.e. UTF-8</p> |
| </li> |
| <li>so if an encoding was specified, either at the API level or on the |
| document, libxml will again canonicalize the encoding name, lookup for a |
| converter in the registered set or through iconv. If not found the |
| function will return an error code</li> |
| <li>the converter is placed before the I/O buffer layer, as another kind of |
| buffer, then libxml will simply push the UTF-8 serialization to through |
| that buffer, which will then progressively be converted and pushed onto |
| the I/O layer.</li> |
| <li>It is possible that the converter code fails on some input, for example |
| trying to push an UTF-8 encoded Chinese character through the UTF-8 to |
| ISO-8859-1 converter won't work. Since the encoders are progressive they |
| will just report the error and the number of bytes converted, at that |
| point libxml will decode the offending character, remove it from the |
| buffer and replace it with the associated charRef encoding &#123; and |
| resume the conversion. This guarantees that any document will be saved |
| without losses (except for markup names where this is not legal, this is |
| a problem in the current version, in practice avoid using non-ascii |
| characters for tags or attributes names @@). A special "ascii" encoding |
| name is used to save documents to a pure ascii form can be used when |
| portability is really crucial</li> |
| </ol> |
| |
| <p>Here is a few examples based on the same test document:</p> |
| <pre>~/XML -> ./xmllint isolat1 |
| <?xml version="1.0" encoding="ISO-8859-1"?> |
| <très>là</très> |
| ~/XML -> ./xmllint --encode UTF-8 isolat1 |
| <?xml version="1.0" encoding="UTF-8"?> |
| <très>là </très> |
| ~/XML -> </pre> |
| |
| <p>The same processing is applied (and reuse most of the code) for HTML I18N |
| processing. Looking up and modifying the content encoding is a bit more |
| difficult since it is located in a <meta> tag under the <head>, |
| so a couple of functions htmlGetMetaEncoding() and htmlSetMetaEncoding() have |
| been provided. The parser also attempts to switch encoding on the fly when |
| detecting such a tag on input. Except for that the processing is the same |
| (and again reuses the same code).</p> |
| |
| <h3><a name="Default">Default supported encodings</a></h3> |
| |
| <p>libxml has a set of default converters for the following encodings |
| (located in encoding.c):</p> |
| <ol> |
| <li>UTF-8 is supported by default (null handlers)</li> |
| <li>UTF-16, both little and big endian</li> |
| <li>ISO-Latin-1 (ISO-8859-1) covering most western languages</li> |
| <li>ASCII, useful mostly for saving</li> |
| <li>HTML, a specific handler for the conversion of UTF-8 to ASCII with HTML |
| predefined entities like &copy; for the Copyright sign.</li> |
| </ol> |
| |
| <p>More over when compiled on an Unix platform with iconv support the full |
| set of encodings supported by iconv can be instantly be used by libxml. On a |
| linux machine with glibc-2.1 the list of supported encodings and aliases fill |
| 3 full pages, and include UCS-4, the full set of ISO-Latin encodings, and the |
| various Japanese ones.</p> |
| |
| <h4>Encoding aliases</h4> |
| |
| <p>From 2.2.3, libxml has support to register encoding names aliases. The |
| goal is to be able to parse document whose encoding is supported but where |
| the name differs (for example from the default set of names accepted by |
| iconv). The following functions allow to register and handle new aliases for |
| existing encodings. Once registered libxml will automatically lookup the |
| aliases when handling a document:</p> |
| <ul> |
| <li>int xmlAddEncodingAlias(const char *name, const char *alias);</li> |
| <li>int xmlDelEncodingAlias(const char *alias);</li> |
| <li>const char * xmlGetEncodingAlias(const char *alias);</li> |
| <li>void xmlCleanupEncodingAliases(void);</li> |
| </ul> |
| |
| <h3><a name="extend">How to extend the existing support</a></h3> |
| |
| <p>Well adding support for new encoding, or overriding one of the encoders |
| (assuming it is buggy) should not be hard, just write an input and output |
| conversion routines to/from UTF-8, and register them using |
| xmlNewCharEncodingHandler(name, xxxToUTF8, UTF8Toxxx), and they will be |
| called automatically if the parser(s) encounter such an encoding name |
| (register it uppercase, this will help). The description of the encoders, |
| their arguments and expected return values are described in the encoding.h |
| header.</p> |
| |
| <p>A quick note on the topic of subverting the parser to use a different |
| internal encoding than UTF-8, in some case people will absolutely want to |
| keep the internal encoding different, I think it's still possible (but the |
| encoding must be compliant with ASCII on the same subrange) though I didn't |
| tried it. The key is to override the default conversion routines (by |
| registering null encoders/decoders for your charsets), and bypass the UTF-8 |
| checking of the parser by setting the parser context charset |
| (ctxt->charset) to something different than XML_CHAR_ENCODING_UTF8, but |
| there is no guarantee that this will work. You may also have some troubles |
| saving back.</p> |
| |
| <p>Basically proper I18N support is important, this requires at least |
| libxml-2.0.0, but a lot of features and corrections are really available only |
| starting 2.2.</p> |
| |
| <h2><a name="IO">I/O Interfaces</a></h2> |
| |
| <p>Table of Content:</p> |
| <ol> |
| <li><a href="#General1">General overview</a></li> |
| <li><a href="#basic">The basic buffer type</a></li> |
| <li><a href="#Input">Input I/O handlers</a></li> |
| <li><a href="#Output">Output I/O handlers</a></li> |
| <li><a href="#entities">The entities loader</a></li> |
| <li><a href="#Example2">Example of customized I/O</a></li> |
| </ol> |
| |
| <h3><a name="General1">General overview</a></h3> |
| |
| <p>The module <code><a |
| href="http://xmlsoft.org/html/libxml-xmlio.html">xmlIO.h</a></code> provides |
| the interfaces to the libxml I/O system. This consists of 4 main parts:</p> |
| <ul> |
| <li>Entities loader, this is a routine which tries to fetch the entities |
| (files) based on their PUBLIC and SYSTEM identifiers. The default loader |
| don't look at the public identifier since libxml do not maintain a |
| catalog. You can redefine you own entity loader by using |
| <code>xmlGetExternalEntityLoader()</code> and |
| <code>xmlSetExternalEntityLoader()</code>. <a href="#entities">Check the |
| example</a>.</li> |
| <li>Input I/O buffers which are a commodity structure used by the parser(s) |
| input layer to handle fetching the informations to feed the parser. This |
| provides buffering and is also a placeholder where the encoding |
| converters to UTF8 are piggy-backed.</li> |
| <li>Output I/O buffers are similar to the Input ones and fulfill similar |
| task but when generating a serialization from a tree.</li> |
| <li>A mechanism to register sets of I/O callbacks and associate them with |
| specific naming schemes like the protocol part of the URIs. |
| <p>This affect the default I/O operations and allows to use specific I/O |
| handlers for certain names.</p> |
| </li> |
| </ul> |
| |
| <p>The general mechanism used when loading http://rpmfind.net/xml.html for |
| example in the HTML parser is the following:</p> |
| <ol> |
| <li>The default entity loader calls <code>xmlNewInputFromFile()</code> with |
| the parsing context and the URI string.</li> |
| <li>the URI string is checked against the existing registered handlers |
| using their match() callback function, if the HTTP module was compiled |
| in, it is registered and its match() function will succeeds</li> |
| <li>the open() function of the handler is called and if successful will |
| return an I/O Input buffer</li> |
| <li>the parser will the start reading from this buffer and progressively |
| fetch information from the resource, calling the read() function of the |
| handler until the resource is exhausted</li> |
| <li>if an encoding change is detected it will be installed on the input |
| buffer, providing buffering and efficient use of the conversion |
| routines</li> |
| <li>once the parser has finished, the close() function of the handler is |
| called once and the Input buffer and associated resources are |
| deallocated.</li> |
| </ol> |
| |
| <p>The user defined callbacks are checked first to allow overriding of the |
| default libxml I/O routines.</p> |
| |
| <h3><a name="basic">The basic buffer type</a></h3> |
| |
| <p>All the buffer manipulation handling is done using the |
| <code>xmlBuffer</code> type define in <code><a |
| href="http://xmlsoft.org/html/libxml-tree.html">tree.h</a> </code>which is a |
| resizable memory buffer. The buffer allocation strategy can be selected to be |
| either best-fit or use an exponential doubling one (CPU vs. memory use |
| trade-off). The values are <code>XML_BUFFER_ALLOC_EXACT</code> and |
| <code>XML_BUFFER_ALLOC_DOUBLEIT</code>, and can be set individually or on a |
| system wide basis using <code>xmlBufferSetAllocationScheme()</code>. A number |
| of functions allows to manipulate buffers with names starting with the |
| <code>xmlBuffer...</code> prefix.</p> |
| |
| <h3><a name="Input">Input I/O handlers</a></h3> |
| |
| <p>An Input I/O handler is a simple structure |
| <code>xmlParserInputBuffer</code> containing a context associated to the |
| resource (file descriptor, or pointer to a protocol handler), the read() and |
| close() callbacks to use and an xmlBuffer. And extra xmlBuffer and a charset |
| encoding handler are also present to support charset conversion when |
| needed.</p> |
| |
| <h3><a name="Output">Output I/O handlers</a></h3> |
| |
| <p>An Output handler <code>xmlOutputBuffer</code> is completely similar to an |
| Input one except the callbacks are write() and close().</p> |
| |
| <h3><a name="entities">The entities loader</a></h3> |
| |
| <p>The entity loader resolves requests for new entities and create inputs for |
| the parser. Creating an input from a filename or an URI string is done |
| through the xmlNewInputFromFile() routine. The default entity loader do not |
| handle the PUBLIC identifier associated with an entity (if any). So it just |
| calls xmlNewInputFromFile() with the SYSTEM identifier (which is mandatory in |
| XML).</p> |
| |
| <p>If you want to hook up a catalog mechanism then you simply need to |
| override the default entity loader, here is an example:</p> |
| <pre>#include <libxml/xmlIO.h> |
| |
| xmlExternalEntityLoader defaultLoader = NULL; |
| |
| xmlParserInputPtr |
| xmlMyExternalEntityLoader(const char *URL, const char *ID, |
| xmlParserCtxtPtr ctxt) { |
| xmlParserInputPtr ret; |
| const char *fileID = NULL; |
| /* lookup for the fileID depending on ID */ |
| |
| ret = xmlNewInputFromFile(ctxt, fileID); |
| if (ret != NULL) |
| return(ret); |
| if (defaultLoader != NULL) |
| ret = defaultLoader(URL, ID, ctxt); |
| return(ret); |
| } |
| |
| int main(..) { |
| ... |
| |
| /* |
| * Install our own entity loader |
| */ |
| defaultLoader = xmlGetExternalEntityLoader(); |
| xmlSetExternalEntityLoader(xmlMyExternalEntityLoader); |
| |
| ... |
| }</pre> |
| |
| <h3><a name="Example2">Example of customized I/O</a></h3> |
| |
| <p>This example come from <a href="http://xmlsoft.org/messages/0708.html">a |
| real use case</a>, xmlDocDump() closes the FILE * passed by the application |
| and this was a problem. The <a |
| href="http://xmlsoft.org/messages/0711.html">solution</a> was to redefine a |
| new output handler with the closing call deactivated:</p> |
| <ol> |
| <li>First define a new I/O output allocator where the output don't close |
| the file: |
| <pre>xmlOutputBufferPtr |
| xmlOutputBufferCreateOwn(FILE *file, xmlCharEncodingHandlerPtr encoder) { |
| xmlOutputBufferPtr ret; |
| |
| if (xmlOutputCallbackInitialized == 0) |
| xmlRegisterDefaultOutputCallbacks(); |
| |
| if (file == NULL) return(NULL); |
| ret = xmlAllocOutputBuffer(encoder); |
| if (ret != NULL) { |
| ret->context = file; |
| ret->writecallback = xmlFileWrite; |
| ret->closecallback = NULL; /* No close callback */ |
| } |
| return(ret); |
| } </pre> |
| </li> |
| <li>And then use it to save the document: |
| <pre>FILE *f; |
| xmlOutputBufferPtr output; |
| xmlDocPtr doc; |
| int res; |
| |
| f = ... |
| doc = .... |
| |
| output = xmlOutputBufferCreateOwn(f, NULL); |
| res = xmlSaveFileTo(output, doc, NULL); |
| </pre> |
| </li> |
| </ol> |
| |
| <h2><a name="Catalog">Catalog support</a></h2> |
| |
| <p>Table of Content:</p> |
| <ol> |
| <li><a href="General2">General overview</a></li> |
| <li><a href="#definition">The definition</a></li> |
| <li><a href="#Simple">Using catalogs</a></li> |
| <li><a href="#Some">Some examples</a></li> |
| <li><a href="#reference">How to tune catalog usage</a></li> |
| <li><a href="#validate">How to debug catalog processing</a></li> |
| <li><a href="#Declaring">How to create and maintain catalogs</a></li> |
| <li><a href="#implemento">The implementor corner quick review of the |
| API</a></li> |
| <li><a href="#Other">Other resources</a></li> |
| </ol> |
| |
| <h3><a name="General2">General overview</a></h3> |
| |
| <p>What is a catalog? Basically it's a lookup mechanism used when an entity |
| (a file or a remote resource) references another entity. The catalog lookup |
| is inserted between the moment the reference is recognized by the software |
| (XML parser, stylesheet processing, or even images referenced for inclusion |
| in a rendering) and the time where loading that resource is actually |
| started.</p> |
| |
| <p>It is basically used for 3 things:</p> |
| <ul> |
| <li>mapping from "logical" names, the public identifiers and a more |
| concrete name usable for download (and URI). For example it can associate |
| the logical name |
| <p>"-//OASIS//DTD DocBook XML V4.1.2//EN"</p> |
| <p>of the DocBook 4.1.2 XML DTD with the actual URL where it can be |
| downloaded</p> |
| <p>http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd</p> |
| </li> |
| <li>remapping from a given URL to another one, like an HTTP indirection |
| saying that |
| <p>"http://www.oasis-open.org/committes/tr.xsl"</p> |
| <p>should really be looked at</p> |
| <p>"http://www.oasis-open.org/committes/entity/stylesheets/base/tr.xsl"</p> |
| </li> |
| <li>providing a local cache mechanism allowing to load the entities |
| associated to public identifiers or remote resources, this is a really |
| important feature for any significant deployment of XML or SGML since it |
| allows to avoid the aleas and delays associated to fetching remote |
| resources.</li> |
| </ul> |
| |
| <h3><a name="definition">The definitions</a></h3> |
| |
| <p>Libxml, as of 2.4.3 implements 2 kind of catalogs:</p> |
| <ul> |
| <li>the older SGML catalogs, the official spec is SGML Open Technical |
| Resolution TR9401:1997, but is better understood by reading <a |
| href="http://www.jclark.com/sp/catalog.htm">the SP Catalog page</a> from |
| James Clark. This is relatively old and not the preferred mode of |
| operation of libxml.</li> |
| <li><a href="http://www.oasis-open.org/committees/entity/spec.html">XML |
| Catalogs</a> is far more flexible, more recent, uses an XML syntax and |
| should scale quite better. This is the default option of libxml.</li> |
| </ul> |
| |
| <p></p> |
| |
| <h3><a name="Simple">Using catalog</a></h3> |
| |
| <p>In a normal environment libxml will by default check the presence of a |
| catalog in /etc/xml/catalog, and assuming it has been correctly populated, |
| the processing is completely transparent to the document user. To take a |
| concrete example, suppose you are authoring a DocBook document, this one |
| starts with the following DOCTYPE definition:</p> |
| <pre><?xml version='1.0'?> |
| <!DOCTYPE book PUBLIC "-//Norman Walsh//DTD DocBk XML V3.1.4//EN" |
| "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd"></pre> |
| |
| <p>When validating the document with libxml, the catalog will be |
| automatically consulted to lookup the public identifier "-//Norman Walsh//DTD |
| DocBk XML V3.1.4//EN" and the system identifier |
| "http://nwalsh.com/docbook/xml/3.1.4/db3xml.dtd", and if these entities have |
| been installed on your system and the catalogs actually point to them, libxml |
| will fetch them from the local disk.</p> |
| |
| <p style="font-size: 10pt"><strong>Note</strong>: Really don't use this |
| DOCTYPE example it's a really old version, but is fine as an example.</p> |
| |
| <p>Libxml will check the catalog each time that it is requested to load an |
| entity, this includes DTD, external parsed entities, stylesheets, etc ... If |
| your system is correctly configured all the authoring phase and processing |
| should use only local files, even if your document stays portable because it |
| uses the canonical public and system ID, referencing the remote document.</p> |
| |
| <h3><a name="Some">Some examples:</a></h3> |
| |
| <p>Here is a couple of fragments from XML Catalogs used in libxml early |
| regression tests in <code>test/catalogs</code> :</p> |
| <pre><?xml version="1.0"?> |
| <!DOCTYPE catalog PUBLIC |
| "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" |
| "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> |
| <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> |
| <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" |
| uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> |
| ...</pre> |
| |
| <p>This is the beginning of a catalog for DocBook 4.1.2, XML Catalogs are |
| written in XML, there is a specific namespace for catalog elements |
| "urn:oasis:names:tc:entity:xmlns:xml:catalog". The first entry in this |
| catalog is a <code>public</code> mapping it allows to associate a Public |
| Identifier with an URI.</p> |
| <pre>... |
| <rewriteSystem systemIdStartString="http://www.oasis-open.org/docbook/" |
| rewritePrefix="file:///usr/share/xml/docbook/"/> |
| ...</pre> |
| |
| <p>A <code>rewriteSystem</code> is a very powerful instruction, it says that |
| any URI starting with a given prefix should be looked at another URI |
| constructed by replacing the prefix with an new one. In effect this acts like |
| a cache system for a full area of the Web. In practice it is extremely useful |
| with a file prefix if you have installed a copy of those resources on your |
| local system.</p> |
| <pre>... |
| <delegatePublic publicIdStartString="-//OASIS//DTD XML Catalog //" |
| catalog="file:///usr/share/xml/docbook.xml"/> |
| <delegatePublic publicIdStartString="-//OASIS//ENTITIES DocBook XML" |
| catalog="file:///usr/share/xml/docbook.xml"/> |
| <delegatePublic publicIdStartString="-//OASIS//DTD DocBook XML" |
| catalog="file:///usr/share/xml/docbook.xml"/> |
| <delegateSystem systemIdStartString="http://www.oasis-open.org/docbook/" |
| catalog="file:///usr/share/xml/docbook.xml"/> |
| <delegateURI uriStartString="http://www.oasis-open.org/docbook/" |
| catalog="file:///usr/share/xml/docbook.xml"/> |
| ...</pre> |
| |
| <p>Delegation is the core features which allows to build a tree of catalogs, |
| easier to maintain than a single catalog, based on Public Identifier, System |
| Identifier or URI prefixes it instructs the catalog software to look up |
| entries in another resource. This feature allow to build hierarchies of |
| catalogs, the set of entries presented should be sufficient to redirect the |
| resolution of all DocBook references to the specific catalog in |
| <code>/usr/share/xml/docbook.xml</code> this one in turn could delegate all |
| references for DocBook 4.2.1 to a specific catalog installed at the same time |
| as the DocBook resources on the local machine.</p> |
| |
| <h3><a name="reference">How to tune catalog usage:</a></h3> |
| |
| <p>The user can change the default catalog behaviour by redirecting queries |
| to its own set of catalogs, this can be done by setting the |
| <code>XML_CATALOG_FILES</code> environment variable to a list of catalogs, an |
| empty one should deactivate loading the default <code>/etc/xml/catalog</code> |
| default catalog</p> |
| |
| <h3><a name="validate">How to debug catalog processing:</a></h3> |
| |
| <p>Setting up the <code>XML_DEBUG_CATALOG</code> environment variable will |
| make libxml output debugging informations for each catalog operations, for |
| example:</p> |
| <pre>orchis:~/XML -> xmllint --memory --noout test/ent2 |
| warning: failed to load external entity "title.xml" |
| orchis:~/XML -> export XML_DEBUG_CATALOG= |
| orchis:~/XML -> xmllint --memory --noout test/ent2 |
| Failed to parse catalog /etc/xml/catalog |
| Failed to parse catalog /etc/xml/catalog |
| warning: failed to load external entity "title.xml" |
| Catalogs cleanup |
| orchis:~/XML -> </pre> |
| |
| <p>The test/ent2 references an entity, running the parser from memory makes |
| the base URI unavailable and the the "title.xml" entity cannot be loaded. |
| Setting up the debug environment variable allows to detect that an attempt is |
| made to load the <code>/etc/xml/catalog</code> but since it's not present the |
| resolution fails.</p> |
| |
| <p>But the most advanced way to debug XML catalog processing is to use the |
| <strong>xmlcatalog</strong> command shipped with libxml2, it allows to load |
| catalogs and make resolution queries to see what is going on. This is also |
| used for the regression tests:</p> |
| <pre>orchis:~/XML -> ./xmlcatalog test/catalogs/docbook.xml \ |
| "-//OASIS//DTD DocBook XML V4.1.2//EN" |
| http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd |
| orchis:~/XML -> </pre> |
| |
| <p>For debugging what is going on, adding one -v flags increase the verbosity |
| level to indicate the processing done (adding a second flag also indicate |
| what elements are recognized at parsing):</p> |
| <pre>orchis:~/XML -> ./xmlcatalog -v test/catalogs/docbook.xml \ |
| "-//OASIS//DTD DocBook XML V4.1.2//EN" |
| Parsing catalog test/catalogs/docbook.xml's content |
| Found public match -//OASIS//DTD DocBook XML V4.1.2//EN |
| http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd |
| Catalogs cleanup |
| orchis:~/XML -> </pre> |
| |
| <p>A shell interface is also available to debug and process multiple queries |
| (and for regression tests):</p> |
| <pre>orchis:~/XML -> ./xmlcatalog -shell test/catalogs/docbook.xml \ |
| "-//OASIS//DTD DocBook XML V4.1.2//EN" |
| > help |
| Commands available: |
| public PublicID: make a PUBLIC identifier lookup |
| system SystemID: make a SYSTEM identifier lookup |
| resolve PublicID SystemID: do a full resolver lookup |
| add 'type' 'orig' 'replace' : add an entry |
| del 'values' : remove values |
| dump: print the current catalog state |
| debug: increase the verbosity level |
| quiet: decrease the verbosity level |
| exit: quit the shell |
| > public "-//OASIS//DTD DocBook XML V4.1.2//EN" |
| http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd |
| > quit |
| orchis:~/XML -> </pre> |
| |
| <p>This should be sufficient for most debugging purpose, this was actually |
| used heavily to debug the XML Catalog implementation itself.</p> |
| |
| <h3><a name="Declaring">How to create and maintain</a> catalogs:</h3> |
| |
| <p>Basically XML Catalogs are XML files, you can either use XML tools to |
| manage them or use <strong>xmlcatalog</strong> for this. The basic step is |
| to create a catalog the -create option provide this facility:</p> |
| <pre>orchis:~/XML -> ./xmlcatalog --create tst.xml |
| <?xml version="1.0"?> |
| <!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" |
| "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> |
| <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> |
| orchis:~/XML -> </pre> |
| |
| <p>By default xmlcatalog does not overwrite the original catalog and save the |
| result on the standard output, this can be overridden using the -noout |
| option. The <code>-add</code> command allows to add entries in the |
| catalog:</p> |
| <pre>orchis:~/XML -> ./xmlcatalog --noout --create --add "public" \ |
| "-//OASIS//DTD DocBook XML V4.1.2//EN" \ |
| http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd tst.xml |
| orchis:~/XML -> cat tst.xml |
| <?xml version="1.0"?> |
| <!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" \ |
| "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> |
| <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"> |
| <public publicId="-//OASIS//DTD DocBook XML V4.1.2//EN" |
| uri="http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd"/> |
| </catalog> |
| orchis:~/XML -> </pre> |
| |
| <p>The <code>-add</code> option will always take 3 parameters even if some of |
| the XML Catalog constructs (like nextCatalog) will have only a single |
| argument, just pass a third empty string, it will be ignored.</p> |
| |
| <p>Similarly the <code>-del</code> option remove matching entries from the |
| catalog:</p> |
| <pre>orchis:~/XML -> ./xmlcatalog --del \ |
| "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" tst.xml |
| <?xml version="1.0"?> |
| <!DOCTYPE catalog PUBLIC "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN" |
| "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"> |
| <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog"/> |
| orchis:~/XML -> </pre> |
| |
| <p>The catalog is now empty. Note that the matching of <code>-del</code> is |
| exact and would have worked in a similar fashion with the Public ID |
| string.</p> |
| |
| <p>This is rudimentary but should be sufficient to manage a not too complex |
| catalog tree of resources.</p> |
| |
| <h3><a name="implemento">The implementor corner quick review of the |
| API:</a></h3> |
| |
| <p>First, and like for every other module of libxml, there is an |
| automatically generated <a href="html/libxml-catalog.html">API page for |
| catalog support</a>.</p> |
| |
| <p>The header for the catalog interfaces should be included as:</p> |
| <pre>#include <libxml/catalog.h></pre> |
| |
| <p>The API is voluntarily kept very simple. First it is not obvious that |
| applications really need access to it since it is the default behaviour of |
| libxml (Note: it is possible to completely override libxml default catalog by |
| using <a href="html/libxml-parser.html">xmlSetExternalEntityLoader</a> to |
| plug an application specific resolver).</p> |
| |
| <p>Basically libxml support 2 catalog lists:</p> |
| <ul> |
| <li>the default one, global shared by all the application</li> |
| <li>a per-document catalog, this one is built if the document uses the |
| <code>oasis-xml-catalog</code> PIs to specify its own catalog list, it is |
| associated to the parser context and destroyed when the parsing context |
| is destroyed.</li> |
| </ul> |
| |
| <p>the document one will be used first if it exists.</p> |
| |
| <h4>Initialization routines:</h4> |
| |
| <p>xmlInitializeCatalog(), xmlLoadCatalog() and xmlLoadCatalogs() should be |
| used at startup to initialize the catalog, if the catalog should be |
| initialized with specific values xmlLoadCatalog() or xmlLoadCatalogs() |
| should be called before xmlInitializeCatalog() which would otherwise do a |
| default initialization first.</p> |
| |
| <p>The xmlCatalogAddLocal() call is used by the parser to grow the document |
| own catalog list if needed.</p> |
| |
| <h4>Preferences setup:</h4> |
| |
| <p>The XML Catalog spec requires the possibility to select default |
| preferences between public and system delegation, |
| xmlCatalogSetDefaultPrefer() allows this, xmlCatalogSetDefaults() and |
| xmlCatalogGetDefaults() allow to control if XML Catalogs resolution should |
| be forbidden, allowed for global catalog, for document catalog or both, the |
| default is to allow both.</p> |
| |
| <p>And of course xmlCatalogSetDebug() allows to generate debug messages |
| (through the xmlGenericError() mechanism).</p> |
| |
| <h4>Querying routines:</h4> |
| |
| <p>xmlCatalogResolve(), xmlCatalogResolveSystem(), xmlCatalogResolvePublic() |
| and xmlCatalogResolveURI() are relatively explicit if you read the XML |
| Catalog specification they correspond to section 7 algorithms, they should |
| also work if you have loaded an SGML catalog with a simplified semantic.</p> |
| |
| <p>xmlCatalogLocalResolve() and xmlCatalogLocalResolveURI() are the same but |
| operate on the document catalog list</p> |
| |
| <h4>Cleanup and Miscellaneous:</h4> |
| |
| <p>xmlCatalogCleanup() free-up the global catalog, xmlCatalogFreeLocal() is |
| the per-document equivalent.</p> |
| |
| <p>xmlCatalogAdd() and xmlCatalogRemove() are used to dynamically modify the |
| first catalog in the global list, and xmlCatalogDump() allows to dump a |
| catalog state, those routines are primarily designed for xmlcatalog, I'm not |
| sure that exposing more complex interfaces (like navigation ones) would be |
| really useful.</p> |
| |
| <p>The xmlParseCatalogFile() is a function used to load XML Catalog files, |
| it's similar as xmlParseFile() except it bypass all catalog lookups, it's |
| provided because this functionality may be useful for client tools.</p> |
| |
| <h4>threaded environments:</h4> |
| |
| <p>Since the catalog tree is built progressively, some care has been taken to |
| try to avoid troubles in multithreaded environments. The code is now thread |
| safe assuming that the libxml library has been compiled with threads |
| support.</p> |
| |
| <p></p> |
| |
| <h3><a name="Other">Other resources</a></h3> |
| |
| <p>The XML Catalog specification is relatively recent so there isn't much |
| literature to point at:</p> |
| <ul> |
| <li>You can find a good rant from Norm Walsh about <a |
| href="http://www.arbortext.com/Think_Tank/XML_Resources/Issue_Three/issue_three.html">the |
| need for catalogs</a>, it provides a lot of context informations even if |
| I don't agree with everything presented. Norm also wrote a more recent |
| article <a |
| href="http://wwws.sun.com/software/xml/developers/resolver/article/">XML |
| entities and URI resolvers</a> describing them.</li> |
| <li>An <a href="http://home.ccil.org/~cowan/XML/XCatalog.html">old XML |
| catalog proposal</a> from John Cowan</li> |
| <li>The <a href="http://www.rddl.org/">Resource Directory Description |
| Language</a> (RDDL) another catalog system but more oriented toward |
| providing metadata for XML namespaces.</li> |
| <li>the page from the OASIS Technical <a |
| href="http://www.oasis-open.org/committees/entity/">Committee on Entity |
| Resolution</a> who maintains XML Catalog, you will find pointers to the |
| specification update, some background and pointers to others tools |
| providing XML Catalog support</li> |
| <li>Here is a <a href="buildDocBookCatalog">shell script</a> to generate |
| XML Catalogs for DocBook 4.1.2 . If it can write to the /etc/xml/ |
| directory, it will set-up /etc/xml/catalog and /etc/xml/docbook based on |
| the resources found on the system. Otherwise it will just create |
| ~/xmlcatalog and ~/dbkxmlcatalog and doing: |
| <p><code>export XML_CATALOG_FILES=$HOME/xmlcatalog</code></p> |
| <p>should allow to process DocBook documentations without requiring |
| network accesses for the DTD or stylesheets</p> |
| </li> |
| <li>I have uploaded <a href="ftp://xmlsoft.org/test/dbk412catalog.tar.gz">a |
| small tarball</a> containing XML Catalogs for DocBook 4.1.2 which seems |
| to work fine for me too</li> |
| <li>The <a href="http://www.xmlsoft.org/xmlcatalog_man.html">xmlcatalog |
| manual page</a></li> |
| </ul> |
| |
| <p>If you have suggestions for corrections or additions, simply contact |
| me:</p> |
| |
| <h2><a name="library">The parser interfaces</a></h2> |
| |
| <p>This section is directly intended to help programmers getting bootstrapped |
| using the XML library from the C language. It is not intended to be |
| extensive. I hope the automatically generated documents will provide the |
| completeness required, but as a separate set of documents. The interfaces of |
| the XML library are by principle low level, there is nearly zero abstraction. |
| Those interested in a higher level API should <a href="#DOM">look at |
| DOM</a>.</p> |
| |
| <p>The <a href="html/libxml-parser.html">parser interfaces for XML</a> are |
| separated from the <a href="html/libxml-htmlparser.html">HTML parser |
| interfaces</a>. Let's have a look at how the XML parser can be called:</p> |
| |
| <h3><a name="Invoking">Invoking the parser : the pull method</a></h3> |
| |
| <p>Usually, the first thing to do is to read an XML input. The parser accepts |
| documents either from in-memory strings or from files. The functions are |
| defined in "parser.h":</p> |
| <dl> |
| <dt><code>xmlDocPtr xmlParseMemory(char *buffer, int size);</code></dt> |
| <dd><p>Parse a null-terminated string containing the document.</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>xmlDocPtr xmlParseFile(const char *filename);</code></dt> |
| <dd><p>Parse an XML document contained in a (possibly compressed) |
| file.</p> |
| </dd> |
| </dl> |
| |
| <p>The parser returns a pointer to the document structure (or NULL in case of |
| failure).</p> |
| |
| <h3 id="Invoking1">Invoking the parser: the push method</h3> |
| |
| <p>In order for the application to keep the control when the document is |
| being fetched (which is common for GUI based programs) libxml provides a push |
| interface, too, as of version 1.8.3. Here are the interface functions:</p> |
| <pre>xmlParserCtxtPtr xmlCreatePushParserCtxt(xmlSAXHandlerPtr sax, |
| void *user_data, |
| const char *chunk, |
| int size, |
| const char *filename); |
| int xmlParseChunk (xmlParserCtxtPtr ctxt, |
| const char *chunk, |
| int size, |
| int terminate);</pre> |
| |
| <p>and here is a simple example showing how to use the interface:</p> |
| <pre> FILE *f; |
| |
| f = fopen(filename, "r"); |
| if (f != NULL) { |
| int res, size = 1024; |
| char chars[1024]; |
| xmlParserCtxtPtr ctxt; |
| |
| res = fread(chars, 1, 4, f); |
| if (res > 0) { |
| ctxt = xmlCreatePushParserCtxt(NULL, NULL, |
| chars, res, filename); |
| while ((res = fread(chars, 1, size, f)) > 0) { |
| xmlParseChunk(ctxt, chars, res, 0); |
| } |
| xmlParseChunk(ctxt, chars, 0, 1); |
| doc = ctxt->myDoc; |
| xmlFreeParserCtxt(ctxt); |
| } |
| }</pre> |
| |
| <p>The HTML parser embedded into libxml also has a push interface; the |
| functions are just prefixed by "html" rather than "xml".</p> |
| |
| <h3 id="Invoking2">Invoking the parser: the SAX interface</h3> |
| |
| <p>The tree-building interface makes the parser memory-hungry, first loading |
| the document in memory and then building the tree itself. Reading a document |
| without building the tree is possible using the SAX interfaces (see SAX.h and |
| <a href="http://www.daa.com.au/~james/gnome/xml-sax/xml-sax.html">James |
| Henstridge's documentation</a>). Note also that the push interface can be |
| limited to SAX: just use the two first arguments of |
| <code>xmlCreatePushParserCtxt()</code>.</p> |
| |
| <h3><a name="Building">Building a tree from scratch</a></h3> |
| |
| <p>The other way to get an XML tree in memory is by building it. Basically |
| there is a set of functions dedicated to building new elements. (These are |
| also described in <libxml/tree.h>.) For example, here is a piece of |
| code that produces the XML document used in the previous examples:</p> |
| <pre> #include <libxml/tree.h> |
| xmlDocPtr doc; |
| xmlNodePtr tree, subtree; |
| |
| doc = xmlNewDoc("1.0"); |
| doc->children = xmlNewDocNode(doc, NULL, "EXAMPLE", NULL); |
| xmlSetProp(doc->children, "prop1", "gnome is great"); |
| xmlSetProp(doc->children, "prop2", "& linux too"); |
| tree = xmlNewChild(doc->children, NULL, "head", NULL); |
| subtree = xmlNewChild(tree, NULL, "title", "Welcome to Gnome"); |
| tree = xmlNewChild(doc->children, NULL, "chapter", NULL); |
| subtree = xmlNewChild(tree, NULL, "title", "The Linux adventure"); |
| subtree = xmlNewChild(tree, NULL, "p", "bla bla bla ..."); |
| subtree = xmlNewChild(tree, NULL, "image", NULL); |
| xmlSetProp(subtree, "href", "linus.gif");</pre> |
| |
| <p>Not really rocket science ...</p> |
| |
| <h3><a name="Traversing">Traversing the tree</a></h3> |
| |
| <p>Basically by <a href="html/libxml-tree.html">including "tree.h"</a> your |
| code has access to the internal structure of all the elements of the tree. |
| The names should be somewhat simple like <strong>parent</strong>, |
| <strong>children</strong>, <strong>next</strong>, <strong>prev</strong>, |
| <strong>properties</strong>, etc... For example, still with the previous |
| example:</p> |
| <pre><code>doc->children->children->children</code></pre> |
| |
| <p>points to the title element,</p> |
| <pre>doc->children->children->next->children->children</pre> |
| |
| <p>points to the text node containing the chapter title "The Linux |
| adventure".</p> |
| |
| <p><strong>NOTE</strong>: XML allows <em>PI</em>s and <em>comments</em> to be |
| present before the document root, so <code>doc->children</code> may point |
| to an element which is not the document Root Element; a function |
| <code>xmlDocGetRootElement()</code> was added for this purpose.</p> |
| |
| <h3><a name="Modifying">Modifying the tree</a></h3> |
| |
| <p>Functions are provided for reading and writing the document content. Here |
| is an excerpt from the <a href="html/libxml-tree.html">tree API</a>:</p> |
| <dl> |
| <dt><code>xmlAttrPtr xmlSetProp(xmlNodePtr node, const xmlChar *name, const |
| xmlChar *value);</code></dt> |
| <dd><p>This sets (or changes) an attribute carried by an ELEMENT node. |
| The value can be NULL.</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>const xmlChar *xmlGetProp(xmlNodePtr node, const xmlChar |
| *name);</code></dt> |
| <dd><p>This function returns a pointer to new copy of the property |
| content. Note that the user must deallocate the result.</p> |
| </dd> |
| </dl> |
| |
| <p>Two functions are provided for reading and writing the text associated |
| with elements:</p> |
| <dl> |
| <dt><code>xmlNodePtr xmlStringGetNodeList(xmlDocPtr doc, const xmlChar |
| *value);</code></dt> |
| <dd><p>This function takes an "external" string and converts it to one |
| text node or possibly to a list of entity and text nodes. All |
| non-predefined entity references like &Gnome; will be stored |
| internally as entity nodes, hence the result of the function may not be |
| a single node.</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>xmlChar *xmlNodeListGetString(xmlDocPtr doc, xmlNodePtr list, int |
| inLine);</code></dt> |
| <dd><p>This function is the inverse of |
| <code>xmlStringGetNodeList()</code>. It generates a new string |
| containing the content of the text and entity nodes. Note the extra |
| argument inLine. If this argument is set to 1, the function will expand |
| entity references. For example, instead of returning the &Gnome; |
| XML encoding in the string, it will substitute it with its value (say, |
| "GNU Network Object Model Environment").</p> |
| </dd> |
| </dl> |
| |
| <h3><a name="Saving">Saving a tree</a></h3> |
| |
| <p>Basically 3 options are possible:</p> |
| <dl> |
| <dt><code>void xmlDocDumpMemory(xmlDocPtr cur, xmlChar**mem, int |
| *size);</code></dt> |
| <dd><p>Returns a buffer into which the document has been saved.</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>extern void xmlDocDump(FILE *f, xmlDocPtr doc);</code></dt> |
| <dd><p>Dumps a document to an open file descriptor.</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>int xmlSaveFile(const char *filename, xmlDocPtr cur);</code></dt> |
| <dd><p>Saves the document to a file. In this case, the compression |
| interface is triggered if it has been turned on.</p> |
| </dd> |
| </dl> |
| |
| <h3><a name="Compressio">Compression</a></h3> |
| |
| <p>The library transparently handles compression when doing file-based |
| accesses. The level of compression on saves can be turned on either globally |
| or individually for one file:</p> |
| <dl> |
| <dt><code>int xmlGetDocCompressMode (xmlDocPtr doc);</code></dt> |
| <dd><p>Gets the document compression ratio (0-9).</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>void xmlSetDocCompressMode (xmlDocPtr doc, int mode);</code></dt> |
| <dd><p>Sets the document compression ratio.</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>int xmlGetCompressMode(void);</code></dt> |
| <dd><p>Gets the default compression ratio.</p> |
| </dd> |
| </dl> |
| <dl> |
| <dt><code>void xmlSetCompressMode(int mode);</code></dt> |
| <dd><p>Sets the default compression ratio.</p> |
| </dd> |
| </dl> |
| |
| <h2><a name="Entities">Entities or no entities</a></h2> |
| |
| <p>Entities in principle are similar to simple C macros. An entity defines an |
| abbreviation for a given string that you can reuse many times throughout the |
| content of your document. Entities are especially useful when a given string |
| may occur frequently within a document, or to confine the change needed to a |
| document to a restricted area in the internal subset of the document (at the |
| beginning). Example:</p> |
| <pre>1 <?xml version="1.0"?> |
| 2 <!DOCTYPE EXAMPLE SYSTEM "example.dtd" [ |
| 3 <!ENTITY xml "Extensible Markup Language"> |
| 4 ]> |
| 5 <EXAMPLE> |
| 6 &xml; |
| 7 </EXAMPLE></pre> |
| |
| <p>Line 3 declares the xml entity. Line 6 uses the xml entity, by prefixing |
| its name with '&' and following it by ';' without any spaces added. There |
| are 5 predefined entities in libxml allowing you to escape characters with |
| predefined meaning in some parts of the xml document content: |
| <strong>&lt;</strong> for the character '<', <strong>&gt;</strong> |
| for the character '>', <strong>&apos;</strong> for the character ''', |
| <strong>&quot;</strong> for the character '"', and |
| <strong>&amp;</strong> for the character '&'.</p> |
| |
| <p>One of the problems related to entities is that you may want the parser to |
| substitute an entity's content so that you can see the replacement text in |
| your application. Or you may prefer to keep entity references as such in the |
| content to be able to save the document back without losing this usually |
| precious information (if the user went through the pain of explicitly |
| defining entities, he may have a a rather negative attitude if you blindly |
| substitute them as saving time). The <a |
| href="html/libxml-parser.html#XMLSUBSTITUTEENTITIESDEFAULT">xmlSubstituteEntitiesDefault()</a> |
| function allows you to check and change the behaviour, which is to not |
| substitute entities by default.</p> |
| |
| <p>Here is the DOM tree built by libxml for the previous document in the |
| default case:</p> |
| <pre>/gnome/src/gnome-xml -> ./xmllint --debug test/ent1 |
| DOCUMENT |
| version=1.0 |
| ELEMENT EXAMPLE |
| TEXT |
| content= |
| ENTITY_REF |
| INTERNAL_GENERAL_ENTITY xml |
| content=Extensible Markup Language |
| TEXT |
| content=</pre> |
| |
| <p>And here is the result when substituting entities:</p> |
| <pre>/gnome/src/gnome-xml -> ./tester --debug --noent test/ent1 |
| DOCUMENT |
| version=1.0 |
| ELEMENT EXAMPLE |
| TEXT |
| content= Extensible Markup Language</pre> |
| |
| <p>So, entities or no entities? Basically, it depends on your use case. I |
| suggest that you keep the non-substituting default behaviour and avoid using |
| entities in your XML document or data if you are not willing to handle the |
| entity references elements in the DOM tree.</p> |
| |
| <p>Note that at save time libxml enforces the conversion of the predefined |
| entities where necessary to prevent well-formedness problems, and will also |
| transparently replace those with chars (i.e. it will not generate entity |
| reference elements in the DOM tree or call the reference() SAX callback when |
| finding them in the input).</p> |
| |
| <p><span style="background-color: #FF0000">WARNING</span>: handling entities |
| on top of the libxml SAX interface is difficult!!! If you plan to use |
| non-predefined entities in your documents, then the learning curve to handle |
| then using the SAX API may be long. If you plan to use complex documents, I |
| strongly suggest you consider using the DOM interface instead and let libxml |
| deal with the complexity rather than trying to do it yourself.</p> |
| |
| <h2><a name="Namespaces">Namespaces</a></h2> |
| |
| <p>The libxml library implements <a |
| href="http://www.w3.org/TR/REC-xml-names/">XML namespaces</a> support by |
| recognizing namespace constructs in the input, and does namespace lookup |
| automatically when building the DOM tree. A namespace declaration is |
| associated with an in-memory structure and all elements or attributes within |
| that namespace point to it. Hence testing the namespace is a simple and fast |
| equality operation at the user level.</p> |
| |
| <p>I suggest that people using libxml use a namespace, and declare it in the |
| root element of their document as the default namespace. Then they don't need |
| to use the prefix in the content but we will have a basis for future semantic |
| refinement and merging of data from different sources. This doesn't increase |
| the size of the XML output significantly, but significantly increases its |
| value in the long-term. Example:</p> |
| <pre><mydoc xmlns="http://mydoc.example.org/schemas/"> |
| <elem1>...</elem1> |
| <elem2>...</elem2> |
| </mydoc></pre> |
| |
| <p>The namespace value has to be an absolute URL, but the URL doesn't have to |
| point to any existing resource on the Web. It will bind all the element and |
| attributes with that URL. I suggest to use an URL within a domain you |
| control, and that the URL should contain some kind of version information if |
| possible. For example, <code>"http://www.gnome.org/gnumeric/1.0/"</code> is a |
| good namespace scheme.</p> |
| |
| <p>Then when you load a file, make sure that a namespace carrying the |
| version-independent prefix is installed on the root element of your document, |
| and if the version information don't match something you know, warn the user |
| and be liberal in what you accept as the input. Also do *not* try to base |
| namespace checking on the prefix value. <foo:text> may be exactly the |
| same as <bar:text> in another document. What really matters is the URI |
| associated with the element or the attribute, not the prefix string (which is |
| just a shortcut for the full URI). In libxml, element and attributes have an |
| <code>ns</code> field pointing to an xmlNs structure detailing the namespace |
| prefix and its URI.</p> |
| |
| <p>@@Interfaces@@</p> |
| |
| <p>@@Examples@@</p> |
| |
| <p>Usually people object to using namespaces together with validity checking. |
| I will try to make sure that using namespaces won't break validity checking, |
| so even if you plan to use or currently are using validation I strongly |
| suggest adding namespaces to your document. A default namespace scheme |
| <code>xmlns="http://...."</code> should not break validity even on less |
| flexible parsers. Using namespaces to mix and differentiate content coming |
| from multiple DTDs will certainly break current validation schemes. I will |
| try to provide ways to do this, but this may not be portable or |
| standardized.</p> |
| |
| <h2><a name="Upgrading">Upgrading 1.x code</a></h2> |
| |
| <p>Incompatible changes:</p> |
| |
| <p>Version 2 of libxml is the first version introducing serious backward |
| incompatible changes. The main goals were:</p> |
| <ul> |
| <li>a general cleanup. A number of mistakes inherited from the very early |
| versions couldn't be changed due to compatibility constraints. Example |
| the "childs" element in the nodes.</li> |
| <li>Uniformization of the various nodes, at least for their header and link |
| parts (doc, parent, children, prev, next), the goal is a simpler |
| programming model and simplifying the task of the DOM implementors.</li> |
| <li>better conformances to the XML specification, for example version 1.x |
| had an heuristic to try to detect ignorable white spaces. As a result the |
| SAX event generated were ignorableWhitespace() while the spec requires |
| character() in that case. This also mean that a number of DOM node |
| containing blank text may populate the DOM tree which were not present |
| before.</li> |
| </ul> |
| |
| <h3>How to fix libxml-1.x code:</h3> |
| |
| <p>So client code of libxml designed to run with version 1.x may have to be |
| changed to compile against version 2.x of libxml. Here is a list of changes |
| that I have collected, they may not be sufficient, so in case you find other |
| change which are required, <a href="mailto:Daniel.Ïeillardw3.org">drop me a |
| mail</a>:</p> |
| <ol> |
| <li>The package name have changed from libxml to libxml2, the library name |
| is now -lxml2 . There is a new xml2-config script which should be used to |
| select the right parameters libxml2</li> |
| <li>Node <strong>childs</strong> field has been renamed |
| <strong>children</strong> so s/childs/children/g should be applied |
| (probability of having "childs" anywhere else is close to 0+</li> |
| <li>The document don't have anymore a <strong>root</strong> element it has |
| been replaced by <strong>children</strong> and usually you will get a |
| list of element here. For example a Dtd element for the internal subset |
| and it's declaration may be found in that list, as well as processing |
| instructions or comments found before or after the document root element. |
| Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of |
| a document. Alternatively if you are sure to not reference DTDs nor have |
| PIs or comments before or after the root element |
| s/->root/->children/g will probably do it.</li> |
| <li>The white space issue, this one is more complex, unless special case of |
| validating parsing, the line breaks and spaces usually used for indenting |
| and formatting the document content becomes significant. So they are |
| reported by SAX and if your using the DOM tree, corresponding nodes are |
| generated. Too approach can be taken: |
| <ol> |
| <li>lazy one, use the compatibility call |
| <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are |
| relying on a special (and possibly broken) set of heuristics of |
| libxml to detect ignorable blanks. Don't complain if it breaks or |
| make your application not 100% clean w.r.t. to it's input.</li> |
| <li>the Right Way: change you code to accept possibly insignificant |
| blanks characters, or have your tree populated with weird blank text |
| nodes. You can spot them using the commodity function |
| <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank |
| nodes.</li> |
| </ol> |
| <p>Note also that with the new default the output functions don't add any |
| extra indentation when saving a tree in order to be able to round trip |
| (read and save) without inflating the document with extra formatting |
| chars.</p> |
| </li> |
| <li>The include path has changed to $prefix/libxml/ and the includes |
| themselves uses this new prefix in includes instructions... If you are |
| using (as expected) the |
| <pre>xml2-config --cflags</pre> |
| <p>output to generate you compile commands this will probably work out of |
| the box</p> |
| </li> |
| <li>xmlDetectCharEncoding takes an extra argument indicating the length in |
| byte of the head of the document available for character detection.</li> |
| </ol> |
| |
| <h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3> |
| |
| <p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released |
| to allow smooth upgrade of existing libxml v1code while retaining |
| compatibility. They offers the following:</p> |
| <ol> |
| <li>similar include naming, one should use |
| <strong>#include<libxml/...></strong> in both cases.</li> |
| <li>similar identifiers defined via macros for the child and root fields: |
| respectively <strong>xmlChildrenNode</strong> and |
| <strong>xmlRootNode</strong></li> |
| <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be |
| inserted once in the client code</li> |
| </ol> |
| |
| <p>So the roadmap to upgrade your existing libxml applications is the |
| following:</p> |
| <ol> |
| <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> |
| <li>find all occurrences where the xmlDoc <strong>root</strong> field is |
| used and change it to <strong>xmlRootNode</strong></li> |
| <li>similarly find all occurrences where the xmlNode |
| <strong>childs</strong> field is used and change it to |
| <strong>xmlChildrenNode</strong></li> |
| <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your |
| <strong>main()</strong> or in the library init entry point</li> |
| <li>Recompile, check compatibility, it should still work</li> |
| <li>Change your configure script to look first for xml2-config and fall |
| back using xml-config . Use the --cflags and --libs output of the command |
| as the Include and Linking parameters needed to use libxml.</li> |
| <li>install libxml2-2.3.x and libxml2-devel-2.3.x (libxml-1.8.y and |
| libxml-devel-1.8.y can be kept simultaneously)</li> |
| <li>remove your config.cache, relaunch your configuration mechanism, and |
| recompile, if steps 2 and 3 were done right it should compile as-is</li> |
| <li>Test that your application is still running correctly, if not this may |
| be due to extra empty nodes due to formating spaces being kept in libxml2 |
| contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your |
| code before calling the parser (next to |
| <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li> |
| </ol> |
| |
| <p>Following those steps should work. It worked for some of my own code.</p> |
| |
| <p>Let me put some emphasis on the fact that there is far more changes from |
| libxml 1.x to 2.x than the ones you may have to patch for. The overall code |
| has been considerably cleaned up and the conformance to the XML specification |
| has been drastically improved too. Don't take those changes as an excuse to |
| not upgrade, it may cost a lot on the long term ...</p> |
| |
| <h2><a name="Thread">Thread safety</a></h2> |
| |
| <p>Starting with 2.4.7, libxml makes provisions to ensure that concurrent |
| threads can safely work in parallel parsing different documents. There is |
| however a couple of things to do to ensure it:</p> |
| <ul> |
| <li>configure the library accordingly using the --with-threads options</li> |
| <li>call xmlInitParser() in the "main" thread before using any of the |
| libxml API (except possibly selecting a different memory allocator)</li> |
| </ul> |
| |
| <p>Note that the thread safety cannot be ensured for multiple threads sharing |
| the same document, the locking must be done at the application level, libxml |
| exports a basic mutex and reentrant mutexes API in <libxml/threads.h>. |
| The parts of the library checked for thread safety are:</p> |
| <ul> |
| <li>concurrent loading</li> |
| <li>file access resolution</li> |
| <li>catalog access</li> |
| <li>catalog building</li> |
| <li>entities lookup/accesses</li> |
| <li>validation</li> |
| <li>global variables per-thread override</li> |
| <li>memory handling</li> |
| </ul> |
| |
| <p>XPath is supposed to be thread safe now, but this wasn't tested |
| seriously.</p> |
| |
| <h2><a name="DOM"></a><a name="Principles">DOM Principles</a></h2> |
| |
| <p><a href="http://www.w3.org/DOM/">DOM</a> stands for the <em>Document |
| Object Model</em>; this is an API for accessing XML or HTML structured |
| documents. Native support for DOM in Gnome is on the way (module gnome-dom), |
| and will be based on gnome-xml. This will be a far cleaner interface to |
| manipulate XML files within Gnome since it won't expose the internal |
| structure.</p> |
| |
| <p>The current DOM implementation on top of libxml is the <a |
| href="http://cvs.gnome.org/lxr/source/gdome2/">gdome2 Gnome module</a>, this |
| is a full DOM interface, thanks to Paolo Casarini, check the <a |
| href="http://www.cs.unibo.it/~casarini/gdome2/">Gdome2 homepage</a> for more |
| informations.</p> |
| |
| <h2><a name="Example"></a><a name="real">A real example</a></h2> |
| |
| <p>Here is a real size example, where the actual content of the application |
| data is not kept in the DOM tree but uses internal structures. It is based on |
| a proposal to keep a database of jobs related to Gnome, with an XML based |
| storage structure. Here is an <a href="gjobs.xml">XML encoded jobs |
| base</a>:</p> |
| <pre><?xml version="1.0"?> |
| <gjob:Helping xmlns:gjob="http://www.gnome.org/some-location"> |
| <gjob:Jobs> |
| |
| <gjob:Job> |
| <gjob:Project ID="3"/> |
| <gjob:Application>GBackup</gjob:Application> |
| <gjob:Category>Development</gjob:Category> |
| |
| <gjob:Update> |
| <gjob:Status>Open</gjob:Status> |
| <gjob:Modified>Mon, 07 Jun 1999 20:27:45 -0400 MET DST</gjob:Modified> |
| <gjob:Salary>USD 0.00</gjob:Salary> |
| </gjob:Update> |
| |
| <gjob:Developers> |
| <gjob:Developer> |
| </gjob:Developer> |
| </gjob:Developers> |
| |
| <gjob:Contact> |
| <gjob:Person>Nathan Clemons</gjob:Person> |
| <gjob:Email>nathan@windsofstorm.net</gjob:Email> |
| <gjob:Company> |
| </gjob:Company> |
| <gjob:Organisation> |
| </gjob:Organisation> |
| <gjob:Webpage> |
| </gjob:Webpage> |
| <gjob:Snailmail> |
| </gjob:Snailmail> |
| <gjob:Phone> |
| </gjob:Phone> |
| </gjob:Contact> |
| |
| <gjob:Requirements> |
| The program should be released as free software, under the GPL. |
| </gjob:Requirements> |
| |
| <gjob:Skills> |
| </gjob:Skills> |
| |
| <gjob:Details> |
| A GNOME based system that will allow a superuser to configure |
| compressed and uncompressed files and/or file systems to be backed |
| up with a supported media in the system. This should be able to |
| perform via find commands generating a list of files that are passed |
| to tar, dd, cpio, cp, gzip, etc., to be directed to the tape machine |
| or via operations performed on the filesystem itself. Email |
| notification and GUI status display very important. |
| </gjob:Details> |
| |
| </gjob:Job> |
| |
| </gjob:Jobs> |
| </gjob:Helping></pre> |
| |
| <p>While loading the XML file into an internal DOM tree is a matter of |
| calling only a couple of functions, browsing the tree to gather the data and |
| generate the internal structures is harder, and more error prone.</p> |
| |
| <p>The suggested principle is to be tolerant with respect to the input |
| structure. For example, the ordering of the attributes is not significant, |
| the XML specification is clear about it. It's also usually a good idea not to |
| depend on the order of the children of a given node, unless it really makes |
| things harder. Here is some code to parse the information for a person:</p> |
| <pre>/* |
| * A person record |
| */ |
| typedef struct person { |
| char *name; |
| char *email; |
| char *company; |
| char *organisation; |
| char *smail; |
| char *webPage; |
| char *phone; |
| } person, *personPtr; |
| |
| /* |
| * And the code needed to parse it |
| */ |
| personPtr parsePerson(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { |
| personPtr ret = NULL; |
| |
| DEBUG("parsePerson\n"); |
| /* |
| * allocate the struct |
| */ |
| ret = (personPtr) malloc(sizeof(person)); |
| if (ret == NULL) { |
| fprintf(stderr,"out of memory\n"); |
| return(NULL); |
| } |
| memset(ret, 0, sizeof(person)); |
| |
| /* We don't care what the top level element name is */ |
| cur = cur->xmlChildrenNode; |
| while (cur != NULL) { |
| if ((!strcmp(cur->name, "Person")) && (cur->ns == ns)) |
| ret->name = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
| if ((!strcmp(cur->name, "Email")) && (cur->ns == ns)) |
| ret->email = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
| cur = cur->next; |
| } |
| |
| return(ret); |
| }</pre> |
| |
| <p>Here are a couple of things to notice:</p> |
| <ul> |
| <li>Usually a recursive parsing style is the more convenient one: XML data |
| is by nature subject to repetitive constructs and usually exhibits highly |
| structured patterns.</li> |
| <li>The two arguments of type <em>xmlDocPtr</em> and <em>xmlNsPtr</em>, |
| i.e. the pointer to the global XML document and the namespace reserved to |
| the application. Document wide information are needed for example to |
| decode entities and it's a good coding practice to define a namespace for |
| your application set of data and test that the element and attributes |
| you're analyzing actually pertains to your application space. This is |
| done by a simple equality test (cur->ns == ns).</li> |
| <li>To retrieve text and attributes value, you can use the function |
| <em>xmlNodeListGetString</em> to gather all the text and entity reference |
| nodes generated by the DOM output and produce an single text string.</li> |
| </ul> |
| |
| <p>Here is another piece of code used to parse another level of the |
| structure:</p> |
| <pre>#include <libxml/tree.h> |
| /* |
| * a Description for a Job |
| */ |
| typedef struct job { |
| char *projectID; |
| char *application; |
| char *category; |
| personPtr contact; |
| int nbDevelopers; |
| personPtr developers[100]; /* using dynamic alloc is left as an exercise */ |
| } job, *jobPtr; |
| |
| /* |
| * And the code needed to parse it |
| */ |
| jobPtr parseJob(xmlDocPtr doc, xmlNsPtr ns, xmlNodePtr cur) { |
| jobPtr ret = NULL; |
| |
| DEBUG("parseJob\n"); |
| /* |
| * allocate the struct |
| */ |
| ret = (jobPtr) malloc(sizeof(job)); |
| if (ret == NULL) { |
| fprintf(stderr,"out of memory\n"); |
| return(NULL); |
| } |
| memset(ret, 0, sizeof(job)); |
| |
| /* We don't care what the top level element name is */ |
| cur = cur->xmlChildrenNode; |
| while (cur != NULL) { |
| |
| if ((!strcmp(cur->name, "Project")) && (cur->ns == ns)) { |
| ret->projectID = xmlGetProp(cur, "ID"); |
| if (ret->projectID == NULL) { |
| fprintf(stderr, "Project has no ID\n"); |
| } |
| } |
| if ((!strcmp(cur->name, "Application")) && (cur->ns == ns)) |
| ret->application = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
| if ((!strcmp(cur->name, "Category")) && (cur->ns == ns)) |
| ret->category = xmlNodeListGetString(doc, cur->xmlChildrenNode, 1); |
| if ((!strcmp(cur->name, "Contact")) && (cur->ns == ns)) |
| ret->contact = parsePerson(doc, ns, cur); |
| cur = cur->next; |
| } |
| |
| return(ret); |
| }</pre> |
| |
| <p>Once you are used to it, writing this kind of code is quite simple, but |
| boring. Ultimately, it could be possible to write stubbers taking either C |
| data structure definitions, a set of XML examples or an XML DTD and produce |
| the code needed to import and export the content between C data and XML |
| storage. This is left as an exercise to the reader :-)</p> |
| |
| <p>Feel free to use <a href="example/gjobread.c">the code for the full C |
| parsing example</a> as a template, it is also available with Makefile in the |
| Gnome CVS base under gnome-xml/example</p> |
| |
| <h2><a name="Contributi">Contributions</a></h2> |
| <ul> |
| <li>Bjorn Reese, William Brack and Thomas Broyer have provided a number of |
| patches, Gary Pennington worked on the validation API, threading support |
| and Solaris port.</li> |
| <li>John Fleck helps maintaining the documentation and man pages.</li> |
| <li><a href="mailto:igor@zlatkovic.com">Igor Zlatkovic</a> is now the |
| maintainer of the Windows port, <a |
| href="http://www.zlatkovic.com/projects/libxml/index.html">he provides |
| binaries</a></li> |
| <li><a href="mailto:Gary.Pennington@sun.com">Gary Pennington</a> provides |
| <a href="http://garypennington.net/libxml2/">Solaris binaries</a></li> |
| <li><a |
| href="http://mail.gnome.org/archives/xml/2001-March/msg00014.html">Matt |
| Sergeant</a> developed <a |
| href="http://axkit.org/download/">XML::LibXSLT</a>, a Perl wrapper for |
| libxml2/libxslt as part of the <a href="http://axkit.com/">AxKit XML |
| application server</a></li> |
| <li><a href="mailto:fnatter@gmx.net">Felix Natter</a> and <a |
| href="mailto:geertk@ai.rug.nl">Geert Kloosterman</a> provide <a |
| href="libxml-doc.el">an emacs module</a> to lookup libxml(2) functions |
| documentation</li> |
| <li><a href="mailto:sherwin@nlm.nih.gov">Ziying Sherwin</a> provided <a |
| href="http://xmlsoft.org/messages/0488.html">man pages</a></li> |
| <li>there is a module for <a |
| href="http://acs-misc.sourceforge.net/nsxml.html">libxml/libxslt support |
| in OpenNSD/AOLServer</a></li> |
| <li><a href="mailto:dkuhlman@cutter.rexx.com">Dave Kuhlman</a> provided the |
| first version of libxml/libxslt <a |
| href="http://www.rexx.com/~dkuhlman">wrappers for Python</a></li> |
| <li>Petr Kozelka provides <a |
| href="http://sourceforge.net/projects/libxml2-pas">Pascal units to glue |
| libxml2</a> with Kylix and Delphi and other Pascal compilers</li> |
| <li><a href="mailto:aleksey@aleksey.com">Aleksey Sanin</a> implemented the |
| <a href="http://www.w3.org/Signature/">XML Canonicalization and XML |
| Digital Signature</a> <a |
| href="http://www.aleksey.com/xmlsec/">implementations for libxml2</a></li> |
| <li><a href="mailto:Steve.Ball@zveno.com">Steve Ball</a>, <a |
| href="http://www.zveno.com/">Zveno</a> and contributors maintain <a |
| href="http://tclxml.sourceforge.net/">tcl bindings for libxml2 and |
| libxslt</a>, as well as <a |
| href="http://tclxml.sf.net/tkxmllint.html">tkxmllint</a> a GUI for |
| xmllint and <a href="http://tclxml.sf.net/tkxsltproc.html">tkxsltproc</a> |
| a GUI for xsltproc.</li> |
| </ul> |
| |
| <p></p> |
| </body> |
| </html> |