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295 lines
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HTML
295 lines
13 KiB
HTML
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
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<html>
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<head>
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<title>Libxml Frequently Asked Questions</title>
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<meta name="GENERATOR" content="amaya V5.0">
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<meta http-equiv="Content-Type" content="text/html">
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<body bgcolor="#ffffff">
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<h1 align="center">Libxml Frequently Asked Questions</h1>
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<p>Location: <a
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href="http://xmlsoft.org/FAQ.html">http://xmlsoft.org/FAQ.html</a></p>
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<p>Libxml home page: <a href="http://xmlsoft.org/">http://xmlsoft.org/</a></p>
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<p>Mailing-list archive: <a
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href="http://xmlsoft.org/messages/">http://xmlsoft.org/messages/</a></p>
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<p>Version: $Revision$</p>
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<p>Table of Content:</p>
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<ul>
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<li><a href="#Licence">Licence(s)</a></li>
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<li><a href="#Installati">Installation</a></li>
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<li><a href="#Compilatio">Compilation</a></li>
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<li><a href="#Developer">Developer corner</a></li>
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</ul>
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<h2><a name="Licence">Licence</a>(s)</h2>
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<ol>
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<li><em>Licensing Terms for libxml</em>
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<p>libxml is released under 2 (compatible) licences:</p>
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<ul>
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<li>the <a href="http://www.gnu.org/copyleft/lgpl.html">LGPL</a>: GNU
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Library General Public License</li>
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<li>the <a
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href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
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IPR</a>: very similar to the XWindow licence</li>
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</ul>
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</li>
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<li><em>Can I embed libxml in a proprietary application ?</em>
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<p>Yes. The W3C IPR allows you to also keep proprietary the changes you
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made to libxml, but it would be graceful to provide back bugfixes and
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improvements as patches for possible incorporation in the main
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development tree</p>
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</li>
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</ol>
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<h2><a name="Installati">Installation</a></h2>
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<ol>
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<li>Unless you are forced to because your application links with a Gnome
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library requiring it, <strong><span style="background-color: #FF0000">Do
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Not Use libxml1</span></strong>, use libxml2</li>
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<li><em>Where can I get libxml</em>
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?
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<p>The original distribution comes from <a
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href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a
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href="ftp://ftp.gnome.org/pub/GNOME/stable/sources/libxml/">gnome.org</a></p>
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<p>Most linux and Bsd distribution includes libxml, this is probably the
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safer way for end-users</p>
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<p>David Doolin provides precompiled Windows versions at <a
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href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p>
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</li>
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<li><em>I see libxml and libxml2 releases, which one should I install ?</em>
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<ul>
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<li>If you are not concerned by any existing backward compatibility
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with existing application, install libxml2 only</li>
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<li>If you are not doing development, you can safely install both.
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usually the packages <a
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href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a
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href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are
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compatible (this is not the case for development packages)</li>
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<li>If you are a developer and your system provides separate packaging
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for shared libraries and the development components, it is possible
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to install libxml and libxml2, and also <a
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href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
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and <a
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href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a>
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too for libxml2 >= 2.3.0</li>
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<li>If you are developing a new application, please develop against
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libxml2(-devel)</li>
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</ul>
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</li>
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<li><em>I can't install the libxml package it conflicts with libxml0</em>
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<p>You probably have an old libxml0 package used to provide the shared
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library for libxml.so.0, you can probably safely remove it. Anyway the
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libxml packages provided on <a
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href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provides
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libxml.so.0</p>
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</li>
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<li><em>I can't install the libxml(2) RPM package due to failed
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dependancies</em>
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<p>The most generic solution is to refetch the latest src.rpm , and
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rebuild it locally with</p>
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<p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code></p>
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<p>if everything goes well it will generate two binary rpm (one providing
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the shared libs and xmllint, and the other one, the -devel package
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providing includes, static libraries and scripts needed to build
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applications with libxml(2)) that you can install locally.</p>
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</li>
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</ol>
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<h2><a name="Compilatio">Compilation</a></h2>
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<ol>
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<li><em>What is the process to compile libxml ?</em>
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<p>As most UNIX libraries libxml follows the "standard":</p>
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<p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p>
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<p><code>cd libxml-xxxx</code></p>
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<p><code>./configure --help</code></p>
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<p>to see the options, then the compilation/installation proper</p>
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<p><code>./configure [possible options]</code></p>
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<p><code>make</code></p>
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<p><code>make install</code></p>
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<p>At that point you may have to rerun ldconfig or similar utility to
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update your list of installed shared libs.</p>
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</li>
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<li><em>What other libraries are needed to compile/install libxml ?</em>
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<p>Libxml does not requires any other library, the normal C ANSI API
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should be sufficient (please report any violation to this rule you may
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find).</p>
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<p>However if found at configuration time libxml will detect and use the
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following libs:</p>
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<ul>
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<li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a>
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: a highly portable and available widely compression library</li>
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<li>iconv: a powerful character encoding conversion library. It's
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included by default on recent glibc libraries, so it doesn't need to
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be installed specifically on linux. It seems it's now <a
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href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part
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of the official UNIX</a> specification. Here is one <a
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href="http://clisp.cons.org/~haible/packages-libiconv.html">implementation
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of the library</a> which source can be found <a
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href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li>
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</ul>
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</li>
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<li><em>libxml does not compile with HP-UX's optional ANSI-C compiler</em>
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<p>this is due to macro limitations. Try to add " -Wp,-H16800 -Ae" to the
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CFLAGS</p>
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<p>you can also install and use gcc instead or use a precompiled version
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of libxml, both available from the <a
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href="http://hpux.cae.wisc.edu/hppd/auto/summary_all.html">HP-UX Porting
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and Archive Centre</a></p>
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</li>
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<li><em>make check fails on some platforms</em>
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<p>Sometime the regression tests results don't completely match the value
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produced by the parser, and the makefile uses diff to print the delta. On
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some platforms the diff return breaks the compilation process, if the
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diff is small this is probably not a serious problem</p>
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</li>
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<li><em>I use the CVS version and there is no configure script</em>
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<p>The configure (and other Makefiles) are generated. Use the autogen.sh
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script to regenerate the configure and Makefiles, like:</p>
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<p><code>./autogen.sh --prefix=/usr --disable-shared</code></p>
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</li>
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<li><em>I have troubles when running make tests with gcc-3.0</em>
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<p>It seems the initial release of gcc-3.0 has a problem with the
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optimizer which miscompiles the URI module. Please use another
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compiler</p>
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</li>
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</ol>
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<h2><a name="Developer">Developer</a> corner</h2>
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<ol>
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<li><em>xmlDocDump() generates output on one line</em>
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<p>libxml will not <strong>invent</strong> spaces in the content of a
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document since <strong>all spaces in the content of a document are
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significant</strong>. If you build a tree from the API and want
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indentation:</p>
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<ol>
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<li>the correct way is to generate those yourself too</li>
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<li>the dangerous way is to ask libxml to add those blanks to your
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content <strong>modifying the content of your document in the
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process</strong>. The result may not be what you expect. There is
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<strong>NO</strong> way to guarantee that such a modification won't
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impact other part of the content of your document. See <a
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href="http://xmlsoft.org/html/libxml-parser.html#XMLKEEPBLANKSDEFAULT">xmlKeepBlanksDefault
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()</a> and <a
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href="http://xmlsoft.org/html/libxml-tree.html#XMLSAVEFORMATFILE">xmlSaveFormatFile
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()</a></li>
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</ol>
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</li>
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<li>Extra nodes in the document:
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<p><em>For a XML file as below:</em></p>
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<pre><?xml version="1.0"?>
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<PLAN xmlns="http://www.argus.ca/autotest/1.0/">
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<NODE CommFlag="0"/>
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<NODE CommFlag="1"/>
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</PLAN></pre>
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<p><em>after parsing it with the function
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pxmlDoc=xmlParseFile(...);</em></p>
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<p><em>I want to the get the content of the first node (node with the
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CommFlag="0")</em></p>
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<p><em>so I did it as following;</em></p>
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<pre>xmlNodePtr pode;
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pnode=pxmlDoc->children->children;</pre>
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<p><em>but it does not work. If I change it to</em></p>
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<pre>pnode=pxmlDoc->children->children->next;</pre>
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<p><em>then it works. Can someone explain it to me.</em></p>
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<p></p>
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<p>In XML all characters in the content of the document are significant
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<strong>including blanks and formatting line breaks</strong>.</p>
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<p>The extra nodes you are wondering about are just that, text nodes with
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the formatting spaces wich are part of the document but that people tend
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to forget. There is a function <a
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href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault
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()</a> to remove those at parse time, but that's an heuristic, and its
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use should be limited to case where you are sure there is no
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mixed-content in the document.</p>
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</li>
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<li><em>I get compilation errors of existing code like when accessing
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<strong>root</strong> or <strong>childs fields</strong> of nodes</em>
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<p>You are compiling code developed for libxml version 1 and using a
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libxml2 development environment. Either switch back to libxml v1 devel or
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even better fix the code to compile with libxml2 (or both) by <a
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href="upgrade.html">following the instructions</a>.</p>
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</li>
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<li><em>I get compilation errors about non existing
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<strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong>
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fields</em>
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<p>The source code you are using has been <a
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href="upgrade.html">upgraded</a> to be able to compile with both libxml
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and libxml2, but you need to install a more recent version:
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libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p>
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</li>
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<li><em>XPath implementation looks seriously broken</em>
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<p>XPath implementation prior to 2.3.0 was really incomplete, upgrade to
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a recent version, the implementation and debug of libxslt generated fixes
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for most obvious problems.</p>
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</li>
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<li><em>The example provided in the web page does not compile</em>
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<p>It's hard to maintain the documentation in sync with the code
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<grin/> ...</p>
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<p>Check the previous points 1/ and 2/ raised before, and send
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patches.</p>
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</li>
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<li><em>Where can I get more examples and informations than in the web
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page</em>
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<p>Ideally a libxml book would be nice. I have no such plan ... But you
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can:</p>
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<ul>
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<li>check more deeply the <a href="html/libxml-lib.html">existing
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generated doc</a></li>
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<li>looks for examples of use for libxml function using the Gnome code
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for example the following will query the full Gnome CVs base for the
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use of the <strong>xmlAddChild()</strong> function:
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<p><a
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href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p>
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<p>This may be slow, a large hardware donation to the gnome project
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could cure this :-)</p>
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</li>
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<li><a
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href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse
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the libxml source</a>
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, I try to write code as clean and documented as possible, so
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looking at it may be helpful</li>
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</ul>
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</li>
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<li>What about C++ ?
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<p>libxml is written in pure C in order to allow easy reuse on a number
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of platforms, including embedded systems. I don't intend to convert to
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C++.</p>
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<p>There is however a C++ wrapper provided by Ari Johnson
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<ari@btigate.com> which may fullfill your needs:</p>
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<p>Website: <a
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href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p>
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<p>Download: <a
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href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p>
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</li>
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<li>How to validate a document a posteriori ?
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<p>It is possible to validate documents which had not been validated at
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initial parsing time or documents who have been built from scratch using
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the API. Use the <a
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href="http://xmlsoft.org/html/libxml-valid.html#XMLVALIDATEDTD">xmlValidateDtd()</a>
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function. It is also possible to simply add a Dtd to an existing
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document:</p>
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<pre>xmlDocPtr doc; /* your existing document */
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xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */
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dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */
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doc->intSubset = dtd;
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if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd);
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else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd);
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</pre>
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</li>
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<li>etc ...</li>
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</ol>
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<p><a href="mailto:daniel@veillard.com">Daniel Veillard</a></p>
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<p>$Id$</p>
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</body>
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</html>
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