doc/FAQ.html - fp2-dev/platform/external/libxml2 - Gitiles

 <html>
 <head>
   <title>Libxml Frequently Asked Questions</title>
   <meta name="GENERATOR" content="amaya V4.1">
   <meta http-equiv="Content-Type" content="text/html">
 </head>

 <body bgcolor="#ffffff">
 <h1 align="center">Libxml Frequently Asked Questions</h1>

 <p>Location: <a
 href="http://xmlsoft.org/FAQ.html">http://xmlsoft.org/FAQ.html</a></p>

 <p>Libxml home page: <a href="http://xmlsoft.org/">http://xmlsoft.org/</a></p>

 <p>Mailing-list archive:  <a
 href="http://xmlsoft.org/messages/">http://xmlsoft.org/messages/</a></p>

 <p>Version: $Revision$</p>

 <p>Table of Content:</p>
 <ul>
   <li><a href="#Licence">Licence(s)</a></li>
   <li><a href="#Installati">Installation</a></li>
   <li><a href="#Compilatio">Compilation</a></li>
   <li><a href="#Developer">Developer corner</a></li>
 </ul>

 <h2><a name="Licence">Licence</a>(s)</h2>
 <ol>
   <li><em>Licensing Terms for libxml</em>
     <p>libxml is released under 2 (compatible) licences:</p>
     <ul>
       <li>the <a href="http://www.gnu.org/copyleft/lgpl.html">LGPL</a>: GNU
         Library General Public License</li>
       <li>the <a
         href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
         IPR</a>: very similar to the XWindow licence</li>
     </ul>
   </li>
   <li><em>Can I embed libxml in a proprietary application ?</em>
     <p>Yes. The W3C IPR allows you to also keep proprietary the changes you
     made to libxml, but it would be graceful to provide back bugfixes and
     improvements as patches for possible incorporation in the main development
     tree</p>
   </li>
 </ol>

 <h2><a name="Installati">Installation</a></h2>
 <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/stable/sources/libxml/">gnome.org</a></p>
     <p>Most linux and Bsd distribution includes libxml, this is probably the
     safer way for end-users</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 concerned by any existing backward compatibility with
         existing application, 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 &gt;= 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. Anyway the
     libxml packages provided on <a
     href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provides
     libxml.so.0</p>
   </li>
 </ol>

 <h2><a name="Compilatio">Compilation</a></h2>
 <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 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 requires 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's
         included by default on recent glibc libraries, so it doesn't need to
         be installed specifically on linux. It seems it's now <a
         href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part of
         the official UNIX</a> specification. Here is one <a
         href="http://clisp.cons.org/~haible/packages-libiconv.html">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>libxml does not compile with HP-UX's optional ANSI-C compiler</em>
     <p>this is due to macro limitations. Try to add " -Wp,-H16800 -Ae" to the
     CFLAGS</p>
     <p>you can also install and use gcc instead or use a precompiled version
     of libxml, both available from the <a
     href="http://hpux.cae.wisc.edu/hppd/auto/summary_all.html">HP-UX Porting
     and Archive Centre</a></p>
   </li>
   <li><em>make check fails on some platforms</em>
     <p>Sometime 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>
   </li>
 </ol>

 <h2><a name="Developer">Developer</a> corner</h2>
 <ol>
   <li>Extra nodes in the document:
     <p><em>For a XML file as below:</em></p>
     <pre>&lt;?xml version="1.0"?&gt;
 &lt;PLAN xmlns="http://www.argus.ca/autotest/1.0/"&gt;
 &lt;NODE CommFlag="0"/&gt;
 &lt;NODE CommFlag="1"/&gt;
 &lt;/PLAN&gt;</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 pode;
 pnode=pxmlDoc-&gt;children-&gt;children;</pre>
     <p><em>but it does not work. If I change it to</em></p>
     <pre>pnode=pxmlDoc-&gt;children-&gt;children-&gt;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 wich 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 case where you are sure 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>childs 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)
     &gt;= 1.8.8 or libxml2(-devel) &gt;= 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, the implementation and debug of libxslt generated fixes
     for most obvious problems.</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
     &lt;grin/&gt; ...</p>
     <p>Check the previous points 1/ and 2/ raised before, and send
     patches.</p>
   </li>
   <li><em>Where can I get more examples and informations than in 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>looks 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&amp;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</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 is however a C++ wrapper provided by Ari Johnson
     &lt;ari@btigate.com&gt; which may fullfill your needs:</p>
     <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>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 who 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-&gt;name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */

         doc-&gt;intSubset = dtd;
         if (doc-&gt;children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd);
         else xmlAddPrevSibling(doc-&gt;children, (xmlNodePtr)dtd);
           </pre>
   </li>
   <li>etc ...</li>
 </ol>

 <p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>

 <p>$Id$</p>
 </body>
 </html>
	<html>
	<head>
	<title>Libxml Frequently Asked Questions</title>
	<meta name="GENERATOR" content="amaya V4.1">
	<meta http-equiv="Content-Type" content="text/html">
	</head>

	<body bgcolor="#ffffff">
	<h1 align="center">Libxml Frequently Asked Questions</h1>

	<p>Location: <a
	href="http://xmlsoft.org/FAQ.html">http://xmlsoft.org/FAQ.html</a></p>

	<p>Libxml home page: <a href="http://xmlsoft.org/">http://xmlsoft.org/</a></p>

	<p>Mailing-list archive: <a
	href="http://xmlsoft.org/messages/">http://xmlsoft.org/messages/</a></p>

	<p>Version: $Revision$</p>

	<p>Table of Content:</p>
	<ul>
	<li><a href="#Licence">Licence(s)</a></li>
	<li><a href="#Installati">Installation</a></li>
	<li><a href="#Compilatio">Compilation</a></li>
	<li><a href="#Developer">Developer corner</a></li>
	</ul>

	<h2><a name="Licence">Licence</a>(s)</h2>
	<ol>
	<li><em>Licensing Terms for libxml</em>
	<p>libxml is released under 2 (compatible) licences:</p>
	<ul>
	<li>the <a href="http://www.gnu.org/copyleft/lgpl.html">LGPL</a>: GNU
	Library General Public License</li>
	<li>the <a
	href="http://www.w3.org/Consortium/Legal/copyright-software-19980720.html">W3C
	IPR</a>: very similar to the XWindow licence</li>
	</ul>
	</li>
	<li><em>Can I embed libxml in a proprietary application ?</em>
	<p>Yes. The W3C IPR allows you to also keep proprietary the changes you
	made to libxml, but it would be graceful to provide back bugfixes and
	improvements as patches for possible incorporation in the main development
	tree</p>
	</li>
	</ol>

	<h2><a name="Installati">Installation</a></h2>
	<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/stable/sources/libxml/">gnome.org</a></p>
	<p>Most linux and Bsd distribution includes libxml, this is probably the
	safer way for end-users</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 concerned by any existing backward compatibility with
	existing application, 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. Anyway the
	libxml packages provided on <a
	href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provides
	libxml.so.0</p>
	</li>
	</ol>

	<h2><a name="Compilatio">Compilation</a></h2>
	<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 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 requires 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's
	included by default on recent glibc libraries, so it doesn't need to
	be installed specifically on linux. It seems it's now <a
	href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part of
	the official UNIX</a> specification. Here is one <a
	href="http://clisp.cons.org/~haible/packages-libiconv.html">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>libxml does not compile with HP-UX's optional ANSI-C compiler</em>
	<p>this is due to macro limitations. Try to add " -Wp,-H16800 -Ae" to the
	CFLAGS</p>
	<p>you can also install and use gcc instead or use a precompiled version
	of libxml, both available from the <a
	href="http://hpux.cae.wisc.edu/hppd/auto/summary_all.html">HP-UX Porting
	and Archive Centre</a></p>
	</li>
	<li><em>make check fails on some platforms</em>
	<p>Sometime 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>
	</li>
	</ol>

	<h2><a name="Developer">Developer</a> corner</h2>
	<ol>
	<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 pode;
	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 wich 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 case where you are sure 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>childs 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, the implementation and debug of libxslt generated fixes
	for most obvious problems.</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 send
	patches.</p>
	</li>
	<li><em>Where can I get more examples and informations than in 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>looks 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</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 is however a C++ wrapper provided by Ari Johnson
	<ari@btigate.com> which may fullfill your needs:</p>
	<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>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 who 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>etc ...</li>
	</ol>

	<p><a href="mailto:Daniel.Veillard@w3.org">Daniel Veillard</a></p>

	<p>$Id$</p>
	</body>
	</html>