xml.html

libxml,在UNIX/LINUX下非常重要的一个库,为XML相关应用提供方便.目前上载的是最新版本,若要取得最新版本,请参考里面的readme.

    <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 libxml2 ?</em>
    <p>Libxml2 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 libxml2 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>I want to install my own copy of libxml2 in my home directory and link
    my programs against it, but it doesn't work</em>
    <p>There are many different ways to accomplish this.  Here is one way to
      do this under Linux.  Suppose your home directory is <code>/home/user.
      </code>Then:</p>
    <ul><li>Create a subdirectory, let's call it <code>myxml</code></li>
      <li>unpack the libxml2 distribution into that subdirectory</li>
      <li>chdir into the unpacked distribution (<code>/home/user/myxml/libxml2
        </code>)</li>
      <li>configure the library using the "<code>--prefix</code>" switch,
      specifying an installation subdirectory in <code>/home/user/myxml</code>,
      e.g.
      <p><code>./configure --prefix /home/user/myxml/xmlinst</code> {other
      configuration options}</p></li>
      <li>now run <code>make</code> followed by <code>make install</code></li>
      <li>At this point, the installation subdirectory contains the complete
      "private" include files, library files and binary program files (e.g.
      xmllint), located in
      <p> <code>/home/user/myxml/xmlinst/lib, /home/user/myxml/xmlinst/include
      </code> and <code> /home/user/myxml/xmlinst/bin</code></p>
      respectively.</li>
      <li>In order to use this "private" library, you should first add it
      to the beginning of your default PATH (so that your own private
      program files such as xmllint will be used instead of the normal
      system ones).  To do this, the Bash command would be
      <p><code>export PATH=/home/user/myxml/xmlinst/bin:$PATH</code></p></li>
      <li>Now suppose you have a program <code>test1.c</code> that you would
      like to compile with your "private" library.  Simply compile it
      using the command <p><code>gcc `xml2-config --cflags --libs` -o test
      test.c</code></p>  Note that, because your PATH has been set with <code>
      /home/user/myxml/xmlinst/bin</code> at the beginning, the
      xml2-config program which you just installed will be used instead of
      the system default one, and this will <em>automatically</em> get the
      correct libraries linked with your program.</li></ul>
  </li><p/>
  <li><em>xmlDocDump() generates output on one line.</em>
    <p>Libxml2 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 libxml2 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>&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 pnode;
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 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) &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, 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
    &lt;grin/&gt; ...</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 provided on the
    web page?</em>
    <p>Ideally a libxml2 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>have a look at <a href="examples/index.html">the set of
        examples</a>.</li>
      <li>look for examples of use for libxml2 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 libxml2 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>libxml2 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 which may fulfill your needs:</p>
    <ul>
      <li>by Ari Johnson &lt;[e-mail]&gt;:
        <p>Website: <a
        href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a></p>
        <p>Download: <a
        href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a></p>
      </li>
      <!-- Website is currently unavailable as of 2003-08-02
      <li>by Peter Jones &lt;[e-mail]&gt;
      <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-&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>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 Menu</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 look up
  information.</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.</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