libstdc++-v3/doc/xml/manual/ctype.xml

<section xmlns="http://docbook.org/ns/docbook" version="5.0"
	 xml:id="std.localization.facet.ctype" xreflabel="ctype">
<?dbhtml filename="ctype.html"?>

<info><title>ctype</title>
  <keywordset>
    <keyword>ISO C++</keyword>
    <keyword>ctype</keyword>
  </keywordset>
</info>



<section xml:id="facet.ctype.impl"><info><title>Implementation</title></info>


  <section xml:id="facet.ctype.impl.spec"><info><title>Specializations</title></info>


<para>
For the required specialization <classname>codecvt&lt;wchar_t, char, mbstate_t&gt;</classname>,
conversions are made between the internal character set (always UCS4
on GNU/Linux) and whatever the currently selected locale for the
<code>LC_CTYPE</code> category implements.
</para>

<para>
The two required specializations are implemented as follows:
</para>

<para>
<code>
ctype&lt;char&gt;
</code>
</para>
<para>
This is simple specialization. Implementing this was a piece of cake.
</para>

<para>
<code>
ctype&lt;wchar_t&gt;
</code>
</para>
<para>
This specialization, by specifying all the template parameters, pretty
much ties the hands of implementors. As such, the implementation is
straightforward, involving <function>mcsrtombs</function> for the
conversions between <type>char</type> to <type>wchar_t</type> and
<function>wcsrtombs</function> for conversions between <type>wchar_t</type>
and <type>char</type>.
</para>

<para>
Neither of these two required specializations deals with Unicode
characters.
</para>

  </section>
</section>

<section xml:id="facet.ctype.future"><info><title>Future</title></info>



<itemizedlist>
   <listitem>
   <para>
   How to deal with the global locale issue?
   </para></listitem>

   <listitem>
   <para>
   How to deal with types other than <type>char</type>, <type>wchar_t</type>?
   </para></listitem>

   <listitem><para>
   Overlap between codecvt/ctype: narrow/widen
   </para></listitem>

   <listitem>
     <para>
       <type>mask</type> typedef in <classname>codecvt_base</classname>,
       argument types in <type>codecvt</type>.  what is know about this type?
   </para></listitem>

   <listitem>
   <para>
   Why mask* argument in codecvt?
   </para></listitem>

   <listitem>
     <para>
       Can this be made (more) generic? is there a simple way to
       straighten out the configure-time mess that is a by-product of
       this class?
   </para></listitem>

   <listitem>
     <para>
       Get the <type>ctype&lt;wchar_t&gt;::mask</type> stuff under control.
       Need to make some kind of static table, and not do lookup every time
       somebody hits the <code>do_is...</code> functions. Too bad we can't
       just redefine <type>mask</type> for
       <classname>ctype&lt;wchar_t&gt;</classname>
   </para></listitem>

   <listitem>
     <para>
       Rename abstract base class. See if just smash-overriding is a
       better approach. Clarify, add sanity to naming.
     </para>
   </listitem>

</itemizedlist>


</section>


<bibliography xml:id="facet.ctype.biblio"><info><title>Bibliography</title></info>


  <biblioentry>
    <citetitle>
      The GNU C Library
    </citetitle>
    <author><personname><surname>McGrath</surname><firstname>Roland</firstname></personname></author>
    <author><personname><surname>Drepper</surname><firstname>Ulrich</firstname></personname></author>
    <copyright>
      <year>2007</year>
      <holder>FSF</holder>
    </copyright>
    <pagenums>Chapters 6  Character Set Handling and 7 Locales and Internationalization</pagenums>
  </biblioentry>

  <biblioentry>
    <citetitle>
      Correspondence
    </citetitle>
    <author><personname><surname>Drepper</surname><firstname>Ulrich</firstname></personname></author>
    <copyright>
      <year>2002</year>
      <holder/>
    </copyright>
  </biblioentry>

  <biblioentry>
    <citetitle>
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    </citetitle>
    <copyright>
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      <holder>ISO</holder>
    </copyright>
  </biblioentry>

  <biblioentry>
    <citetitle>
      ISO/IEC 9899:1999 Programming languages - C
    </citetitle>
    <copyright>
      <year>1999</year>
      <holder>ISO</holder>
    </copyright>
  </biblioentry>

  <biblioentry>
      <title>
	<link xmlns:xlink="http://www.w3.org/1999/xlink"
	      xlink:href="https://www.unix.org/version3/ieee_std.html">
	The Open Group Base Specifications, Issue 6 (IEEE Std. 1003.1-2004)
	</link>
      </title>

    <copyright>
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      The Open Group/The Institute of Electrical and Electronics Engineers, Inc.</holder>
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  </biblioentry>

  <biblioentry>
    <citetitle>
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    </citetitle>
    <author><personname><surname>Stroustrup</surname><firstname>Bjarne</firstname></personname></author>
    <copyright>
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    </copyright>
    <pagenums>Appendix D</pagenums>
    <publisher>
      <publishername>
	Addison Wesley
      </publishername>
    </publisher>
  </biblioentry>

  <biblioentry>
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      Standard C++ IOStreams and Locales
    </citetitle>
    <subtitle>
      Advanced Programmer's Guide and Reference
    </subtitle>
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    </copyright>
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	Addison Wesley Longman
      </publishername>
    </publisher>
  </biblioentry>

</bibliography>

</section>