<?xml version="1.0" encoding="UTF-8" standalone="no"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>Chapter 15. Facets aka Categories</title><meta name="generator" content="DocBook XSL Stylesheets V1.74.0" /><meta name="keywords" content=" ISO C++ , library " /><link rel="home" href="../spine.html" title="The GNU C++ Library Documentation" /><link rel="up" href="localization.html" title="Part VI. Localization" /><link rel="prev" href="locales.html" title="Chapter 14. Locales" /><link rel="next" href="codecvt.html" title="codecvt" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 15. Facets aka Categories</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="locales.html">Prev</a> </td><th width="60%" align="center">Part VI. Localization </th><td width="20%" align="right"> <a accesskey="n" href="codecvt.html">Next</a></td></tr></table><hr /></div><div class="chapter" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title"><a id="manual.localization.facet"></a>Chapter 15. Facets aka Categories</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="facets.html#manual.localization.facet.ctype">ctype</a></span></dt><dd><dl><dt><span class="sect2"><a href="facets.html#facet.ctype.impl">Implementation</a></span></dt><dt><span class="sect2"><a href="facets.html#facet.ctype.future">Future</a></span></dt></dl></dd><dt><span class="sect1"><a href="codecvt.html">codecvt</a></span></dt><dd><dl><dt><span class="sect2"><a href="codecvt.html#facet.codecvt.req">Requirements</a></span></dt><dt><span class="sect2"><a href="codecvt.html#facet.codecvt.design">Design</a></span></dt><dt><span class="sect2"><a href="codecvt.html#facet.codecvt.impl">Implementation</a></span></dt><dt><span class="sect2"><a href="codecvt.html#facet.codecvt.use">Use</a></span></dt><dt><span class="sect2"><a href="codecvt.html#facet.codecvt.future">Future</a></span></dt></dl></dd><dt><span class="sect1"><a href="messages.html">messages</a></span></dt><dd><dl><dt><span class="sect2"><a href="messages.html#facet.messages.req">Requirements</a></span></dt><dt><span class="sect2"><a href="messages.html#facet.messages.design">Design</a></span></dt><dt><span class="sect2"><a href="messages.html#facet.messages.impl">Implementation</a></span></dt><dt><span class="sect2"><a href="messages.html#facet.messages.use">Use</a></span></dt><dt><span class="sect2"><a href="messages.html#facet.messages.future">Future</a></span></dt></dl></dd></dl></div><div class="sect1" lang="en" xml:lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="manual.localization.facet.ctype"></a>ctype</h2></div></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="facet.ctype.impl"></a>Implementation</h3></div></div></div><div class="sect3" lang="en" xml:lang="en"><div class="titlepage"><div><div><h4 class="title"><a id="id393159"></a>Specializations</h4></div></div></div><p> For the required specialization codecvt<wchar_t, char, mbstate_t> , conversions are made between the internal character set (always UCS4 on GNU/Linux) and whatever the currently selected locale for the LC_CTYPE category implements. </p><p> The two required specializations are implemented as follows: </p><p> <code class="code"> ctype<char> </code> </p><p> This is simple specialization. Implementing this was a piece of cake. </p><p> <code class="code"> ctype<wchar_t> </code> </p><p> This specialization, by specifying all the template parameters, pretty much ties the hands of implementors. As such, the implementation is straightforward, involving mcsrtombs for the conversions between char to wchar_t and wcsrtombs for conversions between wchar_t and char. </p><p> Neither of these two required specializations deals with Unicode characters. </p></div></div><div class="sect2" lang="en" xml:lang="en"><div class="titlepage"><div><div><h3 class="title"><a id="facet.ctype.future"></a>Future</h3></div></div></div><div class="itemizedlist"><ul type="disc"><li><p> How to deal with the global locale issue? </p></li><li><p> How to deal with different types than char, wchar_t? </p></li><li><p> Overlap between codecvt/ctype: narrow/widen </p></li><li><p> Mask typedef in codecvt_base, argument types in codecvt. what is know about this type? </p></li><li><p> Why mask* argument in codecvt? </p></li><li><p> 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? </p></li><li><p> Get the ctype<wchar_t>::mask stuff under control. Need to make some kind of static table, and not do lookup every time somebody hits the do_is... functions. Too bad we can't just redefine mask for ctype<wchar_t> </p></li><li><p> Rename abstract base class. See if just smash-overriding is a better approach. Clarify, add sanity to naming. </p></li></ul></div></div><div class="bibliography"><div class="titlepage"><div><div><h3 class="title"><a id="facet.ctype.biblio"></a>Bibliography</h3></div></div></div><div class="biblioentry"><a id="id471356"></a><p><span class="title"><i> The GNU C Library </i>. </span><span class="author"><span class="firstname">Roland</span> <span class="surname">McGrath</span>. </span><span class="author"><span class="firstname">Ulrich</span> <span class="surname">Drepper</span>. </span><span class="copyright">Copyright © 2007 FSF. </span><span class="pagenums">Chapters 6 Character Set Handling and 7 Locales and Internationalization. </span></p></div><div class="biblioentry"><a id="id413436"></a><p><span class="title"><i> Correspondence </i>. </span><span class="author"><span class="firstname">Ulrich</span> <span class="surname">Drepper</span>. </span><span class="copyright">Copyright © 2002 . </span></p></div><div class="biblioentry"><a id="id424158"></a><p><span class="title"><i> ISO/IEC 14882:1998 Programming languages - C++ </i>. </span><span class="copyright">Copyright © 1998 ISO. </span></p></div><div class="biblioentry"><a id="id424176"></a><p><span class="title"><i> ISO/IEC 9899:1999 Programming languages - C </i>. </span><span class="copyright">Copyright © 1999 ISO. </span></p></div><div class="biblioentry"><a id="id461050"></a><p><span class="title"><i> System Interface Definitions, Issue 6 (IEEE Std. 1003.1-200x) </i>. </span><span class="copyright">Copyright © 1999 The Open Group/The Institute of Electrical and Electronics Engineers, Inc.. </span><span class="biblioid"> <a class="ulink" href="http://www.opennc.org/austin/docreg.html" target="_top"> </a> . </span></p></div><div class="biblioentry"><a id="id461076"></a><p><span class="title"><i> The C++ Programming Language, Special Edition </i>. </span><span class="author"><span class="firstname">Bjarne</span> <span class="surname">Stroustrup</span>. </span><span class="copyright">Copyright © 2000 Addison Wesley, Inc.. </span><span class="pagenums">Appendix D. </span><span class="publisher"><span class="publishername"> Addison Wesley . </span></span></p></div><div class="biblioentry"><a id="id426264"></a><p><span class="title"><i> Standard C++ IOStreams and Locales </i>. </span><span class="subtitle"> Advanced Programmer's Guide and Reference . </span><span class="author"><span class="firstname">Angelika</span> <span class="surname">Langer</span>. </span><span class="author"><span class="firstname">Klaus</span> <span class="surname">Kreft</span>. </span><span class="copyright">Copyright © 2000 Addison Wesley Longman, Inc.. </span><span class="publisher"><span class="publishername"> Addison Wesley Longman . </span></span></p></div></div></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="locales.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="localization.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="codecvt.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 14. 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