libstdc++-v3/docs/html/22_locale/ctype.html

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   9    <meta name="AUTHOR" content="bkoz@redhat.com (Benjamin Kosnik)" />
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  11    <meta name="DESCRIPTION" content="Notes on the ctype implementation." />
  12    <title>Notes on the ctype implementation.</title>
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  16   <h1>
  17   Notes on the ctype implementation.
  18   </h1>
  19 <em>
  20 prepared by Benjamin Kosnik (bkoz@redhat.com) on August 30, 2000
  21 </em>
  22
  23 <h2>
  24 1. Abstract
  25 </h2>
  26 <p>
  27 Woe is me.
  28 </p>
  29
  30 <h2>
  31 2. What the standard says
  32 </h2>
  33
  34
  35 <h2>
  36 3. Problems with &quot;C&quot; ctype : global locales, termination.
  37 </h2>
  38
  39 <p>
  40 For the required specialization codecvt&lt;wchar_t, char, mbstate_t&gt; ,
  41 conversions are made between the internal character set (always UCS4
  42 on GNU/Linux) and whatever the currently selected locale for the
  43 LC_CTYPE category implements.
  44 </p>
  45
  46 <h2>
  47 4. Design
  48 </h2>
  49 The two required specializations are implemented as follows:
  50
  51 <p>
  52 <code>
  53 ctype&lt;char&gt;
  54 </code>
  55 </p>
  56 <p>
  57 This is simple specialization. Implementing this was a piece of cake.
  58 </p>
  59
  60 <p>
  61 <code>
  62 ctype&lt;wchar_t&gt;
  63 </code>
  64 </p>
  65 <p>
  66 This specialization, by specifying all the template parameters, pretty
  67 much ties the hands of implementors. As such, the implementation is
  68 straightforward, involving mcsrtombs for the conversions between char
  69 to wchar_t and wcsrtombs for conversions between wchar_t and char.
  70 </p>
  71
  72 <p>
  73 Neither of these two required specializations deals with Unicode
  74 characters. As such, libstdc++-v3 implements
  75 </p>
  76
  77 <h2>
  78 5.  Examples
  79 </h2>
  80
  81 <pre>
  82   typedef ctype&lt;char&gt; cctype;
  83 </pre>
  84
  85 More information can be found in the following testcases:
  86 <ul>
  87 <li> testsuite/22_locale/ctype_char_members.cc    </li>
  88 <li> testsuite/22_locale/ctype_wchar_t_members.cc </li>
  89 </ul>
  90
  91 <h2>
  92 6.  Unresolved Issues
  93 </h2>
  94
  95 <ul>
  96    <li> how to deal with the global locale issue? </li>
  97
  98    <li> how to deal with different types than char, wchar_t? </li>
  99
 100    <li> codecvt/ctype overlap: narrow/widen </li>
 101
 102    <li> mask typedef in codecvt_base, argument types in codecvt.
 103    what is know about this type? </li>
 104
 105    <li> why mask* argument in codecvt? </li>
 106
 107    <li> can this be made (more) generic? is there a simple way to
 108    straighten out the configure-time mess that is a by-product of
 109    this class? </li>
 110
 111    <li> get the ctype&lt;wchar_t&gt;::mask stuff under control. Need to
 112    make some kind of static table, and not do lookup evertime
 113    somebody hits the do_is... functions. Too bad we can't just
 114    redefine mask for ctype&lt;wchar_t&gt; </li>
 115
 116    <li> rename abstract base class. See if just smash-overriding
 117    is a better approach. Clarify, add sanity to naming. </li>
 118
 119 </ul>
 120
 121
 122 <h2>
 123 7. Acknowledgments
 124 </h2>
 125 Ulrich Drepper for patient answering of late-night questions, skeletal
 126 examples, and C language expertise.
 127
 128 <h2>
 129 8. Bibliography / Referenced Documents
 130 </h2>
 131
 132 Drepper, Ulrich, GNU libc (glibc) 2.2 manual. In particular, Chapters &quot;6. Character Set Handling&quot; and &quot;7 Locales and Internationalization&quot;
 133
 134 <p>
 135 Drepper, Ulrich, Numerous, late-night email correspondence
 136 </p>
 137
 138 <p>
 139 ISO/IEC 14882:1998 Programming languages - C++
 140 </p>
 141
 142 <p>
 143 ISO/IEC 9899:1999 Programming languages - C
 144 </p>
 145
 146 <p>
 147 Langer, Angelika and Klaus Kreft, Standard C++ IOStreams and Locales, Advanced Programmer's Guide and Reference, Addison Wesley Longman, Inc. 2000
 148 </p>
 149
 150 <p>
 151 Stroustrup, Bjarne, Appendix D, The C++ Programming Language, Special Edition, Addison Wesley, Inc. 2000
 152 </p>
 153
 154 <p>
 155 System Interface Definitions, Issue 6 (IEEE Std. 1003.1-200x)
 156 The Open Group/The Institute of Electrical and Electronics Engineers, Inc.
 157 http://www.opennc.org/austin/docreg.html
 158 </p>
 159
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