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- <meta name="AUTHOR" content="bkoz@redhat.com (Benjamin Kosnik)" />
- <meta name="KEYWORDS" content="HOWTO, libstdc++, locale name LC_ALL" />
- <meta name="DESCRIPTION" content="Notes on the locale implementation." />
- <title>Notes on the locale implementation.</title>
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-<body>
- <h1>
- Notes on the locale implementation.
- </h1>
-<em>
-prepared by Benjamin Kosnik (bkoz@redhat.com) on October 14, 2002
-</em>
-
-<h2>
-1. Abstract
-</h2>
-<p>
-Describes the basic locale object, including nested
-classes id, facet, and the reference-counted implementation object,
-class _Impl.
-</p>
-
-<h2>
-2. What the standard says
-</h2>
-Class locale is non-templatized and has two distinct types nested
-inside of it:
-
-<blockquote>
-<em>
-class facet
-22.1.1.1.2 Class locale::facet
-</em>
-</blockquote>
-
-<p>
-Facets actually implement locale functionality. For instance, a facet
-called numpunct is the data objects that can be used to query for the
-thousands separator is in the German locale.
-</p>
-
-Literally, a facet is strictly defined:
-<ul>
- <li>containing the following public data member:
- <p>
- <code>static locale::id id;</code>
- </p>
- </li>
-
- <li>derived from another facet:
- <p>
- <code> class gnu_codecvt: public std::ctype<user-defined-type></code>
- </p>
- </li>
-</ul>
-
-<p>
-Of interest in this class are the memory management options explicitly
-specified as an argument to facet's constructor. Each constructor of a
-facet class takes a std::size_t __refs argument: if __refs == 0, the
-facet is deleted when the locale containing it is destroyed. If __refs
-== 1, the facet is not destroyed, even when it is no longer
-referenced.
-</p>
-
-<blockquote>
-<em>
-class id
-22.1.1.1.3 - Class locale::id
-</em>
-</blockquote>
-
-<p>
-Provides an index for looking up specific facets.
-</p>
-
-
-<h2>
-3. Interacting with "C" locales.
-</h2>
-
-<p>
-Some help on determining the underlying support for locales on a system.
-Note, this is specific to linux (and glibc-2.3.x)
-</p>
-
-<ul>
- <li> <code>`locale -a`</code> displays available locales.
-<blockquote>
-<pre>
-af_ZA
-ar_AE
-ar_AE.utf8
-ar_BH
-ar_BH.utf8
-ar_DZ
-ar_DZ.utf8
-ar_EG
-ar_EG.utf8
-ar_IN
-ar_IQ
-ar_IQ.utf8
-ar_JO
-ar_JO.utf8
-ar_KW
-ar_KW.utf8
-ar_LB
-ar_LB.utf8
-ar_LY
-ar_LY.utf8
-ar_MA
-ar_MA.utf8
-ar_OM
-ar_OM.utf8
-ar_QA
-ar_QA.utf8
-ar_SA
-ar_SA.utf8
-ar_SD
-ar_SD.utf8
-ar_SY
-ar_SY.utf8
-ar_TN
-ar_TN.utf8
-ar_YE
-ar_YE.utf8
-be_BY
-be_BY.utf8
-bg_BG
-bg_BG.utf8
-br_FR
-bs_BA
-C
-ca_ES
-ca_ES@euro
-ca_ES.utf8
-ca_ES.utf8@euro
-cs_CZ
-cs_CZ.utf8
-cy_GB
-da_DK
-da_DK.iso885915
-da_DK.utf8
-de_AT
-de_AT@euro
-de_AT.utf8
-de_AT.utf8@euro
-de_BE
-de_BE@euro
-de_BE.utf8
-de_BE.utf8@euro
-de_CH
-de_CH.utf8
-de_DE
-de_DE@euro
-de_DE.utf8
-de_DE.utf8@euro
-de_LU
-de_LU@euro
-de_LU.utf8
-de_LU.utf8@euro
-el_GR
-el_GR.utf8
-en_AU
-en_AU.utf8
-en_BW
-en_BW.utf8
-en_CA
-en_CA.utf8
-en_DK
-en_DK.utf8
-en_GB
-en_GB.iso885915
-en_GB.utf8
-en_HK
-en_HK.utf8
-en_IE
-en_IE@euro
-en_IE.utf8
-en_IE.utf8@euro
-en_IN
-en_NZ
-en_NZ.utf8
-en_PH
-en_PH.utf8
-en_SG
-en_SG.utf8
-en_US
-en_US.iso885915
-en_US.utf8
-en_ZA
-en_ZA.utf8
-en_ZW
-en_ZW.utf8
-es_AR
-es_AR.utf8
-es_BO
-es_BO.utf8
-es_CL
-es_CL.utf8
-es_CO
-es_CO.utf8
-es_CR
-es_CR.utf8
-es_DO
-es_DO.utf8
-es_EC
-es_EC.utf8
-es_ES
-es_ES@euro
-es_ES.utf8
-es_ES.utf8@euro
-es_GT
-es_GT.utf8
-es_HN
-es_HN.utf8
-es_MX
-es_MX.utf8
-es_NI
-es_NI.utf8
-es_PA
-es_PA.utf8
-es_PE
-es_PE.utf8
-es_PR
-es_PR.utf8
-es_PY
-es_PY.utf8
-es_SV
-es_SV.utf8
-es_US
-es_US.utf8
-es_UY
-es_UY.utf8
-es_VE
-es_VE.utf8
-et_EE
-et_EE.utf8
-eu_ES
-eu_ES@euro
-eu_ES.utf8
-eu_ES.utf8@euro
-fa_IR
-fi_FI
-fi_FI@euro
-fi_FI.utf8
-fi_FI.utf8@euro
-fo_FO
-fo_FO.utf8
-fr_BE
-fr_BE@euro
-fr_BE.utf8
-fr_BE.utf8@euro
-fr_CA
-fr_CA.utf8
-fr_CH
-fr_CH.utf8
-fr_FR
-fr_FR@euro
-fr_FR.utf8
-fr_FR.utf8@euro
-fr_LU
-fr_LU@euro
-fr_LU.utf8
-fr_LU.utf8@euro
-ga_IE
-ga_IE@euro
-ga_IE.utf8
-ga_IE.utf8@euro
-gl_ES
-gl_ES@euro
-gl_ES.utf8
-gl_ES.utf8@euro
-gv_GB
-gv_GB.utf8
-he_IL
-he_IL.utf8
-hi_IN
-hr_HR
-hr_HR.utf8
-hu_HU
-hu_HU.utf8
-id_ID
-id_ID.utf8
-is_IS
-is_IS.utf8
-it_CH
-it_CH.utf8
-it_IT
-it_IT@euro
-it_IT.utf8
-it_IT.utf8@euro
-iw_IL
-iw_IL.utf8
-ja_JP.eucjp
-ja_JP.utf8
-ka_GE
-kl_GL
-kl_GL.utf8
-ko_KR.euckr
-ko_KR.utf8
-kw_GB
-kw_GB.utf8
-lt_LT
-lt_LT.utf8
-lv_LV
-lv_LV.utf8
-mi_NZ
-mk_MK
-mk_MK.utf8
-mr_IN
-ms_MY
-ms_MY.utf8
-mt_MT
-mt_MT.utf8
-nl_BE
-nl_BE@euro
-nl_BE.utf8
-nl_BE.utf8@euro
-nl_NL
-nl_NL@euro
-nl_NL.utf8
-nl_NL.utf8@euro
-nn_NO
-nn_NO.utf8
-no_NO
-no_NO.utf8
-oc_FR
-pl_PL
-pl_PL.utf8
-POSIX
-pt_BR
-pt_BR.utf8
-pt_PT
-pt_PT@euro
-pt_PT.utf8
-pt_PT.utf8@euro
-ro_RO
-ro_RO.utf8
-ru_RU
-ru_RU.koi8r
-ru_RU.utf8
-ru_UA
-ru_UA.utf8
-se_NO
-sk_SK
-sk_SK.utf8
-sl_SI
-sl_SI.utf8
-sq_AL
-sq_AL.utf8
-sr_YU
-sr_YU@cyrillic
-sr_YU.utf8
-sr_YU.utf8@cyrillic
-sv_FI
-sv_FI@euro
-sv_FI.utf8
-sv_FI.utf8@euro
-sv_SE
-sv_SE.iso885915
-sv_SE.utf8
-ta_IN
-te_IN
-tg_TJ
-th_TH
-th_TH.utf8
-tl_PH
-tr_TR
-tr_TR.utf8
-uk_UA
-uk_UA.utf8
-ur_PK
-uz_UZ
-vi_VN
-vi_VN.tcvn
-wa_BE
-wa_BE@euro
-yi_US
-zh_CN
-zh_CN.gb18030
-zh_CN.gbk
-zh_CN.utf8
-zh_HK
-zh_HK.utf8
-zh_TW
-zh_TW.euctw
-zh_TW.utf8
-</pre>
-</blockquote>
-</li>
-
- <li> <code>`locale`</code> displays environmental variables
- that impact how locale("") will be deduced.
-
-<blockquote>
-<pre>
-LANG=en_US
-LC_CTYPE="en_US"
-LC_NUMERIC="en_US"
-LC_TIME="en_US"
-LC_COLLATE="en_US"
-LC_MONETARY="en_US"
-LC_MESSAGES="en_US"
-LC_PAPER="en_US"
-LC_NAME="en_US"
-LC_ADDRESS="en_US"
-LC_TELEPHONE="en_US"
-LC_MEASUREMENT="en_US"
-LC_IDENTIFICATION="en_US"
-LC_ALL=
-</pre>
-</blockquote>
-</li>
-</ul>
-
-<p>
-From Josuttis, p. 697-698, which says, that "there is only *one*
-relation (of the C++ locale mechanism) to the C locale mechanism: the
-global C locale is modified if a named C++ locale object is set as the
-global locale" (emphasis Paolo), that is:
-</p>
- <code>std::locale::global(std::locale(""));</code>
-
-<p>affects the C functions as if the following call was made:</p>
-
- <code>std::setlocale(LC_ALL, "");</code>
-
-<p>
-On the other hand, there is *no* viceversa, that is, calling setlocale
-has *no* whatsoever on the C++ locale mechanism, in particular on the
-working of locale(""), which constructs the locale object from the
-environment of the running program, that is, in practice, the set of
-LC_ALL, LANG, etc. variable of the shell.
-</p>
-
-
-<h2>
-4. Design
-</h2>
-
-
-<p>
-The major design challenge is fitting an object-orientated and
-non-global locale design ontop of POSIX and other relevant stanards,
-which include the Single Unix (nee X/Open.)
-</p>
-
-<p>
-Because POSIX falls down so completely, portibility is an issue.
-</p>
-
-class _Impl
-The internal representation of the std::locale object.
-
-
-<h2>
-5. Examples
-</h2>
-
-More information can be found in the following testcases:
-<ul>
-<li> testsuite/22_locale/all </li>
-</ul>
-
-<h2>
-6. Unresolved Issues
-</h2>
-
-<ul>
- <li> locale initialization: at what point does _S_classic,
- _S_global get initialized? Can named locales assume this
- initialization has already taken place? </li>
-
- <li> document how named locales error check when filling data
- members. Ie, a fr_FR locale that doesn't have
- numpunct::truename(): does it use "true"? Or is it a blank
- string? What's the convention? </li>
-
- <li> explain how locale aliasing happens. When does "de_DE"
- use "de" information? What is the rule for locales composed of
- just an ISO language code (say, "de") and locales with both an
- ISO language code and ISO country code (say, "de_DE"). </li>
-
- <li> what should non-required facet instantiations do? If the
- generic implemenation is provided, then how to end-users
- provide specializations? </li>
-</ul>
-
-<h2>
-7. Acknowledgments
-</h2>
-
-<h2>
-8. Bibliography / Referenced Documents
-</h2>
-
-Drepper, Ulrich, GNU libc (glibc) 2.2 manual. In particular, Chapters "6. Character Set Handling" and "7 Locales and Internationalization"
-
-<p>
-Drepper, Ulrich, Numerous, late-night email correspondence
-</p>
-
-<p>
-ISO/IEC 14882:1998 Programming languages - C++
-</p>
-
-<p>
-ISO/IEC 9899:1999 Programming languages - C
-</p>
-
-<p>
-Langer, Angelika and Klaus Kreft, Standard C++ IOStreams and Locales, Advanced Programmer's Guide and Reference, Addison Wesley Longman, Inc. 2000
-</p>
-
-<p>
-Stroustrup, Bjarne, Appendix D, The C++ Programming Language, Special Edition, Addison Wesley, Inc. 2000
-</p>
-
-<p>
-System Interface Definitions, Issue 6 (IEEE Std. 1003.1-200x)
-The Open Group/The Institute of Electrical and Electronics Engineers, Inc.
-http://www.opennc.org/austin/docreg.html
-</p>
-
-</body>
-</html>
-
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