X-Git-Url: https://oss.titaniummirror.com/gitweb?a=blobdiff_plain;f=libstdc%2B%2B-v3%2Fdocs%2Fhtml%2F22_locale%2Fmessages.html;fp=libstdc%2B%2B-v3%2Fdocs%2Fhtml%2F22_locale%2Fmessages.html;h=0000000000000000000000000000000000000000;hb=6fed43773c9b0ce596dca5686f37ac3fc0fa11c0;hp=b57f45411835f4cd06c72dcc05db3c1253761b77;hpb=27b11d56b743098deb193d510b337ba22dc52e5c;p=msp430-gcc.git diff --git a/libstdc++-v3/docs/html/22_locale/messages.html b/libstdc++-v3/docs/html/22_locale/messages.html deleted file mode 100644 index b57f4541..00000000 --- a/libstdc++-v3/docs/html/22_locale/messages.html +++ /dev/null @@ -1,456 +0,0 @@ - - - - - - - - - - Notes on the messages implementation. - - - -

-Notes on the messages implementation. -

- -prepared by Benjamin Kosnik (bkoz@redhat.com) on August 8, 2001 - - -

-1. Abstract -

-The std::messages facet implements message retrieval functionality -equivalent to Java's java.text.MessageFormat .using either GNU gettext -or IEEE 1003.1-200 functions. -

- -

-2. What the standard says -

-The std::messages facet is probably the most vaguely defined facet in -the standard library. It's assumed that this facility was built into -the standard library in order to convert string literals from one -locale to the other. For instance, converting the "C" locale's -const char* c = "please" to a German-localized "bitte" -during program execution. - -

-22.2.7.1 - Template class messages [lib.locale.messages] -

- -This class has three public member functions, which directly -correspond to three protected virtual member functions. - -The public member functions are: - -

-catalog open(const string&, const locale&) const -

- -

-string_type get(catalog, int, int, const string_type&) const -

- -

-void close(catalog) const -

- -

-While the virtual functions are: -

- -

-catalog do_open(const string&, const locale&) const -

- --1- Returns: A value that may be passed to get() to retrieve a -message, from the message catalog identified by the string name -according to an implementation-defined mapping. The result can be used -until it is passed to close(). Returns a value less than 0 if no such -catalog can be opened. - -

- -

-string_type do_get(catalog, int, int, const string_type&) const -

- --3- Requires: A catalog cat obtained from open() and not yet closed. --4- Returns: A message identified by arguments set, msgid, and dfault, -according to an implementation-defined mapping. If no such message can -be found, returns dfault. - -

- -

-void do_close(catalog) const -

- --5- Requires: A catalog cat obtained from open() and not yet closed. --6- Effects: Releases unspecified resources associated with cat. --7- Notes: The limit on such resources, if any, is implementation-defined. - -

- - -

-3. Problems with "C" messages: thread safety, -over-specification, and assumptions. -

-A couple of notes on the standard. - -

-First, why is messages_base::catalog specified as a typedef -to int? This makes sense for implementations that use -catopen, but not for others. Fortunately, it's not heavily -used and so only a minor irritant. -

- -

-Second, by making the member functions const, it is -impossible to save state in them. Thus, storing away information used -in the 'open' member function for use in 'get' is impossible. This is -unfortunate. -

- -

-The 'open' member function in particular seems to be oddly -designed. The signature seems quite peculiar. Why specify a const -string& argument, for instance, instead of just const -char*? Or, why specify a const locale& argument that is -to be used in the 'get' member function? How, exactly, is this locale -argument useful? What was the intent? It might make sense if a locale -argument was associated with a given default message string in the -'open' member function, for instance. Quite murky and unclear, on -reflection. -

- -

-Lastly, it seems odd that messages, which explicitly require code -conversion, don't use the codecvt facet. Because the messages facet -has only one template parameter, it is assumed that ctype, and not -codecvt, is to be used to convert between character sets. -

- -

-It is implicitly assumed that the locale for the default message -string in 'get' is in the "C" locale. Thus, all source code is assumed -to be written in English, so translations are always from "en_US" to -other, explicitly named locales. -

- -

-4. Design and Implementation Details -

-This is a relatively simple class, on the face of it. The standard -specifies very little in concrete terms, so generic implementations -that are conforming yet do very little are the norm. Adding -functionality that would be useful to programmers and comparable to -Java's java.text.MessageFormat takes a bit of work, and is highly -dependent on the capabilities of the underlying operating system. - -

-Three different mechanisms have been provided, selectable via -configure flags: -

- -

generic -
- This model does very little, and is what is used by default. -
-
gnu -
- The gnu model is complete and fully tested. It's based on the - GNU gettext package, which is part of glibc. It uses the functions - textdomain, bindtextdomain, gettext - to implement full functionality. Creating message - catalogs is a relatively straight-forward process and is - lightly documented below, and fully documented in gettext's - distributed documentation. -
-
ieee_1003.1-200x -
- This is a complete, though untested, implementation based on - the IEEE standard. The functions - catopen, catgets, catclose - are used to retrieve locale-specific messages given the - appropriate message catalogs that have been constructed for - their use. Note, the script po2msg.sed that is part - of the gettext distribution can convert gettext catalogs into - catalogs that catopen can use. -
-

- -

-A new, standards-conformant non-virtual member function signature was -added for 'open' so that a directory could be specified with a given -message catalog. This simplifies calling conventions for the gnu -model. -

- -

-The rest of this document discusses details of the GNU model. -

- -

-The messages facet, because it is retrieving and converting between -characters sets, depends on the ctype and perhaps the codecvt facet in -a given locale. In addition, underlying "C" library locale support is -necessary for more than just the LC_MESSAGES mask: -LC_CTYPE is also necessary. To avoid any unpleasantness, all -bits of the "C" mask (ie LC_ALL) are set before retrieving -messages. -

- -

-Making the message catalogs can be initially tricky, but become quite -simple with practice. For complete info, see the gettext -documentation. Here's an idea of what is required: -

- -

Make a source file with the required string literals - that need to be translated. See - intl/string_literals.cc for an example. -
Make initial catalog (see "4 Making the PO Template File" - from the gettext docs). -
- xgettext --c++ --debug string_literals.cc -o libstdc++.pot -
-
Make language and country-specific locale catalogs. -
- cp libstdc++.pot fr_FR.po -
-
- cp libstdc++.pot de_DE.po -
-
Edit localized catalogs in emacs so that strings are - translated. -
- emacs fr_FR.po -
-
Make the binary mo files. -
- msgfmt fr_FR.po -o fr_FR.mo -
-
- msgfmt de_DE.po -o de_DE.mo -
-
Copy the binary files into the correct directory structure. -
- cp fr_FR.mo (dir)/fr_FR/LC_MESSAGES/libstdc++-v3.mo -
-
- cp de_DE.mo (dir)/de_DE/LC_MESSAGES/libstdc++-v3.mo -
-
Use the new message catalogs. -
- locale loc_de("de_DE"); -
-
- - use_facet<messages<char> >(loc_de).open("libstdc++", locale(), dir); - -
-

- -

-5. Examples -

- -

message converting, simple example using the GNU model. - -

-#include <iostream>
-#include <locale>
-using namespace std;
-
-void test01()
-{
-  typedef messages<char>::catalog catalog;
-  const char* dir =
-  "/mnt/egcs/build/i686-pc-linux-gnu/libstdc++-v3/po/share/locale";  
-  const locale loc_de("de_DE");
-  const messages<char>& mssg_de = use_facet<messages<char> >(loc_de); 
-
-  catalog cat_de = mssg_de.open("libstdc++", loc_de, dir);
-  string s01 = mssg_de.get(cat_de, 0, 0, "please");
-  string s02 = mssg_de.get(cat_de, 0, 0, "thank you");
-  cout << "please in german:" << s01 << '\n';
-  cout << "thank you in german:" << s02 << '\n';
-  mssg_de.close(cat_de);
-}
-

- -More information can be found in the following testcases: -

testsuite/22_locale/messages.cc
testsuite/22_locale/messages_byname.cc
testsuite/22_locale/messages_char_members.cc

- -

-6. Unresolved Issues -

Things that are sketchy, or remain unimplemented: -
- _M_convert_from_char, _M_convert_to_char are in - flux, depending on how the library ends up doing - character set conversions. It might not be possible to - do a real character set based conversion, due to the - fact that the template parameter for messages is not - enough to instantiate the codecvt facet (1 supplied, - need at least 2 but would prefer 3). -
- There are issues with gettext needing the global - locale set to extract a message. This dependence on - the global locale makes the current "gnu" model non - MT-safe. Future versions of glibc, ie glibc 2.3.x will - fix this, and the C++ library bits are already in - place. -
-
Development versions of the GNU "C" library, glibc 2.3 will allow - a more efficient, MT implementation of std::messages, and will - allow the removal of the _M_name_messages data member. If this - is done, it will change the library ABI. The C++ parts to - support glibc 2.3 have already been coded, but are not in use: - once this version of the "C" library is released, the marked - parts of the messages implementation can be switched over to - the new "C" library functionality. -
At some point in the near future, std::numpunct will probably use - std::messages facilities to implement truename/falename - correctly. This is currently not done, but entries in - libstdc++.pot have already been made for "true" and "false" - string literals, so all that remains is the std::numpunct - coding and the configure/make hassles to make the installed - library search its own catalog. Currently the libstdc++.mo - catalog is only searched for the testsuite cases involving - messages members. -
The following member functions: - -
- - catalog - open(const basic_string<char>& __s, const locale& __loc) const - -
- -
- - catalog - open(const basic_string<char>&, const locale&, const char*) const; - -
- -
- Don't actually return a "value less than 0 if no such catalog - can be opened" as required by the standard in the "gnu" - model. As of this writing, it is unknown how to query to see - if a specified message catalog exists using the gettext - package. -
-

- -

-7. Acknowledgments -

-Ulrich Drepper for the character set explanations, gettext details, -and patient answering of late-night questions, Tom Tromey for the java details. - - -

-8. Bibliography / Referenced Documents -

- -Drepper, Ulrich, GNU libc (glibc) 2.2 manual. In particular, Chapters -"7 Locales and Internationalization" - -

-Drepper, Ulrich, Thread-Aware Locale Model, A proposal. This is a -draft document describing the design of glibc 2.3 MT locale -functionality. -

- -

-Drepper, Ulrich, Numerous, late-night email correspondence -

- -

-ISO/IEC 9899:1999 Programming languages - C -

- -

-ISO/IEC 14882:1998 Programming languages - C++ -

- -

-Java 2 Platform, Standard Edition, v 1.3.1 API Specification. In -particular, java.util.Properties, java.text.MessageFormat, -java.util.Locale, java.util.ResourceBundle. -http://java.sun.com/j2se/1.3/docs/api -

- -

-System Interface Definitions, Issue 7 (IEEE Std. 1003.1-200x) -The Open Group/The Institute of Electrical and Electronics Engineers, Inc. -In particular see lines 5268-5427. -http://www.opennc.org/austin/docreg.html -

- -

GNU gettext tools, version 0.10.38, Native Language Support -Library and Tools. -http://sources.redhat.com/gettext -

- -

-Langer, Angelika and Klaus Kreft, Standard C++ IOStreams and Locales, -Advanced Programmer's Guide and Reference, Addison Wesley Longman, -Inc. 2000. See page 725, Internationalized Messages. -

- -

-Stroustrup, Bjarne, Appendix D, The C++ Programming Language, Special Edition, Addison Wesley, Inc. 2000 -

- - - -