std::messages<CharT>::open, std::messages<CharT>::do_open

 

C++

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Technical specifications

Symbols index

External libraries

 

Localization library

Locales and facets
Locales
has_facet use_facet	locale
Facet category base classes
ctype_base codecvt_base messages_base	time_base money_base
ctype facets
ctype ctype<char> ctype_byname	codecvt codecvt_byname
numeric facets
num_get num_put	numpunct numpunct_byname
collate facets
collate	collate_byname
time facets
time_get time_put	time_get_byname time_put_byname
monetary facets
money_get money_put	moneypunct moneypunct_byname
messages facets
messages	messages_byname

Character classification and conversion
Character classification
isspace isblank (C++11) iscntrl	isupper islower isalpha	ispunct isdigit isxdigit	isalnum isprint isgraph

Character conversions

toupper

tolower

String and stream conversions

wstring_convert (C++11/17/26*)

wbuffer_convert (C++11/17/26*)

Text encoding identifications

text_encoding (C++26)

Unicode conversion facets

codecvt_utf8 (C++11/17/26*)

codecvt_utf16 (C++11/17/26*)

codecvt_utf8_utf16 (C++11/17/26*)

codecvt_mode (C++11/17/26*)

C library locales
LC_ALLLC_COLLATELC_CTYPELC_MONETARYLC_NUMERICLC_TIME	setlocale localeconv lconv

 

std::messages

Member functions

messages::messages

messages::~messages

messages::openmessages::do_open

messages::getmessages::do_get

messages::closemessages::do_close

 

Defined in header <locale>
public: catalog open( const std::basic_string<char>& name, const std::locale& loc ) const;	(1)
protected: virtual catalog do_open( const std::basic_string<char>& name, const std::locale& loc ) const;	(2)

1) Public member function, calls the protected virtual member function do_open of the most derived class.

2) Obtains a value of type catalog (inherited from std::messages_base), which can be passed to get() to retrieve messages from the message catalog named by name. This value is usable until passed to close().

Parameters

name	-	name of the message catalog to open
loc	-	a locale object that provides additional facets that may be required to read messages from the catalog, such as std::codecvt to perform wide/multibyte conversions

Return value

The non-negative value of type catalog that can be used with get() and close(). Returns a negative value if the catalog could not be opened.

Notes

On POSIX systems, this function call usually translates to a call to catopen(). In GNU libstdc++, it calls textdomain.

The actual catalog location is implementation-defined: for the catalog "sed" (message catalogs installed with the Unix utility 'sed') in German locale, for example, the file opened by this function call may be /usr/lib/nls/msg/de_DE/sed.cat, /usr/lib/locale/de_DE/LC_MESSAGES/sed.cat, or /usr/share/locale/de/LC_MESSAGES/sed.mo.

Example

The following example demonstrated retrieval of messages: on a typical GNU/Linux system it reads from /usr/share/locale/de/LC_MESSAGES/sed.mo.

Run this code

#include <iostream>
#include <locale>
 
int main()
{
    std::locale loc("de_DE.utf8");
    std::cout.imbue(loc);
    auto& facet = std::use_facet<std::messages<char>>(loc);
    auto cat = facet.open("sed", loc);
    if (cat < 0)
        std::cout << "Could not open german \"sed\" message catalog\n";
    else
        std::cout << "\"No match\" in German: "
                  << facet.get(cat, 0, 0, "No match") << '\n'
                  << "\"Memory exhausted\" in German: "
                  << facet.get(cat, 0, 0, "Memory exhausted") << '\n';
    facet.close(cat);
}

Possible output:

"No match" in German: Keine Übereinstimmung
"Memory exhausted" in German: Speicher erschöpft