std::wstring_convert<Codecvt,Elem,Wide_alloc,Byte_alloc>::wstring_convert

 

C++

Compiler support

Freestanding and hosted

Language

Standard library

Standard library headers

Named requirements

Feature test macros (C++20)

Language support library

Concepts library (C++20)

Metaprogramming library (C++11)

Diagnostics library

General utilities library

Strings library

Containers library

Iterators library

Ranges library (C++20)

Algorithms library

Numerics library

Localizations library

Input/output library

Filesystem library (C++17)

Regular expressions library (C++11)

Concurrency support library (C++11)

Execution support library (C++26)

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::wstring_convert

Member functions

wstring_convert::wstring_convert

wstring_convert::~wstring_convert

wstring_convert::from_bytes

wstring_convert::to_bytes

wstring_convert::converted

wstring_convert::state

 

wstring_convert() : wstring_convert( new Codecvt ) {}	(1)
explicit wstring_convert( Codecvt* pcvt );	(2)
wstring_convert( Codecvt* pcvt, state_type state );	(3)
explicit wstring_convert( const byte_string& byte_err,                           const wide_string& wide_err = wide_string() );	(4)
wstring_convert( const std::wstring_convert& ) = delete;	(5)	(since C++14)

Overload	Data members
	byte_err_string	wide_err_string	cvtptr	cvtstate	cvtcount
(1)	default-initialized		new Codecvt	default-initialized	uninitialized
(2)			pcvt
(3)				state
(4)	byte_err	wide_err	new Codecvt	state_type()

2,3) If pcvt is a null pointer, the behavior is undefined.

5) The copy constructor is deleted, wstring_convert is not CopyConstructible.

Parameters

pcvt	-	pointer to the conversion facet
state	-	initial value of the conversion shift state
byte_err	-	narrow string to display on errors
wide_err	-	wide string to display on errors

Example

Run this code

#include <codecvt>
#include <locale>
#include <utility>
 
// utility wrapper to adapt locale-bound facets for wstring/wbuffer convert
template<class Facet>
struct deletable_facet : Facet
{
    using Facet::Facet; // inherit constructors
    ~deletable_facet() {}
};
 
int main()
{
    // UTF-16le / UCS4 conversion
    std::wstring_convert
        <std::codecvt_utf16<char32_t, 0x10ffff, std::little_endian>> u16to32;
 
    // UTF-8 / wide string conversion with custom messages
    std::wstring_convert<std::codecvt_utf8<wchar_t>> u8towide("Error!", L"Error!");
 
    // GB18030 / wide string conversion facet
    using F = deletable_facet<std::codecvt_byname<wchar_t, char, std::mbstate_t>>;
    std::wstring_convert<F> gbtowide(new F("zh_CN.gb18030"));
}

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2175	C++11	pcvt could be a null pointer	the behavior is undefined in this case
LWG 2176	C++11	constructors accepting single argument were implicit	made explicit
P0935R0	C++11	the default constructor was explicit	made implicit