class template
<locale>

std::codecvt

template <class internT, class externT, class stateT> class codecvt;
Convert codeset facet

The codecvt standard facet translates between two different character encodings: an internal character type (generally some type of wide character) and an external character type (generally representing a multibyte sequence).

The codecvt class template has a protected destructor: Programs shall only construct objects of derived classes, or use those installed in locale objects (through use_facet).

All standard locale objects support at least the following facet instantiations of the codecvt class template (as part of the ctype category):
facets in locale objectsdescription
codecvt<char,char,mbstate_t>performs no conversion
codecvt<wchar_t,char,mbstate_t>converts between native wide and narrow character sets
facets in locale objectsdescription
codecvt<char,char,mbstate_t>performs no conversion
codecvt<wchar_t,char,mbstate_t>converts between native wide and narrow character sets
codecvt<char16_t,char,mbstate_t>converts between UTF16 and UTF8 encodings
codecvt<char32_t,char,mbstate_t>converts between UTF32 and UTF8 encodings

Header <codecvt> defines additional stand-alone facet objects derived from codecvt (for more info, see header <codecvt>).

Template parameters

internT
Internal character type: Typically, this is the wide character type.
Aliased as member intern_type.
externT
External character type: Typically, this is the multi-byte type.
Aliased as member extern_type.
stateT
A state type: Typically, this is an object able to keep track of the state of the conversion, such as mbstate_t (or, more generically, char_traits<externT>::state_type).
Aliased as member state_type.

Member types

member typedefinitiondescription
intern_typeThe first template parameter (internT)Internal character type
extern_typeThe second template parameter (externT)External character type
state_typeThe third template parameter (stateT)State type
The class also inherits codecvt_base::result, which is used as the return type for members in, out and unshift.

Member constants

The following member constants are inherited from codecvt_base (as labels of enum type codecvt_base::result); They are used as return values by certain member functions.
member constanttypevaluedescription
okcodecvt_base::result0Conversion successful
partialcodecvt_base::result1Partial conversion
errorcodecvt_base::result2Conversion error
noconvcodecvt_base::result3No conversion

The class also contains a public static constant of type locale::id, that uniquely identifies facets with codecvt semantics.

Public member functions

(constructor)
codecvt constructor (public member function )

Conversion functions

in
Translate in characters (public member function )
out
Translate out characters (public member function )
unshift
Unshift translation state (public member function )

Character encoding properties

always_noconv
Return noconv characteristics (public member function )
encoding
Return encoding width (public member function )
length
Return length of translated sequence (public member function )
max_length
Return max length of one character (public member function )

Virtual protected member functions

The class defines the virtual protected members which implement the behavior by default of their respective public member functions:
do_always_noconv
Return noconv characteristics [virtual] (protected virtual member function )
do_encoding
Return encoding width [virtual] (protected virtual member function )
do_in
Translate in characters [virtual] (protected virtual member function )
do_length
Return length of translated sequence [virtual] (public member function )
do_max_length
Return max length of one character [virtual] (protected virtual member function )
do_out
Translate out characters [virtual] (protected virtual member function )
do_unshift
Unshift translation state [virtual] (protected virtual member function )

Along with the class destructor:
(destructor)
codecvt destructor (protected member function )

The class contains a public static constant of type locale::id that uniquely identifies facets with codecvt semantics.

Specializations

At least the following specializations of this template are provided in all library implementations:
specialization
codecvt<char,char,mbstate_t>
codecvt<wchar_t,char,mbstate_t>
specialization
codecvt<char,char,mbstate_t>
codecvt<wchar_t,char,mbstate_t>
codecvt<char16_t,char,mbstate_t>
codecvt<char32_t,char,mbstate_t>

C++