# std::wstring_convert

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< cpp‎ | locale

Defined in header `<locale>` |  |
template< class Codecvt, class Elem = wchar_t, class Wide_alloc = std::allocator <Elem>, class Byte_alloc = std::allocator <char> > class wstring_convert; |  | (since C++11) (deprecated in C++17) (removed in C++26)

Class template `std::wstring_convert` performs conversions between byte string std::string and wide string std::basic_string <Elem>, using an individual code conversion facet `Codecvt`. `std::wstring_convert` assumes ownership of the conversion facet, and cannot use a facet managed by a locale.

The standard facets suitable for use with `std::wstring_convert` are std::codecvt_utf8 for UTF-8/UCS-2 and UTF-8/UCS-4 conversions and std::codecvt_utf8_utf16 for UTF-8/UTF-16 conversions.

### Nested types

Type | Definition
`byte_string` | std::basic_string <char, std::char_traits <char>, Byte_alloc>
`wide_string` | std::basic_string <Elem, std::char_traits <Elem>, Wide_alloc>
`state_type` | typename Codecvt::state_type
`int_type` | typename wide_string::traits_type::int_type

### Data members

Member | Description
`byte_string` `byte_err_string` | the byte string to display on errors (exposition-only member object*)
`wide_string` `wide_err_string` | the wide string to display on errors (exposition-only member object*)
Codecvt* `cvtptr` | a pointer to the allocated conversion object (exposition-only member object*)
`state_type` `cvtstate` | the conversion state object (exposition-only member object*)
std::size_t `cvtcount` | the conversion count (exposition-only member object*)

### Member functions

(constructor) | constructs a new `wstring_convert` (public member function)
operator= | the copy assignment operator is deleted (public member function)
(destructor) | destructs the `wstring_convert` and its conversion facet (public member function)
from_bytes | converts a byte string into a wide string (public member function)
to_bytes | converts a wide string into a byte string (public member function)
converted | returns the number of characters successfully converted (public member function)
state | returns the current conversion state (public member function)

### See also

Character conversions | locale-defined multibyte (UTF-8, GB18030) | UTF-8 | UTF-16
--- | --- | --- | ---
UTF-16 | `mbrtoc16` / `c16rtomb` (with C11's DR488) | `codecvt` <char16_t,char,mbstate_t> `codecvt_utf8_utf16` <char16_t> `codecvt_utf8_utf16` <char32_t> `codecvt_utf8_utf16` <wchar_t> | N/A
UCS-2 | `c16rtomb` (without C11's DR488) | `codecvt_utf8` <char16_t> | `codecvt_utf16` <char16_t>
UTF-32 | `mbrtoc32` / `c32rtomb` | `codecvt` <char32_t,char,mbstate_t> `codecvt_utf8` <char32_t> | `codecvt_utf16` <char32_t>
system wchar_t: UTF-32 (non-Windows) UCS-2 (Windows) | `mbsrtowcs` / `wcsrtombs` `use_facet` < `codecvt` <wchar_t,char,mbstate_t>>(`locale`) | `codecvt_utf8` <wchar_t> | `codecvt_utf16` <wchar_t>

wbuffer_convert (C++11)(deprecated in C++17)(removed in C++26) | performs conversion between a byte stream buffer and a wide stream buffer (class template)
codecvt_utf8 (C++11)(deprecated in C++17)(removed in C++26) | converts between UTF-8 and UCS-2/UCS-4 (class template)
codecvt_utf8_utf16 (C++11)(deprecated in C++17)(removed in C++26) | converts between UTF-8 and UTF-16 (class template)

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