std::codecvt_utf8_utf16 - cppreference.com (original) (raw)

std::codecvt_utf8_utf16 is a std::codecvt facet which encapsulates conversion between a UTF-8 encoded byte string and UTF-16 encoded character string. If Elem is a 32-bit type, one UTF-16 code unit will be stored in each 32-bit character of the output sequence.

This is an N:M conversion facet, and cannot be used with std::basic_filebuf (which only permits 1:N conversions, such as UTF-32/UTF-8, between the internal and the external encodings). This facet can be used with std::wstring_convert.

Contents

[edit] Template Parameters

Elem - either char16_t, char32_t, or wchar_t
Maxcode - the largest value of Elem that this facet will read or write without error
Mode - a constant of type std::codecvt_mode

[edit] Member functions

| | constructs a new codecvt_utf8_utf16 facet (public member function) | | ----------------------------------------------------------------------- | | | destroys a codecvt_utf8_utf16 facet (public member function) |

std::codecvt_utf8_utf16::codecvt_utf8_utf16

Constructs a new std::codecvt_utf8_utf16 facet, passes the initial reference counter refs to the base class.

Parameters

refs - the number of references that link to the facet

std::codecvt_utf8_utf16::~codecvt_utf8_utf16

Destroys the facet. Unlike the locale-managed facets, this facet's destructor is public.

Inherited from std::codecvt

Nested types

Type Definition
intern_type internT
extern_type externT
state_type stateT

[edit] Data members

Member functions

out invokes do_out (public member function of std::codecvt<InternT,ExternT,StateT>) [edit]
in invokes do_in (public member function of std::codecvt<InternT,ExternT,StateT>) [edit]
unshift invokes do_unshift (public member function of std::codecvt<InternT,ExternT,StateT>) [edit]
encoding invokes do_encoding (public member function of std::codecvt<InternT,ExternT,StateT>) [edit]
always_noconv invokes do_always_noconv (public member function of std::codecvt<InternT,ExternT,StateT>) [edit]
length invokes do_length (public member function of std::codecvt<InternT,ExternT,StateT>) [edit]
max_length invokes do_max_length (public member function of std::codecvt<InternT,ExternT,StateT>) [edit]

Protected member functions

do_out[virtual] converts a string from InternT to ExternT, such as when writing to file (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]
do_in[virtual] converts a string from ExternT to InternT, such as when reading from file (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]
do_unshift[virtual] generates the termination character sequence of ExternT characters for incomplete conversion (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]
do_encoding[virtual] returns the number of ExternT characters necessary to produce one InternT character, if constant (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]
do_always_noconv[virtual] tests if the facet encodes an identity conversion for all valid argument values (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]
do_length[virtual] calculates the length of the ExternT string that would be consumed by conversion into given InternT buffer (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]
do_max_length[virtual] returns the maximum number of ExternT characters that could be converted into a single InternT character (virtual protected member function of std::codecvt<InternT,ExternT,StateT>) [edit]

Inherited from std::codecvt_base

Nested type Definition
enum result { ok, partial, error, noconv }; Unscoped enumeration type
Enumeration constant Definition
ok conversion was completed with no error
partial not all source characters were converted
error encountered an invalid character
noconv no conversion required, input and output types are the same

[edit] Example

Output:

UTF-8 to UTF-16 conversion produced 5 code units: 0x7a 0xdf 0x6c34 0xd83c 0xdf4c UTF-16 to UTF-8 conversion produced 10 bytes: 0x7a 0xc3 0x9f 0xe6 0xb0 0xb4 0xf0 0x9f 0x8d 0x8c

[edit] 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 2229 C++98 the constructor and destructor were not specified specifies them

[edit] See also

Characterconversions 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>

| | converts between character encodings, including UTF-8, UTF-16, UTF-32 (class template) [edit] | | | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | (C++11)(deprecated in C++17)(removed in C++26) | tags to alter behavior of the standard codecvt facets (enum) [edit] | | (C++11)(deprecated in C++17)(removed in C++26) | converts between UTF-8 and UCS-2/UCS-4 (class template) [edit] | | (C++11)(deprecated in C++17)(removed in C++26) | converts between UTF-16 and UCS-2/UCS-4 (class template) [edit] |