namespace std {
class codecvt_base {
public:
enum result { ok, partial, error, noconv };
};
template<class internT, class externT, class stateT>
class codecvt : public locale::facet, public codecvt_base {
public:
using intern_type = internT;
using extern_type = externT;
using state_type = stateT;
explicit codecvt(size_t refs = 0);
result out(
stateT& state,
const internT* from, const internT* from_end, const internT*& from_next,
externT* to, externT* to_end, externT*& to_next) const;
result unshift(
stateT& state,
externT* to, externT* to_end, externT*& to_next) const;
result in(
stateT& state,
const externT* from, const externT* from_end, const externT*& from_next,
internT* to, internT* to_end, internT*& to_next) const;
int encoding() const noexcept;
bool always_noconv() const noexcept;
int length(stateT&, const externT* from, const externT* end, size_t max) const;
int max_length() const noexcept;
static locale::id id;
protected:
~codecvt();
virtual result do_out(
stateT& state,
const internT* from, const internT* from_end, const internT*& from_next,
externT* to, externT* to_end, externT*& to_next) const;
virtual result do_in(
stateT& state,
const externT* from, const externT* from_end, const externT*& from_next,
internT* to, internT* to_end, internT*& to_next) const;
virtual result do_unshift(
stateT& state,
externT* to, externT* to_end, externT*& to_next) const;
virtual int do_encoding() const noexcept;
virtual bool do_always_noconv() const noexcept;
virtual int do_length(stateT&, const externT* from, const externT* end, size_t max) const;
virtual int do_max_length() const noexcept;
};
}
The class
codecvt<internT, externT, stateT>
is for use when
converting from one character encoding to another, such as from wide characters
to multibyte characters or between wide character encodings such as
UTF-32 and EUC
.The
stateT
argument selects the pair of character encodings being mapped between
.The specializations required in Table
102 (
[locale.category])
convert the implementation-defined native character set
.codecvt<char, char, mbstate_t>
implements a degenerate conversion;
it does not convert at all
. The specialization
codecvt<char16_t, char8_t, mbstate_t>
converts between the UTF-16 and UTF-8 encoding forms, and
the specialization
codecvt <char32_t, char8_t, mbstate_t>
converts between the UTF-32 and UTF-8 encoding forms
.codecvt<wchar_t, char, mbstate_t>
converts between the native character sets for ordinary and wide characters
. Specializations on
mbstate_t
perform conversion between encodings known to the library implementer
.Other encodings can be converted by specializing on a program-defined
stateT
type
.Objects of type
stateT
can contain any state that is useful to communicate to or from
the specialized
do_in
or
do_out
members
.