Standard C++ Library Reference ISO/IEC (VERSION3)

a value less than zero if the stream is left byte oriented●
In no event will the function alter the orientation of a stream once it has been oriented.
fwprintf
int fwprintf(FILE *stream, const wchar_t *format, ...);
The function generates formatted text, under the control of the format format and any additional
arguments, and writes each generated wide character to the stream stream. It returns the number of wide
characters generated, or it returns a negative value if the function sets the error indicator for the stream.
fwscanf
int fwscanf(FILE *stream, const wchar_t *format, ...);
The function scans formatted text, under the control of the format format and any additional arguments.
It obtains each scanned character from the stream stream. It returns the number of input items matched
and assigned, or it returns EOF if the function does not store values before it sets the end-of-file or error
indicator for the stream.
getwc
wint_t getwc(FILE *stream);
The function has the same effect as fgetwc(stream) except that a macro version of getwc can
evaluate stream more than once.
getwchar
wint_t getwchar(void);
The function has the same effect as fgetwc(stdin).
mbrlen
size_t mbrlen(const char *s, size_t n, mbstate_t *ps);
The function is equivalent to the call:
mbrtowc(0, s, n, ps != 0 ? ps : &internal)
where internal is an object of type mbstate_t internal to the mbrlen function. At program startup,
internal is initialized to the initial conversion state. No other library function alters the value stored in
internal.
The function returns:
(size_t)-2 if, after converting all n characters, the resulting conversion state indicates an
incomplete multibyte character
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