mbrtowc - convert a multibyte sequence to a wide character
size_t mbrtowc (wchar_t *pwc, const char *s, size_t n, mbstate_t *ps);
The main case for this function is when s is not NULL and pwc is not
NULL. In this case, the mbrtowc function inspects at most n bytes of
the multibyte string starting at s, extracts the next complete multibyte
character, converts it to a wide character and stores it at *pwc.
It updates the shift state *ps. If the converted wide character is not
L'\0', it returns the number of bytes that were consumed from s. If the
converted wide character is L'\0', it resets the shift state *ps to the
initial state and returns 0.
If the n bytes starting at s do not contain a complete multibyte character,
mbrtowc returns (size_t)(-2). This can happen even if n >=
MB_CUR_MAX, if the multibyte string contains redundant shift sequences.
If the multibyte string starting at s contains an invalid multibyte
sequence before the next complete character, mbrtowc returns
(size_t)(-1) and sets errno to EILSEQ. In this case, the effects on *ps
A different case is when s is not NULL but pwc is NULL. In this case
the mbrtowc function behaves as above, excepts that it does not store
the converted wide character in memory.
A third case is when s is NULL. In this case, pwc and n are ignored.
The mbrtowc function puts *ps in the initial state and returns 0.
In all of the above cases, if ps is a NULL pointer, a static anonymous
state only known to the mbrtowc function is used instead.
The mbrtowc function returns the number of bytes parsed from the multibyte
sequence starting at s, if a non-L'\0' wide character was recognized.
It returns 0, if a L'\0' wide character was recognized. It
returns (size_t)(-1) and sets errno to EILSEQ, if an invalid multibyte
sequence was encountered. It returns (size_t)(-2) if it couldn't parse
a complete multibyte character, meaning that n should be increased.
ISO/ANSI C, UNIX98
The behaviour of mbrtowc depends on the LC_CTYPE category of the current
GNU 1999-07-25 MBRTOWC(3)
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