mbrlen - determine number of bytes in next multibyte character
size_t mbrlen(const char *restrict s, size_t n,
mbstate_t *restrict ps);
The mbrlen() function inspects at most n bytes of the multibyte
string starting at s and extracts the next complete multibyte
character. It updates the shift state *ps. If the multibyte character
is not the null wide character, it returns the number of bytes that were
consumed from s. If the multibyte character is the null wide character,
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, mbrlen() returns
(size_t) -2. This can happen even if n >=
MB_CUR_MAX, if the multibyte string contains redundant shift
If the multibyte string starting at s contains an invalid
multibyte sequence before the next complete character, mbrlen()
returns (size_t) -1 and sets errno to EILSEQ. In
this case, the effects on *ps are undefined.
If ps is NULL, a static anonymous state known only to the
mbrlen() function is used instead.
The mbrlen() function returns the number of bytes parsed from the
multibyte sequence starting at s, if a non-null wide character was
recognized. It returns 0, if a null 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.
For an explanation of the terms used in this section, see attributes(7).
POSIX.1-2001, POSIX.1-2008, C99.
The behavior of mbrlen() depends on the LC_CTYPE category of the
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