mbrlen - determine number of bytes in next multibyte character

       For an explanation of the terms used in this section, see attributes(7).
       ┌───────────────────────────────────────────────────────────┬───────────────┬───────────────────────────┐
       │ Interface                                                 │ Attribute     │ Value                     │
       ├───────────────────────────────────────────────────────────┼───────────────┼───────────────────────────┤
       │ mbrlen()                                                  │ Thread safety │ MT-Unsafe race:mbrlen/!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 sequences.

       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.

       POSIX.1-2001, C99.

       Standard C library (libc, -lc)

       mbrlen - determine number of bytes in next multibyte character

       The behavior of mbrlen() depends on the LC_CTYPE category of the current locale.

       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.

mbrtowc(3)

Linux man-pages 6.9.1                              2024-05-02                                          mbrlen(3)

       C11, POSIX.1-2008.

#include<wchar.h>size_tmbrlen(constchars[restrict.n],size_tn,mbstate_t*restrictps);