NAME

       mbrtowc - convert a multibyte sequence to a wide character

SYNOPSIS

       #include <wchar.h>

       size_t mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *ps);

DESCRIPTION

       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' (the null wide character), 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 are
       undefined.

       A different case is when s is not NULL but pwc is NULL.  In this case, the mbrtowc() function behaves  as
       above, except 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.  If the conversion state
       represented by *ps denotes an incomplete multibyte character conversion, the mbrtowc()  function  returns
       (size_t) -1,  sets  errno  to  EILSEQ,  and  leaves  *ps in an undefined state.  Otherwise, the mbrtowc()
       function puts *ps in the initial state and returns 0.

       In all of the above cases, if ps is NULL, a static anonymous state known only to the  mbrtowc()  function
       is  used  instead.   Otherwise,  *ps  must  be  a  valid  mbstate_t object.  An mbstate_t object a can be
       initialized to the initial state by zeroing it, for example using

           memset(&a, 0, sizeof(a));

RETURN VALUE

       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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────┬───────────────┬────────────────────────────┐
       │Interface │ Attribute     │ Value                      │
       ├──────────┼───────────────┼────────────────────────────┤
       │mbrtowc() │ Thread safety │ MT-Unsafe race:mbrtowc/!ps │
       └──────────┴───────────────┴────────────────────────────┘

CONFORMING TO

       POSIX.1-2001, POSIX.1-2008, C99.

NOTES

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

SEE ALSO

       mbsinit(3), mbsrtowcs(3)

COLOPHON

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