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MBRTOWC(3) Linux Programmer's Manual MBRTOWC(3)

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 multi-
     byte 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  char-
     acter,  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 multi-
     byte 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  ini-
     tialized 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  multi-
     byte  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  cur-
     rent locale.