NAME

       mbsrtowcs - convert a multibyte string to a wide-character string (restartable)

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <wchar.h>

       size_t mbsrtowcs(wchar_t dest[restrict .dsize],
                        const char **restrict src,
                        size_t dsize, mbstate_t *restrict ps);

DESCRIPTION

       If dest is not NULL, convert the multibyte string *src to a wide-character string starting
       at dest.  At most dsize wide characters are written to  dest.   The  shift  state  *ps  is
       updated.   The  conversion  is  effectively  performed by repeatedly calling mbrtowc(dest,
       *src, n, ps) where n is some positive number, as long as  this  call  succeeds,  and  then
       incrementing  dest  by  one  and *src by the number of bytes consumed.  The conversion can
       stop for three reasons:

       •  An invalid multibyte sequence has  been  encountered.   In  this  case,  *src  is  left
          pointing  to  the invalid multibyte sequence, (size_t) -1 is returned, and errno is set
          to EILSEQ.

       •  dsize non-L'\0' wide characters have been stored at dest.  In this case, *src  is  left
          pointing  to  the  next  multibyte  sequence  to  be  converted, and the number of wide
          characters written to dest is returned.

       •  The multibyte string has been completely converted, including the terminating null wide
          character  ('\0'), which has the side effect of bringing back *ps to the initial state.
          In this case, *src is set to NULL, and the number of wide characters written  to  dest,
          excluding the terminating null wide character, is returned.

       If  dest  is NULL, dsize is ignored, and the conversion proceeds as above, except that the
       converted wide characters are not written out to memory, and that no length limit exists.

       In both of the above cases, if ps is NULL, a static anonymous  state  known  only  to  the
       mbsrtowcs() function is used instead.

       In  order to avoid the case 2 above, the programmer should make sure dsize is greater than
       or equal to mbsrtowcs(NULL,src,0,ps)+1.

       The programmer must ensure that there is room for at least dsize wide characters at dest.

       This function is a restartable version of mbstowcs(3).

RETURN VALUE

       The number of wide characters that make  up  the  converted  part  of  the  wide-character
       string,  not  including  the  terminating  null  wide  character.  If an invalid multibyte
       sequence was encountered, (size_t) -1 is returned, and errno set to EILSEQ.

ATTRIBUTES

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

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

STANDARDS

       C11, POSIX.1-2008.

HISTORY

       POSIX.1-2001, C99.

NOTES

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

       Passing NULL as ps is not multithread safe.

SEE ALSO

       iconv(3), mbrtowc(3), mbsinit(3), mbsnrtowcs(3), mbstowcs(3)