NAME

       mbsrtowcs - convert a multibyte string to a wide-character string

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <wchar.h>

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

DESCRIPTION

       If  dest  is  not  NULL,  the mbsrtowcs() function converts the multibyte string *src to a
       wide-character string starting at dest.  At most len 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.

       •  len 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,  len 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.

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

RETURN VALUE

       The  mbsrtowcs() function returns 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

       POSIX.1-2001, POSIX.1-2008, 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)