oracular (3) mbsrtowcs.3.gz

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)