mbsrtowcs(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | NOTES | SEE ALSO | COLOPHON

mbsrtowcs(3)            Library Functions Manual            mbsrtowcs(3)

NAME         top

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

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <wchar.h>

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

DESCRIPTION         top

       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         top

       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         top

       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         top

       C11, POSIX.1-2008.

HISTORY         top

       POSIX.1-2001, C99.

NOTES         top

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

       Passing NULL as ps is not multithread safe.

SEE ALSO         top

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

COLOPHON         top

       This page is part of the man-pages (Linux kernel and C library
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       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
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Linux man-pages 6.9.1          2024-06-15                   mbsrtowcs(3)

Pages that refer to this page: mbrtowc(3)mbsinit(3)mbsnrtowcs(3)mbstate_t(3type)mbstowcs(3)unicode(7)utf-8(7)