mbsrtowcs

       #include <wchar.h>

       size_t mbsrtowcs(wchar_t *dest, const char **src,
                         size_t len, mbstate_t *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  mbr-
       towc(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:

       1. 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.

       2. 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.

       3. 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, exclud-
          ing 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 mem-
       ory, 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 |
       +------------+---------------+------------------------------+

COLOPHON
       This  page  is  part of release 4.04 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       http://www.kernel.org/doc/man-pages/.

GNU                               2015-08-08                      MBSRTOWCS(3)
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