#include <wchar.h>

       size_t mbsnrtowcs(wchar_t *dest, const char **src,
                         size_t nms, size_t len, mbstate_t *ps);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

           Since glibc 2.10:
               _XOPEN_SOURCE >= 700 || _POSIX_C_SOURCE >= 200809L
           Before glibc 2.10:

       The  mbsnrtowcs()  function  is  like the mbsrtowcs(3) function, except
       that the number of bytes to be converted, starting at *src, is  limited
       to nms.

       If  dest  is  not a NULL pointer, the mbsnrtowcs() function converts at
       most nms bytes from 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  incre-
       menting dest by one and *src by the number of bytes consumed.  The con-
       version 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. The nms limit forces a stop, or 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  charac-
          ters 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 destination length limit exists.

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

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

       Passing NULL as ps is not multithread safe.

       iconv(3), mbsrtowcs(3)

       This  page  is  part of release 3.54 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

GNU                               2011-10-01                     MBSNRTOWCS(3)
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