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


       #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:
               _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 at most nms bytes.

       If dest is not NULL, 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 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. 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 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,
          excluding the terminating null wide character, is returned.

       According to POSIX.1, if the input  buffer  ends  with  an  incomplete  character,  it  is
       unspecified  whether conversion stops at the end of the previous character (if any), or at
       the end of the input buffer.  The glibc implementation adopts the former behavior.

       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 destination length
       limit exists.

       In both of the above cases, if ps is NULL, 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.


       The mbsnrtowcs() 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


       For an explanation of the terms used in this section, see attributes(7).

       │InterfaceAttributeValue                         │
       │mbsnrtowcs() │ Thread safety │ MT-Unsafe race:mbsnrtowcs/!ps │




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

       Passing NULL as ps is not multithread safe.


       iconv(3), mbrtowc(3) mbsinit(3), mbsrtowcs(3)


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