#include <wchar.h>

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

       If  dest  is  not a NULL pointer, the wcsrtombs() function converts the
       wide-character string *src to a multibyte string starting at dest.   At
       most  len  bytes  are written to dest.  The shift state *ps is updated.
       The conversion is effectively  performed  by  repeatedly  calling  wcr-
       tomb(dest,  *src,  ps),  as long as this call succeeds, and then incre-
       menting dest by the number of bytes written and *src by one.  The  con-
       version can stop for three reasons:

       1. A wide character has been encountered that can not be represented as
       a multibyte sequence (according to the current locale).  In  this  case
       *src  is  left  pointing  to the invalid wide character, (size_t) -1 is
       returned, and errno is set to EILSEQ.

       2. The length limit forces a stop.  In this case *src is left  pointing
       to  the  next  wide  character to be converted, and the number of bytes
       written to dest is returned.

       3. The wide-character string has been completely  converted,  including
       the  terminating null wide character (L'\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 bytes written to dest, excluding the terminat-
       ing null byte ('\0'), is returned.

       If dest is NULL, len is ignored, and the conversion proceeds as  above,
       except that the converted bytes are not written out to memory, and that
       no length limit exists.

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

       The programmer must ensure that there is room for at least len bytes at

       The wcsrtombs() function returns the number of bytes that make  up  the
       converted  part  of  multibyte  sequence, not including the terminating
       null byte.  If a wide character was encountered which could not be con-
       verted, (size_t) -1 is returned, and errno set to EILSEQ.


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

GNU                               2011-10-16                      WCSRTOMBS(3)
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