wchar_t and XS

[Alberto Simões]

Hello

I really need to make my code work with XS and wchar_t.
As far as I can tell there is no typemap for that in the core:
xs/NATools.c:733: warning: passing argument 3 of ‘Perl_sv_setpv’ from 
incompatible pointer type

I googled for that, and found a typemap, but I do not understand how 
typemaps work. My typemap looks like:

------ 8< ----------


TYPEMAP
wchar_t

INPUT
T_WCHAR
   {
   // Alloc memory for wide char string. This could be a bit more
   // then necessary.
   Newz(0, $var, SvLEN($arg), wchar_t);

   U8* src = (U8*) SvPV_nolen($arg);
   wchar_t* dst = (wchar_t*) $var;

   if (SvUTF8($arg)) {
      // UTF8 to wide char mapping
      STRLEN len;
      while (*src) {
          *dst++ = utf8_to_uvuni(src, &len);
          src += len;
      }
   } else {
       // char to wide char mapping
       while (*src) {
           *dst++ = (wchar_t) *src++;
       }
   }
   *dst = 0;
   SAVEFREEPV($var);
   }
------ 8< -------------

But then, this seems to be a Perl => wchar only. I would need the other 
way around too.

Any help?

Thanks
Ambs