XS(XS_widget)
{
    dXSARGS;

    FILE* in = PerlIO_findFILE(IoIFP(sv_2io(ST(0))));
    FILE* out = PerlIO_findFILE(IoIFP(sv_2io(ST(1))));

    /* copy in to out */
}

##</code><code>##

char*
read(fd,count)
   FILE* fd
   int count
  CODE:
   ...