$ perl -le 'print unpack "h*", pack "D", sqrt 2;'
4846ed9f333f405bfff3000000000000

##</code><code>##

....
  n = bits == 64 ? 10 : 16;
#ifdef MPFR_HAVE_BENDIAN /* Big Endian architecture */
  for (i = 0; i < n; i++) {
#else
  for (i = n - 1; i >= 0; i--) {
#endif
  // code that does something with byte i