n = ((n >>  1) & 0x55555555) | ((n <<  1) & 0xaaaaaaaa);
   n = ((n >>  2) & 0x33333333) | ((n <<  2) & 0xcccccccc);
   n = ((n >>  4) & 0x0f0f0f0f) | ((n <<  4) & 0xf0f0f0f0);
   n = ((n >>  8) & 0x00ff00ff) | ((n <<  8) & 0xff00ff00);
   n = ((n >> 16) & 0x0000ffff) | ((n << 16) & 0xffff0000);

		-- C code which reverses the bits in a word.