
	extern "C" double __cdecl modf(double x, double *iptr)
	{
		union {double f; unsigned long long i;} u = {x};
		unsigned long long mask;
		int e = (int)(u.i>>52 & 0x7ff) - 0x3ff;

		/* no fractional part */
		if (e >= 52) {
			*iptr = x;
			if (e == 0x400 && u.i<<12 != 0) /* nan */
				return x;
			u.i &= 1ULL<<63;
			return u.f;
		}

		/* no integral part*/
		if (e < 0) {
			u.i &= 1ULL<<63;
			*iptr = u.f;
			return x;
		}

		mask = -1ULL>>12>>e;
		if ((u.i & mask) == 0) {
			*iptr = x;
			u.i &= 1ULL<<63;
			return u.f;
		}
		u.i &= ~mask;
		*iptr = u.f;
		return x - u.f;
	}
