static Bigint * multadd(Bigint *b, int m, int a) /* multiply by m and add a */
{
	int i, wds;
	ULong *x, y;
#ifdef Pack_32
	ULong xi, z;
#endif
	Bigint *b1;

	wds = b->wds;
	x = b->x;
	i = 0;
	do {
#ifdef Pack_32
		xi = *x;
		y = (xi & 0xffff) * m + a;
		z = (xi >> 16) * m + (y >> 16);
		a = (int)(z >> 16);
		*x++ = (z << 16) + (y & 0xffff);
#else
		y = *x * m + a;
		a = (int)(y >> 16);
		*x++ = y & 0xffff;
#endif
	}
	while(++i < wds);
	if (a) {
		if (wds >= b->maxwds) {
			b1 = Balloc(b->k+1);
			Bcopy(b1, b);
			Bfree(b);
			b = b1;
		}
		b->x[wds++] = a;
		b->wds = wds;
	}
	return b;
}