Function fxBigInt_usub

xs/sources/xsBigInt.c:1493–1544

}

txBigInt *fxBigInt_usub(txMachine* the, txBigInt *rr, txBigInt *aa, txBigInt *bb)
{
	int i, n;
	txU4 a, b, r, t;
	txU4 *ap, *bp, *rp;
	txU4 c = 0;

	if (rr == NULL)
		rr = fxBigInt_alloc(the, MAX(aa->size, bb->size));
	rr->sign = (aa->size < bb->size ||
		    (aa->size == bb->size && fxBigInt_ucomp(aa, bb) < 0));
	if (rr->sign) {
		txBigInt *tt = aa;
		aa = bb;
		bb = tt;
	}
	ap = aa->data;
	bp = bb->data;
	rp = rr->data;
	n = MIN(aa->size, bb->size);
	for (i = 0; i < n; i++) {
		a = ap[i];
		b = bp[i];
		t = a - b;
		r = t - c;
		rp[i] = r;
		c = a < b || r > t;
	}
	if (aa->size >= bb->size) {
		n = aa->size;
		for (; i < n; i++) {
			t = ap[i];
			r = t - c;
			rp[i] = r;
			c = r > t;
		}
	}
	else {
		n = bb->size;
		for (; i < n; i++) {
			t = 0 - bp[i];
			r = t - c;
			rp[i] = r;
			c = r > t;
		}
	}
	/* remove leading 0s */
	while (--i > 0 && rp[i] == 0)
		;
	rr->size = i + 1;
	return(rr);
}

txBigInt *fxBigInt_mul(txMachine* the, txBigInt *rr, txBigInt *aa, txBigInt *bb)
{