mac static method
Implementation
static List<BigInt> mac(BigInt a, BigInt b, BigInt c, BigInt carry) {
final BigInt prod = a + (b * c) + carry;
assert(prod <= BinaryOps.maxU128);
final BigInt low = prod.toU64;
final BigInt high = prod >> 64;
assert(high <= BinaryOps.maxU64);
return [low, high];
}