updateBigInt method
Implementation
void updateBigInt(BigInt x) {
Uint8List xBytes = encodeBigInt(x);
bool padX = x.bitLength > 0 && x.bitLength % 8 == 0;
updateInt(xBytes.length + (padX ? 1 : 0));
if (padX) digest.updateByte(0);
digest.update(xBytes, 0, xBytes.length);
}