public static BigInteger ModPow(BigInteger value, BigInteger exponent, BigInteger modulus)
{
if (exponent.Sign < 0)
{
throw new ArgumentOutOfRangeException(nameof(exponent));
}
value.AssertValid();
exponent.AssertValid();
modulus.AssertValid();
bool trivialValue = value._bits == null;
bool trivialExponent = exponent._bits == null;
bool trivialModulus = modulus._bits == null;
if (trivialModulus)
{
uint bits = trivialValue && trivialExponent?BigIntegerCalculator.Pow(NumericsHelpers.Abs(value._sign), NumericsHelpers.Abs(exponent._sign), NumericsHelpers.Abs(modulus._sign)) :
trivialValue?BigIntegerCalculator.Pow(NumericsHelpers.Abs(value._sign), exponent._bits, NumericsHelpers.Abs(modulus._sign)) :
trivialExponent?BigIntegerCalculator.Pow(value._bits, NumericsHelpers.Abs(exponent._sign), NumericsHelpers.Abs(modulus._sign)) :
BigIntegerCalculator.Pow(value._bits, exponent._bits, NumericsHelpers.Abs(modulus._sign));
return(value._sign < 0 && !exponent.IsEven ? -1 * bits : bits);
}
else
{
uint[] bits = trivialValue && trivialExponent?BigIntegerCalculator.Pow(NumericsHelpers.Abs(value._sign), NumericsHelpers.Abs(exponent._sign), modulus._bits) :
trivialValue?BigIntegerCalculator.Pow(NumericsHelpers.Abs(value._sign), exponent._bits, modulus._bits) :
trivialExponent?BigIntegerCalculator.Pow(value._bits, NumericsHelpers.Abs(exponent._sign), modulus._bits) :
BigIntegerCalculator.Pow(value._bits, exponent._bits, modulus._bits);
return(new BigInteger(bits, value._sign < 0 && !exponent.IsEven));
}
}
