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output/Libraries/BouncyCastle.Crypto/Org/BouncyCastle/Math/Field/FiniteFields.cs

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+using System;
+
+namespace Org.BouncyCastle.Math.Field;
+
+public abstract class FiniteFields
+{
+	internal static readonly IFiniteField GF_2 = new PrimeField(BigInteger.ValueOf(2L));
+
+	internal static readonly IFiniteField GF_3 = new PrimeField(BigInteger.ValueOf(3L));
+
+	public static IPolynomialExtensionField GetBinaryExtensionField(int[] exponents)
+	{
+		if (exponents[0] != 0)
+		{
+			throw new ArgumentException("Irreducible polynomials in GF(2) must have constant term", "exponents");
+		}
+		for (int i = 1; i < exponents.Length; i++)
+		{
+			if (exponents[i] <= exponents[i - 1])
+			{
+				throw new ArgumentException("Polynomial exponents must be montonically increasing", "exponents");
+			}
+		}
+		return new GenericPolynomialExtensionField(GF_2, new GF2Polynomial(exponents));
+	}
+
+	public static IFiniteField GetPrimeField(BigInteger characteristic)
+	{
+		int bitLength = characteristic.BitLength;
+		if (characteristic.SignValue <= 0 || bitLength < 2)
+		{
+			throw new ArgumentException("Must be >= 2", "characteristic");
+		}
+		if (bitLength < 3)
+		{
+			switch (characteristic.IntValue)
+			{
+			case 2:
+				return GF_2;
+			case 3:
+				return GF_3;
+			}
+		}
+		return new PrimeField(characteristic);
+	}
+}