public void Encode(int[] toEncode, int ecBytes) { if (ecBytes == 0) { throw new ArgumentException("No error correction bytes"); } int dataBytes = toEncode.Length - ecBytes; if (dataBytes <= 0) { throw new ArgumentException("No data bytes provided"); } GF256Poly generator = BuildGenerator(ecBytes); int[] infoCoefficients = new int[dataBytes]; System.Array.Copy(toEncode, 0, infoCoefficients, 0, dataBytes); GF256Poly info = new GF256Poly(field, infoCoefficients); info = info.MultiplyByMonomial(ecBytes, 1); GF256Poly remainder = info.Divide(generator)[1]; int[] coefficients = remainder.GetCoefficients(); int numZeroCoefficients = ecBytes - coefficients.Length; for (int i = 0; i < numZeroCoefficients; i++) { toEncode[dataBytes + i] = 0; } System.Array.Copy(coefficients, 0, toEncode, dataBytes + numZeroCoefficients, coefficients.Length); }
internal GF256Poly[] Divide(GF256Poly other) { if (!field.Equals(other.field)) { throw new ArgumentException("GF256Polys do not have same GF256 field"); } if (other.IsZero()) { throw new DivideByZeroException("Divide by 0"); } GF256Poly quotient = field.GetZero(); GF256Poly remainder = this; int denominatorLeadingTerm = other.GetCoefficient(other.GetDegree()); int inverseDenominatorLeadingTerm = field.Inverse(denominatorLeadingTerm); while (remainder.GetDegree() >= other.GetDegree() && !remainder.IsZero()) { int degreeDifference = remainder.GetDegree() - other.GetDegree(); int scale = field.Multiply(remainder.GetCoefficient(remainder.GetDegree()), inverseDenominatorLeadingTerm); GF256Poly term = other.MultiplyByMonomial(degreeDifference, scale); GF256Poly iterationQuotient = field.BuildMonomial(degreeDifference, scale); quotient = quotient.AddOrSubtract(iterationQuotient); remainder = remainder.AddOrSubtract(term); } return(new GF256Poly[] { quotient, remainder }); }