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 });
}