private GF256Poly buildGenerator(int degree)
{
if (degree >= cachedGenerators.Count)
{
GF256Poly lastGenerator = (GF256Poly)cachedGenerators[cachedGenerators.Count - 1];
for (int d = cachedGenerators.Count; d <= degree; d++)
{
GF256Poly nextGenerator = lastGenerator.multiply(new GF256Poly(field, new int[] { 1, field.exp(d - 1) }));
cachedGenerators.Add(nextGenerator);
lastGenerator = nextGenerator;
}
}
return((GF256Poly)cachedGenerators[degree]);
}
private int[] MathForReferenceImplementation(int[] aCoeff, int[] bCoeff, string option)
{
GF256 field = GF256.QR_CODE_FIELD;
GF256Poly aPoly = new GF256Poly(field, aCoeff);
GF256Poly bPoly = new GF256Poly(field, bCoeff);
switch(option)
{
case "xor":
return aPoly.addOrSubtract(bPoly).Coefficients;
case "multy":
return aPoly.multiply(bPoly).Coefficients;
default:
throw new ArgumentException("No such test option");
}
}
private GF256Poly[] runEuclideanAlgorithm(GF256Poly a, GF256Poly b, int R)
{
// Assume a's degree is >= b's
if (a.Degree < b.Degree)
{
GF256Poly temp = a;
a = b;
b = temp;
}
GF256Poly rLast = a;
GF256Poly r = b;
GF256Poly sLast = field.One;
GF256Poly s = field.Zero;
GF256Poly tLast = field.Zero;
GF256Poly t = field.One;
// Run Euclidean algorithm until r's degree is less than R/2
while (r.Degree >= R / 2)
{
GF256Poly rLastLast = rLast;
GF256Poly sLastLast = sLast;
GF256Poly tLastLast = tLast;
rLast = r;
sLast = s;
tLast = t;
// Divide rLastLast by rLast, with quotient in q and remainder in r
if (rLast.Zero)
{
// Oops, Euclidean algorithm already terminated?
throw new ReedSolomonException("r_{i-1} was zero");
}
r = rLastLast;
GF256Poly q = field.Zero;
int denominatorLeadingTerm = rLast.getCoefficient(rLast.Degree);
int dltInverse = field.inverse(denominatorLeadingTerm);
while (r.Degree >= rLast.Degree && !r.Zero)
{
int degreeDiff = r.Degree - rLast.Degree;
int scale = field.multiply(r.getCoefficient(r.Degree), dltInverse);
q = q.addOrSubtract(field.buildMonomial(degreeDiff, scale));
r = r.addOrSubtract(rLast.multiplyByMonomial(degreeDiff, scale));
}
s = q.multiply(sLast).addOrSubtract(sLastLast);
t = q.multiply(tLast).addOrSubtract(tLastLast);
}
int sigmaTildeAtZero = t.getCoefficient(0);
if (sigmaTildeAtZero == 0)
{
throw new ReedSolomonException("sigmaTilde(0) was zero");
}
int inverse = field.inverse(sigmaTildeAtZero);
GF256Poly sigma = t.multiply(inverse);
GF256Poly omega = r.multiply(inverse);
return(new GF256Poly[] { sigma, omega });
}
