// Method added by Sonic-The-Hedgehog-LNK1123 (github.com/Sonic-The-Hedgehog-LNK1123)
internal GenericGFPoly calculateForneySyndromes(GenericGFPoly syndromes, int[] positions, int messageLength)
{
int[] positionsReversed = new int[positions.Length];
for (int i = 0; i < positions.Length; i++)
{
positionsReversed[i] = messageLength - 1 - positions[i];
}
int forneySyndromesLength = syndromes.Coefficients.Length;
int[] syndromeCoefficients = new int[syndromes.Coefficients.Length];
Array.Copy(syndromes.Coefficients, 0, syndromeCoefficients, 0, syndromes.Coefficients.Length);
GenericGFPoly forneySyndromes = new GenericGFPoly(field, syndromeCoefficients, false);
for (int i = 0; i < positions.Length; i++)
{
int x = field.exp(positionsReversed[i]);
for (int j = 0; j < forneySyndromes.Coefficients.Length - 1; j++)
{
forneySyndromes.Coefficients[forneySyndromesLength - j - 1] = GenericGF.addOrSubtract(field.multiply(forneySyndromes.getCoefficient(j), x), forneySyndromes.getCoefficient(j + 1));
}
}
return(forneySyndromes);
}
/// <summary>
/// evaluation of this polynomial at a given point
/// </summary>
/// <param name="a">A.</param>
/// <returns>evaluation of this polynomial at a given point</returns>
internal int evaluateAt(int a)
{
int result = 0;
if (a == 0)
{
// Just return the x^0 coefficient
return(getCoefficient(0));
}
int size = coefficients.Length;
if (a == 1)
{
// Just the sum of the coefficients
foreach (var coefficient in coefficients)
{
result = GenericGF.addOrSubtract(result, coefficient);
}
return(result);
}
result = coefficients[0];
for (int i = 1; i < size; i++)
{
result = GenericGF.addOrSubtract(field.multiply(a, result), coefficients[i]);
}
return(result);
}