|
private multiplyByMonomial ( int degree, int coefficient ) : |
||
| degree | int | |
| coefficient | int | |
| return | ||
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);
var infoCoefficients = new int[dataBytes];
Array.Copy(toEncode, 0, infoCoefficients, 0, dataBytes);
var info = new GF256Poly(field, infoCoefficients);
info = info.multiplyByMonomial(ecBytes, 1);
GF256Poly remainder = info.divide(generator)[1];
int[] coefficients = remainder.Coefficients;
int numZeroCoefficients = ecBytes - coefficients.Length;
for (int i = 0; i < numZeroCoefficients; i++)
{
toEncode[dataBytes + i] = 0;
}
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.Zero)
{
throw new ArgumentException("Divide by 0");
}
GF256Poly quotient = field.Zero;
GF256Poly remainder = this;
int denominatorLeadingTerm = other.getCoefficient(other.Degree);
int inverseDenominatorLeadingTerm = field.inverse(denominatorLeadingTerm);
while (remainder.Degree >= other.Degree && !remainder.Zero)
{
int degreeDifference = remainder.Degree - other.Degree;
int scale = field.multiply(remainder.getCoefficient(remainder.Degree), inverseDenominatorLeadingTerm);
GF256Poly term = other.multiplyByMonomial(degreeDifference, scale);
GF256Poly iterationQuotient = field.buildMonomial(degreeDifference, scale);
quotient = quotient.addOrSubtract(iterationQuotient);
remainder = remainder.addOrSubtract(term);
}
return new[] {quotient, remainder};
}
