/// <summary>
/// Enlarges the size of this PolynomialGF2n to <c>k</c> + 1
/// </summary>
///
/// <param name="K">The new maximum degree</param>
public void Enlarge(int K)
{
if (K <= _size)
{
return;
}
int i;
GF2nElement[] res = new GF2nElement[K];
Array.Copy(_coeff, 0, res, 0, _size);
GF2nField f = _coeff[0].GetField();
if (_coeff[0] is GF2nPolynomialElement)
{
for (i = _size; i < K; i++)
{
res[i] = GF2nPolynomialElement.Zero((GF2nPolynomialField)f);
}
}
else if (_coeff[0] is GF2nONBElement)
{
for (i = _size; i < K; i++)
{
res[i] = GF2nONBElement.Zero((GF2nONBField)f);
}
}
_size = K;
_coeff = res;
}
/// <summary>
/// Sets the coefficient at <c>Index</c> to <c>Element</c>
/// </summary>
///
/// <param name="Index">The index</param>
/// <param name="E">The GF2nElement to store as coefficient <c>Index</c></param>
public void Set(int Index, GF2nElement E)
{
if (!(E is GF2nPolynomialElement) && !(E is GF2nONBElement))
{
throw new ArgumentException("GF2nPolynomial: PolynomialGF2n.Set f must be an instance of either GF2nPolynomialElement or GF2nONBElement!");
}
_coeff[Index] = (GF2nElement)E.Clone();
}
/// <summary>
/// Creates a new PolynomialGF2n of size <c>Degree</c> and elem as coefficients
/// </summary>
///
/// <param name="Degree">The maximum degree + 1</param>
/// <param name="Element">A GF2nElement</param>
public GF2nPolynomial(int Degree, GF2nElement Element)
{
_size = Degree;
_coeff = new GF2nElement[_size];
for (int i = 0; i < _size; i++)
{
_coeff[i] = (GF2nElement)Element.Clone();
}
}
/// <summary>
/// Multiplies the scalar <c>E</c> to each coefficient of this PolynomialGF2n and returns the result in a new PolynomialGF2n
/// </summary>
///
/// <param name="E">The scalar to multiply</param>
///
/// <returns>Returns <c>this</c> x <c>E</c></returns>
public GF2nPolynomial ScalarMultiply(GF2nElement E)
{
GF2nPolynomial result = new GF2nPolynomial(Size);
for (int i = 0; i < Size; i++)
{
result._coeff[i] = (GF2nElement)_coeff[i].Multiply(E);
}
return(result);
}
/// <summary>
/// Shrink the size of this PolynomialGF2n
/// </summary>
public void Shrink()
{
int i = _size - 1;
while (_coeff[i].IsZero() && (i > 0))
{
i--;
}
i++;
if (i < _size)
{
GF2nElement[] res = new GF2nElement[i];
Array.Copy(_coeff, 0, res, 0, i);
_coeff = res;
_size = i;
}
}
/// <summary>
/// Multiplicatively invert of this element (overwrite <c>this</c>)
/// </summary>
public void InvertThis()
{
if (IsZero())
{
throw new ArithmeticException();
}
int r = 31; // mDegree kann nur 31 Bits lang sein!!!
// Bitlaenge von mDegree:
for (bool found = false; !found && r >= 0; r--)
{
if (((mDegree - 1) & _mBitmask[r]) != 0)
{
found = true;
}
}
r++;
GF2nElement m = Zero((GF2nONBField)mField);
GF2nElement n = new GF2nONBElement(this);
int k = 1;
for (int i = r - 1; i >= 0; i--)
{
m = (GF2nElement)n.Clone();
for (int j = 1; j <= k; j++)
{
m.SquareThis();
}
n.MultiplyThisBy(m);
k <<= 1;
if (((mDegree - 1) & _mBitmask[i]) != 0)
{
n.SquareThis();
n.MultiplyThisBy(this);
k++;
}
}
n.SquareThis();
}
/// <summary>
/// Divides <c>this</c> by <c>b</c> and stores the result in a new PolynomialGF2n[2], quotient in result[0] and remainder in result[1]
/// </summary>
///
/// <param name="B">The divisor</param>
///
/// <returns>Retuens the quotient and remainder of <c>this</c> / <c>b</c></returns>
public GF2nPolynomial[] Divide(GF2nPolynomial B)
{
GF2nPolynomial[] result = new GF2nPolynomial[2];
GF2nPolynomial a = new GF2nPolynomial(this);
a.Shrink();
GF2nPolynomial shift;
GF2nElement factor;
int bDegree = B.Degree;
GF2nElement inv = (GF2nElement)B._coeff[bDegree].Invert();
if (a.Degree < bDegree)
{
result[0] = new GF2nPolynomial(this);
result[0].AssignZeroToElements();
result[0].Shrink();
result[1] = new GF2nPolynomial(this);
result[1].Shrink();
return(result);
}
result[0] = new GF2nPolynomial(this);
result[0].AssignZeroToElements();
int i = a.Degree - bDegree;
while (i >= 0)
{
factor = (GF2nElement)a._coeff[a.Degree].Multiply(inv);
shift = B.ScalarMultiply(factor);
shift.ShiftThisLeft(i);
a = a.Add(shift);
a.Shrink();
result[0]._coeff[i] = (GF2nElement)factor.Clone();
i = a.Degree - bDegree;
}
result[1] = a;
result[0].Shrink();
return(result);
}
/// <summary>
/// Converts the given element in representation according to this field to a new element in
/// representation according to B1 using the change-of-basis matrix calculated by computeCOBMatrix.
/// </summary>
///
/// <param name="Elem">The GF2nElement to convert</param>
/// <param name="Basis">The basis to convert <c>Elem</c> to</param>
///
/// <returns>Returns <c>Elem</c> converted to a new element representation according to <c>basis</c></returns>
public GF2nElement Convert(GF2nElement Elem, GF2nField Basis)
{
if (Basis == this)
{
return((GF2nElement)Elem.Clone());
}
if (FieldPoly.Equals(Basis.FieldPoly))
{
return((GF2nElement)Elem.Clone());
}
if (DegreeN != Basis.DegreeN)
{
throw new Exception("GF2nField.Convert: B1 has a different degree and thus cannot be coverted to!");
}
int i;
GF2Polynomial[] COBMatrix;
i = Fields.IndexOf(Basis);
if (i == -1)
{
ComputeCOBMatrix(Basis);
i = Fields.IndexOf(Basis);
}
COBMatrix = (GF2Polynomial[])Matrices[i];
GF2nElement elemCopy = (GF2nElement)Elem.Clone();
if (elemCopy is GF2nONBElement)
{
((GF2nONBElement)elemCopy).ReverseOrder();
}
GF2Polynomial bs = new GF2Polynomial(DegreeN, elemCopy.ToFlexiBigInt());
bs.ExpandN(DegreeN);
GF2Polynomial result = new GF2Polynomial(DegreeN);
for (i = 0; i < DegreeN; i++)
{
if (bs.VectorMult(COBMatrix[i]))
{
result.SetBit(DegreeN - 1 - i);
}
}
if (Basis is GF2nPolynomialField)
{
return(new GF2nPolynomialElement((GF2nPolynomialField)Basis, result));
}
else if (Basis is GF2nONBField)
{
GF2nONBElement res = new GF2nONBElement((GF2nONBField)Basis, result.ToFlexiBigInt());
res.ReverseOrder();
return(res);
}
else
{
throw new Exception("GF2nField.convert: B1 must be an instance of GF2nPolynomialField or GF2nONBField!");
}
}
