Class GF256Poly


  • final class GF256Poly
    extends java.lang.Object
    Represents a polynomial whose coefficients are elements of GF(256). Instances of this class are immutable.

    Much credit is due to William Rucklidge since portions of this code are an indirect port of his C++ Reed-Solomon implementation.

    • Field Detail

      • field

        private final GF256 field
      • coefficients

        private final int[] coefficients
    • Constructor Detail

      • GF256Poly

        GF256Poly​(GF256 field,
                  int[] coefficients)
        Parameters:
        field - the GF256 instance representing the field to use to perform computations
        coefficients - coefficients as ints representing elements of GF(256), arranged from most significant (highest-power term) coefficient to least significant
        Throws:
        java.lang.IllegalArgumentException - if argument is null or empty, or if leading coefficient is 0 and this is not a constant polynomial (that is, it is not the monomial "0")
    • Method Detail

      • getCoefficients

        int[] getCoefficients()
      • getDegree

        int getDegree()
        Returns:
        degree of this polynomial
      • isZero

        boolean isZero()
        Returns:
        true iff this polynomial is the monomial "0"
      • getCoefficient

        int getCoefficient​(int degree)
        Returns:
        coefficient of x^degree term in this polynomial
      • evaluateAt

        int evaluateAt​(int a)
        Returns:
        evaluation of this polynomial at a given point
      • addOrSubtract

        GF256Poly addOrSubtract​(GF256Poly other)
        GF addition or subtraction (they are identical for a GF(2^n)
        Parameters:
        other - the other GF-poly
        Returns:
        new GF256Poly obtained by summing this GF and other
      • multiply

        GF256Poly multiply​(GF256Poly other)
        GF multiplication
        Parameters:
        other - the other GF-poly
        Returns:
        new GF-poly obtained by multiplying this with other
      • multiply

        GF256Poly multiply​(int scalar)
        GF scalar multiplication
        Parameters:
        scalar - scalar
        Returns:
        new GF-poly obtained by multiplying every element of this with the scalar.
      • multiplyByMonomial

        GF256Poly multiplyByMonomial​(int degree,
                                     int coefficient)
      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object
        Returns:
        String representation of the Galois Field polynomial.