ReedSolomonEC.cs

using System;
 
namespace Waher.Content.QR.Encoding
{
    public class ReedSolomonEC
    {
        private readonly GF256Px generatorPolynomial;
        private readonly int nrCorrectionCodeWords;
 
        public ReedSolomonEC(int NrCorrectionCodeWords)
        {
            if (NrCorrectionCodeWords <= 0)
                throw new ArgumentException("Number of correction code words must be positive.", nameof(NrCorrectionCodeWords));
 
            GF256Px P = new GF256Px(new byte[] { 1, 1 });   // X-1 = X-α^0
            int i = 0;
 
            while (++i < NrCorrectionCodeWords)
                P = P.Multiply(new GF256Px(new byte[] { 1, GF256.PowerOf2Table[i] })); // X-α^i
 
            this.generatorPolynomial = P;
            this.nrCorrectionCodeWords = NrCorrectionCodeWords;
        }
 
        public GF256Px GeneratorPolynomial => this.generatorPolynomial;
 
        public byte[] GenerateCorrectionCode(byte[] Message)
        {
            byte[] C = new byte[Message.Length + this.nrCorrectionCodeWords];
            Message.CopyTo(C, 0);
 
            GF256Px M = new GF256Px(C);
            GF256Px Resiue = M.Residue(this.generatorPolynomial);
 
            return Resiue.Coefficients;
        }
    }
}