C# - Decode strings encoded with ISO-8859-1

Question

My purpose in writing the following program was to encode a set of strings using ISO-8859-1. I am now in need of getting it decoded. Consequently, I should receive "100, 200, 300, Test String One, Test String Two, Test String Three" back.

class Program
{
    private const int ENC_INT_SEED = 2136;
    private const int ENC_CHAR_SEED = 43;
    private const int ENC_INT_VAL = 3765;
    private const int ENC_CHAR_VAL = 139;
    private const int ENC_DUMMY_COUNT = 17;

    static void Main(string[] args)
    {
        string fileName = @"C:\Users\User\Documents\Test.DTA";

        FileStream fs = new FileStream(fileName, FileMode.Create, 
                    FileAccess.Write);
        BinaryWriter bw = new BinaryWriter(fs);

        int dummy = 0;
        for (int i = 0; i < ENC_DUMMY_COUNT; i++)
        {
            bw.Write(dummy);
        }

        int int_seed = ENC_INT_SEED;
        char char_seed = (char)ENC_CHAR_SEED;            

        for (int i = 0; i < 30; i++)
        {

            SaveInt(100, bw, ref int_seed);
            SaveInt(200, bw, ref int_seed);
            SaveInt(300, bw, ref int_seed);

            SaveString("Test String One", bw, ref int_seed, ref char_seed);
            SaveString("Test String Two", bw, ref int_seed, ref char_seed);
            SaveString("Test String Three", bw, ref int_seed, ref 
            char_seed);

        }

        bw.Close();
        fs.Close();

        Console.ReadLine();
    }
    private static void SaveString(string str, BinaryWriter bw, ref int 
                     int_seed, ref char char_seed)
    {
        int len = str.Length;

        Encoding encLatin_1 = Encoding.GetEncoding("ISO-8859-1");
        byte[] c = encLatin_1.GetBytes(str);

        int_seed = int_seed + ENC_INT_VAL + len;
        bw.Write(int_seed);

        for (int i = 0; i < len; i++)
        {
            int temp = char_seed + ENC_CHAR_VAL + c[i];
            char_seed = (char)temp;
            c[i] = (byte)char_seed;
        }
        bw.Write(c, 0, len);
    }
    private static void SaveInt(int i, BinaryWriter bw, ref int seed)
    {
        seed = seed + ENC_INT_VAL + i;
        bw.Write(seed);
    }
}

I need some help with decoding as I am no expert in this matter and just managed to do the encoding. Please help

Do you really want to do it yourself, or can you use [built-in support for encodings](https://stackoverflow.com/a/1922253/3883866)? — Jesse de Wit, Aug 10 '19 at 13:00
Well, decoding is easy, just use `encLatin_1.GetString(bytes)`. The problem will probably be to determine where the bytes start and where they end as you don't write the length of the string to the file. As far as I understand, at least. — Klaus Gütter, Aug 10 '19 at 13:02
The decoding steps should be exactly the same as encoding except the done in the reverse order. Be careful the sizes of objects must be deterministic. Encoding will not work if the end of each object cannot be found when decoding. lines in a document always terminate with a "\n". Removing the "\n" would make the document hard to read because words at end of one line will be merged with word on next line unless there is a space. — jdweng, Aug 10 '19 at 13:05

score 2 · Answer 1 · answered Aug 10 '19 at 13:04

I wouldn't bother writing your own method for this, since C# has built-in support for encodings:

byte[] inputBytes = // get your bytes

// There is built-in support for encodings in C#
string result = Encoding.GetEncoding("ISO-8859-1").GetString(inputBytes);

C# - Decode strings encoded with ISO-8859-1

1 Answers1