DCing algorithm

[Dia6lo]

My version of the code:

CSHARP-Code: public class ReadFile {    public static string main(String FileName)    {        string text = "";        FileStream finp = new FileStream(FileName,FileMode.Open);        int counta = 0;        int b;        byte d;        finp.Seek(123,SeekOrigin.Begin);        while((b = finp.ReadByte()) != -1)        {            d = DecryptByte(counta, (byte)b);            counta++;            if (counta > 36)            {                counta = 0;            }            text += (char)d;        }        finp.Close();        return text;    }      public static byte DecryptByte(int counta, byte b)    {        String plainEncryptionKey = "odBearBecauseHeIsVeryGoodSiuHungIsAGo";        b -= (byte)plainEncryptionKey[counta];        return b;    } }

Okay, guys, it seems that you just can't give up on LF ;). And I also noticed that you need some helping hand with C#, so I wrote a much faster program:

CSHARP-Code: static class DatDecryptor    {        static IEnumerator<char> EncryptionKey = "odBearBecauseHeIsVeryGoodSiuHungIsAGo".GetEnumerator();          static void Main(string[] args)        {            var fileName = Console.ReadLine();            if (fileName == null || !File.Exists(fileName)) return;            // First 123 bytes of lf2 .dat files are useless            var bytes = File.ReadAllBytes(fileName).Skip(123);            var text = DecryptByteSequence(bytes);            // Put here your code that outputs decrypted text to wherever you want        }          static string DecryptByteSequence(IEnumerable<byte> byteStream)        {            EncryptionKey.Reset();            return new string(byteStream.Select(DecryptByte).ToArray());        }          static Func<byte, char> DecryptByte = b => (char)(b - NextEncryptionByte());          static byte NextEncryptionByte()        { if (!EncryptionKey.MoveNext()) { EncryptionKey.Reset(); EncryptionKey.MoveNext(); } return (byte)EncryptionKey.Current; }    }

Here is comparison to Someone else's code(on davis.dat):

Code:

My program: 9 ms
Someone else's program: 6297 ms

As you can see, perfomance skyrockets by almost x700 times(mainly because you open file every time you read a single byte, while I do it only once). Yes, this code contains no dirty hacks and it doesn't use any third-party libraries, just System:

CSHARP-Code: using System; using System.Collections.Generic; using System.IO; using System.Linq;

P.S: One can say that I should parse filename from args, but I don't think it's a big deal to do it so I omitted it.