Методы модификации машинного кода: «селекция» vs. «генная инженерия»

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO;

class NesFile
{
	public string FileName;

	public byte[] Header;
	public byte[] Trainer;
	public List<byte[]> PRG;
	public List<byte[]> CHR;
	public byte[] Attach;

	public NesFile(string filename)
	{
		FileName = filename;

		var ROM = File.ReadAllBytes(FileName);
		if (ROM[0] != 'N' || ROM[1] != 'E' || ROM[2] != 'S' || ROM[3] != 0x1A)
		{
			throw new Exception("Invalid iNES header");
		}

		Header = new byte[16];
		Array.Copy(ROM, 0, Header, 0, 16);
		var offset = 16;

		if ((Header[6] & 0x04) != 0)
		{
			Trainer = new byte[512];
			Array.Copy(ROM, offset, Trainer, 0, Trainer.Length);
			offset += Trainer.Length;
		}

		PRG = new List<byte[]>();
		for (var i = 0; i < Header[4]; i++)
		{
			PRG.Add(new byte[16384]);
			Array.Copy(ROM, offset, PRG[i], 0, PRG[i].Length);
			offset += PRG[i].Length;
		}

		CHR = new List<byte[]>();
		for (var i = 0; i < Header[5]; i++)
		{
			CHR.Add(new byte[8192]);
			Array.Copy(ROM, offset, CHR[i], 0, CHR[i].Length);
			offset += CHR[i].Length;
		}

		if (ROM.Length > offset)
		{
			Attach = new byte[ROM.Length - offset];
			Array.Copy(ROM, offset, Attach, 0, Attach.Length);
		}
	}

	public void PrepareHeader()
	{
		Header[4] = (byte)PRG.Count;
		Header[5] = (byte)CHR.Count;
	}

	public void Save(string filename = null)
	{
		PrepareHeader();

		if (filename != null)
		{
			FileName = filename;
		}

		using (var fs = File.OpenWrite(FileName))
		{
			fs.Write(Header, 0, Header.Length);

			if (Trainer != null)
			{
				fs.Write(Trainer, 0, Trainer.Length);
			}

			for (var i = 0; i < PRG.Count; i++)
			{
				fs.Write(PRG[i], 0, PRG[0].Length);
			}

			for (var i = 0; i < CHR.Count; i++)
			{
				fs.Write(CHR[i], 0, CHR[0].Length);
			}

			if (Attach != null)
			{
				fs.Write(Attach, 0, Attach.Length);
			}
		}
	}
}

class Mutagen
{
	static void Main(string[] args)
	{
		if (args.Length < 4) return;
		var nes = new NesFile(args[0]);
		var rnd = new Random(args[2].GetHashCode());
		var crb = Int32.Parse(args[3]);
		for (int i = 0; i < crb; i++)
		{
			var prg = rnd.Next(nes.PRG.Count);
			var pos = rnd.Next(nes.PRG[prg].Length);
			var shift = rnd.Next(-2, +2);
			int value = nes.PRG[prg][pos] + shift;
			nes.PRG[prg][pos] = (byte)(value & 0xFF);
		}
		nes.Save(args[1]);
	}
}