using System;
using System.IO;

class FileReader
{
	public FileStream m_File;
	bool m_Open;

	public FileReader(string Filename)
	{
		m_File = File.OpenRead(Filename);	
		m_Open = true;
	}
	~FileReader()
	{
		if (m_Open) m_File.Close();
	}

	public byte[] Read()
	{
		return Read((int)m_File.Length);
	}

	public byte[] Read(int Length)
	{
		if (Length < 0) throw new Exception("Invalid length " + Length);

		byte[] tmp_Buffer, Buffer = new byte[Length];
		int Index = 0;
		int ByteCount, BytesRemaining = Length;

		do
		{
			tmp_Buffer = new byte[BytesRemaining];
			ByteCount = m_File.Read(tmp_Buffer, 0, BytesRemaining);
				
			for (int i = 0; i < ByteCount; i++) Buffer[Index + i] = tmp_Buffer[i];
			Index += ByteCount; BytesRemaining -= ByteCount;
		}
		while (ByteCount > 0 && BytesRemaining > 0);

		return Buffer;
	}

	public void Close()
	{
		if (!m_Open) throw new Exception("Trying to close an unopened file");
		m_File.Close();
		m_Open = false;
	}
}

class FileWriter
{
	public FileStream m_File;
	bool m_Open;

	public FileWriter(string Filename)
	{
		m_File = File.OpenWrite(Filename);
		m_Open = true;
	}
	~FileWriter()
	{
		if (m_Open) m_File.Close();
	}

	public void Truncate()
	{
		if (!m_Open) throw new Exception("Trying to truncate an unopened file");
		m_File.SetLength(0);
	}

	public void Write(byte[] Buffer)
	{
		Write(Buffer, Buffer.Length);
	}

	public void Write(byte[] Buffer, int Length)
	{
		if (Length < 0) throw new Exception("Invalid length " + Length);
		m_File.Write(Buffer, 0, Length);
	}

	public void Close()
	{
		if (!m_Open) throw new Exception("Trying to close an unopened file");
		m_File.Close();
		m_Open = false;
	}
}