public class LineReader : IDisposable
{
	private Stream stream;
	private BinaryReader reader;

	public LineReader(Stream stream) { reader = new BinaryReader(stream); }

	public string ReadLine()
	{
		StringBuilder result = new StringBuilder();
		char lastChar = reader.ReadChar();
		// an EndOfStreamException here would propogate to the caller

		try
		{
			char newChar = reader.ReadChar();
			if (lastChar == 'r' && newChar == 'n')
				return result.ToString();

			result.Append(lastChar);
			lastChar = newChar;
		}
		catch (EndOfStreamException)
		{
			result.Append(lastChar);
			return result.ToString();
		}
	}

	public void Dispose()
	{
		reader.Close();
	}
}

public class LineReader : BinaryReader
{
    private Encoding _encoding;
    private Decoder _decoder;

    const int bufferSize = 1024;
    private char[] _LineBuffer = new char[bufferSize];

    public LineReader(Stream stream, int bufferSize, Encoding encoding)
        : base(stream, encoding)
    {
        this._encoding = encoding;
        this._decoder = encoding.GetDecoder();
    }

    public string ReadLine()
    {
        int pos = 0;

        char[] buf = new char[2];

        StringBuilder stringBuffer = null;
        bool lineEndFound = false;

        while(base.Read(buf, 0, 2) > 0)
        {
            if (buf[1] == 'r')
            {
                // grab buf[0]
                this._LineBuffer[pos++] = buf[0];
                // get the 'n'
                char ch = base.ReadChar();
                Debug.Assert(ch == 'n');

                lineEndFound = true;
            }
            else if (buf[0] == 'r')
            {
                lineEndFound = true;
            }
            else
            {
                this._LineBuffer[pos] = buf[0];
                this._LineBuffer[pos+1] = buf[1];
                pos += 2;

                if (pos >= bufferSize)
                {
                    stringBuffer = new StringBuilder(bufferSize + 80);
                    stringBuffer.Append(this._LineBuffer, 0, bufferSize);
                    pos = 0;
                }
            }

            if (lineEndFound)
            {
                if (stringBuffer == null)
                {
                    if (pos > 0)
                        return new string(this._LineBuffer, 0, pos);
                    else
                        return string.Empty;
                }
                else
                {
                    if (pos > 0)
                        stringBuffer.Append(this._LineBuffer, 0, pos);
                    return stringBuffer.ToString();
                }
            }
        }

        if (stringBuffer != null)
        {
            if (pos > 0)
                stringBuffer.Append(this._LineBuffer, 0, pos);
            return stringBuffer.ToString();
        }
        else
        {
            if (pos > 0)
                return new string(this._LineBuffer, 0, pos);
            else
                return null;
        }
    }

}