public SimpleArchiveFileSystem(string filename)
        {
            if (!File.Exists(filename))
            {
                CreateArchive(filename);
            }
            stream = new FileStream(filename, FileMode.Open);
            BinaryReader br = new BinaryReader(stream);

            header = new FileHeader();
            header.Read(br);

            br.BaseStream.Position = header.FileIndexOffset;
            fileIndex = new FileIndex();
            fileIndex.Read(br);

            br.BaseStream.Position = header.FolderIndexOffset;
            folderIndex            = new FolderIndex();
            folderIndex.Read(br);
        }