TXFCHeader = packed record
  XFCSignature : string[3]; // XCF
  UserSignature : string[5];
  Version : Word;
  FileCount : Word;
  Sizes : array of Cardinal;
end;

procedure TXFCMain.SaveContainer(const AFileName: string);
var
  container : TFileStream;
  b : string;
  i : Word;
begin
  FFileName := AFileName;

  container := TFileStream.Create(AFileName, fmCreate);
  try
    // Write Header
    b := FHeader.XFCSignature + FHeader.UserSignature;
    container.Write(Pointer(b)^, 8);
    container.Write(FHeader.Version, SizeOf(FHeader.Version));
    container.Write(FHeader.FileCount, SizeOf(FHeader.FileCount));
    i := 0;
    while i < FHeader.FileCount do
    begin
      container.Write(FHeader.Sizes[i], SizeOf(FHeader.Sizes[i]));
      inc(i);
    end;
    // Header written
  finally
    container.Free;
  end;
end;

procedure TXFCMain.LoadContainer(const AFileName: string);
var
   container : TFileStream;
  b : string;
  i : Integer;
begin
   if FileExists(AFileName) then
  begin
     container := TFileStream.Create(AFileName, fmOpenRead or fmShareDenyWrite);
    try
       // Read Header
      b := '';
      container.Read(Pointer(b)^, 3);
      if (b <> 'XFC') and (not FDisableNoContainerException) then // Wrong Signature
         raise ENoContainerException.CreateFmt(NO_XFC_SIGNATURE, [AFileName, b]);

      container.Read(Pointer(b)^, 5);
      FHeader.UserSignature := b;
      container.Read(FHeader.Version, SizeOf(FHeader.Version));
      container.Read(FHeader.FileCount, SizeOf(FHeader.FileCount));
      i := 0;
      while i < FHeader.FileCount do
      begin
        container.Read(FHeader.Sizes[i], SizeOf(FHeader.Sizes[i]));
        inc(i);
      end;
      // Header read;
    finally
      container.Free;
    end;
  end else
  begin
    raise ENoContainerException.CreateFmt(DOES_NOT_EXISTS, [AFileName]);
  end;
end;