public void EnumerateVolume(
                out Dictionary <UInt64, FileNameAndParentFrn> files, string[] fileExtensions)
            {
                files = new Dictionary <ulong, FileNameAndParentFrn>();
                IntPtr medBuffer = IntPtr.Zero;

                try
                {
                    GetRootFrnEntry();
                    GetRootHandle();

                    CreateChangeJournal();

                    SetupMFT_Enum_DataBuffer(ref medBuffer);
                    EnumerateFiles(medBuffer, ref files, fileExtensions);
                }
                catch (Exception e)
                {
                    //	Log.Info(e.Message, e);
                    Exception innerException = e.InnerException;
                    while (innerException != null)
                    {
                        //		Log.Info(innerException.Message, innerException);
                        innerException = innerException.InnerException;
                    }
                    throw new ApplicationException("Error in EnumerateVolume()", e);
                }
                finally
                {
                    if (_changeJournalRootHandle.ToInt32() != PInvokeWin32.INVALID_HANDLE_VALUE)
                    {
                        PInvokeWin32.CloseHandle(_changeJournalRootHandle);
                    }
                    if (medBuffer != IntPtr.Zero)
                    {
                        Marshal.FreeHGlobal(medBuffer);
                    }
                }
            }
            private void GetRootFrnEntry()
            {
                string driveRoot = string.Concat("\\\\.\\", _drive);

                driveRoot = string.Concat(driveRoot, Path.DirectorySeparatorChar);
                IntPtr hRoot = PInvokeWin32.CreateFile(driveRoot,
                                                       0,
                                                       PInvokeWin32.FILE_SHARE_READ | PInvokeWin32.FILE_SHARE_WRITE,
                                                       IntPtr.Zero,
                                                       PInvokeWin32.OPEN_EXISTING,
                                                       PInvokeWin32.FILE_FLAG_BACKUP_SEMANTICS,
                                                       IntPtr.Zero);

                if (hRoot.ToInt32() != PInvokeWin32.INVALID_HANDLE_VALUE)
                {
                    PInvokeWin32.BY_HANDLE_FILE_INFORMATION fi = new PInvokeWin32.BY_HANDLE_FILE_INFORMATION();
                    bool bRtn = PInvokeWin32.GetFileInformationByHandle(hRoot, out fi);
                    if (bRtn)
                    {
                        UInt64 fileIndexHigh = (UInt64)fi.FileIndexHigh;
                        UInt64 indexRoot     = (fileIndexHigh << 32) | fi.FileIndexLow;

                        FileNameAndParentFrn f = new FileNameAndParentFrn(driveRoot, 0);
                        _directories.Add(indexRoot, f);
                    }
                    else
                    {
                        throw new IOException("GetFileInformationbyHandle() returned invalid handle",
                                              new Win32Exception(Marshal.GetLastWin32Error()));
                    }
                    PInvokeWin32.CloseHandle(hRoot);
                }
                else
                {
                    throw new IOException("Unable to get root frn entry", new Win32Exception(Marshal.GetLastWin32Error()));
                }
            }