/// <summary>
 /// Creates this file with the following data.
 /// </summary>
 /// <param name="diskIo"></param>
 /// <param name="header"></param>
 /// <param name="file"></param>
 /// <param name="isReadOnly"></param>
 public SubFileDiskIoSessionPool(DiskIo diskIo, FileHeaderBlock header, SubFileHeader file, bool isReadOnly)
 {
     LastReadonlyBlock = diskIo.LastCommittedHeader.LastAllocatedBlock;
     File        = file;
     Header      = header;
     IsReadOnly  = isReadOnly;
     SourceData  = diskIo.CreateDiskIoSession(header, file);
     SourceIndex = diskIo.CreateDiskIoSession(header, file);
     if (!isReadOnly)
     {
         DestinationData  = diskIo.CreateDiskIoSession(header, file);
         DestinationIndex = diskIo.CreateDiskIoSession(header, file);
     }
 }