private long FileHeaderUsage() { int headerLength = _db.GetFileHeader().Length(); int usage = _blockConverter.BlockAlignedBytes(headerLength); FileHeaderVariablePart2 variablePart = (FileHeaderVariablePart2)FieldValue(_db.GetFileHeader (), "_variablePart"); usage += _blockConverter.BlockAlignedBytes(variablePart.MarshalledLength()); _slots.Add(new Db4objects.Db4o.Internal.Slots.Slot(0, headerLength)); _slots.Add(new Db4objects.Db4o.Internal.Slots.Slot(variablePart.Address(), variablePart .MarshalledLength())); return(usage); }