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);
}