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Java > Open Source Codes > com > db4o > inside > slots > ReferencedSlot


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.inside.slots;
22
23 import com.db4o.*;
24 import com.db4o.foundation.Tree;
25
26 /**
27  * @exclude
28  */
29 public class ReferencedSlot extends TreeInt {
30
31     private Slot _slot;
32
33     private int _references;
34
35     public ReferencedSlot(int a_key) {
36         super(a_key);
37     }
38
39     public Object JavaDoc shallowClone() {
40         ReferencedSlot rs = new ReferencedSlot(_key);
41         rs._slot = _slot;
42         rs._references = _references;
43         return super.shallowCloneInternal(rs);
44     }
45
46     public void pointTo(Slot slot) {
47         _slot = slot;
48     }
49
50     public Tree free(YapFile file, Tree treeRoot, Slot slot) {
51         file.free(_slot._address, _slot._length);
52         if (removeReferenceIsLast()) {
53             return treeRoot.removeNode(this);
54         }
55         pointTo(slot);
56         return treeRoot;
57     }
58
59     public boolean addReferenceIsFirst() {
60         _references++;
61         return (_references == 1);
62     }
63
64     public boolean removeReferenceIsLast() {
65         _references--;
66         return _references < 1;
67     }
68
69     public Slot slot() {
70         return _slot;
71     }
72
73 }
74
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