1 /*
2 * Copyright (C) 2006, 2007, 2009, 2010 Apple Inc. All rights reserved.
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Library General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
8 *
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Library General Public License for more details.
13 *
14 * You should have received a copy of the GNU Library General Public License
15 * along with this library; see the file COPYING.LIB. If not, write to
16 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
17 * Boston, MA 02110-1301, USA.
18 *
19 */
20
21 #ifndef TreeShared_h
22 #define TreeShared_h
23
24 #include <wtf/Assertions.h>
25 #include <wtf/Noncopyable.h>
26 #include <wtf/Threading.h>
27
28 namespace WebCore {
29
30 #ifndef NDEBUG
31 template<typename T> class TreeShared;
32 template<typename T> void adopted(TreeShared<T>*);
33 #endif
34
35 template<typename T> class TreeShared {
36 WTF_MAKE_NONCOPYABLE(TreeShared);
37 public:
TreeShared()38 TreeShared()
39 : m_refCount(1)
40 , m_parent(0)
41 #ifndef NDEBUG
42 , m_adoptionIsRequired(true)
43 #endif
44 {
45 ASSERT(isMainThread());
46 #ifndef NDEBUG
47 m_deletionHasBegun = false;
48 m_inRemovedLastRefFunction = false;
49 #endif
50 }
~TreeShared()51 virtual ~TreeShared()
52 {
53 ASSERT(isMainThread());
54 ASSERT(!m_refCount);
55 ASSERT(m_deletionHasBegun);
56 ASSERT(!m_adoptionIsRequired);
57 }
58
ref()59 void ref()
60 {
61 ASSERT(isMainThread());
62 ASSERT(!m_deletionHasBegun);
63 ASSERT(!m_inRemovedLastRefFunction);
64 ASSERT(!m_adoptionIsRequired);
65 ++m_refCount;
66 }
67
deref()68 void deref()
69 {
70 ASSERT(isMainThread());
71 ASSERT(m_refCount >= 0);
72 ASSERT(!m_deletionHasBegun);
73 ASSERT(!m_inRemovedLastRefFunction);
74 ASSERT(!m_adoptionIsRequired);
75 if (--m_refCount <= 0 && !m_parent) {
76 #ifndef NDEBUG
77 m_inRemovedLastRefFunction = true;
78 #endif
79 removedLastRef();
80 }
81 }
82
hasOneRef()83 bool hasOneRef() const
84 {
85 ASSERT(!m_deletionHasBegun);
86 ASSERT(!m_inRemovedLastRefFunction);
87 return m_refCount == 1;
88 }
89
refCount()90 int refCount() const
91 {
92 return m_refCount;
93 }
94
setParent(T * parent)95 void setParent(T* parent)
96 {
97 ASSERT(isMainThread());
98 m_parent = parent;
99 }
100
parent()101 T* parent() const
102 {
103 ASSERT(isMainThread());
104 return m_parent;
105 }
106
107 #ifndef NDEBUG
108 bool m_deletionHasBegun;
109 bool m_inRemovedLastRefFunction;
110 #endif
111
112 protected:
removedLastRef()113 virtual void removedLastRef()
114 {
115 #ifndef NDEBUG
116 m_deletionHasBegun = true;
117 #endif
118 delete this;
119 }
120
121 private:
122 #ifndef NDEBUG
123 friend void adopted<>(TreeShared<T>*);
124 #endif
125
126 int m_refCount;
127 T* m_parent;
128 #ifndef NDEBUG
129 bool m_adoptionIsRequired;
130 #endif
131 };
132
133 #ifndef NDEBUG
134
adopted(TreeShared<T> * object)135 template<typename T> inline void adopted(TreeShared<T>* object)
136 {
137 if (!object)
138 return;
139 ASSERT(!object->m_deletionHasBegun);
140 ASSERT(!object->m_inRemovedLastRefFunction);
141 object->m_adoptionIsRequired = false;
142 }
143
144 #endif
145
146 }
147
148 #endif // TreeShared.h
149