1/****************************************************************************
2**
3** Copyright (C) 2016 The Qt Company Ltd.
4** Contact: https://www.qt.io/licensing/
5**
6** This file is part of the QtCore module of the Qt Toolkit.
7**
8** $QT_BEGIN_LICENSE:LGPL$
9** Commercial License Usage
10** Licensees holding valid commercial Qt licenses may use this file in
11** accordance with the commercial license agreement provided with the
12** Software or, alternatively, in accordance with the terms contained in
13** a written agreement between you and The Qt Company. For licensing terms
14** and conditions see https://www.qt.io/terms-conditions. For further
15** information use the contact form at https://www.qt.io/contact-us.
16**
17** GNU Lesser General Public License Usage
18** Alternatively, this file may be used under the terms of the GNU Lesser
19** General Public License version 3 as published by the Free Software
20** Foundation and appearing in the file LICENSE.LGPL3 included in the
21** packaging of this file. Please review the following information to
22** ensure the GNU Lesser General Public License version 3 requirements
23** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
24**
25** GNU General Public License Usage
26** Alternatively, this file may be used under the terms of the GNU
27** General Public License version 2.0 or (at your option) the GNU General
28** Public license version 3 or any later version approved by the KDE Free
29** Qt Foundation. The licenses are as published by the Free Software
30** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
31** included in the packaging of this file. Please review the following
32** information to ensure the GNU General Public License requirements will
33** be met: https://www.gnu.org/licenses/gpl-2.0.html and
34** https://www.gnu.org/licenses/gpl-3.0.html.
35**
36** $QT_END_LICENSE$
37**
38****************************************************************************/
39
40#ifndef QREFCOUNT_H
41#define QREFCOUNT_H
42
43#include <QtCore/qatomic.h>
44
45QT_BEGIN_NAMESPACE
46
47
48namespace QtPrivate
49{
50
51class RefCount
52{
53public:
54 inline bool ref() noexcept {
55 int count = atomic.loadRelaxed();
56#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
57 if (count == 0) // !isSharable
58 return false;
59#endif
60 if (count != -1) // !isStatic
61 atomic.ref();
62 return true;
63 }
64
65 inline bool deref() noexcept {
66 int count = atomic.loadRelaxed();
67#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
68 if (count == 0) // !isSharable
69 return false;
70#endif
71 if (count == -1) // isStatic
72 return true;
73 return atomic.deref();
74 }
75
76#if !defined(QT_NO_UNSHARABLE_CONTAINERS)
77 bool setSharable(bool sharable) noexcept
78 {
79 Q_ASSERT(!isShared());
80 if (sharable)
81 return atomic.testAndSetRelaxed(0, 1);
82 else
83 return atomic.testAndSetRelaxed(1, 0);
84 }
85
86 bool isSharable() const noexcept
87 {
88 // Sharable === Shared ownership.
89 return atomic.loadRelaxed() != 0;
90 }
91#endif
92
93 bool isStatic() const noexcept
94 {
95 // Persistent object, never deleted
96 return atomic.loadRelaxed() == -1;
97 }
98
99 bool isShared() const noexcept
100 {
101 int count = atomic.loadRelaxed();
102 return (count != 1) && (count != 0);
103 }
104
105 void initializeOwned() noexcept { atomic.storeRelaxed(1); }
106 void initializeUnsharable() noexcept { atomic.storeRelaxed(0); }
107
108 QBasicAtomicInt atomic;
109};
110
111}
112
113#define Q_REFCOUNT_INITIALIZE_STATIC { Q_BASIC_ATOMIC_INITIALIZER(-1) }
114
115QT_END_NAMESPACE
116
117#endif
118