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39 
40 #ifndef QREFCOUNT_H
41 #define QREFCOUNT_H
42 
43 #include <QtCore/qatomic.h>
44 
45 QT_BEGIN_NAMESPACE
46 
47 
48 namespace QtPrivate
49 {
50 
51 class RefCount
52 {
53 public:
ref()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 
deref()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)
setSharable(bool sharable)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 
isSharable()86     bool isSharable() const noexcept
87     {
88         // Sharable === Shared ownership.
89         return atomic.loadRelaxed() != 0;
90     }
91 #endif
92 
isStatic()93     bool isStatic() const noexcept
94     {
95         // Persistent object, never deleted
96         return atomic.loadRelaxed() == -1;
97     }
98 
isShared()99     bool isShared() const noexcept
100     {
101         int count = atomic.loadRelaxed();
102         return (count != 1) && (count != 0);
103     }
104 
initializeOwned()105     void initializeOwned() noexcept { atomic.storeRelaxed(1); }
initializeUnsharable()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 
115 QT_END_NAMESPACE
116 
117 #endif
118