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28 | |
29 | |
30 | #ifndef QTHREADONCE_H |
31 | #define QTHREADONCE_H |
32 | |
33 | #include <QtCore/qglobal.h> |
34 | #include <QtCore/qatomic.h> |
35 | |
36 | |
37 | class QOnceControl |
38 | { |
39 | public: |
40 | QOnceControl(QBasicAtomicInt *); |
41 | ~QOnceControl(); |
42 | |
43 | bool mustRunCode(); |
44 | void done(); |
45 | |
46 | private: |
47 | QBasicAtomicInt *gv; |
48 | union { |
49 | qint32 ; |
50 | void *d; |
51 | }; |
52 | }; |
53 | |
54 | #define Q_ONCE_GV_NAME2(prefix, line) prefix ## line |
55 | #define Q_ONCE_GV_NAME(prefix, line) Q_ONCE_GV_NAME2(prefix, line) |
56 | #define Q_ONCE_GV Q_ONCE_GV_NAME(_q_once_, __LINE__) |
57 | |
58 | #define Q_ONCE \ |
59 | static QBasicAtomicInt Q_ONCE_GV = Q_BASIC_ATOMIC_INITIALIZER(0); \ |
60 | if (0){} else \ |
61 | for (QOnceControl _control_(&Q_ONCE_GV); _control_.mustRunCode(); _control_.done()) |
62 | |
63 | template<typename T> |
64 | class QSingleton |
65 | { |
66 | // this is a POD-like class |
67 | struct Destructor |
68 | { |
69 | T *&pointer; |
70 | Destructor(T *&ptr) : pointer(ptr) {} |
71 | ~Destructor() { delete pointer; } |
72 | }; |
73 | |
74 | public: |
75 | T *_q_value; |
76 | QBasicAtomicInt _q_guard; |
77 | |
78 | inline T *value() |
79 | { |
80 | for (QOnceControl control(&_q_guard); control.mustRunCode(); control.done()) { |
81 | _q_value = new T(); |
82 | static Destructor cleanup(_q_value); |
83 | } |
84 | return _q_value; |
85 | } |
86 | |
87 | inline T& operator*() { return *value(); } |
88 | inline T* operator->() { return value(); } |
89 | inline operator T*() { return value(); } |
90 | }; |
91 | |
92 | #endif |
93 | |