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39 | |
40 | #ifndef QTAGGEDPOINTER_H |
41 | #define QTAGGEDPOINTER_H |
42 | |
43 | #include <QtCore/qglobal.h> |
44 | #include <QtCore/qalgorithms.h> |
45 | #include <QtCore/qmath.h> |
46 | #include <QtCore/qtypeinfo.h> |
47 | |
48 | QT_BEGIN_NAMESPACE |
49 | |
50 | namespace QtPrivate { |
51 | constexpr quint8 nextByteSize(quint8 bits) { return (bits + 7) / 8; } |
52 | |
53 | template <typename T> |
54 | struct TagInfo |
55 | { |
56 | static constexpr size_t alignment = alignof(T); |
57 | static_assert((alignment & (alignment - 1)) == 0, |
58 | "Alignment of template parameter must be power of two" ); |
59 | |
60 | static constexpr quint8 tagBits = QtPrivate::qConstexprCountTrailingZeroBits(alignment); |
61 | static_assert(tagBits > 0, |
62 | "Alignment of template parameter does not allow any tags" ); |
63 | |
64 | static constexpr size_t tagSize = QtPrivate::qConstexprNextPowerOfTwo(nextByteSize(tagBits)); |
65 | static_assert(tagSize < sizeof(quintptr), |
66 | "Alignment of template parameter allows tags masking away pointer" ); |
67 | |
68 | using TagType = typename QIntegerForSize<tagSize>::Unsigned; |
69 | }; |
70 | } |
71 | |
72 | template <typename T, typename Tag = typename QtPrivate::TagInfo<T>::TagType> |
73 | class QTaggedPointer |
74 | { |
75 | public: |
76 | using Type = T; |
77 | using TagType = Tag; |
78 | |
79 | static constexpr quintptr tagMask() { return QtPrivate::TagInfo<T>::alignment - 1; } |
80 | static constexpr quintptr pointerMask() { return ~tagMask(); } |
81 | |
82 | constexpr QTaggedPointer() noexcept : d(0) {} |
83 | constexpr QTaggedPointer(std::nullptr_t) noexcept : QTaggedPointer() {} |
84 | |
85 | explicit QTaggedPointer(T *pointer, Tag tag = Tag()) noexcept |
86 | : d(quintptr(pointer)) |
87 | { |
88 | static_assert(sizeof(Type*) == sizeof(QTaggedPointer)); |
89 | |
90 | Q_ASSERT_X((quintptr(pointer) & tagMask()) == 0, |
91 | "QTaggedPointer<T, Tag>" , "Pointer is not aligned" ); |
92 | |
93 | setTag(tag); |
94 | } |
95 | |
96 | Type &operator*() const noexcept |
97 | { |
98 | Q_ASSERT(data()); |
99 | return *data(); |
100 | } |
101 | |
102 | Type *operator->() const noexcept |
103 | { |
104 | return data(); |
105 | } |
106 | |
107 | explicit operator bool() const noexcept |
108 | { |
109 | return !isNull(); |
110 | } |
111 | |
112 | QTaggedPointer &operator=(T *other) noexcept |
113 | { |
114 | d = reinterpret_cast<quintptr>(other) | (d & tagMask()); |
115 | return *this; |
116 | } |
117 | |
118 | static constexpr Tag maximumTag() noexcept |
119 | { |
120 | return TagType(typename QtPrivate::TagInfo<T>::TagType(tagMask())); |
121 | } |
122 | |
123 | void setTag(Tag tag) |
124 | { |
125 | Q_ASSERT_X((static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & pointerMask()) == 0, |
126 | "QTaggedPointer<T, Tag>::setTag" , "Tag is larger than allowed by number of available tag bits" ); |
127 | |
128 | d = (d & pointerMask()) | (static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & tagMask()); |
129 | } |
130 | |
131 | Tag tag() const noexcept |
132 | { |
133 | return TagType(typename QtPrivate::TagInfo<T>::TagType(d & tagMask())); |
134 | } |
135 | |
136 | T* data() const noexcept |
137 | { |
138 | return reinterpret_cast<T*>(d & pointerMask()); |
139 | } |
140 | |
141 | bool isNull() const noexcept |
142 | { |
143 | return !data(); |
144 | } |
145 | |
146 | void swap(QTaggedPointer &other) noexcept |
147 | { |
148 | qSwap(d, other.d); |
149 | } |
150 | |
151 | friend inline bool operator==(QTaggedPointer lhs, QTaggedPointer rhs) noexcept |
152 | { |
153 | return lhs.data() == rhs.data(); |
154 | } |
155 | |
156 | friend inline bool operator!=(QTaggedPointer lhs, QTaggedPointer rhs) noexcept |
157 | { |
158 | return lhs.data() != rhs.data(); |
159 | } |
160 | |
161 | friend inline bool operator==(QTaggedPointer lhs, std::nullptr_t) noexcept |
162 | { |
163 | return lhs.isNull(); |
164 | } |
165 | |
166 | friend inline bool operator==(std::nullptr_t, QTaggedPointer rhs) noexcept |
167 | { |
168 | return rhs.isNull(); |
169 | } |
170 | |
171 | friend inline bool operator!=(QTaggedPointer lhs, std::nullptr_t) noexcept |
172 | { |
173 | return !lhs.isNull(); |
174 | } |
175 | |
176 | friend inline bool operator!=(std::nullptr_t, QTaggedPointer rhs) noexcept |
177 | { |
178 | return !rhs.isNull(); |
179 | } |
180 | |
181 | friend inline bool operator!(QTaggedPointer ptr) noexcept |
182 | { |
183 | return !ptr.data(); |
184 | } |
185 | |
186 | friend inline void swap(QTaggedPointer &p1, QTaggedPointer &p2) noexcept |
187 | { |
188 | p1.swap(p2); |
189 | } |
190 | |
191 | protected: |
192 | quintptr d; |
193 | }; |
194 | |
195 | template <typename T, typename Tag> |
196 | constexpr inline std::size_t qHash(QTaggedPointer<T, Tag> p, std::size_t seed = 0) noexcept |
197 | { return qHash(p.data(), seed); } |
198 | |
199 | template <typename T, typename Tag> |
200 | class QTypeInfo<QTaggedPointer<T, Tag>> |
201 | : public QTypeInfoMerger<QTaggedPointer<T, Tag>, quintptr> {}; |
202 | |
203 | QT_END_NAMESPACE |
204 | |
205 | #endif // QTAGGEDPOINTER_H |
206 | |