1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
|
// Copyright (C) 2020 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QTAGGEDPOINTER_H
#define QTAGGEDPOINTER_H
#include <QtCore/qglobal.h>
#include <QtCore/qalgorithms.h>
#include <QtCore/qmath.h>
#include <QtCore/qtypeinfo.h>
QT_BEGIN_NAMESPACE
namespace QtPrivate {
constexpr quint8 nextByteSize(quint8 bits) { return quint8((bits + 7) / 8); }
template <typename T>
struct TagInfo
{
static constexpr size_t alignment = alignof(T);
static_assert((alignment & (alignment - 1)) == 0,
"Alignment of template parameter must be power of two");
static constexpr quint8 tagBits = QtPrivate::qConstexprCountTrailingZeroBits(alignment);
static_assert(tagBits > 0,
"Alignment of template parameter does not allow any tags");
static constexpr size_t tagSize = QtPrivate::qConstexprNextPowerOfTwo(nextByteSize(tagBits));
static_assert(tagSize < sizeof(quintptr),
"Alignment of template parameter allows tags masking away pointer");
using TagType = typename QIntegerForSize<tagSize>::Unsigned;
};
}
template <typename T, typename Tag = typename QtPrivate::TagInfo<T>::TagType>
class QTaggedPointer
{
public:
using Type = T;
using TagType = Tag;
static constexpr quintptr tagMask() { return QtPrivate::TagInfo<T>::alignment - 1; }
static constexpr quintptr pointerMask() { return ~tagMask(); }
constexpr QTaggedPointer() noexcept : d(0) {}
constexpr QTaggedPointer(std::nullptr_t) noexcept : QTaggedPointer() {}
explicit QTaggedPointer(T *pointer, Tag tag = Tag()) noexcept
: d(quintptr(pointer) | quintptr(tag))
{
static_assert(sizeof(Type*) == sizeof(QTaggedPointer));
Q_ASSERT_X((quintptr(pointer) & tagMask()) == 0, "QTaggedPointer<T, Tag>", "Pointer is not aligned");
Q_ASSERT_X((static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & pointerMask()) == 0,
"QTaggedPointer<T, Tag>::setTag", "Tag is larger than allowed by number of available tag bits");
}
Type &operator*() const noexcept
{
Q_ASSERT(data());
return *data();
}
Type *operator->() const noexcept
{
return data();
}
explicit operator bool() const noexcept
{
return !isNull();
}
QTaggedPointer &operator=(T *other) noexcept
{
d = reinterpret_cast<quintptr>(other) | (d & tagMask());
return *this;
}
static constexpr Tag maximumTag() noexcept
{
return TagType(typename QtPrivate::TagInfo<T>::TagType(tagMask()));
}
void setTag(Tag tag)
{
Q_ASSERT_X((static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & pointerMask()) == 0,
"QTaggedPointer<T, Tag>::setTag", "Tag is larger than allowed by number of available tag bits");
d = (d & pointerMask()) | static_cast<quintptr>(tag);
}
Tag tag() const noexcept
{
return TagType(typename QtPrivate::TagInfo<T>::TagType(d & tagMask()));
}
T* data() const noexcept
{
return reinterpret_cast<T*>(d & pointerMask());
}
bool isNull() const noexcept
{
return !data();
}
void swap(QTaggedPointer &other) noexcept
{
std::swap(d, other.d);
}
friend inline bool operator==(QTaggedPointer lhs, QTaggedPointer rhs) noexcept
{
return lhs.data() == rhs.data();
}
friend inline bool operator!=(QTaggedPointer lhs, QTaggedPointer rhs) noexcept
{
return lhs.data() != rhs.data();
}
friend inline bool operator==(QTaggedPointer lhs, std::nullptr_t) noexcept
{
return lhs.isNull();
}
friend inline bool operator==(std::nullptr_t, QTaggedPointer rhs) noexcept
{
return rhs.isNull();
}
friend inline bool operator!=(QTaggedPointer lhs, std::nullptr_t) noexcept
{
return !lhs.isNull();
}
friend inline bool operator!=(std::nullptr_t, QTaggedPointer rhs) noexcept
{
return !rhs.isNull();
}
friend inline bool operator!(QTaggedPointer ptr) noexcept
{
return !ptr.data();
}
friend inline void swap(QTaggedPointer &p1, QTaggedPointer &p2) noexcept
{
p1.swap(p2);
}
protected:
quintptr d;
};
template <typename T, typename Tag>
constexpr inline std::size_t qHash(QTaggedPointer<T, Tag> p, std::size_t seed = 0) noexcept
{ return qHash(p.data(), seed); }
template <typename T, typename Tag>
class QTypeInfo<QTaggedPointer<T, Tag>>
: public QTypeInfoMerger<QTaggedPointer<T, Tag>, quintptr> {};
QT_END_NAMESPACE
#endif // QTAGGEDPOINTER_H
|
