include/QtCore/qshareddata_impl.h

0001 // Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
0002 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
0003 // Qt-Security score:significant reason:default
0004
0005 #if 0
0006 #pragma qt_sync_skip_header_check
0007 #pragma qt_sync_stop_processing
0008 #endif
0009
0010 #ifndef QSHAREDDATA_IMPL_H
0011 #define QSHAREDDATA_IMPL_H
0012
0013 #include <QtCore/qcompare.h>
0014 #include <QtCore/qglobal.h>
0015 #include <QtCore/qshareddata.h>
0016
0017 QT_BEGIN_NAMESPACE
0018
0019 namespace QtPrivate {
0020
0021 template <typename T>
0022 class QExplicitlySharedDataPointerV2
0023 {
0024     Qt::totally_ordered_wrapper<T *> d;
0025
0026 public:
0027     constexpr QExplicitlySharedDataPointerV2() noexcept : d(nullptr) {}
0028
0029     explicit QExplicitlySharedDataPointerV2(T *t) noexcept
0030         : d(t)
0031     {
0032         if (d)
0033             d->ref.ref();
0034     }
0035
0036     QExplicitlySharedDataPointerV2(T *t, QAdoptSharedDataTag) noexcept
0037         : d(t)
0038     {
0039     }
0040
0041     QExplicitlySharedDataPointerV2(const QExplicitlySharedDataPointerV2 &other) noexcept
0042         : d(other.d)
0043     {
0044         if (d)
0045             d->ref.ref();
0046     }
0047
0048     QExplicitlySharedDataPointerV2 &operator=(const QExplicitlySharedDataPointerV2 &other) noexcept
0049     {
0050         QExplicitlySharedDataPointerV2 copy(other);
0051         swap(copy);
0052         return *this;
0053     }
0054
0055     QExplicitlySharedDataPointerV2(QExplicitlySharedDataPointerV2 &&other) noexcept
0056         : d(std::exchange(other.d, nullptr))
0057     {
0058     }
0059
0060     QExplicitlySharedDataPointerV2 &operator=(QExplicitlySharedDataPointerV2 &&other) noexcept
0061     {
0062         QExplicitlySharedDataPointerV2 moved(std::move(other));
0063         swap(moved);
0064         return *this;
0065     }
0066
0067     ~QExplicitlySharedDataPointerV2()
0068     {
0069         if (d && !d->ref.deref())
0070             delete d.get();
0071     }
0072
0073     void detach()
0074     {
0075         if (!d) {
0076             // should this codepath be here on in all user's detach()?
0077             d.reset(new T);
0078             d->ref.ref();
0079         } else if (d->ref.loadRelaxed() != 1) {
0080             // TODO: qAtomicDetach here...?
0081             QExplicitlySharedDataPointerV2 copy(new T(*d));
0082             swap(copy);
0083         }
0084     }
0085
0086     void reset(T *t = nullptr) noexcept
0087     {
0088         if (d && !d->ref.deref())
0089             delete d.get();
0090         d.reset(t);
0091         if (d)
0092             d->ref.ref();
0093     }
0094
0095     constexpr T *take() noexcept
0096     {
0097         return std::exchange(d, nullptr).get();
0098     }
0099
0100     bool isShared() const noexcept
0101     {
0102         return d && d->ref.loadRelaxed() != 1;
0103     }
0104
0105     constexpr void swap(QExplicitlySharedDataPointerV2 &other) noexcept
0106     {
0107         qt_ptr_swap(d, other.d);
0108     }
0109
0110     // important change from QExplicitlySharedDataPointer: deep const
0111     constexpr T &operator*() { return *(d.get()); }
0112     constexpr T *operator->() { return d.get(); }
0113     constexpr const T &operator*() const { return *(d.get()); }
0114     constexpr const T *operator->() const { return d.get(); }
0115
0116     constexpr T *data() noexcept { return d.get(); }
0117     constexpr const T *data() const noexcept { return d.get(); }
0118
0119     constexpr explicit operator bool() const noexcept { return d.get(); }
0120
0121 private:
0122     constexpr friend bool comparesEqual(const QExplicitlySharedDataPointerV2 &lhs,
0123                                         const QExplicitlySharedDataPointerV2 &rhs) noexcept
0124     { return lhs.d == rhs.d; }
0125     constexpr friend Qt::strong_ordering
0126     compareThreeWay(const QExplicitlySharedDataPointerV2 &lhs,
0127                     const QExplicitlySharedDataPointerV2 &rhs) noexcept
0128     { return Qt::compareThreeWay(lhs.d, rhs.d); }
0129     Q_DECLARE_STRONGLY_ORDERED_LITERAL_TYPE(QExplicitlySharedDataPointerV2)
0130
0131     constexpr friend bool
0132     comparesEqual(const QExplicitlySharedDataPointerV2 &lhs, std::nullptr_t) noexcept
0133     { return lhs.d == nullptr; }
0134     constexpr friend Qt::strong_ordering
0135     compareThreeWay(const QExplicitlySharedDataPointerV2 &lhs, std::nullptr_t) noexcept
0136     { return Qt::compareThreeWay(lhs.d, nullptr); }
0137     Q_DECLARE_STRONGLY_ORDERED_LITERAL_TYPE(QExplicitlySharedDataPointerV2, std::nullptr_t)
0138 };
0139
0140 template <typename T>
0141 constexpr void swap(QExplicitlySharedDataPointerV2<T> &lhs, QExplicitlySharedDataPointerV2<T> &rhs) noexcept
0142 {
0143     lhs.swap(rhs);
0144 }
0145
0146 } // namespace QtPrivate
0147
0148 QT_END_NAMESPACE
0149
0150 #endif // QSHAREDDATA_IMPL_H