qshareddata_impl.h

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// Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com>
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#if 0
#pragma qt_sync_skip_header_check
#pragma qt_sync_stop_processing
#endif
 
#ifndef QSHAREDDATA_IMPL_H
#define QSHAREDDATA_IMPL_H
 
#include <QtCore/qglobal.h>
#include <QtCore/qshareddata.h>
 
QT_BEGIN_NAMESPACE
 
namespace QtPrivate {
 
template <typename T>
class QExplicitlySharedDataPointerV2
{
    T *d;
 
public:
    constexpr QExplicitlySharedDataPointerV2() noexcept : d(nullptr) {}
 
    explicit QExplicitlySharedDataPointerV2(T *t) noexcept
        : d(t)
    {
        if (d)
            d->ref.ref();
    }
 
    QExplicitlySharedDataPointerV2(T *t, QAdoptSharedDataTag) noexcept
        : d(t)
    {
    }
 
    QExplicitlySharedDataPointerV2(const QExplicitlySharedDataPointerV2 &other) noexcept
        : d(other.d)
    {
        if (d)
            d->ref.ref();
    }
 
    QExplicitlySharedDataPointerV2 &operator=(const QExplicitlySharedDataPointerV2 &other) noexcept
    {
        QExplicitlySharedDataPointerV2 copy(other);
        swap(copy);
        return *this;
    }
 
    QExplicitlySharedDataPointerV2(QExplicitlySharedDataPointerV2 &&other) noexcept
        : d(std::exchange(other.d, nullptr))
    {
    }
 
    QExplicitlySharedDataPointerV2 &operator=(QExplicitlySharedDataPointerV2 &&other) noexcept
    {
        QExplicitlySharedDataPointerV2 moved(std::move(other));
        swap(moved);
        return *this;
    }
 
    ~QExplicitlySharedDataPointerV2()
    {
        if (d && !d->ref.deref())
            delete d;
    }
 
    void detach()
    {
        if (!d) {
            // should this codepath be here on in all user's detach()?
            d = new T;
            d->ref.ref();
        } else if (d->ref.loadRelaxed() != 1) {
            // TODO: qAtomicDetach here...?
            QExplicitlySharedDataPointerV2 copy(new T(*d));
            swap(copy);
        }
    }
 
    void reset(T *t = nullptr) noexcept
    {
        if (d && !d->ref.deref())
            delete d;
        d = t;
        if (d)
            d->ref.ref();
    }
 
    constexpr T *take() noexcept
    {
        return std::exchange(d, nullptr);
    }
 
    bool isShared() const noexcept
    {
        return d && d->ref.loadRelaxed() != 1;
    }
 
    constexpr void swap(QExplicitlySharedDataPointerV2 &other) noexcept
    {
        qt_ptr_swap(d, other.d);
    }
 
    // important change from QExplicitlySharedDataPointer: deep const
    constexpr T &operator*() { return *d; }
    constexpr T *operator->() { return d; }
    constexpr const T &operator*() const { return *d; }
    constexpr const T *operator->() const { return d; }
 
    constexpr T *data() noexcept { return d; }
    constexpr const T *data() const noexcept { return d; }
 
    constexpr explicit operator bool() const noexcept { return d; }
 
    constexpr friend bool operator==(const QExplicitlySharedDataPointerV2 &lhs,
                                     const QExplicitlySharedDataPointerV2 &rhs) noexcept
    {
        return lhs.d == rhs.d;
    }
 
    constexpr friend bool operator!=(const QExplicitlySharedDataPointerV2 &lhs,
                                     const QExplicitlySharedDataPointerV2 &rhs) noexcept
    {
        return lhs.d != rhs.d;
    }
};
 
template <typename T>
constexpr void swap(QExplicitlySharedDataPointerV2<T> &lhs, QExplicitlySharedDataPointerV2<T> &rhs) noexcept
{
    lhs.swap(rhs);
}
 
} // namespace QtPrivate
 
QT_END_NAMESPACE
 
#endif // QSHAREDDATA_IMPL_H