qcomtaskresource_p.h

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// Copyright (C) 2023 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
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
 
#ifndef QCOMTASKRESOURCE_P_H
#define QCOMTASKRESOURCE_P_H
 
#include <QtCore/qassert.h>
 
#include <objbase.h>
#include <algorithm>
#include <type_traits>
#include <utility>
 
QT_BEGIN_NAMESPACE
 
class QEmptyDeleter final
{
public:
    template<typename T>
    void operator()(T /*element*/) const
    {
    }
};
 
class QComDeleter final
{
public:
    template<typename T>
    void operator()(T element) const
    {
        element->Release();
    }
};
 
template<typename T>
class QComTaskResourceBase
{
public:
    QComTaskResourceBase(const QComTaskResourceBase<T> &source) = delete;
    QComTaskResourceBase &operator=(const QComTaskResourceBase<T> &right) = delete;
 
    explicit operator bool() const { return m_resource != nullptr; }
 
    T *get() const { return m_resource; }
 
protected:
    QComTaskResourceBase() = default;
    explicit QComTaskResourceBase(T *const resource) : m_resource(resource) { }
 
    T *release() { return std::exchange(m_resource, nullptr); }
 
    void reset(T *const resource = nullptr)
    {
        if (m_resource != resource) {
            if (m_resource)
                CoTaskMemFree(m_resource);
            m_resource = resource;
        }
    }
 
    T *m_resource = nullptr;
};
 
template<typename T, typename TElementDeleter = QEmptyDeleter>
class QComTaskResource final : public QComTaskResourceBase<T>
{
    using Base = QComTaskResourceBase<T>;
 
public:
    using Base::QComTaskResourceBase;
 
    ~QComTaskResource() { reset(); }
 
    T *operator->() const { return m_resource; }
    T &operator*() const { return *m_resource; }
 
    T **address()
    {
        Q_ASSERT(m_resource == nullptr);
        return &m_resource;
    }
 
    using Base::release;
    using Base::reset;
 
private:
    using Base::m_resource;
};
 
template<typename T, typename TElementDeleter>
class QComTaskResource<T[], TElementDeleter> final : public QComTaskResourceBase<T>
{
    using Base = QComTaskResourceBase<T>;
 
public:
    QComTaskResource() = default;
    explicit QComTaskResource(T *const resource, const std::size_t size)
        : Base(resource), m_size(size)
    {
    }
 
    ~QComTaskResource() { reset(); }
 
    T &operator[](const std::size_t index) const
    {
        Q_ASSERT(index < m_size);
        return m_resource[index];
    }
 
    T *release()
    {
        m_size = 0;
 
        return Base::release();
    }
 
    void reset() { reset(nullptr, 0); }
 
    void reset(T *const resource, const std::size_t size)
    {
        if (m_resource != resource) {
            resetElements();
 
            Base::reset(resource);
 
            m_size = size;
        }
    }
 
private:
    void resetElements()
    {
        if constexpr (!std::is_same_v<TElementDeleter, QEmptyDeleter>) {
            std::for_each(m_resource, m_resource + m_size, TElementDeleter());
        }
    }
 
    std::size_t m_size = 0;
 
    using Base::m_resource;
};
 
QT_END_NAMESPACE
 
#endif