qfunctionaltools_impl.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
 
#if 0
#pragma qt_sync_skip_header_check
#pragma qt_sync_stop_processing
#endif
 
#ifndef QFUNCTIONALTOOLS_IMPL_H
#define QFUNCTIONALTOOLS_IMPL_H
 
#include <QtCore/qtconfigmacros.h>
 
#include <type_traits>
#include <utility>
 
QT_BEGIN_NAMESPACE
 
namespace QtPrivate {
 
namespace detail {
 
#define FOR_EACH_CVREF(op)
    op(&)
    op(const &)
    op(&&)
    op(const &&)
    /* end */
 
 
template <typename Object, typename = void>
struct StorageByValue
{
    Object o;
#define MAKE_GETTER(cvref)
    constexpr Object cvref object() cvref noexcept
    { return static_cast<Object cvref>(o); }
    FOR_EACH_CVREF(MAKE_GETTER)
#undef MAKE_GETTER
};
 
template <typename Object, typename Tag = void>
struct StorageEmptyBaseClassOptimization : Object
{
    StorageEmptyBaseClassOptimization() = default;
    StorageEmptyBaseClassOptimization(Object &&o)
        : Object(std::move(o))
    {}
    StorageEmptyBaseClassOptimization(const Object &o)
        : Object(o)
    {}
 
#define MAKE_GETTER(cvref)
    constexpr Object cvref object() cvref noexcept
    { return static_cast<Object cvref>(*this); }
    FOR_EACH_CVREF(MAKE_GETTER)
#undef MAKE_GETTER
};
} // namespace detail
 
template <typename Object, typename Tag = void>
using CompactStorage = typename std::conditional_t<
        std::conjunction_v<
            std::is_empty<Object>,
            std::negation<std::is_final<Object>>
        >,
        detail::StorageEmptyBaseClassOptimization<Object, Tag>,
        detail::StorageByValue<Object, Tag>
    >;
 
} // namespace QtPrivate
 
#undef FOR_EACH_CVREF
 
QT_END_NAMESPACE
 
#endif // QFUNCTIONALTOOLS_IMPL_H