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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
#ifndef QVARIANT_P_H
#define QVARIANT_P_H
//
// 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.
//
#include "qvariant.h"
QT_BEGIN_NAMESPACE
inline auto customConstructSharedImpl(size_t size, size_t align)
{
struct Deleter {
void operator()(QVariant::PrivateShared *p) const
{ QVariant::PrivateShared::free(p); }
};
// this is exception-safe
std::unique_ptr<QVariant::PrivateShared, Deleter> ptr;
ptr.reset(QVariant::PrivateShared::create(size, align));
return ptr;
}
template <typename F> static QVariant::PrivateShared *
customConstructShared(size_t size, size_t align, F &&construct)
{
auto ptr = customConstructSharedImpl(size, align);
construct(ptr->data());
return ptr.release();
}
inline int QVariant::PrivateShared::computeOffset(PrivateShared *ps, size_t align)
{
return int(((quintptr(ps) + sizeof(PrivateShared) + align - 1) & ~(align - 1)) - quintptr(ps));
}
inline size_t QVariant::PrivateShared::computeAllocationSize(size_t size, size_t align)
{
size += sizeof(PrivateShared);
if (align > sizeof(PrivateShared)) {
// The alignment is larger than the alignment we can guarantee for the pointer
// directly following PrivateShared, so we need to allocate some additional
// memory to be able to fit the object into the available memory with suitable
// alignment.
size += align - sizeof(PrivateShared);
}
return size;
}
inline QVariant::PrivateShared *QVariant::PrivateShared::create(size_t size, size_t align)
{
size = computeAllocationSize(size, align);
void *data = operator new(size);
auto *ps = new (data) QVariant::PrivateShared();
ps->offset = computeOffset(ps, align);
return ps;
}
inline void QVariant::PrivateShared::free(PrivateShared *p)
{
p->~PrivateShared();
operator delete(p);
}
inline QVariant::Private::Private(const QtPrivate::QMetaTypeInterface *iface) noexcept
: is_shared(false), is_null(false), packedType(quintptr(iface) >> 2)
{
Q_ASSERT((quintptr(iface) & 0x3) == 0);
}
template <typename T> inline
QVariant::Private::Private(std::piecewise_construct_t, const T &t)
: is_shared(!CanUseInternalSpace<T>), is_null(std::is_same_v<T, std::nullptr_t>)
{
// confirm noexceptness
static constexpr bool isNothrowQVariantConstructible = noexcept(QVariant(t));
static constexpr bool isNothrowCopyConstructible = std::is_nothrow_copy_constructible_v<T>;
static constexpr bool isNothrowCopyAssignable = std::is_nothrow_copy_assignable_v<T>;
const QtPrivate::QMetaTypeInterface *iface = QtPrivate::qMetaTypeInterfaceForType<T>();
Q_ASSERT((quintptr(iface) & 0x3) == 0);
packedType = quintptr(iface) >> 2;
if constexpr (CanUseInternalSpace<T>) {
static_assert(isNothrowQVariantConstructible == isNothrowCopyConstructible);
static_assert(isNothrowQVariantConstructible == isNothrowCopyAssignable);
new (data.data) T(t);
} else {
static_assert(!isNothrowQVariantConstructible); // we allocate memory, even if T doesn't
data.shared = customConstructShared(sizeof(T), alignof(T), [=](void *where) {
new (where) T(t);
});
}
}
QT_END_NAMESPACE
#endif // QVARIANT_P_H
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