QVariant: introduce ShouldDeleteVariantData flag
This flag is used in QSequentialIterable and QAssociativeIterable to indicate that the data pointer in VariantData should be deleted after the variant has been constructed. The use case for this is https://codereview.qt-project.org/c/qt/qtdeclarative/+/284151, where we have a proxy iterator and cannot easily return a pointer to already owned data, as it is hard to manage its lifetime in the iterator. In contrast, it is clear that we can release the memory in the QSequentialIterable functions, as it has already been copied into the QVariant there. Change-Id: I2b33497d991cd4f752153e0ebda767b82e4bb851 Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
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Fabian Kosmale
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07838840e8
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c15d6a155c
@ -4520,15 +4520,24 @@ QSequentialIterable::const_iterator QSequentialIterable::end() const
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return it;
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}
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static const QVariant variantFromVariantDataHelper(const QtMetaTypePrivate::VariantData &d) {
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QVariant v;
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if (d.metaTypeId == qMetaTypeId<QVariant>())
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v = *reinterpret_cast<const QVariant*>(d.data);
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else
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v = QVariant(d.metaTypeId, d.data, d.flags & ~QVariantConstructionFlags::ShouldDeleteVariantData);
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if (d.flags & QVariantConstructionFlags::ShouldDeleteVariantData)
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QMetaType::destroy(d.metaTypeId, const_cast<void *>(d.data));
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return v;
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}
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/*!
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Returns the element at position \a idx in the container.
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*/
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QVariant QSequentialIterable::at(int idx) const
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{
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const QtMetaTypePrivate::VariantData d = m_impl.at(idx);
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if (d.metaTypeId == qMetaTypeId<QVariant>())
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return *reinterpret_cast<const QVariant*>(d.data);
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return QVariant(d.metaTypeId, d.data, d.flags);
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return variantFromVariantDataHelper(d);
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}
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/*!
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@ -4605,9 +4614,7 @@ QSequentialIterable::const_iterator::operator=(const const_iterator &other)
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const QVariant QSequentialIterable::const_iterator::operator*() const
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{
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const QtMetaTypePrivate::VariantData d = m_impl.getCurrent();
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if (d.metaTypeId == qMetaTypeId<QVariant>())
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return *reinterpret_cast<const QVariant*>(d.data);
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return QVariant(d.metaTypeId, d.data, d.flags);
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return variantFromVariantDataHelper(d);
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}
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/*!
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@ -4939,10 +4946,7 @@ QAssociativeIterable::const_iterator::operator=(const const_iterator &other)
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const QVariant QAssociativeIterable::const_iterator::operator*() const
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{
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const QtMetaTypePrivate::VariantData d = m_impl.getCurrentValue();
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QVariant v(d.metaTypeId, d.data, d.flags);
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if (d.metaTypeId == qMetaTypeId<QVariant>())
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return *reinterpret_cast<const QVariant*>(d.data);
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return v;
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return variantFromVariantDataHelper(d);
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}
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/*!
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@ -4951,10 +4955,7 @@ const QVariant QAssociativeIterable::const_iterator::operator*() const
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const QVariant QAssociativeIterable::const_iterator::key() const
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{
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const QtMetaTypePrivate::VariantData d = m_impl.getCurrentKey();
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QVariant v(d.metaTypeId, d.data, d.flags);
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if (d.metaTypeId == qMetaTypeId<QVariant>())
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return *reinterpret_cast<const QVariant*>(d.data);
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return v;
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return variantFromVariantDataHelper(d);
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}
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/*!
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@ -4962,11 +4963,7 @@ const QVariant QAssociativeIterable::const_iterator::key() const
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*/
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const QVariant QAssociativeIterable::const_iterator::value() const
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{
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const QtMetaTypePrivate::VariantData d = m_impl.getCurrentValue();
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QVariant v(d.metaTypeId, d.data, d.flags);
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if (d.metaTypeId == qMetaTypeId<QVariant>())
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return *reinterpret_cast<const QVariant*>(d.data);
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return v;
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return operator*();
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}
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/*!
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@ -105,6 +105,11 @@ inline T *v_cast(QVariant::Private *d, T * = nullptr)
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#endif
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enum QVariantConstructionFlags : uint {
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Default = 0x0,
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PointerType = 0x1,
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ShouldDeleteVariantData = 0x2 // only used in Q*Iterable
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};
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//a simple template that avoids to allocate 2 memory chunks when creating a QVariant
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template <class T> class QVariantPrivateSharedEx : public QVariant::PrivateShared
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@ -31,6 +31,7 @@
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#include <QtTest/QtTest>
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#include <qvariant.h>
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#include <QtCore/private/qvariant_p.h>
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#include <qbitarray.h>
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#include <qbytearraylist.h>
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#include <qdatetime.h>
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@ -276,7 +277,8 @@ private slots:
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void nullConvert();
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void accessSequentialContainerKey();
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void shouldDeleteVariantDataWorksForSequential();
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void shouldDeleteVariantDataWorksForAssociative();
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void fromStdVariant();
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void qt4UuidDataStream();
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@ -4990,6 +4992,99 @@ void tst_QVariant::accessSequentialContainerKey()
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QCOMPARE(nameResult, QStringLiteral("Seven"));
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}
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void tst_QVariant::shouldDeleteVariantDataWorksForSequential()
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{
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QCOMPARE(instanceCount, 0);
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{
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QtMetaTypePrivate::QSequentialIterableImpl iterator {};
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iterator._iteratorCapabilities = QtMetaTypePrivate::RandomAccessCapability |
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QtMetaTypePrivate::BiDirectionalCapability |
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QtMetaTypePrivate::ForwardCapability;
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iterator._metaType_flags = QVariantConstructionFlags::ShouldDeleteVariantData;
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iterator._size = [](const void *) {return 1;};
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iterator._metaType_id = qMetaTypeId<MyType>();
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iterator._moveToBegin = [](const void *, void **) {};
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iterator._moveToEnd = [](const void *, void **) {};
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iterator._advance = [](void **, int) {};
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iterator._destroyIter = [](void **){};
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iterator._equalIter = [](void * const *, void * const *){return true; /*all iterators are nullptr*/};
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iterator._destroyIter = [](void **){};
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iterator._at = [](const void *, int ) -> void const * {
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MyType mytype {1, "eins"};
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return QMetaType::create(qMetaTypeId<MyType>(), &mytype);
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};
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iterator._get = [](void * const *, int, uint) -> QtMetaTypePrivate::VariantData {
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MyType mytype {2, "zwei"};
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return {qMetaTypeId<MyType>(), QMetaType::create(qMetaTypeId<MyType>(), &mytype), QVariantConstructionFlags::ShouldDeleteVariantData};
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};
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QSequentialIterable iterable {iterator};
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QVariant value1 = iterable.at(0);
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QVERIFY(value1.canConvert<MyType>());
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QCOMPARE(value1.value<MyType>().number, 1);
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QVariant value2 = *iterable.begin();
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QVERIFY(value2.canConvert<MyType>());
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QCOMPARE(value2.value<MyType>().number, 2);
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}
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QCOMPARE(instanceCount, 0);
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}
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void tst_QVariant::shouldDeleteVariantDataWorksForAssociative()
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{
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QCOMPARE(instanceCount, 0);
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{
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QtMetaTypePrivate::QAssociativeIterableImpl iterator {};
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iterator._metaType_flags_key = QVariantConstructionFlags::ShouldDeleteVariantData;
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iterator._metaType_flags_value = QVariantConstructionFlags::ShouldDeleteVariantData;
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iterator._size = [](const void *) {return 1;};
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iterator._metaType_id_value = qMetaTypeId<MyType>();
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iterator._metaType_id_key = qMetaTypeId<MyType>();
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iterator._begin = [](const void *, void **) {};
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iterator._end = [](const void *, void **) {};
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iterator._advance = [](void **, int) {};
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iterator._destroyIter = [](void **){};
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iterator._equalIter = [](void * const *, void * const *){return true; /*all iterators are nullptr*/};
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iterator._destroyIter = [](void **){};
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iterator._find = [](const void *, const void *, void **iterator ) -> void {
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(*iterator) = reinterpret_cast<void *>(quintptr(42));
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};
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iterator._getKey = [](void * const *iterator, int, uint) -> QtMetaTypePrivate::VariantData {
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MyType mytype {1, "key"};
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if (reinterpret_cast<quintptr>(*iterator) == 42) {
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mytype.number = 42;
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mytype.text = "find_key";
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}
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return {qMetaTypeId<MyType>(), QMetaType::create(qMetaTypeId<MyType>(), &mytype), QVariantConstructionFlags::ShouldDeleteVariantData};
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};
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iterator._getValue = [](void * const *iterator, int, uint) -> QtMetaTypePrivate::VariantData {
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MyType mytype {2, "value"};
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if (reinterpret_cast<quintptr>(*iterator) == 42) {
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mytype.number = 42;
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mytype.text = "find_value";
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}
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return {qMetaTypeId<MyType>(), QMetaType::create(qMetaTypeId<MyType>(), &mytype), QVariantConstructionFlags::ShouldDeleteVariantData};
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};
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QAssociativeIterable iterable {iterator};
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auto it = iterable.begin();
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QVariant value1 = it.key();
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QVERIFY(value1.canConvert<MyType>());
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QCOMPARE(value1.value<MyType>().number, 1);
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QCOMPARE(value1.value<MyType>().text, "key");
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QVariant value2 = it.value();
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QVERIFY(value2.canConvert<MyType>());
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QCOMPARE(value2.value<MyType>().number, 2);
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auto findIt = iterable.find(QVariant::fromValue(MyType {}));
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value1 = findIt.key();
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QCOMPARE(value1.value<MyType>().number, 42);
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QCOMPARE(value1.value<MyType>().text, "find_key");
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value2 = findIt.value();
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QCOMPARE(value2.value<MyType>().number, 42);
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QCOMPARE(value2.value<MyType>().text, "find_value");
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}
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QCOMPARE(instanceCount, 0);
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}
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void tst_QVariant::fromStdVariant()
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{
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#if __has_include(<variant>) && __cplusplus >= 201703L
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