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Diffstat (limited to 'src/corelib/tools/qtaggedpointer.h')
| -rw-r--r-- | src/corelib/tools/qtaggedpointer.h | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/src/corelib/tools/qtaggedpointer.h b/src/corelib/tools/qtaggedpointer.h new file mode 100644 index 0000000000..0c48fa6e4f --- /dev/null +++ b/src/corelib/tools/qtaggedpointer.h @@ -0,0 +1,205 @@ +/**************************************************************************** +** +** Copyright (C) 2020 The Qt Company Ltd. +** Contact: https://www.qt.io/licensing/ +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** Commercial License Usage +** Licensees holding valid commercial Qt licenses may use this file in +** accordance with the commercial license agreement provided with the +** Software or, alternatively, in accordance with the terms contained in +** a written agreement between you and The Qt Company. For licensing terms +** and conditions see https://www.qt.io/terms-conditions. For further +** information use the contact form at https://www.qt.io/contact-us. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 3 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL3 included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 3 requirements +** will be met: https://www.gnu.org/licenses/lgpl-3.0.html. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 2.0 or (at your option) the GNU General +** Public license version 3 or any later version approved by the KDE Free +** Qt Foundation. The licenses are as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3 +** included in the packaging of this file. Please review the following +** information to ensure the GNU General Public License requirements will +** be met: https://www.gnu.org/licenses/gpl-2.0.html and +** https://www.gnu.org/licenses/gpl-3.0.html. +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#ifndef QTAGGEDPOINTER_H +#define QTAGGEDPOINTER_H + +#include <QtCore/qglobal.h> +#include <QtCore/qalgorithms.h> +#include <QtCore/qmath.h> + +#include <limits.h> + +QT_BEGIN_NAMESPACE + +namespace QtPrivate { + constexpr quint8 nextByteSize(quint8 bits) { return (bits + 7) / 8; } + + template <typename T> + struct TagInfo + { + static constexpr size_t alignment = alignof(T); + static_assert((alignment & (alignment - 1)) == 0, + "Alignment of template parameter must be power of two"); + + static constexpr quint8 tagBits = QtPrivate::qConstexprCountTrailingZeroBits(alignment); + static_assert(tagBits > 0, + "Alignment of template parameter does not allow any tags"); + + static constexpr size_t tagSize = QtPrivate::qConstexprNextPowerOfTwo(nextByteSize(tagBits)); + static_assert(tagSize < sizeof(quintptr), + "Alignment of template parameter allows tags masking away pointer"); + + using TagType = typename QIntegerForSize<tagSize>::Unsigned; + }; +} + +template <typename T, typename Tag = typename QtPrivate::TagInfo<T>::TagType> +class QTaggedPointer +{ +public: + using Type = T; + using TagType = Tag; + + static constexpr quintptr tagMask() { return QtPrivate::TagInfo<T>::alignment - 1; } + static constexpr quintptr pointerMask() { return ~tagMask(); } + + explicit QTaggedPointer(T *pointer = nullptr, Tag tag = Tag()) noexcept + : d(quintptr(pointer)) + { + Q_STATIC_ASSERT(sizeof(Type*) == sizeof(QTaggedPointer<Type>)); + + Q_ASSERT_X((quintptr(pointer) & tagMask()) == 0, + "QTaggedPointer<T, Tag>", "Pointer is not aligned"); + + setTag(tag); + } + + Type &operator*() const noexcept + { + Q_ASSERT(data()); + return *data(); + } + + Type *operator->() const noexcept + { + return data(); + } + + explicit operator bool() const noexcept + { + return !isNull(); + } + + QTaggedPointer<T, Tag> &operator=(T *other) noexcept + { + d = reinterpret_cast<quintptr>(other) | (d & tagMask()); + return *this; + } + + QTaggedPointer<T, Tag> &operator=(std::nullptr_t) noexcept + { + d &= tagMask(); + return *this; + } + + static constexpr Tag maximumTag() noexcept + { + return TagType(typename QtPrivate::TagInfo<T>::TagType(tagMask())); + } + + void setTag(Tag tag) + { + Q_ASSERT_X((static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & pointerMask()) == 0, + "QTaggedPointer<T, Tag>::setTag", "Tag is larger than allowed by number of available tag bits"); + + d = (d & pointerMask()) | (static_cast<typename QtPrivate::TagInfo<T>::TagType>(tag) & tagMask()); + } + + Tag tag() const noexcept + { + return TagType(typename QtPrivate::TagInfo<T>::TagType(d & tagMask())); + } + + T* data() const noexcept + { + return reinterpret_cast<T*>(d & pointerMask()); + } + + bool isNull() const noexcept + { + return !data(); + } + + void swap(QTaggedPointer<T, Tag> &other) noexcept + { + qSwap(d, other.d); + } + + friend inline bool operator==(const QTaggedPointer<T, Tag> &lhs, const QTaggedPointer<T, Tag> &rhs) noexcept + { + return lhs.data() == rhs.data(); + } + + friend inline bool operator!=(const QTaggedPointer<T, Tag> &lhs, const QTaggedPointer<T, Tag> &rhs) noexcept + { + return lhs.data() != rhs.data(); + } + + friend inline bool operator==(const QTaggedPointer<T, Tag> &lhs, std::nullptr_t) noexcept + { + return lhs.isNull(); + } + + friend inline bool operator==(std::nullptr_t, const QTaggedPointer<T, Tag> &rhs) noexcept + { + return rhs.isNull(); + } + + friend inline bool operator!=(const QTaggedPointer<T, Tag> &lhs, std::nullptr_t) noexcept + { + return !lhs.isNull(); + } + + friend inline bool operator!=(std::nullptr_t, const QTaggedPointer<T, Tag> &rhs) noexcept + { + return !rhs.isNull(); + } + + friend inline bool operator!(const QTaggedPointer<T, Tag> &ptr) noexcept + { + return !ptr.data(); + } + +protected: + quintptr d; +}; + +template <typename T> +Q_DECLARE_TYPEINFO_BODY(QTaggedPointer<T>, Q_MOVABLE_TYPE); + +template <typename T, typename Tag> +inline void swap(QTaggedPointer<T, Tag> &p1, QTaggedPointer<T, Tag> &p2) noexcept +{ + p1.swap(p2); +} + +QT_END_NAMESPACE + +#endif // QTAGGEDPOINTER_H |