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Diffstat (limited to 'src/corelib/global/qcompare.h')
| -rw-r--r-- | src/corelib/global/qcompare.h | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/src/corelib/global/qcompare.h b/src/corelib/global/qcompare.h new file mode 100644 index 0000000000..07f4589984 --- /dev/null +++ b/src/corelib/global/qcompare.h @@ -0,0 +1,143 @@ +/**************************************************************************** +** +** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Giuseppe D'Angelo <giuseppe.dangelo@kdab.com> +** Contact: http://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 QCOMPARE_H +#define QCOMPARE_H + +#if 0 +#pragma qt_class(QtCompare) +#endif + +#include <QtCore/qglobal.h> + +QT_BEGIN_NAMESPACE + +namespace QtPrivate { +using CompareUnderlyingType = qint8; + +// [cmp.categories.pre] / 1 +enum class Ordering : CompareUnderlyingType +{ + Equal = 0, + Equivalent = Equal, + Less = -1, + Greater = 1 +}; + +enum class Uncomparable : CompareUnderlyingType +{ + Unordered = -127 +}; + +// [cmp.categories.pre] / 3, but using a safe bool trick +// and also rejecting std::nullptr_t (unlike the example) +class CompareAgainstLiteralZero { +public: + using SafeZero = void (CompareAgainstLiteralZero::*)(); + Q_IMPLICIT constexpr CompareAgainstLiteralZero(SafeZero) noexcept {} + + template <typename T, std::enable_if_t<!std::is_same_v<T, int>, bool> = false> + CompareAgainstLiteralZero(T) = delete; +}; +} // namespace QtPrivate + +// [cmp.partialord] +class QPartialOrdering +{ +public: + static const QPartialOrdering Less; + static const QPartialOrdering Equivalent; + static const QPartialOrdering Greater; + static const QPartialOrdering Unordered; + + friend constexpr bool operator==(QPartialOrdering p, QtPrivate::CompareAgainstLiteralZero) noexcept + { return p.isOrdered() && p.m_order == 0; } + friend constexpr bool operator!=(QPartialOrdering p, QtPrivate::CompareAgainstLiteralZero) noexcept + { return p.isOrdered() && p.m_order != 0; } + friend constexpr bool operator< (QPartialOrdering p, QtPrivate::CompareAgainstLiteralZero) noexcept + { return p.isOrdered() && p.m_order < 0; } + friend constexpr bool operator<=(QPartialOrdering p, QtPrivate::CompareAgainstLiteralZero) noexcept + { return p.isOrdered() && p.m_order <= 0; } + friend constexpr bool operator> (QPartialOrdering p, QtPrivate::CompareAgainstLiteralZero) noexcept + { return p.isOrdered() && p.m_order > 0; } + friend constexpr bool operator>=(QPartialOrdering p, QtPrivate::CompareAgainstLiteralZero) noexcept + { return p.isOrdered() && p.m_order >= 0; } + + friend constexpr bool operator==(QtPrivate::CompareAgainstLiteralZero, QPartialOrdering p) noexcept + { return p.isOrdered() && 0 == p.m_order; } + friend constexpr bool operator!=(QtPrivate::CompareAgainstLiteralZero, QPartialOrdering p) noexcept + { return p.isOrdered() && 0 != p.m_order; } + friend constexpr bool operator< (QtPrivate::CompareAgainstLiteralZero, QPartialOrdering p) noexcept + { return p.isOrdered() && 0 < p.m_order; } + friend constexpr bool operator<=(QtPrivate::CompareAgainstLiteralZero, QPartialOrdering p) noexcept + { return p.isOrdered() && 0 <= p.m_order; } + friend constexpr bool operator> (QtPrivate::CompareAgainstLiteralZero, QPartialOrdering p) noexcept + { return p.isOrdered() && 0 > p.m_order; } + friend constexpr bool operator>=(QtPrivate::CompareAgainstLiteralZero, QPartialOrdering p) noexcept + { return p.isOrdered() && 0 >= p.m_order; } + + friend constexpr bool operator==(QPartialOrdering p1, QPartialOrdering p2) noexcept + { return p1.m_order == p2.m_order; } + friend constexpr bool operator!=(QPartialOrdering p1, QPartialOrdering p2) noexcept + { return p1.m_order != p2.m_order; } + +private: + constexpr explicit QPartialOrdering(QtPrivate::Ordering order) noexcept + : m_order(static_cast<QtPrivate::CompareUnderlyingType>(order)) + {} + constexpr explicit QPartialOrdering(QtPrivate::Uncomparable order) noexcept + : m_order(static_cast<QtPrivate::CompareUnderlyingType>(order)) + {} + + // instead of the exposition only is_ordered member in [cmp.partialord], + // use a private function + constexpr bool isOrdered() noexcept + { return m_order != static_cast<QtPrivate::CompareUnderlyingType>(QtPrivate::Uncomparable::Unordered); } + + QtPrivate::CompareUnderlyingType m_order; +}; + +inline constexpr QPartialOrdering QPartialOrdering::Less(QtPrivate::Ordering::Less); +inline constexpr QPartialOrdering QPartialOrdering::Equivalent(QtPrivate::Ordering::Equivalent); +inline constexpr QPartialOrdering QPartialOrdering::Greater(QtPrivate::Ordering::Greater); +inline constexpr QPartialOrdering QPartialOrdering::Unordered(QtPrivate::Uncomparable::Unordered); + +QT_END_NAMESPACE + +#endif // QCOMPARE_H |