70 lines
1.9 KiB
C++
70 lines
1.9 KiB
C++
// Copyright (C) 2024 The Qt Company Ltd.
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// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
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#ifndef Q26NUMERIC_H
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#define Q26NUMERIC_H
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#include <QtCore/qglobal.h>
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//
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// W A R N I N G
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// -------------
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//
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// This file is not part of the Qt API. Types and functions defined in this
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// file can reliably be replaced by their std counterparts, once available.
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// You may use these definitions in your own code, but be aware that we
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// will remove them once Qt depends on the C++ version that supports
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// them in namespace std. There will be NO deprecation warning, the
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// definitions will JUST go away.
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//
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// If you can't agree to these terms, don't use these definitions!
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//
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// We mean it.
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//
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#include <numeric>
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#include <limits>
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#include <type_traits>
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QT_BEGIN_NAMESPACE
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namespace q26 {
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// Like std::saturate_cast
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#ifdef __cpp_lib_saturation_arithmetic
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using std::saturate_cast;
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#else
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template <typename To, typename From>
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constexpr auto saturate_cast(From x)
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{
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static_assert(std::is_integral_v<To>);
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static_assert(std::is_integral_v<From>);
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[[maybe_unused]]
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constexpr auto Lo = (std::numeric_limits<To>::min)();
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constexpr auto Hi = (std::numeric_limits<To>::max)();
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if constexpr (std::is_signed_v<From> == std::is_signed_v<To>) {
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// same signedness, we can accept regular integer conversion rules
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return x < Lo ? Lo :
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x > Hi ? Hi :
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/*else*/ To(x);
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} else {
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if constexpr (std::is_signed_v<From>) { // ie. !is_signed_v<To>
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if (x < From{0})
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return To{0};
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}
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// from here on, x >= 0
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using FromU = std::make_unsigned_t<From>;
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using ToU = std::make_unsigned_t<To>;
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return FromU(x) > ToU(Hi) ? Hi : To(x); // assumes Hi >= 0
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}
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}
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#endif // __cpp_lib_saturation_arithmetic
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} // namespace q26
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QT_END_NAMESPACE
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#endif /* Q26NUMERIC_H */
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