| 1 | // Copyright (C) 2025 The Qt Company Ltd. |
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| 2 | // 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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| 3 | // Qt-Security score:significant reason:default |
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| 4 | |
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| 5 | #ifndef QTCLASSHELPER_P_H |
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| 6 | #define QTCLASSHELPER_P_H |
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| 7 | |
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| 8 | #include <QtCore/private/qglobal_p.h> |
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| 9 | |
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| 10 | // |
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| 11 | // W A R N I N G |
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| 12 | // ------------- |
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| 13 | // |
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| 14 | // This file is not part of the Qt API. It exists purely as an |
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| 15 | // implementation detail. This header file may change from version to |
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| 16 | // version without notice, or even be removed. |
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| 17 | // |
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| 18 | // We mean it. |
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| 19 | // |
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| 20 | |
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| 21 | #include <type_traits> |
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| 22 | #include <utility> |
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| 23 | |
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| 24 | QT_BEGIN_NAMESPACE |
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| 25 | |
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| 26 | /* |
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| 27 | Helper for setters overloaded on lvalue/rvalue. If the setter is doing a |
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| 28 | lot of work around the actual assignment, a common pattern is to create a |
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| 29 | private helper method |
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| 30 | |
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| 31 | void doSetFoo(const Foo &lvalue, Foo *rvalue); |
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| 32 | |
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| 33 | and implement the two setters inline by calling that function: |
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| 34 | |
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| 35 | void setFoo(const Foo &f) { doSetFoo(f, nullptr); } |
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| 36 | void setFoo(Foo &&f) { doSetFoo(f, &f); } |
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| 37 | |
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| 38 | Then, in doSetFoo(), when assigning the argument to the member, use this |
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| 39 | function: |
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| 40 | |
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| 41 | q_choose_assign(m_foo, lvalue, rvalue); |
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| 42 | |
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| 43 | or, when appending to a container, |
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| 44 | |
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| 45 | q_choose_append(m_container, lvalue, rvalue); |
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| 46 | |
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| 47 | The functions mandate (in the C++ sense) that all arguments are the same |
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| 48 | type, so they deduce each argument separately and then static_assert that |
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| 49 | they're the same. If we need std::exchange()-like mixed types later, it's |
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| 50 | easy to relax. For now, avoid being overly general. |
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| 51 | */ |
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| 52 | template <typename T, typename U, typename V> |
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| 53 | decltype(auto) q_choose_assign(T &var, const U &lvalue, V *rvalue) |
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| 54 | { |
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| 55 | static_assert(std::is_same_v<T, U>, "all arguments must be of the same type" ); |
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| 56 | static_assert(std::is_same_v<U, V>, "all arguments must be of the same type" ); |
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| 57 | if (rvalue) |
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| 58 | return var = std::move(*rvalue); |
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| 59 | else |
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| 60 | return var = lvalue; |
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| 61 | } |
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| 62 | |
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| 63 | template <typename Container, typename U, typename V> |
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| 64 | decltype(auto) q_choose_append(Container &c, const U &lvalue, V *rvalue) |
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| 65 | { |
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| 66 | static_assert(std::is_same_v<typename Container::value_type, U>, "arguments must match container" ); |
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| 67 | static_assert(std::is_same_v<U, V>, "all arguments must be of the same type" ); |
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| 68 | if (rvalue) |
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| 69 | c.push_back(std::move(*rvalue)); |
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| 70 | else |
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| 71 | c.push_back(lvalue); |
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| 72 | return c.back(); |
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| 73 | } |
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| 74 | |
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| 75 | QT_END_NAMESPACE |
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| 76 | |
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| 77 | #endif // QTCLASSHELPER_P_H |
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| 78 | |
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