fcb8d040e8
Instead of lengthy blurbs, switch to single-line, machine-readable standardized (https://spdx.dev) license identifiers. The Linux kernel switched long ago, so there is strong precedent. Three cases are handled: AGPL-only, Apache-only, and dual licensed. For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0), reasoning that our changes are extensive enough to apply our license. The changes we applied mechanically with a script, except to licenses/README.md. Closes #9937
37 lines
961 B
C++
37 lines
961 B
C++
/*
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* Copyright (C) 2021-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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#pragma once
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#include <variant>
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#include <type_traits>
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namespace utils {
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// Given type T and an std::variant Variant, return std::true_type if T is a variant element
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// This is also the recursion base case (empty variant), so return false.
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template <typename T, typename Variant>
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struct is_variant_element : std::false_type {
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};
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// Match - return true
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template <typename T, typename... Elements>
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struct is_variant_element<T, std::variant<T, Elements...>> : std::true_type {
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};
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// No match - recurse
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template <typename T, typename U, typename... Elements>
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struct is_variant_element<T, std::variant<U, Elements...>> : is_variant_element<T, std::variant<Elements...>> {
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};
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// Givent type T and std::variant, true if T is one of the variant elements.
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template <typename T, typename Variant>
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concept VariantElement = is_variant_element<T, Variant>::value;
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}
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