60 lines
1.6 KiB
C
60 lines
1.6 KiB
C
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/*
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* Copyright 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <type_traits>
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#include <variant>
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namespace android::ftl::details {
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template <typename... Ms>
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struct Matcher : Ms... {
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using Ms::operator()...;
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};
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// Deduction guide.
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template <typename... Ms>
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Matcher(Ms...) -> Matcher<Ms...>;
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template <typename Matcher, typename... Ts>
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constexpr bool is_exhaustive_match_v = (std::is_invocable_v<Matcher, Ts> && ...);
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template <typename...>
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struct Match;
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template <typename T, typename U, typename... Ts>
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struct Match<T, U, Ts...> {
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template <typename Variant, typename Matcher>
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static decltype(auto) match(Variant& variant, const Matcher& matcher) {
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if (auto* const ptr = std::get_if<T>(&variant)) {
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return matcher(*ptr);
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} else {
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return Match<U, Ts...>::match(variant, matcher);
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}
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}
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};
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template <typename T>
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struct Match<T> {
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template <typename Variant, typename Matcher>
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static decltype(auto) match(Variant& variant, const Matcher& matcher) {
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return matcher(std::get<T>(variant));
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}
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};
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} // namespace android::ftl::details
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