f3eade2f62
Drop the AGPL license in favor of a source-available license. See the blog post [1] for details. [1] https://www.scylladb.com/2024/12/18/why-were-moving-to-a-source-available-license/
48 lines
2.1 KiB
C++
48 lines
2.1 KiB
C++
/*
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* Copyright (C) 2023-present ScyllaDB
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*
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*/
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/*
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* SPDX-License-Identifier: (LicenseRef-ScyllaDB-Source-Available-1.0 and Apache-2.0)
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*/
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#pragma once
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#include <functional>
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#include <tuple>
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namespace utils {
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template <typename T>
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constexpr auto tuple_ex_size_v = std::tuple_size_v<std::remove_reference_t<T>>;
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template<typename T>
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concept Tuple = requires(T item) {
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std::invoke([]<typename... U>(const std::tuple<U...>& t) {}, item);
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};
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// Insert a new item of type NewItem into SourceTuple to produce ResultTuple.
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// ResultTuple mirrors SourceTuple, with the inclusion of an extra element of type NewItem.
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// SourceTuple and ResultTuple can be arbitrary specialisations of std::tuple or rpc::tuple.
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template<Tuple ResultTuple, Tuple SourceTuple, typename NewItem>
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requires (tuple_ex_size_v<SourceTuple> + 1 == tuple_ex_size_v<ResultTuple>)
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static ResultTuple tuple_insert(SourceTuple&& source_tuple, NewItem&& new_item) {
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constexpr auto source_size = tuple_ex_size_v<SourceTuple>;
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constexpr auto result_size = tuple_ex_size_v<ResultTuple>;
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constexpr auto match = std::invoke([]<std::size_t... Is>(std::index_sequence<Is...>) {
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auto index = result_size;
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const auto count = (0 + ... + (std::is_same_v<std::tuple_element_t<Is, ResultTuple>, NewItem> ? (index = Is, 1) : 0));
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return std::pair(index, count);
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}, std::make_index_sequence<result_size>());
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static_assert(match.second == 1, "ResultTuple should contain exactly one NewItem");
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constexpr auto item_index = match.first;
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return std::invoke([&]<std::size_t... Left, std::size_t... Right>(std::index_sequence<Left...>, std::index_sequence<Right...>) {
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return ResultTuple {
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std::get<Left>(std::forward<SourceTuple>(source_tuple))...,
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std::forward<NewItem>(new_item),
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std::get<Right + item_index>(std::forward<SourceTuple>(source_tuple))...
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};
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}, std::make_index_sequence<item_index>(), std::make_index_sequence<source_size - item_index>());
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}
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}
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