mirror of https://gitee.com/bigwinds/arangodb
88 lines
2.7 KiB
C++
88 lines
2.7 KiB
C++
////////////////////////////////////////////////////////////////////////////////
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/// DISCLAIMER
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///
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/// Copyright 2018 ArangoDB GmbH, Cologne, Germany
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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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/// Copyright holder is ArangoDB GmbH, Cologne, Germany
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///
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/// @author Simon Grätzer
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////////////////////////////////////////////////////////////////////////////////
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#ifndef ARANGOD_FUTURES_BACKPORTS_H
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#define ARANGOD_FUTURES_BACKPORTS_H 1
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#if __cplusplus >= 201703L
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#include <type_traits>
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#include <utility>
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#endif
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#include <functional>
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namespace arangodb {
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namespace futures {
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/// Backports from C++17 of:
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/// std::in_place_t
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/// std::in_place
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/// std::is_invocable
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/// std::is_invocable_r
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/// std::invoke
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#if __cplusplus < 201703L
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struct in_place_tag {};
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using in_place_t = in_place_tag (&)(in_place_tag);
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inline in_place_tag in_place(in_place_tag = {}) { return {}; }
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template <typename F, typename... Args>
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struct is_invocable
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: std::is_constructible<std::function<void(Args...)>,
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std::reference_wrapper<typename std::remove_reference<F>::type>> {
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};
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template <typename R, typename F, typename... Args>
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struct is_invocable_r
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: std::is_constructible<std::function<R(Args...)>, std::reference_wrapper<typename std::remove_reference<F>::type>> {
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};
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// mimic: std::invoke, C++17
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template <typename F, typename... Args>
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constexpr auto invoke(F&& f, Args&&... args) noexcept(
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noexcept(static_cast<F&&>(f)(static_cast<Args&&>(args)...)))
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-> decltype(static_cast<F&&>(f)(static_cast<Args&&>(args)...)) {
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return static_cast<F&&>(f)(static_cast<Args&&>(args)...);
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}
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template <typename M, typename C, typename... Args>
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constexpr auto invoke(M(C::*d), Args&&... args)
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-> decltype(std::mem_fn(d)(static_cast<Args&&>(args)...)) {
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return std::mem_fn(d)(static_cast<Args&&>(args)...);
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}
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#else
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using std::invoke;
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using in_place_t = std::in_place_t;
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inline constexpr in_place_t in_place{};
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template <class R, class FN, class... ArgTypes>
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using is_invocable_r = std::is_invocable_r<R, FN, ArgTypes...>;
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template <class FN, class... ArgTypes>
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using is_invocable = std::is_invocable<FN, ArgTypes...>;
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#endif
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} // namespace futures
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} // namespace arangodb
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#endif
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