99 lines
2.2 KiB
C++
99 lines
2.2 KiB
C++
/*
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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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namespace android::ftl {
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template <typename, template <typename> class>
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class Future;
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namespace details {
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template <typename T>
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struct future_result {
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using type = T;
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};
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template <typename T>
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struct future_result<std::future<T>> {
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using type = T;
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};
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template <typename T>
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struct future_result<std::shared_future<T>> {
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using type = T;
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};
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template <typename T, template <typename> class FutureImpl>
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struct future_result<Future<T, FutureImpl>> {
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using type = T;
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};
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template <typename T>
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using future_result_t = typename future_result<T>::type;
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struct ValueTag {};
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template <typename, typename T, template <typename> class>
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class BaseFuture;
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template <typename Self, typename T>
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class BaseFuture<Self, T, std::future> {
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using Impl = std::future<T>;
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public:
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Future<T, std::shared_future> share() {
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if (T* value = std::get_if<T>(&self())) {
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return {ValueTag{}, std::move(*value)};
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}
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return std::get<Impl>(self()).share();
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}
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protected:
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T get() {
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if (T* value = std::get_if<T>(&self())) {
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return std::move(*value);
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}
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return std::get<Impl>(self()).get();
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}
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private:
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auto& self() { return static_cast<Self&>(*this).future_; }
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};
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template <typename Self, typename T>
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class BaseFuture<Self, T, std::shared_future> {
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using Impl = std::shared_future<T>;
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protected:
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const T& get() const {
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if (const T* value = std::get_if<T>(&self())) {
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return *value;
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}
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return std::get<Impl>(self()).get();
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}
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private:
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const auto& self() const { return static_cast<const Self&>(*this).future_; }
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};
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} // namespace details
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} // namespace android::ftl
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