| /* |
| * Copyright (C) 2023 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef INCLUDE_PERFETTO_EXT_BASE_THREADING_FUTURE_COMBINATORS_H_ |
| #define INCLUDE_PERFETTO_EXT_BASE_THREADING_FUTURE_COMBINATORS_H_ |
| |
| #include <optional> |
| #include <utility> |
| #include <vector> |
| |
| #include "perfetto/base/status.h" |
| #include "perfetto/ext/base/threading/poll.h" |
| |
| namespace perfetto { |
| namespace base { |
| |
| template <typename T> |
| class Future; |
| |
| // For a Function which Future<U>, returns the U. |
| template <typename Function, typename T> |
| using FutureReturn = typename std::invoke_result<Function, T>::type::PollT; |
| |
| // Implementation of FuturePollable for creating a Future<T> from a T. |
| template <typename T> |
| class ImmediateImpl : public FuturePollable<T> { |
| public: |
| explicit ImmediateImpl(T value) : value_(std::move(value)) {} |
| |
| FuturePollResult<T> Poll(PollContext*) override { return std::move(value_); } |
| |
| private: |
| T value_; |
| }; |
| |
| // Implementation of FuturePollable backing Future::ContinueWith. |
| template <typename Function, typename A, typename B = FutureReturn<Function, A>> |
| class ContinueWithImpl : public FuturePollable<B> { |
| public: |
| ContinueWithImpl(Future<A> first, Function second_fn) |
| : first_(std::move(first)), second_fn_(std::move(second_fn)) {} |
| |
| FuturePollResult<B> Poll(PollContext* context) override { |
| PERFETTO_CHECK((first_ && second_fn_) || second_); |
| if (first_) { |
| ASSIGN_OR_RETURN_IF_PENDING_FUTURE(res, first_->Poll(context)); |
| first_ = std::nullopt; |
| second_ = (*second_fn_)(std::move(res)); |
| second_fn_ = std::nullopt; |
| } |
| return second_->Poll(context); |
| } |
| |
| private: |
| std::optional<Future<A>> first_; |
| std::optional<Function> second_fn_; |
| std::optional<Future<B>> second_; |
| }; |
| |
| } // namespace base |
| } // namespace perfetto |
| |
| #endif // INCLUDE_PERFETTO_EXT_BASE_THREADING_FUTURE_COMBINATORS_H_ |