82 lines
2.5 KiB
C++
82 lines
2.5 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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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 <folly/functional/Invoke.h>
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#include <folly/futures/Future.h>
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namespace folly {
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template <typename ExecutorImpl>
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class FutureExecutor : public ExecutorImpl {
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public:
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template <typename... Args>
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explicit FutureExecutor(Args&&... args)
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: ExecutorImpl(std::forward<Args>(args)...) {}
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/*
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* Given a function func that returns a Future<T>, adds that function to the
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* contained Executor and returns a Future<T> which will be fulfilled with
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* func's result once it has been executed.
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*
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* For example: auto f = futureExecutor.addFuture([](){
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* return doAsyncWorkAndReturnAFuture();
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* });
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*/
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template <typename F>
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typename std::enable_if<
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folly::isFuture<invoke_result_t<F>>::value,
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invoke_result_t<F>>::type
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addFuture(F func) {
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using T = typename invoke_result_t<F>::value_type;
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folly::Promise<T> promise;
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auto future = promise.getFuture();
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ExecutorImpl::add([promise = std::move(promise),
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func = std::move(func)]() mutable {
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func().then([promise = std::move(promise)](folly::Try<T>&& t) mutable {
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promise.setTry(std::move(t));
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});
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});
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return future;
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}
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/*
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* Similar to addFuture above, but takes a func that returns some non-Future
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* type T.
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*
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* For example: auto f = futureExecutor.addFuture([]() {
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* return 42;
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* });
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*/
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template <typename F>
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typename std::enable_if<
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!folly::isFuture<invoke_result_t<F>>::value,
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folly::Future<folly::lift_unit_t<invoke_result_t<F>>>>::type
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addFuture(F func) {
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using T = folly::lift_unit_t<invoke_result_t<F>>;
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folly::Promise<T> promise;
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auto future = promise.getFuture();
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ExecutorImpl::add(
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[promise = std::move(promise), func = std::move(func)]() mutable {
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promise.setWith(std::move(func));
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});
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return future;
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}
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};
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} // namespace folly
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