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https://github.com/kidfromjupiter/nearby.git
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69 lines
2.3 KiB
C++
69 lines
2.3 KiB
C++
// Copyright 2020 Google LLC
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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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// https://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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#ifndef PLATFORM_PUBLIC_FUTURE_H_
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#define PLATFORM_PUBLIC_FUTURE_H_
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#include <memory>
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#include <utility>
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#include "absl/time/time.h"
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#include "internal/platform/exception.h"
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#include "internal/platform/implementation/executor.h"
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#include "internal/platform/settable_future.h"
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namespace nearby {
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template <typename T>
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class Future final {
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public:
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using FutureCallback = typename SettableFuture<T>::FutureCallback;
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// Default Future. Does not time out.
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Future() : impl_(std::make_shared<SettableFuture<T>>()) {}
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// Creates a Future with a timeout.
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explicit Future(absl::Duration timeout)
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: impl_(std::make_shared<SettableFuture<T>>(timeout)) {}
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virtual bool Set(T value) { return impl_->Set(std::move(value)); }
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virtual bool SetException(Exception exception) {
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return impl_->SetException(exception);
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}
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virtual ExceptionOr<T> Get() { return impl_->Get(); }
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virtual ExceptionOr<T> Get(absl::Duration timeout) {
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return impl_->Get(timeout);
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}
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void AddListener(FutureCallback callback, api::Executor* executor) {
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impl_->AddListener(std::move(callback), executor);
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}
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bool IsSet() const { return impl_->IsSet(); }
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private:
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// Instance of future implementation is wrapped in shared_ptr<> to make
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// it possible to pass Future by value and share the implementation.
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// This allows for the following constructions:
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// 1)
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// Future<bool> future;
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// RunOnXyzThread([future]() { future.Set(DoTheJobAndReport()); });
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// if (future.Get().Ok()) { /*...*/ }
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// 2)
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// Future<bool> future = DoSomeAsyncWork(); // Returns future, but keeps copy.
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// if (future.Get().Ok()) { /*...*/ }
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std::shared_ptr<SettableFuture<T>> impl_;
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};
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} // namespace nearby
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#endif // PLATFORM_PUBLIC_FUTURE_H_
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