Wait.h

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/*
 * Copyright 2017-present Facebook, Inc.
 *
 * 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.
 */
#pragma once

#include <experimental/coroutine>
#include <future>

namespace folly {
namespace coro {

class Wait {
 public:
  class promise_type {
   public:
    Wait get_return_object() {
      return Wait(promise_.get_future());
    }

    std::experimental::suspend_never initial_suspend() {
      return {};
    }

    std::experimental::suspend_never final_suspend() {
      return {};
    }

    void return_void() {
      promise_.set_value();
    }

    void unhandled_exception() {
      promise_.set_exception(std::current_exception());
    }

   private:
    std::promise<void> promise_;
  };

  explicit Wait(std::future<void> future) : future_(std::move(future)) {}

  Wait(Wait&&) = default;

  void detach() {
    future_ = {};
  }

  ~Wait() {
    if (future_.valid()) {
      future_.get();
    }
  }

 private:
  std::future<void> future_;
};
} // namespace coro
} // namespace folly