text: /*
   * Copyright (c) Facebook, Inc. and its affiliates.
   *
   * 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 <type_traits>
  
  #include <folly/experimental/coro/Baton.h>
  #include <folly/experimental/coro/Invoke.h>
  #include <folly/experimental/coro/Task.h>
  #include <folly/experimental/coro/Traits.h>
  #include <folly/experimental/coro/detail/Helpers.h>
  
  namespace folly {
  namespace coro {
  template <typename Awaitable>
  Task<semi_await_result_t<Awaitable>> detachOnCancel(Awaitable awaitable) {
    auto posted = std::make_unique<std::atomic<bool>>(false);
    Baton baton;
    Try<detail::lift_lvalue_reference_t<semi_await_result_t<Awaitable>>> result;
  
    co_invoke(
        [awaitable = std::move(
             awaitable)]() mutable -> Task<semi_await_result_t<Awaitable>> {
          co_return co_await std::move(awaitable);
        })
        .scheduleOn(co_await co_current_executor)
        .startInlineUnsafe(
            [postedPtr = posted.get(), &baton, &result](auto&& r) {
              std::unique_ptr<std::atomic<bool>> p(postedPtr);
              if (!p->exchange(true, std::memory_order_relaxed)) {
                p.release();
                tryAssign(result, std::move(r));
                baton.post();
              }
            },
            co_await co_current_cancellation_token);
    {
      CancellationCallback cancelCallback(
          co_await co_current_cancellation_token, [&posted, &baton, &result] {
            if (!posted->exchange(true, std::memory_order_relaxed)) {
              posted.release();
              result.emplaceException(folly::OperationCancelled{});
              baton.post();
            }
          });
      co_await baton;
    }
  
    if (result.hasException()) {
      co_yield folly::coro::co_error(result.exception());
    }
  
    co_return std::move(result).value();
  }
  } // namespace coro
  } // namespace folly
  