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.
   */
  
  #include <folly/futures/Future.h>
  #include <folly/Likely.h>
  #include <folly/futures/ThreadWheelTimekeeper.h>
  
  namespace folly {
  namespace futures {
  
  SemiFuture<Unit> sleep(HighResDuration dur, Timekeeper* tk) {
    std::shared_ptr<Timekeeper> tks;
    if (LIKELY(!tk)) {
      tks = folly::detail::getTimekeeperSingleton();
      tk = tks.get();
    }
  
    if (UNLIKELY(!tk)) {
      return makeSemiFuture<Unit>(FutureNoTimekeeper());
    }
  
    return tk->after(dur);
  }
  
  Future<Unit> sleepUnsafe(HighResDuration dur, Timekeeper* tk) {
    return sleep(dur, tk).toUnsafeFuture();
  }
  
  #if FOLLY_FUTURE_USING_FIBER
  
  namespace {
  template <typename Ptr>
  class FutureWaiter : public fibers::Baton::Waiter {
   public:
    FutureWaiter(Promise<Unit> promise, Ptr baton)
        : promise_(std::move(promise)), baton_(std::move(baton)) {
      baton_->setWaiter(*this);
    }
  
    void post() override {
      promise_.setValue();
      delete this;
    }
  
   private:
    Promise<Unit> promise_;
    Ptr baton_;
  };
  } // namespace
  
  SemiFuture<Unit> wait(std::unique_ptr<fibers::Baton> baton) {
    Promise<Unit> promise;
    auto sf = promise.getSemiFuture();
    new FutureWaiter<std::unique_ptr<fibers::Baton>>(
        std::move(promise), std::move(baton));
    return sf;
  }
  SemiFuture<Unit> wait(std::shared_ptr<fibers::Baton> baton) {
    Promise<Unit> promise;
    auto sf = promise.getSemiFuture();
    new FutureWaiter<std::shared_ptr<fibers::Baton>>(
        std::move(promise), std::move(baton));
    return sf;
  }
  
  #endif
  
  } // namespace futures
  } // namespace folly
  