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-// Copyright 2017 The Abseil Authors.
-//
-// 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
-//
-//      https://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.
-//
-// -----------------------------------------------------------------------------
-// notification.h
-// -----------------------------------------------------------------------------
-//
-// This header file defines a `Notification` abstraction, which allows threads
-// to receive notification of a single occurrence of a single event.
-//
-// The `Notification` object maintains a private boolean "notified" state that
-// transitions to `true` at most once. The `Notification` class provides the
-// following primary member functions:
-//   * `HasBeenNotified() `to query its state
-//   * `WaitForNotification*()` to have threads wait until the "notified" state
-//      is `true`.
-//   * `Notify()` to set the notification's "notified" state to `true` and
-//     notify all waiting threads that the event has occurred.
-//     This method may only be called once.
-//
-// Note that while `Notify()` may only be called once, it is perfectly valid to
-// call any of the `WaitForNotification*()` methods multiple times, from
-// multiple threads -- even after the notification's "notified" state has been
-// set -- in which case those methods will immediately return.
-//
-// Note that the lifetime of a `Notification` requires careful consideration;
-// it might not be safe to destroy a notification after calling `Notify()` since
-// it is still legal for other threads to call `WaitForNotification*()` methods
-// on the notification. However, observers responding to a "notified" state of
-// `true` can safely delete the notification without interfering with the call
-// to `Notify()` in the other thread.
-//
-// Memory ordering: For any threads X and Y, if X calls `Notify()`, then any
-// action taken by X before it calls `Notify()` is visible to thread Y after:
-//  * Y returns from `WaitForNotification()`, or
-//  * Y receives a `true` return value from either `HasBeenNotified()` or
-//    `WaitForNotificationWithTimeout()`.
-
-#ifndef ABSL_SYNCHRONIZATION_NOTIFICATION_H_
-#define ABSL_SYNCHRONIZATION_NOTIFICATION_H_
-
-#include <atomic>
-
-#include "absl/base/macros.h"
-#include "absl/synchronization/mutex.h"
-#include "absl/time/time.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-
-// -----------------------------------------------------------------------------
-// Notification
-// -----------------------------------------------------------------------------
-class Notification {
- public:
-  // Initializes the "notified" state to unnotified.
-  Notification() : notified_yet_(false) {}
-  explicit Notification(bool prenotify) : notified_yet_(prenotify) {}
-  Notification(const Notification&) = delete;
-  Notification& operator=(const Notification&) = delete;
-  ~Notification();
-
-  // Notification::HasBeenNotified()
-  //
-  // Returns the value of the notification's internal "notified" state.
-  bool HasBeenNotified() const {
-    return HasBeenNotifiedInternal(&this->notified_yet_);
-  }
-
-  // Notification::WaitForNotification()
-  //
-  // Blocks the calling thread until the notification's "notified" state is
-  // `true`. Note that if `Notify()` has been previously called on this
-  // notification, this function will immediately return.
-  void WaitForNotification() const;
-
-  // Notification::WaitForNotificationWithTimeout()
-  //
-  // Blocks until either the notification's "notified" state is `true` (which
-  // may occur immediately) or the timeout has elapsed, returning the value of
-  // its "notified" state in either case.
-  bool WaitForNotificationWithTimeout(absl::Duration timeout) const;
-
-  // Notification::WaitForNotificationWithDeadline()
-  //
-  // Blocks until either the notification's "notified" state is `true` (which
-  // may occur immediately) or the deadline has expired, returning the value of
-  // its "notified" state in either case.
-  bool WaitForNotificationWithDeadline(absl::Time deadline) const;
-
-  // Notification::Notify()
-  //
-  // Sets the "notified" state of this notification to `true` and wakes waiting
-  // threads. Note: do not call `Notify()` multiple times on the same
-  // `Notification`; calling `Notify()` more than once on the same notification
-  // results in undefined behavior.
-  void Notify();
-
- private:
-  static inline bool HasBeenNotifiedInternal(
-      const std::atomic<bool>* notified_yet) {
-    return notified_yet->load(std::memory_order_acquire);
-  }
-
-  mutable Mutex mutex_;
-  std::atomic<bool> notified_yet_;  // written under mutex_
-};
-
-ABSL_NAMESPACE_END
-}  // namespace absl
-
-#endif  // ABSL_SYNCHRONIZATION_NOTIFICATION_H_