text: /* Copyright (c) 2014-present, Facebook, Inc.
   * All rights reserved.
   *
   * This source code is licensed under the BSD-style license found in the
   * LICENSE file in the root directory of this source tree. An additional grant
   * of patent rights can be found in the PATENTS file in the same directory.
   */
  
  #import <Foundation/Foundation.h>
  
  /**
   @summary We want to avoid capturing layer instances on a background queue, but we want a way to cancel rendering
   immediately if another display pass begins.  ASSentinel is owned by the layer and passed to the background
   block.
   */
  @interface ASSentinel : NSObject
  
  /**
   Returns the current value of the sentinel.
   */
  - (int32_t)value;
  
  /**
   Atomically increments the value and returns the new value.
   */
  - (int32_t)increment;
  
  @end
  