text: /**
   * Copyright (c) Facebook, Inc. and its affiliates.
   *
   * This source code is licensed under the MIT license found in the
   * LICENSE file in the root directory of this source tree.
   */
  
  #import <Foundation/Foundation.h>
  
  #import <ReactABI34_0_0/ABI34_0_0RCTAssert.h>
  #import <ReactABI34_0_0/ABI34_0_0RCTDefines.h>
  
  /**
   * Queues Problem Intro:
   * UIManager queue is a special queue because it has a special relationship with
   * the Main queue.
   *
   * This particular relationship comes from two key factors:
   *  1. UIManager initiates execution of many blocks on the Main queue;
   *  2. In some cases, we want to initiate (and wait for) some UIManager's work *synchronously* from
   *     the Main queue.
   *
   * So, how can we meet these criteria?
   * "Pseudo UIManager queue" comes to rescue!
   *
   * "Pseudo UIManager queue" means the safe execution of typical UIManager's work
   * on the Main queue while the UIManager queue is explicitly blocked for preventing
   * simultaneous/concurrent memory access.
   *
   * So, how can we technically do this?
   *  1. `ABI34_0_0RCTAssertUIManagerQueue` is okay with execution on both actual UIManager and
   *     Pseudo UIManager queues.
   *  2. Both `ABI34_0_0RCTExecuteOnUIManagerQueue` and `ABI34_0_0RCTUnsafeExecuteOnUIManagerQueueSync`
   *     execute given block *synchronously* if they were called on actual UIManager
   *     or Pseudo UIManager queues.
   *  3. `ABI34_0_0RCTExecuteOnMainQueue` executes given block *synchronously* if we already on
   *     the Main queue.
   *  4. `ABI34_0_0RCTUnsafeExecuteOnUIManagerQueueSync` is smart enough to do the trick:
   *     It detects calling on the Main queue and in this case, instead of doing
   *     trivial *synchronous* dispatch, it does:
   *       - Block the Main queue;
   *       - Dispatch the special block on UIManager queue to block the queue and
   *         concurrent memory access;
   *       - Execute the given block on the Main queue;
   *       - Unblock the UIManager queue.
   *
   * Imagine the analogy: We have two queues: the Main one and UIManager one.
   * And these queues are two lanes of railway that go in parallel. Then,
   * at some point, we merge UIManager lane with the Main lane, and all cars use
   * the unified the Main lane.
   * And then we split lanes again.
   *
   * This solution assumes that the code running on UIManager queue will never
   * *explicitly* block the Main queue via calling `ABI34_0_0RCTUnsafeExecuteOnMainQueueSync`.
   * Otherwise, it can cause a deadlock.
   */
  
  /**
   * Returns UIManager queue.
   */
  ABI34_0_0RCT_EXTERN dispatch_queue_t ABI34_0_0RCTGetUIManagerQueue(void);
  
  /**
   * Default name for the UIManager queue.
   */
  ABI34_0_0RCT_EXTERN char *const ABI34_0_0RCTUIManagerQueueName;
  
  /**
   * Check if we are currently on UIManager queue.
   * Please do not use this unless you really know what you're doing.
   */
  ABI34_0_0RCT_EXTERN BOOL ABI34_0_0RCTIsUIManagerQueue(void);
  
  /**
   * Check if we are currently on Pseudo UIManager queue.
   * Please do not use this unless you really know what you're doing.
   */
  ABI34_0_0RCT_EXTERN BOOL ABI34_0_0RCTIsPseudoUIManagerQueue(void);
  
  /**
   * *Asynchronously* executes the specified block on the UIManager queue.
   * Unlike `dispatch_async()` this will execute the block immediately
   * if we're already on the UIManager queue.
   */
  ABI34_0_0RCT_EXTERN void ABI34_0_0RCTExecuteOnUIManagerQueue(dispatch_block_t block);
  
  /**
   * *Synchorously* executes the specified block on the UIManager queue.
   * Unlike `dispatch_sync()` this will execute the block immediately
   * if we're already on the UIManager queue.
   * Please do not use this unless you really know what you're doing.
   */
  ABI34_0_0RCT_EXTERN void ABI34_0_0RCTUnsafeExecuteOnUIManagerQueueSync(dispatch_block_t block);
  
  /**
   * Convenience macro for asserting that we're running on UIManager queue.
   */
  #define ABI34_0_0RCTAssertUIManagerQueue() ABI34_0_0RCTAssert(ABI34_0_0RCTIsUIManagerQueue() || ABI34_0_0RCTIsPseudoUIManagerQueue(), \
  @"This function must be called on the UIManager queue")
  
  /**
   * Returns new unique root view tag.
   */
  ABI34_0_0RCT_EXTERN NSNumber *ABI34_0_0RCTAllocateRootViewTag(void);
  