text: /******************************************************************************
   *
   *  Copyright (C) 2014 Google, Inc.
   *
   *  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
  
  typedef struct future_t future_t;
  
  #define FUTURE_SUCCESS ((void *)1)
  #define FUTURE_FAIL ((void *)0)
  
  // Constructs a new future_t object. Returns NULL on failure.
  future_t *future_new(void);
  
  // Constructs a new future_t object with an immediate |value|. No waiting will
  // occur in the call to |future_await| because the value is already present.
  // Returns NULL on failure.
  future_t *future_new_immediate(void *value);
  
  // Signals that the |future| is ready, passing |value| back to the context
  // waiting for the result. Must only be called once for every future.
  // |future| may not be NULL.
  void future_ready(future_t *future, void *value);
  
  // Waits for the |future| to be ready. Returns the value set in |future_ready|.
  // Frees the future before return. |future| may not be NULL.
  void *future_await(future_t *async_result);
  