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      1 /******************************************************************************
      2  *
      3  *  Copyright (C) 2014 Google, Inc.
      4  *
      5  *  Licensed under the Apache License, Version 2.0 (the "License");
      6  *  you may not use this file except in compliance with the License.
      7  *  You may obtain a copy of the License at:
      8  *
      9  *  http://www.apache.org/licenses/LICENSE-2.0
     10  *
     11  *  Unless required by applicable law or agreed to in writing, software
     12  *  distributed under the License is distributed on an "AS IS" BASIS,
     13  *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     14  *  See the License for the specific language governing permissions and
     15  *  limitations under the License.
     16  *
     17  ******************************************************************************/
     18 
     19 #pragma once
     20 
     21 typedef struct future_t future_t;
     22 
     23 #define FUTURE_SUCCESS ((void*)1)
     24 #define FUTURE_FAIL ((void*)0)
     25 
     26 // Constructs a new future_t object. Returns NULL on failure.
     27 future_t* future_new(void);
     28 
     29 // Constructs a new future_t object with an immediate |value|. No waiting will
     30 // occur in the call to |future_await| because the value is already present.
     31 // Returns NULL on failure.
     32 future_t* future_new_immediate(void* value);
     33 
     34 // Signals that the |future| is ready, passing |value| back to the context
     35 // waiting for the result. Must only be called once for every future.
     36 // |future| may not be NULL.
     37 void future_ready(future_t* future, void* value);
     38 
     39 // Waits for the |future| to be ready. Returns the value set in |future_ready|.
     40 // Frees the future before return. |future| may not be NULL.
     41 void* future_await(future_t* async_result);
     42