1 /******************************************************************************
2  *
3  *  Copyright 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 #define LOG_TAG "bt_osi_future"
20 
21 #include "osi/include/future.h"
22 
23 #include <base/logging.h>
24 
25 #include "osi/include/allocator.h"
26 #include "osi/include/log.h"
27 #include "osi/include/osi.h"
28 #include "osi/include/semaphore.h"
29 
30 struct future_t {
31   bool ready_can_be_called;
32   semaphore_t* semaphore;  // NULL semaphore means immediate future
33   void* result;
34 };
35 
36 static void future_free(future_t* future);
37 
future_new(void)38 future_t* future_new(void) {
39   future_t* ret = static_cast<future_t*>(osi_calloc(sizeof(future_t)));
40 
41   ret->semaphore = semaphore_new(0);
42   if (!ret->semaphore) {
43     LOG_ERROR("%s unable to allocate memory for the semaphore.", __func__);
44     goto error;
45   }
46 
47   ret->ready_can_be_called = true;
48   return ret;
49 error:;
50   future_free(ret);
51   return NULL;
52 }
53 
future_new_immediate(void * value)54 future_t* future_new_immediate(void* value) {
55   future_t* ret = static_cast<future_t*>(osi_calloc(sizeof(future_t)));
56 
57   ret->result = value;
58   ret->ready_can_be_called = false;
59   return ret;
60 }
61 
future_ready(future_t * future,void * value)62 void future_ready(future_t* future, void* value) {
63   CHECK(future != NULL);
64   CHECK(future->ready_can_be_called);
65 
66   future->ready_can_be_called = false;
67   future->result = value;
68   semaphore_post(future->semaphore);
69 }
70 
future_await(future_t * future)71 void* future_await(future_t* future) {
72   CHECK(future != NULL);
73 
74   // If the future is immediate, it will not have a semaphore
75   if (future->semaphore) semaphore_wait(future->semaphore);
76 
77   void* result = future->result;
78   future_free(future);
79   return result;
80 }
81 
future_free(future_t * future)82 static void future_free(future_t* future) {
83   if (!future) return;
84 
85   semaphore_free(future->semaphore);
86   osi_free(future);
87 }
88