1 /*
2  * Copyright (C) 2016 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #ifndef LIBMEMUNREACHABLE_SEMAPHORE_H_
18 #define LIBMEMUNREACHABLE_SEMAPHORE_H_
19 
20 #include <chrono>
21 #include <mutex>
22 
23 #include "android-base/macros.h"
24 
25 namespace android {
26 
27 class Semaphore {
28  public:
29   explicit Semaphore(int count = 0) : count_(count) {}
30   ~Semaphore() = default;
31 
32   void Wait(std::chrono::milliseconds ms) {
33     std::unique_lock<std::mutex> lk(m_);
34     cv_.wait_for(lk, ms, [&] {
35       if (count_ > 0) {
36         count_--;
37         return true;
38       }
39       return false;
40     });
41   }
42   void Post() {
43     {
44       std::lock_guard<std::mutex> lk(m_);
45       count_++;
46     }
47     cv_.notify_one();
48   }
49 
50  private:
51   DISALLOW_COPY_AND_ASSIGN(Semaphore);
52 
53   int count_;
54   std::mutex m_;
55   std::condition_variable cv_;
56 };
57 
58 }  // namespace android
59 
60 #endif  // LIBMEMUNREACHABLE_SEMAPHORE_H_
61