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  1. #include <atomic>
  2. #include <condition_variable>
  3. #include <iostream>
  4. #include <mutex>
  5. #include <queue>
  6. #include <string>
  7. #include <thread>
  8.  
  9. template <typename T>
  10. class ThreadSafeQueue
  11. {
  12. public:
  13.     ThreadSafeQueue() { }
  14.     ~ThreadSafeQueue() { }
  15.  
  16.     bool
  17.     empty()
  18.     {
  19.         return(_queue.empty());
  20.     }
  21.  
  22.     T
  23.     pop()
  24.     {
  25.         std::unique_lock<std::mutex> mlock(_mutex);
  26.         while (_queue.empty())
  27.         {
  28.             _cond.wait(mlock);
  29.         }
  30.  
  31.         auto item = _queue.front();
  32.         _queue.pop();
  33.  
  34.         return(item);
  35.     }
  36.  
  37.     void
  38.     pop(T& item)
  39.     {
  40.         std::unique_lock<std::mutex> mlock(_mutex);
  41.  
  42.         while (_queue.empty())
  43.         {
  44.           _cond.wait(mlock);
  45.         }
  46.  
  47.         item = _queue.front();
  48.         _queue.pop();
  49.     }
  50.  
  51.     void
  52.     push(const T& item)
  53.     {
  54.         std::unique_lock<std::mutex> mlock(_mutex);
  55.  
  56.         _queue.push(item);
  57.         mlock.unlock();
  58.         _cond.notify_one();
  59.     }
  60.  
  61.     void
  62.     push(T&& item)
  63.     {
  64.         std::unique_lock<std::mutex> mlock(_mutex);
  65.         _queue.push(std::move(item));
  66.         mlock.unlock();
  67.         _cond.notify_one();
  68.     }
  69.  
  70. private:
  71.     std::queue<T> _queue;
  72.     std::mutex _mutex;
  73.     std::condition_variable _cond;
  74. };
  75.  
  76. int main() {
  77. 	ThreadSafeQueue<std::string> q;
  78. 	const int TOTAL = 100000;
  79. 	const int N = 10; // must evenly divide TOTAL
  80.  
  81. 	std::atomic<int> count;
  82. 	std::vector<std::thread> poppers;
  83.  
  84.     for (int i = 0; i < N; ++i)
  85. 		poppers.emplace_back([&]{ for(int i = 0; i < TOTAL / N; ++i) if (q.pop() == "foo") ++count; });
  86.  
  87. 	std::thread pusher([&]{ for(int i = 0; i < TOTAL; ++i) q.push("foo"); });
  88.  
  89. 	pusher.join();
  90.  	for (auto& popper : poppers)
  91. 		popper.join();
  92.  
  93.     std::cout << "Queue is " << (q.empty() ? "" : "NOT ") << "empty" << std::endl;
  94.     std::cout << "Number of elements pushed = " << TOTAL << std::endl;
  95.     std::cout << "Number of elements popped = " << count << std::endl;
  96.  
  97. 	return 0;
  98. }
Success #stdin #stdout 0.01s 7188KB
comments (?)
stdin 
Standard input is empty
stdout 
Queue is empty
Number of elements pushed = 100000
Number of elements popped = 111007
https://ideone.com/CSRoG3
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
secret

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