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  1. #include <iostream>
  2. #include <list>
  3. #include <thread>
  4. #include <mutex>
  5. #include <condition_variable>
  6.  
  7. using namespace std;
  8. //list element
  9. class myitem
  10. {
  11. public:
  12.     myitem() { val = -1; };
  13.     myitem(int n, int c){ val = n; chr = c; };
  14.     int val;
  15.     char chr;
  16. };
  17.  
  18. // mutex and condition variable to protect the list.
  19. std::mutex mymtx;
  20. condition_variable mycv;
  21.     // the list to be protected
  22.     std::list<myitem> mylist;  
  23.     // the atomic flag to test.
  24.     std::atomic_flag testlk;
  25.  
  26. void datagenthread(char c)
  27. {
  28.    int n = 10*1000*1000;
  29.    while(n >0)
  30.    {
  31.       myitem item(n, c);
  32.       {
  33.          unique_lock<mutex> lk(mymtx); // get the lock
  34.          if( testlk.test_and_set() != false) { // test the atomic flag
  35.             cout<<"error in thread"<<c<<" for test lock"<<endl; 
  36.          } 
  37.          mylist.push_back(item);
  38.          testlk.clear(); // clear the atomic before unlock.
  39.       }
  40.       mycv.notify_one();
  41.       n--;
  42.    }
  43. }
  44.  
  45. void datareadthread()
  46. {
  47.    int count = 0;
  48.    int readc = 0;
  49.    while ( count <2)  {
  50.       {
  51.          unique_lock<mutex> lk(mymtx); // acquire lock
  52.          while ( mylist.size() <= 0)   {
  53.             mycv.wait(lk); // block until the thread get notified and get lock again.
  54.          }
  55.          if( testlk.test_and_set()!= false)  {// test the atomic flag.
  56.             cout<<"error in reader thread"<<endl; 
  57.          }
  58.          myitem readitem;
  59.          readitem = mylist.front();
  60.          mylist.pop_front();
  61.          readc++;
  62.          if ( readitem.val == 1)
  63.          {
  64.             cout<<" get last one last item form a thread,"<<endl;
  65.             count++;
  66.          }
  67.          testlk.clear(); // clear the atomic flag before unlock
  68.       }//unique_lock destruct
  69.    }//end while
  70. }
  71. int main()
  72. {
  73.    std::thread cons(   datareadthread);
  74.    std::thread gen1(   datagenthread, 'a');
  75.    std::thread gen2(   datagenthread, 'b');
  76.    gen1.join();
  77.    gen2.join();
  78.    cons.join();
  79.    cout << "all done\n";
  80.    return 0;
  81. }
Success #stdin #stdout 2.81s 152448KB
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Standard input is empty
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 get last one last item form a thread,
 get last one last item form a thread,
all done
https://ideone.com/ld07Du
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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