c 2b 2b synchronization primitives example programs

1 
2#include <queue>
3#include <memory>
4#include <mutex>
5#include <condition_variable>
6template<typename T>
7class threadsafe_queue
8{
9private:
10    mutable std::mutex mut;      ❶ 
11    std::queue<T> data_queue;
12    std::condition_variable data_cond;
13public:
14    threadsafe_queue()
15    {}
16    threadsafe_queue(threadsafe_queue const& other)
17    {
18        std::lock_guard<std::mutex> lk(other.mut);
19        data_queue=other.data_queue;
20    }
21    void push(T new_value)
22    {
23        std::lock_guard<std::mutex> lk(mut);
24        data_queue.push(new_value);
25        data_cond.notify_one();
26    }
27    void wait_and_pop(T& value)
28    {
29        std::unique_lock<std::mutex> lk(mut);
30        data_cond.wait(lk,[this]{return !data_queue.empty();});
31        value=data_queue.front();
32        data_queue.pop();
33    }
34    std::shared_ptr<T> wait_and_pop()
35    {
36        std::unique_lock<std::mutex> lk(mut);
37        data_cond.wait(lk,[this]{return !data_queue.empty();});
38        std::shared_ptr<T> res(std::make_shared<T>(data_queue.front()));
39        data_queue.pop();
40        return res;
41    }
42    bool try_pop(T& value)
43    {
44        std::lock_guard<std::mutex> lk(mut);
45        if(data_queue.empty())
46            return false;
47        value=data_queue.front();
48        data_queue.pop();
49        return true;
50    }
51    std::shared_ptr<T> try_pop()
52    {
53        std::lock_guard<std::mutex> lk(mut);
54        if(data_queue.empty())
55            return std::shared_ptr<T>();
56        std::shared_ptr<T> res(std::make_shared<T>(data_queue.front()));
57        data_queue.pop();
58        return res;
59    }
60    bool empty() const
61    {
62        std::lock_guard<std::mutex> lk(mut);
63        return data_queue.empty();
64    }
65};
66 
67