Examples of stop_token
Example 1
In the below code, we will make use of the above syntax to demonstrate the use of the <stop_token> Header.
C++
// C++ Program to illustrate the stop_token #include <chrono> #include <iostream> #include <stop_token> #include <thread> using namespace std; // callable function for thread void worker(stop_token stopToken) { // checking if the stop request is made using // stop_request method of stop_token class while (!stopToken.stop_requested()) { cout << "Working..." << endl; this_thread::sleep_for(chrono::seconds(1)); } cout << "Cancelled." << endl; } // driver code int main() { // creating stop_source object stop_source stopSource; // creating stop_token object stop_token stopToken = stopSource.get_token(); // starting thread thread t(worker, stopToken); this_thread::sleep_for(chrono::seconds(5)); // requesting stop stopSource.request_stop(); t.join(); return 0; } |
Output
Working... Working... Working... Working... Working... Cancelled.
Explanation: In this example, A novel std::stop_source is established along with its associate, a std::stop_token. After passing the stopToken object as a parameter to the worker function, a new thread is initiated.
The worker function employs the stop_requested() function to verify if there are any cancellation petitions. After waiting for approximately 5 seconds, it seeks for cancellation by requesting the stopSource object to stop via the request_stop() function. Finally, we join the thread and exit the program.
Example 2
C++
// C++ program to illustrate the use of stop_token #include <chrono> #include <iostream> #include <stop_token> #include <thread> using namespace std; // thread callable class Worker { public: void run(stop_token stopToken) { while (!stopToken.stop_requested()) { cout << "Working..." << endl; this_thread::sleep_for(chrono::seconds(1)); } cout << "Cancelled." << endl; } }; // driver code int main() { // creating stop_source and stop_token objects stop_source stopSource; stop_token stopToken = stopSource.get_token(); // initializing thread Worker worker; thread t(&Worker::run, &worker, stopToken); this_thread::sleep_for(chrono::seconds(5)); // requesting stop after 5 seconds stopSource.request_stop(); t.join(); return 0; } |
Output
Working... Working... Working... Cancelled.
Explanation: In this example, Upon defining a class named Worker, we create a function run that expects a stopToken of std::type to be passed as a parameter. We initiate a thread to run the Worker object’s run method, providing the stopToken object as an argument. The run method frequently checks the stop_requested() function of the stopToken object to ensure that the cancellation requests are taken into consideration.
C++ 20 – Header
C++20 has introduced the <stop_token> Header, presenting an alternative method for canceling asynchronous operations. A new class std::stop_token is provided by the <stop_token> header that allows for seamless communication of a termination request between two threads.
In this article, we will discuss the basics of <stop_token> and how to use it in C++20.
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