std::stop_source - cppreference.com (original) (raw)
| | | | | ------------------- | | ------------- | | class stop_source; | | (since C++20) |
The stop_source class provides the means to issue a stop request, such as for std::jthread cancellation. A stop request made for one stop_source object is visible to all stop_sources and std::stop_tokens of the same associated stop-state; any std::stop_callback(s) registered for associated std::stop_token(s) will be invoked, and any std::condition_variable_any objects waiting on associated std::stop_token(s) will be awoken.
Once a stop is requested, it cannot be withdrawn. Additional stop requests have no effect.
Contents
[edit] Member functions
| (constructor) | constructs new stop_source object (public member function) [edit] |
|---|---|
| (destructor) | destructs the stop_source object (public member function) [edit] |
| operator= | assigns the stop_source object (public member function) [edit] |
| Modifiers | |
| request_stop | makes a stop request for the associated stop-state, if any (public member function) [edit] |
| swap | swaps two stop_source objects (public member function) [edit] |
| Observers | |
| get_token | returns a stop_token for the associated stop-state (public member function) [edit] |
| stop_requested | checks whether the associated stop-state has been requested to stop (public member function) [edit] |
| stop_possible | checks whether associated stop-state can be requested to stop (public member function) [edit] |
[edit] Non-member functions
[edit] Helper tags
[edit] Notes
For the purposes of std::jthread cancellation the stop_source object should be retrieved from the std::jthread object using get_stop_source(); or stop should be requested directly from the std::jthread object using request_stop(). This will then use the same associated stop-state as that passed into the std::jthread's invoked function argument (i.e., the function being executed on its thread).
For other uses, however, a stop_source can be constructed separately using the default constructor, which creates new stop-state.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
| __cpp_lib_jthread | 201911L | (C++20) | Stop token and joining thread |
[edit] Example
#include #include #include #include using namespace std::chrono_literals; void worker_fun(int id, std::stop_token stoken) { for (int i = 10; i; --i) { std::this_thread::sleep_for(300ms); if (stoken.stop_requested()) { std::printf(" worker%d is requested to stop\n", id); return; } std::printf(" worker%d goes back to sleep\n", id); } } int main() { std::jthread threads[4]; std::cout << std::boolalpha; auto print = [](const std::stop_source& source) { std::printf("stop_source stop_possible = %s, stop_requested = %s\n", source.stop_possible() ? "true" : "false", source.stop_requested() ? "true" : "false"); }; // Common source std::stop_source stop_source; print(stop_source); // Create worker threads for (int i = 0; i < 4; ++i) threads[i] = std::jthread(worker_fun, i + 1, stop_source.get_token()); std::this_thread::sleep_for(500ms); std::puts("Request stop"); stop_source.request_stop(); print(stop_source); // Note: destructor of jthreads will call join so no need for explicit calls }
Possible output:
stop_source stop_possible = true, stop_requested = false worker2 goes back to sleep worker3 goes back to sleep worker1 goes back to sleep worker4 goes back to sleep Request stop stop_source stop_possible = true, stop_requested = true worker3 is requested to stop worker1 is requested to stop worker2 is requested to stop worker4 is requested to stop