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Defined in header <stop_token> | ||
class stop_source; | (since C++20) | |
Thestop_source class provides the means to issue a stop request, such as forstd::jthread cancellation. A stop request made for onestop_source object is visible to allstop_sources andstd::stop_tokens of the same associated stop-state; anystd::stop_callback(s) registered for associatedstd::stop_token(s) will be invoked, and anystd::condition_variable_any objects waiting on associatedstd::stop_token(s) will be awoken.
Once a stop is requested, it cannot be withdrawn. Additional stop requests have no effect.
Contents |
constructs newstop_source object(public member function)[edit] | |
destructs thestop_source object(public member function)[edit] | |
assigns thestop_source object(public member function)[edit] | |
Modifiers | |
| makes a stop request for the associated stop-state, if any (public member function)[edit] | |
swaps twostop_source objects(public member function)[edit] | |
Observers | |
returns astop_token for the associated stop-state(public member function)[edit] | |
| checks whether the associated stop-state has been requested to stop (public member function)[edit] | |
| checks whether associated stop-state can be requested to stop (public member function)[edit] | |
(C++20) | compares twostd::stop_source objects(function)[edit] |
(C++20) | specializes thestd::swap algorithm (function)[edit] |
(C++20) | a tag used forstop_source to indicate no associated stop-state upon construction(tag)[edit] |
For the purposes ofstd::jthread cancellation thestop_source object should be retrieved from thestd::jthread object usingget_stop_source(); or stop should be requested directly from thestd::jthread object usingrequest_stop(). This will then use the same associated stop-state as that passed into thestd::jthread's invoked function argument (i.e., the function being executed on its thread).
For other uses, however, astop_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 andjoining thread |
#include <chrono>#include <iostream>#include <stop_token>#include <thread> usingnamespace 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 threadsfor(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 sleepRequest stopstop_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
