std::condition_variable::wait_for - cppreference.com
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(1) | (desde C++11) |
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(2) | (desde C++11) |
1)
Atomicamente libera lock, bloqueia a thread atual em execução, e acrescenta-lo à lista de espera da thread em *this. A discussão será desbloqueado quando notify_all() ou notify_one() é executado, ou quando o tempo limite rel_time relativa expirar. Também pode ser desbloqueado spuriously. Quando desbloqueado, independentemente do motivo, lock é readquirido e sai wait_for(). Se esta função saídas via de exceção, lock também é readquirida.
Original:
Atomically releases lock, blocks the current executing thread, and adds it to the list of threads waiting on *this. The thread will be unblocked when notify_all() or notify_one() is executed, or when the relative timeout rel_time expires. It may also be unblocked spuriously. When unblocked, regardless of the reason, lock is reacquired and wait_for() exits. If this function exits via exception, lock is also reacquired.
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2)
Equivalente a
Original:
Equivalent to
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while (!pred()) if (wait_for(lock, rel_time) == std::cv_status::timeout) return pred(); return true;
Essa sobrecarga pode ser usada para ignorar despertares espúrios.
Original:
This overload may be used to ignore spurious awakenings.
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Parâmetros
| lock | - | um objeto de Original: an object of type The text has been machine-translated via Google Translate. |
| rel_time | - | um objeto de std::chrono::duration tipo que representa o tempo máximo de espera para gastar Original: an object of type std::chrono::duration representing the maximum time to spend waiting The text has been machine-translated via Google Translate. |
| pred | - | predicate which returns false se o tempo de espera deve ser continuado Original: if the waiting should be continued The text has been machine-translated via Google Translate. The signature of the predicate function should be equivalent to the following:
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Valor de retorno
1)
std::cv_status::timeout se o tempo limite relativo especificado pelo rel_time expirado, std::cv_status::no_timeout overwise.
Original:
std::cv_status::timeout if the relative timeout specified by rel_time expired, std::cv_status::no_timeout overwise.
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2)
false se o predicado pred ainda avalia a false após o tempo limite expirou rel_time, caso contrário true.
Original:
false if the predicate pred still evaluates to false after the rel_time timeout expired, otherwise true.
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Exceções
Pode lançar std::system_error, também podem propagar exceções lançadas por lock.lock() ou lock.unlock().
Original:
May throw std::system_error, may also propagate exceptions thrown by lock.lock() or lock.unlock().
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Notas
Chamar essa função se lock.mutex() não está bloqueada pelo atual segmento é um comportamento indefinido.
Original:
Calling this function if lock.mutex() is not locked by the current thread is undefined behavior.
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Chamar essa função se lock.mutex() não é o mesmo mutex como o utilizado por todos os outros segmentos que estão aguardando na variável mesma condição é um comportamento indefinido.
Original:
Calling this function if lock.mutex() is not the same mutex as the one used by all other threads that are currently waiting on the same condition variable is undefined behavior.
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Exemplo
#include <iostream> #include <atomic> #include <condition_variable> #include <thread> #include <chrono> std::condition_variable cv; std::mutex cv_m; std::atomic<int> i = ATOMIC_VAR_INIT(0); void waits(int idx) { std::unique_lock<std::mutex> lk(cv_m); if(cv.wait_for(lk, std::chrono::milliseconds(idx*100), [](){return i == 1;})) std::cerr << "Thread " << idx << " finished waiting. i == " << i << '\n'; else std::cerr << "Thread " << idx << " timed out. i == " << i << '\n'; } void signals() { std::this_thread::sleep_for(std::chrono::milliseconds(120)); std::cerr << "Notifying...\n"; cv.notify_all(); std::this_thread::sleep_for(std::chrono::milliseconds(100)); i = 1; std::cerr << "Notifying again...\n"; cv.notify_all(); } int main() { std::thread t1(waits, 1), t2(waits, 2), t3(waits, 3), t4(signals); t1.join(); t2.join(), t3.join(), t4.join(); }
Saída:
Thread 1 timed out. i == 0 Notifying... Thread 2 timed out. i == 0 Notifying again... Thread 3 finished waiting. i == 1
Veja também
bloqueia o segmento atual até que a variável de condição é acordado Original: blocks the current thread until the condition variable is woken up The text has been machine-translated via Google Translate. (função pública membro) [edit] | |
bloqueia o segmento atual até que a variável de condição é acordado ou até ponto de tempo especificado foi alcançado Original: blocks the current thread until the condition variable is woken up or until specified time point has been reached The text has been machine-translated via Google Translate. (função pública membro) [edit] | |