std::condition_variable::wait_until
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<tbody> </tbody> template< class Clock, class Duration > std::cv_status wait_until( std::unique_lock<std::mutex>& lock, const std::chrono::time_point<Clock, Duration>& abs_time); |
(1) | (desde C++11) |
template< class Clock, class Duration, class Predicate > bool wait_until( std::unique_lock<mutex>& lock, const std::chrono::time_point<Clock, Duration>& abs_time, Predicate pred); |
(2) | (desde C++11) |
wait_until faz com que o thread atual para bloquear até que a variável de condição é notificado, um tempo específico é alcançado, ou um despertar espúria ocorre, opcionalmente looping até que algum predicado é satisfeito.Original:
wait_until causes the current thread to block until the condition variable is notified, a specific time is reached, or a spurious wakeup occurs, optionally looping until some predicate is satisfied.The text has been machine-translated via Google Translate.
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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 abs_time ponto absoluto de tempo for atingido. Também pode ser desbloqueado spuriously. Quando desbloqueado, independentemente do motivo, lock é readquirido e sai wait_until. 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 absolute time point abs_time is reached. It may also be unblocked spuriously. When unblocked, regardless of the reason, lock is reacquired and wait_until exits. If this function exits via exception, lock is also reacquired.The text has been machine-translated via Google Translate.
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2)
Equivalente a
Original:
Equivalent to
The text has been machine-translated via Google Translate.
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while (!pred()) if (wait_until(lock, abs_time) == std::cv_status::timeout) return pred(); return true;
Essa sobrecarga pode ser usada para ignorar wakeups espúrios.
Original:
This overload may be used to ignore spurious wakeups.
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Parâmetros
| lock | - | um objeto de tipo std :: unique_lock <std::mutex>, que deve ser bloqueado pelo thread atual
Original: an object of type std::unique_lock<std::mutex>, which must be locked by the current thread The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| abs_time | - | um objecto do tipo std::chrono::time_point representando o momento em que parar de esperar
Original: an object of type std::chrono::time_point representing the time when to stop waiting The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
| 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. You can help to correct and verify the translation. Click here for instructions. The signature of the predicate function should be equivalent to the following:
|
Valor de retorno
1)
std::cv_status::timeout se o tempo limite absoluto especificado por
abs_time foi alcançado, std::cv_status::no_timeout overwise.Original:
std::cv_status::timeout if the absolute timeout specified by
abs_time was reached, std::cv_status::no_timeout overwise.The text has been machine-translated via Google Translate.
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2)
false se o predicado pred ainda avalia a false após o tempo limite expirou abs_time, caso contrário true.Original:
false if the predicate pred still evaluates to false after the abs_time timeout expired, otherwise true.The text has been machine-translated via Google Translate.
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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().The text has been machine-translated via Google Translate.
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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.The text has been machine-translated via Google Translate.
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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.The text has been machine-translated via Google Translate.
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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);
auto now = std::chrono::system_clock::now();
if(cv.wait_until(lk, now + 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();
}
Potencial 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. You can help to correct and verify the translation. Click here for instructions. (função pública membro) | |
Bloqueia o segmento atual até que a variável de condição é acordado ou após o período de tempo limite especificado Original: blocks the current thread until the condition variable is woken up or after the specified timeout duration The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro) | |