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std::condition_variable::wait

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C++
 
Bibliothèque de support fil
Threads
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Threads
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thread (C++11)
this_thread espace de noms
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this_thread namespace
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get_id (C++11)
yield (C++11)
sleep_for (C++11)
sleep_until (C++11)
L'exclusion mutuelle
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Mutual exclusion
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mutex (C++11)
timed_mutex (C++11)
Gestion du verrouillage générique
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Generic lock management
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lock_guard (C++11)
unique_lock (C++11)
defer_lock_t
try_to_lock_t
adopt_lock_t		 (C++11)
(C++11)
(C++11)
lock (C++11)
try_lock (C++11)
defer_lock
try_to_lock
adopt_lock		 (C++11)
(C++11)
(C++11)
Les variables de condition
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Condition variables
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condition_variable (C++11)
condition_variable_any (C++11)
notify_all_at_thread_exit (C++11)
cv_status (C++11)
Futures
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Futures
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promise (C++11)
future (C++11)
shared_future (C++11)
packaged_task (C++11)
async (C++11)
launch (C++11)
future_status (C++11)
future_error (C++11)
future_category (C++11)
future_errc (C++11)
 
std::condition_variable
Les fonctions membres
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Member functions
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condition_variable::condition_variable
condition_variable::~condition_variable
Notification
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Notification
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condition_variable::notify_one
condition_variable::notify_all
D'attente
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Waiting
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condition_variable::wait
condition_variable::wait_for
condition_variable::wait_until
Handle natif
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Native handle
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condition_variable::native handle
 
void wait( std::unique_lock<std::mutex>& lock );
 (1) (depuis C++11)
template< class Predicate >
void wait( std::unique_lock<std::mutex>& lock, Predicate pred );
 (2) (depuis C++11)
wait provoque le thread courant de bloquer jusqu'à ce que la variable de condition est notifié ou un service de réveil parasite se produit, éventuellement en boucle jusqu'à ce qu'un prédicat est satisfait .
Original:
wait causes the current thread to block until the condition variable is notified or a spurious wakeup occurs, optionally looping until some predicate is satisfied.
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1)
Libère atomiquement lock, bloque le thread en cours d'exécution, et l'ajoute à la liste des threads en attente sur *this. Le fil sera débloqué lorsque notify_all() ou notify_one() est exécutée. Il peut également être débloqué faussement. Lorsque débloqué, quelle que soit la raison, lock est recouvré et sorties wait. Si cette fonction sort par exception, lock est également acquis de nouveau .
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. It may also be unblocked spuriously. When unblocked, regardless of the reason, lock is reacquired and wait exits. If this function exits via exception, lock is also reacquired.
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2)
Équivalent à
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Equivalent to
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while (!pred()) {
  wait(lock);
}

Cette surcharge peut être utilisée pour ignorer réveils parasites dans l'attente d'une condition spécifique pour devenir vrai .
Original:
This overload may be used to ignore spurious awakenings while waiting for a specific condition to become true.
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Sommaire

[modifier] Paramètres

lock -
un objet de std::unique_lock<std::mutex> type, qui doit être verrouillé par le thread courant
Original:
an object of type std::unique_lock<std::mutex>, which must be locked by the current thread
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pred - predicate which returns ​false
si l'attente doit être poursuivie
Original:
if the waiting should be continued
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.

The signature of the predicate function should be equivalent to the following:

 bool pred();​

[modifier] Retourne la valeur

(Aucun)
Original:
(none)
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[modifier] Exceptions

Peut générer std::system_error, peuvent également propager les exceptions levées par 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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[modifier] Notes

L'appel de cette fonction si lock.mutex() n'est pas verrouillé par le thread courant est un comportement indéfini .
Original:
Calling this function if lock.mutex() is not locked by the current thread is undefined behavior.
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L'appel de cette fonction si lock.mutex() n'est pas le mutex même que celui utilisé par les autres threads qui sont actuellement en attente sur la variable de condition même comportement indéfini .
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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[modifier] Exemple

[edit]
#include <iostream>
#include <condition_variable>
#include <thread>
#include <chrono>
 
std::condition_variable cv;
std::mutex cv_m;
int i = 0;
 
void waits()
{
    std::unique_lock<std::mutex> lk(cv_m);
    std::cerr << "Waiting... \n";
    cv.wait(lk, [](){return i == 1;});
    std::cerr << "...finished waiting. i == 1\n";
}
 
void signals()
{
    std::this_thread::sleep_for(std::chrono::seconds(1));
    std::cerr << "Notifying...\n";
    cv.notify_all();
    std::this_thread::sleep_for(std::chrono::seconds(1));
    i = 1;
    std::cerr << "Notifying again...\n";
    cv.notify_all();
}
 
int main()
{
    std::thread t1(waits), t2(waits), t3(waits), t4(signals);
    t1.join(); 
    t2.join(); 
    t3.join();
    t4.join();
}

Résultat : 

Waiting...
Waiting...
Waiting...
Notifying...
Notifying again...
...finished waiting. i == 1
...finished waiting. i == 1
...finished waiting. i == 1

[modifier] Voir aussi
Bloque le thread actuel jusqu'à ce que la condition_variable soit réveillée ou que la durée de temporisation spécifiée soit écoulée
Original:
blocks the current thread until the condition variable is woken up or after the specified timeout duration
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(fonction membre publique) [edit]
Bloque le thread en cours jusqu'à ce que la condition_variable soit réveillée ou jusqu'à ce que le point temporel (time point) spécifié soit atteint
Original:
blocks the current thread until the condition variable is woken up or until specified time point has been reached
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(fonction membre publique) [edit]
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