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std::try_lock

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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)
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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
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lock (C++11)
try_lock (C++11)
defer_lock
try_to_lock
adopt_lock
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Les variables de condition
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Condition variables
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Defined in header <mutex>
template< class Lockable1, class Lockable2, class LockableN... >
int try_lock( Lockable1& lock1, Lockable2& lock2, LockableN& lockn... );
(depuis C++11)
Essaie de verrouiller chacun des objets donnés Lockable lock1, lock2, ..., lockn en appelant try_lock ordre en commençant avec le premier .
Original:
Tries to lock each of the given Lockable objects lock1, lock2, ..., lockn by calling try_lock in order beginning with the first.
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Si un appel à try_lock échoue, unlock est appelée pour tous les objets verrouillés et un indice basé sur 0 de l'objet qui a échoué à verrouiller est retourné .
Original:
If a call to try_lock fails, unlock is called for any locked objects and a 0-based index of the object that failed to lock is returned.
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Si un appel aux résultats try_lock une exception, unlock est appelée pour tous les objets verrouillés avant rethrowing .
Original:
If a call to try_lock results in an exception, unlock is called for any locked objects before rethrowing.
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Sommaire

[modifier] Paramètres

lock1, lock2, ... , lockn -
l'Lockable objets à verrouiller
Original:
the Lockable objects to lock
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[modifier] Retourne la valeur

-1 en cas de succès, ou la valeur d'index basée sur 0 de l'objet qui a échoué pour verrouiller .
Original:
-1 on success, or 0-based index value of the object that failed to lock.
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[modifier] Exemple

L'exemple suivant utilise std::try_lock périodiquement de pointage et compteurs de reset en cours d'exécution dans des threads séparés .
Original:
The following example uses std::try_lock to periodically tally and reset counters running in separate threads.
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#include <mutex>
#include <vector>
#include <thread>
#include <iostream>
#include <functional>
#include <chrono>
 
int main()
{
    int foo_count = 0;
    std::mutex foo_count_mutex;
    int bar_count = 0;
    std::mutex bar_count_mutex;
    int overall_count = 0;
    bool done = false;
    std::mutex done_mutex;
 
    auto increment = [](int &counter, std::mutex &m,  const char *desc) {
        for (int i = 0; i < 10; ++i) {
            std::unique_lock<std::mutex> lock(m);
            ++counter;
            std::cout << desc << ": " << counter << '\n';
            lock.unlock();
            std::this_thread::sleep_for(std::chrono::seconds(1));
        }
    };
 
    std::thread increment_foo(increment, std::ref(foo_count), 
        std::ref(foo_count_mutex), "foo");
    std::thread increment_bar(increment, std::ref(bar_count), 
        std::ref(bar_count_mutex), "bar");
 
    std::thread update_overall([&]() {
        done_mutex.lock();
        while (!done) {
            done_mutex.unlock();
            int result = std::try_lock(foo_count_mutex, bar_count_mutex);
            if (result == -1) {
                overall_count += foo_count + bar_count;
                foo_count = 0;
                bar_count = 0;
                std::cout << "overall: " << overall_count << '\n';
                foo_count_mutex.unlock();
                bar_count_mutex.unlock();
            }
            std::this_thread::sleep_for(std::chrono::seconds(2));
            done_mutex.lock();
        }
        done_mutex.unlock();
    });
 
    increment_foo.join();
    increment_bar.join();
    done_mutex.lock();
    done = true;
    done_mutex.unlock();
    update_overall.join();
 
    std::cout << "Done processing\n"
              << "foo: " << foo_count << '\n'
              << "bar: " << bar_count << '\n'
              << "overall: " << overall_count << '\n';
}

Résultat possible :

bar: 1
foo: 1
foo: 2
bar: 2
foo: 3
overall: 5
bar: 1
foo: 1
bar: 2
foo: 2
bar: 3
overall: 10
bar: 1
foo: 1
bar: 2
foo: 2
overall: 14
bar: 1
foo: 1
bar: 2
overall: 17
foo: 1
bar: 1
foo: 2
overall: 20
Done processing
foo: 0
bar: 0
overall: 20

[modifier] Voir aussi

(C++11)
verrouille les mutex, les blocs spécifiés le cas échéant ne sont pas disponibles
Original:
locks specified mutexes, blocks if any are unavailable
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(fonction générique) [edit]