std::condition_variable::wait_for

 

C++

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Espressioni regolari(C++11)

Operazioni atomicche(C++11)

Multithreading(C++11)

 

Discussione libreria di supporto

Threads Original: Threads The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
thread (C++11)
this_thread spazio dei nomi Original: this_thread namespace The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
get_id (C++11) yield (C++11)	sleep_for (C++11) sleep_until (C++11)
Mutua esclusione Original: Mutual exclusion The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
mutex (C++11) timed_mutex (C++11)	recursive_mutex (C++11) recursive_timed_mutex (C++11)
Blocco di gestione generico Original: Generic lock management The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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)
Condizioni variabili Original: Condition variables The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
condition_variable (C++11)
condition_variable_any (C++11)
notify_all_at_thread_exit (C++11)
cv_status (C++11)
Futures Original: Futures The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.
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

Membri funzioni Original: Member functions The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

condition_variable::condition_variable

condition_variable::~condition_variable

Notifica Original: Notification The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

condition_variable::notify_one

condition_variable::notify_all

In attesa Original: Waiting The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

condition_variable::wait

condition_variable::wait_for

condition_variable::wait_until

Maniglia nativo Original: Native handle The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions.

condition_variable::native handle

 

template<class Rep, class Period > std::cv_status wait_for(std::unique_lock<std::mutex>& lock,                          conststd::chrono::duration<Rep, Period>& rel_time);	(1)	(dal C++11)
template<class Rep, class Period, class Predicate > bool wait_for(std::unique_lock<std::mutex>& lock,                conststd::chrono::duration<Rep, Period>& rel_time,                Predicate pred);	(2)	(dal C++11)

1)

Rilascia atomico lock, blocca il thread corrente di esecuzione, e lo aggiunge alla lista di thread in attesa su *this. Il filo sarà sbloccato quando notify_all() o notify_one() viene eseguito, o quando il timeout rel_time relativa scadenza. Essa può anche essere sbloccato spurio. Quando sbloccato, indipendentemente dal motivo, lock è riacquisito ed esce wait_for(). Se questa funzione termina via eccezionale, lock anche riacquistata.

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();
returntrue;

Questo sovraccarico può essere utilizzato per ignorare risvegli spurie.

Original:

This overload may be used to ignore spurious awakenings.

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Parametri

lock	-	un oggetto di std::unique_lock<std::mutex> tipo, che deve essere bloccato dal thread corrente 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.
rel_time	-	un oggetto di std::chrono::duration tipo che rappresenta il tempo massimo di attesa di spendere Original: an object of type std::chrono::duration representing the maximum time to spend 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 l'attesa deve essere continuato 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:  bool pred();​

Valore di ritorno

1)

std::cv_status::timeout se il timeout relativo specificato da rel_time scaduto, 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 il pred predicato restituisce ancora false dopo il timeout rel_time scaduto, altrimenti true.

Original:

false if the predicate pred still evaluates to false after the rel_time timeout expired, otherwise true.

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Eccezioni

Può lanciare std::system_error, può anche propagare eccezioni generate dal lock.lock() o lock.unlock().

Original:

May throw std::system_error, may also propagate exceptions thrown by lock.lock() or lock.unlock().

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Note

Chiamare questa funzione se lock.mutex() non è bloccato dal thread corrente è un comportamento indefinito.

Original:

Calling this function if lock.mutex() is not locked by the current thread is undefined behavior.

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Chiamare questa funzione se lock.mutex() non è lo stesso mutex come quello utilizzato da tutti gli altri thread che sono attualmente in attesa sulla variabile stessa condizione è un comportamento indefinito.

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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Esempio

#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';elsestd::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();}

Output:

Thread 1 timed out. i == 0 Notifying... Thread 2 timed out. i == 0 Notifying again... Thread 3 finished waiting. i == 1

Vedi anche

wait	blocca il thread corrente fino a quando la variabile di condizione è svegliato 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. (metodo pubblico)
wait_until	blocca il thread corrente fino a quando la variabile di condizione è svegliato o fino a che punto nel tempo specificato è stato raggiunto 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. You can help to correct and verify the translation. Click here for instructions. (metodo pubblico)