Varianti

    std::condition_variable_any::wait_for

    Da cppreference.com.

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    <metanoindex/>

     
    C++
     
    Discussione libreria di supporto
    Threads
    Original:
    Threads
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    thread(C++11)
    this_thread spazio dei nomi
    Original:
    this_thread namespace
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    get_id(C++11)
    yield(C++11)
    sleep_for(C++11)
    sleep_until(C++11)
    Mutua esclusione
    Original:
    Mutual exclusion
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    mutex(C++11)
    timed_mutex(C++11)
    Blocco di gestione generico
    Original:
    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)
    Condizioni variabili
    Original:
    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_any
    Membri funzioni
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    Member functions
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    condition_variable_any::condition_variable_any
    condition_variable_any::~condition_variable_any
    Notifica
    Original:
    Notification
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    condition_variable_any::notify_one
    condition_variable_any::notify_all
    In attesa
    Original:
    Waiting
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    condition_variable_any::wait
    condition_variable_any::wait_for
    condition_variable_any::wait_until
     
    <tbody> </tbody>
    template< class Lock, class Rep, class Period > std::cv_status wait_for( Lock& lock, const std::chrono::duration<Rep, Period>& rel_time);
    		 (1) (dal C++11)
    template< class Lock, class Rep, class Period, class Predicate > bool wait_for( Lock& lock, const std::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(); return true;

    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 tipo Lock che soddisfi i requisiti BasicLockable, che devono essere bloccati dal thread corrente
    Original:
    an object of type Lock that meets the BasicLockable requirements, which must be locked by the current thread
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    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
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    pred - predicate which returns ​false
    se l'attesa deve essere continuato
    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();​

    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_any 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();
}

    Output: 

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

    Vedi anche
    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
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    (metodo pubblico) [modifica]
    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
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    (metodo pubblico) [modifica]