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    std::condition_variable::wait_for

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    <metanoindex/>

     
    C++
     
    Thema Support-Bibliothek
    Threads
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    Threads
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    thread(C++11)
    this_thread Namespace
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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)
    Gegenseitigen Ausschluss
    Original:
    Mutual exclusion
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    mutex(C++11)
    timed_mutex(C++11)
    Generische Sperrverwaltung
    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)
    Zustand Variablen
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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
    Member-Funktionen
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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
    Warten
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    Waiting
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    condition_variable::wait
    condition_variable::wait_for
    condition_variable::wait_until
    Ureinwohner Griff
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    Native handle
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    condition_variable::native handle
     
    <tbody> </tbody>
    template< class Rep, class Period > std::cv_status wait_for( std::unique_lock<std::mutex>& lock, const std::chrono::duration<Rep, Period>& rel_time);
    		 (1) (seit C++11)
    template< class Rep, class Period, class Predicate > bool wait_for( std::unique_lock<std::mutex>& lock, const std::chrono::duration<Rep, Period>& rel_time, Predicate pred);
    		 (2) (seit C++11)

    1)

    Atomar freigibt lock, blockiert den aktuellen ausgeführten Threads, und fügt sie in die Liste der wartenden Threads auf *this. Der Faden wird entsperrt, wenn notify_all() oder notify_one() ausgeführt werden, oder wenn die relative Timeout rel_time abläuft. Es kann auch fälschlicherweise entsperrt werden. Wenn freigegeben, egal aus welchem ​​Grund, ist lock reacquired und wait_for() beendet. Wenn diese Funktion tritt über Ausnahme ist lock auch zurückerworben .
    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)

    Entspricht
    Original:
    Equivalent to
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    while (!pred()) if (wait_for(lock, rel_time) == std::cv_status::timeout) return pred(); return true;

    Diese Überlastung kann verwendet werden, um falsche Erwachen ignorieren .
    Original:
    This overload may be used to ignore spurious awakenings.
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    Parameter

    lock -
    ein Objekt des Typs std::unique_lock<std::mutex>, die durch den aktuellen Thread gesperrt werden muss
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    an object of type std::unique_lock<std::mutex>, which must be locked by the current thread
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    rel_time -
    ein Objekt vom Typ std::chrono::duration, die die maximale Zeit mit Warten verbringen
    Original:
    an object of type std::chrono::duration representing the maximum time to spend waiting
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    pred - predicate which returns ​false
    wenn das Warten sollte fortgesetzt werden
    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();​

    Rückgabewert

    1)

    std::cv_status::timeout wenn die relative Timeout durch rel_time angegebenen abgelaufen, 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 wenn das Prädikat pred noch ausgewertet false nach dem rel_time Timeout abgelaufen, sonst true .
    Original:
    false if the predicate pred still evaluates to false after the rel_time timeout expired, otherwise true.
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    Ausnahmen

    Kann std::system_error werfen, kann auch propagieren Ausnahmen lock.lock() geworfen oder lock.unlock() .
    Original:
    May throw std::system_error, may also propagate exceptions thrown by lock.lock() or lock.unlock().
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    Notes

    Der Aufruf dieser Funktion, wenn lock.mutex() nicht durch den aktuellen Thread gesperrt ist undefiniert .
    Original:
    Calling this function if lock.mutex() is not locked by the current thread is undefined behavior.
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    Der Aufruf dieser Funktion, wenn lock.mutex() nicht das gleiche Mutex als ein von allen anderen Threads, wartet derzeit auf der gleichen Bedingung variabel ist undefiniert verwendet .
    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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    Beispiel

    #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';
    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

    Siehe auch
    Blockiert den aktuellen Thread, bis die condition variable geweckt wird
    Original:
    blocks the current thread until the condition variable is woken up
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    (öffentliche Elementfunktion) [edit]
    Blockiert den aktuellen Thread, bis die condition variable geweckt wird oder bis der angegebenene Zeitpunkt erreicht wurde
    Original:
    blocks the current thread until the condition variable is woken up or until specified time point has been reached
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    (öffentliche Elementfunktion) [edit]