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std::condition_variable::wait_until

提供: cppreference.com

 
 
スレッドのサポートライブラリ
スレッド
Original:
Threads
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thread(C++11)
this_thread空間
Original:
this_thread namespace
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get_id(C++11)
yield(C++11)
sleep_for(C++11)
sleep_until(C++11)
相互排除
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Mutual exclusion
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mutex(C++11)
timed_mutex(C++11)
汎用のロック管理
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)
条件変数
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)
先物
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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
メンバ関数
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Member functions
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condition_variable::condition_variable
condition_variable::~condition_variable
通知
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Notification
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condition_variable::notify_one
condition_variable::notify_all
待っています
Original:
Waiting
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condition_variable::wait
condition_variable::wait_for
condition_variable::wait_until
ネイティブハンドル
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Native handle
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condition_variable::native handle
 
template< class Clock, class Duration >

std::cv_status wait_until( std::unique_lock<std::mutex>& lock,

                           const std::chrono::time_point<Clock, Duration>& abs_time);
(1) (C + + 11以来)
template< class Clock, class Duration, class Predicate >

bool wait_until( std::unique_lock<mutex>& lock,
                 const std::chrono::time_point<Clock, Duration>& abs_time,

                 Predicate pred);
(2) (C + + 11以来)
wait_untilは、条件変数は、特定の時間に達した時点で、通知されるまで、現在のスレッドがブロックされたり、見せかけの起動が発生し、ある述語が満たされるまで、必要に応じてループ.
Original:
wait_until causes the current thread to block until the condition variable is notified, a specific time is reached, or a spurious wakeup occurs, optionally looping until some predicate is satisfied.
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1)
アトミックlock、ブロックは現在実行中のスレッドを解放し、*thisで待機しているスレッドのリストに追加します。 notify_all()またはnotify_one()実行されたときにスレッドのブロックが解除され、または絶対時刻abs_timeに達したとき。また、偽ってブロックを解除することができる。ブロックを解除する場合は、理由に関わらず、lockは再取得さwait_until終了です。例外によってこの関数が終了した場合は、lockも再取得される.
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 absolute time point abs_time is reached. It may also be unblocked spuriously. When unblocked, regardless of the reason, lock is reacquired and wait_until exits. If this function exits via exception, lock is also reacquired.
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2)
に相当する
Original:
Equivalent to
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while (!pred())
    if (wait_until(lock, abs_time) == std::cv_status::timeout)
        return pred();
return true;

このオーバーロードは、スプリアスウェイクアップを無視するように使用されるかもしれません.
Original:
This overload may be used to ignore spurious wakeups.
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目次

[編集] パラメータ

lock -
型std ::オブジェクトの現在のスレッドによってロックされている必要がありunique_lock <std::mutex>、
Original:
an object of type std::unique_lock<std::mutex>, which must be locked by the current thread
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abs_time -
型のオブジェクトstd::chrono::time_point待機を停止する時間を表す
Original:
an object of type std::chrono::time_point representing the time when to stop waiting
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pred - predicate which returns ​false
待機している場合は、継続すべきである
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();

[編集] 値を返します

1)
std::cv_status::timeoutabs_timeで指定された絶対的なタイムアウトに達した場合は、並外れて賢明なstd::cv_status::no_timeout.
Original:
std::cv_status::timeout if the absolute timeout specified by abs_time was reached, std::cv_status::no_timeout overwise.
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2)
falsepredタイムアウトが期限切れになった後に述語falseはまだabs_timeに評価された場合は、そうでなければtrue.
Original:
false if the predicate pred still evaluates to false after the abs_time timeout expired, otherwise true.
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[編集] 例外

std::system_errorをスローする可能性があり、またlock.lock()またはlock.unlock()によってスローされた例外を伝播する可能性.
Original:
May throw std::system_error, may also propagate exceptions thrown by lock.lock() or lock.unlock().
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[編集] ノート

lock.mutex()が現在のスレッドによってロックされていない場合は、この関数を呼び出すと、未定義の動作です.
Original:
Calling this function if lock.mutex() is not locked by the current thread is undefined behavior.
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lock.mutex()は現在同じ条件変数で待っている他のすべてのスレッドが使用するものと同じミューテックスない場合は、この関数を呼び出すと、未定義の動作です.
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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[編集]

#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);
    auto now = std::chrono::system_clock::now();
    if(cv.wait_until(lk, now + 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();
}

Possible output:

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

[編集] も参照してください

条件変数はウェイクアップされるまで、現在のスレッドをブロックします
Original:
blocks the current thread until the condition variable is woken up
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(パブリックメンバ関数) [edit]
現在のスレッドのブロックを条件変数が目覚めたり、指定されたタイムアウト期間の後にされるまで
Original:
blocks the current thread until the condition variable is woken up or after the specified timeout duration
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(パブリックメンバ関数) [edit]