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    std::future

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    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
    Original:
    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::future
    future::future
    future::~future
    future::operator=
    future::share
    Ottenere il risultato
    Original:
    Getting the result
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    future::get
    Stato
    Original:
    State
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    future::valid
    future::wait
    future::wait_for
    future::wait_until
     
    <tbody> </tbody>
    Elemento definito nell'header <future>
    template< class T > class future;
    		 (1) (dal C++11)
    template< class T > class future<T&>;
    		 (2) (dal C++11)
    template<> class future<void>;
    		 (3) (dal C++11)
    Il std::future modello di classe fornisce un meccanismo per accedere al risultato delle operazioni asincrone:
    Original:
    The class template std::future provides a mechanism to access the result of asynchronous operations:
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    • Un'operazione asincrona (creato tramite std::async, std::packaged_task o std::promise) in grado di fornire un oggetto std::future al creatore di tale operazione asincrona.
      Original:
      An asynchronous operation (created via std::async, std::packaged_task, or std::promise) can provide a std::future object to the creator of that asynchronous operation.
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    • Il creatore dell'operazione asincrona può utilizzare una varietà di metodi per le query, aspettare, o estrarre un valore dal std::future. Questi metodi possono bloccare se l'operazione asincrona non ha ancora fornito un valore.
      Original:
      The creator of the asynchronous operation can then use a variety of methods to query, wait for, or extract a value from the std::future. These methods may block if the asynchronous operation has not yet provided a value.
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    • Quando l'operazione asincrona è pronto per inviare un risultato al creatore, può farlo mediante la modifica dello stato condiviso (ad esempio std::promise::set_value) che è legata alla std::future del creatore.
      Original:
      When the asynchronous operation is ready to send a result to the creator, it can do so by modifying shared state (e.g. std::promise::set_value) that is linked to the creator's std::future.
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    Si noti che i riferimenti std::future stato condiviso che non sia condivisa con altri oggetti di ritorno asincroni (a differenza std::shared_future).
    Original:
    Note that std::future references shared state that is not shared with any other asynchronous return objects (as opposed to std::shared_future).
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    Membri funzioni
    costruisce l'oggetto futuro
    Original:
    constructs the future object
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    (metodo pubblico) [modifica]
    distrugge l'oggetto futuro
    Original:
    destructs the future object
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    (metodo pubblico) [modifica]
    sposta l'oggetto futuro
    Original:
    moves the future object
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    (metodo pubblico) [modifica]
    restituisce un shared_future riferimento al risultato associato al *this
    Original:
    returns a shared_future referring to the result associated to *this
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    (metodo pubblico) [modifica]
    Ottenere il risultato
    Original:
    Getting the result
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    restituisce il risultato
    Original:
    returns the result
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    (metodo pubblico) [modifica]
    Stato
    Original:
    State
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    Verifica se il futuro è stato condiviso con una promessa
    Original:
    checks if the future has shared state with a promise
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    (metodo pubblico) [modifica]
    attende il risultato diventi disponibile
    Original:
    waits for the result to become available
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    (metodo pubblico) [modifica]
    		waits for the result, returns if it is not available for the specified timeout duration
    (metodo pubblico) [modifica]
    aspetta il risultato, restituisce se non è disponibile fino punto di tempo specificato è stato raggiunto
    Original:
    waits for the result, returns if it is not available until specified time point has been reached
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    (metodo pubblico) [modifica]

    Esempio

    #include <iostream>
#include <future>
#include <thread>

int main()
{
    // future from a packaged_task
    std::packaged_task<int()> task([](){ return 7; }); // wrap the function
    std::future<int> f1 = task.get_future();  // get a future
    std::thread(std::move(task)).detach(); // launch on a thread

    // future from an async()
    std::future<int> f2 = std::async(std::launch::async, [](){ return 8; });

    // future from a promise
    std::promise<int> p;
    std::future<int> f3 = p.get_future();
    std::thread( [](std::promise<int>& p){ p.set_value(9); }, 
                 std::ref(p) ).detach();

    std::cout << "Waiting...";
    f1.wait();
    f2.wait();
    f3.wait();
    std::cout << "Done!\nResults are: "
              << f1.get() << ' ' << f2.get() << ' ' << f3.get() << '\n';
}

    Output: 

    Waiting...Done!
Results are: 7 8 9

    Vedi anche

    (C++11)
    esegue una funzione in modo asincrono (potenzialmente in un nuovo thread) e restituisce un std::future che conterrà il risultato
    Original:
    runs a function asynchronously (potentially in a new thread) and returns a std::future that will hold the result
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    (funzione di modello) [modifica]
    (C++11)
    attende un valore (eventualmente riferimento altri futuri) che è impostato in modo asincrono
    Original:
    waits for a value (possibly referenced by other futures) that is set asynchronously
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    (classe template) [modifica]