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std::future

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Biblioteca de suporte a discussão
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)
Exclusão mútua
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Mutual exclusion
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mutex(C++11)
timed_mutex(C++11)
Gestão de bloqueio genérico
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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)
Variáveis ​​de condição
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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)
Futuros
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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::future
future::future
future::~future
future::operator=
future::share
Obtendo o resultado
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Getting the result
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future::get
Estado
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State
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future::valid
future::wait
future::wait_for
future::wait_until
 
Defined in header <future>
template< class T > class future;
(1) (a partir do C++ 11)
template< class T > class future<T&>;
(2) (a partir do C++ 11)
template<>          class future<void>;
(3) (a partir do C++ 11)
O std::future modelo de classe fornece um mecanismo para acessar o resultado de operações assíncronas:
Original:
The class template std::future provides a mechanism to access the result of asynchronous operations:
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  • Uma operação assíncrona (criado através std::async, std::packaged_task, ou std::promise) pode fornecer um objeto std::future para o criador do que a operação assíncrona.
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    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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  • O criador da operação assíncrona pode então usar uma variedade de métodos para consulta, aguarde, ou extrair um valor da std::future. Estes métodos podem bloquear se a operação assíncrona ainda não forneceu um valor.
    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 a operação assíncrona está pronto para enviar um resultado para o criador, ele pode fazer isso modificando o estado compartilhado' (por exemplo std::promise::set_value) que está ligado a std::future do criador.
    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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Note que as referências std::future compartilhada estado que não é compartilhado com todos os objetos assíncronos outras retorno (ao contrário de 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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Índice

[editar] Funções de membro

constrói o objeto futuro
Original:
constructs the future object
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(função pública membro) [edit]
destrói o objeto futuro
Original:
destructs the future object
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(função pública membro) [edit]
move o objeto futuro
Original:
moves the future object
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(função pública membro) [edit]
devolve uma shared_future referindo-se ao resultado, associado à *this
Original:
returns a shared_future referring to the result associated to *this
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(função pública membro) [edit]
Obtendo o resultado
Original:
Getting the result
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devolve o resultado
Original:
returns the result
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(função pública membro) [edit]
Estado
Original:
State
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Verifica se o futuro tem estado compartilhado com uma promessa
Original:
checks if the future has shared state with a promise
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(função pública membro) [edit]
aguarda o resultado de se tornarem disponíveis
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waits for the result to become available
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(função pública membro) [edit]
waits for the result, returns if it is not available for the specified timeout duration
(função pública membro) [edit]
aguarda o resultado, retorna se ele não está disponível até que ponto de tempo especificado, foi atingido
Original:
waits for the result, returns if it is not available until specified time point has been reached
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(função pública membro) [edit]

[editar] Exemplo

#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

[editar] Veja também

(C++11)
executa uma função de forma assíncrona (potencialmente em um novo segmento) e retorna uma std::future que vai segurar o resultado
Original:
runs a function asynchronously (potentially in a new thread) and returns a std::future that will hold the result
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(modelo de função) [edit]
espera por um valor (possivelmente relacionado por outros futuros) que é definido de forma assíncrona
Original:
waits for a value (possibly referenced by other futures) that is set asynchronously
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(modelo de classe) [edit]