std::future - cppreference.com
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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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      (C++11)
      this_thread namespace
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      this_thread namespace
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      (C++11)
      (C++11)
      (C++11)
      (C++11)
      Exclusão mútua
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      Mutual exclusion
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      (C++11)
      (C++11)
      Gestão de bloqueio genérico
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      Generic lock management
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      (C++11)
      (C++11)
      (C++11)(C++11)(C++11)
      (C++11)
      (C++11)
      (C++11)(C++11)(C++11)
      Variáveis ​​de condição
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      Condition variables
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      (C++11)
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      (C++11)
      (C++11)
      Futuros
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      Futures
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      (C++11)
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      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
       
      <tbody> </tbody>
      Definido no cabeçalho <future>
      template< class T > class future;
      		 (1) (desde C++11)
      template< class T > class future<T&>;
      		 (2) (desde C++11)
      template<> class future<void>;
      		 (3) (desde C++11)
      O std::future modelo de classe fornece um mecanismo para acessar o resultado de operações assíncronas:
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      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).
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      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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      Funções de membro
      constrói o objeto futuro
      Original:
      constructs the future object
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      (função pública membro) [edit]
      destrói o objeto futuro
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      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
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      returns a shared_future referring to the result associated to *this
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      (função pública membro) [edit]
      Obtendo o resultado
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      Getting the result
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      devolve o resultado
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      returns the result
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      (função pública membro) [edit]
      Estado
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      State
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      Verifica se o futuro tem estado compartilhado com uma promessa
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      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
      Original:
      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
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      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]

      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';
}

      Saída: 

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

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