Làm thế nào để bạn đăng một packaged_task tăng lên một io_service trong C++ 03?

Question

Đây là một sự theo dõi từ một câu hỏi trước (here), nhưng tôi đang làm việc trên một ứng dụng đa luồng và tôi muốn đăng một gói packaged_task Boost lên một luồng io_service. Tôi đang mắc kẹt bằng cách sử dụng một trình biên dịch C + + 03 (vì vậy std :: di chuyển là ra), và packaged_task không phải là copyable. Tôi đã thử gói nó trong một shared_ptr và đi qua đó, và rất nhiều thứ khác. Đây là nỗ lực hiện tại của tôi và các lỗi trình biên dịch tiếp theo. Bất kỳ ý tưởng làm thế nào để có được điều này để làm việc?

boost::asio::io_service io_service; 
boost::thread_group threads; 
boost::asio::io_service::work work(io_service); 
for (int i = 0; i < maxNumThreads; ++i) 
{ 
    threads.create_thread(boost::bind(&boost::asio::io_service::run, 
     &io_service)); 
} 
std::vector<boost::shared_future<bool> > pending_data; // vector of futures 

bool process_data(int,int){...} 
... 

for(int theTime = 0; theTime != totalScenarioTime; ++theTime) 
{ 
    for(int i = 0; i < numSmallTasks; ++i) 
    { 
     boost::packaged_task<bool> task(boost::bind(&process_data,i,theTime)); 
     boost::shared_future<bool> fut(task.get_future()); 
     pending_data.push_back(fut); // C++11 possible: (std::move(fut) when fut is a unique_future); 
     io_service.post(task); // C++11 possible: (std::move(task));  
    } 
    // After loop - wait until all futures are evaluated 
    boost::wait_for_all(pending_data.begin(), pending_data.end()); 
    pending_data.clear(); 
} 

Điều này dẫn đến:

In file included from ../boostlibs/boost/asio/io_service.hpp:767:0, 
      from ../boostlibs/boost/asio/basic_io_object.hpp:19, 
      from ../boostlibs/boost/asio/basic_socket.hpp:19, 
      from ../boostlibs/boost/asio/basic_datagram_socket.hpp:20, 
      from ../boostlibs/boost/asio.hpp:20, 
      from ../main.cpp:13: 
../boostlibs/boost/asio/impl/io_service.hpp: In member function ‘void boost::asio::io_service::post(const CompletionHandler&) [with CompletionHandler = boost::packaged_task<bool>]’: 
../main.cpp:256:23: instantiated from here 
../boostlibs/boost/asio/impl/io_service.hpp:95:67: error: no matching function for call to ‘boost::packaged_task<bool>::packaged_task(const boost::packaged_task<bool>&)’ 
../boostlibs/boost/asio/impl/io_service.hpp:95:67: note: candidates are: 
../boostlibs/boost/thread/future.hpp:1372:9: note: boost::packaged_task<R>::packaged_task(boost::detail::thread_move_t<boost::packaged_task<R> >) [with R = bool] 
../boostlibs/boost/thread/future.hpp:1372:9: note: no known conversion for argument 1 from ‘const boost::packaged_task<bool>’ to ‘boost::detail::thread_move_t<boost::packaged_task<bool> >’ 
../boostlibs/boost/thread/future.hpp:1318:9: note: boost::packaged_task<R>::packaged_task() [with R = bool] 
../boostlibs/boost/thread/future.hpp:1318:9: note: candidate expects 0 arguments, 1 provided 
../boostlibs/boost/thread/future.hpp:1314:9: note: boost::packaged_task<R>::packaged_task(boost::packaged_task<R>&) [with R = bool, boost::packaged_task<R> = boost::packaged_task<bool>] 
../boostlibs/boost/thread/future.hpp:1314:9: note: no known conversion for argument 1 from ‘const boost::packaged_task<bool>’ to ‘boost::packaged_task<bool>&’ 
../boostlibs/boost/asio/detail/handler_type_requirements.hpp:95:26: error: initializing argument 1 of ‘T& boost::asio::detail::lvref(T) [with T = boost::packaged_task<bool>]’ 
../boostlibs/boost/asio/impl/io_service.hpp:95:67: error: no matching function for call to ‘boost::packaged_task<bool>::packaged_task(const boost::packaged_task<bool>&)’ 
../boostlibs/boost/asio/impl/io_service.hpp:95:67: note: candidates are: 
../boostlibs/boost/thread/future.hpp:1372:9: note: boost::packaged_task<R>::packaged_task(boost::detail::thread_move_t<boost::packaged_task<R> >) [with R = bool] 
../boostlibs/boost/thread/future.hpp:1372:9: note: no known conversion for argument 1 from ‘const boost::packaged_task<bool>’ to ‘boost::detail::thread_move_t<boost::packaged_task<bool> >’ 
../boostlibs/boost/thread/future.hpp:1318:9: note: boost::packaged_task<R>::packaged_task() [with R = bool] 
../boostlibs/boost/thread/future.hpp:1318:9: note: candidate expects 0 arguments, 1 provided 
../boostlibs/boost/thread/future.hpp:1314:9: note: boost::packaged_task<R>::packaged_task(boost::packaged_task<R>&) [with R = bool, boost::packaged_task<R> = boost::packaged_task<bool>] 
../boostlibs/boost/thread/future.hpp:1314:9: note: no known conversion for argument 1 from ‘const boost::packaged_task<bool>’ to ‘boost::packaged_task<bool>&’ 
../boostlibs/boost/asio/detail/handler_type_requirements.hpp:96:32: error: initializing argument 1 of ‘const T& boost::asio::detail::clvref(T) [with T = boost::packaged_task<bool>]’ 
../boostlibs/boost/asio/impl/io_service.hpp:97:3: error: no matching function for call to ‘boost::packaged_task<bool>::packaged_task(const boost::packaged_task<bool>&)’ 
../boostlibs/boost/asio/impl/io_service.hpp:97:3: note: candidates are: 
../boostlibs/boost/thread/future.hpp:1372:9: note: boost::packaged_task<R>::packaged_task(boost::detail::thread_move_t<boost::packaged_task<R> >) [with R = bool] 
../boostlibs/boost/thread/future.hpp:1372:9: note: no known conversion for argument 1 from ‘const boost::packaged_task<bool>’ to ‘boost::detail::thread_move_t<boost::packaged_task<bool> >’ 
../boostlibs/boost/thread/future.hpp:1318:9: note: boost::packaged_task<R>::packaged_task() [with R = bool] 
../boostlibs/boost/thread/future.hpp:1318:9: note: candidate expects 0 arguments, 1 provided 
../boostlibs/boost/thread/future.hpp:1314:9: note: boost::packaged_task<R>::packaged_task(boost::packaged_task<R>&) [with R = bool, boost::packaged_task<R> = boost::packaged_task<bool>] 
../boostlibs/boost/thread/future.hpp:1314:9: note: no known conversion for argument 1 from ‘const boost::packaged_task<bool>’ to ‘boost::packaged_task<bool>&’ 
../boostlibs/boost/asio/detail/impl/task_io_service.hpp:54:6: error: initializing argument 1 of ‘void boost::asio::detail::task_io_service::post(Handler) [with Handler = boost::packaged_task<bool>]’ 

Sử dụng boost :: kết quả di chuyển (nhiệm vụ) trong hai lỗi:

error: no match for call to ‘(boost::detail::thread_move_t<boost::packaged_task<bool> >)()’ 
error: no match for call to ‘(boost::detail::thread_move_t<boost::packaged_task<bool> >)()’ 

Answer 1

boost::packaged_task hỗ trợ boost::move từ Boost phiên bản 1.50, xem tương ứng ticket .

Nhưng vấn đề là thông số xử lý hoàn thành io_service::post phải là CopyConstructible như được ghi chú trong Asio handler requirements. Do đó, không thể đăng trực tiếp hoặc bằng cách di chuyển boost::packaged_task. (Cảm ơn Igor R. về vấn đề này).

Có cách giải quyết khác bằng cách sử dụng con trỏ, ví dụ: bạn có thể quấn boost::packaged_task với boost::shared_ptr và liên kết nó với operator():

typedef boost::packaged_task<bool> task_t; 
boost::shared_ptr<task_t> task = boost::make_shared<task_t>(
    boost::bind(&process_data, i, theTime)); 

io_service.post(boost::bind(&task_t::operator(), task));