ceph/src/boost/libs/asio/example/cpp14/executors/async_2.cpp

   1 #include <boost/asio/ts/executor.hpp>
   2 #include <boost/asio/thread_pool.hpp>
   3 #include <iostream>
   4 #include <string>
   5
   6 using boost::asio::bind_executor;
   7 using boost::asio::dispatch;
   8 using boost::asio::get_associated_executor;
   9 using boost::asio::make_work_guard;
  10 using boost::asio::post;
  11 using boost::asio::thread_pool;
  12
  13 // A function to asynchronously read a single line from an input stream.
  14 template <class Handler>
  15 void async_getline(std::istream& is, Handler handler)
  16 {
  17   // Create executor_work for the handler's associated executor.
  18   auto work = make_work_guard(handler);
  19
  20   // Post a function object to do the work asynchronously.
  21   post([&is, work, handler=std::move(handler)]() mutable
  22       {
  23         std::string line;
  24         std::getline(is, line);
  25
  26         // Pass the result to the handler, via the associated executor.
  27         dispatch(work.get_executor(),
  28             [line=std::move(line), handler=std::move(handler)]() mutable
  29             {
  30               handler(std::move(line));
  31             });
  32       });
  33 }
  34
  35 // A function to asynchronously read multiple lines from an input stream.
  36 template <class Handler>
  37 void async_getlines(std::istream& is, std::string init, Handler handler)
  38 {
  39   // Get the final handler's associated executor.
  40   auto ex = get_associated_executor(handler);
  41
  42   // Use the associated executor for each operation in the composition.
  43   async_getline(is,
  44       bind_executor(ex,
  45         [&is, lines=std::move(init), handler=std::move(handler)]
  46         (std::string line) mutable
  47         {
  48           if (line.empty())
  49             handler(lines);
  50           else
  51             async_getlines(is, lines + line + "\n", std::move(handler));
  52         }));
  53 }
  54
  55 int main()
  56 {
  57   thread_pool pool;
  58
  59   std::cout << "Enter text, terminating with a blank line:\n";
  60
  61   async_getlines(std::cin, "",
  62       bind_executor(pool, [](std::string lines)
  63         {
  64           std::cout << "Lines:\n" << lines << "\n";
  65         }));
  66
  67   pool.join();
  68 }