Method create

example/cpp14/operations/c_callback_wrapper.cpp:52–84

Create the state using the handler's associated allocator.

  // Create the state using the handler's associated allocator.
  static read_input_state* create(Handler&& handler)
  {
    // A unique_ptr deleter that is used to destroy uninitialised objects.
    struct deleter
    {
      // Get the handler's associated allocator type. If the handler does not
      // specify an associated allocator, we will use a recycling allocator as
      // the default. As the associated allocator is a proto-allocator, we must
      // rebind it to the correct type before we can use it to allocate objects.
      typename std::allocator_traits<
        boost::asio::associated_allocator_t<Handler,
          boost::asio::recycling_allocator<void>>>::template
            rebind_alloc<read_input_state> alloc;

      void operator()(read_input_state* ptr)
      {
        std::allocator_traits<decltype(alloc)>::deallocate(alloc, ptr, 1);
      }
    } d{boost::asio::get_associated_allocator(handler,
          boost::asio::recycling_allocator<void>())};

    // Allocate memory for the state.
    std::unique_ptr<read_input_state, deleter> uninit_ptr(
        std::allocator_traits<decltype(d.alloc)>::allocate(d.alloc, 1), d);

    // Construct the state into the newly allocated memory. This might throw.
    read_input_state* ptr =
      new (uninit_ptr.get()) read_input_state(std::move(handler));

    // Release ownership of the memory and return the newly allocated state.
    uninit_ptr.release();
    return ptr;
  }

  static void callback(void* arg, const char* result)
  {