completion_handler.hpp 2.8 KB

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  1. //
  2. // detail/completion_handler.hpp
  3. // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  4. //
  5. // Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com)
  6. //
  7. // Distributed under the Boost Software License, Version 1.0. (See accompanying
  8. // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  9. //
  10. #ifndef BOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP
  11. #define BOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP
  12. #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  13. # pragma once
  14. #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  15. #include <boost/asio/detail/config.hpp>
  16. #include <boost/asio/detail/fenced_block.hpp>
  17. #include <boost/asio/detail/handler_alloc_helpers.hpp>
  18. #include <boost/asio/detail/handler_work.hpp>
  19. #include <boost/asio/detail/memory.hpp>
  20. #include <boost/asio/detail/operation.hpp>
  21. #include <boost/asio/detail/push_options.hpp>
  22. namespace boost {
  23. namespace asio {
  24. namespace detail {
  25. template <typename Handler, typename IoExecutor>
  26. class completion_handler : public operation
  27. {
  28. public:
  29. BOOST_ASIO_DEFINE_HANDLER_PTR(completion_handler);
  30. completion_handler(Handler& h, const IoExecutor& io_ex)
  31. : operation(&completion_handler::do_complete),
  32. handler_(BOOST_ASIO_MOVE_CAST(Handler)(h)),
  33. work_(handler_, io_ex)
  34. {
  35. }
  36. static void do_complete(void* owner, operation* base,
  37. const boost::system::error_code& /*ec*/,
  38. std::size_t /*bytes_transferred*/)
  39. {
  40. // Take ownership of the handler object.
  41. completion_handler* h(static_cast<completion_handler*>(base));
  42. ptr p = { boost::asio::detail::addressof(h->handler_), h, h };
  43. BOOST_ASIO_HANDLER_COMPLETION((*h));
  44. // Take ownership of the operation's outstanding work.
  45. handler_work<Handler, IoExecutor> w(
  46. BOOST_ASIO_MOVE_CAST2(handler_work<Handler, IoExecutor>)(
  47. h->work_));
  48. // Make a copy of the handler so that the memory can be deallocated before
  49. // the upcall is made. Even if we're not about to make an upcall, a
  50. // sub-object of the handler may be the true owner of the memory associated
  51. // with the handler. Consequently, a local copy of the handler is required
  52. // to ensure that any owning sub-object remains valid until after we have
  53. // deallocated the memory here.
  54. Handler handler(BOOST_ASIO_MOVE_CAST(Handler)(h->handler_));
  55. p.h = boost::asio::detail::addressof(handler);
  56. p.reset();
  57. // Make the upcall if required.
  58. if (owner)
  59. {
  60. fenced_block b(fenced_block::half);
  61. BOOST_ASIO_HANDLER_INVOCATION_BEGIN(());
  62. w.complete(handler, handler);
  63. BOOST_ASIO_HANDLER_INVOCATION_END;
  64. }
  65. }
  66. private:
  67. Handler handler_;
  68. handler_work<Handler, IoExecutor> work_;
  69. };
  70. } // namespace detail
  71. } // namespace asio
  72. } // namespace boost
  73. #include <boost/asio/detail/pop_options.hpp>
  74. #endif // BOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP