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  1. //
  2. // detail/completion_handler.hpp
  3. // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  4. //
  5. // Copyright (c) 2003-2019 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 ASIO_DETAIL_COMPLETION_HANDLER_HPP
  11. #define 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 "asio/detail/config.hpp"
  16. #include "asio/detail/fenced_block.hpp"
  17. #include "asio/detail/handler_alloc_helpers.hpp"
  18. #include "asio/detail/handler_work.hpp"
  19. #include "asio/detail/memory.hpp"
  20. #include "asio/detail/operation.hpp"
  21. #include "asio/detail/push_options.hpp"
  22. namespace asio {
  23. namespace detail {
  24. template <typename Handler>
  25. class completion_handler : public operation
  26. {
  27. public:
  28. ASIO_DEFINE_HANDLER_PTR(completion_handler);
  29. completion_handler(Handler& h)
  30. : operation(&completion_handler::do_complete),
  31. handler_(ASIO_MOVE_CAST(Handler)(h))
  32. {
  33. handler_work<Handler>::start(handler_);
  34. }
  35. static void do_complete(void* owner, operation* base,
  36. const asio::error_code& /*ec*/,
  37. std::size_t /*bytes_transferred*/)
  38. {
  39. // Take ownership of the handler object.
  40. completion_handler* h(static_cast<completion_handler*>(base));
  41. ptr p = { asio::detail::addressof(h->handler_), h, h };
  42. handler_work<Handler> w(h->handler_);
  43. ASIO_HANDLER_COMPLETION((*h));
  44. // Make a copy of the handler so that the memory can be deallocated before
  45. // the upcall is made. Even if we're not about to make an upcall, a
  46. // sub-object of the handler may be the true owner of the memory associated
  47. // with the handler. Consequently, a local copy of the handler is required
  48. // to ensure that any owning sub-object remains valid until after we have
  49. // deallocated the memory here.
  50. Handler handler(ASIO_MOVE_CAST(Handler)(h->handler_));
  51. p.h = asio::detail::addressof(handler);
  52. p.reset();
  53. // Make the upcall if required.
  54. if (owner)
  55. {
  56. fenced_block b(fenced_block::half);
  57. ASIO_HANDLER_INVOCATION_BEGIN(());
  58. w.complete(handler, handler);
  59. ASIO_HANDLER_INVOCATION_END;
  60. }
  61. }
  62. private:
  63. Handler handler_;
  64. };
  65. } // namespace detail
  66. } // namespace asio
  67. #include "asio/detail/pop_options.hpp"
  68. #endif // ASIO_DETAIL_COMPLETION_HANDLER_HPP