require_member.hpp 2.8 KB

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  1. //
  2. // traits/require_member.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_TRAITS_REQUIRE_MEMBER_HPP
  11. #define BOOST_ASIO_TRAITS_REQUIRE_MEMBER_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/type_traits.hpp>
  17. #if defined(BOOST_ASIO_HAS_DECLTYPE) \
  18. && defined(BOOST_ASIO_HAS_NOEXCEPT) \
  19. && defined(BOOST_ASIO_HAS_WORKING_EXPRESSION_SFINAE)
  20. # define BOOST_ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT 1
  21. #endif // defined(BOOST_ASIO_HAS_DECLTYPE)
  22. // && defined(BOOST_ASIO_HAS_NOEXCEPT)
  23. // && defined(BOOST_ASIO_HAS_WORKING_EXPRESSION_SFINAE)
  24. #include <boost/asio/detail/push_options.hpp>
  25. namespace boost {
  26. namespace asio {
  27. namespace traits {
  28. template <typename T, typename Property, typename = void>
  29. struct require_member_default;
  30. template <typename T, typename Property, typename = void>
  31. struct require_member;
  32. } // namespace traits
  33. namespace detail {
  34. struct no_require_member
  35. {
  36. BOOST_ASIO_STATIC_CONSTEXPR(bool, is_valid = false);
  37. BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
  38. };
  39. #if defined(BOOST_ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
  40. template <typename T, typename Property, typename = void>
  41. struct require_member_trait : no_require_member
  42. {
  43. };
  44. template <typename T, typename Property>
  45. struct require_member_trait<T, Property,
  46. typename void_type<
  47. decltype(declval<T>().require(declval<Property>()))
  48. >::type>
  49. {
  50. BOOST_ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
  51. using result_type = decltype(
  52. declval<T>().require(declval<Property>()));
  53. BOOST_ASIO_STATIC_CONSTEXPR(bool, is_noexcept = noexcept(
  54. declval<T>().require(declval<Property>())));
  55. };
  56. #else // defined(BOOST_ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
  57. template <typename T, typename Property, typename = void>
  58. struct require_member_trait :
  59. conditional<
  60. is_same<T, typename decay<T>::type>::value
  61. && is_same<Property, typename decay<Property>::type>::value,
  62. no_require_member,
  63. traits::require_member<
  64. typename decay<T>::type,
  65. typename decay<Property>::type>
  66. >::type
  67. {
  68. };
  69. #endif // defined(BOOST_ASIO_HAS_DEDUCED_REQUIRE_MEMBER_TRAIT)
  70. } // namespace detail
  71. namespace traits {
  72. template <typename T, typename Property, typename>
  73. struct require_member_default :
  74. detail::require_member_trait<T, Property>
  75. {
  76. };
  77. template <typename T, typename Property, typename>
  78. struct require_member :
  79. require_member_default<T, Property>
  80. {
  81. };
  82. } // namespace traits
  83. } // namespace asio
  84. } // namespace boost
  85. #include <boost/asio/detail/pop_options.hpp>
  86. #endif // BOOST_ASIO_TRAITS_REQUIRE_MEMBER_HPP