ceph/src/boost/boost/asio/associated_executor.hpp

   1 //
   2 // associated_executor.hpp
   3 // ~~~~~~~~~~~~~~~~~~~~~~~
   4 //
   5 // Copyright (c) 2003-2017 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
  11 #ifndef BOOST_ASIO_ASSOCIATED_EXECUTOR_HPP
  12 #define BOOST_ASIO_ASSOCIATED_EXECUTOR_HPP
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  15 # pragma once
  16 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  17
  18 #include <boost/asio/detail/config.hpp>
  19 #include <boost/asio/detail/type_traits.hpp>
  20 #include <boost/asio/is_executor.hpp>
  21 #include <boost/asio/system_executor.hpp>
  22
  23 #include <boost/asio/detail/push_options.hpp>
  24
  25 namespace boost {
  26 namespace asio {
  27 namespace detail {
  28
  29 template <typename>
  30 struct associated_executor_check
  31 {
  32   typedef void type;
  33 };
  34
  35 template <typename T, typename E, typename = void>
  36 struct associated_executor_impl
  37 {
  38   typedef E type;
  39
  40   static type get(const T&, const E& e) BOOST_ASIO_NOEXCEPT
  41   {
  42     return e;
  43   }
  44 };
  45
  46 template <typename T, typename E>
  47 struct associated_executor_impl<T, E,
  48   typename associated_executor_check<typename T::executor_type>::type>
  49 {
  50   typedef typename T::executor_type type;
  51
  52   static type get(const T& t, const E&) BOOST_ASIO_NOEXCEPT
  53   {
  54     return t.get_executor();
  55   }
  56 };
  57
  58 } // namespace detail
  59
  60 /// Traits type used to obtain the executor associated with an object.
  61 /**
  62  * A program may specialise this traits type if the @c T template parameter in
  63  * the specialisation is a user-defined type. The template parameter @c
  64  * Executor shall be a type meeting the Executor requirements.
  65  *
  66  * Specialisations shall meet the following requirements, where @c t is a const
  67  * reference to an object of type @c T, and @c e is an object of type @c
  68  * Executor.
  69  *
  70  * @li Provide a nested typedef @c type that identifies a type meeting the
  71  * Executor requirements.
  72  *
  73  * @li Provide a noexcept static member function named @c get, callable as @c
  74  * get(t) and with return type @c type.
  75  *
  76  * @li Provide a noexcept static member function named @c get, callable as @c
  77  * get(t,e) and with return type @c type.
  78  */
  79 template <typename T, typename Executor = system_executor>
  80 struct associated_executor
  81 {
  82   /// If @c T has a nested type @c executor_type, <tt>T::executor_type</tt>.
  83   /// Otherwise @c Executor.
  84 #if defined(GENERATING_DOCUMENTATION)
  85   typedef see_below type;
  86 #else // defined(GENERATING_DOCUMENTATION)
  87   typedef typename detail::associated_executor_impl<T, Executor>::type type;
  88 #endif // defined(GENERATING_DOCUMENTATION)
  89
  90   /// If @c T has a nested type @c executor_type, returns
  91   /// <tt>t.get_executor()</tt>. Otherwise returns @c ex.
  92   static type get(const T& t,
  93       const Executor& ex = Executor()) BOOST_ASIO_NOEXCEPT
  94   {
  95     return detail::associated_executor_impl<T, Executor>::get(t, ex);
  96   }
  97 };
  98
  99 /// Helper function to obtain an object's associated executor.
 100 /**
 101  * @returns <tt>associated_executor<T>::get(t)</tt>
 102  */
 103 template <typename T>
 104 inline typename associated_executor<T>::type
 105 get_associated_executor(const T& t) BOOST_ASIO_NOEXCEPT
 106 {
 107   return associated_executor<T>::get(t);
 108 }
 109
 110 /// Helper function to obtain an object's associated executor.
 111 /**
 112  * @returns <tt>associated_executor<T, Executor>::get(t, ex)</tt>
 113  */
 114 template <typename T, typename Executor>
 115 inline typename associated_executor<T, Executor>::type
 116 get_associated_executor(const T& t, const Executor& ex,
 117     typename enable_if<is_executor<
 118       Executor>::value>::type* = 0) BOOST_ASIO_NOEXCEPT
 119 {
 120   return associated_executor<T, Executor>::get(t, ex);
 121 }
 122
 123 /// Helper function to obtain an object's associated executor.
 124 /**
 125  * @returns <tt>associated_executor<T, typename
 126  * ExecutionContext::executor_type>::get(t, ctx.get_executor())</tt>
 127  */
 128 template <typename T, typename ExecutionContext>
 129 inline typename associated_executor<T,
 130   typename ExecutionContext::executor_type>::type
 131 get_associated_executor(const T& t, ExecutionContext& ctx,
 132     typename enable_if<is_convertible<ExecutionContext&,
 133       execution_context&>::value>::type* = 0) BOOST_ASIO_NOEXCEPT
 134 {
 135   return associated_executor<T,
 136     typename ExecutionContext::executor_type>::get(t, ctx.get_executor());
 137 }
 138
 139 #if defined(BOOST_ASIO_HAS_ALIAS_TEMPLATES)
 140
 141 template <typename T, typename Executor = system_executor>
 142 using associated_executor_t = typename associated_executor<T, Executor>::type;
 143
 144 #endif // defined(BOOST_ASIO_HAS_ALIAS_TEMPLATES)
 145
 146 } // namespace asio
 147 } // namespace boost
 148
 149 #include <boost/asio/detail/pop_options.hpp>
 150
 151 #endif // BOOST_ASIO_ASSOCIATED_EXECUTOR_HPP