ceph/src/boost/boost/asio/uses_executor.hpp

   1 //
   2 // uses_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_USES_EXECUTOR_HPP
  12 #define BOOST_ASIO_USES_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
  21 #include <boost/asio/detail/push_options.hpp>
  22
  23 namespace boost {
  24 namespace asio {
  25
  26 /// A special type, similar to std::nothrow_t, used to disambiguate
  27 /// constructors that accept executor arguments.
  28 /**
  29  * The executor_arg_t struct is an empty structure type used as a unique type
  30  * to disambiguate constructor and function overloading. Specifically, some
  31  * types have constructors with executor_arg_t as the first argument,
  32  * immediately followed by an argument of a type that satisfies the Executor
  33  * type requirements.
  34  */
  35 struct executor_arg_t
  36 {
  37   /// Constructor.
  38   BOOST_ASIO_CONSTEXPR executor_arg_t() BOOST_ASIO_NOEXCEPT
  39   {
  40   }
  41 };
  42
  43 /// A special value, similar to std::nothrow, used to disambiguate constructors
  44 /// that accept executor arguments.
  45 /**
  46  * See boost::asio::executor_arg_t and boost::asio::uses_executor
  47  * for more information.
  48  */
  49 #if defined(BOOST_ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION)
  50 constexpr executor_arg_t executor_arg;
  51 #elif defined(BOOST_ASIO_MSVC)
  52 __declspec(selectany) executor_arg_t executor_arg;
  53 #endif
  54
  55 /// The uses_executor trait detects whether a type T has an associated executor
  56 /// that is convertible from type Executor.
  57 /**
  58  * Meets the BinaryTypeTrait requirements. The Asio library provides a
  59  * definition that is derived from false_type. A program may specialize this
  60  * template to derive from true_type for a user-defined type T that can be
  61  * constructed with an executor, where the first argument of a constructor has
  62  * type executor_arg_t and the second argument is convertible from type
  63  * Executor.
  64  */
  65 template <typename T, typename Executor>
  66 struct uses_executor : false_type {};
  67
  68 } // namespace asio
  69 } // namespace boost
  70
  71 #include <boost/asio/detail/pop_options.hpp>
  72
  73 #endif // BOOST_ASIO_USES_EXECUTOR_HPP