1//
2// as_tuple.hpp
3// ~~~~~~~~~~~~
4//
5// Copyright (c) 2003-2024 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_AS_TUPLE_HPP
12#define BOOST_ASIO_AS_TUPLE_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
23namespace boost {
24namespace asio {
25
26/// A @ref completion_token adapter used to specify that the completion handler
27/// arguments should be combined into a single tuple argument.
28/**
29 * The as_tuple_t class is used to indicate that any arguments to the
30 * completion handler should be combined and passed as a single tuple argument.
31 * The arguments are first moved into a @c std::tuple and that tuple is then
32 * passed to the completion handler.
33 */
34template <typename CompletionToken>
35class as_tuple_t
36{
37public:
38 /// Tag type used to prevent the "default" constructor from being used for
39 /// conversions.
40 struct default_constructor_tag {};
41
42 /// Default constructor.
43 /**
44 * This constructor is only valid if the underlying completion token is
45 * default constructible and move constructible. The underlying completion
46 * token is itself defaulted as an argument to allow it to capture a source
47 * location.
48 */
49 constexpr as_tuple_t(
50 default_constructor_tag = default_constructor_tag(),
51 CompletionToken token = CompletionToken())
52 : token_(static_cast<CompletionToken&&>(token))
53 {
54 }
55
56 /// Constructor.
57 template <typename T>
58 constexpr explicit as_tuple_t(
59 T&& completion_token)
60 : token_(static_cast<T&&>(completion_token))
61 {
62 }
63
64 /// Adapts an executor to add the @c as_tuple_t completion token as the
65 /// default.
66 template <typename InnerExecutor>
67 struct executor_with_default : InnerExecutor
68 {
69 /// Specify @c as_tuple_t as the default completion token type.
70 typedef as_tuple_t default_completion_token_type;
71
72 /// Construct the adapted executor from the inner executor type.
73 template <typename InnerExecutor1>
74 executor_with_default(const InnerExecutor1& ex,
75 constraint_t<
76 conditional_t<
77 !is_same<InnerExecutor1, executor_with_default>::value,
78 is_convertible<InnerExecutor1, InnerExecutor>,
79 false_type
80 >::value
81 > = 0) noexcept
82 : InnerExecutor(ex)
83 {
84 }
85 };
86
87 /// Type alias to adapt an I/O object to use @c as_tuple_t as its
88 /// default completion token type.
89 template <typename T>
90 using as_default_on_t = typename T::template rebind_executor<
91 executor_with_default<typename T::executor_type>>::other;
92
93 /// Function helper to adapt an I/O object to use @c as_tuple_t as its
94 /// default completion token type.
95 template <typename T>
96 static typename decay_t<T>::template rebind_executor<
97 executor_with_default<typename decay_t<T>::executor_type>
98 >::other
99 as_default_on(T&& object)
100 {
101 return typename decay_t<T>::template rebind_executor<
102 executor_with_default<typename decay_t<T>::executor_type>
103 >::other(static_cast<T&&>(object));
104 }
105
106//private:
107 CompletionToken token_;
108};
109
110/// Adapt a @ref completion_token to specify that the completion handler
111/// arguments should be combined into a single tuple argument.
112template <typename CompletionToken>
113BOOST_ASIO_NODISCARD inline
114constexpr as_tuple_t<decay_t<CompletionToken>>
115as_tuple(CompletionToken&& completion_token)
116{
117 return as_tuple_t<decay_t<CompletionToken>>(
118 static_cast<CompletionToken&&>(completion_token));
119}
120
121} // namespace asio
122} // namespace boost
123
124#include <boost/asio/detail/pop_options.hpp>
125
126#include <boost/asio/impl/as_tuple.hpp>
127
128#endif // BOOST_ASIO_AS_TUPLE_HPP
129

source code of boost/libs/asio/include/boost/asio/as_tuple.hpp