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1 | // |
2 | // handler_invoke_hook.hpp | |
3 | // ~~~~~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
f67539c2 | 5 | // Copyright (c) 2003-2020 Christopher M. Kohlhoff (chris at kohlhoff dot com) |
7c673cae FG |
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_HANDLER_INVOKE_HOOK_HPP | |
12 | #define BOOST_ASIO_HANDLER_INVOKE_HOOK_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 | ||
20 | #include <boost/asio/detail/push_options.hpp> | |
21 | ||
22 | namespace boost { | |
23 | namespace asio { | |
24 | ||
25 | /** @defgroup asio_handler_invoke boost::asio::asio_handler_invoke | |
26 | * | |
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27 | * @brief (Deprecated: Use the associated_executor trait.) Default invoke |
28 | * function for handlers. | |
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29 | * |
30 | * Completion handlers for asynchronous operations are invoked by the | |
b32b8144 | 31 | * io_context associated with the corresponding object (e.g. a socket or |
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32 | * deadline_timer). Certain guarantees are made on when the handler may be |
33 | * invoked, in particular that a handler can only be invoked from a thread that | |
b32b8144 | 34 | * is currently calling @c run() on the corresponding io_context object. |
7c673cae | 35 | * Handlers may subsequently be invoked through other objects (such as |
b32b8144 | 36 | * io_context::strand objects) that provide additional guarantees. |
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37 | * |
38 | * When asynchronous operations are composed from other asynchronous | |
39 | * operations, all intermediate handlers should be invoked using the same | |
40 | * method as the final handler. This is required to ensure that user-defined | |
41 | * objects are not accessed in a way that may violate the guarantees. This | |
42 | * hooking function ensures that the invoked method used for the final handler | |
43 | * is accessible at each intermediate step. | |
44 | * | |
45 | * Implement asio_handler_invoke for your own handlers to specify a custom | |
46 | * invocation strategy. | |
47 | * | |
48 | * This default implementation invokes the function object like so: | |
49 | * @code function(); @endcode | |
50 | * If necessary, the default implementation makes a copy of the function object | |
51 | * so that the non-const operator() can be used. | |
52 | * | |
53 | * @par Example | |
54 | * @code | |
55 | * class my_handler; | |
56 | * | |
57 | * template <typename Function> | |
58 | * void asio_handler_invoke(Function function, my_handler* context) | |
59 | * { | |
60 | * context->strand_.dispatch(function); | |
61 | * } | |
62 | * @endcode | |
63 | */ | |
64 | /*@{*/ | |
65 | ||
20effc67 TL |
66 | #if defined(BOOST_ASIO_NO_DEPRECATED) |
67 | ||
68 | // Places in asio that would have previously called the invocation hook to | |
69 | // execute a handler, now call it only to check whether the result type is this | |
70 | // type. If the result is not this type, it indicates that the user code still | |
71 | // has the old hooks in place, and if so we want to trigger a compile error. | |
72 | enum asio_handler_invoke_is_no_longer_used {}; | |
73 | ||
74 | typedef asio_handler_invoke_is_no_longer_used | |
75 | asio_handler_invoke_is_deprecated; | |
76 | ||
77 | #else // defined(BOOST_ASIO_NO_DEPRECATED) | |
78 | ||
79 | typedef void asio_handler_invoke_is_deprecated; | |
80 | ||
81 | #endif // defined(BOOST_ASIO_NO_DEPRECATED) | |
82 | ||
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83 | /// Default handler invocation hook used for non-const function objects. |
84 | template <typename Function> | |
20effc67 TL |
85 | inline asio_handler_invoke_is_deprecated |
86 | asio_handler_invoke(Function& function, ...) | |
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87 | { |
88 | function(); | |
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89 | #if defined(BOOST_ASIO_NO_DEPRECATED) |
90 | return asio_handler_invoke_is_no_longer_used(); | |
91 | #endif // defined(BOOST_ASIO_NO_DEPRECATED) | |
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92 | } |
93 | ||
94 | /// Default handler invocation hook used for const function objects. | |
95 | template <typename Function> | |
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96 | inline asio_handler_invoke_is_deprecated |
97 | asio_handler_invoke(const Function& function, ...) | |
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98 | { |
99 | Function tmp(function); | |
100 | tmp(); | |
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101 | #if defined(BOOST_ASIO_NO_DEPRECATED) |
102 | return asio_handler_invoke_is_no_longer_used(); | |
103 | #endif // defined(BOOST_ASIO_NO_DEPRECATED) | |
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104 | } |
105 | ||
106 | /*@}*/ | |
107 | ||
108 | } // namespace asio | |
109 | } // namespace boost | |
110 | ||
111 | #include <boost/asio/detail/pop_options.hpp> | |
112 | ||
113 | #endif // BOOST_ASIO_HANDLER_INVOKE_HOOK_HPP |