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1 | // |
2 | // handler_invoke_hook.hpp | |
3 | // ~~~~~~~~~~~~~~~~~~~~~~~ | |
4 | // | |
5 | // Copyright (c) 2003-2016 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_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 | * | |
27 | * @brief Default invoke function for handlers. | |
28 | * | |
29 | * Completion handlers for asynchronous operations are invoked by the | |
30 | * io_service associated with the corresponding object (e.g. a socket or | |
31 | * deadline_timer). Certain guarantees are made on when the handler may be | |
32 | * invoked, in particular that a handler can only be invoked from a thread that | |
33 | * is currently calling @c run() on the corresponding io_service object. | |
34 | * Handlers may subsequently be invoked through other objects (such as | |
35 | * io_service::strand objects) that provide additional guarantees. | |
36 | * | |
37 | * When asynchronous operations are composed from other asynchronous | |
38 | * operations, all intermediate handlers should be invoked using the same | |
39 | * method as the final handler. This is required to ensure that user-defined | |
40 | * objects are not accessed in a way that may violate the guarantees. This | |
41 | * hooking function ensures that the invoked method used for the final handler | |
42 | * is accessible at each intermediate step. | |
43 | * | |
44 | * Implement asio_handler_invoke for your own handlers to specify a custom | |
45 | * invocation strategy. | |
46 | * | |
47 | * This default implementation invokes the function object like so: | |
48 | * @code function(); @endcode | |
49 | * If necessary, the default implementation makes a copy of the function object | |
50 | * so that the non-const operator() can be used. | |
51 | * | |
52 | * @par Example | |
53 | * @code | |
54 | * class my_handler; | |
55 | * | |
56 | * template <typename Function> | |
57 | * void asio_handler_invoke(Function function, my_handler* context) | |
58 | * { | |
59 | * context->strand_.dispatch(function); | |
60 | * } | |
61 | * @endcode | |
62 | */ | |
63 | /*@{*/ | |
64 | ||
65 | /// Default handler invocation hook used for non-const function objects. | |
66 | template <typename Function> | |
67 | inline void asio_handler_invoke(Function& function, ...) | |
68 | { | |
69 | function(); | |
70 | } | |
71 | ||
72 | /// Default handler invocation hook used for const function objects. | |
73 | template <typename Function> | |
74 | inline void asio_handler_invoke(const Function& function, ...) | |
75 | { | |
76 | Function tmp(function); | |
77 | tmp(); | |
78 | } | |
79 | ||
80 | /*@}*/ | |
81 | ||
82 | } // namespace asio | |
83 | } // namespace boost | |
84 | ||
85 | #include <boost/asio/detail/pop_options.hpp> | |
86 | ||
87 | #endif // BOOST_ASIO_HANDLER_INVOKE_HOOK_HPP |