1//
2// handler_invoke_hook.hpp
3// ~~~~~~~~~~~~~~~~~~~~~~~
4//
5// Copyright (c) 2003-2015 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
22namespace boost {
23namespace 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.
66template <typename Function>
67inline void asio_handler_invoke(Function& function, ...)
68{
69 function();
70}
71
72/// Default handler invocation hook used for const function objects.
73template <typename Function>
74inline 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
88