asio_handler_invoke.html
6.31 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>asio_handler_invoke</title>
<link rel="stylesheet" href="../../boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
<link rel="home" href="../../index.html" title="Asio">
<link rel="up" href="../reference.html" title="Reference">
<link rel="prev" href="asio_handler_deallocate.html" title="asio_handler_deallocate">
<link rel="next" href="asio_handler_invoke/overload1.html" title="asio_handler_invoke (1 of 2 overloads)">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../asio.png"></td></tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="asio_handler_deallocate.html"><img src="../../prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../home.png" alt="Home"></a><a accesskey="n" href="asio_handler_invoke/overload1.html"><img src="../../next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="asio.reference.asio_handler_invoke"></a><a class="link" href="asio_handler_invoke.html" title="asio_handler_invoke">asio_handler_invoke</a>
</h3></div></div></div>
<p>
<a class="indexterm" name="asio.indexterm.asio_handler_invoke"></a>
(Deprecated: Use the
<a class="link" href="associated_executor.html" title="associated_executor"><code class="computeroutput">associated_executor</code></a>
trait.) Default invoke function for handlers.
</p>
<p>
Default handler invocation hook used for non-const function objects.
</p>
<pre class="programlisting">template<
typename Function>
asio_handler_invoke_is_deprecated <a class="link" href="asio_handler_invoke/overload1.html" title="asio_handler_invoke (1 of 2 overloads)">asio_handler_invoke</a>(
Function & function,
... );
<span class="emphasis"><em>» <a class="link" href="asio_handler_invoke/overload1.html" title="asio_handler_invoke (1 of 2 overloads)">more...</a></em></span>
</pre>
<p>
Default handler invocation hook used for const function objects.
</p>
<pre class="programlisting">template<
typename Function>
asio_handler_invoke_is_deprecated <a class="link" href="asio_handler_invoke/overload2.html" title="asio_handler_invoke (2 of 2 overloads)">asio_handler_invoke</a>(
const Function & function,
... );
<span class="emphasis"><em>» <a class="link" href="asio_handler_invoke/overload2.html" title="asio_handler_invoke (2 of 2 overloads)">more...</a></em></span>
</pre>
<p>
Completion handlers for asynchronous operations are invoked by the <a class="link" href="io_context.html" title="io_context"><code class="computeroutput">io_context</code></a> associated
with the corresponding object (e.g. a socket or deadline_timer). Certain
guarantees are made on when the handler may be invoked, in particular that
a handler can only be invoked from a thread that is currently calling <code class="computeroutput">run()</code>
on the corresponding <a class="link" href="io_context.html" title="io_context"><code class="computeroutput">io_context</code></a>
object. Handlers may subsequently be invoked through other objects (such
as <a class="link" href="io_context__strand.html" title="io_context::strand"><code class="computeroutput">io_context::strand</code></a>
objects) that provide additional guarantees.
</p>
<p>
When asynchronous operations are composed from other asynchronous operations,
all intermediate handlers should be invoked using the same method as the
final handler. This is required to ensure that user-defined objects are not
accessed in a way that may violate the guarantees. This hooking function
ensures that the invoked method used for the final handler is accessible
at each intermediate step.
</p>
<p>
Implement asio_handler_invoke for your own handlers to specify a custom invocation
strategy.
</p>
<p>
This default implementation invokes the function object like so:
</p>
<pre class="programlisting">function();
</pre>
<p>
If necessary, the default implementation makes a copy of the function object
so that the non-const operator() can be used.
</p>
<h5>
<a name="asio.reference.asio_handler_invoke.h0"></a>
<span><a name="asio.reference.asio_handler_invoke.example"></a></span><a class="link" href="asio_handler_invoke.html#asio.reference.asio_handler_invoke.example">Example</a>
</h5>
<pre class="programlisting">class my_handler;
template <typename Function>
void asio_handler_invoke(Function function, my_handler* context)
{
context->strand_.dispatch(function);
}
</pre>
<h5>
<a name="asio.reference.asio_handler_invoke.h1"></a>
<span><a name="asio.reference.asio_handler_invoke.requirements"></a></span><a class="link" href="asio_handler_invoke.html#asio.reference.asio_handler_invoke.requirements">Requirements</a>
</h5>
<p>
<span class="emphasis"><em>Header: </em></span><code class="literal">asio/handler_invoke_hook.hpp</code>
</p>
<p>
<span class="emphasis"><em>Convenience header: </em></span><code class="literal">asio.hpp</code>
</p>
</div>
<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
<td align="left"></td>
<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M.
Kohlhoff<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
</p>
</div></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="asio_handler_deallocate.html"><img src="../../prev.png" alt="Prev"></a><a accesskey="u" href="../reference.html"><img src="../../up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../home.png" alt="Home"></a><a accesskey="n" href="asio_handler_invoke/overload1.html"><img src="../../next.png" alt="Next"></a>
</div>
</body>
</html>