blob: 162f4c5de05ac7b20ba46c244154f093bcf9df84 (
plain)
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
|
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Timers</title>
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.76.1">
<link rel="home" href="../../boost_asio.html" title="Boost.Asio">
<link rel="up" href="../overview.html" title="Overview">
<link rel="prev" href="networking/bsd_sockets.html" title="The BSD Socket API and Boost.Asio">
<link rel="next" href="serial_ports.html" title="Serial Ports">
</head>
<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
<table cellpadding="2" width="100%"><tr>
<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td>
<td align="center"><a href="../../../../index.html">Home</a></td>
<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td>
<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
<td align="center"><a href="../../../../more/index.htm">More</a></td>
</tr></table>
<hr>
<div class="spirit-nav">
<a accesskey="p" href="networking/bsd_sockets.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../overview.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../boost_asio.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="serial_ports.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
<div class="section">
<div class="titlepage"><div><div><h3 class="title">
<a name="boost_asio.overview.timers"></a><a class="link" href="timers.html" title="Timers">Timers</a>
</h3></div></div></div>
<p>
Long running I/O operations will often have a deadline by which they must
have completed. These deadlines may be expressed as absolute times, but are
often calculated relative to the current time.
</p>
<p>
As a simple example, to perform a synchronous wait operation on a timer using
a relative time one may write:
</p>
<pre class="programlisting"><span class="identifier">io_service</span> <span class="identifier">i</span><span class="special">;</span>
<span class="special">...</span>
<span class="identifier">deadline_timer</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span>
<span class="identifier">t</span><span class="special">.</span><span class="identifier">expires_from_now</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">));</span>
<span class="identifier">t</span><span class="special">.</span><span class="identifier">wait</span><span class="special">();</span>
</pre>
<p>
More commonly, a program will perform an asynchronous wait operation on a
timer:
</p>
<pre class="programlisting"><span class="keyword">void</span> <span class="identifier">handler</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span> <span class="identifier">ec</span><span class="special">)</span> <span class="special">{</span> <span class="special">...</span> <span class="special">}</span>
<span class="special">...</span>
<span class="identifier">io_service</span> <span class="identifier">i</span><span class="special">;</span>
<span class="special">...</span>
<span class="identifier">deadline_timer</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span>
<span class="identifier">t</span><span class="special">.</span><span class="identifier">expires_from_now</span><span class="special">(</span><span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">::</span><span class="identifier">milliseconds</span><span class="special">(</span><span class="number">400</span><span class="special">));</span>
<span class="identifier">t</span><span class="special">.</span><span class="identifier">async_wait</span><span class="special">(</span><span class="identifier">handler</span><span class="special">);</span>
<span class="special">...</span>
<span class="identifier">i</span><span class="special">.</span><span class="identifier">run</span><span class="special">();</span>
</pre>
<p>
The deadline associated with a timer may also be obtained as a relative time:
</p>
<pre class="programlisting"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">::</span><span class="identifier">time_duration</span> <span class="identifier">time_until_expiry</span>
<span class="special">=</span> <span class="identifier">t</span><span class="special">.</span><span class="identifier">expires_from_now</span><span class="special">();</span>
</pre>
<p>
or as an absolute time to allow composition of timers:
</p>
<pre class="programlisting"><span class="identifier">deadline_timer</span> <span class="identifier">t2</span><span class="special">(</span><span class="identifier">i</span><span class="special">);</span>
<span class="identifier">t2</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">(</span><span class="identifier">t</span><span class="special">.</span><span class="identifier">expires_at</span><span class="special">()</span> <span class="special">+</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">posix_time</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">30</span><span class="special">));</span>
</pre>
<h5>
<a name="boost_asio.overview.timers.h0"></a>
<span><a name="boost_asio.overview.timers.see_also"></a></span><a class="link" href="timers.html#boost_asio.overview.timers.see_also">See
Also</a>
</h5>
<p>
<a class="link" href="../reference/basic_deadline_timer.html" title="basic_deadline_timer">basic_deadline_timer</a>,
<a class="link" href="../reference/deadline_timer.html" title="deadline_timer">deadline_timer</a>,
<a class="link" href="../reference/deadline_timer_service.html" title="deadline_timer_service">deadline_timer_service</a>,
<a class="link" href="../tutorial/tuttimer1.html" title="Timer.1 - Using a timer synchronously">timer tutorials</a>.
</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 © 2003-2012 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="networking/bsd_sockets.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../overview.html"><img src="../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../boost_asio.html"><img src="../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="serial_ports.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>
|
