doc/html/boost_asio/reference/WaitTraits.html


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
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136

<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
<title>Wait traits requirements</title>
<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css">
<meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
<link rel="home" href="../../boost_asio.html" title="Boost.Asio">
<link rel="up" href="../reference.html" title="Reference">
<link rel="prev" href="WaitHandler.html" title="Wait handler requirements">
<link rel="next" href="WriteHandler.html" title="Write handler requirements">
</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="WaitHandler.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="WriteHandler.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.reference.WaitTraits"></a><a class="link" href="WaitTraits.html" title="Wait traits requirements">Wait traits requirements</a>
</h3></div></div></div>
<p>
        The <code class="computeroutput">basic_waitable_timer</code> template uses wait traits to allow
        programs to customize <code class="computeroutput">wait</code> and <code class="computeroutput">async_wait</code> behavior.
        [<span class="emphasis"><em>Note:</em></span> Possible uses of wait traits include:<br> &#8212; To
        enable timers based on non-realtime clocks.<br> &#8212; Determining how quickly
        wallclock-based timers respond to system time changes.<br> &#8212; Correcting for
        errors or rounding timeouts to boundaries.<br> &#8212; Preventing duration overflow.
        That is, a program may set a timer's expiry <code class="computeroutput">e</code> to be <code class="computeroutput">Clock::max()</code>
        (meaning never reached) or <code class="computeroutput">Clock::min()</code> (meaning always in the
        past). As a result, computing the duration until timer expiry as <code class="computeroutput">e
        - Clock::now()</code> may cause overflow. &#8212;<span class="emphasis"><em>end note</em></span>]
      </p>
<p>
        For a type <code class="computeroutput">Clock</code> meeting the <code class="computeroutput">Clock</code> requirements
        (C++Std [time.clock.req]), a type <code class="computeroutput">X</code> meets the <code class="computeroutput">WaitTraits</code>
        requirements if it satisfies the requirements listed below.
      </p>
<p>
        In the table below, <code class="computeroutput">t</code> denotes a (possibly const) value of type
        <code class="computeroutput">Clock::time_point</code>; and <code class="computeroutput">d</code> denotes a (possibly const)
        value of type <code class="computeroutput">Clock::duration</code>.
      </p>
<div class="table">
<a name="boost_asio.reference.WaitTraits.t0"></a><p class="title"><b>Table&#160;31.&#160;WaitTraits requirements</b></p>
<div class="table-contents"><table class="table" summary="WaitTraits requirements">
<colgroup>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>
                <p>
                  expression
                </p>
              </th>
<th>
                <p>
                  return type
                </p>
              </th>
<th>
                <p>
                  assertion/note<br> pre/post-condition
                </p>
              </th>
</tr></thead>
<tbody>
<tr>
<td>
                <p>
                  <code class="computeroutput">X::to_wait_duration(d)</code>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput">Clock::duration</code>
                </p>
              </td>
<td>
                <p>
                  Returns a <code class="computeroutput">Clock::duration</code> value to be used in a <code class="computeroutput">wait</code>
                  or <code class="computeroutput">async_wait</code> operation. [<span class="emphasis"><em>Note:</em></span>
                  The return value is typically representative of the duration <code class="computeroutput">d</code>.
                  &#8212;<span class="emphasis"><em>end note</em></span>]
                </p>
              </td>
</tr>
<tr>
<td>
                <p>
                  <code class="computeroutput">X::to_wait_duration(t)</code>
                </p>
              </td>
<td>
                <p>
                  <code class="computeroutput">Clock::duration</code>
                </p>
              </td>
<td>
                <p>
                  Returns a <code class="computeroutput">Clock::duration</code> value to be used in a <code class="computeroutput">wait</code>
                  or <code class="computeroutput">async_wait</code> operation. [<span class="emphasis"><em>Note:</em></span>
                  The return value is typically representative of the duration from
                  <code class="computeroutput">Clock::now()</code> until the time point <code class="computeroutput">t</code>.
                  &#8212;<span class="emphasis"><em>end note</em></span>]
                </p>
              </td>
</tr>
</tbody>
</table></div>
</div>
<br class="table-break">
</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 &#169; 2003-2018 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="WaitHandler.html"><img src="../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../reference.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="WriteHandler.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a>
</div>
</body>
</html>