100 lines
6.7 KiB
HTML
100 lines
6.7 KiB
HTML
<html>
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
|
|
<title>Timer.1 - Using a timer synchronously</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="../tutorial.html" title="Tutorial">
|
|
<link rel="prev" href="../tutorial.html" title="Tutorial">
|
|
<link rel="next" href="tuttimer1/src.html" title="Source listing for Timer.1">
|
|
<meta name="viewport" content="width=device-width, initial-scale=1">
|
|
</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="../tutorial.html"><img src="../../prev.png" alt="Prev"></a><a accesskey="u" href="../tutorial.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="tuttimer1/src.html"><img src="../../next.png" alt="Next"></a>
|
|
</div>
|
|
<div class="section">
|
|
<div class="titlepage"><div><div><h3 class="title">
|
|
<a name="asio.tutorial.tuttimer1"></a><a class="link" href="tuttimer1.html" title="Timer.1 - Using a timer synchronously">Timer.1 - Using a timer synchronously</a>
|
|
</h3></div></div></div>
|
|
<p>
|
|
This tutorial program introduces asio by showing how to perform a blocking
|
|
wait on a timer.
|
|
</p>
|
|
<p>
|
|
We start by including the necessary header files.
|
|
</p>
|
|
<p>
|
|
All of the asio classes can be used by simply including the <code class="computeroutput"><span class="string">"asio.hpp"</span></code> header file.
|
|
</p>
|
|
<pre class="programlisting"><span class="special">#</span><span class="identifier">include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span>
|
|
<span class="special">#</span><span class="identifier">include</span> <span class="special"><</span><span class="identifier">asio</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
|
|
</pre>
|
|
<p>
|
|
All programs that use asio need to have at least one I/O execution context,
|
|
such as an <a class="link" href="../reference/io_context.html" title="io_context">io_context</a> or
|
|
<a class="link" href="../reference/thread_pool.html" title="thread_pool">thread_pool</a> object. An
|
|
I/O execution context provides access to I/O functionality. We declare an
|
|
object of type <a class="link" href="../reference/io_context.html" title="io_context">io_context</a>
|
|
first thing in the main function.
|
|
</p>
|
|
<pre class="programlisting"><span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
|
|
<span class="special">{</span>
|
|
<span class="identifier">asio</span><span class="special">::</span><span class="identifier">io_context</span> <span class="identifier">io</span><span class="special">;</span>
|
|
</pre>
|
|
<p>
|
|
Next we declare an object of type asio::steady_timer. The core asio classes
|
|
that provide I/O functionality (or as in this case timer functionality) always
|
|
take an executor, or a reference to an execution context (such as <a class="link" href="../reference/io_context.html" title="io_context">io_context</a>),
|
|
as their first constructor argument. The second argument to the constructor
|
|
sets the timer to expire 5 seconds from now.
|
|
</p>
|
|
<pre class="programlisting"> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">steady_timer</span> <span class="identifier">t</span><span class="special">(</span><span class="identifier">io</span><span class="special">,</span> <span class="identifier">asio</span><span class="special">::</span><span class="identifier">chrono</span><span class="special">::</span><span class="identifier">seconds</span><span class="special">(</span><span class="number">5</span><span class="special">));</span>
|
|
</pre>
|
|
<p>
|
|
In this simple example we perform a blocking wait on the timer. That is,
|
|
the call to <a class="link" href="../reference/basic_waitable_timer/wait.html" title="basic_waitable_timer::wait">steady_timer::wait()</a>
|
|
will not return until the timer has expired, 5 seconds after it was created
|
|
(i.e. not from when the wait starts).
|
|
</p>
|
|
<p>
|
|
A timer is always in one of two states: "expired" or "not
|
|
expired". If the <a class="link" href="../reference/basic_waitable_timer/wait.html" title="basic_waitable_timer::wait">steady_timer::wait()</a>
|
|
function is called on an expired timer, it will return immediately.
|
|
</p>
|
|
<pre class="programlisting"> <span class="identifier">t</span><span class="special">.</span><span class="identifier">wait</span><span class="special">();</span>
|
|
</pre>
|
|
<p>
|
|
Finally we print the obligatory <code class="computeroutput"><span class="string">"Hello,
|
|
world!"</span></code> message to show when the timer has expired.
|
|
</p>
|
|
<pre class="programlisting"> <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"Hello, world!"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
|
|
|
|
<span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
|
|
<span class="special">}</span>
|
|
</pre>
|
|
<p>
|
|
See the <a class="link" href="tuttimer1/src.html" title="Source listing for Timer.1">full source listing</a>
|
|
</p>
|
|
<p>
|
|
Return to the <a class="link" href="../tutorial.html" title="Tutorial">tutorial index</a>
|
|
</p>
|
|
<p>
|
|
Next: <a class="link" href="tuttimer2.html" title="Timer.2 - Using a timer asynchronously">Timer.2 - Using a timer asynchronously</a>
|
|
</p>
|
|
</div>
|
|
<div class="copyright-footer">Copyright © 2003-2023 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>
|
|
<hr>
|
|
<div class="spirit-nav">
|
|
<a accesskey="p" href="../tutorial.html"><img src="../../prev.png" alt="Prev"></a><a accesskey="u" href="../tutorial.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="tuttimer1/src.html"><img src="../../next.png" alt="Next"></a>
|
|
</div>
|
|
</body>
|
|
</html>
|