74 lines
6.2 KiB
HTML
74 lines
6.2 KiB
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
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<title>Service requirements</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.75.2">
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<link rel="home" href="../../index.html" title="Asio">
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<link rel="up" href="../reference.html" title="Reference">
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<link rel="prev" href="Sender.html" title="Sender concepts">
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<link rel="next" href="SettableSerialPortOption.html" title="Settable serial port option requirements">
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<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
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<table cellpadding="2" width="100%"><tr><td valign="top"><img alt="asio C++ library" width="250" height="60" src="../../asio.png"></td></tr></table>
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<hr>
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<div class="spirit-nav">
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<a accesskey="p" href="Sender.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="SettableSerialPortOption.html"><img src="../../next.png" alt="Next"></a>
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</div>
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<div class="section">
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<div class="titlepage"><div><div><h3 class="title">
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<a name="asio.reference.Service"></a><a class="link" href="Service.html" title="Service requirements">Service requirements</a>
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</h3></div></div></div>
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<p>
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A class is a <span class="emphasis"><em>service</em></span> if it is publicly and unambiguously
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derived from <code class="computeroutput"><span class="identifier">execution_context</span><span class="special">::</span><span class="identifier">service</span></code>,
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or if it is publicly and unambiguously derived from another service. For
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a service <code class="computeroutput"><span class="identifier">S</span></code>, <code class="computeroutput"><span class="identifier">S</span><span class="special">::</span><span class="identifier">key_type</span></code>
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shall be valid and denote a type (C++Std [temp.deduct]), <code class="computeroutput"><span class="identifier">is_base_of_v</span><span class="special"><</span><span class="keyword">typename</span> <span class="identifier">S</span><span class="special">::</span><span class="identifier">key_type</span><span class="special">,</span> <span class="identifier">S</span><span class="special">></span></code>
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shall be <code class="computeroutput"><span class="keyword">true</span></code>, and <code class="computeroutput"><span class="identifier">S</span></code> shall satisfy the <code class="computeroutput"><span class="identifier">Destructible</span></code>
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requirements (C++Std [destructible]).
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</p>
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<p>
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The first parameter of all service constructors shall be an lvalue reference
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to <code class="computeroutput"><span class="identifier">execution_context</span></code>. This
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parameter denotes the <code class="computeroutput"><span class="identifier">execution_context</span></code>
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object that represents a set of services, of which the service object will
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be a member. [<span class="emphasis"><em>Note:</em></span> These constructors may be called
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by the <code class="computeroutput"><span class="identifier">make_service</span></code> function.
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—<span class="emphasis"><em>end note</em></span>]
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</p>
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<p>
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A service shall provide an explicit constructor with a single parameter of
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lvalue reference to <code class="computeroutput"><span class="identifier">execution_context</span></code>.
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[<span class="emphasis"><em>Note:</em></span> This constructor may be called by the <code class="computeroutput"><span class="identifier">use_service</span></code> function. —<span class="emphasis"><em>end note</em></span>]
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</p>
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<pre class="programlisting"><span class="keyword">class</span> <span class="identifier">my_service</span> <span class="special">:</span> <span class="keyword">public</span> <span class="identifier">execution_context</span><span class="special">::</span><span class="identifier">service</span>
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<span class="special">{</span>
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<span class="keyword">public</span><span class="special">:</span>
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<span class="keyword">typedef</span> <span class="identifier">my_service</span> <span class="identifier">key_type</span><span class="special">;</span>
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<span class="keyword">explicit</span> <span class="identifier">my_service</span><span class="special">(</span><span class="identifier">execution_context</span><span class="special">&</span> <span class="identifier">ctx</span><span class="special">);</span>
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<span class="identifier">my_service</span><span class="special">(</span><span class="identifier">execution_context</span><span class="special">&</span> <span class="identifier">ctx</span><span class="special">,</span> <span class="keyword">int</span> <span class="identifier">some_value</span><span class="special">);</span>
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<span class="keyword">private</span><span class="special">:</span>
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<span class="keyword">virtual</span> <span class="keyword">void</span> <span class="identifier">shutdown</span><span class="special">()</span> <span class="keyword">noexcept</span> <span class="identifier">override</span><span class="special">;</span>
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<span class="special">...</span>
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<span class="special">};</span>
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</pre>
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<p>
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A service's <code class="computeroutput"><span class="identifier">shutdown</span></code> member
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function shall destroy all copies of user-defined function objects that are
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held by the service.
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</p>
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</div>
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<div class="copyright-footer">Copyright © 2003-2023 Christopher M. Kohlhoff<p>
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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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>)
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</p>
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</div>
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<hr>
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<div class="spirit-nav">
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<a accesskey="p" href="Sender.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="SettableSerialPortOption.html"><img src="../../next.png" alt="Next"></a>
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