65 lines
3.8 KiB
HTML
65 lines
3.8 KiB
HTML
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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>Cancellation</title>
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<link rel="stylesheet" href="../../../boostbook.css" type="text/css">
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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="../model.html" title="Asynchronous Model">
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<link rel="prev" href="allocators.html" title="Allocators">
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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="allocators.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../model.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="completion_tokens.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><h4 class="title">
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<a name="asio.overview.model.cancellation"></a><a class="link" href="cancellation.html" title="Cancellation">Cancellation</a>
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</h4></div></div></div>
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<p>
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In Asio, many objects, such as sockets and timers, support object-wide
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cancellation of outstanding asynchronous operations via their close or
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cancel member functions. However, certain asynchronous operations also
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support individual, targeted cancellation. This per-operation cancellation
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is enabled by specifying that every asynchronous agent has an associated
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<span class="emphasis"><em>cancellation slot</em></span>.
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</p>
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<p>
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To support cancellation, an asynchronous operation installs a cancellation
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handler into the agent's slot. The cancellation handler is a function object
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that will be invoked when a cancellation signal is emitted by the user
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into the slot. Since a cancellation slot is associated with a single agent,
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the slot holds at most one handler at a time, and installing a new handler
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will overwrite any previously installed handler. Thus, the same slot is
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reused for subsequent asynchronous operations within the agent.
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</p>
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<p>
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Cancellation is particularly useful when an asynchronous operation contains
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multiple child agents. For example, one child agent may be complete and
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the other is then cancelled, as its side effects are no longer required.
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</p>
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<h6>
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<a name="asio.overview.model.cancellation.h0"></a>
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<span><a name="asio.overview.model.cancellation.see_also"></a></span><a class="link" href="cancellation.html#asio.overview.model.cancellation.see_also">See
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Also</a>
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</h6>
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<p>
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<a class="link" href="../core/cancellation.html" title="Per-Operation Cancellation">Per-Operation Cancellation</a>.
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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="allocators.html"><img src="../../../prev.png" alt="Prev"></a><a accesskey="u" href="../model.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="completion_tokens.html"><img src="../../../next.png" alt="Next"></a>
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