1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Operation state concept</title> 5<link rel="stylesheet" href="../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../boost_asio.html" title="Boost.Asio"> 8<link rel="up" href="../reference.html" title="Reference"> 9<link rel="prev" href="MutableBufferSequence.html" title="Mutable buffer sequence requirements"> 10<link rel="next" href="ProtoAllocator.html" title="Proto-allocator requirements"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../boost.png"></td> 15<td align="center"><a href="../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="MutableBufferSequence.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="ProtoAllocator.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h3 class="title"> 27<a name="boost_asio.reference.OperationState"></a><a class="link" href="OperationState.html" title="Operation state concept">Operation state 28 concept</a> 29</h3></div></div></div> 30<pre class="programlisting">template<class O> 31 concept operation_state = 32 destructible<O> && 33 is_object_v<O> && 34 requires (O& o) { 35 { execution::start(o) } noexcept; 36 }; 37</pre> 38<p> 39 An object whose type satisfies <code class="computeroutput">operation_state</code> represents the 40 state of an asynchronous operation. It is the result of calling <code class="computeroutput">execution::connect</code> 41 with a <code class="computeroutput">sender</code> and a <code class="computeroutput">receiver</code>. 42 </p> 43<p> 44 <code class="computeroutput">execution::start</code> may be called on an <code class="computeroutput">operation_state</code> 45 object at most once. Once <code class="computeroutput">execution::start</code> has been invoked, 46 the caller shall ensure that the start of a non-exceptional invocation of 47 one of the receiver's completion-signalling operations strongly happens before 48 [intro.multithread] the call to the <code class="computeroutput">operation_state</code> destructor. 49 </p> 50<p> 51 The start of the invocation of <code class="computeroutput">execution::start</code> shall strongly 52 happen before [intro.multithread] the invocation of one of the three receiver 53 operations. 54 </p> 55<p> 56 <code class="computeroutput">execution::start</code> may or may not block pending the successful 57 transfer of execution to one of the three receiver operations. 58 </p> 59</div> 60<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 61<td align="left"></td> 62<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 63 Kohlhoff<p> 64 Distributed under the Boost Software License, Version 1.0. (See accompanying 65 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>) 66 </p> 67</div></td> 68</tr></table> 69<hr> 70<div class="spirit-nav"> 71<a accesskey="p" href="MutableBufferSequence.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="ProtoAllocator.html"><img src="../../../../doc/src/images/next.png" alt="Next"></a> 72</div> 73</body> 74</html> 75
