1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>co_spawn (5 of 6 overloads)</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="../co_spawn.html" title="co_spawn"> 9<link rel="prev" href="overload4.html" title="co_spawn (4 of 6 overloads)"> 10<link rel="next" href="overload6.html" title="co_spawn (6 of 6 overloads)"> 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="overload4.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../co_spawn.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="overload6.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h4 class="title"> 27<a name="boost_asio.reference.co_spawn.overload5"></a><a class="link" href="overload5.html" title="co_spawn (5 of 6 overloads)">co_spawn (5 28 of 6 overloads)</a> 29</h4></div></div></div> 30<p> 31 Spawn a new coroutined-based thread of execution. 32 </p> 33<pre class="programlisting">template< 34 typename <a class="link" href="../Executor1.html" title="Executor requirements">Executor</a>, 35 typename F, 36 typename CompletionToken = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>> 37<a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> co_spawn( 38 const Executor & ex, 39 F && f, 40 CompletionToken && token = <a class="link" href="../asynchronous_operations.html#boost_asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>, 41 typename enable_if< is_executor< Executor >::value||execution::is_executor< Executor >::value >::type * = 0); 42</pre> 43<h6> 44<a name="boost_asio.reference.co_spawn.overload5.h0"></a> 45 <span class="phrase"><a name="boost_asio.reference.co_spawn.overload5.parameters"></a></span><a class="link" href="overload5.html#boost_asio.reference.co_spawn.overload5.parameters">Parameters</a> 46 </h6> 47<div class="variablelist"> 48<p class="title"><b></b></p> 49<dl class="variablelist"> 50<dt><span class="term">ex</span></dt> 51<dd><p> 52 The executor that will be used to schedule the new thread of execution. 53 </p></dd> 54<dt><span class="term">f</span></dt> 55<dd><p> 56 A nullary function object with a return type of the form <code class="computeroutput">boost::asio::awaitable<R,E></code> 57 that will be used as the coroutine's entry point. 58 </p></dd> 59<dt><span class="term">token</span></dt> 60<dd><p> 61 The completion token that will handle the notification that the thread 62 of execution has completed. If <code class="computeroutput">R</code> is <code class="computeroutput">void</code>, 63 the function signature of the completion handler must be: 64 </p></dd> 65</dl> 66</div> 67<pre class="programlisting">void handler(std::exception_ptr); 68</pre> 69<p> 70 Otherwise, the function signature of the completion handler must be: 71 </p> 72<pre class="programlisting">void handler(std::exception_ptr, R); 73</pre> 74<h6> 75<a name="boost_asio.reference.co_spawn.overload5.h1"></a> 76 <span class="phrase"><a name="boost_asio.reference.co_spawn.overload5.example"></a></span><a class="link" href="overload5.html#boost_asio.reference.co_spawn.overload5.example">Example</a> 77 </h6> 78<pre class="programlisting">boost::asio::awaitable<std::size_t> echo(tcp::socket socket) 79{ 80 std::size_t bytes_transferred = 0; 81 82 try 83 { 84 char data[1024]; 85 for (;;) 86 { 87 std::size_t n = co_await socket.async_read_some( 88 boost::asio::buffer(data), boost::asio::use_awaitable); 89 90 co_await boost::asio::async_write(socket, 91 boost::asio::buffer(data, n), boost::asio::use_awaitable); 92 93 bytes_transferred += n; 94 } 95 } 96 catch (const std::exception&) 97 { 98 } 99 100 co_return bytes_transferred; 101} 102 103// ... 104 105boost::asio::co_spawn(my_executor, 106 [socket = std::move(my_tcp_socket)]() mutable 107 -> boost::asio::awaitable<void> 108 { 109 try 110 { 111 char data[1024]; 112 for (;;) 113 { 114 std::size_t n = co_await socket.async_read_some( 115 boost::asio::buffer(data), boost::asio::use_awaitable); 116 117 co_await boost::asio::async_write(socket, 118 boost::asio::buffer(data, n), boost::asio::use_awaitable); 119 } 120 } 121 catch (const std::exception& e) 122 { 123 std::cerr << "Exception: " << e.what() << "\n"; 124 } 125 }, boost::asio::detached); 126</pre> 127</div> 128<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 129<td align="left"></td> 130<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 131 Kohlhoff<p> 132 Distributed under the Boost Software License, Version 1.0. (See accompanying 133 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>) 134 </p> 135</div></td> 136</tr></table> 137<hr> 138<div class="spirit-nav"> 139<a accesskey="p" href="overload4.html"><img src="../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../co_spawn.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="overload6.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 140</div> 141</body> 142</html> 143
