1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>co_spawn (3 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="overload2.html" title="co_spawn (2 of 6 overloads)"> 10<link rel="next" href="overload4.html" title="co_spawn (4 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="overload2.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="overload4.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.overload3"></a><a class="link" href="overload3.html" title="co_spawn (3 of 6 overloads)">co_spawn (3 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 ExecutionContext, 35 typename T, 36 typename <a class="link" href="../Executor1.html" title="Executor requirements">AwaitableExecutor</a>, 37 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>> 38<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( 39 ExecutionContext & ctx, 40 awaitable< T, AwaitableExecutor > a, 41 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>, 42 typename enable_if< is_convertible< ExecutionContext &, execution_context & >::value &&is_convertible< typename ExecutionContext::executor_type, AwaitableExecutor >::value >::type * = 0); 43</pre> 44<h6> 45<a name="boost_asio.reference.co_spawn.overload3.h0"></a> 46 <span class="phrase"><a name="boost_asio.reference.co_spawn.overload3.parameters"></a></span><a class="link" href="overload3.html#boost_asio.reference.co_spawn.overload3.parameters">Parameters</a> 47 </h6> 48<div class="variablelist"> 49<p class="title"><b></b></p> 50<dl class="variablelist"> 51<dt><span class="term">ctx</span></dt> 52<dd><p> 53 An execution context that will provide the executor to be used to 54 schedule the new thread of execution. 55 </p></dd> 56<dt><span class="term">a</span></dt> 57<dd><p> 58 The <a class="link" href="../awaitable.html" title="awaitable"><code class="computeroutput">awaitable</code></a> 59 object that is the result of calling the coroutine's entry point 60 function. 61 </p></dd> 62<dt><span class="term">token</span></dt> 63<dd> 64<p> 65 The completion token that will handle the notification that the thread 66 of execution has completed. The function signature of the completion 67 handler must be: 68</p> 69<pre class="programlisting">void handler(std::exception_ptr); 70</pre> 71<p> 72 </p> 73</dd> 74</dl> 75</div> 76<h6> 77<a name="boost_asio.reference.co_spawn.overload3.h1"></a> 78 <span class="phrase"><a name="boost_asio.reference.co_spawn.overload3.example"></a></span><a class="link" href="overload3.html#boost_asio.reference.co_spawn.overload3.example">Example</a> 79 </h6> 80<pre class="programlisting">boost::asio::awaitable<std::size_t> echo(tcp::socket socket) 81{ 82 std::size_t bytes_transferred = 0; 83 84 try 85 { 86 char data[1024]; 87 for (;;) 88 { 89 std::size_t n = co_await socket.async_read_some( 90 boost::asio::buffer(data), boost::asio::use_awaitable); 91 92 co_await boost::asio::async_write(socket, 93 boost::asio::buffer(data, n), boost::asio::use_awaitable); 94 95 bytes_transferred += n; 96 } 97 } 98 catch (const std::exception&) 99 { 100 } 101 102 co_return bytes_transferred; 103} 104 105// ... 106 107boost::asio::co_spawn(my_io_context, 108 echo(std::move(my_tcp_socket)), 109 [](std::exception_ptr e, std::size_t n) 110 { 111 std::cout << "transferred " << n << "\n"; 112 }); 113</pre> 114</div> 115<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 116<td align="left"></td> 117<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M. 118 Kohlhoff<p> 119 Distributed under the Boost Software License, Version 1.0. (See accompanying 120 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>) 121 </p> 122</div></td> 123</tr></table> 124<hr> 125<div class="spirit-nav"> 126<a accesskey="p" href="overload2.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="overload4.html"><img src="../../../../../doc/src/images/next.png" alt="Next"></a> 127</div> 128</body> 129</html> 130
