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<div class="titlepage"><div><div><h4 class="title">
<a name="asio.reference.co_spawn.overload5"></a><a class="link" href="overload5.html" title="co_spawn (5 of 6 overloads)">co_spawn (5 of 6
        overloads)</a>
</h4></div></div></div>
<p>
          Spawn a new coroutined-based thread of execution.
        </p>
<pre class="programlisting">template&lt;
    typename <a class="link" href="../Executor1.html" title="Executor requirements">Executor</a>,
    typename F,
    typename CompletionToken = <a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>&gt;
<a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.automatic_deduction_of_initiating_function_return_type"><span class="emphasis"><em>DEDUCED</em></span></a> co_spawn(
    const Executor &amp; ex,
    F &amp;&amp; f,
    CompletionToken &amp;&amp; token = <a class="link" href="../asynchronous_operations.html#asio.reference.asynchronous_operations.default_completion_tokens"><span class="emphasis"><em>DEFAULT</em></span></a>,
    typename enable_if&lt; is_executor&lt; Executor &gt;::value||execution::is_executor&lt; Executor &gt;::value &gt;::type *  = 0);
</pre>
<h6>
<a name="asio.reference.co_spawn.overload5.h0"></a>
          <span><a name="asio.reference.co_spawn.overload5.parameters"></a></span><a class="link" href="overload5.html#asio.reference.co_spawn.overload5.parameters">Parameters</a>
        </h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl>
<dt><span class="term">ex</span></dt>
<dd><p>
                The executor that will be used to schedule the new thread of execution.
              </p></dd>
<dt><span class="term">f</span></dt>
<dd><p>
                A nullary function object with a return type of the form <code class="computeroutput">asio::awaitable&lt;R,E&gt;</code>
                that will be used as the coroutine's entry point.
              </p></dd>
<dt><span class="term">token</span></dt>
<dd><p>
                The completion token that will handle the notification that the thread
                of execution has completed. If <code class="computeroutput">R</code> is <code class="computeroutput">void</code>,
                the function signature of the completion handler must be:
              </p></dd>
</dl>
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<pre class="programlisting">void handler(std::exception_ptr);
</pre>
<p>
          Otherwise, the function signature of the completion handler must be:
        </p>
<pre class="programlisting">void handler(std::exception_ptr, R);
</pre>
<h6>
<a name="asio.reference.co_spawn.overload5.h1"></a>
          <span><a name="asio.reference.co_spawn.overload5.example"></a></span><a class="link" href="overload5.html#asio.reference.co_spawn.overload5.example">Example</a>
        </h6>
<pre class="programlisting">asio::awaitable&lt;std::size_t&gt; echo(tcp::socket socket)
{
  std::size_t bytes_transferred = 0;

  try
  {
    char data[1024];
    for (;;)
    {
      std::size_t n = co_await socket.async_read_some(
          asio::buffer(data), asio::use_awaitable);

      co_await asio::async_write(socket,
          asio::buffer(data, n), asio::use_awaitable);

      bytes_transferred += n;
    }
  }
  catch (const std::exception&amp;)
  {
  }

  co_return bytes_transferred;
}

// ...

asio::co_spawn(my_executor,
  [socket = std::move(my_tcp_socket)]() mutable
    -&gt; asio::awaitable&lt;void&gt;
  {
    try
    {
      char data[1024];
      for (;;)
      {
        std::size_t n = co_await socket.async_read_some(
            asio::buffer(data), asio::use_awaitable);

        co_await asio::async_write(socket,
            asio::buffer(data, n), asio::use_awaitable);
      }
    }
    catch (const std::exception&amp; e)
    {
      std::cerr &lt;&lt; "Exception: " &lt;&lt; e.what() &lt;&lt; "\n";
    }
  }, asio::detached);
</pre>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2020 Christopher M.
      Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        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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