man/tip/nng_aio_begin.3.html


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---
version: tip
layout: manpage_v2
title: nng_aio_begin(3)
---
<h1>nng_aio_begin(3)</h1>
<div class="sect1">
<h2 id="_name">NAME</h2>
<div class="sectionbody">
<div class="paragraph">
<p>nng_aio_begin - begin asynchronous I/O operation</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_synopsis">SYNOPSIS</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="content">
<pre class="pygments highlight"><code data-lang="c"><span></span><span class="tok-cp">#include</span><span class="tok-w"> </span><span class="tok-cpf">&lt;nng/nng.h&gt;</span>

<span class="tok-kt">bool</span><span class="tok-w"> </span><span class="tok-nf">nng_aio_begin</span><span class="tok-p">(</span><span class="tok-n">nng_aio</span><span class="tok-w"> </span><span class="tok-o">*</span><span class="tok-n">aio</span><span class="tok-p">);</span></code></pre>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The <code>nng_aio_begin()</code> function is called by the I/O provider to indicate that
it is going to process the operation.</p>
</div>
<div class="paragraph">
<p>The function may return <code>false</code>, indicating that the <em>aio</em> has been closed
by the caller asynchronously.
In this case the provider should abandon the operation and do nothing else.</p>
</div>
<div class="paragraph">
<p>This operation should be called at the start of any I/O operation, and must
be called not more than once for a given I/O operation on a given <em>aio</em>.</p>
</div>
<div class="paragraph">
<p>Once this function is called, if <code>true</code> is returned, then the provider MUST
guarantee that <a href="nng_aio_finish.3.html"><code>nng_aio_finish()</code></a> is called for the <em>aio</em>
exactly once, when the operation is complete or canceled.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
This function is only for I/O providers (those actually performing
the operation such as HTTP handler functions or transport providers); ordinary
users of the <em>aio</em> should not call this function.
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_return_values">RETURN VALUES</h2>
<div class="sectionbody">
<div class="hdlist">
<table>
<tr>
<td class="hdlist1">
<code>true</code>
</td>
<td class="hdlist2">
<p>The operation has been started.</p>
</td>
</tr>
<tr>
<td class="hdlist1">
<code>false</code>
</td>
<td class="hdlist2">
<p>The operation cannot be started.</p>
</td>
</tr>
</table>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_errors">ERRORS</h2>
<div class="sectionbody">
<div class="paragraph">
<p>None.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">SEE ALSO</h2>
<div class="sectionbody">
<div class="paragraph text-left">
<p><a href="nng_aio_alloc.3.html">nng_aio_alloc(3)</a>,
<a href="nng_aio_cancel.3.html">nng_aio_cancel(3)</a>,
<a href="nng_aio_defer.3.html">nng_aio_defer(3)</a>,
<a href="nng_aio_finish.3.html">nng_aio_finish(3)</a>,
<a href="nng_aio_result.3.html">nng_aio_result(3)</a>,
<a href="nng_aio.5.html">nng_aio(5)</a>,
<a href="nng.7.html">nng(7)</a></p>
</div>
</div>
</div>