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<span class="target" id="imap-developer-guidance-prot-layer"></span><section id="cyrus-imap-server-prot-layer">
<h1>Cyrus IMAP Server: prot layer<a class="headerlink" href="#cyrus-imap-server-prot-layer" title="Permalink to this heading"></a></h1>
<p>The prot layer, defined in <code class="docutils literal notranslate"><span class="pre">prot.h</span></code>, is a stdio replacement for
network i/o. It does the standard buffering of input and output and
allows certain operations especially suited for request/response
protocols like IMAP.</p>
<section id="events">
<h2>Events<a class="headerlink" href="#events" title="Permalink to this heading"></a></h2>
<p>The prot layer allows "events" to be associated with each prot stream.
These events are trigger at the given time or after when the protstream
is attempted to be read from.</p>
<p>An event is currently represented by the following datastructure:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">struct</span> <span class="n">prot_waitevent</span><span class="p">;</span>
<span class="n">typedef</span> <span class="n">struct</span> <span class="n">prot_waitevent</span> <span class="o">*</span><span class="n">prot_waiteventcallback_t</span><span class="p">(</span><span class="n">struct</span> <span class="n">protstream</span> <span class="o">*</span><span class="n">s</span><span class="p">,</span>
<span class="n">struct</span> <span class="n">prot_waitevent</span> <span class="o">*</span><span class="n">ev</span><span class="p">,</span>
<span class="n">void</span> <span class="o">*</span><span class="n">rock</span><span class="p">);</span>
<span class="n">struct</span> <span class="n">prot_waitevent</span> <span class="p">{</span>
<span class="n">time_t</span> <span class="n">mark</span><span class="p">;</span>
<span class="n">prot_waiteventcallback_t</span> <span class="o">*</span><span class="n">proc</span><span class="p">;</span>
<span class="n">void</span> <span class="o">*</span><span class="n">rock</span><span class="p">;</span>
<span class="n">struct</span> <span class="n">prot_waitevent</span> <span class="o">*</span><span class="nb">next</span><span class="p">;</span>
<span class="p">};</span>
</pre></div>
</div>
<p>The application is currently allowed to modify <em>mark</em>, <em>proc</em>, and
<em>rock</em> as desired when there are no active calls to a prot function on
the stream which this event is associated.</p>
<p>The API is as follows:</p>
<ul>
<li><p>Use <code class="docutils literal notranslate"><span class="pre">prot_addwaitevent()</span></code> to add an event callback onto the stream:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">extern</span> <span class="n">struct</span> <span class="n">prot_waitevent</span> <span class="o">*</span><span class="n">prot_addwaitevent</span><span class="p">(</span><span class="n">struct</span> <span class="n">protstream</span> <span class="o">*</span><span class="n">s</span><span class="p">,</span>
<span class="n">time_t</span> <span class="n">mark</span><span class="p">,</span>
<span class="n">prot_waiteventcallback_t</span> <span class="o">*</span><span class="n">proc</span><span class="p">,</span>
<span class="n">void</span> <span class="o">*</span><span class="n">rock</span><span class="p">);</span>
</pre></div>
</div>
<p>where <em>s</em> is the stream to add the event to, <em>mark</em> is the time to
trigger the event, <em>proc</em> is the callback to make, and <em>rock</em> is an
opaque data item handed to the callback. It returns a pointer to the
event structure; this is the pointer that must be used to remove the
event or modify it in some way.</p>
</li>
<li><p>Use <code class="docutils literal notranslate"><span class="pre">prot_removewaitevent()</span></code> to remove an event:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">extern</span> <span class="n">void</span> <span class="n">prot_removewaitevent</span><span class="p">(</span><span class="n">struct</span> <span class="n">protstream</span> <span class="o">*</span><span class="n">s</span><span class="p">,</span>
<span class="n">struct</span> <span class="n">prot_waitevent</span> <span class="o">*</span><span class="n">event</span><span class="p">);</span>
</pre></div>
</div>
<p>It requires <em>event</em> to have been returned from
<code class="docutils literal notranslate"><span class="pre">prot_addwaitevent()</span></code> previously. No further references are allowed
to <em>event</em> or its fields. <em>event->rock</em> is not free'd nor examined in
any way. This function may be called while inside the callback
<em>event->proc()</em>. If an event is removed inside of its callback, that
callback must return <code class="docutils literal notranslate"><span class="pre">NULL</span></code>.</p>
</li>
</ul>
<p>Some common things to do with events:</p>
<ul class="simple">
<li><p>To reschedule an event <em>ev</em>, simply set <em>ev->mark</em> to the next time
it should trigger. If currently in <em>ev->proc()</em>, it should return
<em>ev</em>.</p></li>
</ul>
<hr class="docutils" />
<p>last modified: $Date: 2003/08/06 21:28:05 $</p>
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