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<h1>Module <a href="type_File_descr_watcher_intf.html">File_descr_watcher_intf</a></h1>
<pre><span class="keyword">module</span> File_descr_watcher_intf: <code class="code">sig</code> <a href="File_descr_watcher_intf.html">..</a> <code class="code">end</code></pre><div class="info module top">
<code class="code">File_descr_watcher_intf.S</code> provides an API for for watching a set of file descriptors
to see if they are ready for reading or writing.
<p>
We have two implementations, one using epoll, and one using select.
<p>
None of the functions need to be thread-safe, with the exception of
<code class="code">thread_safe_check</code>. So that implementations can easily do non-thread-safe actions,
checking for ready I/O is always done in three steps:
<p>
1. <code class="code">pre_check</code>, while holding the async lock
2. <code class="code">thread_safe_check</code>, while not holding the async lock
3. <code class="code">post_check</code>, while holding the async lock<br>
</div>
<hr width="100%">
<pre><span id="VAL__pa_ounit_275876e34cf609db118f3d84b799a790"><span class="keyword">val</span> __pa_ounit_275876e34cf609db118f3d84b799a790</span> : <code class="type">string</code></pre><br>
<code class="code">File_descr_watcher_intf.S</code> provides an API for for watching a set of file descriptors
to see if they are ready for reading or writing.
<p>
We have two implementations, one using epoll, and one using select.
<p>
None of the functions need to be thread-safe, with the exception of
<code class="code">thread_safe_check</code>. So that implementations can easily do non-thread-safe actions,
checking for ready I/O is always done in three steps:
<p>
1. <code class="code">pre_check</code>, while holding the async lock
2. <code class="code">thread_safe_check</code>, while not holding the async lock
3. <code class="code">post_check</code>, while holding the async lock<br>
<pre><span class="keyword">module</span> <a href="File_descr_watcher_intf.Post.html">Post</a>: <code class="code">sig</code> <a href="File_descr_watcher_intf.Post.html">..</a> <code class="code">end</code></pre>
<pre><span class="keyword">module</span> <a href="File_descr_watcher_intf.Timeout.html">Timeout</a>: <code class="code">sig</code> <a href="File_descr_watcher_intf.Timeout.html">..</a> <code class="code">end</code></pre>
<pre><span class="keyword">module type</span> <a href="File_descr_watcher_intf.S.html">S</a> = <code class="code">sig</code> <a href="File_descr_watcher_intf.S.html">..</a> <code class="code">end</code></pre><br>
<code class="code">File_descr_watcher_intf.S</code> provides an API for for watching a set of file descriptors
to see if they are ready for reading or writing.
<p>
We have two implementations, one using epoll, and one using select.
<p>
None of the functions need to be thread-safe, with the exception of
<code class="code">thread_safe_check</code>. So that implementations can easily do non-thread-safe actions,
checking for ready I/O is always done in three steps:
<p>
1. <code class="code">pre_check</code>, while holding the async lock
2. <code class="code">thread_safe_check</code>, while not holding the async lock
3. <code class="code">post_check</code>, while holding the async lock<br>
<br>
A file-descr-watcher is essentially a map from <code class="code">File_descr.t</code> to <code class="code">bool
Read_write.t</code>, which defines the set of file descriptors being watched, and for each
file descriptor, whether it is being watched for read, write, or both. If a file
descriptor is not being watched for neither, it is not in the map.<br>
<br>
<code class="code">create ~num_file_descrs</code> creates a new file-descr-watcher that is able to watch
file descriptors in <pre class="codepre"><code class="code"> [0, num_file_descrs) </code></pre>.<br>
<br>
<code class="code">set</code> alters the map of file descriptors being watched. It will take effect on the
next call to <code class="code">thread_safe_check</code>. Calling <code class="code">set fd</code> with <code class="code">{ read = false, write =
false }</code> removes <code class="code">fd</code> from the map.<br>
<br>
<code class="code">iter t ~f</code> iterates over every file descriptor in the map, apply <code class="code">f</code> to it once
for each of {`Read,`Write} that it is being watched for.<br>
<br>
<code class="code">pre_check t</code> does whatever non-thread-safe work is necessary to prepare for the
system call that checks file descriptors being ready for read or write. <code class="code">pre_check</code>
does not side effect <code class="code">t</code>.<br>
<br>
<code class="code">thread_safe_check t pre ~timeout</code> checks the file descriptors for their status and
returns when at least one is available, or the <code class="code">timeout</code> passes.
<code class="code">thread_safe_check</code> does not side effect <code class="code">t</code>. Unlike the rest of the functions in
this module, <code class="code">thread_safe_check</code> is thread safe.<br>
<br>
<code class="code">post_check t check_result</code> returns the file descriptors available for read and
write. Any file descriptor appearing in <code class="code">post</code> for read must have been watched
for read, as per <code class="code">set</code>. Similarly for write.<br>
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