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<body class="manpage">
<div id="header">
<h1>
zmq_timers(3) Manual Page
</h1>
<h2>NAME</h2>
<div class="sectionbody">
<p>zmq_timers -
helper functions for cross-platform timers callbacks
</p>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_synopsis">SYNOPSIS</h2>
<div class="sectionbody">
<div class="paragraph"><p><strong>typedef void(zmq_timer_fn) (int <em>timer_id</em>, void *<em>arg</em>);</strong></p></div>
<div class="paragraph"><p><strong>void *zmq_timers_new (void);</strong></p></div>
<div class="paragraph"><p><strong>int zmq_timers_destroy (void *</strong><em>timers_p</em>);*</p></div>
<div class="paragraph"><p><strong>int zmq_timers_add (void *<em>timers</em>, size_t <em>interval</em>, zmq_timer_fn <em>handler</em>, void *<em>arg</em>);</strong></p></div>
<div class="paragraph"><p><strong>int zmq_timers_cancel (void *<em>timers</em>, int <em>timer_id</em>);</strong></p></div>
<div class="paragraph"><p><strong>int zmq_timers_set_interval (void *<em>timers</em>, int <em>timer_id</em>, size_t <em>interval</em>);</strong></p></div>
<div class="paragraph"><p><strong>int zmq_timers_reset (void *<em>timers</em>, int <em>timer_id</em>);</strong></p></div>
<div class="paragraph"><p><strong>long zmq_timers_timeout (void *<em>timers</em>);</strong></p></div>
<div class="paragraph"><p><strong>int zmq_timers_execute (void *<em>timers</em>);</strong></p></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph"><p>The <em>zmq_timers</em>*_ functions provide cross-platform access to timers callbacks.
Once a timer has been registered, it will repeat at the specified interval until
it gets manually cancelled. To run the callbacks, <em>zmq_timers_execute</em> must be
ran.</p></div>
<div class="paragraph"><p><em>zmq_timers_new</em> and <em>zmq_timers_destroy</em> manage the lifetime of a timer
instance. <em>zmq_timers_new</em> creates and returns a new timer instance, while
<em>zmq_timers_destroy</em> destroys it. A pointer to a valid timer must be passed
as the <em>timers_p</em> argument of <em>zmq_timers_destroy</em>. In particular,
<em>zmq_timers_destroy</em> may not be called multiple times for the same timer
instance. <em>zmq_timers_destroy</em> sets the passed pointer to NULL in case of a
successful execution.</p></div>
<div class="paragraph"><p><em>zmq_timers_add</em> and <em>zmq_timers_cancel</em> manage the timers registered.</p></div>
<div class="paragraph"><p><em>zmq_timers_add</em> registers a new <em>timer</em> with a given instance. <em>timers</em> must
point to a valid <em>timers</em> object. The <em>interval</em> parameter specifies the
expiration of the timer in milliseconds. <em>handler</em> and <em>arg</em> specify the callback
that will be invoked on expiration and the optional parameter that will be passed
through. The callback must be a valid function implementing the <em>zmq_timer_fn</em>
prototype. An ID will be returned that can be used to modify or cancel the timer.</p></div>
<div class="paragraph"><p><em>zmq_timers_cancel</em> will cancel the timer associated with <em>timer_id</em> from the
instance <em>timers</em>.</p></div>
<div class="paragraph"><p><em>zmq_timers_set_interval</em> will set the expiration of the timer associated with
<em>timer_id</em> from the instance <em>timers</em> to <em>interval</em> milliseconds into the future.</p></div>
<div class="paragraph"><p><em>zmq_timers_reset</em> will restart the timer associated with <em>timer_id</em> from the
instance <em>timers</em>.</p></div>
<div class="paragraph"><p><em>zmq_timers_timeout</em> will return the time left in milliseconds until the next
timer registered with <em>timers</em> expires.</p></div>
<div class="paragraph"><p><em>zmq_timers_execute</em> will run callbacks of all expired timers from the instance
<em>timers</em>.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_thread_safety">THREAD SAFETY</h2>
<div class="sectionbody">
<div class="paragraph"><p>Like most other ØMQ objects, timers are not thread-safe. All operations must
be called from the same thread. Otherwise, behaviour is undefined.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_return_value">RETURN VALUE</h2>
<div class="sectionbody">
<div class="paragraph"><p><em>zmq_timers_new</em> always returns a valid pointer to a poller.</p></div>
<div class="paragraph"><p>All functions that return an int, return -1 in case of a failure. In that case,
zmq_errno() can be used to query the type of the error as described below.</p></div>
<div class="paragraph"><p><em>zmq_timers_timeout</em> returns the time left in milliseconds until the next
timer registered with <em>timers</em> expires, or -1 if there are no timers left.</p></div>
<div class="paragraph"><p>All other functions return 0 in case of a successful execution.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_errors">ERRORS</h2>
<div class="sectionbody">
<div class="paragraph"><p>On <em>zmq_timers_destroy</em>, <em>zmq_poller_cancel</em>, <em>zmq_timers_set_interval</em>,
<em>zmq_timers_reset</em>, zmq_timers_timeout_, and <em>zmq_timers_execute</em>:
<strong>EFAULT</strong>::
<em>timers</em> did not point to a valid timer. Note that passing an
invalid pointer (e.g. pointer to deallocated memory) may cause undefined
behaviour (e.g. an access violation).</p></div>
<div class="paragraph"><p>On <em>zmq_timers_add</em>:
<strong>EFAULT</strong>::
<em>timers</em> did not point to a valid timer or <em>handler</em> did not point to a valid
function.</p></div>
<div class="paragraph"><p>On <em>zmq_poller_cancel</em>, <em>zmq_timers_set_interval</em> and zmq_timers_timeout_:
<strong>EINVAL</strong>::
<em>timer_id</em> did not exist or was already cancelled.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_example">EXAMPLE</h2>
<div class="sectionbody">
<div class="listingblock">
<div class="title">Add one timer with a simple callback that changes a boolean.</div>
<div class="content">
<pre><code> void handler (int timer_id_, void *arg_)
{
(void) timer_id_; // Stop 'unused' compiler warnings
*((bool *) arg_) = true;
}
...
void *timers = zmq_timers_new ();
assert (timers);
bool timer_invoked = false;
const unsigned long full_timeout = 100;
int timer_id =
zmq_timers_add (timers, full_timeout, handler, &timer_invoked);
assert (timer_id);
// Timer should not have been invoked yet
int rc = zmq_timers_execute (timers);
assert (rc == 0);
// Wait half the time and check again
long timeout = zmq_timers_timeout (timers);
assert (rc != -1);
msleep (timeout / 2);
rc = zmq_timers_execute (timers);
assert (rc == 0);
// Wait until the end
rc = msleep (zmq_timers_timeout (timers));
assert (rc == 0);
assert (timer_invoked);
rc = zmq_timers_destroy (&timers);
assert (rc == 0);</code></pre>
</div></div>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">SEE ALSO</h2>
<div class="sectionbody">
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ØMQ 4.3.2<br />
Last updated 2019-07-08 16:19:27 UTC
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