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Diffstat (limited to 'ev.html')
| -rw-r--r-- | ev.html | 30 |
1 files changed, 20 insertions, 10 deletions
@@ -6,7 +6,7 @@ <meta name="description" content="Pod documentation for libev" /> <meta name="inputfile" content="<standard input>" /> <meta name="outputfile" content="<standard output>" /> - <meta name="created" content="Sat Dec 8 23:11:11 2007" /> + <meta name="created" content="Sun Dec 9 20:30:11 2007" /> <meta name="generator" content="Pod::Xhtml 1.57" /> <link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> <body> @@ -1099,10 +1099,10 @@ to trigger "at" some specific point in time. For example, if you tell periodic watcher to trigger in 10 seconds (by specifiying e.g. <code>ev_now () + 10.</code>) and then reset your system clock to the last year, then it will take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger -roughly 10 seconds later and of course not if you reset your system time -again).</p> +roughly 10 seconds later).</p> <p>They can also be used to implement vastly more complex timers, such as -triggering an event on eahc midnight, local time.</p> +triggering an event on each midnight, local time or other, complicated, +rules.</p> <p>As with timers, the callback is guarenteed to be invoked only when the time (<code>at</code>) has been passed, but if multiple periodic timers become ready during the same loop iteration then order of execution is undefined.</p> @@ -1114,18 +1114,18 @@ during the same loop iteration then order of execution is undefined.</p> operation, and we will explain them from simplest to complex:</p> <p> <dl> - <dt>* absolute timer (interval = reschedule_cb = 0)</dt> + <dt>* absolute timer (at = time, interval = reschedule_cb = 0)</dt> <dd> <p>In this configuration the watcher triggers an event at the wallclock time <code>at</code> and doesn't repeat. It will not adjust when a time jump occurs, that is, if it is to be run at January 1st 2011 then it will run when the system time reaches or surpasses this time.</p> </dd> - <dt>* non-repeating interval timer (interval > 0, reschedule_cb = 0)</dt> + <dt>* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)</dt> <dd> <p>In this mode the watcher will always be scheduled to time out at the next -<code>at + N * interval</code> time (for some integer N) and then repeat, regardless -of any time jumps.</p> +<code>at + N * interval</code> time (for some integer N, which can also be negative) +and then repeat, regardless of any time jumps.</p> <p>This can be used to create timers that do not drift with respect to system time:</p> <pre> ev_periodic_set (&periodic, 0., 3600., 0); @@ -1138,8 +1138,11 @@ by 3600.</p> <p>Another way to think about it (for the mathematically inclined) is that <code>ev_periodic</code> will try to run the callback in this mode at the next possible time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> + <p>For numerical stability it is preferable that the <code>at</code> value is near +<code>ev_now ()</code> (the current time), but there is no range requirement for +this value.</p> </dd> - <dt>* manual reschedule mode (reschedule_cb = callback)</dt> + <dt>* manual reschedule mode (at and interval ignored, reschedule_cb = callback)</dt> <dd> <p>In this mode the values for <code>interval</code> and <code>at</code> are both being ignored. Instead, each time the periodic watcher gets scheduled, the @@ -1148,7 +1151,7 @@ current time as second argument.</p> <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher, ever, or make any event loop modifications</i>. If you need to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by -starting a prepare watcher).</p> +starting an <code>ev_prepare</code> watcher, which is legal).</p> <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now)</code>, e.g.:</p> <pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) @@ -1179,6 +1182,13 @@ when you changed some parameters or the reschedule callback would return a different time than the last time it was called (e.g. in a crond like program when the crontabs have changed).</p> </dd> + <dt>ev_tstamp offset [read-write]</dt> + <dd> + <p>When repeating, this contains the offset value, otherwise this is the +absolute point in time (the <code>at</code> value passed to <code>ev_periodic_set</code>).</p> + <p>Can be modified any time, but changes only take effect when the periodic +timer fires or <code>ev_periodic_again</code> is being called.</p> + </dd> <dt>ev_tstamp interval [read-write]</dt> <dd> <p>The current interval value. Can be modified any time, but changes only |