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4<head> 4<head>
5 <title>libev</title> 5 <title>libev</title>
6 <meta name="description" content="Pod documentation for libev" /> 6 <meta name="description" content="Pod documentation for libev" />
7 <meta name="inputfile" content="&lt;standard input&gt;" /> 7 <meta name="inputfile" content="&lt;standard input&gt;" />
8 <meta name="outputfile" content="&lt;standard output&gt;" /> 8 <meta name="outputfile" content="&lt;standard output&gt;" />
9 <meta name="created" content="Mon Nov 12 09:32:51 2007" /> 9 <meta name="created" content="Sun Nov 18 04:43:20 2007" />
10 <meta name="generator" content="Pod::Xhtml 1.57" /> 10 <meta name="generator" content="Pod::Xhtml 1.57" />
11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head> 11<link rel="stylesheet" href="http://res.tst.eu/pod.css"/></head>
12<body> 12<body>
13<div class="pod"> 13<div class="pod">
14<!-- INDEX START --> 14<!-- INDEX START -->
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17<ul><li><a href="#NAME">NAME</a></li> 17<ul><li><a href="#NAME">NAME</a></li>
18<li><a href="#SYNOPSIS">SYNOPSIS</a></li> 18<li><a href="#SYNOPSIS">SYNOPSIS</a></li>
19<li><a href="#DESCRIPTION">DESCRIPTION</a></li> 19<li><a href="#DESCRIPTION">DESCRIPTION</a></li>
20<li><a href="#FEATURES">FEATURES</a></li> 20<li><a href="#FEATURES">FEATURES</a></li>
21<li><a href="#CONVENTIONS">CONVENTIONS</a></li> 21<li><a href="#CONVENTIONS">CONVENTIONS</a></li>
22<li><a href="#TIME_REPRESENTATION">TIME REPRESENTATION</a></li>
22<li><a href="#TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</a></li> 23<li><a href="#GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</a></li>
23<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li> 24<li><a href="#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP">FUNCTIONS CONTROLLING THE EVENT LOOP</a></li>
24<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a> 25<li><a href="#ANATOMY_OF_A_WATCHER">ANATOMY OF A WATCHER</a>
25<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li> 26<ul><li><a href="#ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</a></li>
26</ul> 27</ul>
27</li> 28</li>
28<li><a href="#WATCHER_TYPES">WATCHER TYPES</a> 29<li><a href="#WATCHER_TYPES">WATCHER TYPES</a>
29<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li> 30<ul><li><a href="#code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</a></li>
30<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li> 31<li><a href="#code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</a></li>
31<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</a></li> 32<li><a href="#code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</a></li>
32<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li> 33<li><a href="#code_ev_signal_code_signal_me_when_a"><code>ev_signal</code> - signal me when a signal gets signalled</a></li>
33<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li> 34<li><a href="#code_ev_child_code_wait_for_pid_stat"><code>ev_child</code> - wait for pid status changes</a></li>
34<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li> 35<li><a href="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</a></li>
35<li><a href="#prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</a></li> 36<li><a href="#code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</a></li>
36</ul> 37</ul>
37</li> 38</li>
38<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li> 39<li><a href="#OTHER_FUNCTIONS">OTHER FUNCTIONS</a></li>
40<li><a href="#LIBEVENT_EMULATION">LIBEVENT EMULATION</a></li>
41<li><a href="#C_SUPPORT">C++ SUPPORT</a></li>
39<li><a href="#AUTHOR">AUTHOR</a> 42<li><a href="#AUTHOR">AUTHOR</a>
40</li> 43</li>
41</ul><hr /> 44</ul><hr />
42<!-- INDEX END --> 45<!-- INDEX END -->
43 46
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87support for multiple event loops, then all functions taking an initial 90support for multiple event loops, then all functions taking an initial
88argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>) 91argument of name <code>loop</code> (which is always of type <code>struct ev_loop *</code>)
89will not have this argument.</p> 92will not have this argument.</p>
90 93
91</div> 94</div>
92<h1 id="TIME_AND_OTHER_GLOBAL_FUNCTIONS">TIME AND OTHER GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 95<h1 id="TIME_REPRESENTATION">TIME REPRESENTATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
93<div id="TIME_AND_OTHER_GLOBAL_FUNCTIONS_CONT"> 96<div id="TIME_REPRESENTATION_CONTENT">
94<p>Libev represents time as a single floating point number, representing the 97<p>Libev represents time as a single floating point number, representing the
95(fractional) number of seconds since the (POSIX) epoch (somewhere near 98(fractional) number of seconds since the (POSIX) epoch (somewhere near
96the beginning of 1970, details are complicated, don't ask). This type is 99the beginning of 1970, details are complicated, don't ask). This type is
97called <code>ev_tstamp</code>, which is what you should use too. It usually aliases 100called <code>ev_tstamp</code>, which is what you should use too. It usually aliases
98to the double type in C.</p> 101to the double type in C.</p>
102
103</div>
104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
105<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the
107library in any way.</p>
99<dl> 108<dl>
100 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
101 <dd> 110 <dd>
102 <p>Returns the current time as libev would use it.</p> 111 <p>Returns the current time as libev would use it. Please note that the
112<code>ev_now</code> function is usually faster and also often returns the timestamp
113you actually want to know.</p>
103 </dd> 114 </dd>
104 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
105 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
106 <dd> 117 <dd>
107 <p>You can find out the major and minor version numbers of the library 118 <p>You can find out the major and minor version numbers of the library
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142<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 153<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2">
143<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two 154<p>An event loop is described by a <code>struct ev_loop *</code>. The library knows two
144types of such loops, the <i>default</i> loop, which supports signals and child 155types of such loops, the <i>default</i> loop, which supports signals and child
145events, and dynamically created loops which do not.</p> 156events, and dynamically created loops which do not.</p>
146<p>If you use threads, a common model is to run the default event loop 157<p>If you use threads, a common model is to run the default event loop
147in your main thread (or in a separate thrad) and for each thread you 158in your main thread (or in a separate thread) and for each thread you
148create, you also create another event loop. Libev itself does no locking 159create, you also create another event loop. Libev itself does no locking
149whatsoever, so if you mix calls to the same event loop in different 160whatsoever, so if you mix calls to the same event loop in different
150threads, make sure you lock (this is usually a bad idea, though, even if 161threads, make sure you lock (this is usually a bad idea, though, even if
151done correctly, because it's hideous and inefficient).</p> 162done correctly, because it's hideous and inefficient).</p>
152<dl> 163<dl>
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259your process until at least one new event arrives, and will return after 270your process until at least one new event arrives, and will return after
260one iteration of the loop.</p> 271one iteration of the loop.</p>
261 <p>This flags value could be used to implement alternative looping 272 <p>This flags value could be used to implement alternative looping
262constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 273constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
263more generic mechanism.</p> 274more generic mechanism.</p>
275 <p>Here are the gory details of what ev_loop does:</p>
276<pre> 1. If there are no active watchers (reference count is zero), return.
277 2. Queue and immediately call all prepare watchers.
278 3. If we have been forked, recreate the kernel state.
279 4. Update the kernel state with all outstanding changes.
280 5. Update the &quot;event loop time&quot;.
281 6. Calculate for how long to block.
282 7. Block the process, waiting for events.
283 8. Update the &quot;event loop time&quot; and do time jump handling.
284 9. Queue all outstanding timers.
285 10. Queue all outstanding periodics.
286 11. If no events are pending now, queue all idle watchers.
287 12. Queue all check watchers.
288 13. Call all queued watchers in reverse order (i.e. check watchers first).
289 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
290 was used, return, otherwise continue with step #1.
291
292</pre>
264 </dd> 293 </dd>
265 <dt>ev_unloop (loop, how)</dt> 294 <dt>ev_unloop (loop, how)</dt>
266 <dd> 295 <dd>
267 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 296 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
268has processed all outstanding events). The <code>how</code> argument must be either 297has processed all outstanding events). The <code>how</code> argument must be either
269<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or 298<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
270<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> 299<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
271 </dd> 300 </dd>
272 <dt>ev_ref (loop)</dt> 301 <dt>ev_ref (loop)</dt>
273 <dt>ev_unref (loop)</dt> 302 <dt>ev_unref (loop)</dt>
274 <dd> 303 <dd>
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322*)</code>), and you can stop watching for events at any time by calling the 351*)</code>), and you can stop watching for events at any time by calling the
323corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p> 352corresponding stop function (<code>ev_&lt;type&gt;_stop (loop, watcher *)</code>.</p>
324<p>As long as your watcher is active (has been started but not stopped) you 353<p>As long as your watcher is active (has been started but not stopped) you
325must not touch the values stored in it. Most specifically you must never 354must not touch the values stored in it. Most specifically you must never
326reinitialise it or call its set method.</p> 355reinitialise it or call its set method.</p>
327<p>You cna check whether an event is active by calling the <code>ev_is_active 356<p>You can check whether an event is active by calling the <code>ev_is_active
328(watcher *)</code> macro. To see whether an event is outstanding (but the 357(watcher *)</code> macro. To see whether an event is outstanding (but the
329callback for it has not been called yet) you cna use the <code>ev_is_pending 358callback for it has not been called yet) you can use the <code>ev_is_pending
330(watcher *)</code> macro.</p> 359(watcher *)</code> macro.</p>
331<p>Each and every callback receives the event loop pointer as first, the 360<p>Each and every callback receives the event loop pointer as first, the
332registered watcher structure as second, and a bitset of received events as 361registered watcher structure as second, and a bitset of received events as
333third argument.</p> 362third argument.</p>
334<p>The rceeived events usually include a single bit per event type received 363<p>The received events usually include a single bit per event type received
335(you can receive multiple events at the same time). The possible bit masks 364(you can receive multiple events at the same time). The possible bit masks
336are:</p> 365are:</p>
337<dl> 366<dl>
338 <dt><code>EV_READ</code></dt> 367 <dt><code>EV_READ</code></dt>
339 <dt><code>EV_WRITE</code></dt> 368 <dt><code>EV_WRITE</code></dt>
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389 418
390</div> 419</div>
391<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 420<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2>
392<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2"> 421<div id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH-2">
393<p>Each watcher has, by default, a member <code>void *data</code> that you can change 422<p>Each watcher has, by default, a member <code>void *data</code> that you can change
394and read at any time, libev will completely ignore it. This cna be used 423and read at any time, libev will completely ignore it. This can be used
395to associate arbitrary data with your watcher. If you need more data and 424to associate arbitrary data with your watcher. If you need more data and
396don't want to allocate memory and store a pointer to it in that data 425don't want to allocate memory and store a pointer to it in that data
397member, you can also &quot;subclass&quot; the watcher type and provide your own 426member, you can also &quot;subclass&quot; the watcher type and provide your own
398data:</p> 427data:</p>
399<pre> struct my_io 428<pre> struct my_io
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431<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 460<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2>
432<div id="code_ev_io_code_is_this_file_descrip-2"> 461<div id="code_ev_io_code_is_this_file_descrip-2">
433<p>I/O watchers check whether a file descriptor is readable or writable 462<p>I/O watchers check whether a file descriptor is readable or writable
434in each iteration of the event loop (This behaviour is called 463in each iteration of the event loop (This behaviour is called
435level-triggering because you keep receiving events as long as the 464level-triggering because you keep receiving events as long as the
436condition persists. Remember you cna stop the watcher if you don't want to 465condition persists. Remember you can stop the watcher if you don't want to
437act on the event and neither want to receive future events).</p> 466act on the event and neither want to receive future events).</p>
438<p>In general you can register as many read and/or write event watchers oer 467<p>In general you can register as many read and/or write event watchers per
439fd as you want (as long as you don't confuse yourself). Setting all file 468fd as you want (as long as you don't confuse yourself). Setting all file
440descriptors to non-blocking mode is also usually a good idea (but not 469descriptors to non-blocking mode is also usually a good idea (but not
441required if you know what you are doing).</p> 470required if you know what you are doing).</p>
442<p>You have to be careful with dup'ed file descriptors, though. Some backends 471<p>You have to be careful with dup'ed file descriptors, though. Some backends
443(the linux epoll backend is a notable example) cannot handle dup'ed file 472(the linux epoll backend is a notable example) cannot handle dup'ed file
444descriptors correctly if you register interest in two or more fds pointing 473descriptors correctly if you register interest in two or more fds pointing
445to the same file/socket etc. description.</p> 474to the same underlying file/socket etc. description (that is, they share
475the same underlying &quot;file open&quot;).</p>
446<p>If you must do this, then force the use of a known-to-be-good backend 476<p>If you must do this, then force the use of a known-to-be-good backend
447(at the time of this writing, this includes only EVMETHOD_SELECT and 477(at the time of this writing, this includes only EVMETHOD_SELECT and
448EVMETHOD_POLL).</p> 478EVMETHOD_POLL).</p>
449<dl> 479<dl>
450 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 480 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
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460<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 490<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
461<div id="code_ev_timer_code_relative_and_opti-2"> 491<div id="code_ev_timer_code_relative_and_opti-2">
462<p>Timer watchers are simple relative timers that generate an event after a 492<p>Timer watchers are simple relative timers that generate an event after a
463given time, and optionally repeating in regular intervals after that.</p> 493given time, and optionally repeating in regular intervals after that.</p>
464<p>The timers are based on real time, that is, if you register an event that 494<p>The timers are based on real time, that is, if you register an event that
465times out after an hour and youreset your system clock to last years 495times out after an hour and you reset your system clock to last years
466time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 496time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
467detecting time jumps is hard, and soem inaccuracies are unavoidable (the 497detecting time jumps is hard, and some inaccuracies are unavoidable (the
468monotonic clock option helps a lot here).</p> 498monotonic clock option helps a lot here).</p>
469<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 499<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
470time. This is usually the right thing as this timestamp refers to the time 500time. This is usually the right thing as this timestamp refers to the time
471of the event triggering whatever timeout you are modifying/starting. If 501of the event triggering whatever timeout you are modifying/starting. If
472you suspect event processing to be delayed and you *need* to base the timeout 502you suspect event processing to be delayed and you <i>need</i> to base the timeout
473ion the current time, use something like this to adjust for this:</p> 503on the current time, use something like this to adjust for this:</p>
474<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.); 504<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
475 505
476</pre> 506</pre>
507<p>The callback is guarenteed to be invoked only when its timeout has passed,
508but if multiple timers become ready during the same loop iteration then
509order of execution is undefined.</p>
477<dl> 510<dl>
478 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 511 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
479 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 512 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
480 <dd> 513 <dd>
481 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 514 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
483timer will automatically be configured to trigger again <code>repeat</code> seconds 516timer will automatically be configured to trigger again <code>repeat</code> seconds
484later, again, and again, until stopped manually.</p> 517later, again, and again, until stopped manually.</p>
485 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 518 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
486configure a timer to trigger every 10 seconds, then it will trigger at 519configure a timer to trigger every 10 seconds, then it will trigger at
487exactly 10 second intervals. If, however, your program cannot keep up with 520exactly 10 second intervals. If, however, your program cannot keep up with
488the timer (ecause it takes longer than those 10 seconds to do stuff) the 521the timer (because it takes longer than those 10 seconds to do stuff) the
489timer will not fire more than once per event loop iteration.</p> 522timer will not fire more than once per event loop iteration.</p>
490 </dd> 523 </dd>
491 <dt>ev_timer_again (loop)</dt> 524 <dt>ev_timer_again (loop)</dt>
492 <dd> 525 <dd>
493 <p>This will act as if the timer timed out and restart it again if it is 526 <p>This will act as if the timer timed out and restart it again if it is
… …
505the timer, and again will automatically restart it if need be.</p> 538the timer, and again will automatically restart it if need be.</p>
506 </dd> 539 </dd>
507</dl> 540</dl>
508 541
509</div> 542</div>
510<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</h2> 543<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron</h2>
511<div id="code_ev_periodic_code_to_cron_or_not-2"> 544<div id="code_ev_periodic_code_to_cron_or_not-2">
512<p>Periodic watchers are also timers of a kind, but they are very versatile 545<p>Periodic watchers are also timers of a kind, but they are very versatile
513(and unfortunately a bit complex).</p> 546(and unfortunately a bit complex).</p>
514<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 547<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time)
515but on wallclock time (absolute time). You can tell a periodic watcher 548but on wallclock time (absolute time). You can tell a periodic watcher
… …
519take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 552take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
520roughly 10 seconds later and of course not if you reset your system time 553roughly 10 seconds later and of course not if you reset your system time
521again).</p> 554again).</p>
522<p>They can also be used to implement vastly more complex timers, such as 555<p>They can also be used to implement vastly more complex timers, such as
523triggering an event on eahc midnight, local time.</p> 556triggering an event on eahc midnight, local time.</p>
557<p>As with timers, the callback is guarenteed to be invoked only when the
558time (<code>at</code>) has been passed, but if multiple periodic timers become ready
559during the same loop iteration then order of execution is undefined.</p>
524<dl> 560<dl>
525 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 561 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
526 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 562 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
527 <dd> 563 <dd>
528 <p>Lots of arguments, lets sort it out... There are basically three modes of 564 <p>Lots of arguments, lets sort it out... There are basically three modes of
529operation, and we will explain them from simplest to complex:</p> 565operation, and we will explain them from simplest to complex:</p>
530
531
532
533
534 <p> 566 <p>
535 <dl> 567 <dl>
536 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 568 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
537 <dd> 569 <dd>
538 <p>In this configuration the watcher triggers an event at the wallclock time 570 <p>In this configuration the watcher triggers an event at the wallclock time
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550<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0); 582<pre> ev_periodic_set (&amp;periodic, 0., 3600., 0);
551 583
552</pre> 584</pre>
553 <p>This doesn't mean there will always be 3600 seconds in between triggers, 585 <p>This doesn't mean there will always be 3600 seconds in between triggers,
554but only that the the callback will be called when the system time shows a 586but only that the the callback will be called when the system time shows a
555full hour (UTC), or more correct, when the system time is evenly divisible 587full hour (UTC), or more correctly, when the system time is evenly divisible
556by 3600.</p> 588by 3600.</p>
557 <p>Another way to think about it (for the mathematically inclined) is that 589 <p>Another way to think about it (for the mathematically inclined) is that
558<code>ev_periodic</code> will try to run the callback in this mode at the next possible 590<code>ev_periodic</code> will try to run the callback in this mode at the next possible
559time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p> 591time where <code>time = at (mod interval)</code>, regardless of any time jumps.</p>
560 </dd> 592 </dd>
… …
562 <dd> 594 <dd>
563 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 595 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
564ignored. Instead, each time the periodic watcher gets scheduled, the 596ignored. Instead, each time the periodic watcher gets scheduled, the
565reschedule callback will be called with the watcher as first, and the 597reschedule callback will be called with the watcher as first, and the
566current time as second argument.</p> 598current time as second argument.</p>
567 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 599 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
568periodic watcher, ever, or make any event loop modificstions</i>. If you need 600ever, or make any event loop modifications</i>. If you need to stop it,
569to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards.</p> 601return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
602starting a prepare watcher).</p>
570 <p>Its prototype is c&lt;ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 603 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
571ev_tstamp now)&gt;, e.g.:</p> 604ev_tstamp now)</code>, e.g.:</p>
572<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 605<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
573 { 606 {
574 return now + 60.; 607 return now + 60.;
575 } 608 }
576 609
577</pre> 610</pre>
578 <p>It must return the next time to trigger, based on the passed time value 611 <p>It must return the next time to trigger, based on the passed time value
579(that is, the lowest time value larger than to the second argument). It 612(that is, the lowest time value larger than to the second argument). It
580will usually be called just before the callback will be triggered, but 613will usually be called just before the callback will be triggered, but
581might be called at other times, too.</p> 614might be called at other times, too.</p>
615 <p>NOTE: <i>This callback must always return a time that is later than the
616passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
582 <p>This can be used to create very complex timers, such as a timer that 617 <p>This can be used to create very complex timers, such as a timer that
583triggers on each midnight, local time. To do this, you would calculate the 618triggers on each midnight, local time. To do this, you would calculate the
584next midnight after <code>now</code> and return the timestamp value for this. How you do this 619next midnight after <code>now</code> and return the timestamp value for this. How
585is, again, up to you (but it is not trivial).</p> 620you do this is, again, up to you (but it is not trivial, which is the main
621reason I omitted it as an example).</p>
586 </dd> 622 </dd>
587 </dl> 623 </dl>
588 </p> 624 </p>
589 </dd> 625 </dd>
590 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 626 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
601<div id="code_ev_signal_code_signal_me_when_a-2"> 637<div id="code_ev_signal_code_signal_me_when_a-2">
602<p>Signal watchers will trigger an event when the process receives a specific 638<p>Signal watchers will trigger an event when the process receives a specific
603signal one or more times. Even though signals are very asynchronous, libev 639signal one or more times. Even though signals are very asynchronous, libev
604will try it's best to deliver signals synchronously, i.e. as part of the 640will try it's best to deliver signals synchronously, i.e. as part of the
605normal event processing, like any other event.</p> 641normal event processing, like any other event.</p>
606<p>You cna configure as many watchers as you like per signal. Only when the 642<p>You can configure as many watchers as you like per signal. Only when the
607first watcher gets started will libev actually register a signal watcher 643first watcher gets started will libev actually register a signal watcher
608with the kernel (thus it coexists with your own signal handlers as long 644with the kernel (thus it coexists with your own signal handlers as long
609as you don't register any with libev). Similarly, when the last signal 645as you don't register any with libev). Similarly, when the last signal
610watcher for a signal is stopped libev will reset the signal handler to 646watcher for a signal is stopped libev will reset the signal handler to
611SIG_DFL (regardless of what it was set to before).</p> 647SIG_DFL (regardless of what it was set to before).</p>
… …
628 <dt>ev_child_set (ev_child *, int pid)</dt> 664 <dt>ev_child_set (ev_child *, int pid)</dt>
629 <dd> 665 <dd>
630 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 666 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
631<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 667<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
632at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 668at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
633the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 669the status word (use the macros from <code>sys/wait.h</code> and see your systems
670<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
634contains the pid of the process causing the status change.</p> 671process causing the status change.</p>
635 </dd> 672 </dd>
636</dl> 673</dl>
637 674
638</div> 675</div>
639<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 676<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
640<div id="code_ev_idle_code_when_you_ve_got_no-2"> 677<div id="code_ev_idle_code_when_you_ve_got_no-2">
641<p>Idle watchers trigger events when there are no other I/O or timer (or 678<p>Idle watchers trigger events when there are no other events are pending
642periodic) events pending. That is, as long as your process is busy 679(prepare, check and other idle watchers do not count). That is, as long
643handling sockets or timeouts it will not be called. But when your process 680as your process is busy handling sockets or timeouts (or even signals,
644is idle all idle watchers are being called again and again - until 681imagine) it will not be triggered. But when your process is idle all idle
682watchers are being called again and again, once per event loop iteration -
645stopped, that is, or your process receives more events.</p> 683until stopped, that is, or your process receives more events and becomes
684busy.</p>
646<p>The most noteworthy effect is that as long as any idle watchers are 685<p>The most noteworthy effect is that as long as any idle watchers are
647active, the process will not block when waiting for new events.</p> 686active, the process will not block when waiting for new events.</p>
648<p>Apart from keeping your process non-blocking (which is a useful 687<p>Apart from keeping your process non-blocking (which is a useful
649effect on its own sometimes), idle watchers are a good place to do 688effect on its own sometimes), idle watchers are a good place to do
650&quot;pseudo-background processing&quot;, or delay processing stuff to after the 689&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
657believe me.</p> 696believe me.</p>
658 </dd> 697 </dd>
659</dl> 698</dl>
660 699
661</div> 700</div>
662<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 701<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
663<div id="prepare_and_check_your_hooks_into_th-2"> 702<div id="code_ev_prepare_code_and_code_ev_che-2">
664<p>Prepare and check watchers usually (but not always) are used in 703<p>Prepare and check watchers are usually (but not always) used in tandem:
665tandom. Prepare watchers get invoked before the process blocks and check 704prepare watchers get invoked before the process blocks and check watchers
666watchers afterwards.</p> 705afterwards.</p>
667<p>Their main purpose is to integrate other event mechanisms into libev. This 706<p>Their main purpose is to integrate other event mechanisms into libev. This
668could be used, for example, to track variable changes, implement your own 707could be used, for example, to track variable changes, implement your own
669watchers, integrate net-snmp or a coroutine library and lots more.</p> 708watchers, integrate net-snmp or a coroutine library and lots more.</p>
670<p>This is done by examining in each prepare call which file descriptors need 709<p>This is done by examining in each prepare call which file descriptors need
671to be watched by the other library, registering <code>ev_io</code> watchers for them 710to be watched by the other library, registering <code>ev_io</code> watchers for
672and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide 711them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
673just this functionality). Then, in the check watcher you check for any 712provide just this functionality). Then, in the check watcher you check for
674events that occured (by making your callbacks set soem flags for example) 713any events that occured (by checking the pending status of all watchers
675and call back into the library.</p> 714and stopping them) and call back into the library. The I/O and timer
715callbacks will never actually be called (but must be valid nevertheless,
716because you never know, you know?).</p>
676<p>As another example, the perl Coro module uses these hooks to integrate 717<p>As another example, the Perl Coro module uses these hooks to integrate
677coroutines into libev programs, by yielding to other active coroutines 718coroutines into libev programs, by yielding to other active coroutines
678during each prepare and only letting the process block if no coroutines 719during each prepare and only letting the process block if no coroutines
679are ready to run.</p> 720are ready to run (it's actually more complicated: it only runs coroutines
721with priority higher than or equal to the event loop and one coroutine
722of lower priority, but only once, using idle watchers to keep the event
723loop from blocking if lower-priority coroutines are active, thus mapping
724low-priority coroutines to idle/background tasks).</p>
680<dl> 725<dl>
681 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 726 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
682 <dt>ev_check_init (ev_check *, callback)</dt> 727 <dt>ev_check_init (ev_check *, callback)</dt>
683 <dd> 728 <dd>
684 <p>Initialises and configures the prepare or check watcher - they have no 729 <p>Initialises and configures the prepare or check watcher - they have no
685parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 730parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
686macros, but using them is utterly, utterly pointless.</p> 731macros, but using them is utterly, utterly and completely pointless.</p>
687 </dd> 732 </dd>
688</dl> 733</dl>
689 734
690</div> 735</div>
691<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 736<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
692<div id="OTHER_FUNCTIONS_CONTENT"> 737<div id="OTHER_FUNCTIONS_CONTENT">
693<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 738<p>There are some other functions of possible interest. Described. Here. Now.</p>
694<dl> 739<dl>
695 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 740 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
696 <dd> 741 <dd>
697 <p>This function combines a simple timer and an I/O watcher, calls your 742 <p>This function combines a simple timer and an I/O watcher, calls your
698callback on whichever event happens first and automatically stop both 743callback on whichever event happens first and automatically stop both
699watchers. This is useful if you want to wait for a single event on an fd 744watchers. This is useful if you want to wait for a single event on an fd
700or timeout without havign to allocate/configure/start/stop/free one or 745or timeout without having to allocate/configure/start/stop/free one or
701more watchers yourself.</p> 746more watchers yourself.</p>
702 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 747 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
703ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set 748is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
704will be craeted and started.</p> 749<code>events</code> set will be craeted and started.</p>
705 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 750 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
706started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat 751started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
707= 0) will be started.</p> 752repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
753dubious value.</p>
708 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 754 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
709gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>, 755passed an <code>revents</code> set like normal event callbacks (a combination of
710<code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 756<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
757value passed to <code>ev_once</code>:</p>
711<pre> static void stdin_ready (int revents, void *arg) 758<pre> static void stdin_ready (int revents, void *arg)
712 { 759 {
713 if (revents &amp; EV_TIMEOUT) 760 if (revents &amp; EV_TIMEOUT)
714 /* doh, nothing entered */ 761 /* doh, nothing entered */;
715 else if (revents &amp; EV_READ) 762 else if (revents &amp; EV_READ)
716 /* stdin might have data for us, joy! */ 763 /* stdin might have data for us, joy! */;
717 } 764 }
718 765
719 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 766 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
720 767
721</pre> 768</pre>
722 </dd> 769 </dd>
723 <dt>ev_feed_event (loop, watcher, int events)</dt> 770 <dt>ev_feed_event (loop, watcher, int events)</dt>
724 <dd> 771 <dd>
725 <p>Feeds the given event set into the event loop, as if the specified event 772 <p>Feeds the given event set into the event loop, as if the specified event
726has happened for the specified watcher (which must be a pointer to an 773had happened for the specified watcher (which must be a pointer to an
727initialised but not necessarily active event watcher).</p> 774initialised but not necessarily started event watcher).</p>
728 </dd> 775 </dd>
729 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 776 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
730 <dd> 777 <dd>
731 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 778 <p>Feed an event on the given fd, as if a file descriptor backend detected
779the given events it.</p>
732 </dd> 780 </dd>
733 <dt>ev_feed_signal_event (loop, int signum)</dt> 781 <dt>ev_feed_signal_event (loop, int signum)</dt>
734 <dd> 782 <dd>
735 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 783 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
736 </dd> 784 </dd>
737</dl> 785</dl>
786
787</div>
788<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
789<div id="LIBEVENT_EMULATION_CONTENT">
790<p>Libev offers a compatibility emulation layer for libevent. It cannot
791emulate the internals of libevent, so here are some usage hints:</p>
792<dl>
793 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
794 <dt>* The following members are fully supported: ev_base, ev_callback,
795ev_arg, ev_fd, ev_res, ev_events.</dt>
796 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
797maintained by libev, it does not work exactly the same way as in libevent (consider
798it a private API).</dt>
799 <dt>* Priorities are not currently supported. Initialising priorities
800will fail and all watchers will have the same priority, even though there
801is an ev_pri field.</dt>
802 <dt>* Other members are not supported.</dt>
803 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
804to use the libev header file and library.</dt>
805</dl>
806
807</div>
808<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
809<div id="C_SUPPORT_CONTENT">
810<p>TBD.</p>
738 811
739</div> 812</div>
740<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 813<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
741<div id="AUTHOR_CONTENT"> 814<div id="AUTHOR_CONTENT">
742<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 815<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

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