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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 09:35:36 2007" /> 9 <meta name="created" content="Mon Nov 12 20:19:59 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.</p>
103 </dd> 112 </dd>
… …
142<div id="FUNCTIONS_CONTROLLING_THE_EVENT_LOOP-2"> 151<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 152<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 153types of such loops, the <i>default</i> loop, which supports signals and child
145events, and dynamically created loops which do not.</p> 154events, and dynamically created loops which do not.</p>
146<p>If you use threads, a common model is to run the default event loop 155<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 156in 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 157create, you also create another event loop. Libev itself does no locking
149whatsoever, so if you mix calls to the same event loop in different 158whatsoever, 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 159threads, make sure you lock (this is usually a bad idea, though, even if
151done correctly, because it's hideous and inefficient).</p> 160done correctly, because it's hideous and inefficient).</p>
152<dl> 161<dl>
… …
322*)</code>), and you can stop watching for events at any time by calling the 331*)</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> 332corresponding 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 333<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 334must not touch the values stored in it. Most specifically you must never
326reinitialise it or call its set method.</p> 335reinitialise it or call its set method.</p>
327<p>You cna check whether an event is active by calling the <code>ev_is_active 336<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 337(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 338callback for it has not been called yet) you can use the <code>ev_is_pending
330(watcher *)</code> macro.</p> 339(watcher *)</code> macro.</p>
331<p>Each and every callback receives the event loop pointer as first, the 340<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 341registered watcher structure as second, and a bitset of received events as
333third argument.</p> 342third argument.</p>
334<p>The rceeived events usually include a single bit per event type received 343<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 344(you can receive multiple events at the same time). The possible bit masks
336are:</p> 345are:</p>
337<dl> 346<dl>
338 <dt><code>EV_READ</code></dt> 347 <dt><code>EV_READ</code></dt>
339 <dt><code>EV_WRITE</code></dt> 348 <dt><code>EV_WRITE</code></dt>
… …
389 398
390</div> 399</div>
391<h2 id="ASSOCIATING_CUSTOM_DATA_WITH_A_WATCH">ASSOCIATING CUSTOM DATA WITH A WATCHER</h2> 400<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"> 401<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 402<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 403and 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 404to 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 405don'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 406member, you can also &quot;subclass&quot; the watcher type and provide your own
398data:</p> 407data:</p>
399<pre> struct my_io 408<pre> struct my_io
… …
431<h2 id="code_ev_io_code_is_this_file_descrip"><code>ev_io</code> - is this file descriptor readable or writable</h2> 440<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"> 441<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 442<p>I/O watchers check whether a file descriptor is readable or writable
434in each iteration of the event loop (This behaviour is called 443in each iteration of the event loop (This behaviour is called
435level-triggering because you keep receiving events as long as the 444level-triggering because you keep receiving events as long as the
436condition persists. Remember you cna stop the watcher if you don't want to 445condition 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> 446act 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 447<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 448fd 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 449descriptors to non-blocking mode is also usually a good idea (but not
441required if you know what you are doing).</p> 450required if you know what you are doing).</p>
442<p>You have to be careful with dup'ed file descriptors, though. Some backends 451<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 452(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 453descriptors correctly if you register interest in two or more fds pointing
445to the same file/socket etc. description.</p> 454to the same underlying file/socket etc. description (that is, they share
455the 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 456<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 457(at the time of this writing, this includes only EVMETHOD_SELECT and
448EVMETHOD_POLL).</p> 458EVMETHOD_POLL).</p>
449<dl> 459<dl>
450 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 460 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
… …
460<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 470<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"> 471<div id="code_ev_timer_code_relative_and_opti-2">
462<p>Timer watchers are simple relative timers that generate an event after a 472<p>Timer watchers are simple relative timers that generate an event after a
463given time, and optionally repeating in regular intervals after that.</p> 473given 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 474<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 475times 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 476time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
467detecting time jumps is hard, and soem inaccuracies are unavoidable (the 477detecting time jumps is hard, and soem inaccuracies are unavoidable (the
468monotonic clock option helps a lot here).</p> 478monotonic clock option helps a lot here).</p>
469<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 479<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 480time. This is usually the right thing as this timestamp refers to the time
471of the event triggering whatever timeout you are modifying/starting. If 481of the event triggering whatever timeout you are modifying/starting. If
472you suspect event processing to be delayed and you *need* to base the timeout 482you suspect event processing to be delayed and you *need* to base the timeout
473ion the current time, use something like this to adjust for this:</p> 483on 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.); 484<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
475 485
476</pre> 486</pre>
477<dl> 487<dl>
478 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 488 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
… …
483timer will automatically be configured to trigger again <code>repeat</code> seconds 493timer will automatically be configured to trigger again <code>repeat</code> seconds
484later, again, and again, until stopped manually.</p> 494later, again, and again, until stopped manually.</p>
485 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 495 <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 496configure a timer to trigger every 10 seconds, then it will trigger at
487exactly 10 second intervals. If, however, your program cannot keep up with 497exactly 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 498the 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> 499timer will not fire more than once per event loop iteration.</p>
490 </dd> 500 </dd>
491 <dt>ev_timer_again (loop)</dt> 501 <dt>ev_timer_again (loop)</dt>
492 <dd> 502 <dd>
493 <p>This will act as if the timer timed out and restart it again if it is 503 <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> 515the timer, and again will automatically restart it if need be.</p>
506 </dd> 516 </dd>
507</dl> 517</dl>
508 518
509</div> 519</div>
510<h2 id="code_ev_periodic_code_to_cron_or_not"><code>ev_periodic</code> - to cron or not to cron it</h2> 520<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"> 521<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 522<p>Periodic watchers are also timers of a kind, but they are very versatile
513(and unfortunately a bit complex).</p> 523(and unfortunately a bit complex).</p>
514<p>Unlike <code>ev_timer</code>'s, they are not based on real time (or relative time) 524<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 525but on wallclock time (absolute time). You can tell a periodic watcher
… …
562 <dd> 572 <dd>
563 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 573 <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 574ignored. Instead, each time the periodic watcher gets scheduled, the
565reschedule callback will be called with the watcher as first, and the 575reschedule callback will be called with the watcher as first, and the
566current time as second argument.</p> 576current time as second argument.</p>
567 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 577 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
568periodic watcher, ever, or make any event loop modifications</i>. If you need 578ever, or make any event loop modifications</i>. If you need to stop it,
569to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> 579return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
570 <p>Also, <i>this callback must always return a time that is later than the 580starting a prepare watcher).</p>
571passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
572 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 581 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
573ev_tstamp now)</code>, e.g.:</p> 582ev_tstamp now)</code>, e.g.:</p>
574<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 583<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
575 { 584 {
576 return now + 60.; 585 return now + 60.;
… …
579</pre> 588</pre>
580 <p>It must return the next time to trigger, based on the passed time value 589 <p>It must return the next time to trigger, based on the passed time value
581(that is, the lowest time value larger than to the second argument). It 590(that is, the lowest time value larger than to the second argument). It
582will usually be called just before the callback will be triggered, but 591will usually be called just before the callback will be triggered, but
583might be called at other times, too.</p> 592might be called at other times, too.</p>
593 <p>NOTE: <i>This callback must always return a time that is later than the
594passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
584 <p>This can be used to create very complex timers, such as a timer that 595 <p>This can be used to create very complex timers, such as a timer that
585triggers on each midnight, local time. To do this, you would calculate the 596triggers on each midnight, local time. To do this, you would calculate the
586next midnight after <code>now</code> and return the timestamp value for this. How you do this 597next midnight after <code>now</code> and return the timestamp value for this. How
587is, again, up to you (but it is not trivial).</p> 598you do this is, again, up to you (but it is not trivial, which is the main
599reason I omitted it as an example).</p>
588 </dd> 600 </dd>
589 </dl> 601 </dl>
590 </p> 602 </p>
591 </dd> 603 </dd>
592 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 604 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
603<div id="code_ev_signal_code_signal_me_when_a-2"> 615<div id="code_ev_signal_code_signal_me_when_a-2">
604<p>Signal watchers will trigger an event when the process receives a specific 616<p>Signal watchers will trigger an event when the process receives a specific
605signal one or more times. Even though signals are very asynchronous, libev 617signal one or more times. Even though signals are very asynchronous, libev
606will try it's best to deliver signals synchronously, i.e. as part of the 618will try it's best to deliver signals synchronously, i.e. as part of the
607normal event processing, like any other event.</p> 619normal event processing, like any other event.</p>
608<p>You cna configure as many watchers as you like per signal. Only when the 620<p>You can configure as many watchers as you like per signal. Only when the
609first watcher gets started will libev actually register a signal watcher 621first watcher gets started will libev actually register a signal watcher
610with the kernel (thus it coexists with your own signal handlers as long 622with the kernel (thus it coexists with your own signal handlers as long
611as you don't register any with libev). Similarly, when the last signal 623as you don't register any with libev). Similarly, when the last signal
612watcher for a signal is stopped libev will reset the signal handler to 624watcher for a signal is stopped libev will reset the signal handler to
613SIG_DFL (regardless of what it was set to before).</p> 625SIG_DFL (regardless of what it was set to before).</p>
… …
630 <dt>ev_child_set (ev_child *, int pid)</dt> 642 <dt>ev_child_set (ev_child *, int pid)</dt>
631 <dd> 643 <dd>
632 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or 644 <p>Configures the watcher to wait for status changes of process <code>pid</code> (or
633<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look 645<i>any</i> process if <code>pid</code> is specified as <code>0</code>). The callback can look
634at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see 646at the <code>rstatus</code> member of the <code>ev_child</code> watcher structure to see
635the status word (use the macros from <code>sys/wait.h</code>). The <code>rpid</code> member 647the status word (use the macros from <code>sys/wait.h</code> and see your systems
648<code>waitpid</code> documentation). The <code>rpid</code> member contains the pid of the
636contains the pid of the process causing the status change.</p> 649process causing the status change.</p>
637 </dd> 650 </dd>
638</dl> 651</dl>
639 652
640</div> 653</div>
641<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2> 654<h2 id="code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</h2>
642<div id="code_ev_idle_code_when_you_ve_got_no-2"> 655<div id="code_ev_idle_code_when_you_ve_got_no-2">
643<p>Idle watchers trigger events when there are no other I/O or timer (or 656<p>Idle watchers trigger events when there are no other events are pending
644periodic) events pending. That is, as long as your process is busy 657(prepare, check and other idle watchers do not count). That is, as long
645handling sockets or timeouts it will not be called. But when your process 658as your process is busy handling sockets or timeouts (or even signals,
646is idle all idle watchers are being called again and again - until 659imagine) it will not be triggered. But when your process is idle all idle
660watchers are being called again and again, once per event loop iteration -
647stopped, that is, or your process receives more events.</p> 661until stopped, that is, or your process receives more events and becomes
662busy.</p>
648<p>The most noteworthy effect is that as long as any idle watchers are 663<p>The most noteworthy effect is that as long as any idle watchers are
649active, the process will not block when waiting for new events.</p> 664active, the process will not block when waiting for new events.</p>
650<p>Apart from keeping your process non-blocking (which is a useful 665<p>Apart from keeping your process non-blocking (which is a useful
651effect on its own sometimes), idle watchers are a good place to do 666effect on its own sometimes), idle watchers are a good place to do
652&quot;pseudo-background processing&quot;, or delay processing stuff to after the 667&quot;pseudo-background processing&quot;, or delay processing stuff to after the
… …
659believe me.</p> 674believe me.</p>
660 </dd> 675 </dd>
661</dl> 676</dl>
662 677
663</div> 678</div>
664<h2 id="prepare_and_check_your_hooks_into_th">prepare and check - your hooks into the event loop</h2> 679<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
665<div id="prepare_and_check_your_hooks_into_th-2"> 680<div id="code_ev_prepare_code_and_code_ev_che-2">
666<p>Prepare and check watchers usually (but not always) are used in 681<p>Prepare and check watchers are usually (but not always) used in tandem:
667tandom. Prepare watchers get invoked before the process blocks and check 682prepare watchers get invoked before the process blocks and check watchers
668watchers afterwards.</p> 683afterwards.</p>
669<p>Their main purpose is to integrate other event mechanisms into libev. This 684<p>Their main purpose is to integrate other event mechanisms into libev. This
670could be used, for example, to track variable changes, implement your own 685could be used, for example, to track variable changes, implement your own
671watchers, integrate net-snmp or a coroutine library and lots more.</p> 686watchers, integrate net-snmp or a coroutine library and lots more.</p>
672<p>This is done by examining in each prepare call which file descriptors need 687<p>This is done by examining in each prepare call which file descriptors need
673to be watched by the other library, registering <code>ev_io</code> watchers for them 688to be watched by the other library, registering <code>ev_io</code> watchers for
674and starting an <code>ev_timer</code> watcher for any timeouts (many libraries provide 689them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
675just this functionality). Then, in the check watcher you check for any 690provide just this functionality). Then, in the check watcher you check for
676events that occured (by making your callbacks set soem flags for example) 691any events that occured (by checking the pending status of all watchers
677and call back into the library.</p> 692and stopping them) and call back into the library. The I/O and timer
693callbacks will never actually be called (but must be valid nevertheless,
694because you never know, you know?).</p>
678<p>As another example, the perl Coro module uses these hooks to integrate 695<p>As another example, the Perl Coro module uses these hooks to integrate
679coroutines into libev programs, by yielding to other active coroutines 696coroutines into libev programs, by yielding to other active coroutines
680during each prepare and only letting the process block if no coroutines 697during each prepare and only letting the process block if no coroutines
681are ready to run.</p> 698are ready to run (it's actually more complicated: it only runs coroutines
699with priority higher than or equal to the event loop and one coroutine
700of lower priority, but only once, using idle watchers to keep the event
701loop from blocking if lower-priority coroutines are active, thus mapping
702low-priority coroutines to idle/background tasks).</p>
682<dl> 703<dl>
683 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 704 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
684 <dt>ev_check_init (ev_check *, callback)</dt> 705 <dt>ev_check_init (ev_check *, callback)</dt>
685 <dd> 706 <dd>
686 <p>Initialises and configures the prepare or check watcher - they have no 707 <p>Initialises and configures the prepare or check watcher - they have no
687parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code> 708parameters of any kind. There are <code>ev_prepare_set</code> and <code>ev_check_set</code>
688macros, but using them is utterly, utterly pointless.</p> 709macros, but using them is utterly, utterly and completely pointless.</p>
689 </dd> 710 </dd>
690</dl> 711</dl>
691 712
692</div> 713</div>
693<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 714<h1 id="OTHER_FUNCTIONS">OTHER FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
694<div id="OTHER_FUNCTIONS_CONTENT"> 715<div id="OTHER_FUNCTIONS_CONTENT">
695<p>There are some other fucntions of possible interest. Described. Here. Now.</p> 716<p>There are some other functions of possible interest. Described. Here. Now.</p>
696<dl> 717<dl>
697 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 718 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
698 <dd> 719 <dd>
699 <p>This function combines a simple timer and an I/O watcher, calls your 720 <p>This function combines a simple timer and an I/O watcher, calls your
700callback on whichever event happens first and automatically stop both 721callback on whichever event happens first and automatically stop both
701watchers. This is useful if you want to wait for a single event on an fd 722watchers. This is useful if you want to wait for a single event on an fd
702or timeout without havign to allocate/configure/start/stop/free one or 723or timeout without having to allocate/configure/start/stop/free one or
703more watchers yourself.</p> 724more watchers yourself.</p>
704 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events is 725 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
705ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and <code>events</code> set 726is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
706will be craeted and started.</p> 727<code>events</code> set will be craeted and started.</p>
707 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 728 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
708started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and repeat 729started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
709= 0) will be started.</p> 730repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
731dubious value.</p>
710 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and 732 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
711gets passed an events set (normally a combination of <code>EV_ERROR</code>, <code>EV_READ</code>, 733passed an <code>revents</code> set like normal event callbacks (a combination of
712<code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> value passed to <code>ev_once</code>:</p> 734<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
735value passed to <code>ev_once</code>:</p>
713<pre> static void stdin_ready (int revents, void *arg) 736<pre> static void stdin_ready (int revents, void *arg)
714 { 737 {
715 if (revents &amp; EV_TIMEOUT) 738 if (revents &amp; EV_TIMEOUT)
716 /* doh, nothing entered */ 739 /* doh, nothing entered */;
717 else if (revents &amp; EV_READ) 740 else if (revents &amp; EV_READ)
718 /* stdin might have data for us, joy! */ 741 /* stdin might have data for us, joy! */;
719 } 742 }
720 743
721 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 744 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
722 745
723</pre> 746</pre>
724 </dd> 747 </dd>
725 <dt>ev_feed_event (loop, watcher, int events)</dt> 748 <dt>ev_feed_event (loop, watcher, int events)</dt>
726 <dd> 749 <dd>
727 <p>Feeds the given event set into the event loop, as if the specified event 750 <p>Feeds the given event set into the event loop, as if the specified event
728has happened for the specified watcher (which must be a pointer to an 751had happened for the specified watcher (which must be a pointer to an
729initialised but not necessarily active event watcher).</p> 752initialised but not necessarily started event watcher).</p>
730 </dd> 753 </dd>
731 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt> 754 <dt>ev_feed_fd_event (loop, int fd, int revents)</dt>
732 <dd> 755 <dd>
733 <p>Feed an event on the given fd, as if a file descriptor backend detected it.</p> 756 <p>Feed an event on the given fd, as if a file descriptor backend detected
757the given events it.</p>
734 </dd> 758 </dd>
735 <dt>ev_feed_signal_event (loop, int signum)</dt> 759 <dt>ev_feed_signal_event (loop, int signum)</dt>
736 <dd> 760 <dd>
737 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 761 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
738 </dd> 762 </dd>
739</dl> 763</dl>
764
765</div>
766<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
767<div id="LIBEVENT_EMULATION_CONTENT">
768<p>Libev offers a compatibility emulation layer for libevent. It cannot
769emulate the internals of libevent, so here are some usage hints:</p>
770<dl>
771 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
772 <dt>* The following members are fully supported: ev_base, ev_callback,
773ev_arg, ev_fd, ev_res, ev_events.</dt>
774 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
775maintained by libev, it does not work exactly the same way as in libevent (consider
776it a private API).</dt>
777 <dt>* Priorities are not currently supported. Initialising priorities
778will fail and all watchers will have the same priority, even though there
779is an ev_pri field.</dt>
780 <dt>* Other members are not supported.</dt>
781 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
782to use the libev header file and library.</dt>
783</dl>
784
785</div>
786<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
787<div id="C_SUPPORT_CONTENT">
788<p>TBD.</p>
740 789
741</div> 790</div>
742<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 791<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
743<div id="AUTHOR_CONTENT"> 792<div id="AUTHOR_CONTENT">
744<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 793<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>

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