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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 09:57:02 2007" /> 9 <meta name="created" content="Thu Nov 22 13:26:17 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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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="#code_ev_idle_code_when_you_ve_got_no"><code>ev_idle</code> - when you've got nothing better to do</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<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>
37</ul> 37</ul>
38</li> 38</li>
39<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>
40<li><a href="#AUTHOR">AUTHOR</a> 42<li><a href="#AUTHOR">AUTHOR</a>
41</li> 43</li>
42</ul><hr /> 44</ul><hr />
43<!-- INDEX END --> 45<!-- INDEX END -->
44 46
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99to the double type in C.</p> 101to the double type in C.</p>
100 102
101</div> 103</div>
102<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p> 104<h1 id="GLOBAL_FUNCTIONS">GLOBAL FUNCTIONS</h1><p><a href="#TOP" class="toplink">Top</a></p>
103<div id="GLOBAL_FUNCTIONS_CONTENT"> 105<div id="GLOBAL_FUNCTIONS_CONTENT">
106<p>These functions can be called anytime, even before initialising the
107library in any way.</p>
104<dl> 108<dl>
105 <dt>ev_tstamp ev_time ()</dt> 109 <dt>ev_tstamp ev_time ()</dt>
106 <dd> 110 <dd>
107 <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>
108 </dd> 114 </dd>
109 <dt>int ev_version_major ()</dt> 115 <dt>int ev_version_major ()</dt>
110 <dt>int ev_version_minor ()</dt> 116 <dt>int ev_version_minor ()</dt>
111 <dd> 117 <dd>
112 <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
… …
180<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will 186<code>LIBEV_FLAGS</code>. Otherwise (the default), this environment variable will
181override the flags completely if it is found in the environment. This is 187override the flags completely if it is found in the environment. This is
182useful to try out specific backends to test their performance, or to work 188useful to try out specific backends to test their performance, or to work
183around bugs.</p> 189around bugs.</p>
184 </dd> 190 </dd>
185 <dt><code>EVMETHOD_SELECT</code> (portable select backend)</dt> 191 <dt><code>EVMETHOD_SELECT</code> (value 1, portable select backend)</dt>
192 <dd>
193 <p>This is your standard select(2) backend. Not <i>completely</i> standard, as
194libev tries to roll its own fd_set with no limits on the number of fds,
195but if that fails, expect a fairly low limit on the number of fds when
196using this backend. It doesn't scale too well (O(highest_fd)), but its usually
197the fastest backend for a low number of fds.</p>
198 </dd>
186 <dt><code>EVMETHOD_POLL</code> (poll backend, available everywhere except on windows)</dt> 199 <dt><code>EVMETHOD_POLL</code> (value 2, poll backend, available everywhere except on windows)</dt>
187 <dt><code>EVMETHOD_EPOLL</code> (linux only)</dt> 200 <dd>
188 <dt><code>EVMETHOD_KQUEUE</code> (some bsds only)</dt> 201 <p>And this is your standard poll(2) backend. It's more complicated than
189 <dt><code>EVMETHOD_DEVPOLL</code> (solaris 8 only)</dt> 202select, but handles sparse fds better and has no artificial limit on the
190 <dt><code>EVMETHOD_PORT</code> (solaris 10 only)</dt> 203number of fds you can use (except it will slow down considerably with a
204lot of inactive fds). It scales similarly to select, i.e. O(total_fds).</p>
191 <dd> 205 </dd>
192 <p>If one or more of these are ored into the flags value, then only these 206 <dt><code>EVMETHOD_EPOLL</code> (value 4, Linux)</dt>
193backends will be tried (in the reverse order as given here). If one are 207 <dd>
194specified, any backend will do.</p> 208 <p>For few fds, this backend is a bit little slower than poll and select,
209but it scales phenomenally better. While poll and select usually scale like
210O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
211either O(1) or O(active_fds).</p>
212 <p>While stopping and starting an I/O watcher in the same iteration will
213result in some caching, there is still a syscall per such incident
214(because the fd could point to a different file description now), so its
215best to avoid that. Also, dup()ed file descriptors might not work very
216well if you register events for both fds.</p>
217 </dd>
218 <dt><code>EVMETHOD_KQUEUE</code> (value 8, most BSD clones)</dt>
219 <dd>
220 <p>Kqueue deserves special mention, as at the time of this writing, it
221was broken on all BSDs except NetBSD (usually it doesn't work with
222anything but sockets and pipes, except on Darwin, where of course its
223completely useless). For this reason its not being &quot;autodetected&quot; unless
224you explicitly specify the flags (i.e. you don't use EVFLAG_AUTO).</p>
225 <p>It scales in the same way as the epoll backend, but the interface to the
226kernel is more efficient (which says nothing about its actual speed, of
227course). While starting and stopping an I/O watcher does not cause an
228extra syscall as with epoll, it still adds up to four event changes per
229incident, so its best to avoid that.</p>
230 </dd>
231 <dt><code>EVMETHOD_DEVPOLL</code> (value 16, Solaris 8)</dt>
232 <dd>
233 <p>This is not implemented yet (and might never be).</p>
234 </dd>
235 <dt><code>EVMETHOD_PORT</code> (value 32, Solaris 10)</dt>
236 <dd>
237 <p>This uses the Solaris 10 port mechanism. As with everything on Solaris,
238it's really slow, but it still scales very well (O(active_fds)).</p>
239 </dd>
240 <dt><code>EVMETHOD_ALL</code></dt>
241 <dd>
242 <p>Try all backends (even potentially broken ones). Since this is a mask, you
243can do stuff like <code>EVMETHOD_ALL &amp; ~EVMETHOD_KQUEUE</code>.</p>
195 </dd> 244 </dd>
196 </dl> 245 </dl>
197 </p> 246 </p>
247 <p>If one or more of these are ored into the flags value, then only these
248backends will be tried (in the reverse order as given here). If none are
249specified, most compiled-in backend will be tried, usually in reverse
250order of their flag values :)</p>
198 </dd> 251 </dd>
199 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt> 252 <dt>struct ev_loop *ev_loop_new (unsigned int flags)</dt>
200 <dd> 253 <dd>
201 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is 254 <p>Similar to <code>ev_default_loop</code>, but always creates a new event loop that is
202always distinct from the default loop. Unlike the default loop, it cannot 255always distinct from the default loop. Unlike the default loop, it cannot
… …
264your process until at least one new event arrives, and will return after 317your process until at least one new event arrives, and will return after
265one iteration of the loop.</p> 318one iteration of the loop.</p>
266 <p>This flags value could be used to implement alternative looping 319 <p>This flags value could be used to implement alternative looping
267constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and 320constructs, but the <code>prepare</code> and <code>check</code> watchers provide a better and
268more generic mechanism.</p> 321more generic mechanism.</p>
322 <p>Here are the gory details of what ev_loop does:</p>
323<pre> 1. If there are no active watchers (reference count is zero), return.
324 2. Queue and immediately call all prepare watchers.
325 3. If we have been forked, recreate the kernel state.
326 4. Update the kernel state with all outstanding changes.
327 5. Update the &quot;event loop time&quot;.
328 6. Calculate for how long to block.
329 7. Block the process, waiting for events.
330 8. Update the &quot;event loop time&quot; and do time jump handling.
331 9. Queue all outstanding timers.
332 10. Queue all outstanding periodics.
333 11. If no events are pending now, queue all idle watchers.
334 12. Queue all check watchers.
335 13. Call all queued watchers in reverse order (i.e. check watchers first).
336 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
337 was used, return, otherwise continue with step #1.
338
339</pre>
269 </dd> 340 </dd>
270 <dt>ev_unloop (loop, how)</dt> 341 <dt>ev_unloop (loop, how)</dt>
271 <dd> 342 <dd>
272 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it 343 <p>Can be used to make a call to <code>ev_loop</code> return early (but only after it
273has processed all outstanding events). The <code>how</code> argument must be either 344has processed all outstanding events). The <code>how</code> argument must be either
274<code>EVUNLOOP_ONCE</code>, which will make the innermost <code>ev_loop</code> call return, or 345<code>EVUNLOOP_ONE</code>, which will make the innermost <code>ev_loop</code> call return, or
275<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p> 346<code>EVUNLOOP_ALL</code>, which will make all nested <code>ev_loop</code> calls return.</p>
276 </dd> 347 </dd>
277 <dt>ev_ref (loop)</dt> 348 <dt>ev_ref (loop)</dt>
278 <dt>ev_unref (loop)</dt> 349 <dt>ev_unref (loop)</dt>
279 <dd> 350 <dd>
… …
438<p>I/O watchers check whether a file descriptor is readable or writable 509<p>I/O watchers check whether a file descriptor is readable or writable
439in each iteration of the event loop (This behaviour is called 510in each iteration of the event loop (This behaviour is called
440level-triggering because you keep receiving events as long as the 511level-triggering because you keep receiving events as long as the
441condition persists. Remember you can stop the watcher if you don't want to 512condition persists. Remember you can stop the watcher if you don't want to
442act on the event and neither want to receive future events).</p> 513act on the event and neither want to receive future events).</p>
443<p>In general you can register as many read and/or write event watchers oer 514<p>In general you can register as many read and/or write event watchers per
444fd as you want (as long as you don't confuse yourself). Setting all file 515fd as you want (as long as you don't confuse yourself). Setting all file
445descriptors to non-blocking mode is also usually a good idea (but not 516descriptors to non-blocking mode is also usually a good idea (but not
446required if you know what you are doing).</p> 517required if you know what you are doing).</p>
447<p>You have to be careful with dup'ed file descriptors, though. Some backends 518<p>You have to be careful with dup'ed file descriptors, though. Some backends
448(the linux epoll backend is a notable example) cannot handle dup'ed file 519(the linux epoll backend is a notable example) cannot handle dup'ed file
449descriptors correctly if you register interest in two or more fds pointing 520descriptors correctly if you register interest in two or more fds pointing
450to the same file/socket etc. description.</p> 521to the same underlying file/socket etc. description (that is, they share
522the same underlying &quot;file open&quot;).</p>
451<p>If you must do this, then force the use of a known-to-be-good backend 523<p>If you must do this, then force the use of a known-to-be-good backend
452(at the time of this writing, this includes only EVMETHOD_SELECT and 524(at the time of this writing, this includes only EVMETHOD_SELECT and
453EVMETHOD_POLL).</p> 525EVMETHOD_POLL).</p>
454<dl> 526<dl>
455 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt> 527 <dt>ev_io_init (ev_io *, callback, int fd, int events)</dt>
… …
465<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2> 537<h2 id="code_ev_timer_code_relative_and_opti"><code>ev_timer</code> - relative and optionally recurring timeouts</h2>
466<div id="code_ev_timer_code_relative_and_opti-2"> 538<div id="code_ev_timer_code_relative_and_opti-2">
467<p>Timer watchers are simple relative timers that generate an event after a 539<p>Timer watchers are simple relative timers that generate an event after a
468given time, and optionally repeating in regular intervals after that.</p> 540given time, and optionally repeating in regular intervals after that.</p>
469<p>The timers are based on real time, that is, if you register an event that 541<p>The timers are based on real time, that is, if you register an event that
470times out after an hour and youreset your system clock to last years 542times out after an hour and you reset your system clock to last years
471time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because 543time, it will still time out after (roughly) and hour. &quot;Roughly&quot; because
472detecting time jumps is hard, and soem inaccuracies are unavoidable (the 544detecting time jumps is hard, and some inaccuracies are unavoidable (the
473monotonic clock option helps a lot here).</p> 545monotonic clock option helps a lot here).</p>
474<p>The relative timeouts are calculated relative to the <code>ev_now ()</code> 546<p>The relative timeouts are calculated relative to the <code>ev_now ()</code>
475time. This is usually the right thing as this timestamp refers to the time 547time. This is usually the right thing as this timestamp refers to the time
476of the event triggering whatever timeout you are modifying/starting. If 548of the event triggering whatever timeout you are modifying/starting. If
477you suspect event processing to be delayed and you *need* to base the timeout 549you suspect event processing to be delayed and you <i>need</i> to base the timeout
478ion the current time, use something like this to adjust for this:</p> 550on the current time, use something like this to adjust for this:</p>
479<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.); 551<pre> ev_timer_set (&amp;timer, after + ev_now () - ev_time (), 0.);
480 552
481</pre> 553</pre>
554<p>The callback is guarenteed to be invoked only when its timeout has passed,
555but if multiple timers become ready during the same loop iteration then
556order of execution is undefined.</p>
482<dl> 557<dl>
483 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt> 558 <dt>ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)</dt>
484 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt> 559 <dt>ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)</dt>
485 <dd> 560 <dd>
486 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is 561 <p>Configure the timer to trigger after <code>after</code> seconds. If <code>repeat</code> is
… …
488timer will automatically be configured to trigger again <code>repeat</code> seconds 563timer will automatically be configured to trigger again <code>repeat</code> seconds
489later, again, and again, until stopped manually.</p> 564later, again, and again, until stopped manually.</p>
490 <p>The timer itself will do a best-effort at avoiding drift, that is, if you 565 <p>The timer itself will do a best-effort at avoiding drift, that is, if you
491configure a timer to trigger every 10 seconds, then it will trigger at 566configure a timer to trigger every 10 seconds, then it will trigger at
492exactly 10 second intervals. If, however, your program cannot keep up with 567exactly 10 second intervals. If, however, your program cannot keep up with
493the timer (ecause it takes longer than those 10 seconds to do stuff) the 568the timer (because it takes longer than those 10 seconds to do stuff) the
494timer will not fire more than once per event loop iteration.</p> 569timer will not fire more than once per event loop iteration.</p>
495 </dd> 570 </dd>
496 <dt>ev_timer_again (loop)</dt> 571 <dt>ev_timer_again (loop)</dt>
497 <dd> 572 <dd>
498 <p>This will act as if the timer timed out and restart it again if it is 573 <p>This will act as if the timer timed out and restart it again if it is
… …
524take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger 599take a year to trigger the event (unlike an <code>ev_timer</code>, which would trigger
525roughly 10 seconds later and of course not if you reset your system time 600roughly 10 seconds later and of course not if you reset your system time
526again).</p> 601again).</p>
527<p>They can also be used to implement vastly more complex timers, such as 602<p>They can also be used to implement vastly more complex timers, such as
528triggering an event on eahc midnight, local time.</p> 603triggering an event on eahc midnight, local time.</p>
604<p>As with timers, the callback is guarenteed to be invoked only when the
605time (<code>at</code>) has been passed, but if multiple periodic timers become ready
606during the same loop iteration then order of execution is undefined.</p>
529<dl> 607<dl>
530 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt> 608 <dt>ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)</dt>
531 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt> 609 <dt>ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)</dt>
532 <dd> 610 <dd>
533 <p>Lots of arguments, lets sort it out... There are basically three modes of 611 <p>Lots of arguments, lets sort it out... There are basically three modes of
534operation, and we will explain them from simplest to complex:</p> 612operation, and we will explain them from simplest to complex:</p>
535
536
537
538
539 <p> 613 <p>
540 <dl> 614 <dl>
541 <dt>* absolute timer (interval = reschedule_cb = 0)</dt> 615 <dt>* absolute timer (interval = reschedule_cb = 0)</dt>
542 <dd> 616 <dd>
543 <p>In this configuration the watcher triggers an event at the wallclock time 617 <p>In this configuration the watcher triggers an event at the wallclock time
… …
567 <dd> 641 <dd>
568 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being 642 <p>In this mode the values for <code>interval</code> and <code>at</code> are both being
569ignored. Instead, each time the periodic watcher gets scheduled, the 643ignored. Instead, each time the periodic watcher gets scheduled, the
570reschedule callback will be called with the watcher as first, and the 644reschedule callback will be called with the watcher as first, and the
571current time as second argument.</p> 645current time as second argument.</p>
572 <p>NOTE: <i>This callback MUST NOT stop or destroy the periodic or any other 646 <p>NOTE: <i>This callback MUST NOT stop or destroy any periodic watcher,
573periodic watcher, ever, or make any event loop modifications</i>. If you need 647ever, or make any event loop modifications</i>. If you need to stop it,
574to stop it, return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards.</p> 648return <code>now + 1e30</code> (or so, fudge fudge) and stop it afterwards (e.g. by
575 <p>Also, <i>this callback must always return a time that is later than the 649starting a prepare watcher).</p>
576passed <code>now</code> value</i>. Not even <code>now</code> itself will be ok.</p>
577 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 650 <p>Its prototype is <code>ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
578ev_tstamp now)</code>, e.g.:</p> 651ev_tstamp now)</code>, e.g.:</p>
579<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 652<pre> static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
580 { 653 {
581 return now + 60.; 654 return now + 60.;
… …
584</pre> 657</pre>
585 <p>It must return the next time to trigger, based on the passed time value 658 <p>It must return the next time to trigger, based on the passed time value
586(that is, the lowest time value larger than to the second argument). It 659(that is, the lowest time value larger than to the second argument). It
587will usually be called just before the callback will be triggered, but 660will usually be called just before the callback will be triggered, but
588might be called at other times, too.</p> 661might be called at other times, too.</p>
662 <p>NOTE: <i>This callback must always return a time that is later than the
663passed <code>now</code> value</i>. Not even <code>now</code> itself will do, it <i>must</i> be larger.</p>
589 <p>This can be used to create very complex timers, such as a timer that 664 <p>This can be used to create very complex timers, such as a timer that
590triggers on each midnight, local time. To do this, you would calculate the 665triggers on each midnight, local time. To do this, you would calculate the
591next midnight after <code>now</code> and return the timestamp value for this. How you do this 666next midnight after <code>now</code> and return the timestamp value for this. How
592is, again, up to you (but it is not trivial).</p> 667you do this is, again, up to you (but it is not trivial, which is the main
668reason I omitted it as an example).</p>
593 </dd> 669 </dd>
594 </dl> 670 </dl>
595 </p> 671 </p>
596 </dd> 672 </dd>
597 <dt>ev_periodic_again (loop, ev_periodic *)</dt> 673 <dt>ev_periodic_again (loop, ev_periodic *)</dt>
… …
670 746
671</div> 747</div>
672<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2> 748<h2 id="code_ev_prepare_code_and_code_ev_che"><code>ev_prepare</code> and <code>ev_check</code> - customise your event loop</h2>
673<div id="code_ev_prepare_code_and_code_ev_che-2"> 749<div id="code_ev_prepare_code_and_code_ev_che-2">
674<p>Prepare and check watchers are usually (but not always) used in tandem: 750<p>Prepare and check watchers are usually (but not always) used in tandem:
675Prepare watchers get invoked before the process blocks and check watchers 751prepare watchers get invoked before the process blocks and check watchers
676afterwards.</p> 752afterwards.</p>
677<p>Their main purpose is to integrate other event mechanisms into libev. This 753<p>Their main purpose is to integrate other event mechanisms into libev. This
678could be used, for example, to track variable changes, implement your own 754could be used, for example, to track variable changes, implement your own
679watchers, integrate net-snmp or a coroutine library and lots more.</p> 755watchers, integrate net-snmp or a coroutine library and lots more.</p>
680<p>This is done by examining in each prepare call which file descriptors need 756<p>This is done by examining in each prepare call which file descriptors need
681to be watched by the other library, registering <code>ev_io</code> watchers for 757to be watched by the other library, registering <code>ev_io</code> watchers for
682them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries 758them and starting an <code>ev_timer</code> watcher for any timeouts (many libraries
683provide just this functionality). Then, in the check watcher you check for 759provide just this functionality). Then, in the check watcher you check for
684any events that occured (by checking the pending status of all watchers 760any events that occured (by checking the pending status of all watchers
685and stopping them) and call back into the library. The I/O and timer 761and stopping them) and call back into the library. The I/O and timer
686callbacks will never actually be called (but must be valid neverthelles, 762callbacks will never actually be called (but must be valid nevertheless,
687because you never know, you know?).</p> 763because you never know, you know?).</p>
688<p>As another example, the Perl Coro module uses these hooks to integrate 764<p>As another example, the Perl Coro module uses these hooks to integrate
689coroutines into libev programs, by yielding to other active coroutines 765coroutines into libev programs, by yielding to other active coroutines
690during each prepare and only letting the process block if no coroutines 766during each prepare and only letting the process block if no coroutines
691are ready to run (its actually more complicated, it only runs coroutines 767are ready to run (it's actually more complicated: it only runs coroutines
692with priority higher than the event loop and one lower priority once, 768with priority higher than or equal to the event loop and one coroutine
693using idle watchers to keep the event loop from blocking if lower-priority 769of lower priority, but only once, using idle watchers to keep the event
694coroutines exist, thus mapping low-priority coroutines to idle/background 770loop from blocking if lower-priority coroutines are active, thus mapping
695tasks).</p> 771low-priority coroutines to idle/background tasks).</p>
696<dl> 772<dl>
697 <dt>ev_prepare_init (ev_prepare *, callback)</dt> 773 <dt>ev_prepare_init (ev_prepare *, callback)</dt>
698 <dt>ev_check_init (ev_check *, callback)</dt> 774 <dt>ev_check_init (ev_check *, callback)</dt>
699 <dd> 775 <dd>
700 <p>Initialises and configures the prepare or check watcher - they have no 776 <p>Initialises and configures the prepare or check watcher - they have no
… …
711 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt> 787 <dt>ev_once (loop, int fd, int events, ev_tstamp timeout, callback)</dt>
712 <dd> 788 <dd>
713 <p>This function combines a simple timer and an I/O watcher, calls your 789 <p>This function combines a simple timer and an I/O watcher, calls your
714callback on whichever event happens first and automatically stop both 790callback on whichever event happens first and automatically stop both
715watchers. This is useful if you want to wait for a single event on an fd 791watchers. This is useful if you want to wait for a single event on an fd
716or timeout without havign to allocate/configure/start/stop/free one or 792or timeout without having to allocate/configure/start/stop/free one or
717more watchers yourself.</p> 793more watchers yourself.</p>
718 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events 794 <p>If <code>fd</code> is less than 0, then no I/O watcher will be started and events
719is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and 795is being ignored. Otherwise, an <code>ev_io</code> watcher for the given <code>fd</code> and
720<code>events</code> set will be craeted and started.</p> 796<code>events</code> set will be craeted and started.</p>
721 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be 797 <p>If <code>timeout</code> is less than 0, then no timeout watcher will be
722started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and 798started. Otherwise an <code>ev_timer</code> watcher with after = <code>timeout</code> (and
723repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of 799repeat = 0) will be started. While <code>0</code> is a valid timeout, it is of
724dubious value.</p> 800dubious value.</p>
725 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets 801 <p>The callback has the type <code>void (*cb)(int revents, void *arg)</code> and gets
726passed an events set like normal event callbacks (with a combination of 802passed an <code>revents</code> set like normal event callbacks (a combination of
727<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code> 803<code>EV_ERROR</code>, <code>EV_READ</code>, <code>EV_WRITE</code> or <code>EV_TIMEOUT</code>) and the <code>arg</code>
728value passed to <code>ev_once</code>:</p> 804value passed to <code>ev_once</code>:</p>
729<pre> static void stdin_ready (int revents, void *arg) 805<pre> static void stdin_ready (int revents, void *arg)
730 { 806 {
731 if (revents &amp; EV_TIMEOUT) 807 if (revents &amp; EV_TIMEOUT)
… …
754 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p> 830 <p>Feed an event as if the given signal occured (loop must be the default loop!).</p>
755 </dd> 831 </dd>
756</dl> 832</dl>
757 833
758</div> 834</div>
835<h1 id="LIBEVENT_EMULATION">LIBEVENT EMULATION</h1><p><a href="#TOP" class="toplink">Top</a></p>
836<div id="LIBEVENT_EMULATION_CONTENT">
837<p>Libev offers a compatibility emulation layer for libevent. It cannot
838emulate the internals of libevent, so here are some usage hints:</p>
839<dl>
840 <dt>* Use it by including &lt;event.h&gt;, as usual.</dt>
841 <dt>* The following members are fully supported: ev_base, ev_callback,
842ev_arg, ev_fd, ev_res, ev_events.</dt>
843 <dt>* Avoid using ev_flags and the EVLIST_*-macros, while it is
844maintained by libev, it does not work exactly the same way as in libevent (consider
845it a private API).</dt>
846 <dt>* Priorities are not currently supported. Initialising priorities
847will fail and all watchers will have the same priority, even though there
848is an ev_pri field.</dt>
849 <dt>* Other members are not supported.</dt>
850 <dt>* The libev emulation is <i>not</i> ABI compatible to libevent, you need
851to use the libev header file and library.</dt>
852</dl>
853
854</div>
855<h1 id="C_SUPPORT">C++ SUPPORT</h1><p><a href="#TOP" class="toplink">Top</a></p>
856<div id="C_SUPPORT_CONTENT">
857<p>TBD.</p>
858
859</div>
759<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p> 860<h1 id="AUTHOR">AUTHOR</h1><p><a href="#TOP" class="toplink">Top</a></p>
760<div id="AUTHOR_CONTENT"> 861<div id="AUTHOR_CONTENT">
761<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p> 862<p>Marc Lehmann &lt;libev@schmorp.de&gt;.</p>
762 863
763</div> 864</div>

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