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Revision: 1.72
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# Content
1 =head1 NAME
2
3 EV - perl interface to libev, a high performance full-featured event loop
4
5 =head1 SYNOPSIS
6
7 use EV;
8
9 # TIMERS
10
11 my $w = EV::timer 2, 0, sub {
12 warn "is called after 2s";
13 };
14
15 my $w = EV::timer 2, 2, sub {
16 warn "is called roughly every 2s (repeat = 2)";
17 };
18
19 undef $w; # destroy event watcher again
20
21 my $w = EV::periodic 0, 60, 0, sub {
22 warn "is called every minute, on the minute, exactly";
23 };
24
25 # IO
26
27 my $w = EV::io *STDIN, EV::READ, sub {
28 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
29 warn "stdin is readable, you entered: ", <STDIN>;
30 };
31
32 # SIGNALS
33
34 my $w = EV::signal 'QUIT', sub {
35 warn "sigquit received\n";
36 };
37
38 # CHILD/PID STATUS CHANGES
39
40 my $w = EV::child 666, sub {
41 my ($w, $revents) = @_;
42 my $status = $w->rstatus;
43 };
44
45 # STAT CHANGES
46 my $w = EV::stat "/etc/passwd", 10, sub {
47 my ($w, $revents) = @_;
48 warn $w->path, " has changed somehow.\n";
49 };
50
51 # MAINLOOP
52 EV::loop; # loop until EV::unloop is called or all watchers stop
53 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
54 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
55
56 =head1 DESCRIPTION
57
58 This module provides an interface to libev
59 (L<http://software.schmorp.de/pkg/libev.html>). While the documentation
60 below is comprehensive, one might also consult the documentation of libev
61 itself (L<http://cvs.schmorp.de/libev/ev.html>) for more subtle details on
62 watcher semantics or some discussion on the available backends, or how to
63 force a specific backend with C<LIBEV_FLAGS>, or just about in any case
64 because it has much more detailed information.
65
66 =cut
67
68 package EV;
69
70 use strict;
71
72 BEGIN {
73 our $VERSION = '2.0';
74 use XSLoader;
75 XSLoader::load "EV", $VERSION;
76 }
77
78 @EV::IO::ISA =
79 @EV::Timer::ISA =
80 @EV::Periodic::ISA =
81 @EV::Signal::ISA =
82 @EV::Child::ISA =
83 @EV::Stat::ISA =
84 @EV::Idle::ISA =
85 @EV::Prepare::ISA =
86 @EV::Check::ISA =
87 @EV::Embed::ISA =
88 @EV::Fork::ISA =
89 "EV::Watcher";
90
91 @EV::Loop::Default::ISA = "EV::Loop";
92
93 =head1 BASIC INTERFACE
94
95 =over 4
96
97 =item $EV::DIED
98
99 Must contain a reference to a function that is called when a callback
100 throws an exception (with $@ containing the error). The default prints an
101 informative message and continues.
102
103 If this callback throws an exception it will be silently ignored.
104
105 =item $time = EV::time
106
107 Returns the current time in (fractional) seconds since the epoch.
108
109 =item $time = EV::now
110
111 Returns the time the last event loop iteration has been started. This
112 is the time that (relative) timers are based on, and refering to it is
113 usually faster then calling EV::time.
114
115 =item $method = EV::method
116
117 Returns an integer describing the backend used by libev (EV::METHOD_SELECT
118 or EV::METHOD_EPOLL).
119
120 =item EV::loop [$flags]
121
122 Begin checking for events and calling callbacks. It returns when a
123 callback calls EV::unloop.
124
125 The $flags argument can be one of the following:
126
127 0 as above
128 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
129 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
130
131 =item EV::unloop [$how]
132
133 When called with no arguments or an argument of EV::UNLOOP_ONE, makes the
134 innermost call to EV::loop return.
135
136 When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as
137 fast as possible.
138
139 =item $count = EV::loop_count
140
141 Return the number of times the event loop has polled for new
142 events. Sometiems useful as a generation counter.
143
144 =item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
145
146 This function rolls together an I/O and a timer watcher for a single
147 one-shot event without the need for managing a watcher object.
148
149 If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
150 must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
151 | EV::WRITE>, indicating the type of I/O event you want to wait for. If
152 you do not want to wait for some I/O event, specify C<undef> for
153 C<$fh_or_undef> and C<0> for C<$events>).
154
155 If timeout is C<undef> or negative, then there will be no
156 timeout. Otherwise a EV::timer with this value will be started.
157
158 When an error occurs or either the timeout or I/O watcher triggers, then
159 the callback will be called with the received event set (in general
160 you can expect it to be a combination of C<EV:ERROR>, C<EV::READ>,
161 C<EV::WRITE> and C<EV::TIMEOUT>).
162
163 EV::once doesn't return anything: the watchers stay active till either
164 of them triggers, then they will be stopped and freed, and the callback
165 invoked.
166
167 =item EV::feed_fd_event ($fd, $revents)
168
169 Feed an event on a file descriptor into EV. EV will react to this call as
170 if the readyness notifications specified by C<$revents> (a combination of
171 C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>.
172
173 =item EV::feed_signal_event ($signal)
174
175 Feed a signal event into EV. EV will react to this call as if the signal
176 specified by C<$signal> had occured.
177
178 =back
179
180
181 =head2 WATCHER OBJECTS
182
183 A watcher is an object that gets created to record your interest in some
184 event. For instance, if you want to wait for STDIN to become readable, you
185 would create an EV::io watcher for that:
186
187 my $watcher = EV::io *STDIN, EV::READ, sub {
188 my ($watcher, $revents) = @_;
189 warn "yeah, STDIN should not be readable without blocking!\n"
190 };
191
192 All watchers can be active (waiting for events) or inactive (paused). Only
193 active watchers will have their callbacks invoked. All callbacks will be
194 called with at least two arguments: the watcher and a bitmask of received
195 events.
196
197 Each watcher type has its associated bit in revents, so you can use the
198 same callback for multiple watchers. The event mask is named after the
199 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
200 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
201 (which can set both EV::READ and EV::WRITE bits), and EV::timer (which
202 uses EV::TIMEOUT).
203
204 In the rare case where one wants to create a watcher but not start it at
205 the same time, each constructor has a variant with a trailing C<_ns> in
206 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
207
208 Please note that a watcher will automatically be stopped when the watcher
209 object is destroyed, so you I<need> to keep the watcher objects returned by
210 the constructors.
211
212 Also, all methods changing some aspect of a watcher (->set, ->priority,
213 ->fh and so on) automatically stop and start it again if it is active,
214 which means pending events get lost.
215
216 =head2 COMMON WATCHER METHODS
217
218 This section lists methods common to all watchers.
219
220 =over 4
221
222 =item $w->start
223
224 Starts a watcher if it isn't active already. Does nothing to an already
225 active watcher. By default, all watchers start out in the active state
226 (see the description of the C<_ns> variants if you need stopped watchers).
227
228 =item $w->stop
229
230 Stop a watcher if it is active. Also clear any pending events (events that
231 have been received but that didn't yet result in a callback invocation),
232 regardless of whether the watcher was active or not.
233
234 =item $bool = $w->is_active
235
236 Returns true if the watcher is active, false otherwise.
237
238 =item $current_data = $w->data
239
240 =item $old_data = $w->data ($new_data)
241
242 Queries a freely usable data scalar on the watcher and optionally changes
243 it. This is a way to associate custom data with a watcher:
244
245 my $w = EV::timer 60, 0, sub {
246 warn $_[0]->data;
247 };
248 $w->data ("print me!");
249
250 =item $current_cb = $w->cb
251
252 =item $old_cb = $w->cb ($new_cb)
253
254 Queries the callback on the watcher and optionally changes it. You can do
255 this at any time without the watcher restarting.
256
257 =item $current_priority = $w->priority
258
259 =item $old_priority = $w->priority ($new_priority)
260
261 Queries the priority on the watcher and optionally changes it. Pending
262 watchers with higher priority will be invoked first. The valid range of
263 priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
264 -2). If the priority is outside this range it will automatically be
265 normalised to the nearest valid priority.
266
267 The default priority of any newly-created watcher is 0.
268
269 Note that the priority semantics have not yet been fleshed out and are
270 subject to almost certain change.
271
272 =item $w->invoke ($revents)
273
274 Call the callback *now* with the given event mask.
275
276 =item $w->feed_event ($revents)
277
278 Feed some events on this watcher into EV. EV will react to this call as if
279 the watcher had received the given C<$revents> mask.
280
281 =item $revents = $w->clear_pending
282
283 If the watcher is pending, this function returns clears its pending status
284 and returns its C<$revents> bitset (as if its callback was invoked). If the
285 watcher isn't pending it does nothing and returns C<0>.
286
287 =item $previous_state = $w->keepalive ($bool)
288
289 Normally, C<EV::loop> will return when there are no active watchers
290 (which is a "deadlock" because no progress can be made anymore). This is
291 convinient because it allows you to start your watchers (and your jobs),
292 call C<EV::loop> once and when it returns you know that all your jobs are
293 finished (or they forgot to register some watchers for their task :).
294
295 Sometimes, however, this gets in your way, for example when you the module
296 that calls C<EV::loop> (usually the main program) is not the same module
297 as a long-living watcher (for example a DNS client module written by
298 somebody else even). Then you might want any outstanding requests to be
299 handled, but you would not want to keep C<EV::loop> from returning just
300 because you happen to have this long-running UDP port watcher.
301
302 In this case you can clear the keepalive status, which means that even
303 though your watcher is active, it won't keep C<EV::loop> from returning.
304
305 The initial value for keepalive is true (enabled), and you cna change it
306 any time.
307
308 Example: Register an I/O watcher for some UDP socket but do not keep the
309 event loop from running just because of that watcher.
310
311 my $udp_socket = ...
312 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
313 $udp_watcher->keepalive (0);
314
315 =back
316
317
318 =head2 WATCHER TYPES
319
320 Each of the following subsections describes a single watcher type.
321
322 =head3 I/O WATCHERS - is this file descriptor readable or writable?
323
324 =over 4
325
326 =item $w = EV::io $fileno_or_fh, $eventmask, $callback
327
328 =item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
329
330 As long as the returned watcher object is alive, call the C<$callback>
331 when at least one of events specified in C<$eventmask> occurs.
332
333 The $eventmask can be one or more of these constants ORed together:
334
335 EV::READ wait until read() wouldn't block anymore
336 EV::WRITE wait until write() wouldn't block anymore
337
338 The C<io_ns> variant doesn't start (activate) the newly created watcher.
339
340 =item $w->set ($fileno_or_fh, $eventmask)
341
342 Reconfigures the watcher, see the constructor above for details. Can be
343 called at any time.
344
345 =item $current_fh = $w->fh
346
347 =item $old_fh = $w->fh ($new_fh)
348
349 Returns the previously set filehandle and optionally set a new one.
350
351 =item $current_eventmask = $w->events
352
353 =item $old_eventmask = $w->events ($new_eventmask)
354
355 Returns the previously set event mask and optionally set a new one.
356
357 =back
358
359
360 =head3 TIMER WATCHERS - relative and optionally repeating timeouts
361
362 =over 4
363
364 =item $w = EV::timer $after, $repeat, $callback
365
366 =item $w = EV::timer_ns $after, $repeat, $callback
367
368 Calls the callback after C<$after> seconds (which may be fractional). If
369 C<$repeat> is non-zero, the timer will be restarted (with the $repeat
370 value as $after) after the callback returns.
371
372 This means that the callback would be called roughly after C<$after>
373 seconds, and then every C<$repeat> seconds. The timer does his best not
374 to drift, but it will not invoke the timer more often then once per event
375 loop iteration, and might drift in other cases. If that isn't acceptable,
376 look at EV::periodic, which can provide long-term stable timers.
377
378 The timer is based on a monotonic clock, that is, if somebody is sitting
379 in front of the machine while the timer is running and changes the system
380 clock, the timer will nevertheless run (roughly) the same time.
381
382 The C<timer_ns> variant doesn't start (activate) the newly created watcher.
383
384 =item $w->set ($after, $repeat)
385
386 Reconfigures the watcher, see the constructor above for details. Can be called at
387 any time.
388
389 =item $w->again
390
391 Similar to the C<start> method, but has special semantics for repeating timers:
392
393 If the timer is active and non-repeating, it will be stopped.
394
395 If the timer is active and repeating, reset the timeout to occur
396 C<$repeat> seconds after now.
397
398 If the timer is inactive and repeating, start it using the repeat value.
399
400 Otherwise do nothing.
401
402 This behaviour is useful when you have a timeout for some IO
403 operation. You create a timer object with the same value for C<$after> and
404 C<$repeat>, and then, in the read/write watcher, run the C<again> method
405 on the timeout.
406
407 =back
408
409
410 =head3 PERIODIC WATCHERS - to cron or not to cron?
411
412 =over 4
413
414 =item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
415
416 =item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
417
418 Similar to EV::timer, but is not based on relative timeouts but on
419 absolute times. Apart from creating "simple" timers that trigger "at" the
420 specified time, it can also be used for non-drifting absolute timers and
421 more complex, cron-like, setups that are not adversely affected by time
422 jumps (i.e. when the system clock is changed by explicit date -s or other
423 means such as ntpd). It is also the most complex watcher type in EV.
424
425 It has three distinct "modes":
426
427 =over 4
428
429 =item * absolute timer ($interval = $reschedule_cb = 0)
430
431 This time simply fires at the wallclock time C<$at> and doesn't repeat. It
432 will not adjust when a time jump occurs, that is, if it is to be run
433 at January 1st 2011 then it will run when the system time reaches or
434 surpasses this time.
435
436 =item * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
437
438 In this mode the watcher will always be scheduled to time out at the
439 next C<$at + N * $interval> time (for some integer N) and then repeat,
440 regardless of any time jumps.
441
442 This can be used to create timers that do not drift with respect to system
443 time:
444
445 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
446
447 That doesn't mean there will always be 3600 seconds in between triggers,
448 but only that the the clalback will be called when the system time shows a
449 full hour (UTC).
450
451 Another way to think about it (for the mathematically inclined) is that
452 EV::periodic will try to run the callback in this mode at the next
453 possible time where C<$time = $at (mod $interval)>, regardless of any time
454 jumps.
455
456 =item * manual reschedule mode ($reschedule_cb = coderef)
457
458 In this mode $interval and $at are both being ignored. Instead, each
459 time the periodic watcher gets scheduled, the reschedule callback
460 ($reschedule_cb) will be called with the watcher as first, and the current
461 time as second argument.
462
463 I<This callback MUST NOT stop or destroy this or any other periodic
464 watcher, ever>. If you need to stop it, return 1e30 and stop it
465 afterwards.
466
467 It must return the next time to trigger, based on the passed time value
468 (that is, the lowest time value larger than to the second argument). It
469 will usually be called just before the callback will be triggered, but
470 might be called at other times, too.
471
472 This can be used to create very complex timers, such as a timer that
473 triggers on each midnight, local time (actually 24 hours after the last
474 midnight, to keep the example simple. If you know a way to do it correctly
475 in about the same space (without requiring elaborate modules), drop me a
476 note :):
477
478 my $daily = EV::periodic 0, 0, sub {
479 my ($w, $now) = @_;
480
481 use Time::Local ();
482 my (undef, undef, undef, $d, $m, $y) = localtime $now;
483 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
484 }, sub {
485 print "it's midnight or likely shortly after, now\n";
486 };
487
488 =back
489
490 The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
491
492 =item $w->set ($at, $interval, $reschedule_cb)
493
494 Reconfigures the watcher, see the constructor above for details. Can be called at
495 any time.
496
497 =item $w->again
498
499 Simply stops and starts the watcher again.
500
501 =item $time = $w->at
502
503 Return the time that the watcher is expected to trigger next.
504
505 =back
506
507
508 =head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
509
510 =over 4
511
512 =item $w = EV::signal $signal, $callback
513
514 =item $w = EV::signal_ns $signal, $callback
515
516 Call the callback when $signal is received (the signal can be specified by
517 number or by name, just as with C<kill> or C<%SIG>).
518
519 EV will grab the signal for the process (the kernel only allows one
520 component to receive a signal at a time) when you start a signal watcher,
521 and removes it again when you stop it. Perl does the same when you
522 add/remove callbacks to C<%SIG>, so watch out.
523
524 You can have as many signal watchers per signal as you want.
525
526 The C<signal_ns> variant doesn't start (activate) the newly created watcher.
527
528 =item $w->set ($signal)
529
530 Reconfigures the watcher, see the constructor above for details. Can be
531 called at any time.
532
533 =item $current_signum = $w->signal
534
535 =item $old_signum = $w->signal ($new_signal)
536
537 Returns the previously set signal (always as a number not name) and
538 optionally set a new one.
539
540 =back
541
542
543 =head3 CHILD WATCHERS - watch out for process status changes
544
545 =over 4
546
547 =item $w = EV::child $pid, $callback
548
549 =item $w = EV::child_ns $pid, $callback
550
551 Call the callback when a status change for pid C<$pid> (or any pid if
552 C<$pid> is 0) has been received. More precisely: when the process receives
553 a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
554 changed/zombie children and call the callback.
555
556 It is valid (and fully supported) to install a child watcher after a child
557 has exited but before the event loop has started its next iteration (for
558 example, first you C<fork>, then the new child process might exit, and
559 only then do you install a child watcher in the parent for the new pid).
560
561 You can access both exit (or tracing) status and pid by using the
562 C<rstatus> and C<rpid> methods on the watcher object.
563
564 You can have as many pid watchers per pid as you want, they will all be
565 called.
566
567 The C<child_ns> variant doesn't start (activate) the newly created watcher.
568
569 =item $w->set ($pid)
570
571 Reconfigures the watcher, see the constructor above for details. Can be called at
572 any time.
573
574 =item $current_pid = $w->pid
575
576 =item $old_pid = $w->pid ($new_pid)
577
578 Returns the previously set process id and optionally set a new one.
579
580 =item $exit_status = $w->rstatus
581
582 Return the exit/wait status (as returned by waitpid, see the waitpid entry
583 in perlfunc).
584
585 =item $pid = $w->rpid
586
587 Return the pid of the awaited child (useful when you have installed a
588 watcher for all pids).
589
590 =back
591
592
593 =head3 STAT WATCHERS - did the file attributes just change?
594
595 =over 4
596
597 =item $w = EV::stat $path, $interval, $callback
598
599 =item $w = EV::stat_ns $path, $interval, $callback
600
601 Call the callback when a file status change has been detected on
602 C<$path>. The C<$path> does not need to exist, changing from "path exists"
603 to "path does not exist" is a status change like any other.
604
605 The C<$interval> is a recommended polling interval for systems where
606 OS-supported change notifications don't exist or are not supported. If
607 you use C<0> then an unspecified default is used (which is highly
608 recommended!), which is to be expected to be around five seconds usually.
609
610 This watcher type is not meant for massive numbers of stat watchers,
611 as even with OS-supported change notifications, this can be
612 resource-intensive.
613
614 The C<stat_ns> variant doesn't start (activate) the newly created watcher.
615
616 =item ... = $w->stat
617
618 This call is very similar to the perl C<stat> built-in: It stats (using
619 C<lstat>) the path specified in the watcher and sets perls stat cache (as
620 well as EV's idea of the current stat values) to the values found.
621
622 In scalar context, a boolean is return indicating success or failure of
623 the stat. In list context, the same 13-value list as with stat is returned
624 (except that the blksize and blocks fields are not reliable).
625
626 In the case of an error, errno is set to C<ENOENT> (regardless of the
627 actual error value) and the C<nlink> value is forced to zero (if the stat
628 was successful then nlink is guaranteed to be non-zero).
629
630 See also the next two entries for more info.
631
632 =item ... = $w->attr
633
634 Just like C<< $w->stat >>, but without the initial stat'ing: this returns
635 the values most recently detected by EV. See the next entry for more info.
636
637 =item ... = $w->prev
638
639 Just like C<< $w->stat >>, but without the initial stat'ing: this returns
640 the previous set of values, before the change.
641
642 That is, when the watcher callback is invoked, C<< $w->prev >> will be set
643 to the values found I<before> a change was detected, while C<< $w->attr >>
644 returns the values found leading to the change detection. The difference (if any)
645 between C<prev> and C<attr> is what triggered the callback.
646
647 If you did something to the filesystem object and do not want to trigger
648 yet another change, you can call C<stat> to update EV's idea of what the
649 current attributes are.
650
651 =item $w->set ($path, $interval)
652
653 Reconfigures the watcher, see the constructor above for details. Can be
654 called at any time.
655
656 =item $current_path = $w->path
657
658 =item $old_path = $w->path ($new_path)
659
660 Returns the previously set path and optionally set a new one.
661
662 =item $current_interval = $w->interval
663
664 =item $old_interval = $w->interval ($new_interval)
665
666 Returns the previously set interval and optionally set a new one. Can be
667 used to query the actual interval used.
668
669 =back
670
671
672 =head3 IDLE WATCHERS - when you've got nothing better to do...
673
674 =over 4
675
676 =item $w = EV::idle $callback
677
678 =item $w = EV::idle_ns $callback
679
680 Call the callback when there are no other pending watchers of the same or
681 higher priority (excluding check, prepare and other idle watchers of the
682 same or lower priority, of course). They are called idle watchers because
683 when the watcher is the highest priority pending event in the process, the
684 process is considered to be idle at that priority.
685
686 If you want a watcher that is only ever called when I<no> other events are
687 outstanding you have to set the priority to C<EV::MINPRI>.
688
689 The process will not block as long as any idle watchers are active, and
690 they will be called repeatedly until stopped.
691
692 For example, if you have idle watchers at priority C<0> and C<1>, and
693 an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
694 and the I/O watcher will always run when ready. Only when the idle watcher
695 at priority C<1> is stopped and the I/O watcher at priority C<0> is not
696 pending with the C<0>-priority idle watcher be invoked.
697
698 The C<idle_ns> variant doesn't start (activate) the newly created watcher.
699
700 =back
701
702
703 =head3 PREPARE WATCHERS - customise your event loop!
704
705 =over 4
706
707 =item $w = EV::prepare $callback
708
709 =item $w = EV::prepare_ns $callback
710
711 Call the callback just before the process would block. You can still
712 create/modify any watchers at this point.
713
714 See the EV::check watcher, below, for explanations and an example.
715
716 The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
717
718 =back
719
720
721 =head3 CHECK WATCHERS - customise your event loop even more!
722
723 =over 4
724
725 =item $w = EV::check $callback
726
727 =item $w = EV::check_ns $callback
728
729 Call the callback just after the process wakes up again (after it has
730 gathered events), but before any other callbacks have been invoked.
731
732 This is used to integrate other event-based software into the EV
733 mainloop: You register a prepare callback and in there, you create io and
734 timer watchers as required by the other software. Here is a real-world
735 example of integrating Net::SNMP (with some details left out):
736
737 our @snmp_watcher;
738
739 our $snmp_prepare = EV::prepare sub {
740 # do nothing unless active
741 $dispatcher->{_event_queue_h}
742 or return;
743
744 # make the dispatcher handle any outstanding stuff
745 ... not shown
746
747 # create an I/O watcher for each and every socket
748 @snmp_watcher = (
749 (map { EV::io $_, EV::READ, sub { } }
750 keys %{ $dispatcher->{_descriptors} }),
751
752 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
753 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
754 0, sub { },
755 );
756 };
757
758 The callbacks are irrelevant (and are not even being called), the
759 only purpose of those watchers is to wake up the process as soon as
760 one of those events occurs (socket readable, or timer timed out). The
761 corresponding EV::check watcher will then clean up:
762
763 our $snmp_check = EV::check sub {
764 # destroy all watchers
765 @snmp_watcher = ();
766
767 # make the dispatcher handle any new stuff
768 ... not shown
769 };
770
771 The callbacks of the created watchers will not be called as the watchers
772 are destroyed before this cna happen (remember EV::check gets called
773 first).
774
775 The C<check_ns> variant doesn't start (activate) the newly created watcher.
776
777 =back
778
779
780 =head3 FORK WATCHERS - the audacity to resume the event loop after a fork
781
782 Fork watchers are called when a C<fork ()> was detected. The invocation
783 is done before the event loop blocks next and before C<check> watchers
784 are being called, and only in the child after the fork.
785
786 =over 4
787
788 =item $w = EV::fork $callback
789
790 =item $w = EV::fork_ns $callback
791
792 Call the callback before the event loop is resumed in the child process
793 after a fork.
794
795 The C<fork_ns> variant doesn't start (activate) the newly created watcher.
796
797 =back
798
799
800 =head1 PERL SIGNALS
801
802 While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
803 with EV is as the same as any other C library: Perl-signals will only be
804 handled when Perl runs, which means your signal handler might be invoked
805 only the next time an event callback is invoked.
806
807 The solution is to use EV signal watchers (see C<EV::signal>), which will
808 ensure proper operations with regards to other event watchers.
809
810 If you cannot do this for whatever reason, you can also force a watcher
811 to be called on every event loop iteration by installing a C<EV::check>
812 watcher:
813
814 my $async_check = EV::check sub { };
815
816 This ensures that perl shortly gets into control for a short time, and
817 also ensures slower overall operation.
818
819 =head1 THREADS
820
821 Threads are not supported by this module in any way. Perl pseudo-threads
822 is evil stuff and must die. As soon as Perl gains real threads I will work
823 on thread support for it.
824
825 =head1 FORK
826
827 Most of the "improved" event delivering mechanisms of modern operating
828 systems have quite a few problems with fork(2) (to put it bluntly: it is
829 not supported and usually destructive). Libev makes it possible to work
830 around this by having a function that recreates the kernel state after
831 fork in the child.
832
833 On non-win32 platforms, this module requires the pthread_atfork
834 functionality to do this automatically for you. This function is quite
835 buggy on most BSDs, though, so YMMV. The overhead for this is quite
836 negligible, because everything the function currently does is set a flag
837 that is checked only when the event loop gets used the next time, so when
838 you do fork but not use EV, the overhead is minimal.
839
840 On win32, there is no notion of fork so all this doesn't apply, of course.
841
842 =cut
843
844 our $DIED = sub {
845 warn "EV: error in callback (ignoring): $@";
846 };
847
848 default_loop
849 or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
850
851 1;
852
853 =head1 SEE ALSO
854
855 L<EV::ADNS> (asynchronous dns), L<Glib::EV> (makes Glib/Gtk2 use EV as
856 event loop), L<Coro::EV> (efficient coroutines with EV).
857
858 =head1 AUTHOR
859
860 Marc Lehmann <schmorp@schmorp.de>
861 http://home.schmorp.de/
862
863 =cut
864