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Revision 1.9 by root, Sun Oct 28 06:40:46 2007 UTC vs.
Revision 1.118 by root, Tue Jul 14 20:31:21 2009 UTC

1=head1 NAME 1=head1 NAME
2 2
3EV - perl interface to libevent, monkey.org/~provos/libevent/ 3EV - perl interface to libev, a high performance full-featured event loop
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 use EV; 7 use EV;
8 8
9 # TIMER 9 # TIMERS
10 10
11 my $w = EV::timer 2, 0, sub { 11 my $w = EV::timer 2, 0, sub {
12 warn "is called after 2s"; 12 warn "is called after 2s";
13 }; 13 };
14 14
15 my $w = EV::timer 2, 1, sub { 15 my $w = EV::timer 2, 2, sub {
16 warn "is called roughly every 2s (repeat = 1)"; 16 warn "is called roughly every 2s (repeat = 2)";
17 }; 17 };
18 18
19 undef $w; # destroy event watcher again 19 undef $w; # destroy event watcher again
20 20
21 # IO
22
23 my $w = EV::timer_abs 0, 60, sub { 21 my $w = EV::periodic 0, 60, 0, sub {
24 warn "is called every minute, on the minute, exactly"; 22 warn "is called every minute, on the minute, exactly";
25 }; 23 };
26 24
25 # IO
26
27 my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { 27 my $w = EV::io *STDIN, EV::READ, sub {
28 my ($w, $events) = @_; # all callbacks get the watcher object and event mask 28 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
29 if ($events & EV::TIMEOUT) {
30 warn "nothign received on stdin for 10 seconds, retrying";
31 } else {
32 warn "stdin is readable, you entered: ", <STDIN>; 29 warn "stdin is readable, you entered: ", <STDIN>;
33 } 30 };
31
32 # SIGNALS
33
34 my $w = EV::signal 'QUIT', sub {
35 warn "sigquit received\n";
34 }; 36 };
35 $w->timeout (10); 37
36 38 # CHILD/PID STATUS CHANGES
39
40 my $w = EV::child 666, 0, sub {
41 my ($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
37 # MAINLOOP 51 # MAINLOOP
38 EV::dispatch; # loop as long as watchers are active 52 EV::loop; # loop until EV::unloop is called or all watchers stop
39 EV::loop; # the same thing 53 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
40 EV::loop EV::LOOP_ONCE; 54 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
41 EV::loop EV::LOOP_ONSHOT;
42 55
43=head1 DESCRIPTION 56=head1 DESCRIPTION
44 57
45This module provides an interface to libevent 58This module provides an interface to libev
46(L<http://monkey.org/~provos/libevent/>). You probably should acquaint 59(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
47yourself with its documentation and source code to be able to use this 60below is comprehensive, one might also consult the documentation of
48module fully. 61libev itself (L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
62F<perldoc EV::libev>) for more subtle details on watcher semantics or some
63discussion on the available backends, or how to force a specific backend
64with C<LIBEV_FLAGS>, or just about in any case because it has much more
65detailed information.
49 66
50Please note thta this module disables the libevent EPOLL method by 67This module is very fast and scalable. It is actually so fast that you
51default, see BUGS, below, if you need to enable it. 68can use it through the L<AnyEvent> module, stay portable to other event
69loops (if you don't rely on any watcher types not available through it)
70and still be faster than with any other event loop currently supported in
71Perl.
72
73=head2 MODULE EXPORTS
74
75This module does not export any symbols.
52 76
53=cut 77=cut
54 78
55package EV; 79package EV;
56 80
57use strict; 81use common::sense;
58 82
59BEGIN { 83BEGIN {
60 our $VERSION = '0.02'; 84 our $VERSION = '3.7';
61 use XSLoader; 85 use XSLoader;
62 XSLoader::load "EV", $VERSION; 86 XSLoader::load "EV", $VERSION;
63} 87}
64 88
89@EV::IO::ISA =
90@EV::Timer::ISA =
91@EV::Periodic::ISA =
92@EV::Signal::ISA =
93@EV::Child::ISA =
94@EV::Stat::ISA =
95@EV::Idle::ISA =
96@EV::Prepare::ISA =
97@EV::Check::ISA =
98@EV::Embed::ISA =
99@EV::Fork::ISA =
100@EV::Async::ISA =
101 "EV::Watcher";
102
103@EV::Loop::Default::ISA = "EV::Loop";
104
105=head1 EVENT LOOPS
106
107EV supports multiple event loops: There is a single "default event loop"
108that can handle everything including signals and child watchers, and any
109number of "dynamic event loops" that can use different backends (with
110various limitations), but no child and signal watchers.
111
112You do not have to do anything to create the default event loop: When
113the module is loaded a suitable backend is selected on the premise of
114selecting a working backend (which for example rules out kqueue on most
115BSDs). Modules should, unless they have "special needs" always use the
116default loop as this is fastest (perl-wise), best supported by other
117modules (e.g. AnyEvent or Coro) and most portable event loop.
118
119For specific programs you can create additional event loops dynamically.
120
121If you want to take advantage of kqueue (which often works properly for
122sockets only) even though the default loop doesn't enable it, you can
123I<embed> a kqueue loop into the default loop: running the default loop
124will then also service the kqueue loop to some extent. See the example in
125the section about embed watchers for an example on how to achieve that.
126
127=over 4
128
129=item $loop = new EV::Loop [$flags]
130
131Create a new event loop as per the specified flags. Please refer to
132the C<ev_loop_new ()> function description in the libev documentation
133(L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTIONS>,
134or locally-installed as F<EV::libev> manpage) for more info.
135
136The loop will automatically be destroyed when it is no longer referenced
137by any watcher and the loop object goes out of scope.
138
139If you are not embedding the loop, then Using C<EV::FLAG_FORKCHECK>
140is recommended, as only the default event loop is protected by this
141module. If you I<are> embedding this loop in the default loop, this is not
142necessary, as C<EV::embed> automatically does the right thing on fork.
143
144=item $loop->loop_fork
145
146Must be called after a fork in the child, before entering or continuing
147the event loop. An alternative is to use C<EV::FLAG_FORKCHECK> which calls
148this function automatically, at some performance loss (refer to the libev
149documentation).
150
151=item $loop->loop_verify
152
153Calls C<ev_verify> to make internal consistency checks (for debugging
154libev) and abort the program if any data structures were found to be
155corrupted.
156
157=item $loop = EV::default_loop [$flags]
158
159Return the default loop (which is a singleton object). Since this module
160already creates the default loop with default flags, specifying flags here
161will not have any effect unless you destroy the default loop first, which
162isn't supported. So in short: don't do it, and if you break it, you get to
163keep the pieces.
164
165=back
166
167
65=head1 BASIC INTERFACE 168=head1 BASIC INTERFACE
66 169
67=over 4 170=over 4
68 171
69=item $EV::NPRI
70
71How many priority levels are available.
72
73=item $EV::DIED 172=item $EV::DIED
74 173
75Must contain a reference to a function that is called when a callback 174Must contain a reference to a function that is called when a callback
76throws an exception (with $@ containing thr error). The default prints an 175throws an exception (with $@ containing the error). The default prints an
77informative message and continues. 176informative message and continues.
78 177
79If this callback throws an exception it will be silently ignored. 178If this callback throws an exception it will be silently ignored.
80 179
180=item $flags = EV::supported_backends
181
182=item $flags = EV::recommended_backends
183
184=item $flags = EV::embeddable_backends
185
186Returns the set (see C<EV::BACKEND_*> flags) of backends supported by this
187instance of EV, the set of recommended backends (supposed to be good) for
188this platform and the set of embeddable backends (see EMBED WATCHERS).
189
190=item EV::sleep $seconds
191
192Block the process for the given number of (fractional) seconds.
193
194=item $time = EV::time
195
196Returns the current time in (fractional) seconds since the epoch.
197
81=item $time = EV::now 198=item $time = EV::now
82 199
83Returns the time in (fractional) seconds since the epoch. 200=item $time = $loop->now
84 201
85=item $version = EV::version 202Returns the time the last event loop iteration has been started. This
203is the time that (relative) timers are based on, and referring to it is
204usually faster then calling EV::time.
86 205
87=item $method = EV::method 206=item EV::now_update
88 207
89Return version string and event polling method used. 208=item $loop->now_update
90 209
91=item EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 210Establishes the current time by querying the kernel, updating the time
211returned by C<EV::now> in the progress. This is a costly operation and
212is usually done automatically within C<EV::loop>.
92 213
93=item EV::loopexit $after 214This function is rarely useful, but when some event callback runs for a
215very long time without entering the event loop, updating libev's idea of
216the current time is a good idea.
94 217
95Exit any active loop or dispatch after C<$after> seconds or immediately if 218=item EV::suspend
96C<$after> is missing or zero.
97 219
98=item EV::dispatch 220=item $loop->suspend
99 221
100Same as C<EV::loop 0>. 222=item EV::resume
101 223
102=item EV::event $callback 224=item $loop->resume
103 225
104Creates a new event watcher waiting for nothing, calling the given callback. 226These two functions suspend and resume a loop, for use when the loop is
227not used for a while and timeouts should not be processed.
105 228
229A typical use case would be an interactive program such as a game: When
230the user presses C<^Z> to suspend the game and resumes it an hour later it
231would be best to handle timeouts as if no time had actually passed while
232the program was suspended. This can be achieved by calling C<suspend>
233in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
234C<resume> directly afterwards to resume timer processing.
235
236Effectively, all C<timer> watchers will be delayed by the time spend
237between C<suspend> and C<resume>, and all C<periodic> watchers
238will be rescheduled (that is, they will lose any events that would have
239occured while suspended).
240
241After calling C<suspend> you B<must not> call I<any> function on the given
242loop other than C<resume>, and you B<must not> call C<resume>
243without a previous call to C<suspend>.
244
245Calling C<suspend>/C<resume> has the side effect of updating the event
246loop time (see C<now_update>).
247
248=item $backend = EV::backend
249
250=item $backend = $loop->backend
251
252Returns an integer describing the backend used by libev (EV::BACKEND_SELECT
253or EV::BACKEND_EPOLL).
254
255=item EV::loop [$flags]
256
257=item $loop->loop ([$flags])
258
259Begin checking for events and calling callbacks. It returns when a
260callback calls EV::unloop.
261
262The $flags argument can be one of the following:
263
264 0 as above
265 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
266 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
267
268=item EV::unloop [$how]
269
270=item $loop->unloop ([$how])
271
272When called with no arguments or an argument of EV::UNLOOP_ONE, makes the
273innermost call to EV::loop return.
274
275When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as
276fast as possible.
277
278=item $count = EV::loop_count
279
280=item $count = $loop->loop_count
281
282Return the number of times the event loop has polled for new
283events. Sometimes useful as a generation counter.
284
285=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
286
287=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
288
289This function rolls together an I/O and a timer watcher for a single
290one-shot event without the need for managing a watcher object.
291
292If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
293must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
294| EV::WRITE>, indicating the type of I/O event you want to wait for. If
295you do not want to wait for some I/O event, specify C<undef> for
296C<$fh_or_undef> and C<0> for C<$events>).
297
298If timeout is C<undef> or negative, then there will be no
299timeout. Otherwise a EV::timer with this value will be started.
300
301When an error occurs or either the timeout or I/O watcher triggers, then
302the callback will be called with the received event set (in general
303you can expect it to be a combination of C<EV::ERROR>, C<EV::READ>,
304C<EV::WRITE> and C<EV::TIMEOUT>).
305
306EV::once doesn't return anything: the watchers stay active till either
307of them triggers, then they will be stopped and freed, and the callback
308invoked.
309
310=item EV::feed_fd_event ($fd, $revents)
311
312=item $loop->feed_fd_event ($fd, $revents)
313
314Feed an event on a file descriptor into EV. EV will react to this call as
315if the readyness notifications specified by C<$revents> (a combination of
316C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>.
317
318=item EV::feed_signal_event ($signal)
319
320Feed a signal event into EV. EV will react to this call as if the signal
321specified by C<$signal> had occured.
322
323=item EV::set_io_collect_interval $time
324
325=item $loop->set_io_collect_interval ($time)
326
327=item EV::set_timeout_collect_interval $time
328
329=item $loop->set_timeout_collect_interval ($time)
330
331These advanced functions set the minimum block interval when polling for I/O events and the minimum
332wait interval for timer events. See the libev documentation at
333L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP>
334(locally installed as F<EV::libev>) for a more detailed discussion.
335
336=back
337
338
339=head1 WATCHER OBJECTS
340
341A watcher is an object that gets created to record your interest in some
342event. For instance, if you want to wait for STDIN to become readable, you
343would create an EV::io watcher for that:
344
345 my $watcher = EV::io *STDIN, EV::READ, sub {
346 my ($watcher, $revents) = @_;
347 warn "yeah, STDIN should now be readable without blocking!\n"
348 };
349
350All watchers can be active (waiting for events) or inactive (paused). Only
351active watchers will have their callbacks invoked. All callbacks will be
352called with at least two arguments: the watcher and a bitmask of received
353events.
354
355Each watcher type has its associated bit in revents, so you can use the
356same callback for multiple watchers. The event mask is named after the
357type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
358EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
359(which can set both EV::READ and EV::WRITE bits), and EV::timer (which
360uses EV::TIMEOUT).
361
362In the rare case where one wants to create a watcher but not start it at
363the same time, each constructor has a variant with a trailing C<_ns> in
364its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
365
366Please note that a watcher will automatically be stopped when the watcher
367object is destroyed, so you I<need> to keep the watcher objects returned by
368the constructors.
369
370Also, all methods changing some aspect of a watcher (->set, ->priority,
371->fh and so on) automatically stop and start it again if it is active,
372which means pending events get lost.
373
374=head2 COMMON WATCHER METHODS
375
376This section lists methods common to all watchers.
377
378=over 4
379
380=item $w->start
381
382Starts a watcher if it isn't active already. Does nothing to an already
383active watcher. By default, all watchers start out in the active state
384(see the description of the C<_ns> variants if you need stopped watchers).
385
386=item $w->stop
387
388Stop a watcher if it is active. Also clear any pending events (events that
389have been received but that didn't yet result in a callback invocation),
390regardless of whether the watcher was active or not.
391
392=item $bool = $w->is_active
393
394Returns true if the watcher is active, false otherwise.
395
396=item $current_data = $w->data
397
398=item $old_data = $w->data ($new_data)
399
400Queries a freely usable data scalar on the watcher and optionally changes
401it. This is a way to associate custom data with a watcher:
402
403 my $w = EV::timer 60, 0, sub {
404 warn $_[0]->data;
405 };
406 $w->data ("print me!");
407
408=item $current_cb = $w->cb
409
410=item $old_cb = $w->cb ($new_cb)
411
412Queries the callback on the watcher and optionally changes it. You can do
413this at any time without the watcher restarting.
414
415=item $current_priority = $w->priority
416
417=item $old_priority = $w->priority ($new_priority)
418
419Queries the priority on the watcher and optionally changes it. Pending
420watchers with higher priority will be invoked first. The valid range of
421priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
422-2). If the priority is outside this range it will automatically be
423normalised to the nearest valid priority.
424
425The default priority of any newly-created watcher is 0.
426
427Note that the priority semantics have not yet been fleshed out and are
428subject to almost certain change.
429
430=item $w->invoke ($revents)
431
432Call the callback *now* with the given event mask.
433
434=item $w->feed_event ($revents)
435
436Feed some events on this watcher into EV. EV will react to this call as if
437the watcher had received the given C<$revents> mask.
438
439=item $revents = $w->clear_pending
440
441If the watcher is pending, this function clears its pending status and
442returns its C<$revents> bitset (as if its callback was invoked). If the
443watcher isn't pending it does nothing and returns C<0>.
444
445=item $previous_state = $w->keepalive ($bool)
446
447Normally, C<EV::loop> will return when there are no active watchers
448(which is a "deadlock" because no progress can be made anymore). This is
449convinient because it allows you to start your watchers (and your jobs),
450call C<EV::loop> once and when it returns you know that all your jobs are
451finished (or they forgot to register some watchers for their task :).
452
453Sometimes, however, this gets in your way, for example when the module
454that calls C<EV::loop> (usually the main program) is not the same module
455as a long-living watcher (for example a DNS client module written by
456somebody else even). Then you might want any outstanding requests to be
457handled, but you would not want to keep C<EV::loop> from returning just
458because you happen to have this long-running UDP port watcher.
459
460In this case you can clear the keepalive status, which means that even
461though your watcher is active, it won't keep C<EV::loop> from returning.
462
463The initial value for keepalive is true (enabled), and you can change it
464any time.
465
466Example: Register an I/O watcher for some UDP socket but do not keep the
467event loop from running just because of that watcher.
468
469 my $udp_socket = ...
470 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
471 $udp_watcher->keepalive (0);
472
473=item $loop = $w->loop
474
475Return the loop that this watcher is attached to.
476
477=back
478
479
480=head1 WATCHER TYPES
481
482Each of the following subsections describes a single watcher type.
483
484=head3 I/O WATCHERS - is this file descriptor readable or writable?
485
486=over 4
487
106=item my $w = EV::io $fileno_or_fh, $eventmask, $callback 488=item $w = EV::io $fileno_or_fh, $eventmask, $callback
107 489
108=item my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 490=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
491
492=item $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
493
494=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
109 495
110As long as the returned watcher object is alive, call the C<$callback> 496As long as the returned watcher object is alive, call the C<$callback>
111when the events specified in C<$eventmask> happen. Initially, the timeout 497when at least one of events specified in C<$eventmask> occurs.
112is disabled.
113 498
114Youc an additionall set a timeout to occur on the watcher, but note that
115this timeout will not be reset when you get an I/O event in the EV::PERSIST
116case, and reaching a timeout will always stop the watcher even in the
117EV::PERSIST case.
118
119If you want a timeout to occur only after a specific time of inactivity, set
120a repeating timeout and do NOT use EV::PERSIST.
121
122Eventmask can be one or more of these constants ORed together: 499The $eventmask can be one or more of these constants ORed together:
123 500
124 EV::READ wait until read() wouldn't block anymore 501 EV::READ wait until read() wouldn't block anymore
125 EV::WRITE wait until write() wouldn't block anymore 502 EV::WRITE wait until write() wouldn't block anymore
126 EV::PERSIST stay active after a (non-timeout) event occured
127 503
128The C<io_ns> variant doesn't add/start the newly created watcher. 504The C<io_ns> variant doesn't start (activate) the newly created watcher.
129 505
506=item $w->set ($fileno_or_fh, $eventmask)
507
508Reconfigures the watcher, see the constructor above for details. Can be
509called at any time.
510
511=item $current_fh = $w->fh
512
513=item $old_fh = $w->fh ($new_fh)
514
515Returns the previously set filehandle and optionally set a new one.
516
517=item $current_eventmask = $w->events
518
519=item $old_eventmask = $w->events ($new_eventmask)
520
521Returns the previously set event mask and optionally set a new one.
522
523=back
524
525
526=head3 TIMER WATCHERS - relative and optionally repeating timeouts
527
528=over 4
529
130=item my $w = EV::timer $after, $repeat, $callback 530=item $w = EV::timer $after, $repeat, $callback
131 531
132=item my $w = EV::timer_ns $after, $repeat, $callback 532=item $w = EV::timer_ns $after, $repeat, $callback
133 533
134Calls the callback after C<$after> seconds. If C<$repeat> is true, the 534=item $w = $loop->timer ($after, $repeat, $callback)
135timer will be restarted after the callback returns. This means that the
136callback would be called roughly every C<$after> seconds, prolonged by the
137time the callback takes.
138 535
536=item $w = $loop->timer_ns ($after, $repeat, $callback)
537
538Calls the callback after C<$after> seconds (which may be fractional). If
539C<$repeat> is non-zero, the timer will be restarted (with the $repeat
540value as $after) after the callback returns.
541
542This means that the callback would be called roughly after C<$after>
543seconds, and then every C<$repeat> seconds. The timer does his best not
544to drift, but it will not invoke the timer more often then once per event
545loop iteration, and might drift in other cases. If that isn't acceptable,
546look at EV::periodic, which can provide long-term stable timers.
547
548The timer is based on a monotonic clock, that is, if somebody is sitting
549in front of the machine while the timer is running and changes the system
550clock, the timer will nevertheless run (roughly) the same time.
551
139The C<timer_ns> variant doesn't add/start the newly created watcher. 552The C<timer_ns> variant doesn't start (activate) the newly created watcher.
140 553
141=item my $w = EV::timer_abs $at, $interval, $callback 554=item $w->set ($after, $repeat)
142 555
143=item my $w = EV::timer_abs_ns $at, $interval, $callback 556Reconfigures the watcher, see the constructor above for details. Can be called at
557any time.
144 558
145Similar to EV::timer, but the time is given as an absolute point in time 559=item $w->again
146(C<$at>), plus an optional C<$interval>.
147 560
148If the C<$interval> is zero, then the callback will be called at the time 561Similar to the C<start> method, but has special semantics for repeating timers:
149C<$at> if that is in the future, or as soon as possible if its in the
150past. It will not automatically repeat.
151 562
152If the C<$interval> is nonzero, then the watcher will always be scheduled 563If the timer is active and non-repeating, it will be stopped.
153to time out at the next C<$at + integer * $interval> time.
154 564
155This can be used to schedule a callback to run at very regular intervals, 565If the timer is active and repeating, reset the timeout to occur
156as long as the processing time is less then the interval (otherwise 566C<$repeat> seconds after now.
157obviously events will be skipped). 567
568If the timer is inactive and repeating, start it using the repeat value.
569
570Otherwise do nothing.
571
572This behaviour is useful when you have a timeout for some IO
573operation. You create a timer object with the same value for C<$after> and
574C<$repeat>, and then, in the read/write watcher, run the C<again> method
575on the timeout.
576
577=back
578
579
580=head3 PERIODIC WATCHERS - to cron or not to cron?
581
582=over 4
583
584=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
585
586=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
587
588=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
589
590=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
591
592Similar to EV::timer, but is not based on relative timeouts but on
593absolute times. Apart from creating "simple" timers that trigger "at" the
594specified time, it can also be used for non-drifting absolute timers and
595more complex, cron-like, setups that are not adversely affected by time
596jumps (i.e. when the system clock is changed by explicit date -s or other
597means such as ntpd). It is also the most complex watcher type in EV.
598
599It has three distinct "modes":
600
601=over 4
602
603=item * absolute timer ($interval = $reschedule_cb = 0)
604
605This time simply fires at the wallclock time C<$at> and doesn't repeat. It
606will not adjust when a time jump occurs, that is, if it is to be run
607at January 1st 2011 then it will run when the system time reaches or
608surpasses this time.
609
610=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
611
612In this mode the watcher will always be scheduled to time out at the
613next C<$at + N * $interval> time (for some integer N) and then repeat,
614regardless of any time jumps.
615
616This can be used to create timers that do not drift with respect to system
617time:
618
619 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
620
621That doesn't mean there will always be 3600 seconds in between triggers,
622but only that the the clalback will be called when the system time shows a
623full hour (UTC).
158 624
159Another way to think about it (for the mathematically inclined) is that 625Another way to think about it (for the mathematically inclined) is that
160C<timer_abs> will try to tun the callback at the next possible time where 626EV::periodic will try to run the callback in this mode at the next
161C<$time = $at (mod $interval)>, regardless of any time jumps. 627possible time where C<$time = $at (mod $interval)>, regardless of any time
628jumps.
162 629
630=item * manual reschedule mode ($reschedule_cb = coderef)
631
632In this mode $interval and $at are both being ignored. Instead, each
633time the periodic watcher gets scheduled, the reschedule callback
634($reschedule_cb) will be called with the watcher as first, and the current
635time as second argument.
636
637I<This callback MUST NOT stop or destroy this or any other periodic
638watcher, ever, and MUST NOT call any event loop functions or methods>. If
639you need to stop it, return 1e30 and stop it afterwards. You may create
640and start a C<EV::prepare> watcher for this task.
641
642It must return the next time to trigger, based on the passed time value
643(that is, the lowest time value larger than or equal to to the second
644argument). It will usually be called just before the callback will be
645triggered, but might be called at other times, too.
646
647This can be used to create very complex timers, such as a timer that
648triggers on each midnight, local time (actually 24 hours after the last
649midnight, to keep the example simple. If you know a way to do it correctly
650in about the same space (without requiring elaborate modules), drop me a
651note :):
652
653 my $daily = EV::periodic 0, 0, sub {
654 my ($w, $now) = @_;
655
656 use Time::Local ();
657 my (undef, undef, undef, $d, $m, $y) = localtime $now;
658 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
659 }, sub {
660 print "it's midnight or likely shortly after, now\n";
661 };
662
663=back
664
163The C<timer_abs_ns> variant doesn't add/start the newly created watcher. 665The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
164 666
667=item $w->set ($at, $interval, $reschedule_cb)
668
669Reconfigures the watcher, see the constructor above for details. Can be called at
670any time.
671
672=item $w->again
673
674Simply stops and starts the watcher again.
675
676=item $time = $w->at
677
678Return the time that the watcher is expected to trigger next.
679
680=back
681
682
683=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
684
685=over 4
686
165=item my $w = EV::signal $signum, $callback 687=item $w = EV::signal $signal, $callback
166 688
167=item my $w = EV::signal_ns $signum, $callback 689=item $w = EV::signal_ns $signal, $callback
168 690
169Call the callback when signal $signum is received. 691Call the callback when $signal is received (the signal can be specified by
692number or by name, just as with C<kill> or C<%SIG>).
170 693
694EV will grab the signal for the process (the kernel only allows one
695component to receive a signal at a time) when you start a signal watcher,
696and removes it again when you stop it. Perl does the same when you
697add/remove callbacks to C<%SIG>, so watch out.
698
699You can have as many signal watchers per signal as you want.
700
171The C<signal_ns> variant doesn't add/start the newly created watcher. 701The C<signal_ns> variant doesn't start (activate) the newly created watcher.
172 702
173=back 703=item $w->set ($signal)
174 704
175=head1 THE EV::Event CLASS 705Reconfigures the watcher, see the constructor above for details. Can be
706called at any time.
176 707
177All EV functions creating an event watcher (designated by C<my $w => 708=item $current_signum = $w->signal
178above) support the following methods on the returned watcher object:
179 709
180=over 4 710=item $old_signum = $w->signal ($new_signal)
181 711
182=item $w->add ($timeout) 712Returns the previously set signal (always as a number not name) and
713optionally set a new one.
183 714
184Stops and (re-)starts the event watcher, setting the optional timeout to 715=back
185the given value, or clearing the timeout if none is given.
186 716
717
718=head3 CHILD WATCHERS - watch out for process status changes
719
720=over 4
721
722=item $w = EV::child $pid, $trace, $callback
723
724=item $w = EV::child_ns $pid, $trace, $callback
725
726=item $w = $loop->child ($pid, $trace, $callback)
727
728=item $w = $loop->child_ns ($pid, $trace, $callback)
729
730Call the callback when a status change for pid C<$pid> (or any pid
731if C<$pid> is 0) has been received (a status change happens when the
732process terminates or is killed, or, when trace is true, additionally when
733it is stopped or continued). More precisely: when the process receives
734a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
735changed/zombie children and call the callback.
736
737It is valid (and fully supported) to install a child watcher after a child
738has exited but before the event loop has started its next iteration (for
739example, first you C<fork>, then the new child process might exit, and
740only then do you install a child watcher in the parent for the new pid).
741
742You can access both exit (or tracing) status and pid by using the
743C<rstatus> and C<rpid> methods on the watcher object.
744
745You can have as many pid watchers per pid as you want, they will all be
746called.
747
748The C<child_ns> variant doesn't start (activate) the newly created watcher.
749
750=item $w->set ($pid, $trace)
751
752Reconfigures the watcher, see the constructor above for details. Can be called at
753any time.
754
755=item $current_pid = $w->pid
756
757Returns the previously set process id and optionally set a new one.
758
759=item $exit_status = $w->rstatus
760
761Return the exit/wait status (as returned by waitpid, see the waitpid entry
762in perlfunc).
763
764=item $pid = $w->rpid
765
766Return the pid of the awaited child (useful when you have installed a
767watcher for all pids).
768
769=back
770
771
772=head3 STAT WATCHERS - did the file attributes just change?
773
774=over 4
775
776=item $w = EV::stat $path, $interval, $callback
777
778=item $w = EV::stat_ns $path, $interval, $callback
779
780=item $w = $loop->stat ($path, $interval, $callback)
781
782=item $w = $loop->stat_ns ($path, $interval, $callback)
783
784Call the callback when a file status change has been detected on
785C<$path>. The C<$path> does not need to exist, changing from "path exists"
786to "path does not exist" is a status change like any other.
787
788The C<$interval> is a recommended polling interval for systems where
789OS-supported change notifications don't exist or are not supported. If
790you use C<0> then an unspecified default is used (which is highly
791recommended!), which is to be expected to be around five seconds usually.
792
793This watcher type is not meant for massive numbers of stat watchers,
794as even with OS-supported change notifications, this can be
795resource-intensive.
796
797The C<stat_ns> variant doesn't start (activate) the newly created watcher.
798
187=item $w->start 799=item ... = $w->stat
188 800
189Stops and (re-)starts the event watcher without touching the timeout. 801This call is very similar to the perl C<stat> built-in: It stats (using
802C<lstat>) the path specified in the watcher and sets perls stat cache (as
803well as EV's idea of the current stat values) to the values found.
190 804
191=item $w->del 805In scalar context, a boolean is return indicating success or failure of
806the stat. In list context, the same 13-value list as with stat is returned
807(except that the blksize and blocks fields are not reliable).
192 808
193=item $w->stop 809In the case of an error, errno is set to C<ENOENT> (regardless of the
810actual error value) and the C<nlink> value is forced to zero (if the stat
811was successful then nlink is guaranteed to be non-zero).
194 812
195Stop the event watcher if it was started. 813See also the next two entries for more info.
196 814
197=item $current_callback = $w->cb 815=item ... = $w->attr
198 816
199=item $old_callback = $w->cb ($new_callback) 817Just like C<< $w->stat >>, but without the initial stat'ing: this returns
818the values most recently detected by EV. See the next entry for more info.
200 819
820=item ... = $w->prev
821
822Just like C<< $w->stat >>, but without the initial stat'ing: this returns
823the previous set of values, before the change.
824
825That is, when the watcher callback is invoked, C<< $w->prev >> will be set
826to the values found I<before> a change was detected, while C<< $w->attr >>
827returns the values found leading to the change detection. The difference (if any)
828between C<prev> and C<attr> is what triggered the callback.
829
830If you did something to the filesystem object and do not want to trigger
831yet another change, you can call C<stat> to update EV's idea of what the
832current attributes are.
833
834=item $w->set ($path, $interval)
835
836Reconfigures the watcher, see the constructor above for details. Can be
837called at any time.
838
839=item $current_path = $w->path
840
841=item $old_path = $w->path ($new_path)
842
201Return the previously set callback and optionally set a new one. 843Returns the previously set path and optionally set a new one.
202 844
203=item $current_fh = $w->fh 845=item $current_interval = $w->interval
204 846
205=item $old_fh = $w->fh ($new_fh) 847=item $old_interval = $w->interval ($new_interval)
206 848
207Returns the previously set filehandle and optionally set a new one.
208
209=item $current_eventmask = $w->events
210
211=item $old_eventmask = $w->events ($new_eventmask)
212
213Returns the previously set event mask and optionally set a new one. 849Returns the previously set interval and optionally set a new one. Can be
850used to query the actual interval used.
214 851
215=item $w->timeout ($after, $repeat)
216
217Resets the timeout (see C<EV::timer> for details).
218
219=item $w->timeout_abs ($at, $interval)
220
221Resets the timeout (see C<EV::timer_abs> for details).
222
223=item $w->priority_set ($priority)
224
225Set the priority of the watcher to C<$priority> (0 <= $priority < $EV::NPRI).
226
227=back 852=back
228 853
229=head1 BUGS
230 854
231Lots. Libevent itself isn't well tested and rather buggy, and this module 855=head3 IDLE WATCHERS - when you've got nothing better to do...
232is quite new at the moment.
233 856
234Please note that the epoll method is not, in general, reliable in programs 857=over 4
235that use fork (even if no libveent calls are being made in the forked
236process). If your program behaves erratically, try setting the environment
237variable C<EVENT_NOEPOLL> first when running the program.
238 858
239In general, if you fork, then you can only use the EV module in one of the 859=item $w = EV::idle $callback
240children. 860
861=item $w = EV::idle_ns $callback
862
863=item $w = $loop->idle ($callback)
864
865=item $w = $loop->idle_ns ($callback)
866
867Call the callback when there are no other pending watchers of the same or
868higher priority (excluding check, prepare and other idle watchers of the
869same or lower priority, of course). They are called idle watchers because
870when the watcher is the highest priority pending event in the process, the
871process is considered to be idle at that priority.
872
873If you want a watcher that is only ever called when I<no> other events are
874outstanding you have to set the priority to C<EV::MINPRI>.
875
876The process will not block as long as any idle watchers are active, and
877they will be called repeatedly until stopped.
878
879For example, if you have idle watchers at priority C<0> and C<1>, and
880an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
881and the I/O watcher will always run when ready. Only when the idle watcher
882at priority C<1> is stopped and the I/O watcher at priority C<0> is not
883pending with the C<0>-priority idle watcher be invoked.
884
885The C<idle_ns> variant doesn't start (activate) the newly created watcher.
886
887=back
888
889
890=head3 PREPARE WATCHERS - customise your event loop!
891
892=over 4
893
894=item $w = EV::prepare $callback
895
896=item $w = EV::prepare_ns $callback
897
898=item $w = $loop->prepare ($callback)
899
900=item $w = $loop->prepare_ns ($callback)
901
902Call the callback just before the process would block. You can still
903create/modify any watchers at this point.
904
905See the EV::check watcher, below, for explanations and an example.
906
907The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
908
909=back
910
911
912=head3 CHECK WATCHERS - customise your event loop even more!
913
914=over 4
915
916=item $w = EV::check $callback
917
918=item $w = EV::check_ns $callback
919
920=item $w = $loop->check ($callback)
921
922=item $w = $loop->check_ns ($callback)
923
924Call the callback just after the process wakes up again (after it has
925gathered events), but before any other callbacks have been invoked.
926
927This is used to integrate other event-based software into the EV
928mainloop: You register a prepare callback and in there, you create io and
929timer watchers as required by the other software. Here is a real-world
930example of integrating Net::SNMP (with some details left out):
931
932 our @snmp_watcher;
933
934 our $snmp_prepare = EV::prepare sub {
935 # do nothing unless active
936 $dispatcher->{_event_queue_h}
937 or return;
938
939 # make the dispatcher handle any outstanding stuff
940 ... not shown
941
942 # create an I/O watcher for each and every socket
943 @snmp_watcher = (
944 (map { EV::io $_, EV::READ, sub { } }
945 keys %{ $dispatcher->{_descriptors} }),
946
947 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
948 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
949 0, sub { },
950 );
951 };
952
953The callbacks are irrelevant (and are not even being called), the
954only purpose of those watchers is to wake up the process as soon as
955one of those events occurs (socket readable, or timer timed out). The
956corresponding EV::check watcher will then clean up:
957
958 our $snmp_check = EV::check sub {
959 # destroy all watchers
960 @snmp_watcher = ();
961
962 # make the dispatcher handle any new stuff
963 ... not shown
964 };
965
966The callbacks of the created watchers will not be called as the watchers
967are destroyed before this can happen (remember EV::check gets called
968first).
969
970The C<check_ns> variant doesn't start (activate) the newly created watcher.
971
972=back
973
974
975=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
976
977Fork watchers are called when a C<fork ()> was detected. The invocation
978is done before the event loop blocks next and before C<check> watchers
979are being called, and only in the child after the fork.
980
981=over 4
982
983=item $w = EV::fork $callback
984
985=item $w = EV::fork_ns $callback
986
987=item $w = $loop->fork ($callback)
988
989=item $w = $loop->fork_ns ($callback)
990
991Call the callback before the event loop is resumed in the child process
992after a fork.
993
994The C<fork_ns> variant doesn't start (activate) the newly created watcher.
995
996=back
997
998
999=head3 EMBED WATCHERS - when one backend isn't enough...
1000
1001This is a rather advanced watcher type that lets you embed one event loop
1002into another (currently only IO events are supported in the embedded
1003loop, other types of watchers might be handled in a delayed or incorrect
1004fashion and must not be used).
1005
1006See the libev documentation at
1007L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
1008(locally installed as F<EV::libev>) for more details.
1009
1010In short, this watcher is most useful on BSD systems without working
1011kqueue to still be able to handle a large number of sockets:
1012
1013 my $socket_loop;
1014
1015 # check wether we use SELECT or POLL _and_ KQUEUE is supported
1016 if (
1017 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
1018 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
1019 ) {
1020 # use kqueue for sockets
1021 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
1022 }
1023
1024 # use the default loop otherwise
1025 $socket_loop ||= EV::default_loop;
1026
1027=over 4
1028
1029=item $w = EV::embed $otherloop[, $callback]
1030
1031=item $w = EV::embed_ns $otherloop[, $callback]
1032
1033=item $w = $loop->embed ($otherloop[, $callback])
1034
1035=item $w = $loop->embed_ns ($otherloop[, $callback])
1036
1037Call the callback when the embedded event loop (C<$otherloop>) has any
1038I/O activity. The C<$callback> is optional: if it is missing, then the
1039embedded event loop will be managed automatically (which is recommended),
1040otherwise you have to invoke C<sweep> yourself.
1041
1042The C<embed_ns> variant doesn't start (activate) the newly created watcher.
1043
1044=back
1045
1046=head3 ASYNC WATCHERS - how to wake up another event loop
1047
1048Async watchers are provided by EV, but have little use in perl directly,
1049as perl neither supports threads running in parallel nor direct access to
1050signal handlers or other contexts where they could be of value.
1051
1052It is, however, possible to use them from the XS level.
1053
1054Please see the libev documentation for further details.
1055
1056=over 4
1057
1058=item $w = EV::async $callback
1059
1060=item $w = EV::async_ns $callback
1061
1062=item $w->send
1063
1064=item $bool = $w->async_pending
1065
1066=back
1067
1068
1069=head1 PERL SIGNALS
1070
1071While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
1072with EV is as the same as any other C library: Perl-signals will only be
1073handled when Perl runs, which means your signal handler might be invoked
1074only the next time an event callback is invoked.
1075
1076The solution is to use EV signal watchers (see C<EV::signal>), which will
1077ensure proper operations with regards to other event watchers.
1078
1079If you cannot do this for whatever reason, you can also force a watcher
1080to be called on every event loop iteration by installing a C<EV::check>
1081watcher:
1082
1083 my $async_check = EV::check sub { };
1084
1085This ensures that perl gets into control for a short time to handle any
1086pending signals, and also ensures (slightly) slower overall operation.
1087
1088=head1 ITHREADS
1089
1090Ithreads are not supported by this module in any way. Perl pseudo-threads
1091is evil stuff and must die. Real threads as provided by Coro are fully
1092supported (and enhanced support is available via L<Coro::EV>).
1093
1094=head1 FORK
1095
1096Most of the "improved" event delivering mechanisms of modern operating
1097systems have quite a few problems with fork(2) (to put it bluntly: it is
1098not supported and usually destructive). Libev makes it possible to work
1099around this by having a function that recreates the kernel state after
1100fork in the child.
1101
1102On non-win32 platforms, this module requires the pthread_atfork
1103functionality to do this automatically for you. This function is quite
1104buggy on most BSDs, though, so YMMV. The overhead for this is quite
1105negligible, because everything the function currently does is set a flag
1106that is checked only when the event loop gets used the next time, so when
1107you do fork but not use EV, the overhead is minimal.
1108
1109On win32, there is no notion of fork so all this doesn't apply, of course.
241 1110
242=cut 1111=cut
243 1112
244our $DIED = sub { 1113our $DIED = sub {
245 warn "EV: error in callback (ignoring): $@"; 1114 warn "EV: error in callback (ignoring): $@";
246}; 1115};
247 1116
248our $NPRI = 4; 1117default_loop
249our $BASE = init; 1118 or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
250priority_init $NPRI;
251
252push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
253 1119
2541; 11201;
255 1121
256=head1 SEE ALSO 1122=head1 SEE ALSO
257 1123
258 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 1124L<EV::ADNS> (asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as
259 L<EV::AnyEvent>. 1125event loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient
1126coroutines with EV), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
1127event-loop agnostic and portable event driven programming.
260 1128
261=head1 AUTHOR 1129=head1 AUTHOR
262 1130
263 Marc Lehmann <schmorp@schmorp.de> 1131 Marc Lehmann <schmorp@schmorp.de>
264 http://home.schmorp.de/ 1132 http://home.schmorp.de/
265 1133
266=cut 1134=cut
267 1135

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