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1NAME 1NAME
2 EV - perl interface to libevent, monkey.org/~provos/libevent/ 2 EV - perl interface to libev, a high performance full-featured event
3 loop
3 4
4SYNOPSIS 5SYNOPSIS
5 use EV; 6 use EV;
6 7
7 # TIMER 8 # TIMERS
8 9
9 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
10 warn "is called after 2s"; 11 warn "is called after 2s";
11 }; 12 };
12 13
13 my $w = EV::timer 2, 1, sub { 14 my $w = EV::timer 2, 2, sub {
14 warn "is called roughly every 2s (repeat = 1)"; 15 warn "is called roughly every 2s (repeat = 2)";
15 }; 16 };
16 17
17 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
18 19
19 # IO
20
21 my $w = EV::timer_abs 0, 60, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
22 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
23 }; 22 };
24 23
24 # IO
25
25 my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
26 my ($w, $events) = @_; # all callbacks get the watcher object and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
27 if ($events & EV::TIMEOUT) {
28 warn "nothign received on stdin for 10 seconds, retrying";
29 } else {
30 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
31 }
32 }; 29 };
33 $w->timeout (10); 30
31 # SIGNALS
32
33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n";
35 };
36
37 # CHILD/PID STATUS CHANGES
34 38
39 my $w = EV::child 666, sub {
40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
42 };
43
35 # MAINLOOP 44 # MAINLOOP
36 EV::dispatch; # loop as long as watchers are active 45 EV::loop; # loop until EV::unloop is called or all watchers stop
37 EV::loop; # the same thing 46 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
38 EV::loop EV::LOOP_ONCE; 47 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
39 EV::loop EV::LOOP_ONSHOT;
40 48
41DESCRIPTION 49DESCRIPTION
42 This module provides an interface to libevent 50 This module provides an interface to libev
43 (<http://monkey.org/~provos/libevent/>). You probably should acquaint 51 (<http://software.schmorp.de/pkg/libev.html>).
44 yourself with its documentation and source code to be able to use this
45 module fully.
46
47 Please note thta this module disables the libevent EPOLL method by
48 default, see BUGS, below, if you need to enable it.
49 52
50BASIC INTERFACE 53BASIC INTERFACE
51 $EV::NPRI
52 How many priority levels are available.
53
54 $EV::DIED 54 $EV::DIED
55 Must contain a reference to a function that is called when a 55 Must contain a reference to a function that is called when a
56 callback throws an exception (with $@ containing thr error). The 56 callback throws an exception (with $@ containing thr error). The
57 default prints an informative message and continues. 57 default prints an informative message and continues.
58 58
59 If this callback throws an exception it will be silently ignored. 59 If this callback throws an exception it will be silently ignored.
60 60
61 $time = EV::time
62 Returns the current time in (fractional) seconds since the epoch.
63
61 $time = EV::now 64 $time = EV::now
62 Returns the time in (fractional) seconds since the epoch. 65 Returns the time the last event loop iteration has been started.
66 This is the time that (relative) timers are based on, and refering
67 to it is usually faster then calling EV::time.
63 68
64 $version = EV::version
65 $method = EV::method 69 $method = EV::method
66 Return version string and event polling method used. 70 Returns an integer describing the backend used by libev
71 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
67 72
68 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 73 EV::loop [$flags]
69 EV::loopexit $after 74 Begin checking for events and calling callbacks. It returns when a
70 Exit any active loop or dispatch after $after seconds or immediately 75 callback calls EV::unloop.
71 if $after is missing or zero.
72 76
73 EV::dispatch 77 The $flags argument can be one of the following:
74 Same as "EV::loop 0".
75 78
76 EV::event $callback 79 0 as above
77 Creates a new event watcher waiting for nothing, calling the given 80 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
78 callback. 81 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
79 82
83 EV::unloop [$how]
84 When called with no arguments or an argument of EV::UNLOOP_ONE,
85 makes the innermost call to EV::loop return.
86
87 When called with an argument of EV::UNLOOP_ALL, all calls to
88 EV::loop will return as fast as possible.
89
90 WATCHER
91 A watcher is an object that gets created to record your interest in some
92 event. For instance, if you want to wait for STDIN to become readable,
93 you would create an EV::io watcher for that:
94
95 my $watcher = EV::io *STDIN, EV::READ, sub {
96 my ($watcher, $revents) = @_;
97 warn "yeah, STDIN should not be readable without blocking!\n"
98 };
99
100 All watchers can be active (waiting for events) or inactive (paused).
101 Only active watchers will have their callbacks invoked. All callbacks
102 will be called with at least two arguments: the watcher and a bitmask of
103 received events.
104
105 Each watcher type has its associated bit in revents, so you can use the
106 same callback for multiple watchers. The event mask is named after the
107 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
108 EV::periodic sets EV::PERIODIC and so on, with the exception of IO
109 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
110 (which uses EV::TIMEOUT).
111
112 In the rare case where one wants to create a watcher but not start it at
113 the same time, each constructor has a variant with a trailing "_ns" in
114 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
115
116 Please note that a watcher will automatically be stopped when the
117 watcher object is destroyed, so you *need* to keep the watcher objects
118 returned by the constructors.
119
120 Also, all methods changing some aspect of a watcher (->set, ->priority,
121 ->fh and so on) automatically stop and start it again if it is active,
122 which means pending events get lost.
123
124 WATCHER TYPES
125 Now lets move to the existing watcher types and asociated methods.
126
127 The following methods are available for all watchers. Then followes a
128 description of each watcher constructor (EV::io, EV::timer,
129 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
130 EV::check), followed by any type-specific methods (if any).
131
132 $w->start
133 Starts a watcher if it isn't active already. Does nothing to an
134 already active watcher. By default, all watchers start out in the
135 active state (see the description of the "_ns" variants if you need
136 stopped watchers).
137
138 $w->stop
139 Stop a watcher if it is active. Also clear any pending events
140 (events that have been received but that didn't yet result in a
141 callback invocation), regardless of wether the watcher was active or
142 not.
143
144 $bool = $w->is_active
145 Returns true if the watcher is active, false otherwise.
146
147 $current_data = $w->data
148 $old_data = $w->data ($new_data)
149 Queries a freely usable data scalar on the watcher and optionally
150 changes it. This is a way to associate custom data with a watcher:
151
152 my $w = EV::timer 60, 0, sub {
153 warn $_[0]->data;
154 };
155 $w->data ("print me!");
156
157 $current_cb = $w->cb
158 $old_cb = $w->cb ($new_cb)
159 Queries the callback on the watcher and optionally changes it. You
160 can do this at any time without the watcher restarting.
161
162 $current_priority = $w->priority
163 $old_priority = $w->priority ($new_priority)
164 Queries the priority on the watcher and optionally changes it.
165 Pending watchers with higher priority will be invoked first. The
166 valid range of priorities lies between EV::MAXPRI (default 2) and
167 EV::MINPRI (default -2). If the priority is outside this range it
168 will automatically be normalised to the nearest valid priority.
169
170 The default priority of any newly-created weatcher is 0.
171
172 $w->trigger ($revents)
173 Call the callback *now* with the given event mask.
174
80 my $w = EV::io $fileno_or_fh, $eventmask, $callback 175 $w = EV::io $fileno_or_fh, $eventmask, $callback
81 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 176 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
82 As long as the returned watcher object is alive, call the $callback 177 As long as the returned watcher object is alive, call the $callback
83 when the events specified in $eventmask happen. Initially, the 178 when the events specified in $eventmask.
84 timeout is disabled.
85 179
86 Youc an additionall set a timeout to occur on the watcher, but note
87 that this timeout will not be reset when you get an I/O event in the
88 EV::PERSIST case, and reaching a timeout will always stop the
89 watcher even in the EV::PERSIST case.
90
91 If you want a timeout to occur only after a specific time of
92 inactivity, set a repeating timeout and do NOT use EV::PERSIST.
93
94 Eventmask can be one or more of these constants ORed together: 180 The $eventmask can be one or more of these constants ORed together:
95 181
96 EV::READ wait until read() wouldn't block anymore 182 EV::READ wait until read() wouldn't block anymore
97 EV::WRITE wait until write() wouldn't block anymore 183 EV::WRITE wait until write() wouldn't block anymore
98 EV::PERSIST stay active after a (non-timeout) event occured
99 184
100 The "io_ns" variant doesn't add/start the newly created watcher. 185 The "io_ns" variant doesn't start (activate) the newly created
101
102 my $w = EV::timer $after, $repeat, $callback
103 my $w = EV::timer_ns $after, $repeat, $callback
104 Calls the callback after $after seconds. If $repeat is true, the
105 timer will be restarted after the callback returns. This means that
106 the callback would be called roughly every $after seconds, prolonged
107 by the time the callback takes.
108
109 The "timer_ns" variant doesn't add/start the newly created watcher.
110
111 my $w = EV::timer_abs $at, $interval, $callback
112 my $w = EV::timer_abs_ns $at, $interval, $callback
113 Similar to EV::timer, but the time is given as an absolute point in
114 time ($at), plus an optional $interval.
115
116 If the $interval is zero, then the callback will be called at the
117 time $at if that is in the future, or as soon as possible if its in
118 the past. It will not automatically repeat.
119
120 If the $interval is nonzero, then the watcher will always be
121 scheduled to time out at the next "$at + integer * $interval" time.
122
123 This can be used to schedule a callback to run at very regular
124 intervals, as long as the processing time is less then the interval
125 (otherwise obviously events will be skipped).
126
127 Another way to think about it (for the mathematically inclined) is
128 that "timer_abs" will try to tun the callback at the next possible
129 time where "$time = $at (mod $interval)", regardless of any time
130 jumps.
131
132 The "timer_abs_ns" variant doesn't add/start the newly created
133 watcher. 186 watcher.
134 187
135 my $w = EV::signal $signum, $callback 188 $w->set ($fileno_or_fh, $eventmask)
136 my $w = EV::signal_ns $signum, $callback 189 Reconfigures the watcher, see the constructor above for details. Can
137 Call the callback when signal $signum is received. 190 be called at any time.
138
139 The "signal_ns" variant doesn't add/start the newly created watcher.
140
141THE EV::Event CLASS
142 All EV functions creating an event watcher (designated by "my $w ="
143 above) support the following methods on the returned watcher object:
144
145 $w->add ($timeout)
146 Stops and (re-)starts the event watcher, setting the optional
147 timeout to the given value, or clearing the timeout if none is
148 given.
149
150 $w->start
151 Stops and (re-)starts the event watcher without touching the
152 timeout.
153
154 $w->del
155 $w->stop
156 Stop the event watcher if it was started.
157
158 $current_callback = $w->cb
159 $old_callback = $w->cb ($new_callback)
160 Return the previously set callback and optionally set a new one.
161 191
162 $current_fh = $w->fh 192 $current_fh = $w->fh
163 $old_fh = $w->fh ($new_fh) 193 $old_fh = $w->fh ($new_fh)
164 Returns the previously set filehandle and optionally set a new one. 194 Returns the previously set filehandle and optionally set a new one.
165 195
166 $current_eventmask = $w->events 196 $current_eventmask = $w->events
167 $old_eventmask = $w->events ($new_eventmask) 197 $old_eventmask = $w->events ($new_eventmask)
168 Returns the previously set event mask and optionally set a new one. 198 Returns the previously set event mask and optionally set a new one.
169 199
200 $w = EV::timer $after, $repeat, $callback
201 $w = EV::timer_ns $after, $repeat, $callback
202 Calls the callback after $after seconds. If $repeat is non-zero, the
203 timer will be restarted (with the $repeat value as $after) after the
204 callback returns.
205
206 This means that the callback would be called roughly after $after
207 seconds, and then every $repeat seconds. The timer does his best not
208 to drift, but it will not invoke the timer more often then once per
209 event loop iteration, and might drift in other cases. If that isn't
210 acceptable, look at EV::periodic, which can provide long-term stable
211 timers.
212
213 The timer is based on a monotonic clock, that is, if somebody is
214 sitting in front of the machine while the timer is running and
215 changes the system clock, the timer will nevertheless run (roughly)
216 the same time.
217
218 The "timer_ns" variant doesn't start (activate) the newly created
219 watcher.
220
170 $w->timeout ($after, $repeat) 221 $w->set ($after, $repeat)
171 Resets the timeout (see "EV::timer" for details). 222 Reconfigures the watcher, see the constructor above for details. Can
223 be at any time.
172 224
173 $w->timeout_abs ($at, $interval) 225 $w->again
174 Resets the timeout (see "EV::timer_abs" for details). 226 Similar to the "start" method, but has special semantics for
227 repeating timers:
175 228
176 $w->priority_set ($priority) 229 If the timer is active and non-repeating, it will be stopped.
177 Set the priority of the watcher to $priority (0 <= $priority <
178 $EV::NPRI).
179 230
180BUGS 231 If the timer is active and repeating, reset the timeout to occur
181 Lots. Libevent itself isn't well tested and rather buggy, and this 232 $repeat seconds after now.
182 module is quite new at the moment.
183 233
184 Please note that the epoll method is not, in general, reliable in 234 If the timer is inactive and repeating, start it using the repeat
185 programs that use fork (even if no libveent calls are being made in the 235 value.
186 forked process). If your program behaves erratically, try setting the
187 environment variable "EVENT_NOEPOLL" first when running the program.
188 236
189 In general, if you fork, then you can only use the EV module in one of 237 Otherwise do nothing.
190 the children. 238
239 This behaviour is useful when you have a timeout for some IO
240 operation. You create a timer object with the same value for $after
241 and $repeat, and then, in the read/write watcher, run the "again"
242 method on the timeout.
243
244 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
245 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
246 Similar to EV::timer, but is not based on relative timeouts but on
247 absolute times. Apart from creating "simple" timers that trigger
248 "at" the specified time, it can also be used for non-drifting
249 absolute timers and more complex, cron-like, setups that are not
250 adversely affected by time jumps (i.e. when the system clock is
251 changed by explicit date -s or other means such as ntpd). It is also
252 the most complex watcher type in EV.
253
254 It has three distinct "modes":
255
256 * absolute timer ($interval = $reschedule_cb = 0)
257 This time simply fires at the wallclock time $at and doesn't
258 repeat. It will not adjust when a time jump occurs, that is, if
259 it is to be run at January 1st 2011 then it will run when the
260 system time reaches or surpasses this time.
261
262 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
263 In this mode the watcher will always be scheduled to time out at
264 the next "$at + N * $interval" time (for some integer N) and
265 then repeat, regardless of any time jumps.
266
267 This can be used to create timers that do not drift with respect
268 to system time:
269
270 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
271
272 That doesn't mean there will always be 3600 seconds in between
273 triggers, but only that the the clalback will be called when the
274 system time shows a full hour (UTC).
275
276 Another way to think about it (for the mathematically inclined)
277 is that EV::periodic will try to run the callback in this mode
278 at the next possible time where "$time = $at (mod $interval)",
279 regardless of any time jumps.
280
281 * manual reschedule mode ($reschedule_cb = coderef)
282 In this mode $interval and $at are both being ignored. Instead,
283 each time the periodic watcher gets scheduled, the reschedule
284 callback ($reschedule_cb) will be called with the watcher as
285 first, and the current time as second argument.
286
287 *This callback MUST NOT stop or destroy this or any other
288 periodic watcher, ever*. If you need to stop it, return 1e30 and
289 stop it afterwards.
290
291 It must return the next time to trigger, based on the passed
292 time value (that is, the lowest time value larger than to the
293 second argument). It will usually be called just before the
294 callback will be triggered, but might be called at other times,
295 too.
296
297 This can be used to create very complex timers, such as a timer
298 that triggers on each midnight, local time (actually 24 hours
299 after the last midnight, to keep the example simple. If you know
300 a way to do it correctly in about the same space (without
301 requiring elaborate modules), drop me a note :):
302
303 my $daily = EV::periodic 0, 0, sub {
304 my ($w, $now) = @_;
305
306 use Time::Local ();
307 my (undef, undef, undef, $d, $m, $y) = localtime $now;
308 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
309 }, sub {
310 print "it's midnight or likely shortly after, now\n";
311 };
312
313 The "periodic_ns" variant doesn't start (activate) the newly created
314 watcher.
315
316 $w->set ($at, $interval, $reschedule_cb)
317 Reconfigures the watcher, see the constructor above for details. Can
318 be at any time.
319
320 $w->again
321 Simply stops and starts the watcher again.
322
323 $w = EV::signal $signal, $callback
324 $w = EV::signal_ns $signal, $callback
325 Call the callback when $signal is received (the signal can be
326 specified by number or by name, just as with kill or %SIG).
327
328 EV will grab the signal for the process (the kernel only allows one
329 component to receive a signal at a time) when you start a signal
330 watcher, and removes it again when you stop it. Perl does the same
331 when you add/remove callbacks to %SIG, so watch out.
332
333 You can have as many signal watchers per signal as you want.
334
335 The "signal_ns" variant doesn't start (activate) the newly created
336 watcher.
337
338 $w->set ($signal)
339 Reconfigures the watcher, see the constructor above for details. Can
340 be at any time.
341
342 $current_signum = $w->signal
343 $old_signum = $w->signal ($new_signal)
344 Returns the previously set signal (always as a number not name) and
345 optionally set a new one.
346
347 $w = EV::child $pid, $callback
348 $w = EV::child_ns $pid, $callback
349 Call the callback when a status change for pid $pid (or any pid if
350 $pid is 0) has been received. More precisely: when the process
351 receives a SIGCHLD, EV will fetch the outstanding exit/wait status
352 for all changed/zombie children and call the callback.
353
354 You can access both status and pid by using the "rstatus" and "rpid"
355 methods on the watcher object.
356
357 You can have as many pid watchers per pid as you want.
358
359 The "child_ns" variant doesn't start (activate) the newly created
360 watcher.
361
362 $w->set ($pid)
363 Reconfigures the watcher, see the constructor above for details. Can
364 be at any time.
365
366 $current_pid = $w->pid
367 $old_pid = $w->pid ($new_pid)
368 Returns the previously set process id and optionally set a new one.
369
370 $exit_status = $w->rstatus
371 Return the exit/wait status (as returned by waitpid, see the waitpid
372 entry in perlfunc).
373
374 $pid = $w->rpid
375 Return the pid of the awaited child (useful when you have installed
376 a watcher for all pids).
377
378 $w = EV::idle $callback
379 $w = EV::idle_ns $callback
380 Call the callback when there are no pending io, timer/periodic,
381 signal or child events, i.e. when the process is idle.
382
383 The process will not block as long as any idle watchers are active,
384 and they will be called repeatedly until stopped.
385
386 The "idle_ns" variant doesn't start (activate) the newly created
387 watcher.
388
389 $w = EV::prepare $callback
390 $w = EV::prepare_ns $callback
391 Call the callback just before the process would block. You can still
392 create/modify any watchers at this point.
393
394 See the EV::check watcher, below, for explanations and an example.
395
396 The "prepare_ns" variant doesn't start (activate) the newly created
397 watcher.
398
399 $w = EV::check $callback
400 $w = EV::check_ns $callback
401 Call the callback just after the process wakes up again (after it
402 has gathered events), but before any other callbacks have been
403 invoked.
404
405 This is used to integrate other event-based software into the EV
406 mainloop: You register a prepare callback and in there, you create
407 io and timer watchers as required by the other software. Here is a
408 real-world example of integrating Net::SNMP (with some details left
409 out):
410
411 our @snmp_watcher;
412
413 our $snmp_prepare = EV::prepare sub {
414 # do nothing unless active
415 $dispatcher->{_event_queue_h}
416 or return;
417
418 # make the dispatcher handle any outstanding stuff
419
420 # create an IO watcher for each and every socket
421 @snmp_watcher = (
422 (map { EV::io $_, EV::READ, sub { } }
423 keys %{ $dispatcher->{_descriptors} }),
424 );
425
426 # if there are any timeouts, also create a timer
427 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
428 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
429 };
430
431 The callbacks are irrelevant, the only purpose of those watchers is
432 to wake up the process as soon as one of those events occurs (socket
433 readable, or timer timed out). The corresponding EV::check watcher
434 will then clean up:
435
436 our $snmp_check = EV::check sub {
437 # destroy all watchers
438 @snmp_watcher = ();
439
440 # make the dispatcher handle any new stuff
441 };
442
443 The callbacks of the created watchers will not be called as the
444 watchers are destroyed before this cna happen (remember EV::check
445 gets called first).
446
447 The "check_ns" variant doesn't start (activate) the newly created
448 watcher.
449
450THREADS
451 Threads are not supported by this in any way. Perl pseudo-threads is
452 evil stuff and must die.
191 453
192SEE ALSO 454SEE ALSO
193 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 455 L<EV::DNS>.
194 L<EV::AnyEvent>.
195 456
196AUTHOR 457AUTHOR
197 Marc Lehmann <schmorp@schmorp.de> 458 Marc Lehmann <schmorp@schmorp.de>
198 http://home.schmorp.de/ 459 http://home.schmorp.de/
199 460

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