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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;
7
8 # TIMERS
9
10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s";
12 };
13
14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 2)";
16 };
17
18 undef $w; # destroy event watcher again
19
20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly";
22 };
23
24 # IO
25
26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>;
29 };
30
31 # SIGNALS
32
33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n";
35 };
36
37 # CHILD/PID STATUS CHANGES
6 38
7 # TIMER 39 my $w = EV::child 666, 0, sub {
40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
42 };
8 43
9 my $w = EV::timer 2, 0, sub { 44 # STAT CHANGES
10 warn "is called after 2s"; 45 my $w = EV::stat "/etc/passwd", 10, sub {
11 };
12
13 my $w = EV::timer 2, 1, sub {
14 warn "is called roughly every 2s (repeat = 1)";
15 };
16
17 undef $w; # destroy event watcher again
18
19 my $w = EV::timer_abs 0, 60, sub {
20 warn "is called every minute, on the minute, exactly";
21 };
22
23 # IO
24
25 my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub {
26 my ($w, $events) = @_; # all callbacks get the watcher object and event mask
27 if ($events & EV::TIMEOUT) {
28 warn "nothing received on stdin for 10 seconds, retrying";
29 } else {
30 warn "stdin is readable, you entered: ", <STDIN>;
31 }
32 };
33 $w->timeout (10);
34
35 my $w = EV::timed_io \*STDIN, EV::READ, 30, sub {
36 my ($w, $events) = @_; 46 my ($w, $revents) = @_;
37 if ($_[1] & EV::TIMEOUT) { 47 warn $w->path, " has changed somehow.\n";
38 warn "nothing entered within 30 seconds, bye bye.\n";
39 $w->stop;
40 } else {
41 my $line = <STDIN>;
42 warn "you entered something, you again have 30 seconds.\n";
43 }
44 }; 48 };
45 49
46 # SIGNALS
47
48 my $w = EV::signal 'QUIT', sub {
49 warn "sigquit received\n";
50 };
51
52 my $w = EV::signal 3, sub {
53 warn "sigquit received (this is GNU/Linux, right?)\n";
54 };
55
56 # MAINLOOP 50 # MAINLOOP
57 EV::dispatch; # loop as long as watchers are active 51 EV::run; # loop until EV::unloop is called or all watchers stop
58 EV::loop; # the same thing
59 EV::loop EV::LOOP_ONCE; # block until some events could be handles 52 EV::run EV::RUN_ONCE; # block until at least one event could be handled
60 EV::loop EV::LOOP_NONBLOCK; # check and handle some events, but do not wait 53 EV::run EV::RUN_NOWAIT; # try to handle same events, but do not block
54
55BEFORE YOU START USING THIS MODULE
56 If you only need timer, I/O, signal, child and idle watchers and not the
57 advanced functionality of this module, consider using AnyEvent instead,
58 specifically the simplified API described in AE.
59
60 When used with EV as backend, the AE API is as fast as the native EV
61 API, but your programs/modules will still run with many other event
62 loops.
61 63
62DESCRIPTION 64DESCRIPTION
63 This module provides an interface to libevent 65 This module provides an interface to libev
64 (<http://monkey.org/~provos/libevent/>). You probably should acquaint 66 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
65 yourself with its documentation and source code to be able to use this 67 below is comprehensive, one might also consult the documentation of
66 module fully. 68 libev itself (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
69 perldoc EV::libev) for more subtle details on watcher semantics or some
70 discussion on the available backends, or how to force a specific backend
71 with "LIBEV_FLAGS", or just about in any case because it has much more
72 detailed information.
67 73
68 Please note thta this module disables the libevent EPOLL method by 74 This module is very fast and scalable. It is actually so fast that you
69 default, see BUGS, below, if you need to enable it. 75 can use it through the AnyEvent module, stay portable to other event
76 loops (if you don't rely on any watcher types not available through it)
77 and still be faster than with any other event loop currently supported
78 in Perl.
79
80 PORTING FROM EV 3.X to 4.X
81 EV version 4 introduces a number of incompatible changes summarised
82 here. According to the depreciation strategy used by libev, there is a
83 compatibility layer in place so programs should continue to run
84 unchanged (the XS interface lacks this layer, so programs using that one
85 need to be updated).
86
87 This compatibility layer will be switched off in some future release.
88
89 All changes relevant to Perl are renames of symbols, functions and
90 methods:
91
92 EV::loop => EV::run
93 EV::LOOP_NONBLOCK => EV::RUN_NOWAIT
94 EV::LOOP_ONESHOT => EV::RUN_ONCE
95
96 EV::unloop => EV::break
97 EV::UNLOOP_CANCEL => EV::BREAK_CANCEL
98 EV::UNLOOP_ONE => EV::BREAK_ONE
99 EV::UNLOOP_ALL => EV::BREAK_ALL
100
101 EV::TIMEOUT => EV::TIMER
102
103 EV::loop_count => EV::iteration
104 EV::loop_depth => EV::depth
105 EV::loop_verify => EV::verify
106
107 The loop object methods corresponding to the functions above have been
108 similarly renamed.
109
110 MODULE EXPORTS
111 This module does not export any symbols.
112
113EVENT LOOPS
114 EV supports multiple event loops: There is a single "default event loop"
115 that can handle everything including signals and child watchers, and any
116 number of "dynamic event loops" that can use different backends (with
117 various limitations), but no child and signal watchers.
118
119 You do not have to do anything to create the default event loop: When
120 the module is loaded a suitable backend is selected on the premise of
121 selecting a working backend (which for example rules out kqueue on most
122 BSDs). Modules should, unless they have "special needs" always use the
123 default loop as this is fastest (perl-wise), best supported by other
124 modules (e.g. AnyEvent or Coro) and most portable event loop.
125
126 For specific programs you can create additional event loops dynamically.
127
128 If you want to take advantage of kqueue (which often works properly for
129 sockets only) even though the default loop doesn't enable it, you can
130 *embed* a kqueue loop into the default loop: running the default loop
131 will then also service the kqueue loop to some extent. See the example
132 in the section about embed watchers for an example on how to achieve
133 that.
134
135 $loop = new EV::Loop [$flags]
136 Create a new event loop as per the specified flags. Please refer to
137 the "ev_loop_new ()" function description in the libev documentation
138 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
139 ONS>, or locally-installed as EV::libev manpage) for more info.
140
141 The loop will automatically be destroyed when it is no longer
142 referenced by any watcher and the loop object goes out of scope.
143
144 If you are not embedding the loop, then Using "EV::FLAG_FORKCHECK"
145 is recommended, as only the default event loop is protected by this
146 module. If you *are* embedding this loop in the default loop, this
147 is not necessary, as "EV::embed" automatically does the right thing
148 on fork.
149
150 $loop->loop_fork
151 Must be called after a fork in the child, before entering or
152 continuing the event loop. An alternative is to use
153 "EV::FLAG_FORKCHECK" which calls this function automatically, at
154 some performance loss (refer to the libev documentation).
155
156 $loop->verify
157 Calls "ev_verify" to make internal consistency checks (for debugging
158 libev) and abort the program if any data structures were found to be
159 corrupted.
160
161 $loop = EV::default_loop [$flags]
162 Return the default loop (which is a singleton object). Since this
163 module already creates the default loop with default flags,
164 specifying flags here will not have any effect unless you destroy
165 the default loop first, which isn't supported. So in short: don't do
166 it, and if you break it, you get to keep the pieces.
70 167
71BASIC INTERFACE 168BASIC INTERFACE
72 $EV::NPRI
73 How many priority levels are available.
74
75 $EV::DIED 169 $EV::DIED
76 Must contain a reference to a function that is called when a 170 Must contain a reference to a function that is called when a
77 callback throws an exception (with $@ containing thr error). The 171 callback throws an exception (with $@ containing the error). The
78 default prints an informative message and continues. 172 default prints an informative message and continues.
79 173
80 If this callback throws an exception it will be silently ignored. 174 If this callback throws an exception it will be silently ignored.
81 175
176 $flags = EV::supported_backends
177 $flags = EV::recommended_backends
178 $flags = EV::embeddable_backends
179 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
180 this instance of EV, the set of recommended backends (supposed to be
181 good) for this platform and the set of embeddable backends (see
182 EMBED WATCHERS).
183
184 EV::sleep $seconds
185 Block the process for the given number of (fractional) seconds.
186
187 $time = EV::time
188 Returns the current time in (fractional) seconds since the epoch.
189
82 $time = EV::now 190 $time = EV::now
83 Returns the time in (fractional) seconds since the epoch. 191 $time = $loop->now
192 Returns the time the last event loop iteration has been started.
193 This is the time that (relative) timers are based on, and referring
194 to it is usually faster then calling EV::time.
84 195
85 $version = EV::version 196 EV::now_update
86 $method = EV::method 197 $loop->now_update
87 Return version string and event polling method used. 198 Establishes the current time by querying the kernel, updating the
199 time returned by "EV::now" in the progress. This is a costly
200 operation and is usually done automatically within "EV::loop".
88 201
89 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 202 This function is rarely useful, but when some event callback runs
90 EV::loopexit $after 203 for a very long time without entering the event loop, updating
91 Exit any active loop or dispatch after $after seconds or immediately 204 libev's idea of the current time is a good idea.
92 if $after is missing or zero.
93 205
94 EV::dispatch 206 EV::suspend
95 Same as "EV::loop 0". 207 $loop->suspend
208 EV::resume
209 $loop->resume
210 These two functions suspend and resume a loop, for use when the loop
211 is not used for a while and timeouts should not be processed.
96 212
97 EV::event $callback 213 A typical use case would be an interactive program such as a game:
98 Creates a new event watcher waiting for nothing, calling the given 214 When the user presses "^Z" to suspend the game and resumes it an
99 callback. 215 hour later it would be best to handle timeouts as if no time had
216 actually passed while the program was suspended. This can be
217 achieved by calling "suspend" in your "SIGTSTP" handler, sending
218 yourself a "SIGSTOP" and calling "resume" directly afterwards to
219 resume timer processing.
100 220
221 Effectively, all "timer" watchers will be delayed by the time spend
222 between "suspend" and "resume", and all "periodic" watchers will be
223 rescheduled (that is, they will lose any events that would have
224 occured while suspended).
225
226 After calling "suspend" you must not call *any* function on the
227 given loop other than "resume", and you must not call "resume"
228 without a previous call to "suspend".
229
230 Calling "suspend"/"resume" has the side effect of updating the event
231 loop time (see "now_update").
232
233 $backend = EV::backend
234 $backend = $loop->backend
235 Returns an integer describing the backend used by libev
236 (EV::BACKEND_SELECT or EV::BACKEND_EPOLL).
237
238 $active = EV::run [$flags]
239 $active = $loop->run ([$flags])
240 Begin checking for events and calling callbacks. It returns when a
241 callback calls EV::unloop or the flasg are nonzero (in which case
242 the return value is true) or when there are no active watchers which
243 reference the loop (keepalive is true), in which case the return
244 value will be false. The returnv alue can generally be interpreted
245 as "if true, there is more work left to do".
246
247 The $flags argument can be one of the following:
248
249 0 as above
250 EV::RUN_ONCE block at most once (wait, but do not loop)
251 EV::RUN_NOWAIT do not block at all (fetch/handle events but do not wait)
252
253 EV::break [$how]
254 $loop->break ([$how])
255 When called with no arguments or an argument of EV::BREAK_ONE, makes
256 the innermost call to EV::loop return.
257
258 When called with an argument of EV::BREAK_ALL, all calls to EV::loop
259 will return as fast as possible.
260
261 When called with an argument of EV::BREAK_CANCEL, any pending break
262 will be cancelled.
263
264 $count = EV::iteration
265 $count = $loop->iteration
266 Return the number of times the event loop has polled for new events.
267 Sometimes useful as a generation counter.
268
269 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
270 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
271 This function rolls together an I/O and a timer watcher for a single
272 one-shot event without the need for managing a watcher object.
273
274 If $fh_or_undef is a filehandle or file descriptor, then $events
275 must be a bitset containing either "EV::READ", "EV::WRITE" or
276 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
277 wait for. If you do not want to wait for some I/O event, specify
278 "undef" for $fh_or_undef and 0 for $events).
279
280 If timeout is "undef" or negative, then there will be no timeout.
281 Otherwise a EV::timer with this value will be started.
282
283 When an error occurs or either the timeout or I/O watcher triggers,
284 then the callback will be called with the received event set (in
285 general you can expect it to be a combination of "EV::ERROR",
286 "EV::READ", "EV::WRITE" and "EV::TIMER").
287
288 EV::once doesn't return anything: the watchers stay active till
289 either of them triggers, then they will be stopped and freed, and
290 the callback invoked.
291
292 EV::feed_fd_event $fd, $revents
293 $loop->feed_fd_event ($fd, $revents)
294 Feed an event on a file descriptor into EV. EV will react to this
295 call as if the readyness notifications specified by $revents (a
296 combination of "EV::READ" and "EV::WRITE") happened on the file
297 descriptor $fd.
298
299 EV::feed_signal_event $signal
300 Feed a signal event into the default loop. EV will react to this
301 call as if the signal specified by $signal had occured.
302
303 EV::feed_signal $signal
304 Feed a signal event into EV - unlike "EV::feed_signal_event", this
305 works regardless of which loop has registered the signal, and is
306 mainly useful fro custom signal implementations.
307
308 EV::set_io_collect_interval $time
309 $loop->set_io_collect_interval ($time)
310 EV::set_timeout_collect_interval $time
311 $loop->set_timeout_collect_interval ($time)
312 These advanced functions set the minimum block interval when polling
313 for I/O events and the minimum wait interval for timer events. See
314 the libev documentation at
315 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
316 ROLLING_THE_EVENT_LOOP> (locally installed as EV::libev) for a more
317 detailed discussion.
318
319 $count = EV::pending_count
320 $count = $loop->pending_count
321 Returns the number of currently pending watchers.
322
323 EV::invoke_pending
324 $loop->invoke_pending
325 Invoke all currently pending watchers.
326
327WATCHER OBJECTS
328 A watcher is an object that gets created to record your interest in some
329 event. For instance, if you want to wait for STDIN to become readable,
330 you would create an EV::io watcher for that:
331
332 my $watcher = EV::io *STDIN, EV::READ, sub {
333 my ($watcher, $revents) = @_;
334 warn "yeah, STDIN should now be readable without blocking!\n"
335 };
336
337 All watchers can be active (waiting for events) or inactive (paused).
338 Only active watchers will have their callbacks invoked. All callbacks
339 will be called with at least two arguments: the watcher and a bitmask of
340 received events.
341
342 Each watcher type has its associated bit in revents, so you can use the
343 same callback for multiple watchers. The event mask is named after the
344 type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
345 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
346 events (which can set both EV::READ and EV::WRITE bits).
347
348 In the rare case where one wants to create a watcher but not start it at
349 the same time, each constructor has a variant with a trailing "_ns" in
350 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
351
352 Please note that a watcher will automatically be stopped when the
353 watcher object is destroyed, so you *need* to keep the watcher objects
354 returned by the constructors.
355
356 Also, all methods changing some aspect of a watcher (->set, ->priority,
357 ->fh and so on) automatically stop and start it again if it is active,
358 which means pending events get lost.
359
360 COMMON WATCHER METHODS
361 This section lists methods common to all watchers.
362
363 $w->start
364 Starts a watcher if it isn't active already. Does nothing to an
365 already active watcher. By default, all watchers start out in the
366 active state (see the description of the "_ns" variants if you need
367 stopped watchers).
368
369 $w->stop
370 Stop a watcher if it is active. Also clear any pending events
371 (events that have been received but that didn't yet result in a
372 callback invocation), regardless of whether the watcher was active
373 or not.
374
375 $bool = $w->is_active
376 Returns true if the watcher is active, false otherwise.
377
378 $current_data = $w->data
379 $old_data = $w->data ($new_data)
380 Queries a freely usable data scalar on the watcher and optionally
381 changes it. This is a way to associate custom data with a watcher:
382
383 my $w = EV::timer 60, 0, sub {
384 warn $_[0]->data;
385 };
386 $w->data ("print me!");
387
388 $current_cb = $w->cb
389 $old_cb = $w->cb ($new_cb)
390 Queries the callback on the watcher and optionally changes it. You
391 can do this at any time without the watcher restarting.
392
393 $current_priority = $w->priority
394 $old_priority = $w->priority ($new_priority)
395 Queries the priority on the watcher and optionally changes it.
396 Pending watchers with higher priority will be invoked first. The
397 valid range of priorities lies between EV::MAXPRI (default 2) and
398 EV::MINPRI (default -2). If the priority is outside this range it
399 will automatically be normalised to the nearest valid priority.
400
401 The default priority of any newly-created watcher is 0.
402
403 Note that the priority semantics have not yet been fleshed out and
404 are subject to almost certain change.
405
406 $w->invoke ($revents)
407 Call the callback *now* with the given event mask.
408
409 $w->feed_event ($revents)
410 Feed some events on this watcher into EV. EV will react to this call
411 as if the watcher had received the given $revents mask.
412
413 $revents = $w->clear_pending
414 If the watcher is pending, this function clears its pending status
415 and returns its $revents bitset (as if its callback was invoked). If
416 the watcher isn't pending it does nothing and returns 0.
417
418 $previous_state = $w->keepalive ($bool)
419 Normally, "EV::loop" will return when there are no active watchers
420 (which is a "deadlock" because no progress can be made anymore).
421 This is convenient because it allows you to start your watchers (and
422 your jobs), call "EV::loop" once and when it returns you know that
423 all your jobs are finished (or they forgot to register some watchers
424 for their task :).
425
426 Sometimes, however, this gets in your way, for example when the
427 module that calls "EV::loop" (usually the main program) is not the
428 same module as a long-living watcher (for example a DNS client
429 module written by somebody else even). Then you might want any
430 outstanding requests to be handled, but you would not want to keep
431 "EV::loop" from returning just because you happen to have this
432 long-running UDP port watcher.
433
434 In this case you can clear the keepalive status, which means that
435 even though your watcher is active, it won't keep "EV::loop" from
436 returning.
437
438 The initial value for keepalive is true (enabled), and you can
439 change it any time.
440
441 Example: Register an I/O watcher for some UDP socket but do not keep
442 the event loop from running just because of that watcher.
443
444 my $udp_socket = ...
445 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
446 $udp_watcher->keepalive (0);
447
448 $loop = $w->loop
449 Return the loop that this watcher is attached to.
450
451WATCHER TYPES
452 Each of the following subsections describes a single watcher type.
453
454 I/O WATCHERS - is this file descriptor readable or writable?
101 my $w = EV::io $fileno_or_fh, $eventmask, $callback 455 $w = EV::io $fileno_or_fh, $eventmask, $callback
102 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 456 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
457 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
458 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
103 As long as the returned watcher object is alive, call the $callback 459 As long as the returned watcher object is alive, call the $callback
104 when the events specified in $eventmask happen. Initially, the 460 when at least one of events specified in $eventmask occurs.
105 timeout is disabled.
106 461
107 You can additionall set a timeout to occur on the watcher, but note
108 that this timeout will not be reset when you get an I/O event in the
109 EV::PERSIST case, and reaching a timeout will always stop the
110 watcher even in the EV::PERSIST case.
111
112 If you want a timeout to occur only after a specific time of
113 inactivity, set a repeating timeout and do NOT use EV::PERSIST.
114
115 Eventmask can be one or more of these constants ORed together: 462 The $eventmask can be one or more of these constants ORed together:
116 463
117 EV::READ wait until read() wouldn't block anymore 464 EV::READ wait until read() wouldn't block anymore
118 EV::WRITE wait until write() wouldn't block anymore 465 EV::WRITE wait until write() wouldn't block anymore
119 EV::PERSIST stay active after a (non-timeout) event occured
120 466
121 The "io_ns" variant doesn't add/start the newly created watcher. 467 The "io_ns" variant doesn't start (activate) the newly created
122
123 my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback
124 my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback
125 Same as "io" and "io_ns", but also specifies a timeout (as if there
126 was a call to "$w->timeout ($timout, 1)". The persist flag is not
127 allowed and will automatically be cleared. The watcher will be
128 restarted after each event.
129
130 If the timeout is zero or undef, no timeout will be set, and a
131 normal watcher (with the persist flag set!) will be created.
132
133 This has the effect of timing out after the specified period of
134 inactivity has happened.
135
136 Due to the design of libevent, this is also relatively inefficient,
137 having one or two io watchers and a separate timeout watcher that
138 you reset on activity (by calling its "start" method) is usually
139 more efficient.
140
141 my $w = EV::timer $after, $repeat, $callback
142 my $w = EV::timer_ns $after, $repeat, $callback
143 Calls the callback after $after seconds. If $repeat is true, the
144 timer will be restarted after the callback returns. This means that
145 the callback would be called roughly every $after seconds, prolonged
146 by the time the callback takes.
147
148 The "timer_ns" variant doesn't add/start the newly created watcher.
149
150 my $w = EV::timer_abs $at, $interval, $callback
151 my $w = EV::timer_abs_ns $at, $interval, $callback
152 Similar to EV::timer, but the time is given as an absolute point in
153 time ($at), plus an optional $interval.
154
155 If the $interval is zero, then the callback will be called at the
156 time $at if that is in the future, or as soon as possible if its in
157 the past. It will not automatically repeat.
158
159 If the $interval is nonzero, then the watcher will always be
160 scheduled to time out at the next "$at + integer * $interval" time.
161
162 This can be used to schedule a callback to run at very regular
163 intervals, as long as the processing time is less then the interval
164 (otherwise obviously events will be skipped).
165
166 Another way to think about it (for the mathematically inclined) is
167 that "timer_abs" will try to tun the callback at the next possible
168 time where "$time = $at (mod $interval)", regardless of any time
169 jumps.
170
171 The "timer_abs_ns" variant doesn't add/start the newly created
172 watcher. 468 watcher.
173 469
174 my $w = EV::signal $signal, $callback 470 $w->set ($fileno_or_fh, $eventmask)
175 my $w = EV::signal_ns $signal, $callback 471 Reconfigures the watcher, see the constructor above for details. Can
176 Call the callback when $signal is received (the signal can be 472 be called at any time.
177 specified by number or by name, just as with kill or %SIG). Signal
178 watchers are persistent no natter what.
179
180 EV will grab the signal for the process (the kernel only allows one
181 component to receive signals) when you start a signal watcher, and
182 removes it again when you stop it. Pelr does the same when you
183 add/remove callbacks to %SIG, so watch out.
184
185 Unfortunately, only one handler can be registered per signal. Screw
186 libevent.
187
188 The "signal_ns" variant doesn't add/start the newly created watcher.
189
190THE EV::Event CLASS
191 All EV functions creating an event watcher (designated by "my $w ="
192 above) support the following methods on the returned watcher object:
193
194 $w->add ($timeout)
195 Stops and (re-)starts the event watcher, setting the optional
196 timeout to the given value, or clearing the timeout if none is
197 given.
198
199 $w->start
200 Stops and (re-)starts the event watcher without touching the
201 timeout.
202
203 $w->del
204 $w->stop
205 Stop the event watcher if it was started.
206
207 $current_callback = $w->cb
208 $old_callback = $w->cb ($new_callback)
209 Return the previously set callback and optionally set a new one.
210 473
211 $current_fh = $w->fh 474 $current_fh = $w->fh
212 $old_fh = $w->fh ($new_fh) 475 $old_fh = $w->fh ($new_fh)
213 Returns the previously set filehandle and optionally set a new one 476 Returns the previously set filehandle and optionally set a new one.
214 (also clears the EV::SIGNAL flag when setting a filehandle).
215
216 $current_signal = $w->signal
217 $old_signal = $w->signal ($new_signal)
218 Returns the previously set signal number and optionally set a new
219 one (also sets the EV::SIGNAL flag when setting a signal).
220 477
221 $current_eventmask = $w->events 478 $current_eventmask = $w->events
222 $old_eventmask = $w->events ($new_eventmask) 479 $old_eventmask = $w->events ($new_eventmask)
223 Returns the previously set event mask and optionally set a new one. 480 Returns the previously set event mask and optionally set a new one.
224 481
482 TIMER WATCHERS - relative and optionally repeating timeouts
483 $w = EV::timer $after, $repeat, $callback
484 $w = EV::timer_ns $after, $repeat, $callback
485 $w = $loop->timer ($after, $repeat, $callback)
486 $w = $loop->timer_ns ($after, $repeat, $callback)
487 Calls the callback after $after seconds (which may be fractional).
488 If $repeat is non-zero, the timer will be restarted (with the
489 $repeat value as $after) after the callback returns.
490
491 This means that the callback would be called roughly after $after
492 seconds, and then every $repeat seconds. The timer does his best not
493 to drift, but it will not invoke the timer more often then once per
494 event loop iteration, and might drift in other cases. If that isn't
495 acceptable, look at EV::periodic, which can provide long-term stable
496 timers.
497
498 The timer is based on a monotonic clock, that is, if somebody is
499 sitting in front of the machine while the timer is running and
500 changes the system clock, the timer will nevertheless run (roughly)
501 the same time.
502
503 The "timer_ns" variant doesn't start (activate) the newly created
504 watcher.
505
225 $w->timeout ($after, $repeat) 506 $w->set ($after, $repeat)
226 Resets the timeout (see "EV::timer" for details). 507 Reconfigures the watcher, see the constructor above for details. Can
508 be called at any time.
227 509
510 $w->again
511 Similar to the "start" method, but has special semantics for
512 repeating timers:
513
514 If the timer is active and non-repeating, it will be stopped.
515
516 If the timer is active and repeating, reset the timeout to occur
517 $repeat seconds after now.
518
519 If the timer is inactive and repeating, start it using the repeat
520 value.
521
522 Otherwise do nothing.
523
524 This behaviour is useful when you have a timeout for some IO
525 operation. You create a timer object with the same value for $after
526 and $repeat, and then, in the read/write watcher, run the "again"
527 method on the timeout.
528
529 PERIODIC WATCHERS - to cron or not to cron?
530 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
531 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
532 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
533 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
534 Similar to EV::timer, but is not based on relative timeouts but on
535 absolute times. Apart from creating "simple" timers that trigger
536 "at" the specified time, it can also be used for non-drifting
537 absolute timers and more complex, cron-like, setups that are not
538 adversely affected by time jumps (i.e. when the system clock is
539 changed by explicit date -s or other means such as ntpd). It is also
540 the most complex watcher type in EV.
541
542 It has three distinct "modes":
543
544 * absolute timer ($interval = $reschedule_cb = 0)
545
546 This time simply fires at the wallclock time $at and doesn't
547 repeat. It will not adjust when a time jump occurs, that is, if
548 it is to be run at January 1st 2011 then it will run when the
549 system time reaches or surpasses this time.
550
551 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
552
553 In this mode the watcher will always be scheduled to time out at
554 the next "$at + N * $interval" time (for some integer N) and
555 then repeat, regardless of any time jumps.
556
557 This can be used to create timers that do not drift with respect
558 to system time:
559
560 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
561
562 That doesn't mean there will always be 3600 seconds in between
563 triggers, but only that the the clalback will be called when the
564 system time shows a full hour (UTC).
565
566 Another way to think about it (for the mathematically inclined)
567 is that EV::periodic will try to run the callback in this mode
568 at the next possible time where "$time = $at (mod $interval)",
569 regardless of any time jumps.
570
571 * manual reschedule mode ($reschedule_cb = coderef)
572
573 In this mode $interval and $at are both being ignored. Instead,
574 each time the periodic watcher gets scheduled, the reschedule
575 callback ($reschedule_cb) will be called with the watcher as
576 first, and the current time as second argument.
577
578 *This callback MUST NOT stop or destroy this or any other
579 periodic watcher, ever, and MUST NOT call any event loop
580 functions or methods*. If you need to stop it, return 1e30 and
581 stop it afterwards. You may create and start a "EV::prepare"
582 watcher for this task.
583
584 It must return the next time to trigger, based on the passed
585 time value (that is, the lowest time value larger than or equal
586 to to the second argument). It will usually be called just
587 before the callback will be triggered, but might be called at
588 other times, too.
589
590 This can be used to create very complex timers, such as a timer
591 that triggers on each midnight, local time (actually 24 hours
592 after the last midnight, to keep the example simple. If you know
593 a way to do it correctly in about the same space (without
594 requiring elaborate modules), drop me a note :):
595
596 my $daily = EV::periodic 0, 0, sub {
597 my ($w, $now) = @_;
598
599 use Time::Local ();
600 my (undef, undef, undef, $d, $m, $y) = localtime $now;
601 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
602 }, sub {
603 print "it's midnight or likely shortly after, now\n";
604 };
605
606 The "periodic_ns" variant doesn't start (activate) the newly created
607 watcher.
608
609 $w->set ($at, $interval, $reschedule_cb)
610 Reconfigures the watcher, see the constructor above for details. Can
611 be called at any time.
612
613 $w->again
614 Simply stops and starts the watcher again.
615
616 $time = $w->at
617 Return the time that the watcher is expected to trigger next.
618
619 SIGNAL WATCHERS - signal me when a signal gets signalled!
620 $w = EV::signal $signal, $callback
621 $w = EV::signal_ns $signal, $callback
622 $w = $loop->signal ($signal, $callback)
623 $w = $loop->signal_ns ($signal, $callback)
624 Call the callback when $signal is received (the signal can be
625 specified by number or by name, just as with "kill" or %SIG).
626
627 Only one event loop can grab a given signal - attempting to grab the
628 same signal from two EV loops will crash the program immediately or
629 cause data corruption.
630
631 EV will grab the signal for the process (the kernel only allows one
632 component to receive a signal at a time) when you start a signal
633 watcher, and removes it again when you stop it. Perl does the same
634 when you add/remove callbacks to %SIG, so watch out.
635
636 You can have as many signal watchers per signal as you want.
637
638 The "signal_ns" variant doesn't start (activate) the newly created
639 watcher.
640
641 $w->set ($signal)
642 Reconfigures the watcher, see the constructor above for details. Can
643 be called at any time.
644
645 $current_signum = $w->signal
646 $old_signum = $w->signal ($new_signal)
647 Returns the previously set signal (always as a number not name) and
648 optionally set a new one.
649
650 CHILD WATCHERS - watch out for process status changes
651 $w = EV::child $pid, $trace, $callback
652 $w = EV::child_ns $pid, $trace, $callback
653 $w = $loop->child ($pid, $trace, $callback)
654 $w = $loop->child_ns ($pid, $trace, $callback)
655 Call the callback when a status change for pid $pid (or any pid if
656 $pid is 0) has been received (a status change happens when the
657 process terminates or is killed, or, when trace is true,
658 additionally when it is stopped or continued). More precisely: when
659 the process receives a "SIGCHLD", EV will fetch the outstanding
660 exit/wait status for all changed/zombie children and call the
661 callback.
662
663 It is valid (and fully supported) to install a child watcher after a
664 child has exited but before the event loop has started its next
665 iteration (for example, first you "fork", then the new child process
666 might exit, and only then do you install a child watcher in the
667 parent for the new pid).
668
669 You can access both exit (or tracing) status and pid by using the
670 "rstatus" and "rpid" methods on the watcher object.
671
672 You can have as many pid watchers per pid as you want, they will all
673 be called.
674
675 The "child_ns" variant doesn't start (activate) the newly created
676 watcher.
677
678 $w->set ($pid, $trace)
679 Reconfigures the watcher, see the constructor above for details. Can
680 be called at any time.
681
682 $current_pid = $w->pid
683 Returns the previously set process id and optionally set a new one.
684
685 $exit_status = $w->rstatus
686 Return the exit/wait status (as returned by waitpid, see the waitpid
687 entry in perlfunc).
688
689 $pid = $w->rpid
690 Return the pid of the awaited child (useful when you have installed
691 a watcher for all pids).
692
693 STAT WATCHERS - did the file attributes just change?
694 $w = EV::stat $path, $interval, $callback
695 $w = EV::stat_ns $path, $interval, $callback
696 $w = $loop->stat ($path, $interval, $callback)
697 $w = $loop->stat_ns ($path, $interval, $callback)
698 Call the callback when a file status change has been detected on
699 $path. The $path does not need to exist, changing from "path exists"
700 to "path does not exist" is a status change like any other.
701
702 The $interval is a recommended polling interval for systems where
703 OS-supported change notifications don't exist or are not supported.
704 If you use 0 then an unspecified default is used (which is highly
705 recommended!), which is to be expected to be around five seconds
706 usually.
707
708 This watcher type is not meant for massive numbers of stat watchers,
709 as even with OS-supported change notifications, this can be
710 resource-intensive.
711
712 The "stat_ns" variant doesn't start (activate) the newly created
713 watcher.
714
715 ... = $w->stat
716 This call is very similar to the perl "stat" built-in: It stats
717 (using "lstat") the path specified in the watcher and sets perls
718 stat cache (as well as EV's idea of the current stat values) to the
719 values found.
720
721 In scalar context, a boolean is return indicating success or failure
722 of the stat. In list context, the same 13-value list as with stat is
723 returned (except that the blksize and blocks fields are not
724 reliable).
725
726 In the case of an error, errno is set to "ENOENT" (regardless of the
727 actual error value) and the "nlink" value is forced to zero (if the
728 stat was successful then nlink is guaranteed to be non-zero).
729
730 See also the next two entries for more info.
731
732 ... = $w->attr
733 Just like "$w->stat", but without the initial stat'ing: this returns
734 the values most recently detected by EV. See the next entry for more
735 info.
736
737 ... = $w->prev
738 Just like "$w->stat", but without the initial stat'ing: this returns
739 the previous set of values, before the change.
740
741 That is, when the watcher callback is invoked, "$w->prev" will be
742 set to the values found *before* a change was detected, while
743 "$w->attr" returns the values found leading to the change detection.
744 The difference (if any) between "prev" and "attr" is what triggered
745 the callback.
746
747 If you did something to the filesystem object and do not want to
748 trigger yet another change, you can call "stat" to update EV's idea
749 of what the current attributes are.
750
228 $w->timeout_abs ($at, $interval) 751 $w->set ($path, $interval)
229 Resets the timeout (see "EV::timer_abs" for details). 752 Reconfigures the watcher, see the constructor above for details. Can
753 be called at any time.
230 754
231 $w->priority_set ($priority) 755 $current_path = $w->path
232 Set the priority of the watcher to $priority (0 <= $priority < 756 $old_path = $w->path ($new_path)
233 $EV::NPRI). 757 Returns the previously set path and optionally set a new one.
234 758
235BUGS 759 $current_interval = $w->interval
236 Lots. Libevent itself isn't well tested and rather buggy, and this 760 $old_interval = $w->interval ($new_interval)
237 module is quite new at the moment. 761 Returns the previously set interval and optionally set a new one.
762 Can be used to query the actual interval used.
238 763
239 Please note that the epoll method is not, in general, reliable in 764 IDLE WATCHERS - when you've got nothing better to do...
240 programs that use fork (even if no libveent calls are being made in the 765 $w = EV::idle $callback
241 forked process). If your program behaves erratically, try setting the 766 $w = EV::idle_ns $callback
242 environment variable "EVENT_NOEPOLL" first when running the program. 767 $w = $loop->idle ($callback)
768 $w = $loop->idle_ns ($callback)
769 Call the callback when there are no other pending watchers of the
770 same or higher priority (excluding check, prepare and other idle
771 watchers of the same or lower priority, of course). They are called
772 idle watchers because when the watcher is the highest priority
773 pending event in the process, the process is considered to be idle
774 at that priority.
243 775
244 In general, if you fork, then you can only use the EV module in one of 776 If you want a watcher that is only ever called when *no* other
245 the children. 777 events are outstanding you have to set the priority to "EV::MINPRI".
778
779 The process will not block as long as any idle watchers are active,
780 and they will be called repeatedly until stopped.
781
782 For example, if you have idle watchers at priority 0 and 1, and an
783 I/O watcher at priority 0, then the idle watcher at priority 1 and
784 the I/O watcher will always run when ready. Only when the idle
785 watcher at priority 1 is stopped and the I/O watcher at priority 0
786 is not pending with the 0-priority idle watcher be invoked.
787
788 The "idle_ns" variant doesn't start (activate) the newly created
789 watcher.
790
791 PREPARE WATCHERS - customise your event loop!
792 $w = EV::prepare $callback
793 $w = EV::prepare_ns $callback
794 $w = $loop->prepare ($callback)
795 $w = $loop->prepare_ns ($callback)
796 Call the callback just before the process would block. You can still
797 create/modify any watchers at this point.
798
799 See the EV::check watcher, below, for explanations and an example.
800
801 The "prepare_ns" variant doesn't start (activate) the newly created
802 watcher.
803
804 CHECK WATCHERS - customise your event loop even more!
805 $w = EV::check $callback
806 $w = EV::check_ns $callback
807 $w = $loop->check ($callback)
808 $w = $loop->check_ns ($callback)
809 Call the callback just after the process wakes up again (after it
810 has gathered events), but before any other callbacks have been
811 invoked.
812
813 This can be used to integrate other event-based software into the EV
814 mainloop: You register a prepare callback and in there, you create
815 io and timer watchers as required by the other software. Here is a
816 real-world example of integrating Net::SNMP (with some details left
817 out):
818
819 our @snmp_watcher;
820
821 our $snmp_prepare = EV::prepare sub {
822 # do nothing unless active
823 $dispatcher->{_event_queue_h}
824 or return;
825
826 # make the dispatcher handle any outstanding stuff
827 ... not shown
828
829 # create an I/O watcher for each and every socket
830 @snmp_watcher = (
831 (map { EV::io $_, EV::READ, sub { } }
832 keys %{ $dispatcher->{_descriptors} }),
833
834 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
835 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
836 0, sub { },
837 );
838 };
839
840 The callbacks are irrelevant (and are not even being called), the
841 only purpose of those watchers is to wake up the process as soon as
842 one of those events occurs (socket readable, or timer timed out).
843 The corresponding EV::check watcher will then clean up:
844
845 our $snmp_check = EV::check sub {
846 # destroy all watchers
847 @snmp_watcher = ();
848
849 # make the dispatcher handle any new stuff
850 ... not shown
851 };
852
853 The callbacks of the created watchers will not be called as the
854 watchers are destroyed before this can happen (remember EV::check
855 gets called first).
856
857 The "check_ns" variant doesn't start (activate) the newly created
858 watcher.
859
860 EV::CHECK constant issues
861 Like all other watcher types, there is a bitmask constant for use in
862 $revents and other places. The "EV::CHECK" is special as it has the
863 same name as the "CHECK" sub called by Perl. This doesn't cause big
864 issues on newer perls (beginning with 5.8.9), but it means thatthe
865 constant must be *inlined*, i.e. runtime calls will not work. That
866 means that as long as you always "use EV" and then "EV::CHECK" you
867 are on the safe side.
868
869 FORK WATCHERS - the audacity to resume the event loop after a fork
870 Fork watchers are called when a "fork ()" was detected. The invocation
871 is done before the event loop blocks next and before "check" watchers
872 are being called, and only in the child after the fork.
873
874 $w = EV::fork $callback
875 $w = EV::fork_ns $callback
876 $w = $loop->fork ($callback)
877 $w = $loop->fork_ns ($callback)
878 Call the callback before the event loop is resumed in the child
879 process after a fork.
880
881 The "fork_ns" variant doesn't start (activate) the newly created
882 watcher.
883
884 EMBED WATCHERS - when one backend isn't enough...
885 This is a rather advanced watcher type that lets you embed one event
886 loop into another (currently only IO events are supported in the
887 embedded loop, other types of watchers might be handled in a delayed or
888 incorrect fashion and must not be used).
889
890 See the libev documentation at
891 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
892 _when_one_backend_> (locally installed as EV::libev) for more details.
893
894 In short, this watcher is most useful on BSD systems without working
895 kqueue to still be able to handle a large number of sockets:
896
897 my $socket_loop;
898
899 # check wether we use SELECT or POLL _and_ KQUEUE is supported
900 if (
901 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
902 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
903 ) {
904 # use kqueue for sockets
905 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
906 }
907
908 # use the default loop otherwise
909 $socket_loop ||= EV::default_loop;
910
911 $w = EV::embed $otherloop[, $callback]
912 $w = EV::embed_ns $otherloop[, $callback]
913 $w = $loop->embed ($otherloop[, $callback])
914 $w = $loop->embed_ns ($otherloop[, $callback])
915 Call the callback when the embedded event loop ($otherloop) has any
916 I/O activity. The $callback is optional: if it is missing, then the
917 embedded event loop will be managed automatically (which is
918 recommended), otherwise you have to invoke "sweep" yourself.
919
920 The "embed_ns" variant doesn't start (activate) the newly created
921 watcher.
922
923 ASYNC WATCHERS - how to wake up another event loop
924 Async watchers are provided by EV, but have little use in perl directly,
925 as perl neither supports threads running in parallel nor direct access
926 to signal handlers or other contexts where they could be of value.
927
928 It is, however, possible to use them from the XS level.
929
930 Please see the libev documentation for further details.
931
932 $w = EV::async $callback
933 $w = EV::async_ns $callback
934 $w = $loop->async ($callback)
935 $w = $loop->async_ns ($callback)
936 $w->send
937 $bool = $w->async_pending
938
939 CLEANUP WATCHERS - how to clean up when the event loop goes away
940 Cleanup watchers are not supported on the Perl level, they can only be
941 used via XS currently.
942
943PERL SIGNALS
944 While Perl signal handling (%SIG) is not affected by EV, the behaviour
945 with EV is as the same as any other C library: Perl-signals will only be
946 handled when Perl runs, which means your signal handler might be invoked
947 only the next time an event callback is invoked.
948
949 The solution is to use EV signal watchers (see "EV::signal"), which will
950 ensure proper operations with regards to other event watchers.
951
952 If you cannot do this for whatever reason, you can also force a watcher
953 to be called on every event loop iteration by installing a "EV::check"
954 watcher:
955
956 my $async_check = EV::check sub { };
957
958 This ensures that perl gets into control for a short time to handle any
959 pending signals, and also ensures (slightly) slower overall operation.
960
961ITHREADS
962 Ithreads are not supported by this module in any way. Perl
963 pseudo-threads is evil stuff and must die. Real threads as provided by
964 Coro are fully supported (and enhanced support is available via
965 Coro::EV).
966
967FORK
968 Most of the "improved" event delivering mechanisms of modern operating
969 systems have quite a few problems with fork(2) (to put it bluntly: it is
970 not supported and usually destructive). Libev makes it possible to work
971 around this by having a function that recreates the kernel state after
972 fork in the child.
973
974 On non-win32 platforms, this module requires the pthread_atfork
975 functionality to do this automatically for you. This function is quite
976 buggy on most BSDs, though, so YMMV. The overhead for this is quite
977 negligible, because everything the function currently does is set a flag
978 that is checked only when the event loop gets used the next time, so
979 when you do fork but not use EV, the overhead is minimal.
980
981 On win32, there is no notion of fork so all this doesn't apply, of
982 course.
246 983
247SEE ALSO 984SEE ALSO
248 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 985 EV::MakeMaker - MakeMaker interface to XS API, EV::ADNS (asynchronous
249 L<EV::AnyEvent>. 986 DNS), Glib::EV (makes Glib/Gtk2 use EV as event loop), EV::Glib (embed
987 Glib into EV), Coro::EV (efficient thread integration), Net::SNMP::EV
988 (asynchronous SNMP), AnyEvent for event-loop agnostic and portable event
989 driven programming.
250 990
251AUTHOR 991AUTHOR
252 Marc Lehmann <schmorp@schmorp.de> 992 Marc Lehmann <schmorp@schmorp.de>
253 http://home.schmorp.de/ 993 http://home.schmorp.de/
254 994

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