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2 EV - perl interface to libev, a high performance full-featured event 2 EV - perl interface to libev, a high performance full-featured event
3 loop 3 loop
4 4
5SYNOPSIS 5SYNOPSIS
6 use EV; 6 use EV;
7 7
8 # TIMERS 8 # TIMERS
9 9
10 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s"; 11 warn "is called after 2s";
12 }; 12 };
13 13
14 my $w = EV::timer 2, 2, sub { 14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 2)"; 15 warn "is called roughly every 2s (repeat = 2)";
16 }; 16 };
17 17
18 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
19 19
20 my $w = EV::periodic 0, 60, 0, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
22 }; 22 };
23
24 # IO 23
25 24 # IO
25
26 my $w = EV::io *STDIN, EV::READ, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
29 }; 29 };
30 30
31 # SIGNALS 31 # SIGNALS
32 32
33 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n"; 34 warn "sigquit received\n";
35 }; 35 };
36 36
37 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
38 38
39 my $w = EV::child 666, sub { 39 my $w = EV::child 666, 0, sub {
40 my ($w, $revents) = @_; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus; 41 my $status = $w->rstatus;
42 }; 42 };
43 43
44 # STAT CHANGES
45 my $w = EV::stat "/etc/passwd", 10, sub {
46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
48 };
49
44 # MAINLOOP 50 # MAINLOOP
45 EV::loop; # loop until EV::unloop is called or all watchers stop 51 EV::loop; # loop until EV::unloop is called or all watchers stop
46 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled 52 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
47 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block 53 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
48 54
49DESCRIPTION 55DESCRIPTION
50 This module provides an interface to libev 56 This module provides an interface to libev
51 (<http://software.schmorp.de/pkg/libev.html>). 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
58 below is comprehensive, one might also consult the documentation of
59 libev itself (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>)
60 for more subtle details on watcher semantics or some discussion on the
61 available backends, or how to force a specific backend with
62 "LIBEV_FLAGS", or just about in any case because it has much more
63 detailed information.
64
65 This module is very fast and scalable. It is actually so fast that you
66 can use it through the AnyEvent module, stay portable to other event
67 loops (if you don't rely on any watcher types not available through it)
68 and still be faster than with any other event loop currently supported
69 in Perl.
70
71EVENT LOOPS
72 EV supports multiple event loops: There is a single "default event loop"
73 that can handle everything including signals and child watchers, and any
74 number of "dynamic event loops" that can use different backends (with
75 various limitations), but no child and signal watchers.
76
77 You do not have to do anything to create the default event loop: When
78 the module is loaded a suitable backend is selected on the premise of
79 selecting a working backend (which for example rules out kqueue on most
80 BSDs). Modules should, unless they have "special needs" always use the
81 default loop as this is fastest (perl-wise), best supported by other
82 modules (e.g. AnyEvent or Coro) and most portable event loop.
83
84 For specific programs you can create additional event loops dynamically.
85
86 $loop = new EV::loop [$flags]
87 Create a new event loop as per the specified flags. Please refer to
88 the "ev_loop_new ()" function description in the libev documentation
89 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
90 ONS>) for more info.
91
92 The loop will automatically be destroyed when it is no longer
93 referenced by any watcher and the loop object goes out of scope.
94
95 Using "EV::FLAG_FORKCHECK" is recommended, as only the default event
96 loop is protected by this module.
97
98 $loop->loop_fork
99 Must be called after a fork in the child, before entering or
100 continuing the event loop. An alternative is to use
101 "EV::FLAG_FORKCHECK" which calls this function automatically, at
102 some performance loss (refer to the libev documentation).
103
104 $loop->loop_verify
105 Calls "ev_verify" to make internal consistency checks (for debugging
106 libev) and abort the program if any data structures wree found to be
107 corrupted.
108
109 $loop = EV::default_loop [$flags]
110 Return the default loop (which is a singleton object). Since this
111 module already creates the default loop with default flags,
112 specifying flags here will not have any effect unless you destroy
113 the default loop.
52 114
53BASIC INTERFACE 115BASIC INTERFACE
54 $EV::DIED 116 $EV::DIED
55 Must contain a reference to a function that is called when a 117 Must contain a reference to a function that is called when a
56 callback throws an exception (with $@ containing thr error). The 118 callback throws an exception (with $@ containing the error). The
57 default prints an informative message and continues. 119 default prints an informative message and continues.
58 120
59 If this callback throws an exception it will be silently ignored. 121 If this callback throws an exception it will be silently ignored.
122
123 $flags = EV::supported_backends
124 $flags = EV::recommended_backends
125 $flags = EV::embeddable_backends
126 Returns the set (see "EV::BACKEND_*" flags) of backends supported by
127 this instance of EV, the set of recommended backends (supposed to be
128 good) for this platform and the set of embeddable backends (see
129 EMBED WATCHERS).
130
131 EV::sleep $seconds
132 Block the process for the given number of (fractional) seconds.
60 133
61 $time = EV::time 134 $time = EV::time
62 Returns the current time in (fractional) seconds since the epoch. 135 Returns the current time in (fractional) seconds since the epoch.
63 136
64 $time = EV::now 137 $time = EV::now
138 $time = $loop->now
65 Returns the time the last event loop iteration has been started. 139 Returns the time the last event loop iteration has been started.
66 This is the time that (relative) timers are based on, and refering 140 This is the time that (relative) timers are based on, and refering
67 to it is usually faster then calling EV::time. 141 to it is usually faster then calling EV::time.
68 142
69 $method = EV::ev_method 143 $backend = EV::backend
144 $backend = $loop->backend
70 Returns an integer describing the backend used by libev 145 Returns an integer describing the backend used by libev
71 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 146 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
72 147
73 EV::loop [$flags] 148 EV::loop [$flags]
149 $loop->loop ([$flags])
74 Begin checking for events and calling callbacks. It returns when a 150 Begin checking for events and calling callbacks. It returns when a
75 callback calls EV::unloop. 151 callback calls EV::unloop.
76 152
77 The $flags argument can be one of the following: 153 The $flags argument can be one of the following:
78 154
79 0 as above 155 0 as above
80 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 156 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
81 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 157 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
82 158
83 EV::unloop [$how] 159 EV::unloop [$how]
160 $loop->unloop ([$how])
84 When called with no arguments or an argument of EV::UNLOOP_ONE, 161 When called with no arguments or an argument of EV::UNLOOP_ONE,
85 makes the innermost call to EV::loop return. 162 makes the innermost call to EV::loop return.
86 163
87 When called with an argument of EV::UNLOOP_ALL, all calls to 164 When called with an argument of EV::UNLOOP_ALL, all calls to
88 EV::loop will return as fast as possible. 165 EV::loop will return as fast as possible.
89 166
90 WATCHER 167 $count = EV::loop_count
168 $count = $loop->loop_count
169 Return the number of times the event loop has polled for new events.
170 Sometiems useful as a generation counter.
171
172 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
173 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
174 This function rolls together an I/O and a timer watcher for a single
175 one-shot event without the need for managing a watcher object.
176
177 If $fh_or_undef is a filehandle or file descriptor, then $events
178 must be a bitset containing either "EV::READ", "EV::WRITE" or
179 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
180 wait for. If you do not want to wait for some I/O event, specify
181 "undef" for $fh_or_undef and 0 for $events).
182
183 If timeout is "undef" or negative, then there will be no timeout.
184 Otherwise a EV::timer with this value will be started.
185
186 When an error occurs or either the timeout or I/O watcher triggers,
187 then the callback will be called with the received event set (in
188 general you can expect it to be a combination of "EV::ERROR",
189 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
190
191 EV::once doesn't return anything: the watchers stay active till
192 either of them triggers, then they will be stopped and freed, and
193 the callback invoked.
194
195 EV::feed_fd_event ($fd, $revents)
196 $loop->feed_fd_event ($fd, $revents)
197 Feed an event on a file descriptor into EV. EV will react to this
198 call as if the readyness notifications specified by $revents (a
199 combination of "EV::READ" and "EV::WRITE") happened on the file
200 descriptor $fd.
201
202 EV::feed_signal_event ($signal)
203 Feed a signal event into EV. EV will react to this call as if the
204 signal specified by $signal had occured.
205
206 EV::set_io_collect_interval $time
207 $loop->set_io_collect_interval ($time)
208 EV::set_timeout_collect_interval $time
209 $loop->set_timeout_collect_interval ($time)
210 These advanced functions set the minimum block interval when polling
211 for I/O events and the minimum wait interval for timer events. See
212 the libev documentation at
213 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONT
214 ROLLING_THE_EVENT_LOOP> for a more detailed discussion.
215
216WATCHER OBJECTS
91 A watcher is an object that gets created to record your interest in some 217 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, 218 event. For instance, if you want to wait for STDIN to become readable,
93 you would create an EV::io watcher for that: 219 you would create an EV::io watcher for that:
94 220
95 my $watcher = EV::io *STDIN, EV::READ, sub { 221 my $watcher = EV::io *STDIN, EV::READ, sub {
96 my ($watcher, $revents) = @_; 222 my ($watcher, $revents) = @_;
97 warn "yeah, STDIN should not be readable without blocking!\n" 223 warn "yeah, STDIN should now be readable without blocking!\n"
98 }; 224 };
99 225
100 All watchers can be active (waiting for events) or inactive (paused). 226 All watchers can be active (waiting for events) or inactive (paused).
101 Only active watchers will have their callbacks invoked. All callbacks 227 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 228 will be called with at least two arguments: the watcher and a bitmask of
103 received events. 229 received events.
104 230
105 Each watcher type has its associated bit in revents, so you can use the 231 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 232 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, 233 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 234 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
109 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 235 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
110 (which uses EV::TIMEOUT). 236 (which uses EV::TIMEOUT).
111 237
112 In the rare case where one wants to create a watcher but not start it at 238 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 239 the same time, each constructor has a variant with a trailing "_ns" in
… …
119 245
120 Also, all methods changing some aspect of a watcher (->set, ->priority, 246 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, 247 ->fh and so on) automatically stop and start it again if it is active,
122 which means pending events get lost. 248 which means pending events get lost.
123 249
124 WATCHER TYPES 250 COMMON WATCHER METHODS
125 Now lets move to the existing watcher types and asociated methods. 251 This section lists methods common to all watchers.
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).
131 252
132 $w->start 253 $w->start
133 Starts a watcher if it isn't active already. Does nothing to an 254 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 255 already active watcher. By default, all watchers start out in the
135 active state (see the description of the "_ns" variants if you need 256 active state (see the description of the "_ns" variants if you need
136 stopped watchers). 257 stopped watchers).
137 258
138 $w->stop 259 $w->stop
139 Stop a watcher if it is active. Also clear any pending events 260 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 261 (events that have been received but that didn't yet result in a
141 callback invocation), regardless of wether the watcher was active or 262 callback invocation), regardless of whether the watcher was active
142 not. 263 or not.
143 264
144 $bool = $w->is_active 265 $bool = $w->is_active
145 Returns true if the watcher is active, false otherwise. 266 Returns true if the watcher is active, false otherwise.
146 267
147 $current_data = $w->data 268 $current_data = $w->data
… …
165 Pending watchers with higher priority will be invoked first. The 286 Pending watchers with higher priority will be invoked first. The
166 valid range of priorities lies between EV::MAXPRI (default 2) and 287 valid range of priorities lies between EV::MAXPRI (default 2) and
167 EV::MINPRI (default -2). If the priority is outside this range it 288 EV::MINPRI (default -2). If the priority is outside this range it
168 will automatically be normalised to the nearest valid priority. 289 will automatically be normalised to the nearest valid priority.
169 290
170 The default priority of any newly-created weatcher is 0. 291 The default priority of any newly-created watcher is 0.
171 292
293 Note that the priority semantics have not yet been fleshed out and
294 are subject to almost certain change.
295
172 $w->trigger ($revents) 296 $w->invoke ($revents)
173 Call the callback *now* with the given event mask. 297 Call the callback *now* with the given event mask.
174 298
299 $w->feed_event ($revents)
300 Feed some events on this watcher into EV. EV will react to this call
301 as if the watcher had received the given $revents mask.
302
303 $revents = $w->clear_pending
304 If the watcher is pending, this function clears its pending status
305 and returns its $revents bitset (as if its callback was invoked). If
306 the watcher isn't pending it does nothing and returns 0.
307
308 $previous_state = $w->keepalive ($bool)
309 Normally, "EV::loop" will return when there are no active watchers
310 (which is a "deadlock" because no progress can be made anymore).
311 This is convinient because it allows you to start your watchers (and
312 your jobs), call "EV::loop" once and when it returns you know that
313 all your jobs are finished (or they forgot to register some watchers
314 for their task :).
315
316 Sometimes, however, this gets in your way, for example when the
317 module that calls "EV::loop" (usually the main program) is not the
318 same module as a long-living watcher (for example a DNS client
319 module written by somebody else even). Then you might want any
320 outstanding requests to be handled, but you would not want to keep
321 "EV::loop" from returning just because you happen to have this
322 long-running UDP port watcher.
323
324 In this case you can clear the keepalive status, which means that
325 even though your watcher is active, it won't keep "EV::loop" from
326 returning.
327
328 The initial value for keepalive is true (enabled), and you cna
329 change it any time.
330
331 Example: Register an I/O watcher for some UDP socket but do not keep
332 the event loop from running just because of that watcher.
333
334 my $udp_socket = ...
335 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
336 $1000udp_watcher->keepalive (0);
337
338 $loop = $w->loop
339 Return the loop that this watcher is attached to.
340
341WATCHER TYPES
342 Each of the following subsections describes a single watcher type.
343
344 I/O WATCHERS - is this file descriptor readable or writable?
175 $w = EV::io $fileno_or_fh, $eventmask, $callback 345 $w = EV::io $fileno_or_fh, $eventmask, $callback
176 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 346 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
347 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
348 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
177 As long as the returned watcher object is alive, call the $callback 349 As long as the returned watcher object is alive, call the $callback
178 when the events specified in $eventmask. 350 when at least one of events specified in $eventmask occurs.
179 351
180 The $eventmask can be one or more of these constants ORed together: 352 The $eventmask can be one or more of these constants ORed together:
181 353
182 EV::READ wait until read() wouldn't block anymore 354 EV::READ wait until read() wouldn't block anymore
183 EV::WRITE wait until write() wouldn't block anymore 355 EV::WRITE wait until write() wouldn't block anymore
… …
195 367
196 $current_eventmask = $w->events 368 $current_eventmask = $w->events
197 $old_eventmask = $w->events ($new_eventmask) 369 $old_eventmask = $w->events ($new_eventmask)
198 Returns the previously set event mask and optionally set a new one. 370 Returns the previously set event mask and optionally set a new one.
199 371
372 TIMER WATCHERS - relative and optionally repeating timeouts
200 $w = EV::timer $after, $repeat, $callback 373 $w = EV::timer $after, $repeat, $callback
201 $w = EV::timer_ns $after, $repeat, $callback 374 $w = EV::timer_ns $after, $repeat, $callback
202 Calls the callback after $after seconds. If $repeat is non-zero, the 375 $w = $loop->timer ($after, $repeat, $callback)
203 timer will be restarted (with the $repeat value as $after) after the 376 $w = $loop->timer_ns ($after, $repeat, $callback)
204 callback returns. 377 Calls the callback after $after seconds (which may be fractional).
378 If $repeat is non-zero, the timer will be restarted (with the
379 $repeat value as $after) after the callback returns.
205 380
206 This means that the callback would be called roughly after $after 381 This means that the callback would be called roughly after $after
207 seconds, and then every $repeat seconds. The timer does his best not 382 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 383 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 384 event loop iteration, and might drift in other cases. If that isn't
… …
218 The "timer_ns" variant doesn't start (activate) the newly created 393 The "timer_ns" variant doesn't start (activate) the newly created
219 watcher. 394 watcher.
220 395
221 $w->set ($after, $repeat) 396 $w->set ($after, $repeat)
222 Reconfigures the watcher, see the constructor above for details. Can 397 Reconfigures the watcher, see the constructor above for details. Can
223 be at any time. 398 be called at any time.
224 399
225 $w->again 400 $w->again
226 Similar to the "start" method, but has special semantics for 401 Similar to the "start" method, but has special semantics for
227 repeating timers: 402 repeating timers:
228 403
… …
239 This behaviour is useful when you have a timeout for some IO 414 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 415 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" 416 and $repeat, and then, in the read/write watcher, run the "again"
242 method on the timeout. 417 method on the timeout.
243 418
419 PERIODIC WATCHERS - to cron or not to cron?
244 $w = EV::periodic $at, $interval, $reschedule_cb, $callback 420 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
245 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback 421 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
422 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
423 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
246 Similar to EV::timer, but is not based on relative timeouts but on 424 Similar to EV::timer, but is not based on relative timeouts but on
247 absolute times. Apart from creating "simple" timers that trigger 425 absolute times. Apart from creating "simple" timers that trigger
248 "at" the specified time, it can also be used for non-drifting 426 "at" the specified time, it can also be used for non-drifting
249 absolute timers and more complex, cron-like, setups that are not 427 absolute timers and more complex, cron-like, setups that are not
250 adversely affected by time jumps (i.e. when the system clock is 428 adversely affected by time jumps (i.e. when the system clock is
251 changed by explicit date -s or other means such as ntpd). It is also 429 changed by explicit date -s or other means such as ntpd). It is also
252 the most complex watcher type in EV. 430 the most complex watcher type in EV.
253 431
254 It has three distinct "modes": 432 It has three distinct "modes":
255 433
256 * absolute timer ($interval = $reschedule_cb = 0) 434 * absolute timer ($interval = $reschedule_cb = 0)
435
257 This time simply fires at the wallclock time $at and doesn't 436 This time simply fires at the wallclock time $at and doesn't
258 repeat. It will not adjust when a time jump occurs, that is, if 437 repeat. It will not adjust when a time jump occurs, that is, if
259 it is to be run at January 1st 2011 then it will run when the 438 it is to be run at January 1st 2011 then it will run when the
260 system time reaches or surpasses this time. 439 system time reaches or surpasses this time.
261 440
262 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0) 441 * repeating interval timer ($interval > 0, $reschedule_cb = 0)
442
263 In this mode the watcher will always be scheduled to time out at 443 In this mode the watcher will always be scheduled to time out at
264 the next "$at + N * $interval" time (for some integer N) and 444 the next "$at + N * $interval" time (for some integer N) and
265 then repeat, regardless of any time jumps. 445 then repeat, regardless of any time jumps.
266 446
267 This can be used to create timers that do not drift with respect 447 This can be used to create timers that do not drift with respect
… …
276 Another way to think about it (for the mathematically inclined) 456 Another way to think about it (for the mathematically inclined)
277 is that EV::periodic will try to run the callback in this mode 457 is that EV::periodic will try to run the callback in this mode
278 at the next possible time where "$time = $at (mod $interval)", 458 at the next possible time where "$time = $at (mod $interval)",
279 regardless of any time jumps. 459 regardless of any time jumps.
280 460
281 * manual reschedule mode ($reschedule_cb = coderef) 461 * manual reschedule mode ($reschedule_cb = coderef)
462
282 In this mode $interval and $at are both being ignored. Instead, 463 In this mode $interval and $at are both being ignored. Instead,
283 each time the periodic watcher gets scheduled, the reschedule 464 each time the periodic watcher gets scheduled, the reschedule
284 callback ($reschedule_cb) will be called with the watcher as 465 callback ($reschedule_cb) will be called with the watcher as
285 first, and the current time as second argument. 466 first, and the current time as second argument.
286 467
287 *This callback MUST NOT stop or destroy this or any other 468 *This callback MUST NOT stop or destroy this or any other
469 periodic watcher, ever, and MUST NOT call any event loop
288 periodic watcher, ever*. If you need to stop it, return 1e30 and 470 functions or methods*. If you need to stop it, return 1e30 and
289 stop it afterwards. 471 stop it afterwards. You may create and start a "EV::prepare"
472 watcher for this task.
290 473
291 It must return the next time to trigger, based on the passed 474 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 475 time value (that is, the lowest time value larger than or equal
293 second argument). It will usually be called just before the 476 to to the second argument). It will usually be called just
294 callback will be triggered, but might be called at other times, 477 before the callback will be triggered, but might be called at
295 too. 478 other times, too.
296 479
297 This can be used to create very complex timers, such as a timer 480 This can be used to create very complex timers, such as a timer
298 that triggers on each midnight, local time (actually 24 hours 481 that triggers on each midnight, local time (actually 24 hours
299 after the last midnight, to keep the example simple. If you know 482 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 483 a way to do it correctly in about the same space (without
… …
313 The "periodic_ns" variant doesn't start (activate) the newly created 496 The "periodic_ns" variant doesn't start (activate) the newly created
314 watcher. 497 watcher.
315 498
316 $w->set ($at, $interval, $reschedule_cb) 499 $w->set ($at, $interval, $reschedule_cb)
317 Reconfigures the watcher, see the constructor above for details. Can 500 Reconfigures the watcher, see the constructor above for details. Can
318 be at any time. 501 be called at any time.
319 502
320 $w->again 503 $w->again
321 Simply stops and starts the watcher again. 504 Simply stops and starts the watcher again.
322 505
506 $time = $w->at
507 Return the time that the watcher is expected to trigger next.
508
509 SIGNAL WATCHERS - signal me when a signal gets signalled!
323 $w = EV::signal $signal, $callback 510 $w = EV::signal $signal, $callback
324 $w = EV::signal_ns $signal, $callback 511 $w = EV::signal_ns $signal, $callback
325 Call the callback when $signal is received (the signal can be 512 Call the callback when $signal is received (the signal can be
326 specified by number or by name, just as with kill or %SIG). 513 specified by number or by name, just as with "kill" or %SIG).
327 514
328 EV will grab the signal for the process (the kernel only allows one 515 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 516 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 517 watcher, and removes it again when you stop it. Perl does the same
331 when you add/remove callbacks to %SIG, so watch out. 518 when you add/remove callbacks to %SIG, so watch out.
… …
335 The "signal_ns" variant doesn't start (activate) the newly created 522 The "signal_ns" variant doesn't start (activate) the newly created
336 watcher. 523 watcher.
337 524
338 $w->set ($signal) 525 $w->set ($signal)
339 Reconfigures the watcher, see the constructor above for details. Can 526 Reconfigures the watcher, see the constructor above for details. Can
340 be at any time. 527 be called at any time.
341 528
342 $current_signum = $w->signal 529 $current_signum = $w->signal
343 $old_signum = $w->signal ($new_signal) 530 $old_signum = $w->signal ($new_signal)
344 Returns the previously set signal (always as a number not name) and 531 Returns the previously set signal (always as a number not name) and
345 optionally set a new one. 532 optionally set a new one.
346 533
534 CHILD WATCHERS - watch out for process status changes
347 $w = EV::child $pid, $callback 535 $w = EV::child $pid, $trace, $callback
348 $w = EV::child_ns $pid, $callback 536 $w = EV::child_ns $pid, $trace, $callback
537 $w = $loop->child ($pid, $trace, $callback)
538 $w = $loop->child_ns ($pid, $trace, $callback)
349 Call the callback when a status change for pid $pid (or any pid if 539 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 540 $pid is 0) has been received (a status change happens when the
541 process terminates or is killed, or, when trace is true,
542 additionally when it is stopped or continued). More precisely: when
351 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 543 the process receives a "SIGCHLD", EV will fetch the outstanding
352 for all changed/zombie children and call the callback. 544 exit/wait status for all changed/zombie children and call the
545 callback.
353 546
354 You can access both status and pid by using the "rstatus" and "rpid" 547 It is valid (and fully supported) to install a child watcher after a
548 child has exited but before the event loop has started its next
549 iteration (for example, first you "fork", then the new child process
550 might exit, and only then do you install a child watcher in the
551 parent for the new pid).
552
553 You can access both exit (or tracing) status and pid by using the
355 methods on the watcher object. 554 "rstatus" and "rpid" methods on the watcher object.
356 555
357 You can have as many pid watchers per pid as you want. 556 You can have as many pid watchers per pid as you want, they will all
557 be called.
358 558
359 The "child_ns" variant doesn't start (activate) the newly created 559 The "child_ns" variant doesn't start (activate) the newly created
360 watcher. 560 watcher.
361 561
362 $w->set ($pid) 562 $w->set ($pid, $trace)
363 Reconfigures the watcher, see the constructor above for details. Can 563 Reconfigures the watcher, see the constructor above for details. Can
364 be at any time. 564 be called at any time.
365 565
366 $current_pid = $w->pid 566 $current_pid = $w->pid
367 $old_pid = $w->pid ($new_pid)
368 Returns the previously set process id and optionally set a new one. 567 Returns the previously set process id and optionally set a new one.
369 568
370 $exit_status = $w->rstatus 569 $exit_status = $w->rstatus
371 Return the exit/wait status (as returned by waitpid, see the waitpid 570 Return the exit/wait status (as returned by waitpid, see the waitpid
372 entry in perlfunc). 571 entry in perlfunc).
373 572
374 $pid = $w->rpid 573 $pid = $w->rpid
375 Return the pid of the awaited child (useful when you have installed 574 Return the pid of the awaited child (useful when you have installed
376 a watcher for all pids). 575 a watcher for all pids).
377 576
577 STAT WATCHERS - did the file attributes just change?
578 $w = EV::stat $path, $interval, $callback
579 $w = EV::stat_ns $path, $interval, $callback
580 $w = $loop->stat ($path, $interval, $callback)
581 $w = $loop->stat_ns ($path, $interval, $callback)
582 Call the callback when a file status change has been detected on
583 $path. The $path does not need to exist, changing from "path exists"
584 to "path does not exist" is a status change like any other.
585
586 The $interval is a recommended polling interval for systems where
587 OS-supported change notifications don't exist or are not supported.
588 If you use 0 then an unspecified default is used (which is highly
589 recommended!), which is to be expected to be around five seconds
590 usually.
591
592 This watcher type is not meant for massive numbers of stat watchers,
593 as even with OS-supported change notifications, this can be
594 resource-intensive.
595
596 The "stat_ns" variant doesn't start (activate) the newly created
597 watcher.
598
599 ... = $w->stat
600 This call is very similar to the perl "stat" built-in: It stats
601 (using "lstat") the path specified in the watcher and sets perls
602 stat cache (as well as EV's idea of the current stat values) to the
603 values found.
604
605 In scalar context, a boolean is return indicating success or failure
606 of the stat. In list context, the same 13-value list as with stat is
607 returned (except that the blksize and blocks fields are not
608 reliable).
609
610 In the case of an error, errno is set to "ENOENT" (regardless of the
611 actual error value) and the "nlink" value is forced to zero (if the
612 stat was successful then nlink is guaranteed to be non-zero).
613
614 See also the next two entries for more info.
615
616 ... = $w->attr
617 Just like "$w->stat", but without the initial stat'ing: this returns
618 the values most recently detected by EV. See the next entry for more
619 info.
620
621 ... = $w->prev
622 Just like "$w->stat", but without the initial stat'ing: this returns
623 the previous set of values, before the change.
624
625 That is, when the watcher callback is invoked, "$w->prev" will be
626 set to the values found *before* a change was detected, while
627 "$w->attr" returns the values found leading to the change detection.
628 The difference (if any) between "prev" and "attr" is what triggered
629 the callback.
630
631 If you did something to the filesystem object and do not want to
632 trigger yet another change, you can call "stat" to update EV's idea
633 of what the current attributes are.
634
635 $w->set ($path, $interval)
636 Reconfigures the watcher, see the constructor above for details. Can
637 be called at any time.
638
639 $current_path = $w->path
640 $old_path = $w->path ($new_path)
641 Returns the previously set path and optionally set a new one.
642
643 $current_interval = $w->interval
644 $old_interval = $w->interval ($new_interval)
645 Returns the previously set interval and optionally set a new one.
646 Can be used to query the actual interval used.
647
648 IDLE WATCHERS - when you've got nothing better to do...
378 $w = EV::idle $callback 649 $w = EV::idle $callback
379 $w = EV::idle_ns $callback 650 $w = EV::idle_ns $callback
651 $w = $loop->idle ($callback)
652 $w = $loop->idle_ns ($callback)
380 Call the callback when there are no pending io, timer/periodic, 653 Call the callback when there are no other pending watchers of the
381 signal or child events, i.e. when the process is idle. 654 same or higher priority (excluding check, prepare and other idle
655 watchers of the same or lower priority, of course). They are called
656 idle watchers because when the watcher is the highest priority
657 pending event in the process, the process is considered to be idle
658 at that priority.
659
660 If you want a watcher that is only ever called when *no* other
661 events are outstanding you have to set the priority to "EV::MINPRI".
382 662
383 The process will not block as long as any idle watchers are active, 663 The process will not block as long as any idle watchers are active,
384 and they will be called repeatedly until stopped. 664 and they will be called repeatedly until stopped.
385 665
666 For example, if you have idle watchers at priority 0 and 1, and an
667 I/O watcher at priority 0, then the idle watcher at priority 1 and
668 the I/O watcher will always run when ready. Only when the idle
669 watcher at priority 1 is stopped and the I/O watcher at priority 0
670 is not pending with the 0-priority idle watcher be invoked.
671
386 The "idle_ns" variant doesn't start (activate) the newly created 672 The "idle_ns" variant doesn't start (activate) the newly created
387 watcher. 673 watcher.
388 674
675 PREPARE WATCHERS - customise your event loop!
389 $w = EV::prepare $callback 676 $w = EV::prepare $callback
390 $w = EV::prepare_ns $callback 677 $w = EV::prepare_ns $callback
678 $w = $loop->prepare ($callback)
679 $w = $loop->prepare_ns ($callback)
391 Call the callback just before the process would block. You can still 680 Call the callback just before the process would block. You can still
392 create/modify any watchers at this point. 681 create/modify any watchers at this point.
393 682
394 See the EV::check watcher, below, for explanations and an example. 683 See the EV::check watcher, below, for explanations and an example.
395 684
396 The "prepare_ns" variant doesn't start (activate) the newly created 685 The "prepare_ns" variant doesn't start (activate) the newly created
397 watcher. 686 watcher.
398 687
688 CHECK WATCHERS - customise your event loop even more!
399 $w = EV::check $callback 689 $w = EV::check $callback
400 $w = EV::check_ns $callback 690 $w = EV::check_ns $callback
691 $w = $loop->check ($callback)
692 $w = $loop->check_ns ($callback)
401 Call the callback just after the process wakes up again (after it 693 Call the callback just after the process wakes up again (after it
402 has gathered events), but before any other callbacks have been 694 has gathered events), but before any other callbacks have been
403 invoked. 695 invoked.
404 696
405 This is used to integrate other event-based software into the EV 697 This is used to integrate other event-based software into the EV
… …
414 # do nothing unless active 706 # do nothing unless active
415 $dispatcher->{_event_queue_h} 707 $dispatcher->{_event_queue_h}
416 or return; 708 or return;
417 709
418 # make the dispatcher handle any outstanding stuff 710 # make the dispatcher handle any outstanding stuff
711 ... not shown
419 712
420 # create an IO watcher for each and every socket 713 # create an I/O watcher for each and every socket
421 @snmp_watcher = ( 714 @snmp_watcher = (
422 (map { EV::io $_, EV::READ, sub { } } 715 (map { EV::io $_, EV::READ, sub { } }
423 keys %{ $dispatcher->{_descriptors} }), 716 keys %{ $dispatcher->{_descriptors} }),
717
718 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
719 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
720 0, sub { },
424 ); 721 );
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 }; 722 };
430 723
431 The callbacks are irrelevant, the only purpose of those watchers is 724 The callbacks are irrelevant (and are not even being called), the
432 to wake up the process as soon as one of those events occurs (socket 725 only purpose of those watchers is to wake up the process as soon as
433 readable, or timer timed out). The corresponding EV::check watcher 726 one of those events occurs (socket readable, or timer timed out).
434 will then clean up: 727 The corresponding EV::check watcher will then clean up:
435 728
436 our $snmp_check = EV::check sub { 729 our $snmp_check = EV::check sub {
437 # destroy all watchers 730 # destroy all watchers
438 @snmp_watcher = (); 731 @snmp_watcher = ();
439 732
440 # make the dispatcher handle any new stuff 733 # make the dispatcher handle any new stuff
734 ... not shown
441 }; 735 };
442 736
443 The callbacks of the created watchers will not be called as the 737 The callbacks of the created watchers will not be called as the
444 watchers are destroyed before this cna happen (remember EV::check 738 watchers are destroyed before this cna happen (remember EV::check
445 gets called first). 739 gets called first).
446 740
447 The "check_ns" variant doesn't start (activate) the newly created 741 The "check_ns" variant doesn't start (activate) the newly created
448 watcher. 742 watcher.
449 743
744 FORK WATCHERS - the audacity to resume the event loop after a fork
745 Fork watchers are called when a "fork ()" was detected. The invocation
746 is done before the event loop blocks next and before "check" watchers
747 are being called, and only in the child after the fork.
748
749 $w = EV::fork $callback
750 $w = EV::fork_ns $callback
751 $w = $loop->fork ($callback)
752 $w = $loop->fork_ns ($callback)
753 Call the callback before the event loop is resumed in the child
754 process after a fork.
755
756 The "fork_ns" variant doesn't start (activate) the newly created
757 watcher.
758
759 EMBED WATCHERS - when one backend isn't enough...
760 This is a rather advanced watcher type that lets you embed one event
761 loop into another (currently only IO events are supported in the
762 embedded loop, other types of watchers might be handled in a delayed or
763 incorrect fashion and must not be used).
764
765 See the libev documentation at
766 <http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code
767 _when_one_backend_> for more details.
768
769 In short, this watcher is most useful on BSD systems without working
770 kqueue to still be able to handle a large number of sockets:
771
772 my $socket_loop;
773
774 # check wether we use SELECT or POLL _and_ KQUEUE is supported
775 if (
776 (EV::backend & (EV::BACKEND_POLL | EV::BACKEND_SELECT))
777 && (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
778 ) {
779 # use kqueue for sockets
780 $socket_loop = new EV::Loop EV::BACKEND_KQUEUE | EV::FLAG_NOENV;
781 }
782
783 # use the default loop otherwise
784 $socket_loop ||= EV::default_loop;
785
786 $w = EV::embed $otherloop, $callback
787 $w = EV::embed_ns $otherloop, $callback
788 $w = $loop->embed ($otherloop, $callback)
789 $w = $loop->embed_ns ($otherloop, $callback)
790 Call the callback when the embedded event loop ($otherloop) has any
791 I/O activity. The $callback should alwas be specified as "undef" in
792 this version of EV, which means the embedded event loop will be
793 managed automatically.
794
795 The "embed_ns" variant doesn't start (activate) the newly created
796 watcher.
797
798 ASYNC WATCHERS - how to wake up another event loop
799 Async watchers are provided by EV, but have little use in perl directly,
800 as perl neither supports threads nor direct access to signal handlers or
801 other contexts where they could be of value.
802
803 It is, however, possible to use them from the XS level.
804
805 Please see the libev documentation for further details.
806
807 $w = EV::async $callback
808 $w = EV::async_ns $callback
809 $w->send
810 $bool = $w->async_pending
811
812PERL SIGNALS
813 While Perl signal handling (%SIG) is not affected by EV, the behaviour
814 with EV is as the same as any other C library: Perl-signals will only be
815 handled when Perl runs, which means your signal handler might be invoked
816 only the next time an event callback is invoked.
817
818 The solution is to use EV signal watchers (see "EV::signal"), which will
819 ensure proper operations with regards to other event watchers.
820
821 If you cannot do this for whatever reason, you can also force a watcher
822 to be called on every event loop iteration by installing a "EV::check"
823 watcher:
824
825 my $async_check = EV::check sub { };
826
827 This ensures that perl gets into control for a short time to handle any
828 pending signals, and also ensures (slightly) slower overall operation.
829
450THREADS 830THREADS
451 Threads are not supported by this in any way. Perl pseudo-threads is 831 Threads are not supported by this module in any way. Perl pseudo-threads
452 evil stuff and must die. 832 is evil stuff and must die. As soon as Perl gains real threads I will
833 work on thread support for it.
834
835FORK
836 Most of the "improved" event delivering mechanisms of modern operating
837 systems have quite a few problems with fork(2) (to put it bluntly: it is
838 not supported and usually destructive). Libev makes it possible to work
839 around this by having a function that recreates the kernel state after
840 fork in the child.
841
842 On non-win32 platforms, this module requires the pthread_atfork
843 functionality to do this automatically for you. This function is quite
844 buggy on most BSDs, though, so YMMV. The overhead for this is quite
845 negligible, because everything the function currently does is set a flag
846 that is checked only when the event loop gets used the next time, so
847 when you do fork but not use EV, the overhead is minimal.
848
849 On win32, there is no notion of fork so all this doesn't apply, of
850 course.
453 851
454SEE ALSO 852SEE ALSO
455 L<EV::DNS>, L<EV::AnyEvent>. 853 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
854 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
855 with EV), Net::SNMP::EV (asynchronous SNMP), AnyEvent for event-loop
856 agnostic and portable event driven programming.
456 857
457AUTHOR 858AUTHOR
458 Marc Lehmann <schmorp@schmorp.de> 859 Marc Lehmann <schmorp@schmorp.de>
459 http://home.schmorp.de/ 860 http://home.schmorp.de/
460 861

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