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Revision 1.6 by root, Thu Nov 1 17:32:39 2007 UTC vs.
Revision 1.14 by root, Wed Nov 28 19:22:16 2007 UTC

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, 1, sub { 14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 1)"; 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, 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 23
24 # IO 24 # IO
25 25
26 my $w = EV::io *STDIN, EV::READ, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks get the watcher object and event mask 27 my ($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 my $w = EV::signal 3, sub {
38 warn "sigquit received (this is GNU/Linux, right?)\n";
39 };
40
41 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
42 38
43 my $w = EV::child 666, sub { 39 my $w = EV::child 666, sub {
44 my ($w, $revents, $status) = @_; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus;
42 };
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";
45 }; 48 };
46 49
47 # MAINLOOP 50 # MAINLOOP
48 EV::loop; # loop until EV::loop_done is called 51 EV::loop; # loop until EV::unloop is called or all watchers stop
49 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
50 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
51 54
52DESCRIPTION 55DESCRIPTION
53 This module provides an interface to libev 56 This module provides an interface to libev
54 (<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://cvs.schmorp.de/libev/ev.html>) for more subtle
60 details on watcher semantics or some discussion on the available
61 backends, or how to force a specific backend with "LIBEV_FLAGS".
55 62
56BASIC INTERFACE 63BASIC INTERFACE
57 $EV::DIED 64 $EV::DIED
58 Must contain a reference to a function that is called when a 65 Must contain a reference to a function that is called when a
59 callback throws an exception (with $@ containing thr error). The 66 callback throws an exception (with $@ containing thr error). The
67 $time = EV::now 74 $time = EV::now
68 Returns the time the last event loop iteration has been started. 75 Returns the time the last event loop iteration has been started.
69 This is the time that (relative) timers are based on, and refering 76 This is the time that (relative) timers are based on, and refering
70 to it is usually faster then calling EV::time. 77 to it is usually faster then calling EV::time.
71 78
72 $method = EV::ev_method 79 $method = EV::method
73 Returns an integer describing the backend used by libev 80 Returns an integer describing the backend used by libev
74 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 81 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
75 82
76 EV::loop [$flags] 83 EV::loop [$flags]
77 Begin checking for events and calling callbacks. It returns when a 84 Begin checking for events and calling callbacks. It returns when a
78 callback calls EV::loop_done. 85 callback calls EV::unloop.
79 86
80 The $flags argument can be one of the following: 87 The $flags argument can be one of the following:
81 88
82 0 as above 89 0 as above
83 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 90 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
84 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 91 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
85 92
86 EV::loop_done [$how] 93 EV::unloop [$how]
87 When called with no arguments or an argument of 1, makes the 94 When called with no arguments or an argument of EV::UNLOOP_ONE,
88 innermost call to EV::loop return. 95 makes the innermost call to EV::loop return.
89 96
90 When called with an agrument of 2, all calls to EV::loop will return 97 When called with an argument of EV::UNLOOP_ALL, all calls to
91 as fast as possible. 98 EV::loop will return as fast as possible.
92 99
93 WATCHER 100 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
101 This function rolls together an I/O and a timer watcher for a single
102 one-shot event without the need for managing a watcher object.
103
104 If $fh_or_undef is a filehandle or file descriptor, then $events
105 must be a bitset containing either "EV::READ", "EV::WRITE" or
106 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
107 wait for. If you do not want to wait for some I/O event, specify
108 "undef" for $fh_or_undef and 0 for $events).
109
110 If timeout is "undef" or negative, then there will be no timeout.
111 Otherwise a EV::timer with this value will be started.
112
113 When an error occurs or either the timeout or I/O watcher triggers,
114 then the callback will be called with the received event set (in
115 general you can expect it to be a combination of "EV:ERROR",
116 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
117
118 EV::once doesn't return anything: the watchers stay active till
119 either of them triggers, then they will be stopped and freed, and
120 the callback invoked.
121
122 WATCHER OBJECTS
94 A watcher is an object that gets created to record your interest in some 123 A watcher is an object that gets created to record your interest in some
95 event. For instance, if you want to wait for STDIN to become readable, 124 event. For instance, if you want to wait for STDIN to become readable,
96 you would create an EV::io watcher for that: 125 you would create an EV::io watcher for that:
97 126
98 my $watcher = EV::io *STDIN, EV::READ, sub { 127 my $watcher = EV::io *STDIN, EV::READ, sub {
115 In the rare case where one wants to create a watcher but not start it at 144 In the rare case where one wants to create a watcher but not start it at
116 the same time, each constructor has a variant with a trailing "_ns" in 145 the same time, each constructor has a variant with a trailing "_ns" in
117 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on. 146 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
118 147
119 Please note that a watcher will automatically be stopped when the 148 Please note that a watcher will automatically be stopped when the
120 watcher object is returned, so you *need* to keep the watcher objects 149 watcher object is destroyed, so you *need* to keep the watcher objects
121 returned by the constructors. 150 returned by the constructors.
122 151
123 WATCHER TYPES 152 Also, all methods changing some aspect of a watcher (->set, ->priority,
124 Now lets move to the existing watcher types and asociated methods. 153 ->fh and so on) automatically stop and start it again if it is active,
154 which means pending events get lost.
125 155
126 The following methods are available for all watchers. Then followes a 156 COMMON WATCHER METHODS
127 description of each watcher constructor (EV::io, EV::timer, 157 This section lists methods common to all watchers.
128 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
129 EV::check), followed by any type-specific methods (if any).
130 158
131 $w->start 159 $w->start
132 Starts a watcher if it isn't active already. Does nothing to an 160 Starts a watcher if it isn't active already. Does nothing to an
133 already active watcher. By default, all watchers start out in the 161 already active watcher. By default, all watchers start out in the
134 active state (see the description of the "_ns" variants if you need 162 active state (see the description of the "_ns" variants if you need
141 not. 169 not.
142 170
143 $bool = $w->is_active 171 $bool = $w->is_active
144 Returns true if the watcher is active, false otherwise. 172 Returns true if the watcher is active, false otherwise.
145 173
174 $current_data = $w->data
175 $old_data = $w->data ($new_data)
176 Queries a freely usable data scalar on the watcher and optionally
177 changes it. This is a way to associate custom data with a watcher:
178
179 my $w = EV::timer 60, 0, sub {
180 warn $_[0]->data;
181 };
182 $w->data ("print me!");
183
146 $current_cb = $w->cb 184 $current_cb = $w->cb
147 $old_cb = $w->cb ($new_cb) 185 $old_cb = $w->cb ($new_cb)
148 Queries the callback on the watcher and optionally changes it. You 186 Queries the callback on the watcher and optionally changes it. You
149 cna do this at any time. 187 can do this at any time without the watcher restarting.
188
189 $current_priority = $w->priority
190 $old_priority = $w->priority ($new_priority)
191 Queries the priority on the watcher and optionally changes it.
192 Pending watchers with higher priority will be invoked first. The
193 valid range of priorities lies between EV::MAXPRI (default 2) and
194 EV::MINPRI (default -2). If the priority is outside this range it
195 will automatically be normalised to the nearest valid priority.
196
197 The default priority of any newly-created watcher is 0.
198
199 Note that the priority semantics have not yet been fleshed out and
200 are subject to almost certain change.
150 201
151 $w->trigger ($revents) 202 $w->trigger ($revents)
152 Call the callback *now* with the given event mask. 203 Call the callback *now* with the given event mask.
153 204
205 $previous_state = $w->keepalive ($bool)
206 Normally, "EV::loop" will return when there are no active watchers
207 (which is a "deadlock" because no progress can be made anymore).
208 This is convinient because it allows you to start your watchers (and
209 your jobs), call "EV::loop" once and when it returns you know that
210 all your jobs are finished (or they forgot to register some watchers
211 for their task :).
212
213 Sometimes, however, this gets in your way, for example when you the
214 module that calls "EV::loop" (usually the main program) is not the
215 same module as a long-living watcher (for example a DNS client
216 module written by somebody else even). Then you might want any
217 outstanding requests to be handled, but you would not want to keep
218 "EV::loop" from returning just because you happen to have this
219 long-running UDP port watcher.
220
221 In this case you can clear the keepalive status, which means that
222 even though your watcher is active, it won't keep "EV::loop" from
223 returning.
224
225 The initial value for keepalive is true (enabled), and you cna
226 change it any time.
227
228 Example: Register an IO watcher for some UDP socket but do not keep
229 the event loop from running just because of that watcher.
230
231 my $udp_socket = ...
232 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
233 $udp_watcher->keepalive (0);
234
235 WATCHER TYPES
236 Each of the following subsections describes a single watcher type.
237
238 IO WATCHERS - is this file descriptor readable or writable?
154 $w = EV::io $fileno_or_fh, $eventmask, $callback 239 $w = EV::io $fileno_or_fh, $eventmask, $callback
155 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 240 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
156 As long as the returned watcher object is alive, call the $callback 241 As long as the returned watcher object is alive, call the $callback
157 when the events specified in $eventmask. 242 when at least one of events specified in $eventmask occurs.
158 243
159 The $eventmask can be one or more of these constants ORed together: 244 The $eventmask can be one or more of these constants ORed together:
160 245
161 EV::READ wait until read() wouldn't block anymore 246 EV::READ wait until read() wouldn't block anymore
162 EV::WRITE wait until write() wouldn't block anymore 247 EV::WRITE wait until write() wouldn't block anymore
174 259
175 $current_eventmask = $w->events 260 $current_eventmask = $w->events
176 $old_eventmask = $w->events ($new_eventmask) 261 $old_eventmask = $w->events ($new_eventmask)
177 Returns the previously set event mask and optionally set a new one. 262 Returns the previously set event mask and optionally set a new one.
178 263
264 TIMER WATCHERS - relative and optionally repeating timeouts
179 $w = EV::timer $after, $repeat, $callback 265 $w = EV::timer $after, $repeat, $callback
180 $w = EV::timer_ns $after, $repeat, $callback 266 $w = EV::timer_ns $after, $repeat, $callback
181 Calls the callback after $after seconds. If $repeat is non-zero, the 267 Calls the callback after $after seconds (which may be fractional).
182 timer will be restarted (with the $repeat value as $after) after the 268 If $repeat is non-zero, the timer will be restarted (with the
183 callback returns. 269 $repeat value as $after) after the callback returns.
184 270
185 This means that the callback would be called roughly after $after 271 This means that the callback would be called roughly after $after
186 seconds, and then every $repeat seconds. "Roughly" because the time 272 seconds, and then every $repeat seconds. The timer does his best not
187 of callback processing is not taken into account, so the timer will 273 to drift, but it will not invoke the timer more often then once per
188 slowly drift. If that isn't acceptable, look at EV::periodic. 274 event loop iteration, and might drift in other cases. If that isn't
275 acceptable, look at EV::periodic, which can provide long-term stable
276 timers.
189 277
190 The timer is based on a monotonic clock, that is if somebody is 278 The timer is based on a monotonic clock, that is, if somebody is
191 sitting in front of the machine while the timer is running and 279 sitting in front of the machine while the timer is running and
192 changes the system clock, the timer will nevertheless run (roughly) 280 changes the system clock, the timer will nevertheless run (roughly)
193 the same time. 281 the same time.
194 282
195 The "timer_ns" variant doesn't start (activate) the newly created 283 The "timer_ns" variant doesn't start (activate) the newly created
196 watcher. 284 watcher.
197 285
198 $w->set ($after, $repeat) 286 $w->set ($after, $repeat)
199 Reconfigures the watcher, see the constructor above for details. Can 287 Reconfigures the watcher, see the constructor above for details. Can
200 be at any time. 288 be called at any time.
201 289
202 $w->again 290 $w->again
203 Similar to the "start" method, but has special semantics for 291 Similar to the "start" method, but has special semantics for
204 repeating timers: 292 repeating timers:
205 293
294 If the timer is active and non-repeating, it will be stopped.
295
206 If the timer is active and repeating, reset the timeout to occur 296 If the timer is active and repeating, reset the timeout to occur
207 $repeat seconds after now. 297 $repeat seconds after now.
208 298
209 If the timer is active and non-repeating, it will be stopped.
210
211 If the timer is in active and repeating, start it. 299 If the timer is inactive and repeating, start it using the repeat
300 value.
212 301
213 Otherwise do nothing. 302 Otherwise do nothing.
214 303
215 This behaviour is useful when you have a timeout for some IO 304 This behaviour is useful when you have a timeout for some IO
216 operation. You create a timer object with the same value for $after 305 operation. You create a timer object with the same value for $after
217 and $repeat, and then, in the read/write watcher, run the "again" 306 and $repeat, and then, in the read/write watcher, run the "again"
218 method on the timeout. 307 method on the timeout.
219 308
309 PERIODIC WATCHERS - to cron or not to cron?
220 $w = EV::periodic $at, $interval, $callback 310 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
221 $w = EV::periodic_ns $at, $interval, $callback 311 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
222 Similar to EV::timer, but the time is given as an absolute point in 312 Similar to EV::timer, but is not based on relative timeouts but on
223 time ($at), plus an optional $interval. 313 absolute times. Apart from creating "simple" timers that trigger
314 "at" the specified time, it can also be used for non-drifting
315 absolute timers and more complex, cron-like, setups that are not
316 adversely affected by time jumps (i.e. when the system clock is
317 changed by explicit date -s or other means such as ntpd). It is also
318 the most complex watcher type in EV.
224 319
225 If the $interval is zero, then the callback will be called at the 320 It has three distinct "modes":
226 time $at if that is in the future, or as soon as possible if it is
227 in the past. It will not automatically repeat.
228 321
229 If the $interval is nonzero, then the watcher will always be 322 * absolute timer ($interval = $reschedule_cb = 0)
230 scheduled to time out at the next "$at + N * $interval" time. 323 This time simply fires at the wallclock time $at and doesn't
324 repeat. It will not adjust when a time jump occurs, that is, if
325 it is to be run at January 1st 2011 then it will run when the
326 system time reaches or surpasses this time.
231 327
232 This can be used to schedule a callback to run at very regular 328 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
233 intervals, as long as the processing time is less then the interval 329 In this mode the watcher will always be scheduled to time out at
234 (otherwise obviously events will be skipped). 330 the next "$at + N * $interval" time (for some integer N) and
331 then repeat, regardless of any time jumps.
235 332
333 This can be used to create timers that do not drift with respect
334 to system time:
335
336 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
337
338 That doesn't mean there will always be 3600 seconds in between
339 triggers, but only that the the clalback will be called when the
340 system time shows a full hour (UTC).
341
236 Another way to think about it (for the mathematically inclined) is 342 Another way to think about it (for the mathematically inclined)
237 that EV::periodic will try to run the callback at the next possible 343 is that EV::periodic will try to run the callback in this mode
238 time where "$time = $at (mod $interval)", regardless of any time 344 at the next possible time where "$time = $at (mod $interval)",
239 jumps. 345 regardless of any time jumps.
240 346
241 This periodic timer is based on "wallclock time", that is, if the 347 * manual reschedule mode ($reschedule_cb = coderef)
242 clock changes ("ntp", "date -s" etc.), then the timer will 348 In this mode $interval and $at are both being ignored. Instead,
243 nevertheless run at the specified time. This means it will never 349 each time the periodic watcher gets scheduled, the reschedule
244 drift (it might jitter, but it will not drift). 350 callback ($reschedule_cb) will be called with the watcher as
351 first, and the current time as second argument.
352
353 *This callback MUST NOT stop or destroy this or any other
354 periodic watcher, ever*. If you need to stop it, return 1e30 and
355 stop it afterwards.
356
357 It must return the next time to trigger, based on the passed
358 time value (that is, the lowest time value larger than to the
359 second argument). It will usually be called just before the
360 callback will be triggered, but might be called at other times,
361 too.
362
363 This can be used to create very complex timers, such as a timer
364 that triggers on each midnight, local time (actually 24 hours
365 after the last midnight, to keep the example simple. If you know
366 a way to do it correctly in about the same space (without
367 requiring elaborate modules), drop me a note :):
368
369 my $daily = EV::periodic 0, 0, sub {
370 my ($w, $now) = @_;
371
372 use Time::Local ();
373 my (undef, undef, undef, $d, $m, $y) = localtime $now;
374 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
375 }, sub {
376 print "it's midnight or likely shortly after, now\n";
377 };
245 378
246 The "periodic_ns" variant doesn't start (activate) the newly created 379 The "periodic_ns" variant doesn't start (activate) the newly created
247 watcher. 380 watcher.
248 381
249 $w->set ($at, $interval) 382 $w->set ($at, $interval, $reschedule_cb)
250 Reconfigures the watcher, see the constructor above for details. Can 383 Reconfigures the watcher, see the constructor above for details. Can
251 be at any time. 384 be called at any time.
252 385
386 $w->again
387 Simply stops and starts the watcher again.
388
389 SIGNAL WATCHERS - signal me when a signal gets signalled!
253 $w = EV::signal $signal, $callback 390 $w = EV::signal $signal, $callback
254 $w = EV::signal_ns $signal, $callback 391 $w = EV::signal_ns $signal, $callback
255 Call the callback when $signal is received (the signal can be 392 Call the callback when $signal is received (the signal can be
256 specified by number or by name, just as with kill or %SIG). 393 specified by number or by name, just as with "kill" or %SIG).
257 394
258 EV will grab the signal for the process (the kernel only allows one 395 EV will grab the signal for the process (the kernel only allows one
259 component to receive a signal at a time) when you start a signal 396 component to receive a signal at a time) when you start a signal
260 watcher, and removes it again when you stop it. Perl does the same 397 watcher, and removes it again when you stop it. Perl does the same
261 when you add/remove callbacks to %SIG, so watch out. 398 when you add/remove callbacks to %SIG, so watch out.
265 The "signal_ns" variant doesn't start (activate) the newly created 402 The "signal_ns" variant doesn't start (activate) the newly created
266 watcher. 403 watcher.
267 404
268 $w->set ($signal) 405 $w->set ($signal)
269 Reconfigures the watcher, see the constructor above for details. Can 406 Reconfigures the watcher, see the constructor above for details. Can
270 be at any time. 407 be called at any time.
271 408
409 $current_signum = $w->signal
410 $old_signum = $w->signal ($new_signal)
411 Returns the previously set signal (always as a number not name) and
412 optionally set a new one.
413
414 CHILD WATCHERS - watch out for process status changes
272 $w = EV::child $pid, $callback 415 $w = EV::child $pid, $callback
273 $w = EV::child_ns $pid, $callback 416 $w = EV::child_ns $pid, $callback
274 Call the callback when a status change for pid $pid (or any pid if 417 Call the callback when a status change for pid $pid (or any pid if
275 $pid is 0) has been received. More precisely: when the process 418 $pid is 0) has been received. More precisely: when the process
276 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 419 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
277 for all changed/zombie children and call the callback. 420 for all changed/zombie children and call the callback.
278 421
279 Unlike all other callbacks, this callback will be called with an 422 It is valid (and fully supported) to install a child watcher after a
280 additional third argument which is the exit status. See the 423 child has exited but before the event loop has started its next
281 "waitpid" function for details. 424 iteration (for example, first you "fork", then the new child process
425 might exit, and only then do you install a child watcher in the
426 parent for the new pid).
282 427
428 You can access both exit (or tracing) status and pid by using the
429 "rstatus" and "rpid" methods on the watcher object.
430
283 You can have as many pid watchers per pid as you want. 431 You can have as many pid watchers per pid as you want, they will all
432 be called.
284 433
285 The "child_ns" variant doesn't start (activate) the newly created 434 The "child_ns" variant doesn't start (activate) the newly created
286 watcher. 435 watcher.
287 436
288 $w->set ($pid) 437 $w->set ($pid)
289 Reconfigures the watcher, see the constructor above for details. Can 438 Reconfigures the watcher, see the constructor above for details. Can
290 be at any time. 439 be called at any time.
291 440
441 $current_pid = $w->pid
442 $old_pid = $w->pid ($new_pid)
443 Returns the previously set process id and optionally set a new one.
444
445 $exit_status = $w->rstatus
446 Return the exit/wait status (as returned by waitpid, see the waitpid
447 entry in perlfunc).
448
449 $pid = $w->rpid
450 Return the pid of the awaited child (useful when you have installed
451 a watcher for all pids).
452
453 STAT WATCHERS - did the file attributes just change?
454 $w = EV::stat $path, $interval, $callback
455 $w = EV::stat_ns $path, $interval, $callback
456 Call the callback when a file status change has been detected on
457 $path. The $path does not need to exist, changing from "path exists"
458 to "path does not exist" is a status change like any other.
459
460 The $interval is a recommended polling interval for systems where
461 OS-supported change notifications don't exist or are not supported.
462 If you use 0 then an unspecified default is used (which is highly
463 recommended!), which is to be expected to be around five seconds
464 usually.
465
466 This watcher type is not meant for massive numbers of stat watchers,
467 as even with OS-supported change notifications, this can be
468 resource-intensive.
469
470 The "stat_ns" variant doesn't start (activate) the newly created
471 watcher.
472
473 ... = $w->stat
474 This call is very similar to the perl "stat" built-in: It stats
475 (using "lstat") the path specified in the watcher and sets perls
476 stat cache (as well as EV's idea of the current stat values) to the
477 values found.
478
479 In scalar context, a boolean is return indicating success or failure
480 of the stat. In list context, the same 13-value list as with stat is
481 returned (except that the blksize and blocks fields are not
482 reliable).
483
484 In the case of an error, errno is set to "ENOENT" (regardless of the
485 actual error value) and the "nlink" value is forced to zero (if the
486 stat was successful then nlink is guaranteed to be non-zero).
487
488 See also the next two entries for more info.
489
490 ... = $w->attr
491 Just like "$w->stat", but without the initial stat'ing: this returns
492 the values most recently detected by EV. See the next entry for more
493 info.
494
495 ... = $w->prev
496 Just like "$w->stat", but without the initial stat'ing: this returns
497 the previous set of values, before the change.
498
499 That is, when the watcher callback is invoked, "$w->prev" will be
500 set to the values found *before* a change was detected, while
501 "$w->attr" returns the values found leading to the change detection.
502 The difference (if any) between "prev" and "attr" is what triggered
503 the callback.
504
505 If you did something to the filesystem object and do not want to
506 trigger yet another change, you can call "stat" to update EV's idea
507 of what the current attributes are.
508
509 $w->set ($path, $interval)
510 Reconfigures the watcher, see the constructor above for details. Can
511 be called at any time.
512
513 $current_path = $w->path
514 $old_path = $w->path ($new_path)
515 Returns the previously set path and optionally set a new one.
516
517 $current_interval = $w->interval
518 $old_interval = $w->interval ($new_interval)
519 Returns the previously set interval and optionally set a new one.
520 Can be used to query the actual interval used.
521
522 IDLE WATCHERS - when you've got nothing better to do...
292 $w = EV::idle $callback 523 $w = EV::idle $callback
293 $w = EV::idle_ns $callback 524 $w = EV::idle_ns $callback
294 Call the callback when there are no pending io, timer/periodic, 525 Call the callback when there are no pending io, timer/periodic,
295 signal or child events, i.e. when the process is idle. 526 signal or child events, i.e. when the process is idle.
296 527
298 and they will be called repeatedly until stopped. 529 and they will be called repeatedly until stopped.
299 530
300 The "idle_ns" variant doesn't start (activate) the newly created 531 The "idle_ns" variant doesn't start (activate) the newly created
301 watcher. 532 watcher.
302 533
534 PREPARE WATCHERS - customise your event loop!
303 $w = EV::prepare $callback 535 $w = EV::prepare $callback
304 $w = EV::prepare_ns $callback 536 $w = EV::prepare_ns $callback
305 Call the callback just before the process would block. You can still 537 Call the callback just before the process would block. You can still
306 create/modify any watchers at this point. 538 create/modify any watchers at this point.
307 539
308 See the EV::check watcher, below, for explanations and an example. 540 See the EV::check watcher, below, for explanations and an example.
309 541
310 The "prepare_ns" variant doesn't start (activate) the newly created 542 The "prepare_ns" variant doesn't start (activate) the newly created
311 watcher. 543 watcher.
312 544
545 CHECK WATCHERS - customise your event loop even more!
313 $w = EV::check $callback 546 $w = EV::check $callback
314 $w = EV::check_ns $callback 547 $w = EV::check_ns $callback
315 Call the callback just after the process wakes up again (after it 548 Call the callback just after the process wakes up again (after it
316 has gathered events), but before any other callbacks have been 549 has gathered events), but before any other callbacks have been
317 invoked. 550 invoked.
328 # do nothing unless active 561 # do nothing unless active
329 $dispatcher->{_event_queue_h} 562 $dispatcher->{_event_queue_h}
330 or return; 563 or return;
331 564
332 # make the dispatcher handle any outstanding stuff 565 # make the dispatcher handle any outstanding stuff
566 ... not shown
333 567
334 # create an IO watcher for each and every socket 568 # create an IO watcher for each and every socket
335 @snmp_watcher = ( 569 @snmp_watcher = (
336 (map { EV::io $_, EV::READ, sub { } } 570 (map { EV::io $_, EV::READ, sub { } }
337 keys %{ $dispatcher->{_descriptors} }), 571 keys %{ $dispatcher->{_descriptors} }),
572
573 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
574 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
575 0, sub { },
338 ); 576 );
339
340 # if there are any timeouts, also create a timer
341 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
342 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
343 }; 577 };
344 578
345 The callbacks are irrelevant, the only purpose of those watchers is 579 The callbacks are irrelevant (and are not even being called), the
346 to wake up the process as soon as one of those events occurs (socket 580 only purpose of those watchers is to wake up the process as soon as
347 readable, or timer timed out). The corresponding EV::check watcher 581 one of those events occurs (socket readable, or timer timed out).
348 will then clean up: 582 The corresponding EV::check watcher will then clean up:
349 583
350 our $snmp_check = EV::check sub { 584 our $snmp_check = EV::check sub {
351 # destroy all watchers 585 # destroy all watchers
352 @snmp_watcher = (); 586 @snmp_watcher = ();
353 587
354 # make the dispatcher handle any new stuff 588 # make the dispatcher handle any new stuff
589 ... not shown
355 }; 590 };
356 591
357 The callbacks of the created watchers will not be called as the 592 The callbacks of the created watchers will not be called as the
358 watchers are destroyed before this cna happen (remember EV::check 593 watchers are destroyed before this cna happen (remember EV::check
359 gets called first). 594 gets called first).
360 595
361 The "check_ns" variant doesn't start (activate) the newly created 596 The "check_ns" variant doesn't start (activate) the newly created
362 watcher. 597 watcher.
363 598
599 FORK WATCHERS - the audacity to resume the event loop after a fork
600 Fork watchers are called when a "fork ()" was detected. The invocation
601 is done before the event loop blocks next and before "check" watchers
602 are being called, and only in the child after the fork.
603
604 $w = EV::fork $callback
605 $w = EV::fork_ns $callback
606 Call the callback before the event loop is resumed in the child
607 process after a fork.
608
609 The "fork_ns" variant doesn't start (activate) the newly created
610 watcher.
611
364THREADS 612THREADS
365 Threads are not supported by this in any way. Perl pseudo-threads is 613 Threads are not supported by this module in any way. Perl pseudo-threads
366 evil stuff and must die. 614 is evil stuff and must die. As soon as Perl gains real threads I will
615 work on thread support for it.
616
617FORK
618 Most of the "improved" event delivering mechanisms of modern operating
619 systems have quite a few problems with fork(2) (to put it bluntly: it is
620 not supported and usually destructive). Libev makes it possible to work
621 around this by having a function that recreates the kernel state after
622 fork in the child.
623
624 On non-win32 platforms, this module requires the pthread_atfork
625 functionality to do this automatically for you. This function is quite
626 buggy on most BSDs, though, so YMMV. The overhead for this is quite
627 negligible, because everything the function currently does is set a flag
628 that is checked only when the event loop gets used the next time, so
629 when you do fork but not use EV, the overhead is minimal.
630
631 On win32, there is no notion of fork so all this doesn't apply, of
632 course.
367 633
368SEE ALSO 634SEE ALSO
369 L<EV::DNS>, L<EV::AnyEvent>. 635 EV::DNS.
370 636
371AUTHOR 637AUTHOR
372 Marc Lehmann <schmorp@schmorp.de> 638 Marc Lehmann <schmorp@schmorp.de>
373 http://home.schmorp.de/ 639 http://home.schmorp.de/
374 640

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