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Revision 1.6 by root, Thu Nov 1 17:32:39 2007 UTC vs.
Revision 1.15 by root, Wed Dec 5 14:06:50 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 $count = EV::loop_count
101 Return the number of times the event loop has polled for new events.
102 Sometiems useful as a generation counter.
103
104 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
105 This function rolls together an I/O and a timer watcher for a single
106 one-shot event without the need for managing a watcher object.
107
108 If $fh_or_undef is a filehandle or file descriptor, then $events
109 must be a bitset containing either "EV::READ", "EV::WRITE" or
110 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
111 wait for. If you do not want to wait for some I/O event, specify
112 "undef" for $fh_or_undef and 0 for $events).
113
114 If timeout is "undef" or negative, then there will be no timeout.
115 Otherwise a EV::timer with this value will be started.
116
117 When an error occurs or either the timeout or I/O watcher triggers,
118 then the callback will be called with the received event set (in
119 general you can expect it to be a combination of "EV:ERROR",
120 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
121
122 EV::once doesn't return anything: the watchers stay active till
123 either of them triggers, then they will be stopped and freed, and
124 the callback invoked.
125
126 WATCHER OBJECTS
94 A watcher is an object that gets created to record your interest in some 127 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, 128 event. For instance, if you want to wait for STDIN to become readable,
96 you would create an EV::io watcher for that: 129 you would create an EV::io watcher for that:
97 130
98 my $watcher = EV::io *STDIN, EV::READ, sub { 131 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 148 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 149 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. 150 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
118 151
119 Please note that a watcher will automatically be stopped when the 152 Please note that a watcher will automatically be stopped when the
120 watcher object is returned, so you *need* to keep the watcher objects 153 watcher object is destroyed, so you *need* to keep the watcher objects
121 returned by the constructors. 154 returned by the constructors.
122 155
123 WATCHER TYPES 156 Also, all methods changing some aspect of a watcher (->set, ->priority,
124 Now lets move to the existing watcher types and asociated methods. 157 ->fh and so on) automatically stop and start it again if it is active,
158 which means pending events get lost.
125 159
126 The following methods are available for all watchers. Then followes a 160 COMMON WATCHER METHODS
127 description of each watcher constructor (EV::io, EV::timer, 161 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).
130 162
131 $w->start 163 $w->start
132 Starts a watcher if it isn't active already. Does nothing to an 164 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 165 already active watcher. By default, all watchers start out in the
134 active state (see the description of the "_ns" variants if you need 166 active state (see the description of the "_ns" variants if you need
… …
141 not. 173 not.
142 174
143 $bool = $w->is_active 175 $bool = $w->is_active
144 Returns true if the watcher is active, false otherwise. 176 Returns true if the watcher is active, false otherwise.
145 177
178 $current_data = $w->data
179 $old_data = $w->data ($new_data)
180 Queries a freely usable data scalar on the watcher and optionally
181 changes it. This is a way to associate custom data with a watcher:
182
183 my $w = EV::timer 60, 0, sub {
184 warn $_[0]->data;
185 };
186 $w->data ("print me!");
187
146 $current_cb = $w->cb 188 $current_cb = $w->cb
147 $old_cb = $w->cb ($new_cb) 189 $old_cb = $w->cb ($new_cb)
148 Queries the callback on the watcher and optionally changes it. You 190 Queries the callback on the watcher and optionally changes it. You
149 cna do this at any time. 191 can do this at any time without the watcher restarting.
192
193 $current_priority = $w->priority
194 $old_priority = $w->priority ($new_priority)
195 Queries the priority on the watcher and optionally changes it.
196 Pending watchers with higher priority will be invoked first. The
197 valid range of priorities lies between EV::MAXPRI (default 2) and
198 EV::MINPRI (default -2). If the priority is outside this range it
199 will automatically be normalised to the nearest valid priority.
200
201 The default priority of any newly-created watcher is 0.
202
203 Note that the priority semantics have not yet been fleshed out and
204 are subject to almost certain change.
150 205
151 $w->trigger ($revents) 206 $w->trigger ($revents)
152 Call the callback *now* with the given event mask. 207 Call the callback *now* with the given event mask.
153 208
209 $previous_state = $w->keepalive ($bool)
210 Normally, "EV::loop" will return when there are no active watchers
211 (which is a "deadlock" because no progress can be made anymore).
212 This is convinient because it allows you to start your watchers (and
213 your jobs), call "EV::loop" once and when it returns you know that
214 all your jobs are finished (or they forgot to register some watchers
215 for their task :).
216
217 Sometimes, however, this gets in your way, for example when you the
218 module that calls "EV::loop" (usually the main program) is not the
219 same module as a long-living watcher (for example a DNS client
220 module written by somebody else even). Then you might want any
221 outstanding requests to be handled, but you would not want to keep
222 "EV::loop" from returning just because you happen to have this
223 long-running UDP port watcher.
224
225 In this case you can clear the keepalive status, which means that
226 even though your watcher is active, it won't keep "EV::loop" from
227 returning.
228
229 The initial value for keepalive is true (enabled), and you cna
230 change it any time.
231
232 Example: Register an IO watcher for some UDP socket but do not keep
233 the event loop from running just because of that watcher.
234
235 my $udp_socket = ...
236 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
237 $udp_watcher->keepalive (0);
238
239 WATCHER TYPES
240 Each of the following subsections describes a single watcher type.
241
242 IO WATCHERS - is this file descriptor readable or writable?
154 $w = EV::io $fileno_or_fh, $eventmask, $callback 243 $w = EV::io $fileno_or_fh, $eventmask, $callback
155 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 244 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
156 As long as the returned watcher object is alive, call the $callback 245 As long as the returned watcher object is alive, call the $callback
157 when the events specified in $eventmask. 246 when at least one of events specified in $eventmask occurs.
158 247
159 The $eventmask can be one or more of these constants ORed together: 248 The $eventmask can be one or more of these constants ORed together:
160 249
161 EV::READ wait until read() wouldn't block anymore 250 EV::READ wait until read() wouldn't block anymore
162 EV::WRITE wait until write() wouldn't block anymore 251 EV::WRITE wait until write() wouldn't block anymore
… …
174 263
175 $current_eventmask = $w->events 264 $current_eventmask = $w->events
176 $old_eventmask = $w->events ($new_eventmask) 265 $old_eventmask = $w->events ($new_eventmask)
177 Returns the previously set event mask and optionally set a new one. 266 Returns the previously set event mask and optionally set a new one.
178 267
268 TIMER WATCHERS - relative and optionally repeating timeouts
179 $w = EV::timer $after, $repeat, $callback 269 $w = EV::timer $after, $repeat, $callback
180 $w = EV::timer_ns $after, $repeat, $callback 270 $w = EV::timer_ns $after, $repeat, $callback
181 Calls the callback after $after seconds. If $repeat is non-zero, the 271 Calls the callback after $after seconds (which may be fractional).
182 timer will be restarted (with the $repeat value as $after) after the 272 If $repeat is non-zero, the timer will be restarted (with the
183 callback returns. 273 $repeat value as $after) after the callback returns.
184 274
185 This means that the callback would be called roughly after $after 275 This means that the callback would be called roughly after $after
186 seconds, and then every $repeat seconds. "Roughly" because the time 276 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 277 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. 278 event loop iteration, and might drift in other cases. If that isn't
279 acceptable, look at EV::periodic, which can provide long-term stable
280 timers.
189 281
190 The timer is based on a monotonic clock, that is if somebody is 282 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 283 sitting in front of the machine while the timer is running and
192 changes the system clock, the timer will nevertheless run (roughly) 284 changes the system clock, the timer will nevertheless run (roughly)
193 the same time. 285 the same time.
194 286
195 The "timer_ns" variant doesn't start (activate) the newly created 287 The "timer_ns" variant doesn't start (activate) the newly created
196 watcher. 288 watcher.
197 289
198 $w->set ($after, $repeat) 290 $w->set ($after, $repeat)
199 Reconfigures the watcher, see the constructor above for details. Can 291 Reconfigures the watcher, see the constructor above for details. Can
200 be at any time. 292 be called at any time.
201 293
202 $w->again 294 $w->again
203 Similar to the "start" method, but has special semantics for 295 Similar to the "start" method, but has special semantics for
204 repeating timers: 296 repeating timers:
205 297
298 If the timer is active and non-repeating, it will be stopped.
299
206 If the timer is active and repeating, reset the timeout to occur 300 If the timer is active and repeating, reset the timeout to occur
207 $repeat seconds after now. 301 $repeat seconds after now.
208 302
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. 303 If the timer is inactive and repeating, start it using the repeat
304 value.
212 305
213 Otherwise do nothing. 306 Otherwise do nothing.
214 307
215 This behaviour is useful when you have a timeout for some IO 308 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 309 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" 310 and $repeat, and then, in the read/write watcher, run the "again"
218 method on the timeout. 311 method on the timeout.
219 312
313 PERIODIC WATCHERS - to cron or not to cron?
220 $w = EV::periodic $at, $interval, $callback 314 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
221 $w = EV::periodic_ns $at, $interval, $callback 315 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
222 Similar to EV::timer, but the time is given as an absolute point in 316 Similar to EV::timer, but is not based on relative timeouts but on
223 time ($at), plus an optional $interval. 317 absolute times. Apart from creating "simple" timers that trigger
318 "at" the specified time, it can also be used for non-drifting
319 absolute timers and more complex, cron-like, setups that are not
320 adversely affected by time jumps (i.e. when the system clock is
321 changed by explicit date -s or other means such as ntpd). It is also
322 the most complex watcher type in EV.
224 323
225 If the $interval is zero, then the callback will be called at the 324 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.
228 325
229 If the $interval is nonzero, then the watcher will always be 326 * absolute timer ($interval = $reschedule_cb = 0)
230 scheduled to time out at the next "$at + N * $interval" time. 327 This time simply fires at the wallclock time $at and doesn't
328 repeat. It will not adjust when a time jump occurs, that is, if
329 it is to be run at January 1st 2011 then it will run when the
330 system time reaches or surpasses this time.
231 331
232 This can be used to schedule a callback to run at very regular 332 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
233 intervals, as long as the processing time is less then the interval 333 In this mode the watcher will always be scheduled to time out at
234 (otherwise obviously events will be skipped). 334 the next "$at + N * $interval" time (for some integer N) and
335 then repeat, regardless of any time jumps.
235 336
337 This can be used to create timers that do not drift with respect
338 to system time:
339
340 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
341
342 That doesn't mean there will always be 3600 seconds in between
343 triggers, but only that the the clalback will be called when the
344 system time shows a full hour (UTC).
345
236 Another way to think about it (for the mathematically inclined) is 346 Another way to think about it (for the mathematically inclined)
237 that EV::periodic will try to run the callback at the next possible 347 is that EV::periodic will try to run the callback in this mode
238 time where "$time = $at (mod $interval)", regardless of any time 348 at the next possible time where "$time = $at (mod $interval)",
239 jumps. 349 regardless of any time jumps.
240 350
241 This periodic timer is based on "wallclock time", that is, if the 351 * manual reschedule mode ($reschedule_cb = coderef)
242 clock changes ("ntp", "date -s" etc.), then the timer will 352 In this mode $interval and $at are both being ignored. Instead,
243 nevertheless run at the specified time. This means it will never 353 each time the periodic watcher gets scheduled, the reschedule
244 drift (it might jitter, but it will not drift). 354 callback ($reschedule_cb) will be called with the watcher as
355 first, and the current time as second argument.
356
357 *This callback MUST NOT stop or destroy this or any other
358 periodic watcher, ever*. If you need to stop it, return 1e30 and
359 stop it afterwards.
360
361 It must return the next time to trigger, based on the passed
362 time value (that is, the lowest time value larger than to the
363 second argument). It will usually be called just before the
364 callback will be triggered, but might be called at other times,
365 too.
366
367 This can be used to create very complex timers, such as a timer
368 that triggers on each midnight, local time (actually 24 hours
369 after the last midnight, to keep the example simple. If you know
370 a way to do it correctly in about the same space (without
371 requiring elaborate modules), drop me a note :):
372
373 my $daily = EV::periodic 0, 0, sub {
374 my ($w, $now) = @_;
375
376 use Time::Local ();
377 my (undef, undef, undef, $d, $m, $y) = localtime $now;
378 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
379 }, sub {
380 print "it's midnight or likely shortly after, now\n";
381 };
245 382
246 The "periodic_ns" variant doesn't start (activate) the newly created 383 The "periodic_ns" variant doesn't start (activate) the newly created
247 watcher. 384 watcher.
248 385
249 $w->set ($at, $interval) 386 $w->set ($at, $interval, $reschedule_cb)
250 Reconfigures the watcher, see the constructor above for details. Can 387 Reconfigures the watcher, see the constructor above for details. Can
251 be at any time. 388 be called at any time.
252 389
390 $w->again
391 Simply stops and starts the watcher again.
392
393 SIGNAL WATCHERS - signal me when a signal gets signalled!
253 $w = EV::signal $signal, $callback 394 $w = EV::signal $signal, $callback
254 $w = EV::signal_ns $signal, $callback 395 $w = EV::signal_ns $signal, $callback
255 Call the callback when $signal is received (the signal can be 396 Call the callback when $signal is received (the signal can be
256 specified by number or by name, just as with kill or %SIG). 397 specified by number or by name, just as with "kill" or %SIG).
257 398
258 EV will grab the signal for the process (the kernel only allows one 399 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 400 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 401 watcher, and removes it again when you stop it. Perl does the same
261 when you add/remove callbacks to %SIG, so watch out. 402 when you add/remove callbacks to %SIG, so watch out.
… …
265 The "signal_ns" variant doesn't start (activate) the newly created 406 The "signal_ns" variant doesn't start (activate) the newly created
266 watcher. 407 watcher.
267 408
268 $w->set ($signal) 409 $w->set ($signal)
269 Reconfigures the watcher, see the constructor above for details. Can 410 Reconfigures the watcher, see the constructor above for details. Can
270 be at any time. 411 be called at any time.
271 412
413 $current_signum = $w->signal
414 $old_signum = $w->signal ($new_signal)
415 Returns the previously set signal (always as a number not name) and
416 optionally set a new one.
417
418 CHILD WATCHERS - watch out for process status changes
272 $w = EV::child $pid, $callback 419 $w = EV::child $pid, $callback
273 $w = EV::child_ns $pid, $callback 420 $w = EV::child_ns $pid, $callback
274 Call the callback when a status change for pid $pid (or any pid if 421 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 422 $pid is 0) has been received. More precisely: when the process
276 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 423 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
277 for all changed/zombie children and call the callback. 424 for all changed/zombie children and call the callback.
278 425
279 Unlike all other callbacks, this callback will be called with an 426 It is valid (and fully supported) to install a child watcher after a
280 additional third argument which is the exit status. See the 427 child has exited but before the event loop has started its next
281 "waitpid" function for details. 428 iteration (for example, first you "fork", then the new child process
429 might exit, and only then do you install a child watcher in the
430 parent for the new pid).
282 431
432 You can access both exit (or tracing) status and pid by using the
433 "rstatus" and "rpid" methods on the watcher object.
434
283 You can have as many pid watchers per pid as you want. 435 You can have as many pid watchers per pid as you want, they will all
436 be called.
284 437
285 The "child_ns" variant doesn't start (activate) the newly created 438 The "child_ns" variant doesn't start (activate) the newly created
286 watcher. 439 watcher.
287 440
288 $w->set ($pid) 441 $w->set ($pid)
289 Reconfigures the watcher, see the constructor above for details. Can 442 Reconfigures the watcher, see the constructor above for details. Can
290 be at any time. 443 be called at any time.
291 444
445 $current_pid = $w->pid
446 $old_pid = $w->pid ($new_pid)
447 Returns the previously set process id and optionally set a new one.
448
449 $exit_status = $w->rstatus
450 Return the exit/wait status (as returned by waitpid, see the waitpid
451 entry in perlfunc).
452
453 $pid = $w->rpid
454 Return the pid of the awaited child (useful when you have installed
455 a watcher for all pids).
456
457 STAT WATCHERS - did the file attributes just change?
458 $w = EV::stat $path, $interval, $callback
459 $w = EV::stat_ns $path, $interval, $callback
460 Call the callback when a file status change has been detected on
461 $path. The $path does not need to exist, changing from "path exists"
462 to "path does not exist" is a status change like any other.
463
464 The $interval is a recommended polling interval for systems where
465 OS-supported change notifications don't exist or are not supported.
466 If you use 0 then an unspecified default is used (which is highly
467 recommended!), which is to be expected to be around five seconds
468 usually.
469
470 This watcher type is not meant for massive numbers of stat watchers,
471 as even with OS-supported change notifications, this can be
472 resource-intensive.
473
474 The "stat_ns" variant doesn't start (activate) the newly created
475 watcher.
476
477 ... = $w->stat
478 This call is very similar to the perl "stat" built-in: It stats
479 (using "lstat") the path specified in the watcher and sets perls
480 stat cache (as well as EV's idea of the current stat values) to the
481 values found.
482
483 In scalar context, a boolean is return indicating success or failure
484 of the stat. In list context, the same 13-value list as with stat is
485 returned (except that the blksize and blocks fields are not
486 reliable).
487
488 In the case of an error, errno is set to "ENOENT" (regardless of the
489 actual error value) and the "nlink" value is forced to zero (if the
490 stat was successful then nlink is guaranteed to be non-zero).
491
492 See also the next two entries for more info.
493
494 ... = $w->attr
495 Just like "$w->stat", but without the initial stat'ing: this returns
496 the values most recently detected by EV. See the next entry for more
497 info.
498
499 ... = $w->prev
500 Just like "$w->stat", but without the initial stat'ing: this returns
501 the previous set of values, before the change.
502
503 That is, when the watcher callback is invoked, "$w->prev" will be
504 set to the values found *before* a change was detected, while
505 "$w->attr" returns the values found leading to the change detection.
506 The difference (if any) between "prev" and "attr" is what triggered
507 the callback.
508
509 If you did something to the filesystem object and do not want to
510 trigger yet another change, you can call "stat" to update EV's idea
511 of what the current attributes are.
512
513 $w->set ($path, $interval)
514 Reconfigures the watcher, see the constructor above for details. Can
515 be called at any time.
516
517 $current_path = $w->path
518 $old_path = $w->path ($new_path)
519 Returns the previously set path and optionally set a new one.
520
521 $current_interval = $w->interval
522 $old_interval = $w->interval ($new_interval)
523 Returns the previously set interval and optionally set a new one.
524 Can be used to query the actual interval used.
525
526 IDLE WATCHERS - when you've got nothing better to do...
292 $w = EV::idle $callback 527 $w = EV::idle $callback
293 $w = EV::idle_ns $callback 528 $w = EV::idle_ns $callback
294 Call the callback when there are no pending io, timer/periodic, 529 Call the callback when there are no pending io, timer/periodic,
295 signal or child events, i.e. when the process is idle. 530 signal or child events, i.e. when the process is idle.
296 531
… …
298 and they will be called repeatedly until stopped. 533 and they will be called repeatedly until stopped.
299 534
300 The "idle_ns" variant doesn't start (activate) the newly created 535 The "idle_ns" variant doesn't start (activate) the newly created
301 watcher. 536 watcher.
302 537
538 PREPARE WATCHERS - customise your event loop!
303 $w = EV::prepare $callback 539 $w = EV::prepare $callback
304 $w = EV::prepare_ns $callback 540 $w = EV::prepare_ns $callback
305 Call the callback just before the process would block. You can still 541 Call the callback just before the process would block. You can still
306 create/modify any watchers at this point. 542 create/modify any watchers at this point.
307 543
308 See the EV::check watcher, below, for explanations and an example. 544 See the EV::check watcher, below, for explanations and an example.
309 545
310 The "prepare_ns" variant doesn't start (activate) the newly created 546 The "prepare_ns" variant doesn't start (activate) the newly created
311 watcher. 547 watcher.
312 548
549 CHECK WATCHERS - customise your event loop even more!
313 $w = EV::check $callback 550 $w = EV::check $callback
314 $w = EV::check_ns $callback 551 $w = EV::check_ns $callback
315 Call the callback just after the process wakes up again (after it 552 Call the callback just after the process wakes up again (after it
316 has gathered events), but before any other callbacks have been 553 has gathered events), but before any other callbacks have been
317 invoked. 554 invoked.
… …
328 # do nothing unless active 565 # do nothing unless active
329 $dispatcher->{_event_queue_h} 566 $dispatcher->{_event_queue_h}
330 or return; 567 or return;
331 568
332 # make the dispatcher handle any outstanding stuff 569 # make the dispatcher handle any outstanding stuff
570 ... not shown
333 571
334 # create an IO watcher for each and every socket 572 # create an IO watcher for each and every socket
335 @snmp_watcher = ( 573 @snmp_watcher = (
336 (map { EV::io $_, EV::READ, sub { } } 574 (map { EV::io $_, EV::READ, sub { } }
337 keys %{ $dispatcher->{_descriptors} }), 575 keys %{ $dispatcher->{_descriptors} }),
576
577 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
578 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
579 0, sub { },
338 ); 580 );
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 }; 581 };
344 582
345 The callbacks are irrelevant, the only purpose of those watchers is 583 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 584 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 585 one of those events occurs (socket readable, or timer timed out).
348 will then clean up: 586 The corresponding EV::check watcher will then clean up:
349 587
350 our $snmp_check = EV::check sub { 588 our $snmp_check = EV::check sub {
351 # destroy all watchers 589 # destroy all watchers
352 @snmp_watcher = (); 590 @snmp_watcher = ();
353 591
354 # make the dispatcher handle any new stuff 592 # make the dispatcher handle any new stuff
593 ... not shown
355 }; 594 };
356 595
357 The callbacks of the created watchers will not be called as the 596 The callbacks of the created watchers will not be called as the
358 watchers are destroyed before this cna happen (remember EV::check 597 watchers are destroyed before this cna happen (remember EV::check
359 gets called first). 598 gets called first).
360 599
361 The "check_ns" variant doesn't start (activate) the newly created 600 The "check_ns" variant doesn't start (activate) the newly created
362 watcher. 601 watcher.
363 602
603 FORK WATCHERS - the audacity to resume the event loop after a fork
604 Fork watchers are called when a "fork ()" was detected. The invocation
605 is done before the event loop blocks next and before "check" watchers
606 are being called, and only in the child after the fork.
607
608 $w = EV::fork $callback
609 $w = EV::fork_ns $callback
610 Call the callback before the event loop is resumed in the child
611 process after a fork.
612
613 The "fork_ns" variant doesn't start (activate) the newly created
614 watcher.
615
364THREADS 616THREADS
365 Threads are not supported by this in any way. Perl pseudo-threads is 617 Threads are not supported by this module in any way. Perl pseudo-threads
366 evil stuff and must die. 618 is evil stuff and must die. As soon as Perl gains real threads I will
619 work on thread support for it.
620
621FORK
622 Most of the "improved" event delivering mechanisms of modern operating
623 systems have quite a few problems with fork(2) (to put it bluntly: it is
624 not supported and usually destructive). Libev makes it possible to work
625 around this by having a function that recreates the kernel state after
626 fork in the child.
627
628 On non-win32 platforms, this module requires the pthread_atfork
629 functionality to do this automatically for you. This function is quite
630 buggy on most BSDs, though, so YMMV. The overhead for this is quite
631 negligible, because everything the function currently does is set a flag
632 that is checked only when the event loop gets used the next time, so
633 when you do fork but not use EV, the overhead is minimal.
634
635 On win32, there is no notion of fork so all this doesn't apply, of
636 course.
367 637
368SEE ALSO 638SEE ALSO
369 L<EV::DNS>, L<EV::AnyEvent>. 639 EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event
640 loop), Coro::EV (efficient coroutines with EV).
370 641
371AUTHOR 642AUTHOR
372 Marc Lehmann <schmorp@schmorp.de> 643 Marc Lehmann <schmorp@schmorp.de>
373 http://home.schmorp.de/ 644 http://home.schmorp.de/
374 645

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