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1NAME 1NAME
2 EV - perl interface to libevent, monkey.org/~provos/libevent/ 2 EV - perl interface to libev, a high performance full-featured event
3 loop
3 4
4SYNOPSIS 5SYNOPSIS
5 use EV; 6 use EV;
6 7
7 # TIMER 8 # TIMERS
8 9
9 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
10 warn "is called after 2s"; 11 warn "is called after 2s";
11 }; 12 };
12 13
13 my $w = EV::timer 2, 1, sub { 14 my $w = EV::timer 2, 2, sub {
14 warn "is called roughly every 2s (repeat = 1)"; 15 warn "is called roughly every 2s (repeat = 2)";
15 }; 16 };
16 17
17 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
18 19
19 my $w = EV::timer_abs 0, 60, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
20 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
21 }; 22 };
22 23
23 # IO 24 # IO
24 25
25 my $w = EV::io \*STDIN, EV::READ | EV::PERSIST, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
26 my ($w, $revents) = @_; # all callbacks get the watcher object and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
27 if ($revents & EV::TIMEOUT) {
28 warn "nothing received on stdin for 10 seconds, retrying";
29 } else {
30 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
31 }
32 };
33 $w->timeout (10);
34
35 my $w = EV::timed_io \*STDIN, EV::READ, 30, sub {
36 my ($w, $revents) = @_;
37 if ($revents & EV::TIMEOUT) {
38 warn "nothing entered within 30 seconds, bye bye.\n";
39 $w->stop;
40 } else {
41 my $line = <STDIN>;
42 warn "you entered something, you again have 30 seconds.\n";
43 }
44 }; 29 };
45 30
46 # SIGNALS 31 # SIGNALS
47 32
48 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
49 warn "sigquit received\n"; 34 warn "sigquit received\n";
50 }; 35 };
51 36
52 my $w = EV::signal 3, sub {
53 warn "sigquit received (this is GNU/Linux, right?)\n";
54 };
55
56 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
57 38
58 my $w = EV::child 666, sub { 39 my $w = EV::child 666, sub {
59 my ($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";
60 }; 48 };
61 49
62 # MAINLOOP 50 # MAINLOOP
63 EV::dispatch; # loop as long as watchers are active 51 EV::loop; # loop until EV::unloop is called or all watchers stop
64 EV::loop; # the same thing
65 EV::loop EV::LOOP_ONESHOT; # block until some events could be handles 52 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
66 EV::loop EV::LOOP_NONBLOCK; # check and handle some events, but do not wait 53 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
67 54
68DESCRIPTION 55DESCRIPTION
69 This module provides an interface to libev 56 This module provides an interface to libev
70 (<http://software.schmorp.de/pkg/libev.html>). You probably should 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
71 acquaint yourself with its documentation and source code to be able to 58 below is comprehensive, one might also consult the documentation of
72 use this module fully. 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", or just
62 about in any case because it has much more detailed information.
73 63
74BASIC INTERFACE 64BASIC INTERFACE
75 $EV::NPRI
76 How many priority levels are available.
77
78 $EV::DIED 65 $EV::DIED
79 Must contain a reference to a function that is called when a 66 Must contain a reference to a function that is called when a
80 callback throws an exception (with $@ containing thr error). The 67 callback throws an exception (with $@ containing thr error). The
81 default prints an informative message and continues. 68 default prints an informative message and continues.
82 69
83 If this callback throws an exception it will be silently ignored. 70 If this callback throws an exception it will be silently ignored.
84 71
72 $time = EV::time
73 Returns the current time in (fractional) seconds since the epoch.
74
85 $time = EV::now 75 $time = EV::now
86 Returns the time in (fractional) seconds since the epoch. 76 Returns the time the last event loop iteration has been started.
77 This is the time that (relative) timers are based on, and refering
78 to it is usually faster then calling EV::time.
87 79
88 $version = EV::version
89 $method = EV::method 80 $method = EV::method
90 Return version string and event polling method used. 81 Returns an integer describing the backend used by libev
82 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
91 83
92 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 84 EV::loop [$flags]
93 EV::loopexit $after 85 Begin checking for events and calling callbacks. It returns when a
94 Exit any active loop or dispatch after $after seconds or immediately 86 callback calls EV::unloop.
95 if $after is missing or zero.
96 87
97 EV::dispatch 88 The $flags argument can be one of the following:
98 Same as "EV::loop 0".
99 89
100 EV::event $callback 90 0 as above
101 Creates a new event watcher waiting for nothing, calling the given 91 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
102 callback. 92 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
103 93
94 EV::unloop [$how]
95 When called with no arguments or an argument of EV::UNLOOP_ONE,
96 makes the innermost call to EV::loop return.
97
98 When called with an argument of EV::UNLOOP_ALL, all calls to
99 EV::loop will return as fast as possible.
100
101 $count = EV::loop_count
102 Return the number of times the event loop has polled for new events.
103 Sometiems useful as a generation counter.
104
105 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
106 This function rolls together an I/O and a timer watcher for a single
107 one-shot event without the need for managing a watcher object.
108
109 If $fh_or_undef is a filehandle or file descriptor, then $events
110 must be a bitset containing either "EV::READ", "EV::WRITE" or
111 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
112 wait for. If you do not want to wait for some I/O event, specify
113 "undef" for $fh_or_undef and 0 for $events).
114
115 If timeout is "undef" or negative, then there will be no timeout.
116 Otherwise a EV::timer with this value will be started.
117
118 When an error occurs or either the timeout or I/O watcher triggers,
119 then the callback will be called with the received event set (in
120 general you can expect it to be a combination of "EV:ERROR",
121 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
122
123 EV::once doesn't return anything: the watchers stay active till
124 either of them triggers, then they will be stopped and freed, and
125 the callback invoked.
126
127 WATCHER OBJECTS
128 A watcher is an object that gets created to record your interest in some
129 event. For instance, if you want to wait for STDIN to become readable,
130 you would create an EV::io watcher for that:
131
132 my $watcher = EV::io *STDIN, EV::READ, sub {
133 my ($watcher, $revents) = @_;
134 warn "yeah, STDIN should not be readable without blocking!\n"
135 };
136
137 All watchers can be active (waiting for events) or inactive (paused).
138 Only active watchers will have their callbacks invoked. All callbacks
139 will be called with at least two arguments: the watcher and a bitmask of
140 received events.
141
142 Each watcher type has its associated bit in revents, so you can use the
143 same callback for multiple watchers. The event mask is named after the
144 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
145 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
146 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
147 (which uses EV::TIMEOUT).
148
149 In the rare case where one wants to create a watcher but not start it at
150 the same time, each constructor has a variant with a trailing "_ns" in
151 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
152
153 Please note that a watcher will automatically be stopped when the
154 watcher object is destroyed, so you *need* to keep the watcher objects
155 returned by the constructors.
156
157 Also, all methods changing some aspect of a watcher (->set, ->priority,
158 ->fh and so on) automatically stop and start it again if it is active,
159 which means pending events get lost.
160
161 COMMON WATCHER METHODS
162 This section lists methods common to all watchers.
163
164 $w->start
165 Starts a watcher if it isn't active already. Does nothing to an
166 already active watcher. By default, all watchers start out in the
167 active state (see the description of the "_ns" variants if you need
168 stopped watchers).
169
170 $w->stop
171 Stop a watcher if it is active. Also clear any pending events
172 (events that have been received but that didn't yet result in a
173 callback invocation), regardless of whether the watcher was active
174 or not.
175
176 $bool = $w->is_active
177 Returns true if the watcher is active, false otherwise.
178
179 $current_data = $w->data
180 $old_data = $w->data ($new_data)
181 Queries a freely usable data scalar on the watcher and optionally
182 changes it. This is a way to associate custom data with a watcher:
183
184 my $w = EV::timer 60, 0, sub {
185 warn $_[0]->data;
186 };
187 $w->data ("print me!");
188
189 $current_cb = $w->cb
190 $old_cb = $w->cb ($new_cb)
191 Queries the callback on the watcher and optionally changes it. You
192 can do this at any time without the watcher restarting.
193
194 $current_priority = $w->priority
195 $old_priority = $w->priority ($new_priority)
196 Queries the priority on the watcher and optionally changes it.
197 Pending watchers with higher priority will be invoked first. The
198 valid range of priorities lies between EV::MAXPRI (default 2) and
199 EV::MINPRI (default -2). If the priority is outside this range it
200 will automatically be normalised to the nearest valid priority.
201
202 The default priority of any newly-created watcher is 0.
203
204 Note that the priority semantics have not yet been fleshed out and
205 are subject to almost certain change.
206
207 $w->trigger ($revents)
208 Call the callback *now* with the given event mask.
209
210 $previous_state = $w->keepalive ($bool)
211 Normally, "EV::loop" will return when there are no active watchers
212 (which is a "deadlock" because no progress can be made anymore).
213 This is convinient because it allows you to start your watchers (and
214 your jobs), call "EV::loop" once and when it returns you know that
215 all your jobs are finished (or they forgot to register some watchers
216 for their task :).
217
218 Sometimes, however, this gets in your way, for example when you the
219 module that calls "EV::loop" (usually the main program) is not the
220 same module as a long-living watcher (for example a DNS client
221 module written by somebody else even). Then you might want any
222 outstanding requests to be handled, but you would not want to keep
223 "EV::loop" from returning just because you happen to have this
224 long-running UDP port watcher.
225
226 In this case you can clear the keepalive status, which means that
227 even though your watcher is active, it won't keep "EV::loop" from
228 returning.
229
230 The initial value for keepalive is true (enabled), and you cna
231 change it any time.
232
233 Example: Register an I/O watcher for some UDP socket but do not keep
234 the event loop from running just because of that watcher.
235
236 my $udp_socket = ...
237 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
238 $udp_watcher->keepalive (0);
239
240 WATCHER TYPES
241 Each of the following subsections describes a single watcher type.
242
243 I/O WATCHERS - is this file descriptor readable or writable?
104 my $w = EV::io $fileno_or_fh, $eventmask, $callback 244 $w = EV::io $fileno_or_fh, $eventmask, $callback
105 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 245 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
106 As long as the returned watcher object is alive, call the $callback 246 As long as the returned watcher object is alive, call the $callback
107 when the events specified in $eventmask happen. Initially, the 247 when at least one of events specified in $eventmask occurs.
108 timeout is disabled.
109 248
110 You can additionall set a timeout to occur on the watcher, but note
111 that this timeout will not be reset when you get an I/O event in the
112 EV::PERSIST case, and reaching a timeout will always stop the
113 watcher even in the EV::PERSIST case.
114
115 If you want a timeout to occur only after a specific time of
116 inactivity, set a repeating timeout and do NOT use EV::PERSIST.
117
118 Eventmask can be one or more of these constants ORed together: 249 The $eventmask can be one or more of these constants ORed together:
119 250
120 EV::READ wait until read() wouldn't block anymore 251 EV::READ wait until read() wouldn't block anymore
121 EV::WRITE wait until write() wouldn't block anymore 252 EV::WRITE wait until write() wouldn't block anymore
122 EV::PERSIST stay active after a (non-timeout) event occured
123 253
124 The "io_ns" variant doesn't add/start the newly created watcher. 254 The "io_ns" variant doesn't start (activate) the newly created
125
126 my $w = EV::timed_io $fileno_or_fh, $eventmask, $timeout, $callback
127 my $w = EV::timed_io_ns $fileno_or_fh, $eventmask, $timeout, $callback
128 Same as "io" and "io_ns", but also specifies a timeout (as if there
129 was a call to "$w->timeout ($timout, 1)". The persist flag is not
130 allowed and will automatically be cleared. The watcher will be
131 restarted after each event.
132
133 If the timeout is zero or undef, no timeout will be set, and a
134 normal watcher (with the persist flag set!) will be created.
135
136 This has the effect of timing out after the specified period of
137 inactivity has happened.
138
139 Due to the design of libevent, this is also relatively inefficient,
140 having one or two io watchers and a separate timeout watcher that
141 you reset on activity (by calling its "start" method) is usually
142 more efficient.
143
144 my $w = EV::timer $after, $repeat, $callback
145 my $w = EV::timer_ns $after, $repeat, $callback
146 Calls the callback after $after seconds. If $repeat is true, the
147 timer will be restarted after the callback returns. This means that
148 the callback would be called roughly every $after seconds, prolonged
149 by the time the callback takes.
150
151 The "timer_ns" variant doesn't add/start the newly created watcher.
152
153 my $w = EV::timer_abs $at, $interval, $callback
154 my $w = EV::timer_abs_ns $at, $interval, $callback
155 Similar to EV::timer, but the time is given as an absolute point in
156 time ($at), plus an optional $interval.
157
158 If the $interval is zero, then the callback will be called at the
159 time $at if that is in the future, or as soon as possible if its in
160 the past. It will not automatically repeat.
161
162 If the $interval is nonzero, then the watcher will always be
163 scheduled to time out at the next "$at + integer * $interval" time.
164
165 This can be used to schedule a callback to run at very regular
166 intervals, as long as the processing time is less then the interval
167 (otherwise obviously events will be skipped).
168
169 Another way to think about it (for the mathematically inclined) is
170 that "timer_abs" will try to tun the callback at the next possible
171 time where "$time = $at (mod $interval)", regardless of any time
172 jumps.
173
174 The "timer_abs_ns" variant doesn't add/start the newly created
175 watcher. 255 watcher.
176 256
177 my $w = EV::signal $signal, $callback 257 $w->set ($fileno_or_fh, $eventmask)
178 my $w = EV::signal_ns $signal, $callback 258 Reconfigures the watcher, see the constructor above for details. Can
179 Call the callback when $signal is received (the signal can be 259 be called at any time.
180 specified by number or by name, just as with kill or %SIG). Signal
181 watchers are persistent no natter what.
182
183 EV will grab the signal for the process (the kernel only allows one
184 component to receive signals) when you start a signal watcher, and
185 removes it again when you stop it. Pelr does the same when you
186 add/remove callbacks to %SIG, so watch out.
187
188 Unfortunately, only one handler can be registered per signal. Screw
189 libevent.
190
191 The "signal_ns" variant doesn't add/start the newly created watcher.
192
193THE EV::Event CLASS
194 All EV functions creating an event watcher (designated by "my $w ="
195 above) support the following methods on the returned watcher object:
196
197 $w->add ($timeout)
198 Stops and (re-)starts the event watcher, setting the optional
199 timeout to the given value, or clearing the timeout if none is
200 given.
201
202 $w->start
203 Stops and (re-)starts the event watcher without touching the
204 timeout.
205
206 $w->del
207 $w->stop
208 Stop the event watcher if it was started.
209
210 $current_callback = $w->cb
211 $old_callback = $w->cb ($new_callback)
212 Return the previously set callback and optionally set a new one.
213 260
214 $current_fh = $w->fh 261 $current_fh = $w->fh
215 $old_fh = $w->fh ($new_fh) 262 $old_fh = $w->fh ($new_fh)
216 Returns the previously set filehandle and optionally set a new one 263 Returns the previously set filehandle and optionally set a new one.
217 (also clears the EV::SIGNAL flag when setting a filehandle).
218
219 $current_signal = $w->signal
220 $old_signal = $w->signal ($new_signal)
221 Returns the previously set signal number and optionally set a new
222 one (also sets the EV::SIGNAL flag when setting a signal).
223 264
224 $current_eventmask = $w->events 265 $current_eventmask = $w->events
225 $old_eventmask = $w->events ($new_eventmask) 266 $old_eventmask = $w->events ($new_eventmask)
226 Returns the previously set event mask and optionally set a new one. 267 Returns the previously set event mask and optionally set a new one.
227 268
269 TIMER WATCHERS - relative and optionally repeating timeouts
270 $w = EV::timer $after, $repeat, $callback
271 $w = EV::timer_ns $after, $repeat, $callback
272 Calls the callback after $after seconds (which may be fractional).
273 If $repeat is non-zero, the timer will be restarted (with the
274 $repeat value as $after) after the callback returns.
275
276 This means that the callback would be called roughly after $after
277 seconds, and then every $repeat seconds. The timer does his best not
278 to drift, but it will not invoke the timer more often then once per
279 event loop iteration, and might drift in other cases. If that isn't
280 acceptable, look at EV::periodic, which can provide long-term stable
281 timers.
282
283 The timer is based on a monotonic clock, that is, if somebody is
284 sitting in front of the machine while the timer is running and
285 changes the system clock, the timer will nevertheless run (roughly)
286 the same time.
287
288 The "timer_ns" variant doesn't start (activate) the newly created
289 watcher.
290
228 $w->timeout ($after, $repeat) 291 $w->set ($after, $repeat)
229 Resets the timeout (see "EV::timer" for details). 292 Reconfigures the watcher, see the constructor above for details. Can
293 be called at any time.
230 294
295 $w->again
296 Similar to the "start" method, but has special semantics for
297 repeating timers:
298
299 If the timer is active and non-repeating, it will be stopped.
300
301 If the timer is active and repeating, reset the timeout to occur
302 $repeat seconds after now.
303
304 If the timer is inactive and repeating, start it using the repeat
305 value.
306
307 Otherwise do nothing.
308
309 This behaviour is useful when you have a timeout for some IO
310 operation. You create a timer object with the same value for $after
311 and $repeat, and then, in the read/write watcher, run the "again"
312 method on the timeout.
313
314 PERIODIC WATCHERS - to cron or not to cron?
315 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
316 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
317 Similar to EV::timer, but is not based on relative timeouts but on
318 absolute times. Apart from creating "simple" timers that trigger
319 "at" the specified time, it can also be used for non-drifting
320 absolute timers and more complex, cron-like, setups that are not
321 adversely affected by time jumps (i.e. when the system clock is
322 changed by explicit date -s or other means such as ntpd). It is also
323 the most complex watcher type in EV.
324
325 It has three distinct "modes":
326
327 * absolute timer ($interval = $reschedule_cb = 0)
328 This time simply fires at the wallclock time $at and doesn't
329 repeat. It will not adjust when a time jump occurs, that is, if
330 it is to be run at January 1st 2011 then it will run when the
331 system time reaches or surpasses this time.
332
333 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
334 In this mode the watcher will always be scheduled to time out at
335 the next "$at + N * $interval" time (for some integer N) and
336 then repeat, regardless of any time jumps.
337
338 This can be used to create timers that do not drift with respect
339 to system time:
340
341 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
342
343 That doesn't mean there will always be 3600 seconds in between
344 triggers, but only that the the clalback will be called when the
345 system time shows a full hour (UTC).
346
347 Another way to think about it (for the mathematically inclined)
348 is that EV::periodic will try to run the callback in this mode
349 at the next possible time where "$time = $at (mod $interval)",
350 regardless of any time jumps.
351
352 * manual reschedule mode ($reschedule_cb = coderef)
353 In this mode $interval and $at are both being ignored. Instead,
354 each time the periodic watcher gets scheduled, the reschedule
355 callback ($reschedule_cb) will be called with the watcher as
356 first, and the current time as second argument.
357
358 *This callback MUST NOT stop or destroy this or any other
359 periodic watcher, ever*. If you need to stop it, return 1e30 and
360 stop it afterwards.
361
362 It must return the next time to trigger, based on the passed
363 time value (that is, the lowest time value larger than to the
364 second argument). It will usually be called just before the
365 callback will be triggered, but might be called at other times,
366 too.
367
368 This can be used to create very complex timers, such as a timer
369 that triggers on each midnight, local time (actually 24 hours
370 after the last midnight, to keep the example simple. If you know
371 a way to do it correctly in about the same space (without
372 requiring elaborate modules), drop me a note :):
373
374 my $daily = EV::periodic 0, 0, sub {
375 my ($w, $now) = @_;
376
377 use Time::Local ();
378 my (undef, undef, undef, $d, $m, $y) = localtime $now;
379 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
380 }, sub {
381 print "it's midnight or likely shortly after, now\n";
382 };
383
384 The "periodic_ns" variant doesn't start (activate) the newly created
385 watcher.
386
387 $w->set ($at, $interval, $reschedule_cb)
388 Reconfigures the watcher, see the constructor above for details. Can
389 be called at any time.
390
391 $w->again
392 Simply stops and starts the watcher again.
393
394 SIGNAL WATCHERS - signal me when a signal gets signalled!
395 $w = EV::signal $signal, $callback
396 $w = EV::signal_ns $signal, $callback
397 Call the callback when $signal is received (the signal can be
398 specified by number or by name, just as with "kill" or %SIG).
399
400 EV will grab the signal for the process (the kernel only allows one
401 component to receive a signal at a time) when you start a signal
402 watcher, and removes it again when you stop it. Perl does the same
403 when you add/remove callbacks to %SIG, so watch out.
404
405 You can have as many signal watchers per signal as you want.
406
407 The "signal_ns" variant doesn't start (activate) the newly created
408 watcher.
409
410 $w->set ($signal)
411 Reconfigures the watcher, see the constructor above for details. Can
412 be called at any time.
413
414 $current_signum = $w->signal
415 $old_signum = $w->signal ($new_signal)
416 Returns the previously set signal (always as a number not name) and
417 optionally set a new one.
418
419 CHILD WATCHERS - watch out for process status changes
420 $w = EV::child $pid, $callback
421 $w = EV::child_ns $pid, $callback
422 Call the callback when a status change for pid $pid (or any pid if
423 $pid is 0) has been received. More precisely: when the process
424 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
425 for all changed/zombie children and call the callback.
426
427 It is valid (and fully supported) to install a child watcher after a
428 child has exited but before the event loop has started its next
429 iteration (for example, first you "fork", then the new child process
430 might exit, and only then do you install a child watcher in the
431 parent for the new pid).
432
433 You can access both exit (or tracing) status and pid by using the
434 "rstatus" and "rpid" methods on the watcher object.
435
436 You can have as many pid watchers per pid as you want, they will all
437 be called.
438
439 The "child_ns" variant doesn't start (activate) the newly created
440 watcher.
441
442 $w->set ($pid)
443 Reconfigures the watcher, see the constructor above for details. Can
444 be called at any time.
445
446 $current_pid = $w->pid
447 $old_pid = $w->pid ($new_pid)
448 Returns the previously set process id and optionally set a new one.
449
450 $exit_status = $w->rstatus
451 Return the exit/wait status (as returned by waitpid, see the waitpid
452 entry in perlfunc).
453
454 $pid = $w->rpid
455 Return the pid of the awaited child (useful when you have installed
456 a watcher for all pids).
457
458 STAT WATCHERS - did the file attributes just change?
459 $w = EV::stat $path, $interval, $callback
460 $w = EV::stat_ns $path, $interval, $callback
461 Call the callback when a file status change has been detected on
462 $path. The $path does not need to exist, changing from "path exists"
463 to "path does not exist" is a status change like any other.
464
465 The $interval is a recommended polling interval for systems where
466 OS-supported change notifications don't exist or are not supported.
467 If you use 0 then an unspecified default is used (which is highly
468 recommended!), which is to be expected to be around five seconds
469 usually.
470
471 This watcher type is not meant for massive numbers of stat watchers,
472 as even with OS-supported change notifications, this can be
473 resource-intensive.
474
475 The "stat_ns" variant doesn't start (activate) the newly created
476 watcher.
477
478 ... = $w->stat
479 This call is very similar to the perl "stat" built-in: It stats
480 (using "lstat") the path specified in the watcher and sets perls
481 stat cache (as well as EV's idea of the current stat values) to the
482 values found.
483
484 In scalar context, a boolean is return indicating success or failure
485 of the stat. In list context, the same 13-value list as with stat is
486 returned (except that the blksize and blocks fields are not
487 reliable).
488
489 In the case of an error, errno is set to "ENOENT" (regardless of the
490 actual error value) and the "nlink" value is forced to zero (if the
491 stat was successful then nlink is guaranteed to be non-zero).
492
493 See also the next two entries for more info.
494
495 ... = $w->attr
496 Just like "$w->stat", but without the initial stat'ing: this returns
497 the values most recently detected by EV. See the next entry for more
498 info.
499
500 ... = $w->prev
501 Just like "$w->stat", but without the initial stat'ing: this returns
502 the previous set of values, before the change.
503
504 That is, when the watcher callback is invoked, "$w->prev" will be
505 set to the values found *before* a change was detected, while
506 "$w->attr" returns the values found leading to the change detection.
507 The difference (if any) between "prev" and "attr" is what triggered
508 the callback.
509
510 If you did something to the filesystem object and do not want to
511 trigger yet another change, you can call "stat" to update EV's idea
512 of what the current attributes are.
513
231 $w->timeout_abs ($at, $interval) 514 $w->set ($path, $interval)
232 Resets the timeout (see "EV::timer_abs" for details). 515 Reconfigures the watcher, see the constructor above for details. Can
516 be called at any time.
233 517
234 $w->priority_set ($priority) 518 $current_path = $w->path
235 Set the priority of the watcher to $priority (0 <= $priority < 519 $old_path = $w->path ($new_path)
236 $EV::NPRI). 520 Returns the previously set path and optionally set a new one.
521
522 $current_interval = $w->interval
523 $old_interval = $w->interval ($new_interval)
524 Returns the previously set interval and optionally set a new one.
525 Can be used to query the actual interval used.
526
527 IDLE WATCHERS - when you've got nothing better to do...
528 $w = EV::idle $callback
529 $w = EV::idle_ns $callback
530 Call the callback when there are no other pending watchers of the
531 same or higher priority (excluding check, prepare and other idle
532 watchers of the same or lower priority, of course). They are called
533 idle watchers because when the watcher is the highest priority
534 pending event in the process, the process is considered to be idle
535 at that priority.
536
537 If you want a watcher that is only ever called when *no* other
538 events are outstanding you have to set the priority to "EV::MINPRI".
539
540 The process will not block as long as any idle watchers are active,
541 and they will be called repeatedly until stopped.
542
543 For example, if you have idle watchers at priority 0 and 1, and an
544 I/O watcher at priority 0, then the idle watcher at priority 1 and
545 the I/O watcher will always run when ready. Only when the idle
546 watcher at priority 1 is stopped and the I/O watcher at priority 0
547 is not pending with the 0-priority idle watcher be invoked.
548
549 The "idle_ns" variant doesn't start (activate) the newly created
550 watcher.
551
552 PREPARE WATCHERS - customise your event loop!
553 $w = EV::prepare $callback
554 $w = EV::prepare_ns $callback
555 Call the callback just before the process would block. You can still
556 create/modify any watchers at this point.
557
558 See the EV::check watcher, below, for explanations and an example.
559
560 The "prepare_ns" variant doesn't start (activate) the newly created
561 watcher.
562
563 CHECK WATCHERS - customise your event loop even more!
564 $w = EV::check $callback
565 $w = EV::check_ns $callback
566 Call the callback just after the process wakes up again (after it
567 has gathered events), but before any other callbacks have been
568 invoked.
569
570 This is used to integrate other event-based software into the EV
571 mainloop: You register a prepare callback and in there, you create
572 io and timer watchers as required by the other software. Here is a
573 real-world example of integrating Net::SNMP (with some details left
574 out):
575
576 our @snmp_watcher;
577
578 our $snmp_prepare = EV::prepare sub {
579 # do nothing unless active
580 $dispatcher->{_event_queue_h}
581 or return;
582
583 # make the dispatcher handle any outstanding stuff
584 ... not shown
585
586 # create an I/O watcher for each and every socket
587 @snmp_watcher = (
588 (map { EV::io $_, EV::READ, sub { } }
589 keys %{ $dispatcher->{_descriptors} }),
590
591 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
592 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
593 0, sub { },
594 );
595 };
596
597 The callbacks are irrelevant (and are not even being called), the
598 only purpose of those watchers is to wake up the process as soon as
599 one of those events occurs (socket readable, or timer timed out).
600 The corresponding EV::check watcher will then clean up:
601
602 our $snmp_check = EV::check sub {
603 # destroy all watchers
604 @snmp_watcher = ();
605
606 # make the dispatcher handle any new stuff
607 ... not shown
608 };
609
610 The callbacks of the created watchers will not be called as the
611 watchers are destroyed before this cna happen (remember EV::check
612 gets called first).
613
614 The "check_ns" variant doesn't start (activate) the newly created
615 watcher.
616
617 FORK WATCHERS - the audacity to resume the event loop after a fork
618 Fork watchers are called when a "fork ()" was detected. The invocation
619 is done before the event loop blocks next and before "check" watchers
620 are being called, and only in the child after the fork.
621
622 $w = EV::fork $callback
623 $w = EV::fork_ns $callback
624 Call the callback before the event loop is resumed in the child
625 process after a fork.
626
627 The "fork_ns" variant doesn't start (activate) the newly created
628 watcher.
629
630PERL SIGNALS
631 While Perl signal handling (%SIG) is not affected by EV, the behaviour
632 with EV is as the same as any other C library: Perl-signals will only be
633 handled when Perl runs, which means your signal handler might be invoked
634 only the next time an event callback is invoked.
635
636 The solution is to use EV signal watchers (see "EV::signal"), which will
637 ensure proper operations with regards to other event watchers.
638
639 If you cannot do this for whatever reason, you can also force a watcher
640 to be called on every event loop iteration by installing a "EV::check"
641 watcher:
642
643 my $async_check = EV::check sub { };
644
645 This ensures that perl shortly gets into control for a short time, and
646 also ensures slower overall operation.
237 647
238THREADS 648THREADS
239 Threads are not supported by this in any way. Perl pseudo-threads is 649 Threads are not supported by this module in any way. Perl pseudo-threads
240 evil and must die. 650 is evil stuff and must die. As soon as Perl gains real threads I will
651 work on thread support for it.
652
653FORK
654 Most of the "improved" event delivering mechanisms of modern operating
655 systems have quite a few problems with fork(2) (to put it bluntly: it is
656 not supported and usually destructive). Libev makes it possible to work
657 around this by having a function that recreates the kernel state after
658 fork in the child.
659
660 On non-win32 platforms, this module requires the pthread_atfork
661 functionality to do this automatically for you. This function is quite
662 buggy on most BSDs, though, so YMMV. The overhead for this is quite
663 negligible, because everything the function currently does is set a flag
664 that is checked only when the event loop gets used the next time, so
665 when you do fork but not use EV, the overhead is minimal.
666
667 On win32, there is no notion of fork so all this doesn't apply, of
668 course.
241 669
242SEE ALSO 670SEE ALSO
243 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 671 EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event
244 L<EV::AnyEvent>. 672 loop), Coro::EV (efficient coroutines with EV).
245 673
246AUTHOR 674AUTHOR
247 Marc Lehmann <schmorp@schmorp.de> 675 Marc Lehmann <schmorp@schmorp.de>
248 http://home.schmorp.de/ 676 http://home.schmorp.de/
249 677

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