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Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC

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;
60 }; 42 };
61 43
62 # MAINLOOP 44 # MAINLOOP
63 EV::dispatch; # loop as long as watchers are active 45 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 46 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 47 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
67 48
68DESCRIPTION 49DESCRIPTION
69 This module provides an interface to libev 50 This module provides an interface to libev
70 (<http://software.schmorp.de/pkg/libev.html>). You probably should 51 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
71 acquaint yourself with its documentation and source code to be able to 52 below is comprehensive, one might also consult the documentation of
72 use this module fully. 53 libev itself (<http://cvs.schmorp.de/libev/ev.html>) for more subtle
54 details on watcher semantics or some discussion on the available
55 backends, or how to force a specific backend with "LIBEV_FLAGS".
73 56
74BASIC INTERFACE 57BASIC INTERFACE
75 $EV::NPRI
76 How many priority levels are available.
77
78 $EV::DIED 58 $EV::DIED
79 Must contain a reference to a function that is called when a 59 Must contain a reference to a function that is called when a
80 callback throws an exception (with $@ containing thr error). The 60 callback throws an exception (with $@ containing thr error). The
81 default prints an informative message and continues. 61 default prints an informative message and continues.
82 62
83 If this callback throws an exception it will be silently ignored. 63 If this callback throws an exception it will be silently ignored.
84 64
65 $time = EV::time
66 Returns the current time in (fractional) seconds since the epoch.
67
85 $time = EV::now 68 $time = EV::now
86 Returns the time in (fractional) seconds since the epoch. 69 Returns the time the last event loop iteration has been started.
70 This is the time that (relative) timers are based on, and refering
71 to it is usually faster then calling EV::time.
87 72
88 $version = EV::version
89 $method = EV::method 73 $method = EV::method
90 Return version string and event polling method used. 74 Returns an integer describing the backend used by libev
75 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
91 76
92 EV::loop $flags # EV::LOOP_ONCE, EV::LOOP_ONESHOT 77 EV::loop [$flags]
93 EV::loopexit $after 78 Begin checking for events and calling callbacks. It returns when a
94 Exit any active loop or dispatch after $after seconds or immediately 79 callback calls EV::unloop.
95 if $after is missing or zero.
96 80
97 EV::dispatch 81 The $flags argument can be one of the following:
98 Same as "EV::loop 0".
99 82
100 EV::event $callback 83 0 as above
101 Creates a new event watcher waiting for nothing, calling the given 84 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
102 callback. 85 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
103 86
87 EV::unloop [$how]
88 When called with no arguments or an argument of EV::UNLOOP_ONE,
89 makes the innermost call to EV::loop return.
90
91 When called with an argument of EV::UNLOOP_ALL, all calls to
92 EV::loop will return as fast as possible.
93
94 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
95 This function rolls together an I/O and a timer watcher for a single
96 one-shot event without the need for managing a watcher object.
97
98 If $fh_or_undef is a filehandle or file descriptor, then $events
99 must be a bitset containing either "EV::READ", "EV::WRITE" or
100 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
101 wait for. If you do not want to wait for some I/O event, specify
102 "undef" for $fh_or_undef and 0 for $events).
103
104 If timeout is "undef" or negative, then there will be no timeout.
105 Otherwise a EV::timer with this value will be started.
106
107 When an error occurs or either the timeout or I/O watcher triggers,
108 then the callback will be called with the received event set (in
109 general you can expect it to be a combination of "EV:ERROR",
110 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
111
112 EV::once doesn't return anything: the watchers stay active till
113 either of them triggers, then they will be stopped and freed, and
114 the callback invoked.
115
116 WATCHER
117 A watcher is an object that gets created to record your interest in some
118 event. For instance, if you want to wait for STDIN to become readable,
119 you would create an EV::io watcher for that:
120
121 my $watcher = EV::io *STDIN, EV::READ, sub {
122 my ($watcher, $revents) = @_;
123 warn "yeah, STDIN should not be readable without blocking!\n"
124 };
125
126 All watchers can be active (waiting for events) or inactive (paused).
127 Only active watchers will have their callbacks invoked. All callbacks
128 will be called with at least two arguments: the watcher and a bitmask of
129 received events.
130
131 Each watcher type has its associated bit in revents, so you can use the
132 same callback for multiple watchers. The event mask is named after the
133 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
134 EV::periodic sets EV::PERIODIC and so on, with the exception of IO
135 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
136 (which uses EV::TIMEOUT).
137
138 In the rare case where one wants to create a watcher but not start it at
139 the same time, each constructor has a variant with a trailing "_ns" in
140 its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
141
142 Please note that a watcher will automatically be stopped when the
143 watcher object is destroyed, so you *need* to keep the watcher objects
144 returned by the constructors.
145
146 Also, all methods changing some aspect of a watcher (->set, ->priority,
147 ->fh and so on) automatically stop and start it again if it is active,
148 which means pending events get lost.
149
150 WATCHER TYPES
151 Now lets move to the existing watcher types and asociated methods.
152
153 The following methods are available for all watchers. Then followes a
154 description of each watcher constructor (EV::io, EV::timer,
155 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
156 EV::check), followed by any type-specific methods (if any).
157
158 $w->start
159 Starts a watcher if it isn't active already. Does nothing to an
160 already active watcher. By default, all watchers start out in the
161 active state (see the description of the "_ns" variants if you need
162 stopped watchers).
163
164 $w->stop
165 Stop a watcher if it is active. Also clear any pending events
166 (events that have been received but that didn't yet result in a
167 callback invocation), regardless of wether the watcher was active or
168 not.
169
170 $bool = $w->is_active
171 Returns true if the watcher is active, false otherwise.
172
173 $current_data = $w->data
174 $old_data = $w->data ($new_data)
175 Queries a freely usable data scalar on the watcher and optionally
176 changes it. This is a way to associate custom data with a watcher:
177
178 my $w = EV::timer 60, 0, sub {
179 warn $_[0]->data;
180 };
181 $w->data ("print me!");
182
183 $current_cb = $w->cb
184 $old_cb = $w->cb ($new_cb)
185 Queries the callback on the watcher and optionally changes it. You
186 can do this at any time without the watcher restarting.
187
188 $current_priority = $w->priority
189 $old_priority = $w->priority ($new_priority)
190 Queries the priority on the watcher and optionally changes it.
191 Pending watchers with higher priority will be invoked first. The
192 valid range of priorities lies between EV::MAXPRI (default 2) and
193 EV::MINPRI (default -2). If the priority is outside this range it
194 will automatically be normalised to the nearest valid priority.
195
196 The default priority of any newly-created watcher is 0.
197
198 Note that the priority semantics have not yet been fleshed out and
199 are subject to almost certain change.
200
201 $w->trigger ($revents)
202 Call the callback *now* with the given event mask.
203
204 $previous_state = $w->keepalive ($bool)
205 Normally, "EV::loop" will return when there are no active watchers
206 (which is a "deadlock" because no progress can be made anymore).
207 This is convinient because it allows you to start your watchers (and
208 your jobs), call "EV::loop" once and when it returns you know that
209 all your jobs are finished (or they forgot to register some watchers
210 for their task :).
211
212 Sometimes, however, this gets in your way, for example when you the
213 module that calls "EV::loop" (usually the main program) is not the
214 same module as a long-living watcher (for example a DNS client
215 module written by somebody else even). Then you might want any
216 outstanding requests to be handled, but you would not want to keep
217 "EV::loop" from returning just because you happen to have this
218 long-running UDP port watcher.
219
220 In this case you can clear the keepalive status, which means that
221 even though your watcher is active, it won't keep "EV::loop" from
222 returning.
223
224 The initial value for keepalive is true (enabled), and you cna
225 change it any time.
226
227 Example: Register an IO watcher for some UDP socket but do not keep
228 the event loop from running just because of that watcher.
229
230 my $udp_socket = ...
231 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
232 $udp_watcher->keepalive (0);
233
104 my $w = EV::io $fileno_or_fh, $eventmask, $callback 234 $w = EV::io $fileno_or_fh, $eventmask, $callback
105 my $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 235 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
106 As long as the returned watcher object is alive, call the $callback 236 As long as the returned watcher object is alive, call the $callback
107 when the events specified in $eventmask happen. Initially, the 237 when the events specified in $eventmask.
108 timeout is disabled.
109 238
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: 239 The $eventmask can be one or more of these constants ORed together:
119 240
120 EV::READ wait until read() wouldn't block anymore 241 EV::READ wait until read() wouldn't block anymore
121 EV::WRITE wait until write() wouldn't block anymore 242 EV::WRITE wait until write() wouldn't block anymore
122 EV::PERSIST stay active after a (non-timeout) event occured
123 243
124 The "io_ns" variant doesn't add/start the newly created watcher. 244 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. 245 watcher.
176 246
177 my $w = EV::signal $signal, $callback 247 $w->set ($fileno_or_fh, $eventmask)
178 my $w = EV::signal_ns $signal, $callback 248 Reconfigures the watcher, see the constructor above for details. Can
179 Call the callback when $signal is received (the signal can be 249 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.
213 250
214 $current_fh = $w->fh 251 $current_fh = $w->fh
215 $old_fh = $w->fh ($new_fh) 252 $old_fh = $w->fh ($new_fh)
216 Returns the previously set filehandle and optionally set a new one 253 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).
223 254
224 $current_eventmask = $w->events 255 $current_eventmask = $w->events
225 $old_eventmask = $w->events ($new_eventmask) 256 $old_eventmask = $w->events ($new_eventmask)
226 Returns the previously set event mask and optionally set a new one. 257 Returns the previously set event mask and optionally set a new one.
227 258
259 $w = EV::timer $after, $repeat, $callback
260 $w = EV::timer_ns $after, $repeat, $callback
261 Calls the callback after $after seconds (which may be fractional).
262 If $repeat is non-zero, the timer will be restarted (with the
263 $repeat value as $after) after the callback returns.
264
265 This means that the callback would be called roughly after $after
266 seconds, and then every $repeat seconds. The timer does his best not
267 to drift, but it will not invoke the timer more often then once per
268 event loop iteration, and might drift in other cases. If that isn't
269 acceptable, look at EV::periodic, which can provide long-term stable
270 timers.
271
272 The timer is based on a monotonic clock, that is, if somebody is
273 sitting in front of the machine while the timer is running and
274 changes the system clock, the timer will nevertheless run (roughly)
275 the same time.
276
277 The "timer_ns" variant doesn't start (activate) the newly created
278 watcher.
279
228 $w->timeout ($after, $repeat) 280 $w->set ($after, $repeat)
229 Resets the timeout (see "EV::timer" for details). 281 Reconfigures the watcher, see the constructor above for details. Can
282 be at any time.
230 283
231 $w->timeout_abs ($at, $interval) 284 $w->again
232 Resets the timeout (see "EV::timer_abs" for details). 285 Similar to the "start" method, but has special semantics for
286 repeating timers:
233 287
234 $w->priority_set ($priority) 288 If the timer is active and non-repeating, it will be stopped.
235 Set the priority of the watcher to $priority (0 <= $priority < 289
236 $EV::NPRI). 290 If the timer is active and repeating, reset the timeout to occur
291 $repeat seconds after now.
292
293 If the timer is inactive and repeating, start it using the repeat
294 value.
295
296 Otherwise do nothing.
297
298 This behaviour is useful when you have a timeout for some IO
299 operation. You create a timer object with the same value for $after
300 and $repeat, and then, in the read/write watcher, run the "again"
301 method on the timeout.
302
303 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
304 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
305 Similar to EV::timer, but is not based on relative timeouts but on
306 absolute times. Apart from creating "simple" timers that trigger
307 "at" the specified time, it can also be used for non-drifting
308 absolute timers and more complex, cron-like, setups that are not
309 adversely affected by time jumps (i.e. when the system clock is
310 changed by explicit date -s or other means such as ntpd). It is also
311 the most complex watcher type in EV.
312
313 It has three distinct "modes":
314
315 * absolute timer ($interval = $reschedule_cb = 0)
316 This time simply fires at the wallclock time $at and doesn't
317 repeat. It will not adjust when a time jump occurs, that is, if
318 it is to be run at January 1st 2011 then it will run when the
319 system time reaches or surpasses this time.
320
321 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
322 In this mode the watcher will always be scheduled to time out at
323 the next "$at + N * $interval" time (for some integer N) and
324 then repeat, regardless of any time jumps.
325
326 This can be used to create timers that do not drift with respect
327 to system time:
328
329 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
330
331 That doesn't mean there will always be 3600 seconds in between
332 triggers, but only that the the clalback will be called when the
333 system time shows a full hour (UTC).
334
335 Another way to think about it (for the mathematically inclined)
336 is that EV::periodic will try to run the callback in this mode
337 at the next possible time where "$time = $at (mod $interval)",
338 regardless of any time jumps.
339
340 * manual reschedule mode ($reschedule_cb = coderef)
341 In this mode $interval and $at are both being ignored. Instead,
342 each time the periodic watcher gets scheduled, the reschedule
343 callback ($reschedule_cb) will be called with the watcher as
344 first, and the current time as second argument.
345
346 *This callback MUST NOT stop or destroy this or any other
347 periodic watcher, ever*. If you need to stop it, return 1e30 and
348 stop it afterwards.
349
350 It must return the next time to trigger, based on the passed
351 time value (that is, the lowest time value larger than to the
352 second argument). It will usually be called just before the
353 callback will be triggered, but might be called at other times,
354 too.
355
356 This can be used to create very complex timers, such as a timer
357 that triggers on each midnight, local time (actually 24 hours
358 after the last midnight, to keep the example simple. If you know
359 a way to do it correctly in about the same space (without
360 requiring elaborate modules), drop me a note :):
361
362 my $daily = EV::periodic 0, 0, sub {
363 my ($w, $now) = @_;
364
365 use Time::Local ();
366 my (undef, undef, undef, $d, $m, $y) = localtime $now;
367 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
368 }, sub {
369 print "it's midnight or likely shortly after, now\n";
370 };
371
372 The "periodic_ns" variant doesn't start (activate) the newly created
373 watcher.
374
375 $w->set ($at, $interval, $reschedule_cb)
376 Reconfigures the watcher, see the constructor above for details. Can
377 be at any time.
378
379 $w->again
380 Simply stops and starts the watcher again.
381
382 $w = EV::signal $signal, $callback
383 $w = EV::signal_ns $signal, $callback
384 Call the callback when $signal is received (the signal can be
385 specified by number or by name, just as with kill or %SIG).
386
387 EV will grab the signal for the process (the kernel only allows one
388 component to receive a signal at a time) when you start a signal
389 watcher, and removes it again when you stop it. Perl does the same
390 when you add/remove callbacks to %SIG, so watch out.
391
392 You can have as many signal watchers per signal as you want.
393
394 The "signal_ns" variant doesn't start (activate) the newly created
395 watcher.
396
397 $w->set ($signal)
398 Reconfigures the watcher, see the constructor above for details. Can
399 be at any time.
400
401 $current_signum = $w->signal
402 $old_signum = $w->signal ($new_signal)
403 Returns the previously set signal (always as a number not name) and
404 optionally set a new one.
405
406 $w = EV::child $pid, $callback
407 $w = EV::child_ns $pid, $callback
408 Call the callback when a status change for pid $pid (or any pid if
409 $pid is 0) has been received. More precisely: when the process
410 receives a SIGCHLD, EV will fetch the outstanding exit/wait status
411 for all changed/zombie children and call the callback.
412
413 You can access both status and pid by using the "rstatus" and "rpid"
414 methods on the watcher object.
415
416 You can have as many pid watchers per pid as you want.
417
418 The "child_ns" variant doesn't start (activate) the newly created
419 watcher.
420
421 $w->set ($pid)
422 Reconfigures the watcher, see the constructor above for details. Can
423 be at any time.
424
425 $current_pid = $w->pid
426 $old_pid = $w->pid ($new_pid)
427 Returns the previously set process id and optionally set a new one.
428
429 $exit_status = $w->rstatus
430 Return the exit/wait status (as returned by waitpid, see the waitpid
431 entry in perlfunc).
432
433 $pid = $w->rpid
434 Return the pid of the awaited child (useful when you have installed
435 a watcher for all pids).
436
437 $w = EV::idle $callback
438 $w = EV::idle_ns $callback
439 Call the callback when there are no pending io, timer/periodic,
440 signal or child events, i.e. when the process is idle.
441
442 The process will not block as long as any idle watchers are active,
443 and they will be called repeatedly until stopped.
444
445 The "idle_ns" variant doesn't start (activate) the newly created
446 watcher.
447
448 $w = EV::prepare $callback
449 $w = EV::prepare_ns $callback
450 Call the callback just before the process would block. You can still
451 create/modify any watchers at this point.
452
453 See the EV::check watcher, below, for explanations and an example.
454
455 The "prepare_ns" variant doesn't start (activate) the newly created
456 watcher.
457
458 $w = EV::check $callback
459 $w = EV::check_ns $callback
460 Call the callback just after the process wakes up again (after it
461 has gathered events), but before any other callbacks have been
462 invoked.
463
464 This is used to integrate other event-based software into the EV
465 mainloop: You register a prepare callback and in there, you create
466 io and timer watchers as required by the other software. Here is a
467 real-world example of integrating Net::SNMP (with some details left
468 out):
469
470 our @snmp_watcher;
471
472 our $snmp_prepare = EV::prepare sub {
473 # do nothing unless active
474 $dispatcher->{_event_queue_h}
475 or return;
476
477 # make the dispatcher handle any outstanding stuff
478 ... not shown
479
480 # create an IO watcher for each and every socket
481 @snmp_watcher = (
482 (map { EV::io $_, EV::READ, sub { } }
483 keys %{ $dispatcher->{_descriptors} }),
484
485 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
486 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
487 0, sub { },
488 );
489 };
490
491 The callbacks are irrelevant (and are not even being called), the
492 only purpose of those watchers is to wake up the process as soon as
493 one of those events occurs (socket readable, or timer timed out).
494 The corresponding EV::check watcher will then clean up:
495
496 our $snmp_check = EV::check sub {
497 # destroy all watchers
498 @snmp_watcher = ();
499
500 # make the dispatcher handle any new stuff
501 ... not shown
502 };
503
504 The callbacks of the created watchers will not be called as the
505 watchers are destroyed before this cna happen (remember EV::check
506 gets called first).
507
508 The "check_ns" variant doesn't start (activate) the newly created
509 watcher.
237 510
238THREADS 511THREADS
239 Threads are not supported by this in any way. Perl pseudo-threads is 512 Threads are not supported by this module in any way. Perl pseudo-threads
240 evil and must die. 513 is evil stuff and must die. As soon as Perl gains real threads I will
514 work on thread support for it.
515
516FORK
517 Most of the "improved" event delivering mechanisms of modern operating
518 systems have quite a few problems with fork(2) (to put it bluntly: it is
519 not supported and usually destructive). Libev makes it possible to work
520 around this by having a function that recreates the kernel state after
521 fork in the child.
522
523 On non-win32 platforms, this module requires the pthread_atfork
524 functionality to do this automatically for you. This function is quite
525 buggy on most BSDs, though, so YMMV. The overhead for this is quite
526 negligible, because everything the function currently does is set a flag
527 that is checked only when the event loop gets used the next time, so
528 when you do fork but not use EV, the overhead is minimal.
529
530 On win32, there is no notion of fork so all this doesn't apply, of
531 course.
241 532
242SEE ALSO 533SEE ALSO
243 L<EV::DNS>, L<event(3)>, L<event.h>, L<evdns.h>. 534 L<EV::DNS>.
244 L<EV::AnyEvent>.
245 535
246AUTHOR 536AUTHOR
247 Marc Lehmann <schmorp@schmorp.de> 537 Marc Lehmann <schmorp@schmorp.de>
248 http://home.schmorp.de/ 538 http://home.schmorp.de/
249 539

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