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Revision 1.8 by root, Thu Nov 8 17:02:10 2007 UTC vs.
Revision 1.20 by root, Sat Dec 22 12:05:42 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, 0, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
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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, $revents) = @_; 40 my ($w, $revents) = @_;
45 # my $pid = $w->rpid;
46 my $status = $w->rstatus; 41 my $status = $w->rstatus;
47 }; 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";
48 };
48 49
49 # MAINLOOP 50 # MAINLOOP
50 EV::loop; # loop until EV::loop_done is called 51 EV::loop; # loop until EV::unloop is called or all watchers stop
51 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
52 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
53 54
54DESCRIPTION 55DESCRIPTION
55 This module provides an interface to libev 56 This module provides an interface to libev
56 (<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", or just
62 about in any case because it has much more detailed information.
63
64EVENT LOOPS
65 EV supports multiple event loops: There is a single "default event loop"
66 that can handle everything including signals and child watchers, and any
67 number of "dynamic event loops" that can use different backends (with
68 various limitations), but no child and signal watchers.
69
70 You do not have to do anything to create the default event loop: When
71 the module is loaded a suitable backend is selected on the premise of
72 selecting a working backend (which for example rules out kqueue on most
73 BSDs). Modules should, unless they have "special needs" always use the
74 default loop as this is fastest (perl-wise), best supported by other
75 modules (e.g. AnyEvent or Coro) and most portable event loop.
76
77 For specific programs you cna create additional event loops dynamically.
78
79 $loop = new EV::loop [$flags]
80 Create a new event loop as per the specified flags. Please refer to
81 the "ev_loop_new ()" function description in the libev documentation
82 (<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTI
83 ONS>) for more info.
84
85 The loop will automatically be destroyed when it is no longer
86 referenced by any watcher and the loop object goes out of scope.
87
88 Using "EV::FLAG_FORKCHECK" is recommended, as only the default event
89 loop is protected by this module.
90
91 $loop->loop_fork
92 Must be called after a fork in the child, before entering or
93 continuing the event loop. An alternative is to use
94 "EV::FLAG_FORKCHECK" which calls this fucntion automatically, at
95 some performance loss (refer to the libev documentation).
57 96
58BASIC INTERFACE 97BASIC INTERFACE
59 $EV::DIED 98 $EV::DIED
60 Must contain a reference to a function that is called when a 99 Must contain a reference to a function that is called when a
61 callback throws an exception (with $@ containing thr error). The 100 callback throws an exception (with $@ containing the error). The
62 default prints an informative message and continues. 101 default prints an informative message and continues.
63 102
64 If this callback throws an exception it will be silently ignored. 103 If this callback throws an exception it will be silently ignored.
65 104
66 $time = EV::time 105 $time = EV::time
67 Returns the current time in (fractional) seconds since the epoch. 106 Returns the current time in (fractional) seconds since the epoch.
68 107
69 $time = EV::now 108 $time = EV::now
109 $time = $loop->now
70 Returns the time the last event loop iteration has been started. 110 Returns the time the last event loop iteration has been started.
71 This is the time that (relative) timers are based on, and refering 111 This is the time that (relative) timers are based on, and refering
72 to it is usually faster then calling EV::time. 112 to it is usually faster then calling EV::time.
73 113
74 $method = EV::ev_method 114 $backend = EV::backend
115 $backend = $loop->backend
75 Returns an integer describing the backend used by libev 116 Returns an integer describing the backend used by libev
76 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 117 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
77 118
78 EV::loop [$flags] 119 EV::loop [$flags]
120 $loop->loop ([$flags])
79 Begin checking for events and calling callbacks. It returns when a 121 Begin checking for events and calling callbacks. It returns when a
80 callback calls EV::loop_done. 122 callback calls EV::unloop.
81 123
82 The $flags argument can be one of the following: 124 The $flags argument can be one of the following:
83 125
84 0 as above 126 0 as above
85 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 127 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
86 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 128 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
87 129
88 EV::loop_done [$how] 130 EV::unloop [$how]
131 $loop->unloop ([$how])
89 When called with no arguments or an argument of 1, makes the 132 When called with no arguments or an argument of EV::UNLOOP_ONE,
90 innermost call to EV::loop return. 133 makes the innermost call to EV::loop return.
91 134
92 When called with an agrument of 2, all calls to EV::loop will return 135 When called with an argument of EV::UNLOOP_ALL, all calls to
93 as fast as possible. 136 EV::loop will return as fast as possible.
94 137
95 WATCHER 138 $count = EV::loop_count
139 $count = $loop->loop_count
140 Return the number of times the event loop has polled for new events.
141 Sometiems useful as a generation counter.
142
143 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
144 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
145 This function rolls together an I/O and a timer watcher for a single
146 one-shot event without the need for managing a watcher object.
147
148 If $fh_or_undef is a filehandle or file descriptor, then $events
149 must be a bitset containing either "EV::READ", "EV::WRITE" or
150 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
151 wait for. If you do not want to wait for some I/O event, specify
152 "undef" for $fh_or_undef and 0 for $events).
153
154 If timeout is "undef" or negative, then there will be no timeout.
155 Otherwise a EV::timer with this value will be started.
156
157 When an error occurs or either the timeout or I/O watcher triggers,
158 then the callback will be called with the received event set (in
159 general you can expect it to be a combination of "EV::ERROR",
160 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
161
162 EV::once doesn't return anything: the watchers stay active till
163 either of them triggers, then they will be stopped and freed, and
164 the callback invoked.
165
166 EV::feed_fd_event ($fd, $revents)
167 $loop->feed_fd_event ($fd, $revents)
168 Feed an event on a file descriptor into EV. EV will react to this
169 call as if the readyness notifications specified by $revents (a
170 combination of "EV::READ" and "EV::WRITE") happened on the file
171 descriptor $fd.
172
173 EV::feed_signal_event ($signal)
174 Feed a signal event into EV. EV will react to this call as if the
175 signal specified by $signal had occured.
176
177WATCHER OBJECTS
96 A watcher is an object that gets created to record your interest in some 178 A watcher is an object that gets created to record your interest in some
97 event. For instance, if you want to wait for STDIN to become readable, 179 event. For instance, if you want to wait for STDIN to become readable,
98 you would create an EV::io watcher for that: 180 you would create an EV::io watcher for that:
99 181
100 my $watcher = EV::io *STDIN, EV::READ, sub { 182 my $watcher = EV::io *STDIN, EV::READ, sub {
101 my ($watcher, $revents) = @_; 183 my ($watcher, $revents) = @_;
102 warn "yeah, STDIN should not be readable without blocking!\n" 184 warn "yeah, STDIN should now be readable without blocking!\n"
103 }; 185 };
104 186
105 All watchers can be active (waiting for events) or inactive (paused). 187 All watchers can be active (waiting for events) or inactive (paused).
106 Only active watchers will have their callbacks invoked. All callbacks 188 Only active watchers will have their callbacks invoked. All callbacks
107 will be called with at least two arguments: the watcher and a bitmask of 189 will be called with at least two arguments: the watcher and a bitmask of
108 received events. 190 received events.
109 191
110 Each watcher type has its associated bit in revents, so you can use the 192 Each watcher type has its associated bit in revents, so you can use the
111 same callback for multiple watchers. The event mask is named after the 193 same callback for multiple watchers. The event mask is named after the
112 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, 194 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
113 EV::periodic sets EV::PERIODIC and so on, with the exception of IO 195 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
114 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 196 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
115 (which uses EV::TIMEOUT). 197 (which uses EV::TIMEOUT).
116 198
117 In the rare case where one wants to create a watcher but not start it at 199 In the rare case where one wants to create a watcher but not start it at
118 the same time, each constructor has a variant with a trailing "_ns" in 200 the same time, each constructor has a variant with a trailing "_ns" in
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124 206
125 Also, all methods changing some aspect of a watcher (->set, ->priority, 207 Also, all methods changing some aspect of a watcher (->set, ->priority,
126 ->fh and so on) automatically stop and start it again if it is active, 208 ->fh and so on) automatically stop and start it again if it is active,
127 which means pending events get lost. 209 which means pending events get lost.
128 210
129 WATCHER TYPES 211 COMMON WATCHER METHODS
130 Now lets move to the existing watcher types and asociated methods. 212 This section lists methods common to all watchers.
131
132 The following methods are available for all watchers. Then followes a
133 description of each watcher constructor (EV::io, EV::timer,
134 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
135 EV::check), followed by any type-specific methods (if any).
136 213
137 $w->start 214 $w->start
138 Starts a watcher if it isn't active already. Does nothing to an 215 Starts a watcher if it isn't active already. Does nothing to an
139 already active watcher. By default, all watchers start out in the 216 already active watcher. By default, all watchers start out in the
140 active state (see the description of the "_ns" variants if you need 217 active state (see the description of the "_ns" variants if you need
141 stopped watchers). 218 stopped watchers).
142 219
143 $w->stop 220 $w->stop
144 Stop a watcher if it is active. Also clear any pending events 221 Stop a watcher if it is active. Also clear any pending events
145 (events that have been received but that didn't yet result in a 222 (events that have been received but that didn't yet result in a
146 callback invocation), regardless of wether the watcher was active or 223 callback invocation), regardless of whether the watcher was active
147 not. 224 or not.
148 225
149 $bool = $w->is_active 226 $bool = $w->is_active
150 Returns true if the watcher is active, false otherwise. 227 Returns true if the watcher is active, false otherwise.
151 228
152 $current_data = $w->data 229 $current_data = $w->data
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170 Pending watchers with higher priority will be invoked first. The 247 Pending watchers with higher priority will be invoked first. The
171 valid range of priorities lies between EV::MAXPRI (default 2) and 248 valid range of priorities lies between EV::MAXPRI (default 2) and
172 EV::MINPRI (default -2). If the priority is outside this range it 249 EV::MINPRI (default -2). If the priority is outside this range it
173 will automatically be normalised to the nearest valid priority. 250 will automatically be normalised to the nearest valid priority.
174 251
175 The default priority of any newly-created weatcher is 0. 252 The default priority of any newly-created watcher is 0.
176 253
254 Note that the priority semantics have not yet been fleshed out and
255 are subject to almost certain change.
256
177 $w->trigger ($revents) 257 $w->invoke ($revents)
178 Call the callback *now* with the given event mask. 258 Call the callback *now* with the given event mask.
179 259
260 $w->feed_event ($revents)
261 Feed some events on this watcher into EV. EV will react to this call
262 as if the watcher had received the given $revents mask.
263
264 $revents = $w->clear_pending
265 If the watcher is pending, this function clears its pending status
266 and returns its $revents bitset (as if its callback was invoked). If
267 the watcher isn't pending it does nothing and returns 0.
268
269 $previous_state = $w->keepalive ($bool)
270 Normally, "EV::loop" will return when there are no active watchers
271 (which is a "deadlock" because no progress can be made anymore).
272 This is convinient because it allows you to start your watchers (and
273 your jobs), call "EV::loop" once and when it returns you know that
274 all your jobs are finished (or they forgot to register some watchers
275 for their task :).
276
277 Sometimes, however, this gets in your way, for example when the
278 module that calls "EV::loop" (usually the main program) is not the
279 same module as a long-living watcher (for example a DNS client
280 module written by somebody else even). Then you might want any
281 outstanding requests to be handled, but you would not want to keep
282 "EV::loop" from returning just because you happen to have this
283 long-running UDP port watcher.
284
285 In this case you can clear the keepalive status, which means that
286 even though your watcher is active, it won't keep "EV::loop" from
287 returning.
288
289 The initial value for keepalive is true (enabled), and you cna
290 change it any time.
291
292 Example: Register an I/O watcher for some UDP socket but do not keep
293 the event loop from running just because of that watcher.
294
295 my $udp_socket = ...
296 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
297 $1000udp_watcher->keepalive (0);
298
299 $loop = $w->loop
300 Return the loop that this watcher is attached to.
301
302WATCHER TYPES
303 Each of the following subsections describes a single watcher type.
304
305 I/O WATCHERS - is this file descriptor readable or writable?
180 $w = EV::io $fileno_or_fh, $eventmask, $callback 306 $w = EV::io $fileno_or_fh, $eventmask, $callback
181 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 307 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
308 $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
309 $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
182 As long as the returned watcher object is alive, call the $callback 310 As long as the returned watcher object is alive, call the $callback
183 when the events specified in $eventmask. 311 when at least one of events specified in $eventmask occurs.
184 312
185 The $eventmask can be one or more of these constants ORed together: 313 The $eventmask can be one or more of these constants ORed together:
186 314
187 EV::READ wait until read() wouldn't block anymore 315 EV::READ wait until read() wouldn't block anymore
188 EV::WRITE wait until write() wouldn't block anymore 316 EV::WRITE wait until write() wouldn't block anymore
… …
200 328
201 $current_eventmask = $w->events 329 $current_eventmask = $w->events
202 $old_eventmask = $w->events ($new_eventmask) 330 $old_eventmask = $w->events ($new_eventmask)
203 Returns the previously set event mask and optionally set a new one. 331 Returns the previously set event mask and optionally set a new one.
204 332
333 TIMER WATCHERS - relative and optionally repeating timeouts
205 $w = EV::timer $after, $repeat, $callback 334 $w = EV::timer $after, $repeat, $callback
206 $w = EV::timer_ns $after, $repeat, $callback 335 $w = EV::timer_ns $after, $repeat, $callback
207 Calls the callback after $after seconds. If $repeat is non-zero, the 336 $w = $loop->timer ($after, $repeat, $callback)
208 timer will be restarted (with the $repeat value as $after) after the 337 $w = $loop->timer_ns ($after, $repeat, $callback)
209 callback returns. 338 Calls the callback after $after seconds (which may be fractional).
339 If $repeat is non-zero, the timer will be restarted (with the
340 $repeat value as $after) after the callback returns.
210 341
211 This means that the callback would be called roughly after $after 342 This means that the callback would be called roughly after $after
212 seconds, and then every $repeat seconds. "Roughly" because the time 343 seconds, and then every $repeat seconds. The timer does his best not
213 of callback processing is not taken into account, so the timer will 344 to drift, but it will not invoke the timer more often then once per
214 slowly drift. If that isn't acceptable, look at EV::periodic. 345 event loop iteration, and might drift in other cases. If that isn't
346 acceptable, look at EV::periodic, which can provide long-term stable
347 timers.
215 348
216 The timer is based on a monotonic clock, that is if somebody is 349 The timer is based on a monotonic clock, that is, if somebody is
217 sitting in front of the machine while the timer is running and 350 sitting in front of the machine while the timer is running and
218 changes the system clock, the timer will nevertheless run (roughly) 351 changes the system clock, the timer will nevertheless run (roughly)
219 the same time. 352 the same time.
220 353
221 The "timer_ns" variant doesn't start (activate) the newly created 354 The "timer_ns" variant doesn't start (activate) the newly created
222 watcher. 355 watcher.
223 356
224 $w->set ($after, $repeat) 357 $w->set ($after, $repeat)
225 Reconfigures the watcher, see the constructor above for details. Can 358 Reconfigures the watcher, see the constructor above for details. Can
226 be at any time. 359 be called at any time.
227 360
228 $w->again 361 $w->again
229 Similar to the "start" method, but has special semantics for 362 Similar to the "start" method, but has special semantics for
230 repeating timers: 363 repeating timers:
231 364
365 If the timer is active and non-repeating, it will be stopped.
366
232 If the timer is active and repeating, reset the timeout to occur 367 If the timer is active and repeating, reset the timeout to occur
233 $repeat seconds after now. 368 $repeat seconds after now.
234 369
235 If the timer is active and non-repeating, it will be stopped.
236
237 If the timer is in active and repeating, start it. 370 If the timer is inactive and repeating, start it using the repeat
371 value.
238 372
239 Otherwise do nothing. 373 Otherwise do nothing.
240 374
241 This behaviour is useful when you have a timeout for some IO 375 This behaviour is useful when you have a timeout for some IO
242 operation. You create a timer object with the same value for $after 376 operation. You create a timer object with the same value for $after
243 and $repeat, and then, in the read/write watcher, run the "again" 377 and $repeat, and then, in the read/write watcher, run the "again"
244 method on the timeout. 378 method on the timeout.
245 379
380 PERIODIC WATCHERS - to cron or not to cron?
246 $w = EV::periodic $at, $interval, $reschedule_cb, $callback 381 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
247 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback 382 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
383 $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
384 $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
248 Similar to EV::timer, but is not based on relative timeouts but on 385 Similar to EV::timer, but is not based on relative timeouts but on
249 absolute times. Apart from creating "simple" timers that trigger 386 absolute times. Apart from creating "simple" timers that trigger
250 "at" the specified time, it can also be used for non-drifting 387 "at" the specified time, it can also be used for non-drifting
251 absolute timers and more complex, cron-like, setups that are not 388 absolute timers and more complex, cron-like, setups that are not
252 adversely affected by time jumps (i.e. when the system clock is 389 adversely affected by time jumps (i.e. when the system clock is
… …
280 at the next possible time where "$time = $at (mod $interval)", 417 at the next possible time where "$time = $at (mod $interval)",
281 regardless of any time jumps. 418 regardless of any time jumps.
282 419
283 * manual reschedule mode ($reschedule_cb = coderef) 420 * manual reschedule mode ($reschedule_cb = coderef)
284 In this mode $interval and $at are both being ignored. Instead, 421 In this mode $interval and $at are both being ignored. Instead,
285 each time the periodic watcher gets scheduled, the first 422 each time the periodic watcher gets scheduled, the reschedule
286 callback ($reschedule_cb) will be called with the watcher as 423 callback ($reschedule_cb) will be called with the watcher as
287 first, and the current time as second argument. 424 first, and the current time as second argument.
288 425
289 *This callback MUST NOT stop or destroy this or any other 426 *This callback MUST NOT stop or destroy this or any other
290 periodic watcher, ever*. If you need to stop it, return 1e30 and 427 periodic watcher, ever*. If you need to stop it, return 1e30 and
… …
315 The "periodic_ns" variant doesn't start (activate) the newly created 452 The "periodic_ns" variant doesn't start (activate) the newly created
316 watcher. 453 watcher.
317 454
318 $w->set ($at, $interval, $reschedule_cb) 455 $w->set ($at, $interval, $reschedule_cb)
319 Reconfigures the watcher, see the constructor above for details. Can 456 Reconfigures the watcher, see the constructor above for details. Can
320 be at any time. 457 be called at any time.
321 458
322 $w->again 459 $w->again
323 Simply stops and starts the watcher again. 460 Simply stops and starts the watcher again.
324 461
462 $time = $w->at
463 Return the time that the watcher is expected to trigger next.
464
465 SIGNAL WATCHERS - signal me when a signal gets signalled!
325 $w = EV::signal $signal, $callback 466 $w = EV::signal $signal, $callback
326 $w = EV::signal_ns $signal, $callback 467 $w = EV::signal_ns $signal, $callback
327 Call the callback when $signal is received (the signal can be 468 Call the callback when $signal is received (the signal can be
328 specified by number or by name, just as with kill or %SIG). 469 specified by number or by name, just as with "kill" or %SIG).
329 470
330 EV will grab the signal for the process (the kernel only allows one 471 EV will grab the signal for the process (the kernel only allows one
331 component to receive a signal at a time) when you start a signal 472 component to receive a signal at a time) when you start a signal
332 watcher, and removes it again when you stop it. Perl does the same 473 watcher, and removes it again when you stop it. Perl does the same
333 when you add/remove callbacks to %SIG, so watch out. 474 when you add/remove callbacks to %SIG, so watch out.
… …
337 The "signal_ns" variant doesn't start (activate) the newly created 478 The "signal_ns" variant doesn't start (activate) the newly created
338 watcher. 479 watcher.
339 480
340 $w->set ($signal) 481 $w->set ($signal)
341 Reconfigures the watcher, see the constructor above for details. Can 482 Reconfigures the watcher, see the constructor above for details. Can
342 be at any time. 483 be called at any time.
343 484
344 $current_signum = $w->signal 485 $current_signum = $w->signal
345 $old_signum = $w->signal ($new_signal) 486 $old_signum = $w->signal ($new_signal)
346 Returns the previously set signal (always as a number not name) and 487 Returns the previously set signal (always as a number not name) and
347 optionally set a new one. 488 optionally set a new one.
348 489
490 CHILD WATCHERS - watch out for process status changes
349 $w = EV::child $pid, $callback 491 $w = EV::child $pid, $callback
350 $w = EV::child_ns $pid, $callback 492 $w = EV::child_ns $pid, $callback
493 $w = $loop->child ($pid, $callback)
494 $w = $loop->child_ns ($pid, $callback)
351 Call the callback when a status change for pid $pid (or any pid if 495 Call the callback when a status change for pid $pid (or any pid if
352 $pid is 0) has been received. More precisely: when the process 496 $pid is 0) has been received. More precisely: when the process
353 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 497 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
354 for all changed/zombie children and call the callback. 498 for all changed/zombie children and call the callback.
355 499
356 You can access both status and pid by using the "rstatus" and "rpid" 500 It is valid (and fully supported) to install a child watcher after a
501 child has exited but before the event loop has started its next
502 iteration (for example, first you "fork", then the new child process
503 might exit, and only then do you install a child watcher in the
504 parent for the new pid).
505
506 You can access both exit (or tracing) status and pid by using the
357 methods on the watcher object. 507 "rstatus" and "rpid" methods on the watcher object.
358 508
359 You can have as many pid watchers per pid as you want. 509 You can have as many pid watchers per pid as you want, they will all
510 be called.
360 511
361 The "child_ns" variant doesn't start (activate) the newly created 512 The "child_ns" variant doesn't start (activate) the newly created
362 watcher. 513 watcher.
363 514
364 $w->set ($pid) 515 $w->set ($pid)
365 Reconfigures the watcher, see the constructor above for details. Can 516 Reconfigures the watcher, see the constructor above for details. Can
366 be at any time. 517 be called at any time.
367 518
368 $current_pid = $w->pid 519 $current_pid = $w->pid
369 $old_pid = $w->pid ($new_pid) 520 $old_pid = $w->pid ($new_pid)
370 Returns the previously set process id and optionally set a new one. 521 Returns the previously set process id and optionally set a new one.
371 522
… …
375 526
376 $pid = $w->rpid 527 $pid = $w->rpid
377 Return the pid of the awaited child (useful when you have installed 528 Return the pid of the awaited child (useful when you have installed
378 a watcher for all pids). 529 a watcher for all pids).
379 530
531 STAT WATCHERS - did the file attributes just change?
532 $w = EV::stat $path, $interval, $callback
533 $w = EV::stat_ns $path, $interval, $callback
534 $w = $loop->stat ($path, $interval, $callback)
535 $w = $loop->stat_ns ($path, $interval, $callback)
536 Call the callback when a file status change has been detected on
537 $path. The $path does not need to exist, changing from "path exists"
538 to "path does not exist" is a status change like any other.
539
540 The $interval is a recommended polling interval for systems where
541 OS-supported change notifications don't exist or are not supported.
542 If you use 0 then an unspecified default is used (which is highly
543 recommended!), which is to be expected to be around five seconds
544 usually.
545
546 This watcher type is not meant for massive numbers of stat watchers,
547 as even with OS-supported change notifications, this can be
548 resource-intensive.
549
550 The "stat_ns" variant doesn't start (activate) the newly created
551 watcher.
552
553 ... = $w->stat
554 This call is very similar to the perl "stat" built-in: It stats
555 (using "lstat") the path specified in the watcher and sets perls
556 stat cache (as well as EV's idea of the current stat values) to the
557 values found.
558
559 In scalar context, a boolean is return indicating success or failure
560 of the stat. In list context, the same 13-value list as with stat is
561 returned (except that the blksize and blocks fields are not
562 reliable).
563
564 In the case of an error, errno is set to "ENOENT" (regardless of the
565 actual error value) and the "nlink" value is forced to zero (if the
566 stat was successful then nlink is guaranteed to be non-zero).
567
568 See also the next two entries for more info.
569
570 ... = $w->attr
571 Just like "$w->stat", but without the initial stat'ing: this returns
572 the values most recently detected by EV. See the next entry for more
573 info.
574
575 ... = $w->prev
576 Just like "$w->stat", but without the initial stat'ing: this returns
577 the previous set of values, before the change.
578
579 That is, when the watcher callback is invoked, "$w->prev" will be
580 set to the values found *before* a change was detected, while
581 "$w->attr" returns the values found leading to the change detection.
582 The difference (if any) between "prev" and "attr" is what triggered
583 the callback.
584
585 If you did something to the filesystem object and do not want to
586 trigger yet another change, you can call "stat" to update EV's idea
587 of what the current attributes are.
588
589 $w->set ($path, $interval)
590 Reconfigures the watcher, see the constructor above for details. Can
591 be called at any time.
592
593 $current_path = $w->path
594 $old_path = $w->path ($new_path)
595 Returns the previously set path and optionally set a new one.
596
597 $current_interval = $w->interval
598 $old_interval = $w->interval ($new_interval)
599 Returns the previously set interval and optionally set a new one.
600 Can be used to query the actual interval used.
601
602 IDLE WATCHERS - when you've got nothing better to do...
380 $w = EV::idle $callback 603 $w = EV::idle $callback
381 $w = EV::idle_ns $callback 604 $w = EV::idle_ns $callback
605 $w = $loop->idle ($callback)
606 $w = $loop->idle_ns ($callback)
382 Call the callback when there are no pending io, timer/periodic, 607 Call the callback when there are no other pending watchers of the
383 signal or child events, i.e. when the process is idle. 608 same or higher priority (excluding check, prepare and other idle
609 watchers of the same or lower priority, of course). They are called
610 idle watchers because when the watcher is the highest priority
611 pending event in the process, the process is considered to be idle
612 at that priority.
613
614 If you want a watcher that is only ever called when *no* other
615 events are outstanding you have to set the priority to "EV::MINPRI".
384 616
385 The process will not block as long as any idle watchers are active, 617 The process will not block as long as any idle watchers are active,
386 and they will be called repeatedly until stopped. 618 and they will be called repeatedly until stopped.
387 619
620 For example, if you have idle watchers at priority 0 and 1, and an
621 I/O watcher at priority 0, then the idle watcher at priority 1 and
622 the I/O watcher will always run when ready. Only when the idle
623 watcher at priority 1 is stopped and the I/O watcher at priority 0
624 is not pending with the 0-priority idle watcher be invoked.
625
388 The "idle_ns" variant doesn't start (activate) the newly created 626 The "idle_ns" variant doesn't start (activate) the newly created
389 watcher. 627 watcher.
390 628
629 PREPARE WATCHERS - customise your event loop!
391 $w = EV::prepare $callback 630 $w = EV::prepare $callback
392 $w = EV::prepare_ns $callback 631 $w = EV::prepare_ns $callback
632 $w = $loop->prepare ($callback)
633 $w = $loop->prepare_ns ($callback)
393 Call the callback just before the process would block. You can still 634 Call the callback just before the process would block. You can still
394 create/modify any watchers at this point. 635 create/modify any watchers at this point.
395 636
396 See the EV::check watcher, below, for explanations and an example. 637 See the EV::check watcher, below, for explanations and an example.
397 638
398 The "prepare_ns" variant doesn't start (activate) the newly created 639 The "prepare_ns" variant doesn't start (activate) the newly created
399 watcher. 640 watcher.
400 641
642 CHECK WATCHERS - customise your event loop even more!
401 $w = EV::check $callback 643 $w = EV::check $callback
402 $w = EV::check_ns $callback 644 $w = EV::check_ns $callback
645 $w = $loop->check ($callback)
646 $w = $loop->check_ns ($callback)
403 Call the callback just after the process wakes up again (after it 647 Call the callback just after the process wakes up again (after it
404 has gathered events), but before any other callbacks have been 648 has gathered events), but before any other callbacks have been
405 invoked. 649 invoked.
406 650
407 This is used to integrate other event-based software into the EV 651 This is used to integrate other event-based software into the EV
… …
416 # do nothing unless active 660 # do nothing unless active
417 $dispatcher->{_event_queue_h} 661 $dispatcher->{_event_queue_h}
418 or return; 662 or return;
419 663
420 # make the dispatcher handle any outstanding stuff 664 # make the dispatcher handle any outstanding stuff
665 ... not shown
421 666
422 # create an IO watcher for each and every socket 667 # create an I/O watcher for each and every socket
423 @snmp_watcher = ( 668 @snmp_watcher = (
424 (map { EV::io $_, EV::READ, sub { } } 669 (map { EV::io $_, EV::READ, sub { } }
425 keys %{ $dispatcher->{_descriptors} }), 670 keys %{ $dispatcher->{_descriptors} }),
671
672 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
673 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
674 0, sub { },
426 ); 675 );
427
428 # if there are any timeouts, also create a timer
429 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
430 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
431 }; 676 };
432 677
433 The callbacks are irrelevant, the only purpose of those watchers is 678 The callbacks are irrelevant (and are not even being called), the
434 to wake up the process as soon as one of those events occurs (socket 679 only purpose of those watchers is to wake up the process as soon as
435 readable, or timer timed out). The corresponding EV::check watcher 680 one of those events occurs (socket readable, or timer timed out).
436 will then clean up: 681 The corresponding EV::check watcher will then clean up:
437 682
438 our $snmp_check = EV::check sub { 683 our $snmp_check = EV::check sub {
439 # destroy all watchers 684 # destroy all watchers
440 @snmp_watcher = (); 685 @snmp_watcher = ();
441 686
442 # make the dispatcher handle any new stuff 687 # make the dispatcher handle any new stuff
688 ... not shown
443 }; 689 };
444 690
445 The callbacks of the created watchers will not be called as the 691 The callbacks of the created watchers will not be called as the
446 watchers are destroyed before this cna happen (remember EV::check 692 watchers are destroyed before this cna happen (remember EV::check
447 gets called first). 693 gets called first).
448 694
449 The "check_ns" variant doesn't start (activate) the newly created 695 The "check_ns" variant doesn't start (activate) the newly created
450 watcher. 696 watcher.
451 697
698 FORK WATCHERS - the audacity to resume the event loop after a fork
699 Fork watchers are called when a "fork ()" was detected. The invocation
700 is done before the event loop blocks next and before "check" watchers
701 are being called, and only in the child after the fork.
702
703 $w = EV::fork $callback
704 $w = EV::fork_ns $callback
705 $w = $loop->fork ($callback)
706 $w = $loop->fork_ns ($callback)
707 Call the callback before the event loop is resumed in the child
708 process after a fork.
709
710 The "fork_ns" variant doesn't start (activate) the newly created
711 watcher.
712
713PERL SIGNALS
714 While Perl signal handling (%SIG) is not affected by EV, the behaviour
715 with EV is as the same as any other C library: Perl-signals will only be
716 handled when Perl runs, which means your signal handler might be invoked
717 only the next time an event callback is invoked.
718
719 The solution is to use EV signal watchers (see "EV::signal"), which will
720 ensure proper operations with regards to other event watchers.
721
722 If you cannot do this for whatever reason, you can also force a watcher
723 to be called on every event loop iteration by installing a "EV::check"
724 watcher:
725
726 my $async_check = EV::check sub { };
727
728 This ensures that perl gets into control for a short time to handle any
729 pending signals, and also ensures (slightly) slower overall operation.
730
452THREADS 731THREADS
453 Threads are not supported by this in any way. Perl pseudo-threads is 732 Threads are not supported by this module in any way. Perl pseudo-threads
454 evil stuff and must die. 733 is evil stuff and must die. As soon as Perl gains real threads I will
734 work on thread support for it.
735
736FORK
737 Most of the "improved" event delivering mechanisms of modern operating
738 systems have quite a few problems with fork(2) (to put it bluntly: it is
739 not supported and usually destructive). Libev makes it possible to work
740 around this by having a function that recreates the kernel state after
741 fork in the child.
742
743 On non-win32 platforms, this module requires the pthread_atfork
744 functionality to do this automatically for you. This function is quite
745 buggy on most BSDs, though, so YMMV. The overhead for this is quite
746 negligible, because everything the function currently does is set a flag
747 that is checked only when the event loop gets used the next time, so
748 when you do fork but not use EV, the overhead is minimal.
749
750 On win32, there is no notion of fork so all this doesn't apply, of
751 course.
455 752
456SEE ALSO 753SEE ALSO
457 L<EV::DNS>, L<EV::AnyEvent>. 754 EV::ADNS (asynchronous DNS), Glib::EV (makes Glib/Gtk2 use EV as event
755 loop), EV::Glib (embed Glib into EV), Coro::EV (efficient coroutines
756 with EV), Net::SNMP::EV (asynchronous SNMP).
458 757
459AUTHOR 758AUTHOR
460 Marc Lehmann <schmorp@schmorp.de> 759 Marc Lehmann <schmorp@schmorp.de>
461 http://home.schmorp.de/ 760 http://home.schmorp.de/
462 761

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