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Revision 1.12 by root, Tue Nov 27 07:27:10 2007 UTC vs.
Revision 1.20 by root, Sat Dec 22 12:05:42 2007 UTC

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37 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
38 38
39 my $w = EV::child 666, sub { 39 my $w = EV::child 666, sub {
40 my ($w, $revents) = @_; 40 my ($w, $revents) = @_;
41 my $status = $w->rstatus; 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";
42 }; 48 };
43 49
44 # MAINLOOP 50 # MAINLOOP
45 EV::loop; # loop until EV::unloop is called or all watchers stop 51 EV::loop; # loop until EV::unloop is called or all watchers stop
46 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
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50 This module provides an interface to libev 56 This module provides an interface to libev
51 (<http://software.schmorp.de/pkg/libev.html>). While the documentation 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
52 below is comprehensive, one might also consult the documentation of 58 below is comprehensive, one might also consult the documentation of
53 libev itself (<http://cvs.schmorp.de/libev/ev.html>) for more subtle 59 libev itself (<http://cvs.schmorp.de/libev/ev.html>) for more subtle
54 details on watcher semantics or some discussion on the available 60 details on watcher semantics or some discussion on the available
55 backends, or how to force a specific backend with "LIBEV_FLAGS". 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).
56 96
57BASIC INTERFACE 97BASIC INTERFACE
58 $EV::DIED 98 $EV::DIED
59 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
60 callback throws an exception (with $@ containing thr error). The 100 callback throws an exception (with $@ containing the error). The
61 default prints an informative message and continues. 101 default prints an informative message and continues.
62 102
63 If this callback throws an exception it will be silently ignored. 103 If this callback throws an exception it will be silently ignored.
64 104
65 $time = EV::time 105 $time = EV::time
66 Returns the current time in (fractional) seconds since the epoch. 106 Returns the current time in (fractional) seconds since the epoch.
67 107
68 $time = EV::now 108 $time = EV::now
109 $time = $loop->now
69 Returns the time the last event loop iteration has been started. 110 Returns the time the last event loop iteration has been started.
70 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
71 to it is usually faster then calling EV::time. 112 to it is usually faster then calling EV::time.
72 113
73 $method = EV::method 114 $backend = EV::backend
115 $backend = $loop->backend
74 Returns an integer describing the backend used by libev 116 Returns an integer describing the backend used by libev
75 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 117 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
76 118
77 EV::loop [$flags] 119 EV::loop [$flags]
120 $loop->loop ([$flags])
78 Begin checking for events and calling callbacks. It returns when a 121 Begin checking for events and calling callbacks. It returns when a
79 callback calls EV::unloop. 122 callback calls EV::unloop.
80 123
81 The $flags argument can be one of the following: 124 The $flags argument can be one of the following:
82 125
83 0 as above 126 0 as above
84 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 127 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
85 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 128 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
86 129
87 EV::unloop [$how] 130 EV::unloop [$how]
131 $loop->unloop ([$how])
88 When called with no arguments or an argument of EV::UNLOOP_ONE, 132 When called with no arguments or an argument of EV::UNLOOP_ONE,
89 makes the innermost call to EV::loop return. 133 makes the innermost call to EV::loop return.
90 134
91 When called with an argument of EV::UNLOOP_ALL, all calls to 135 When called with an argument of EV::UNLOOP_ALL, all calls to
92 EV::loop will return as fast as possible. 136 EV::loop will return as fast as possible.
93 137
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
94 EV::once $fh_or_undef, $events, $timeout, $cb->($revents) 143 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
144 $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
95 This function rolls together an I/O and a timer watcher for a single 145 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. 146 one-shot event without the need for managing a watcher object.
97 147
98 If $fh_or_undef is a filehandle or file descriptor, then $events 148 If $fh_or_undef is a filehandle or file descriptor, then $events
99 must be a bitset containing either "EV::READ", "EV::WRITE" or 149 must be a bitset containing either "EV::READ", "EV::WRITE" or
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104 If timeout is "undef" or negative, then there will be no timeout. 154 If timeout is "undef" or negative, then there will be no timeout.
105 Otherwise a EV::timer with this value will be started. 155 Otherwise a EV::timer with this value will be started.
106 156
107 When an error occurs or either the timeout or I/O watcher triggers, 157 When an error occurs or either the timeout or I/O watcher triggers,
108 then the callback will be called with the received event set (in 158 then the callback will be called with the received event set (in
109 general you can expect it to be a combination of "EV:ERROR", 159 general you can expect it to be a combination of "EV::ERROR",
110 "EV::READ", "EV::WRITE" and "EV::TIMEOUT"). 160 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
111 161
112 EV::once doesn't return anything: the watchers stay active till 162 EV::once doesn't return anything: the watchers stay active till
113 either of them triggers, then they will be stopped and freed, and 163 either of them triggers, then they will be stopped and freed, and
114 the callback invoked. 164 the callback invoked.
115 165
116 WATCHER 166 EV::feed_fd_event ($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
117 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
118 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,
119 you would create an EV::io watcher for that: 180 you would create an EV::io watcher for that:
120 181
121 my $watcher = EV::io *STDIN, EV::READ, sub { 182 my $watcher = EV::io *STDIN, EV::READ, sub {
122 my ($watcher, $revents) = @_; 183 my ($watcher, $revents) = @_;
123 warn "yeah, STDIN should not be readable without blocking!\n" 184 warn "yeah, STDIN should now be readable without blocking!\n"
124 }; 185 };
125 186
126 All watchers can be active (waiting for events) or inactive (paused). 187 All watchers can be active (waiting for events) or inactive (paused).
127 Only active watchers will have their callbacks invoked. All callbacks 188 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 189 will be called with at least two arguments: the watcher and a bitmask of
129 received events. 190 received events.
130 191
131 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
132 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
133 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,
134 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
135 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
136 (which uses EV::TIMEOUT). 197 (which uses EV::TIMEOUT).
137 198
138 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
139 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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145 206
146 Also, all methods changing some aspect of a watcher (->set, ->priority, 207 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, 208 ->fh and so on) automatically stop and start it again if it is active,
148 which means pending events get lost. 209 which means pending events get lost.
149 210
150 WATCHER TYPES 211 COMMON WATCHER METHODS
151 Now lets move to the existing watcher types and asociated methods. 212 This section lists methods common to all watchers.
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).
157 213
158 $w->start 214 $w->start
159 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
160 already active watcher. By default, all watchers start out in the 216 already active watcher. By default, all watchers start out in the
161 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
162 stopped watchers). 218 stopped watchers).
163 219
164 $w->stop 220 $w->stop
165 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
166 (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
167 callback invocation), regardless of wether the watcher was active or 223 callback invocation), regardless of whether the watcher was active
168 not. 224 or not.
169 225
170 $bool = $w->is_active 226 $bool = $w->is_active
171 Returns true if the watcher is active, false otherwise. 227 Returns true if the watcher is active, false otherwise.
172 228
173 $current_data = $w->data 229 $current_data = $w->data
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196 The default priority of any newly-created watcher is 0. 252 The default priority of any newly-created watcher is 0.
197 253
198 Note that the priority semantics have not yet been fleshed out and 254 Note that the priority semantics have not yet been fleshed out and
199 are subject to almost certain change. 255 are subject to almost certain change.
200 256
201 $w->trigger ($revents) 257 $w->invoke ($revents)
202 Call the callback *now* with the given event mask. 258 Call the callback *now* with the given event mask.
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.
203 268
204 $previous_state = $w->keepalive ($bool) 269 $previous_state = $w->keepalive ($bool)
205 Normally, "EV::loop" will return when there are no active watchers 270 Normally, "EV::loop" will return when there are no active watchers
206 (which is a "deadlock" because no progress can be made anymore). 271 (which is a "deadlock" because no progress can be made anymore).
207 This is convinient because it allows you to start your watchers (and 272 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 273 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 274 all your jobs are finished (or they forgot to register some watchers
210 for their task :). 275 for their task :).
211 276
212 Sometimes, however, this gets in your way, for example when you the 277 Sometimes, however, this gets in your way, for example when the
213 module that calls "EV::loop" (usually the main program) is not the 278 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 279 same module as a long-living watcher (for example a DNS client
215 module written by somebody else even). Then you might want any 280 module written by somebody else even). Then you might want any
216 outstanding requests to be handled, but you would not want to keep 281 outstanding requests to be handled, but you would not want to keep
217 "EV::loop" from returning just because you happen to have this 282 "EV::loop" from returning just because you happen to have this
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222 returning. 287 returning.
223 288
224 The initial value for keepalive is true (enabled), and you cna 289 The initial value for keepalive is true (enabled), and you cna
225 change it any time. 290 change it any time.
226 291
227 Example: Register an IO watcher for some UDP socket but do not keep 292 Example: Register an I/O watcher for some UDP socket but do not keep
228 the event loop from running just because of that watcher. 293 the event loop from running just because of that watcher.
229 294
230 my $udp_socket = ... 295 my $udp_socket = ...
231 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... }; 296 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
232 $udp_watcher->keepalive (0); 297 $1000udp_watcher->keepalive (0);
233 298
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?
234 $w = EV::io $fileno_or_fh, $eventmask, $callback 306 $w = EV::io $fileno_or_fh, $eventmask, $callback
235 $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)
236 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
237 when the events specified in $eventmask. 311 when at least one of events specified in $eventmask occurs.
238 312
239 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:
240 314
241 EV::READ wait until read() wouldn't block anymore 315 EV::READ wait until read() wouldn't block anymore
242 EV::WRITE wait until write() wouldn't block anymore 316 EV::WRITE wait until write() wouldn't block anymore
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254 328
255 $current_eventmask = $w->events 329 $current_eventmask = $w->events
256 $old_eventmask = $w->events ($new_eventmask) 330 $old_eventmask = $w->events ($new_eventmask)
257 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.
258 332
333 TIMER WATCHERS - relative and optionally repeating timeouts
259 $w = EV::timer $after, $repeat, $callback 334 $w = EV::timer $after, $repeat, $callback
260 $w = EV::timer_ns $after, $repeat, $callback 335 $w = EV::timer_ns $after, $repeat, $callback
336 $w = $loop->timer ($after, $repeat, $callback)
337 $w = $loop->timer_ns ($after, $repeat, $callback)
261 Calls the callback after $after seconds (which may be fractional). 338 Calls the callback after $after seconds (which may be fractional).
262 If $repeat is non-zero, the timer will be restarted (with the 339 If $repeat is non-zero, the timer will be restarted (with the
263 $repeat value as $after) after the callback returns. 340 $repeat value as $after) after the callback returns.
264 341
265 This means that the callback would be called roughly after $after 342 This means that the callback would be called roughly after $after
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277 The "timer_ns" variant doesn't start (activate) the newly created 354 The "timer_ns" variant doesn't start (activate) the newly created
278 watcher. 355 watcher.
279 356
280 $w->set ($after, $repeat) 357 $w->set ($after, $repeat)
281 Reconfigures the watcher, see the constructor above for details. Can 358 Reconfigures the watcher, see the constructor above for details. Can
282 be at any time. 359 be called at any time.
283 360
284 $w->again 361 $w->again
285 Similar to the "start" method, but has special semantics for 362 Similar to the "start" method, but has special semantics for
286 repeating timers: 363 repeating timers:
287 364
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298 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
299 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
300 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"
301 method on the timeout. 378 method on the timeout.
302 379
380 PERIODIC WATCHERS - to cron or not to cron?
303 $w = EV::periodic $at, $interval, $reschedule_cb, $callback 381 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
304 $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)
305 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
306 absolute times. Apart from creating "simple" timers that trigger 386 absolute times. Apart from creating "simple" timers that trigger
307 "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
308 absolute timers and more complex, cron-like, setups that are not 388 absolute timers and more complex, cron-like, setups that are not
309 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
… …
372 The "periodic_ns" variant doesn't start (activate) the newly created 452 The "periodic_ns" variant doesn't start (activate) the newly created
373 watcher. 453 watcher.
374 454
375 $w->set ($at, $interval, $reschedule_cb) 455 $w->set ($at, $interval, $reschedule_cb)
376 Reconfigures the watcher, see the constructor above for details. Can 456 Reconfigures the watcher, see the constructor above for details. Can
377 be at any time. 457 be called at any time.
378 458
379 $w->again 459 $w->again
380 Simply stops and starts the watcher again. 460 Simply stops and starts the watcher again.
381 461
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!
382 $w = EV::signal $signal, $callback 466 $w = EV::signal $signal, $callback
383 $w = EV::signal_ns $signal, $callback 467 $w = EV::signal_ns $signal, $callback
384 Call the callback when $signal is received (the signal can be 468 Call the callback when $signal is received (the signal can be
385 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).
386 470
387 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
388 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
389 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
390 when you add/remove callbacks to %SIG, so watch out. 474 when you add/remove callbacks to %SIG, so watch out.
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394 The "signal_ns" variant doesn't start (activate) the newly created 478 The "signal_ns" variant doesn't start (activate) the newly created
395 watcher. 479 watcher.
396 480
397 $w->set ($signal) 481 $w->set ($signal)
398 Reconfigures the watcher, see the constructor above for details. Can 482 Reconfigures the watcher, see the constructor above for details. Can
399 be at any time. 483 be called at any time.
400 484
401 $current_signum = $w->signal 485 $current_signum = $w->signal
402 $old_signum = $w->signal ($new_signal) 486 $old_signum = $w->signal ($new_signal)
403 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
404 optionally set a new one. 488 optionally set a new one.
405 489
490 CHILD WATCHERS - watch out for process status changes
406 $w = EV::child $pid, $callback 491 $w = EV::child $pid, $callback
407 $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)
408 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
409 $pid is 0) has been received. More precisely: when the process 496 $pid is 0) has been received. More precisely: when the process
410 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 497 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
411 for all changed/zombie children and call the callback. 498 for all changed/zombie children and call the callback.
412 499
413 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
414 methods on the watcher object. 507 "rstatus" and "rpid" methods on the watcher object.
415 508
416 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.
417 511
418 The "child_ns" variant doesn't start (activate) the newly created 512 The "child_ns" variant doesn't start (activate) the newly created
419 watcher. 513 watcher.
420 514
421 $w->set ($pid) 515 $w->set ($pid)
422 Reconfigures the watcher, see the constructor above for details. Can 516 Reconfigures the watcher, see the constructor above for details. Can
423 be at any time. 517 be called at any time.
424 518
425 $current_pid = $w->pid 519 $current_pid = $w->pid
426 $old_pid = $w->pid ($new_pid) 520 $old_pid = $w->pid ($new_pid)
427 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.
428 522
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432 526
433 $pid = $w->rpid 527 $pid = $w->rpid
434 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
435 a watcher for all pids). 529 a watcher for all pids).
436 530
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...
437 $w = EV::idle $callback 603 $w = EV::idle $callback
438 $w = EV::idle_ns $callback 604 $w = EV::idle_ns $callback
605 $w = $loop->idle ($callback)
606 $w = $loop->idle_ns ($callback)
439 Call the callback when there are no pending io, timer/periodic, 607 Call the callback when there are no other pending watchers of the
440 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".
441 616
442 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,
443 and they will be called repeatedly until stopped. 618 and they will be called repeatedly until stopped.
444 619
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
445 The "idle_ns" variant doesn't start (activate) the newly created 626 The "idle_ns" variant doesn't start (activate) the newly created
446 watcher. 627 watcher.
447 628
629 PREPARE WATCHERS - customise your event loop!
448 $w = EV::prepare $callback 630 $w = EV::prepare $callback
449 $w = EV::prepare_ns $callback 631 $w = EV::prepare_ns $callback
632 $w = $loop->prepare ($callback)
633 $w = $loop->prepare_ns ($callback)
450 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
451 create/modify any watchers at this point. 635 create/modify any watchers at this point.
452 636
453 See the EV::check watcher, below, for explanations and an example. 637 See the EV::check watcher, below, for explanations and an example.
454 638
455 The "prepare_ns" variant doesn't start (activate) the newly created 639 The "prepare_ns" variant doesn't start (activate) the newly created
456 watcher. 640 watcher.
457 641
642 CHECK WATCHERS - customise your event loop even more!
458 $w = EV::check $callback 643 $w = EV::check $callback
459 $w = EV::check_ns $callback 644 $w = EV::check_ns $callback
645 $w = $loop->check ($callback)
646 $w = $loop->check_ns ($callback)
460 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
461 has gathered events), but before any other callbacks have been 648 has gathered events), but before any other callbacks have been
462 invoked. 649 invoked.
463 650
464 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
… …
475 or return; 662 or return;
476 663
477 # make the dispatcher handle any outstanding stuff 664 # make the dispatcher handle any outstanding stuff
478 ... not shown 665 ... not shown
479 666
480 # create an IO watcher for each and every socket 667 # create an I/O watcher for each and every socket
481 @snmp_watcher = ( 668 @snmp_watcher = (
482 (map { EV::io $_, EV::READ, sub { } } 669 (map { EV::io $_, EV::READ, sub { } }
483 keys %{ $dispatcher->{_descriptors} }), 670 keys %{ $dispatcher->{_descriptors} }),
484 671
485 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE] 672 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
… …
505 watchers are destroyed before this cna happen (remember EV::check 692 watchers are destroyed before this cna happen (remember EV::check
506 gets called first). 693 gets called first).
507 694
508 The "check_ns" variant doesn't start (activate) the newly created 695 The "check_ns" variant doesn't start (activate) the newly created
509 watcher. 696 watcher.
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.
510 730
511THREADS 731THREADS
512 Threads are not supported by this module in any way. Perl pseudo-threads 732 Threads are not supported by this module in any way. Perl pseudo-threads
513 is evil stuff and must die. As soon as Perl gains real threads I will 733 is evil stuff and must die. As soon as Perl gains real threads I will
514 work on thread support for it. 734 work on thread support for it.
… …
529 749
530 On win32, there is no notion of fork so all this doesn't apply, of 750 On win32, there is no notion of fork so all this doesn't apply, of
531 course. 751 course.
532 752
533SEE ALSO 753SEE ALSO
534 L<EV::DNS>. 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).
535 757
536AUTHOR 758AUTHOR
537 Marc Lehmann <schmorp@schmorp.de> 759 Marc Lehmann <schmorp@schmorp.de>
538 http://home.schmorp.de/ 760 http://home.schmorp.de/
539 761

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