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39F<README.embed> in the libev distribution. If libev was configured without 39F<README.embed> in the libev distribution. If libev was configured without
40support for multiple event loops, then all functions taking an initial 40support for multiple event loops, then all functions taking an initial
41argument of name C<loop> (which is always of type C<struct ev_loop *>) 41argument of name C<loop> (which is always of type C<struct ev_loop *>)
42will not have this argument. 42will not have this argument.
43 43
44=head1 TIME AND OTHER GLOBAL FUNCTIONS 44=head1 TIME REPRESENTATION
45 45
46Libev represents time as a single floating point number, representing the 46Libev represents time as a single floating point number, representing the
47(fractional) number of seconds since the (POSIX) epoch (somewhere near 47(fractional) number of seconds since the (POSIX) epoch (somewhere near
48the beginning of 1970, details are complicated, don't ask). This type is 48the beginning of 1970, details are complicated, don't ask). This type is
49called C<ev_tstamp>, which is what you should use too. It usually aliases 49called C<ev_tstamp>, which is what you should use too. It usually aliases
50to the double type in C. 50to the double type in C.
51 51
52=head1 GLOBAL FUNCTIONS
53
52=over 4 54=over 4
53 55
54=item ev_tstamp ev_time () 56=item ev_tstamp ev_time ()
55 57
56Returns the current time as libev would use it. 58Returns the current time as libev would use it.
63you linked against by calling the functions C<ev_version_major> and 65you linked against by calling the functions C<ev_version_major> and
64C<ev_version_minor>. If you want, you can compare against the global 66C<ev_version_minor>. If you want, you can compare against the global
65symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 67symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66version of the library your program was compiled against. 68version of the library your program was compiled against.
67 69
68Usually, its a good idea to terminate if the major versions mismatch, 70Usually, it's a good idea to terminate if the major versions mismatch,
69as this indicates an incompatible change. Minor versions are usually 71as this indicates an incompatible change. Minor versions are usually
70compatible to older versions, so a larger minor version alone is usually 72compatible to older versions, so a larger minor version alone is usually
71not a problem. 73not a problem.
72 74
73=item ev_set_allocator (void *(*cb)(void *ptr, long size)) 75=item ev_set_allocator (void *(*cb)(void *ptr, long size))
99An event loop is described by a C<struct ev_loop *>. The library knows two 101An event loop is described by a C<struct ev_loop *>. The library knows two
100types of such loops, the I<default> loop, which supports signals and child 102types of such loops, the I<default> loop, which supports signals and child
101events, and dynamically created loops which do not. 103events, and dynamically created loops which do not.
102 104
103If you use threads, a common model is to run the default event loop 105If you use threads, a common model is to run the default event loop
104in your main thread (or in a separate thrad) and for each thread you 106in your main thread (or in a separate thread) and for each thread you
105create, you also create another event loop. Libev itself does no locking 107create, you also create another event loop. Libev itself does no locking
106whatsoever, so if you mix calls to the same event loop in different 108whatsoever, so if you mix calls to the same event loop in different
107threads, make sure you lock (this is usually a bad idea, though, even if 109threads, make sure you lock (this is usually a bad idea, though, even if
108done correctly, because its hideous and inefficient). 110done correctly, because it's hideous and inefficient).
109 111
110=over 4 112=over 4
111 113
112=item struct ev_loop *ev_default_loop (unsigned int flags) 114=item struct ev_loop *ev_default_loop (unsigned int flags)
113 115
118 120
119If you don't know what event loop to use, use the one returned from this 121If you don't know what event loop to use, use the one returned from this
120function. 122function.
121 123
122The flags argument can be used to specify special behaviour or specific 124The flags argument can be used to specify special behaviour or specific
123backends to use, and is usually specified as 0 (or EVFLAG_AUTO) 125backends to use, and is usually specified as 0 (or EVFLAG_AUTO).
124 126
125It supports the following flags: 127It supports the following flags:
126 128
127=over 4 129=over 4
128 130
129=item EVFLAG_AUTO 131=item C<EVFLAG_AUTO>
130 132
131The default flags value. Use this if you have no clue (its the right 133The default flags value. Use this if you have no clue (it's the right
132thing, believe me). 134thing, believe me).
133 135
134=item EVFLAG_NOENV 136=item C<EVFLAG_NOENV>
135 137
136If this flag bit is ored into the flag value then libev will I<not> look 138If this flag bit is ored into the flag value (or the program runs setuid
137at the environment variable C<LIBEV_FLAGS>. Otherwise (the default), this 139or setgid) then libev will I<not> look at the environment variable
138environment variable will override the flags completely. This is useful 140C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
141override the flags completely if it is found in the environment. This is
139to try out specific backends to tets their performance, or to work around 142useful to try out specific backends to test their performance, or to work
140bugs. 143around bugs.
141 144
142=item EVMETHOD_SELECT portable select backend 145=item C<EVMETHOD_SELECT> (portable select backend)
143 146
144=item EVMETHOD_POLL poll backend (everywhere except windows) 147=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)
145 148
146=item EVMETHOD_EPOLL linux only 149=item C<EVMETHOD_EPOLL> (linux only)
147 150
148=item EVMETHOD_KQUEUE some bsds only 151=item C<EVMETHOD_KQUEUE> (some bsds only)
149 152
150=item EVMETHOD_DEVPOLL solaris 8 only 153=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
151 154
152=item EVMETHOD_PORT solaris 10 only 155=item C<EVMETHOD_PORT> (solaris 10 only)
153 156
154If one or more of these are ored into the flags value, then only these 157If one or more of these are ored into the flags value, then only these
155backends will be tried (in the reverse order as given here). If one are 158backends will be tried (in the reverse order as given here). If one are
156specified, any backend will do. 159specified, any backend will do.
157 160
166 169
167=item ev_default_destroy () 170=item ev_default_destroy ()
168 171
169Destroys the default loop again (frees all memory and kernel state 172Destroys the default loop again (frees all memory and kernel state
170etc.). This stops all registered event watchers (by not touching them in 173etc.). This stops all registered event watchers (by not touching them in
171any way whatsoever, although you cnanot rely on this :). 174any way whatsoever, although you cannot rely on this :).
172 175
173=item ev_loop_destroy (loop) 176=item ev_loop_destroy (loop)
174 177
175Like C<ev_default_destroy>, but destroys an event loop created by an 178Like C<ev_default_destroy>, but destroys an event loop created by an
176earlier call to C<ev_loop_new>. 179earlier call to C<ev_loop_new>.
184 187
185You I<must> call this function after forking if and only if you want to 188You I<must> call this function after forking if and only if you want to
186use the event library in both processes. If you just fork+exec, you don't 189use the event library in both processes. If you just fork+exec, you don't
187have to call it. 190have to call it.
188 191
189The function itself is quite fast and its usually not a problem to call 192The function itself is quite fast and it's usually not a problem to call
190it just in case after a fork. To make this easy, the function will fit in 193it just in case after a fork. To make this easy, the function will fit in
191quite nicely into a call to C<pthread_atfork>: 194quite nicely into a call to C<pthread_atfork>:
192 195
193 pthread_atfork (0, 0, ev_default_fork); 196 pthread_atfork (0, 0, ev_default_fork);
194 197
201=item unsigned int ev_method (loop) 204=item unsigned int ev_method (loop)
202 205
203Returns one of the C<EVMETHOD_*> flags indicating the event backend in 206Returns one of the C<EVMETHOD_*> flags indicating the event backend in
204use. 207use.
205 208
206=item ev_tstamp = ev_now (loop) 209=item ev_tstamp ev_now (loop)
207 210
208Returns the current "event loop time", which is the time the event loop 211Returns the current "event loop time", which is the time the event loop
209got events and started processing them. This timestamp does not change 212got events and started processing them. This timestamp does not change
210as long as callbacks are being processed, and this is also the base time 213as long as callbacks are being processed, and this is also the base time
211used for relative timers. You can treat it as the timestamp of the event 214used for relative timers. You can treat it as the timestamp of the event
220If the flags argument is specified as 0, it will not return until either 223If the flags argument is specified as 0, it will not return until either
221no event watchers are active anymore or C<ev_unloop> was called. 224no event watchers are active anymore or C<ev_unloop> was called.
222 225
223A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle 226A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle
224those events and any outstanding ones, but will not block your process in 227those events and any outstanding ones, but will not block your process in
225case there are no events. 228case there are no events and will return after one iteration of the loop.
226 229
227A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if 230A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if
228neccessary) and will handle those and any outstanding ones. It will block 231neccessary) and will handle those and any outstanding ones. It will block
229your process until at least one new event arrives. 232your process until at least one new event arrives, and will return after
233one iteration of the loop.
230 234
231This flags value could be used to implement alternative looping 235This flags value could be used to implement alternative looping
232constructs, but the C<prepare> and C<check> watchers provide a better and 236constructs, but the C<prepare> and C<check> watchers provide a better and
233more generic mechanism. 237more generic mechanism.
234 238
235=item ev_unloop (loop, how) 239=item ev_unloop (loop, how)
236 240
237Can be used to make a call to C<ev_loop> return early. The C<how> argument 241Can be used to make a call to C<ev_loop> return early (but only after it
242has processed all outstanding events). The C<how> argument must be either
238must be either C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> 243C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or
239call return, or C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> 244C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
240calls return.
241 245
242=item ev_ref (loop) 246=item ev_ref (loop)
243 247
244=item ev_unref (loop) 248=item ev_unref (loop)
245 249
246Ref/unref can be used to add or remove a refcount on the event loop: Every 250Ref/unref can be used to add or remove a reference count on the event
247watcher keeps one reference. If you have a long-runing watcher you never 251loop: Every watcher keeps one reference, and as long as the reference
248unregister that should not keep ev_loop from running, ev_unref() after 252count is nonzero, C<ev_loop> will not return on its own. If you have
249starting, and ev_ref() before stopping it. Libev itself uses this for 253a watcher you never unregister that should not keep C<ev_loop> from
250example for its internal signal pipe: It is not visible to you as a user 254returning, ev_unref() after starting, and ev_ref() before stopping it. For
251and should not keep C<ev_loop> from exiting if the work is done. It is 255example, libev itself uses this for its internal signal pipe: It is not
252also an excellent way to do this for generic recurring timers or from 256visible to the libev user and should not keep C<ev_loop> from exiting if
253within third-party libraries. Just remember to unref after start and ref 257no event watchers registered by it are active. It is also an excellent
254before stop. 258way to do this for generic recurring timers or from within third-party
259libraries. Just remember to I<unref after start> and I<ref before stop>.
255 260
256=back 261=back
257 262
258=head1 ANATOMY OF A WATCHER 263=head1 ANATOMY OF A WATCHER
259 264
260A watcher is a structure that you create and register to record your 265A watcher is a structure that you create and register to record your
261interest in some event. For instance, if you want to wait for STDIN to 266interest in some event. For instance, if you want to wait for STDIN to
262become readable, you would create an ev_io watcher for that: 267become readable, you would create an C<ev_io> watcher for that:
263 268
264 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 269 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
265 { 270 {
266 ev_io_stop (w); 271 ev_io_stop (w);
267 ev_unloop (loop, EVUNLOOP_ALL); 272 ev_unloop (loop, EVUNLOOP_ALL);
296 301
297As long as your watcher is active (has been started but not stopped) you 302As long as your watcher is active (has been started but not stopped) you
298must not touch the values stored in it. Most specifically you must never 303must not touch the values stored in it. Most specifically you must never
299reinitialise it or call its set method. 304reinitialise it or call its set method.
300 305
301You cna check whether an event is active by calling the C<ev_is_active 306You can check whether an event is active by calling the C<ev_is_active
302(watcher *)> macro. To see whether an event is outstanding (but the 307(watcher *)> macro. To see whether an event is outstanding (but the
303callback for it has not been called yet) you cna use the C<ev_is_pending 308callback for it has not been called yet) you can use the C<ev_is_pending
304(watcher *)> macro. 309(watcher *)> macro.
305 310
306Each and every callback receives the event loop pointer as first, the 311Each and every callback receives the event loop pointer as first, the
307registered watcher structure as second, and a bitset of received events as 312registered watcher structure as second, and a bitset of received events as
308third argument. 313third argument.
309 314
310The rceeived events usually include a single bit per event type received 315The received events usually include a single bit per event type received
311(you can receive multiple events at the same time). The possible bit masks 316(you can receive multiple events at the same time). The possible bit masks
312are: 317are:
313 318
314=over 4 319=over 4
315 320
316=item EV_READ 321=item C<EV_READ>
317 322
318=item EV_WRITE 323=item C<EV_WRITE>
319 324
320The file descriptor in the ev_io watcher has become readable and/or 325The file descriptor in the C<ev_io> watcher has become readable and/or
321writable. 326writable.
322 327
323=item EV_TIMEOUT 328=item C<EV_TIMEOUT>
324 329
325The ev_timer watcher has timed out. 330The C<ev_timer> watcher has timed out.
326 331
327=item EV_PERIODIC 332=item C<EV_PERIODIC>
328 333
329The ev_periodic watcher has timed out. 334The C<ev_periodic> watcher has timed out.
330 335
331=item EV_SIGNAL 336=item C<EV_SIGNAL>
332 337
333The signal specified in the ev_signal watcher has been received by a thread. 338The signal specified in the C<ev_signal> watcher has been received by a thread.
334 339
335=item EV_CHILD 340=item C<EV_CHILD>
336 341
337The pid specified in the ev_child watcher has received a status change. 342The pid specified in the C<ev_child> watcher has received a status change.
338 343
339=item EV_IDLE 344=item C<EV_IDLE>
340 345
341The ev_idle watcher has determined that you have nothing better to do. 346The C<ev_idle> watcher has determined that you have nothing better to do.
342 347
343=item EV_PREPARE 348=item C<EV_PREPARE>
344 349
345=item EV_CHECK 350=item C<EV_CHECK>
346 351
347All ev_prepare watchers are invoked just I<before> C<ev_loop> starts 352All C<ev_prepare> watchers are invoked just I<before> C<ev_loop> starts
348to gather new events, and all ev_check watchers are invoked just after 353to gather new events, and all C<ev_check> watchers are invoked just after
349C<ev_loop> has gathered them, but before it invokes any callbacks for any 354C<ev_loop> has gathered them, but before it invokes any callbacks for any
350received events. Callbacks of both watcher types can start and stop as 355received events. Callbacks of both watcher types can start and stop as
351many watchers as they want, and all of them will be taken into account 356many watchers as they want, and all of them will be taken into account
352(for example, a ev_prepare watcher might start an idle watcher to keep 357(for example, a C<ev_prepare> watcher might start an idle watcher to keep
353C<ev_loop> from blocking). 358C<ev_loop> from blocking).
354 359
355=item EV_ERROR 360=item C<EV_ERROR>
356 361
357An unspecified error has occured, the watcher has been stopped. This might 362An unspecified error has occured, the watcher has been stopped. This might
358happen because the watcher could not be properly started because libev 363happen because the watcher could not be properly started because libev
359ran out of memory, a file descriptor was found to be closed or any other 364ran out of memory, a file descriptor was found to be closed or any other
360problem. You best act on it by reporting the problem and somehow coping 365problem. You best act on it by reporting the problem and somehow coping
369=back 374=back
370 375
371=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 376=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
372 377
373Each watcher has, by default, a member C<void *data> that you can change 378Each watcher has, by default, a member C<void *data> that you can change
374and read at any time, libev will completely ignore it. This cna be used 379and read at any time, libev will completely ignore it. This can be used
375to associate arbitrary data with your watcher. If you need more data and 380to associate arbitrary data with your watcher. If you need more data and
376don't want to allocate memory and store a pointer to it in that data 381don't want to allocate memory and store a pointer to it in that data
377member, you can also "subclass" the watcher type and provide your own 382member, you can also "subclass" the watcher type and provide your own
378data: 383data:
379 384
401=head1 WATCHER TYPES 406=head1 WATCHER TYPES
402 407
403This section describes each watcher in detail, but will not repeat 408This section describes each watcher in detail, but will not repeat
404information given in the last section. 409information given in the last section.
405 410
406=head2 struct ev_io - is my file descriptor readable or writable 411=head2 C<ev_io> - is this file descriptor readable or writable
407 412
408I/O watchers check whether a file descriptor is readable or writable 413I/O watchers check whether a file descriptor is readable or writable
409in each iteration of the event loop (This behaviour is called 414in each iteration of the event loop (This behaviour is called
410level-triggering because you keep receiving events as long as the 415level-triggering because you keep receiving events as long as the
411condition persists. Remember you cna stop the watcher if you don't want to 416condition persists. Remember you can stop the watcher if you don't want to
412act on the event and neither want to receive future events). 417act on the event and neither want to receive future events).
413 418
419In general you can register as many read and/or write event watchers oer
420fd as you want (as long as you don't confuse yourself). Setting all file
421descriptors to non-blocking mode is also usually a good idea (but not
422required if you know what you are doing).
423
424You have to be careful with dup'ed file descriptors, though. Some backends
425(the linux epoll backend is a notable example) cannot handle dup'ed file
426descriptors correctly if you register interest in two or more fds pointing
427to the same file/socket etc. description.
428
429If you must do this, then force the use of a known-to-be-good backend
430(at the time of this writing, this includes only EVMETHOD_SELECT and
431EVMETHOD_POLL).
432
414=over 4 433=over 4
415 434
416=item ev_io_init (ev_io *, callback, int fd, int events) 435=item ev_io_init (ev_io *, callback, int fd, int events)
417 436
418=item ev_io_set (ev_io *, int fd, int events) 437=item ev_io_set (ev_io *, int fd, int events)
419 438
420Configures an ev_io watcher. The fd is the file descriptor to rceeive 439Configures an C<ev_io> watcher. The fd is the file descriptor to rceeive
421events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ | 440events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
422EV_WRITE> to receive the given events. 441EV_WRITE> to receive the given events.
423 442
424=back 443=back
425 444
426=head2 struct ev_timer - relative and optionally recurring timeouts 445=head2 C<ev_timer> - relative and optionally recurring timeouts
427 446
428Timer watchers are simple relative timers that generate an event after a 447Timer watchers are simple relative timers that generate an event after a
429given time, and optionally repeating in regular intervals after that. 448given time, and optionally repeating in regular intervals after that.
430 449
431The timers are based on real time, that is, if you register an event that 450The timers are based on real time, that is, if you register an event that
432times out after an hour and youreset your system clock to last years 451times out after an hour and youreset your system clock to last years
433time, it will still time out after (roughly) and hour. "Roughly" because 452time, it will still time out after (roughly) and hour. "Roughly" because
434detecting time jumps is hard, and soem inaccuracies are unavoidable (the 453detecting time jumps is hard, and soem inaccuracies are unavoidable (the
435monotonic clock option helps a lot here). 454monotonic clock option helps a lot here).
436 455
456The relative timeouts are calculated relative to the C<ev_now ()>
457time. This is usually the right thing as this timestamp refers to the time
458of the event triggering whatever timeout you are modifying/starting. If
459you suspect event processing to be delayed and you *need* to base the timeout
460ion the current time, use something like this to adjust for this:
461
462 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
463
437=over 4 464=over 4
438 465
439=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 466=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
440 467
441=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) 468=item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)
463 490
464This sounds a bit complicated, but here is a useful and typical 491This sounds a bit complicated, but here is a useful and typical
465example: Imagine you have a tcp connection and you want a so-called idle 492example: Imagine you have a tcp connection and you want a so-called idle
466timeout, that is, you want to be called when there have been, say, 60 493timeout, that is, you want to be called when there have been, say, 60
467seconds of inactivity on the socket. The easiest way to do this is to 494seconds of inactivity on the socket. The easiest way to do this is to
468configure an ev_timer with after=repeat=60 and calling ev_timer_again each 495configure an C<ev_timer> with after=repeat=60 and calling ev_timer_again each
469time you successfully read or write some data. If you go into an idle 496time you successfully read or write some data. If you go into an idle
470state where you do not expect data to travel on the socket, you can stop 497state where you do not expect data to travel on the socket, you can stop
471the timer, and again will automatically restart it if need be. 498the timer, and again will automatically restart it if need be.
472 499
473=back 500=back
474 501
475=head2 ev_periodic - to cron or not to cron it 502=head2 C<ev_periodic> - to cron or not to cron
476 503
477Periodic watchers are also timers of a kind, but they are very versatile 504Periodic watchers are also timers of a kind, but they are very versatile
478(and unfortunately a bit complex). 505(and unfortunately a bit complex).
479 506
480Unlike ev_timer's, they are not based on real time (or relative time) 507Unlike C<ev_timer>'s, they are not based on real time (or relative time)
481but on wallclock time (absolute time). You can tell a periodic watcher 508but on wallclock time (absolute time). You can tell a periodic watcher
482to trigger "at" some specific point in time. For example, if you tell a 509to trigger "at" some specific point in time. For example, if you tell a
483periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 510periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
484+ 10.>) and then reset your system clock to the last year, then it will 511+ 10.>) and then reset your system clock to the last year, then it will
485take a year to trigger the event (unlike an ev_timer, which would trigger 512take a year to trigger the event (unlike an C<ev_timer>, which would trigger
486roughly 10 seconds later and of course not if you reset your system time 513roughly 10 seconds later and of course not if you reset your system time
487again). 514again).
488 515
489They can also be used to implement vastly more complex timers, such as 516They can also be used to implement vastly more complex timers, such as
490triggering an event on eahc midnight, local time. 517triggering an event on eahc midnight, local time.
519 546
520 ev_periodic_set (&periodic, 0., 3600., 0); 547 ev_periodic_set (&periodic, 0., 3600., 0);
521 548
522This doesn't mean there will always be 3600 seconds in between triggers, 549This doesn't mean there will always be 3600 seconds in between triggers,
523but only that the the callback will be called when the system time shows a 550but only that the the callback will be called when the system time shows a
524full hour (UTC), or more correct, when the system time is evenly divisible 551full hour (UTC), or more correctly, when the system time is evenly divisible
525by 3600. 552by 3600.
526 553
527Another way to think about it (for the mathematically inclined) is that 554Another way to think about it (for the mathematically inclined) is that
528ev_periodic will try to run the callback in this mode at the next possible 555C<ev_periodic> will try to run the callback in this mode at the next possible
529time where C<time = at (mod interval)>, regardless of any time jumps. 556time where C<time = at (mod interval)>, regardless of any time jumps.
530 557
531=item * manual reschedule mode (reschedule_cb = callback) 558=item * manual reschedule mode (reschedule_cb = callback)
532 559
533In this mode the values for C<interval> and C<at> are both being 560In this mode the values for C<interval> and C<at> are both being
534ignored. Instead, each time the periodic watcher gets scheduled, the 561ignored. Instead, each time the periodic watcher gets scheduled, the
535reschedule callback will be called with the watcher as first, and the 562reschedule callback will be called with the watcher as first, and the
536current time as second argument. 563current time as second argument.
537 564
538NOTE: I<This callback MUST NOT stop or destroy the periodic or any other 565NOTE: I<This callback MUST NOT stop or destroy the periodic or any other
539periodic watcher, ever, or make any event loop modificstions>. If you need 566periodic watcher, ever, or make any event loop modifications>. If you need
540to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards. 567to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards.
541 568
569Also, I<< this callback must always return a time that is later than the
570passed C<now> value >>. Not even C<now> itself will be ok.
571
542Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 572Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
543ev_tstamp now)>, e.g.: 573ev_tstamp now)>, e.g.:
544 574
545 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 575 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
546 { 576 {
547 return now + 60.; 577 return now + 60.;
566a different time than the last time it was called (e.g. in a crond like 596a different time than the last time it was called (e.g. in a crond like
567program when the crontabs have changed). 597program when the crontabs have changed).
568 598
569=back 599=back
570 600
571=head2 ev_signal - signal me when a signal gets signalled 601=head2 C<ev_signal> - signal me when a signal gets signalled
572 602
573Signal watchers will trigger an event when the process receives a specific 603Signal watchers will trigger an event when the process receives a specific
574signal one or more times. Even though signals are very asynchronous, libev 604signal one or more times. Even though signals are very asynchronous, libev
575will try its best to deliver signals synchronously, i.e. as part of the 605will try it's best to deliver signals synchronously, i.e. as part of the
576normal event processing, like any other event. 606normal event processing, like any other event.
577 607
578You cna configure as many watchers as you like per signal. Only when the 608You can configure as many watchers as you like per signal. Only when the
579first watcher gets started will libev actually register a signal watcher 609first watcher gets started will libev actually register a signal watcher
580with the kernel (thus it coexists with your own signal handlers as long 610with the kernel (thus it coexists with your own signal handlers as long
581as you don't register any with libev). Similarly, when the last signal 611as you don't register any with libev). Similarly, when the last signal
582watcher for a signal is stopped libev will reset the signal handler to 612watcher for a signal is stopped libev will reset the signal handler to
583SIG_DFL (regardless of what it was set to before). 613SIG_DFL (regardless of what it was set to before).
591Configures the watcher to trigger on the given signal number (usually one 621Configures the watcher to trigger on the given signal number (usually one
592of the C<SIGxxx> constants). 622of the C<SIGxxx> constants).
593 623
594=back 624=back
595 625
596=head2 ev_child - wait for pid status changes 626=head2 C<ev_child> - wait for pid status changes
597 627
598Child watchers trigger when your process receives a SIGCHLD in response to 628Child watchers trigger when your process receives a SIGCHLD in response to
599some child status changes (most typically when a child of yours dies). 629some child status changes (most typically when a child of yours dies).
600 630
601=over 4 631=over 4
605=item ev_child_set (ev_child *, int pid) 635=item ev_child_set (ev_child *, int pid)
606 636
607Configures the watcher to wait for status changes of process C<pid> (or 637Configures the watcher to wait for status changes of process C<pid> (or
608I<any> process if C<pid> is specified as C<0>). The callback can look 638I<any> process if C<pid> is specified as C<0>). The callback can look
609at the C<rstatus> member of the C<ev_child> watcher structure to see 639at the C<rstatus> member of the C<ev_child> watcher structure to see
610the status word (use the macros from C<sys/wait.h>). The C<rpid> member 640the status word (use the macros from C<sys/wait.h> and see your systems
611contains the pid of the process causing the status change. 641C<waitpid> documentation). The C<rpid> member contains the pid of the
642process causing the status change.
612 643
613=back 644=back
614 645
615=head2 ev_idle - when you've got nothing better to do 646=head2 C<ev_idle> - when you've got nothing better to do
616 647
617Idle watchers trigger events when there are no other I/O or timer (or 648Idle watchers trigger events when there are no other events are pending
618periodic) events pending. That is, as long as your process is busy 649(prepare, check and other idle watchers do not count). That is, as long
619handling sockets or timeouts it will not be called. But when your process 650as your process is busy handling sockets or timeouts (or even signals,
620is idle all idle watchers are being called again and again - until 651imagine) it will not be triggered. But when your process is idle all idle
652watchers are being called again and again, once per event loop iteration -
621stopped, that is, or your process receives more events. 653until stopped, that is, or your process receives more events and becomes
654busy.
622 655
623The most noteworthy effect is that as long as any idle watchers are 656The most noteworthy effect is that as long as any idle watchers are
624active, the process will not block when waiting for new events. 657active, the process will not block when waiting for new events.
625 658
626Apart from keeping your process non-blocking (which is a useful 659Apart from keeping your process non-blocking (which is a useful
636kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 669kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
637believe me. 670believe me.
638 671
639=back 672=back
640 673
641=head2 prepare and check - your hooks into the event loop 674=head2 C<ev_prepare> and C<ev_check> - customise your event loop
642 675
643Prepare and check watchers usually (but not always) are used in 676Prepare and check watchers are usually (but not always) used in tandem:
644tandom. Prepare watchers get invoked before the process blocks and check 677Prepare watchers get invoked before the process blocks and check watchers
645watchers afterwards. 678afterwards.
646 679
647Their main purpose is to integrate other event mechanisms into libev. This 680Their main purpose is to integrate other event mechanisms into libev. This
648could be used, for example, to track variable changes, implement your own 681could be used, for example, to track variable changes, implement your own
649watchers, integrate net-snmp or a coroutine library and lots more. 682watchers, integrate net-snmp or a coroutine library and lots more.
650 683
651This is done by examining in each prepare call which file descriptors need 684This is done by examining in each prepare call which file descriptors need
652to be watched by the other library, registering ev_io watchers for them 685to be watched by the other library, registering C<ev_io> watchers for
653and starting an ev_timer watcher for any timeouts (many libraries provide 686them and starting an C<ev_timer> watcher for any timeouts (many libraries
654just this functionality). Then, in the check watcher you check for any 687provide just this functionality). Then, in the check watcher you check for
655events that occured (by making your callbacks set soem flags for example) 688any events that occured (by checking the pending status of all watchers
656and call back into the library. 689and stopping them) and call back into the library. The I/O and timer
690callbacks will never actually be called (but must be valid neverthelles,
691because you never know, you know?).
657 692
658As another example, the perl Coro module uses these hooks to integrate 693As another example, the Perl Coro module uses these hooks to integrate
659coroutines into libev programs, by yielding to other active coroutines 694coroutines into libev programs, by yielding to other active coroutines
660during each prepare and only letting the process block if no coroutines 695during each prepare and only letting the process block if no coroutines
661are ready to run. 696are ready to run (its actually more complicated, it only runs coroutines
697with priority higher than the event loop and one lower priority once,
698using idle watchers to keep the event loop from blocking if lower-priority
699coroutines exist, thus mapping low-priority coroutines to idle/background
700tasks).
662 701
663=over 4 702=over 4
664 703
665=item ev_prepare_init (ev_prepare *, callback) 704=item ev_prepare_init (ev_prepare *, callback)
666 705
667=item ev_check_init (ev_check *, callback) 706=item ev_check_init (ev_check *, callback)
668 707
669Initialises and configures the prepare or check watcher - they have no 708Initialises and configures the prepare or check watcher - they have no
670parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 709parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
671macros, but using them is utterly, utterly pointless. 710macros, but using them is utterly, utterly and completely pointless.
672 711
673=back 712=back
674 713
675=head1 OTHER FUNCTIONS 714=head1 OTHER FUNCTIONS
676 715
677There are some other fucntions of possible interest. Described. Here. Now. 716There are some other functions of possible interest. Described. Here. Now.
678 717
679=over 4 718=over 4
680 719
681=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 720=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
682 721
684callback on whichever event happens first and automatically stop both 723callback on whichever event happens first and automatically stop both
685watchers. This is useful if you want to wait for a single event on an fd 724watchers. This is useful if you want to wait for a single event on an fd
686or timeout without havign to allocate/configure/start/stop/free one or 725or timeout without havign to allocate/configure/start/stop/free one or
687more watchers yourself. 726more watchers yourself.
688 727
689If C<fd> is less than 0, then no I/O watcher will be started and events is 728If C<fd> is less than 0, then no I/O watcher will be started and events
690ignored. Otherwise, an ev_io watcher for the given C<fd> and C<events> set 729is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
691will be craeted and started. 730C<events> set will be craeted and started.
692 731
693If C<timeout> is less than 0, then no timeout watcher will be 732If C<timeout> is less than 0, then no timeout watcher will be
694started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat 733started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
695= 0) will be started. 734repeat = 0) will be started. While C<0> is a valid timeout, it is of
735dubious value.
696 736
697The callback has the type C<void (*cb)(int revents, void *arg)> and 737The callback has the type C<void (*cb)(int revents, void *arg)> and gets
698gets passed an events set (normally a combination of EV_ERROR, EV_READ, 738passed an events set like normal event callbacks (with a combination of
699EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>: 739C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
740value passed to C<ev_once>:
700 741
701 static void stdin_ready (int revents, void *arg) 742 static void stdin_ready (int revents, void *arg)
702 { 743 {
703 if (revents & EV_TIMEOUT) 744 if (revents & EV_TIMEOUT)
704 /* doh, nothing entered */ 745 /* doh, nothing entered */;
705 else if (revents & EV_READ) 746 else if (revents & EV_READ)
706 /* stdin might have data for us, joy! */ 747 /* stdin might have data for us, joy! */;
707 } 748 }
708 749
709 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 750 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
710 751
711=item ev_feed_event (loop, watcher, int events) 752=item ev_feed_event (loop, watcher, int events)
712 753
713Feeds the given event set into the event loop, as if the specified event 754Feeds the given event set into the event loop, as if the specified event
714has happened for the specified watcher (which must be a pointer to an 755had happened for the specified watcher (which must be a pointer to an
715initialised but not necessarily active event watcher). 756initialised but not necessarily started event watcher).
716 757
717=item ev_feed_fd_event (loop, int fd, int revents) 758=item ev_feed_fd_event (loop, int fd, int revents)
718 759
719Feed an event on the given fd, as if a file descriptor backend detected it. 760Feed an event on the given fd, as if a file descriptor backend detected
761the given events it.
720 762
721=item ev_feed_signal_event (loop, int signum) 763=item ev_feed_signal_event (loop, int signum)
722 764
723Feed an event as if the given signal occured (loop must be the default loop!). 765Feed an event as if the given signal occured (loop must be the default loop!).
724 766

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