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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
54These functions can be called anytime, even before initialising the
55library in any way.
56
52=over 4 57=over 4
53 58
54=item ev_tstamp ev_time () 59=item ev_tstamp ev_time ()
55 60
56Returns the current time as libev would use it. 61Returns the current time as libev would use it.
63you linked against by calling the functions C<ev_version_major> and 68you linked against by calling the functions C<ev_version_major> and
64C<ev_version_minor>. If you want, you can compare against the global 69C<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 70symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
66version of the library your program was compiled against. 71version of the library your program was compiled against.
67 72
68Usually, its a good idea to terminate if the major versions mismatch, 73Usually, it's a good idea to terminate if the major versions mismatch,
69as this indicates an incompatible change. Minor versions are usually 74as this indicates an incompatible change. Minor versions are usually
70compatible to older versions, so a larger minor version alone is usually 75compatible to older versions, so a larger minor version alone is usually
71not a problem. 76not a problem.
72 77
73=item ev_set_allocator (void *(*cb)(void *ptr, long size)) 78=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 104An 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 105types of such loops, the I<default> loop, which supports signals and child
101events, and dynamically created loops which do not. 106events, and dynamically created loops which do not.
102 107
103If you use threads, a common model is to run the default event loop 108If 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 109in 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 110create, you also create another event loop. Libev itself does no locking
106whatsoever, so if you mix calls to the same event loop in different 111whatsoever, 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 112threads, make sure you lock (this is usually a bad idea, though, even if
108done correctly, because its hideous and inefficient). 113done correctly, because it's hideous and inefficient).
109 114
110=over 4 115=over 4
111 116
112=item struct ev_loop *ev_default_loop (unsigned int flags) 117=item struct ev_loop *ev_default_loop (unsigned int flags)
113 118
118 123
119If you don't know what event loop to use, use the one returned from this 124If you don't know what event loop to use, use the one returned from this
120function. 125function.
121 126
122The flags argument can be used to specify special behaviour or specific 127The flags argument can be used to specify special behaviour or specific
123backends to use, and is usually specified as 0 (or EVFLAG_AUTO) 128backends to use, and is usually specified as 0 (or EVFLAG_AUTO).
124 129
125It supports the following flags: 130It supports the following flags:
126 131
127=over 4 132=over 4
128 133
129=item EVFLAG_AUTO 134=item C<EVFLAG_AUTO>
130 135
131The default flags value. Use this if you have no clue (its the right 136The default flags value. Use this if you have no clue (it's the right
132thing, believe me). 137thing, believe me).
133 138
134=item EVFLAG_NOENV 139=item C<EVFLAG_NOENV>
135 140
136If this flag bit is ored into the flag value then libev will I<not> look 141If 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 142or setgid) then libev will I<not> look at the environment variable
138environment variable will override the flags completely. This is useful 143C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
144override 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 145useful to try out specific backends to test their performance, or to work
140bugs. 146around bugs.
141 147
142=item EVMETHOD_SELECT portable select backend 148=item C<EVMETHOD_SELECT> (portable select backend)
143 149
144=item EVMETHOD_POLL poll backend (everywhere except windows) 150=item C<EVMETHOD_POLL> (poll backend, available everywhere except on windows)
145 151
146=item EVMETHOD_EPOLL linux only 152=item C<EVMETHOD_EPOLL> (linux only)
147 153
148=item EVMETHOD_KQUEUE some bsds only 154=item C<EVMETHOD_KQUEUE> (some bsds only)
149 155
150=item EVMETHOD_DEVPOLL solaris 8 only 156=item C<EVMETHOD_DEVPOLL> (solaris 8 only)
151 157
152=item EVMETHOD_PORT solaris 10 only 158=item C<EVMETHOD_PORT> (solaris 10 only)
153 159
154If one or more of these are ored into the flags value, then only these 160If 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 161backends will be tried (in the reverse order as given here). If one are
156specified, any backend will do. 162specified, any backend will do.
157 163
166 172
167=item ev_default_destroy () 173=item ev_default_destroy ()
168 174
169Destroys the default loop again (frees all memory and kernel state 175Destroys the default loop again (frees all memory and kernel state
170etc.). This stops all registered event watchers (by not touching them in 176etc.). This stops all registered event watchers (by not touching them in
171any way whatsoever, although you cnanot rely on this :). 177any way whatsoever, although you cannot rely on this :).
172 178
173=item ev_loop_destroy (loop) 179=item ev_loop_destroy (loop)
174 180
175Like C<ev_default_destroy>, but destroys an event loop created by an 181Like C<ev_default_destroy>, but destroys an event loop created by an
176earlier call to C<ev_loop_new>. 182earlier call to C<ev_loop_new>.
184 190
185You I<must> call this function after forking if and only if you want to 191You 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 192use the event library in both processes. If you just fork+exec, you don't
187have to call it. 193have to call it.
188 194
189The function itself is quite fast and its usually not a problem to call 195The 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 196it just in case after a fork. To make this easy, the function will fit in
191quite nicely into a call to C<pthread_atfork>: 197quite nicely into a call to C<pthread_atfork>:
192 198
193 pthread_atfork (0, 0, ev_default_fork); 199 pthread_atfork (0, 0, ev_default_fork);
194 200
201=item unsigned int ev_method (loop) 207=item unsigned int ev_method (loop)
202 208
203Returns one of the C<EVMETHOD_*> flags indicating the event backend in 209Returns one of the C<EVMETHOD_*> flags indicating the event backend in
204use. 210use.
205 211
206=item ev_tstamp = ev_now (loop) 212=item ev_tstamp ev_now (loop)
207 213
208Returns the current "event loop time", which is the time the event loop 214Returns the current "event loop time", which is the time the event loop
209got events and started processing them. This timestamp does not change 215got events and started processing them. This timestamp does not change
210as long as callbacks are being processed, and this is also the base time 216as 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 217used 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 226If 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. 227no event watchers are active anymore or C<ev_unloop> was called.
222 228
223A flags value of C<EVLOOP_NONBLOCK> will look for new events, will handle 229A 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 230those events and any outstanding ones, but will not block your process in
225case there are no events. 231case there are no events and will return after one iteration of the loop.
226 232
227A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if 233A 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 234neccessary) and will handle those and any outstanding ones. It will block
229your process until at least one new event arrives. 235your process until at least one new event arrives, and will return after
236one iteration of the loop.
230 237
231This flags value could be used to implement alternative looping 238This flags value could be used to implement alternative looping
232constructs, but the C<prepare> and C<check> watchers provide a better and 239constructs, but the C<prepare> and C<check> watchers provide a better and
233more generic mechanism. 240more generic mechanism.
234 241
235=item ev_unloop (loop, how) 242=item ev_unloop (loop, how)
236 243
237Can be used to make a call to C<ev_loop> return early. The C<how> argument 244Can be used to make a call to C<ev_loop> return early (but only after it
245has 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> 246C<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> 247C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
240calls return.
241 248
242=item ev_ref (loop) 249=item ev_ref (loop)
243 250
244=item ev_unref (loop) 251=item ev_unref (loop)
245 252
246Ref/unref can be used to add or remove a refcount on the event loop: Every 253Ref/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 254loop: Every watcher keeps one reference, and as long as the reference
248unregister that should not keep ev_loop from running, ev_unref() after 255count 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 256a 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 257returning, 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 258example, 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 259visible 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 260no event watchers registered by it are active. It is also an excellent
254before stop. 261way to do this for generic recurring timers or from within third-party
262libraries. Just remember to I<unref after start> and I<ref before stop>.
255 263
256=back 264=back
257 265
258=head1 ANATOMY OF A WATCHER 266=head1 ANATOMY OF A WATCHER
259 267
260A watcher is a structure that you create and register to record your 268A 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 269interest in some event. For instance, if you want to wait for STDIN to
262become readable, you would create an ev_io watcher for that: 270become readable, you would create an C<ev_io> watcher for that:
263 271
264 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 272 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
265 { 273 {
266 ev_io_stop (w); 274 ev_io_stop (w);
267 ev_unloop (loop, EVUNLOOP_ALL); 275 ev_unloop (loop, EVUNLOOP_ALL);
296 304
297As long as your watcher is active (has been started but not stopped) you 305As 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 306must not touch the values stored in it. Most specifically you must never
299reinitialise it or call its set method. 307reinitialise it or call its set method.
300 308
301You cna check whether an event is active by calling the C<ev_is_active 309You 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 310(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 311callback for it has not been called yet) you can use the C<ev_is_pending
304(watcher *)> macro. 312(watcher *)> macro.
305 313
306Each and every callback receives the event loop pointer as first, the 314Each and every callback receives the event loop pointer as first, the
307registered watcher structure as second, and a bitset of received events as 315registered watcher structure as second, and a bitset of received events as
308third argument. 316third argument.
309 317
310The rceeived events usually include a single bit per event type received 318The 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 319(you can receive multiple events at the same time). The possible bit masks
312are: 320are:
313 321
314=over 4 322=over 4
315 323
316=item EV_READ 324=item C<EV_READ>
317 325
318=item EV_WRITE 326=item C<EV_WRITE>
319 327
320The file descriptor in the ev_io watcher has become readable and/or 328The file descriptor in the C<ev_io> watcher has become readable and/or
321writable. 329writable.
322 330
323=item EV_TIMEOUT 331=item C<EV_TIMEOUT>
324 332
325The ev_timer watcher has timed out. 333The C<ev_timer> watcher has timed out.
326 334
327=item EV_PERIODIC 335=item C<EV_PERIODIC>
328 336
329The ev_periodic watcher has timed out. 337The C<ev_periodic> watcher has timed out.
330 338
331=item EV_SIGNAL 339=item C<EV_SIGNAL>
332 340
333The signal specified in the ev_signal watcher has been received by a thread. 341The signal specified in the C<ev_signal> watcher has been received by a thread.
334 342
335=item EV_CHILD 343=item C<EV_CHILD>
336 344
337The pid specified in the ev_child watcher has received a status change. 345The pid specified in the C<ev_child> watcher has received a status change.
338 346
339=item EV_IDLE 347=item C<EV_IDLE>
340 348
341The ev_idle watcher has determined that you have nothing better to do. 349The C<ev_idle> watcher has determined that you have nothing better to do.
342 350
343=item EV_PREPARE 351=item C<EV_PREPARE>
344 352
345=item EV_CHECK 353=item C<EV_CHECK>
346 354
347All ev_prepare watchers are invoked just I<before> C<ev_loop> starts 355All 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 356to 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 357C<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 358received 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 359many 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 360(for example, a C<ev_prepare> watcher might start an idle watcher to keep
353C<ev_loop> from blocking). 361C<ev_loop> from blocking).
354 362
355=item EV_ERROR 363=item C<EV_ERROR>
356 364
357An unspecified error has occured, the watcher has been stopped. This might 365An unspecified error has occured, the watcher has been stopped. This might
358happen because the watcher could not be properly started because libev 366happen 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 367ran 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 368problem. You best act on it by reporting the problem and somehow coping
369=back 377=back
370 378
371=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 379=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
372 380
373Each watcher has, by default, a member C<void *data> that you can change 381Each 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 382and 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 383to 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 384don'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 385member, you can also "subclass" the watcher type and provide your own
378data: 386data:
379 387
401=head1 WATCHER TYPES 409=head1 WATCHER TYPES
402 410
403This section describes each watcher in detail, but will not repeat 411This section describes each watcher in detail, but will not repeat
404information given in the last section. 412information given in the last section.
405 413
406=head2 struct ev_io - is my file descriptor readable or writable 414=head2 C<ev_io> - is this file descriptor readable or writable
407 415
408I/O watchers check whether a file descriptor is readable or writable 416I/O watchers check whether a file descriptor is readable or writable
409in each iteration of the event loop (This behaviour is called 417in each iteration of the event loop (This behaviour is called
410level-triggering because you keep receiving events as long as the 418level-triggering because you keep receiving events as long as the
411condition persists. Remember you cna stop the watcher if you don't want to 419condition persists. Remember you can stop the watcher if you don't want to
412act on the event and neither want to receive future events). 420act on the event and neither want to receive future events).
413 421
422In general you can register as many read and/or write event watchers per
423fd as you want (as long as you don't confuse yourself). Setting all file
424descriptors to non-blocking mode is also usually a good idea (but not
425required if you know what you are doing).
426
427You have to be careful with dup'ed file descriptors, though. Some backends
428(the linux epoll backend is a notable example) cannot handle dup'ed file
429descriptors correctly if you register interest in two or more fds pointing
430to the same file/socket etc. description (that is, they share the same
431underlying "file open").
432
433If you must do this, then force the use of a known-to-be-good backend
434(at the time of this writing, this includes only EVMETHOD_SELECT and
435EVMETHOD_POLL).
436
414=over 4 437=over 4
415 438
416=item ev_io_init (ev_io *, callback, int fd, int events) 439=item ev_io_init (ev_io *, callback, int fd, int events)
417 440
418=item ev_io_set (ev_io *, int fd, int events) 441=item ev_io_set (ev_io *, int fd, int events)
419 442
420Configures an ev_io watcher. The fd is the file descriptor to rceeive 443Configures 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 | 444events for and events is either C<EV_READ>, C<EV_WRITE> or C<EV_READ |
422EV_WRITE> to receive the given events. 445EV_WRITE> to receive the given events.
423 446
424=back 447=back
425 448
426=head2 struct ev_timer - relative and optionally recurring timeouts 449=head2 C<ev_timer> - relative and optionally recurring timeouts
427 450
428Timer watchers are simple relative timers that generate an event after a 451Timer watchers are simple relative timers that generate an event after a
429given time, and optionally repeating in regular intervals after that. 452given time, and optionally repeating in regular intervals after that.
430 453
431The timers are based on real time, that is, if you register an event that 454The 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 455times out after an hour and you reset your system clock to last years
433time, it will still time out after (roughly) and hour. "Roughly" because 456time, it will still time out after (roughly) and hour. "Roughly" because
434detecting time jumps is hard, and soem inaccuracies are unavoidable (the 457detecting time jumps is hard, and soem inaccuracies are unavoidable (the
435monotonic clock option helps a lot here). 458monotonic clock option helps a lot here).
459
460The relative timeouts are calculated relative to the C<ev_now ()>
461time. This is usually the right thing as this timestamp refers to the time
462of the event triggering whatever timeout you are modifying/starting. If
463you suspect event processing to be delayed and you *need* to base the timeout
464on the current time, use something like this to adjust for this:
465
466 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
436 467
437=over 4 468=over 4
438 469
439=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 470=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
440 471
446later, again, and again, until stopped manually. 477later, again, and again, until stopped manually.
447 478
448The timer itself will do a best-effort at avoiding drift, that is, if you 479The timer itself will do a best-effort at avoiding drift, that is, if you
449configure a timer to trigger every 10 seconds, then it will trigger at 480configure a timer to trigger every 10 seconds, then it will trigger at
450exactly 10 second intervals. If, however, your program cannot keep up with 481exactly 10 second intervals. If, however, your program cannot keep up with
451the timer (ecause it takes longer than those 10 seconds to do stuff) the 482the timer (because it takes longer than those 10 seconds to do stuff) the
452timer will not fire more than once per event loop iteration. 483timer will not fire more than once per event loop iteration.
453 484
454=item ev_timer_again (loop) 485=item ev_timer_again (loop)
455 486
456This will act as if the timer timed out and restart it again if it is 487This will act as if the timer timed out and restart it again if it is
463 494
464This sounds a bit complicated, but here is a useful and typical 495This 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 496example: 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 497timeout, 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 498seconds 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 499configure 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 500time 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 501state 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. 502the timer, and again will automatically restart it if need be.
472 503
473=back 504=back
474 505
475=head2 ev_periodic - to cron or not to cron it 506=head2 C<ev_periodic> - to cron or not to cron
476 507
477Periodic watchers are also timers of a kind, but they are very versatile 508Periodic watchers are also timers of a kind, but they are very versatile
478(and unfortunately a bit complex). 509(and unfortunately a bit complex).
479 510
480Unlike ev_timer's, they are not based on real time (or relative time) 511Unlike 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 512but 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 513to 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 () 514periodic 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 515+ 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 516take 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 517roughly 10 seconds later and of course not if you reset your system time
487again). 518again).
488 519
489They can also be used to implement vastly more complex timers, such as 520They can also be used to implement vastly more complex timers, such as
490triggering an event on eahc midnight, local time. 521triggering an event on eahc midnight, local time.
519 550
520 ev_periodic_set (&periodic, 0., 3600., 0); 551 ev_periodic_set (&periodic, 0., 3600., 0);
521 552
522This doesn't mean there will always be 3600 seconds in between triggers, 553This 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 554but 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 555full hour (UTC), or more correctly, when the system time is evenly divisible
525by 3600. 556by 3600.
526 557
527Another way to think about it (for the mathematically inclined) is that 558Another 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 559C<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. 560time where C<time = at (mod interval)>, regardless of any time jumps.
530 561
531=item * manual reschedule mode (reschedule_cb = callback) 562=item * manual reschedule mode (reschedule_cb = callback)
532 563
533In this mode the values for C<interval> and C<at> are both being 564In this mode the values for C<interval> and C<at> are both being
534ignored. Instead, each time the periodic watcher gets scheduled, the 565ignored. Instead, each time the periodic watcher gets scheduled, the
535reschedule callback will be called with the watcher as first, and the 566reschedule callback will be called with the watcher as first, and the
536current time as second argument. 567current time as second argument.
537 568
538NOTE: I<This callback MUST NOT stop or destroy the periodic or any other 569NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
539periodic watcher, ever, or make any event loop modificstions>. If you need 570ever, or make any event loop modifications>. If you need to stop it,
540to stop it, return 1e30 (or so, fudge fudge) and stop it afterwards. 571return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
572starting a prepare watcher).
541 573
542Its prototype is c<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 574Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
543ev_tstamp now)>, e.g.: 575ev_tstamp now)>, e.g.:
544 576
545 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 577 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
546 { 578 {
547 return now + 60.; 579 return now + 60.;
550It must return the next time to trigger, based on the passed time value 582It must return the next time to trigger, based on the passed time value
551(that is, the lowest time value larger than to the second argument). It 583(that is, the lowest time value larger than to the second argument). It
552will usually be called just before the callback will be triggered, but 584will usually be called just before the callback will be triggered, but
553might be called at other times, too. 585might be called at other times, too.
554 586
587NOTE: I<< This callback must always return a time that is later than the
588passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
589
555This can be used to create very complex timers, such as a timer that 590This can be used to create very complex timers, such as a timer that
556triggers on each midnight, local time. To do this, you would calculate the 591triggers on each midnight, local time. To do this, you would calculate the
557next midnight after C<now> and return the timestamp value for this. How you do this 592next midnight after C<now> and return the timestamp value for this. How
558is, again, up to you (but it is not trivial). 593you do this is, again, up to you (but it is not trivial, which is the main
594reason I omitted it as an example).
559 595
560=back 596=back
561 597
562=item ev_periodic_again (loop, ev_periodic *) 598=item ev_periodic_again (loop, ev_periodic *)
563 599
566a different time than the last time it was called (e.g. in a crond like 602a different time than the last time it was called (e.g. in a crond like
567program when the crontabs have changed). 603program when the crontabs have changed).
568 604
569=back 605=back
570 606
571=head2 ev_signal - signal me when a signal gets signalled 607=head2 C<ev_signal> - signal me when a signal gets signalled
572 608
573Signal watchers will trigger an event when the process receives a specific 609Signal watchers will trigger an event when the process receives a specific
574signal one or more times. Even though signals are very asynchronous, libev 610signal 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 611will try it's best to deliver signals synchronously, i.e. as part of the
576normal event processing, like any other event. 612normal event processing, like any other event.
577 613
578You cna configure as many watchers as you like per signal. Only when the 614You can configure as many watchers as you like per signal. Only when the
579first watcher gets started will libev actually register a signal watcher 615first watcher gets started will libev actually register a signal watcher
580with the kernel (thus it coexists with your own signal handlers as long 616with 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 617as 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 618watcher for a signal is stopped libev will reset the signal handler to
583SIG_DFL (regardless of what it was set to before). 619SIG_DFL (regardless of what it was set to before).
591Configures the watcher to trigger on the given signal number (usually one 627Configures the watcher to trigger on the given signal number (usually one
592of the C<SIGxxx> constants). 628of the C<SIGxxx> constants).
593 629
594=back 630=back
595 631
596=head2 ev_child - wait for pid status changes 632=head2 C<ev_child> - wait for pid status changes
597 633
598Child watchers trigger when your process receives a SIGCHLD in response to 634Child watchers trigger when your process receives a SIGCHLD in response to
599some child status changes (most typically when a child of yours dies). 635some child status changes (most typically when a child of yours dies).
600 636
601=over 4 637=over 4
605=item ev_child_set (ev_child *, int pid) 641=item ev_child_set (ev_child *, int pid)
606 642
607Configures the watcher to wait for status changes of process C<pid> (or 643Configures 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 644I<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 645at 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 646the status word (use the macros from C<sys/wait.h> and see your systems
611contains the pid of the process causing the status change. 647C<waitpid> documentation). The C<rpid> member contains the pid of the
648process causing the status change.
612 649
613=back 650=back
614 651
615=head2 ev_idle - when you've got nothing better to do 652=head2 C<ev_idle> - when you've got nothing better to do
616 653
617Idle watchers trigger events when there are no other I/O or timer (or 654Idle watchers trigger events when there are no other events are pending
618periodic) events pending. That is, as long as your process is busy 655(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 656as your process is busy handling sockets or timeouts (or even signals,
620is idle all idle watchers are being called again and again - until 657imagine) it will not be triggered. But when your process is idle all idle
658watchers are being called again and again, once per event loop iteration -
621stopped, that is, or your process receives more events. 659until stopped, that is, or your process receives more events and becomes
660busy.
622 661
623The most noteworthy effect is that as long as any idle watchers are 662The most noteworthy effect is that as long as any idle watchers are
624active, the process will not block when waiting for new events. 663active, the process will not block when waiting for new events.
625 664
626Apart from keeping your process non-blocking (which is a useful 665Apart 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, 675kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
637believe me. 676believe me.
638 677
639=back 678=back
640 679
641=head2 prepare and check - your hooks into the event loop 680=head2 C<ev_prepare> and C<ev_check> - customise your event loop
642 681
643Prepare and check watchers usually (but not always) are used in 682Prepare and check watchers are usually (but not always) used in tandem:
644tandom. Prepare watchers get invoked before the process blocks and check 683prepare watchers get invoked before the process blocks and check watchers
645watchers afterwards. 684afterwards.
646 685
647Their main purpose is to integrate other event mechanisms into libev. This 686Their main purpose is to integrate other event mechanisms into libev. This
648could be used, for example, to track variable changes, implement your own 687could be used, for example, to track variable changes, implement your own
649watchers, integrate net-snmp or a coroutine library and lots more. 688watchers, integrate net-snmp or a coroutine library and lots more.
650 689
651This is done by examining in each prepare call which file descriptors need 690This 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 691to be watched by the other library, registering C<ev_io> watchers for
653and starting an ev_timer watcher for any timeouts (many libraries provide 692them and starting an C<ev_timer> watcher for any timeouts (many libraries
654just this functionality). Then, in the check watcher you check for any 693provide just this functionality). Then, in the check watcher you check for
655events that occured (by making your callbacks set soem flags for example) 694any events that occured (by checking the pending status of all watchers
656and call back into the library. 695and stopping them) and call back into the library. The I/O and timer
696callbacks will never actually be called (but must be valid nevertheless,
697because you never know, you know?).
657 698
658As another example, the perl Coro module uses these hooks to integrate 699As another example, the Perl Coro module uses these hooks to integrate
659coroutines into libev programs, by yielding to other active coroutines 700coroutines into libev programs, by yielding to other active coroutines
660during each prepare and only letting the process block if no coroutines 701during each prepare and only letting the process block if no coroutines
661are ready to run. 702are ready to run (it's actually more complicated: it only runs coroutines
703with priority higher than or equal to the event loop and one coroutine
704of lower priority, but only once, using idle watchers to keep the event
705loop from blocking if lower-priority coroutines are active, thus mapping
706low-priority coroutines to idle/background tasks).
662 707
663=over 4 708=over 4
664 709
665=item ev_prepare_init (ev_prepare *, callback) 710=item ev_prepare_init (ev_prepare *, callback)
666 711
667=item ev_check_init (ev_check *, callback) 712=item ev_check_init (ev_check *, callback)
668 713
669Initialises and configures the prepare or check watcher - they have no 714Initialises 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> 715parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
671macros, but using them is utterly, utterly pointless. 716macros, but using them is utterly, utterly and completely pointless.
672 717
673=back 718=back
674 719
675=head1 OTHER FUNCTIONS 720=head1 OTHER FUNCTIONS
676 721
677There are some other fucntions of possible interest. Described. Here. Now. 722There are some other functions of possible interest. Described. Here. Now.
678 723
679=over 4 724=over 4
680 725
681=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 726=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
682 727
683This function combines a simple timer and an I/O watcher, calls your 728This function combines a simple timer and an I/O watcher, calls your
684callback on whichever event happens first and automatically stop both 729callback 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 730watchers. 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 731or timeout without having to allocate/configure/start/stop/free one or
687more watchers yourself. 732more watchers yourself.
688 733
689If C<fd> is less than 0, then no I/O watcher will be started and events is 734If 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 735is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
691will be craeted and started. 736C<events> set will be craeted and started.
692 737
693If C<timeout> is less than 0, then no timeout watcher will be 738If C<timeout> is less than 0, then no timeout watcher will be
694started. Otherwise an ev_timer watcher with after = C<timeout> (and repeat 739started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
695= 0) will be started. 740repeat = 0) will be started. While C<0> is a valid timeout, it is of
741dubious value.
696 742
697The callback has the type C<void (*cb)(int revents, void *arg)> and 743The 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, 744passed an C<revents> set like normal event callbacks (a combination of
699EV_WRITE or EV_TIMEOUT) and the C<arg> value passed to C<ev_once>: 745C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
746value passed to C<ev_once>:
700 747
701 static void stdin_ready (int revents, void *arg) 748 static void stdin_ready (int revents, void *arg)
702 { 749 {
703 if (revents & EV_TIMEOUT) 750 if (revents & EV_TIMEOUT)
704 /* doh, nothing entered */ 751 /* doh, nothing entered */;
705 else if (revents & EV_READ) 752 else if (revents & EV_READ)
706 /* stdin might have data for us, joy! */ 753 /* stdin might have data for us, joy! */;
707 } 754 }
708 755
709 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 756 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
710 757
711=item ev_feed_event (loop, watcher, int events) 758=item ev_feed_event (loop, watcher, int events)
712 759
713Feeds the given event set into the event loop, as if the specified event 760Feeds 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 761had happened for the specified watcher (which must be a pointer to an
715initialised but not necessarily active event watcher). 762initialised but not necessarily started event watcher).
716 763
717=item ev_feed_fd_event (loop, int fd, int revents) 764=item ev_feed_fd_event (loop, int fd, int revents)
718 765
719Feed an event on the given fd, as if a file descriptor backend detected it. 766Feed an event on the given fd, as if a file descriptor backend detected
767the given events it.
720 768
721=item ev_feed_signal_event (loop, int signum) 769=item ev_feed_signal_event (loop, int signum)
722 770
723Feed an event as if the given signal occured (loop must be the default loop!). 771Feed an event as if the given signal occured (loop must be the default loop!).
724 772
725=back 773=back
726 774
775=head1 LIBEVENT EMULATION
776
777TBD.
778
779=head1 C++ SUPPORT
780
781TBD.
782
727=head1 AUTHOR 783=head1 AUTHOR
728 784
729Marc Lehmann <libev@schmorp.de>. 785Marc Lehmann <libev@schmorp.de>.
730 786

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