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Revision: 1.38
Committed: Fri Dec 7 18:09:38 2007 UTC (16 years, 5 months ago) by root
Branch: MAIN
CVS Tags: rel-1_71
Changes since 1.37: +3 -3 lines
Log Message:
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File Contents

# User Rev Content
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131     .IX Title ""<STANDARD INPUT>" 1"
132 root 1.37 .TH "<STANDARD INPUT>" 1 "2007-12-07" "perl v5.8.8" "User Contributed Perl Documentation"
133 root 1.1 .SH "NAME"
134     libev \- a high performance full\-featured event loop written in C
135     .SH "SYNOPSIS"
136     .IX Header "SYNOPSIS"
137 root 1.28 .Vb 1
138     \& #include <ev.h>
139     .Ve
140     .SH "EXAMPLE PROGRAM"
141     .IX Header "EXAMPLE PROGRAM"
142     .Vb 1
143 root 1.1 \& #include <ev.h>
144     .Ve
145 root 1.27 .PP
146 root 1.28 .Vb 2
147 root 1.27 \& ev_io stdin_watcher;
148     \& ev_timer timeout_watcher;
149     .Ve
150     .PP
151     .Vb 8
152     \& /* called when data readable on stdin */
153     \& static void
154     \& stdin_cb (EV_P_ struct ev_io *w, int revents)
155     \& {
156     \& /* puts ("stdin ready"); */
157     \& ev_io_stop (EV_A_ w); /* just a syntax example */
158     \& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
159     \& }
160     .Ve
161     .PP
162     .Vb 6
163     \& static void
164     \& timeout_cb (EV_P_ struct ev_timer *w, int revents)
165     \& {
166     \& /* puts ("timeout"); */
167     \& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
168     \& }
169     .Ve
170     .PP
171     .Vb 4
172     \& int
173     \& main (void)
174     \& {
175     \& struct ev_loop *loop = ev_default_loop (0);
176     .Ve
177     .PP
178     .Vb 3
179     \& /* initialise an io watcher, then start it */
180     \& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
181     \& ev_io_start (loop, &stdin_watcher);
182     .Ve
183     .PP
184     .Vb 3
185     \& /* simple non-repeating 5.5 second timeout */
186     \& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187     \& ev_timer_start (loop, &timeout_watcher);
188     .Ve
189     .PP
190     .Vb 2
191     \& /* loop till timeout or data ready */
192     \& ev_loop (loop, 0);
193     .Ve
194     .PP
195     .Vb 2
196     \& return 0;
197     \& }
198     .Ve
199 root 1.1 .SH "DESCRIPTION"
200     .IX Header "DESCRIPTION"
201     Libev is an event loop: you register interest in certain events (such as a
202     file descriptor being readable or a timeout occuring), and it will manage
203     these event sources and provide your program with events.
204     .PP
205     To do this, it must take more or less complete control over your process
206     (or thread) by executing the \fIevent loop\fR handler, and will then
207     communicate events via a callback mechanism.
208     .PP
209     You register interest in certain events by registering so-called \fIevent
210     watchers\fR, which are relatively small C structures you initialise with the
211     details of the event, and then hand it over to libev by \fIstarting\fR the
212     watcher.
213     .SH "FEATURES"
214     .IX Header "FEATURES"
215 root 1.31 Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
216     BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
217     for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
218     (for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
219     with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
220     (\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
221     watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
222 root 1.28 \&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
223     file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
224     (\f(CW\*(C`ev_fork\*(C'\fR).
225     .PP
226     It also is quite fast (see this
227     benchmark comparing it to libevent
228     for example).
229 root 1.1 .SH "CONVENTIONS"
230     .IX Header "CONVENTIONS"
231 root 1.28 Libev is very configurable. In this manual the default configuration will
232     be described, which supports multiple event loops. For more info about
233     various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
234     this manual. If libev was configured without support for multiple event
235     loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
236     (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
237 root 1.1 .SH "TIME REPRESENTATION"
238     .IX Header "TIME REPRESENTATION"
239     Libev represents time as a single floating point number, representing the
240     (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
241     the beginning of 1970, details are complicated, don't ask). This type is
242     called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
243 root 1.9 to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
244     it, you should treat it as such.
245 root 1.1 .SH "GLOBAL FUNCTIONS"
246     .IX Header "GLOBAL FUNCTIONS"
247     These functions can be called anytime, even before initialising the
248     library in any way.
249     .IP "ev_tstamp ev_time ()" 4
250     .IX Item "ev_tstamp ev_time ()"
251 root 1.2 Returns the current time as libev would use it. Please note that the
252     \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
253     you actually want to know.
254 root 1.1 .IP "int ev_version_major ()" 4
255     .IX Item "int ev_version_major ()"
256     .PD 0
257     .IP "int ev_version_minor ()" 4
258     .IX Item "int ev_version_minor ()"
259     .PD
260     You can find out the major and minor version numbers of the library
261     you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
262     \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
263     symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
264     version of the library your program was compiled against.
265     .Sp
266     Usually, it's a good idea to terminate if the major versions mismatch,
267     as this indicates an incompatible change. Minor versions are usually
268     compatible to older versions, so a larger minor version alone is usually
269     not a problem.
270 root 1.9 .Sp
271 root 1.28 Example: Make sure we haven't accidentally been linked against the wrong
272     version.
273 root 1.9 .Sp
274     .Vb 3
275     \& assert (("libev version mismatch",
276     \& ev_version_major () == EV_VERSION_MAJOR
277     \& && ev_version_minor () >= EV_VERSION_MINOR));
278     .Ve
279 root 1.6 .IP "unsigned int ev_supported_backends ()" 4
280     .IX Item "unsigned int ev_supported_backends ()"
281     Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
282     value) compiled into this binary of libev (independent of their
283     availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
284     a description of the set values.
285 root 1.9 .Sp
286     Example: make sure we have the epoll method, because yeah this is cool and
287     a must have and can we have a torrent of it please!!!11
288     .Sp
289     .Vb 2
290     \& assert (("sorry, no epoll, no sex",
291     \& ev_supported_backends () & EVBACKEND_EPOLL));
292     .Ve
293 root 1.6 .IP "unsigned int ev_recommended_backends ()" 4
294     .IX Item "unsigned int ev_recommended_backends ()"
295     Return the set of all backends compiled into this binary of libev and also
296     recommended for this platform. This set is often smaller than the one
297     returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
298     most BSDs and will not be autodetected unless you explicitly request it
299     (assuming you know what you are doing). This is the set of backends that
300 root 1.8 libev will probe for if you specify no backends explicitly.
301 root 1.10 .IP "unsigned int ev_embeddable_backends ()" 4
302     .IX Item "unsigned int ev_embeddable_backends ()"
303     Returns the set of backends that are embeddable in other event loops. This
304     is the theoretical, all\-platform, value. To find which backends
305     might be supported on the current system, you would need to look at
306     \&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
307     recommended ones.
308     .Sp
309     See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
310 root 1.32 .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
311     .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
312     Sets the allocation function to use (the prototype is similar \- the
313     semantics is identical \- to the realloc C function). It is used to
314     allocate and free memory (no surprises here). If it returns zero when
315     memory needs to be allocated, the library might abort or take some
316     potentially destructive action. The default is your system realloc
317     function.
318 root 1.1 .Sp
319     You could override this function in high-availability programs to, say,
320     free some memory if it cannot allocate memory, to use a special allocator,
321     or even to sleep a while and retry until some memory is available.
322 root 1.9 .Sp
323 root 1.28 Example: Replace the libev allocator with one that waits a bit and then
324     retries).
325 root 1.9 .Sp
326     .Vb 6
327     \& static void *
328 root 1.26 \& persistent_realloc (void *ptr, size_t size)
329 root 1.9 \& {
330     \& for (;;)
331     \& {
332     \& void *newptr = realloc (ptr, size);
333     .Ve
334     .Sp
335     .Vb 2
336     \& if (newptr)
337     \& return newptr;
338     .Ve
339     .Sp
340     .Vb 3
341     \& sleep (60);
342     \& }
343     \& }
344     .Ve
345     .Sp
346     .Vb 2
347     \& ...
348     \& ev_set_allocator (persistent_realloc);
349     .Ve
350 root 1.1 .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
351     .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
352     Set the callback function to call on a retryable syscall error (such
353     as failed select, poll, epoll_wait). The message is a printable string
354     indicating the system call or subsystem causing the problem. If this
355     callback is set, then libev will expect it to remedy the sitution, no
356     matter what, when it returns. That is, libev will generally retry the
357     requested operation, or, if the condition doesn't go away, do bad stuff
358     (such as abort).
359 root 1.9 .Sp
360 root 1.28 Example: This is basically the same thing that libev does internally, too.
361 root 1.9 .Sp
362     .Vb 6
363     \& static void
364     \& fatal_error (const char *msg)
365     \& {
366     \& perror (msg);
367     \& abort ();
368     \& }
369     .Ve
370     .Sp
371     .Vb 2
372     \& ...
373     \& ev_set_syserr_cb (fatal_error);
374     .Ve
375 root 1.1 .SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
376     .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
377     An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
378     types of such loops, the \fIdefault\fR loop, which supports signals and child
379     events, and dynamically created loops which do not.
380     .PP
381     If you use threads, a common model is to run the default event loop
382     in your main thread (or in a separate thread) and for each thread you
383     create, you also create another event loop. Libev itself does no locking
384     whatsoever, so if you mix calls to the same event loop in different
385     threads, make sure you lock (this is usually a bad idea, though, even if
386     done correctly, because it's hideous and inefficient).
387     .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
388     .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
389     This will initialise the default event loop if it hasn't been initialised
390     yet and return it. If the default loop could not be initialised, returns
391     false. If it already was initialised it simply returns it (and ignores the
392 root 1.6 flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
393 root 1.1 .Sp
394     If you don't know what event loop to use, use the one returned from this
395     function.
396     .Sp
397     The flags argument can be used to specify special behaviour or specific
398 root 1.8 backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
399 root 1.1 .Sp
400 root 1.8 The following flags are supported:
401 root 1.1 .RS 4
402     .ie n .IP """EVFLAG_AUTO""" 4
403     .el .IP "\f(CWEVFLAG_AUTO\fR" 4
404     .IX Item "EVFLAG_AUTO"
405     The default flags value. Use this if you have no clue (it's the right
406     thing, believe me).
407     .ie n .IP """EVFLAG_NOENV""" 4
408     .el .IP "\f(CWEVFLAG_NOENV\fR" 4
409     .IX Item "EVFLAG_NOENV"
410     If this flag bit is ored into the flag value (or the program runs setuid
411     or setgid) then libev will \fInot\fR look at the environment variable
412     \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
413     override the flags completely if it is found in the environment. This is
414     useful to try out specific backends to test their performance, or to work
415     around bugs.
416 root 1.35 .ie n .IP """EVFLAG_FORKCHECK""" 4
417     .el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
418     .IX Item "EVFLAG_FORKCHECK"
419     Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
420     a fork, you can also make libev check for a fork in each iteration by
421     enabling this flag.
422     .Sp
423     This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
424     and thus this might slow down your event loop if you do a lot of loop
425 root 1.37 iterations and little real work, but is usually not noticeable (on my
426 root 1.35 Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
427     without a syscall and thus \fIvery\fR fast, but my Linux system also has
428     \&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
429     .Sp
430     The big advantage of this flag is that you can forget about fork (and
431     forget about forgetting to tell libev about forking) when you use this
432     flag.
433     .Sp
434     This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
435     environment variable.
436 root 1.6 .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
437     .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
438     .IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
439 root 1.3 This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
440     libev tries to roll its own fd_set with no limits on the number of fds,
441     but if that fails, expect a fairly low limit on the number of fds when
442     using this backend. It doesn't scale too well (O(highest_fd)), but its usually
443     the fastest backend for a low number of fds.
444 root 1.6 .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
445     .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
446     .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
447 root 1.3 And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
448     select, but handles sparse fds better and has no artificial limit on the
449     number of fds you can use (except it will slow down considerably with a
450     lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
451 root 1.6 .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
452     .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
453     .IX Item "EVBACKEND_EPOLL (value 4, Linux)"
454 root 1.3 For few fds, this backend is a bit little slower than poll and select,
455     but it scales phenomenally better. While poll and select usually scale like
456     O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
457     either O(1) or O(active_fds).
458     .Sp
459     While stopping and starting an I/O watcher in the same iteration will
460     result in some caching, there is still a syscall per such incident
461     (because the fd could point to a different file description now), so its
462     best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
463     well if you register events for both fds.
464 root 1.7 .Sp
465     Please note that epoll sometimes generates spurious notifications, so you
466     need to use non-blocking I/O or other means to avoid blocking when no data
467     (or space) is available.
468 root 1.6 .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
469     .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
470     .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
471 root 1.3 Kqueue deserves special mention, as at the time of this writing, it
472     was broken on all BSDs except NetBSD (usually it doesn't work with
473     anything but sockets and pipes, except on Darwin, where of course its
474 root 1.8 completely useless). For this reason its not being \*(L"autodetected\*(R"
475     unless you explicitly specify it explicitly in the flags (i.e. using
476     \&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
477 root 1.3 .Sp
478     It scales in the same way as the epoll backend, but the interface to the
479     kernel is more efficient (which says nothing about its actual speed, of
480     course). While starting and stopping an I/O watcher does not cause an
481     extra syscall as with epoll, it still adds up to four event changes per
482     incident, so its best to avoid that.
483 root 1.6 .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
484     .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
485     .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
486 root 1.3 This is not implemented yet (and might never be).
487 root 1.6 .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
488     .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
489     .IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
490 root 1.3 This uses the Solaris 10 port mechanism. As with everything on Solaris,
491     it's really slow, but it still scales very well (O(active_fds)).
492 root 1.7 .Sp
493     Please note that solaris ports can result in a lot of spurious
494     notifications, so you need to use non-blocking I/O or other means to avoid
495     blocking when no data (or space) is available.
496 root 1.6 .ie n .IP """EVBACKEND_ALL""" 4
497     .el .IP "\f(CWEVBACKEND_ALL\fR" 4
498     .IX Item "EVBACKEND_ALL"
499 root 1.4 Try all backends (even potentially broken ones that wouldn't be tried
500     with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
501 root 1.6 \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
502 root 1.1 .RE
503     .RS 4
504 root 1.3 .Sp
505     If one or more of these are ored into the flags value, then only these
506     backends will be tried (in the reverse order as given here). If none are
507     specified, most compiled-in backend will be tried, usually in reverse
508     order of their flag values :)
509 root 1.8 .Sp
510     The most typical usage is like this:
511     .Sp
512     .Vb 2
513     \& if (!ev_default_loop (0))
514     \& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
515     .Ve
516     .Sp
517     Restrict libev to the select and poll backends, and do not allow
518     environment settings to be taken into account:
519     .Sp
520     .Vb 1
521     \& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
522     .Ve
523     .Sp
524     Use whatever libev has to offer, but make sure that kqueue is used if
525     available (warning, breaks stuff, best use only with your own private
526     event loop and only if you know the \s-1OS\s0 supports your types of fds):
527     .Sp
528     .Vb 1
529     \& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
530     .Ve
531 root 1.1 .RE
532     .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
533     .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
534     Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
535     always distinct from the default loop. Unlike the default loop, it cannot
536     handle signal and child watchers, and attempts to do so will be greeted by
537     undefined behaviour (or a failed assertion if assertions are enabled).
538 root 1.9 .Sp
539 root 1.28 Example: Try to create a event loop that uses epoll and nothing else.
540 root 1.9 .Sp
541     .Vb 3
542     \& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
543     \& if (!epoller)
544     \& fatal ("no epoll found here, maybe it hides under your chair");
545     .Ve
546 root 1.1 .IP "ev_default_destroy ()" 4
547     .IX Item "ev_default_destroy ()"
548     Destroys the default loop again (frees all memory and kernel state
549 root 1.12 etc.). None of the active event watchers will be stopped in the normal
550     sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
551     responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
552     calling this function, or cope with the fact afterwards (which is usually
553     the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
554     for example).
555 root 1.1 .IP "ev_loop_destroy (loop)" 4
556     .IX Item "ev_loop_destroy (loop)"
557     Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
558     earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
559     .IP "ev_default_fork ()" 4
560     .IX Item "ev_default_fork ()"
561     This function reinitialises the kernel state for backends that have
562     one. Despite the name, you can call it anytime, but it makes most sense
563     after forking, in either the parent or child process (or both, but that
564     again makes little sense).
565     .Sp
566 root 1.5 You \fImust\fR call this function in the child process after forking if and
567     only if you want to use the event library in both processes. If you just
568     fork+exec, you don't have to call it.
569 root 1.1 .Sp
570     The function itself is quite fast and it's usually not a problem to call
571     it just in case after a fork. To make this easy, the function will fit in
572     quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
573     .Sp
574     .Vb 1
575     \& pthread_atfork (0, 0, ev_default_fork);
576     .Ve
577 root 1.6 .Sp
578     At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
579     without calling this function, so if you force one of those backends you
580     do not need to care.
581 root 1.1 .IP "ev_loop_fork (loop)" 4
582     .IX Item "ev_loop_fork (loop)"
583     Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
584     \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
585     after fork, and how you do this is entirely your own problem.
586 root 1.37 .IP "unsigned int ev_loop_count (loop)" 4
587     .IX Item "unsigned int ev_loop_count (loop)"
588     Returns the count of loop iterations for the loop, which is identical to
589     the number of times libev did poll for new events. It starts at \f(CW0\fR and
590     happily wraps around with enough iterations.
591     .Sp
592     This value can sometimes be useful as a generation counter of sorts (it
593     \&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
594     \&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
595 root 1.6 .IP "unsigned int ev_backend (loop)" 4
596     .IX Item "unsigned int ev_backend (loop)"
597     Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
598 root 1.1 use.
599     .IP "ev_tstamp ev_now (loop)" 4
600     .IX Item "ev_tstamp ev_now (loop)"
601     Returns the current \*(L"event loop time\*(R", which is the time the event loop
602 root 1.9 received events and started processing them. This timestamp does not
603     change as long as callbacks are being processed, and this is also the base
604     time used for relative timers. You can treat it as the timestamp of the
605     event occuring (or more correctly, libev finding out about it).
606 root 1.1 .IP "ev_loop (loop, int flags)" 4
607     .IX Item "ev_loop (loop, int flags)"
608     Finally, this is it, the event handler. This function usually is called
609     after you initialised all your watchers and you want to start handling
610     events.
611     .Sp
612 root 1.8 If the flags argument is specified as \f(CW0\fR, it will not return until
613     either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
614 root 1.1 .Sp
615 root 1.9 Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
616     relying on all watchers to be stopped when deciding when a program has
617     finished (especially in interactive programs), but having a program that
618     automatically loops as long as it has to and no longer by virtue of
619     relying on its watchers stopping correctly is a thing of beauty.
620     .Sp
621 root 1.1 A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
622     those events and any outstanding ones, but will not block your process in
623     case there are no events and will return after one iteration of the loop.
624     .Sp
625     A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
626     neccessary) and will handle those and any outstanding ones. It will block
627     your process until at least one new event arrives, and will return after
628 root 1.8 one iteration of the loop. This is useful if you are waiting for some
629     external event in conjunction with something not expressible using other
630     libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
631     usually a better approach for this kind of thing.
632     .Sp
633     Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
634     .Sp
635     .Vb 18
636     \& * If there are no active watchers (reference count is zero), return.
637     \& - Queue prepare watchers and then call all outstanding watchers.
638     \& - If we have been forked, recreate the kernel state.
639     \& - Update the kernel state with all outstanding changes.
640     \& - Update the "event loop time".
641     \& - Calculate for how long to block.
642     \& - Block the process, waiting for any events.
643     \& - Queue all outstanding I/O (fd) events.
644     \& - Update the "event loop time" and do time jump handling.
645     \& - Queue all outstanding timers.
646     \& - Queue all outstanding periodics.
647     \& - If no events are pending now, queue all idle watchers.
648     \& - Queue all check watchers.
649     \& - Call all queued watchers in reverse order (i.e. check watchers first).
650     \& Signals and child watchers are implemented as I/O watchers, and will
651     \& be handled here by queueing them when their watcher gets executed.
652     \& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
653     \& were used, return, otherwise continue with step *.
654 root 1.2 .Ve
655 root 1.9 .Sp
656 root 1.28 Example: Queue some jobs and then loop until no events are outsanding
657 root 1.9 anymore.
658     .Sp
659     .Vb 4
660     \& ... queue jobs here, make sure they register event watchers as long
661     \& ... as they still have work to do (even an idle watcher will do..)
662     \& ev_loop (my_loop, 0);
663     \& ... jobs done. yeah!
664     .Ve
665 root 1.1 .IP "ev_unloop (loop, how)" 4
666     .IX Item "ev_unloop (loop, how)"
667     Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
668     has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
669     \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
670     \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.
671     .IP "ev_ref (loop)" 4
672     .IX Item "ev_ref (loop)"
673     .PD 0
674     .IP "ev_unref (loop)" 4
675     .IX Item "ev_unref (loop)"
676     .PD
677     Ref/unref can be used to add or remove a reference count on the event
678     loop: Every watcher keeps one reference, and as long as the reference
679     count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have
680     a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from
681     returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
682     example, libev itself uses this for its internal signal pipe: It is not
683     visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
684     no event watchers registered by it are active. It is also an excellent
685     way to do this for generic recurring timers or from within third-party
686     libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
687 root 1.9 .Sp
688 root 1.28 Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
689 root 1.9 running when nothing else is active.
690     .Sp
691     .Vb 4
692 root 1.28 \& struct ev_signal exitsig;
693 root 1.9 \& ev_signal_init (&exitsig, sig_cb, SIGINT);
694 root 1.28 \& ev_signal_start (loop, &exitsig);
695     \& evf_unref (loop);
696 root 1.9 .Ve
697     .Sp
698 root 1.28 Example: For some weird reason, unregister the above signal handler again.
699 root 1.9 .Sp
700     .Vb 2
701 root 1.28 \& ev_ref (loop);
702     \& ev_signal_stop (loop, &exitsig);
703 root 1.9 .Ve
704 root 1.1 .SH "ANATOMY OF A WATCHER"
705     .IX Header "ANATOMY OF A WATCHER"
706     A watcher is a structure that you create and register to record your
707     interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
708     become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
709     .PP
710     .Vb 5
711     \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
712     \& {
713     \& ev_io_stop (w);
714     \& ev_unloop (loop, EVUNLOOP_ALL);
715     \& }
716     .Ve
717     .PP
718     .Vb 6
719     \& struct ev_loop *loop = ev_default_loop (0);
720     \& struct ev_io stdin_watcher;
721     \& ev_init (&stdin_watcher, my_cb);
722     \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
723     \& ev_io_start (loop, &stdin_watcher);
724     \& ev_loop (loop, 0);
725     .Ve
726     .PP
727     As you can see, you are responsible for allocating the memory for your
728     watcher structures (and it is usually a bad idea to do this on the stack,
729     although this can sometimes be quite valid).
730     .PP
731     Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init
732     (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This
733     callback gets invoked each time the event occurs (or, in the case of io
734     watchers, each time the event loop detects that the file descriptor given
735     is readable and/or writable).
736     .PP
737     Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro
738     with arguments specific to this watcher type. There is also a macro
739     to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init
740     (watcher *, callback, ...)\*(C'\fR.
741     .PP
742     To make the watcher actually watch out for events, you have to start it
743     with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher
744     *)\*(C'\fR), and you can stop watching for events at any time by calling the
745     corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
746     .PP
747     As long as your watcher is active (has been started but not stopped) you
748     must not touch the values stored in it. Most specifically you must never
749 root 1.11 reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
750 root 1.1 .PP
751     Each and every callback receives the event loop pointer as first, the
752     registered watcher structure as second, and a bitset of received events as
753     third argument.
754     .PP
755     The received events usually include a single bit per event type received
756     (you can receive multiple events at the same time). The possible bit masks
757     are:
758     .ie n .IP """EV_READ""" 4
759     .el .IP "\f(CWEV_READ\fR" 4
760     .IX Item "EV_READ"
761     .PD 0
762     .ie n .IP """EV_WRITE""" 4
763     .el .IP "\f(CWEV_WRITE\fR" 4
764     .IX Item "EV_WRITE"
765     .PD
766     The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
767     writable.
768     .ie n .IP """EV_TIMEOUT""" 4
769     .el .IP "\f(CWEV_TIMEOUT\fR" 4
770     .IX Item "EV_TIMEOUT"
771     The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
772     .ie n .IP """EV_PERIODIC""" 4
773     .el .IP "\f(CWEV_PERIODIC\fR" 4
774     .IX Item "EV_PERIODIC"
775     The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
776     .ie n .IP """EV_SIGNAL""" 4
777     .el .IP "\f(CWEV_SIGNAL\fR" 4
778     .IX Item "EV_SIGNAL"
779     The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
780     .ie n .IP """EV_CHILD""" 4
781     .el .IP "\f(CWEV_CHILD\fR" 4
782     .IX Item "EV_CHILD"
783     The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
784 root 1.22 .ie n .IP """EV_STAT""" 4
785     .el .IP "\f(CWEV_STAT\fR" 4
786     .IX Item "EV_STAT"
787     The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
788 root 1.1 .ie n .IP """EV_IDLE""" 4
789     .el .IP "\f(CWEV_IDLE\fR" 4
790     .IX Item "EV_IDLE"
791     The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
792     .ie n .IP """EV_PREPARE""" 4
793     .el .IP "\f(CWEV_PREPARE\fR" 4
794     .IX Item "EV_PREPARE"
795     .PD 0
796     .ie n .IP """EV_CHECK""" 4
797     .el .IP "\f(CWEV_CHECK\fR" 4
798     .IX Item "EV_CHECK"
799     .PD
800     All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts
801     to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after
802     \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
803     received events. Callbacks of both watcher types can start and stop as
804     many watchers as they want, and all of them will be taken into account
805     (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
806     \&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
807 root 1.24 .ie n .IP """EV_EMBED""" 4
808     .el .IP "\f(CWEV_EMBED\fR" 4
809     .IX Item "EV_EMBED"
810     The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
811     .ie n .IP """EV_FORK""" 4
812     .el .IP "\f(CWEV_FORK\fR" 4
813     .IX Item "EV_FORK"
814     The event loop has been resumed in the child process after fork (see
815     \&\f(CW\*(C`ev_fork\*(C'\fR).
816 root 1.1 .ie n .IP """EV_ERROR""" 4
817     .el .IP "\f(CWEV_ERROR\fR" 4
818     .IX Item "EV_ERROR"
819     An unspecified error has occured, the watcher has been stopped. This might
820     happen because the watcher could not be properly started because libev
821     ran out of memory, a file descriptor was found to be closed or any other
822     problem. You best act on it by reporting the problem and somehow coping
823     with the watcher being stopped.
824     .Sp
825     Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
826     for example it might indicate that a fd is readable or writable, and if
827     your callbacks is well-written it can just attempt the operation and cope
828     with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
829     programs, though, so beware.
830 root 1.17 .Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
831     .IX Subsection "GENERIC WATCHER FUNCTIONS"
832 root 1.11 In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
833     e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
834     .ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
835     .el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
836     .IX Item "ev_init (ev_TYPE *watcher, callback)"
837     This macro initialises the generic portion of a watcher. The contents
838     of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
839     the generic parts of the watcher are initialised, you \fIneed\fR to call
840     the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
841     type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
842     which rolls both calls into one.
843     .Sp
844     You can reinitialise a watcher at any time as long as it has been stopped
845     (or never started) and there are no pending events outstanding.
846     .Sp
847 root 1.17 The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
848 root 1.11 int revents)\*(C'\fR.
849     .ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
850     .el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
851     .IX Item "ev_TYPE_set (ev_TYPE *, [args])"
852     This macro initialises the type-specific parts of a watcher. You need to
853     call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
854     call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
855     macro on a watcher that is active (it can be pending, however, which is a
856     difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
857     .Sp
858     Although some watcher types do not have type-specific arguments
859     (e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
860     .ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
861     .el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
862     .IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
863     This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
864     calls into a single call. This is the most convinient method to initialise
865     a watcher. The same limitations apply, of course.
866     .ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
867     .el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
868     .IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
869     Starts (activates) the given watcher. Only active watchers will receive
870     events. If the watcher is already active nothing will happen.
871     .ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
872     .el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
873     .IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
874     Stops the given watcher again (if active) and clears the pending
875     status. It is possible that stopped watchers are pending (for example,
876     non-repeating timers are being stopped when they become pending), but
877     \&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
878     you want to free or reuse the memory used by the watcher it is therefore a
879     good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
880     .IP "bool ev_is_active (ev_TYPE *watcher)" 4
881     .IX Item "bool ev_is_active (ev_TYPE *watcher)"
882     Returns a true value iff the watcher is active (i.e. it has been started
883     and not yet been stopped). As long as a watcher is active you must not modify
884     it.
885     .IP "bool ev_is_pending (ev_TYPE *watcher)" 4
886     .IX Item "bool ev_is_pending (ev_TYPE *watcher)"
887     Returns a true value iff the watcher is pending, (i.e. it has outstanding
888     events but its callback has not yet been invoked). As long as a watcher
889     is pending (but not active) you must not call an init function on it (but
890     \&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
891     libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
892 root 1.29 .IP "callback ev_cb (ev_TYPE *watcher)" 4
893     .IX Item "callback ev_cb (ev_TYPE *watcher)"
894 root 1.11 Returns the callback currently set on the watcher.
895     .IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
896     .IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
897     Change the callback. You can change the callback at virtually any time
898     (modulo threads).
899 root 1.37 .IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
900     .IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
901     .PD 0
902     .IP "int ev_priority (ev_TYPE *watcher)" 4
903     .IX Item "int ev_priority (ev_TYPE *watcher)"
904     .PD
905     Set and query the priority of the watcher. The priority is a small
906     integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
907     (default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
908     before watchers with lower priority, but priority will not keep watchers
909     from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
910     .Sp
911     This means that priorities are \fIonly\fR used for ordering callback
912     invocation after new events have been received. This is useful, for
913     example, to reduce latency after idling, or more often, to bind two
914     watchers on the same event and make sure one is called first.
915     .Sp
916     If you need to suppress invocation when higher priority events are pending
917     you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
918     .Sp
919     The default priority used by watchers when no priority has been set is
920     always \f(CW0\fR, which is supposed to not be too high and not be too low :).
921     .Sp
922     Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
923     fine, as long as you do not mind that the priority value you query might
924     or might not have been adjusted to be within valid range.
925 root 1.1 .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
926     .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
927     Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
928     and read at any time, libev will completely ignore it. This can be used
929     to associate arbitrary data with your watcher. If you need more data and
930     don't want to allocate memory and store a pointer to it in that data
931     member, you can also \*(L"subclass\*(R" the watcher type and provide your own
932     data:
933     .PP
934     .Vb 7
935     \& struct my_io
936     \& {
937     \& struct ev_io io;
938     \& int otherfd;
939     \& void *somedata;
940     \& struct whatever *mostinteresting;
941     \& }
942     .Ve
943     .PP
944     And since your callback will be called with a pointer to the watcher, you
945     can cast it back to your own type:
946     .PP
947     .Vb 5
948     \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
949     \& {
950     \& struct my_io *w = (struct my_io *)w_;
951     \& ...
952     \& }
953     .Ve
954     .PP
955 root 1.29 More interesting and less C\-conformant ways of casting your callback type
956     instead have been omitted.
957     .PP
958     Another common scenario is having some data structure with multiple
959     watchers:
960     .PP
961     .Vb 6
962     \& struct my_biggy
963     \& {
964     \& int some_data;
965     \& ev_timer t1;
966     \& ev_timer t2;
967     \& }
968     .Ve
969     .PP
970     In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
971     you need to use \f(CW\*(C`offsetof\*(C'\fR:
972     .PP
973     .Vb 1
974     \& #include <stddef.h>
975     .Ve
976     .PP
977     .Vb 6
978     \& static void
979     \& t1_cb (EV_P_ struct ev_timer *w, int revents)
980     \& {
981     \& struct my_biggy big = (struct my_biggy *
982     \& (((char *)w) - offsetof (struct my_biggy, t1));
983     \& }
984     .Ve
985     .PP
986     .Vb 6
987     \& static void
988     \& t2_cb (EV_P_ struct ev_timer *w, int revents)
989     \& {
990     \& struct my_biggy big = (struct my_biggy *
991     \& (((char *)w) - offsetof (struct my_biggy, t2));
992     \& }
993     .Ve
994 root 1.1 .SH "WATCHER TYPES"
995     .IX Header "WATCHER TYPES"
996     This section describes each watcher in detail, but will not repeat
997 root 1.22 information given in the last section. Any initialisation/set macros,
998     functions and members specific to the watcher type are explained.
999     .PP
1000     Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1001     while the watcher is active, you can look at the member and expect some
1002     sensible content, but you must not modify it (you can modify it while the
1003     watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1004     means you can expect it to have some sensible content while the watcher
1005     is active, but you can also modify it. Modifying it may not do something
1006     sensible or take immediate effect (or do anything at all), but libev will
1007     not crash or malfunction in any way.
1008 root 1.17 .ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
1009     .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1010     .IX Subsection "ev_io - is this file descriptor readable or writable?"
1011 root 1.1 I/O watchers check whether a file descriptor is readable or writable
1012 root 1.17 in each iteration of the event loop, or, more precisely, when reading
1013     would not block the process and writing would at least be able to write
1014     some data. This behaviour is called level-triggering because you keep
1015     receiving events as long as the condition persists. Remember you can stop
1016     the watcher if you don't want to act on the event and neither want to
1017     receive future events.
1018 root 1.1 .PP
1019     In general you can register as many read and/or write event watchers per
1020     fd as you want (as long as you don't confuse yourself). Setting all file
1021     descriptors to non-blocking mode is also usually a good idea (but not
1022     required if you know what you are doing).
1023     .PP
1024     You have to be careful with dup'ed file descriptors, though. Some backends
1025     (the linux epoll backend is a notable example) cannot handle dup'ed file
1026     descriptors correctly if you register interest in two or more fds pointing
1027 root 1.17 to the same underlying file/socket/etc. description (that is, they share
1028 root 1.1 the same underlying \*(L"file open\*(R").
1029     .PP
1030     If you must do this, then force the use of a known-to-be-good backend
1031 root 1.6 (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
1032     \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1033 root 1.17 .PP
1034     Another thing you have to watch out for is that it is quite easy to
1035     receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1036     be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1037     because there is no data. Not only are some backends known to create a
1038     lot of those (for example solaris ports), it is very easy to get into
1039     this situation even with a relatively standard program structure. Thus
1040     it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1041     \&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1042     .PP
1043     If you cannot run the fd in non-blocking mode (for example you should not
1044     play around with an Xlib connection), then you have to seperately re-test
1045 root 1.38 whether a file descriptor is really ready with a known-to-be good interface
1046 root 1.17 such as poll (fortunately in our Xlib example, Xlib already does this on
1047     its own, so its quite safe to use).
1048 root 1.1 .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
1049     .IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
1050     .PD 0
1051     .IP "ev_io_set (ev_io *, int fd, int events)" 4
1052     .IX Item "ev_io_set (ev_io *, int fd, int events)"
1053     .PD
1054 root 1.17 Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
1055     rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
1056     \&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
1057 root 1.22 .IP "int fd [read\-only]" 4
1058     .IX Item "int fd [read-only]"
1059     The file descriptor being watched.
1060     .IP "int events [read\-only]" 4
1061     .IX Item "int events [read-only]"
1062     The events being watched.
1063 root 1.9 .PP
1064 root 1.28 Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
1065 root 1.9 readable, but only once. Since it is likely line\-buffered, you could
1066 root 1.28 attempt to read a whole line in the callback.
1067 root 1.9 .PP
1068     .Vb 6
1069     \& static void
1070     \& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1071     \& {
1072     \& ev_io_stop (loop, w);
1073     \& .. read from stdin here (or from w->fd) and haqndle any I/O errors
1074     \& }
1075     .Ve
1076     .PP
1077     .Vb 6
1078     \& ...
1079     \& struct ev_loop *loop = ev_default_init (0);
1080     \& struct ev_io stdin_readable;
1081     \& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1082     \& ev_io_start (loop, &stdin_readable);
1083     \& ev_loop (loop, 0);
1084     .Ve
1085 root 1.17 .ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
1086     .el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
1087     .IX Subsection "ev_timer - relative and optionally repeating timeouts"
1088 root 1.1 Timer watchers are simple relative timers that generate an event after a
1089     given time, and optionally repeating in regular intervals after that.
1090     .PP
1091     The timers are based on real time, that is, if you register an event that
1092     times out after an hour and you reset your system clock to last years
1093     time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because
1094 root 1.2 detecting time jumps is hard, and some inaccuracies are unavoidable (the
1095 root 1.1 monotonic clock option helps a lot here).
1096     .PP
1097     The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
1098     time. This is usually the right thing as this timestamp refers to the time
1099 root 1.2 of the event triggering whatever timeout you are modifying/starting. If
1100     you suspect event processing to be delayed and you \fIneed\fR to base the timeout
1101 root 1.1 on the current time, use something like this to adjust for this:
1102     .PP
1103     .Vb 1
1104     \& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
1105     .Ve
1106 root 1.2 .PP
1107     The callback is guarenteed to be invoked only when its timeout has passed,
1108     but if multiple timers become ready during the same loop iteration then
1109     order of execution is undefined.
1110 root 1.1 .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
1111     .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
1112     .PD 0
1113     .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
1114     .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
1115     .PD
1116     Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is
1117     \&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the
1118     timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds
1119     later, again, and again, until stopped manually.
1120     .Sp
1121     The timer itself will do a best-effort at avoiding drift, that is, if you
1122     configure a timer to trigger every 10 seconds, then it will trigger at
1123     exactly 10 second intervals. If, however, your program cannot keep up with
1124     the timer (because it takes longer than those 10 seconds to do stuff) the
1125     timer will not fire more than once per event loop iteration.
1126     .IP "ev_timer_again (loop)" 4
1127     .IX Item "ev_timer_again (loop)"
1128     This will act as if the timer timed out and restart it again if it is
1129     repeating. The exact semantics are:
1130     .Sp
1131 root 1.34 If the timer is pending, its pending status is cleared.
1132 root 1.1 .Sp
1133 root 1.34 If the timer is started but nonrepeating, stop it (as if it timed out).
1134     .Sp
1135     If the timer is repeating, either start it if necessary (with the
1136     \&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
1137 root 1.1 .Sp
1138     This sounds a bit complicated, but here is a useful and typical
1139 root 1.34 example: Imagine you have a tcp connection and you want a so-called idle
1140     timeout, that is, you want to be called when there have been, say, 60
1141     seconds of inactivity on the socket. The easiest way to do this is to
1142     configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
1143 root 1.22 \&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
1144     you go into an idle state where you do not expect data to travel on the
1145 root 1.34 socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1146     automatically restart it if need be.
1147 root 1.22 .Sp
1148 root 1.34 That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1149     altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1150 root 1.22 .Sp
1151     .Vb 8
1152     \& ev_timer_init (timer, callback, 0., 5.);
1153     \& ev_timer_again (loop, timer);
1154     \& ...
1155     \& timer->again = 17.;
1156     \& ev_timer_again (loop, timer);
1157     \& ...
1158     \& timer->again = 10.;
1159     \& ev_timer_again (loop, timer);
1160     .Ve
1161     .Sp
1162 root 1.34 This is more slightly efficient then stopping/starting the timer each time
1163     you want to modify its timeout value.
1164 root 1.22 .IP "ev_tstamp repeat [read\-write]" 4
1165     .IX Item "ev_tstamp repeat [read-write]"
1166     The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1167     or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1168     which is also when any modifications are taken into account.
1169 root 1.9 .PP
1170 root 1.28 Example: Create a timer that fires after 60 seconds.
1171 root 1.9 .PP
1172     .Vb 5
1173     \& static void
1174     \& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1175     \& {
1176     \& .. one minute over, w is actually stopped right here
1177     \& }
1178     .Ve
1179     .PP
1180     .Vb 3
1181     \& struct ev_timer mytimer;
1182     \& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1183     \& ev_timer_start (loop, &mytimer);
1184     .Ve
1185     .PP
1186 root 1.28 Example: Create a timeout timer that times out after 10 seconds of
1187 root 1.9 inactivity.
1188     .PP
1189     .Vb 5
1190     \& static void
1191     \& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1192     \& {
1193     \& .. ten seconds without any activity
1194     \& }
1195     .Ve
1196     .PP
1197     .Vb 4
1198     \& struct ev_timer mytimer;
1199     \& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1200     \& ev_timer_again (&mytimer); /* start timer */
1201     \& ev_loop (loop, 0);
1202     .Ve
1203     .PP
1204     .Vb 3
1205     \& // and in some piece of code that gets executed on any "activity":
1206     \& // reset the timeout to start ticking again at 10 seconds
1207     \& ev_timer_again (&mytimer);
1208     .Ve
1209 root 1.17 .ie n .Sh """ev_periodic"" \- to cron or not to cron?"
1210     .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
1211     .IX Subsection "ev_periodic - to cron or not to cron?"
1212 root 1.1 Periodic watchers are also timers of a kind, but they are very versatile
1213     (and unfortunately a bit complex).
1214     .PP
1215     Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
1216     but on wallclock time (absolute time). You can tell a periodic watcher
1217     to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
1218 root 1.13 periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1219     + 10.\*(C'\fR) and then reset your system clock to the last year, then it will
1220 root 1.1 take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
1221     roughly 10 seconds later and of course not if you reset your system time
1222     again).
1223     .PP
1224     They can also be used to implement vastly more complex timers, such as
1225     triggering an event on eahc midnight, local time.
1226 root 1.2 .PP
1227     As with timers, the callback is guarenteed to be invoked only when the
1228     time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1229     during the same loop iteration then order of execution is undefined.
1230 root 1.1 .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
1231     .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
1232     .PD 0
1233     .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
1234     .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1235     .PD
1236     Lots of arguments, lets sort it out... There are basically three modes of
1237     operation, and we will explain them from simplest to complex:
1238     .RS 4
1239     .IP "* absolute timer (interval = reschedule_cb = 0)" 4
1240     .IX Item "absolute timer (interval = reschedule_cb = 0)"
1241     In this configuration the watcher triggers an event at the wallclock time
1242     \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1243     that is, if it is to be run at January 1st 2011 then it will run when the
1244     system time reaches or surpasses this time.
1245     .IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4
1246     .IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)"
1247     In this mode the watcher will always be scheduled to time out at the next
1248     \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless
1249     of any time jumps.
1250     .Sp
1251     This can be used to create timers that do not drift with respect to system
1252     time:
1253     .Sp
1254     .Vb 1
1255     \& ev_periodic_set (&periodic, 0., 3600., 0);
1256     .Ve
1257     .Sp
1258     This doesn't mean there will always be 3600 seconds in between triggers,
1259     but only that the the callback will be called when the system time shows a
1260     full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
1261     by 3600.
1262     .Sp
1263     Another way to think about it (for the mathematically inclined) is that
1264     \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1265     time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1266     .IP "* manual reschedule mode (reschedule_cb = callback)" 4
1267     .IX Item "manual reschedule mode (reschedule_cb = callback)"
1268     In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1269     ignored. Instead, each time the periodic watcher gets scheduled, the
1270     reschedule callback will be called with the watcher as first, and the
1271     current time as second argument.
1272     .Sp
1273     \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1274     ever, or make any event loop modifications\fR. If you need to stop it,
1275     return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1276     starting a prepare watcher).
1277     .Sp
1278     Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1279     ev_tstamp now)\*(C'\fR, e.g.:
1280     .Sp
1281     .Vb 4
1282     \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1283     \& {
1284     \& return now + 60.;
1285     \& }
1286     .Ve
1287     .Sp
1288     It must return the next time to trigger, based on the passed time value
1289     (that is, the lowest time value larger than to the second argument). It
1290     will usually be called just before the callback will be triggered, but
1291     might be called at other times, too.
1292     .Sp
1293     \&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the
1294     passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger.
1295     .Sp
1296     This can be used to create very complex timers, such as a timer that
1297     triggers on each midnight, local time. To do this, you would calculate the
1298     next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
1299     you do this is, again, up to you (but it is not trivial, which is the main
1300     reason I omitted it as an example).
1301     .RE
1302     .RS 4
1303     .RE
1304     .IP "ev_periodic_again (loop, ev_periodic *)" 4
1305     .IX Item "ev_periodic_again (loop, ev_periodic *)"
1306     Simply stops and restarts the periodic watcher again. This is only useful
1307     when you changed some parameters or the reschedule callback would return
1308     a different time than the last time it was called (e.g. in a crond like
1309     program when the crontabs have changed).
1310 root 1.22 .IP "ev_tstamp interval [read\-write]" 4
1311     .IX Item "ev_tstamp interval [read-write]"
1312     The current interval value. Can be modified any time, but changes only
1313     take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1314     called.
1315     .IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1316     .IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1317     The current reschedule callback, or \f(CW0\fR, if this functionality is
1318     switched off. Can be changed any time, but changes only take effect when
1319     the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1320 root 1.9 .PP
1321 root 1.28 Example: Call a callback every hour, or, more precisely, whenever the
1322 root 1.9 system clock is divisible by 3600. The callback invocation times have
1323     potentially a lot of jittering, but good long-term stability.
1324     .PP
1325     .Vb 5
1326     \& static void
1327     \& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1328     \& {
1329     \& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1330     \& }
1331     .Ve
1332     .PP
1333     .Vb 3
1334     \& struct ev_periodic hourly_tick;
1335     \& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1336     \& ev_periodic_start (loop, &hourly_tick);
1337     .Ve
1338     .PP
1339 root 1.28 Example: The same as above, but use a reschedule callback to do it:
1340 root 1.9 .PP
1341     .Vb 1
1342     \& #include <math.h>
1343     .Ve
1344     .PP
1345     .Vb 5
1346     \& static ev_tstamp
1347     \& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1348     \& {
1349     \& return fmod (now, 3600.) + 3600.;
1350     \& }
1351     .Ve
1352     .PP
1353     .Vb 1
1354     \& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1355     .Ve
1356     .PP
1357 root 1.28 Example: Call a callback every hour, starting now:
1358 root 1.9 .PP
1359     .Vb 4
1360     \& struct ev_periodic hourly_tick;
1361     \& ev_periodic_init (&hourly_tick, clock_cb,
1362     \& fmod (ev_now (loop), 3600.), 3600., 0);
1363     \& ev_periodic_start (loop, &hourly_tick);
1364     .Ve
1365 root 1.17 .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
1366     .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1367     .IX Subsection "ev_signal - signal me when a signal gets signalled!"
1368 root 1.1 Signal watchers will trigger an event when the process receives a specific
1369     signal one or more times. Even though signals are very asynchronous, libev
1370     will try it's best to deliver signals synchronously, i.e. as part of the
1371     normal event processing, like any other event.
1372     .PP
1373     You can configure as many watchers as you like per signal. Only when the
1374     first watcher gets started will libev actually register a signal watcher
1375     with the kernel (thus it coexists with your own signal handlers as long
1376     as you don't register any with libev). Similarly, when the last signal
1377     watcher for a signal is stopped libev will reset the signal handler to
1378     \&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1379     .IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1380     .IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1381     .PD 0
1382     .IP "ev_signal_set (ev_signal *, int signum)" 4
1383     .IX Item "ev_signal_set (ev_signal *, int signum)"
1384     .PD
1385     Configures the watcher to trigger on the given signal number (usually one
1386     of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1387 root 1.22 .IP "int signum [read\-only]" 4
1388     .IX Item "int signum [read-only]"
1389     The signal the watcher watches out for.
1390 root 1.17 .ie n .Sh """ev_child"" \- watch out for process status changes"
1391     .el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1392     .IX Subsection "ev_child - watch out for process status changes"
1393 root 1.1 Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1394     some child status changes (most typically when a child of yours dies).
1395     .IP "ev_child_init (ev_child *, callback, int pid)" 4
1396     .IX Item "ev_child_init (ev_child *, callback, int pid)"
1397     .PD 0
1398     .IP "ev_child_set (ev_child *, int pid)" 4
1399     .IX Item "ev_child_set (ev_child *, int pid)"
1400     .PD
1401     Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
1402     \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1403     at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1404     the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1405     \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1406     process causing the status change.
1407 root 1.22 .IP "int pid [read\-only]" 4
1408     .IX Item "int pid [read-only]"
1409     The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1410     .IP "int rpid [read\-write]" 4
1411     .IX Item "int rpid [read-write]"
1412     The process id that detected a status change.
1413     .IP "int rstatus [read\-write]" 4
1414     .IX Item "int rstatus [read-write]"
1415     The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1416     \&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1417 root 1.9 .PP
1418 root 1.28 Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1419 root 1.9 .PP
1420     .Vb 5
1421     \& static void
1422     \& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1423     \& {
1424     \& ev_unloop (loop, EVUNLOOP_ALL);
1425     \& }
1426     .Ve
1427     .PP
1428     .Vb 3
1429     \& struct ev_signal signal_watcher;
1430     \& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1431     \& ev_signal_start (loop, &sigint_cb);
1432     .Ve
1433 root 1.22 .ie n .Sh """ev_stat"" \- did the file attributes just change?"
1434     .el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1435     .IX Subsection "ev_stat - did the file attributes just change?"
1436     This watches a filesystem path for attribute changes. That is, it calls
1437     \&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1438     compared to the last time, invoking the callback if it did.
1439     .PP
1440     The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1441     not exist\*(R" is a status change like any other. The condition \*(L"path does
1442     not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1443     otherwise always forced to be at least one) and all the other fields of
1444     the stat buffer having unspecified contents.
1445     .PP
1446 root 1.33 The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1447     relative and your working directory changes, the behaviour is undefined.
1448     .PP
1449 root 1.22 Since there is no standard to do this, the portable implementation simply
1450 root 1.30 calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1451 root 1.22 can specify a recommended polling interval for this case. If you specify
1452     a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1453     unspecified default\fR value will be used (which you can expect to be around
1454     five seconds, although this might change dynamically). Libev will also
1455     impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1456     usually overkill.
1457     .PP
1458     This watcher type is not meant for massive numbers of stat watchers,
1459     as even with OS-supported change notifications, this can be
1460     resource\-intensive.
1461     .PP
1462 root 1.30 At the time of this writing, only the Linux inotify interface is
1463     implemented (implementing kqueue support is left as an exercise for the
1464     reader). Inotify will be used to give hints only and should not change the
1465     semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1466     to fall back to regular polling again even with inotify, but changes are
1467     usually detected immediately, and if the file exists there will be no
1468     polling.
1469 root 1.22 .IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1470     .IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1471     .PD 0
1472     .IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1473     .IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1474     .PD
1475     Configures the watcher to wait for status changes of the given
1476     \&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1477     be detected and should normally be specified as \f(CW0\fR to let libev choose
1478     a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1479     path for as long as the watcher is active.
1480     .Sp
1481     The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1482     relative to the attributes at the time the watcher was started (or the
1483     last change was detected).
1484     .IP "ev_stat_stat (ev_stat *)" 4
1485     .IX Item "ev_stat_stat (ev_stat *)"
1486     Updates the stat buffer immediately with new values. If you change the
1487     watched path in your callback, you could call this fucntion to avoid
1488     detecting this change (while introducing a race condition). Can also be
1489     useful simply to find out the new values.
1490     .IP "ev_statdata attr [read\-only]" 4
1491     .IX Item "ev_statdata attr [read-only]"
1492     The most-recently detected attributes of the file. Although the type is of
1493     \&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1494     suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1495     was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1496     .IP "ev_statdata prev [read\-only]" 4
1497     .IX Item "ev_statdata prev [read-only]"
1498     The previous attributes of the file. The callback gets invoked whenever
1499     \&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1500     .IP "ev_tstamp interval [read\-only]" 4
1501     .IX Item "ev_tstamp interval [read-only]"
1502     The specified interval.
1503     .IP "const char *path [read\-only]" 4
1504     .IX Item "const char *path [read-only]"
1505     The filesystem path that is being watched.
1506     .PP
1507     Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1508     .PP
1509     .Vb 15
1510     \& static void
1511     \& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1512     \& {
1513     \& /* /etc/passwd changed in some way */
1514     \& if (w->attr.st_nlink)
1515     \& {
1516     \& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1517     \& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1518     \& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1519     \& }
1520     \& else
1521     \& /* you shalt not abuse printf for puts */
1522     \& puts ("wow, /etc/passwd is not there, expect problems. "
1523     \& "if this is windows, they already arrived\en");
1524     \& }
1525     .Ve
1526     .PP
1527     .Vb 2
1528     \& ...
1529     \& ev_stat passwd;
1530     .Ve
1531     .PP
1532     .Vb 2
1533     \& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1534     \& ev_stat_start (loop, &passwd);
1535     .Ve
1536 root 1.17 .ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1537     .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1538     .IX Subsection "ev_idle - when you've got nothing better to do..."
1539 root 1.37 Idle watchers trigger events when no other events of the same or higher
1540     priority are pending (prepare, check and other idle watchers do not
1541     count).
1542     .PP
1543     That is, as long as your process is busy handling sockets or timeouts
1544     (or even signals, imagine) of the same or higher priority it will not be
1545     triggered. But when your process is idle (or only lower-priority watchers
1546     are pending), the idle watchers are being called once per event loop
1547     iteration \- until stopped, that is, or your process receives more events
1548     and becomes busy again with higher priority stuff.
1549 root 1.1 .PP
1550     The most noteworthy effect is that as long as any idle watchers are
1551     active, the process will not block when waiting for new events.
1552     .PP
1553     Apart from keeping your process non-blocking (which is a useful
1554     effect on its own sometimes), idle watchers are a good place to do
1555     \&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1556     event loop has handled all outstanding events.
1557     .IP "ev_idle_init (ev_signal *, callback)" 4
1558     .IX Item "ev_idle_init (ev_signal *, callback)"
1559     Initialises and configures the idle watcher \- it has no parameters of any
1560     kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1561     believe me.
1562 root 1.9 .PP
1563 root 1.28 Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1564     callback, free it. Also, use no error checking, as usual.
1565 root 1.9 .PP
1566     .Vb 7
1567     \& static void
1568     \& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1569     \& {
1570     \& free (w);
1571     \& // now do something you wanted to do when the program has
1572     \& // no longer asnything immediate to do.
1573     \& }
1574     .Ve
1575     .PP
1576     .Vb 3
1577     \& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1578     \& ev_idle_init (idle_watcher, idle_cb);
1579     \& ev_idle_start (loop, idle_cb);
1580     .Ve
1581 root 1.17 .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
1582     .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1583     .IX Subsection "ev_prepare and ev_check - customise your event loop!"
1584 root 1.1 Prepare and check watchers are usually (but not always) used in tandem:
1585     prepare watchers get invoked before the process blocks and check watchers
1586     afterwards.
1587     .PP
1588 root 1.20 You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1589     the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1590     watchers. Other loops than the current one are fine, however. The
1591     rationale behind this is that you do not need to check for recursion in
1592     those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1593     \&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1594     called in pairs bracketing the blocking call.
1595     .PP
1596 root 1.10 Their main purpose is to integrate other event mechanisms into libev and
1597     their use is somewhat advanced. This could be used, for example, to track
1598     variable changes, implement your own watchers, integrate net-snmp or a
1599 root 1.20 coroutine library and lots more. They are also occasionally useful if
1600     you cache some data and want to flush it before blocking (for example,
1601     in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1602     watcher).
1603 root 1.1 .PP
1604     This is done by examining in each prepare call which file descriptors need
1605     to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1606     them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1607     provide just this functionality). Then, in the check watcher you check for
1608     any events that occured (by checking the pending status of all watchers
1609     and stopping them) and call back into the library. The I/O and timer
1610     callbacks will never actually be called (but must be valid nevertheless,
1611     because you never know, you know?).
1612     .PP
1613     As another example, the Perl Coro module uses these hooks to integrate
1614     coroutines into libev programs, by yielding to other active coroutines
1615     during each prepare and only letting the process block if no coroutines
1616     are ready to run (it's actually more complicated: it only runs coroutines
1617     with priority higher than or equal to the event loop and one coroutine
1618     of lower priority, but only once, using idle watchers to keep the event
1619     loop from blocking if lower-priority coroutines are active, thus mapping
1620     low-priority coroutines to idle/background tasks).
1621     .IP "ev_prepare_init (ev_prepare *, callback)" 4
1622     .IX Item "ev_prepare_init (ev_prepare *, callback)"
1623     .PD 0
1624     .IP "ev_check_init (ev_check *, callback)" 4
1625     .IX Item "ev_check_init (ev_check *, callback)"
1626     .PD
1627     Initialises and configures the prepare or check watcher \- they have no
1628     parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1629     macros, but using them is utterly, utterly and completely pointless.
1630 root 1.9 .PP
1631 root 1.20 Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1632     and a timeout watcher in a prepare handler, as required by libadns, and
1633     in a check watcher, destroy them and call into libadns. What follows is
1634     pseudo-code only of course:
1635     .PP
1636     .Vb 2
1637     \& static ev_io iow [nfd];
1638     \& static ev_timer tw;
1639     .Ve
1640     .PP
1641 root 1.21 .Vb 9
1642 root 1.20 \& static void
1643     \& io_cb (ev_loop *loop, ev_io *w, int revents)
1644     \& {
1645     \& // set the relevant poll flags
1646 root 1.21 \& // could also call adns_processreadable etc. here
1647 root 1.20 \& struct pollfd *fd = (struct pollfd *)w->data;
1648     \& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1649     \& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1650     \& }
1651     .Ve
1652     .PP
1653 root 1.37 .Vb 8
1654 root 1.20 \& // create io watchers for each fd and a timer before blocking
1655     \& static void
1656     \& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1657     \& {
1658 root 1.37 \& int timeout = 3600000;
1659     \& struct pollfd fds [nfd];
1660 root 1.20 \& // actual code will need to loop here and realloc etc.
1661     \& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1662     .Ve
1663     .PP
1664     .Vb 3
1665     \& /* the callback is illegal, but won't be called as we stop during check */
1666     \& ev_timer_init (&tw, 0, timeout * 1e-3);
1667     \& ev_timer_start (loop, &tw);
1668     .Ve
1669     .PP
1670     .Vb 6
1671     \& // create on ev_io per pollfd
1672     \& for (int i = 0; i < nfd; ++i)
1673     \& {
1674     \& ev_io_init (iow + i, io_cb, fds [i].fd,
1675     \& ((fds [i].events & POLLIN ? EV_READ : 0)
1676     \& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1677     .Ve
1678     .PP
1679     .Vb 5
1680     \& fds [i].revents = 0;
1681     \& iow [i].data = fds + i;
1682     \& ev_io_start (loop, iow + i);
1683     \& }
1684     \& }
1685     .Ve
1686     .PP
1687     .Vb 5
1688     \& // stop all watchers after blocking
1689     \& static void
1690     \& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1691     \& {
1692     \& ev_timer_stop (loop, &tw);
1693     .Ve
1694     .PP
1695     .Vb 2
1696     \& for (int i = 0; i < nfd; ++i)
1697     \& ev_io_stop (loop, iow + i);
1698     .Ve
1699     .PP
1700     .Vb 2
1701     \& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1702     \& }
1703     .Ve
1704 root 1.17 .ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1705     .el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1706     .IX Subsection "ev_embed - when one backend isn't enough..."
1707 root 1.10 This is a rather advanced watcher type that lets you embed one event loop
1708 root 1.11 into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1709     loop, other types of watchers might be handled in a delayed or incorrect
1710     fashion and must not be used).
1711 root 1.10 .PP
1712     There are primarily two reasons you would want that: work around bugs and
1713     prioritise I/O.
1714     .PP
1715     As an example for a bug workaround, the kqueue backend might only support
1716     sockets on some platform, so it is unusable as generic backend, but you
1717     still want to make use of it because you have many sockets and it scales
1718     so nicely. In this case, you would create a kqueue-based loop and embed it
1719     into your default loop (which might use e.g. poll). Overall operation will
1720     be a bit slower because first libev has to poll and then call kevent, but
1721     at least you can use both at what they are best.
1722     .PP
1723     As for prioritising I/O: rarely you have the case where some fds have
1724     to be watched and handled very quickly (with low latency), and even
1725     priorities and idle watchers might have too much overhead. In this case
1726     you would put all the high priority stuff in one loop and all the rest in
1727     a second one, and embed the second one in the first.
1728     .PP
1729 root 1.11 As long as the watcher is active, the callback will be invoked every time
1730     there might be events pending in the embedded loop. The callback must then
1731     call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1732     their callbacks (you could also start an idle watcher to give the embedded
1733     loop strictly lower priority for example). You can also set the callback
1734     to \f(CW0\fR, in which case the embed watcher will automatically execute the
1735     embedded loop sweep.
1736     .PP
1737 root 1.10 As long as the watcher is started it will automatically handle events. The
1738     callback will be invoked whenever some events have been handled. You can
1739     set the callback to \f(CW0\fR to avoid having to specify one if you are not
1740     interested in that.
1741     .PP
1742     Also, there have not currently been made special provisions for forking:
1743     when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1744     but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1745     yourself.
1746     .PP
1747     Unfortunately, not all backends are embeddable, only the ones returned by
1748     \&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1749     portable one.
1750     .PP
1751     So when you want to use this feature you will always have to be prepared
1752     that you cannot get an embeddable loop. The recommended way to get around
1753     this is to have a separate variables for your embeddable loop, try to
1754     create it, and if that fails, use the normal loop for everything:
1755     .PP
1756     .Vb 3
1757     \& struct ev_loop *loop_hi = ev_default_init (0);
1758     \& struct ev_loop *loop_lo = 0;
1759     \& struct ev_embed embed;
1760     .Ve
1761     .PP
1762     .Vb 5
1763     \& // see if there is a chance of getting one that works
1764     \& // (remember that a flags value of 0 means autodetection)
1765     \& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1766     \& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1767     \& : 0;
1768     .Ve
1769     .PP
1770     .Vb 8
1771     \& // if we got one, then embed it, otherwise default to loop_hi
1772     \& if (loop_lo)
1773     \& {
1774     \& ev_embed_init (&embed, 0, loop_lo);
1775     \& ev_embed_start (loop_hi, &embed);
1776     \& }
1777     \& else
1778     \& loop_lo = loop_hi;
1779     .Ve
1780 root 1.11 .IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1781     .IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1782 root 1.10 .PD 0
1783 root 1.11 .IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1784     .IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1785 root 1.10 .PD
1786 root 1.11 Configures the watcher to embed the given loop, which must be
1787     embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1788     invoked automatically, otherwise it is the responsibility of the callback
1789     to invoke it (it will continue to be called until the sweep has been done,
1790     if you do not want thta, you need to temporarily stop the embed watcher).
1791     .IP "ev_embed_sweep (loop, ev_embed *)" 4
1792     .IX Item "ev_embed_sweep (loop, ev_embed *)"
1793     Make a single, non-blocking sweep over the embedded loop. This works
1794     similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1795     apropriate way for embedded loops.
1796 root 1.22 .IP "struct ev_loop *loop [read\-only]" 4
1797     .IX Item "struct ev_loop *loop [read-only]"
1798     The embedded event loop.
1799 root 1.24 .ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1800     .el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1801     .IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1802     Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1803     whoever is a good citizen cared to tell libev about it by calling
1804     \&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1805     event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1806     and only in the child after the fork. If whoever good citizen calling
1807     \&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1808     handlers will be invoked, too, of course.
1809     .IP "ev_fork_init (ev_signal *, callback)" 4
1810     .IX Item "ev_fork_init (ev_signal *, callback)"
1811     Initialises and configures the fork watcher \- it has no parameters of any
1812     kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1813     believe me.
1814 root 1.1 .SH "OTHER FUNCTIONS"
1815     .IX Header "OTHER FUNCTIONS"
1816     There are some other functions of possible interest. Described. Here. Now.
1817     .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1818     .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
1819     This function combines a simple timer and an I/O watcher, calls your
1820     callback on whichever event happens first and automatically stop both
1821     watchers. This is useful if you want to wait for a single event on an fd
1822     or timeout without having to allocate/configure/start/stop/free one or
1823     more watchers yourself.
1824     .Sp
1825     If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events
1826     is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and
1827     \&\f(CW\*(C`events\*(C'\fR set will be craeted and started.
1828     .Sp
1829     If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
1830     started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
1831     repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of
1832     dubious value.
1833     .Sp
1834     The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets
1835     passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
1836     \&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR
1837     value passed to \f(CW\*(C`ev_once\*(C'\fR:
1838     .Sp
1839     .Vb 7
1840     \& static void stdin_ready (int revents, void *arg)
1841     \& {
1842     \& if (revents & EV_TIMEOUT)
1843     \& /* doh, nothing entered */;
1844     \& else if (revents & EV_READ)
1845     \& /* stdin might have data for us, joy! */;
1846     \& }
1847     .Ve
1848     .Sp
1849     .Vb 1
1850     \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1851     .Ve
1852 root 1.11 .IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
1853     .IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
1854 root 1.1 Feeds the given event set into the event loop, as if the specified event
1855     had happened for the specified watcher (which must be a pointer to an
1856     initialised but not necessarily started event watcher).
1857 root 1.11 .IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
1858     .IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
1859 root 1.1 Feed an event on the given fd, as if a file descriptor backend detected
1860     the given events it.
1861 root 1.11 .IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
1862     .IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
1863     Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1864     loop!).
1865 root 1.1 .SH "LIBEVENT EMULATION"
1866     .IX Header "LIBEVENT EMULATION"
1867     Libev offers a compatibility emulation layer for libevent. It cannot
1868     emulate the internals of libevent, so here are some usage hints:
1869     .IP "* Use it by including <event.h>, as usual." 4
1870     .IX Item "Use it by including <event.h>, as usual."
1871     .PD 0
1872     .IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4
1873     .IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events."
1874     .IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4
1875     .IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)."
1876     .IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4
1877     .IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field."
1878     .IP "* Other members are not supported." 4
1879     .IX Item "Other members are not supported."
1880     .IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1881     .IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1882     .PD
1883     .SH "\*(C+ SUPPORT"
1884     .IX Header " SUPPORT"
1885 root 1.13 Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1886     you to use some convinience methods to start/stop watchers and also change
1887     the callback model to a model using method callbacks on objects.
1888     .PP
1889     To use it,
1890     .PP
1891     .Vb 1
1892     \& #include <ev++.h>
1893     .Ve
1894     .PP
1895     (it is not installed by default). This automatically includes \fIev.h\fR
1896     and puts all of its definitions (many of them macros) into the global
1897     namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1898     .PP
1899     It should support all the same embedding options as \fIev.h\fR, most notably
1900     \&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1901     .PP
1902     Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1903     .ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1904     .el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1905     .IX Item "ev::READ, ev::WRITE etc."
1906     These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1907     macros from \fIev.h\fR.
1908     .ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1909     .el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1910     .IX Item "ev::tstamp, ev::now"
1911     Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1912     .ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
1913     .el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1914     .IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1915     For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1916     the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1917     which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1918     defines by many implementations.
1919     .Sp
1920     All of those classes have these methods:
1921     .RS 4
1922     .IP "ev::TYPE::TYPE (object *, object::method *)" 4
1923     .IX Item "ev::TYPE::TYPE (object *, object::method *)"
1924     .PD 0
1925     .IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1926     .IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1927     .IP "ev::TYPE::~TYPE" 4
1928     .IX Item "ev::TYPE::~TYPE"
1929     .PD
1930     The constructor takes a pointer to an object and a method pointer to
1931     the event handler callback to call in this class. The constructor calls
1932     \&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1933     before starting it. If you do not specify a loop then the constructor
1934     automatically associates the default loop with this watcher.
1935     .Sp
1936     The destructor automatically stops the watcher if it is active.
1937     .IP "w\->set (struct ev_loop *)" 4
1938     .IX Item "w->set (struct ev_loop *)"
1939     Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1940     do this when the watcher is inactive (and not pending either).
1941     .IP "w\->set ([args])" 4
1942     .IX Item "w->set ([args])"
1943     Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1944     called at least once. Unlike the C counterpart, an active watcher gets
1945     automatically stopped and restarted.
1946     .IP "w\->start ()" 4
1947     .IX Item "w->start ()"
1948     Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1949     constructor already takes the loop.
1950     .IP "w\->stop ()" 4
1951     .IX Item "w->stop ()"
1952     Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1953     .ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1954     .el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1955     .IX Item "w->again () ev::timer, ev::periodic only"
1956     For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1957     \&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1958     .ie n .IP "w\->sweep () ""ev::embed"" only" 4
1959     .el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1960     .IX Item "w->sweep () ev::embed only"
1961     Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1962 root 1.23 .ie n .IP "w\->update () ""ev::stat"" only" 4
1963     .el .IP "w\->update () \f(CWev::stat\fR only" 4
1964     .IX Item "w->update () ev::stat only"
1965     Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1966 root 1.13 .RE
1967     .RS 4
1968     .RE
1969     .PP
1970     Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1971     the constructor.
1972     .PP
1973     .Vb 4
1974     \& class myclass
1975     \& {
1976     \& ev_io io; void io_cb (ev::io &w, int revents);
1977     \& ev_idle idle void idle_cb (ev::idle &w, int revents);
1978     .Ve
1979     .PP
1980     .Vb 2
1981     \& myclass ();
1982     \& }
1983     .Ve
1984     .PP
1985     .Vb 6
1986     \& myclass::myclass (int fd)
1987     \& : io (this, &myclass::io_cb),
1988     \& idle (this, &myclass::idle_cb)
1989     \& {
1990     \& io.start (fd, ev::READ);
1991     \& }
1992     .Ve
1993 root 1.24 .SH "MACRO MAGIC"
1994     .IX Header "MACRO MAGIC"
1995     Libev can be compiled with a variety of options, the most fundemantal is
1996 root 1.38 \&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
1997 root 1.24 callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1998     .PP
1999     To make it easier to write programs that cope with either variant, the
2000     following macros are defined:
2001     .ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2002     .el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2003     .IX Item "EV_A, EV_A_"
2004     This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2005     loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2006     \&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2007     .Sp
2008     .Vb 3
2009     \& ev_unref (EV_A);
2010     \& ev_timer_add (EV_A_ watcher);
2011     \& ev_loop (EV_A_ 0);
2012     .Ve
2013     .Sp
2014     It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2015     which is often provided by the following macro.
2016     .ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2017     .el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2018     .IX Item "EV_P, EV_P_"
2019     This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2020     loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2021     \&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2022     .Sp
2023     .Vb 2
2024     \& // this is how ev_unref is being declared
2025     \& static void ev_unref (EV_P);
2026     .Ve
2027     .Sp
2028     .Vb 2
2029     \& // this is how you can declare your typical callback
2030     \& static void cb (EV_P_ ev_timer *w, int revents)
2031     .Ve
2032     .Sp
2033     It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2034     suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2035     .ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2036     .el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2037     .IX Item "EV_DEFAULT, EV_DEFAULT_"
2038     Similar to the other two macros, this gives you the value of the default
2039     loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2040     .PP
2041 root 1.36 Example: Declare and initialise a check watcher, utilising the above
2042 root 1.38 macros so it will work regardless of whether multiple loops are supported
2043 root 1.36 or not.
2044 root 1.24 .PP
2045     .Vb 5
2046     \& static void
2047     \& check_cb (EV_P_ ev_timer *w, int revents)
2048     \& {
2049     \& ev_check_stop (EV_A_ w);
2050     \& }
2051     .Ve
2052     .PP
2053     .Vb 4
2054     \& ev_check check;
2055     \& ev_check_init (&check, check_cb);
2056     \& ev_check_start (EV_DEFAULT_ &check);
2057     \& ev_loop (EV_DEFAULT_ 0);
2058     .Ve
2059 root 1.14 .SH "EMBEDDING"
2060     .IX Header "EMBEDDING"
2061     Libev can (and often is) directly embedded into host
2062     applications. Examples of applications that embed it include the Deliantra
2063     Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2064     and rxvt\-unicode.
2065     .PP
2066     The goal is to enable you to just copy the neecssary files into your
2067     source directory without having to change even a single line in them, so
2068     you can easily upgrade by simply copying (or having a checked-out copy of
2069     libev somewhere in your source tree).
2070     .Sh "\s-1FILESETS\s0"
2071     .IX Subsection "FILESETS"
2072     Depending on what features you need you need to include one or more sets of files
2073     in your app.
2074     .PP
2075     \fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2076     .IX Subsection "CORE EVENT LOOP"
2077     .PP
2078     To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2079     configuration (no autoconf):
2080     .PP
2081     .Vb 2
2082     \& #define EV_STANDALONE 1
2083     \& #include "ev.c"
2084     .Ve
2085     .PP
2086     This will automatically include \fIev.h\fR, too, and should be done in a
2087     single C source file only to provide the function implementations. To use
2088     it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2089     done by writing a wrapper around \fIev.h\fR that you can include instead and
2090     where you can put other configuration options):
2091     .PP
2092     .Vb 2
2093     \& #define EV_STANDALONE 1
2094     \& #include "ev.h"
2095     .Ve
2096     .PP
2097     Both header files and implementation files can be compiled with a \*(C+
2098     compiler (at least, thats a stated goal, and breakage will be treated
2099     as a bug).
2100     .PP
2101     You need the following files in your source tree, or in a directory
2102     in your include path (e.g. in libev/ when using \-Ilibev):
2103     .PP
2104     .Vb 4
2105     \& ev.h
2106     \& ev.c
2107     \& ev_vars.h
2108     \& ev_wrap.h
2109     .Ve
2110     .PP
2111     .Vb 1
2112     \& ev_win32.c required on win32 platforms only
2113     .Ve
2114     .PP
2115     .Vb 5
2116 root 1.36 \& ev_select.c only when select backend is enabled (which is enabled by default)
2117 root 1.14 \& ev_poll.c only when poll backend is enabled (disabled by default)
2118     \& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2119     \& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2120     \& ev_port.c only when the solaris port backend is enabled (disabled by default)
2121     .Ve
2122     .PP
2123     \&\fIev.c\fR includes the backend files directly when enabled, so you only need
2124 root 1.18 to compile this single file.
2125 root 1.14 .PP
2126     \fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2127     .IX Subsection "LIBEVENT COMPATIBILITY API"
2128     .PP
2129     To include the libevent compatibility \s-1API\s0, also include:
2130     .PP
2131     .Vb 1
2132     \& #include "event.c"
2133     .Ve
2134     .PP
2135     in the file including \fIev.c\fR, and:
2136     .PP
2137     .Vb 1
2138     \& #include "event.h"
2139     .Ve
2140     .PP
2141     in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2142     .PP
2143     You need the following additional files for this:
2144     .PP
2145     .Vb 2
2146     \& event.h
2147     \& event.c
2148     .Ve
2149     .PP
2150     \fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2151     .IX Subsection "AUTOCONF SUPPORT"
2152     .PP
2153     Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2154     whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2155 root 1.18 \&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2156     include \fIconfig.h\fR and configure itself accordingly.
2157 root 1.14 .PP
2158     For this of course you need the m4 file:
2159     .PP
2160     .Vb 1
2161     \& libev.m4
2162     .Ve
2163     .Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2164     .IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2165     Libev can be configured via a variety of preprocessor symbols you have to define
2166     before including any of its files. The default is not to build for multiplicity
2167     and only include the select backend.
2168     .IP "\s-1EV_STANDALONE\s0" 4
2169     .IX Item "EV_STANDALONE"
2170     Must always be \f(CW1\fR if you do not use autoconf configuration, which
2171     keeps libev from including \fIconfig.h\fR, and it also defines dummy
2172     implementations for some libevent functions (such as logging, which is not
2173     supported). It will also not define any of the structs usually found in
2174     \&\fIevent.h\fR that are not directly supported by the libev core alone.
2175     .IP "\s-1EV_USE_MONOTONIC\s0" 4
2176     .IX Item "EV_USE_MONOTONIC"
2177     If defined to be \f(CW1\fR, libev will try to detect the availability of the
2178     monotonic clock option at both compiletime and runtime. Otherwise no use
2179     of the monotonic clock option will be attempted. If you enable this, you
2180     usually have to link against librt or something similar. Enabling it when
2181     the functionality isn't available is safe, though, althoguh you have
2182     to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2183     function is hiding in (often \fI\-lrt\fR).
2184     .IP "\s-1EV_USE_REALTIME\s0" 4
2185     .IX Item "EV_USE_REALTIME"
2186     If defined to be \f(CW1\fR, libev will try to detect the availability of the
2187     realtime clock option at compiletime (and assume its availability at
2188     runtime if successful). Otherwise no use of the realtime clock option will
2189     be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2190     (CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2191     in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2192     .IP "\s-1EV_USE_SELECT\s0" 4
2193     .IX Item "EV_USE_SELECT"
2194     If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2195     \&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2196     other method takes over, select will be it. Otherwise the select backend
2197     will not be compiled in.
2198     .IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2199     .IX Item "EV_SELECT_USE_FD_SET"
2200     If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2201     structure. This is useful if libev doesn't compile due to a missing
2202     \&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2203     exotic systems. This usually limits the range of file descriptors to some
2204     low limit such as 1024 or might have other limitations (winsocket only
2205     allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2206     influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2207     .IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2208     .IX Item "EV_SELECT_IS_WINSOCKET"
2209     When defined to \f(CW1\fR, the select backend will assume that
2210     select/socket/connect etc. don't understand file descriptors but
2211     wants osf handles on win32 (this is the case when the select to
2212     be used is the winsock select). This means that it will call
2213     \&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2214     it is assumed that all these functions actually work on fds, even
2215     on win32. Should not be defined on non\-win32 platforms.
2216     .IP "\s-1EV_USE_POLL\s0" 4
2217     .IX Item "EV_USE_POLL"
2218     If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2219     backend. Otherwise it will be enabled on non\-win32 platforms. It
2220     takes precedence over select.
2221     .IP "\s-1EV_USE_EPOLL\s0" 4
2222     .IX Item "EV_USE_EPOLL"
2223     If defined to be \f(CW1\fR, libev will compile in support for the Linux
2224     \&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2225     otherwise another method will be used as fallback. This is the
2226     preferred backend for GNU/Linux systems.
2227     .IP "\s-1EV_USE_KQUEUE\s0" 4
2228     .IX Item "EV_USE_KQUEUE"
2229     If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2230     \&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2231     otherwise another method will be used as fallback. This is the preferred
2232     backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2233     supports some types of fds correctly (the only platform we found that
2234     supports ptys for example was NetBSD), so kqueue might be compiled in, but
2235     not be used unless explicitly requested. The best way to use it is to find
2236 root 1.16 out whether kqueue supports your type of fd properly and use an embedded
2237 root 1.14 kqueue loop.
2238     .IP "\s-1EV_USE_PORT\s0" 4
2239     .IX Item "EV_USE_PORT"
2240     If defined to be \f(CW1\fR, libev will compile in support for the Solaris
2241     10 port style backend. Its availability will be detected at runtime,
2242     otherwise another method will be used as fallback. This is the preferred
2243     backend for Solaris 10 systems.
2244     .IP "\s-1EV_USE_DEVPOLL\s0" 4
2245     .IX Item "EV_USE_DEVPOLL"
2246     reserved for future expansion, works like the \s-1USE\s0 symbols above.
2247 root 1.30 .IP "\s-1EV_USE_INOTIFY\s0" 4
2248     .IX Item "EV_USE_INOTIFY"
2249     If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2250     interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2251     be detected at runtime.
2252 root 1.14 .IP "\s-1EV_H\s0" 4
2253     .IX Item "EV_H"
2254     The name of the \fIev.h\fR header file used to include it. The default if
2255     undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2256     can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2257     .IP "\s-1EV_CONFIG_H\s0" 4
2258     .IX Item "EV_CONFIG_H"
2259     If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2260     \&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2261     \&\f(CW\*(C`EV_H\*(C'\fR, above.
2262     .IP "\s-1EV_EVENT_H\s0" 4
2263     .IX Item "EV_EVENT_H"
2264     Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2265     of how the \fIevent.h\fR header can be found.
2266     .IP "\s-1EV_PROTOTYPES\s0" 4
2267     .IX Item "EV_PROTOTYPES"
2268     If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2269     prototypes, but still define all the structs and other symbols. This is
2270     occasionally useful if you want to provide your own wrapper functions
2271     around libev functions.
2272     .IP "\s-1EV_MULTIPLICITY\s0" 4
2273     .IX Item "EV_MULTIPLICITY"
2274     If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2275     will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2276     additional independent event loops. Otherwise there will be no support
2277     for multiple event loops and there is no first event loop pointer
2278     argument. Instead, all functions act on the single default loop.
2279 root 1.22 .IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2280     .IX Item "EV_PERIODIC_ENABLE"
2281     If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2282     defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2283     code.
2284 root 1.37 .IP "\s-1EV_IDLE_ENABLE\s0" 4
2285     .IX Item "EV_IDLE_ENABLE"
2286     If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2287     defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2288     code.
2289 root 1.22 .IP "\s-1EV_EMBED_ENABLE\s0" 4
2290     .IX Item "EV_EMBED_ENABLE"
2291     If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2292     defined to be \f(CW0\fR, then they are not.
2293     .IP "\s-1EV_STAT_ENABLE\s0" 4
2294     .IX Item "EV_STAT_ENABLE"
2295     If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2296     defined to be \f(CW0\fR, then they are not.
2297 root 1.24 .IP "\s-1EV_FORK_ENABLE\s0" 4
2298     .IX Item "EV_FORK_ENABLE"
2299     If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2300     defined to be \f(CW0\fR, then they are not.
2301 root 1.22 .IP "\s-1EV_MINIMAL\s0" 4
2302     .IX Item "EV_MINIMAL"
2303     If you need to shave off some kilobytes of code at the expense of some
2304     speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2305     some inlining decisions, saves roughly 30% codesize of amd64.
2306 root 1.25 .IP "\s-1EV_PID_HASHSIZE\s0" 4
2307     .IX Item "EV_PID_HASHSIZE"
2308     \&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2309     pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2310     than enough. If you need to manage thousands of children you might want to
2311 root 1.30 increase this value (\fImust\fR be a power of two).
2312     .IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2313     .IX Item "EV_INOTIFY_HASHSIZE"
2314     \&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2315     inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2316     usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2317     watchers you might want to increase this value (\fImust\fR be a power of
2318     two).
2319 root 1.14 .IP "\s-1EV_COMMON\s0" 4
2320     .IX Item "EV_COMMON"
2321     By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2322     this macro to a something else you can include more and other types of
2323     members. You have to define it each time you include one of the files,
2324     though, and it must be identical each time.
2325     .Sp
2326     For example, the perl \s-1EV\s0 module uses something like this:
2327     .Sp
2328     .Vb 3
2329     \& #define EV_COMMON \e
2330     \& SV *self; /* contains this struct */ \e
2331     \& SV *cb_sv, *fh /* note no trailing ";" */
2332     .Ve
2333 root 1.19 .IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2334     .IX Item "EV_CB_DECLARE (type)"
2335 root 1.14 .PD 0
2336 root 1.19 .IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2337     .IX Item "EV_CB_INVOKE (watcher, revents)"
2338     .IP "ev_set_cb (ev, cb)" 4
2339     .IX Item "ev_set_cb (ev, cb)"
2340 root 1.14 .PD
2341     Can be used to change the callback member declaration in each watcher,
2342     and the way callbacks are invoked and set. Must expand to a struct member
2343     definition and a statement, respectively. See the \fIev.v\fR header file for
2344     their default definitions. One possible use for overriding these is to
2345 root 1.19 avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2346     method calls instead of plain function calls in \*(C+.
2347 root 1.14 .Sh "\s-1EXAMPLES\s0"
2348     .IX Subsection "EXAMPLES"
2349     For a real-world example of a program the includes libev
2350     verbatim, you can have a look at the \s-1EV\s0 perl module
2351     (<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2352     the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2353     interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2354     will be compiled. It is pretty complex because it provides its own header
2355     file.
2356     .Sp
2357     The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2358 root 1.36 that everybody includes and which overrides some configure choices:
2359 root 1.14 .Sp
2360 root 1.36 .Vb 9
2361     \& #define EV_MINIMAL 1
2362 root 1.15 \& #define EV_USE_POLL 0
2363     \& #define EV_MULTIPLICITY 0
2364 root 1.36 \& #define EV_PERIODIC_ENABLE 0
2365     \& #define EV_STAT_ENABLE 0
2366     \& #define EV_FORK_ENABLE 0
2367 root 1.15 \& #define EV_CONFIG_H <config.h>
2368 root 1.36 \& #define EV_MINPRI 0
2369     \& #define EV_MAXPRI 0
2370 root 1.14 .Ve
2371     .Sp
2372     .Vb 1
2373 root 1.15 \& #include "ev++.h"
2374 root 1.14 .Ve
2375     .Sp
2376     And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2377     .Sp
2378     .Vb 2
2379 root 1.15 \& #include "ev_cpp.h"
2380     \& #include "ev.c"
2381 root 1.14 .Ve
2382 root 1.21 .SH "COMPLEXITIES"
2383     .IX Header "COMPLEXITIES"
2384     In this section the complexities of (many of) the algorithms used inside
2385     libev will be explained. For complexity discussions about backends see the
2386     documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2387     .RS 4
2388     .IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2389     .IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2390     .PD 0
2391     .IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2392     .IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2393     .IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2394     .IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2395     .IP "Stopping check/prepare/idle watchers: O(1)" 4
2396     .IX Item "Stopping check/prepare/idle watchers: O(1)"
2397 root 1.30 .IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2398     .IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2399 root 1.21 .IP "Finding the next timer per loop iteration: O(1)" 4
2400     .IX Item "Finding the next timer per loop iteration: O(1)"
2401     .IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2402     .IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2403     .IP "Activating one watcher: O(1)" 4
2404     .IX Item "Activating one watcher: O(1)"
2405     .RE
2406     .RS 4
2407     .PD
2408 root 1.1 .SH "AUTHOR"
2409     .IX Header "AUTHOR"
2410     Marc Lehmann <libev@schmorp.de>.