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Revision: 1.6
Committed: Fri Nov 23 05:14:58 2007 UTC (16 years, 5 months ago) by root
Branch: MAIN
Changes since 1.5: +48 -30 lines
Log Message:
still renaming

File Contents

# User Rev Content
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131     .IX Title ""<STANDARD INPUT>" 1"
132 root 1.5 .TH "<STANDARD INPUT>" 1 "2007-11-23" "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     .Vb 1
138     \& #include <ev.h>
139     .Ve
140     .SH "DESCRIPTION"
141     .IX Header "DESCRIPTION"
142     Libev is an event loop: you register interest in certain events (such as a
143     file descriptor being readable or a timeout occuring), and it will manage
144     these event sources and provide your program with events.
145     .PP
146     To do this, it must take more or less complete control over your process
147     (or thread) by executing the \fIevent loop\fR handler, and will then
148     communicate events via a callback mechanism.
149     .PP
150     You register interest in certain events by registering so-called \fIevent
151     watchers\fR, which are relatively small C structures you initialise with the
152     details of the event, and then hand it over to libev by \fIstarting\fR the
153     watcher.
154     .SH "FEATURES"
155     .IX Header "FEATURES"
156     Libev supports select, poll, the linux-specific epoll and the bsd-specific
157     kqueue mechanisms for file descriptor events, relative timers, absolute
158     timers with customised rescheduling, signal events, process status change
159     events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event
160     loop mechanism itself (idle, prepare and check watchers). It also is quite
161     fast (see this benchmark comparing
162     it to libevent for example).
163     .SH "CONVENTIONS"
164     .IX Header "CONVENTIONS"
165     Libev is very configurable. In this manual the default configuration
166     will be described, which supports multiple event loops. For more info
167     about various configuration options please have a look at the file
168     \&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without
169     support for multiple event loops, then all functions taking an initial
170     argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR)
171     will not have this argument.
172     .SH "TIME REPRESENTATION"
173     .IX Header "TIME REPRESENTATION"
174     Libev represents time as a single floating point number, representing the
175     (fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176     the beginning of 1970, details are complicated, don't ask). This type is
177     called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178     to the double type in C.
179     .SH "GLOBAL FUNCTIONS"
180     .IX Header "GLOBAL FUNCTIONS"
181     These functions can be called anytime, even before initialising the
182     library in any way.
183     .IP "ev_tstamp ev_time ()" 4
184     .IX Item "ev_tstamp ev_time ()"
185 root 1.2 Returns the current time as libev would use it. Please note that the
186     \&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
187     you actually want to know.
188 root 1.1 .IP "int ev_version_major ()" 4
189     .IX Item "int ev_version_major ()"
190     .PD 0
191     .IP "int ev_version_minor ()" 4
192     .IX Item "int ev_version_minor ()"
193     .PD
194     You can find out the major and minor version numbers of the library
195     you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
196     \&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
197     symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
198     version of the library your program was compiled against.
199     .Sp
200     Usually, it's a good idea to terminate if the major versions mismatch,
201     as this indicates an incompatible change. Minor versions are usually
202     compatible to older versions, so a larger minor version alone is usually
203     not a problem.
204 root 1.6 .IP "unsigned int ev_supported_backends ()" 4
205     .IX Item "unsigned int ev_supported_backends ()"
206     Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
207     value) compiled into this binary of libev (independent of their
208     availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
209     a description of the set values.
210     .IP "unsigned int ev_recommended_backends ()" 4
211     .IX Item "unsigned int ev_recommended_backends ()"
212     Return the set of all backends compiled into this binary of libev and also
213     recommended for this platform. This set is often smaller than the one
214     returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
215     most BSDs and will not be autodetected unless you explicitly request it
216     (assuming you know what you are doing). This is the set of backends that
217     \&\f(CW\*(C`EVFLAG_AUTO\*(C'\fR will probe for.
218 root 1.1 .IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
219     .IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
220     Sets the allocation function to use (the prototype is similar to the
221     realloc C function, the semantics are identical). It is used to allocate
222     and free memory (no surprises here). If it returns zero when memory
223     needs to be allocated, the library might abort or take some potentially
224     destructive action. The default is your system realloc function.
225     .Sp
226     You could override this function in high-availability programs to, say,
227     free some memory if it cannot allocate memory, to use a special allocator,
228     or even to sleep a while and retry until some memory is available.
229     .IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
230     .IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
231     Set the callback function to call on a retryable syscall error (such
232     as failed select, poll, epoll_wait). The message is a printable string
233     indicating the system call or subsystem causing the problem. If this
234     callback is set, then libev will expect it to remedy the sitution, no
235     matter what, when it returns. That is, libev will generally retry the
236     requested operation, or, if the condition doesn't go away, do bad stuff
237     (such as abort).
238     .SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
239     .IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
240     An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
241     types of such loops, the \fIdefault\fR loop, which supports signals and child
242     events, and dynamically created loops which do not.
243     .PP
244     If you use threads, a common model is to run the default event loop
245     in your main thread (or in a separate thread) and for each thread you
246     create, you also create another event loop. Libev itself does no locking
247     whatsoever, so if you mix calls to the same event loop in different
248     threads, make sure you lock (this is usually a bad idea, though, even if
249     done correctly, because it's hideous and inefficient).
250     .IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
251     .IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
252     This will initialise the default event loop if it hasn't been initialised
253     yet and return it. If the default loop could not be initialised, returns
254     false. If it already was initialised it simply returns it (and ignores the
255 root 1.6 flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
256 root 1.1 .Sp
257     If you don't know what event loop to use, use the one returned from this
258     function.
259     .Sp
260     The flags argument can be used to specify special behaviour or specific
261 root 1.6 backends to use, and is usually specified as \f(CW0\fR (or \s-1EVFLAG_AUTO\s0).
262 root 1.1 .Sp
263     It supports the following flags:
264     .RS 4
265     .ie n .IP """EVFLAG_AUTO""" 4
266     .el .IP "\f(CWEVFLAG_AUTO\fR" 4
267     .IX Item "EVFLAG_AUTO"
268     The default flags value. Use this if you have no clue (it's the right
269     thing, believe me).
270     .ie n .IP """EVFLAG_NOENV""" 4
271     .el .IP "\f(CWEVFLAG_NOENV\fR" 4
272     .IX Item "EVFLAG_NOENV"
273     If this flag bit is ored into the flag value (or the program runs setuid
274     or setgid) then libev will \fInot\fR look at the environment variable
275     \&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
276     override the flags completely if it is found in the environment. This is
277     useful to try out specific backends to test their performance, or to work
278     around bugs.
279 root 1.6 .ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
280     .el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
281     .IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
282 root 1.3 This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
283     libev tries to roll its own fd_set with no limits on the number of fds,
284     but if that fails, expect a fairly low limit on the number of fds when
285     using this backend. It doesn't scale too well (O(highest_fd)), but its usually
286     the fastest backend for a low number of fds.
287 root 1.6 .ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
288     .el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
289     .IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
290 root 1.3 And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
291     select, but handles sparse fds better and has no artificial limit on the
292     number of fds you can use (except it will slow down considerably with a
293     lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
294 root 1.6 .ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
295     .el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
296     .IX Item "EVBACKEND_EPOLL (value 4, Linux)"
297 root 1.3 For few fds, this backend is a bit little slower than poll and select,
298     but it scales phenomenally better. While poll and select usually scale like
299     O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
300     either O(1) or O(active_fds).
301     .Sp
302     While stopping and starting an I/O watcher in the same iteration will
303     result in some caching, there is still a syscall per such incident
304     (because the fd could point to a different file description now), so its
305     best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
306     well if you register events for both fds.
307 root 1.6 .ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
308     .el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
309     .IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
310 root 1.3 Kqueue deserves special mention, as at the time of this writing, it
311     was broken on all BSDs except NetBSD (usually it doesn't work with
312     anything but sockets and pipes, except on Darwin, where of course its
313     completely useless). For this reason its not being \*(L"autodetected\*(R" unless
314     you explicitly specify the flags (i.e. you don't use \s-1EVFLAG_AUTO\s0).
315     .Sp
316     It scales in the same way as the epoll backend, but the interface to the
317     kernel is more efficient (which says nothing about its actual speed, of
318     course). While starting and stopping an I/O watcher does not cause an
319     extra syscall as with epoll, it still adds up to four event changes per
320     incident, so its best to avoid that.
321 root 1.6 .ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
322     .el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
323     .IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
324 root 1.3 This is not implemented yet (and might never be).
325 root 1.6 .ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
326     .el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
327     .IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
328 root 1.3 This uses the Solaris 10 port mechanism. As with everything on Solaris,
329     it's really slow, but it still scales very well (O(active_fds)).
330 root 1.6 .ie n .IP """EVBACKEND_ALL""" 4
331     .el .IP "\f(CWEVBACKEND_ALL\fR" 4
332     .IX Item "EVBACKEND_ALL"
333 root 1.4 Try all backends (even potentially broken ones that wouldn't be tried
334     with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
335 root 1.6 \&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
336 root 1.1 .RE
337     .RS 4
338 root 1.3 .Sp
339     If one or more of these are ored into the flags value, then only these
340     backends will be tried (in the reverse order as given here). If none are
341     specified, most compiled-in backend will be tried, usually in reverse
342     order of their flag values :)
343 root 1.1 .RE
344     .IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
345     .IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
346     Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
347     always distinct from the default loop. Unlike the default loop, it cannot
348     handle signal and child watchers, and attempts to do so will be greeted by
349     undefined behaviour (or a failed assertion if assertions are enabled).
350     .IP "ev_default_destroy ()" 4
351     .IX Item "ev_default_destroy ()"
352     Destroys the default loop again (frees all memory and kernel state
353     etc.). This stops all registered event watchers (by not touching them in
354     any way whatsoever, although you cannot rely on this :).
355     .IP "ev_loop_destroy (loop)" 4
356     .IX Item "ev_loop_destroy (loop)"
357     Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
358     earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
359     .IP "ev_default_fork ()" 4
360     .IX Item "ev_default_fork ()"
361     This function reinitialises the kernel state for backends that have
362     one. Despite the name, you can call it anytime, but it makes most sense
363     after forking, in either the parent or child process (or both, but that
364     again makes little sense).
365     .Sp
366 root 1.5 You \fImust\fR call this function in the child process after forking if and
367     only if you want to use the event library in both processes. If you just
368     fork+exec, you don't have to call it.
369 root 1.1 .Sp
370     The function itself is quite fast and it's usually not a problem to call
371     it just in case after a fork. To make this easy, the function will fit in
372     quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
373     .Sp
374     .Vb 1
375     \& pthread_atfork (0, 0, ev_default_fork);
376     .Ve
377 root 1.6 .Sp
378     At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
379     without calling this function, so if you force one of those backends you
380     do not need to care.
381 root 1.1 .IP "ev_loop_fork (loop)" 4
382     .IX Item "ev_loop_fork (loop)"
383     Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
384     \&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
385     after fork, and how you do this is entirely your own problem.
386 root 1.6 .IP "unsigned int ev_backend (loop)" 4
387     .IX Item "unsigned int ev_backend (loop)"
388     Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
389 root 1.1 use.
390     .IP "ev_tstamp ev_now (loop)" 4
391     .IX Item "ev_tstamp ev_now (loop)"
392     Returns the current \*(L"event loop time\*(R", which is the time the event loop
393     got events and started processing them. This timestamp does not change
394     as long as callbacks are being processed, and this is also the base time
395     used for relative timers. You can treat it as the timestamp of the event
396     occuring (or more correctly, the mainloop finding out about it).
397     .IP "ev_loop (loop, int flags)" 4
398     .IX Item "ev_loop (loop, int flags)"
399     Finally, this is it, the event handler. This function usually is called
400     after you initialised all your watchers and you want to start handling
401     events.
402     .Sp
403     If the flags argument is specified as 0, it will not return until either
404     no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
405     .Sp
406     A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
407     those events and any outstanding ones, but will not block your process in
408     case there are no events and will return after one iteration of the loop.
409     .Sp
410     A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
411     neccessary) and will handle those and any outstanding ones. It will block
412     your process until at least one new event arrives, and will return after
413     one iteration of the loop.
414     .Sp
415     This flags value could be used to implement alternative looping
416     constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and
417     more generic mechanism.
418 root 1.2 .Sp
419     Here are the gory details of what ev_loop does:
420     .Sp
421     .Vb 15
422     \& 1. If there are no active watchers (reference count is zero), return.
423     \& 2. Queue and immediately call all prepare watchers.
424     \& 3. If we have been forked, recreate the kernel state.
425     \& 4. Update the kernel state with all outstanding changes.
426     \& 5. Update the "event loop time".
427     \& 6. Calculate for how long to block.
428     \& 7. Block the process, waiting for events.
429     \& 8. Update the "event loop time" and do time jump handling.
430     \& 9. Queue all outstanding timers.
431     \& 10. Queue all outstanding periodics.
432     \& 11. If no events are pending now, queue all idle watchers.
433     \& 12. Queue all check watchers.
434     \& 13. Call all queued watchers in reverse order (i.e. check watchers first).
435     \& 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
436     \& was used, return, otherwise continue with step #1.
437     .Ve
438 root 1.1 .IP "ev_unloop (loop, how)" 4
439     .IX Item "ev_unloop (loop, how)"
440     Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
441     has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
442     \&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or
443     \&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return.
444     .IP "ev_ref (loop)" 4
445     .IX Item "ev_ref (loop)"
446     .PD 0
447     .IP "ev_unref (loop)" 4
448     .IX Item "ev_unref (loop)"
449     .PD
450     Ref/unref can be used to add or remove a reference count on the event
451     loop: Every watcher keeps one reference, and as long as the reference
452     count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have
453     a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from
454     returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For
455     example, libev itself uses this for its internal signal pipe: It is not
456     visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
457     no event watchers registered by it are active. It is also an excellent
458     way to do this for generic recurring timers or from within third-party
459     libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
460     .SH "ANATOMY OF A WATCHER"
461     .IX Header "ANATOMY OF A WATCHER"
462     A watcher is a structure that you create and register to record your
463     interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
464     become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
465     .PP
466     .Vb 5
467     \& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents)
468     \& {
469     \& ev_io_stop (w);
470     \& ev_unloop (loop, EVUNLOOP_ALL);
471     \& }
472     .Ve
473     .PP
474     .Vb 6
475     \& struct ev_loop *loop = ev_default_loop (0);
476     \& struct ev_io stdin_watcher;
477     \& ev_init (&stdin_watcher, my_cb);
478     \& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
479     \& ev_io_start (loop, &stdin_watcher);
480     \& ev_loop (loop, 0);
481     .Ve
482     .PP
483     As you can see, you are responsible for allocating the memory for your
484     watcher structures (and it is usually a bad idea to do this on the stack,
485     although this can sometimes be quite valid).
486     .PP
487     Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init
488     (watcher *, callback)\*(C'\fR, which expects a callback to be provided. This
489     callback gets invoked each time the event occurs (or, in the case of io
490     watchers, each time the event loop detects that the file descriptor given
491     is readable and/or writable).
492     .PP
493     Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro
494     with arguments specific to this watcher type. There is also a macro
495     to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init
496     (watcher *, callback, ...)\*(C'\fR.
497     .PP
498     To make the watcher actually watch out for events, you have to start it
499     with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher
500     *)\*(C'\fR), and you can stop watching for events at any time by calling the
501     corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
502     .PP
503     As long as your watcher is active (has been started but not stopped) you
504     must not touch the values stored in it. Most specifically you must never
505 root 1.6 reinitialise it or call its set macro.
506 root 1.1 .PP
507     You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
508     (watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
509     callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
510     (watcher *)\*(C'\fR macro.
511     .PP
512     Each and every callback receives the event loop pointer as first, the
513     registered watcher structure as second, and a bitset of received events as
514     third argument.
515     .PP
516     The received events usually include a single bit per event type received
517     (you can receive multiple events at the same time). The possible bit masks
518     are:
519     .ie n .IP """EV_READ""" 4
520     .el .IP "\f(CWEV_READ\fR" 4
521     .IX Item "EV_READ"
522     .PD 0
523     .ie n .IP """EV_WRITE""" 4
524     .el .IP "\f(CWEV_WRITE\fR" 4
525     .IX Item "EV_WRITE"
526     .PD
527     The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or
528     writable.
529     .ie n .IP """EV_TIMEOUT""" 4
530     .el .IP "\f(CWEV_TIMEOUT\fR" 4
531     .IX Item "EV_TIMEOUT"
532     The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out.
533     .ie n .IP """EV_PERIODIC""" 4
534     .el .IP "\f(CWEV_PERIODIC\fR" 4
535     .IX Item "EV_PERIODIC"
536     The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out.
537     .ie n .IP """EV_SIGNAL""" 4
538     .el .IP "\f(CWEV_SIGNAL\fR" 4
539     .IX Item "EV_SIGNAL"
540     The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
541     .ie n .IP """EV_CHILD""" 4
542     .el .IP "\f(CWEV_CHILD\fR" 4
543     .IX Item "EV_CHILD"
544     The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
545     .ie n .IP """EV_IDLE""" 4
546     .el .IP "\f(CWEV_IDLE\fR" 4
547     .IX Item "EV_IDLE"
548     The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
549     .ie n .IP """EV_PREPARE""" 4
550     .el .IP "\f(CWEV_PREPARE\fR" 4
551     .IX Item "EV_PREPARE"
552     .PD 0
553     .ie n .IP """EV_CHECK""" 4
554     .el .IP "\f(CWEV_CHECK\fR" 4
555     .IX Item "EV_CHECK"
556     .PD
557     All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts
558     to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after
559     \&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
560     received events. Callbacks of both watcher types can start and stop as
561     many watchers as they want, and all of them will be taken into account
562     (for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
563     \&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
564     .ie n .IP """EV_ERROR""" 4
565     .el .IP "\f(CWEV_ERROR\fR" 4
566     .IX Item "EV_ERROR"
567     An unspecified error has occured, the watcher has been stopped. This might
568     happen because the watcher could not be properly started because libev
569     ran out of memory, a file descriptor was found to be closed or any other
570     problem. You best act on it by reporting the problem and somehow coping
571     with the watcher being stopped.
572     .Sp
573     Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
574     for example it might indicate that a fd is readable or writable, and if
575     your callbacks is well-written it can just attempt the operation and cope
576     with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
577     programs, though, so beware.
578     .Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
579     .IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
580     Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
581     and read at any time, libev will completely ignore it. This can be used
582     to associate arbitrary data with your watcher. If you need more data and
583     don't want to allocate memory and store a pointer to it in that data
584     member, you can also \*(L"subclass\*(R" the watcher type and provide your own
585     data:
586     .PP
587     .Vb 7
588     \& struct my_io
589     \& {
590     \& struct ev_io io;
591     \& int otherfd;
592     \& void *somedata;
593     \& struct whatever *mostinteresting;
594     \& }
595     .Ve
596     .PP
597     And since your callback will be called with a pointer to the watcher, you
598     can cast it back to your own type:
599     .PP
600     .Vb 5
601     \& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents)
602     \& {
603     \& struct my_io *w = (struct my_io *)w_;
604     \& ...
605     \& }
606     .Ve
607     .PP
608     More interesting and less C\-conformant ways of catsing your callback type
609     have been omitted....
610     .SH "WATCHER TYPES"
611     .IX Header "WATCHER TYPES"
612     This section describes each watcher in detail, but will not repeat
613     information given in the last section.
614     .ie n .Sh """ev_io"" \- is this file descriptor readable or writable"
615     .el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable"
616     .IX Subsection "ev_io - is this file descriptor readable or writable"
617     I/O watchers check whether a file descriptor is readable or writable
618     in each iteration of the event loop (This behaviour is called
619     level-triggering because you keep receiving events as long as the
620     condition persists. Remember you can stop the watcher if you don't want to
621     act on the event and neither want to receive future events).
622     .PP
623     In general you can register as many read and/or write event watchers per
624     fd as you want (as long as you don't confuse yourself). Setting all file
625     descriptors to non-blocking mode is also usually a good idea (but not
626     required if you know what you are doing).
627     .PP
628     You have to be careful with dup'ed file descriptors, though. Some backends
629     (the linux epoll backend is a notable example) cannot handle dup'ed file
630     descriptors correctly if you register interest in two or more fds pointing
631     to the same underlying file/socket etc. description (that is, they share
632     the same underlying \*(L"file open\*(R").
633     .PP
634     If you must do this, then force the use of a known-to-be-good backend
635 root 1.6 (at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
636     \&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
637 root 1.1 .IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
638     .IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
639     .PD 0
640     .IP "ev_io_set (ev_io *, int fd, int events)" 4
641     .IX Item "ev_io_set (ev_io *, int fd, int events)"
642     .PD
643     Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive
644     events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ |
645     EV_WRITE\*(C'\fR to receive the given events.
646     .ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"
647     .el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"
648     .IX Subsection "ev_timer - relative and optionally recurring timeouts"
649     Timer watchers are simple relative timers that generate an event after a
650     given time, and optionally repeating in regular intervals after that.
651     .PP
652     The timers are based on real time, that is, if you register an event that
653     times out after an hour and you reset your system clock to last years
654     time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because
655 root 1.2 detecting time jumps is hard, and some inaccuracies are unavoidable (the
656 root 1.1 monotonic clock option helps a lot here).
657     .PP
658     The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
659     time. This is usually the right thing as this timestamp refers to the time
660 root 1.2 of the event triggering whatever timeout you are modifying/starting. If
661     you suspect event processing to be delayed and you \fIneed\fR to base the timeout
662 root 1.1 on the current time, use something like this to adjust for this:
663     .PP
664     .Vb 1
665     \& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
666     .Ve
667 root 1.2 .PP
668     The callback is guarenteed to be invoked only when its timeout has passed,
669     but if multiple timers become ready during the same loop iteration then
670     order of execution is undefined.
671 root 1.1 .IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
672     .IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
673     .PD 0
674     .IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
675     .IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
676     .PD
677     Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is
678     \&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the
679     timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds
680     later, again, and again, until stopped manually.
681     .Sp
682     The timer itself will do a best-effort at avoiding drift, that is, if you
683     configure a timer to trigger every 10 seconds, then it will trigger at
684     exactly 10 second intervals. If, however, your program cannot keep up with
685     the timer (because it takes longer than those 10 seconds to do stuff) the
686     timer will not fire more than once per event loop iteration.
687     .IP "ev_timer_again (loop)" 4
688     .IX Item "ev_timer_again (loop)"
689     This will act as if the timer timed out and restart it again if it is
690     repeating. The exact semantics are:
691     .Sp
692     If the timer is started but nonrepeating, stop it.
693     .Sp
694     If the timer is repeating, either start it if necessary (with the repeat
695     value), or reset the running timer to the repeat value.
696     .Sp
697     This sounds a bit complicated, but here is a useful and typical
698     example: Imagine you have a tcp connection and you want a so-called idle
699     timeout, that is, you want to be called when there have been, say, 60
700     seconds of inactivity on the socket. The easiest way to do this is to
701     configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each
702     time you successfully read or write some data. If you go into an idle
703     state where you do not expect data to travel on the socket, you can stop
704     the timer, and again will automatically restart it if need be.
705     .ie n .Sh """ev_periodic"" \- to cron or not to cron"
706     .el .Sh "\f(CWev_periodic\fP \- to cron or not to cron"
707     .IX Subsection "ev_periodic - to cron or not to cron"
708     Periodic watchers are also timers of a kind, but they are very versatile
709     (and unfortunately a bit complex).
710     .PP
711     Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
712     but on wallclock time (absolute time). You can tell a periodic watcher
713     to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
714     periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now ()
715     + 10.>) and then reset your system clock to the last year, then it will
716     take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
717     roughly 10 seconds later and of course not if you reset your system time
718     again).
719     .PP
720     They can also be used to implement vastly more complex timers, such as
721     triggering an event on eahc midnight, local time.
722 root 1.2 .PP
723     As with timers, the callback is guarenteed to be invoked only when the
724     time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
725     during the same loop iteration then order of execution is undefined.
726 root 1.1 .IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
727     .IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
728     .PD 0
729     .IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
730     .IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
731     .PD
732     Lots of arguments, lets sort it out... There are basically three modes of
733     operation, and we will explain them from simplest to complex:
734     .RS 4
735     .IP "* absolute timer (interval = reschedule_cb = 0)" 4
736     .IX Item "absolute timer (interval = reschedule_cb = 0)"
737     In this configuration the watcher triggers an event at the wallclock time
738     \&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
739     that is, if it is to be run at January 1st 2011 then it will run when the
740     system time reaches or surpasses this time.
741     .IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4
742     .IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)"
743     In this mode the watcher will always be scheduled to time out at the next
744     \&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless
745     of any time jumps.
746     .Sp
747     This can be used to create timers that do not drift with respect to system
748     time:
749     .Sp
750     .Vb 1
751     \& ev_periodic_set (&periodic, 0., 3600., 0);
752     .Ve
753     .Sp
754     This doesn't mean there will always be 3600 seconds in between triggers,
755     but only that the the callback will be called when the system time shows a
756     full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible
757     by 3600.
758     .Sp
759     Another way to think about it (for the mathematically inclined) is that
760     \&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
761     time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
762     .IP "* manual reschedule mode (reschedule_cb = callback)" 4
763     .IX Item "manual reschedule mode (reschedule_cb = callback)"
764     In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
765     ignored. Instead, each time the periodic watcher gets scheduled, the
766     reschedule callback will be called with the watcher as first, and the
767     current time as second argument.
768     .Sp
769     \&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
770     ever, or make any event loop modifications\fR. If you need to stop it,
771     return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
772     starting a prepare watcher).
773     .Sp
774     Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
775     ev_tstamp now)\*(C'\fR, e.g.:
776     .Sp
777     .Vb 4
778     \& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
779     \& {
780     \& return now + 60.;
781     \& }
782     .Ve
783     .Sp
784     It must return the next time to trigger, based on the passed time value
785     (that is, the lowest time value larger than to the second argument). It
786     will usually be called just before the callback will be triggered, but
787     might be called at other times, too.
788     .Sp
789     \&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the
790     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.
791     .Sp
792     This can be used to create very complex timers, such as a timer that
793     triggers on each midnight, local time. To do this, you would calculate the
794     next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How
795     you do this is, again, up to you (but it is not trivial, which is the main
796     reason I omitted it as an example).
797     .RE
798     .RS 4
799     .RE
800     .IP "ev_periodic_again (loop, ev_periodic *)" 4
801     .IX Item "ev_periodic_again (loop, ev_periodic *)"
802     Simply stops and restarts the periodic watcher again. This is only useful
803     when you changed some parameters or the reschedule callback would return
804     a different time than the last time it was called (e.g. in a crond like
805     program when the crontabs have changed).
806     .ie n .Sh """ev_signal"" \- signal me when a signal gets signalled"
807     .el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled"
808     .IX Subsection "ev_signal - signal me when a signal gets signalled"
809     Signal watchers will trigger an event when the process receives a specific
810     signal one or more times. Even though signals are very asynchronous, libev
811     will try it's best to deliver signals synchronously, i.e. as part of the
812     normal event processing, like any other event.
813     .PP
814     You can configure as many watchers as you like per signal. Only when the
815     first watcher gets started will libev actually register a signal watcher
816     with the kernel (thus it coexists with your own signal handlers as long
817     as you don't register any with libev). Similarly, when the last signal
818     watcher for a signal is stopped libev will reset the signal handler to
819     \&\s-1SIG_DFL\s0 (regardless of what it was set to before).
820     .IP "ev_signal_init (ev_signal *, callback, int signum)" 4
821     .IX Item "ev_signal_init (ev_signal *, callback, int signum)"
822     .PD 0
823     .IP "ev_signal_set (ev_signal *, int signum)" 4
824     .IX Item "ev_signal_set (ev_signal *, int signum)"
825     .PD
826     Configures the watcher to trigger on the given signal number (usually one
827     of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
828     .ie n .Sh """ev_child"" \- wait for pid status changes"
829     .el .Sh "\f(CWev_child\fP \- wait for pid status changes"
830     .IX Subsection "ev_child - wait for pid status changes"
831     Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
832     some child status changes (most typically when a child of yours dies).
833     .IP "ev_child_init (ev_child *, callback, int pid)" 4
834     .IX Item "ev_child_init (ev_child *, callback, int pid)"
835     .PD 0
836     .IP "ev_child_set (ev_child *, int pid)" 4
837     .IX Item "ev_child_set (ev_child *, int pid)"
838     .PD
839     Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or
840     \&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
841     at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
842     the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
843     \&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
844     process causing the status change.
845     .ie n .Sh """ev_idle"" \- when you've got nothing better to do"
846     .el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do"
847     .IX Subsection "ev_idle - when you've got nothing better to do"
848     Idle watchers trigger events when there are no other events are pending
849     (prepare, check and other idle watchers do not count). That is, as long
850     as your process is busy handling sockets or timeouts (or even signals,
851     imagine) it will not be triggered. But when your process is idle all idle
852     watchers are being called again and again, once per event loop iteration \-
853     until stopped, that is, or your process receives more events and becomes
854     busy.
855     .PP
856     The most noteworthy effect is that as long as any idle watchers are
857     active, the process will not block when waiting for new events.
858     .PP
859     Apart from keeping your process non-blocking (which is a useful
860     effect on its own sometimes), idle watchers are a good place to do
861     \&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
862     event loop has handled all outstanding events.
863     .IP "ev_idle_init (ev_signal *, callback)" 4
864     .IX Item "ev_idle_init (ev_signal *, callback)"
865     Initialises and configures the idle watcher \- it has no parameters of any
866     kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
867     believe me.
868     .ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop"
869     .el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop"
870     .IX Subsection "ev_prepare and ev_check - customise your event loop"
871     Prepare and check watchers are usually (but not always) used in tandem:
872     prepare watchers get invoked before the process blocks and check watchers
873     afterwards.
874     .PP
875     Their main purpose is to integrate other event mechanisms into libev. This
876     could be used, for example, to track variable changes, implement your own
877     watchers, integrate net-snmp or a coroutine library and lots more.
878     .PP
879     This is done by examining in each prepare call which file descriptors need
880     to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
881     them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
882     provide just this functionality). Then, in the check watcher you check for
883     any events that occured (by checking the pending status of all watchers
884     and stopping them) and call back into the library. The I/O and timer
885     callbacks will never actually be called (but must be valid nevertheless,
886     because you never know, you know?).
887     .PP
888     As another example, the Perl Coro module uses these hooks to integrate
889     coroutines into libev programs, by yielding to other active coroutines
890     during each prepare and only letting the process block if no coroutines
891     are ready to run (it's actually more complicated: it only runs coroutines
892     with priority higher than or equal to the event loop and one coroutine
893     of lower priority, but only once, using idle watchers to keep the event
894     loop from blocking if lower-priority coroutines are active, thus mapping
895     low-priority coroutines to idle/background tasks).
896     .IP "ev_prepare_init (ev_prepare *, callback)" 4
897     .IX Item "ev_prepare_init (ev_prepare *, callback)"
898     .PD 0
899     .IP "ev_check_init (ev_check *, callback)" 4
900     .IX Item "ev_check_init (ev_check *, callback)"
901     .PD
902     Initialises and configures the prepare or check watcher \- they have no
903     parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
904     macros, but using them is utterly, utterly and completely pointless.
905     .SH "OTHER FUNCTIONS"
906     .IX Header "OTHER FUNCTIONS"
907     There are some other functions of possible interest. Described. Here. Now.
908     .IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
909     .IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
910     This function combines a simple timer and an I/O watcher, calls your
911     callback on whichever event happens first and automatically stop both
912     watchers. This is useful if you want to wait for a single event on an fd
913     or timeout without having to allocate/configure/start/stop/free one or
914     more watchers yourself.
915     .Sp
916     If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events
917     is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and
918     \&\f(CW\*(C`events\*(C'\fR set will be craeted and started.
919     .Sp
920     If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be
921     started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and
922     repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of
923     dubious value.
924     .Sp
925     The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets
926     passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of
927     \&\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
928     value passed to \f(CW\*(C`ev_once\*(C'\fR:
929     .Sp
930     .Vb 7
931     \& static void stdin_ready (int revents, void *arg)
932     \& {
933     \& if (revents & EV_TIMEOUT)
934     \& /* doh, nothing entered */;
935     \& else if (revents & EV_READ)
936     \& /* stdin might have data for us, joy! */;
937     \& }
938     .Ve
939     .Sp
940     .Vb 1
941     \& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
942     .Ve
943     .IP "ev_feed_event (loop, watcher, int events)" 4
944     .IX Item "ev_feed_event (loop, watcher, int events)"
945     Feeds the given event set into the event loop, as if the specified event
946     had happened for the specified watcher (which must be a pointer to an
947     initialised but not necessarily started event watcher).
948     .IP "ev_feed_fd_event (loop, int fd, int revents)" 4
949     .IX Item "ev_feed_fd_event (loop, int fd, int revents)"
950     Feed an event on the given fd, as if a file descriptor backend detected
951     the given events it.
952     .IP "ev_feed_signal_event (loop, int signum)" 4
953     .IX Item "ev_feed_signal_event (loop, int signum)"
954     Feed an event as if the given signal occured (loop must be the default loop!).
955     .SH "LIBEVENT EMULATION"
956     .IX Header "LIBEVENT EMULATION"
957     Libev offers a compatibility emulation layer for libevent. It cannot
958     emulate the internals of libevent, so here are some usage hints:
959     .IP "* Use it by including <event.h>, as usual." 4
960     .IX Item "Use it by including <event.h>, as usual."
961     .PD 0
962     .IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4
963     .IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events."
964     .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
965     .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)."
966     .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
967     .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."
968     .IP "* Other members are not supported." 4
969     .IX Item "Other members are not supported."
970     .IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
971     .IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
972     .PD
973     .SH "\*(C+ SUPPORT"
974     .IX Header " SUPPORT"
975     \&\s-1TBD\s0.
976     .SH "AUTHOR"
977     .IX Header "AUTHOR"
978     Marc Lehmann <libev@schmorp.de>.