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Revision 1.33 by root, Wed Nov 28 18:29:29 2007 UTC

… …
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
138\& #include <ev.h> 138\& #include <ev.h>
139.Ve 139.Ve
140.SH "EXAMPLE PROGRAM"
141.IX Header "EXAMPLE PROGRAM"
142.Vb 1
143\& #include <ev.h>
144.Ve
145.PP
146.Vb 2
147\& 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
140.SH "DESCRIPTION" 199.SH "DESCRIPTION"
141.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
142Libev is an event loop: you register interest in certain events (such as a 201Libev is an event loop: you register interest in certain events (such as a
143file descriptor being readable or a timeout occuring), and it will manage 202file descriptor being readable or a timeout occuring), and it will manage
144these event sources and provide your program with events. 203these event sources and provide your program with events.
… …
151watchers\fR, which are relatively small C structures you initialise with the 210watchers\fR, which are relatively small C structures you initialise with the
152details of the event, and then hand it over to libev by \fIstarting\fR the 211details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 212watcher.
154.SH "FEATURES" 213.SH "FEATURES"
155.IX Header "FEATURES" 214.IX Header "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 215Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
157kqueue mechanisms for file descriptor events, relative timers, absolute 216BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 217for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
159events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event 218(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
160loop mechanism itself (idle, prepare and check watchers). It also is quite 219with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
161fast (see this benchmark comparing 220(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
162it to libevent for example). 221watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
222\&\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
223file 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
226It also is quite fast (see this
227benchmark comparing it to libevent
228for example).
163.SH "CONVENTIONS" 229.SH "CONVENTIONS"
164.IX Header "CONVENTIONS" 230.IX Header "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 231Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 232be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 233various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
168\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without 234this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 235loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
170argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) 236(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
171will not have this argument.
172.SH "TIME REPRESENTATION" 237.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 238.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 239Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 240(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176the beginning of 1970, details are complicated, don't ask). This type is 241the beginning of 1970, details are complicated, don't ask). This type is
177called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 242called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178to the double type in C. 243to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
244it, you should treat it as such.
179.SH "GLOBAL FUNCTIONS" 245.SH "GLOBAL FUNCTIONS"
180.IX Header "GLOBAL FUNCTIONS" 246.IX Header "GLOBAL FUNCTIONS"
181These functions can be called anytime, even before initialising the 247These functions can be called anytime, even before initialising the
182library in any way. 248library in any way.
183.IP "ev_tstamp ev_time ()" 4 249.IP "ev_tstamp ev_time ()" 4
… …
199.Sp 265.Sp
200Usually, it's a good idea to terminate if the major versions mismatch, 266Usually, it's a good idea to terminate if the major versions mismatch,
201as this indicates an incompatible change. Minor versions are usually 267as this indicates an incompatible change. Minor versions are usually
202compatible to older versions, so a larger minor version alone is usually 268compatible to older versions, so a larger minor version alone is usually
203not a problem. 269not a problem.
270.Sp
271Example: Make sure we haven't accidentally been linked against the wrong
272version.
273.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
204.IP "unsigned int ev_supported_backends ()" 4 279.IP "unsigned int ev_supported_backends ()" 4
205.IX Item "unsigned int ev_supported_backends ()" 280.IX Item "unsigned int ev_supported_backends ()"
206Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR 281Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
207value) compiled into this binary of libev (independent of their 282value) compiled into this binary of libev (independent of their
208availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for 283availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
209a description of the set values. 284a description of the set values.
285.Sp
286Example: make sure we have the epoll method, because yeah this is cool and
287a 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
210.IP "unsigned int ev_recommended_backends ()" 4 293.IP "unsigned int ev_recommended_backends ()" 4
211.IX Item "unsigned int ev_recommended_backends ()" 294.IX Item "unsigned int ev_recommended_backends ()"
212Return the set of all backends compiled into this binary of libev and also 295Return the set of all backends compiled into this binary of libev and also
213recommended for this platform. This set is often smaller than the one 296recommended for this platform. This set is often smaller than the one
214returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on 297returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
215most BSDs and will not be autodetected unless you explicitly request it 298most 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 299(assuming you know what you are doing). This is the set of backends that
217libev will probe for if you specify no backends explicitly. 300libev will probe for if you specify no backends explicitly.
301.IP "unsigned int ev_embeddable_backends ()" 4
302.IX Item "unsigned int ev_embeddable_backends ()"
303Returns the set of backends that are embeddable in other event loops. This
304is the theoretical, all\-platform, value. To find which backends
305might 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
307recommended ones.
308.Sp
309See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
218.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 310.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 311.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
220Sets the allocation function to use (the prototype is similar to the 312Sets the allocation function to use (the prototype is similar \- the
221realloc C function, the semantics are identical). It is used to allocate 313semantics is identical \- to the realloc C function). It is used to
222and free memory (no surprises here). If it returns zero when memory 314allocate and free memory (no surprises here). If it returns zero when
223needs to be allocated, the library might abort or take some potentially 315memory needs to be allocated, the library might abort or take some
224destructive action. The default is your system realloc function. 316potentially destructive action. The default is your system realloc
317function.
225.Sp 318.Sp
226You could override this function in high-availability programs to, say, 319You could override this function in high-availability programs to, say,
227free some memory if it cannot allocate memory, to use a special allocator, 320free some memory if it cannot allocate memory, to use a special allocator,
228or even to sleep a while and retry until some memory is available. 321or even to sleep a while and retry until some memory is available.
322.Sp
323Example: Replace the libev allocator with one that waits a bit and then
324retries).
325.Sp
326.Vb 6
327\& static void *
328\& persistent_realloc (void *ptr, size_t size)
329\& {
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
229.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 350.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
230.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 351.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
231Set the callback function to call on a retryable syscall error (such 352Set the callback function to call on a retryable syscall error (such
232as failed select, poll, epoll_wait). The message is a printable string 353as failed select, poll, epoll_wait). The message is a printable string
233indicating the system call or subsystem causing the problem. If this 354indicating the system call or subsystem causing the problem. If this
234callback is set, then libev will expect it to remedy the sitution, no 355callback is set, then libev will expect it to remedy the sitution, no
235matter what, when it returns. That is, libev will generally retry the 356matter what, when it returns. That is, libev will generally retry the
236requested operation, or, if the condition doesn't go away, do bad stuff 357requested operation, or, if the condition doesn't go away, do bad stuff
237(such as abort). 358(such as abort).
359.Sp
360Example: This is basically the same thing that libev does internally, too.
361.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
238.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 375.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
239.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 376.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
240An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two 377An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
241types of such loops, the \fIdefault\fR loop, which supports signals and child 378types of such loops, the \fIdefault\fR loop, which supports signals and child
242events, and dynamically created loops which do not. 379events, and dynamically created loops which do not.
… …
376.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 513.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
377Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 514Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
378always distinct from the default loop. Unlike the default loop, it cannot 515always distinct from the default loop. Unlike the default loop, it cannot
379handle signal and child watchers, and attempts to do so will be greeted by 516handle signal and child watchers, and attempts to do so will be greeted by
380undefined behaviour (or a failed assertion if assertions are enabled). 517undefined behaviour (or a failed assertion if assertions are enabled).
518.Sp
519Example: Try to create a event loop that uses epoll and nothing else.
520.Sp
521.Vb 3
522\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
523\& if (!epoller)
524\& fatal ("no epoll found here, maybe it hides under your chair");
525.Ve
381.IP "ev_default_destroy ()" 4 526.IP "ev_default_destroy ()" 4
382.IX Item "ev_default_destroy ()" 527.IX Item "ev_default_destroy ()"
383Destroys the default loop again (frees all memory and kernel state 528Destroys the default loop again (frees all memory and kernel state
384etc.). This stops all registered event watchers (by not touching them in 529etc.). None of the active event watchers will be stopped in the normal
385any way whatsoever, although you cannot rely on this :). 530sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
531responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
532calling this function, or cope with the fact afterwards (which is usually
533the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
534for example).
386.IP "ev_loop_destroy (loop)" 4 535.IP "ev_loop_destroy (loop)" 4
387.IX Item "ev_loop_destroy (loop)" 536.IX Item "ev_loop_destroy (loop)"
388Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 537Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
389earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 538earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
390.IP "ev_default_fork ()" 4 539.IP "ev_default_fork ()" 4
… …
419Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 568Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
420use. 569use.
421.IP "ev_tstamp ev_now (loop)" 4 570.IP "ev_tstamp ev_now (loop)" 4
422.IX Item "ev_tstamp ev_now (loop)" 571.IX Item "ev_tstamp ev_now (loop)"
423Returns the current \*(L"event loop time\*(R", which is the time the event loop 572Returns the current \*(L"event loop time\*(R", which is the time the event loop
424got events and started processing them. This timestamp does not change 573received events and started processing them. This timestamp does not
425as long as callbacks are being processed, and this is also the base time 574change as long as callbacks are being processed, and this is also the base
426used for relative timers. You can treat it as the timestamp of the event 575time used for relative timers. You can treat it as the timestamp of the
427occuring (or more correctly, the mainloop finding out about it). 576event occuring (or more correctly, libev finding out about it).
428.IP "ev_loop (loop, int flags)" 4 577.IP "ev_loop (loop, int flags)" 4
429.IX Item "ev_loop (loop, int flags)" 578.IX Item "ev_loop (loop, int flags)"
430Finally, this is it, the event handler. This function usually is called 579Finally, this is it, the event handler. This function usually is called
431after you initialised all your watchers and you want to start handling 580after you initialised all your watchers and you want to start handling
432events. 581events.
433.Sp 582.Sp
434If the flags argument is specified as \f(CW0\fR, it will not return until 583If the flags argument is specified as \f(CW0\fR, it will not return until
435either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 584either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
585.Sp
586Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
587relying on all watchers to be stopped when deciding when a program has
588finished (especially in interactive programs), but having a program that
589automatically loops as long as it has to and no longer by virtue of
590relying on its watchers stopping correctly is a thing of beauty.
436.Sp 591.Sp
437A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 592A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
438those events and any outstanding ones, but will not block your process in 593those events and any outstanding ones, but will not block your process in
439case there are no events and will return after one iteration of the loop. 594case there are no events and will return after one iteration of the loop.
440.Sp 595.Sp
… …
465\& - Call all queued watchers in reverse order (i.e. check watchers first). 620\& - Call all queued watchers in reverse order (i.e. check watchers first).
466\& Signals and child watchers are implemented as I/O watchers, and will 621\& Signals and child watchers are implemented as I/O watchers, and will
467\& be handled here by queueing them when their watcher gets executed. 622\& be handled here by queueing them when their watcher gets executed.
468\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 623\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
469\& were used, return, otherwise continue with step *. 624\& were used, return, otherwise continue with step *.
625.Ve
626.Sp
627Example: Queue some jobs and then loop until no events are outsanding
628anymore.
629.Sp
630.Vb 4
631\& ... queue jobs here, make sure they register event watchers as long
632\& ... as they still have work to do (even an idle watcher will do..)
633\& ev_loop (my_loop, 0);
634\& ... jobs done. yeah!
470.Ve 635.Ve
471.IP "ev_unloop (loop, how)" 4 636.IP "ev_unloop (loop, how)" 4
472.IX Item "ev_unloop (loop, how)" 637.IX Item "ev_unloop (loop, how)"
473Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 638Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
474has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 639has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
… …
488example, libev itself uses this for its internal signal pipe: It is not 653example, libev itself uses this for its internal signal pipe: It is not
489visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 654visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
490no event watchers registered by it are active. It is also an excellent 655no event watchers registered by it are active. It is also an excellent
491way to do this for generic recurring timers or from within third-party 656way to do this for generic recurring timers or from within third-party
492libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 657libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
658.Sp
659Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
660running when nothing else is active.
661.Sp
662.Vb 4
663\& struct ev_signal exitsig;
664\& ev_signal_init (&exitsig, sig_cb, SIGINT);
665\& ev_signal_start (loop, &exitsig);
666\& evf_unref (loop);
667.Ve
668.Sp
669Example: For some weird reason, unregister the above signal handler again.
670.Sp
671.Vb 2
672\& ev_ref (loop);
673\& ev_signal_stop (loop, &exitsig);
674.Ve
493.SH "ANATOMY OF A WATCHER" 675.SH "ANATOMY OF A WATCHER"
494.IX Header "ANATOMY OF A WATCHER" 676.IX Header "ANATOMY OF A WATCHER"
495A watcher is a structure that you create and register to record your 677A watcher is a structure that you create and register to record your
496interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 678interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
497become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 679become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
533*)\*(C'\fR), and you can stop watching for events at any time by calling the 715*)\*(C'\fR), and you can stop watching for events at any time by calling the
534corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 716corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
535.PP 717.PP
536As long as your watcher is active (has been started but not stopped) you 718As long as your watcher is active (has been started but not stopped) you
537must not touch the values stored in it. Most specifically you must never 719must not touch the values stored in it. Most specifically you must never
538reinitialise it or call its set macro. 720reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
539.PP
540You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
541(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
542callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
543(watcher *)\*(C'\fR macro.
544.PP 721.PP
545Each and every callback receives the event loop pointer as first, the 722Each and every callback receives the event loop pointer as first, the
546registered watcher structure as second, and a bitset of received events as 723registered watcher structure as second, and a bitset of received events as
547third argument. 724third argument.
548.PP 725.PP
… …
573The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 750The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
574.ie n .IP """EV_CHILD""" 4 751.ie n .IP """EV_CHILD""" 4
575.el .IP "\f(CWEV_CHILD\fR" 4 752.el .IP "\f(CWEV_CHILD\fR" 4
576.IX Item "EV_CHILD" 753.IX Item "EV_CHILD"
577The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 754The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
755.ie n .IP """EV_STAT""" 4
756.el .IP "\f(CWEV_STAT\fR" 4
757.IX Item "EV_STAT"
758The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
578.ie n .IP """EV_IDLE""" 4 759.ie n .IP """EV_IDLE""" 4
579.el .IP "\f(CWEV_IDLE\fR" 4 760.el .IP "\f(CWEV_IDLE\fR" 4
580.IX Item "EV_IDLE" 761.IX Item "EV_IDLE"
581The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 762The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
582.ie n .IP """EV_PREPARE""" 4 763.ie n .IP """EV_PREPARE""" 4
… …
592\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 773\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
593received events. Callbacks of both watcher types can start and stop as 774received events. Callbacks of both watcher types can start and stop as
594many watchers as they want, and all of them will be taken into account 775many watchers as they want, and all of them will be taken into account
595(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 776(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
596\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 777\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
778.ie n .IP """EV_EMBED""" 4
779.el .IP "\f(CWEV_EMBED\fR" 4
780.IX Item "EV_EMBED"
781The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
782.ie n .IP """EV_FORK""" 4
783.el .IP "\f(CWEV_FORK\fR" 4
784.IX Item "EV_FORK"
785The event loop has been resumed in the child process after fork (see
786\&\f(CW\*(C`ev_fork\*(C'\fR).
597.ie n .IP """EV_ERROR""" 4 787.ie n .IP """EV_ERROR""" 4
598.el .IP "\f(CWEV_ERROR\fR" 4 788.el .IP "\f(CWEV_ERROR\fR" 4
599.IX Item "EV_ERROR" 789.IX Item "EV_ERROR"
600An unspecified error has occured, the watcher has been stopped. This might 790An unspecified error has occured, the watcher has been stopped. This might
601happen because the watcher could not be properly started because libev 791happen because the watcher could not be properly started because libev
… …
606Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 796Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
607for example it might indicate that a fd is readable or writable, and if 797for example it might indicate that a fd is readable or writable, and if
608your callbacks is well-written it can just attempt the operation and cope 798your callbacks is well-written it can just attempt the operation and cope
609with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 799with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
610programs, though, so beware. 800programs, though, so beware.
801.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
802.IX Subsection "GENERIC WATCHER FUNCTIONS"
803In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
804e.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.
805.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
806.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
807.IX Item "ev_init (ev_TYPE *watcher, callback)"
808This macro initialises the generic portion of a watcher. The contents
809of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
810the generic parts of the watcher are initialised, you \fIneed\fR to call
811the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
812type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
813which rolls both calls into one.
814.Sp
815You can reinitialise a watcher at any time as long as it has been stopped
816(or never started) and there are no pending events outstanding.
817.Sp
818The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
819int revents)\*(C'\fR.
820.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
821.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
822.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
823This macro initialises the type-specific parts of a watcher. You need to
824call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
825call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
826macro on a watcher that is active (it can be pending, however, which is a
827difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
828.Sp
829Although some watcher types do not have type-specific arguments
830(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
831.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
832.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
833.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
834This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
835calls into a single call. This is the most convinient method to initialise
836a watcher. The same limitations apply, of course.
837.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
838.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
839.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
840Starts (activates) the given watcher. Only active watchers will receive
841events. If the watcher is already active nothing will happen.
842.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
843.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
844.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
845Stops the given watcher again (if active) and clears the pending
846status. It is possible that stopped watchers are pending (for example,
847non-repeating timers are being stopped when they become pending), but
848\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
849you want to free or reuse the memory used by the watcher it is therefore a
850good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
851.IP "bool ev_is_active (ev_TYPE *watcher)" 4
852.IX Item "bool ev_is_active (ev_TYPE *watcher)"
853Returns a true value iff the watcher is active (i.e. it has been started
854and not yet been stopped). As long as a watcher is active you must not modify
855it.
856.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
857.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
858Returns a true value iff the watcher is pending, (i.e. it has outstanding
859events but its callback has not yet been invoked). As long as a watcher
860is pending (but not active) you must not call an init function on it (but
861\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
862libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
863.IP "callback ev_cb (ev_TYPE *watcher)" 4
864.IX Item "callback ev_cb (ev_TYPE *watcher)"
865Returns the callback currently set on the watcher.
866.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
867.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
868Change the callback. You can change the callback at virtually any time
869(modulo threads).
611.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 870.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
612.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 871.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
613Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 872Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
614and read at any time, libev will completely ignore it. This can be used 873and read at any time, libev will completely ignore it. This can be used
615to associate arbitrary data with your watcher. If you need more data and 874to associate arbitrary data with your watcher. If you need more data and
… …
636\& struct my_io *w = (struct my_io *)w_; 895\& struct my_io *w = (struct my_io *)w_;
637\& ... 896\& ...
638\& } 897\& }
639.Ve 898.Ve
640.PP 899.PP
641More interesting and less C\-conformant ways of catsing your callback type 900More interesting and less C\-conformant ways of casting your callback type
642have been omitted.... 901instead have been omitted.
902.PP
903Another common scenario is having some data structure with multiple
904watchers:
905.PP
906.Vb 6
907\& struct my_biggy
908\& {
909\& int some_data;
910\& ev_timer t1;
911\& ev_timer t2;
912\& }
913.Ve
914.PP
915In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
916you need to use \f(CW\*(C`offsetof\*(C'\fR:
917.PP
918.Vb 1
919\& #include <stddef.h>
920.Ve
921.PP
922.Vb 6
923\& static void
924\& t1_cb (EV_P_ struct ev_timer *w, int revents)
925\& {
926\& struct my_biggy big = (struct my_biggy *
927\& (((char *)w) - offsetof (struct my_biggy, t1));
928\& }
929.Ve
930.PP
931.Vb 6
932\& static void
933\& t2_cb (EV_P_ struct ev_timer *w, int revents)
934\& {
935\& struct my_biggy big = (struct my_biggy *
936\& (((char *)w) - offsetof (struct my_biggy, t2));
937\& }
938.Ve
643.SH "WATCHER TYPES" 939.SH "WATCHER TYPES"
644.IX Header "WATCHER TYPES" 940.IX Header "WATCHER TYPES"
645This section describes each watcher in detail, but will not repeat 941This section describes each watcher in detail, but will not repeat
646information given in the last section. 942information given in the last section. Any initialisation/set macros,
943functions and members specific to the watcher type are explained.
944.PP
945Members are additionally marked with either \fI[read\-only]\fR, meaning that,
946while the watcher is active, you can look at the member and expect some
947sensible content, but you must not modify it (you can modify it while the
948watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
949means you can expect it to have some sensible content while the watcher
950is active, but you can also modify it. Modifying it may not do something
951sensible or take immediate effect (or do anything at all), but libev will
952not crash or malfunction in any way.
647.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 953.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
648.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 954.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
649.IX Subsection "ev_io - is this file descriptor readable or writable" 955.IX Subsection "ev_io - is this file descriptor readable or writable?"
650I/O watchers check whether a file descriptor is readable or writable 956I/O watchers check whether a file descriptor is readable or writable
651in each iteration of the event loop (This behaviour is called 957in each iteration of the event loop, or, more precisely, when reading
652level-triggering because you keep receiving events as long as the 958would not block the process and writing would at least be able to write
653condition persists. Remember you can stop the watcher if you don't want to 959some data. This behaviour is called level-triggering because you keep
654act on the event and neither want to receive future events). 960receiving events as long as the condition persists. Remember you can stop
961the watcher if you don't want to act on the event and neither want to
962receive future events.
655.PP 963.PP
656In general you can register as many read and/or write event watchers per 964In general you can register as many read and/or write event watchers per
657fd as you want (as long as you don't confuse yourself). Setting all file 965fd as you want (as long as you don't confuse yourself). Setting all file
658descriptors to non-blocking mode is also usually a good idea (but not 966descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing). 967required if you know what you are doing).
660.PP 968.PP
661You have to be careful with dup'ed file descriptors, though. Some backends 969You have to be careful with dup'ed file descriptors, though. Some backends
662(the linux epoll backend is a notable example) cannot handle dup'ed file 970(the linux epoll backend is a notable example) cannot handle dup'ed file
663descriptors correctly if you register interest in two or more fds pointing 971descriptors correctly if you register interest in two or more fds pointing
664to the same underlying file/socket etc. description (that is, they share 972to the same underlying file/socket/etc. description (that is, they share
665the same underlying \*(L"file open\*(R"). 973the same underlying \*(L"file open\*(R").
666.PP 974.PP
667If you must do this, then force the use of a known-to-be-good backend 975If you must do this, then force the use of a known-to-be-good backend
668(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 976(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
669\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 977\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
978.PP
979Another thing you have to watch out for is that it is quite easy to
980receive \*(L"spurious\*(R" readyness notifications, that is your callback might
981be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
982because there is no data. Not only are some backends known to create a
983lot of those (for example solaris ports), it is very easy to get into
984this situation even with a relatively standard program structure. Thus
985it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
986\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
987.PP
988If you cannot run the fd in non-blocking mode (for example you should not
989play around with an Xlib connection), then you have to seperately re-test
990wether a file descriptor is really ready with a known-to-be good interface
991such as poll (fortunately in our Xlib example, Xlib already does this on
992its own, so its quite safe to use).
670.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 993.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
671.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 994.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
672.PD 0 995.PD 0
673.IP "ev_io_set (ev_io *, int fd, int events)" 4 996.IP "ev_io_set (ev_io *, int fd, int events)" 4
674.IX Item "ev_io_set (ev_io *, int fd, int events)" 997.IX Item "ev_io_set (ev_io *, int fd, int events)"
675.PD 998.PD
676Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 999Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
677events 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 | 1000rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
678EV_WRITE\*(C'\fR to receive the given events. 1001\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
679.Sp 1002.IP "int fd [read\-only]" 4
680Please note that most of the more scalable backend mechanisms (for example 1003.IX Item "int fd [read-only]"
681epoll and solaris ports) can result in spurious readyness notifications 1004The file descriptor being watched.
682for file descriptors, so you practically need to use non-blocking I/O (and 1005.IP "int events [read\-only]" 4
683treat callback invocation as hint only), or retest separately with a safe 1006.IX Item "int events [read-only]"
684interface before doing I/O (XLib can do this), or force the use of either 1007The events being watched.
685\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this 1008.PP
686problem. Also note that it is quite easy to have your callback invoked 1009Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
687when the readyness condition is no longer valid even when employing 1010readable, but only once. Since it is likely line\-buffered, you could
688typical ways of handling events, so its a good idea to use non-blocking 1011attempt to read a whole line in the callback.
689I/O unconditionally. 1012.PP
1013.Vb 6
1014\& static void
1015\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1016\& {
1017\& ev_io_stop (loop, w);
1018\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
1019\& }
1020.Ve
1021.PP
1022.Vb 6
1023\& ...
1024\& struct ev_loop *loop = ev_default_init (0);
1025\& struct ev_io stdin_readable;
1026\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1027\& ev_io_start (loop, &stdin_readable);
1028\& ev_loop (loop, 0);
1029.Ve
690.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1030.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
691.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1031.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
692.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1032.IX Subsection "ev_timer - relative and optionally repeating timeouts"
693Timer watchers are simple relative timers that generate an event after a 1033Timer watchers are simple relative timers that generate an event after a
694given time, and optionally repeating in regular intervals after that. 1034given time, and optionally repeating in regular intervals after that.
695.PP 1035.PP
696The timers are based on real time, that is, if you register an event that 1036The timers are based on real time, that is, if you register an event that
697times out after an hour and you reset your system clock to last years 1037times out after an hour and you reset your system clock to last years
… …
737.Sp 1077.Sp
738If the timer is repeating, either start it if necessary (with the repeat 1078If the timer is repeating, either start it if necessary (with the repeat
739value), or reset the running timer to the repeat value. 1079value), or reset the running timer to the repeat value.
740.Sp 1080.Sp
741This sounds a bit complicated, but here is a useful and typical 1081This sounds a bit complicated, but here is a useful and typical
742example: Imagine you have a tcp connection and you want a so-called idle 1082example: Imagine you have a tcp connection and you want a so-called
743timeout, that is, you want to be called when there have been, say, 60 1083idle timeout, that is, you want to be called when there have been,
744seconds of inactivity on the socket. The easiest way to do this is to 1084say, 60 seconds of inactivity on the socket. The easiest way to do
745configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1085this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling
746time you successfully read or write some data. If you go into an idle 1086\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
747state where you do not expect data to travel on the socket, you can stop 1087you go into an idle state where you do not expect data to travel on the
748the timer, and again will automatically restart it if need be. 1088socket, you can stop the timer, and again will automatically restart it if
1089need be.
1090.Sp
1091You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
1092and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
1093.Sp
1094.Vb 8
1095\& ev_timer_init (timer, callback, 0., 5.);
1096\& ev_timer_again (loop, timer);
1097\& ...
1098\& timer->again = 17.;
1099\& ev_timer_again (loop, timer);
1100\& ...
1101\& timer->again = 10.;
1102\& ev_timer_again (loop, timer);
1103.Ve
1104.Sp
1105This is more efficient then stopping/starting the timer eahc time you want
1106to modify its timeout value.
1107.IP "ev_tstamp repeat [read\-write]" 4
1108.IX Item "ev_tstamp repeat [read-write]"
1109The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1110or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1111which is also when any modifications are taken into account.
1112.PP
1113Example: Create a timer that fires after 60 seconds.
1114.PP
1115.Vb 5
1116\& static void
1117\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1118\& {
1119\& .. one minute over, w is actually stopped right here
1120\& }
1121.Ve
1122.PP
1123.Vb 3
1124\& struct ev_timer mytimer;
1125\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1126\& ev_timer_start (loop, &mytimer);
1127.Ve
1128.PP
1129Example: Create a timeout timer that times out after 10 seconds of
1130inactivity.
1131.PP
1132.Vb 5
1133\& static void
1134\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1135\& {
1136\& .. ten seconds without any activity
1137\& }
1138.Ve
1139.PP
1140.Vb 4
1141\& struct ev_timer mytimer;
1142\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1143\& ev_timer_again (&mytimer); /* start timer */
1144\& ev_loop (loop, 0);
1145.Ve
1146.PP
1147.Vb 3
1148\& // and in some piece of code that gets executed on any "activity":
1149\& // reset the timeout to start ticking again at 10 seconds
1150\& ev_timer_again (&mytimer);
1151.Ve
749.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1152.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
750.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1153.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
751.IX Subsection "ev_periodic - to cron or not to cron" 1154.IX Subsection "ev_periodic - to cron or not to cron?"
752Periodic watchers are also timers of a kind, but they are very versatile 1155Periodic watchers are also timers of a kind, but they are very versatile
753(and unfortunately a bit complex). 1156(and unfortunately a bit complex).
754.PP 1157.PP
755Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1158Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
756but on wallclock time (absolute time). You can tell a periodic watcher 1159but on wallclock time (absolute time). You can tell a periodic watcher
757to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1160to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
758periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1161periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
759+ 10.>) and then reset your system clock to the last year, then it will 1162+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
760take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1163take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
761roughly 10 seconds later and of course not if you reset your system time 1164roughly 10 seconds later and of course not if you reset your system time
762again). 1165again).
763.PP 1166.PP
764They can also be used to implement vastly more complex timers, such as 1167They can also be used to implement vastly more complex timers, such as
… …
845.IX Item "ev_periodic_again (loop, ev_periodic *)" 1248.IX Item "ev_periodic_again (loop, ev_periodic *)"
846Simply stops and restarts the periodic watcher again. This is only useful 1249Simply stops and restarts the periodic watcher again. This is only useful
847when you changed some parameters or the reschedule callback would return 1250when you changed some parameters or the reschedule callback would return
848a different time than the last time it was called (e.g. in a crond like 1251a different time than the last time it was called (e.g. in a crond like
849program when the crontabs have changed). 1252program when the crontabs have changed).
1253.IP "ev_tstamp interval [read\-write]" 4
1254.IX Item "ev_tstamp interval [read-write]"
1255The current interval value. Can be modified any time, but changes only
1256take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1257called.
1258.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1259.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1260The current reschedule callback, or \f(CW0\fR, if this functionality is
1261switched off. Can be changed any time, but changes only take effect when
1262the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1263.PP
1264Example: Call a callback every hour, or, more precisely, whenever the
1265system clock is divisible by 3600. The callback invocation times have
1266potentially a lot of jittering, but good long-term stability.
1267.PP
1268.Vb 5
1269\& static void
1270\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1271\& {
1272\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1273\& }
1274.Ve
1275.PP
1276.Vb 3
1277\& struct ev_periodic hourly_tick;
1278\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1279\& ev_periodic_start (loop, &hourly_tick);
1280.Ve
1281.PP
1282Example: The same as above, but use a reschedule callback to do it:
1283.PP
1284.Vb 1
1285\& #include <math.h>
1286.Ve
1287.PP
1288.Vb 5
1289\& static ev_tstamp
1290\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1291\& {
1292\& return fmod (now, 3600.) + 3600.;
1293\& }
1294.Ve
1295.PP
1296.Vb 1
1297\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1298.Ve
1299.PP
1300Example: Call a callback every hour, starting now:
1301.PP
1302.Vb 4
1303\& struct ev_periodic hourly_tick;
1304\& ev_periodic_init (&hourly_tick, clock_cb,
1305\& fmod (ev_now (loop), 3600.), 3600., 0);
1306\& ev_periodic_start (loop, &hourly_tick);
1307.Ve
850.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1308.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
851.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1309.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
852.IX Subsection "ev_signal - signal me when a signal gets signalled" 1310.IX Subsection "ev_signal - signal me when a signal gets signalled!"
853Signal watchers will trigger an event when the process receives a specific 1311Signal watchers will trigger an event when the process receives a specific
854signal one or more times. Even though signals are very asynchronous, libev 1312signal one or more times. Even though signals are very asynchronous, libev
855will try it's best to deliver signals synchronously, i.e. as part of the 1313will try it's best to deliver signals synchronously, i.e. as part of the
856normal event processing, like any other event. 1314normal event processing, like any other event.
857.PP 1315.PP
… …
867.IP "ev_signal_set (ev_signal *, int signum)" 4 1325.IP "ev_signal_set (ev_signal *, int signum)" 4
868.IX Item "ev_signal_set (ev_signal *, int signum)" 1326.IX Item "ev_signal_set (ev_signal *, int signum)"
869.PD 1327.PD
870Configures the watcher to trigger on the given signal number (usually one 1328Configures the watcher to trigger on the given signal number (usually one
871of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1329of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1330.IP "int signum [read\-only]" 4
1331.IX Item "int signum [read-only]"
1332The signal the watcher watches out for.
872.ie n .Sh """ev_child"" \- wait for pid status changes" 1333.ie n .Sh """ev_child"" \- watch out for process status changes"
873.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1334.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
874.IX Subsection "ev_child - wait for pid status changes" 1335.IX Subsection "ev_child - watch out for process status changes"
875Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1336Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
876some child status changes (most typically when a child of yours dies). 1337some child status changes (most typically when a child of yours dies).
877.IP "ev_child_init (ev_child *, callback, int pid)" 4 1338.IP "ev_child_init (ev_child *, callback, int pid)" 4
878.IX Item "ev_child_init (ev_child *, callback, int pid)" 1339.IX Item "ev_child_init (ev_child *, callback, int pid)"
879.PD 0 1340.PD 0
… …
884\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1345\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
885at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1346at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
886the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1347the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
887\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1348\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
888process causing the status change. 1349process causing the status change.
1350.IP "int pid [read\-only]" 4
1351.IX Item "int pid [read-only]"
1352The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1353.IP "int rpid [read\-write]" 4
1354.IX Item "int rpid [read-write]"
1355The process id that detected a status change.
1356.IP "int rstatus [read\-write]" 4
1357.IX Item "int rstatus [read-write]"
1358The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1359\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1360.PP
1361Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1362.PP
1363.Vb 5
1364\& static void
1365\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1366\& {
1367\& ev_unloop (loop, EVUNLOOP_ALL);
1368\& }
1369.Ve
1370.PP
1371.Vb 3
1372\& struct ev_signal signal_watcher;
1373\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1374\& ev_signal_start (loop, &sigint_cb);
1375.Ve
1376.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1377.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1378.IX Subsection "ev_stat - did the file attributes just change?"
1379This watches a filesystem path for attribute changes. That is, it calls
1380\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1381compared to the last time, invoking the callback if it did.
1382.PP
1383The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1384not exist\*(R" is a status change like any other. The condition \*(L"path does
1385not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1386otherwise always forced to be at least one) and all the other fields of
1387the stat buffer having unspecified contents.
1388.PP
1389The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1390relative and your working directory changes, the behaviour is undefined.
1391.PP
1392Since there is no standard to do this, the portable implementation simply
1393calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1394can specify a recommended polling interval for this case. If you specify
1395a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1396unspecified default\fR value will be used (which you can expect to be around
1397five seconds, although this might change dynamically). Libev will also
1398impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1399usually overkill.
1400.PP
1401This watcher type is not meant for massive numbers of stat watchers,
1402as even with OS-supported change notifications, this can be
1403resource\-intensive.
1404.PP
1405At the time of this writing, only the Linux inotify interface is
1406implemented (implementing kqueue support is left as an exercise for the
1407reader). Inotify will be used to give hints only and should not change the
1408semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1409to fall back to regular polling again even with inotify, but changes are
1410usually detected immediately, and if the file exists there will be no
1411polling.
1412.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1413.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1414.PD 0
1415.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1416.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1417.PD
1418Configures the watcher to wait for status changes of the given
1419\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1420be detected and should normally be specified as \f(CW0\fR to let libev choose
1421a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1422path for as long as the watcher is active.
1423.Sp
1424The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1425relative to the attributes at the time the watcher was started (or the
1426last change was detected).
1427.IP "ev_stat_stat (ev_stat *)" 4
1428.IX Item "ev_stat_stat (ev_stat *)"
1429Updates the stat buffer immediately with new values. If you change the
1430watched path in your callback, you could call this fucntion to avoid
1431detecting this change (while introducing a race condition). Can also be
1432useful simply to find out the new values.
1433.IP "ev_statdata attr [read\-only]" 4
1434.IX Item "ev_statdata attr [read-only]"
1435The most-recently detected attributes of the file. Although the type is of
1436\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1437suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1438was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1439.IP "ev_statdata prev [read\-only]" 4
1440.IX Item "ev_statdata prev [read-only]"
1441The previous attributes of the file. The callback gets invoked whenever
1442\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1443.IP "ev_tstamp interval [read\-only]" 4
1444.IX Item "ev_tstamp interval [read-only]"
1445The specified interval.
1446.IP "const char *path [read\-only]" 4
1447.IX Item "const char *path [read-only]"
1448The filesystem path that is being watched.
1449.PP
1450Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1451.PP
1452.Vb 15
1453\& static void
1454\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1455\& {
1456\& /* /etc/passwd changed in some way */
1457\& if (w->attr.st_nlink)
1458\& {
1459\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1460\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1461\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1462\& }
1463\& else
1464\& /* you shalt not abuse printf for puts */
1465\& puts ("wow, /etc/passwd is not there, expect problems. "
1466\& "if this is windows, they already arrived\en");
1467\& }
1468.Ve
1469.PP
1470.Vb 2
1471\& ...
1472\& ev_stat passwd;
1473.Ve
1474.PP
1475.Vb 2
1476\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1477\& ev_stat_start (loop, &passwd);
1478.Ve
889.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1479.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
890.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1480.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
891.IX Subsection "ev_idle - when you've got nothing better to do" 1481.IX Subsection "ev_idle - when you've got nothing better to do..."
892Idle watchers trigger events when there are no other events are pending 1482Idle watchers trigger events when there are no other events are pending
893(prepare, check and other idle watchers do not count). That is, as long 1483(prepare, check and other idle watchers do not count). That is, as long
894as your process is busy handling sockets or timeouts (or even signals, 1484as your process is busy handling sockets or timeouts (or even signals,
895imagine) it will not be triggered. But when your process is idle all idle 1485imagine) it will not be triggered. But when your process is idle all idle
896watchers are being called again and again, once per event loop iteration \- 1486watchers are being called again and again, once per event loop iteration \-
… …
907.IP "ev_idle_init (ev_signal *, callback)" 4 1497.IP "ev_idle_init (ev_signal *, callback)" 4
908.IX Item "ev_idle_init (ev_signal *, callback)" 1498.IX Item "ev_idle_init (ev_signal *, callback)"
909Initialises and configures the idle watcher \- it has no parameters of any 1499Initialises and configures the idle watcher \- it has no parameters of any
910kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1500kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
911believe me. 1501believe me.
1502.PP
1503Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1504callback, free it. Also, use no error checking, as usual.
1505.PP
1506.Vb 7
1507\& static void
1508\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1509\& {
1510\& free (w);
1511\& // now do something you wanted to do when the program has
1512\& // no longer asnything immediate to do.
1513\& }
1514.Ve
1515.PP
1516.Vb 3
1517\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1518\& ev_idle_init (idle_watcher, idle_cb);
1519\& ev_idle_start (loop, idle_cb);
1520.Ve
912.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1521.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
913.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1522.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
914.IX Subsection "ev_prepare and ev_check - customise your event loop" 1523.IX Subsection "ev_prepare and ev_check - customise your event loop!"
915Prepare and check watchers are usually (but not always) used in tandem: 1524Prepare and check watchers are usually (but not always) used in tandem:
916prepare watchers get invoked before the process blocks and check watchers 1525prepare watchers get invoked before the process blocks and check watchers
917afterwards. 1526afterwards.
918.PP 1527.PP
1528You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1529the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1530watchers. Other loops than the current one are fine, however. The
1531rationale behind this is that you do not need to check for recursion in
1532those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1533\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1534called in pairs bracketing the blocking call.
1535.PP
919Their main purpose is to integrate other event mechanisms into libev. This 1536Their main purpose is to integrate other event mechanisms into libev and
920could be used, for example, to track variable changes, implement your own 1537their use is somewhat advanced. This could be used, for example, to track
921watchers, integrate net-snmp or a coroutine library and lots more. 1538variable changes, implement your own watchers, integrate net-snmp or a
1539coroutine library and lots more. They are also occasionally useful if
1540you cache some data and want to flush it before blocking (for example,
1541in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1542watcher).
922.PP 1543.PP
923This is done by examining in each prepare call which file descriptors need 1544This is done by examining in each prepare call which file descriptors need
924to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1545to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
925them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1546them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
926provide just this functionality). Then, in the check watcher you check for 1547provide just this functionality). Then, in the check watcher you check for
… …
944.IX Item "ev_check_init (ev_check *, callback)" 1565.IX Item "ev_check_init (ev_check *, callback)"
945.PD 1566.PD
946Initialises and configures the prepare or check watcher \- they have no 1567Initialises and configures the prepare or check watcher \- they have no
947parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1568parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
948macros, but using them is utterly, utterly and completely pointless. 1569macros, but using them is utterly, utterly and completely pointless.
1570.PP
1571Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1572and a timeout watcher in a prepare handler, as required by libadns, and
1573in a check watcher, destroy them and call into libadns. What follows is
1574pseudo-code only of course:
1575.PP
1576.Vb 2
1577\& static ev_io iow [nfd];
1578\& static ev_timer tw;
1579.Ve
1580.PP
1581.Vb 9
1582\& static void
1583\& io_cb (ev_loop *loop, ev_io *w, int revents)
1584\& {
1585\& // set the relevant poll flags
1586\& // could also call adns_processreadable etc. here
1587\& struct pollfd *fd = (struct pollfd *)w->data;
1588\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1589\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1590\& }
1591.Ve
1592.PP
1593.Vb 7
1594\& // create io watchers for each fd and a timer before blocking
1595\& static void
1596\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1597\& {
1598\& int timeout = 3600000;truct pollfd fds [nfd];
1599\& // actual code will need to loop here and realloc etc.
1600\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1601.Ve
1602.PP
1603.Vb 3
1604\& /* the callback is illegal, but won't be called as we stop during check */
1605\& ev_timer_init (&tw, 0, timeout * 1e-3);
1606\& ev_timer_start (loop, &tw);
1607.Ve
1608.PP
1609.Vb 6
1610\& // create on ev_io per pollfd
1611\& for (int i = 0; i < nfd; ++i)
1612\& {
1613\& ev_io_init (iow + i, io_cb, fds [i].fd,
1614\& ((fds [i].events & POLLIN ? EV_READ : 0)
1615\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1616.Ve
1617.PP
1618.Vb 5
1619\& fds [i].revents = 0;
1620\& iow [i].data = fds + i;
1621\& ev_io_start (loop, iow + i);
1622\& }
1623\& }
1624.Ve
1625.PP
1626.Vb 5
1627\& // stop all watchers after blocking
1628\& static void
1629\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1630\& {
1631\& ev_timer_stop (loop, &tw);
1632.Ve
1633.PP
1634.Vb 2
1635\& for (int i = 0; i < nfd; ++i)
1636\& ev_io_stop (loop, iow + i);
1637.Ve
1638.PP
1639.Vb 2
1640\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1641\& }
1642.Ve
1643.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1644.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1645.IX Subsection "ev_embed - when one backend isn't enough..."
1646This is a rather advanced watcher type that lets you embed one event loop
1647into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1648loop, other types of watchers might be handled in a delayed or incorrect
1649fashion and must not be used).
1650.PP
1651There are primarily two reasons you would want that: work around bugs and
1652prioritise I/O.
1653.PP
1654As an example for a bug workaround, the kqueue backend might only support
1655sockets on some platform, so it is unusable as generic backend, but you
1656still want to make use of it because you have many sockets and it scales
1657so nicely. In this case, you would create a kqueue-based loop and embed it
1658into your default loop (which might use e.g. poll). Overall operation will
1659be a bit slower because first libev has to poll and then call kevent, but
1660at least you can use both at what they are best.
1661.PP
1662As for prioritising I/O: rarely you have the case where some fds have
1663to be watched and handled very quickly (with low latency), and even
1664priorities and idle watchers might have too much overhead. In this case
1665you would put all the high priority stuff in one loop and all the rest in
1666a second one, and embed the second one in the first.
1667.PP
1668As long as the watcher is active, the callback will be invoked every time
1669there might be events pending in the embedded loop. The callback must then
1670call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1671their callbacks (you could also start an idle watcher to give the embedded
1672loop strictly lower priority for example). You can also set the callback
1673to \f(CW0\fR, in which case the embed watcher will automatically execute the
1674embedded loop sweep.
1675.PP
1676As long as the watcher is started it will automatically handle events. The
1677callback will be invoked whenever some events have been handled. You can
1678set the callback to \f(CW0\fR to avoid having to specify one if you are not
1679interested in that.
1680.PP
1681Also, there have not currently been made special provisions for forking:
1682when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1683but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1684yourself.
1685.PP
1686Unfortunately, not all backends are embeddable, only the ones returned by
1687\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1688portable one.
1689.PP
1690So when you want to use this feature you will always have to be prepared
1691that you cannot get an embeddable loop. The recommended way to get around
1692this is to have a separate variables for your embeddable loop, try to
1693create it, and if that fails, use the normal loop for everything:
1694.PP
1695.Vb 3
1696\& struct ev_loop *loop_hi = ev_default_init (0);
1697\& struct ev_loop *loop_lo = 0;
1698\& struct ev_embed embed;
1699.Ve
1700.PP
1701.Vb 5
1702\& // see if there is a chance of getting one that works
1703\& // (remember that a flags value of 0 means autodetection)
1704\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1705\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1706\& : 0;
1707.Ve
1708.PP
1709.Vb 8
1710\& // if we got one, then embed it, otherwise default to loop_hi
1711\& if (loop_lo)
1712\& {
1713\& ev_embed_init (&embed, 0, loop_lo);
1714\& ev_embed_start (loop_hi, &embed);
1715\& }
1716\& else
1717\& loop_lo = loop_hi;
1718.Ve
1719.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1720.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1721.PD 0
1722.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1723.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1724.PD
1725Configures the watcher to embed the given loop, which must be
1726embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1727invoked automatically, otherwise it is the responsibility of the callback
1728to invoke it (it will continue to be called until the sweep has been done,
1729if you do not want thta, you need to temporarily stop the embed watcher).
1730.IP "ev_embed_sweep (loop, ev_embed *)" 4
1731.IX Item "ev_embed_sweep (loop, ev_embed *)"
1732Make a single, non-blocking sweep over the embedded loop. This works
1733similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1734apropriate way for embedded loops.
1735.IP "struct ev_loop *loop [read\-only]" 4
1736.IX Item "struct ev_loop *loop [read-only]"
1737The embedded event loop.
1738.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1739.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1740.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1741Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1742whoever is a good citizen cared to tell libev about it by calling
1743\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1744event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1745and only in the child after the fork. If whoever good citizen calling
1746\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1747handlers will be invoked, too, of course.
1748.IP "ev_fork_init (ev_signal *, callback)" 4
1749.IX Item "ev_fork_init (ev_signal *, callback)"
1750Initialises and configures the fork watcher \- it has no parameters of any
1751kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1752believe me.
949.SH "OTHER FUNCTIONS" 1753.SH "OTHER FUNCTIONS"
950.IX Header "OTHER FUNCTIONS" 1754.IX Header "OTHER FUNCTIONS"
951There are some other functions of possible interest. Described. Here. Now. 1755There are some other functions of possible interest. Described. Here. Now.
952.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1756.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
953.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1757.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
982.Ve 1786.Ve
983.Sp 1787.Sp
984.Vb 1 1788.Vb 1
985\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1789\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
986.Ve 1790.Ve
987.IP "ev_feed_event (loop, watcher, int events)" 4 1791.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
988.IX Item "ev_feed_event (loop, watcher, int events)" 1792.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
989Feeds the given event set into the event loop, as if the specified event 1793Feeds the given event set into the event loop, as if the specified event
990had happened for the specified watcher (which must be a pointer to an 1794had happened for the specified watcher (which must be a pointer to an
991initialised but not necessarily started event watcher). 1795initialised but not necessarily started event watcher).
992.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1796.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
993.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1797.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
994Feed an event on the given fd, as if a file descriptor backend detected 1798Feed an event on the given fd, as if a file descriptor backend detected
995the given events it. 1799the given events it.
996.IP "ev_feed_signal_event (loop, int signum)" 4 1800.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
997.IX Item "ev_feed_signal_event (loop, int signum)" 1801.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
998Feed an event as if the given signal occured (loop must be the default loop!). 1802Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1803loop!).
999.SH "LIBEVENT EMULATION" 1804.SH "LIBEVENT EMULATION"
1000.IX Header "LIBEVENT EMULATION" 1805.IX Header "LIBEVENT EMULATION"
1001Libev offers a compatibility emulation layer for libevent. It cannot 1806Libev offers a compatibility emulation layer for libevent. It cannot
1002emulate the internals of libevent, so here are some usage hints: 1807emulate the internals of libevent, so here are some usage hints:
1003.IP "* Use it by including <event.h>, as usual." 4 1808.IP "* Use it by including <event.h>, as usual." 4
… …
1014.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1819.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1015.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1820.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1016.PD 1821.PD
1017.SH "\*(C+ SUPPORT" 1822.SH "\*(C+ SUPPORT"
1018.IX Header " SUPPORT" 1823.IX Header " SUPPORT"
1019\&\s-1TBD\s0. 1824Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1825you to use some convinience methods to start/stop watchers and also change
1826the callback model to a model using method callbacks on objects.
1827.PP
1828To use it,
1829.PP
1830.Vb 1
1831\& #include <ev++.h>
1832.Ve
1833.PP
1834(it is not installed by default). This automatically includes \fIev.h\fR
1835and puts all of its definitions (many of them macros) into the global
1836namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1837.PP
1838It should support all the same embedding options as \fIev.h\fR, most notably
1839\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1840.PP
1841Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1842.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1843.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1844.IX Item "ev::READ, ev::WRITE etc."
1845These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1846macros from \fIev.h\fR.
1847.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1848.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1849.IX Item "ev::tstamp, ev::now"
1850Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1851.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
1852.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1853.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1854For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1855the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1856which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1857defines by many implementations.
1858.Sp
1859All of those classes have these methods:
1860.RS 4
1861.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1862.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1863.PD 0
1864.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1865.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1866.IP "ev::TYPE::~TYPE" 4
1867.IX Item "ev::TYPE::~TYPE"
1868.PD
1869The constructor takes a pointer to an object and a method pointer to
1870the event handler callback to call in this class. The constructor calls
1871\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1872before starting it. If you do not specify a loop then the constructor
1873automatically associates the default loop with this watcher.
1874.Sp
1875The destructor automatically stops the watcher if it is active.
1876.IP "w\->set (struct ev_loop *)" 4
1877.IX Item "w->set (struct ev_loop *)"
1878Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1879do this when the watcher is inactive (and not pending either).
1880.IP "w\->set ([args])" 4
1881.IX Item "w->set ([args])"
1882Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1883called at least once. Unlike the C counterpart, an active watcher gets
1884automatically stopped and restarted.
1885.IP "w\->start ()" 4
1886.IX Item "w->start ()"
1887Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1888constructor already takes the loop.
1889.IP "w\->stop ()" 4
1890.IX Item "w->stop ()"
1891Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1892.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1893.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1894.IX Item "w->again () ev::timer, ev::periodic only"
1895For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1896\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1897.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1898.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1899.IX Item "w->sweep () ev::embed only"
1900Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1901.ie n .IP "w\->update () ""ev::stat"" only" 4
1902.el .IP "w\->update () \f(CWev::stat\fR only" 4
1903.IX Item "w->update () ev::stat only"
1904Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1905.RE
1906.RS 4
1907.RE
1908.PP
1909Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1910the constructor.
1911.PP
1912.Vb 4
1913\& class myclass
1914\& {
1915\& ev_io io; void io_cb (ev::io &w, int revents);
1916\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1917.Ve
1918.PP
1919.Vb 2
1920\& myclass ();
1921\& }
1922.Ve
1923.PP
1924.Vb 6
1925\& myclass::myclass (int fd)
1926\& : io (this, &myclass::io_cb),
1927\& idle (this, &myclass::idle_cb)
1928\& {
1929\& io.start (fd, ev::READ);
1930\& }
1931.Ve
1932.SH "MACRO MAGIC"
1933.IX Header "MACRO MAGIC"
1934Libev can be compiled with a variety of options, the most fundemantal is
1935\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
1936callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1937.PP
1938To make it easier to write programs that cope with either variant, the
1939following macros are defined:
1940.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
1941.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
1942.IX Item "EV_A, EV_A_"
1943This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
1944loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
1945\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
1946.Sp
1947.Vb 3
1948\& ev_unref (EV_A);
1949\& ev_timer_add (EV_A_ watcher);
1950\& ev_loop (EV_A_ 0);
1951.Ve
1952.Sp
1953It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
1954which is often provided by the following macro.
1955.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
1956.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
1957.IX Item "EV_P, EV_P_"
1958This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
1959loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
1960\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
1961.Sp
1962.Vb 2
1963\& // this is how ev_unref is being declared
1964\& static void ev_unref (EV_P);
1965.Ve
1966.Sp
1967.Vb 2
1968\& // this is how you can declare your typical callback
1969\& static void cb (EV_P_ ev_timer *w, int revents)
1970.Ve
1971.Sp
1972It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
1973suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
1974.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
1975.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
1976.IX Item "EV_DEFAULT, EV_DEFAULT_"
1977Similar to the other two macros, this gives you the value of the default
1978loop, if multiple loops are supported (\*(L"ev loop default\*(R").
1979.PP
1980Example: Declare and initialise a check watcher, working regardless of
1981wether multiple loops are supported or not.
1982.PP
1983.Vb 5
1984\& static void
1985\& check_cb (EV_P_ ev_timer *w, int revents)
1986\& {
1987\& ev_check_stop (EV_A_ w);
1988\& }
1989.Ve
1990.PP
1991.Vb 4
1992\& ev_check check;
1993\& ev_check_init (&check, check_cb);
1994\& ev_check_start (EV_DEFAULT_ &check);
1995\& ev_loop (EV_DEFAULT_ 0);
1996.Ve
1997.SH "EMBEDDING"
1998.IX Header "EMBEDDING"
1999Libev can (and often is) directly embedded into host
2000applications. Examples of applications that embed it include the Deliantra
2001Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2002and rxvt\-unicode.
2003.PP
2004The goal is to enable you to just copy the neecssary files into your
2005source directory without having to change even a single line in them, so
2006you can easily upgrade by simply copying (or having a checked-out copy of
2007libev somewhere in your source tree).
2008.Sh "\s-1FILESETS\s0"
2009.IX Subsection "FILESETS"
2010Depending on what features you need you need to include one or more sets of files
2011in your app.
2012.PP
2013\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2014.IX Subsection "CORE EVENT LOOP"
2015.PP
2016To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2017configuration (no autoconf):
2018.PP
2019.Vb 2
2020\& #define EV_STANDALONE 1
2021\& #include "ev.c"
2022.Ve
2023.PP
2024This will automatically include \fIev.h\fR, too, and should be done in a
2025single C source file only to provide the function implementations. To use
2026it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2027done by writing a wrapper around \fIev.h\fR that you can include instead and
2028where you can put other configuration options):
2029.PP
2030.Vb 2
2031\& #define EV_STANDALONE 1
2032\& #include "ev.h"
2033.Ve
2034.PP
2035Both header files and implementation files can be compiled with a \*(C+
2036compiler (at least, thats a stated goal, and breakage will be treated
2037as a bug).
2038.PP
2039You need the following files in your source tree, or in a directory
2040in your include path (e.g. in libev/ when using \-Ilibev):
2041.PP
2042.Vb 4
2043\& ev.h
2044\& ev.c
2045\& ev_vars.h
2046\& ev_wrap.h
2047.Ve
2048.PP
2049.Vb 1
2050\& ev_win32.c required on win32 platforms only
2051.Ve
2052.PP
2053.Vb 5
2054\& ev_select.c only when select backend is enabled (which is by default)
2055\& ev_poll.c only when poll backend is enabled (disabled by default)
2056\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2057\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2058\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2059.Ve
2060.PP
2061\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2062to compile this single file.
2063.PP
2064\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2065.IX Subsection "LIBEVENT COMPATIBILITY API"
2066.PP
2067To include the libevent compatibility \s-1API\s0, also include:
2068.PP
2069.Vb 1
2070\& #include "event.c"
2071.Ve
2072.PP
2073in the file including \fIev.c\fR, and:
2074.PP
2075.Vb 1
2076\& #include "event.h"
2077.Ve
2078.PP
2079in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2080.PP
2081You need the following additional files for this:
2082.PP
2083.Vb 2
2084\& event.h
2085\& event.c
2086.Ve
2087.PP
2088\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2089.IX Subsection "AUTOCONF SUPPORT"
2090.PP
2091Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2092whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2093\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2094include \fIconfig.h\fR and configure itself accordingly.
2095.PP
2096For this of course you need the m4 file:
2097.PP
2098.Vb 1
2099\& libev.m4
2100.Ve
2101.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2102.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2103Libev can be configured via a variety of preprocessor symbols you have to define
2104before including any of its files. The default is not to build for multiplicity
2105and only include the select backend.
2106.IP "\s-1EV_STANDALONE\s0" 4
2107.IX Item "EV_STANDALONE"
2108Must always be \f(CW1\fR if you do not use autoconf configuration, which
2109keeps libev from including \fIconfig.h\fR, and it also defines dummy
2110implementations for some libevent functions (such as logging, which is not
2111supported). It will also not define any of the structs usually found in
2112\&\fIevent.h\fR that are not directly supported by the libev core alone.
2113.IP "\s-1EV_USE_MONOTONIC\s0" 4
2114.IX Item "EV_USE_MONOTONIC"
2115If defined to be \f(CW1\fR, libev will try to detect the availability of the
2116monotonic clock option at both compiletime and runtime. Otherwise no use
2117of the monotonic clock option will be attempted. If you enable this, you
2118usually have to link against librt or something similar. Enabling it when
2119the functionality isn't available is safe, though, althoguh you have
2120to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2121function is hiding in (often \fI\-lrt\fR).
2122.IP "\s-1EV_USE_REALTIME\s0" 4
2123.IX Item "EV_USE_REALTIME"
2124If defined to be \f(CW1\fR, libev will try to detect the availability of the
2125realtime clock option at compiletime (and assume its availability at
2126runtime if successful). Otherwise no use of the realtime clock option will
2127be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2128(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2129in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2130.IP "\s-1EV_USE_SELECT\s0" 4
2131.IX Item "EV_USE_SELECT"
2132If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2133\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2134other method takes over, select will be it. Otherwise the select backend
2135will not be compiled in.
2136.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2137.IX Item "EV_SELECT_USE_FD_SET"
2138If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2139structure. This is useful if libev doesn't compile due to a missing
2140\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2141exotic systems. This usually limits the range of file descriptors to some
2142low limit such as 1024 or might have other limitations (winsocket only
2143allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2144influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2145.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2146.IX Item "EV_SELECT_IS_WINSOCKET"
2147When defined to \f(CW1\fR, the select backend will assume that
2148select/socket/connect etc. don't understand file descriptors but
2149wants osf handles on win32 (this is the case when the select to
2150be used is the winsock select). This means that it will call
2151\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2152it is assumed that all these functions actually work on fds, even
2153on win32. Should not be defined on non\-win32 platforms.
2154.IP "\s-1EV_USE_POLL\s0" 4
2155.IX Item "EV_USE_POLL"
2156If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2157backend. Otherwise it will be enabled on non\-win32 platforms. It
2158takes precedence over select.
2159.IP "\s-1EV_USE_EPOLL\s0" 4
2160.IX Item "EV_USE_EPOLL"
2161If defined to be \f(CW1\fR, libev will compile in support for the Linux
2162\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2163otherwise another method will be used as fallback. This is the
2164preferred backend for GNU/Linux systems.
2165.IP "\s-1EV_USE_KQUEUE\s0" 4
2166.IX Item "EV_USE_KQUEUE"
2167If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2168\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2169otherwise another method will be used as fallback. This is the preferred
2170backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2171supports some types of fds correctly (the only platform we found that
2172supports ptys for example was NetBSD), so kqueue might be compiled in, but
2173not be used unless explicitly requested. The best way to use it is to find
2174out whether kqueue supports your type of fd properly and use an embedded
2175kqueue loop.
2176.IP "\s-1EV_USE_PORT\s0" 4
2177.IX Item "EV_USE_PORT"
2178If defined to be \f(CW1\fR, libev will compile in support for the Solaris
217910 port style backend. Its availability will be detected at runtime,
2180otherwise another method will be used as fallback. This is the preferred
2181backend for Solaris 10 systems.
2182.IP "\s-1EV_USE_DEVPOLL\s0" 4
2183.IX Item "EV_USE_DEVPOLL"
2184reserved for future expansion, works like the \s-1USE\s0 symbols above.
2185.IP "\s-1EV_USE_INOTIFY\s0" 4
2186.IX Item "EV_USE_INOTIFY"
2187If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2188interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2189be detected at runtime.
2190.IP "\s-1EV_H\s0" 4
2191.IX Item "EV_H"
2192The name of the \fIev.h\fR header file used to include it. The default if
2193undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2194can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2195.IP "\s-1EV_CONFIG_H\s0" 4
2196.IX Item "EV_CONFIG_H"
2197If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2198\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2199\&\f(CW\*(C`EV_H\*(C'\fR, above.
2200.IP "\s-1EV_EVENT_H\s0" 4
2201.IX Item "EV_EVENT_H"
2202Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2203of how the \fIevent.h\fR header can be found.
2204.IP "\s-1EV_PROTOTYPES\s0" 4
2205.IX Item "EV_PROTOTYPES"
2206If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2207prototypes, but still define all the structs and other symbols. This is
2208occasionally useful if you want to provide your own wrapper functions
2209around libev functions.
2210.IP "\s-1EV_MULTIPLICITY\s0" 4
2211.IX Item "EV_MULTIPLICITY"
2212If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2213will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2214additional independent event loops. Otherwise there will be no support
2215for multiple event loops and there is no first event loop pointer
2216argument. Instead, all functions act on the single default loop.
2217.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2218.IX Item "EV_PERIODIC_ENABLE"
2219If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2220defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2221code.
2222.IP "\s-1EV_EMBED_ENABLE\s0" 4
2223.IX Item "EV_EMBED_ENABLE"
2224If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2225defined to be \f(CW0\fR, then they are not.
2226.IP "\s-1EV_STAT_ENABLE\s0" 4
2227.IX Item "EV_STAT_ENABLE"
2228If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2229defined to be \f(CW0\fR, then they are not.
2230.IP "\s-1EV_FORK_ENABLE\s0" 4
2231.IX Item "EV_FORK_ENABLE"
2232If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2233defined to be \f(CW0\fR, then they are not.
2234.IP "\s-1EV_MINIMAL\s0" 4
2235.IX Item "EV_MINIMAL"
2236If you need to shave off some kilobytes of code at the expense of some
2237speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2238some inlining decisions, saves roughly 30% codesize of amd64.
2239.IP "\s-1EV_PID_HASHSIZE\s0" 4
2240.IX Item "EV_PID_HASHSIZE"
2241\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2242pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2243than enough. If you need to manage thousands of children you might want to
2244increase this value (\fImust\fR be a power of two).
2245.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2246.IX Item "EV_INOTIFY_HASHSIZE"
2247\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2248inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2249usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2250watchers you might want to increase this value (\fImust\fR be a power of
2251two).
2252.IP "\s-1EV_COMMON\s0" 4
2253.IX Item "EV_COMMON"
2254By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2255this macro to a something else you can include more and other types of
2256members. You have to define it each time you include one of the files,
2257though, and it must be identical each time.
2258.Sp
2259For example, the perl \s-1EV\s0 module uses something like this:
2260.Sp
2261.Vb 3
2262\& #define EV_COMMON \e
2263\& SV *self; /* contains this struct */ \e
2264\& SV *cb_sv, *fh /* note no trailing ";" */
2265.Ve
2266.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2267.IX Item "EV_CB_DECLARE (type)"
2268.PD 0
2269.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2270.IX Item "EV_CB_INVOKE (watcher, revents)"
2271.IP "ev_set_cb (ev, cb)" 4
2272.IX Item "ev_set_cb (ev, cb)"
2273.PD
2274Can be used to change the callback member declaration in each watcher,
2275and the way callbacks are invoked and set. Must expand to a struct member
2276definition and a statement, respectively. See the \fIev.v\fR header file for
2277their default definitions. One possible use for overriding these is to
2278avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2279method calls instead of plain function calls in \*(C+.
2280.Sh "\s-1EXAMPLES\s0"
2281.IX Subsection "EXAMPLES"
2282For a real-world example of a program the includes libev
2283verbatim, you can have a look at the \s-1EV\s0 perl module
2284(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2285the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2286interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2287will be compiled. It is pretty complex because it provides its own header
2288file.
2289.Sp
2290The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2291that everybody includes and which overrides some autoconf choices:
2292.Sp
2293.Vb 4
2294\& #define EV_USE_POLL 0
2295\& #define EV_MULTIPLICITY 0
2296\& #define EV_PERIODICS 0
2297\& #define EV_CONFIG_H <config.h>
2298.Ve
2299.Sp
2300.Vb 1
2301\& #include "ev++.h"
2302.Ve
2303.Sp
2304And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2305.Sp
2306.Vb 2
2307\& #include "ev_cpp.h"
2308\& #include "ev.c"
2309.Ve
2310.SH "COMPLEXITIES"
2311.IX Header "COMPLEXITIES"
2312In this section the complexities of (many of) the algorithms used inside
2313libev will be explained. For complexity discussions about backends see the
2314documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2315.RS 4
2316.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2317.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2318.PD 0
2319.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2320.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2321.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2322.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2323.IP "Stopping check/prepare/idle watchers: O(1)" 4
2324.IX Item "Stopping check/prepare/idle watchers: O(1)"
2325.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2326.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2327.IP "Finding the next timer per loop iteration: O(1)" 4
2328.IX Item "Finding the next timer per loop iteration: O(1)"
2329.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2330.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2331.IP "Activating one watcher: O(1)" 4
2332.IX Item "Activating one watcher: O(1)"
2333.RE
2334.RS 4
2335.PD
1020.SH "AUTHOR" 2336.SH "AUTHOR"
1021.IX Header "AUTHOR" 2337.IX Header "AUTHOR"
1022Marc Lehmann <libev@schmorp.de>. 2338Marc Lehmann <libev@schmorp.de>.

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