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Revision 1.9 by root, Fri Nov 23 16:17:12 2007 UTC vs.
Revision 1.37 by root, Fri Dec 7 16:49:49 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 "2007-12-07" "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
… …
201Usually, 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,
202as this indicates an incompatible change. Minor versions are usually 267as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 268compatible to older versions, so a larger minor version alone is usually
204not a problem. 269not a problem.
205.Sp 270.Sp
206Example: make sure we haven't accidentally been linked against the wrong 271Example: Make sure we haven't accidentally been linked against the wrong
207version: 272version.
208.Sp 273.Sp
209.Vb 3 274.Vb 3
210\& assert (("libev version mismatch", 275\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 276\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 277\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
231recommended for this platform. This set is often smaller than the one 296recommended for this platform. This set is often smaller than the one
232returned 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
233most BSDs and will not be autodetected unless you explicitly request it 298most BSDs and will not be autodetected unless you explicitly request it
234(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
235libev 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.
236.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 310.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
237.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 311.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
238Sets the allocation function to use (the prototype is similar to the 312Sets the allocation function to use (the prototype is similar \- the
239realloc C function, the semantics are identical). It is used to allocate 313semantics is identical \- to the realloc C function). It is used to
240and free memory (no surprises here). If it returns zero when memory 314allocate and free memory (no surprises here). If it returns zero when
241needs to be allocated, the library might abort or take some potentially 315memory needs to be allocated, the library might abort or take some
242destructive action. The default is your system realloc function. 316potentially destructive action. The default is your system realloc
317function.
243.Sp 318.Sp
244You could override this function in high-availability programs to, say, 319You could override this function in high-availability programs to, say,
245free 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,
246or 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.
247.Sp 322.Sp
248Example: replace the libev allocator with one that waits a bit and then 323Example: Replace the libev allocator with one that waits a bit and then
249retries: better than mine). 324retries).
250.Sp 325.Sp
251.Vb 6 326.Vb 6
252\& static void * 327\& static void *
253\& persistent_realloc (void *ptr, long size) 328\& persistent_realloc (void *ptr, size_t size)
254\& { 329\& {
255\& for (;;) 330\& for (;;)
256\& { 331\& {
257\& void *newptr = realloc (ptr, size); 332\& void *newptr = realloc (ptr, size);
258.Ve 333.Ve
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280callback 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
281matter what, when it returns. That is, libev will generally retry the 356matter what, when it returns. That is, libev will generally retry the
282requested 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
283(such as abort). 358(such as abort).
284.Sp 359.Sp
285Example: do the same thing as libev does internally: 360Example: This is basically the same thing that libev does internally, too.
286.Sp 361.Sp
287.Vb 6 362.Vb 6
288\& static void 363\& static void
289\& fatal_error (const char *msg) 364\& fatal_error (const char *msg)
290\& { 365\& {
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336or setgid) then libev will \fInot\fR look at the environment variable 411or setgid) then libev will \fInot\fR look at the environment variable
337\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 412\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
338override the flags completely if it is found in the environment. This is 413override the flags completely if it is found in the environment. This is
339useful to try out specific backends to test their performance, or to work 414useful to try out specific backends to test their performance, or to work
340around bugs. 415around bugs.
416.ie n .IP """EVFLAG_FORKCHECK""" 4
417.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
418.IX Item "EVFLAG_FORKCHECK"
419Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
420a fork, you can also make libev check for a fork in each iteration by
421enabling this flag.
422.Sp
423This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
424and thus this might slow down your event loop if you do a lot of loop
425iterations and little real work, but is usually not noticeable (on my
426Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
427without a syscall and thus \fIvery\fR fast, but my Linux system also has
428\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
429.Sp
430The big advantage of this flag is that you can forget about fork (and
431forget about forgetting to tell libev about forking) when you use this
432flag.
433.Sp
434This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
435environment variable.
341.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 436.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
342.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 437.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
343.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 438.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
344This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 439This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
345libev tries to roll its own fd_set with no limits on the number of fds, 440libev tries to roll its own fd_set with no limits on the number of fds,
… …
439Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 534Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
440always distinct from the default loop. Unlike the default loop, it cannot 535always distinct from the default loop. Unlike the default loop, it cannot
441handle signal and child watchers, and attempts to do so will be greeted by 536handle signal and child watchers, and attempts to do so will be greeted by
442undefined behaviour (or a failed assertion if assertions are enabled). 537undefined behaviour (or a failed assertion if assertions are enabled).
443.Sp 538.Sp
444Example: try to create a event loop that uses epoll and nothing else. 539Example: Try to create a event loop that uses epoll and nothing else.
445.Sp 540.Sp
446.Vb 3 541.Vb 3
447\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 542\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
448\& if (!epoller) 543\& if (!epoller)
449\& fatal ("no epoll found here, maybe it hides under your chair"); 544\& fatal ("no epoll found here, maybe it hides under your chair");
450.Ve 545.Ve
451.IP "ev_default_destroy ()" 4 546.IP "ev_default_destroy ()" 4
452.IX Item "ev_default_destroy ()" 547.IX Item "ev_default_destroy ()"
453Destroys the default loop again (frees all memory and kernel state 548Destroys the default loop again (frees all memory and kernel state
454etc.). This stops all registered event watchers (by not touching them in 549etc.). None of the active event watchers will be stopped in the normal
455any way whatsoever, although you cannot rely on this :). 550sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
551responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
552calling this function, or cope with the fact afterwards (which is usually
553the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
554for example).
456.IP "ev_loop_destroy (loop)" 4 555.IP "ev_loop_destroy (loop)" 4
457.IX Item "ev_loop_destroy (loop)" 556.IX Item "ev_loop_destroy (loop)"
458Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 557Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
459earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 558earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
460.IP "ev_default_fork ()" 4 559.IP "ev_default_fork ()" 4
… …
482.IP "ev_loop_fork (loop)" 4 581.IP "ev_loop_fork (loop)" 4
483.IX Item "ev_loop_fork (loop)" 582.IX Item "ev_loop_fork (loop)"
484Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 583Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
485\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 584\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
486after fork, and how you do this is entirely your own problem. 585after fork, and how you do this is entirely your own problem.
586.IP "unsigned int ev_loop_count (loop)" 4
587.IX Item "unsigned int ev_loop_count (loop)"
588Returns the count of loop iterations for the loop, which is identical to
589the number of times libev did poll for new events. It starts at \f(CW0\fR and
590happily wraps around with enough iterations.
591.Sp
592This value can sometimes be useful as a generation counter of sorts (it
593\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
594\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
487.IP "unsigned int ev_backend (loop)" 4 595.IP "unsigned int ev_backend (loop)" 4
488.IX Item "unsigned int ev_backend (loop)" 596.IX Item "unsigned int ev_backend (loop)"
489Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 597Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
490use. 598use.
491.IP "ev_tstamp ev_now (loop)" 4 599.IP "ev_tstamp ev_now (loop)" 4
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543\& be handled here by queueing them when their watcher gets executed. 651\& be handled here by queueing them when their watcher gets executed.
544\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 652\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
545\& were used, return, otherwise continue with step *. 653\& were used, return, otherwise continue with step *.
546.Ve 654.Ve
547.Sp 655.Sp
548Example: queue some jobs and then loop until no events are outsanding 656Example: Queue some jobs and then loop until no events are outsanding
549anymore. 657anymore.
550.Sp 658.Sp
551.Vb 4 659.Vb 4
552\& ... queue jobs here, make sure they register event watchers as long 660\& ... queue jobs here, make sure they register event watchers as long
553\& ... as they still have work to do (even an idle watcher will do..) 661\& ... as they still have work to do (even an idle watcher will do..)
… …
575visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 683visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
576no event watchers registered by it are active. It is also an excellent 684no event watchers registered by it are active. It is also an excellent
577way to do this for generic recurring timers or from within third-party 685way to do this for generic recurring timers or from within third-party
578libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 686libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
579.Sp 687.Sp
580Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 688Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
581running when nothing else is active. 689running when nothing else is active.
582.Sp 690.Sp
583.Vb 4 691.Vb 4
584\& struct dv_signal exitsig; 692\& struct ev_signal exitsig;
585\& ev_signal_init (&exitsig, sig_cb, SIGINT); 693\& ev_signal_init (&exitsig, sig_cb, SIGINT);
586\& ev_signal_start (myloop, &exitsig); 694\& ev_signal_start (loop, &exitsig);
587\& evf_unref (myloop); 695\& evf_unref (loop);
588.Ve 696.Ve
589.Sp 697.Sp
590Example: for some weird reason, unregister the above signal handler again. 698Example: For some weird reason, unregister the above signal handler again.
591.Sp 699.Sp
592.Vb 2 700.Vb 2
593\& ev_ref (myloop); 701\& ev_ref (loop);
594\& ev_signal_stop (myloop, &exitsig); 702\& ev_signal_stop (loop, &exitsig);
595.Ve 703.Ve
596.SH "ANATOMY OF A WATCHER" 704.SH "ANATOMY OF A WATCHER"
597.IX Header "ANATOMY OF A WATCHER" 705.IX Header "ANATOMY OF A WATCHER"
598A watcher is a structure that you create and register to record your 706A watcher is a structure that you create and register to record your
599interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 707interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
… …
636*)\*(C'\fR), and you can stop watching for events at any time by calling the 744*)\*(C'\fR), and you can stop watching for events at any time by calling the
637corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 745corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
638.PP 746.PP
639As long as your watcher is active (has been started but not stopped) you 747As long as your watcher is active (has been started but not stopped) you
640must not touch the values stored in it. Most specifically you must never 748must not touch the values stored in it. Most specifically you must never
641reinitialise it or call its set macro. 749reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
642.PP
643You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
644(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
645callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
646(watcher *)\*(C'\fR macro.
647.PP 750.PP
648Each and every callback receives the event loop pointer as first, the 751Each and every callback receives the event loop pointer as first, the
649registered watcher structure as second, and a bitset of received events as 752registered watcher structure as second, and a bitset of received events as
650third argument. 753third argument.
651.PP 754.PP
… …
676The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 779The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
677.ie n .IP """EV_CHILD""" 4 780.ie n .IP """EV_CHILD""" 4
678.el .IP "\f(CWEV_CHILD\fR" 4 781.el .IP "\f(CWEV_CHILD\fR" 4
679.IX Item "EV_CHILD" 782.IX Item "EV_CHILD"
680The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 783The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
784.ie n .IP """EV_STAT""" 4
785.el .IP "\f(CWEV_STAT\fR" 4
786.IX Item "EV_STAT"
787The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
681.ie n .IP """EV_IDLE""" 4 788.ie n .IP """EV_IDLE""" 4
682.el .IP "\f(CWEV_IDLE\fR" 4 789.el .IP "\f(CWEV_IDLE\fR" 4
683.IX Item "EV_IDLE" 790.IX Item "EV_IDLE"
684The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 791The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
685.ie n .IP """EV_PREPARE""" 4 792.ie n .IP """EV_PREPARE""" 4
… …
695\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 802\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
696received events. Callbacks of both watcher types can start and stop as 803received events. Callbacks of both watcher types can start and stop as
697many watchers as they want, and all of them will be taken into account 804many watchers as they want, and all of them will be taken into account
698(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 805(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
699\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 806\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
807.ie n .IP """EV_EMBED""" 4
808.el .IP "\f(CWEV_EMBED\fR" 4
809.IX Item "EV_EMBED"
810The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
811.ie n .IP """EV_FORK""" 4
812.el .IP "\f(CWEV_FORK\fR" 4
813.IX Item "EV_FORK"
814The event loop has been resumed in the child process after fork (see
815\&\f(CW\*(C`ev_fork\*(C'\fR).
700.ie n .IP """EV_ERROR""" 4 816.ie n .IP """EV_ERROR""" 4
701.el .IP "\f(CWEV_ERROR\fR" 4 817.el .IP "\f(CWEV_ERROR\fR" 4
702.IX Item "EV_ERROR" 818.IX Item "EV_ERROR"
703An unspecified error has occured, the watcher has been stopped. This might 819An unspecified error has occured, the watcher has been stopped. This might
704happen because the watcher could not be properly started because libev 820happen because the watcher could not be properly started because libev
… …
709Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 825Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
710for example it might indicate that a fd is readable or writable, and if 826for example it might indicate that a fd is readable or writable, and if
711your callbacks is well-written it can just attempt the operation and cope 827your callbacks is well-written it can just attempt the operation and cope
712with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 828with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
713programs, though, so beware. 829programs, though, so beware.
830.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
831.IX Subsection "GENERIC WATCHER FUNCTIONS"
832In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
833e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
834.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
835.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
836.IX Item "ev_init (ev_TYPE *watcher, callback)"
837This macro initialises the generic portion of a watcher. The contents
838of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
839the generic parts of the watcher are initialised, you \fIneed\fR to call
840the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
841type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
842which rolls both calls into one.
843.Sp
844You can reinitialise a watcher at any time as long as it has been stopped
845(or never started) and there are no pending events outstanding.
846.Sp
847The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
848int revents)\*(C'\fR.
849.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
850.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
851.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
852This macro initialises the type-specific parts of a watcher. You need to
853call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
854call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
855macro on a watcher that is active (it can be pending, however, which is a
856difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
857.Sp
858Although some watcher types do not have type-specific arguments
859(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
860.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
861.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
862.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
863This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
864calls into a single call. This is the most convinient method to initialise
865a watcher. The same limitations apply, of course.
866.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
867.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
868.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
869Starts (activates) the given watcher. Only active watchers will receive
870events. If the watcher is already active nothing will happen.
871.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
872.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
873.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
874Stops the given watcher again (if active) and clears the pending
875status. It is possible that stopped watchers are pending (for example,
876non-repeating timers are being stopped when they become pending), but
877\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
878you want to free or reuse the memory used by the watcher it is therefore a
879good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
880.IP "bool ev_is_active (ev_TYPE *watcher)" 4
881.IX Item "bool ev_is_active (ev_TYPE *watcher)"
882Returns a true value iff the watcher is active (i.e. it has been started
883and not yet been stopped). As long as a watcher is active you must not modify
884it.
885.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
886.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
887Returns a true value iff the watcher is pending, (i.e. it has outstanding
888events but its callback has not yet been invoked). As long as a watcher
889is pending (but not active) you must not call an init function on it (but
890\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
891libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
892.IP "callback ev_cb (ev_TYPE *watcher)" 4
893.IX Item "callback ev_cb (ev_TYPE *watcher)"
894Returns the callback currently set on the watcher.
895.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
896.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
897Change the callback. You can change the callback at virtually any time
898(modulo threads).
899.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
900.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
901.PD 0
902.IP "int ev_priority (ev_TYPE *watcher)" 4
903.IX Item "int ev_priority (ev_TYPE *watcher)"
904.PD
905Set and query the priority of the watcher. The priority is a small
906integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
907(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
908before watchers with lower priority, but priority will not keep watchers
909from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
910.Sp
911This means that priorities are \fIonly\fR used for ordering callback
912invocation after new events have been received. This is useful, for
913example, to reduce latency after idling, or more often, to bind two
914watchers on the same event and make sure one is called first.
915.Sp
916If you need to suppress invocation when higher priority events are pending
917you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
918.Sp
919The default priority used by watchers when no priority has been set is
920always \f(CW0\fR, which is supposed to not be too high and not be too low :).
921.Sp
922Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
923fine, as long as you do not mind that the priority value you query might
924or might not have been adjusted to be within valid range.
714.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 925.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
715.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 926.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
716Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 927Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
717and read at any time, libev will completely ignore it. This can be used 928and read at any time, libev will completely ignore it. This can be used
718to associate arbitrary data with your watcher. If you need more data and 929to associate arbitrary data with your watcher. If you need more data and
… …
739\& struct my_io *w = (struct my_io *)w_; 950\& struct my_io *w = (struct my_io *)w_;
740\& ... 951\& ...
741\& } 952\& }
742.Ve 953.Ve
743.PP 954.PP
744More interesting and less C\-conformant ways of catsing your callback type 955More interesting and less C\-conformant ways of casting your callback type
745have been omitted.... 956instead have been omitted.
957.PP
958Another common scenario is having some data structure with multiple
959watchers:
960.PP
961.Vb 6
962\& struct my_biggy
963\& {
964\& int some_data;
965\& ev_timer t1;
966\& ev_timer t2;
967\& }
968.Ve
969.PP
970In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
971you need to use \f(CW\*(C`offsetof\*(C'\fR:
972.PP
973.Vb 1
974\& #include <stddef.h>
975.Ve
976.PP
977.Vb 6
978\& static void
979\& t1_cb (EV_P_ struct ev_timer *w, int revents)
980\& {
981\& struct my_biggy big = (struct my_biggy *
982\& (((char *)w) - offsetof (struct my_biggy, t1));
983\& }
984.Ve
985.PP
986.Vb 6
987\& static void
988\& t2_cb (EV_P_ struct ev_timer *w, int revents)
989\& {
990\& struct my_biggy big = (struct my_biggy *
991\& (((char *)w) - offsetof (struct my_biggy, t2));
992\& }
993.Ve
746.SH "WATCHER TYPES" 994.SH "WATCHER TYPES"
747.IX Header "WATCHER TYPES" 995.IX Header "WATCHER TYPES"
748This section describes each watcher in detail, but will not repeat 996This section describes each watcher in detail, but will not repeat
749information given in the last section. 997information given in the last section. Any initialisation/set macros,
998functions and members specific to the watcher type are explained.
999.PP
1000Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1001while the watcher is active, you can look at the member and expect some
1002sensible content, but you must not modify it (you can modify it while the
1003watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1004means you can expect it to have some sensible content while the watcher
1005is active, but you can also modify it. Modifying it may not do something
1006sensible or take immediate effect (or do anything at all), but libev will
1007not crash or malfunction in any way.
750.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1008.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
751.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1009.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
752.IX Subsection "ev_io - is this file descriptor readable or writable" 1010.IX Subsection "ev_io - is this file descriptor readable or writable?"
753I/O watchers check whether a file descriptor is readable or writable 1011I/O watchers check whether a file descriptor is readable or writable
754in each iteration of the event loop (This behaviour is called 1012in each iteration of the event loop, or, more precisely, when reading
755level-triggering because you keep receiving events as long as the 1013would not block the process and writing would at least be able to write
756condition persists. Remember you can stop the watcher if you don't want to 1014some data. This behaviour is called level-triggering because you keep
757act on the event and neither want to receive future events). 1015receiving events as long as the condition persists. Remember you can stop
1016the watcher if you don't want to act on the event and neither want to
1017receive future events.
758.PP 1018.PP
759In general you can register as many read and/or write event watchers per 1019In general you can register as many read and/or write event watchers per
760fd as you want (as long as you don't confuse yourself). Setting all file 1020fd as you want (as long as you don't confuse yourself). Setting all file
761descriptors to non-blocking mode is also usually a good idea (but not 1021descriptors to non-blocking mode is also usually a good idea (but not
762required if you know what you are doing). 1022required if you know what you are doing).
763.PP 1023.PP
764You have to be careful with dup'ed file descriptors, though. Some backends 1024You have to be careful with dup'ed file descriptors, though. Some backends
765(the linux epoll backend is a notable example) cannot handle dup'ed file 1025(the linux epoll backend is a notable example) cannot handle dup'ed file
766descriptors correctly if you register interest in two or more fds pointing 1026descriptors correctly if you register interest in two or more fds pointing
767to the same underlying file/socket etc. description (that is, they share 1027to the same underlying file/socket/etc. description (that is, they share
768the same underlying \*(L"file open\*(R"). 1028the same underlying \*(L"file open\*(R").
769.PP 1029.PP
770If you must do this, then force the use of a known-to-be-good backend 1030If you must do this, then force the use of a known-to-be-good backend
771(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1031(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
772\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1032\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1033.PP
1034Another thing you have to watch out for is that it is quite easy to
1035receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1036be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1037because there is no data. Not only are some backends known to create a
1038lot of those (for example solaris ports), it is very easy to get into
1039this situation even with a relatively standard program structure. Thus
1040it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1041\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1042.PP
1043If you cannot run the fd in non-blocking mode (for example you should not
1044play around with an Xlib connection), then you have to seperately re-test
1045wether a file descriptor is really ready with a known-to-be good interface
1046such as poll (fortunately in our Xlib example, Xlib already does this on
1047its own, so its quite safe to use).
773.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1048.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
774.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1049.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
775.PD 0 1050.PD 0
776.IP "ev_io_set (ev_io *, int fd, int events)" 4 1051.IP "ev_io_set (ev_io *, int fd, int events)" 4
777.IX Item "ev_io_set (ev_io *, int fd, int events)" 1052.IX Item "ev_io_set (ev_io *, int fd, int events)"
778.PD 1053.PD
779Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1054Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
780events 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 | 1055rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
781EV_WRITE\*(C'\fR to receive the given events. 1056\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
782.Sp 1057.IP "int fd [read\-only]" 4
783Please note that most of the more scalable backend mechanisms (for example 1058.IX Item "int fd [read-only]"
784epoll and solaris ports) can result in spurious readyness notifications 1059The file descriptor being watched.
785for file descriptors, so you practically need to use non-blocking I/O (and 1060.IP "int events [read\-only]" 4
786treat callback invocation as hint only), or retest separately with a safe 1061.IX Item "int events [read-only]"
787interface before doing I/O (XLib can do this), or force the use of either 1062The events being watched.
788\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
789problem. Also note that it is quite easy to have your callback invoked
790when the readyness condition is no longer valid even when employing
791typical ways of handling events, so its a good idea to use non-blocking
792I/O unconditionally.
793.PP 1063.PP
794Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1064Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
795readable, but only once. Since it is likely line\-buffered, you could 1065readable, but only once. Since it is likely line\-buffered, you could
796attempt to read a whole line in the callback: 1066attempt to read a whole line in the callback.
797.PP 1067.PP
798.Vb 6 1068.Vb 6
799\& static void 1069\& static void
800\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1070\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
801\& { 1071\& {
… …
810\& struct ev_io stdin_readable; 1080\& struct ev_io stdin_readable;
811\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1081\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
812\& ev_io_start (loop, &stdin_readable); 1082\& ev_io_start (loop, &stdin_readable);
813\& ev_loop (loop, 0); 1083\& ev_loop (loop, 0);
814.Ve 1084.Ve
815.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1085.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
816.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1086.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
817.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1087.IX Subsection "ev_timer - relative and optionally repeating timeouts"
818Timer watchers are simple relative timers that generate an event after a 1088Timer watchers are simple relative timers that generate an event after a
819given time, and optionally repeating in regular intervals after that. 1089given time, and optionally repeating in regular intervals after that.
820.PP 1090.PP
821The timers are based on real time, that is, if you register an event that 1091The timers are based on real time, that is, if you register an event that
822times out after an hour and you reset your system clock to last years 1092times out after an hour and you reset your system clock to last years
… …
856.IP "ev_timer_again (loop)" 4 1126.IP "ev_timer_again (loop)" 4
857.IX Item "ev_timer_again (loop)" 1127.IX Item "ev_timer_again (loop)"
858This will act as if the timer timed out and restart it again if it is 1128This will act as if the timer timed out and restart it again if it is
859repeating. The exact semantics are: 1129repeating. The exact semantics are:
860.Sp 1130.Sp
1131If the timer is pending, its pending status is cleared.
1132.Sp
861If the timer is started but nonrepeating, stop it. 1133If the timer is started but nonrepeating, stop it (as if it timed out).
862.Sp 1134.Sp
863If the timer is repeating, either start it if necessary (with the repeat 1135If the timer is repeating, either start it if necessary (with the
864value), or reset the running timer to the repeat value. 1136\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
865.Sp 1137.Sp
866This sounds a bit complicated, but here is a useful and typical 1138This sounds a bit complicated, but here is a useful and typical
867example: Imagine you have a tcp connection and you want a so-called idle 1139example: Imagine you have a tcp connection and you want a so-called idle
868timeout, that is, you want to be called when there have been, say, 60 1140timeout, that is, you want to be called when there have been, say, 60
869seconds of inactivity on the socket. The easiest way to do this is to 1141seconds of inactivity on the socket. The easiest way to do this is to
870configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1142configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
871time you successfully read or write some data. If you go into an idle 1143\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
872state where you do not expect data to travel on the socket, you can stop 1144you go into an idle state where you do not expect data to travel on the
873the timer, and again will automatically restart it if need be. 1145socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1146automatically restart it if need be.
1147.Sp
1148That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1149altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1150.Sp
1151.Vb 8
1152\& ev_timer_init (timer, callback, 0., 5.);
1153\& ev_timer_again (loop, timer);
1154\& ...
1155\& timer->again = 17.;
1156\& ev_timer_again (loop, timer);
1157\& ...
1158\& timer->again = 10.;
1159\& ev_timer_again (loop, timer);
1160.Ve
1161.Sp
1162This is more slightly efficient then stopping/starting the timer each time
1163you want to modify its timeout value.
1164.IP "ev_tstamp repeat [read\-write]" 4
1165.IX Item "ev_tstamp repeat [read-write]"
1166The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1167or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1168which is also when any modifications are taken into account.
874.PP 1169.PP
875Example: create a timer that fires after 60 seconds. 1170Example: Create a timer that fires after 60 seconds.
876.PP 1171.PP
877.Vb 5 1172.Vb 5
878\& static void 1173\& static void
879\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1174\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
880\& { 1175\& {
… …
886\& struct ev_timer mytimer; 1181\& struct ev_timer mytimer;
887\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1182\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
888\& ev_timer_start (loop, &mytimer); 1183\& ev_timer_start (loop, &mytimer);
889.Ve 1184.Ve
890.PP 1185.PP
891Example: create a timeout timer that times out after 10 seconds of 1186Example: Create a timeout timer that times out after 10 seconds of
892inactivity. 1187inactivity.
893.PP 1188.PP
894.Vb 5 1189.Vb 5
895\& static void 1190\& static void
896\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1191\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
909.Vb 3 1204.Vb 3
910\& // and in some piece of code that gets executed on any "activity": 1205\& // and in some piece of code that gets executed on any "activity":
911\& // reset the timeout to start ticking again at 10 seconds 1206\& // reset the timeout to start ticking again at 10 seconds
912\& ev_timer_again (&mytimer); 1207\& ev_timer_again (&mytimer);
913.Ve 1208.Ve
914.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1209.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
915.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1210.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
916.IX Subsection "ev_periodic - to cron or not to cron" 1211.IX Subsection "ev_periodic - to cron or not to cron?"
917Periodic watchers are also timers of a kind, but they are very versatile 1212Periodic watchers are also timers of a kind, but they are very versatile
918(and unfortunately a bit complex). 1213(and unfortunately a bit complex).
919.PP 1214.PP
920Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1215Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
921but on wallclock time (absolute time). You can tell a periodic watcher 1216but on wallclock time (absolute time). You can tell a periodic watcher
922to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1217to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
923periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1218periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
924+ 10.>) and then reset your system clock to the last year, then it will 1219+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
925take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1220take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
926roughly 10 seconds later and of course not if you reset your system time 1221roughly 10 seconds later and of course not if you reset your system time
927again). 1222again).
928.PP 1223.PP
929They can also be used to implement vastly more complex timers, such as 1224They can also be used to implement vastly more complex timers, such as
… …
1010.IX Item "ev_periodic_again (loop, ev_periodic *)" 1305.IX Item "ev_periodic_again (loop, ev_periodic *)"
1011Simply stops and restarts the periodic watcher again. This is only useful 1306Simply stops and restarts the periodic watcher again. This is only useful
1012when you changed some parameters or the reschedule callback would return 1307when you changed some parameters or the reschedule callback would return
1013a different time than the last time it was called (e.g. in a crond like 1308a different time than the last time it was called (e.g. in a crond like
1014program when the crontabs have changed). 1309program when the crontabs have changed).
1310.IP "ev_tstamp interval [read\-write]" 4
1311.IX Item "ev_tstamp interval [read-write]"
1312The current interval value. Can be modified any time, but changes only
1313take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1314called.
1315.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1316.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1317The current reschedule callback, or \f(CW0\fR, if this functionality is
1318switched off. Can be changed any time, but changes only take effect when
1319the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1015.PP 1320.PP
1016Example: call a callback every hour, or, more precisely, whenever the 1321Example: Call a callback every hour, or, more precisely, whenever the
1017system clock is divisible by 3600. The callback invocation times have 1322system clock is divisible by 3600. The callback invocation times have
1018potentially a lot of jittering, but good long-term stability. 1323potentially a lot of jittering, but good long-term stability.
1019.PP 1324.PP
1020.Vb 5 1325.Vb 5
1021\& static void 1326\& static void
… …
1029\& struct ev_periodic hourly_tick; 1334\& struct ev_periodic hourly_tick;
1030\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1335\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1031\& ev_periodic_start (loop, &hourly_tick); 1336\& ev_periodic_start (loop, &hourly_tick);
1032.Ve 1337.Ve
1033.PP 1338.PP
1034Example: the same as above, but use a reschedule callback to do it: 1339Example: The same as above, but use a reschedule callback to do it:
1035.PP 1340.PP
1036.Vb 1 1341.Vb 1
1037\& #include <math.h> 1342\& #include <math.h>
1038.Ve 1343.Ve
1039.PP 1344.PP
… …
1047.PP 1352.PP
1048.Vb 1 1353.Vb 1
1049\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1354\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1050.Ve 1355.Ve
1051.PP 1356.PP
1052Example: call a callback every hour, starting now: 1357Example: Call a callback every hour, starting now:
1053.PP 1358.PP
1054.Vb 4 1359.Vb 4
1055\& struct ev_periodic hourly_tick; 1360\& struct ev_periodic hourly_tick;
1056\& ev_periodic_init (&hourly_tick, clock_cb, 1361\& ev_periodic_init (&hourly_tick, clock_cb,
1057\& fmod (ev_now (loop), 3600.), 3600., 0); 1362\& fmod (ev_now (loop), 3600.), 3600., 0);
1058\& ev_periodic_start (loop, &hourly_tick); 1363\& ev_periodic_start (loop, &hourly_tick);
1059.Ve 1364.Ve
1060.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1365.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
1061.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1366.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1062.IX Subsection "ev_signal - signal me when a signal gets signalled" 1367.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1063Signal watchers will trigger an event when the process receives a specific 1368Signal watchers will trigger an event when the process receives a specific
1064signal one or more times. Even though signals are very asynchronous, libev 1369signal one or more times. Even though signals are very asynchronous, libev
1065will try it's best to deliver signals synchronously, i.e. as part of the 1370will try it's best to deliver signals synchronously, i.e. as part of the
1066normal event processing, like any other event. 1371normal event processing, like any other event.
1067.PP 1372.PP
… …
1077.IP "ev_signal_set (ev_signal *, int signum)" 4 1382.IP "ev_signal_set (ev_signal *, int signum)" 4
1078.IX Item "ev_signal_set (ev_signal *, int signum)" 1383.IX Item "ev_signal_set (ev_signal *, int signum)"
1079.PD 1384.PD
1080Configures the watcher to trigger on the given signal number (usually one 1385Configures the watcher to trigger on the given signal number (usually one
1081of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1386of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1387.IP "int signum [read\-only]" 4
1388.IX Item "int signum [read-only]"
1389The signal the watcher watches out for.
1082.ie n .Sh """ev_child"" \- wait for pid status changes" 1390.ie n .Sh """ev_child"" \- watch out for process status changes"
1083.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1391.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1084.IX Subsection "ev_child - wait for pid status changes" 1392.IX Subsection "ev_child - watch out for process status changes"
1085Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1393Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1086some child status changes (most typically when a child of yours dies). 1394some child status changes (most typically when a child of yours dies).
1087.IP "ev_child_init (ev_child *, callback, int pid)" 4 1395.IP "ev_child_init (ev_child *, callback, int pid)" 4
1088.IX Item "ev_child_init (ev_child *, callback, int pid)" 1396.IX Item "ev_child_init (ev_child *, callback, int pid)"
1089.PD 0 1397.PD 0
… …
1094\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1402\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1095at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1403at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1096the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1404the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1097\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1405\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1098process causing the status change. 1406process causing the status change.
1407.IP "int pid [read\-only]" 4
1408.IX Item "int pid [read-only]"
1409The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1410.IP "int rpid [read\-write]" 4
1411.IX Item "int rpid [read-write]"
1412The process id that detected a status change.
1413.IP "int rstatus [read\-write]" 4
1414.IX Item "int rstatus [read-write]"
1415The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1416\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1099.PP 1417.PP
1100Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1418Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1101.PP 1419.PP
1102.Vb 5 1420.Vb 5
1103\& static void 1421\& static void
1104\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1422\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1105\& { 1423\& {
… …
1110.Vb 3 1428.Vb 3
1111\& struct ev_signal signal_watcher; 1429\& struct ev_signal signal_watcher;
1112\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1430\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1113\& ev_signal_start (loop, &sigint_cb); 1431\& ev_signal_start (loop, &sigint_cb);
1114.Ve 1432.Ve
1433.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1434.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1435.IX Subsection "ev_stat - did the file attributes just change?"
1436This watches a filesystem path for attribute changes. That is, it calls
1437\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1438compared to the last time, invoking the callback if it did.
1439.PP
1440The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1441not exist\*(R" is a status change like any other. The condition \*(L"path does
1442not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1443otherwise always forced to be at least one) and all the other fields of
1444the stat buffer having unspecified contents.
1445.PP
1446The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1447relative and your working directory changes, the behaviour is undefined.
1448.PP
1449Since there is no standard to do this, the portable implementation simply
1450calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1451can specify a recommended polling interval for this case. If you specify
1452a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1453unspecified default\fR value will be used (which you can expect to be around
1454five seconds, although this might change dynamically). Libev will also
1455impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1456usually overkill.
1457.PP
1458This watcher type is not meant for massive numbers of stat watchers,
1459as even with OS-supported change notifications, this can be
1460resource\-intensive.
1461.PP
1462At the time of this writing, only the Linux inotify interface is
1463implemented (implementing kqueue support is left as an exercise for the
1464reader). Inotify will be used to give hints only and should not change the
1465semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1466to fall back to regular polling again even with inotify, but changes are
1467usually detected immediately, and if the file exists there will be no
1468polling.
1469.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1470.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1471.PD 0
1472.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1473.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1474.PD
1475Configures the watcher to wait for status changes of the given
1476\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1477be detected and should normally be specified as \f(CW0\fR to let libev choose
1478a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1479path for as long as the watcher is active.
1480.Sp
1481The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1482relative to the attributes at the time the watcher was started (or the
1483last change was detected).
1484.IP "ev_stat_stat (ev_stat *)" 4
1485.IX Item "ev_stat_stat (ev_stat *)"
1486Updates the stat buffer immediately with new values. If you change the
1487watched path in your callback, you could call this fucntion to avoid
1488detecting this change (while introducing a race condition). Can also be
1489useful simply to find out the new values.
1490.IP "ev_statdata attr [read\-only]" 4
1491.IX Item "ev_statdata attr [read-only]"
1492The most-recently detected attributes of the file. Although the type is of
1493\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1494suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1495was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1496.IP "ev_statdata prev [read\-only]" 4
1497.IX Item "ev_statdata prev [read-only]"
1498The previous attributes of the file. The callback gets invoked whenever
1499\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1500.IP "ev_tstamp interval [read\-only]" 4
1501.IX Item "ev_tstamp interval [read-only]"
1502The specified interval.
1503.IP "const char *path [read\-only]" 4
1504.IX Item "const char *path [read-only]"
1505The filesystem path that is being watched.
1506.PP
1507Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1508.PP
1509.Vb 15
1510\& static void
1511\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1512\& {
1513\& /* /etc/passwd changed in some way */
1514\& if (w->attr.st_nlink)
1515\& {
1516\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1517\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1518\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1519\& }
1520\& else
1521\& /* you shalt not abuse printf for puts */
1522\& puts ("wow, /etc/passwd is not there, expect problems. "
1523\& "if this is windows, they already arrived\en");
1524\& }
1525.Ve
1526.PP
1527.Vb 2
1528\& ...
1529\& ev_stat passwd;
1530.Ve
1531.PP
1532.Vb 2
1533\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1534\& ev_stat_start (loop, &passwd);
1535.Ve
1115.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1536.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1116.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1537.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1117.IX Subsection "ev_idle - when you've got nothing better to do" 1538.IX Subsection "ev_idle - when you've got nothing better to do..."
1118Idle watchers trigger events when there are no other events are pending 1539Idle watchers trigger events when no other events of the same or higher
1119(prepare, check and other idle watchers do not count). That is, as long 1540priority are pending (prepare, check and other idle watchers do not
1120as your process is busy handling sockets or timeouts (or even signals, 1541count).
1121imagine) it will not be triggered. But when your process is idle all idle 1542.PP
1122watchers are being called again and again, once per event loop iteration \- 1543That is, as long as your process is busy handling sockets or timeouts
1544(or even signals, imagine) of the same or higher priority it will not be
1545triggered. But when your process is idle (or only lower-priority watchers
1546are pending), the idle watchers are being called once per event loop
1123until stopped, that is, or your process receives more events and becomes 1547iteration \- until stopped, that is, or your process receives more events
1124busy. 1548and becomes busy again with higher priority stuff.
1125.PP 1549.PP
1126The most noteworthy effect is that as long as any idle watchers are 1550The most noteworthy effect is that as long as any idle watchers are
1127active, the process will not block when waiting for new events. 1551active, the process will not block when waiting for new events.
1128.PP 1552.PP
1129Apart from keeping your process non-blocking (which is a useful 1553Apart from keeping your process non-blocking (which is a useful
… …
1134.IX Item "ev_idle_init (ev_signal *, callback)" 1558.IX Item "ev_idle_init (ev_signal *, callback)"
1135Initialises and configures the idle watcher \- it has no parameters of any 1559Initialises and configures the idle watcher \- it has no parameters of any
1136kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1560kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1137believe me. 1561believe me.
1138.PP 1562.PP
1139Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1563Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1140callback, free it. Alos, use no error checking, as usual. 1564callback, free it. Also, use no error checking, as usual.
1141.PP 1565.PP
1142.Vb 7 1566.Vb 7
1143\& static void 1567\& static void
1144\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1568\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1145\& { 1569\& {
… …
1152.Vb 3 1576.Vb 3
1153\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1577\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1154\& ev_idle_init (idle_watcher, idle_cb); 1578\& ev_idle_init (idle_watcher, idle_cb);
1155\& ev_idle_start (loop, idle_cb); 1579\& ev_idle_start (loop, idle_cb);
1156.Ve 1580.Ve
1157.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1581.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
1158.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1582.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1159.IX Subsection "ev_prepare and ev_check - customise your event loop" 1583.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1160Prepare and check watchers are usually (but not always) used in tandem: 1584Prepare and check watchers are usually (but not always) used in tandem:
1161prepare watchers get invoked before the process blocks and check watchers 1585prepare watchers get invoked before the process blocks and check watchers
1162afterwards. 1586afterwards.
1163.PP 1587.PP
1588You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1589the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1590watchers. Other loops than the current one are fine, however. The
1591rationale behind this is that you do not need to check for recursion in
1592those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1593\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1594called in pairs bracketing the blocking call.
1595.PP
1164Their main purpose is to integrate other event mechanisms into libev. This 1596Their main purpose is to integrate other event mechanisms into libev and
1165could be used, for example, to track variable changes, implement your own 1597their use is somewhat advanced. This could be used, for example, to track
1166watchers, integrate net-snmp or a coroutine library and lots more. 1598variable changes, implement your own watchers, integrate net-snmp or a
1599coroutine library and lots more. They are also occasionally useful if
1600you cache some data and want to flush it before blocking (for example,
1601in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1602watcher).
1167.PP 1603.PP
1168This is done by examining in each prepare call which file descriptors need 1604This is done by examining in each prepare call which file descriptors need
1169to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1605to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1170them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1606them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1171provide just this functionality). Then, in the check watcher you check for 1607provide just this functionality). Then, in the check watcher you check for
… …
1190.PD 1626.PD
1191Initialises and configures the prepare or check watcher \- they have no 1627Initialises and configures the prepare or check watcher \- they have no
1192parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1628parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1193macros, but using them is utterly, utterly and completely pointless. 1629macros, but using them is utterly, utterly and completely pointless.
1194.PP 1630.PP
1195Example: *TODO*. 1631Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1632and a timeout watcher in a prepare handler, as required by libadns, and
1633in a check watcher, destroy them and call into libadns. What follows is
1634pseudo-code only of course:
1635.PP
1636.Vb 2
1637\& static ev_io iow [nfd];
1638\& static ev_timer tw;
1639.Ve
1640.PP
1641.Vb 9
1642\& static void
1643\& io_cb (ev_loop *loop, ev_io *w, int revents)
1644\& {
1645\& // set the relevant poll flags
1646\& // could also call adns_processreadable etc. here
1647\& struct pollfd *fd = (struct pollfd *)w->data;
1648\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1649\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1650\& }
1651.Ve
1652.PP
1653.Vb 8
1654\& // create io watchers for each fd and a timer before blocking
1655\& static void
1656\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1657\& {
1658\& int timeout = 3600000;
1659\& struct pollfd fds [nfd];
1660\& // actual code will need to loop here and realloc etc.
1661\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1662.Ve
1663.PP
1664.Vb 3
1665\& /* the callback is illegal, but won't be called as we stop during check */
1666\& ev_timer_init (&tw, 0, timeout * 1e-3);
1667\& ev_timer_start (loop, &tw);
1668.Ve
1669.PP
1670.Vb 6
1671\& // create on ev_io per pollfd
1672\& for (int i = 0; i < nfd; ++i)
1673\& {
1674\& ev_io_init (iow + i, io_cb, fds [i].fd,
1675\& ((fds [i].events & POLLIN ? EV_READ : 0)
1676\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1677.Ve
1678.PP
1679.Vb 5
1680\& fds [i].revents = 0;
1681\& iow [i].data = fds + i;
1682\& ev_io_start (loop, iow + i);
1683\& }
1684\& }
1685.Ve
1686.PP
1687.Vb 5
1688\& // stop all watchers after blocking
1689\& static void
1690\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1691\& {
1692\& ev_timer_stop (loop, &tw);
1693.Ve
1694.PP
1695.Vb 2
1696\& for (int i = 0; i < nfd; ++i)
1697\& ev_io_stop (loop, iow + i);
1698.Ve
1699.PP
1700.Vb 2
1701\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1702\& }
1703.Ve
1704.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1705.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1706.IX Subsection "ev_embed - when one backend isn't enough..."
1707This is a rather advanced watcher type that lets you embed one event loop
1708into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1709loop, other types of watchers might be handled in a delayed or incorrect
1710fashion and must not be used).
1711.PP
1712There are primarily two reasons you would want that: work around bugs and
1713prioritise I/O.
1714.PP
1715As an example for a bug workaround, the kqueue backend might only support
1716sockets on some platform, so it is unusable as generic backend, but you
1717still want to make use of it because you have many sockets and it scales
1718so nicely. In this case, you would create a kqueue-based loop and embed it
1719into your default loop (which might use e.g. poll). Overall operation will
1720be a bit slower because first libev has to poll and then call kevent, but
1721at least you can use both at what they are best.
1722.PP
1723As for prioritising I/O: rarely you have the case where some fds have
1724to be watched and handled very quickly (with low latency), and even
1725priorities and idle watchers might have too much overhead. In this case
1726you would put all the high priority stuff in one loop and all the rest in
1727a second one, and embed the second one in the first.
1728.PP
1729As long as the watcher is active, the callback will be invoked every time
1730there might be events pending in the embedded loop. The callback must then
1731call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1732their callbacks (you could also start an idle watcher to give the embedded
1733loop strictly lower priority for example). You can also set the callback
1734to \f(CW0\fR, in which case the embed watcher will automatically execute the
1735embedded loop sweep.
1736.PP
1737As long as the watcher is started it will automatically handle events. The
1738callback will be invoked whenever some events have been handled. You can
1739set the callback to \f(CW0\fR to avoid having to specify one if you are not
1740interested in that.
1741.PP
1742Also, there have not currently been made special provisions for forking:
1743when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1744but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1745yourself.
1746.PP
1747Unfortunately, not all backends are embeddable, only the ones returned by
1748\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1749portable one.
1750.PP
1751So when you want to use this feature you will always have to be prepared
1752that you cannot get an embeddable loop. The recommended way to get around
1753this is to have a separate variables for your embeddable loop, try to
1754create it, and if that fails, use the normal loop for everything:
1755.PP
1756.Vb 3
1757\& struct ev_loop *loop_hi = ev_default_init (0);
1758\& struct ev_loop *loop_lo = 0;
1759\& struct ev_embed embed;
1760.Ve
1761.PP
1762.Vb 5
1763\& // see if there is a chance of getting one that works
1764\& // (remember that a flags value of 0 means autodetection)
1765\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1766\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1767\& : 0;
1768.Ve
1769.PP
1770.Vb 8
1771\& // if we got one, then embed it, otherwise default to loop_hi
1772\& if (loop_lo)
1773\& {
1774\& ev_embed_init (&embed, 0, loop_lo);
1775\& ev_embed_start (loop_hi, &embed);
1776\& }
1777\& else
1778\& loop_lo = loop_hi;
1779.Ve
1780.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1781.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1782.PD 0
1783.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1784.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1785.PD
1786Configures the watcher to embed the given loop, which must be
1787embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1788invoked automatically, otherwise it is the responsibility of the callback
1789to invoke it (it will continue to be called until the sweep has been done,
1790if you do not want thta, you need to temporarily stop the embed watcher).
1791.IP "ev_embed_sweep (loop, ev_embed *)" 4
1792.IX Item "ev_embed_sweep (loop, ev_embed *)"
1793Make a single, non-blocking sweep over the embedded loop. This works
1794similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1795apropriate way for embedded loops.
1796.IP "struct ev_loop *loop [read\-only]" 4
1797.IX Item "struct ev_loop *loop [read-only]"
1798The embedded event loop.
1799.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1800.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1801.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1802Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1803whoever is a good citizen cared to tell libev about it by calling
1804\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1805event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1806and only in the child after the fork. If whoever good citizen calling
1807\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1808handlers will be invoked, too, of course.
1809.IP "ev_fork_init (ev_signal *, callback)" 4
1810.IX Item "ev_fork_init (ev_signal *, callback)"
1811Initialises and configures the fork watcher \- it has no parameters of any
1812kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1813believe me.
1196.SH "OTHER FUNCTIONS" 1814.SH "OTHER FUNCTIONS"
1197.IX Header "OTHER FUNCTIONS" 1815.IX Header "OTHER FUNCTIONS"
1198There are some other functions of possible interest. Described. Here. Now. 1816There are some other functions of possible interest. Described. Here. Now.
1199.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1817.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1200.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1818.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1229.Ve 1847.Ve
1230.Sp 1848.Sp
1231.Vb 1 1849.Vb 1
1232\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1850\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1233.Ve 1851.Ve
1234.IP "ev_feed_event (loop, watcher, int events)" 4 1852.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
1235.IX Item "ev_feed_event (loop, watcher, int events)" 1853.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
1236Feeds the given event set into the event loop, as if the specified event 1854Feeds the given event set into the event loop, as if the specified event
1237had happened for the specified watcher (which must be a pointer to an 1855had happened for the specified watcher (which must be a pointer to an
1238initialised but not necessarily started event watcher). 1856initialised but not necessarily started event watcher).
1239.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1857.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
1240.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1858.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
1241Feed an event on the given fd, as if a file descriptor backend detected 1859Feed an event on the given fd, as if a file descriptor backend detected
1242the given events it. 1860the given events it.
1243.IP "ev_feed_signal_event (loop, int signum)" 4 1861.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
1244.IX Item "ev_feed_signal_event (loop, int signum)" 1862.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
1245Feed an event as if the given signal occured (loop must be the default loop!). 1863Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1864loop!).
1246.SH "LIBEVENT EMULATION" 1865.SH "LIBEVENT EMULATION"
1247.IX Header "LIBEVENT EMULATION" 1866.IX Header "LIBEVENT EMULATION"
1248Libev offers a compatibility emulation layer for libevent. It cannot 1867Libev offers a compatibility emulation layer for libevent. It cannot
1249emulate the internals of libevent, so here are some usage hints: 1868emulate the internals of libevent, so here are some usage hints:
1250.IP "* Use it by including <event.h>, as usual." 4 1869.IP "* Use it by including <event.h>, as usual." 4
… …
1261.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1880.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1262.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1881.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1263.PD 1882.PD
1264.SH "\*(C+ SUPPORT" 1883.SH "\*(C+ SUPPORT"
1265.IX Header " SUPPORT" 1884.IX Header " SUPPORT"
1266\&\s-1TBD\s0. 1885Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1886you to use some convinience methods to start/stop watchers and also change
1887the callback model to a model using method callbacks on objects.
1888.PP
1889To use it,
1890.PP
1891.Vb 1
1892\& #include <ev++.h>
1893.Ve
1894.PP
1895(it is not installed by default). This automatically includes \fIev.h\fR
1896and puts all of its definitions (many of them macros) into the global
1897namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1898.PP
1899It should support all the same embedding options as \fIev.h\fR, most notably
1900\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1901.PP
1902Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1903.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1904.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1905.IX Item "ev::READ, ev::WRITE etc."
1906These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1907macros from \fIev.h\fR.
1908.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1909.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1910.IX Item "ev::tstamp, ev::now"
1911Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1912.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
1913.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1914.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1915For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1916the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1917which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1918defines by many implementations.
1919.Sp
1920All of those classes have these methods:
1921.RS 4
1922.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1923.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1924.PD 0
1925.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1926.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1927.IP "ev::TYPE::~TYPE" 4
1928.IX Item "ev::TYPE::~TYPE"
1929.PD
1930The constructor takes a pointer to an object and a method pointer to
1931the event handler callback to call in this class. The constructor calls
1932\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1933before starting it. If you do not specify a loop then the constructor
1934automatically associates the default loop with this watcher.
1935.Sp
1936The destructor automatically stops the watcher if it is active.
1937.IP "w\->set (struct ev_loop *)" 4
1938.IX Item "w->set (struct ev_loop *)"
1939Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1940do this when the watcher is inactive (and not pending either).
1941.IP "w\->set ([args])" 4
1942.IX Item "w->set ([args])"
1943Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1944called at least once. Unlike the C counterpart, an active watcher gets
1945automatically stopped and restarted.
1946.IP "w\->start ()" 4
1947.IX Item "w->start ()"
1948Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1949constructor already takes the loop.
1950.IP "w\->stop ()" 4
1951.IX Item "w->stop ()"
1952Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1953.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1954.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1955.IX Item "w->again () ev::timer, ev::periodic only"
1956For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1957\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1958.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1959.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1960.IX Item "w->sweep () ev::embed only"
1961Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1962.ie n .IP "w\->update () ""ev::stat"" only" 4
1963.el .IP "w\->update () \f(CWev::stat\fR only" 4
1964.IX Item "w->update () ev::stat only"
1965Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1966.RE
1967.RS 4
1968.RE
1969.PP
1970Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1971the constructor.
1972.PP
1973.Vb 4
1974\& class myclass
1975\& {
1976\& ev_io io; void io_cb (ev::io &w, int revents);
1977\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1978.Ve
1979.PP
1980.Vb 2
1981\& myclass ();
1982\& }
1983.Ve
1984.PP
1985.Vb 6
1986\& myclass::myclass (int fd)
1987\& : io (this, &myclass::io_cb),
1988\& idle (this, &myclass::idle_cb)
1989\& {
1990\& io.start (fd, ev::READ);
1991\& }
1992.Ve
1993.SH "MACRO MAGIC"
1994.IX Header "MACRO MAGIC"
1995Libev can be compiled with a variety of options, the most fundemantal is
1996\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
1997callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1998.PP
1999To make it easier to write programs that cope with either variant, the
2000following macros are defined:
2001.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2002.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2003.IX Item "EV_A, EV_A_"
2004This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2005loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2006\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2007.Sp
2008.Vb 3
2009\& ev_unref (EV_A);
2010\& ev_timer_add (EV_A_ watcher);
2011\& ev_loop (EV_A_ 0);
2012.Ve
2013.Sp
2014It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2015which is often provided by the following macro.
2016.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2017.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2018.IX Item "EV_P, EV_P_"
2019This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2020loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2021\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2022.Sp
2023.Vb 2
2024\& // this is how ev_unref is being declared
2025\& static void ev_unref (EV_P);
2026.Ve
2027.Sp
2028.Vb 2
2029\& // this is how you can declare your typical callback
2030\& static void cb (EV_P_ ev_timer *w, int revents)
2031.Ve
2032.Sp
2033It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2034suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2035.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2036.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2037.IX Item "EV_DEFAULT, EV_DEFAULT_"
2038Similar to the other two macros, this gives you the value of the default
2039loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2040.PP
2041Example: Declare and initialise a check watcher, utilising the above
2042macros so it will work regardless of wether multiple loops are supported
2043or not.
2044.PP
2045.Vb 5
2046\& static void
2047\& check_cb (EV_P_ ev_timer *w, int revents)
2048\& {
2049\& ev_check_stop (EV_A_ w);
2050\& }
2051.Ve
2052.PP
2053.Vb 4
2054\& ev_check check;
2055\& ev_check_init (&check, check_cb);
2056\& ev_check_start (EV_DEFAULT_ &check);
2057\& ev_loop (EV_DEFAULT_ 0);
2058.Ve
2059.SH "EMBEDDING"
2060.IX Header "EMBEDDING"
2061Libev can (and often is) directly embedded into host
2062applications. Examples of applications that embed it include the Deliantra
2063Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2064and rxvt\-unicode.
2065.PP
2066The goal is to enable you to just copy the neecssary files into your
2067source directory without having to change even a single line in them, so
2068you can easily upgrade by simply copying (or having a checked-out copy of
2069libev somewhere in your source tree).
2070.Sh "\s-1FILESETS\s0"
2071.IX Subsection "FILESETS"
2072Depending on what features you need you need to include one or more sets of files
2073in your app.
2074.PP
2075\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2076.IX Subsection "CORE EVENT LOOP"
2077.PP
2078To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2079configuration (no autoconf):
2080.PP
2081.Vb 2
2082\& #define EV_STANDALONE 1
2083\& #include "ev.c"
2084.Ve
2085.PP
2086This will automatically include \fIev.h\fR, too, and should be done in a
2087single C source file only to provide the function implementations. To use
2088it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2089done by writing a wrapper around \fIev.h\fR that you can include instead and
2090where you can put other configuration options):
2091.PP
2092.Vb 2
2093\& #define EV_STANDALONE 1
2094\& #include "ev.h"
2095.Ve
2096.PP
2097Both header files and implementation files can be compiled with a \*(C+
2098compiler (at least, thats a stated goal, and breakage will be treated
2099as a bug).
2100.PP
2101You need the following files in your source tree, or in a directory
2102in your include path (e.g. in libev/ when using \-Ilibev):
2103.PP
2104.Vb 4
2105\& ev.h
2106\& ev.c
2107\& ev_vars.h
2108\& ev_wrap.h
2109.Ve
2110.PP
2111.Vb 1
2112\& ev_win32.c required on win32 platforms only
2113.Ve
2114.PP
2115.Vb 5
2116\& ev_select.c only when select backend is enabled (which is enabled by default)
2117\& ev_poll.c only when poll backend is enabled (disabled by default)
2118\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2119\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2120\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2121.Ve
2122.PP
2123\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2124to compile this single file.
2125.PP
2126\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2127.IX Subsection "LIBEVENT COMPATIBILITY API"
2128.PP
2129To include the libevent compatibility \s-1API\s0, also include:
2130.PP
2131.Vb 1
2132\& #include "event.c"
2133.Ve
2134.PP
2135in the file including \fIev.c\fR, and:
2136.PP
2137.Vb 1
2138\& #include "event.h"
2139.Ve
2140.PP
2141in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2142.PP
2143You need the following additional files for this:
2144.PP
2145.Vb 2
2146\& event.h
2147\& event.c
2148.Ve
2149.PP
2150\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2151.IX Subsection "AUTOCONF SUPPORT"
2152.PP
2153Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2154whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2155\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2156include \fIconfig.h\fR and configure itself accordingly.
2157.PP
2158For this of course you need the m4 file:
2159.PP
2160.Vb 1
2161\& libev.m4
2162.Ve
2163.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2164.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2165Libev can be configured via a variety of preprocessor symbols you have to define
2166before including any of its files. The default is not to build for multiplicity
2167and only include the select backend.
2168.IP "\s-1EV_STANDALONE\s0" 4
2169.IX Item "EV_STANDALONE"
2170Must always be \f(CW1\fR if you do not use autoconf configuration, which
2171keeps libev from including \fIconfig.h\fR, and it also defines dummy
2172implementations for some libevent functions (such as logging, which is not
2173supported). It will also not define any of the structs usually found in
2174\&\fIevent.h\fR that are not directly supported by the libev core alone.
2175.IP "\s-1EV_USE_MONOTONIC\s0" 4
2176.IX Item "EV_USE_MONOTONIC"
2177If defined to be \f(CW1\fR, libev will try to detect the availability of the
2178monotonic clock option at both compiletime and runtime. Otherwise no use
2179of the monotonic clock option will be attempted. If you enable this, you
2180usually have to link against librt or something similar. Enabling it when
2181the functionality isn't available is safe, though, althoguh you have
2182to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2183function is hiding in (often \fI\-lrt\fR).
2184.IP "\s-1EV_USE_REALTIME\s0" 4
2185.IX Item "EV_USE_REALTIME"
2186If defined to be \f(CW1\fR, libev will try to detect the availability of the
2187realtime clock option at compiletime (and assume its availability at
2188runtime if successful). Otherwise no use of the realtime clock option will
2189be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2190(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2191in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2192.IP "\s-1EV_USE_SELECT\s0" 4
2193.IX Item "EV_USE_SELECT"
2194If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2195\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2196other method takes over, select will be it. Otherwise the select backend
2197will not be compiled in.
2198.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2199.IX Item "EV_SELECT_USE_FD_SET"
2200If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2201structure. This is useful if libev doesn't compile due to a missing
2202\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2203exotic systems. This usually limits the range of file descriptors to some
2204low limit such as 1024 or might have other limitations (winsocket only
2205allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2206influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2207.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2208.IX Item "EV_SELECT_IS_WINSOCKET"
2209When defined to \f(CW1\fR, the select backend will assume that
2210select/socket/connect etc. don't understand file descriptors but
2211wants osf handles on win32 (this is the case when the select to
2212be used is the winsock select). This means that it will call
2213\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2214it is assumed that all these functions actually work on fds, even
2215on win32. Should not be defined on non\-win32 platforms.
2216.IP "\s-1EV_USE_POLL\s0" 4
2217.IX Item "EV_USE_POLL"
2218If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2219backend. Otherwise it will be enabled on non\-win32 platforms. It
2220takes precedence over select.
2221.IP "\s-1EV_USE_EPOLL\s0" 4
2222.IX Item "EV_USE_EPOLL"
2223If defined to be \f(CW1\fR, libev will compile in support for the Linux
2224\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2225otherwise another method will be used as fallback. This is the
2226preferred backend for GNU/Linux systems.
2227.IP "\s-1EV_USE_KQUEUE\s0" 4
2228.IX Item "EV_USE_KQUEUE"
2229If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2230\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2231otherwise another method will be used as fallback. This is the preferred
2232backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2233supports some types of fds correctly (the only platform we found that
2234supports ptys for example was NetBSD), so kqueue might be compiled in, but
2235not be used unless explicitly requested. The best way to use it is to find
2236out whether kqueue supports your type of fd properly and use an embedded
2237kqueue loop.
2238.IP "\s-1EV_USE_PORT\s0" 4
2239.IX Item "EV_USE_PORT"
2240If defined to be \f(CW1\fR, libev will compile in support for the Solaris
224110 port style backend. Its availability will be detected at runtime,
2242otherwise another method will be used as fallback. This is the preferred
2243backend for Solaris 10 systems.
2244.IP "\s-1EV_USE_DEVPOLL\s0" 4
2245.IX Item "EV_USE_DEVPOLL"
2246reserved for future expansion, works like the \s-1USE\s0 symbols above.
2247.IP "\s-1EV_USE_INOTIFY\s0" 4
2248.IX Item "EV_USE_INOTIFY"
2249If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2250interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2251be detected at runtime.
2252.IP "\s-1EV_H\s0" 4
2253.IX Item "EV_H"
2254The name of the \fIev.h\fR header file used to include it. The default if
2255undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2256can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2257.IP "\s-1EV_CONFIG_H\s0" 4
2258.IX Item "EV_CONFIG_H"
2259If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2260\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2261\&\f(CW\*(C`EV_H\*(C'\fR, above.
2262.IP "\s-1EV_EVENT_H\s0" 4
2263.IX Item "EV_EVENT_H"
2264Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2265of how the \fIevent.h\fR header can be found.
2266.IP "\s-1EV_PROTOTYPES\s0" 4
2267.IX Item "EV_PROTOTYPES"
2268If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2269prototypes, but still define all the structs and other symbols. This is
2270occasionally useful if you want to provide your own wrapper functions
2271around libev functions.
2272.IP "\s-1EV_MULTIPLICITY\s0" 4
2273.IX Item "EV_MULTIPLICITY"
2274If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2275will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2276additional independent event loops. Otherwise there will be no support
2277for multiple event loops and there is no first event loop pointer
2278argument. Instead, all functions act on the single default loop.
2279.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2280.IX Item "EV_PERIODIC_ENABLE"
2281If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2282defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2283code.
2284.IP "\s-1EV_IDLE_ENABLE\s0" 4
2285.IX Item "EV_IDLE_ENABLE"
2286If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2287defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2288code.
2289.IP "\s-1EV_EMBED_ENABLE\s0" 4
2290.IX Item "EV_EMBED_ENABLE"
2291If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2292defined to be \f(CW0\fR, then they are not.
2293.IP "\s-1EV_STAT_ENABLE\s0" 4
2294.IX Item "EV_STAT_ENABLE"
2295If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2296defined to be \f(CW0\fR, then they are not.
2297.IP "\s-1EV_FORK_ENABLE\s0" 4
2298.IX Item "EV_FORK_ENABLE"
2299If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2300defined to be \f(CW0\fR, then they are not.
2301.IP "\s-1EV_MINIMAL\s0" 4
2302.IX Item "EV_MINIMAL"
2303If you need to shave off some kilobytes of code at the expense of some
2304speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2305some inlining decisions, saves roughly 30% codesize of amd64.
2306.IP "\s-1EV_PID_HASHSIZE\s0" 4
2307.IX Item "EV_PID_HASHSIZE"
2308\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2309pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2310than enough. If you need to manage thousands of children you might want to
2311increase this value (\fImust\fR be a power of two).
2312.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2313.IX Item "EV_INOTIFY_HASHSIZE"
2314\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2315inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2316usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2317watchers you might want to increase this value (\fImust\fR be a power of
2318two).
2319.IP "\s-1EV_COMMON\s0" 4
2320.IX Item "EV_COMMON"
2321By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2322this macro to a something else you can include more and other types of
2323members. You have to define it each time you include one of the files,
2324though, and it must be identical each time.
2325.Sp
2326For example, the perl \s-1EV\s0 module uses something like this:
2327.Sp
2328.Vb 3
2329\& #define EV_COMMON \e
2330\& SV *self; /* contains this struct */ \e
2331\& SV *cb_sv, *fh /* note no trailing ";" */
2332.Ve
2333.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2334.IX Item "EV_CB_DECLARE (type)"
2335.PD 0
2336.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2337.IX Item "EV_CB_INVOKE (watcher, revents)"
2338.IP "ev_set_cb (ev, cb)" 4
2339.IX Item "ev_set_cb (ev, cb)"
2340.PD
2341Can be used to change the callback member declaration in each watcher,
2342and the way callbacks are invoked and set. Must expand to a struct member
2343definition and a statement, respectively. See the \fIev.v\fR header file for
2344their default definitions. One possible use for overriding these is to
2345avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2346method calls instead of plain function calls in \*(C+.
2347.Sh "\s-1EXAMPLES\s0"
2348.IX Subsection "EXAMPLES"
2349For a real-world example of a program the includes libev
2350verbatim, you can have a look at the \s-1EV\s0 perl module
2351(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2352the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2353interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2354will be compiled. It is pretty complex because it provides its own header
2355file.
2356.Sp
2357The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2358that everybody includes and which overrides some configure choices:
2359.Sp
2360.Vb 9
2361\& #define EV_MINIMAL 1
2362\& #define EV_USE_POLL 0
2363\& #define EV_MULTIPLICITY 0
2364\& #define EV_PERIODIC_ENABLE 0
2365\& #define EV_STAT_ENABLE 0
2366\& #define EV_FORK_ENABLE 0
2367\& #define EV_CONFIG_H <config.h>
2368\& #define EV_MINPRI 0
2369\& #define EV_MAXPRI 0
2370.Ve
2371.Sp
2372.Vb 1
2373\& #include "ev++.h"
2374.Ve
2375.Sp
2376And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2377.Sp
2378.Vb 2
2379\& #include "ev_cpp.h"
2380\& #include "ev.c"
2381.Ve
2382.SH "COMPLEXITIES"
2383.IX Header "COMPLEXITIES"
2384In this section the complexities of (many of) the algorithms used inside
2385libev will be explained. For complexity discussions about backends see the
2386documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2387.RS 4
2388.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2389.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2390.PD 0
2391.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2392.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2393.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2394.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2395.IP "Stopping check/prepare/idle watchers: O(1)" 4
2396.IX Item "Stopping check/prepare/idle watchers: O(1)"
2397.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2398.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2399.IP "Finding the next timer per loop iteration: O(1)" 4
2400.IX Item "Finding the next timer per loop iteration: O(1)"
2401.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2402.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2403.IP "Activating one watcher: O(1)" 4
2404.IX Item "Activating one watcher: O(1)"
2405.RE
2406.RS 4
2407.PD
1267.SH "AUTHOR" 2408.SH "AUTHOR"
1268.IX Header "AUTHOR" 2409.IX Header "AUTHOR"
1269Marc Lehmann <libev@schmorp.de>. 2410Marc Lehmann <libev@schmorp.de>.

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