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Revision 1.30 by root, Wed Nov 28 11:27:29 2007 UTC

… …
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
138\& #include <ev.h> 138\& #include <ev.h>
139.Ve 139.Ve
140.SH "EXAMPLE PROGRAM"
141.IX Header "EXAMPLE PROGRAM"
142.Vb 1
143\& #include <ev.h>
144.Ve
145.PP
146.Vb 2
147\& ev_io stdin_watcher;
148\& ev_timer timeout_watcher;
149.Ve
150.PP
151.Vb 8
152\& /* called when data readable on stdin */
153\& static void
154\& stdin_cb (EV_P_ struct ev_io *w, int revents)
155\& {
156\& /* puts ("stdin ready"); */
157\& ev_io_stop (EV_A_ w); /* just a syntax example */
158\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
159\& }
160.Ve
161.PP
162.Vb 6
163\& static void
164\& timeout_cb (EV_P_ struct ev_timer *w, int revents)
165\& {
166\& /* puts ("timeout"); */
167\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
168\& }
169.Ve
170.PP
171.Vb 4
172\& int
173\& main (void)
174\& {
175\& struct ev_loop *loop = ev_default_loop (0);
176.Ve
177.PP
178.Vb 3
179\& /* initialise an io watcher, then start it */
180\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
181\& ev_io_start (loop, &stdin_watcher);
182.Ve
183.PP
184.Vb 3
185\& /* simple non-repeating 5.5 second timeout */
186\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187\& ev_timer_start (loop, &timeout_watcher);
188.Ve
189.PP
190.Vb 2
191\& /* loop till timeout or data ready */
192\& ev_loop (loop, 0);
193.Ve
194.PP
195.Vb 2
196\& return 0;
197\& }
198.Ve
140.SH "DESCRIPTION" 199.SH "DESCRIPTION"
141.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
142Libev is an event loop: you register interest in certain events (such as a 201Libev is an event loop: you register interest in certain events (such as a
143file descriptor being readable or a timeout occuring), and it will manage 202file descriptor being readable or a timeout occuring), and it will manage
144these event sources and provide your program with events. 203these event sources and provide your program with events.
… …
151watchers\fR, which are relatively small C structures you initialise with the 210watchers\fR, which are relatively small C structures you initialise with the
152details of the event, and then hand it over to libev by \fIstarting\fR the 211details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 212watcher.
154.SH "FEATURES" 213.SH "FEATURES"
155.IX Header "FEATURES" 214.IX Header "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 215Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the linux-specific \f(CW\*(C`epoll\*(C'\fR, the
157kqueue mechanisms for file descriptor events, relative timers, absolute 216bsd-specific \f(CW\*(C`kqueue\*(C'\fR and the solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 217for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR),
159events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event 218absolute timers with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous
160loop mechanism itself (idle, prepare and check watchers). It also is quite 219signals (\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and
161fast (see this benchmark comparing 220event watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
162it to libevent for example). 221\&\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
222file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
223(\f(CW\*(C`ev_fork\*(C'\fR).
224.PP
225It also is quite fast (see this
226benchmark comparing it to libevent
227for example).
163.SH "CONVENTIONS" 228.SH "CONVENTIONS"
164.IX Header "CONVENTIONS" 229.IX Header "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 230Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 231be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 232various 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 233this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 234loops, 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) 235(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" 236.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 237.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 238Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 239(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 240the beginning of 1970, details are complicated, don't ask). This type is
177called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 241called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178to the double type in C. 242to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
243it, you should treat it as such.
179.SH "GLOBAL FUNCTIONS" 244.SH "GLOBAL FUNCTIONS"
180.IX Header "GLOBAL FUNCTIONS" 245.IX Header "GLOBAL FUNCTIONS"
181These functions can be called anytime, even before initialising the 246These functions can be called anytime, even before initialising the
182library in any way. 247library in any way.
183.IP "ev_tstamp ev_time ()" 4 248.IP "ev_tstamp ev_time ()" 4
… …
199.Sp 264.Sp
200Usually, it's a good idea to terminate if the major versions mismatch, 265Usually, it's a good idea to terminate if the major versions mismatch,
201as this indicates an incompatible change. Minor versions are usually 266as this indicates an incompatible change. Minor versions are usually
202compatible to older versions, so a larger minor version alone is usually 267compatible to older versions, so a larger minor version alone is usually
203not a problem. 268not a problem.
269.Sp
270Example: Make sure we haven't accidentally been linked against the wrong
271version.
272.Sp
273.Vb 3
274\& assert (("libev version mismatch",
275\& ev_version_major () == EV_VERSION_MAJOR
276\& && ev_version_minor () >= EV_VERSION_MINOR));
277.Ve
204.IP "unsigned int ev_supported_backends ()" 4 278.IP "unsigned int ev_supported_backends ()" 4
205.IX Item "unsigned int ev_supported_backends ()" 279.IX Item "unsigned int ev_supported_backends ()"
206Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR 280Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
207value) compiled into this binary of libev (independent of their 281value) compiled into this binary of libev (independent of their
208availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for 282availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
209a description of the set values. 283a description of the set values.
284.Sp
285Example: make sure we have the epoll method, because yeah this is cool and
286a must have and can we have a torrent of it please!!!11
287.Sp
288.Vb 2
289\& assert (("sorry, no epoll, no sex",
290\& ev_supported_backends () & EVBACKEND_EPOLL));
291.Ve
210.IP "unsigned int ev_recommended_backends ()" 4 292.IP "unsigned int ev_recommended_backends ()" 4
211.IX Item "unsigned int ev_recommended_backends ()" 293.IX Item "unsigned int ev_recommended_backends ()"
212Return the set of all backends compiled into this binary of libev and also 294Return the set of all backends compiled into this binary of libev and also
213recommended for this platform. This set is often smaller than the one 295recommended for this platform. This set is often smaller than the one
214returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on 296returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
215most BSDs and will not be autodetected unless you explicitly request it 297most BSDs and will not be autodetected unless you explicitly request it
216(assuming you know what you are doing). This is the set of backends that 298(assuming you know what you are doing). This is the set of backends that
217libev will probe for if you specify no backends explicitly. 299libev will probe for if you specify no backends explicitly.
300.IP "unsigned int ev_embeddable_backends ()" 4
301.IX Item "unsigned int ev_embeddable_backends ()"
302Returns the set of backends that are embeddable in other event loops. This
303is the theoretical, all\-platform, value. To find which backends
304might be supported on the current system, you would need to look at
305\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
306recommended ones.
307.Sp
308See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
218.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 309.IP "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" 4
219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 310.IX Item "ev_set_allocator (void *(*cb)(void *ptr, size_t size))"
220Sets the allocation function to use (the prototype is similar to the 311Sets the allocation function to use (the prototype and semantics are
221realloc C function, the semantics are identical). It is used to allocate 312identical to the realloc C function). It is used to allocate and free
222and free memory (no surprises here). If it returns zero when memory 313memory (no surprises here). If it returns zero when memory needs to be
223needs to be allocated, the library might abort or take some potentially 314allocated, the library might abort or take some potentially destructive
224destructive action. The default is your system realloc function. 315action. The default is your system realloc function.
225.Sp 316.Sp
226You could override this function in high-availability programs to, say, 317You could override this function in high-availability programs to, say,
227free some memory if it cannot allocate memory, to use a special allocator, 318free some memory if it cannot allocate memory, to use a special allocator,
228or even to sleep a while and retry until some memory is available. 319or even to sleep a while and retry until some memory is available.
320.Sp
321Example: Replace the libev allocator with one that waits a bit and then
322retries).
323.Sp
324.Vb 6
325\& static void *
326\& persistent_realloc (void *ptr, size_t size)
327\& {
328\& for (;;)
329\& {
330\& void *newptr = realloc (ptr, size);
331.Ve
332.Sp
333.Vb 2
334\& if (newptr)
335\& return newptr;
336.Ve
337.Sp
338.Vb 3
339\& sleep (60);
340\& }
341\& }
342.Ve
343.Sp
344.Vb 2
345\& ...
346\& ev_set_allocator (persistent_realloc);
347.Ve
229.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 348.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
230.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 349.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
231Set the callback function to call on a retryable syscall error (such 350Set the callback function to call on a retryable syscall error (such
232as failed select, poll, epoll_wait). The message is a printable string 351as failed select, poll, epoll_wait). The message is a printable string
233indicating the system call or subsystem causing the problem. If this 352indicating the system call or subsystem causing the problem. If this
234callback is set, then libev will expect it to remedy the sitution, no 353callback is set, then libev will expect it to remedy the sitution, no
235matter what, when it returns. That is, libev will generally retry the 354matter what, when it returns. That is, libev will generally retry the
236requested operation, or, if the condition doesn't go away, do bad stuff 355requested operation, or, if the condition doesn't go away, do bad stuff
237(such as abort). 356(such as abort).
357.Sp
358Example: This is basically the same thing that libev does internally, too.
359.Sp
360.Vb 6
361\& static void
362\& fatal_error (const char *msg)
363\& {
364\& perror (msg);
365\& abort ();
366\& }
367.Ve
368.Sp
369.Vb 2
370\& ...
371\& ev_set_syserr_cb (fatal_error);
372.Ve
238.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 373.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
239.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 374.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
240An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two 375An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
241types of such loops, the \fIdefault\fR loop, which supports signals and child 376types of such loops, the \fIdefault\fR loop, which supports signals and child
242events, and dynamically created loops which do not. 377events, and dynamically created loops which do not.
… …
376.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 511.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
377Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 512Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
378always distinct from the default loop. Unlike the default loop, it cannot 513always distinct from the default loop. Unlike the default loop, it cannot
379handle signal and child watchers, and attempts to do so will be greeted by 514handle signal and child watchers, and attempts to do so will be greeted by
380undefined behaviour (or a failed assertion if assertions are enabled). 515undefined behaviour (or a failed assertion if assertions are enabled).
516.Sp
517Example: Try to create a event loop that uses epoll and nothing else.
518.Sp
519.Vb 3
520\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
521\& if (!epoller)
522\& fatal ("no epoll found here, maybe it hides under your chair");
523.Ve
381.IP "ev_default_destroy ()" 4 524.IP "ev_default_destroy ()" 4
382.IX Item "ev_default_destroy ()" 525.IX Item "ev_default_destroy ()"
383Destroys the default loop again (frees all memory and kernel state 526Destroys the default loop again (frees all memory and kernel state
384etc.). This stops all registered event watchers (by not touching them in 527etc.). None of the active event watchers will be stopped in the normal
385any way whatsoever, although you cannot rely on this :). 528sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
529responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
530calling this function, or cope with the fact afterwards (which is usually
531the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
532for example).
386.IP "ev_loop_destroy (loop)" 4 533.IP "ev_loop_destroy (loop)" 4
387.IX Item "ev_loop_destroy (loop)" 534.IX Item "ev_loop_destroy (loop)"
388Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 535Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
389earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 536earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
390.IP "ev_default_fork ()" 4 537.IP "ev_default_fork ()" 4
… …
419Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 566Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
420use. 567use.
421.IP "ev_tstamp ev_now (loop)" 4 568.IP "ev_tstamp ev_now (loop)" 4
422.IX Item "ev_tstamp ev_now (loop)" 569.IX Item "ev_tstamp ev_now (loop)"
423Returns the current \*(L"event loop time\*(R", which is the time the event loop 570Returns the current \*(L"event loop time\*(R", which is the time the event loop
424got events and started processing them. This timestamp does not change 571received events and started processing them. This timestamp does not
425as long as callbacks are being processed, and this is also the base time 572change as long as callbacks are being processed, and this is also the base
426used for relative timers. You can treat it as the timestamp of the event 573time used for relative timers. You can treat it as the timestamp of the
427occuring (or more correctly, the mainloop finding out about it). 574event occuring (or more correctly, libev finding out about it).
428.IP "ev_loop (loop, int flags)" 4 575.IP "ev_loop (loop, int flags)" 4
429.IX Item "ev_loop (loop, int flags)" 576.IX Item "ev_loop (loop, int flags)"
430Finally, this is it, the event handler. This function usually is called 577Finally, this is it, the event handler. This function usually is called
431after you initialised all your watchers and you want to start handling 578after you initialised all your watchers and you want to start handling
432events. 579events.
433.Sp 580.Sp
434If the flags argument is specified as \f(CW0\fR, it will not return until 581If the flags argument is specified as \f(CW0\fR, it will not return until
435either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 582either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
583.Sp
584Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
585relying on all watchers to be stopped when deciding when a program has
586finished (especially in interactive programs), but having a program that
587automatically loops as long as it has to and no longer by virtue of
588relying on its watchers stopping correctly is a thing of beauty.
436.Sp 589.Sp
437A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 590A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
438those events and any outstanding ones, but will not block your process in 591those events and any outstanding ones, but will not block your process in
439case there are no events and will return after one iteration of the loop. 592case there are no events and will return after one iteration of the loop.
440.Sp 593.Sp
… …
465\& - Call all queued watchers in reverse order (i.e. check watchers first). 618\& - Call all queued watchers in reverse order (i.e. check watchers first).
466\& Signals and child watchers are implemented as I/O watchers, and will 619\& Signals and child watchers are implemented as I/O watchers, and will
467\& be handled here by queueing them when their watcher gets executed. 620\& be handled here by queueing them when their watcher gets executed.
468\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 621\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
469\& were used, return, otherwise continue with step *. 622\& were used, return, otherwise continue with step *.
623.Ve
624.Sp
625Example: Queue some jobs and then loop until no events are outsanding
626anymore.
627.Sp
628.Vb 4
629\& ... queue jobs here, make sure they register event watchers as long
630\& ... as they still have work to do (even an idle watcher will do..)
631\& ev_loop (my_loop, 0);
632\& ... jobs done. yeah!
470.Ve 633.Ve
471.IP "ev_unloop (loop, how)" 4 634.IP "ev_unloop (loop, how)" 4
472.IX Item "ev_unloop (loop, how)" 635.IX Item "ev_unloop (loop, how)"
473Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 636Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
474has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 637has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
… …
488example, libev itself uses this for its internal signal pipe: It is not 651example, libev itself uses this for its internal signal pipe: It is not
489visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 652visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
490no event watchers registered by it are active. It is also an excellent 653no event watchers registered by it are active. It is also an excellent
491way to do this for generic recurring timers or from within third-party 654way to do this for generic recurring timers or from within third-party
492libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 655libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
656.Sp
657Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
658running when nothing else is active.
659.Sp
660.Vb 4
661\& struct ev_signal exitsig;
662\& ev_signal_init (&exitsig, sig_cb, SIGINT);
663\& ev_signal_start (loop, &exitsig);
664\& evf_unref (loop);
665.Ve
666.Sp
667Example: For some weird reason, unregister the above signal handler again.
668.Sp
669.Vb 2
670\& ev_ref (loop);
671\& ev_signal_stop (loop, &exitsig);
672.Ve
493.SH "ANATOMY OF A WATCHER" 673.SH "ANATOMY OF A WATCHER"
494.IX Header "ANATOMY OF A WATCHER" 674.IX Header "ANATOMY OF A WATCHER"
495A watcher is a structure that you create and register to record your 675A watcher is a structure that you create and register to record your
496interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 676interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
497become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 677become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
533*)\*(C'\fR), and you can stop watching for events at any time by calling the 713*)\*(C'\fR), and you can stop watching for events at any time by calling the
534corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 714corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
535.PP 715.PP
536As long as your watcher is active (has been started but not stopped) you 716As long as your watcher is active (has been started but not stopped) you
537must not touch the values stored in it. Most specifically you must never 717must not touch the values stored in it. Most specifically you must never
538reinitialise it or call its set macro. 718reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
539.PP
540You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
541(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
542callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
543(watcher *)\*(C'\fR macro.
544.PP 719.PP
545Each and every callback receives the event loop pointer as first, the 720Each and every callback receives the event loop pointer as first, the
546registered watcher structure as second, and a bitset of received events as 721registered watcher structure as second, and a bitset of received events as
547third argument. 722third argument.
548.PP 723.PP
… …
573The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 748The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
574.ie n .IP """EV_CHILD""" 4 749.ie n .IP """EV_CHILD""" 4
575.el .IP "\f(CWEV_CHILD\fR" 4 750.el .IP "\f(CWEV_CHILD\fR" 4
576.IX Item "EV_CHILD" 751.IX Item "EV_CHILD"
577The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 752The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
753.ie n .IP """EV_STAT""" 4
754.el .IP "\f(CWEV_STAT\fR" 4
755.IX Item "EV_STAT"
756The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
578.ie n .IP """EV_IDLE""" 4 757.ie n .IP """EV_IDLE""" 4
579.el .IP "\f(CWEV_IDLE\fR" 4 758.el .IP "\f(CWEV_IDLE\fR" 4
580.IX Item "EV_IDLE" 759.IX Item "EV_IDLE"
581The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 760The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
582.ie n .IP """EV_PREPARE""" 4 761.ie n .IP """EV_PREPARE""" 4
… …
592\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 771\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
593received events. Callbacks of both watcher types can start and stop as 772received events. Callbacks of both watcher types can start and stop as
594many watchers as they want, and all of them will be taken into account 773many watchers as they want, and all of them will be taken into account
595(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 774(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
596\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 775\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
776.ie n .IP """EV_EMBED""" 4
777.el .IP "\f(CWEV_EMBED\fR" 4
778.IX Item "EV_EMBED"
779The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
780.ie n .IP """EV_FORK""" 4
781.el .IP "\f(CWEV_FORK\fR" 4
782.IX Item "EV_FORK"
783The event loop has been resumed in the child process after fork (see
784\&\f(CW\*(C`ev_fork\*(C'\fR).
597.ie n .IP """EV_ERROR""" 4 785.ie n .IP """EV_ERROR""" 4
598.el .IP "\f(CWEV_ERROR\fR" 4 786.el .IP "\f(CWEV_ERROR\fR" 4
599.IX Item "EV_ERROR" 787.IX Item "EV_ERROR"
600An unspecified error has occured, the watcher has been stopped. This might 788An unspecified error has occured, the watcher has been stopped. This might
601happen because the watcher could not be properly started because libev 789happen because the watcher could not be properly started because libev
… …
606Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 794Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
607for example it might indicate that a fd is readable or writable, and if 795for example it might indicate that a fd is readable or writable, and if
608your callbacks is well-written it can just attempt the operation and cope 796your callbacks is well-written it can just attempt the operation and cope
609with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 797with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
610programs, though, so beware. 798programs, though, so beware.
799.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
800.IX Subsection "GENERIC WATCHER FUNCTIONS"
801In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
802e.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.
803.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
804.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
805.IX Item "ev_init (ev_TYPE *watcher, callback)"
806This macro initialises the generic portion of a watcher. The contents
807of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
808the generic parts of the watcher are initialised, you \fIneed\fR to call
809the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
810type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
811which rolls both calls into one.
812.Sp
813You can reinitialise a watcher at any time as long as it has been stopped
814(or never started) and there are no pending events outstanding.
815.Sp
816The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
817int revents)\*(C'\fR.
818.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
819.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
820.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
821This macro initialises the type-specific parts of a watcher. You need to
822call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
823call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
824macro on a watcher that is active (it can be pending, however, which is a
825difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
826.Sp
827Although some watcher types do not have type-specific arguments
828(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
829.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
830.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
831.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
832This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
833calls into a single call. This is the most convinient method to initialise
834a watcher. The same limitations apply, of course.
835.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
836.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
837.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
838Starts (activates) the given watcher. Only active watchers will receive
839events. If the watcher is already active nothing will happen.
840.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
841.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
842.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
843Stops the given watcher again (if active) and clears the pending
844status. It is possible that stopped watchers are pending (for example,
845non-repeating timers are being stopped when they become pending), but
846\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
847you want to free or reuse the memory used by the watcher it is therefore a
848good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
849.IP "bool ev_is_active (ev_TYPE *watcher)" 4
850.IX Item "bool ev_is_active (ev_TYPE *watcher)"
851Returns a true value iff the watcher is active (i.e. it has been started
852and not yet been stopped). As long as a watcher is active you must not modify
853it.
854.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
855.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
856Returns a true value iff the watcher is pending, (i.e. it has outstanding
857events but its callback has not yet been invoked). As long as a watcher
858is pending (but not active) you must not call an init function on it (but
859\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
860libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
861.IP "callback ev_cb (ev_TYPE *watcher)" 4
862.IX Item "callback ev_cb (ev_TYPE *watcher)"
863Returns the callback currently set on the watcher.
864.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
865.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
866Change the callback. You can change the callback at virtually any time
867(modulo threads).
611.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 868.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
612.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 869.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
613Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 870Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
614and read at any time, libev will completely ignore it. This can be used 871and read at any time, libev will completely ignore it. This can be used
615to associate arbitrary data with your watcher. If you need more data and 872to associate arbitrary data with your watcher. If you need more data and
… …
636\& struct my_io *w = (struct my_io *)w_; 893\& struct my_io *w = (struct my_io *)w_;
637\& ... 894\& ...
638\& } 895\& }
639.Ve 896.Ve
640.PP 897.PP
641More interesting and less C\-conformant ways of catsing your callback type 898More interesting and less C\-conformant ways of casting your callback type
642have been omitted.... 899instead have been omitted.
900.PP
901Another common scenario is having some data structure with multiple
902watchers:
903.PP
904.Vb 6
905\& struct my_biggy
906\& {
907\& int some_data;
908\& ev_timer t1;
909\& ev_timer t2;
910\& }
911.Ve
912.PP
913In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
914you need to use \f(CW\*(C`offsetof\*(C'\fR:
915.PP
916.Vb 1
917\& #include <stddef.h>
918.Ve
919.PP
920.Vb 6
921\& static void
922\& t1_cb (EV_P_ struct ev_timer *w, int revents)
923\& {
924\& struct my_biggy big = (struct my_biggy *
925\& (((char *)w) - offsetof (struct my_biggy, t1));
926\& }
927.Ve
928.PP
929.Vb 6
930\& static void
931\& t2_cb (EV_P_ struct ev_timer *w, int revents)
932\& {
933\& struct my_biggy big = (struct my_biggy *
934\& (((char *)w) - offsetof (struct my_biggy, t2));
935\& }
936.Ve
643.SH "WATCHER TYPES" 937.SH "WATCHER TYPES"
644.IX Header "WATCHER TYPES" 938.IX Header "WATCHER TYPES"
645This section describes each watcher in detail, but will not repeat 939This section describes each watcher in detail, but will not repeat
646information given in the last section. 940information given in the last section. Any initialisation/set macros,
941functions and members specific to the watcher type are explained.
942.PP
943Members are additionally marked with either \fI[read\-only]\fR, meaning that,
944while the watcher is active, you can look at the member and expect some
945sensible content, but you must not modify it (you can modify it while the
946watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
947means you can expect it to have some sensible content while the watcher
948is active, but you can also modify it. Modifying it may not do something
949sensible or take immediate effect (or do anything at all), but libev will
950not crash or malfunction in any way.
647.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 951.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
648.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 952.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
649.IX Subsection "ev_io - is this file descriptor readable or writable" 953.IX Subsection "ev_io - is this file descriptor readable or writable?"
650I/O watchers check whether a file descriptor is readable or writable 954I/O watchers check whether a file descriptor is readable or writable
651in each iteration of the event loop (This behaviour is called 955in each iteration of the event loop, or, more precisely, when reading
652level-triggering because you keep receiving events as long as the 956would not block the process and writing would at least be able to write
653condition persists. Remember you can stop the watcher if you don't want to 957some data. This behaviour is called level-triggering because you keep
654act on the event and neither want to receive future events). 958receiving events as long as the condition persists. Remember you can stop
959the watcher if you don't want to act on the event and neither want to
960receive future events.
655.PP 961.PP
656In general you can register as many read and/or write event watchers per 962In general you can register as many read and/or write event watchers per
657fd as you want (as long as you don't confuse yourself). Setting all file 963fd as you want (as long as you don't confuse yourself). Setting all file
658descriptors to non-blocking mode is also usually a good idea (but not 964descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing). 965required if you know what you are doing).
660.PP 966.PP
661You have to be careful with dup'ed file descriptors, though. Some backends 967You have to be careful with dup'ed file descriptors, though. Some backends
662(the linux epoll backend is a notable example) cannot handle dup'ed file 968(the linux epoll backend is a notable example) cannot handle dup'ed file
663descriptors correctly if you register interest in two or more fds pointing 969descriptors correctly if you register interest in two or more fds pointing
664to the same underlying file/socket etc. description (that is, they share 970to the same underlying file/socket/etc. description (that is, they share
665the same underlying \*(L"file open\*(R"). 971the same underlying \*(L"file open\*(R").
666.PP 972.PP
667If you must do this, then force the use of a known-to-be-good backend 973If you must do this, then force the use of a known-to-be-good backend
668(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 974(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
669\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 975\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
976.PP
977Another thing you have to watch out for is that it is quite easy to
978receive \*(L"spurious\*(R" readyness notifications, that is your callback might
979be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
980because there is no data. Not only are some backends known to create a
981lot of those (for example solaris ports), it is very easy to get into
982this situation even with a relatively standard program structure. Thus
983it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
984\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
985.PP
986If you cannot run the fd in non-blocking mode (for example you should not
987play around with an Xlib connection), then you have to seperately re-test
988wether a file descriptor is really ready with a known-to-be good interface
989such as poll (fortunately in our Xlib example, Xlib already does this on
990its own, so its quite safe to use).
670.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 991.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
671.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 992.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
672.PD 0 993.PD 0
673.IP "ev_io_set (ev_io *, int fd, int events)" 4 994.IP "ev_io_set (ev_io *, int fd, int events)" 4
674.IX Item "ev_io_set (ev_io *, int fd, int events)" 995.IX Item "ev_io_set (ev_io *, int fd, int events)"
675.PD 996.PD
676Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 997Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
677events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 998rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
678EV_WRITE\*(C'\fR to receive the given events. 999\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
679.Sp 1000.IP "int fd [read\-only]" 4
680Please note that most of the more scalable backend mechanisms (for example 1001.IX Item "int fd [read-only]"
681epoll and solaris ports) can result in spurious readyness notifications 1002The file descriptor being watched.
682for file descriptors, so you practically need to use non-blocking I/O (and 1003.IP "int events [read\-only]" 4
683treat callback invocation as hint only), or retest separately with a safe 1004.IX Item "int events [read-only]"
684interface before doing I/O (XLib can do this), or force the use of either 1005The events being watched.
685\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this 1006.PP
686problem. Also note that it is quite easy to have your callback invoked 1007Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
687when the readyness condition is no longer valid even when employing 1008readable, but only once. Since it is likely line\-buffered, you could
688typical ways of handling events, so its a good idea to use non-blocking 1009attempt to read a whole line in the callback.
689I/O unconditionally. 1010.PP
1011.Vb 6
1012\& static void
1013\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1014\& {
1015\& ev_io_stop (loop, w);
1016\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
1017\& }
1018.Ve
1019.PP
1020.Vb 6
1021\& ...
1022\& struct ev_loop *loop = ev_default_init (0);
1023\& struct ev_io stdin_readable;
1024\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1025\& ev_io_start (loop, &stdin_readable);
1026\& ev_loop (loop, 0);
1027.Ve
690.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1028.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
691.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1029.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
692.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1030.IX Subsection "ev_timer - relative and optionally repeating timeouts"
693Timer watchers are simple relative timers that generate an event after a 1031Timer watchers are simple relative timers that generate an event after a
694given time, and optionally repeating in regular intervals after that. 1032given time, and optionally repeating in regular intervals after that.
695.PP 1033.PP
696The timers are based on real time, that is, if you register an event that 1034The timers are based on real time, that is, if you register an event that
697times out after an hour and you reset your system clock to last years 1035times out after an hour and you reset your system clock to last years
… …
737.Sp 1075.Sp
738If the timer is repeating, either start it if necessary (with the repeat 1076If the timer is repeating, either start it if necessary (with the repeat
739value), or reset the running timer to the repeat value. 1077value), or reset the running timer to the repeat value.
740.Sp 1078.Sp
741This sounds a bit complicated, but here is a useful and typical 1079This sounds a bit complicated, but here is a useful and typical
742example: Imagine you have a tcp connection and you want a so-called idle 1080example: Imagine you have a tcp connection and you want a so-called
743timeout, that is, you want to be called when there have been, say, 60 1081idle timeout, that is, you want to be called when there have been,
744seconds of inactivity on the socket. The easiest way to do this is to 1082say, 60 seconds of inactivity on the socket. The easiest way to do
745configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1083this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling
746time you successfully read or write some data. If you go into an idle 1084\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
747state where you do not expect data to travel on the socket, you can stop 1085you go into an idle state where you do not expect data to travel on the
748the timer, and again will automatically restart it if need be. 1086socket, you can stop the timer, and again will automatically restart it if
1087need be.
1088.Sp
1089You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
1090and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
1091.Sp
1092.Vb 8
1093\& ev_timer_init (timer, callback, 0., 5.);
1094\& ev_timer_again (loop, timer);
1095\& ...
1096\& timer->again = 17.;
1097\& ev_timer_again (loop, timer);
1098\& ...
1099\& timer->again = 10.;
1100\& ev_timer_again (loop, timer);
1101.Ve
1102.Sp
1103This is more efficient then stopping/starting the timer eahc time you want
1104to modify its timeout value.
1105.IP "ev_tstamp repeat [read\-write]" 4
1106.IX Item "ev_tstamp repeat [read-write]"
1107The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1108or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1109which is also when any modifications are taken into account.
1110.PP
1111Example: Create a timer that fires after 60 seconds.
1112.PP
1113.Vb 5
1114\& static void
1115\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1116\& {
1117\& .. one minute over, w is actually stopped right here
1118\& }
1119.Ve
1120.PP
1121.Vb 3
1122\& struct ev_timer mytimer;
1123\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1124\& ev_timer_start (loop, &mytimer);
1125.Ve
1126.PP
1127Example: Create a timeout timer that times out after 10 seconds of
1128inactivity.
1129.PP
1130.Vb 5
1131\& static void
1132\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1133\& {
1134\& .. ten seconds without any activity
1135\& }
1136.Ve
1137.PP
1138.Vb 4
1139\& struct ev_timer mytimer;
1140\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1141\& ev_timer_again (&mytimer); /* start timer */
1142\& ev_loop (loop, 0);
1143.Ve
1144.PP
1145.Vb 3
1146\& // and in some piece of code that gets executed on any "activity":
1147\& // reset the timeout to start ticking again at 10 seconds
1148\& ev_timer_again (&mytimer);
1149.Ve
749.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1150.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
750.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1151.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
751.IX Subsection "ev_periodic - to cron or not to cron" 1152.IX Subsection "ev_periodic - to cron or not to cron?"
752Periodic watchers are also timers of a kind, but they are very versatile 1153Periodic watchers are also timers of a kind, but they are very versatile
753(and unfortunately a bit complex). 1154(and unfortunately a bit complex).
754.PP 1155.PP
755Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1156Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
756but on wallclock time (absolute time). You can tell a periodic watcher 1157but on wallclock time (absolute time). You can tell a periodic watcher
757to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1158to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
758periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1159periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
759+ 10.>) and then reset your system clock to the last year, then it will 1160+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
760take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1161take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
761roughly 10 seconds later and of course not if you reset your system time 1162roughly 10 seconds later and of course not if you reset your system time
762again). 1163again).
763.PP 1164.PP
764They can also be used to implement vastly more complex timers, such as 1165They can also be used to implement vastly more complex timers, such as
… …
845.IX Item "ev_periodic_again (loop, ev_periodic *)" 1246.IX Item "ev_periodic_again (loop, ev_periodic *)"
846Simply stops and restarts the periodic watcher again. This is only useful 1247Simply stops and restarts the periodic watcher again. This is only useful
847when you changed some parameters or the reschedule callback would return 1248when you changed some parameters or the reschedule callback would return
848a different time than the last time it was called (e.g. in a crond like 1249a different time than the last time it was called (e.g. in a crond like
849program when the crontabs have changed). 1250program when the crontabs have changed).
1251.IP "ev_tstamp interval [read\-write]" 4
1252.IX Item "ev_tstamp interval [read-write]"
1253The current interval value. Can be modified any time, but changes only
1254take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1255called.
1256.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1257.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1258The current reschedule callback, or \f(CW0\fR, if this functionality is
1259switched off. Can be changed any time, but changes only take effect when
1260the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1261.PP
1262Example: Call a callback every hour, or, more precisely, whenever the
1263system clock is divisible by 3600. The callback invocation times have
1264potentially a lot of jittering, but good long-term stability.
1265.PP
1266.Vb 5
1267\& static void
1268\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1269\& {
1270\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1271\& }
1272.Ve
1273.PP
1274.Vb 3
1275\& struct ev_periodic hourly_tick;
1276\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1277\& ev_periodic_start (loop, &hourly_tick);
1278.Ve
1279.PP
1280Example: The same as above, but use a reschedule callback to do it:
1281.PP
1282.Vb 1
1283\& #include <math.h>
1284.Ve
1285.PP
1286.Vb 5
1287\& static ev_tstamp
1288\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1289\& {
1290\& return fmod (now, 3600.) + 3600.;
1291\& }
1292.Ve
1293.PP
1294.Vb 1
1295\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1296.Ve
1297.PP
1298Example: Call a callback every hour, starting now:
1299.PP
1300.Vb 4
1301\& struct ev_periodic hourly_tick;
1302\& ev_periodic_init (&hourly_tick, clock_cb,
1303\& fmod (ev_now (loop), 3600.), 3600., 0);
1304\& ev_periodic_start (loop, &hourly_tick);
1305.Ve
850.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1306.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
851.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1307.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
852.IX Subsection "ev_signal - signal me when a signal gets signalled" 1308.IX Subsection "ev_signal - signal me when a signal gets signalled!"
853Signal watchers will trigger an event when the process receives a specific 1309Signal watchers will trigger an event when the process receives a specific
854signal one or more times. Even though signals are very asynchronous, libev 1310signal one or more times. Even though signals are very asynchronous, libev
855will try it's best to deliver signals synchronously, i.e. as part of the 1311will try it's best to deliver signals synchronously, i.e. as part of the
856normal event processing, like any other event. 1312normal event processing, like any other event.
857.PP 1313.PP
… …
867.IP "ev_signal_set (ev_signal *, int signum)" 4 1323.IP "ev_signal_set (ev_signal *, int signum)" 4
868.IX Item "ev_signal_set (ev_signal *, int signum)" 1324.IX Item "ev_signal_set (ev_signal *, int signum)"
869.PD 1325.PD
870Configures the watcher to trigger on the given signal number (usually one 1326Configures the watcher to trigger on the given signal number (usually one
871of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1327of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1328.IP "int signum [read\-only]" 4
1329.IX Item "int signum [read-only]"
1330The signal the watcher watches out for.
872.ie n .Sh """ev_child"" \- wait for pid status changes" 1331.ie n .Sh """ev_child"" \- watch out for process status changes"
873.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1332.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
874.IX Subsection "ev_child - wait for pid status changes" 1333.IX Subsection "ev_child - watch out for process status changes"
875Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1334Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
876some child status changes (most typically when a child of yours dies). 1335some child status changes (most typically when a child of yours dies).
877.IP "ev_child_init (ev_child *, callback, int pid)" 4 1336.IP "ev_child_init (ev_child *, callback, int pid)" 4
878.IX Item "ev_child_init (ev_child *, callback, int pid)" 1337.IX Item "ev_child_init (ev_child *, callback, int pid)"
879.PD 0 1338.PD 0
… …
884\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1343\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
885at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1344at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
886the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1345the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
887\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1346\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
888process causing the status change. 1347process causing the status change.
1348.IP "int pid [read\-only]" 4
1349.IX Item "int pid [read-only]"
1350The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1351.IP "int rpid [read\-write]" 4
1352.IX Item "int rpid [read-write]"
1353The process id that detected a status change.
1354.IP "int rstatus [read\-write]" 4
1355.IX Item "int rstatus [read-write]"
1356The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1357\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1358.PP
1359Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1360.PP
1361.Vb 5
1362\& static void
1363\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1364\& {
1365\& ev_unloop (loop, EVUNLOOP_ALL);
1366\& }
1367.Ve
1368.PP
1369.Vb 3
1370\& struct ev_signal signal_watcher;
1371\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1372\& ev_signal_start (loop, &sigint_cb);
1373.Ve
1374.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1375.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1376.IX Subsection "ev_stat - did the file attributes just change?"
1377This watches a filesystem path for attribute changes. That is, it calls
1378\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1379compared to the last time, invoking the callback if it did.
1380.PP
1381The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1382not exist\*(R" is a status change like any other. The condition \*(L"path does
1383not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1384otherwise always forced to be at least one) and all the other fields of
1385the stat buffer having unspecified contents.
1386.PP
1387Since there is no standard to do this, the portable implementation simply
1388calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1389can specify a recommended polling interval for this case. If you specify
1390a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1391unspecified default\fR value will be used (which you can expect to be around
1392five seconds, although this might change dynamically). Libev will also
1393impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1394usually overkill.
1395.PP
1396This watcher type is not meant for massive numbers of stat watchers,
1397as even with OS-supported change notifications, this can be
1398resource\-intensive.
1399.PP
1400At the time of this writing, only the Linux inotify interface is
1401implemented (implementing kqueue support is left as an exercise for the
1402reader). Inotify will be used to give hints only and should not change the
1403semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1404to fall back to regular polling again even with inotify, but changes are
1405usually detected immediately, and if the file exists there will be no
1406polling.
1407.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1408.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1409.PD 0
1410.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1411.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1412.PD
1413Configures the watcher to wait for status changes of the given
1414\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1415be detected and should normally be specified as \f(CW0\fR to let libev choose
1416a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1417path for as long as the watcher is active.
1418.Sp
1419The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1420relative to the attributes at the time the watcher was started (or the
1421last change was detected).
1422.IP "ev_stat_stat (ev_stat *)" 4
1423.IX Item "ev_stat_stat (ev_stat *)"
1424Updates the stat buffer immediately with new values. If you change the
1425watched path in your callback, you could call this fucntion to avoid
1426detecting this change (while introducing a race condition). Can also be
1427useful simply to find out the new values.
1428.IP "ev_statdata attr [read\-only]" 4
1429.IX Item "ev_statdata attr [read-only]"
1430The most-recently detected attributes of the file. Although the type is of
1431\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1432suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1433was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1434.IP "ev_statdata prev [read\-only]" 4
1435.IX Item "ev_statdata prev [read-only]"
1436The previous attributes of the file. The callback gets invoked whenever
1437\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1438.IP "ev_tstamp interval [read\-only]" 4
1439.IX Item "ev_tstamp interval [read-only]"
1440The specified interval.
1441.IP "const char *path [read\-only]" 4
1442.IX Item "const char *path [read-only]"
1443The filesystem path that is being watched.
1444.PP
1445Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1446.PP
1447.Vb 15
1448\& static void
1449\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1450\& {
1451\& /* /etc/passwd changed in some way */
1452\& if (w->attr.st_nlink)
1453\& {
1454\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1455\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1456\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1457\& }
1458\& else
1459\& /* you shalt not abuse printf for puts */
1460\& puts ("wow, /etc/passwd is not there, expect problems. "
1461\& "if this is windows, they already arrived\en");
1462\& }
1463.Ve
1464.PP
1465.Vb 2
1466\& ...
1467\& ev_stat passwd;
1468.Ve
1469.PP
1470.Vb 2
1471\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1472\& ev_stat_start (loop, &passwd);
1473.Ve
889.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1474.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
890.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1475.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
891.IX Subsection "ev_idle - when you've got nothing better to do" 1476.IX Subsection "ev_idle - when you've got nothing better to do..."
892Idle watchers trigger events when there are no other events are pending 1477Idle watchers trigger events when there are no other events are pending
893(prepare, check and other idle watchers do not count). That is, as long 1478(prepare, check and other idle watchers do not count). That is, as long
894as your process is busy handling sockets or timeouts (or even signals, 1479as your process is busy handling sockets or timeouts (or even signals,
895imagine) it will not be triggered. But when your process is idle all idle 1480imagine) it will not be triggered. But when your process is idle all idle
896watchers are being called again and again, once per event loop iteration \- 1481watchers are being called again and again, once per event loop iteration \-
… …
907.IP "ev_idle_init (ev_signal *, callback)" 4 1492.IP "ev_idle_init (ev_signal *, callback)" 4
908.IX Item "ev_idle_init (ev_signal *, callback)" 1493.IX Item "ev_idle_init (ev_signal *, callback)"
909Initialises and configures the idle watcher \- it has no parameters of any 1494Initialises and configures the idle watcher \- it has no parameters of any
910kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1495kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
911believe me. 1496believe me.
1497.PP
1498Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1499callback, free it. Also, use no error checking, as usual.
1500.PP
1501.Vb 7
1502\& static void
1503\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1504\& {
1505\& free (w);
1506\& // now do something you wanted to do when the program has
1507\& // no longer asnything immediate to do.
1508\& }
1509.Ve
1510.PP
1511.Vb 3
1512\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1513\& ev_idle_init (idle_watcher, idle_cb);
1514\& ev_idle_start (loop, idle_cb);
1515.Ve
912.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1516.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
913.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1517.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
914.IX Subsection "ev_prepare and ev_check - customise your event loop" 1518.IX Subsection "ev_prepare and ev_check - customise your event loop!"
915Prepare and check watchers are usually (but not always) used in tandem: 1519Prepare and check watchers are usually (but not always) used in tandem:
916prepare watchers get invoked before the process blocks and check watchers 1520prepare watchers get invoked before the process blocks and check watchers
917afterwards. 1521afterwards.
918.PP 1522.PP
1523You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1524the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1525watchers. Other loops than the current one are fine, however. The
1526rationale behind this is that you do not need to check for recursion in
1527those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1528\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1529called in pairs bracketing the blocking call.
1530.PP
919Their main purpose is to integrate other event mechanisms into libev. This 1531Their main purpose is to integrate other event mechanisms into libev and
920could be used, for example, to track variable changes, implement your own 1532their use is somewhat advanced. This could be used, for example, to track
921watchers, integrate net-snmp or a coroutine library and lots more. 1533variable changes, implement your own watchers, integrate net-snmp or a
1534coroutine library and lots more. They are also occasionally useful if
1535you cache some data and want to flush it before blocking (for example,
1536in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1537watcher).
922.PP 1538.PP
923This is done by examining in each prepare call which file descriptors need 1539This is done by examining in each prepare call which file descriptors need
924to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1540to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
925them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1541them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
926provide just this functionality). Then, in the check watcher you check for 1542provide just this functionality). Then, in the check watcher you check for
… …
944.IX Item "ev_check_init (ev_check *, callback)" 1560.IX Item "ev_check_init (ev_check *, callback)"
945.PD 1561.PD
946Initialises and configures the prepare or check watcher \- they have no 1562Initialises and configures the prepare or check watcher \- they have no
947parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1563parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
948macros, but using them is utterly, utterly and completely pointless. 1564macros, but using them is utterly, utterly and completely pointless.
1565.PP
1566Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1567and a timeout watcher in a prepare handler, as required by libadns, and
1568in a check watcher, destroy them and call into libadns. What follows is
1569pseudo-code only of course:
1570.PP
1571.Vb 2
1572\& static ev_io iow [nfd];
1573\& static ev_timer tw;
1574.Ve
1575.PP
1576.Vb 9
1577\& static void
1578\& io_cb (ev_loop *loop, ev_io *w, int revents)
1579\& {
1580\& // set the relevant poll flags
1581\& // could also call adns_processreadable etc. here
1582\& struct pollfd *fd = (struct pollfd *)w->data;
1583\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1584\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1585\& }
1586.Ve
1587.PP
1588.Vb 7
1589\& // create io watchers for each fd and a timer before blocking
1590\& static void
1591\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1592\& {
1593\& int timeout = 3600000;truct pollfd fds [nfd];
1594\& // actual code will need to loop here and realloc etc.
1595\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1596.Ve
1597.PP
1598.Vb 3
1599\& /* the callback is illegal, but won't be called as we stop during check */
1600\& ev_timer_init (&tw, 0, timeout * 1e-3);
1601\& ev_timer_start (loop, &tw);
1602.Ve
1603.PP
1604.Vb 6
1605\& // create on ev_io per pollfd
1606\& for (int i = 0; i < nfd; ++i)
1607\& {
1608\& ev_io_init (iow + i, io_cb, fds [i].fd,
1609\& ((fds [i].events & POLLIN ? EV_READ : 0)
1610\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1611.Ve
1612.PP
1613.Vb 5
1614\& fds [i].revents = 0;
1615\& iow [i].data = fds + i;
1616\& ev_io_start (loop, iow + i);
1617\& }
1618\& }
1619.Ve
1620.PP
1621.Vb 5
1622\& // stop all watchers after blocking
1623\& static void
1624\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1625\& {
1626\& ev_timer_stop (loop, &tw);
1627.Ve
1628.PP
1629.Vb 2
1630\& for (int i = 0; i < nfd; ++i)
1631\& ev_io_stop (loop, iow + i);
1632.Ve
1633.PP
1634.Vb 2
1635\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1636\& }
1637.Ve
1638.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1639.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1640.IX Subsection "ev_embed - when one backend isn't enough..."
1641This is a rather advanced watcher type that lets you embed one event loop
1642into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1643loop, other types of watchers might be handled in a delayed or incorrect
1644fashion and must not be used).
1645.PP
1646There are primarily two reasons you would want that: work around bugs and
1647prioritise I/O.
1648.PP
1649As an example for a bug workaround, the kqueue backend might only support
1650sockets on some platform, so it is unusable as generic backend, but you
1651still want to make use of it because you have many sockets and it scales
1652so nicely. In this case, you would create a kqueue-based loop and embed it
1653into your default loop (which might use e.g. poll). Overall operation will
1654be a bit slower because first libev has to poll and then call kevent, but
1655at least you can use both at what they are best.
1656.PP
1657As for prioritising I/O: rarely you have the case where some fds have
1658to be watched and handled very quickly (with low latency), and even
1659priorities and idle watchers might have too much overhead. In this case
1660you would put all the high priority stuff in one loop and all the rest in
1661a second one, and embed the second one in the first.
1662.PP
1663As long as the watcher is active, the callback will be invoked every time
1664there might be events pending in the embedded loop. The callback must then
1665call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1666their callbacks (you could also start an idle watcher to give the embedded
1667loop strictly lower priority for example). You can also set the callback
1668to \f(CW0\fR, in which case the embed watcher will automatically execute the
1669embedded loop sweep.
1670.PP
1671As long as the watcher is started it will automatically handle events. The
1672callback will be invoked whenever some events have been handled. You can
1673set the callback to \f(CW0\fR to avoid having to specify one if you are not
1674interested in that.
1675.PP
1676Also, there have not currently been made special provisions for forking:
1677when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1678but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1679yourself.
1680.PP
1681Unfortunately, not all backends are embeddable, only the ones returned by
1682\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1683portable one.
1684.PP
1685So when you want to use this feature you will always have to be prepared
1686that you cannot get an embeddable loop. The recommended way to get around
1687this is to have a separate variables for your embeddable loop, try to
1688create it, and if that fails, use the normal loop for everything:
1689.PP
1690.Vb 3
1691\& struct ev_loop *loop_hi = ev_default_init (0);
1692\& struct ev_loop *loop_lo = 0;
1693\& struct ev_embed embed;
1694.Ve
1695.PP
1696.Vb 5
1697\& // see if there is a chance of getting one that works
1698\& // (remember that a flags value of 0 means autodetection)
1699\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1700\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1701\& : 0;
1702.Ve
1703.PP
1704.Vb 8
1705\& // if we got one, then embed it, otherwise default to loop_hi
1706\& if (loop_lo)
1707\& {
1708\& ev_embed_init (&embed, 0, loop_lo);
1709\& ev_embed_start (loop_hi, &embed);
1710\& }
1711\& else
1712\& loop_lo = loop_hi;
1713.Ve
1714.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1715.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1716.PD 0
1717.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1718.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1719.PD
1720Configures the watcher to embed the given loop, which must be
1721embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1722invoked automatically, otherwise it is the responsibility of the callback
1723to invoke it (it will continue to be called until the sweep has been done,
1724if you do not want thta, you need to temporarily stop the embed watcher).
1725.IP "ev_embed_sweep (loop, ev_embed *)" 4
1726.IX Item "ev_embed_sweep (loop, ev_embed *)"
1727Make a single, non-blocking sweep over the embedded loop. This works
1728similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1729apropriate way for embedded loops.
1730.IP "struct ev_loop *loop [read\-only]" 4
1731.IX Item "struct ev_loop *loop [read-only]"
1732The embedded event loop.
1733.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1734.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1735.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1736Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1737whoever is a good citizen cared to tell libev about it by calling
1738\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1739event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1740and only in the child after the fork. If whoever good citizen calling
1741\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1742handlers will be invoked, too, of course.
1743.IP "ev_fork_init (ev_signal *, callback)" 4
1744.IX Item "ev_fork_init (ev_signal *, callback)"
1745Initialises and configures the fork watcher \- it has no parameters of any
1746kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1747believe me.
949.SH "OTHER FUNCTIONS" 1748.SH "OTHER FUNCTIONS"
950.IX Header "OTHER FUNCTIONS" 1749.IX Header "OTHER FUNCTIONS"
951There are some other functions of possible interest. Described. Here. Now. 1750There are some other functions of possible interest. Described. Here. Now.
952.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1751.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
953.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1752.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
982.Ve 1781.Ve
983.Sp 1782.Sp
984.Vb 1 1783.Vb 1
985\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1784\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
986.Ve 1785.Ve
987.IP "ev_feed_event (loop, watcher, int events)" 4 1786.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
988.IX Item "ev_feed_event (loop, watcher, int events)" 1787.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
989Feeds the given event set into the event loop, as if the specified event 1788Feeds the given event set into the event loop, as if the specified event
990had happened for the specified watcher (which must be a pointer to an 1789had happened for the specified watcher (which must be a pointer to an
991initialised but not necessarily started event watcher). 1790initialised but not necessarily started event watcher).
992.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1791.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
993.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1792.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
994Feed an event on the given fd, as if a file descriptor backend detected 1793Feed an event on the given fd, as if a file descriptor backend detected
995the given events it. 1794the given events it.
996.IP "ev_feed_signal_event (loop, int signum)" 4 1795.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
997.IX Item "ev_feed_signal_event (loop, int signum)" 1796.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
998Feed an event as if the given signal occured (loop must be the default loop!). 1797Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1798loop!).
999.SH "LIBEVENT EMULATION" 1799.SH "LIBEVENT EMULATION"
1000.IX Header "LIBEVENT EMULATION" 1800.IX Header "LIBEVENT EMULATION"
1001Libev offers a compatibility emulation layer for libevent. It cannot 1801Libev offers a compatibility emulation layer for libevent. It cannot
1002emulate the internals of libevent, so here are some usage hints: 1802emulate the internals of libevent, so here are some usage hints:
1003.IP "* Use it by including <event.h>, as usual." 4 1803.IP "* Use it by including <event.h>, as usual." 4
… …
1014.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1814.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1015.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1815.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1016.PD 1816.PD
1017.SH "\*(C+ SUPPORT" 1817.SH "\*(C+ SUPPORT"
1018.IX Header " SUPPORT" 1818.IX Header " SUPPORT"
1019\&\s-1TBD\s0. 1819Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1820you to use some convinience methods to start/stop watchers and also change
1821the callback model to a model using method callbacks on objects.
1822.PP
1823To use it,
1824.PP
1825.Vb 1
1826\& #include <ev++.h>
1827.Ve
1828.PP
1829(it is not installed by default). This automatically includes \fIev.h\fR
1830and puts all of its definitions (many of them macros) into the global
1831namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1832.PP
1833It should support all the same embedding options as \fIev.h\fR, most notably
1834\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1835.PP
1836Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1837.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1838.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1839.IX Item "ev::READ, ev::WRITE etc."
1840These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1841macros from \fIev.h\fR.
1842.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1843.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1844.IX Item "ev::tstamp, ev::now"
1845Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1846.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
1847.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1848.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1849For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1850the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1851which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1852defines by many implementations.
1853.Sp
1854All of those classes have these methods:
1855.RS 4
1856.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1857.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1858.PD 0
1859.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1860.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1861.IP "ev::TYPE::~TYPE" 4
1862.IX Item "ev::TYPE::~TYPE"
1863.PD
1864The constructor takes a pointer to an object and a method pointer to
1865the event handler callback to call in this class. The constructor calls
1866\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1867before starting it. If you do not specify a loop then the constructor
1868automatically associates the default loop with this watcher.
1869.Sp
1870The destructor automatically stops the watcher if it is active.
1871.IP "w\->set (struct ev_loop *)" 4
1872.IX Item "w->set (struct ev_loop *)"
1873Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1874do this when the watcher is inactive (and not pending either).
1875.IP "w\->set ([args])" 4
1876.IX Item "w->set ([args])"
1877Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1878called at least once. Unlike the C counterpart, an active watcher gets
1879automatically stopped and restarted.
1880.IP "w\->start ()" 4
1881.IX Item "w->start ()"
1882Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1883constructor already takes the loop.
1884.IP "w\->stop ()" 4
1885.IX Item "w->stop ()"
1886Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1887.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1888.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1889.IX Item "w->again () ev::timer, ev::periodic only"
1890For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1891\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1892.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1893.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1894.IX Item "w->sweep () ev::embed only"
1895Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1896.ie n .IP "w\->update () ""ev::stat"" only" 4
1897.el .IP "w\->update () \f(CWev::stat\fR only" 4
1898.IX Item "w->update () ev::stat only"
1899Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1900.RE
1901.RS 4
1902.RE
1903.PP
1904Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1905the constructor.
1906.PP
1907.Vb 4
1908\& class myclass
1909\& {
1910\& ev_io io; void io_cb (ev::io &w, int revents);
1911\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1912.Ve
1913.PP
1914.Vb 2
1915\& myclass ();
1916\& }
1917.Ve
1918.PP
1919.Vb 6
1920\& myclass::myclass (int fd)
1921\& : io (this, &myclass::io_cb),
1922\& idle (this, &myclass::idle_cb)
1923\& {
1924\& io.start (fd, ev::READ);
1925\& }
1926.Ve
1927.SH "MACRO MAGIC"
1928.IX Header "MACRO MAGIC"
1929Libev can be compiled with a variety of options, the most fundemantal is
1930\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
1931callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1932.PP
1933To make it easier to write programs that cope with either variant, the
1934following macros are defined:
1935.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
1936.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
1937.IX Item "EV_A, EV_A_"
1938This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
1939loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
1940\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
1941.Sp
1942.Vb 3
1943\& ev_unref (EV_A);
1944\& ev_timer_add (EV_A_ watcher);
1945\& ev_loop (EV_A_ 0);
1946.Ve
1947.Sp
1948It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
1949which is often provided by the following macro.
1950.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
1951.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
1952.IX Item "EV_P, EV_P_"
1953This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
1954loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
1955\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
1956.Sp
1957.Vb 2
1958\& // this is how ev_unref is being declared
1959\& static void ev_unref (EV_P);
1960.Ve
1961.Sp
1962.Vb 2
1963\& // this is how you can declare your typical callback
1964\& static void cb (EV_P_ ev_timer *w, int revents)
1965.Ve
1966.Sp
1967It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
1968suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
1969.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
1970.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
1971.IX Item "EV_DEFAULT, EV_DEFAULT_"
1972Similar to the other two macros, this gives you the value of the default
1973loop, if multiple loops are supported (\*(L"ev loop default\*(R").
1974.PP
1975Example: Declare and initialise a check watcher, working regardless of
1976wether multiple loops are supported or not.
1977.PP
1978.Vb 5
1979\& static void
1980\& check_cb (EV_P_ ev_timer *w, int revents)
1981\& {
1982\& ev_check_stop (EV_A_ w);
1983\& }
1984.Ve
1985.PP
1986.Vb 4
1987\& ev_check check;
1988\& ev_check_init (&check, check_cb);
1989\& ev_check_start (EV_DEFAULT_ &check);
1990\& ev_loop (EV_DEFAULT_ 0);
1991.Ve
1992.SH "EMBEDDING"
1993.IX Header "EMBEDDING"
1994Libev can (and often is) directly embedded into host
1995applications. Examples of applications that embed it include the Deliantra
1996Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1997and rxvt\-unicode.
1998.PP
1999The goal is to enable you to just copy the neecssary files into your
2000source directory without having to change even a single line in them, so
2001you can easily upgrade by simply copying (or having a checked-out copy of
2002libev somewhere in your source tree).
2003.Sh "\s-1FILESETS\s0"
2004.IX Subsection "FILESETS"
2005Depending on what features you need you need to include one or more sets of files
2006in your app.
2007.PP
2008\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2009.IX Subsection "CORE EVENT LOOP"
2010.PP
2011To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2012configuration (no autoconf):
2013.PP
2014.Vb 2
2015\& #define EV_STANDALONE 1
2016\& #include "ev.c"
2017.Ve
2018.PP
2019This will automatically include \fIev.h\fR, too, and should be done in a
2020single C source file only to provide the function implementations. To use
2021it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2022done by writing a wrapper around \fIev.h\fR that you can include instead and
2023where you can put other configuration options):
2024.PP
2025.Vb 2
2026\& #define EV_STANDALONE 1
2027\& #include "ev.h"
2028.Ve
2029.PP
2030Both header files and implementation files can be compiled with a \*(C+
2031compiler (at least, thats a stated goal, and breakage will be treated
2032as a bug).
2033.PP
2034You need the following files in your source tree, or in a directory
2035in your include path (e.g. in libev/ when using \-Ilibev):
2036.PP
2037.Vb 4
2038\& ev.h
2039\& ev.c
2040\& ev_vars.h
2041\& ev_wrap.h
2042.Ve
2043.PP
2044.Vb 1
2045\& ev_win32.c required on win32 platforms only
2046.Ve
2047.PP
2048.Vb 5
2049\& ev_select.c only when select backend is enabled (which is by default)
2050\& ev_poll.c only when poll backend is enabled (disabled by default)
2051\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2052\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2053\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2054.Ve
2055.PP
2056\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2057to compile this single file.
2058.PP
2059\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2060.IX Subsection "LIBEVENT COMPATIBILITY API"
2061.PP
2062To include the libevent compatibility \s-1API\s0, also include:
2063.PP
2064.Vb 1
2065\& #include "event.c"
2066.Ve
2067.PP
2068in the file including \fIev.c\fR, and:
2069.PP
2070.Vb 1
2071\& #include "event.h"
2072.Ve
2073.PP
2074in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2075.PP
2076You need the following additional files for this:
2077.PP
2078.Vb 2
2079\& event.h
2080\& event.c
2081.Ve
2082.PP
2083\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2084.IX Subsection "AUTOCONF SUPPORT"
2085.PP
2086Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2087whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2088\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2089include \fIconfig.h\fR and configure itself accordingly.
2090.PP
2091For this of course you need the m4 file:
2092.PP
2093.Vb 1
2094\& libev.m4
2095.Ve
2096.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2097.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2098Libev can be configured via a variety of preprocessor symbols you have to define
2099before including any of its files. The default is not to build for multiplicity
2100and only include the select backend.
2101.IP "\s-1EV_STANDALONE\s0" 4
2102.IX Item "EV_STANDALONE"
2103Must always be \f(CW1\fR if you do not use autoconf configuration, which
2104keeps libev from including \fIconfig.h\fR, and it also defines dummy
2105implementations for some libevent functions (such as logging, which is not
2106supported). It will also not define any of the structs usually found in
2107\&\fIevent.h\fR that are not directly supported by the libev core alone.
2108.IP "\s-1EV_USE_MONOTONIC\s0" 4
2109.IX Item "EV_USE_MONOTONIC"
2110If defined to be \f(CW1\fR, libev will try to detect the availability of the
2111monotonic clock option at both compiletime and runtime. Otherwise no use
2112of the monotonic clock option will be attempted. If you enable this, you
2113usually have to link against librt or something similar. Enabling it when
2114the functionality isn't available is safe, though, althoguh you have
2115to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2116function is hiding in (often \fI\-lrt\fR).
2117.IP "\s-1EV_USE_REALTIME\s0" 4
2118.IX Item "EV_USE_REALTIME"
2119If defined to be \f(CW1\fR, libev will try to detect the availability of the
2120realtime clock option at compiletime (and assume its availability at
2121runtime if successful). Otherwise no use of the realtime clock option will
2122be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2123(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2124in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2125.IP "\s-1EV_USE_SELECT\s0" 4
2126.IX Item "EV_USE_SELECT"
2127If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2128\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2129other method takes over, select will be it. Otherwise the select backend
2130will not be compiled in.
2131.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2132.IX Item "EV_SELECT_USE_FD_SET"
2133If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2134structure. This is useful if libev doesn't compile due to a missing
2135\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2136exotic systems. This usually limits the range of file descriptors to some
2137low limit such as 1024 or might have other limitations (winsocket only
2138allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2139influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2140.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2141.IX Item "EV_SELECT_IS_WINSOCKET"
2142When defined to \f(CW1\fR, the select backend will assume that
2143select/socket/connect etc. don't understand file descriptors but
2144wants osf handles on win32 (this is the case when the select to
2145be used is the winsock select). This means that it will call
2146\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2147it is assumed that all these functions actually work on fds, even
2148on win32. Should not be defined on non\-win32 platforms.
2149.IP "\s-1EV_USE_POLL\s0" 4
2150.IX Item "EV_USE_POLL"
2151If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2152backend. Otherwise it will be enabled on non\-win32 platforms. It
2153takes precedence over select.
2154.IP "\s-1EV_USE_EPOLL\s0" 4
2155.IX Item "EV_USE_EPOLL"
2156If defined to be \f(CW1\fR, libev will compile in support for the Linux
2157\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2158otherwise another method will be used as fallback. This is the
2159preferred backend for GNU/Linux systems.
2160.IP "\s-1EV_USE_KQUEUE\s0" 4
2161.IX Item "EV_USE_KQUEUE"
2162If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2163\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2164otherwise another method will be used as fallback. This is the preferred
2165backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2166supports some types of fds correctly (the only platform we found that
2167supports ptys for example was NetBSD), so kqueue might be compiled in, but
2168not be used unless explicitly requested. The best way to use it is to find
2169out whether kqueue supports your type of fd properly and use an embedded
2170kqueue loop.
2171.IP "\s-1EV_USE_PORT\s0" 4
2172.IX Item "EV_USE_PORT"
2173If defined to be \f(CW1\fR, libev will compile in support for the Solaris
217410 port style backend. Its availability will be detected at runtime,
2175otherwise another method will be used as fallback. This is the preferred
2176backend for Solaris 10 systems.
2177.IP "\s-1EV_USE_DEVPOLL\s0" 4
2178.IX Item "EV_USE_DEVPOLL"
2179reserved for future expansion, works like the \s-1USE\s0 symbols above.
2180.IP "\s-1EV_USE_INOTIFY\s0" 4
2181.IX Item "EV_USE_INOTIFY"
2182If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2183interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2184be detected at runtime.
2185.IP "\s-1EV_H\s0" 4
2186.IX Item "EV_H"
2187The name of the \fIev.h\fR header file used to include it. The default if
2188undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2189can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2190.IP "\s-1EV_CONFIG_H\s0" 4
2191.IX Item "EV_CONFIG_H"
2192If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2193\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2194\&\f(CW\*(C`EV_H\*(C'\fR, above.
2195.IP "\s-1EV_EVENT_H\s0" 4
2196.IX Item "EV_EVENT_H"
2197Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2198of how the \fIevent.h\fR header can be found.
2199.IP "\s-1EV_PROTOTYPES\s0" 4
2200.IX Item "EV_PROTOTYPES"
2201If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2202prototypes, but still define all the structs and other symbols. This is
2203occasionally useful if you want to provide your own wrapper functions
2204around libev functions.
2205.IP "\s-1EV_MULTIPLICITY\s0" 4
2206.IX Item "EV_MULTIPLICITY"
2207If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2208will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2209additional independent event loops. Otherwise there will be no support
2210for multiple event loops and there is no first event loop pointer
2211argument. Instead, all functions act on the single default loop.
2212.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2213.IX Item "EV_PERIODIC_ENABLE"
2214If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2215defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2216code.
2217.IP "\s-1EV_EMBED_ENABLE\s0" 4
2218.IX Item "EV_EMBED_ENABLE"
2219If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2220defined to be \f(CW0\fR, then they are not.
2221.IP "\s-1EV_STAT_ENABLE\s0" 4
2222.IX Item "EV_STAT_ENABLE"
2223If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2224defined to be \f(CW0\fR, then they are not.
2225.IP "\s-1EV_FORK_ENABLE\s0" 4
2226.IX Item "EV_FORK_ENABLE"
2227If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2228defined to be \f(CW0\fR, then they are not.
2229.IP "\s-1EV_MINIMAL\s0" 4
2230.IX Item "EV_MINIMAL"
2231If you need to shave off some kilobytes of code at the expense of some
2232speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2233some inlining decisions, saves roughly 30% codesize of amd64.
2234.IP "\s-1EV_PID_HASHSIZE\s0" 4
2235.IX Item "EV_PID_HASHSIZE"
2236\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2237pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2238than enough. If you need to manage thousands of children you might want to
2239increase this value (\fImust\fR be a power of two).
2240.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2241.IX Item "EV_INOTIFY_HASHSIZE"
2242\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2243inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2244usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2245watchers you might want to increase this value (\fImust\fR be a power of
2246two).
2247.IP "\s-1EV_COMMON\s0" 4
2248.IX Item "EV_COMMON"
2249By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2250this macro to a something else you can include more and other types of
2251members. You have to define it each time you include one of the files,
2252though, and it must be identical each time.
2253.Sp
2254For example, the perl \s-1EV\s0 module uses something like this:
2255.Sp
2256.Vb 3
2257\& #define EV_COMMON \e
2258\& SV *self; /* contains this struct */ \e
2259\& SV *cb_sv, *fh /* note no trailing ";" */
2260.Ve
2261.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2262.IX Item "EV_CB_DECLARE (type)"
2263.PD 0
2264.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2265.IX Item "EV_CB_INVOKE (watcher, revents)"
2266.IP "ev_set_cb (ev, cb)" 4
2267.IX Item "ev_set_cb (ev, cb)"
2268.PD
2269Can be used to change the callback member declaration in each watcher,
2270and the way callbacks are invoked and set. Must expand to a struct member
2271definition and a statement, respectively. See the \fIev.v\fR header file for
2272their default definitions. One possible use for overriding these is to
2273avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2274method calls instead of plain function calls in \*(C+.
2275.Sh "\s-1EXAMPLES\s0"
2276.IX Subsection "EXAMPLES"
2277For a real-world example of a program the includes libev
2278verbatim, you can have a look at the \s-1EV\s0 perl module
2279(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2280the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2281interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2282will be compiled. It is pretty complex because it provides its own header
2283file.
2284.Sp
2285The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2286that everybody includes and which overrides some autoconf choices:
2287.Sp
2288.Vb 4
2289\& #define EV_USE_POLL 0
2290\& #define EV_MULTIPLICITY 0
2291\& #define EV_PERIODICS 0
2292\& #define EV_CONFIG_H <config.h>
2293.Ve
2294.Sp
2295.Vb 1
2296\& #include "ev++.h"
2297.Ve
2298.Sp
2299And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2300.Sp
2301.Vb 2
2302\& #include "ev_cpp.h"
2303\& #include "ev.c"
2304.Ve
2305.SH "COMPLEXITIES"
2306.IX Header "COMPLEXITIES"
2307In this section the complexities of (many of) the algorithms used inside
2308libev will be explained. For complexity discussions about backends see the
2309documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2310.RS 4
2311.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2312.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2313.PD 0
2314.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2315.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2316.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2317.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2318.IP "Stopping check/prepare/idle watchers: O(1)" 4
2319.IX Item "Stopping check/prepare/idle watchers: O(1)"
2320.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2321.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2322.IP "Finding the next timer per loop iteration: O(1)" 4
2323.IX Item "Finding the next timer per loop iteration: O(1)"
2324.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2325.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2326.IP "Activating one watcher: O(1)" 4
2327.IX Item "Activating one watcher: O(1)"
2328.RE
2329.RS 4
2330.PD
1020.SH "AUTHOR" 2331.SH "AUTHOR"
1021.IX Header "AUTHOR" 2332.IX Header "AUTHOR"
1022Marc Lehmann <libev@schmorp.de>. 2333Marc Lehmann <libev@schmorp.de>.

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