ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev.3
(Generate patch)

Comparing libev/ev.3 (file contents):
Revision 1.10 by root, Sat Nov 24 06:23:27 2007 UTC vs.
Revision 1.43 by root, Sat Dec 8 14:27:38 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 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-08" "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"
201The newest version of this document is also available as a html-formatted
202web page you might find easier to navigate when reading it for the first
203time: <http://cvs.schmorp.de/libev/ev.html>.
204.PP
142Libev is an event loop: you register interest in certain events (such as a 205Libev 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 206file descriptor being readable or a timeout occuring), and it will manage
144these event sources and provide your program with events. 207these event sources and provide your program with events.
145.PP 208.PP
146To do this, it must take more or less complete control over your process 209To do this, it must take more or less complete control over your process
… …
151watchers\fR, which are relatively small C structures you initialise with the 214watchers\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 215details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 216watcher.
154.SH "FEATURES" 217.SH "FEATURES"
155.IX Header "FEATURES" 218.IX Header "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 219Libev 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 220BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 221for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
159events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event 222(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
160loop mechanism itself (idle, prepare and check watchers). It also is quite 223with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
161fast (see this benchmark comparing 224(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
162it to libevent for example). 225watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
226\&\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
227file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
228(\f(CW\*(C`ev_fork\*(C'\fR).
229.PP
230It also is quite fast (see this
231benchmark comparing it to libevent
232for example).
163.SH "CONVENTIONS" 233.SH "CONVENTIONS"
164.IX Header "CONVENTIONS" 234.IX Header "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 235Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 236be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 237various 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 238this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 239loops, 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) 240(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" 241.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 242.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 243Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 244(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 245the beginning of 1970, details are complicated, don't ask). This type is
… …
201Usually, it's a good idea to terminate if the major versions mismatch, 270Usually, it's a good idea to terminate if the major versions mismatch,
202as this indicates an incompatible change. Minor versions are usually 271as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 272compatible to older versions, so a larger minor version alone is usually
204not a problem. 273not a problem.
205.Sp 274.Sp
206Example: make sure we haven't accidentally been linked against the wrong 275Example: Make sure we haven't accidentally been linked against the wrong
207version: 276version.
208.Sp 277.Sp
209.Vb 3 278.Vb 3
210\& assert (("libev version mismatch", 279\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 280\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 281\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
242recommended ones. 311recommended ones.
243.Sp 312.Sp
244See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 313See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
245.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 314.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 315.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
247Sets the allocation function to use (the prototype is similar to the 316Sets the allocation function to use (the prototype is similar \- the
248realloc C function, the semantics are identical). It is used to allocate 317semantics is identical \- to the realloc C function). It is used to
249and free memory (no surprises here). If it returns zero when memory 318allocate and free memory (no surprises here). If it returns zero when
250needs to be allocated, the library might abort or take some potentially 319memory needs to be allocated, the library might abort or take some
251destructive action. The default is your system realloc function. 320potentially destructive action. The default is your system realloc
321function.
252.Sp 322.Sp
253You could override this function in high-availability programs to, say, 323You could override this function in high-availability programs to, say,
254free some memory if it cannot allocate memory, to use a special allocator, 324free some memory if it cannot allocate memory, to use a special allocator,
255or even to sleep a while and retry until some memory is available. 325or even to sleep a while and retry until some memory is available.
256.Sp 326.Sp
257Example: replace the libev allocator with one that waits a bit and then 327Example: Replace the libev allocator with one that waits a bit and then
258retries: better than mine). 328retries).
259.Sp 329.Sp
260.Vb 6 330.Vb 6
261\& static void * 331\& static void *
262\& persistent_realloc (void *ptr, long size) 332\& persistent_realloc (void *ptr, size_t size)
263\& { 333\& {
264\& for (;;) 334\& for (;;)
265\& { 335\& {
266\& void *newptr = realloc (ptr, size); 336\& void *newptr = realloc (ptr, size);
267.Ve 337.Ve
… …
289callback is set, then libev will expect it to remedy the sitution, no 359callback is set, then libev will expect it to remedy the sitution, no
290matter what, when it returns. That is, libev will generally retry the 360matter what, when it returns. That is, libev will generally retry the
291requested operation, or, if the condition doesn't go away, do bad stuff 361requested operation, or, if the condition doesn't go away, do bad stuff
292(such as abort). 362(such as abort).
293.Sp 363.Sp
294Example: do the same thing as libev does internally: 364Example: This is basically the same thing that libev does internally, too.
295.Sp 365.Sp
296.Vb 6 366.Vb 6
297\& static void 367\& static void
298\& fatal_error (const char *msg) 368\& fatal_error (const char *msg)
299\& { 369\& {
… …
345or setgid) then libev will \fInot\fR look at the environment variable 415or setgid) then libev will \fInot\fR look at the environment variable
346\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 416\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
347override the flags completely if it is found in the environment. This is 417override the flags completely if it is found in the environment. This is
348useful to try out specific backends to test their performance, or to work 418useful to try out specific backends to test their performance, or to work
349around bugs. 419around bugs.
420.ie n .IP """EVFLAG_FORKCHECK""" 4
421.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
422.IX Item "EVFLAG_FORKCHECK"
423Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
424a fork, you can also make libev check for a fork in each iteration by
425enabling this flag.
426.Sp
427This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
428and thus this might slow down your event loop if you do a lot of loop
429iterations and little real work, but is usually not noticeable (on my
430Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
431without a syscall and thus \fIvery\fR fast, but my Linux system also has
432\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
433.Sp
434The big advantage of this flag is that you can forget about fork (and
435forget about forgetting to tell libev about forking) when you use this
436flag.
437.Sp
438This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
439environment variable.
350.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 440.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
351.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 441.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
352.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 442.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
353This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 443This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
354libev tries to roll its own fd_set with no limits on the number of fds, 444libev tries to roll its own fd_set with no limits on the number of fds,
… …
448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 538Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
449always distinct from the default loop. Unlike the default loop, it cannot 539always distinct from the default loop. Unlike the default loop, it cannot
450handle signal and child watchers, and attempts to do so will be greeted by 540handle signal and child watchers, and attempts to do so will be greeted by
451undefined behaviour (or a failed assertion if assertions are enabled). 541undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp 542.Sp
453Example: try to create a event loop that uses epoll and nothing else. 543Example: Try to create a event loop that uses epoll and nothing else.
454.Sp 544.Sp
455.Vb 3 545.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 546\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller) 547\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair"); 548\& fatal ("no epoll found here, maybe it hides under your chair");
459.Ve 549.Ve
460.IP "ev_default_destroy ()" 4 550.IP "ev_default_destroy ()" 4
461.IX Item "ev_default_destroy ()" 551.IX Item "ev_default_destroy ()"
462Destroys the default loop again (frees all memory and kernel state 552Destroys the default loop again (frees all memory and kernel state
463etc.). This stops all registered event watchers (by not touching them in 553etc.). None of the active event watchers will be stopped in the normal
464any way whatsoever, although you cannot rely on this :). 554sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
555responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
556calling this function, or cope with the fact afterwards (which is usually
557the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
558for example).
465.IP "ev_loop_destroy (loop)" 4 559.IP "ev_loop_destroy (loop)" 4
466.IX Item "ev_loop_destroy (loop)" 560.IX Item "ev_loop_destroy (loop)"
467Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 561Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
468earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 562earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
469.IP "ev_default_fork ()" 4 563.IP "ev_default_fork ()" 4
… …
491.IP "ev_loop_fork (loop)" 4 585.IP "ev_loop_fork (loop)" 4
492.IX Item "ev_loop_fork (loop)" 586.IX Item "ev_loop_fork (loop)"
493Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 587Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
494\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 588\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
495after fork, and how you do this is entirely your own problem. 589after fork, and how you do this is entirely your own problem.
590.IP "unsigned int ev_loop_count (loop)" 4
591.IX Item "unsigned int ev_loop_count (loop)"
592Returns the count of loop iterations for the loop, which is identical to
593the number of times libev did poll for new events. It starts at \f(CW0\fR and
594happily wraps around with enough iterations.
595.Sp
596This value can sometimes be useful as a generation counter of sorts (it
597\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
598\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
496.IP "unsigned int ev_backend (loop)" 4 599.IP "unsigned int ev_backend (loop)" 4
497.IX Item "unsigned int ev_backend (loop)" 600.IX Item "unsigned int ev_backend (loop)"
498Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 601Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
499use. 602use.
500.IP "ev_tstamp ev_now (loop)" 4 603.IP "ev_tstamp ev_now (loop)" 4
… …
552\& be handled here by queueing them when their watcher gets executed. 655\& be handled here by queueing them when their watcher gets executed.
553\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 656\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
554\& were used, return, otherwise continue with step *. 657\& were used, return, otherwise continue with step *.
555.Ve 658.Ve
556.Sp 659.Sp
557Example: queue some jobs and then loop until no events are outsanding 660Example: Queue some jobs and then loop until no events are outsanding
558anymore. 661anymore.
559.Sp 662.Sp
560.Vb 4 663.Vb 4
561\& ... queue jobs here, make sure they register event watchers as long 664\& ... queue jobs here, make sure they register event watchers as long
562\& ... as they still have work to do (even an idle watcher will do..) 665\& ... as they still have work to do (even an idle watcher will do..)
… …
584visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 687visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
585no event watchers registered by it are active. It is also an excellent 688no event watchers registered by it are active. It is also an excellent
586way to do this for generic recurring timers or from within third-party 689way to do this for generic recurring timers or from within third-party
587libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 690libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
588.Sp 691.Sp
589Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 692Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
590running when nothing else is active. 693running when nothing else is active.
591.Sp 694.Sp
592.Vb 4 695.Vb 4
593\& struct dv_signal exitsig; 696\& struct ev_signal exitsig;
594\& ev_signal_init (&exitsig, sig_cb, SIGINT); 697\& ev_signal_init (&exitsig, sig_cb, SIGINT);
595\& ev_signal_start (myloop, &exitsig); 698\& ev_signal_start (loop, &exitsig);
596\& evf_unref (myloop); 699\& evf_unref (loop);
597.Ve 700.Ve
598.Sp 701.Sp
599Example: for some weird reason, unregister the above signal handler again. 702Example: For some weird reason, unregister the above signal handler again.
600.Sp 703.Sp
601.Vb 2 704.Vb 2
602\& ev_ref (myloop); 705\& ev_ref (loop);
603\& ev_signal_stop (myloop, &exitsig); 706\& ev_signal_stop (loop, &exitsig);
604.Ve 707.Ve
605.SH "ANATOMY OF A WATCHER" 708.SH "ANATOMY OF A WATCHER"
606.IX Header "ANATOMY OF A WATCHER" 709.IX Header "ANATOMY OF A WATCHER"
607A watcher is a structure that you create and register to record your 710A watcher is a structure that you create and register to record your
608interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 711interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
… …
645*)\*(C'\fR), and you can stop watching for events at any time by calling the 748*)\*(C'\fR), and you can stop watching for events at any time by calling the
646corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 749corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
647.PP 750.PP
648As long as your watcher is active (has been started but not stopped) you 751As long as your watcher is active (has been started but not stopped) you
649must not touch the values stored in it. Most specifically you must never 752must not touch the values stored in it. Most specifically you must never
650reinitialise it or call its set macro. 753reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
651.PP
652You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
653(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
654callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
655(watcher *)\*(C'\fR macro.
656.PP 754.PP
657Each and every callback receives the event loop pointer as first, the 755Each and every callback receives the event loop pointer as first, the
658registered watcher structure as second, and a bitset of received events as 756registered watcher structure as second, and a bitset of received events as
659third argument. 757third argument.
660.PP 758.PP
… …
685The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 783The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
686.ie n .IP """EV_CHILD""" 4 784.ie n .IP """EV_CHILD""" 4
687.el .IP "\f(CWEV_CHILD\fR" 4 785.el .IP "\f(CWEV_CHILD\fR" 4
688.IX Item "EV_CHILD" 786.IX Item "EV_CHILD"
689The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 787The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
788.ie n .IP """EV_STAT""" 4
789.el .IP "\f(CWEV_STAT\fR" 4
790.IX Item "EV_STAT"
791The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
690.ie n .IP """EV_IDLE""" 4 792.ie n .IP """EV_IDLE""" 4
691.el .IP "\f(CWEV_IDLE\fR" 4 793.el .IP "\f(CWEV_IDLE\fR" 4
692.IX Item "EV_IDLE" 794.IX Item "EV_IDLE"
693The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 795The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
694.ie n .IP """EV_PREPARE""" 4 796.ie n .IP """EV_PREPARE""" 4
… …
704\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 806\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
705received events. Callbacks of both watcher types can start and stop as 807received events. Callbacks of both watcher types can start and stop as
706many watchers as they want, and all of them will be taken into account 808many watchers as they want, and all of them will be taken into account
707(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 809(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
708\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 810\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
811.ie n .IP """EV_EMBED""" 4
812.el .IP "\f(CWEV_EMBED\fR" 4
813.IX Item "EV_EMBED"
814The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
815.ie n .IP """EV_FORK""" 4
816.el .IP "\f(CWEV_FORK\fR" 4
817.IX Item "EV_FORK"
818The event loop has been resumed in the child process after fork (see
819\&\f(CW\*(C`ev_fork\*(C'\fR).
709.ie n .IP """EV_ERROR""" 4 820.ie n .IP """EV_ERROR""" 4
710.el .IP "\f(CWEV_ERROR\fR" 4 821.el .IP "\f(CWEV_ERROR\fR" 4
711.IX Item "EV_ERROR" 822.IX Item "EV_ERROR"
712An unspecified error has occured, the watcher has been stopped. This might 823An unspecified error has occured, the watcher has been stopped. This might
713happen because the watcher could not be properly started because libev 824happen because the watcher could not be properly started because libev
… …
718Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 829Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
719for example it might indicate that a fd is readable or writable, and if 830for example it might indicate that a fd is readable or writable, and if
720your callbacks is well-written it can just attempt the operation and cope 831your callbacks is well-written it can just attempt the operation and cope
721with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 832with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
722programs, though, so beware. 833programs, though, so beware.
834.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
835.IX Subsection "GENERIC WATCHER FUNCTIONS"
836In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
837e.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.
838.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
839.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
840.IX Item "ev_init (ev_TYPE *watcher, callback)"
841This macro initialises the generic portion of a watcher. The contents
842of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
843the generic parts of the watcher are initialised, you \fIneed\fR to call
844the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
845type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
846which rolls both calls into one.
847.Sp
848You can reinitialise a watcher at any time as long as it has been stopped
849(or never started) and there are no pending events outstanding.
850.Sp
851The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
852int revents)\*(C'\fR.
853.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
854.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
855.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
856This macro initialises the type-specific parts of a watcher. You need to
857call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
858call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
859macro on a watcher that is active (it can be pending, however, which is a
860difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
861.Sp
862Although some watcher types do not have type-specific arguments
863(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
864.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
865.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
866.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
867This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
868calls into a single call. This is the most convinient method to initialise
869a watcher. The same limitations apply, of course.
870.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
871.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
872.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
873Starts (activates) the given watcher. Only active watchers will receive
874events. If the watcher is already active nothing will happen.
875.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
876.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
877.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
878Stops the given watcher again (if active) and clears the pending
879status. It is possible that stopped watchers are pending (for example,
880non-repeating timers are being stopped when they become pending), but
881\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
882you want to free or reuse the memory used by the watcher it is therefore a
883good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
884.IP "bool ev_is_active (ev_TYPE *watcher)" 4
885.IX Item "bool ev_is_active (ev_TYPE *watcher)"
886Returns a true value iff the watcher is active (i.e. it has been started
887and not yet been stopped). As long as a watcher is active you must not modify
888it.
889.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
890.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
891Returns a true value iff the watcher is pending, (i.e. it has outstanding
892events but its callback has not yet been invoked). As long as a watcher
893is pending (but not active) you must not call an init function on it (but
894\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
895make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
896it).
897.IP "callback ev_cb (ev_TYPE *watcher)" 4
898.IX Item "callback ev_cb (ev_TYPE *watcher)"
899Returns the callback currently set on the watcher.
900.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
901.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
902Change the callback. You can change the callback at virtually any time
903(modulo threads).
904.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
905.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
906.PD 0
907.IP "int ev_priority (ev_TYPE *watcher)" 4
908.IX Item "int ev_priority (ev_TYPE *watcher)"
909.PD
910Set and query the priority of the watcher. The priority is a small
911integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
912(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
913before watchers with lower priority, but priority will not keep watchers
914from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
915.Sp
916This means that priorities are \fIonly\fR used for ordering callback
917invocation after new events have been received. This is useful, for
918example, to reduce latency after idling, or more often, to bind two
919watchers on the same event and make sure one is called first.
920.Sp
921If you need to suppress invocation when higher priority events are pending
922you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
923.Sp
924You \fImust not\fR change the priority of a watcher as long as it is active or
925pending.
926.Sp
927The default priority used by watchers when no priority has been set is
928always \f(CW0\fR, which is supposed to not be too high and not be too low :).
929.Sp
930Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
931fine, as long as you do not mind that the priority value you query might
932or might not have been adjusted to be within valid range.
933.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
934.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
935Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
936\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
937can deal with that fact.
938.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
939.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
940If the watcher is pending, this function returns clears its pending status
941and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
942watcher isn't pending it does nothing and returns \f(CW0\fR.
723.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 943.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
724.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 944.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
725Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 945Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
726and read at any time, libev will completely ignore it. This can be used 946and read at any time, libev will completely ignore it. This can be used
727to associate arbitrary data with your watcher. If you need more data and 947to associate arbitrary data with your watcher. If you need more data and
… …
748\& struct my_io *w = (struct my_io *)w_; 968\& struct my_io *w = (struct my_io *)w_;
749\& ... 969\& ...
750\& } 970\& }
751.Ve 971.Ve
752.PP 972.PP
753More interesting and less C\-conformant ways of catsing your callback type 973More interesting and less C\-conformant ways of casting your callback type
754have been omitted.... 974instead have been omitted.
975.PP
976Another common scenario is having some data structure with multiple
977watchers:
978.PP
979.Vb 6
980\& struct my_biggy
981\& {
982\& int some_data;
983\& ev_timer t1;
984\& ev_timer t2;
985\& }
986.Ve
987.PP
988In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
989you need to use \f(CW\*(C`offsetof\*(C'\fR:
990.PP
991.Vb 1
992\& #include <stddef.h>
993.Ve
994.PP
995.Vb 6
996\& static void
997\& t1_cb (EV_P_ struct ev_timer *w, int revents)
998\& {
999\& struct my_biggy big = (struct my_biggy *
1000\& (((char *)w) - offsetof (struct my_biggy, t1));
1001\& }
1002.Ve
1003.PP
1004.Vb 6
1005\& static void
1006\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1007\& {
1008\& struct my_biggy big = (struct my_biggy *
1009\& (((char *)w) - offsetof (struct my_biggy, t2));
1010\& }
1011.Ve
755.SH "WATCHER TYPES" 1012.SH "WATCHER TYPES"
756.IX Header "WATCHER TYPES" 1013.IX Header "WATCHER TYPES"
757This section describes each watcher in detail, but will not repeat 1014This section describes each watcher in detail, but will not repeat
758information given in the last section. 1015information given in the last section. Any initialisation/set macros,
1016functions and members specific to the watcher type are explained.
1017.PP
1018Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1019while the watcher is active, you can look at the member and expect some
1020sensible content, but you must not modify it (you can modify it while the
1021watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1022means you can expect it to have some sensible content while the watcher
1023is active, but you can also modify it. Modifying it may not do something
1024sensible or take immediate effect (or do anything at all), but libev will
1025not crash or malfunction in any way.
759.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1026.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
760.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1027.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
761.IX Subsection "ev_io - is this file descriptor readable or writable" 1028.IX Subsection "ev_io - is this file descriptor readable or writable?"
762I/O watchers check whether a file descriptor is readable or writable 1029I/O watchers check whether a file descriptor is readable or writable
763in each iteration of the event loop (This behaviour is called 1030in each iteration of the event loop, or, more precisely, when reading
764level-triggering because you keep receiving events as long as the 1031would not block the process and writing would at least be able to write
765condition persists. Remember you can stop the watcher if you don't want to 1032some data. This behaviour is called level-triggering because you keep
766act on the event and neither want to receive future events). 1033receiving events as long as the condition persists. Remember you can stop
1034the watcher if you don't want to act on the event and neither want to
1035receive future events.
767.PP 1036.PP
768In general you can register as many read and/or write event watchers per 1037In general you can register as many read and/or write event watchers per
769fd as you want (as long as you don't confuse yourself). Setting all file 1038fd as you want (as long as you don't confuse yourself). Setting all file
770descriptors to non-blocking mode is also usually a good idea (but not 1039descriptors to non-blocking mode is also usually a good idea (but not
771required if you know what you are doing). 1040required if you know what you are doing).
772.PP 1041.PP
773You have to be careful with dup'ed file descriptors, though. Some backends 1042You have to be careful with dup'ed file descriptors, though. Some backends
774(the linux epoll backend is a notable example) cannot handle dup'ed file 1043(the linux epoll backend is a notable example) cannot handle dup'ed file
775descriptors correctly if you register interest in two or more fds pointing 1044descriptors correctly if you register interest in two or more fds pointing
776to the same underlying file/socket etc. description (that is, they share 1045to the same underlying file/socket/etc. description (that is, they share
777the same underlying \*(L"file open\*(R"). 1046the same underlying \*(L"file open\*(R").
778.PP 1047.PP
779If you must do this, then force the use of a known-to-be-good backend 1048If you must do this, then force the use of a known-to-be-good backend
780(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1049(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
781\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1050\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1051.PP
1052Another thing you have to watch out for is that it is quite easy to
1053receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1054be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1055because there is no data. Not only are some backends known to create a
1056lot of those (for example solaris ports), it is very easy to get into
1057this situation even with a relatively standard program structure. Thus
1058it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1059\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1060.PP
1061If you cannot run the fd in non-blocking mode (for example you should not
1062play around with an Xlib connection), then you have to seperately re-test
1063whether a file descriptor is really ready with a known-to-be good interface
1064such as poll (fortunately in our Xlib example, Xlib already does this on
1065its own, so its quite safe to use).
782.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1066.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
783.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1067.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
784.PD 0 1068.PD 0
785.IP "ev_io_set (ev_io *, int fd, int events)" 4 1069.IP "ev_io_set (ev_io *, int fd, int events)" 4
786.IX Item "ev_io_set (ev_io *, int fd, int events)" 1070.IX Item "ev_io_set (ev_io *, int fd, int events)"
787.PD 1071.PD
788Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1072Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
789events 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 | 1073rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
790EV_WRITE\*(C'\fR to receive the given events. 1074\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
791.Sp 1075.IP "int fd [read\-only]" 4
792Please note that most of the more scalable backend mechanisms (for example 1076.IX Item "int fd [read-only]"
793epoll and solaris ports) can result in spurious readyness notifications 1077The file descriptor being watched.
794for file descriptors, so you practically need to use non-blocking I/O (and 1078.IP "int events [read\-only]" 4
795treat callback invocation as hint only), or retest separately with a safe 1079.IX Item "int events [read-only]"
796interface before doing I/O (XLib can do this), or force the use of either 1080The events being watched.
797\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
798problem. Also note that it is quite easy to have your callback invoked
799when the readyness condition is no longer valid even when employing
800typical ways of handling events, so its a good idea to use non-blocking
801I/O unconditionally.
802.PP 1081.PP
803Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1082Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
804readable, but only once. Since it is likely line\-buffered, you could 1083readable, but only once. Since it is likely line\-buffered, you could
805attempt to read a whole line in the callback: 1084attempt to read a whole line in the callback.
806.PP 1085.PP
807.Vb 6 1086.Vb 6
808\& static void 1087\& static void
809\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1088\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
810\& { 1089\& {
… …
819\& struct ev_io stdin_readable; 1098\& struct ev_io stdin_readable;
820\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1099\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
821\& ev_io_start (loop, &stdin_readable); 1100\& ev_io_start (loop, &stdin_readable);
822\& ev_loop (loop, 0); 1101\& ev_loop (loop, 0);
823.Ve 1102.Ve
824.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1103.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
825.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1104.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
826.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1105.IX Subsection "ev_timer - relative and optionally repeating timeouts"
827Timer watchers are simple relative timers that generate an event after a 1106Timer watchers are simple relative timers that generate an event after a
828given time, and optionally repeating in regular intervals after that. 1107given time, and optionally repeating in regular intervals after that.
829.PP 1108.PP
830The timers are based on real time, that is, if you register an event that 1109The timers are based on real time, that is, if you register an event that
831times out after an hour and you reset your system clock to last years 1110times out after an hour and you reset your system clock to last years
… …
865.IP "ev_timer_again (loop)" 4 1144.IP "ev_timer_again (loop)" 4
866.IX Item "ev_timer_again (loop)" 1145.IX Item "ev_timer_again (loop)"
867This will act as if the timer timed out and restart it again if it is 1146This will act as if the timer timed out and restart it again if it is
868repeating. The exact semantics are: 1147repeating. The exact semantics are:
869.Sp 1148.Sp
1149If the timer is pending, its pending status is cleared.
1150.Sp
870If the timer is started but nonrepeating, stop it. 1151If the timer is started but nonrepeating, stop it (as if it timed out).
871.Sp 1152.Sp
872If the timer is repeating, either start it if necessary (with the repeat 1153If the timer is repeating, either start it if necessary (with the
873value), or reset the running timer to the repeat value. 1154\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
874.Sp 1155.Sp
875This sounds a bit complicated, but here is a useful and typical 1156This sounds a bit complicated, but here is a useful and typical
876example: Imagine you have a tcp connection and you want a so-called idle 1157example: Imagine you have a tcp connection and you want a so-called idle
877timeout, that is, you want to be called when there have been, say, 60 1158timeout, that is, you want to be called when there have been, say, 60
878seconds of inactivity on the socket. The easiest way to do this is to 1159seconds of inactivity on the socket. The easiest way to do this is to
879configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1160configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
880time you successfully read or write some data. If you go into an idle 1161\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
881state where you do not expect data to travel on the socket, you can stop 1162you go into an idle state where you do not expect data to travel on the
882the timer, and again will automatically restart it if need be. 1163socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1164automatically restart it if need be.
1165.Sp
1166That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1167altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1168.Sp
1169.Vb 8
1170\& ev_timer_init (timer, callback, 0., 5.);
1171\& ev_timer_again (loop, timer);
1172\& ...
1173\& timer->again = 17.;
1174\& ev_timer_again (loop, timer);
1175\& ...
1176\& timer->again = 10.;
1177\& ev_timer_again (loop, timer);
1178.Ve
1179.Sp
1180This is more slightly efficient then stopping/starting the timer each time
1181you want to modify its timeout value.
1182.IP "ev_tstamp repeat [read\-write]" 4
1183.IX Item "ev_tstamp repeat [read-write]"
1184The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1185or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1186which is also when any modifications are taken into account.
883.PP 1187.PP
884Example: create a timer that fires after 60 seconds. 1188Example: Create a timer that fires after 60 seconds.
885.PP 1189.PP
886.Vb 5 1190.Vb 5
887\& static void 1191\& static void
888\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1192\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
889\& { 1193\& {
… …
895\& struct ev_timer mytimer; 1199\& struct ev_timer mytimer;
896\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1200\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
897\& ev_timer_start (loop, &mytimer); 1201\& ev_timer_start (loop, &mytimer);
898.Ve 1202.Ve
899.PP 1203.PP
900Example: create a timeout timer that times out after 10 seconds of 1204Example: Create a timeout timer that times out after 10 seconds of
901inactivity. 1205inactivity.
902.PP 1206.PP
903.Vb 5 1207.Vb 5
904\& static void 1208\& static void
905\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1209\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
918.Vb 3 1222.Vb 3
919\& // and in some piece of code that gets executed on any "activity": 1223\& // and in some piece of code that gets executed on any "activity":
920\& // reset the timeout to start ticking again at 10 seconds 1224\& // reset the timeout to start ticking again at 10 seconds
921\& ev_timer_again (&mytimer); 1225\& ev_timer_again (&mytimer);
922.Ve 1226.Ve
923.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1227.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
924.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1228.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
925.IX Subsection "ev_periodic - to cron or not to cron" 1229.IX Subsection "ev_periodic - to cron or not to cron?"
926Periodic watchers are also timers of a kind, but they are very versatile 1230Periodic watchers are also timers of a kind, but they are very versatile
927(and unfortunately a bit complex). 1231(and unfortunately a bit complex).
928.PP 1232.PP
929Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1233Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
930but on wallclock time (absolute time). You can tell a periodic watcher 1234but on wallclock time (absolute time). You can tell a periodic watcher
931to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1235to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
932periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1236periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
933+ 10.>) and then reset your system clock to the last year, then it will 1237+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
934take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1238take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
935roughly 10 seconds later and of course not if you reset your system time 1239roughly 10 seconds later and of course not if you reset your system time
936again). 1240again).
937.PP 1241.PP
938They can also be used to implement vastly more complex timers, such as 1242They can also be used to implement vastly more complex timers, such as
… …
1019.IX Item "ev_periodic_again (loop, ev_periodic *)" 1323.IX Item "ev_periodic_again (loop, ev_periodic *)"
1020Simply stops and restarts the periodic watcher again. This is only useful 1324Simply stops and restarts the periodic watcher again. This is only useful
1021when you changed some parameters or the reschedule callback would return 1325when you changed some parameters or the reschedule callback would return
1022a different time than the last time it was called (e.g. in a crond like 1326a different time than the last time it was called (e.g. in a crond like
1023program when the crontabs have changed). 1327program when the crontabs have changed).
1328.IP "ev_tstamp interval [read\-write]" 4
1329.IX Item "ev_tstamp interval [read-write]"
1330The current interval value. Can be modified any time, but changes only
1331take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1332called.
1333.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1334.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1335The current reschedule callback, or \f(CW0\fR, if this functionality is
1336switched off. Can be changed any time, but changes only take effect when
1337the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1024.PP 1338.PP
1025Example: call a callback every hour, or, more precisely, whenever the 1339Example: Call a callback every hour, or, more precisely, whenever the
1026system clock is divisible by 3600. The callback invocation times have 1340system clock is divisible by 3600. The callback invocation times have
1027potentially a lot of jittering, but good long-term stability. 1341potentially a lot of jittering, but good long-term stability.
1028.PP 1342.PP
1029.Vb 5 1343.Vb 5
1030\& static void 1344\& static void
… …
1038\& struct ev_periodic hourly_tick; 1352\& struct ev_periodic hourly_tick;
1039\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1353\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1040\& ev_periodic_start (loop, &hourly_tick); 1354\& ev_periodic_start (loop, &hourly_tick);
1041.Ve 1355.Ve
1042.PP 1356.PP
1043Example: the same as above, but use a reschedule callback to do it: 1357Example: The same as above, but use a reschedule callback to do it:
1044.PP 1358.PP
1045.Vb 1 1359.Vb 1
1046\& #include <math.h> 1360\& #include <math.h>
1047.Ve 1361.Ve
1048.PP 1362.PP
… …
1056.PP 1370.PP
1057.Vb 1 1371.Vb 1
1058\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1372\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1059.Ve 1373.Ve
1060.PP 1374.PP
1061Example: call a callback every hour, starting now: 1375Example: Call a callback every hour, starting now:
1062.PP 1376.PP
1063.Vb 4 1377.Vb 4
1064\& struct ev_periodic hourly_tick; 1378\& struct ev_periodic hourly_tick;
1065\& ev_periodic_init (&hourly_tick, clock_cb, 1379\& ev_periodic_init (&hourly_tick, clock_cb,
1066\& fmod (ev_now (loop), 3600.), 3600., 0); 1380\& fmod (ev_now (loop), 3600.), 3600., 0);
1067\& ev_periodic_start (loop, &hourly_tick); 1381\& ev_periodic_start (loop, &hourly_tick);
1068.Ve 1382.Ve
1069.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1383.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
1070.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1384.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1071.IX Subsection "ev_signal - signal me when a signal gets signalled" 1385.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1072Signal watchers will trigger an event when the process receives a specific 1386Signal watchers will trigger an event when the process receives a specific
1073signal one or more times. Even though signals are very asynchronous, libev 1387signal one or more times. Even though signals are very asynchronous, libev
1074will try it's best to deliver signals synchronously, i.e. as part of the 1388will try it's best to deliver signals synchronously, i.e. as part of the
1075normal event processing, like any other event. 1389normal event processing, like any other event.
1076.PP 1390.PP
… …
1086.IP "ev_signal_set (ev_signal *, int signum)" 4 1400.IP "ev_signal_set (ev_signal *, int signum)" 4
1087.IX Item "ev_signal_set (ev_signal *, int signum)" 1401.IX Item "ev_signal_set (ev_signal *, int signum)"
1088.PD 1402.PD
1089Configures the watcher to trigger on the given signal number (usually one 1403Configures the watcher to trigger on the given signal number (usually one
1090of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1404of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1405.IP "int signum [read\-only]" 4
1406.IX Item "int signum [read-only]"
1407The signal the watcher watches out for.
1091.ie n .Sh """ev_child"" \- wait for pid status changes" 1408.ie n .Sh """ev_child"" \- watch out for process status changes"
1092.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1409.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1093.IX Subsection "ev_child - wait for pid status changes" 1410.IX Subsection "ev_child - watch out for process status changes"
1094Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1411Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1095some child status changes (most typically when a child of yours dies). 1412some child status changes (most typically when a child of yours dies).
1096.IP "ev_child_init (ev_child *, callback, int pid)" 4 1413.IP "ev_child_init (ev_child *, callback, int pid)" 4
1097.IX Item "ev_child_init (ev_child *, callback, int pid)" 1414.IX Item "ev_child_init (ev_child *, callback, int pid)"
1098.PD 0 1415.PD 0
… …
1103\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1420\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1104at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1421at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1105the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1422the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1106\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1423\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1107process causing the status change. 1424process causing the status change.
1425.IP "int pid [read\-only]" 4
1426.IX Item "int pid [read-only]"
1427The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1428.IP "int rpid [read\-write]" 4
1429.IX Item "int rpid [read-write]"
1430The process id that detected a status change.
1431.IP "int rstatus [read\-write]" 4
1432.IX Item "int rstatus [read-write]"
1433The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1434\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1108.PP 1435.PP
1109Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1436Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1110.PP 1437.PP
1111.Vb 5 1438.Vb 5
1112\& static void 1439\& static void
1113\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1440\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1114\& { 1441\& {
… …
1119.Vb 3 1446.Vb 3
1120\& struct ev_signal signal_watcher; 1447\& struct ev_signal signal_watcher;
1121\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1448\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1122\& ev_signal_start (loop, &sigint_cb); 1449\& ev_signal_start (loop, &sigint_cb);
1123.Ve 1450.Ve
1451.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1452.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1453.IX Subsection "ev_stat - did the file attributes just change?"
1454This watches a filesystem path for attribute changes. That is, it calls
1455\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1456compared to the last time, invoking the callback if it did.
1457.PP
1458The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1459not exist\*(R" is a status change like any other. The condition \*(L"path does
1460not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1461otherwise always forced to be at least one) and all the other fields of
1462the stat buffer having unspecified contents.
1463.PP
1464The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1465relative and your working directory changes, the behaviour is undefined.
1466.PP
1467Since there is no standard to do this, the portable implementation simply
1468calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1469can specify a recommended polling interval for this case. If you specify
1470a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1471unspecified default\fR value will be used (which you can expect to be around
1472five seconds, although this might change dynamically). Libev will also
1473impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1474usually overkill.
1475.PP
1476This watcher type is not meant for massive numbers of stat watchers,
1477as even with OS-supported change notifications, this can be
1478resource\-intensive.
1479.PP
1480At the time of this writing, only the Linux inotify interface is
1481implemented (implementing kqueue support is left as an exercise for the
1482reader). Inotify will be used to give hints only and should not change the
1483semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1484to fall back to regular polling again even with inotify, but changes are
1485usually detected immediately, and if the file exists there will be no
1486polling.
1487.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1488.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1489.PD 0
1490.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1491.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1492.PD
1493Configures the watcher to wait for status changes of the given
1494\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1495be detected and should normally be specified as \f(CW0\fR to let libev choose
1496a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1497path for as long as the watcher is active.
1498.Sp
1499The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1500relative to the attributes at the time the watcher was started (or the
1501last change was detected).
1502.IP "ev_stat_stat (ev_stat *)" 4
1503.IX Item "ev_stat_stat (ev_stat *)"
1504Updates the stat buffer immediately with new values. If you change the
1505watched path in your callback, you could call this fucntion to avoid
1506detecting this change (while introducing a race condition). Can also be
1507useful simply to find out the new values.
1508.IP "ev_statdata attr [read\-only]" 4
1509.IX Item "ev_statdata attr [read-only]"
1510The most-recently detected attributes of the file. Although the type is of
1511\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1512suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1513was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1514.IP "ev_statdata prev [read\-only]" 4
1515.IX Item "ev_statdata prev [read-only]"
1516The previous attributes of the file. The callback gets invoked whenever
1517\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1518.IP "ev_tstamp interval [read\-only]" 4
1519.IX Item "ev_tstamp interval [read-only]"
1520The specified interval.
1521.IP "const char *path [read\-only]" 4
1522.IX Item "const char *path [read-only]"
1523The filesystem path that is being watched.
1524.PP
1525Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1526.PP
1527.Vb 15
1528\& static void
1529\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1530\& {
1531\& /* /etc/passwd changed in some way */
1532\& if (w->attr.st_nlink)
1533\& {
1534\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1535\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1536\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1537\& }
1538\& else
1539\& /* you shalt not abuse printf for puts */
1540\& puts ("wow, /etc/passwd is not there, expect problems. "
1541\& "if this is windows, they already arrived\en");
1542\& }
1543.Ve
1544.PP
1545.Vb 2
1546\& ...
1547\& ev_stat passwd;
1548.Ve
1549.PP
1550.Vb 2
1551\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1552\& ev_stat_start (loop, &passwd);
1553.Ve
1124.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1554.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1125.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1555.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1126.IX Subsection "ev_idle - when you've got nothing better to do" 1556.IX Subsection "ev_idle - when you've got nothing better to do..."
1127Idle watchers trigger events when there are no other events are pending 1557Idle watchers trigger events when no other events of the same or higher
1128(prepare, check and other idle watchers do not count). That is, as long 1558priority are pending (prepare, check and other idle watchers do not
1129as your process is busy handling sockets or timeouts (or even signals, 1559count).
1130imagine) it will not be triggered. But when your process is idle all idle 1560.PP
1131watchers are being called again and again, once per event loop iteration \- 1561That is, as long as your process is busy handling sockets or timeouts
1562(or even signals, imagine) of the same or higher priority it will not be
1563triggered. But when your process is idle (or only lower-priority watchers
1564are pending), the idle watchers are being called once per event loop
1132until stopped, that is, or your process receives more events and becomes 1565iteration \- until stopped, that is, or your process receives more events
1133busy. 1566and becomes busy again with higher priority stuff.
1134.PP 1567.PP
1135The most noteworthy effect is that as long as any idle watchers are 1568The most noteworthy effect is that as long as any idle watchers are
1136active, the process will not block when waiting for new events. 1569active, the process will not block when waiting for new events.
1137.PP 1570.PP
1138Apart from keeping your process non-blocking (which is a useful 1571Apart from keeping your process non-blocking (which is a useful
… …
1143.IX Item "ev_idle_init (ev_signal *, callback)" 1576.IX Item "ev_idle_init (ev_signal *, callback)"
1144Initialises and configures the idle watcher \- it has no parameters of any 1577Initialises and configures the idle watcher \- it has no parameters of any
1145kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1578kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1146believe me. 1579believe me.
1147.PP 1580.PP
1148Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1581Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1149callback, free it. Alos, use no error checking, as usual. 1582callback, free it. Also, use no error checking, as usual.
1150.PP 1583.PP
1151.Vb 7 1584.Vb 7
1152\& static void 1585\& static void
1153\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1586\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1154\& { 1587\& {
… …
1161.Vb 3 1594.Vb 3
1162\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1595\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1163\& ev_idle_init (idle_watcher, idle_cb); 1596\& ev_idle_init (idle_watcher, idle_cb);
1164\& ev_idle_start (loop, idle_cb); 1597\& ev_idle_start (loop, idle_cb);
1165.Ve 1598.Ve
1166.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1599.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
1167.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1600.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1168.IX Subsection "ev_prepare and ev_check - customise your event loop" 1601.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1169Prepare and check watchers are usually (but not always) used in tandem: 1602Prepare and check watchers are usually (but not always) used in tandem:
1170prepare watchers get invoked before the process blocks and check watchers 1603prepare watchers get invoked before the process blocks and check watchers
1171afterwards. 1604afterwards.
1172.PP 1605.PP
1606You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1607the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1608watchers. Other loops than the current one are fine, however. The
1609rationale behind this is that you do not need to check for recursion in
1610those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1611\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1612called in pairs bracketing the blocking call.
1613.PP
1173Their main purpose is to integrate other event mechanisms into libev and 1614Their main purpose is to integrate other event mechanisms into libev and
1174their use is somewhat advanced. This could be used, for example, to track 1615their use is somewhat advanced. This could be used, for example, to track
1175variable changes, implement your own watchers, integrate net-snmp or a 1616variable changes, implement your own watchers, integrate net-snmp or a
1176coroutine library and lots more. 1617coroutine library and lots more. They are also occasionally useful if
1618you cache some data and want to flush it before blocking (for example,
1619in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1620watcher).
1177.PP 1621.PP
1178This is done by examining in each prepare call which file descriptors need 1622This is done by examining in each prepare call which file descriptors need
1179to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1623to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1180them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1624them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1181provide just this functionality). Then, in the check watcher you check for 1625provide just this functionality). Then, in the check watcher you check for
… …
1200.PD 1644.PD
1201Initialises and configures the prepare or check watcher \- they have no 1645Initialises and configures the prepare or check watcher \- they have no
1202parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1646parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1203macros, but using them is utterly, utterly and completely pointless. 1647macros, but using them is utterly, utterly and completely pointless.
1204.PP 1648.PP
1205Example: *TODO*. 1649Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1650and a timeout watcher in a prepare handler, as required by libadns, and
1651in a check watcher, destroy them and call into libadns. What follows is
1652pseudo-code only of course:
1653.PP
1654.Vb 2
1655\& static ev_io iow [nfd];
1656\& static ev_timer tw;
1657.Ve
1658.PP
1659.Vb 9
1660\& static void
1661\& io_cb (ev_loop *loop, ev_io *w, int revents)
1662\& {
1663\& // set the relevant poll flags
1664\& // could also call adns_processreadable etc. here
1665\& struct pollfd *fd = (struct pollfd *)w->data;
1666\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1667\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1668\& }
1669.Ve
1670.PP
1671.Vb 8
1672\& // create io watchers for each fd and a timer before blocking
1673\& static void
1674\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1675\& {
1676\& int timeout = 3600000;
1677\& struct pollfd fds [nfd];
1678\& // actual code will need to loop here and realloc etc.
1679\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1680.Ve
1681.PP
1682.Vb 3
1683\& /* the callback is illegal, but won't be called as we stop during check */
1684\& ev_timer_init (&tw, 0, timeout * 1e-3);
1685\& ev_timer_start (loop, &tw);
1686.Ve
1687.PP
1688.Vb 6
1689\& // create on ev_io per pollfd
1690\& for (int i = 0; i < nfd; ++i)
1691\& {
1692\& ev_io_init (iow + i, io_cb, fds [i].fd,
1693\& ((fds [i].events & POLLIN ? EV_READ : 0)
1694\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1695.Ve
1696.PP
1697.Vb 5
1698\& fds [i].revents = 0;
1699\& iow [i].data = fds + i;
1700\& ev_io_start (loop, iow + i);
1701\& }
1702\& }
1703.Ve
1704.PP
1705.Vb 5
1706\& // stop all watchers after blocking
1707\& static void
1708\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1709\& {
1710\& ev_timer_stop (loop, &tw);
1711.Ve
1712.PP
1713.Vb 2
1714\& for (int i = 0; i < nfd; ++i)
1715\& ev_io_stop (loop, iow + i);
1716.Ve
1717.PP
1718.Vb 2
1719\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1720\& }
1721.Ve
1206.ie n .Sh """ev_embed"" \- when one backend isn't enough" 1722.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1207.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough" 1723.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1208.IX Subsection "ev_embed - when one backend isn't enough" 1724.IX Subsection "ev_embed - when one backend isn't enough..."
1209This is a rather advanced watcher type that lets you embed one event loop 1725This is a rather advanced watcher type that lets you embed one event loop
1210into another. 1726into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1727loop, other types of watchers might be handled in a delayed or incorrect
1728fashion and must not be used).
1211.PP 1729.PP
1212There are primarily two reasons you would want that: work around bugs and 1730There are primarily two reasons you would want that: work around bugs and
1213prioritise I/O. 1731prioritise I/O.
1214.PP 1732.PP
1215As an example for a bug workaround, the kqueue backend might only support 1733As an example for a bug workaround, the kqueue backend might only support
… …
1223As for prioritising I/O: rarely you have the case where some fds have 1741As for prioritising I/O: rarely you have the case where some fds have
1224to be watched and handled very quickly (with low latency), and even 1742to be watched and handled very quickly (with low latency), and even
1225priorities and idle watchers might have too much overhead. In this case 1743priorities and idle watchers might have too much overhead. In this case
1226you would put all the high priority stuff in one loop and all the rest in 1744you would put all the high priority stuff in one loop and all the rest in
1227a second one, and embed the second one in the first. 1745a second one, and embed the second one in the first.
1746.PP
1747As long as the watcher is active, the callback will be invoked every time
1748there might be events pending in the embedded loop. The callback must then
1749call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1750their callbacks (you could also start an idle watcher to give the embedded
1751loop strictly lower priority for example). You can also set the callback
1752to \f(CW0\fR, in which case the embed watcher will automatically execute the
1753embedded loop sweep.
1228.PP 1754.PP
1229As long as the watcher is started it will automatically handle events. The 1755As long as the watcher is started it will automatically handle events. The
1230callback will be invoked whenever some events have been handled. You can 1756callback will be invoked whenever some events have been handled. You can
1231set the callback to \f(CW0\fR to avoid having to specify one if you are not 1757set the callback to \f(CW0\fR to avoid having to specify one if you are not
1232interested in that. 1758interested in that.
… …
1267\& ev_embed_start (loop_hi, &embed); 1793\& ev_embed_start (loop_hi, &embed);
1268\& } 1794\& }
1269\& else 1795\& else
1270\& loop_lo = loop_hi; 1796\& loop_lo = loop_hi;
1271.Ve 1797.Ve
1272.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *loop)" 4 1798.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1273.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *loop)" 1799.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1274.PD 0 1800.PD 0
1275.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *loop)" 4 1801.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1276.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *loop)" 1802.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1277.PD 1803.PD
1278Configures the watcher to embed the given loop, which must be embeddable. 1804Configures the watcher to embed the given loop, which must be
1805embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1806invoked automatically, otherwise it is the responsibility of the callback
1807to invoke it (it will continue to be called until the sweep has been done,
1808if you do not want thta, you need to temporarily stop the embed watcher).
1809.IP "ev_embed_sweep (loop, ev_embed *)" 4
1810.IX Item "ev_embed_sweep (loop, ev_embed *)"
1811Make a single, non-blocking sweep over the embedded loop. This works
1812similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1813apropriate way for embedded loops.
1814.IP "struct ev_loop *loop [read\-only]" 4
1815.IX Item "struct ev_loop *loop [read-only]"
1816The embedded event loop.
1817.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1818.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1819.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1820Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1821whoever is a good citizen cared to tell libev about it by calling
1822\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1823event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1824and only in the child after the fork. If whoever good citizen calling
1825\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1826handlers will be invoked, too, of course.
1827.IP "ev_fork_init (ev_signal *, callback)" 4
1828.IX Item "ev_fork_init (ev_signal *, callback)"
1829Initialises and configures the fork watcher \- it has no parameters of any
1830kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1831believe me.
1279.SH "OTHER FUNCTIONS" 1832.SH "OTHER FUNCTIONS"
1280.IX Header "OTHER FUNCTIONS" 1833.IX Header "OTHER FUNCTIONS"
1281There are some other functions of possible interest. Described. Here. Now. 1834There are some other functions of possible interest. Described. Here. Now.
1282.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1835.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1283.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1836.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1312.Ve 1865.Ve
1313.Sp 1866.Sp
1314.Vb 1 1867.Vb 1
1315\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1868\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1316.Ve 1869.Ve
1317.IP "ev_feed_event (loop, watcher, int events)" 4 1870.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
1318.IX Item "ev_feed_event (loop, watcher, int events)" 1871.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
1319Feeds the given event set into the event loop, as if the specified event 1872Feeds the given event set into the event loop, as if the specified event
1320had happened for the specified watcher (which must be a pointer to an 1873had happened for the specified watcher (which must be a pointer to an
1321initialised but not necessarily started event watcher). 1874initialised but not necessarily started event watcher).
1322.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1875.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
1323.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1876.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
1324Feed an event on the given fd, as if a file descriptor backend detected 1877Feed an event on the given fd, as if a file descriptor backend detected
1325the given events it. 1878the given events it.
1326.IP "ev_feed_signal_event (loop, int signum)" 4 1879.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
1327.IX Item "ev_feed_signal_event (loop, int signum)" 1880.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
1328Feed an event as if the given signal occured (loop must be the default loop!). 1881Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1882loop!).
1329.SH "LIBEVENT EMULATION" 1883.SH "LIBEVENT EMULATION"
1330.IX Header "LIBEVENT EMULATION" 1884.IX Header "LIBEVENT EMULATION"
1331Libev offers a compatibility emulation layer for libevent. It cannot 1885Libev offers a compatibility emulation layer for libevent. It cannot
1332emulate the internals of libevent, so here are some usage hints: 1886emulate the internals of libevent, so here are some usage hints:
1333.IP "* Use it by including <event.h>, as usual." 4 1887.IP "* Use it by including <event.h>, as usual." 4
… …
1344.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1898.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1345.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1899.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1346.PD 1900.PD
1347.SH "\*(C+ SUPPORT" 1901.SH "\*(C+ SUPPORT"
1348.IX Header " SUPPORT" 1902.IX Header " SUPPORT"
1349\&\s-1TBD\s0. 1903Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1904you to use some convinience methods to start/stop watchers and also change
1905the callback model to a model using method callbacks on objects.
1906.PP
1907To use it,
1908.PP
1909.Vb 1
1910\& #include <ev++.h>
1911.Ve
1912.PP
1913This automatically includes \fIev.h\fR and puts all of its definitions (many
1914of them macros) into the global namespace. All \*(C+ specific things are
1915put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
1916options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1917.PP
1918Care has been taken to keep the overhead low. The only data member the \*(C+
1919classes add (compared to plain C\-style watchers) is the event loop pointer
1920that the watcher is associated with (or no additional members at all if
1921you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
1922.PP
1923Currently, functions, and static and non-static member functions can be
1924used as callbacks. Other types should be easy to add as long as they only
1925need one additional pointer for context. If you need support for other
1926types of functors please contact the author (preferably after implementing
1927it).
1928.PP
1929Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1930.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1931.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1932.IX Item "ev::READ, ev::WRITE etc."
1933These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1934macros from \fIev.h\fR.
1935.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1936.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1937.IX Item "ev::tstamp, ev::now"
1938Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1939.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
1940.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1941.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1942For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1943the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1944which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1945defines by many implementations.
1946.Sp
1947All of those classes have these methods:
1948.RS 4
1949.IP "ev::TYPE::TYPE ()" 4
1950.IX Item "ev::TYPE::TYPE ()"
1951.PD 0
1952.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
1953.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
1954.IP "ev::TYPE::~TYPE" 4
1955.IX Item "ev::TYPE::~TYPE"
1956.PD
1957The constructor (optionally) takes an event loop to associate the watcher
1958with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
1959.Sp
1960The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
1961\&\f(CW\*(C`set\*(C'\fR method before starting it.
1962.Sp
1963It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
1964method to set a callback before you can start the watcher.
1965.Sp
1966(The reason why you have to use a method is a limitation in \*(C+ which does
1967not allow explicit template arguments for constructors).
1968.Sp
1969The destructor automatically stops the watcher if it is active.
1970.IP "w\->set<class, &class::method> (object *)" 4
1971.IX Item "w->set<class, &class::method> (object *)"
1972This method sets the callback method to call. The method has to have a
1973signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
1974first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
1975parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
1976.Sp
1977This method synthesizes efficient thunking code to call your method from
1978the C callback that libev requires. If your compiler can inline your
1979callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
1980your compiler is good :), then the method will be fully inlined into the
1981thunking function, making it as fast as a direct C callback.
1982.Sp
1983Example: simple class declaration and watcher initialisation
1984.Sp
1985.Vb 4
1986\& struct myclass
1987\& {
1988\& void io_cb (ev::io &w, int revents) { }
1989\& }
1990.Ve
1991.Sp
1992.Vb 3
1993\& myclass obj;
1994\& ev::io iow;
1995\& iow.set <myclass, &myclass::io_cb> (&obj);
1996.Ve
1997.IP "w\->set<function> (void *data = 0)" 4
1998.IX Item "w->set<function> (void *data = 0)"
1999Also sets a callback, but uses a static method or plain function as
2000callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2001\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2002.Sp
2003The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2004.Sp
2005See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2006.Sp
2007Example:
2008.Sp
2009.Vb 2
2010\& static void io_cb (ev::io &w, int revents) { }
2011\& iow.set <io_cb> ();
2012.Ve
2013.IP "w\->set (struct ev_loop *)" 4
2014.IX Item "w->set (struct ev_loop *)"
2015Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2016do this when the watcher is inactive (and not pending either).
2017.IP "w\->set ([args])" 4
2018.IX Item "w->set ([args])"
2019Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
2020called at least once. Unlike the C counterpart, an active watcher gets
2021automatically stopped and restarted when reconfiguring it with this
2022method.
2023.IP "w\->start ()" 4
2024.IX Item "w->start ()"
2025Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2026constructor already stores the event loop.
2027.IP "w\->stop ()" 4
2028.IX Item "w->stop ()"
2029Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2030.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
2031.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
2032.IX Item "w->again () ev::timer, ev::periodic only"
2033For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2034\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2035.ie n .IP "w\->sweep () ""ev::embed"" only" 4
2036.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
2037.IX Item "w->sweep () ev::embed only"
2038Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2039.ie n .IP "w\->update () ""ev::stat"" only" 4
2040.el .IP "w\->update () \f(CWev::stat\fR only" 4
2041.IX Item "w->update () ev::stat only"
2042Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2043.RE
2044.RS 4
2045.RE
2046.PP
2047Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2048the constructor.
2049.PP
2050.Vb 4
2051\& class myclass
2052\& {
2053\& ev_io io; void io_cb (ev::io &w, int revents);
2054\& ev_idle idle void idle_cb (ev::idle &w, int revents);
2055.Ve
2056.PP
2057.Vb 2
2058\& myclass ();
2059\& }
2060.Ve
2061.PP
2062.Vb 4
2063\& myclass::myclass (int fd)
2064\& {
2065\& io .set <myclass, &myclass::io_cb > (this);
2066\& idle.set <myclass, &myclass::idle_cb> (this);
2067.Ve
2068.PP
2069.Vb 2
2070\& io.start (fd, ev::READ);
2071\& }
2072.Ve
2073.SH "MACRO MAGIC"
2074.IX Header "MACRO MAGIC"
2075Libev can be compiled with a variety of options, the most fundemantal is
2076\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
2077callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2078.PP
2079To make it easier to write programs that cope with either variant, the
2080following macros are defined:
2081.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2082.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2083.IX Item "EV_A, EV_A_"
2084This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2085loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2086\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2087.Sp
2088.Vb 3
2089\& ev_unref (EV_A);
2090\& ev_timer_add (EV_A_ watcher);
2091\& ev_loop (EV_A_ 0);
2092.Ve
2093.Sp
2094It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2095which is often provided by the following macro.
2096.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2097.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2098.IX Item "EV_P, EV_P_"
2099This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2100loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2101\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2102.Sp
2103.Vb 2
2104\& // this is how ev_unref is being declared
2105\& static void ev_unref (EV_P);
2106.Ve
2107.Sp
2108.Vb 2
2109\& // this is how you can declare your typical callback
2110\& static void cb (EV_P_ ev_timer *w, int revents)
2111.Ve
2112.Sp
2113It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2114suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2115.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2116.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2117.IX Item "EV_DEFAULT, EV_DEFAULT_"
2118Similar to the other two macros, this gives you the value of the default
2119loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2120.PP
2121Example: Declare and initialise a check watcher, utilising the above
2122macros so it will work regardless of whether multiple loops are supported
2123or not.
2124.PP
2125.Vb 5
2126\& static void
2127\& check_cb (EV_P_ ev_timer *w, int revents)
2128\& {
2129\& ev_check_stop (EV_A_ w);
2130\& }
2131.Ve
2132.PP
2133.Vb 4
2134\& ev_check check;
2135\& ev_check_init (&check, check_cb);
2136\& ev_check_start (EV_DEFAULT_ &check);
2137\& ev_loop (EV_DEFAULT_ 0);
2138.Ve
2139.SH "EMBEDDING"
2140.IX Header "EMBEDDING"
2141Libev can (and often is) directly embedded into host
2142applications. Examples of applications that embed it include the Deliantra
2143Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2144and rxvt\-unicode.
2145.PP
2146The goal is to enable you to just copy the neecssary files into your
2147source directory without having to change even a single line in them, so
2148you can easily upgrade by simply copying (or having a checked-out copy of
2149libev somewhere in your source tree).
2150.Sh "\s-1FILESETS\s0"
2151.IX Subsection "FILESETS"
2152Depending on what features you need you need to include one or more sets of files
2153in your app.
2154.PP
2155\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2156.IX Subsection "CORE EVENT LOOP"
2157.PP
2158To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2159configuration (no autoconf):
2160.PP
2161.Vb 2
2162\& #define EV_STANDALONE 1
2163\& #include "ev.c"
2164.Ve
2165.PP
2166This will automatically include \fIev.h\fR, too, and should be done in a
2167single C source file only to provide the function implementations. To use
2168it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2169done by writing a wrapper around \fIev.h\fR that you can include instead and
2170where you can put other configuration options):
2171.PP
2172.Vb 2
2173\& #define EV_STANDALONE 1
2174\& #include "ev.h"
2175.Ve
2176.PP
2177Both header files and implementation files can be compiled with a \*(C+
2178compiler (at least, thats a stated goal, and breakage will be treated
2179as a bug).
2180.PP
2181You need the following files in your source tree, or in a directory
2182in your include path (e.g. in libev/ when using \-Ilibev):
2183.PP
2184.Vb 4
2185\& ev.h
2186\& ev.c
2187\& ev_vars.h
2188\& ev_wrap.h
2189.Ve
2190.PP
2191.Vb 1
2192\& ev_win32.c required on win32 platforms only
2193.Ve
2194.PP
2195.Vb 5
2196\& ev_select.c only when select backend is enabled (which is enabled by default)
2197\& ev_poll.c only when poll backend is enabled (disabled by default)
2198\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2199\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2200\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2201.Ve
2202.PP
2203\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2204to compile this single file.
2205.PP
2206\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2207.IX Subsection "LIBEVENT COMPATIBILITY API"
2208.PP
2209To include the libevent compatibility \s-1API\s0, also include:
2210.PP
2211.Vb 1
2212\& #include "event.c"
2213.Ve
2214.PP
2215in the file including \fIev.c\fR, and:
2216.PP
2217.Vb 1
2218\& #include "event.h"
2219.Ve
2220.PP
2221in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2222.PP
2223You need the following additional files for this:
2224.PP
2225.Vb 2
2226\& event.h
2227\& event.c
2228.Ve
2229.PP
2230\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2231.IX Subsection "AUTOCONF SUPPORT"
2232.PP
2233Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2234whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2235\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2236include \fIconfig.h\fR and configure itself accordingly.
2237.PP
2238For this of course you need the m4 file:
2239.PP
2240.Vb 1
2241\& libev.m4
2242.Ve
2243.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2244.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2245Libev can be configured via a variety of preprocessor symbols you have to define
2246before including any of its files. The default is not to build for multiplicity
2247and only include the select backend.
2248.IP "\s-1EV_STANDALONE\s0" 4
2249.IX Item "EV_STANDALONE"
2250Must always be \f(CW1\fR if you do not use autoconf configuration, which
2251keeps libev from including \fIconfig.h\fR, and it also defines dummy
2252implementations for some libevent functions (such as logging, which is not
2253supported). It will also not define any of the structs usually found in
2254\&\fIevent.h\fR that are not directly supported by the libev core alone.
2255.IP "\s-1EV_USE_MONOTONIC\s0" 4
2256.IX Item "EV_USE_MONOTONIC"
2257If defined to be \f(CW1\fR, libev will try to detect the availability of the
2258monotonic clock option at both compiletime and runtime. Otherwise no use
2259of the monotonic clock option will be attempted. If you enable this, you
2260usually have to link against librt or something similar. Enabling it when
2261the functionality isn't available is safe, though, althoguh you have
2262to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2263function is hiding in (often \fI\-lrt\fR).
2264.IP "\s-1EV_USE_REALTIME\s0" 4
2265.IX Item "EV_USE_REALTIME"
2266If defined to be \f(CW1\fR, libev will try to detect the availability of the
2267realtime clock option at compiletime (and assume its availability at
2268runtime if successful). Otherwise no use of the realtime clock option will
2269be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2270(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2271in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2272.IP "\s-1EV_USE_SELECT\s0" 4
2273.IX Item "EV_USE_SELECT"
2274If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2275\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2276other method takes over, select will be it. Otherwise the select backend
2277will not be compiled in.
2278.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2279.IX Item "EV_SELECT_USE_FD_SET"
2280If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2281structure. This is useful if libev doesn't compile due to a missing
2282\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2283exotic systems. This usually limits the range of file descriptors to some
2284low limit such as 1024 or might have other limitations (winsocket only
2285allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2286influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2287.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2288.IX Item "EV_SELECT_IS_WINSOCKET"
2289When defined to \f(CW1\fR, the select backend will assume that
2290select/socket/connect etc. don't understand file descriptors but
2291wants osf handles on win32 (this is the case when the select to
2292be used is the winsock select). This means that it will call
2293\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2294it is assumed that all these functions actually work on fds, even
2295on win32. Should not be defined on non\-win32 platforms.
2296.IP "\s-1EV_USE_POLL\s0" 4
2297.IX Item "EV_USE_POLL"
2298If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2299backend. Otherwise it will be enabled on non\-win32 platforms. It
2300takes precedence over select.
2301.IP "\s-1EV_USE_EPOLL\s0" 4
2302.IX Item "EV_USE_EPOLL"
2303If defined to be \f(CW1\fR, libev will compile in support for the Linux
2304\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2305otherwise another method will be used as fallback. This is the
2306preferred backend for GNU/Linux systems.
2307.IP "\s-1EV_USE_KQUEUE\s0" 4
2308.IX Item "EV_USE_KQUEUE"
2309If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2310\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2311otherwise another method will be used as fallback. This is the preferred
2312backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2313supports some types of fds correctly (the only platform we found that
2314supports ptys for example was NetBSD), so kqueue might be compiled in, but
2315not be used unless explicitly requested. The best way to use it is to find
2316out whether kqueue supports your type of fd properly and use an embedded
2317kqueue loop.
2318.IP "\s-1EV_USE_PORT\s0" 4
2319.IX Item "EV_USE_PORT"
2320If defined to be \f(CW1\fR, libev will compile in support for the Solaris
232110 port style backend. Its availability will be detected at runtime,
2322otherwise another method will be used as fallback. This is the preferred
2323backend for Solaris 10 systems.
2324.IP "\s-1EV_USE_DEVPOLL\s0" 4
2325.IX Item "EV_USE_DEVPOLL"
2326reserved for future expansion, works like the \s-1USE\s0 symbols above.
2327.IP "\s-1EV_USE_INOTIFY\s0" 4
2328.IX Item "EV_USE_INOTIFY"
2329If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2330interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2331be detected at runtime.
2332.IP "\s-1EV_H\s0" 4
2333.IX Item "EV_H"
2334The name of the \fIev.h\fR header file used to include it. The default if
2335undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2336can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2337.IP "\s-1EV_CONFIG_H\s0" 4
2338.IX Item "EV_CONFIG_H"
2339If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2340\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2341\&\f(CW\*(C`EV_H\*(C'\fR, above.
2342.IP "\s-1EV_EVENT_H\s0" 4
2343.IX Item "EV_EVENT_H"
2344Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2345of how the \fIevent.h\fR header can be found.
2346.IP "\s-1EV_PROTOTYPES\s0" 4
2347.IX Item "EV_PROTOTYPES"
2348If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2349prototypes, but still define all the structs and other symbols. This is
2350occasionally useful if you want to provide your own wrapper functions
2351around libev functions.
2352.IP "\s-1EV_MULTIPLICITY\s0" 4
2353.IX Item "EV_MULTIPLICITY"
2354If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2355will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2356additional independent event loops. Otherwise there will be no support
2357for multiple event loops and there is no first event loop pointer
2358argument. Instead, all functions act on the single default loop.
2359.IP "\s-1EV_MINPRI\s0" 4
2360.IX Item "EV_MINPRI"
2361.PD 0
2362.IP "\s-1EV_MAXPRI\s0" 4
2363.IX Item "EV_MAXPRI"
2364.PD
2365The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2366\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2367provide for more priorities by overriding those symbols (usually defined
2368to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2369.Sp
2370When doing priority-based operations, libev usually has to linearly search
2371all the priorities, so having many of them (hundreds) uses a lot of space
2372and time, so using the defaults of five priorities (\-2 .. +2) is usually
2373fine.
2374.Sp
2375If your embedding app does not need any priorities, defining these both to
2376\&\f(CW0\fR will save some memory and cpu.
2377.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2378.IX Item "EV_PERIODIC_ENABLE"
2379If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2380defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2381code.
2382.IP "\s-1EV_IDLE_ENABLE\s0" 4
2383.IX Item "EV_IDLE_ENABLE"
2384If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2385defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2386code.
2387.IP "\s-1EV_EMBED_ENABLE\s0" 4
2388.IX Item "EV_EMBED_ENABLE"
2389If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2390defined to be \f(CW0\fR, then they are not.
2391.IP "\s-1EV_STAT_ENABLE\s0" 4
2392.IX Item "EV_STAT_ENABLE"
2393If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2394defined to be \f(CW0\fR, then they are not.
2395.IP "\s-1EV_FORK_ENABLE\s0" 4
2396.IX Item "EV_FORK_ENABLE"
2397If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2398defined to be \f(CW0\fR, then they are not.
2399.IP "\s-1EV_MINIMAL\s0" 4
2400.IX Item "EV_MINIMAL"
2401If you need to shave off some kilobytes of code at the expense of some
2402speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2403some inlining decisions, saves roughly 30% codesize of amd64.
2404.IP "\s-1EV_PID_HASHSIZE\s0" 4
2405.IX Item "EV_PID_HASHSIZE"
2406\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2407pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2408than enough. If you need to manage thousands of children you might want to
2409increase this value (\fImust\fR be a power of two).
2410.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2411.IX Item "EV_INOTIFY_HASHSIZE"
2412\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2413inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2414usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2415watchers you might want to increase this value (\fImust\fR be a power of
2416two).
2417.IP "\s-1EV_COMMON\s0" 4
2418.IX Item "EV_COMMON"
2419By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2420this macro to a something else you can include more and other types of
2421members. You have to define it each time you include one of the files,
2422though, and it must be identical each time.
2423.Sp
2424For example, the perl \s-1EV\s0 module uses something like this:
2425.Sp
2426.Vb 3
2427\& #define EV_COMMON \e
2428\& SV *self; /* contains this struct */ \e
2429\& SV *cb_sv, *fh /* note no trailing ";" */
2430.Ve
2431.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2432.IX Item "EV_CB_DECLARE (type)"
2433.PD 0
2434.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2435.IX Item "EV_CB_INVOKE (watcher, revents)"
2436.IP "ev_set_cb (ev, cb)" 4
2437.IX Item "ev_set_cb (ev, cb)"
2438.PD
2439Can be used to change the callback member declaration in each watcher,
2440and the way callbacks are invoked and set. Must expand to a struct member
2441definition and a statement, respectively. See the \fIev.v\fR header file for
2442their default definitions. One possible use for overriding these is to
2443avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2444method calls instead of plain function calls in \*(C+.
2445.Sh "\s-1EXAMPLES\s0"
2446.IX Subsection "EXAMPLES"
2447For a real-world example of a program the includes libev
2448verbatim, you can have a look at the \s-1EV\s0 perl module
2449(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2450the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2451interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2452will be compiled. It is pretty complex because it provides its own header
2453file.
2454.Sp
2455The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2456that everybody includes and which overrides some configure choices:
2457.Sp
2458.Vb 9
2459\& #define EV_MINIMAL 1
2460\& #define EV_USE_POLL 0
2461\& #define EV_MULTIPLICITY 0
2462\& #define EV_PERIODIC_ENABLE 0
2463\& #define EV_STAT_ENABLE 0
2464\& #define EV_FORK_ENABLE 0
2465\& #define EV_CONFIG_H <config.h>
2466\& #define EV_MINPRI 0
2467\& #define EV_MAXPRI 0
2468.Ve
2469.Sp
2470.Vb 1
2471\& #include "ev++.h"
2472.Ve
2473.Sp
2474And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2475.Sp
2476.Vb 2
2477\& #include "ev_cpp.h"
2478\& #include "ev.c"
2479.Ve
2480.SH "COMPLEXITIES"
2481.IX Header "COMPLEXITIES"
2482In this section the complexities of (many of) the algorithms used inside
2483libev will be explained. For complexity discussions about backends see the
2484documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2485.Sp
2486All of the following are about amortised time: If an array needs to be
2487extended, libev needs to realloc and move the whole array, but this
2488happens asymptotically never with higher number of elements, so O(1) might
2489mean it might do a lengthy realloc operation in rare cases, but on average
2490it is much faster and asymptotically approaches constant time.
2491.RS 4
2492.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2493.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2494This means that, when you have a watcher that triggers in one hour and
2495there are 100 watchers that would trigger before that then inserting will
2496have to skip those 100 watchers.
2497.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2498.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2499That means that for changing a timer costs less than removing/adding them
2500as only the relative motion in the event queue has to be paid for.
2501.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2502.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2503These just add the watcher into an array or at the head of a list.
2504=item Stopping check/prepare/idle watchers: O(1)
2505.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2506.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2507These watchers are stored in lists then need to be walked to find the
2508correct watcher to remove. The lists are usually short (you don't usually
2509have many watchers waiting for the same fd or signal).
2510.IP "Finding the next timer per loop iteration: O(1)" 4
2511.IX Item "Finding the next timer per loop iteration: O(1)"
2512.PD 0
2513.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2514.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2515.PD
2516A change means an I/O watcher gets started or stopped, which requires
2517libev to recalculate its status (and possibly tell the kernel).
2518.IP "Activating one watcher: O(1)" 4
2519.IX Item "Activating one watcher: O(1)"
2520.PD 0
2521.IP "Priority handling: O(number_of_priorities)" 4
2522.IX Item "Priority handling: O(number_of_priorities)"
2523.PD
2524Priorities are implemented by allocating some space for each
2525priority. When doing priority-based operations, libev usually has to
2526linearly search all the priorities.
2527.RE
2528.RS 4
1350.SH "AUTHOR" 2529.SH "AUTHOR"
1351.IX Header "AUTHOR" 2530.IX Header "AUTHOR"
1352Marc Lehmann <libev@schmorp.de>. 2531Marc Lehmann <libev@schmorp.de>.

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines