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Revision 1.9 by root, Fri Nov 23 16:17:12 2007 UTC vs.
Revision 1.50 by root, Wed Dec 12 17:55:05 2007 UTC

… …
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-12" "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
… …
190.IX Item "int ev_version_major ()" 259.IX Item "int ev_version_major ()"
191.PD 0 260.PD 0
192.IP "int ev_version_minor ()" 4 261.IP "int ev_version_minor ()" 4
193.IX Item "int ev_version_minor ()" 262.IX Item "int ev_version_minor ()"
194.PD 263.PD
195You can find out the major and minor version numbers of the library 264You can find out the major and minor \s-1ABI\s0 version numbers of the library
196you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and 265you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
197\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global 266\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
198symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the 267symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
199version of the library your program was compiled against. 268version of the library your program was compiled against.
200.Sp 269.Sp
270These version numbers refer to the \s-1ABI\s0 version of the library, not the
271release version.
272.Sp
201Usually, it's a good idea to terminate if the major versions mismatch, 273Usually, it's a good idea to terminate if the major versions mismatch,
202as this indicates an incompatible change. Minor versions are usually 274as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 275compatible to older versions, so a larger minor version alone is usually
204not a problem. 276not a problem.
205.Sp 277.Sp
206Example: make sure we haven't accidentally been linked against the wrong 278Example: Make sure we haven't accidentally been linked against the wrong
207version: 279version.
208.Sp 280.Sp
209.Vb 3 281.Vb 3
210\& assert (("libev version mismatch", 282\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 283\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 284\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
231recommended for this platform. This set is often smaller than the one 303recommended for this platform. This set is often smaller than the one
232returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on 304returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
233most BSDs and will not be autodetected unless you explicitly request it 305most BSDs and will not be autodetected unless you explicitly request it
234(assuming you know what you are doing). This is the set of backends that 306(assuming you know what you are doing). This is the set of backends that
235libev will probe for if you specify no backends explicitly. 307libev will probe for if you specify no backends explicitly.
308.IP "unsigned int ev_embeddable_backends ()" 4
309.IX Item "unsigned int ev_embeddable_backends ()"
310Returns the set of backends that are embeddable in other event loops. This
311is the theoretical, all\-platform, value. To find which backends
312might be supported on the current system, you would need to look at
313\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
314recommended ones.
315.Sp
316See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
236.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 317.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
237.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 318.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
238Sets the allocation function to use (the prototype is similar to the 319Sets the allocation function to use (the prototype is similar \- the
239realloc C function, the semantics are identical). It is used to allocate 320semantics is identical \- to the realloc C function). It is used to
240and free memory (no surprises here). If it returns zero when memory 321allocate and free memory (no surprises here). If it returns zero when
241needs to be allocated, the library might abort or take some potentially 322memory needs to be allocated, the library might abort or take some
242destructive action. The default is your system realloc function. 323potentially destructive action. The default is your system realloc
324function.
243.Sp 325.Sp
244You could override this function in high-availability programs to, say, 326You could override this function in high-availability programs to, say,
245free some memory if it cannot allocate memory, to use a special allocator, 327free some memory if it cannot allocate memory, to use a special allocator,
246or even to sleep a while and retry until some memory is available. 328or even to sleep a while and retry until some memory is available.
247.Sp 329.Sp
248Example: replace the libev allocator with one that waits a bit and then 330Example: Replace the libev allocator with one that waits a bit and then
249retries: better than mine). 331retries).
250.Sp 332.Sp
251.Vb 6 333.Vb 6
252\& static void * 334\& static void *
253\& persistent_realloc (void *ptr, long size) 335\& persistent_realloc (void *ptr, size_t size)
254\& { 336\& {
255\& for (;;) 337\& for (;;)
256\& { 338\& {
257\& void *newptr = realloc (ptr, size); 339\& void *newptr = realloc (ptr, size);
258.Ve 340.Ve
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280callback is set, then libev will expect it to remedy the sitution, no 362callback is set, then libev will expect it to remedy the sitution, no
281matter what, when it returns. That is, libev will generally retry the 363matter what, when it returns. That is, libev will generally retry the
282requested operation, or, if the condition doesn't go away, do bad stuff 364requested operation, or, if the condition doesn't go away, do bad stuff
283(such as abort). 365(such as abort).
284.Sp 366.Sp
285Example: do the same thing as libev does internally: 367Example: This is basically the same thing that libev does internally, too.
286.Sp 368.Sp
287.Vb 6 369.Vb 6
288\& static void 370\& static void
289\& fatal_error (const char *msg) 371\& fatal_error (const char *msg)
290\& { 372\& {
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336or setgid) then libev will \fInot\fR look at the environment variable 418or setgid) then libev will \fInot\fR look at the environment variable
337\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 419\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
338override the flags completely if it is found in the environment. This is 420override the flags completely if it is found in the environment. This is
339useful to try out specific backends to test their performance, or to work 421useful to try out specific backends to test their performance, or to work
340around bugs. 422around bugs.
423.ie n .IP """EVFLAG_FORKCHECK""" 4
424.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
425.IX Item "EVFLAG_FORKCHECK"
426Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
427a fork, you can also make libev check for a fork in each iteration by
428enabling this flag.
429.Sp
430This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
431and thus this might slow down your event loop if you do a lot of loop
432iterations and little real work, but is usually not noticeable (on my
433Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
434without a syscall and thus \fIvery\fR fast, but my Linux system also has
435\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
436.Sp
437The big advantage of this flag is that you can forget about fork (and
438forget about forgetting to tell libev about forking) when you use this
439flag.
440.Sp
441This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
442environment variable.
341.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 443.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
342.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 444.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
343.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 445.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
344This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 446This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
345libev tries to roll its own fd_set with no limits on the number of fds, 447libev tries to roll its own fd_set with no limits on the number of fds,
… …
439Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 541Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
440always distinct from the default loop. Unlike the default loop, it cannot 542always distinct from the default loop. Unlike the default loop, it cannot
441handle signal and child watchers, and attempts to do so will be greeted by 543handle signal and child watchers, and attempts to do so will be greeted by
442undefined behaviour (or a failed assertion if assertions are enabled). 544undefined behaviour (or a failed assertion if assertions are enabled).
443.Sp 545.Sp
444Example: try to create a event loop that uses epoll and nothing else. 546Example: Try to create a event loop that uses epoll and nothing else.
445.Sp 547.Sp
446.Vb 3 548.Vb 3
447\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 549\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
448\& if (!epoller) 550\& if (!epoller)
449\& fatal ("no epoll found here, maybe it hides under your chair"); 551\& fatal ("no epoll found here, maybe it hides under your chair");
450.Ve 552.Ve
451.IP "ev_default_destroy ()" 4 553.IP "ev_default_destroy ()" 4
452.IX Item "ev_default_destroy ()" 554.IX Item "ev_default_destroy ()"
453Destroys the default loop again (frees all memory and kernel state 555Destroys the default loop again (frees all memory and kernel state
454etc.). This stops all registered event watchers (by not touching them in 556etc.). None of the active event watchers will be stopped in the normal
455any way whatsoever, although you cannot rely on this :). 557sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
558responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
559calling this function, or cope with the fact afterwards (which is usually
560the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
561for example).
456.IP "ev_loop_destroy (loop)" 4 562.IP "ev_loop_destroy (loop)" 4
457.IX Item "ev_loop_destroy (loop)" 563.IX Item "ev_loop_destroy (loop)"
458Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 564Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
459earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 565earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
460.IP "ev_default_fork ()" 4 566.IP "ev_default_fork ()" 4
… …
482.IP "ev_loop_fork (loop)" 4 588.IP "ev_loop_fork (loop)" 4
483.IX Item "ev_loop_fork (loop)" 589.IX Item "ev_loop_fork (loop)"
484Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 590Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
485\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 591\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
486after fork, and how you do this is entirely your own problem. 592after fork, and how you do this is entirely your own problem.
593.IP "unsigned int ev_loop_count (loop)" 4
594.IX Item "unsigned int ev_loop_count (loop)"
595Returns the count of loop iterations for the loop, which is identical to
596the number of times libev did poll for new events. It starts at \f(CW0\fR and
597happily wraps around with enough iterations.
598.Sp
599This value can sometimes be useful as a generation counter of sorts (it
600\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
601\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
487.IP "unsigned int ev_backend (loop)" 4 602.IP "unsigned int ev_backend (loop)" 4
488.IX Item "unsigned int ev_backend (loop)" 603.IX Item "unsigned int ev_backend (loop)"
489Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 604Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
490use. 605use.
491.IP "ev_tstamp ev_now (loop)" 4 606.IP "ev_tstamp ev_now (loop)" 4
… …
522libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 637libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
523usually a better approach for this kind of thing. 638usually a better approach for this kind of thing.
524.Sp 639.Sp
525Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 640Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
526.Sp 641.Sp
527.Vb 18 642.Vb 19
643\& - Before the first iteration, call any pending watchers.
528\& * If there are no active watchers (reference count is zero), return. 644\& * If there are no active watchers (reference count is zero), return.
529\& - Queue prepare watchers and then call all outstanding watchers. 645\& - Queue all prepare watchers and then call all outstanding watchers.
530\& - If we have been forked, recreate the kernel state. 646\& - If we have been forked, recreate the kernel state.
531\& - Update the kernel state with all outstanding changes. 647\& - Update the kernel state with all outstanding changes.
532\& - Update the "event loop time". 648\& - Update the "event loop time".
533\& - Calculate for how long to block. 649\& - Calculate for how long to block.
534\& - Block the process, waiting for any events. 650\& - Block the process, waiting for any events.
… …
543\& be handled here by queueing them when their watcher gets executed. 659\& be handled here by queueing them when their watcher gets executed.
544\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 660\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
545\& were used, return, otherwise continue with step *. 661\& were used, return, otherwise continue with step *.
546.Ve 662.Ve
547.Sp 663.Sp
548Example: queue some jobs and then loop until no events are outsanding 664Example: Queue some jobs and then loop until no events are outsanding
549anymore. 665anymore.
550.Sp 666.Sp
551.Vb 4 667.Vb 4
552\& ... queue jobs here, make sure they register event watchers as long 668\& ... queue jobs here, make sure they register event watchers as long
553\& ... as they still have work to do (even an idle watcher will do..) 669\& ... as they still have work to do (even an idle watcher will do..)
… …
575visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 691visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
576no event watchers registered by it are active. It is also an excellent 692no event watchers registered by it are active. It is also an excellent
577way to do this for generic recurring timers or from within third-party 693way to do this for generic recurring timers or from within third-party
578libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 694libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
579.Sp 695.Sp
580Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 696Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
581running when nothing else is active. 697running when nothing else is active.
582.Sp 698.Sp
583.Vb 4 699.Vb 4
584\& struct dv_signal exitsig; 700\& struct ev_signal exitsig;
585\& ev_signal_init (&exitsig, sig_cb, SIGINT); 701\& ev_signal_init (&exitsig, sig_cb, SIGINT);
586\& ev_signal_start (myloop, &exitsig); 702\& ev_signal_start (loop, &exitsig);
587\& evf_unref (myloop); 703\& evf_unref (loop);
588.Ve 704.Ve
589.Sp 705.Sp
590Example: for some weird reason, unregister the above signal handler again. 706Example: For some weird reason, unregister the above signal handler again.
591.Sp 707.Sp
592.Vb 2 708.Vb 2
593\& ev_ref (myloop); 709\& ev_ref (loop);
594\& ev_signal_stop (myloop, &exitsig); 710\& ev_signal_stop (loop, &exitsig);
595.Ve 711.Ve
596.SH "ANATOMY OF A WATCHER" 712.SH "ANATOMY OF A WATCHER"
597.IX Header "ANATOMY OF A WATCHER" 713.IX Header "ANATOMY OF A WATCHER"
598A watcher is a structure that you create and register to record your 714A watcher is a structure that you create and register to record your
599interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 715interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
… …
636*)\*(C'\fR), and you can stop watching for events at any time by calling the 752*)\*(C'\fR), and you can stop watching for events at any time by calling the
637corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 753corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
638.PP 754.PP
639As long as your watcher is active (has been started but not stopped) you 755As long as your watcher is active (has been started but not stopped) you
640must not touch the values stored in it. Most specifically you must never 756must not touch the values stored in it. Most specifically you must never
641reinitialise it or call its set macro. 757reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
642.PP
643You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
644(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
645callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
646(watcher *)\*(C'\fR macro.
647.PP 758.PP
648Each and every callback receives the event loop pointer as first, the 759Each and every callback receives the event loop pointer as first, the
649registered watcher structure as second, and a bitset of received events as 760registered watcher structure as second, and a bitset of received events as
650third argument. 761third argument.
651.PP 762.PP
… …
676The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 787The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
677.ie n .IP """EV_CHILD""" 4 788.ie n .IP """EV_CHILD""" 4
678.el .IP "\f(CWEV_CHILD\fR" 4 789.el .IP "\f(CWEV_CHILD\fR" 4
679.IX Item "EV_CHILD" 790.IX Item "EV_CHILD"
680The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 791The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
792.ie n .IP """EV_STAT""" 4
793.el .IP "\f(CWEV_STAT\fR" 4
794.IX Item "EV_STAT"
795The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
681.ie n .IP """EV_IDLE""" 4 796.ie n .IP """EV_IDLE""" 4
682.el .IP "\f(CWEV_IDLE\fR" 4 797.el .IP "\f(CWEV_IDLE\fR" 4
683.IX Item "EV_IDLE" 798.IX Item "EV_IDLE"
684The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 799The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
685.ie n .IP """EV_PREPARE""" 4 800.ie n .IP """EV_PREPARE""" 4
… …
695\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 810\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
696received events. Callbacks of both watcher types can start and stop as 811received events. Callbacks of both watcher types can start and stop as
697many watchers as they want, and all of them will be taken into account 812many watchers as they want, and all of them will be taken into account
698(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 813(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
699\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 814\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
815.ie n .IP """EV_EMBED""" 4
816.el .IP "\f(CWEV_EMBED\fR" 4
817.IX Item "EV_EMBED"
818The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
819.ie n .IP """EV_FORK""" 4
820.el .IP "\f(CWEV_FORK\fR" 4
821.IX Item "EV_FORK"
822The event loop has been resumed in the child process after fork (see
823\&\f(CW\*(C`ev_fork\*(C'\fR).
700.ie n .IP """EV_ERROR""" 4 824.ie n .IP """EV_ERROR""" 4
701.el .IP "\f(CWEV_ERROR\fR" 4 825.el .IP "\f(CWEV_ERROR\fR" 4
702.IX Item "EV_ERROR" 826.IX Item "EV_ERROR"
703An unspecified error has occured, the watcher has been stopped. This might 827An unspecified error has occured, the watcher has been stopped. This might
704happen because the watcher could not be properly started because libev 828happen because the watcher could not be properly started because libev
… …
709Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 833Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
710for example it might indicate that a fd is readable or writable, and if 834for example it might indicate that a fd is readable or writable, and if
711your callbacks is well-written it can just attempt the operation and cope 835your callbacks is well-written it can just attempt the operation and cope
712with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 836with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
713programs, though, so beware. 837programs, though, so beware.
838.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
839.IX Subsection "GENERIC WATCHER FUNCTIONS"
840In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
841e.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.
842.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
843.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
844.IX Item "ev_init (ev_TYPE *watcher, callback)"
845This macro initialises the generic portion of a watcher. The contents
846of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
847the generic parts of the watcher are initialised, you \fIneed\fR to call
848the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
849type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
850which rolls both calls into one.
851.Sp
852You can reinitialise a watcher at any time as long as it has been stopped
853(or never started) and there are no pending events outstanding.
854.Sp
855The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
856int revents)\*(C'\fR.
857.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
858.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
859.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
860This macro initialises the type-specific parts of a watcher. You need to
861call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
862call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
863macro on a watcher that is active (it can be pending, however, which is a
864difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
865.Sp
866Although some watcher types do not have type-specific arguments
867(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
868.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
869.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
870.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
871This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
872calls into a single call. This is the most convinient method to initialise
873a watcher. The same limitations apply, of course.
874.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
875.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
876.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
877Starts (activates) the given watcher. Only active watchers will receive
878events. If the watcher is already active nothing will happen.
879.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
880.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
881.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
882Stops the given watcher again (if active) and clears the pending
883status. It is possible that stopped watchers are pending (for example,
884non-repeating timers are being stopped when they become pending), but
885\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
886you want to free or reuse the memory used by the watcher it is therefore a
887good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
888.IP "bool ev_is_active (ev_TYPE *watcher)" 4
889.IX Item "bool ev_is_active (ev_TYPE *watcher)"
890Returns a true value iff the watcher is active (i.e. it has been started
891and not yet been stopped). As long as a watcher is active you must not modify
892it.
893.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
894.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
895Returns a true value iff the watcher is pending, (i.e. it has outstanding
896events but its callback has not yet been invoked). As long as a watcher
897is pending (but not active) you must not call an init function on it (but
898\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
899make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
900it).
901.IP "callback ev_cb (ev_TYPE *watcher)" 4
902.IX Item "callback ev_cb (ev_TYPE *watcher)"
903Returns the callback currently set on the watcher.
904.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
905.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
906Change the callback. You can change the callback at virtually any time
907(modulo threads).
908.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
909.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
910.PD 0
911.IP "int ev_priority (ev_TYPE *watcher)" 4
912.IX Item "int ev_priority (ev_TYPE *watcher)"
913.PD
914Set and query the priority of the watcher. The priority is a small
915integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
916(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
917before watchers with lower priority, but priority will not keep watchers
918from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
919.Sp
920This means that priorities are \fIonly\fR used for ordering callback
921invocation after new events have been received. This is useful, for
922example, to reduce latency after idling, or more often, to bind two
923watchers on the same event and make sure one is called first.
924.Sp
925If you need to suppress invocation when higher priority events are pending
926you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
927.Sp
928You \fImust not\fR change the priority of a watcher as long as it is active or
929pending.
930.Sp
931The default priority used by watchers when no priority has been set is
932always \f(CW0\fR, which is supposed to not be too high and not be too low :).
933.Sp
934Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
935fine, as long as you do not mind that the priority value you query might
936or might not have been adjusted to be within valid range.
937.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
938.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
939Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
940\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
941can deal with that fact.
942.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
943.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
944If the watcher is pending, this function returns clears its pending status
945and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
946watcher isn't pending it does nothing and returns \f(CW0\fR.
714.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 947.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
715.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 948.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
716Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 949Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
717and read at any time, libev will completely ignore it. This can be used 950and read at any time, libev will completely ignore it. This can be used
718to associate arbitrary data with your watcher. If you need more data and 951to associate arbitrary data with your watcher. If you need more data and
… …
739\& struct my_io *w = (struct my_io *)w_; 972\& struct my_io *w = (struct my_io *)w_;
740\& ... 973\& ...
741\& } 974\& }
742.Ve 975.Ve
743.PP 976.PP
744More interesting and less C\-conformant ways of catsing your callback type 977More interesting and less C\-conformant ways of casting your callback type
745have been omitted.... 978instead have been omitted.
979.PP
980Another common scenario is having some data structure with multiple
981watchers:
982.PP
983.Vb 6
984\& struct my_biggy
985\& {
986\& int some_data;
987\& ev_timer t1;
988\& ev_timer t2;
989\& }
990.Ve
991.PP
992In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
993you need to use \f(CW\*(C`offsetof\*(C'\fR:
994.PP
995.Vb 1
996\& #include <stddef.h>
997.Ve
998.PP
999.Vb 6
1000\& static void
1001\& t1_cb (EV_P_ struct ev_timer *w, int revents)
1002\& {
1003\& struct my_biggy big = (struct my_biggy *
1004\& (((char *)w) - offsetof (struct my_biggy, t1));
1005\& }
1006.Ve
1007.PP
1008.Vb 6
1009\& static void
1010\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1011\& {
1012\& struct my_biggy big = (struct my_biggy *
1013\& (((char *)w) - offsetof (struct my_biggy, t2));
1014\& }
1015.Ve
746.SH "WATCHER TYPES" 1016.SH "WATCHER TYPES"
747.IX Header "WATCHER TYPES" 1017.IX Header "WATCHER TYPES"
748This section describes each watcher in detail, but will not repeat 1018This section describes each watcher in detail, but will not repeat
749information given in the last section. 1019information given in the last section. Any initialisation/set macros,
1020functions and members specific to the watcher type are explained.
1021.PP
1022Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1023while the watcher is active, you can look at the member and expect some
1024sensible content, but you must not modify it (you can modify it while the
1025watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1026means you can expect it to have some sensible content while the watcher
1027is active, but you can also modify it. Modifying it may not do something
1028sensible or take immediate effect (or do anything at all), but libev will
1029not crash or malfunction in any way.
750.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1030.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
751.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1031.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
752.IX Subsection "ev_io - is this file descriptor readable or writable" 1032.IX Subsection "ev_io - is this file descriptor readable or writable?"
753I/O watchers check whether a file descriptor is readable or writable 1033I/O watchers check whether a file descriptor is readable or writable
754in each iteration of the event loop (This behaviour is called 1034in each iteration of the event loop, or, more precisely, when reading
755level-triggering because you keep receiving events as long as the 1035would not block the process and writing would at least be able to write
756condition persists. Remember you can stop the watcher if you don't want to 1036some data. This behaviour is called level-triggering because you keep
757act on the event and neither want to receive future events). 1037receiving events as long as the condition persists. Remember you can stop
1038the watcher if you don't want to act on the event and neither want to
1039receive future events.
758.PP 1040.PP
759In general you can register as many read and/or write event watchers per 1041In general you can register as many read and/or write event watchers per
760fd as you want (as long as you don't confuse yourself). Setting all file 1042fd as you want (as long as you don't confuse yourself). Setting all file
761descriptors to non-blocking mode is also usually a good idea (but not 1043descriptors to non-blocking mode is also usually a good idea (but not
762required if you know what you are doing). 1044required if you know what you are doing).
763.PP 1045.PP
764You have to be careful with dup'ed file descriptors, though. Some backends 1046You have to be careful with dup'ed file descriptors, though. Some backends
765(the linux epoll backend is a notable example) cannot handle dup'ed file 1047(the linux epoll backend is a notable example) cannot handle dup'ed file
766descriptors correctly if you register interest in two or more fds pointing 1048descriptors correctly if you register interest in two or more fds pointing
767to the same underlying file/socket etc. description (that is, they share 1049to the same underlying file/socket/etc. description (that is, they share
768the same underlying \*(L"file open\*(R"). 1050the same underlying \*(L"file open\*(R").
769.PP 1051.PP
770If you must do this, then force the use of a known-to-be-good backend 1052If you must do this, then force the use of a known-to-be-good backend
771(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1053(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
772\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1054\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1055.PP
1056Another thing you have to watch out for is that it is quite easy to
1057receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1058be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1059because there is no data. Not only are some backends known to create a
1060lot of those (for example solaris ports), it is very easy to get into
1061this situation even with a relatively standard program structure. Thus
1062it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1063\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1064.PP
1065If you cannot run the fd in non-blocking mode (for example you should not
1066play around with an Xlib connection), then you have to seperately re-test
1067whether a file descriptor is really ready with a known-to-be good interface
1068such as poll (fortunately in our Xlib example, Xlib already does this on
1069its own, so its quite safe to use).
1070.PP
1071\fIThe special problem of disappearing file descriptors\fR
1072.IX Subsection "The special problem of disappearing file descriptors"
1073.PP
1074Some backends (e.g kqueue, epoll) need to be told about closing a file
1075descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1076such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1077descriptor, but when it goes away, the operating system will silently drop
1078this interest. If another file descriptor with the same number then is
1079registered with libev, there is no efficient way to see that this is, in
1080fact, a different file descriptor.
1081.PP
1082To avoid having to explicitly tell libev about such cases, libev follows
1083the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1084will assume that this is potentially a new file descriptor, otherwise
1085it is assumed that the file descriptor stays the same. That means that
1086you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
1087descriptor even if the file descriptor number itself did not change.
1088.PP
1089This is how one would do it normally anyway, the important point is that
1090the libev application should not optimise around libev but should leave
1091optimisations to libev.
1092.PP
1093\fIWatcher-Specific Functions\fR
1094.IX Subsection "Watcher-Specific Functions"
773.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1095.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
774.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1096.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
775.PD 0 1097.PD 0
776.IP "ev_io_set (ev_io *, int fd, int events)" 4 1098.IP "ev_io_set (ev_io *, int fd, int events)" 4
777.IX Item "ev_io_set (ev_io *, int fd, int events)" 1099.IX Item "ev_io_set (ev_io *, int fd, int events)"
778.PD 1100.PD
779Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1101Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
780events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 1102rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
781EV_WRITE\*(C'\fR to receive the given events. 1103\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
782.Sp 1104.IP "int fd [read\-only]" 4
783Please note that most of the more scalable backend mechanisms (for example 1105.IX Item "int fd [read-only]"
784epoll and solaris ports) can result in spurious readyness notifications 1106The file descriptor being watched.
785for file descriptors, so you practically need to use non-blocking I/O (and 1107.IP "int events [read\-only]" 4
786treat callback invocation as hint only), or retest separately with a safe 1108.IX Item "int events [read-only]"
787interface before doing I/O (XLib can do this), or force the use of either 1109The events being watched.
788\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
789problem. Also note that it is quite easy to have your callback invoked
790when the readyness condition is no longer valid even when employing
791typical ways of handling events, so its a good idea to use non-blocking
792I/O unconditionally.
793.PP 1110.PP
794Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1111Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
795readable, but only once. Since it is likely line\-buffered, you could 1112readable, but only once. Since it is likely line\-buffered, you could
796attempt to read a whole line in the callback: 1113attempt to read a whole line in the callback.
797.PP 1114.PP
798.Vb 6 1115.Vb 6
799\& static void 1116\& static void
800\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1117\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
801\& { 1118\& {
… …
810\& struct ev_io stdin_readable; 1127\& struct ev_io stdin_readable;
811\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1128\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
812\& ev_io_start (loop, &stdin_readable); 1129\& ev_io_start (loop, &stdin_readable);
813\& ev_loop (loop, 0); 1130\& ev_loop (loop, 0);
814.Ve 1131.Ve
815.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1132.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
816.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1133.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
817.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1134.IX Subsection "ev_timer - relative and optionally repeating timeouts"
818Timer watchers are simple relative timers that generate an event after a 1135Timer watchers are simple relative timers that generate an event after a
819given time, and optionally repeating in regular intervals after that. 1136given time, and optionally repeating in regular intervals after that.
820.PP 1137.PP
821The timers are based on real time, that is, if you register an event that 1138The timers are based on real time, that is, if you register an event that
822times out after an hour and you reset your system clock to last years 1139times out after an hour and you reset your system clock to last years
… …
835.Ve 1152.Ve
836.PP 1153.PP
837The callback is guarenteed to be invoked only when its timeout has passed, 1154The callback is guarenteed to be invoked only when its timeout has passed,
838but if multiple timers become ready during the same loop iteration then 1155but if multiple timers become ready during the same loop iteration then
839order of execution is undefined. 1156order of execution is undefined.
1157.PP
1158\fIWatcher-Specific Functions and Data Members\fR
1159.IX Subsection "Watcher-Specific Functions and Data Members"
840.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1160.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
841.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1161.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
842.PD 0 1162.PD 0
843.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1163.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
844.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1164.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
856.IP "ev_timer_again (loop)" 4 1176.IP "ev_timer_again (loop)" 4
857.IX Item "ev_timer_again (loop)" 1177.IX Item "ev_timer_again (loop)"
858This will act as if the timer timed out and restart it again if it is 1178This will act as if the timer timed out and restart it again if it is
859repeating. The exact semantics are: 1179repeating. The exact semantics are:
860.Sp 1180.Sp
1181If the timer is pending, its pending status is cleared.
1182.Sp
861If the timer is started but nonrepeating, stop it. 1183If the timer is started but nonrepeating, stop it (as if it timed out).
862.Sp 1184.Sp
863If the timer is repeating, either start it if necessary (with the repeat 1185If the timer is repeating, either start it if necessary (with the
864value), or reset the running timer to the repeat value. 1186\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
865.Sp 1187.Sp
866This sounds a bit complicated, but here is a useful and typical 1188This sounds a bit complicated, but here is a useful and typical
867example: Imagine you have a tcp connection and you want a so-called idle 1189example: Imagine you have a tcp connection and you want a so-called idle
868timeout, that is, you want to be called when there have been, say, 60 1190timeout, that is, you want to be called when there have been, say, 60
869seconds of inactivity on the socket. The easiest way to do this is to 1191seconds of inactivity on the socket. The easiest way to do this is to
870configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1192configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
871time you successfully read or write some data. If you go into an idle 1193\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
872state where you do not expect data to travel on the socket, you can stop 1194you go into an idle state where you do not expect data to travel on the
873the timer, and again will automatically restart it if need be. 1195socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1196automatically restart it if need be.
1197.Sp
1198That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1199altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1200.Sp
1201.Vb 8
1202\& ev_timer_init (timer, callback, 0., 5.);
1203\& ev_timer_again (loop, timer);
1204\& ...
1205\& timer->again = 17.;
1206\& ev_timer_again (loop, timer);
1207\& ...
1208\& timer->again = 10.;
1209\& ev_timer_again (loop, timer);
1210.Ve
1211.Sp
1212This is more slightly efficient then stopping/starting the timer each time
1213you want to modify its timeout value.
1214.IP "ev_tstamp repeat [read\-write]" 4
1215.IX Item "ev_tstamp repeat [read-write]"
1216The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1217or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1218which is also when any modifications are taken into account.
874.PP 1219.PP
875Example: create a timer that fires after 60 seconds. 1220Example: Create a timer that fires after 60 seconds.
876.PP 1221.PP
877.Vb 5 1222.Vb 5
878\& static void 1223\& static void
879\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1224\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
880\& { 1225\& {
… …
886\& struct ev_timer mytimer; 1231\& struct ev_timer mytimer;
887\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1232\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
888\& ev_timer_start (loop, &mytimer); 1233\& ev_timer_start (loop, &mytimer);
889.Ve 1234.Ve
890.PP 1235.PP
891Example: create a timeout timer that times out after 10 seconds of 1236Example: Create a timeout timer that times out after 10 seconds of
892inactivity. 1237inactivity.
893.PP 1238.PP
894.Vb 5 1239.Vb 5
895\& static void 1240\& static void
896\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1241\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
909.Vb 3 1254.Vb 3
910\& // and in some piece of code that gets executed on any "activity": 1255\& // and in some piece of code that gets executed on any "activity":
911\& // reset the timeout to start ticking again at 10 seconds 1256\& // reset the timeout to start ticking again at 10 seconds
912\& ev_timer_again (&mytimer); 1257\& ev_timer_again (&mytimer);
913.Ve 1258.Ve
914.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1259.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
915.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1260.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
916.IX Subsection "ev_periodic - to cron or not to cron" 1261.IX Subsection "ev_periodic - to cron or not to cron?"
917Periodic watchers are also timers of a kind, but they are very versatile 1262Periodic watchers are also timers of a kind, but they are very versatile
918(and unfortunately a bit complex). 1263(and unfortunately a bit complex).
919.PP 1264.PP
920Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1265Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
921but on wallclock time (absolute time). You can tell a periodic watcher 1266but on wallclock time (absolute time). You can tell a periodic watcher
922to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1267to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
923periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1268periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
924+ 10.>) and then reset your system clock to the last year, then it will 1269+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
925take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1270take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
926roughly 10 seconds later and of course not if you reset your system time 1271roughly 10 seconds later).
927again).
928.PP 1272.PP
929They can also be used to implement vastly more complex timers, such as 1273They can also be used to implement vastly more complex timers, such as
930triggering an event on eahc midnight, local time. 1274triggering an event on each midnight, local time or other, complicated,
1275rules.
931.PP 1276.PP
932As with timers, the callback is guarenteed to be invoked only when the 1277As with timers, the callback is guarenteed to be invoked only when the
933time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1278time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
934during the same loop iteration then order of execution is undefined. 1279during the same loop iteration then order of execution is undefined.
1280.PP
1281\fIWatcher-Specific Functions and Data Members\fR
1282.IX Subsection "Watcher-Specific Functions and Data Members"
935.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1283.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
936.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1284.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
937.PD 0 1285.PD 0
938.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1286.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
939.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1287.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
940.PD 1288.PD
941Lots of arguments, lets sort it out... There are basically three modes of 1289Lots of arguments, lets sort it out... There are basically three modes of
942operation, and we will explain them from simplest to complex: 1290operation, and we will explain them from simplest to complex:
943.RS 4 1291.RS 4
944.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1292.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
945.IX Item "absolute timer (interval = reschedule_cb = 0)" 1293.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
946In this configuration the watcher triggers an event at the wallclock time 1294In this configuration the watcher triggers an event at the wallclock time
947\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1295\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
948that is, if it is to be run at January 1st 2011 then it will run when the 1296that is, if it is to be run at January 1st 2011 then it will run when the
949system time reaches or surpasses this time. 1297system time reaches or surpasses this time.
950.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1298.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
951.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1299.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
952In this mode the watcher will always be scheduled to time out at the next 1300In this mode the watcher will always be scheduled to time out at the next
953\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1301\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
954of any time jumps. 1302and then repeat, regardless of any time jumps.
955.Sp 1303.Sp
956This can be used to create timers that do not drift with respect to system 1304This can be used to create timers that do not drift with respect to system
957time: 1305time:
958.Sp 1306.Sp
959.Vb 1 1307.Vb 1
… …
966by 3600. 1314by 3600.
967.Sp 1315.Sp
968Another way to think about it (for the mathematically inclined) is that 1316Another way to think about it (for the mathematically inclined) is that
969\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1317\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
970time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1318time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1319.Sp
1320For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1321\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1322this value.
971.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1323.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
972.IX Item "manual reschedule mode (reschedule_cb = callback)" 1324.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
973In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1325In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
974ignored. Instead, each time the periodic watcher gets scheduled, the 1326ignored. Instead, each time the periodic watcher gets scheduled, the
975reschedule callback will be called with the watcher as first, and the 1327reschedule callback will be called with the watcher as first, and the
976current time as second argument. 1328current time as second argument.
977.Sp 1329.Sp
978\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1330\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
979ever, or make any event loop modifications\fR. If you need to stop it, 1331ever, or make any event loop modifications\fR. If you need to stop it,
980return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1332return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
981starting a prepare watcher). 1333starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
982.Sp 1334.Sp
983Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1335Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
984ev_tstamp now)\*(C'\fR, e.g.: 1336ev_tstamp now)\*(C'\fR, e.g.:
985.Sp 1337.Sp
986.Vb 4 1338.Vb 4
… …
1010.IX Item "ev_periodic_again (loop, ev_periodic *)" 1362.IX Item "ev_periodic_again (loop, ev_periodic *)"
1011Simply stops and restarts the periodic watcher again. This is only useful 1363Simply stops and restarts the periodic watcher again. This is only useful
1012when you changed some parameters or the reschedule callback would return 1364when you changed some parameters or the reschedule callback would return
1013a different time than the last time it was called (e.g. in a crond like 1365a different time than the last time it was called (e.g. in a crond like
1014program when the crontabs have changed). 1366program when the crontabs have changed).
1367.IP "ev_tstamp offset [read\-write]" 4
1368.IX Item "ev_tstamp offset [read-write]"
1369When repeating, this contains the offset value, otherwise this is the
1370absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1371.Sp
1372Can be modified any time, but changes only take effect when the periodic
1373timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1374.IP "ev_tstamp interval [read\-write]" 4
1375.IX Item "ev_tstamp interval [read-write]"
1376The current interval value. Can be modified any time, but changes only
1377take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1378called.
1379.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1380.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1381The current reschedule callback, or \f(CW0\fR, if this functionality is
1382switched off. Can be changed any time, but changes only take effect when
1383the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1015.PP 1384.PP
1016Example: call a callback every hour, or, more precisely, whenever the 1385Example: Call a callback every hour, or, more precisely, whenever the
1017system clock is divisible by 3600. The callback invocation times have 1386system clock is divisible by 3600. The callback invocation times have
1018potentially a lot of jittering, but good long-term stability. 1387potentially a lot of jittering, but good long-term stability.
1019.PP 1388.PP
1020.Vb 5 1389.Vb 5
1021\& static void 1390\& static void
… …
1029\& struct ev_periodic hourly_tick; 1398\& struct ev_periodic hourly_tick;
1030\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1399\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1031\& ev_periodic_start (loop, &hourly_tick); 1400\& ev_periodic_start (loop, &hourly_tick);
1032.Ve 1401.Ve
1033.PP 1402.PP
1034Example: the same as above, but use a reschedule callback to do it: 1403Example: The same as above, but use a reschedule callback to do it:
1035.PP 1404.PP
1036.Vb 1 1405.Vb 1
1037\& #include <math.h> 1406\& #include <math.h>
1038.Ve 1407.Ve
1039.PP 1408.PP
… …
1047.PP 1416.PP
1048.Vb 1 1417.Vb 1
1049\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1418\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1050.Ve 1419.Ve
1051.PP 1420.PP
1052Example: call a callback every hour, starting now: 1421Example: Call a callback every hour, starting now:
1053.PP 1422.PP
1054.Vb 4 1423.Vb 4
1055\& struct ev_periodic hourly_tick; 1424\& struct ev_periodic hourly_tick;
1056\& ev_periodic_init (&hourly_tick, clock_cb, 1425\& ev_periodic_init (&hourly_tick, clock_cb,
1057\& fmod (ev_now (loop), 3600.), 3600., 0); 1426\& fmod (ev_now (loop), 3600.), 3600., 0);
1058\& ev_periodic_start (loop, &hourly_tick); 1427\& ev_periodic_start (loop, &hourly_tick);
1059.Ve 1428.Ve
1060.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1429.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
1061.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1430.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1062.IX Subsection "ev_signal - signal me when a signal gets signalled" 1431.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1063Signal watchers will trigger an event when the process receives a specific 1432Signal watchers will trigger an event when the process receives a specific
1064signal one or more times. Even though signals are very asynchronous, libev 1433signal one or more times. Even though signals are very asynchronous, libev
1065will try it's best to deliver signals synchronously, i.e. as part of the 1434will try it's best to deliver signals synchronously, i.e. as part of the
1066normal event processing, like any other event. 1435normal event processing, like any other event.
1067.PP 1436.PP
… …
1069first watcher gets started will libev actually register a signal watcher 1438first watcher gets started will libev actually register a signal watcher
1070with the kernel (thus it coexists with your own signal handlers as long 1439with the kernel (thus it coexists with your own signal handlers as long
1071as you don't register any with libev). Similarly, when the last signal 1440as you don't register any with libev). Similarly, when the last signal
1072watcher for a signal is stopped libev will reset the signal handler to 1441watcher for a signal is stopped libev will reset the signal handler to
1073\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1442\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1443.PP
1444\fIWatcher-Specific Functions and Data Members\fR
1445.IX Subsection "Watcher-Specific Functions and Data Members"
1074.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1446.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1075.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1447.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1076.PD 0 1448.PD 0
1077.IP "ev_signal_set (ev_signal *, int signum)" 4 1449.IP "ev_signal_set (ev_signal *, int signum)" 4
1078.IX Item "ev_signal_set (ev_signal *, int signum)" 1450.IX Item "ev_signal_set (ev_signal *, int signum)"
1079.PD 1451.PD
1080Configures the watcher to trigger on the given signal number (usually one 1452Configures the watcher to trigger on the given signal number (usually one
1081of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1453of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1454.IP "int signum [read\-only]" 4
1455.IX Item "int signum [read-only]"
1456The signal the watcher watches out for.
1082.ie n .Sh """ev_child"" \- wait for pid status changes" 1457.ie n .Sh """ev_child"" \- watch out for process status changes"
1083.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1458.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1084.IX Subsection "ev_child - wait for pid status changes" 1459.IX Subsection "ev_child - watch out for process status changes"
1085Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1460Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1086some child status changes (most typically when a child of yours dies). 1461some child status changes (most typically when a child of yours dies).
1462.PP
1463\fIWatcher-Specific Functions and Data Members\fR
1464.IX Subsection "Watcher-Specific Functions and Data Members"
1087.IP "ev_child_init (ev_child *, callback, int pid)" 4 1465.IP "ev_child_init (ev_child *, callback, int pid)" 4
1088.IX Item "ev_child_init (ev_child *, callback, int pid)" 1466.IX Item "ev_child_init (ev_child *, callback, int pid)"
1089.PD 0 1467.PD 0
1090.IP "ev_child_set (ev_child *, int pid)" 4 1468.IP "ev_child_set (ev_child *, int pid)" 4
1091.IX Item "ev_child_set (ev_child *, int pid)" 1469.IX Item "ev_child_set (ev_child *, int pid)"
… …
1094\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1472\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1095at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1473at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1096the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1474the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1097\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1475\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1098process causing the status change. 1476process causing the status change.
1477.IP "int pid [read\-only]" 4
1478.IX Item "int pid [read-only]"
1479The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1480.IP "int rpid [read\-write]" 4
1481.IX Item "int rpid [read-write]"
1482The process id that detected a status change.
1483.IP "int rstatus [read\-write]" 4
1484.IX Item "int rstatus [read-write]"
1485The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1486\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1099.PP 1487.PP
1100Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1488Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1101.PP 1489.PP
1102.Vb 5 1490.Vb 5
1103\& static void 1491\& static void
1104\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1492\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1105\& { 1493\& {
… …
1110.Vb 3 1498.Vb 3
1111\& struct ev_signal signal_watcher; 1499\& struct ev_signal signal_watcher;
1112\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1500\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1113\& ev_signal_start (loop, &sigint_cb); 1501\& ev_signal_start (loop, &sigint_cb);
1114.Ve 1502.Ve
1503.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1504.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1505.IX Subsection "ev_stat - did the file attributes just change?"
1506This watches a filesystem path for attribute changes. That is, it calls
1507\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1508compared to the last time, invoking the callback if it did.
1509.PP
1510The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1511not exist\*(R" is a status change like any other. The condition \*(L"path does
1512not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1513otherwise always forced to be at least one) and all the other fields of
1514the stat buffer having unspecified contents.
1515.PP
1516The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1517relative and your working directory changes, the behaviour is undefined.
1518.PP
1519Since there is no standard to do this, the portable implementation simply
1520calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1521can specify a recommended polling interval for this case. If you specify
1522a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1523unspecified default\fR value will be used (which you can expect to be around
1524five seconds, although this might change dynamically). Libev will also
1525impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1526usually overkill.
1527.PP
1528This watcher type is not meant for massive numbers of stat watchers,
1529as even with OS-supported change notifications, this can be
1530resource\-intensive.
1531.PP
1532At the time of this writing, only the Linux inotify interface is
1533implemented (implementing kqueue support is left as an exercise for the
1534reader). Inotify will be used to give hints only and should not change the
1535semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1536to fall back to regular polling again even with inotify, but changes are
1537usually detected immediately, and if the file exists there will be no
1538polling.
1539.PP
1540\fIWatcher-Specific Functions and Data Members\fR
1541.IX Subsection "Watcher-Specific Functions and Data Members"
1542.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1543.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1544.PD 0
1545.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1546.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1547.PD
1548Configures the watcher to wait for status changes of the given
1549\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1550be detected and should normally be specified as \f(CW0\fR to let libev choose
1551a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1552path for as long as the watcher is active.
1553.Sp
1554The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1555relative to the attributes at the time the watcher was started (or the
1556last change was detected).
1557.IP "ev_stat_stat (ev_stat *)" 4
1558.IX Item "ev_stat_stat (ev_stat *)"
1559Updates the stat buffer immediately with new values. If you change the
1560watched path in your callback, you could call this fucntion to avoid
1561detecting this change (while introducing a race condition). Can also be
1562useful simply to find out the new values.
1563.IP "ev_statdata attr [read\-only]" 4
1564.IX Item "ev_statdata attr [read-only]"
1565The most-recently detected attributes of the file. Although the type is of
1566\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1567suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1568was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1569.IP "ev_statdata prev [read\-only]" 4
1570.IX Item "ev_statdata prev [read-only]"
1571The previous attributes of the file. The callback gets invoked whenever
1572\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1573.IP "ev_tstamp interval [read\-only]" 4
1574.IX Item "ev_tstamp interval [read-only]"
1575The specified interval.
1576.IP "const char *path [read\-only]" 4
1577.IX Item "const char *path [read-only]"
1578The filesystem path that is being watched.
1579.PP
1580Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1581.PP
1582.Vb 15
1583\& static void
1584\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1585\& {
1586\& /* /etc/passwd changed in some way */
1587\& if (w->attr.st_nlink)
1588\& {
1589\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1590\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1591\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1592\& }
1593\& else
1594\& /* you shalt not abuse printf for puts */
1595\& puts ("wow, /etc/passwd is not there, expect problems. "
1596\& "if this is windows, they already arrived\en");
1597\& }
1598.Ve
1599.PP
1600.Vb 2
1601\& ...
1602\& ev_stat passwd;
1603.Ve
1604.PP
1605.Vb 2
1606\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1607\& ev_stat_start (loop, &passwd);
1608.Ve
1115.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1609.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1116.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1610.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1117.IX Subsection "ev_idle - when you've got nothing better to do" 1611.IX Subsection "ev_idle - when you've got nothing better to do..."
1118Idle watchers trigger events when there are no other events are pending 1612Idle watchers trigger events when no other events of the same or higher
1119(prepare, check and other idle watchers do not count). That is, as long 1613priority are pending (prepare, check and other idle watchers do not
1120as your process is busy handling sockets or timeouts (or even signals, 1614count).
1121imagine) it will not be triggered. But when your process is idle all idle 1615.PP
1122watchers are being called again and again, once per event loop iteration \- 1616That is, as long as your process is busy handling sockets or timeouts
1617(or even signals, imagine) of the same or higher priority it will not be
1618triggered. But when your process is idle (or only lower-priority watchers
1619are pending), the idle watchers are being called once per event loop
1123until stopped, that is, or your process receives more events and becomes 1620iteration \- until stopped, that is, or your process receives more events
1124busy. 1621and becomes busy again with higher priority stuff.
1125.PP 1622.PP
1126The most noteworthy effect is that as long as any idle watchers are 1623The most noteworthy effect is that as long as any idle watchers are
1127active, the process will not block when waiting for new events. 1624active, the process will not block when waiting for new events.
1128.PP 1625.PP
1129Apart from keeping your process non-blocking (which is a useful 1626Apart from keeping your process non-blocking (which is a useful
1130effect on its own sometimes), idle watchers are a good place to do 1627effect on its own sometimes), idle watchers are a good place to do
1131\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1628\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1132event loop has handled all outstanding events. 1629event loop has handled all outstanding events.
1630.PP
1631\fIWatcher-Specific Functions and Data Members\fR
1632.IX Subsection "Watcher-Specific Functions and Data Members"
1133.IP "ev_idle_init (ev_signal *, callback)" 4 1633.IP "ev_idle_init (ev_signal *, callback)" 4
1134.IX Item "ev_idle_init (ev_signal *, callback)" 1634.IX Item "ev_idle_init (ev_signal *, callback)"
1135Initialises and configures the idle watcher \- it has no parameters of any 1635Initialises and configures the idle watcher \- it has no parameters of any
1136kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1636kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1137believe me. 1637believe me.
1138.PP 1638.PP
1139Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1639Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1140callback, free it. Alos, use no error checking, as usual. 1640callback, free it. Also, use no error checking, as usual.
1141.PP 1641.PP
1142.Vb 7 1642.Vb 7
1143\& static void 1643\& static void
1144\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1644\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1145\& { 1645\& {
… …
1152.Vb 3 1652.Vb 3
1153\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1653\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1154\& ev_idle_init (idle_watcher, idle_cb); 1654\& ev_idle_init (idle_watcher, idle_cb);
1155\& ev_idle_start (loop, idle_cb); 1655\& ev_idle_start (loop, idle_cb);
1156.Ve 1656.Ve
1157.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1657.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
1158.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1658.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1159.IX Subsection "ev_prepare and ev_check - customise your event loop" 1659.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1160Prepare and check watchers are usually (but not always) used in tandem: 1660Prepare and check watchers are usually (but not always) used in tandem:
1161prepare watchers get invoked before the process blocks and check watchers 1661prepare watchers get invoked before the process blocks and check watchers
1162afterwards. 1662afterwards.
1163.PP 1663.PP
1664You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1665the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1666watchers. Other loops than the current one are fine, however. The
1667rationale behind this is that you do not need to check for recursion in
1668those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1669\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1670called in pairs bracketing the blocking call.
1671.PP
1164Their main purpose is to integrate other event mechanisms into libev. This 1672Their main purpose is to integrate other event mechanisms into libev and
1165could be used, for example, to track variable changes, implement your own 1673their use is somewhat advanced. This could be used, for example, to track
1166watchers, integrate net-snmp or a coroutine library and lots more. 1674variable changes, implement your own watchers, integrate net-snmp or a
1675coroutine library and lots more. They are also occasionally useful if
1676you cache some data and want to flush it before blocking (for example,
1677in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1678watcher).
1167.PP 1679.PP
1168This is done by examining in each prepare call which file descriptors need 1680This is done by examining in each prepare call which file descriptors need
1169to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1681to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1170them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1682them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1171provide just this functionality). Then, in the check watcher you check for 1683provide just this functionality). Then, in the check watcher you check for
… …
1180are ready to run (it's actually more complicated: it only runs coroutines 1692are ready to run (it's actually more complicated: it only runs coroutines
1181with priority higher than or equal to the event loop and one coroutine 1693with priority higher than or equal to the event loop and one coroutine
1182of lower priority, but only once, using idle watchers to keep the event 1694of lower priority, but only once, using idle watchers to keep the event
1183loop from blocking if lower-priority coroutines are active, thus mapping 1695loop from blocking if lower-priority coroutines are active, thus mapping
1184low-priority coroutines to idle/background tasks). 1696low-priority coroutines to idle/background tasks).
1697.PP
1698It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1699priority, to ensure that they are being run before any other watchers
1700after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1701too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1702supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1703their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1704loops those other event loops might be in an unusable state until their
1705\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1706others).
1707.PP
1708\fIWatcher-Specific Functions and Data Members\fR
1709.IX Subsection "Watcher-Specific Functions and Data Members"
1185.IP "ev_prepare_init (ev_prepare *, callback)" 4 1710.IP "ev_prepare_init (ev_prepare *, callback)" 4
1186.IX Item "ev_prepare_init (ev_prepare *, callback)" 1711.IX Item "ev_prepare_init (ev_prepare *, callback)"
1187.PD 0 1712.PD 0
1188.IP "ev_check_init (ev_check *, callback)" 4 1713.IP "ev_check_init (ev_check *, callback)" 4
1189.IX Item "ev_check_init (ev_check *, callback)" 1714.IX Item "ev_check_init (ev_check *, callback)"
1190.PD 1715.PD
1191Initialises and configures the prepare or check watcher \- they have no 1716Initialises and configures the prepare or check watcher \- they have no
1192parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1717parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1193macros, but using them is utterly, utterly and completely pointless. 1718macros, but using them is utterly, utterly and completely pointless.
1194.PP 1719.PP
1195Example: *TODO*. 1720There are a number of principal ways to embed other event loops or modules
1721into libev. Here are some ideas on how to include libadns into libev
1722(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1723use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1724embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1725into the Glib event loop).
1726.PP
1727Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1728and in a check watcher, destroy them and call into libadns. What follows
1729is pseudo-code only of course. This requires you to either use a low
1730priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1731the callbacks for the IO/timeout watchers might not have been called yet.
1732.PP
1733.Vb 2
1734\& static ev_io iow [nfd];
1735\& static ev_timer tw;
1736.Ve
1737.PP
1738.Vb 4
1739\& static void
1740\& io_cb (ev_loop *loop, ev_io *w, int revents)
1741\& {
1742\& }
1743.Ve
1744.PP
1745.Vb 8
1746\& // create io watchers for each fd and a timer before blocking
1747\& static void
1748\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1749\& {
1750\& int timeout = 3600000;
1751\& struct pollfd fds [nfd];
1752\& // actual code will need to loop here and realloc etc.
1753\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1754.Ve
1755.PP
1756.Vb 3
1757\& /* the callback is illegal, but won't be called as we stop during check */
1758\& ev_timer_init (&tw, 0, timeout * 1e-3);
1759\& ev_timer_start (loop, &tw);
1760.Ve
1761.PP
1762.Vb 6
1763\& // create one ev_io per pollfd
1764\& for (int i = 0; i < nfd; ++i)
1765\& {
1766\& ev_io_init (iow + i, io_cb, fds [i].fd,
1767\& ((fds [i].events & POLLIN ? EV_READ : 0)
1768\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1769.Ve
1770.PP
1771.Vb 4
1772\& fds [i].revents = 0;
1773\& ev_io_start (loop, iow + i);
1774\& }
1775\& }
1776.Ve
1777.PP
1778.Vb 5
1779\& // stop all watchers after blocking
1780\& static void
1781\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1782\& {
1783\& ev_timer_stop (loop, &tw);
1784.Ve
1785.PP
1786.Vb 8
1787\& for (int i = 0; i < nfd; ++i)
1788\& {
1789\& // set the relevant poll flags
1790\& // could also call adns_processreadable etc. here
1791\& struct pollfd *fd = fds + i;
1792\& int revents = ev_clear_pending (iow + i);
1793\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1794\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1795.Ve
1796.PP
1797.Vb 3
1798\& // now stop the watcher
1799\& ev_io_stop (loop, iow + i);
1800\& }
1801.Ve
1802.PP
1803.Vb 2
1804\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1805\& }
1806.Ve
1807.PP
1808Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1809in the prepare watcher and would dispose of the check watcher.
1810.PP
1811Method 3: If the module to be embedded supports explicit event
1812notification (adns does), you can also make use of the actual watcher
1813callbacks, and only destroy/create the watchers in the prepare watcher.
1814.PP
1815.Vb 5
1816\& static void
1817\& timer_cb (EV_P_ ev_timer *w, int revents)
1818\& {
1819\& adns_state ads = (adns_state)w->data;
1820\& update_now (EV_A);
1821.Ve
1822.PP
1823.Vb 2
1824\& adns_processtimeouts (ads, &tv_now);
1825\& }
1826.Ve
1827.PP
1828.Vb 5
1829\& static void
1830\& io_cb (EV_P_ ev_io *w, int revents)
1831\& {
1832\& adns_state ads = (adns_state)w->data;
1833\& update_now (EV_A);
1834.Ve
1835.PP
1836.Vb 3
1837\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1838\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1839\& }
1840.Ve
1841.PP
1842.Vb 1
1843\& // do not ever call adns_afterpoll
1844.Ve
1845.PP
1846Method 4: Do not use a prepare or check watcher because the module you
1847want to embed is too inflexible to support it. Instead, youc na override
1848their poll function. The drawback with this solution is that the main
1849loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1850this.
1851.PP
1852.Vb 4
1853\& static gint
1854\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1855\& {
1856\& int got_events = 0;
1857.Ve
1858.PP
1859.Vb 2
1860\& for (n = 0; n < nfds; ++n)
1861\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1862.Ve
1863.PP
1864.Vb 2
1865\& if (timeout >= 0)
1866\& // create/start timer
1867.Ve
1868.PP
1869.Vb 2
1870\& // poll
1871\& ev_loop (EV_A_ 0);
1872.Ve
1873.PP
1874.Vb 3
1875\& // stop timer again
1876\& if (timeout >= 0)
1877\& ev_timer_stop (EV_A_ &to);
1878.Ve
1879.PP
1880.Vb 3
1881\& // stop io watchers again - their callbacks should have set
1882\& for (n = 0; n < nfds; ++n)
1883\& ev_io_stop (EV_A_ iow [n]);
1884.Ve
1885.PP
1886.Vb 2
1887\& return got_events;
1888\& }
1889.Ve
1890.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1891.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1892.IX Subsection "ev_embed - when one backend isn't enough..."
1893This is a rather advanced watcher type that lets you embed one event loop
1894into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1895loop, other types of watchers might be handled in a delayed or incorrect
1896fashion and must not be used).
1897.PP
1898There are primarily two reasons you would want that: work around bugs and
1899prioritise I/O.
1900.PP
1901As an example for a bug workaround, the kqueue backend might only support
1902sockets on some platform, so it is unusable as generic backend, but you
1903still want to make use of it because you have many sockets and it scales
1904so nicely. In this case, you would create a kqueue-based loop and embed it
1905into your default loop (which might use e.g. poll). Overall operation will
1906be a bit slower because first libev has to poll and then call kevent, but
1907at least you can use both at what they are best.
1908.PP
1909As for prioritising I/O: rarely you have the case where some fds have
1910to be watched and handled very quickly (with low latency), and even
1911priorities and idle watchers might have too much overhead. In this case
1912you would put all the high priority stuff in one loop and all the rest in
1913a second one, and embed the second one in the first.
1914.PP
1915As long as the watcher is active, the callback will be invoked every time
1916there might be events pending in the embedded loop. The callback must then
1917call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1918their callbacks (you could also start an idle watcher to give the embedded
1919loop strictly lower priority for example). You can also set the callback
1920to \f(CW0\fR, in which case the embed watcher will automatically execute the
1921embedded loop sweep.
1922.PP
1923As long as the watcher is started it will automatically handle events. The
1924callback will be invoked whenever some events have been handled. You can
1925set the callback to \f(CW0\fR to avoid having to specify one if you are not
1926interested in that.
1927.PP
1928Also, there have not currently been made special provisions for forking:
1929when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1930but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1931yourself.
1932.PP
1933Unfortunately, not all backends are embeddable, only the ones returned by
1934\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1935portable one.
1936.PP
1937So when you want to use this feature you will always have to be prepared
1938that you cannot get an embeddable loop. The recommended way to get around
1939this is to have a separate variables for your embeddable loop, try to
1940create it, and if that fails, use the normal loop for everything:
1941.PP
1942.Vb 3
1943\& struct ev_loop *loop_hi = ev_default_init (0);
1944\& struct ev_loop *loop_lo = 0;
1945\& struct ev_embed embed;
1946.Ve
1947.PP
1948.Vb 5
1949\& // see if there is a chance of getting one that works
1950\& // (remember that a flags value of 0 means autodetection)
1951\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1952\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1953\& : 0;
1954.Ve
1955.PP
1956.Vb 8
1957\& // if we got one, then embed it, otherwise default to loop_hi
1958\& if (loop_lo)
1959\& {
1960\& ev_embed_init (&embed, 0, loop_lo);
1961\& ev_embed_start (loop_hi, &embed);
1962\& }
1963\& else
1964\& loop_lo = loop_hi;
1965.Ve
1966.PP
1967\fIWatcher-Specific Functions and Data Members\fR
1968.IX Subsection "Watcher-Specific Functions and Data Members"
1969.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1970.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1971.PD 0
1972.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1973.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1974.PD
1975Configures the watcher to embed the given loop, which must be
1976embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1977invoked automatically, otherwise it is the responsibility of the callback
1978to invoke it (it will continue to be called until the sweep has been done,
1979if you do not want thta, you need to temporarily stop the embed watcher).
1980.IP "ev_embed_sweep (loop, ev_embed *)" 4
1981.IX Item "ev_embed_sweep (loop, ev_embed *)"
1982Make a single, non-blocking sweep over the embedded loop. This works
1983similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1984apropriate way for embedded loops.
1985.IP "struct ev_loop *loop [read\-only]" 4
1986.IX Item "struct ev_loop *loop [read-only]"
1987The embedded event loop.
1988.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1989.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1990.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1991Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1992whoever is a good citizen cared to tell libev about it by calling
1993\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1994event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1995and only in the child after the fork. If whoever good citizen calling
1996\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1997handlers will be invoked, too, of course.
1998.IP "ev_fork_init (ev_signal *, callback)" 4
1999.IX Item "ev_fork_init (ev_signal *, callback)"
2000Initialises and configures the fork watcher \- it has no parameters of any
2001kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2002believe me.
1196.SH "OTHER FUNCTIONS" 2003.SH "OTHER FUNCTIONS"
1197.IX Header "OTHER FUNCTIONS" 2004.IX Header "OTHER FUNCTIONS"
1198There are some other functions of possible interest. Described. Here. Now. 2005There are some other functions of possible interest. Described. Here. Now.
1199.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 2006.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1200.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 2007.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1229.Ve 2036.Ve
1230.Sp 2037.Sp
1231.Vb 1 2038.Vb 1
1232\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2039\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
1233.Ve 2040.Ve
1234.IP "ev_feed_event (loop, watcher, int events)" 4 2041.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
1235.IX Item "ev_feed_event (loop, watcher, int events)" 2042.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
1236Feeds the given event set into the event loop, as if the specified event 2043Feeds the given event set into the event loop, as if the specified event
1237had happened for the specified watcher (which must be a pointer to an 2044had happened for the specified watcher (which must be a pointer to an
1238initialised but not necessarily started event watcher). 2045initialised but not necessarily started event watcher).
1239.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 2046.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
1240.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 2047.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
1241Feed an event on the given fd, as if a file descriptor backend detected 2048Feed an event on the given fd, as if a file descriptor backend detected
1242the given events it. 2049the given events it.
1243.IP "ev_feed_signal_event (loop, int signum)" 4 2050.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
1244.IX Item "ev_feed_signal_event (loop, int signum)" 2051.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
1245Feed an event as if the given signal occured (loop must be the default loop!). 2052Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
2053loop!).
1246.SH "LIBEVENT EMULATION" 2054.SH "LIBEVENT EMULATION"
1247.IX Header "LIBEVENT EMULATION" 2055.IX Header "LIBEVENT EMULATION"
1248Libev offers a compatibility emulation layer for libevent. It cannot 2056Libev offers a compatibility emulation layer for libevent. It cannot
1249emulate the internals of libevent, so here are some usage hints: 2057emulate the internals of libevent, so here are some usage hints:
1250.IP "* Use it by including <event.h>, as usual." 4 2058.IP "* Use it by including <event.h>, as usual." 4
… …
1261.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 2069.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1262.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 2070.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1263.PD 2071.PD
1264.SH "\*(C+ SUPPORT" 2072.SH "\*(C+ SUPPORT"
1265.IX Header " SUPPORT" 2073.IX Header " SUPPORT"
1266\&\s-1TBD\s0. 2074Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2075you to use some convinience methods to start/stop watchers and also change
2076the callback model to a model using method callbacks on objects.
2077.PP
2078To use it,
2079.PP
2080.Vb 1
2081\& #include <ev++.h>
2082.Ve
2083.PP
2084This automatically includes \fIev.h\fR and puts all of its definitions (many
2085of them macros) into the global namespace. All \*(C+ specific things are
2086put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2087options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
2088.PP
2089Care has been taken to keep the overhead low. The only data member the \*(C+
2090classes add (compared to plain C\-style watchers) is the event loop pointer
2091that the watcher is associated with (or no additional members at all if
2092you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2093.PP
2094Currently, functions, and static and non-static member functions can be
2095used as callbacks. Other types should be easy to add as long as they only
2096need one additional pointer for context. If you need support for other
2097types of functors please contact the author (preferably after implementing
2098it).
2099.PP
2100Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2101.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
2102.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2103.IX Item "ev::READ, ev::WRITE etc."
2104These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2105macros from \fIev.h\fR.
2106.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
2107.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2108.IX Item "ev::tstamp, ev::now"
2109Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2110.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
2111.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2112.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2113For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2114the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2115which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2116defines by many implementations.
2117.Sp
2118All of those classes have these methods:
2119.RS 4
2120.IP "ev::TYPE::TYPE ()" 4
2121.IX Item "ev::TYPE::TYPE ()"
2122.PD 0
2123.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
2124.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
2125.IP "ev::TYPE::~TYPE" 4
2126.IX Item "ev::TYPE::~TYPE"
2127.PD
2128The constructor (optionally) takes an event loop to associate the watcher
2129with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
2130.Sp
2131The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
2132\&\f(CW\*(C`set\*(C'\fR method before starting it.
2133.Sp
2134It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2135method to set a callback before you can start the watcher.
2136.Sp
2137(The reason why you have to use a method is a limitation in \*(C+ which does
2138not allow explicit template arguments for constructors).
2139.Sp
2140The destructor automatically stops the watcher if it is active.
2141.IP "w\->set<class, &class::method> (object *)" 4
2142.IX Item "w->set<class, &class::method> (object *)"
2143This method sets the callback method to call. The method has to have a
2144signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2145first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2146parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2147.Sp
2148This method synthesizes efficient thunking code to call your method from
2149the C callback that libev requires. If your compiler can inline your
2150callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2151your compiler is good :), then the method will be fully inlined into the
2152thunking function, making it as fast as a direct C callback.
2153.Sp
2154Example: simple class declaration and watcher initialisation
2155.Sp
2156.Vb 4
2157\& struct myclass
2158\& {
2159\& void io_cb (ev::io &w, int revents) { }
2160\& }
2161.Ve
2162.Sp
2163.Vb 3
2164\& myclass obj;
2165\& ev::io iow;
2166\& iow.set <myclass, &myclass::io_cb> (&obj);
2167.Ve
2168.IP "w\->set<function> (void *data = 0)" 4
2169.IX Item "w->set<function> (void *data = 0)"
2170Also sets a callback, but uses a static method or plain function as
2171callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2172\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2173.Sp
2174The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2175.Sp
2176See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2177.Sp
2178Example:
2179.Sp
2180.Vb 2
2181\& static void io_cb (ev::io &w, int revents) { }
2182\& iow.set <io_cb> ();
2183.Ve
2184.IP "w\->set (struct ev_loop *)" 4
2185.IX Item "w->set (struct ev_loop *)"
2186Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2187do this when the watcher is inactive (and not pending either).
2188.IP "w\->set ([args])" 4
2189.IX Item "w->set ([args])"
2190Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
2191called at least once. Unlike the C counterpart, an active watcher gets
2192automatically stopped and restarted when reconfiguring it with this
2193method.
2194.IP "w\->start ()" 4
2195.IX Item "w->start ()"
2196Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2197constructor already stores the event loop.
2198.IP "w\->stop ()" 4
2199.IX Item "w->stop ()"
2200Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2201.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
2202.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
2203.IX Item "w->again () ev::timer, ev::periodic only"
2204For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2205\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2206.ie n .IP "w\->sweep () ""ev::embed"" only" 4
2207.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
2208.IX Item "w->sweep () ev::embed only"
2209Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2210.ie n .IP "w\->update () ""ev::stat"" only" 4
2211.el .IP "w\->update () \f(CWev::stat\fR only" 4
2212.IX Item "w->update () ev::stat only"
2213Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2214.RE
2215.RS 4
2216.RE
2217.PP
2218Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2219the constructor.
2220.PP
2221.Vb 4
2222\& class myclass
2223\& {
2224\& ev_io io; void io_cb (ev::io &w, int revents);
2225\& ev_idle idle void idle_cb (ev::idle &w, int revents);
2226.Ve
2227.PP
2228.Vb 2
2229\& myclass ();
2230\& }
2231.Ve
2232.PP
2233.Vb 4
2234\& myclass::myclass (int fd)
2235\& {
2236\& io .set <myclass, &myclass::io_cb > (this);
2237\& idle.set <myclass, &myclass::idle_cb> (this);
2238.Ve
2239.PP
2240.Vb 2
2241\& io.start (fd, ev::READ);
2242\& }
2243.Ve
2244.SH "MACRO MAGIC"
2245.IX Header "MACRO MAGIC"
2246Libev can be compiled with a variety of options, the most fundemantal is
2247\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
2248callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2249.PP
2250To make it easier to write programs that cope with either variant, the
2251following macros are defined:
2252.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2253.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2254.IX Item "EV_A, EV_A_"
2255This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2256loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2257\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2258.Sp
2259.Vb 3
2260\& ev_unref (EV_A);
2261\& ev_timer_add (EV_A_ watcher);
2262\& ev_loop (EV_A_ 0);
2263.Ve
2264.Sp
2265It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2266which is often provided by the following macro.
2267.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2268.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2269.IX Item "EV_P, EV_P_"
2270This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2271loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2272\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2273.Sp
2274.Vb 2
2275\& // this is how ev_unref is being declared
2276\& static void ev_unref (EV_P);
2277.Ve
2278.Sp
2279.Vb 2
2280\& // this is how you can declare your typical callback
2281\& static void cb (EV_P_ ev_timer *w, int revents)
2282.Ve
2283.Sp
2284It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2285suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2286.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2287.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2288.IX Item "EV_DEFAULT, EV_DEFAULT_"
2289Similar to the other two macros, this gives you the value of the default
2290loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2291.PP
2292Example: Declare and initialise a check watcher, utilising the above
2293macros so it will work regardless of whether multiple loops are supported
2294or not.
2295.PP
2296.Vb 5
2297\& static void
2298\& check_cb (EV_P_ ev_timer *w, int revents)
2299\& {
2300\& ev_check_stop (EV_A_ w);
2301\& }
2302.Ve
2303.PP
2304.Vb 4
2305\& ev_check check;
2306\& ev_check_init (&check, check_cb);
2307\& ev_check_start (EV_DEFAULT_ &check);
2308\& ev_loop (EV_DEFAULT_ 0);
2309.Ve
2310.SH "EMBEDDING"
2311.IX Header "EMBEDDING"
2312Libev can (and often is) directly embedded into host
2313applications. Examples of applications that embed it include the Deliantra
2314Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2315and rxvt\-unicode.
2316.PP
2317The goal is to enable you to just copy the neecssary files into your
2318source directory without having to change even a single line in them, so
2319you can easily upgrade by simply copying (or having a checked-out copy of
2320libev somewhere in your source tree).
2321.Sh "\s-1FILESETS\s0"
2322.IX Subsection "FILESETS"
2323Depending on what features you need you need to include one or more sets of files
2324in your app.
2325.PP
2326\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2327.IX Subsection "CORE EVENT LOOP"
2328.PP
2329To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2330configuration (no autoconf):
2331.PP
2332.Vb 2
2333\& #define EV_STANDALONE 1
2334\& #include "ev.c"
2335.Ve
2336.PP
2337This will automatically include \fIev.h\fR, too, and should be done in a
2338single C source file only to provide the function implementations. To use
2339it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2340done by writing a wrapper around \fIev.h\fR that you can include instead and
2341where you can put other configuration options):
2342.PP
2343.Vb 2
2344\& #define EV_STANDALONE 1
2345\& #include "ev.h"
2346.Ve
2347.PP
2348Both header files and implementation files can be compiled with a \*(C+
2349compiler (at least, thats a stated goal, and breakage will be treated
2350as a bug).
2351.PP
2352You need the following files in your source tree, or in a directory
2353in your include path (e.g. in libev/ when using \-Ilibev):
2354.PP
2355.Vb 4
2356\& ev.h
2357\& ev.c
2358\& ev_vars.h
2359\& ev_wrap.h
2360.Ve
2361.PP
2362.Vb 1
2363\& ev_win32.c required on win32 platforms only
2364.Ve
2365.PP
2366.Vb 5
2367\& ev_select.c only when select backend is enabled (which is enabled by default)
2368\& ev_poll.c only when poll backend is enabled (disabled by default)
2369\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2370\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2371\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2372.Ve
2373.PP
2374\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2375to compile this single file.
2376.PP
2377\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2378.IX Subsection "LIBEVENT COMPATIBILITY API"
2379.PP
2380To include the libevent compatibility \s-1API\s0, also include:
2381.PP
2382.Vb 1
2383\& #include "event.c"
2384.Ve
2385.PP
2386in the file including \fIev.c\fR, and:
2387.PP
2388.Vb 1
2389\& #include "event.h"
2390.Ve
2391.PP
2392in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2393.PP
2394You need the following additional files for this:
2395.PP
2396.Vb 2
2397\& event.h
2398\& event.c
2399.Ve
2400.PP
2401\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2402.IX Subsection "AUTOCONF SUPPORT"
2403.PP
2404Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2405whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2406\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2407include \fIconfig.h\fR and configure itself accordingly.
2408.PP
2409For this of course you need the m4 file:
2410.PP
2411.Vb 1
2412\& libev.m4
2413.Ve
2414.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2415.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2416Libev can be configured via a variety of preprocessor symbols you have to define
2417before including any of its files. The default is not to build for multiplicity
2418and only include the select backend.
2419.IP "\s-1EV_STANDALONE\s0" 4
2420.IX Item "EV_STANDALONE"
2421Must always be \f(CW1\fR if you do not use autoconf configuration, which
2422keeps libev from including \fIconfig.h\fR, and it also defines dummy
2423implementations for some libevent functions (such as logging, which is not
2424supported). It will also not define any of the structs usually found in
2425\&\fIevent.h\fR that are not directly supported by the libev core alone.
2426.IP "\s-1EV_USE_MONOTONIC\s0" 4
2427.IX Item "EV_USE_MONOTONIC"
2428If defined to be \f(CW1\fR, libev will try to detect the availability of the
2429monotonic clock option at both compiletime and runtime. Otherwise no use
2430of the monotonic clock option will be attempted. If you enable this, you
2431usually have to link against librt or something similar. Enabling it when
2432the functionality isn't available is safe, though, althoguh you have
2433to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2434function is hiding in (often \fI\-lrt\fR).
2435.IP "\s-1EV_USE_REALTIME\s0" 4
2436.IX Item "EV_USE_REALTIME"
2437If defined to be \f(CW1\fR, libev will try to detect the availability of the
2438realtime clock option at compiletime (and assume its availability at
2439runtime if successful). Otherwise no use of the realtime clock option will
2440be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2441(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2442in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2443.IP "\s-1EV_USE_SELECT\s0" 4
2444.IX Item "EV_USE_SELECT"
2445If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2446\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2447other method takes over, select will be it. Otherwise the select backend
2448will not be compiled in.
2449.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2450.IX Item "EV_SELECT_USE_FD_SET"
2451If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2452structure. This is useful if libev doesn't compile due to a missing
2453\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2454exotic systems. This usually limits the range of file descriptors to some
2455low limit such as 1024 or might have other limitations (winsocket only
2456allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2457influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2458.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2459.IX Item "EV_SELECT_IS_WINSOCKET"
2460When defined to \f(CW1\fR, the select backend will assume that
2461select/socket/connect etc. don't understand file descriptors but
2462wants osf handles on win32 (this is the case when the select to
2463be used is the winsock select). This means that it will call
2464\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2465it is assumed that all these functions actually work on fds, even
2466on win32. Should not be defined on non\-win32 platforms.
2467.IP "\s-1EV_USE_POLL\s0" 4
2468.IX Item "EV_USE_POLL"
2469If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2470backend. Otherwise it will be enabled on non\-win32 platforms. It
2471takes precedence over select.
2472.IP "\s-1EV_USE_EPOLL\s0" 4
2473.IX Item "EV_USE_EPOLL"
2474If defined to be \f(CW1\fR, libev will compile in support for the Linux
2475\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2476otherwise another method will be used as fallback. This is the
2477preferred backend for GNU/Linux systems.
2478.IP "\s-1EV_USE_KQUEUE\s0" 4
2479.IX Item "EV_USE_KQUEUE"
2480If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2481\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2482otherwise another method will be used as fallback. This is the preferred
2483backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2484supports some types of fds correctly (the only platform we found that
2485supports ptys for example was NetBSD), so kqueue might be compiled in, but
2486not be used unless explicitly requested. The best way to use it is to find
2487out whether kqueue supports your type of fd properly and use an embedded
2488kqueue loop.
2489.IP "\s-1EV_USE_PORT\s0" 4
2490.IX Item "EV_USE_PORT"
2491If defined to be \f(CW1\fR, libev will compile in support for the Solaris
249210 port style backend. Its availability will be detected at runtime,
2493otherwise another method will be used as fallback. This is the preferred
2494backend for Solaris 10 systems.
2495.IP "\s-1EV_USE_DEVPOLL\s0" 4
2496.IX Item "EV_USE_DEVPOLL"
2497reserved for future expansion, works like the \s-1USE\s0 symbols above.
2498.IP "\s-1EV_USE_INOTIFY\s0" 4
2499.IX Item "EV_USE_INOTIFY"
2500If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2501interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2502be detected at runtime.
2503.IP "\s-1EV_H\s0" 4
2504.IX Item "EV_H"
2505The name of the \fIev.h\fR header file used to include it. The default if
2506undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2507can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2508.IP "\s-1EV_CONFIG_H\s0" 4
2509.IX Item "EV_CONFIG_H"
2510If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2511\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2512\&\f(CW\*(C`EV_H\*(C'\fR, above.
2513.IP "\s-1EV_EVENT_H\s0" 4
2514.IX Item "EV_EVENT_H"
2515Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2516of how the \fIevent.h\fR header can be found.
2517.IP "\s-1EV_PROTOTYPES\s0" 4
2518.IX Item "EV_PROTOTYPES"
2519If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2520prototypes, but still define all the structs and other symbols. This is
2521occasionally useful if you want to provide your own wrapper functions
2522around libev functions.
2523.IP "\s-1EV_MULTIPLICITY\s0" 4
2524.IX Item "EV_MULTIPLICITY"
2525If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2526will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2527additional independent event loops. Otherwise there will be no support
2528for multiple event loops and there is no first event loop pointer
2529argument. Instead, all functions act on the single default loop.
2530.IP "\s-1EV_MINPRI\s0" 4
2531.IX Item "EV_MINPRI"
2532.PD 0
2533.IP "\s-1EV_MAXPRI\s0" 4
2534.IX Item "EV_MAXPRI"
2535.PD
2536The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2537\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2538provide for more priorities by overriding those symbols (usually defined
2539to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2540.Sp
2541When doing priority-based operations, libev usually has to linearly search
2542all the priorities, so having many of them (hundreds) uses a lot of space
2543and time, so using the defaults of five priorities (\-2 .. +2) is usually
2544fine.
2545.Sp
2546If your embedding app does not need any priorities, defining these both to
2547\&\f(CW0\fR will save some memory and cpu.
2548.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2549.IX Item "EV_PERIODIC_ENABLE"
2550If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2551defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2552code.
2553.IP "\s-1EV_IDLE_ENABLE\s0" 4
2554.IX Item "EV_IDLE_ENABLE"
2555If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2556defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2557code.
2558.IP "\s-1EV_EMBED_ENABLE\s0" 4
2559.IX Item "EV_EMBED_ENABLE"
2560If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2561defined to be \f(CW0\fR, then they are not.
2562.IP "\s-1EV_STAT_ENABLE\s0" 4
2563.IX Item "EV_STAT_ENABLE"
2564If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2565defined to be \f(CW0\fR, then they are not.
2566.IP "\s-1EV_FORK_ENABLE\s0" 4
2567.IX Item "EV_FORK_ENABLE"
2568If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2569defined to be \f(CW0\fR, then they are not.
2570.IP "\s-1EV_MINIMAL\s0" 4
2571.IX Item "EV_MINIMAL"
2572If you need to shave off some kilobytes of code at the expense of some
2573speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2574some inlining decisions, saves roughly 30% codesize of amd64.
2575.IP "\s-1EV_PID_HASHSIZE\s0" 4
2576.IX Item "EV_PID_HASHSIZE"
2577\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2578pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2579than enough. If you need to manage thousands of children you might want to
2580increase this value (\fImust\fR be a power of two).
2581.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2582.IX Item "EV_INOTIFY_HASHSIZE"
2583\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2584inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2585usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2586watchers you might want to increase this value (\fImust\fR be a power of
2587two).
2588.IP "\s-1EV_COMMON\s0" 4
2589.IX Item "EV_COMMON"
2590By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2591this macro to a something else you can include more and other types of
2592members. You have to define it each time you include one of the files,
2593though, and it must be identical each time.
2594.Sp
2595For example, the perl \s-1EV\s0 module uses something like this:
2596.Sp
2597.Vb 3
2598\& #define EV_COMMON \e
2599\& SV *self; /* contains this struct */ \e
2600\& SV *cb_sv, *fh /* note no trailing ";" */
2601.Ve
2602.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2603.IX Item "EV_CB_DECLARE (type)"
2604.PD 0
2605.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2606.IX Item "EV_CB_INVOKE (watcher, revents)"
2607.IP "ev_set_cb (ev, cb)" 4
2608.IX Item "ev_set_cb (ev, cb)"
2609.PD
2610Can be used to change the callback member declaration in each watcher,
2611and the way callbacks are invoked and set. Must expand to a struct member
2612definition and a statement, respectively. See the \fIev.v\fR header file for
2613their default definitions. One possible use for overriding these is to
2614avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2615method calls instead of plain function calls in \*(C+.
2616.Sh "\s-1EXAMPLES\s0"
2617.IX Subsection "EXAMPLES"
2618For a real-world example of a program the includes libev
2619verbatim, you can have a look at the \s-1EV\s0 perl module
2620(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2621the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2622interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2623will be compiled. It is pretty complex because it provides its own header
2624file.
2625.Sp
2626The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2627that everybody includes and which overrides some configure choices:
2628.Sp
2629.Vb 9
2630\& #define EV_MINIMAL 1
2631\& #define EV_USE_POLL 0
2632\& #define EV_MULTIPLICITY 0
2633\& #define EV_PERIODIC_ENABLE 0
2634\& #define EV_STAT_ENABLE 0
2635\& #define EV_FORK_ENABLE 0
2636\& #define EV_CONFIG_H <config.h>
2637\& #define EV_MINPRI 0
2638\& #define EV_MAXPRI 0
2639.Ve
2640.Sp
2641.Vb 1
2642\& #include "ev++.h"
2643.Ve
2644.Sp
2645And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2646.Sp
2647.Vb 2
2648\& #include "ev_cpp.h"
2649\& #include "ev.c"
2650.Ve
2651.SH "COMPLEXITIES"
2652.IX Header "COMPLEXITIES"
2653In this section the complexities of (many of) the algorithms used inside
2654libev will be explained. For complexity discussions about backends see the
2655documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2656.Sp
2657All of the following are about amortised time: If an array needs to be
2658extended, libev needs to realloc and move the whole array, but this
2659happens asymptotically never with higher number of elements, so O(1) might
2660mean it might do a lengthy realloc operation in rare cases, but on average
2661it is much faster and asymptotically approaches constant time.
2662.RS 4
2663.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2664.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2665This means that, when you have a watcher that triggers in one hour and
2666there are 100 watchers that would trigger before that then inserting will
2667have to skip those 100 watchers.
2668.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2669.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2670That means that for changing a timer costs less than removing/adding them
2671as only the relative motion in the event queue has to be paid for.
2672.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2673.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2674These just add the watcher into an array or at the head of a list.
2675=item Stopping check/prepare/idle watchers: O(1)
2676.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2677.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2678These watchers are stored in lists then need to be walked to find the
2679correct watcher to remove. The lists are usually short (you don't usually
2680have many watchers waiting for the same fd or signal).
2681.IP "Finding the next timer per loop iteration: O(1)" 4
2682.IX Item "Finding the next timer per loop iteration: O(1)"
2683.PD 0
2684.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2685.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2686.PD
2687A change means an I/O watcher gets started or stopped, which requires
2688libev to recalculate its status (and possibly tell the kernel).
2689.IP "Activating one watcher: O(1)" 4
2690.IX Item "Activating one watcher: O(1)"
2691.PD 0
2692.IP "Priority handling: O(number_of_priorities)" 4
2693.IX Item "Priority handling: O(number_of_priorities)"
2694.PD
2695Priorities are implemented by allocating some space for each
2696priority. When doing priority-based operations, libev usually has to
2697linearly search all the priorities.
2698.RE
2699.RS 4
1267.SH "AUTHOR" 2700.SH "AUTHOR"
1268.IX Header "AUTHOR" 2701.IX Header "AUTHOR"
1269Marc Lehmann <libev@schmorp.de>. 2702Marc Lehmann <libev@schmorp.de>.

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