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Revision 1.13 by root, Sat Nov 24 09:48:38 2007 UTC vs.
Revision 1.51 by root, Wed Dec 12 17:55:30 2007 UTC

… …
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-12" "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));
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242recommended ones. 314recommended ones.
243.Sp 315.Sp
244See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 316See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
245.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 317.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 318.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
247Sets the allocation function to use (the prototype is similar to the 319Sets the allocation function to use (the prototype is similar \- the
248realloc C function, the semantics are identical). It is used to allocate 320semantics is identical \- to the realloc C function). It is used to
249and free memory (no surprises here). If it returns zero when memory 321allocate and free memory (no surprises here). If it returns zero when
250needs to be allocated, the library might abort or take some potentially 322memory needs to be allocated, the library might abort or take some
251destructive action. The default is your system realloc function. 323potentially destructive action. The default is your system realloc
324function.
252.Sp 325.Sp
253You could override this function in high-availability programs to, say, 326You could override this function in high-availability programs to, say,
254free 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,
255or 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.
256.Sp 329.Sp
257Example: 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
258retries: better than mine). 331retries).
259.Sp 332.Sp
260.Vb 6 333.Vb 6
261\& static void * 334\& static void *
262\& persistent_realloc (void *ptr, long size) 335\& persistent_realloc (void *ptr, size_t size)
263\& { 336\& {
264\& for (;;) 337\& for (;;)
265\& { 338\& {
266\& void *newptr = realloc (ptr, size); 339\& void *newptr = realloc (ptr, size);
267.Ve 340.Ve
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289callback 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
290matter what, when it returns. That is, libev will generally retry the 363matter what, when it returns. That is, libev will generally retry the
291requested 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
292(such as abort). 365(such as abort).
293.Sp 366.Sp
294Example: do the same thing as libev does internally: 367Example: This is basically the same thing that libev does internally, too.
295.Sp 368.Sp
296.Vb 6 369.Vb 6
297\& static void 370\& static void
298\& fatal_error (const char *msg) 371\& fatal_error (const char *msg)
299\& { 372\& {
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345or setgid) then libev will \fInot\fR look at the environment variable 418or setgid) then libev will \fInot\fR look at the environment variable
346\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 419\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
347override the flags completely if it is found in the environment. This is 420override the flags completely if it is found in the environment. This is
348useful to try out specific backends to test their performance, or to work 421useful to try out specific backends to test their performance, or to work
349around 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.
350.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 443.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
351.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
352.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 445.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
353This 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
354libev 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,
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448Similar 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
449always distinct from the default loop. Unlike the default loop, it cannot 542always distinct from the default loop. Unlike the default loop, it cannot
450handle signal and child watchers, and attempts to do so will be greeted by 543handle signal and child watchers, and attempts to do so will be greeted by
451undefined behaviour (or a failed assertion if assertions are enabled). 544undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp 545.Sp
453Example: 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.
454.Sp 547.Sp
455.Vb 3 548.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 549\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller) 550\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair"); 551\& fatal ("no epoll found here, maybe it hides under your chair");
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495.IP "ev_loop_fork (loop)" 4 588.IP "ev_loop_fork (loop)" 4
496.IX Item "ev_loop_fork (loop)" 589.IX Item "ev_loop_fork (loop)"
497Like \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
498\&\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
499after 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.
500.IP "unsigned int ev_backend (loop)" 4 602.IP "unsigned int ev_backend (loop)" 4
501.IX Item "unsigned int ev_backend (loop)" 603.IX Item "unsigned int ev_backend (loop)"
502Returns 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
503use. 605use.
504.IP "ev_tstamp ev_now (loop)" 4 606.IP "ev_tstamp ev_now (loop)" 4
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535libev 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
536usually a better approach for this kind of thing. 638usually a better approach for this kind of thing.
537.Sp 639.Sp
538Here 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:
539.Sp 641.Sp
540.Vb 18 642.Vb 19
643\& - Before the first iteration, call any pending watchers.
541\& * If there are no active watchers (reference count is zero), return. 644\& * If there are no active watchers (reference count is zero), return.
542\& - Queue prepare watchers and then call all outstanding watchers. 645\& - Queue all prepare watchers and then call all outstanding watchers.
543\& - If we have been forked, recreate the kernel state. 646\& - If we have been forked, recreate the kernel state.
544\& - Update the kernel state with all outstanding changes. 647\& - Update the kernel state with all outstanding changes.
545\& - Update the "event loop time". 648\& - Update the "event loop time".
546\& - Calculate for how long to block. 649\& - Calculate for how long to block.
547\& - Block the process, waiting for any events. 650\& - Block the process, waiting for any events.
… …
556\& be handled here by queueing them when their watcher gets executed. 659\& be handled here by queueing them when their watcher gets executed.
557\& - 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
558\& were used, return, otherwise continue with step *. 661\& were used, return, otherwise continue with step *.
559.Ve 662.Ve
560.Sp 663.Sp
561Example: queue some jobs and then loop until no events are outsanding 664Example: Queue some jobs and then loop until no events are outsanding
562anymore. 665anymore.
563.Sp 666.Sp
564.Vb 4 667.Vb 4
565\& ... queue jobs here, make sure they register event watchers as long 668\& ... queue jobs here, make sure they register event watchers as long
566\& ... 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..)
… …
588visible 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
589no 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
590way 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
591libraries. 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.
592.Sp 695.Sp
593Example: 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
594running when nothing else is active. 697running when nothing else is active.
595.Sp 698.Sp
596.Vb 4 699.Vb 4
597\& struct dv_signal exitsig; 700\& struct ev_signal exitsig;
598\& ev_signal_init (&exitsig, sig_cb, SIGINT); 701\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599\& ev_signal_start (myloop, &exitsig); 702\& ev_signal_start (loop, &exitsig);
600\& evf_unref (myloop); 703\& evf_unref (loop);
601.Ve 704.Ve
602.Sp 705.Sp
603Example: for some weird reason, unregister the above signal handler again. 706Example: For some weird reason, unregister the above signal handler again.
604.Sp 707.Sp
605.Vb 2 708.Vb 2
606\& ev_ref (myloop); 709\& ev_ref (loop);
607\& ev_signal_stop (myloop, &exitsig); 710\& ev_signal_stop (loop, &exitsig);
608.Ve 711.Ve
609.SH "ANATOMY OF A WATCHER" 712.SH "ANATOMY OF A WATCHER"
610.IX Header "ANATOMY OF A WATCHER" 713.IX Header "ANATOMY OF A WATCHER"
611A 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
612interest 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
… …
684The 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.
685.ie n .IP """EV_CHILD""" 4 788.ie n .IP """EV_CHILD""" 4
686.el .IP "\f(CWEV_CHILD\fR" 4 789.el .IP "\f(CWEV_CHILD\fR" 4
687.IX Item "EV_CHILD" 790.IX Item "EV_CHILD"
688The 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.
689.ie n .IP """EV_IDLE""" 4 796.ie n .IP """EV_IDLE""" 4
690.el .IP "\f(CWEV_IDLE\fR" 4 797.el .IP "\f(CWEV_IDLE\fR" 4
691.IX Item "EV_IDLE" 798.IX Item "EV_IDLE"
692The \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.
693.ie n .IP """EV_PREPARE""" 4 800.ie n .IP """EV_PREPARE""" 4
… …
703\&\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
704received events. Callbacks of both watcher types can start and stop as 811received events. Callbacks of both watcher types can start and stop as
705many 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
706(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
707\&\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).
708.ie n .IP """EV_ERROR""" 4 824.ie n .IP """EV_ERROR""" 4
709.el .IP "\f(CWEV_ERROR\fR" 4 825.el .IP "\f(CWEV_ERROR\fR" 4
710.IX Item "EV_ERROR" 826.IX Item "EV_ERROR"
711An unspecified error has occured, the watcher has been stopped. This might 827An unspecified error has occured, the watcher has been stopped. This might
712happen because the watcher could not be properly started because libev 828happen because the watcher could not be properly started because libev
… …
717Libev 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,
718for 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
719your 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
720with 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
721programs, though, so beware. 837programs, though, so beware.
722.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" 838.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
723.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS" 839.IX Subsection "GENERIC WATCHER FUNCTIONS"
724In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, 840In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
725e.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. 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.
726.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 842.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
727.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 843.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
728.IX Item "ev_init (ev_TYPE *watcher, callback)" 844.IX Item "ev_init (ev_TYPE *watcher, callback)"
… …
734which rolls both calls into one. 850which rolls both calls into one.
735.Sp 851.Sp
736You can reinitialise a watcher at any time as long as it has been stopped 852You can reinitialise a watcher at any time as long as it has been stopped
737(or never started) and there are no pending events outstanding. 853(or never started) and there are no pending events outstanding.
738.Sp 854.Sp
739The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, 855The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
740int revents)\*(C'\fR. 856int revents)\*(C'\fR.
741.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 857.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
742.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 858.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
743.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 859.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
744This macro initialises the type-specific parts of a watcher. You need to 860This macro initialises the type-specific parts of a watcher. You need to
… …
777.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 893.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
778.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 894.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
779Returns a true value iff the watcher is pending, (i.e. it has outstanding 895Returns a true value iff the watcher is pending, (i.e. it has outstanding
780events but its callback has not yet been invoked). As long as a watcher 896events but its callback has not yet been invoked). As long as a watcher
781is pending (but not active) you must not call an init function on it (but 897is pending (but not active) you must not call an init function on it (but
782\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to 898\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
783libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). 899make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
900it).
784.IP "callback = ev_cb (ev_TYPE *watcher)" 4 901.IP "callback ev_cb (ev_TYPE *watcher)" 4
785.IX Item "callback = ev_cb (ev_TYPE *watcher)" 902.IX Item "callback ev_cb (ev_TYPE *watcher)"
786Returns the callback currently set on the watcher. 903Returns the callback currently set on the watcher.
787.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 904.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
788.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 905.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
789Change the callback. You can change the callback at virtually any time 906Change the callback. You can change the callback at virtually any time
790(modulo threads). 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.
791.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"
792.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 948.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
793Each 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
794and 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
795to 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
… …
816\& struct my_io *w = (struct my_io *)w_; 972\& struct my_io *w = (struct my_io *)w_;
817\& ... 973\& ...
818\& } 974\& }
819.Ve 975.Ve
820.PP 976.PP
821More interesting and less C\-conformant ways of catsing your callback type 977More interesting and less C\-conformant ways of casting your callback type
822have 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
823.SH "WATCHER TYPES" 1016.SH "WATCHER TYPES"
824.IX Header "WATCHER TYPES" 1017.IX Header "WATCHER TYPES"
825This section describes each watcher in detail, but will not repeat 1018This section describes each watcher in detail, but will not repeat
826information 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.
827.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?"
828.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?"
829.IX Subsection "ev_io - is this file descriptor readable or writable" 1032.IX Subsection "ev_io - is this file descriptor readable or writable?"
830I/O watchers check whether a file descriptor is readable or writable 1033I/O watchers check whether a file descriptor is readable or writable
831in each iteration of the event loop (This behaviour is called 1034in each iteration of the event loop, or, more precisely, when reading
832level-triggering because you keep receiving events as long as the 1035would not block the process and writing would at least be able to write
833condition persists. Remember you can stop the watcher if you don't want to 1036some data. This behaviour is called level-triggering because you keep
834act 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.
835.PP 1040.PP
836In 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
837fd 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
838descriptors 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
839required if you know what you are doing). 1044required if you know what you are doing).
840.PP 1045.PP
841You 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
842(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
843descriptors correctly if you register interest in two or more fds pointing 1048descriptors correctly if you register interest in two or more fds pointing
844to the same underlying file/socket etc. description (that is, they share 1049to the same underlying file/socket/etc. description (that is, they share
845the same underlying \*(L"file open\*(R"). 1050the same underlying \*(L"file open\*(R").
846.PP 1051.PP
847If 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
848(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
849\&\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"
850.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
851.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)"
852.PD 0 1097.PD 0
853.IP "ev_io_set (ev_io *, int fd, int events)" 4 1098.IP "ev_io_set (ev_io *, int fd, int events)" 4
854.IX Item "ev_io_set (ev_io *, int fd, int events)" 1099.IX Item "ev_io_set (ev_io *, int fd, int events)"
855.PD 1100.PD
856Configures 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
857events 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
858EV_WRITE\*(C'\fR to receive the given events. 1103\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
859.Sp 1104.IP "int fd [read\-only]" 4
860Please note that most of the more scalable backend mechanisms (for example 1105.IX Item "int fd [read-only]"
861epoll and solaris ports) can result in spurious readyness notifications 1106The file descriptor being watched.
862for file descriptors, so you practically need to use non-blocking I/O (and 1107.IP "int events [read\-only]" 4
863treat callback invocation as hint only), or retest separately with a safe 1108.IX Item "int events [read-only]"
864interface before doing I/O (XLib can do this), or force the use of either 1109The events being watched.
865\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
866problem. Also note that it is quite easy to have your callback invoked
867when the readyness condition is no longer valid even when employing
868typical ways of handling events, so its a good idea to use non-blocking
869I/O unconditionally.
870.PP 1110.PP
871Example: 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
872readable, but only once. Since it is likely line\-buffered, you could 1112readable, but only once. Since it is likely line\-buffered, you could
873attempt to read a whole line in the callback: 1113attempt to read a whole line in the callback.
874.PP 1114.PP
875.Vb 6 1115.Vb 6
876\& static void 1116\& static void
877\& 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)
878\& { 1118\& {
… …
887\& struct ev_io stdin_readable; 1127\& struct ev_io stdin_readable;
888\& 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);
889\& ev_io_start (loop, &stdin_readable); 1129\& ev_io_start (loop, &stdin_readable);
890\& ev_loop (loop, 0); 1130\& ev_loop (loop, 0);
891.Ve 1131.Ve
892.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1132.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
893.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1133.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
894.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1134.IX Subsection "ev_timer - relative and optionally repeating timeouts"
895Timer watchers are simple relative timers that generate an event after a 1135Timer watchers are simple relative timers that generate an event after a
896given time, and optionally repeating in regular intervals after that. 1136given time, and optionally repeating in regular intervals after that.
897.PP 1137.PP
898The 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
899times 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
… …
912.Ve 1152.Ve
913.PP 1153.PP
914The 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,
915but if multiple timers become ready during the same loop iteration then 1155but if multiple timers become ready during the same loop iteration then
916order 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"
917.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
918.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)"
919.PD 0 1162.PD 0
920.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
921.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)"
… …
933.IP "ev_timer_again (loop)" 4 1176.IP "ev_timer_again (loop)" 4
934.IX Item "ev_timer_again (loop)" 1177.IX Item "ev_timer_again (loop)"
935This 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
936repeating. The exact semantics are: 1179repeating. The exact semantics are:
937.Sp 1180.Sp
1181If the timer is pending, its pending status is cleared.
1182.Sp
938If the timer is started but nonrepeating, stop it. 1183If the timer is started but nonrepeating, stop it (as if it timed out).
939.Sp 1184.Sp
940If the timer is repeating, either start it if necessary (with the repeat 1185If the timer is repeating, either start it if necessary (with the
941value), 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.
942.Sp 1187.Sp
943This sounds a bit complicated, but here is a useful and typical 1188This sounds a bit complicated, but here is a useful and typical
944example: 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
945timeout, 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
946seconds 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
947configure 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
948time 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
949state 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
950the 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.
951.PP 1219.PP
952Example: create a timer that fires after 60 seconds. 1220Example: Create a timer that fires after 60 seconds.
953.PP 1221.PP
954.Vb 5 1222.Vb 5
955\& static void 1223\& static void
956\& 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)
957\& { 1225\& {
… …
963\& struct ev_timer mytimer; 1231\& struct ev_timer mytimer;
964\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1232\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
965\& ev_timer_start (loop, &mytimer); 1233\& ev_timer_start (loop, &mytimer);
966.Ve 1234.Ve
967.PP 1235.PP
968Example: create a timeout timer that times out after 10 seconds of 1236Example: Create a timeout timer that times out after 10 seconds of
969inactivity. 1237inactivity.
970.PP 1238.PP
971.Vb 5 1239.Vb 5
972\& static void 1240\& static void
973\& 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)
… …
986.Vb 3 1254.Vb 3
987\& // 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":
988\& // reset the timeout to start ticking again at 10 seconds 1256\& // reset the timeout to start ticking again at 10 seconds
989\& ev_timer_again (&mytimer); 1257\& ev_timer_again (&mytimer);
990.Ve 1258.Ve
991.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1259.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
992.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?"
993.IX Subsection "ev_periodic - to cron or not to cron" 1261.IX Subsection "ev_periodic - to cron or not to cron?"
994Periodic 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
995(and unfortunately a bit complex). 1263(and unfortunately a bit complex).
996.PP 1264.PP
997Unlike \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)
998but on wallclock time (absolute time). You can tell a periodic watcher 1266but on wallclock time (absolute time). You can tell a periodic watcher
999to 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
1000periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 1268periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1001+ 10.\*(C'\fR) 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
1002take 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
1003roughly 10 seconds later and of course not if you reset your system time 1271roughly 10 seconds later).
1004again).
1005.PP 1272.PP
1006They 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
1007triggering an event on eahc midnight, local time. 1274triggering an event on each midnight, local time or other, complicated,
1275rules.
1008.PP 1276.PP
1009As 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
1010time (\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
1011during 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"
1012.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
1013.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)"
1014.PD 0 1285.PD 0
1015.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
1016.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)"
1017.PD 1288.PD
1018Lots 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
1019operation, and we will explain them from simplest to complex: 1290operation, and we will explain them from simplest to complex:
1020.RS 4 1291.RS 4
1021.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1292.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
1022.IX Item "absolute timer (interval = reschedule_cb = 0)" 1293.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
1023In this configuration the watcher triggers an event at the wallclock time 1294In this configuration the watcher triggers an event at the wallclock time
1024\&\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,
1025that 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
1026system time reaches or surpasses this time. 1297system time reaches or surpasses this time.
1027.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
1028.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)"
1029In 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
1030\&\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)
1031of any time jumps. 1302and then repeat, regardless of any time jumps.
1032.Sp 1303.Sp
1033This 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
1034time: 1305time:
1035.Sp 1306.Sp
1036.Vb 1 1307.Vb 1
… …
1043by 3600. 1314by 3600.
1044.Sp 1315.Sp
1045Another way to think about it (for the mathematically inclined) is that 1316Another way to think about it (for the mathematically inclined) is that
1046\&\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
1047time 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.
1048.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1323.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
1049.IX Item "manual reschedule mode (reschedule_cb = callback)" 1324.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
1050In 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
1051ignored. Instead, each time the periodic watcher gets scheduled, the 1326ignored. Instead, each time the periodic watcher gets scheduled, the
1052reschedule callback will be called with the watcher as first, and the 1327reschedule callback will be called with the watcher as first, and the
1053current time as second argument. 1328current time as second argument.
1054.Sp 1329.Sp
1055\&\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,
1056ever, 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,
1057return \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
1058starting a prepare watcher). 1333starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1059.Sp 1334.Sp
1060Its 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,
1061ev_tstamp now)\*(C'\fR, e.g.: 1336ev_tstamp now)\*(C'\fR, e.g.:
1062.Sp 1337.Sp
1063.Vb 4 1338.Vb 4
… …
1087.IX Item "ev_periodic_again (loop, ev_periodic *)" 1362.IX Item "ev_periodic_again (loop, ev_periodic *)"
1088Simply stops and restarts the periodic watcher again. This is only useful 1363Simply stops and restarts the periodic watcher again. This is only useful
1089when you changed some parameters or the reschedule callback would return 1364when you changed some parameters or the reschedule callback would return
1090a 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
1091program 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.
1092.PP 1384.PP
1093Example: call a callback every hour, or, more precisely, whenever the 1385Example: Call a callback every hour, or, more precisely, whenever the
1094system clock is divisible by 3600. The callback invocation times have 1386system clock is divisible by 3600. The callback invocation times have
1095potentially a lot of jittering, but good long-term stability. 1387potentially a lot of jittering, but good long-term stability.
1096.PP 1388.PP
1097.Vb 5 1389.Vb 5
1098\& static void 1390\& static void
… …
1106\& struct ev_periodic hourly_tick; 1398\& struct ev_periodic hourly_tick;
1107\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1399\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1108\& ev_periodic_start (loop, &hourly_tick); 1400\& ev_periodic_start (loop, &hourly_tick);
1109.Ve 1401.Ve
1110.PP 1402.PP
1111Example: 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:
1112.PP 1404.PP
1113.Vb 1 1405.Vb 1
1114\& #include <math.h> 1406\& #include <math.h>
1115.Ve 1407.Ve
1116.PP 1408.PP
… …
1124.PP 1416.PP
1125.Vb 1 1417.Vb 1
1126\& 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);
1127.Ve 1419.Ve
1128.PP 1420.PP
1129Example: call a callback every hour, starting now: 1421Example: Call a callback every hour, starting now:
1130.PP 1422.PP
1131.Vb 4 1423.Vb 4
1132\& struct ev_periodic hourly_tick; 1424\& struct ev_periodic hourly_tick;
1133\& ev_periodic_init (&hourly_tick, clock_cb, 1425\& ev_periodic_init (&hourly_tick, clock_cb,
1134\& fmod (ev_now (loop), 3600.), 3600., 0); 1426\& fmod (ev_now (loop), 3600.), 3600., 0);
1135\& ev_periodic_start (loop, &hourly_tick); 1427\& ev_periodic_start (loop, &hourly_tick);
1136.Ve 1428.Ve
1137.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!"
1138.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!"
1139.IX Subsection "ev_signal - signal me when a signal gets signalled" 1431.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1140Signal watchers will trigger an event when the process receives a specific 1432Signal watchers will trigger an event when the process receives a specific
1141signal one or more times. Even though signals are very asynchronous, libev 1433signal one or more times. Even though signals are very asynchronous, libev
1142will 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
1143normal event processing, like any other event. 1435normal event processing, like any other event.
1144.PP 1436.PP
… …
1146first watcher gets started will libev actually register a signal watcher 1438first watcher gets started will libev actually register a signal watcher
1147with 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
1148as 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
1149watcher 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
1150\&\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"
1151.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1446.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1152.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1447.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1153.PD 0 1448.PD 0
1154.IP "ev_signal_set (ev_signal *, int signum)" 4 1449.IP "ev_signal_set (ev_signal *, int signum)" 4
1155.IX Item "ev_signal_set (ev_signal *, int signum)" 1450.IX Item "ev_signal_set (ev_signal *, int signum)"
1156.PD 1451.PD
1157Configures the watcher to trigger on the given signal number (usually one 1452Configures the watcher to trigger on the given signal number (usually one
1158of 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.
1159.ie n .Sh """ev_child"" \- wait for pid status changes" 1457.ie n .Sh """ev_child"" \- watch out for process status changes"
1160.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1458.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1161.IX Subsection "ev_child - wait for pid status changes" 1459.IX Subsection "ev_child - watch out for process status changes"
1162Child 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
1163some 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"
1164.IP "ev_child_init (ev_child *, callback, int pid)" 4 1465.IP "ev_child_init (ev_child *, callback, int pid)" 4
1165.IX Item "ev_child_init (ev_child *, callback, int pid)" 1466.IX Item "ev_child_init (ev_child *, callback, int pid)"
1166.PD 0 1467.PD 0
1167.IP "ev_child_set (ev_child *, int pid)" 4 1468.IP "ev_child_set (ev_child *, int pid)" 4
1168.IX Item "ev_child_set (ev_child *, int pid)" 1469.IX Item "ev_child_set (ev_child *, int pid)"
… …
1171\&\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
1172at 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
1173the 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
1174\&\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
1175process 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).
1176.PP 1487.PP
1177Example: 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.
1178.PP 1489.PP
1179.Vb 5 1490.Vb 5
1180\& static void 1491\& static void
1181\& 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)
1182\& { 1493\& {
… …
1187.Vb 3 1498.Vb 3
1188\& struct ev_signal signal_watcher; 1499\& struct ev_signal signal_watcher;
1189\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1500\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1190\& ev_signal_start (loop, &sigint_cb); 1501\& ev_signal_start (loop, &sigint_cb);
1191.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
1192.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..."
1193.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..."
1194.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..."
1195Idle watchers trigger events when there are no other events are pending 1612Idle watchers trigger events when no other events of the same or higher
1196(prepare, check and other idle watchers do not count). That is, as long 1613priority are pending (prepare, check and other idle watchers do not
1197as your process is busy handling sockets or timeouts (or even signals, 1614count).
1198imagine) it will not be triggered. But when your process is idle all idle 1615.PP
1199watchers 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
1200until stopped, that is, or your process receives more events and becomes 1620iteration \- until stopped, that is, or your process receives more events
1201busy. 1621and becomes busy again with higher priority stuff.
1202.PP 1622.PP
1203The 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
1204active, the process will not block when waiting for new events. 1624active, the process will not block when waiting for new events.
1205.PP 1625.PP
1206Apart from keeping your process non-blocking (which is a useful 1626Apart from keeping your process non-blocking (which is a useful
1207effect 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
1208\&\*(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
1209event 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"
1210.IP "ev_idle_init (ev_signal *, callback)" 4 1633.IP "ev_idle_init (ev_signal *, callback)" 4
1211.IX Item "ev_idle_init (ev_signal *, callback)" 1634.IX Item "ev_idle_init (ev_signal *, callback)"
1212Initialises and configures the idle watcher \- it has no parameters of any 1635Initialises and configures the idle watcher \- it has no parameters of any
1213kind. 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,
1214believe me. 1637believe me.
1215.PP 1638.PP
1216Example: 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
1217callback, free it. Alos, use no error checking, as usual. 1640callback, free it. Also, use no error checking, as usual.
1218.PP 1641.PP
1219.Vb 7 1642.Vb 7
1220\& static void 1643\& static void
1221\& 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)
1222\& { 1645\& {
… …
1229.Vb 3 1652.Vb 3
1230\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1653\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1231\& ev_idle_init (idle_watcher, idle_cb); 1654\& ev_idle_init (idle_watcher, idle_cb);
1232\& ev_idle_start (loop, idle_cb); 1655\& ev_idle_start (loop, idle_cb);
1233.Ve 1656.Ve
1234.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!"
1235.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!"
1236.IX Subsection "ev_prepare and ev_check - customise your event loop" 1659.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1237Prepare and check watchers are usually (but not always) used in tandem: 1660Prepare and check watchers are usually (but not always) used in tandem:
1238prepare watchers get invoked before the process blocks and check watchers 1661prepare watchers get invoked before the process blocks and check watchers
1239afterwards. 1662afterwards.
1240.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
1241Their main purpose is to integrate other event mechanisms into libev and 1672Their main purpose is to integrate other event mechanisms into libev and
1242their use is somewhat advanced. This could be used, for example, to track 1673their use is somewhat advanced. This could be used, for example, to track
1243variable changes, implement your own watchers, integrate net-snmp or a 1674variable changes, implement your own watchers, integrate net-snmp or a
1244coroutine library and lots more. 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).
1245.PP 1679.PP
1246This 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
1247to 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
1248them 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
1249provide just this functionality). Then, in the check watcher you check for 1683provide just this functionality). Then, in the check watcher you check for
… …
1258are 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
1259with 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
1260of 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
1261loop from blocking if lower-priority coroutines are active, thus mapping 1695loop from blocking if lower-priority coroutines are active, thus mapping
1262low-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"
1263.IP "ev_prepare_init (ev_prepare *, callback)" 4 1710.IP "ev_prepare_init (ev_prepare *, callback)" 4
1264.IX Item "ev_prepare_init (ev_prepare *, callback)" 1711.IX Item "ev_prepare_init (ev_prepare *, callback)"
1265.PD 0 1712.PD 0
1266.IP "ev_check_init (ev_check *, callback)" 4 1713.IP "ev_check_init (ev_check *, callback)" 4
1267.IX Item "ev_check_init (ev_check *, callback)" 1714.IX Item "ev_check_init (ev_check *, callback)"
1268.PD 1715.PD
1269Initialises and configures the prepare or check watcher \- they have no 1716Initialises and configures the prepare or check watcher \- they have no
1270parameters 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
1271macros, but using them is utterly, utterly and completely pointless. 1718macros, but using them is utterly, utterly and completely pointless.
1272.PP 1719.PP
1273Example: *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
1274.ie n .Sh """ev_embed"" \- when one backend isn't enough" 1890.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1275.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough" 1891.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1276.IX Subsection "ev_embed - when one backend isn't enough" 1892.IX Subsection "ev_embed - when one backend isn't enough..."
1277This is a rather advanced watcher type that lets you embed one event loop 1893This is a rather advanced watcher type that lets you embed one event loop
1278into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded 1894into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1279loop, other types of watchers might be handled in a delayed or incorrect 1895loop, other types of watchers might be handled in a delayed or incorrect
1280fashion and must not be used). 1896fashion and must not be used).
1281.PP 1897.PP
… …
1345\& ev_embed_start (loop_hi, &embed); 1961\& ev_embed_start (loop_hi, &embed);
1346\& } 1962\& }
1347\& else 1963\& else
1348\& loop_lo = loop_hi; 1964\& loop_lo = loop_hi;
1349.Ve 1965.Ve
1966.PP
1967\fIWatcher-Specific Functions and Data Members\fR
1968.IX Subsection "Watcher-Specific Functions and Data Members"
1350.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 1969.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1351.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 1970.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1352.PD 0 1971.PD 0
1353.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 1972.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1354.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 1973.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
… …
1361.IP "ev_embed_sweep (loop, ev_embed *)" 4 1980.IP "ev_embed_sweep (loop, ev_embed *)" 4
1362.IX Item "ev_embed_sweep (loop, ev_embed *)" 1981.IX Item "ev_embed_sweep (loop, ev_embed *)"
1363Make a single, non-blocking sweep over the embedded loop. This works 1982Make a single, non-blocking sweep over the embedded loop. This works
1364similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most 1983similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1365apropriate way for embedded loops. 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.PP
1999\fIWatcher-Specific Functions and Data Members\fR
2000.IX Subsection "Watcher-Specific Functions and Data Members"
2001.IP "ev_fork_init (ev_signal *, callback)" 4
2002.IX Item "ev_fork_init (ev_signal *, callback)"
2003Initialises and configures the fork watcher \- it has no parameters of any
2004kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2005believe me.
1366.SH "OTHER FUNCTIONS" 2006.SH "OTHER FUNCTIONS"
1367.IX Header "OTHER FUNCTIONS" 2007.IX Header "OTHER FUNCTIONS"
1368There are some other functions of possible interest. Described. Here. Now. 2008There are some other functions of possible interest. Described. Here. Now.
1369.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 2009.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1370.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 2010.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1442.PP 2082.PP
1443.Vb 1 2083.Vb 1
1444\& #include <ev++.h> 2084\& #include <ev++.h>
1445.Ve 2085.Ve
1446.PP 2086.PP
1447(it is not installed by default). This automatically includes \fIev.h\fR 2087This automatically includes \fIev.h\fR and puts all of its definitions (many
1448and puts all of its definitions (many of them macros) into the global 2088of them macros) into the global namespace. All \*(C+ specific things are
1449namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. 2089put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2090options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1450.PP 2091.PP
1451It should support all the same embedding options as \fIev.h\fR, most notably 2092Care has been taken to keep the overhead low. The only data member the \*(C+
1452\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. 2093classes add (compared to plain C\-style watchers) is the event loop pointer
2094that the watcher is associated with (or no additional members at all if
2095you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2096.PP
2097Currently, functions, and static and non-static member functions can be
2098used as callbacks. Other types should be easy to add as long as they only
2099need one additional pointer for context. If you need support for other
2100types of functors please contact the author (preferably after implementing
2101it).
1453.PP 2102.PP
1454Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: 2103Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1455.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 2104.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1456.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 2105.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1457.IX Item "ev::READ, ev::WRITE etc." 2106.IX Item "ev::READ, ev::WRITE etc."
… …
1469which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro 2118which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1470defines by many implementations. 2119defines by many implementations.
1471.Sp 2120.Sp
1472All of those classes have these methods: 2121All of those classes have these methods:
1473.RS 4 2122.RS 4
1474.IP "ev::TYPE::TYPE (object *, object::method *)" 4 2123.IP "ev::TYPE::TYPE ()" 4
1475.IX Item "ev::TYPE::TYPE (object *, object::method *)" 2124.IX Item "ev::TYPE::TYPE ()"
1476.PD 0 2125.PD 0
1477.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 2126.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
1478.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 2127.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
1479.IP "ev::TYPE::~TYPE" 4 2128.IP "ev::TYPE::~TYPE" 4
1480.IX Item "ev::TYPE::~TYPE" 2129.IX Item "ev::TYPE::~TYPE"
1481.PD 2130.PD
1482The constructor takes a pointer to an object and a method pointer to 2131The constructor (optionally) takes an event loop to associate the watcher
1483the event handler callback to call in this class. The constructor calls 2132with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
1484\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method 2133.Sp
1485before starting it. If you do not specify a loop then the constructor 2134The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
1486automatically associates the default loop with this watcher. 2135\&\f(CW\*(C`set\*(C'\fR method before starting it.
2136.Sp
2137It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2138method to set a callback before you can start the watcher.
2139.Sp
2140(The reason why you have to use a method is a limitation in \*(C+ which does
2141not allow explicit template arguments for constructors).
1487.Sp 2142.Sp
1488The destructor automatically stops the watcher if it is active. 2143The destructor automatically stops the watcher if it is active.
2144.IP "w\->set<class, &class::method> (object *)" 4
2145.IX Item "w->set<class, &class::method> (object *)"
2146This method sets the callback method to call. The method has to have a
2147signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2148first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2149parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2150.Sp
2151This method synthesizes efficient thunking code to call your method from
2152the C callback that libev requires. If your compiler can inline your
2153callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2154your compiler is good :), then the method will be fully inlined into the
2155thunking function, making it as fast as a direct C callback.
2156.Sp
2157Example: simple class declaration and watcher initialisation
2158.Sp
2159.Vb 4
2160\& struct myclass
2161\& {
2162\& void io_cb (ev::io &w, int revents) { }
2163\& }
2164.Ve
2165.Sp
2166.Vb 3
2167\& myclass obj;
2168\& ev::io iow;
2169\& iow.set <myclass, &myclass::io_cb> (&obj);
2170.Ve
2171.IP "w\->set<function> (void *data = 0)" 4
2172.IX Item "w->set<function> (void *data = 0)"
2173Also sets a callback, but uses a static method or plain function as
2174callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2175\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2176.Sp
2177The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2178.Sp
2179See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2180.Sp
2181Example:
2182.Sp
2183.Vb 2
2184\& static void io_cb (ev::io &w, int revents) { }
2185\& iow.set <io_cb> ();
2186.Ve
1489.IP "w\->set (struct ev_loop *)" 4 2187.IP "w\->set (struct ev_loop *)" 4
1490.IX Item "w->set (struct ev_loop *)" 2188.IX Item "w->set (struct ev_loop *)"
1491Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 2189Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1492do this when the watcher is inactive (and not pending either). 2190do this when the watcher is inactive (and not pending either).
1493.IP "w\->set ([args])" 4 2191.IP "w\->set ([args])" 4
1494.IX Item "w->set ([args])" 2192.IX Item "w->set ([args])"
1495Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be 2193Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1496called at least once. Unlike the C counterpart, an active watcher gets 2194called at least once. Unlike the C counterpart, an active watcher gets
1497automatically stopped and restarted. 2195automatically stopped and restarted when reconfiguring it with this
2196method.
1498.IP "w\->start ()" 4 2197.IP "w\->start ()" 4
1499.IX Item "w->start ()" 2198.IX Item "w->start ()"
1500Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the 2199Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
1501constructor already takes the loop. 2200constructor already stores the event loop.
1502.IP "w\->stop ()" 4 2201.IP "w\->stop ()" 4
1503.IX Item "w->stop ()" 2202.IX Item "w->stop ()"
1504Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. 2203Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1505.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 2204.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1506.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 2205.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
… …
1509\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. 2208\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1510.ie n .IP "w\->sweep () ""ev::embed"" only" 4 2209.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1511.el .IP "w\->sweep () \f(CWev::embed\fR only" 4 2210.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1512.IX Item "w->sweep () ev::embed only" 2211.IX Item "w->sweep () ev::embed only"
1513Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. 2212Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2213.ie n .IP "w\->update () ""ev::stat"" only" 4
2214.el .IP "w\->update () \f(CWev::stat\fR only" 4
2215.IX Item "w->update () ev::stat only"
2216Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1514.RE 2217.RE
1515.RS 4 2218.RS 4
1516.RE 2219.RE
1517.PP 2220.PP
1518Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in 2221Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
… …
1528.Vb 2 2231.Vb 2
1529\& myclass (); 2232\& myclass ();
1530\& } 2233\& }
1531.Ve 2234.Ve
1532.PP 2235.PP
1533.Vb 6 2236.Vb 4
1534\& myclass::myclass (int fd) 2237\& myclass::myclass (int fd)
1535\& : io (this, &myclass::io_cb),
1536\& idle (this, &myclass::idle_cb)
1537\& { 2238\& {
2239\& io .set <myclass, &myclass::io_cb > (this);
2240\& idle.set <myclass, &myclass::idle_cb> (this);
2241.Ve
2242.PP
2243.Vb 2
1538\& io.start (fd, ev::READ); 2244\& io.start (fd, ev::READ);
1539\& } 2245\& }
1540.Ve 2246.Ve
2247.SH "MACRO MAGIC"
2248.IX Header "MACRO MAGIC"
2249Libev can be compiled with a variety of options, the most fundemantal is
2250\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
2251callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2252.PP
2253To make it easier to write programs that cope with either variant, the
2254following macros are defined:
2255.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2256.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2257.IX Item "EV_A, EV_A_"
2258This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2259loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2260\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2261.Sp
2262.Vb 3
2263\& ev_unref (EV_A);
2264\& ev_timer_add (EV_A_ watcher);
2265\& ev_loop (EV_A_ 0);
2266.Ve
2267.Sp
2268It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2269which is often provided by the following macro.
2270.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2271.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2272.IX Item "EV_P, EV_P_"
2273This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2274loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2275\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2276.Sp
2277.Vb 2
2278\& // this is how ev_unref is being declared
2279\& static void ev_unref (EV_P);
2280.Ve
2281.Sp
2282.Vb 2
2283\& // this is how you can declare your typical callback
2284\& static void cb (EV_P_ ev_timer *w, int revents)
2285.Ve
2286.Sp
2287It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2288suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2289.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2290.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2291.IX Item "EV_DEFAULT, EV_DEFAULT_"
2292Similar to the other two macros, this gives you the value of the default
2293loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2294.PP
2295Example: Declare and initialise a check watcher, utilising the above
2296macros so it will work regardless of whether multiple loops are supported
2297or not.
2298.PP
2299.Vb 5
2300\& static void
2301\& check_cb (EV_P_ ev_timer *w, int revents)
2302\& {
2303\& ev_check_stop (EV_A_ w);
2304\& }
2305.Ve
2306.PP
2307.Vb 4
2308\& ev_check check;
2309\& ev_check_init (&check, check_cb);
2310\& ev_check_start (EV_DEFAULT_ &check);
2311\& ev_loop (EV_DEFAULT_ 0);
2312.Ve
2313.SH "EMBEDDING"
2314.IX Header "EMBEDDING"
2315Libev can (and often is) directly embedded into host
2316applications. Examples of applications that embed it include the Deliantra
2317Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2318and rxvt\-unicode.
2319.PP
2320The goal is to enable you to just copy the neecssary files into your
2321source directory without having to change even a single line in them, so
2322you can easily upgrade by simply copying (or having a checked-out copy of
2323libev somewhere in your source tree).
2324.Sh "\s-1FILESETS\s0"
2325.IX Subsection "FILESETS"
2326Depending on what features you need you need to include one or more sets of files
2327in your app.
2328.PP
2329\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2330.IX Subsection "CORE EVENT LOOP"
2331.PP
2332To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2333configuration (no autoconf):
2334.PP
2335.Vb 2
2336\& #define EV_STANDALONE 1
2337\& #include "ev.c"
2338.Ve
2339.PP
2340This will automatically include \fIev.h\fR, too, and should be done in a
2341single C source file only to provide the function implementations. To use
2342it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2343done by writing a wrapper around \fIev.h\fR that you can include instead and
2344where you can put other configuration options):
2345.PP
2346.Vb 2
2347\& #define EV_STANDALONE 1
2348\& #include "ev.h"
2349.Ve
2350.PP
2351Both header files and implementation files can be compiled with a \*(C+
2352compiler (at least, thats a stated goal, and breakage will be treated
2353as a bug).
2354.PP
2355You need the following files in your source tree, or in a directory
2356in your include path (e.g. in libev/ when using \-Ilibev):
2357.PP
2358.Vb 4
2359\& ev.h
2360\& ev.c
2361\& ev_vars.h
2362\& ev_wrap.h
2363.Ve
2364.PP
2365.Vb 1
2366\& ev_win32.c required on win32 platforms only
2367.Ve
2368.PP
2369.Vb 5
2370\& ev_select.c only when select backend is enabled (which is enabled by default)
2371\& ev_poll.c only when poll backend is enabled (disabled by default)
2372\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2373\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2374\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2375.Ve
2376.PP
2377\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2378to compile this single file.
2379.PP
2380\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2381.IX Subsection "LIBEVENT COMPATIBILITY API"
2382.PP
2383To include the libevent compatibility \s-1API\s0, also include:
2384.PP
2385.Vb 1
2386\& #include "event.c"
2387.Ve
2388.PP
2389in the file including \fIev.c\fR, and:
2390.PP
2391.Vb 1
2392\& #include "event.h"
2393.Ve
2394.PP
2395in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2396.PP
2397You need the following additional files for this:
2398.PP
2399.Vb 2
2400\& event.h
2401\& event.c
2402.Ve
2403.PP
2404\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2405.IX Subsection "AUTOCONF SUPPORT"
2406.PP
2407Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2408whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2409\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2410include \fIconfig.h\fR and configure itself accordingly.
2411.PP
2412For this of course you need the m4 file:
2413.PP
2414.Vb 1
2415\& libev.m4
2416.Ve
2417.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2418.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2419Libev can be configured via a variety of preprocessor symbols you have to define
2420before including any of its files. The default is not to build for multiplicity
2421and only include the select backend.
2422.IP "\s-1EV_STANDALONE\s0" 4
2423.IX Item "EV_STANDALONE"
2424Must always be \f(CW1\fR if you do not use autoconf configuration, which
2425keeps libev from including \fIconfig.h\fR, and it also defines dummy
2426implementations for some libevent functions (such as logging, which is not
2427supported). It will also not define any of the structs usually found in
2428\&\fIevent.h\fR that are not directly supported by the libev core alone.
2429.IP "\s-1EV_USE_MONOTONIC\s0" 4
2430.IX Item "EV_USE_MONOTONIC"
2431If defined to be \f(CW1\fR, libev will try to detect the availability of the
2432monotonic clock option at both compiletime and runtime. Otherwise no use
2433of the monotonic clock option will be attempted. If you enable this, you
2434usually have to link against librt or something similar. Enabling it when
2435the functionality isn't available is safe, though, althoguh you have
2436to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2437function is hiding in (often \fI\-lrt\fR).
2438.IP "\s-1EV_USE_REALTIME\s0" 4
2439.IX Item "EV_USE_REALTIME"
2440If defined to be \f(CW1\fR, libev will try to detect the availability of the
2441realtime clock option at compiletime (and assume its availability at
2442runtime if successful). Otherwise no use of the realtime clock option will
2443be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2444(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2445in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2446.IP "\s-1EV_USE_SELECT\s0" 4
2447.IX Item "EV_USE_SELECT"
2448If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2449\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2450other method takes over, select will be it. Otherwise the select backend
2451will not be compiled in.
2452.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2453.IX Item "EV_SELECT_USE_FD_SET"
2454If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2455structure. This is useful if libev doesn't compile due to a missing
2456\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2457exotic systems. This usually limits the range of file descriptors to some
2458low limit such as 1024 or might have other limitations (winsocket only
2459allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2460influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2461.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2462.IX Item "EV_SELECT_IS_WINSOCKET"
2463When defined to \f(CW1\fR, the select backend will assume that
2464select/socket/connect etc. don't understand file descriptors but
2465wants osf handles on win32 (this is the case when the select to
2466be used is the winsock select). This means that it will call
2467\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2468it is assumed that all these functions actually work on fds, even
2469on win32. Should not be defined on non\-win32 platforms.
2470.IP "\s-1EV_USE_POLL\s0" 4
2471.IX Item "EV_USE_POLL"
2472If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2473backend. Otherwise it will be enabled on non\-win32 platforms. It
2474takes precedence over select.
2475.IP "\s-1EV_USE_EPOLL\s0" 4
2476.IX Item "EV_USE_EPOLL"
2477If defined to be \f(CW1\fR, libev will compile in support for the Linux
2478\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2479otherwise another method will be used as fallback. This is the
2480preferred backend for GNU/Linux systems.
2481.IP "\s-1EV_USE_KQUEUE\s0" 4
2482.IX Item "EV_USE_KQUEUE"
2483If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2484\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2485otherwise another method will be used as fallback. This is the preferred
2486backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2487supports some types of fds correctly (the only platform we found that
2488supports ptys for example was NetBSD), so kqueue might be compiled in, but
2489not be used unless explicitly requested. The best way to use it is to find
2490out whether kqueue supports your type of fd properly and use an embedded
2491kqueue loop.
2492.IP "\s-1EV_USE_PORT\s0" 4
2493.IX Item "EV_USE_PORT"
2494If defined to be \f(CW1\fR, libev will compile in support for the Solaris
249510 port style backend. Its availability will be detected at runtime,
2496otherwise another method will be used as fallback. This is the preferred
2497backend for Solaris 10 systems.
2498.IP "\s-1EV_USE_DEVPOLL\s0" 4
2499.IX Item "EV_USE_DEVPOLL"
2500reserved for future expansion, works like the \s-1USE\s0 symbols above.
2501.IP "\s-1EV_USE_INOTIFY\s0" 4
2502.IX Item "EV_USE_INOTIFY"
2503If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2504interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2505be detected at runtime.
2506.IP "\s-1EV_H\s0" 4
2507.IX Item "EV_H"
2508The name of the \fIev.h\fR header file used to include it. The default if
2509undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2510can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2511.IP "\s-1EV_CONFIG_H\s0" 4
2512.IX Item "EV_CONFIG_H"
2513If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2514\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2515\&\f(CW\*(C`EV_H\*(C'\fR, above.
2516.IP "\s-1EV_EVENT_H\s0" 4
2517.IX Item "EV_EVENT_H"
2518Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2519of how the \fIevent.h\fR header can be found.
2520.IP "\s-1EV_PROTOTYPES\s0" 4
2521.IX Item "EV_PROTOTYPES"
2522If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2523prototypes, but still define all the structs and other symbols. This is
2524occasionally useful if you want to provide your own wrapper functions
2525around libev functions.
2526.IP "\s-1EV_MULTIPLICITY\s0" 4
2527.IX Item "EV_MULTIPLICITY"
2528If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2529will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2530additional independent event loops. Otherwise there will be no support
2531for multiple event loops and there is no first event loop pointer
2532argument. Instead, all functions act on the single default loop.
2533.IP "\s-1EV_MINPRI\s0" 4
2534.IX Item "EV_MINPRI"
2535.PD 0
2536.IP "\s-1EV_MAXPRI\s0" 4
2537.IX Item "EV_MAXPRI"
2538.PD
2539The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2540\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2541provide for more priorities by overriding those symbols (usually defined
2542to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2543.Sp
2544When doing priority-based operations, libev usually has to linearly search
2545all the priorities, so having many of them (hundreds) uses a lot of space
2546and time, so using the defaults of five priorities (\-2 .. +2) is usually
2547fine.
2548.Sp
2549If your embedding app does not need any priorities, defining these both to
2550\&\f(CW0\fR will save some memory and cpu.
2551.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2552.IX Item "EV_PERIODIC_ENABLE"
2553If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2554defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2555code.
2556.IP "\s-1EV_IDLE_ENABLE\s0" 4
2557.IX Item "EV_IDLE_ENABLE"
2558If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2559defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2560code.
2561.IP "\s-1EV_EMBED_ENABLE\s0" 4
2562.IX Item "EV_EMBED_ENABLE"
2563If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2564defined to be \f(CW0\fR, then they are not.
2565.IP "\s-1EV_STAT_ENABLE\s0" 4
2566.IX Item "EV_STAT_ENABLE"
2567If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2568defined to be \f(CW0\fR, then they are not.
2569.IP "\s-1EV_FORK_ENABLE\s0" 4
2570.IX Item "EV_FORK_ENABLE"
2571If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2572defined to be \f(CW0\fR, then they are not.
2573.IP "\s-1EV_MINIMAL\s0" 4
2574.IX Item "EV_MINIMAL"
2575If you need to shave off some kilobytes of code at the expense of some
2576speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2577some inlining decisions, saves roughly 30% codesize of amd64.
2578.IP "\s-1EV_PID_HASHSIZE\s0" 4
2579.IX Item "EV_PID_HASHSIZE"
2580\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2581pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2582than enough. If you need to manage thousands of children you might want to
2583increase this value (\fImust\fR be a power of two).
2584.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2585.IX Item "EV_INOTIFY_HASHSIZE"
2586\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2587inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2588usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2589watchers you might want to increase this value (\fImust\fR be a power of
2590two).
2591.IP "\s-1EV_COMMON\s0" 4
2592.IX Item "EV_COMMON"
2593By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2594this macro to a something else you can include more and other types of
2595members. You have to define it each time you include one of the files,
2596though, and it must be identical each time.
2597.Sp
2598For example, the perl \s-1EV\s0 module uses something like this:
2599.Sp
2600.Vb 3
2601\& #define EV_COMMON \e
2602\& SV *self; /* contains this struct */ \e
2603\& SV *cb_sv, *fh /* note no trailing ";" */
2604.Ve
2605.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2606.IX Item "EV_CB_DECLARE (type)"
2607.PD 0
2608.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2609.IX Item "EV_CB_INVOKE (watcher, revents)"
2610.IP "ev_set_cb (ev, cb)" 4
2611.IX Item "ev_set_cb (ev, cb)"
2612.PD
2613Can be used to change the callback member declaration in each watcher,
2614and the way callbacks are invoked and set. Must expand to a struct member
2615definition and a statement, respectively. See the \fIev.v\fR header file for
2616their default definitions. One possible use for overriding these is to
2617avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2618method calls instead of plain function calls in \*(C+.
2619.Sh "\s-1EXAMPLES\s0"
2620.IX Subsection "EXAMPLES"
2621For a real-world example of a program the includes libev
2622verbatim, you can have a look at the \s-1EV\s0 perl module
2623(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2624the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2625interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2626will be compiled. It is pretty complex because it provides its own header
2627file.
2628.Sp
2629The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2630that everybody includes and which overrides some configure choices:
2631.Sp
2632.Vb 9
2633\& #define EV_MINIMAL 1
2634\& #define EV_USE_POLL 0
2635\& #define EV_MULTIPLICITY 0
2636\& #define EV_PERIODIC_ENABLE 0
2637\& #define EV_STAT_ENABLE 0
2638\& #define EV_FORK_ENABLE 0
2639\& #define EV_CONFIG_H <config.h>
2640\& #define EV_MINPRI 0
2641\& #define EV_MAXPRI 0
2642.Ve
2643.Sp
2644.Vb 1
2645\& #include "ev++.h"
2646.Ve
2647.Sp
2648And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2649.Sp
2650.Vb 2
2651\& #include "ev_cpp.h"
2652\& #include "ev.c"
2653.Ve
2654.SH "COMPLEXITIES"
2655.IX Header "COMPLEXITIES"
2656In this section the complexities of (many of) the algorithms used inside
2657libev will be explained. For complexity discussions about backends see the
2658documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2659.Sp
2660All of the following are about amortised time: If an array needs to be
2661extended, libev needs to realloc and move the whole array, but this
2662happens asymptotically never with higher number of elements, so O(1) might
2663mean it might do a lengthy realloc operation in rare cases, but on average
2664it is much faster and asymptotically approaches constant time.
2665.RS 4
2666.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2667.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2668This means that, when you have a watcher that triggers in one hour and
2669there are 100 watchers that would trigger before that then inserting will
2670have to skip those 100 watchers.
2671.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2672.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2673That means that for changing a timer costs less than removing/adding them
2674as only the relative motion in the event queue has to be paid for.
2675.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2676.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2677These just add the watcher into an array or at the head of a list.
2678=item Stopping check/prepare/idle watchers: O(1)
2679.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2680.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2681These watchers are stored in lists then need to be walked to find the
2682correct watcher to remove. The lists are usually short (you don't usually
2683have many watchers waiting for the same fd or signal).
2684.IP "Finding the next timer per loop iteration: O(1)" 4
2685.IX Item "Finding the next timer per loop iteration: O(1)"
2686.PD 0
2687.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2688.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2689.PD
2690A change means an I/O watcher gets started or stopped, which requires
2691libev to recalculate its status (and possibly tell the kernel).
2692.IP "Activating one watcher: O(1)" 4
2693.IX Item "Activating one watcher: O(1)"
2694.PD 0
2695.IP "Priority handling: O(number_of_priorities)" 4
2696.IX Item "Priority handling: O(number_of_priorities)"
2697.PD
2698Priorities are implemented by allocating some space for each
2699priority. When doing priority-based operations, libev usually has to
2700linearly search all the priorities.
2701.RE
2702.RS 4
1541.SH "AUTHOR" 2703.SH "AUTHOR"
1542.IX Header "AUTHOR" 2704.IX Header "AUTHOR"
1543Marc Lehmann <libev@schmorp.de>. 2705Marc Lehmann <libev@schmorp.de>.

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