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Revision 1.12 by root, Sat Nov 24 07:20:42 2007 UTC vs.
Revision 1.31 by root, Wed Nov 28 11:31:34 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 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
138\& #include <ev.h> 138\& #include <ev.h>
139.Ve 139.Ve
140.SH "EXAMPLE PROGRAM"
141.IX Header "EXAMPLE PROGRAM"
142.Vb 1
143\& #include <ev.h>
144.Ve
145.PP
146.Vb 2
147\& ev_io stdin_watcher;
148\& ev_timer timeout_watcher;
149.Ve
150.PP
151.Vb 8
152\& /* called when data readable on stdin */
153\& static void
154\& stdin_cb (EV_P_ struct ev_io *w, int revents)
155\& {
156\& /* puts ("stdin ready"); */
157\& ev_io_stop (EV_A_ w); /* just a syntax example */
158\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
159\& }
160.Ve
161.PP
162.Vb 6
163\& static void
164\& timeout_cb (EV_P_ struct ev_timer *w, int revents)
165\& {
166\& /* puts ("timeout"); */
167\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
168\& }
169.Ve
170.PP
171.Vb 4
172\& int
173\& main (void)
174\& {
175\& struct ev_loop *loop = ev_default_loop (0);
176.Ve
177.PP
178.Vb 3
179\& /* initialise an io watcher, then start it */
180\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
181\& ev_io_start (loop, &stdin_watcher);
182.Ve
183.PP
184.Vb 3
185\& /* simple non-repeating 5.5 second timeout */
186\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187\& ev_timer_start (loop, &timeout_watcher);
188.Ve
189.PP
190.Vb 2
191\& /* loop till timeout or data ready */
192\& ev_loop (loop, 0);
193.Ve
194.PP
195.Vb 2
196\& return 0;
197\& }
198.Ve
140.SH "DESCRIPTION" 199.SH "DESCRIPTION"
141.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
142Libev is an event loop: you register interest in certain events (such as a 201Libev is an event loop: you register interest in certain events (such as a
143file descriptor being readable or a timeout occuring), and it will manage 202file descriptor being readable or a timeout occuring), and it will manage
144these event sources and provide your program with events. 203these event sources and provide your program with events.
… …
151watchers\fR, which are relatively small C structures you initialise with the 210watchers\fR, which are relatively small C structures you initialise with the
152details of the event, and then hand it over to libev by \fIstarting\fR the 211details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 212watcher.
154.SH "FEATURES" 213.SH "FEATURES"
155.IX Header "FEATURES" 214.IX Header "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 215Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
157kqueue mechanisms for file descriptor events, relative timers, absolute 216BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 217for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
159events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event 218(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
160loop mechanism itself (idle, prepare and check watchers). It also is quite 219with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
161fast (see this benchmark comparing 220(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
162it to libevent for example). 221watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
222\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
223file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
224(\f(CW\*(C`ev_fork\*(C'\fR).
225.PP
226It also is quite fast (see this
227benchmark comparing it to libevent
228for example).
163.SH "CONVENTIONS" 229.SH "CONVENTIONS"
164.IX Header "CONVENTIONS" 230.IX Header "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 231Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 232be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 233various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
168\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without 234this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 235loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
170argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) 236(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
171will not have this argument.
172.SH "TIME REPRESENTATION" 237.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 238.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 239Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 240(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176the beginning of 1970, details are complicated, don't ask). This type is 241the beginning of 1970, details are complicated, don't ask). This type is
… …
201Usually, it's a good idea to terminate if the major versions mismatch, 266Usually, it's a good idea to terminate if the major versions mismatch,
202as this indicates an incompatible change. Minor versions are usually 267as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 268compatible to older versions, so a larger minor version alone is usually
204not a problem. 269not a problem.
205.Sp 270.Sp
206Example: make sure we haven't accidentally been linked against the wrong 271Example: Make sure we haven't accidentally been linked against the wrong
207version: 272version.
208.Sp 273.Sp
209.Vb 3 274.Vb 3
210\& assert (("libev version mismatch", 275\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 276\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 277\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
240might be supported on the current system, you would need to look at 305might be supported on the current system, you would need to look at
241\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for 306\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
242recommended ones. 307recommended ones.
243.Sp 308.Sp
244See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 309See 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))" 4 310.IP "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" 4
246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 311.IX Item "ev_set_allocator (void *(*cb)(void *ptr, size_t size))"
247Sets the allocation function to use (the prototype is similar to the 312Sets the allocation function to use (the prototype and semantics are
248realloc C function, the semantics are identical). It is used to allocate 313identical to the realloc C function). It is used to allocate and free
249and free memory (no surprises here). If it returns zero when memory 314memory (no surprises here). If it returns zero when memory needs to be
250needs to be allocated, the library might abort or take some potentially 315allocated, the library might abort or take some potentially destructive
251destructive action. The default is your system realloc function. 316action. The default is your system realloc function.
252.Sp 317.Sp
253You could override this function in high-availability programs to, say, 318You could override this function in high-availability programs to, say,
254free some memory if it cannot allocate memory, to use a special allocator, 319free 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. 320or even to sleep a while and retry until some memory is available.
256.Sp 321.Sp
257Example: replace the libev allocator with one that waits a bit and then 322Example: Replace the libev allocator with one that waits a bit and then
258retries: better than mine). 323retries).
259.Sp 324.Sp
260.Vb 6 325.Vb 6
261\& static void * 326\& static void *
262\& persistent_realloc (void *ptr, long size) 327\& persistent_realloc (void *ptr, size_t size)
263\& { 328\& {
264\& for (;;) 329\& for (;;)
265\& { 330\& {
266\& void *newptr = realloc (ptr, size); 331\& void *newptr = realloc (ptr, size);
267.Ve 332.Ve
… …
289callback is set, then libev will expect it to remedy the sitution, no 354callback is set, then libev will expect it to remedy the sitution, no
290matter what, when it returns. That is, libev will generally retry the 355matter what, when it returns. That is, libev will generally retry the
291requested operation, or, if the condition doesn't go away, do bad stuff 356requested operation, or, if the condition doesn't go away, do bad stuff
292(such as abort). 357(such as abort).
293.Sp 358.Sp
294Example: do the same thing as libev does internally: 359Example: This is basically the same thing that libev does internally, too.
295.Sp 360.Sp
296.Vb 6 361.Vb 6
297\& static void 362\& static void
298\& fatal_error (const char *msg) 363\& fatal_error (const char *msg)
299\& { 364\& {
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448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 513Similar 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 514always 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 515handle signal and child watchers, and attempts to do so will be greeted by
451undefined behaviour (or a failed assertion if assertions are enabled). 516undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp 517.Sp
453Example: try to create a event loop that uses epoll and nothing else. 518Example: Try to create a event loop that uses epoll and nothing else.
454.Sp 519.Sp
455.Vb 3 520.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 521\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller) 522\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair"); 523\& fatal ("no epoll found here, maybe it hides under your chair");
… …
556\& be handled here by queueing them when their watcher gets executed. 621\& be handled here by queueing them when their watcher gets executed.
557\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 622\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
558\& were used, return, otherwise continue with step *. 623\& were used, return, otherwise continue with step *.
559.Ve 624.Ve
560.Sp 625.Sp
561Example: queue some jobs and then loop until no events are outsanding 626Example: Queue some jobs and then loop until no events are outsanding
562anymore. 627anymore.
563.Sp 628.Sp
564.Vb 4 629.Vb 4
565\& ... queue jobs here, make sure they register event watchers as long 630\& ... 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..) 631\& ... 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 653visible 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 654no 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 655way 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. 656libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
592.Sp 657.Sp
593Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 658Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
594running when nothing else is active. 659running when nothing else is active.
595.Sp 660.Sp
596.Vb 4 661.Vb 4
597\& struct dv_signal exitsig; 662\& struct ev_signal exitsig;
598\& ev_signal_init (&exitsig, sig_cb, SIGINT); 663\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599\& ev_signal_start (myloop, &exitsig); 664\& ev_signal_start (loop, &exitsig);
600\& evf_unref (myloop); 665\& evf_unref (loop);
601.Ve 666.Ve
602.Sp 667.Sp
603Example: for some weird reason, unregister the above signal handler again. 668Example: For some weird reason, unregister the above signal handler again.
604.Sp 669.Sp
605.Vb 2 670.Vb 2
606\& ev_ref (myloop); 671\& ev_ref (loop);
607\& ev_signal_stop (myloop, &exitsig); 672\& ev_signal_stop (loop, &exitsig);
608.Ve 673.Ve
609.SH "ANATOMY OF A WATCHER" 674.SH "ANATOMY OF A WATCHER"
610.IX Header "ANATOMY OF A WATCHER" 675.IX Header "ANATOMY OF A WATCHER"
611A watcher is a structure that you create and register to record your 676A 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 677interest 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. 749The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
685.ie n .IP """EV_CHILD""" 4 750.ie n .IP """EV_CHILD""" 4
686.el .IP "\f(CWEV_CHILD\fR" 4 751.el .IP "\f(CWEV_CHILD\fR" 4
687.IX Item "EV_CHILD" 752.IX Item "EV_CHILD"
688The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 753The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
754.ie n .IP """EV_STAT""" 4
755.el .IP "\f(CWEV_STAT\fR" 4
756.IX Item "EV_STAT"
757The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
689.ie n .IP """EV_IDLE""" 4 758.ie n .IP """EV_IDLE""" 4
690.el .IP "\f(CWEV_IDLE\fR" 4 759.el .IP "\f(CWEV_IDLE\fR" 4
691.IX Item "EV_IDLE" 760.IX Item "EV_IDLE"
692The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 761The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
693.ie n .IP """EV_PREPARE""" 4 762.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 772\&\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 773received 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 774many 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 775(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). 776\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
777.ie n .IP """EV_EMBED""" 4
778.el .IP "\f(CWEV_EMBED\fR" 4
779.IX Item "EV_EMBED"
780The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
781.ie n .IP """EV_FORK""" 4
782.el .IP "\f(CWEV_FORK\fR" 4
783.IX Item "EV_FORK"
784The event loop has been resumed in the child process after fork (see
785\&\f(CW\*(C`ev_fork\*(C'\fR).
708.ie n .IP """EV_ERROR""" 4 786.ie n .IP """EV_ERROR""" 4
709.el .IP "\f(CWEV_ERROR\fR" 4 787.el .IP "\f(CWEV_ERROR\fR" 4
710.IX Item "EV_ERROR" 788.IX Item "EV_ERROR"
711An unspecified error has occured, the watcher has been stopped. This might 789An unspecified error has occured, the watcher has been stopped. This might
712happen because the watcher could not be properly started because libev 790happen because the watcher could not be properly started because libev
… …
717Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 795Libev 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 796for 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 797your 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 798with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
721programs, though, so beware. 799programs, though, so beware.
722.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" 800.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
723.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS" 801.IX Subsection "GENERIC WATCHER FUNCTIONS"
724In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, 802In 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. 803e.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)" 4 804.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
727.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 805.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
728.IX Item "ev_init (ev_TYPE *watcher, callback)" 806.IX Item "ev_init (ev_TYPE *watcher, callback)"
… …
734which rolls both calls into one. 812which rolls both calls into one.
735.Sp 813.Sp
736You can reinitialise a watcher at any time as long as it has been stopped 814You 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. 815(or never started) and there are no pending events outstanding.
738.Sp 816.Sp
739The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, 817The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
740int revents)\*(C'\fR. 818int revents)\*(C'\fR.
741.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 819.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
742.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 820.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
743.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 821.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
744This macro initialises the type-specific parts of a watcher. You need to 822This macro initialises the type-specific parts of a watcher. You need to
… …
779Returns a true value iff the watcher is pending, (i.e. it has outstanding 857Returns 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 858events 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 859is 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 860\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
783libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). 861libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
784.IP "callback = ev_cb (ev_TYPE *watcher)" 4 862.IP "callback ev_cb (ev_TYPE *watcher)" 4
785.IX Item "callback = ev_cb (ev_TYPE *watcher)" 863.IX Item "callback ev_cb (ev_TYPE *watcher)"
786Returns the callback currently set on the watcher. 864Returns the callback currently set on the watcher.
787.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 865.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
788.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 866.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
789Change the callback. You can change the callback at virtually any time 867Change the callback. You can change the callback at virtually any time
790(modulo threads). 868(modulo threads).
… …
816\& struct my_io *w = (struct my_io *)w_; 894\& struct my_io *w = (struct my_io *)w_;
817\& ... 895\& ...
818\& } 896\& }
819.Ve 897.Ve
820.PP 898.PP
821More interesting and less C\-conformant ways of catsing your callback type 899More interesting and less C\-conformant ways of casting your callback type
822have been omitted.... 900instead have been omitted.
901.PP
902Another common scenario is having some data structure with multiple
903watchers:
904.PP
905.Vb 6
906\& struct my_biggy
907\& {
908\& int some_data;
909\& ev_timer t1;
910\& ev_timer t2;
911\& }
912.Ve
913.PP
914In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
915you need to use \f(CW\*(C`offsetof\*(C'\fR:
916.PP
917.Vb 1
918\& #include <stddef.h>
919.Ve
920.PP
921.Vb 6
922\& static void
923\& t1_cb (EV_P_ struct ev_timer *w, int revents)
924\& {
925\& struct my_biggy big = (struct my_biggy *
926\& (((char *)w) - offsetof (struct my_biggy, t1));
927\& }
928.Ve
929.PP
930.Vb 6
931\& static void
932\& t2_cb (EV_P_ struct ev_timer *w, int revents)
933\& {
934\& struct my_biggy big = (struct my_biggy *
935\& (((char *)w) - offsetof (struct my_biggy, t2));
936\& }
937.Ve
823.SH "WATCHER TYPES" 938.SH "WATCHER TYPES"
824.IX Header "WATCHER TYPES" 939.IX Header "WATCHER TYPES"
825This section describes each watcher in detail, but will not repeat 940This section describes each watcher in detail, but will not repeat
826information given in the last section. 941information given in the last section. Any initialisation/set macros,
942functions and members specific to the watcher type are explained.
943.PP
944Members are additionally marked with either \fI[read\-only]\fR, meaning that,
945while the watcher is active, you can look at the member and expect some
946sensible content, but you must not modify it (you can modify it while the
947watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
948means you can expect it to have some sensible content while the watcher
949is active, but you can also modify it. Modifying it may not do something
950sensible or take immediate effect (or do anything at all), but libev will
951not crash or malfunction in any way.
827.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 952.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" 953.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" 954.IX Subsection "ev_io - is this file descriptor readable or writable?"
830I/O watchers check whether a file descriptor is readable or writable 955I/O watchers check whether a file descriptor is readable or writable
831in each iteration of the event loop (This behaviour is called 956in each iteration of the event loop, or, more precisely, when reading
832level-triggering because you keep receiving events as long as the 957would 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 958some data. This behaviour is called level-triggering because you keep
834act on the event and neither want to receive future events). 959receiving events as long as the condition persists. Remember you can stop
960the watcher if you don't want to act on the event and neither want to
961receive future events.
835.PP 962.PP
836In general you can register as many read and/or write event watchers per 963In 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 964fd 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 965descriptors to non-blocking mode is also usually a good idea (but not
839required if you know what you are doing). 966required if you know what you are doing).
840.PP 967.PP
841You have to be careful with dup'ed file descriptors, though. Some backends 968You 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 969(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 970descriptors correctly if you register interest in two or more fds pointing
844to the same underlying file/socket etc. description (that is, they share 971to the same underlying file/socket/etc. description (that is, they share
845the same underlying \*(L"file open\*(R"). 972the same underlying \*(L"file open\*(R").
846.PP 973.PP
847If you must do this, then force the use of a known-to-be-good backend 974If 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 975(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). 976\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
977.PP
978Another thing you have to watch out for is that it is quite easy to
979receive \*(L"spurious\*(R" readyness notifications, that is your callback might
980be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
981because there is no data. Not only are some backends known to create a
982lot of those (for example solaris ports), it is very easy to get into
983this situation even with a relatively standard program structure. Thus
984it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
985\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
986.PP
987If you cannot run the fd in non-blocking mode (for example you should not
988play around with an Xlib connection), then you have to seperately re-test
989wether a file descriptor is really ready with a known-to-be good interface
990such as poll (fortunately in our Xlib example, Xlib already does this on
991its own, so its quite safe to use).
850.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 992.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)" 993.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
852.PD 0 994.PD 0
853.IP "ev_io_set (ev_io *, int fd, int events)" 4 995.IP "ev_io_set (ev_io *, int fd, int events)" 4
854.IX Item "ev_io_set (ev_io *, int fd, int events)" 996.IX Item "ev_io_set (ev_io *, int fd, int events)"
855.PD 997.PD
856Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 998Configures 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 | 999rceeive 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. 1000\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
859.Sp 1001.IP "int fd [read\-only]" 4
860Please note that most of the more scalable backend mechanisms (for example 1002.IX Item "int fd [read-only]"
861epoll and solaris ports) can result in spurious readyness notifications 1003The file descriptor being watched.
862for file descriptors, so you practically need to use non-blocking I/O (and 1004.IP "int events [read\-only]" 4
863treat callback invocation as hint only), or retest separately with a safe 1005.IX Item "int events [read-only]"
864interface before doing I/O (XLib can do this), or force the use of either 1006The 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 1007.PP
871Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1008Example: 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 1009readable, but only once. Since it is likely line\-buffered, you could
873attempt to read a whole line in the callback: 1010attempt to read a whole line in the callback.
874.PP 1011.PP
875.Vb 6 1012.Vb 6
876\& static void 1013\& static void
877\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1014\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
878\& { 1015\& {
… …
887\& struct ev_io stdin_readable; 1024\& struct ev_io stdin_readable;
888\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1025\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
889\& ev_io_start (loop, &stdin_readable); 1026\& ev_io_start (loop, &stdin_readable);
890\& ev_loop (loop, 0); 1027\& ev_loop (loop, 0);
891.Ve 1028.Ve
892.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1029.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
893.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1030.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
894.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1031.IX Subsection "ev_timer - relative and optionally repeating timeouts"
895Timer watchers are simple relative timers that generate an event after a 1032Timer watchers are simple relative timers that generate an event after a
896given time, and optionally repeating in regular intervals after that. 1033given time, and optionally repeating in regular intervals after that.
897.PP 1034.PP
898The timers are based on real time, that is, if you register an event that 1035The 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 1036times out after an hour and you reset your system clock to last years
… …
939.Sp 1076.Sp
940If the timer is repeating, either start it if necessary (with the repeat 1077If the timer is repeating, either start it if necessary (with the repeat
941value), or reset the running timer to the repeat value. 1078value), or reset the running timer to the repeat value.
942.Sp 1079.Sp
943This sounds a bit complicated, but here is a useful and typical 1080This 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 1081example: Imagine you have a tcp connection and you want a so-called
945timeout, that is, you want to be called when there have been, say, 60 1082idle timeout, that is, you want to be called when there have been,
946seconds of inactivity on the socket. The easiest way to do this is to 1083say, 60 seconds of inactivity on the socket. The easiest way to do
947configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1084this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling
948time you successfully read or write some data. If you go into an idle 1085\&\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 1086you 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. 1087socket, you can stop the timer, and again will automatically restart it if
1088need be.
1089.Sp
1090You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
1091and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
1092.Sp
1093.Vb 8
1094\& ev_timer_init (timer, callback, 0., 5.);
1095\& ev_timer_again (loop, timer);
1096\& ...
1097\& timer->again = 17.;
1098\& ev_timer_again (loop, timer);
1099\& ...
1100\& timer->again = 10.;
1101\& ev_timer_again (loop, timer);
1102.Ve
1103.Sp
1104This is more efficient then stopping/starting the timer eahc time you want
1105to modify its timeout value.
1106.IP "ev_tstamp repeat [read\-write]" 4
1107.IX Item "ev_tstamp repeat [read-write]"
1108The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1109or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1110which is also when any modifications are taken into account.
951.PP 1111.PP
952Example: create a timer that fires after 60 seconds. 1112Example: Create a timer that fires after 60 seconds.
953.PP 1113.PP
954.Vb 5 1114.Vb 5
955\& static void 1115\& static void
956\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1116\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
957\& { 1117\& {
… …
963\& struct ev_timer mytimer; 1123\& struct ev_timer mytimer;
964\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1124\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
965\& ev_timer_start (loop, &mytimer); 1125\& ev_timer_start (loop, &mytimer);
966.Ve 1126.Ve
967.PP 1127.PP
968Example: create a timeout timer that times out after 10 seconds of 1128Example: Create a timeout timer that times out after 10 seconds of
969inactivity. 1129inactivity.
970.PP 1130.PP
971.Vb 5 1131.Vb 5
972\& static void 1132\& static void
973\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1133\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
986.Vb 3 1146.Vb 3
987\& // and in some piece of code that gets executed on any "activity": 1147\& // and in some piece of code that gets executed on any "activity":
988\& // reset the timeout to start ticking again at 10 seconds 1148\& // reset the timeout to start ticking again at 10 seconds
989\& ev_timer_again (&mytimer); 1149\& ev_timer_again (&mytimer);
990.Ve 1150.Ve
991.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1151.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
992.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1152.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
993.IX Subsection "ev_periodic - to cron or not to cron" 1153.IX Subsection "ev_periodic - to cron or not to cron?"
994Periodic watchers are also timers of a kind, but they are very versatile 1154Periodic watchers are also timers of a kind, but they are very versatile
995(and unfortunately a bit complex). 1155(and unfortunately a bit complex).
996.PP 1156.PP
997Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1157Unlike \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 1158but 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 1159to 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. c<ev_now () 1160periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1001+ 10.>) and then reset your system clock to the last year, then it will 1161+ 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 1162take 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 1163roughly 10 seconds later and of course not if you reset your system time
1004again). 1164again).
1005.PP 1165.PP
1006They can also be used to implement vastly more complex timers, such as 1166They can also be used to implement vastly more complex timers, such as
… …
1087.IX Item "ev_periodic_again (loop, ev_periodic *)" 1247.IX Item "ev_periodic_again (loop, ev_periodic *)"
1088Simply stops and restarts the periodic watcher again. This is only useful 1248Simply stops and restarts the periodic watcher again. This is only useful
1089when you changed some parameters or the reschedule callback would return 1249when 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 1250a different time than the last time it was called (e.g. in a crond like
1091program when the crontabs have changed). 1251program when the crontabs have changed).
1252.IP "ev_tstamp interval [read\-write]" 4
1253.IX Item "ev_tstamp interval [read-write]"
1254The current interval value. Can be modified any time, but changes only
1255take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1256called.
1257.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1258.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1259The current reschedule callback, or \f(CW0\fR, if this functionality is
1260switched off. Can be changed any time, but changes only take effect when
1261the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1092.PP 1262.PP
1093Example: call a callback every hour, or, more precisely, whenever the 1263Example: Call a callback every hour, or, more precisely, whenever the
1094system clock is divisible by 3600. The callback invocation times have 1264system clock is divisible by 3600. The callback invocation times have
1095potentially a lot of jittering, but good long-term stability. 1265potentially a lot of jittering, but good long-term stability.
1096.PP 1266.PP
1097.Vb 5 1267.Vb 5
1098\& static void 1268\& static void
… …
1106\& struct ev_periodic hourly_tick; 1276\& struct ev_periodic hourly_tick;
1107\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1277\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1108\& ev_periodic_start (loop, &hourly_tick); 1278\& ev_periodic_start (loop, &hourly_tick);
1109.Ve 1279.Ve
1110.PP 1280.PP
1111Example: the same as above, but use a reschedule callback to do it: 1281Example: The same as above, but use a reschedule callback to do it:
1112.PP 1282.PP
1113.Vb 1 1283.Vb 1
1114\& #include <math.h> 1284\& #include <math.h>
1115.Ve 1285.Ve
1116.PP 1286.PP
… …
1124.PP 1294.PP
1125.Vb 1 1295.Vb 1
1126\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1296\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1127.Ve 1297.Ve
1128.PP 1298.PP
1129Example: call a callback every hour, starting now: 1299Example: Call a callback every hour, starting now:
1130.PP 1300.PP
1131.Vb 4 1301.Vb 4
1132\& struct ev_periodic hourly_tick; 1302\& struct ev_periodic hourly_tick;
1133\& ev_periodic_init (&hourly_tick, clock_cb, 1303\& ev_periodic_init (&hourly_tick, clock_cb,
1134\& fmod (ev_now (loop), 3600.), 3600., 0); 1304\& fmod (ev_now (loop), 3600.), 3600., 0);
1135\& ev_periodic_start (loop, &hourly_tick); 1305\& ev_periodic_start (loop, &hourly_tick);
1136.Ve 1306.Ve
1137.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1307.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" 1308.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" 1309.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1140Signal watchers will trigger an event when the process receives a specific 1310Signal watchers will trigger an event when the process receives a specific
1141signal one or more times. Even though signals are very asynchronous, libev 1311signal 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 1312will try it's best to deliver signals synchronously, i.e. as part of the
1143normal event processing, like any other event. 1313normal event processing, like any other event.
1144.PP 1314.PP
… …
1154.IP "ev_signal_set (ev_signal *, int signum)" 4 1324.IP "ev_signal_set (ev_signal *, int signum)" 4
1155.IX Item "ev_signal_set (ev_signal *, int signum)" 1325.IX Item "ev_signal_set (ev_signal *, int signum)"
1156.PD 1326.PD
1157Configures the watcher to trigger on the given signal number (usually one 1327Configures the watcher to trigger on the given signal number (usually one
1158of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1328of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1329.IP "int signum [read\-only]" 4
1330.IX Item "int signum [read-only]"
1331The signal the watcher watches out for.
1159.ie n .Sh """ev_child"" \- wait for pid status changes" 1332.ie n .Sh """ev_child"" \- watch out for process status changes"
1160.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1333.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1161.IX Subsection "ev_child - wait for pid status changes" 1334.IX Subsection "ev_child - watch out for process status changes"
1162Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1335Child 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). 1336some child status changes (most typically when a child of yours dies).
1164.IP "ev_child_init (ev_child *, callback, int pid)" 4 1337.IP "ev_child_init (ev_child *, callback, int pid)" 4
1165.IX Item "ev_child_init (ev_child *, callback, int pid)" 1338.IX Item "ev_child_init (ev_child *, callback, int pid)"
1166.PD 0 1339.PD 0
… …
1171\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1344\&\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 1345at 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 1346the 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 1347\&\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. 1348process causing the status change.
1349.IP "int pid [read\-only]" 4
1350.IX Item "int pid [read-only]"
1351The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1352.IP "int rpid [read\-write]" 4
1353.IX Item "int rpid [read-write]"
1354The process id that detected a status change.
1355.IP "int rstatus [read\-write]" 4
1356.IX Item "int rstatus [read-write]"
1357The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1358\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1176.PP 1359.PP
1177Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1360Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1178.PP 1361.PP
1179.Vb 5 1362.Vb 5
1180\& static void 1363\& static void
1181\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1364\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1182\& { 1365\& {
… …
1187.Vb 3 1370.Vb 3
1188\& struct ev_signal signal_watcher; 1371\& struct ev_signal signal_watcher;
1189\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1372\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1190\& ev_signal_start (loop, &sigint_cb); 1373\& ev_signal_start (loop, &sigint_cb);
1191.Ve 1374.Ve
1375.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1376.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1377.IX Subsection "ev_stat - did the file attributes just change?"
1378This watches a filesystem path for attribute changes. That is, it calls
1379\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1380compared to the last time, invoking the callback if it did.
1381.PP
1382The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1383not exist\*(R" is a status change like any other. The condition \*(L"path does
1384not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1385otherwise always forced to be at least one) and all the other fields of
1386the stat buffer having unspecified contents.
1387.PP
1388Since there is no standard to do this, the portable implementation simply
1389calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1390can specify a recommended polling interval for this case. If you specify
1391a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1392unspecified default\fR value will be used (which you can expect to be around
1393five seconds, although this might change dynamically). Libev will also
1394impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1395usually overkill.
1396.PP
1397This watcher type is not meant for massive numbers of stat watchers,
1398as even with OS-supported change notifications, this can be
1399resource\-intensive.
1400.PP
1401At the time of this writing, only the Linux inotify interface is
1402implemented (implementing kqueue support is left as an exercise for the
1403reader). Inotify will be used to give hints only and should not change the
1404semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1405to fall back to regular polling again even with inotify, but changes are
1406usually detected immediately, and if the file exists there will be no
1407polling.
1408.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1409.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1410.PD 0
1411.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1412.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1413.PD
1414Configures the watcher to wait for status changes of the given
1415\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1416be detected and should normally be specified as \f(CW0\fR to let libev choose
1417a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1418path for as long as the watcher is active.
1419.Sp
1420The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1421relative to the attributes at the time the watcher was started (or the
1422last change was detected).
1423.IP "ev_stat_stat (ev_stat *)" 4
1424.IX Item "ev_stat_stat (ev_stat *)"
1425Updates the stat buffer immediately with new values. If you change the
1426watched path in your callback, you could call this fucntion to avoid
1427detecting this change (while introducing a race condition). Can also be
1428useful simply to find out the new values.
1429.IP "ev_statdata attr [read\-only]" 4
1430.IX Item "ev_statdata attr [read-only]"
1431The most-recently detected attributes of the file. Although the type is of
1432\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1433suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1434was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1435.IP "ev_statdata prev [read\-only]" 4
1436.IX Item "ev_statdata prev [read-only]"
1437The previous attributes of the file. The callback gets invoked whenever
1438\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1439.IP "ev_tstamp interval [read\-only]" 4
1440.IX Item "ev_tstamp interval [read-only]"
1441The specified interval.
1442.IP "const char *path [read\-only]" 4
1443.IX Item "const char *path [read-only]"
1444The filesystem path that is being watched.
1445.PP
1446Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1447.PP
1448.Vb 15
1449\& static void
1450\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1451\& {
1452\& /* /etc/passwd changed in some way */
1453\& if (w->attr.st_nlink)
1454\& {
1455\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1456\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1457\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1458\& }
1459\& else
1460\& /* you shalt not abuse printf for puts */
1461\& puts ("wow, /etc/passwd is not there, expect problems. "
1462\& "if this is windows, they already arrived\en");
1463\& }
1464.Ve
1465.PP
1466.Vb 2
1467\& ...
1468\& ev_stat passwd;
1469.Ve
1470.PP
1471.Vb 2
1472\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1473\& ev_stat_start (loop, &passwd);
1474.Ve
1192.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1475.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" 1476.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" 1477.IX Subsection "ev_idle - when you've got nothing better to do..."
1195Idle watchers trigger events when there are no other events are pending 1478Idle watchers trigger events when there are no other events are pending
1196(prepare, check and other idle watchers do not count). That is, as long 1479(prepare, check and other idle watchers do not count). That is, as long
1197as your process is busy handling sockets or timeouts (or even signals, 1480as your process is busy handling sockets or timeouts (or even signals,
1198imagine) it will not be triggered. But when your process is idle all idle 1481imagine) it will not be triggered. But when your process is idle all idle
1199watchers are being called again and again, once per event loop iteration \- 1482watchers are being called again and again, once per event loop iteration \-
… …
1211.IX Item "ev_idle_init (ev_signal *, callback)" 1494.IX Item "ev_idle_init (ev_signal *, callback)"
1212Initialises and configures the idle watcher \- it has no parameters of any 1495Initialises 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, 1496kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1214believe me. 1497believe me.
1215.PP 1498.PP
1216Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1499Example: 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. 1500callback, free it. Also, use no error checking, as usual.
1218.PP 1501.PP
1219.Vb 7 1502.Vb 7
1220\& static void 1503\& static void
1221\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1504\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1222\& { 1505\& {
… …
1229.Vb 3 1512.Vb 3
1230\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1513\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1231\& ev_idle_init (idle_watcher, idle_cb); 1514\& ev_idle_init (idle_watcher, idle_cb);
1232\& ev_idle_start (loop, idle_cb); 1515\& ev_idle_start (loop, idle_cb);
1233.Ve 1516.Ve
1234.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1517.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" 1518.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" 1519.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1237Prepare and check watchers are usually (but not always) used in tandem: 1520Prepare and check watchers are usually (but not always) used in tandem:
1238prepare watchers get invoked before the process blocks and check watchers 1521prepare watchers get invoked before the process blocks and check watchers
1239afterwards. 1522afterwards.
1240.PP 1523.PP
1524You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1525the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1526watchers. Other loops than the current one are fine, however. The
1527rationale behind this is that you do not need to check for recursion in
1528those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1529\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1530called in pairs bracketing the blocking call.
1531.PP
1241Their main purpose is to integrate other event mechanisms into libev and 1532Their main purpose is to integrate other event mechanisms into libev and
1242their use is somewhat advanced. This could be used, for example, to track 1533their use is somewhat advanced. This could be used, for example, to track
1243variable changes, implement your own watchers, integrate net-snmp or a 1534variable changes, implement your own watchers, integrate net-snmp or a
1244coroutine library and lots more. 1535coroutine library and lots more. They are also occasionally useful if
1536you cache some data and want to flush it before blocking (for example,
1537in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1538watcher).
1245.PP 1539.PP
1246This is done by examining in each prepare call which file descriptors need 1540This 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 1541to 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 1542them 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 1543provide just this functionality). Then, in the check watcher you check for
… …
1268.PD 1562.PD
1269Initialises and configures the prepare or check watcher \- they have no 1563Initialises 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 1564parameters 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. 1565macros, but using them is utterly, utterly and completely pointless.
1272.PP 1566.PP
1273Example: *TODO*. 1567Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1568and a timeout watcher in a prepare handler, as required by libadns, and
1569in a check watcher, destroy them and call into libadns. What follows is
1570pseudo-code only of course:
1571.PP
1572.Vb 2
1573\& static ev_io iow [nfd];
1574\& static ev_timer tw;
1575.Ve
1576.PP
1577.Vb 9
1578\& static void
1579\& io_cb (ev_loop *loop, ev_io *w, int revents)
1580\& {
1581\& // set the relevant poll flags
1582\& // could also call adns_processreadable etc. here
1583\& struct pollfd *fd = (struct pollfd *)w->data;
1584\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1585\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1586\& }
1587.Ve
1588.PP
1589.Vb 7
1590\& // create io watchers for each fd and a timer before blocking
1591\& static void
1592\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1593\& {
1594\& int timeout = 3600000;truct pollfd fds [nfd];
1595\& // actual code will need to loop here and realloc etc.
1596\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1597.Ve
1598.PP
1599.Vb 3
1600\& /* the callback is illegal, but won't be called as we stop during check */
1601\& ev_timer_init (&tw, 0, timeout * 1e-3);
1602\& ev_timer_start (loop, &tw);
1603.Ve
1604.PP
1605.Vb 6
1606\& // create on ev_io per pollfd
1607\& for (int i = 0; i < nfd; ++i)
1608\& {
1609\& ev_io_init (iow + i, io_cb, fds [i].fd,
1610\& ((fds [i].events & POLLIN ? EV_READ : 0)
1611\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1612.Ve
1613.PP
1614.Vb 5
1615\& fds [i].revents = 0;
1616\& iow [i].data = fds + i;
1617\& ev_io_start (loop, iow + i);
1618\& }
1619\& }
1620.Ve
1621.PP
1622.Vb 5
1623\& // stop all watchers after blocking
1624\& static void
1625\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1626\& {
1627\& ev_timer_stop (loop, &tw);
1628.Ve
1629.PP
1630.Vb 2
1631\& for (int i = 0; i < nfd; ++i)
1632\& ev_io_stop (loop, iow + i);
1633.Ve
1634.PP
1635.Vb 2
1636\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1637\& }
1638.Ve
1274.ie n .Sh """ev_embed"" \- when one backend isn't enough" 1639.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1275.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough" 1640.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1276.IX Subsection "ev_embed - when one backend isn't enough" 1641.IX Subsection "ev_embed - when one backend isn't enough..."
1277This is a rather advanced watcher type that lets you embed one event loop 1642This 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 1643into 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 1644loop, other types of watchers might be handled in a delayed or incorrect
1280fashion and must not be used). 1645fashion and must not be used).
1281.PP 1646.PP
… …
1361.IP "ev_embed_sweep (loop, ev_embed *)" 4 1726.IP "ev_embed_sweep (loop, ev_embed *)" 4
1362.IX Item "ev_embed_sweep (loop, ev_embed *)" 1727.IX Item "ev_embed_sweep (loop, ev_embed *)"
1363Make a single, non-blocking sweep over the embedded loop. This works 1728Make 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 1729similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1365apropriate way for embedded loops. 1730apropriate way for embedded loops.
1731.IP "struct ev_loop *loop [read\-only]" 4
1732.IX Item "struct ev_loop *loop [read-only]"
1733The embedded event loop.
1734.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1735.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1736.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1737Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1738whoever is a good citizen cared to tell libev about it by calling
1739\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1740event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1741and only in the child after the fork. If whoever good citizen calling
1742\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1743handlers will be invoked, too, of course.
1744.IP "ev_fork_init (ev_signal *, callback)" 4
1745.IX Item "ev_fork_init (ev_signal *, callback)"
1746Initialises and configures the fork watcher \- it has no parameters of any
1747kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1748believe me.
1366.SH "OTHER FUNCTIONS" 1749.SH "OTHER FUNCTIONS"
1367.IX Header "OTHER FUNCTIONS" 1750.IX Header "OTHER FUNCTIONS"
1368There are some other functions of possible interest. Described. Here. Now. 1751There are some other functions of possible interest. Described. Here. Now.
1369.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1752.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)" 1753.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1432.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1815.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1433.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1816.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1434.PD 1817.PD
1435.SH "\*(C+ SUPPORT" 1818.SH "\*(C+ SUPPORT"
1436.IX Header " SUPPORT" 1819.IX Header " SUPPORT"
1437\&\s-1TBD\s0. 1820Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1821you to use some convinience methods to start/stop watchers and also change
1822the callback model to a model using method callbacks on objects.
1823.PP
1824To use it,
1825.PP
1826.Vb 1
1827\& #include <ev++.h>
1828.Ve
1829.PP
1830(it is not installed by default). This automatically includes \fIev.h\fR
1831and puts all of its definitions (many of them macros) into the global
1832namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1833.PP
1834It should support all the same embedding options as \fIev.h\fR, most notably
1835\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1836.PP
1837Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1838.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1839.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1840.IX Item "ev::READ, ev::WRITE etc."
1841These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1842macros from \fIev.h\fR.
1843.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1844.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1845.IX Item "ev::tstamp, ev::now"
1846Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1847.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
1848.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1849.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1850For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1851the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1852which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1853defines by many implementations.
1854.Sp
1855All of those classes have these methods:
1856.RS 4
1857.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1858.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1859.PD 0
1860.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1861.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1862.IP "ev::TYPE::~TYPE" 4
1863.IX Item "ev::TYPE::~TYPE"
1864.PD
1865The constructor takes a pointer to an object and a method pointer to
1866the event handler callback to call in this class. The constructor calls
1867\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1868before starting it. If you do not specify a loop then the constructor
1869automatically associates the default loop with this watcher.
1870.Sp
1871The destructor automatically stops the watcher if it is active.
1872.IP "w\->set (struct ev_loop *)" 4
1873.IX Item "w->set (struct ev_loop *)"
1874Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1875do this when the watcher is inactive (and not pending either).
1876.IP "w\->set ([args])" 4
1877.IX Item "w->set ([args])"
1878Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1879called at least once. Unlike the C counterpart, an active watcher gets
1880automatically stopped and restarted.
1881.IP "w\->start ()" 4
1882.IX Item "w->start ()"
1883Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1884constructor already takes the loop.
1885.IP "w\->stop ()" 4
1886.IX Item "w->stop ()"
1887Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1888.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1889.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1890.IX Item "w->again () ev::timer, ev::periodic only"
1891For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1892\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1893.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1894.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1895.IX Item "w->sweep () ev::embed only"
1896Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1897.ie n .IP "w\->update () ""ev::stat"" only" 4
1898.el .IP "w\->update () \f(CWev::stat\fR only" 4
1899.IX Item "w->update () ev::stat only"
1900Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1901.RE
1902.RS 4
1903.RE
1904.PP
1905Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1906the constructor.
1907.PP
1908.Vb 4
1909\& class myclass
1910\& {
1911\& ev_io io; void io_cb (ev::io &w, int revents);
1912\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1913.Ve
1914.PP
1915.Vb 2
1916\& myclass ();
1917\& }
1918.Ve
1919.PP
1920.Vb 6
1921\& myclass::myclass (int fd)
1922\& : io (this, &myclass::io_cb),
1923\& idle (this, &myclass::idle_cb)
1924\& {
1925\& io.start (fd, ev::READ);
1926\& }
1927.Ve
1928.SH "MACRO MAGIC"
1929.IX Header "MACRO MAGIC"
1930Libev can be compiled with a variety of options, the most fundemantal is
1931\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
1932callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1933.PP
1934To make it easier to write programs that cope with either variant, the
1935following macros are defined:
1936.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
1937.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
1938.IX Item "EV_A, EV_A_"
1939This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
1940loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
1941\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
1942.Sp
1943.Vb 3
1944\& ev_unref (EV_A);
1945\& ev_timer_add (EV_A_ watcher);
1946\& ev_loop (EV_A_ 0);
1947.Ve
1948.Sp
1949It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
1950which is often provided by the following macro.
1951.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
1952.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
1953.IX Item "EV_P, EV_P_"
1954This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
1955loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
1956\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
1957.Sp
1958.Vb 2
1959\& // this is how ev_unref is being declared
1960\& static void ev_unref (EV_P);
1961.Ve
1962.Sp
1963.Vb 2
1964\& // this is how you can declare your typical callback
1965\& static void cb (EV_P_ ev_timer *w, int revents)
1966.Ve
1967.Sp
1968It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
1969suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
1970.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
1971.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
1972.IX Item "EV_DEFAULT, EV_DEFAULT_"
1973Similar to the other two macros, this gives you the value of the default
1974loop, if multiple loops are supported (\*(L"ev loop default\*(R").
1975.PP
1976Example: Declare and initialise a check watcher, working regardless of
1977wether multiple loops are supported or not.
1978.PP
1979.Vb 5
1980\& static void
1981\& check_cb (EV_P_ ev_timer *w, int revents)
1982\& {
1983\& ev_check_stop (EV_A_ w);
1984\& }
1985.Ve
1986.PP
1987.Vb 4
1988\& ev_check check;
1989\& ev_check_init (&check, check_cb);
1990\& ev_check_start (EV_DEFAULT_ &check);
1991\& ev_loop (EV_DEFAULT_ 0);
1992.Ve
1993.SH "EMBEDDING"
1994.IX Header "EMBEDDING"
1995Libev can (and often is) directly embedded into host
1996applications. Examples of applications that embed it include the Deliantra
1997Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1998and rxvt\-unicode.
1999.PP
2000The goal is to enable you to just copy the neecssary files into your
2001source directory without having to change even a single line in them, so
2002you can easily upgrade by simply copying (or having a checked-out copy of
2003libev somewhere in your source tree).
2004.Sh "\s-1FILESETS\s0"
2005.IX Subsection "FILESETS"
2006Depending on what features you need you need to include one or more sets of files
2007in your app.
2008.PP
2009\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2010.IX Subsection "CORE EVENT LOOP"
2011.PP
2012To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2013configuration (no autoconf):
2014.PP
2015.Vb 2
2016\& #define EV_STANDALONE 1
2017\& #include "ev.c"
2018.Ve
2019.PP
2020This will automatically include \fIev.h\fR, too, and should be done in a
2021single C source file only to provide the function implementations. To use
2022it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2023done by writing a wrapper around \fIev.h\fR that you can include instead and
2024where you can put other configuration options):
2025.PP
2026.Vb 2
2027\& #define EV_STANDALONE 1
2028\& #include "ev.h"
2029.Ve
2030.PP
2031Both header files and implementation files can be compiled with a \*(C+
2032compiler (at least, thats a stated goal, and breakage will be treated
2033as a bug).
2034.PP
2035You need the following files in your source tree, or in a directory
2036in your include path (e.g. in libev/ when using \-Ilibev):
2037.PP
2038.Vb 4
2039\& ev.h
2040\& ev.c
2041\& ev_vars.h
2042\& ev_wrap.h
2043.Ve
2044.PP
2045.Vb 1
2046\& ev_win32.c required on win32 platforms only
2047.Ve
2048.PP
2049.Vb 5
2050\& ev_select.c only when select backend is enabled (which is by default)
2051\& ev_poll.c only when poll backend is enabled (disabled by default)
2052\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2053\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2054\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2055.Ve
2056.PP
2057\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2058to compile this single file.
2059.PP
2060\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2061.IX Subsection "LIBEVENT COMPATIBILITY API"
2062.PP
2063To include the libevent compatibility \s-1API\s0, also include:
2064.PP
2065.Vb 1
2066\& #include "event.c"
2067.Ve
2068.PP
2069in the file including \fIev.c\fR, and:
2070.PP
2071.Vb 1
2072\& #include "event.h"
2073.Ve
2074.PP
2075in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2076.PP
2077You need the following additional files for this:
2078.PP
2079.Vb 2
2080\& event.h
2081\& event.c
2082.Ve
2083.PP
2084\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2085.IX Subsection "AUTOCONF SUPPORT"
2086.PP
2087Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2088whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2089\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2090include \fIconfig.h\fR and configure itself accordingly.
2091.PP
2092For this of course you need the m4 file:
2093.PP
2094.Vb 1
2095\& libev.m4
2096.Ve
2097.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2098.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2099Libev can be configured via a variety of preprocessor symbols you have to define
2100before including any of its files. The default is not to build for multiplicity
2101and only include the select backend.
2102.IP "\s-1EV_STANDALONE\s0" 4
2103.IX Item "EV_STANDALONE"
2104Must always be \f(CW1\fR if you do not use autoconf configuration, which
2105keeps libev from including \fIconfig.h\fR, and it also defines dummy
2106implementations for some libevent functions (such as logging, which is not
2107supported). It will also not define any of the structs usually found in
2108\&\fIevent.h\fR that are not directly supported by the libev core alone.
2109.IP "\s-1EV_USE_MONOTONIC\s0" 4
2110.IX Item "EV_USE_MONOTONIC"
2111If defined to be \f(CW1\fR, libev will try to detect the availability of the
2112monotonic clock option at both compiletime and runtime. Otherwise no use
2113of the monotonic clock option will be attempted. If you enable this, you
2114usually have to link against librt or something similar. Enabling it when
2115the functionality isn't available is safe, though, althoguh you have
2116to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2117function is hiding in (often \fI\-lrt\fR).
2118.IP "\s-1EV_USE_REALTIME\s0" 4
2119.IX Item "EV_USE_REALTIME"
2120If defined to be \f(CW1\fR, libev will try to detect the availability of the
2121realtime clock option at compiletime (and assume its availability at
2122runtime if successful). Otherwise no use of the realtime clock option will
2123be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2124(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2125in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2126.IP "\s-1EV_USE_SELECT\s0" 4
2127.IX Item "EV_USE_SELECT"
2128If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2129\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2130other method takes over, select will be it. Otherwise the select backend
2131will not be compiled in.
2132.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2133.IX Item "EV_SELECT_USE_FD_SET"
2134If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2135structure. This is useful if libev doesn't compile due to a missing
2136\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2137exotic systems. This usually limits the range of file descriptors to some
2138low limit such as 1024 or might have other limitations (winsocket only
2139allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2140influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2141.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2142.IX Item "EV_SELECT_IS_WINSOCKET"
2143When defined to \f(CW1\fR, the select backend will assume that
2144select/socket/connect etc. don't understand file descriptors but
2145wants osf handles on win32 (this is the case when the select to
2146be used is the winsock select). This means that it will call
2147\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2148it is assumed that all these functions actually work on fds, even
2149on win32. Should not be defined on non\-win32 platforms.
2150.IP "\s-1EV_USE_POLL\s0" 4
2151.IX Item "EV_USE_POLL"
2152If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2153backend. Otherwise it will be enabled on non\-win32 platforms. It
2154takes precedence over select.
2155.IP "\s-1EV_USE_EPOLL\s0" 4
2156.IX Item "EV_USE_EPOLL"
2157If defined to be \f(CW1\fR, libev will compile in support for the Linux
2158\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2159otherwise another method will be used as fallback. This is the
2160preferred backend for GNU/Linux systems.
2161.IP "\s-1EV_USE_KQUEUE\s0" 4
2162.IX Item "EV_USE_KQUEUE"
2163If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2164\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2165otherwise another method will be used as fallback. This is the preferred
2166backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2167supports some types of fds correctly (the only platform we found that
2168supports ptys for example was NetBSD), so kqueue might be compiled in, but
2169not be used unless explicitly requested. The best way to use it is to find
2170out whether kqueue supports your type of fd properly and use an embedded
2171kqueue loop.
2172.IP "\s-1EV_USE_PORT\s0" 4
2173.IX Item "EV_USE_PORT"
2174If defined to be \f(CW1\fR, libev will compile in support for the Solaris
217510 port style backend. Its availability will be detected at runtime,
2176otherwise another method will be used as fallback. This is the preferred
2177backend for Solaris 10 systems.
2178.IP "\s-1EV_USE_DEVPOLL\s0" 4
2179.IX Item "EV_USE_DEVPOLL"
2180reserved for future expansion, works like the \s-1USE\s0 symbols above.
2181.IP "\s-1EV_USE_INOTIFY\s0" 4
2182.IX Item "EV_USE_INOTIFY"
2183If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2184interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2185be detected at runtime.
2186.IP "\s-1EV_H\s0" 4
2187.IX Item "EV_H"
2188The name of the \fIev.h\fR header file used to include it. The default if
2189undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2190can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2191.IP "\s-1EV_CONFIG_H\s0" 4
2192.IX Item "EV_CONFIG_H"
2193If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2194\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2195\&\f(CW\*(C`EV_H\*(C'\fR, above.
2196.IP "\s-1EV_EVENT_H\s0" 4
2197.IX Item "EV_EVENT_H"
2198Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2199of how the \fIevent.h\fR header can be found.
2200.IP "\s-1EV_PROTOTYPES\s0" 4
2201.IX Item "EV_PROTOTYPES"
2202If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2203prototypes, but still define all the structs and other symbols. This is
2204occasionally useful if you want to provide your own wrapper functions
2205around libev functions.
2206.IP "\s-1EV_MULTIPLICITY\s0" 4
2207.IX Item "EV_MULTIPLICITY"
2208If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2209will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2210additional independent event loops. Otherwise there will be no support
2211for multiple event loops and there is no first event loop pointer
2212argument. Instead, all functions act on the single default loop.
2213.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2214.IX Item "EV_PERIODIC_ENABLE"
2215If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2216defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2217code.
2218.IP "\s-1EV_EMBED_ENABLE\s0" 4
2219.IX Item "EV_EMBED_ENABLE"
2220If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2221defined to be \f(CW0\fR, then they are not.
2222.IP "\s-1EV_STAT_ENABLE\s0" 4
2223.IX Item "EV_STAT_ENABLE"
2224If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2225defined to be \f(CW0\fR, then they are not.
2226.IP "\s-1EV_FORK_ENABLE\s0" 4
2227.IX Item "EV_FORK_ENABLE"
2228If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2229defined to be \f(CW0\fR, then they are not.
2230.IP "\s-1EV_MINIMAL\s0" 4
2231.IX Item "EV_MINIMAL"
2232If you need to shave off some kilobytes of code at the expense of some
2233speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2234some inlining decisions, saves roughly 30% codesize of amd64.
2235.IP "\s-1EV_PID_HASHSIZE\s0" 4
2236.IX Item "EV_PID_HASHSIZE"
2237\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2238pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2239than enough. If you need to manage thousands of children you might want to
2240increase this value (\fImust\fR be a power of two).
2241.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2242.IX Item "EV_INOTIFY_HASHSIZE"
2243\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2244inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2245usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2246watchers you might want to increase this value (\fImust\fR be a power of
2247two).
2248.IP "\s-1EV_COMMON\s0" 4
2249.IX Item "EV_COMMON"
2250By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2251this macro to a something else you can include more and other types of
2252members. You have to define it each time you include one of the files,
2253though, and it must be identical each time.
2254.Sp
2255For example, the perl \s-1EV\s0 module uses something like this:
2256.Sp
2257.Vb 3
2258\& #define EV_COMMON \e
2259\& SV *self; /* contains this struct */ \e
2260\& SV *cb_sv, *fh /* note no trailing ";" */
2261.Ve
2262.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2263.IX Item "EV_CB_DECLARE (type)"
2264.PD 0
2265.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2266.IX Item "EV_CB_INVOKE (watcher, revents)"
2267.IP "ev_set_cb (ev, cb)" 4
2268.IX Item "ev_set_cb (ev, cb)"
2269.PD
2270Can be used to change the callback member declaration in each watcher,
2271and the way callbacks are invoked and set. Must expand to a struct member
2272definition and a statement, respectively. See the \fIev.v\fR header file for
2273their default definitions. One possible use for overriding these is to
2274avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2275method calls instead of plain function calls in \*(C+.
2276.Sh "\s-1EXAMPLES\s0"
2277.IX Subsection "EXAMPLES"
2278For a real-world example of a program the includes libev
2279verbatim, you can have a look at the \s-1EV\s0 perl module
2280(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2281the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2282interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2283will be compiled. It is pretty complex because it provides its own header
2284file.
2285.Sp
2286The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2287that everybody includes and which overrides some autoconf choices:
2288.Sp
2289.Vb 4
2290\& #define EV_USE_POLL 0
2291\& #define EV_MULTIPLICITY 0
2292\& #define EV_PERIODICS 0
2293\& #define EV_CONFIG_H <config.h>
2294.Ve
2295.Sp
2296.Vb 1
2297\& #include "ev++.h"
2298.Ve
2299.Sp
2300And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2301.Sp
2302.Vb 2
2303\& #include "ev_cpp.h"
2304\& #include "ev.c"
2305.Ve
2306.SH "COMPLEXITIES"
2307.IX Header "COMPLEXITIES"
2308In this section the complexities of (many of) the algorithms used inside
2309libev will be explained. For complexity discussions about backends see the
2310documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2311.RS 4
2312.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2313.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2314.PD 0
2315.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2316.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2317.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2318.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2319.IP "Stopping check/prepare/idle watchers: O(1)" 4
2320.IX Item "Stopping check/prepare/idle watchers: O(1)"
2321.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2322.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2323.IP "Finding the next timer per loop iteration: O(1)" 4
2324.IX Item "Finding the next timer per loop iteration: O(1)"
2325.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2326.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2327.IP "Activating one watcher: O(1)" 4
2328.IX Item "Activating one watcher: O(1)"
2329.RE
2330.RS 4
2331.PD
1438.SH "AUTHOR" 2332.SH "AUTHOR"
1439.IX Header "AUTHOR" 2333.IX Header "AUTHOR"
1440Marc Lehmann <libev@schmorp.de>. 2334Marc Lehmann <libev@schmorp.de>.

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