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Revision 1.12 by root, Sat Nov 24 07:20:42 2007 UTC vs.
Revision 1.32 by root, Wed Nov 28 17:32:24 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));
… …
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, long size))" 4
246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 311.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
247Sets the allocation function to use (the prototype is similar to the 312Sets the allocation function to use (the prototype is similar \- the
248realloc C function, the semantics are identical). It is used to allocate 313semantics is identical \- to the realloc C function). It is used to
249and free memory (no surprises here). If it returns zero when memory 314allocate and free memory (no surprises here). If it returns zero when
250needs to be allocated, the library might abort or take some potentially 315memory needs to be allocated, the library might abort or take some
251destructive action. The default is your system realloc function. 316potentially destructive action. The default is your system realloc
317function.
252.Sp 318.Sp
253You could override this function in high-availability programs to, say, 319You could override this function in high-availability programs to, say,
254free some memory if it cannot allocate memory, to use a special allocator, 320free 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. 321or even to sleep a while and retry until some memory is available.
256.Sp 322.Sp
257Example: replace the libev allocator with one that waits a bit and then 323Example: Replace the libev allocator with one that waits a bit and then
258retries: better than mine). 324retries).
259.Sp 325.Sp
260.Vb 6 326.Vb 6
261\& static void * 327\& static void *
262\& persistent_realloc (void *ptr, long size) 328\& persistent_realloc (void *ptr, size_t size)
263\& { 329\& {
264\& for (;;) 330\& for (;;)
265\& { 331\& {
266\& void *newptr = realloc (ptr, size); 332\& void *newptr = realloc (ptr, size);
267.Ve 333.Ve
… …
289callback is set, then libev will expect it to remedy the sitution, no 355callback is set, then libev will expect it to remedy the sitution, no
290matter what, when it returns. That is, libev will generally retry the 356matter what, when it returns. That is, libev will generally retry the
291requested operation, or, if the condition doesn't go away, do bad stuff 357requested operation, or, if the condition doesn't go away, do bad stuff
292(such as abort). 358(such as abort).
293.Sp 359.Sp
294Example: do the same thing as libev does internally: 360Example: This is basically the same thing that libev does internally, too.
295.Sp 361.Sp
296.Vb 6 362.Vb 6
297\& static void 363\& static void
298\& fatal_error (const char *msg) 364\& fatal_error (const char *msg)
299\& { 365\& {
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448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 514Similar 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 515always 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 516handle signal and child watchers, and attempts to do so will be greeted by
451undefined behaviour (or a failed assertion if assertions are enabled). 517undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp 518.Sp
453Example: try to create a event loop that uses epoll and nothing else. 519Example: Try to create a event loop that uses epoll and nothing else.
454.Sp 520.Sp
455.Vb 3 521.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 522\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller) 523\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair"); 524\& fatal ("no epoll found here, maybe it hides under your chair");
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556\& be handled here by queueing them when their watcher gets executed. 622\& be handled here by queueing them when their watcher gets executed.
557\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 623\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
558\& were used, return, otherwise continue with step *. 624\& were used, return, otherwise continue with step *.
559.Ve 625.Ve
560.Sp 626.Sp
561Example: queue some jobs and then loop until no events are outsanding 627Example: Queue some jobs and then loop until no events are outsanding
562anymore. 628anymore.
563.Sp 629.Sp
564.Vb 4 630.Vb 4
565\& ... queue jobs here, make sure they register event watchers as long 631\& ... 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..) 632\& ... 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 654visible 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 655no 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 656way 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. 657libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
592.Sp 658.Sp
593Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 659Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
594running when nothing else is active. 660running when nothing else is active.
595.Sp 661.Sp
596.Vb 4 662.Vb 4
597\& struct dv_signal exitsig; 663\& struct ev_signal exitsig;
598\& ev_signal_init (&exitsig, sig_cb, SIGINT); 664\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599\& ev_signal_start (myloop, &exitsig); 665\& ev_signal_start (loop, &exitsig);
600\& evf_unref (myloop); 666\& evf_unref (loop);
601.Ve 667.Ve
602.Sp 668.Sp
603Example: for some weird reason, unregister the above signal handler again. 669Example: For some weird reason, unregister the above signal handler again.
604.Sp 670.Sp
605.Vb 2 671.Vb 2
606\& ev_ref (myloop); 672\& ev_ref (loop);
607\& ev_signal_stop (myloop, &exitsig); 673\& ev_signal_stop (loop, &exitsig);
608.Ve 674.Ve
609.SH "ANATOMY OF A WATCHER" 675.SH "ANATOMY OF A WATCHER"
610.IX Header "ANATOMY OF A WATCHER" 676.IX Header "ANATOMY OF A WATCHER"
611A watcher is a structure that you create and register to record your 677A 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 678interest 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. 750The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
685.ie n .IP """EV_CHILD""" 4 751.ie n .IP """EV_CHILD""" 4
686.el .IP "\f(CWEV_CHILD\fR" 4 752.el .IP "\f(CWEV_CHILD\fR" 4
687.IX Item "EV_CHILD" 753.IX Item "EV_CHILD"
688The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 754The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
755.ie n .IP """EV_STAT""" 4
756.el .IP "\f(CWEV_STAT\fR" 4
757.IX Item "EV_STAT"
758The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
689.ie n .IP """EV_IDLE""" 4 759.ie n .IP """EV_IDLE""" 4
690.el .IP "\f(CWEV_IDLE\fR" 4 760.el .IP "\f(CWEV_IDLE\fR" 4
691.IX Item "EV_IDLE" 761.IX Item "EV_IDLE"
692The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 762The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
693.ie n .IP """EV_PREPARE""" 4 763.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 773\&\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 774received 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 775many 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 776(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). 777\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
778.ie n .IP """EV_EMBED""" 4
779.el .IP "\f(CWEV_EMBED\fR" 4
780.IX Item "EV_EMBED"
781The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
782.ie n .IP """EV_FORK""" 4
783.el .IP "\f(CWEV_FORK\fR" 4
784.IX Item "EV_FORK"
785The event loop has been resumed in the child process after fork (see
786\&\f(CW\*(C`ev_fork\*(C'\fR).
708.ie n .IP """EV_ERROR""" 4 787.ie n .IP """EV_ERROR""" 4
709.el .IP "\f(CWEV_ERROR\fR" 4 788.el .IP "\f(CWEV_ERROR\fR" 4
710.IX Item "EV_ERROR" 789.IX Item "EV_ERROR"
711An unspecified error has occured, the watcher has been stopped. This might 790An unspecified error has occured, the watcher has been stopped. This might
712happen because the watcher could not be properly started because libev 791happen because the watcher could not be properly started because libev
… …
717Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 796Libev 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 797for 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 798your 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 799with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
721programs, though, so beware. 800programs, though, so beware.
722.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" 801.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
723.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS" 802.IX Subsection "GENERIC WATCHER FUNCTIONS"
724In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, 803In 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. 804e.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)" 4 805.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
727.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 806.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
728.IX Item "ev_init (ev_TYPE *watcher, callback)" 807.IX Item "ev_init (ev_TYPE *watcher, callback)"
… …
734which rolls both calls into one. 813which rolls both calls into one.
735.Sp 814.Sp
736You can reinitialise a watcher at any time as long as it has been stopped 815You 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. 816(or never started) and there are no pending events outstanding.
738.Sp 817.Sp
739The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, 818The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
740int revents)\*(C'\fR. 819int revents)\*(C'\fR.
741.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 820.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
742.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 821.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
743.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 822.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
744This macro initialises the type-specific parts of a watcher. You need to 823This 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 858Returns 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 859events 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 860is 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 861\&\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). 862libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
784.IP "callback = ev_cb (ev_TYPE *watcher)" 4 863.IP "callback ev_cb (ev_TYPE *watcher)" 4
785.IX Item "callback = ev_cb (ev_TYPE *watcher)" 864.IX Item "callback ev_cb (ev_TYPE *watcher)"
786Returns the callback currently set on the watcher. 865Returns the callback currently set on the watcher.
787.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 866.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
788.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 867.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
789Change the callback. You can change the callback at virtually any time 868Change the callback. You can change the callback at virtually any time
790(modulo threads). 869(modulo threads).
… …
816\& struct my_io *w = (struct my_io *)w_; 895\& struct my_io *w = (struct my_io *)w_;
817\& ... 896\& ...
818\& } 897\& }
819.Ve 898.Ve
820.PP 899.PP
821More interesting and less C\-conformant ways of catsing your callback type 900More interesting and less C\-conformant ways of casting your callback type
822have been omitted.... 901instead have been omitted.
902.PP
903Another common scenario is having some data structure with multiple
904watchers:
905.PP
906.Vb 6
907\& struct my_biggy
908\& {
909\& int some_data;
910\& ev_timer t1;
911\& ev_timer t2;
912\& }
913.Ve
914.PP
915In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
916you need to use \f(CW\*(C`offsetof\*(C'\fR:
917.PP
918.Vb 1
919\& #include <stddef.h>
920.Ve
921.PP
922.Vb 6
923\& static void
924\& t1_cb (EV_P_ struct ev_timer *w, int revents)
925\& {
926\& struct my_biggy big = (struct my_biggy *
927\& (((char *)w) - offsetof (struct my_biggy, t1));
928\& }
929.Ve
930.PP
931.Vb 6
932\& static void
933\& t2_cb (EV_P_ struct ev_timer *w, int revents)
934\& {
935\& struct my_biggy big = (struct my_biggy *
936\& (((char *)w) - offsetof (struct my_biggy, t2));
937\& }
938.Ve
823.SH "WATCHER TYPES" 939.SH "WATCHER TYPES"
824.IX Header "WATCHER TYPES" 940.IX Header "WATCHER TYPES"
825This section describes each watcher in detail, but will not repeat 941This section describes each watcher in detail, but will not repeat
826information given in the last section. 942information given in the last section. Any initialisation/set macros,
943functions and members specific to the watcher type are explained.
944.PP
945Members are additionally marked with either \fI[read\-only]\fR, meaning that,
946while the watcher is active, you can look at the member and expect some
947sensible content, but you must not modify it (you can modify it while the
948watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
949means you can expect it to have some sensible content while the watcher
950is active, but you can also modify it. Modifying it may not do something
951sensible or take immediate effect (or do anything at all), but libev will
952not crash or malfunction in any way.
827.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 953.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" 954.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" 955.IX Subsection "ev_io - is this file descriptor readable or writable?"
830I/O watchers check whether a file descriptor is readable or writable 956I/O watchers check whether a file descriptor is readable or writable
831in each iteration of the event loop (This behaviour is called 957in each iteration of the event loop, or, more precisely, when reading
832level-triggering because you keep receiving events as long as the 958would 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 959some data. This behaviour is called level-triggering because you keep
834act on the event and neither want to receive future events). 960receiving events as long as the condition persists. Remember you can stop
961the watcher if you don't want to act on the event and neither want to
962receive future events.
835.PP 963.PP
836In general you can register as many read and/or write event watchers per 964In 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 965fd 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 966descriptors to non-blocking mode is also usually a good idea (but not
839required if you know what you are doing). 967required if you know what you are doing).
840.PP 968.PP
841You have to be careful with dup'ed file descriptors, though. Some backends 969You 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 970(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 971descriptors correctly if you register interest in two or more fds pointing
844to the same underlying file/socket etc. description (that is, they share 972to the same underlying file/socket/etc. description (that is, they share
845the same underlying \*(L"file open\*(R"). 973the same underlying \*(L"file open\*(R").
846.PP 974.PP
847If you must do this, then force the use of a known-to-be-good backend 975If 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 976(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). 977\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
978.PP
979Another thing you have to watch out for is that it is quite easy to
980receive \*(L"spurious\*(R" readyness notifications, that is your callback might
981be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
982because there is no data. Not only are some backends known to create a
983lot of those (for example solaris ports), it is very easy to get into
984this situation even with a relatively standard program structure. Thus
985it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
986\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
987.PP
988If you cannot run the fd in non-blocking mode (for example you should not
989play around with an Xlib connection), then you have to seperately re-test
990wether a file descriptor is really ready with a known-to-be good interface
991such as poll (fortunately in our Xlib example, Xlib already does this on
992its own, so its quite safe to use).
850.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 993.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)" 994.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
852.PD 0 995.PD 0
853.IP "ev_io_set (ev_io *, int fd, int events)" 4 996.IP "ev_io_set (ev_io *, int fd, int events)" 4
854.IX Item "ev_io_set (ev_io *, int fd, int events)" 997.IX Item "ev_io_set (ev_io *, int fd, int events)"
855.PD 998.PD
856Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 999Configures 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 | 1000rceeive 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. 1001\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
859.Sp 1002.IP "int fd [read\-only]" 4
860Please note that most of the more scalable backend mechanisms (for example 1003.IX Item "int fd [read-only]"
861epoll and solaris ports) can result in spurious readyness notifications 1004The file descriptor being watched.
862for file descriptors, so you practically need to use non-blocking I/O (and 1005.IP "int events [read\-only]" 4
863treat callback invocation as hint only), or retest separately with a safe 1006.IX Item "int events [read-only]"
864interface before doing I/O (XLib can do this), or force the use of either 1007The 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 1008.PP
871Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1009Example: 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 1010readable, but only once. Since it is likely line\-buffered, you could
873attempt to read a whole line in the callback: 1011attempt to read a whole line in the callback.
874.PP 1012.PP
875.Vb 6 1013.Vb 6
876\& static void 1014\& static void
877\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1015\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
878\& { 1016\& {
… …
887\& struct ev_io stdin_readable; 1025\& struct ev_io stdin_readable;
888\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1026\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
889\& ev_io_start (loop, &stdin_readable); 1027\& ev_io_start (loop, &stdin_readable);
890\& ev_loop (loop, 0); 1028\& ev_loop (loop, 0);
891.Ve 1029.Ve
892.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1030.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
893.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1031.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
894.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1032.IX Subsection "ev_timer - relative and optionally repeating timeouts"
895Timer watchers are simple relative timers that generate an event after a 1033Timer watchers are simple relative timers that generate an event after a
896given time, and optionally repeating in regular intervals after that. 1034given time, and optionally repeating in regular intervals after that.
897.PP 1035.PP
898The timers are based on real time, that is, if you register an event that 1036The 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 1037times out after an hour and you reset your system clock to last years
… …
939.Sp 1077.Sp
940If the timer is repeating, either start it if necessary (with the repeat 1078If the timer is repeating, either start it if necessary (with the repeat
941value), or reset the running timer to the repeat value. 1079value), or reset the running timer to the repeat value.
942.Sp 1080.Sp
943This sounds a bit complicated, but here is a useful and typical 1081This 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 1082example: 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 1083idle 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 1084say, 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 1085this 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 1086\&\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 1087you 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. 1088socket, you can stop the timer, and again will automatically restart it if
1089need be.
1090.Sp
1091You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
1092and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
1093.Sp
1094.Vb 8
1095\& ev_timer_init (timer, callback, 0., 5.);
1096\& ev_timer_again (loop, timer);
1097\& ...
1098\& timer->again = 17.;
1099\& ev_timer_again (loop, timer);
1100\& ...
1101\& timer->again = 10.;
1102\& ev_timer_again (loop, timer);
1103.Ve
1104.Sp
1105This is more efficient then stopping/starting the timer eahc time you want
1106to modify its timeout value.
1107.IP "ev_tstamp repeat [read\-write]" 4
1108.IX Item "ev_tstamp repeat [read-write]"
1109The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1110or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1111which is also when any modifications are taken into account.
951.PP 1112.PP
952Example: create a timer that fires after 60 seconds. 1113Example: Create a timer that fires after 60 seconds.
953.PP 1114.PP
954.Vb 5 1115.Vb 5
955\& static void 1116\& static void
956\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1117\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
957\& { 1118\& {
… …
963\& struct ev_timer mytimer; 1124\& struct ev_timer mytimer;
964\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1125\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
965\& ev_timer_start (loop, &mytimer); 1126\& ev_timer_start (loop, &mytimer);
966.Ve 1127.Ve
967.PP 1128.PP
968Example: create a timeout timer that times out after 10 seconds of 1129Example: Create a timeout timer that times out after 10 seconds of
969inactivity. 1130inactivity.
970.PP 1131.PP
971.Vb 5 1132.Vb 5
972\& static void 1133\& static void
973\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1134\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
986.Vb 3 1147.Vb 3
987\& // and in some piece of code that gets executed on any "activity": 1148\& // and in some piece of code that gets executed on any "activity":
988\& // reset the timeout to start ticking again at 10 seconds 1149\& // reset the timeout to start ticking again at 10 seconds
989\& ev_timer_again (&mytimer); 1150\& ev_timer_again (&mytimer);
990.Ve 1151.Ve
991.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1152.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
992.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1153.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
993.IX Subsection "ev_periodic - to cron or not to cron" 1154.IX Subsection "ev_periodic - to cron or not to cron?"
994Periodic watchers are also timers of a kind, but they are very versatile 1155Periodic watchers are also timers of a kind, but they are very versatile
995(and unfortunately a bit complex). 1156(and unfortunately a bit complex).
996.PP 1157.PP
997Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1158Unlike \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 1159but 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 1160to 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 () 1161periodic 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 1162+ 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 1163take 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 1164roughly 10 seconds later and of course not if you reset your system time
1004again). 1165again).
1005.PP 1166.PP
1006They can also be used to implement vastly more complex timers, such as 1167They can also be used to implement vastly more complex timers, such as
… …
1087.IX Item "ev_periodic_again (loop, ev_periodic *)" 1248.IX Item "ev_periodic_again (loop, ev_periodic *)"
1088Simply stops and restarts the periodic watcher again. This is only useful 1249Simply stops and restarts the periodic watcher again. This is only useful
1089when you changed some parameters or the reschedule callback would return 1250when 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 1251a different time than the last time it was called (e.g. in a crond like
1091program when the crontabs have changed). 1252program when the crontabs have changed).
1253.IP "ev_tstamp interval [read\-write]" 4
1254.IX Item "ev_tstamp interval [read-write]"
1255The current interval value. Can be modified any time, but changes only
1256take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1257called.
1258.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1259.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1260The current reschedule callback, or \f(CW0\fR, if this functionality is
1261switched off. Can be changed any time, but changes only take effect when
1262the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1092.PP 1263.PP
1093Example: call a callback every hour, or, more precisely, whenever the 1264Example: Call a callback every hour, or, more precisely, whenever the
1094system clock is divisible by 3600. The callback invocation times have 1265system clock is divisible by 3600. The callback invocation times have
1095potentially a lot of jittering, but good long-term stability. 1266potentially a lot of jittering, but good long-term stability.
1096.PP 1267.PP
1097.Vb 5 1268.Vb 5
1098\& static void 1269\& static void
… …
1106\& struct ev_periodic hourly_tick; 1277\& struct ev_periodic hourly_tick;
1107\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1278\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1108\& ev_periodic_start (loop, &hourly_tick); 1279\& ev_periodic_start (loop, &hourly_tick);
1109.Ve 1280.Ve
1110.PP 1281.PP
1111Example: the same as above, but use a reschedule callback to do it: 1282Example: The same as above, but use a reschedule callback to do it:
1112.PP 1283.PP
1113.Vb 1 1284.Vb 1
1114\& #include <math.h> 1285\& #include <math.h>
1115.Ve 1286.Ve
1116.PP 1287.PP
… …
1124.PP 1295.PP
1125.Vb 1 1296.Vb 1
1126\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1297\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1127.Ve 1298.Ve
1128.PP 1299.PP
1129Example: call a callback every hour, starting now: 1300Example: Call a callback every hour, starting now:
1130.PP 1301.PP
1131.Vb 4 1302.Vb 4
1132\& struct ev_periodic hourly_tick; 1303\& struct ev_periodic hourly_tick;
1133\& ev_periodic_init (&hourly_tick, clock_cb, 1304\& ev_periodic_init (&hourly_tick, clock_cb,
1134\& fmod (ev_now (loop), 3600.), 3600., 0); 1305\& fmod (ev_now (loop), 3600.), 3600., 0);
1135\& ev_periodic_start (loop, &hourly_tick); 1306\& ev_periodic_start (loop, &hourly_tick);
1136.Ve 1307.Ve
1137.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1308.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" 1309.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" 1310.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1140Signal watchers will trigger an event when the process receives a specific 1311Signal watchers will trigger an event when the process receives a specific
1141signal one or more times. Even though signals are very asynchronous, libev 1312signal 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 1313will try it's best to deliver signals synchronously, i.e. as part of the
1143normal event processing, like any other event. 1314normal event processing, like any other event.
1144.PP 1315.PP
… …
1154.IP "ev_signal_set (ev_signal *, int signum)" 4 1325.IP "ev_signal_set (ev_signal *, int signum)" 4
1155.IX Item "ev_signal_set (ev_signal *, int signum)" 1326.IX Item "ev_signal_set (ev_signal *, int signum)"
1156.PD 1327.PD
1157Configures the watcher to trigger on the given signal number (usually one 1328Configures the watcher to trigger on the given signal number (usually one
1158of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1329of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1330.IP "int signum [read\-only]" 4
1331.IX Item "int signum [read-only]"
1332The signal the watcher watches out for.
1159.ie n .Sh """ev_child"" \- wait for pid status changes" 1333.ie n .Sh """ev_child"" \- watch out for process status changes"
1160.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1334.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1161.IX Subsection "ev_child - wait for pid status changes" 1335.IX Subsection "ev_child - watch out for process status changes"
1162Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1336Child 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). 1337some child status changes (most typically when a child of yours dies).
1164.IP "ev_child_init (ev_child *, callback, int pid)" 4 1338.IP "ev_child_init (ev_child *, callback, int pid)" 4
1165.IX Item "ev_child_init (ev_child *, callback, int pid)" 1339.IX Item "ev_child_init (ev_child *, callback, int pid)"
1166.PD 0 1340.PD 0
… …
1171\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1345\&\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 1346at 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 1347the 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 1348\&\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. 1349process causing the status change.
1350.IP "int pid [read\-only]" 4
1351.IX Item "int pid [read-only]"
1352The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1353.IP "int rpid [read\-write]" 4
1354.IX Item "int rpid [read-write]"
1355The process id that detected a status change.
1356.IP "int rstatus [read\-write]" 4
1357.IX Item "int rstatus [read-write]"
1358The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1359\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1176.PP 1360.PP
1177Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1361Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1178.PP 1362.PP
1179.Vb 5 1363.Vb 5
1180\& static void 1364\& static void
1181\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1365\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1182\& { 1366\& {
… …
1187.Vb 3 1371.Vb 3
1188\& struct ev_signal signal_watcher; 1372\& struct ev_signal signal_watcher;
1189\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1373\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1190\& ev_signal_start (loop, &sigint_cb); 1374\& ev_signal_start (loop, &sigint_cb);
1191.Ve 1375.Ve
1376.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1377.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1378.IX Subsection "ev_stat - did the file attributes just change?"
1379This watches a filesystem path for attribute changes. That is, it calls
1380\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1381compared to the last time, invoking the callback if it did.
1382.PP
1383The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1384not exist\*(R" is a status change like any other. The condition \*(L"path does
1385not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1386otherwise always forced to be at least one) and all the other fields of
1387the stat buffer having unspecified contents.
1388.PP
1389Since there is no standard to do this, the portable implementation simply
1390calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1391can specify a recommended polling interval for this case. If you specify
1392a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1393unspecified default\fR value will be used (which you can expect to be around
1394five seconds, although this might change dynamically). Libev will also
1395impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1396usually overkill.
1397.PP
1398This watcher type is not meant for massive numbers of stat watchers,
1399as even with OS-supported change notifications, this can be
1400resource\-intensive.
1401.PP
1402At the time of this writing, only the Linux inotify interface is
1403implemented (implementing kqueue support is left as an exercise for the
1404reader). Inotify will be used to give hints only and should not change the
1405semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1406to fall back to regular polling again even with inotify, but changes are
1407usually detected immediately, and if the file exists there will be no
1408polling.
1409.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1410.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1411.PD 0
1412.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1413.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1414.PD
1415Configures the watcher to wait for status changes of the given
1416\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1417be detected and should normally be specified as \f(CW0\fR to let libev choose
1418a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1419path for as long as the watcher is active.
1420.Sp
1421The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1422relative to the attributes at the time the watcher was started (or the
1423last change was detected).
1424.IP "ev_stat_stat (ev_stat *)" 4
1425.IX Item "ev_stat_stat (ev_stat *)"
1426Updates the stat buffer immediately with new values. If you change the
1427watched path in your callback, you could call this fucntion to avoid
1428detecting this change (while introducing a race condition). Can also be
1429useful simply to find out the new values.
1430.IP "ev_statdata attr [read\-only]" 4
1431.IX Item "ev_statdata attr [read-only]"
1432The most-recently detected attributes of the file. Although the type is of
1433\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1434suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1435was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1436.IP "ev_statdata prev [read\-only]" 4
1437.IX Item "ev_statdata prev [read-only]"
1438The previous attributes of the file. The callback gets invoked whenever
1439\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1440.IP "ev_tstamp interval [read\-only]" 4
1441.IX Item "ev_tstamp interval [read-only]"
1442The specified interval.
1443.IP "const char *path [read\-only]" 4
1444.IX Item "const char *path [read-only]"
1445The filesystem path that is being watched.
1446.PP
1447Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1448.PP
1449.Vb 15
1450\& static void
1451\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1452\& {
1453\& /* /etc/passwd changed in some way */
1454\& if (w->attr.st_nlink)
1455\& {
1456\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1457\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1458\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1459\& }
1460\& else
1461\& /* you shalt not abuse printf for puts */
1462\& puts ("wow, /etc/passwd is not there, expect problems. "
1463\& "if this is windows, they already arrived\en");
1464\& }
1465.Ve
1466.PP
1467.Vb 2
1468\& ...
1469\& ev_stat passwd;
1470.Ve
1471.PP
1472.Vb 2
1473\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1474\& ev_stat_start (loop, &passwd);
1475.Ve
1192.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1476.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" 1477.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" 1478.IX Subsection "ev_idle - when you've got nothing better to do..."
1195Idle watchers trigger events when there are no other events are pending 1479Idle 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 1480(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, 1481as 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 1482imagine) 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 \- 1483watchers are being called again and again, once per event loop iteration \-
… …
1211.IX Item "ev_idle_init (ev_signal *, callback)" 1495.IX Item "ev_idle_init (ev_signal *, callback)"
1212Initialises and configures the idle watcher \- it has no parameters of any 1496Initialises 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, 1497kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1214believe me. 1498believe me.
1215.PP 1499.PP
1216Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1500Example: 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. 1501callback, free it. Also, use no error checking, as usual.
1218.PP 1502.PP
1219.Vb 7 1503.Vb 7
1220\& static void 1504\& static void
1221\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1505\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1222\& { 1506\& {
… …
1229.Vb 3 1513.Vb 3
1230\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1514\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1231\& ev_idle_init (idle_watcher, idle_cb); 1515\& ev_idle_init (idle_watcher, idle_cb);
1232\& ev_idle_start (loop, idle_cb); 1516\& ev_idle_start (loop, idle_cb);
1233.Ve 1517.Ve
1234.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1518.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" 1519.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" 1520.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1237Prepare and check watchers are usually (but not always) used in tandem: 1521Prepare and check watchers are usually (but not always) used in tandem:
1238prepare watchers get invoked before the process blocks and check watchers 1522prepare watchers get invoked before the process blocks and check watchers
1239afterwards. 1523afterwards.
1240.PP 1524.PP
1525You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1526the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1527watchers. Other loops than the current one are fine, however. The
1528rationale behind this is that you do not need to check for recursion in
1529those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1530\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1531called in pairs bracketing the blocking call.
1532.PP
1241Their main purpose is to integrate other event mechanisms into libev and 1533Their main purpose is to integrate other event mechanisms into libev and
1242their use is somewhat advanced. This could be used, for example, to track 1534their use is somewhat advanced. This could be used, for example, to track
1243variable changes, implement your own watchers, integrate net-snmp or a 1535variable changes, implement your own watchers, integrate net-snmp or a
1244coroutine library and lots more. 1536coroutine library and lots more. They are also occasionally useful if
1537you cache some data and want to flush it before blocking (for example,
1538in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1539watcher).
1245.PP 1540.PP
1246This is done by examining in each prepare call which file descriptors need 1541This 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 1542to 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 1543them 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 1544provide just this functionality). Then, in the check watcher you check for
… …
1268.PD 1563.PD
1269Initialises and configures the prepare or check watcher \- they have no 1564Initialises 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 1565parameters 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. 1566macros, but using them is utterly, utterly and completely pointless.
1272.PP 1567.PP
1273Example: *TODO*. 1568Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1569and a timeout watcher in a prepare handler, as required by libadns, and
1570in a check watcher, destroy them and call into libadns. What follows is
1571pseudo-code only of course:
1572.PP
1573.Vb 2
1574\& static ev_io iow [nfd];
1575\& static ev_timer tw;
1576.Ve
1577.PP
1578.Vb 9
1579\& static void
1580\& io_cb (ev_loop *loop, ev_io *w, int revents)
1581\& {
1582\& // set the relevant poll flags
1583\& // could also call adns_processreadable etc. here
1584\& struct pollfd *fd = (struct pollfd *)w->data;
1585\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1586\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1587\& }
1588.Ve
1589.PP
1590.Vb 7
1591\& // create io watchers for each fd and a timer before blocking
1592\& static void
1593\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1594\& {
1595\& int timeout = 3600000;truct pollfd fds [nfd];
1596\& // actual code will need to loop here and realloc etc.
1597\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1598.Ve
1599.PP
1600.Vb 3
1601\& /* the callback is illegal, but won't be called as we stop during check */
1602\& ev_timer_init (&tw, 0, timeout * 1e-3);
1603\& ev_timer_start (loop, &tw);
1604.Ve
1605.PP
1606.Vb 6
1607\& // create on ev_io per pollfd
1608\& for (int i = 0; i < nfd; ++i)
1609\& {
1610\& ev_io_init (iow + i, io_cb, fds [i].fd,
1611\& ((fds [i].events & POLLIN ? EV_READ : 0)
1612\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1613.Ve
1614.PP
1615.Vb 5
1616\& fds [i].revents = 0;
1617\& iow [i].data = fds + i;
1618\& ev_io_start (loop, iow + i);
1619\& }
1620\& }
1621.Ve
1622.PP
1623.Vb 5
1624\& // stop all watchers after blocking
1625\& static void
1626\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1627\& {
1628\& ev_timer_stop (loop, &tw);
1629.Ve
1630.PP
1631.Vb 2
1632\& for (int i = 0; i < nfd; ++i)
1633\& ev_io_stop (loop, iow + i);
1634.Ve
1635.PP
1636.Vb 2
1637\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1638\& }
1639.Ve
1274.ie n .Sh """ev_embed"" \- when one backend isn't enough" 1640.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1275.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough" 1641.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1276.IX Subsection "ev_embed - when one backend isn't enough" 1642.IX Subsection "ev_embed - when one backend isn't enough..."
1277This is a rather advanced watcher type that lets you embed one event loop 1643This 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 1644into 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 1645loop, other types of watchers might be handled in a delayed or incorrect
1280fashion and must not be used). 1646fashion and must not be used).
1281.PP 1647.PP
… …
1361.IP "ev_embed_sweep (loop, ev_embed *)" 4 1727.IP "ev_embed_sweep (loop, ev_embed *)" 4
1362.IX Item "ev_embed_sweep (loop, ev_embed *)" 1728.IX Item "ev_embed_sweep (loop, ev_embed *)"
1363Make a single, non-blocking sweep over the embedded loop. This works 1729Make 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 1730similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1365apropriate way for embedded loops. 1731apropriate way for embedded loops.
1732.IP "struct ev_loop *loop [read\-only]" 4
1733.IX Item "struct ev_loop *loop [read-only]"
1734The embedded event loop.
1735.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1736.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1737.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1738Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1739whoever is a good citizen cared to tell libev about it by calling
1740\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1741event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1742and only in the child after the fork. If whoever good citizen calling
1743\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1744handlers will be invoked, too, of course.
1745.IP "ev_fork_init (ev_signal *, callback)" 4
1746.IX Item "ev_fork_init (ev_signal *, callback)"
1747Initialises and configures the fork watcher \- it has no parameters of any
1748kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1749believe me.
1366.SH "OTHER FUNCTIONS" 1750.SH "OTHER FUNCTIONS"
1367.IX Header "OTHER FUNCTIONS" 1751.IX Header "OTHER FUNCTIONS"
1368There are some other functions of possible interest. Described. Here. Now. 1752There are some other functions of possible interest. Described. Here. Now.
1369.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1753.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)" 1754.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 1816.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." 1817.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1434.PD 1818.PD
1435.SH "\*(C+ SUPPORT" 1819.SH "\*(C+ SUPPORT"
1436.IX Header " SUPPORT" 1820.IX Header " SUPPORT"
1437\&\s-1TBD\s0. 1821Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1822you to use some convinience methods to start/stop watchers and also change
1823the callback model to a model using method callbacks on objects.
1824.PP
1825To use it,
1826.PP
1827.Vb 1
1828\& #include <ev++.h>
1829.Ve
1830.PP
1831(it is not installed by default). This automatically includes \fIev.h\fR
1832and puts all of its definitions (many of them macros) into the global
1833namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1834.PP
1835It should support all the same embedding options as \fIev.h\fR, most notably
1836\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1837.PP
1838Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1839.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1840.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1841.IX Item "ev::READ, ev::WRITE etc."
1842These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1843macros from \fIev.h\fR.
1844.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1845.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1846.IX Item "ev::tstamp, ev::now"
1847Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1848.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
1849.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1850.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1851For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1852the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1853which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1854defines by many implementations.
1855.Sp
1856All of those classes have these methods:
1857.RS 4
1858.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1859.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1860.PD 0
1861.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1862.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1863.IP "ev::TYPE::~TYPE" 4
1864.IX Item "ev::TYPE::~TYPE"
1865.PD
1866The constructor takes a pointer to an object and a method pointer to
1867the event handler callback to call in this class. The constructor calls
1868\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1869before starting it. If you do not specify a loop then the constructor
1870automatically associates the default loop with this watcher.
1871.Sp
1872The destructor automatically stops the watcher if it is active.
1873.IP "w\->set (struct ev_loop *)" 4
1874.IX Item "w->set (struct ev_loop *)"
1875Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1876do this when the watcher is inactive (and not pending either).
1877.IP "w\->set ([args])" 4
1878.IX Item "w->set ([args])"
1879Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1880called at least once. Unlike the C counterpart, an active watcher gets
1881automatically stopped and restarted.
1882.IP "w\->start ()" 4
1883.IX Item "w->start ()"
1884Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1885constructor already takes the loop.
1886.IP "w\->stop ()" 4
1887.IX Item "w->stop ()"
1888Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1889.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1890.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1891.IX Item "w->again () ev::timer, ev::periodic only"
1892For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1893\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1894.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1895.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1896.IX Item "w->sweep () ev::embed only"
1897Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1898.ie n .IP "w\->update () ""ev::stat"" only" 4
1899.el .IP "w\->update () \f(CWev::stat\fR only" 4
1900.IX Item "w->update () ev::stat only"
1901Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1902.RE
1903.RS 4
1904.RE
1905.PP
1906Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1907the constructor.
1908.PP
1909.Vb 4
1910\& class myclass
1911\& {
1912\& ev_io io; void io_cb (ev::io &w, int revents);
1913\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1914.Ve
1915.PP
1916.Vb 2
1917\& myclass ();
1918\& }
1919.Ve
1920.PP
1921.Vb 6
1922\& myclass::myclass (int fd)
1923\& : io (this, &myclass::io_cb),
1924\& idle (this, &myclass::idle_cb)
1925\& {
1926\& io.start (fd, ev::READ);
1927\& }
1928.Ve
1929.SH "MACRO MAGIC"
1930.IX Header "MACRO MAGIC"
1931Libev can be compiled with a variety of options, the most fundemantal is
1932\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
1933callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1934.PP
1935To make it easier to write programs that cope with either variant, the
1936following macros are defined:
1937.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
1938.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
1939.IX Item "EV_A, EV_A_"
1940This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
1941loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
1942\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
1943.Sp
1944.Vb 3
1945\& ev_unref (EV_A);
1946\& ev_timer_add (EV_A_ watcher);
1947\& ev_loop (EV_A_ 0);
1948.Ve
1949.Sp
1950It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
1951which is often provided by the following macro.
1952.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
1953.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
1954.IX Item "EV_P, EV_P_"
1955This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
1956loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
1957\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
1958.Sp
1959.Vb 2
1960\& // this is how ev_unref is being declared
1961\& static void ev_unref (EV_P);
1962.Ve
1963.Sp
1964.Vb 2
1965\& // this is how you can declare your typical callback
1966\& static void cb (EV_P_ ev_timer *w, int revents)
1967.Ve
1968.Sp
1969It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
1970suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
1971.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
1972.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
1973.IX Item "EV_DEFAULT, EV_DEFAULT_"
1974Similar to the other two macros, this gives you the value of the default
1975loop, if multiple loops are supported (\*(L"ev loop default\*(R").
1976.PP
1977Example: Declare and initialise a check watcher, working regardless of
1978wether multiple loops are supported or not.
1979.PP
1980.Vb 5
1981\& static void
1982\& check_cb (EV_P_ ev_timer *w, int revents)
1983\& {
1984\& ev_check_stop (EV_A_ w);
1985\& }
1986.Ve
1987.PP
1988.Vb 4
1989\& ev_check check;
1990\& ev_check_init (&check, check_cb);
1991\& ev_check_start (EV_DEFAULT_ &check);
1992\& ev_loop (EV_DEFAULT_ 0);
1993.Ve
1994.SH "EMBEDDING"
1995.IX Header "EMBEDDING"
1996Libev can (and often is) directly embedded into host
1997applications. Examples of applications that embed it include the Deliantra
1998Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1999and rxvt\-unicode.
2000.PP
2001The goal is to enable you to just copy the neecssary files into your
2002source directory without having to change even a single line in them, so
2003you can easily upgrade by simply copying (or having a checked-out copy of
2004libev somewhere in your source tree).
2005.Sh "\s-1FILESETS\s0"
2006.IX Subsection "FILESETS"
2007Depending on what features you need you need to include one or more sets of files
2008in your app.
2009.PP
2010\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2011.IX Subsection "CORE EVENT LOOP"
2012.PP
2013To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2014configuration (no autoconf):
2015.PP
2016.Vb 2
2017\& #define EV_STANDALONE 1
2018\& #include "ev.c"
2019.Ve
2020.PP
2021This will automatically include \fIev.h\fR, too, and should be done in a
2022single C source file only to provide the function implementations. To use
2023it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2024done by writing a wrapper around \fIev.h\fR that you can include instead and
2025where you can put other configuration options):
2026.PP
2027.Vb 2
2028\& #define EV_STANDALONE 1
2029\& #include "ev.h"
2030.Ve
2031.PP
2032Both header files and implementation files can be compiled with a \*(C+
2033compiler (at least, thats a stated goal, and breakage will be treated
2034as a bug).
2035.PP
2036You need the following files in your source tree, or in a directory
2037in your include path (e.g. in libev/ when using \-Ilibev):
2038.PP
2039.Vb 4
2040\& ev.h
2041\& ev.c
2042\& ev_vars.h
2043\& ev_wrap.h
2044.Ve
2045.PP
2046.Vb 1
2047\& ev_win32.c required on win32 platforms only
2048.Ve
2049.PP
2050.Vb 5
2051\& ev_select.c only when select backend is enabled (which is by default)
2052\& ev_poll.c only when poll backend is enabled (disabled by default)
2053\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2054\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2055\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2056.Ve
2057.PP
2058\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2059to compile this single file.
2060.PP
2061\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2062.IX Subsection "LIBEVENT COMPATIBILITY API"
2063.PP
2064To include the libevent compatibility \s-1API\s0, also include:
2065.PP
2066.Vb 1
2067\& #include "event.c"
2068.Ve
2069.PP
2070in the file including \fIev.c\fR, and:
2071.PP
2072.Vb 1
2073\& #include "event.h"
2074.Ve
2075.PP
2076in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2077.PP
2078You need the following additional files for this:
2079.PP
2080.Vb 2
2081\& event.h
2082\& event.c
2083.Ve
2084.PP
2085\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2086.IX Subsection "AUTOCONF SUPPORT"
2087.PP
2088Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2089whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2090\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2091include \fIconfig.h\fR and configure itself accordingly.
2092.PP
2093For this of course you need the m4 file:
2094.PP
2095.Vb 1
2096\& libev.m4
2097.Ve
2098.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2099.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2100Libev can be configured via a variety of preprocessor symbols you have to define
2101before including any of its files. The default is not to build for multiplicity
2102and only include the select backend.
2103.IP "\s-1EV_STANDALONE\s0" 4
2104.IX Item "EV_STANDALONE"
2105Must always be \f(CW1\fR if you do not use autoconf configuration, which
2106keeps libev from including \fIconfig.h\fR, and it also defines dummy
2107implementations for some libevent functions (such as logging, which is not
2108supported). It will also not define any of the structs usually found in
2109\&\fIevent.h\fR that are not directly supported by the libev core alone.
2110.IP "\s-1EV_USE_MONOTONIC\s0" 4
2111.IX Item "EV_USE_MONOTONIC"
2112If defined to be \f(CW1\fR, libev will try to detect the availability of the
2113monotonic clock option at both compiletime and runtime. Otherwise no use
2114of the monotonic clock option will be attempted. If you enable this, you
2115usually have to link against librt or something similar. Enabling it when
2116the functionality isn't available is safe, though, althoguh you have
2117to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2118function is hiding in (often \fI\-lrt\fR).
2119.IP "\s-1EV_USE_REALTIME\s0" 4
2120.IX Item "EV_USE_REALTIME"
2121If defined to be \f(CW1\fR, libev will try to detect the availability of the
2122realtime clock option at compiletime (and assume its availability at
2123runtime if successful). Otherwise no use of the realtime clock option will
2124be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2125(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2126in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2127.IP "\s-1EV_USE_SELECT\s0" 4
2128.IX Item "EV_USE_SELECT"
2129If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2130\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2131other method takes over, select will be it. Otherwise the select backend
2132will not be compiled in.
2133.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2134.IX Item "EV_SELECT_USE_FD_SET"
2135If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2136structure. This is useful if libev doesn't compile due to a missing
2137\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2138exotic systems. This usually limits the range of file descriptors to some
2139low limit such as 1024 or might have other limitations (winsocket only
2140allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2141influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2142.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2143.IX Item "EV_SELECT_IS_WINSOCKET"
2144When defined to \f(CW1\fR, the select backend will assume that
2145select/socket/connect etc. don't understand file descriptors but
2146wants osf handles on win32 (this is the case when the select to
2147be used is the winsock select). This means that it will call
2148\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2149it is assumed that all these functions actually work on fds, even
2150on win32. Should not be defined on non\-win32 platforms.
2151.IP "\s-1EV_USE_POLL\s0" 4
2152.IX Item "EV_USE_POLL"
2153If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2154backend. Otherwise it will be enabled on non\-win32 platforms. It
2155takes precedence over select.
2156.IP "\s-1EV_USE_EPOLL\s0" 4
2157.IX Item "EV_USE_EPOLL"
2158If defined to be \f(CW1\fR, libev will compile in support for the Linux
2159\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2160otherwise another method will be used as fallback. This is the
2161preferred backend for GNU/Linux systems.
2162.IP "\s-1EV_USE_KQUEUE\s0" 4
2163.IX Item "EV_USE_KQUEUE"
2164If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2165\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2166otherwise another method will be used as fallback. This is the preferred
2167backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2168supports some types of fds correctly (the only platform we found that
2169supports ptys for example was NetBSD), so kqueue might be compiled in, but
2170not be used unless explicitly requested. The best way to use it is to find
2171out whether kqueue supports your type of fd properly and use an embedded
2172kqueue loop.
2173.IP "\s-1EV_USE_PORT\s0" 4
2174.IX Item "EV_USE_PORT"
2175If defined to be \f(CW1\fR, libev will compile in support for the Solaris
217610 port style backend. Its availability will be detected at runtime,
2177otherwise another method will be used as fallback. This is the preferred
2178backend for Solaris 10 systems.
2179.IP "\s-1EV_USE_DEVPOLL\s0" 4
2180.IX Item "EV_USE_DEVPOLL"
2181reserved for future expansion, works like the \s-1USE\s0 symbols above.
2182.IP "\s-1EV_USE_INOTIFY\s0" 4
2183.IX Item "EV_USE_INOTIFY"
2184If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2185interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2186be detected at runtime.
2187.IP "\s-1EV_H\s0" 4
2188.IX Item "EV_H"
2189The name of the \fIev.h\fR header file used to include it. The default if
2190undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2191can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2192.IP "\s-1EV_CONFIG_H\s0" 4
2193.IX Item "EV_CONFIG_H"
2194If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2195\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2196\&\f(CW\*(C`EV_H\*(C'\fR, above.
2197.IP "\s-1EV_EVENT_H\s0" 4
2198.IX Item "EV_EVENT_H"
2199Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2200of how the \fIevent.h\fR header can be found.
2201.IP "\s-1EV_PROTOTYPES\s0" 4
2202.IX Item "EV_PROTOTYPES"
2203If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2204prototypes, but still define all the structs and other symbols. This is
2205occasionally useful if you want to provide your own wrapper functions
2206around libev functions.
2207.IP "\s-1EV_MULTIPLICITY\s0" 4
2208.IX Item "EV_MULTIPLICITY"
2209If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2210will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2211additional independent event loops. Otherwise there will be no support
2212for multiple event loops and there is no first event loop pointer
2213argument. Instead, all functions act on the single default loop.
2214.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2215.IX Item "EV_PERIODIC_ENABLE"
2216If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2217defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2218code.
2219.IP "\s-1EV_EMBED_ENABLE\s0" 4
2220.IX Item "EV_EMBED_ENABLE"
2221If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2222defined to be \f(CW0\fR, then they are not.
2223.IP "\s-1EV_STAT_ENABLE\s0" 4
2224.IX Item "EV_STAT_ENABLE"
2225If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2226defined to be \f(CW0\fR, then they are not.
2227.IP "\s-1EV_FORK_ENABLE\s0" 4
2228.IX Item "EV_FORK_ENABLE"
2229If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2230defined to be \f(CW0\fR, then they are not.
2231.IP "\s-1EV_MINIMAL\s0" 4
2232.IX Item "EV_MINIMAL"
2233If you need to shave off some kilobytes of code at the expense of some
2234speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2235some inlining decisions, saves roughly 30% codesize of amd64.
2236.IP "\s-1EV_PID_HASHSIZE\s0" 4
2237.IX Item "EV_PID_HASHSIZE"
2238\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2239pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2240than enough. If you need to manage thousands of children you might want to
2241increase this value (\fImust\fR be a power of two).
2242.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2243.IX Item "EV_INOTIFY_HASHSIZE"
2244\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2245inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2246usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2247watchers you might want to increase this value (\fImust\fR be a power of
2248two).
2249.IP "\s-1EV_COMMON\s0" 4
2250.IX Item "EV_COMMON"
2251By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2252this macro to a something else you can include more and other types of
2253members. You have to define it each time you include one of the files,
2254though, and it must be identical each time.
2255.Sp
2256For example, the perl \s-1EV\s0 module uses something like this:
2257.Sp
2258.Vb 3
2259\& #define EV_COMMON \e
2260\& SV *self; /* contains this struct */ \e
2261\& SV *cb_sv, *fh /* note no trailing ";" */
2262.Ve
2263.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2264.IX Item "EV_CB_DECLARE (type)"
2265.PD 0
2266.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2267.IX Item "EV_CB_INVOKE (watcher, revents)"
2268.IP "ev_set_cb (ev, cb)" 4
2269.IX Item "ev_set_cb (ev, cb)"
2270.PD
2271Can be used to change the callback member declaration in each watcher,
2272and the way callbacks are invoked and set. Must expand to a struct member
2273definition and a statement, respectively. See the \fIev.v\fR header file for
2274their default definitions. One possible use for overriding these is to
2275avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2276method calls instead of plain function calls in \*(C+.
2277.Sh "\s-1EXAMPLES\s0"
2278.IX Subsection "EXAMPLES"
2279For a real-world example of a program the includes libev
2280verbatim, you can have a look at the \s-1EV\s0 perl module
2281(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2282the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2283interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2284will be compiled. It is pretty complex because it provides its own header
2285file.
2286.Sp
2287The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2288that everybody includes and which overrides some autoconf choices:
2289.Sp
2290.Vb 4
2291\& #define EV_USE_POLL 0
2292\& #define EV_MULTIPLICITY 0
2293\& #define EV_PERIODICS 0
2294\& #define EV_CONFIG_H <config.h>
2295.Ve
2296.Sp
2297.Vb 1
2298\& #include "ev++.h"
2299.Ve
2300.Sp
2301And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2302.Sp
2303.Vb 2
2304\& #include "ev_cpp.h"
2305\& #include "ev.c"
2306.Ve
2307.SH "COMPLEXITIES"
2308.IX Header "COMPLEXITIES"
2309In this section the complexities of (many of) the algorithms used inside
2310libev will be explained. For complexity discussions about backends see the
2311documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2312.RS 4
2313.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2314.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2315.PD 0
2316.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2317.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2318.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2319.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2320.IP "Stopping check/prepare/idle watchers: O(1)" 4
2321.IX Item "Stopping check/prepare/idle watchers: O(1)"
2322.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2323.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2324.IP "Finding the next timer per loop iteration: O(1)" 4
2325.IX Item "Finding the next timer per loop iteration: O(1)"
2326.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2327.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2328.IP "Activating one watcher: O(1)" 4
2329.IX Item "Activating one watcher: O(1)"
2330.RE
2331.RS 4
2332.PD
1438.SH "AUTHOR" 2333.SH "AUTHOR"
1439.IX Header "AUTHOR" 2334.IX Header "AUTHOR"
1440Marc Lehmann <libev@schmorp.de>. 2335Marc Lehmann <libev@schmorp.de>.

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