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Revision 1.48 by root, Tue Nov 27 08:11:52 2007 UTC vs.
Revision 1.64 by root, Sat Dec 1 15:32:53 2007 UTC

3libev - a high performance full-featured event loop written in C 3libev - a high performance full-featured event loop written in C
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 #include <ev.h> 7 #include <ev.h>
8
9=head1 EXAMPLE PROGRAM
10
11 #include <ev.h>
12
13 ev_io stdin_watcher;
14 ev_timer timeout_watcher;
15
16 /* called when data readable on stdin */
17 static void
18 stdin_cb (EV_P_ struct ev_io *w, int revents)
19 {
20 /* puts ("stdin ready"); */
21 ev_io_stop (EV_A_ w); /* just a syntax example */
22 ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
23 }
24
25 static void
26 timeout_cb (EV_P_ struct ev_timer *w, int revents)
27 {
28 /* puts ("timeout"); */
29 ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
30 }
31
32 int
33 main (void)
34 {
35 struct ev_loop *loop = ev_default_loop (0);
36
37 /* initialise an io watcher, then start it */
38 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
39 ev_io_start (loop, &stdin_watcher);
40
41 /* simple non-repeating 5.5 second timeout */
42 ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
43 ev_timer_start (loop, &timeout_watcher);
44
45 /* loop till timeout or data ready */
46 ev_loop (loop, 0);
47
48 return 0;
49 }
8 50
9=head1 DESCRIPTION 51=head1 DESCRIPTION
10 52
11Libev is an event loop: you register interest in certain events (such as a 53Libev is an event loop: you register interest in certain events (such as a
12file descriptor being readable or a timeout occuring), and it will manage 54file descriptor being readable or a timeout occuring), and it will manage
21details of the event, and then hand it over to libev by I<starting> the 63details of the event, and then hand it over to libev by I<starting> the
22watcher. 64watcher.
23 65
24=head1 FEATURES 66=head1 FEATURES
25 67
26Libev supports select, poll, the linux-specific epoll and the bsd-specific 68Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
27kqueue mechanisms for file descriptor events, relative timers, absolute 69BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
28timers with customised rescheduling, signal events, process status change 70for file descriptor events (C<ev_io>), the Linux C<inotify> interface
29events (related to SIGCHLD), and event watchers dealing with the event 71(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
30loop mechanism itself (idle, prepare and check watchers). It also is quite 72with customised rescheduling (C<ev_periodic>), synchronous signals
73(C<ev_signal>), process status change events (C<ev_child>), and event
74watchers dealing with the event loop mechanism itself (C<ev_idle>,
75C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
76file watchers (C<ev_stat>) and even limited support for fork events
77(C<ev_fork>).
78
79It also is quite fast (see this
31fast (see this L<benchmark|http://libev.schmorp.de/bench.html> comparing 80L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
32it to libevent for example). 81for example).
33 82
34=head1 CONVENTIONS 83=head1 CONVENTIONS
35 84
36Libev is very configurable. In this manual the default configuration 85Libev is very configurable. In this manual the default configuration will
37will be described, which supports multiple event loops. For more info 86be described, which supports multiple event loops. For more info about
38about various configuration options please have a look at the file 87various configuration options please have a look at B<EMBED> section in
39F<README.embed> in the libev distribution. If libev was configured without 88this manual. If libev was configured without support for multiple event
40support for multiple event loops, then all functions taking an initial 89loops, then all functions taking an initial argument of name C<loop>
41argument of name C<loop> (which is always of type C<struct ev_loop *>) 90(which is always of type C<struct ev_loop *>) will not have this argument.
42will not have this argument.
43 91
44=head1 TIME REPRESENTATION 92=head1 TIME REPRESENTATION
45 93
46Libev represents time as a single floating point number, representing the 94Libev represents time as a single floating point number, representing the
47(fractional) number of seconds since the (POSIX) epoch (somewhere near 95(fractional) number of seconds since the (POSIX) epoch (somewhere near
48the beginning of 1970, details are complicated, don't ask). This type is 96the beginning of 1970, details are complicated, don't ask). This type is
49called C<ev_tstamp>, which is what you should use too. It usually aliases 97called C<ev_tstamp>, which is what you should use too. It usually aliases
50to the C<double> type in C, and when you need to do any calculations on 98to the C<double> type in C, and when you need to do any calculations on
51it, you should treat it as such. 99it, you should treat it as such.
52 100
53
54=head1 GLOBAL FUNCTIONS 101=head1 GLOBAL FUNCTIONS
55 102
56These functions can be called anytime, even before initialising the 103These functions can be called anytime, even before initialising the
57library in any way. 104library in any way.
58 105
77Usually, it's a good idea to terminate if the major versions mismatch, 124Usually, it's a good idea to terminate if the major versions mismatch,
78as this indicates an incompatible change. Minor versions are usually 125as this indicates an incompatible change. Minor versions are usually
79compatible to older versions, so a larger minor version alone is usually 126compatible to older versions, so a larger minor version alone is usually
80not a problem. 127not a problem.
81 128
82Example: make sure we haven't accidentally been linked against the wrong 129Example: Make sure we haven't accidentally been linked against the wrong
83version: 130version.
84 131
85 assert (("libev version mismatch", 132 assert (("libev version mismatch",
86 ev_version_major () == EV_VERSION_MAJOR 133 ev_version_major () == EV_VERSION_MAJOR
87 && ev_version_minor () >= EV_VERSION_MINOR)); 134 && ev_version_minor () >= EV_VERSION_MINOR));
88 135
118 165
119See the description of C<ev_embed> watchers for more info. 166See the description of C<ev_embed> watchers for more info.
120 167
121=item ev_set_allocator (void *(*cb)(void *ptr, long size)) 168=item ev_set_allocator (void *(*cb)(void *ptr, long size))
122 169
123Sets the allocation function to use (the prototype is similar to the 170Sets the allocation function to use (the prototype is similar - the
124realloc C function, the semantics are identical). It is used to allocate 171semantics is identical - to the realloc C function). It is used to
125and free memory (no surprises here). If it returns zero when memory 172allocate and free memory (no surprises here). If it returns zero when
126needs to be allocated, the library might abort or take some potentially 173memory needs to be allocated, the library might abort or take some
127destructive action. The default is your system realloc function. 174potentially destructive action. The default is your system realloc
175function.
128 176
129You could override this function in high-availability programs to, say, 177You could override this function in high-availability programs to, say,
130free some memory if it cannot allocate memory, to use a special allocator, 178free some memory if it cannot allocate memory, to use a special allocator,
131or even to sleep a while and retry until some memory is available. 179or even to sleep a while and retry until some memory is available.
132 180
133Example: replace the libev allocator with one that waits a bit and then 181Example: Replace the libev allocator with one that waits a bit and then
134retries: better than mine). 182retries).
135 183
136 static void * 184 static void *
137 persistent_realloc (void *ptr, long size) 185 persistent_realloc (void *ptr, size_t size)
138 { 186 {
139 for (;;) 187 for (;;)
140 { 188 {
141 void *newptr = realloc (ptr, size); 189 void *newptr = realloc (ptr, size);
142 190
158callback is set, then libev will expect it to remedy the sitution, no 206callback is set, then libev will expect it to remedy the sitution, no
159matter what, when it returns. That is, libev will generally retry the 207matter what, when it returns. That is, libev will generally retry the
160requested operation, or, if the condition doesn't go away, do bad stuff 208requested operation, or, if the condition doesn't go away, do bad stuff
161(such as abort). 209(such as abort).
162 210
163Example: do the same thing as libev does internally: 211Example: This is basically the same thing that libev does internally, too.
164 212
165 static void 213 static void
166 fatal_error (const char *msg) 214 fatal_error (const char *msg)
167 { 215 {
168 perror (msg); 216 perror (msg);
218C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will 266C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
219override the flags completely if it is found in the environment. This is 267override the flags completely if it is found in the environment. This is
220useful to try out specific backends to test their performance, or to work 268useful to try out specific backends to test their performance, or to work
221around bugs. 269around bugs.
222 270
271=item C<EVFLAG_FORKCHECK>
272
273Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
274a fork, you can also make libev check for a fork in each iteration by
275enabling this flag.
276
277This works by calling C<getpid ()> on every iteration of the loop,
278and thus this might slow down your event loop if you do a lot of loop
279iterations and little real work, but is usually not noticable (on my
280Linux system for example, C<getpid> is actually a simple 5-insn sequence
281without a syscall and thus I<very> fast, but my Linux system also has
282C<pthread_atfork> which is even faster).
283
284The big advantage of this flag is that you can forget about fork (and
285forget about forgetting to tell libev about forking) when you use this
286flag.
287
288This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
289environment variable.
290
223=item C<EVBACKEND_SELECT> (value 1, portable select backend) 291=item C<EVBACKEND_SELECT> (value 1, portable select backend)
224 292
225This is your standard select(2) backend. Not I<completely> standard, as 293This is your standard select(2) backend. Not I<completely> standard, as
226libev tries to roll its own fd_set with no limits on the number of fds, 294libev tries to roll its own fd_set with no limits on the number of fds,
227but if that fails, expect a fairly low limit on the number of fds when 295but if that fails, expect a fairly low limit on the number of fds when
314Similar to C<ev_default_loop>, but always creates a new event loop that is 382Similar to C<ev_default_loop>, but always creates a new event loop that is
315always distinct from the default loop. Unlike the default loop, it cannot 383always distinct from the default loop. Unlike the default loop, it cannot
316handle signal and child watchers, and attempts to do so will be greeted by 384handle signal and child watchers, and attempts to do so will be greeted by
317undefined behaviour (or a failed assertion if assertions are enabled). 385undefined behaviour (or a failed assertion if assertions are enabled).
318 386
319Example: try to create a event loop that uses epoll and nothing else. 387Example: Try to create a event loop that uses epoll and nothing else.
320 388
321 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 389 struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
322 if (!epoller) 390 if (!epoller)
323 fatal ("no epoll found here, maybe it hides under your chair"); 391 fatal ("no epoll found here, maybe it hides under your chair");
324 392
423 Signals and child watchers are implemented as I/O watchers, and will 491 Signals and child watchers are implemented as I/O watchers, and will
424 be handled here by queueing them when their watcher gets executed. 492 be handled here by queueing them when their watcher gets executed.
425 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 493 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
426 were used, return, otherwise continue with step *. 494 were used, return, otherwise continue with step *.
427 495
428Example: queue some jobs and then loop until no events are outsanding 496Example: Queue some jobs and then loop until no events are outsanding
429anymore. 497anymore.
430 498
431 ... queue jobs here, make sure they register event watchers as long 499 ... queue jobs here, make sure they register event watchers as long
432 ... as they still have work to do (even an idle watcher will do..) 500 ... as they still have work to do (even an idle watcher will do..)
433 ev_loop (my_loop, 0); 501 ev_loop (my_loop, 0);
453visible to the libev user and should not keep C<ev_loop> from exiting if 521visible to the libev user and should not keep C<ev_loop> from exiting if
454no event watchers registered by it are active. It is also an excellent 522no event watchers registered by it are active. It is also an excellent
455way to do this for generic recurring timers or from within third-party 523way to do this for generic recurring timers or from within third-party
456libraries. Just remember to I<unref after start> and I<ref before stop>. 524libraries. Just remember to I<unref after start> and I<ref before stop>.
457 525
458Example: create a signal watcher, but keep it from keeping C<ev_loop> 526Example: Create a signal watcher, but keep it from keeping C<ev_loop>
459running when nothing else is active. 527running when nothing else is active.
460 528
461 struct dv_signal exitsig; 529 struct ev_signal exitsig;
462 ev_signal_init (&exitsig, sig_cb, SIGINT); 530 ev_signal_init (&exitsig, sig_cb, SIGINT);
463 ev_signal_start (myloop, &exitsig); 531 ev_signal_start (loop, &exitsig);
464 evf_unref (myloop); 532 evf_unref (loop);
465 533
466Example: for some weird reason, unregister the above signal handler again. 534Example: For some weird reason, unregister the above signal handler again.
467 535
468 ev_ref (myloop); 536 ev_ref (loop);
469 ev_signal_stop (myloop, &exitsig); 537 ev_signal_stop (loop, &exitsig);
470 538
471=back 539=back
472 540
473 541
474=head1 ANATOMY OF A WATCHER 542=head1 ANATOMY OF A WATCHER
565received events. Callbacks of both watcher types can start and stop as 633received events. Callbacks of both watcher types can start and stop as
566many watchers as they want, and all of them will be taken into account 634many watchers as they want, and all of them will be taken into account
567(for example, a C<ev_prepare> watcher might start an idle watcher to keep 635(for example, a C<ev_prepare> watcher might start an idle watcher to keep
568C<ev_loop> from blocking). 636C<ev_loop> from blocking).
569 637
638=item C<EV_EMBED>
639
640The embedded event loop specified in the C<ev_embed> watcher needs attention.
641
642=item C<EV_FORK>
643
644The event loop has been resumed in the child process after fork (see
645C<ev_fork>).
646
570=item C<EV_ERROR> 647=item C<EV_ERROR>
571 648
572An unspecified error has occured, the watcher has been stopped. This might 649An unspecified error has occured, the watcher has been stopped. This might
573happen because the watcher could not be properly started because libev 650happen because the watcher could not be properly started because libev
574ran out of memory, a file descriptor was found to be closed or any other 651ran out of memory, a file descriptor was found to be closed or any other
648events but its callback has not yet been invoked). As long as a watcher 725events but its callback has not yet been invoked). As long as a watcher
649is pending (but not active) you must not call an init function on it (but 726is pending (but not active) you must not call an init function on it (but
650C<ev_TYPE_set> is safe) and you must make sure the watcher is available to 727C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
651libev (e.g. you cnanot C<free ()> it). 728libev (e.g. you cnanot C<free ()> it).
652 729
653=item callback = ev_cb (ev_TYPE *watcher) 730=item callback ev_cb (ev_TYPE *watcher)
654 731
655Returns the callback currently set on the watcher. 732Returns the callback currently set on the watcher.
656 733
657=item ev_cb_set (ev_TYPE *watcher, callback) 734=item ev_cb_set (ev_TYPE *watcher, callback)
658 735
686 { 763 {
687 struct my_io *w = (struct my_io *)w_; 764 struct my_io *w = (struct my_io *)w_;
688 ... 765 ...
689 } 766 }
690 767
691More interesting and less C-conformant ways of catsing your callback type 768More interesting and less C-conformant ways of casting your callback type
692have been omitted.... 769instead have been omitted.
770
771Another common scenario is having some data structure with multiple
772watchers:
773
774 struct my_biggy
775 {
776 int some_data;
777 ev_timer t1;
778 ev_timer t2;
779 }
780
781In this case getting the pointer to C<my_biggy> is a bit more complicated,
782you need to use C<offsetof>:
783
784 #include <stddef.h>
785
786 static void
787 t1_cb (EV_P_ struct ev_timer *w, int revents)
788 {
789 struct my_biggy big = (struct my_biggy *
790 (((char *)w) - offsetof (struct my_biggy, t1));
791 }
792
793 static void
794 t2_cb (EV_P_ struct ev_timer *w, int revents)
795 {
796 struct my_biggy big = (struct my_biggy *
797 (((char *)w) - offsetof (struct my_biggy, t2));
798 }
693 799
694 800
695=head1 WATCHER TYPES 801=head1 WATCHER TYPES
696 802
697This section describes each watcher in detail, but will not repeat 803This section describes each watcher in detail, but will not repeat
766 872
767The events being watched. 873The events being watched.
768 874
769=back 875=back
770 876
771Example: call C<stdin_readable_cb> when STDIN_FILENO has become, well 877Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
772readable, but only once. Since it is likely line-buffered, you could 878readable, but only once. Since it is likely line-buffered, you could
773attempt to read a whole line in the callback: 879attempt to read a whole line in the callback.
774 880
775 static void 881 static void
776 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 882 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
777 { 883 {
778 ev_io_stop (loop, w); 884 ev_io_stop (loop, w);
830=item ev_timer_again (loop) 936=item ev_timer_again (loop)
831 937
832This will act as if the timer timed out and restart it again if it is 938This will act as if the timer timed out and restart it again if it is
833repeating. The exact semantics are: 939repeating. The exact semantics are:
834 940
941If the timer is pending, its pending status is cleared.
942
835If the timer is started but nonrepeating, stop it. 943If the timer is started but nonrepeating, stop it (as if it timed out).
836 944
837If the timer is repeating, either start it if necessary (with the repeat 945If the timer is repeating, either start it if necessary (with the
838value), or reset the running timer to the repeat value. 946C<repeat> value), or reset the running timer to the C<repeat> value.
839 947
840This sounds a bit complicated, but here is a useful and typical 948This sounds a bit complicated, but here is a useful and typical
841example: Imagine you have a tcp connection and you want a so-called 949example: Imagine you have a tcp connection and you want a so-called idle
842idle timeout, that is, you want to be called when there have been, 950timeout, that is, you want to be called when there have been, say, 60
843say, 60 seconds of inactivity on the socket. The easiest way to do 951seconds of inactivity on the socket. The easiest way to do this is to
844this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling 952configure an C<ev_timer> with a C<repeat> value of C<60> and then call
845C<ev_timer_again> each time you successfully read or write some data. If 953C<ev_timer_again> each time you successfully read or write some data. If
846you go into an idle state where you do not expect data to travel on the 954you go into an idle state where you do not expect data to travel on the
847socket, you can stop the timer, and again will automatically restart it if 955socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
848need be. 956automatically restart it if need be.
849 957
850You can also ignore the C<after> value and C<ev_timer_start> altogether 958That means you can ignore the C<after> value and C<ev_timer_start>
851and only ever use the C<repeat> value: 959altogether and only ever use the C<repeat> value and C<ev_timer_again>:
852 960
853 ev_timer_init (timer, callback, 0., 5.); 961 ev_timer_init (timer, callback, 0., 5.);
854 ev_timer_again (loop, timer); 962 ev_timer_again (loop, timer);
855 ... 963 ...
856 timer->again = 17.; 964 timer->again = 17.;
857 ev_timer_again (loop, timer); 965 ev_timer_again (loop, timer);
858 ... 966 ...
859 timer->again = 10.; 967 timer->again = 10.;
860 ev_timer_again (loop, timer); 968 ev_timer_again (loop, timer);
861 969
862This is more efficient then stopping/starting the timer eahc time you want 970This is more slightly efficient then stopping/starting the timer each time
863to modify its timeout value. 971you want to modify its timeout value.
864 972
865=item ev_tstamp repeat [read-write] 973=item ev_tstamp repeat [read-write]
866 974
867The current C<repeat> value. Will be used each time the watcher times out 975The current C<repeat> value. Will be used each time the watcher times out
868or C<ev_timer_again> is called and determines the next timeout (if any), 976or C<ev_timer_again> is called and determines the next timeout (if any),
869which is also when any modifications are taken into account. 977which is also when any modifications are taken into account.
870 978
871=back 979=back
872 980
873Example: create a timer that fires after 60 seconds. 981Example: Create a timer that fires after 60 seconds.
874 982
875 static void 983 static void
876 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 984 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
877 { 985 {
878 .. one minute over, w is actually stopped right here 986 .. one minute over, w is actually stopped right here
880 988
881 struct ev_timer mytimer; 989 struct ev_timer mytimer;
882 ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 990 ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
883 ev_timer_start (loop, &mytimer); 991 ev_timer_start (loop, &mytimer);
884 992
885Example: create a timeout timer that times out after 10 seconds of 993Example: Create a timeout timer that times out after 10 seconds of
886inactivity. 994inactivity.
887 995
888 static void 996 static void
889 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 997 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
890 { 998 {
1015switched off. Can be changed any time, but changes only take effect when 1123switched off. Can be changed any time, but changes only take effect when
1016the periodic timer fires or C<ev_periodic_again> is being called. 1124the periodic timer fires or C<ev_periodic_again> is being called.
1017 1125
1018=back 1126=back
1019 1127
1020Example: call a callback every hour, or, more precisely, whenever the 1128Example: Call a callback every hour, or, more precisely, whenever the
1021system clock is divisible by 3600. The callback invocation times have 1129system clock is divisible by 3600. The callback invocation times have
1022potentially a lot of jittering, but good long-term stability. 1130potentially a lot of jittering, but good long-term stability.
1023 1131
1024 static void 1132 static void
1025 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1133 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1029 1137
1030 struct ev_periodic hourly_tick; 1138 struct ev_periodic hourly_tick;
1031 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1139 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1032 ev_periodic_start (loop, &hourly_tick); 1140 ev_periodic_start (loop, &hourly_tick);
1033 1141
1034Example: the same as above, but use a reschedule callback to do it: 1142Example: The same as above, but use a reschedule callback to do it:
1035 1143
1036 #include <math.h> 1144 #include <math.h>
1037 1145
1038 static ev_tstamp 1146 static ev_tstamp
1039 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1147 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1041 return fmod (now, 3600.) + 3600.; 1149 return fmod (now, 3600.) + 3600.;
1042 } 1150 }
1043 1151
1044 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1152 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1045 1153
1046Example: call a callback every hour, starting now: 1154Example: Call a callback every hour, starting now:
1047 1155
1048 struct ev_periodic hourly_tick; 1156 struct ev_periodic hourly_tick;
1049 ev_periodic_init (&hourly_tick, clock_cb, 1157 ev_periodic_init (&hourly_tick, clock_cb,
1050 fmod (ev_now (loop), 3600.), 3600., 0); 1158 fmod (ev_now (loop), 3600.), 3600., 0);
1051 ev_periodic_start (loop, &hourly_tick); 1159 ev_periodic_start (loop, &hourly_tick);
1112The process exit/trace status caused by C<rpid> (see your systems 1220The process exit/trace status caused by C<rpid> (see your systems
1113C<waitpid> and C<sys/wait.h> documentation for details). 1221C<waitpid> and C<sys/wait.h> documentation for details).
1114 1222
1115=back 1223=back
1116 1224
1117Example: try to exit cleanly on SIGINT and SIGTERM. 1225Example: Try to exit cleanly on SIGINT and SIGTERM.
1118 1226
1119 static void 1227 static void
1120 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1228 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1121 { 1229 {
1122 ev_unloop (loop, EVUNLOOP_ALL); 1230 ev_unloop (loop, EVUNLOOP_ALL);
1137not exist" is a status change like any other. The condition "path does 1245not exist" is a status change like any other. The condition "path does
1138not exist" is signified by the C<st_nlink> field being zero (which is 1246not exist" is signified by the C<st_nlink> field being zero (which is
1139otherwise always forced to be at least one) and all the other fields of 1247otherwise always forced to be at least one) and all the other fields of
1140the stat buffer having unspecified contents. 1248the stat buffer having unspecified contents.
1141 1249
1250The path I<should> be absolute and I<must not> end in a slash. If it is
1251relative and your working directory changes, the behaviour is undefined.
1252
1142Since there is no standard to do this, the portable implementation simply 1253Since there is no standard to do this, the portable implementation simply
1143calls C<stat (2)> regulalry on the path to see if it changed somehow. You 1254calls C<stat (2)> regularly on the path to see if it changed somehow. You
1144can specify a recommended polling interval for this case. If you specify 1255can specify a recommended polling interval for this case. If you specify
1145a polling interval of C<0> (highly recommended!) then a I<suitable, 1256a polling interval of C<0> (highly recommended!) then a I<suitable,
1146unspecified default> value will be used (which you can expect to be around 1257unspecified default> value will be used (which you can expect to be around
1147five seconds, although this might change dynamically). Libev will also 1258five seconds, although this might change dynamically). Libev will also
1148impose a minimum interval which is currently around C<0.1>, but thats 1259impose a minimum interval which is currently around C<0.1>, but thats
1150 1261
1151This watcher type is not meant for massive numbers of stat watchers, 1262This watcher type is not meant for massive numbers of stat watchers,
1152as even with OS-supported change notifications, this can be 1263as even with OS-supported change notifications, this can be
1153resource-intensive. 1264resource-intensive.
1154 1265
1155At the time of this writing, no specific OS backends are implemented, but 1266At the time of this writing, only the Linux inotify interface is
1156if demand increases, at least a kqueue and inotify backend will be added. 1267implemented (implementing kqueue support is left as an exercise for the
1268reader). Inotify will be used to give hints only and should not change the
1269semantics of C<ev_stat> watchers, which means that libev sometimes needs
1270to fall back to regular polling again even with inotify, but changes are
1271usually detected immediately, and if the file exists there will be no
1272polling.
1157 1273
1158=over 4 1274=over 4
1159 1275
1160=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1276=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1161 1277
1251kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1367kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1252believe me. 1368believe me.
1253 1369
1254=back 1370=back
1255 1371
1256Example: dynamically allocate an C<ev_idle>, start it, and in the 1372Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1257callback, free it. Alos, use no error checking, as usual. 1373callback, free it. Also, use no error checking, as usual.
1258 1374
1259 static void 1375 static void
1260 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1376 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1261 { 1377 {
1262 free (w); 1378 free (w);
1341 1457
1342 // create io watchers for each fd and a timer before blocking 1458 // create io watchers for each fd and a timer before blocking
1343 static void 1459 static void
1344 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1460 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1345 { 1461 {
1346 int timeout = 3600000;truct pollfd fds [nfd]; 1462 int timeout = 3600000;
1463 struct pollfd fds [nfd];
1347 // actual code will need to loop here and realloc etc. 1464 // actual code will need to loop here and realloc etc.
1348 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 1465 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1349 1466
1350 /* the callback is illegal, but won't be called as we stop during check */ 1467 /* the callback is illegal, but won't be called as we stop during check */
1351 ev_timer_init (&tw, 0, timeout * 1e-3); 1468 ev_timer_init (&tw, 0, timeout * 1e-3);
1470The embedded event loop. 1587The embedded event loop.
1471 1588
1472=back 1589=back
1473 1590
1474 1591
1592=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1593
1594Fork watchers are called when a C<fork ()> was detected (usually because
1595whoever is a good citizen cared to tell libev about it by calling
1596C<ev_default_fork> or C<ev_loop_fork>). The invocation is done before the
1597event loop blocks next and before C<ev_check> watchers are being called,
1598and only in the child after the fork. If whoever good citizen calling
1599C<ev_default_fork> cheats and calls it in the wrong process, the fork
1600handlers will be invoked, too, of course.
1601
1602=over 4
1603
1604=item ev_fork_init (ev_signal *, callback)
1605
1606Initialises and configures the fork watcher - it has no parameters of any
1607kind. There is a C<ev_fork_set> macro, but using it is utterly pointless,
1608believe me.
1609
1610=back
1611
1612
1475=head1 OTHER FUNCTIONS 1613=head1 OTHER FUNCTIONS
1476 1614
1477There are some other functions of possible interest. Described. Here. Now. 1615There are some other functions of possible interest. Described. Here. Now.
1478 1616
1479=over 4 1617=over 4
1638 1776
1639=item w->sweep () C<ev::embed> only 1777=item w->sweep () C<ev::embed> only
1640 1778
1641Invokes C<ev_embed_sweep>. 1779Invokes C<ev_embed_sweep>.
1642 1780
1781=item w->update () C<ev::stat> only
1782
1783Invokes C<ev_stat_stat>.
1784
1643=back 1785=back
1644 1786
1645=back 1787=back
1646 1788
1647Example: Define a class with an IO and idle watcher, start one of them in 1789Example: Define a class with an IO and idle watcher, start one of them in
1659 : io (this, &myclass::io_cb), 1801 : io (this, &myclass::io_cb),
1660 idle (this, &myclass::idle_cb) 1802 idle (this, &myclass::idle_cb)
1661 { 1803 {
1662 io.start (fd, ev::READ); 1804 io.start (fd, ev::READ);
1663 } 1805 }
1806
1807
1808=head1 MACRO MAGIC
1809
1810Libev can be compiled with a variety of options, the most fundemantal is
1811C<EV_MULTIPLICITY>. This option determines wether (most) functions and
1812callbacks have an initial C<struct ev_loop *> argument.
1813
1814To make it easier to write programs that cope with either variant, the
1815following macros are defined:
1816
1817=over 4
1818
1819=item C<EV_A>, C<EV_A_>
1820
1821This provides the loop I<argument> for functions, if one is required ("ev
1822loop argument"). The C<EV_A> form is used when this is the sole argument,
1823C<EV_A_> is used when other arguments are following. Example:
1824
1825 ev_unref (EV_A);
1826 ev_timer_add (EV_A_ watcher);
1827 ev_loop (EV_A_ 0);
1828
1829It assumes the variable C<loop> of type C<struct ev_loop *> is in scope,
1830which is often provided by the following macro.
1831
1832=item C<EV_P>, C<EV_P_>
1833
1834This provides the loop I<parameter> for functions, if one is required ("ev
1835loop parameter"). The C<EV_P> form is used when this is the sole parameter,
1836C<EV_P_> is used when other parameters are following. Example:
1837
1838 // this is how ev_unref is being declared
1839 static void ev_unref (EV_P);
1840
1841 // this is how you can declare your typical callback
1842 static void cb (EV_P_ ev_timer *w, int revents)
1843
1844It declares a parameter C<loop> of type C<struct ev_loop *>, quite
1845suitable for use with C<EV_A>.
1846
1847=item C<EV_DEFAULT>, C<EV_DEFAULT_>
1848
1849Similar to the other two macros, this gives you the value of the default
1850loop, if multiple loops are supported ("ev loop default").
1851
1852=back
1853
1854Example: Declare and initialise a check watcher, utilising the above
1855macros so it will work regardless of wether multiple loops are supported
1856or not.
1857
1858 static void
1859 check_cb (EV_P_ ev_timer *w, int revents)
1860 {
1861 ev_check_stop (EV_A_ w);
1862 }
1863
1864 ev_check check;
1865 ev_check_init (&check, check_cb);
1866 ev_check_start (EV_DEFAULT_ &check);
1867 ev_loop (EV_DEFAULT_ 0);
1664 1868
1665=head1 EMBEDDING 1869=head1 EMBEDDING
1666 1870
1667Libev can (and often is) directly embedded into host 1871Libev can (and often is) directly embedded into host
1668applications. Examples of applications that embed it include the Deliantra 1872applications. Examples of applications that embed it include the Deliantra
1708 ev_vars.h 1912 ev_vars.h
1709 ev_wrap.h 1913 ev_wrap.h
1710 1914
1711 ev_win32.c required on win32 platforms only 1915 ev_win32.c required on win32 platforms only
1712 1916
1713 ev_select.c only when select backend is enabled (which is by default) 1917 ev_select.c only when select backend is enabled (which is enabled by default)
1714 ev_poll.c only when poll backend is enabled (disabled by default) 1918 ev_poll.c only when poll backend is enabled (disabled by default)
1715 ev_epoll.c only when the epoll backend is enabled (disabled by default) 1919 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1716 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 1920 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1717 ev_port.c only when the solaris port backend is enabled (disabled by default) 1921 ev_port.c only when the solaris port backend is enabled (disabled by default)
1718 1922
1843 2047
1844=item EV_USE_DEVPOLL 2048=item EV_USE_DEVPOLL
1845 2049
1846reserved for future expansion, works like the USE symbols above. 2050reserved for future expansion, works like the USE symbols above.
1847 2051
2052=item EV_USE_INOTIFY
2053
2054If defined to be C<1>, libev will compile in support for the Linux inotify
2055interface to speed up C<ev_stat> watchers. Its actual availability will
2056be detected at runtime.
2057
1848=item EV_H 2058=item EV_H
1849 2059
1850The name of the F<ev.h> header file used to include it. The default if 2060The name of the F<ev.h> header file used to include it. The default if
1851undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2061undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1852can be used to virtually rename the F<ev.h> header file in case of conflicts. 2062can be used to virtually rename the F<ev.h> header file in case of conflicts.
1891=item EV_STAT_ENABLE 2101=item EV_STAT_ENABLE
1892 2102
1893If undefined or defined to be C<1>, then stat watchers are supported. If 2103If undefined or defined to be C<1>, then stat watchers are supported. If
1894defined to be C<0>, then they are not. 2104defined to be C<0>, then they are not.
1895 2105
2106=item EV_FORK_ENABLE
2107
2108If undefined or defined to be C<1>, then fork watchers are supported. If
2109defined to be C<0>, then they are not.
2110
1896=item EV_MINIMAL 2111=item EV_MINIMAL
1897 2112
1898If you need to shave off some kilobytes of code at the expense of some 2113If you need to shave off some kilobytes of code at the expense of some
1899speed, define this symbol to C<1>. Currently only used for gcc to override 2114speed, define this symbol to C<1>. Currently only used for gcc to override
1900some inlining decisions, saves roughly 30% codesize of amd64. 2115some inlining decisions, saves roughly 30% codesize of amd64.
2116
2117=item EV_PID_HASHSIZE
2118
2119C<ev_child> watchers use a small hash table to distribute workload by
2120pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2121than enough. If you need to manage thousands of children you might want to
2122increase this value (I<must> be a power of two).
2123
2124=item EV_INOTIFY_HASHSIZE
2125
2126C<ev_staz> watchers use a small hash table to distribute workload by
2127inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2128usually more than enough. If you need to manage thousands of C<ev_stat>
2129watchers you might want to increase this value (I<must> be a power of
2130two).
1901 2131
1902=item EV_COMMON 2132=item EV_COMMON
1903 2133
1904By default, all watchers have a C<void *data> member. By redefining 2134By default, all watchers have a C<void *data> member. By redefining
1905this macro to a something else you can include more and other types of 2135this macro to a something else you can include more and other types of
1934interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file 2164interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
1935will be compiled. It is pretty complex because it provides its own header 2165will be compiled. It is pretty complex because it provides its own header
1936file. 2166file.
1937 2167
1938The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 2168The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
1939that everybody includes and which overrides some autoconf choices: 2169that everybody includes and which overrides some configure choices:
1940 2170
2171 #define EV_MINIMAL 1
1941 #define EV_USE_POLL 0 2172 #define EV_USE_POLL 0
1942 #define EV_MULTIPLICITY 0 2173 #define EV_MULTIPLICITY 0
1943 #define EV_PERIODICS 0 2174 #define EV_PERIODIC_ENABLE 0
2175 #define EV_STAT_ENABLE 0
2176 #define EV_FORK_ENABLE 0
1944 #define EV_CONFIG_H <config.h> 2177 #define EV_CONFIG_H <config.h>
2178 #define EV_MINPRI 0
2179 #define EV_MAXPRI 0
1945 2180
1946 #include "ev++.h" 2181 #include "ev++.h"
1947 2182
1948And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 2183And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
1949 2184
1965 2200
1966=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2201=item Starting io/check/prepare/idle/signal/child watchers: O(1)
1967 2202
1968=item Stopping check/prepare/idle watchers: O(1) 2203=item Stopping check/prepare/idle watchers: O(1)
1969 2204
1970=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16)) 2205=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
1971 2206
1972=item Finding the next timer per loop iteration: O(1) 2207=item Finding the next timer per loop iteration: O(1)
1973 2208
1974=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2209=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
1975 2210

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