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47 47
48 return 0; 48 return 0;
49 } 49 }
50 50
51=head1 DESCRIPTION 51=head1 DESCRIPTION
52
53The newest version of this document is also available as a html-formatted
54web page you might find easier to navigate when reading it for the first
55time: L<http://cvs.schmorp.de/libev/ev.html>.
52 56
53Libev is an event loop: you register interest in certain events (such as a 57Libev is an event loop: you register interest in certain events (such as a
54file descriptor being readable or a timeout occuring), and it will manage 58file descriptor being readable or a timeout occuring), and it will manage
55these event sources and provide your program with events. 59these event sources and provide your program with events.
56 60
113 117
114=item int ev_version_major () 118=item int ev_version_major ()
115 119
116=item int ev_version_minor () 120=item int ev_version_minor ()
117 121
118You can find out the major and minor version numbers of the library 122You can find out the major and minor ABI version numbers of the library
119you linked against by calling the functions C<ev_version_major> and 123you linked against by calling the functions C<ev_version_major> and
120C<ev_version_minor>. If you want, you can compare against the global 124C<ev_version_minor>. If you want, you can compare against the global
121symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 125symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
122version of the library your program was compiled against. 126version of the library your program was compiled against.
123 127
128These version numbers refer to the ABI version of the library, not the
129release version.
130
124Usually, it's a good idea to terminate if the major versions mismatch, 131Usually, it's a good idea to terminate if the major versions mismatch,
125as this indicates an incompatible change. Minor versions are usually 132as this indicates an incompatible change. Minor versions are usually
126compatible to older versions, so a larger minor version alone is usually 133compatible to older versions, so a larger minor version alone is usually
127not a problem. 134not a problem.
128 135
129Example: Make sure we haven't accidentally been linked against the wrong 136Example: Make sure we haven't accidentally been linked against the wrong
130version. 137version.
163C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for 170C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
164recommended ones. 171recommended ones.
165 172
166See the description of C<ev_embed> watchers for more info. 173See the description of C<ev_embed> watchers for more info.
167 174
168=item ev_set_allocator (void *(*cb)(void *ptr, size_t size)) 175=item ev_set_allocator (void *(*cb)(void *ptr, long size))
169 176
170Sets the allocation function to use (the prototype and semantics are 177Sets the allocation function to use (the prototype is similar - the
171identical to the realloc C function). It is used to allocate and free 178semantics is identical - to the realloc C function). It is used to
172memory (no surprises here). If it returns zero when memory needs to be 179allocate and free memory (no surprises here). If it returns zero when
173allocated, the library might abort or take some potentially destructive 180memory needs to be allocated, the library might abort or take some
174action. The default is your system realloc function. 181potentially destructive action. The default is your system realloc
182function.
175 183
176You could override this function in high-availability programs to, say, 184You could override this function in high-availability programs to, say,
177free some memory if it cannot allocate memory, to use a special allocator, 185free some memory if it cannot allocate memory, to use a special allocator,
178or even to sleep a while and retry until some memory is available. 186or even to sleep a while and retry until some memory is available.
179 187
265C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will 273C<LIBEV_FLAGS>. Otherwise (the default), this environment variable will
266override the flags completely if it is found in the environment. This is 274override the flags completely if it is found in the environment. This is
267useful to try out specific backends to test their performance, or to work 275useful to try out specific backends to test their performance, or to work
268around bugs. 276around bugs.
269 277
278=item C<EVFLAG_FORKCHECK>
279
280Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after
281a fork, you can also make libev check for a fork in each iteration by
282enabling this flag.
283
284This works by calling C<getpid ()> on every iteration of the loop,
285and thus this might slow down your event loop if you do a lot of loop
286iterations and little real work, but is usually not noticeable (on my
287Linux system for example, C<getpid> is actually a simple 5-insn sequence
288without a syscall and thus I<very> fast, but my Linux system also has
289C<pthread_atfork> which is even faster).
290
291The big advantage of this flag is that you can forget about fork (and
292forget about forgetting to tell libev about forking) when you use this
293flag.
294
295This flag setting cannot be overriden or specified in the C<LIBEV_FLAGS>
296environment variable.
297
270=item C<EVBACKEND_SELECT> (value 1, portable select backend) 298=item C<EVBACKEND_SELECT> (value 1, portable select backend)
271 299
272This is your standard select(2) backend. Not I<completely> standard, as 300This is your standard select(2) backend. Not I<completely> standard, as
273libev tries to roll its own fd_set with no limits on the number of fds, 301libev tries to roll its own fd_set with no limits on the number of fds,
274but if that fails, expect a fairly low limit on the number of fds when 302but if that fails, expect a fairly low limit on the number of fds when
409 437
410Like C<ev_default_fork>, but acts on an event loop created by 438Like C<ev_default_fork>, but acts on an event loop created by
411C<ev_loop_new>. Yes, you have to call this on every allocated event loop 439C<ev_loop_new>. Yes, you have to call this on every allocated event loop
412after fork, and how you do this is entirely your own problem. 440after fork, and how you do this is entirely your own problem.
413 441
442=item unsigned int ev_loop_count (loop)
443
444Returns the count of loop iterations for the loop, which is identical to
445the number of times libev did poll for new events. It starts at C<0> and
446happily wraps around with enough iterations.
447
448This value can sometimes be useful as a generation counter of sorts (it
449"ticks" the number of loop iterations), as it roughly corresponds with
450C<ev_prepare> and C<ev_check> calls.
451
414=item unsigned int ev_backend (loop) 452=item unsigned int ev_backend (loop)
415 453
416Returns one of the C<EVBACKEND_*> flags indicating the event backend in 454Returns one of the C<EVBACKEND_*> flags indicating the event backend in
417use. 455use.
418 456
451libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is 489libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
452usually a better approach for this kind of thing. 490usually a better approach for this kind of thing.
453 491
454Here are the gory details of what C<ev_loop> does: 492Here are the gory details of what C<ev_loop> does:
455 493
494 - Before the first iteration, call any pending watchers.
456 * If there are no active watchers (reference count is zero), return. 495 * If there are no active watchers (reference count is zero), return.
457 - Queue prepare watchers and then call all outstanding watchers. 496 - Queue all prepare watchers and then call all outstanding watchers.
458 - If we have been forked, recreate the kernel state. 497 - If we have been forked, recreate the kernel state.
459 - Update the kernel state with all outstanding changes. 498 - Update the kernel state with all outstanding changes.
460 - Update the "event loop time". 499 - Update the "event loop time".
461 - Calculate for how long to block. 500 - Calculate for how long to block.
462 - Block the process, waiting for any events. 501 - Block the process, waiting for any events.
701=item bool ev_is_pending (ev_TYPE *watcher) 740=item bool ev_is_pending (ev_TYPE *watcher)
702 741
703Returns a true value iff the watcher is pending, (i.e. it has outstanding 742Returns a true value iff the watcher is pending, (i.e. it has outstanding
704events but its callback has not yet been invoked). As long as a watcher 743events but its callback has not yet been invoked). As long as a watcher
705is pending (but not active) you must not call an init function on it (but 744is pending (but not active) you must not call an init function on it (but
706C<ev_TYPE_set> is safe) and you must make sure the watcher is available to 745C<ev_TYPE_set> is safe), you must not change its priority, and you must
707libev (e.g. you cnanot C<free ()> it). 746make sure the watcher is available to libev (e.g. you cannot C<free ()>
747it).
708 748
709=item callback ev_cb (ev_TYPE *watcher) 749=item callback ev_cb (ev_TYPE *watcher)
710 750
711Returns the callback currently set on the watcher. 751Returns the callback currently set on the watcher.
712 752
713=item ev_cb_set (ev_TYPE *watcher, callback) 753=item ev_cb_set (ev_TYPE *watcher, callback)
714 754
715Change the callback. You can change the callback at virtually any time 755Change the callback. You can change the callback at virtually any time
716(modulo threads). 756(modulo threads).
757
758=item ev_set_priority (ev_TYPE *watcher, priority)
759
760=item int ev_priority (ev_TYPE *watcher)
761
762Set and query the priority of the watcher. The priority is a small
763integer between C<EV_MAXPRI> (default: C<2>) and C<EV_MINPRI>
764(default: C<-2>). Pending watchers with higher priority will be invoked
765before watchers with lower priority, but priority will not keep watchers
766from being executed (except for C<ev_idle> watchers).
767
768This means that priorities are I<only> used for ordering callback
769invocation after new events have been received. This is useful, for
770example, to reduce latency after idling, or more often, to bind two
771watchers on the same event and make sure one is called first.
772
773If you need to suppress invocation when higher priority events are pending
774you need to look at C<ev_idle> watchers, which provide this functionality.
775
776You I<must not> change the priority of a watcher as long as it is active or
777pending.
778
779The default priority used by watchers when no priority has been set is
780always C<0>, which is supposed to not be too high and not be too low :).
781
782Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
783fine, as long as you do not mind that the priority value you query might
784or might not have been adjusted to be within valid range.
785
786=item ev_invoke (loop, ev_TYPE *watcher, int revents)
787
788Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
789C<loop> nor C<revents> need to be valid as long as the watcher callback
790can deal with that fact.
791
792=item int ev_clear_pending (loop, ev_TYPE *watcher)
793
794If the watcher is pending, this function returns clears its pending status
795and returns its C<revents> bitset (as if its callback was invoked). If the
796watcher isn't pending it does nothing and returns C<0>.
717 797
718=back 798=back
719 799
720 800
721=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 801=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
827it is best to always use non-blocking I/O: An extra C<read>(2) returning 907it is best to always use non-blocking I/O: An extra C<read>(2) returning
828C<EAGAIN> is far preferable to a program hanging until some data arrives. 908C<EAGAIN> is far preferable to a program hanging until some data arrives.
829 909
830If you cannot run the fd in non-blocking mode (for example you should not 910If you cannot run the fd in non-blocking mode (for example you should not
831play around with an Xlib connection), then you have to seperately re-test 911play around with an Xlib connection), then you have to seperately re-test
832wether a file descriptor is really ready with a known-to-be good interface 912whether a file descriptor is really ready with a known-to-be good interface
833such as poll (fortunately in our Xlib example, Xlib already does this on 913such as poll (fortunately in our Xlib example, Xlib already does this on
834its own, so its quite safe to use). 914its own, so its quite safe to use).
835 915
836=over 4 916=over 4
837 917
915=item ev_timer_again (loop) 995=item ev_timer_again (loop)
916 996
917This will act as if the timer timed out and restart it again if it is 997This will act as if the timer timed out and restart it again if it is
918repeating. The exact semantics are: 998repeating. The exact semantics are:
919 999
1000If the timer is pending, its pending status is cleared.
1001
920If the timer is started but nonrepeating, stop it. 1002If the timer is started but nonrepeating, stop it (as if it timed out).
921 1003
922If the timer is repeating, either start it if necessary (with the repeat 1004If the timer is repeating, either start it if necessary (with the
923value), or reset the running timer to the repeat value. 1005C<repeat> value), or reset the running timer to the C<repeat> value.
924 1006
925This sounds a bit complicated, but here is a useful and typical 1007This sounds a bit complicated, but here is a useful and typical
926example: Imagine you have a tcp connection and you want a so-called 1008example: Imagine you have a tcp connection and you want a so-called idle
927idle timeout, that is, you want to be called when there have been, 1009timeout, that is, you want to be called when there have been, say, 60
928say, 60 seconds of inactivity on the socket. The easiest way to do 1010seconds of inactivity on the socket. The easiest way to do this is to
929this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling 1011configure an C<ev_timer> with a C<repeat> value of C<60> and then call
930C<ev_timer_again> each time you successfully read or write some data. If 1012C<ev_timer_again> each time you successfully read or write some data. If
931you go into an idle state where you do not expect data to travel on the 1013you go into an idle state where you do not expect data to travel on the
932socket, you can stop the timer, and again will automatically restart it if 1014socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
933need be. 1015automatically restart it if need be.
934 1016
935You can also ignore the C<after> value and C<ev_timer_start> altogether 1017That means you can ignore the C<after> value and C<ev_timer_start>
936and only ever use the C<repeat> value: 1018altogether and only ever use the C<repeat> value and C<ev_timer_again>:
937 1019
938 ev_timer_init (timer, callback, 0., 5.); 1020 ev_timer_init (timer, callback, 0., 5.);
939 ev_timer_again (loop, timer); 1021 ev_timer_again (loop, timer);
940 ... 1022 ...
941 timer->again = 17.; 1023 timer->again = 17.;
942 ev_timer_again (loop, timer); 1024 ev_timer_again (loop, timer);
943 ... 1025 ...
944 timer->again = 10.; 1026 timer->again = 10.;
945 ev_timer_again (loop, timer); 1027 ev_timer_again (loop, timer);
946 1028
947This is more efficient then stopping/starting the timer eahc time you want 1029This is more slightly efficient then stopping/starting the timer each time
948to modify its timeout value. 1030you want to modify its timeout value.
949 1031
950=item ev_tstamp repeat [read-write] 1032=item ev_tstamp repeat [read-write]
951 1033
952The current C<repeat> value. Will be used each time the watcher times out 1034The current C<repeat> value. Will be used each time the watcher times out
953or C<ev_timer_again> is called and determines the next timeout (if any), 1035or C<ev_timer_again> is called and determines the next timeout (if any),
995but on wallclock time (absolute time). You can tell a periodic watcher 1077but on wallclock time (absolute time). You can tell a periodic watcher
996to trigger "at" some specific point in time. For example, if you tell a 1078to trigger "at" some specific point in time. For example, if you tell a
997periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () 1079periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
998+ 10.>) and then reset your system clock to the last year, then it will 1080+ 10.>) and then reset your system clock to the last year, then it will
999take a year to trigger the event (unlike an C<ev_timer>, which would trigger 1081take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1000roughly 10 seconds later and of course not if you reset your system time 1082roughly 10 seconds later).
1001again).
1002 1083
1003They can also be used to implement vastly more complex timers, such as 1084They can also be used to implement vastly more complex timers, such as
1004triggering an event on eahc midnight, local time. 1085triggering an event on each midnight, local time or other, complicated,
1086rules.
1005 1087
1006As with timers, the callback is guarenteed to be invoked only when the 1088As with timers, the callback is guarenteed to be invoked only when the
1007time (C<at>) has been passed, but if multiple periodic timers become ready 1089time (C<at>) has been passed, but if multiple periodic timers become ready
1008during the same loop iteration then order of execution is undefined. 1090during the same loop iteration then order of execution is undefined.
1009 1091
1016Lots of arguments, lets sort it out... There are basically three modes of 1098Lots of arguments, lets sort it out... There are basically three modes of
1017operation, and we will explain them from simplest to complex: 1099operation, and we will explain them from simplest to complex:
1018 1100
1019=over 4 1101=over 4
1020 1102
1021=item * absolute timer (interval = reschedule_cb = 0) 1103=item * absolute timer (at = time, interval = reschedule_cb = 0)
1022 1104
1023In this configuration the watcher triggers an event at the wallclock time 1105In this configuration the watcher triggers an event at the wallclock time
1024C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1106C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1025that is, if it is to be run at January 1st 2011 then it will run when the 1107that is, if it is to be run at January 1st 2011 then it will run when the
1026system time reaches or surpasses this time. 1108system time reaches or surpasses this time.
1027 1109
1028=item * non-repeating interval timer (interval > 0, reschedule_cb = 0) 1110=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1029 1111
1030In this mode the watcher will always be scheduled to time out at the next 1112In this mode the watcher will always be scheduled to time out at the next
1031C<at + N * interval> time (for some integer N) and then repeat, regardless 1113C<at + N * interval> time (for some integer N, which can also be negative)
1032of any time jumps. 1114and then repeat, regardless of any time jumps.
1033 1115
1034This can be used to create timers that do not drift with respect to system 1116This can be used to create timers that do not drift with respect to system
1035time: 1117time:
1036 1118
1037 ev_periodic_set (&periodic, 0., 3600., 0); 1119 ev_periodic_set (&periodic, 0., 3600., 0);
1043 1125
1044Another way to think about it (for the mathematically inclined) is that 1126Another way to think about it (for the mathematically inclined) is that
1045C<ev_periodic> will try to run the callback in this mode at the next possible 1127C<ev_periodic> will try to run the callback in this mode at the next possible
1046time where C<time = at (mod interval)>, regardless of any time jumps. 1128time where C<time = at (mod interval)>, regardless of any time jumps.
1047 1129
1130For numerical stability it is preferable that the C<at> value is near
1131C<ev_now ()> (the current time), but there is no range requirement for
1132this value.
1133
1048=item * manual reschedule mode (reschedule_cb = callback) 1134=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1049 1135
1050In this mode the values for C<interval> and C<at> are both being 1136In this mode the values for C<interval> and C<at> are both being
1051ignored. Instead, each time the periodic watcher gets scheduled, the 1137ignored. Instead, each time the periodic watcher gets scheduled, the
1052reschedule callback will be called with the watcher as first, and the 1138reschedule callback will be called with the watcher as first, and the
1053current time as second argument. 1139current time as second argument.
1054 1140
1055NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, 1141NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1056ever, or make any event loop modifications>. If you need to stop it, 1142ever, or make any event loop modifications>. If you need to stop it,
1057return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by 1143return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1058starting a prepare watcher). 1144starting an C<ev_prepare> watcher, which is legal).
1059 1145
1060Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1146Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1061ev_tstamp now)>, e.g.: 1147ev_tstamp now)>, e.g.:
1062 1148
1063 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1149 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1085 1171
1086Simply stops and restarts the periodic watcher again. This is only useful 1172Simply stops and restarts the periodic watcher again. This is only useful
1087when you changed some parameters or the reschedule callback would return 1173when you changed some parameters or the reschedule callback would return
1088a different time than the last time it was called (e.g. in a crond like 1174a different time than the last time it was called (e.g. in a crond like
1089program when the crontabs have changed). 1175program when the crontabs have changed).
1176
1177=item ev_tstamp offset [read-write]
1178
1179When repeating, this contains the offset value, otherwise this is the
1180absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1181
1182Can be modified any time, but changes only take effect when the periodic
1183timer fires or C<ev_periodic_again> is being called.
1090 1184
1091=item ev_tstamp interval [read-write] 1185=item ev_tstamp interval [read-write]
1092 1186
1093The current interval value. Can be modified any time, but changes only 1187The current interval value. Can be modified any time, but changes only
1094take effect when the periodic timer fires or C<ev_periodic_again> is being 1188take effect when the periodic timer fires or C<ev_periodic_again> is being
1221The path does not need to exist: changing from "path exists" to "path does 1315The path does not need to exist: changing from "path exists" to "path does
1222not exist" is a status change like any other. The condition "path does 1316not exist" is a status change like any other. The condition "path does
1223not exist" is signified by the C<st_nlink> field being zero (which is 1317not exist" is signified by the C<st_nlink> field being zero (which is
1224otherwise always forced to be at least one) and all the other fields of 1318otherwise always forced to be at least one) and all the other fields of
1225the stat buffer having unspecified contents. 1319the stat buffer having unspecified contents.
1320
1321The path I<should> be absolute and I<must not> end in a slash. If it is
1322relative and your working directory changes, the behaviour is undefined.
1226 1323
1227Since there is no standard to do this, the portable implementation simply 1324Since there is no standard to do this, the portable implementation simply
1228calls C<stat (2)> regularly on the path to see if it changed somehow. You 1325calls C<stat (2)> regularly on the path to see if it changed somehow. You
1229can specify a recommended polling interval for this case. If you specify 1326can specify a recommended polling interval for this case. If you specify
1230a polling interval of C<0> (highly recommended!) then a I<suitable, 1327a polling interval of C<0> (highly recommended!) then a I<suitable,
1315 ev_stat_start (loop, &passwd); 1412 ev_stat_start (loop, &passwd);
1316 1413
1317 1414
1318=head2 C<ev_idle> - when you've got nothing better to do... 1415=head2 C<ev_idle> - when you've got nothing better to do...
1319 1416
1320Idle watchers trigger events when there are no other events are pending 1417Idle watchers trigger events when no other events of the same or higher
1321(prepare, check and other idle watchers do not count). That is, as long 1418priority are pending (prepare, check and other idle watchers do not
1322as your process is busy handling sockets or timeouts (or even signals, 1419count).
1323imagine) it will not be triggered. But when your process is idle all idle 1420
1324watchers are being called again and again, once per event loop iteration - 1421That is, as long as your process is busy handling sockets or timeouts
1422(or even signals, imagine) of the same or higher priority it will not be
1423triggered. But when your process is idle (or only lower-priority watchers
1424are pending), the idle watchers are being called once per event loop
1325until stopped, that is, or your process receives more events and becomes 1425iteration - until stopped, that is, or your process receives more events
1326busy. 1426and becomes busy again with higher priority stuff.
1327 1427
1328The most noteworthy effect is that as long as any idle watchers are 1428The most noteworthy effect is that as long as any idle watchers are
1329active, the process will not block when waiting for new events. 1429active, the process will not block when waiting for new events.
1330 1430
1331Apart from keeping your process non-blocking (which is a useful 1431Apart from keeping your process non-blocking (which is a useful
1397with priority higher than or equal to the event loop and one coroutine 1497with priority higher than or equal to the event loop and one coroutine
1398of lower priority, but only once, using idle watchers to keep the event 1498of lower priority, but only once, using idle watchers to keep the event
1399loop from blocking if lower-priority coroutines are active, thus mapping 1499loop from blocking if lower-priority coroutines are active, thus mapping
1400low-priority coroutines to idle/background tasks). 1500low-priority coroutines to idle/background tasks).
1401 1501
1502It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1503priority, to ensure that they are being run before any other watchers
1504after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1505too) should not activate ("feed") events into libev. While libev fully
1506supports this, they will be called before other C<ev_check> watchers did
1507their job. As C<ev_check> watchers are often used to embed other event
1508loops those other event loops might be in an unusable state until their
1509C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1510others).
1511
1402=over 4 1512=over 4
1403 1513
1404=item ev_prepare_init (ev_prepare *, callback) 1514=item ev_prepare_init (ev_prepare *, callback)
1405 1515
1406=item ev_check_init (ev_check *, callback) 1516=item ev_check_init (ev_check *, callback)
1409parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1519parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1410macros, but using them is utterly, utterly and completely pointless. 1520macros, but using them is utterly, utterly and completely pointless.
1411 1521
1412=back 1522=back
1413 1523
1414Example: To include a library such as adns, you would add IO watchers 1524There are a number of principal ways to embed other event loops or modules
1415and a timeout watcher in a prepare handler, as required by libadns, and 1525into libev. Here are some ideas on how to include libadns into libev
1526(there is a Perl module named C<EV::ADNS> that does this, which you could
1527use for an actually working example. Another Perl module named C<EV::Glib>
1528embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
1529into the Glib event loop).
1530
1531Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1416in a check watcher, destroy them and call into libadns. What follows is 1532and in a check watcher, destroy them and call into libadns. What follows
1417pseudo-code only of course: 1533is pseudo-code only of course. This requires you to either use a low
1534priority for the check watcher or use C<ev_clear_pending> explicitly, as
1535the callbacks for the IO/timeout watchers might not have been called yet.
1418 1536
1419 static ev_io iow [nfd]; 1537 static ev_io iow [nfd];
1420 static ev_timer tw; 1538 static ev_timer tw;
1421 1539
1422 static void 1540 static void
1423 io_cb (ev_loop *loop, ev_io *w, int revents) 1541 io_cb (ev_loop *loop, ev_io *w, int revents)
1424 { 1542 {
1425 // set the relevant poll flags
1426 // could also call adns_processreadable etc. here
1427 struct pollfd *fd = (struct pollfd *)w->data;
1428 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1429 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1430 } 1543 }
1431 1544
1432 // create io watchers for each fd and a timer before blocking 1545 // create io watchers for each fd and a timer before blocking
1433 static void 1546 static void
1434 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1547 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1435 { 1548 {
1436 int timeout = 3600000;truct pollfd fds [nfd]; 1549 int timeout = 3600000;
1550 struct pollfd fds [nfd];
1437 // actual code will need to loop here and realloc etc. 1551 // actual code will need to loop here and realloc etc.
1438 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 1552 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1439 1553
1440 /* the callback is illegal, but won't be called as we stop during check */ 1554 /* the callback is illegal, but won't be called as we stop during check */
1441 ev_timer_init (&tw, 0, timeout * 1e-3); 1555 ev_timer_init (&tw, 0, timeout * 1e-3);
1442 ev_timer_start (loop, &tw); 1556 ev_timer_start (loop, &tw);
1443 1557
1444 // create on ev_io per pollfd 1558 // create one ev_io per pollfd
1445 for (int i = 0; i < nfd; ++i) 1559 for (int i = 0; i < nfd; ++i)
1446 { 1560 {
1447 ev_io_init (iow + i, io_cb, fds [i].fd, 1561 ev_io_init (iow + i, io_cb, fds [i].fd,
1448 ((fds [i].events & POLLIN ? EV_READ : 0) 1562 ((fds [i].events & POLLIN ? EV_READ : 0)
1449 | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1563 | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1450 1564
1451 fds [i].revents = 0; 1565 fds [i].revents = 0;
1452 iow [i].data = fds + i;
1453 ev_io_start (loop, iow + i); 1566 ev_io_start (loop, iow + i);
1454 } 1567 }
1455 } 1568 }
1456 1569
1457 // stop all watchers after blocking 1570 // stop all watchers after blocking
1459 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1572 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1460 { 1573 {
1461 ev_timer_stop (loop, &tw); 1574 ev_timer_stop (loop, &tw);
1462 1575
1463 for (int i = 0; i < nfd; ++i) 1576 for (int i = 0; i < nfd; ++i)
1577 {
1578 // set the relevant poll flags
1579 // could also call adns_processreadable etc. here
1580 struct pollfd *fd = fds + i;
1581 int revents = ev_clear_pending (iow + i);
1582 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1583 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1584
1585 // now stop the watcher
1464 ev_io_stop (loop, iow + i); 1586 ev_io_stop (loop, iow + i);
1587 }
1465 1588
1466 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1589 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1590 }
1591
1592Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1593in the prepare watcher and would dispose of the check watcher.
1594
1595Method 3: If the module to be embedded supports explicit event
1596notification (adns does), you can also make use of the actual watcher
1597callbacks, and only destroy/create the watchers in the prepare watcher.
1598
1599 static void
1600 timer_cb (EV_P_ ev_timer *w, int revents)
1601 {
1602 adns_state ads = (adns_state)w->data;
1603 update_now (EV_A);
1604
1605 adns_processtimeouts (ads, &tv_now);
1606 }
1607
1608 static void
1609 io_cb (EV_P_ ev_io *w, int revents)
1610 {
1611 adns_state ads = (adns_state)w->data;
1612 update_now (EV_A);
1613
1614 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1615 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1616 }
1617
1618 // do not ever call adns_afterpoll
1619
1620Method 4: Do not use a prepare or check watcher because the module you
1621want to embed is too inflexible to support it. Instead, youc na override
1622their poll function. The drawback with this solution is that the main
1623loop is now no longer controllable by EV. The C<Glib::EV> module does
1624this.
1625
1626 static gint
1627 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1628 {
1629 int got_events = 0;
1630
1631 for (n = 0; n < nfds; ++n)
1632 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1633
1634 if (timeout >= 0)
1635 // create/start timer
1636
1637 // poll
1638 ev_loop (EV_A_ 0);
1639
1640 // stop timer again
1641 if (timeout >= 0)
1642 ev_timer_stop (EV_A_ &to);
1643
1644 // stop io watchers again - their callbacks should have set
1645 for (n = 0; n < nfds; ++n)
1646 ev_io_stop (EV_A_ iow [n]);
1647
1648 return got_events;
1467 } 1649 }
1468 1650
1469 1651
1470=head2 C<ev_embed> - when one backend isn't enough... 1652=head2 C<ev_embed> - when one backend isn't enough...
1471 1653
1675 1857
1676To use it, 1858To use it,
1677 1859
1678 #include <ev++.h> 1860 #include <ev++.h>
1679 1861
1680(it is not installed by default). This automatically includes F<ev.h> 1862This automatically includes F<ev.h> and puts all of its definitions (many
1681and puts all of its definitions (many of them macros) into the global 1863of them macros) into the global namespace. All C++ specific things are
1682namespace. All C++ specific things are put into the C<ev> namespace. 1864put into the C<ev> namespace. It should support all the same embedding
1865options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1683 1866
1684It should support all the same embedding options as F<ev.h>, most notably 1867Care has been taken to keep the overhead low. The only data member the C++
1685C<EV_MULTIPLICITY>. 1868classes add (compared to plain C-style watchers) is the event loop pointer
1869that the watcher is associated with (or no additional members at all if
1870you disable C<EV_MULTIPLICITY> when embedding libev).
1871
1872Currently, functions, and static and non-static member functions can be
1873used as callbacks. Other types should be easy to add as long as they only
1874need one additional pointer for context. If you need support for other
1875types of functors please contact the author (preferably after implementing
1876it).
1686 1877
1687Here is a list of things available in the C<ev> namespace: 1878Here is a list of things available in the C<ev> namespace:
1688 1879
1689=over 4 1880=over 4
1690 1881
1706 1897
1707All of those classes have these methods: 1898All of those classes have these methods:
1708 1899
1709=over 4 1900=over 4
1710 1901
1711=item ev::TYPE::TYPE (object *, object::method *) 1902=item ev::TYPE::TYPE ()
1712 1903
1713=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *) 1904=item ev::TYPE::TYPE (struct ev_loop *)
1714 1905
1715=item ev::TYPE::~TYPE 1906=item ev::TYPE::~TYPE
1716 1907
1717The constructor takes a pointer to an object and a method pointer to 1908The constructor (optionally) takes an event loop to associate the watcher
1718the event handler callback to call in this class. The constructor calls 1909with. If it is omitted, it will use C<EV_DEFAULT>.
1719C<ev_init> for you, which means you have to call the C<set> method 1910
1720before starting it. If you do not specify a loop then the constructor 1911The constructor calls C<ev_init> for you, which means you have to call the
1721automatically associates the default loop with this watcher. 1912C<set> method before starting it.
1913
1914It will not set a callback, however: You have to call the templated C<set>
1915method to set a callback before you can start the watcher.
1916
1917(The reason why you have to use a method is a limitation in C++ which does
1918not allow explicit template arguments for constructors).
1722 1919
1723The destructor automatically stops the watcher if it is active. 1920The destructor automatically stops the watcher if it is active.
1921
1922=item w->set<class, &class::method> (object *)
1923
1924This method sets the callback method to call. The method has to have a
1925signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
1926first argument and the C<revents> as second. The object must be given as
1927parameter and is stored in the C<data> member of the watcher.
1928
1929This method synthesizes efficient thunking code to call your method from
1930the C callback that libev requires. If your compiler can inline your
1931callback (i.e. it is visible to it at the place of the C<set> call and
1932your compiler is good :), then the method will be fully inlined into the
1933thunking function, making it as fast as a direct C callback.
1934
1935Example: simple class declaration and watcher initialisation
1936
1937 struct myclass
1938 {
1939 void io_cb (ev::io &w, int revents) { }
1940 }
1941
1942 myclass obj;
1943 ev::io iow;
1944 iow.set <myclass, &myclass::io_cb> (&obj);
1945
1946=item w->set<function> (void *data = 0)
1947
1948Also sets a callback, but uses a static method or plain function as
1949callback. The optional C<data> argument will be stored in the watcher's
1950C<data> member and is free for you to use.
1951
1952The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
1953
1954See the method-C<set> above for more details.
1955
1956Example:
1957
1958 static void io_cb (ev::io &w, int revents) { }
1959 iow.set <io_cb> ();
1724 1960
1725=item w->set (struct ev_loop *) 1961=item w->set (struct ev_loop *)
1726 1962
1727Associates a different C<struct ev_loop> with this watcher. You can only 1963Associates a different C<struct ev_loop> with this watcher. You can only
1728do this when the watcher is inactive (and not pending either). 1964do this when the watcher is inactive (and not pending either).
1729 1965
1730=item w->set ([args]) 1966=item w->set ([args])
1731 1967
1732Basically the same as C<ev_TYPE_set>, with the same args. Must be 1968Basically the same as C<ev_TYPE_set>, with the same args. Must be
1733called at least once. Unlike the C counterpart, an active watcher gets 1969called at least once. Unlike the C counterpart, an active watcher gets
1734automatically stopped and restarted. 1970automatically stopped and restarted when reconfiguring it with this
1971method.
1735 1972
1736=item w->start () 1973=item w->start ()
1737 1974
1738Starts the watcher. Note that there is no C<loop> argument as the 1975Starts the watcher. Note that there is no C<loop> argument, as the
1739constructor already takes the loop. 1976constructor already stores the event loop.
1740 1977
1741=item w->stop () 1978=item w->stop ()
1742 1979
1743Stops the watcher if it is active. Again, no C<loop> argument. 1980Stops the watcher if it is active. Again, no C<loop> argument.
1744 1981
1769 2006
1770 myclass (); 2007 myclass ();
1771 } 2008 }
1772 2009
1773 myclass::myclass (int fd) 2010 myclass::myclass (int fd)
1774 : io (this, &myclass::io_cb),
1775 idle (this, &myclass::idle_cb)
1776 { 2011 {
2012 io .set <myclass, &myclass::io_cb > (this);
2013 idle.set <myclass, &myclass::idle_cb> (this);
2014
1777 io.start (fd, ev::READ); 2015 io.start (fd, ev::READ);
1778 } 2016 }
1779 2017
1780 2018
1781=head1 MACRO MAGIC 2019=head1 MACRO MAGIC
1782 2020
1783Libev can be compiled with a variety of options, the most fundemantal is 2021Libev can be compiled with a variety of options, the most fundemantal is
1784C<EV_MULTIPLICITY>. This option determines wether (most) functions and 2022C<EV_MULTIPLICITY>. This option determines whether (most) functions and
1785callbacks have an initial C<struct ev_loop *> argument. 2023callbacks have an initial C<struct ev_loop *> argument.
1786 2024
1787To make it easier to write programs that cope with either variant, the 2025To make it easier to write programs that cope with either variant, the
1788following macros are defined: 2026following macros are defined:
1789 2027
1822Similar to the other two macros, this gives you the value of the default 2060Similar to the other two macros, this gives you the value of the default
1823loop, if multiple loops are supported ("ev loop default"). 2061loop, if multiple loops are supported ("ev loop default").
1824 2062
1825=back 2063=back
1826 2064
1827Example: Declare and initialise a check watcher, working regardless of 2065Example: Declare and initialise a check watcher, utilising the above
1828wether multiple loops are supported or not. 2066macros so it will work regardless of whether multiple loops are supported
2067or not.
1829 2068
1830 static void 2069 static void
1831 check_cb (EV_P_ ev_timer *w, int revents) 2070 check_cb (EV_P_ ev_timer *w, int revents)
1832 { 2071 {
1833 ev_check_stop (EV_A_ w); 2072 ev_check_stop (EV_A_ w);
1835 2074
1836 ev_check check; 2075 ev_check check;
1837 ev_check_init (&check, check_cb); 2076 ev_check_init (&check, check_cb);
1838 ev_check_start (EV_DEFAULT_ &check); 2077 ev_check_start (EV_DEFAULT_ &check);
1839 ev_loop (EV_DEFAULT_ 0); 2078 ev_loop (EV_DEFAULT_ 0);
1840
1841 2079
1842=head1 EMBEDDING 2080=head1 EMBEDDING
1843 2081
1844Libev can (and often is) directly embedded into host 2082Libev can (and often is) directly embedded into host
1845applications. Examples of applications that embed it include the Deliantra 2083applications. Examples of applications that embed it include the Deliantra
1885 ev_vars.h 2123 ev_vars.h
1886 ev_wrap.h 2124 ev_wrap.h
1887 2125
1888 ev_win32.c required on win32 platforms only 2126 ev_win32.c required on win32 platforms only
1889 2127
1890 ev_select.c only when select backend is enabled (which is by default) 2128 ev_select.c only when select backend is enabled (which is enabled by default)
1891 ev_poll.c only when poll backend is enabled (disabled by default) 2129 ev_poll.c only when poll backend is enabled (disabled by default)
1892 ev_epoll.c only when the epoll backend is enabled (disabled by default) 2130 ev_epoll.c only when the epoll backend is enabled (disabled by default)
1893 ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2131 ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1894 ev_port.c only when the solaris port backend is enabled (disabled by default) 2132 ev_port.c only when the solaris port backend is enabled (disabled by default)
1895 2133
2058will have the C<struct ev_loop *> as first argument, and you can create 2296will have the C<struct ev_loop *> as first argument, and you can create
2059additional independent event loops. Otherwise there will be no support 2297additional independent event loops. Otherwise there will be no support
2060for multiple event loops and there is no first event loop pointer 2298for multiple event loops and there is no first event loop pointer
2061argument. Instead, all functions act on the single default loop. 2299argument. Instead, all functions act on the single default loop.
2062 2300
2301=item EV_MINPRI
2302
2303=item EV_MAXPRI
2304
2305The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
2306C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
2307provide for more priorities by overriding those symbols (usually defined
2308to be C<-2> and C<2>, respectively).
2309
2310When doing priority-based operations, libev usually has to linearly search
2311all the priorities, so having many of them (hundreds) uses a lot of space
2312and time, so using the defaults of five priorities (-2 .. +2) is usually
2313fine.
2314
2315If your embedding app does not need any priorities, defining these both to
2316C<0> will save some memory and cpu.
2317
2063=item EV_PERIODIC_ENABLE 2318=item EV_PERIODIC_ENABLE
2064 2319
2065If undefined or defined to be C<1>, then periodic timers are supported. If 2320If undefined or defined to be C<1>, then periodic timers are supported. If
2321defined to be C<0>, then they are not. Disabling them saves a few kB of
2322code.
2323
2324=item EV_IDLE_ENABLE
2325
2326If undefined or defined to be C<1>, then idle watchers are supported. If
2066defined to be C<0>, then they are not. Disabling them saves a few kB of 2327defined to be C<0>, then they are not. Disabling them saves a few kB of
2067code. 2328code.
2068 2329
2069=item EV_EMBED_ENABLE 2330=item EV_EMBED_ENABLE
2070 2331
2137interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file 2398interface) and F<EV.xs> (implementation) files. Only the F<EV.xs> file
2138will be compiled. It is pretty complex because it provides its own header 2399will be compiled. It is pretty complex because it provides its own header
2139file. 2400file.
2140 2401
2141The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 2402The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
2142that everybody includes and which overrides some autoconf choices: 2403that everybody includes and which overrides some configure choices:
2143 2404
2405 #define EV_MINIMAL 1
2144 #define EV_USE_POLL 0 2406 #define EV_USE_POLL 0
2145 #define EV_MULTIPLICITY 0 2407 #define EV_MULTIPLICITY 0
2146 #define EV_PERIODICS 0 2408 #define EV_PERIODIC_ENABLE 0
2409 #define EV_STAT_ENABLE 0
2410 #define EV_FORK_ENABLE 0
2147 #define EV_CONFIG_H <config.h> 2411 #define EV_CONFIG_H <config.h>
2412 #define EV_MINPRI 0
2413 #define EV_MAXPRI 0
2148 2414
2149 #include "ev++.h" 2415 #include "ev++.h"
2150 2416
2151And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 2417And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
2152 2418
2158 2424
2159In this section the complexities of (many of) the algorithms used inside 2425In this section the complexities of (many of) the algorithms used inside
2160libev will be explained. For complexity discussions about backends see the 2426libev will be explained. For complexity discussions about backends see the
2161documentation for C<ev_default_init>. 2427documentation for C<ev_default_init>.
2162 2428
2429All of the following are about amortised time: If an array needs to be
2430extended, libev needs to realloc and move the whole array, but this
2431happens asymptotically never with higher number of elements, so O(1) might
2432mean it might do a lengthy realloc operation in rare cases, but on average
2433it is much faster and asymptotically approaches constant time.
2434
2163=over 4 2435=over 4
2164 2436
2165=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2437=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2166 2438
2439This means that, when you have a watcher that triggers in one hour and
2440there are 100 watchers that would trigger before that then inserting will
2441have to skip those 100 watchers.
2442
2167=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2443=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2168 2444
2445That means that for changing a timer costs less than removing/adding them
2446as only the relative motion in the event queue has to be paid for.
2447
2169=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2448=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2170 2449
2450These just add the watcher into an array or at the head of a list.
2171=item Stopping check/prepare/idle watchers: O(1) 2451=item Stopping check/prepare/idle watchers: O(1)
2172 2452
2173=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2453=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2174 2454
2455These watchers are stored in lists then need to be walked to find the
2456correct watcher to remove. The lists are usually short (you don't usually
2457have many watchers waiting for the same fd or signal).
2458
2175=item Finding the next timer per loop iteration: O(1) 2459=item Finding the next timer per loop iteration: O(1)
2176 2460
2177=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2461=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2178 2462
2463A change means an I/O watcher gets started or stopped, which requires
2464libev to recalculate its status (and possibly tell the kernel).
2465
2179=item Activating one watcher: O(1) 2466=item Activating one watcher: O(1)
2180 2467
2468=item Priority handling: O(number_of_priorities)
2469
2470Priorities are implemented by allocating some space for each
2471priority. When doing priority-based operations, libev usually has to
2472linearly search all the priorities.
2473
2181=back 2474=back
2182 2475
2183 2476
2184=head1 AUTHOR 2477=head1 AUTHOR
2185 2478

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