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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.
482libev 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
483usually a better approach for this kind of thing. 490usually a better approach for this kind of thing.
484 491
485Here are the gory details of what C<ev_loop> does: 492Here are the gory details of what C<ev_loop> does:
486 493
494 - Before the first iteration, call any pending watchers.
487 * If there are no active watchers (reference count is zero), return. 495 * If there are no active watchers (reference count is zero), return.
488 - Queue prepare watchers and then call all outstanding watchers. 496 - Queue all prepare watchers and then call all outstanding watchers.
489 - If we have been forked, recreate the kernel state. 497 - If we have been forked, recreate the kernel state.
490 - Update the kernel state with all outstanding changes. 498 - Update the kernel state with all outstanding changes.
491 - Update the "event loop time". 499 - Update the "event loop time".
492 - Calculate for how long to block. 500 - Calculate for how long to block.
493 - Block the process, waiting for any events. 501 - Block the process, waiting for any events.
732=item bool ev_is_pending (ev_TYPE *watcher) 740=item bool ev_is_pending (ev_TYPE *watcher)
733 741
734Returns 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
735events 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
736is 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
737C<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
738libev (e.g. you cnanot C<free ()> it). 746make sure the watcher is available to libev (e.g. you cannot C<free ()>
747it).
739 748
740=item callback ev_cb (ev_TYPE *watcher) 749=item callback ev_cb (ev_TYPE *watcher)
741 750
742Returns the callback currently set on the watcher. 751Returns the callback currently set on the watcher.
743 752
744=item ev_cb_set (ev_TYPE *watcher, callback) 753=item ev_cb_set (ev_TYPE *watcher, callback)
745 754
746Change the callback. You can change the callback at virtually any time 755Change the callback. You can change the callback at virtually any time
747(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>.
748 797
749=back 798=back
750 799
751 800
752=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 801=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
858it 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
859C<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.
860 909
861If 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
862play 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
863wether 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
864such 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
865its own, so its quite safe to use). 914its own, so its quite safe to use).
915
916=head3 The special problem of disappearing file descriptors
917
918Some backends (e.g kqueue, epoll) need to be told about closing a file
919descriptor (either by calling C<close> explicitly or by any other means,
920such as C<dup>). The reason is that you register interest in some file
921descriptor, but when it goes away, the operating system will silently drop
922this interest. If another file descriptor with the same number then is
923registered with libev, there is no efficient way to see that this is, in
924fact, a different file descriptor.
925
926To avoid having to explicitly tell libev about such cases, libev follows
927the following policy: Each time C<ev_io_set> is being called, libev
928will assume that this is potentially a new file descriptor, otherwise
929it is assumed that the file descriptor stays the same. That means that
930you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
931descriptor even if the file descriptor number itself did not change.
932
933This is how one would do it normally anyway, the important point is that
934the libev application should not optimise around libev but should leave
935optimisations to libev.
936
937
938=head3 Watcher-Specific Functions
866 939
867=over 4 940=over 4
868 941
869=item ev_io_init (ev_io *, callback, int fd, int events) 942=item ev_io_init (ev_io *, callback, int fd, int events)
870 943
923 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 996 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
924 997
925The callback is guarenteed to be invoked only when its timeout has passed, 998The callback is guarenteed to be invoked only when its timeout has passed,
926but if multiple timers become ready during the same loop iteration then 999but if multiple timers become ready during the same loop iteration then
927order of execution is undefined. 1000order of execution is undefined.
1001
1002=head3 Watcher-Specific Functions and Data Members
928 1003
929=over 4 1004=over 4
930 1005
931=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1006=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
932 1007
1028but on wallclock time (absolute time). You can tell a periodic watcher 1103but on wallclock time (absolute time). You can tell a periodic watcher
1029to trigger "at" some specific point in time. For example, if you tell a 1104to trigger "at" some specific point in time. For example, if you tell a
1030periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () 1105periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1031+ 10.>) and then reset your system clock to the last year, then it will 1106+ 10.>) and then reset your system clock to the last year, then it will
1032take a year to trigger the event (unlike an C<ev_timer>, which would trigger 1107take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1033roughly 10 seconds later and of course not if you reset your system time 1108roughly 10 seconds later).
1034again).
1035 1109
1036They can also be used to implement vastly more complex timers, such as 1110They can also be used to implement vastly more complex timers, such as
1037triggering an event on eahc midnight, local time. 1111triggering an event on each midnight, local time or other, complicated,
1112rules.
1038 1113
1039As with timers, the callback is guarenteed to be invoked only when the 1114As with timers, the callback is guarenteed to be invoked only when the
1040time (C<at>) has been passed, but if multiple periodic timers become ready 1115time (C<at>) has been passed, but if multiple periodic timers become ready
1041during the same loop iteration then order of execution is undefined. 1116during the same loop iteration then order of execution is undefined.
1042 1117
1118=head3 Watcher-Specific Functions and Data Members
1119
1043=over 4 1120=over 4
1044 1121
1045=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) 1122=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1046 1123
1047=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) 1124=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1049Lots of arguments, lets sort it out... There are basically three modes of 1126Lots of arguments, lets sort it out... There are basically three modes of
1050operation, and we will explain them from simplest to complex: 1127operation, and we will explain them from simplest to complex:
1051 1128
1052=over 4 1129=over 4
1053 1130
1054=item * absolute timer (interval = reschedule_cb = 0) 1131=item * absolute timer (at = time, interval = reschedule_cb = 0)
1055 1132
1056In this configuration the watcher triggers an event at the wallclock time 1133In this configuration the watcher triggers an event at the wallclock time
1057C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1134C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1058that is, if it is to be run at January 1st 2011 then it will run when the 1135that is, if it is to be run at January 1st 2011 then it will run when the
1059system time reaches or surpasses this time. 1136system time reaches or surpasses this time.
1060 1137
1061=item * non-repeating interval timer (interval > 0, reschedule_cb = 0) 1138=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1062 1139
1063In this mode the watcher will always be scheduled to time out at the next 1140In this mode the watcher will always be scheduled to time out at the next
1064C<at + N * interval> time (for some integer N) and then repeat, regardless 1141C<at + N * interval> time (for some integer N, which can also be negative)
1065of any time jumps. 1142and then repeat, regardless of any time jumps.
1066 1143
1067This can be used to create timers that do not drift with respect to system 1144This can be used to create timers that do not drift with respect to system
1068time: 1145time:
1069 1146
1070 ev_periodic_set (&periodic, 0., 3600., 0); 1147 ev_periodic_set (&periodic, 0., 3600., 0);
1076 1153
1077Another way to think about it (for the mathematically inclined) is that 1154Another way to think about it (for the mathematically inclined) is that
1078C<ev_periodic> will try to run the callback in this mode at the next possible 1155C<ev_periodic> will try to run the callback in this mode at the next possible
1079time where C<time = at (mod interval)>, regardless of any time jumps. 1156time where C<time = at (mod interval)>, regardless of any time jumps.
1080 1157
1158For numerical stability it is preferable that the C<at> value is near
1159C<ev_now ()> (the current time), but there is no range requirement for
1160this value.
1161
1081=item * manual reschedule mode (reschedule_cb = callback) 1162=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1082 1163
1083In this mode the values for C<interval> and C<at> are both being 1164In this mode the values for C<interval> and C<at> are both being
1084ignored. Instead, each time the periodic watcher gets scheduled, the 1165ignored. Instead, each time the periodic watcher gets scheduled, the
1085reschedule callback will be called with the watcher as first, and the 1166reschedule callback will be called with the watcher as first, and the
1086current time as second argument. 1167current time as second argument.
1087 1168
1088NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, 1169NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1089ever, or make any event loop modifications>. If you need to stop it, 1170ever, or make any event loop modifications>. If you need to stop it,
1090return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by 1171return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1091starting a prepare watcher). 1172starting an C<ev_prepare> watcher, which is legal).
1092 1173
1093Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1174Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1094ev_tstamp now)>, e.g.: 1175ev_tstamp now)>, e.g.:
1095 1176
1096 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1177 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1118 1199
1119Simply stops and restarts the periodic watcher again. This is only useful 1200Simply stops and restarts the periodic watcher again. This is only useful
1120when you changed some parameters or the reschedule callback would return 1201when you changed some parameters or the reschedule callback would return
1121a different time than the last time it was called (e.g. in a crond like 1202a different time than the last time it was called (e.g. in a crond like
1122program when the crontabs have changed). 1203program when the crontabs have changed).
1204
1205=item ev_tstamp offset [read-write]
1206
1207When repeating, this contains the offset value, otherwise this is the
1208absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1209
1210Can be modified any time, but changes only take effect when the periodic
1211timer fires or C<ev_periodic_again> is being called.
1123 1212
1124=item ev_tstamp interval [read-write] 1213=item ev_tstamp interval [read-write]
1125 1214
1126The current interval value. Can be modified any time, but changes only 1215The current interval value. Can be modified any time, but changes only
1127take effect when the periodic timer fires or C<ev_periodic_again> is being 1216take effect when the periodic timer fires or C<ev_periodic_again> is being
1181with the kernel (thus it coexists with your own signal handlers as long 1270with the kernel (thus it coexists with your own signal handlers as long
1182as you don't register any with libev). Similarly, when the last signal 1271as you don't register any with libev). Similarly, when the last signal
1183watcher for a signal is stopped libev will reset the signal handler to 1272watcher for a signal is stopped libev will reset the signal handler to
1184SIG_DFL (regardless of what it was set to before). 1273SIG_DFL (regardless of what it was set to before).
1185 1274
1275=head3 Watcher-Specific Functions and Data Members
1276
1186=over 4 1277=over 4
1187 1278
1188=item ev_signal_init (ev_signal *, callback, int signum) 1279=item ev_signal_init (ev_signal *, callback, int signum)
1189 1280
1190=item ev_signal_set (ev_signal *, int signum) 1281=item ev_signal_set (ev_signal *, int signum)
1201 1292
1202=head2 C<ev_child> - watch out for process status changes 1293=head2 C<ev_child> - watch out for process status changes
1203 1294
1204Child watchers trigger when your process receives a SIGCHLD in response to 1295Child watchers trigger when your process receives a SIGCHLD in response to
1205some child status changes (most typically when a child of yours dies). 1296some child status changes (most typically when a child of yours dies).
1297
1298=head3 Watcher-Specific Functions and Data Members
1206 1299
1207=over 4 1300=over 4
1208 1301
1209=item ev_child_init (ev_child *, callback, int pid) 1302=item ev_child_init (ev_child *, callback, int pid)
1210 1303
1278reader). Inotify will be used to give hints only and should not change the 1371reader). Inotify will be used to give hints only and should not change the
1279semantics of C<ev_stat> watchers, which means that libev sometimes needs 1372semantics of C<ev_stat> watchers, which means that libev sometimes needs
1280to fall back to regular polling again even with inotify, but changes are 1373to fall back to regular polling again even with inotify, but changes are
1281usually detected immediately, and if the file exists there will be no 1374usually detected immediately, and if the file exists there will be no
1282polling. 1375polling.
1376
1377=head3 Watcher-Specific Functions and Data Members
1283 1378
1284=over 4 1379=over 4
1285 1380
1286=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1381=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1287 1382
1351 ev_stat_start (loop, &passwd); 1446 ev_stat_start (loop, &passwd);
1352 1447
1353 1448
1354=head2 C<ev_idle> - when you've got nothing better to do... 1449=head2 C<ev_idle> - when you've got nothing better to do...
1355 1450
1356Idle watchers trigger events when there are no other events are pending 1451Idle watchers trigger events when no other events of the same or higher
1357(prepare, check and other idle watchers do not count). That is, as long 1452priority are pending (prepare, check and other idle watchers do not
1358as your process is busy handling sockets or timeouts (or even signals, 1453count).
1359imagine) it will not be triggered. But when your process is idle all idle 1454
1360watchers are being called again and again, once per event loop iteration - 1455That is, as long as your process is busy handling sockets or timeouts
1456(or even signals, imagine) of the same or higher priority it will not be
1457triggered. But when your process is idle (or only lower-priority watchers
1458are pending), the idle watchers are being called once per event loop
1361until stopped, that is, or your process receives more events and becomes 1459iteration - until stopped, that is, or your process receives more events
1362busy. 1460and becomes busy again with higher priority stuff.
1363 1461
1364The most noteworthy effect is that as long as any idle watchers are 1462The most noteworthy effect is that as long as any idle watchers are
1365active, the process will not block when waiting for new events. 1463active, the process will not block when waiting for new events.
1366 1464
1367Apart from keeping your process non-blocking (which is a useful 1465Apart from keeping your process non-blocking (which is a useful
1368effect on its own sometimes), idle watchers are a good place to do 1466effect on its own sometimes), idle watchers are a good place to do
1369"pseudo-background processing", or delay processing stuff to after the 1467"pseudo-background processing", or delay processing stuff to after the
1370event loop has handled all outstanding events. 1468event loop has handled all outstanding events.
1469
1470=head3 Watcher-Specific Functions and Data Members
1371 1471
1372=over 4 1472=over 4
1373 1473
1374=item ev_idle_init (ev_signal *, callback) 1474=item ev_idle_init (ev_signal *, callback)
1375 1475
1433with priority higher than or equal to the event loop and one coroutine 1533with priority higher than or equal to the event loop and one coroutine
1434of lower priority, but only once, using idle watchers to keep the event 1534of lower priority, but only once, using idle watchers to keep the event
1435loop from blocking if lower-priority coroutines are active, thus mapping 1535loop from blocking if lower-priority coroutines are active, thus mapping
1436low-priority coroutines to idle/background tasks). 1536low-priority coroutines to idle/background tasks).
1437 1537
1538It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1539priority, to ensure that they are being run before any other watchers
1540after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1541too) should not activate ("feed") events into libev. While libev fully
1542supports this, they will be called before other C<ev_check> watchers did
1543their job. As C<ev_check> watchers are often used to embed other event
1544loops those other event loops might be in an unusable state until their
1545C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1546others).
1547
1548=head3 Watcher-Specific Functions and Data Members
1549
1438=over 4 1550=over 4
1439 1551
1440=item ev_prepare_init (ev_prepare *, callback) 1552=item ev_prepare_init (ev_prepare *, callback)
1441 1553
1442=item ev_check_init (ev_check *, callback) 1554=item ev_check_init (ev_check *, callback)
1445parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1557parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1446macros, but using them is utterly, utterly and completely pointless. 1558macros, but using them is utterly, utterly and completely pointless.
1447 1559
1448=back 1560=back
1449 1561
1450Example: To include a library such as adns, you would add IO watchers 1562There are a number of principal ways to embed other event loops or modules
1451and a timeout watcher in a prepare handler, as required by libadns, and 1563into libev. Here are some ideas on how to include libadns into libev
1564(there is a Perl module named C<EV::ADNS> that does this, which you could
1565use for an actually working example. Another Perl module named C<EV::Glib>
1566embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
1567into the Glib event loop).
1568
1569Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1452in a check watcher, destroy them and call into libadns. What follows is 1570and in a check watcher, destroy them and call into libadns. What follows
1453pseudo-code only of course: 1571is pseudo-code only of course. This requires you to either use a low
1572priority for the check watcher or use C<ev_clear_pending> explicitly, as
1573the callbacks for the IO/timeout watchers might not have been called yet.
1454 1574
1455 static ev_io iow [nfd]; 1575 static ev_io iow [nfd];
1456 static ev_timer tw; 1576 static ev_timer tw;
1457 1577
1458 static void 1578 static void
1459 io_cb (ev_loop *loop, ev_io *w, int revents) 1579 io_cb (ev_loop *loop, ev_io *w, int revents)
1460 { 1580 {
1461 // set the relevant poll flags
1462 // could also call adns_processreadable etc. here
1463 struct pollfd *fd = (struct pollfd *)w->data;
1464 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1465 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1466 } 1581 }
1467 1582
1468 // create io watchers for each fd and a timer before blocking 1583 // create io watchers for each fd and a timer before blocking
1469 static void 1584 static void
1470 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1585 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1476 1591
1477 /* the callback is illegal, but won't be called as we stop during check */ 1592 /* the callback is illegal, but won't be called as we stop during check */
1478 ev_timer_init (&tw, 0, timeout * 1e-3); 1593 ev_timer_init (&tw, 0, timeout * 1e-3);
1479 ev_timer_start (loop, &tw); 1594 ev_timer_start (loop, &tw);
1480 1595
1481 // create on ev_io per pollfd 1596 // create one ev_io per pollfd
1482 for (int i = 0; i < nfd; ++i) 1597 for (int i = 0; i < nfd; ++i)
1483 { 1598 {
1484 ev_io_init (iow + i, io_cb, fds [i].fd, 1599 ev_io_init (iow + i, io_cb, fds [i].fd,
1485 ((fds [i].events & POLLIN ? EV_READ : 0) 1600 ((fds [i].events & POLLIN ? EV_READ : 0)
1486 | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1601 | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1487 1602
1488 fds [i].revents = 0; 1603 fds [i].revents = 0;
1489 iow [i].data = fds + i;
1490 ev_io_start (loop, iow + i); 1604 ev_io_start (loop, iow + i);
1491 } 1605 }
1492 } 1606 }
1493 1607
1494 // stop all watchers after blocking 1608 // stop all watchers after blocking
1496 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1610 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1497 { 1611 {
1498 ev_timer_stop (loop, &tw); 1612 ev_timer_stop (loop, &tw);
1499 1613
1500 for (int i = 0; i < nfd; ++i) 1614 for (int i = 0; i < nfd; ++i)
1615 {
1616 // set the relevant poll flags
1617 // could also call adns_processreadable etc. here
1618 struct pollfd *fd = fds + i;
1619 int revents = ev_clear_pending (iow + i);
1620 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1621 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1622
1623 // now stop the watcher
1501 ev_io_stop (loop, iow + i); 1624 ev_io_stop (loop, iow + i);
1625 }
1502 1626
1503 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1627 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1628 }
1629
1630Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1631in the prepare watcher and would dispose of the check watcher.
1632
1633Method 3: If the module to be embedded supports explicit event
1634notification (adns does), you can also make use of the actual watcher
1635callbacks, and only destroy/create the watchers in the prepare watcher.
1636
1637 static void
1638 timer_cb (EV_P_ ev_timer *w, int revents)
1639 {
1640 adns_state ads = (adns_state)w->data;
1641 update_now (EV_A);
1642
1643 adns_processtimeouts (ads, &tv_now);
1644 }
1645
1646 static void
1647 io_cb (EV_P_ ev_io *w, int revents)
1648 {
1649 adns_state ads = (adns_state)w->data;
1650 update_now (EV_A);
1651
1652 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1653 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1654 }
1655
1656 // do not ever call adns_afterpoll
1657
1658Method 4: Do not use a prepare or check watcher because the module you
1659want to embed is too inflexible to support it. Instead, youc na override
1660their poll function. The drawback with this solution is that the main
1661loop is now no longer controllable by EV. The C<Glib::EV> module does
1662this.
1663
1664 static gint
1665 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1666 {
1667 int got_events = 0;
1668
1669 for (n = 0; n < nfds; ++n)
1670 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1671
1672 if (timeout >= 0)
1673 // create/start timer
1674
1675 // poll
1676 ev_loop (EV_A_ 0);
1677
1678 // stop timer again
1679 if (timeout >= 0)
1680 ev_timer_stop (EV_A_ &to);
1681
1682 // stop io watchers again - their callbacks should have set
1683 for (n = 0; n < nfds; ++n)
1684 ev_io_stop (EV_A_ iow [n]);
1685
1686 return got_events;
1504 } 1687 }
1505 1688
1506 1689
1507=head2 C<ev_embed> - when one backend isn't enough... 1690=head2 C<ev_embed> - when one backend isn't enough...
1508 1691
1572 ev_embed_start (loop_hi, &embed); 1755 ev_embed_start (loop_hi, &embed);
1573 } 1756 }
1574 else 1757 else
1575 loop_lo = loop_hi; 1758 loop_lo = loop_hi;
1576 1759
1760=head3 Watcher-Specific Functions and Data Members
1761
1577=over 4 1762=over 4
1578 1763
1579=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 1764=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1580 1765
1581=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 1766=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1607event loop blocks next and before C<ev_check> watchers are being called, 1792event loop blocks next and before C<ev_check> watchers are being called,
1608and only in the child after the fork. If whoever good citizen calling 1793and only in the child after the fork. If whoever good citizen calling
1609C<ev_default_fork> cheats and calls it in the wrong process, the fork 1794C<ev_default_fork> cheats and calls it in the wrong process, the fork
1610handlers will be invoked, too, of course. 1795handlers will be invoked, too, of course.
1611 1796
1797=head3 Watcher-Specific Functions and Data Members
1798
1612=over 4 1799=over 4
1613 1800
1614=item ev_fork_init (ev_signal *, callback) 1801=item ev_fork_init (ev_signal *, callback)
1615 1802
1616Initialises and configures the fork watcher - it has no parameters of any 1803Initialises and configures the fork watcher - it has no parameters of any
1712 1899
1713To use it, 1900To use it,
1714 1901
1715 #include <ev++.h> 1902 #include <ev++.h>
1716 1903
1717(it is not installed by default). This automatically includes F<ev.h> 1904This automatically includes F<ev.h> and puts all of its definitions (many
1718and puts all of its definitions (many of them macros) into the global 1905of them macros) into the global namespace. All C++ specific things are
1719namespace. All C++ specific things are put into the C<ev> namespace. 1906put into the C<ev> namespace. It should support all the same embedding
1907options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1720 1908
1721It should support all the same embedding options as F<ev.h>, most notably 1909Care has been taken to keep the overhead low. The only data member the C++
1722C<EV_MULTIPLICITY>. 1910classes add (compared to plain C-style watchers) is the event loop pointer
1911that the watcher is associated with (or no additional members at all if
1912you disable C<EV_MULTIPLICITY> when embedding libev).
1913
1914Currently, functions, and static and non-static member functions can be
1915used as callbacks. Other types should be easy to add as long as they only
1916need one additional pointer for context. If you need support for other
1917types of functors please contact the author (preferably after implementing
1918it).
1723 1919
1724Here is a list of things available in the C<ev> namespace: 1920Here is a list of things available in the C<ev> namespace:
1725 1921
1726=over 4 1922=over 4
1727 1923
1743 1939
1744All of those classes have these methods: 1940All of those classes have these methods:
1745 1941
1746=over 4 1942=over 4
1747 1943
1748=item ev::TYPE::TYPE (object *, object::method *) 1944=item ev::TYPE::TYPE ()
1749 1945
1750=item ev::TYPE::TYPE (object *, object::method *, struct ev_loop *) 1946=item ev::TYPE::TYPE (struct ev_loop *)
1751 1947
1752=item ev::TYPE::~TYPE 1948=item ev::TYPE::~TYPE
1753 1949
1754The constructor takes a pointer to an object and a method pointer to 1950The constructor (optionally) takes an event loop to associate the watcher
1755the event handler callback to call in this class. The constructor calls 1951with. If it is omitted, it will use C<EV_DEFAULT>.
1756C<ev_init> for you, which means you have to call the C<set> method 1952
1757before starting it. If you do not specify a loop then the constructor 1953The constructor calls C<ev_init> for you, which means you have to call the
1758automatically associates the default loop with this watcher. 1954C<set> method before starting it.
1955
1956It will not set a callback, however: You have to call the templated C<set>
1957method to set a callback before you can start the watcher.
1958
1959(The reason why you have to use a method is a limitation in C++ which does
1960not allow explicit template arguments for constructors).
1759 1961
1760The destructor automatically stops the watcher if it is active. 1962The destructor automatically stops the watcher if it is active.
1963
1964=item w->set<class, &class::method> (object *)
1965
1966This method sets the callback method to call. The method has to have a
1967signature of C<void (*)(ev_TYPE &, int)>, it receives the watcher as
1968first argument and the C<revents> as second. The object must be given as
1969parameter and is stored in the C<data> member of the watcher.
1970
1971This method synthesizes efficient thunking code to call your method from
1972the C callback that libev requires. If your compiler can inline your
1973callback (i.e. it is visible to it at the place of the C<set> call and
1974your compiler is good :), then the method will be fully inlined into the
1975thunking function, making it as fast as a direct C callback.
1976
1977Example: simple class declaration and watcher initialisation
1978
1979 struct myclass
1980 {
1981 void io_cb (ev::io &w, int revents) { }
1982 }
1983
1984 myclass obj;
1985 ev::io iow;
1986 iow.set <myclass, &myclass::io_cb> (&obj);
1987
1988=item w->set<function> (void *data = 0)
1989
1990Also sets a callback, but uses a static method or plain function as
1991callback. The optional C<data> argument will be stored in the watcher's
1992C<data> member and is free for you to use.
1993
1994The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
1995
1996See the method-C<set> above for more details.
1997
1998Example:
1999
2000 static void io_cb (ev::io &w, int revents) { }
2001 iow.set <io_cb> ();
1761 2002
1762=item w->set (struct ev_loop *) 2003=item w->set (struct ev_loop *)
1763 2004
1764Associates a different C<struct ev_loop> with this watcher. You can only 2005Associates a different C<struct ev_loop> with this watcher. You can only
1765do this when the watcher is inactive (and not pending either). 2006do this when the watcher is inactive (and not pending either).
1766 2007
1767=item w->set ([args]) 2008=item w->set ([args])
1768 2009
1769Basically the same as C<ev_TYPE_set>, with the same args. Must be 2010Basically the same as C<ev_TYPE_set>, with the same args. Must be
1770called at least once. Unlike the C counterpart, an active watcher gets 2011called at least once. Unlike the C counterpart, an active watcher gets
1771automatically stopped and restarted. 2012automatically stopped and restarted when reconfiguring it with this
2013method.
1772 2014
1773=item w->start () 2015=item w->start ()
1774 2016
1775Starts the watcher. Note that there is no C<loop> argument as the 2017Starts the watcher. Note that there is no C<loop> argument, as the
1776constructor already takes the loop. 2018constructor already stores the event loop.
1777 2019
1778=item w->stop () 2020=item w->stop ()
1779 2021
1780Stops the watcher if it is active. Again, no C<loop> argument. 2022Stops the watcher if it is active. Again, no C<loop> argument.
1781 2023
1782=item w->again () C<ev::timer>, C<ev::periodic> only 2024=item w->again () (C<ev::timer>, C<ev::periodic> only)
1783 2025
1784For C<ev::timer> and C<ev::periodic>, this invokes the corresponding 2026For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1785C<ev_TYPE_again> function. 2027C<ev_TYPE_again> function.
1786 2028
1787=item w->sweep () C<ev::embed> only 2029=item w->sweep () (C<ev::embed> only)
1788 2030
1789Invokes C<ev_embed_sweep>. 2031Invokes C<ev_embed_sweep>.
1790 2032
1791=item w->update () C<ev::stat> only 2033=item w->update () (C<ev::stat> only)
1792 2034
1793Invokes C<ev_stat_stat>. 2035Invokes C<ev_stat_stat>.
1794 2036
1795=back 2037=back
1796 2038
1806 2048
1807 myclass (); 2049 myclass ();
1808 } 2050 }
1809 2051
1810 myclass::myclass (int fd) 2052 myclass::myclass (int fd)
1811 : io (this, &myclass::io_cb),
1812 idle (this, &myclass::idle_cb)
1813 { 2053 {
2054 io .set <myclass, &myclass::io_cb > (this);
2055 idle.set <myclass, &myclass::idle_cb> (this);
2056
1814 io.start (fd, ev::READ); 2057 io.start (fd, ev::READ);
1815 } 2058 }
1816 2059
1817 2060
1818=head1 MACRO MAGIC 2061=head1 MACRO MAGIC
1819 2062
1820Libev can be compiled with a variety of options, the most fundemantal is 2063Libev can be compiled with a variety of options, the most fundamantal
1821C<EV_MULTIPLICITY>. This option determines wether (most) functions and 2064of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1822callbacks have an initial C<struct ev_loop *> argument. 2065functions and callbacks have an initial C<struct ev_loop *> argument.
1823 2066
1824To make it easier to write programs that cope with either variant, the 2067To make it easier to write programs that cope with either variant, the
1825following macros are defined: 2068following macros are defined:
1826 2069
1827=over 4 2070=over 4
1860loop, if multiple loops are supported ("ev loop default"). 2103loop, if multiple loops are supported ("ev loop default").
1861 2104
1862=back 2105=back
1863 2106
1864Example: Declare and initialise a check watcher, utilising the above 2107Example: Declare and initialise a check watcher, utilising the above
1865macros so it will work regardless of wether multiple loops are supported 2108macros so it will work regardless of whether multiple loops are supported
1866or not. 2109or not.
1867 2110
1868 static void 2111 static void
1869 check_cb (EV_P_ ev_timer *w, int revents) 2112 check_cb (EV_P_ ev_timer *w, int revents)
1870 { 2113 {
2095will have the C<struct ev_loop *> as first argument, and you can create 2338will have the C<struct ev_loop *> as first argument, and you can create
2096additional independent event loops. Otherwise there will be no support 2339additional independent event loops. Otherwise there will be no support
2097for multiple event loops and there is no first event loop pointer 2340for multiple event loops and there is no first event loop pointer
2098argument. Instead, all functions act on the single default loop. 2341argument. Instead, all functions act on the single default loop.
2099 2342
2343=item EV_MINPRI
2344
2345=item EV_MAXPRI
2346
2347The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to
2348C<EV_MAXPRI>, but otherwise there are no non-obvious limitations. You can
2349provide for more priorities by overriding those symbols (usually defined
2350to be C<-2> and C<2>, respectively).
2351
2352When doing priority-based operations, libev usually has to linearly search
2353all the priorities, so having many of them (hundreds) uses a lot of space
2354and time, so using the defaults of five priorities (-2 .. +2) is usually
2355fine.
2356
2357If your embedding app does not need any priorities, defining these both to
2358C<0> will save some memory and cpu.
2359
2100=item EV_PERIODIC_ENABLE 2360=item EV_PERIODIC_ENABLE
2101 2361
2102If undefined or defined to be C<1>, then periodic timers are supported. If 2362If undefined or defined to be C<1>, then periodic timers are supported. If
2363defined to be C<0>, then they are not. Disabling them saves a few kB of
2364code.
2365
2366=item EV_IDLE_ENABLE
2367
2368If undefined or defined to be C<1>, then idle watchers are supported. If
2103defined to be C<0>, then they are not. Disabling them saves a few kB of 2369defined to be C<0>, then they are not. Disabling them saves a few kB of
2104code. 2370code.
2105 2371
2106=item EV_EMBED_ENABLE 2372=item EV_EMBED_ENABLE
2107 2373
2200 2466
2201In this section the complexities of (many of) the algorithms used inside 2467In this section the complexities of (many of) the algorithms used inside
2202libev will be explained. For complexity discussions about backends see the 2468libev will be explained. For complexity discussions about backends see the
2203documentation for C<ev_default_init>. 2469documentation for C<ev_default_init>.
2204 2470
2471All of the following are about amortised time: If an array needs to be
2472extended, libev needs to realloc and move the whole array, but this
2473happens asymptotically never with higher number of elements, so O(1) might
2474mean it might do a lengthy realloc operation in rare cases, but on average
2475it is much faster and asymptotically approaches constant time.
2476
2205=over 4 2477=over 4
2206 2478
2207=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2479=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2208 2480
2481This means that, when you have a watcher that triggers in one hour and
2482there are 100 watchers that would trigger before that then inserting will
2483have to skip those 100 watchers.
2484
2209=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2485=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)
2210 2486
2487That means that for changing a timer costs less than removing/adding them
2488as only the relative motion in the event queue has to be paid for.
2489
2211=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2490=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2212 2491
2492These just add the watcher into an array or at the head of a list.
2213=item Stopping check/prepare/idle watchers: O(1) 2493=item Stopping check/prepare/idle watchers: O(1)
2214 2494
2215=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2495=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2216 2496
2497These watchers are stored in lists then need to be walked to find the
2498correct watcher to remove. The lists are usually short (you don't usually
2499have many watchers waiting for the same fd or signal).
2500
2217=item Finding the next timer per loop iteration: O(1) 2501=item Finding the next timer per loop iteration: O(1)
2218 2502
2219=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2503=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2220 2504
2505A change means an I/O watcher gets started or stopped, which requires
2506libev to recalculate its status (and possibly tell the kernel).
2507
2221=item Activating one watcher: O(1) 2508=item Activating one watcher: O(1)
2222 2509
2510=item Priority handling: O(number_of_priorities)
2511
2512Priorities are implemented by allocating some space for each
2513priority. When doing priority-based operations, libev usually has to
2514linearly search all the priorities.
2515
2223=back 2516=back
2224 2517
2225 2518
2226=head1 AUTHOR 2519=head1 AUTHOR
2227 2520

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