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Revision 1.71 by root, Fri Dec 7 20:13:09 2007 UTC vs.
Revision 1.90 by root, Thu Dec 20 01:18:37 2007 UTC

98Libev represents time as a single floating point number, representing the 98Libev represents time as a single floating point number, representing the
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 99(fractional) number of seconds since the (POSIX) epoch (somewhere near
100the beginning of 1970, details are complicated, don't ask). This type is 100the beginning of 1970, details are complicated, don't ask). This type is
101called C<ev_tstamp>, which is what you should use too. It usually aliases 101called C<ev_tstamp>, which is what you should use too. It usually aliases
102to the C<double> type in C, and when you need to do any calculations on 102to the C<double> type in C, and when you need to do any calculations on
103it, you should treat it as such. 103it, you should treat it as some floatingpoint value. Unlike the name
104component C<stamp> might indicate, it is also used for time differences
105throughout libev.
104 106
105=head1 GLOBAL FUNCTIONS 107=head1 GLOBAL FUNCTIONS
106 108
107These functions can be called anytime, even before initialising the 109These functions can be called anytime, even before initialising the
108library in any way. 110library in any way.
117 119
118=item int ev_version_major () 120=item int ev_version_major ()
119 121
120=item int ev_version_minor () 122=item int ev_version_minor ()
121 123
122You can find out the major and minor version numbers of the library 124You can find out the major and minor ABI version numbers of the library
123you linked against by calling the functions C<ev_version_major> and 125you linked against by calling the functions C<ev_version_major> and
124C<ev_version_minor>. If you want, you can compare against the global 126C<ev_version_minor>. If you want, you can compare against the global
125symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 127symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126version of the library your program was compiled against. 128version of the library your program was compiled against.
127 129
130These version numbers refer to the ABI version of the library, not the
131release version.
132
128Usually, it's a good idea to terminate if the major versions mismatch, 133Usually, it's a good idea to terminate if the major versions mismatch,
129as this indicates an incompatible change. Minor versions are usually 134as this indicates an incompatible change. Minor versions are usually
130compatible to older versions, so a larger minor version alone is usually 135compatible to older versions, so a larger minor version alone is usually
131not a problem. 136not a problem.
132 137
133Example: Make sure we haven't accidentally been linked against the wrong 138Example: Make sure we haven't accidentally been linked against the wrong
134version. 139version.
326 331
327=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 332=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328 333
329Kqueue deserves special mention, as at the time of this writing, it 334Kqueue deserves special mention, as at the time of this writing, it
330was broken on all BSDs except NetBSD (usually it doesn't work with 335was broken on all BSDs except NetBSD (usually it doesn't work with
331anything but sockets and pipes, except on Darwin, where of course its 336anything but sockets and pipes, except on Darwin, where of course it's
332completely useless). For this reason its not being "autodetected" 337completely useless). For this reason it's not being "autodetected"
333unless you explicitly specify it explicitly in the flags (i.e. using 338unless you explicitly specify it explicitly in the flags (i.e. using
334C<EVBACKEND_KQUEUE>). 339C<EVBACKEND_KQUEUE>).
335 340
336It scales in the same way as the epoll backend, but the interface to the 341It scales in the same way as the epoll backend, but the interface to the
337kernel is more efficient (which says nothing about its actual speed, of 342kernel is more efficient (which says nothing about its actual speed, of
399Destroys the default loop again (frees all memory and kernel state 404Destroys the default loop again (frees all memory and kernel state
400etc.). None of the active event watchers will be stopped in the normal 405etc.). None of the active event watchers will be stopped in the normal
401sense, so e.g. C<ev_is_active> might still return true. It is your 406sense, so e.g. C<ev_is_active> might still return true. It is your
402responsibility to either stop all watchers cleanly yoursef I<before> 407responsibility to either stop all watchers cleanly yoursef I<before>
403calling this function, or cope with the fact afterwards (which is usually 408calling this function, or cope with the fact afterwards (which is usually
404the easiest thing, youc na just ignore the watchers and/or C<free ()> them 409the easiest thing, you can just ignore the watchers and/or C<free ()> them
405for example). 410for example).
411
412Note that certain global state, such as signal state, will not be freed by
413this function, and related watchers (such as signal and child watchers)
414would need to be stopped manually.
415
416In general it is not advisable to call this function except in the
417rare occasion where you really need to free e.g. the signal handling
418pipe fds. If you need dynamically allocated loops it is better to use
419C<ev_loop_new> and C<ev_loop_destroy>).
406 420
407=item ev_loop_destroy (loop) 421=item ev_loop_destroy (loop)
408 422
409Like C<ev_default_destroy>, but destroys an event loop created by an 423Like C<ev_default_destroy>, but destroys an event loop created by an
410earlier call to C<ev_loop_new>. 424earlier call to C<ev_loop_new>.
486libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is 500libev watchers. However, a pair of C<ev_prepare>/C<ev_check> watchers is
487usually a better approach for this kind of thing. 501usually a better approach for this kind of thing.
488 502
489Here are the gory details of what C<ev_loop> does: 503Here are the gory details of what C<ev_loop> does:
490 504
505 - Before the first iteration, call any pending watchers.
491 * If there are no active watchers (reference count is zero), return. 506 * If there are no active watchers (reference count is zero), return.
492 - Queue prepare watchers and then call all outstanding watchers. 507 - Queue all prepare watchers and then call all outstanding watchers.
493 - If we have been forked, recreate the kernel state. 508 - If we have been forked, recreate the kernel state.
494 - Update the kernel state with all outstanding changes. 509 - Update the kernel state with all outstanding changes.
495 - Update the "event loop time". 510 - Update the "event loop time".
496 - Calculate for how long to block. 511 - Calculate for how long to block.
497 - Block the process, waiting for any events. 512 - Block the process, waiting for any events.
736=item bool ev_is_pending (ev_TYPE *watcher) 751=item bool ev_is_pending (ev_TYPE *watcher)
737 752
738Returns a true value iff the watcher is pending, (i.e. it has outstanding 753Returns a true value iff the watcher is pending, (i.e. it has outstanding
739events but its callback has not yet been invoked). As long as a watcher 754events but its callback has not yet been invoked). As long as a watcher
740is pending (but not active) you must not call an init function on it (but 755is pending (but not active) you must not call an init function on it (but
741C<ev_TYPE_set> is safe) and you must make sure the watcher is available to 756C<ev_TYPE_set> is safe), you must not change its priority, and you must
742libev (e.g. you cnanot C<free ()> it). 757make sure the watcher is available to libev (e.g. you cannot C<free ()>
758it).
743 759
744=item callback ev_cb (ev_TYPE *watcher) 760=item callback ev_cb (ev_TYPE *watcher)
745 761
746Returns the callback currently set on the watcher. 762Returns the callback currently set on the watcher.
747 763
766watchers on the same event and make sure one is called first. 782watchers on the same event and make sure one is called first.
767 783
768If you need to suppress invocation when higher priority events are pending 784If you need to suppress invocation when higher priority events are pending
769you need to look at C<ev_idle> watchers, which provide this functionality. 785you need to look at C<ev_idle> watchers, which provide this functionality.
770 786
787You I<must not> change the priority of a watcher as long as it is active or
788pending.
789
771The default priority used by watchers when no priority has been set is 790The default priority used by watchers when no priority has been set is
772always C<0>, which is supposed to not be too high and not be too low :). 791always C<0>, which is supposed to not be too high and not be too low :).
773 792
774Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is 793Setting a priority outside the range of C<EV_MINPRI> to C<EV_MAXPRI> is
775fine, as long as you do not mind that the priority value you query might 794fine, as long as you do not mind that the priority value you query might
776or might not have been adjusted to be within valid range. 795or might not have been adjusted to be within valid range.
796
797=item ev_invoke (loop, ev_TYPE *watcher, int revents)
798
799Invoke the C<watcher> with the given C<loop> and C<revents>. Neither
800C<loop> nor C<revents> need to be valid as long as the watcher callback
801can deal with that fact.
802
803=item int ev_clear_pending (loop, ev_TYPE *watcher)
804
805If the watcher is pending, this function returns clears its pending status
806and returns its C<revents> bitset (as if its callback was invoked). If the
807watcher isn't pending it does nothing and returns C<0>.
777 808
778=back 809=back
779 810
780 811
781=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 812=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
891play around with an Xlib connection), then you have to seperately re-test 922play around with an Xlib connection), then you have to seperately re-test
892whether a file descriptor is really ready with a known-to-be good interface 923whether a file descriptor is really ready with a known-to-be good interface
893such as poll (fortunately in our Xlib example, Xlib already does this on 924such as poll (fortunately in our Xlib example, Xlib already does this on
894its own, so its quite safe to use). 925its own, so its quite safe to use).
895 926
927=head3 The special problem of disappearing file descriptors
928
929Some backends (e.g kqueue, epoll) need to be told about closing a file
930descriptor (either by calling C<close> explicitly or by any other means,
931such as C<dup>). The reason is that you register interest in some file
932descriptor, but when it goes away, the operating system will silently drop
933this interest. If another file descriptor with the same number then is
934registered with libev, there is no efficient way to see that this is, in
935fact, a different file descriptor.
936
937To avoid having to explicitly tell libev about such cases, libev follows
938the following policy: Each time C<ev_io_set> is being called, libev
939will assume that this is potentially a new file descriptor, otherwise
940it is assumed that the file descriptor stays the same. That means that
941you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
942descriptor even if the file descriptor number itself did not change.
943
944This is how one would do it normally anyway, the important point is that
945the libev application should not optimise around libev but should leave
946optimisations to libev.
947
948
949=head3 Watcher-Specific Functions
950
896=over 4 951=over 4
897 952
898=item ev_io_init (ev_io *, callback, int fd, int events) 953=item ev_io_init (ev_io *, callback, int fd, int events)
899 954
900=item ev_io_set (ev_io *, int fd, int events) 955=item ev_io_set (ev_io *, int fd, int events)
952 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1007 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
953 1008
954The callback is guarenteed to be invoked only when its timeout has passed, 1009The callback is guarenteed to be invoked only when its timeout has passed,
955but if multiple timers become ready during the same loop iteration then 1010but if multiple timers become ready during the same loop iteration then
956order of execution is undefined. 1011order of execution is undefined.
1012
1013=head3 Watcher-Specific Functions and Data Members
957 1014
958=over 4 1015=over 4
959 1016
960=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1017=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
961 1018
1057but on wallclock time (absolute time). You can tell a periodic watcher 1114but on wallclock time (absolute time). You can tell a periodic watcher
1058to trigger "at" some specific point in time. For example, if you tell a 1115to trigger "at" some specific point in time. For example, if you tell a
1059periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () 1116periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1060+ 10.>) and then reset your system clock to the last year, then it will 1117+ 10.>) and then reset your system clock to the last year, then it will
1061take a year to trigger the event (unlike an C<ev_timer>, which would trigger 1118take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1062roughly 10 seconds later and of course not if you reset your system time 1119roughly 10 seconds later).
1063again).
1064 1120
1065They can also be used to implement vastly more complex timers, such as 1121They can also be used to implement vastly more complex timers, such as
1066triggering an event on eahc midnight, local time. 1122triggering an event on each midnight, local time or other, complicated,
1123rules.
1067 1124
1068As with timers, the callback is guarenteed to be invoked only when the 1125As with timers, the callback is guarenteed to be invoked only when the
1069time (C<at>) has been passed, but if multiple periodic timers become ready 1126time (C<at>) has been passed, but if multiple periodic timers become ready
1070during the same loop iteration then order of execution is undefined. 1127during the same loop iteration then order of execution is undefined.
1071 1128
1129=head3 Watcher-Specific Functions and Data Members
1130
1072=over 4 1131=over 4
1073 1132
1074=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) 1133=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1075 1134
1076=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) 1135=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
1078Lots of arguments, lets sort it out... There are basically three modes of 1137Lots of arguments, lets sort it out... There are basically three modes of
1079operation, and we will explain them from simplest to complex: 1138operation, and we will explain them from simplest to complex:
1080 1139
1081=over 4 1140=over 4
1082 1141
1083=item * absolute timer (interval = reschedule_cb = 0) 1142=item * absolute timer (at = time, interval = reschedule_cb = 0)
1084 1143
1085In this configuration the watcher triggers an event at the wallclock time 1144In this configuration the watcher triggers an event at the wallclock time
1086C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1145C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1087that is, if it is to be run at January 1st 2011 then it will run when the 1146that is, if it is to be run at January 1st 2011 then it will run when the
1088system time reaches or surpasses this time. 1147system time reaches or surpasses this time.
1089 1148
1090=item * non-repeating interval timer (interval > 0, reschedule_cb = 0) 1149=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1091 1150
1092In this mode the watcher will always be scheduled to time out at the next 1151In this mode the watcher will always be scheduled to time out at the next
1093C<at + N * interval> time (for some integer N) and then repeat, regardless 1152C<at + N * interval> time (for some integer N, which can also be negative)
1094of any time jumps. 1153and then repeat, regardless of any time jumps.
1095 1154
1096This can be used to create timers that do not drift with respect to system 1155This can be used to create timers that do not drift with respect to system
1097time: 1156time:
1098 1157
1099 ev_periodic_set (&periodic, 0., 3600., 0); 1158 ev_periodic_set (&periodic, 0., 3600., 0);
1105 1164
1106Another way to think about it (for the mathematically inclined) is that 1165Another way to think about it (for the mathematically inclined) is that
1107C<ev_periodic> will try to run the callback in this mode at the next possible 1166C<ev_periodic> will try to run the callback in this mode at the next possible
1108time where C<time = at (mod interval)>, regardless of any time jumps. 1167time where C<time = at (mod interval)>, regardless of any time jumps.
1109 1168
1169For numerical stability it is preferable that the C<at> value is near
1170C<ev_now ()> (the current time), but there is no range requirement for
1171this value.
1172
1110=item * manual reschedule mode (reschedule_cb = callback) 1173=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1111 1174
1112In this mode the values for C<interval> and C<at> are both being 1175In this mode the values for C<interval> and C<at> are both being
1113ignored. Instead, each time the periodic watcher gets scheduled, the 1176ignored. Instead, each time the periodic watcher gets scheduled, the
1114reschedule callback will be called with the watcher as first, and the 1177reschedule callback will be called with the watcher as first, and the
1115current time as second argument. 1178current time as second argument.
1116 1179
1117NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, 1180NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1118ever, or make any event loop modifications>. If you need to stop it, 1181ever, or make any event loop modifications>. If you need to stop it,
1119return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by 1182return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1120starting a prepare watcher). 1183starting an C<ev_prepare> watcher, which is legal).
1121 1184
1122Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1185Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1123ev_tstamp now)>, e.g.: 1186ev_tstamp now)>, e.g.:
1124 1187
1125 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1188 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
1148Simply stops and restarts the periodic watcher again. This is only useful 1211Simply stops and restarts the periodic watcher again. This is only useful
1149when you changed some parameters or the reschedule callback would return 1212when you changed some parameters or the reschedule callback would return
1150a different time than the last time it was called (e.g. in a crond like 1213a different time than the last time it was called (e.g. in a crond like
1151program when the crontabs have changed). 1214program when the crontabs have changed).
1152 1215
1216=item ev_tstamp offset [read-write]
1217
1218When repeating, this contains the offset value, otherwise this is the
1219absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1220
1221Can be modified any time, but changes only take effect when the periodic
1222timer fires or C<ev_periodic_again> is being called.
1223
1153=item ev_tstamp interval [read-write] 1224=item ev_tstamp interval [read-write]
1154 1225
1155The current interval value. Can be modified any time, but changes only 1226The current interval value. Can be modified any time, but changes only
1156take effect when the periodic timer fires or C<ev_periodic_again> is being 1227take effect when the periodic timer fires or C<ev_periodic_again> is being
1157called. 1228called.
1159=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] 1230=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]
1160 1231
1161The current reschedule callback, or C<0>, if this functionality is 1232The current reschedule callback, or C<0>, if this functionality is
1162switched off. Can be changed any time, but changes only take effect when 1233switched off. Can be changed any time, but changes only take effect when
1163the periodic timer fires or C<ev_periodic_again> is being called. 1234the periodic timer fires or C<ev_periodic_again> is being called.
1235
1236=item ev_tstamp at [read-only]
1237
1238When active, contains the absolute time that the watcher is supposed to
1239trigger next.
1164 1240
1165=back 1241=back
1166 1242
1167Example: Call a callback every hour, or, more precisely, whenever the 1243Example: Call a callback every hour, or, more precisely, whenever the
1168system clock is divisible by 3600. The callback invocation times have 1244system clock is divisible by 3600. The callback invocation times have
1210with the kernel (thus it coexists with your own signal handlers as long 1286with the kernel (thus it coexists with your own signal handlers as long
1211as you don't register any with libev). Similarly, when the last signal 1287as you don't register any with libev). Similarly, when the last signal
1212watcher for a signal is stopped libev will reset the signal handler to 1288watcher for a signal is stopped libev will reset the signal handler to
1213SIG_DFL (regardless of what it was set to before). 1289SIG_DFL (regardless of what it was set to before).
1214 1290
1291=head3 Watcher-Specific Functions and Data Members
1292
1215=over 4 1293=over 4
1216 1294
1217=item ev_signal_init (ev_signal *, callback, int signum) 1295=item ev_signal_init (ev_signal *, callback, int signum)
1218 1296
1219=item ev_signal_set (ev_signal *, int signum) 1297=item ev_signal_set (ev_signal *, int signum)
1230 1308
1231=head2 C<ev_child> - watch out for process status changes 1309=head2 C<ev_child> - watch out for process status changes
1232 1310
1233Child watchers trigger when your process receives a SIGCHLD in response to 1311Child watchers trigger when your process receives a SIGCHLD in response to
1234some child status changes (most typically when a child of yours dies). 1312some child status changes (most typically when a child of yours dies).
1313
1314=head3 Watcher-Specific Functions and Data Members
1235 1315
1236=over 4 1316=over 4
1237 1317
1238=item ev_child_init (ev_child *, callback, int pid) 1318=item ev_child_init (ev_child *, callback, int pid)
1239 1319
1307reader). Inotify will be used to give hints only and should not change the 1387reader). Inotify will be used to give hints only and should not change the
1308semantics of C<ev_stat> watchers, which means that libev sometimes needs 1388semantics of C<ev_stat> watchers, which means that libev sometimes needs
1309to fall back to regular polling again even with inotify, but changes are 1389to fall back to regular polling again even with inotify, but changes are
1310usually detected immediately, and if the file exists there will be no 1390usually detected immediately, and if the file exists there will be no
1311polling. 1391polling.
1392
1393=head3 Watcher-Specific Functions and Data Members
1312 1394
1313=over 4 1395=over 4
1314 1396
1315=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1397=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1316 1398
1399Apart from keeping your process non-blocking (which is a useful 1481Apart from keeping your process non-blocking (which is a useful
1400effect on its own sometimes), idle watchers are a good place to do 1482effect on its own sometimes), idle watchers are a good place to do
1401"pseudo-background processing", or delay processing stuff to after the 1483"pseudo-background processing", or delay processing stuff to after the
1402event loop has handled all outstanding events. 1484event loop has handled all outstanding events.
1403 1485
1486=head3 Watcher-Specific Functions and Data Members
1487
1404=over 4 1488=over 4
1405 1489
1406=item ev_idle_init (ev_signal *, callback) 1490=item ev_idle_init (ev_signal *, callback)
1407 1491
1408Initialises and configures the idle watcher - it has no parameters of any 1492Initialises and configures the idle watcher - it has no parameters of any
1465with priority higher than or equal to the event loop and one coroutine 1549with priority higher than or equal to the event loop and one coroutine
1466of lower priority, but only once, using idle watchers to keep the event 1550of lower priority, but only once, using idle watchers to keep the event
1467loop from blocking if lower-priority coroutines are active, thus mapping 1551loop from blocking if lower-priority coroutines are active, thus mapping
1468low-priority coroutines to idle/background tasks). 1552low-priority coroutines to idle/background tasks).
1469 1553
1554It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1555priority, to ensure that they are being run before any other watchers
1556after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1557too) should not activate ("feed") events into libev. While libev fully
1558supports this, they will be called before other C<ev_check> watchers did
1559their job. As C<ev_check> watchers are often used to embed other event
1560loops those other event loops might be in an unusable state until their
1561C<ev_check> watcher ran (always remind yourself to coexist peacefully with
1562others).
1563
1564=head3 Watcher-Specific Functions and Data Members
1565
1470=over 4 1566=over 4
1471 1567
1472=item ev_prepare_init (ev_prepare *, callback) 1568=item ev_prepare_init (ev_prepare *, callback)
1473 1569
1474=item ev_check_init (ev_check *, callback) 1570=item ev_check_init (ev_check *, callback)
1477parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1573parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1478macros, but using them is utterly, utterly and completely pointless. 1574macros, but using them is utterly, utterly and completely pointless.
1479 1575
1480=back 1576=back
1481 1577
1482Example: To include a library such as adns, you would add IO watchers 1578There are a number of principal ways to embed other event loops or modules
1483and a timeout watcher in a prepare handler, as required by libadns, and 1579into libev. Here are some ideas on how to include libadns into libev
1580(there is a Perl module named C<EV::ADNS> that does this, which you could
1581use for an actually working example. Another Perl module named C<EV::Glib>
1582embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
1583into the Glib event loop).
1584
1585Method 1: Add IO watchers and a timeout watcher in a prepare handler,
1484in a check watcher, destroy them and call into libadns. What follows is 1586and in a check watcher, destroy them and call into libadns. What follows
1485pseudo-code only of course: 1587is pseudo-code only of course. This requires you to either use a low
1588priority for the check watcher or use C<ev_clear_pending> explicitly, as
1589the callbacks for the IO/timeout watchers might not have been called yet.
1486 1590
1487 static ev_io iow [nfd]; 1591 static ev_io iow [nfd];
1488 static ev_timer tw; 1592 static ev_timer tw;
1489 1593
1490 static void 1594 static void
1491 io_cb (ev_loop *loop, ev_io *w, int revents) 1595 io_cb (ev_loop *loop, ev_io *w, int revents)
1492 { 1596 {
1493 // set the relevant poll flags
1494 // could also call adns_processreadable etc. here
1495 struct pollfd *fd = (struct pollfd *)w->data;
1496 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1497 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1498 } 1597 }
1499 1598
1500 // create io watchers for each fd and a timer before blocking 1599 // create io watchers for each fd and a timer before blocking
1501 static void 1600 static void
1502 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1601 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1508 1607
1509 /* the callback is illegal, but won't be called as we stop during check */ 1608 /* the callback is illegal, but won't be called as we stop during check */
1510 ev_timer_init (&tw, 0, timeout * 1e-3); 1609 ev_timer_init (&tw, 0, timeout * 1e-3);
1511 ev_timer_start (loop, &tw); 1610 ev_timer_start (loop, &tw);
1512 1611
1513 // create on ev_io per pollfd 1612 // create one ev_io per pollfd
1514 for (int i = 0; i < nfd; ++i) 1613 for (int i = 0; i < nfd; ++i)
1515 { 1614 {
1516 ev_io_init (iow + i, io_cb, fds [i].fd, 1615 ev_io_init (iow + i, io_cb, fds [i].fd,
1517 ((fds [i].events & POLLIN ? EV_READ : 0) 1616 ((fds [i].events & POLLIN ? EV_READ : 0)
1518 | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1617 | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1519 1618
1520 fds [i].revents = 0; 1619 fds [i].revents = 0;
1521 iow [i].data = fds + i;
1522 ev_io_start (loop, iow + i); 1620 ev_io_start (loop, iow + i);
1523 } 1621 }
1524 } 1622 }
1525 1623
1526 // stop all watchers after blocking 1624 // stop all watchers after blocking
1528 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1626 adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1529 { 1627 {
1530 ev_timer_stop (loop, &tw); 1628 ev_timer_stop (loop, &tw);
1531 1629
1532 for (int i = 0; i < nfd; ++i) 1630 for (int i = 0; i < nfd; ++i)
1631 {
1632 // set the relevant poll flags
1633 // could also call adns_processreadable etc. here
1634 struct pollfd *fd = fds + i;
1635 int revents = ev_clear_pending (iow + i);
1636 if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1637 if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1638
1639 // now stop the watcher
1533 ev_io_stop (loop, iow + i); 1640 ev_io_stop (loop, iow + i);
1641 }
1534 1642
1535 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1643 adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1644 }
1645
1646Method 2: This would be just like method 1, but you run C<adns_afterpoll>
1647in the prepare watcher and would dispose of the check watcher.
1648
1649Method 3: If the module to be embedded supports explicit event
1650notification (adns does), you can also make use of the actual watcher
1651callbacks, and only destroy/create the watchers in the prepare watcher.
1652
1653 static void
1654 timer_cb (EV_P_ ev_timer *w, int revents)
1655 {
1656 adns_state ads = (adns_state)w->data;
1657 update_now (EV_A);
1658
1659 adns_processtimeouts (ads, &tv_now);
1660 }
1661
1662 static void
1663 io_cb (EV_P_ ev_io *w, int revents)
1664 {
1665 adns_state ads = (adns_state)w->data;
1666 update_now (EV_A);
1667
1668 if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1669 if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1670 }
1671
1672 // do not ever call adns_afterpoll
1673
1674Method 4: Do not use a prepare or check watcher because the module you
1675want to embed is too inflexible to support it. Instead, youc na override
1676their poll function. The drawback with this solution is that the main
1677loop is now no longer controllable by EV. The C<Glib::EV> module does
1678this.
1679
1680 static gint
1681 event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1682 {
1683 int got_events = 0;
1684
1685 for (n = 0; n < nfds; ++n)
1686 // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1687
1688 if (timeout >= 0)
1689 // create/start timer
1690
1691 // poll
1692 ev_loop (EV_A_ 0);
1693
1694 // stop timer again
1695 if (timeout >= 0)
1696 ev_timer_stop (EV_A_ &to);
1697
1698 // stop io watchers again - their callbacks should have set
1699 for (n = 0; n < nfds; ++n)
1700 ev_io_stop (EV_A_ iow [n]);
1701
1702 return got_events;
1536 } 1703 }
1537 1704
1538 1705
1539=head2 C<ev_embed> - when one backend isn't enough... 1706=head2 C<ev_embed> - when one backend isn't enough...
1540 1707
1604 ev_embed_start (loop_hi, &embed); 1771 ev_embed_start (loop_hi, &embed);
1605 } 1772 }
1606 else 1773 else
1607 loop_lo = loop_hi; 1774 loop_lo = loop_hi;
1608 1775
1776=head3 Watcher-Specific Functions and Data Members
1777
1609=over 4 1778=over 4
1610 1779
1611=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 1780=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1612 1781
1613=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 1782=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1639event loop blocks next and before C<ev_check> watchers are being called, 1808event loop blocks next and before C<ev_check> watchers are being called,
1640and only in the child after the fork. If whoever good citizen calling 1809and only in the child after the fork. If whoever good citizen calling
1641C<ev_default_fork> cheats and calls it in the wrong process, the fork 1810C<ev_default_fork> cheats and calls it in the wrong process, the fork
1642handlers will be invoked, too, of course. 1811handlers will be invoked, too, of course.
1643 1812
1813=head3 Watcher-Specific Functions and Data Members
1814
1644=over 4 1815=over 4
1645 1816
1646=item ev_fork_init (ev_signal *, callback) 1817=item ev_fork_init (ev_signal *, callback)
1647 1818
1648Initialises and configures the fork watcher - it has no parameters of any 1819Initialises and configures the fork watcher - it has no parameters of any
1749This automatically includes F<ev.h> and puts all of its definitions (many 1920This automatically includes F<ev.h> and puts all of its definitions (many
1750of them macros) into the global namespace. All C++ specific things are 1921of them macros) into the global namespace. All C++ specific things are
1751put into the C<ev> namespace. It should support all the same embedding 1922put into the C<ev> namespace. It should support all the same embedding
1752options as F<ev.h>, most notably C<EV_MULTIPLICITY>. 1923options as F<ev.h>, most notably C<EV_MULTIPLICITY>.
1753 1924
1754Care has been taken to keep the overhead low. The only data member added 1925Care has been taken to keep the overhead low. The only data member the C++
1755to the C-style watchers is the event loop the watcher is associated with 1926classes add (compared to plain C-style watchers) is the event loop pointer
1756(or no additional members at all if you disable C<EV_MULTIPLICITY> when 1927that the watcher is associated with (or no additional members at all if
1757embedding libev). 1928you disable C<EV_MULTIPLICITY> when embedding libev).
1758 1929
1759Currently, functions and static and non-static member functions can be 1930Currently, functions, and static and non-static member functions can be
1760used as callbacks. Other types should be easy to add as long as they only 1931used as callbacks. Other types should be easy to add as long as they only
1761need one additional pointer for context. If you need support for other 1932need one additional pointer for context. If you need support for other
1762types of functors please contact the author (preferably after implementing 1933types of functors please contact the author (preferably after implementing
1763it). 1934it).
1764 1935
1828 1999
1829 myclass obj; 2000 myclass obj;
1830 ev::io iow; 2001 ev::io iow;
1831 iow.set <myclass, &myclass::io_cb> (&obj); 2002 iow.set <myclass, &myclass::io_cb> (&obj);
1832 2003
1833=item w->set (void (*function)(watcher &w, int), void *data = 0) 2004=item w->set<function> (void *data = 0)
1834 2005
1835Also sets a callback, but uses a static method or plain function as 2006Also sets a callback, but uses a static method or plain function as
1836callback. The optional C<data> argument will be stored in the watcher's 2007callback. The optional C<data> argument will be stored in the watcher's
1837C<data> member and is free for you to use. 2008C<data> member and is free for you to use.
1838 2009
2010The prototype of the C<function> must be C<void (*)(ev::TYPE &w, int)>.
2011
1839See the method-C<set> above for more details. 2012See the method-C<set> above for more details.
2013
2014Example:
2015
2016 static void io_cb (ev::io &w, int revents) { }
2017 iow.set <io_cb> ();
1840 2018
1841=item w->set (struct ev_loop *) 2019=item w->set (struct ev_loop *)
1842 2020
1843Associates a different C<struct ev_loop> with this watcher. You can only 2021Associates a different C<struct ev_loop> with this watcher. You can only
1844do this when the watcher is inactive (and not pending either). 2022do this when the watcher is inactive (and not pending either).
1857 2035
1858=item w->stop () 2036=item w->stop ()
1859 2037
1860Stops the watcher if it is active. Again, no C<loop> argument. 2038Stops the watcher if it is active. Again, no C<loop> argument.
1861 2039
1862=item w->again () C<ev::timer>, C<ev::periodic> only 2040=item w->again () (C<ev::timer>, C<ev::periodic> only)
1863 2041
1864For C<ev::timer> and C<ev::periodic>, this invokes the corresponding 2042For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1865C<ev_TYPE_again> function. 2043C<ev_TYPE_again> function.
1866 2044
1867=item w->sweep () C<ev::embed> only 2045=item w->sweep () (C<ev::embed> only)
1868 2046
1869Invokes C<ev_embed_sweep>. 2047Invokes C<ev_embed_sweep>.
1870 2048
1871=item w->update () C<ev::stat> only 2049=item w->update () (C<ev::stat> only)
1872 2050
1873Invokes C<ev_stat_stat>. 2051Invokes C<ev_stat_stat>.
1874 2052
1875=back 2053=back
1876 2054
1896 } 2074 }
1897 2075
1898 2076
1899=head1 MACRO MAGIC 2077=head1 MACRO MAGIC
1900 2078
1901Libev can be compiled with a variety of options, the most fundemantal is 2079Libev can be compiled with a variety of options, the most fundamantal
1902C<EV_MULTIPLICITY>. This option determines whether (most) functions and 2080of which is C<EV_MULTIPLICITY>. This option determines whether (most)
1903callbacks have an initial C<struct ev_loop *> argument. 2081functions and callbacks have an initial C<struct ev_loop *> argument.
1904 2082
1905To make it easier to write programs that cope with either variant, the 2083To make it easier to write programs that cope with either variant, the
1906following macros are defined: 2084following macros are defined:
1907 2085
1908=over 4 2086=over 4
2072 2250
2073If defined to be C<1>, libev will try to detect the availability of the 2251If defined to be C<1>, libev will try to detect the availability of the
2074realtime clock option at compiletime (and assume its availability at 2252realtime clock option at compiletime (and assume its availability at
2075runtime if successful). Otherwise no use of the realtime clock option will 2253runtime if successful). Otherwise no use of the realtime clock option will
2076be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2254be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2077(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries 2255(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2078in the description of C<EV_USE_MONOTONIC>, though. 2256note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2079 2257
2080=item EV_USE_SELECT 2258=item EV_USE_SELECT
2081 2259
2082If undefined or defined to be C<1>, libev will compile in support for the 2260If undefined or defined to be C<1>, libev will compile in support for the
2083C<select>(2) backend. No attempt at autodetection will be done: if no 2261C<select>(2) backend. No attempt at autodetection will be done: if no
2267definition and a statement, respectively. See the F<ev.v> header file for 2445definition and a statement, respectively. See the F<ev.v> header file for
2268their default definitions. One possible use for overriding these is to 2446their default definitions. One possible use for overriding these is to
2269avoid the C<struct ev_loop *> as first argument in all cases, or to use 2447avoid the C<struct ev_loop *> as first argument in all cases, or to use
2270method calls instead of plain function calls in C++. 2448method calls instead of plain function calls in C++.
2271 2449
2450=head2 EXPORTED API SYMBOLS
2451
2452If you need to re-export the API (e.g. via a dll) and you need a list of
2453exported symbols, you can use the provided F<Symbol.*> files which list
2454all public symbols, one per line:
2455
2456 Symbols.ev for libev proper
2457 Symbols.event for the libevent emulation
2458
2459This can also be used to rename all public symbols to avoid clashes with
2460multiple versions of libev linked together (which is obviously bad in
2461itself, but sometimes it is inconvinient to avoid this).
2462
2463A sed comamnd like this will create wrapper C<#define>'s that you need to
2464include before including F<ev.h>:
2465
2466 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2467
2468This would create a file F<wrap.h> which essentially looks like this:
2469
2470 #define ev_backend myprefix_ev_backend
2471 #define ev_check_start myprefix_ev_check_start
2472 #define ev_check_stop myprefix_ev_check_stop
2473 ...
2474
2272=head2 EXAMPLES 2475=head2 EXAMPLES
2273 2476
2274For a real-world example of a program the includes libev 2477For a real-world example of a program the includes libev
2275verbatim, you can have a look at the EV perl module 2478verbatim, you can have a look at the EV perl module
2276(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in 2479(L<http://software.schmorp.de/pkg/EV.html>). It has the libev files in

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