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Revision 1.191 by root, Tue Sep 30 19:45:23 2008 UTC vs.
Revision 1.198 by root, Thu Oct 23 06:30:48 2008 UTC

17 ev_timer timeout_watcher; 17 ev_timer timeout_watcher;
18 18
19 // all watcher callbacks have a similar signature 19 // all watcher callbacks have a similar signature
20 // this callback is called when data is readable on stdin 20 // this callback is called when data is readable on stdin
21 static void 21 static void
22 stdin_cb (EV_P_ struct ev_io *w, int revents) 22 stdin_cb (EV_P_ ev_io *w, int revents)
23 { 23 {
24 puts ("stdin ready"); 24 puts ("stdin ready");
25 // for one-shot events, one must manually stop the watcher 25 // for one-shot events, one must manually stop the watcher
26 // with its corresponding stop function. 26 // with its corresponding stop function.
27 ev_io_stop (EV_A_ w); 27 ev_io_stop (EV_A_ w);
30 ev_unloop (EV_A_ EVUNLOOP_ALL); 30 ev_unloop (EV_A_ EVUNLOOP_ALL);
31 } 31 }
32 32
33 // another callback, this time for a time-out 33 // another callback, this time for a time-out
34 static void 34 static void
35 timeout_cb (EV_P_ struct ev_timer *w, int revents) 35 timeout_cb (EV_P_ ev_timer *w, int revents)
36 { 36 {
37 puts ("timeout"); 37 puts ("timeout");
38 // this causes the innermost ev_loop to stop iterating 38 // this causes the innermost ev_loop to stop iterating
39 ev_unloop (EV_A_ EVUNLOOP_ONE); 39 ev_unloop (EV_A_ EVUNLOOP_ONE);
40 } 40 }
41 41
42 int 42 int
43 main (void) 43 main (void)
44 { 44 {
45 // use the default event loop unless you have special needs 45 // use the default event loop unless you have special needs
46 struct ev_loop *loop = ev_default_loop (0); 46 ev_loop *loop = ev_default_loop (0);
47 47
48 // initialise an io watcher, then start it 48 // initialise an io watcher, then start it
49 // this one will watch for stdin to become readable 49 // this one will watch for stdin to become readable
50 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); 50 ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
51 ev_io_start (loop, &stdin_watcher); 51 ev_io_start (loop, &stdin_watcher);
103Libev is very configurable. In this manual the default (and most common) 103Libev is very configurable. In this manual the default (and most common)
104configuration will be described, which supports multiple event loops. For 104configuration will be described, which supports multiple event loops. For
105more info about various configuration options please have a look at 105more info about various configuration options please have a look at
106B<EMBED> section in this manual. If libev was configured without support 106B<EMBED> section in this manual. If libev was configured without support
107for multiple event loops, then all functions taking an initial argument of 107for multiple event loops, then all functions taking an initial argument of
108name C<loop> (which is always of type C<struct ev_loop *>) will not have 108name C<loop> (which is always of type C<ev_loop *>) will not have
109this argument. 109this argument.
110 110
111=head2 TIME REPRESENTATION 111=head2 TIME REPRESENTATION
112 112
113Libev represents time as a single floating point number, representing the 113Libev represents time as a single floating point number, representing the
276 276
277=back 277=back
278 278
279=head1 FUNCTIONS CONTROLLING THE EVENT LOOP 279=head1 FUNCTIONS CONTROLLING THE EVENT LOOP
280 280
281An event loop is described by a C<struct ev_loop *>. The library knows two 281An event loop is described by a C<ev_loop *>. The library knows two
282types of such loops, the I<default> loop, which supports signals and child 282types of such loops, the I<default> loop, which supports signals and child
283events, and dynamically created loops which do not. 283events, and dynamically created loops which do not.
284 284
285=over 4 285=over 4
286 286
685C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 685C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
686C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 686C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
687 687
688This "unloop state" will be cleared when entering C<ev_loop> again. 688This "unloop state" will be cleared when entering C<ev_loop> again.
689 689
690It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls.
691
690=item ev_ref (loop) 692=item ev_ref (loop)
691 693
692=item ev_unref (loop) 694=item ev_unref (loop)
693 695
694Ref/unref can be used to add or remove a reference count on the event 696Ref/unref can be used to add or remove a reference count on the event
708respectively). 710respectively).
709 711
710Example: Create a signal watcher, but keep it from keeping C<ev_loop> 712Example: Create a signal watcher, but keep it from keeping C<ev_loop>
711running when nothing else is active. 713running when nothing else is active.
712 714
713 struct ev_signal exitsig; 715 ev_signal exitsig;
714 ev_signal_init (&exitsig, sig_cb, SIGINT); 716 ev_signal_init (&exitsig, sig_cb, SIGINT);
715 ev_signal_start (loop, &exitsig); 717 ev_signal_start (loop, &exitsig);
716 evf_unref (loop); 718 evf_unref (loop);
717 719
718Example: For some weird reason, unregister the above signal handler again. 720Example: For some weird reason, unregister the above signal handler again.
784 786
785A watcher is a structure that you create and register to record your 787A watcher is a structure that you create and register to record your
786interest in some event. For instance, if you want to wait for STDIN to 788interest in some event. For instance, if you want to wait for STDIN to
787become readable, you would create an C<ev_io> watcher for that: 789become readable, you would create an C<ev_io> watcher for that:
788 790
789 static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) 791 static void my_cb (struct ev_loop *loop, ev_io *w, int revents)
790 { 792 {
791 ev_io_stop (w); 793 ev_io_stop (w);
792 ev_unloop (loop, EVUNLOOP_ALL); 794 ev_unloop (loop, EVUNLOOP_ALL);
793 } 795 }
794 796
795 struct ev_loop *loop = ev_default_loop (0); 797 struct ev_loop *loop = ev_default_loop (0);
796 struct ev_io stdin_watcher; 798 ev_io stdin_watcher;
797 ev_init (&stdin_watcher, my_cb); 799 ev_init (&stdin_watcher, my_cb);
798 ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); 800 ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ);
799 ev_io_start (loop, &stdin_watcher); 801 ev_io_start (loop, &stdin_watcher);
800 ev_loop (loop, 0); 802 ev_loop (loop, 0);
801 803
892=item C<EV_ERROR> 894=item C<EV_ERROR>
893 895
894An unspecified error has occurred, the watcher has been stopped. This might 896An unspecified error has occurred, the watcher has been stopped. This might
895happen because the watcher could not be properly started because libev 897happen because the watcher could not be properly started because libev
896ran out of memory, a file descriptor was found to be closed or any other 898ran out of memory, a file descriptor was found to be closed or any other
899problem. Libev considers these application bugs.
900
897problem. You best act on it by reporting the problem and somehow coping 901You best act on it by reporting the problem and somehow coping with the
898with the watcher being stopped. 902watcher being stopped. Note that well-written programs should not receive
903an error ever, so when your watcher receives it, this usually indicates a
904bug in your program.
899 905
900Libev will usually signal a few "dummy" events together with an error, for 906Libev will usually signal a few "dummy" events together with an error, for
901example it might indicate that a fd is readable or writable, and if your 907example it might indicate that a fd is readable or writable, and if your
902callbacks is well-written it can just attempt the operation and cope with 908callbacks is well-written it can just attempt the operation and cope with
903the error from read() or write(). This will not work in multi-threaded 909the error from read() or write(). This will not work in multi-threaded
923which rolls both calls into one. 929which rolls both calls into one.
924 930
925You can reinitialise a watcher at any time as long as it has been stopped 931You can reinitialise a watcher at any time as long as it has been stopped
926(or never started) and there are no pending events outstanding. 932(or never started) and there are no pending events outstanding.
927 933
928The callback is always of type C<void (*)(ev_loop *loop, ev_TYPE *watcher, 934The callback is always of type C<void (*)(struct ev_loop *loop, ev_TYPE *watcher,
929int revents)>. 935int revents)>.
930 936
931Example: Initialise an C<ev_io> watcher in two steps. 937Example: Initialise an C<ev_io> watcher in two steps.
932 938
933 ev_io w; 939 ev_io w;
967 973
968 ev_io_start (EV_DEFAULT_UC, &w); 974 ev_io_start (EV_DEFAULT_UC, &w);
969 975
970=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher) 976=item C<ev_TYPE_stop> (loop *, ev_TYPE *watcher)
971 977
972Stops the given watcher again (if active) and clears the pending 978Stops the given watcher if active, and clears the pending status (whether
979the watcher was active or not).
980
973status. It is possible that stopped watchers are pending (for example, 981It is possible that stopped watchers are pending - for example,
974non-repeating timers are being stopped when they become pending), but 982non-repeating timers are being stopped when they become pending - but
975C<ev_TYPE_stop> ensures that the watcher is neither active nor pending. If 983calling C<ev_TYPE_stop> ensures that the watcher is neither active nor
976you want to free or reuse the memory used by the watcher it is therefore a 984pending. If you want to free or reuse the memory used by the watcher it is
977good idea to always call its C<ev_TYPE_stop> function. 985therefore a good idea to always call its C<ev_TYPE_stop> function.
978 986
979=item bool ev_is_active (ev_TYPE *watcher) 987=item bool ev_is_active (ev_TYPE *watcher)
980 988
981Returns a true value iff the watcher is active (i.e. it has been started 989Returns a true value iff the watcher is active (i.e. it has been started
982and not yet been stopped). As long as a watcher is active you must not modify 990and not yet been stopped). As long as a watcher is active you must not modify
1056member, you can also "subclass" the watcher type and provide your own 1064member, you can also "subclass" the watcher type and provide your own
1057data: 1065data:
1058 1066
1059 struct my_io 1067 struct my_io
1060 { 1068 {
1061 struct ev_io io; 1069 ev_io io;
1062 int otherfd; 1070 int otherfd;
1063 void *somedata; 1071 void *somedata;
1064 struct whatever *mostinteresting; 1072 struct whatever *mostinteresting;
1065 }; 1073 };
1066 1074
1069 ev_io_init (&w.io, my_cb, fd, EV_READ); 1077 ev_io_init (&w.io, my_cb, fd, EV_READ);
1070 1078
1071And since your callback will be called with a pointer to the watcher, you 1079And since your callback will be called with a pointer to the watcher, you
1072can cast it back to your own type: 1080can cast it back to your own type:
1073 1081
1074 static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) 1082 static void my_cb (struct ev_loop *loop, ev_io *w_, int revents)
1075 { 1083 {
1076 struct my_io *w = (struct my_io *)w_; 1084 struct my_io *w = (struct my_io *)w_;
1077 ... 1085 ...
1078 } 1086 }
1079 1087
1097programmers): 1105programmers):
1098 1106
1099 #include <stddef.h> 1107 #include <stddef.h>
1100 1108
1101 static void 1109 static void
1102 t1_cb (EV_P_ struct ev_timer *w, int revents) 1110 t1_cb (EV_P_ ev_timer *w, int revents)
1103 { 1111 {
1104 struct my_biggy big = (struct my_biggy * 1112 struct my_biggy big = (struct my_biggy *
1105 (((char *)w) - offsetof (struct my_biggy, t1)); 1113 (((char *)w) - offsetof (struct my_biggy, t1));
1106 } 1114 }
1107 1115
1108 static void 1116 static void
1109 t2_cb (EV_P_ struct ev_timer *w, int revents) 1117 t2_cb (EV_P_ ev_timer *w, int revents)
1110 { 1118 {
1111 struct my_biggy big = (struct my_biggy * 1119 struct my_biggy big = (struct my_biggy *
1112 (((char *)w) - offsetof (struct my_biggy, t2)); 1120 (((char *)w) - offsetof (struct my_biggy, t2));
1113 } 1121 }
1114 1122
1249Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1257Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1250readable, but only once. Since it is likely line-buffered, you could 1258readable, but only once. Since it is likely line-buffered, you could
1251attempt to read a whole line in the callback. 1259attempt to read a whole line in the callback.
1252 1260
1253 static void 1261 static void
1254 stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1262 stdin_readable_cb (struct ev_loop *loop, ev_io *w, int revents)
1255 { 1263 {
1256 ev_io_stop (loop, w); 1264 ev_io_stop (loop, w);
1257 .. read from stdin here (or from w->fd) and handle any I/O errors 1265 .. read from stdin here (or from w->fd) and handle any I/O errors
1258 } 1266 }
1259 1267
1260 ... 1268 ...
1261 struct ev_loop *loop = ev_default_init (0); 1269 struct ev_loop *loop = ev_default_init (0);
1262 struct ev_io stdin_readable; 1270 ev_io stdin_readable;
1263 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1271 ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1264 ev_io_start (loop, &stdin_readable); 1272 ev_io_start (loop, &stdin_readable);
1265 ev_loop (loop, 0); 1273 ev_loop (loop, 0);
1266 1274
1267 1275
1278 1286
1279The callback is guaranteed to be invoked only I<after> its timeout has 1287The callback is guaranteed to be invoked only I<after> its timeout has
1280passed, but if multiple timers become ready during the same loop iteration 1288passed, but if multiple timers become ready during the same loop iteration
1281then order of execution is undefined. 1289then order of execution is undefined.
1282 1290
1291=head3 Be smart about timeouts
1292
1293Many real-world problems invole some kind of time-out, usually for error
1294recovery. A typical example is an HTTP request - if the other side hangs,
1295you want to raise some error after a while.
1296
1297Here are some ways on how to handle this problem, from simple and
1298inefficient to very efficient.
1299
1300In the following examples a 60 second activity timeout is assumed - a
1301timeout that gets reset to 60 seconds each time some data ("a lifesign")
1302was received.
1303
1304=over 4
1305
1306=item 1. Use a timer and stop, reinitialise, start it on activity.
1307
1308This is the most obvious, but not the most simple way: In the beginning,
1309start the watcher:
1310
1311 ev_timer_init (timer, callback, 60., 0.);
1312 ev_timer_start (loop, timer);
1313
1314Then, each time there is some activity, C<ev_timer_stop> the timer,
1315initialise it again, and start it:
1316
1317 ev_timer_stop (loop, timer);
1318 ev_timer_set (timer, 60., 0.);
1319 ev_timer_start (loop, timer);
1320
1321This is relatively simple to implement, but means that each time there
1322is some activity, libev will first have to remove the timer from it's
1323internal data strcuture and then add it again.
1324
1325=item 2. Use a timer and re-start it with C<ev_timer_again> inactivity.
1326
1327This is the easiest way, and involves using C<ev_timer_again> instead of
1328C<ev_timer_start>.
1329
1330For this, configure an C<ev_timer> with a C<repeat> value of C<60> and
1331then call C<ev_timer_again> at start and each time you successfully read
1332or write some data. If you go into an idle state where you do not expect
1333data to travel on the socket, you can C<ev_timer_stop> the timer, and
1334C<ev_timer_again> will automatically restart it if need be.
1335
1336That means you can ignore the C<after> value and C<ev_timer_start>
1337altogether and only ever use the C<repeat> value and C<ev_timer_again>.
1338
1339At start:
1340
1341 ev_timer_init (timer, callback, 0., 60.);
1342 ev_timer_again (loop, timer);
1343
1344Each time you receive some data:
1345
1346 ev_timer_again (loop, timer);
1347
1348It is even possible to change the time-out on the fly:
1349
1350 timer->repeat = 30.;
1351 ev_timer_again (loop, timer);
1352
1353This is slightly more efficient then stopping/starting the timer each time
1354you want to modify its timeout value, as libev does not have to completely
1355remove and re-insert the timer from/into it's internal data structure.
1356
1357=item 3. Let the timer time out, but then re-arm it as required.
1358
1359This method is more tricky, but usually most efficient: Most timeouts are
1360relatively long compared to the loop iteration time - in our example,
1361within 60 seconds, there are usually many I/O events with associated
1362activity resets.
1363
1364In this case, it would be more efficient to leave the C<ev_timer> alone,
1365but remember the time of last activity, and check for a real timeout only
1366within the callback:
1367
1368 ev_tstamp last_activity; // time of last activity
1369
1370 static void
1371 callback (EV_P_ ev_timer *w, int revents)
1372 {
1373 ev_tstamp now = ev_now (EV_A);
1374 ev_tstamp timeout = last_activity + 60.;
1375
1376 // if last_activity is older than now - timeout, we did time out
1377 if (timeout < now)
1378 {
1379 // timeout occured, take action
1380 }
1381 else
1382 {
1383 // callback was invoked, but there was some activity, re-arm
1384 // to fire in last_activity + 60.
1385 w->again = timeout - now;
1386 ev_timer_again (EV_A_ w);
1387 }
1388 }
1389
1390To summarise the callback: first calculate the real time-out (defined as
1391"60 seconds after the last activity"), then check if that time has been
1392reached, which means there was a real timeout. Otherwise the callback was
1393invoked too early (timeout is in the future), so re-schedule the timer to
1394fire at that future time.
1395
1396Note how C<ev_timer_again> is used, taking advantage of the
1397C<ev_timer_again> optimisation when the timer is already running.
1398
1399This scheme causes more callback invocations (about one every 60 seconds),
1400but virtually no calls to libev to change the timeout.
1401
1402To start the timer, simply intiialise the watcher and C<last_activity>,
1403then call the callback:
1404
1405 ev_timer_init (timer, callback);
1406 last_activity = ev_now (loop);
1407 callback (loop, timer, EV_TIMEOUT);
1408
1409And when there is some activity, simply remember the time in
1410C<last_activity>:
1411
1412 last_actiivty = ev_now (loop);
1413
1414This technique is slightly more complex, but in most cases where the
1415time-out is unlikely to be triggered, much more efficient.
1416
1417=back
1418
1283=head3 The special problem of time updates 1419=head3 The special problem of time updates
1284 1420
1285Establishing the current time is a costly operation (it usually takes at 1421Establishing the current time is a costly operation (it usually takes at
1286least two system calls): EV therefore updates its idea of the current 1422least two system calls): EV therefore updates its idea of the current
1287time only before and after C<ev_loop> collects new events, which causes a 1423time only before and after C<ev_loop> collects new events, which causes a
1330If the timer is started but non-repeating, stop it (as if it timed out). 1466If the timer is started but non-repeating, stop it (as if it timed out).
1331 1467
1332If the timer is repeating, either start it if necessary (with the 1468If the timer is repeating, either start it if necessary (with the
1333C<repeat> value), or reset the running timer to the C<repeat> value. 1469C<repeat> value), or reset the running timer to the C<repeat> value.
1334 1470
1335This sounds a bit complicated, but here is a useful and typical 1471This sounds a bit complicated, see "Be smart about timeouts", above, for a
1336example: Imagine you have a TCP connection and you want a so-called idle 1472usage example.
1337timeout, that is, you want to be called when there have been, say, 60
1338seconds of inactivity on the socket. The easiest way to do this is to
1339configure an C<ev_timer> with a C<repeat> value of C<60> and then call
1340C<ev_timer_again> each time you successfully read or write some data. If
1341you go into an idle state where you do not expect data to travel on the
1342socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
1343automatically restart it if need be.
1344
1345That means you can ignore the C<after> value and C<ev_timer_start>
1346altogether and only ever use the C<repeat> value and C<ev_timer_again>:
1347
1348 ev_timer_init (timer, callback, 0., 5.);
1349 ev_timer_again (loop, timer);
1350 ...
1351 timer->again = 17.;
1352 ev_timer_again (loop, timer);
1353 ...
1354 timer->again = 10.;
1355 ev_timer_again (loop, timer);
1356
1357This is more slightly efficient then stopping/starting the timer each time
1358you want to modify its timeout value.
1359
1360Note, however, that it is often even more efficient to remember the
1361time of the last activity and let the timer time-out naturally. In the
1362callback, you then check whether the time-out is real, or, if there was
1363some activity, you reschedule the watcher to time-out in "last_activity +
1364timeout - ev_now ()" seconds.
1365 1473
1366=item ev_tstamp repeat [read-write] 1474=item ev_tstamp repeat [read-write]
1367 1475
1368The current C<repeat> value. Will be used each time the watcher times out 1476The current C<repeat> value. Will be used each time the watcher times out
1369or C<ev_timer_again> is called, and determines the next timeout (if any), 1477or C<ev_timer_again> is called, and determines the next timeout (if any),
1374=head3 Examples 1482=head3 Examples
1375 1483
1376Example: Create a timer that fires after 60 seconds. 1484Example: Create a timer that fires after 60 seconds.
1377 1485
1378 static void 1486 static void
1379 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1487 one_minute_cb (struct ev_loop *loop, ev_timer *w, int revents)
1380 { 1488 {
1381 .. one minute over, w is actually stopped right here 1489 .. one minute over, w is actually stopped right here
1382 } 1490 }
1383 1491
1384 struct ev_timer mytimer; 1492 ev_timer mytimer;
1385 ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1493 ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1386 ev_timer_start (loop, &mytimer); 1494 ev_timer_start (loop, &mytimer);
1387 1495
1388Example: Create a timeout timer that times out after 10 seconds of 1496Example: Create a timeout timer that times out after 10 seconds of
1389inactivity. 1497inactivity.
1390 1498
1391 static void 1499 static void
1392 timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1500 timeout_cb (struct ev_loop *loop, ev_timer *w, int revents)
1393 { 1501 {
1394 .. ten seconds without any activity 1502 .. ten seconds without any activity
1395 } 1503 }
1396 1504
1397 struct ev_timer mytimer; 1505 ev_timer mytimer;
1398 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ 1506 ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1399 ev_timer_again (&mytimer); /* start timer */ 1507 ev_timer_again (&mytimer); /* start timer */
1400 ev_loop (loop, 0); 1508 ev_loop (loop, 0);
1401 1509
1402 // and in some piece of code that gets executed on any "activity": 1510 // and in some piece of code that gets executed on any "activity":
1488 1596
1489If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop 1597If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop
1490it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the 1598it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the
1491only event loop modification you are allowed to do). 1599only event loop modification you are allowed to do).
1492 1600
1493The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic 1601The callback prototype is C<ev_tstamp (*reschedule_cb)(ev_periodic
1494*w, ev_tstamp now)>, e.g.: 1602*w, ev_tstamp now)>, e.g.:
1495 1603
1604 static ev_tstamp
1496 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1605 my_rescheduler (ev_periodic *w, ev_tstamp now)
1497 { 1606 {
1498 return now + 60.; 1607 return now + 60.;
1499 } 1608 }
1500 1609
1501It must return the next time to trigger, based on the passed time value 1610It must return the next time to trigger, based on the passed time value
1538 1647
1539The current interval value. Can be modified any time, but changes only 1648The current interval value. Can be modified any time, but changes only
1540take effect when the periodic timer fires or C<ev_periodic_again> is being 1649take effect when the periodic timer fires or C<ev_periodic_again> is being
1541called. 1650called.
1542 1651
1543=item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] 1652=item ev_tstamp (*reschedule_cb)(ev_periodic *w, ev_tstamp now) [read-write]
1544 1653
1545The current reschedule callback, or C<0>, if this functionality is 1654The current reschedule callback, or C<0>, if this functionality is
1546switched off. Can be changed any time, but changes only take effect when 1655switched off. Can be changed any time, but changes only take effect when
1547the periodic timer fires or C<ev_periodic_again> is being called. 1656the periodic timer fires or C<ev_periodic_again> is being called.
1548 1657
1553Example: Call a callback every hour, or, more precisely, whenever the 1662Example: Call a callback every hour, or, more precisely, whenever the
1554system time is divisible by 3600. The callback invocation times have 1663system time is divisible by 3600. The callback invocation times have
1555potentially a lot of jitter, but good long-term stability. 1664potentially a lot of jitter, but good long-term stability.
1556 1665
1557 static void 1666 static void
1558 clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1667 clock_cb (struct ev_loop *loop, ev_io *w, int revents)
1559 { 1668 {
1560 ... its now a full hour (UTC, or TAI or whatever your clock follows) 1669 ... its now a full hour (UTC, or TAI or whatever your clock follows)
1561 } 1670 }
1562 1671
1563 struct ev_periodic hourly_tick; 1672 ev_periodic hourly_tick;
1564 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1673 ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1565 ev_periodic_start (loop, &hourly_tick); 1674 ev_periodic_start (loop, &hourly_tick);
1566 1675
1567Example: The same as above, but use a reschedule callback to do it: 1676Example: The same as above, but use a reschedule callback to do it:
1568 1677
1569 #include <math.h> 1678 #include <math.h>
1570 1679
1571 static ev_tstamp 1680 static ev_tstamp
1572 my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) 1681 my_scheduler_cb (ev_periodic *w, ev_tstamp now)
1573 { 1682 {
1574 return now + (3600. - fmod (now, 3600.)); 1683 return now + (3600. - fmod (now, 3600.));
1575 } 1684 }
1576 1685
1577 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1686 ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1578 1687
1579Example: Call a callback every hour, starting now: 1688Example: Call a callback every hour, starting now:
1580 1689
1581 struct ev_periodic hourly_tick; 1690 ev_periodic hourly_tick;
1582 ev_periodic_init (&hourly_tick, clock_cb, 1691 ev_periodic_init (&hourly_tick, clock_cb,
1583 fmod (ev_now (loop), 3600.), 3600., 0); 1692 fmod (ev_now (loop), 3600.), 3600., 0);
1584 ev_periodic_start (loop, &hourly_tick); 1693 ev_periodic_start (loop, &hourly_tick);
1585 1694
1586 1695
1628=head3 Examples 1737=head3 Examples
1629 1738
1630Example: Try to exit cleanly on SIGINT. 1739Example: Try to exit cleanly on SIGINT.
1631 1740
1632 static void 1741 static void
1633 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1742 sigint_cb (struct ev_loop *loop, ev_signal *w, int revents)
1634 { 1743 {
1635 ev_unloop (loop, EVUNLOOP_ALL); 1744 ev_unloop (loop, EVUNLOOP_ALL);
1636 } 1745 }
1637 1746
1638 struct ev_signal signal_watcher; 1747 ev_signal signal_watcher;
1639 ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1748 ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1640 ev_signal_start (loop, &signal_watcher); 1749 ev_signal_start (loop, &signal_watcher);
1641 1750
1642 1751
1643=head2 C<ev_child> - watch out for process status changes 1752=head2 C<ev_child> - watch out for process status changes
1718its completion. 1827its completion.
1719 1828
1720 ev_child cw; 1829 ev_child cw;
1721 1830
1722 static void 1831 static void
1723 child_cb (EV_P_ struct ev_child *w, int revents) 1832 child_cb (EV_P_ ev_child *w, int revents)
1724 { 1833 {
1725 ev_child_stop (EV_A_ w); 1834 ev_child_stop (EV_A_ w);
1726 printf ("process %d exited with status %x\n", w->rpid, w->rstatus); 1835 printf ("process %d exited with status %x\n", w->rpid, w->rstatus);
1727 } 1836 }
1728 1837
1792to exchange stat structures with application programs compiled using the 1901to exchange stat structures with application programs compiled using the
1793default compilation environment. 1902default compilation environment.
1794 1903
1795=head3 Inotify and Kqueue 1904=head3 Inotify and Kqueue
1796 1905
1797When C<inotify (7)> support has been compiled into libev (generally only 1906When C<inotify (7)> support has been compiled into libev (generally
1907only available with Linux 2.6.25 or above due to bugs in earlier
1798available with Linux) and present at runtime, it will be used to speed up 1908implementations) and present at runtime, it will be used to speed up
1799change detection where possible. The inotify descriptor will be created lazily 1909change detection where possible. The inotify descriptor will be created
1800when the first C<ev_stat> watcher is being started. 1910lazily when the first C<ev_stat> watcher is being started.
1801 1911
1802Inotify presence does not change the semantics of C<ev_stat> watchers 1912Inotify presence does not change the semantics of C<ev_stat> watchers
1803except that changes might be detected earlier, and in some cases, to avoid 1913except that changes might be detected earlier, and in some cases, to avoid
1804making regular C<stat> calls. Even in the presence of inotify support 1914making regular C<stat> calls. Even in the presence of inotify support
1805there are many cases where libev has to resort to regular C<stat> polling, 1915there are many cases where libev has to resort to regular C<stat> polling,
1979 2089
1980Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 2090Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1981callback, free it. Also, use no error checking, as usual. 2091callback, free it. Also, use no error checking, as usual.
1982 2092
1983 static void 2093 static void
1984 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 2094 idle_cb (struct ev_loop *loop, ev_idle *w, int revents)
1985 { 2095 {
1986 free (w); 2096 free (w);
1987 // now do something you wanted to do when the program has 2097 // now do something you wanted to do when the program has
1988 // no longer anything immediate to do. 2098 // no longer anything immediate to do.
1989 } 2099 }
1990 2100
1991 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 2101 ev_idle *idle_watcher = malloc (sizeof (ev_idle));
1992 ev_idle_init (idle_watcher, idle_cb); 2102 ev_idle_init (idle_watcher, idle_cb);
1993 ev_idle_start (loop, idle_cb); 2103 ev_idle_start (loop, idle_cb);
1994 2104
1995 2105
1996=head2 C<ev_prepare> and C<ev_check> - customise your event loop! 2106=head2 C<ev_prepare> and C<ev_check> - customise your event loop!
2077 2187
2078 static ev_io iow [nfd]; 2188 static ev_io iow [nfd];
2079 static ev_timer tw; 2189 static ev_timer tw;
2080 2190
2081 static void 2191 static void
2082 io_cb (ev_loop *loop, ev_io *w, int revents) 2192 io_cb (struct ev_loop *loop, ev_io *w, int revents)
2083 { 2193 {
2084 } 2194 }
2085 2195
2086 // create io watchers for each fd and a timer before blocking 2196 // create io watchers for each fd and a timer before blocking
2087 static void 2197 static void
2088 adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 2198 adns_prepare_cb (struct ev_loop *loop, ev_prepare *w, int revents)
2089 { 2199 {
2090 int timeout = 3600000; 2200 int timeout = 3600000;
2091 struct pollfd fds [nfd]; 2201 struct pollfd fds [nfd];
2092 // actual code will need to loop here and realloc etc. 2202 // actual code will need to loop here and realloc etc.
2093 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 2203 adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
2108 } 2218 }
2109 } 2219 }
2110 2220
2111 // stop all watchers after blocking 2221 // stop all watchers after blocking
2112 static void 2222 static void
2113 adns_check_cb (ev_loop *loop, ev_check *w, int revents) 2223 adns_check_cb (struct ev_loop *loop, ev_check *w, int revents)
2114 { 2224 {
2115 ev_timer_stop (loop, &tw); 2225 ev_timer_stop (loop, &tw);
2116 2226
2117 for (int i = 0; i < nfd; ++i) 2227 for (int i = 0; i < nfd; ++i)
2118 { 2228 {
2286C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be 2396C<loop_lo> (which is C<loop_hi> in the case no embeddable loop can be
2287used). 2397used).
2288 2398
2289 struct ev_loop *loop_hi = ev_default_init (0); 2399 struct ev_loop *loop_hi = ev_default_init (0);
2290 struct ev_loop *loop_lo = 0; 2400 struct ev_loop *loop_lo = 0;
2291 struct ev_embed embed; 2401 ev_embed embed;
2292 2402
2293 // see if there is a chance of getting one that works 2403 // see if there is a chance of getting one that works
2294 // (remember that a flags value of 0 means autodetection) 2404 // (remember that a flags value of 0 means autodetection)
2295 loop_lo = ev_embeddable_backends () & ev_recommended_backends () 2405 loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
2296 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) 2406 ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
2310kqueue implementation). Store the kqueue/socket-only event loop in 2420kqueue implementation). Store the kqueue/socket-only event loop in
2311C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too). 2421C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
2312 2422
2313 struct ev_loop *loop = ev_default_init (0); 2423 struct ev_loop *loop = ev_default_init (0);
2314 struct ev_loop *loop_socket = 0; 2424 struct ev_loop *loop_socket = 0;
2315 struct ev_embed embed; 2425 ev_embed embed;
2316 2426
2317 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) 2427 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2318 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) 2428 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2319 { 2429 {
2320 ev_embed_init (&embed, 0, loop_socket); 2430 ev_embed_init (&embed, 0, loop_socket);
2502=over 4 2612=over 4
2503 2613
2504=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 2614=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
2505 2615
2506This function combines a simple timer and an I/O watcher, calls your 2616This function combines a simple timer and an I/O watcher, calls your
2507callback on whichever event happens first and automatically stop both 2617callback on whichever event happens first and automatically stops both
2508watchers. This is useful if you want to wait for a single event on an fd 2618watchers. This is useful if you want to wait for a single event on an fd
2509or timeout without having to allocate/configure/start/stop/free one or 2619or timeout without having to allocate/configure/start/stop/free one or
2510more watchers yourself. 2620more watchers yourself.
2511 2621
2512If C<fd> is less than 0, then no I/O watcher will be started and events 2622If C<fd> is less than 0, then no I/O watcher will be started and the
2513is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and 2623C<events> argument is being ignored. Otherwise, an C<ev_io> watcher for
2514C<events> set will be created and started. 2624the given C<fd> and C<events> set will be created and started.
2515 2625
2516If C<timeout> is less than 0, then no timeout watcher will be 2626If C<timeout> is less than 0, then no timeout watcher will be
2517started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 2627started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
2518repeat = 0) will be started. While C<0> is a valid timeout, it is of 2628repeat = 0) will be started. C<0> is a valid timeout.
2519dubious value.
2520 2629
2521The callback has the type C<void (*cb)(int revents, void *arg)> and gets 2630The callback has the type C<void (*cb)(int revents, void *arg)> and gets
2522passed an C<revents> set like normal event callbacks (a combination of 2631passed an C<revents> set like normal event callbacks (a combination of
2523C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> 2632C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
2524value passed to C<ev_once>: 2633value passed to C<ev_once>. Note that it is possible to receive I<both>
2634a timeout and an io event at the same time - you probably should give io
2635events precedence.
2636
2637Example: wait up to ten seconds for data to appear on STDIN_FILENO.
2525 2638
2526 static void stdin_ready (int revents, void *arg) 2639 static void stdin_ready (int revents, void *arg)
2527 { 2640 {
2641 if (revents & EV_READ)
2642 /* stdin might have data for us, joy! */;
2528 if (revents & EV_TIMEOUT) 2643 else if (revents & EV_TIMEOUT)
2529 /* doh, nothing entered */; 2644 /* doh, nothing entered */;
2530 else if (revents & EV_READ)
2531 /* stdin might have data for us, joy! */;
2532 } 2645 }
2533 2646
2534 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 2647 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
2535 2648
2536=item ev_feed_event (ev_loop *, watcher *, int revents) 2649=item ev_feed_event (struct ev_loop *, watcher *, int revents)
2537 2650
2538Feeds the given event set into the event loop, as if the specified event 2651Feeds the given event set into the event loop, as if the specified event
2539had happened for the specified watcher (which must be a pointer to an 2652had happened for the specified watcher (which must be a pointer to an
2540initialised but not necessarily started event watcher). 2653initialised but not necessarily started event watcher).
2541 2654
2542=item ev_feed_fd_event (ev_loop *, int fd, int revents) 2655=item ev_feed_fd_event (struct ev_loop *, int fd, int revents)
2543 2656
2544Feed an event on the given fd, as if a file descriptor backend detected 2657Feed an event on the given fd, as if a file descriptor backend detected
2545the given events it. 2658the given events it.
2546 2659
2547=item ev_feed_signal_event (ev_loop *loop, int signum) 2660=item ev_feed_signal_event (struct ev_loop *loop, int signum)
2548 2661
2549Feed an event as if the given signal occurred (C<loop> must be the default 2662Feed an event as if the given signal occurred (C<loop> must be the default
2550loop!). 2663loop!).
2551 2664
2552=back 2665=back

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