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Revision 1.105 by root, Sun Dec 23 03:50:10 2007 UTC vs.
Revision 1.131 by root, Tue Feb 19 17:09:28 2008 UTC

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260flags. If that is troubling you, check C<ev_backend ()> afterwards). 260flags. If that is troubling you, check C<ev_backend ()> afterwards).
261 261
262If you don't know what event loop to use, use the one returned from this 262If you don't know what event loop to use, use the one returned from this
263function. 263function.
264 264
265The default loop is the only loop that can handle C<ev_signal> and
266C<ev_child> watchers, and to do this, it always registers a handler
267for C<SIGCHLD>. If this is a problem for your app you can either
268create a dynamic loop with C<ev_loop_new> that doesn't do that, or you
269can simply overwrite the C<SIGCHLD> signal handler I<after> calling
270C<ev_default_init>.
271
265The flags argument can be used to specify special behaviour or specific 272The flags argument can be used to specify special behaviour or specific
266backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). 273backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>).
267 274
268The following flags are supported: 275The following flags are supported:
269 276
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403While this backend scales well, it requires one system call per active 410While this backend scales well, it requires one system call per active
404file descriptor per loop iteration. For small and medium numbers of file 411file descriptor per loop iteration. For small and medium numbers of file
405descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend 412descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406might perform better. 413might perform better.
407 414
415On the positive side, ignoring the spurious readyness notifications, this
416backend actually performed to specification in all tests and is fully
417embeddable, which is a rare feat among the OS-specific backends.
418
408=item C<EVBACKEND_ALL> 419=item C<EVBACKEND_ALL>
409 420
410Try all backends (even potentially broken ones that wouldn't be tried 421Try all backends (even potentially broken ones that wouldn't be tried
411with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as 422with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
412C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 423C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
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414It is definitely not recommended to use this flag. 425It is definitely not recommended to use this flag.
415 426
416=back 427=back
417 428
418If one or more of these are ored into the flags value, then only these 429If one or more of these are ored into the flags value, then only these
419backends will be tried (in the reverse order as given here). If none are 430backends will be tried (in the reverse order as listed here). If none are
420specified, most compiled-in backend will be tried, usually in reverse 431specified, all backends in C<ev_recommended_backends ()> will be tried.
421order of their flag values :)
422 432
423The most typical usage is like this: 433The most typical usage is like this:
424 434
425 if (!ev_default_loop (0)) 435 if (!ev_default_loop (0))
426 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 436 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
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473Like C<ev_default_destroy>, but destroys an event loop created by an 483Like C<ev_default_destroy>, but destroys an event loop created by an
474earlier call to C<ev_loop_new>. 484earlier call to C<ev_loop_new>.
475 485
476=item ev_default_fork () 486=item ev_default_fork ()
477 487
488This function sets a flag that causes subsequent C<ev_loop> iterations
478This function reinitialises the kernel state for backends that have 489to reinitialise the kernel state for backends that have one. Despite the
479one. Despite the name, you can call it anytime, but it makes most sense 490name, you can call it anytime, but it makes most sense after forking, in
480after forking, in either the parent or child process (or both, but that 491the child process (or both child and parent, but that again makes little
481again makes little sense). 492sense). You I<must> call it in the child before using any of the libev
493functions, and it will only take effect at the next C<ev_loop> iteration.
482 494
483You I<must> call this function in the child process after forking if and 495On the other hand, you only need to call this function in the child
484only if you want to use the event library in both processes. If you just 496process if and only if you want to use the event library in the child. If
485fork+exec, you don't have to call it. 497you just fork+exec, you don't have to call it at all.
486 498
487The function itself is quite fast and it's usually not a problem to call 499The function itself is quite fast and it's usually not a problem to call
488it just in case after a fork. To make this easy, the function will fit in 500it just in case after a fork. To make this easy, the function will fit in
489quite nicely into a call to C<pthread_atfork>: 501quite nicely into a call to C<pthread_atfork>:
490 502
491 pthread_atfork (0, 0, ev_default_fork); 503 pthread_atfork (0, 0, ev_default_fork);
492 504
493At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
494without calling this function, so if you force one of those backends you
495do not need to care.
496
497=item ev_loop_fork (loop) 505=item ev_loop_fork (loop)
498 506
499Like C<ev_default_fork>, but acts on an event loop created by 507Like C<ev_default_fork>, but acts on an event loop created by
500C<ev_loop_new>. Yes, you have to call this on every allocated event loop 508C<ev_loop_new>. Yes, you have to call this on every allocated event loop
501after fork, and how you do this is entirely your own problem. 509after fork, and how you do this is entirely your own problem.
510
511=item int ev_is_default_loop (loop)
512
513Returns true when the given loop actually is the default loop, false otherwise.
502 514
503=item unsigned int ev_loop_count (loop) 515=item unsigned int ev_loop_count (loop)
504 516
505Returns the count of loop iterations for the loop, which is identical to 517Returns the count of loop iterations for the loop, which is identical to
506the number of times libev did poll for new events. It starts at C<0> and 518the number of times libev did poll for new events. It starts at C<0> and
… …
551usually a better approach for this kind of thing. 563usually a better approach for this kind of thing.
552 564
553Here are the gory details of what C<ev_loop> does: 565Here are the gory details of what C<ev_loop> does:
554 566
555 - Before the first iteration, call any pending watchers. 567 - Before the first iteration, call any pending watchers.
556 * If there are no active watchers (reference count is zero), return. 568 * If EVFLAG_FORKCHECK was used, check for a fork.
557 - Queue all prepare watchers and then call all outstanding watchers. 569 - If a fork was detected, queue and call all fork watchers.
570 - Queue and call all prepare watchers.
558 - If we have been forked, recreate the kernel state. 571 - If we have been forked, recreate the kernel state.
559 - Update the kernel state with all outstanding changes. 572 - Update the kernel state with all outstanding changes.
560 - Update the "event loop time". 573 - Update the "event loop time".
561 - Calculate for how long to block. 574 - Calculate for how long to sleep or block, if at all
575 (active idle watchers, EVLOOP_NONBLOCK or not having
576 any active watchers at all will result in not sleeping).
577 - Sleep if the I/O and timer collect interval say so.
562 - Block the process, waiting for any events. 578 - Block the process, waiting for any events.
563 - Queue all outstanding I/O (fd) events. 579 - Queue all outstanding I/O (fd) events.
564 - Update the "event loop time" and do time jump handling. 580 - Update the "event loop time" and do time jump handling.
565 - Queue all outstanding timers. 581 - Queue all outstanding timers.
566 - Queue all outstanding periodics. 582 - Queue all outstanding periodics.
567 - If no events are pending now, queue all idle watchers. 583 - If no events are pending now, queue all idle watchers.
568 - Queue all check watchers. 584 - Queue all check watchers.
569 - Call all queued watchers in reverse order (i.e. check watchers first). 585 - Call all queued watchers in reverse order (i.e. check watchers first).
570 Signals and child watchers are implemented as I/O watchers, and will 586 Signals and child watchers are implemented as I/O watchers, and will
571 be handled here by queueing them when their watcher gets executed. 587 be handled here by queueing them when their watcher gets executed.
572 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 588 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
573 were used, return, otherwise continue with step *. 589 were used, or there are no active watchers, return, otherwise
590 continue with step *.
574 591
575Example: Queue some jobs and then loop until no events are outsanding 592Example: Queue some jobs and then loop until no events are outstanding
576anymore. 593anymore.
577 594
578 ... queue jobs here, make sure they register event watchers as long 595 ... queue jobs here, make sure they register event watchers as long
579 ... as they still have work to do (even an idle watcher will do..) 596 ... as they still have work to do (even an idle watcher will do..)
580 ev_loop (my_loop, 0); 597 ev_loop (my_loop, 0);
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584 601
585Can be used to make a call to C<ev_loop> return early (but only after it 602Can be used to make a call to C<ev_loop> return early (but only after it
586has processed all outstanding events). The C<how> argument must be either 603has processed all outstanding events). The C<how> argument must be either
587C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 604C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
588C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 605C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
606
607This "unloop state" will be cleared when entering C<ev_loop> again.
589 608
590=item ev_ref (loop) 609=item ev_ref (loop)
591 610
592=item ev_unref (loop) 611=item ev_unref (loop)
593 612
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598returning, ev_unref() after starting, and ev_ref() before stopping it. For 617returning, ev_unref() after starting, and ev_ref() before stopping it. For
599example, libev itself uses this for its internal signal pipe: It is not 618example, libev itself uses this for its internal signal pipe: It is not
600visible to the libev user and should not keep C<ev_loop> from exiting if 619visible to the libev user and should not keep C<ev_loop> from exiting if
601no event watchers registered by it are active. It is also an excellent 620no event watchers registered by it are active. It is also an excellent
602way to do this for generic recurring timers or from within third-party 621way to do this for generic recurring timers or from within third-party
603libraries. Just remember to I<unref after start> and I<ref before stop>. 622libraries. Just remember to I<unref after start> and I<ref before stop>
623(but only if the watcher wasn't active before, or was active before,
624respectively).
604 625
605Example: Create a signal watcher, but keep it from keeping C<ev_loop> 626Example: Create a signal watcher, but keep it from keeping C<ev_loop>
606running when nothing else is active. 627running when nothing else is active.
607 628
608 struct ev_signal exitsig; 629 struct ev_signal exitsig;
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756 777
757=item C<EV_FORK> 778=item C<EV_FORK>
758 779
759The event loop has been resumed in the child process after fork (see 780The event loop has been resumed in the child process after fork (see
760C<ev_fork>). 781C<ev_fork>).
782
783=item C<EV_ASYNC>
784
785The given async watcher has been asynchronously notified (see C<ev_async>).
761 786
762=item C<EV_ERROR> 787=item C<EV_ERROR>
763 788
764An unspecified error has occured, the watcher has been stopped. This might 789An unspecified error has occured, the watcher has been stopped. This might
765happen because the watcher could not be properly started because libev 790happen because the watcher could not be properly started because libev
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983In general you can register as many read and/or write event watchers per 1008In general you can register as many read and/or write event watchers per
984fd as you want (as long as you don't confuse yourself). Setting all file 1009fd as you want (as long as you don't confuse yourself). Setting all file
985descriptors to non-blocking mode is also usually a good idea (but not 1010descriptors to non-blocking mode is also usually a good idea (but not
986required if you know what you are doing). 1011required if you know what you are doing).
987 1012
988You have to be careful with dup'ed file descriptors, though. Some backends
989(the linux epoll backend is a notable example) cannot handle dup'ed file
990descriptors correctly if you register interest in two or more fds pointing
991to the same underlying file/socket/etc. description (that is, they share
992the same underlying "file open").
993
994If you must do this, then force the use of a known-to-be-good backend 1013If you must do this, then force the use of a known-to-be-good backend
995(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1014(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
996C<EVBACKEND_POLL>). 1015C<EVBACKEND_POLL>).
997 1016
998Another thing you have to watch out for is that it is quite easy to 1017Another thing you have to watch out for is that it is quite easy to
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1033 1052
1034=head3 The special problem of dup'ed file descriptors 1053=head3 The special problem of dup'ed file descriptors
1035 1054
1036Some backends (e.g. epoll), cannot register events for file descriptors, 1055Some backends (e.g. epoll), cannot register events for file descriptors,
1037but only events for the underlying file descriptions. That means when you 1056but only events for the underlying file descriptions. That means when you
1038have C<dup ()>'ed file descriptors and register events for them, only one 1057have C<dup ()>'ed file descriptors or weirder constellations, and register
1039file descriptor might actually receive events. 1058events for them, only one file descriptor might actually receive events.
1040 1059
1041There is no workaround possible except not registering events 1060There is no workaround possible except not registering events
1042for potentially C<dup ()>'ed file descriptors, or to resort to 1061for potentially C<dup ()>'ed file descriptors, or to resort to
1043C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. 1062C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1044 1063
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1073=item int events [read-only] 1092=item int events [read-only]
1074 1093
1075The events being watched. 1094The events being watched.
1076 1095
1077=back 1096=back
1097
1098=head3 Examples
1078 1099
1079Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1100Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1080readable, but only once. Since it is likely line-buffered, you could 1101readable, but only once. Since it is likely line-buffered, you could
1081attempt to read a whole line in the callback. 1102attempt to read a whole line in the callback.
1082 1103
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1180or C<ev_timer_again> is called and determines the next timeout (if any), 1201or C<ev_timer_again> is called and determines the next timeout (if any),
1181which is also when any modifications are taken into account. 1202which is also when any modifications are taken into account.
1182 1203
1183=back 1204=back
1184 1205
1206=head3 Examples
1207
1185Example: Create a timer that fires after 60 seconds. 1208Example: Create a timer that fires after 60 seconds.
1186 1209
1187 static void 1210 static void
1188 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1211 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1189 { 1212 {
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1346When active, contains the absolute time that the watcher is supposed to 1369When active, contains the absolute time that the watcher is supposed to
1347trigger next. 1370trigger next.
1348 1371
1349=back 1372=back
1350 1373
1374=head3 Examples
1375
1351Example: Call a callback every hour, or, more precisely, whenever the 1376Example: Call a callback every hour, or, more precisely, whenever the
1352system clock is divisible by 3600. The callback invocation times have 1377system clock is divisible by 3600. The callback invocation times have
1353potentially a lot of jittering, but good long-term stability. 1378potentially a lot of jittering, but good long-term stability.
1354 1379
1355 static void 1380 static void
… …
1421 1446
1422=head3 Watcher-Specific Functions and Data Members 1447=head3 Watcher-Specific Functions and Data Members
1423 1448
1424=over 4 1449=over 4
1425 1450
1426=item ev_child_init (ev_child *, callback, int pid) 1451=item ev_child_init (ev_child *, callback, int pid, int trace)
1427 1452
1428=item ev_child_set (ev_child *, int pid) 1453=item ev_child_set (ev_child *, int pid, int trace)
1429 1454
1430Configures the watcher to wait for status changes of process C<pid> (or 1455Configures the watcher to wait for status changes of process C<pid> (or
1431I<any> process if C<pid> is specified as C<0>). The callback can look 1456I<any> process if C<pid> is specified as C<0>). The callback can look
1432at the C<rstatus> member of the C<ev_child> watcher structure to see 1457at the C<rstatus> member of the C<ev_child> watcher structure to see
1433the status word (use the macros from C<sys/wait.h> and see your systems 1458the status word (use the macros from C<sys/wait.h> and see your systems
1434C<waitpid> documentation). The C<rpid> member contains the pid of the 1459C<waitpid> documentation). The C<rpid> member contains the pid of the
1435process causing the status change. 1460process causing the status change. C<trace> must be either C<0> (only
1461activate the watcher when the process terminates) or C<1> (additionally
1462activate the watcher when the process is stopped or continued).
1436 1463
1437=item int pid [read-only] 1464=item int pid [read-only]
1438 1465
1439The process id this watcher watches out for, or C<0>, meaning any process id. 1466The process id this watcher watches out for, or C<0>, meaning any process id.
1440 1467
… …
1446 1473
1447The process exit/trace status caused by C<rpid> (see your systems 1474The process exit/trace status caused by C<rpid> (see your systems
1448C<waitpid> and C<sys/wait.h> documentation for details). 1475C<waitpid> and C<sys/wait.h> documentation for details).
1449 1476
1450=back 1477=back
1478
1479=head3 Examples
1451 1480
1452Example: Try to exit cleanly on SIGINT and SIGTERM. 1481Example: Try to exit cleanly on SIGINT and SIGTERM.
1453 1482
1454 static void 1483 static void
1455 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1484 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1496semantics of C<ev_stat> watchers, which means that libev sometimes needs 1525semantics of C<ev_stat> watchers, which means that libev sometimes needs
1497to fall back to regular polling again even with inotify, but changes are 1526to fall back to regular polling again even with inotify, but changes are
1498usually detected immediately, and if the file exists there will be no 1527usually detected immediately, and if the file exists there will be no
1499polling. 1528polling.
1500 1529
1530=head3 Inotify
1531
1532When C<inotify (7)> support has been compiled into libev (generally only
1533available on Linux) and present at runtime, it will be used to speed up
1534change detection where possible. The inotify descriptor will be created lazily
1535when the first C<ev_stat> watcher is being started.
1536
1537Inotify presense does not change the semantics of C<ev_stat> watchers
1538except that changes might be detected earlier, and in some cases, to avoid
1539making regular C<stat> calls. Even in the presense of inotify support
1540there are many cases where libev has to resort to regular C<stat> polling.
1541
1542(There is no support for kqueue, as apparently it cannot be used to
1543implement this functionality, due to the requirement of having a file
1544descriptor open on the object at all times).
1545
1546=head3 The special problem of stat time resolution
1547
1548The C<stat ()> syscall only supports full-second resolution portably, and
1549even on systems where the resolution is higher, many filesystems still
1550only support whole seconds.
1551
1552That means that, if the time is the only thing that changes, you might
1553miss updates: on the first update, C<ev_stat> detects a change and calls
1554your callback, which does something. When there is another update within
1555the same second, C<ev_stat> will be unable to detect it.
1556
1557The solution to this is to delay acting on a change for a second (or till
1558the next second boundary), using a roughly one-second delay C<ev_timer>
1559(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1560is added to work around small timing inconsistencies of some operating
1561systems.
1562
1501=head3 Watcher-Specific Functions and Data Members 1563=head3 Watcher-Specific Functions and Data Members
1502 1564
1503=over 4 1565=over 4
1504 1566
1505=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1567=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
… …
1542=item const char *path [read-only] 1604=item const char *path [read-only]
1543 1605
1544The filesystem path that is being watched. 1606The filesystem path that is being watched.
1545 1607
1546=back 1608=back
1609
1610=head3 Examples
1547 1611
1548Example: Watch C</etc/passwd> for attribute changes. 1612Example: Watch C</etc/passwd> for attribute changes.
1549 1613
1550 static void 1614 static void
1551 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1615 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1564 } 1628 }
1565 1629
1566 ... 1630 ...
1567 ev_stat passwd; 1631 ev_stat passwd;
1568 1632
1569 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1633 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1570 ev_stat_start (loop, &passwd); 1634 ev_stat_start (loop, &passwd);
1635
1636Example: Like above, but additionally use a one-second delay so we do not
1637miss updates (however, frequent updates will delay processing, too, so
1638one might do the work both on C<ev_stat> callback invocation I<and> on
1639C<ev_timer> callback invocation).
1640
1641 static ev_stat passwd;
1642 static ev_timer timer;
1643
1644 static void
1645 timer_cb (EV_P_ ev_timer *w, int revents)
1646 {
1647 ev_timer_stop (EV_A_ w);
1648
1649 /* now it's one second after the most recent passwd change */
1650 }
1651
1652 static void
1653 stat_cb (EV_P_ ev_stat *w, int revents)
1654 {
1655 /* reset the one-second timer */
1656 ev_timer_again (EV_A_ &timer);
1657 }
1658
1659 ...
1660 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1661 ev_stat_start (loop, &passwd);
1662 ev_timer_init (&timer, timer_cb, 0., 1.01);
1571 1663
1572 1664
1573=head2 C<ev_idle> - when you've got nothing better to do... 1665=head2 C<ev_idle> - when you've got nothing better to do...
1574 1666
1575Idle watchers trigger events when no other events of the same or higher 1667Idle watchers trigger events when no other events of the same or higher
… …
1601kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1693kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1602believe me. 1694believe me.
1603 1695
1604=back 1696=back
1605 1697
1698=head3 Examples
1699
1606Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1700Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1607callback, free it. Also, use no error checking, as usual. 1701callback, free it. Also, use no error checking, as usual.
1608 1702
1609 static void 1703 static void
1610 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1704 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1611 { 1705 {
1612 free (w); 1706 free (w);
1613 // now do something you wanted to do when the program has 1707 // now do something you wanted to do when the program has
1614 // no longer asnything immediate to do. 1708 // no longer anything immediate to do.
1615 } 1709 }
1616 1710
1617 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1711 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1618 ev_idle_init (idle_watcher, idle_cb); 1712 ev_idle_init (idle_watcher, idle_cb);
1619 ev_idle_start (loop, idle_cb); 1713 ev_idle_start (loop, idle_cb);
… …
1681parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1775parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1682macros, but using them is utterly, utterly and completely pointless. 1776macros, but using them is utterly, utterly and completely pointless.
1683 1777
1684=back 1778=back
1685 1779
1780=head3 Examples
1781
1686There are a number of principal ways to embed other event loops or modules 1782There are a number of principal ways to embed other event loops or modules
1687into libev. Here are some ideas on how to include libadns into libev 1783into libev. Here are some ideas on how to include libadns into libev
1688(there is a Perl module named C<EV::ADNS> that does this, which you could 1784(there is a Perl module named C<EV::ADNS> that does this, which you could
1689use for an actually working example. Another Perl module named C<EV::Glib> 1785use for an actually working example. Another Perl module named C<EV::Glib>
1690embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV 1786embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
… …
1858portable one. 1954portable one.
1859 1955
1860So when you want to use this feature you will always have to be prepared 1956So when you want to use this feature you will always have to be prepared
1861that you cannot get an embeddable loop. The recommended way to get around 1957that you cannot get an embeddable loop. The recommended way to get around
1862this is to have a separate variables for your embeddable loop, try to 1958this is to have a separate variables for your embeddable loop, try to
1863create it, and if that fails, use the normal loop for everything: 1959create it, and if that fails, use the normal loop for everything.
1960
1961=head3 Watcher-Specific Functions and Data Members
1962
1963=over 4
1964
1965=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1966
1967=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1968
1969Configures the watcher to embed the given loop, which must be
1970embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1971invoked automatically, otherwise it is the responsibility of the callback
1972to invoke it (it will continue to be called until the sweep has been done,
1973if you do not want thta, you need to temporarily stop the embed watcher).
1974
1975=item ev_embed_sweep (loop, ev_embed *)
1976
1977Make a single, non-blocking sweep over the embedded loop. This works
1978similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1979apropriate way for embedded loops.
1980
1981=item struct ev_loop *other [read-only]
1982
1983The embedded event loop.
1984
1985=back
1986
1987=head3 Examples
1988
1989Example: Try to get an embeddable event loop and embed it into the default
1990event loop. If that is not possible, use the default loop. The default
1991loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1992C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1993used).
1864 1994
1865 struct ev_loop *loop_hi = ev_default_init (0); 1995 struct ev_loop *loop_hi = ev_default_init (0);
1866 struct ev_loop *loop_lo = 0; 1996 struct ev_loop *loop_lo = 0;
1867 struct ev_embed embed; 1997 struct ev_embed embed;
1868 1998
… …
1879 ev_embed_start (loop_hi, &embed); 2009 ev_embed_start (loop_hi, &embed);
1880 } 2010 }
1881 else 2011 else
1882 loop_lo = loop_hi; 2012 loop_lo = loop_hi;
1883 2013
1884=head3 Watcher-Specific Functions and Data Members 2014Example: Check if kqueue is available but not recommended and create
2015a kqueue backend for use with sockets (which usually work with any
2016kqueue implementation). Store the kqueue/socket-only event loop in
2017C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1885 2018
1886=over 4 2019 struct ev_loop *loop = ev_default_init (0);
2020 struct ev_loop *loop_socket = 0;
2021 struct ev_embed embed;
2022
2023 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2024 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2025 {
2026 ev_embed_init (&embed, 0, loop_socket);
2027 ev_embed_start (loop, &embed);
2028 }
1887 2029
1888=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2030 if (!loop_socket)
2031 loop_socket = loop;
1889 2032
1890=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2033 // now use loop_socket for all sockets, and loop for everything else
1891
1892Configures the watcher to embed the given loop, which must be
1893embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1894invoked automatically, otherwise it is the responsibility of the callback
1895to invoke it (it will continue to be called until the sweep has been done,
1896if you do not want thta, you need to temporarily stop the embed watcher).
1897
1898=item ev_embed_sweep (loop, ev_embed *)
1899
1900Make a single, non-blocking sweep over the embedded loop. This works
1901similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1902apropriate way for embedded loops.
1903
1904=item struct ev_loop *other [read-only]
1905
1906The embedded event loop.
1907
1908=back
1909 2034
1910 2035
1911=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2036=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1912 2037
1913Fork watchers are called when a C<fork ()> was detected (usually because 2038Fork watchers are called when a C<fork ()> was detected (usually because
… …
1929believe me. 2054believe me.
1930 2055
1931=back 2056=back
1932 2057
1933 2058
2059=head2 C<ev_async> - how to wake up another event loop
2060
2061In general, you cannot use an C<ev_loop> from multiple threads or other
2062asynchronous sources such as signal handlers (as opposed to multiple event
2063loops - those are of course safe to use in different threads).
2064
2065Sometimes, however, you need to wake up another event loop you do not
2066control, for example because it belongs to another thread. This is what
2067C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
2068can signal it by calling C<ev_async_send>, which is thread- and signal
2069safe.
2070
2071This functionality is very similar to C<ev_signal> watchers, as signals,
2072too, are asynchronous in nature, and signals, too, will be compressed
2073(i.e. the number of callback invocations may be less than the number of
2074C<ev_async_sent> calls).
2075
2076Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2077just the default loop.
2078
2079=head3 Queueing
2080
2081C<ev_async> does not support queueing of data in any way. The reason
2082is that the author does not know of a simple (or any) algorithm for a
2083multiple-writer-single-reader queue that works in all cases and doesn't
2084need elaborate support such as pthreads.
2085
2086That means that if you want to queue data, you have to provide your own
2087queue. But at least I can tell you would implement locking around your
2088queue:
2089
2090=over 4
2091
2092=item queueing from a signal handler context
2093
2094To implement race-free queueing, you simply add to the queue in the signal
2095handler but you block the signal handler in the watcher callback. Here is an example that does that for
2096some fictitiuous SIGUSR1 handler:
2097
2098 static ev_async mysig;
2099
2100 static void
2101 sigusr1_handler (void)
2102 {
2103 sometype data;
2104
2105 // no locking etc.
2106 queue_put (data);
2107 ev_async_send (DEFAULT_ &mysig);
2108 }
2109
2110 static void
2111 mysig_cb (EV_P_ ev_async *w, int revents)
2112 {
2113 sometype data;
2114 sigset_t block, prev;
2115
2116 sigemptyset (&block);
2117 sigaddset (&block, SIGUSR1);
2118 sigprocmask (SIG_BLOCK, &block, &prev);
2119
2120 while (queue_get (&data))
2121 process (data);
2122
2123 if (sigismember (&prev, SIGUSR1)
2124 sigprocmask (SIG_UNBLOCK, &block, 0);
2125 }
2126
2127(Note: pthreads in theory requires you to use C<pthread_setmask>
2128instead of C<sigprocmask> when you use threads, but libev doesn't do it
2129either...).
2130
2131=item queueing from a thread context
2132
2133The strategy for threads is different, as you cannot (easily) block
2134threads but you can easily preempt them, so to queue safely you need to
2135employ a traditional mutex lock, such as in this pthread example:
2136
2137 static ev_async mysig;
2138 static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2139
2140 static void
2141 otherthread (void)
2142 {
2143 // only need to lock the actual queueing operation
2144 pthread_mutex_lock (&mymutex);
2145 queue_put (data);
2146 pthread_mutex_unlock (&mymutex);
2147
2148 ev_async_send (DEFAULT_ &mysig);
2149 }
2150
2151 static void
2152 mysig_cb (EV_P_ ev_async *w, int revents)
2153 {
2154 pthread_mutex_lock (&mymutex);
2155
2156 while (queue_get (&data))
2157 process (data);
2158
2159 pthread_mutex_unlock (&mymutex);
2160 }
2161
2162=back
2163
2164
2165=head3 Watcher-Specific Functions and Data Members
2166
2167=over 4
2168
2169=item ev_async_init (ev_async *, callback)
2170
2171Initialises and configures the async watcher - it has no parameters of any
2172kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2173believe me.
2174
2175=item ev_async_send (loop, ev_async *)
2176
2177Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2178an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2179C<ev_feed_event>, this call is safe to do in other threads, signal or
2180similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
2181section below on what exactly this means).
2182
2183This call incurs the overhead of a syscall only once per loop iteration,
2184so while the overhead might be noticable, it doesn't apply to repeated
2185calls to C<ev_async_send>.
2186
2187=back
2188
2189
1934=head1 OTHER FUNCTIONS 2190=head1 OTHER FUNCTIONS
1935 2191
1936There are some other functions of possible interest. Described. Here. Now. 2192There are some other functions of possible interest. Described. Here. Now.
1937 2193
1938=over 4 2194=over 4
… …
2165Example: Define a class with an IO and idle watcher, start one of them in 2421Example: Define a class with an IO and idle watcher, start one of them in
2166the constructor. 2422the constructor.
2167 2423
2168 class myclass 2424 class myclass
2169 { 2425 {
2170 ev_io io; void io_cb (ev::io &w, int revents); 2426 ev::io io; void io_cb (ev::io &w, int revents);
2171 ev_idle idle void idle_cb (ev::idle &w, int revents); 2427 ev:idle idle void idle_cb (ev::idle &w, int revents);
2172 2428
2173 myclass (); 2429 myclass (int fd)
2174 }
2175
2176 myclass::myclass (int fd)
2177 { 2430 {
2178 io .set <myclass, &myclass::io_cb > (this); 2431 io .set <myclass, &myclass::io_cb > (this);
2179 idle.set <myclass, &myclass::idle_cb> (this); 2432 idle.set <myclass, &myclass::idle_cb> (this);
2180 2433
2181 io.start (fd, ev::READ); 2434 io.start (fd, ev::READ);
2435 }
2182 } 2436 };
2183 2437
2184 2438
2185=head1 MACRO MAGIC 2439=head1 MACRO MAGIC
2186 2440
2187Libev can be compiled with a variety of options, the most fundamantal 2441Libev can be compiled with a variety of options, the most fundamantal
… …
2392wants osf handles on win32 (this is the case when the select to 2646wants osf handles on win32 (this is the case when the select to
2393be used is the winsock select). This means that it will call 2647be used is the winsock select). This means that it will call
2394C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2648C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2395it is assumed that all these functions actually work on fds, even 2649it is assumed that all these functions actually work on fds, even
2396on win32. Should not be defined on non-win32 platforms. 2650on win32. Should not be defined on non-win32 platforms.
2651
2652=item EV_FD_TO_WIN32_HANDLE
2653
2654If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2655file descriptors to socket handles. When not defining this symbol (the
2656default), then libev will call C<_get_osfhandle>, which is usually
2657correct. In some cases, programs use their own file descriptor management,
2658in which case they can provide this function to map fds to socket handles.
2397 2659
2398=item EV_USE_POLL 2660=item EV_USE_POLL
2399 2661
2400If defined to be C<1>, libev will compile in support for the C<poll>(2) 2662If defined to be C<1>, libev will compile in support for the C<poll>(2)
2401backend. Otherwise it will be enabled on non-win32 platforms. It 2663backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2435 2697
2436If defined to be C<1>, libev will compile in support for the Linux inotify 2698If defined to be C<1>, libev will compile in support for the Linux inotify
2437interface to speed up C<ev_stat> watchers. Its actual availability will 2699interface to speed up C<ev_stat> watchers. Its actual availability will
2438be detected at runtime. 2700be detected at runtime.
2439 2701
2702=item EV_ATOMIC_T
2703
2704Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2705access is atomic with respect to other threads or signal contexts. No such
2706type is easily found in the C language, so you can provide your own type
2707that you know is safe for your purposes. It is used both for signal handler "locking"
2708as well as for signal and thread safety in C<ev_async> watchers.
2709
2710In the absense of this define, libev will use C<sig_atomic_t volatile>
2711(from F<signal.h>), which is usually good enough on most platforms.
2712
2440=item EV_H 2713=item EV_H
2441 2714
2442The name of the F<ev.h> header file used to include it. The default if 2715The name of the F<ev.h> header file used to include it. The default if
2443undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2716undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2444can be used to virtually rename the F<ev.h> header file in case of conflicts. 2717used to virtually rename the F<ev.h> header file in case of conflicts.
2445 2718
2446=item EV_CONFIG_H 2719=item EV_CONFIG_H
2447 2720
2448If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2721If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2449F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2722F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2450C<EV_H>, above. 2723C<EV_H>, above.
2451 2724
2452=item EV_EVENT_H 2725=item EV_EVENT_H
2453 2726
2454Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2727Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2455of how the F<event.h> header can be found. 2728of how the F<event.h> header can be found, the default is C<"event.h">.
2456 2729
2457=item EV_PROTOTYPES 2730=item EV_PROTOTYPES
2458 2731
2459If defined to be C<0>, then F<ev.h> will not define any function 2732If defined to be C<0>, then F<ev.h> will not define any function
2460prototypes, but still define all the structs and other symbols. This is 2733prototypes, but still define all the structs and other symbols. This is
… …
2509defined to be C<0>, then they are not. 2782defined to be C<0>, then they are not.
2510 2783
2511=item EV_FORK_ENABLE 2784=item EV_FORK_ENABLE
2512 2785
2513If undefined or defined to be C<1>, then fork watchers are supported. If 2786If undefined or defined to be C<1>, then fork watchers are supported. If
2787defined to be C<0>, then they are not.
2788
2789=item EV_ASYNC_ENABLE
2790
2791If undefined or defined to be C<1>, then async watchers are supported. If
2514defined to be C<0>, then they are not. 2792defined to be C<0>, then they are not.
2515 2793
2516=item EV_MINIMAL 2794=item EV_MINIMAL
2517 2795
2518If you need to shave off some kilobytes of code at the expense of some 2796If you need to shave off some kilobytes of code at the expense of some
… …
2632 2910
2633=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2911=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2634 2912
2635This means that, when you have a watcher that triggers in one hour and 2913This means that, when you have a watcher that triggers in one hour and
2636there are 100 watchers that would trigger before that then inserting will 2914there are 100 watchers that would trigger before that then inserting will
2637have to skip those 100 watchers. 2915have to skip roughly seven (C<ld 100>) of these watchers.
2638 2916
2639=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2917=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2640 2918
2641That means that for changing a timer costs less than removing/adding them 2919That means that changing a timer costs less than removing/adding them
2642as only the relative motion in the event queue has to be paid for. 2920as only the relative motion in the event queue has to be paid for.
2643 2921
2644=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2922=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2645 2923
2646These just add the watcher into an array or at the head of a list. 2924These just add the watcher into an array or at the head of a list.
2925
2647=item Stopping check/prepare/idle watchers: O(1) 2926=item Stopping check/prepare/idle/fork/async watchers: O(1)
2648 2927
2649=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2928=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2650 2929
2651These watchers are stored in lists then need to be walked to find the 2930These watchers are stored in lists then need to be walked to find the
2652correct watcher to remove. The lists are usually short (you don't usually 2931correct watcher to remove. The lists are usually short (you don't usually
2653have many watchers waiting for the same fd or signal). 2932have many watchers waiting for the same fd or signal).
2654 2933
2655=item Finding the next timer per loop iteration: O(1) 2934=item Finding the next timer in each loop iteration: O(1)
2935
2936By virtue of using a binary heap, the next timer is always found at the
2937beginning of the storage array.
2656 2938
2657=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2939=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2658 2940
2659A change means an I/O watcher gets started or stopped, which requires 2941A change means an I/O watcher gets started or stopped, which requires
2660libev to recalculate its status (and possibly tell the kernel). 2942libev to recalculate its status (and possibly tell the kernel, depending
2943on backend and wether C<ev_io_set> was used).
2661 2944
2662=item Activating one watcher: O(1) 2945=item Activating one watcher (putting it into the pending state): O(1)
2663 2946
2664=item Priority handling: O(number_of_priorities) 2947=item Priority handling: O(number_of_priorities)
2665 2948
2666Priorities are implemented by allocating some space for each 2949Priorities are implemented by allocating some space for each
2667priority. When doing priority-based operations, libev usually has to 2950priority. When doing priority-based operations, libev usually has to
2668linearly search all the priorities. 2951linearly search all the priorities, but starting/stopping and activating
2952watchers becomes O(1) w.r.t. priority handling.
2953
2954=item Sending an ev_async: O(1)
2955
2956=item Processing ev_async_send: O(number_of_async_watchers)
2957
2958=item Processing signals: O(max_signal_number)
2959
2960Sending involves a syscall I<iff> there were no other C<ev_async_send>
2961calls in the current loop iteration. Checking for async and signal events
2962involves iterating over all running async watchers or all signal numbers.
2669 2963
2670=back 2964=back
2671 2965
2672 2966
2967=head1 Win32 platform limitations and workarounds
2968
2969Win32 doesn't support any of the standards (e.g. POSIX) that libev
2970requires, and its I/O model is fundamentally incompatible with the POSIX
2971model. Libev still offers limited functionality on this platform in
2972the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2973descriptors. This only applies when using Win32 natively, not when using
2974e.g. cygwin.
2975
2976There is no supported compilation method available on windows except
2977embedding it into other applications.
2978
2979Due to the many, low, and arbitrary limits on the win32 platform and the
2980abysmal performance of winsockets, using a large number of sockets is not
2981recommended (and not reasonable). If your program needs to use more than
2982a hundred or so sockets, then likely it needs to use a totally different
2983implementation for windows, as libev offers the POSIX model, which cannot
2984be implemented efficiently on windows (microsoft monopoly games).
2985
2986=over 4
2987
2988=item The winsocket select function
2989
2990The winsocket C<select> function doesn't follow POSIX in that it requires
2991socket I<handles> and not socket I<file descriptors>. This makes select
2992very inefficient, and also requires a mapping from file descriptors
2993to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2994C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2995symbols for more info.
2996
2997The configuration for a "naked" win32 using the microsoft runtime
2998libraries and raw winsocket select is:
2999
3000 #define EV_USE_SELECT 1
3001 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3002
3003Note that winsockets handling of fd sets is O(n), so you can easily get a
3004complexity in the O(n²) range when using win32.
3005
3006=item Limited number of file descriptors
3007
3008Windows has numerous arbitrary (and low) limits on things. Early versions
3009of winsocket's select only supported waiting for a max. of C<64> handles
3010(probably owning to the fact that all windows kernels can only wait for
3011C<64> things at the same time internally; microsoft recommends spawning a
3012chain of threads and wait for 63 handles and the previous thread in each).
3013
3014Newer versions support more handles, but you need to define C<FD_SETSIZE>
3015to some high number (e.g. C<2048>) before compiling the winsocket select
3016call (which might be in libev or elsewhere, for example, perl does its own
3017select emulation on windows).
3018
3019Another limit is the number of file descriptors in the microsoft runtime
3020libraries, which by default is C<64> (there must be a hidden I<64> fetish
3021or something like this inside microsoft). You can increase this by calling
3022C<_setmaxstdio>, which can increase this limit to C<2048> (another
3023arbitrary limit), but is broken in many versions of the microsoft runtime
3024libraries.
3025
3026This might get you to about C<512> or C<2048> sockets (depending on
3027windows version and/or the phase of the moon). To get more, you need to
3028wrap all I/O functions and provide your own fd management, but the cost of
3029calling select (O(n²)) will likely make this unworkable.
3030
3031=back
3032
3033
2673=head1 AUTHOR 3034=head1 AUTHOR
2674 3035
2675Marc Lehmann <libev@schmorp.de>. 3036Marc Lehmann <libev@schmorp.de>.
2676 3037

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