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Revision 1.101 by ayin, Sat Dec 22 14:11:25 2007 UTC vs.
Revision 1.114 by root, Mon Dec 31 01:31:30 2007 UTC

… …
4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 #include <ev.h> 7 #include <ev.h>
8 8
9=head1 EXAMPLE PROGRAM 9=head2 EXAMPLE PROGRAM
10 10
11 #include <ev.h> 11 #include <ev.h>
12 12
13 ev_io stdin_watcher; 13 ev_io stdin_watcher;
14 ev_timer timeout_watcher; 14 ev_timer timeout_watcher;
… …
65You register interest in certain events by registering so-called I<event 65You register interest in certain events by registering so-called I<event
66watchers>, which are relatively small C structures you initialise with the 66watchers>, which are relatively small C structures you initialise with the
67details of the event, and then hand it over to libev by I<starting> the 67details of the event, and then hand it over to libev by I<starting> the
68watcher. 68watcher.
69 69
70=head1 FEATURES 70=head2 FEATURES
71 71
72Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the 72Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73BSD-specific C<kqueue> and the Solaris-specific event port mechanisms 73BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74for file descriptor events (C<ev_io>), the Linux C<inotify> interface 74for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers 75(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
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82 82
83It also is quite fast (see this 83It also is quite fast (see this
84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent 84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85for example). 85for example).
86 86
87=head1 CONVENTIONS 87=head2 CONVENTIONS
88 88
89Libev is very configurable. In this manual the default configuration will 89Libev is very configurable. In this manual the default configuration will
90be described, which supports multiple event loops. For more info about 90be described, which supports multiple event loops. For more info about
91various configuration options please have a look at B<EMBED> section in 91various configuration options please have a look at B<EMBED> section in
92this manual. If libev was configured without support for multiple event 92this manual. If libev was configured without support for multiple event
93loops, then all functions taking an initial argument of name C<loop> 93loops, then all functions taking an initial argument of name C<loop>
94(which is always of type C<struct ev_loop *>) will not have this argument. 94(which is always of type C<struct ev_loop *>) will not have this argument.
95 95
96=head1 TIME REPRESENTATION 96=head2 TIME REPRESENTATION
97 97
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
… …
306=item C<EVBACKEND_SELECT> (value 1, portable select backend) 306=item C<EVBACKEND_SELECT> (value 1, portable select backend)
307 307
308This is your standard select(2) backend. Not I<completely> standard, as 308This is your standard select(2) backend. Not I<completely> standard, as
309libev tries to roll its own fd_set with no limits on the number of fds, 309libev tries to roll its own fd_set with no limits on the number of fds,
310but if that fails, expect a fairly low limit on the number of fds when 310but if that fails, expect a fairly low limit on the number of fds when
311using this backend. It doesn't scale too well (O(highest_fd)), but its usually 311using this backend. It doesn't scale too well (O(highest_fd)), but its
312the fastest backend for a low number of fds. 312usually the fastest backend for a low number of (low-numbered :) fds.
313
314To get good performance out of this backend you need a high amount of
315parallelity (most of the file descriptors should be busy). If you are
316writing a server, you should C<accept ()> in a loop to accept as many
317connections as possible during one iteration. You might also want to have
318a look at C<ev_set_io_collect_interval ()> to increase the amount of
319readyness notifications you get per iteration.
313 320
314=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) 321=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
315 322
316And this is your standard poll(2) backend. It's more complicated than 323And this is your standard poll(2) backend. It's more complicated
317select, but handles sparse fds better and has no artificial limit on the 324than select, but handles sparse fds better and has no artificial
318number of fds you can use (except it will slow down considerably with a 325limit on the number of fds you can use (except it will slow down
319lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 326considerably with a lot of inactive fds). It scales similarly to select,
327i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
328performance tips.
320 329
321=item C<EVBACKEND_EPOLL> (value 4, Linux) 330=item C<EVBACKEND_EPOLL> (value 4, Linux)
322 331
323For few fds, this backend is a bit little slower than poll and select, 332For few fds, this backend is a bit little slower than poll and select,
324but it scales phenomenally better. While poll and select usually scale 333but it scales phenomenally better. While poll and select usually scale
325like O(total_fds) where n is the total number of fds (or the highest fd), 334like O(total_fds) where n is the total number of fds (or the highest fd),
326epoll scales either O(1) or O(active_fds). The epoll design has a number 335epoll scales either O(1) or O(active_fds). The epoll design has a number
327of shortcomings, such as silently dropping events in some hard-to-detect 336of shortcomings, such as silently dropping events in some hard-to-detect
328cases and rewiring a syscall per fd change, no fork support and bad 337cases and rewiring a syscall per fd change, no fork support and bad
329support for dup: 338support for dup.
330 339
331While stopping, setting and starting an I/O watcher in the same iteration 340While stopping, setting and starting an I/O watcher in the same iteration
332will result in some caching, there is still a syscall per such incident 341will result in some caching, there is still a syscall per such incident
333(because the fd could point to a different file description now), so its 342(because the fd could point to a different file description now), so its
334best to avoid that. Also, C<dup ()>'ed file descriptors might not work 343best to avoid that. Also, C<dup ()>'ed file descriptors might not work
335very well if you register events for both fds. 344very well if you register events for both fds.
336 345
337Please note that epoll sometimes generates spurious notifications, so you 346Please note that epoll sometimes generates spurious notifications, so you
338need to use non-blocking I/O or other means to avoid blocking when no data 347need to use non-blocking I/O or other means to avoid blocking when no data
339(or space) is available. 348(or space) is available.
349
350Best performance from this backend is achieved by not unregistering all
351watchers for a file descriptor until it has been closed, if possible, i.e.
352keep at least one watcher active per fd at all times.
353
354While nominally embeddeble in other event loops, this feature is broken in
355all kernel versions tested so far.
340 356
341=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 357=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
342 358
343Kqueue deserves special mention, as at the time of this writing, it 359Kqueue deserves special mention, as at the time of this writing, it
344was broken on all BSDs except NetBSD (usually it doesn't work reliably 360was broken on all BSDs except NetBSD (usually it doesn't work reliably
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357course). While stopping, setting and starting an I/O watcher does never 373course). While stopping, setting and starting an I/O watcher does never
358cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to 374cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
359two event changes per incident, support for C<fork ()> is very bad and it 375two event changes per incident, support for C<fork ()> is very bad and it
360drops fds silently in similarly hard-to-detect cases. 376drops fds silently in similarly hard-to-detect cases.
361 377
378This backend usually performs well under most conditions.
379
380While nominally embeddable in other event loops, this doesn't work
381everywhere, so you might need to test for this. And since it is broken
382almost everywhere, you should only use it when you have a lot of sockets
383(for which it usually works), by embedding it into another event loop
384(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
385sockets.
386
362=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) 387=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
363 388
364This is not implemented yet (and might never be). 389This is not implemented yet (and might never be, unless you send me an
390implementation). According to reports, C</dev/poll> only supports sockets
391and is not embeddable, which would limit the usefulness of this backend
392immensely.
365 393
366=item C<EVBACKEND_PORT> (value 32, Solaris 10) 394=item C<EVBACKEND_PORT> (value 32, Solaris 10)
367 395
368This uses the Solaris 10 event port mechanism. As with everything on Solaris, 396This uses the Solaris 10 event port mechanism. As with everything on Solaris,
369it's really slow, but it still scales very well (O(active_fds)). 397it's really slow, but it still scales very well (O(active_fds)).
370 398
371Please note that solaris event ports can deliver a lot of spurious 399Please note that solaris event ports can deliver a lot of spurious
372notifications, so you need to use non-blocking I/O or other means to avoid 400notifications, so you need to use non-blocking I/O or other means to avoid
373blocking when no data (or space) is available. 401blocking when no data (or space) is available.
374 402
403While this backend scales well, it requires one system call per active
404file descriptor per loop iteration. For small and medium numbers of file
405descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406might perform better.
407
375=item C<EVBACKEND_ALL> 408=item C<EVBACKEND_ALL>
376 409
377Try all backends (even potentially broken ones that wouldn't be tried 410Try all backends (even potentially broken ones that wouldn't be tried
378with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as 411with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
379C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 412C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413
414It is definitely not recommended to use this flag.
380 415
381=back 416=back
382 417
383If one or more of these are ored into the flags value, then only these 418If one or more of these are ored into the flags value, then only these
384backends will be tried (in the reverse order as given here). If none are 419backends will be tried (in the reverse order as given here). If none are
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516usually a better approach for this kind of thing. 551usually a better approach for this kind of thing.
517 552
518Here are the gory details of what C<ev_loop> does: 553Here are the gory details of what C<ev_loop> does:
519 554
520 - Before the first iteration, call any pending watchers. 555 - Before the first iteration, call any pending watchers.
521 * If there are no active watchers (reference count is zero), return. 556 * If EVFLAG_FORKCHECK was used, check for a fork.
522 - Queue all prepare watchers and then call all outstanding watchers. 557 - If a fork was detected, queue and call all fork watchers.
558 - Queue and call all prepare watchers.
523 - If we have been forked, recreate the kernel state. 559 - If we have been forked, recreate the kernel state.
524 - Update the kernel state with all outstanding changes. 560 - Update the kernel state with all outstanding changes.
525 - Update the "event loop time". 561 - Update the "event loop time".
526 - Calculate for how long to block. 562 - Calculate for how long to sleep or block, if at all
563 (active idle watchers, EVLOOP_NONBLOCK or not having
564 any active watchers at all will result in not sleeping).
565 - Sleep if the I/O and timer collect interval say so.
527 - Block the process, waiting for any events. 566 - Block the process, waiting for any events.
528 - Queue all outstanding I/O (fd) events. 567 - Queue all outstanding I/O (fd) events.
529 - Update the "event loop time" and do time jump handling. 568 - Update the "event loop time" and do time jump handling.
530 - Queue all outstanding timers. 569 - Queue all outstanding timers.
531 - Queue all outstanding periodics. 570 - Queue all outstanding periodics.
532 - If no events are pending now, queue all idle watchers. 571 - If no events are pending now, queue all idle watchers.
533 - Queue all check watchers. 572 - Queue all check watchers.
534 - Call all queued watchers in reverse order (i.e. check watchers first). 573 - Call all queued watchers in reverse order (i.e. check watchers first).
535 Signals and child watchers are implemented as I/O watchers, and will 574 Signals and child watchers are implemented as I/O watchers, and will
536 be handled here by queueing them when their watcher gets executed. 575 be handled here by queueing them when their watcher gets executed.
537 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 576 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
538 were used, return, otherwise continue with step *. 577 were used, or there are no active watchers, return, otherwise
578 continue with step *.
539 579
540Example: Queue some jobs and then loop until no events are outsanding 580Example: Queue some jobs and then loop until no events are outstanding
541anymore. 581anymore.
542 582
543 ... queue jobs here, make sure they register event watchers as long 583 ... queue jobs here, make sure they register event watchers as long
544 ... as they still have work to do (even an idle watcher will do..) 584 ... as they still have work to do (even an idle watcher will do..)
545 ev_loop (my_loop, 0); 585 ev_loop (my_loop, 0);
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948In general you can register as many read and/or write event watchers per 988In general you can register as many read and/or write event watchers per
949fd as you want (as long as you don't confuse yourself). Setting all file 989fd as you want (as long as you don't confuse yourself). Setting all file
950descriptors to non-blocking mode is also usually a good idea (but not 990descriptors to non-blocking mode is also usually a good idea (but not
951required if you know what you are doing). 991required if you know what you are doing).
952 992
953You have to be careful with dup'ed file descriptors, though. Some backends
954(the linux epoll backend is a notable example) cannot handle dup'ed file
955descriptors correctly if you register interest in two or more fds pointing
956to the same underlying file/socket/etc. description (that is, they share
957the same underlying "file open").
958
959If you must do this, then force the use of a known-to-be-good backend 993If you must do this, then force the use of a known-to-be-good backend
960(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 994(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
961C<EVBACKEND_POLL>). 995C<EVBACKEND_POLL>).
962 996
963Another thing you have to watch out for is that it is quite easy to 997Another thing you have to watch out for is that it is quite easy to
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997optimisations to libev. 1031optimisations to libev.
998 1032
999=head3 The special problem of dup'ed file descriptors 1033=head3 The special problem of dup'ed file descriptors
1000 1034
1001Some backends (e.g. epoll), cannot register events for file descriptors, 1035Some backends (e.g. epoll), cannot register events for file descriptors,
1002but only events for the underlying file descriptions. That menas when you 1036but only events for the underlying file descriptions. That means when you
1003have C<dup ()>'ed file descriptors and register events for them, only one 1037have C<dup ()>'ed file descriptors or weirder constellations, and register
1004file descriptor might actually receive events. 1038events for them, only one file descriptor might actually receive events.
1005 1039
1006There is no workaorund possible except not registering events 1040There is no workaround possible except not registering events
1007for potentially C<dup ()>'ed file descriptors or to resort to 1041for potentially C<dup ()>'ed file descriptors, or to resort to
1008C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. 1042C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1009 1043
1010=head3 The special problem of fork 1044=head3 The special problem of fork
1011 1045
1012Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit 1046Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
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1038=item int events [read-only] 1072=item int events [read-only]
1039 1073
1040The events being watched. 1074The events being watched.
1041 1075
1042=back 1076=back
1077
1078=head3 Examples
1043 1079
1044Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1080Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
1045readable, but only once. Since it is likely line-buffered, you could 1081readable, but only once. Since it is likely line-buffered, you could
1046attempt to read a whole line in the callback. 1082attempt to read a whole line in the callback.
1047 1083
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1145or C<ev_timer_again> is called and determines the next timeout (if any), 1181or C<ev_timer_again> is called and determines the next timeout (if any),
1146which is also when any modifications are taken into account. 1182which is also when any modifications are taken into account.
1147 1183
1148=back 1184=back
1149 1185
1186=head3 Examples
1187
1150Example: Create a timer that fires after 60 seconds. 1188Example: Create a timer that fires after 60 seconds.
1151 1189
1152 static void 1190 static void
1153 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1191 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1154 { 1192 {
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1311When active, contains the absolute time that the watcher is supposed to 1349When active, contains the absolute time that the watcher is supposed to
1312trigger next. 1350trigger next.
1313 1351
1314=back 1352=back
1315 1353
1354=head3 Examples
1355
1316Example: Call a callback every hour, or, more precisely, whenever the 1356Example: Call a callback every hour, or, more precisely, whenever the
1317system clock is divisible by 3600. The callback invocation times have 1357system clock is divisible by 3600. The callback invocation times have
1318potentially a lot of jittering, but good long-term stability. 1358potentially a lot of jittering, but good long-term stability.
1319 1359
1320 static void 1360 static void
… …
1411 1451
1412The process exit/trace status caused by C<rpid> (see your systems 1452The process exit/trace status caused by C<rpid> (see your systems
1413C<waitpid> and C<sys/wait.h> documentation for details). 1453C<waitpid> and C<sys/wait.h> documentation for details).
1414 1454
1415=back 1455=back
1456
1457=head3 Examples
1416 1458
1417Example: Try to exit cleanly on SIGINT and SIGTERM. 1459Example: Try to exit cleanly on SIGINT and SIGTERM.
1418 1460
1419 static void 1461 static void
1420 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1462 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
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1461semantics of C<ev_stat> watchers, which means that libev sometimes needs 1503semantics of C<ev_stat> watchers, which means that libev sometimes needs
1462to fall back to regular polling again even with inotify, but changes are 1504to fall back to regular polling again even with inotify, but changes are
1463usually detected immediately, and if the file exists there will be no 1505usually detected immediately, and if the file exists there will be no
1464polling. 1506polling.
1465 1507
1508=head3 Inotify
1509
1510When C<inotify (7)> support has been compiled into libev (generally only
1511available on Linux) and present at runtime, it will be used to speed up
1512change detection where possible. The inotify descriptor will be created lazily
1513when the first C<ev_stat> watcher is being started.
1514
1515Inotify presense does not change the semantics of C<ev_stat> watchers
1516except that changes might be detected earlier, and in some cases, to avoid
1517making regular C<stat> calls. Even in the presense of inotify support
1518there are many cases where libev has to resort to regular C<stat> polling.
1519
1520(There is no support for kqueue, as apparently it cannot be used to
1521implement this functionality, due to the requirement of having a file
1522descriptor open on the object at all times).
1523
1524=head3 The special problem of stat time resolution
1525
1526The C<stat ()> syscall only supports full-second resolution portably, and
1527even on systems where the resolution is higher, many filesystems still
1528only support whole seconds.
1529
1530That means that, if the time is the only thing that changes, you might
1531miss updates: on the first update, C<ev_stat> detects a change and calls
1532your callback, which does something. When there is another update within
1533the same second, C<ev_stat> will be unable to detect it.
1534
1535The solution to this is to delay acting on a change for a second (or till
1536the next second boundary), using a roughly one-second delay C<ev_timer>
1537(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1538is added to work around small timing inconsistencies of some operating
1539systems.
1540
1466=head3 Watcher-Specific Functions and Data Members 1541=head3 Watcher-Specific Functions and Data Members
1467 1542
1468=over 4 1543=over 4
1469 1544
1470=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1545=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
… …
1507=item const char *path [read-only] 1582=item const char *path [read-only]
1508 1583
1509The filesystem path that is being watched. 1584The filesystem path that is being watched.
1510 1585
1511=back 1586=back
1587
1588=head3 Examples
1512 1589
1513Example: Watch C</etc/passwd> for attribute changes. 1590Example: Watch C</etc/passwd> for attribute changes.
1514 1591
1515 static void 1592 static void
1516 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1593 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1529 } 1606 }
1530 1607
1531 ... 1608 ...
1532 ev_stat passwd; 1609 ev_stat passwd;
1533 1610
1534 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1611 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1535 ev_stat_start (loop, &passwd); 1612 ev_stat_start (loop, &passwd);
1613
1614Example: Like above, but additionally use a one-second delay so we do not
1615miss updates (however, frequent updates will delay processing, too, so
1616one might do the work both on C<ev_stat> callback invocation I<and> on
1617C<ev_timer> callback invocation).
1618
1619 static ev_stat passwd;
1620 static ev_timer timer;
1621
1622 static void
1623 timer_cb (EV_P_ ev_timer *w, int revents)
1624 {
1625 ev_timer_stop (EV_A_ w);
1626
1627 /* now it's one second after the most recent passwd change */
1628 }
1629
1630 static void
1631 stat_cb (EV_P_ ev_stat *w, int revents)
1632 {
1633 /* reset the one-second timer */
1634 ev_timer_again (EV_A_ &timer);
1635 }
1636
1637 ...
1638 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1639 ev_stat_start (loop, &passwd);
1640 ev_timer_init (&timer, timer_cb, 0., 1.01);
1536 1641
1537 1642
1538=head2 C<ev_idle> - when you've got nothing better to do... 1643=head2 C<ev_idle> - when you've got nothing better to do...
1539 1644
1540Idle watchers trigger events when no other events of the same or higher 1645Idle watchers trigger events when no other events of the same or higher
… …
1565Initialises and configures the idle watcher - it has no parameters of any 1670Initialises and configures the idle watcher - it has no parameters of any
1566kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1671kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1567believe me. 1672believe me.
1568 1673
1569=back 1674=back
1675
1676=head3 Examples
1570 1677
1571Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1678Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1572callback, free it. Also, use no error checking, as usual. 1679callback, free it. Also, use no error checking, as usual.
1573 1680
1574 static void 1681 static void
… …
1646parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1753parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1647macros, but using them is utterly, utterly and completely pointless. 1754macros, but using them is utterly, utterly and completely pointless.
1648 1755
1649=back 1756=back
1650 1757
1758=head3 Examples
1759
1651There are a number of principal ways to embed other event loops or modules 1760There are a number of principal ways to embed other event loops or modules
1652into libev. Here are some ideas on how to include libadns into libev 1761into libev. Here are some ideas on how to include libadns into libev
1653(there is a Perl module named C<EV::ADNS> that does this, which you could 1762(there is a Perl module named C<EV::ADNS> that does this, which you could
1654use for an actually working example. Another Perl module named C<EV::Glib> 1763use for an actually working example. Another Perl module named C<EV::Glib>
1655embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV 1764embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV
… …
1823portable one. 1932portable one.
1824 1933
1825So when you want to use this feature you will always have to be prepared 1934So when you want to use this feature you will always have to be prepared
1826that you cannot get an embeddable loop. The recommended way to get around 1935that you cannot get an embeddable loop. The recommended way to get around
1827this is to have a separate variables for your embeddable loop, try to 1936this is to have a separate variables for your embeddable loop, try to
1828create it, and if that fails, use the normal loop for everything: 1937create it, and if that fails, use the normal loop for everything.
1938
1939=head3 Watcher-Specific Functions and Data Members
1940
1941=over 4
1942
1943=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1944
1945=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1946
1947Configures the watcher to embed the given loop, which must be
1948embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1949invoked automatically, otherwise it is the responsibility of the callback
1950to invoke it (it will continue to be called until the sweep has been done,
1951if you do not want thta, you need to temporarily stop the embed watcher).
1952
1953=item ev_embed_sweep (loop, ev_embed *)
1954
1955Make a single, non-blocking sweep over the embedded loop. This works
1956similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1957apropriate way for embedded loops.
1958
1959=item struct ev_loop *other [read-only]
1960
1961The embedded event loop.
1962
1963=back
1964
1965=head3 Examples
1966
1967Example: Try to get an embeddable event loop and embed it into the default
1968event loop. If that is not possible, use the default loop. The default
1969loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1970C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1971used).
1829 1972
1830 struct ev_loop *loop_hi = ev_default_init (0); 1973 struct ev_loop *loop_hi = ev_default_init (0);
1831 struct ev_loop *loop_lo = 0; 1974 struct ev_loop *loop_lo = 0;
1832 struct ev_embed embed; 1975 struct ev_embed embed;
1833 1976
… …
1844 ev_embed_start (loop_hi, &embed); 1987 ev_embed_start (loop_hi, &embed);
1845 } 1988 }
1846 else 1989 else
1847 loop_lo = loop_hi; 1990 loop_lo = loop_hi;
1848 1991
1849=head3 Watcher-Specific Functions and Data Members 1992Example: Check if kqueue is available but not recommended and create
1993a kqueue backend for use with sockets (which usually work with any
1994kqueue implementation). Store the kqueue/socket-only event loop in
1995C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1850 1996
1851=over 4 1997 struct ev_loop *loop = ev_default_init (0);
1998 struct ev_loop *loop_socket = 0;
1999 struct ev_embed embed;
2000
2001 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2002 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2003 {
2004 ev_embed_init (&embed, 0, loop_socket);
2005 ev_embed_start (loop, &embed);
2006 }
1852 2007
1853=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2008 if (!loop_socket)
2009 loop_socket = loop;
1854 2010
1855=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2011 // now use loop_socket for all sockets, and loop for everything else
1856
1857Configures the watcher to embed the given loop, which must be
1858embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1859invoked automatically, otherwise it is the responsibility of the callback
1860to invoke it (it will continue to be called until the sweep has been done,
1861if you do not want thta, you need to temporarily stop the embed watcher).
1862
1863=item ev_embed_sweep (loop, ev_embed *)
1864
1865Make a single, non-blocking sweep over the embedded loop. This works
1866similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1867apropriate way for embedded loops.
1868
1869=item struct ev_loop *other [read-only]
1870
1871The embedded event loop.
1872
1873=back
1874 2012
1875 2013
1876=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2014=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1877 2015
1878Fork watchers are called when a C<fork ()> was detected (usually because 2016Fork watchers are called when a C<fork ()> was detected (usually because
… …
2357wants osf handles on win32 (this is the case when the select to 2495wants osf handles on win32 (this is the case when the select to
2358be used is the winsock select). This means that it will call 2496be used is the winsock select). This means that it will call
2359C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2497C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2360it is assumed that all these functions actually work on fds, even 2498it is assumed that all these functions actually work on fds, even
2361on win32. Should not be defined on non-win32 platforms. 2499on win32. Should not be defined on non-win32 platforms.
2500
2501=item EV_FD_TO_WIN32_HANDLE
2502
2503If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2504file descriptors to socket handles. When not defining this symbol (the
2505default), then libev will call C<_get_osfhandle>, which is usually
2506correct. In some cases, programs use their own file descriptor management,
2507in which case they can provide this function to map fds to socket handles.
2362 2508
2363=item EV_USE_POLL 2509=item EV_USE_POLL
2364 2510
2365If defined to be C<1>, libev will compile in support for the C<poll>(2) 2511If defined to be C<1>, libev will compile in support for the C<poll>(2)
2366backend. Otherwise it will be enabled on non-win32 platforms. It 2512backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2403be detected at runtime. 2549be detected at runtime.
2404 2550
2405=item EV_H 2551=item EV_H
2406 2552
2407The name of the F<ev.h> header file used to include it. The default if 2553The name of the F<ev.h> header file used to include it. The default if
2408undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2554undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2409can be used to virtually rename the F<ev.h> header file in case of conflicts. 2555virtually rename the F<ev.h> header file in case of conflicts.
2410 2556
2411=item EV_CONFIG_H 2557=item EV_CONFIG_H
2412 2558
2413If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2559If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2414F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2560F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2415C<EV_H>, above. 2561C<EV_H>, above.
2416 2562
2417=item EV_EVENT_H 2563=item EV_EVENT_H
2418 2564
2419Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2565Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2420of how the F<event.h> header can be found. 2566of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2421 2567
2422=item EV_PROTOTYPES 2568=item EV_PROTOTYPES
2423 2569
2424If defined to be C<0>, then F<ev.h> will not define any function 2570If defined to be C<0>, then F<ev.h> will not define any function
2425prototypes, but still define all the structs and other symbols. This is 2571prototypes, but still define all the structs and other symbols. This is
… …
2491than enough. If you need to manage thousands of children you might want to 2637than enough. If you need to manage thousands of children you might want to
2492increase this value (I<must> be a power of two). 2638increase this value (I<must> be a power of two).
2493 2639
2494=item EV_INOTIFY_HASHSIZE 2640=item EV_INOTIFY_HASHSIZE
2495 2641
2496C<ev_staz> watchers use a small hash table to distribute workload by 2642C<ev_stat> watchers use a small hash table to distribute workload by
2497inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 2643inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2498usually more than enough. If you need to manage thousands of C<ev_stat> 2644usually more than enough. If you need to manage thousands of C<ev_stat>
2499watchers you might want to increase this value (I<must> be a power of 2645watchers you might want to increase this value (I<must> be a power of
2500two). 2646two).
2501 2647
… …
2597 2743
2598=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2744=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2599 2745
2600This means that, when you have a watcher that triggers in one hour and 2746This means that, when you have a watcher that triggers in one hour and
2601there are 100 watchers that would trigger before that then inserting will 2747there are 100 watchers that would trigger before that then inserting will
2602have to skip those 100 watchers. 2748have to skip roughly seven (C<ld 100>) of these watchers.
2603 2749
2604=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2750=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2605 2751
2606That means that for changing a timer costs less than removing/adding them 2752That means that changing a timer costs less than removing/adding them
2607as only the relative motion in the event queue has to be paid for. 2753as only the relative motion in the event queue has to be paid for.
2608 2754
2609=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2755=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2610 2756
2611These just add the watcher into an array or at the head of a list. 2757These just add the watcher into an array or at the head of a list.
2758
2612=item Stopping check/prepare/idle watchers: O(1) 2759=item Stopping check/prepare/idle watchers: O(1)
2613 2760
2614=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2761=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2615 2762
2616These watchers are stored in lists then need to be walked to find the 2763These watchers are stored in lists then need to be walked to find the
2617correct watcher to remove. The lists are usually short (you don't usually 2764correct watcher to remove. The lists are usually short (you don't usually
2618have many watchers waiting for the same fd or signal). 2765have many watchers waiting for the same fd or signal).
2619 2766
2620=item Finding the next timer per loop iteration: O(1) 2767=item Finding the next timer in each loop iteration: O(1)
2768
2769By virtue of using a binary heap, the next timer is always found at the
2770beginning of the storage array.
2621 2771
2622=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2772=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2623 2773
2624A change means an I/O watcher gets started or stopped, which requires 2774A change means an I/O watcher gets started or stopped, which requires
2625libev to recalculate its status (and possibly tell the kernel). 2775libev to recalculate its status (and possibly tell the kernel, depending
2776on backend and wether C<ev_io_set> was used).
2626 2777
2627=item Activating one watcher: O(1) 2778=item Activating one watcher (putting it into the pending state): O(1)
2628 2779
2629=item Priority handling: O(number_of_priorities) 2780=item Priority handling: O(number_of_priorities)
2630 2781
2631Priorities are implemented by allocating some space for each 2782Priorities are implemented by allocating some space for each
2632priority. When doing priority-based operations, libev usually has to 2783priority. When doing priority-based operations, libev usually has to
2633linearly search all the priorities. 2784linearly search all the priorities, but starting/stopping and activating
2785watchers becomes O(1) w.r.t. prioritiy handling.
2634 2786
2635=back 2787=back
2636 2788
2637 2789
2790=head1 Win32 platform limitations and workarounds
2791
2792Win32 doesn't support any of the standards (e.g. POSIX) that libev
2793requires, and its I/O model is fundamentally incompatible with the POSIX
2794model. Libev still offers limited functionality on this platform in
2795the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2796descriptors. This only applies when using Win32 natively, not when using
2797e.g. cygwin.
2798
2799There is no supported compilation method available on windows except
2800embedding it into other applications.
2801
2802Due to the many, low, and arbitrary limits on the win32 platform and the
2803abysmal performance of winsockets, using a large number of sockets is not
2804recommended (and not reasonable). If your program needs to use more than
2805a hundred or so sockets, then likely it needs to use a totally different
2806implementation for windows, as libev offers the POSIX model, which cannot
2807be implemented efficiently on windows (microsoft monopoly games).
2808
2809=over 4
2810
2811=item The winsocket select function
2812
2813The winsocket C<select> function doesn't follow POSIX in that it requires
2814socket I<handles> and not socket I<file descriptors>. This makes select
2815very inefficient, and also requires a mapping from file descriptors
2816to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2817C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2818symbols for more info.
2819
2820The configuration for a "naked" win32 using the microsoft runtime
2821libraries and raw winsocket select is:
2822
2823 #define EV_USE_SELECT 1
2824 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2825
2826Note that winsockets handling of fd sets is O(n), so you can easily get a
2827complexity in the O(n²) range when using win32.
2828
2829=item Limited number of file descriptors
2830
2831Windows has numerous arbitrary (and low) limits on things. Early versions
2832of winsocket's select only supported waiting for a max. of C<64> handles
2833(probably owning to the fact that all windows kernels can only wait for
2834C<64> things at the same time internally; microsoft recommends spawning a
2835chain of threads and wait for 63 handles and the previous thread in each).
2836
2837Newer versions support more handles, but you need to define C<FD_SETSIZE>
2838to some high number (e.g. C<2048>) before compiling the winsocket select
2839call (which might be in libev or elsewhere, for example, perl does its own
2840select emulation on windows).
2841
2842Another limit is the number of file descriptors in the microsoft runtime
2843libraries, which by default is C<64> (there must be a hidden I<64> fetish
2844or something like this inside microsoft). You can increase this by calling
2845C<_setmaxstdio>, which can increase this limit to C<2048> (another
2846arbitrary limit), but is broken in many versions of the microsoft runtime
2847libraries.
2848
2849This might get you to about C<512> or C<2048> sockets (depending on
2850windows version and/or the phase of the moon). To get more, you need to
2851wrap all I/O functions and provide your own fd management, but the cost of
2852calling select (O(n²)) will likely make this unworkable.
2853
2854=back
2855
2856
2638=head1 AUTHOR 2857=head1 AUTHOR
2639 2858
2640Marc Lehmann <libev@schmorp.de>. 2859Marc Lehmann <libev@schmorp.de>.
2641 2860

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