ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev.pod
(Generate patch)

Comparing libev/ev.pod (file contents):
Revision 1.89 by root, Wed Dec 19 01:59:29 2007 UTC vs.
Revision 1.130 by root, Wed Feb 6 18:34:24 2008 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;
… …
53The newest version of this document is also available as a html-formatted 53The newest version of this document is also available as a html-formatted
54web page you might find easier to navigate when reading it for the first 54web page you might find easier to navigate when reading it for the first
55time: L<http://cvs.schmorp.de/libev/ev.html>. 55time: L<http://cvs.schmorp.de/libev/ev.html>.
56 56
57Libev is an event loop: you register interest in certain events (such as a 57Libev is an event loop: you register interest in certain events (such as a
58file descriptor being readable or a timeout occuring), and it will manage 58file descriptor being readable or a timeout occurring), and it will manage
59these event sources and provide your program with events. 59these event sources and provide your program with events.
60 60
61To do this, it must take more or less complete control over your process 61To do this, it must take more or less complete control over your process
62(or thread) by executing the I<event loop> handler, and will then 62(or thread) by executing the I<event loop> handler, and will then
63communicate events via a callback mechanism. 63communicate events via a callback mechanism.
… …
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
… …
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
… …
115 115
116Returns the current time as libev would use it. Please note that the 116Returns the current time as libev would use it. Please note that the
117C<ev_now> function is usually faster and also often returns the timestamp 117C<ev_now> function is usually faster and also often returns the timestamp
118you actually want to know. 118you actually want to know.
119 119
120=item ev_sleep (ev_tstamp interval)
121
122Sleep for the given interval: The current thread will be blocked until
123either it is interrupted or the given time interval has passed. Basically
124this is a subsecond-resolution C<sleep ()>.
125
120=item int ev_version_major () 126=item int ev_version_major ()
121 127
122=item int ev_version_minor () 128=item int ev_version_minor ()
123 129
124You can find out the major and minor ABI version numbers of the library 130You can find out the major and minor ABI version numbers of the library
… …
254flags. If that is troubling you, check C<ev_backend ()> afterwards). 260flags. If that is troubling you, check C<ev_backend ()> afterwards).
255 261
256If 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
257function. 263function.
258 264
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
259The flags argument can be used to specify special behaviour or specific 272The flags argument can be used to specify special behaviour or specific
260backends 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>).
261 274
262The following flags are supported: 275The following flags are supported:
263 276
… …
300=item C<EVBACKEND_SELECT> (value 1, portable select backend) 313=item C<EVBACKEND_SELECT> (value 1, portable select backend)
301 314
302This is your standard select(2) backend. Not I<completely> standard, as 315This is your standard select(2) backend. Not I<completely> standard, as
303libev tries to roll its own fd_set with no limits on the number of fds, 316libev tries to roll its own fd_set with no limits on the number of fds,
304but if that fails, expect a fairly low limit on the number of fds when 317but if that fails, expect a fairly low limit on the number of fds when
305using this backend. It doesn't scale too well (O(highest_fd)), but its usually 318using this backend. It doesn't scale too well (O(highest_fd)), but its
306the fastest backend for a low number of fds. 319usually the fastest backend for a low number of (low-numbered :) fds.
320
321To get good performance out of this backend you need a high amount of
322parallelity (most of the file descriptors should be busy). If you are
323writing a server, you should C<accept ()> in a loop to accept as many
324connections as possible during one iteration. You might also want to have
325a look at C<ev_set_io_collect_interval ()> to increase the amount of
326readyness notifications you get per iteration.
307 327
308=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) 328=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
309 329
310And this is your standard poll(2) backend. It's more complicated than 330And this is your standard poll(2) backend. It's more complicated
311select, but handles sparse fds better and has no artificial limit on the 331than select, but handles sparse fds better and has no artificial
312number of fds you can use (except it will slow down considerably with a 332limit on the number of fds you can use (except it will slow down
313lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 333considerably with a lot of inactive fds). It scales similarly to select,
334i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
335performance tips.
314 336
315=item C<EVBACKEND_EPOLL> (value 4, Linux) 337=item C<EVBACKEND_EPOLL> (value 4, Linux)
316 338
317For few fds, this backend is a bit little slower than poll and select, 339For few fds, this backend is a bit little slower than poll and select,
318but it scales phenomenally better. While poll and select usually scale like 340but it scales phenomenally better. While poll and select usually scale
319O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 341like O(total_fds) where n is the total number of fds (or the highest fd),
320either O(1) or O(active_fds). 342epoll scales either O(1) or O(active_fds). The epoll design has a number
343of shortcomings, such as silently dropping events in some hard-to-detect
344cases and rewiring a syscall per fd change, no fork support and bad
345support for dup.
321 346
322While stopping and starting an I/O watcher in the same iteration will 347While stopping, setting and starting an I/O watcher in the same iteration
323result in some caching, there is still a syscall per such incident 348will result in some caching, there is still a syscall per such incident
324(because the fd could point to a different file description now), so its 349(because the fd could point to a different file description now), so its
325best to avoid that. Also, dup()ed file descriptors might not work very 350best to avoid that. Also, C<dup ()>'ed file descriptors might not work
326well if you register events for both fds. 351very well if you register events for both fds.
327 352
328Please note that epoll sometimes generates spurious notifications, so you 353Please note that epoll sometimes generates spurious notifications, so you
329need to use non-blocking I/O or other means to avoid blocking when no data 354need to use non-blocking I/O or other means to avoid blocking when no data
330(or space) is available. 355(or space) is available.
331 356
357Best performance from this backend is achieved by not unregistering all
358watchers for a file descriptor until it has been closed, if possible, i.e.
359keep at least one watcher active per fd at all times.
360
361While nominally embeddeble in other event loops, this feature is broken in
362all kernel versions tested so far.
363
332=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 364=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
333 365
334Kqueue deserves special mention, as at the time of this writing, it 366Kqueue deserves special mention, as at the time of this writing, it
335was broken on all BSDs except NetBSD (usually it doesn't work with 367was broken on all BSDs except NetBSD (usually it doesn't work reliably
336anything but sockets and pipes, except on Darwin, where of course its 368with anything but sockets and pipes, except on Darwin, where of course
337completely useless). For this reason its not being "autodetected" 369it's completely useless). For this reason it's not being "autodetected"
338unless you explicitly specify it explicitly in the flags (i.e. using 370unless you explicitly specify it explicitly in the flags (i.e. using
339C<EVBACKEND_KQUEUE>). 371C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
372system like NetBSD.
373
374You still can embed kqueue into a normal poll or select backend and use it
375only for sockets (after having made sure that sockets work with kqueue on
376the target platform). See C<ev_embed> watchers for more info.
340 377
341It scales in the same way as the epoll backend, but the interface to the 378It scales in the same way as the epoll backend, but the interface to the
342kernel is more efficient (which says nothing about its actual speed, of 379kernel is more efficient (which says nothing about its actual speed, of
343course). While starting and stopping an I/O watcher does not cause an 380course). While stopping, setting and starting an I/O watcher does never
344extra syscall as with epoll, it still adds up to four event changes per 381cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
345incident, so its best to avoid that. 382two event changes per incident, support for C<fork ()> is very bad and it
383drops fds silently in similarly hard-to-detect cases.
384
385This backend usually performs well under most conditions.
386
387While nominally embeddable in other event loops, this doesn't work
388everywhere, so you might need to test for this. And since it is broken
389almost everywhere, you should only use it when you have a lot of sockets
390(for which it usually works), by embedding it into another event loop
391(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
392sockets.
346 393
347=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) 394=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
348 395
349This is not implemented yet (and might never be). 396This is not implemented yet (and might never be, unless you send me an
397implementation). According to reports, C</dev/poll> only supports sockets
398and is not embeddable, which would limit the usefulness of this backend
399immensely.
350 400
351=item C<EVBACKEND_PORT> (value 32, Solaris 10) 401=item C<EVBACKEND_PORT> (value 32, Solaris 10)
352 402
353This uses the Solaris 10 port mechanism. As with everything on Solaris, 403This uses the Solaris 10 event port mechanism. As with everything on Solaris,
354it's really slow, but it still scales very well (O(active_fds)). 404it's really slow, but it still scales very well (O(active_fds)).
355 405
356Please note that solaris ports can result in a lot of spurious 406Please note that solaris event ports can deliver a lot of spurious
357notifications, so you need to use non-blocking I/O or other means to avoid 407notifications, so you need to use non-blocking I/O or other means to avoid
358blocking when no data (or space) is available. 408blocking when no data (or space) is available.
409
410While this backend scales well, it requires one system call per active
411file descriptor per loop iteration. For small and medium numbers of file
412descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
413might perform better.
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.
359 418
360=item C<EVBACKEND_ALL> 419=item C<EVBACKEND_ALL>
361 420
362Try all backends (even potentially broken ones that wouldn't be tried 421Try all backends (even potentially broken ones that wouldn't be tried
363with 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
364C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 423C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
365 424
425It is definitely not recommended to use this flag.
426
366=back 427=back
367 428
368If 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
369backends 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
370specified, most compiled-in backend will be tried, usually in reverse 431specified, all backends in C<ev_recommended_backends ()> will be tried.
371order of their flag values :)
372 432
373The most typical usage is like this: 433The most typical usage is like this:
374 434
375 if (!ev_default_loop (0)) 435 if (!ev_default_loop (0))
376 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 436 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
… …
423Like 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
424earlier call to C<ev_loop_new>. 484earlier call to C<ev_loop_new>.
425 485
426=item ev_default_fork () 486=item ev_default_fork ()
427 487
488This function sets a flag that causes subsequent C<ev_loop> iterations
428This function reinitialises the kernel state for backends that have 489to reinitialise the kernel state for backends that have one. Despite the
429one. 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
430after 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
431again 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.
432 494
433You 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
434only 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
435fork+exec, you don't have to call it. 497you just fork+exec, you don't have to call it at all.
436 498
437The 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
438it 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
439quite nicely into a call to C<pthread_atfork>: 501quite nicely into a call to C<pthread_atfork>:
440 502
441 pthread_atfork (0, 0, ev_default_fork); 503 pthread_atfork (0, 0, ev_default_fork);
442
443At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
444without calling this function, so if you force one of those backends you
445do not need to care.
446 504
447=item ev_loop_fork (loop) 505=item ev_loop_fork (loop)
448 506
449Like 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
450C<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
… …
469 527
470Returns the current "event loop time", which is the time the event loop 528Returns the current "event loop time", which is the time the event loop
471received events and started processing them. This timestamp does not 529received events and started processing them. This timestamp does not
472change as long as callbacks are being processed, and this is also the base 530change as long as callbacks are being processed, and this is also the base
473time used for relative timers. You can treat it as the timestamp of the 531time used for relative timers. You can treat it as the timestamp of the
474event occuring (or more correctly, libev finding out about it). 532event occurring (or more correctly, libev finding out about it).
475 533
476=item ev_loop (loop, int flags) 534=item ev_loop (loop, int flags)
477 535
478Finally, this is it, the event handler. This function usually is called 536Finally, this is it, the event handler. This function usually is called
479after you initialised all your watchers and you want to start handling 537after you initialised all your watchers and you want to start handling
… …
501usually a better approach for this kind of thing. 559usually a better approach for this kind of thing.
502 560
503Here are the gory details of what C<ev_loop> does: 561Here are the gory details of what C<ev_loop> does:
504 562
505 - Before the first iteration, call any pending watchers. 563 - Before the first iteration, call any pending watchers.
506 * If there are no active watchers (reference count is zero), return. 564 * If EVFLAG_FORKCHECK was used, check for a fork.
507 - Queue all prepare watchers and then call all outstanding watchers. 565 - If a fork was detected, queue and call all fork watchers.
566 - Queue and call all prepare watchers.
508 - If we have been forked, recreate the kernel state. 567 - If we have been forked, recreate the kernel state.
509 - Update the kernel state with all outstanding changes. 568 - Update the kernel state with all outstanding changes.
510 - Update the "event loop time". 569 - Update the "event loop time".
511 - Calculate for how long to block. 570 - Calculate for how long to sleep or block, if at all
571 (active idle watchers, EVLOOP_NONBLOCK or not having
572 any active watchers at all will result in not sleeping).
573 - Sleep if the I/O and timer collect interval say so.
512 - Block the process, waiting for any events. 574 - Block the process, waiting for any events.
513 - Queue all outstanding I/O (fd) events. 575 - Queue all outstanding I/O (fd) events.
514 - Update the "event loop time" and do time jump handling. 576 - Update the "event loop time" and do time jump handling.
515 - Queue all outstanding timers. 577 - Queue all outstanding timers.
516 - Queue all outstanding periodics. 578 - Queue all outstanding periodics.
517 - If no events are pending now, queue all idle watchers. 579 - If no events are pending now, queue all idle watchers.
518 - Queue all check watchers. 580 - Queue all check watchers.
519 - Call all queued watchers in reverse order (i.e. check watchers first). 581 - Call all queued watchers in reverse order (i.e. check watchers first).
520 Signals and child watchers are implemented as I/O watchers, and will 582 Signals and child watchers are implemented as I/O watchers, and will
521 be handled here by queueing them when their watcher gets executed. 583 be handled here by queueing them when their watcher gets executed.
522 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 584 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
523 were used, return, otherwise continue with step *. 585 were used, or there are no active watchers, return, otherwise
586 continue with step *.
524 587
525Example: Queue some jobs and then loop until no events are outsanding 588Example: Queue some jobs and then loop until no events are outstanding
526anymore. 589anymore.
527 590
528 ... queue jobs here, make sure they register event watchers as long 591 ... queue jobs here, make sure they register event watchers as long
529 ... as they still have work to do (even an idle watcher will do..) 592 ... as they still have work to do (even an idle watcher will do..)
530 ev_loop (my_loop, 0); 593 ev_loop (my_loop, 0);
… …
534 597
535Can be used to make a call to C<ev_loop> return early (but only after it 598Can be used to make a call to C<ev_loop> return early (but only after it
536has processed all outstanding events). The C<how> argument must be either 599has processed all outstanding events). The C<how> argument must be either
537C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 600C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
538C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 601C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
602
603This "unloop state" will be cleared when entering C<ev_loop> again.
539 604
540=item ev_ref (loop) 605=item ev_ref (loop)
541 606
542=item ev_unref (loop) 607=item ev_unref (loop)
543 608
… …
548returning, ev_unref() after starting, and ev_ref() before stopping it. For 613returning, ev_unref() after starting, and ev_ref() before stopping it. For
549example, libev itself uses this for its internal signal pipe: It is not 614example, libev itself uses this for its internal signal pipe: It is not
550visible to the libev user and should not keep C<ev_loop> from exiting if 615visible to the libev user and should not keep C<ev_loop> from exiting if
551no event watchers registered by it are active. It is also an excellent 616no event watchers registered by it are active. It is also an excellent
552way to do this for generic recurring timers or from within third-party 617way to do this for generic recurring timers or from within third-party
553libraries. Just remember to I<unref after start> and I<ref before stop>. 618libraries. Just remember to I<unref after start> and I<ref before stop>
619(but only if the watcher wasn't active before, or was active before,
620respectively).
554 621
555Example: Create a signal watcher, but keep it from keeping C<ev_loop> 622Example: Create a signal watcher, but keep it from keeping C<ev_loop>
556running when nothing else is active. 623running when nothing else is active.
557 624
558 struct ev_signal exitsig; 625 struct ev_signal exitsig;
… …
562 629
563Example: For some weird reason, unregister the above signal handler again. 630Example: For some weird reason, unregister the above signal handler again.
564 631
565 ev_ref (loop); 632 ev_ref (loop);
566 ev_signal_stop (loop, &exitsig); 633 ev_signal_stop (loop, &exitsig);
634
635=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636
637=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638
639These advanced functions influence the time that libev will spend waiting
640for events. Both are by default C<0>, meaning that libev will try to
641invoke timer/periodic callbacks and I/O callbacks with minimum latency.
642
643Setting these to a higher value (the C<interval> I<must> be >= C<0>)
644allows libev to delay invocation of I/O and timer/periodic callbacks to
645increase efficiency of loop iterations.
646
647The background is that sometimes your program runs just fast enough to
648handle one (or very few) event(s) per loop iteration. While this makes
649the program responsive, it also wastes a lot of CPU time to poll for new
650events, especially with backends like C<select ()> which have a high
651overhead for the actual polling but can deliver many events at once.
652
653By setting a higher I<io collect interval> you allow libev to spend more
654time collecting I/O events, so you can handle more events per iteration,
655at the cost of increasing latency. Timeouts (both C<ev_periodic> and
656C<ev_timer>) will be not affected. Setting this to a non-null value will
657introduce an additional C<ev_sleep ()> call into most loop iterations.
658
659Likewise, by setting a higher I<timeout collect interval> you allow libev
660to spend more time collecting timeouts, at the expense of increased
661latency (the watcher callback will be called later). C<ev_io> watchers
662will not be affected. Setting this to a non-null value will not introduce
663any overhead in libev.
664
665Many (busy) programs can usually benefit by setting the io collect
666interval to a value near C<0.1> or so, which is often enough for
667interactive servers (of course not for games), likewise for timeouts. It
668usually doesn't make much sense to set it to a lower value than C<0.01>,
669as this approsaches the timing granularity of most systems.
567 670
568=back 671=back
569 672
570 673
571=head1 ANATOMY OF A WATCHER 674=head1 ANATOMY OF A WATCHER
… …
670 773
671=item C<EV_FORK> 774=item C<EV_FORK>
672 775
673The event loop has been resumed in the child process after fork (see 776The event loop has been resumed in the child process after fork (see
674C<ev_fork>). 777C<ev_fork>).
778
779=item C<EV_ASYNC>
780
781The given async watcher has been asynchronously notified (see C<ev_async>).
675 782
676=item C<EV_ERROR> 783=item C<EV_ERROR>
677 784
678An unspecified error has occured, the watcher has been stopped. This might 785An unspecified error has occured, the watcher has been stopped. This might
679happen because the watcher could not be properly started because libev 786happen because the watcher could not be properly started because libev
… …
897In general you can register as many read and/or write event watchers per 1004In general you can register as many read and/or write event watchers per
898fd as you want (as long as you don't confuse yourself). Setting all file 1005fd as you want (as long as you don't confuse yourself). Setting all file
899descriptors to non-blocking mode is also usually a good idea (but not 1006descriptors to non-blocking mode is also usually a good idea (but not
900required if you know what you are doing). 1007required if you know what you are doing).
901 1008
902You have to be careful with dup'ed file descriptors, though. Some backends
903(the linux epoll backend is a notable example) cannot handle dup'ed file
904descriptors correctly if you register interest in two or more fds pointing
905to the same underlying file/socket/etc. description (that is, they share
906the same underlying "file open").
907
908If you must do this, then force the use of a known-to-be-good backend 1009If you must do this, then force the use of a known-to-be-good backend
909(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1010(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
910C<EVBACKEND_POLL>). 1011C<EVBACKEND_POLL>).
911 1012
912Another thing you have to watch out for is that it is quite easy to 1013Another thing you have to watch out for is that it is quite easy to
… …
924such as poll (fortunately in our Xlib example, Xlib already does this on 1025such as poll (fortunately in our Xlib example, Xlib already does this on
925its own, so its quite safe to use). 1026its own, so its quite safe to use).
926 1027
927=head3 The special problem of disappearing file descriptors 1028=head3 The special problem of disappearing file descriptors
928 1029
929Some backends (e.g kqueue, epoll) need to be told about closing a file 1030Some backends (e.g. kqueue, epoll) need to be told about closing a file
930descriptor (either by calling C<close> explicitly or by any other means, 1031descriptor (either by calling C<close> explicitly or by any other means,
931such as C<dup>). The reason is that you register interest in some file 1032such as C<dup>). The reason is that you register interest in some file
932descriptor, but when it goes away, the operating system will silently drop 1033descriptor, but when it goes away, the operating system will silently drop
933this interest. If another file descriptor with the same number then is 1034this interest. If another file descriptor with the same number then is
934registered with libev, there is no efficient way to see that this is, in 1035registered with libev, there is no efficient way to see that this is, in
… …
943 1044
944This is how one would do it normally anyway, the important point is that 1045This is how one would do it normally anyway, the important point is that
945the libev application should not optimise around libev but should leave 1046the libev application should not optimise around libev but should leave
946optimisations to libev. 1047optimisations to libev.
947 1048
1049=head3 The special problem of dup'ed file descriptors
1050
1051Some backends (e.g. epoll), cannot register events for file descriptors,
1052but only events for the underlying file descriptions. That means when you
1053have C<dup ()>'ed file descriptors or weirder constellations, and register
1054events for them, only one file descriptor might actually receive events.
1055
1056There is no workaround possible except not registering events
1057for potentially C<dup ()>'ed file descriptors, or to resort to
1058C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1059
1060=head3 The special problem of fork
1061
1062Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1063useless behaviour. Libev fully supports fork, but needs to be told about
1064it in the child.
1065
1066To support fork in your programs, you either have to call
1067C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1068enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1069C<EVBACKEND_POLL>.
1070
948 1071
949=head3 Watcher-Specific Functions 1072=head3 Watcher-Specific Functions
950 1073
951=over 4 1074=over 4
952 1075
… …
965=item int events [read-only] 1088=item int events [read-only]
966 1089
967The events being watched. 1090The events being watched.
968 1091
969=back 1092=back
1093
1094=head3 Examples
970 1095
971Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1096Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
972readable, but only once. Since it is likely line-buffered, you could 1097readable, but only once. Since it is likely line-buffered, you could
973attempt to read a whole line in the callback. 1098attempt to read a whole line in the callback.
974 1099
… …
1072or C<ev_timer_again> is called and determines the next timeout (if any), 1197or C<ev_timer_again> is called and determines the next timeout (if any),
1073which is also when any modifications are taken into account. 1198which is also when any modifications are taken into account.
1074 1199
1075=back 1200=back
1076 1201
1202=head3 Examples
1203
1077Example: Create a timer that fires after 60 seconds. 1204Example: Create a timer that fires after 60 seconds.
1078 1205
1079 static void 1206 static void
1080 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1207 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1081 { 1208 {
… …
1238When active, contains the absolute time that the watcher is supposed to 1365When active, contains the absolute time that the watcher is supposed to
1239trigger next. 1366trigger next.
1240 1367
1241=back 1368=back
1242 1369
1370=head3 Examples
1371
1243Example: Call a callback every hour, or, more precisely, whenever the 1372Example: Call a callback every hour, or, more precisely, whenever the
1244system clock is divisible by 3600. The callback invocation times have 1373system clock is divisible by 3600. The callback invocation times have
1245potentially a lot of jittering, but good long-term stability. 1374potentially a lot of jittering, but good long-term stability.
1246 1375
1247 static void 1376 static void
… …
1313 1442
1314=head3 Watcher-Specific Functions and Data Members 1443=head3 Watcher-Specific Functions and Data Members
1315 1444
1316=over 4 1445=over 4
1317 1446
1318=item ev_child_init (ev_child *, callback, int pid) 1447=item ev_child_init (ev_child *, callback, int pid, int trace)
1319 1448
1320=item ev_child_set (ev_child *, int pid) 1449=item ev_child_set (ev_child *, int pid, int trace)
1321 1450
1322Configures the watcher to wait for status changes of process C<pid> (or 1451Configures the watcher to wait for status changes of process C<pid> (or
1323I<any> process if C<pid> is specified as C<0>). The callback can look 1452I<any> process if C<pid> is specified as C<0>). The callback can look
1324at the C<rstatus> member of the C<ev_child> watcher structure to see 1453at the C<rstatus> member of the C<ev_child> watcher structure to see
1325the status word (use the macros from C<sys/wait.h> and see your systems 1454the status word (use the macros from C<sys/wait.h> and see your systems
1326C<waitpid> documentation). The C<rpid> member contains the pid of the 1455C<waitpid> documentation). The C<rpid> member contains the pid of the
1327process causing the status change. 1456process causing the status change. C<trace> must be either C<0> (only
1457activate the watcher when the process terminates) or C<1> (additionally
1458activate the watcher when the process is stopped or continued).
1328 1459
1329=item int pid [read-only] 1460=item int pid [read-only]
1330 1461
1331The process id this watcher watches out for, or C<0>, meaning any process id. 1462The process id this watcher watches out for, or C<0>, meaning any process id.
1332 1463
… …
1338 1469
1339The process exit/trace status caused by C<rpid> (see your systems 1470The process exit/trace status caused by C<rpid> (see your systems
1340C<waitpid> and C<sys/wait.h> documentation for details). 1471C<waitpid> and C<sys/wait.h> documentation for details).
1341 1472
1342=back 1473=back
1474
1475=head3 Examples
1343 1476
1344Example: Try to exit cleanly on SIGINT and SIGTERM. 1477Example: Try to exit cleanly on SIGINT and SIGTERM.
1345 1478
1346 static void 1479 static void
1347 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1480 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1388semantics of C<ev_stat> watchers, which means that libev sometimes needs 1521semantics of C<ev_stat> watchers, which means that libev sometimes needs
1389to fall back to regular polling again even with inotify, but changes are 1522to fall back to regular polling again even with inotify, but changes are
1390usually detected immediately, and if the file exists there will be no 1523usually detected immediately, and if the file exists there will be no
1391polling. 1524polling.
1392 1525
1526=head3 Inotify
1527
1528When C<inotify (7)> support has been compiled into libev (generally only
1529available on Linux) and present at runtime, it will be used to speed up
1530change detection where possible. The inotify descriptor will be created lazily
1531when the first C<ev_stat> watcher is being started.
1532
1533Inotify presense does not change the semantics of C<ev_stat> watchers
1534except that changes might be detected earlier, and in some cases, to avoid
1535making regular C<stat> calls. Even in the presense of inotify support
1536there are many cases where libev has to resort to regular C<stat> polling.
1537
1538(There is no support for kqueue, as apparently it cannot be used to
1539implement this functionality, due to the requirement of having a file
1540descriptor open on the object at all times).
1541
1542=head3 The special problem of stat time resolution
1543
1544The C<stat ()> syscall only supports full-second resolution portably, and
1545even on systems where the resolution is higher, many filesystems still
1546only support whole seconds.
1547
1548That means that, if the time is the only thing that changes, you might
1549miss updates: on the first update, C<ev_stat> detects a change and calls
1550your callback, which does something. When there is another update within
1551the same second, C<ev_stat> will be unable to detect it.
1552
1553The solution to this is to delay acting on a change for a second (or till
1554the next second boundary), using a roughly one-second delay C<ev_timer>
1555(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1556is added to work around small timing inconsistencies of some operating
1557systems.
1558
1393=head3 Watcher-Specific Functions and Data Members 1559=head3 Watcher-Specific Functions and Data Members
1394 1560
1395=over 4 1561=over 4
1396 1562
1397=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1563=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
… …
1434=item const char *path [read-only] 1600=item const char *path [read-only]
1435 1601
1436The filesystem path that is being watched. 1602The filesystem path that is being watched.
1437 1603
1438=back 1604=back
1605
1606=head3 Examples
1439 1607
1440Example: Watch C</etc/passwd> for attribute changes. 1608Example: Watch C</etc/passwd> for attribute changes.
1441 1609
1442 static void 1610 static void
1443 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1611 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1456 } 1624 }
1457 1625
1458 ... 1626 ...
1459 ev_stat passwd; 1627 ev_stat passwd;
1460 1628
1461 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1629 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1462 ev_stat_start (loop, &passwd); 1630 ev_stat_start (loop, &passwd);
1631
1632Example: Like above, but additionally use a one-second delay so we do not
1633miss updates (however, frequent updates will delay processing, too, so
1634one might do the work both on C<ev_stat> callback invocation I<and> on
1635C<ev_timer> callback invocation).
1636
1637 static ev_stat passwd;
1638 static ev_timer timer;
1639
1640 static void
1641 timer_cb (EV_P_ ev_timer *w, int revents)
1642 {
1643 ev_timer_stop (EV_A_ w);
1644
1645 /* now it's one second after the most recent passwd change */
1646 }
1647
1648 static void
1649 stat_cb (EV_P_ ev_stat *w, int revents)
1650 {
1651 /* reset the one-second timer */
1652 ev_timer_again (EV_A_ &timer);
1653 }
1654
1655 ...
1656 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1657 ev_stat_start (loop, &passwd);
1658 ev_timer_init (&timer, timer_cb, 0., 1.01);
1463 1659
1464 1660
1465=head2 C<ev_idle> - when you've got nothing better to do... 1661=head2 C<ev_idle> - when you've got nothing better to do...
1466 1662
1467Idle watchers trigger events when no other events of the same or higher 1663Idle watchers trigger events when no other events of the same or higher
… …
1493kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1689kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1494believe me. 1690believe me.
1495 1691
1496=back 1692=back
1497 1693
1694=head3 Examples
1695
1498Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1696Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1499callback, free it. Also, use no error checking, as usual. 1697callback, free it. Also, use no error checking, as usual.
1500 1698
1501 static void 1699 static void
1502 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1700 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1503 { 1701 {
1504 free (w); 1702 free (w);
1505 // now do something you wanted to do when the program has 1703 // now do something you wanted to do when the program has
1506 // no longer asnything immediate to do. 1704 // no longer anything immediate to do.
1507 } 1705 }
1508 1706
1509 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1707 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1510 ev_idle_init (idle_watcher, idle_cb); 1708 ev_idle_init (idle_watcher, idle_cb);
1511 ev_idle_start (loop, idle_cb); 1709 ev_idle_start (loop, idle_cb);
… …
1553 1751
1554It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) 1752It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1555priority, to ensure that they are being run before any other watchers 1753priority, to ensure that they are being run before any other watchers
1556after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, 1754after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1557too) should not activate ("feed") events into libev. While libev fully 1755too) should not activate ("feed") events into libev. While libev fully
1558supports this, they will be called before other C<ev_check> watchers did 1756supports this, they will be called before other C<ev_check> watchers
1559their job. As C<ev_check> watchers are often used to embed other event 1757did their job. As C<ev_check> watchers are often used to embed other
1560loops those other event loops might be in an unusable state until their 1758(non-libev) event loops those other event loops might be in an unusable
1561C<ev_check> watcher ran (always remind yourself to coexist peacefully with 1759state until their C<ev_check> watcher ran (always remind yourself to
1562others). 1760coexist peacefully with others).
1563 1761
1564=head3 Watcher-Specific Functions and Data Members 1762=head3 Watcher-Specific Functions and Data Members
1565 1763
1566=over 4 1764=over 4
1567 1765
… …
1572Initialises and configures the prepare or check watcher - they have no 1770Initialises and configures the prepare or check watcher - they have no
1573parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1771parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1574macros, but using them is utterly, utterly and completely pointless. 1772macros, but using them is utterly, utterly and completely pointless.
1575 1773
1576=back 1774=back
1775
1776=head3 Examples
1577 1777
1578There are a number of principal ways to embed other event loops or modules 1778There are a number of principal ways to embed other event loops or modules
1579into libev. Here are some ideas on how to include libadns into libev 1779into libev. Here are some ideas on how to include libadns into libev
1580(there is a Perl module named C<EV::ADNS> that does this, which you could 1780(there is a Perl module named C<EV::ADNS> that does this, which you could
1581use for an actually working example. Another Perl module named C<EV::Glib> 1781use for an actually working example. Another Perl module named C<EV::Glib>
… …
1750portable one. 1950portable one.
1751 1951
1752So when you want to use this feature you will always have to be prepared 1952So when you want to use this feature you will always have to be prepared
1753that you cannot get an embeddable loop. The recommended way to get around 1953that you cannot get an embeddable loop. The recommended way to get around
1754this is to have a separate variables for your embeddable loop, try to 1954this is to have a separate variables for your embeddable loop, try to
1755create it, and if that fails, use the normal loop for everything: 1955create it, and if that fails, use the normal loop for everything.
1956
1957=head3 Watcher-Specific Functions and Data Members
1958
1959=over 4
1960
1961=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1962
1963=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1964
1965Configures the watcher to embed the given loop, which must be
1966embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1967invoked automatically, otherwise it is the responsibility of the callback
1968to invoke it (it will continue to be called until the sweep has been done,
1969if you do not want thta, you need to temporarily stop the embed watcher).
1970
1971=item ev_embed_sweep (loop, ev_embed *)
1972
1973Make a single, non-blocking sweep over the embedded loop. This works
1974similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1975apropriate way for embedded loops.
1976
1977=item struct ev_loop *other [read-only]
1978
1979The embedded event loop.
1980
1981=back
1982
1983=head3 Examples
1984
1985Example: Try to get an embeddable event loop and embed it into the default
1986event loop. If that is not possible, use the default loop. The default
1987loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1988C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1989used).
1756 1990
1757 struct ev_loop *loop_hi = ev_default_init (0); 1991 struct ev_loop *loop_hi = ev_default_init (0);
1758 struct ev_loop *loop_lo = 0; 1992 struct ev_loop *loop_lo = 0;
1759 struct ev_embed embed; 1993 struct ev_embed embed;
1760 1994
… …
1771 ev_embed_start (loop_hi, &embed); 2005 ev_embed_start (loop_hi, &embed);
1772 } 2006 }
1773 else 2007 else
1774 loop_lo = loop_hi; 2008 loop_lo = loop_hi;
1775 2009
1776=head3 Watcher-Specific Functions and Data Members 2010Example: Check if kqueue is available but not recommended and create
2011a kqueue backend for use with sockets (which usually work with any
2012kqueue implementation). Store the kqueue/socket-only event loop in
2013C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1777 2014
1778=over 4 2015 struct ev_loop *loop = ev_default_init (0);
2016 struct ev_loop *loop_socket = 0;
2017 struct ev_embed embed;
2018
2019 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2020 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2021 {
2022 ev_embed_init (&embed, 0, loop_socket);
2023 ev_embed_start (loop, &embed);
2024 }
1779 2025
1780=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2026 if (!loop_socket)
2027 loop_socket = loop;
1781 2028
1782=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2029 // now use loop_socket for all sockets, and loop for everything else
1783
1784Configures the watcher to embed the given loop, which must be
1785embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1786invoked automatically, otherwise it is the responsibility of the callback
1787to invoke it (it will continue to be called until the sweep has been done,
1788if you do not want thta, you need to temporarily stop the embed watcher).
1789
1790=item ev_embed_sweep (loop, ev_embed *)
1791
1792Make a single, non-blocking sweep over the embedded loop. This works
1793similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1794apropriate way for embedded loops.
1795
1796=item struct ev_loop *loop [read-only]
1797
1798The embedded event loop.
1799
1800=back
1801 2030
1802 2031
1803=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2032=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1804 2033
1805Fork watchers are called when a C<fork ()> was detected (usually because 2034Fork watchers are called when a C<fork ()> was detected (usually because
… …
1821believe me. 2050believe me.
1822 2051
1823=back 2052=back
1824 2053
1825 2054
2055=head2 C<ev_async> - how to wake up another event loop
2056
2057In general, you cannot use an C<ev_loop> from multiple threads or other
2058asynchronous sources such as signal handlers (as opposed to multiple event
2059loops - those are of course safe to use in different threads).
2060
2061Sometimes, however, you need to wake up another event loop you do not
2062control, for example because it belongs to another thread. This is what
2063C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
2064can signal it by calling C<ev_async_send>, which is thread- and signal
2065safe.
2066
2067This functionality is very similar to C<ev_signal> watchers, as signals,
2068too, are asynchronous in nature, and signals, too, will be compressed
2069(i.e. the number of callback invocations may be less than the number of
2070C<ev_async_sent> calls).
2071
2072Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2073just the default loop.
2074
2075=head3 Queueing
2076
2077C<ev_async> does not support queueing of data in any way. The reason
2078is that the author does not know of a simple (or any) algorithm for a
2079multiple-writer-single-reader queue that works in all cases and doesn't
2080need elaborate support such as pthreads.
2081
2082That means that if you want to queue data, you have to provide your own
2083queue. But at least I can tell you would implement locking around your
2084queue:
2085
2086=over 4
2087
2088=item queueing from a signal handler context
2089
2090To implement race-free queueing, you simply add to the queue in the signal
2091handler but you block the signal handler in the watcher callback. Here is an example that does that for
2092some fictitiuous SIGUSR1 handler:
2093
2094 static ev_async mysig;
2095
2096 static void
2097 sigusr1_handler (void)
2098 {
2099 sometype data;
2100
2101 // no locking etc.
2102 queue_put (data);
2103 ev_async_send (DEFAULT_ &mysig);
2104 }
2105
2106 static void
2107 mysig_cb (EV_P_ ev_async *w, int revents)
2108 {
2109 sometype data;
2110 sigset_t block, prev;
2111
2112 sigemptyset (&block);
2113 sigaddset (&block, SIGUSR1);
2114 sigprocmask (SIG_BLOCK, &block, &prev);
2115
2116 while (queue_get (&data))
2117 process (data);
2118
2119 if (sigismember (&prev, SIGUSR1)
2120 sigprocmask (SIG_UNBLOCK, &block, 0);
2121 }
2122
2123(Note: pthreads in theory requires you to use C<pthread_setmask>
2124instead of C<sigprocmask> when you use threads, but libev doesn't do it
2125either...).
2126
2127=item queueing from a thread context
2128
2129The strategy for threads is different, as you cannot (easily) block
2130threads but you can easily preempt them, so to queue safely you need to
2131employ a traditional mutex lock, such as in this pthread example:
2132
2133 static ev_async mysig;
2134 static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2135
2136 static void
2137 otherthread (void)
2138 {
2139 // only need to lock the actual queueing operation
2140 pthread_mutex_lock (&mymutex);
2141 queue_put (data);
2142 pthread_mutex_unlock (&mymutex);
2143
2144 ev_async_send (DEFAULT_ &mysig);
2145 }
2146
2147 static void
2148 mysig_cb (EV_P_ ev_async *w, int revents)
2149 {
2150 pthread_mutex_lock (&mymutex);
2151
2152 while (queue_get (&data))
2153 process (data);
2154
2155 pthread_mutex_unlock (&mymutex);
2156 }
2157
2158=back
2159
2160
2161=head3 Watcher-Specific Functions and Data Members
2162
2163=over 4
2164
2165=item ev_async_init (ev_async *, callback)
2166
2167Initialises and configures the async watcher - it has no parameters of any
2168kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2169believe me.
2170
2171=item ev_async_send (loop, ev_async *)
2172
2173Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2174an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2175C<ev_feed_event>, this call is safe to do in other threads, signal or
2176similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
2177section below on what exactly this means).
2178
2179This call incurs the overhead of a syscall only once per loop iteration,
2180so while the overhead might be noticable, it doesn't apply to repeated
2181calls to C<ev_async_send>.
2182
2183=back
2184
2185
1826=head1 OTHER FUNCTIONS 2186=head1 OTHER FUNCTIONS
1827 2187
1828There are some other functions of possible interest. Described. Here. Now. 2188There are some other functions of possible interest. Described. Here. Now.
1829 2189
1830=over 4 2190=over 4
… …
2057Example: Define a class with an IO and idle watcher, start one of them in 2417Example: Define a class with an IO and idle watcher, start one of them in
2058the constructor. 2418the constructor.
2059 2419
2060 class myclass 2420 class myclass
2061 { 2421 {
2062 ev_io io; void io_cb (ev::io &w, int revents); 2422 ev::io io; void io_cb (ev::io &w, int revents);
2063 ev_idle idle void idle_cb (ev::idle &w, int revents); 2423 ev:idle idle void idle_cb (ev::idle &w, int revents);
2064 2424
2065 myclass (); 2425 myclass (int fd)
2066 }
2067
2068 myclass::myclass (int fd)
2069 { 2426 {
2070 io .set <myclass, &myclass::io_cb > (this); 2427 io .set <myclass, &myclass::io_cb > (this);
2071 idle.set <myclass, &myclass::idle_cb> (this); 2428 idle.set <myclass, &myclass::idle_cb> (this);
2072 2429
2073 io.start (fd, ev::READ); 2430 io.start (fd, ev::READ);
2431 }
2074 } 2432 };
2075 2433
2076 2434
2077=head1 MACRO MAGIC 2435=head1 MACRO MAGIC
2078 2436
2079Libev can be compiled with a variety of options, the most fundamantal 2437Libev can be compiled with a variety of options, the most fundamantal
… …
2140Libev can (and often is) directly embedded into host 2498Libev can (and often is) directly embedded into host
2141applications. Examples of applications that embed it include the Deliantra 2499applications. Examples of applications that embed it include the Deliantra
2142Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2500Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2143and rxvt-unicode. 2501and rxvt-unicode.
2144 2502
2145The goal is to enable you to just copy the neecssary files into your 2503The goal is to enable you to just copy the necessary files into your
2146source directory without having to change even a single line in them, so 2504source directory without having to change even a single line in them, so
2147you can easily upgrade by simply copying (or having a checked-out copy of 2505you can easily upgrade by simply copying (or having a checked-out copy of
2148libev somewhere in your source tree). 2506libev somewhere in your source tree).
2149 2507
2150=head2 FILESETS 2508=head2 FILESETS
… …
2240 2598
2241If defined to be C<1>, libev will try to detect the availability of the 2599If defined to be C<1>, libev will try to detect the availability of the
2242monotonic clock option at both compiletime and runtime. Otherwise no use 2600monotonic clock option at both compiletime and runtime. Otherwise no use
2243of the monotonic clock option will be attempted. If you enable this, you 2601of the monotonic clock option will be attempted. If you enable this, you
2244usually have to link against librt or something similar. Enabling it when 2602usually have to link against librt or something similar. Enabling it when
2245the functionality isn't available is safe, though, althoguh you have 2603the functionality isn't available is safe, though, although you have
2246to make sure you link against any libraries where the C<clock_gettime> 2604to make sure you link against any libraries where the C<clock_gettime>
2247function is hiding in (often F<-lrt>). 2605function is hiding in (often F<-lrt>).
2248 2606
2249=item EV_USE_REALTIME 2607=item EV_USE_REALTIME
2250 2608
2251If defined to be C<1>, libev will try to detect the availability of the 2609If defined to be C<1>, libev will try to detect the availability of the
2252realtime clock option at compiletime (and assume its availability at 2610realtime clock option at compiletime (and assume its availability at
2253runtime if successful). Otherwise no use of the realtime clock option will 2611runtime if successful). Otherwise no use of the realtime clock option will
2254be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2612be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2255(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries 2613(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2256in the description of C<EV_USE_MONOTONIC>, though. 2614note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2615
2616=item EV_USE_NANOSLEEP
2617
2618If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2619and will use it for delays. Otherwise it will use C<select ()>.
2257 2620
2258=item EV_USE_SELECT 2621=item EV_USE_SELECT
2259 2622
2260If undefined or defined to be C<1>, libev will compile in support for the 2623If undefined or defined to be C<1>, libev will compile in support for the
2261C<select>(2) backend. No attempt at autodetection will be done: if no 2624C<select>(2) backend. No attempt at autodetection will be done: if no
… …
2279wants osf handles on win32 (this is the case when the select to 2642wants osf handles on win32 (this is the case when the select to
2280be used is the winsock select). This means that it will call 2643be used is the winsock select). This means that it will call
2281C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2644C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2282it is assumed that all these functions actually work on fds, even 2645it is assumed that all these functions actually work on fds, even
2283on win32. Should not be defined on non-win32 platforms. 2646on win32. Should not be defined on non-win32 platforms.
2647
2648=item EV_FD_TO_WIN32_HANDLE
2649
2650If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2651file descriptors to socket handles. When not defining this symbol (the
2652default), then libev will call C<_get_osfhandle>, which is usually
2653correct. In some cases, programs use their own file descriptor management,
2654in which case they can provide this function to map fds to socket handles.
2284 2655
2285=item EV_USE_POLL 2656=item EV_USE_POLL
2286 2657
2287If defined to be C<1>, libev will compile in support for the C<poll>(2) 2658If defined to be C<1>, libev will compile in support for the C<poll>(2)
2288backend. Otherwise it will be enabled on non-win32 platforms. It 2659backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2322 2693
2323If defined to be C<1>, libev will compile in support for the Linux inotify 2694If defined to be C<1>, libev will compile in support for the Linux inotify
2324interface to speed up C<ev_stat> watchers. Its actual availability will 2695interface to speed up C<ev_stat> watchers. Its actual availability will
2325be detected at runtime. 2696be detected at runtime.
2326 2697
2698=item EV_ATOMIC_T
2699
2700Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2701access is atomic with respect to other threads or signal contexts. No such
2702type is easily found in the C language, so you can provide your own type
2703that you know is safe for your purposes. It is used both for signal handler "locking"
2704as well as for signal and thread safety in C<ev_async> watchers.
2705
2706In the absense of this define, libev will use C<sig_atomic_t volatile>
2707(from F<signal.h>), which is usually good enough on most platforms.
2708
2327=item EV_H 2709=item EV_H
2328 2710
2329The name of the F<ev.h> header file used to include it. The default if 2711The name of the F<ev.h> header file used to include it. The default if
2330undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2712undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2331can be used to virtually rename the F<ev.h> header file in case of conflicts. 2713used to virtually rename the F<ev.h> header file in case of conflicts.
2332 2714
2333=item EV_CONFIG_H 2715=item EV_CONFIG_H
2334 2716
2335If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2717If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2336F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2718F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2337C<EV_H>, above. 2719C<EV_H>, above.
2338 2720
2339=item EV_EVENT_H 2721=item EV_EVENT_H
2340 2722
2341Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2723Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2342of how the F<event.h> header can be found. 2724of how the F<event.h> header can be found, the default is C<"event.h">.
2343 2725
2344=item EV_PROTOTYPES 2726=item EV_PROTOTYPES
2345 2727
2346If defined to be C<0>, then F<ev.h> will not define any function 2728If defined to be C<0>, then F<ev.h> will not define any function
2347prototypes, but still define all the structs and other symbols. This is 2729prototypes, but still define all the structs and other symbols. This is
… …
2398=item EV_FORK_ENABLE 2780=item EV_FORK_ENABLE
2399 2781
2400If undefined or defined to be C<1>, then fork watchers are supported. If 2782If undefined or defined to be C<1>, then fork watchers are supported. If
2401defined to be C<0>, then they are not. 2783defined to be C<0>, then they are not.
2402 2784
2785=item EV_ASYNC_ENABLE
2786
2787If undefined or defined to be C<1>, then async watchers are supported. If
2788defined to be C<0>, then they are not.
2789
2403=item EV_MINIMAL 2790=item EV_MINIMAL
2404 2791
2405If you need to shave off some kilobytes of code at the expense of some 2792If you need to shave off some kilobytes of code at the expense of some
2406speed, define this symbol to C<1>. Currently only used for gcc to override 2793speed, define this symbol to C<1>. Currently only used for gcc to override
2407some inlining decisions, saves roughly 30% codesize of amd64. 2794some inlining decisions, saves roughly 30% codesize of amd64.
… …
2413than enough. If you need to manage thousands of children you might want to 2800than enough. If you need to manage thousands of children you might want to
2414increase this value (I<must> be a power of two). 2801increase this value (I<must> be a power of two).
2415 2802
2416=item EV_INOTIFY_HASHSIZE 2803=item EV_INOTIFY_HASHSIZE
2417 2804
2418C<ev_staz> watchers use a small hash table to distribute workload by 2805C<ev_stat> watchers use a small hash table to distribute workload by
2419inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 2806inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2420usually more than enough. If you need to manage thousands of C<ev_stat> 2807usually more than enough. If you need to manage thousands of C<ev_stat>
2421watchers you might want to increase this value (I<must> be a power of 2808watchers you might want to increase this value (I<must> be a power of
2422two). 2809two).
2423 2810
… …
2440 2827
2441=item ev_set_cb (ev, cb) 2828=item ev_set_cb (ev, cb)
2442 2829
2443Can be used to change the callback member declaration in each watcher, 2830Can be used to change the callback member declaration in each watcher,
2444and the way callbacks are invoked and set. Must expand to a struct member 2831and the way callbacks are invoked and set. Must expand to a struct member
2445definition and a statement, respectively. See the F<ev.v> header file for 2832definition and a statement, respectively. See the F<ev.h> header file for
2446their default definitions. One possible use for overriding these is to 2833their default definitions. One possible use for overriding these is to
2447avoid the C<struct ev_loop *> as first argument in all cases, or to use 2834avoid the C<struct ev_loop *> as first argument in all cases, or to use
2448method calls instead of plain function calls in C++. 2835method calls instead of plain function calls in C++.
2449 2836
2450=head2 EXPORTED API SYMBOLS 2837=head2 EXPORTED API SYMBOLS
… …
2458 2845
2459This can also be used to rename all public symbols to avoid clashes with 2846This can also be used to rename all public symbols to avoid clashes with
2460multiple versions of libev linked together (which is obviously bad in 2847multiple versions of libev linked together (which is obviously bad in
2461itself, but sometimes it is inconvinient to avoid this). 2848itself, but sometimes it is inconvinient to avoid this).
2462 2849
2463A sed comamnd like this will create wrapper C<#define>'s that you need to 2850A sed command like this will create wrapper C<#define>'s that you need to
2464include before including F<ev.h>: 2851include before including F<ev.h>:
2465 2852
2466 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h 2853 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2467 2854
2468This would create a file F<wrap.h> which essentially looks like this: 2855This would create a file F<wrap.h> which essentially looks like this:
… …
2519 2906
2520=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2907=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2521 2908
2522This means that, when you have a watcher that triggers in one hour and 2909This means that, when you have a watcher that triggers in one hour and
2523there are 100 watchers that would trigger before that then inserting will 2910there are 100 watchers that would trigger before that then inserting will
2524have to skip those 100 watchers. 2911have to skip roughly seven (C<ld 100>) of these watchers.
2525 2912
2526=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2913=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2527 2914
2528That means that for changing a timer costs less than removing/adding them 2915That means that changing a timer costs less than removing/adding them
2529as only the relative motion in the event queue has to be paid for. 2916as only the relative motion in the event queue has to be paid for.
2530 2917
2531=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2918=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2532 2919
2533These just add the watcher into an array or at the head of a list. 2920These just add the watcher into an array or at the head of a list.
2921
2534=item Stopping check/prepare/idle watchers: O(1) 2922=item Stopping check/prepare/idle/fork/async watchers: O(1)
2535 2923
2536=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2924=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2537 2925
2538These watchers are stored in lists then need to be walked to find the 2926These watchers are stored in lists then need to be walked to find the
2539correct watcher to remove. The lists are usually short (you don't usually 2927correct watcher to remove. The lists are usually short (you don't usually
2540have many watchers waiting for the same fd or signal). 2928have many watchers waiting for the same fd or signal).
2541 2929
2542=item Finding the next timer per loop iteration: O(1) 2930=item Finding the next timer in each loop iteration: O(1)
2931
2932By virtue of using a binary heap, the next timer is always found at the
2933beginning of the storage array.
2543 2934
2544=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2935=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2545 2936
2546A change means an I/O watcher gets started or stopped, which requires 2937A change means an I/O watcher gets started or stopped, which requires
2547libev to recalculate its status (and possibly tell the kernel). 2938libev to recalculate its status (and possibly tell the kernel, depending
2939on backend and wether C<ev_io_set> was used).
2548 2940
2549=item Activating one watcher: O(1) 2941=item Activating one watcher (putting it into the pending state): O(1)
2550 2942
2551=item Priority handling: O(number_of_priorities) 2943=item Priority handling: O(number_of_priorities)
2552 2944
2553Priorities are implemented by allocating some space for each 2945Priorities are implemented by allocating some space for each
2554priority. When doing priority-based operations, libev usually has to 2946priority. When doing priority-based operations, libev usually has to
2555linearly search all the priorities. 2947linearly search all the priorities, but starting/stopping and activating
2948watchers becomes O(1) w.r.t. priority handling.
2949
2950=item Sending an ev_async: O(1)
2951
2952=item Processing ev_async_send: O(number_of_async_watchers)
2953
2954=item Processing signals: O(max_signal_number)
2955
2956Sending involves a syscall I<iff> there were no other C<ev_async_send>
2957calls in the current loop iteration. Checking for async and signal events
2958involves iterating over all running async watchers or all signal numbers.
2556 2959
2557=back 2960=back
2558 2961
2559 2962
2963=head1 Win32 platform limitations and workarounds
2964
2965Win32 doesn't support any of the standards (e.g. POSIX) that libev
2966requires, and its I/O model is fundamentally incompatible with the POSIX
2967model. Libev still offers limited functionality on this platform in
2968the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2969descriptors. This only applies when using Win32 natively, not when using
2970e.g. cygwin.
2971
2972There is no supported compilation method available on windows except
2973embedding it into other applications.
2974
2975Due to the many, low, and arbitrary limits on the win32 platform and the
2976abysmal performance of winsockets, using a large number of sockets is not
2977recommended (and not reasonable). If your program needs to use more than
2978a hundred or so sockets, then likely it needs to use a totally different
2979implementation for windows, as libev offers the POSIX model, which cannot
2980be implemented efficiently on windows (microsoft monopoly games).
2981
2982=over 4
2983
2984=item The winsocket select function
2985
2986The winsocket C<select> function doesn't follow POSIX in that it requires
2987socket I<handles> and not socket I<file descriptors>. This makes select
2988very inefficient, and also requires a mapping from file descriptors
2989to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2990C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2991symbols for more info.
2992
2993The configuration for a "naked" win32 using the microsoft runtime
2994libraries and raw winsocket select is:
2995
2996 #define EV_USE_SELECT 1
2997 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2998
2999Note that winsockets handling of fd sets is O(n), so you can easily get a
3000complexity in the O(n²) range when using win32.
3001
3002=item Limited number of file descriptors
3003
3004Windows has numerous arbitrary (and low) limits on things. Early versions
3005of winsocket's select only supported waiting for a max. of C<64> handles
3006(probably owning to the fact that all windows kernels can only wait for
3007C<64> things at the same time internally; microsoft recommends spawning a
3008chain of threads and wait for 63 handles and the previous thread in each).
3009
3010Newer versions support more handles, but you need to define C<FD_SETSIZE>
3011to some high number (e.g. C<2048>) before compiling the winsocket select
3012call (which might be in libev or elsewhere, for example, perl does its own
3013select emulation on windows).
3014
3015Another limit is the number of file descriptors in the microsoft runtime
3016libraries, which by default is C<64> (there must be a hidden I<64> fetish
3017or something like this inside microsoft). You can increase this by calling
3018C<_setmaxstdio>, which can increase this limit to C<2048> (another
3019arbitrary limit), but is broken in many versions of the microsoft runtime
3020libraries.
3021
3022This might get you to about C<512> or C<2048> sockets (depending on
3023windows version and/or the phase of the moon). To get more, you need to
3024wrap all I/O functions and provide your own fd management, but the cost of
3025calling select (O(n²)) will likely make this unworkable.
3026
3027=back
3028
3029
2560=head1 AUTHOR 3030=head1 AUTHOR
2561 3031
2562Marc Lehmann <libev@schmorp.de>. 3032Marc Lehmann <libev@schmorp.de>.
2563 3033

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines