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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;
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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
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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
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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
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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 it's 368with anything but sockets and pipes, except on Darwin, where of course
337completely useless). For this reason it's 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?");
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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);
442 504
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
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
451after fork, and how you do this is entirely your own problem. 509after fork, and how you do this is entirely your own problem.
510
511=item int ev_is_default_loop (loop)
512
513Returns true when the given loop actually is the default loop, false otherwise.
452 514
453=item unsigned int ev_loop_count (loop) 515=item unsigned int ev_loop_count (loop)
454 516
455Returns the count of loop iterations for the loop, which is identical to 517Returns the count of loop iterations for the loop, which is identical to
456the number of times libev did poll for new events. It starts at C<0> and 518the number of times libev did poll for new events. It starts at C<0> and
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501usually a better approach for this kind of thing. 563usually a better approach for this kind of thing.
502 564
503Here are the gory details of what C<ev_loop> does: 565Here are the gory details of what C<ev_loop> does:
504 566
505 - Before the first iteration, call any pending watchers. 567 - Before the first iteration, call any pending watchers.
506 * If there are no active watchers (reference count is zero), return. 568 * If EVFLAG_FORKCHECK was used, check for a fork.
507 - Queue all prepare watchers and then call all outstanding watchers. 569 - If a fork was detected, queue and call all fork watchers.
570 - Queue and call all prepare watchers.
508 - If we have been forked, recreate the kernel state. 571 - If we have been forked, recreate the kernel state.
509 - Update the kernel state with all outstanding changes. 572 - Update the kernel state with all outstanding changes.
510 - Update the "event loop time". 573 - Update the "event loop time".
511 - Calculate for how long to block. 574 - Calculate for how long to sleep or block, if at all
575 (active idle watchers, EVLOOP_NONBLOCK or not having
576 any active watchers at all will result in not sleeping).
577 - Sleep if the I/O and timer collect interval say so.
512 - Block the process, waiting for any events. 578 - Block the process, waiting for any events.
513 - Queue all outstanding I/O (fd) events. 579 - Queue all outstanding I/O (fd) events.
514 - Update the "event loop time" and do time jump handling. 580 - Update the "event loop time" and do time jump handling.
515 - Queue all outstanding timers. 581 - Queue all outstanding timers.
516 - Queue all outstanding periodics. 582 - Queue all outstanding periodics.
517 - If no events are pending now, queue all idle watchers. 583 - If no events are pending now, queue all idle watchers.
518 - Queue all check watchers. 584 - Queue all check watchers.
519 - Call all queued watchers in reverse order (i.e. check watchers first). 585 - Call all queued watchers in reverse order (i.e. check watchers first).
520 Signals and child watchers are implemented as I/O watchers, and will 586 Signals and child watchers are implemented as I/O watchers, and will
521 be handled here by queueing them when their watcher gets executed. 587 be handled here by queueing them when their watcher gets executed.
522 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 588 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
523 were used, return, otherwise continue with step *. 589 were used, or there are no active watchers, return, otherwise
590 continue with step *.
524 591
525Example: Queue some jobs and then loop until no events are outsanding 592Example: Queue some jobs and then loop until no events are outstanding
526anymore. 593anymore.
527 594
528 ... queue jobs here, make sure they register event watchers as long 595 ... 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..) 596 ... as they still have work to do (even an idle watcher will do..)
530 ev_loop (my_loop, 0); 597 ev_loop (my_loop, 0);
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534 601
535Can be used to make a call to C<ev_loop> return early (but only after it 602Can be used to make a call to C<ev_loop> return early (but only after it
536has processed all outstanding events). The C<how> argument must be either 603has 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 604C<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. 605C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
606
607This "unloop state" will be cleared when entering C<ev_loop> again.
539 608
540=item ev_ref (loop) 609=item ev_ref (loop)
541 610
542=item ev_unref (loop) 611=item ev_unref (loop)
543 612
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548returning, ev_unref() after starting, and ev_ref() before stopping it. For 617returning, ev_unref() after starting, and ev_ref() before stopping it. For
549example, libev itself uses this for its internal signal pipe: It is not 618example, libev itself uses this for its internal signal pipe: It is not
550visible to the libev user and should not keep C<ev_loop> from exiting if 619visible to the libev user and should not keep C<ev_loop> from exiting if
551no event watchers registered by it are active. It is also an excellent 620no event watchers registered by it are active. It is also an excellent
552way to do this for generic recurring timers or from within third-party 621way to do this for generic recurring timers or from within third-party
553libraries. Just remember to I<unref after start> and I<ref before stop>. 622libraries. Just remember to I<unref after start> and I<ref before stop>
623(but only if the watcher wasn't active before, or was active before,
624respectively).
554 625
555Example: Create a signal watcher, but keep it from keeping C<ev_loop> 626Example: Create a signal watcher, but keep it from keeping C<ev_loop>
556running when nothing else is active. 627running when nothing else is active.
557 628
558 struct ev_signal exitsig; 629 struct ev_signal exitsig;
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562 633
563Example: For some weird reason, unregister the above signal handler again. 634Example: For some weird reason, unregister the above signal handler again.
564 635
565 ev_ref (loop); 636 ev_ref (loop);
566 ev_signal_stop (loop, &exitsig); 637 ev_signal_stop (loop, &exitsig);
638
639=item ev_set_io_collect_interval (loop, ev_tstamp interval)
640
641=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
642
643These advanced functions influence the time that libev will spend waiting
644for events. Both are by default C<0>, meaning that libev will try to
645invoke timer/periodic callbacks and I/O callbacks with minimum latency.
646
647Setting these to a higher value (the C<interval> I<must> be >= C<0>)
648allows libev to delay invocation of I/O and timer/periodic callbacks to
649increase efficiency of loop iterations.
650
651The background is that sometimes your program runs just fast enough to
652handle one (or very few) event(s) per loop iteration. While this makes
653the program responsive, it also wastes a lot of CPU time to poll for new
654events, especially with backends like C<select ()> which have a high
655overhead for the actual polling but can deliver many events at once.
656
657By setting a higher I<io collect interval> you allow libev to spend more
658time collecting I/O events, so you can handle more events per iteration,
659at the cost of increasing latency. Timeouts (both C<ev_periodic> and
660C<ev_timer>) will be not affected. Setting this to a non-null value will
661introduce an additional C<ev_sleep ()> call into most loop iterations.
662
663Likewise, by setting a higher I<timeout collect interval> you allow libev
664to spend more time collecting timeouts, at the expense of increased
665latency (the watcher callback will be called later). C<ev_io> watchers
666will not be affected. Setting this to a non-null value will not introduce
667any overhead in libev.
668
669Many (busy) programs can usually benefit by setting the io collect
670interval to a value near C<0.1> or so, which is often enough for
671interactive servers (of course not for games), likewise for timeouts. It
672usually doesn't make much sense to set it to a lower value than C<0.01>,
673as this approsaches the timing granularity of most systems.
567 674
568=back 675=back
569 676
570 677
571=head1 ANATOMY OF A WATCHER 678=head1 ANATOMY OF A WATCHER
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670 777
671=item C<EV_FORK> 778=item C<EV_FORK>
672 779
673The event loop has been resumed in the child process after fork (see 780The event loop has been resumed in the child process after fork (see
674C<ev_fork>). 781C<ev_fork>).
782
783=item C<EV_ASYNC>
784
785The given async watcher has been asynchronously notified (see C<ev_async>).
675 786
676=item C<EV_ERROR> 787=item C<EV_ERROR>
677 788
678An unspecified error has occured, the watcher has been stopped. This might 789An unspecified error has occured, the watcher has been stopped. This might
679happen because the watcher could not be properly started because libev 790happen because the watcher could not be properly started because libev
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897In general you can register as many read and/or write event watchers per 1008In general you can register as many read and/or write event watchers per
898fd as you want (as long as you don't confuse yourself). Setting all file 1009fd as you want (as long as you don't confuse yourself). Setting all file
899descriptors to non-blocking mode is also usually a good idea (but not 1010descriptors to non-blocking mode is also usually a good idea (but not
900required if you know what you are doing). 1011required if you know what you are doing).
901 1012
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 1013If 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 1014(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
910C<EVBACKEND_POLL>). 1015C<EVBACKEND_POLL>).
911 1016
912Another thing you have to watch out for is that it is quite easy to 1017Another thing you have to watch out for is that it is quite easy to
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924such as poll (fortunately in our Xlib example, Xlib already does this on 1029such as poll (fortunately in our Xlib example, Xlib already does this on
925its own, so its quite safe to use). 1030its own, so its quite safe to use).
926 1031
927=head3 The special problem of disappearing file descriptors 1032=head3 The special problem of disappearing file descriptors
928 1033
929Some backends (e.g kqueue, epoll) need to be told about closing a file 1034Some 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, 1035descriptor (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 1036such 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 1037descriptor, but when it goes away, the operating system will silently drop
933this interest. If another file descriptor with the same number then is 1038this 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 1039registered with libev, there is no efficient way to see that this is, in
… …
943 1048
944This is how one would do it normally anyway, the important point is that 1049This is how one would do it normally anyway, the important point is that
945the libev application should not optimise around libev but should leave 1050the libev application should not optimise around libev but should leave
946optimisations to libev. 1051optimisations to libev.
947 1052
1053=head3 The special problem of dup'ed file descriptors
1054
1055Some backends (e.g. epoll), cannot register events for file descriptors,
1056but only events for the underlying file descriptions. That means when you
1057have C<dup ()>'ed file descriptors or weirder constellations, and register
1058events for them, only one file descriptor might actually receive events.
1059
1060There is no workaround possible except not registering events
1061for potentially C<dup ()>'ed file descriptors, or to resort to
1062C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1063
1064=head3 The special problem of fork
1065
1066Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1067useless behaviour. Libev fully supports fork, but needs to be told about
1068it in the child.
1069
1070To support fork in your programs, you either have to call
1071C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1072enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1073C<EVBACKEND_POLL>.
1074
948 1075
949=head3 Watcher-Specific Functions 1076=head3 Watcher-Specific Functions
950 1077
951=over 4 1078=over 4
952 1079
… …
965=item int events [read-only] 1092=item int events [read-only]
966 1093
967The events being watched. 1094The events being watched.
968 1095
969=back 1096=back
1097
1098=head3 Examples
970 1099
971Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1100Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
972readable, but only once. Since it is likely line-buffered, you could 1101readable, but only once. Since it is likely line-buffered, you could
973attempt to read a whole line in the callback. 1102attempt to read a whole line in the callback.
974 1103
… …
1072or C<ev_timer_again> is called and determines the next timeout (if any), 1201or C<ev_timer_again> is called and determines the next timeout (if any),
1073which is also when any modifications are taken into account. 1202which is also when any modifications are taken into account.
1074 1203
1075=back 1204=back
1076 1205
1206=head3 Examples
1207
1077Example: Create a timer that fires after 60 seconds. 1208Example: Create a timer that fires after 60 seconds.
1078 1209
1079 static void 1210 static void
1080 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1211 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1081 { 1212 {
… …
1238When active, contains the absolute time that the watcher is supposed to 1369When active, contains the absolute time that the watcher is supposed to
1239trigger next. 1370trigger next.
1240 1371
1241=back 1372=back
1242 1373
1374=head3 Examples
1375
1243Example: Call a callback every hour, or, more precisely, whenever the 1376Example: Call a callback every hour, or, more precisely, whenever the
1244system clock is divisible by 3600. The callback invocation times have 1377system clock is divisible by 3600. The callback invocation times have
1245potentially a lot of jittering, but good long-term stability. 1378potentially a lot of jittering, but good long-term stability.
1246 1379
1247 static void 1380 static void
… …
1313 1446
1314=head3 Watcher-Specific Functions and Data Members 1447=head3 Watcher-Specific Functions and Data Members
1315 1448
1316=over 4 1449=over 4
1317 1450
1318=item ev_child_init (ev_child *, callback, int pid) 1451=item ev_child_init (ev_child *, callback, int pid, int trace)
1319 1452
1320=item ev_child_set (ev_child *, int pid) 1453=item ev_child_set (ev_child *, int pid, int trace)
1321 1454
1322Configures the watcher to wait for status changes of process C<pid> (or 1455Configures the watcher to wait for status changes of process C<pid> (or
1323I<any> process if C<pid> is specified as C<0>). The callback can look 1456I<any> process if C<pid> is specified as C<0>). The callback can look
1324at the C<rstatus> member of the C<ev_child> watcher structure to see 1457at the C<rstatus> member of the C<ev_child> watcher structure to see
1325the status word (use the macros from C<sys/wait.h> and see your systems 1458the status word (use the macros from C<sys/wait.h> and see your systems
1326C<waitpid> documentation). The C<rpid> member contains the pid of the 1459C<waitpid> documentation). The C<rpid> member contains the pid of the
1327process causing the status change. 1460process causing the status change. C<trace> must be either C<0> (only
1461activate the watcher when the process terminates) or C<1> (additionally
1462activate the watcher when the process is stopped or continued).
1328 1463
1329=item int pid [read-only] 1464=item int pid [read-only]
1330 1465
1331The process id this watcher watches out for, or C<0>, meaning any process id. 1466The process id this watcher watches out for, or C<0>, meaning any process id.
1332 1467
… …
1338 1473
1339The process exit/trace status caused by C<rpid> (see your systems 1474The process exit/trace status caused by C<rpid> (see your systems
1340C<waitpid> and C<sys/wait.h> documentation for details). 1475C<waitpid> and C<sys/wait.h> documentation for details).
1341 1476
1342=back 1477=back
1478
1479=head3 Examples
1343 1480
1344Example: Try to exit cleanly on SIGINT and SIGTERM. 1481Example: Try to exit cleanly on SIGINT and SIGTERM.
1345 1482
1346 static void 1483 static void
1347 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1484 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1388semantics of C<ev_stat> watchers, which means that libev sometimes needs 1525semantics of C<ev_stat> watchers, which means that libev sometimes needs
1389to fall back to regular polling again even with inotify, but changes are 1526to fall back to regular polling again even with inotify, but changes are
1390usually detected immediately, and if the file exists there will be no 1527usually detected immediately, and if the file exists there will be no
1391polling. 1528polling.
1392 1529
1530=head3 Inotify
1531
1532When C<inotify (7)> support has been compiled into libev (generally only
1533available on Linux) and present at runtime, it will be used to speed up
1534change detection where possible. The inotify descriptor will be created lazily
1535when the first C<ev_stat> watcher is being started.
1536
1537Inotify presense does not change the semantics of C<ev_stat> watchers
1538except that changes might be detected earlier, and in some cases, to avoid
1539making regular C<stat> calls. Even in the presense of inotify support
1540there are many cases where libev has to resort to regular C<stat> polling.
1541
1542(There is no support for kqueue, as apparently it cannot be used to
1543implement this functionality, due to the requirement of having a file
1544descriptor open on the object at all times).
1545
1546=head3 The special problem of stat time resolution
1547
1548The C<stat ()> syscall only supports full-second resolution portably, and
1549even on systems where the resolution is higher, many filesystems still
1550only support whole seconds.
1551
1552That means that, if the time is the only thing that changes, you might
1553miss updates: on the first update, C<ev_stat> detects a change and calls
1554your callback, which does something. When there is another update within
1555the same second, C<ev_stat> will be unable to detect it.
1556
1557The solution to this is to delay acting on a change for a second (or till
1558the next second boundary), using a roughly one-second delay C<ev_timer>
1559(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1560is added to work around small timing inconsistencies of some operating
1561systems.
1562
1393=head3 Watcher-Specific Functions and Data Members 1563=head3 Watcher-Specific Functions and Data Members
1394 1564
1395=over 4 1565=over 4
1396 1566
1397=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1567=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
… …
1434=item const char *path [read-only] 1604=item const char *path [read-only]
1435 1605
1436The filesystem path that is being watched. 1606The filesystem path that is being watched.
1437 1607
1438=back 1608=back
1609
1610=head3 Examples
1439 1611
1440Example: Watch C</etc/passwd> for attribute changes. 1612Example: Watch C</etc/passwd> for attribute changes.
1441 1613
1442 static void 1614 static void
1443 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1615 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1456 } 1628 }
1457 1629
1458 ... 1630 ...
1459 ev_stat passwd; 1631 ev_stat passwd;
1460 1632
1461 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1633 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1462 ev_stat_start (loop, &passwd); 1634 ev_stat_start (loop, &passwd);
1635
1636Example: Like above, but additionally use a one-second delay so we do not
1637miss updates (however, frequent updates will delay processing, too, so
1638one might do the work both on C<ev_stat> callback invocation I<and> on
1639C<ev_timer> callback invocation).
1640
1641 static ev_stat passwd;
1642 static ev_timer timer;
1643
1644 static void
1645 timer_cb (EV_P_ ev_timer *w, int revents)
1646 {
1647 ev_timer_stop (EV_A_ w);
1648
1649 /* now it's one second after the most recent passwd change */
1650 }
1651
1652 static void
1653 stat_cb (EV_P_ ev_stat *w, int revents)
1654 {
1655 /* reset the one-second timer */
1656 ev_timer_again (EV_A_ &timer);
1657 }
1658
1659 ...
1660 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1661 ev_stat_start (loop, &passwd);
1662 ev_timer_init (&timer, timer_cb, 0., 1.01);
1463 1663
1464 1664
1465=head2 C<ev_idle> - when you've got nothing better to do... 1665=head2 C<ev_idle> - when you've got nothing better to do...
1466 1666
1467Idle watchers trigger events when no other events of the same or higher 1667Idle watchers trigger events when no other events of the same or higher
… …
1493kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1693kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1494believe me. 1694believe me.
1495 1695
1496=back 1696=back
1497 1697
1698=head3 Examples
1699
1498Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1700Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1499callback, free it. Also, use no error checking, as usual. 1701callback, free it. Also, use no error checking, as usual.
1500 1702
1501 static void 1703 static void
1502 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1704 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1503 { 1705 {
1504 free (w); 1706 free (w);
1505 // now do something you wanted to do when the program has 1707 // now do something you wanted to do when the program has
1506 // no longer asnything immediate to do. 1708 // no longer anything immediate to do.
1507 } 1709 }
1508 1710
1509 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1711 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1510 ev_idle_init (idle_watcher, idle_cb); 1712 ev_idle_init (idle_watcher, idle_cb);
1511 ev_idle_start (loop, idle_cb); 1713 ev_idle_start (loop, idle_cb);
… …
1553 1755
1554It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) 1756It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1555priority, to ensure that they are being run before any other watchers 1757priority, to ensure that they are being run before any other watchers
1556after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, 1758after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1557too) should not activate ("feed") events into libev. While libev fully 1759too) should not activate ("feed") events into libev. While libev fully
1558supports this, they will be called before other C<ev_check> watchers did 1760supports 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 1761did 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 1762(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 1763state until their C<ev_check> watcher ran (always remind yourself to
1562others). 1764coexist peacefully with others).
1563 1765
1564=head3 Watcher-Specific Functions and Data Members 1766=head3 Watcher-Specific Functions and Data Members
1565 1767
1566=over 4 1768=over 4
1567 1769
… …
1572Initialises and configures the prepare or check watcher - they have no 1774Initialises 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> 1775parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1574macros, but using them is utterly, utterly and completely pointless. 1776macros, but using them is utterly, utterly and completely pointless.
1575 1777
1576=back 1778=back
1779
1780=head3 Examples
1577 1781
1578There are a number of principal ways to embed other event loops or modules 1782There are a number of principal ways to embed other event loops or modules
1579into libev. Here are some ideas on how to include libadns into libev 1783into libev. Here are some ideas on how to include libadns into libev
1580(there is a Perl module named C<EV::ADNS> that does this, which you could 1784(there is a Perl module named C<EV::ADNS> that does this, which you could
1581use for an actually working example. Another Perl module named C<EV::Glib> 1785use for an actually working example. Another Perl module named C<EV::Glib>
… …
1750portable one. 1954portable one.
1751 1955
1752So when you want to use this feature you will always have to be prepared 1956So when you want to use this feature you will always have to be prepared
1753that you cannot get an embeddable loop. The recommended way to get around 1957that you cannot get an embeddable loop. The recommended way to get around
1754this is to have a separate variables for your embeddable loop, try to 1958this is to have a separate variables for your embeddable loop, try to
1755create it, and if that fails, use the normal loop for everything: 1959create it, and if that fails, use the normal loop for everything.
1960
1961=head3 Watcher-Specific Functions and Data Members
1962
1963=over 4
1964
1965=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1966
1967=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1968
1969Configures the watcher to embed the given loop, which must be
1970embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1971invoked automatically, otherwise it is the responsibility of the callback
1972to invoke it (it will continue to be called until the sweep has been done,
1973if you do not want thta, you need to temporarily stop the embed watcher).
1974
1975=item ev_embed_sweep (loop, ev_embed *)
1976
1977Make a single, non-blocking sweep over the embedded loop. This works
1978similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1979apropriate way for embedded loops.
1980
1981=item struct ev_loop *other [read-only]
1982
1983The embedded event loop.
1984
1985=back
1986
1987=head3 Examples
1988
1989Example: Try to get an embeddable event loop and embed it into the default
1990event loop. If that is not possible, use the default loop. The default
1991loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1992C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1993used).
1756 1994
1757 struct ev_loop *loop_hi = ev_default_init (0); 1995 struct ev_loop *loop_hi = ev_default_init (0);
1758 struct ev_loop *loop_lo = 0; 1996 struct ev_loop *loop_lo = 0;
1759 struct ev_embed embed; 1997 struct ev_embed embed;
1760 1998
… …
1771 ev_embed_start (loop_hi, &embed); 2009 ev_embed_start (loop_hi, &embed);
1772 } 2010 }
1773 else 2011 else
1774 loop_lo = loop_hi; 2012 loop_lo = loop_hi;
1775 2013
1776=head3 Watcher-Specific Functions and Data Members 2014Example: Check if kqueue is available but not recommended and create
2015a kqueue backend for use with sockets (which usually work with any
2016kqueue implementation). Store the kqueue/socket-only event loop in
2017C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1777 2018
1778=over 4 2019 struct ev_loop *loop = ev_default_init (0);
2020 struct ev_loop *loop_socket = 0;
2021 struct ev_embed embed;
2022
2023 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2024 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2025 {
2026 ev_embed_init (&embed, 0, loop_socket);
2027 ev_embed_start (loop, &embed);
2028 }
1779 2029
1780=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2030 if (!loop_socket)
2031 loop_socket = loop;
1781 2032
1782=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2033 // now use loop_socket for all sockets, and loop for everything else
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 *other [read-only]
1797
1798The embedded event loop.
1799
1800=back
1801 2034
1802 2035
1803=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2036=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1804 2037
1805Fork watchers are called when a C<fork ()> was detected (usually because 2038Fork watchers are called when a C<fork ()> was detected (usually because
… …
1821believe me. 2054believe me.
1822 2055
1823=back 2056=back
1824 2057
1825 2058
2059=head2 C<ev_async> - how to wake up another event loop
2060
2061In general, you cannot use an C<ev_loop> from multiple threads or other
2062asynchronous sources such as signal handlers (as opposed to multiple event
2063loops - those are of course safe to use in different threads).
2064
2065Sometimes, however, you need to wake up another event loop you do not
2066control, for example because it belongs to another thread. This is what
2067C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you
2068can signal it by calling C<ev_async_send>, which is thread- and signal
2069safe.
2070
2071This functionality is very similar to C<ev_signal> watchers, as signals,
2072too, are asynchronous in nature, and signals, too, will be compressed
2073(i.e. the number of callback invocations may be less than the number of
2074C<ev_async_sent> calls).
2075
2076Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not
2077just the default loop.
2078
2079=head3 Queueing
2080
2081C<ev_async> does not support queueing of data in any way. The reason
2082is that the author does not know of a simple (or any) algorithm for a
2083multiple-writer-single-reader queue that works in all cases and doesn't
2084need elaborate support such as pthreads.
2085
2086That means that if you want to queue data, you have to provide your own
2087queue. But at least I can tell you would implement locking around your
2088queue:
2089
2090=over 4
2091
2092=item queueing from a signal handler context
2093
2094To implement race-free queueing, you simply add to the queue in the signal
2095handler but you block the signal handler in the watcher callback. Here is an example that does that for
2096some fictitiuous SIGUSR1 handler:
2097
2098 static ev_async mysig;
2099
2100 static void
2101 sigusr1_handler (void)
2102 {
2103 sometype data;
2104
2105 // no locking etc.
2106 queue_put (data);
2107 ev_async_send (DEFAULT_ &mysig);
2108 }
2109
2110 static void
2111 mysig_cb (EV_P_ ev_async *w, int revents)
2112 {
2113 sometype data;
2114 sigset_t block, prev;
2115
2116 sigemptyset (&block);
2117 sigaddset (&block, SIGUSR1);
2118 sigprocmask (SIG_BLOCK, &block, &prev);
2119
2120 while (queue_get (&data))
2121 process (data);
2122
2123 if (sigismember (&prev, SIGUSR1)
2124 sigprocmask (SIG_UNBLOCK, &block, 0);
2125 }
2126
2127(Note: pthreads in theory requires you to use C<pthread_setmask>
2128instead of C<sigprocmask> when you use threads, but libev doesn't do it
2129either...).
2130
2131=item queueing from a thread context
2132
2133The strategy for threads is different, as you cannot (easily) block
2134threads but you can easily preempt them, so to queue safely you need to
2135employ a traditional mutex lock, such as in this pthread example:
2136
2137 static ev_async mysig;
2138 static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER;
2139
2140 static void
2141 otherthread (void)
2142 {
2143 // only need to lock the actual queueing operation
2144 pthread_mutex_lock (&mymutex);
2145 queue_put (data);
2146 pthread_mutex_unlock (&mymutex);
2147
2148 ev_async_send (DEFAULT_ &mysig);
2149 }
2150
2151 static void
2152 mysig_cb (EV_P_ ev_async *w, int revents)
2153 {
2154 pthread_mutex_lock (&mymutex);
2155
2156 while (queue_get (&data))
2157 process (data);
2158
2159 pthread_mutex_unlock (&mymutex);
2160 }
2161
2162=back
2163
2164
2165=head3 Watcher-Specific Functions and Data Members
2166
2167=over 4
2168
2169=item ev_async_init (ev_async *, callback)
2170
2171Initialises and configures the async watcher - it has no parameters of any
2172kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless,
2173believe me.
2174
2175=item ev_async_send (loop, ev_async *)
2176
2177Sends/signals/activates the given C<ev_async> watcher, that is, feeds
2178an C<EV_ASYNC> event on the watcher into the event loop. Unlike
2179C<ev_feed_event>, this call is safe to do in other threads, signal or
2180similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding
2181section below on what exactly this means).
2182
2183This call incurs the overhead of a syscall only once per loop iteration,
2184so while the overhead might be noticable, it doesn't apply to repeated
2185calls to C<ev_async_send>.
2186
2187=back
2188
2189
1826=head1 OTHER FUNCTIONS 2190=head1 OTHER FUNCTIONS
1827 2191
1828There are some other functions of possible interest. Described. Here. Now. 2192There are some other functions of possible interest. Described. Here. Now.
1829 2193
1830=over 4 2194=over 4
… …
2057Example: Define a class with an IO and idle watcher, start one of them in 2421Example: Define a class with an IO and idle watcher, start one of them in
2058the constructor. 2422the constructor.
2059 2423
2060 class myclass 2424 class myclass
2061 { 2425 {
2062 ev_io io; void io_cb (ev::io &w, int revents); 2426 ev::io io; void io_cb (ev::io &w, int revents);
2063 ev_idle idle void idle_cb (ev::idle &w, int revents); 2427 ev:idle idle void idle_cb (ev::idle &w, int revents);
2064 2428
2065 myclass (); 2429 myclass (int fd)
2066 }
2067
2068 myclass::myclass (int fd)
2069 { 2430 {
2070 io .set <myclass, &myclass::io_cb > (this); 2431 io .set <myclass, &myclass::io_cb > (this);
2071 idle.set <myclass, &myclass::idle_cb> (this); 2432 idle.set <myclass, &myclass::idle_cb> (this);
2072 2433
2073 io.start (fd, ev::READ); 2434 io.start (fd, ev::READ);
2435 }
2074 } 2436 };
2075 2437
2076 2438
2077=head1 MACRO MAGIC 2439=head1 MACRO MAGIC
2078 2440
2079Libev can be compiled with a variety of options, the most fundamantal 2441Libev can be compiled with a variety of options, the most fundamantal
… …
2253runtime if successful). Otherwise no use of the realtime clock option will 2615runtime if successful). Otherwise no use of the realtime clock option will
2254be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2616be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2255(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the 2617(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2256note about libraries in the description of C<EV_USE_MONOTONIC>, though. 2618note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2257 2619
2620=item EV_USE_NANOSLEEP
2621
2622If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2623and will use it for delays. Otherwise it will use C<select ()>.
2624
2258=item EV_USE_SELECT 2625=item EV_USE_SELECT
2259 2626
2260If undefined or defined to be C<1>, libev will compile in support for the 2627If 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 2628C<select>(2) backend. No attempt at autodetection will be done: if no
2262other method takes over, select will be it. Otherwise the select backend 2629other method takes over, select will be it. Otherwise the select backend
… …
2279wants osf handles on win32 (this is the case when the select to 2646wants osf handles on win32 (this is the case when the select to
2280be used is the winsock select). This means that it will call 2647be 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, 2648C<_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 2649it is assumed that all these functions actually work on fds, even
2283on win32. Should not be defined on non-win32 platforms. 2650on win32. Should not be defined on non-win32 platforms.
2651
2652=item EV_FD_TO_WIN32_HANDLE
2653
2654If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2655file descriptors to socket handles. When not defining this symbol (the
2656default), then libev will call C<_get_osfhandle>, which is usually
2657correct. In some cases, programs use their own file descriptor management,
2658in which case they can provide this function to map fds to socket handles.
2284 2659
2285=item EV_USE_POLL 2660=item EV_USE_POLL
2286 2661
2287If defined to be C<1>, libev will compile in support for the C<poll>(2) 2662If defined to be C<1>, libev will compile in support for the C<poll>(2)
2288backend. Otherwise it will be enabled on non-win32 platforms. It 2663backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2322 2697
2323If defined to be C<1>, libev will compile in support for the Linux inotify 2698If defined to be C<1>, libev will compile in support for the Linux inotify
2324interface to speed up C<ev_stat> watchers. Its actual availability will 2699interface to speed up C<ev_stat> watchers. Its actual availability will
2325be detected at runtime. 2700be detected at runtime.
2326 2701
2702=item EV_ATOMIC_T
2703
2704Libev requires an integer type (suitable for storing C<0> or C<1>) whose
2705access is atomic with respect to other threads or signal contexts. No such
2706type is easily found in the C language, so you can provide your own type
2707that you know is safe for your purposes. It is used both for signal handler "locking"
2708as well as for signal and thread safety in C<ev_async> watchers.
2709
2710In the absense of this define, libev will use C<sig_atomic_t volatile>
2711(from F<signal.h>), which is usually good enough on most platforms.
2712
2327=item EV_H 2713=item EV_H
2328 2714
2329The name of the F<ev.h> header file used to include it. The default if 2715The name of the F<ev.h> header file used to include it. The default if
2330undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2716undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2331can be used to virtually rename the F<ev.h> header file in case of conflicts. 2717used to virtually rename the F<ev.h> header file in case of conflicts.
2332 2718
2333=item EV_CONFIG_H 2719=item EV_CONFIG_H
2334 2720
2335If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2721If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2336F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2722F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2337C<EV_H>, above. 2723C<EV_H>, above.
2338 2724
2339=item EV_EVENT_H 2725=item EV_EVENT_H
2340 2726
2341Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2727Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2342of how the F<event.h> header can be found. 2728of how the F<event.h> header can be found, the default is C<"event.h">.
2343 2729
2344=item EV_PROTOTYPES 2730=item EV_PROTOTYPES
2345 2731
2346If defined to be C<0>, then F<ev.h> will not define any function 2732If defined to be C<0>, then F<ev.h> will not define any function
2347prototypes, but still define all the structs and other symbols. This is 2733prototypes, but still define all the structs and other symbols. This is
… …
2398=item EV_FORK_ENABLE 2784=item EV_FORK_ENABLE
2399 2785
2400If undefined or defined to be C<1>, then fork watchers are supported. If 2786If undefined or defined to be C<1>, then fork watchers are supported. If
2401defined to be C<0>, then they are not. 2787defined to be C<0>, then they are not.
2402 2788
2789=item EV_ASYNC_ENABLE
2790
2791If undefined or defined to be C<1>, then async watchers are supported. If
2792defined to be C<0>, then they are not.
2793
2403=item EV_MINIMAL 2794=item EV_MINIMAL
2404 2795
2405If you need to shave off some kilobytes of code at the expense of some 2796If you need to shave off some kilobytes of code at the expense of some
2406speed, define this symbol to C<1>. Currently only used for gcc to override 2797speed, define this symbol to C<1>. Currently only used for gcc to override
2407some inlining decisions, saves roughly 30% codesize of amd64. 2798some inlining decisions, saves roughly 30% codesize of amd64.
… …
2413than enough. If you need to manage thousands of children you might want to 2804than enough. If you need to manage thousands of children you might want to
2414increase this value (I<must> be a power of two). 2805increase this value (I<must> be a power of two).
2415 2806
2416=item EV_INOTIFY_HASHSIZE 2807=item EV_INOTIFY_HASHSIZE
2417 2808
2418C<ev_staz> watchers use a small hash table to distribute workload by 2809C<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>), 2810inotify 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> 2811usually 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 2812watchers you might want to increase this value (I<must> be a power of
2422two). 2813two).
2423 2814
… …
2440 2831
2441=item ev_set_cb (ev, cb) 2832=item ev_set_cb (ev, cb)
2442 2833
2443Can be used to change the callback member declaration in each watcher, 2834Can 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 2835and the way callbacks are invoked and set. Must expand to a struct member
2445definition and a statement, respectively. See the F<ev.c> header file for 2836definition and a statement, respectively. See the F<ev.h> header file for
2446their default definitions. One possible use for overriding these is to 2837their 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 2838avoid the C<struct ev_loop *> as first argument in all cases, or to use
2448method calls instead of plain function calls in C++. 2839method calls instead of plain function calls in C++.
2449 2840
2450=head2 EXPORTED API SYMBOLS 2841=head2 EXPORTED API SYMBOLS
… …
2519 2910
2520=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2911=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2521 2912
2522This means that, when you have a watcher that triggers in one hour and 2913This means that, when you have a watcher that triggers in one hour and
2523there are 100 watchers that would trigger before that then inserting will 2914there are 100 watchers that would trigger before that then inserting will
2524have to skip those 100 watchers. 2915have to skip roughly seven (C<ld 100>) of these watchers.
2525 2916
2526=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2917=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2527 2918
2528That means that for changing a timer costs less than removing/adding them 2919That 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. 2920as only the relative motion in the event queue has to be paid for.
2530 2921
2531=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2922=item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1)
2532 2923
2533These just add the watcher into an array or at the head of a list. 2924These just add the watcher into an array or at the head of a list.
2925
2534=item Stopping check/prepare/idle watchers: O(1) 2926=item Stopping check/prepare/idle/fork/async watchers: O(1)
2535 2927
2536=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2928=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2537 2929
2538These watchers are stored in lists then need to be walked to find the 2930These watchers are stored in lists then need to be walked to find the
2539correct watcher to remove. The lists are usually short (you don't usually 2931correct watcher to remove. The lists are usually short (you don't usually
2540have many watchers waiting for the same fd or signal). 2932have many watchers waiting for the same fd or signal).
2541 2933
2542=item Finding the next timer per loop iteration: O(1) 2934=item Finding the next timer in each loop iteration: O(1)
2935
2936By virtue of using a binary heap, the next timer is always found at the
2937beginning of the storage array.
2543 2938
2544=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2939=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2545 2940
2546A change means an I/O watcher gets started or stopped, which requires 2941A change means an I/O watcher gets started or stopped, which requires
2547libev to recalculate its status (and possibly tell the kernel). 2942libev to recalculate its status (and possibly tell the kernel, depending
2943on backend and wether C<ev_io_set> was used).
2548 2944
2549=item Activating one watcher: O(1) 2945=item Activating one watcher (putting it into the pending state): O(1)
2550 2946
2551=item Priority handling: O(number_of_priorities) 2947=item Priority handling: O(number_of_priorities)
2552 2948
2553Priorities are implemented by allocating some space for each 2949Priorities are implemented by allocating some space for each
2554priority. When doing priority-based operations, libev usually has to 2950priority. When doing priority-based operations, libev usually has to
2555linearly search all the priorities. 2951linearly search all the priorities, but starting/stopping and activating
2952watchers becomes O(1) w.r.t. priority handling.
2953
2954=item Sending an ev_async: O(1)
2955
2956=item Processing ev_async_send: O(number_of_async_watchers)
2957
2958=item Processing signals: O(max_signal_number)
2959
2960Sending involves a syscall I<iff> there were no other C<ev_async_send>
2961calls in the current loop iteration. Checking for async and signal events
2962involves iterating over all running async watchers or all signal numbers.
2556 2963
2557=back 2964=back
2558 2965
2559 2966
2967=head1 Win32 platform limitations and workarounds
2968
2969Win32 doesn't support any of the standards (e.g. POSIX) that libev
2970requires, and its I/O model is fundamentally incompatible with the POSIX
2971model. Libev still offers limited functionality on this platform in
2972the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2973descriptors. This only applies when using Win32 natively, not when using
2974e.g. cygwin.
2975
2976There is no supported compilation method available on windows except
2977embedding it into other applications.
2978
2979Due to the many, low, and arbitrary limits on the win32 platform and the
2980abysmal performance of winsockets, using a large number of sockets is not
2981recommended (and not reasonable). If your program needs to use more than
2982a hundred or so sockets, then likely it needs to use a totally different
2983implementation for windows, as libev offers the POSIX model, which cannot
2984be implemented efficiently on windows (microsoft monopoly games).
2985
2986=over 4
2987
2988=item The winsocket select function
2989
2990The winsocket C<select> function doesn't follow POSIX in that it requires
2991socket I<handles> and not socket I<file descriptors>. This makes select
2992very inefficient, and also requires a mapping from file descriptors
2993to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2994C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2995symbols for more info.
2996
2997The configuration for a "naked" win32 using the microsoft runtime
2998libraries and raw winsocket select is:
2999
3000 #define EV_USE_SELECT 1
3001 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
3002
3003Note that winsockets handling of fd sets is O(n), so you can easily get a
3004complexity in the O(n²) range when using win32.
3005
3006=item Limited number of file descriptors
3007
3008Windows has numerous arbitrary (and low) limits on things. Early versions
3009of winsocket's select only supported waiting for a max. of C<64> handles
3010(probably owning to the fact that all windows kernels can only wait for
3011C<64> things at the same time internally; microsoft recommends spawning a
3012chain of threads and wait for 63 handles and the previous thread in each).
3013
3014Newer versions support more handles, but you need to define C<FD_SETSIZE>
3015to some high number (e.g. C<2048>) before compiling the winsocket select
3016call (which might be in libev or elsewhere, for example, perl does its own
3017select emulation on windows).
3018
3019Another limit is the number of file descriptors in the microsoft runtime
3020libraries, which by default is C<64> (there must be a hidden I<64> fetish
3021or something like this inside microsoft). You can increase this by calling
3022C<_setmaxstdio>, which can increase this limit to C<2048> (another
3023arbitrary limit), but is broken in many versions of the microsoft runtime
3024libraries.
3025
3026This might get you to about C<512> or C<2048> sockets (depending on
3027windows version and/or the phase of the moon). To get more, you need to
3028wrap all I/O functions and provide your own fd management, but the cost of
3029calling select (O(n²)) will likely make this unworkable.
3030
3031=back
3032
3033
2560=head1 AUTHOR 3034=head1 AUTHOR
2561 3035
2562Marc Lehmann <libev@schmorp.de>. 3036Marc Lehmann <libev@schmorp.de>.
2563 3037

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