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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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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.
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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
102to the C<double> type in C, and when you need to do any calculations on 102to the C<double> type in C, and when you need to do any calculations on
103it, you should treat it as such. 103it, you should treat it as some floatingpoint value. Unlike the name
104component C<stamp> might indicate, it is also used for time differences
105throughout libev.
104 106
105=head1 GLOBAL FUNCTIONS 107=head1 GLOBAL FUNCTIONS
106 108
107These functions can be called anytime, even before initialising the 109These functions can be called anytime, even before initialising the
108library in any way. 110library in any way.
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113 115
114Returns 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
115C<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
116you actually want to know. 118you actually want to know.
117 119
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
118=item int ev_version_major () 126=item int ev_version_major ()
119 127
120=item int ev_version_minor () 128=item int ev_version_minor ()
121 129
122You can find out the major and minor version numbers of the library 130You can find out the major and minor ABI version numbers of the library
123you linked against by calling the functions C<ev_version_major> and 131you linked against by calling the functions C<ev_version_major> and
124C<ev_version_minor>. If you want, you can compare against the global 132C<ev_version_minor>. If you want, you can compare against the global
125symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 133symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126version of the library your program was compiled against. 134version of the library your program was compiled against.
127 135
136These version numbers refer to the ABI version of the library, not the
137release version.
138
128Usually, it's a good idea to terminate if the major versions mismatch, 139Usually, it's a good idea to terminate if the major versions mismatch,
129as this indicates an incompatible change. Minor versions are usually 140as this indicates an incompatible change. Minor versions are usually
130compatible to older versions, so a larger minor version alone is usually 141compatible to older versions, so a larger minor version alone is usually
131not a problem. 142not a problem.
132 143
133Example: Make sure we haven't accidentally been linked against the wrong 144Example: Make sure we haven't accidentally been linked against the wrong
134version. 145version.
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295=item C<EVBACKEND_SELECT> (value 1, portable select backend) 306=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296 307
297This is your standard select(2) backend. Not I<completely> standard, as 308This is your standard select(2) backend. Not I<completely> standard, as
298libev tries to roll its own fd_set with no limits on the number of fds, 309libev tries to roll its own fd_set with no limits on the number of fds,
299but if that fails, expect a fairly low limit on the number of fds when 310but if that fails, expect a fairly low limit on the number of fds when
300using this backend. It doesn't scale too well (O(highest_fd)), but its usually 311using this backend. It doesn't scale too well (O(highest_fd)), but its
301the fastest backend for a low number of fds. 312usually the fastest backend for a low number of (low-numbered :) fds.
313
314To get good performance out of this backend you need a high amount of
315parallelity (most of the file descriptors should be busy). If you are
316writing a server, you should C<accept ()> in a loop to accept as many
317connections as possible during one iteration. You might also want to have
318a look at C<ev_set_io_collect_interval ()> to increase the amount of
319readyness notifications you get per iteration.
302 320
303=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) 321=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304 322
305And this is your standard poll(2) backend. It's more complicated than 323And this is your standard poll(2) backend. It's more complicated
306select, but handles sparse fds better and has no artificial limit on the 324than select, but handles sparse fds better and has no artificial
307number of fds you can use (except it will slow down considerably with a 325limit on the number of fds you can use (except it will slow down
308lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 326considerably with a lot of inactive fds). It scales similarly to select,
327i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
328performance tips.
309 329
310=item C<EVBACKEND_EPOLL> (value 4, Linux) 330=item C<EVBACKEND_EPOLL> (value 4, Linux)
311 331
312For few fds, this backend is a bit little slower than poll and select, 332For few fds, this backend is a bit little slower than poll and select,
313but it scales phenomenally better. While poll and select usually scale like 333but it scales phenomenally better. While poll and select usually scale
314O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 334like O(total_fds) where n is the total number of fds (or the highest fd),
315either O(1) or O(active_fds). 335epoll scales either O(1) or O(active_fds). The epoll design has a number
336of shortcomings, such as silently dropping events in some hard-to-detect
337cases and rewiring a syscall per fd change, no fork support and bad
338support for dup.
316 339
317While stopping and starting an I/O watcher in the same iteration will 340While stopping, setting and starting an I/O watcher in the same iteration
318result in some caching, there is still a syscall per such incident 341will result in some caching, there is still a syscall per such incident
319(because the fd could point to a different file description now), so its 342(because the fd could point to a different file description now), so its
320best to avoid that. Also, dup()ed file descriptors might not work very 343best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321well if you register events for both fds. 344very well if you register events for both fds.
322 345
323Please note that epoll sometimes generates spurious notifications, so you 346Please note that epoll sometimes generates spurious notifications, so you
324need to use non-blocking I/O or other means to avoid blocking when no data 347need to use non-blocking I/O or other means to avoid blocking when no data
325(or space) is available. 348(or space) is available.
326 349
350Best performance from this backend is achieved by not unregistering all
351watchers for a file descriptor until it has been closed, if possible, i.e.
352keep at least one watcher active per fd at all times.
353
354While nominally embeddeble in other event loops, this feature is broken in
355all kernel versions tested so far.
356
327=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 357=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328 358
329Kqueue deserves special mention, as at the time of this writing, it 359Kqueue deserves special mention, as at the time of this writing, it
330was broken on all BSDs except NetBSD (usually it doesn't work with 360was broken on all BSDs except NetBSD (usually it doesn't work reliably
331anything but sockets and pipes, except on Darwin, where of course its 361with anything but sockets and pipes, except on Darwin, where of course
332completely useless). For this reason its not being "autodetected" 362it's completely useless). For this reason it's not being "autodetected"
333unless you explicitly specify it explicitly in the flags (i.e. using 363unless you explicitly specify it explicitly in the flags (i.e. using
334C<EVBACKEND_KQUEUE>). 364C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
365system like NetBSD.
366
367You still can embed kqueue into a normal poll or select backend and use it
368only for sockets (after having made sure that sockets work with kqueue on
369the target platform). See C<ev_embed> watchers for more info.
335 370
336It scales in the same way as the epoll backend, but the interface to the 371It scales in the same way as the epoll backend, but the interface to the
337kernel is more efficient (which says nothing about its actual speed, of 372kernel is more efficient (which says nothing about its actual speed, of
338course). While starting and stopping an I/O watcher does not cause an 373course). While stopping, setting and starting an I/O watcher does never
339extra syscall as with epoll, it still adds up to four event changes per 374cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340incident, so its best to avoid that. 375two event changes per incident, support for C<fork ()> is very bad and it
376drops fds silently in similarly hard-to-detect cases.
377
378This backend usually performs well under most conditions.
379
380While nominally embeddable in other event loops, this doesn't work
381everywhere, so you might need to test for this. And since it is broken
382almost everywhere, you should only use it when you have a lot of sockets
383(for which it usually works), by embedding it into another event loop
384(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
385sockets.
341 386
342=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) 387=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343 388
344This is not implemented yet (and might never be). 389This is not implemented yet (and might never be, unless you send me an
390implementation). According to reports, C</dev/poll> only supports sockets
391and is not embeddable, which would limit the usefulness of this backend
392immensely.
345 393
346=item C<EVBACKEND_PORT> (value 32, Solaris 10) 394=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347 395
348This uses the Solaris 10 port mechanism. As with everything on Solaris, 396This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349it's really slow, but it still scales very well (O(active_fds)). 397it's really slow, but it still scales very well (O(active_fds)).
350 398
351Please note that solaris ports can result in a lot of spurious 399Please note that solaris event ports can deliver a lot of spurious
352notifications, so you need to use non-blocking I/O or other means to avoid 400notifications, so you need to use non-blocking I/O or other means to avoid
353blocking when no data (or space) is available. 401blocking when no data (or space) is available.
402
403While this backend scales well, it requires one system call per active
404file descriptor per loop iteration. For small and medium numbers of file
405descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406might perform better.
407
408On the positive side, ignoring the spurious readyness notifications, this
409backend actually performed to specification in all tests and is fully
410embeddable, which is a rare feat among the OS-specific backends.
354 411
355=item C<EVBACKEND_ALL> 412=item C<EVBACKEND_ALL>
356 413
357Try all backends (even potentially broken ones that wouldn't be tried 414Try all backends (even potentially broken ones that wouldn't be tried
358with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as 415with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 416C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
360 417
418It is definitely not recommended to use this flag.
419
361=back 420=back
362 421
363If one or more of these are ored into the flags value, then only these 422If one or more of these are ored into the flags value, then only these
364backends will be tried (in the reverse order as given here). If none are 423backends will be tried (in the reverse order as listed here). If none are
365specified, most compiled-in backend will be tried, usually in reverse 424specified, all backends in C<ev_recommended_backends ()> will be tried.
366order of their flag values :)
367 425
368The most typical usage is like this: 426The most typical usage is like this:
369 427
370 if (!ev_default_loop (0)) 428 if (!ev_default_loop (0))
371 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); 429 fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
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399Destroys the default loop again (frees all memory and kernel state 457Destroys the default loop again (frees all memory and kernel state
400etc.). None of the active event watchers will be stopped in the normal 458etc.). None of the active event watchers will be stopped in the normal
401sense, so e.g. C<ev_is_active> might still return true. It is your 459sense, so e.g. C<ev_is_active> might still return true. It is your
402responsibility to either stop all watchers cleanly yoursef I<before> 460responsibility to either stop all watchers cleanly yoursef I<before>
403calling this function, or cope with the fact afterwards (which is usually 461calling this function, or cope with the fact afterwards (which is usually
404the easiest thing, youc na just ignore the watchers and/or C<free ()> them 462the easiest thing, you can just ignore the watchers and/or C<free ()> them
405for example). 463for example).
464
465Note that certain global state, such as signal state, will not be freed by
466this function, and related watchers (such as signal and child watchers)
467would need to be stopped manually.
468
469In general it is not advisable to call this function except in the
470rare occasion where you really need to free e.g. the signal handling
471pipe fds. If you need dynamically allocated loops it is better to use
472C<ev_loop_new> and C<ev_loop_destroy>).
406 473
407=item ev_loop_destroy (loop) 474=item ev_loop_destroy (loop)
408 475
409Like C<ev_default_destroy>, but destroys an event loop created by an 476Like C<ev_default_destroy>, but destroys an event loop created by an
410earlier call to C<ev_loop_new>. 477earlier call to C<ev_loop_new>.
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455 522
456Returns the current "event loop time", which is the time the event loop 523Returns the current "event loop time", which is the time the event loop
457received events and started processing them. This timestamp does not 524received events and started processing them. This timestamp does not
458change as long as callbacks are being processed, and this is also the base 525change as long as callbacks are being processed, and this is also the base
459time used for relative timers. You can treat it as the timestamp of the 526time used for relative timers. You can treat it as the timestamp of the
460event occuring (or more correctly, libev finding out about it). 527event occurring (or more correctly, libev finding out about it).
461 528
462=item ev_loop (loop, int flags) 529=item ev_loop (loop, int flags)
463 530
464Finally, this is it, the event handler. This function usually is called 531Finally, this is it, the event handler. This function usually is called
465after you initialised all your watchers and you want to start handling 532after you initialised all your watchers and you want to start handling
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487usually a better approach for this kind of thing. 554usually a better approach for this kind of thing.
488 555
489Here are the gory details of what C<ev_loop> does: 556Here are the gory details of what C<ev_loop> does:
490 557
491 - Before the first iteration, call any pending watchers. 558 - Before the first iteration, call any pending watchers.
492 * If there are no active watchers (reference count is zero), return. 559 * If EVFLAG_FORKCHECK was used, check for a fork.
493 - Queue all prepare watchers and then call all outstanding watchers. 560 - If a fork was detected, queue and call all fork watchers.
561 - Queue and call all prepare watchers.
494 - If we have been forked, recreate the kernel state. 562 - If we have been forked, recreate the kernel state.
495 - Update the kernel state with all outstanding changes. 563 - Update the kernel state with all outstanding changes.
496 - Update the "event loop time". 564 - Update the "event loop time".
497 - Calculate for how long to block. 565 - Calculate for how long to sleep or block, if at all
566 (active idle watchers, EVLOOP_NONBLOCK or not having
567 any active watchers at all will result in not sleeping).
568 - Sleep if the I/O and timer collect interval say so.
498 - Block the process, waiting for any events. 569 - Block the process, waiting for any events.
499 - Queue all outstanding I/O (fd) events. 570 - Queue all outstanding I/O (fd) events.
500 - Update the "event loop time" and do time jump handling. 571 - Update the "event loop time" and do time jump handling.
501 - Queue all outstanding timers. 572 - Queue all outstanding timers.
502 - Queue all outstanding periodics. 573 - Queue all outstanding periodics.
503 - If no events are pending now, queue all idle watchers. 574 - If no events are pending now, queue all idle watchers.
504 - Queue all check watchers. 575 - Queue all check watchers.
505 - Call all queued watchers in reverse order (i.e. check watchers first). 576 - Call all queued watchers in reverse order (i.e. check watchers first).
506 Signals and child watchers are implemented as I/O watchers, and will 577 Signals and child watchers are implemented as I/O watchers, and will
507 be handled here by queueing them when their watcher gets executed. 578 be handled here by queueing them when their watcher gets executed.
508 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 579 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
509 were used, return, otherwise continue with step *. 580 were used, or there are no active watchers, return, otherwise
581 continue with step *.
510 582
511Example: Queue some jobs and then loop until no events are outsanding 583Example: Queue some jobs and then loop until no events are outstanding
512anymore. 584anymore.
513 585
514 ... queue jobs here, make sure they register event watchers as long 586 ... queue jobs here, make sure they register event watchers as long
515 ... as they still have work to do (even an idle watcher will do..) 587 ... as they still have work to do (even an idle watcher will do..)
516 ev_loop (my_loop, 0); 588 ev_loop (my_loop, 0);
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520 592
521Can be used to make a call to C<ev_loop> return early (but only after it 593Can be used to make a call to C<ev_loop> return early (but only after it
522has processed all outstanding events). The C<how> argument must be either 594has processed all outstanding events). The C<how> argument must be either
523C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 595C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
524C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 596C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
597
598This "unloop state" will be cleared when entering C<ev_loop> again.
525 599
526=item ev_ref (loop) 600=item ev_ref (loop)
527 601
528=item ev_unref (loop) 602=item ev_unref (loop)
529 603
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534returning, ev_unref() after starting, and ev_ref() before stopping it. For 608returning, ev_unref() after starting, and ev_ref() before stopping it. For
535example, libev itself uses this for its internal signal pipe: It is not 609example, libev itself uses this for its internal signal pipe: It is not
536visible to the libev user and should not keep C<ev_loop> from exiting if 610visible to the libev user and should not keep C<ev_loop> from exiting if
537no event watchers registered by it are active. It is also an excellent 611no event watchers registered by it are active. It is also an excellent
538way to do this for generic recurring timers or from within third-party 612way to do this for generic recurring timers or from within third-party
539libraries. Just remember to I<unref after start> and I<ref before stop>. 613libraries. Just remember to I<unref after start> and I<ref before stop>
614(but only if the watcher wasn't active before, or was active before,
615respectively).
540 616
541Example: Create a signal watcher, but keep it from keeping C<ev_loop> 617Example: Create a signal watcher, but keep it from keeping C<ev_loop>
542running when nothing else is active. 618running when nothing else is active.
543 619
544 struct ev_signal exitsig; 620 struct ev_signal exitsig;
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548 624
549Example: For some weird reason, unregister the above signal handler again. 625Example: For some weird reason, unregister the above signal handler again.
550 626
551 ev_ref (loop); 627 ev_ref (loop);
552 ev_signal_stop (loop, &exitsig); 628 ev_signal_stop (loop, &exitsig);
629
630=item ev_set_io_collect_interval (loop, ev_tstamp interval)
631
632=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
633
634These advanced functions influence the time that libev will spend waiting
635for events. Both are by default C<0>, meaning that libev will try to
636invoke timer/periodic callbacks and I/O callbacks with minimum latency.
637
638Setting these to a higher value (the C<interval> I<must> be >= C<0>)
639allows libev to delay invocation of I/O and timer/periodic callbacks to
640increase efficiency of loop iterations.
641
642The background is that sometimes your program runs just fast enough to
643handle one (or very few) event(s) per loop iteration. While this makes
644the program responsive, it also wastes a lot of CPU time to poll for new
645events, especially with backends like C<select ()> which have a high
646overhead for the actual polling but can deliver many events at once.
647
648By setting a higher I<io collect interval> you allow libev to spend more
649time collecting I/O events, so you can handle more events per iteration,
650at the cost of increasing latency. Timeouts (both C<ev_periodic> and
651C<ev_timer>) will be not affected. Setting this to a non-null value will
652introduce an additional C<ev_sleep ()> call into most loop iterations.
653
654Likewise, by setting a higher I<timeout collect interval> you allow libev
655to spend more time collecting timeouts, at the expense of increased
656latency (the watcher callback will be called later). C<ev_io> watchers
657will not be affected. Setting this to a non-null value will not introduce
658any overhead in libev.
659
660Many (busy) programs can usually benefit by setting the io collect
661interval to a value near C<0.1> or so, which is often enough for
662interactive servers (of course not for games), likewise for timeouts. It
663usually doesn't make much sense to set it to a lower value than C<0.01>,
664as this approsaches the timing granularity of most systems.
553 665
554=back 666=back
555 667
556 668
557=head1 ANATOMY OF A WATCHER 669=head1 ANATOMY OF A WATCHER
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883In general you can register as many read and/or write event watchers per 995In general you can register as many read and/or write event watchers per
884fd as you want (as long as you don't confuse yourself). Setting all file 996fd as you want (as long as you don't confuse yourself). Setting all file
885descriptors to non-blocking mode is also usually a good idea (but not 997descriptors to non-blocking mode is also usually a good idea (but not
886required if you know what you are doing). 998required if you know what you are doing).
887 999
888You have to be careful with dup'ed file descriptors, though. Some backends
889(the linux epoll backend is a notable example) cannot handle dup'ed file
890descriptors correctly if you register interest in two or more fds pointing
891to the same underlying file/socket/etc. description (that is, they share
892the same underlying "file open").
893
894If you must do this, then force the use of a known-to-be-good backend 1000If you must do this, then force the use of a known-to-be-good backend
895(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1001(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
896C<EVBACKEND_POLL>). 1002C<EVBACKEND_POLL>).
897 1003
898Another thing you have to watch out for is that it is quite easy to 1004Another thing you have to watch out for is that it is quite easy to
… …
908play around with an Xlib connection), then you have to seperately re-test 1014play around with an Xlib connection), then you have to seperately re-test
909whether a file descriptor is really ready with a known-to-be good interface 1015whether a file descriptor is really ready with a known-to-be good interface
910such as poll (fortunately in our Xlib example, Xlib already does this on 1016such as poll (fortunately in our Xlib example, Xlib already does this on
911its own, so its quite safe to use). 1017its own, so its quite safe to use).
912 1018
1019=head3 The special problem of disappearing file descriptors
1020
1021Some backends (e.g. kqueue, epoll) need to be told about closing a file
1022descriptor (either by calling C<close> explicitly or by any other means,
1023such as C<dup>). The reason is that you register interest in some file
1024descriptor, but when it goes away, the operating system will silently drop
1025this interest. If another file descriptor with the same number then is
1026registered with libev, there is no efficient way to see that this is, in
1027fact, a different file descriptor.
1028
1029To avoid having to explicitly tell libev about such cases, libev follows
1030the following policy: Each time C<ev_io_set> is being called, libev
1031will assume that this is potentially a new file descriptor, otherwise
1032it is assumed that the file descriptor stays the same. That means that
1033you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
1034descriptor even if the file descriptor number itself did not change.
1035
1036This is how one would do it normally anyway, the important point is that
1037the libev application should not optimise around libev but should leave
1038optimisations to libev.
1039
1040=head3 The special problem of dup'ed file descriptors
1041
1042Some backends (e.g. epoll), cannot register events for file descriptors,
1043but only events for the underlying file descriptions. That means when you
1044have C<dup ()>'ed file descriptors or weirder constellations, and register
1045events for them, only one file descriptor might actually receive events.
1046
1047There is no workaround possible except not registering events
1048for potentially C<dup ()>'ed file descriptors, or to resort to
1049C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1050
1051=head3 The special problem of fork
1052
1053Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1054useless behaviour. Libev fully supports fork, but needs to be told about
1055it in the child.
1056
1057To support fork in your programs, you either have to call
1058C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1059enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1060C<EVBACKEND_POLL>.
1061
1062
1063=head3 Watcher-Specific Functions
1064
913=over 4 1065=over 4
914 1066
915=item ev_io_init (ev_io *, callback, int fd, int events) 1067=item ev_io_init (ev_io *, callback, int fd, int events)
916 1068
917=item ev_io_set (ev_io *, int fd, int events) 1069=item ev_io_set (ev_io *, int fd, int events)
… …
927=item int events [read-only] 1079=item int events [read-only]
928 1080
929The events being watched. 1081The events being watched.
930 1082
931=back 1083=back
1084
1085=head3 Examples
932 1086
933Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1087Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
934readable, but only once. Since it is likely line-buffered, you could 1088readable, but only once. Since it is likely line-buffered, you could
935attempt to read a whole line in the callback. 1089attempt to read a whole line in the callback.
936 1090
… …
969 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1123 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
970 1124
971The callback is guarenteed to be invoked only when its timeout has passed, 1125The callback is guarenteed to be invoked only when its timeout has passed,
972but if multiple timers become ready during the same loop iteration then 1126but if multiple timers become ready during the same loop iteration then
973order of execution is undefined. 1127order of execution is undefined.
1128
1129=head3 Watcher-Specific Functions and Data Members
974 1130
975=over 4 1131=over 4
976 1132
977=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1133=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
978 1134
… …
1032or C<ev_timer_again> is called and determines the next timeout (if any), 1188or C<ev_timer_again> is called and determines the next timeout (if any),
1033which is also when any modifications are taken into account. 1189which is also when any modifications are taken into account.
1034 1190
1035=back 1191=back
1036 1192
1193=head3 Examples
1194
1037Example: Create a timer that fires after 60 seconds. 1195Example: Create a timer that fires after 60 seconds.
1038 1196
1039 static void 1197 static void
1040 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1198 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1041 { 1199 {
… …
1084 1242
1085As with timers, the callback is guarenteed to be invoked only when the 1243As with timers, the callback is guarenteed to be invoked only when the
1086time (C<at>) has been passed, but if multiple periodic timers become ready 1244time (C<at>) has been passed, but if multiple periodic timers become ready
1087during the same loop iteration then order of execution is undefined. 1245during the same loop iteration then order of execution is undefined.
1088 1246
1247=head3 Watcher-Specific Functions and Data Members
1248
1089=over 4 1249=over 4
1090 1250
1091=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) 1251=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1092 1252
1093=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) 1253=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
… …
1189 1349
1190The current reschedule callback, or C<0>, if this functionality is 1350The current reschedule callback, or C<0>, if this functionality is
1191switched off. Can be changed any time, but changes only take effect when 1351switched off. Can be changed any time, but changes only take effect when
1192the periodic timer fires or C<ev_periodic_again> is being called. 1352the periodic timer fires or C<ev_periodic_again> is being called.
1193 1353
1354=item ev_tstamp at [read-only]
1355
1356When active, contains the absolute time that the watcher is supposed to
1357trigger next.
1358
1194=back 1359=back
1360
1361=head3 Examples
1195 1362
1196Example: Call a callback every hour, or, more precisely, whenever the 1363Example: Call a callback every hour, or, more precisely, whenever the
1197system clock is divisible by 3600. The callback invocation times have 1364system clock is divisible by 3600. The callback invocation times have
1198potentially a lot of jittering, but good long-term stability. 1365potentially a lot of jittering, but good long-term stability.
1199 1366
… …
1239with the kernel (thus it coexists with your own signal handlers as long 1406with the kernel (thus it coexists with your own signal handlers as long
1240as you don't register any with libev). Similarly, when the last signal 1407as you don't register any with libev). Similarly, when the last signal
1241watcher for a signal is stopped libev will reset the signal handler to 1408watcher for a signal is stopped libev will reset the signal handler to
1242SIG_DFL (regardless of what it was set to before). 1409SIG_DFL (regardless of what it was set to before).
1243 1410
1411=head3 Watcher-Specific Functions and Data Members
1412
1244=over 4 1413=over 4
1245 1414
1246=item ev_signal_init (ev_signal *, callback, int signum) 1415=item ev_signal_init (ev_signal *, callback, int signum)
1247 1416
1248=item ev_signal_set (ev_signal *, int signum) 1417=item ev_signal_set (ev_signal *, int signum)
… …
1259 1428
1260=head2 C<ev_child> - watch out for process status changes 1429=head2 C<ev_child> - watch out for process status changes
1261 1430
1262Child watchers trigger when your process receives a SIGCHLD in response to 1431Child watchers trigger when your process receives a SIGCHLD in response to
1263some child status changes (most typically when a child of yours dies). 1432some child status changes (most typically when a child of yours dies).
1433
1434=head3 Watcher-Specific Functions and Data Members
1264 1435
1265=over 4 1436=over 4
1266 1437
1267=item ev_child_init (ev_child *, callback, int pid) 1438=item ev_child_init (ev_child *, callback, int pid)
1268 1439
… …
1287 1458
1288The process exit/trace status caused by C<rpid> (see your systems 1459The process exit/trace status caused by C<rpid> (see your systems
1289C<waitpid> and C<sys/wait.h> documentation for details). 1460C<waitpid> and C<sys/wait.h> documentation for details).
1290 1461
1291=back 1462=back
1463
1464=head3 Examples
1292 1465
1293Example: Try to exit cleanly on SIGINT and SIGTERM. 1466Example: Try to exit cleanly on SIGINT and SIGTERM.
1294 1467
1295 static void 1468 static void
1296 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1469 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1337semantics of C<ev_stat> watchers, which means that libev sometimes needs 1510semantics of C<ev_stat> watchers, which means that libev sometimes needs
1338to fall back to regular polling again even with inotify, but changes are 1511to fall back to regular polling again even with inotify, but changes are
1339usually detected immediately, and if the file exists there will be no 1512usually detected immediately, and if the file exists there will be no
1340polling. 1513polling.
1341 1514
1515=head3 Inotify
1516
1517When C<inotify (7)> support has been compiled into libev (generally only
1518available on Linux) and present at runtime, it will be used to speed up
1519change detection where possible. The inotify descriptor will be created lazily
1520when the first C<ev_stat> watcher is being started.
1521
1522Inotify presense does not change the semantics of C<ev_stat> watchers
1523except that changes might be detected earlier, and in some cases, to avoid
1524making regular C<stat> calls. Even in the presense of inotify support
1525there are many cases where libev has to resort to regular C<stat> polling.
1526
1527(There is no support for kqueue, as apparently it cannot be used to
1528implement this functionality, due to the requirement of having a file
1529descriptor open on the object at all times).
1530
1531=head3 The special problem of stat time resolution
1532
1533The C<stat ()> syscall only supports full-second resolution portably, and
1534even on systems where the resolution is higher, many filesystems still
1535only support whole seconds.
1536
1537That means that, if the time is the only thing that changes, you might
1538miss updates: on the first update, C<ev_stat> detects a change and calls
1539your callback, which does something. When there is another update within
1540the same second, C<ev_stat> will be unable to detect it.
1541
1542The solution to this is to delay acting on a change for a second (or till
1543the next second boundary), using a roughly one-second delay C<ev_timer>
1544(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1545is added to work around small timing inconsistencies of some operating
1546systems.
1547
1548=head3 Watcher-Specific Functions and Data Members
1549
1342=over 4 1550=over 4
1343 1551
1344=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1552=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1345 1553
1346=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) 1554=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
… …
1381=item const char *path [read-only] 1589=item const char *path [read-only]
1382 1590
1383The filesystem path that is being watched. 1591The filesystem path that is being watched.
1384 1592
1385=back 1593=back
1594
1595=head3 Examples
1386 1596
1387Example: Watch C</etc/passwd> for attribute changes. 1597Example: Watch C</etc/passwd> for attribute changes.
1388 1598
1389 static void 1599 static void
1390 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1600 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1403 } 1613 }
1404 1614
1405 ... 1615 ...
1406 ev_stat passwd; 1616 ev_stat passwd;
1407 1617
1408 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1618 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1409 ev_stat_start (loop, &passwd); 1619 ev_stat_start (loop, &passwd);
1620
1621Example: Like above, but additionally use a one-second delay so we do not
1622miss updates (however, frequent updates will delay processing, too, so
1623one might do the work both on C<ev_stat> callback invocation I<and> on
1624C<ev_timer> callback invocation).
1625
1626 static ev_stat passwd;
1627 static ev_timer timer;
1628
1629 static void
1630 timer_cb (EV_P_ ev_timer *w, int revents)
1631 {
1632 ev_timer_stop (EV_A_ w);
1633
1634 /* now it's one second after the most recent passwd change */
1635 }
1636
1637 static void
1638 stat_cb (EV_P_ ev_stat *w, int revents)
1639 {
1640 /* reset the one-second timer */
1641 ev_timer_again (EV_A_ &timer);
1642 }
1643
1644 ...
1645 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1646 ev_stat_start (loop, &passwd);
1647 ev_timer_init (&timer, timer_cb, 0., 1.01);
1410 1648
1411 1649
1412=head2 C<ev_idle> - when you've got nothing better to do... 1650=head2 C<ev_idle> - when you've got nothing better to do...
1413 1651
1414Idle watchers trigger events when no other events of the same or higher 1652Idle watchers trigger events when no other events of the same or higher
… …
1428Apart from keeping your process non-blocking (which is a useful 1666Apart from keeping your process non-blocking (which is a useful
1429effect on its own sometimes), idle watchers are a good place to do 1667effect on its own sometimes), idle watchers are a good place to do
1430"pseudo-background processing", or delay processing stuff to after the 1668"pseudo-background processing", or delay processing stuff to after the
1431event loop has handled all outstanding events. 1669event loop has handled all outstanding events.
1432 1670
1671=head3 Watcher-Specific Functions and Data Members
1672
1433=over 4 1673=over 4
1434 1674
1435=item ev_idle_init (ev_signal *, callback) 1675=item ev_idle_init (ev_signal *, callback)
1436 1676
1437Initialises and configures the idle watcher - it has no parameters of any 1677Initialises and configures the idle watcher - it has no parameters of any
1438kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1678kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1439believe me. 1679believe me.
1440 1680
1441=back 1681=back
1682
1683=head3 Examples
1442 1684
1443Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1685Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1444callback, free it. Also, use no error checking, as usual. 1686callback, free it. Also, use no error checking, as usual.
1445 1687
1446 static void 1688 static void
… …
1498 1740
1499It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) 1741It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1500priority, to ensure that they are being run before any other watchers 1742priority, to ensure that they are being run before any other watchers
1501after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, 1743after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1502too) should not activate ("feed") events into libev. While libev fully 1744too) should not activate ("feed") events into libev. While libev fully
1503supports this, they will be called before other C<ev_check> watchers did 1745supports this, they will be called before other C<ev_check> watchers
1504their job. As C<ev_check> watchers are often used to embed other event 1746did their job. As C<ev_check> watchers are often used to embed other
1505loops those other event loops might be in an unusable state until their 1747(non-libev) event loops those other event loops might be in an unusable
1506C<ev_check> watcher ran (always remind yourself to coexist peacefully with 1748state until their C<ev_check> watcher ran (always remind yourself to
1507others). 1749coexist peacefully with others).
1750
1751=head3 Watcher-Specific Functions and Data Members
1508 1752
1509=over 4 1753=over 4
1510 1754
1511=item ev_prepare_init (ev_prepare *, callback) 1755=item ev_prepare_init (ev_prepare *, callback)
1512 1756
… …
1515Initialises and configures the prepare or check watcher - they have no 1759Initialises and configures the prepare or check watcher - they have no
1516parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1760parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1517macros, but using them is utterly, utterly and completely pointless. 1761macros, but using them is utterly, utterly and completely pointless.
1518 1762
1519=back 1763=back
1764
1765=head3 Examples
1520 1766
1521There are a number of principal ways to embed other event loops or modules 1767There are a number of principal ways to embed other event loops or modules
1522into libev. Here are some ideas on how to include libadns into libev 1768into libev. Here are some ideas on how to include libadns into libev
1523(there is a Perl module named C<EV::ADNS> that does this, which you could 1769(there is a Perl module named C<EV::ADNS> that does this, which you could
1524use for an actually working example. Another Perl module named C<EV::Glib> 1770use for an actually working example. Another Perl module named C<EV::Glib>
… …
1693portable one. 1939portable one.
1694 1940
1695So when you want to use this feature you will always have to be prepared 1941So when you want to use this feature you will always have to be prepared
1696that you cannot get an embeddable loop. The recommended way to get around 1942that you cannot get an embeddable loop. The recommended way to get around
1697this is to have a separate variables for your embeddable loop, try to 1943this is to have a separate variables for your embeddable loop, try to
1698create it, and if that fails, use the normal loop for everything: 1944create it, and if that fails, use the normal loop for everything.
1945
1946=head3 Watcher-Specific Functions and Data Members
1947
1948=over 4
1949
1950=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1951
1952=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1953
1954Configures the watcher to embed the given loop, which must be
1955embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1956invoked automatically, otherwise it is the responsibility of the callback
1957to invoke it (it will continue to be called until the sweep has been done,
1958if you do not want thta, you need to temporarily stop the embed watcher).
1959
1960=item ev_embed_sweep (loop, ev_embed *)
1961
1962Make a single, non-blocking sweep over the embedded loop. This works
1963similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1964apropriate way for embedded loops.
1965
1966=item struct ev_loop *other [read-only]
1967
1968The embedded event loop.
1969
1970=back
1971
1972=head3 Examples
1973
1974Example: Try to get an embeddable event loop and embed it into the default
1975event loop. If that is not possible, use the default loop. The default
1976loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1977C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1978used).
1699 1979
1700 struct ev_loop *loop_hi = ev_default_init (0); 1980 struct ev_loop *loop_hi = ev_default_init (0);
1701 struct ev_loop *loop_lo = 0; 1981 struct ev_loop *loop_lo = 0;
1702 struct ev_embed embed; 1982 struct ev_embed embed;
1703 1983
… …
1714 ev_embed_start (loop_hi, &embed); 1994 ev_embed_start (loop_hi, &embed);
1715 } 1995 }
1716 else 1996 else
1717 loop_lo = loop_hi; 1997 loop_lo = loop_hi;
1718 1998
1719=over 4 1999Example: Check if kqueue is available but not recommended and create
2000a kqueue backend for use with sockets (which usually work with any
2001kqueue implementation). Store the kqueue/socket-only event loop in
2002C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1720 2003
1721=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2004 struct ev_loop *loop = ev_default_init (0);
2005 struct ev_loop *loop_socket = 0;
2006 struct ev_embed embed;
2007
2008 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2009 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2010 {
2011 ev_embed_init (&embed, 0, loop_socket);
2012 ev_embed_start (loop, &embed);
2013 }
1722 2014
1723=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2015 if (!loop_socket)
2016 loop_socket = loop;
1724 2017
1725Configures the watcher to embed the given loop, which must be 2018 // now use loop_socket for all sockets, and loop for everything else
1726embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1727invoked automatically, otherwise it is the responsibility of the callback
1728to invoke it (it will continue to be called until the sweep has been done,
1729if you do not want thta, you need to temporarily stop the embed watcher).
1730
1731=item ev_embed_sweep (loop, ev_embed *)
1732
1733Make a single, non-blocking sweep over the embedded loop. This works
1734similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1735apropriate way for embedded loops.
1736
1737=item struct ev_loop *loop [read-only]
1738
1739The embedded event loop.
1740
1741=back
1742 2019
1743 2020
1744=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2021=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1745 2022
1746Fork watchers are called when a C<fork ()> was detected (usually because 2023Fork watchers are called when a C<fork ()> was detected (usually because
… …
1749event loop blocks next and before C<ev_check> watchers are being called, 2026event loop blocks next and before C<ev_check> watchers are being called,
1750and only in the child after the fork. If whoever good citizen calling 2027and only in the child after the fork. If whoever good citizen calling
1751C<ev_default_fork> cheats and calls it in the wrong process, the fork 2028C<ev_default_fork> cheats and calls it in the wrong process, the fork
1752handlers will be invoked, too, of course. 2029handlers will be invoked, too, of course.
1753 2030
2031=head3 Watcher-Specific Functions and Data Members
2032
1754=over 4 2033=over 4
1755 2034
1756=item ev_fork_init (ev_signal *, callback) 2035=item ev_fork_init (ev_signal *, callback)
1757 2036
1758Initialises and configures the fork watcher - it has no parameters of any 2037Initialises and configures the fork watcher - it has no parameters of any
… …
1974 2253
1975=item w->stop () 2254=item w->stop ()
1976 2255
1977Stops the watcher if it is active. Again, no C<loop> argument. 2256Stops the watcher if it is active. Again, no C<loop> argument.
1978 2257
1979=item w->again () C<ev::timer>, C<ev::periodic> only 2258=item w->again () (C<ev::timer>, C<ev::periodic> only)
1980 2259
1981For C<ev::timer> and C<ev::periodic>, this invokes the corresponding 2260For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1982C<ev_TYPE_again> function. 2261C<ev_TYPE_again> function.
1983 2262
1984=item w->sweep () C<ev::embed> only 2263=item w->sweep () (C<ev::embed> only)
1985 2264
1986Invokes C<ev_embed_sweep>. 2265Invokes C<ev_embed_sweep>.
1987 2266
1988=item w->update () C<ev::stat> only 2267=item w->update () (C<ev::stat> only)
1989 2268
1990Invokes C<ev_stat_stat>. 2269Invokes C<ev_stat_stat>.
1991 2270
1992=back 2271=back
1993 2272
… …
2013 } 2292 }
2014 2293
2015 2294
2016=head1 MACRO MAGIC 2295=head1 MACRO MAGIC
2017 2296
2018Libev can be compiled with a variety of options, the most fundemantal is 2297Libev can be compiled with a variety of options, the most fundamantal
2019C<EV_MULTIPLICITY>. This option determines whether (most) functions and 2298of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2020callbacks have an initial C<struct ev_loop *> argument. 2299functions and callbacks have an initial C<struct ev_loop *> argument.
2021 2300
2022To make it easier to write programs that cope with either variant, the 2301To make it easier to write programs that cope with either variant, the
2023following macros are defined: 2302following macros are defined:
2024 2303
2025=over 4 2304=over 4
… …
2079Libev can (and often is) directly embedded into host 2358Libev can (and often is) directly embedded into host
2080applications. Examples of applications that embed it include the Deliantra 2359applications. Examples of applications that embed it include the Deliantra
2081Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2360Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2082and rxvt-unicode. 2361and rxvt-unicode.
2083 2362
2084The goal is to enable you to just copy the neecssary files into your 2363The goal is to enable you to just copy the necessary files into your
2085source directory without having to change even a single line in them, so 2364source directory without having to change even a single line in them, so
2086you can easily upgrade by simply copying (or having a checked-out copy of 2365you can easily upgrade by simply copying (or having a checked-out copy of
2087libev somewhere in your source tree). 2366libev somewhere in your source tree).
2088 2367
2089=head2 FILESETS 2368=head2 FILESETS
… …
2179 2458
2180If defined to be C<1>, libev will try to detect the availability of the 2459If defined to be C<1>, libev will try to detect the availability of the
2181monotonic clock option at both compiletime and runtime. Otherwise no use 2460monotonic clock option at both compiletime and runtime. Otherwise no use
2182of the monotonic clock option will be attempted. If you enable this, you 2461of the monotonic clock option will be attempted. If you enable this, you
2183usually have to link against librt or something similar. Enabling it when 2462usually have to link against librt or something similar. Enabling it when
2184the functionality isn't available is safe, though, althoguh you have 2463the functionality isn't available is safe, though, although you have
2185to make sure you link against any libraries where the C<clock_gettime> 2464to make sure you link against any libraries where the C<clock_gettime>
2186function is hiding in (often F<-lrt>). 2465function is hiding in (often F<-lrt>).
2187 2466
2188=item EV_USE_REALTIME 2467=item EV_USE_REALTIME
2189 2468
2190If defined to be C<1>, libev will try to detect the availability of the 2469If defined to be C<1>, libev will try to detect the availability of the
2191realtime clock option at compiletime (and assume its availability at 2470realtime clock option at compiletime (and assume its availability at
2192runtime if successful). Otherwise no use of the realtime clock option will 2471runtime if successful). Otherwise no use of the realtime clock option will
2193be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2472be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2194(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries 2473(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2195in the description of C<EV_USE_MONOTONIC>, though. 2474note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2475
2476=item EV_USE_NANOSLEEP
2477
2478If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2479and will use it for delays. Otherwise it will use C<select ()>.
2196 2480
2197=item EV_USE_SELECT 2481=item EV_USE_SELECT
2198 2482
2199If undefined or defined to be C<1>, libev will compile in support for the 2483If undefined or defined to be C<1>, libev will compile in support for the
2200C<select>(2) backend. No attempt at autodetection will be done: if no 2484C<select>(2) backend. No attempt at autodetection will be done: if no
… …
2218wants osf handles on win32 (this is the case when the select to 2502wants osf handles on win32 (this is the case when the select to
2219be used is the winsock select). This means that it will call 2503be used is the winsock select). This means that it will call
2220C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2504C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2221it is assumed that all these functions actually work on fds, even 2505it is assumed that all these functions actually work on fds, even
2222on win32. Should not be defined on non-win32 platforms. 2506on win32. Should not be defined on non-win32 platforms.
2507
2508=item EV_FD_TO_WIN32_HANDLE
2509
2510If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2511file descriptors to socket handles. When not defining this symbol (the
2512default), then libev will call C<_get_osfhandle>, which is usually
2513correct. In some cases, programs use their own file descriptor management,
2514in which case they can provide this function to map fds to socket handles.
2223 2515
2224=item EV_USE_POLL 2516=item EV_USE_POLL
2225 2517
2226If defined to be C<1>, libev will compile in support for the C<poll>(2) 2518If defined to be C<1>, libev will compile in support for the C<poll>(2)
2227backend. Otherwise it will be enabled on non-win32 platforms. It 2519backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2264be detected at runtime. 2556be detected at runtime.
2265 2557
2266=item EV_H 2558=item EV_H
2267 2559
2268The name of the F<ev.h> header file used to include it. The default if 2560The name of the F<ev.h> header file used to include it. The default if
2269undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2561undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2270can be used to virtually rename the F<ev.h> header file in case of conflicts. 2562virtually rename the F<ev.h> header file in case of conflicts.
2271 2563
2272=item EV_CONFIG_H 2564=item EV_CONFIG_H
2273 2565
2274If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2566If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2275F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2567F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2276C<EV_H>, above. 2568C<EV_H>, above.
2277 2569
2278=item EV_EVENT_H 2570=item EV_EVENT_H
2279 2571
2280Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2572Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2281of how the F<event.h> header can be found. 2573of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2282 2574
2283=item EV_PROTOTYPES 2575=item EV_PROTOTYPES
2284 2576
2285If defined to be C<0>, then F<ev.h> will not define any function 2577If defined to be C<0>, then F<ev.h> will not define any function
2286prototypes, but still define all the structs and other symbols. This is 2578prototypes, but still define all the structs and other symbols. This is
… …
2352than enough. If you need to manage thousands of children you might want to 2644than enough. If you need to manage thousands of children you might want to
2353increase this value (I<must> be a power of two). 2645increase this value (I<must> be a power of two).
2354 2646
2355=item EV_INOTIFY_HASHSIZE 2647=item EV_INOTIFY_HASHSIZE
2356 2648
2357C<ev_staz> watchers use a small hash table to distribute workload by 2649C<ev_stat> watchers use a small hash table to distribute workload by
2358inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 2650inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2359usually more than enough. If you need to manage thousands of C<ev_stat> 2651usually more than enough. If you need to manage thousands of C<ev_stat>
2360watchers you might want to increase this value (I<must> be a power of 2652watchers you might want to increase this value (I<must> be a power of
2361two). 2653two).
2362 2654
… …
2379 2671
2380=item ev_set_cb (ev, cb) 2672=item ev_set_cb (ev, cb)
2381 2673
2382Can be used to change the callback member declaration in each watcher, 2674Can be used to change the callback member declaration in each watcher,
2383and the way callbacks are invoked and set. Must expand to a struct member 2675and the way callbacks are invoked and set. Must expand to a struct member
2384definition and a statement, respectively. See the F<ev.v> header file for 2676definition and a statement, respectively. See the F<ev.h> header file for
2385their default definitions. One possible use for overriding these is to 2677their default definitions. One possible use for overriding these is to
2386avoid the C<struct ev_loop *> as first argument in all cases, or to use 2678avoid the C<struct ev_loop *> as first argument in all cases, or to use
2387method calls instead of plain function calls in C++. 2679method calls instead of plain function calls in C++.
2680
2681=head2 EXPORTED API SYMBOLS
2682
2683If you need to re-export the API (e.g. via a dll) and you need a list of
2684exported symbols, you can use the provided F<Symbol.*> files which list
2685all public symbols, one per line:
2686
2687 Symbols.ev for libev proper
2688 Symbols.event for the libevent emulation
2689
2690This can also be used to rename all public symbols to avoid clashes with
2691multiple versions of libev linked together (which is obviously bad in
2692itself, but sometimes it is inconvinient to avoid this).
2693
2694A sed command like this will create wrapper C<#define>'s that you need to
2695include before including F<ev.h>:
2696
2697 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2698
2699This would create a file F<wrap.h> which essentially looks like this:
2700
2701 #define ev_backend myprefix_ev_backend
2702 #define ev_check_start myprefix_ev_check_start
2703 #define ev_check_stop myprefix_ev_check_stop
2704 ...
2388 2705
2389=head2 EXAMPLES 2706=head2 EXAMPLES
2390 2707
2391For a real-world example of a program the includes libev 2708For a real-world example of a program the includes libev
2392verbatim, you can have a look at the EV perl module 2709verbatim, you can have a look at the EV perl module
… …
2433 2750
2434=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2751=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2435 2752
2436This means that, when you have a watcher that triggers in one hour and 2753This means that, when you have a watcher that triggers in one hour and
2437there are 100 watchers that would trigger before that then inserting will 2754there are 100 watchers that would trigger before that then inserting will
2438have to skip those 100 watchers. 2755have to skip roughly seven (C<ld 100>) of these watchers.
2439 2756
2440=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2757=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2441 2758
2442That means that for changing a timer costs less than removing/adding them 2759That means that changing a timer costs less than removing/adding them
2443as only the relative motion in the event queue has to be paid for. 2760as only the relative motion in the event queue has to be paid for.
2444 2761
2445=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2762=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2446 2763
2447These just add the watcher into an array or at the head of a list. 2764These just add the watcher into an array or at the head of a list.
2765
2448=item Stopping check/prepare/idle watchers: O(1) 2766=item Stopping check/prepare/idle watchers: O(1)
2449 2767
2450=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2768=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2451 2769
2452These watchers are stored in lists then need to be walked to find the 2770These watchers are stored in lists then need to be walked to find the
2453correct watcher to remove. The lists are usually short (you don't usually 2771correct watcher to remove. The lists are usually short (you don't usually
2454have many watchers waiting for the same fd or signal). 2772have many watchers waiting for the same fd or signal).
2455 2773
2456=item Finding the next timer per loop iteration: O(1) 2774=item Finding the next timer in each loop iteration: O(1)
2775
2776By virtue of using a binary heap, the next timer is always found at the
2777beginning of the storage array.
2457 2778
2458=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2779=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2459 2780
2460A change means an I/O watcher gets started or stopped, which requires 2781A change means an I/O watcher gets started or stopped, which requires
2461libev to recalculate its status (and possibly tell the kernel). 2782libev to recalculate its status (and possibly tell the kernel, depending
2783on backend and wether C<ev_io_set> was used).
2462 2784
2463=item Activating one watcher: O(1) 2785=item Activating one watcher (putting it into the pending state): O(1)
2464 2786
2465=item Priority handling: O(number_of_priorities) 2787=item Priority handling: O(number_of_priorities)
2466 2788
2467Priorities are implemented by allocating some space for each 2789Priorities are implemented by allocating some space for each
2468priority. When doing priority-based operations, libev usually has to 2790priority. When doing priority-based operations, libev usually has to
2469linearly search all the priorities. 2791linearly search all the priorities, but starting/stopping and activating
2792watchers becomes O(1) w.r.t. prioritiy handling.
2470 2793
2471=back 2794=back
2472 2795
2473 2796
2797=head1 Win32 platform limitations and workarounds
2798
2799Win32 doesn't support any of the standards (e.g. POSIX) that libev
2800requires, and its I/O model is fundamentally incompatible with the POSIX
2801model. Libev still offers limited functionality on this platform in
2802the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2803descriptors. This only applies when using Win32 natively, not when using
2804e.g. cygwin.
2805
2806There is no supported compilation method available on windows except
2807embedding it into other applications.
2808
2809Due to the many, low, and arbitrary limits on the win32 platform and the
2810abysmal performance of winsockets, using a large number of sockets is not
2811recommended (and not reasonable). If your program needs to use more than
2812a hundred or so sockets, then likely it needs to use a totally different
2813implementation for windows, as libev offers the POSIX model, which cannot
2814be implemented efficiently on windows (microsoft monopoly games).
2815
2816=over 4
2817
2818=item The winsocket select function
2819
2820The winsocket C<select> function doesn't follow POSIX in that it requires
2821socket I<handles> and not socket I<file descriptors>. This makes select
2822very inefficient, and also requires a mapping from file descriptors
2823to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2824C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2825symbols for more info.
2826
2827The configuration for a "naked" win32 using the microsoft runtime
2828libraries and raw winsocket select is:
2829
2830 #define EV_USE_SELECT 1
2831 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2832
2833Note that winsockets handling of fd sets is O(n), so you can easily get a
2834complexity in the O(n²) range when using win32.
2835
2836=item Limited number of file descriptors
2837
2838Windows has numerous arbitrary (and low) limits on things. Early versions
2839of winsocket's select only supported waiting for a max. of C<64> handles
2840(probably owning to the fact that all windows kernels can only wait for
2841C<64> things at the same time internally; microsoft recommends spawning a
2842chain of threads and wait for 63 handles and the previous thread in each).
2843
2844Newer versions support more handles, but you need to define C<FD_SETSIZE>
2845to some high number (e.g. C<2048>) before compiling the winsocket select
2846call (which might be in libev or elsewhere, for example, perl does its own
2847select emulation on windows).
2848
2849Another limit is the number of file descriptors in the microsoft runtime
2850libraries, which by default is C<64> (there must be a hidden I<64> fetish
2851or something like this inside microsoft). You can increase this by calling
2852C<_setmaxstdio>, which can increase this limit to C<2048> (another
2853arbitrary limit), but is broken in many versions of the microsoft runtime
2854libraries.
2855
2856This might get you to about C<512> or C<2048> sockets (depending on
2857windows version and/or the phase of the moon). To get more, you need to
2858wrap all I/O functions and provide your own fd management, but the cost of
2859calling select (O(n²)) will likely make this unworkable.
2860
2861=back
2862
2863
2474=head1 AUTHOR 2864=head1 AUTHOR
2475 2865
2476Marc Lehmann <libev@schmorp.de>. 2866Marc Lehmann <libev@schmorp.de>.
2477 2867

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