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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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112=item ev_tstamp ev_time () 114=item ev_tstamp ev_time ()
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.
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 ()>.
117 125
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
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252flags. If that is troubling you, check C<ev_backend ()> afterwards). 260flags. If that is troubling you, check C<ev_backend ()> afterwards).
253 261
254If 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
255function. 263function.
256 264
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
257The flags argument can be used to specify special behaviour or specific 272The flags argument can be used to specify special behaviour or specific
258backends 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>).
259 274
260The following flags are supported: 275The following flags are supported:
261 276
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298=item C<EVBACKEND_SELECT> (value 1, portable select backend) 313=item C<EVBACKEND_SELECT> (value 1, portable select backend)
299 314
300This is your standard select(2) backend. Not I<completely> standard, as 315This is your standard select(2) backend. Not I<completely> standard, as
301libev 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,
302but 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
303using 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
304the 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.
305 327
306=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)
307 329
308And this is your standard poll(2) backend. It's more complicated than 330And this is your standard poll(2) backend. It's more complicated
309select, but handles sparse fds better and has no artificial limit on the 331than select, but handles sparse fds better and has no artificial
310number 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
311lot 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.
312 336
313=item C<EVBACKEND_EPOLL> (value 4, Linux) 337=item C<EVBACKEND_EPOLL> (value 4, Linux)
314 338
315For 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,
316but it scales phenomenally better. While poll and select usually scale like 340but it scales phenomenally better. While poll and select usually scale
317O(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),
318either 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.
319 346
320While 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
321result in some caching, there is still a syscall per such incident 348will result in some caching, there is still a syscall per such incident
322(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
323best 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
324well if you register events for both fds. 351very well if you register events for both fds.
325 352
326Please note that epoll sometimes generates spurious notifications, so you 353Please note that epoll sometimes generates spurious notifications, so you
327need 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
328(or space) is available. 355(or space) is available.
329 356
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
330=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 364=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
331 365
332Kqueue deserves special mention, as at the time of this writing, it 366Kqueue deserves special mention, as at the time of this writing, it
333was 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
334anything but sockets and pipes, except on Darwin, where of course its 368with anything but sockets and pipes, except on Darwin, where of course
335completely useless). For this reason its not being "autodetected" 369it's completely useless). For this reason it's not being "autodetected"
336unless you explicitly specify it explicitly in the flags (i.e. using 370unless you explicitly specify it explicitly in the flags (i.e. using
337C<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.
338 377
339It 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
340kernel is more efficient (which says nothing about its actual speed, of 379kernel is more efficient (which says nothing about its actual speed, of
341course). While starting and stopping an I/O watcher does not cause an 380course). While stopping, setting and starting an I/O watcher does never
342extra 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
343incident, 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.
344 393
345=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) 394=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
346 395
347This 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.
348 400
349=item C<EVBACKEND_PORT> (value 32, Solaris 10) 401=item C<EVBACKEND_PORT> (value 32, Solaris 10)
350 402
351This uses the Solaris 10 port mechanism. As with everything on Solaris, 403This uses the Solaris 10 event port mechanism. As with everything on Solaris,
352it'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)).
353 405
354Please note that solaris ports can result in a lot of spurious 406Please note that solaris event ports can deliver a lot of spurious
355notifications, 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
356blocking 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.
357 418
358=item C<EVBACKEND_ALL> 419=item C<EVBACKEND_ALL>
359 420
360Try all backends (even potentially broken ones that wouldn't be tried 421Try all backends (even potentially broken ones that wouldn't be tried
361with 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
362C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 423C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
363 424
425It is definitely not recommended to use this flag.
426
364=back 427=back
365 428
366If 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
367backends 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
368specified, most compiled-in backend will be tried, usually in reverse 431specified, all backends in C<ev_recommended_backends ()> will be tried.
369order of their flag values :)
370 432
371The most typical usage is like this: 433The most typical usage is like this:
372 434
373 if (!ev_default_loop (0)) 435 if (!ev_default_loop (0))
374 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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402Destroys the default loop again (frees all memory and kernel state 464Destroys the default loop again (frees all memory and kernel state
403etc.). None of the active event watchers will be stopped in the normal 465etc.). None of the active event watchers will be stopped in the normal
404sense, so e.g. C<ev_is_active> might still return true. It is your 466sense, so e.g. C<ev_is_active> might still return true. It is your
405responsibility to either stop all watchers cleanly yoursef I<before> 467responsibility to either stop all watchers cleanly yoursef I<before>
406calling this function, or cope with the fact afterwards (which is usually 468calling this function, or cope with the fact afterwards (which is usually
407the easiest thing, youc na just ignore the watchers and/or C<free ()> them 469the easiest thing, you can just ignore the watchers and/or C<free ()> them
408for example). 470for example).
471
472Note that certain global state, such as signal state, will not be freed by
473this function, and related watchers (such as signal and child watchers)
474would need to be stopped manually.
475
476In general it is not advisable to call this function except in the
477rare occasion where you really need to free e.g. the signal handling
478pipe fds. If you need dynamically allocated loops it is better to use
479C<ev_loop_new> and C<ev_loop_destroy>).
409 480
410=item ev_loop_destroy (loop) 481=item ev_loop_destroy (loop)
411 482
412Like 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
413earlier call to C<ev_loop_new>. 484earlier call to C<ev_loop_new>.
414 485
415=item ev_default_fork () 486=item ev_default_fork ()
416 487
488This function sets a flag that causes subsequent C<ev_loop> iterations
417This function reinitialises the kernel state for backends that have 489to reinitialise the kernel state for backends that have one. Despite the
418one. 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
419after 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
420again 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.
421 494
422You 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
423only 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
424fork+exec, you don't have to call it. 497you just fork+exec, you don't have to call it at all.
425 498
426The 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
427it 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
428quite nicely into a call to C<pthread_atfork>: 501quite nicely into a call to C<pthread_atfork>:
429 502
430 pthread_atfork (0, 0, ev_default_fork); 503 pthread_atfork (0, 0, ev_default_fork);
431
432At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use
433without calling this function, so if you force one of those backends you
434do not need to care.
435 504
436=item ev_loop_fork (loop) 505=item ev_loop_fork (loop)
437 506
438Like 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
439C<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
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458 527
459Returns the current "event loop time", which is the time the event loop 528Returns the current "event loop time", which is the time the event loop
460received events and started processing them. This timestamp does not 529received events and started processing them. This timestamp does not
461change as long as callbacks are being processed, and this is also the base 530change as long as callbacks are being processed, and this is also the base
462time used for relative timers. You can treat it as the timestamp of the 531time used for relative timers. You can treat it as the timestamp of the
463event occuring (or more correctly, libev finding out about it). 532event occurring (or more correctly, libev finding out about it).
464 533
465=item ev_loop (loop, int flags) 534=item ev_loop (loop, int flags)
466 535
467Finally, this is it, the event handler. This function usually is called 536Finally, this is it, the event handler. This function usually is called
468after you initialised all your watchers and you want to start handling 537after you initialised all your watchers and you want to start handling
… …
490usually a better approach for this kind of thing. 559usually a better approach for this kind of thing.
491 560
492Here are the gory details of what C<ev_loop> does: 561Here are the gory details of what C<ev_loop> does:
493 562
494 - Before the first iteration, call any pending watchers. 563 - Before the first iteration, call any pending watchers.
495 * If there are no active watchers (reference count is zero), return. 564 * If EVFLAG_FORKCHECK was used, check for a fork.
496 - Queue all prepare watchers and then call all outstanding watchers. 565 - If a fork was detected, queue and call all fork watchers.
566 - Queue and call all prepare watchers.
497 - If we have been forked, recreate the kernel state. 567 - If we have been forked, recreate the kernel state.
498 - Update the kernel state with all outstanding changes. 568 - Update the kernel state with all outstanding changes.
499 - Update the "event loop time". 569 - Update the "event loop time".
500 - Calculate for how long to block. 570 - Calculate for how long to sleep or block, if at all
571 (active idle watchers, EVLOOP_NONBLOCK or not having
572 any active watchers at all will result in not sleeping).
573 - Sleep if the I/O and timer collect interval say so.
501 - Block the process, waiting for any events. 574 - Block the process, waiting for any events.
502 - Queue all outstanding I/O (fd) events. 575 - Queue all outstanding I/O (fd) events.
503 - Update the "event loop time" and do time jump handling. 576 - Update the "event loop time" and do time jump handling.
504 - Queue all outstanding timers. 577 - Queue all outstanding timers.
505 - Queue all outstanding periodics. 578 - Queue all outstanding periodics.
506 - If no events are pending now, queue all idle watchers. 579 - If no events are pending now, queue all idle watchers.
507 - Queue all check watchers. 580 - Queue all check watchers.
508 - Call all queued watchers in reverse order (i.e. check watchers first). 581 - Call all queued watchers in reverse order (i.e. check watchers first).
509 Signals and child watchers are implemented as I/O watchers, and will 582 Signals and child watchers are implemented as I/O watchers, and will
510 be handled here by queueing them when their watcher gets executed. 583 be handled here by queueing them when their watcher gets executed.
511 - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 584 - If ev_unloop has been called, or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
512 were used, return, otherwise continue with step *. 585 were used, or there are no active watchers, return, otherwise
586 continue with step *.
513 587
514Example: Queue some jobs and then loop until no events are outsanding 588Example: Queue some jobs and then loop until no events are outstanding
515anymore. 589anymore.
516 590
517 ... queue jobs here, make sure they register event watchers as long 591 ... queue jobs here, make sure they register event watchers as long
518 ... as they still have work to do (even an idle watcher will do..) 592 ... as they still have work to do (even an idle watcher will do..)
519 ev_loop (my_loop, 0); 593 ev_loop (my_loop, 0);
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523 597
524Can be used to make a call to C<ev_loop> return early (but only after it 598Can be used to make a call to C<ev_loop> return early (but only after it
525has processed all outstanding events). The C<how> argument must be either 599has processed all outstanding events). The C<how> argument must be either
526C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 600C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
527C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 601C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
602
603This "unloop state" will be cleared when entering C<ev_loop> again.
528 604
529=item ev_ref (loop) 605=item ev_ref (loop)
530 606
531=item ev_unref (loop) 607=item ev_unref (loop)
532 608
… …
537returning, ev_unref() after starting, and ev_ref() before stopping it. For 613returning, ev_unref() after starting, and ev_ref() before stopping it. For
538example, libev itself uses this for its internal signal pipe: It is not 614example, libev itself uses this for its internal signal pipe: It is not
539visible to the libev user and should not keep C<ev_loop> from exiting if 615visible to the libev user and should not keep C<ev_loop> from exiting if
540no event watchers registered by it are active. It is also an excellent 616no event watchers registered by it are active. It is also an excellent
541way to do this for generic recurring timers or from within third-party 617way to do this for generic recurring timers or from within third-party
542libraries. Just remember to I<unref after start> and I<ref before stop>. 618libraries. Just remember to I<unref after start> and I<ref before stop>
619(but only if the watcher wasn't active before, or was active before,
620respectively).
543 621
544Example: Create a signal watcher, but keep it from keeping C<ev_loop> 622Example: Create a signal watcher, but keep it from keeping C<ev_loop>
545running when nothing else is active. 623running when nothing else is active.
546 624
547 struct ev_signal exitsig; 625 struct ev_signal exitsig;
… …
551 629
552Example: For some weird reason, unregister the above signal handler again. 630Example: For some weird reason, unregister the above signal handler again.
553 631
554 ev_ref (loop); 632 ev_ref (loop);
555 ev_signal_stop (loop, &exitsig); 633 ev_signal_stop (loop, &exitsig);
634
635=item ev_set_io_collect_interval (loop, ev_tstamp interval)
636
637=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
638
639These advanced functions influence the time that libev will spend waiting
640for events. Both are by default C<0>, meaning that libev will try to
641invoke timer/periodic callbacks and I/O callbacks with minimum latency.
642
643Setting these to a higher value (the C<interval> I<must> be >= C<0>)
644allows libev to delay invocation of I/O and timer/periodic callbacks to
645increase efficiency of loop iterations.
646
647The background is that sometimes your program runs just fast enough to
648handle one (or very few) event(s) per loop iteration. While this makes
649the program responsive, it also wastes a lot of CPU time to poll for new
650events, especially with backends like C<select ()> which have a high
651overhead for the actual polling but can deliver many events at once.
652
653By setting a higher I<io collect interval> you allow libev to spend more
654time collecting I/O events, so you can handle more events per iteration,
655at the cost of increasing latency. Timeouts (both C<ev_periodic> and
656C<ev_timer>) will be not affected. Setting this to a non-null value will
657introduce an additional C<ev_sleep ()> call into most loop iterations.
658
659Likewise, by setting a higher I<timeout collect interval> you allow libev
660to spend more time collecting timeouts, at the expense of increased
661latency (the watcher callback will be called later). C<ev_io> watchers
662will not be affected. Setting this to a non-null value will not introduce
663any overhead in libev.
664
665Many (busy) programs can usually benefit by setting the io collect
666interval to a value near C<0.1> or so, which is often enough for
667interactive servers (of course not for games), likewise for timeouts. It
668usually doesn't make much sense to set it to a lower value than C<0.01>,
669as this approsaches the timing granularity of most systems.
556 670
557=back 671=back
558 672
559 673
560=head1 ANATOMY OF A WATCHER 674=head1 ANATOMY OF A WATCHER
… …
886In general you can register as many read and/or write event watchers per 1000In general you can register as many read and/or write event watchers per
887fd as you want (as long as you don't confuse yourself). Setting all file 1001fd as you want (as long as you don't confuse yourself). Setting all file
888descriptors to non-blocking mode is also usually a good idea (but not 1002descriptors to non-blocking mode is also usually a good idea (but not
889required if you know what you are doing). 1003required if you know what you are doing).
890 1004
891You have to be careful with dup'ed file descriptors, though. Some backends
892(the linux epoll backend is a notable example) cannot handle dup'ed file
893descriptors correctly if you register interest in two or more fds pointing
894to the same underlying file/socket/etc. description (that is, they share
895the same underlying "file open").
896
897If you must do this, then force the use of a known-to-be-good backend 1005If you must do this, then force the use of a known-to-be-good backend
898(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 1006(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
899C<EVBACKEND_POLL>). 1007C<EVBACKEND_POLL>).
900 1008
901Another thing you have to watch out for is that it is quite easy to 1009Another thing you have to watch out for is that it is quite easy to
… …
913such as poll (fortunately in our Xlib example, Xlib already does this on 1021such as poll (fortunately in our Xlib example, Xlib already does this on
914its own, so its quite safe to use). 1022its own, so its quite safe to use).
915 1023
916=head3 The special problem of disappearing file descriptors 1024=head3 The special problem of disappearing file descriptors
917 1025
918Some backends (e.g kqueue, epoll) need to be told about closing a file 1026Some backends (e.g. kqueue, epoll) need to be told about closing a file
919descriptor (either by calling C<close> explicitly or by any other means, 1027descriptor (either by calling C<close> explicitly or by any other means,
920such as C<dup>). The reason is that you register interest in some file 1028such as C<dup>). The reason is that you register interest in some file
921descriptor, but when it goes away, the operating system will silently drop 1029descriptor, but when it goes away, the operating system will silently drop
922this interest. If another file descriptor with the same number then is 1030this interest. If another file descriptor with the same number then is
923registered with libev, there is no efficient way to see that this is, in 1031registered with libev, there is no efficient way to see that this is, in
… …
932 1040
933This is how one would do it normally anyway, the important point is that 1041This is how one would do it normally anyway, the important point is that
934the libev application should not optimise around libev but should leave 1042the libev application should not optimise around libev but should leave
935optimisations to libev. 1043optimisations to libev.
936 1044
1045=head3 The special problem of dup'ed file descriptors
1046
1047Some backends (e.g. epoll), cannot register events for file descriptors,
1048but only events for the underlying file descriptions. That means when you
1049have C<dup ()>'ed file descriptors or weirder constellations, and register
1050events for them, only one file descriptor might actually receive events.
1051
1052There is no workaround possible except not registering events
1053for potentially C<dup ()>'ed file descriptors, or to resort to
1054C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1055
1056=head3 The special problem of fork
1057
1058Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1059useless behaviour. Libev fully supports fork, but needs to be told about
1060it in the child.
1061
1062To support fork in your programs, you either have to call
1063C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1064enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1065C<EVBACKEND_POLL>.
1066
937 1067
938=head3 Watcher-Specific Functions 1068=head3 Watcher-Specific Functions
939 1069
940=over 4 1070=over 4
941 1071
… …
954=item int events [read-only] 1084=item int events [read-only]
955 1085
956The events being watched. 1086The events being watched.
957 1087
958=back 1088=back
1089
1090=head3 Examples
959 1091
960Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1092Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
961readable, but only once. Since it is likely line-buffered, you could 1093readable, but only once. Since it is likely line-buffered, you could
962attempt to read a whole line in the callback. 1094attempt to read a whole line in the callback.
963 1095
… …
1061or C<ev_timer_again> is called and determines the next timeout (if any), 1193or C<ev_timer_again> is called and determines the next timeout (if any),
1062which is also when any modifications are taken into account. 1194which is also when any modifications are taken into account.
1063 1195
1064=back 1196=back
1065 1197
1198=head3 Examples
1199
1066Example: Create a timer that fires after 60 seconds. 1200Example: Create a timer that fires after 60 seconds.
1067 1201
1068 static void 1202 static void
1069 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1203 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1070 { 1204 {
… …
1227When active, contains the absolute time that the watcher is supposed to 1361When active, contains the absolute time that the watcher is supposed to
1228trigger next. 1362trigger next.
1229 1363
1230=back 1364=back
1231 1365
1366=head3 Examples
1367
1232Example: Call a callback every hour, or, more precisely, whenever the 1368Example: Call a callback every hour, or, more precisely, whenever the
1233system clock is divisible by 3600. The callback invocation times have 1369system clock is divisible by 3600. The callback invocation times have
1234potentially a lot of jittering, but good long-term stability. 1370potentially a lot of jittering, but good long-term stability.
1235 1371
1236 static void 1372 static void
… …
1302 1438
1303=head3 Watcher-Specific Functions and Data Members 1439=head3 Watcher-Specific Functions and Data Members
1304 1440
1305=over 4 1441=over 4
1306 1442
1307=item ev_child_init (ev_child *, callback, int pid) 1443=item ev_child_init (ev_child *, callback, int pid, int trace)
1308 1444
1309=item ev_child_set (ev_child *, int pid) 1445=item ev_child_set (ev_child *, int pid, int trace)
1310 1446
1311Configures the watcher to wait for status changes of process C<pid> (or 1447Configures the watcher to wait for status changes of process C<pid> (or
1312I<any> process if C<pid> is specified as C<0>). The callback can look 1448I<any> process if C<pid> is specified as C<0>). The callback can look
1313at the C<rstatus> member of the C<ev_child> watcher structure to see 1449at the C<rstatus> member of the C<ev_child> watcher structure to see
1314the status word (use the macros from C<sys/wait.h> and see your systems 1450the status word (use the macros from C<sys/wait.h> and see your systems
1315C<waitpid> documentation). The C<rpid> member contains the pid of the 1451C<waitpid> documentation). The C<rpid> member contains the pid of the
1316process causing the status change. 1452process causing the status change. C<trace> must be either C<0> (only
1453activate the watcher when the process terminates) or C<1> (additionally
1454activate the watcher when the process is stopped or continued).
1317 1455
1318=item int pid [read-only] 1456=item int pid [read-only]
1319 1457
1320The process id this watcher watches out for, or C<0>, meaning any process id. 1458The process id this watcher watches out for, or C<0>, meaning any process id.
1321 1459
… …
1327 1465
1328The process exit/trace status caused by C<rpid> (see your systems 1466The process exit/trace status caused by C<rpid> (see your systems
1329C<waitpid> and C<sys/wait.h> documentation for details). 1467C<waitpid> and C<sys/wait.h> documentation for details).
1330 1468
1331=back 1469=back
1470
1471=head3 Examples
1332 1472
1333Example: Try to exit cleanly on SIGINT and SIGTERM. 1473Example: Try to exit cleanly on SIGINT and SIGTERM.
1334 1474
1335 static void 1475 static void
1336 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1476 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1377semantics of C<ev_stat> watchers, which means that libev sometimes needs 1517semantics of C<ev_stat> watchers, which means that libev sometimes needs
1378to fall back to regular polling again even with inotify, but changes are 1518to fall back to regular polling again even with inotify, but changes are
1379usually detected immediately, and if the file exists there will be no 1519usually detected immediately, and if the file exists there will be no
1380polling. 1520polling.
1381 1521
1522=head3 Inotify
1523
1524When C<inotify (7)> support has been compiled into libev (generally only
1525available on Linux) and present at runtime, it will be used to speed up
1526change detection where possible. The inotify descriptor will be created lazily
1527when the first C<ev_stat> watcher is being started.
1528
1529Inotify presense does not change the semantics of C<ev_stat> watchers
1530except that changes might be detected earlier, and in some cases, to avoid
1531making regular C<stat> calls. Even in the presense of inotify support
1532there are many cases where libev has to resort to regular C<stat> polling.
1533
1534(There is no support for kqueue, as apparently it cannot be used to
1535implement this functionality, due to the requirement of having a file
1536descriptor open on the object at all times).
1537
1538=head3 The special problem of stat time resolution
1539
1540The C<stat ()> syscall only supports full-second resolution portably, and
1541even on systems where the resolution is higher, many filesystems still
1542only support whole seconds.
1543
1544That means that, if the time is the only thing that changes, you might
1545miss updates: on the first update, C<ev_stat> detects a change and calls
1546your callback, which does something. When there is another update within
1547the same second, C<ev_stat> will be unable to detect it.
1548
1549The solution to this is to delay acting on a change for a second (or till
1550the next second boundary), using a roughly one-second delay C<ev_timer>
1551(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1552is added to work around small timing inconsistencies of some operating
1553systems.
1554
1382=head3 Watcher-Specific Functions and Data Members 1555=head3 Watcher-Specific Functions and Data Members
1383 1556
1384=over 4 1557=over 4
1385 1558
1386=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1559=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
… …
1423=item const char *path [read-only] 1596=item const char *path [read-only]
1424 1597
1425The filesystem path that is being watched. 1598The filesystem path that is being watched.
1426 1599
1427=back 1600=back
1601
1602=head3 Examples
1428 1603
1429Example: Watch C</etc/passwd> for attribute changes. 1604Example: Watch C</etc/passwd> for attribute changes.
1430 1605
1431 static void 1606 static void
1432 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1607 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1445 } 1620 }
1446 1621
1447 ... 1622 ...
1448 ev_stat passwd; 1623 ev_stat passwd;
1449 1624
1450 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1625 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1451 ev_stat_start (loop, &passwd); 1626 ev_stat_start (loop, &passwd);
1627
1628Example: Like above, but additionally use a one-second delay so we do not
1629miss updates (however, frequent updates will delay processing, too, so
1630one might do the work both on C<ev_stat> callback invocation I<and> on
1631C<ev_timer> callback invocation).
1632
1633 static ev_stat passwd;
1634 static ev_timer timer;
1635
1636 static void
1637 timer_cb (EV_P_ ev_timer *w, int revents)
1638 {
1639 ev_timer_stop (EV_A_ w);
1640
1641 /* now it's one second after the most recent passwd change */
1642 }
1643
1644 static void
1645 stat_cb (EV_P_ ev_stat *w, int revents)
1646 {
1647 /* reset the one-second timer */
1648 ev_timer_again (EV_A_ &timer);
1649 }
1650
1651 ...
1652 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1653 ev_stat_start (loop, &passwd);
1654 ev_timer_init (&timer, timer_cb, 0., 1.01);
1452 1655
1453 1656
1454=head2 C<ev_idle> - when you've got nothing better to do... 1657=head2 C<ev_idle> - when you've got nothing better to do...
1455 1658
1456Idle watchers trigger events when no other events of the same or higher 1659Idle watchers trigger events when no other events of the same or higher
… …
1482kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1685kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1483believe me. 1686believe me.
1484 1687
1485=back 1688=back
1486 1689
1690=head3 Examples
1691
1487Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1692Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1488callback, free it. Also, use no error checking, as usual. 1693callback, free it. Also, use no error checking, as usual.
1489 1694
1490 static void 1695 static void
1491 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1696 idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1492 { 1697 {
1493 free (w); 1698 free (w);
1494 // now do something you wanted to do when the program has 1699 // now do something you wanted to do when the program has
1495 // no longer asnything immediate to do. 1700 // no longer anything immediate to do.
1496 } 1701 }
1497 1702
1498 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1703 struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1499 ev_idle_init (idle_watcher, idle_cb); 1704 ev_idle_init (idle_watcher, idle_cb);
1500 ev_idle_start (loop, idle_cb); 1705 ev_idle_start (loop, idle_cb);
… …
1542 1747
1543It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) 1748It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1544priority, to ensure that they are being run before any other watchers 1749priority, to ensure that they are being run before any other watchers
1545after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, 1750after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1546too) should not activate ("feed") events into libev. While libev fully 1751too) should not activate ("feed") events into libev. While libev fully
1547supports this, they will be called before other C<ev_check> watchers did 1752supports this, they will be called before other C<ev_check> watchers
1548their job. As C<ev_check> watchers are often used to embed other event 1753did their job. As C<ev_check> watchers are often used to embed other
1549loops those other event loops might be in an unusable state until their 1754(non-libev) event loops those other event loops might be in an unusable
1550C<ev_check> watcher ran (always remind yourself to coexist peacefully with 1755state until their C<ev_check> watcher ran (always remind yourself to
1551others). 1756coexist peacefully with others).
1552 1757
1553=head3 Watcher-Specific Functions and Data Members 1758=head3 Watcher-Specific Functions and Data Members
1554 1759
1555=over 4 1760=over 4
1556 1761
… …
1561Initialises and configures the prepare or check watcher - they have no 1766Initialises and configures the prepare or check watcher - they have no
1562parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1767parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1563macros, but using them is utterly, utterly and completely pointless. 1768macros, but using them is utterly, utterly and completely pointless.
1564 1769
1565=back 1770=back
1771
1772=head3 Examples
1566 1773
1567There are a number of principal ways to embed other event loops or modules 1774There are a number of principal ways to embed other event loops or modules
1568into libev. Here are some ideas on how to include libadns into libev 1775into libev. Here are some ideas on how to include libadns into libev
1569(there is a Perl module named C<EV::ADNS> that does this, which you could 1776(there is a Perl module named C<EV::ADNS> that does this, which you could
1570use for an actually working example. Another Perl module named C<EV::Glib> 1777use for an actually working example. Another Perl module named C<EV::Glib>
… …
1739portable one. 1946portable one.
1740 1947
1741So when you want to use this feature you will always have to be prepared 1948So when you want to use this feature you will always have to be prepared
1742that you cannot get an embeddable loop. The recommended way to get around 1949that you cannot get an embeddable loop. The recommended way to get around
1743this is to have a separate variables for your embeddable loop, try to 1950this is to have a separate variables for your embeddable loop, try to
1744create it, and if that fails, use the normal loop for everything: 1951create it, and if that fails, use the normal loop for everything.
1952
1953=head3 Watcher-Specific Functions and Data Members
1954
1955=over 4
1956
1957=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1958
1959=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1960
1961Configures the watcher to embed the given loop, which must be
1962embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1963invoked automatically, otherwise it is the responsibility of the callback
1964to invoke it (it will continue to be called until the sweep has been done,
1965if you do not want thta, you need to temporarily stop the embed watcher).
1966
1967=item ev_embed_sweep (loop, ev_embed *)
1968
1969Make a single, non-blocking sweep over the embedded loop. This works
1970similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1971apropriate way for embedded loops.
1972
1973=item struct ev_loop *other [read-only]
1974
1975The embedded event loop.
1976
1977=back
1978
1979=head3 Examples
1980
1981Example: Try to get an embeddable event loop and embed it into the default
1982event loop. If that is not possible, use the default loop. The default
1983loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1984C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1985used).
1745 1986
1746 struct ev_loop *loop_hi = ev_default_init (0); 1987 struct ev_loop *loop_hi = ev_default_init (0);
1747 struct ev_loop *loop_lo = 0; 1988 struct ev_loop *loop_lo = 0;
1748 struct ev_embed embed; 1989 struct ev_embed embed;
1749 1990
… …
1760 ev_embed_start (loop_hi, &embed); 2001 ev_embed_start (loop_hi, &embed);
1761 } 2002 }
1762 else 2003 else
1763 loop_lo = loop_hi; 2004 loop_lo = loop_hi;
1764 2005
1765=head3 Watcher-Specific Functions and Data Members 2006Example: Check if kqueue is available but not recommended and create
2007a kqueue backend for use with sockets (which usually work with any
2008kqueue implementation). Store the kqueue/socket-only event loop in
2009C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1766 2010
1767=over 4 2011 struct ev_loop *loop = ev_default_init (0);
2012 struct ev_loop *loop_socket = 0;
2013 struct ev_embed embed;
2014
2015 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
2016 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
2017 {
2018 ev_embed_init (&embed, 0, loop_socket);
2019 ev_embed_start (loop, &embed);
2020 }
1768 2021
1769=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 2022 if (!loop_socket)
2023 loop_socket = loop;
1770 2024
1771=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2025 // now use loop_socket for all sockets, and loop for everything else
1772
1773Configures the watcher to embed the given loop, which must be
1774embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1775invoked automatically, otherwise it is the responsibility of the callback
1776to invoke it (it will continue to be called until the sweep has been done,
1777if you do not want thta, you need to temporarily stop the embed watcher).
1778
1779=item ev_embed_sweep (loop, ev_embed *)
1780
1781Make a single, non-blocking sweep over the embedded loop. This works
1782similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1783apropriate way for embedded loops.
1784
1785=item struct ev_loop *loop [read-only]
1786
1787The embedded event loop.
1788
1789=back
1790 2026
1791 2027
1792=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2028=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1793 2029
1794Fork watchers are called when a C<fork ()> was detected (usually because 2030Fork watchers are called when a C<fork ()> was detected (usually because
… …
2046Example: Define a class with an IO and idle watcher, start one of them in 2282Example: Define a class with an IO and idle watcher, start one of them in
2047the constructor. 2283the constructor.
2048 2284
2049 class myclass 2285 class myclass
2050 { 2286 {
2051 ev_io io; void io_cb (ev::io &w, int revents); 2287 ev::io io; void io_cb (ev::io &w, int revents);
2052 ev_idle idle void idle_cb (ev::idle &w, int revents); 2288 ev:idle idle void idle_cb (ev::idle &w, int revents);
2053 2289
2054 myclass (); 2290 myclass (int fd)
2055 }
2056
2057 myclass::myclass (int fd)
2058 { 2291 {
2059 io .set <myclass, &myclass::io_cb > (this); 2292 io .set <myclass, &myclass::io_cb > (this);
2060 idle.set <myclass, &myclass::idle_cb> (this); 2293 idle.set <myclass, &myclass::idle_cb> (this);
2061 2294
2062 io.start (fd, ev::READ); 2295 io.start (fd, ev::READ);
2296 }
2063 } 2297 };
2064 2298
2065 2299
2066=head1 MACRO MAGIC 2300=head1 MACRO MAGIC
2067 2301
2068Libev can be compiled with a variety of options, the most fundamantal 2302Libev can be compiled with a variety of options, the most fundamantal
… …
2129Libev can (and often is) directly embedded into host 2363Libev can (and often is) directly embedded into host
2130applications. Examples of applications that embed it include the Deliantra 2364applications. Examples of applications that embed it include the Deliantra
2131Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2365Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2132and rxvt-unicode. 2366and rxvt-unicode.
2133 2367
2134The goal is to enable you to just copy the neecssary files into your 2368The goal is to enable you to just copy the necessary files into your
2135source directory without having to change even a single line in them, so 2369source directory without having to change even a single line in them, so
2136you can easily upgrade by simply copying (or having a checked-out copy of 2370you can easily upgrade by simply copying (or having a checked-out copy of
2137libev somewhere in your source tree). 2371libev somewhere in your source tree).
2138 2372
2139=head2 FILESETS 2373=head2 FILESETS
… …
2229 2463
2230If defined to be C<1>, libev will try to detect the availability of the 2464If defined to be C<1>, libev will try to detect the availability of the
2231monotonic clock option at both compiletime and runtime. Otherwise no use 2465monotonic clock option at both compiletime and runtime. Otherwise no use
2232of the monotonic clock option will be attempted. If you enable this, you 2466of the monotonic clock option will be attempted. If you enable this, you
2233usually have to link against librt or something similar. Enabling it when 2467usually have to link against librt or something similar. Enabling it when
2234the functionality isn't available is safe, though, althoguh you have 2468the functionality isn't available is safe, though, although you have
2235to make sure you link against any libraries where the C<clock_gettime> 2469to make sure you link against any libraries where the C<clock_gettime>
2236function is hiding in (often F<-lrt>). 2470function is hiding in (often F<-lrt>).
2237 2471
2238=item EV_USE_REALTIME 2472=item EV_USE_REALTIME
2239 2473
2240If defined to be C<1>, libev will try to detect the availability of the 2474If defined to be C<1>, libev will try to detect the availability of the
2241realtime clock option at compiletime (and assume its availability at 2475realtime clock option at compiletime (and assume its availability at
2242runtime if successful). Otherwise no use of the realtime clock option will 2476runtime if successful). Otherwise no use of the realtime clock option will
2243be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2477be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2244(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries 2478(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2245in the description of C<EV_USE_MONOTONIC>, though. 2479note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2480
2481=item EV_USE_NANOSLEEP
2482
2483If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2484and will use it for delays. Otherwise it will use C<select ()>.
2246 2485
2247=item EV_USE_SELECT 2486=item EV_USE_SELECT
2248 2487
2249If undefined or defined to be C<1>, libev will compile in support for the 2488If undefined or defined to be C<1>, libev will compile in support for the
2250C<select>(2) backend. No attempt at autodetection will be done: if no 2489C<select>(2) backend. No attempt at autodetection will be done: if no
… …
2268wants osf handles on win32 (this is the case when the select to 2507wants osf handles on win32 (this is the case when the select to
2269be used is the winsock select). This means that it will call 2508be used is the winsock select). This means that it will call
2270C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2509C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2271it is assumed that all these functions actually work on fds, even 2510it is assumed that all these functions actually work on fds, even
2272on win32. Should not be defined on non-win32 platforms. 2511on win32. Should not be defined on non-win32 platforms.
2512
2513=item EV_FD_TO_WIN32_HANDLE
2514
2515If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2516file descriptors to socket handles. When not defining this symbol (the
2517default), then libev will call C<_get_osfhandle>, which is usually
2518correct. In some cases, programs use their own file descriptor management,
2519in which case they can provide this function to map fds to socket handles.
2273 2520
2274=item EV_USE_POLL 2521=item EV_USE_POLL
2275 2522
2276If defined to be C<1>, libev will compile in support for the C<poll>(2) 2523If defined to be C<1>, libev will compile in support for the C<poll>(2)
2277backend. Otherwise it will be enabled on non-win32 platforms. It 2524backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2314be detected at runtime. 2561be detected at runtime.
2315 2562
2316=item EV_H 2563=item EV_H
2317 2564
2318The name of the F<ev.h> header file used to include it. The default if 2565The name of the F<ev.h> header file used to include it. The default if
2319undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2566undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
2320can be used to virtually rename the F<ev.h> header file in case of conflicts. 2567used to virtually rename the F<ev.h> header file in case of conflicts.
2321 2568
2322=item EV_CONFIG_H 2569=item EV_CONFIG_H
2323 2570
2324If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2571If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2325F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2572F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2326C<EV_H>, above. 2573C<EV_H>, above.
2327 2574
2328=item EV_EVENT_H 2575=item EV_EVENT_H
2329 2576
2330Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2577Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2331of how the F<event.h> header can be found. 2578of how the F<event.h> header can be found, the default is C<"event.h">.
2332 2579
2333=item EV_PROTOTYPES 2580=item EV_PROTOTYPES
2334 2581
2335If defined to be C<0>, then F<ev.h> will not define any function 2582If defined to be C<0>, then F<ev.h> will not define any function
2336prototypes, but still define all the structs and other symbols. This is 2583prototypes, but still define all the structs and other symbols. This is
… …
2402than enough. If you need to manage thousands of children you might want to 2649than enough. If you need to manage thousands of children you might want to
2403increase this value (I<must> be a power of two). 2650increase this value (I<must> be a power of two).
2404 2651
2405=item EV_INOTIFY_HASHSIZE 2652=item EV_INOTIFY_HASHSIZE
2406 2653
2407C<ev_staz> watchers use a small hash table to distribute workload by 2654C<ev_stat> watchers use a small hash table to distribute workload by
2408inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 2655inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2409usually more than enough. If you need to manage thousands of C<ev_stat> 2656usually more than enough. If you need to manage thousands of C<ev_stat>
2410watchers you might want to increase this value (I<must> be a power of 2657watchers you might want to increase this value (I<must> be a power of
2411two). 2658two).
2412 2659
… …
2429 2676
2430=item ev_set_cb (ev, cb) 2677=item ev_set_cb (ev, cb)
2431 2678
2432Can be used to change the callback member declaration in each watcher, 2679Can be used to change the callback member declaration in each watcher,
2433and the way callbacks are invoked and set. Must expand to a struct member 2680and the way callbacks are invoked and set. Must expand to a struct member
2434definition and a statement, respectively. See the F<ev.v> header file for 2681definition and a statement, respectively. See the F<ev.h> header file for
2435their default definitions. One possible use for overriding these is to 2682their default definitions. One possible use for overriding these is to
2436avoid the C<struct ev_loop *> as first argument in all cases, or to use 2683avoid the C<struct ev_loop *> as first argument in all cases, or to use
2437method calls instead of plain function calls in C++. 2684method calls instead of plain function calls in C++.
2685
2686=head2 EXPORTED API SYMBOLS
2687
2688If you need to re-export the API (e.g. via a dll) and you need a list of
2689exported symbols, you can use the provided F<Symbol.*> files which list
2690all public symbols, one per line:
2691
2692 Symbols.ev for libev proper
2693 Symbols.event for the libevent emulation
2694
2695This can also be used to rename all public symbols to avoid clashes with
2696multiple versions of libev linked together (which is obviously bad in
2697itself, but sometimes it is inconvinient to avoid this).
2698
2699A sed command like this will create wrapper C<#define>'s that you need to
2700include before including F<ev.h>:
2701
2702 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2703
2704This would create a file F<wrap.h> which essentially looks like this:
2705
2706 #define ev_backend myprefix_ev_backend
2707 #define ev_check_start myprefix_ev_check_start
2708 #define ev_check_stop myprefix_ev_check_stop
2709 ...
2438 2710
2439=head2 EXAMPLES 2711=head2 EXAMPLES
2440 2712
2441For a real-world example of a program the includes libev 2713For a real-world example of a program the includes libev
2442verbatim, you can have a look at the EV perl module 2714verbatim, you can have a look at the EV perl module
… …
2483 2755
2484=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2756=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2485 2757
2486This means that, when you have a watcher that triggers in one hour and 2758This means that, when you have a watcher that triggers in one hour and
2487there are 100 watchers that would trigger before that then inserting will 2759there are 100 watchers that would trigger before that then inserting will
2488have to skip those 100 watchers. 2760have to skip roughly seven (C<ld 100>) of these watchers.
2489 2761
2490=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2762=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2491 2763
2492That means that for changing a timer costs less than removing/adding them 2764That means that changing a timer costs less than removing/adding them
2493as only the relative motion in the event queue has to be paid for. 2765as only the relative motion in the event queue has to be paid for.
2494 2766
2495=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2767=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2496 2768
2497These just add the watcher into an array or at the head of a list. 2769These just add the watcher into an array or at the head of a list.
2770
2498=item Stopping check/prepare/idle watchers: O(1) 2771=item Stopping check/prepare/idle watchers: O(1)
2499 2772
2500=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2773=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2501 2774
2502These watchers are stored in lists then need to be walked to find the 2775These watchers are stored in lists then need to be walked to find the
2503correct watcher to remove. The lists are usually short (you don't usually 2776correct watcher to remove. The lists are usually short (you don't usually
2504have many watchers waiting for the same fd or signal). 2777have many watchers waiting for the same fd or signal).
2505 2778
2506=item Finding the next timer per loop iteration: O(1) 2779=item Finding the next timer in each loop iteration: O(1)
2780
2781By virtue of using a binary heap, the next timer is always found at the
2782beginning of the storage array.
2507 2783
2508=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2784=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2509 2785
2510A change means an I/O watcher gets started or stopped, which requires 2786A change means an I/O watcher gets started or stopped, which requires
2511libev to recalculate its status (and possibly tell the kernel). 2787libev to recalculate its status (and possibly tell the kernel, depending
2788on backend and wether C<ev_io_set> was used).
2512 2789
2513=item Activating one watcher: O(1) 2790=item Activating one watcher (putting it into the pending state): O(1)
2514 2791
2515=item Priority handling: O(number_of_priorities) 2792=item Priority handling: O(number_of_priorities)
2516 2793
2517Priorities are implemented by allocating some space for each 2794Priorities are implemented by allocating some space for each
2518priority. When doing priority-based operations, libev usually has to 2795priority. When doing priority-based operations, libev usually has to
2519linearly search all the priorities. 2796linearly search all the priorities, but starting/stopping and activating
2797watchers becomes O(1) w.r.t. prioritiy handling.
2520 2798
2521=back 2799=back
2522 2800
2523 2801
2802=head1 Win32 platform limitations and workarounds
2803
2804Win32 doesn't support any of the standards (e.g. POSIX) that libev
2805requires, and its I/O model is fundamentally incompatible with the POSIX
2806model. Libev still offers limited functionality on this platform in
2807the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2808descriptors. This only applies when using Win32 natively, not when using
2809e.g. cygwin.
2810
2811There is no supported compilation method available on windows except
2812embedding it into other applications.
2813
2814Due to the many, low, and arbitrary limits on the win32 platform and the
2815abysmal performance of winsockets, using a large number of sockets is not
2816recommended (and not reasonable). If your program needs to use more than
2817a hundred or so sockets, then likely it needs to use a totally different
2818implementation for windows, as libev offers the POSIX model, which cannot
2819be implemented efficiently on windows (microsoft monopoly games).
2820
2821=over 4
2822
2823=item The winsocket select function
2824
2825The winsocket C<select> function doesn't follow POSIX in that it requires
2826socket I<handles> and not socket I<file descriptors>. This makes select
2827very inefficient, and also requires a mapping from file descriptors
2828to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2829C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2830symbols for more info.
2831
2832The configuration for a "naked" win32 using the microsoft runtime
2833libraries and raw winsocket select is:
2834
2835 #define EV_USE_SELECT 1
2836 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2837
2838Note that winsockets handling of fd sets is O(n), so you can easily get a
2839complexity in the O(n²) range when using win32.
2840
2841=item Limited number of file descriptors
2842
2843Windows has numerous arbitrary (and low) limits on things. Early versions
2844of winsocket's select only supported waiting for a max. of C<64> handles
2845(probably owning to the fact that all windows kernels can only wait for
2846C<64> things at the same time internally; microsoft recommends spawning a
2847chain of threads and wait for 63 handles and the previous thread in each).
2848
2849Newer versions support more handles, but you need to define C<FD_SETSIZE>
2850to some high number (e.g. C<2048>) before compiling the winsocket select
2851call (which might be in libev or elsewhere, for example, perl does its own
2852select emulation on windows).
2853
2854Another limit is the number of file descriptors in the microsoft runtime
2855libraries, which by default is C<64> (there must be a hidden I<64> fetish
2856or something like this inside microsoft). You can increase this by calling
2857C<_setmaxstdio>, which can increase this limit to C<2048> (another
2858arbitrary limit), but is broken in many versions of the microsoft runtime
2859libraries.
2860
2861This might get you to about C<512> or C<2048> sockets (depending on
2862windows version and/or the phase of the moon). To get more, you need to
2863wrap all I/O functions and provide your own fd management, but the cost of
2864calling select (O(n²)) will likely make this unworkable.
2865
2866=back
2867
2868
2524=head1 AUTHOR 2869=head1 AUTHOR
2525 2870
2526Marc Lehmann <libev@schmorp.de>. 2871Marc Lehmann <libev@schmorp.de>.
2527 2872

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