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Revision 1.33 by root, Wed Nov 28 18:29:29 2007 UTC vs.
Revision 1.58 by root, Sat Dec 22 16:53:56 2007 UTC

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126. ds Ae AE 126. ds Ae AE
127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title "EV 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH EV 1 "2007-12-22" "perl v5.8.8" "User Contributed Perl Documentation"
133.SH "NAME" 133.SH "NAME"
134libev \- a high performance full\-featured event loop written in C 134libev \- a high performance full\-featured event loop written in C
135.SH "SYNOPSIS" 135.SH "SYNOPSIS"
136.IX Header "SYNOPSIS" 136.IX Header "SYNOPSIS"
137.Vb 1 137.Vb 1
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196\& return 0; 196\& return 0;
197\& } 197\& }
198.Ve 198.Ve
199.SH "DESCRIPTION" 199.SH "DESCRIPTION"
200.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
201The newest version of this document is also available as a html-formatted
202web page you might find easier to navigate when reading it for the first
203time: <http://cvs.schmorp.de/libev/ev.html>.
204.PP
201Libev is an event loop: you register interest in certain events (such as a 205Libev is an event loop: you register interest in certain events (such as a
202file descriptor being readable or a timeout occuring), and it will manage 206file descriptor being readable or a timeout occurring), and it will manage
203these event sources and provide your program with events. 207these event sources and provide your program with events.
204.PP 208.PP
205To do this, it must take more or less complete control over your process 209To do this, it must take more or less complete control over your process
206(or thread) by executing the \fIevent loop\fR handler, and will then 210(or thread) by executing the \fIevent loop\fR handler, and will then
207communicate events via a callback mechanism. 211communicate events via a callback mechanism.
… …
239Libev represents time as a single floating point number, representing the 243Libev represents time as a single floating point number, representing the
240(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 244(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
241the beginning of 1970, details are complicated, don't ask). This type is 245the beginning of 1970, details are complicated, don't ask). This type is
242called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 246called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
243to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on 247to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
244it, you should treat it as such. 248it, you should treat it as some floatingpoint value. Unlike the name
249component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
250throughout libev.
245.SH "GLOBAL FUNCTIONS" 251.SH "GLOBAL FUNCTIONS"
246.IX Header "GLOBAL FUNCTIONS" 252.IX Header "GLOBAL FUNCTIONS"
247These functions can be called anytime, even before initialising the 253These functions can be called anytime, even before initialising the
248library in any way. 254library in any way.
249.IP "ev_tstamp ev_time ()" 4 255.IP "ev_tstamp ev_time ()" 4
250.IX Item "ev_tstamp ev_time ()" 256.IX Item "ev_tstamp ev_time ()"
251Returns the current time as libev would use it. Please note that the 257Returns the current time as libev would use it. Please note that the
252\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp 258\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp
253you actually want to know. 259you actually want to know.
260.IP "ev_sleep (ev_tstamp interval)" 4
261.IX Item "ev_sleep (ev_tstamp interval)"
262Sleep for the given interval: The current thread will be blocked until
263either it is interrupted or the given time interval has passed. Basically
264this is a subsecond-resolution \f(CW\*(C`sleep ()\*(C'\fR.
254.IP "int ev_version_major ()" 4 265.IP "int ev_version_major ()" 4
255.IX Item "int ev_version_major ()" 266.IX Item "int ev_version_major ()"
256.PD 0 267.PD 0
257.IP "int ev_version_minor ()" 4 268.IP "int ev_version_minor ()" 4
258.IX Item "int ev_version_minor ()" 269.IX Item "int ev_version_minor ()"
259.PD 270.PD
260You can find out the major and minor version numbers of the library 271You can find out the major and minor \s-1ABI\s0 version numbers of the library
261you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and 272you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
262\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global 273\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
263symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the 274symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
264version of the library your program was compiled against. 275version of the library your program was compiled against.
265.Sp 276.Sp
277These version numbers refer to the \s-1ABI\s0 version of the library, not the
278release version.
279.Sp
266Usually, it's a good idea to terminate if the major versions mismatch, 280Usually, it's a good idea to terminate if the major versions mismatch,
267as this indicates an incompatible change. Minor versions are usually 281as this indicates an incompatible change. Minor versions are usually
268compatible to older versions, so a larger minor version alone is usually 282compatible to older versions, so a larger minor version alone is usually
269not a problem. 283not a problem.
270.Sp 284.Sp
271Example: Make sure we haven't accidentally been linked against the wrong 285Example: Make sure we haven't accidentally been linked against the wrong
272version. 286version.
… …
411or setgid) then libev will \fInot\fR look at the environment variable 425or setgid) then libev will \fInot\fR look at the environment variable
412\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 426\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
413override the flags completely if it is found in the environment. This is 427override the flags completely if it is found in the environment. This is
414useful to try out specific backends to test their performance, or to work 428useful to try out specific backends to test their performance, or to work
415around bugs. 429around bugs.
430.ie n .IP """EVFLAG_FORKCHECK""" 4
431.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
432.IX Item "EVFLAG_FORKCHECK"
433Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
434a fork, you can also make libev check for a fork in each iteration by
435enabling this flag.
436.Sp
437This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
438and thus this might slow down your event loop if you do a lot of loop
439iterations and little real work, but is usually not noticeable (on my
440Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
441without a syscall and thus \fIvery\fR fast, but my Linux system also has
442\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
443.Sp
444The big advantage of this flag is that you can forget about fork (and
445forget about forgetting to tell libev about forking) when you use this
446flag.
447.Sp
448This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
449environment variable.
416.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 450.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
417.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 451.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
418.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 452.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
419This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 453This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
420libev tries to roll its own fd_set with no limits on the number of fds, 454libev tries to roll its own fd_set with no limits on the number of fds,
421but if that fails, expect a fairly low limit on the number of fds when 455but if that fails, expect a fairly low limit on the number of fds when
422using this backend. It doesn't scale too well (O(highest_fd)), but its usually 456using this backend. It doesn't scale too well (O(highest_fd)), but its
423the fastest backend for a low number of fds. 457usually the fastest backend for a low number of (low\-numbered :) fds.
458.Sp
459To get good performance out of this backend you need a high amount of
460parallelity (most of the file descriptors should be busy). If you are
461writing a server, you should \f(CW\*(C`accept ()\*(C'\fR in a loop to accept as many
462connections as possible during one iteration. You might also want to have
463a look at \f(CW\*(C`ev_set_io_collect_interval ()\*(C'\fR to increase the amount of
464readyness notifications you get per iteration.
424.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 465.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
425.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 466.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
426.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" 467.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
427And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than 468And this is your standard \fIpoll\fR\|(2) backend. It's more complicated
428select, but handles sparse fds better and has no artificial limit on the 469than select, but handles sparse fds better and has no artificial
429number of fds you can use (except it will slow down considerably with a 470limit on the number of fds you can use (except it will slow down
430lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 471considerably with a lot of inactive fds). It scales similarly to select,
472i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
473performance tips.
431.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 474.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
432.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 475.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
433.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 476.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
434For few fds, this backend is a bit little slower than poll and select, 477For few fds, this backend is a bit little slower than poll and select,
435but it scales phenomenally better. While poll and select usually scale like 478but it scales phenomenally better. While poll and select usually scale
436O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 479like O(total_fds) where n is the total number of fds (or the highest fd),
437either O(1) or O(active_fds). 480epoll scales either O(1) or O(active_fds). The epoll design has a number
481of shortcomings, such as silently dropping events in some hard-to-detect
482cases and rewiring a syscall per fd change, no fork support and bad
483support for dup.
438.Sp 484.Sp
439While stopping and starting an I/O watcher in the same iteration will 485While stopping, setting and starting an I/O watcher in the same iteration
440result in some caching, there is still a syscall per such incident 486will result in some caching, there is still a syscall per such incident
441(because the fd could point to a different file description now), so its 487(because the fd could point to a different file description now), so its
442best to avoid that. Also, \fIdup()\fRed file descriptors might not work very 488best to avoid that. Also, \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors might not work
443well if you register events for both fds. 489very well if you register events for both fds.
444.Sp 490.Sp
445Please note that epoll sometimes generates spurious notifications, so you 491Please note that epoll sometimes generates spurious notifications, so you
446need to use non-blocking I/O or other means to avoid blocking when no data 492need to use non-blocking I/O or other means to avoid blocking when no data
447(or space) is available. 493(or space) is available.
494.Sp
495Best performance from this backend is achieved by not unregistering all
496watchers for a file descriptor until it has been closed, if possible, i.e.
497keep at least one watcher active per fd at all times.
498.Sp
499While nominally embeddeble in other event loops, this feature is broken in
500all kernel versions tested so far.
448.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 501.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
449.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 502.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
450.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 503.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
451Kqueue deserves special mention, as at the time of this writing, it 504Kqueue deserves special mention, as at the time of this writing, it
452was broken on all BSDs except NetBSD (usually it doesn't work with 505was broken on all BSDs except NetBSD (usually it doesn't work reliably
453anything but sockets and pipes, except on Darwin, where of course its 506with anything but sockets and pipes, except on Darwin, where of course
454completely useless). For this reason its not being \*(L"autodetected\*(R" 507it's completely useless). For this reason it's not being \*(L"autodetected\*(R"
455unless you explicitly specify it explicitly in the flags (i.e. using 508unless you explicitly specify it explicitly in the flags (i.e. using
456\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). 509\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough)
510system like NetBSD.
511.Sp
512You still can embed kqueue into a normal poll or select backend and use it
513only for sockets (after having made sure that sockets work with kqueue on
514the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
457.Sp 515.Sp
458It scales in the same way as the epoll backend, but the interface to the 516It scales in the same way as the epoll backend, but the interface to the
459kernel is more efficient (which says nothing about its actual speed, of 517kernel is more efficient (which says nothing about its actual speed, of
460course). While starting and stopping an I/O watcher does not cause an 518course). While stopping, setting and starting an I/O watcher does never
461extra syscall as with epoll, it still adds up to four event changes per 519cause an extra syscall as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
462incident, so its best to avoid that. 520two event changes per incident, support for \f(CW\*(C`fork ()\*(C'\fR is very bad and it
521drops fds silently in similarly hard-to-detect cases.
522.Sp
523This backend usually performs well under most conditions.
524.Sp
525While nominally embeddable in other event loops, this doesn't work
526everywhere, so you might need to test for this. And since it is broken
527almost everywhere, you should only use it when you have a lot of sockets
528(for which it usually works), by embedding it into another event loop
529(e.g. \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR) and using it only for
530sockets.
463.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 531.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
464.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 532.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
465.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" 533.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
466This is not implemented yet (and might never be). 534This is not implemented yet (and might never be, unless you send me an
535implementation). According to reports, \f(CW\*(C`/dev/poll\*(C'\fR only supports sockets
536and is not embeddable, which would limit the usefulness of this backend
537immensely.
467.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 538.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
468.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 539.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
469.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" 540.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
470This uses the Solaris 10 port mechanism. As with everything on Solaris, 541This uses the Solaris 10 event port mechanism. As with everything on Solaris,
471it's really slow, but it still scales very well (O(active_fds)). 542it's really slow, but it still scales very well (O(active_fds)).
472.Sp 543.Sp
473Please note that solaris ports can result in a lot of spurious 544Please note that solaris event ports can deliver a lot of spurious
474notifications, so you need to use non-blocking I/O or other means to avoid 545notifications, so you need to use non-blocking I/O or other means to avoid
475blocking when no data (or space) is available. 546blocking when no data (or space) is available.
547.Sp
548While this backend scales well, it requires one system call per active
549file descriptor per loop iteration. For small and medium numbers of file
550descriptors a \*(L"slow\*(R" \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR backend
551might perform better.
476.ie n .IP """EVBACKEND_ALL""" 4 552.ie n .IP """EVBACKEND_ALL""" 4
477.el .IP "\f(CWEVBACKEND_ALL\fR" 4 553.el .IP "\f(CWEVBACKEND_ALL\fR" 4
478.IX Item "EVBACKEND_ALL" 554.IX Item "EVBACKEND_ALL"
479Try all backends (even potentially broken ones that wouldn't be tried 555Try all backends (even potentially broken ones that wouldn't be tried
480with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as 556with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
481\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. 557\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
558.Sp
559It is definitely not recommended to use this flag.
482.RE 560.RE
483.RS 4 561.RS 4
484.Sp 562.Sp
485If one or more of these are ored into the flags value, then only these 563If one or more of these are ored into the flags value, then only these
486backends will be tried (in the reverse order as given here). If none are 564backends will be tried (in the reverse order as given here). If none are
… …
528Destroys the default loop again (frees all memory and kernel state 606Destroys the default loop again (frees all memory and kernel state
529etc.). None of the active event watchers will be stopped in the normal 607etc.). None of the active event watchers will be stopped in the normal
530sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your 608sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
531responsibility to either stop all watchers cleanly yoursef \fIbefore\fR 609responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
532calling this function, or cope with the fact afterwards (which is usually 610calling this function, or cope with the fact afterwards (which is usually
533the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them 611the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
534for example). 612for example).
613.Sp
614Note that certain global state, such as signal state, will not be freed by
615this function, and related watchers (such as signal and child watchers)
616would need to be stopped manually.
617.Sp
618In general it is not advisable to call this function except in the
619rare occasion where you really need to free e.g. the signal handling
620pipe fds. If you need dynamically allocated loops it is better to use
621\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
535.IP "ev_loop_destroy (loop)" 4 622.IP "ev_loop_destroy (loop)" 4
536.IX Item "ev_loop_destroy (loop)" 623.IX Item "ev_loop_destroy (loop)"
537Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 624Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
538earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 625earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
539.IP "ev_default_fork ()" 4 626.IP "ev_default_fork ()" 4
… …
561.IP "ev_loop_fork (loop)" 4 648.IP "ev_loop_fork (loop)" 4
562.IX Item "ev_loop_fork (loop)" 649.IX Item "ev_loop_fork (loop)"
563Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 650Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
564\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 651\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
565after fork, and how you do this is entirely your own problem. 652after fork, and how you do this is entirely your own problem.
653.IP "unsigned int ev_loop_count (loop)" 4
654.IX Item "unsigned int ev_loop_count (loop)"
655Returns the count of loop iterations for the loop, which is identical to
656the number of times libev did poll for new events. It starts at \f(CW0\fR and
657happily wraps around with enough iterations.
658.Sp
659This value can sometimes be useful as a generation counter of sorts (it
660\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
661\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
566.IP "unsigned int ev_backend (loop)" 4 662.IP "unsigned int ev_backend (loop)" 4
567.IX Item "unsigned int ev_backend (loop)" 663.IX Item "unsigned int ev_backend (loop)"
568Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 664Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
569use. 665use.
570.IP "ev_tstamp ev_now (loop)" 4 666.IP "ev_tstamp ev_now (loop)" 4
571.IX Item "ev_tstamp ev_now (loop)" 667.IX Item "ev_tstamp ev_now (loop)"
572Returns the current \*(L"event loop time\*(R", which is the time the event loop 668Returns the current \*(L"event loop time\*(R", which is the time the event loop
573received events and started processing them. This timestamp does not 669received events and started processing them. This timestamp does not
574change as long as callbacks are being processed, and this is also the base 670change as long as callbacks are being processed, and this is also the base
575time used for relative timers. You can treat it as the timestamp of the 671time used for relative timers. You can treat it as the timestamp of the
576event occuring (or more correctly, libev finding out about it). 672event occurring (or more correctly, libev finding out about it).
577.IP "ev_loop (loop, int flags)" 4 673.IP "ev_loop (loop, int flags)" 4
578.IX Item "ev_loop (loop, int flags)" 674.IX Item "ev_loop (loop, int flags)"
579Finally, this is it, the event handler. This function usually is called 675Finally, this is it, the event handler. This function usually is called
580after you initialised all your watchers and you want to start handling 676after you initialised all your watchers and you want to start handling
581events. 677events.
… …
601libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 697libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
602usually a better approach for this kind of thing. 698usually a better approach for this kind of thing.
603.Sp 699.Sp
604Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 700Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
605.Sp 701.Sp
606.Vb 18 702.Vb 19
703\& - Before the first iteration, call any pending watchers.
607\& * If there are no active watchers (reference count is zero), return. 704\& * If there are no active watchers (reference count is zero), return.
608\& - Queue prepare watchers and then call all outstanding watchers. 705\& - Queue all prepare watchers and then call all outstanding watchers.
609\& - If we have been forked, recreate the kernel state. 706\& - If we have been forked, recreate the kernel state.
610\& - Update the kernel state with all outstanding changes. 707\& - Update the kernel state with all outstanding changes.
611\& - Update the "event loop time". 708\& - Update the "event loop time".
612\& - Calculate for how long to block. 709\& - Calculate for how long to block.
613\& - Block the process, waiting for any events. 710\& - Block the process, waiting for any events.
… …
670.Sp 767.Sp
671.Vb 2 768.Vb 2
672\& ev_ref (loop); 769\& ev_ref (loop);
673\& ev_signal_stop (loop, &exitsig); 770\& ev_signal_stop (loop, &exitsig);
674.Ve 771.Ve
772.IP "ev_set_io_collect_interval (loop, ev_tstamp interval)" 4
773.IX Item "ev_set_io_collect_interval (loop, ev_tstamp interval)"
774.PD 0
775.IP "ev_set_timeout_collect_interval (loop, ev_tstamp interval)" 4
776.IX Item "ev_set_timeout_collect_interval (loop, ev_tstamp interval)"
777.PD
778These advanced functions influence the time that libev will spend waiting
779for events. Both are by default \f(CW0\fR, meaning that libev will try to
780invoke timer/periodic callbacks and I/O callbacks with minimum latency.
781.Sp
782Setting these to a higher value (the \f(CW\*(C`interval\*(C'\fR \fImust\fR be >= \f(CW0\fR)
783allows libev to delay invocation of I/O and timer/periodic callbacks to
784increase efficiency of loop iterations.
785.Sp
786The background is that sometimes your program runs just fast enough to
787handle one (or very few) event(s) per loop iteration. While this makes
788the program responsive, it also wastes a lot of \s-1CPU\s0 time to poll for new
789events, especially with backends like \f(CW\*(C`select ()\*(C'\fR which have a high
790overhead for the actual polling but can deliver many events at once.
791.Sp
792By setting a higher \fIio collect interval\fR you allow libev to spend more
793time collecting I/O events, so you can handle more events per iteration,
794at the cost of increasing latency. Timeouts (both \f(CW\*(C`ev_periodic\*(C'\fR and
795\&\f(CW\*(C`ev_timer\*(C'\fR) will be not affected. Setting this to a non-null value will
796introduce an additional \f(CW\*(C`ev_sleep ()\*(C'\fR call into most loop iterations.
797.Sp
798Likewise, by setting a higher \fItimeout collect interval\fR you allow libev
799to spend more time collecting timeouts, at the expense of increased
800latency (the watcher callback will be called later). \f(CW\*(C`ev_io\*(C'\fR watchers
801will not be affected. Setting this to a non-null value will not introduce
802any overhead in libev.
803.Sp
804Many (busy) programs can usually benefit by setting the io collect
805interval to a value near \f(CW0.1\fR or so, which is often enough for
806interactive servers (of course not for games), likewise for timeouts. It
807usually doesn't make much sense to set it to a lower value than \f(CW0.01\fR,
808as this approsaches the timing granularity of most systems.
675.SH "ANATOMY OF A WATCHER" 809.SH "ANATOMY OF A WATCHER"
676.IX Header "ANATOMY OF A WATCHER" 810.IX Header "ANATOMY OF A WATCHER"
677A watcher is a structure that you create and register to record your 811A watcher is a structure that you create and register to record your
678interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 812interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
679become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 813become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
856.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 990.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
857.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 991.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
858Returns a true value iff the watcher is pending, (i.e. it has outstanding 992Returns a true value iff the watcher is pending, (i.e. it has outstanding
859events but its callback has not yet been invoked). As long as a watcher 993events but its callback has not yet been invoked). As long as a watcher
860is pending (but not active) you must not call an init function on it (but 994is pending (but not active) you must not call an init function on it (but
861\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to 995\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
862libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). 996make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
997it).
863.IP "callback ev_cb (ev_TYPE *watcher)" 4 998.IP "callback ev_cb (ev_TYPE *watcher)" 4
864.IX Item "callback ev_cb (ev_TYPE *watcher)" 999.IX Item "callback ev_cb (ev_TYPE *watcher)"
865Returns the callback currently set on the watcher. 1000Returns the callback currently set on the watcher.
866.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 1001.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
867.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 1002.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
868Change the callback. You can change the callback at virtually any time 1003Change the callback. You can change the callback at virtually any time
869(modulo threads). 1004(modulo threads).
1005.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
1006.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
1007.PD 0
1008.IP "int ev_priority (ev_TYPE *watcher)" 4
1009.IX Item "int ev_priority (ev_TYPE *watcher)"
1010.PD
1011Set and query the priority of the watcher. The priority is a small
1012integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
1013(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
1014before watchers with lower priority, but priority will not keep watchers
1015from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
1016.Sp
1017This means that priorities are \fIonly\fR used for ordering callback
1018invocation after new events have been received. This is useful, for
1019example, to reduce latency after idling, or more often, to bind two
1020watchers on the same event and make sure one is called first.
1021.Sp
1022If you need to suppress invocation when higher priority events are pending
1023you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
1024.Sp
1025You \fImust not\fR change the priority of a watcher as long as it is active or
1026pending.
1027.Sp
1028The default priority used by watchers when no priority has been set is
1029always \f(CW0\fR, which is supposed to not be too high and not be too low :).
1030.Sp
1031Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
1032fine, as long as you do not mind that the priority value you query might
1033or might not have been adjusted to be within valid range.
1034.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
1035.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
1036Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
1037\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
1038can deal with that fact.
1039.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
1040.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
1041If the watcher is pending, this function returns clears its pending status
1042and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
1043watcher isn't pending it does nothing and returns \f(CW0\fR.
870.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 1044.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
871.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 1045.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
872Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 1046Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
873and read at any time, libev will completely ignore it. This can be used 1047and read at any time, libev will completely ignore it. This can be used
874to associate arbitrary data with your watcher. If you need more data and 1048to associate arbitrary data with your watcher. If you need more data and
… …
985it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning 1159it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
986\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. 1160\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
987.PP 1161.PP
988If you cannot run the fd in non-blocking mode (for example you should not 1162If you cannot run the fd in non-blocking mode (for example you should not
989play around with an Xlib connection), then you have to seperately re-test 1163play around with an Xlib connection), then you have to seperately re-test
990wether a file descriptor is really ready with a known-to-be good interface 1164whether a file descriptor is really ready with a known-to-be good interface
991such as poll (fortunately in our Xlib example, Xlib already does this on 1165such as poll (fortunately in our Xlib example, Xlib already does this on
992its own, so its quite safe to use). 1166its own, so its quite safe to use).
1167.PP
1168\fIThe special problem of disappearing file descriptors\fR
1169.IX Subsection "The special problem of disappearing file descriptors"
1170.PP
1171Some backends (e.g. kqueue, epoll) need to be told about closing a file
1172descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1173such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1174descriptor, but when it goes away, the operating system will silently drop
1175this interest. If another file descriptor with the same number then is
1176registered with libev, there is no efficient way to see that this is, in
1177fact, a different file descriptor.
1178.PP
1179To avoid having to explicitly tell libev about such cases, libev follows
1180the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1181will assume that this is potentially a new file descriptor, otherwise
1182it is assumed that the file descriptor stays the same. That means that
1183you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
1184descriptor even if the file descriptor number itself did not change.
1185.PP
1186This is how one would do it normally anyway, the important point is that
1187the libev application should not optimise around libev but should leave
1188optimisations to libev.
1189.PP
1190\fIThe special problem of dup'ed file descriptors\fR
1191.IX Subsection "The special problem of dup'ed file descriptors"
1192.PP
1193Some backends (e.g. epoll), cannot register events for file descriptors,
1194but only events for the underlying file descriptions. That menas when you
1195have \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors and register events for them, only one
1196file descriptor might actually receive events.
1197.PP
1198There is no workaorund possible except not registering events
1199for potentially \f(CW\*(C`dup ()\*(C'\fR'ed file descriptors or to resort to
1200\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1201.PP
1202\fIThe special problem of fork\fR
1203.IX Subsection "The special problem of fork"
1204.PP
1205Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit
1206useless behaviour. Libev fully supports fork, but needs to be told about
1207it in the child.
1208.PP
1209To support fork in your programs, you either have to call
1210\&\f(CW\*(C`ev_default_fork ()\*(C'\fR or \f(CW\*(C`ev_loop_fork ()\*(C'\fR after a fork in the child,
1211enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or
1212\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1213.PP
1214\fIWatcher-Specific Functions\fR
1215.IX Subsection "Watcher-Specific Functions"
993.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1216.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
994.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1217.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
995.PD 0 1218.PD 0
996.IP "ev_io_set (ev_io *, int fd, int events)" 4 1219.IP "ev_io_set (ev_io *, int fd, int events)" 4
997.IX Item "ev_io_set (ev_io *, int fd, int events)" 1220.IX Item "ev_io_set (ev_io *, int fd, int events)"
… …
1050.Ve 1273.Ve
1051.PP 1274.PP
1052The callback is guarenteed to be invoked only when its timeout has passed, 1275The callback is guarenteed to be invoked only when its timeout has passed,
1053but if multiple timers become ready during the same loop iteration then 1276but if multiple timers become ready during the same loop iteration then
1054order of execution is undefined. 1277order of execution is undefined.
1278.PP
1279\fIWatcher-Specific Functions and Data Members\fR
1280.IX Subsection "Watcher-Specific Functions and Data Members"
1055.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1281.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
1056.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1282.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
1057.PD 0 1283.PD 0
1058.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1284.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
1059.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1285.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
1071.IP "ev_timer_again (loop)" 4 1297.IP "ev_timer_again (loop)" 4
1072.IX Item "ev_timer_again (loop)" 1298.IX Item "ev_timer_again (loop)"
1073This will act as if the timer timed out and restart it again if it is 1299This will act as if the timer timed out and restart it again if it is
1074repeating. The exact semantics are: 1300repeating. The exact semantics are:
1075.Sp 1301.Sp
1302If the timer is pending, its pending status is cleared.
1303.Sp
1076If the timer is started but nonrepeating, stop it. 1304If the timer is started but nonrepeating, stop it (as if it timed out).
1077.Sp 1305.Sp
1078If the timer is repeating, either start it if necessary (with the repeat 1306If the timer is repeating, either start it if necessary (with the
1079value), or reset the running timer to the repeat value. 1307\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
1080.Sp 1308.Sp
1081This sounds a bit complicated, but here is a useful and typical 1309This sounds a bit complicated, but here is a useful and typical
1082example: Imagine you have a tcp connection and you want a so-called 1310example: Imagine you have a tcp connection and you want a so-called idle
1083idle timeout, that is, you want to be called when there have been, 1311timeout, that is, you want to be called when there have been, say, 60
1084say, 60 seconds of inactivity on the socket. The easiest way to do 1312seconds of inactivity on the socket. The easiest way to do this is to
1085this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling 1313configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
1086\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If 1314\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
1087you go into an idle state where you do not expect data to travel on the 1315you go into an idle state where you do not expect data to travel on the
1088socket, you can stop the timer, and again will automatically restart it if 1316socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1089need be. 1317automatically restart it if need be.
1090.Sp 1318.Sp
1091You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether 1319That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1092and only ever use the \f(CW\*(C`repeat\*(C'\fR value: 1320altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1093.Sp 1321.Sp
1094.Vb 8 1322.Vb 8
1095\& ev_timer_init (timer, callback, 0., 5.); 1323\& ev_timer_init (timer, callback, 0., 5.);
1096\& ev_timer_again (loop, timer); 1324\& ev_timer_again (loop, timer);
1097\& ... 1325\& ...
… …
1100\& ... 1328\& ...
1101\& timer->again = 10.; 1329\& timer->again = 10.;
1102\& ev_timer_again (loop, timer); 1330\& ev_timer_again (loop, timer);
1103.Ve 1331.Ve
1104.Sp 1332.Sp
1105This is more efficient then stopping/starting the timer eahc time you want 1333This is more slightly efficient then stopping/starting the timer each time
1106to modify its timeout value. 1334you want to modify its timeout value.
1107.IP "ev_tstamp repeat [read\-write]" 4 1335.IP "ev_tstamp repeat [read\-write]" 4
1108.IX Item "ev_tstamp repeat [read-write]" 1336.IX Item "ev_tstamp repeat [read-write]"
1109The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out 1337The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1110or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), 1338or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1111which is also when any modifications are taken into account. 1339which is also when any modifications are taken into account.
… …
1159but on wallclock time (absolute time). You can tell a periodic watcher 1387but on wallclock time (absolute time). You can tell a periodic watcher
1160to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1388to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
1161periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () 1389periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1162+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will 1390+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
1163take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1391take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
1164roughly 10 seconds later and of course not if you reset your system time 1392roughly 10 seconds later).
1165again).
1166.PP 1393.PP
1167They can also be used to implement vastly more complex timers, such as 1394They can also be used to implement vastly more complex timers, such as
1168triggering an event on eahc midnight, local time. 1395triggering an event on each midnight, local time or other, complicated,
1396rules.
1169.PP 1397.PP
1170As with timers, the callback is guarenteed to be invoked only when the 1398As with timers, the callback is guarenteed to be invoked only when the
1171time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1399time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1172during the same loop iteration then order of execution is undefined. 1400during the same loop iteration then order of execution is undefined.
1401.PP
1402\fIWatcher-Specific Functions and Data Members\fR
1403.IX Subsection "Watcher-Specific Functions and Data Members"
1173.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1404.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
1174.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1405.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
1175.PD 0 1406.PD 0
1176.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1407.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
1177.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1408.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1178.PD 1409.PD
1179Lots of arguments, lets sort it out... There are basically three modes of 1410Lots of arguments, lets sort it out... There are basically three modes of
1180operation, and we will explain them from simplest to complex: 1411operation, and we will explain them from simplest to complex:
1181.RS 4 1412.RS 4
1182.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1413.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
1183.IX Item "absolute timer (interval = reschedule_cb = 0)" 1414.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
1184In this configuration the watcher triggers an event at the wallclock time 1415In this configuration the watcher triggers an event at the wallclock time
1185\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1416\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1186that is, if it is to be run at January 1st 2011 then it will run when the 1417that is, if it is to be run at January 1st 2011 then it will run when the
1187system time reaches or surpasses this time. 1418system time reaches or surpasses this time.
1188.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1419.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
1189.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1420.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
1190In this mode the watcher will always be scheduled to time out at the next 1421In this mode the watcher will always be scheduled to time out at the next
1191\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1422\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
1192of any time jumps. 1423and then repeat, regardless of any time jumps.
1193.Sp 1424.Sp
1194This can be used to create timers that do not drift with respect to system 1425This can be used to create timers that do not drift with respect to system
1195time: 1426time:
1196.Sp 1427.Sp
1197.Vb 1 1428.Vb 1
… …
1204by 3600. 1435by 3600.
1205.Sp 1436.Sp
1206Another way to think about it (for the mathematically inclined) is that 1437Another way to think about it (for the mathematically inclined) is that
1207\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1438\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1208time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1439time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1440.Sp
1441For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1442\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1443this value.
1209.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1444.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
1210.IX Item "manual reschedule mode (reschedule_cb = callback)" 1445.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
1211In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1446In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1212ignored. Instead, each time the periodic watcher gets scheduled, the 1447ignored. Instead, each time the periodic watcher gets scheduled, the
1213reschedule callback will be called with the watcher as first, and the 1448reschedule callback will be called with the watcher as first, and the
1214current time as second argument. 1449current time as second argument.
1215.Sp 1450.Sp
1216\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1451\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1217ever, or make any event loop modifications\fR. If you need to stop it, 1452ever, or make any event loop modifications\fR. If you need to stop it,
1218return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1453return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1219starting a prepare watcher). 1454starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1220.Sp 1455.Sp
1221Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1456Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1222ev_tstamp now)\*(C'\fR, e.g.: 1457ev_tstamp now)\*(C'\fR, e.g.:
1223.Sp 1458.Sp
1224.Vb 4 1459.Vb 4
… …
1248.IX Item "ev_periodic_again (loop, ev_periodic *)" 1483.IX Item "ev_periodic_again (loop, ev_periodic *)"
1249Simply stops and restarts the periodic watcher again. This is only useful 1484Simply stops and restarts the periodic watcher again. This is only useful
1250when you changed some parameters or the reschedule callback would return 1485when you changed some parameters or the reschedule callback would return
1251a different time than the last time it was called (e.g. in a crond like 1486a different time than the last time it was called (e.g. in a crond like
1252program when the crontabs have changed). 1487program when the crontabs have changed).
1488.IP "ev_tstamp offset [read\-write]" 4
1489.IX Item "ev_tstamp offset [read-write]"
1490When repeating, this contains the offset value, otherwise this is the
1491absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1492.Sp
1493Can be modified any time, but changes only take effect when the periodic
1494timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1253.IP "ev_tstamp interval [read\-write]" 4 1495.IP "ev_tstamp interval [read\-write]" 4
1254.IX Item "ev_tstamp interval [read-write]" 1496.IX Item "ev_tstamp interval [read-write]"
1255The current interval value. Can be modified any time, but changes only 1497The current interval value. Can be modified any time, but changes only
1256take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being 1498take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1257called. 1499called.
1258.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 1500.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1259.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" 1501.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1260The current reschedule callback, or \f(CW0\fR, if this functionality is 1502The current reschedule callback, or \f(CW0\fR, if this functionality is
1261switched off. Can be changed any time, but changes only take effect when 1503switched off. Can be changed any time, but changes only take effect when
1262the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. 1504the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1505.IP "ev_tstamp at [read\-only]" 4
1506.IX Item "ev_tstamp at [read-only]"
1507When active, contains the absolute time that the watcher is supposed to
1508trigger next.
1263.PP 1509.PP
1264Example: Call a callback every hour, or, more precisely, whenever the 1510Example: Call a callback every hour, or, more precisely, whenever the
1265system clock is divisible by 3600. The callback invocation times have 1511system clock is divisible by 3600. The callback invocation times have
1266potentially a lot of jittering, but good long-term stability. 1512potentially a lot of jittering, but good long-term stability.
1267.PP 1513.PP
… …
1317first watcher gets started will libev actually register a signal watcher 1563first watcher gets started will libev actually register a signal watcher
1318with the kernel (thus it coexists with your own signal handlers as long 1564with the kernel (thus it coexists with your own signal handlers as long
1319as you don't register any with libev). Similarly, when the last signal 1565as you don't register any with libev). Similarly, when the last signal
1320watcher for a signal is stopped libev will reset the signal handler to 1566watcher for a signal is stopped libev will reset the signal handler to
1321\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1567\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1568.PP
1569\fIWatcher-Specific Functions and Data Members\fR
1570.IX Subsection "Watcher-Specific Functions and Data Members"
1322.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1571.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1323.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1572.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1324.PD 0 1573.PD 0
1325.IP "ev_signal_set (ev_signal *, int signum)" 4 1574.IP "ev_signal_set (ev_signal *, int signum)" 4
1326.IX Item "ev_signal_set (ev_signal *, int signum)" 1575.IX Item "ev_signal_set (ev_signal *, int signum)"
… …
1333.ie n .Sh """ev_child"" \- watch out for process status changes" 1582.ie n .Sh """ev_child"" \- watch out for process status changes"
1334.el .Sh "\f(CWev_child\fP \- watch out for process status changes" 1583.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1335.IX Subsection "ev_child - watch out for process status changes" 1584.IX Subsection "ev_child - watch out for process status changes"
1336Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1585Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1337some child status changes (most typically when a child of yours dies). 1586some child status changes (most typically when a child of yours dies).
1587.PP
1588\fIWatcher-Specific Functions and Data Members\fR
1589.IX Subsection "Watcher-Specific Functions and Data Members"
1338.IP "ev_child_init (ev_child *, callback, int pid)" 4 1590.IP "ev_child_init (ev_child *, callback, int pid)" 4
1339.IX Item "ev_child_init (ev_child *, callback, int pid)" 1591.IX Item "ev_child_init (ev_child *, callback, int pid)"
1340.PD 0 1592.PD 0
1341.IP "ev_child_set (ev_child *, int pid)" 4 1593.IP "ev_child_set (ev_child *, int pid)" 4
1342.IX Item "ev_child_set (ev_child *, int pid)" 1594.IX Item "ev_child_set (ev_child *, int pid)"
… …
1407reader). Inotify will be used to give hints only and should not change the 1659reader). Inotify will be used to give hints only and should not change the
1408semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs 1660semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1409to fall back to regular polling again even with inotify, but changes are 1661to fall back to regular polling again even with inotify, but changes are
1410usually detected immediately, and if the file exists there will be no 1662usually detected immediately, and if the file exists there will be no
1411polling. 1663polling.
1664.PP
1665\fIWatcher-Specific Functions and Data Members\fR
1666.IX Subsection "Watcher-Specific Functions and Data Members"
1412.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 1667.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1413.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 1668.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1414.PD 0 1669.PD 0
1415.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 1670.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1416.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 1671.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
… …
1477\& ev_stat_start (loop, &passwd); 1732\& ev_stat_start (loop, &passwd);
1478.Ve 1733.Ve
1479.ie n .Sh """ev_idle"" \- when you've got nothing better to do..." 1734.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1480.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." 1735.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1481.IX Subsection "ev_idle - when you've got nothing better to do..." 1736.IX Subsection "ev_idle - when you've got nothing better to do..."
1482Idle watchers trigger events when there are no other events are pending 1737Idle watchers trigger events when no other events of the same or higher
1483(prepare, check and other idle watchers do not count). That is, as long 1738priority are pending (prepare, check and other idle watchers do not
1484as your process is busy handling sockets or timeouts (or even signals, 1739count).
1485imagine) it will not be triggered. But when your process is idle all idle 1740.PP
1486watchers are being called again and again, once per event loop iteration \- 1741That is, as long as your process is busy handling sockets or timeouts
1742(or even signals, imagine) of the same or higher priority it will not be
1743triggered. But when your process is idle (or only lower-priority watchers
1744are pending), the idle watchers are being called once per event loop
1487until stopped, that is, or your process receives more events and becomes 1745iteration \- until stopped, that is, or your process receives more events
1488busy. 1746and becomes busy again with higher priority stuff.
1489.PP 1747.PP
1490The most noteworthy effect is that as long as any idle watchers are 1748The most noteworthy effect is that as long as any idle watchers are
1491active, the process will not block when waiting for new events. 1749active, the process will not block when waiting for new events.
1492.PP 1750.PP
1493Apart from keeping your process non-blocking (which is a useful 1751Apart from keeping your process non-blocking (which is a useful
1494effect on its own sometimes), idle watchers are a good place to do 1752effect on its own sometimes), idle watchers are a good place to do
1495\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1753\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1496event loop has handled all outstanding events. 1754event loop has handled all outstanding events.
1755.PP
1756\fIWatcher-Specific Functions and Data Members\fR
1757.IX Subsection "Watcher-Specific Functions and Data Members"
1497.IP "ev_idle_init (ev_signal *, callback)" 4 1758.IP "ev_idle_init (ev_signal *, callback)" 4
1498.IX Item "ev_idle_init (ev_signal *, callback)" 1759.IX Item "ev_idle_init (ev_signal *, callback)"
1499Initialises and configures the idle watcher \- it has no parameters of any 1760Initialises and configures the idle watcher \- it has no parameters of any
1500kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1761kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1501believe me. 1762believe me.
… …
1556are ready to run (it's actually more complicated: it only runs coroutines 1817are ready to run (it's actually more complicated: it only runs coroutines
1557with priority higher than or equal to the event loop and one coroutine 1818with priority higher than or equal to the event loop and one coroutine
1558of lower priority, but only once, using idle watchers to keep the event 1819of lower priority, but only once, using idle watchers to keep the event
1559loop from blocking if lower-priority coroutines are active, thus mapping 1820loop from blocking if lower-priority coroutines are active, thus mapping
1560low-priority coroutines to idle/background tasks). 1821low-priority coroutines to idle/background tasks).
1822.PP
1823It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1824priority, to ensure that they are being run before any other watchers
1825after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1826too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1827supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers
1828did their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other
1829(non\-libev) event loops those other event loops might be in an unusable
1830state until their \f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to
1831coexist peacefully with others).
1832.PP
1833\fIWatcher-Specific Functions and Data Members\fR
1834.IX Subsection "Watcher-Specific Functions and Data Members"
1561.IP "ev_prepare_init (ev_prepare *, callback)" 4 1835.IP "ev_prepare_init (ev_prepare *, callback)" 4
1562.IX Item "ev_prepare_init (ev_prepare *, callback)" 1836.IX Item "ev_prepare_init (ev_prepare *, callback)"
1563.PD 0 1837.PD 0
1564.IP "ev_check_init (ev_check *, callback)" 4 1838.IP "ev_check_init (ev_check *, callback)" 4
1565.IX Item "ev_check_init (ev_check *, callback)" 1839.IX Item "ev_check_init (ev_check *, callback)"
1566.PD 1840.PD
1567Initialises and configures the prepare or check watcher \- they have no 1841Initialises and configures the prepare or check watcher \- they have no
1568parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1842parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1569macros, but using them is utterly, utterly and completely pointless. 1843macros, but using them is utterly, utterly and completely pointless.
1570.PP 1844.PP
1571Example: To include a library such as adns, you would add \s-1IO\s0 watchers 1845There are a number of principal ways to embed other event loops or modules
1572and a timeout watcher in a prepare handler, as required by libadns, and 1846into libev. Here are some ideas on how to include libadns into libev
1847(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1848use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1849embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1850into the Glib event loop).
1851.PP
1852Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1573in a check watcher, destroy them and call into libadns. What follows is 1853and in a check watcher, destroy them and call into libadns. What follows
1574pseudo-code only of course: 1854is pseudo-code only of course. This requires you to either use a low
1855priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1856the callbacks for the IO/timeout watchers might not have been called yet.
1575.PP 1857.PP
1576.Vb 2 1858.Vb 2
1577\& static ev_io iow [nfd]; 1859\& static ev_io iow [nfd];
1578\& static ev_timer tw; 1860\& static ev_timer tw;
1579.Ve 1861.Ve
1580.PP 1862.PP
1581.Vb 9 1863.Vb 4
1582\& static void 1864\& static void
1583\& io_cb (ev_loop *loop, ev_io *w, int revents) 1865\& io_cb (ev_loop *loop, ev_io *w, int revents)
1584\& { 1866\& {
1585\& // set the relevant poll flags
1586\& // could also call adns_processreadable etc. here
1587\& struct pollfd *fd = (struct pollfd *)w->data;
1588\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1589\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1590\& } 1867\& }
1591.Ve 1868.Ve
1592.PP 1869.PP
1593.Vb 7 1870.Vb 8
1594\& // create io watchers for each fd and a timer before blocking 1871\& // create io watchers for each fd and a timer before blocking
1595\& static void 1872\& static void
1596\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) 1873\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1597\& { 1874\& {
1598\& int timeout = 3600000;truct pollfd fds [nfd]; 1875\& int timeout = 3600000;
1876\& struct pollfd fds [nfd];
1599\& // actual code will need to loop here and realloc etc. 1877\& // actual code will need to loop here and realloc etc.
1600\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); 1878\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1601.Ve 1879.Ve
1602.PP 1880.PP
1603.Vb 3 1881.Vb 3
… …
1605\& ev_timer_init (&tw, 0, timeout * 1e-3); 1883\& ev_timer_init (&tw, 0, timeout * 1e-3);
1606\& ev_timer_start (loop, &tw); 1884\& ev_timer_start (loop, &tw);
1607.Ve 1885.Ve
1608.PP 1886.PP
1609.Vb 6 1887.Vb 6
1610\& // create on ev_io per pollfd 1888\& // create one ev_io per pollfd
1611\& for (int i = 0; i < nfd; ++i) 1889\& for (int i = 0; i < nfd; ++i)
1612\& { 1890\& {
1613\& ev_io_init (iow + i, io_cb, fds [i].fd, 1891\& ev_io_init (iow + i, io_cb, fds [i].fd,
1614\& ((fds [i].events & POLLIN ? EV_READ : 0) 1892\& ((fds [i].events & POLLIN ? EV_READ : 0)
1615\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); 1893\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1616.Ve 1894.Ve
1617.PP 1895.PP
1618.Vb 5 1896.Vb 4
1619\& fds [i].revents = 0; 1897\& fds [i].revents = 0;
1620\& iow [i].data = fds + i;
1621\& ev_io_start (loop, iow + i); 1898\& ev_io_start (loop, iow + i);
1622\& } 1899\& }
1623\& } 1900\& }
1624.Ve 1901.Ve
1625.PP 1902.PP
… …
1629\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) 1906\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1630\& { 1907\& {
1631\& ev_timer_stop (loop, &tw); 1908\& ev_timer_stop (loop, &tw);
1632.Ve 1909.Ve
1633.PP 1910.PP
1634.Vb 2 1911.Vb 8
1635\& for (int i = 0; i < nfd; ++i) 1912\& for (int i = 0; i < nfd; ++i)
1913\& {
1914\& // set the relevant poll flags
1915\& // could also call adns_processreadable etc. here
1916\& struct pollfd *fd = fds + i;
1917\& int revents = ev_clear_pending (iow + i);
1918\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1919\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1920.Ve
1921.PP
1922.Vb 3
1923\& // now stop the watcher
1636\& ev_io_stop (loop, iow + i); 1924\& ev_io_stop (loop, iow + i);
1925\& }
1637.Ve 1926.Ve
1638.PP 1927.PP
1639.Vb 2 1928.Vb 2
1640\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); 1929\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1930\& }
1931.Ve
1932.PP
1933Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1934in the prepare watcher and would dispose of the check watcher.
1935.PP
1936Method 3: If the module to be embedded supports explicit event
1937notification (adns does), you can also make use of the actual watcher
1938callbacks, and only destroy/create the watchers in the prepare watcher.
1939.PP
1940.Vb 5
1941\& static void
1942\& timer_cb (EV_P_ ev_timer *w, int revents)
1943\& {
1944\& adns_state ads = (adns_state)w->data;
1945\& update_now (EV_A);
1946.Ve
1947.PP
1948.Vb 2
1949\& adns_processtimeouts (ads, &tv_now);
1950\& }
1951.Ve
1952.PP
1953.Vb 5
1954\& static void
1955\& io_cb (EV_P_ ev_io *w, int revents)
1956\& {
1957\& adns_state ads = (adns_state)w->data;
1958\& update_now (EV_A);
1959.Ve
1960.PP
1961.Vb 3
1962\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1963\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1964\& }
1965.Ve
1966.PP
1967.Vb 1
1968\& // do not ever call adns_afterpoll
1969.Ve
1970.PP
1971Method 4: Do not use a prepare or check watcher because the module you
1972want to embed is too inflexible to support it. Instead, youc na override
1973their poll function. The drawback with this solution is that the main
1974loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1975this.
1976.PP
1977.Vb 4
1978\& static gint
1979\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1980\& {
1981\& int got_events = 0;
1982.Ve
1983.PP
1984.Vb 2
1985\& for (n = 0; n < nfds; ++n)
1986\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1987.Ve
1988.PP
1989.Vb 2
1990\& if (timeout >= 0)
1991\& // create/start timer
1992.Ve
1993.PP
1994.Vb 2
1995\& // poll
1996\& ev_loop (EV_A_ 0);
1997.Ve
1998.PP
1999.Vb 3
2000\& // stop timer again
2001\& if (timeout >= 0)
2002\& ev_timer_stop (EV_A_ &to);
2003.Ve
2004.PP
2005.Vb 3
2006\& // stop io watchers again - their callbacks should have set
2007\& for (n = 0; n < nfds; ++n)
2008\& ev_io_stop (EV_A_ iow [n]);
2009.Ve
2010.PP
2011.Vb 2
2012\& return got_events;
1641\& } 2013\& }
1642.Ve 2014.Ve
1643.ie n .Sh """ev_embed"" \- when one backend isn't enough..." 2015.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1644.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." 2016.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1645.IX Subsection "ev_embed - when one backend isn't enough..." 2017.IX Subsection "ev_embed - when one backend isn't enough..."
… …
1714\& ev_embed_start (loop_hi, &embed); 2086\& ev_embed_start (loop_hi, &embed);
1715\& } 2087\& }
1716\& else 2088\& else
1717\& loop_lo = loop_hi; 2089\& loop_lo = loop_hi;
1718.Ve 2090.Ve
2091.PP
2092\fIWatcher-Specific Functions and Data Members\fR
2093.IX Subsection "Watcher-Specific Functions and Data Members"
1719.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 2094.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1720.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 2095.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1721.PD 0 2096.PD 0
1722.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 2097.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1723.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 2098.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
… …
1730.IP "ev_embed_sweep (loop, ev_embed *)" 4 2105.IP "ev_embed_sweep (loop, ev_embed *)" 4
1731.IX Item "ev_embed_sweep (loop, ev_embed *)" 2106.IX Item "ev_embed_sweep (loop, ev_embed *)"
1732Make a single, non-blocking sweep over the embedded loop. This works 2107Make a single, non-blocking sweep over the embedded loop. This works
1733similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most 2108similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1734apropriate way for embedded loops. 2109apropriate way for embedded loops.
1735.IP "struct ev_loop *loop [read\-only]" 4 2110.IP "struct ev_loop *other [read\-only]" 4
1736.IX Item "struct ev_loop *loop [read-only]" 2111.IX Item "struct ev_loop *other [read-only]"
1737The embedded event loop. 2112The embedded event loop.
1738.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" 2113.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1739.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" 2114.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1740.IX Subsection "ev_fork - the audacity to resume the event loop after a fork" 2115.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1741Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because 2116Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
… …
1743\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the 2118\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1744event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, 2119event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1745and only in the child after the fork. If whoever good citizen calling 2120and only in the child after the fork. If whoever good citizen calling
1746\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork 2121\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1747handlers will be invoked, too, of course. 2122handlers will be invoked, too, of course.
2123.PP
2124\fIWatcher-Specific Functions and Data Members\fR
2125.IX Subsection "Watcher-Specific Functions and Data Members"
1748.IP "ev_fork_init (ev_signal *, callback)" 4 2126.IP "ev_fork_init (ev_signal *, callback)" 4
1749.IX Item "ev_fork_init (ev_signal *, callback)" 2127.IX Item "ev_fork_init (ev_signal *, callback)"
1750Initialises and configures the fork watcher \- it has no parameters of any 2128Initialises and configures the fork watcher \- it has no parameters of any
1751kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, 2129kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1752believe me. 2130believe me.
… …
1829.PP 2207.PP
1830.Vb 1 2208.Vb 1
1831\& #include <ev++.h> 2209\& #include <ev++.h>
1832.Ve 2210.Ve
1833.PP 2211.PP
1834(it is not installed by default). This automatically includes \fIev.h\fR 2212This automatically includes \fIev.h\fR and puts all of its definitions (many
1835and puts all of its definitions (many of them macros) into the global 2213of them macros) into the global namespace. All \*(C+ specific things are
1836namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. 2214put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2215options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1837.PP 2216.PP
1838It should support all the same embedding options as \fIev.h\fR, most notably 2217Care has been taken to keep the overhead low. The only data member the \*(C+
1839\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. 2218classes add (compared to plain C\-style watchers) is the event loop pointer
2219that the watcher is associated with (or no additional members at all if
2220you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2221.PP
2222Currently, functions, and static and non-static member functions can be
2223used as callbacks. Other types should be easy to add as long as they only
2224need one additional pointer for context. If you need support for other
2225types of functors please contact the author (preferably after implementing
2226it).
1840.PP 2227.PP
1841Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: 2228Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1842.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 2229.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1843.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 2230.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1844.IX Item "ev::READ, ev::WRITE etc." 2231.IX Item "ev::READ, ev::WRITE etc."
… …
1856which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro 2243which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1857defines by many implementations. 2244defines by many implementations.
1858.Sp 2245.Sp
1859All of those classes have these methods: 2246All of those classes have these methods:
1860.RS 4 2247.RS 4
1861.IP "ev::TYPE::TYPE (object *, object::method *)" 4 2248.IP "ev::TYPE::TYPE ()" 4
1862.IX Item "ev::TYPE::TYPE (object *, object::method *)" 2249.IX Item "ev::TYPE::TYPE ()"
1863.PD 0 2250.PD 0
1864.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 2251.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
1865.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 2252.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
1866.IP "ev::TYPE::~TYPE" 4 2253.IP "ev::TYPE::~TYPE" 4
1867.IX Item "ev::TYPE::~TYPE" 2254.IX Item "ev::TYPE::~TYPE"
1868.PD 2255.PD
1869The constructor takes a pointer to an object and a method pointer to 2256The constructor (optionally) takes an event loop to associate the watcher
1870the event handler callback to call in this class. The constructor calls 2257with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
1871\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method 2258.Sp
1872before starting it. If you do not specify a loop then the constructor 2259The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
1873automatically associates the default loop with this watcher. 2260\&\f(CW\*(C`set\*(C'\fR method before starting it.
2261.Sp
2262It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2263method to set a callback before you can start the watcher.
2264.Sp
2265(The reason why you have to use a method is a limitation in \*(C+ which does
2266not allow explicit template arguments for constructors).
1874.Sp 2267.Sp
1875The destructor automatically stops the watcher if it is active. 2268The destructor automatically stops the watcher if it is active.
2269.IP "w\->set<class, &class::method> (object *)" 4
2270.IX Item "w->set<class, &class::method> (object *)"
2271This method sets the callback method to call. The method has to have a
2272signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2273first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2274parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2275.Sp
2276This method synthesizes efficient thunking code to call your method from
2277the C callback that libev requires. If your compiler can inline your
2278callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2279your compiler is good :), then the method will be fully inlined into the
2280thunking function, making it as fast as a direct C callback.
2281.Sp
2282Example: simple class declaration and watcher initialisation
2283.Sp
2284.Vb 4
2285\& struct myclass
2286\& {
2287\& void io_cb (ev::io &w, int revents) { }
2288\& }
2289.Ve
2290.Sp
2291.Vb 3
2292\& myclass obj;
2293\& ev::io iow;
2294\& iow.set <myclass, &myclass::io_cb> (&obj);
2295.Ve
2296.IP "w\->set<function> (void *data = 0)" 4
2297.IX Item "w->set<function> (void *data = 0)"
2298Also sets a callback, but uses a static method or plain function as
2299callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2300\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2301.Sp
2302The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2303.Sp
2304See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2305.Sp
2306Example:
2307.Sp
2308.Vb 2
2309\& static void io_cb (ev::io &w, int revents) { }
2310\& iow.set <io_cb> ();
2311.Ve
1876.IP "w\->set (struct ev_loop *)" 4 2312.IP "w\->set (struct ev_loop *)" 4
1877.IX Item "w->set (struct ev_loop *)" 2313.IX Item "w->set (struct ev_loop *)"
1878Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only 2314Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1879do this when the watcher is inactive (and not pending either). 2315do this when the watcher is inactive (and not pending either).
1880.IP "w\->set ([args])" 4 2316.IP "w\->set ([args])" 4
1881.IX Item "w->set ([args])" 2317.IX Item "w->set ([args])"
1882Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be 2318Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1883called at least once. Unlike the C counterpart, an active watcher gets 2319called at least once. Unlike the C counterpart, an active watcher gets
1884automatically stopped and restarted. 2320automatically stopped and restarted when reconfiguring it with this
2321method.
1885.IP "w\->start ()" 4 2322.IP "w\->start ()" 4
1886.IX Item "w->start ()" 2323.IX Item "w->start ()"
1887Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the 2324Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
1888constructor already takes the loop. 2325constructor already stores the event loop.
1889.IP "w\->stop ()" 4 2326.IP "w\->stop ()" 4
1890.IX Item "w->stop ()" 2327.IX Item "w->stop ()"
1891Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. 2328Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1892.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 2329.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
1893.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 2330.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
1894.IX Item "w->again () ev::timer, ev::periodic only" 2331.IX Item "w->again () (ev::timer, ev::periodic only)"
1895For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding 2332For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1896\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. 2333\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1897.ie n .IP "w\->sweep () ""ev::embed"" only" 4 2334.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
1898.el .IP "w\->sweep () \f(CWev::embed\fR only" 4 2335.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
1899.IX Item "w->sweep () ev::embed only" 2336.IX Item "w->sweep () (ev::embed only)"
1900Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. 2337Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1901.ie n .IP "w\->update () ""ev::stat"" only" 4 2338.ie n .IP "w\->update () (""ev::stat"" only)" 4
1902.el .IP "w\->update () \f(CWev::stat\fR only" 4 2339.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
1903.IX Item "w->update () ev::stat only" 2340.IX Item "w->update () (ev::stat only)"
1904Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. 2341Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1905.RE 2342.RE
1906.RS 4 2343.RS 4
1907.RE 2344.RE
1908.PP 2345.PP
… …
1919.Vb 2 2356.Vb 2
1920\& myclass (); 2357\& myclass ();
1921\& } 2358\& }
1922.Ve 2359.Ve
1923.PP 2360.PP
1924.Vb 6 2361.Vb 4
1925\& myclass::myclass (int fd) 2362\& myclass::myclass (int fd)
1926\& : io (this, &myclass::io_cb),
1927\& idle (this, &myclass::idle_cb)
1928\& { 2363\& {
2364\& io .set <myclass, &myclass::io_cb > (this);
2365\& idle.set <myclass, &myclass::idle_cb> (this);
2366.Ve
2367.PP
2368.Vb 2
1929\& io.start (fd, ev::READ); 2369\& io.start (fd, ev::READ);
1930\& } 2370\& }
1931.Ve 2371.Ve
1932.SH "MACRO MAGIC" 2372.SH "MACRO MAGIC"
1933.IX Header "MACRO MAGIC" 2373.IX Header "MACRO MAGIC"
1934Libev can be compiled with a variety of options, the most fundemantal is 2374Libev can be compiled with a variety of options, the most fundamantal
1935\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and 2375of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
1936callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. 2376functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1937.PP 2377.PP
1938To make it easier to write programs that cope with either variant, the 2378To make it easier to write programs that cope with either variant, the
1939following macros are defined: 2379following macros are defined:
1940.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 2380.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
1941.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 2381.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
… …
1975.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 2415.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
1976.IX Item "EV_DEFAULT, EV_DEFAULT_" 2416.IX Item "EV_DEFAULT, EV_DEFAULT_"
1977Similar to the other two macros, this gives you the value of the default 2417Similar to the other two macros, this gives you the value of the default
1978loop, if multiple loops are supported (\*(L"ev loop default\*(R"). 2418loop, if multiple loops are supported (\*(L"ev loop default\*(R").
1979.PP 2419.PP
1980Example: Declare and initialise a check watcher, working regardless of 2420Example: Declare and initialise a check watcher, utilising the above
1981wether multiple loops are supported or not. 2421macros so it will work regardless of whether multiple loops are supported
2422or not.
1982.PP 2423.PP
1983.Vb 5 2424.Vb 5
1984\& static void 2425\& static void
1985\& check_cb (EV_P_ ev_timer *w, int revents) 2426\& check_cb (EV_P_ ev_timer *w, int revents)
1986\& { 2427\& {
… …
1999Libev can (and often is) directly embedded into host 2440Libev can (and often is) directly embedded into host
2000applications. Examples of applications that embed it include the Deliantra 2441applications. Examples of applications that embed it include the Deliantra
2001Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) 2442Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2002and rxvt\-unicode. 2443and rxvt\-unicode.
2003.PP 2444.PP
2004The goal is to enable you to just copy the neecssary files into your 2445The goal is to enable you to just copy the necessary files into your
2005source directory without having to change even a single line in them, so 2446source directory without having to change even a single line in them, so
2006you can easily upgrade by simply copying (or having a checked-out copy of 2447you can easily upgrade by simply copying (or having a checked-out copy of
2007libev somewhere in your source tree). 2448libev somewhere in your source tree).
2008.Sh "\s-1FILESETS\s0" 2449.Sh "\s-1FILESETS\s0"
2009.IX Subsection "FILESETS" 2450.IX Subsection "FILESETS"
… …
2049.Vb 1 2490.Vb 1
2050\& ev_win32.c required on win32 platforms only 2491\& ev_win32.c required on win32 platforms only
2051.Ve 2492.Ve
2052.PP 2493.PP
2053.Vb 5 2494.Vb 5
2054\& ev_select.c only when select backend is enabled (which is by default) 2495\& ev_select.c only when select backend is enabled (which is enabled by default)
2055\& ev_poll.c only when poll backend is enabled (disabled by default) 2496\& ev_poll.c only when poll backend is enabled (disabled by default)
2056\& ev_epoll.c only when the epoll backend is enabled (disabled by default) 2497\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2057\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 2498\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2058\& ev_port.c only when the solaris port backend is enabled (disabled by default) 2499\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2059.Ve 2500.Ve
… …
2114.IX Item "EV_USE_MONOTONIC" 2555.IX Item "EV_USE_MONOTONIC"
2115If defined to be \f(CW1\fR, libev will try to detect the availability of the 2556If defined to be \f(CW1\fR, libev will try to detect the availability of the
2116monotonic clock option at both compiletime and runtime. Otherwise no use 2557monotonic clock option at both compiletime and runtime. Otherwise no use
2117of the monotonic clock option will be attempted. If you enable this, you 2558of the monotonic clock option will be attempted. If you enable this, you
2118usually have to link against librt or something similar. Enabling it when 2559usually have to link against librt or something similar. Enabling it when
2119the functionality isn't available is safe, though, althoguh you have 2560the functionality isn't available is safe, though, although you have
2120to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR 2561to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2121function is hiding in (often \fI\-lrt\fR). 2562function is hiding in (often \fI\-lrt\fR).
2122.IP "\s-1EV_USE_REALTIME\s0" 4 2563.IP "\s-1EV_USE_REALTIME\s0" 4
2123.IX Item "EV_USE_REALTIME" 2564.IX Item "EV_USE_REALTIME"
2124If defined to be \f(CW1\fR, libev will try to detect the availability of the 2565If defined to be \f(CW1\fR, libev will try to detect the availability of the
2125realtime clock option at compiletime (and assume its availability at 2566realtime clock option at compiletime (and assume its availability at
2126runtime if successful). Otherwise no use of the realtime clock option will 2567runtime if successful). Otherwise no use of the realtime clock option will
2127be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get 2568be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2128(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries 2569(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See the
2129in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. 2570note about libraries in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2571.IP "\s-1EV_USE_NANOSLEEP\s0" 4
2572.IX Item "EV_USE_NANOSLEEP"
2573If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
2574and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
2130.IP "\s-1EV_USE_SELECT\s0" 4 2575.IP "\s-1EV_USE_SELECT\s0" 4
2131.IX Item "EV_USE_SELECT" 2576.IX Item "EV_USE_SELECT"
2132If undefined or defined to be \f(CW1\fR, libev will compile in support for the 2577If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2133\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no 2578\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2134other method takes over, select will be it. Otherwise the select backend 2579other method takes over, select will be it. Otherwise the select backend
… …
2212If undefined or defined to \f(CW1\fR, then all event-loop-specific functions 2657If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2213will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create 2658will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2214additional independent event loops. Otherwise there will be no support 2659additional independent event loops. Otherwise there will be no support
2215for multiple event loops and there is no first event loop pointer 2660for multiple event loops and there is no first event loop pointer
2216argument. Instead, all functions act on the single default loop. 2661argument. Instead, all functions act on the single default loop.
2662.IP "\s-1EV_MINPRI\s0" 4
2663.IX Item "EV_MINPRI"
2664.PD 0
2665.IP "\s-1EV_MAXPRI\s0" 4
2666.IX Item "EV_MAXPRI"
2667.PD
2668The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2669\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2670provide for more priorities by overriding those symbols (usually defined
2671to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2672.Sp
2673When doing priority-based operations, libev usually has to linearly search
2674all the priorities, so having many of them (hundreds) uses a lot of space
2675and time, so using the defaults of five priorities (\-2 .. +2) is usually
2676fine.
2677.Sp
2678If your embedding app does not need any priorities, defining these both to
2679\&\f(CW0\fR will save some memory and cpu.
2217.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 2680.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2218.IX Item "EV_PERIODIC_ENABLE" 2681.IX Item "EV_PERIODIC_ENABLE"
2219If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If 2682If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2683defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2684code.
2685.IP "\s-1EV_IDLE_ENABLE\s0" 4
2686.IX Item "EV_IDLE_ENABLE"
2687If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2220defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of 2688defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2221code. 2689code.
2222.IP "\s-1EV_EMBED_ENABLE\s0" 4 2690.IP "\s-1EV_EMBED_ENABLE\s0" 4
2223.IX Item "EV_EMBED_ENABLE" 2691.IX Item "EV_EMBED_ENABLE"
2224If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If 2692If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
… …
2271.IP "ev_set_cb (ev, cb)" 4 2739.IP "ev_set_cb (ev, cb)" 4
2272.IX Item "ev_set_cb (ev, cb)" 2740.IX Item "ev_set_cb (ev, cb)"
2273.PD 2741.PD
2274Can be used to change the callback member declaration in each watcher, 2742Can be used to change the callback member declaration in each watcher,
2275and the way callbacks are invoked and set. Must expand to a struct member 2743and the way callbacks are invoked and set. Must expand to a struct member
2276definition and a statement, respectively. See the \fIev.v\fR header file for 2744definition and a statement, respectively. See the \fIev.h\fR header file for
2277their default definitions. One possible use for overriding these is to 2745their default definitions. One possible use for overriding these is to
2278avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use 2746avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2279method calls instead of plain function calls in \*(C+. 2747method calls instead of plain function calls in \*(C+.
2748.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
2749.IX Subsection "EXPORTED API SYMBOLS"
2750If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of
2751exported symbols, you can use the provided \fISymbol.*\fR files which list
2752all public symbols, one per line:
2753.Sp
2754.Vb 2
2755\& Symbols.ev for libev proper
2756\& Symbols.event for the libevent emulation
2757.Ve
2758.Sp
2759This can also be used to rename all public symbols to avoid clashes with
2760multiple versions of libev linked together (which is obviously bad in
2761itself, but sometimes it is inconvinient to avoid this).
2762.Sp
2763A sed command like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
2764include before including \fIev.h\fR:
2765.Sp
2766.Vb 1
2767\& <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2768.Ve
2769.Sp
2770This would create a file \fIwrap.h\fR which essentially looks like this:
2771.Sp
2772.Vb 4
2773\& #define ev_backend myprefix_ev_backend
2774\& #define ev_check_start myprefix_ev_check_start
2775\& #define ev_check_stop myprefix_ev_check_stop
2776\& ...
2777.Ve
2280.Sh "\s-1EXAMPLES\s0" 2778.Sh "\s-1EXAMPLES\s0"
2281.IX Subsection "EXAMPLES" 2779.IX Subsection "EXAMPLES"
2282For a real-world example of a program the includes libev 2780For a real-world example of a program the includes libev
2283verbatim, you can have a look at the \s-1EV\s0 perl module 2781verbatim, you can have a look at the \s-1EV\s0 perl module
2284(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in 2782(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
… …
2286interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file 2784interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2287will be compiled. It is pretty complex because it provides its own header 2785will be compiled. It is pretty complex because it provides its own header
2288file. 2786file.
2289.Sp 2787.Sp
2290The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file 2788The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2291that everybody includes and which overrides some autoconf choices: 2789that everybody includes and which overrides some configure choices:
2292.Sp 2790.Sp
2293.Vb 4 2791.Vb 9
2792\& #define EV_MINIMAL 1
2294\& #define EV_USE_POLL 0 2793\& #define EV_USE_POLL 0
2295\& #define EV_MULTIPLICITY 0 2794\& #define EV_MULTIPLICITY 0
2296\& #define EV_PERIODICS 0 2795\& #define EV_PERIODIC_ENABLE 0
2796\& #define EV_STAT_ENABLE 0
2797\& #define EV_FORK_ENABLE 0
2297\& #define EV_CONFIG_H <config.h> 2798\& #define EV_CONFIG_H <config.h>
2799\& #define EV_MINPRI 0
2800\& #define EV_MAXPRI 0
2298.Ve 2801.Ve
2299.Sp 2802.Sp
2300.Vb 1 2803.Vb 1
2301\& #include "ev++.h" 2804\& #include "ev++.h"
2302.Ve 2805.Ve
… …
2310.SH "COMPLEXITIES" 2813.SH "COMPLEXITIES"
2311.IX Header "COMPLEXITIES" 2814.IX Header "COMPLEXITIES"
2312In this section the complexities of (many of) the algorithms used inside 2815In this section the complexities of (many of) the algorithms used inside
2313libev will be explained. For complexity discussions about backends see the 2816libev will be explained. For complexity discussions about backends see the
2314documentation for \f(CW\*(C`ev_default_init\*(C'\fR. 2817documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2818.Sp
2819All of the following are about amortised time: If an array needs to be
2820extended, libev needs to realloc and move the whole array, but this
2821happens asymptotically never with higher number of elements, so O(1) might
2822mean it might do a lengthy realloc operation in rare cases, but on average
2823it is much faster and asymptotically approaches constant time.
2315.RS 4 2824.RS 4
2316.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 2825.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2317.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 2826.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2318.PD 0 2827This means that, when you have a watcher that triggers in one hour and
2828there are 100 watchers that would trigger before that then inserting will
2829have to skip those 100 watchers.
2319.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4 2830.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2320.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 2831.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2832That means that for changing a timer costs less than removing/adding them
2833as only the relative motion in the event queue has to be paid for.
2321.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4 2834.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2322.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)" 2835.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2323.IP "Stopping check/prepare/idle watchers: O(1)" 4 2836These just add the watcher into an array or at the head of a list.
2324.IX Item "Stopping check/prepare/idle watchers: O(1)" 2837=item Stopping check/prepare/idle watchers: O(1)
2325.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 2838.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2326.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" 2839.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2840These watchers are stored in lists then need to be walked to find the
2841correct watcher to remove. The lists are usually short (you don't usually
2842have many watchers waiting for the same fd or signal).
2327.IP "Finding the next timer per loop iteration: O(1)" 4 2843.IP "Finding the next timer per loop iteration: O(1)" 4
2328.IX Item "Finding the next timer per loop iteration: O(1)" 2844.IX Item "Finding the next timer per loop iteration: O(1)"
2845.PD 0
2329.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 2846.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2330.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 2847.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2848.PD
2849A change means an I/O watcher gets started or stopped, which requires
2850libev to recalculate its status (and possibly tell the kernel).
2331.IP "Activating one watcher: O(1)" 4 2851.IP "Activating one watcher: O(1)" 4
2332.IX Item "Activating one watcher: O(1)" 2852.IX Item "Activating one watcher: O(1)"
2853.PD 0
2854.IP "Priority handling: O(number_of_priorities)" 4
2855.IX Item "Priority handling: O(number_of_priorities)"
2856.PD
2857Priorities are implemented by allocating some space for each
2858priority. When doing priority-based operations, libev usually has to
2859linearly search all the priorities.
2333.RE 2860.RE
2334.RS 4 2861.RS 4
2335.PD
2336.SH "AUTHOR" 2862.SH "AUTHOR"
2337.IX Header "AUTHOR" 2863.IX Header "AUTHOR"
2338Marc Lehmann <libev@schmorp.de>. 2864Marc Lehmann <libev@schmorp.de>.

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