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Revision 1.2 by root, Sun Nov 18 03:43:24 2007 UTC vs.
Revision 1.8 by root, Fri Nov 23 15:26:08 2007 UTC

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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 ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-18" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-11-23" "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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199.Sp 199.Sp
200Usually, it's a good idea to terminate if the major versions mismatch, 200Usually, it's a good idea to terminate if the major versions mismatch,
201as this indicates an incompatible change. Minor versions are usually 201as this indicates an incompatible change. Minor versions are usually
202compatible to older versions, so a larger minor version alone is usually 202compatible to older versions, so a larger minor version alone is usually
203not a problem. 203not a problem.
204.IP "unsigned int ev_supported_backends ()" 4
205.IX Item "unsigned int ev_supported_backends ()"
206Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
207value) compiled into this binary of libev (independent of their
208availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
209a description of the set values.
210.IP "unsigned int ev_recommended_backends ()" 4
211.IX Item "unsigned int ev_recommended_backends ()"
212Return the set of all backends compiled into this binary of libev and also
213recommended for this platform. This set is often smaller than the one
214returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
215most BSDs and will not be autodetected unless you explicitly request it
216(assuming you know what you are doing). This is the set of backends that
217libev will probe for if you specify no backends explicitly.
204.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 218.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
205.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
206Sets the allocation function to use (the prototype is similar to the 220Sets the allocation function to use (the prototype is similar to the
207realloc C function, the semantics are identical). It is used to allocate 221realloc C function, the semantics are identical). It is used to allocate
208and free memory (no surprises here). If it returns zero when memory 222and free memory (no surprises here). If it returns zero when memory
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236.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 250.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
237.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" 251.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
238This will initialise the default event loop if it hasn't been initialised 252This will initialise the default event loop if it hasn't been initialised
239yet and return it. If the default loop could not be initialised, returns 253yet and return it. If the default loop could not be initialised, returns
240false. If it already was initialised it simply returns it (and ignores the 254false. If it already was initialised it simply returns it (and ignores the
241flags). 255flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
242.Sp 256.Sp
243If you don't know what event loop to use, use the one returned from this 257If you don't know what event loop to use, use the one returned from this
244function. 258function.
245.Sp 259.Sp
246The flags argument can be used to specify special behaviour or specific 260The flags argument can be used to specify special behaviour or specific
247backends to use, and is usually specified as 0 (or \s-1EVFLAG_AUTO\s0). 261backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
248.Sp 262.Sp
249It supports the following flags: 263The following flags are supported:
250.RS 4 264.RS 4
251.ie n .IP """EVFLAG_AUTO""" 4 265.ie n .IP """EVFLAG_AUTO""" 4
252.el .IP "\f(CWEVFLAG_AUTO\fR" 4 266.el .IP "\f(CWEVFLAG_AUTO\fR" 4
253.IX Item "EVFLAG_AUTO" 267.IX Item "EVFLAG_AUTO"
254The default flags value. Use this if you have no clue (it's the right 268The default flags value. Use this if you have no clue (it's the right
… …
260or setgid) then libev will \fInot\fR look at the environment variable 274or setgid) then libev will \fInot\fR look at the environment variable
261\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 275\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
262override the flags completely if it is found in the environment. This is 276override the flags completely if it is found in the environment. This is
263useful to try out specific backends to test their performance, or to work 277useful to try out specific backends to test their performance, or to work
264around bugs. 278around bugs.
265.ie n .IP """EVMETHOD_SELECT"" (portable select backend)" 4 279.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
266.el .IP "\f(CWEVMETHOD_SELECT\fR (portable select backend)" 4 280.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
267.IX Item "EVMETHOD_SELECT (portable select backend)" 281.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
268.PD 0 282This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
283libev tries to roll its own fd_set with no limits on the number of fds,
284but if that fails, expect a fairly low limit on the number of fds when
285using this backend. It doesn't scale too well (O(highest_fd)), but its usually
286the fastest backend for a low number of fds.
269.ie n .IP """EVMETHOD_POLL"" (poll backend, available everywhere except on windows)" 4 287.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
270.el .IP "\f(CWEVMETHOD_POLL\fR (poll backend, available everywhere except on windows)" 4 288.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
271.IX Item "EVMETHOD_POLL (poll backend, available everywhere except on windows)" 289.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
290And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
291select, but handles sparse fds better and has no artificial limit on the
292number of fds you can use (except it will slow down considerably with a
293lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
272.ie n .IP """EVMETHOD_EPOLL"" (linux only)" 4 294.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
273.el .IP "\f(CWEVMETHOD_EPOLL\fR (linux only)" 4 295.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
274.IX Item "EVMETHOD_EPOLL (linux only)" 296.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
275.ie n .IP """EVMETHOD_KQUEUE"" (some bsds only)" 4 297For few fds, this backend is a bit little slower than poll and select,
276.el .IP "\f(CWEVMETHOD_KQUEUE\fR (some bsds only)" 4 298but it scales phenomenally better. While poll and select usually scale like
277.IX Item "EVMETHOD_KQUEUE (some bsds only)" 299O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
300either O(1) or O(active_fds).
301.Sp
302While stopping and starting an I/O watcher in the same iteration will
303result in some caching, there is still a syscall per such incident
304(because the fd could point to a different file description now), so its
305best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
306well if you register events for both fds.
307.Sp
308Please note that epoll sometimes generates spurious notifications, so you
309need to use non-blocking I/O or other means to avoid blocking when no data
310(or space) is available.
311.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
312.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
313.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
314Kqueue deserves special mention, as at the time of this writing, it
315was broken on all BSDs except NetBSD (usually it doesn't work with
316anything but sockets and pipes, except on Darwin, where of course its
317completely useless). For this reason its not being \*(L"autodetected\*(R"
318unless you explicitly specify it explicitly in the flags (i.e. using
319\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
320.Sp
321It scales in the same way as the epoll backend, but the interface to the
322kernel is more efficient (which says nothing about its actual speed, of
323course). While starting and stopping an I/O watcher does not cause an
324extra syscall as with epoll, it still adds up to four event changes per
325incident, so its best to avoid that.
278.ie n .IP """EVMETHOD_DEVPOLL"" (solaris 8 only)" 4 326.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
279.el .IP "\f(CWEVMETHOD_DEVPOLL\fR (solaris 8 only)" 4 327.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
280.IX Item "EVMETHOD_DEVPOLL (solaris 8 only)" 328.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
329This is not implemented yet (and might never be).
281.ie n .IP """EVMETHOD_PORT"" (solaris 10 only)" 4 330.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
282.el .IP "\f(CWEVMETHOD_PORT\fR (solaris 10 only)" 4 331.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
283.IX Item "EVMETHOD_PORT (solaris 10 only)" 332.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
284.PD 333This uses the Solaris 10 port mechanism. As with everything on Solaris,
285If one or more of these are ored into the flags value, then only these 334it's really slow, but it still scales very well (O(active_fds)).
286backends will be tried (in the reverse order as given here). If one are 335.Sp
287specified, any backend will do. 336Please note that solaris ports can result in a lot of spurious
337notifications, so you need to use non-blocking I/O or other means to avoid
338blocking when no data (or space) is available.
339.ie n .IP """EVBACKEND_ALL""" 4
340.el .IP "\f(CWEVBACKEND_ALL\fR" 4
341.IX Item "EVBACKEND_ALL"
342Try all backends (even potentially broken ones that wouldn't be tried
343with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
344\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
288.RE 345.RE
289.RS 4 346.RS 4
347.Sp
348If one or more of these are ored into the flags value, then only these
349backends will be tried (in the reverse order as given here). If none are
350specified, most compiled-in backend will be tried, usually in reverse
351order of their flag values :)
352.Sp
353The most typical usage is like this:
354.Sp
355.Vb 2
356\& if (!ev_default_loop (0))
357\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
358.Ve
359.Sp
360Restrict libev to the select and poll backends, and do not allow
361environment settings to be taken into account:
362.Sp
363.Vb 1
364\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
365.Ve
366.Sp
367Use whatever libev has to offer, but make sure that kqueue is used if
368available (warning, breaks stuff, best use only with your own private
369event loop and only if you know the \s-1OS\s0 supports your types of fds):
370.Sp
371.Vb 1
372\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
373.Ve
290.RE 374.RE
291.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 375.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
292.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 376.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
293Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 377Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
294always distinct from the default loop. Unlike the default loop, it cannot 378always distinct from the default loop. Unlike the default loop, it cannot
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308This function reinitialises the kernel state for backends that have 392This function reinitialises the kernel state for backends that have
309one. Despite the name, you can call it anytime, but it makes most sense 393one. Despite the name, you can call it anytime, but it makes most sense
310after forking, in either the parent or child process (or both, but that 394after forking, in either the parent or child process (or both, but that
311again makes little sense). 395again makes little sense).
312.Sp 396.Sp
313You \fImust\fR call this function after forking if and only if you want to 397You \fImust\fR call this function in the child process after forking if and
314use the event library in both processes. If you just fork+exec, you don't 398only if you want to use the event library in both processes. If you just
315have to call it. 399fork+exec, you don't have to call it.
316.Sp 400.Sp
317The function itself is quite fast and it's usually not a problem to call 401The function itself is quite fast and it's usually not a problem to call
318it just in case after a fork. To make this easy, the function will fit in 402it just in case after a fork. To make this easy, the function will fit in
319quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: 403quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
320.Sp 404.Sp
321.Vb 1 405.Vb 1
322\& pthread_atfork (0, 0, ev_default_fork); 406\& pthread_atfork (0, 0, ev_default_fork);
323.Ve 407.Ve
408.Sp
409At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
410without calling this function, so if you force one of those backends you
411do not need to care.
324.IP "ev_loop_fork (loop)" 4 412.IP "ev_loop_fork (loop)" 4
325.IX Item "ev_loop_fork (loop)" 413.IX Item "ev_loop_fork (loop)"
326Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 414Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
327\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 415\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
328after fork, and how you do this is entirely your own problem. 416after fork, and how you do this is entirely your own problem.
329.IP "unsigned int ev_method (loop)" 4 417.IP "unsigned int ev_backend (loop)" 4
330.IX Item "unsigned int ev_method (loop)" 418.IX Item "unsigned int ev_backend (loop)"
331Returns one of the \f(CW\*(C`EVMETHOD_*\*(C'\fR flags indicating the event backend in 419Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
332use. 420use.
333.IP "ev_tstamp ev_now (loop)" 4 421.IP "ev_tstamp ev_now (loop)" 4
334.IX Item "ev_tstamp ev_now (loop)" 422.IX Item "ev_tstamp ev_now (loop)"
335Returns the current \*(L"event loop time\*(R", which is the time the event loop 423Returns the current \*(L"event loop time\*(R", which is the time the event loop
336got events and started processing them. This timestamp does not change 424got events and started processing them. This timestamp does not change
… …
341.IX Item "ev_loop (loop, int flags)" 429.IX Item "ev_loop (loop, int flags)"
342Finally, this is it, the event handler. This function usually is called 430Finally, this is it, the event handler. This function usually is called
343after you initialised all your watchers and you want to start handling 431after you initialised all your watchers and you want to start handling
344events. 432events.
345.Sp 433.Sp
346If the flags argument is specified as 0, it will not return until either 434If the flags argument is specified as \f(CW0\fR, it will not return until
347no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 435either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
348.Sp 436.Sp
349A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 437A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
350those events and any outstanding ones, but will not block your process in 438those events and any outstanding ones, but will not block your process in
351case there are no events and will return after one iteration of the loop. 439case there are no events and will return after one iteration of the loop.
352.Sp 440.Sp
353A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if 441A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
354neccessary) and will handle those and any outstanding ones. It will block 442neccessary) and will handle those and any outstanding ones. It will block
355your process until at least one new event arrives, and will return after 443your process until at least one new event arrives, and will return after
356one iteration of the loop. 444one iteration of the loop. This is useful if you are waiting for some
445external event in conjunction with something not expressible using other
446libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
447usually a better approach for this kind of thing.
357.Sp 448.Sp
358This flags value could be used to implement alternative looping
359constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and
360more generic mechanism.
361.Sp
362Here are the gory details of what ev_loop does: 449Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
363.Sp 450.Sp
364.Vb 15 451.Vb 18
365\& 1. If there are no active watchers (reference count is zero), return. 452\& * If there are no active watchers (reference count is zero), return.
366\& 2. Queue and immediately call all prepare watchers. 453\& - Queue prepare watchers and then call all outstanding watchers.
367\& 3. If we have been forked, recreate the kernel state. 454\& - If we have been forked, recreate the kernel state.
368\& 4. Update the kernel state with all outstanding changes. 455\& - Update the kernel state with all outstanding changes.
369\& 5. Update the "event loop time". 456\& - Update the "event loop time".
370\& 6. Calculate for how long to block. 457\& - Calculate for how long to block.
371\& 7. Block the process, waiting for events. 458\& - Block the process, waiting for any events.
459\& - Queue all outstanding I/O (fd) events.
372\& 8. Update the "event loop time" and do time jump handling. 460\& - Update the "event loop time" and do time jump handling.
373\& 9. Queue all outstanding timers. 461\& - Queue all outstanding timers.
374\& 10. Queue all outstanding periodics. 462\& - Queue all outstanding periodics.
375\& 11. If no events are pending now, queue all idle watchers. 463\& - If no events are pending now, queue all idle watchers.
376\& 12. Queue all check watchers. 464\& - Queue all check watchers.
377\& 13. Call all queued watchers in reverse order (i.e. check watchers first). 465\& - Call all queued watchers in reverse order (i.e. check watchers first).
466\& Signals and child watchers are implemented as I/O watchers, and will
467\& be handled here by queueing them when their watcher gets executed.
378\& 14. If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 468\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
379\& was used, return, otherwise continue with step #1. 469\& were used, return, otherwise continue with step *.
380.Ve 470.Ve
381.IP "ev_unloop (loop, how)" 4 471.IP "ev_unloop (loop, how)" 4
382.IX Item "ev_unloop (loop, how)" 472.IX Item "ev_unloop (loop, how)"
383Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 473Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
384has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 474has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
… …
443*)\*(C'\fR), and you can stop watching for events at any time by calling the 533*)\*(C'\fR), and you can stop watching for events at any time by calling the
444corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 534corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
445.PP 535.PP
446As long as your watcher is active (has been started but not stopped) you 536As long as your watcher is active (has been started but not stopped) you
447must not touch the values stored in it. Most specifically you must never 537must not touch the values stored in it. Most specifically you must never
448reinitialise it or call its set method. 538reinitialise it or call its set macro.
449.PP 539.PP
450You can check whether an event is active by calling the \f(CW\*(C`ev_is_active 540You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
451(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the 541(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
452callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending 542callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
453(watcher *)\*(C'\fR macro. 543(watcher *)\*(C'\fR macro.
… …
573descriptors correctly if you register interest in two or more fds pointing 663descriptors correctly if you register interest in two or more fds pointing
574to the same underlying file/socket etc. description (that is, they share 664to the same underlying file/socket etc. description (that is, they share
575the same underlying \*(L"file open\*(R"). 665the same underlying \*(L"file open\*(R").
576.PP 666.PP
577If you must do this, then force the use of a known-to-be-good backend 667If you must do this, then force the use of a known-to-be-good backend
578(at the time of this writing, this includes only \s-1EVMETHOD_SELECT\s0 and 668(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
579\&\s-1EVMETHOD_POLL\s0). 669\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
580.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 670.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
581.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 671.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
582.PD 0 672.PD 0
583.IP "ev_io_set (ev_io *, int fd, int events)" 4 673.IP "ev_io_set (ev_io *, int fd, int events)" 4
584.IX Item "ev_io_set (ev_io *, int fd, int events)" 674.IX Item "ev_io_set (ev_io *, int fd, int events)"
585.PD 675.PD
586Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 676Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive
587events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 677events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ |
588EV_WRITE\*(C'\fR to receive the given events. 678EV_WRITE\*(C'\fR to receive the given events.
679.Sp
680Please note that most of the more scalable backend mechanisms (for example
681epoll and solaris ports) can result in spurious readyness notifications
682for file descriptors, so you practically need to use non-blocking I/O (and
683treat callback invocation as hint only), or retest separately with a safe
684interface before doing I/O (XLib can do this), or force the use of either
685\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
686problem. Also note that it is quite easy to have your callback invoked
687when the readyness condition is no longer valid even when employing
688typical ways of handling events, so its a good idea to use non-blocking
689I/O unconditionally.
589.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 690.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts"
590.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 691.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts"
591.IX Subsection "ev_timer - relative and optionally recurring timeouts" 692.IX Subsection "ev_timer - relative and optionally recurring timeouts"
592Timer watchers are simple relative timers that generate an event after a 693Timer watchers are simple relative timers that generate an event after a
593given time, and optionally repeating in regular intervals after that. 694given time, and optionally repeating in regular intervals after that.

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