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Comparing libev/ev.3 (file contents):
Revision 1.8 by root, Fri Nov 23 15:26:08 2007 UTC vs.
Revision 1.23 by root, Tue Nov 27 08:20:42 2007 UTC

… …
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 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-11-27" "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
… …
173.IX Header "TIME REPRESENTATION" 173.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 174Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176the beginning of 1970, details are complicated, don't ask). This type is 176the beginning of 1970, details are complicated, don't ask). This type is
177called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 177called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178to the double type in C. 178to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
179it, you should treat it as such.
179.SH "GLOBAL FUNCTIONS" 180.SH "GLOBAL FUNCTIONS"
180.IX Header "GLOBAL FUNCTIONS" 181.IX Header "GLOBAL FUNCTIONS"
181These functions can be called anytime, even before initialising the 182These functions can be called anytime, even before initialising the
182library in any way. 183library in any way.
183.IP "ev_tstamp ev_time ()" 4 184.IP "ev_tstamp ev_time ()" 4
… …
199.Sp 200.Sp
200Usually, it's a good idea to terminate if the major versions mismatch, 201Usually, it's a good idea to terminate if the major versions mismatch,
201as this indicates an incompatible change. Minor versions are usually 202as this indicates an incompatible change. Minor versions are usually
202compatible to older versions, so a larger minor version alone is usually 203compatible to older versions, so a larger minor version alone is usually
203not a problem. 204not a problem.
205.Sp
206Example: make sure we haven't accidentally been linked against the wrong
207version:
208.Sp
209.Vb 3
210\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR));
213.Ve
204.IP "unsigned int ev_supported_backends ()" 4 214.IP "unsigned int ev_supported_backends ()" 4
205.IX Item "unsigned int ev_supported_backends ()" 215.IX Item "unsigned int ev_supported_backends ()"
206Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR 216Return 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 217value) 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 218availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
209a description of the set values. 219a description of the set values.
220.Sp
221Example: make sure we have the epoll method, because yeah this is cool and
222a must have and can we have a torrent of it please!!!11
223.Sp
224.Vb 2
225\& assert (("sorry, no epoll, no sex",
226\& ev_supported_backends () & EVBACKEND_EPOLL));
227.Ve
210.IP "unsigned int ev_recommended_backends ()" 4 228.IP "unsigned int ev_recommended_backends ()" 4
211.IX Item "unsigned int ev_recommended_backends ()" 229.IX Item "unsigned int ev_recommended_backends ()"
212Return the set of all backends compiled into this binary of libev and also 230Return 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 231recommended 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 232returned 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 233most 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 234(assuming you know what you are doing). This is the set of backends that
217libev will probe for if you specify no backends explicitly. 235libev will probe for if you specify no backends explicitly.
236.IP "unsigned int ev_embeddable_backends ()" 4
237.IX Item "unsigned int ev_embeddable_backends ()"
238Returns the set of backends that are embeddable in other event loops. This
239is the theoretical, all\-platform, value. To find which backends
240might be supported on the current system, you would need to look at
241\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
242recommended ones.
243.Sp
244See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
218.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 245.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
220Sets the allocation function to use (the prototype is similar to the 247Sets the allocation function to use (the prototype is similar to the
221realloc C function, the semantics are identical). It is used to allocate 248realloc C function, the semantics are identical). It is used to allocate
222and free memory (no surprises here). If it returns zero when memory 249and free memory (no surprises here). If it returns zero when memory
… …
224destructive action. The default is your system realloc function. 251destructive action. The default is your system realloc function.
225.Sp 252.Sp
226You could override this function in high-availability programs to, say, 253You could override this function in high-availability programs to, say,
227free some memory if it cannot allocate memory, to use a special allocator, 254free some memory if it cannot allocate memory, to use a special allocator,
228or even to sleep a while and retry until some memory is available. 255or even to sleep a while and retry until some memory is available.
256.Sp
257Example: replace the libev allocator with one that waits a bit and then
258retries: better than mine).
259.Sp
260.Vb 6
261\& static void *
262\& persistent_realloc (void *ptr, long size)
263\& {
264\& for (;;)
265\& {
266\& void *newptr = realloc (ptr, size);
267.Ve
268.Sp
269.Vb 2
270\& if (newptr)
271\& return newptr;
272.Ve
273.Sp
274.Vb 3
275\& sleep (60);
276\& }
277\& }
278.Ve
279.Sp
280.Vb 2
281\& ...
282\& ev_set_allocator (persistent_realloc);
283.Ve
229.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 284.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
230.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 285.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
231Set the callback function to call on a retryable syscall error (such 286Set the callback function to call on a retryable syscall error (such
232as failed select, poll, epoll_wait). The message is a printable string 287as failed select, poll, epoll_wait). The message is a printable string
233indicating the system call or subsystem causing the problem. If this 288indicating the system call or subsystem causing the problem. If this
234callback is set, then libev will expect it to remedy the sitution, no 289callback is set, then libev will expect it to remedy the sitution, no
235matter what, when it returns. That is, libev will generally retry the 290matter what, when it returns. That is, libev will generally retry the
236requested operation, or, if the condition doesn't go away, do bad stuff 291requested operation, or, if the condition doesn't go away, do bad stuff
237(such as abort). 292(such as abort).
293.Sp
294Example: do the same thing as libev does internally:
295.Sp
296.Vb 6
297\& static void
298\& fatal_error (const char *msg)
299\& {
300\& perror (msg);
301\& abort ();
302\& }
303.Ve
304.Sp
305.Vb 2
306\& ...
307\& ev_set_syserr_cb (fatal_error);
308.Ve
238.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 309.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
239.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 310.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
240An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two 311An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two
241types of such loops, the \fIdefault\fR loop, which supports signals and child 312types of such loops, the \fIdefault\fR loop, which supports signals and child
242events, and dynamically created loops which do not. 313events, and dynamically created loops which do not.
… …
376.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 447.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
377Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
378always distinct from the default loop. Unlike the default loop, it cannot 449always distinct from the default loop. Unlike the default loop, it cannot
379handle signal and child watchers, and attempts to do so will be greeted by 450handle signal and child watchers, and attempts to do so will be greeted by
380undefined behaviour (or a failed assertion if assertions are enabled). 451undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp
453Example: try to create a event loop that uses epoll and nothing else.
454.Sp
455.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair");
459.Ve
381.IP "ev_default_destroy ()" 4 460.IP "ev_default_destroy ()" 4
382.IX Item "ev_default_destroy ()" 461.IX Item "ev_default_destroy ()"
383Destroys the default loop again (frees all memory and kernel state 462Destroys the default loop again (frees all memory and kernel state
384etc.). This stops all registered event watchers (by not touching them in 463etc.). None of the active event watchers will be stopped in the normal
385any way whatsoever, although you cannot rely on this :). 464sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
465responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
466calling this function, or cope with the fact afterwards (which is usually
467the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
468for example).
386.IP "ev_loop_destroy (loop)" 4 469.IP "ev_loop_destroy (loop)" 4
387.IX Item "ev_loop_destroy (loop)" 470.IX Item "ev_loop_destroy (loop)"
388Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 471Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
389earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 472earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
390.IP "ev_default_fork ()" 4 473.IP "ev_default_fork ()" 4
… …
419Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 502Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
420use. 503use.
421.IP "ev_tstamp ev_now (loop)" 4 504.IP "ev_tstamp ev_now (loop)" 4
422.IX Item "ev_tstamp ev_now (loop)" 505.IX Item "ev_tstamp ev_now (loop)"
423Returns the current \*(L"event loop time\*(R", which is the time the event loop 506Returns the current \*(L"event loop time\*(R", which is the time the event loop
424got events and started processing them. This timestamp does not change 507received events and started processing them. This timestamp does not
425as long as callbacks are being processed, and this is also the base time 508change as long as callbacks are being processed, and this is also the base
426used for relative timers. You can treat it as the timestamp of the event 509time used for relative timers. You can treat it as the timestamp of the
427occuring (or more correctly, the mainloop finding out about it). 510event occuring (or more correctly, libev finding out about it).
428.IP "ev_loop (loop, int flags)" 4 511.IP "ev_loop (loop, int flags)" 4
429.IX Item "ev_loop (loop, int flags)" 512.IX Item "ev_loop (loop, int flags)"
430Finally, this is it, the event handler. This function usually is called 513Finally, this is it, the event handler. This function usually is called
431after you initialised all your watchers and you want to start handling 514after you initialised all your watchers and you want to start handling
432events. 515events.
433.Sp 516.Sp
434If the flags argument is specified as \f(CW0\fR, it will not return until 517If the flags argument is specified as \f(CW0\fR, it will not return until
435either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 518either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
519.Sp
520Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
521relying on all watchers to be stopped when deciding when a program has
522finished (especially in interactive programs), but having a program that
523automatically loops as long as it has to and no longer by virtue of
524relying on its watchers stopping correctly is a thing of beauty.
436.Sp 525.Sp
437A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 526A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
438those events and any outstanding ones, but will not block your process in 527those events and any outstanding ones, but will not block your process in
439case there are no events and will return after one iteration of the loop. 528case there are no events and will return after one iteration of the loop.
440.Sp 529.Sp
… …
465\& - Call all queued watchers in reverse order (i.e. check watchers first). 554\& - 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 555\& Signals and child watchers are implemented as I/O watchers, and will
467\& be handled here by queueing them when their watcher gets executed. 556\& be handled here by queueing them when their watcher gets executed.
468\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 557\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
469\& were used, return, otherwise continue with step *. 558\& were used, return, otherwise continue with step *.
559.Ve
560.Sp
561Example: queue some jobs and then loop until no events are outsanding
562anymore.
563.Sp
564.Vb 4
565\& ... queue jobs here, make sure they register event watchers as long
566\& ... as they still have work to do (even an idle watcher will do..)
567\& ev_loop (my_loop, 0);
568\& ... jobs done. yeah!
470.Ve 569.Ve
471.IP "ev_unloop (loop, how)" 4 570.IP "ev_unloop (loop, how)" 4
472.IX Item "ev_unloop (loop, how)" 571.IX Item "ev_unloop (loop, how)"
473Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 572Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
474has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 573has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
… …
488example, libev itself uses this for its internal signal pipe: It is not 587example, libev itself uses this for its internal signal pipe: It is not
489visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 588visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
490no event watchers registered by it are active. It is also an excellent 589no event watchers registered by it are active. It is also an excellent
491way to do this for generic recurring timers or from within third-party 590way to do this for generic recurring timers or from within third-party
492libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 591libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
592.Sp
593Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
594running when nothing else is active.
595.Sp
596.Vb 4
597\& struct dv_signal exitsig;
598\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599\& ev_signal_start (myloop, &exitsig);
600\& evf_unref (myloop);
601.Ve
602.Sp
603Example: for some weird reason, unregister the above signal handler again.
604.Sp
605.Vb 2
606\& ev_ref (myloop);
607\& ev_signal_stop (myloop, &exitsig);
608.Ve
493.SH "ANATOMY OF A WATCHER" 609.SH "ANATOMY OF A WATCHER"
494.IX Header "ANATOMY OF A WATCHER" 610.IX Header "ANATOMY OF A WATCHER"
495A watcher is a structure that you create and register to record your 611A watcher is a structure that you create and register to record your
496interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 612interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
497become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 613become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
533*)\*(C'\fR), and you can stop watching for events at any time by calling the 649*)\*(C'\fR), and you can stop watching for events at any time by calling the
534corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 650corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
535.PP 651.PP
536As long as your watcher is active (has been started but not stopped) you 652As long as your watcher is active (has been started but not stopped) you
537must not touch the values stored in it. Most specifically you must never 653must not touch the values stored in it. Most specifically you must never
538reinitialise it or call its set macro. 654reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
539.PP
540You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
541(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
542callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
543(watcher *)\*(C'\fR macro.
544.PP 655.PP
545Each and every callback receives the event loop pointer as first, the 656Each and every callback receives the event loop pointer as first, the
546registered watcher structure as second, and a bitset of received events as 657registered watcher structure as second, and a bitset of received events as
547third argument. 658third argument.
548.PP 659.PP
… …
573The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 684The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
574.ie n .IP """EV_CHILD""" 4 685.ie n .IP """EV_CHILD""" 4
575.el .IP "\f(CWEV_CHILD\fR" 4 686.el .IP "\f(CWEV_CHILD\fR" 4
576.IX Item "EV_CHILD" 687.IX Item "EV_CHILD"
577The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 688The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
689.ie n .IP """EV_STAT""" 4
690.el .IP "\f(CWEV_STAT\fR" 4
691.IX Item "EV_STAT"
692The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
578.ie n .IP """EV_IDLE""" 4 693.ie n .IP """EV_IDLE""" 4
579.el .IP "\f(CWEV_IDLE\fR" 4 694.el .IP "\f(CWEV_IDLE\fR" 4
580.IX Item "EV_IDLE" 695.IX Item "EV_IDLE"
581The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 696The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
582.ie n .IP """EV_PREPARE""" 4 697.ie n .IP """EV_PREPARE""" 4
… …
606Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 721Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
607for example it might indicate that a fd is readable or writable, and if 722for example it might indicate that a fd is readable or writable, and if
608your callbacks is well-written it can just attempt the operation and cope 723your callbacks is well-written it can just attempt the operation and cope
609with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 724with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
610programs, though, so beware. 725programs, though, so beware.
726.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
727.IX Subsection "GENERIC WATCHER FUNCTIONS"
728In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
729e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
730.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
731.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
732.IX Item "ev_init (ev_TYPE *watcher, callback)"
733This macro initialises the generic portion of a watcher. The contents
734of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
735the generic parts of the watcher are initialised, you \fIneed\fR to call
736the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
737type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
738which rolls both calls into one.
739.Sp
740You can reinitialise a watcher at any time as long as it has been stopped
741(or never started) and there are no pending events outstanding.
742.Sp
743The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
744int revents)\*(C'\fR.
745.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
746.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
747.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
748This macro initialises the type-specific parts of a watcher. You need to
749call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
750call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
751macro on a watcher that is active (it can be pending, however, which is a
752difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
753.Sp
754Although some watcher types do not have type-specific arguments
755(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
756.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
757.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
758.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
759This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
760calls into a single call. This is the most convinient method to initialise
761a watcher. The same limitations apply, of course.
762.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
763.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
764.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
765Starts (activates) the given watcher. Only active watchers will receive
766events. If the watcher is already active nothing will happen.
767.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
768.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
769.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
770Stops the given watcher again (if active) and clears the pending
771status. It is possible that stopped watchers are pending (for example,
772non-repeating timers are being stopped when they become pending), but
773\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
774you want to free or reuse the memory used by the watcher it is therefore a
775good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
776.IP "bool ev_is_active (ev_TYPE *watcher)" 4
777.IX Item "bool ev_is_active (ev_TYPE *watcher)"
778Returns a true value iff the watcher is active (i.e. it has been started
779and not yet been stopped). As long as a watcher is active you must not modify
780it.
781.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
782.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
783Returns a true value iff the watcher is pending, (i.e. it has outstanding
784events but its callback has not yet been invoked). As long as a watcher
785is pending (but not active) you must not call an init function on it (but
786\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
787libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
788.IP "callback = ev_cb (ev_TYPE *watcher)" 4
789.IX Item "callback = ev_cb (ev_TYPE *watcher)"
790Returns the callback currently set on the watcher.
791.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
792.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
793Change the callback. You can change the callback at virtually any time
794(modulo threads).
611.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 795.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
612.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 796.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
613Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 797Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
614and read at any time, libev will completely ignore it. This can be used 798and read at any time, libev will completely ignore it. This can be used
615to associate arbitrary data with your watcher. If you need more data and 799to associate arbitrary data with your watcher. If you need more data and
… …
641More interesting and less C\-conformant ways of catsing your callback type 825More interesting and less C\-conformant ways of catsing your callback type
642have been omitted.... 826have been omitted....
643.SH "WATCHER TYPES" 827.SH "WATCHER TYPES"
644.IX Header "WATCHER TYPES" 828.IX Header "WATCHER TYPES"
645This section describes each watcher in detail, but will not repeat 829This section describes each watcher in detail, but will not repeat
646information given in the last section. 830information given in the last section. Any initialisation/set macros,
831functions and members specific to the watcher type are explained.
832.PP
833Members are additionally marked with either \fI[read\-only]\fR, meaning that,
834while the watcher is active, you can look at the member and expect some
835sensible content, but you must not modify it (you can modify it while the
836watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
837means you can expect it to have some sensible content while the watcher
838is active, but you can also modify it. Modifying it may not do something
839sensible or take immediate effect (or do anything at all), but libev will
840not crash or malfunction in any way.
647.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 841.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
648.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 842.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
649.IX Subsection "ev_io - is this file descriptor readable or writable" 843.IX Subsection "ev_io - is this file descriptor readable or writable?"
650I/O watchers check whether a file descriptor is readable or writable 844I/O watchers check whether a file descriptor is readable or writable
651in each iteration of the event loop (This behaviour is called 845in each iteration of the event loop, or, more precisely, when reading
652level-triggering because you keep receiving events as long as the 846would not block the process and writing would at least be able to write
653condition persists. Remember you can stop the watcher if you don't want to 847some data. This behaviour is called level-triggering because you keep
654act on the event and neither want to receive future events). 848receiving events as long as the condition persists. Remember you can stop
849the watcher if you don't want to act on the event and neither want to
850receive future events.
655.PP 851.PP
656In general you can register as many read and/or write event watchers per 852In general you can register as many read and/or write event watchers per
657fd as you want (as long as you don't confuse yourself). Setting all file 853fd as you want (as long as you don't confuse yourself). Setting all file
658descriptors to non-blocking mode is also usually a good idea (but not 854descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing). 855required if you know what you are doing).
660.PP 856.PP
661You have to be careful with dup'ed file descriptors, though. Some backends 857You have to be careful with dup'ed file descriptors, though. Some backends
662(the linux epoll backend is a notable example) cannot handle dup'ed file 858(the linux epoll backend is a notable example) cannot handle dup'ed file
663descriptors correctly if you register interest in two or more fds pointing 859descriptors correctly if you register interest in two or more fds pointing
664to the same underlying file/socket etc. description (that is, they share 860to the same underlying file/socket/etc. description (that is, they share
665the same underlying \*(L"file open\*(R"). 861the same underlying \*(L"file open\*(R").
666.PP 862.PP
667If you must do this, then force the use of a known-to-be-good backend 863If you must do this, then force the use of a known-to-be-good backend
668(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 864(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
669\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 865\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
866.PP
867Another thing you have to watch out for is that it is quite easy to
868receive \*(L"spurious\*(R" readyness notifications, that is your callback might
869be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
870because there is no data. Not only are some backends known to create a
871lot of those (for example solaris ports), it is very easy to get into
872this situation even with a relatively standard program structure. Thus
873it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
874\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
875.PP
876If you cannot run the fd in non-blocking mode (for example you should not
877play around with an Xlib connection), then you have to seperately re-test
878wether a file descriptor is really ready with a known-to-be good interface
879such as poll (fortunately in our Xlib example, Xlib already does this on
880its own, so its quite safe to use).
670.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 881.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
671.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 882.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
672.PD 0 883.PD 0
673.IP "ev_io_set (ev_io *, int fd, int events)" 4 884.IP "ev_io_set (ev_io *, int fd, int events)" 4
674.IX Item "ev_io_set (ev_io *, int fd, int events)" 885.IX Item "ev_io_set (ev_io *, int fd, int events)"
675.PD 886.PD
676Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 887Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
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 | 888rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
678EV_WRITE\*(C'\fR to receive the given events. 889\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
679.Sp 890.IP "int fd [read\-only]" 4
680Please note that most of the more scalable backend mechanisms (for example 891.IX Item "int fd [read-only]"
681epoll and solaris ports) can result in spurious readyness notifications 892The file descriptor being watched.
682for file descriptors, so you practically need to use non-blocking I/O (and 893.IP "int events [read\-only]" 4
683treat callback invocation as hint only), or retest separately with a safe 894.IX Item "int events [read-only]"
684interface before doing I/O (XLib can do this), or force the use of either 895The events being watched.
685\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this 896.PP
686problem. Also note that it is quite easy to have your callback invoked 897Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
687when the readyness condition is no longer valid even when employing 898readable, but only once. Since it is likely line\-buffered, you could
688typical ways of handling events, so its a good idea to use non-blocking 899attempt to read a whole line in the callback:
689I/O unconditionally. 900.PP
901.Vb 6
902\& static void
903\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
904\& {
905\& ev_io_stop (loop, w);
906\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
907\& }
908.Ve
909.PP
910.Vb 6
911\& ...
912\& struct ev_loop *loop = ev_default_init (0);
913\& struct ev_io stdin_readable;
914\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
915\& ev_io_start (loop, &stdin_readable);
916\& ev_loop (loop, 0);
917.Ve
690.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 918.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
691.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 919.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
692.IX Subsection "ev_timer - relative and optionally recurring timeouts" 920.IX Subsection "ev_timer - relative and optionally repeating timeouts"
693Timer watchers are simple relative timers that generate an event after a 921Timer watchers are simple relative timers that generate an event after a
694given time, and optionally repeating in regular intervals after that. 922given time, and optionally repeating in regular intervals after that.
695.PP 923.PP
696The timers are based on real time, that is, if you register an event that 924The timers are based on real time, that is, if you register an event that
697times out after an hour and you reset your system clock to last years 925times out after an hour and you reset your system clock to last years
… …
737.Sp 965.Sp
738If the timer is repeating, either start it if necessary (with the repeat 966If the timer is repeating, either start it if necessary (with the repeat
739value), or reset the running timer to the repeat value. 967value), or reset the running timer to the repeat value.
740.Sp 968.Sp
741This sounds a bit complicated, but here is a useful and typical 969This sounds a bit complicated, but here is a useful and typical
742example: Imagine you have a tcp connection and you want a so-called idle 970example: Imagine you have a tcp connection and you want a so-called
743timeout, that is, you want to be called when there have been, say, 60 971idle timeout, that is, you want to be called when there have been,
744seconds of inactivity on the socket. The easiest way to do this is to 972say, 60 seconds of inactivity on the socket. The easiest way to do
745configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 973this 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
746time you successfully read or write some data. If you go into an idle 974\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
747state where you do not expect data to travel on the socket, you can stop 975you go into an idle state where you do not expect data to travel on the
748the timer, and again will automatically restart it if need be. 976socket, you can stop the timer, and again will automatically restart it if
977need be.
978.Sp
979You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
980and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
981.Sp
982.Vb 8
983\& ev_timer_init (timer, callback, 0., 5.);
984\& ev_timer_again (loop, timer);
985\& ...
986\& timer->again = 17.;
987\& ev_timer_again (loop, timer);
988\& ...
989\& timer->again = 10.;
990\& ev_timer_again (loop, timer);
991.Ve
992.Sp
993This is more efficient then stopping/starting the timer eahc time you want
994to modify its timeout value.
995.IP "ev_tstamp repeat [read\-write]" 4
996.IX Item "ev_tstamp repeat [read-write]"
997The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
998or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
999which is also when any modifications are taken into account.
1000.PP
1001Example: create a timer that fires after 60 seconds.
1002.PP
1003.Vb 5
1004\& static void
1005\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1006\& {
1007\& .. one minute over, w is actually stopped right here
1008\& }
1009.Ve
1010.PP
1011.Vb 3
1012\& struct ev_timer mytimer;
1013\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1014\& ev_timer_start (loop, &mytimer);
1015.Ve
1016.PP
1017Example: create a timeout timer that times out after 10 seconds of
1018inactivity.
1019.PP
1020.Vb 5
1021\& static void
1022\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1023\& {
1024\& .. ten seconds without any activity
1025\& }
1026.Ve
1027.PP
1028.Vb 4
1029\& struct ev_timer mytimer;
1030\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1031\& ev_timer_again (&mytimer); /* start timer */
1032\& ev_loop (loop, 0);
1033.Ve
1034.PP
1035.Vb 3
1036\& // and in some piece of code that gets executed on any "activity":
1037\& // reset the timeout to start ticking again at 10 seconds
1038\& ev_timer_again (&mytimer);
1039.Ve
749.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1040.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
750.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1041.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
751.IX Subsection "ev_periodic - to cron or not to cron" 1042.IX Subsection "ev_periodic - to cron or not to cron?"
752Periodic watchers are also timers of a kind, but they are very versatile 1043Periodic watchers are also timers of a kind, but they are very versatile
753(and unfortunately a bit complex). 1044(and unfortunately a bit complex).
754.PP 1045.PP
755Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1046Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
756but on wallclock time (absolute time). You can tell a periodic watcher 1047but on wallclock time (absolute time). You can tell a periodic watcher
757to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1048to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
758periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1049periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
759+ 10.>) and then reset your system clock to the last year, then it will 1050+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
760take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1051take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
761roughly 10 seconds later and of course not if you reset your system time 1052roughly 10 seconds later and of course not if you reset your system time
762again). 1053again).
763.PP 1054.PP
764They can also be used to implement vastly more complex timers, such as 1055They can also be used to implement vastly more complex timers, such as
… …
845.IX Item "ev_periodic_again (loop, ev_periodic *)" 1136.IX Item "ev_periodic_again (loop, ev_periodic *)"
846Simply stops and restarts the periodic watcher again. This is only useful 1137Simply stops and restarts the periodic watcher again. This is only useful
847when you changed some parameters or the reschedule callback would return 1138when you changed some parameters or the reschedule callback would return
848a different time than the last time it was called (e.g. in a crond like 1139a different time than the last time it was called (e.g. in a crond like
849program when the crontabs have changed). 1140program when the crontabs have changed).
1141.IP "ev_tstamp interval [read\-write]" 4
1142.IX Item "ev_tstamp interval [read-write]"
1143The current interval value. Can be modified any time, but changes only
1144take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1145called.
1146.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1147.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1148The current reschedule callback, or \f(CW0\fR, if this functionality is
1149switched off. Can be changed any time, but changes only take effect when
1150the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1151.PP
1152Example: call a callback every hour, or, more precisely, whenever the
1153system clock is divisible by 3600. The callback invocation times have
1154potentially a lot of jittering, but good long-term stability.
1155.PP
1156.Vb 5
1157\& static void
1158\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1159\& {
1160\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1161\& }
1162.Ve
1163.PP
1164.Vb 3
1165\& struct ev_periodic hourly_tick;
1166\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1167\& ev_periodic_start (loop, &hourly_tick);
1168.Ve
1169.PP
1170Example: the same as above, but use a reschedule callback to do it:
1171.PP
1172.Vb 1
1173\& #include <math.h>
1174.Ve
1175.PP
1176.Vb 5
1177\& static ev_tstamp
1178\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1179\& {
1180\& return fmod (now, 3600.) + 3600.;
1181\& }
1182.Ve
1183.PP
1184.Vb 1
1185\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1186.Ve
1187.PP
1188Example: call a callback every hour, starting now:
1189.PP
1190.Vb 4
1191\& struct ev_periodic hourly_tick;
1192\& ev_periodic_init (&hourly_tick, clock_cb,
1193\& fmod (ev_now (loop), 3600.), 3600., 0);
1194\& ev_periodic_start (loop, &hourly_tick);
1195.Ve
850.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1196.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
851.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1197.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
852.IX Subsection "ev_signal - signal me when a signal gets signalled" 1198.IX Subsection "ev_signal - signal me when a signal gets signalled!"
853Signal watchers will trigger an event when the process receives a specific 1199Signal watchers will trigger an event when the process receives a specific
854signal one or more times. Even though signals are very asynchronous, libev 1200signal one or more times. Even though signals are very asynchronous, libev
855will try it's best to deliver signals synchronously, i.e. as part of the 1201will try it's best to deliver signals synchronously, i.e. as part of the
856normal event processing, like any other event. 1202normal event processing, like any other event.
857.PP 1203.PP
… …
867.IP "ev_signal_set (ev_signal *, int signum)" 4 1213.IP "ev_signal_set (ev_signal *, int signum)" 4
868.IX Item "ev_signal_set (ev_signal *, int signum)" 1214.IX Item "ev_signal_set (ev_signal *, int signum)"
869.PD 1215.PD
870Configures the watcher to trigger on the given signal number (usually one 1216Configures the watcher to trigger on the given signal number (usually one
871of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1217of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1218.IP "int signum [read\-only]" 4
1219.IX Item "int signum [read-only]"
1220The signal the watcher watches out for.
872.ie n .Sh """ev_child"" \- wait for pid status changes" 1221.ie n .Sh """ev_child"" \- watch out for process status changes"
873.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1222.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
874.IX Subsection "ev_child - wait for pid status changes" 1223.IX Subsection "ev_child - watch out for process status changes"
875Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1224Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
876some child status changes (most typically when a child of yours dies). 1225some child status changes (most typically when a child of yours dies).
877.IP "ev_child_init (ev_child *, callback, int pid)" 4 1226.IP "ev_child_init (ev_child *, callback, int pid)" 4
878.IX Item "ev_child_init (ev_child *, callback, int pid)" 1227.IX Item "ev_child_init (ev_child *, callback, int pid)"
879.PD 0 1228.PD 0
… …
884\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1233\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
885at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1234at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
886the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1235the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
887\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1236\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
888process causing the status change. 1237process causing the status change.
1238.IP "int pid [read\-only]" 4
1239.IX Item "int pid [read-only]"
1240The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1241.IP "int rpid [read\-write]" 4
1242.IX Item "int rpid [read-write]"
1243The process id that detected a status change.
1244.IP "int rstatus [read\-write]" 4
1245.IX Item "int rstatus [read-write]"
1246The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1247\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1248.PP
1249Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1250.PP
1251.Vb 5
1252\& static void
1253\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1254\& {
1255\& ev_unloop (loop, EVUNLOOP_ALL);
1256\& }
1257.Ve
1258.PP
1259.Vb 3
1260\& struct ev_signal signal_watcher;
1261\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1262\& ev_signal_start (loop, &sigint_cb);
1263.Ve
1264.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1265.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1266.IX Subsection "ev_stat - did the file attributes just change?"
1267This watches a filesystem path for attribute changes. That is, it calls
1268\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1269compared to the last time, invoking the callback if it did.
1270.PP
1271The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1272not exist\*(R" is a status change like any other. The condition \*(L"path does
1273not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1274otherwise always forced to be at least one) and all the other fields of
1275the stat buffer having unspecified contents.
1276.PP
1277Since there is no standard to do this, the portable implementation simply
1278calls \f(CW\*(C`stat (2)\*(C'\fR regulalry on the path to see if it changed somehow. You
1279can specify a recommended polling interval for this case. If you specify
1280a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1281unspecified default\fR value will be used (which you can expect to be around
1282five seconds, although this might change dynamically). Libev will also
1283impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1284usually overkill.
1285.PP
1286This watcher type is not meant for massive numbers of stat watchers,
1287as even with OS-supported change notifications, this can be
1288resource\-intensive.
1289.PP
1290At the time of this writing, no specific \s-1OS\s0 backends are implemented, but
1291if demand increases, at least a kqueue and inotify backend will be added.
1292.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1293.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1294.PD 0
1295.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1296.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1297.PD
1298Configures the watcher to wait for status changes of the given
1299\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1300be detected and should normally be specified as \f(CW0\fR to let libev choose
1301a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1302path for as long as the watcher is active.
1303.Sp
1304The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1305relative to the attributes at the time the watcher was started (or the
1306last change was detected).
1307.IP "ev_stat_stat (ev_stat *)" 4
1308.IX Item "ev_stat_stat (ev_stat *)"
1309Updates the stat buffer immediately with new values. If you change the
1310watched path in your callback, you could call this fucntion to avoid
1311detecting this change (while introducing a race condition). Can also be
1312useful simply to find out the new values.
1313.IP "ev_statdata attr [read\-only]" 4
1314.IX Item "ev_statdata attr [read-only]"
1315The most-recently detected attributes of the file. Although the type is of
1316\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1317suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1318was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1319.IP "ev_statdata prev [read\-only]" 4
1320.IX Item "ev_statdata prev [read-only]"
1321The previous attributes of the file. The callback gets invoked whenever
1322\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1323.IP "ev_tstamp interval [read\-only]" 4
1324.IX Item "ev_tstamp interval [read-only]"
1325The specified interval.
1326.IP "const char *path [read\-only]" 4
1327.IX Item "const char *path [read-only]"
1328The filesystem path that is being watched.
1329.PP
1330Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1331.PP
1332.Vb 15
1333\& static void
1334\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1335\& {
1336\& /* /etc/passwd changed in some way */
1337\& if (w->attr.st_nlink)
1338\& {
1339\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1340\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1341\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1342\& }
1343\& else
1344\& /* you shalt not abuse printf for puts */
1345\& puts ("wow, /etc/passwd is not there, expect problems. "
1346\& "if this is windows, they already arrived\en");
1347\& }
1348.Ve
1349.PP
1350.Vb 2
1351\& ...
1352\& ev_stat passwd;
1353.Ve
1354.PP
1355.Vb 2
1356\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1357\& ev_stat_start (loop, &passwd);
1358.Ve
889.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1359.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
890.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1360.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
891.IX Subsection "ev_idle - when you've got nothing better to do" 1361.IX Subsection "ev_idle - when you've got nothing better to do..."
892Idle watchers trigger events when there are no other events are pending 1362Idle watchers trigger events when there are no other events are pending
893(prepare, check and other idle watchers do not count). That is, as long 1363(prepare, check and other idle watchers do not count). That is, as long
894as your process is busy handling sockets or timeouts (or even signals, 1364as your process is busy handling sockets or timeouts (or even signals,
895imagine) it will not be triggered. But when your process is idle all idle 1365imagine) it will not be triggered. But when your process is idle all idle
896watchers are being called again and again, once per event loop iteration \- 1366watchers are being called again and again, once per event loop iteration \-
… …
907.IP "ev_idle_init (ev_signal *, callback)" 4 1377.IP "ev_idle_init (ev_signal *, callback)" 4
908.IX Item "ev_idle_init (ev_signal *, callback)" 1378.IX Item "ev_idle_init (ev_signal *, callback)"
909Initialises and configures the idle watcher \- it has no parameters of any 1379Initialises and configures the idle watcher \- it has no parameters of any
910kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1380kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
911believe me. 1381believe me.
1382.PP
1383Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the
1384callback, free it. Alos, use no error checking, as usual.
1385.PP
1386.Vb 7
1387\& static void
1388\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1389\& {
1390\& free (w);
1391\& // now do something you wanted to do when the program has
1392\& // no longer asnything immediate to do.
1393\& }
1394.Ve
1395.PP
1396.Vb 3
1397\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1398\& ev_idle_init (idle_watcher, idle_cb);
1399\& ev_idle_start (loop, idle_cb);
1400.Ve
912.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1401.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
913.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1402.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
914.IX Subsection "ev_prepare and ev_check - customise your event loop" 1403.IX Subsection "ev_prepare and ev_check - customise your event loop!"
915Prepare and check watchers are usually (but not always) used in tandem: 1404Prepare and check watchers are usually (but not always) used in tandem:
916prepare watchers get invoked before the process blocks and check watchers 1405prepare watchers get invoked before the process blocks and check watchers
917afterwards. 1406afterwards.
918.PP 1407.PP
1408You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1409the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1410watchers. Other loops than the current one are fine, however. The
1411rationale behind this is that you do not need to check for recursion in
1412those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1413\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1414called in pairs bracketing the blocking call.
1415.PP
919Their main purpose is to integrate other event mechanisms into libev. This 1416Their main purpose is to integrate other event mechanisms into libev and
920could be used, for example, to track variable changes, implement your own 1417their use is somewhat advanced. This could be used, for example, to track
921watchers, integrate net-snmp or a coroutine library and lots more. 1418variable changes, implement your own watchers, integrate net-snmp or a
1419coroutine library and lots more. They are also occasionally useful if
1420you cache some data and want to flush it before blocking (for example,
1421in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1422watcher).
922.PP 1423.PP
923This is done by examining in each prepare call which file descriptors need 1424This is done by examining in each prepare call which file descriptors need
924to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1425to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
925them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1426them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
926provide just this functionality). Then, in the check watcher you check for 1427provide just this functionality). Then, in the check watcher you check for
… …
944.IX Item "ev_check_init (ev_check *, callback)" 1445.IX Item "ev_check_init (ev_check *, callback)"
945.PD 1446.PD
946Initialises and configures the prepare or check watcher \- they have no 1447Initialises and configures the prepare or check watcher \- they have no
947parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1448parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
948macros, but using them is utterly, utterly and completely pointless. 1449macros, but using them is utterly, utterly and completely pointless.
1450.PP
1451Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1452and a timeout watcher in a prepare handler, as required by libadns, and
1453in a check watcher, destroy them and call into libadns. What follows is
1454pseudo-code only of course:
1455.PP
1456.Vb 2
1457\& static ev_io iow [nfd];
1458\& static ev_timer tw;
1459.Ve
1460.PP
1461.Vb 9
1462\& static void
1463\& io_cb (ev_loop *loop, ev_io *w, int revents)
1464\& {
1465\& // set the relevant poll flags
1466\& // could also call adns_processreadable etc. here
1467\& struct pollfd *fd = (struct pollfd *)w->data;
1468\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1469\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1470\& }
1471.Ve
1472.PP
1473.Vb 7
1474\& // create io watchers for each fd and a timer before blocking
1475\& static void
1476\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1477\& {
1478\& int timeout = 3600000;truct pollfd fds [nfd];
1479\& // actual code will need to loop here and realloc etc.
1480\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1481.Ve
1482.PP
1483.Vb 3
1484\& /* the callback is illegal, but won't be called as we stop during check */
1485\& ev_timer_init (&tw, 0, timeout * 1e-3);
1486\& ev_timer_start (loop, &tw);
1487.Ve
1488.PP
1489.Vb 6
1490\& // create on ev_io per pollfd
1491\& for (int i = 0; i < nfd; ++i)
1492\& {
1493\& ev_io_init (iow + i, io_cb, fds [i].fd,
1494\& ((fds [i].events & POLLIN ? EV_READ : 0)
1495\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1496.Ve
1497.PP
1498.Vb 5
1499\& fds [i].revents = 0;
1500\& iow [i].data = fds + i;
1501\& ev_io_start (loop, iow + i);
1502\& }
1503\& }
1504.Ve
1505.PP
1506.Vb 5
1507\& // stop all watchers after blocking
1508\& static void
1509\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1510\& {
1511\& ev_timer_stop (loop, &tw);
1512.Ve
1513.PP
1514.Vb 2
1515\& for (int i = 0; i < nfd; ++i)
1516\& ev_io_stop (loop, iow + i);
1517.Ve
1518.PP
1519.Vb 2
1520\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1521\& }
1522.Ve
1523.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1524.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1525.IX Subsection "ev_embed - when one backend isn't enough..."
1526This is a rather advanced watcher type that lets you embed one event loop
1527into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1528loop, other types of watchers might be handled in a delayed or incorrect
1529fashion and must not be used).
1530.PP
1531There are primarily two reasons you would want that: work around bugs and
1532prioritise I/O.
1533.PP
1534As an example for a bug workaround, the kqueue backend might only support
1535sockets on some platform, so it is unusable as generic backend, but you
1536still want to make use of it because you have many sockets and it scales
1537so nicely. In this case, you would create a kqueue-based loop and embed it
1538into your default loop (which might use e.g. poll). Overall operation will
1539be a bit slower because first libev has to poll and then call kevent, but
1540at least you can use both at what they are best.
1541.PP
1542As for prioritising I/O: rarely you have the case where some fds have
1543to be watched and handled very quickly (with low latency), and even
1544priorities and idle watchers might have too much overhead. In this case
1545you would put all the high priority stuff in one loop and all the rest in
1546a second one, and embed the second one in the first.
1547.PP
1548As long as the watcher is active, the callback will be invoked every time
1549there might be events pending in the embedded loop. The callback must then
1550call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1551their callbacks (you could also start an idle watcher to give the embedded
1552loop strictly lower priority for example). You can also set the callback
1553to \f(CW0\fR, in which case the embed watcher will automatically execute the
1554embedded loop sweep.
1555.PP
1556As long as the watcher is started it will automatically handle events. The
1557callback will be invoked whenever some events have been handled. You can
1558set the callback to \f(CW0\fR to avoid having to specify one if you are not
1559interested in that.
1560.PP
1561Also, there have not currently been made special provisions for forking:
1562when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1563but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1564yourself.
1565.PP
1566Unfortunately, not all backends are embeddable, only the ones returned by
1567\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1568portable one.
1569.PP
1570So when you want to use this feature you will always have to be prepared
1571that you cannot get an embeddable loop. The recommended way to get around
1572this is to have a separate variables for your embeddable loop, try to
1573create it, and if that fails, use the normal loop for everything:
1574.PP
1575.Vb 3
1576\& struct ev_loop *loop_hi = ev_default_init (0);
1577\& struct ev_loop *loop_lo = 0;
1578\& struct ev_embed embed;
1579.Ve
1580.PP
1581.Vb 5
1582\& // see if there is a chance of getting one that works
1583\& // (remember that a flags value of 0 means autodetection)
1584\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1585\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1586\& : 0;
1587.Ve
1588.PP
1589.Vb 8
1590\& // if we got one, then embed it, otherwise default to loop_hi
1591\& if (loop_lo)
1592\& {
1593\& ev_embed_init (&embed, 0, loop_lo);
1594\& ev_embed_start (loop_hi, &embed);
1595\& }
1596\& else
1597\& loop_lo = loop_hi;
1598.Ve
1599.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1600.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1601.PD 0
1602.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1603.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1604.PD
1605Configures the watcher to embed the given loop, which must be
1606embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1607invoked automatically, otherwise it is the responsibility of the callback
1608to invoke it (it will continue to be called until the sweep has been done,
1609if you do not want thta, you need to temporarily stop the embed watcher).
1610.IP "ev_embed_sweep (loop, ev_embed *)" 4
1611.IX Item "ev_embed_sweep (loop, ev_embed *)"
1612Make a single, non-blocking sweep over the embedded loop. This works
1613similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1614apropriate way for embedded loops.
1615.IP "struct ev_loop *loop [read\-only]" 4
1616.IX Item "struct ev_loop *loop [read-only]"
1617The embedded event loop.
949.SH "OTHER FUNCTIONS" 1618.SH "OTHER FUNCTIONS"
950.IX Header "OTHER FUNCTIONS" 1619.IX Header "OTHER FUNCTIONS"
951There are some other functions of possible interest. Described. Here. Now. 1620There are some other functions of possible interest. Described. Here. Now.
952.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1621.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
953.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1622.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
982.Ve 1651.Ve
983.Sp 1652.Sp
984.Vb 1 1653.Vb 1
985\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1654\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
986.Ve 1655.Ve
987.IP "ev_feed_event (loop, watcher, int events)" 4 1656.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
988.IX Item "ev_feed_event (loop, watcher, int events)" 1657.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
989Feeds the given event set into the event loop, as if the specified event 1658Feeds the given event set into the event loop, as if the specified event
990had happened for the specified watcher (which must be a pointer to an 1659had happened for the specified watcher (which must be a pointer to an
991initialised but not necessarily started event watcher). 1660initialised but not necessarily started event watcher).
992.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1661.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
993.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1662.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
994Feed an event on the given fd, as if a file descriptor backend detected 1663Feed an event on the given fd, as if a file descriptor backend detected
995the given events it. 1664the given events it.
996.IP "ev_feed_signal_event (loop, int signum)" 4 1665.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
997.IX Item "ev_feed_signal_event (loop, int signum)" 1666.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
998Feed an event as if the given signal occured (loop must be the default loop!). 1667Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1668loop!).
999.SH "LIBEVENT EMULATION" 1669.SH "LIBEVENT EMULATION"
1000.IX Header "LIBEVENT EMULATION" 1670.IX Header "LIBEVENT EMULATION"
1001Libev offers a compatibility emulation layer for libevent. It cannot 1671Libev offers a compatibility emulation layer for libevent. It cannot
1002emulate the internals of libevent, so here are some usage hints: 1672emulate the internals of libevent, so here are some usage hints:
1003.IP "* Use it by including <event.h>, as usual." 4 1673.IP "* Use it by including <event.h>, as usual." 4
… …
1014.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1684.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1015.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1685.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1016.PD 1686.PD
1017.SH "\*(C+ SUPPORT" 1687.SH "\*(C+ SUPPORT"
1018.IX Header " SUPPORT" 1688.IX Header " SUPPORT"
1019\&\s-1TBD\s0. 1689Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1690you to use some convinience methods to start/stop watchers and also change
1691the callback model to a model using method callbacks on objects.
1692.PP
1693To use it,
1694.PP
1695.Vb 1
1696\& #include <ev++.h>
1697.Ve
1698.PP
1699(it is not installed by default). This automatically includes \fIev.h\fR
1700and puts all of its definitions (many of them macros) into the global
1701namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1702.PP
1703It should support all the same embedding options as \fIev.h\fR, most notably
1704\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1705.PP
1706Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1707.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1708.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1709.IX Item "ev::READ, ev::WRITE etc."
1710These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1711macros from \fIev.h\fR.
1712.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1713.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1714.IX Item "ev::tstamp, ev::now"
1715Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1716.ie n .IP """ev::io""\fR, \f(CW""ev::timer""\fR, \f(CW""ev::periodic""\fR, \f(CW""ev::idle""\fR, \f(CW""ev::sig"" etc." 4
1717.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1718.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1719For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1720the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1721which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1722defines by many implementations.
1723.Sp
1724All of those classes have these methods:
1725.RS 4
1726.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1727.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1728.PD 0
1729.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1730.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1731.IP "ev::TYPE::~TYPE" 4
1732.IX Item "ev::TYPE::~TYPE"
1733.PD
1734The constructor takes a pointer to an object and a method pointer to
1735the event handler callback to call in this class. The constructor calls
1736\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1737before starting it. If you do not specify a loop then the constructor
1738automatically associates the default loop with this watcher.
1739.Sp
1740The destructor automatically stops the watcher if it is active.
1741.IP "w\->set (struct ev_loop *)" 4
1742.IX Item "w->set (struct ev_loop *)"
1743Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1744do this when the watcher is inactive (and not pending either).
1745.IP "w\->set ([args])" 4
1746.IX Item "w->set ([args])"
1747Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1748called at least once. Unlike the C counterpart, an active watcher gets
1749automatically stopped and restarted.
1750.IP "w\->start ()" 4
1751.IX Item "w->start ()"
1752Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1753constructor already takes the loop.
1754.IP "w\->stop ()" 4
1755.IX Item "w->stop ()"
1756Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1757.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1758.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1759.IX Item "w->again () ev::timer, ev::periodic only"
1760For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1761\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1762.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1763.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1764.IX Item "w->sweep () ev::embed only"
1765Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1766.ie n .IP "w\->update () ""ev::stat"" only" 4
1767.el .IP "w\->update () \f(CWev::stat\fR only" 4
1768.IX Item "w->update () ev::stat only"
1769Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1770.RE
1771.RS 4
1772.RE
1773.PP
1774Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1775the constructor.
1776.PP
1777.Vb 4
1778\& class myclass
1779\& {
1780\& ev_io io; void io_cb (ev::io &w, int revents);
1781\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1782.Ve
1783.PP
1784.Vb 2
1785\& myclass ();
1786\& }
1787.Ve
1788.PP
1789.Vb 6
1790\& myclass::myclass (int fd)
1791\& : io (this, &myclass::io_cb),
1792\& idle (this, &myclass::idle_cb)
1793\& {
1794\& io.start (fd, ev::READ);
1795\& }
1796.Ve
1797.SH "EMBEDDING"
1798.IX Header "EMBEDDING"
1799Libev can (and often is) directly embedded into host
1800applications. Examples of applications that embed it include the Deliantra
1801Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1802and rxvt\-unicode.
1803.PP
1804The goal is to enable you to just copy the neecssary files into your
1805source directory without having to change even a single line in them, so
1806you can easily upgrade by simply copying (or having a checked-out copy of
1807libev somewhere in your source tree).
1808.Sh "\s-1FILESETS\s0"
1809.IX Subsection "FILESETS"
1810Depending on what features you need you need to include one or more sets of files
1811in your app.
1812.PP
1813\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
1814.IX Subsection "CORE EVENT LOOP"
1815.PP
1816To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
1817configuration (no autoconf):
1818.PP
1819.Vb 2
1820\& #define EV_STANDALONE 1
1821\& #include "ev.c"
1822.Ve
1823.PP
1824This will automatically include \fIev.h\fR, too, and should be done in a
1825single C source file only to provide the function implementations. To use
1826it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
1827done by writing a wrapper around \fIev.h\fR that you can include instead and
1828where you can put other configuration options):
1829.PP
1830.Vb 2
1831\& #define EV_STANDALONE 1
1832\& #include "ev.h"
1833.Ve
1834.PP
1835Both header files and implementation files can be compiled with a \*(C+
1836compiler (at least, thats a stated goal, and breakage will be treated
1837as a bug).
1838.PP
1839You need the following files in your source tree, or in a directory
1840in your include path (e.g. in libev/ when using \-Ilibev):
1841.PP
1842.Vb 4
1843\& ev.h
1844\& ev.c
1845\& ev_vars.h
1846\& ev_wrap.h
1847.Ve
1848.PP
1849.Vb 1
1850\& ev_win32.c required on win32 platforms only
1851.Ve
1852.PP
1853.Vb 5
1854\& ev_select.c only when select backend is enabled (which is by default)
1855\& ev_poll.c only when poll backend is enabled (disabled by default)
1856\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
1857\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1858\& ev_port.c only when the solaris port backend is enabled (disabled by default)
1859.Ve
1860.PP
1861\&\fIev.c\fR includes the backend files directly when enabled, so you only need
1862to compile this single file.
1863.PP
1864\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
1865.IX Subsection "LIBEVENT COMPATIBILITY API"
1866.PP
1867To include the libevent compatibility \s-1API\s0, also include:
1868.PP
1869.Vb 1
1870\& #include "event.c"
1871.Ve
1872.PP
1873in the file including \fIev.c\fR, and:
1874.PP
1875.Vb 1
1876\& #include "event.h"
1877.Ve
1878.PP
1879in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
1880.PP
1881You need the following additional files for this:
1882.PP
1883.Vb 2
1884\& event.h
1885\& event.c
1886.Ve
1887.PP
1888\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
1889.IX Subsection "AUTOCONF SUPPORT"
1890.PP
1891Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
1892whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
1893\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
1894include \fIconfig.h\fR and configure itself accordingly.
1895.PP
1896For this of course you need the m4 file:
1897.PP
1898.Vb 1
1899\& libev.m4
1900.Ve
1901.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
1902.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
1903Libev can be configured via a variety of preprocessor symbols you have to define
1904before including any of its files. The default is not to build for multiplicity
1905and only include the select backend.
1906.IP "\s-1EV_STANDALONE\s0" 4
1907.IX Item "EV_STANDALONE"
1908Must always be \f(CW1\fR if you do not use autoconf configuration, which
1909keeps libev from including \fIconfig.h\fR, and it also defines dummy
1910implementations for some libevent functions (such as logging, which is not
1911supported). It will also not define any of the structs usually found in
1912\&\fIevent.h\fR that are not directly supported by the libev core alone.
1913.IP "\s-1EV_USE_MONOTONIC\s0" 4
1914.IX Item "EV_USE_MONOTONIC"
1915If defined to be \f(CW1\fR, libev will try to detect the availability of the
1916monotonic clock option at both compiletime and runtime. Otherwise no use
1917of the monotonic clock option will be attempted. If you enable this, you
1918usually have to link against librt or something similar. Enabling it when
1919the functionality isn't available is safe, though, althoguh you have
1920to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
1921function is hiding in (often \fI\-lrt\fR).
1922.IP "\s-1EV_USE_REALTIME\s0" 4
1923.IX Item "EV_USE_REALTIME"
1924If defined to be \f(CW1\fR, libev will try to detect the availability of the
1925realtime clock option at compiletime (and assume its availability at
1926runtime if successful). Otherwise no use of the realtime clock option will
1927be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
1928(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
1929in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
1930.IP "\s-1EV_USE_SELECT\s0" 4
1931.IX Item "EV_USE_SELECT"
1932If undefined or defined to be \f(CW1\fR, libev will compile in support for the
1933\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
1934other method takes over, select will be it. Otherwise the select backend
1935will not be compiled in.
1936.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
1937.IX Item "EV_SELECT_USE_FD_SET"
1938If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
1939structure. This is useful if libev doesn't compile due to a missing
1940\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
1941exotic systems. This usually limits the range of file descriptors to some
1942low limit such as 1024 or might have other limitations (winsocket only
1943allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
1944influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
1945.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
1946.IX Item "EV_SELECT_IS_WINSOCKET"
1947When defined to \f(CW1\fR, the select backend will assume that
1948select/socket/connect etc. don't understand file descriptors but
1949wants osf handles on win32 (this is the case when the select to
1950be used is the winsock select). This means that it will call
1951\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
1952it is assumed that all these functions actually work on fds, even
1953on win32. Should not be defined on non\-win32 platforms.
1954.IP "\s-1EV_USE_POLL\s0" 4
1955.IX Item "EV_USE_POLL"
1956If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
1957backend. Otherwise it will be enabled on non\-win32 platforms. It
1958takes precedence over select.
1959.IP "\s-1EV_USE_EPOLL\s0" 4
1960.IX Item "EV_USE_EPOLL"
1961If defined to be \f(CW1\fR, libev will compile in support for the Linux
1962\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
1963otherwise another method will be used as fallback. This is the
1964preferred backend for GNU/Linux systems.
1965.IP "\s-1EV_USE_KQUEUE\s0" 4
1966.IX Item "EV_USE_KQUEUE"
1967If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
1968\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
1969otherwise another method will be used as fallback. This is the preferred
1970backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
1971supports some types of fds correctly (the only platform we found that
1972supports ptys for example was NetBSD), so kqueue might be compiled in, but
1973not be used unless explicitly requested. The best way to use it is to find
1974out whether kqueue supports your type of fd properly and use an embedded
1975kqueue loop.
1976.IP "\s-1EV_USE_PORT\s0" 4
1977.IX Item "EV_USE_PORT"
1978If defined to be \f(CW1\fR, libev will compile in support for the Solaris
197910 port style backend. Its availability will be detected at runtime,
1980otherwise another method will be used as fallback. This is the preferred
1981backend for Solaris 10 systems.
1982.IP "\s-1EV_USE_DEVPOLL\s0" 4
1983.IX Item "EV_USE_DEVPOLL"
1984reserved for future expansion, works like the \s-1USE\s0 symbols above.
1985.IP "\s-1EV_H\s0" 4
1986.IX Item "EV_H"
1987The name of the \fIev.h\fR header file used to include it. The default if
1988undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
1989can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
1990.IP "\s-1EV_CONFIG_H\s0" 4
1991.IX Item "EV_CONFIG_H"
1992If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
1993\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
1994\&\f(CW\*(C`EV_H\*(C'\fR, above.
1995.IP "\s-1EV_EVENT_H\s0" 4
1996.IX Item "EV_EVENT_H"
1997Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
1998of how the \fIevent.h\fR header can be found.
1999.IP "\s-1EV_PROTOTYPES\s0" 4
2000.IX Item "EV_PROTOTYPES"
2001If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2002prototypes, but still define all the structs and other symbols. This is
2003occasionally useful if you want to provide your own wrapper functions
2004around libev functions.
2005.IP "\s-1EV_MULTIPLICITY\s0" 4
2006.IX Item "EV_MULTIPLICITY"
2007If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2008will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2009additional independent event loops. Otherwise there will be no support
2010for multiple event loops and there is no first event loop pointer
2011argument. Instead, all functions act on the single default loop.
2012.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2013.IX Item "EV_PERIODIC_ENABLE"
2014If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2015defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2016code.
2017.IP "\s-1EV_EMBED_ENABLE\s0" 4
2018.IX Item "EV_EMBED_ENABLE"
2019If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2020defined to be \f(CW0\fR, then they are not.
2021.IP "\s-1EV_STAT_ENABLE\s0" 4
2022.IX Item "EV_STAT_ENABLE"
2023If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2024defined to be \f(CW0\fR, then they are not.
2025.IP "\s-1EV_MINIMAL\s0" 4
2026.IX Item "EV_MINIMAL"
2027If you need to shave off some kilobytes of code at the expense of some
2028speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2029some inlining decisions, saves roughly 30% codesize of amd64.
2030.IP "\s-1EV_COMMON\s0" 4
2031.IX Item "EV_COMMON"
2032By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2033this macro to a something else you can include more and other types of
2034members. You have to define it each time you include one of the files,
2035though, and it must be identical each time.
2036.Sp
2037For example, the perl \s-1EV\s0 module uses something like this:
2038.Sp
2039.Vb 3
2040\& #define EV_COMMON \e
2041\& SV *self; /* contains this struct */ \e
2042\& SV *cb_sv, *fh /* note no trailing ";" */
2043.Ve
2044.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2045.IX Item "EV_CB_DECLARE (type)"
2046.PD 0
2047.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2048.IX Item "EV_CB_INVOKE (watcher, revents)"
2049.IP "ev_set_cb (ev, cb)" 4
2050.IX Item "ev_set_cb (ev, cb)"
2051.PD
2052Can be used to change the callback member declaration in each watcher,
2053and the way callbacks are invoked and set. Must expand to a struct member
2054definition and a statement, respectively. See the \fIev.v\fR header file for
2055their default definitions. One possible use for overriding these is to
2056avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2057method calls instead of plain function calls in \*(C+.
2058.Sh "\s-1EXAMPLES\s0"
2059.IX Subsection "EXAMPLES"
2060For a real-world example of a program the includes libev
2061verbatim, you can have a look at the \s-1EV\s0 perl module
2062(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2063the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2064interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2065will be compiled. It is pretty complex because it provides its own header
2066file.
2067.Sp
2068The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2069that everybody includes and which overrides some autoconf choices:
2070.Sp
2071.Vb 4
2072\& #define EV_USE_POLL 0
2073\& #define EV_MULTIPLICITY 0
2074\& #define EV_PERIODICS 0
2075\& #define EV_CONFIG_H <config.h>
2076.Ve
2077.Sp
2078.Vb 1
2079\& #include "ev++.h"
2080.Ve
2081.Sp
2082And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2083.Sp
2084.Vb 2
2085\& #include "ev_cpp.h"
2086\& #include "ev.c"
2087.Ve
2088.SH "COMPLEXITIES"
2089.IX Header "COMPLEXITIES"
2090In this section the complexities of (many of) the algorithms used inside
2091libev will be explained. For complexity discussions about backends see the
2092documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2093.RS 4
2094.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2095.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2096.PD 0
2097.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2098.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2099.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2100.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2101.IP "Stopping check/prepare/idle watchers: O(1)" 4
2102.IX Item "Stopping check/prepare/idle watchers: O(1)"
2103.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" 4
2104.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))"
2105.IP "Finding the next timer per loop iteration: O(1)" 4
2106.IX Item "Finding the next timer per loop iteration: O(1)"
2107.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2108.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2109.IP "Activating one watcher: O(1)" 4
2110.IX Item "Activating one watcher: O(1)"
2111.RE
2112.RS 4
2113.PD
1020.SH "AUTHOR" 2114.SH "AUTHOR"
1021.IX Header "AUTHOR" 2115.IX Header "AUTHOR"
1022Marc Lehmann <libev@schmorp.de>. 2116Marc Lehmann <libev@schmorp.de>.

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