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Revision 1.7 by root, Fri Nov 23 08:36:35 2007 UTC vs.
Revision 1.25 by root, Tue Nov 27 19:23:31 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
217\&\f(CW\*(C`EVFLAG_AUTO\*(C'\fR will probe for. 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.
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256.Sp 327.Sp
257If you don't know what event loop to use, use the one returned from this 328If you don't know what event loop to use, use the one returned from this
258function. 329function.
259.Sp 330.Sp
260The flags argument can be used to specify special behaviour or specific 331The flags argument can be used to specify special behaviour or specific
261backends to use, and is usually specified as \f(CW0\fR (or \s-1EVFLAG_AUTO\s0). 332backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
262.Sp 333.Sp
263It supports the following flags: 334The following flags are supported:
264.RS 4 335.RS 4
265.ie n .IP """EVFLAG_AUTO""" 4 336.ie n .IP """EVFLAG_AUTO""" 4
266.el .IP "\f(CWEVFLAG_AUTO\fR" 4 337.el .IP "\f(CWEVFLAG_AUTO\fR" 4
267.IX Item "EVFLAG_AUTO" 338.IX Item "EVFLAG_AUTO"
268The default flags value. Use this if you have no clue (it's the right 339The default flags value. Use this if you have no clue (it's the right
… …
312.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 383.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
313.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 384.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
314Kqueue deserves special mention, as at the time of this writing, it 385Kqueue deserves special mention, as at the time of this writing, it
315was broken on all BSDs except NetBSD (usually it doesn't work with 386was broken on all BSDs except NetBSD (usually it doesn't work with
316anything but sockets and pipes, except on Darwin, where of course its 387anything but sockets and pipes, except on Darwin, where of course its
317completely useless). For this reason its not being \*(L"autodetected\*(R" unless 388completely useless). For this reason its not being \*(L"autodetected\*(R"
318you explicitly specify the flags (i.e. you don't use \s-1EVFLAG_AUTO\s0). 389unless you explicitly specify it explicitly in the flags (i.e. using
390\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
319.Sp 391.Sp
320It scales in the same way as the epoll backend, but the interface to the 392It scales in the same way as the epoll backend, but the interface to the
321kernel is more efficient (which says nothing about its actual speed, of 393kernel is more efficient (which says nothing about its actual speed, of
322course). While starting and stopping an I/O watcher does not cause an 394course). While starting and stopping an I/O watcher does not cause an
323extra syscall as with epoll, it still adds up to four event changes per 395extra syscall as with epoll, it still adds up to four event changes per
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346.Sp 418.Sp
347If one or more of these are ored into the flags value, then only these 419If one or more of these are ored into the flags value, then only these
348backends will be tried (in the reverse order as given here). If none are 420backends will be tried (in the reverse order as given here). If none are
349specified, most compiled-in backend will be tried, usually in reverse 421specified, most compiled-in backend will be tried, usually in reverse
350order of their flag values :) 422order of their flag values :)
423.Sp
424The most typical usage is like this:
425.Sp
426.Vb 2
427\& if (!ev_default_loop (0))
428\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?");
429.Ve
430.Sp
431Restrict libev to the select and poll backends, and do not allow
432environment settings to be taken into account:
433.Sp
434.Vb 1
435\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV);
436.Ve
437.Sp
438Use whatever libev has to offer, but make sure that kqueue is used if
439available (warning, breaks stuff, best use only with your own private
440event loop and only if you know the \s-1OS\s0 supports your types of fds):
441.Sp
442.Vb 1
443\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
444.Ve
351.RE 445.RE
352.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 446.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
353.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 447.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
354Similar 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
355always distinct from the default loop. Unlike the default loop, it cannot 449always distinct from the default loop. Unlike the default loop, it cannot
356handle 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
357undefined 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
358.IP "ev_default_destroy ()" 4 460.IP "ev_default_destroy ()" 4
359.IX Item "ev_default_destroy ()" 461.IX Item "ev_default_destroy ()"
360Destroys the default loop again (frees all memory and kernel state 462Destroys the default loop again (frees all memory and kernel state
361etc.). This stops all registered event watchers (by not touching them in 463etc.). None of the active event watchers will be stopped in the normal
362any 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).
363.IP "ev_loop_destroy (loop)" 4 469.IP "ev_loop_destroy (loop)" 4
364.IX Item "ev_loop_destroy (loop)" 470.IX Item "ev_loop_destroy (loop)"
365Like \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
366earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 472earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
367.IP "ev_default_fork ()" 4 473.IP "ev_default_fork ()" 4
… …
396Returns 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
397use. 503use.
398.IP "ev_tstamp ev_now (loop)" 4 504.IP "ev_tstamp ev_now (loop)" 4
399.IX Item "ev_tstamp ev_now (loop)" 505.IX Item "ev_tstamp ev_now (loop)"
400Returns 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
401got events and started processing them. This timestamp does not change 507received events and started processing them. This timestamp does not
402as 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
403used 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
404occuring (or more correctly, the mainloop finding out about it). 510event occuring (or more correctly, libev finding out about it).
405.IP "ev_loop (loop, int flags)" 4 511.IP "ev_loop (loop, int flags)" 4
406.IX Item "ev_loop (loop, int flags)" 512.IX Item "ev_loop (loop, int flags)"
407Finally, this is it, the event handler. This function usually is called 513Finally, this is it, the event handler. This function usually is called
408after you initialised all your watchers and you want to start handling 514after you initialised all your watchers and you want to start handling
409events. 515events.
410.Sp 516.Sp
411If the flags argument is specified as 0, it will not return until either 517If the flags argument is specified as \f(CW0\fR, it will not return until
412no 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.
413.Sp 525.Sp
414A 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
415those 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
416case 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.
417.Sp 529.Sp
418A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if 530A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if
419neccessary) and will handle those and any outstanding ones. It will block 531neccessary) and will handle those and any outstanding ones. It will block
420your process until at least one new event arrives, and will return after 532your process until at least one new event arrives, and will return after
421one iteration of the loop. 533one iteration of the loop. This is useful if you are waiting for some
534external event in conjunction with something not expressible using other
535libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
536usually a better approach for this kind of thing.
422.Sp 537.Sp
423This flags value could be used to implement alternative looping
424constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and
425more generic mechanism.
426.Sp
427Here are the gory details of what ev_loop does: 538Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
428.Sp 539.Sp
429.Vb 15 540.Vb 18
430\& 1. If there are no active watchers (reference count is zero), return. 541\& * If there are no active watchers (reference count is zero), return.
431\& 2. Queue and immediately call all prepare watchers. 542\& - Queue prepare watchers and then call all outstanding watchers.
432\& 3. If we have been forked, recreate the kernel state. 543\& - If we have been forked, recreate the kernel state.
433\& 4. Update the kernel state with all outstanding changes. 544\& - Update the kernel state with all outstanding changes.
434\& 5. Update the "event loop time". 545\& - Update the "event loop time".
435\& 6. Calculate for how long to block. 546\& - Calculate for how long to block.
436\& 7. Block the process, waiting for events. 547\& - Block the process, waiting for any events.
548\& - Queue all outstanding I/O (fd) events.
437\& 8. Update the "event loop time" and do time jump handling. 549\& - Update the "event loop time" and do time jump handling.
438\& 9. Queue all outstanding timers. 550\& - Queue all outstanding timers.
439\& 10. Queue all outstanding periodics. 551\& - Queue all outstanding periodics.
440\& 11. If no events are pending now, queue all idle watchers. 552\& - If no events are pending now, queue all idle watchers.
441\& 12. Queue all check watchers. 553\& - Queue all check watchers.
442\& 13. 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).
555\& Signals and child watchers are implemented as I/O watchers, and will
556\& be handled here by queueing them when their watcher gets executed.
443\& 14. 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
444\& was used, return, otherwise continue with step #1. 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!
445.Ve 569.Ve
446.IP "ev_unloop (loop, how)" 4 570.IP "ev_unloop (loop, how)" 4
447.IX Item "ev_unloop (loop, how)" 571.IX Item "ev_unloop (loop, how)"
448Can 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
449has 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
… …
463example, 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
464visible 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
465no 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
466way 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
467libraries. 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
468.SH "ANATOMY OF A WATCHER" 609.SH "ANATOMY OF A WATCHER"
469.IX Header "ANATOMY OF A WATCHER" 610.IX Header "ANATOMY OF A WATCHER"
470A 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
471interest 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
472become 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:
… …
508*)\*(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
509corresponding 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.
510.PP 651.PP
511As 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
512must 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
513reinitialise it or call its set macro. 654reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
514.PP
515You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
516(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
517callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
518(watcher *)\*(C'\fR macro.
519.PP 655.PP
520Each and every callback receives the event loop pointer as first, the 656Each and every callback receives the event loop pointer as first, the
521registered watcher structure as second, and a bitset of received events as 657registered watcher structure as second, and a bitset of received events as
522third argument. 658third argument.
523.PP 659.PP
… …
548The 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.
549.ie n .IP """EV_CHILD""" 4 685.ie n .IP """EV_CHILD""" 4
550.el .IP "\f(CWEV_CHILD\fR" 4 686.el .IP "\f(CWEV_CHILD\fR" 4
551.IX Item "EV_CHILD" 687.IX Item "EV_CHILD"
552The 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.
553.ie n .IP """EV_IDLE""" 4 693.ie n .IP """EV_IDLE""" 4
554.el .IP "\f(CWEV_IDLE\fR" 4 694.el .IP "\f(CWEV_IDLE\fR" 4
555.IX Item "EV_IDLE" 695.IX Item "EV_IDLE"
556The \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.
557.ie n .IP """EV_PREPARE""" 4 697.ie n .IP """EV_PREPARE""" 4
… …
567\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 707\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
568received events. Callbacks of both watcher types can start and stop as 708received events. Callbacks of both watcher types can start and stop as
569many watchers as they want, and all of them will be taken into account 709many watchers as they want, and all of them will be taken into account
570(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 710(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
571\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 711\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
712.ie n .IP """EV_EMBED""" 4
713.el .IP "\f(CWEV_EMBED\fR" 4
714.IX Item "EV_EMBED"
715The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
716.ie n .IP """EV_FORK""" 4
717.el .IP "\f(CWEV_FORK\fR" 4
718.IX Item "EV_FORK"
719The event loop has been resumed in the child process after fork (see
720\&\f(CW\*(C`ev_fork\*(C'\fR).
572.ie n .IP """EV_ERROR""" 4 721.ie n .IP """EV_ERROR""" 4
573.el .IP "\f(CWEV_ERROR\fR" 4 722.el .IP "\f(CWEV_ERROR\fR" 4
574.IX Item "EV_ERROR" 723.IX Item "EV_ERROR"
575An unspecified error has occured, the watcher has been stopped. This might 724An unspecified error has occured, the watcher has been stopped. This might
576happen because the watcher could not be properly started because libev 725happen because the watcher could not be properly started because libev
… …
581Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 730Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
582for example it might indicate that a fd is readable or writable, and if 731for example it might indicate that a fd is readable or writable, and if
583your callbacks is well-written it can just attempt the operation and cope 732your callbacks is well-written it can just attempt the operation and cope
584with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 733with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
585programs, though, so beware. 734programs, though, so beware.
735.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
736.IX Subsection "GENERIC WATCHER FUNCTIONS"
737In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
738e.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.
739.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
740.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
741.IX Item "ev_init (ev_TYPE *watcher, callback)"
742This macro initialises the generic portion of a watcher. The contents
743of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
744the generic parts of the watcher are initialised, you \fIneed\fR to call
745the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
746type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
747which rolls both calls into one.
748.Sp
749You can reinitialise a watcher at any time as long as it has been stopped
750(or never started) and there are no pending events outstanding.
751.Sp
752The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
753int revents)\*(C'\fR.
754.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
755.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
756.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
757This macro initialises the type-specific parts of a watcher. You need to
758call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
759call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
760macro on a watcher that is active (it can be pending, however, which is a
761difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
762.Sp
763Although some watcher types do not have type-specific arguments
764(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
765.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
766.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
767.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
768This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
769calls into a single call. This is the most convinient method to initialise
770a watcher. The same limitations apply, of course.
771.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
772.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
773.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
774Starts (activates) the given watcher. Only active watchers will receive
775events. If the watcher is already active nothing will happen.
776.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
777.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
778.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
779Stops the given watcher again (if active) and clears the pending
780status. It is possible that stopped watchers are pending (for example,
781non-repeating timers are being stopped when they become pending), but
782\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
783you want to free or reuse the memory used by the watcher it is therefore a
784good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
785.IP "bool ev_is_active (ev_TYPE *watcher)" 4
786.IX Item "bool ev_is_active (ev_TYPE *watcher)"
787Returns a true value iff the watcher is active (i.e. it has been started
788and not yet been stopped). As long as a watcher is active you must not modify
789it.
790.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
791.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
792Returns a true value iff the watcher is pending, (i.e. it has outstanding
793events but its callback has not yet been invoked). As long as a watcher
794is pending (but not active) you must not call an init function on it (but
795\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
796libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
797.IP "callback = ev_cb (ev_TYPE *watcher)" 4
798.IX Item "callback = ev_cb (ev_TYPE *watcher)"
799Returns the callback currently set on the watcher.
800.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
801.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
802Change the callback. You can change the callback at virtually any time
803(modulo threads).
586.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 804.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
587.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 805.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
588Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 806Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
589and read at any time, libev will completely ignore it. This can be used 807and read at any time, libev will completely ignore it. This can be used
590to associate arbitrary data with your watcher. If you need more data and 808to associate arbitrary data with your watcher. If you need more data and
… …
616More interesting and less C\-conformant ways of catsing your callback type 834More interesting and less C\-conformant ways of catsing your callback type
617have been omitted.... 835have been omitted....
618.SH "WATCHER TYPES" 836.SH "WATCHER TYPES"
619.IX Header "WATCHER TYPES" 837.IX Header "WATCHER TYPES"
620This section describes each watcher in detail, but will not repeat 838This section describes each watcher in detail, but will not repeat
621information given in the last section. 839information given in the last section. Any initialisation/set macros,
840functions and members specific to the watcher type are explained.
841.PP
842Members are additionally marked with either \fI[read\-only]\fR, meaning that,
843while the watcher is active, you can look at the member and expect some
844sensible content, but you must not modify it (you can modify it while the
845watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
846means you can expect it to have some sensible content while the watcher
847is active, but you can also modify it. Modifying it may not do something
848sensible or take immediate effect (or do anything at all), but libev will
849not crash or malfunction in any way.
622.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 850.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
623.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 851.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
624.IX Subsection "ev_io - is this file descriptor readable or writable" 852.IX Subsection "ev_io - is this file descriptor readable or writable?"
625I/O watchers check whether a file descriptor is readable or writable 853I/O watchers check whether a file descriptor is readable or writable
626in each iteration of the event loop (This behaviour is called 854in each iteration of the event loop, or, more precisely, when reading
627level-triggering because you keep receiving events as long as the 855would not block the process and writing would at least be able to write
628condition persists. Remember you can stop the watcher if you don't want to 856some data. This behaviour is called level-triggering because you keep
629act on the event and neither want to receive future events). 857receiving events as long as the condition persists. Remember you can stop
858the watcher if you don't want to act on the event and neither want to
859receive future events.
630.PP 860.PP
631In general you can register as many read and/or write event watchers per 861In general you can register as many read and/or write event watchers per
632fd as you want (as long as you don't confuse yourself). Setting all file 862fd as you want (as long as you don't confuse yourself). Setting all file
633descriptors to non-blocking mode is also usually a good idea (but not 863descriptors to non-blocking mode is also usually a good idea (but not
634required if you know what you are doing). 864required if you know what you are doing).
635.PP 865.PP
636You have to be careful with dup'ed file descriptors, though. Some backends 866You have to be careful with dup'ed file descriptors, though. Some backends
637(the linux epoll backend is a notable example) cannot handle dup'ed file 867(the linux epoll backend is a notable example) cannot handle dup'ed file
638descriptors correctly if you register interest in two or more fds pointing 868descriptors correctly if you register interest in two or more fds pointing
639to the same underlying file/socket etc. description (that is, they share 869to the same underlying file/socket/etc. description (that is, they share
640the same underlying \*(L"file open\*(R"). 870the same underlying \*(L"file open\*(R").
641.PP 871.PP
642If you must do this, then force the use of a known-to-be-good backend 872If you must do this, then force the use of a known-to-be-good backend
643(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 873(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
644\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 874\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
875.PP
876Another thing you have to watch out for is that it is quite easy to
877receive \*(L"spurious\*(R" readyness notifications, that is your callback might
878be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
879because there is no data. Not only are some backends known to create a
880lot of those (for example solaris ports), it is very easy to get into
881this situation even with a relatively standard program structure. Thus
882it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
883\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
884.PP
885If you cannot run the fd in non-blocking mode (for example you should not
886play around with an Xlib connection), then you have to seperately re-test
887wether a file descriptor is really ready with a known-to-be good interface
888such as poll (fortunately in our Xlib example, Xlib already does this on
889its own, so its quite safe to use).
645.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 890.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
646.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 891.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
647.PD 0 892.PD 0
648.IP "ev_io_set (ev_io *, int fd, int events)" 4 893.IP "ev_io_set (ev_io *, int fd, int events)" 4
649.IX Item "ev_io_set (ev_io *, int fd, int events)" 894.IX Item "ev_io_set (ev_io *, int fd, int events)"
650.PD 895.PD
651Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 896Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
652events 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 | 897rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
653EV_WRITE\*(C'\fR to receive the given events. 898\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
654.Sp 899.IP "int fd [read\-only]" 4
655Please note that most of the more scalable backend mechanisms (for example 900.IX Item "int fd [read-only]"
656epoll and solaris ports) can result in spurious readyness notifications 901The file descriptor being watched.
657for file descriptors, so you practically need to use non-blocking I/O (and 902.IP "int events [read\-only]" 4
658treat callback invocation as hint only), or retest separately with a safe 903.IX Item "int events [read-only]"
659interface before doing I/O (XLib can do this), or force the use of either 904The events being watched.
660\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this 905.PP
661problem. Also note that it is quite easy to have your callback invoked 906Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
662when the readyness condition is no longer valid even when employing 907readable, but only once. Since it is likely line\-buffered, you could
663typical ways of handling events, so its a good idea to use non-blocking 908attempt to read a whole line in the callback:
664I/O unconditionally. 909.PP
910.Vb 6
911\& static void
912\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
913\& {
914\& ev_io_stop (loop, w);
915\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
916\& }
917.Ve
918.PP
919.Vb 6
920\& ...
921\& struct ev_loop *loop = ev_default_init (0);
922\& struct ev_io stdin_readable;
923\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
924\& ev_io_start (loop, &stdin_readable);
925\& ev_loop (loop, 0);
926.Ve
665.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 927.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
666.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 928.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
667.IX Subsection "ev_timer - relative and optionally recurring timeouts" 929.IX Subsection "ev_timer - relative and optionally repeating timeouts"
668Timer watchers are simple relative timers that generate an event after a 930Timer watchers are simple relative timers that generate an event after a
669given time, and optionally repeating in regular intervals after that. 931given time, and optionally repeating in regular intervals after that.
670.PP 932.PP
671The timers are based on real time, that is, if you register an event that 933The timers are based on real time, that is, if you register an event that
672times out after an hour and you reset your system clock to last years 934times out after an hour and you reset your system clock to last years
… …
712.Sp 974.Sp
713If the timer is repeating, either start it if necessary (with the repeat 975If the timer is repeating, either start it if necessary (with the repeat
714value), or reset the running timer to the repeat value. 976value), or reset the running timer to the repeat value.
715.Sp 977.Sp
716This sounds a bit complicated, but here is a useful and typical 978This sounds a bit complicated, but here is a useful and typical
717example: Imagine you have a tcp connection and you want a so-called idle 979example: Imagine you have a tcp connection and you want a so-called
718timeout, that is, you want to be called when there have been, say, 60 980idle timeout, that is, you want to be called when there have been,
719seconds of inactivity on the socket. The easiest way to do this is to 981say, 60 seconds of inactivity on the socket. The easiest way to do
720configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 982this 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
721time you successfully read or write some data. If you go into an idle 983\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
722state where you do not expect data to travel on the socket, you can stop 984you go into an idle state where you do not expect data to travel on the
723the timer, and again will automatically restart it if need be. 985socket, you can stop the timer, and again will automatically restart it if
986need be.
987.Sp
988You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether
989and only ever use the \f(CW\*(C`repeat\*(C'\fR value:
990.Sp
991.Vb 8
992\& ev_timer_init (timer, callback, 0., 5.);
993\& ev_timer_again (loop, timer);
994\& ...
995\& timer->again = 17.;
996\& ev_timer_again (loop, timer);
997\& ...
998\& timer->again = 10.;
999\& ev_timer_again (loop, timer);
1000.Ve
1001.Sp
1002This is more efficient then stopping/starting the timer eahc time you want
1003to modify its timeout value.
1004.IP "ev_tstamp repeat [read\-write]" 4
1005.IX Item "ev_tstamp repeat [read-write]"
1006The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1007or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1008which is also when any modifications are taken into account.
1009.PP
1010Example: create a timer that fires after 60 seconds.
1011.PP
1012.Vb 5
1013\& static void
1014\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1015\& {
1016\& .. one minute over, w is actually stopped right here
1017\& }
1018.Ve
1019.PP
1020.Vb 3
1021\& struct ev_timer mytimer;
1022\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1023\& ev_timer_start (loop, &mytimer);
1024.Ve
1025.PP
1026Example: create a timeout timer that times out after 10 seconds of
1027inactivity.
1028.PP
1029.Vb 5
1030\& static void
1031\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1032\& {
1033\& .. ten seconds without any activity
1034\& }
1035.Ve
1036.PP
1037.Vb 4
1038\& struct ev_timer mytimer;
1039\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1040\& ev_timer_again (&mytimer); /* start timer */
1041\& ev_loop (loop, 0);
1042.Ve
1043.PP
1044.Vb 3
1045\& // and in some piece of code that gets executed on any "activity":
1046\& // reset the timeout to start ticking again at 10 seconds
1047\& ev_timer_again (&mytimer);
1048.Ve
724.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1049.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
725.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1050.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
726.IX Subsection "ev_periodic - to cron or not to cron" 1051.IX Subsection "ev_periodic - to cron or not to cron?"
727Periodic watchers are also timers of a kind, but they are very versatile 1052Periodic watchers are also timers of a kind, but they are very versatile
728(and unfortunately a bit complex). 1053(and unfortunately a bit complex).
729.PP 1054.PP
730Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1055Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
731but on wallclock time (absolute time). You can tell a periodic watcher 1056but on wallclock time (absolute time). You can tell a periodic watcher
732to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1057to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
733periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1058periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
734+ 10.>) and then reset your system clock to the last year, then it will 1059+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
735take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1060take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
736roughly 10 seconds later and of course not if you reset your system time 1061roughly 10 seconds later and of course not if you reset your system time
737again). 1062again).
738.PP 1063.PP
739They can also be used to implement vastly more complex timers, such as 1064They can also be used to implement vastly more complex timers, such as
… …
820.IX Item "ev_periodic_again (loop, ev_periodic *)" 1145.IX Item "ev_periodic_again (loop, ev_periodic *)"
821Simply stops and restarts the periodic watcher again. This is only useful 1146Simply stops and restarts the periodic watcher again. This is only useful
822when you changed some parameters or the reschedule callback would return 1147when you changed some parameters or the reschedule callback would return
823a different time than the last time it was called (e.g. in a crond like 1148a different time than the last time it was called (e.g. in a crond like
824program when the crontabs have changed). 1149program when the crontabs have changed).
1150.IP "ev_tstamp interval [read\-write]" 4
1151.IX Item "ev_tstamp interval [read-write]"
1152The current interval value. Can be modified any time, but changes only
1153take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1154called.
1155.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1156.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1157The current reschedule callback, or \f(CW0\fR, if this functionality is
1158switched off. Can be changed any time, but changes only take effect when
1159the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1160.PP
1161Example: call a callback every hour, or, more precisely, whenever the
1162system clock is divisible by 3600. The callback invocation times have
1163potentially a lot of jittering, but good long-term stability.
1164.PP
1165.Vb 5
1166\& static void
1167\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1168\& {
1169\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1170\& }
1171.Ve
1172.PP
1173.Vb 3
1174\& struct ev_periodic hourly_tick;
1175\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1176\& ev_periodic_start (loop, &hourly_tick);
1177.Ve
1178.PP
1179Example: the same as above, but use a reschedule callback to do it:
1180.PP
1181.Vb 1
1182\& #include <math.h>
1183.Ve
1184.PP
1185.Vb 5
1186\& static ev_tstamp
1187\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1188\& {
1189\& return fmod (now, 3600.) + 3600.;
1190\& }
1191.Ve
1192.PP
1193.Vb 1
1194\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1195.Ve
1196.PP
1197Example: call a callback every hour, starting now:
1198.PP
1199.Vb 4
1200\& struct ev_periodic hourly_tick;
1201\& ev_periodic_init (&hourly_tick, clock_cb,
1202\& fmod (ev_now (loop), 3600.), 3600., 0);
1203\& ev_periodic_start (loop, &hourly_tick);
1204.Ve
825.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1205.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
826.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1206.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
827.IX Subsection "ev_signal - signal me when a signal gets signalled" 1207.IX Subsection "ev_signal - signal me when a signal gets signalled!"
828Signal watchers will trigger an event when the process receives a specific 1208Signal watchers will trigger an event when the process receives a specific
829signal one or more times. Even though signals are very asynchronous, libev 1209signal one or more times. Even though signals are very asynchronous, libev
830will try it's best to deliver signals synchronously, i.e. as part of the 1210will try it's best to deliver signals synchronously, i.e. as part of the
831normal event processing, like any other event. 1211normal event processing, like any other event.
832.PP 1212.PP
… …
842.IP "ev_signal_set (ev_signal *, int signum)" 4 1222.IP "ev_signal_set (ev_signal *, int signum)" 4
843.IX Item "ev_signal_set (ev_signal *, int signum)" 1223.IX Item "ev_signal_set (ev_signal *, int signum)"
844.PD 1224.PD
845Configures the watcher to trigger on the given signal number (usually one 1225Configures the watcher to trigger on the given signal number (usually one
846of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1226of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1227.IP "int signum [read\-only]" 4
1228.IX Item "int signum [read-only]"
1229The signal the watcher watches out for.
847.ie n .Sh """ev_child"" \- wait for pid status changes" 1230.ie n .Sh """ev_child"" \- watch out for process status changes"
848.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1231.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
849.IX Subsection "ev_child - wait for pid status changes" 1232.IX Subsection "ev_child - watch out for process status changes"
850Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1233Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
851some child status changes (most typically when a child of yours dies). 1234some child status changes (most typically when a child of yours dies).
852.IP "ev_child_init (ev_child *, callback, int pid)" 4 1235.IP "ev_child_init (ev_child *, callback, int pid)" 4
853.IX Item "ev_child_init (ev_child *, callback, int pid)" 1236.IX Item "ev_child_init (ev_child *, callback, int pid)"
854.PD 0 1237.PD 0
… …
859\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1242\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
860at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1243at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
861the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1244the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
862\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1245\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
863process causing the status change. 1246process causing the status change.
1247.IP "int pid [read\-only]" 4
1248.IX Item "int pid [read-only]"
1249The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1250.IP "int rpid [read\-write]" 4
1251.IX Item "int rpid [read-write]"
1252The process id that detected a status change.
1253.IP "int rstatus [read\-write]" 4
1254.IX Item "int rstatus [read-write]"
1255The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1256\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1257.PP
1258Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1259.PP
1260.Vb 5
1261\& static void
1262\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1263\& {
1264\& ev_unloop (loop, EVUNLOOP_ALL);
1265\& }
1266.Ve
1267.PP
1268.Vb 3
1269\& struct ev_signal signal_watcher;
1270\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1271\& ev_signal_start (loop, &sigint_cb);
1272.Ve
1273.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1274.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1275.IX Subsection "ev_stat - did the file attributes just change?"
1276This watches a filesystem path for attribute changes. That is, it calls
1277\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1278compared to the last time, invoking the callback if it did.
1279.PP
1280The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1281not exist\*(R" is a status change like any other. The condition \*(L"path does
1282not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1283otherwise always forced to be at least one) and all the other fields of
1284the stat buffer having unspecified contents.
1285.PP
1286Since there is no standard to do this, the portable implementation simply
1287calls \f(CW\*(C`stat (2)\*(C'\fR regulalry on the path to see if it changed somehow. You
1288can specify a recommended polling interval for this case. If you specify
1289a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1290unspecified default\fR value will be used (which you can expect to be around
1291five seconds, although this might change dynamically). Libev will also
1292impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1293usually overkill.
1294.PP
1295This watcher type is not meant for massive numbers of stat watchers,
1296as even with OS-supported change notifications, this can be
1297resource\-intensive.
1298.PP
1299At the time of this writing, no specific \s-1OS\s0 backends are implemented, but
1300if demand increases, at least a kqueue and inotify backend will be added.
1301.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1302.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1303.PD 0
1304.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1305.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1306.PD
1307Configures the watcher to wait for status changes of the given
1308\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1309be detected and should normally be specified as \f(CW0\fR to let libev choose
1310a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1311path for as long as the watcher is active.
1312.Sp
1313The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1314relative to the attributes at the time the watcher was started (or the
1315last change was detected).
1316.IP "ev_stat_stat (ev_stat *)" 4
1317.IX Item "ev_stat_stat (ev_stat *)"
1318Updates the stat buffer immediately with new values. If you change the
1319watched path in your callback, you could call this fucntion to avoid
1320detecting this change (while introducing a race condition). Can also be
1321useful simply to find out the new values.
1322.IP "ev_statdata attr [read\-only]" 4
1323.IX Item "ev_statdata attr [read-only]"
1324The most-recently detected attributes of the file. Although the type is of
1325\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1326suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1327was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1328.IP "ev_statdata prev [read\-only]" 4
1329.IX Item "ev_statdata prev [read-only]"
1330The previous attributes of the file. The callback gets invoked whenever
1331\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1332.IP "ev_tstamp interval [read\-only]" 4
1333.IX Item "ev_tstamp interval [read-only]"
1334The specified interval.
1335.IP "const char *path [read\-only]" 4
1336.IX Item "const char *path [read-only]"
1337The filesystem path that is being watched.
1338.PP
1339Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1340.PP
1341.Vb 15
1342\& static void
1343\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1344\& {
1345\& /* /etc/passwd changed in some way */
1346\& if (w->attr.st_nlink)
1347\& {
1348\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1349\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1350\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1351\& }
1352\& else
1353\& /* you shalt not abuse printf for puts */
1354\& puts ("wow, /etc/passwd is not there, expect problems. "
1355\& "if this is windows, they already arrived\en");
1356\& }
1357.Ve
1358.PP
1359.Vb 2
1360\& ...
1361\& ev_stat passwd;
1362.Ve
1363.PP
1364.Vb 2
1365\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1366\& ev_stat_start (loop, &passwd);
1367.Ve
864.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1368.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
865.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1369.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
866.IX Subsection "ev_idle - when you've got nothing better to do" 1370.IX Subsection "ev_idle - when you've got nothing better to do..."
867Idle watchers trigger events when there are no other events are pending 1371Idle watchers trigger events when there are no other events are pending
868(prepare, check and other idle watchers do not count). That is, as long 1372(prepare, check and other idle watchers do not count). That is, as long
869as your process is busy handling sockets or timeouts (or even signals, 1373as your process is busy handling sockets or timeouts (or even signals,
870imagine) it will not be triggered. But when your process is idle all idle 1374imagine) it will not be triggered. But when your process is idle all idle
871watchers are being called again and again, once per event loop iteration \- 1375watchers are being called again and again, once per event loop iteration \-
… …
882.IP "ev_idle_init (ev_signal *, callback)" 4 1386.IP "ev_idle_init (ev_signal *, callback)" 4
883.IX Item "ev_idle_init (ev_signal *, callback)" 1387.IX Item "ev_idle_init (ev_signal *, callback)"
884Initialises and configures the idle watcher \- it has no parameters of any 1388Initialises and configures the idle watcher \- it has no parameters of any
885kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1389kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
886believe me. 1390believe me.
1391.PP
1392Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the
1393callback, free it. Alos, use no error checking, as usual.
1394.PP
1395.Vb 7
1396\& static void
1397\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1398\& {
1399\& free (w);
1400\& // now do something you wanted to do when the program has
1401\& // no longer asnything immediate to do.
1402\& }
1403.Ve
1404.PP
1405.Vb 3
1406\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1407\& ev_idle_init (idle_watcher, idle_cb);
1408\& ev_idle_start (loop, idle_cb);
1409.Ve
887.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1410.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
888.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1411.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
889.IX Subsection "ev_prepare and ev_check - customise your event loop" 1412.IX Subsection "ev_prepare and ev_check - customise your event loop!"
890Prepare and check watchers are usually (but not always) used in tandem: 1413Prepare and check watchers are usually (but not always) used in tandem:
891prepare watchers get invoked before the process blocks and check watchers 1414prepare watchers get invoked before the process blocks and check watchers
892afterwards. 1415afterwards.
893.PP 1416.PP
1417You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1418the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1419watchers. Other loops than the current one are fine, however. The
1420rationale behind this is that you do not need to check for recursion in
1421those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1422\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1423called in pairs bracketing the blocking call.
1424.PP
894Their main purpose is to integrate other event mechanisms into libev. This 1425Their main purpose is to integrate other event mechanisms into libev and
895could be used, for example, to track variable changes, implement your own 1426their use is somewhat advanced. This could be used, for example, to track
896watchers, integrate net-snmp or a coroutine library and lots more. 1427variable changes, implement your own watchers, integrate net-snmp or a
1428coroutine library and lots more. They are also occasionally useful if
1429you cache some data and want to flush it before blocking (for example,
1430in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1431watcher).
897.PP 1432.PP
898This is done by examining in each prepare call which file descriptors need 1433This is done by examining in each prepare call which file descriptors need
899to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1434to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
900them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1435them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
901provide just this functionality). Then, in the check watcher you check for 1436provide just this functionality). Then, in the check watcher you check for
… …
919.IX Item "ev_check_init (ev_check *, callback)" 1454.IX Item "ev_check_init (ev_check *, callback)"
920.PD 1455.PD
921Initialises and configures the prepare or check watcher \- they have no 1456Initialises and configures the prepare or check watcher \- they have no
922parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1457parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
923macros, but using them is utterly, utterly and completely pointless. 1458macros, but using them is utterly, utterly and completely pointless.
1459.PP
1460Example: To include a library such as adns, you would add \s-1IO\s0 watchers
1461and a timeout watcher in a prepare handler, as required by libadns, and
1462in a check watcher, destroy them and call into libadns. What follows is
1463pseudo-code only of course:
1464.PP
1465.Vb 2
1466\& static ev_io iow [nfd];
1467\& static ev_timer tw;
1468.Ve
1469.PP
1470.Vb 9
1471\& static void
1472\& io_cb (ev_loop *loop, ev_io *w, int revents)
1473\& {
1474\& // set the relevant poll flags
1475\& // could also call adns_processreadable etc. here
1476\& struct pollfd *fd = (struct pollfd *)w->data;
1477\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1478\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1479\& }
1480.Ve
1481.PP
1482.Vb 7
1483\& // create io watchers for each fd and a timer before blocking
1484\& static void
1485\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1486\& {
1487\& int timeout = 3600000;truct pollfd fds [nfd];
1488\& // actual code will need to loop here and realloc etc.
1489\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1490.Ve
1491.PP
1492.Vb 3
1493\& /* the callback is illegal, but won't be called as we stop during check */
1494\& ev_timer_init (&tw, 0, timeout * 1e-3);
1495\& ev_timer_start (loop, &tw);
1496.Ve
1497.PP
1498.Vb 6
1499\& // create on ev_io per pollfd
1500\& for (int i = 0; i < nfd; ++i)
1501\& {
1502\& ev_io_init (iow + i, io_cb, fds [i].fd,
1503\& ((fds [i].events & POLLIN ? EV_READ : 0)
1504\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1505.Ve
1506.PP
1507.Vb 5
1508\& fds [i].revents = 0;
1509\& iow [i].data = fds + i;
1510\& ev_io_start (loop, iow + i);
1511\& }
1512\& }
1513.Ve
1514.PP
1515.Vb 5
1516\& // stop all watchers after blocking
1517\& static void
1518\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1519\& {
1520\& ev_timer_stop (loop, &tw);
1521.Ve
1522.PP
1523.Vb 2
1524\& for (int i = 0; i < nfd; ++i)
1525\& ev_io_stop (loop, iow + i);
1526.Ve
1527.PP
1528.Vb 2
1529\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1530\& }
1531.Ve
1532.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1533.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1534.IX Subsection "ev_embed - when one backend isn't enough..."
1535This is a rather advanced watcher type that lets you embed one event loop
1536into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1537loop, other types of watchers might be handled in a delayed or incorrect
1538fashion and must not be used).
1539.PP
1540There are primarily two reasons you would want that: work around bugs and
1541prioritise I/O.
1542.PP
1543As an example for a bug workaround, the kqueue backend might only support
1544sockets on some platform, so it is unusable as generic backend, but you
1545still want to make use of it because you have many sockets and it scales
1546so nicely. In this case, you would create a kqueue-based loop and embed it
1547into your default loop (which might use e.g. poll). Overall operation will
1548be a bit slower because first libev has to poll and then call kevent, but
1549at least you can use both at what they are best.
1550.PP
1551As for prioritising I/O: rarely you have the case where some fds have
1552to be watched and handled very quickly (with low latency), and even
1553priorities and idle watchers might have too much overhead. In this case
1554you would put all the high priority stuff in one loop and all the rest in
1555a second one, and embed the second one in the first.
1556.PP
1557As long as the watcher is active, the callback will be invoked every time
1558there might be events pending in the embedded loop. The callback must then
1559call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1560their callbacks (you could also start an idle watcher to give the embedded
1561loop strictly lower priority for example). You can also set the callback
1562to \f(CW0\fR, in which case the embed watcher will automatically execute the
1563embedded loop sweep.
1564.PP
1565As long as the watcher is started it will automatically handle events. The
1566callback will be invoked whenever some events have been handled. You can
1567set the callback to \f(CW0\fR to avoid having to specify one if you are not
1568interested in that.
1569.PP
1570Also, there have not currently been made special provisions for forking:
1571when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1572but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1573yourself.
1574.PP
1575Unfortunately, not all backends are embeddable, only the ones returned by
1576\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1577portable one.
1578.PP
1579So when you want to use this feature you will always have to be prepared
1580that you cannot get an embeddable loop. The recommended way to get around
1581this is to have a separate variables for your embeddable loop, try to
1582create it, and if that fails, use the normal loop for everything:
1583.PP
1584.Vb 3
1585\& struct ev_loop *loop_hi = ev_default_init (0);
1586\& struct ev_loop *loop_lo = 0;
1587\& struct ev_embed embed;
1588.Ve
1589.PP
1590.Vb 5
1591\& // see if there is a chance of getting one that works
1592\& // (remember that a flags value of 0 means autodetection)
1593\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1594\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1595\& : 0;
1596.Ve
1597.PP
1598.Vb 8
1599\& // if we got one, then embed it, otherwise default to loop_hi
1600\& if (loop_lo)
1601\& {
1602\& ev_embed_init (&embed, 0, loop_lo);
1603\& ev_embed_start (loop_hi, &embed);
1604\& }
1605\& else
1606\& loop_lo = loop_hi;
1607.Ve
1608.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1609.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1610.PD 0
1611.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1612.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1613.PD
1614Configures the watcher to embed the given loop, which must be
1615embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1616invoked automatically, otherwise it is the responsibility of the callback
1617to invoke it (it will continue to be called until the sweep has been done,
1618if you do not want thta, you need to temporarily stop the embed watcher).
1619.IP "ev_embed_sweep (loop, ev_embed *)" 4
1620.IX Item "ev_embed_sweep (loop, ev_embed *)"
1621Make a single, non-blocking sweep over the embedded loop. This works
1622similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1623apropriate way for embedded loops.
1624.IP "struct ev_loop *loop [read\-only]" 4
1625.IX Item "struct ev_loop *loop [read-only]"
1626The embedded event loop.
1627.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1628.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1629.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1630Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1631whoever is a good citizen cared to tell libev about it by calling
1632\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1633event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1634and only in the child after the fork. If whoever good citizen calling
1635\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1636handlers will be invoked, too, of course.
1637.IP "ev_fork_init (ev_signal *, callback)" 4
1638.IX Item "ev_fork_init (ev_signal *, callback)"
1639Initialises and configures the fork watcher \- it has no parameters of any
1640kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1641believe me.
924.SH "OTHER FUNCTIONS" 1642.SH "OTHER FUNCTIONS"
925.IX Header "OTHER FUNCTIONS" 1643.IX Header "OTHER FUNCTIONS"
926There are some other functions of possible interest. Described. Here. Now. 1644There are some other functions of possible interest. Described. Here. Now.
927.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1645.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
928.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1646.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
957.Ve 1675.Ve
958.Sp 1676.Sp
959.Vb 1 1677.Vb 1
960\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1678\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
961.Ve 1679.Ve
962.IP "ev_feed_event (loop, watcher, int events)" 4 1680.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
963.IX Item "ev_feed_event (loop, watcher, int events)" 1681.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
964Feeds the given event set into the event loop, as if the specified event 1682Feeds the given event set into the event loop, as if the specified event
965had happened for the specified watcher (which must be a pointer to an 1683had happened for the specified watcher (which must be a pointer to an
966initialised but not necessarily started event watcher). 1684initialised but not necessarily started event watcher).
967.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1685.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
968.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1686.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
969Feed an event on the given fd, as if a file descriptor backend detected 1687Feed an event on the given fd, as if a file descriptor backend detected
970the given events it. 1688the given events it.
971.IP "ev_feed_signal_event (loop, int signum)" 4 1689.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
972.IX Item "ev_feed_signal_event (loop, int signum)" 1690.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
973Feed an event as if the given signal occured (loop must be the default loop!). 1691Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1692loop!).
974.SH "LIBEVENT EMULATION" 1693.SH "LIBEVENT EMULATION"
975.IX Header "LIBEVENT EMULATION" 1694.IX Header "LIBEVENT EMULATION"
976Libev offers a compatibility emulation layer for libevent. It cannot 1695Libev offers a compatibility emulation layer for libevent. It cannot
977emulate the internals of libevent, so here are some usage hints: 1696emulate the internals of libevent, so here are some usage hints:
978.IP "* Use it by including <event.h>, as usual." 4 1697.IP "* Use it by including <event.h>, as usual." 4
… …
989.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1708.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
990.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1709.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
991.PD 1710.PD
992.SH "\*(C+ SUPPORT" 1711.SH "\*(C+ SUPPORT"
993.IX Header " SUPPORT" 1712.IX Header " SUPPORT"
994\&\s-1TBD\s0. 1713Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1714you to use some convinience methods to start/stop watchers and also change
1715the callback model to a model using method callbacks on objects.
1716.PP
1717To use it,
1718.PP
1719.Vb 1
1720\& #include <ev++.h>
1721.Ve
1722.PP
1723(it is not installed by default). This automatically includes \fIev.h\fR
1724and puts all of its definitions (many of them macros) into the global
1725namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1726.PP
1727It should support all the same embedding options as \fIev.h\fR, most notably
1728\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1729.PP
1730Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1731.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1732.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1733.IX Item "ev::READ, ev::WRITE etc."
1734These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1735macros from \fIev.h\fR.
1736.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1737.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1738.IX Item "ev::tstamp, ev::now"
1739Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1740.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
1741.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1742.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1743For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1744the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1745which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1746defines by many implementations.
1747.Sp
1748All of those classes have these methods:
1749.RS 4
1750.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1751.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1752.PD 0
1753.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1754.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1755.IP "ev::TYPE::~TYPE" 4
1756.IX Item "ev::TYPE::~TYPE"
1757.PD
1758The constructor takes a pointer to an object and a method pointer to
1759the event handler callback to call in this class. The constructor calls
1760\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1761before starting it. If you do not specify a loop then the constructor
1762automatically associates the default loop with this watcher.
1763.Sp
1764The destructor automatically stops the watcher if it is active.
1765.IP "w\->set (struct ev_loop *)" 4
1766.IX Item "w->set (struct ev_loop *)"
1767Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1768do this when the watcher is inactive (and not pending either).
1769.IP "w\->set ([args])" 4
1770.IX Item "w->set ([args])"
1771Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1772called at least once. Unlike the C counterpart, an active watcher gets
1773automatically stopped and restarted.
1774.IP "w\->start ()" 4
1775.IX Item "w->start ()"
1776Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1777constructor already takes the loop.
1778.IP "w\->stop ()" 4
1779.IX Item "w->stop ()"
1780Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1781.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1782.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1783.IX Item "w->again () ev::timer, ev::periodic only"
1784For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1785\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1786.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1787.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1788.IX Item "w->sweep () ev::embed only"
1789Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1790.ie n .IP "w\->update () ""ev::stat"" only" 4
1791.el .IP "w\->update () \f(CWev::stat\fR only" 4
1792.IX Item "w->update () ev::stat only"
1793Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
1794.RE
1795.RS 4
1796.RE
1797.PP
1798Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1799the constructor.
1800.PP
1801.Vb 4
1802\& class myclass
1803\& {
1804\& ev_io io; void io_cb (ev::io &w, int revents);
1805\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1806.Ve
1807.PP
1808.Vb 2
1809\& myclass ();
1810\& }
1811.Ve
1812.PP
1813.Vb 6
1814\& myclass::myclass (int fd)
1815\& : io (this, &myclass::io_cb),
1816\& idle (this, &myclass::idle_cb)
1817\& {
1818\& io.start (fd, ev::READ);
1819\& }
1820.Ve
1821.SH "MACRO MAGIC"
1822.IX Header "MACRO MAGIC"
1823Libev can be compiled with a variety of options, the most fundemantal is
1824\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and
1825callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
1826.PP
1827To make it easier to write programs that cope with either variant, the
1828following macros are defined:
1829.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
1830.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
1831.IX Item "EV_A, EV_A_"
1832This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
1833loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
1834\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
1835.Sp
1836.Vb 3
1837\& ev_unref (EV_A);
1838\& ev_timer_add (EV_A_ watcher);
1839\& ev_loop (EV_A_ 0);
1840.Ve
1841.Sp
1842It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
1843which is often provided by the following macro.
1844.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
1845.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
1846.IX Item "EV_P, EV_P_"
1847This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
1848loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
1849\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
1850.Sp
1851.Vb 2
1852\& // this is how ev_unref is being declared
1853\& static void ev_unref (EV_P);
1854.Ve
1855.Sp
1856.Vb 2
1857\& // this is how you can declare your typical callback
1858\& static void cb (EV_P_ ev_timer *w, int revents)
1859.Ve
1860.Sp
1861It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
1862suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
1863.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
1864.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
1865.IX Item "EV_DEFAULT, EV_DEFAULT_"
1866Similar to the other two macros, this gives you the value of the default
1867loop, if multiple loops are supported (\*(L"ev loop default\*(R").
1868.PP
1869Example: Declare and initialise a check watcher, working regardless of
1870wether multiple loops are supported or not.
1871.PP
1872.Vb 5
1873\& static void
1874\& check_cb (EV_P_ ev_timer *w, int revents)
1875\& {
1876\& ev_check_stop (EV_A_ w);
1877\& }
1878.Ve
1879.PP
1880.Vb 4
1881\& ev_check check;
1882\& ev_check_init (&check, check_cb);
1883\& ev_check_start (EV_DEFAULT_ &check);
1884\& ev_loop (EV_DEFAULT_ 0);
1885.Ve
1886.SH "EMBEDDING"
1887.IX Header "EMBEDDING"
1888Libev can (and often is) directly embedded into host
1889applications. Examples of applications that embed it include the Deliantra
1890Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1891and rxvt\-unicode.
1892.PP
1893The goal is to enable you to just copy the neecssary files into your
1894source directory without having to change even a single line in them, so
1895you can easily upgrade by simply copying (or having a checked-out copy of
1896libev somewhere in your source tree).
1897.Sh "\s-1FILESETS\s0"
1898.IX Subsection "FILESETS"
1899Depending on what features you need you need to include one or more sets of files
1900in your app.
1901.PP
1902\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
1903.IX Subsection "CORE EVENT LOOP"
1904.PP
1905To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
1906configuration (no autoconf):
1907.PP
1908.Vb 2
1909\& #define EV_STANDALONE 1
1910\& #include "ev.c"
1911.Ve
1912.PP
1913This will automatically include \fIev.h\fR, too, and should be done in a
1914single C source file only to provide the function implementations. To use
1915it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
1916done by writing a wrapper around \fIev.h\fR that you can include instead and
1917where you can put other configuration options):
1918.PP
1919.Vb 2
1920\& #define EV_STANDALONE 1
1921\& #include "ev.h"
1922.Ve
1923.PP
1924Both header files and implementation files can be compiled with a \*(C+
1925compiler (at least, thats a stated goal, and breakage will be treated
1926as a bug).
1927.PP
1928You need the following files in your source tree, or in a directory
1929in your include path (e.g. in libev/ when using \-Ilibev):
1930.PP
1931.Vb 4
1932\& ev.h
1933\& ev.c
1934\& ev_vars.h
1935\& ev_wrap.h
1936.Ve
1937.PP
1938.Vb 1
1939\& ev_win32.c required on win32 platforms only
1940.Ve
1941.PP
1942.Vb 5
1943\& ev_select.c only when select backend is enabled (which is by default)
1944\& ev_poll.c only when poll backend is enabled (disabled by default)
1945\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
1946\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1947\& ev_port.c only when the solaris port backend is enabled (disabled by default)
1948.Ve
1949.PP
1950\&\fIev.c\fR includes the backend files directly when enabled, so you only need
1951to compile this single file.
1952.PP
1953\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
1954.IX Subsection "LIBEVENT COMPATIBILITY API"
1955.PP
1956To include the libevent compatibility \s-1API\s0, also include:
1957.PP
1958.Vb 1
1959\& #include "event.c"
1960.Ve
1961.PP
1962in the file including \fIev.c\fR, and:
1963.PP
1964.Vb 1
1965\& #include "event.h"
1966.Ve
1967.PP
1968in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
1969.PP
1970You need the following additional files for this:
1971.PP
1972.Vb 2
1973\& event.h
1974\& event.c
1975.Ve
1976.PP
1977\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
1978.IX Subsection "AUTOCONF SUPPORT"
1979.PP
1980Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
1981whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
1982\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
1983include \fIconfig.h\fR and configure itself accordingly.
1984.PP
1985For this of course you need the m4 file:
1986.PP
1987.Vb 1
1988\& libev.m4
1989.Ve
1990.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
1991.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
1992Libev can be configured via a variety of preprocessor symbols you have to define
1993before including any of its files. The default is not to build for multiplicity
1994and only include the select backend.
1995.IP "\s-1EV_STANDALONE\s0" 4
1996.IX Item "EV_STANDALONE"
1997Must always be \f(CW1\fR if you do not use autoconf configuration, which
1998keeps libev from including \fIconfig.h\fR, and it also defines dummy
1999implementations for some libevent functions (such as logging, which is not
2000supported). It will also not define any of the structs usually found in
2001\&\fIevent.h\fR that are not directly supported by the libev core alone.
2002.IP "\s-1EV_USE_MONOTONIC\s0" 4
2003.IX Item "EV_USE_MONOTONIC"
2004If defined to be \f(CW1\fR, libev will try to detect the availability of the
2005monotonic clock option at both compiletime and runtime. Otherwise no use
2006of the monotonic clock option will be attempted. If you enable this, you
2007usually have to link against librt or something similar. Enabling it when
2008the functionality isn't available is safe, though, althoguh you have
2009to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2010function is hiding in (often \fI\-lrt\fR).
2011.IP "\s-1EV_USE_REALTIME\s0" 4
2012.IX Item "EV_USE_REALTIME"
2013If defined to be \f(CW1\fR, libev will try to detect the availability of the
2014realtime clock option at compiletime (and assume its availability at
2015runtime if successful). Otherwise no use of the realtime clock option will
2016be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2017(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2018in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2019.IP "\s-1EV_USE_SELECT\s0" 4
2020.IX Item "EV_USE_SELECT"
2021If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2022\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2023other method takes over, select will be it. Otherwise the select backend
2024will not be compiled in.
2025.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2026.IX Item "EV_SELECT_USE_FD_SET"
2027If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2028structure. This is useful if libev doesn't compile due to a missing
2029\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2030exotic systems. This usually limits the range of file descriptors to some
2031low limit such as 1024 or might have other limitations (winsocket only
2032allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2033influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2034.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2035.IX Item "EV_SELECT_IS_WINSOCKET"
2036When defined to \f(CW1\fR, the select backend will assume that
2037select/socket/connect etc. don't understand file descriptors but
2038wants osf handles on win32 (this is the case when the select to
2039be used is the winsock select). This means that it will call
2040\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2041it is assumed that all these functions actually work on fds, even
2042on win32. Should not be defined on non\-win32 platforms.
2043.IP "\s-1EV_USE_POLL\s0" 4
2044.IX Item "EV_USE_POLL"
2045If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2046backend. Otherwise it will be enabled on non\-win32 platforms. It
2047takes precedence over select.
2048.IP "\s-1EV_USE_EPOLL\s0" 4
2049.IX Item "EV_USE_EPOLL"
2050If defined to be \f(CW1\fR, libev will compile in support for the Linux
2051\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2052otherwise another method will be used as fallback. This is the
2053preferred backend for GNU/Linux systems.
2054.IP "\s-1EV_USE_KQUEUE\s0" 4
2055.IX Item "EV_USE_KQUEUE"
2056If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2057\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2058otherwise another method will be used as fallback. This is the preferred
2059backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2060supports some types of fds correctly (the only platform we found that
2061supports ptys for example was NetBSD), so kqueue might be compiled in, but
2062not be used unless explicitly requested. The best way to use it is to find
2063out whether kqueue supports your type of fd properly and use an embedded
2064kqueue loop.
2065.IP "\s-1EV_USE_PORT\s0" 4
2066.IX Item "EV_USE_PORT"
2067If defined to be \f(CW1\fR, libev will compile in support for the Solaris
206810 port style backend. Its availability will be detected at runtime,
2069otherwise another method will be used as fallback. This is the preferred
2070backend for Solaris 10 systems.
2071.IP "\s-1EV_USE_DEVPOLL\s0" 4
2072.IX Item "EV_USE_DEVPOLL"
2073reserved for future expansion, works like the \s-1USE\s0 symbols above.
2074.IP "\s-1EV_H\s0" 4
2075.IX Item "EV_H"
2076The name of the \fIev.h\fR header file used to include it. The default if
2077undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2078can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2079.IP "\s-1EV_CONFIG_H\s0" 4
2080.IX Item "EV_CONFIG_H"
2081If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2082\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2083\&\f(CW\*(C`EV_H\*(C'\fR, above.
2084.IP "\s-1EV_EVENT_H\s0" 4
2085.IX Item "EV_EVENT_H"
2086Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2087of how the \fIevent.h\fR header can be found.
2088.IP "\s-1EV_PROTOTYPES\s0" 4
2089.IX Item "EV_PROTOTYPES"
2090If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2091prototypes, but still define all the structs and other symbols. This is
2092occasionally useful if you want to provide your own wrapper functions
2093around libev functions.
2094.IP "\s-1EV_MULTIPLICITY\s0" 4
2095.IX Item "EV_MULTIPLICITY"
2096If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2097will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2098additional independent event loops. Otherwise there will be no support
2099for multiple event loops and there is no first event loop pointer
2100argument. Instead, all functions act on the single default loop.
2101.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2102.IX Item "EV_PERIODIC_ENABLE"
2103If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2104defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2105code.
2106.IP "\s-1EV_EMBED_ENABLE\s0" 4
2107.IX Item "EV_EMBED_ENABLE"
2108If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2109defined to be \f(CW0\fR, then they are not.
2110.IP "\s-1EV_STAT_ENABLE\s0" 4
2111.IX Item "EV_STAT_ENABLE"
2112If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2113defined to be \f(CW0\fR, then they are not.
2114.IP "\s-1EV_FORK_ENABLE\s0" 4
2115.IX Item "EV_FORK_ENABLE"
2116If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2117defined to be \f(CW0\fR, then they are not.
2118.IP "\s-1EV_MINIMAL\s0" 4
2119.IX Item "EV_MINIMAL"
2120If you need to shave off some kilobytes of code at the expense of some
2121speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2122some inlining decisions, saves roughly 30% codesize of amd64.
2123.IP "\s-1EV_PID_HASHSIZE\s0" 4
2124.IX Item "EV_PID_HASHSIZE"
2125\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2126pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2127than enough. If you need to manage thousands of children you might want to
2128increase this value.
2129.IP "\s-1EV_COMMON\s0" 4
2130.IX Item "EV_COMMON"
2131By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2132this macro to a something else you can include more and other types of
2133members. You have to define it each time you include one of the files,
2134though, and it must be identical each time.
2135.Sp
2136For example, the perl \s-1EV\s0 module uses something like this:
2137.Sp
2138.Vb 3
2139\& #define EV_COMMON \e
2140\& SV *self; /* contains this struct */ \e
2141\& SV *cb_sv, *fh /* note no trailing ";" */
2142.Ve
2143.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2144.IX Item "EV_CB_DECLARE (type)"
2145.PD 0
2146.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2147.IX Item "EV_CB_INVOKE (watcher, revents)"
2148.IP "ev_set_cb (ev, cb)" 4
2149.IX Item "ev_set_cb (ev, cb)"
2150.PD
2151Can be used to change the callback member declaration in each watcher,
2152and the way callbacks are invoked and set. Must expand to a struct member
2153definition and a statement, respectively. See the \fIev.v\fR header file for
2154their default definitions. One possible use for overriding these is to
2155avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2156method calls instead of plain function calls in \*(C+.
2157.Sh "\s-1EXAMPLES\s0"
2158.IX Subsection "EXAMPLES"
2159For a real-world example of a program the includes libev
2160verbatim, you can have a look at the \s-1EV\s0 perl module
2161(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2162the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2163interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2164will be compiled. It is pretty complex because it provides its own header
2165file.
2166.Sp
2167The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2168that everybody includes and which overrides some autoconf choices:
2169.Sp
2170.Vb 4
2171\& #define EV_USE_POLL 0
2172\& #define EV_MULTIPLICITY 0
2173\& #define EV_PERIODICS 0
2174\& #define EV_CONFIG_H <config.h>
2175.Ve
2176.Sp
2177.Vb 1
2178\& #include "ev++.h"
2179.Ve
2180.Sp
2181And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2182.Sp
2183.Vb 2
2184\& #include "ev_cpp.h"
2185\& #include "ev.c"
2186.Ve
2187.SH "COMPLEXITIES"
2188.IX Header "COMPLEXITIES"
2189In this section the complexities of (many of) the algorithms used inside
2190libev will be explained. For complexity discussions about backends see the
2191documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2192.RS 4
2193.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2194.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2195.PD 0
2196.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2197.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2198.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2199.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2200.IP "Stopping check/prepare/idle watchers: O(1)" 4
2201.IX Item "Stopping check/prepare/idle watchers: O(1)"
2202.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))" 4
2203.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16))"
2204.IP "Finding the next timer per loop iteration: O(1)" 4
2205.IX Item "Finding the next timer per loop iteration: O(1)"
2206.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2207.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2208.IP "Activating one watcher: O(1)" 4
2209.IX Item "Activating one watcher: O(1)"
2210.RE
2211.RS 4
2212.PD
995.SH "AUTHOR" 2213.SH "AUTHOR"
996.IX Header "AUTHOR" 2214.IX Header "AUTHOR"
997Marc Lehmann <libev@schmorp.de>. 2215Marc Lehmann <libev@schmorp.de>.

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