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Revision 1.2 by root, Sun Nov 18 03:43:24 2007 UTC vs.
Revision 1.19 by root, Sat Nov 24 16:57:38 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 "2007-11-18" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-11-24" "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
214.IP "unsigned int ev_supported_backends ()" 4
215.IX Item "unsigned int ev_supported_backends ()"
216Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR
217value) compiled into this binary of libev (independent of their
218availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
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
228.IP "unsigned int ev_recommended_backends ()" 4
229.IX Item "unsigned int ev_recommended_backends ()"
230Return the set of all backends compiled into this binary of libev and also
231recommended for this platform. This set is often smaller than the one
232returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on
233most BSDs and will not be autodetected unless you explicitly request it
234(assuming you know what you are doing). This is the set of backends that
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.
204.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 245.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
205.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
206Sets the allocation function to use (the prototype is similar to the 247Sets the allocation function to use (the prototype is similar to the
207realloc C function, the semantics are identical). It is used to allocate 248realloc C function, the semantics are identical). It is used to allocate
208and free memory (no surprises here). If it returns zero when memory 249and free memory (no surprises here). If it returns zero when memory
… …
210destructive action. The default is your system realloc function. 251destructive action. The default is your system realloc function.
211.Sp 252.Sp
212You could override this function in high-availability programs to, say, 253You could override this function in high-availability programs to, say,
213free 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,
214or 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
215.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 284.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
216.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 285.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
217Set the callback function to call on a retryable syscall error (such 286Set the callback function to call on a retryable syscall error (such
218as failed select, poll, epoll_wait). The message is a printable string 287as failed select, poll, epoll_wait). The message is a printable string
219indicating the system call or subsystem causing the problem. If this 288indicating the system call or subsystem causing the problem. If this
220callback 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
221matter what, when it returns. That is, libev will generally retry the 290matter what, when it returns. That is, libev will generally retry the
222requested 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
223(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
224.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 309.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
225.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 310.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP"
226An 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
227types 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
228events, and dynamically created loops which do not. 313events, and dynamically created loops which do not.
… …
236.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 321.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4
237.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" 322.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)"
238This will initialise the default event loop if it hasn't been initialised 323This will initialise the default event loop if it hasn't been initialised
239yet and return it. If the default loop could not be initialised, returns 324yet and return it. If the default loop could not be initialised, returns
240false. If it already was initialised it simply returns it (and ignores the 325false. If it already was initialised it simply returns it (and ignores the
241flags). 326flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards).
242.Sp 327.Sp
243If 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
244function. 329function.
245.Sp 330.Sp
246The flags argument can be used to specify special behaviour or specific 331The flags argument can be used to specify special behaviour or specific
247backends to use, and is usually specified as 0 (or \s-1EVFLAG_AUTO\s0). 332backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR).
248.Sp 333.Sp
249It supports the following flags: 334The following flags are supported:
250.RS 4 335.RS 4
251.ie n .IP """EVFLAG_AUTO""" 4 336.ie n .IP """EVFLAG_AUTO""" 4
252.el .IP "\f(CWEVFLAG_AUTO\fR" 4 337.el .IP "\f(CWEVFLAG_AUTO\fR" 4
253.IX Item "EVFLAG_AUTO" 338.IX Item "EVFLAG_AUTO"
254The 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
… …
260or setgid) then libev will \fInot\fR look at the environment variable 345or setgid) then libev will \fInot\fR look at the environment variable
261\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 346\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
262override the flags completely if it is found in the environment. This is 347override the flags completely if it is found in the environment. This is
263useful to try out specific backends to test their performance, or to work 348useful to try out specific backends to test their performance, or to work
264around bugs. 349around bugs.
265.ie n .IP """EVMETHOD_SELECT"" (portable select backend)" 4 350.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
266.el .IP "\f(CWEVMETHOD_SELECT\fR (portable select backend)" 4 351.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
267.IX Item "EVMETHOD_SELECT (portable select backend)" 352.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
268.PD 0 353This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
354libev tries to roll its own fd_set with no limits on the number of fds,
355but if that fails, expect a fairly low limit on the number of fds when
356using this backend. It doesn't scale too well (O(highest_fd)), but its usually
357the fastest backend for a low number of fds.
269.ie n .IP """EVMETHOD_POLL"" (poll backend, available everywhere except on windows)" 4 358.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
270.el .IP "\f(CWEVMETHOD_POLL\fR (poll backend, available everywhere except on windows)" 4 359.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
271.IX Item "EVMETHOD_POLL (poll backend, available everywhere except on windows)" 360.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
361And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than
362select, but handles sparse fds better and has no artificial limit on the
363number of fds you can use (except it will slow down considerably with a
364lot of inactive fds). It scales similarly to select, i.e. O(total_fds).
272.ie n .IP """EVMETHOD_EPOLL"" (linux only)" 4 365.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
273.el .IP "\f(CWEVMETHOD_EPOLL\fR (linux only)" 4 366.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
274.IX Item "EVMETHOD_EPOLL (linux only)" 367.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
275.ie n .IP """EVMETHOD_KQUEUE"" (some bsds only)" 4 368For few fds, this backend is a bit little slower than poll and select,
276.el .IP "\f(CWEVMETHOD_KQUEUE\fR (some bsds only)" 4 369but it scales phenomenally better. While poll and select usually scale like
277.IX Item "EVMETHOD_KQUEUE (some bsds only)" 370O(total_fds) where n is the total number of fds (or the highest fd), epoll scales
371either O(1) or O(active_fds).
372.Sp
373While stopping and starting an I/O watcher in the same iteration will
374result in some caching, there is still a syscall per such incident
375(because the fd could point to a different file description now), so its
376best to avoid that. Also, \fIdup()\fRed file descriptors might not work very
377well if you register events for both fds.
378.Sp
379Please note that epoll sometimes generates spurious notifications, so you
380need to use non-blocking I/O or other means to avoid blocking when no data
381(or space) is available.
382.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
383.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
384.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
385Kqueue deserves special mention, as at the time of this writing, it
386was broken on all BSDs except NetBSD (usually it doesn't work with
387anything but sockets and pipes, except on Darwin, where of course its
388completely useless). For this reason its not being \*(L"autodetected\*(R"
389unless you explicitly specify it explicitly in the flags (i.e. using
390\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR).
391.Sp
392It scales in the same way as the epoll backend, but the interface to the
393kernel is more efficient (which says nothing about its actual speed, of
394course). While starting and stopping an I/O watcher does not cause an
395extra syscall as with epoll, it still adds up to four event changes per
396incident, so its best to avoid that.
278.ie n .IP """EVMETHOD_DEVPOLL"" (solaris 8 only)" 4 397.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4
279.el .IP "\f(CWEVMETHOD_DEVPOLL\fR (solaris 8 only)" 4 398.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4
280.IX Item "EVMETHOD_DEVPOLL (solaris 8 only)" 399.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)"
400This is not implemented yet (and might never be).
281.ie n .IP """EVMETHOD_PORT"" (solaris 10 only)" 4 401.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4
282.el .IP "\f(CWEVMETHOD_PORT\fR (solaris 10 only)" 4 402.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4
283.IX Item "EVMETHOD_PORT (solaris 10 only)" 403.IX Item "EVBACKEND_PORT (value 32, Solaris 10)"
284.PD 404This uses the Solaris 10 port mechanism. As with everything on Solaris,
285If one or more of these are ored into the flags value, then only these 405it's really slow, but it still scales very well (O(active_fds)).
286backends will be tried (in the reverse order as given here). If one are 406.Sp
287specified, any backend will do. 407Please note that solaris ports can result in a lot of spurious
408notifications, so you need to use non-blocking I/O or other means to avoid
409blocking when no data (or space) is available.
410.ie n .IP """EVBACKEND_ALL""" 4
411.el .IP "\f(CWEVBACKEND_ALL\fR" 4
412.IX Item "EVBACKEND_ALL"
413Try all backends (even potentially broken ones that wouldn't be tried
414with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as
415\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR.
288.RE 416.RE
289.RS 4 417.RS 4
418.Sp
419If one or more of these are ored into the flags value, then only these
420backends will be tried (in the reverse order as given here). If none are
421specified, most compiled-in backend will be tried, usually in reverse
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
290.RE 445.RE
291.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 446.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4
292.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 447.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
293Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
294always distinct from the default loop. Unlike the default loop, it cannot 449always distinct from the default loop. Unlike the default loop, it cannot
295handle 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
296undefined 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
297.IP "ev_default_destroy ()" 4 460.IP "ev_default_destroy ()" 4
298.IX Item "ev_default_destroy ()" 461.IX Item "ev_default_destroy ()"
299Destroys the default loop again (frees all memory and kernel state 462Destroys the default loop again (frees all memory and kernel state
300etc.). This stops all registered event watchers (by not touching them in 463etc.). None of the active event watchers will be stopped in the normal
301any 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).
302.IP "ev_loop_destroy (loop)" 4 469.IP "ev_loop_destroy (loop)" 4
303.IX Item "ev_loop_destroy (loop)" 470.IX Item "ev_loop_destroy (loop)"
304Like \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
305earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 472earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
306.IP "ev_default_fork ()" 4 473.IP "ev_default_fork ()" 4
… …
308This function reinitialises the kernel state for backends that have 475This function reinitialises the kernel state for backends that have
309one. Despite the name, you can call it anytime, but it makes most sense 476one. Despite the name, you can call it anytime, but it makes most sense
310after forking, in either the parent or child process (or both, but that 477after forking, in either the parent or child process (or both, but that
311again makes little sense). 478again makes little sense).
312.Sp 479.Sp
313You \fImust\fR call this function after forking if and only if you want to 480You \fImust\fR call this function in the child process after forking if and
314use the event library in both processes. If you just fork+exec, you don't 481only if you want to use the event library in both processes. If you just
315have to call it. 482fork+exec, you don't have to call it.
316.Sp 483.Sp
317The function itself is quite fast and it's usually not a problem to call 484The function itself is quite fast and it's usually not a problem to call
318it just in case after a fork. To make this easy, the function will fit in 485it just in case after a fork. To make this easy, the function will fit in
319quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: 486quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR:
320.Sp 487.Sp
321.Vb 1 488.Vb 1
322\& pthread_atfork (0, 0, ev_default_fork); 489\& pthread_atfork (0, 0, ev_default_fork);
323.Ve 490.Ve
491.Sp
492At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use
493without calling this function, so if you force one of those backends you
494do not need to care.
324.IP "ev_loop_fork (loop)" 4 495.IP "ev_loop_fork (loop)" 4
325.IX Item "ev_loop_fork (loop)" 496.IX Item "ev_loop_fork (loop)"
326Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 497Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
327\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 498\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
328after fork, and how you do this is entirely your own problem. 499after fork, and how you do this is entirely your own problem.
329.IP "unsigned int ev_method (loop)" 4 500.IP "unsigned int ev_backend (loop)" 4
330.IX Item "unsigned int ev_method (loop)" 501.IX Item "unsigned int ev_backend (loop)"
331Returns one of the \f(CW\*(C`EVMETHOD_*\*(C'\fR flags indicating the event backend in 502Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
332use. 503use.
333.IP "ev_tstamp ev_now (loop)" 4 504.IP "ev_tstamp ev_now (loop)" 4
334.IX Item "ev_tstamp ev_now (loop)" 505.IX Item "ev_tstamp ev_now (loop)"
335Returns 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
336got events and started processing them. This timestamp does not change 507received events and started processing them. This timestamp does not
337as 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
338used 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
339occuring (or more correctly, the mainloop finding out about it). 510event occuring (or more correctly, libev finding out about it).
340.IP "ev_loop (loop, int flags)" 4 511.IP "ev_loop (loop, int flags)" 4
341.IX Item "ev_loop (loop, int flags)" 512.IX Item "ev_loop (loop, int flags)"
342Finally, this is it, the event handler. This function usually is called 513Finally, this is it, the event handler. This function usually is called
343after you initialised all your watchers and you want to start handling 514after you initialised all your watchers and you want to start handling
344events. 515events.
345.Sp 516.Sp
346If 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
347no 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.
348.Sp 525.Sp
349A 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
350those 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
351case 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.
352.Sp 529.Sp
353A 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
354neccessary) and will handle those and any outstanding ones. It will block 531neccessary) and will handle those and any outstanding ones. It will block
355your 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
356one 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.
357.Sp 537.Sp
358This flags value could be used to implement alternative looping
359constructs, but the \f(CW\*(C`prepare\*(C'\fR and \f(CW\*(C`check\*(C'\fR watchers provide a better and
360more generic mechanism.
361.Sp
362Here are the gory details of what ev_loop does: 538Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
363.Sp 539.Sp
364.Vb 15 540.Vb 18
365\& 1. If there are no active watchers (reference count is zero), return. 541\& * If there are no active watchers (reference count is zero), return.
366\& 2. Queue and immediately call all prepare watchers. 542\& - Queue prepare watchers and then call all outstanding watchers.
367\& 3. If we have been forked, recreate the kernel state. 543\& - If we have been forked, recreate the kernel state.
368\& 4. Update the kernel state with all outstanding changes. 544\& - Update the kernel state with all outstanding changes.
369\& 5. Update the "event loop time". 545\& - Update the "event loop time".
370\& 6. Calculate for how long to block. 546\& - Calculate for how long to block.
371\& 7. Block the process, waiting for events. 547\& - Block the process, waiting for any events.
548\& - Queue all outstanding I/O (fd) events.
372\& 8. Update the "event loop time" and do time jump handling. 549\& - Update the "event loop time" and do time jump handling.
373\& 9. Queue all outstanding timers. 550\& - Queue all outstanding timers.
374\& 10. Queue all outstanding periodics. 551\& - Queue all outstanding periodics.
375\& 11. If no events are pending now, queue all idle watchers. 552\& - If no events are pending now, queue all idle watchers.
376\& 12. Queue all check watchers. 553\& - Queue all check watchers.
377\& 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.
378\& 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
379\& 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!
380.Ve 569.Ve
381.IP "ev_unloop (loop, how)" 4 570.IP "ev_unloop (loop, how)" 4
382.IX Item "ev_unloop (loop, how)" 571.IX Item "ev_unloop (loop, how)"
383Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 572Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
384has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 573has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
… …
398example, 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
399visible 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
400no 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
401way 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
402libraries. 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
403.SH "ANATOMY OF A WATCHER" 609.SH "ANATOMY OF A WATCHER"
404.IX Header "ANATOMY OF A WATCHER" 610.IX Header "ANATOMY OF A WATCHER"
405A 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
406interest 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
407become 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:
… …
443*)\*(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
444corresponding 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.
445.PP 651.PP
446As 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
447must 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
448reinitialise it or call its set method. 654reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
449.PP
450You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
451(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
452callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
453(watcher *)\*(C'\fR macro.
454.PP 655.PP
455Each and every callback receives the event loop pointer as first, the 656Each and every callback receives the event loop pointer as first, the
456registered watcher structure as second, and a bitset of received events as 657registered watcher structure as second, and a bitset of received events as
457third argument. 658third argument.
458.PP 659.PP
… …
516Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 717Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
517for example it might indicate that a fd is readable or writable, and if 718for example it might indicate that a fd is readable or writable, and if
518your callbacks is well-written it can just attempt the operation and cope 719your callbacks is well-written it can just attempt the operation and cope
519with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 720with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
520programs, though, so beware. 721programs, though, so beware.
722.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
723.IX Subsection "GENERIC WATCHER FUNCTIONS"
724In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
725e.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.
726.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
727.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
728.IX Item "ev_init (ev_TYPE *watcher, callback)"
729This macro initialises the generic portion of a watcher. The contents
730of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
731the generic parts of the watcher are initialised, you \fIneed\fR to call
732the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
733type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
734which rolls both calls into one.
735.Sp
736You can reinitialise a watcher at any time as long as it has been stopped
737(or never started) and there are no pending events outstanding.
738.Sp
739The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
740int revents)\*(C'\fR.
741.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
742.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
743.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
744This macro initialises the type-specific parts of a watcher. You need to
745call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
746call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
747macro on a watcher that is active (it can be pending, however, which is a
748difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
749.Sp
750Although some watcher types do not have type-specific arguments
751(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
752.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
753.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
754.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
755This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
756calls into a single call. This is the most convinient method to initialise
757a watcher. The same limitations apply, of course.
758.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
759.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
760.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
761Starts (activates) the given watcher. Only active watchers will receive
762events. If the watcher is already active nothing will happen.
763.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
764.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
765.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
766Stops the given watcher again (if active) and clears the pending
767status. It is possible that stopped watchers are pending (for example,
768non-repeating timers are being stopped when they become pending), but
769\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
770you want to free or reuse the memory used by the watcher it is therefore a
771good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
772.IP "bool ev_is_active (ev_TYPE *watcher)" 4
773.IX Item "bool ev_is_active (ev_TYPE *watcher)"
774Returns a true value iff the watcher is active (i.e. it has been started
775and not yet been stopped). As long as a watcher is active you must not modify
776it.
777.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
778.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
779Returns a true value iff the watcher is pending, (i.e. it has outstanding
780events but its callback has not yet been invoked). As long as a watcher
781is pending (but not active) you must not call an init function on it (but
782\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to
783libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it).
784.IP "callback = ev_cb (ev_TYPE *watcher)" 4
785.IX Item "callback = ev_cb (ev_TYPE *watcher)"
786Returns the callback currently set on the watcher.
787.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
788.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
789Change the callback. You can change the callback at virtually any time
790(modulo threads).
521.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 791.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
522.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 792.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
523Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 793Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
524and read at any time, libev will completely ignore it. This can be used 794and read at any time, libev will completely ignore it. This can be used
525to associate arbitrary data with your watcher. If you need more data and 795to associate arbitrary data with your watcher. If you need more data and
… …
552have been omitted.... 822have been omitted....
553.SH "WATCHER TYPES" 823.SH "WATCHER TYPES"
554.IX Header "WATCHER TYPES" 824.IX Header "WATCHER TYPES"
555This section describes each watcher in detail, but will not repeat 825This section describes each watcher in detail, but will not repeat
556information given in the last section. 826information given in the last section.
557.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 827.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
558.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 828.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
559.IX Subsection "ev_io - is this file descriptor readable or writable" 829.IX Subsection "ev_io - is this file descriptor readable or writable?"
560I/O watchers check whether a file descriptor is readable or writable 830I/O watchers check whether a file descriptor is readable or writable
561in each iteration of the event loop (This behaviour is called 831in each iteration of the event loop, or, more precisely, when reading
562level-triggering because you keep receiving events as long as the 832would not block the process and writing would at least be able to write
563condition persists. Remember you can stop the watcher if you don't want to 833some data. This behaviour is called level-triggering because you keep
564act on the event and neither want to receive future events). 834receiving events as long as the condition persists. Remember you can stop
835the watcher if you don't want to act on the event and neither want to
836receive future events.
565.PP 837.PP
566In general you can register as many read and/or write event watchers per 838In general you can register as many read and/or write event watchers per
567fd as you want (as long as you don't confuse yourself). Setting all file 839fd as you want (as long as you don't confuse yourself). Setting all file
568descriptors to non-blocking mode is also usually a good idea (but not 840descriptors to non-blocking mode is also usually a good idea (but not
569required if you know what you are doing). 841required if you know what you are doing).
570.PP 842.PP
571You have to be careful with dup'ed file descriptors, though. Some backends 843You have to be careful with dup'ed file descriptors, though. Some backends
572(the linux epoll backend is a notable example) cannot handle dup'ed file 844(the linux epoll backend is a notable example) cannot handle dup'ed file
573descriptors correctly if you register interest in two or more fds pointing 845descriptors correctly if you register interest in two or more fds pointing
574to the same underlying file/socket etc. description (that is, they share 846to the same underlying file/socket/etc. description (that is, they share
575the same underlying \*(L"file open\*(R"). 847the same underlying \*(L"file open\*(R").
576.PP 848.PP
577If you must do this, then force the use of a known-to-be-good backend 849If you must do this, then force the use of a known-to-be-good backend
578(at the time of this writing, this includes only \s-1EVMETHOD_SELECT\s0 and 850(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
579\&\s-1EVMETHOD_POLL\s0). 851\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
852.PP
853Another thing you have to watch out for is that it is quite easy to
854receive \*(L"spurious\*(R" readyness notifications, that is your callback might
855be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
856because there is no data. Not only are some backends known to create a
857lot of those (for example solaris ports), it is very easy to get into
858this situation even with a relatively standard program structure. Thus
859it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
860\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
861.PP
862If you cannot run the fd in non-blocking mode (for example you should not
863play around with an Xlib connection), then you have to seperately re-test
864wether a file descriptor is really ready with a known-to-be good interface
865such as poll (fortunately in our Xlib example, Xlib already does this on
866its own, so its quite safe to use).
580.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 867.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
581.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 868.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
582.PD 0 869.PD 0
583.IP "ev_io_set (ev_io *, int fd, int events)" 4 870.IP "ev_io_set (ev_io *, int fd, int events)" 4
584.IX Item "ev_io_set (ev_io *, int fd, int events)" 871.IX Item "ev_io_set (ev_io *, int fd, int events)"
585.PD 872.PD
586Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 873Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
587events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 874rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
588EV_WRITE\*(C'\fR to receive the given events. 875\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
876.PP
877Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
878readable, but only once. Since it is likely line\-buffered, you could
879attempt to read a whole line in the callback:
880.PP
881.Vb 6
882\& static void
883\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
884\& {
885\& ev_io_stop (loop, w);
886\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
887\& }
888.Ve
889.PP
890.Vb 6
891\& ...
892\& struct ev_loop *loop = ev_default_init (0);
893\& struct ev_io stdin_readable;
894\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
895\& ev_io_start (loop, &stdin_readable);
896\& ev_loop (loop, 0);
897.Ve
589.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 898.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
590.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 899.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
591.IX Subsection "ev_timer - relative and optionally recurring timeouts" 900.IX Subsection "ev_timer - relative and optionally repeating timeouts"
592Timer watchers are simple relative timers that generate an event after a 901Timer watchers are simple relative timers that generate an event after a
593given time, and optionally repeating in regular intervals after that. 902given time, and optionally repeating in regular intervals after that.
594.PP 903.PP
595The timers are based on real time, that is, if you register an event that 904The timers are based on real time, that is, if you register an event that
596times out after an hour and you reset your system clock to last years 905times out after an hour and you reset your system clock to last years
… …
643seconds of inactivity on the socket. The easiest way to do this is to 952seconds of inactivity on the socket. The easiest way to do this is to
644configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 953configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each
645time you successfully read or write some data. If you go into an idle 954time you successfully read or write some data. If you go into an idle
646state where you do not expect data to travel on the socket, you can stop 955state where you do not expect data to travel on the socket, you can stop
647the timer, and again will automatically restart it if need be. 956the timer, and again will automatically restart it if need be.
957.PP
958Example: create a timer that fires after 60 seconds.
959.PP
960.Vb 5
961\& static void
962\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
963\& {
964\& .. one minute over, w is actually stopped right here
965\& }
966.Ve
967.PP
968.Vb 3
969\& struct ev_timer mytimer;
970\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
971\& ev_timer_start (loop, &mytimer);
972.Ve
973.PP
974Example: create a timeout timer that times out after 10 seconds of
975inactivity.
976.PP
977.Vb 5
978\& static void
979\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
980\& {
981\& .. ten seconds without any activity
982\& }
983.Ve
984.PP
985.Vb 4
986\& struct ev_timer mytimer;
987\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
988\& ev_timer_again (&mytimer); /* start timer */
989\& ev_loop (loop, 0);
990.Ve
991.PP
992.Vb 3
993\& // and in some piece of code that gets executed on any "activity":
994\& // reset the timeout to start ticking again at 10 seconds
995\& ev_timer_again (&mytimer);
996.Ve
648.ie n .Sh """ev_periodic"" \- to cron or not to cron" 997.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
649.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 998.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
650.IX Subsection "ev_periodic - to cron or not to cron" 999.IX Subsection "ev_periodic - to cron or not to cron?"
651Periodic watchers are also timers of a kind, but they are very versatile 1000Periodic watchers are also timers of a kind, but they are very versatile
652(and unfortunately a bit complex). 1001(and unfortunately a bit complex).
653.PP 1002.PP
654Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1003Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
655but on wallclock time (absolute time). You can tell a periodic watcher 1004but on wallclock time (absolute time). You can tell a periodic watcher
656to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1005to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
657periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1006periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
658+ 10.>) and then reset your system clock to the last year, then it will 1007+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
659take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1008take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
660roughly 10 seconds later and of course not if you reset your system time 1009roughly 10 seconds later and of course not if you reset your system time
661again). 1010again).
662.PP 1011.PP
663They can also be used to implement vastly more complex timers, such as 1012They can also be used to implement vastly more complex timers, such as
… …
744.IX Item "ev_periodic_again (loop, ev_periodic *)" 1093.IX Item "ev_periodic_again (loop, ev_periodic *)"
745Simply stops and restarts the periodic watcher again. This is only useful 1094Simply stops and restarts the periodic watcher again. This is only useful
746when you changed some parameters or the reschedule callback would return 1095when you changed some parameters or the reschedule callback would return
747a different time than the last time it was called (e.g. in a crond like 1096a different time than the last time it was called (e.g. in a crond like
748program when the crontabs have changed). 1097program when the crontabs have changed).
1098.PP
1099Example: call a callback every hour, or, more precisely, whenever the
1100system clock is divisible by 3600. The callback invocation times have
1101potentially a lot of jittering, but good long-term stability.
1102.PP
1103.Vb 5
1104\& static void
1105\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1106\& {
1107\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1108\& }
1109.Ve
1110.PP
1111.Vb 3
1112\& struct ev_periodic hourly_tick;
1113\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1114\& ev_periodic_start (loop, &hourly_tick);
1115.Ve
1116.PP
1117Example: the same as above, but use a reschedule callback to do it:
1118.PP
1119.Vb 1
1120\& #include <math.h>
1121.Ve
1122.PP
1123.Vb 5
1124\& static ev_tstamp
1125\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1126\& {
1127\& return fmod (now, 3600.) + 3600.;
1128\& }
1129.Ve
1130.PP
1131.Vb 1
1132\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1133.Ve
1134.PP
1135Example: call a callback every hour, starting now:
1136.PP
1137.Vb 4
1138\& struct ev_periodic hourly_tick;
1139\& ev_periodic_init (&hourly_tick, clock_cb,
1140\& fmod (ev_now (loop), 3600.), 3600., 0);
1141\& ev_periodic_start (loop, &hourly_tick);
1142.Ve
749.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1143.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
750.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1144.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
751.IX Subsection "ev_signal - signal me when a signal gets signalled" 1145.IX Subsection "ev_signal - signal me when a signal gets signalled!"
752Signal watchers will trigger an event when the process receives a specific 1146Signal watchers will trigger an event when the process receives a specific
753signal one or more times. Even though signals are very asynchronous, libev 1147signal one or more times. Even though signals are very asynchronous, libev
754will try it's best to deliver signals synchronously, i.e. as part of the 1148will try it's best to deliver signals synchronously, i.e. as part of the
755normal event processing, like any other event. 1149normal event processing, like any other event.
756.PP 1150.PP
… …
766.IP "ev_signal_set (ev_signal *, int signum)" 4 1160.IP "ev_signal_set (ev_signal *, int signum)" 4
767.IX Item "ev_signal_set (ev_signal *, int signum)" 1161.IX Item "ev_signal_set (ev_signal *, int signum)"
768.PD 1162.PD
769Configures the watcher to trigger on the given signal number (usually one 1163Configures the watcher to trigger on the given signal number (usually one
770of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1164of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
771.ie n .Sh """ev_child"" \- wait for pid status changes" 1165.ie n .Sh """ev_child"" \- watch out for process status changes"
772.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1166.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
773.IX Subsection "ev_child - wait for pid status changes" 1167.IX Subsection "ev_child - watch out for process status changes"
774Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1168Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
775some child status changes (most typically when a child of yours dies). 1169some child status changes (most typically when a child of yours dies).
776.IP "ev_child_init (ev_child *, callback, int pid)" 4 1170.IP "ev_child_init (ev_child *, callback, int pid)" 4
777.IX Item "ev_child_init (ev_child *, callback, int pid)" 1171.IX Item "ev_child_init (ev_child *, callback, int pid)"
778.PD 0 1172.PD 0
… …
783\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1177\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
784at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1178at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
785the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1179the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
786\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1180\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
787process causing the status change. 1181process causing the status change.
1182.PP
1183Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1184.PP
1185.Vb 5
1186\& static void
1187\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1188\& {
1189\& ev_unloop (loop, EVUNLOOP_ALL);
1190\& }
1191.Ve
1192.PP
1193.Vb 3
1194\& struct ev_signal signal_watcher;
1195\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1196\& ev_signal_start (loop, &sigint_cb);
1197.Ve
788.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1198.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
789.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1199.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
790.IX Subsection "ev_idle - when you've got nothing better to do" 1200.IX Subsection "ev_idle - when you've got nothing better to do..."
791Idle watchers trigger events when there are no other events are pending 1201Idle watchers trigger events when there are no other events are pending
792(prepare, check and other idle watchers do not count). That is, as long 1202(prepare, check and other idle watchers do not count). That is, as long
793as your process is busy handling sockets or timeouts (or even signals, 1203as your process is busy handling sockets or timeouts (or even signals,
794imagine) it will not be triggered. But when your process is idle all idle 1204imagine) it will not be triggered. But when your process is idle all idle
795watchers are being called again and again, once per event loop iteration \- 1205watchers are being called again and again, once per event loop iteration \-
… …
806.IP "ev_idle_init (ev_signal *, callback)" 4 1216.IP "ev_idle_init (ev_signal *, callback)" 4
807.IX Item "ev_idle_init (ev_signal *, callback)" 1217.IX Item "ev_idle_init (ev_signal *, callback)"
808Initialises and configures the idle watcher \- it has no parameters of any 1218Initialises and configures the idle watcher \- it has no parameters of any
809kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1219kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
810believe me. 1220believe me.
1221.PP
1222Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the
1223callback, free it. Alos, use no error checking, as usual.
1224.PP
1225.Vb 7
1226\& static void
1227\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1228\& {
1229\& free (w);
1230\& // now do something you wanted to do when the program has
1231\& // no longer asnything immediate to do.
1232\& }
1233.Ve
1234.PP
1235.Vb 3
1236\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1237\& ev_idle_init (idle_watcher, idle_cb);
1238\& ev_idle_start (loop, idle_cb);
1239.Ve
811.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1240.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
812.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1241.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
813.IX Subsection "ev_prepare and ev_check - customise your event loop" 1242.IX Subsection "ev_prepare and ev_check - customise your event loop!"
814Prepare and check watchers are usually (but not always) used in tandem: 1243Prepare and check watchers are usually (but not always) used in tandem:
815prepare watchers get invoked before the process blocks and check watchers 1244prepare watchers get invoked before the process blocks and check watchers
816afterwards. 1245afterwards.
817.PP 1246.PP
818Their main purpose is to integrate other event mechanisms into libev. This 1247Their main purpose is to integrate other event mechanisms into libev and
819could be used, for example, to track variable changes, implement your own 1248their use is somewhat advanced. This could be used, for example, to track
820watchers, integrate net-snmp or a coroutine library and lots more. 1249variable changes, implement your own watchers, integrate net-snmp or a
1250coroutine library and lots more.
821.PP 1251.PP
822This is done by examining in each prepare call which file descriptors need 1252This is done by examining in each prepare call which file descriptors need
823to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1253to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
824them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1254them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
825provide just this functionality). Then, in the check watcher you check for 1255provide just this functionality). Then, in the check watcher you check for
… …
843.IX Item "ev_check_init (ev_check *, callback)" 1273.IX Item "ev_check_init (ev_check *, callback)"
844.PD 1274.PD
845Initialises and configures the prepare or check watcher \- they have no 1275Initialises and configures the prepare or check watcher \- they have no
846parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1276parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
847macros, but using them is utterly, utterly and completely pointless. 1277macros, but using them is utterly, utterly and completely pointless.
1278.PP
1279Example: *TODO*.
1280.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1281.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1282.IX Subsection "ev_embed - when one backend isn't enough..."
1283This is a rather advanced watcher type that lets you embed one event loop
1284into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1285loop, other types of watchers might be handled in a delayed or incorrect
1286fashion and must not be used).
1287.PP
1288There are primarily two reasons you would want that: work around bugs and
1289prioritise I/O.
1290.PP
1291As an example for a bug workaround, the kqueue backend might only support
1292sockets on some platform, so it is unusable as generic backend, but you
1293still want to make use of it because you have many sockets and it scales
1294so nicely. In this case, you would create a kqueue-based loop and embed it
1295into your default loop (which might use e.g. poll). Overall operation will
1296be a bit slower because first libev has to poll and then call kevent, but
1297at least you can use both at what they are best.
1298.PP
1299As for prioritising I/O: rarely you have the case where some fds have
1300to be watched and handled very quickly (with low latency), and even
1301priorities and idle watchers might have too much overhead. In this case
1302you would put all the high priority stuff in one loop and all the rest in
1303a second one, and embed the second one in the first.
1304.PP
1305As long as the watcher is active, the callback will be invoked every time
1306there might be events pending in the embedded loop. The callback must then
1307call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1308their callbacks (you could also start an idle watcher to give the embedded
1309loop strictly lower priority for example). You can also set the callback
1310to \f(CW0\fR, in which case the embed watcher will automatically execute the
1311embedded loop sweep.
1312.PP
1313As long as the watcher is started it will automatically handle events. The
1314callback will be invoked whenever some events have been handled. You can
1315set the callback to \f(CW0\fR to avoid having to specify one if you are not
1316interested in that.
1317.PP
1318Also, there have not currently been made special provisions for forking:
1319when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1320but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1321yourself.
1322.PP
1323Unfortunately, not all backends are embeddable, only the ones returned by
1324\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1325portable one.
1326.PP
1327So when you want to use this feature you will always have to be prepared
1328that you cannot get an embeddable loop. The recommended way to get around
1329this is to have a separate variables for your embeddable loop, try to
1330create it, and if that fails, use the normal loop for everything:
1331.PP
1332.Vb 3
1333\& struct ev_loop *loop_hi = ev_default_init (0);
1334\& struct ev_loop *loop_lo = 0;
1335\& struct ev_embed embed;
1336.Ve
1337.PP
1338.Vb 5
1339\& // see if there is a chance of getting one that works
1340\& // (remember that a flags value of 0 means autodetection)
1341\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1342\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1343\& : 0;
1344.Ve
1345.PP
1346.Vb 8
1347\& // if we got one, then embed it, otherwise default to loop_hi
1348\& if (loop_lo)
1349\& {
1350\& ev_embed_init (&embed, 0, loop_lo);
1351\& ev_embed_start (loop_hi, &embed);
1352\& }
1353\& else
1354\& loop_lo = loop_hi;
1355.Ve
1356.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1357.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1358.PD 0
1359.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1360.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1361.PD
1362Configures the watcher to embed the given loop, which must be
1363embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1364invoked automatically, otherwise it is the responsibility of the callback
1365to invoke it (it will continue to be called until the sweep has been done,
1366if you do not want thta, you need to temporarily stop the embed watcher).
1367.IP "ev_embed_sweep (loop, ev_embed *)" 4
1368.IX Item "ev_embed_sweep (loop, ev_embed *)"
1369Make a single, non-blocking sweep over the embedded loop. This works
1370similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1371apropriate way for embedded loops.
848.SH "OTHER FUNCTIONS" 1372.SH "OTHER FUNCTIONS"
849.IX Header "OTHER FUNCTIONS" 1373.IX Header "OTHER FUNCTIONS"
850There are some other functions of possible interest. Described. Here. Now. 1374There are some other functions of possible interest. Described. Here. Now.
851.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1375.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
852.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1376.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
881.Ve 1405.Ve
882.Sp 1406.Sp
883.Vb 1 1407.Vb 1
884\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1408\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
885.Ve 1409.Ve
886.IP "ev_feed_event (loop, watcher, int events)" 4 1410.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
887.IX Item "ev_feed_event (loop, watcher, int events)" 1411.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
888Feeds the given event set into the event loop, as if the specified event 1412Feeds the given event set into the event loop, as if the specified event
889had happened for the specified watcher (which must be a pointer to an 1413had happened for the specified watcher (which must be a pointer to an
890initialised but not necessarily started event watcher). 1414initialised but not necessarily started event watcher).
891.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1415.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
892.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1416.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
893Feed an event on the given fd, as if a file descriptor backend detected 1417Feed an event on the given fd, as if a file descriptor backend detected
894the given events it. 1418the given events it.
895.IP "ev_feed_signal_event (loop, int signum)" 4 1419.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
896.IX Item "ev_feed_signal_event (loop, int signum)" 1420.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
897Feed an event as if the given signal occured (loop must be the default loop!). 1421Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1422loop!).
898.SH "LIBEVENT EMULATION" 1423.SH "LIBEVENT EMULATION"
899.IX Header "LIBEVENT EMULATION" 1424.IX Header "LIBEVENT EMULATION"
900Libev offers a compatibility emulation layer for libevent. It cannot 1425Libev offers a compatibility emulation layer for libevent. It cannot
901emulate the internals of libevent, so here are some usage hints: 1426emulate the internals of libevent, so here are some usage hints:
902.IP "* Use it by including <event.h>, as usual." 4 1427.IP "* Use it by including <event.h>, as usual." 4
… …
913.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 1438.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
914.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 1439.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
915.PD 1440.PD
916.SH "\*(C+ SUPPORT" 1441.SH "\*(C+ SUPPORT"
917.IX Header " SUPPORT" 1442.IX Header " SUPPORT"
918\&\s-1TBD\s0. 1443Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
1444you to use some convinience methods to start/stop watchers and also change
1445the callback model to a model using method callbacks on objects.
1446.PP
1447To use it,
1448.PP
1449.Vb 1
1450\& #include <ev++.h>
1451.Ve
1452.PP
1453(it is not installed by default). This automatically includes \fIev.h\fR
1454and puts all of its definitions (many of them macros) into the global
1455namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace.
1456.PP
1457It should support all the same embedding options as \fIev.h\fR, most notably
1458\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
1459.PP
1460Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
1461.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
1462.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
1463.IX Item "ev::READ, ev::WRITE etc."
1464These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
1465macros from \fIev.h\fR.
1466.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
1467.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
1468.IX Item "ev::tstamp, ev::now"
1469Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
1470.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
1471.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
1472.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
1473For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
1474the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
1475which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
1476defines by many implementations.
1477.Sp
1478All of those classes have these methods:
1479.RS 4
1480.IP "ev::TYPE::TYPE (object *, object::method *)" 4
1481.IX Item "ev::TYPE::TYPE (object *, object::method *)"
1482.PD 0
1483.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4
1484.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)"
1485.IP "ev::TYPE::~TYPE" 4
1486.IX Item "ev::TYPE::~TYPE"
1487.PD
1488The constructor takes a pointer to an object and a method pointer to
1489the event handler callback to call in this class. The constructor calls
1490\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method
1491before starting it. If you do not specify a loop then the constructor
1492automatically associates the default loop with this watcher.
1493.Sp
1494The destructor automatically stops the watcher if it is active.
1495.IP "w\->set (struct ev_loop *)" 4
1496.IX Item "w->set (struct ev_loop *)"
1497Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
1498do this when the watcher is inactive (and not pending either).
1499.IP "w\->set ([args])" 4
1500.IX Item "w->set ([args])"
1501Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
1502called at least once. Unlike the C counterpart, an active watcher gets
1503automatically stopped and restarted.
1504.IP "w\->start ()" 4
1505.IX Item "w->start ()"
1506Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the
1507constructor already takes the loop.
1508.IP "w\->stop ()" 4
1509.IX Item "w->stop ()"
1510Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
1511.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
1512.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
1513.IX Item "w->again () ev::timer, ev::periodic only"
1514For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
1515\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
1516.ie n .IP "w\->sweep () ""ev::embed"" only" 4
1517.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
1518.IX Item "w->sweep () ev::embed only"
1519Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
1520.RE
1521.RS 4
1522.RE
1523.PP
1524Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
1525the constructor.
1526.PP
1527.Vb 4
1528\& class myclass
1529\& {
1530\& ev_io io; void io_cb (ev::io &w, int revents);
1531\& ev_idle idle void idle_cb (ev::idle &w, int revents);
1532.Ve
1533.PP
1534.Vb 2
1535\& myclass ();
1536\& }
1537.Ve
1538.PP
1539.Vb 6
1540\& myclass::myclass (int fd)
1541\& : io (this, &myclass::io_cb),
1542\& idle (this, &myclass::idle_cb)
1543\& {
1544\& io.start (fd, ev::READ);
1545\& }
1546.Ve
1547.SH "EMBEDDING"
1548.IX Header "EMBEDDING"
1549Libev can (and often is) directly embedded into host
1550applications. Examples of applications that embed it include the Deliantra
1551Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
1552and rxvt\-unicode.
1553.PP
1554The goal is to enable you to just copy the neecssary files into your
1555source directory without having to change even a single line in them, so
1556you can easily upgrade by simply copying (or having a checked-out copy of
1557libev somewhere in your source tree).
1558.Sh "\s-1FILESETS\s0"
1559.IX Subsection "FILESETS"
1560Depending on what features you need you need to include one or more sets of files
1561in your app.
1562.PP
1563\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
1564.IX Subsection "CORE EVENT LOOP"
1565.PP
1566To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
1567configuration (no autoconf):
1568.PP
1569.Vb 2
1570\& #define EV_STANDALONE 1
1571\& #include "ev.c"
1572.Ve
1573.PP
1574This will automatically include \fIev.h\fR, too, and should be done in a
1575single C source file only to provide the function implementations. To use
1576it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
1577done by writing a wrapper around \fIev.h\fR that you can include instead and
1578where you can put other configuration options):
1579.PP
1580.Vb 2
1581\& #define EV_STANDALONE 1
1582\& #include "ev.h"
1583.Ve
1584.PP
1585Both header files and implementation files can be compiled with a \*(C+
1586compiler (at least, thats a stated goal, and breakage will be treated
1587as a bug).
1588.PP
1589You need the following files in your source tree, or in a directory
1590in your include path (e.g. in libev/ when using \-Ilibev):
1591.PP
1592.Vb 4
1593\& ev.h
1594\& ev.c
1595\& ev_vars.h
1596\& ev_wrap.h
1597.Ve
1598.PP
1599.Vb 1
1600\& ev_win32.c required on win32 platforms only
1601.Ve
1602.PP
1603.Vb 5
1604\& ev_select.c only when select backend is enabled (which is by default)
1605\& ev_poll.c only when poll backend is enabled (disabled by default)
1606\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
1607\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
1608\& ev_port.c only when the solaris port backend is enabled (disabled by default)
1609.Ve
1610.PP
1611\&\fIev.c\fR includes the backend files directly when enabled, so you only need
1612to compile this single file.
1613.PP
1614\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
1615.IX Subsection "LIBEVENT COMPATIBILITY API"
1616.PP
1617To include the libevent compatibility \s-1API\s0, also include:
1618.PP
1619.Vb 1
1620\& #include "event.c"
1621.Ve
1622.PP
1623in the file including \fIev.c\fR, and:
1624.PP
1625.Vb 1
1626\& #include "event.h"
1627.Ve
1628.PP
1629in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
1630.PP
1631You need the following additional files for this:
1632.PP
1633.Vb 2
1634\& event.h
1635\& event.c
1636.Ve
1637.PP
1638\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
1639.IX Subsection "AUTOCONF SUPPORT"
1640.PP
1641Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
1642whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
1643\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
1644include \fIconfig.h\fR and configure itself accordingly.
1645.PP
1646For this of course you need the m4 file:
1647.PP
1648.Vb 1
1649\& libev.m4
1650.Ve
1651.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
1652.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
1653Libev can be configured via a variety of preprocessor symbols you have to define
1654before including any of its files. The default is not to build for multiplicity
1655and only include the select backend.
1656.IP "\s-1EV_STANDALONE\s0" 4
1657.IX Item "EV_STANDALONE"
1658Must always be \f(CW1\fR if you do not use autoconf configuration, which
1659keeps libev from including \fIconfig.h\fR, and it also defines dummy
1660implementations for some libevent functions (such as logging, which is not
1661supported). It will also not define any of the structs usually found in
1662\&\fIevent.h\fR that are not directly supported by the libev core alone.
1663.IP "\s-1EV_USE_MONOTONIC\s0" 4
1664.IX Item "EV_USE_MONOTONIC"
1665If defined to be \f(CW1\fR, libev will try to detect the availability of the
1666monotonic clock option at both compiletime and runtime. Otherwise no use
1667of the monotonic clock option will be attempted. If you enable this, you
1668usually have to link against librt or something similar. Enabling it when
1669the functionality isn't available is safe, though, althoguh you have
1670to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
1671function is hiding in (often \fI\-lrt\fR).
1672.IP "\s-1EV_USE_REALTIME\s0" 4
1673.IX Item "EV_USE_REALTIME"
1674If defined to be \f(CW1\fR, libev will try to detect the availability of the
1675realtime clock option at compiletime (and assume its availability at
1676runtime if successful). Otherwise no use of the realtime clock option will
1677be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
1678(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
1679in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
1680.IP "\s-1EV_USE_SELECT\s0" 4
1681.IX Item "EV_USE_SELECT"
1682If undefined or defined to be \f(CW1\fR, libev will compile in support for the
1683\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
1684other method takes over, select will be it. Otherwise the select backend
1685will not be compiled in.
1686.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
1687.IX Item "EV_SELECT_USE_FD_SET"
1688If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
1689structure. This is useful if libev doesn't compile due to a missing
1690\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
1691exotic systems. This usually limits the range of file descriptors to some
1692low limit such as 1024 or might have other limitations (winsocket only
1693allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
1694influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
1695.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
1696.IX Item "EV_SELECT_IS_WINSOCKET"
1697When defined to \f(CW1\fR, the select backend will assume that
1698select/socket/connect etc. don't understand file descriptors but
1699wants osf handles on win32 (this is the case when the select to
1700be used is the winsock select). This means that it will call
1701\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
1702it is assumed that all these functions actually work on fds, even
1703on win32. Should not be defined on non\-win32 platforms.
1704.IP "\s-1EV_USE_POLL\s0" 4
1705.IX Item "EV_USE_POLL"
1706If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
1707backend. Otherwise it will be enabled on non\-win32 platforms. It
1708takes precedence over select.
1709.IP "\s-1EV_USE_EPOLL\s0" 4
1710.IX Item "EV_USE_EPOLL"
1711If defined to be \f(CW1\fR, libev will compile in support for the Linux
1712\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
1713otherwise another method will be used as fallback. This is the
1714preferred backend for GNU/Linux systems.
1715.IP "\s-1EV_USE_KQUEUE\s0" 4
1716.IX Item "EV_USE_KQUEUE"
1717If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
1718\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
1719otherwise another method will be used as fallback. This is the preferred
1720backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
1721supports some types of fds correctly (the only platform we found that
1722supports ptys for example was NetBSD), so kqueue might be compiled in, but
1723not be used unless explicitly requested. The best way to use it is to find
1724out whether kqueue supports your type of fd properly and use an embedded
1725kqueue loop.
1726.IP "\s-1EV_USE_PORT\s0" 4
1727.IX Item "EV_USE_PORT"
1728If defined to be \f(CW1\fR, libev will compile in support for the Solaris
172910 port style backend. Its availability will be detected at runtime,
1730otherwise another method will be used as fallback. This is the preferred
1731backend for Solaris 10 systems.
1732.IP "\s-1EV_USE_DEVPOLL\s0" 4
1733.IX Item "EV_USE_DEVPOLL"
1734reserved for future expansion, works like the \s-1USE\s0 symbols above.
1735.IP "\s-1EV_H\s0" 4
1736.IX Item "EV_H"
1737The name of the \fIev.h\fR header file used to include it. The default if
1738undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
1739can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
1740.IP "\s-1EV_CONFIG_H\s0" 4
1741.IX Item "EV_CONFIG_H"
1742If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
1743\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
1744\&\f(CW\*(C`EV_H\*(C'\fR, above.
1745.IP "\s-1EV_EVENT_H\s0" 4
1746.IX Item "EV_EVENT_H"
1747Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
1748of how the \fIevent.h\fR header can be found.
1749.IP "\s-1EV_PROTOTYPES\s0" 4
1750.IX Item "EV_PROTOTYPES"
1751If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
1752prototypes, but still define all the structs and other symbols. This is
1753occasionally useful if you want to provide your own wrapper functions
1754around libev functions.
1755.IP "\s-1EV_MULTIPLICITY\s0" 4
1756.IX Item "EV_MULTIPLICITY"
1757If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
1758will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
1759additional independent event loops. Otherwise there will be no support
1760for multiple event loops and there is no first event loop pointer
1761argument. Instead, all functions act on the single default loop.
1762.IP "\s-1EV_PERIODICS\s0" 4
1763.IX Item "EV_PERIODICS"
1764If undefined or defined to be \f(CW1\fR, then periodic timers are supported,
1765otherwise not. This saves a few kb of code.
1766.IP "\s-1EV_COMMON\s0" 4
1767.IX Item "EV_COMMON"
1768By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
1769this macro to a something else you can include more and other types of
1770members. You have to define it each time you include one of the files,
1771though, and it must be identical each time.
1772.Sp
1773For example, the perl \s-1EV\s0 module uses something like this:
1774.Sp
1775.Vb 3
1776\& #define EV_COMMON \e
1777\& SV *self; /* contains this struct */ \e
1778\& SV *cb_sv, *fh /* note no trailing ";" */
1779.Ve
1780.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
1781.IX Item "EV_CB_DECLARE (type)"
1782.PD 0
1783.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
1784.IX Item "EV_CB_INVOKE (watcher, revents)"
1785.IP "ev_set_cb (ev, cb)" 4
1786.IX Item "ev_set_cb (ev, cb)"
1787.PD
1788Can be used to change the callback member declaration in each watcher,
1789and the way callbacks are invoked and set. Must expand to a struct member
1790definition and a statement, respectively. See the \fIev.v\fR header file for
1791their default definitions. One possible use for overriding these is to
1792avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
1793method calls instead of plain function calls in \*(C+.
1794.Sh "\s-1EXAMPLES\s0"
1795.IX Subsection "EXAMPLES"
1796For a real-world example of a program the includes libev
1797verbatim, you can have a look at the \s-1EV\s0 perl module
1798(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
1799the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
1800interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
1801will be compiled. It is pretty complex because it provides its own header
1802file.
1803.Sp
1804The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
1805that everybody includes and which overrides some autoconf choices:
1806.Sp
1807.Vb 4
1808\& #define EV_USE_POLL 0
1809\& #define EV_MULTIPLICITY 0
1810\& #define EV_PERIODICS 0
1811\& #define EV_CONFIG_H <config.h>
1812.Ve
1813.Sp
1814.Vb 1
1815\& #include "ev++.h"
1816.Ve
1817.Sp
1818And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
1819.Sp
1820.Vb 2
1821\& #include "ev_cpp.h"
1822\& #include "ev.c"
1823.Ve
919.SH "AUTHOR" 1824.SH "AUTHOR"
920.IX Header "AUTHOR" 1825.IX Header "AUTHOR"
921Marc Lehmann <libev@schmorp.de>. 1826Marc Lehmann <libev@schmorp.de>.

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