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127.\} 127.\}
128.rm #[ #] #H #V #F C 128.rm #[ #] #H #V #F C
129.\" ======================================================================== 129.\" ========================================================================
130.\" 130.\"
131.IX Title ""<STANDARD INPUT>" 1" 131.IX Title ""<STANDARD INPUT>" 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-23" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH "<STANDARD INPUT>" 1 "2007-12-08" "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
138\& #include <ev.h> 138\& #include <ev.h>
139.Ve 139.Ve
140.SH "EXAMPLE PROGRAM"
141.IX Header "EXAMPLE PROGRAM"
142.Vb 1
143\& #include <ev.h>
144.Ve
145.PP
146.Vb 2
147\& ev_io stdin_watcher;
148\& ev_timer timeout_watcher;
149.Ve
150.PP
151.Vb 8
152\& /* called when data readable on stdin */
153\& static void
154\& stdin_cb (EV_P_ struct ev_io *w, int revents)
155\& {
156\& /* puts ("stdin ready"); */
157\& ev_io_stop (EV_A_ w); /* just a syntax example */
158\& ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */
159\& }
160.Ve
161.PP
162.Vb 6
163\& static void
164\& timeout_cb (EV_P_ struct ev_timer *w, int revents)
165\& {
166\& /* puts ("timeout"); */
167\& ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */
168\& }
169.Ve
170.PP
171.Vb 4
172\& int
173\& main (void)
174\& {
175\& struct ev_loop *loop = ev_default_loop (0);
176.Ve
177.PP
178.Vb 3
179\& /* initialise an io watcher, then start it */
180\& ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ);
181\& ev_io_start (loop, &stdin_watcher);
182.Ve
183.PP
184.Vb 3
185\& /* simple non-repeating 5.5 second timeout */
186\& ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.);
187\& ev_timer_start (loop, &timeout_watcher);
188.Ve
189.PP
190.Vb 2
191\& /* loop till timeout or data ready */
192\& ev_loop (loop, 0);
193.Ve
194.PP
195.Vb 2
196\& return 0;
197\& }
198.Ve
140.SH "DESCRIPTION" 199.SH "DESCRIPTION"
141.IX Header "DESCRIPTION" 200.IX Header "DESCRIPTION"
201The newest version of this document is also available as a html-formatted
202web page you might find easier to navigate when reading it for the first
203time: <http://cvs.schmorp.de/libev/ev.html>.
204.PP
142Libev is an event loop: you register interest in certain events (such as a 205Libev is an event loop: you register interest in certain events (such as a
143file descriptor being readable or a timeout occuring), and it will manage 206file descriptor being readable or a timeout occuring), and it will manage
144these event sources and provide your program with events. 207these event sources and provide your program with events.
145.PP 208.PP
146To do this, it must take more or less complete control over your process 209To do this, it must take more or less complete control over your process
… …
151watchers\fR, which are relatively small C structures you initialise with the 214watchers\fR, which are relatively small C structures you initialise with the
152details of the event, and then hand it over to libev by \fIstarting\fR the 215details of the event, and then hand it over to libev by \fIstarting\fR the
153watcher. 216watcher.
154.SH "FEATURES" 217.SH "FEATURES"
155.IX Header "FEATURES" 218.IX Header "FEATURES"
156Libev supports select, poll, the linux-specific epoll and the bsd-specific 219Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the
157kqueue mechanisms for file descriptor events, relative timers, absolute 220BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms
158timers with customised rescheduling, signal events, process status change 221for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface
159events (related to \s-1SIGCHLD\s0), and event watchers dealing with the event 222(for \f(CW\*(C`ev_stat\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers
160loop mechanism itself (idle, prepare and check watchers). It also is quite 223with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals
161fast (see this benchmark comparing 224(\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and event
162it to libevent for example). 225watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR,
226\&\f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR watchers) as well as
227file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events
228(\f(CW\*(C`ev_fork\*(C'\fR).
229.PP
230It also is quite fast (see this
231benchmark comparing it to libevent
232for example).
163.SH "CONVENTIONS" 233.SH "CONVENTIONS"
164.IX Header "CONVENTIONS" 234.IX Header "CONVENTIONS"
165Libev is very configurable. In this manual the default configuration 235Libev is very configurable. In this manual the default configuration will
166will be described, which supports multiple event loops. For more info 236be described, which supports multiple event loops. For more info about
167about various configuration options please have a look at the file 237various configuration options please have a look at \fB\s-1EMBED\s0\fR section in
168\&\fI\s-1README\s0.embed\fR in the libev distribution. If libev was configured without 238this manual. If libev was configured without support for multiple event
169support for multiple event loops, then all functions taking an initial 239loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR
170argument of name \f(CW\*(C`loop\*(C'\fR (which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) 240(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument.
171will not have this argument.
172.SH "TIME REPRESENTATION" 241.SH "TIME REPRESENTATION"
173.IX Header "TIME REPRESENTATION" 242.IX Header "TIME REPRESENTATION"
174Libev represents time as a single floating point number, representing the 243Libev represents time as a single floating point number, representing the
175(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near 244(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near
176the beginning of 1970, details are complicated, don't ask). This type is 245the beginning of 1970, details are complicated, don't ask). This type is
177called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases 246called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases
178to the double type in C. 247to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
248it, you should treat it as such.
179.SH "GLOBAL FUNCTIONS" 249.SH "GLOBAL FUNCTIONS"
180.IX Header "GLOBAL FUNCTIONS" 250.IX Header "GLOBAL FUNCTIONS"
181These functions can be called anytime, even before initialising the 251These functions can be called anytime, even before initialising the
182library in any way. 252library in any way.
183.IP "ev_tstamp ev_time ()" 4 253.IP "ev_tstamp ev_time ()" 4
… …
199.Sp 269.Sp
200Usually, it's a good idea to terminate if the major versions mismatch, 270Usually, it's a good idea to terminate if the major versions mismatch,
201as this indicates an incompatible change. Minor versions are usually 271as this indicates an incompatible change. Minor versions are usually
202compatible to older versions, so a larger minor version alone is usually 272compatible to older versions, so a larger minor version alone is usually
203not a problem. 273not a problem.
274.Sp
275Example: Make sure we haven't accidentally been linked against the wrong
276version.
277.Sp
278.Vb 3
279\& assert (("libev version mismatch",
280\& ev_version_major () == EV_VERSION_MAJOR
281\& && ev_version_minor () >= EV_VERSION_MINOR));
282.Ve
204.IP "unsigned int ev_supported_backends ()" 4 283.IP "unsigned int ev_supported_backends ()" 4
205.IX Item "unsigned int ev_supported_backends ()" 284.IX Item "unsigned int ev_supported_backends ()"
206Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR 285Return 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 286value) 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 287availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for
209a description of the set values. 288a description of the set values.
289.Sp
290Example: make sure we have the epoll method, because yeah this is cool and
291a must have and can we have a torrent of it please!!!11
292.Sp
293.Vb 2
294\& assert (("sorry, no epoll, no sex",
295\& ev_supported_backends () & EVBACKEND_EPOLL));
296.Ve
210.IP "unsigned int ev_recommended_backends ()" 4 297.IP "unsigned int ev_recommended_backends ()" 4
211.IX Item "unsigned int ev_recommended_backends ()" 298.IX Item "unsigned int ev_recommended_backends ()"
212Return the set of all backends compiled into this binary of libev and also 299Return 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 300recommended 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 301returned 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 302most 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 303(assuming you know what you are doing). This is the set of backends that
217libev will probe for if you specify no backends explicitly. 304libev will probe for if you specify no backends explicitly.
305.IP "unsigned int ev_embeddable_backends ()" 4
306.IX Item "unsigned int ev_embeddable_backends ()"
307Returns the set of backends that are embeddable in other event loops. This
308is the theoretical, all\-platform, value. To find which backends
309might be supported on the current system, you would need to look at
310\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for
311recommended ones.
312.Sp
313See 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))" 4 314.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
219.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 315.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
220Sets the allocation function to use (the prototype is similar to the 316Sets the allocation function to use (the prototype is similar \- the
221realloc C function, the semantics are identical). It is used to allocate 317semantics is identical \- to the realloc C function). It is used to
222and free memory (no surprises here). If it returns zero when memory 318allocate and free memory (no surprises here). If it returns zero when
223needs to be allocated, the library might abort or take some potentially 319memory needs to be allocated, the library might abort or take some
224destructive action. The default is your system realloc function. 320potentially destructive action. The default is your system realloc
321function.
225.Sp 322.Sp
226You could override this function in high-availability programs to, say, 323You could override this function in high-availability programs to, say,
227free some memory if it cannot allocate memory, to use a special allocator, 324free 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. 325or even to sleep a while and retry until some memory is available.
326.Sp
327Example: Replace the libev allocator with one that waits a bit and then
328retries).
329.Sp
330.Vb 6
331\& static void *
332\& persistent_realloc (void *ptr, size_t size)
333\& {
334\& for (;;)
335\& {
336\& void *newptr = realloc (ptr, size);
337.Ve
338.Sp
339.Vb 2
340\& if (newptr)
341\& return newptr;
342.Ve
343.Sp
344.Vb 3
345\& sleep (60);
346\& }
347\& }
348.Ve
349.Sp
350.Vb 2
351\& ...
352\& ev_set_allocator (persistent_realloc);
353.Ve
229.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 354.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4
230.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" 355.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));"
231Set the callback function to call on a retryable syscall error (such 356Set the callback function to call on a retryable syscall error (such
232as failed select, poll, epoll_wait). The message is a printable string 357as failed select, poll, epoll_wait). The message is a printable string
233indicating the system call or subsystem causing the problem. If this 358indicating the system call or subsystem causing the problem. If this
234callback is set, then libev will expect it to remedy the sitution, no 359callback is set, then libev will expect it to remedy the sitution, no
235matter what, when it returns. That is, libev will generally retry the 360matter what, when it returns. That is, libev will generally retry the
236requested operation, or, if the condition doesn't go away, do bad stuff 361requested operation, or, if the condition doesn't go away, do bad stuff
237(such as abort). 362(such as abort).
363.Sp
364Example: This is basically the same thing that libev does internally, too.
365.Sp
366.Vb 6
367\& static void
368\& fatal_error (const char *msg)
369\& {
370\& perror (msg);
371\& abort ();
372\& }
373.Ve
374.Sp
375.Vb 2
376\& ...
377\& ev_set_syserr_cb (fatal_error);
378.Ve
238.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" 379.SH "FUNCTIONS CONTROLLING THE EVENT LOOP"
239.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" 380.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 381An 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 382types of such loops, the \fIdefault\fR loop, which supports signals and child
242events, and dynamically created loops which do not. 383events, and dynamically created loops which do not.
… …
274or setgid) then libev will \fInot\fR look at the environment variable 415or setgid) then libev will \fInot\fR look at the environment variable
275\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 416\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
276override the flags completely if it is found in the environment. This is 417override the flags completely if it is found in the environment. This is
277useful to try out specific backends to test their performance, or to work 418useful to try out specific backends to test their performance, or to work
278around bugs. 419around bugs.
420.ie n .IP """EVFLAG_FORKCHECK""" 4
421.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
422.IX Item "EVFLAG_FORKCHECK"
423Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
424a fork, you can also make libev check for a fork in each iteration by
425enabling this flag.
426.Sp
427This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
428and thus this might slow down your event loop if you do a lot of loop
429iterations and little real work, but is usually not noticeable (on my
430Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
431without a syscall and thus \fIvery\fR fast, but my Linux system also has
432\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
433.Sp
434The big advantage of this flag is that you can forget about fork (and
435forget about forgetting to tell libev about forking) when you use this
436flag.
437.Sp
438This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
439environment variable.
279.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 440.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
280.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 441.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
281.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 442.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
282This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 443This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
283libev tries to roll its own fd_set with no limits on the number of fds, 444libev tries to roll its own fd_set with no limits on the number of fds,
… …
376.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" 537.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)"
377Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 538Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
378always distinct from the default loop. Unlike the default loop, it cannot 539always distinct from the default loop. Unlike the default loop, it cannot
379handle signal and child watchers, and attempts to do so will be greeted by 540handle signal and child watchers, and attempts to do so will be greeted by
380undefined behaviour (or a failed assertion if assertions are enabled). 541undefined behaviour (or a failed assertion if assertions are enabled).
542.Sp
543Example: Try to create a event loop that uses epoll and nothing else.
544.Sp
545.Vb 3
546\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
547\& if (!epoller)
548\& fatal ("no epoll found here, maybe it hides under your chair");
549.Ve
381.IP "ev_default_destroy ()" 4 550.IP "ev_default_destroy ()" 4
382.IX Item "ev_default_destroy ()" 551.IX Item "ev_default_destroy ()"
383Destroys the default loop again (frees all memory and kernel state 552Destroys the default loop again (frees all memory and kernel state
384etc.). This stops all registered event watchers (by not touching them in 553etc.). None of the active event watchers will be stopped in the normal
385any way whatsoever, although you cannot rely on this :). 554sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
555responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
556calling this function, or cope with the fact afterwards (which is usually
557the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
558for example).
386.IP "ev_loop_destroy (loop)" 4 559.IP "ev_loop_destroy (loop)" 4
387.IX Item "ev_loop_destroy (loop)" 560.IX Item "ev_loop_destroy (loop)"
388Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 561Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
389earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 562earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
390.IP "ev_default_fork ()" 4 563.IP "ev_default_fork ()" 4
… …
412.IP "ev_loop_fork (loop)" 4 585.IP "ev_loop_fork (loop)" 4
413.IX Item "ev_loop_fork (loop)" 586.IX Item "ev_loop_fork (loop)"
414Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 587Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
415\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 588\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
416after fork, and how you do this is entirely your own problem. 589after fork, and how you do this is entirely your own problem.
590.IP "unsigned int ev_loop_count (loop)" 4
591.IX Item "unsigned int ev_loop_count (loop)"
592Returns the count of loop iterations for the loop, which is identical to
593the number of times libev did poll for new events. It starts at \f(CW0\fR and
594happily wraps around with enough iterations.
595.Sp
596This value can sometimes be useful as a generation counter of sorts (it
597\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
598\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
417.IP "unsigned int ev_backend (loop)" 4 599.IP "unsigned int ev_backend (loop)" 4
418.IX Item "unsigned int ev_backend (loop)" 600.IX Item "unsigned int ev_backend (loop)"
419Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 601Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
420use. 602use.
421.IP "ev_tstamp ev_now (loop)" 4 603.IP "ev_tstamp ev_now (loop)" 4
422.IX Item "ev_tstamp ev_now (loop)" 604.IX Item "ev_tstamp ev_now (loop)"
423Returns the current \*(L"event loop time\*(R", which is the time the event loop 605Returns the current \*(L"event loop time\*(R", which is the time the event loop
424got events and started processing them. This timestamp does not change 606received events and started processing them. This timestamp does not
425as long as callbacks are being processed, and this is also the base time 607change as long as callbacks are being processed, and this is also the base
426used for relative timers. You can treat it as the timestamp of the event 608time used for relative timers. You can treat it as the timestamp of the
427occuring (or more correctly, the mainloop finding out about it). 609event occuring (or more correctly, libev finding out about it).
428.IP "ev_loop (loop, int flags)" 4 610.IP "ev_loop (loop, int flags)" 4
429.IX Item "ev_loop (loop, int flags)" 611.IX Item "ev_loop (loop, int flags)"
430Finally, this is it, the event handler. This function usually is called 612Finally, this is it, the event handler. This function usually is called
431after you initialised all your watchers and you want to start handling 613after you initialised all your watchers and you want to start handling
432events. 614events.
433.Sp 615.Sp
434If the flags argument is specified as \f(CW0\fR, it will not return until 616If the flags argument is specified as \f(CW0\fR, it will not return until
435either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. 617either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called.
618.Sp
619Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than
620relying on all watchers to be stopped when deciding when a program has
621finished (especially in interactive programs), but having a program that
622automatically loops as long as it has to and no longer by virtue of
623relying on its watchers stopping correctly is a thing of beauty.
436.Sp 624.Sp
437A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle 625A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle
438those events and any outstanding ones, but will not block your process in 626those events and any outstanding ones, but will not block your process in
439case there are no events and will return after one iteration of the loop. 627case there are no events and will return after one iteration of the loop.
440.Sp 628.Sp
… …
446libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 634libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
447usually a better approach for this kind of thing. 635usually a better approach for this kind of thing.
448.Sp 636.Sp
449Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 637Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
450.Sp 638.Sp
451.Vb 18 639.Vb 19
640\& - Before the first iteration, call any pending watchers.
452\& * If there are no active watchers (reference count is zero), return. 641\& * If there are no active watchers (reference count is zero), return.
453\& - Queue prepare watchers and then call all outstanding watchers. 642\& - Queue all prepare watchers and then call all outstanding watchers.
454\& - If we have been forked, recreate the kernel state. 643\& - If we have been forked, recreate the kernel state.
455\& - Update the kernel state with all outstanding changes. 644\& - Update the kernel state with all outstanding changes.
456\& - Update the "event loop time". 645\& - Update the "event loop time".
457\& - Calculate for how long to block. 646\& - Calculate for how long to block.
458\& - Block the process, waiting for any events. 647\& - Block the process, waiting for any events.
… …
465\& - Call all queued watchers in reverse order (i.e. check watchers first). 654\& - Call all queued watchers in reverse order (i.e. check watchers first).
466\& Signals and child watchers are implemented as I/O watchers, and will 655\& Signals and child watchers are implemented as I/O watchers, and will
467\& be handled here by queueing them when their watcher gets executed. 656\& be handled here by queueing them when their watcher gets executed.
468\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 657\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
469\& were used, return, otherwise continue with step *. 658\& were used, return, otherwise continue with step *.
659.Ve
660.Sp
661Example: Queue some jobs and then loop until no events are outsanding
662anymore.
663.Sp
664.Vb 4
665\& ... queue jobs here, make sure they register event watchers as long
666\& ... as they still have work to do (even an idle watcher will do..)
667\& ev_loop (my_loop, 0);
668\& ... jobs done. yeah!
470.Ve 669.Ve
471.IP "ev_unloop (loop, how)" 4 670.IP "ev_unloop (loop, how)" 4
472.IX Item "ev_unloop (loop, how)" 671.IX Item "ev_unloop (loop, how)"
473Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it 672Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it
474has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either 673has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either
… …
488example, libev itself uses this for its internal signal pipe: It is not 687example, libev itself uses this for its internal signal pipe: It is not
489visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 688visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
490no event watchers registered by it are active. It is also an excellent 689no event watchers registered by it are active. It is also an excellent
491way to do this for generic recurring timers or from within third-party 690way to do this for generic recurring timers or from within third-party
492libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 691libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
692.Sp
693Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
694running when nothing else is active.
695.Sp
696.Vb 4
697\& struct ev_signal exitsig;
698\& ev_signal_init (&exitsig, sig_cb, SIGINT);
699\& ev_signal_start (loop, &exitsig);
700\& evf_unref (loop);
701.Ve
702.Sp
703Example: For some weird reason, unregister the above signal handler again.
704.Sp
705.Vb 2
706\& ev_ref (loop);
707\& ev_signal_stop (loop, &exitsig);
708.Ve
493.SH "ANATOMY OF A WATCHER" 709.SH "ANATOMY OF A WATCHER"
494.IX Header "ANATOMY OF A WATCHER" 710.IX Header "ANATOMY OF A WATCHER"
495A watcher is a structure that you create and register to record your 711A watcher is a structure that you create and register to record your
496interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 712interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
497become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: 713become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that:
… …
533*)\*(C'\fR), and you can stop watching for events at any time by calling the 749*)\*(C'\fR), and you can stop watching for events at any time by calling the
534corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. 750corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR.
535.PP 751.PP
536As long as your watcher is active (has been started but not stopped) you 752As long as your watcher is active (has been started but not stopped) you
537must not touch the values stored in it. Most specifically you must never 753must not touch the values stored in it. Most specifically you must never
538reinitialise it or call its set macro. 754reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro.
539.PP
540You can check whether an event is active by calling the \f(CW\*(C`ev_is_active
541(watcher *)\*(C'\fR macro. To see whether an event is outstanding (but the
542callback for it has not been called yet) you can use the \f(CW\*(C`ev_is_pending
543(watcher *)\*(C'\fR macro.
544.PP 755.PP
545Each and every callback receives the event loop pointer as first, the 756Each and every callback receives the event loop pointer as first, the
546registered watcher structure as second, and a bitset of received events as 757registered watcher structure as second, and a bitset of received events as
547third argument. 758third argument.
548.PP 759.PP
… …
573The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 784The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
574.ie n .IP """EV_CHILD""" 4 785.ie n .IP """EV_CHILD""" 4
575.el .IP "\f(CWEV_CHILD\fR" 4 786.el .IP "\f(CWEV_CHILD\fR" 4
576.IX Item "EV_CHILD" 787.IX Item "EV_CHILD"
577The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 788The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
789.ie n .IP """EV_STAT""" 4
790.el .IP "\f(CWEV_STAT\fR" 4
791.IX Item "EV_STAT"
792The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
578.ie n .IP """EV_IDLE""" 4 793.ie n .IP """EV_IDLE""" 4
579.el .IP "\f(CWEV_IDLE\fR" 4 794.el .IP "\f(CWEV_IDLE\fR" 4
580.IX Item "EV_IDLE" 795.IX Item "EV_IDLE"
581The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 796The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
582.ie n .IP """EV_PREPARE""" 4 797.ie n .IP """EV_PREPARE""" 4
… …
592\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 807\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
593received events. Callbacks of both watcher types can start and stop as 808received events. Callbacks of both watcher types can start and stop as
594many watchers as they want, and all of them will be taken into account 809many watchers as they want, and all of them will be taken into account
595(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 810(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
596\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 811\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
812.ie n .IP """EV_EMBED""" 4
813.el .IP "\f(CWEV_EMBED\fR" 4
814.IX Item "EV_EMBED"
815The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
816.ie n .IP """EV_FORK""" 4
817.el .IP "\f(CWEV_FORK\fR" 4
818.IX Item "EV_FORK"
819The event loop has been resumed in the child process after fork (see
820\&\f(CW\*(C`ev_fork\*(C'\fR).
597.ie n .IP """EV_ERROR""" 4 821.ie n .IP """EV_ERROR""" 4
598.el .IP "\f(CWEV_ERROR\fR" 4 822.el .IP "\f(CWEV_ERROR\fR" 4
599.IX Item "EV_ERROR" 823.IX Item "EV_ERROR"
600An unspecified error has occured, the watcher has been stopped. This might 824An unspecified error has occured, the watcher has been stopped. This might
601happen because the watcher could not be properly started because libev 825happen because the watcher could not be properly started because libev
… …
606Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 830Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
607for example it might indicate that a fd is readable or writable, and if 831for example it might indicate that a fd is readable or writable, and if
608your callbacks is well-written it can just attempt the operation and cope 832your callbacks is well-written it can just attempt the operation and cope
609with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 833with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
610programs, though, so beware. 834programs, though, so beware.
835.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
836.IX Subsection "GENERIC WATCHER FUNCTIONS"
837In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
838e.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.
839.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
840.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
841.IX Item "ev_init (ev_TYPE *watcher, callback)"
842This macro initialises the generic portion of a watcher. The contents
843of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only
844the generic parts of the watcher are initialised, you \fIneed\fR to call
845the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the
846type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro
847which rolls both calls into one.
848.Sp
849You can reinitialise a watcher at any time as long as it has been stopped
850(or never started) and there are no pending events outstanding.
851.Sp
852The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
853int revents)\*(C'\fR.
854.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
855.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
856.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
857This macro initialises the type-specific parts of a watcher. You need to
858call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can
859call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this
860macro on a watcher that is active (it can be pending, however, which is a
861difference to the \f(CW\*(C`ev_init\*(C'\fR macro).
862.Sp
863Although some watcher types do not have type-specific arguments
864(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro.
865.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4
866.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4
867.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])"
868This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro
869calls into a single call. This is the most convinient method to initialise
870a watcher. The same limitations apply, of course.
871.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4
872.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4
873.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)"
874Starts (activates) the given watcher. Only active watchers will receive
875events. If the watcher is already active nothing will happen.
876.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4
877.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4
878.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)"
879Stops the given watcher again (if active) and clears the pending
880status. It is possible that stopped watchers are pending (for example,
881non-repeating timers are being stopped when they become pending), but
882\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If
883you want to free or reuse the memory used by the watcher it is therefore a
884good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
885.IP "bool ev_is_active (ev_TYPE *watcher)" 4
886.IX Item "bool ev_is_active (ev_TYPE *watcher)"
887Returns a true value iff the watcher is active (i.e. it has been started
888and not yet been stopped). As long as a watcher is active you must not modify
889it.
890.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
891.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
892Returns a true value iff the watcher is pending, (i.e. it has outstanding
893events but its callback has not yet been invoked). As long as a watcher
894is pending (but not active) you must not call an init function on it (but
895\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
896make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
897it).
898.IP "callback ev_cb (ev_TYPE *watcher)" 4
899.IX Item "callback ev_cb (ev_TYPE *watcher)"
900Returns the callback currently set on the watcher.
901.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
902.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
903Change the callback. You can change the callback at virtually any time
904(modulo threads).
905.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
906.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
907.PD 0
908.IP "int ev_priority (ev_TYPE *watcher)" 4
909.IX Item "int ev_priority (ev_TYPE *watcher)"
910.PD
911Set and query the priority of the watcher. The priority is a small
912integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
913(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
914before watchers with lower priority, but priority will not keep watchers
915from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
916.Sp
917This means that priorities are \fIonly\fR used for ordering callback
918invocation after new events have been received. This is useful, for
919example, to reduce latency after idling, or more often, to bind two
920watchers on the same event and make sure one is called first.
921.Sp
922If you need to suppress invocation when higher priority events are pending
923you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
924.Sp
925You \fImust not\fR change the priority of a watcher as long as it is active or
926pending.
927.Sp
928The default priority used by watchers when no priority has been set is
929always \f(CW0\fR, which is supposed to not be too high and not be too low :).
930.Sp
931Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
932fine, as long as you do not mind that the priority value you query might
933or might not have been adjusted to be within valid range.
934.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
935.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
936Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
937\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
938can deal with that fact.
939.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
940.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
941If the watcher is pending, this function returns clears its pending status
942and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
943watcher isn't pending it does nothing and returns \f(CW0\fR.
611.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 944.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
612.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 945.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
613Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 946Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
614and read at any time, libev will completely ignore it. This can be used 947and read at any time, libev will completely ignore it. This can be used
615to associate arbitrary data with your watcher. If you need more data and 948to associate arbitrary data with your watcher. If you need more data and
… …
636\& struct my_io *w = (struct my_io *)w_; 969\& struct my_io *w = (struct my_io *)w_;
637\& ... 970\& ...
638\& } 971\& }
639.Ve 972.Ve
640.PP 973.PP
641More interesting and less C\-conformant ways of catsing your callback type 974More interesting and less C\-conformant ways of casting your callback type
642have been omitted.... 975instead have been omitted.
976.PP
977Another common scenario is having some data structure with multiple
978watchers:
979.PP
980.Vb 6
981\& struct my_biggy
982\& {
983\& int some_data;
984\& ev_timer t1;
985\& ev_timer t2;
986\& }
987.Ve
988.PP
989In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
990you need to use \f(CW\*(C`offsetof\*(C'\fR:
991.PP
992.Vb 1
993\& #include <stddef.h>
994.Ve
995.PP
996.Vb 6
997\& static void
998\& t1_cb (EV_P_ struct ev_timer *w, int revents)
999\& {
1000\& struct my_biggy big = (struct my_biggy *
1001\& (((char *)w) - offsetof (struct my_biggy, t1));
1002\& }
1003.Ve
1004.PP
1005.Vb 6
1006\& static void
1007\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1008\& {
1009\& struct my_biggy big = (struct my_biggy *
1010\& (((char *)w) - offsetof (struct my_biggy, t2));
1011\& }
1012.Ve
643.SH "WATCHER TYPES" 1013.SH "WATCHER TYPES"
644.IX Header "WATCHER TYPES" 1014.IX Header "WATCHER TYPES"
645This section describes each watcher in detail, but will not repeat 1015This section describes each watcher in detail, but will not repeat
646information given in the last section. 1016information given in the last section. Any initialisation/set macros,
1017functions and members specific to the watcher type are explained.
1018.PP
1019Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1020while the watcher is active, you can look at the member and expect some
1021sensible content, but you must not modify it (you can modify it while the
1022watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1023means you can expect it to have some sensible content while the watcher
1024is active, but you can also modify it. Modifying it may not do something
1025sensible or take immediate effect (or do anything at all), but libev will
1026not crash or malfunction in any way.
647.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1027.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
648.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1028.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
649.IX Subsection "ev_io - is this file descriptor readable or writable" 1029.IX Subsection "ev_io - is this file descriptor readable or writable?"
650I/O watchers check whether a file descriptor is readable or writable 1030I/O watchers check whether a file descriptor is readable or writable
651in each iteration of the event loop (This behaviour is called 1031in each iteration of the event loop, or, more precisely, when reading
652level-triggering because you keep receiving events as long as the 1032would not block the process and writing would at least be able to write
653condition persists. Remember you can stop the watcher if you don't want to 1033some data. This behaviour is called level-triggering because you keep
654act on the event and neither want to receive future events). 1034receiving events as long as the condition persists. Remember you can stop
1035the watcher if you don't want to act on the event and neither want to
1036receive future events.
655.PP 1037.PP
656In general you can register as many read and/or write event watchers per 1038In general you can register as many read and/or write event watchers per
657fd as you want (as long as you don't confuse yourself). Setting all file 1039fd as you want (as long as you don't confuse yourself). Setting all file
658descriptors to non-blocking mode is also usually a good idea (but not 1040descriptors to non-blocking mode is also usually a good idea (but not
659required if you know what you are doing). 1041required if you know what you are doing).
660.PP 1042.PP
661You have to be careful with dup'ed file descriptors, though. Some backends 1043You have to be careful with dup'ed file descriptors, though. Some backends
662(the linux epoll backend is a notable example) cannot handle dup'ed file 1044(the linux epoll backend is a notable example) cannot handle dup'ed file
663descriptors correctly if you register interest in two or more fds pointing 1045descriptors correctly if you register interest in two or more fds pointing
664to the same underlying file/socket etc. description (that is, they share 1046to the same underlying file/socket/etc. description (that is, they share
665the same underlying \*(L"file open\*(R"). 1047the same underlying \*(L"file open\*(R").
666.PP 1048.PP
667If you must do this, then force the use of a known-to-be-good backend 1049If you must do this, then force the use of a known-to-be-good backend
668(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1050(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
669\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1051\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1052.PP
1053Another thing you have to watch out for is that it is quite easy to
1054receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1055be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1056because there is no data. Not only are some backends known to create a
1057lot of those (for example solaris ports), it is very easy to get into
1058this situation even with a relatively standard program structure. Thus
1059it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1060\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1061.PP
1062If you cannot run the fd in non-blocking mode (for example you should not
1063play around with an Xlib connection), then you have to seperately re-test
1064whether a file descriptor is really ready with a known-to-be good interface
1065such as poll (fortunately in our Xlib example, Xlib already does this on
1066its own, so its quite safe to use).
670.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1067.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
671.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1068.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
672.PD 0 1069.PD 0
673.IP "ev_io_set (ev_io *, int fd, int events)" 4 1070.IP "ev_io_set (ev_io *, int fd, int events)" 4
674.IX Item "ev_io_set (ev_io *, int fd, int events)" 1071.IX Item "ev_io_set (ev_io *, int fd, int events)"
675.PD 1072.PD
676Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1073Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
677events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_READ | 1074rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
678EV_WRITE\*(C'\fR to receive the given events. 1075\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
679.Sp 1076.IP "int fd [read\-only]" 4
680Please note that most of the more scalable backend mechanisms (for example 1077.IX Item "int fd [read-only]"
681epoll and solaris ports) can result in spurious readyness notifications 1078The file descriptor being watched.
682for file descriptors, so you practically need to use non-blocking I/O (and 1079.IP "int events [read\-only]" 4
683treat callback invocation as hint only), or retest separately with a safe 1080.IX Item "int events [read-only]"
684interface before doing I/O (XLib can do this), or force the use of either 1081The events being watched.
685\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this 1082.PP
686problem. Also note that it is quite easy to have your callback invoked 1083Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
687when the readyness condition is no longer valid even when employing 1084readable, but only once. Since it is likely line\-buffered, you could
688typical ways of handling events, so its a good idea to use non-blocking 1085attempt to read a whole line in the callback.
689I/O unconditionally. 1086.PP
1087.Vb 6
1088\& static void
1089\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1090\& {
1091\& ev_io_stop (loop, w);
1092\& .. read from stdin here (or from w->fd) and haqndle any I/O errors
1093\& }
1094.Ve
1095.PP
1096.Vb 6
1097\& ...
1098\& struct ev_loop *loop = ev_default_init (0);
1099\& struct ev_io stdin_readable;
1100\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
1101\& ev_io_start (loop, &stdin_readable);
1102\& ev_loop (loop, 0);
1103.Ve
690.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1104.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
691.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1105.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
692.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1106.IX Subsection "ev_timer - relative and optionally repeating timeouts"
693Timer watchers are simple relative timers that generate an event after a 1107Timer watchers are simple relative timers that generate an event after a
694given time, and optionally repeating in regular intervals after that. 1108given time, and optionally repeating in regular intervals after that.
695.PP 1109.PP
696The timers are based on real time, that is, if you register an event that 1110The timers are based on real time, that is, if you register an event that
697times out after an hour and you reset your system clock to last years 1111times out after an hour and you reset your system clock to last years
… …
731.IP "ev_timer_again (loop)" 4 1145.IP "ev_timer_again (loop)" 4
732.IX Item "ev_timer_again (loop)" 1146.IX Item "ev_timer_again (loop)"
733This will act as if the timer timed out and restart it again if it is 1147This will act as if the timer timed out and restart it again if it is
734repeating. The exact semantics are: 1148repeating. The exact semantics are:
735.Sp 1149.Sp
1150If the timer is pending, its pending status is cleared.
1151.Sp
736If the timer is started but nonrepeating, stop it. 1152If the timer is started but nonrepeating, stop it (as if it timed out).
737.Sp 1153.Sp
738If the timer is repeating, either start it if necessary (with the repeat 1154If the timer is repeating, either start it if necessary (with the
739value), or reset the running timer to the repeat value. 1155\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
740.Sp 1156.Sp
741This sounds a bit complicated, but here is a useful and typical 1157This sounds a bit complicated, but here is a useful and typical
742example: Imagine you have a tcp connection and you want a so-called idle 1158example: Imagine you have a tcp connection and you want a so-called idle
743timeout, that is, you want to be called when there have been, say, 60 1159timeout, that is, you want to be called when there have been, say, 60
744seconds of inactivity on the socket. The easiest way to do this is to 1160seconds of inactivity on the socket. The easiest way to do this is to
745configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1161configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
746time you successfully read or write some data. If you go into an idle 1162\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
747state where you do not expect data to travel on the socket, you can stop 1163you go into an idle state where you do not expect data to travel on the
748the timer, and again will automatically restart it if need be. 1164socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1165automatically restart it if need be.
1166.Sp
1167That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1168altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1169.Sp
1170.Vb 8
1171\& ev_timer_init (timer, callback, 0., 5.);
1172\& ev_timer_again (loop, timer);
1173\& ...
1174\& timer->again = 17.;
1175\& ev_timer_again (loop, timer);
1176\& ...
1177\& timer->again = 10.;
1178\& ev_timer_again (loop, timer);
1179.Ve
1180.Sp
1181This is more slightly efficient then stopping/starting the timer each time
1182you want to modify its timeout value.
1183.IP "ev_tstamp repeat [read\-write]" 4
1184.IX Item "ev_tstamp repeat [read-write]"
1185The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1186or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1187which is also when any modifications are taken into account.
1188.PP
1189Example: Create a timer that fires after 60 seconds.
1190.PP
1191.Vb 5
1192\& static void
1193\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1194\& {
1195\& .. one minute over, w is actually stopped right here
1196\& }
1197.Ve
1198.PP
1199.Vb 3
1200\& struct ev_timer mytimer;
1201\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
1202\& ev_timer_start (loop, &mytimer);
1203.Ve
1204.PP
1205Example: Create a timeout timer that times out after 10 seconds of
1206inactivity.
1207.PP
1208.Vb 5
1209\& static void
1210\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1211\& {
1212\& .. ten seconds without any activity
1213\& }
1214.Ve
1215.PP
1216.Vb 4
1217\& struct ev_timer mytimer;
1218\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */
1219\& ev_timer_again (&mytimer); /* start timer */
1220\& ev_loop (loop, 0);
1221.Ve
1222.PP
1223.Vb 3
1224\& // and in some piece of code that gets executed on any "activity":
1225\& // reset the timeout to start ticking again at 10 seconds
1226\& ev_timer_again (&mytimer);
1227.Ve
749.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1228.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
750.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1229.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
751.IX Subsection "ev_periodic - to cron or not to cron" 1230.IX Subsection "ev_periodic - to cron or not to cron?"
752Periodic watchers are also timers of a kind, but they are very versatile 1231Periodic watchers are also timers of a kind, but they are very versatile
753(and unfortunately a bit complex). 1232(and unfortunately a bit complex).
754.PP 1233.PP
755Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1234Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
756but on wallclock time (absolute time). You can tell a periodic watcher 1235but on wallclock time (absolute time). You can tell a periodic watcher
757to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1236to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
758periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1237periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
759+ 10.>) and then reset your system clock to the last year, then it will 1238+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
760take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1239take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
761roughly 10 seconds later and of course not if you reset your system time 1240roughly 10 seconds later and of course not if you reset your system time
762again). 1241again).
763.PP 1242.PP
764They can also be used to implement vastly more complex timers, such as 1243They can also be used to implement vastly more complex timers, such as
… …
845.IX Item "ev_periodic_again (loop, ev_periodic *)" 1324.IX Item "ev_periodic_again (loop, ev_periodic *)"
846Simply stops and restarts the periodic watcher again. This is only useful 1325Simply stops and restarts the periodic watcher again. This is only useful
847when you changed some parameters or the reschedule callback would return 1326when you changed some parameters or the reschedule callback would return
848a different time than the last time it was called (e.g. in a crond like 1327a different time than the last time it was called (e.g. in a crond like
849program when the crontabs have changed). 1328program when the crontabs have changed).
1329.IP "ev_tstamp interval [read\-write]" 4
1330.IX Item "ev_tstamp interval [read-write]"
1331The current interval value. Can be modified any time, but changes only
1332take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1333called.
1334.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1335.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1336The current reschedule callback, or \f(CW0\fR, if this functionality is
1337switched off. Can be changed any time, but changes only take effect when
1338the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1339.PP
1340Example: Call a callback every hour, or, more precisely, whenever the
1341system clock is divisible by 3600. The callback invocation times have
1342potentially a lot of jittering, but good long-term stability.
1343.PP
1344.Vb 5
1345\& static void
1346\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents)
1347\& {
1348\& ... its now a full hour (UTC, or TAI or whatever your clock follows)
1349\& }
1350.Ve
1351.PP
1352.Vb 3
1353\& struct ev_periodic hourly_tick;
1354\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1355\& ev_periodic_start (loop, &hourly_tick);
1356.Ve
1357.PP
1358Example: The same as above, but use a reschedule callback to do it:
1359.PP
1360.Vb 1
1361\& #include <math.h>
1362.Ve
1363.PP
1364.Vb 5
1365\& static ev_tstamp
1366\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now)
1367\& {
1368\& return fmod (now, 3600.) + 3600.;
1369\& }
1370.Ve
1371.PP
1372.Vb 1
1373\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1374.Ve
1375.PP
1376Example: Call a callback every hour, starting now:
1377.PP
1378.Vb 4
1379\& struct ev_periodic hourly_tick;
1380\& ev_periodic_init (&hourly_tick, clock_cb,
1381\& fmod (ev_now (loop), 3600.), 3600., 0);
1382\& ev_periodic_start (loop, &hourly_tick);
1383.Ve
850.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1384.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
851.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1385.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
852.IX Subsection "ev_signal - signal me when a signal gets signalled" 1386.IX Subsection "ev_signal - signal me when a signal gets signalled!"
853Signal watchers will trigger an event when the process receives a specific 1387Signal watchers will trigger an event when the process receives a specific
854signal one or more times. Even though signals are very asynchronous, libev 1388signal one or more times. Even though signals are very asynchronous, libev
855will try it's best to deliver signals synchronously, i.e. as part of the 1389will try it's best to deliver signals synchronously, i.e. as part of the
856normal event processing, like any other event. 1390normal event processing, like any other event.
857.PP 1391.PP
… …
867.IP "ev_signal_set (ev_signal *, int signum)" 4 1401.IP "ev_signal_set (ev_signal *, int signum)" 4
868.IX Item "ev_signal_set (ev_signal *, int signum)" 1402.IX Item "ev_signal_set (ev_signal *, int signum)"
869.PD 1403.PD
870Configures the watcher to trigger on the given signal number (usually one 1404Configures the watcher to trigger on the given signal number (usually one
871of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1405of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1406.IP "int signum [read\-only]" 4
1407.IX Item "int signum [read-only]"
1408The signal the watcher watches out for.
872.ie n .Sh """ev_child"" \- wait for pid status changes" 1409.ie n .Sh """ev_child"" \- watch out for process status changes"
873.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1410.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
874.IX Subsection "ev_child - wait for pid status changes" 1411.IX Subsection "ev_child - watch out for process status changes"
875Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1412Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
876some child status changes (most typically when a child of yours dies). 1413some child status changes (most typically when a child of yours dies).
877.IP "ev_child_init (ev_child *, callback, int pid)" 4 1414.IP "ev_child_init (ev_child *, callback, int pid)" 4
878.IX Item "ev_child_init (ev_child *, callback, int pid)" 1415.IX Item "ev_child_init (ev_child *, callback, int pid)"
879.PD 0 1416.PD 0
… …
884\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1421\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
885at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1422at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
886the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1423the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
887\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1424\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
888process causing the status change. 1425process causing the status change.
1426.IP "int pid [read\-only]" 4
1427.IX Item "int pid [read-only]"
1428The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1429.IP "int rpid [read\-write]" 4
1430.IX Item "int rpid [read-write]"
1431The process id that detected a status change.
1432.IP "int rstatus [read\-write]" 4
1433.IX Item "int rstatus [read-write]"
1434The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1435\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1436.PP
1437Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1438.PP
1439.Vb 5
1440\& static void
1441\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1442\& {
1443\& ev_unloop (loop, EVUNLOOP_ALL);
1444\& }
1445.Ve
1446.PP
1447.Vb 3
1448\& struct ev_signal signal_watcher;
1449\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1450\& ev_signal_start (loop, &sigint_cb);
1451.Ve
1452.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1453.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1454.IX Subsection "ev_stat - did the file attributes just change?"
1455This watches a filesystem path for attribute changes. That is, it calls
1456\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1457compared to the last time, invoking the callback if it did.
1458.PP
1459The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1460not exist\*(R" is a status change like any other. The condition \*(L"path does
1461not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1462otherwise always forced to be at least one) and all the other fields of
1463the stat buffer having unspecified contents.
1464.PP
1465The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1466relative and your working directory changes, the behaviour is undefined.
1467.PP
1468Since there is no standard to do this, the portable implementation simply
1469calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1470can specify a recommended polling interval for this case. If you specify
1471a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1472unspecified default\fR value will be used (which you can expect to be around
1473five seconds, although this might change dynamically). Libev will also
1474impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1475usually overkill.
1476.PP
1477This watcher type is not meant for massive numbers of stat watchers,
1478as even with OS-supported change notifications, this can be
1479resource\-intensive.
1480.PP
1481At the time of this writing, only the Linux inotify interface is
1482implemented (implementing kqueue support is left as an exercise for the
1483reader). Inotify will be used to give hints only and should not change the
1484semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1485to fall back to regular polling again even with inotify, but changes are
1486usually detected immediately, and if the file exists there will be no
1487polling.
1488.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1489.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1490.PD 0
1491.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1492.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1493.PD
1494Configures the watcher to wait for status changes of the given
1495\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1496be detected and should normally be specified as \f(CW0\fR to let libev choose
1497a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1498path for as long as the watcher is active.
1499.Sp
1500The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1501relative to the attributes at the time the watcher was started (or the
1502last change was detected).
1503.IP "ev_stat_stat (ev_stat *)" 4
1504.IX Item "ev_stat_stat (ev_stat *)"
1505Updates the stat buffer immediately with new values. If you change the
1506watched path in your callback, you could call this fucntion to avoid
1507detecting this change (while introducing a race condition). Can also be
1508useful simply to find out the new values.
1509.IP "ev_statdata attr [read\-only]" 4
1510.IX Item "ev_statdata attr [read-only]"
1511The most-recently detected attributes of the file. Although the type is of
1512\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1513suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1514was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1515.IP "ev_statdata prev [read\-only]" 4
1516.IX Item "ev_statdata prev [read-only]"
1517The previous attributes of the file. The callback gets invoked whenever
1518\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1519.IP "ev_tstamp interval [read\-only]" 4
1520.IX Item "ev_tstamp interval [read-only]"
1521The specified interval.
1522.IP "const char *path [read\-only]" 4
1523.IX Item "const char *path [read-only]"
1524The filesystem path that is being watched.
1525.PP
1526Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1527.PP
1528.Vb 15
1529\& static void
1530\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1531\& {
1532\& /* /etc/passwd changed in some way */
1533\& if (w->attr.st_nlink)
1534\& {
1535\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1536\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1537\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1538\& }
1539\& else
1540\& /* you shalt not abuse printf for puts */
1541\& puts ("wow, /etc/passwd is not there, expect problems. "
1542\& "if this is windows, they already arrived\en");
1543\& }
1544.Ve
1545.PP
1546.Vb 2
1547\& ...
1548\& ev_stat passwd;
1549.Ve
1550.PP
1551.Vb 2
1552\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1553\& ev_stat_start (loop, &passwd);
1554.Ve
889.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1555.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
890.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1556.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
891.IX Subsection "ev_idle - when you've got nothing better to do" 1557.IX Subsection "ev_idle - when you've got nothing better to do..."
892Idle watchers trigger events when there are no other events are pending 1558Idle watchers trigger events when no other events of the same or higher
893(prepare, check and other idle watchers do not count). That is, as long 1559priority are pending (prepare, check and other idle watchers do not
894as your process is busy handling sockets or timeouts (or even signals, 1560count).
895imagine) it will not be triggered. But when your process is idle all idle 1561.PP
896watchers are being called again and again, once per event loop iteration \- 1562That is, as long as your process is busy handling sockets or timeouts
1563(or even signals, imagine) of the same or higher priority it will not be
1564triggered. But when your process is idle (or only lower-priority watchers
1565are pending), the idle watchers are being called once per event loop
897until stopped, that is, or your process receives more events and becomes 1566iteration \- until stopped, that is, or your process receives more events
898busy. 1567and becomes busy again with higher priority stuff.
899.PP 1568.PP
900The most noteworthy effect is that as long as any idle watchers are 1569The most noteworthy effect is that as long as any idle watchers are
901active, the process will not block when waiting for new events. 1570active, the process will not block when waiting for new events.
902.PP 1571.PP
903Apart from keeping your process non-blocking (which is a useful 1572Apart from keeping your process non-blocking (which is a useful
… …
907.IP "ev_idle_init (ev_signal *, callback)" 4 1576.IP "ev_idle_init (ev_signal *, callback)" 4
908.IX Item "ev_idle_init (ev_signal *, callback)" 1577.IX Item "ev_idle_init (ev_signal *, callback)"
909Initialises and configures the idle watcher \- it has no parameters of any 1578Initialises and configures the idle watcher \- it has no parameters of any
910kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1579kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
911believe me. 1580believe me.
1581.PP
1582Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1583callback, free it. Also, use no error checking, as usual.
1584.PP
1585.Vb 7
1586\& static void
1587\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1588\& {
1589\& free (w);
1590\& // now do something you wanted to do when the program has
1591\& // no longer asnything immediate to do.
1592\& }
1593.Ve
1594.PP
1595.Vb 3
1596\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1597\& ev_idle_init (idle_watcher, idle_cb);
1598\& ev_idle_start (loop, idle_cb);
1599.Ve
912.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1600.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
913.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1601.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
914.IX Subsection "ev_prepare and ev_check - customise your event loop" 1602.IX Subsection "ev_prepare and ev_check - customise your event loop!"
915Prepare and check watchers are usually (but not always) used in tandem: 1603Prepare and check watchers are usually (but not always) used in tandem:
916prepare watchers get invoked before the process blocks and check watchers 1604prepare watchers get invoked before the process blocks and check watchers
917afterwards. 1605afterwards.
918.PP 1606.PP
1607You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1608the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1609watchers. Other loops than the current one are fine, however. The
1610rationale behind this is that you do not need to check for recursion in
1611those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1612\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1613called in pairs bracketing the blocking call.
1614.PP
919Their main purpose is to integrate other event mechanisms into libev. This 1615Their main purpose is to integrate other event mechanisms into libev and
920could be used, for example, to track variable changes, implement your own 1616their use is somewhat advanced. This could be used, for example, to track
921watchers, integrate net-snmp or a coroutine library and lots more. 1617variable changes, implement your own watchers, integrate net-snmp or a
1618coroutine library and lots more. They are also occasionally useful if
1619you cache some data and want to flush it before blocking (for example,
1620in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1621watcher).
922.PP 1622.PP
923This is done by examining in each prepare call which file descriptors need 1623This is done by examining in each prepare call which file descriptors need
924to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1624to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
925them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1625them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
926provide just this functionality). Then, in the check watcher you check for 1626provide just this functionality). Then, in the check watcher you check for
… …
935are ready to run (it's actually more complicated: it only runs coroutines 1635are ready to run (it's actually more complicated: it only runs coroutines
936with priority higher than or equal to the event loop and one coroutine 1636with priority higher than or equal to the event loop and one coroutine
937of lower priority, but only once, using idle watchers to keep the event 1637of lower priority, but only once, using idle watchers to keep the event
938loop from blocking if lower-priority coroutines are active, thus mapping 1638loop from blocking if lower-priority coroutines are active, thus mapping
939low-priority coroutines to idle/background tasks). 1639low-priority coroutines to idle/background tasks).
1640.PP
1641It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1642priority, to ensure that they are being run before any other watchers
1643after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1644too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1645supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1646their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1647loops those other event loops might be in an unusable state until their
1648\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1649others).
940.IP "ev_prepare_init (ev_prepare *, callback)" 4 1650.IP "ev_prepare_init (ev_prepare *, callback)" 4
941.IX Item "ev_prepare_init (ev_prepare *, callback)" 1651.IX Item "ev_prepare_init (ev_prepare *, callback)"
942.PD 0 1652.PD 0
943.IP "ev_check_init (ev_check *, callback)" 4 1653.IP "ev_check_init (ev_check *, callback)" 4
944.IX Item "ev_check_init (ev_check *, callback)" 1654.IX Item "ev_check_init (ev_check *, callback)"
945.PD 1655.PD
946Initialises and configures the prepare or check watcher \- they have no 1656Initialises and configures the prepare or check watcher \- they have no
947parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1657parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
948macros, but using them is utterly, utterly and completely pointless. 1658macros, but using them is utterly, utterly and completely pointless.
1659.PP
1660There are a number of principal ways to embed other event loops or modules
1661into libev. Here are some ideas on how to include libadns into libev
1662(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1663use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1664embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1665into the Glib event loop).
1666.PP
1667Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1668and in a check watcher, destroy them and call into libadns. What follows
1669is pseudo-code only of course. This requires you to either use a low
1670priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1671the callbacks for the IO/timeout watchers might not have been called yet.
1672.PP
1673.Vb 2
1674\& static ev_io iow [nfd];
1675\& static ev_timer tw;
1676.Ve
1677.PP
1678.Vb 4
1679\& static void
1680\& io_cb (ev_loop *loop, ev_io *w, int revents)
1681\& {
1682\& }
1683.Ve
1684.PP
1685.Vb 8
1686\& // create io watchers for each fd and a timer before blocking
1687\& static void
1688\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1689\& {
1690\& int timeout = 3600000;
1691\& struct pollfd fds [nfd];
1692\& // actual code will need to loop here and realloc etc.
1693\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1694.Ve
1695.PP
1696.Vb 3
1697\& /* the callback is illegal, but won't be called as we stop during check */
1698\& ev_timer_init (&tw, 0, timeout * 1e-3);
1699\& ev_timer_start (loop, &tw);
1700.Ve
1701.PP
1702.Vb 6
1703\& // create one ev_io per pollfd
1704\& for (int i = 0; i < nfd; ++i)
1705\& {
1706\& ev_io_init (iow + i, io_cb, fds [i].fd,
1707\& ((fds [i].events & POLLIN ? EV_READ : 0)
1708\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1709.Ve
1710.PP
1711.Vb 4
1712\& fds [i].revents = 0;
1713\& ev_io_start (loop, iow + i);
1714\& }
1715\& }
1716.Ve
1717.PP
1718.Vb 5
1719\& // stop all watchers after blocking
1720\& static void
1721\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1722\& {
1723\& ev_timer_stop (loop, &tw);
1724.Ve
1725.PP
1726.Vb 8
1727\& for (int i = 0; i < nfd; ++i)
1728\& {
1729\& // set the relevant poll flags
1730\& // could also call adns_processreadable etc. here
1731\& struct pollfd *fd = fds + i;
1732\& int revents = ev_clear_pending (iow + i);
1733\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1734\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1735.Ve
1736.PP
1737.Vb 3
1738\& // now stop the watcher
1739\& ev_io_stop (loop, iow + i);
1740\& }
1741.Ve
1742.PP
1743.Vb 2
1744\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1745\& }
1746.Ve
1747.PP
1748Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1749in the prepare watcher and would dispose of the check watcher.
1750.PP
1751Method 3: If the module to be embedded supports explicit event
1752notification (adns does), you can also make use of the actual watcher
1753callbacks, and only destroy/create the watchers in the prepare watcher.
1754.PP
1755.Vb 5
1756\& static void
1757\& timer_cb (EV_P_ ev_timer *w, int revents)
1758\& {
1759\& adns_state ads = (adns_state)w->data;
1760\& update_now (EV_A);
1761.Ve
1762.PP
1763.Vb 2
1764\& adns_processtimeouts (ads, &tv_now);
1765\& }
1766.Ve
1767.PP
1768.Vb 5
1769\& static void
1770\& io_cb (EV_P_ ev_io *w, int revents)
1771\& {
1772\& adns_state ads = (adns_state)w->data;
1773\& update_now (EV_A);
1774.Ve
1775.PP
1776.Vb 3
1777\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1778\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1779\& }
1780.Ve
1781.PP
1782.Vb 1
1783\& // do not ever call adns_afterpoll
1784.Ve
1785.PP
1786Method 4: Do not use a prepare or check watcher because the module you
1787want to embed is too inflexible to support it. Instead, youc na override
1788their poll function. The drawback with this solution is that the main
1789loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1790this.
1791.PP
1792.Vb 4
1793\& static gint
1794\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1795\& {
1796\& int got_events = 0;
1797.Ve
1798.PP
1799.Vb 2
1800\& for (n = 0; n < nfds; ++n)
1801\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1802.Ve
1803.PP
1804.Vb 2
1805\& if (timeout >= 0)
1806\& // create/start timer
1807.Ve
1808.PP
1809.Vb 2
1810\& // poll
1811\& ev_loop (EV_A_ 0);
1812.Ve
1813.PP
1814.Vb 3
1815\& // stop timer again
1816\& if (timeout >= 0)
1817\& ev_timer_stop (EV_A_ &to);
1818.Ve
1819.PP
1820.Vb 3
1821\& // stop io watchers again - their callbacks should have set
1822\& for (n = 0; n < nfds; ++n)
1823\& ev_io_stop (EV_A_ iow [n]);
1824.Ve
1825.PP
1826.Vb 2
1827\& return got_events;
1828\& }
1829.Ve
1830.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1831.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1832.IX Subsection "ev_embed - when one backend isn't enough..."
1833This is a rather advanced watcher type that lets you embed one event loop
1834into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1835loop, other types of watchers might be handled in a delayed or incorrect
1836fashion and must not be used).
1837.PP
1838There are primarily two reasons you would want that: work around bugs and
1839prioritise I/O.
1840.PP
1841As an example for a bug workaround, the kqueue backend might only support
1842sockets on some platform, so it is unusable as generic backend, but you
1843still want to make use of it because you have many sockets and it scales
1844so nicely. In this case, you would create a kqueue-based loop and embed it
1845into your default loop (which might use e.g. poll). Overall operation will
1846be a bit slower because first libev has to poll and then call kevent, but
1847at least you can use both at what they are best.
1848.PP
1849As for prioritising I/O: rarely you have the case where some fds have
1850to be watched and handled very quickly (with low latency), and even
1851priorities and idle watchers might have too much overhead. In this case
1852you would put all the high priority stuff in one loop and all the rest in
1853a second one, and embed the second one in the first.
1854.PP
1855As long as the watcher is active, the callback will be invoked every time
1856there might be events pending in the embedded loop. The callback must then
1857call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke
1858their callbacks (you could also start an idle watcher to give the embedded
1859loop strictly lower priority for example). You can also set the callback
1860to \f(CW0\fR, in which case the embed watcher will automatically execute the
1861embedded loop sweep.
1862.PP
1863As long as the watcher is started it will automatically handle events. The
1864callback will be invoked whenever some events have been handled. You can
1865set the callback to \f(CW0\fR to avoid having to specify one if you are not
1866interested in that.
1867.PP
1868Also, there have not currently been made special provisions for forking:
1869when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops,
1870but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers
1871yourself.
1872.PP
1873Unfortunately, not all backends are embeddable, only the ones returned by
1874\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any
1875portable one.
1876.PP
1877So when you want to use this feature you will always have to be prepared
1878that you cannot get an embeddable loop. The recommended way to get around
1879this is to have a separate variables for your embeddable loop, try to
1880create it, and if that fails, use the normal loop for everything:
1881.PP
1882.Vb 3
1883\& struct ev_loop *loop_hi = ev_default_init (0);
1884\& struct ev_loop *loop_lo = 0;
1885\& struct ev_embed embed;
1886.Ve
1887.PP
1888.Vb 5
1889\& // see if there is a chance of getting one that works
1890\& // (remember that a flags value of 0 means autodetection)
1891\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
1892\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
1893\& : 0;
1894.Ve
1895.PP
1896.Vb 8
1897\& // if we got one, then embed it, otherwise default to loop_hi
1898\& if (loop_lo)
1899\& {
1900\& ev_embed_init (&embed, 0, loop_lo);
1901\& ev_embed_start (loop_hi, &embed);
1902\& }
1903\& else
1904\& loop_lo = loop_hi;
1905.Ve
1906.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1907.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1908.PD 0
1909.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1910.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
1911.PD
1912Configures the watcher to embed the given loop, which must be
1913embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be
1914invoked automatically, otherwise it is the responsibility of the callback
1915to invoke it (it will continue to be called until the sweep has been done,
1916if you do not want thta, you need to temporarily stop the embed watcher).
1917.IP "ev_embed_sweep (loop, ev_embed *)" 4
1918.IX Item "ev_embed_sweep (loop, ev_embed *)"
1919Make a single, non-blocking sweep over the embedded loop. This works
1920similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1921apropriate way for embedded loops.
1922.IP "struct ev_loop *loop [read\-only]" 4
1923.IX Item "struct ev_loop *loop [read-only]"
1924The embedded event loop.
1925.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
1926.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
1927.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
1928Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
1929whoever is a good citizen cared to tell libev about it by calling
1930\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
1931event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
1932and only in the child after the fork. If whoever good citizen calling
1933\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
1934handlers will be invoked, too, of course.
1935.IP "ev_fork_init (ev_signal *, callback)" 4
1936.IX Item "ev_fork_init (ev_signal *, callback)"
1937Initialises and configures the fork watcher \- it has no parameters of any
1938kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
1939believe me.
949.SH "OTHER FUNCTIONS" 1940.SH "OTHER FUNCTIONS"
950.IX Header "OTHER FUNCTIONS" 1941.IX Header "OTHER FUNCTIONS"
951There are some other functions of possible interest. Described. Here. Now. 1942There are some other functions of possible interest. Described. Here. Now.
952.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 1943.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
953.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 1944.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
982.Ve 1973.Ve
983.Sp 1974.Sp
984.Vb 1 1975.Vb 1
985\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 1976\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
986.Ve 1977.Ve
987.IP "ev_feed_event (loop, watcher, int events)" 4 1978.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4
988.IX Item "ev_feed_event (loop, watcher, int events)" 1979.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)"
989Feeds the given event set into the event loop, as if the specified event 1980Feeds the given event set into the event loop, as if the specified event
990had happened for the specified watcher (which must be a pointer to an 1981had happened for the specified watcher (which must be a pointer to an
991initialised but not necessarily started event watcher). 1982initialised but not necessarily started event watcher).
992.IP "ev_feed_fd_event (loop, int fd, int revents)" 4 1983.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4
993.IX Item "ev_feed_fd_event (loop, int fd, int revents)" 1984.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)"
994Feed an event on the given fd, as if a file descriptor backend detected 1985Feed an event on the given fd, as if a file descriptor backend detected
995the given events it. 1986the given events it.
996.IP "ev_feed_signal_event (loop, int signum)" 4 1987.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4
997.IX Item "ev_feed_signal_event (loop, int signum)" 1988.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)"
998Feed an event as if the given signal occured (loop must be the default loop!). 1989Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default
1990loop!).
999.SH "LIBEVENT EMULATION" 1991.SH "LIBEVENT EMULATION"
1000.IX Header "LIBEVENT EMULATION" 1992.IX Header "LIBEVENT EMULATION"
1001Libev offers a compatibility emulation layer for libevent. It cannot 1993Libev offers a compatibility emulation layer for libevent. It cannot
1002emulate the internals of libevent, so here are some usage hints: 1994emulate the internals of libevent, so here are some usage hints:
1003.IP "* Use it by including <event.h>, as usual." 4 1995.IP "* Use it by including <event.h>, as usual." 4
… …
1014.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 2006.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1015.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 2007.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1016.PD 2008.PD
1017.SH "\*(C+ SUPPORT" 2009.SH "\*(C+ SUPPORT"
1018.IX Header " SUPPORT" 2010.IX Header " SUPPORT"
1019\&\s-1TBD\s0. 2011Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2012you to use some convinience methods to start/stop watchers and also change
2013the callback model to a model using method callbacks on objects.
2014.PP
2015To use it,
2016.PP
2017.Vb 1
2018\& #include <ev++.h>
2019.Ve
2020.PP
2021This automatically includes \fIev.h\fR and puts all of its definitions (many
2022of them macros) into the global namespace. All \*(C+ specific things are
2023put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2024options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
2025.PP
2026Care has been taken to keep the overhead low. The only data member the \*(C+
2027classes add (compared to plain C\-style watchers) is the event loop pointer
2028that the watcher is associated with (or no additional members at all if
2029you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2030.PP
2031Currently, functions, and static and non-static member functions can be
2032used as callbacks. Other types should be easy to add as long as they only
2033need one additional pointer for context. If you need support for other
2034types of functors please contact the author (preferably after implementing
2035it).
2036.PP
2037Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2038.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
2039.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2040.IX Item "ev::READ, ev::WRITE etc."
2041These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2042macros from \fIev.h\fR.
2043.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
2044.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2045.IX Item "ev::tstamp, ev::now"
2046Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2047.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
2048.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2049.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2050For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2051the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2052which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2053defines by many implementations.
2054.Sp
2055All of those classes have these methods:
2056.RS 4
2057.IP "ev::TYPE::TYPE ()" 4
2058.IX Item "ev::TYPE::TYPE ()"
2059.PD 0
2060.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
2061.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
2062.IP "ev::TYPE::~TYPE" 4
2063.IX Item "ev::TYPE::~TYPE"
2064.PD
2065The constructor (optionally) takes an event loop to associate the watcher
2066with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
2067.Sp
2068The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
2069\&\f(CW\*(C`set\*(C'\fR method before starting it.
2070.Sp
2071It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2072method to set a callback before you can start the watcher.
2073.Sp
2074(The reason why you have to use a method is a limitation in \*(C+ which does
2075not allow explicit template arguments for constructors).
2076.Sp
2077The destructor automatically stops the watcher if it is active.
2078.IP "w\->set<class, &class::method> (object *)" 4
2079.IX Item "w->set<class, &class::method> (object *)"
2080This method sets the callback method to call. The method has to have a
2081signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2082first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2083parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2084.Sp
2085This method synthesizes efficient thunking code to call your method from
2086the C callback that libev requires. If your compiler can inline your
2087callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2088your compiler is good :), then the method will be fully inlined into the
2089thunking function, making it as fast as a direct C callback.
2090.Sp
2091Example: simple class declaration and watcher initialisation
2092.Sp
2093.Vb 4
2094\& struct myclass
2095\& {
2096\& void io_cb (ev::io &w, int revents) { }
2097\& }
2098.Ve
2099.Sp
2100.Vb 3
2101\& myclass obj;
2102\& ev::io iow;
2103\& iow.set <myclass, &myclass::io_cb> (&obj);
2104.Ve
2105.IP "w\->set<function> (void *data = 0)" 4
2106.IX Item "w->set<function> (void *data = 0)"
2107Also sets a callback, but uses a static method or plain function as
2108callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2109\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2110.Sp
2111The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2112.Sp
2113See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2114.Sp
2115Example:
2116.Sp
2117.Vb 2
2118\& static void io_cb (ev::io &w, int revents) { }
2119\& iow.set <io_cb> ();
2120.Ve
2121.IP "w\->set (struct ev_loop *)" 4
2122.IX Item "w->set (struct ev_loop *)"
2123Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2124do this when the watcher is inactive (and not pending either).
2125.IP "w\->set ([args])" 4
2126.IX Item "w->set ([args])"
2127Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
2128called at least once. Unlike the C counterpart, an active watcher gets
2129automatically stopped and restarted when reconfiguring it with this
2130method.
2131.IP "w\->start ()" 4
2132.IX Item "w->start ()"
2133Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2134constructor already stores the event loop.
2135.IP "w\->stop ()" 4
2136.IX Item "w->stop ()"
2137Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2138.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4
2139.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4
2140.IX Item "w->again () ev::timer, ev::periodic only"
2141For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2142\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2143.ie n .IP "w\->sweep () ""ev::embed"" only" 4
2144.el .IP "w\->sweep () \f(CWev::embed\fR only" 4
2145.IX Item "w->sweep () ev::embed only"
2146Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2147.ie n .IP "w\->update () ""ev::stat"" only" 4
2148.el .IP "w\->update () \f(CWev::stat\fR only" 4
2149.IX Item "w->update () ev::stat only"
2150Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2151.RE
2152.RS 4
2153.RE
2154.PP
2155Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2156the constructor.
2157.PP
2158.Vb 4
2159\& class myclass
2160\& {
2161\& ev_io io; void io_cb (ev::io &w, int revents);
2162\& ev_idle idle void idle_cb (ev::idle &w, int revents);
2163.Ve
2164.PP
2165.Vb 2
2166\& myclass ();
2167\& }
2168.Ve
2169.PP
2170.Vb 4
2171\& myclass::myclass (int fd)
2172\& {
2173\& io .set <myclass, &myclass::io_cb > (this);
2174\& idle.set <myclass, &myclass::idle_cb> (this);
2175.Ve
2176.PP
2177.Vb 2
2178\& io.start (fd, ev::READ);
2179\& }
2180.Ve
2181.SH "MACRO MAGIC"
2182.IX Header "MACRO MAGIC"
2183Libev can be compiled with a variety of options, the most fundemantal is
2184\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most) functions and
2185callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2186.PP
2187To make it easier to write programs that cope with either variant, the
2188following macros are defined:
2189.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2190.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2191.IX Item "EV_A, EV_A_"
2192This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2193loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2194\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2195.Sp
2196.Vb 3
2197\& ev_unref (EV_A);
2198\& ev_timer_add (EV_A_ watcher);
2199\& ev_loop (EV_A_ 0);
2200.Ve
2201.Sp
2202It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2203which is often provided by the following macro.
2204.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2205.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2206.IX Item "EV_P, EV_P_"
2207This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2208loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2209\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2210.Sp
2211.Vb 2
2212\& // this is how ev_unref is being declared
2213\& static void ev_unref (EV_P);
2214.Ve
2215.Sp
2216.Vb 2
2217\& // this is how you can declare your typical callback
2218\& static void cb (EV_P_ ev_timer *w, int revents)
2219.Ve
2220.Sp
2221It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2222suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2223.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2224.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2225.IX Item "EV_DEFAULT, EV_DEFAULT_"
2226Similar to the other two macros, this gives you the value of the default
2227loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2228.PP
2229Example: Declare and initialise a check watcher, utilising the above
2230macros so it will work regardless of whether multiple loops are supported
2231or not.
2232.PP
2233.Vb 5
2234\& static void
2235\& check_cb (EV_P_ ev_timer *w, int revents)
2236\& {
2237\& ev_check_stop (EV_A_ w);
2238\& }
2239.Ve
2240.PP
2241.Vb 4
2242\& ev_check check;
2243\& ev_check_init (&check, check_cb);
2244\& ev_check_start (EV_DEFAULT_ &check);
2245\& ev_loop (EV_DEFAULT_ 0);
2246.Ve
2247.SH "EMBEDDING"
2248.IX Header "EMBEDDING"
2249Libev can (and often is) directly embedded into host
2250applications. Examples of applications that embed it include the Deliantra
2251Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2252and rxvt\-unicode.
2253.PP
2254The goal is to enable you to just copy the neecssary files into your
2255source directory without having to change even a single line in them, so
2256you can easily upgrade by simply copying (or having a checked-out copy of
2257libev somewhere in your source tree).
2258.Sh "\s-1FILESETS\s0"
2259.IX Subsection "FILESETS"
2260Depending on what features you need you need to include one or more sets of files
2261in your app.
2262.PP
2263\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2264.IX Subsection "CORE EVENT LOOP"
2265.PP
2266To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2267configuration (no autoconf):
2268.PP
2269.Vb 2
2270\& #define EV_STANDALONE 1
2271\& #include "ev.c"
2272.Ve
2273.PP
2274This will automatically include \fIev.h\fR, too, and should be done in a
2275single C source file only to provide the function implementations. To use
2276it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2277done by writing a wrapper around \fIev.h\fR that you can include instead and
2278where you can put other configuration options):
2279.PP
2280.Vb 2
2281\& #define EV_STANDALONE 1
2282\& #include "ev.h"
2283.Ve
2284.PP
2285Both header files and implementation files can be compiled with a \*(C+
2286compiler (at least, thats a stated goal, and breakage will be treated
2287as a bug).
2288.PP
2289You need the following files in your source tree, or in a directory
2290in your include path (e.g. in libev/ when using \-Ilibev):
2291.PP
2292.Vb 4
2293\& ev.h
2294\& ev.c
2295\& ev_vars.h
2296\& ev_wrap.h
2297.Ve
2298.PP
2299.Vb 1
2300\& ev_win32.c required on win32 platforms only
2301.Ve
2302.PP
2303.Vb 5
2304\& ev_select.c only when select backend is enabled (which is enabled by default)
2305\& ev_poll.c only when poll backend is enabled (disabled by default)
2306\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2307\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2308\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2309.Ve
2310.PP
2311\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2312to compile this single file.
2313.PP
2314\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2315.IX Subsection "LIBEVENT COMPATIBILITY API"
2316.PP
2317To include the libevent compatibility \s-1API\s0, also include:
2318.PP
2319.Vb 1
2320\& #include "event.c"
2321.Ve
2322.PP
2323in the file including \fIev.c\fR, and:
2324.PP
2325.Vb 1
2326\& #include "event.h"
2327.Ve
2328.PP
2329in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2330.PP
2331You need the following additional files for this:
2332.PP
2333.Vb 2
2334\& event.h
2335\& event.c
2336.Ve
2337.PP
2338\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2339.IX Subsection "AUTOCONF SUPPORT"
2340.PP
2341Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2342whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2343\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2344include \fIconfig.h\fR and configure itself accordingly.
2345.PP
2346For this of course you need the m4 file:
2347.PP
2348.Vb 1
2349\& libev.m4
2350.Ve
2351.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2352.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2353Libev can be configured via a variety of preprocessor symbols you have to define
2354before including any of its files. The default is not to build for multiplicity
2355and only include the select backend.
2356.IP "\s-1EV_STANDALONE\s0" 4
2357.IX Item "EV_STANDALONE"
2358Must always be \f(CW1\fR if you do not use autoconf configuration, which
2359keeps libev from including \fIconfig.h\fR, and it also defines dummy
2360implementations for some libevent functions (such as logging, which is not
2361supported). It will also not define any of the structs usually found in
2362\&\fIevent.h\fR that are not directly supported by the libev core alone.
2363.IP "\s-1EV_USE_MONOTONIC\s0" 4
2364.IX Item "EV_USE_MONOTONIC"
2365If defined to be \f(CW1\fR, libev will try to detect the availability of the
2366monotonic clock option at both compiletime and runtime. Otherwise no use
2367of the monotonic clock option will be attempted. If you enable this, you
2368usually have to link against librt or something similar. Enabling it when
2369the functionality isn't available is safe, though, althoguh you have
2370to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2371function is hiding in (often \fI\-lrt\fR).
2372.IP "\s-1EV_USE_REALTIME\s0" 4
2373.IX Item "EV_USE_REALTIME"
2374If defined to be \f(CW1\fR, libev will try to detect the availability of the
2375realtime clock option at compiletime (and assume its availability at
2376runtime if successful). Otherwise no use of the realtime clock option will
2377be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2378(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2379in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2380.IP "\s-1EV_USE_SELECT\s0" 4
2381.IX Item "EV_USE_SELECT"
2382If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2383\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2384other method takes over, select will be it. Otherwise the select backend
2385will not be compiled in.
2386.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2387.IX Item "EV_SELECT_USE_FD_SET"
2388If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2389structure. This is useful if libev doesn't compile due to a missing
2390\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2391exotic systems. This usually limits the range of file descriptors to some
2392low limit such as 1024 or might have other limitations (winsocket only
2393allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2394influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2395.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2396.IX Item "EV_SELECT_IS_WINSOCKET"
2397When defined to \f(CW1\fR, the select backend will assume that
2398select/socket/connect etc. don't understand file descriptors but
2399wants osf handles on win32 (this is the case when the select to
2400be used is the winsock select). This means that it will call
2401\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2402it is assumed that all these functions actually work on fds, even
2403on win32. Should not be defined on non\-win32 platforms.
2404.IP "\s-1EV_USE_POLL\s0" 4
2405.IX Item "EV_USE_POLL"
2406If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2407backend. Otherwise it will be enabled on non\-win32 platforms. It
2408takes precedence over select.
2409.IP "\s-1EV_USE_EPOLL\s0" 4
2410.IX Item "EV_USE_EPOLL"
2411If defined to be \f(CW1\fR, libev will compile in support for the Linux
2412\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2413otherwise another method will be used as fallback. This is the
2414preferred backend for GNU/Linux systems.
2415.IP "\s-1EV_USE_KQUEUE\s0" 4
2416.IX Item "EV_USE_KQUEUE"
2417If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2418\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2419otherwise another method will be used as fallback. This is the preferred
2420backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2421supports some types of fds correctly (the only platform we found that
2422supports ptys for example was NetBSD), so kqueue might be compiled in, but
2423not be used unless explicitly requested. The best way to use it is to find
2424out whether kqueue supports your type of fd properly and use an embedded
2425kqueue loop.
2426.IP "\s-1EV_USE_PORT\s0" 4
2427.IX Item "EV_USE_PORT"
2428If defined to be \f(CW1\fR, libev will compile in support for the Solaris
242910 port style backend. Its availability will be detected at runtime,
2430otherwise another method will be used as fallback. This is the preferred
2431backend for Solaris 10 systems.
2432.IP "\s-1EV_USE_DEVPOLL\s0" 4
2433.IX Item "EV_USE_DEVPOLL"
2434reserved for future expansion, works like the \s-1USE\s0 symbols above.
2435.IP "\s-1EV_USE_INOTIFY\s0" 4
2436.IX Item "EV_USE_INOTIFY"
2437If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2438interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2439be detected at runtime.
2440.IP "\s-1EV_H\s0" 4
2441.IX Item "EV_H"
2442The name of the \fIev.h\fR header file used to include it. The default if
2443undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2444can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2445.IP "\s-1EV_CONFIG_H\s0" 4
2446.IX Item "EV_CONFIG_H"
2447If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2448\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2449\&\f(CW\*(C`EV_H\*(C'\fR, above.
2450.IP "\s-1EV_EVENT_H\s0" 4
2451.IX Item "EV_EVENT_H"
2452Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2453of how the \fIevent.h\fR header can be found.
2454.IP "\s-1EV_PROTOTYPES\s0" 4
2455.IX Item "EV_PROTOTYPES"
2456If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2457prototypes, but still define all the structs and other symbols. This is
2458occasionally useful if you want to provide your own wrapper functions
2459around libev functions.
2460.IP "\s-1EV_MULTIPLICITY\s0" 4
2461.IX Item "EV_MULTIPLICITY"
2462If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2463will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2464additional independent event loops. Otherwise there will be no support
2465for multiple event loops and there is no first event loop pointer
2466argument. Instead, all functions act on the single default loop.
2467.IP "\s-1EV_MINPRI\s0" 4
2468.IX Item "EV_MINPRI"
2469.PD 0
2470.IP "\s-1EV_MAXPRI\s0" 4
2471.IX Item "EV_MAXPRI"
2472.PD
2473The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2474\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2475provide for more priorities by overriding those symbols (usually defined
2476to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2477.Sp
2478When doing priority-based operations, libev usually has to linearly search
2479all the priorities, so having many of them (hundreds) uses a lot of space
2480and time, so using the defaults of five priorities (\-2 .. +2) is usually
2481fine.
2482.Sp
2483If your embedding app does not need any priorities, defining these both to
2484\&\f(CW0\fR will save some memory and cpu.
2485.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2486.IX Item "EV_PERIODIC_ENABLE"
2487If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2488defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2489code.
2490.IP "\s-1EV_IDLE_ENABLE\s0" 4
2491.IX Item "EV_IDLE_ENABLE"
2492If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2493defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2494code.
2495.IP "\s-1EV_EMBED_ENABLE\s0" 4
2496.IX Item "EV_EMBED_ENABLE"
2497If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2498defined to be \f(CW0\fR, then they are not.
2499.IP "\s-1EV_STAT_ENABLE\s0" 4
2500.IX Item "EV_STAT_ENABLE"
2501If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2502defined to be \f(CW0\fR, then they are not.
2503.IP "\s-1EV_FORK_ENABLE\s0" 4
2504.IX Item "EV_FORK_ENABLE"
2505If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2506defined to be \f(CW0\fR, then they are not.
2507.IP "\s-1EV_MINIMAL\s0" 4
2508.IX Item "EV_MINIMAL"
2509If you need to shave off some kilobytes of code at the expense of some
2510speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2511some inlining decisions, saves roughly 30% codesize of amd64.
2512.IP "\s-1EV_PID_HASHSIZE\s0" 4
2513.IX Item "EV_PID_HASHSIZE"
2514\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2515pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2516than enough. If you need to manage thousands of children you might want to
2517increase this value (\fImust\fR be a power of two).
2518.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2519.IX Item "EV_INOTIFY_HASHSIZE"
2520\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2521inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2522usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2523watchers you might want to increase this value (\fImust\fR be a power of
2524two).
2525.IP "\s-1EV_COMMON\s0" 4
2526.IX Item "EV_COMMON"
2527By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2528this macro to a something else you can include more and other types of
2529members. You have to define it each time you include one of the files,
2530though, and it must be identical each time.
2531.Sp
2532For example, the perl \s-1EV\s0 module uses something like this:
2533.Sp
2534.Vb 3
2535\& #define EV_COMMON \e
2536\& SV *self; /* contains this struct */ \e
2537\& SV *cb_sv, *fh /* note no trailing ";" */
2538.Ve
2539.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2540.IX Item "EV_CB_DECLARE (type)"
2541.PD 0
2542.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2543.IX Item "EV_CB_INVOKE (watcher, revents)"
2544.IP "ev_set_cb (ev, cb)" 4
2545.IX Item "ev_set_cb (ev, cb)"
2546.PD
2547Can be used to change the callback member declaration in each watcher,
2548and the way callbacks are invoked and set. Must expand to a struct member
2549definition and a statement, respectively. See the \fIev.v\fR header file for
2550their default definitions. One possible use for overriding these is to
2551avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2552method calls instead of plain function calls in \*(C+.
2553.Sh "\s-1EXAMPLES\s0"
2554.IX Subsection "EXAMPLES"
2555For a real-world example of a program the includes libev
2556verbatim, you can have a look at the \s-1EV\s0 perl module
2557(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2558the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2559interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2560will be compiled. It is pretty complex because it provides its own header
2561file.
2562.Sp
2563The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2564that everybody includes and which overrides some configure choices:
2565.Sp
2566.Vb 9
2567\& #define EV_MINIMAL 1
2568\& #define EV_USE_POLL 0
2569\& #define EV_MULTIPLICITY 0
2570\& #define EV_PERIODIC_ENABLE 0
2571\& #define EV_STAT_ENABLE 0
2572\& #define EV_FORK_ENABLE 0
2573\& #define EV_CONFIG_H <config.h>
2574\& #define EV_MINPRI 0
2575\& #define EV_MAXPRI 0
2576.Ve
2577.Sp
2578.Vb 1
2579\& #include "ev++.h"
2580.Ve
2581.Sp
2582And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2583.Sp
2584.Vb 2
2585\& #include "ev_cpp.h"
2586\& #include "ev.c"
2587.Ve
2588.SH "COMPLEXITIES"
2589.IX Header "COMPLEXITIES"
2590In this section the complexities of (many of) the algorithms used inside
2591libev will be explained. For complexity discussions about backends see the
2592documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2593.Sp
2594All of the following are about amortised time: If an array needs to be
2595extended, libev needs to realloc and move the whole array, but this
2596happens asymptotically never with higher number of elements, so O(1) might
2597mean it might do a lengthy realloc operation in rare cases, but on average
2598it is much faster and asymptotically approaches constant time.
2599.RS 4
2600.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2601.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2602This means that, when you have a watcher that triggers in one hour and
2603there are 100 watchers that would trigger before that then inserting will
2604have to skip those 100 watchers.
2605.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2606.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2607That means that for changing a timer costs less than removing/adding them
2608as only the relative motion in the event queue has to be paid for.
2609.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2610.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2611These just add the watcher into an array or at the head of a list.
2612=item Stopping check/prepare/idle watchers: O(1)
2613.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2614.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2615These watchers are stored in lists then need to be walked to find the
2616correct watcher to remove. The lists are usually short (you don't usually
2617have many watchers waiting for the same fd or signal).
2618.IP "Finding the next timer per loop iteration: O(1)" 4
2619.IX Item "Finding the next timer per loop iteration: O(1)"
2620.PD 0
2621.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2622.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2623.PD
2624A change means an I/O watcher gets started or stopped, which requires
2625libev to recalculate its status (and possibly tell the kernel).
2626.IP "Activating one watcher: O(1)" 4
2627.IX Item "Activating one watcher: O(1)"
2628.PD 0
2629.IP "Priority handling: O(number_of_priorities)" 4
2630.IX Item "Priority handling: O(number_of_priorities)"
2631.PD
2632Priorities are implemented by allocating some space for each
2633priority. When doing priority-based operations, libev usually has to
2634linearly search all the priorities.
2635.RE
2636.RS 4
1020.SH "AUTHOR" 2637.SH "AUTHOR"
1021.IX Header "AUTHOR" 2638.IX Header "AUTHOR"
1022Marc Lehmann <libev@schmorp.de>. 2639Marc Lehmann <libev@schmorp.de>.

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