ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev.3
(Generate patch)

Comparing libev/ev.3 (file contents):
Revision 1.12 by root, Sat Nov 24 07:20:42 2007 UTC vs.
Revision 1.53 by root, Wed Dec 19 01:59:29 2007 UTC

… …
126. ds Ae AE 126. ds Ae AE
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 "EV 1"
132.TH "<STANDARD INPUT>" 1 "2007-11-24" "perl v5.8.8" "User Contributed Perl Documentation" 132.TH EV 1 "2007-12-19" "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 \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on 247to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on
179it, you should treat it as such. 248it, you should treat it as some floatingpoint value. Unlike the name
249component \f(CW\*(C`stamp\*(C'\fR might indicate, it is also used for time differences
250throughout libev.
180.SH "GLOBAL FUNCTIONS" 251.SH "GLOBAL FUNCTIONS"
181.IX Header "GLOBAL FUNCTIONS" 252.IX Header "GLOBAL FUNCTIONS"
182These functions can be called anytime, even before initialising the 253These functions can be called anytime, even before initialising the
183library in any way. 254library in any way.
184.IP "ev_tstamp ev_time ()" 4 255.IP "ev_tstamp ev_time ()" 4
… …
190.IX Item "int ev_version_major ()" 261.IX Item "int ev_version_major ()"
191.PD 0 262.PD 0
192.IP "int ev_version_minor ()" 4 263.IP "int ev_version_minor ()" 4
193.IX Item "int ev_version_minor ()" 264.IX Item "int ev_version_minor ()"
194.PD 265.PD
195You can find out the major and minor version numbers of the library 266You can find out the major and minor \s-1ABI\s0 version numbers of the library
196you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and 267you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and
197\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global 268\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global
198symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the 269symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the
199version of the library your program was compiled against. 270version of the library your program was compiled against.
200.Sp 271.Sp
272These version numbers refer to the \s-1ABI\s0 version of the library, not the
273release version.
274.Sp
201Usually, it's a good idea to terminate if the major versions mismatch, 275Usually, it's a good idea to terminate if the major versions mismatch,
202as this indicates an incompatible change. Minor versions are usually 276as this indicates an incompatible change. Minor versions are usually
203compatible to older versions, so a larger minor version alone is usually 277compatible to older versions, so a larger minor version alone is usually
204not a problem. 278not a problem.
205.Sp 279.Sp
206Example: make sure we haven't accidentally been linked against the wrong 280Example: Make sure we haven't accidentally been linked against the wrong
207version: 281version.
208.Sp 282.Sp
209.Vb 3 283.Vb 3
210\& assert (("libev version mismatch", 284\& assert (("libev version mismatch",
211\& ev_version_major () == EV_VERSION_MAJOR 285\& ev_version_major () == EV_VERSION_MAJOR
212\& && ev_version_minor () >= EV_VERSION_MINOR)); 286\& && ev_version_minor () >= EV_VERSION_MINOR));
… …
242recommended ones. 316recommended ones.
243.Sp 317.Sp
244See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 318See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
245.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4 319.IP "ev_set_allocator (void *(*cb)(void *ptr, long size))" 4
246.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))" 320.IX Item "ev_set_allocator (void *(*cb)(void *ptr, long size))"
247Sets the allocation function to use (the prototype is similar to the 321Sets the allocation function to use (the prototype is similar \- the
248realloc C function, the semantics are identical). It is used to allocate 322semantics is identical \- to the realloc C function). It is used to
249and free memory (no surprises here). If it returns zero when memory 323allocate and free memory (no surprises here). If it returns zero when
250needs to be allocated, the library might abort or take some potentially 324memory needs to be allocated, the library might abort or take some
251destructive action. The default is your system realloc function. 325potentially destructive action. The default is your system realloc
326function.
252.Sp 327.Sp
253You could override this function in high-availability programs to, say, 328You could override this function in high-availability programs to, say,
254free some memory if it cannot allocate memory, to use a special allocator, 329free some memory if it cannot allocate memory, to use a special allocator,
255or even to sleep a while and retry until some memory is available. 330or even to sleep a while and retry until some memory is available.
256.Sp 331.Sp
257Example: replace the libev allocator with one that waits a bit and then 332Example: Replace the libev allocator with one that waits a bit and then
258retries: better than mine). 333retries).
259.Sp 334.Sp
260.Vb 6 335.Vb 6
261\& static void * 336\& static void *
262\& persistent_realloc (void *ptr, long size) 337\& persistent_realloc (void *ptr, size_t size)
263\& { 338\& {
264\& for (;;) 339\& for (;;)
265\& { 340\& {
266\& void *newptr = realloc (ptr, size); 341\& void *newptr = realloc (ptr, size);
267.Ve 342.Ve
… …
289callback is set, then libev will expect it to remedy the sitution, no 364callback is set, then libev will expect it to remedy the sitution, no
290matter what, when it returns. That is, libev will generally retry the 365matter what, when it returns. That is, libev will generally retry the
291requested operation, or, if the condition doesn't go away, do bad stuff 366requested operation, or, if the condition doesn't go away, do bad stuff
292(such as abort). 367(such as abort).
293.Sp 368.Sp
294Example: do the same thing as libev does internally: 369Example: This is basically the same thing that libev does internally, too.
295.Sp 370.Sp
296.Vb 6 371.Vb 6
297\& static void 372\& static void
298\& fatal_error (const char *msg) 373\& fatal_error (const char *msg)
299\& { 374\& {
… …
345or setgid) then libev will \fInot\fR look at the environment variable 420or setgid) then libev will \fInot\fR look at the environment variable
346\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will 421\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will
347override the flags completely if it is found in the environment. This is 422override the flags completely if it is found in the environment. This is
348useful to try out specific backends to test their performance, or to work 423useful to try out specific backends to test their performance, or to work
349around bugs. 424around bugs.
425.ie n .IP """EVFLAG_FORKCHECK""" 4
426.el .IP "\f(CWEVFLAG_FORKCHECK\fR" 4
427.IX Item "EVFLAG_FORKCHECK"
428Instead of calling \f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR manually after
429a fork, you can also make libev check for a fork in each iteration by
430enabling this flag.
431.Sp
432This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
433and thus this might slow down your event loop if you do a lot of loop
434iterations and little real work, but is usually not noticeable (on my
435Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence
436without a syscall and thus \fIvery\fR fast, but my Linux system also has
437\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster).
438.Sp
439The big advantage of this flag is that you can forget about fork (and
440forget about forgetting to tell libev about forking) when you use this
441flag.
442.Sp
443This flag setting cannot be overriden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
444environment variable.
350.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 445.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
351.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 446.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
352.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 447.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
353This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 448This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
354libev tries to roll its own fd_set with no limits on the number of fds, 449libev tries to roll its own fd_set with no limits on the number of fds,
… …
448Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is 543Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is
449always distinct from the default loop. Unlike the default loop, it cannot 544always distinct from the default loop. Unlike the default loop, it cannot
450handle signal and child watchers, and attempts to do so will be greeted by 545handle signal and child watchers, and attempts to do so will be greeted by
451undefined behaviour (or a failed assertion if assertions are enabled). 546undefined behaviour (or a failed assertion if assertions are enabled).
452.Sp 547.Sp
453Example: try to create a event loop that uses epoll and nothing else. 548Example: Try to create a event loop that uses epoll and nothing else.
454.Sp 549.Sp
455.Vb 3 550.Vb 3
456\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); 551\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV);
457\& if (!epoller) 552\& if (!epoller)
458\& fatal ("no epoll found here, maybe it hides under your chair"); 553\& fatal ("no epoll found here, maybe it hides under your chair");
… …
462Destroys the default loop again (frees all memory and kernel state 557Destroys the default loop again (frees all memory and kernel state
463etc.). None of the active event watchers will be stopped in the normal 558etc.). None of the active event watchers will be stopped in the normal
464sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your 559sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your
465responsibility to either stop all watchers cleanly yoursef \fIbefore\fR 560responsibility to either stop all watchers cleanly yoursef \fIbefore\fR
466calling this function, or cope with the fact afterwards (which is usually 561calling this function, or cope with the fact afterwards (which is usually
467the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them 562the easiest thing, you can just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them
468for example). 563for example).
564.Sp
565Not that certain global state, such as signal state, will not be freed by
566this function, and related watchers (such as signal and child watchers)
567would need to be stopped manually.
568.Sp
569In general it is not advisable to call this function except in the
570rare occasion where you really need to free e.g. the signal handling
571pipe fds. If you need dynamically allocated loops it is better to use
572\&\f(CW\*(C`ev_loop_new\*(C'\fR and \f(CW\*(C`ev_loop_destroy\*(C'\fR).
469.IP "ev_loop_destroy (loop)" 4 573.IP "ev_loop_destroy (loop)" 4
470.IX Item "ev_loop_destroy (loop)" 574.IX Item "ev_loop_destroy (loop)"
471Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an 575Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an
472earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. 576earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR.
473.IP "ev_default_fork ()" 4 577.IP "ev_default_fork ()" 4
… …
495.IP "ev_loop_fork (loop)" 4 599.IP "ev_loop_fork (loop)" 4
496.IX Item "ev_loop_fork (loop)" 600.IX Item "ev_loop_fork (loop)"
497Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by 601Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by
498\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop 602\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop
499after fork, and how you do this is entirely your own problem. 603after fork, and how you do this is entirely your own problem.
604.IP "unsigned int ev_loop_count (loop)" 4
605.IX Item "unsigned int ev_loop_count (loop)"
606Returns the count of loop iterations for the loop, which is identical to
607the number of times libev did poll for new events. It starts at \f(CW0\fR and
608happily wraps around with enough iterations.
609.Sp
610This value can sometimes be useful as a generation counter of sorts (it
611\&\*(L"ticks\*(R" the number of loop iterations), as it roughly corresponds with
612\&\f(CW\*(C`ev_prepare\*(C'\fR and \f(CW\*(C`ev_check\*(C'\fR calls.
500.IP "unsigned int ev_backend (loop)" 4 613.IP "unsigned int ev_backend (loop)" 4
501.IX Item "unsigned int ev_backend (loop)" 614.IX Item "unsigned int ev_backend (loop)"
502Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in 615Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in
503use. 616use.
504.IP "ev_tstamp ev_now (loop)" 4 617.IP "ev_tstamp ev_now (loop)" 4
… …
535libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is 648libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is
536usually a better approach for this kind of thing. 649usually a better approach for this kind of thing.
537.Sp 650.Sp
538Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: 651Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does:
539.Sp 652.Sp
540.Vb 18 653.Vb 19
654\& - Before the first iteration, call any pending watchers.
541\& * If there are no active watchers (reference count is zero), return. 655\& * If there are no active watchers (reference count is zero), return.
542\& - Queue prepare watchers and then call all outstanding watchers. 656\& - Queue all prepare watchers and then call all outstanding watchers.
543\& - If we have been forked, recreate the kernel state. 657\& - If we have been forked, recreate the kernel state.
544\& - Update the kernel state with all outstanding changes. 658\& - Update the kernel state with all outstanding changes.
545\& - Update the "event loop time". 659\& - Update the "event loop time".
546\& - Calculate for how long to block. 660\& - Calculate for how long to block.
547\& - Block the process, waiting for any events. 661\& - Block the process, waiting for any events.
… …
556\& be handled here by queueing them when their watcher gets executed. 670\& be handled here by queueing them when their watcher gets executed.
557\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK 671\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK
558\& were used, return, otherwise continue with step *. 672\& were used, return, otherwise continue with step *.
559.Ve 673.Ve
560.Sp 674.Sp
561Example: queue some jobs and then loop until no events are outsanding 675Example: Queue some jobs and then loop until no events are outsanding
562anymore. 676anymore.
563.Sp 677.Sp
564.Vb 4 678.Vb 4
565\& ... queue jobs here, make sure they register event watchers as long 679\& ... queue jobs here, make sure they register event watchers as long
566\& ... as they still have work to do (even an idle watcher will do..) 680\& ... as they still have work to do (even an idle watcher will do..)
… …
588visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if 702visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if
589no event watchers registered by it are active. It is also an excellent 703no event watchers registered by it are active. It is also an excellent
590way to do this for generic recurring timers or from within third-party 704way to do this for generic recurring timers or from within third-party
591libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. 705libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR.
592.Sp 706.Sp
593Example: create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR 707Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR
594running when nothing else is active. 708running when nothing else is active.
595.Sp 709.Sp
596.Vb 4 710.Vb 4
597\& struct dv_signal exitsig; 711\& struct ev_signal exitsig;
598\& ev_signal_init (&exitsig, sig_cb, SIGINT); 712\& ev_signal_init (&exitsig, sig_cb, SIGINT);
599\& ev_signal_start (myloop, &exitsig); 713\& ev_signal_start (loop, &exitsig);
600\& evf_unref (myloop); 714\& evf_unref (loop);
601.Ve 715.Ve
602.Sp 716.Sp
603Example: for some weird reason, unregister the above signal handler again. 717Example: For some weird reason, unregister the above signal handler again.
604.Sp 718.Sp
605.Vb 2 719.Vb 2
606\& ev_ref (myloop); 720\& ev_ref (loop);
607\& ev_signal_stop (myloop, &exitsig); 721\& ev_signal_stop (loop, &exitsig);
608.Ve 722.Ve
609.SH "ANATOMY OF A WATCHER" 723.SH "ANATOMY OF A WATCHER"
610.IX Header "ANATOMY OF A WATCHER" 724.IX Header "ANATOMY OF A WATCHER"
611A watcher is a structure that you create and register to record your 725A watcher is a structure that you create and register to record your
612interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to 726interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to
… …
684The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. 798The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread.
685.ie n .IP """EV_CHILD""" 4 799.ie n .IP """EV_CHILD""" 4
686.el .IP "\f(CWEV_CHILD\fR" 4 800.el .IP "\f(CWEV_CHILD\fR" 4
687.IX Item "EV_CHILD" 801.IX Item "EV_CHILD"
688The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. 802The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change.
803.ie n .IP """EV_STAT""" 4
804.el .IP "\f(CWEV_STAT\fR" 4
805.IX Item "EV_STAT"
806The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow.
689.ie n .IP """EV_IDLE""" 4 807.ie n .IP """EV_IDLE""" 4
690.el .IP "\f(CWEV_IDLE\fR" 4 808.el .IP "\f(CWEV_IDLE\fR" 4
691.IX Item "EV_IDLE" 809.IX Item "EV_IDLE"
692The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. 810The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do.
693.ie n .IP """EV_PREPARE""" 4 811.ie n .IP """EV_PREPARE""" 4
… …
703\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any 821\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any
704received events. Callbacks of both watcher types can start and stop as 822received events. Callbacks of both watcher types can start and stop as
705many watchers as they want, and all of them will be taken into account 823many watchers as they want, and all of them will be taken into account
706(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep 824(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep
707\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). 825\&\f(CW\*(C`ev_loop\*(C'\fR from blocking).
826.ie n .IP """EV_EMBED""" 4
827.el .IP "\f(CWEV_EMBED\fR" 4
828.IX Item "EV_EMBED"
829The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention.
830.ie n .IP """EV_FORK""" 4
831.el .IP "\f(CWEV_FORK\fR" 4
832.IX Item "EV_FORK"
833The event loop has been resumed in the child process after fork (see
834\&\f(CW\*(C`ev_fork\*(C'\fR).
708.ie n .IP """EV_ERROR""" 4 835.ie n .IP """EV_ERROR""" 4
709.el .IP "\f(CWEV_ERROR\fR" 4 836.el .IP "\f(CWEV_ERROR\fR" 4
710.IX Item "EV_ERROR" 837.IX Item "EV_ERROR"
711An unspecified error has occured, the watcher has been stopped. This might 838An unspecified error has occured, the watcher has been stopped. This might
712happen because the watcher could not be properly started because libev 839happen because the watcher could not be properly started because libev
… …
717Libev will usually signal a few \*(L"dummy\*(R" events together with an error, 844Libev will usually signal a few \*(L"dummy\*(R" events together with an error,
718for example it might indicate that a fd is readable or writable, and if 845for example it might indicate that a fd is readable or writable, and if
719your callbacks is well-written it can just attempt the operation and cope 846your callbacks is well-written it can just attempt the operation and cope
720with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded 847with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded
721programs, though, so beware. 848programs, though, so beware.
722.Sh "\s-1SUMMARY\s0 \s-1OF\s0 \s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" 849.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0"
723.IX Subsection "SUMMARY OF GENERIC WATCHER FUNCTIONS" 850.IX Subsection "GENERIC WATCHER FUNCTIONS"
724In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, 851In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type,
725e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers. 852e.g. \f(CW\*(C`timer\*(C'\fR for \f(CW\*(C`ev_timer\*(C'\fR watchers and \f(CW\*(C`io\*(C'\fR for \f(CW\*(C`ev_io\*(C'\fR watchers.
726.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 853.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
727.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 854.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4
728.IX Item "ev_init (ev_TYPE *watcher, callback)" 855.IX Item "ev_init (ev_TYPE *watcher, callback)"
… …
734which rolls both calls into one. 861which rolls both calls into one.
735.Sp 862.Sp
736You can reinitialise a watcher at any time as long as it has been stopped 863You can reinitialise a watcher at any time as long as it has been stopped
737(or never started) and there are no pending events outstanding. 864(or never started) and there are no pending events outstanding.
738.Sp 865.Sp
739The callbakc is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, 866The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher,
740int revents)\*(C'\fR. 867int revents)\*(C'\fR.
741.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 868.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4
742.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 869.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4
743.IX Item "ev_TYPE_set (ev_TYPE *, [args])" 870.IX Item "ev_TYPE_set (ev_TYPE *, [args])"
744This macro initialises the type-specific parts of a watcher. You need to 871This macro initialises the type-specific parts of a watcher. You need to
… …
777.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 904.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
778.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 905.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
779Returns a true value iff the watcher is pending, (i.e. it has outstanding 906Returns a true value iff the watcher is pending, (i.e. it has outstanding
780events but its callback has not yet been invoked). As long as a watcher 907events but its callback has not yet been invoked). As long as a watcher
781is pending (but not active) you must not call an init function on it (but 908is pending (but not active) you must not call an init function on it (but
782\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to 909\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe), you must not change its priority, and you must
783libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). 910make sure the watcher is available to libev (e.g. you cannot \f(CW\*(C`free ()\*(C'\fR
911it).
784.IP "callback = ev_cb (ev_TYPE *watcher)" 4 912.IP "callback ev_cb (ev_TYPE *watcher)" 4
785.IX Item "callback = ev_cb (ev_TYPE *watcher)" 913.IX Item "callback ev_cb (ev_TYPE *watcher)"
786Returns the callback currently set on the watcher. 914Returns the callback currently set on the watcher.
787.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 915.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4
788.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" 916.IX Item "ev_cb_set (ev_TYPE *watcher, callback)"
789Change the callback. You can change the callback at virtually any time 917Change the callback. You can change the callback at virtually any time
790(modulo threads). 918(modulo threads).
919.IP "ev_set_priority (ev_TYPE *watcher, priority)" 4
920.IX Item "ev_set_priority (ev_TYPE *watcher, priority)"
921.PD 0
922.IP "int ev_priority (ev_TYPE *watcher)" 4
923.IX Item "int ev_priority (ev_TYPE *watcher)"
924.PD
925Set and query the priority of the watcher. The priority is a small
926integer between \f(CW\*(C`EV_MAXPRI\*(C'\fR (default: \f(CW2\fR) and \f(CW\*(C`EV_MINPRI\*(C'\fR
927(default: \f(CW\*(C`\-2\*(C'\fR). Pending watchers with higher priority will be invoked
928before watchers with lower priority, but priority will not keep watchers
929from being executed (except for \f(CW\*(C`ev_idle\*(C'\fR watchers).
930.Sp
931This means that priorities are \fIonly\fR used for ordering callback
932invocation after new events have been received. This is useful, for
933example, to reduce latency after idling, or more often, to bind two
934watchers on the same event and make sure one is called first.
935.Sp
936If you need to suppress invocation when higher priority events are pending
937you need to look at \f(CW\*(C`ev_idle\*(C'\fR watchers, which provide this functionality.
938.Sp
939You \fImust not\fR change the priority of a watcher as long as it is active or
940pending.
941.Sp
942The default priority used by watchers when no priority has been set is
943always \f(CW0\fR, which is supposed to not be too high and not be too low :).
944.Sp
945Setting a priority outside the range of \f(CW\*(C`EV_MINPRI\*(C'\fR to \f(CW\*(C`EV_MAXPRI\*(C'\fR is
946fine, as long as you do not mind that the priority value you query might
947or might not have been adjusted to be within valid range.
948.IP "ev_invoke (loop, ev_TYPE *watcher, int revents)" 4
949.IX Item "ev_invoke (loop, ev_TYPE *watcher, int revents)"
950Invoke the \f(CW\*(C`watcher\*(C'\fR with the given \f(CW\*(C`loop\*(C'\fR and \f(CW\*(C`revents\*(C'\fR. Neither
951\&\f(CW\*(C`loop\*(C'\fR nor \f(CW\*(C`revents\*(C'\fR need to be valid as long as the watcher callback
952can deal with that fact.
953.IP "int ev_clear_pending (loop, ev_TYPE *watcher)" 4
954.IX Item "int ev_clear_pending (loop, ev_TYPE *watcher)"
955If the watcher is pending, this function returns clears its pending status
956and returns its \f(CW\*(C`revents\*(C'\fR bitset (as if its callback was invoked). If the
957watcher isn't pending it does nothing and returns \f(CW0\fR.
791.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" 958.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0"
792.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" 959.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER"
793Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change 960Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change
794and read at any time, libev will completely ignore it. This can be used 961and read at any time, libev will completely ignore it. This can be used
795to associate arbitrary data with your watcher. If you need more data and 962to associate arbitrary data with your watcher. If you need more data and
… …
816\& struct my_io *w = (struct my_io *)w_; 983\& struct my_io *w = (struct my_io *)w_;
817\& ... 984\& ...
818\& } 985\& }
819.Ve 986.Ve
820.PP 987.PP
821More interesting and less C\-conformant ways of catsing your callback type 988More interesting and less C\-conformant ways of casting your callback type
822have been omitted.... 989instead have been omitted.
990.PP
991Another common scenario is having some data structure with multiple
992watchers:
993.PP
994.Vb 6
995\& struct my_biggy
996\& {
997\& int some_data;
998\& ev_timer t1;
999\& ev_timer t2;
1000\& }
1001.Ve
1002.PP
1003In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated,
1004you need to use \f(CW\*(C`offsetof\*(C'\fR:
1005.PP
1006.Vb 1
1007\& #include <stddef.h>
1008.Ve
1009.PP
1010.Vb 6
1011\& static void
1012\& t1_cb (EV_P_ struct ev_timer *w, int revents)
1013\& {
1014\& struct my_biggy big = (struct my_biggy *
1015\& (((char *)w) - offsetof (struct my_biggy, t1));
1016\& }
1017.Ve
1018.PP
1019.Vb 6
1020\& static void
1021\& t2_cb (EV_P_ struct ev_timer *w, int revents)
1022\& {
1023\& struct my_biggy big = (struct my_biggy *
1024\& (((char *)w) - offsetof (struct my_biggy, t2));
1025\& }
1026.Ve
823.SH "WATCHER TYPES" 1027.SH "WATCHER TYPES"
824.IX Header "WATCHER TYPES" 1028.IX Header "WATCHER TYPES"
825This section describes each watcher in detail, but will not repeat 1029This section describes each watcher in detail, but will not repeat
826information given in the last section. 1030information given in the last section. Any initialisation/set macros,
1031functions and members specific to the watcher type are explained.
1032.PP
1033Members are additionally marked with either \fI[read\-only]\fR, meaning that,
1034while the watcher is active, you can look at the member and expect some
1035sensible content, but you must not modify it (you can modify it while the
1036watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1037means you can expect it to have some sensible content while the watcher
1038is active, but you can also modify it. Modifying it may not do something
1039sensible or take immediate effect (or do anything at all), but libev will
1040not crash or malfunction in any way.
827.ie n .Sh """ev_io"" \- is this file descriptor readable or writable" 1041.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?"
828.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable" 1042.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?"
829.IX Subsection "ev_io - is this file descriptor readable or writable" 1043.IX Subsection "ev_io - is this file descriptor readable or writable?"
830I/O watchers check whether a file descriptor is readable or writable 1044I/O watchers check whether a file descriptor is readable or writable
831in each iteration of the event loop (This behaviour is called 1045in each iteration of the event loop, or, more precisely, when reading
832level-triggering because you keep receiving events as long as the 1046would not block the process and writing would at least be able to write
833condition persists. Remember you can stop the watcher if you don't want to 1047some data. This behaviour is called level-triggering because you keep
834act on the event and neither want to receive future events). 1048receiving events as long as the condition persists. Remember you can stop
1049the watcher if you don't want to act on the event and neither want to
1050receive future events.
835.PP 1051.PP
836In general you can register as many read and/or write event watchers per 1052In general you can register as many read and/or write event watchers per
837fd as you want (as long as you don't confuse yourself). Setting all file 1053fd as you want (as long as you don't confuse yourself). Setting all file
838descriptors to non-blocking mode is also usually a good idea (but not 1054descriptors to non-blocking mode is also usually a good idea (but not
839required if you know what you are doing). 1055required if you know what you are doing).
840.PP 1056.PP
841You have to be careful with dup'ed file descriptors, though. Some backends 1057You have to be careful with dup'ed file descriptors, though. Some backends
842(the linux epoll backend is a notable example) cannot handle dup'ed file 1058(the linux epoll backend is a notable example) cannot handle dup'ed file
843descriptors correctly if you register interest in two or more fds pointing 1059descriptors correctly if you register interest in two or more fds pointing
844to the same underlying file/socket etc. description (that is, they share 1060to the same underlying file/socket/etc. description (that is, they share
845the same underlying \*(L"file open\*(R"). 1061the same underlying \*(L"file open\*(R").
846.PP 1062.PP
847If you must do this, then force the use of a known-to-be-good backend 1063If you must do this, then force the use of a known-to-be-good backend
848(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and 1064(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and
849\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). 1065\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR).
1066.PP
1067Another thing you have to watch out for is that it is quite easy to
1068receive \*(L"spurious\*(R" readyness notifications, that is your callback might
1069be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block
1070because there is no data. Not only are some backends known to create a
1071lot of those (for example solaris ports), it is very easy to get into
1072this situation even with a relatively standard program structure. Thus
1073it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning
1074\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives.
1075.PP
1076If you cannot run the fd in non-blocking mode (for example you should not
1077play around with an Xlib connection), then you have to seperately re-test
1078whether a file descriptor is really ready with a known-to-be good interface
1079such as poll (fortunately in our Xlib example, Xlib already does this on
1080its own, so its quite safe to use).
1081.PP
1082\fIThe special problem of disappearing file descriptors\fR
1083.IX Subsection "The special problem of disappearing file descriptors"
1084.PP
1085Some backends (e.g kqueue, epoll) need to be told about closing a file
1086descriptor (either by calling \f(CW\*(C`close\*(C'\fR explicitly or by any other means,
1087such as \f(CW\*(C`dup\*(C'\fR). The reason is that you register interest in some file
1088descriptor, but when it goes away, the operating system will silently drop
1089this interest. If another file descriptor with the same number then is
1090registered with libev, there is no efficient way to see that this is, in
1091fact, a different file descriptor.
1092.PP
1093To avoid having to explicitly tell libev about such cases, libev follows
1094the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1095will assume that this is potentially a new file descriptor, otherwise
1096it is assumed that the file descriptor stays the same. That means that
1097you \fIhave\fR to call \f(CW\*(C`ev_io_set\*(C'\fR (or \f(CW\*(C`ev_io_init\*(C'\fR) when you change the
1098descriptor even if the file descriptor number itself did not change.
1099.PP
1100This is how one would do it normally anyway, the important point is that
1101the libev application should not optimise around libev but should leave
1102optimisations to libev.
1103.PP
1104\fIWatcher-Specific Functions\fR
1105.IX Subsection "Watcher-Specific Functions"
850.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 1106.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4
851.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" 1107.IX Item "ev_io_init (ev_io *, callback, int fd, int events)"
852.PD 0 1108.PD 0
853.IP "ev_io_set (ev_io *, int fd, int events)" 4 1109.IP "ev_io_set (ev_io *, int fd, int events)" 4
854.IX Item "ev_io_set (ev_io *, int fd, int events)" 1110.IX Item "ev_io_set (ev_io *, int fd, int events)"
855.PD 1111.PD
856Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The fd is the file descriptor to rceeive 1112Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
857events 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 | 1113rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or
858EV_WRITE\*(C'\fR to receive the given events. 1114\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events.
859.Sp 1115.IP "int fd [read\-only]" 4
860Please note that most of the more scalable backend mechanisms (for example 1116.IX Item "int fd [read-only]"
861epoll and solaris ports) can result in spurious readyness notifications 1117The file descriptor being watched.
862for file descriptors, so you practically need to use non-blocking I/O (and 1118.IP "int events [read\-only]" 4
863treat callback invocation as hint only), or retest separately with a safe 1119.IX Item "int events [read-only]"
864interface before doing I/O (XLib can do this), or force the use of either 1120The events being watched.
865\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR, which don't suffer from this
866problem. Also note that it is quite easy to have your callback invoked
867when the readyness condition is no longer valid even when employing
868typical ways of handling events, so its a good idea to use non-blocking
869I/O unconditionally.
870.PP 1121.PP
871Example: call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1122Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
872readable, but only once. Since it is likely line\-buffered, you could 1123readable, but only once. Since it is likely line\-buffered, you could
873attempt to read a whole line in the callback: 1124attempt to read a whole line in the callback.
874.PP 1125.PP
875.Vb 6 1126.Vb 6
876\& static void 1127\& static void
877\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) 1128\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents)
878\& { 1129\& {
… …
887\& struct ev_io stdin_readable; 1138\& struct ev_io stdin_readable;
888\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); 1139\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ);
889\& ev_io_start (loop, &stdin_readable); 1140\& ev_io_start (loop, &stdin_readable);
890\& ev_loop (loop, 0); 1141\& ev_loop (loop, 0);
891.Ve 1142.Ve
892.ie n .Sh """ev_timer"" \- relative and optionally recurring timeouts" 1143.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts"
893.el .Sh "\f(CWev_timer\fP \- relative and optionally recurring timeouts" 1144.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts"
894.IX Subsection "ev_timer - relative and optionally recurring timeouts" 1145.IX Subsection "ev_timer - relative and optionally repeating timeouts"
895Timer watchers are simple relative timers that generate an event after a 1146Timer watchers are simple relative timers that generate an event after a
896given time, and optionally repeating in regular intervals after that. 1147given time, and optionally repeating in regular intervals after that.
897.PP 1148.PP
898The timers are based on real time, that is, if you register an event that 1149The timers are based on real time, that is, if you register an event that
899times out after an hour and you reset your system clock to last years 1150times out after an hour and you reset your system clock to last years
… …
912.Ve 1163.Ve
913.PP 1164.PP
914The callback is guarenteed to be invoked only when its timeout has passed, 1165The callback is guarenteed to be invoked only when its timeout has passed,
915but if multiple timers become ready during the same loop iteration then 1166but if multiple timers become ready during the same loop iteration then
916order of execution is undefined. 1167order of execution is undefined.
1168.PP
1169\fIWatcher-Specific Functions and Data Members\fR
1170.IX Subsection "Watcher-Specific Functions and Data Members"
917.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 1171.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4
918.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 1172.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
919.PD 0 1173.PD 0
920.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 1174.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
921.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 1175.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
… …
933.IP "ev_timer_again (loop)" 4 1187.IP "ev_timer_again (loop)" 4
934.IX Item "ev_timer_again (loop)" 1188.IX Item "ev_timer_again (loop)"
935This will act as if the timer timed out and restart it again if it is 1189This will act as if the timer timed out and restart it again if it is
936repeating. The exact semantics are: 1190repeating. The exact semantics are:
937.Sp 1191.Sp
1192If the timer is pending, its pending status is cleared.
1193.Sp
938If the timer is started but nonrepeating, stop it. 1194If the timer is started but nonrepeating, stop it (as if it timed out).
939.Sp 1195.Sp
940If the timer is repeating, either start it if necessary (with the repeat 1196If the timer is repeating, either start it if necessary (with the
941value), or reset the running timer to the repeat value. 1197\&\f(CW\*(C`repeat\*(C'\fR value), or reset the running timer to the \f(CW\*(C`repeat\*(C'\fR value.
942.Sp 1198.Sp
943This sounds a bit complicated, but here is a useful and typical 1199This sounds a bit complicated, but here is a useful and typical
944example: Imagine you have a tcp connection and you want a so-called idle 1200example: Imagine you have a tcp connection and you want a so-called idle
945timeout, that is, you want to be called when there have been, say, 60 1201timeout, that is, you want to be called when there have been, say, 60
946seconds of inactivity on the socket. The easiest way to do this is to 1202seconds of inactivity on the socket. The easiest way to do this is to
947configure an \f(CW\*(C`ev_timer\*(C'\fR with after=repeat=60 and calling ev_timer_again each 1203configure an \f(CW\*(C`ev_timer\*(C'\fR with a \f(CW\*(C`repeat\*(C'\fR value of \f(CW60\fR and then call
948time you successfully read or write some data. If you go into an idle 1204\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If
949state where you do not expect data to travel on the socket, you can stop 1205you go into an idle state where you do not expect data to travel on the
950the timer, and again will automatically restart it if need be. 1206socket, you can \f(CW\*(C`ev_timer_stop\*(C'\fR the timer, and \f(CW\*(C`ev_timer_again\*(C'\fR will
1207automatically restart it if need be.
1208.Sp
1209That means you can ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR
1210altogether and only ever use the \f(CW\*(C`repeat\*(C'\fR value and \f(CW\*(C`ev_timer_again\*(C'\fR:
1211.Sp
1212.Vb 8
1213\& ev_timer_init (timer, callback, 0., 5.);
1214\& ev_timer_again (loop, timer);
1215\& ...
1216\& timer->again = 17.;
1217\& ev_timer_again (loop, timer);
1218\& ...
1219\& timer->again = 10.;
1220\& ev_timer_again (loop, timer);
1221.Ve
1222.Sp
1223This is more slightly efficient then stopping/starting the timer each time
1224you want to modify its timeout value.
1225.IP "ev_tstamp repeat [read\-write]" 4
1226.IX Item "ev_tstamp repeat [read-write]"
1227The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out
1228or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any),
1229which is also when any modifications are taken into account.
951.PP 1230.PP
952Example: create a timer that fires after 60 seconds. 1231Example: Create a timer that fires after 60 seconds.
953.PP 1232.PP
954.Vb 5 1233.Vb 5
955\& static void 1234\& static void
956\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1235\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
957\& { 1236\& {
… …
963\& struct ev_timer mytimer; 1242\& struct ev_timer mytimer;
964\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); 1243\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.);
965\& ev_timer_start (loop, &mytimer); 1244\& ev_timer_start (loop, &mytimer);
966.Ve 1245.Ve
967.PP 1246.PP
968Example: create a timeout timer that times out after 10 seconds of 1247Example: Create a timeout timer that times out after 10 seconds of
969inactivity. 1248inactivity.
970.PP 1249.PP
971.Vb 5 1250.Vb 5
972\& static void 1251\& static void
973\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1252\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
… …
986.Vb 3 1265.Vb 3
987\& // and in some piece of code that gets executed on any "activity": 1266\& // and in some piece of code that gets executed on any "activity":
988\& // reset the timeout to start ticking again at 10 seconds 1267\& // reset the timeout to start ticking again at 10 seconds
989\& ev_timer_again (&mytimer); 1268\& ev_timer_again (&mytimer);
990.Ve 1269.Ve
991.ie n .Sh """ev_periodic"" \- to cron or not to cron" 1270.ie n .Sh """ev_periodic"" \- to cron or not to cron?"
992.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron" 1271.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?"
993.IX Subsection "ev_periodic - to cron or not to cron" 1272.IX Subsection "ev_periodic - to cron or not to cron?"
994Periodic watchers are also timers of a kind, but they are very versatile 1273Periodic watchers are also timers of a kind, but they are very versatile
995(and unfortunately a bit complex). 1274(and unfortunately a bit complex).
996.PP 1275.PP
997Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) 1276Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time)
998but on wallclock time (absolute time). You can tell a periodic watcher 1277but on wallclock time (absolute time). You can tell a periodic watcher
999to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a 1278to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a
1000periodic watcher to trigger in 10 seconds (by specifiying e.g. c<ev_now () 1279periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now ()
1001+ 10.>) and then reset your system clock to the last year, then it will 1280+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will
1002take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger 1281take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger
1003roughly 10 seconds later and of course not if you reset your system time 1282roughly 10 seconds later).
1004again).
1005.PP 1283.PP
1006They can also be used to implement vastly more complex timers, such as 1284They can also be used to implement vastly more complex timers, such as
1007triggering an event on eahc midnight, local time. 1285triggering an event on each midnight, local time or other, complicated,
1286rules.
1008.PP 1287.PP
1009As with timers, the callback is guarenteed to be invoked only when the 1288As with timers, the callback is guarenteed to be invoked only when the
1010time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready 1289time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready
1011during the same loop iteration then order of execution is undefined. 1290during the same loop iteration then order of execution is undefined.
1291.PP
1292\fIWatcher-Specific Functions and Data Members\fR
1293.IX Subsection "Watcher-Specific Functions and Data Members"
1012.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 1294.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4
1013.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 1295.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)"
1014.PD 0 1296.PD 0
1015.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 1297.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4
1016.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 1298.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)"
1017.PD 1299.PD
1018Lots of arguments, lets sort it out... There are basically three modes of 1300Lots of arguments, lets sort it out... There are basically three modes of
1019operation, and we will explain them from simplest to complex: 1301operation, and we will explain them from simplest to complex:
1020.RS 4 1302.RS 4
1021.IP "* absolute timer (interval = reschedule_cb = 0)" 4 1303.IP "* absolute timer (at = time, interval = reschedule_cb = 0)" 4
1022.IX Item "absolute timer (interval = reschedule_cb = 0)" 1304.IX Item "absolute timer (at = time, interval = reschedule_cb = 0)"
1023In this configuration the watcher triggers an event at the wallclock time 1305In this configuration the watcher triggers an event at the wallclock time
1024\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, 1306\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs,
1025that is, if it is to be run at January 1st 2011 then it will run when the 1307that is, if it is to be run at January 1st 2011 then it will run when the
1026system time reaches or surpasses this time. 1308system time reaches or surpasses this time.
1027.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 1309.IP "* non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)" 4
1028.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" 1310.IX Item "non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)"
1029In this mode the watcher will always be scheduled to time out at the next 1311In this mode the watcher will always be scheduled to time out at the next
1030\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless 1312\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N, which can also be negative)
1031of any time jumps. 1313and then repeat, regardless of any time jumps.
1032.Sp 1314.Sp
1033This can be used to create timers that do not drift with respect to system 1315This can be used to create timers that do not drift with respect to system
1034time: 1316time:
1035.Sp 1317.Sp
1036.Vb 1 1318.Vb 1
… …
1043by 3600. 1325by 3600.
1044.Sp 1326.Sp
1045Another way to think about it (for the mathematically inclined) is that 1327Another way to think about it (for the mathematically inclined) is that
1046\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible 1328\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible
1047time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. 1329time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps.
1330.Sp
1331For numerical stability it is preferable that the \f(CW\*(C`at\*(C'\fR value is near
1332\&\f(CW\*(C`ev_now ()\*(C'\fR (the current time), but there is no range requirement for
1333this value.
1048.IP "* manual reschedule mode (reschedule_cb = callback)" 4 1334.IP "* manual reschedule mode (at and interval ignored, reschedule_cb = callback)" 4
1049.IX Item "manual reschedule mode (reschedule_cb = callback)" 1335.IX Item "manual reschedule mode (at and interval ignored, reschedule_cb = callback)"
1050In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being 1336In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being
1051ignored. Instead, each time the periodic watcher gets scheduled, the 1337ignored. Instead, each time the periodic watcher gets scheduled, the
1052reschedule callback will be called with the watcher as first, and the 1338reschedule callback will be called with the watcher as first, and the
1053current time as second argument. 1339current time as second argument.
1054.Sp 1340.Sp
1055\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, 1341\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher,
1056ever, or make any event loop modifications\fR. If you need to stop it, 1342ever, or make any event loop modifications\fR. If you need to stop it,
1057return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by 1343return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by
1058starting a prepare watcher). 1344starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is legal).
1059.Sp 1345.Sp
1060Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1346Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1061ev_tstamp now)\*(C'\fR, e.g.: 1347ev_tstamp now)\*(C'\fR, e.g.:
1062.Sp 1348.Sp
1063.Vb 4 1349.Vb 4
… …
1087.IX Item "ev_periodic_again (loop, ev_periodic *)" 1373.IX Item "ev_periodic_again (loop, ev_periodic *)"
1088Simply stops and restarts the periodic watcher again. This is only useful 1374Simply stops and restarts the periodic watcher again. This is only useful
1089when you changed some parameters or the reschedule callback would return 1375when you changed some parameters or the reschedule callback would return
1090a different time than the last time it was called (e.g. in a crond like 1376a different time than the last time it was called (e.g. in a crond like
1091program when the crontabs have changed). 1377program when the crontabs have changed).
1378.IP "ev_tstamp offset [read\-write]" 4
1379.IX Item "ev_tstamp offset [read-write]"
1380When repeating, this contains the offset value, otherwise this is the
1381absolute point in time (the \f(CW\*(C`at\*(C'\fR value passed to \f(CW\*(C`ev_periodic_set\*(C'\fR).
1382.Sp
1383Can be modified any time, but changes only take effect when the periodic
1384timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1385.IP "ev_tstamp interval [read\-write]" 4
1386.IX Item "ev_tstamp interval [read-write]"
1387The current interval value. Can be modified any time, but changes only
1388take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being
1389called.
1390.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4
1391.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]"
1392The current reschedule callback, or \f(CW0\fR, if this functionality is
1393switched off. Can be changed any time, but changes only take effect when
1394the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called.
1395.IP "ev_tstamp at [read\-only]" 4
1396.IX Item "ev_tstamp at [read-only]"
1397When active, contains the absolute time that the watcher is supposed to
1398trigger next.
1092.PP 1399.PP
1093Example: call a callback every hour, or, more precisely, whenever the 1400Example: Call a callback every hour, or, more precisely, whenever the
1094system clock is divisible by 3600. The callback invocation times have 1401system clock is divisible by 3600. The callback invocation times have
1095potentially a lot of jittering, but good long-term stability. 1402potentially a lot of jittering, but good long-term stability.
1096.PP 1403.PP
1097.Vb 5 1404.Vb 5
1098\& static void 1405\& static void
… …
1106\& struct ev_periodic hourly_tick; 1413\& struct ev_periodic hourly_tick;
1107\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); 1414\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0);
1108\& ev_periodic_start (loop, &hourly_tick); 1415\& ev_periodic_start (loop, &hourly_tick);
1109.Ve 1416.Ve
1110.PP 1417.PP
1111Example: the same as above, but use a reschedule callback to do it: 1418Example: The same as above, but use a reschedule callback to do it:
1112.PP 1419.PP
1113.Vb 1 1420.Vb 1
1114\& #include <math.h> 1421\& #include <math.h>
1115.Ve 1422.Ve
1116.PP 1423.PP
… …
1124.PP 1431.PP
1125.Vb 1 1432.Vb 1
1126\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); 1433\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb);
1127.Ve 1434.Ve
1128.PP 1435.PP
1129Example: call a callback every hour, starting now: 1436Example: Call a callback every hour, starting now:
1130.PP 1437.PP
1131.Vb 4 1438.Vb 4
1132\& struct ev_periodic hourly_tick; 1439\& struct ev_periodic hourly_tick;
1133\& ev_periodic_init (&hourly_tick, clock_cb, 1440\& ev_periodic_init (&hourly_tick, clock_cb,
1134\& fmod (ev_now (loop), 3600.), 3600., 0); 1441\& fmod (ev_now (loop), 3600.), 3600., 0);
1135\& ev_periodic_start (loop, &hourly_tick); 1442\& ev_periodic_start (loop, &hourly_tick);
1136.Ve 1443.Ve
1137.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled" 1444.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!"
1138.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled" 1445.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!"
1139.IX Subsection "ev_signal - signal me when a signal gets signalled" 1446.IX Subsection "ev_signal - signal me when a signal gets signalled!"
1140Signal watchers will trigger an event when the process receives a specific 1447Signal watchers will trigger an event when the process receives a specific
1141signal one or more times. Even though signals are very asynchronous, libev 1448signal one or more times. Even though signals are very asynchronous, libev
1142will try it's best to deliver signals synchronously, i.e. as part of the 1449will try it's best to deliver signals synchronously, i.e. as part of the
1143normal event processing, like any other event. 1450normal event processing, like any other event.
1144.PP 1451.PP
… …
1146first watcher gets started will libev actually register a signal watcher 1453first watcher gets started will libev actually register a signal watcher
1147with the kernel (thus it coexists with your own signal handlers as long 1454with the kernel (thus it coexists with your own signal handlers as long
1148as you don't register any with libev). Similarly, when the last signal 1455as you don't register any with libev). Similarly, when the last signal
1149watcher for a signal is stopped libev will reset the signal handler to 1456watcher for a signal is stopped libev will reset the signal handler to
1150\&\s-1SIG_DFL\s0 (regardless of what it was set to before). 1457\&\s-1SIG_DFL\s0 (regardless of what it was set to before).
1458.PP
1459\fIWatcher-Specific Functions and Data Members\fR
1460.IX Subsection "Watcher-Specific Functions and Data Members"
1151.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 1461.IP "ev_signal_init (ev_signal *, callback, int signum)" 4
1152.IX Item "ev_signal_init (ev_signal *, callback, int signum)" 1462.IX Item "ev_signal_init (ev_signal *, callback, int signum)"
1153.PD 0 1463.PD 0
1154.IP "ev_signal_set (ev_signal *, int signum)" 4 1464.IP "ev_signal_set (ev_signal *, int signum)" 4
1155.IX Item "ev_signal_set (ev_signal *, int signum)" 1465.IX Item "ev_signal_set (ev_signal *, int signum)"
1156.PD 1466.PD
1157Configures the watcher to trigger on the given signal number (usually one 1467Configures the watcher to trigger on the given signal number (usually one
1158of the \f(CW\*(C`SIGxxx\*(C'\fR constants). 1468of the \f(CW\*(C`SIGxxx\*(C'\fR constants).
1469.IP "int signum [read\-only]" 4
1470.IX Item "int signum [read-only]"
1471The signal the watcher watches out for.
1159.ie n .Sh """ev_child"" \- wait for pid status changes" 1472.ie n .Sh """ev_child"" \- watch out for process status changes"
1160.el .Sh "\f(CWev_child\fP \- wait for pid status changes" 1473.el .Sh "\f(CWev_child\fP \- watch out for process status changes"
1161.IX Subsection "ev_child - wait for pid status changes" 1474.IX Subsection "ev_child - watch out for process status changes"
1162Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to 1475Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to
1163some child status changes (most typically when a child of yours dies). 1476some child status changes (most typically when a child of yours dies).
1477.PP
1478\fIWatcher-Specific Functions and Data Members\fR
1479.IX Subsection "Watcher-Specific Functions and Data Members"
1164.IP "ev_child_init (ev_child *, callback, int pid)" 4 1480.IP "ev_child_init (ev_child *, callback, int pid)" 4
1165.IX Item "ev_child_init (ev_child *, callback, int pid)" 1481.IX Item "ev_child_init (ev_child *, callback, int pid)"
1166.PD 0 1482.PD 0
1167.IP "ev_child_set (ev_child *, int pid)" 4 1483.IP "ev_child_set (ev_child *, int pid)" 4
1168.IX Item "ev_child_set (ev_child *, int pid)" 1484.IX Item "ev_child_set (ev_child *, int pid)"
… …
1171\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look 1487\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look
1172at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see 1488at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see
1173the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems 1489the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems
1174\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the 1490\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the
1175process causing the status change. 1491process causing the status change.
1492.IP "int pid [read\-only]" 4
1493.IX Item "int pid [read-only]"
1494The process id this watcher watches out for, or \f(CW0\fR, meaning any process id.
1495.IP "int rpid [read\-write]" 4
1496.IX Item "int rpid [read-write]"
1497The process id that detected a status change.
1498.IP "int rstatus [read\-write]" 4
1499.IX Item "int rstatus [read-write]"
1500The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems
1501\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details).
1176.PP 1502.PP
1177Example: try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. 1503Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0.
1178.PP 1504.PP
1179.Vb 5 1505.Vb 5
1180\& static void 1506\& static void
1181\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1507\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
1182\& { 1508\& {
… …
1187.Vb 3 1513.Vb 3
1188\& struct ev_signal signal_watcher; 1514\& struct ev_signal signal_watcher;
1189\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); 1515\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT);
1190\& ev_signal_start (loop, &sigint_cb); 1516\& ev_signal_start (loop, &sigint_cb);
1191.Ve 1517.Ve
1518.ie n .Sh """ev_stat"" \- did the file attributes just change?"
1519.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?"
1520.IX Subsection "ev_stat - did the file attributes just change?"
1521This watches a filesystem path for attribute changes. That is, it calls
1522\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed
1523compared to the last time, invoking the callback if it did.
1524.PP
1525The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does
1526not exist\*(R" is a status change like any other. The condition \*(L"path does
1527not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is
1528otherwise always forced to be at least one) and all the other fields of
1529the stat buffer having unspecified contents.
1530.PP
1531The path \fIshould\fR be absolute and \fImust not\fR end in a slash. If it is
1532relative and your working directory changes, the behaviour is undefined.
1533.PP
1534Since there is no standard to do this, the portable implementation simply
1535calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You
1536can specify a recommended polling interval for this case. If you specify
1537a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable,
1538unspecified default\fR value will be used (which you can expect to be around
1539five seconds, although this might change dynamically). Libev will also
1540impose a minimum interval which is currently around \f(CW0.1\fR, but thats
1541usually overkill.
1542.PP
1543This watcher type is not meant for massive numbers of stat watchers,
1544as even with OS-supported change notifications, this can be
1545resource\-intensive.
1546.PP
1547At the time of this writing, only the Linux inotify interface is
1548implemented (implementing kqueue support is left as an exercise for the
1549reader). Inotify will be used to give hints only and should not change the
1550semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs
1551to fall back to regular polling again even with inotify, but changes are
1552usually detected immediately, and if the file exists there will be no
1553polling.
1554.PP
1555\fIWatcher-Specific Functions and Data Members\fR
1556.IX Subsection "Watcher-Specific Functions and Data Members"
1557.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4
1558.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)"
1559.PD 0
1560.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4
1561.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)"
1562.PD
1563Configures the watcher to wait for status changes of the given
1564\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to
1565be detected and should normally be specified as \f(CW0\fR to let libev choose
1566a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same
1567path for as long as the watcher is active.
1568.Sp
1569The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected,
1570relative to the attributes at the time the watcher was started (or the
1571last change was detected).
1572.IP "ev_stat_stat (ev_stat *)" 4
1573.IX Item "ev_stat_stat (ev_stat *)"
1574Updates the stat buffer immediately with new values. If you change the
1575watched path in your callback, you could call this fucntion to avoid
1576detecting this change (while introducing a race condition). Can also be
1577useful simply to find out the new values.
1578.IP "ev_statdata attr [read\-only]" 4
1579.IX Item "ev_statdata attr [read-only]"
1580The most-recently detected attributes of the file. Although the type is of
1581\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types
1582suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there
1583was some error while \f(CW\*(C`stat\*(C'\fRing the file.
1584.IP "ev_statdata prev [read\-only]" 4
1585.IX Item "ev_statdata prev [read-only]"
1586The previous attributes of the file. The callback gets invoked whenever
1587\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR.
1588.IP "ev_tstamp interval [read\-only]" 4
1589.IX Item "ev_tstamp interval [read-only]"
1590The specified interval.
1591.IP "const char *path [read\-only]" 4
1592.IX Item "const char *path [read-only]"
1593The filesystem path that is being watched.
1594.PP
1595Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes.
1596.PP
1597.Vb 15
1598\& static void
1599\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
1600\& {
1601\& /* /etc/passwd changed in some way */
1602\& if (w->attr.st_nlink)
1603\& {
1604\& printf ("passwd current size %ld\en", (long)w->attr.st_size);
1605\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime);
1606\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime);
1607\& }
1608\& else
1609\& /* you shalt not abuse printf for puts */
1610\& puts ("wow, /etc/passwd is not there, expect problems. "
1611\& "if this is windows, they already arrived\en");
1612\& }
1613.Ve
1614.PP
1615.Vb 2
1616\& ...
1617\& ev_stat passwd;
1618.Ve
1619.PP
1620.Vb 2
1621\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd");
1622\& ev_stat_start (loop, &passwd);
1623.Ve
1192.ie n .Sh """ev_idle"" \- when you've got nothing better to do" 1624.ie n .Sh """ev_idle"" \- when you've got nothing better to do..."
1193.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do" 1625.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..."
1194.IX Subsection "ev_idle - when you've got nothing better to do" 1626.IX Subsection "ev_idle - when you've got nothing better to do..."
1195Idle watchers trigger events when there are no other events are pending 1627Idle watchers trigger events when no other events of the same or higher
1196(prepare, check and other idle watchers do not count). That is, as long 1628priority are pending (prepare, check and other idle watchers do not
1197as your process is busy handling sockets or timeouts (or even signals, 1629count).
1198imagine) it will not be triggered. But when your process is idle all idle 1630.PP
1199watchers are being called again and again, once per event loop iteration \- 1631That is, as long as your process is busy handling sockets or timeouts
1632(or even signals, imagine) of the same or higher priority it will not be
1633triggered. But when your process is idle (or only lower-priority watchers
1634are pending), the idle watchers are being called once per event loop
1200until stopped, that is, or your process receives more events and becomes 1635iteration \- until stopped, that is, or your process receives more events
1201busy. 1636and becomes busy again with higher priority stuff.
1202.PP 1637.PP
1203The most noteworthy effect is that as long as any idle watchers are 1638The most noteworthy effect is that as long as any idle watchers are
1204active, the process will not block when waiting for new events. 1639active, the process will not block when waiting for new events.
1205.PP 1640.PP
1206Apart from keeping your process non-blocking (which is a useful 1641Apart from keeping your process non-blocking (which is a useful
1207effect on its own sometimes), idle watchers are a good place to do 1642effect on its own sometimes), idle watchers are a good place to do
1208\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the 1643\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the
1209event loop has handled all outstanding events. 1644event loop has handled all outstanding events.
1645.PP
1646\fIWatcher-Specific Functions and Data Members\fR
1647.IX Subsection "Watcher-Specific Functions and Data Members"
1210.IP "ev_idle_init (ev_signal *, callback)" 4 1648.IP "ev_idle_init (ev_signal *, callback)" 4
1211.IX Item "ev_idle_init (ev_signal *, callback)" 1649.IX Item "ev_idle_init (ev_signal *, callback)"
1212Initialises and configures the idle watcher \- it has no parameters of any 1650Initialises and configures the idle watcher \- it has no parameters of any
1213kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, 1651kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless,
1214believe me. 1652believe me.
1215.PP 1653.PP
1216Example: dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR, start it, and in the 1654Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the
1217callback, free it. Alos, use no error checking, as usual. 1655callback, free it. Also, use no error checking, as usual.
1218.PP 1656.PP
1219.Vb 7 1657.Vb 7
1220\& static void 1658\& static void
1221\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) 1659\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents)
1222\& { 1660\& {
… …
1229.Vb 3 1667.Vb 3
1230\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); 1668\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle));
1231\& ev_idle_init (idle_watcher, idle_cb); 1669\& ev_idle_init (idle_watcher, idle_cb);
1232\& ev_idle_start (loop, idle_cb); 1670\& ev_idle_start (loop, idle_cb);
1233.Ve 1671.Ve
1234.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop" 1672.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!"
1235.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop" 1673.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!"
1236.IX Subsection "ev_prepare and ev_check - customise your event loop" 1674.IX Subsection "ev_prepare and ev_check - customise your event loop!"
1237Prepare and check watchers are usually (but not always) used in tandem: 1675Prepare and check watchers are usually (but not always) used in tandem:
1238prepare watchers get invoked before the process blocks and check watchers 1676prepare watchers get invoked before the process blocks and check watchers
1239afterwards. 1677afterwards.
1240.PP 1678.PP
1679You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter
1680the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR
1681watchers. Other loops than the current one are fine, however. The
1682rationale behind this is that you do not need to check for recursion in
1683those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking,
1684\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be
1685called in pairs bracketing the blocking call.
1686.PP
1241Their main purpose is to integrate other event mechanisms into libev and 1687Their main purpose is to integrate other event mechanisms into libev and
1242their use is somewhat advanced. This could be used, for example, to track 1688their use is somewhat advanced. This could be used, for example, to track
1243variable changes, implement your own watchers, integrate net-snmp or a 1689variable changes, implement your own watchers, integrate net-snmp or a
1244coroutine library and lots more. 1690coroutine library and lots more. They are also occasionally useful if
1691you cache some data and want to flush it before blocking (for example,
1692in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR
1693watcher).
1245.PP 1694.PP
1246This is done by examining in each prepare call which file descriptors need 1695This is done by examining in each prepare call which file descriptors need
1247to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for 1696to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for
1248them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries 1697them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries
1249provide just this functionality). Then, in the check watcher you check for 1698provide just this functionality). Then, in the check watcher you check for
… …
1258are ready to run (it's actually more complicated: it only runs coroutines 1707are ready to run (it's actually more complicated: it only runs coroutines
1259with priority higher than or equal to the event loop and one coroutine 1708with priority higher than or equal to the event loop and one coroutine
1260of lower priority, but only once, using idle watchers to keep the event 1709of lower priority, but only once, using idle watchers to keep the event
1261loop from blocking if lower-priority coroutines are active, thus mapping 1710loop from blocking if lower-priority coroutines are active, thus mapping
1262low-priority coroutines to idle/background tasks). 1711low-priority coroutines to idle/background tasks).
1712.PP
1713It is recommended to give \f(CW\*(C`ev_check\*(C'\fR watchers highest (\f(CW\*(C`EV_MAXPRI\*(C'\fR)
1714priority, to ensure that they are being run before any other watchers
1715after the poll. Also, \f(CW\*(C`ev_check\*(C'\fR watchers (and \f(CW\*(C`ev_prepare\*(C'\fR watchers,
1716too) should not activate (\*(L"feed\*(R") events into libev. While libev fully
1717supports this, they will be called before other \f(CW\*(C`ev_check\*(C'\fR watchers did
1718their job. As \f(CW\*(C`ev_check\*(C'\fR watchers are often used to embed other event
1719loops those other event loops might be in an unusable state until their
1720\&\f(CW\*(C`ev_check\*(C'\fR watcher ran (always remind yourself to coexist peacefully with
1721others).
1722.PP
1723\fIWatcher-Specific Functions and Data Members\fR
1724.IX Subsection "Watcher-Specific Functions and Data Members"
1263.IP "ev_prepare_init (ev_prepare *, callback)" 4 1725.IP "ev_prepare_init (ev_prepare *, callback)" 4
1264.IX Item "ev_prepare_init (ev_prepare *, callback)" 1726.IX Item "ev_prepare_init (ev_prepare *, callback)"
1265.PD 0 1727.PD 0
1266.IP "ev_check_init (ev_check *, callback)" 4 1728.IP "ev_check_init (ev_check *, callback)" 4
1267.IX Item "ev_check_init (ev_check *, callback)" 1729.IX Item "ev_check_init (ev_check *, callback)"
1268.PD 1730.PD
1269Initialises and configures the prepare or check watcher \- they have no 1731Initialises and configures the prepare or check watcher \- they have no
1270parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR 1732parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR
1271macros, but using them is utterly, utterly and completely pointless. 1733macros, but using them is utterly, utterly and completely pointless.
1272.PP 1734.PP
1273Example: *TODO*. 1735There are a number of principal ways to embed other event loops or modules
1736into libev. Here are some ideas on how to include libadns into libev
1737(there is a Perl module named \f(CW\*(C`EV::ADNS\*(C'\fR that does this, which you could
1738use for an actually working example. Another Perl module named \f(CW\*(C`EV::Glib\*(C'\fR
1739embeds a Glib main context into libev, and finally, \f(CW\*(C`Glib::EV\*(C'\fR embeds \s-1EV\s0
1740into the Glib event loop).
1741.PP
1742Method 1: Add \s-1IO\s0 watchers and a timeout watcher in a prepare handler,
1743and in a check watcher, destroy them and call into libadns. What follows
1744is pseudo-code only of course. This requires you to either use a low
1745priority for the check watcher or use \f(CW\*(C`ev_clear_pending\*(C'\fR explicitly, as
1746the callbacks for the IO/timeout watchers might not have been called yet.
1747.PP
1748.Vb 2
1749\& static ev_io iow [nfd];
1750\& static ev_timer tw;
1751.Ve
1752.PP
1753.Vb 4
1754\& static void
1755\& io_cb (ev_loop *loop, ev_io *w, int revents)
1756\& {
1757\& }
1758.Ve
1759.PP
1760.Vb 8
1761\& // create io watchers for each fd and a timer before blocking
1762\& static void
1763\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents)
1764\& {
1765\& int timeout = 3600000;
1766\& struct pollfd fds [nfd];
1767\& // actual code will need to loop here and realloc etc.
1768\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ()));
1769.Ve
1770.PP
1771.Vb 3
1772\& /* the callback is illegal, but won't be called as we stop during check */
1773\& ev_timer_init (&tw, 0, timeout * 1e-3);
1774\& ev_timer_start (loop, &tw);
1775.Ve
1776.PP
1777.Vb 6
1778\& // create one ev_io per pollfd
1779\& for (int i = 0; i < nfd; ++i)
1780\& {
1781\& ev_io_init (iow + i, io_cb, fds [i].fd,
1782\& ((fds [i].events & POLLIN ? EV_READ : 0)
1783\& | (fds [i].events & POLLOUT ? EV_WRITE : 0)));
1784.Ve
1785.PP
1786.Vb 4
1787\& fds [i].revents = 0;
1788\& ev_io_start (loop, iow + i);
1789\& }
1790\& }
1791.Ve
1792.PP
1793.Vb 5
1794\& // stop all watchers after blocking
1795\& static void
1796\& adns_check_cb (ev_loop *loop, ev_check *w, int revents)
1797\& {
1798\& ev_timer_stop (loop, &tw);
1799.Ve
1800.PP
1801.Vb 8
1802\& for (int i = 0; i < nfd; ++i)
1803\& {
1804\& // set the relevant poll flags
1805\& // could also call adns_processreadable etc. here
1806\& struct pollfd *fd = fds + i;
1807\& int revents = ev_clear_pending (iow + i);
1808\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN;
1809\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT;
1810.Ve
1811.PP
1812.Vb 3
1813\& // now stop the watcher
1814\& ev_io_stop (loop, iow + i);
1815\& }
1816.Ve
1817.PP
1818.Vb 2
1819\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop));
1820\& }
1821.Ve
1822.PP
1823Method 2: This would be just like method 1, but you run \f(CW\*(C`adns_afterpoll\*(C'\fR
1824in the prepare watcher and would dispose of the check watcher.
1825.PP
1826Method 3: If the module to be embedded supports explicit event
1827notification (adns does), you can also make use of the actual watcher
1828callbacks, and only destroy/create the watchers in the prepare watcher.
1829.PP
1830.Vb 5
1831\& static void
1832\& timer_cb (EV_P_ ev_timer *w, int revents)
1833\& {
1834\& adns_state ads = (adns_state)w->data;
1835\& update_now (EV_A);
1836.Ve
1837.PP
1838.Vb 2
1839\& adns_processtimeouts (ads, &tv_now);
1840\& }
1841.Ve
1842.PP
1843.Vb 5
1844\& static void
1845\& io_cb (EV_P_ ev_io *w, int revents)
1846\& {
1847\& adns_state ads = (adns_state)w->data;
1848\& update_now (EV_A);
1849.Ve
1850.PP
1851.Vb 3
1852\& if (revents & EV_READ ) adns_processreadable (ads, w->fd, &tv_now);
1853\& if (revents & EV_WRITE) adns_processwriteable (ads, w->fd, &tv_now);
1854\& }
1855.Ve
1856.PP
1857.Vb 1
1858\& // do not ever call adns_afterpoll
1859.Ve
1860.PP
1861Method 4: Do not use a prepare or check watcher because the module you
1862want to embed is too inflexible to support it. Instead, youc na override
1863their poll function. The drawback with this solution is that the main
1864loop is now no longer controllable by \s-1EV\s0. The \f(CW\*(C`Glib::EV\*(C'\fR module does
1865this.
1866.PP
1867.Vb 4
1868\& static gint
1869\& event_poll_func (GPollFD *fds, guint nfds, gint timeout)
1870\& {
1871\& int got_events = 0;
1872.Ve
1873.PP
1874.Vb 2
1875\& for (n = 0; n < nfds; ++n)
1876\& // create/start io watcher that sets the relevant bits in fds[n] and increment got_events
1877.Ve
1878.PP
1879.Vb 2
1880\& if (timeout >= 0)
1881\& // create/start timer
1882.Ve
1883.PP
1884.Vb 2
1885\& // poll
1886\& ev_loop (EV_A_ 0);
1887.Ve
1888.PP
1889.Vb 3
1890\& // stop timer again
1891\& if (timeout >= 0)
1892\& ev_timer_stop (EV_A_ &to);
1893.Ve
1894.PP
1895.Vb 3
1896\& // stop io watchers again - their callbacks should have set
1897\& for (n = 0; n < nfds; ++n)
1898\& ev_io_stop (EV_A_ iow [n]);
1899.Ve
1900.PP
1901.Vb 2
1902\& return got_events;
1903\& }
1904.Ve
1274.ie n .Sh """ev_embed"" \- when one backend isn't enough" 1905.ie n .Sh """ev_embed"" \- when one backend isn't enough..."
1275.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough" 1906.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..."
1276.IX Subsection "ev_embed - when one backend isn't enough" 1907.IX Subsection "ev_embed - when one backend isn't enough..."
1277This is a rather advanced watcher type that lets you embed one event loop 1908This is a rather advanced watcher type that lets you embed one event loop
1278into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded 1909into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded
1279loop, other types of watchers might be handled in a delayed or incorrect 1910loop, other types of watchers might be handled in a delayed or incorrect
1280fashion and must not be used). 1911fashion and must not be used).
1281.PP 1912.PP
… …
1345\& ev_embed_start (loop_hi, &embed); 1976\& ev_embed_start (loop_hi, &embed);
1346\& } 1977\& }
1347\& else 1978\& else
1348\& loop_lo = loop_hi; 1979\& loop_lo = loop_hi;
1349.Ve 1980.Ve
1981.PP
1982\fIWatcher-Specific Functions and Data Members\fR
1983.IX Subsection "Watcher-Specific Functions and Data Members"
1350.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 1984.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1351.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 1985.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)"
1352.PD 0 1986.PD 0
1353.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 1987.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4
1354.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 1988.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)"
… …
1361.IP "ev_embed_sweep (loop, ev_embed *)" 4 1995.IP "ev_embed_sweep (loop, ev_embed *)" 4
1362.IX Item "ev_embed_sweep (loop, ev_embed *)" 1996.IX Item "ev_embed_sweep (loop, ev_embed *)"
1363Make a single, non-blocking sweep over the embedded loop. This works 1997Make a single, non-blocking sweep over the embedded loop. This works
1364similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most 1998similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most
1365apropriate way for embedded loops. 1999apropriate way for embedded loops.
2000.IP "struct ev_loop *loop [read\-only]" 4
2001.IX Item "struct ev_loop *loop [read-only]"
2002The embedded event loop.
2003.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork"
2004.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork"
2005.IX Subsection "ev_fork - the audacity to resume the event loop after a fork"
2006Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because
2007whoever is a good citizen cared to tell libev about it by calling
2008\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the
2009event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called,
2010and only in the child after the fork. If whoever good citizen calling
2011\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork
2012handlers will be invoked, too, of course.
2013.PP
2014\fIWatcher-Specific Functions and Data Members\fR
2015.IX Subsection "Watcher-Specific Functions and Data Members"
2016.IP "ev_fork_init (ev_signal *, callback)" 4
2017.IX Item "ev_fork_init (ev_signal *, callback)"
2018Initialises and configures the fork watcher \- it has no parameters of any
2019kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless,
2020believe me.
1366.SH "OTHER FUNCTIONS" 2021.SH "OTHER FUNCTIONS"
1367.IX Header "OTHER FUNCTIONS" 2022.IX Header "OTHER FUNCTIONS"
1368There are some other functions of possible interest. Described. Here. Now. 2023There are some other functions of possible interest. Described. Here. Now.
1369.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 2024.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4
1370.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 2025.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)"
… …
1432.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 2087.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4
1433.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." 2088.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library."
1434.PD 2089.PD
1435.SH "\*(C+ SUPPORT" 2090.SH "\*(C+ SUPPORT"
1436.IX Header " SUPPORT" 2091.IX Header " SUPPORT"
1437\&\s-1TBD\s0. 2092Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow
2093you to use some convinience methods to start/stop watchers and also change
2094the callback model to a model using method callbacks on objects.
2095.PP
2096To use it,
2097.PP
2098.Vb 1
2099\& #include <ev++.h>
2100.Ve
2101.PP
2102This automatically includes \fIev.h\fR and puts all of its definitions (many
2103of them macros) into the global namespace. All \*(C+ specific things are
2104put into the \f(CW\*(C`ev\*(C'\fR namespace. It should support all the same embedding
2105options as \fIev.h\fR, most notably \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR.
2106.PP
2107Care has been taken to keep the overhead low. The only data member the \*(C+
2108classes add (compared to plain C\-style watchers) is the event loop pointer
2109that the watcher is associated with (or no additional members at all if
2110you disable \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR when embedding libev).
2111.PP
2112Currently, functions, and static and non-static member functions can be
2113used as callbacks. Other types should be easy to add as long as they only
2114need one additional pointer for context. If you need support for other
2115types of functors please contact the author (preferably after implementing
2116it).
2117.PP
2118Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace:
2119.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4
2120.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4
2121.IX Item "ev::READ, ev::WRITE etc."
2122These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc.
2123macros from \fIev.h\fR.
2124.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4
2125.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4
2126.IX Item "ev::tstamp, ev::now"
2127Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix.
2128.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
2129.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4
2130.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc."
2131For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of
2132the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR
2133which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro
2134defines by many implementations.
2135.Sp
2136All of those classes have these methods:
2137.RS 4
2138.IP "ev::TYPE::TYPE ()" 4
2139.IX Item "ev::TYPE::TYPE ()"
2140.PD 0
2141.IP "ev::TYPE::TYPE (struct ev_loop *)" 4
2142.IX Item "ev::TYPE::TYPE (struct ev_loop *)"
2143.IP "ev::TYPE::~TYPE" 4
2144.IX Item "ev::TYPE::~TYPE"
2145.PD
2146The constructor (optionally) takes an event loop to associate the watcher
2147with. If it is omitted, it will use \f(CW\*(C`EV_DEFAULT\*(C'\fR.
2148.Sp
2149The constructor calls \f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the
2150\&\f(CW\*(C`set\*(C'\fR method before starting it.
2151.Sp
2152It will not set a callback, however: You have to call the templated \f(CW\*(C`set\*(C'\fR
2153method to set a callback before you can start the watcher.
2154.Sp
2155(The reason why you have to use a method is a limitation in \*(C+ which does
2156not allow explicit template arguments for constructors).
2157.Sp
2158The destructor automatically stops the watcher if it is active.
2159.IP "w\->set<class, &class::method> (object *)" 4
2160.IX Item "w->set<class, &class::method> (object *)"
2161This method sets the callback method to call. The method has to have a
2162signature of \f(CW\*(C`void (*)(ev_TYPE &, int)\*(C'\fR, it receives the watcher as
2163first argument and the \f(CW\*(C`revents\*(C'\fR as second. The object must be given as
2164parameter and is stored in the \f(CW\*(C`data\*(C'\fR member of the watcher.
2165.Sp
2166This method synthesizes efficient thunking code to call your method from
2167the C callback that libev requires. If your compiler can inline your
2168callback (i.e. it is visible to it at the place of the \f(CW\*(C`set\*(C'\fR call and
2169your compiler is good :), then the method will be fully inlined into the
2170thunking function, making it as fast as a direct C callback.
2171.Sp
2172Example: simple class declaration and watcher initialisation
2173.Sp
2174.Vb 4
2175\& struct myclass
2176\& {
2177\& void io_cb (ev::io &w, int revents) { }
2178\& }
2179.Ve
2180.Sp
2181.Vb 3
2182\& myclass obj;
2183\& ev::io iow;
2184\& iow.set <myclass, &myclass::io_cb> (&obj);
2185.Ve
2186.IP "w\->set<function> (void *data = 0)" 4
2187.IX Item "w->set<function> (void *data = 0)"
2188Also sets a callback, but uses a static method or plain function as
2189callback. The optional \f(CW\*(C`data\*(C'\fR argument will be stored in the watcher's
2190\&\f(CW\*(C`data\*(C'\fR member and is free for you to use.
2191.Sp
2192The prototype of the \f(CW\*(C`function\*(C'\fR must be \f(CW\*(C`void (*)(ev::TYPE &w, int)\*(C'\fR.
2193.Sp
2194See the method\-\f(CW\*(C`set\*(C'\fR above for more details.
2195.Sp
2196Example:
2197.Sp
2198.Vb 2
2199\& static void io_cb (ev::io &w, int revents) { }
2200\& iow.set <io_cb> ();
2201.Ve
2202.IP "w\->set (struct ev_loop *)" 4
2203.IX Item "w->set (struct ev_loop *)"
2204Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only
2205do this when the watcher is inactive (and not pending either).
2206.IP "w\->set ([args])" 4
2207.IX Item "w->set ([args])"
2208Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be
2209called at least once. Unlike the C counterpart, an active watcher gets
2210automatically stopped and restarted when reconfiguring it with this
2211method.
2212.IP "w\->start ()" 4
2213.IX Item "w->start ()"
2214Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
2215constructor already stores the event loop.
2216.IP "w\->stop ()" 4
2217.IX Item "w->stop ()"
2218Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument.
2219.ie n .IP "w\->again () (""ev::timer""\fR, \f(CW""ev::periodic"" only)" 4
2220.el .IP "w\->again () (\f(CWev::timer\fR, \f(CWev::periodic\fR only)" 4
2221.IX Item "w->again () (ev::timer, ev::periodic only)"
2222For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding
2223\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function.
2224.ie n .IP "w\->sweep () (""ev::embed"" only)" 4
2225.el .IP "w\->sweep () (\f(CWev::embed\fR only)" 4
2226.IX Item "w->sweep () (ev::embed only)"
2227Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR.
2228.ie n .IP "w\->update () (""ev::stat"" only)" 4
2229.el .IP "w\->update () (\f(CWev::stat\fR only)" 4
2230.IX Item "w->update () (ev::stat only)"
2231Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR.
2232.RE
2233.RS 4
2234.RE
2235.PP
2236Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in
2237the constructor.
2238.PP
2239.Vb 4
2240\& class myclass
2241\& {
2242\& ev_io io; void io_cb (ev::io &w, int revents);
2243\& ev_idle idle void idle_cb (ev::idle &w, int revents);
2244.Ve
2245.PP
2246.Vb 2
2247\& myclass ();
2248\& }
2249.Ve
2250.PP
2251.Vb 4
2252\& myclass::myclass (int fd)
2253\& {
2254\& io .set <myclass, &myclass::io_cb > (this);
2255\& idle.set <myclass, &myclass::idle_cb> (this);
2256.Ve
2257.PP
2258.Vb 2
2259\& io.start (fd, ev::READ);
2260\& }
2261.Ve
2262.SH "MACRO MAGIC"
2263.IX Header "MACRO MAGIC"
2264Libev can be compiled with a variety of options, the most fundamantal
2265of which is \f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines whether (most)
2266functions and callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument.
2267.PP
2268To make it easier to write programs that cope with either variant, the
2269following macros are defined:
2270.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4
2271.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4
2272.IX Item "EV_A, EV_A_"
2273This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev
2274loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument,
2275\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example:
2276.Sp
2277.Vb 3
2278\& ev_unref (EV_A);
2279\& ev_timer_add (EV_A_ watcher);
2280\& ev_loop (EV_A_ 0);
2281.Ve
2282.Sp
2283It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope,
2284which is often provided by the following macro.
2285.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4
2286.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4
2287.IX Item "EV_P, EV_P_"
2288This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev
2289loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter,
2290\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example:
2291.Sp
2292.Vb 2
2293\& // this is how ev_unref is being declared
2294\& static void ev_unref (EV_P);
2295.Ve
2296.Sp
2297.Vb 2
2298\& // this is how you can declare your typical callback
2299\& static void cb (EV_P_ ev_timer *w, int revents)
2300.Ve
2301.Sp
2302It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite
2303suitable for use with \f(CW\*(C`EV_A\*(C'\fR.
2304.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4
2305.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4
2306.IX Item "EV_DEFAULT, EV_DEFAULT_"
2307Similar to the other two macros, this gives you the value of the default
2308loop, if multiple loops are supported (\*(L"ev loop default\*(R").
2309.PP
2310Example: Declare and initialise a check watcher, utilising the above
2311macros so it will work regardless of whether multiple loops are supported
2312or not.
2313.PP
2314.Vb 5
2315\& static void
2316\& check_cb (EV_P_ ev_timer *w, int revents)
2317\& {
2318\& ev_check_stop (EV_A_ w);
2319\& }
2320.Ve
2321.PP
2322.Vb 4
2323\& ev_check check;
2324\& ev_check_init (&check, check_cb);
2325\& ev_check_start (EV_DEFAULT_ &check);
2326\& ev_loop (EV_DEFAULT_ 0);
2327.Ve
2328.SH "EMBEDDING"
2329.IX Header "EMBEDDING"
2330Libev can (and often is) directly embedded into host
2331applications. Examples of applications that embed it include the Deliantra
2332Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe)
2333and rxvt\-unicode.
2334.PP
2335The goal is to enable you to just copy the neecssary files into your
2336source directory without having to change even a single line in them, so
2337you can easily upgrade by simply copying (or having a checked-out copy of
2338libev somewhere in your source tree).
2339.Sh "\s-1FILESETS\s0"
2340.IX Subsection "FILESETS"
2341Depending on what features you need you need to include one or more sets of files
2342in your app.
2343.PP
2344\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR
2345.IX Subsection "CORE EVENT LOOP"
2346.PP
2347To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual
2348configuration (no autoconf):
2349.PP
2350.Vb 2
2351\& #define EV_STANDALONE 1
2352\& #include "ev.c"
2353.Ve
2354.PP
2355This will automatically include \fIev.h\fR, too, and should be done in a
2356single C source file only to provide the function implementations. To use
2357it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
2358done by writing a wrapper around \fIev.h\fR that you can include instead and
2359where you can put other configuration options):
2360.PP
2361.Vb 2
2362\& #define EV_STANDALONE 1
2363\& #include "ev.h"
2364.Ve
2365.PP
2366Both header files and implementation files can be compiled with a \*(C+
2367compiler (at least, thats a stated goal, and breakage will be treated
2368as a bug).
2369.PP
2370You need the following files in your source tree, or in a directory
2371in your include path (e.g. in libev/ when using \-Ilibev):
2372.PP
2373.Vb 4
2374\& ev.h
2375\& ev.c
2376\& ev_vars.h
2377\& ev_wrap.h
2378.Ve
2379.PP
2380.Vb 1
2381\& ev_win32.c required on win32 platforms only
2382.Ve
2383.PP
2384.Vb 5
2385\& ev_select.c only when select backend is enabled (which is enabled by default)
2386\& ev_poll.c only when poll backend is enabled (disabled by default)
2387\& ev_epoll.c only when the epoll backend is enabled (disabled by default)
2388\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default)
2389\& ev_port.c only when the solaris port backend is enabled (disabled by default)
2390.Ve
2391.PP
2392\&\fIev.c\fR includes the backend files directly when enabled, so you only need
2393to compile this single file.
2394.PP
2395\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR
2396.IX Subsection "LIBEVENT COMPATIBILITY API"
2397.PP
2398To include the libevent compatibility \s-1API\s0, also include:
2399.PP
2400.Vb 1
2401\& #include "event.c"
2402.Ve
2403.PP
2404in the file including \fIev.c\fR, and:
2405.PP
2406.Vb 1
2407\& #include "event.h"
2408.Ve
2409.PP
2410in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR.
2411.PP
2412You need the following additional files for this:
2413.PP
2414.Vb 2
2415\& event.h
2416\& event.c
2417.Ve
2418.PP
2419\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR
2420.IX Subsection "AUTOCONF SUPPORT"
2421.PP
2422Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in
2423whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your
2424\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then
2425include \fIconfig.h\fR and configure itself accordingly.
2426.PP
2427For this of course you need the m4 file:
2428.PP
2429.Vb 1
2430\& libev.m4
2431.Ve
2432.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0"
2433.IX Subsection "PREPROCESSOR SYMBOLS/MACROS"
2434Libev can be configured via a variety of preprocessor symbols you have to define
2435before including any of its files. The default is not to build for multiplicity
2436and only include the select backend.
2437.IP "\s-1EV_STANDALONE\s0" 4
2438.IX Item "EV_STANDALONE"
2439Must always be \f(CW1\fR if you do not use autoconf configuration, which
2440keeps libev from including \fIconfig.h\fR, and it also defines dummy
2441implementations for some libevent functions (such as logging, which is not
2442supported). It will also not define any of the structs usually found in
2443\&\fIevent.h\fR that are not directly supported by the libev core alone.
2444.IP "\s-1EV_USE_MONOTONIC\s0" 4
2445.IX Item "EV_USE_MONOTONIC"
2446If defined to be \f(CW1\fR, libev will try to detect the availability of the
2447monotonic clock option at both compiletime and runtime. Otherwise no use
2448of the monotonic clock option will be attempted. If you enable this, you
2449usually have to link against librt or something similar. Enabling it when
2450the functionality isn't available is safe, though, althoguh you have
2451to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR
2452function is hiding in (often \fI\-lrt\fR).
2453.IP "\s-1EV_USE_REALTIME\s0" 4
2454.IX Item "EV_USE_REALTIME"
2455If defined to be \f(CW1\fR, libev will try to detect the availability of the
2456realtime clock option at compiletime (and assume its availability at
2457runtime if successful). Otherwise no use of the realtime clock option will
2458be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get
2459(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries
2460in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though.
2461.IP "\s-1EV_USE_SELECT\s0" 4
2462.IX Item "EV_USE_SELECT"
2463If undefined or defined to be \f(CW1\fR, libev will compile in support for the
2464\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no
2465other method takes over, select will be it. Otherwise the select backend
2466will not be compiled in.
2467.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4
2468.IX Item "EV_SELECT_USE_FD_SET"
2469If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR
2470structure. This is useful if libev doesn't compile due to a missing
2471\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on
2472exotic systems. This usually limits the range of file descriptors to some
2473low limit such as 1024 or might have other limitations (winsocket only
2474allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might
2475influence the size of the \f(CW\*(C`fd_set\*(C'\fR used.
2476.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4
2477.IX Item "EV_SELECT_IS_WINSOCKET"
2478When defined to \f(CW1\fR, the select backend will assume that
2479select/socket/connect etc. don't understand file descriptors but
2480wants osf handles on win32 (this is the case when the select to
2481be used is the winsock select). This means that it will call
2482\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise,
2483it is assumed that all these functions actually work on fds, even
2484on win32. Should not be defined on non\-win32 platforms.
2485.IP "\s-1EV_USE_POLL\s0" 4
2486.IX Item "EV_USE_POLL"
2487If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2)
2488backend. Otherwise it will be enabled on non\-win32 platforms. It
2489takes precedence over select.
2490.IP "\s-1EV_USE_EPOLL\s0" 4
2491.IX Item "EV_USE_EPOLL"
2492If defined to be \f(CW1\fR, libev will compile in support for the Linux
2493\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
2494otherwise another method will be used as fallback. This is the
2495preferred backend for GNU/Linux systems.
2496.IP "\s-1EV_USE_KQUEUE\s0" 4
2497.IX Item "EV_USE_KQUEUE"
2498If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
2499\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
2500otherwise another method will be used as fallback. This is the preferred
2501backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only
2502supports some types of fds correctly (the only platform we found that
2503supports ptys for example was NetBSD), so kqueue might be compiled in, but
2504not be used unless explicitly requested. The best way to use it is to find
2505out whether kqueue supports your type of fd properly and use an embedded
2506kqueue loop.
2507.IP "\s-1EV_USE_PORT\s0" 4
2508.IX Item "EV_USE_PORT"
2509If defined to be \f(CW1\fR, libev will compile in support for the Solaris
251010 port style backend. Its availability will be detected at runtime,
2511otherwise another method will be used as fallback. This is the preferred
2512backend for Solaris 10 systems.
2513.IP "\s-1EV_USE_DEVPOLL\s0" 4
2514.IX Item "EV_USE_DEVPOLL"
2515reserved for future expansion, works like the \s-1USE\s0 symbols above.
2516.IP "\s-1EV_USE_INOTIFY\s0" 4
2517.IX Item "EV_USE_INOTIFY"
2518If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify
2519interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will
2520be detected at runtime.
2521.IP "\s-1EV_H\s0" 4
2522.IX Item "EV_H"
2523The name of the \fIev.h\fR header file used to include it. The default if
2524undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This
2525can be used to virtually rename the \fIev.h\fR header file in case of conflicts.
2526.IP "\s-1EV_CONFIG_H\s0" 4
2527.IX Item "EV_CONFIG_H"
2528If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
2529\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
2530\&\f(CW\*(C`EV_H\*(C'\fR, above.
2531.IP "\s-1EV_EVENT_H\s0" 4
2532.IX Item "EV_EVENT_H"
2533Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
2534of how the \fIevent.h\fR header can be found.
2535.IP "\s-1EV_PROTOTYPES\s0" 4
2536.IX Item "EV_PROTOTYPES"
2537If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
2538prototypes, but still define all the structs and other symbols. This is
2539occasionally useful if you want to provide your own wrapper functions
2540around libev functions.
2541.IP "\s-1EV_MULTIPLICITY\s0" 4
2542.IX Item "EV_MULTIPLICITY"
2543If undefined or defined to \f(CW1\fR, then all event-loop-specific functions
2544will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create
2545additional independent event loops. Otherwise there will be no support
2546for multiple event loops and there is no first event loop pointer
2547argument. Instead, all functions act on the single default loop.
2548.IP "\s-1EV_MINPRI\s0" 4
2549.IX Item "EV_MINPRI"
2550.PD 0
2551.IP "\s-1EV_MAXPRI\s0" 4
2552.IX Item "EV_MAXPRI"
2553.PD
2554The range of allowed priorities. \f(CW\*(C`EV_MINPRI\*(C'\fR must be smaller or equal to
2555\&\f(CW\*(C`EV_MAXPRI\*(C'\fR, but otherwise there are no non-obvious limitations. You can
2556provide for more priorities by overriding those symbols (usually defined
2557to be \f(CW\*(C`\-2\*(C'\fR and \f(CW2\fR, respectively).
2558.Sp
2559When doing priority-based operations, libev usually has to linearly search
2560all the priorities, so having many of them (hundreds) uses a lot of space
2561and time, so using the defaults of five priorities (\-2 .. +2) is usually
2562fine.
2563.Sp
2564If your embedding app does not need any priorities, defining these both to
2565\&\f(CW0\fR will save some memory and cpu.
2566.IP "\s-1EV_PERIODIC_ENABLE\s0" 4
2567.IX Item "EV_PERIODIC_ENABLE"
2568If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If
2569defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2570code.
2571.IP "\s-1EV_IDLE_ENABLE\s0" 4
2572.IX Item "EV_IDLE_ENABLE"
2573If undefined or defined to be \f(CW1\fR, then idle watchers are supported. If
2574defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of
2575code.
2576.IP "\s-1EV_EMBED_ENABLE\s0" 4
2577.IX Item "EV_EMBED_ENABLE"
2578If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If
2579defined to be \f(CW0\fR, then they are not.
2580.IP "\s-1EV_STAT_ENABLE\s0" 4
2581.IX Item "EV_STAT_ENABLE"
2582If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If
2583defined to be \f(CW0\fR, then they are not.
2584.IP "\s-1EV_FORK_ENABLE\s0" 4
2585.IX Item "EV_FORK_ENABLE"
2586If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If
2587defined to be \f(CW0\fR, then they are not.
2588.IP "\s-1EV_MINIMAL\s0" 4
2589.IX Item "EV_MINIMAL"
2590If you need to shave off some kilobytes of code at the expense of some
2591speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override
2592some inlining decisions, saves roughly 30% codesize of amd64.
2593.IP "\s-1EV_PID_HASHSIZE\s0" 4
2594.IX Item "EV_PID_HASHSIZE"
2595\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by
2596pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more
2597than enough. If you need to manage thousands of children you might want to
2598increase this value (\fImust\fR be a power of two).
2599.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4
2600.IX Item "EV_INOTIFY_HASHSIZE"
2601\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by
2602inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR),
2603usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR
2604watchers you might want to increase this value (\fImust\fR be a power of
2605two).
2606.IP "\s-1EV_COMMON\s0" 4
2607.IX Item "EV_COMMON"
2608By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
2609this macro to a something else you can include more and other types of
2610members. You have to define it each time you include one of the files,
2611though, and it must be identical each time.
2612.Sp
2613For example, the perl \s-1EV\s0 module uses something like this:
2614.Sp
2615.Vb 3
2616\& #define EV_COMMON \e
2617\& SV *self; /* contains this struct */ \e
2618\& SV *cb_sv, *fh /* note no trailing ";" */
2619.Ve
2620.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
2621.IX Item "EV_CB_DECLARE (type)"
2622.PD 0
2623.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
2624.IX Item "EV_CB_INVOKE (watcher, revents)"
2625.IP "ev_set_cb (ev, cb)" 4
2626.IX Item "ev_set_cb (ev, cb)"
2627.PD
2628Can be used to change the callback member declaration in each watcher,
2629and the way callbacks are invoked and set. Must expand to a struct member
2630definition and a statement, respectively. See the \fIev.v\fR header file for
2631their default definitions. One possible use for overriding these is to
2632avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
2633method calls instead of plain function calls in \*(C+.
2634.Sh "\s-1EXPORTED\s0 \s-1API\s0 \s-1SYMBOLS\s0"
2635.IX Subsection "EXPORTED API SYMBOLS"
2636If you need to re-export the \s-1API\s0 (e.g. via a dll) and you need a list of
2637exported symbols, you can use the provided \fISymbol.*\fR files which list
2638all public symbols, one per line:
2639.Sp
2640.Vb 2
2641\& Symbols.ev for libev proper
2642\& Symbols.event for the libevent emulation
2643.Ve
2644.Sp
2645This can also be used to rename all public symbols to avoid clashes with
2646multiple versions of libev linked together (which is obviously bad in
2647itself, but sometimes it is inconvinient to avoid this).
2648.Sp
2649A sed comamnd like this will create wrapper \f(CW\*(C`#define\*(C'\fR's that you need to
2650include before including \fIev.h\fR:
2651.Sp
2652.Vb 1
2653\& <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2654.Ve
2655.Sp
2656This would create a file \fIwrap.h\fR which essentially looks like this:
2657.Sp
2658.Vb 4
2659\& #define ev_backend myprefix_ev_backend
2660\& #define ev_check_start myprefix_ev_check_start
2661\& #define ev_check_stop myprefix_ev_check_stop
2662\& ...
2663.Ve
2664.Sh "\s-1EXAMPLES\s0"
2665.IX Subsection "EXAMPLES"
2666For a real-world example of a program the includes libev
2667verbatim, you can have a look at the \s-1EV\s0 perl module
2668(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in
2669the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public
2670interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file
2671will be compiled. It is pretty complex because it provides its own header
2672file.
2673.Sp
2674The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file
2675that everybody includes and which overrides some configure choices:
2676.Sp
2677.Vb 9
2678\& #define EV_MINIMAL 1
2679\& #define EV_USE_POLL 0
2680\& #define EV_MULTIPLICITY 0
2681\& #define EV_PERIODIC_ENABLE 0
2682\& #define EV_STAT_ENABLE 0
2683\& #define EV_FORK_ENABLE 0
2684\& #define EV_CONFIG_H <config.h>
2685\& #define EV_MINPRI 0
2686\& #define EV_MAXPRI 0
2687.Ve
2688.Sp
2689.Vb 1
2690\& #include "ev++.h"
2691.Ve
2692.Sp
2693And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled:
2694.Sp
2695.Vb 2
2696\& #include "ev_cpp.h"
2697\& #include "ev.c"
2698.Ve
2699.SH "COMPLEXITIES"
2700.IX Header "COMPLEXITIES"
2701In this section the complexities of (many of) the algorithms used inside
2702libev will be explained. For complexity discussions about backends see the
2703documentation for \f(CW\*(C`ev_default_init\*(C'\fR.
2704.Sp
2705All of the following are about amortised time: If an array needs to be
2706extended, libev needs to realloc and move the whole array, but this
2707happens asymptotically never with higher number of elements, so O(1) might
2708mean it might do a lengthy realloc operation in rare cases, but on average
2709it is much faster and asymptotically approaches constant time.
2710.RS 4
2711.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4
2712.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)"
2713This means that, when you have a watcher that triggers in one hour and
2714there are 100 watchers that would trigger before that then inserting will
2715have to skip those 100 watchers.
2716.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4
2717.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)"
2718That means that for changing a timer costs less than removing/adding them
2719as only the relative motion in the event queue has to be paid for.
2720.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4
2721.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)"
2722These just add the watcher into an array or at the head of a list.
2723=item Stopping check/prepare/idle watchers: O(1)
2724.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4
2725.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))"
2726These watchers are stored in lists then need to be walked to find the
2727correct watcher to remove. The lists are usually short (you don't usually
2728have many watchers waiting for the same fd or signal).
2729.IP "Finding the next timer per loop iteration: O(1)" 4
2730.IX Item "Finding the next timer per loop iteration: O(1)"
2731.PD 0
2732.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4
2733.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)"
2734.PD
2735A change means an I/O watcher gets started or stopped, which requires
2736libev to recalculate its status (and possibly tell the kernel).
2737.IP "Activating one watcher: O(1)" 4
2738.IX Item "Activating one watcher: O(1)"
2739.PD 0
2740.IP "Priority handling: O(number_of_priorities)" 4
2741.IX Item "Priority handling: O(number_of_priorities)"
2742.PD
2743Priorities are implemented by allocating some space for each
2744priority. When doing priority-based operations, libev usually has to
2745linearly search all the priorities.
2746.RE
2747.RS 4
1438.SH "AUTHOR" 2748.SH "AUTHOR"
1439.IX Header "AUTHOR" 2749.IX Header "AUTHOR"
1440Marc Lehmann <libev@schmorp.de>. 2750Marc Lehmann <libev@schmorp.de>.

Diff Legend

– Removed lines
+ Added lines
< Changed lines
> Changed lines