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.\" ======================================================================== |
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.\" |
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.IX Title ""<STANDARD INPUT>" 1" |
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.TH "<STANDARD INPUT>" 1 "2007-11-28" "perl v5.8.8" "User Contributed Perl Documentation" |
133 |
.SH "NAME" |
134 |
libev \- a high performance full\-featured event loop written in C |
135 |
.SH "SYNOPSIS" |
136 |
.IX Header "SYNOPSIS" |
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.Vb 1 |
138 |
\& #include <ev.h> |
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 |
199 |
.SH "DESCRIPTION" |
200 |
.IX Header "DESCRIPTION" |
201 |
Libev is an event loop: you register interest in certain events (such as a |
202 |
file descriptor being readable or a timeout occuring), and it will manage |
203 |
these event sources and provide your program with events. |
204 |
.PP |
205 |
To do this, it must take more or less complete control over your process |
206 |
(or thread) by executing the \fIevent loop\fR handler, and will then |
207 |
communicate events via a callback mechanism. |
208 |
.PP |
209 |
You register interest in certain events by registering so-called \fIevent |
210 |
watchers\fR, which are relatively small C structures you initialise with the |
211 |
details of the event, and then hand it over to libev by \fIstarting\fR the |
212 |
watcher. |
213 |
.SH "FEATURES" |
214 |
.IX Header "FEATURES" |
215 |
Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the linux-specific \f(CW\*(C`epoll\*(C'\fR, the |
216 |
bsd-specific \f(CW\*(C`kqueue\*(C'\fR and the solaris-specific event port mechanisms |
217 |
for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), relative timers (\f(CW\*(C`ev_timer\*(C'\fR), |
218 |
absolute timers with customised rescheduling (\f(CW\*(C`ev_periodic\*(C'\fR), synchronous |
219 |
signals (\f(CW\*(C`ev_signal\*(C'\fR), process status change events (\f(CW\*(C`ev_child\*(C'\fR), and |
220 |
event watchers dealing with the event loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, |
221 |
\&\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 |
222 |
file watchers (\f(CW\*(C`ev_stat\*(C'\fR) and even limited support for fork events |
223 |
(\f(CW\*(C`ev_fork\*(C'\fR). |
224 |
.PP |
225 |
It also is quite fast (see this |
226 |
benchmark comparing it to libevent |
227 |
for example). |
228 |
.SH "CONVENTIONS" |
229 |
.IX Header "CONVENTIONS" |
230 |
Libev is very configurable. In this manual the default configuration will |
231 |
be described, which supports multiple event loops. For more info about |
232 |
various configuration options please have a look at \fB\s-1EMBED\s0\fR section in |
233 |
this manual. If libev was configured without support for multiple event |
234 |
loops, then all functions taking an initial argument of name \f(CW\*(C`loop\*(C'\fR |
235 |
(which is always of type \f(CW\*(C`struct ev_loop *\*(C'\fR) will not have this argument. |
236 |
.SH "TIME REPRESENTATION" |
237 |
.IX Header "TIME REPRESENTATION" |
238 |
Libev represents time as a single floating point number, representing the |
239 |
(fractional) number of seconds since the (\s-1POSIX\s0) epoch (somewhere near |
240 |
the beginning of 1970, details are complicated, don't ask). This type is |
241 |
called \f(CW\*(C`ev_tstamp\*(C'\fR, which is what you should use too. It usually aliases |
242 |
to the \f(CW\*(C`double\*(C'\fR type in C, and when you need to do any calculations on |
243 |
it, you should treat it as such. |
244 |
.SH "GLOBAL FUNCTIONS" |
245 |
.IX Header "GLOBAL FUNCTIONS" |
246 |
These functions can be called anytime, even before initialising the |
247 |
library in any way. |
248 |
.IP "ev_tstamp ev_time ()" 4 |
249 |
.IX Item "ev_tstamp ev_time ()" |
250 |
Returns the current time as libev would use it. Please note that the |
251 |
\&\f(CW\*(C`ev_now\*(C'\fR function is usually faster and also often returns the timestamp |
252 |
you actually want to know. |
253 |
.IP "int ev_version_major ()" 4 |
254 |
.IX Item "int ev_version_major ()" |
255 |
.PD 0 |
256 |
.IP "int ev_version_minor ()" 4 |
257 |
.IX Item "int ev_version_minor ()" |
258 |
.PD |
259 |
You can find out the major and minor version numbers of the library |
260 |
you linked against by calling the functions \f(CW\*(C`ev_version_major\*(C'\fR and |
261 |
\&\f(CW\*(C`ev_version_minor\*(C'\fR. If you want, you can compare against the global |
262 |
symbols \f(CW\*(C`EV_VERSION_MAJOR\*(C'\fR and \f(CW\*(C`EV_VERSION_MINOR\*(C'\fR, which specify the |
263 |
version of the library your program was compiled against. |
264 |
.Sp |
265 |
Usually, it's a good idea to terminate if the major versions mismatch, |
266 |
as this indicates an incompatible change. Minor versions are usually |
267 |
compatible to older versions, so a larger minor version alone is usually |
268 |
not a problem. |
269 |
.Sp |
270 |
Example: Make sure we haven't accidentally been linked against the wrong |
271 |
version. |
272 |
.Sp |
273 |
.Vb 3 |
274 |
\& assert (("libev version mismatch", |
275 |
\& ev_version_major () == EV_VERSION_MAJOR |
276 |
\& && ev_version_minor () >= EV_VERSION_MINOR)); |
277 |
.Ve |
278 |
.IP "unsigned int ev_supported_backends ()" 4 |
279 |
.IX Item "unsigned int ev_supported_backends ()" |
280 |
Return the set of all backends (i.e. their corresponding \f(CW\*(C`EV_BACKEND_*\*(C'\fR |
281 |
value) compiled into this binary of libev (independent of their |
282 |
availability on the system you are running on). See \f(CW\*(C`ev_default_loop\*(C'\fR for |
283 |
a description of the set values. |
284 |
.Sp |
285 |
Example: make sure we have the epoll method, because yeah this is cool and |
286 |
a must have and can we have a torrent of it please!!!11 |
287 |
.Sp |
288 |
.Vb 2 |
289 |
\& assert (("sorry, no epoll, no sex", |
290 |
\& ev_supported_backends () & EVBACKEND_EPOLL)); |
291 |
.Ve |
292 |
.IP "unsigned int ev_recommended_backends ()" 4 |
293 |
.IX Item "unsigned int ev_recommended_backends ()" |
294 |
Return the set of all backends compiled into this binary of libev and also |
295 |
recommended for this platform. This set is often smaller than the one |
296 |
returned by \f(CW\*(C`ev_supported_backends\*(C'\fR, as for example kqueue is broken on |
297 |
most BSDs and will not be autodetected unless you explicitly request it |
298 |
(assuming you know what you are doing). This is the set of backends that |
299 |
libev will probe for if you specify no backends explicitly. |
300 |
.IP "unsigned int ev_embeddable_backends ()" 4 |
301 |
.IX Item "unsigned int ev_embeddable_backends ()" |
302 |
Returns the set of backends that are embeddable in other event loops. This |
303 |
is the theoretical, all\-platform, value. To find which backends |
304 |
might be supported on the current system, you would need to look at |
305 |
\&\f(CW\*(C`ev_embeddable_backends () & ev_supported_backends ()\*(C'\fR, likewise for |
306 |
recommended ones. |
307 |
.Sp |
308 |
See the description of \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. |
309 |
.IP "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" 4 |
310 |
.IX Item "ev_set_allocator (void *(*cb)(void *ptr, size_t size))" |
311 |
Sets the allocation function to use (the prototype and semantics are |
312 |
identical to the realloc C function). It is used to allocate and free |
313 |
memory (no surprises here). If it returns zero when memory needs to be |
314 |
allocated, the library might abort or take some potentially destructive |
315 |
action. The default is your system realloc function. |
316 |
.Sp |
317 |
You could override this function in high-availability programs to, say, |
318 |
free some memory if it cannot allocate memory, to use a special allocator, |
319 |
or even to sleep a while and retry until some memory is available. |
320 |
.Sp |
321 |
Example: Replace the libev allocator with one that waits a bit and then |
322 |
retries). |
323 |
.Sp |
324 |
.Vb 6 |
325 |
\& static void * |
326 |
\& persistent_realloc (void *ptr, size_t size) |
327 |
\& { |
328 |
\& for (;;) |
329 |
\& { |
330 |
\& void *newptr = realloc (ptr, size); |
331 |
.Ve |
332 |
.Sp |
333 |
.Vb 2 |
334 |
\& if (newptr) |
335 |
\& return newptr; |
336 |
.Ve |
337 |
.Sp |
338 |
.Vb 3 |
339 |
\& sleep (60); |
340 |
\& } |
341 |
\& } |
342 |
.Ve |
343 |
.Sp |
344 |
.Vb 2 |
345 |
\& ... |
346 |
\& ev_set_allocator (persistent_realloc); |
347 |
.Ve |
348 |
.IP "ev_set_syserr_cb (void (*cb)(const char *msg));" 4 |
349 |
.IX Item "ev_set_syserr_cb (void (*cb)(const char *msg));" |
350 |
Set the callback function to call on a retryable syscall error (such |
351 |
as failed select, poll, epoll_wait). The message is a printable string |
352 |
indicating the system call or subsystem causing the problem. If this |
353 |
callback is set, then libev will expect it to remedy the sitution, no |
354 |
matter what, when it returns. That is, libev will generally retry the |
355 |
requested operation, or, if the condition doesn't go away, do bad stuff |
356 |
(such as abort). |
357 |
.Sp |
358 |
Example: This is basically the same thing that libev does internally, too. |
359 |
.Sp |
360 |
.Vb 6 |
361 |
\& static void |
362 |
\& fatal_error (const char *msg) |
363 |
\& { |
364 |
\& perror (msg); |
365 |
\& abort (); |
366 |
\& } |
367 |
.Ve |
368 |
.Sp |
369 |
.Vb 2 |
370 |
\& ... |
371 |
\& ev_set_syserr_cb (fatal_error); |
372 |
.Ve |
373 |
.SH "FUNCTIONS CONTROLLING THE EVENT LOOP" |
374 |
.IX Header "FUNCTIONS CONTROLLING THE EVENT LOOP" |
375 |
An event loop is described by a \f(CW\*(C`struct ev_loop *\*(C'\fR. The library knows two |
376 |
types of such loops, the \fIdefault\fR loop, which supports signals and child |
377 |
events, and dynamically created loops which do not. |
378 |
.PP |
379 |
If you use threads, a common model is to run the default event loop |
380 |
in your main thread (or in a separate thread) and for each thread you |
381 |
create, you also create another event loop. Libev itself does no locking |
382 |
whatsoever, so if you mix calls to the same event loop in different |
383 |
threads, make sure you lock (this is usually a bad idea, though, even if |
384 |
done correctly, because it's hideous and inefficient). |
385 |
.IP "struct ev_loop *ev_default_loop (unsigned int flags)" 4 |
386 |
.IX Item "struct ev_loop *ev_default_loop (unsigned int flags)" |
387 |
This will initialise the default event loop if it hasn't been initialised |
388 |
yet and return it. If the default loop could not be initialised, returns |
389 |
false. If it already was initialised it simply returns it (and ignores the |
390 |
flags. If that is troubling you, check \f(CW\*(C`ev_backend ()\*(C'\fR afterwards). |
391 |
.Sp |
392 |
If you don't know what event loop to use, use the one returned from this |
393 |
function. |
394 |
.Sp |
395 |
The flags argument can be used to specify special behaviour or specific |
396 |
backends to use, and is usually specified as \f(CW0\fR (or \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). |
397 |
.Sp |
398 |
The following flags are supported: |
399 |
.RS 4 |
400 |
.ie n .IP """EVFLAG_AUTO""" 4 |
401 |
.el .IP "\f(CWEVFLAG_AUTO\fR" 4 |
402 |
.IX Item "EVFLAG_AUTO" |
403 |
The default flags value. Use this if you have no clue (it's the right |
404 |
thing, believe me). |
405 |
.ie n .IP """EVFLAG_NOENV""" 4 |
406 |
.el .IP "\f(CWEVFLAG_NOENV\fR" 4 |
407 |
.IX Item "EVFLAG_NOENV" |
408 |
If this flag bit is ored into the flag value (or the program runs setuid |
409 |
or setgid) then libev will \fInot\fR look at the environment variable |
410 |
\&\f(CW\*(C`LIBEV_FLAGS\*(C'\fR. Otherwise (the default), this environment variable will |
411 |
override the flags completely if it is found in the environment. This is |
412 |
useful to try out specific backends to test their performance, or to work |
413 |
around bugs. |
414 |
.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 |
415 |
.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 |
416 |
.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" |
417 |
This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as |
418 |
libev tries to roll its own fd_set with no limits on the number of fds, |
419 |
but if that fails, expect a fairly low limit on the number of fds when |
420 |
using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
421 |
the fastest backend for a low number of fds. |
422 |
.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 |
423 |
.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 |
424 |
.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" |
425 |
And this is your standard \fIpoll\fR\|(2) backend. It's more complicated than |
426 |
select, but handles sparse fds better and has no artificial limit on the |
427 |
number of fds you can use (except it will slow down considerably with a |
428 |
lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
429 |
.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 |
430 |
.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 |
431 |
.IX Item "EVBACKEND_EPOLL (value 4, Linux)" |
432 |
For few fds, this backend is a bit little slower than poll and select, |
433 |
but it scales phenomenally better. While poll and select usually scale like |
434 |
O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
435 |
either O(1) or O(active_fds). |
436 |
.Sp |
437 |
While stopping and starting an I/O watcher in the same iteration will |
438 |
result in some caching, there is still a syscall per such incident |
439 |
(because the fd could point to a different file description now), so its |
440 |
best to avoid that. Also, \fIdup()\fRed file descriptors might not work very |
441 |
well if you register events for both fds. |
442 |
.Sp |
443 |
Please note that epoll sometimes generates spurious notifications, so you |
444 |
need to use non-blocking I/O or other means to avoid blocking when no data |
445 |
(or space) is available. |
446 |
.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 |
447 |
.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 |
448 |
.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" |
449 |
Kqueue deserves special mention, as at the time of this writing, it |
450 |
was broken on all BSDs except NetBSD (usually it doesn't work with |
451 |
anything but sockets and pipes, except on Darwin, where of course its |
452 |
completely useless). For this reason its not being \*(L"autodetected\*(R" |
453 |
unless you explicitly specify it explicitly in the flags (i.e. using |
454 |
\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR). |
455 |
.Sp |
456 |
It scales in the same way as the epoll backend, but the interface to the |
457 |
kernel is more efficient (which says nothing about its actual speed, of |
458 |
course). While starting and stopping an I/O watcher does not cause an |
459 |
extra syscall as with epoll, it still adds up to four event changes per |
460 |
incident, so its best to avoid that. |
461 |
.ie n .IP """EVBACKEND_DEVPOLL"" (value 16, Solaris 8)" 4 |
462 |
.el .IP "\f(CWEVBACKEND_DEVPOLL\fR (value 16, Solaris 8)" 4 |
463 |
.IX Item "EVBACKEND_DEVPOLL (value 16, Solaris 8)" |
464 |
This is not implemented yet (and might never be). |
465 |
.ie n .IP """EVBACKEND_PORT"" (value 32, Solaris 10)" 4 |
466 |
.el .IP "\f(CWEVBACKEND_PORT\fR (value 32, Solaris 10)" 4 |
467 |
.IX Item "EVBACKEND_PORT (value 32, Solaris 10)" |
468 |
This uses the Solaris 10 port mechanism. As with everything on Solaris, |
469 |
it's really slow, but it still scales very well (O(active_fds)). |
470 |
.Sp |
471 |
Please note that solaris ports can result in a lot of spurious |
472 |
notifications, so you need to use non-blocking I/O or other means to avoid |
473 |
blocking when no data (or space) is available. |
474 |
.ie n .IP """EVBACKEND_ALL""" 4 |
475 |
.el .IP "\f(CWEVBACKEND_ALL\fR" 4 |
476 |
.IX Item "EVBACKEND_ALL" |
477 |
Try all backends (even potentially broken ones that wouldn't be tried |
478 |
with \f(CW\*(C`EVFLAG_AUTO\*(C'\fR). Since this is a mask, you can do stuff such as |
479 |
\&\f(CW\*(C`EVBACKEND_ALL & ~EVBACKEND_KQUEUE\*(C'\fR. |
480 |
.RE |
481 |
.RS 4 |
482 |
.Sp |
483 |
If one or more of these are ored into the flags value, then only these |
484 |
backends will be tried (in the reverse order as given here). If none are |
485 |
specified, most compiled-in backend will be tried, usually in reverse |
486 |
order of their flag values :) |
487 |
.Sp |
488 |
The most typical usage is like this: |
489 |
.Sp |
490 |
.Vb 2 |
491 |
\& if (!ev_default_loop (0)) |
492 |
\& fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
493 |
.Ve |
494 |
.Sp |
495 |
Restrict libev to the select and poll backends, and do not allow |
496 |
environment settings to be taken into account: |
497 |
.Sp |
498 |
.Vb 1 |
499 |
\& ev_default_loop (EVBACKEND_POLL | EVBACKEND_SELECT | EVFLAG_NOENV); |
500 |
.Ve |
501 |
.Sp |
502 |
Use whatever libev has to offer, but make sure that kqueue is used if |
503 |
available (warning, breaks stuff, best use only with your own private |
504 |
event loop and only if you know the \s-1OS\s0 supports your types of fds): |
505 |
.Sp |
506 |
.Vb 1 |
507 |
\& ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); |
508 |
.Ve |
509 |
.RE |
510 |
.IP "struct ev_loop *ev_loop_new (unsigned int flags)" 4 |
511 |
.IX Item "struct ev_loop *ev_loop_new (unsigned int flags)" |
512 |
Similar to \f(CW\*(C`ev_default_loop\*(C'\fR, but always creates a new event loop that is |
513 |
always distinct from the default loop. Unlike the default loop, it cannot |
514 |
handle signal and child watchers, and attempts to do so will be greeted by |
515 |
undefined behaviour (or a failed assertion if assertions are enabled). |
516 |
.Sp |
517 |
Example: Try to create a event loop that uses epoll and nothing else. |
518 |
.Sp |
519 |
.Vb 3 |
520 |
\& struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
521 |
\& if (!epoller) |
522 |
\& fatal ("no epoll found here, maybe it hides under your chair"); |
523 |
.Ve |
524 |
.IP "ev_default_destroy ()" 4 |
525 |
.IX Item "ev_default_destroy ()" |
526 |
Destroys the default loop again (frees all memory and kernel state |
527 |
etc.). None of the active event watchers will be stopped in the normal |
528 |
sense, so e.g. \f(CW\*(C`ev_is_active\*(C'\fR might still return true. It is your |
529 |
responsibility to either stop all watchers cleanly yoursef \fIbefore\fR |
530 |
calling this function, or cope with the fact afterwards (which is usually |
531 |
the easiest thing, youc na just ignore the watchers and/or \f(CW\*(C`free ()\*(C'\fR them |
532 |
for example). |
533 |
.IP "ev_loop_destroy (loop)" 4 |
534 |
.IX Item "ev_loop_destroy (loop)" |
535 |
Like \f(CW\*(C`ev_default_destroy\*(C'\fR, but destroys an event loop created by an |
536 |
earlier call to \f(CW\*(C`ev_loop_new\*(C'\fR. |
537 |
.IP "ev_default_fork ()" 4 |
538 |
.IX Item "ev_default_fork ()" |
539 |
This function reinitialises the kernel state for backends that have |
540 |
one. Despite the name, you can call it anytime, but it makes most sense |
541 |
after forking, in either the parent or child process (or both, but that |
542 |
again makes little sense). |
543 |
.Sp |
544 |
You \fImust\fR call this function in the child process after forking if and |
545 |
only if you want to use the event library in both processes. If you just |
546 |
fork+exec, you don't have to call it. |
547 |
.Sp |
548 |
The function itself is quite fast and it's usually not a problem to call |
549 |
it just in case after a fork. To make this easy, the function will fit in |
550 |
quite nicely into a call to \f(CW\*(C`pthread_atfork\*(C'\fR: |
551 |
.Sp |
552 |
.Vb 1 |
553 |
\& pthread_atfork (0, 0, ev_default_fork); |
554 |
.Ve |
555 |
.Sp |
556 |
At the moment, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and \f(CW\*(C`EVBACKEND_POLL\*(C'\fR are safe to use |
557 |
without calling this function, so if you force one of those backends you |
558 |
do not need to care. |
559 |
.IP "ev_loop_fork (loop)" 4 |
560 |
.IX Item "ev_loop_fork (loop)" |
561 |
Like \f(CW\*(C`ev_default_fork\*(C'\fR, but acts on an event loop created by |
562 |
\&\f(CW\*(C`ev_loop_new\*(C'\fR. Yes, you have to call this on every allocated event loop |
563 |
after fork, and how you do this is entirely your own problem. |
564 |
.IP "unsigned int ev_backend (loop)" 4 |
565 |
.IX Item "unsigned int ev_backend (loop)" |
566 |
Returns one of the \f(CW\*(C`EVBACKEND_*\*(C'\fR flags indicating the event backend in |
567 |
use. |
568 |
.IP "ev_tstamp ev_now (loop)" 4 |
569 |
.IX Item "ev_tstamp ev_now (loop)" |
570 |
Returns the current \*(L"event loop time\*(R", which is the time the event loop |
571 |
received events and started processing them. This timestamp does not |
572 |
change as long as callbacks are being processed, and this is also the base |
573 |
time used for relative timers. You can treat it as the timestamp of the |
574 |
event occuring (or more correctly, libev finding out about it). |
575 |
.IP "ev_loop (loop, int flags)" 4 |
576 |
.IX Item "ev_loop (loop, int flags)" |
577 |
Finally, this is it, the event handler. This function usually is called |
578 |
after you initialised all your watchers and you want to start handling |
579 |
events. |
580 |
.Sp |
581 |
If the flags argument is specified as \f(CW0\fR, it will not return until |
582 |
either no event watchers are active anymore or \f(CW\*(C`ev_unloop\*(C'\fR was called. |
583 |
.Sp |
584 |
Please note that an explicit \f(CW\*(C`ev_unloop\*(C'\fR is usually better than |
585 |
relying on all watchers to be stopped when deciding when a program has |
586 |
finished (especially in interactive programs), but having a program that |
587 |
automatically loops as long as it has to and no longer by virtue of |
588 |
relying on its watchers stopping correctly is a thing of beauty. |
589 |
.Sp |
590 |
A flags value of \f(CW\*(C`EVLOOP_NONBLOCK\*(C'\fR will look for new events, will handle |
591 |
those events and any outstanding ones, but will not block your process in |
592 |
case there are no events and will return after one iteration of the loop. |
593 |
.Sp |
594 |
A flags value of \f(CW\*(C`EVLOOP_ONESHOT\*(C'\fR will look for new events (waiting if |
595 |
neccessary) and will handle those and any outstanding ones. It will block |
596 |
your process until at least one new event arrives, and will return after |
597 |
one iteration of the loop. This is useful if you are waiting for some |
598 |
external event in conjunction with something not expressible using other |
599 |
libev watchers. However, a pair of \f(CW\*(C`ev_prepare\*(C'\fR/\f(CW\*(C`ev_check\*(C'\fR watchers is |
600 |
usually a better approach for this kind of thing. |
601 |
.Sp |
602 |
Here are the gory details of what \f(CW\*(C`ev_loop\*(C'\fR does: |
603 |
.Sp |
604 |
.Vb 18 |
605 |
\& * If there are no active watchers (reference count is zero), return. |
606 |
\& - Queue prepare watchers and then call all outstanding watchers. |
607 |
\& - If we have been forked, recreate the kernel state. |
608 |
\& - Update the kernel state with all outstanding changes. |
609 |
\& - Update the "event loop time". |
610 |
\& - Calculate for how long to block. |
611 |
\& - Block the process, waiting for any events. |
612 |
\& - Queue all outstanding I/O (fd) events. |
613 |
\& - Update the "event loop time" and do time jump handling. |
614 |
\& - Queue all outstanding timers. |
615 |
\& - Queue all outstanding periodics. |
616 |
\& - If no events are pending now, queue all idle watchers. |
617 |
\& - Queue all check watchers. |
618 |
\& - Call all queued watchers in reverse order (i.e. check watchers first). |
619 |
\& Signals and child watchers are implemented as I/O watchers, and will |
620 |
\& be handled here by queueing them when their watcher gets executed. |
621 |
\& - If ev_unloop has been called or EVLOOP_ONESHOT or EVLOOP_NONBLOCK |
622 |
\& were used, return, otherwise continue with step *. |
623 |
.Ve |
624 |
.Sp |
625 |
Example: Queue some jobs and then loop until no events are outsanding |
626 |
anymore. |
627 |
.Sp |
628 |
.Vb 4 |
629 |
\& ... queue jobs here, make sure they register event watchers as long |
630 |
\& ... as they still have work to do (even an idle watcher will do..) |
631 |
\& ev_loop (my_loop, 0); |
632 |
\& ... jobs done. yeah! |
633 |
.Ve |
634 |
.IP "ev_unloop (loop, how)" 4 |
635 |
.IX Item "ev_unloop (loop, how)" |
636 |
Can be used to make a call to \f(CW\*(C`ev_loop\*(C'\fR return early (but only after it |
637 |
has processed all outstanding events). The \f(CW\*(C`how\*(C'\fR argument must be either |
638 |
\&\f(CW\*(C`EVUNLOOP_ONE\*(C'\fR, which will make the innermost \f(CW\*(C`ev_loop\*(C'\fR call return, or |
639 |
\&\f(CW\*(C`EVUNLOOP_ALL\*(C'\fR, which will make all nested \f(CW\*(C`ev_loop\*(C'\fR calls return. |
640 |
.IP "ev_ref (loop)" 4 |
641 |
.IX Item "ev_ref (loop)" |
642 |
.PD 0 |
643 |
.IP "ev_unref (loop)" 4 |
644 |
.IX Item "ev_unref (loop)" |
645 |
.PD |
646 |
Ref/unref can be used to add or remove a reference count on the event |
647 |
loop: Every watcher keeps one reference, and as long as the reference |
648 |
count is nonzero, \f(CW\*(C`ev_loop\*(C'\fR will not return on its own. If you have |
649 |
a watcher you never unregister that should not keep \f(CW\*(C`ev_loop\*(C'\fR from |
650 |
returning, \fIev_unref()\fR after starting, and \fIev_ref()\fR before stopping it. For |
651 |
example, libev itself uses this for its internal signal pipe: It is not |
652 |
visible to the libev user and should not keep \f(CW\*(C`ev_loop\*(C'\fR from exiting if |
653 |
no event watchers registered by it are active. It is also an excellent |
654 |
way to do this for generic recurring timers or from within third-party |
655 |
libraries. Just remember to \fIunref after start\fR and \fIref before stop\fR. |
656 |
.Sp |
657 |
Example: Create a signal watcher, but keep it from keeping \f(CW\*(C`ev_loop\*(C'\fR |
658 |
running when nothing else is active. |
659 |
.Sp |
660 |
.Vb 4 |
661 |
\& struct ev_signal exitsig; |
662 |
\& ev_signal_init (&exitsig, sig_cb, SIGINT); |
663 |
\& ev_signal_start (loop, &exitsig); |
664 |
\& evf_unref (loop); |
665 |
.Ve |
666 |
.Sp |
667 |
Example: For some weird reason, unregister the above signal handler again. |
668 |
.Sp |
669 |
.Vb 2 |
670 |
\& ev_ref (loop); |
671 |
\& ev_signal_stop (loop, &exitsig); |
672 |
.Ve |
673 |
.SH "ANATOMY OF A WATCHER" |
674 |
.IX Header "ANATOMY OF A WATCHER" |
675 |
A watcher is a structure that you create and register to record your |
676 |
interest in some event. For instance, if you want to wait for \s-1STDIN\s0 to |
677 |
become readable, you would create an \f(CW\*(C`ev_io\*(C'\fR watcher for that: |
678 |
.PP |
679 |
.Vb 5 |
680 |
\& static void my_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
681 |
\& { |
682 |
\& ev_io_stop (w); |
683 |
\& ev_unloop (loop, EVUNLOOP_ALL); |
684 |
\& } |
685 |
.Ve |
686 |
.PP |
687 |
.Vb 6 |
688 |
\& struct ev_loop *loop = ev_default_loop (0); |
689 |
\& struct ev_io stdin_watcher; |
690 |
\& ev_init (&stdin_watcher, my_cb); |
691 |
\& ev_io_set (&stdin_watcher, STDIN_FILENO, EV_READ); |
692 |
\& ev_io_start (loop, &stdin_watcher); |
693 |
\& ev_loop (loop, 0); |
694 |
.Ve |
695 |
.PP |
696 |
As you can see, you are responsible for allocating the memory for your |
697 |
watcher structures (and it is usually a bad idea to do this on the stack, |
698 |
although this can sometimes be quite valid). |
699 |
.PP |
700 |
Each watcher structure must be initialised by a call to \f(CW\*(C`ev_init |
701 |
(watcher *, callback)\*(C'\fR, which expects a callback to be provided. This |
702 |
callback gets invoked each time the event occurs (or, in the case of io |
703 |
watchers, each time the event loop detects that the file descriptor given |
704 |
is readable and/or writable). |
705 |
.PP |
706 |
Each watcher type has its own \f(CW\*(C`ev_<type>_set (watcher *, ...)\*(C'\fR macro |
707 |
with arguments specific to this watcher type. There is also a macro |
708 |
to combine initialisation and setting in one call: \f(CW\*(C`ev_<type>_init |
709 |
(watcher *, callback, ...)\*(C'\fR. |
710 |
.PP |
711 |
To make the watcher actually watch out for events, you have to start it |
712 |
with a watcher-specific start function (\f(CW\*(C`ev_<type>_start (loop, watcher |
713 |
*)\*(C'\fR), and you can stop watching for events at any time by calling the |
714 |
corresponding stop function (\f(CW\*(C`ev_<type>_stop (loop, watcher *)\*(C'\fR. |
715 |
.PP |
716 |
As long as your watcher is active (has been started but not stopped) you |
717 |
must not touch the values stored in it. Most specifically you must never |
718 |
reinitialise it or call its \f(CW\*(C`set\*(C'\fR macro. |
719 |
.PP |
720 |
Each and every callback receives the event loop pointer as first, the |
721 |
registered watcher structure as second, and a bitset of received events as |
722 |
third argument. |
723 |
.PP |
724 |
The received events usually include a single bit per event type received |
725 |
(you can receive multiple events at the same time). The possible bit masks |
726 |
are: |
727 |
.ie n .IP """EV_READ""" 4 |
728 |
.el .IP "\f(CWEV_READ\fR" 4 |
729 |
.IX Item "EV_READ" |
730 |
.PD 0 |
731 |
.ie n .IP """EV_WRITE""" 4 |
732 |
.el .IP "\f(CWEV_WRITE\fR" 4 |
733 |
.IX Item "EV_WRITE" |
734 |
.PD |
735 |
The file descriptor in the \f(CW\*(C`ev_io\*(C'\fR watcher has become readable and/or |
736 |
writable. |
737 |
.ie n .IP """EV_TIMEOUT""" 4 |
738 |
.el .IP "\f(CWEV_TIMEOUT\fR" 4 |
739 |
.IX Item "EV_TIMEOUT" |
740 |
The \f(CW\*(C`ev_timer\*(C'\fR watcher has timed out. |
741 |
.ie n .IP """EV_PERIODIC""" 4 |
742 |
.el .IP "\f(CWEV_PERIODIC\fR" 4 |
743 |
.IX Item "EV_PERIODIC" |
744 |
The \f(CW\*(C`ev_periodic\*(C'\fR watcher has timed out. |
745 |
.ie n .IP """EV_SIGNAL""" 4 |
746 |
.el .IP "\f(CWEV_SIGNAL\fR" 4 |
747 |
.IX Item "EV_SIGNAL" |
748 |
The signal specified in the \f(CW\*(C`ev_signal\*(C'\fR watcher has been received by a thread. |
749 |
.ie n .IP """EV_CHILD""" 4 |
750 |
.el .IP "\f(CWEV_CHILD\fR" 4 |
751 |
.IX Item "EV_CHILD" |
752 |
The pid specified in the \f(CW\*(C`ev_child\*(C'\fR watcher has received a status change. |
753 |
.ie n .IP """EV_STAT""" 4 |
754 |
.el .IP "\f(CWEV_STAT\fR" 4 |
755 |
.IX Item "EV_STAT" |
756 |
The path specified in the \f(CW\*(C`ev_stat\*(C'\fR watcher changed its attributes somehow. |
757 |
.ie n .IP """EV_IDLE""" 4 |
758 |
.el .IP "\f(CWEV_IDLE\fR" 4 |
759 |
.IX Item "EV_IDLE" |
760 |
The \f(CW\*(C`ev_idle\*(C'\fR watcher has determined that you have nothing better to do. |
761 |
.ie n .IP """EV_PREPARE""" 4 |
762 |
.el .IP "\f(CWEV_PREPARE\fR" 4 |
763 |
.IX Item "EV_PREPARE" |
764 |
.PD 0 |
765 |
.ie n .IP """EV_CHECK""" 4 |
766 |
.el .IP "\f(CWEV_CHECK\fR" 4 |
767 |
.IX Item "EV_CHECK" |
768 |
.PD |
769 |
All \f(CW\*(C`ev_prepare\*(C'\fR watchers are invoked just \fIbefore\fR \f(CW\*(C`ev_loop\*(C'\fR starts |
770 |
to gather new events, and all \f(CW\*(C`ev_check\*(C'\fR watchers are invoked just after |
771 |
\&\f(CW\*(C`ev_loop\*(C'\fR has gathered them, but before it invokes any callbacks for any |
772 |
received events. Callbacks of both watcher types can start and stop as |
773 |
many watchers as they want, and all of them will be taken into account |
774 |
(for example, a \f(CW\*(C`ev_prepare\*(C'\fR watcher might start an idle watcher to keep |
775 |
\&\f(CW\*(C`ev_loop\*(C'\fR from blocking). |
776 |
.ie n .IP """EV_EMBED""" 4 |
777 |
.el .IP "\f(CWEV_EMBED\fR" 4 |
778 |
.IX Item "EV_EMBED" |
779 |
The embedded event loop specified in the \f(CW\*(C`ev_embed\*(C'\fR watcher needs attention. |
780 |
.ie n .IP """EV_FORK""" 4 |
781 |
.el .IP "\f(CWEV_FORK\fR" 4 |
782 |
.IX Item "EV_FORK" |
783 |
The event loop has been resumed in the child process after fork (see |
784 |
\&\f(CW\*(C`ev_fork\*(C'\fR). |
785 |
.ie n .IP """EV_ERROR""" 4 |
786 |
.el .IP "\f(CWEV_ERROR\fR" 4 |
787 |
.IX Item "EV_ERROR" |
788 |
An unspecified error has occured, the watcher has been stopped. This might |
789 |
happen because the watcher could not be properly started because libev |
790 |
ran out of memory, a file descriptor was found to be closed or any other |
791 |
problem. You best act on it by reporting the problem and somehow coping |
792 |
with the watcher being stopped. |
793 |
.Sp |
794 |
Libev will usually signal a few \*(L"dummy\*(R" events together with an error, |
795 |
for example it might indicate that a fd is readable or writable, and if |
796 |
your callbacks is well-written it can just attempt the operation and cope |
797 |
with the error from \fIread()\fR or \fIwrite()\fR. This will not work in multithreaded |
798 |
programs, though, so beware. |
799 |
.Sh "\s-1GENERIC\s0 \s-1WATCHER\s0 \s-1FUNCTIONS\s0" |
800 |
.IX Subsection "GENERIC WATCHER FUNCTIONS" |
801 |
In the following description, \f(CW\*(C`TYPE\*(C'\fR stands for the watcher type, |
802 |
e.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. |
803 |
.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 |
804 |
.el .IP "\f(CWev_init\fR (ev_TYPE *watcher, callback)" 4 |
805 |
.IX Item "ev_init (ev_TYPE *watcher, callback)" |
806 |
This macro initialises the generic portion of a watcher. The contents |
807 |
of the watcher object can be arbitrary (so \f(CW\*(C`malloc\*(C'\fR will do). Only |
808 |
the generic parts of the watcher are initialised, you \fIneed\fR to call |
809 |
the type-specific \f(CW\*(C`ev_TYPE_set\*(C'\fR macro afterwards to initialise the |
810 |
type-specific parts. For each type there is also a \f(CW\*(C`ev_TYPE_init\*(C'\fR macro |
811 |
which rolls both calls into one. |
812 |
.Sp |
813 |
You can reinitialise a watcher at any time as long as it has been stopped |
814 |
(or never started) and there are no pending events outstanding. |
815 |
.Sp |
816 |
The callback is always of type \f(CW\*(C`void (*)(ev_loop *loop, ev_TYPE *watcher, |
817 |
int revents)\*(C'\fR. |
818 |
.ie n .IP """ev_TYPE_set"" (ev_TYPE *, [args])" 4 |
819 |
.el .IP "\f(CWev_TYPE_set\fR (ev_TYPE *, [args])" 4 |
820 |
.IX Item "ev_TYPE_set (ev_TYPE *, [args])" |
821 |
This macro initialises the type-specific parts of a watcher. You need to |
822 |
call \f(CW\*(C`ev_init\*(C'\fR at least once before you call this macro, but you can |
823 |
call \f(CW\*(C`ev_TYPE_set\*(C'\fR any number of times. You must not, however, call this |
824 |
macro on a watcher that is active (it can be pending, however, which is a |
825 |
difference to the \f(CW\*(C`ev_init\*(C'\fR macro). |
826 |
.Sp |
827 |
Although some watcher types do not have type-specific arguments |
828 |
(e.g. \f(CW\*(C`ev_prepare\*(C'\fR) you still need to call its \f(CW\*(C`set\*(C'\fR macro. |
829 |
.ie n .IP """ev_TYPE_init"" (ev_TYPE *watcher, callback, [args])" 4 |
830 |
.el .IP "\f(CWev_TYPE_init\fR (ev_TYPE *watcher, callback, [args])" 4 |
831 |
.IX Item "ev_TYPE_init (ev_TYPE *watcher, callback, [args])" |
832 |
This convinience macro rolls both \f(CW\*(C`ev_init\*(C'\fR and \f(CW\*(C`ev_TYPE_set\*(C'\fR macro |
833 |
calls into a single call. This is the most convinient method to initialise |
834 |
a watcher. The same limitations apply, of course. |
835 |
.ie n .IP """ev_TYPE_start"" (loop *, ev_TYPE *watcher)" 4 |
836 |
.el .IP "\f(CWev_TYPE_start\fR (loop *, ev_TYPE *watcher)" 4 |
837 |
.IX Item "ev_TYPE_start (loop *, ev_TYPE *watcher)" |
838 |
Starts (activates) the given watcher. Only active watchers will receive |
839 |
events. If the watcher is already active nothing will happen. |
840 |
.ie n .IP """ev_TYPE_stop"" (loop *, ev_TYPE *watcher)" 4 |
841 |
.el .IP "\f(CWev_TYPE_stop\fR (loop *, ev_TYPE *watcher)" 4 |
842 |
.IX Item "ev_TYPE_stop (loop *, ev_TYPE *watcher)" |
843 |
Stops the given watcher again (if active) and clears the pending |
844 |
status. It is possible that stopped watchers are pending (for example, |
845 |
non-repeating timers are being stopped when they become pending), but |
846 |
\&\f(CW\*(C`ev_TYPE_stop\*(C'\fR ensures that the watcher is neither active nor pending. If |
847 |
you want to free or reuse the memory used by the watcher it is therefore a |
848 |
good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. |
849 |
.IP "bool ev_is_active (ev_TYPE *watcher)" 4 |
850 |
.IX Item "bool ev_is_active (ev_TYPE *watcher)" |
851 |
Returns a true value iff the watcher is active (i.e. it has been started |
852 |
and not yet been stopped). As long as a watcher is active you must not modify |
853 |
it. |
854 |
.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 |
855 |
.IX Item "bool ev_is_pending (ev_TYPE *watcher)" |
856 |
Returns a true value iff the watcher is pending, (i.e. it has outstanding |
857 |
events but its callback has not yet been invoked). As long as a watcher |
858 |
is pending (but not active) you must not call an init function on it (but |
859 |
\&\f(CW\*(C`ev_TYPE_set\*(C'\fR is safe) and you must make sure the watcher is available to |
860 |
libev (e.g. you cnanot \f(CW\*(C`free ()\*(C'\fR it). |
861 |
.IP "callback ev_cb (ev_TYPE *watcher)" 4 |
862 |
.IX Item "callback ev_cb (ev_TYPE *watcher)" |
863 |
Returns the callback currently set on the watcher. |
864 |
.IP "ev_cb_set (ev_TYPE *watcher, callback)" 4 |
865 |
.IX Item "ev_cb_set (ev_TYPE *watcher, callback)" |
866 |
Change the callback. You can change the callback at virtually any time |
867 |
(modulo threads). |
868 |
.Sh "\s-1ASSOCIATING\s0 \s-1CUSTOM\s0 \s-1DATA\s0 \s-1WITH\s0 A \s-1WATCHER\s0" |
869 |
.IX Subsection "ASSOCIATING CUSTOM DATA WITH A WATCHER" |
870 |
Each watcher has, by default, a member \f(CW\*(C`void *data\*(C'\fR that you can change |
871 |
and read at any time, libev will completely ignore it. This can be used |
872 |
to associate arbitrary data with your watcher. If you need more data and |
873 |
don't want to allocate memory and store a pointer to it in that data |
874 |
member, you can also \*(L"subclass\*(R" the watcher type and provide your own |
875 |
data: |
876 |
.PP |
877 |
.Vb 7 |
878 |
\& struct my_io |
879 |
\& { |
880 |
\& struct ev_io io; |
881 |
\& int otherfd; |
882 |
\& void *somedata; |
883 |
\& struct whatever *mostinteresting; |
884 |
\& } |
885 |
.Ve |
886 |
.PP |
887 |
And since your callback will be called with a pointer to the watcher, you |
888 |
can cast it back to your own type: |
889 |
.PP |
890 |
.Vb 5 |
891 |
\& static void my_cb (struct ev_loop *loop, struct ev_io *w_, int revents) |
892 |
\& { |
893 |
\& struct my_io *w = (struct my_io *)w_; |
894 |
\& ... |
895 |
\& } |
896 |
.Ve |
897 |
.PP |
898 |
More interesting and less C\-conformant ways of casting your callback type |
899 |
instead have been omitted. |
900 |
.PP |
901 |
Another common scenario is having some data structure with multiple |
902 |
watchers: |
903 |
.PP |
904 |
.Vb 6 |
905 |
\& struct my_biggy |
906 |
\& { |
907 |
\& int some_data; |
908 |
\& ev_timer t1; |
909 |
\& ev_timer t2; |
910 |
\& } |
911 |
.Ve |
912 |
.PP |
913 |
In this case getting the pointer to \f(CW\*(C`my_biggy\*(C'\fR is a bit more complicated, |
914 |
you need to use \f(CW\*(C`offsetof\*(C'\fR: |
915 |
.PP |
916 |
.Vb 1 |
917 |
\& #include <stddef.h> |
918 |
.Ve |
919 |
.PP |
920 |
.Vb 6 |
921 |
\& static void |
922 |
\& t1_cb (EV_P_ struct ev_timer *w, int revents) |
923 |
\& { |
924 |
\& struct my_biggy big = (struct my_biggy * |
925 |
\& (((char *)w) - offsetof (struct my_biggy, t1)); |
926 |
\& } |
927 |
.Ve |
928 |
.PP |
929 |
.Vb 6 |
930 |
\& static void |
931 |
\& t2_cb (EV_P_ struct ev_timer *w, int revents) |
932 |
\& { |
933 |
\& struct my_biggy big = (struct my_biggy * |
934 |
\& (((char *)w) - offsetof (struct my_biggy, t2)); |
935 |
\& } |
936 |
.Ve |
937 |
.SH "WATCHER TYPES" |
938 |
.IX Header "WATCHER TYPES" |
939 |
This section describes each watcher in detail, but will not repeat |
940 |
information given in the last section. Any initialisation/set macros, |
941 |
functions and members specific to the watcher type are explained. |
942 |
.PP |
943 |
Members are additionally marked with either \fI[read\-only]\fR, meaning that, |
944 |
while the watcher is active, you can look at the member and expect some |
945 |
sensible content, but you must not modify it (you can modify it while the |
946 |
watcher is stopped to your hearts content), or \fI[read\-write]\fR, which |
947 |
means you can expect it to have some sensible content while the watcher |
948 |
is active, but you can also modify it. Modifying it may not do something |
949 |
sensible or take immediate effect (or do anything at all), but libev will |
950 |
not crash or malfunction in any way. |
951 |
.ie n .Sh """ev_io"" \- is this file descriptor readable or writable?" |
952 |
.el .Sh "\f(CWev_io\fP \- is this file descriptor readable or writable?" |
953 |
.IX Subsection "ev_io - is this file descriptor readable or writable?" |
954 |
I/O watchers check whether a file descriptor is readable or writable |
955 |
in each iteration of the event loop, or, more precisely, when reading |
956 |
would not block the process and writing would at least be able to write |
957 |
some data. This behaviour is called level-triggering because you keep |
958 |
receiving events as long as the condition persists. Remember you can stop |
959 |
the watcher if you don't want to act on the event and neither want to |
960 |
receive future events. |
961 |
.PP |
962 |
In general you can register as many read and/or write event watchers per |
963 |
fd as you want (as long as you don't confuse yourself). Setting all file |
964 |
descriptors to non-blocking mode is also usually a good idea (but not |
965 |
required if you know what you are doing). |
966 |
.PP |
967 |
You have to be careful with dup'ed file descriptors, though. Some backends |
968 |
(the linux epoll backend is a notable example) cannot handle dup'ed file |
969 |
descriptors correctly if you register interest in two or more fds pointing |
970 |
to the same underlying file/socket/etc. description (that is, they share |
971 |
the same underlying \*(L"file open\*(R"). |
972 |
.PP |
973 |
If you must do this, then force the use of a known-to-be-good backend |
974 |
(at the time of this writing, this includes only \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR and |
975 |
\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR). |
976 |
.PP |
977 |
Another thing you have to watch out for is that it is quite easy to |
978 |
receive \*(L"spurious\*(R" readyness notifications, that is your callback might |
979 |
be called with \f(CW\*(C`EV_READ\*(C'\fR but a subsequent \f(CW\*(C`read\*(C'\fR(2) will actually block |
980 |
because there is no data. Not only are some backends known to create a |
981 |
lot of those (for example solaris ports), it is very easy to get into |
982 |
this situation even with a relatively standard program structure. Thus |
983 |
it is best to always use non-blocking I/O: An extra \f(CW\*(C`read\*(C'\fR(2) returning |
984 |
\&\f(CW\*(C`EAGAIN\*(C'\fR is far preferable to a program hanging until some data arrives. |
985 |
.PP |
986 |
If you cannot run the fd in non-blocking mode (for example you should not |
987 |
play around with an Xlib connection), then you have to seperately re-test |
988 |
wether a file descriptor is really ready with a known-to-be good interface |
989 |
such as poll (fortunately in our Xlib example, Xlib already does this on |
990 |
its own, so its quite safe to use). |
991 |
.IP "ev_io_init (ev_io *, callback, int fd, int events)" 4 |
992 |
.IX Item "ev_io_init (ev_io *, callback, int fd, int events)" |
993 |
.PD 0 |
994 |
.IP "ev_io_set (ev_io *, int fd, int events)" 4 |
995 |
.IX Item "ev_io_set (ev_io *, int fd, int events)" |
996 |
.PD |
997 |
Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to |
998 |
rceeive events for and events is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or |
999 |
\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR to receive the given events. |
1000 |
.IP "int fd [read\-only]" 4 |
1001 |
.IX Item "int fd [read-only]" |
1002 |
The file descriptor being watched. |
1003 |
.IP "int events [read\-only]" 4 |
1004 |
.IX Item "int events [read-only]" |
1005 |
The events being watched. |
1006 |
.PP |
1007 |
Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well |
1008 |
readable, but only once. Since it is likely line\-buffered, you could |
1009 |
attempt to read a whole line in the callback. |
1010 |
.PP |
1011 |
.Vb 6 |
1012 |
\& static void |
1013 |
\& stdin_readable_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1014 |
\& { |
1015 |
\& ev_io_stop (loop, w); |
1016 |
\& .. read from stdin here (or from w->fd) and haqndle any I/O errors |
1017 |
\& } |
1018 |
.Ve |
1019 |
.PP |
1020 |
.Vb 6 |
1021 |
\& ... |
1022 |
\& struct ev_loop *loop = ev_default_init (0); |
1023 |
\& struct ev_io stdin_readable; |
1024 |
\& ev_io_init (&stdin_readable, stdin_readable_cb, STDIN_FILENO, EV_READ); |
1025 |
\& ev_io_start (loop, &stdin_readable); |
1026 |
\& ev_loop (loop, 0); |
1027 |
.Ve |
1028 |
.ie n .Sh """ev_timer"" \- relative and optionally repeating timeouts" |
1029 |
.el .Sh "\f(CWev_timer\fP \- relative and optionally repeating timeouts" |
1030 |
.IX Subsection "ev_timer - relative and optionally repeating timeouts" |
1031 |
Timer watchers are simple relative timers that generate an event after a |
1032 |
given time, and optionally repeating in regular intervals after that. |
1033 |
.PP |
1034 |
The timers are based on real time, that is, if you register an event that |
1035 |
times out after an hour and you reset your system clock to last years |
1036 |
time, it will still time out after (roughly) and hour. \*(L"Roughly\*(R" because |
1037 |
detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1038 |
monotonic clock option helps a lot here). |
1039 |
.PP |
1040 |
The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR |
1041 |
time. This is usually the right thing as this timestamp refers to the time |
1042 |
of the event triggering whatever timeout you are modifying/starting. If |
1043 |
you suspect event processing to be delayed and you \fIneed\fR to base the timeout |
1044 |
on the current time, use something like this to adjust for this: |
1045 |
.PP |
1046 |
.Vb 1 |
1047 |
\& ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1048 |
.Ve |
1049 |
.PP |
1050 |
The callback is guarenteed to be invoked only when its timeout has passed, |
1051 |
but if multiple timers become ready during the same loop iteration then |
1052 |
order of execution is undefined. |
1053 |
.IP "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 4 |
1054 |
.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" |
1055 |
.PD 0 |
1056 |
.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 |
1057 |
.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" |
1058 |
.PD |
1059 |
Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR is |
1060 |
\&\f(CW0.\fR, then it will automatically be stopped. If it is positive, then the |
1061 |
timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds |
1062 |
later, again, and again, until stopped manually. |
1063 |
.Sp |
1064 |
The timer itself will do a best-effort at avoiding drift, that is, if you |
1065 |
configure a timer to trigger every 10 seconds, then it will trigger at |
1066 |
exactly 10 second intervals. If, however, your program cannot keep up with |
1067 |
the timer (because it takes longer than those 10 seconds to do stuff) the |
1068 |
timer will not fire more than once per event loop iteration. |
1069 |
.IP "ev_timer_again (loop)" 4 |
1070 |
.IX Item "ev_timer_again (loop)" |
1071 |
This will act as if the timer timed out and restart it again if it is |
1072 |
repeating. The exact semantics are: |
1073 |
.Sp |
1074 |
If the timer is started but nonrepeating, stop it. |
1075 |
.Sp |
1076 |
If the timer is repeating, either start it if necessary (with the repeat |
1077 |
value), or reset the running timer to the repeat value. |
1078 |
.Sp |
1079 |
This sounds a bit complicated, but here is a useful and typical |
1080 |
example: Imagine you have a tcp connection and you want a so-called |
1081 |
idle timeout, that is, you want to be called when there have been, |
1082 |
say, 60 seconds of inactivity on the socket. The easiest way to do |
1083 |
this is to configure an \f(CW\*(C`ev_timer\*(C'\fR with \f(CW\*(C`after\*(C'\fR=\f(CW\*(C`repeat\*(C'\fR=\f(CW60\fR and calling |
1084 |
\&\f(CW\*(C`ev_timer_again\*(C'\fR each time you successfully read or write some data. If |
1085 |
you go into an idle state where you do not expect data to travel on the |
1086 |
socket, you can stop the timer, and again will automatically restart it if |
1087 |
need be. |
1088 |
.Sp |
1089 |
You can also ignore the \f(CW\*(C`after\*(C'\fR value and \f(CW\*(C`ev_timer_start\*(C'\fR altogether |
1090 |
and only ever use the \f(CW\*(C`repeat\*(C'\fR value: |
1091 |
.Sp |
1092 |
.Vb 8 |
1093 |
\& ev_timer_init (timer, callback, 0., 5.); |
1094 |
\& ev_timer_again (loop, timer); |
1095 |
\& ... |
1096 |
\& timer->again = 17.; |
1097 |
\& ev_timer_again (loop, timer); |
1098 |
\& ... |
1099 |
\& timer->again = 10.; |
1100 |
\& ev_timer_again (loop, timer); |
1101 |
.Ve |
1102 |
.Sp |
1103 |
This is more efficient then stopping/starting the timer eahc time you want |
1104 |
to modify its timeout value. |
1105 |
.IP "ev_tstamp repeat [read\-write]" 4 |
1106 |
.IX Item "ev_tstamp repeat [read-write]" |
1107 |
The current \f(CW\*(C`repeat\*(C'\fR value. Will be used each time the watcher times out |
1108 |
or \f(CW\*(C`ev_timer_again\*(C'\fR is called and determines the next timeout (if any), |
1109 |
which is also when any modifications are taken into account. |
1110 |
.PP |
1111 |
Example: Create a timer that fires after 60 seconds. |
1112 |
.PP |
1113 |
.Vb 5 |
1114 |
\& static void |
1115 |
\& one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1116 |
\& { |
1117 |
\& .. one minute over, w is actually stopped right here |
1118 |
\& } |
1119 |
.Ve |
1120 |
.PP |
1121 |
.Vb 3 |
1122 |
\& struct ev_timer mytimer; |
1123 |
\& ev_timer_init (&mytimer, one_minute_cb, 60., 0.); |
1124 |
\& ev_timer_start (loop, &mytimer); |
1125 |
.Ve |
1126 |
.PP |
1127 |
Example: Create a timeout timer that times out after 10 seconds of |
1128 |
inactivity. |
1129 |
.PP |
1130 |
.Vb 5 |
1131 |
\& static void |
1132 |
\& timeout_cb (struct ev_loop *loop, struct ev_timer *w, int revents) |
1133 |
\& { |
1134 |
\& .. ten seconds without any activity |
1135 |
\& } |
1136 |
.Ve |
1137 |
.PP |
1138 |
.Vb 4 |
1139 |
\& struct ev_timer mytimer; |
1140 |
\& ev_timer_init (&mytimer, timeout_cb, 0., 10.); /* note, only repeat used */ |
1141 |
\& ev_timer_again (&mytimer); /* start timer */ |
1142 |
\& ev_loop (loop, 0); |
1143 |
.Ve |
1144 |
.PP |
1145 |
.Vb 3 |
1146 |
\& // and in some piece of code that gets executed on any "activity": |
1147 |
\& // reset the timeout to start ticking again at 10 seconds |
1148 |
\& ev_timer_again (&mytimer); |
1149 |
.Ve |
1150 |
.ie n .Sh """ev_periodic"" \- to cron or not to cron?" |
1151 |
.el .Sh "\f(CWev_periodic\fP \- to cron or not to cron?" |
1152 |
.IX Subsection "ev_periodic - to cron or not to cron?" |
1153 |
Periodic watchers are also timers of a kind, but they are very versatile |
1154 |
(and unfortunately a bit complex). |
1155 |
.PP |
1156 |
Unlike \f(CW\*(C`ev_timer\*(C'\fR's, they are not based on real time (or relative time) |
1157 |
but on wallclock time (absolute time). You can tell a periodic watcher |
1158 |
to trigger \*(L"at\*(R" some specific point in time. For example, if you tell a |
1159 |
periodic watcher to trigger in 10 seconds (by specifiying e.g. \f(CW\*(C`ev_now () |
1160 |
+ 10.\*(C'\fR) and then reset your system clock to the last year, then it will |
1161 |
take a year to trigger the event (unlike an \f(CW\*(C`ev_timer\*(C'\fR, which would trigger |
1162 |
roughly 10 seconds later and of course not if you reset your system time |
1163 |
again). |
1164 |
.PP |
1165 |
They can also be used to implement vastly more complex timers, such as |
1166 |
triggering an event on eahc midnight, local time. |
1167 |
.PP |
1168 |
As with timers, the callback is guarenteed to be invoked only when the |
1169 |
time (\f(CW\*(C`at\*(C'\fR) has been passed, but if multiple periodic timers become ready |
1170 |
during the same loop iteration then order of execution is undefined. |
1171 |
.IP "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" 4 |
1172 |
.IX Item "ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)" |
1173 |
.PD 0 |
1174 |
.IP "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" 4 |
1175 |
.IX Item "ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)" |
1176 |
.PD |
1177 |
Lots of arguments, lets sort it out... There are basically three modes of |
1178 |
operation, and we will explain them from simplest to complex: |
1179 |
.RS 4 |
1180 |
.IP "* absolute timer (interval = reschedule_cb = 0)" 4 |
1181 |
.IX Item "absolute timer (interval = reschedule_cb = 0)" |
1182 |
In this configuration the watcher triggers an event at the wallclock time |
1183 |
\&\f(CW\*(C`at\*(C'\fR and doesn't repeat. It will not adjust when a time jump occurs, |
1184 |
that is, if it is to be run at January 1st 2011 then it will run when the |
1185 |
system time reaches or surpasses this time. |
1186 |
.IP "* non-repeating interval timer (interval > 0, reschedule_cb = 0)" 4 |
1187 |
.IX Item "non-repeating interval timer (interval > 0, reschedule_cb = 0)" |
1188 |
In this mode the watcher will always be scheduled to time out at the next |
1189 |
\&\f(CW\*(C`at + N * interval\*(C'\fR time (for some integer N) and then repeat, regardless |
1190 |
of any time jumps. |
1191 |
.Sp |
1192 |
This can be used to create timers that do not drift with respect to system |
1193 |
time: |
1194 |
.Sp |
1195 |
.Vb 1 |
1196 |
\& ev_periodic_set (&periodic, 0., 3600., 0); |
1197 |
.Ve |
1198 |
.Sp |
1199 |
This doesn't mean there will always be 3600 seconds in between triggers, |
1200 |
but only that the the callback will be called when the system time shows a |
1201 |
full hour (\s-1UTC\s0), or more correctly, when the system time is evenly divisible |
1202 |
by 3600. |
1203 |
.Sp |
1204 |
Another way to think about it (for the mathematically inclined) is that |
1205 |
\&\f(CW\*(C`ev_periodic\*(C'\fR will try to run the callback in this mode at the next possible |
1206 |
time where \f(CW\*(C`time = at (mod interval)\*(C'\fR, regardless of any time jumps. |
1207 |
.IP "* manual reschedule mode (reschedule_cb = callback)" 4 |
1208 |
.IX Item "manual reschedule mode (reschedule_cb = callback)" |
1209 |
In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`at\*(C'\fR are both being |
1210 |
ignored. Instead, each time the periodic watcher gets scheduled, the |
1211 |
reschedule callback will be called with the watcher as first, and the |
1212 |
current time as second argument. |
1213 |
.Sp |
1214 |
\&\s-1NOTE:\s0 \fIThis callback \s-1MUST\s0 \s-1NOT\s0 stop or destroy any periodic watcher, |
1215 |
ever, or make any event loop modifications\fR. If you need to stop it, |
1216 |
return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop it afterwards (e.g. by |
1217 |
starting a prepare watcher). |
1218 |
.Sp |
1219 |
Its prototype is \f(CW\*(C`ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1220 |
ev_tstamp now)\*(C'\fR, e.g.: |
1221 |
.Sp |
1222 |
.Vb 4 |
1223 |
\& static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1224 |
\& { |
1225 |
\& return now + 60.; |
1226 |
\& } |
1227 |
.Ve |
1228 |
.Sp |
1229 |
It must return the next time to trigger, based on the passed time value |
1230 |
(that is, the lowest time value larger than to the second argument). It |
1231 |
will usually be called just before the callback will be triggered, but |
1232 |
might be called at other times, too. |
1233 |
.Sp |
1234 |
\&\s-1NOTE:\s0 \fIThis callback must always return a time that is later than the |
1235 |
passed \f(CI\*(C`now\*(C'\fI value\fR. Not even \f(CW\*(C`now\*(C'\fR itself will do, it \fImust\fR be larger. |
1236 |
.Sp |
1237 |
This can be used to create very complex timers, such as a timer that |
1238 |
triggers on each midnight, local time. To do this, you would calculate the |
1239 |
next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How |
1240 |
you do this is, again, up to you (but it is not trivial, which is the main |
1241 |
reason I omitted it as an example). |
1242 |
.RE |
1243 |
.RS 4 |
1244 |
.RE |
1245 |
.IP "ev_periodic_again (loop, ev_periodic *)" 4 |
1246 |
.IX Item "ev_periodic_again (loop, ev_periodic *)" |
1247 |
Simply stops and restarts the periodic watcher again. This is only useful |
1248 |
when you changed some parameters or the reschedule callback would return |
1249 |
a different time than the last time it was called (e.g. in a crond like |
1250 |
program when the crontabs have changed). |
1251 |
.IP "ev_tstamp interval [read\-write]" 4 |
1252 |
.IX Item "ev_tstamp interval [read-write]" |
1253 |
The current interval value. Can be modified any time, but changes only |
1254 |
take effect when the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being |
1255 |
called. |
1256 |
.IP "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read\-write]" 4 |
1257 |
.IX Item "ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write]" |
1258 |
The current reschedule callback, or \f(CW0\fR, if this functionality is |
1259 |
switched off. Can be changed any time, but changes only take effect when |
1260 |
the periodic timer fires or \f(CW\*(C`ev_periodic_again\*(C'\fR is being called. |
1261 |
.PP |
1262 |
Example: Call a callback every hour, or, more precisely, whenever the |
1263 |
system clock is divisible by 3600. The callback invocation times have |
1264 |
potentially a lot of jittering, but good long-term stability. |
1265 |
.PP |
1266 |
.Vb 5 |
1267 |
\& static void |
1268 |
\& clock_cb (struct ev_loop *loop, struct ev_io *w, int revents) |
1269 |
\& { |
1270 |
\& ... its now a full hour (UTC, or TAI or whatever your clock follows) |
1271 |
\& } |
1272 |
.Ve |
1273 |
.PP |
1274 |
.Vb 3 |
1275 |
\& struct ev_periodic hourly_tick; |
1276 |
\& ev_periodic_init (&hourly_tick, clock_cb, 0., 3600., 0); |
1277 |
\& ev_periodic_start (loop, &hourly_tick); |
1278 |
.Ve |
1279 |
.PP |
1280 |
Example: The same as above, but use a reschedule callback to do it: |
1281 |
.PP |
1282 |
.Vb 1 |
1283 |
\& #include <math.h> |
1284 |
.Ve |
1285 |
.PP |
1286 |
.Vb 5 |
1287 |
\& static ev_tstamp |
1288 |
\& my_scheduler_cb (struct ev_periodic *w, ev_tstamp now) |
1289 |
\& { |
1290 |
\& return fmod (now, 3600.) + 3600.; |
1291 |
\& } |
1292 |
.Ve |
1293 |
.PP |
1294 |
.Vb 1 |
1295 |
\& ev_periodic_init (&hourly_tick, clock_cb, 0., 0., my_scheduler_cb); |
1296 |
.Ve |
1297 |
.PP |
1298 |
Example: Call a callback every hour, starting now: |
1299 |
.PP |
1300 |
.Vb 4 |
1301 |
\& struct ev_periodic hourly_tick; |
1302 |
\& ev_periodic_init (&hourly_tick, clock_cb, |
1303 |
\& fmod (ev_now (loop), 3600.), 3600., 0); |
1304 |
\& ev_periodic_start (loop, &hourly_tick); |
1305 |
.Ve |
1306 |
.ie n .Sh """ev_signal"" \- signal me when a signal gets signalled!" |
1307 |
.el .Sh "\f(CWev_signal\fP \- signal me when a signal gets signalled!" |
1308 |
.IX Subsection "ev_signal - signal me when a signal gets signalled!" |
1309 |
Signal watchers will trigger an event when the process receives a specific |
1310 |
signal one or more times. Even though signals are very asynchronous, libev |
1311 |
will try it's best to deliver signals synchronously, i.e. as part of the |
1312 |
normal event processing, like any other event. |
1313 |
.PP |
1314 |
You can configure as many watchers as you like per signal. Only when the |
1315 |
first watcher gets started will libev actually register a signal watcher |
1316 |
with the kernel (thus it coexists with your own signal handlers as long |
1317 |
as you don't register any with libev). Similarly, when the last signal |
1318 |
watcher for a signal is stopped libev will reset the signal handler to |
1319 |
\&\s-1SIG_DFL\s0 (regardless of what it was set to before). |
1320 |
.IP "ev_signal_init (ev_signal *, callback, int signum)" 4 |
1321 |
.IX Item "ev_signal_init (ev_signal *, callback, int signum)" |
1322 |
.PD 0 |
1323 |
.IP "ev_signal_set (ev_signal *, int signum)" 4 |
1324 |
.IX Item "ev_signal_set (ev_signal *, int signum)" |
1325 |
.PD |
1326 |
Configures the watcher to trigger on the given signal number (usually one |
1327 |
of the \f(CW\*(C`SIGxxx\*(C'\fR constants). |
1328 |
.IP "int signum [read\-only]" 4 |
1329 |
.IX Item "int signum [read-only]" |
1330 |
The signal the watcher watches out for. |
1331 |
.ie n .Sh """ev_child"" \- watch out for process status changes" |
1332 |
.el .Sh "\f(CWev_child\fP \- watch out for process status changes" |
1333 |
.IX Subsection "ev_child - watch out for process status changes" |
1334 |
Child watchers trigger when your process receives a \s-1SIGCHLD\s0 in response to |
1335 |
some child status changes (most typically when a child of yours dies). |
1336 |
.IP "ev_child_init (ev_child *, callback, int pid)" 4 |
1337 |
.IX Item "ev_child_init (ev_child *, callback, int pid)" |
1338 |
.PD 0 |
1339 |
.IP "ev_child_set (ev_child *, int pid)" 4 |
1340 |
.IX Item "ev_child_set (ev_child *, int pid)" |
1341 |
.PD |
1342 |
Configures the watcher to wait for status changes of process \f(CW\*(C`pid\*(C'\fR (or |
1343 |
\&\fIany\fR process if \f(CW\*(C`pid\*(C'\fR is specified as \f(CW0\fR). The callback can look |
1344 |
at the \f(CW\*(C`rstatus\*(C'\fR member of the \f(CW\*(C`ev_child\*(C'\fR watcher structure to see |
1345 |
the status word (use the macros from \f(CW\*(C`sys/wait.h\*(C'\fR and see your systems |
1346 |
\&\f(CW\*(C`waitpid\*(C'\fR documentation). The \f(CW\*(C`rpid\*(C'\fR member contains the pid of the |
1347 |
process causing the status change. |
1348 |
.IP "int pid [read\-only]" 4 |
1349 |
.IX Item "int pid [read-only]" |
1350 |
The process id this watcher watches out for, or \f(CW0\fR, meaning any process id. |
1351 |
.IP "int rpid [read\-write]" 4 |
1352 |
.IX Item "int rpid [read-write]" |
1353 |
The process id that detected a status change. |
1354 |
.IP "int rstatus [read\-write]" 4 |
1355 |
.IX Item "int rstatus [read-write]" |
1356 |
The process exit/trace status caused by \f(CW\*(C`rpid\*(C'\fR (see your systems |
1357 |
\&\f(CW\*(C`waitpid\*(C'\fR and \f(CW\*(C`sys/wait.h\*(C'\fR documentation for details). |
1358 |
.PP |
1359 |
Example: Try to exit cleanly on \s-1SIGINT\s0 and \s-1SIGTERM\s0. |
1360 |
.PP |
1361 |
.Vb 5 |
1362 |
\& static void |
1363 |
\& sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1364 |
\& { |
1365 |
\& ev_unloop (loop, EVUNLOOP_ALL); |
1366 |
\& } |
1367 |
.Ve |
1368 |
.PP |
1369 |
.Vb 3 |
1370 |
\& struct ev_signal signal_watcher; |
1371 |
\& ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1372 |
\& ev_signal_start (loop, &sigint_cb); |
1373 |
.Ve |
1374 |
.ie n .Sh """ev_stat"" \- did the file attributes just change?" |
1375 |
.el .Sh "\f(CWev_stat\fP \- did the file attributes just change?" |
1376 |
.IX Subsection "ev_stat - did the file attributes just change?" |
1377 |
This watches a filesystem path for attribute changes. That is, it calls |
1378 |
\&\f(CW\*(C`stat\*(C'\fR regularly (or when the \s-1OS\s0 says it changed) and sees if it changed |
1379 |
compared to the last time, invoking the callback if it did. |
1380 |
.PP |
1381 |
The path does not need to exist: changing from \*(L"path exists\*(R" to \*(L"path does |
1382 |
not exist\*(R" is a status change like any other. The condition \*(L"path does |
1383 |
not exist\*(R" is signified by the \f(CW\*(C`st_nlink\*(C'\fR field being zero (which is |
1384 |
otherwise always forced to be at least one) and all the other fields of |
1385 |
the stat buffer having unspecified contents. |
1386 |
.PP |
1387 |
Since there is no standard to do this, the portable implementation simply |
1388 |
calls \f(CW\*(C`stat (2)\*(C'\fR regularly on the path to see if it changed somehow. You |
1389 |
can specify a recommended polling interval for this case. If you specify |
1390 |
a polling interval of \f(CW0\fR (highly recommended!) then a \fIsuitable, |
1391 |
unspecified default\fR value will be used (which you can expect to be around |
1392 |
five seconds, although this might change dynamically). Libev will also |
1393 |
impose a minimum interval which is currently around \f(CW0.1\fR, but thats |
1394 |
usually overkill. |
1395 |
.PP |
1396 |
This watcher type is not meant for massive numbers of stat watchers, |
1397 |
as even with OS-supported change notifications, this can be |
1398 |
resource\-intensive. |
1399 |
.PP |
1400 |
At the time of this writing, only the Linux inotify interface is |
1401 |
implemented (implementing kqueue support is left as an exercise for the |
1402 |
reader). Inotify will be used to give hints only and should not change the |
1403 |
semantics of \f(CW\*(C`ev_stat\*(C'\fR watchers, which means that libev sometimes needs |
1404 |
to fall back to regular polling again even with inotify, but changes are |
1405 |
usually detected immediately, and if the file exists there will be no |
1406 |
polling. |
1407 |
.IP "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" 4 |
1408 |
.IX Item "ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)" |
1409 |
.PD 0 |
1410 |
.IP "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" 4 |
1411 |
.IX Item "ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)" |
1412 |
.PD |
1413 |
Configures the watcher to wait for status changes of the given |
1414 |
\&\f(CW\*(C`path\*(C'\fR. The \f(CW\*(C`interval\*(C'\fR is a hint on how quickly a change is expected to |
1415 |
be detected and should normally be specified as \f(CW0\fR to let libev choose |
1416 |
a suitable value. The memory pointed to by \f(CW\*(C`path\*(C'\fR must point to the same |
1417 |
path for as long as the watcher is active. |
1418 |
.Sp |
1419 |
The callback will be receive \f(CW\*(C`EV_STAT\*(C'\fR when a change was detected, |
1420 |
relative to the attributes at the time the watcher was started (or the |
1421 |
last change was detected). |
1422 |
.IP "ev_stat_stat (ev_stat *)" 4 |
1423 |
.IX Item "ev_stat_stat (ev_stat *)" |
1424 |
Updates the stat buffer immediately with new values. If you change the |
1425 |
watched path in your callback, you could call this fucntion to avoid |
1426 |
detecting this change (while introducing a race condition). Can also be |
1427 |
useful simply to find out the new values. |
1428 |
.IP "ev_statdata attr [read\-only]" 4 |
1429 |
.IX Item "ev_statdata attr [read-only]" |
1430 |
The most-recently detected attributes of the file. Although the type is of |
1431 |
\&\f(CW\*(C`ev_statdata\*(C'\fR, this is usually the (or one of the) \f(CW\*(C`struct stat\*(C'\fR types |
1432 |
suitable for your system. If the \f(CW\*(C`st_nlink\*(C'\fR member is \f(CW0\fR, then there |
1433 |
was some error while \f(CW\*(C`stat\*(C'\fRing the file. |
1434 |
.IP "ev_statdata prev [read\-only]" 4 |
1435 |
.IX Item "ev_statdata prev [read-only]" |
1436 |
The previous attributes of the file. The callback gets invoked whenever |
1437 |
\&\f(CW\*(C`prev\*(C'\fR != \f(CW\*(C`attr\*(C'\fR. |
1438 |
.IP "ev_tstamp interval [read\-only]" 4 |
1439 |
.IX Item "ev_tstamp interval [read-only]" |
1440 |
The specified interval. |
1441 |
.IP "const char *path [read\-only]" 4 |
1442 |
.IX Item "const char *path [read-only]" |
1443 |
The filesystem path that is being watched. |
1444 |
.PP |
1445 |
Example: Watch \f(CW\*(C`/etc/passwd\*(C'\fR for attribute changes. |
1446 |
.PP |
1447 |
.Vb 15 |
1448 |
\& static void |
1449 |
\& passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1450 |
\& { |
1451 |
\& /* /etc/passwd changed in some way */ |
1452 |
\& if (w->attr.st_nlink) |
1453 |
\& { |
1454 |
\& printf ("passwd current size %ld\en", (long)w->attr.st_size); |
1455 |
\& printf ("passwd current atime %ld\en", (long)w->attr.st_mtime); |
1456 |
\& printf ("passwd current mtime %ld\en", (long)w->attr.st_mtime); |
1457 |
\& } |
1458 |
\& else |
1459 |
\& /* you shalt not abuse printf for puts */ |
1460 |
\& puts ("wow, /etc/passwd is not there, expect problems. " |
1461 |
\& "if this is windows, they already arrived\en"); |
1462 |
\& } |
1463 |
.Ve |
1464 |
.PP |
1465 |
.Vb 2 |
1466 |
\& ... |
1467 |
\& ev_stat passwd; |
1468 |
.Ve |
1469 |
.PP |
1470 |
.Vb 2 |
1471 |
\& ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
1472 |
\& ev_stat_start (loop, &passwd); |
1473 |
.Ve |
1474 |
.ie n .Sh """ev_idle"" \- when you've got nothing better to do..." |
1475 |
.el .Sh "\f(CWev_idle\fP \- when you've got nothing better to do..." |
1476 |
.IX Subsection "ev_idle - when you've got nothing better to do..." |
1477 |
Idle watchers trigger events when there are no other events are pending |
1478 |
(prepare, check and other idle watchers do not count). That is, as long |
1479 |
as your process is busy handling sockets or timeouts (or even signals, |
1480 |
imagine) it will not be triggered. But when your process is idle all idle |
1481 |
watchers are being called again and again, once per event loop iteration \- |
1482 |
until stopped, that is, or your process receives more events and becomes |
1483 |
busy. |
1484 |
.PP |
1485 |
The most noteworthy effect is that as long as any idle watchers are |
1486 |
active, the process will not block when waiting for new events. |
1487 |
.PP |
1488 |
Apart from keeping your process non-blocking (which is a useful |
1489 |
effect on its own sometimes), idle watchers are a good place to do |
1490 |
\&\*(L"pseudo\-background processing\*(R", or delay processing stuff to after the |
1491 |
event loop has handled all outstanding events. |
1492 |
.IP "ev_idle_init (ev_signal *, callback)" 4 |
1493 |
.IX Item "ev_idle_init (ev_signal *, callback)" |
1494 |
Initialises and configures the idle watcher \- it has no parameters of any |
1495 |
kind. There is a \f(CW\*(C`ev_idle_set\*(C'\fR macro, but using it is utterly pointless, |
1496 |
believe me. |
1497 |
.PP |
1498 |
Example: Dynamically allocate an \f(CW\*(C`ev_idle\*(C'\fR watcher, start it, and in the |
1499 |
callback, free it. Also, use no error checking, as usual. |
1500 |
.PP |
1501 |
.Vb 7 |
1502 |
\& static void |
1503 |
\& idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1504 |
\& { |
1505 |
\& free (w); |
1506 |
\& // now do something you wanted to do when the program has |
1507 |
\& // no longer asnything immediate to do. |
1508 |
\& } |
1509 |
.Ve |
1510 |
.PP |
1511 |
.Vb 3 |
1512 |
\& struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1513 |
\& ev_idle_init (idle_watcher, idle_cb); |
1514 |
\& ev_idle_start (loop, idle_cb); |
1515 |
.Ve |
1516 |
.ie n .Sh """ev_prepare""\fP and \f(CW""ev_check"" \- customise your event loop!" |
1517 |
.el .Sh "\f(CWev_prepare\fP and \f(CWev_check\fP \- customise your event loop!" |
1518 |
.IX Subsection "ev_prepare and ev_check - customise your event loop!" |
1519 |
Prepare and check watchers are usually (but not always) used in tandem: |
1520 |
prepare watchers get invoked before the process blocks and check watchers |
1521 |
afterwards. |
1522 |
.PP |
1523 |
You \fImust not\fR call \f(CW\*(C`ev_loop\*(C'\fR or similar functions that enter |
1524 |
the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR |
1525 |
watchers. Other loops than the current one are fine, however. The |
1526 |
rationale behind this is that you do not need to check for recursion in |
1527 |
those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, |
1528 |
\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be |
1529 |
called in pairs bracketing the blocking call. |
1530 |
.PP |
1531 |
Their main purpose is to integrate other event mechanisms into libev and |
1532 |
their use is somewhat advanced. This could be used, for example, to track |
1533 |
variable changes, implement your own watchers, integrate net-snmp or a |
1534 |
coroutine library and lots more. They are also occasionally useful if |
1535 |
you cache some data and want to flush it before blocking (for example, |
1536 |
in X programs you might want to do an \f(CW\*(C`XFlush ()\*(C'\fR in an \f(CW\*(C`ev_prepare\*(C'\fR |
1537 |
watcher). |
1538 |
.PP |
1539 |
This is done by examining in each prepare call which file descriptors need |
1540 |
to be watched by the other library, registering \f(CW\*(C`ev_io\*(C'\fR watchers for |
1541 |
them and starting an \f(CW\*(C`ev_timer\*(C'\fR watcher for any timeouts (many libraries |
1542 |
provide just this functionality). Then, in the check watcher you check for |
1543 |
any events that occured (by checking the pending status of all watchers |
1544 |
and stopping them) and call back into the library. The I/O and timer |
1545 |
callbacks will never actually be called (but must be valid nevertheless, |
1546 |
because you never know, you know?). |
1547 |
.PP |
1548 |
As another example, the Perl Coro module uses these hooks to integrate |
1549 |
coroutines into libev programs, by yielding to other active coroutines |
1550 |
during each prepare and only letting the process block if no coroutines |
1551 |
are ready to run (it's actually more complicated: it only runs coroutines |
1552 |
with priority higher than or equal to the event loop and one coroutine |
1553 |
of lower priority, but only once, using idle watchers to keep the event |
1554 |
loop from blocking if lower-priority coroutines are active, thus mapping |
1555 |
low-priority coroutines to idle/background tasks). |
1556 |
.IP "ev_prepare_init (ev_prepare *, callback)" 4 |
1557 |
.IX Item "ev_prepare_init (ev_prepare *, callback)" |
1558 |
.PD 0 |
1559 |
.IP "ev_check_init (ev_check *, callback)" 4 |
1560 |
.IX Item "ev_check_init (ev_check *, callback)" |
1561 |
.PD |
1562 |
Initialises and configures the prepare or check watcher \- they have no |
1563 |
parameters of any kind. There are \f(CW\*(C`ev_prepare_set\*(C'\fR and \f(CW\*(C`ev_check_set\*(C'\fR |
1564 |
macros, but using them is utterly, utterly and completely pointless. |
1565 |
.PP |
1566 |
Example: To include a library such as adns, you would add \s-1IO\s0 watchers |
1567 |
and a timeout watcher in a prepare handler, as required by libadns, and |
1568 |
in a check watcher, destroy them and call into libadns. What follows is |
1569 |
pseudo-code only of course: |
1570 |
.PP |
1571 |
.Vb 2 |
1572 |
\& static ev_io iow [nfd]; |
1573 |
\& static ev_timer tw; |
1574 |
.Ve |
1575 |
.PP |
1576 |
.Vb 9 |
1577 |
\& static void |
1578 |
\& io_cb (ev_loop *loop, ev_io *w, int revents) |
1579 |
\& { |
1580 |
\& // set the relevant poll flags |
1581 |
\& // could also call adns_processreadable etc. here |
1582 |
\& struct pollfd *fd = (struct pollfd *)w->data; |
1583 |
\& if (revents & EV_READ ) fd->revents |= fd->events & POLLIN; |
1584 |
\& if (revents & EV_WRITE) fd->revents |= fd->events & POLLOUT; |
1585 |
\& } |
1586 |
.Ve |
1587 |
.PP |
1588 |
.Vb 7 |
1589 |
\& // create io watchers for each fd and a timer before blocking |
1590 |
\& static void |
1591 |
\& adns_prepare_cb (ev_loop *loop, ev_prepare *w, int revents) |
1592 |
\& { |
1593 |
\& int timeout = 3600000;truct pollfd fds [nfd]; |
1594 |
\& // actual code will need to loop here and realloc etc. |
1595 |
\& adns_beforepoll (ads, fds, &nfd, &timeout, timeval_from (ev_time ())); |
1596 |
.Ve |
1597 |
.PP |
1598 |
.Vb 3 |
1599 |
\& /* the callback is illegal, but won't be called as we stop during check */ |
1600 |
\& ev_timer_init (&tw, 0, timeout * 1e-3); |
1601 |
\& ev_timer_start (loop, &tw); |
1602 |
.Ve |
1603 |
.PP |
1604 |
.Vb 6 |
1605 |
\& // create on ev_io per pollfd |
1606 |
\& for (int i = 0; i < nfd; ++i) |
1607 |
\& { |
1608 |
\& ev_io_init (iow + i, io_cb, fds [i].fd, |
1609 |
\& ((fds [i].events & POLLIN ? EV_READ : 0) |
1610 |
\& | (fds [i].events & POLLOUT ? EV_WRITE : 0))); |
1611 |
.Ve |
1612 |
.PP |
1613 |
.Vb 5 |
1614 |
\& fds [i].revents = 0; |
1615 |
\& iow [i].data = fds + i; |
1616 |
\& ev_io_start (loop, iow + i); |
1617 |
\& } |
1618 |
\& } |
1619 |
.Ve |
1620 |
.PP |
1621 |
.Vb 5 |
1622 |
\& // stop all watchers after blocking |
1623 |
\& static void |
1624 |
\& adns_check_cb (ev_loop *loop, ev_check *w, int revents) |
1625 |
\& { |
1626 |
\& ev_timer_stop (loop, &tw); |
1627 |
.Ve |
1628 |
.PP |
1629 |
.Vb 2 |
1630 |
\& for (int i = 0; i < nfd; ++i) |
1631 |
\& ev_io_stop (loop, iow + i); |
1632 |
.Ve |
1633 |
.PP |
1634 |
.Vb 2 |
1635 |
\& adns_afterpoll (adns, fds, nfd, timeval_from (ev_now (loop)); |
1636 |
\& } |
1637 |
.Ve |
1638 |
.ie n .Sh """ev_embed"" \- when one backend isn't enough..." |
1639 |
.el .Sh "\f(CWev_embed\fP \- when one backend isn't enough..." |
1640 |
.IX Subsection "ev_embed - when one backend isn't enough..." |
1641 |
This is a rather advanced watcher type that lets you embed one event loop |
1642 |
into another (currently only \f(CW\*(C`ev_io\*(C'\fR events are supported in the embedded |
1643 |
loop, other types of watchers might be handled in a delayed or incorrect |
1644 |
fashion and must not be used). |
1645 |
.PP |
1646 |
There are primarily two reasons you would want that: work around bugs and |
1647 |
prioritise I/O. |
1648 |
.PP |
1649 |
As an example for a bug workaround, the kqueue backend might only support |
1650 |
sockets on some platform, so it is unusable as generic backend, but you |
1651 |
still want to make use of it because you have many sockets and it scales |
1652 |
so nicely. In this case, you would create a kqueue-based loop and embed it |
1653 |
into your default loop (which might use e.g. poll). Overall operation will |
1654 |
be a bit slower because first libev has to poll and then call kevent, but |
1655 |
at least you can use both at what they are best. |
1656 |
.PP |
1657 |
As for prioritising I/O: rarely you have the case where some fds have |
1658 |
to be watched and handled very quickly (with low latency), and even |
1659 |
priorities and idle watchers might have too much overhead. In this case |
1660 |
you would put all the high priority stuff in one loop and all the rest in |
1661 |
a second one, and embed the second one in the first. |
1662 |
.PP |
1663 |
As long as the watcher is active, the callback will be invoked every time |
1664 |
there might be events pending in the embedded loop. The callback must then |
1665 |
call \f(CW\*(C`ev_embed_sweep (mainloop, watcher)\*(C'\fR to make a single sweep and invoke |
1666 |
their callbacks (you could also start an idle watcher to give the embedded |
1667 |
loop strictly lower priority for example). You can also set the callback |
1668 |
to \f(CW0\fR, in which case the embed watcher will automatically execute the |
1669 |
embedded loop sweep. |
1670 |
.PP |
1671 |
As long as the watcher is started it will automatically handle events. The |
1672 |
callback will be invoked whenever some events have been handled. You can |
1673 |
set the callback to \f(CW0\fR to avoid having to specify one if you are not |
1674 |
interested in that. |
1675 |
.PP |
1676 |
Also, there have not currently been made special provisions for forking: |
1677 |
when you fork, you not only have to call \f(CW\*(C`ev_loop_fork\*(C'\fR on both loops, |
1678 |
but you will also have to stop and restart any \f(CW\*(C`ev_embed\*(C'\fR watchers |
1679 |
yourself. |
1680 |
.PP |
1681 |
Unfortunately, not all backends are embeddable, only the ones returned by |
1682 |
\&\f(CW\*(C`ev_embeddable_backends\*(C'\fR are, which, unfortunately, does not include any |
1683 |
portable one. |
1684 |
.PP |
1685 |
So when you want to use this feature you will always have to be prepared |
1686 |
that you cannot get an embeddable loop. The recommended way to get around |
1687 |
this is to have a separate variables for your embeddable loop, try to |
1688 |
create it, and if that fails, use the normal loop for everything: |
1689 |
.PP |
1690 |
.Vb 3 |
1691 |
\& struct ev_loop *loop_hi = ev_default_init (0); |
1692 |
\& struct ev_loop *loop_lo = 0; |
1693 |
\& struct ev_embed embed; |
1694 |
.Ve |
1695 |
.PP |
1696 |
.Vb 5 |
1697 |
\& // see if there is a chance of getting one that works |
1698 |
\& // (remember that a flags value of 0 means autodetection) |
1699 |
\& loop_lo = ev_embeddable_backends () & ev_recommended_backends () |
1700 |
\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) |
1701 |
\& : 0; |
1702 |
.Ve |
1703 |
.PP |
1704 |
.Vb 8 |
1705 |
\& // if we got one, then embed it, otherwise default to loop_hi |
1706 |
\& if (loop_lo) |
1707 |
\& { |
1708 |
\& ev_embed_init (&embed, 0, loop_lo); |
1709 |
\& ev_embed_start (loop_hi, &embed); |
1710 |
\& } |
1711 |
\& else |
1712 |
\& loop_lo = loop_hi; |
1713 |
.Ve |
1714 |
.IP "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
1715 |
.IX Item "ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)" |
1716 |
.PD 0 |
1717 |
.IP "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" 4 |
1718 |
.IX Item "ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)" |
1719 |
.PD |
1720 |
Configures the watcher to embed the given loop, which must be |
1721 |
embeddable. If the callback is \f(CW0\fR, then \f(CW\*(C`ev_embed_sweep\*(C'\fR will be |
1722 |
invoked automatically, otherwise it is the responsibility of the callback |
1723 |
to invoke it (it will continue to be called until the sweep has been done, |
1724 |
if you do not want thta, you need to temporarily stop the embed watcher). |
1725 |
.IP "ev_embed_sweep (loop, ev_embed *)" 4 |
1726 |
.IX Item "ev_embed_sweep (loop, ev_embed *)" |
1727 |
Make a single, non-blocking sweep over the embedded loop. This works |
1728 |
similarly to \f(CW\*(C`ev_loop (embedded_loop, EVLOOP_NONBLOCK)\*(C'\fR, but in the most |
1729 |
apropriate way for embedded loops. |
1730 |
.IP "struct ev_loop *loop [read\-only]" 4 |
1731 |
.IX Item "struct ev_loop *loop [read-only]" |
1732 |
The embedded event loop. |
1733 |
.ie n .Sh """ev_fork"" \- the audacity to resume the event loop after a fork" |
1734 |
.el .Sh "\f(CWev_fork\fP \- the audacity to resume the event loop after a fork" |
1735 |
.IX Subsection "ev_fork - the audacity to resume the event loop after a fork" |
1736 |
Fork watchers are called when a \f(CW\*(C`fork ()\*(C'\fR was detected (usually because |
1737 |
whoever is a good citizen cared to tell libev about it by calling |
1738 |
\&\f(CW\*(C`ev_default_fork\*(C'\fR or \f(CW\*(C`ev_loop_fork\*(C'\fR). The invocation is done before the |
1739 |
event loop blocks next and before \f(CW\*(C`ev_check\*(C'\fR watchers are being called, |
1740 |
and only in the child after the fork. If whoever good citizen calling |
1741 |
\&\f(CW\*(C`ev_default_fork\*(C'\fR cheats and calls it in the wrong process, the fork |
1742 |
handlers will be invoked, too, of course. |
1743 |
.IP "ev_fork_init (ev_signal *, callback)" 4 |
1744 |
.IX Item "ev_fork_init (ev_signal *, callback)" |
1745 |
Initialises and configures the fork watcher \- it has no parameters of any |
1746 |
kind. There is a \f(CW\*(C`ev_fork_set\*(C'\fR macro, but using it is utterly pointless, |
1747 |
believe me. |
1748 |
.SH "OTHER FUNCTIONS" |
1749 |
.IX Header "OTHER FUNCTIONS" |
1750 |
There are some other functions of possible interest. Described. Here. Now. |
1751 |
.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 |
1752 |
.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" |
1753 |
This function combines a simple timer and an I/O watcher, calls your |
1754 |
callback on whichever event happens first and automatically stop both |
1755 |
watchers. This is useful if you want to wait for a single event on an fd |
1756 |
or timeout without having to allocate/configure/start/stop/free one or |
1757 |
more watchers yourself. |
1758 |
.Sp |
1759 |
If \f(CW\*(C`fd\*(C'\fR is less than 0, then no I/O watcher will be started and events |
1760 |
is being ignored. Otherwise, an \f(CW\*(C`ev_io\*(C'\fR watcher for the given \f(CW\*(C`fd\*(C'\fR and |
1761 |
\&\f(CW\*(C`events\*(C'\fR set will be craeted and started. |
1762 |
.Sp |
1763 |
If \f(CW\*(C`timeout\*(C'\fR is less than 0, then no timeout watcher will be |
1764 |
started. Otherwise an \f(CW\*(C`ev_timer\*(C'\fR watcher with after = \f(CW\*(C`timeout\*(C'\fR (and |
1765 |
repeat = 0) will be started. While \f(CW0\fR is a valid timeout, it is of |
1766 |
dubious value. |
1767 |
.Sp |
1768 |
The callback has the type \f(CW\*(C`void (*cb)(int revents, void *arg)\*(C'\fR and gets |
1769 |
passed an \f(CW\*(C`revents\*(C'\fR set like normal event callbacks (a combination of |
1770 |
\&\f(CW\*(C`EV_ERROR\*(C'\fR, \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or \f(CW\*(C`EV_TIMEOUT\*(C'\fR) and the \f(CW\*(C`arg\*(C'\fR |
1771 |
value passed to \f(CW\*(C`ev_once\*(C'\fR: |
1772 |
.Sp |
1773 |
.Vb 7 |
1774 |
\& static void stdin_ready (int revents, void *arg) |
1775 |
\& { |
1776 |
\& if (revents & EV_TIMEOUT) |
1777 |
\& /* doh, nothing entered */; |
1778 |
\& else if (revents & EV_READ) |
1779 |
\& /* stdin might have data for us, joy! */; |
1780 |
\& } |
1781 |
.Ve |
1782 |
.Sp |
1783 |
.Vb 1 |
1784 |
\& ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
1785 |
.Ve |
1786 |
.IP "ev_feed_event (ev_loop *, watcher *, int revents)" 4 |
1787 |
.IX Item "ev_feed_event (ev_loop *, watcher *, int revents)" |
1788 |
Feeds the given event set into the event loop, as if the specified event |
1789 |
had happened for the specified watcher (which must be a pointer to an |
1790 |
initialised but not necessarily started event watcher). |
1791 |
.IP "ev_feed_fd_event (ev_loop *, int fd, int revents)" 4 |
1792 |
.IX Item "ev_feed_fd_event (ev_loop *, int fd, int revents)" |
1793 |
Feed an event on the given fd, as if a file descriptor backend detected |
1794 |
the given events it. |
1795 |
.IP "ev_feed_signal_event (ev_loop *loop, int signum)" 4 |
1796 |
.IX Item "ev_feed_signal_event (ev_loop *loop, int signum)" |
1797 |
Feed an event as if the given signal occured (\f(CW\*(C`loop\*(C'\fR must be the default |
1798 |
loop!). |
1799 |
.SH "LIBEVENT EMULATION" |
1800 |
.IX Header "LIBEVENT EMULATION" |
1801 |
Libev offers a compatibility emulation layer for libevent. It cannot |
1802 |
emulate the internals of libevent, so here are some usage hints: |
1803 |
.IP "* Use it by including <event.h>, as usual." 4 |
1804 |
.IX Item "Use it by including <event.h>, as usual." |
1805 |
.PD 0 |
1806 |
.IP "* The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." 4 |
1807 |
.IX Item "The following members are fully supported: ev_base, ev_callback, ev_arg, ev_fd, ev_res, ev_events." |
1808 |
.IP "* Avoid using ev_flags and the EVLIST_*\-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private \s-1API\s0)." 4 |
1809 |
.IX Item "Avoid using ev_flags and the EVLIST_*-macros, while it is maintained by libev, it does not work exactly the same way as in libevent (consider it a private API)." |
1810 |
.IP "* Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." 4 |
1811 |
.IX Item "Priorities are not currently supported. Initialising priorities will fail and all watchers will have the same priority, even though there is an ev_pri field." |
1812 |
.IP "* Other members are not supported." 4 |
1813 |
.IX Item "Other members are not supported." |
1814 |
.IP "* The libev emulation is \fInot\fR \s-1ABI\s0 compatible to libevent, you need to use the libev header file and library." 4 |
1815 |
.IX Item "The libev emulation is not ABI compatible to libevent, you need to use the libev header file and library." |
1816 |
.PD |
1817 |
.SH "\*(C+ SUPPORT" |
1818 |
.IX Header " SUPPORT" |
1819 |
Libev comes with some simplistic wrapper classes for \*(C+ that mainly allow |
1820 |
you to use some convinience methods to start/stop watchers and also change |
1821 |
the callback model to a model using method callbacks on objects. |
1822 |
.PP |
1823 |
To use it, |
1824 |
.PP |
1825 |
.Vb 1 |
1826 |
\& #include <ev++.h> |
1827 |
.Ve |
1828 |
.PP |
1829 |
(it is not installed by default). This automatically includes \fIev.h\fR |
1830 |
and puts all of its definitions (many of them macros) into the global |
1831 |
namespace. All \*(C+ specific things are put into the \f(CW\*(C`ev\*(C'\fR namespace. |
1832 |
.PP |
1833 |
It should support all the same embedding options as \fIev.h\fR, most notably |
1834 |
\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. |
1835 |
.PP |
1836 |
Here is a list of things available in the \f(CW\*(C`ev\*(C'\fR namespace: |
1837 |
.ie n .IP """ev::READ""\fR, \f(CW""ev::WRITE"" etc." 4 |
1838 |
.el .IP "\f(CWev::READ\fR, \f(CWev::WRITE\fR etc." 4 |
1839 |
.IX Item "ev::READ, ev::WRITE etc." |
1840 |
These are just enum values with the same values as the \f(CW\*(C`EV_READ\*(C'\fR etc. |
1841 |
macros from \fIev.h\fR. |
1842 |
.ie n .IP """ev::tstamp""\fR, \f(CW""ev::now""" 4 |
1843 |
.el .IP "\f(CWev::tstamp\fR, \f(CWev::now\fR" 4 |
1844 |
.IX Item "ev::tstamp, ev::now" |
1845 |
Aliases to the same types/functions as with the \f(CW\*(C`ev_\*(C'\fR prefix. |
1846 |
.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 |
1847 |
.el .IP "\f(CWev::io\fR, \f(CWev::timer\fR, \f(CWev::periodic\fR, \f(CWev::idle\fR, \f(CWev::sig\fR etc." 4 |
1848 |
.IX Item "ev::io, ev::timer, ev::periodic, ev::idle, ev::sig etc." |
1849 |
For each \f(CW\*(C`ev_TYPE\*(C'\fR watcher in \fIev.h\fR there is a corresponding class of |
1850 |
the same name in the \f(CW\*(C`ev\*(C'\fR namespace, with the exception of \f(CW\*(C`ev_signal\*(C'\fR |
1851 |
which is called \f(CW\*(C`ev::sig\*(C'\fR to avoid clashes with the \f(CW\*(C`signal\*(C'\fR macro |
1852 |
defines by many implementations. |
1853 |
.Sp |
1854 |
All of those classes have these methods: |
1855 |
.RS 4 |
1856 |
.IP "ev::TYPE::TYPE (object *, object::method *)" 4 |
1857 |
.IX Item "ev::TYPE::TYPE (object *, object::method *)" |
1858 |
.PD 0 |
1859 |
.IP "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" 4 |
1860 |
.IX Item "ev::TYPE::TYPE (object *, object::method *, struct ev_loop *)" |
1861 |
.IP "ev::TYPE::~TYPE" 4 |
1862 |
.IX Item "ev::TYPE::~TYPE" |
1863 |
.PD |
1864 |
The constructor takes a pointer to an object and a method pointer to |
1865 |
the event handler callback to call in this class. The constructor calls |
1866 |
\&\f(CW\*(C`ev_init\*(C'\fR for you, which means you have to call the \f(CW\*(C`set\*(C'\fR method |
1867 |
before starting it. If you do not specify a loop then the constructor |
1868 |
automatically associates the default loop with this watcher. |
1869 |
.Sp |
1870 |
The destructor automatically stops the watcher if it is active. |
1871 |
.IP "w\->set (struct ev_loop *)" 4 |
1872 |
.IX Item "w->set (struct ev_loop *)" |
1873 |
Associates a different \f(CW\*(C`struct ev_loop\*(C'\fR with this watcher. You can only |
1874 |
do this when the watcher is inactive (and not pending either). |
1875 |
.IP "w\->set ([args])" 4 |
1876 |
.IX Item "w->set ([args])" |
1877 |
Basically the same as \f(CW\*(C`ev_TYPE_set\*(C'\fR, with the same args. Must be |
1878 |
called at least once. Unlike the C counterpart, an active watcher gets |
1879 |
automatically stopped and restarted. |
1880 |
.IP "w\->start ()" 4 |
1881 |
.IX Item "w->start ()" |
1882 |
Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument as the |
1883 |
constructor already takes the loop. |
1884 |
.IP "w\->stop ()" 4 |
1885 |
.IX Item "w->stop ()" |
1886 |
Stops the watcher if it is active. Again, no \f(CW\*(C`loop\*(C'\fR argument. |
1887 |
.ie n .IP "w\->again () ""ev::timer""\fR, \f(CW""ev::periodic"" only" 4 |
1888 |
.el .IP "w\->again () \f(CWev::timer\fR, \f(CWev::periodic\fR only" 4 |
1889 |
.IX Item "w->again () ev::timer, ev::periodic only" |
1890 |
For \f(CW\*(C`ev::timer\*(C'\fR and \f(CW\*(C`ev::periodic\*(C'\fR, this invokes the corresponding |
1891 |
\&\f(CW\*(C`ev_TYPE_again\*(C'\fR function. |
1892 |
.ie n .IP "w\->sweep () ""ev::embed"" only" 4 |
1893 |
.el .IP "w\->sweep () \f(CWev::embed\fR only" 4 |
1894 |
.IX Item "w->sweep () ev::embed only" |
1895 |
Invokes \f(CW\*(C`ev_embed_sweep\*(C'\fR. |
1896 |
.ie n .IP "w\->update () ""ev::stat"" only" 4 |
1897 |
.el .IP "w\->update () \f(CWev::stat\fR only" 4 |
1898 |
.IX Item "w->update () ev::stat only" |
1899 |
Invokes \f(CW\*(C`ev_stat_stat\*(C'\fR. |
1900 |
.RE |
1901 |
.RS 4 |
1902 |
.RE |
1903 |
.PP |
1904 |
Example: Define a class with an \s-1IO\s0 and idle watcher, start one of them in |
1905 |
the constructor. |
1906 |
.PP |
1907 |
.Vb 4 |
1908 |
\& class myclass |
1909 |
\& { |
1910 |
\& ev_io io; void io_cb (ev::io &w, int revents); |
1911 |
\& ev_idle idle void idle_cb (ev::idle &w, int revents); |
1912 |
.Ve |
1913 |
.PP |
1914 |
.Vb 2 |
1915 |
\& myclass (); |
1916 |
\& } |
1917 |
.Ve |
1918 |
.PP |
1919 |
.Vb 6 |
1920 |
\& myclass::myclass (int fd) |
1921 |
\& : io (this, &myclass::io_cb), |
1922 |
\& idle (this, &myclass::idle_cb) |
1923 |
\& { |
1924 |
\& io.start (fd, ev::READ); |
1925 |
\& } |
1926 |
.Ve |
1927 |
.SH "MACRO MAGIC" |
1928 |
.IX Header "MACRO MAGIC" |
1929 |
Libev can be compiled with a variety of options, the most fundemantal is |
1930 |
\&\f(CW\*(C`EV_MULTIPLICITY\*(C'\fR. This option determines wether (most) functions and |
1931 |
callbacks have an initial \f(CW\*(C`struct ev_loop *\*(C'\fR argument. |
1932 |
.PP |
1933 |
To make it easier to write programs that cope with either variant, the |
1934 |
following macros are defined: |
1935 |
.ie n .IP """EV_A""\fR, \f(CW""EV_A_""" 4 |
1936 |
.el .IP "\f(CWEV_A\fR, \f(CWEV_A_\fR" 4 |
1937 |
.IX Item "EV_A, EV_A_" |
1938 |
This provides the loop \fIargument\fR for functions, if one is required (\*(L"ev |
1939 |
loop argument\*(R"). The \f(CW\*(C`EV_A\*(C'\fR form is used when this is the sole argument, |
1940 |
\&\f(CW\*(C`EV_A_\*(C'\fR is used when other arguments are following. Example: |
1941 |
.Sp |
1942 |
.Vb 3 |
1943 |
\& ev_unref (EV_A); |
1944 |
\& ev_timer_add (EV_A_ watcher); |
1945 |
\& ev_loop (EV_A_ 0); |
1946 |
.Ve |
1947 |
.Sp |
1948 |
It assumes the variable \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR is in scope, |
1949 |
which is often provided by the following macro. |
1950 |
.ie n .IP """EV_P""\fR, \f(CW""EV_P_""" 4 |
1951 |
.el .IP "\f(CWEV_P\fR, \f(CWEV_P_\fR" 4 |
1952 |
.IX Item "EV_P, EV_P_" |
1953 |
This provides the loop \fIparameter\fR for functions, if one is required (\*(L"ev |
1954 |
loop parameter\*(R"). The \f(CW\*(C`EV_P\*(C'\fR form is used when this is the sole parameter, |
1955 |
\&\f(CW\*(C`EV_P_\*(C'\fR is used when other parameters are following. Example: |
1956 |
.Sp |
1957 |
.Vb 2 |
1958 |
\& // this is how ev_unref is being declared |
1959 |
\& static void ev_unref (EV_P); |
1960 |
.Ve |
1961 |
.Sp |
1962 |
.Vb 2 |
1963 |
\& // this is how you can declare your typical callback |
1964 |
\& static void cb (EV_P_ ev_timer *w, int revents) |
1965 |
.Ve |
1966 |
.Sp |
1967 |
It declares a parameter \f(CW\*(C`loop\*(C'\fR of type \f(CW\*(C`struct ev_loop *\*(C'\fR, quite |
1968 |
suitable for use with \f(CW\*(C`EV_A\*(C'\fR. |
1969 |
.ie n .IP """EV_DEFAULT""\fR, \f(CW""EV_DEFAULT_""" 4 |
1970 |
.el .IP "\f(CWEV_DEFAULT\fR, \f(CWEV_DEFAULT_\fR" 4 |
1971 |
.IX Item "EV_DEFAULT, EV_DEFAULT_" |
1972 |
Similar to the other two macros, this gives you the value of the default |
1973 |
loop, if multiple loops are supported (\*(L"ev loop default\*(R"). |
1974 |
.PP |
1975 |
Example: Declare and initialise a check watcher, working regardless of |
1976 |
wether multiple loops are supported or not. |
1977 |
.PP |
1978 |
.Vb 5 |
1979 |
\& static void |
1980 |
\& check_cb (EV_P_ ev_timer *w, int revents) |
1981 |
\& { |
1982 |
\& ev_check_stop (EV_A_ w); |
1983 |
\& } |
1984 |
.Ve |
1985 |
.PP |
1986 |
.Vb 4 |
1987 |
\& ev_check check; |
1988 |
\& ev_check_init (&check, check_cb); |
1989 |
\& ev_check_start (EV_DEFAULT_ &check); |
1990 |
\& ev_loop (EV_DEFAULT_ 0); |
1991 |
.Ve |
1992 |
.SH "EMBEDDING" |
1993 |
.IX Header "EMBEDDING" |
1994 |
Libev can (and often is) directly embedded into host |
1995 |
applications. Examples of applications that embed it include the Deliantra |
1996 |
Game Server, the \s-1EV\s0 perl module, the \s-1GNU\s0 Virtual Private Ethernet (gvpe) |
1997 |
and rxvt\-unicode. |
1998 |
.PP |
1999 |
The goal is to enable you to just copy the neecssary files into your |
2000 |
source directory without having to change even a single line in them, so |
2001 |
you can easily upgrade by simply copying (or having a checked-out copy of |
2002 |
libev somewhere in your source tree). |
2003 |
.Sh "\s-1FILESETS\s0" |
2004 |
.IX Subsection "FILESETS" |
2005 |
Depending on what features you need you need to include one or more sets of files |
2006 |
in your app. |
2007 |
.PP |
2008 |
\fI\s-1CORE\s0 \s-1EVENT\s0 \s-1LOOP\s0\fR |
2009 |
.IX Subsection "CORE EVENT LOOP" |
2010 |
.PP |
2011 |
To include only the libev core (all the \f(CW\*(C`ev_*\*(C'\fR functions), with manual |
2012 |
configuration (no autoconf): |
2013 |
.PP |
2014 |
.Vb 2 |
2015 |
\& #define EV_STANDALONE 1 |
2016 |
\& #include "ev.c" |
2017 |
.Ve |
2018 |
.PP |
2019 |
This will automatically include \fIev.h\fR, too, and should be done in a |
2020 |
single C source file only to provide the function implementations. To use |
2021 |
it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best |
2022 |
done by writing a wrapper around \fIev.h\fR that you can include instead and |
2023 |
where you can put other configuration options): |
2024 |
.PP |
2025 |
.Vb 2 |
2026 |
\& #define EV_STANDALONE 1 |
2027 |
\& #include "ev.h" |
2028 |
.Ve |
2029 |
.PP |
2030 |
Both header files and implementation files can be compiled with a \*(C+ |
2031 |
compiler (at least, thats a stated goal, and breakage will be treated |
2032 |
as a bug). |
2033 |
.PP |
2034 |
You need the following files in your source tree, or in a directory |
2035 |
in your include path (e.g. in libev/ when using \-Ilibev): |
2036 |
.PP |
2037 |
.Vb 4 |
2038 |
\& ev.h |
2039 |
\& ev.c |
2040 |
\& ev_vars.h |
2041 |
\& ev_wrap.h |
2042 |
.Ve |
2043 |
.PP |
2044 |
.Vb 1 |
2045 |
\& ev_win32.c required on win32 platforms only |
2046 |
.Ve |
2047 |
.PP |
2048 |
.Vb 5 |
2049 |
\& ev_select.c only when select backend is enabled (which is by default) |
2050 |
\& ev_poll.c only when poll backend is enabled (disabled by default) |
2051 |
\& ev_epoll.c only when the epoll backend is enabled (disabled by default) |
2052 |
\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) |
2053 |
\& ev_port.c only when the solaris port backend is enabled (disabled by default) |
2054 |
.Ve |
2055 |
.PP |
2056 |
\&\fIev.c\fR includes the backend files directly when enabled, so you only need |
2057 |
to compile this single file. |
2058 |
.PP |
2059 |
\fI\s-1LIBEVENT\s0 \s-1COMPATIBILITY\s0 \s-1API\s0\fR |
2060 |
.IX Subsection "LIBEVENT COMPATIBILITY API" |
2061 |
.PP |
2062 |
To include the libevent compatibility \s-1API\s0, also include: |
2063 |
.PP |
2064 |
.Vb 1 |
2065 |
\& #include "event.c" |
2066 |
.Ve |
2067 |
.PP |
2068 |
in the file including \fIev.c\fR, and: |
2069 |
.PP |
2070 |
.Vb 1 |
2071 |
\& #include "event.h" |
2072 |
.Ve |
2073 |
.PP |
2074 |
in the files that want to use the libevent \s-1API\s0. This also includes \fIev.h\fR. |
2075 |
.PP |
2076 |
You need the following additional files for this: |
2077 |
.PP |
2078 |
.Vb 2 |
2079 |
\& event.h |
2080 |
\& event.c |
2081 |
.Ve |
2082 |
.PP |
2083 |
\fI\s-1AUTOCONF\s0 \s-1SUPPORT\s0\fR |
2084 |
.IX Subsection "AUTOCONF SUPPORT" |
2085 |
.PP |
2086 |
Instead of using \f(CW\*(C`EV_STANDALONE=1\*(C'\fR and providing your config in |
2087 |
whatever way you want, you can also \f(CW\*(C`m4_include([libev.m4])\*(C'\fR in your |
2088 |
\&\fIconfigure.ac\fR and leave \f(CW\*(C`EV_STANDALONE\*(C'\fR undefined. \fIev.c\fR will then |
2089 |
include \fIconfig.h\fR and configure itself accordingly. |
2090 |
.PP |
2091 |
For this of course you need the m4 file: |
2092 |
.PP |
2093 |
.Vb 1 |
2094 |
\& libev.m4 |
2095 |
.Ve |
2096 |
.Sh "\s-1PREPROCESSOR\s0 \s-1SYMBOLS/MACROS\s0" |
2097 |
.IX Subsection "PREPROCESSOR SYMBOLS/MACROS" |
2098 |
Libev can be configured via a variety of preprocessor symbols you have to define |
2099 |
before including any of its files. The default is not to build for multiplicity |
2100 |
and only include the select backend. |
2101 |
.IP "\s-1EV_STANDALONE\s0" 4 |
2102 |
.IX Item "EV_STANDALONE" |
2103 |
Must always be \f(CW1\fR if you do not use autoconf configuration, which |
2104 |
keeps libev from including \fIconfig.h\fR, and it also defines dummy |
2105 |
implementations for some libevent functions (such as logging, which is not |
2106 |
supported). It will also not define any of the structs usually found in |
2107 |
\&\fIevent.h\fR that are not directly supported by the libev core alone. |
2108 |
.IP "\s-1EV_USE_MONOTONIC\s0" 4 |
2109 |
.IX Item "EV_USE_MONOTONIC" |
2110 |
If defined to be \f(CW1\fR, libev will try to detect the availability of the |
2111 |
monotonic clock option at both compiletime and runtime. Otherwise no use |
2112 |
of the monotonic clock option will be attempted. If you enable this, you |
2113 |
usually have to link against librt or something similar. Enabling it when |
2114 |
the functionality isn't available is safe, though, althoguh you have |
2115 |
to make sure you link against any libraries where the \f(CW\*(C`clock_gettime\*(C'\fR |
2116 |
function is hiding in (often \fI\-lrt\fR). |
2117 |
.IP "\s-1EV_USE_REALTIME\s0" 4 |
2118 |
.IX Item "EV_USE_REALTIME" |
2119 |
If defined to be \f(CW1\fR, libev will try to detect the availability of the |
2120 |
realtime clock option at compiletime (and assume its availability at |
2121 |
runtime if successful). Otherwise no use of the realtime clock option will |
2122 |
be attempted. This effectively replaces \f(CW\*(C`gettimeofday\*(C'\fR by \f(CW\*(C`clock_get |
2123 |
(CLOCK_REALTIME, ...)\*(C'\fR and will not normally affect correctness. See tzhe note about libraries |
2124 |
in the description of \f(CW\*(C`EV_USE_MONOTONIC\*(C'\fR, though. |
2125 |
.IP "\s-1EV_USE_SELECT\s0" 4 |
2126 |
.IX Item "EV_USE_SELECT" |
2127 |
If undefined or defined to be \f(CW1\fR, libev will compile in support for the |
2128 |
\&\f(CW\*(C`select\*(C'\fR(2) backend. No attempt at autodetection will be done: if no |
2129 |
other method takes over, select will be it. Otherwise the select backend |
2130 |
will not be compiled in. |
2131 |
.IP "\s-1EV_SELECT_USE_FD_SET\s0" 4 |
2132 |
.IX Item "EV_SELECT_USE_FD_SET" |
2133 |
If defined to \f(CW1\fR, then the select backend will use the system \f(CW\*(C`fd_set\*(C'\fR |
2134 |
structure. This is useful if libev doesn't compile due to a missing |
2135 |
\&\f(CW\*(C`NFDBITS\*(C'\fR or \f(CW\*(C`fd_mask\*(C'\fR definition or it misguesses the bitset layout on |
2136 |
exotic systems. This usually limits the range of file descriptors to some |
2137 |
low limit such as 1024 or might have other limitations (winsocket only |
2138 |
allows 64 sockets). The \f(CW\*(C`FD_SETSIZE\*(C'\fR macro, set before compilation, might |
2139 |
influence the size of the \f(CW\*(C`fd_set\*(C'\fR used. |
2140 |
.IP "\s-1EV_SELECT_IS_WINSOCKET\s0" 4 |
2141 |
.IX Item "EV_SELECT_IS_WINSOCKET" |
2142 |
When defined to \f(CW1\fR, the select backend will assume that |
2143 |
select/socket/connect etc. don't understand file descriptors but |
2144 |
wants osf handles on win32 (this is the case when the select to |
2145 |
be used is the winsock select). This means that it will call |
2146 |
\&\f(CW\*(C`_get_osfhandle\*(C'\fR on the fd to convert it to an \s-1OS\s0 handle. Otherwise, |
2147 |
it is assumed that all these functions actually work on fds, even |
2148 |
on win32. Should not be defined on non\-win32 platforms. |
2149 |
.IP "\s-1EV_USE_POLL\s0" 4 |
2150 |
.IX Item "EV_USE_POLL" |
2151 |
If defined to be \f(CW1\fR, libev will compile in support for the \f(CW\*(C`poll\*(C'\fR(2) |
2152 |
backend. Otherwise it will be enabled on non\-win32 platforms. It |
2153 |
takes precedence over select. |
2154 |
.IP "\s-1EV_USE_EPOLL\s0" 4 |
2155 |
.IX Item "EV_USE_EPOLL" |
2156 |
If defined to be \f(CW1\fR, libev will compile in support for the Linux |
2157 |
\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, |
2158 |
otherwise another method will be used as fallback. This is the |
2159 |
preferred backend for GNU/Linux systems. |
2160 |
.IP "\s-1EV_USE_KQUEUE\s0" 4 |
2161 |
.IX Item "EV_USE_KQUEUE" |
2162 |
If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style |
2163 |
\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, |
2164 |
otherwise another method will be used as fallback. This is the preferred |
2165 |
backend for \s-1BSD\s0 and BSD-like systems, although on most BSDs kqueue only |
2166 |
supports some types of fds correctly (the only platform we found that |
2167 |
supports ptys for example was NetBSD), so kqueue might be compiled in, but |
2168 |
not be used unless explicitly requested. The best way to use it is to find |
2169 |
out whether kqueue supports your type of fd properly and use an embedded |
2170 |
kqueue loop. |
2171 |
.IP "\s-1EV_USE_PORT\s0" 4 |
2172 |
.IX Item "EV_USE_PORT" |
2173 |
If defined to be \f(CW1\fR, libev will compile in support for the Solaris |
2174 |
10 port style backend. Its availability will be detected at runtime, |
2175 |
otherwise another method will be used as fallback. This is the preferred |
2176 |
backend for Solaris 10 systems. |
2177 |
.IP "\s-1EV_USE_DEVPOLL\s0" 4 |
2178 |
.IX Item "EV_USE_DEVPOLL" |
2179 |
reserved for future expansion, works like the \s-1USE\s0 symbols above. |
2180 |
.IP "\s-1EV_USE_INOTIFY\s0" 4 |
2181 |
.IX Item "EV_USE_INOTIFY" |
2182 |
If defined to be \f(CW1\fR, libev will compile in support for the Linux inotify |
2183 |
interface to speed up \f(CW\*(C`ev_stat\*(C'\fR watchers. Its actual availability will |
2184 |
be detected at runtime. |
2185 |
.IP "\s-1EV_H\s0" 4 |
2186 |
.IX Item "EV_H" |
2187 |
The name of the \fIev.h\fR header file used to include it. The default if |
2188 |
undefined is \f(CW\*(C`<ev.h>\*(C'\fR in \fIevent.h\fR and \f(CW"ev.h"\fR in \fIev.c\fR. This |
2189 |
can be used to virtually rename the \fIev.h\fR header file in case of conflicts. |
2190 |
.IP "\s-1EV_CONFIG_H\s0" 4 |
2191 |
.IX Item "EV_CONFIG_H" |
2192 |
If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override |
2193 |
\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to |
2194 |
\&\f(CW\*(C`EV_H\*(C'\fR, above. |
2195 |
.IP "\s-1EV_EVENT_H\s0" 4 |
2196 |
.IX Item "EV_EVENT_H" |
2197 |
Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea |
2198 |
of how the \fIevent.h\fR header can be found. |
2199 |
.IP "\s-1EV_PROTOTYPES\s0" 4 |
2200 |
.IX Item "EV_PROTOTYPES" |
2201 |
If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function |
2202 |
prototypes, but still define all the structs and other symbols. This is |
2203 |
occasionally useful if you want to provide your own wrapper functions |
2204 |
around libev functions. |
2205 |
.IP "\s-1EV_MULTIPLICITY\s0" 4 |
2206 |
.IX Item "EV_MULTIPLICITY" |
2207 |
If undefined or defined to \f(CW1\fR, then all event-loop-specific functions |
2208 |
will have the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument, and you can create |
2209 |
additional independent event loops. Otherwise there will be no support |
2210 |
for multiple event loops and there is no first event loop pointer |
2211 |
argument. Instead, all functions act on the single default loop. |
2212 |
.IP "\s-1EV_PERIODIC_ENABLE\s0" 4 |
2213 |
.IX Item "EV_PERIODIC_ENABLE" |
2214 |
If undefined or defined to be \f(CW1\fR, then periodic timers are supported. If |
2215 |
defined to be \f(CW0\fR, then they are not. Disabling them saves a few kB of |
2216 |
code. |
2217 |
.IP "\s-1EV_EMBED_ENABLE\s0" 4 |
2218 |
.IX Item "EV_EMBED_ENABLE" |
2219 |
If undefined or defined to be \f(CW1\fR, then embed watchers are supported. If |
2220 |
defined to be \f(CW0\fR, then they are not. |
2221 |
.IP "\s-1EV_STAT_ENABLE\s0" 4 |
2222 |
.IX Item "EV_STAT_ENABLE" |
2223 |
If undefined or defined to be \f(CW1\fR, then stat watchers are supported. If |
2224 |
defined to be \f(CW0\fR, then they are not. |
2225 |
.IP "\s-1EV_FORK_ENABLE\s0" 4 |
2226 |
.IX Item "EV_FORK_ENABLE" |
2227 |
If undefined or defined to be \f(CW1\fR, then fork watchers are supported. If |
2228 |
defined to be \f(CW0\fR, then they are not. |
2229 |
.IP "\s-1EV_MINIMAL\s0" 4 |
2230 |
.IX Item "EV_MINIMAL" |
2231 |
If you need to shave off some kilobytes of code at the expense of some |
2232 |
speed, define this symbol to \f(CW1\fR. Currently only used for gcc to override |
2233 |
some inlining decisions, saves roughly 30% codesize of amd64. |
2234 |
.IP "\s-1EV_PID_HASHSIZE\s0" 4 |
2235 |
.IX Item "EV_PID_HASHSIZE" |
2236 |
\&\f(CW\*(C`ev_child\*(C'\fR watchers use a small hash table to distribute workload by |
2237 |
pid. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), usually more |
2238 |
than enough. If you need to manage thousands of children you might want to |
2239 |
increase this value (\fImust\fR be a power of two). |
2240 |
.IP "\s-1EV_INOTIFY_HASHSIZE\s0" 4 |
2241 |
.IX Item "EV_INOTIFY_HASHSIZE" |
2242 |
\&\f(CW\*(C`ev_staz\*(C'\fR watchers use a small hash table to distribute workload by |
2243 |
inotify watch id. The default size is \f(CW16\fR (or \f(CW1\fR with \f(CW\*(C`EV_MINIMAL\*(C'\fR), |
2244 |
usually more than enough. If you need to manage thousands of \f(CW\*(C`ev_stat\*(C'\fR |
2245 |
watchers you might want to increase this value (\fImust\fR be a power of |
2246 |
two). |
2247 |
.IP "\s-1EV_COMMON\s0" 4 |
2248 |
.IX Item "EV_COMMON" |
2249 |
By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining |
2250 |
this macro to a something else you can include more and other types of |
2251 |
members. You have to define it each time you include one of the files, |
2252 |
though, and it must be identical each time. |
2253 |
.Sp |
2254 |
For example, the perl \s-1EV\s0 module uses something like this: |
2255 |
.Sp |
2256 |
.Vb 3 |
2257 |
\& #define EV_COMMON \e |
2258 |
\& SV *self; /* contains this struct */ \e |
2259 |
\& SV *cb_sv, *fh /* note no trailing ";" */ |
2260 |
.Ve |
2261 |
.IP "\s-1EV_CB_DECLARE\s0 (type)" 4 |
2262 |
.IX Item "EV_CB_DECLARE (type)" |
2263 |
.PD 0 |
2264 |
.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4 |
2265 |
.IX Item "EV_CB_INVOKE (watcher, revents)" |
2266 |
.IP "ev_set_cb (ev, cb)" 4 |
2267 |
.IX Item "ev_set_cb (ev, cb)" |
2268 |
.PD |
2269 |
Can be used to change the callback member declaration in each watcher, |
2270 |
and the way callbacks are invoked and set. Must expand to a struct member |
2271 |
definition and a statement, respectively. See the \fIev.v\fR header file for |
2272 |
their default definitions. One possible use for overriding these is to |
2273 |
avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use |
2274 |
method calls instead of plain function calls in \*(C+. |
2275 |
.Sh "\s-1EXAMPLES\s0" |
2276 |
.IX Subsection "EXAMPLES" |
2277 |
For a real-world example of a program the includes libev |
2278 |
verbatim, you can have a look at the \s-1EV\s0 perl module |
2279 |
(<http://software.schmorp.de/pkg/EV.html>). It has the libev files in |
2280 |
the \fIlibev/\fR subdirectory and includes them in the \fI\s-1EV/EVAPI\s0.h\fR (public |
2281 |
interface) and \fI\s-1EV\s0.xs\fR (implementation) files. Only the \fI\s-1EV\s0.xs\fR file |
2282 |
will be compiled. It is pretty complex because it provides its own header |
2283 |
file. |
2284 |
.Sp |
2285 |
The usage in rxvt-unicode is simpler. It has a \fIev_cpp.h\fR header file |
2286 |
that everybody includes and which overrides some autoconf choices: |
2287 |
.Sp |
2288 |
.Vb 4 |
2289 |
\& #define EV_USE_POLL 0 |
2290 |
\& #define EV_MULTIPLICITY 0 |
2291 |
\& #define EV_PERIODICS 0 |
2292 |
\& #define EV_CONFIG_H <config.h> |
2293 |
.Ve |
2294 |
.Sp |
2295 |
.Vb 1 |
2296 |
\& #include "ev++.h" |
2297 |
.Ve |
2298 |
.Sp |
2299 |
And a \fIev_cpp.C\fR implementation file that contains libev proper and is compiled: |
2300 |
.Sp |
2301 |
.Vb 2 |
2302 |
\& #include "ev_cpp.h" |
2303 |
\& #include "ev.c" |
2304 |
.Ve |
2305 |
.SH "COMPLEXITIES" |
2306 |
.IX Header "COMPLEXITIES" |
2307 |
In this section the complexities of (many of) the algorithms used inside |
2308 |
libev will be explained. For complexity discussions about backends see the |
2309 |
documentation for \f(CW\*(C`ev_default_init\*(C'\fR. |
2310 |
.RS 4 |
2311 |
.IP "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" 4 |
2312 |
.IX Item "Starting and stopping timer/periodic watchers: O(log skipped_other_timers)" |
2313 |
.PD 0 |
2314 |
.IP "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" 4 |
2315 |
.IX Item "Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers)" |
2316 |
.IP "Starting io/check/prepare/idle/signal/child watchers: O(1)" 4 |
2317 |
.IX Item "Starting io/check/prepare/idle/signal/child watchers: O(1)" |
2318 |
.IP "Stopping check/prepare/idle watchers: O(1)" 4 |
2319 |
.IX Item "Stopping check/prepare/idle watchers: O(1)" |
2320 |
.IP "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % \s-1EV_PID_HASHSIZE\s0))" 4 |
2321 |
.IX Item "Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))" |
2322 |
.IP "Finding the next timer per loop iteration: O(1)" 4 |
2323 |
.IX Item "Finding the next timer per loop iteration: O(1)" |
2324 |
.IP "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" 4 |
2325 |
.IX Item "Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)" |
2326 |
.IP "Activating one watcher: O(1)" 4 |
2327 |
.IX Item "Activating one watcher: O(1)" |
2328 |
.RE |
2329 |
.RS 4 |
2330 |
.PD |
2331 |
.SH "AUTHOR" |
2332 |
.IX Header "AUTHOR" |
2333 |
Marc Lehmann <libev@schmorp.de>. |