… | |
… | |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
|
|
11 | // a single header file is required |
11 | #include <ev.h> |
12 | #include <ev.h> |
12 | |
13 | |
|
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14 | // every watcher type has its own typedef'd struct |
|
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15 | // with the name ev_<type> |
13 | ev_io stdin_watcher; |
16 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
17 | ev_timer timeout_watcher; |
15 | |
18 | |
|
|
19 | // all watcher callbacks have a similar signature |
16 | /* called when data readable on stdin */ |
20 | // this callback is called when data is readable on stdin |
17 | static void |
21 | static void |
18 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
22 | stdin_cb (EV_P_ struct ev_io *w, int revents) |
19 | { |
23 | { |
20 | /* puts ("stdin ready"); */ |
24 | puts ("stdin ready"); |
21 | ev_io_stop (EV_A_ w); /* just a syntax example */ |
25 | // for one-shot events, one must manually stop the watcher |
22 | ev_unloop (EV_A_ EVUNLOOP_ALL); /* leave all loop calls */ |
26 | // with its corresponding stop function. |
|
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27 | ev_io_stop (EV_A_ w); |
|
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28 | |
|
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29 | // this causes all nested ev_loop's to stop iterating |
|
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30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
23 | } |
31 | } |
24 | |
32 | |
|
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33 | // another callback, this time for a time-out |
25 | static void |
34 | static void |
26 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
35 | timeout_cb (EV_P_ struct ev_timer *w, int revents) |
27 | { |
36 | { |
28 | /* puts ("timeout"); */ |
37 | puts ("timeout"); |
29 | ev_unloop (EV_A_ EVUNLOOP_ONE); /* leave one loop call */ |
38 | // this causes the innermost ev_loop to stop iterating |
|
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39 | ev_unloop (EV_A_ EVUNLOOP_ONE); |
30 | } |
40 | } |
31 | |
41 | |
32 | int |
42 | int |
33 | main (void) |
43 | main (void) |
34 | { |
44 | { |
|
|
45 | // use the default event loop unless you have special needs |
35 | struct ev_loop *loop = ev_default_loop (0); |
46 | struct ev_loop *loop = ev_default_loop (0); |
36 | |
47 | |
37 | /* initialise an io watcher, then start it */ |
48 | // initialise an io watcher, then start it |
|
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49 | // this one will watch for stdin to become readable |
38 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
39 | ev_io_start (loop, &stdin_watcher); |
51 | ev_io_start (loop, &stdin_watcher); |
40 | |
52 | |
|
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53 | // initialise a timer watcher, then start it |
41 | /* simple non-repeating 5.5 second timeout */ |
54 | // simple non-repeating 5.5 second timeout |
42 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
55 | ev_timer_init (&timeout_watcher, timeout_cb, 5.5, 0.); |
43 | ev_timer_start (loop, &timeout_watcher); |
56 | ev_timer_start (loop, &timeout_watcher); |
44 | |
57 | |
45 | /* loop till timeout or data ready */ |
58 | // now wait for events to arrive |
46 | ev_loop (loop, 0); |
59 | ev_loop (loop, 0); |
47 | |
60 | |
|
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61 | // unloop was called, so exit |
48 | return 0; |
62 | return 0; |
49 | } |
63 | } |
50 | |
64 | |
51 | =head1 DESCRIPTION |
65 | =head1 DESCRIPTION |
52 | |
66 | |
53 | The newest version of this document is also available as a html-formatted |
67 | The newest version of this document is also available as an html-formatted |
54 | web page you might find easier to navigate when reading it for the first |
68 | web page you might find easier to navigate when reading it for the first |
55 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
69 | time: L<http://cvs.schmorp.de/libev/ev.html>. |
56 | |
70 | |
57 | Libev is an event loop: you register interest in certain events (such as a |
71 | Libev is an event loop: you register interest in certain events (such as a |
58 | file descriptor being readable or a timeout occurring), and it will manage |
72 | file descriptor being readable or a timeout occurring), and it will manage |
… | |
… | |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
98 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
99 | for example). |
86 | |
100 | |
87 | =head2 CONVENTIONS |
101 | =head2 CONVENTIONS |
88 | |
102 | |
89 | Libev is very configurable. In this manual the default configuration will |
103 | Libev is very configurable. In this manual the default (and most common) |
90 | be described, which supports multiple event loops. For more info about |
104 | configuration will be described, which supports multiple event loops. For |
91 | various configuration options please have a look at B<EMBED> section in |
105 | more info about various configuration options please have a look at |
92 | this manual. If libev was configured without support for multiple event |
106 | B<EMBED> section in this manual. If libev was configured without support |
93 | loops, then all functions taking an initial argument of name C<loop> |
107 | for multiple event loops, then all functions taking an initial argument of |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
108 | name C<loop> (which is always of type C<struct ev_loop *>) will not have |
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109 | this argument. |
95 | |
110 | |
96 | =head2 TIME REPRESENTATION |
111 | =head2 TIME REPRESENTATION |
97 | |
112 | |
98 | Libev represents time as a single floating point number, representing the |
113 | Libev represents time as a single floating point number, representing the |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
114 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
… | |
… | |
181 | See the description of C<ev_embed> watchers for more info. |
196 | See the description of C<ev_embed> watchers for more info. |
182 | |
197 | |
183 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
198 | =item ev_set_allocator (void *(*cb)(void *ptr, long size)) |
184 | |
199 | |
185 | Sets the allocation function to use (the prototype is similar - the |
200 | Sets the allocation function to use (the prototype is similar - the |
186 | semantics is identical - to the realloc C function). It is used to |
201 | semantics are identical to the C<realloc> C89/SuS/POSIX function). It is |
187 | allocate and free memory (no surprises here). If it returns zero when |
202 | used to allocate and free memory (no surprises here). If it returns zero |
188 | memory needs to be allocated, the library might abort or take some |
203 | when memory needs to be allocated (C<size != 0>), the library might abort |
189 | potentially destructive action. The default is your system realloc |
204 | or take some potentially destructive action. |
190 | function. |
205 | |
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206 | Since some systems (at least OpenBSD and Darwin) fail to implement |
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207 | correct C<realloc> semantics, libev will use a wrapper around the system |
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208 | C<realloc> and C<free> functions by default. |
191 | |
209 | |
192 | You could override this function in high-availability programs to, say, |
210 | You could override this function in high-availability programs to, say, |
193 | free some memory if it cannot allocate memory, to use a special allocator, |
211 | free some memory if it cannot allocate memory, to use a special allocator, |
194 | or even to sleep a while and retry until some memory is available. |
212 | or even to sleep a while and retry until some memory is available. |
195 | |
213 | |
196 | Example: Replace the libev allocator with one that waits a bit and then |
214 | Example: Replace the libev allocator with one that waits a bit and then |
197 | retries). |
215 | retries (example requires a standards-compliant C<realloc>). |
198 | |
216 | |
199 | static void * |
217 | static void * |
200 | persistent_realloc (void *ptr, size_t size) |
218 | persistent_realloc (void *ptr, size_t size) |
201 | { |
219 | { |
202 | for (;;) |
220 | for (;;) |
… | |
… | |
241 | |
259 | |
242 | An event loop is described by a C<struct ev_loop *>. The library knows two |
260 | An event loop is described by a C<struct ev_loop *>. The library knows two |
243 | types of such loops, the I<default> loop, which supports signals and child |
261 | types of such loops, the I<default> loop, which supports signals and child |
244 | events, and dynamically created loops which do not. |
262 | events, and dynamically created loops which do not. |
245 | |
263 | |
246 | If you use threads, a common model is to run the default event loop |
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247 | in your main thread (or in a separate thread) and for each thread you |
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248 | create, you also create another event loop. Libev itself does no locking |
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249 | whatsoever, so if you mix calls to the same event loop in different |
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250 | threads, make sure you lock (this is usually a bad idea, though, even if |
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251 | done correctly, because it's hideous and inefficient). |
|
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252 | |
|
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253 | =over 4 |
264 | =over 4 |
254 | |
265 | |
255 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
266 | =item struct ev_loop *ev_default_loop (unsigned int flags) |
256 | |
267 | |
257 | This will initialise the default event loop if it hasn't been initialised |
268 | This will initialise the default event loop if it hasn't been initialised |
… | |
… | |
259 | false. If it already was initialised it simply returns it (and ignores the |
270 | false. If it already was initialised it simply returns it (and ignores the |
260 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
271 | flags. If that is troubling you, check C<ev_backend ()> afterwards). |
261 | |
272 | |
262 | If you don't know what event loop to use, use the one returned from this |
273 | If you don't know what event loop to use, use the one returned from this |
263 | function. |
274 | function. |
|
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275 | |
|
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276 | Note that this function is I<not> thread-safe, so if you want to use it |
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277 | from multiple threads, you have to lock (note also that this is unlikely, |
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278 | as loops cannot bes hared easily between threads anyway). |
|
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279 | |
|
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280 | The default loop is the only loop that can handle C<ev_signal> and |
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281 | C<ev_child> watchers, and to do this, it always registers a handler |
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282 | for C<SIGCHLD>. If this is a problem for your app you can either |
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283 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
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284 | can simply overwrite the C<SIGCHLD> signal handler I<after> calling |
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285 | C<ev_default_init>. |
264 | |
286 | |
265 | The flags argument can be used to specify special behaviour or specific |
287 | The flags argument can be used to specify special behaviour or specific |
266 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
288 | backends to use, and is usually specified as C<0> (or C<EVFLAG_AUTO>). |
267 | |
289 | |
268 | The following flags are supported: |
290 | The following flags are supported: |
… | |
… | |
290 | enabling this flag. |
312 | enabling this flag. |
291 | |
313 | |
292 | This works by calling C<getpid ()> on every iteration of the loop, |
314 | This works by calling C<getpid ()> on every iteration of the loop, |
293 | and thus this might slow down your event loop if you do a lot of loop |
315 | and thus this might slow down your event loop if you do a lot of loop |
294 | iterations and little real work, but is usually not noticeable (on my |
316 | iterations and little real work, but is usually not noticeable (on my |
295 | Linux system for example, C<getpid> is actually a simple 5-insn sequence |
317 | GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence |
296 | without a syscall and thus I<very> fast, but my Linux system also has |
318 | without a syscall and thus I<very> fast, but my GNU/Linux system also has |
297 | C<pthread_atfork> which is even faster). |
319 | C<pthread_atfork> which is even faster). |
298 | |
320 | |
299 | The big advantage of this flag is that you can forget about fork (and |
321 | The big advantage of this flag is that you can forget about fork (and |
300 | forget about forgetting to tell libev about forking) when you use this |
322 | forget about forgetting to tell libev about forking) when you use this |
301 | flag. |
323 | flag. |
… | |
… | |
332 | For few fds, this backend is a bit little slower than poll and select, |
354 | For few fds, this backend is a bit little slower than poll and select, |
333 | but it scales phenomenally better. While poll and select usually scale |
355 | but it scales phenomenally better. While poll and select usually scale |
334 | like O(total_fds) where n is the total number of fds (or the highest fd), |
356 | like O(total_fds) where n is the total number of fds (or the highest fd), |
335 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
357 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
336 | of shortcomings, such as silently dropping events in some hard-to-detect |
358 | of shortcomings, such as silently dropping events in some hard-to-detect |
337 | cases and rewiring a syscall per fd change, no fork support and bad |
359 | cases and requiring a syscall per fd change, no fork support and bad |
338 | support for dup. |
360 | support for dup. |
339 | |
361 | |
340 | While stopping, setting and starting an I/O watcher in the same iteration |
362 | While stopping, setting and starting an I/O watcher in the same iteration |
341 | will result in some caching, there is still a syscall per such incident |
363 | will result in some caching, there is still a syscall per such incident |
342 | (because the fd could point to a different file description now), so its |
364 | (because the fd could point to a different file description now), so its |
… | |
… | |
403 | While this backend scales well, it requires one system call per active |
425 | While this backend scales well, it requires one system call per active |
404 | file descriptor per loop iteration. For small and medium numbers of file |
426 | file descriptor per loop iteration. For small and medium numbers of file |
405 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
427 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
406 | might perform better. |
428 | might perform better. |
407 | |
429 | |
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430 | On the positive side, ignoring the spurious readyness notifications, this |
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431 | backend actually performed to specification in all tests and is fully |
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432 | embeddable, which is a rare feat among the OS-specific backends. |
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433 | |
408 | =item C<EVBACKEND_ALL> |
434 | =item C<EVBACKEND_ALL> |
409 | |
435 | |
410 | Try all backends (even potentially broken ones that wouldn't be tried |
436 | Try all backends (even potentially broken ones that wouldn't be tried |
411 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
437 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
412 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
438 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
… | |
… | |
414 | It is definitely not recommended to use this flag. |
440 | It is definitely not recommended to use this flag. |
415 | |
441 | |
416 | =back |
442 | =back |
417 | |
443 | |
418 | If one or more of these are ored into the flags value, then only these |
444 | If one or more of these are ored into the flags value, then only these |
419 | backends will be tried (in the reverse order as given here). If none are |
445 | backends will be tried (in the reverse order as listed here). If none are |
420 | specified, most compiled-in backend will be tried, usually in reverse |
446 | specified, all backends in C<ev_recommended_backends ()> will be tried. |
421 | order of their flag values :) |
|
|
422 | |
447 | |
423 | The most typical usage is like this: |
448 | The most typical usage is like this: |
424 | |
449 | |
425 | if (!ev_default_loop (0)) |
450 | if (!ev_default_loop (0)) |
426 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
451 | fatal ("could not initialise libev, bad $LIBEV_FLAGS in environment?"); |
… | |
… | |
440 | |
465 | |
441 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
466 | Similar to C<ev_default_loop>, but always creates a new event loop that is |
442 | always distinct from the default loop. Unlike the default loop, it cannot |
467 | always distinct from the default loop. Unlike the default loop, it cannot |
443 | handle signal and child watchers, and attempts to do so will be greeted by |
468 | handle signal and child watchers, and attempts to do so will be greeted by |
444 | undefined behaviour (or a failed assertion if assertions are enabled). |
469 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
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470 | |
|
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471 | Note that this function I<is> thread-safe, and the recommended way to use |
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472 | libev with threads is indeed to create one loop per thread, and using the |
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473 | default loop in the "main" or "initial" thread. |
445 | |
474 | |
446 | Example: Try to create a event loop that uses epoll and nothing else. |
475 | Example: Try to create a event loop that uses epoll and nothing else. |
447 | |
476 | |
448 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
477 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
449 | if (!epoller) |
478 | if (!epoller) |
… | |
… | |
473 | Like C<ev_default_destroy>, but destroys an event loop created by an |
502 | Like C<ev_default_destroy>, but destroys an event loop created by an |
474 | earlier call to C<ev_loop_new>. |
503 | earlier call to C<ev_loop_new>. |
475 | |
504 | |
476 | =item ev_default_fork () |
505 | =item ev_default_fork () |
477 | |
506 | |
|
|
507 | This function sets a flag that causes subsequent C<ev_loop> iterations |
478 | This function reinitialises the kernel state for backends that have |
508 | to reinitialise the kernel state for backends that have one. Despite the |
479 | one. Despite the name, you can call it anytime, but it makes most sense |
509 | name, you can call it anytime, but it makes most sense after forking, in |
480 | after forking, in either the parent or child process (or both, but that |
510 | the child process (or both child and parent, but that again makes little |
481 | again makes little sense). |
511 | sense). You I<must> call it in the child before using any of the libev |
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512 | functions, and it will only take effect at the next C<ev_loop> iteration. |
482 | |
513 | |
483 | You I<must> call this function in the child process after forking if and |
514 | On the other hand, you only need to call this function in the child |
484 | only if you want to use the event library in both processes. If you just |
515 | process if and only if you want to use the event library in the child. If |
485 | fork+exec, you don't have to call it. |
516 | you just fork+exec, you don't have to call it at all. |
486 | |
517 | |
487 | The function itself is quite fast and it's usually not a problem to call |
518 | The function itself is quite fast and it's usually not a problem to call |
488 | it just in case after a fork. To make this easy, the function will fit in |
519 | it just in case after a fork. To make this easy, the function will fit in |
489 | quite nicely into a call to C<pthread_atfork>: |
520 | quite nicely into a call to C<pthread_atfork>: |
490 | |
521 | |
491 | pthread_atfork (0, 0, ev_default_fork); |
522 | pthread_atfork (0, 0, ev_default_fork); |
492 | |
523 | |
493 | At the moment, C<EVBACKEND_SELECT> and C<EVBACKEND_POLL> are safe to use |
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494 | without calling this function, so if you force one of those backends you |
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495 | do not need to care. |
|
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496 | |
|
|
497 | =item ev_loop_fork (loop) |
524 | =item ev_loop_fork (loop) |
498 | |
525 | |
499 | Like C<ev_default_fork>, but acts on an event loop created by |
526 | Like C<ev_default_fork>, but acts on an event loop created by |
500 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
527 | C<ev_loop_new>. Yes, you have to call this on every allocated event loop |
501 | after fork, and how you do this is entirely your own problem. |
528 | after fork, and how you do this is entirely your own problem. |
|
|
529 | |
|
|
530 | =item int ev_is_default_loop (loop) |
|
|
531 | |
|
|
532 | Returns true when the given loop actually is the default loop, false otherwise. |
502 | |
533 | |
503 | =item unsigned int ev_loop_count (loop) |
534 | =item unsigned int ev_loop_count (loop) |
504 | |
535 | |
505 | Returns the count of loop iterations for the loop, which is identical to |
536 | Returns the count of loop iterations for the loop, which is identical to |
506 | the number of times libev did poll for new events. It starts at C<0> and |
537 | the number of times libev did poll for new events. It starts at C<0> and |
… | |
… | |
766 | =item C<EV_FORK> |
797 | =item C<EV_FORK> |
767 | |
798 | |
768 | The event loop has been resumed in the child process after fork (see |
799 | The event loop has been resumed in the child process after fork (see |
769 | C<ev_fork>). |
800 | C<ev_fork>). |
770 | |
801 | |
|
|
802 | =item C<EV_ASYNC> |
|
|
803 | |
|
|
804 | The given async watcher has been asynchronously notified (see C<ev_async>). |
|
|
805 | |
771 | =item C<EV_ERROR> |
806 | =item C<EV_ERROR> |
772 | |
807 | |
773 | An unspecified error has occured, the watcher has been stopped. This might |
808 | An unspecified error has occured, the watcher has been stopped. This might |
774 | happen because the watcher could not be properly started because libev |
809 | happen because the watcher could not be properly started because libev |
775 | ran out of memory, a file descriptor was found to be closed or any other |
810 | ran out of memory, a file descriptor was found to be closed or any other |
… | |
… | |
1054 | To support fork in your programs, you either have to call |
1089 | To support fork in your programs, you either have to call |
1055 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1090 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
1056 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1091 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1057 | C<EVBACKEND_POLL>. |
1092 | C<EVBACKEND_POLL>. |
1058 | |
1093 | |
|
|
1094 | =head3 The special problem of SIGPIPE |
|
|
1095 | |
|
|
1096 | While not really specific to libev, it is easy to forget about SIGPIPE: |
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1097 | when reading from a pipe whose other end has been closed, your program |
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1098 | gets send a SIGPIPE, which, by default, aborts your program. For most |
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1099 | programs this is sensible behaviour, for daemons, this is usually |
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1100 | undesirable. |
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1101 | |
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1102 | So when you encounter spurious, unexplained daemon exits, make sure you |
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1103 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
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1104 | somewhere, as that would have given you a big clue). |
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1105 | |
1059 | |
1106 | |
1060 | =head3 Watcher-Specific Functions |
1107 | =head3 Watcher-Specific Functions |
1061 | |
1108 | |
1062 | =over 4 |
1109 | =over 4 |
1063 | |
1110 | |
… | |
… | |
1140 | configure a timer to trigger every 10 seconds, then it will trigger at |
1187 | configure a timer to trigger every 10 seconds, then it will trigger at |
1141 | exactly 10 second intervals. If, however, your program cannot keep up with |
1188 | exactly 10 second intervals. If, however, your program cannot keep up with |
1142 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1189 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1143 | timer will not fire more than once per event loop iteration. |
1190 | timer will not fire more than once per event loop iteration. |
1144 | |
1191 | |
1145 | =item ev_timer_again (loop) |
1192 | =item ev_timer_again (loop, ev_timer *) |
1146 | |
1193 | |
1147 | This will act as if the timer timed out and restart it again if it is |
1194 | This will act as if the timer timed out and restart it again if it is |
1148 | repeating. The exact semantics are: |
1195 | repeating. The exact semantics are: |
1149 | |
1196 | |
1150 | If the timer is pending, its pending status is cleared. |
1197 | If the timer is pending, its pending status is cleared. |
… | |
… | |
1259 | In this configuration the watcher triggers an event at the wallclock time |
1306 | In this configuration the watcher triggers an event at the wallclock time |
1260 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1307 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1261 | that is, if it is to be run at January 1st 2011 then it will run when the |
1308 | that is, if it is to be run at January 1st 2011 then it will run when the |
1262 | system time reaches or surpasses this time. |
1309 | system time reaches or surpasses this time. |
1263 | |
1310 | |
1264 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1311 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1265 | |
1312 | |
1266 | In this mode the watcher will always be scheduled to time out at the next |
1313 | In this mode the watcher will always be scheduled to time out at the next |
1267 | C<at + N * interval> time (for some integer N, which can also be negative) |
1314 | C<at + N * interval> time (for some integer N, which can also be negative) |
1268 | and then repeat, regardless of any time jumps. |
1315 | and then repeat, regardless of any time jumps. |
1269 | |
1316 | |
… | |
… | |
1326 | Simply stops and restarts the periodic watcher again. This is only useful |
1373 | Simply stops and restarts the periodic watcher again. This is only useful |
1327 | when you changed some parameters or the reschedule callback would return |
1374 | when you changed some parameters or the reschedule callback would return |
1328 | a different time than the last time it was called (e.g. in a crond like |
1375 | a different time than the last time it was called (e.g. in a crond like |
1329 | program when the crontabs have changed). |
1376 | program when the crontabs have changed). |
1330 | |
1377 | |
|
|
1378 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1379 | |
|
|
1380 | When active, returns the absolute time that the watcher is supposed to |
|
|
1381 | trigger next. |
|
|
1382 | |
1331 | =item ev_tstamp offset [read-write] |
1383 | =item ev_tstamp offset [read-write] |
1332 | |
1384 | |
1333 | When repeating, this contains the offset value, otherwise this is the |
1385 | When repeating, this contains the offset value, otherwise this is the |
1334 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1386 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1335 | |
1387 | |
… | |
… | |
1345 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1397 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1346 | |
1398 | |
1347 | The current reschedule callback, or C<0>, if this functionality is |
1399 | The current reschedule callback, or C<0>, if this functionality is |
1348 | switched off. Can be changed any time, but changes only take effect when |
1400 | switched off. Can be changed any time, but changes only take effect when |
1349 | the periodic timer fires or C<ev_periodic_again> is being called. |
1401 | the periodic timer fires or C<ev_periodic_again> is being called. |
1350 | |
|
|
1351 | =item ev_tstamp at [read-only] |
|
|
1352 | |
|
|
1353 | When active, contains the absolute time that the watcher is supposed to |
|
|
1354 | trigger next. |
|
|
1355 | |
1402 | |
1356 | =back |
1403 | =back |
1357 | |
1404 | |
1358 | =head3 Examples |
1405 | =head3 Examples |
1359 | |
1406 | |
… | |
… | |
1403 | with the kernel (thus it coexists with your own signal handlers as long |
1450 | with the kernel (thus it coexists with your own signal handlers as long |
1404 | as you don't register any with libev). Similarly, when the last signal |
1451 | as you don't register any with libev). Similarly, when the last signal |
1405 | watcher for a signal is stopped libev will reset the signal handler to |
1452 | watcher for a signal is stopped libev will reset the signal handler to |
1406 | SIG_DFL (regardless of what it was set to before). |
1453 | SIG_DFL (regardless of what it was set to before). |
1407 | |
1454 | |
|
|
1455 | If possible and supported, libev will install its handlers with |
|
|
1456 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
|
|
1457 | interrupted. If you have a problem with syscalls getting interrupted by |
|
|
1458 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1459 | them in an C<ev_prepare> watcher. |
|
|
1460 | |
1408 | =head3 Watcher-Specific Functions and Data Members |
1461 | =head3 Watcher-Specific Functions and Data Members |
1409 | |
1462 | |
1410 | =over 4 |
1463 | =over 4 |
1411 | |
1464 | |
1412 | =item ev_signal_init (ev_signal *, callback, int signum) |
1465 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
1420 | |
1473 | |
1421 | The signal the watcher watches out for. |
1474 | The signal the watcher watches out for. |
1422 | |
1475 | |
1423 | =back |
1476 | =back |
1424 | |
1477 | |
|
|
1478 | =head3 Examples |
|
|
1479 | |
|
|
1480 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1481 | |
|
|
1482 | static void |
|
|
1483 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1484 | { |
|
|
1485 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1486 | } |
|
|
1487 | |
|
|
1488 | struct ev_signal signal_watcher; |
|
|
1489 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1490 | ev_signal_start (loop, &sigint_cb); |
|
|
1491 | |
1425 | |
1492 | |
1426 | =head2 C<ev_child> - watch out for process status changes |
1493 | =head2 C<ev_child> - watch out for process status changes |
1427 | |
1494 | |
1428 | Child watchers trigger when your process receives a SIGCHLD in response to |
1495 | Child watchers trigger when your process receives a SIGCHLD in response to |
1429 | some child status changes (most typically when a child of yours dies). |
1496 | some child status changes (most typically when a child of yours dies). It |
|
|
1497 | is permissible to install a child watcher I<after> the child has been |
|
|
1498 | forked (which implies it might have already exited), as long as the event |
|
|
1499 | loop isn't entered (or is continued from a watcher). |
|
|
1500 | |
|
|
1501 | Only the default event loop is capable of handling signals, and therefore |
|
|
1502 | you can only rgeister child watchers in the default event loop. |
|
|
1503 | |
|
|
1504 | =head3 Process Interaction |
|
|
1505 | |
|
|
1506 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1507 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1508 | the first child watcher is started after the child exits. The occurance |
|
|
1509 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1510 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1511 | children, even ones not watched. |
|
|
1512 | |
|
|
1513 | =head3 Overriding the Built-In Processing |
|
|
1514 | |
|
|
1515 | Libev offers no special support for overriding the built-in child |
|
|
1516 | processing, but if your application collides with libev's default child |
|
|
1517 | handler, you can override it easily by installing your own handler for |
|
|
1518 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1519 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1520 | event-based approach to child reaping and thus use libev's support for |
|
|
1521 | that, so other libev users can use C<ev_child> watchers freely. |
1430 | |
1522 | |
1431 | =head3 Watcher-Specific Functions and Data Members |
1523 | =head3 Watcher-Specific Functions and Data Members |
1432 | |
1524 | |
1433 | =over 4 |
1525 | =over 4 |
1434 | |
1526 | |
1435 | =item ev_child_init (ev_child *, callback, int pid) |
1527 | =item ev_child_init (ev_child *, callback, int pid, int trace) |
1436 | |
1528 | |
1437 | =item ev_child_set (ev_child *, int pid) |
1529 | =item ev_child_set (ev_child *, int pid, int trace) |
1438 | |
1530 | |
1439 | Configures the watcher to wait for status changes of process C<pid> (or |
1531 | Configures the watcher to wait for status changes of process C<pid> (or |
1440 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1532 | I<any> process if C<pid> is specified as C<0>). The callback can look |
1441 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1533 | at the C<rstatus> member of the C<ev_child> watcher structure to see |
1442 | the status word (use the macros from C<sys/wait.h> and see your systems |
1534 | the status word (use the macros from C<sys/wait.h> and see your systems |
1443 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1535 | C<waitpid> documentation). The C<rpid> member contains the pid of the |
1444 | process causing the status change. |
1536 | process causing the status change. C<trace> must be either C<0> (only |
|
|
1537 | activate the watcher when the process terminates) or C<1> (additionally |
|
|
1538 | activate the watcher when the process is stopped or continued). |
1445 | |
1539 | |
1446 | =item int pid [read-only] |
1540 | =item int pid [read-only] |
1447 | |
1541 | |
1448 | The process id this watcher watches out for, or C<0>, meaning any process id. |
1542 | The process id this watcher watches out for, or C<0>, meaning any process id. |
1449 | |
1543 | |
… | |
… | |
1458 | |
1552 | |
1459 | =back |
1553 | =back |
1460 | |
1554 | |
1461 | =head3 Examples |
1555 | =head3 Examples |
1462 | |
1556 | |
1463 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1557 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1558 | its completion. |
|
|
1559 | |
|
|
1560 | ev_child cw; |
1464 | |
1561 | |
1465 | static void |
1562 | static void |
1466 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1563 | child_cb (EV_P_ struct ev_child *w, int revents) |
1467 | { |
1564 | { |
1468 | ev_unloop (loop, EVUNLOOP_ALL); |
1565 | ev_child_stop (EV_A_ w); |
|
|
1566 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1469 | } |
1567 | } |
1470 | |
1568 | |
1471 | struct ev_signal signal_watcher; |
1569 | pid_t pid = fork (); |
1472 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1570 | |
1473 | ev_signal_start (loop, &sigint_cb); |
1571 | if (pid < 0) |
|
|
1572 | // error |
|
|
1573 | else if (pid == 0) |
|
|
1574 | { |
|
|
1575 | // the forked child executes here |
|
|
1576 | exit (1); |
|
|
1577 | } |
|
|
1578 | else |
|
|
1579 | { |
|
|
1580 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1581 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1582 | } |
1474 | |
1583 | |
1475 | |
1584 | |
1476 | =head2 C<ev_stat> - did the file attributes just change? |
1585 | =head2 C<ev_stat> - did the file attributes just change? |
1477 | |
1586 | |
1478 | This watches a filesystem path for attribute changes. That is, it calls |
1587 | This watches a filesystem path for attribute changes. That is, it calls |
… | |
… | |
1501 | as even with OS-supported change notifications, this can be |
1610 | as even with OS-supported change notifications, this can be |
1502 | resource-intensive. |
1611 | resource-intensive. |
1503 | |
1612 | |
1504 | At the time of this writing, only the Linux inotify interface is |
1613 | At the time of this writing, only the Linux inotify interface is |
1505 | implemented (implementing kqueue support is left as an exercise for the |
1614 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1615 | reader, note, however, that the author sees no way of implementing ev_stat |
1506 | reader). Inotify will be used to give hints only and should not change the |
1616 | semantics with kqueue). Inotify will be used to give hints only and should |
1507 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1617 | not change the semantics of C<ev_stat> watchers, which means that libev |
1508 | to fall back to regular polling again even with inotify, but changes are |
1618 | sometimes needs to fall back to regular polling again even with inotify, |
1509 | usually detected immediately, and if the file exists there will be no |
1619 | but changes are usually detected immediately, and if the file exists there |
1510 | polling. |
1620 | will be no polling. |
|
|
1621 | |
|
|
1622 | =head3 ABI Issues (Largefile Support) |
|
|
1623 | |
|
|
1624 | Libev by default (unless the user overrides this) uses the default |
|
|
1625 | compilation environment, which means that on systems with optionally |
|
|
1626 | disabled large file support, you get the 32 bit version of the stat |
|
|
1627 | structure. When using the library from programs that change the ABI to |
|
|
1628 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1629 | compile libev with the same flags to get binary compatibility. This is |
|
|
1630 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1631 | most noticably with ev_stat and largefile support. |
1511 | |
1632 | |
1512 | =head3 Inotify |
1633 | =head3 Inotify |
1513 | |
1634 | |
1514 | When C<inotify (7)> support has been compiled into libev (generally only |
1635 | When C<inotify (7)> support has been compiled into libev (generally only |
1515 | available on Linux) and present at runtime, it will be used to speed up |
1636 | available on Linux) and present at runtime, it will be used to speed up |
1516 | change detection where possible. The inotify descriptor will be created lazily |
1637 | change detection where possible. The inotify descriptor will be created lazily |
1517 | when the first C<ev_stat> watcher is being started. |
1638 | when the first C<ev_stat> watcher is being started. |
1518 | |
1639 | |
1519 | Inotify presense does not change the semantics of C<ev_stat> watchers |
1640 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1520 | except that changes might be detected earlier, and in some cases, to avoid |
1641 | except that changes might be detected earlier, and in some cases, to avoid |
1521 | making regular C<stat> calls. Even in the presense of inotify support |
1642 | making regular C<stat> calls. Even in the presence of inotify support |
1522 | there are many cases where libev has to resort to regular C<stat> polling. |
1643 | there are many cases where libev has to resort to regular C<stat> polling. |
1523 | |
1644 | |
1524 | (There is no support for kqueue, as apparently it cannot be used to |
1645 | (There is no support for kqueue, as apparently it cannot be used to |
1525 | implement this functionality, due to the requirement of having a file |
1646 | implement this functionality, due to the requirement of having a file |
1526 | descriptor open on the object at all times). |
1647 | descriptor open on the object at all times). |
… | |
… | |
1529 | |
1650 | |
1530 | The C<stat ()> syscall only supports full-second resolution portably, and |
1651 | The C<stat ()> syscall only supports full-second resolution portably, and |
1531 | even on systems where the resolution is higher, many filesystems still |
1652 | even on systems where the resolution is higher, many filesystems still |
1532 | only support whole seconds. |
1653 | only support whole seconds. |
1533 | |
1654 | |
1534 | That means that, if the time is the only thing that changes, you might |
1655 | That means that, if the time is the only thing that changes, you can |
1535 | miss updates: on the first update, C<ev_stat> detects a change and calls |
1656 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1536 | your callback, which does something. When there is another update within |
1657 | calls your callback, which does something. When there is another update |
1537 | the same second, C<ev_stat> will be unable to detect it. |
1658 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1659 | data does not change. |
1538 | |
1660 | |
1539 | The solution to this is to delay acting on a change for a second (or till |
1661 | The solution to this is to delay acting on a change for slightly more |
1540 | the next second boundary), using a roughly one-second delay C<ev_timer> |
1662 | than second (or till slightly after the next full second boundary), using |
1541 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
1663 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1542 | is added to work around small timing inconsistencies of some operating |
1664 | ev_timer_again (loop, w)>). |
1543 | systems. |
1665 | |
|
|
1666 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1667 | of some operating systems (where the second counter of the current time |
|
|
1668 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1669 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1670 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1671 | update file times then there will be a small window where the kernel uses |
|
|
1672 | the previous second to update file times but libev might already execute |
|
|
1673 | the timer callback). |
1544 | |
1674 | |
1545 | =head3 Watcher-Specific Functions and Data Members |
1675 | =head3 Watcher-Specific Functions and Data Members |
1546 | |
1676 | |
1547 | =over 4 |
1677 | =over 4 |
1548 | |
1678 | |
… | |
… | |
1554 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1684 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1555 | be detected and should normally be specified as C<0> to let libev choose |
1685 | be detected and should normally be specified as C<0> to let libev choose |
1556 | a suitable value. The memory pointed to by C<path> must point to the same |
1686 | a suitable value. The memory pointed to by C<path> must point to the same |
1557 | path for as long as the watcher is active. |
1687 | path for as long as the watcher is active. |
1558 | |
1688 | |
1559 | The callback will be receive C<EV_STAT> when a change was detected, |
1689 | The callback will receive C<EV_STAT> when a change was detected, relative |
1560 | relative to the attributes at the time the watcher was started (or the |
1690 | to the attributes at the time the watcher was started (or the last change |
1561 | last change was detected). |
1691 | was detected). |
1562 | |
1692 | |
1563 | =item ev_stat_stat (ev_stat *) |
1693 | =item ev_stat_stat (loop, ev_stat *) |
1564 | |
1694 | |
1565 | Updates the stat buffer immediately with new values. If you change the |
1695 | Updates the stat buffer immediately with new values. If you change the |
1566 | watched path in your callback, you could call this fucntion to avoid |
1696 | watched path in your callback, you could call this function to avoid |
1567 | detecting this change (while introducing a race condition). Can also be |
1697 | detecting this change (while introducing a race condition if you are not |
1568 | useful simply to find out the new values. |
1698 | the only one changing the path). Can also be useful simply to find out the |
|
|
1699 | new values. |
1569 | |
1700 | |
1570 | =item ev_statdata attr [read-only] |
1701 | =item ev_statdata attr [read-only] |
1571 | |
1702 | |
1572 | The most-recently detected attributes of the file. Although the type is of |
1703 | The most-recently detected attributes of the file. Although the type is |
1573 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1704 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1574 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
1705 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1706 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1575 | was some error while C<stat>ing the file. |
1707 | some error while C<stat>ing the file. |
1576 | |
1708 | |
1577 | =item ev_statdata prev [read-only] |
1709 | =item ev_statdata prev [read-only] |
1578 | |
1710 | |
1579 | The previous attributes of the file. The callback gets invoked whenever |
1711 | The previous attributes of the file. The callback gets invoked whenever |
1580 | C<prev> != C<attr>. |
1712 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1713 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1714 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1581 | |
1715 | |
1582 | =item ev_tstamp interval [read-only] |
1716 | =item ev_tstamp interval [read-only] |
1583 | |
1717 | |
1584 | The specified interval. |
1718 | The specified interval. |
1585 | |
1719 | |
… | |
… | |
1639 | } |
1773 | } |
1640 | |
1774 | |
1641 | ... |
1775 | ... |
1642 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1776 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1643 | ev_stat_start (loop, &passwd); |
1777 | ev_stat_start (loop, &passwd); |
1644 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1778 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1645 | |
1779 | |
1646 | |
1780 | |
1647 | =head2 C<ev_idle> - when you've got nothing better to do... |
1781 | =head2 C<ev_idle> - when you've got nothing better to do... |
1648 | |
1782 | |
1649 | Idle watchers trigger events when no other events of the same or higher |
1783 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1685 | static void |
1819 | static void |
1686 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1820 | idle_cb (struct ev_loop *loop, struct ev_idle *w, int revents) |
1687 | { |
1821 | { |
1688 | free (w); |
1822 | free (w); |
1689 | // now do something you wanted to do when the program has |
1823 | // now do something you wanted to do when the program has |
1690 | // no longer asnything immediate to do. |
1824 | // no longer anything immediate to do. |
1691 | } |
1825 | } |
1692 | |
1826 | |
1693 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1827 | struct ev_idle *idle_watcher = malloc (sizeof (struct ev_idle)); |
1694 | ev_idle_init (idle_watcher, idle_cb); |
1828 | ev_idle_init (idle_watcher, idle_cb); |
1695 | ev_idle_start (loop, idle_cb); |
1829 | ev_idle_start (loop, idle_cb); |
… | |
… | |
1737 | |
1871 | |
1738 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1872 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1739 | priority, to ensure that they are being run before any other watchers |
1873 | priority, to ensure that they are being run before any other watchers |
1740 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1874 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1741 | too) should not activate ("feed") events into libev. While libev fully |
1875 | too) should not activate ("feed") events into libev. While libev fully |
1742 | supports this, they will be called before other C<ev_check> watchers |
1876 | supports this, they might get executed before other C<ev_check> watchers |
1743 | did their job. As C<ev_check> watchers are often used to embed other |
1877 | did their job. As C<ev_check> watchers are often used to embed other |
1744 | (non-libev) event loops those other event loops might be in an unusable |
1878 | (non-libev) event loops those other event loops might be in an unusable |
1745 | state until their C<ev_check> watcher ran (always remind yourself to |
1879 | state until their C<ev_check> watcher ran (always remind yourself to |
1746 | coexist peacefully with others). |
1880 | coexist peacefully with others). |
1747 | |
1881 | |
… | |
… | |
1762 | =head3 Examples |
1896 | =head3 Examples |
1763 | |
1897 | |
1764 | There are a number of principal ways to embed other event loops or modules |
1898 | There are a number of principal ways to embed other event loops or modules |
1765 | into libev. Here are some ideas on how to include libadns into libev |
1899 | into libev. Here are some ideas on how to include libadns into libev |
1766 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1900 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1767 | use for an actually working example. Another Perl module named C<EV::Glib> |
1901 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1768 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
1902 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1769 | into the Glib event loop). |
1903 | Glib event loop). |
1770 | |
1904 | |
1771 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1905 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1772 | and in a check watcher, destroy them and call into libadns. What follows |
1906 | and in a check watcher, destroy them and call into libadns. What follows |
1773 | is pseudo-code only of course. This requires you to either use a low |
1907 | is pseudo-code only of course. This requires you to either use a low |
1774 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1908 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
… | |
… | |
2036 | believe me. |
2170 | believe me. |
2037 | |
2171 | |
2038 | =back |
2172 | =back |
2039 | |
2173 | |
2040 | |
2174 | |
|
|
2175 | =head2 C<ev_async> - how to wake up another event loop |
|
|
2176 | |
|
|
2177 | In general, you cannot use an C<ev_loop> from multiple threads or other |
|
|
2178 | asynchronous sources such as signal handlers (as opposed to multiple event |
|
|
2179 | loops - those are of course safe to use in different threads). |
|
|
2180 | |
|
|
2181 | Sometimes, however, you need to wake up another event loop you do not |
|
|
2182 | control, for example because it belongs to another thread. This is what |
|
|
2183 | C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you |
|
|
2184 | can signal it by calling C<ev_async_send>, which is thread- and signal |
|
|
2185 | safe. |
|
|
2186 | |
|
|
2187 | This functionality is very similar to C<ev_signal> watchers, as signals, |
|
|
2188 | too, are asynchronous in nature, and signals, too, will be compressed |
|
|
2189 | (i.e. the number of callback invocations may be less than the number of |
|
|
2190 | C<ev_async_sent> calls). |
|
|
2191 | |
|
|
2192 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
2193 | just the default loop. |
|
|
2194 | |
|
|
2195 | =head3 Queueing |
|
|
2196 | |
|
|
2197 | C<ev_async> does not support queueing of data in any way. The reason |
|
|
2198 | is that the author does not know of a simple (or any) algorithm for a |
|
|
2199 | multiple-writer-single-reader queue that works in all cases and doesn't |
|
|
2200 | need elaborate support such as pthreads. |
|
|
2201 | |
|
|
2202 | That means that if you want to queue data, you have to provide your own |
|
|
2203 | queue. But at least I can tell you would implement locking around your |
|
|
2204 | queue: |
|
|
2205 | |
|
|
2206 | =over 4 |
|
|
2207 | |
|
|
2208 | =item queueing from a signal handler context |
|
|
2209 | |
|
|
2210 | To implement race-free queueing, you simply add to the queue in the signal |
|
|
2211 | handler but you block the signal handler in the watcher callback. Here is an example that does that for |
|
|
2212 | some fictitiuous SIGUSR1 handler: |
|
|
2213 | |
|
|
2214 | static ev_async mysig; |
|
|
2215 | |
|
|
2216 | static void |
|
|
2217 | sigusr1_handler (void) |
|
|
2218 | { |
|
|
2219 | sometype data; |
|
|
2220 | |
|
|
2221 | // no locking etc. |
|
|
2222 | queue_put (data); |
|
|
2223 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2224 | } |
|
|
2225 | |
|
|
2226 | static void |
|
|
2227 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2228 | { |
|
|
2229 | sometype data; |
|
|
2230 | sigset_t block, prev; |
|
|
2231 | |
|
|
2232 | sigemptyset (&block); |
|
|
2233 | sigaddset (&block, SIGUSR1); |
|
|
2234 | sigprocmask (SIG_BLOCK, &block, &prev); |
|
|
2235 | |
|
|
2236 | while (queue_get (&data)) |
|
|
2237 | process (data); |
|
|
2238 | |
|
|
2239 | if (sigismember (&prev, SIGUSR1) |
|
|
2240 | sigprocmask (SIG_UNBLOCK, &block, 0); |
|
|
2241 | } |
|
|
2242 | |
|
|
2243 | (Note: pthreads in theory requires you to use C<pthread_setmask> |
|
|
2244 | instead of C<sigprocmask> when you use threads, but libev doesn't do it |
|
|
2245 | either...). |
|
|
2246 | |
|
|
2247 | =item queueing from a thread context |
|
|
2248 | |
|
|
2249 | The strategy for threads is different, as you cannot (easily) block |
|
|
2250 | threads but you can easily preempt them, so to queue safely you need to |
|
|
2251 | employ a traditional mutex lock, such as in this pthread example: |
|
|
2252 | |
|
|
2253 | static ev_async mysig; |
|
|
2254 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
|
|
2255 | |
|
|
2256 | static void |
|
|
2257 | otherthread (void) |
|
|
2258 | { |
|
|
2259 | // only need to lock the actual queueing operation |
|
|
2260 | pthread_mutex_lock (&mymutex); |
|
|
2261 | queue_put (data); |
|
|
2262 | pthread_mutex_unlock (&mymutex); |
|
|
2263 | |
|
|
2264 | ev_async_send (EV_DEFAULT_ &mysig); |
|
|
2265 | } |
|
|
2266 | |
|
|
2267 | static void |
|
|
2268 | mysig_cb (EV_P_ ev_async *w, int revents) |
|
|
2269 | { |
|
|
2270 | pthread_mutex_lock (&mymutex); |
|
|
2271 | |
|
|
2272 | while (queue_get (&data)) |
|
|
2273 | process (data); |
|
|
2274 | |
|
|
2275 | pthread_mutex_unlock (&mymutex); |
|
|
2276 | } |
|
|
2277 | |
|
|
2278 | =back |
|
|
2279 | |
|
|
2280 | |
|
|
2281 | =head3 Watcher-Specific Functions and Data Members |
|
|
2282 | |
|
|
2283 | =over 4 |
|
|
2284 | |
|
|
2285 | =item ev_async_init (ev_async *, callback) |
|
|
2286 | |
|
|
2287 | Initialises and configures the async watcher - it has no parameters of any |
|
|
2288 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
|
|
2289 | believe me. |
|
|
2290 | |
|
|
2291 | =item ev_async_send (loop, ev_async *) |
|
|
2292 | |
|
|
2293 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
|
|
2294 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
|
|
2295 | C<ev_feed_event>, this call is safe to do in other threads, signal or |
|
|
2296 | similar contexts (see the dicusssion of C<EV_ATOMIC_T> in the embedding |
|
|
2297 | section below on what exactly this means). |
|
|
2298 | |
|
|
2299 | This call incurs the overhead of a syscall only once per loop iteration, |
|
|
2300 | so while the overhead might be noticable, it doesn't apply to repeated |
|
|
2301 | calls to C<ev_async_send>. |
|
|
2302 | |
|
|
2303 | =item bool = ev_async_pending (ev_async *) |
|
|
2304 | |
|
|
2305 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2306 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2307 | event loop. |
|
|
2308 | |
|
|
2309 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2310 | the loop iterates next and checks for the watcher to have become active, |
|
|
2311 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2312 | quickly check wether invoking the loop might be a good idea. |
|
|
2313 | |
|
|
2314 | Not that this does I<not> check wether the watcher itself is pending, only |
|
|
2315 | wether it has been requested to make this watcher pending. |
|
|
2316 | |
|
|
2317 | =back |
|
|
2318 | |
|
|
2319 | |
2041 | =head1 OTHER FUNCTIONS |
2320 | =head1 OTHER FUNCTIONS |
2042 | |
2321 | |
2043 | There are some other functions of possible interest. Described. Here. Now. |
2322 | There are some other functions of possible interest. Described. Here. Now. |
2044 | |
2323 | |
2045 | =over 4 |
2324 | =over 4 |
… | |
… | |
2113 | |
2392 | |
2114 | =item * Priorities are not currently supported. Initialising priorities |
2393 | =item * Priorities are not currently supported. Initialising priorities |
2115 | will fail and all watchers will have the same priority, even though there |
2394 | will fail and all watchers will have the same priority, even though there |
2116 | is an ev_pri field. |
2395 | is an ev_pri field. |
2117 | |
2396 | |
|
|
2397 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2398 | first base created (== the default loop) gets the signals. |
|
|
2399 | |
2118 | =item * Other members are not supported. |
2400 | =item * Other members are not supported. |
2119 | |
2401 | |
2120 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2402 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2121 | to use the libev header file and library. |
2403 | to use the libev header file and library. |
2122 | |
2404 | |
… | |
… | |
2272 | Example: Define a class with an IO and idle watcher, start one of them in |
2554 | Example: Define a class with an IO and idle watcher, start one of them in |
2273 | the constructor. |
2555 | the constructor. |
2274 | |
2556 | |
2275 | class myclass |
2557 | class myclass |
2276 | { |
2558 | { |
2277 | ev_io io; void io_cb (ev::io &w, int revents); |
2559 | ev::io io; void io_cb (ev::io &w, int revents); |
2278 | ev_idle idle void idle_cb (ev::idle &w, int revents); |
2560 | ev:idle idle void idle_cb (ev::idle &w, int revents); |
2279 | |
2561 | |
2280 | myclass (); |
2562 | myclass (int fd) |
2281 | } |
|
|
2282 | |
|
|
2283 | myclass::myclass (int fd) |
|
|
2284 | { |
2563 | { |
2285 | io .set <myclass, &myclass::io_cb > (this); |
2564 | io .set <myclass, &myclass::io_cb > (this); |
2286 | idle.set <myclass, &myclass::idle_cb> (this); |
2565 | idle.set <myclass, &myclass::idle_cb> (this); |
2287 | |
2566 | |
2288 | io.start (fd, ev::READ); |
2567 | io.start (fd, ev::READ); |
|
|
2568 | } |
2289 | } |
2569 | }; |
|
|
2570 | |
|
|
2571 | |
|
|
2572 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2573 | |
|
|
2574 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2575 | numbe rof languages exist in the form of third-party packages. If you know |
|
|
2576 | any interesting language binding in addition to the ones listed here, drop |
|
|
2577 | me a note. |
|
|
2578 | |
|
|
2579 | =over 4 |
|
|
2580 | |
|
|
2581 | =item Perl |
|
|
2582 | |
|
|
2583 | The EV module implements the full libev API and is actually used to test |
|
|
2584 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2585 | there are additional modules that implement libev-compatible interfaces |
|
|
2586 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2587 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2588 | |
|
|
2589 | It can be found and installed via CPAN, its homepage is found at |
|
|
2590 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2591 | |
|
|
2592 | =item Ruby |
|
|
2593 | |
|
|
2594 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2595 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
|
|
2596 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2597 | L<http://rev.rubyforge.org/>. |
|
|
2598 | |
|
|
2599 | =item D |
|
|
2600 | |
|
|
2601 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2602 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2603 | |
|
|
2604 | =back |
2290 | |
2605 | |
2291 | |
2606 | |
2292 | =head1 MACRO MAGIC |
2607 | =head1 MACRO MAGIC |
2293 | |
2608 | |
2294 | Libev can be compiled with a variety of options, the most fundamantal |
2609 | Libev can be compiled with a variety of options, the most fundamantal |
… | |
… | |
2330 | |
2645 | |
2331 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2646 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2332 | |
2647 | |
2333 | Similar to the other two macros, this gives you the value of the default |
2648 | Similar to the other two macros, this gives you the value of the default |
2334 | loop, if multiple loops are supported ("ev loop default"). |
2649 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2650 | |
|
|
2651 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2652 | |
|
|
2653 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2654 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2655 | is undefined when the default loop has not been initialised by a previous |
|
|
2656 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2657 | |
|
|
2658 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2659 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2335 | |
2660 | |
2336 | =back |
2661 | =back |
2337 | |
2662 | |
2338 | Example: Declare and initialise a check watcher, utilising the above |
2663 | Example: Declare and initialise a check watcher, utilising the above |
2339 | macros so it will work regardless of whether multiple loops are supported |
2664 | macros so it will work regardless of whether multiple loops are supported |
… | |
… | |
2435 | |
2760 | |
2436 | libev.m4 |
2761 | libev.m4 |
2437 | |
2762 | |
2438 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2763 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2439 | |
2764 | |
2440 | Libev can be configured via a variety of preprocessor symbols you have to define |
2765 | Libev can be configured via a variety of preprocessor symbols you have to |
2441 | before including any of its files. The default is not to build for multiplicity |
2766 | define before including any of its files. The default in the absense of |
2442 | and only include the select backend. |
2767 | autoconf is noted for every option. |
2443 | |
2768 | |
2444 | =over 4 |
2769 | =over 4 |
2445 | |
2770 | |
2446 | =item EV_STANDALONE |
2771 | =item EV_STANDALONE |
2447 | |
2772 | |
… | |
… | |
2473 | =item EV_USE_NANOSLEEP |
2798 | =item EV_USE_NANOSLEEP |
2474 | |
2799 | |
2475 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2800 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2476 | and will use it for delays. Otherwise it will use C<select ()>. |
2801 | and will use it for delays. Otherwise it will use C<select ()>. |
2477 | |
2802 | |
|
|
2803 | =item EV_USE_EVENTFD |
|
|
2804 | |
|
|
2805 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2806 | available and will probe for kernel support at runtime. This will improve |
|
|
2807 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2808 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2809 | 2.7 or newer, otherwise disabled. |
|
|
2810 | |
2478 | =item EV_USE_SELECT |
2811 | =item EV_USE_SELECT |
2479 | |
2812 | |
2480 | If undefined or defined to be C<1>, libev will compile in support for the |
2813 | If undefined or defined to be C<1>, libev will compile in support for the |
2481 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2814 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2482 | other method takes over, select will be it. Otherwise the select backend |
2815 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
2518 | |
2851 | |
2519 | =item EV_USE_EPOLL |
2852 | =item EV_USE_EPOLL |
2520 | |
2853 | |
2521 | If defined to be C<1>, libev will compile in support for the Linux |
2854 | If defined to be C<1>, libev will compile in support for the Linux |
2522 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2855 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2523 | otherwise another method will be used as fallback. This is the |
2856 | otherwise another method will be used as fallback. This is the preferred |
2524 | preferred backend for GNU/Linux systems. |
2857 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2858 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2525 | |
2859 | |
2526 | =item EV_USE_KQUEUE |
2860 | =item EV_USE_KQUEUE |
2527 | |
2861 | |
2528 | If defined to be C<1>, libev will compile in support for the BSD style |
2862 | If defined to be C<1>, libev will compile in support for the BSD style |
2529 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2863 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2548 | |
2882 | |
2549 | =item EV_USE_INOTIFY |
2883 | =item EV_USE_INOTIFY |
2550 | |
2884 | |
2551 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2885 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2552 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2886 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2553 | be detected at runtime. |
2887 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2888 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
|
|
2889 | |
|
|
2890 | =item EV_ATOMIC_T |
|
|
2891 | |
|
|
2892 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
|
|
2893 | access is atomic with respect to other threads or signal contexts. No such |
|
|
2894 | type is easily found in the C language, so you can provide your own type |
|
|
2895 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2896 | as well as for signal and thread safety in C<ev_async> watchers. |
|
|
2897 | |
|
|
2898 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
|
|
2899 | (from F<signal.h>), which is usually good enough on most platforms. |
2554 | |
2900 | |
2555 | =item EV_H |
2901 | =item EV_H |
2556 | |
2902 | |
2557 | The name of the F<ev.h> header file used to include it. The default if |
2903 | The name of the F<ev.h> header file used to include it. The default if |
2558 | undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to |
2904 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2559 | virtually rename the F<ev.h> header file in case of conflicts. |
2905 | used to virtually rename the F<ev.h> header file in case of conflicts. |
2560 | |
2906 | |
2561 | =item EV_CONFIG_H |
2907 | =item EV_CONFIG_H |
2562 | |
2908 | |
2563 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2909 | If C<EV_STANDALONE> isn't C<1>, this variable can be used to override |
2564 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2910 | F<ev.c>'s idea of where to find the F<config.h> file, similarly to |
2565 | C<EV_H>, above. |
2911 | C<EV_H>, above. |
2566 | |
2912 | |
2567 | =item EV_EVENT_H |
2913 | =item EV_EVENT_H |
2568 | |
2914 | |
2569 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2915 | Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea |
2570 | of how the F<event.h> header can be found, the dfeault is C<"event.h">. |
2916 | of how the F<event.h> header can be found, the default is C<"event.h">. |
2571 | |
2917 | |
2572 | =item EV_PROTOTYPES |
2918 | =item EV_PROTOTYPES |
2573 | |
2919 | |
2574 | If defined to be C<0>, then F<ev.h> will not define any function |
2920 | If defined to be C<0>, then F<ev.h> will not define any function |
2575 | prototypes, but still define all the structs and other symbols. This is |
2921 | prototypes, but still define all the structs and other symbols. This is |
… | |
… | |
2624 | defined to be C<0>, then they are not. |
2970 | defined to be C<0>, then they are not. |
2625 | |
2971 | |
2626 | =item EV_FORK_ENABLE |
2972 | =item EV_FORK_ENABLE |
2627 | |
2973 | |
2628 | If undefined or defined to be C<1>, then fork watchers are supported. If |
2974 | If undefined or defined to be C<1>, then fork watchers are supported. If |
|
|
2975 | defined to be C<0>, then they are not. |
|
|
2976 | |
|
|
2977 | =item EV_ASYNC_ENABLE |
|
|
2978 | |
|
|
2979 | If undefined or defined to be C<1>, then async watchers are supported. If |
2629 | defined to be C<0>, then they are not. |
2980 | defined to be C<0>, then they are not. |
2630 | |
2981 | |
2631 | =item EV_MINIMAL |
2982 | =item EV_MINIMAL |
2632 | |
2983 | |
2633 | If you need to shave off some kilobytes of code at the expense of some |
2984 | If you need to shave off some kilobytes of code at the expense of some |
… | |
… | |
2729 | |
3080 | |
2730 | #include "ev_cpp.h" |
3081 | #include "ev_cpp.h" |
2731 | #include "ev.c" |
3082 | #include "ev.c" |
2732 | |
3083 | |
2733 | |
3084 | |
|
|
3085 | =head1 THREADS AND COROUTINES |
|
|
3086 | |
|
|
3087 | =head2 THREADS |
|
|
3088 | |
|
|
3089 | Libev itself is completely threadsafe, but it uses no locking. This |
|
|
3090 | means that you can use as many loops as you want in parallel, as long as |
|
|
3091 | only one thread ever calls into one libev function with the same loop |
|
|
3092 | parameter. |
|
|
3093 | |
|
|
3094 | Or put differently: calls with different loop parameters can be done in |
|
|
3095 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3096 | done serially (but can be done from different threads, as long as only one |
|
|
3097 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3098 | per loop). |
|
|
3099 | |
|
|
3100 | If you want to know which design is best for your problem, then I cannot |
|
|
3101 | help you but by giving some generic advice: |
|
|
3102 | |
|
|
3103 | =over 4 |
|
|
3104 | |
|
|
3105 | =item * most applications have a main thread: use the default libev loop |
|
|
3106 | in that thread, or create a seperate thread running only the default loop. |
|
|
3107 | |
|
|
3108 | This helps integrating other libraries or software modules that use libev |
|
|
3109 | themselves and don't care/know about threading. |
|
|
3110 | |
|
|
3111 | =item * one loop per thread is usually a good model. |
|
|
3112 | |
|
|
3113 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3114 | exists, but it is always a good start. |
|
|
3115 | |
|
|
3116 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3117 | loop is handed through multiple threads in a kind of round-robbin fashion. |
|
|
3118 | |
|
|
3119 | Chosing a model is hard - look around, learn, know that usually you cna do |
|
|
3120 | better than you currently do :-) |
|
|
3121 | |
|
|
3122 | =item * often you need to talk to some other thread which blocks in the |
|
|
3123 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3124 | threads safely (or from signal contexts...). |
|
|
3125 | |
|
|
3126 | =back |
|
|
3127 | |
|
|
3128 | =head2 COROUTINES |
|
|
3129 | |
|
|
3130 | Libev is much more accomodating to coroutines ("cooperative threads"): |
|
|
3131 | libev fully supports nesting calls to it's functions from different |
|
|
3132 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3133 | different coroutines and switch freely between both coroutines running the |
|
|
3134 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3135 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3136 | |
|
|
3137 | Care has been invested into making sure that libev does not keep local |
|
|
3138 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3139 | switches. |
|
|
3140 | |
|
|
3141 | |
2734 | =head1 COMPLEXITIES |
3142 | =head1 COMPLEXITIES |
2735 | |
3143 | |
2736 | In this section the complexities of (many of) the algorithms used inside |
3144 | In this section the complexities of (many of) the algorithms used inside |
2737 | libev will be explained. For complexity discussions about backends see the |
3145 | libev will be explained. For complexity discussions about backends see the |
2738 | documentation for C<ev_default_init>. |
3146 | documentation for C<ev_default_init>. |
… | |
… | |
2754 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3162 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2755 | |
3163 | |
2756 | That means that changing a timer costs less than removing/adding them |
3164 | That means that changing a timer costs less than removing/adding them |
2757 | as only the relative motion in the event queue has to be paid for. |
3165 | as only the relative motion in the event queue has to be paid for. |
2758 | |
3166 | |
2759 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
3167 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
2760 | |
3168 | |
2761 | These just add the watcher into an array or at the head of a list. |
3169 | These just add the watcher into an array or at the head of a list. |
2762 | |
3170 | |
2763 | =item Stopping check/prepare/idle watchers: O(1) |
3171 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
2764 | |
3172 | |
2765 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3173 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2766 | |
3174 | |
2767 | These watchers are stored in lists then need to be walked to find the |
3175 | These watchers are stored in lists then need to be walked to find the |
2768 | correct watcher to remove. The lists are usually short (you don't usually |
3176 | correct watcher to remove. The lists are usually short (you don't usually |
… | |
… | |
2784 | =item Priority handling: O(number_of_priorities) |
3192 | =item Priority handling: O(number_of_priorities) |
2785 | |
3193 | |
2786 | Priorities are implemented by allocating some space for each |
3194 | Priorities are implemented by allocating some space for each |
2787 | priority. When doing priority-based operations, libev usually has to |
3195 | priority. When doing priority-based operations, libev usually has to |
2788 | linearly search all the priorities, but starting/stopping and activating |
3196 | linearly search all the priorities, but starting/stopping and activating |
2789 | watchers becomes O(1) w.r.t. prioritiy handling. |
3197 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3198 | |
|
|
3199 | =item Sending an ev_async: O(1) |
|
|
3200 | |
|
|
3201 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3202 | |
|
|
3203 | =item Processing signals: O(max_signal_number) |
|
|
3204 | |
|
|
3205 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
3206 | calls in the current loop iteration. Checking for async and signal events |
|
|
3207 | involves iterating over all running async watchers or all signal numbers. |
2790 | |
3208 | |
2791 | =back |
3209 | =back |
2792 | |
3210 | |
2793 | |
3211 | |
2794 | =head1 Win32 platform limitations and workarounds |
3212 | =head1 Win32 platform limitations and workarounds |
… | |
… | |
2798 | model. Libev still offers limited functionality on this platform in |
3216 | model. Libev still offers limited functionality on this platform in |
2799 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3217 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
2800 | descriptors. This only applies when using Win32 natively, not when using |
3218 | descriptors. This only applies when using Win32 natively, not when using |
2801 | e.g. cygwin. |
3219 | e.g. cygwin. |
2802 | |
3220 | |
|
|
3221 | Lifting these limitations would basically require the full |
|
|
3222 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3223 | things, then note that glib does exactly that for you in a very portable |
|
|
3224 | way (note also that glib is the slowest event library known to man). |
|
|
3225 | |
2803 | There is no supported compilation method available on windows except |
3226 | There is no supported compilation method available on windows except |
2804 | embedding it into other applications. |
3227 | embedding it into other applications. |
2805 | |
3228 | |
2806 | Due to the many, low, and arbitrary limits on the win32 platform and the |
3229 | Due to the many, low, and arbitrary limits on the win32 platform and |
2807 | abysmal performance of winsockets, using a large number of sockets is not |
3230 | the abysmal performance of winsockets, using a large number of sockets |
2808 | recommended (and not reasonable). If your program needs to use more than |
3231 | is not recommended (and not reasonable). If your program needs to use |
2809 | a hundred or so sockets, then likely it needs to use a totally different |
3232 | more than a hundred or so sockets, then likely it needs to use a totally |
2810 | implementation for windows, as libev offers the POSIX model, which cannot |
3233 | different implementation for windows, as libev offers the POSIX readyness |
2811 | be implemented efficiently on windows (microsoft monopoly games). |
3234 | notification model, which cannot be implemented efficiently on windows |
|
|
3235 | (microsoft monopoly games). |
2812 | |
3236 | |
2813 | =over 4 |
3237 | =over 4 |
2814 | |
3238 | |
2815 | =item The winsocket select function |
3239 | =item The winsocket select function |
2816 | |
3240 | |
… | |
… | |
2830 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3254 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
2831 | complexity in the O(n²) range when using win32. |
3255 | complexity in the O(n²) range when using win32. |
2832 | |
3256 | |
2833 | =item Limited number of file descriptors |
3257 | =item Limited number of file descriptors |
2834 | |
3258 | |
2835 | Windows has numerous arbitrary (and low) limits on things. Early versions |
3259 | Windows has numerous arbitrary (and low) limits on things. |
2836 | of winsocket's select only supported waiting for a max. of C<64> handles |
3260 | |
|
|
3261 | Early versions of winsocket's select only supported waiting for a maximum |
2837 | (probably owning to the fact that all windows kernels can only wait for |
3262 | of C<64> handles (probably owning to the fact that all windows kernels |
2838 | C<64> things at the same time internally; microsoft recommends spawning a |
3263 | can only wait for C<64> things at the same time internally; microsoft |
2839 | chain of threads and wait for 63 handles and the previous thread in each). |
3264 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3265 | previous thread in each. Great). |
2840 | |
3266 | |
2841 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3267 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
2842 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3268 | to some high number (e.g. C<2048>) before compiling the winsocket select |
2843 | call (which might be in libev or elsewhere, for example, perl does its own |
3269 | call (which might be in libev or elsewhere, for example, perl does its own |
2844 | select emulation on windows). |
3270 | select emulation on windows). |
… | |
… | |
2856 | calling select (O(n²)) will likely make this unworkable. |
3282 | calling select (O(n²)) will likely make this unworkable. |
2857 | |
3283 | |
2858 | =back |
3284 | =back |
2859 | |
3285 | |
2860 | |
3286 | |
|
|
3287 | =head1 PORTABILITY REQUIREMENTS |
|
|
3288 | |
|
|
3289 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3290 | additional extensions: |
|
|
3291 | |
|
|
3292 | =over 4 |
|
|
3293 | |
|
|
3294 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3295 | |
|
|
3296 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3297 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3298 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3299 | believed to be sufficiently portable. |
|
|
3300 | |
|
|
3301 | =item C<sigprocmask> must work in a threaded environment |
|
|
3302 | |
|
|
3303 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3304 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3305 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3306 | thread" or will block signals process-wide, both behaviours would |
|
|
3307 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3308 | C<pthread_sigmask> could complicate things, however. |
|
|
3309 | |
|
|
3310 | The most portable way to handle signals is to block signals in all threads |
|
|
3311 | except the initial one, and run the default loop in the initial thread as |
|
|
3312 | well. |
|
|
3313 | |
|
|
3314 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3315 | |
|
|
3316 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3317 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3318 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3319 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3320 | millions of watchers. |
|
|
3321 | |
|
|
3322 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3323 | |
|
|
3324 | The type C<double> is used to represent timestamps. It is required to |
|
|
3325 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3326 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3327 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3328 | |
|
|
3329 | =back |
|
|
3330 | |
|
|
3331 | If you know of other additional requirements drop me a note. |
|
|
3332 | |
|
|
3333 | |
2861 | =head1 AUTHOR |
3334 | =head1 AUTHOR |
2862 | |
3335 | |
2863 | Marc Lehmann <libev@schmorp.de>. |
3336 | Marc Lehmann <libev@schmorp.de>. |
2864 | |
3337 | |