… | |
… | |
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 | |
|
|
14 | // every watcher type has its own typedef'd struct |
|
|
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. |
|
|
27 | ev_io_stop (EV_A_ w); |
|
|
28 | |
|
|
29 | // this causes all nested ev_loop's to stop iterating |
|
|
30 | ev_unloop (EV_A_ EVUNLOOP_ALL); |
23 | } |
31 | } |
24 | |
32 | |
|
|
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 |
|
|
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 |
|
|
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 | |
|
|
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 | |
|
|
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://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod>. |
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 |
59 | these event sources and provide your program with events. |
73 | these event sources and provide your program with events. |
60 | |
74 | |
… | |
… | |
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 |
|
|
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 | |
|
|
206 | Since some systems (at least OpenBSD and Darwin) fail to implement |
|
|
207 | correct C<realloc> semantics, libev will use a wrapper around the system |
|
|
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 |
|
|
247 | in your main thread (or in a separate thread) and for each thread you |
|
|
248 | create, you also create another event loop. Libev itself does no locking |
|
|
249 | whatsoever, so if you mix calls to the same event loop in different |
|
|
250 | threads, make sure you lock (this is usually a bad idea, though, even if |
|
|
251 | done correctly, because it's hideous and inefficient). |
|
|
252 | |
|
|
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. |
|
|
275 | |
|
|
276 | Note that this function is I<not> thread-safe, so if you want to use it |
|
|
277 | from multiple threads, you have to lock (note also that this is unlikely, |
|
|
278 | as loops cannot bes hared easily between threads anyway). |
264 | |
279 | |
265 | The default loop is the only loop that can handle C<ev_signal> and |
280 | The default loop is the only loop that can handle C<ev_signal> and |
266 | C<ev_child> watchers, and to do this, it always registers a handler |
281 | C<ev_child> watchers, and to do this, it always registers a handler |
267 | for C<SIGCHLD>. If this is a problem for your app you can either |
282 | for C<SIGCHLD>. If this is a problem for your app you can either |
268 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
283 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
297 | enabling this flag. |
312 | enabling this flag. |
298 | |
313 | |
299 | 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, |
300 | 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 |
301 | 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 |
302 | 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 |
303 | 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 |
304 | C<pthread_atfork> which is even faster). |
319 | C<pthread_atfork> which is even faster). |
305 | |
320 | |
306 | 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 |
307 | 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 |
308 | flag. |
323 | flag. |
… | |
… | |
321 | To get good performance out of this backend you need a high amount of |
336 | To get good performance out of this backend you need a high amount of |
322 | parallelity (most of the file descriptors should be busy). If you are |
337 | parallelity (most of the file descriptors should be busy). If you are |
323 | writing a server, you should C<accept ()> in a loop to accept as many |
338 | writing a server, you should C<accept ()> in a loop to accept as many |
324 | connections as possible during one iteration. You might also want to have |
339 | connections as possible during one iteration. You might also want to have |
325 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
340 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
326 | readyness notifications you get per iteration. |
341 | readiness notifications you get per iteration. |
327 | |
342 | |
328 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
343 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
329 | |
344 | |
330 | And this is your standard poll(2) backend. It's more complicated |
345 | And this is your standard poll(2) backend. It's more complicated |
331 | than select, but handles sparse fds better and has no artificial |
346 | than select, but handles sparse fds better and has no artificial |
… | |
… | |
339 | 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, |
340 | but it scales phenomenally better. While poll and select usually scale |
355 | but it scales phenomenally better. While poll and select usually scale |
341 | 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), |
342 | 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 |
343 | 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 |
344 | 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 |
345 | support for dup. |
360 | support for dup. |
346 | |
361 | |
347 | 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 |
348 | 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 |
349 | (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 |
… | |
… | |
410 | 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 |
411 | 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 |
412 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
427 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
413 | might perform better. |
428 | might perform better. |
414 | |
429 | |
415 | On the positive side, ignoring the spurious readyness notifications, this |
430 | On the positive side, ignoring the spurious readiness notifications, this |
416 | backend actually performed to specification in all tests and is fully |
431 | backend actually performed to specification in all tests and is fully |
417 | embeddable, which is a rare feat among the OS-specific backends. |
432 | embeddable, which is a rare feat among the OS-specific backends. |
418 | |
433 | |
419 | =item C<EVBACKEND_ALL> |
434 | =item C<EVBACKEND_ALL> |
420 | |
435 | |
… | |
… | |
450 | |
465 | |
451 | 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 |
452 | 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 |
453 | 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 |
454 | undefined behaviour (or a failed assertion if assertions are enabled). |
469 | undefined behaviour (or a failed assertion if assertions are enabled). |
|
|
470 | |
|
|
471 | Note that this function I<is> thread-safe, and the recommended way to use |
|
|
472 | libev with threads is indeed to create one loop per thread, and using the |
|
|
473 | default loop in the "main" or "initial" thread. |
455 | |
474 | |
456 | 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. |
457 | |
476 | |
458 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
477 | struct ev_loop *epoller = ev_loop_new (EVBACKEND_EPOLL | EVFLAG_NOENV); |
459 | if (!epoller) |
478 | if (!epoller) |
… | |
… | |
505 | =item ev_loop_fork (loop) |
524 | =item ev_loop_fork (loop) |
506 | |
525 | |
507 | 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 |
508 | 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 |
509 | 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. |
510 | |
533 | |
511 | =item unsigned int ev_loop_count (loop) |
534 | =item unsigned int ev_loop_count (loop) |
512 | |
535 | |
513 | 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 |
514 | 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 |
… | |
… | |
1009 | If you must do this, then force the use of a known-to-be-good backend |
1032 | If you must do this, then force the use of a known-to-be-good backend |
1010 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1033 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
1011 | C<EVBACKEND_POLL>). |
1034 | C<EVBACKEND_POLL>). |
1012 | |
1035 | |
1013 | Another thing you have to watch out for is that it is quite easy to |
1036 | Another thing you have to watch out for is that it is quite easy to |
1014 | receive "spurious" readyness notifications, that is your callback might |
1037 | receive "spurious" readiness notifications, that is your callback might |
1015 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1038 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1016 | because there is no data. Not only are some backends known to create a |
1039 | because there is no data. Not only are some backends known to create a |
1017 | lot of those (for example solaris ports), it is very easy to get into |
1040 | lot of those (for example solaris ports), it is very easy to get into |
1018 | this situation even with a relatively standard program structure. Thus |
1041 | this situation even with a relatively standard program structure. Thus |
1019 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
1042 | it is best to always use non-blocking I/O: An extra C<read>(2) returning |
… | |
… | |
1066 | To support fork in your programs, you either have to call |
1089 | To support fork in your programs, you either have to call |
1067 | 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, |
1068 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1091 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1069 | C<EVBACKEND_POLL>. |
1092 | C<EVBACKEND_POLL>. |
1070 | |
1093 | |
|
|
1094 | =head3 The special problem of SIGPIPE |
|
|
1095 | |
|
|
1096 | While not really specific to libev, it is easy to forget about SIGPIPE: |
|
|
1097 | when reading from a pipe whose other end has been closed, your program |
|
|
1098 | gets send a SIGPIPE, which, by default, aborts your program. For most |
|
|
1099 | programs this is sensible behaviour, for daemons, this is usually |
|
|
1100 | undesirable. |
|
|
1101 | |
|
|
1102 | So when you encounter spurious, unexplained daemon exits, make sure you |
|
|
1103 | ignore SIGPIPE (and maybe make sure you log the exit status of your daemon |
|
|
1104 | somewhere, as that would have given you a big clue). |
|
|
1105 | |
1071 | |
1106 | |
1072 | =head3 Watcher-Specific Functions |
1107 | =head3 Watcher-Specific Functions |
1073 | |
1108 | |
1074 | =over 4 |
1109 | =over 4 |
1075 | |
1110 | |
… | |
… | |
1116 | |
1151 | |
1117 | Timer watchers are simple relative timers that generate an event after a |
1152 | Timer watchers are simple relative timers that generate an event after a |
1118 | given time, and optionally repeating in regular intervals after that. |
1153 | given time, and optionally repeating in regular intervals after that. |
1119 | |
1154 | |
1120 | The timers are based on real time, that is, if you register an event that |
1155 | The timers are based on real time, that is, if you register an event that |
1121 | times out after an hour and you reset your system clock to last years |
1156 | times out after an hour and you reset your system clock to january last |
1122 | time, it will still time out after (roughly) and hour. "Roughly" because |
1157 | year, it will still time out after (roughly) and hour. "Roughly" because |
1123 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1158 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1124 | monotonic clock option helps a lot here). |
1159 | monotonic clock option helps a lot here). |
1125 | |
1160 | |
1126 | The relative timeouts are calculated relative to the C<ev_now ()> |
1161 | The relative timeouts are calculated relative to the C<ev_now ()> |
1127 | time. This is usually the right thing as this timestamp refers to the time |
1162 | time. This is usually the right thing as this timestamp refers to the time |
… | |
… | |
1129 | you suspect event processing to be delayed and you I<need> to base the timeout |
1164 | you suspect event processing to be delayed and you I<need> to base the timeout |
1130 | on the current time, use something like this to adjust for this: |
1165 | on the current time, use something like this to adjust for this: |
1131 | |
1166 | |
1132 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1167 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1133 | |
1168 | |
1134 | The callback is guarenteed to be invoked only when its timeout has passed, |
1169 | The callback is guarenteed to be invoked only after its timeout has passed, |
1135 | but if multiple timers become ready during the same loop iteration then |
1170 | but if multiple timers become ready during the same loop iteration then |
1136 | order of execution is undefined. |
1171 | order of execution is undefined. |
1137 | |
1172 | |
1138 | =head3 Watcher-Specific Functions and Data Members |
1173 | =head3 Watcher-Specific Functions and Data Members |
1139 | |
1174 | |
… | |
… | |
1141 | |
1176 | |
1142 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1177 | =item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) |
1143 | |
1178 | |
1144 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1179 | =item ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat) |
1145 | |
1180 | |
1146 | Configure the timer to trigger after C<after> seconds. If C<repeat> is |
1181 | Configure the timer to trigger after C<after> seconds. If C<repeat> |
1147 | C<0.>, then it will automatically be stopped. If it is positive, then the |
1182 | is C<0.>, then it will automatically be stopped once the timeout is |
1148 | timer will automatically be configured to trigger again C<repeat> seconds |
1183 | reached. If it is positive, then the timer will automatically be |
1149 | later, again, and again, until stopped manually. |
1184 | configured to trigger again C<repeat> seconds later, again, and again, |
|
|
1185 | until stopped manually. |
1150 | |
1186 | |
1151 | The timer itself will do a best-effort at avoiding drift, that is, if you |
1187 | The timer itself will do a best-effort at avoiding drift, that is, if |
1152 | configure a timer to trigger every 10 seconds, then it will trigger at |
1188 | you configure a timer to trigger every 10 seconds, then it will normally |
1153 | exactly 10 second intervals. If, however, your program cannot keep up with |
1189 | trigger at exactly 10 second intervals. If, however, your program cannot |
1154 | the timer (because it takes longer than those 10 seconds to do stuff) the |
1190 | keep up with the timer (because it takes longer than those 10 seconds to |
1155 | timer will not fire more than once per event loop iteration. |
1191 | do stuff) the timer will not fire more than once per event loop iteration. |
1156 | |
1192 | |
1157 | =item ev_timer_again (loop) |
1193 | =item ev_timer_again (loop, ev_timer *) |
1158 | |
1194 | |
1159 | This will act as if the timer timed out and restart it again if it is |
1195 | This will act as if the timer timed out and restart it again if it is |
1160 | repeating. The exact semantics are: |
1196 | repeating. The exact semantics are: |
1161 | |
1197 | |
1162 | If the timer is pending, its pending status is cleared. |
1198 | If the timer is pending, its pending status is cleared. |
… | |
… | |
1237 | Periodic watchers are also timers of a kind, but they are very versatile |
1273 | Periodic watchers are also timers of a kind, but they are very versatile |
1238 | (and unfortunately a bit complex). |
1274 | (and unfortunately a bit complex). |
1239 | |
1275 | |
1240 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1276 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1241 | but on wallclock time (absolute time). You can tell a periodic watcher |
1277 | but on wallclock time (absolute time). You can tell a periodic watcher |
1242 | to trigger "at" some specific point in time. For example, if you tell a |
1278 | to trigger after some specific point in time. For example, if you tell a |
1243 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1279 | periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () |
1244 | + 10.>) and then reset your system clock to the last year, then it will |
1280 | + 10.>, that is, an absolute time not a delay) and then reset your system |
|
|
1281 | clock to january of the previous year, then it will take more than year |
1245 | take a year to trigger the event (unlike an C<ev_timer>, which would trigger |
1282 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
1246 | roughly 10 seconds later). |
1283 | roughly 10 seconds later as it uses a relative timeout). |
1247 | |
1284 | |
1248 | They can also be used to implement vastly more complex timers, such as |
1285 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1249 | triggering an event on each midnight, local time or other, complicated, |
1286 | such as triggering an event on each "midnight, local time", or other |
1250 | rules. |
1287 | complicated, rules. |
1251 | |
1288 | |
1252 | As with timers, the callback is guarenteed to be invoked only when the |
1289 | As with timers, the callback is guarenteed to be invoked only when the |
1253 | time (C<at>) has been passed, but if multiple periodic timers become ready |
1290 | time (C<at>) has passed, but if multiple periodic timers become ready |
1254 | during the same loop iteration then order of execution is undefined. |
1291 | during the same loop iteration then order of execution is undefined. |
1255 | |
1292 | |
1256 | =head3 Watcher-Specific Functions and Data Members |
1293 | =head3 Watcher-Specific Functions and Data Members |
1257 | |
1294 | |
1258 | =over 4 |
1295 | =over 4 |
… | |
… | |
1266 | |
1303 | |
1267 | =over 4 |
1304 | =over 4 |
1268 | |
1305 | |
1269 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1306 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1270 | |
1307 | |
1271 | In this configuration the watcher triggers an event at the wallclock time |
1308 | In this configuration the watcher triggers an event after the wallclock |
1272 | C<at> and doesn't repeat. It will not adjust when a time jump occurs, |
1309 | time C<at> has passed and doesn't repeat. It will not adjust when a time |
1273 | that is, if it is to be run at January 1st 2011 then it will run when the |
1310 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1274 | system time reaches or surpasses this time. |
1311 | run when the system time reaches or surpasses this time. |
1275 | |
1312 | |
1276 | =item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1313 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1277 | |
1314 | |
1278 | In this mode the watcher will always be scheduled to time out at the next |
1315 | In this mode the watcher will always be scheduled to time out at the next |
1279 | C<at + N * interval> time (for some integer N, which can also be negative) |
1316 | C<at + N * interval> time (for some integer N, which can also be negative) |
1280 | and then repeat, regardless of any time jumps. |
1317 | and then repeat, regardless of any time jumps. |
1281 | |
1318 | |
1282 | This can be used to create timers that do not drift with respect to system |
1319 | This can be used to create timers that do not drift with respect to system |
1283 | time: |
1320 | time, for example, here is a C<ev_periodic> that triggers each hour, on |
|
|
1321 | the hour: |
1284 | |
1322 | |
1285 | ev_periodic_set (&periodic, 0., 3600., 0); |
1323 | ev_periodic_set (&periodic, 0., 3600., 0); |
1286 | |
1324 | |
1287 | This doesn't mean there will always be 3600 seconds in between triggers, |
1325 | This doesn't mean there will always be 3600 seconds in between triggers, |
1288 | but only that the the callback will be called when the system time shows a |
1326 | but only that the the callback will be called when the system time shows a |
… | |
… | |
1293 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1331 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1294 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1332 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1295 | |
1333 | |
1296 | For numerical stability it is preferable that the C<at> value is near |
1334 | For numerical stability it is preferable that the C<at> value is near |
1297 | C<ev_now ()> (the current time), but there is no range requirement for |
1335 | C<ev_now ()> (the current time), but there is no range requirement for |
1298 | this value. |
1336 | this value, and in fact is often specified as zero. |
|
|
1337 | |
|
|
1338 | Note also that there is an upper limit to how often a timer can fire (cpu |
|
|
1339 | speed for example), so if C<interval> is very small then timing stability |
|
|
1340 | will of course detoriate. Libev itself tries to be exact to be about one |
|
|
1341 | millisecond (if the OS supports it and the machine is fast enough). |
1299 | |
1342 | |
1300 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1343 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1301 | |
1344 | |
1302 | In this mode the values for C<interval> and C<at> are both being |
1345 | In this mode the values for C<interval> and C<at> are both being |
1303 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1346 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1304 | reschedule callback will be called with the watcher as first, and the |
1347 | reschedule callback will be called with the watcher as first, and the |
1305 | current time as second argument. |
1348 | current time as second argument. |
1306 | |
1349 | |
1307 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1350 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1308 | ever, or make any event loop modifications>. If you need to stop it, |
1351 | ever, or make ANY event loop modifications whatsoever>. |
1309 | return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by |
|
|
1310 | starting an C<ev_prepare> watcher, which is legal). |
|
|
1311 | |
1352 | |
|
|
1353 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
|
|
1354 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
|
|
1355 | only event loop modification you are allowed to do). |
|
|
1356 | |
1312 | Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, |
1357 | The callback prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic |
1313 | ev_tstamp now)>, e.g.: |
1358 | *w, ev_tstamp now)>, e.g.: |
1314 | |
1359 | |
1315 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1360 | static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) |
1316 | { |
1361 | { |
1317 | return now + 60.; |
1362 | return now + 60.; |
1318 | } |
1363 | } |
… | |
… | |
1320 | It must return the next time to trigger, based on the passed time value |
1365 | It must return the next time to trigger, based on the passed time value |
1321 | (that is, the lowest time value larger than to the second argument). It |
1366 | (that is, the lowest time value larger than to the second argument). It |
1322 | will usually be called just before the callback will be triggered, but |
1367 | will usually be called just before the callback will be triggered, but |
1323 | might be called at other times, too. |
1368 | might be called at other times, too. |
1324 | |
1369 | |
1325 | NOTE: I<< This callback must always return a time that is later than the |
1370 | NOTE: I<< This callback must always return a time that is higher than or |
1326 | passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger. |
1371 | equal to the passed C<now> value >>. |
1327 | |
1372 | |
1328 | This can be used to create very complex timers, such as a timer that |
1373 | This can be used to create very complex timers, such as a timer that |
1329 | triggers on each midnight, local time. To do this, you would calculate the |
1374 | triggers on "next midnight, local time". To do this, you would calculate the |
1330 | next midnight after C<now> and return the timestamp value for this. How |
1375 | next midnight after C<now> and return the timestamp value for this. How |
1331 | you do this is, again, up to you (but it is not trivial, which is the main |
1376 | you do this is, again, up to you (but it is not trivial, which is the main |
1332 | reason I omitted it as an example). |
1377 | reason I omitted it as an example). |
1333 | |
1378 | |
1334 | =back |
1379 | =back |
… | |
… | |
1338 | Simply stops and restarts the periodic watcher again. This is only useful |
1383 | Simply stops and restarts the periodic watcher again. This is only useful |
1339 | when you changed some parameters or the reschedule callback would return |
1384 | when you changed some parameters or the reschedule callback would return |
1340 | a different time than the last time it was called (e.g. in a crond like |
1385 | a different time than the last time it was called (e.g. in a crond like |
1341 | program when the crontabs have changed). |
1386 | program when the crontabs have changed). |
1342 | |
1387 | |
|
|
1388 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1389 | |
|
|
1390 | When active, returns the absolute time that the watcher is supposed to |
|
|
1391 | trigger next. |
|
|
1392 | |
1343 | =item ev_tstamp offset [read-write] |
1393 | =item ev_tstamp offset [read-write] |
1344 | |
1394 | |
1345 | When repeating, this contains the offset value, otherwise this is the |
1395 | When repeating, this contains the offset value, otherwise this is the |
1346 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1396 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1347 | |
1397 | |
… | |
… | |
1357 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1407 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1358 | |
1408 | |
1359 | The current reschedule callback, or C<0>, if this functionality is |
1409 | The current reschedule callback, or C<0>, if this functionality is |
1360 | switched off. Can be changed any time, but changes only take effect when |
1410 | switched off. Can be changed any time, but changes only take effect when |
1361 | the periodic timer fires or C<ev_periodic_again> is being called. |
1411 | the periodic timer fires or C<ev_periodic_again> is being called. |
1362 | |
|
|
1363 | =item ev_tstamp at [read-only] |
|
|
1364 | |
|
|
1365 | When active, contains the absolute time that the watcher is supposed to |
|
|
1366 | trigger next. |
|
|
1367 | |
1412 | |
1368 | =back |
1413 | =back |
1369 | |
1414 | |
1370 | =head3 Examples |
1415 | =head3 Examples |
1371 | |
1416 | |
… | |
… | |
1415 | with the kernel (thus it coexists with your own signal handlers as long |
1460 | with the kernel (thus it coexists with your own signal handlers as long |
1416 | as you don't register any with libev). Similarly, when the last signal |
1461 | as you don't register any with libev). Similarly, when the last signal |
1417 | watcher for a signal is stopped libev will reset the signal handler to |
1462 | watcher for a signal is stopped libev will reset the signal handler to |
1418 | SIG_DFL (regardless of what it was set to before). |
1463 | SIG_DFL (regardless of what it was set to before). |
1419 | |
1464 | |
|
|
1465 | If possible and supported, libev will install its handlers with |
|
|
1466 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
|
|
1467 | interrupted. If you have a problem with syscalls getting interrupted by |
|
|
1468 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1469 | them in an C<ev_prepare> watcher. |
|
|
1470 | |
1420 | =head3 Watcher-Specific Functions and Data Members |
1471 | =head3 Watcher-Specific Functions and Data Members |
1421 | |
1472 | |
1422 | =over 4 |
1473 | =over 4 |
1423 | |
1474 | |
1424 | =item ev_signal_init (ev_signal *, callback, int signum) |
1475 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
1432 | |
1483 | |
1433 | The signal the watcher watches out for. |
1484 | The signal the watcher watches out for. |
1434 | |
1485 | |
1435 | =back |
1486 | =back |
1436 | |
1487 | |
|
|
1488 | =head3 Examples |
|
|
1489 | |
|
|
1490 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
|
|
1491 | |
|
|
1492 | static void |
|
|
1493 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
|
|
1494 | { |
|
|
1495 | ev_unloop (loop, EVUNLOOP_ALL); |
|
|
1496 | } |
|
|
1497 | |
|
|
1498 | struct ev_signal signal_watcher; |
|
|
1499 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
|
|
1500 | ev_signal_start (loop, &sigint_cb); |
|
|
1501 | |
1437 | |
1502 | |
1438 | =head2 C<ev_child> - watch out for process status changes |
1503 | =head2 C<ev_child> - watch out for process status changes |
1439 | |
1504 | |
1440 | Child watchers trigger when your process receives a SIGCHLD in response to |
1505 | Child watchers trigger when your process receives a SIGCHLD in response to |
1441 | some child status changes (most typically when a child of yours dies). |
1506 | some child status changes (most typically when a child of yours dies). It |
|
|
1507 | is permissible to install a child watcher I<after> the child has been |
|
|
1508 | forked (which implies it might have already exited), as long as the event |
|
|
1509 | loop isn't entered (or is continued from a watcher). |
|
|
1510 | |
|
|
1511 | Only the default event loop is capable of handling signals, and therefore |
|
|
1512 | you can only rgeister child watchers in the default event loop. |
|
|
1513 | |
|
|
1514 | =head3 Process Interaction |
|
|
1515 | |
|
|
1516 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1517 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1518 | the first child watcher is started after the child exits. The occurance |
|
|
1519 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1520 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1521 | children, even ones not watched. |
|
|
1522 | |
|
|
1523 | =head3 Overriding the Built-In Processing |
|
|
1524 | |
|
|
1525 | Libev offers no special support for overriding the built-in child |
|
|
1526 | processing, but if your application collides with libev's default child |
|
|
1527 | handler, you can override it easily by installing your own handler for |
|
|
1528 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1529 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1530 | event-based approach to child reaping and thus use libev's support for |
|
|
1531 | that, so other libev users can use C<ev_child> watchers freely. |
1442 | |
1532 | |
1443 | =head3 Watcher-Specific Functions and Data Members |
1533 | =head3 Watcher-Specific Functions and Data Members |
1444 | |
1534 | |
1445 | =over 4 |
1535 | =over 4 |
1446 | |
1536 | |
… | |
… | |
1472 | |
1562 | |
1473 | =back |
1563 | =back |
1474 | |
1564 | |
1475 | =head3 Examples |
1565 | =head3 Examples |
1476 | |
1566 | |
1477 | Example: Try to exit cleanly on SIGINT and SIGTERM. |
1567 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1568 | its completion. |
|
|
1569 | |
|
|
1570 | ev_child cw; |
1478 | |
1571 | |
1479 | static void |
1572 | static void |
1480 | sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) |
1573 | child_cb (EV_P_ struct ev_child *w, int revents) |
1481 | { |
1574 | { |
1482 | ev_unloop (loop, EVUNLOOP_ALL); |
1575 | ev_child_stop (EV_A_ w); |
|
|
1576 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
1483 | } |
1577 | } |
1484 | |
1578 | |
1485 | struct ev_signal signal_watcher; |
1579 | pid_t pid = fork (); |
1486 | ev_signal_init (&signal_watcher, sigint_cb, SIGINT); |
1580 | |
1487 | ev_signal_start (loop, &sigint_cb); |
1581 | if (pid < 0) |
|
|
1582 | // error |
|
|
1583 | else if (pid == 0) |
|
|
1584 | { |
|
|
1585 | // the forked child executes here |
|
|
1586 | exit (1); |
|
|
1587 | } |
|
|
1588 | else |
|
|
1589 | { |
|
|
1590 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1591 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1592 | } |
1488 | |
1593 | |
1489 | |
1594 | |
1490 | =head2 C<ev_stat> - did the file attributes just change? |
1595 | =head2 C<ev_stat> - did the file attributes just change? |
1491 | |
1596 | |
1492 | This watches a filesystem path for attribute changes. That is, it calls |
1597 | This watches a filesystem path for attribute changes. That is, it calls |
… | |
… | |
1515 | as even with OS-supported change notifications, this can be |
1620 | as even with OS-supported change notifications, this can be |
1516 | resource-intensive. |
1621 | resource-intensive. |
1517 | |
1622 | |
1518 | At the time of this writing, only the Linux inotify interface is |
1623 | At the time of this writing, only the Linux inotify interface is |
1519 | implemented (implementing kqueue support is left as an exercise for the |
1624 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1625 | reader, note, however, that the author sees no way of implementing ev_stat |
1520 | reader). Inotify will be used to give hints only and should not change the |
1626 | semantics with kqueue). Inotify will be used to give hints only and should |
1521 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1627 | not change the semantics of C<ev_stat> watchers, which means that libev |
1522 | to fall back to regular polling again even with inotify, but changes are |
1628 | sometimes needs to fall back to regular polling again even with inotify, |
1523 | usually detected immediately, and if the file exists there will be no |
1629 | but changes are usually detected immediately, and if the file exists there |
1524 | polling. |
1630 | will be no polling. |
|
|
1631 | |
|
|
1632 | =head3 ABI Issues (Largefile Support) |
|
|
1633 | |
|
|
1634 | Libev by default (unless the user overrides this) uses the default |
|
|
1635 | compilation environment, which means that on systems with optionally |
|
|
1636 | disabled large file support, you get the 32 bit version of the stat |
|
|
1637 | structure. When using the library from programs that change the ABI to |
|
|
1638 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1639 | compile libev with the same flags to get binary compatibility. This is |
|
|
1640 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1641 | most noticably with ev_stat and largefile support. |
1525 | |
1642 | |
1526 | =head3 Inotify |
1643 | =head3 Inotify |
1527 | |
1644 | |
1528 | When C<inotify (7)> support has been compiled into libev (generally only |
1645 | When C<inotify (7)> support has been compiled into libev (generally only |
1529 | available on Linux) and present at runtime, it will be used to speed up |
1646 | available on Linux) and present at runtime, it will be used to speed up |
1530 | change detection where possible. The inotify descriptor will be created lazily |
1647 | change detection where possible. The inotify descriptor will be created lazily |
1531 | when the first C<ev_stat> watcher is being started. |
1648 | when the first C<ev_stat> watcher is being started. |
1532 | |
1649 | |
1533 | Inotify presense does not change the semantics of C<ev_stat> watchers |
1650 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1534 | except that changes might be detected earlier, and in some cases, to avoid |
1651 | except that changes might be detected earlier, and in some cases, to avoid |
1535 | making regular C<stat> calls. Even in the presense of inotify support |
1652 | making regular C<stat> calls. Even in the presence of inotify support |
1536 | there are many cases where libev has to resort to regular C<stat> polling. |
1653 | there are many cases where libev has to resort to regular C<stat> polling. |
1537 | |
1654 | |
1538 | (There is no support for kqueue, as apparently it cannot be used to |
1655 | (There is no support for kqueue, as apparently it cannot be used to |
1539 | implement this functionality, due to the requirement of having a file |
1656 | implement this functionality, due to the requirement of having a file |
1540 | descriptor open on the object at all times). |
1657 | descriptor open on the object at all times). |
… | |
… | |
1543 | |
1660 | |
1544 | The C<stat ()> syscall only supports full-second resolution portably, and |
1661 | The C<stat ()> syscall only supports full-second resolution portably, and |
1545 | even on systems where the resolution is higher, many filesystems still |
1662 | even on systems where the resolution is higher, many filesystems still |
1546 | only support whole seconds. |
1663 | only support whole seconds. |
1547 | |
1664 | |
1548 | That means that, if the time is the only thing that changes, you might |
1665 | That means that, if the time is the only thing that changes, you can |
1549 | miss updates: on the first update, C<ev_stat> detects a change and calls |
1666 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1550 | your callback, which does something. When there is another update within |
1667 | calls your callback, which does something. When there is another update |
1551 | the same second, C<ev_stat> will be unable to detect it. |
1668 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1669 | data does not change. |
1552 | |
1670 | |
1553 | The solution to this is to delay acting on a change for a second (or till |
1671 | The solution to this is to delay acting on a change for slightly more |
1554 | the next second boundary), using a roughly one-second delay C<ev_timer> |
1672 | than a second (or till slightly after the next full second boundary), using |
1555 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
1673 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1556 | is added to work around small timing inconsistencies of some operating |
1674 | ev_timer_again (loop, w)>). |
1557 | systems. |
1675 | |
|
|
1676 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1677 | of some operating systems (where the second counter of the current time |
|
|
1678 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1679 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1680 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1681 | update file times then there will be a small window where the kernel uses |
|
|
1682 | the previous second to update file times but libev might already execute |
|
|
1683 | the timer callback). |
1558 | |
1684 | |
1559 | =head3 Watcher-Specific Functions and Data Members |
1685 | =head3 Watcher-Specific Functions and Data Members |
1560 | |
1686 | |
1561 | =over 4 |
1687 | =over 4 |
1562 | |
1688 | |
… | |
… | |
1568 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1694 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1569 | be detected and should normally be specified as C<0> to let libev choose |
1695 | be detected and should normally be specified as C<0> to let libev choose |
1570 | a suitable value. The memory pointed to by C<path> must point to the same |
1696 | a suitable value. The memory pointed to by C<path> must point to the same |
1571 | path for as long as the watcher is active. |
1697 | path for as long as the watcher is active. |
1572 | |
1698 | |
1573 | The callback will be receive C<EV_STAT> when a change was detected, |
1699 | The callback will receive C<EV_STAT> when a change was detected, relative |
1574 | relative to the attributes at the time the watcher was started (or the |
1700 | to the attributes at the time the watcher was started (or the last change |
1575 | last change was detected). |
1701 | was detected). |
1576 | |
1702 | |
1577 | =item ev_stat_stat (ev_stat *) |
1703 | =item ev_stat_stat (loop, ev_stat *) |
1578 | |
1704 | |
1579 | Updates the stat buffer immediately with new values. If you change the |
1705 | Updates the stat buffer immediately with new values. If you change the |
1580 | watched path in your callback, you could call this fucntion to avoid |
1706 | watched path in your callback, you could call this function to avoid |
1581 | detecting this change (while introducing a race condition). Can also be |
1707 | detecting this change (while introducing a race condition if you are not |
1582 | useful simply to find out the new values. |
1708 | the only one changing the path). Can also be useful simply to find out the |
|
|
1709 | new values. |
1583 | |
1710 | |
1584 | =item ev_statdata attr [read-only] |
1711 | =item ev_statdata attr [read-only] |
1585 | |
1712 | |
1586 | The most-recently detected attributes of the file. Although the type is of |
1713 | The most-recently detected attributes of the file. Although the type is |
1587 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1714 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1588 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
1715 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1716 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1589 | was some error while C<stat>ing the file. |
1717 | some error while C<stat>ing the file. |
1590 | |
1718 | |
1591 | =item ev_statdata prev [read-only] |
1719 | =item ev_statdata prev [read-only] |
1592 | |
1720 | |
1593 | The previous attributes of the file. The callback gets invoked whenever |
1721 | The previous attributes of the file. The callback gets invoked whenever |
1594 | C<prev> != C<attr>. |
1722 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1723 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1724 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1595 | |
1725 | |
1596 | =item ev_tstamp interval [read-only] |
1726 | =item ev_tstamp interval [read-only] |
1597 | |
1727 | |
1598 | The specified interval. |
1728 | The specified interval. |
1599 | |
1729 | |
… | |
… | |
1653 | } |
1783 | } |
1654 | |
1784 | |
1655 | ... |
1785 | ... |
1656 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1786 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1657 | ev_stat_start (loop, &passwd); |
1787 | ev_stat_start (loop, &passwd); |
1658 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1788 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1659 | |
1789 | |
1660 | |
1790 | |
1661 | =head2 C<ev_idle> - when you've got nothing better to do... |
1791 | =head2 C<ev_idle> - when you've got nothing better to do... |
1662 | |
1792 | |
1663 | Idle watchers trigger events when no other events of the same or higher |
1793 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1751 | |
1881 | |
1752 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1882 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1753 | priority, to ensure that they are being run before any other watchers |
1883 | priority, to ensure that they are being run before any other watchers |
1754 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1884 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1755 | too) should not activate ("feed") events into libev. While libev fully |
1885 | too) should not activate ("feed") events into libev. While libev fully |
1756 | supports this, they will be called before other C<ev_check> watchers |
1886 | supports this, they might get executed before other C<ev_check> watchers |
1757 | did their job. As C<ev_check> watchers are often used to embed other |
1887 | did their job. As C<ev_check> watchers are often used to embed other |
1758 | (non-libev) event loops those other event loops might be in an unusable |
1888 | (non-libev) event loops those other event loops might be in an unusable |
1759 | state until their C<ev_check> watcher ran (always remind yourself to |
1889 | state until their C<ev_check> watcher ran (always remind yourself to |
1760 | coexist peacefully with others). |
1890 | coexist peacefully with others). |
1761 | |
1891 | |
… | |
… | |
1776 | =head3 Examples |
1906 | =head3 Examples |
1777 | |
1907 | |
1778 | There are a number of principal ways to embed other event loops or modules |
1908 | There are a number of principal ways to embed other event loops or modules |
1779 | into libev. Here are some ideas on how to include libadns into libev |
1909 | into libev. Here are some ideas on how to include libadns into libev |
1780 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1910 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1781 | use for an actually working example. Another Perl module named C<EV::Glib> |
1911 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1782 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
1912 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1783 | into the Glib event loop). |
1913 | Glib event loop). |
1784 | |
1914 | |
1785 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1915 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1786 | and in a check watcher, destroy them and call into libadns. What follows |
1916 | and in a check watcher, destroy them and call into libadns. What follows |
1787 | is pseudo-code only of course. This requires you to either use a low |
1917 | is pseudo-code only of course. This requires you to either use a low |
1788 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1918 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
… | |
… | |
2078 | is that the author does not know of a simple (or any) algorithm for a |
2208 | is that the author does not know of a simple (or any) algorithm for a |
2079 | multiple-writer-single-reader queue that works in all cases and doesn't |
2209 | multiple-writer-single-reader queue that works in all cases and doesn't |
2080 | need elaborate support such as pthreads. |
2210 | need elaborate support such as pthreads. |
2081 | |
2211 | |
2082 | That means that if you want to queue data, you have to provide your own |
2212 | That means that if you want to queue data, you have to provide your own |
2083 | queue. And here is how you would implement locking: |
2213 | queue. But at least I can tell you would implement locking around your |
|
|
2214 | queue: |
2084 | |
2215 | |
2085 | =over 4 |
2216 | =over 4 |
2086 | |
2217 | |
2087 | =item queueing from a signal handler context |
2218 | =item queueing from a signal handler context |
2088 | |
2219 | |
… | |
… | |
2097 | { |
2228 | { |
2098 | sometype data; |
2229 | sometype data; |
2099 | |
2230 | |
2100 | // no locking etc. |
2231 | // no locking etc. |
2101 | queue_put (data); |
2232 | queue_put (data); |
2102 | ev_async_send (DEFAULT_ &mysig); |
2233 | ev_async_send (EV_DEFAULT_ &mysig); |
2103 | } |
2234 | } |
2104 | |
2235 | |
2105 | static void |
2236 | static void |
2106 | mysig_cb (EV_P_ ev_async *w, int revents) |
2237 | mysig_cb (EV_P_ ev_async *w, int revents) |
2107 | { |
2238 | { |
… | |
… | |
2125 | |
2256 | |
2126 | =item queueing from a thread context |
2257 | =item queueing from a thread context |
2127 | |
2258 | |
2128 | The strategy for threads is different, as you cannot (easily) block |
2259 | The strategy for threads is different, as you cannot (easily) block |
2129 | threads but you can easily preempt them, so to queue safely you need to |
2260 | threads but you can easily preempt them, so to queue safely you need to |
2130 | emply a traditional mutex lock, such as in this pthread example: |
2261 | employ a traditional mutex lock, such as in this pthread example: |
2131 | |
2262 | |
2132 | static ev_async mysig; |
2263 | static ev_async mysig; |
2133 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2264 | static pthread_mutex_t mymutex = PTHREAD_MUTEX_INITIALIZER; |
2134 | |
2265 | |
2135 | static void |
2266 | static void |
… | |
… | |
2138 | // only need to lock the actual queueing operation |
2269 | // only need to lock the actual queueing operation |
2139 | pthread_mutex_lock (&mymutex); |
2270 | pthread_mutex_lock (&mymutex); |
2140 | queue_put (data); |
2271 | queue_put (data); |
2141 | pthread_mutex_unlock (&mymutex); |
2272 | pthread_mutex_unlock (&mymutex); |
2142 | |
2273 | |
2143 | ev_async_send (DEFAULT_ &mysig); |
2274 | ev_async_send (EV_DEFAULT_ &mysig); |
2144 | } |
2275 | } |
2145 | |
2276 | |
2146 | static void |
2277 | static void |
2147 | mysig_cb (EV_P_ ev_async *w, int revents) |
2278 | mysig_cb (EV_P_ ev_async *w, int revents) |
2148 | { |
2279 | { |
… | |
… | |
2176 | section below on what exactly this means). |
2307 | section below on what exactly this means). |
2177 | |
2308 | |
2178 | This call incurs the overhead of a syscall only once per loop iteration, |
2309 | This call incurs the overhead of a syscall only once per loop iteration, |
2179 | so while the overhead might be noticable, it doesn't apply to repeated |
2310 | so while the overhead might be noticable, it doesn't apply to repeated |
2180 | calls to C<ev_async_send>. |
2311 | calls to C<ev_async_send>. |
|
|
2312 | |
|
|
2313 | =item bool = ev_async_pending (ev_async *) |
|
|
2314 | |
|
|
2315 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2316 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2317 | event loop. |
|
|
2318 | |
|
|
2319 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2320 | the loop iterates next and checks for the watcher to have become active, |
|
|
2321 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2322 | quickly check wether invoking the loop might be a good idea. |
|
|
2323 | |
|
|
2324 | Not that this does I<not> check wether the watcher itself is pending, only |
|
|
2325 | wether it has been requested to make this watcher pending. |
2181 | |
2326 | |
2182 | =back |
2327 | =back |
2183 | |
2328 | |
2184 | |
2329 | |
2185 | =head1 OTHER FUNCTIONS |
2330 | =head1 OTHER FUNCTIONS |
… | |
… | |
2257 | |
2402 | |
2258 | =item * Priorities are not currently supported. Initialising priorities |
2403 | =item * Priorities are not currently supported. Initialising priorities |
2259 | will fail and all watchers will have the same priority, even though there |
2404 | will fail and all watchers will have the same priority, even though there |
2260 | is an ev_pri field. |
2405 | is an ev_pri field. |
2261 | |
2406 | |
|
|
2407 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2408 | first base created (== the default loop) gets the signals. |
|
|
2409 | |
2262 | =item * Other members are not supported. |
2410 | =item * Other members are not supported. |
2263 | |
2411 | |
2264 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2412 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2265 | to use the libev header file and library. |
2413 | to use the libev header file and library. |
2266 | |
2414 | |
… | |
… | |
2429 | io.start (fd, ev::READ); |
2577 | io.start (fd, ev::READ); |
2430 | } |
2578 | } |
2431 | }; |
2579 | }; |
2432 | |
2580 | |
2433 | |
2581 | |
|
|
2582 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2583 | |
|
|
2584 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2585 | numbe rof languages exist in the form of third-party packages. If you know |
|
|
2586 | any interesting language binding in addition to the ones listed here, drop |
|
|
2587 | me a note. |
|
|
2588 | |
|
|
2589 | =over 4 |
|
|
2590 | |
|
|
2591 | =item Perl |
|
|
2592 | |
|
|
2593 | The EV module implements the full libev API and is actually used to test |
|
|
2594 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2595 | there are additional modules that implement libev-compatible interfaces |
|
|
2596 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2597 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2598 | |
|
|
2599 | It can be found and installed via CPAN, its homepage is found at |
|
|
2600 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2601 | |
|
|
2602 | =item Ruby |
|
|
2603 | |
|
|
2604 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2605 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
|
|
2606 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2607 | L<http://rev.rubyforge.org/>. |
|
|
2608 | |
|
|
2609 | =item D |
|
|
2610 | |
|
|
2611 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2612 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2613 | |
|
|
2614 | =back |
|
|
2615 | |
|
|
2616 | |
2434 | =head1 MACRO MAGIC |
2617 | =head1 MACRO MAGIC |
2435 | |
2618 | |
2436 | Libev can be compiled with a variety of options, the most fundamantal |
2619 | Libev can be compiled with a variety of options, the most fundamantal |
2437 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2620 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2438 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2621 | functions and callbacks have an initial C<struct ev_loop *> argument. |
… | |
… | |
2472 | |
2655 | |
2473 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2656 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2474 | |
2657 | |
2475 | Similar to the other two macros, this gives you the value of the default |
2658 | Similar to the other two macros, this gives you the value of the default |
2476 | loop, if multiple loops are supported ("ev loop default"). |
2659 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2660 | |
|
|
2661 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2662 | |
|
|
2663 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2664 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2665 | is undefined when the default loop has not been initialised by a previous |
|
|
2666 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2667 | |
|
|
2668 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2669 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2477 | |
2670 | |
2478 | =back |
2671 | =back |
2479 | |
2672 | |
2480 | Example: Declare and initialise a check watcher, utilising the above |
2673 | Example: Declare and initialise a check watcher, utilising the above |
2481 | macros so it will work regardless of whether multiple loops are supported |
2674 | macros so it will work regardless of whether multiple loops are supported |
… | |
… | |
2577 | |
2770 | |
2578 | libev.m4 |
2771 | libev.m4 |
2579 | |
2772 | |
2580 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2773 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2581 | |
2774 | |
2582 | Libev can be configured via a variety of preprocessor symbols you have to define |
2775 | Libev can be configured via a variety of preprocessor symbols you have to |
2583 | before including any of its files. The default is not to build for multiplicity |
2776 | define before including any of its files. The default in the absense of |
2584 | and only include the select backend. |
2777 | autoconf is noted for every option. |
2585 | |
2778 | |
2586 | =over 4 |
2779 | =over 4 |
2587 | |
2780 | |
2588 | =item EV_STANDALONE |
2781 | =item EV_STANDALONE |
2589 | |
2782 | |
… | |
… | |
2615 | =item EV_USE_NANOSLEEP |
2808 | =item EV_USE_NANOSLEEP |
2616 | |
2809 | |
2617 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2810 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2618 | and will use it for delays. Otherwise it will use C<select ()>. |
2811 | and will use it for delays. Otherwise it will use C<select ()>. |
2619 | |
2812 | |
|
|
2813 | =item EV_USE_EVENTFD |
|
|
2814 | |
|
|
2815 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2816 | available and will probe for kernel support at runtime. This will improve |
|
|
2817 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2818 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2819 | 2.7 or newer, otherwise disabled. |
|
|
2820 | |
2620 | =item EV_USE_SELECT |
2821 | =item EV_USE_SELECT |
2621 | |
2822 | |
2622 | If undefined or defined to be C<1>, libev will compile in support for the |
2823 | If undefined or defined to be C<1>, libev will compile in support for the |
2623 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2824 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2624 | other method takes over, select will be it. Otherwise the select backend |
2825 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
2660 | |
2861 | |
2661 | =item EV_USE_EPOLL |
2862 | =item EV_USE_EPOLL |
2662 | |
2863 | |
2663 | If defined to be C<1>, libev will compile in support for the Linux |
2864 | If defined to be C<1>, libev will compile in support for the Linux |
2664 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2865 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2665 | otherwise another method will be used as fallback. This is the |
2866 | otherwise another method will be used as fallback. This is the preferred |
2666 | preferred backend for GNU/Linux systems. |
2867 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2868 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2667 | |
2869 | |
2668 | =item EV_USE_KQUEUE |
2870 | =item EV_USE_KQUEUE |
2669 | |
2871 | |
2670 | If defined to be C<1>, libev will compile in support for the BSD style |
2872 | If defined to be C<1>, libev will compile in support for the BSD style |
2671 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2873 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2690 | |
2892 | |
2691 | =item EV_USE_INOTIFY |
2893 | =item EV_USE_INOTIFY |
2692 | |
2894 | |
2693 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2895 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2694 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2896 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2695 | be detected at runtime. |
2897 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2898 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2696 | |
2899 | |
2697 | =item EV_ATOMIC_T |
2900 | =item EV_ATOMIC_T |
2698 | |
2901 | |
2699 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2902 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2700 | access is atomic with respect to other threads or signal contexts. No such type |
2903 | access is atomic with respect to other threads or signal contexts. No such |
2701 | is easily found using, so you cna provide your own type that you know is safe. |
2904 | type is easily found in the C language, so you can provide your own type |
|
|
2905 | that you know is safe for your purposes. It is used both for signal handler "locking" |
|
|
2906 | as well as for signal and thread safety in C<ev_async> watchers. |
2702 | |
2907 | |
2703 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
2908 | In the absense of this define, libev will use C<sig_atomic_t volatile> |
2704 | from F<signal.h>, which is usually good enough on most platforms. |
2909 | (from F<signal.h>), which is usually good enough on most platforms. |
2705 | |
2910 | |
2706 | =item EV_H |
2911 | =item EV_H |
2707 | |
2912 | |
2708 | The name of the F<ev.h> header file used to include it. The default if |
2913 | The name of the F<ev.h> header file used to include it. The default if |
2709 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
2914 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
2785 | defined to be C<0>, then they are not. |
2990 | defined to be C<0>, then they are not. |
2786 | |
2991 | |
2787 | =item EV_MINIMAL |
2992 | =item EV_MINIMAL |
2788 | |
2993 | |
2789 | If you need to shave off some kilobytes of code at the expense of some |
2994 | If you need to shave off some kilobytes of code at the expense of some |
2790 | speed, define this symbol to C<1>. Currently only used for gcc to override |
2995 | speed, define this symbol to C<1>. Currently this is used to override some |
2791 | some inlining decisions, saves roughly 30% codesize of amd64. |
2996 | inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
|
|
2997 | much smaller 2-heap for timer management over the default 4-heap. |
2792 | |
2998 | |
2793 | =item EV_PID_HASHSIZE |
2999 | =item EV_PID_HASHSIZE |
2794 | |
3000 | |
2795 | C<ev_child> watchers use a small hash table to distribute workload by |
3001 | C<ev_child> watchers use a small hash table to distribute workload by |
2796 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
3002 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
2802 | C<ev_stat> watchers use a small hash table to distribute workload by |
3008 | C<ev_stat> watchers use a small hash table to distribute workload by |
2803 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
3009 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2804 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3010 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2805 | watchers you might want to increase this value (I<must> be a power of |
3011 | watchers you might want to increase this value (I<must> be a power of |
2806 | two). |
3012 | two). |
|
|
3013 | |
|
|
3014 | =item EV_USE_4HEAP |
|
|
3015 | |
|
|
3016 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3017 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3018 | to C<1>. The 4-heap uses more complicated (longer) code but has |
|
|
3019 | noticably faster performance with many (thousands) of watchers. |
|
|
3020 | |
|
|
3021 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3022 | (disabled). |
|
|
3023 | |
|
|
3024 | =item EV_HEAP_CACHE_AT |
|
|
3025 | |
|
|
3026 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3027 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3028 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3029 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3030 | but avoids random read accesses on heap changes. This improves performance |
|
|
3031 | noticably with with many (hundreds) of watchers. |
|
|
3032 | |
|
|
3033 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3034 | (disabled). |
2807 | |
3035 | |
2808 | =item EV_COMMON |
3036 | =item EV_COMMON |
2809 | |
3037 | |
2810 | By default, all watchers have a C<void *data> member. By redefining |
3038 | By default, all watchers have a C<void *data> member. By redefining |
2811 | this macro to a something else you can include more and other types of |
3039 | this macro to a something else you can include more and other types of |
… | |
… | |
2885 | |
3113 | |
2886 | #include "ev_cpp.h" |
3114 | #include "ev_cpp.h" |
2887 | #include "ev.c" |
3115 | #include "ev.c" |
2888 | |
3116 | |
2889 | |
3117 | |
|
|
3118 | =head1 THREADS AND COROUTINES |
|
|
3119 | |
|
|
3120 | =head2 THREADS |
|
|
3121 | |
|
|
3122 | Libev itself is completely threadsafe, but it uses no locking. This |
|
|
3123 | means that you can use as many loops as you want in parallel, as long as |
|
|
3124 | only one thread ever calls into one libev function with the same loop |
|
|
3125 | parameter. |
|
|
3126 | |
|
|
3127 | Or put differently: calls with different loop parameters can be done in |
|
|
3128 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3129 | done serially (but can be done from different threads, as long as only one |
|
|
3130 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3131 | per loop). |
|
|
3132 | |
|
|
3133 | If you want to know which design is best for your problem, then I cannot |
|
|
3134 | help you but by giving some generic advice: |
|
|
3135 | |
|
|
3136 | =over 4 |
|
|
3137 | |
|
|
3138 | =item * most applications have a main thread: use the default libev loop |
|
|
3139 | in that thread, or create a seperate thread running only the default loop. |
|
|
3140 | |
|
|
3141 | This helps integrating other libraries or software modules that use libev |
|
|
3142 | themselves and don't care/know about threading. |
|
|
3143 | |
|
|
3144 | =item * one loop per thread is usually a good model. |
|
|
3145 | |
|
|
3146 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3147 | exists, but it is always a good start. |
|
|
3148 | |
|
|
3149 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3150 | loop is handed through multiple threads in a kind of round-robbin fashion. |
|
|
3151 | |
|
|
3152 | Chosing a model is hard - look around, learn, know that usually you cna do |
|
|
3153 | better than you currently do :-) |
|
|
3154 | |
|
|
3155 | =item * often you need to talk to some other thread which blocks in the |
|
|
3156 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3157 | threads safely (or from signal contexts...). |
|
|
3158 | |
|
|
3159 | =back |
|
|
3160 | |
|
|
3161 | =head2 COROUTINES |
|
|
3162 | |
|
|
3163 | Libev is much more accomodating to coroutines ("cooperative threads"): |
|
|
3164 | libev fully supports nesting calls to it's functions from different |
|
|
3165 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3166 | different coroutines and switch freely between both coroutines running the |
|
|
3167 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3168 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3169 | |
|
|
3170 | Care has been invested into making sure that libev does not keep local |
|
|
3171 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3172 | switches. |
|
|
3173 | |
|
|
3174 | |
2890 | =head1 COMPLEXITIES |
3175 | =head1 COMPLEXITIES |
2891 | |
3176 | |
2892 | In this section the complexities of (many of) the algorithms used inside |
3177 | In this section the complexities of (many of) the algorithms used inside |
2893 | libev will be explained. For complexity discussions about backends see the |
3178 | libev will be explained. For complexity discussions about backends see the |
2894 | documentation for C<ev_default_init>. |
3179 | documentation for C<ev_default_init>. |
… | |
… | |
2910 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
3195 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2911 | |
3196 | |
2912 | That means that changing a timer costs less than removing/adding them |
3197 | That means that changing a timer costs less than removing/adding them |
2913 | as only the relative motion in the event queue has to be paid for. |
3198 | as only the relative motion in the event queue has to be paid for. |
2914 | |
3199 | |
2915 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
3200 | =item Starting io/check/prepare/idle/signal/child/fork/async watchers: O(1) |
2916 | |
3201 | |
2917 | These just add the watcher into an array or at the head of a list. |
3202 | These just add the watcher into an array or at the head of a list. |
2918 | |
3203 | |
2919 | =item Stopping check/prepare/idle watchers: O(1) |
3204 | =item Stopping check/prepare/idle/fork/async watchers: O(1) |
2920 | |
3205 | |
2921 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
3206 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2922 | |
3207 | |
2923 | These watchers are stored in lists then need to be walked to find the |
3208 | These watchers are stored in lists then need to be walked to find the |
2924 | correct watcher to remove. The lists are usually short (you don't usually |
3209 | correct watcher to remove. The lists are usually short (you don't usually |
2925 | have many watchers waiting for the same fd or signal). |
3210 | have many watchers waiting for the same fd or signal). |
2926 | |
3211 | |
2927 | =item Finding the next timer in each loop iteration: O(1) |
3212 | =item Finding the next timer in each loop iteration: O(1) |
2928 | |
3213 | |
2929 | By virtue of using a binary heap, the next timer is always found at the |
3214 | By virtue of using a binary or 4-heap, the next timer is always found at a |
2930 | beginning of the storage array. |
3215 | fixed position in the storage array. |
2931 | |
3216 | |
2932 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3217 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2933 | |
3218 | |
2934 | A change means an I/O watcher gets started or stopped, which requires |
3219 | A change means an I/O watcher gets started or stopped, which requires |
2935 | libev to recalculate its status (and possibly tell the kernel, depending |
3220 | libev to recalculate its status (and possibly tell the kernel, depending |
… | |
… | |
2940 | =item Priority handling: O(number_of_priorities) |
3225 | =item Priority handling: O(number_of_priorities) |
2941 | |
3226 | |
2942 | Priorities are implemented by allocating some space for each |
3227 | Priorities are implemented by allocating some space for each |
2943 | priority. When doing priority-based operations, libev usually has to |
3228 | priority. When doing priority-based operations, libev usually has to |
2944 | linearly search all the priorities, but starting/stopping and activating |
3229 | linearly search all the priorities, but starting/stopping and activating |
2945 | watchers becomes O(1) w.r.t. prioritiy handling. |
3230 | watchers becomes O(1) w.r.t. priority handling. |
|
|
3231 | |
|
|
3232 | =item Sending an ev_async: O(1) |
|
|
3233 | |
|
|
3234 | =item Processing ev_async_send: O(number_of_async_watchers) |
|
|
3235 | |
|
|
3236 | =item Processing signals: O(max_signal_number) |
|
|
3237 | |
|
|
3238 | Sending involves a syscall I<iff> there were no other C<ev_async_send> |
|
|
3239 | calls in the current loop iteration. Checking for async and signal events |
|
|
3240 | involves iterating over all running async watchers or all signal numbers. |
2946 | |
3241 | |
2947 | =back |
3242 | =back |
2948 | |
3243 | |
2949 | |
3244 | |
2950 | =head1 Win32 platform limitations and workarounds |
3245 | =head1 Win32 platform limitations and workarounds |
… | |
… | |
2954 | model. Libev still offers limited functionality on this platform in |
3249 | model. Libev still offers limited functionality on this platform in |
2955 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3250 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
2956 | descriptors. This only applies when using Win32 natively, not when using |
3251 | descriptors. This only applies when using Win32 natively, not when using |
2957 | e.g. cygwin. |
3252 | e.g. cygwin. |
2958 | |
3253 | |
|
|
3254 | Lifting these limitations would basically require the full |
|
|
3255 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3256 | things, then note that glib does exactly that for you in a very portable |
|
|
3257 | way (note also that glib is the slowest event library known to man). |
|
|
3258 | |
2959 | There is no supported compilation method available on windows except |
3259 | There is no supported compilation method available on windows except |
2960 | embedding it into other applications. |
3260 | embedding it into other applications. |
2961 | |
3261 | |
2962 | Due to the many, low, and arbitrary limits on the win32 platform and the |
3262 | Due to the many, low, and arbitrary limits on the win32 platform and |
2963 | abysmal performance of winsockets, using a large number of sockets is not |
3263 | the abysmal performance of winsockets, using a large number of sockets |
2964 | recommended (and not reasonable). If your program needs to use more than |
3264 | is not recommended (and not reasonable). If your program needs to use |
2965 | a hundred or so sockets, then likely it needs to use a totally different |
3265 | more than a hundred or so sockets, then likely it needs to use a totally |
2966 | implementation for windows, as libev offers the POSIX model, which cannot |
3266 | different implementation for windows, as libev offers the POSIX readiness |
2967 | be implemented efficiently on windows (microsoft monopoly games). |
3267 | notification model, which cannot be implemented efficiently on windows |
|
|
3268 | (microsoft monopoly games). |
2968 | |
3269 | |
2969 | =over 4 |
3270 | =over 4 |
2970 | |
3271 | |
2971 | =item The winsocket select function |
3272 | =item The winsocket select function |
2972 | |
3273 | |
… | |
… | |
2986 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3287 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
2987 | complexity in the O(n²) range when using win32. |
3288 | complexity in the O(n²) range when using win32. |
2988 | |
3289 | |
2989 | =item Limited number of file descriptors |
3290 | =item Limited number of file descriptors |
2990 | |
3291 | |
2991 | Windows has numerous arbitrary (and low) limits on things. Early versions |
3292 | Windows has numerous arbitrary (and low) limits on things. |
2992 | of winsocket's select only supported waiting for a max. of C<64> handles |
3293 | |
|
|
3294 | Early versions of winsocket's select only supported waiting for a maximum |
2993 | (probably owning to the fact that all windows kernels can only wait for |
3295 | of C<64> handles (probably owning to the fact that all windows kernels |
2994 | C<64> things at the same time internally; microsoft recommends spawning a |
3296 | can only wait for C<64> things at the same time internally; microsoft |
2995 | chain of threads and wait for 63 handles and the previous thread in each). |
3297 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3298 | previous thread in each. Great). |
2996 | |
3299 | |
2997 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3300 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
2998 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3301 | to some high number (e.g. C<2048>) before compiling the winsocket select |
2999 | call (which might be in libev or elsewhere, for example, perl does its own |
3302 | call (which might be in libev or elsewhere, for example, perl does its own |
3000 | select emulation on windows). |
3303 | select emulation on windows). |
… | |
… | |
3012 | calling select (O(n²)) will likely make this unworkable. |
3315 | calling select (O(n²)) will likely make this unworkable. |
3013 | |
3316 | |
3014 | =back |
3317 | =back |
3015 | |
3318 | |
3016 | |
3319 | |
|
|
3320 | =head1 PORTABILITY REQUIREMENTS |
|
|
3321 | |
|
|
3322 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3323 | additional extensions: |
|
|
3324 | |
|
|
3325 | =over 4 |
|
|
3326 | |
|
|
3327 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3328 | |
|
|
3329 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3330 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3331 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3332 | believed to be sufficiently portable. |
|
|
3333 | |
|
|
3334 | =item C<sigprocmask> must work in a threaded environment |
|
|
3335 | |
|
|
3336 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3337 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3338 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3339 | thread" or will block signals process-wide, both behaviours would |
|
|
3340 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3341 | C<pthread_sigmask> could complicate things, however. |
|
|
3342 | |
|
|
3343 | The most portable way to handle signals is to block signals in all threads |
|
|
3344 | except the initial one, and run the default loop in the initial thread as |
|
|
3345 | well. |
|
|
3346 | |
|
|
3347 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3348 | |
|
|
3349 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3350 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3351 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3352 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3353 | millions of watchers. |
|
|
3354 | |
|
|
3355 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3356 | |
|
|
3357 | The type C<double> is used to represent timestamps. It is required to |
|
|
3358 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3359 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3360 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3361 | |
|
|
3362 | =back |
|
|
3363 | |
|
|
3364 | If you know of other additional requirements drop me a note. |
|
|
3365 | |
|
|
3366 | |
|
|
3367 | =head1 VALGRIND |
|
|
3368 | |
|
|
3369 | Valgrind has a special section here because it is a popular tool that is |
|
|
3370 | highly useful, but valgrind reports are very hard to interpret. |
|
|
3371 | |
|
|
3372 | If you think you found a bug (memory leak, uninitialised data access etc.) |
|
|
3373 | in libev, then check twice: If valgrind reports something like: |
|
|
3374 | |
|
|
3375 | ==2274== definitely lost: 0 bytes in 0 blocks. |
|
|
3376 | ==2274== possibly lost: 0 bytes in 0 blocks. |
|
|
3377 | ==2274== still reachable: 256 bytes in 1 blocks. |
|
|
3378 | |
|
|
3379 | then there is no memory leak. Similarly, under some circumstances, |
|
|
3380 | valgrind might report kernel bugs as if it were a bug in libev, or it |
|
|
3381 | might be confused (it is a very good tool, but only a tool). |
|
|
3382 | |
|
|
3383 | If you are unsure about something, feel free to contact the mailing list |
|
|
3384 | with the full valgrind report and an explanation on why you think this is |
|
|
3385 | a bug in libev. However, don't be annoyed when you get a brisk "this is |
|
|
3386 | no bug" answer and take the chance of learning how to interpret valgrind |
|
|
3387 | properly. |
|
|
3388 | |
|
|
3389 | If you need, for some reason, empty reports from valgrind for your project |
|
|
3390 | I suggest using suppression lists. |
|
|
3391 | |
|
|
3392 | |
3017 | =head1 AUTHOR |
3393 | =head1 AUTHOR |
3018 | |
3394 | |
3019 | Marc Lehmann <libev@schmorp.de>. |
3395 | Marc Lehmann <libev@schmorp.de>. |
3020 | |
3396 | |