… | |
… | |
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. |
… | |
… | |
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 |
… | |
… | |
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) |
… | |
… | |
1070 | To support fork in your programs, you either have to call |
1089 | To support fork in your programs, you either have to call |
1071 | 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, |
1072 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1091 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
1073 | C<EVBACKEND_POLL>. |
1092 | C<EVBACKEND_POLL>. |
1074 | |
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 | |
1075 | |
1106 | |
1076 | =head3 Watcher-Specific Functions |
1107 | =head3 Watcher-Specific Functions |
1077 | |
1108 | |
1078 | =over 4 |
1109 | =over 4 |
1079 | |
1110 | |
… | |
… | |
1342 | Simply stops and restarts the periodic watcher again. This is only useful |
1373 | Simply stops and restarts the periodic watcher again. This is only useful |
1343 | when you changed some parameters or the reschedule callback would return |
1374 | when you changed some parameters or the reschedule callback would return |
1344 | a different time than the last time it was called (e.g. in a crond like |
1375 | a different time than the last time it was called (e.g. in a crond like |
1345 | program when the crontabs have changed). |
1376 | program when the crontabs have changed). |
1346 | |
1377 | |
|
|
1378 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
|
|
1379 | |
|
|
1380 | When active, returns the absolute time that the watcher is supposed to |
|
|
1381 | trigger next. |
|
|
1382 | |
1347 | =item ev_tstamp offset [read-write] |
1383 | =item ev_tstamp offset [read-write] |
1348 | |
1384 | |
1349 | When repeating, this contains the offset value, otherwise this is the |
1385 | When repeating, this contains the offset value, otherwise this is the |
1350 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1386 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1351 | |
1387 | |
… | |
… | |
1361 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1397 | =item ev_tstamp (*reschedule_cb)(struct ev_periodic *w, ev_tstamp now) [read-write] |
1362 | |
1398 | |
1363 | The current reschedule callback, or C<0>, if this functionality is |
1399 | The current reschedule callback, or C<0>, if this functionality is |
1364 | switched off. Can be changed any time, but changes only take effect when |
1400 | switched off. Can be changed any time, but changes only take effect when |
1365 | the periodic timer fires or C<ev_periodic_again> is being called. |
1401 | the periodic timer fires or C<ev_periodic_again> is being called. |
1366 | |
|
|
1367 | =item ev_tstamp at [read-only] |
|
|
1368 | |
|
|
1369 | When active, contains the absolute time that the watcher is supposed to |
|
|
1370 | trigger next. |
|
|
1371 | |
1402 | |
1372 | =back |
1403 | =back |
1373 | |
1404 | |
1374 | =head3 Examples |
1405 | =head3 Examples |
1375 | |
1406 | |
… | |
… | |
1419 | with the kernel (thus it coexists with your own signal handlers as long |
1450 | with the kernel (thus it coexists with your own signal handlers as long |
1420 | as you don't register any with libev). Similarly, when the last signal |
1451 | as you don't register any with libev). Similarly, when the last signal |
1421 | watcher for a signal is stopped libev will reset the signal handler to |
1452 | watcher for a signal is stopped libev will reset the signal handler to |
1422 | SIG_DFL (regardless of what it was set to before). |
1453 | SIG_DFL (regardless of what it was set to before). |
1423 | |
1454 | |
|
|
1455 | If possible and supported, libev will install its handlers with |
|
|
1456 | C<SA_RESTART> behaviour enabled, so syscalls should not be unduly |
|
|
1457 | interrupted. If you have a problem with syscalls getting interrupted by |
|
|
1458 | signals you can block all signals in an C<ev_check> watcher and unblock |
|
|
1459 | them in an C<ev_prepare> watcher. |
|
|
1460 | |
1424 | =head3 Watcher-Specific Functions and Data Members |
1461 | =head3 Watcher-Specific Functions and Data Members |
1425 | |
1462 | |
1426 | =over 4 |
1463 | =over 4 |
1427 | |
1464 | |
1428 | =item ev_signal_init (ev_signal *, callback, int signum) |
1465 | =item ev_signal_init (ev_signal *, callback, int signum) |
… | |
… | |
1454 | |
1491 | |
1455 | |
1492 | |
1456 | =head2 C<ev_child> - watch out for process status changes |
1493 | =head2 C<ev_child> - watch out for process status changes |
1457 | |
1494 | |
1458 | Child watchers trigger when your process receives a SIGCHLD in response to |
1495 | Child watchers trigger when your process receives a SIGCHLD in response to |
1459 | some child status changes (most typically when a child of yours dies). |
1496 | some child status changes (most typically when a child of yours dies). It |
|
|
1497 | is permissible to install a child watcher I<after> the child has been |
|
|
1498 | forked (which implies it might have already exited), as long as the event |
|
|
1499 | loop isn't entered (or is continued from a watcher). |
|
|
1500 | |
|
|
1501 | Only the default event loop is capable of handling signals, and therefore |
|
|
1502 | you can only rgeister child watchers in the default event loop. |
|
|
1503 | |
|
|
1504 | =head3 Process Interaction |
|
|
1505 | |
|
|
1506 | Libev grabs C<SIGCHLD> as soon as the default event loop is |
|
|
1507 | initialised. This is necessary to guarantee proper behaviour even if |
|
|
1508 | the first child watcher is started after the child exits. The occurance |
|
|
1509 | of C<SIGCHLD> is recorded asynchronously, but child reaping is done |
|
|
1510 | synchronously as part of the event loop processing. Libev always reaps all |
|
|
1511 | children, even ones not watched. |
|
|
1512 | |
|
|
1513 | =head3 Overriding the Built-In Processing |
|
|
1514 | |
|
|
1515 | Libev offers no special support for overriding the built-in child |
|
|
1516 | processing, but if your application collides with libev's default child |
|
|
1517 | handler, you can override it easily by installing your own handler for |
|
|
1518 | C<SIGCHLD> after initialising the default loop, and making sure the |
|
|
1519 | default loop never gets destroyed. You are encouraged, however, to use an |
|
|
1520 | event-based approach to child reaping and thus use libev's support for |
|
|
1521 | that, so other libev users can use C<ev_child> watchers freely. |
1460 | |
1522 | |
1461 | =head3 Watcher-Specific Functions and Data Members |
1523 | =head3 Watcher-Specific Functions and Data Members |
1462 | |
1524 | |
1463 | =over 4 |
1525 | =over 4 |
1464 | |
1526 | |
… | |
… | |
1488 | The process exit/trace status caused by C<rpid> (see your systems |
1550 | The process exit/trace status caused by C<rpid> (see your systems |
1489 | C<waitpid> and C<sys/wait.h> documentation for details). |
1551 | C<waitpid> and C<sys/wait.h> documentation for details). |
1490 | |
1552 | |
1491 | =back |
1553 | =back |
1492 | |
1554 | |
|
|
1555 | =head3 Examples |
|
|
1556 | |
|
|
1557 | Example: C<fork()> a new process and install a child handler to wait for |
|
|
1558 | its completion. |
|
|
1559 | |
|
|
1560 | ev_child cw; |
|
|
1561 | |
|
|
1562 | static void |
|
|
1563 | child_cb (EV_P_ struct ev_child *w, int revents) |
|
|
1564 | { |
|
|
1565 | ev_child_stop (EV_A_ w); |
|
|
1566 | printf ("process %d exited with status %x\n", w->rpid, w->rstatus); |
|
|
1567 | } |
|
|
1568 | |
|
|
1569 | pid_t pid = fork (); |
|
|
1570 | |
|
|
1571 | if (pid < 0) |
|
|
1572 | // error |
|
|
1573 | else if (pid == 0) |
|
|
1574 | { |
|
|
1575 | // the forked child executes here |
|
|
1576 | exit (1); |
|
|
1577 | } |
|
|
1578 | else |
|
|
1579 | { |
|
|
1580 | ev_child_init (&cw, child_cb, pid, 0); |
|
|
1581 | ev_child_start (EV_DEFAULT_ &cw); |
|
|
1582 | } |
|
|
1583 | |
1493 | |
1584 | |
1494 | =head2 C<ev_stat> - did the file attributes just change? |
1585 | =head2 C<ev_stat> - did the file attributes just change? |
1495 | |
1586 | |
1496 | This watches a filesystem path for attribute changes. That is, it calls |
1587 | This watches a filesystem path for attribute changes. That is, it calls |
1497 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1588 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
… | |
… | |
1519 | as even with OS-supported change notifications, this can be |
1610 | as even with OS-supported change notifications, this can be |
1520 | resource-intensive. |
1611 | resource-intensive. |
1521 | |
1612 | |
1522 | At the time of this writing, only the Linux inotify interface is |
1613 | At the time of this writing, only the Linux inotify interface is |
1523 | implemented (implementing kqueue support is left as an exercise for the |
1614 | implemented (implementing kqueue support is left as an exercise for the |
|
|
1615 | reader, note, however, that the author sees no way of implementing ev_stat |
1524 | reader). Inotify will be used to give hints only and should not change the |
1616 | semantics with kqueue). Inotify will be used to give hints only and should |
1525 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1617 | not change the semantics of C<ev_stat> watchers, which means that libev |
1526 | to fall back to regular polling again even with inotify, but changes are |
1618 | sometimes needs to fall back to regular polling again even with inotify, |
1527 | usually detected immediately, and if the file exists there will be no |
1619 | but changes are usually detected immediately, and if the file exists there |
1528 | polling. |
1620 | will be no polling. |
|
|
1621 | |
|
|
1622 | =head3 ABI Issues (Largefile Support) |
|
|
1623 | |
|
|
1624 | Libev by default (unless the user overrides this) uses the default |
|
|
1625 | compilation environment, which means that on systems with optionally |
|
|
1626 | disabled large file support, you get the 32 bit version of the stat |
|
|
1627 | structure. When using the library from programs that change the ABI to |
|
|
1628 | use 64 bit file offsets the programs will fail. In that case you have to |
|
|
1629 | compile libev with the same flags to get binary compatibility. This is |
|
|
1630 | obviously the case with any flags that change the ABI, but the problem is |
|
|
1631 | most noticably with ev_stat and largefile support. |
1529 | |
1632 | |
1530 | =head3 Inotify |
1633 | =head3 Inotify |
1531 | |
1634 | |
1532 | When C<inotify (7)> support has been compiled into libev (generally only |
1635 | When C<inotify (7)> support has been compiled into libev (generally only |
1533 | available on Linux) and present at runtime, it will be used to speed up |
1636 | available on Linux) and present at runtime, it will be used to speed up |
1534 | change detection where possible. The inotify descriptor will be created lazily |
1637 | change detection where possible. The inotify descriptor will be created lazily |
1535 | when the first C<ev_stat> watcher is being started. |
1638 | when the first C<ev_stat> watcher is being started. |
1536 | |
1639 | |
1537 | Inotify presense does not change the semantics of C<ev_stat> watchers |
1640 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1538 | except that changes might be detected earlier, and in some cases, to avoid |
1641 | except that changes might be detected earlier, and in some cases, to avoid |
1539 | making regular C<stat> calls. Even in the presense of inotify support |
1642 | making regular C<stat> calls. Even in the presence of inotify support |
1540 | there are many cases where libev has to resort to regular C<stat> polling. |
1643 | there are many cases where libev has to resort to regular C<stat> polling. |
1541 | |
1644 | |
1542 | (There is no support for kqueue, as apparently it cannot be used to |
1645 | (There is no support for kqueue, as apparently it cannot be used to |
1543 | implement this functionality, due to the requirement of having a file |
1646 | implement this functionality, due to the requirement of having a file |
1544 | descriptor open on the object at all times). |
1647 | descriptor open on the object at all times). |
… | |
… | |
1547 | |
1650 | |
1548 | The C<stat ()> syscall only supports full-second resolution portably, and |
1651 | The C<stat ()> syscall only supports full-second resolution portably, and |
1549 | even on systems where the resolution is higher, many filesystems still |
1652 | even on systems where the resolution is higher, many filesystems still |
1550 | only support whole seconds. |
1653 | only support whole seconds. |
1551 | |
1654 | |
1552 | That means that, if the time is the only thing that changes, you might |
1655 | That means that, if the time is the only thing that changes, you can |
1553 | miss updates: on the first update, C<ev_stat> detects a change and calls |
1656 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1554 | your callback, which does something. When there is another update within |
1657 | calls your callback, which does something. When there is another update |
1555 | the same second, C<ev_stat> will be unable to detect it. |
1658 | within the same second, C<ev_stat> will be unable to detect it as the stat |
|
|
1659 | data does not change. |
1556 | |
1660 | |
1557 | The solution to this is to delay acting on a change for a second (or till |
1661 | The solution to this is to delay acting on a change for slightly more |
1558 | the next second boundary), using a roughly one-second delay C<ev_timer> |
1662 | than second (or till slightly after the next full second boundary), using |
1559 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
1663 | a roughly one-second-delay C<ev_timer> (e.g. C<ev_timer_set (w, 0., 1.02); |
1560 | is added to work around small timing inconsistencies of some operating |
1664 | ev_timer_again (loop, w)>). |
1561 | systems. |
1665 | |
|
|
1666 | The C<.02> offset is added to work around small timing inconsistencies |
|
|
1667 | of some operating systems (where the second counter of the current time |
|
|
1668 | might be be delayed. One such system is the Linux kernel, where a call to |
|
|
1669 | C<gettimeofday> might return a timestamp with a full second later than |
|
|
1670 | a subsequent C<time> call - if the equivalent of C<time ()> is used to |
|
|
1671 | update file times then there will be a small window where the kernel uses |
|
|
1672 | the previous second to update file times but libev might already execute |
|
|
1673 | the timer callback). |
1562 | |
1674 | |
1563 | =head3 Watcher-Specific Functions and Data Members |
1675 | =head3 Watcher-Specific Functions and Data Members |
1564 | |
1676 | |
1565 | =over 4 |
1677 | =over 4 |
1566 | |
1678 | |
… | |
… | |
1572 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1684 | C<path>. The C<interval> is a hint on how quickly a change is expected to |
1573 | be detected and should normally be specified as C<0> to let libev choose |
1685 | be detected and should normally be specified as C<0> to let libev choose |
1574 | a suitable value. The memory pointed to by C<path> must point to the same |
1686 | a suitable value. The memory pointed to by C<path> must point to the same |
1575 | path for as long as the watcher is active. |
1687 | path for as long as the watcher is active. |
1576 | |
1688 | |
1577 | The callback will be receive C<EV_STAT> when a change was detected, |
1689 | The callback will receive C<EV_STAT> when a change was detected, relative |
1578 | relative to the attributes at the time the watcher was started (or the |
1690 | to the attributes at the time the watcher was started (or the last change |
1579 | last change was detected). |
1691 | was detected). |
1580 | |
1692 | |
1581 | =item ev_stat_stat (loop, ev_stat *) |
1693 | =item ev_stat_stat (loop, ev_stat *) |
1582 | |
1694 | |
1583 | Updates the stat buffer immediately with new values. If you change the |
1695 | Updates the stat buffer immediately with new values. If you change the |
1584 | watched path in your callback, you could call this fucntion to avoid |
1696 | watched path in your callback, you could call this function to avoid |
1585 | detecting this change (while introducing a race condition). Can also be |
1697 | detecting this change (while introducing a race condition if you are not |
1586 | useful simply to find out the new values. |
1698 | the only one changing the path). Can also be useful simply to find out the |
|
|
1699 | new values. |
1587 | |
1700 | |
1588 | =item ev_statdata attr [read-only] |
1701 | =item ev_statdata attr [read-only] |
1589 | |
1702 | |
1590 | The most-recently detected attributes of the file. Although the type is of |
1703 | The most-recently detected attributes of the file. Although the type is |
1591 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1704 | C<ev_statdata>, this is usually the (or one of the) C<struct stat> types |
1592 | suitable for your system. If the C<st_nlink> member is C<0>, then there |
1705 | suitable for your system, but you can only rely on the POSIX-standardised |
|
|
1706 | members to be present. If the C<st_nlink> member is C<0>, then there was |
1593 | was some error while C<stat>ing the file. |
1707 | some error while C<stat>ing the file. |
1594 | |
1708 | |
1595 | =item ev_statdata prev [read-only] |
1709 | =item ev_statdata prev [read-only] |
1596 | |
1710 | |
1597 | The previous attributes of the file. The callback gets invoked whenever |
1711 | The previous attributes of the file. The callback gets invoked whenever |
1598 | C<prev> != C<attr>. |
1712 | C<prev> != C<attr>, or, more precisely, one or more of these members |
|
|
1713 | differ: C<st_dev>, C<st_ino>, C<st_mode>, C<st_nlink>, C<st_uid>, |
|
|
1714 | C<st_gid>, C<st_rdev>, C<st_size>, C<st_atime>, C<st_mtime>, C<st_ctime>. |
1599 | |
1715 | |
1600 | =item ev_tstamp interval [read-only] |
1716 | =item ev_tstamp interval [read-only] |
1601 | |
1717 | |
1602 | The specified interval. |
1718 | The specified interval. |
1603 | |
1719 | |
… | |
… | |
1657 | } |
1773 | } |
1658 | |
1774 | |
1659 | ... |
1775 | ... |
1660 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1776 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
1661 | ev_stat_start (loop, &passwd); |
1777 | ev_stat_start (loop, &passwd); |
1662 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1778 | ev_timer_init (&timer, timer_cb, 0., 1.02); |
1663 | |
1779 | |
1664 | |
1780 | |
1665 | =head2 C<ev_idle> - when you've got nothing better to do... |
1781 | =head2 C<ev_idle> - when you've got nothing better to do... |
1666 | |
1782 | |
1667 | Idle watchers trigger events when no other events of the same or higher |
1783 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1755 | |
1871 | |
1756 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1872 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1757 | priority, to ensure that they are being run before any other watchers |
1873 | priority, to ensure that they are being run before any other watchers |
1758 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1874 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1759 | too) should not activate ("feed") events into libev. While libev fully |
1875 | too) should not activate ("feed") events into libev. While libev fully |
1760 | supports this, they will be called before other C<ev_check> watchers |
1876 | supports this, they might get executed before other C<ev_check> watchers |
1761 | did their job. As C<ev_check> watchers are often used to embed other |
1877 | did their job. As C<ev_check> watchers are often used to embed other |
1762 | (non-libev) event loops those other event loops might be in an unusable |
1878 | (non-libev) event loops those other event loops might be in an unusable |
1763 | state until their C<ev_check> watcher ran (always remind yourself to |
1879 | state until their C<ev_check> watcher ran (always remind yourself to |
1764 | coexist peacefully with others). |
1880 | coexist peacefully with others). |
1765 | |
1881 | |
… | |
… | |
1780 | =head3 Examples |
1896 | =head3 Examples |
1781 | |
1897 | |
1782 | There are a number of principal ways to embed other event loops or modules |
1898 | There are a number of principal ways to embed other event loops or modules |
1783 | into libev. Here are some ideas on how to include libadns into libev |
1899 | into libev. Here are some ideas on how to include libadns into libev |
1784 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1900 | (there is a Perl module named C<EV::ADNS> that does this, which you could |
1785 | use for an actually working example. Another Perl module named C<EV::Glib> |
1901 | use as a working example. Another Perl module named C<EV::Glib> embeds a |
1786 | embeds a Glib main context into libev, and finally, C<Glib::EV> embeds EV |
1902 | Glib main context into libev, and finally, C<Glib::EV> embeds EV into the |
1787 | into the Glib event loop). |
1903 | Glib event loop). |
1788 | |
1904 | |
1789 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1905 | Method 1: Add IO watchers and a timeout watcher in a prepare handler, |
1790 | and in a check watcher, destroy them and call into libadns. What follows |
1906 | and in a check watcher, destroy them and call into libadns. What follows |
1791 | is pseudo-code only of course. This requires you to either use a low |
1907 | is pseudo-code only of course. This requires you to either use a low |
1792 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
1908 | priority for the check watcher or use C<ev_clear_pending> explicitly, as |
… | |
… | |
2102 | { |
2218 | { |
2103 | sometype data; |
2219 | sometype data; |
2104 | |
2220 | |
2105 | // no locking etc. |
2221 | // no locking etc. |
2106 | queue_put (data); |
2222 | queue_put (data); |
2107 | ev_async_send (DEFAULT_ &mysig); |
2223 | ev_async_send (EV_DEFAULT_ &mysig); |
2108 | } |
2224 | } |
2109 | |
2225 | |
2110 | static void |
2226 | static void |
2111 | mysig_cb (EV_P_ ev_async *w, int revents) |
2227 | mysig_cb (EV_P_ ev_async *w, int revents) |
2112 | { |
2228 | { |
… | |
… | |
2143 | // only need to lock the actual queueing operation |
2259 | // only need to lock the actual queueing operation |
2144 | pthread_mutex_lock (&mymutex); |
2260 | pthread_mutex_lock (&mymutex); |
2145 | queue_put (data); |
2261 | queue_put (data); |
2146 | pthread_mutex_unlock (&mymutex); |
2262 | pthread_mutex_unlock (&mymutex); |
2147 | |
2263 | |
2148 | ev_async_send (DEFAULT_ &mysig); |
2264 | ev_async_send (EV_DEFAULT_ &mysig); |
2149 | } |
2265 | } |
2150 | |
2266 | |
2151 | static void |
2267 | static void |
2152 | mysig_cb (EV_P_ ev_async *w, int revents) |
2268 | mysig_cb (EV_P_ ev_async *w, int revents) |
2153 | { |
2269 | { |
… | |
… | |
2181 | section below on what exactly this means). |
2297 | section below on what exactly this means). |
2182 | |
2298 | |
2183 | This call incurs the overhead of a syscall only once per loop iteration, |
2299 | This call incurs the overhead of a syscall only once per loop iteration, |
2184 | so while the overhead might be noticable, it doesn't apply to repeated |
2300 | so while the overhead might be noticable, it doesn't apply to repeated |
2185 | calls to C<ev_async_send>. |
2301 | calls to C<ev_async_send>. |
|
|
2302 | |
|
|
2303 | =item bool = ev_async_pending (ev_async *) |
|
|
2304 | |
|
|
2305 | Returns a non-zero value when C<ev_async_send> has been called on the |
|
|
2306 | watcher but the event has not yet been processed (or even noted) by the |
|
|
2307 | event loop. |
|
|
2308 | |
|
|
2309 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
|
|
2310 | the loop iterates next and checks for the watcher to have become active, |
|
|
2311 | it will reset the flag again. C<ev_async_pending> can be used to very |
|
|
2312 | quickly check wether invoking the loop might be a good idea. |
|
|
2313 | |
|
|
2314 | Not that this does I<not> check wether the watcher itself is pending, only |
|
|
2315 | wether it has been requested to make this watcher pending. |
2186 | |
2316 | |
2187 | =back |
2317 | =back |
2188 | |
2318 | |
2189 | |
2319 | |
2190 | =head1 OTHER FUNCTIONS |
2320 | =head1 OTHER FUNCTIONS |
… | |
… | |
2262 | |
2392 | |
2263 | =item * Priorities are not currently supported. Initialising priorities |
2393 | =item * Priorities are not currently supported. Initialising priorities |
2264 | will fail and all watchers will have the same priority, even though there |
2394 | will fail and all watchers will have the same priority, even though there |
2265 | is an ev_pri field. |
2395 | is an ev_pri field. |
2266 | |
2396 | |
|
|
2397 | =item * In libevent, the last base created gets the signals, in libev, the |
|
|
2398 | first base created (== the default loop) gets the signals. |
|
|
2399 | |
2267 | =item * Other members are not supported. |
2400 | =item * Other members are not supported. |
2268 | |
2401 | |
2269 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2402 | =item * The libev emulation is I<not> ABI compatible to libevent, you need |
2270 | to use the libev header file and library. |
2403 | to use the libev header file and library. |
2271 | |
2404 | |
… | |
… | |
2434 | io.start (fd, ev::READ); |
2567 | io.start (fd, ev::READ); |
2435 | } |
2568 | } |
2436 | }; |
2569 | }; |
2437 | |
2570 | |
2438 | |
2571 | |
|
|
2572 | =head1 OTHER LANGUAGE BINDINGS |
|
|
2573 | |
|
|
2574 | Libev does not offer other language bindings itself, but bindings for a |
|
|
2575 | numbe rof languages exist in the form of third-party packages. If you know |
|
|
2576 | any interesting language binding in addition to the ones listed here, drop |
|
|
2577 | me a note. |
|
|
2578 | |
|
|
2579 | =over 4 |
|
|
2580 | |
|
|
2581 | =item Perl |
|
|
2582 | |
|
|
2583 | The EV module implements the full libev API and is actually used to test |
|
|
2584 | libev. EV is developed together with libev. Apart from the EV core module, |
|
|
2585 | there are additional modules that implement libev-compatible interfaces |
|
|
2586 | to C<libadns> (C<EV::ADNS>), C<Net::SNMP> (C<Net::SNMP::EV>) and the |
|
|
2587 | C<libglib> event core (C<Glib::EV> and C<EV::Glib>). |
|
|
2588 | |
|
|
2589 | It can be found and installed via CPAN, its homepage is found at |
|
|
2590 | L<http://software.schmorp.de/pkg/EV>. |
|
|
2591 | |
|
|
2592 | =item Ruby |
|
|
2593 | |
|
|
2594 | Tony Arcieri has written a ruby extension that offers access to a subset |
|
|
2595 | of the libev API and adds filehandle abstractions, asynchronous DNS and |
|
|
2596 | more on top of it. It can be found via gem servers. Its homepage is at |
|
|
2597 | L<http://rev.rubyforge.org/>. |
|
|
2598 | |
|
|
2599 | =item D |
|
|
2600 | |
|
|
2601 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
|
|
2602 | be found at L<http://git.llucax.com.ar/?p=software/ev.d.git;a=summary>. |
|
|
2603 | |
|
|
2604 | =back |
|
|
2605 | |
|
|
2606 | |
2439 | =head1 MACRO MAGIC |
2607 | =head1 MACRO MAGIC |
2440 | |
2608 | |
2441 | Libev can be compiled with a variety of options, the most fundamantal |
2609 | Libev can be compiled with a variety of options, the most fundamantal |
2442 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2610 | of which is C<EV_MULTIPLICITY>. This option determines whether (most) |
2443 | functions and callbacks have an initial C<struct ev_loop *> argument. |
2611 | functions and callbacks have an initial C<struct ev_loop *> argument. |
… | |
… | |
2477 | |
2645 | |
2478 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2646 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
2479 | |
2647 | |
2480 | Similar to the other two macros, this gives you the value of the default |
2648 | Similar to the other two macros, this gives you the value of the default |
2481 | loop, if multiple loops are supported ("ev loop default"). |
2649 | loop, if multiple loops are supported ("ev loop default"). |
|
|
2650 | |
|
|
2651 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
|
|
2652 | |
|
|
2653 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
|
|
2654 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
|
|
2655 | is undefined when the default loop has not been initialised by a previous |
|
|
2656 | execution of C<EV_DEFAULT>, C<EV_DEFAULT_> or C<ev_default_init (...)>. |
|
|
2657 | |
|
|
2658 | It is often prudent to use C<EV_DEFAULT> when initialising the first |
|
|
2659 | watcher in a function but use C<EV_DEFAULT_UC> afterwards. |
2482 | |
2660 | |
2483 | =back |
2661 | =back |
2484 | |
2662 | |
2485 | Example: Declare and initialise a check watcher, utilising the above |
2663 | Example: Declare and initialise a check watcher, utilising the above |
2486 | macros so it will work regardless of whether multiple loops are supported |
2664 | macros so it will work regardless of whether multiple loops are supported |
… | |
… | |
2582 | |
2760 | |
2583 | libev.m4 |
2761 | libev.m4 |
2584 | |
2762 | |
2585 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2763 | =head2 PREPROCESSOR SYMBOLS/MACROS |
2586 | |
2764 | |
2587 | Libev can be configured via a variety of preprocessor symbols you have to define |
2765 | Libev can be configured via a variety of preprocessor symbols you have to |
2588 | before including any of its files. The default is not to build for multiplicity |
2766 | define before including any of its files. The default in the absense of |
2589 | and only include the select backend. |
2767 | autoconf is noted for every option. |
2590 | |
2768 | |
2591 | =over 4 |
2769 | =over 4 |
2592 | |
2770 | |
2593 | =item EV_STANDALONE |
2771 | =item EV_STANDALONE |
2594 | |
2772 | |
… | |
… | |
2620 | =item EV_USE_NANOSLEEP |
2798 | =item EV_USE_NANOSLEEP |
2621 | |
2799 | |
2622 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2800 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
2623 | and will use it for delays. Otherwise it will use C<select ()>. |
2801 | and will use it for delays. Otherwise it will use C<select ()>. |
2624 | |
2802 | |
|
|
2803 | =item EV_USE_EVENTFD |
|
|
2804 | |
|
|
2805 | If defined to be C<1>, then libev will assume that C<eventfd ()> is |
|
|
2806 | available and will probe for kernel support at runtime. This will improve |
|
|
2807 | C<ev_signal> and C<ev_async> performance and reduce resource consumption. |
|
|
2808 | If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc |
|
|
2809 | 2.7 or newer, otherwise disabled. |
|
|
2810 | |
2625 | =item EV_USE_SELECT |
2811 | =item EV_USE_SELECT |
2626 | |
2812 | |
2627 | If undefined or defined to be C<1>, libev will compile in support for the |
2813 | If undefined or defined to be C<1>, libev will compile in support for the |
2628 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2814 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2629 | other method takes over, select will be it. Otherwise the select backend |
2815 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
2665 | |
2851 | |
2666 | =item EV_USE_EPOLL |
2852 | =item EV_USE_EPOLL |
2667 | |
2853 | |
2668 | If defined to be C<1>, libev will compile in support for the Linux |
2854 | If defined to be C<1>, libev will compile in support for the Linux |
2669 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2855 | C<epoll>(7) backend. Its availability will be detected at runtime, |
2670 | otherwise another method will be used as fallback. This is the |
2856 | otherwise another method will be used as fallback. This is the preferred |
2671 | preferred backend for GNU/Linux systems. |
2857 | backend for GNU/Linux systems. If undefined, it will be enabled if the |
|
|
2858 | headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2672 | |
2859 | |
2673 | =item EV_USE_KQUEUE |
2860 | =item EV_USE_KQUEUE |
2674 | |
2861 | |
2675 | If defined to be C<1>, libev will compile in support for the BSD style |
2862 | If defined to be C<1>, libev will compile in support for the BSD style |
2676 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
2863 | C<kqueue>(2) backend. Its actual availability will be detected at runtime, |
… | |
… | |
2695 | |
2882 | |
2696 | =item EV_USE_INOTIFY |
2883 | =item EV_USE_INOTIFY |
2697 | |
2884 | |
2698 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2885 | If defined to be C<1>, libev will compile in support for the Linux inotify |
2699 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2886 | interface to speed up C<ev_stat> watchers. Its actual availability will |
2700 | be detected at runtime. |
2887 | be detected at runtime. If undefined, it will be enabled if the headers |
|
|
2888 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
2701 | |
2889 | |
2702 | =item EV_ATOMIC_T |
2890 | =item EV_ATOMIC_T |
2703 | |
2891 | |
2704 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2892 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
2705 | access is atomic with respect to other threads or signal contexts. No such |
2893 | access is atomic with respect to other threads or signal contexts. No such |
… | |
… | |
2792 | defined to be C<0>, then they are not. |
2980 | defined to be C<0>, then they are not. |
2793 | |
2981 | |
2794 | =item EV_MINIMAL |
2982 | =item EV_MINIMAL |
2795 | |
2983 | |
2796 | If you need to shave off some kilobytes of code at the expense of some |
2984 | If you need to shave off some kilobytes of code at the expense of some |
2797 | speed, define this symbol to C<1>. Currently only used for gcc to override |
2985 | speed, define this symbol to C<1>. Currently this is used to override some |
2798 | some inlining decisions, saves roughly 30% codesize of amd64. |
2986 | inlining decisions, saves roughly 30% codesize of amd64. It also selects a |
|
|
2987 | much smaller 2-heap for timer management over the default 4-heap. |
2799 | |
2988 | |
2800 | =item EV_PID_HASHSIZE |
2989 | =item EV_PID_HASHSIZE |
2801 | |
2990 | |
2802 | C<ev_child> watchers use a small hash table to distribute workload by |
2991 | C<ev_child> watchers use a small hash table to distribute workload by |
2803 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
2992 | pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more |
… | |
… | |
2809 | C<ev_stat> watchers use a small hash table to distribute workload by |
2998 | C<ev_stat> watchers use a small hash table to distribute workload by |
2810 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2999 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2811 | usually more than enough. If you need to manage thousands of C<ev_stat> |
3000 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2812 | watchers you might want to increase this value (I<must> be a power of |
3001 | watchers you might want to increase this value (I<must> be a power of |
2813 | two). |
3002 | two). |
|
|
3003 | |
|
|
3004 | =item EV_USE_4HEAP |
|
|
3005 | |
|
|
3006 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3007 | timer and periodics heap, libev uses a 4-heap when this symbol is defined |
|
|
3008 | to C<1>. The 4-heap uses more complicated (longer) code but has a |
|
|
3009 | noticable after performance with many (thousands) of watchers. |
|
|
3010 | |
|
|
3011 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3012 | (disabled). |
|
|
3013 | |
|
|
3014 | =item EV_HEAP_CACHE_AT |
|
|
3015 | |
|
|
3016 | Heaps are not very cache-efficient. To improve the cache-efficiency of the |
|
|
3017 | timer and periodics heap, libev can cache the timestamp (I<at>) within |
|
|
3018 | the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), |
|
|
3019 | which uses 8-12 bytes more per watcher and a few hundred bytes more code, |
|
|
3020 | but avoids random read accesses on heap changes. This noticably improves |
|
|
3021 | performance noticably with with many (hundreds) of watchers. |
|
|
3022 | |
|
|
3023 | The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> |
|
|
3024 | (disabled). |
2814 | |
3025 | |
2815 | =item EV_COMMON |
3026 | =item EV_COMMON |
2816 | |
3027 | |
2817 | By default, all watchers have a C<void *data> member. By redefining |
3028 | By default, all watchers have a C<void *data> member. By redefining |
2818 | this macro to a something else you can include more and other types of |
3029 | this macro to a something else you can include more and other types of |
… | |
… | |
2892 | |
3103 | |
2893 | #include "ev_cpp.h" |
3104 | #include "ev_cpp.h" |
2894 | #include "ev.c" |
3105 | #include "ev.c" |
2895 | |
3106 | |
2896 | |
3107 | |
|
|
3108 | =head1 THREADS AND COROUTINES |
|
|
3109 | |
|
|
3110 | =head2 THREADS |
|
|
3111 | |
|
|
3112 | Libev itself is completely threadsafe, but it uses no locking. This |
|
|
3113 | means that you can use as many loops as you want in parallel, as long as |
|
|
3114 | only one thread ever calls into one libev function with the same loop |
|
|
3115 | parameter. |
|
|
3116 | |
|
|
3117 | Or put differently: calls with different loop parameters can be done in |
|
|
3118 | parallel from multiple threads, calls with the same loop parameter must be |
|
|
3119 | done serially (but can be done from different threads, as long as only one |
|
|
3120 | thread ever is inside a call at any point in time, e.g. by using a mutex |
|
|
3121 | per loop). |
|
|
3122 | |
|
|
3123 | If you want to know which design is best for your problem, then I cannot |
|
|
3124 | help you but by giving some generic advice: |
|
|
3125 | |
|
|
3126 | =over 4 |
|
|
3127 | |
|
|
3128 | =item * most applications have a main thread: use the default libev loop |
|
|
3129 | in that thread, or create a seperate thread running only the default loop. |
|
|
3130 | |
|
|
3131 | This helps integrating other libraries or software modules that use libev |
|
|
3132 | themselves and don't care/know about threading. |
|
|
3133 | |
|
|
3134 | =item * one loop per thread is usually a good model. |
|
|
3135 | |
|
|
3136 | Doing this is almost never wrong, sometimes a better-performance model |
|
|
3137 | exists, but it is always a good start. |
|
|
3138 | |
|
|
3139 | =item * other models exist, such as the leader/follower pattern, where one |
|
|
3140 | loop is handed through multiple threads in a kind of round-robbin fashion. |
|
|
3141 | |
|
|
3142 | Chosing a model is hard - look around, learn, know that usually you cna do |
|
|
3143 | better than you currently do :-) |
|
|
3144 | |
|
|
3145 | =item * often you need to talk to some other thread which blocks in the |
|
|
3146 | event loop - C<ev_async> watchers can be used to wake them up from other |
|
|
3147 | threads safely (or from signal contexts...). |
|
|
3148 | |
|
|
3149 | =back |
|
|
3150 | |
|
|
3151 | =head2 COROUTINES |
|
|
3152 | |
|
|
3153 | Libev is much more accomodating to coroutines ("cooperative threads"): |
|
|
3154 | libev fully supports nesting calls to it's functions from different |
|
|
3155 | coroutines (e.g. you can call C<ev_loop> on the same loop from two |
|
|
3156 | different coroutines and switch freely between both coroutines running the |
|
|
3157 | loop, as long as you don't confuse yourself). The only exception is that |
|
|
3158 | you must not do this from C<ev_periodic> reschedule callbacks. |
|
|
3159 | |
|
|
3160 | Care has been invested into making sure that libev does not keep local |
|
|
3161 | state inside C<ev_loop>, and other calls do not usually allow coroutine |
|
|
3162 | switches. |
|
|
3163 | |
|
|
3164 | |
2897 | =head1 COMPLEXITIES |
3165 | =head1 COMPLEXITIES |
2898 | |
3166 | |
2899 | In this section the complexities of (many of) the algorithms used inside |
3167 | In this section the complexities of (many of) the algorithms used inside |
2900 | libev will be explained. For complexity discussions about backends see the |
3168 | libev will be explained. For complexity discussions about backends see the |
2901 | documentation for C<ev_default_init>. |
3169 | documentation for C<ev_default_init>. |
… | |
… | |
2931 | correct watcher to remove. The lists are usually short (you don't usually |
3199 | correct watcher to remove. The lists are usually short (you don't usually |
2932 | have many watchers waiting for the same fd or signal). |
3200 | have many watchers waiting for the same fd or signal). |
2933 | |
3201 | |
2934 | =item Finding the next timer in each loop iteration: O(1) |
3202 | =item Finding the next timer in each loop iteration: O(1) |
2935 | |
3203 | |
2936 | By virtue of using a binary heap, the next timer is always found at the |
3204 | By virtue of using a binary or 4-heap, the next timer is always found at a |
2937 | beginning of the storage array. |
3205 | fixed position in the storage array. |
2938 | |
3206 | |
2939 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
3207 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2940 | |
3208 | |
2941 | A change means an I/O watcher gets started or stopped, which requires |
3209 | A change means an I/O watcher gets started or stopped, which requires |
2942 | libev to recalculate its status (and possibly tell the kernel, depending |
3210 | libev to recalculate its status (and possibly tell the kernel, depending |
… | |
… | |
2971 | model. Libev still offers limited functionality on this platform in |
3239 | model. Libev still offers limited functionality on this platform in |
2972 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
3240 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
2973 | descriptors. This only applies when using Win32 natively, not when using |
3241 | descriptors. This only applies when using Win32 natively, not when using |
2974 | e.g. cygwin. |
3242 | e.g. cygwin. |
2975 | |
3243 | |
|
|
3244 | Lifting these limitations would basically require the full |
|
|
3245 | re-implementation of the I/O system. If you are into these kinds of |
|
|
3246 | things, then note that glib does exactly that for you in a very portable |
|
|
3247 | way (note also that glib is the slowest event library known to man). |
|
|
3248 | |
2976 | There is no supported compilation method available on windows except |
3249 | There is no supported compilation method available on windows except |
2977 | embedding it into other applications. |
3250 | embedding it into other applications. |
2978 | |
3251 | |
2979 | Due to the many, low, and arbitrary limits on the win32 platform and the |
3252 | Due to the many, low, and arbitrary limits on the win32 platform and |
2980 | abysmal performance of winsockets, using a large number of sockets is not |
3253 | the abysmal performance of winsockets, using a large number of sockets |
2981 | recommended (and not reasonable). If your program needs to use more than |
3254 | is not recommended (and not reasonable). If your program needs to use |
2982 | a hundred or so sockets, then likely it needs to use a totally different |
3255 | more than a hundred or so sockets, then likely it needs to use a totally |
2983 | implementation for windows, as libev offers the POSIX model, which cannot |
3256 | different implementation for windows, as libev offers the POSIX readyness |
2984 | be implemented efficiently on windows (microsoft monopoly games). |
3257 | notification model, which cannot be implemented efficiently on windows |
|
|
3258 | (microsoft monopoly games). |
2985 | |
3259 | |
2986 | =over 4 |
3260 | =over 4 |
2987 | |
3261 | |
2988 | =item The winsocket select function |
3262 | =item The winsocket select function |
2989 | |
3263 | |
… | |
… | |
3003 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3277 | Note that winsockets handling of fd sets is O(n), so you can easily get a |
3004 | complexity in the O(n²) range when using win32. |
3278 | complexity in the O(n²) range when using win32. |
3005 | |
3279 | |
3006 | =item Limited number of file descriptors |
3280 | =item Limited number of file descriptors |
3007 | |
3281 | |
3008 | Windows has numerous arbitrary (and low) limits on things. Early versions |
3282 | Windows has numerous arbitrary (and low) limits on things. |
3009 | of winsocket's select only supported waiting for a max. of C<64> handles |
3283 | |
|
|
3284 | Early versions of winsocket's select only supported waiting for a maximum |
3010 | (probably owning to the fact that all windows kernels can only wait for |
3285 | of C<64> handles (probably owning to the fact that all windows kernels |
3011 | C<64> things at the same time internally; microsoft recommends spawning a |
3286 | can only wait for C<64> things at the same time internally; microsoft |
3012 | chain of threads and wait for 63 handles and the previous thread in each). |
3287 | recommends spawning a chain of threads and wait for 63 handles and the |
|
|
3288 | previous thread in each. Great). |
3013 | |
3289 | |
3014 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3290 | Newer versions support more handles, but you need to define C<FD_SETSIZE> |
3015 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3291 | to some high number (e.g. C<2048>) before compiling the winsocket select |
3016 | call (which might be in libev or elsewhere, for example, perl does its own |
3292 | call (which might be in libev or elsewhere, for example, perl does its own |
3017 | select emulation on windows). |
3293 | select emulation on windows). |
… | |
… | |
3029 | calling select (O(n²)) will likely make this unworkable. |
3305 | calling select (O(n²)) will likely make this unworkable. |
3030 | |
3306 | |
3031 | =back |
3307 | =back |
3032 | |
3308 | |
3033 | |
3309 | |
|
|
3310 | =head1 PORTABILITY REQUIREMENTS |
|
|
3311 | |
|
|
3312 | In addition to a working ISO-C implementation, libev relies on a few |
|
|
3313 | additional extensions: |
|
|
3314 | |
|
|
3315 | =over 4 |
|
|
3316 | |
|
|
3317 | =item C<sig_atomic_t volatile> must be thread-atomic as well |
|
|
3318 | |
|
|
3319 | The type C<sig_atomic_t volatile> (or whatever is defined as |
|
|
3320 | C<EV_ATOMIC_T>) must be atomic w.r.t. accesses from different |
|
|
3321 | threads. This is not part of the specification for C<sig_atomic_t>, but is |
|
|
3322 | believed to be sufficiently portable. |
|
|
3323 | |
|
|
3324 | =item C<sigprocmask> must work in a threaded environment |
|
|
3325 | |
|
|
3326 | Libev uses C<sigprocmask> to temporarily block signals. This is not |
|
|
3327 | allowed in a threaded program (C<pthread_sigmask> has to be used). Typical |
|
|
3328 | pthread implementations will either allow C<sigprocmask> in the "main |
|
|
3329 | thread" or will block signals process-wide, both behaviours would |
|
|
3330 | be compatible with libev. Interaction between C<sigprocmask> and |
|
|
3331 | C<pthread_sigmask> could complicate things, however. |
|
|
3332 | |
|
|
3333 | The most portable way to handle signals is to block signals in all threads |
|
|
3334 | except the initial one, and run the default loop in the initial thread as |
|
|
3335 | well. |
|
|
3336 | |
|
|
3337 | =item C<long> must be large enough for common memory allocation sizes |
|
|
3338 | |
|
|
3339 | To improve portability and simplify using libev, libev uses C<long> |
|
|
3340 | internally instead of C<size_t> when allocating its data structures. On |
|
|
3341 | non-POSIX systems (Microsoft...) this might be unexpectedly low, but |
|
|
3342 | is still at least 31 bits everywhere, which is enough for hundreds of |
|
|
3343 | millions of watchers. |
|
|
3344 | |
|
|
3345 | =item C<double> must hold a time value in seconds with enough accuracy |
|
|
3346 | |
|
|
3347 | The type C<double> is used to represent timestamps. It is required to |
|
|
3348 | have at least 51 bits of mantissa (and 9 bits of exponent), which is good |
|
|
3349 | enough for at least into the year 4000. This requirement is fulfilled by |
|
|
3350 | implementations implementing IEEE 754 (basically all existing ones). |
|
|
3351 | |
|
|
3352 | =back |
|
|
3353 | |
|
|
3354 | If you know of other additional requirements drop me a note. |
|
|
3355 | |
|
|
3356 | |
3034 | =head1 AUTHOR |
3357 | =head1 AUTHOR |
3035 | |
3358 | |
3036 | Marc Lehmann <libev@schmorp.de>. |
3359 | Marc Lehmann <libev@schmorp.de>. |
3037 | |
3360 | |