… | |
… | |
58 | ev_timer_start (loop, &timeout_watcher); |
58 | ev_timer_start (loop, &timeout_watcher); |
59 | |
59 | |
60 | // now wait for events to arrive |
60 | // now wait for events to arrive |
61 | ev_run (loop, 0); |
61 | ev_run (loop, 0); |
62 | |
62 | |
63 | // unloop was called, so exit |
63 | // break was called, so exit |
64 | return 0; |
64 | return 0; |
65 | } |
65 | } |
66 | |
66 | |
67 | =head1 ABOUT THIS DOCUMENT |
67 | =head1 ABOUT THIS DOCUMENT |
68 | |
68 | |
… | |
… | |
178 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_update_now> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
|
|
185 | passed (approximately - it might return a bit earlier even if not |
|
|
186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
|
|
187 | |
185 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
|
|
189 | |
|
|
190 | The range of the C<interval> is limited - libev only guarantees to work |
|
|
191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
192 | |
187 | =item int ev_version_major () |
193 | =item int ev_version_major () |
188 | |
194 | |
189 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
190 | |
196 | |
… | |
… | |
442 | |
448 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
449 | This behaviour is useful when you want to do your own signal handling, or |
444 | want to handle signals only in specific threads and want to avoid libev |
450 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
451 | unblocking the signals. |
446 | |
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
455 | |
447 | This flag's behaviour will become the default in future versions of libev. |
456 | This flag's behaviour will become the default in future versions of libev. |
448 | |
457 | |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
458 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
450 | |
459 | |
451 | This is your standard select(2) backend. Not I<completely> standard, as |
460 | This is your standard select(2) backend. Not I<completely> standard, as |
… | |
… | |
480 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
489 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
481 | |
490 | |
482 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
491 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
483 | kernels). |
492 | kernels). |
484 | |
493 | |
485 | For few fds, this backend is a bit little slower than poll and select, |
494 | For few fds, this backend is a bit little slower than poll and select, but |
486 | but it scales phenomenally better. While poll and select usually scale |
495 | it scales phenomenally better. While poll and select usually scale like |
487 | like O(total_fds) where n is the total number of fds (or the highest fd), |
496 | O(total_fds) where total_fds is the total number of fds (or the highest |
488 | epoll scales either O(1) or O(active_fds). |
497 | fd), epoll scales either O(1) or O(active_fds). |
489 | |
498 | |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
499 | The epoll mechanism deserves honorable mention as the most misdesigned |
491 | of the more advanced event mechanisms: mere annoyances include silently |
500 | of the more advanced event mechanisms: mere annoyances include silently |
492 | dropping file descriptors, requiring a system call per change per file |
501 | dropping file descriptors, requiring a system call per change per file |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
502 | descriptor (and unnecessary guessing of parameters), problems with dup, |
… | |
… | |
496 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
497 | forks then I<both> parent and child process have to recreate the epoll |
506 | forks then I<both> parent and child process have to recreate the epoll |
498 | set, which can take considerable time (one syscall per file descriptor) |
507 | set, which can take considerable time (one syscall per file descriptor) |
499 | and is of course hard to detect. |
508 | and is of course hard to detect. |
500 | |
509 | |
501 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
502 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
503 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
504 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
505 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
506 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
507 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also errornously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
508 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
509 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
510 | |
522 | |
511 | Epoll is truly the train wreck analog among event poll mechanisms, |
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
512 | a frankenpoll, cobbled together in a hurry, no thought to design or |
524 | cobbled together in a hurry, no thought to design or interaction with |
513 | interaction with others. |
525 | others. Oh, the pain, will it ever stop... |
514 | |
526 | |
515 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
516 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
517 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
518 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
822 | This is useful if you are waiting for some external event in conjunction |
834 | This is useful if you are waiting for some external event in conjunction |
823 | with something not expressible using other libev watchers (i.e. "roll your |
835 | with something not expressible using other libev watchers (i.e. "roll your |
824 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
836 | own C<ev_run>"). However, a pair of C<ev_prepare>/C<ev_check> watchers is |
825 | usually a better approach for this kind of thing. |
837 | usually a better approach for this kind of thing. |
826 | |
838 | |
827 | Here are the gory details of what C<ev_run> does: |
839 | Here are the gory details of what C<ev_run> does (this is for your |
|
|
840 | understanding, not a guarantee that things will work exactly like this in |
|
|
841 | future versions): |
828 | |
842 | |
829 | - Increment loop depth. |
843 | - Increment loop depth. |
830 | - Reset the ev_break status. |
844 | - Reset the ev_break status. |
831 | - Before the first iteration, call any pending watchers. |
845 | - Before the first iteration, call any pending watchers. |
832 | LOOP: |
846 | LOOP: |
… | |
… | |
865 | anymore. |
879 | anymore. |
866 | |
880 | |
867 | ... queue jobs here, make sure they register event watchers as long |
881 | ... queue jobs here, make sure they register event watchers as long |
868 | ... as they still have work to do (even an idle watcher will do..) |
882 | ... as they still have work to do (even an idle watcher will do..) |
869 | ev_run (my_loop, 0); |
883 | ev_run (my_loop, 0); |
870 | ... jobs done or somebody called unloop. yeah! |
884 | ... jobs done or somebody called break. yeah! |
871 | |
885 | |
872 | =item ev_break (loop, how) |
886 | =item ev_break (loop, how) |
873 | |
887 | |
874 | Can be used to make a call to C<ev_run> return early (but only after it |
888 | Can be used to make a call to C<ev_run> return early (but only after it |
875 | has processed all outstanding events). The C<how> argument must be either |
889 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
938 | overhead for the actual polling but can deliver many events at once. |
952 | overhead for the actual polling but can deliver many events at once. |
939 | |
953 | |
940 | By setting a higher I<io collect interval> you allow libev to spend more |
954 | By setting a higher I<io collect interval> you allow libev to spend more |
941 | time collecting I/O events, so you can handle more events per iteration, |
955 | time collecting I/O events, so you can handle more events per iteration, |
942 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
956 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
943 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
957 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
944 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
958 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
945 | sleep time ensures that libev will not poll for I/O events more often then |
959 | sleep time ensures that libev will not poll for I/O events more often then |
946 | once per this interval, on average. |
960 | once per this interval, on average (as long as the host time resolution is |
|
|
961 | good enough). |
947 | |
962 | |
948 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
963 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
949 | to spend more time collecting timeouts, at the expense of increased |
964 | to spend more time collecting timeouts, at the expense of increased |
950 | latency/jitter/inexactness (the watcher callback will be called |
965 | latency/jitter/inexactness (the watcher callback will be called |
951 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
966 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
1357 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1372 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1358 | functions that do not need a watcher. |
1373 | functions that do not need a watcher. |
1359 | |
1374 | |
1360 | =back |
1375 | =back |
1361 | |
1376 | |
1362 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1377 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1363 | |
1378 | OWN COMPOSITE WATCHERS> idioms. |
1364 | Each watcher has, by default, a member C<void *data> that you can change |
|
|
1365 | and read at any time: libev will completely ignore it. This can be used |
|
|
1366 | to associate arbitrary data with your watcher. If you need more data and |
|
|
1367 | don't want to allocate memory and store a pointer to it in that data |
|
|
1368 | member, you can also "subclass" the watcher type and provide your own |
|
|
1369 | data: |
|
|
1370 | |
|
|
1371 | struct my_io |
|
|
1372 | { |
|
|
1373 | ev_io io; |
|
|
1374 | int otherfd; |
|
|
1375 | void *somedata; |
|
|
1376 | struct whatever *mostinteresting; |
|
|
1377 | }; |
|
|
1378 | |
|
|
1379 | ... |
|
|
1380 | struct my_io w; |
|
|
1381 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
1382 | |
|
|
1383 | And since your callback will be called with a pointer to the watcher, you |
|
|
1384 | can cast it back to your own type: |
|
|
1385 | |
|
|
1386 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
1387 | { |
|
|
1388 | struct my_io *w = (struct my_io *)w_; |
|
|
1389 | ... |
|
|
1390 | } |
|
|
1391 | |
|
|
1392 | More interesting and less C-conformant ways of casting your callback type |
|
|
1393 | instead have been omitted. |
|
|
1394 | |
|
|
1395 | Another common scenario is to use some data structure with multiple |
|
|
1396 | embedded watchers: |
|
|
1397 | |
|
|
1398 | struct my_biggy |
|
|
1399 | { |
|
|
1400 | int some_data; |
|
|
1401 | ev_timer t1; |
|
|
1402 | ev_timer t2; |
|
|
1403 | } |
|
|
1404 | |
|
|
1405 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
1406 | complicated: Either you store the address of your C<my_biggy> struct |
|
|
1407 | in the C<data> member of the watcher (for woozies), or you need to use |
|
|
1408 | some pointer arithmetic using C<offsetof> inside your watchers (for real |
|
|
1409 | programmers): |
|
|
1410 | |
|
|
1411 | #include <stddef.h> |
|
|
1412 | |
|
|
1413 | static void |
|
|
1414 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
1415 | { |
|
|
1416 | struct my_biggy big = (struct my_biggy *) |
|
|
1417 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
1418 | } |
|
|
1419 | |
|
|
1420 | static void |
|
|
1421 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
1422 | { |
|
|
1423 | struct my_biggy big = (struct my_biggy *) |
|
|
1424 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
1425 | } |
|
|
1426 | |
1379 | |
1427 | =head2 WATCHER STATES |
1380 | =head2 WATCHER STATES |
1428 | |
1381 | |
1429 | There are various watcher states mentioned throughout this manual - |
1382 | There are various watcher states mentioned throughout this manual - |
1430 | active, pending and so on. In this section these states and the rules to |
1383 | active, pending and so on. In this section these states and the rules to |
… | |
… | |
1437 | |
1390 | |
1438 | Before a watcher can be registered with the event looop it has to be |
1391 | Before a watcher can be registered with the event looop it has to be |
1439 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1392 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1440 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1393 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1441 | |
1394 | |
1442 | In this state it is simply some block of memory that is suitable for use |
1395 | In this state it is simply some block of memory that is suitable for |
1443 | in an event loop. It can be moved around, freed, reused etc. at will. |
1396 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1397 | will - as long as you either keep the memory contents intact, or call |
|
|
1398 | C<ev_TYPE_init> again. |
1444 | |
1399 | |
1445 | =item started/running/active |
1400 | =item started/running/active |
1446 | |
1401 | |
1447 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1402 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1448 | property of the event loop, and is actively waiting for events. While in |
1403 | property of the event loop, and is actively waiting for events. While in |
… | |
… | |
1476 | latter will clear any pending state the watcher might be in, regardless |
1431 | latter will clear any pending state the watcher might be in, regardless |
1477 | of whether it was active or not, so stopping a watcher explicitly before |
1432 | of whether it was active or not, so stopping a watcher explicitly before |
1478 | freeing it is often a good idea. |
1433 | freeing it is often a good idea. |
1479 | |
1434 | |
1480 | While stopped (and not pending) the watcher is essentially in the |
1435 | While stopped (and not pending) the watcher is essentially in the |
1481 | initialised state, that is it can be reused, moved, modified in any way |
1436 | initialised state, that is, it can be reused, moved, modified in any way |
1482 | you wish. |
1437 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1438 | it again). |
1483 | |
1439 | |
1484 | =back |
1440 | =back |
1485 | |
1441 | |
1486 | =head2 WATCHER PRIORITY MODELS |
1442 | =head2 WATCHER PRIORITY MODELS |
1487 | |
1443 | |
… | |
… | |
1680 | always get a readiness notification instantly, and your read (or possibly |
1636 | always get a readiness notification instantly, and your read (or possibly |
1681 | write) will still block on the disk I/O. |
1637 | write) will still block on the disk I/O. |
1682 | |
1638 | |
1683 | Another way to view it is that in the case of sockets, pipes, character |
1639 | Another way to view it is that in the case of sockets, pipes, character |
1684 | devices and so on, there is another party (the sender) that delivers data |
1640 | devices and so on, there is another party (the sender) that delivers data |
1685 | on it's own, but in the case of files, there is no such thing: the disk |
1641 | on its own, but in the case of files, there is no such thing: the disk |
1686 | will not send data on it's own, simply because it doesn't know what you |
1642 | will not send data on its own, simply because it doesn't know what you |
1687 | wish to read - you would first have to request some data. |
1643 | wish to read - you would first have to request some data. |
1688 | |
1644 | |
1689 | Since files are typically not-so-well supported by advanced notification |
1645 | Since files are typically not-so-well supported by advanced notification |
1690 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
1646 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
1691 | to files, even though you should not use it. The reason for this is |
1647 | to files, even though you should not use it. The reason for this is |
… | |
… | |
2207 | |
2163 | |
2208 | Another way to think about it (for the mathematically inclined) is that |
2164 | Another way to think about it (for the mathematically inclined) is that |
2209 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2165 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2210 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2166 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2211 | |
2167 | |
2212 | For numerical stability it is preferable that the C<offset> value is near |
2168 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2213 | C<ev_now ()> (the current time), but there is no range requirement for |
2169 | interval value should be higher than C<1/8192> (which is around 100 |
2214 | this value, and in fact is often specified as zero. |
2170 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2171 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2172 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2173 | C<0> and C<interval>, which is also the recommended range. |
2215 | |
2174 | |
2216 | Note also that there is an upper limit to how often a timer can fire (CPU |
2175 | Note also that there is an upper limit to how often a timer can fire (CPU |
2217 | speed for example), so if C<interval> is very small then timing stability |
2176 | speed for example), so if C<interval> is very small then timing stability |
2218 | will of course deteriorate. Libev itself tries to be exact to be about one |
2177 | will of course deteriorate. Libev itself tries to be exact to be about one |
2219 | millisecond (if the OS supports it and the machine is fast enough). |
2178 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2362 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2321 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2363 | |
2322 | |
2364 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2323 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2365 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2324 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2366 | stopping it again), that is, libev might or might not block the signal, |
2325 | stopping it again), that is, libev might or might not block the signal, |
2367 | and might or might not set or restore the installed signal handler. |
2326 | and might or might not set or restore the installed signal handler (but |
|
|
2327 | see C<EVFLAG_NOSIGMASK>). |
2368 | |
2328 | |
2369 | While this does not matter for the signal disposition (libev never |
2329 | While this does not matter for the signal disposition (libev never |
2370 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2330 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2371 | C<execve>), this matters for the signal mask: many programs do not expect |
2331 | C<execve>), this matters for the signal mask: many programs do not expect |
2372 | certain signals to be blocked. |
2332 | certain signals to be blocked. |
… | |
… | |
3243 | atexit (program_exits); |
3203 | atexit (program_exits); |
3244 | |
3204 | |
3245 | |
3205 | |
3246 | =head2 C<ev_async> - how to wake up an event loop |
3206 | =head2 C<ev_async> - how to wake up an event loop |
3247 | |
3207 | |
3248 | In general, you cannot use an C<ev_run> from multiple threads or other |
3208 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3249 | asynchronous sources such as signal handlers (as opposed to multiple event |
3209 | asynchronous sources such as signal handlers (as opposed to multiple event |
3250 | loops - those are of course safe to use in different threads). |
3210 | loops - those are of course safe to use in different threads). |
3251 | |
3211 | |
3252 | Sometimes, however, you need to wake up an event loop you do not control, |
3212 | Sometimes, however, you need to wake up an event loop you do not control, |
3253 | for example because it belongs to another thread. This is what C<ev_async> |
3213 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3363 | trust me. |
3323 | trust me. |
3364 | |
3324 | |
3365 | =item ev_async_send (loop, ev_async *) |
3325 | =item ev_async_send (loop, ev_async *) |
3366 | |
3326 | |
3367 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3327 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3368 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3328 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3329 | returns. |
|
|
3330 | |
3369 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3331 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3370 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3332 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3371 | section below on what exactly this means). |
3333 | embedding section below on what exactly this means). |
3372 | |
3334 | |
3373 | Note that, as with other watchers in libev, multiple events might get |
3335 | Note that, as with other watchers in libev, multiple events might get |
3374 | compressed into a single callback invocation (another way to look at this |
3336 | compressed into a single callback invocation (another way to look at this |
3375 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3337 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3376 | reset when the event loop detects that). |
3338 | reset when the event loop detects that). |
… | |
… | |
3456 | |
3418 | |
3457 | This section explains some common idioms that are not immediately |
3419 | This section explains some common idioms that are not immediately |
3458 | obvious. Note that examples are sprinkled over the whole manual, and this |
3420 | obvious. Note that examples are sprinkled over the whole manual, and this |
3459 | section only contains stuff that wouldn't fit anywhere else. |
3421 | section only contains stuff that wouldn't fit anywhere else. |
3460 | |
3422 | |
3461 | =over 4 |
3423 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
3462 | |
3424 | |
3463 | =item Model/nested event loop invocations and exit conditions. |
3425 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3426 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3427 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3428 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3429 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3430 | data: |
|
|
3431 | |
|
|
3432 | struct my_io |
|
|
3433 | { |
|
|
3434 | ev_io io; |
|
|
3435 | int otherfd; |
|
|
3436 | void *somedata; |
|
|
3437 | struct whatever *mostinteresting; |
|
|
3438 | }; |
|
|
3439 | |
|
|
3440 | ... |
|
|
3441 | struct my_io w; |
|
|
3442 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3443 | |
|
|
3444 | And since your callback will be called with a pointer to the watcher, you |
|
|
3445 | can cast it back to your own type: |
|
|
3446 | |
|
|
3447 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3448 | { |
|
|
3449 | struct my_io *w = (struct my_io *)w_; |
|
|
3450 | ... |
|
|
3451 | } |
|
|
3452 | |
|
|
3453 | More interesting and less C-conformant ways of casting your callback |
|
|
3454 | function type instead have been omitted. |
|
|
3455 | |
|
|
3456 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3457 | |
|
|
3458 | Another common scenario is to use some data structure with multiple |
|
|
3459 | embedded watchers, in effect creating your own watcher that combines |
|
|
3460 | multiple libev event sources into one "super-watcher": |
|
|
3461 | |
|
|
3462 | struct my_biggy |
|
|
3463 | { |
|
|
3464 | int some_data; |
|
|
3465 | ev_timer t1; |
|
|
3466 | ev_timer t2; |
|
|
3467 | } |
|
|
3468 | |
|
|
3469 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3470 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3471 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3472 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3473 | real programmers): |
|
|
3474 | |
|
|
3475 | #include <stddef.h> |
|
|
3476 | |
|
|
3477 | static void |
|
|
3478 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3479 | { |
|
|
3480 | struct my_biggy big = (struct my_biggy *) |
|
|
3481 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3482 | } |
|
|
3483 | |
|
|
3484 | static void |
|
|
3485 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3486 | { |
|
|
3487 | struct my_biggy big = (struct my_biggy *) |
|
|
3488 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3489 | } |
|
|
3490 | |
|
|
3491 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3464 | |
3492 | |
3465 | Often (especially in GUI toolkits) there are places where you have |
3493 | Often (especially in GUI toolkits) there are places where you have |
3466 | I<modal> interaction, which is most easily implemented by recursively |
3494 | I<modal> interaction, which is most easily implemented by recursively |
3467 | invoking C<ev_run>. |
3495 | invoking C<ev_run>. |
3468 | |
3496 | |
… | |
… | |
3497 | exit_main_loop = 1; |
3525 | exit_main_loop = 1; |
3498 | |
3526 | |
3499 | // exit both |
3527 | // exit both |
3500 | exit_main_loop = exit_nested_loop = 1; |
3528 | exit_main_loop = exit_nested_loop = 1; |
3501 | |
3529 | |
3502 | =item Thread locking example |
3530 | =head2 THREAD LOCKING EXAMPLE |
3503 | |
3531 | |
3504 | Here is a fictitious example of how to run an event loop in a different |
3532 | Here is a fictitious example of how to run an event loop in a different |
3505 | thread than where callbacks are being invoked and watchers are |
3533 | thread from where callbacks are being invoked and watchers are |
3506 | created/added/removed. |
3534 | created/added/removed. |
3507 | |
3535 | |
3508 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3536 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3509 | which uses exactly this technique (which is suited for many high-level |
3537 | which uses exactly this technique (which is suited for many high-level |
3510 | languages). |
3538 | languages). |
… | |
… | |
3536 | // now associate this with the loop |
3564 | // now associate this with the loop |
3537 | ev_set_userdata (EV_A_ u); |
3565 | ev_set_userdata (EV_A_ u); |
3538 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3566 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3539 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3567 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3540 | |
3568 | |
3541 | // then create the thread running ev_loop |
3569 | // then create the thread running ev_run |
3542 | pthread_create (&u->tid, 0, l_run, EV_A); |
3570 | pthread_create (&u->tid, 0, l_run, EV_A); |
3543 | } |
3571 | } |
3544 | |
3572 | |
3545 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3573 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3546 | solely to wake up the event loop so it takes notice of any new watchers |
3574 | solely to wake up the event loop so it takes notice of any new watchers |
… | |
… | |
3635 | Note that sending the C<ev_async> watcher is required because otherwise |
3663 | Note that sending the C<ev_async> watcher is required because otherwise |
3636 | an event loop currently blocking in the kernel will have no knowledge |
3664 | an event loop currently blocking in the kernel will have no knowledge |
3637 | about the newly added timer. By waking up the loop it will pick up any new |
3665 | about the newly added timer. By waking up the loop it will pick up any new |
3638 | watchers in the next event loop iteration. |
3666 | watchers in the next event loop iteration. |
3639 | |
3667 | |
3640 | =back |
3668 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3669 | |
|
|
3670 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3671 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3672 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3673 | doesn't need callbacks anymore. |
|
|
3674 | |
|
|
3675 | Imagine you have coroutines that you can switch to using a function |
|
|
3676 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3677 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3678 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3679 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3680 | the differing C<;> conventions): |
|
|
3681 | |
|
|
3682 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3683 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3684 | |
|
|
3685 | That means instead of having a C callback function, you store the |
|
|
3686 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3687 | your callback, you instead have it switch to that coroutine. |
|
|
3688 | |
|
|
3689 | A coroutine might now wait for an event with a function called |
|
|
3690 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3691 | matter when, or whether the watcher is active or not when this function is |
|
|
3692 | called): |
|
|
3693 | |
|
|
3694 | void |
|
|
3695 | wait_for_event (ev_watcher *w) |
|
|
3696 | { |
|
|
3697 | ev_cb_set (w) = current_coro; |
|
|
3698 | switch_to (libev_coro); |
|
|
3699 | } |
|
|
3700 | |
|
|
3701 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3702 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3703 | this or any other coroutine. I am sure if you sue this your own :) |
|
|
3704 | |
|
|
3705 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3706 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3707 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3708 | any waiters. |
|
|
3709 | |
|
|
3710 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3711 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3712 | |
|
|
3713 | // my_ev.h |
|
|
3714 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3715 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3716 | #include "../libev/ev.h" |
|
|
3717 | |
|
|
3718 | // my_ev.c |
|
|
3719 | #define EV_H "my_ev.h" |
|
|
3720 | #include "../libev/ev.c" |
|
|
3721 | |
|
|
3722 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3723 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3724 | can even use F<ev.h> as header file name directly. |
3641 | |
3725 | |
3642 | |
3726 | |
3643 | =head1 LIBEVENT EMULATION |
3727 | =head1 LIBEVENT EMULATION |
3644 | |
3728 | |
3645 | Libev offers a compatibility emulation layer for libevent. It cannot |
3729 | Libev offers a compatibility emulation layer for libevent. It cannot |
… | |
… | |
4135 | F<event.h> that are not directly supported by the libev core alone. |
4219 | F<event.h> that are not directly supported by the libev core alone. |
4136 | |
4220 | |
4137 | In standalone mode, libev will still try to automatically deduce the |
4221 | In standalone mode, libev will still try to automatically deduce the |
4138 | configuration, but has to be more conservative. |
4222 | configuration, but has to be more conservative. |
4139 | |
4223 | |
|
|
4224 | =item EV_USE_FLOOR |
|
|
4225 | |
|
|
4226 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4227 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4228 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4229 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4230 | function is not available will fail, so the safe default is to not enable |
|
|
4231 | this. |
|
|
4232 | |
4140 | =item EV_USE_MONOTONIC |
4233 | =item EV_USE_MONOTONIC |
4141 | |
4234 | |
4142 | If defined to be C<1>, libev will try to detect the availability of the |
4235 | If defined to be C<1>, libev will try to detect the availability of the |
4143 | monotonic clock option at both compile time and runtime. Otherwise no |
4236 | monotonic clock option at both compile time and runtime. Otherwise no |
4144 | use of the monotonic clock option will be attempted. If you enable this, |
4237 | use of the monotonic clock option will be attempted. If you enable this, |
… | |
… | |
4575 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4668 | And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: |
4576 | |
4669 | |
4577 | #include "ev_cpp.h" |
4670 | #include "ev_cpp.h" |
4578 | #include "ev.c" |
4671 | #include "ev.c" |
4579 | |
4672 | |
4580 | =head1 INTERACTION WITH OTHER PROGRAMS OR LIBRARIES |
4673 | =head1 INTERACTION WITH OTHER PROGRAMS, LIBRARIES OR THE ENVIRONMENT |
4581 | |
4674 | |
4582 | =head2 THREADS AND COROUTINES |
4675 | =head2 THREADS AND COROUTINES |
4583 | |
4676 | |
4584 | =head3 THREADS |
4677 | =head3 THREADS |
4585 | |
4678 | |
… | |
… | |
4636 | default loop and triggering an C<ev_async> watcher from the default loop |
4729 | default loop and triggering an C<ev_async> watcher from the default loop |
4637 | watcher callback into the event loop interested in the signal. |
4730 | watcher callback into the event loop interested in the signal. |
4638 | |
4731 | |
4639 | =back |
4732 | =back |
4640 | |
4733 | |
4641 | See also L<Thread locking example>. |
4734 | See also L<THREAD LOCKING EXAMPLE>. |
4642 | |
4735 | |
4643 | =head3 COROUTINES |
4736 | =head3 COROUTINES |
4644 | |
4737 | |
4645 | Libev is very accommodating to coroutines ("cooperative threads"): |
4738 | Libev is very accommodating to coroutines ("cooperative threads"): |
4646 | libev fully supports nesting calls to its functions from different |
4739 | libev fully supports nesting calls to its functions from different |
… | |
… | |
5155 | The physical time that is observed. It is apparently strictly monotonic :) |
5248 | The physical time that is observed. It is apparently strictly monotonic :) |
5156 | |
5249 | |
5157 | =item wall-clock time |
5250 | =item wall-clock time |
5158 | |
5251 | |
5159 | The time and date as shown on clocks. Unlike real time, it can actually |
5252 | The time and date as shown on clocks. Unlike real time, it can actually |
5160 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5253 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5161 | clock. |
5254 | clock. |
5162 | |
5255 | |
5163 | =item watcher |
5256 | =item watcher |
5164 | |
5257 | |
5165 | A data structure that describes interest in certain events. Watchers need |
5258 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5168 | =back |
5261 | =back |
5169 | |
5262 | |
5170 | =head1 AUTHOR |
5263 | =head1 AUTHOR |
5171 | |
5264 | |
5172 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5265 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5173 | Magnusson and Emanuele Giaquinta. |
5266 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5174 | |
5267 | |