… | |
… | |
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 | |
… | |
… | |
442 | |
442 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
443 | 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 |
444 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
445 | unblocking the signals. |
446 | |
446 | |
|
|
447 | It's also required by POSIX in a threaded program, as libev calls |
|
|
448 | C<sigprocmask>, whose behaviour is officially unspecified. |
|
|
449 | |
447 | This flag's behaviour will become the default in future versions of libev. |
450 | This flag's behaviour will become the default in future versions of libev. |
448 | |
451 | |
449 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
452 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
450 | |
453 | |
451 | This is your standard select(2) backend. Not I<completely> standard, as |
454 | This is your standard select(2) backend. Not I<completely> standard, as |
… | |
… | |
480 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
483 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
481 | |
484 | |
482 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
485 | Use the linux-specific epoll(7) interface (for both pre- and post-2.6.9 |
483 | kernels). |
486 | kernels). |
484 | |
487 | |
485 | For few fds, this backend is a bit little slower than poll and select, |
488 | 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 |
489 | 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), |
490 | 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). |
491 | fd), epoll scales either O(1) or O(active_fds). |
489 | |
492 | |
490 | The epoll mechanism deserves honorable mention as the most misdesigned |
493 | The epoll mechanism deserves honorable mention as the most misdesigned |
491 | of the more advanced event mechanisms: mere annoyances include silently |
494 | of the more advanced event mechanisms: mere annoyances include silently |
492 | dropping file descriptors, requiring a system call per change per file |
495 | dropping file descriptors, requiring a system call per change per file |
493 | descriptor (and unnecessary guessing of parameters), problems with dup, |
496 | descriptor (and unnecessary guessing of parameters), problems with dup, |
… | |
… | |
865 | anymore. |
868 | anymore. |
866 | |
869 | |
867 | ... queue jobs here, make sure they register event watchers as long |
870 | ... 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..) |
871 | ... as they still have work to do (even an idle watcher will do..) |
869 | ev_run (my_loop, 0); |
872 | ev_run (my_loop, 0); |
870 | ... jobs done or somebody called unloop. yeah! |
873 | ... jobs done or somebody called break. yeah! |
871 | |
874 | |
872 | =item ev_break (loop, how) |
875 | =item ev_break (loop, how) |
873 | |
876 | |
874 | Can be used to make a call to C<ev_run> return early (but only after it |
877 | 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 |
878 | has processed all outstanding events). The C<how> argument must be either |
… | |
… | |
1357 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1360 | See also C<ev_feed_fd_event> and C<ev_feed_signal_event> for related |
1358 | functions that do not need a watcher. |
1361 | functions that do not need a watcher. |
1359 | |
1362 | |
1360 | =back |
1363 | =back |
1361 | |
1364 | |
1362 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
1365 | See also the L<ASSOCIATING CUSTOM DATA WITH A WATCHER> and L<BUILDING YOUR |
1363 | |
1366 | 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 | |
1367 | |
1427 | =head2 WATCHER STATES |
1368 | =head2 WATCHER STATES |
1428 | |
1369 | |
1429 | There are various watcher states mentioned throughout this manual - |
1370 | There are various watcher states mentioned throughout this manual - |
1430 | active, pending and so on. In this section these states and the rules to |
1371 | active, pending and so on. In this section these states and the rules to |
… | |
… | |
1437 | |
1378 | |
1438 | Before a watcher can be registered with the event looop it has to be |
1379 | 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 |
1380 | 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. |
1381 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1441 | |
1382 | |
1442 | In this state it is simply some block of memory that is suitable for use |
1383 | 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. |
1384 | use in an event loop. It can be moved around, freed, reused etc. at |
|
|
1385 | will - as long as you either keep the memory contents intact, or call |
|
|
1386 | C<ev_TYPE_init> again. |
1444 | |
1387 | |
1445 | =item started/running/active |
1388 | =item started/running/active |
1446 | |
1389 | |
1447 | Once a watcher has been started with a call to C<ev_TYPE_start> it becomes |
1390 | 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 |
1391 | 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 |
1419 | 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 |
1420 | of whether it was active or not, so stopping a watcher explicitly before |
1478 | freeing it is often a good idea. |
1421 | freeing it is often a good idea. |
1479 | |
1422 | |
1480 | While stopped (and not pending) the watcher is essentially in the |
1423 | 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 |
1424 | initialised state, that is, it can be reused, moved, modified in any way |
1482 | you wish. |
1425 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1426 | it again). |
1483 | |
1427 | |
1484 | =back |
1428 | =back |
1485 | |
1429 | |
1486 | =head2 WATCHER PRIORITY MODELS |
1430 | =head2 WATCHER PRIORITY MODELS |
1487 | |
1431 | |
… | |
… | |
1680 | always get a readiness notification instantly, and your read (or possibly |
1624 | always get a readiness notification instantly, and your read (or possibly |
1681 | write) will still block on the disk I/O. |
1625 | write) will still block on the disk I/O. |
1682 | |
1626 | |
1683 | Another way to view it is that in the case of sockets, pipes, character |
1627 | 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 |
1628 | 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 |
1629 | 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 |
1630 | 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. |
1631 | wish to read - you would first have to request some data. |
1688 | |
1632 | |
1689 | Since files are typically not-so-well supported by advanced notification |
1633 | Since files are typically not-so-well supported by advanced notification |
1690 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
1634 | 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 |
1635 | to files, even though you should not use it. The reason for this is |
… | |
… | |
2207 | |
2151 | |
2208 | Another way to think about it (for the mathematically inclined) is that |
2152 | 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 |
2153 | 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. |
2154 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2211 | |
2155 | |
2212 | For numerical stability it is preferable that the C<offset> value is near |
2156 | 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 |
2157 | interval value should be higher than C<1/8192> (which is around 100 |
2214 | this value, and in fact is often specified as zero. |
2158 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2159 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2160 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2161 | C<0> and C<interval>, which is also the recommended range. |
2215 | |
2162 | |
2216 | Note also that there is an upper limit to how often a timer can fire (CPU |
2163 | 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 |
2164 | 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 |
2165 | 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). |
2166 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2362 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2309 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2363 | |
2310 | |
2364 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2311 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2365 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2312 | (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, |
2313 | 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. |
2314 | and might or might not set or restore the installed signal handler (but |
|
|
2315 | see C<EVFLAG_NOSIGMASK>). |
2368 | |
2316 | |
2369 | While this does not matter for the signal disposition (libev never |
2317 | 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 |
2318 | 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 |
2319 | C<execve>), this matters for the signal mask: many programs do not expect |
2372 | certain signals to be blocked. |
2320 | certain signals to be blocked. |
… | |
… | |
3243 | atexit (program_exits); |
3191 | atexit (program_exits); |
3244 | |
3192 | |
3245 | |
3193 | |
3246 | =head2 C<ev_async> - how to wake up an event loop |
3194 | =head2 C<ev_async> - how to wake up an event loop |
3247 | |
3195 | |
3248 | In general, you cannot use an C<ev_run> from multiple threads or other |
3196 | 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 |
3197 | asynchronous sources such as signal handlers (as opposed to multiple event |
3250 | loops - those are of course safe to use in different threads). |
3198 | loops - those are of course safe to use in different threads). |
3251 | |
3199 | |
3252 | Sometimes, however, you need to wake up an event loop you do not control, |
3200 | 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> |
3201 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3363 | trust me. |
3311 | trust me. |
3364 | |
3312 | |
3365 | =item ev_async_send (loop, ev_async *) |
3313 | =item ev_async_send (loop, ev_async *) |
3366 | |
3314 | |
3367 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3315 | 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 |
3316 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3317 | returns. |
|
|
3318 | |
3369 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3319 | 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 |
3320 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3371 | section below on what exactly this means). |
3321 | embedding section below on what exactly this means). |
3372 | |
3322 | |
3373 | Note that, as with other watchers in libev, multiple events might get |
3323 | 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 |
3324 | 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>, |
3325 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3376 | reset when the event loop detects that). |
3326 | reset when the event loop detects that). |
… | |
… | |
3456 | |
3406 | |
3457 | This section explains some common idioms that are not immediately |
3407 | This section explains some common idioms that are not immediately |
3458 | obvious. Note that examples are sprinkled over the whole manual, and this |
3408 | obvious. Note that examples are sprinkled over the whole manual, and this |
3459 | section only contains stuff that wouldn't fit anywhere else. |
3409 | section only contains stuff that wouldn't fit anywhere else. |
3460 | |
3410 | |
|
|
3411 | =head2 ASSOCIATING CUSTOM DATA WITH A WATCHER |
|
|
3412 | |
|
|
3413 | Each watcher has, by default, a C<void *data> member that you can read |
|
|
3414 | or modify at any time: libev will completely ignore it. This can be used |
|
|
3415 | to associate arbitrary data with your watcher. If you need more data and |
|
|
3416 | don't want to allocate memory separately and store a pointer to it in that |
|
|
3417 | data member, you can also "subclass" the watcher type and provide your own |
|
|
3418 | data: |
|
|
3419 | |
|
|
3420 | struct my_io |
|
|
3421 | { |
|
|
3422 | ev_io io; |
|
|
3423 | int otherfd; |
|
|
3424 | void *somedata; |
|
|
3425 | struct whatever *mostinteresting; |
|
|
3426 | }; |
|
|
3427 | |
|
|
3428 | ... |
|
|
3429 | struct my_io w; |
|
|
3430 | ev_io_init (&w.io, my_cb, fd, EV_READ); |
|
|
3431 | |
|
|
3432 | And since your callback will be called with a pointer to the watcher, you |
|
|
3433 | can cast it back to your own type: |
|
|
3434 | |
|
|
3435 | static void my_cb (struct ev_loop *loop, ev_io *w_, int revents) |
|
|
3436 | { |
|
|
3437 | struct my_io *w = (struct my_io *)w_; |
|
|
3438 | ... |
|
|
3439 | } |
|
|
3440 | |
|
|
3441 | More interesting and less C-conformant ways of casting your callback |
|
|
3442 | function type instead have been omitted. |
|
|
3443 | |
|
|
3444 | =head2 BUILDING YOUR OWN COMPOSITE WATCHERS |
|
|
3445 | |
|
|
3446 | Another common scenario is to use some data structure with multiple |
|
|
3447 | embedded watchers, in effect creating your own watcher that combines |
|
|
3448 | multiple libev event sources into one "super-watcher": |
|
|
3449 | |
|
|
3450 | struct my_biggy |
|
|
3451 | { |
|
|
3452 | int some_data; |
|
|
3453 | ev_timer t1; |
|
|
3454 | ev_timer t2; |
|
|
3455 | } |
|
|
3456 | |
|
|
3457 | In this case getting the pointer to C<my_biggy> is a bit more |
|
|
3458 | complicated: Either you store the address of your C<my_biggy> struct in |
|
|
3459 | the C<data> member of the watcher (for woozies or C++ coders), or you need |
|
|
3460 | to use some pointer arithmetic using C<offsetof> inside your watchers (for |
|
|
3461 | real programmers): |
|
|
3462 | |
|
|
3463 | #include <stddef.h> |
|
|
3464 | |
|
|
3465 | static void |
|
|
3466 | t1_cb (EV_P_ ev_timer *w, int revents) |
|
|
3467 | { |
|
|
3468 | struct my_biggy big = (struct my_biggy *) |
|
|
3469 | (((char *)w) - offsetof (struct my_biggy, t1)); |
|
|
3470 | } |
|
|
3471 | |
|
|
3472 | static void |
|
|
3473 | t2_cb (EV_P_ ev_timer *w, int revents) |
|
|
3474 | { |
|
|
3475 | struct my_biggy big = (struct my_biggy *) |
|
|
3476 | (((char *)w) - offsetof (struct my_biggy, t2)); |
|
|
3477 | } |
|
|
3478 | |
3461 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3479 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3462 | |
3480 | |
3463 | Often (especially in GUI toolkits) there are places where you have |
3481 | Often (especially in GUI toolkits) there are places where you have |
3464 | I<modal> interaction, which is most easily implemented by recursively |
3482 | I<modal> interaction, which is most easily implemented by recursively |
3465 | invoking C<ev_run>. |
3483 | invoking C<ev_run>. |
… | |
… | |
3498 | exit_main_loop = exit_nested_loop = 1; |
3516 | exit_main_loop = exit_nested_loop = 1; |
3499 | |
3517 | |
3500 | =head2 THREAD LOCKING EXAMPLE |
3518 | =head2 THREAD LOCKING EXAMPLE |
3501 | |
3519 | |
3502 | Here is a fictitious example of how to run an event loop in a different |
3520 | Here is a fictitious example of how to run an event loop in a different |
3503 | thread than where callbacks are being invoked and watchers are |
3521 | thread from where callbacks are being invoked and watchers are |
3504 | created/added/removed. |
3522 | created/added/removed. |
3505 | |
3523 | |
3506 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3524 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3507 | which uses exactly this technique (which is suited for many high-level |
3525 | which uses exactly this technique (which is suited for many high-level |
3508 | languages). |
3526 | languages). |
… | |
… | |
3534 | // now associate this with the loop |
3552 | // now associate this with the loop |
3535 | ev_set_userdata (EV_A_ u); |
3553 | ev_set_userdata (EV_A_ u); |
3536 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3554 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3537 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3555 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3538 | |
3556 | |
3539 | // then create the thread running ev_loop |
3557 | // then create the thread running ev_run |
3540 | pthread_create (&u->tid, 0, l_run, EV_A); |
3558 | pthread_create (&u->tid, 0, l_run, EV_A); |
3541 | } |
3559 | } |
3542 | |
3560 | |
3543 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3561 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3544 | solely to wake up the event loop so it takes notice of any new watchers |
3562 | solely to wake up the event loop so it takes notice of any new watchers |
… | |
… | |
3632 | |
3650 | |
3633 | Note that sending the C<ev_async> watcher is required because otherwise |
3651 | Note that sending the C<ev_async> watcher is required because otherwise |
3634 | an event loop currently blocking in the kernel will have no knowledge |
3652 | an event loop currently blocking in the kernel will have no knowledge |
3635 | about the newly added timer. By waking up the loop it will pick up any new |
3653 | about the newly added timer. By waking up the loop it will pick up any new |
3636 | watchers in the next event loop iteration. |
3654 | watchers in the next event loop iteration. |
|
|
3655 | |
|
|
3656 | =head2 THREADS, COROUTINES, CONTINUATIONS, QUEUES... INSTEAD OF CALLBACKS |
|
|
3657 | |
|
|
3658 | While the overhead of a callback that e.g. schedules a thread is small, it |
|
|
3659 | is still an overhead. If you embed libev, and your main usage is with some |
|
|
3660 | kind of threads or coroutines, you might want to customise libev so that |
|
|
3661 | doesn't need callbacks anymore. |
|
|
3662 | |
|
|
3663 | Imagine you have coroutines that you can switch to using a function |
|
|
3664 | C<switch_to (coro)>, that libev runs in a coroutine called C<libev_coro> |
|
|
3665 | and that due to some magic, the currently active coroutine is stored in a |
|
|
3666 | global called C<current_coro>. Then you can build your own "wait for libev |
|
|
3667 | event" primitive by changing C<EV_CB_DECLARE> and C<EV_CB_INVOKE> (note |
|
|
3668 | the differing C<;> conventions): |
|
|
3669 | |
|
|
3670 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3671 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb) |
|
|
3672 | |
|
|
3673 | That means instead of having a C callback function, you store the |
|
|
3674 | coroutine to switch to in each watcher, and instead of having libev call |
|
|
3675 | your callback, you instead have it switch to that coroutine. |
|
|
3676 | |
|
|
3677 | A coroutine might now wait for an event with a function called |
|
|
3678 | C<wait_for_event>. (the watcher needs to be started, as always, but it doesn't |
|
|
3679 | matter when, or whether the watcher is active or not when this function is |
|
|
3680 | called): |
|
|
3681 | |
|
|
3682 | void |
|
|
3683 | wait_for_event (ev_watcher *w) |
|
|
3684 | { |
|
|
3685 | ev_cb_set (w) = current_coro; |
|
|
3686 | switch_to (libev_coro); |
|
|
3687 | } |
|
|
3688 | |
|
|
3689 | That basically suspends the coroutine inside C<wait_for_event> and |
|
|
3690 | continues the libev coroutine, which, when appropriate, switches back to |
|
|
3691 | this or any other coroutine. I am sure if you sue this your own :) |
|
|
3692 | |
|
|
3693 | You can do similar tricks if you have, say, threads with an event queue - |
|
|
3694 | instead of storing a coroutine, you store the queue object and instead of |
|
|
3695 | switching to a coroutine, you push the watcher onto the queue and notify |
|
|
3696 | any waiters. |
|
|
3697 | |
|
|
3698 | To embed libev, see L<EMBEDDING>, but in short, it's easiest to create two |
|
|
3699 | files, F<my_ev.h> and F<my_ev.c> that include the respective libev files: |
|
|
3700 | |
|
|
3701 | // my_ev.h |
|
|
3702 | #define EV_CB_DECLARE(type) struct my_coro *cb; |
|
|
3703 | #define EV_CB_INVOKE(watcher) switch_to ((watcher)->cb); |
|
|
3704 | #include "../libev/ev.h" |
|
|
3705 | |
|
|
3706 | // my_ev.c |
|
|
3707 | #define EV_H "my_ev.h" |
|
|
3708 | #include "../libev/ev.c" |
|
|
3709 | |
|
|
3710 | And then use F<my_ev.h> when you would normally use F<ev.h>, and compile |
|
|
3711 | F<my_ev.c> into your project. When properly specifying include paths, you |
|
|
3712 | can even use F<ev.h> as header file name directly. |
3637 | |
3713 | |
3638 | |
3714 | |
3639 | =head1 LIBEVENT EMULATION |
3715 | =head1 LIBEVENT EMULATION |
3640 | |
3716 | |
3641 | Libev offers a compatibility emulation layer for libevent. It cannot |
3717 | Libev offers a compatibility emulation layer for libevent. It cannot |
… | |
… | |
4131 | F<event.h> that are not directly supported by the libev core alone. |
4207 | F<event.h> that are not directly supported by the libev core alone. |
4132 | |
4208 | |
4133 | In standalone mode, libev will still try to automatically deduce the |
4209 | In standalone mode, libev will still try to automatically deduce the |
4134 | configuration, but has to be more conservative. |
4210 | configuration, but has to be more conservative. |
4135 | |
4211 | |
|
|
4212 | =item EV_USE_FLOOR |
|
|
4213 | |
|
|
4214 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4215 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4216 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4217 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4218 | function is not available will fail, so the safe default is to not enable |
|
|
4219 | this. |
|
|
4220 | |
4136 | =item EV_USE_MONOTONIC |
4221 | =item EV_USE_MONOTONIC |
4137 | |
4222 | |
4138 | If defined to be C<1>, libev will try to detect the availability of the |
4223 | If defined to be C<1>, libev will try to detect the availability of the |
4139 | monotonic clock option at both compile time and runtime. Otherwise no |
4224 | monotonic clock option at both compile time and runtime. Otherwise no |
4140 | use of the monotonic clock option will be attempted. If you enable this, |
4225 | use of the monotonic clock option will be attempted. If you enable this, |
… | |
… | |
5151 | The physical time that is observed. It is apparently strictly monotonic :) |
5236 | The physical time that is observed. It is apparently strictly monotonic :) |
5152 | |
5237 | |
5153 | =item wall-clock time |
5238 | =item wall-clock time |
5154 | |
5239 | |
5155 | The time and date as shown on clocks. Unlike real time, it can actually |
5240 | The time and date as shown on clocks. Unlike real time, it can actually |
5156 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5241 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5157 | clock. |
5242 | clock. |
5158 | |
5243 | |
5159 | =item watcher |
5244 | =item watcher |
5160 | |
5245 | |
5161 | A data structure that describes interest in certain events. Watchers need |
5246 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5164 | =back |
5249 | =back |
5165 | |
5250 | |
5166 | =head1 AUTHOR |
5251 | =head1 AUTHOR |
5167 | |
5252 | |
5168 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5253 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5169 | Magnusson and Emanuele Giaquinta. |
5254 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5170 | |
5255 | |