… | |
… | |
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 | |
… | |
… | |
174 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
175 | |
175 | |
176 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
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_now_update> 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 | |
… | |
… | |
435 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
436 | |
442 | |
437 | =item C<EVFLAG_NOSIGMASK> |
443 | =item C<EVFLAG_NOSIGMASK> |
438 | |
444 | |
439 | When this flag is specified, then libev will avoid to modify the signal |
445 | When this flag is specified, then libev will avoid to modify the signal |
440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
446 | mask. Specifically, this means you have to make sure signals are unblocked |
441 | when you want to receive them. |
447 | when you want to receive them. |
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. |
|
|
452 | |
|
|
453 | It's also required by POSIX in a threaded program, as libev calls |
|
|
454 | C<sigprocmask>, whose behaviour is officially unspecified. |
446 | |
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 | |
… | |
… | |
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 erroneously 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 |
… | |
… | |
596 | among the OS-specific backends (I vastly prefer correctness over speed |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
597 | hacks). |
609 | hacks). |
598 | |
610 | |
599 | On the negative side, the interface is I<bizarre> - so bizarre that |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
600 | even sun itself gets it wrong in their code examples: The event polling |
612 | even sun itself gets it wrong in their code examples: The event polling |
601 | function sometimes returning events to the caller even though an error |
613 | function sometimes returns events to the caller even though an error |
602 | occurred, but with no indication whether it has done so or not (yes, it's |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
603 | even documented that way) - deadly for edge-triggered interfaces where |
615 | even documented that way) - deadly for edge-triggered interfaces where you |
604 | you absolutely have to know whether an event occurred or not because you |
616 | absolutely have to know whether an event occurred or not because you have |
605 | have to re-arm the watcher. |
617 | to re-arm the watcher. |
606 | |
618 | |
607 | Fortunately libev seems to be able to work around these idiocies. |
619 | Fortunately libev seems to be able to work around these idiocies. |
608 | |
620 | |
609 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
610 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
… | |
… | |
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 |
… | |
… | |
1005 | can be done relatively simply by putting mutex_lock/unlock calls around |
1020 | can be done relatively simply by putting mutex_lock/unlock calls around |
1006 | each call to a libev function. |
1021 | each call to a libev function. |
1007 | |
1022 | |
1008 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1023 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1009 | to wait for it to return. One way around this is to wake up the event |
1024 | to wait for it to return. One way around this is to wake up the event |
1010 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1025 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1011 | I<release> and I<acquire> callbacks on the loop. |
1026 | I<release> and I<acquire> callbacks on the loop. |
1012 | |
1027 | |
1013 | When set, then C<release> will be called just before the thread is |
1028 | When set, then C<release> will be called just before the thread is |
1014 | suspended waiting for new events, and C<acquire> is called just |
1029 | suspended waiting for new events, and C<acquire> is called just |
1015 | afterwards. |
1030 | afterwards. |
… | |
… | |
1371 | |
1386 | |
1372 | =over 4 |
1387 | =over 4 |
1373 | |
1388 | |
1374 | =item initialiased |
1389 | =item initialiased |
1375 | |
1390 | |
1376 | Before a watcher can be registered with the event looop it has to be |
1391 | Before a watcher can be registered with the event loop it has to be |
1377 | 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 |
1378 | 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. |
1379 | |
1394 | |
1380 | 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 |
1381 | 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. |
1382 | |
1399 | |
1383 | =item started/running/active |
1400 | =item started/running/active |
1384 | |
1401 | |
1385 | 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 |
1386 | 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 |
… | |
… | |
1414 | 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 |
1415 | 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 |
1416 | freeing it is often a good idea. |
1433 | freeing it is often a good idea. |
1417 | |
1434 | |
1418 | While stopped (and not pending) the watcher is essentially in the |
1435 | While stopped (and not pending) the watcher is essentially in the |
1419 | 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 |
1420 | you wish. |
1437 | you wish (but when you trash the memory block, you need to C<ev_TYPE_init> |
|
|
1438 | it again). |
1421 | |
1439 | |
1422 | =back |
1440 | =back |
1423 | |
1441 | |
1424 | =head2 WATCHER PRIORITY MODELS |
1442 | =head2 WATCHER PRIORITY MODELS |
1425 | |
1443 | |
… | |
… | |
1618 | always get a readiness notification instantly, and your read (or possibly |
1636 | always get a readiness notification instantly, and your read (or possibly |
1619 | write) will still block on the disk I/O. |
1637 | write) will still block on the disk I/O. |
1620 | |
1638 | |
1621 | 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 |
1622 | 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 |
1623 | 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 |
1624 | 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 |
1625 | wish to read - you would first have to request some data. |
1643 | wish to read - you would first have to request some data. |
1626 | |
1644 | |
1627 | Since files are typically not-so-well supported by advanced notification |
1645 | Since files are typically not-so-well supported by advanced notification |
1628 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
1646 | mechanism, libev tries hard to emulate POSIX behaviour with respect |
1629 | 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 |
… | |
… | |
1753 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1771 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1754 | monotonic clock option helps a lot here). |
1772 | monotonic clock option helps a lot here). |
1755 | |
1773 | |
1756 | The callback is guaranteed to be invoked only I<after> its timeout has |
1774 | The callback is guaranteed to be invoked only I<after> its timeout has |
1757 | passed (not I<at>, so on systems with very low-resolution clocks this |
1775 | passed (not I<at>, so on systems with very low-resolution clocks this |
1758 | might introduce a small delay). If multiple timers become ready during the |
1776 | might introduce a small delay, see "the special problem of being too |
|
|
1777 | early", below). If multiple timers become ready during the same loop |
1759 | same loop iteration then the ones with earlier time-out values are invoked |
1778 | iteration then the ones with earlier time-out values are invoked before |
1760 | before ones of the same priority with later time-out values (but this is |
1779 | ones of the same priority with later time-out values (but this is no |
1761 | no longer true when a callback calls C<ev_run> recursively). |
1780 | longer true when a callback calls C<ev_run> recursively). |
1762 | |
1781 | |
1763 | =head3 Be smart about timeouts |
1782 | =head3 Be smart about timeouts |
1764 | |
1783 | |
1765 | Many real-world problems involve some kind of timeout, usually for error |
1784 | Many real-world problems involve some kind of timeout, usually for error |
1766 | recovery. A typical example is an HTTP request - if the other side hangs, |
1785 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1841 | |
1860 | |
1842 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1861 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1843 | but remember the time of last activity, and check for a real timeout only |
1862 | but remember the time of last activity, and check for a real timeout only |
1844 | within the callback: |
1863 | within the callback: |
1845 | |
1864 | |
|
|
1865 | ev_tstamp timeout = 60.; |
1846 | ev_tstamp last_activity; // time of last activity |
1866 | ev_tstamp last_activity; // time of last activity |
|
|
1867 | ev_timer timer; |
1847 | |
1868 | |
1848 | static void |
1869 | static void |
1849 | callback (EV_P_ ev_timer *w, int revents) |
1870 | callback (EV_P_ ev_timer *w, int revents) |
1850 | { |
1871 | { |
1851 | ev_tstamp now = ev_now (EV_A); |
1872 | // calculate when the timeout would happen |
1852 | ev_tstamp timeout = last_activity + 60.; |
1873 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1853 | |
1874 | |
1854 | // if last_activity + 60. is older than now, we did time out |
1875 | // if negative, it means we the timeout already occured |
1855 | if (timeout < now) |
1876 | if (after < 0.) |
1856 | { |
1877 | { |
1857 | // timeout occurred, take action |
1878 | // timeout occurred, take action |
1858 | } |
1879 | } |
1859 | else |
1880 | else |
1860 | { |
1881 | { |
1861 | // callback was invoked, but there was some activity, re-arm |
1882 | // callback was invoked, but there was some recent |
1862 | // the watcher to fire in last_activity + 60, which is |
1883 | // activity. simply restart the timer to time out |
1863 | // guaranteed to be in the future, so "again" is positive: |
1884 | // after "after" seconds, which is the earliest time |
1864 | w->repeat = timeout - now; |
1885 | // the timeout can occur. |
|
|
1886 | ev_timer_set (w, after, 0.); |
1865 | ev_timer_again (EV_A_ w); |
1887 | ev_timer_start (EV_A_ w); |
1866 | } |
1888 | } |
1867 | } |
1889 | } |
1868 | |
1890 | |
1869 | To summarise the callback: first calculate the real timeout (defined |
1891 | To summarise the callback: first calculate in how many seconds the |
1870 | as "60 seconds after the last activity"), then check if that time has |
1892 | timeout will occur (by calculating the absolute time when it would occur, |
1871 | been reached, which means something I<did>, in fact, time out. Otherwise |
1893 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1872 | the callback was invoked too early (C<timeout> is in the future), so |
1894 | (EV_A)> from that). |
1873 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1874 | a timeout then. |
|
|
1875 | |
1895 | |
1876 | Note how C<ev_timer_again> is used, taking advantage of the |
1896 | If this value is negative, then we are already past the timeout, i.e. we |
1877 | C<ev_timer_again> optimisation when the timer is already running. |
1897 | timed out, and need to do whatever is needed in this case. |
|
|
1898 | |
|
|
1899 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1900 | and simply start the timer with this timeout value. |
|
|
1901 | |
|
|
1902 | In other words, each time the callback is invoked it will check whether |
|
|
1903 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1904 | again at the earliest time it could time out. Rinse. Repeat. |
1878 | |
1905 | |
1879 | This scheme causes more callback invocations (about one every 60 seconds |
1906 | This scheme causes more callback invocations (about one every 60 seconds |
1880 | minus half the average time between activity), but virtually no calls to |
1907 | minus half the average time between activity), but virtually no calls to |
1881 | libev to change the timeout. |
1908 | libev to change the timeout. |
1882 | |
1909 | |
1883 | To start the timer, simply initialise the watcher and set C<last_activity> |
1910 | To start the machinery, simply initialise the watcher and set |
1884 | to the current time (meaning we just have some activity :), then call the |
1911 | C<last_activity> to the current time (meaning there was some activity just |
1885 | callback, which will "do the right thing" and start the timer: |
1912 | now), then call the callback, which will "do the right thing" and start |
|
|
1913 | the timer: |
1886 | |
1914 | |
|
|
1915 | last_activity = ev_now (EV_A); |
1887 | ev_init (timer, callback); |
1916 | ev_init (&timer, callback); |
1888 | last_activity = ev_now (loop); |
1917 | callback (EV_A_ &timer, 0); |
1889 | callback (loop, timer, EV_TIMER); |
|
|
1890 | |
1918 | |
1891 | And when there is some activity, simply store the current time in |
1919 | When there is some activity, simply store the current time in |
1892 | C<last_activity>, no libev calls at all: |
1920 | C<last_activity>, no libev calls at all: |
1893 | |
1921 | |
|
|
1922 | if (activity detected) |
1894 | last_activity = ev_now (loop); |
1923 | last_activity = ev_now (EV_A); |
|
|
1924 | |
|
|
1925 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1926 | providing a new value, stopping the timer and calling the callback, which |
|
|
1927 | will agaion do the right thing (for example, time out immediately :). |
|
|
1928 | |
|
|
1929 | timeout = new_value; |
|
|
1930 | ev_timer_stop (EV_A_ &timer); |
|
|
1931 | callback (EV_A_ &timer, 0); |
1895 | |
1932 | |
1896 | This technique is slightly more complex, but in most cases where the |
1933 | This technique is slightly more complex, but in most cases where the |
1897 | time-out is unlikely to be triggered, much more efficient. |
1934 | time-out is unlikely to be triggered, much more efficient. |
1898 | |
|
|
1899 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1900 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1901 | fix things for you. |
|
|
1902 | |
1935 | |
1903 | =item 4. Wee, just use a double-linked list for your timeouts. |
1936 | =item 4. Wee, just use a double-linked list for your timeouts. |
1904 | |
1937 | |
1905 | If there is not one request, but many thousands (millions...), all |
1938 | If there is not one request, but many thousands (millions...), all |
1906 | employing some kind of timeout with the same timeout value, then one can |
1939 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1933 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1966 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1934 | rather complicated, but extremely efficient, something that really pays |
1967 | rather complicated, but extremely efficient, something that really pays |
1935 | off after the first million or so of active timers, i.e. it's usually |
1968 | off after the first million or so of active timers, i.e. it's usually |
1936 | overkill :) |
1969 | overkill :) |
1937 | |
1970 | |
|
|
1971 | =head3 The special problem of being too early |
|
|
1972 | |
|
|
1973 | If you ask a timer to call your callback after three seconds, then |
|
|
1974 | you expect it to be invoked after three seconds - but of course, this |
|
|
1975 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1976 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1977 | process with a STOP signal for a few hours for example. |
|
|
1978 | |
|
|
1979 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1980 | delay has occurred, but cannot guarantee this. |
|
|
1981 | |
|
|
1982 | A less obvious failure mode is calling your callback too early: many event |
|
|
1983 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1984 | this can cause your callback to be invoked much earlier than you would |
|
|
1985 | expect. |
|
|
1986 | |
|
|
1987 | To see why, imagine a system with a clock that only offers full second |
|
|
1988 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1989 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1990 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1991 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1992 | |
|
|
1993 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1994 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1995 | one-second delay was requested - this is being "too early", despite best |
|
|
1996 | intentions. |
|
|
1997 | |
|
|
1998 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
1999 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2000 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2001 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2002 | |
|
|
2003 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2004 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2005 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2006 | late" side of things. |
|
|
2007 | |
1938 | =head3 The special problem of time updates |
2008 | =head3 The special problem of time updates |
1939 | |
2009 | |
1940 | Establishing the current time is a costly operation (it usually takes at |
2010 | Establishing the current time is a costly operation (it usually takes |
1941 | least two system calls): EV therefore updates its idea of the current |
2011 | at least one system call): EV therefore updates its idea of the current |
1942 | time only before and after C<ev_run> collects new events, which causes a |
2012 | time only before and after C<ev_run> collects new events, which causes a |
1943 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2013 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1944 | lots of events in one iteration. |
2014 | lots of events in one iteration. |
1945 | |
2015 | |
1946 | The relative timeouts are calculated relative to the C<ev_now ()> |
2016 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1952 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2022 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1953 | |
2023 | |
1954 | If the event loop is suspended for a long time, you can also force an |
2024 | If the event loop is suspended for a long time, you can also force an |
1955 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2025 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1956 | ()>. |
2026 | ()>. |
|
|
2027 | |
|
|
2028 | =head3 The special problem of unsynchronised clocks |
|
|
2029 | |
|
|
2030 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2031 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2032 | jumps). |
|
|
2033 | |
|
|
2034 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2035 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2036 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2037 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2038 | than a directly following call to C<time>. |
|
|
2039 | |
|
|
2040 | The moral of this is to only compare libev-related timestamps with |
|
|
2041 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2042 | a second or so. |
|
|
2043 | |
|
|
2044 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2045 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2046 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2047 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2048 | |
|
|
2049 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2050 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2051 | I<measured according to the real time>, not the system clock. |
|
|
2052 | |
|
|
2053 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2054 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2055 | exactly the right behaviour. |
|
|
2056 | |
|
|
2057 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2058 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2059 | time, where your comparisons will always generate correct results. |
1957 | |
2060 | |
1958 | =head3 The special problems of suspended animation |
2061 | =head3 The special problems of suspended animation |
1959 | |
2062 | |
1960 | When you leave the server world it is quite customary to hit machines that |
2063 | When you leave the server world it is quite customary to hit machines that |
1961 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2064 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2005 | keep up with the timer (because it takes longer than those 10 seconds to |
2108 | keep up with the timer (because it takes longer than those 10 seconds to |
2006 | do stuff) the timer will not fire more than once per event loop iteration. |
2109 | do stuff) the timer will not fire more than once per event loop iteration. |
2007 | |
2110 | |
2008 | =item ev_timer_again (loop, ev_timer *) |
2111 | =item ev_timer_again (loop, ev_timer *) |
2009 | |
2112 | |
2010 | This will act as if the timer timed out and restart it again if it is |
2113 | This will act as if the timer timed out and restarts it again if it is |
2011 | repeating. The exact semantics are: |
2114 | repeating. The exact semantics are: |
2012 | |
2115 | |
2013 | If the timer is pending, its pending status is cleared. |
2116 | If the timer is pending, its pending status is cleared. |
2014 | |
2117 | |
2015 | If the timer is started but non-repeating, stop it (as if it timed out). |
2118 | If the timer is started but non-repeating, stop it (as if it timed out). |
… | |
… | |
2145 | |
2248 | |
2146 | Another way to think about it (for the mathematically inclined) is that |
2249 | Another way to think about it (for the mathematically inclined) is that |
2147 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2250 | C<ev_periodic> will try to run the callback in this mode at the next possible |
2148 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2251 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
2149 | |
2252 | |
2150 | For numerical stability it is preferable that the C<offset> value is near |
2253 | The C<interval> I<MUST> be positive, and for numerical stability, the |
2151 | C<ev_now ()> (the current time), but there is no range requirement for |
2254 | interval value should be higher than C<1/8192> (which is around 100 |
2152 | this value, and in fact is often specified as zero. |
2255 | microseconds) and C<offset> should be higher than C<0> and should have |
|
|
2256 | at most a similar magnitude as the current time (say, within a factor of |
|
|
2257 | ten). Typical values for offset are, in fact, C<0> or something between |
|
|
2258 | C<0> and C<interval>, which is also the recommended range. |
2153 | |
2259 | |
2154 | Note also that there is an upper limit to how often a timer can fire (CPU |
2260 | Note also that there is an upper limit to how often a timer can fire (CPU |
2155 | speed for example), so if C<interval> is very small then timing stability |
2261 | speed for example), so if C<interval> is very small then timing stability |
2156 | will of course deteriorate. Libev itself tries to be exact to be about one |
2262 | will of course deteriorate. Libev itself tries to be exact to be about one |
2157 | millisecond (if the OS supports it and the machine is fast enough). |
2263 | millisecond (if the OS supports it and the machine is fast enough). |
… | |
… | |
2300 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2406 | =head3 The special problem of inheritance over fork/execve/pthread_create |
2301 | |
2407 | |
2302 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2408 | Both the signal mask (C<sigprocmask>) and the signal disposition |
2303 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2409 | (C<sigaction>) are unspecified after starting a signal watcher (and after |
2304 | stopping it again), that is, libev might or might not block the signal, |
2410 | stopping it again), that is, libev might or might not block the signal, |
2305 | and might or might not set or restore the installed signal handler. |
2411 | and might or might not set or restore the installed signal handler (but |
|
|
2412 | see C<EVFLAG_NOSIGMASK>). |
2306 | |
2413 | |
2307 | While this does not matter for the signal disposition (libev never |
2414 | While this does not matter for the signal disposition (libev never |
2308 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2415 | sets signals to C<SIG_IGN>, so handlers will be reset to C<SIG_DFL> on |
2309 | C<execve>), this matters for the signal mask: many programs do not expect |
2416 | C<execve>), this matters for the signal mask: many programs do not expect |
2310 | certain signals to be blocked. |
2417 | certain signals to be blocked. |
… | |
… | |
3181 | atexit (program_exits); |
3288 | atexit (program_exits); |
3182 | |
3289 | |
3183 | |
3290 | |
3184 | =head2 C<ev_async> - how to wake up an event loop |
3291 | =head2 C<ev_async> - how to wake up an event loop |
3185 | |
3292 | |
3186 | In general, you cannot use an C<ev_run> from multiple threads or other |
3293 | In general, you cannot use an C<ev_loop> from multiple threads or other |
3187 | asynchronous sources such as signal handlers (as opposed to multiple event |
3294 | asynchronous sources such as signal handlers (as opposed to multiple event |
3188 | loops - those are of course safe to use in different threads). |
3295 | loops - those are of course safe to use in different threads). |
3189 | |
3296 | |
3190 | Sometimes, however, you need to wake up an event loop you do not control, |
3297 | Sometimes, however, you need to wake up an event loop you do not control, |
3191 | for example because it belongs to another thread. This is what C<ev_async> |
3298 | for example because it belongs to another thread. This is what C<ev_async> |
… | |
… | |
3198 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3305 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3199 | of "global async watchers" by using a watcher on an otherwise unused |
3306 | of "global async watchers" by using a watcher on an otherwise unused |
3200 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3307 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3201 | even without knowing which loop owns the signal. |
3308 | even without knowing which loop owns the signal. |
3202 | |
3309 | |
3203 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3204 | just the default loop. |
|
|
3205 | |
|
|
3206 | =head3 Queueing |
3310 | =head3 Queueing |
3207 | |
3311 | |
3208 | C<ev_async> does not support queueing of data in any way. The reason |
3312 | C<ev_async> does not support queueing of data in any way. The reason |
3209 | is that the author does not know of a simple (or any) algorithm for a |
3313 | is that the author does not know of a simple (or any) algorithm for a |
3210 | multiple-writer-single-reader queue that works in all cases and doesn't |
3314 | multiple-writer-single-reader queue that works in all cases and doesn't |
… | |
… | |
3301 | trust me. |
3405 | trust me. |
3302 | |
3406 | |
3303 | =item ev_async_send (loop, ev_async *) |
3407 | =item ev_async_send (loop, ev_async *) |
3304 | |
3408 | |
3305 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3409 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
3306 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
3410 | an C<EV_ASYNC> event on the watcher into the event loop, and instantly |
|
|
3411 | returns. |
|
|
3412 | |
3307 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
3413 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3308 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
3414 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3309 | section below on what exactly this means). |
3415 | embedding section below on what exactly this means). |
3310 | |
3416 | |
3311 | Note that, as with other watchers in libev, multiple events might get |
3417 | Note that, as with other watchers in libev, multiple events might get |
3312 | compressed into a single callback invocation (another way to look at this |
3418 | compressed into a single callback invocation (another way to look at |
3313 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3419 | this is that C<ev_async> watchers are level-triggered: they are set on |
3314 | reset when the event loop detects that). |
3420 | C<ev_async_send>, reset when the event loop detects that). |
3315 | |
3421 | |
3316 | This call incurs the overhead of a system call only once per event loop |
3422 | This call incurs the overhead of at most one extra system call per event |
3317 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3423 | loop iteration, if the event loop is blocked, and no syscall at all if |
3318 | repeated calls to C<ev_async_send> for the same event loop. |
3424 | the event loop (or your program) is processing events. That means that |
|
|
3425 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3426 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3427 | zero) under load. |
3319 | |
3428 | |
3320 | =item bool = ev_async_pending (ev_async *) |
3429 | =item bool = ev_async_pending (ev_async *) |
3321 | |
3430 | |
3322 | Returns a non-zero value when C<ev_async_send> has been called on the |
3431 | Returns a non-zero value when C<ev_async_send> has been called on the |
3323 | watcher but the event has not yet been processed (or even noted) by the |
3432 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3378 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3487 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3379 | |
3488 | |
3380 | =item ev_feed_fd_event (loop, int fd, int revents) |
3489 | =item ev_feed_fd_event (loop, int fd, int revents) |
3381 | |
3490 | |
3382 | Feed an event on the given fd, as if a file descriptor backend detected |
3491 | Feed an event on the given fd, as if a file descriptor backend detected |
3383 | the given events it. |
3492 | the given events. |
3384 | |
3493 | |
3385 | =item ev_feed_signal_event (loop, int signum) |
3494 | =item ev_feed_signal_event (loop, int signum) |
3386 | |
3495 | |
3387 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3496 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3388 | which is async-safe. |
3497 | which is async-safe. |
… | |
… | |
3462 | { |
3571 | { |
3463 | struct my_biggy big = (struct my_biggy *) |
3572 | struct my_biggy big = (struct my_biggy *) |
3464 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3573 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3465 | } |
3574 | } |
3466 | |
3575 | |
|
|
3576 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3577 | |
|
|
3578 | Often you have structures like this in event-based programs: |
|
|
3579 | |
|
|
3580 | callback () |
|
|
3581 | { |
|
|
3582 | free (request); |
|
|
3583 | } |
|
|
3584 | |
|
|
3585 | request = start_new_request (..., callback); |
|
|
3586 | |
|
|
3587 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3588 | used to cancel the operation, or do other things with it. |
|
|
3589 | |
|
|
3590 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3591 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3592 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3593 | operation and simply invoke the callback with the result. |
|
|
3594 | |
|
|
3595 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3596 | has returned, so C<request> is not set. |
|
|
3597 | |
|
|
3598 | Even if you pass the request by some safer means to the callback, you |
|
|
3599 | might want to do something to the request after starting it, such as |
|
|
3600 | canceling it, which probably isn't working so well when the callback has |
|
|
3601 | already been invoked. |
|
|
3602 | |
|
|
3603 | A common way around all these issues is to make sure that |
|
|
3604 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3605 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3606 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3607 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3608 | and pushing it into the pending queue: |
|
|
3609 | |
|
|
3610 | ev_set_cb (watcher, callback); |
|
|
3611 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3612 | |
|
|
3613 | This way, C<start_new_request> can safely return before the callback is |
|
|
3614 | invoked, while not delaying callback invocation too much. |
|
|
3615 | |
3467 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3616 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3468 | |
3617 | |
3469 | Often (especially in GUI toolkits) there are places where you have |
3618 | Often (especially in GUI toolkits) there are places where you have |
3470 | I<modal> interaction, which is most easily implemented by recursively |
3619 | I<modal> interaction, which is most easily implemented by recursively |
3471 | invoking C<ev_run>. |
3620 | invoking C<ev_run>. |
… | |
… | |
3484 | int exit_main_loop = 0; |
3633 | int exit_main_loop = 0; |
3485 | |
3634 | |
3486 | while (!exit_main_loop) |
3635 | while (!exit_main_loop) |
3487 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3636 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3488 | |
3637 | |
3489 | // in a model watcher |
3638 | // in a modal watcher |
3490 | int exit_nested_loop = 0; |
3639 | int exit_nested_loop = 0; |
3491 | |
3640 | |
3492 | while (!exit_nested_loop) |
3641 | while (!exit_nested_loop) |
3493 | ev_run (EV_A_ EVRUN_ONCE); |
3642 | ev_run (EV_A_ EVRUN_ONCE); |
3494 | |
3643 | |
… | |
… | |
3504 | exit_main_loop = exit_nested_loop = 1; |
3653 | exit_main_loop = exit_nested_loop = 1; |
3505 | |
3654 | |
3506 | =head2 THREAD LOCKING EXAMPLE |
3655 | =head2 THREAD LOCKING EXAMPLE |
3507 | |
3656 | |
3508 | Here is a fictitious example of how to run an event loop in a different |
3657 | Here is a fictitious example of how to run an event loop in a different |
3509 | thread than where callbacks are being invoked and watchers are |
3658 | thread from where callbacks are being invoked and watchers are |
3510 | created/added/removed. |
3659 | created/added/removed. |
3511 | |
3660 | |
3512 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3661 | For a real-world example, see the C<EV::Loop::Async> perl module, |
3513 | which uses exactly this technique (which is suited for many high-level |
3662 | which uses exactly this technique (which is suited for many high-level |
3514 | languages). |
3663 | languages). |
… | |
… | |
3540 | // now associate this with the loop |
3689 | // now associate this with the loop |
3541 | ev_set_userdata (EV_A_ u); |
3690 | ev_set_userdata (EV_A_ u); |
3542 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3691 | ev_set_invoke_pending_cb (EV_A_ l_invoke); |
3543 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3692 | ev_set_loop_release_cb (EV_A_ l_release, l_acquire); |
3544 | |
3693 | |
3545 | // then create the thread running ev_loop |
3694 | // then create the thread running ev_run |
3546 | pthread_create (&u->tid, 0, l_run, EV_A); |
3695 | pthread_create (&u->tid, 0, l_run, EV_A); |
3547 | } |
3696 | } |
3548 | |
3697 | |
3549 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3698 | The callback for the C<ev_async> watcher does nothing: the watcher is used |
3550 | solely to wake up the event loop so it takes notice of any new watchers |
3699 | solely to wake up the event loop so it takes notice of any new watchers |
… | |
… | |
3674 | switch_to (libev_coro); |
3823 | switch_to (libev_coro); |
3675 | } |
3824 | } |
3676 | |
3825 | |
3677 | That basically suspends the coroutine inside C<wait_for_event> and |
3826 | That basically suspends the coroutine inside C<wait_for_event> and |
3678 | continues the libev coroutine, which, when appropriate, switches back to |
3827 | continues the libev coroutine, which, when appropriate, switches back to |
3679 | this or any other coroutine. I am sure if you sue this your own :) |
3828 | this or any other coroutine. |
3680 | |
3829 | |
3681 | You can do similar tricks if you have, say, threads with an event queue - |
3830 | You can do similar tricks if you have, say, threads with an event queue - |
3682 | instead of storing a coroutine, you store the queue object and instead of |
3831 | instead of storing a coroutine, you store the queue object and instead of |
3683 | switching to a coroutine, you push the watcher onto the queue and notify |
3832 | switching to a coroutine, you push the watcher onto the queue and notify |
3684 | any waiters. |
3833 | any waiters. |
… | |
… | |
3920 | watchers in the constructor. |
4069 | watchers in the constructor. |
3921 | |
4070 | |
3922 | class myclass |
4071 | class myclass |
3923 | { |
4072 | { |
3924 | ev::io io ; void io_cb (ev::io &w, int revents); |
4073 | ev::io io ; void io_cb (ev::io &w, int revents); |
3925 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4074 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3926 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4075 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3927 | |
4076 | |
3928 | myclass (int fd) |
4077 | myclass (int fd) |
3929 | { |
4078 | { |
3930 | io .set <myclass, &myclass::io_cb > (this); |
4079 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3981 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4130 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3982 | |
4131 | |
3983 | =item D |
4132 | =item D |
3984 | |
4133 | |
3985 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4134 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3986 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4135 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
3987 | |
4136 | |
3988 | =item Ocaml |
4137 | =item Ocaml |
3989 | |
4138 | |
3990 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4139 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
3991 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4140 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4039 | suitable for use with C<EV_A>. |
4188 | suitable for use with C<EV_A>. |
4040 | |
4189 | |
4041 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4190 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4042 | |
4191 | |
4043 | Similar to the other two macros, this gives you the value of the default |
4192 | Similar to the other two macros, this gives you the value of the default |
4044 | loop, if multiple loops are supported ("ev loop default"). |
4193 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4194 | will be initialised if it isn't already initialised. |
|
|
4195 | |
|
|
4196 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4197 | to initialise the loop somewhere. |
4045 | |
4198 | |
4046 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4199 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4047 | |
4200 | |
4048 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4201 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4049 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4202 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4194 | supported). It will also not define any of the structs usually found in |
4347 | supported). It will also not define any of the structs usually found in |
4195 | F<event.h> that are not directly supported by the libev core alone. |
4348 | F<event.h> that are not directly supported by the libev core alone. |
4196 | |
4349 | |
4197 | In standalone mode, libev will still try to automatically deduce the |
4350 | In standalone mode, libev will still try to automatically deduce the |
4198 | configuration, but has to be more conservative. |
4351 | configuration, but has to be more conservative. |
|
|
4352 | |
|
|
4353 | =item EV_USE_FLOOR |
|
|
4354 | |
|
|
4355 | If defined to be C<1>, libev will use the C<floor ()> function for its |
|
|
4356 | periodic reschedule calculations, otherwise libev will fall back on a |
|
|
4357 | portable (slower) implementation. If you enable this, you usually have to |
|
|
4358 | link against libm or something equivalent. Enabling this when the C<floor> |
|
|
4359 | function is not available will fail, so the safe default is to not enable |
|
|
4360 | this. |
4199 | |
4361 | |
4200 | =item EV_USE_MONOTONIC |
4362 | =item EV_USE_MONOTONIC |
4201 | |
4363 | |
4202 | If defined to be C<1>, libev will try to detect the availability of the |
4364 | If defined to be C<1>, libev will try to detect the availability of the |
4203 | monotonic clock option at both compile time and runtime. Otherwise no |
4365 | monotonic clock option at both compile time and runtime. Otherwise no |
… | |
… | |
4336 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4498 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4337 | |
4499 | |
4338 | =item EV_ATOMIC_T |
4500 | =item EV_ATOMIC_T |
4339 | |
4501 | |
4340 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4502 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4341 | access is atomic with respect to other threads or signal contexts. No such |
4503 | access is atomic and serialised with respect to other threads or signal |
4342 | type is easily found in the C language, so you can provide your own type |
4504 | contexts. No such type is easily found in the C language, so you can |
4343 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4505 | provide your own type that you know is safe for your purposes. It is used |
4344 | as well as for signal and thread safety in C<ev_async> watchers. |
4506 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4507 | in C<ev_async> watchers. |
4345 | |
4508 | |
4346 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4509 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4347 | (from F<signal.h>), which is usually good enough on most platforms. |
4510 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4511 | although strictly speaking using a type that also implies a memory fence |
|
|
4512 | is required. |
4348 | |
4513 | |
4349 | =item EV_H (h) |
4514 | =item EV_H (h) |
4350 | |
4515 | |
4351 | The name of the F<ev.h> header file used to include it. The default if |
4516 | The name of the F<ev.h> header file used to include it. The default if |
4352 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4517 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4376 | will have the C<struct ev_loop *> as first argument, and you can create |
4541 | will have the C<struct ev_loop *> as first argument, and you can create |
4377 | additional independent event loops. Otherwise there will be no support |
4542 | additional independent event loops. Otherwise there will be no support |
4378 | for multiple event loops and there is no first event loop pointer |
4543 | for multiple event loops and there is no first event loop pointer |
4379 | argument. Instead, all functions act on the single default loop. |
4544 | argument. Instead, all functions act on the single default loop. |
4380 | |
4545 | |
|
|
4546 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4547 | default loop when multiplicity is switched off - you always have to |
|
|
4548 | initialise the loop manually in this case. |
|
|
4549 | |
4381 | =item EV_MINPRI |
4550 | =item EV_MINPRI |
4382 | |
4551 | |
4383 | =item EV_MAXPRI |
4552 | =item EV_MAXPRI |
4384 | |
4553 | |
4385 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4554 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4482 | |
4651 | |
4483 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4652 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4484 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4653 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4485 | your program might be left out as well - a binary starting a timer and an |
4654 | your program might be left out as well - a binary starting a timer and an |
4486 | I/O watcher then might come out at only 5Kb. |
4655 | I/O watcher then might come out at only 5Kb. |
|
|
4656 | |
|
|
4657 | =item EV_API_STATIC |
|
|
4658 | |
|
|
4659 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4660 | will have static linkage. This means that libev will not export any |
|
|
4661 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4662 | when you embed libev, only want to use libev functions in a single file, |
|
|
4663 | and do not want its identifiers to be visible. |
|
|
4664 | |
|
|
4665 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4666 | wants to use libev. |
4487 | |
4667 | |
4488 | =item EV_AVOID_STDIO |
4668 | =item EV_AVOID_STDIO |
4489 | |
4669 | |
4490 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4670 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4491 | functions (printf, scanf, perror etc.). This will increase the code size |
4671 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4871 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5051 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4872 | model. Libev still offers limited functionality on this platform in |
5052 | model. Libev still offers limited functionality on this platform in |
4873 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5053 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4874 | descriptors. This only applies when using Win32 natively, not when using |
5054 | descriptors. This only applies when using Win32 natively, not when using |
4875 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5055 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4876 | as every compielr comes with a slightly differently broken/incompatible |
5056 | as every compiler comes with a slightly differently broken/incompatible |
4877 | environment. |
5057 | environment. |
4878 | |
5058 | |
4879 | Lifting these limitations would basically require the full |
5059 | Lifting these limitations would basically require the full |
4880 | re-implementation of the I/O system. If you are into this kind of thing, |
5060 | re-implementation of the I/O system. If you are into this kind of thing, |
4881 | then note that glib does exactly that for you in a very portable way (note |
5061 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
5014 | |
5194 | |
5015 | The type C<double> is used to represent timestamps. It is required to |
5195 | The type C<double> is used to represent timestamps. It is required to |
5016 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5196 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5017 | good enough for at least into the year 4000 with millisecond accuracy |
5197 | good enough for at least into the year 4000 with millisecond accuracy |
5018 | (the design goal for libev). This requirement is overfulfilled by |
5198 | (the design goal for libev). This requirement is overfulfilled by |
5019 | implementations using IEEE 754, which is basically all existing ones. With |
5199 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5200 | |
5020 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5201 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5202 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5203 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5204 | something like that, just kidding). |
5021 | |
5205 | |
5022 | =back |
5206 | =back |
5023 | |
5207 | |
5024 | If you know of other additional requirements drop me a note. |
5208 | If you know of other additional requirements drop me a note. |
5025 | |
5209 | |
… | |
… | |
5087 | =item Processing ev_async_send: O(number_of_async_watchers) |
5271 | =item Processing ev_async_send: O(number_of_async_watchers) |
5088 | |
5272 | |
5089 | =item Processing signals: O(max_signal_number) |
5273 | =item Processing signals: O(max_signal_number) |
5090 | |
5274 | |
5091 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5275 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5092 | calls in the current loop iteration. Checking for async and signal events |
5276 | calls in the current loop iteration and the loop is currently |
|
|
5277 | blocked. Checking for async and signal events involves iterating over all |
5093 | involves iterating over all running async watchers or all signal numbers. |
5278 | running async watchers or all signal numbers. |
5094 | |
5279 | |
5095 | =back |
5280 | =back |
5096 | |
5281 | |
5097 | |
5282 | |
5098 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5283 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
… | |
… | |
5215 | The physical time that is observed. It is apparently strictly monotonic :) |
5400 | The physical time that is observed. It is apparently strictly monotonic :) |
5216 | |
5401 | |
5217 | =item wall-clock time |
5402 | =item wall-clock time |
5218 | |
5403 | |
5219 | The time and date as shown on clocks. Unlike real time, it can actually |
5404 | The time and date as shown on clocks. Unlike real time, it can actually |
5220 | be wrong and jump forwards and backwards, e.g. when the you adjust your |
5405 | be wrong and jump forwards and backwards, e.g. when you adjust your |
5221 | clock. |
5406 | clock. |
5222 | |
5407 | |
5223 | =item watcher |
5408 | =item watcher |
5224 | |
5409 | |
5225 | A data structure that describes interest in certain events. Watchers need |
5410 | A data structure that describes interest in certain events. Watchers need |
… | |
… | |
5228 | =back |
5413 | =back |
5229 | |
5414 | |
5230 | =head1 AUTHOR |
5415 | =head1 AUTHOR |
5231 | |
5416 | |
5232 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5417 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael |
5233 | Magnusson and Emanuele Giaquinta. |
5418 | Magnusson and Emanuele Giaquinta, and minor corrections by many others. |
5234 | |
5419 | |