… | |
… | |
4 | |
4 | |
5 | =head1 SYNOPSIS |
5 | =head1 SYNOPSIS |
6 | |
6 | |
7 | #include <ev.h> |
7 | #include <ev.h> |
8 | |
8 | |
9 | =head1 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | #include <ev.h> |
11 | #include <ev.h> |
12 | |
12 | |
13 | ev_io stdin_watcher; |
13 | ev_io stdin_watcher; |
14 | ev_timer timeout_watcher; |
14 | ev_timer timeout_watcher; |
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… | |
65 | You register interest in certain events by registering so-called I<event |
65 | You register interest in certain events by registering so-called I<event |
66 | watchers>, which are relatively small C structures you initialise with the |
66 | watchers>, which are relatively small C structures you initialise with the |
67 | details of the event, and then hand it over to libev by I<starting> the |
67 | details of the event, and then hand it over to libev by I<starting> the |
68 | watcher. |
68 | watcher. |
69 | |
69 | |
70 | =head1 FEATURES |
70 | =head2 FEATURES |
71 | |
71 | |
72 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
72 | Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the |
73 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
73 | BSD-specific C<kqueue> and the Solaris-specific event port mechanisms |
74 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
74 | for file descriptor events (C<ev_io>), the Linux C<inotify> interface |
75 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
75 | (for C<ev_stat>), relative timers (C<ev_timer>), absolute timers |
… | |
… | |
82 | |
82 | |
83 | It also is quite fast (see this |
83 | It also is quite fast (see this |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
84 | L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent |
85 | for example). |
85 | for example). |
86 | |
86 | |
87 | =head1 CONVENTIONS |
87 | =head2 CONVENTIONS |
88 | |
88 | |
89 | Libev is very configurable. In this manual the default configuration will |
89 | Libev is very configurable. In this manual the default configuration will |
90 | be described, which supports multiple event loops. For more info about |
90 | be described, which supports multiple event loops. For more info about |
91 | various configuration options please have a look at B<EMBED> section in |
91 | various configuration options please have a look at B<EMBED> section in |
92 | this manual. If libev was configured without support for multiple event |
92 | this manual. If libev was configured without support for multiple event |
93 | loops, then all functions taking an initial argument of name C<loop> |
93 | loops, then all functions taking an initial argument of name C<loop> |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
94 | (which is always of type C<struct ev_loop *>) will not have this argument. |
95 | |
95 | |
96 | =head1 TIME REPRESENTATION |
96 | =head2 TIME REPRESENTATION |
97 | |
97 | |
98 | Libev represents time as a single floating point number, representing the |
98 | Libev represents time as a single floating point number, representing the |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
99 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
100 | the beginning of 1970, details are complicated, don't ask). This type is |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
101 | called C<ev_tstamp>, which is what you should use too. It usually aliases |
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115 | |
115 | |
116 | Returns the current time as libev would use it. Please note that the |
116 | Returns the current time as libev would use it. Please note that the |
117 | C<ev_now> function is usually faster and also often returns the timestamp |
117 | C<ev_now> function is usually faster and also often returns the timestamp |
118 | you actually want to know. |
118 | you actually want to know. |
119 | |
119 | |
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120 | =item ev_sleep (ev_tstamp interval) |
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121 | |
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122 | Sleep for the given interval: The current thread will be blocked until |
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123 | either it is interrupted or the given time interval has passed. Basically |
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124 | this is a subsecond-resolution C<sleep ()>. |
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125 | |
120 | =item int ev_version_major () |
126 | =item int ev_version_major () |
121 | |
127 | |
122 | =item int ev_version_minor () |
128 | =item int ev_version_minor () |
123 | |
129 | |
124 | You can find out the major and minor ABI version numbers of the library |
130 | You can find out the major and minor ABI version numbers of the library |
… | |
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300 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
306 | =item C<EVBACKEND_SELECT> (value 1, portable select backend) |
301 | |
307 | |
302 | This is your standard select(2) backend. Not I<completely> standard, as |
308 | This is your standard select(2) backend. Not I<completely> standard, as |
303 | libev tries to roll its own fd_set with no limits on the number of fds, |
309 | libev tries to roll its own fd_set with no limits on the number of fds, |
304 | but if that fails, expect a fairly low limit on the number of fds when |
310 | but if that fails, expect a fairly low limit on the number of fds when |
305 | using this backend. It doesn't scale too well (O(highest_fd)), but its usually |
311 | using this backend. It doesn't scale too well (O(highest_fd)), but its |
306 | the fastest backend for a low number of fds. |
312 | usually the fastest backend for a low number of (low-numbered :) fds. |
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313 | |
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314 | To get good performance out of this backend you need a high amount of |
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315 | parallelity (most of the file descriptors should be busy). If you are |
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316 | writing a server, you should C<accept ()> in a loop to accept as many |
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317 | connections as possible during one iteration. You might also want to have |
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318 | a look at C<ev_set_io_collect_interval ()> to increase the amount of |
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319 | readyness notifications you get per iteration. |
307 | |
320 | |
308 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
321 | =item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) |
309 | |
322 | |
310 | And this is your standard poll(2) backend. It's more complicated than |
323 | And this is your standard poll(2) backend. It's more complicated |
311 | select, but handles sparse fds better and has no artificial limit on the |
324 | than select, but handles sparse fds better and has no artificial |
312 | number of fds you can use (except it will slow down considerably with a |
325 | limit on the number of fds you can use (except it will slow down |
313 | lot of inactive fds). It scales similarly to select, i.e. O(total_fds). |
326 | considerably with a lot of inactive fds). It scales similarly to select, |
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327 | i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for |
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328 | performance tips. |
314 | |
329 | |
315 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
330 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
316 | |
331 | |
317 | For few fds, this backend is a bit little slower than poll and select, |
332 | For few fds, this backend is a bit little slower than poll and select, |
318 | but it scales phenomenally better. While poll and select usually scale like |
333 | but it scales phenomenally better. While poll and select usually scale |
319 | O(total_fds) where n is the total number of fds (or the highest fd), epoll scales |
334 | like O(total_fds) where n is the total number of fds (or the highest fd), |
320 | either O(1) or O(active_fds). |
335 | epoll scales either O(1) or O(active_fds). The epoll design has a number |
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336 | of shortcomings, such as silently dropping events in some hard-to-detect |
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337 | cases and rewiring a syscall per fd change, no fork support and bad |
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338 | support for dup. |
321 | |
339 | |
322 | While stopping and starting an I/O watcher in the same iteration will |
340 | While stopping, setting and starting an I/O watcher in the same iteration |
323 | result in some caching, there is still a syscall per such incident |
341 | will result in some caching, there is still a syscall per such incident |
324 | (because the fd could point to a different file description now), so its |
342 | (because the fd could point to a different file description now), so its |
325 | best to avoid that. Also, dup()ed file descriptors might not work very |
343 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
326 | well if you register events for both fds. |
344 | very well if you register events for both fds. |
327 | |
345 | |
328 | Please note that epoll sometimes generates spurious notifications, so you |
346 | Please note that epoll sometimes generates spurious notifications, so you |
329 | need to use non-blocking I/O or other means to avoid blocking when no data |
347 | need to use non-blocking I/O or other means to avoid blocking when no data |
330 | (or space) is available. |
348 | (or space) is available. |
331 | |
349 | |
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350 | Best performance from this backend is achieved by not unregistering all |
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351 | watchers for a file descriptor until it has been closed, if possible, i.e. |
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352 | keep at least one watcher active per fd at all times. |
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353 | |
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354 | While nominally embeddeble in other event loops, this feature is broken in |
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355 | all kernel versions tested so far. |
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356 | |
332 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
357 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
333 | |
358 | |
334 | Kqueue deserves special mention, as at the time of this writing, it |
359 | Kqueue deserves special mention, as at the time of this writing, it |
335 | was broken on all BSDs except NetBSD (usually it doesn't work with |
360 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
336 | anything but sockets and pipes, except on Darwin, where of course it's |
361 | with anything but sockets and pipes, except on Darwin, where of course |
337 | completely useless). For this reason it's not being "autodetected" |
362 | it's completely useless). For this reason it's not being "autodetected" |
338 | unless you explicitly specify it explicitly in the flags (i.e. using |
363 | unless you explicitly specify it explicitly in the flags (i.e. using |
339 | C<EVBACKEND_KQUEUE>). |
364 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
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365 | system like NetBSD. |
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366 | |
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367 | You still can embed kqueue into a normal poll or select backend and use it |
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368 | only for sockets (after having made sure that sockets work with kqueue on |
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369 | the target platform). See C<ev_embed> watchers for more info. |
340 | |
370 | |
341 | It scales in the same way as the epoll backend, but the interface to the |
371 | It scales in the same way as the epoll backend, but the interface to the |
342 | kernel is more efficient (which says nothing about its actual speed, of |
372 | kernel is more efficient (which says nothing about its actual speed, of |
343 | course). While starting and stopping an I/O watcher does not cause an |
373 | course). While stopping, setting and starting an I/O watcher does never |
344 | extra syscall as with epoll, it still adds up to four event changes per |
374 | cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to |
345 | incident, so its best to avoid that. |
375 | two event changes per incident, support for C<fork ()> is very bad and it |
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376 | drops fds silently in similarly hard-to-detect cases. |
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377 | |
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378 | This backend usually performs well under most conditions. |
|
|
379 | |
|
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380 | While nominally embeddable in other event loops, this doesn't work |
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381 | everywhere, so you might need to test for this. And since it is broken |
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382 | almost everywhere, you should only use it when you have a lot of sockets |
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383 | (for which it usually works), by embedding it into another event loop |
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384 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for |
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385 | sockets. |
346 | |
386 | |
347 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
387 | =item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) |
348 | |
388 | |
349 | This is not implemented yet (and might never be). |
389 | This is not implemented yet (and might never be, unless you send me an |
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390 | implementation). According to reports, C</dev/poll> only supports sockets |
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391 | and is not embeddable, which would limit the usefulness of this backend |
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392 | immensely. |
350 | |
393 | |
351 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
394 | =item C<EVBACKEND_PORT> (value 32, Solaris 10) |
352 | |
395 | |
353 | This uses the Solaris 10 port mechanism. As with everything on Solaris, |
396 | This uses the Solaris 10 event port mechanism. As with everything on Solaris, |
354 | it's really slow, but it still scales very well (O(active_fds)). |
397 | it's really slow, but it still scales very well (O(active_fds)). |
355 | |
398 | |
356 | Please note that solaris ports can result in a lot of spurious |
399 | Please note that solaris event ports can deliver a lot of spurious |
357 | notifications, so you need to use non-blocking I/O or other means to avoid |
400 | notifications, so you need to use non-blocking I/O or other means to avoid |
358 | blocking when no data (or space) is available. |
401 | blocking when no data (or space) is available. |
|
|
402 | |
|
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403 | While this backend scales well, it requires one system call per active |
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404 | file descriptor per loop iteration. For small and medium numbers of file |
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405 | descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend |
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406 | might perform better. |
359 | |
407 | |
360 | =item C<EVBACKEND_ALL> |
408 | =item C<EVBACKEND_ALL> |
361 | |
409 | |
362 | Try all backends (even potentially broken ones that wouldn't be tried |
410 | Try all backends (even potentially broken ones that wouldn't be tried |
363 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
411 | with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as |
364 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
412 | C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. |
|
|
413 | |
|
|
414 | It is definitely not recommended to use this flag. |
365 | |
415 | |
366 | =back |
416 | =back |
367 | |
417 | |
368 | If one or more of these are ored into the flags value, then only these |
418 | If one or more of these are ored into the flags value, then only these |
369 | backends will be tried (in the reverse order as given here). If none are |
419 | backends will be tried (in the reverse order as given here). If none are |
… | |
… | |
563 | Example: For some weird reason, unregister the above signal handler again. |
613 | Example: For some weird reason, unregister the above signal handler again. |
564 | |
614 | |
565 | ev_ref (loop); |
615 | ev_ref (loop); |
566 | ev_signal_stop (loop, &exitsig); |
616 | ev_signal_stop (loop, &exitsig); |
567 | |
617 | |
|
|
618 | =item ev_set_io_collect_interval (loop, ev_tstamp interval) |
|
|
619 | |
|
|
620 | =item ev_set_timeout_collect_interval (loop, ev_tstamp interval) |
|
|
621 | |
|
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622 | These advanced functions influence the time that libev will spend waiting |
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623 | for events. Both are by default C<0>, meaning that libev will try to |
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624 | invoke timer/periodic callbacks and I/O callbacks with minimum latency. |
|
|
625 | |
|
|
626 | Setting these to a higher value (the C<interval> I<must> be >= C<0>) |
|
|
627 | allows libev to delay invocation of I/O and timer/periodic callbacks to |
|
|
628 | increase efficiency of loop iterations. |
|
|
629 | |
|
|
630 | The background is that sometimes your program runs just fast enough to |
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631 | handle one (or very few) event(s) per loop iteration. While this makes |
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632 | the program responsive, it also wastes a lot of CPU time to poll for new |
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633 | events, especially with backends like C<select ()> which have a high |
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634 | overhead for the actual polling but can deliver many events at once. |
|
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635 | |
|
|
636 | By setting a higher I<io collect interval> you allow libev to spend more |
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637 | time collecting I/O events, so you can handle more events per iteration, |
|
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638 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
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639 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
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640 | introduce an additional C<ev_sleep ()> call into most loop iterations. |
|
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641 | |
|
|
642 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
|
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643 | to spend more time collecting timeouts, at the expense of increased |
|
|
644 | latency (the watcher callback will be called later). C<ev_io> watchers |
|
|
645 | will not be affected. Setting this to a non-null value will not introduce |
|
|
646 | any overhead in libev. |
|
|
647 | |
|
|
648 | Many (busy) programs can usually benefit by setting the io collect |
|
|
649 | interval to a value near C<0.1> or so, which is often enough for |
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650 | interactive servers (of course not for games), likewise for timeouts. It |
|
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651 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
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652 | as this approsaches the timing granularity of most systems. |
|
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653 | |
568 | =back |
654 | =back |
569 | |
655 | |
570 | |
656 | |
571 | =head1 ANATOMY OF A WATCHER |
657 | =head1 ANATOMY OF A WATCHER |
572 | |
658 | |
… | |
… | |
897 | In general you can register as many read and/or write event watchers per |
983 | In general you can register as many read and/or write event watchers per |
898 | fd as you want (as long as you don't confuse yourself). Setting all file |
984 | fd as you want (as long as you don't confuse yourself). Setting all file |
899 | descriptors to non-blocking mode is also usually a good idea (but not |
985 | descriptors to non-blocking mode is also usually a good idea (but not |
900 | required if you know what you are doing). |
986 | required if you know what you are doing). |
901 | |
987 | |
902 | You have to be careful with dup'ed file descriptors, though. Some backends |
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903 | (the linux epoll backend is a notable example) cannot handle dup'ed file |
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904 | descriptors correctly if you register interest in two or more fds pointing |
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|
905 | to the same underlying file/socket/etc. description (that is, they share |
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906 | the same underlying "file open"). |
|
|
907 | |
|
|
908 | If you must do this, then force the use of a known-to-be-good backend |
988 | If you must do this, then force the use of a known-to-be-good backend |
909 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
989 | (at the time of this writing, this includes only C<EVBACKEND_SELECT> and |
910 | C<EVBACKEND_POLL>). |
990 | C<EVBACKEND_POLL>). |
911 | |
991 | |
912 | Another thing you have to watch out for is that it is quite easy to |
992 | Another thing you have to watch out for is that it is quite easy to |
… | |
… | |
924 | such as poll (fortunately in our Xlib example, Xlib already does this on |
1004 | such as poll (fortunately in our Xlib example, Xlib already does this on |
925 | its own, so its quite safe to use). |
1005 | its own, so its quite safe to use). |
926 | |
1006 | |
927 | =head3 The special problem of disappearing file descriptors |
1007 | =head3 The special problem of disappearing file descriptors |
928 | |
1008 | |
929 | Some backends (e.g kqueue, epoll) need to be told about closing a file |
1009 | Some backends (e.g. kqueue, epoll) need to be told about closing a file |
930 | descriptor (either by calling C<close> explicitly or by any other means, |
1010 | descriptor (either by calling C<close> explicitly or by any other means, |
931 | such as C<dup>). The reason is that you register interest in some file |
1011 | such as C<dup>). The reason is that you register interest in some file |
932 | descriptor, but when it goes away, the operating system will silently drop |
1012 | descriptor, but when it goes away, the operating system will silently drop |
933 | this interest. If another file descriptor with the same number then is |
1013 | this interest. If another file descriptor with the same number then is |
934 | registered with libev, there is no efficient way to see that this is, in |
1014 | registered with libev, there is no efficient way to see that this is, in |
… | |
… | |
942 | descriptor even if the file descriptor number itself did not change. |
1022 | descriptor even if the file descriptor number itself did not change. |
943 | |
1023 | |
944 | This is how one would do it normally anyway, the important point is that |
1024 | This is how one would do it normally anyway, the important point is that |
945 | the libev application should not optimise around libev but should leave |
1025 | the libev application should not optimise around libev but should leave |
946 | optimisations to libev. |
1026 | optimisations to libev. |
|
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1027 | |
|
|
1028 | =head3 The special problem of dup'ed file descriptors |
|
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1029 | |
|
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1030 | Some backends (e.g. epoll), cannot register events for file descriptors, |
|
|
1031 | but only events for the underlying file descriptions. That means when you |
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1032 | have C<dup ()>'ed file descriptors or weirder constellations, and register |
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1033 | events for them, only one file descriptor might actually receive events. |
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1034 | |
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1035 | There is no workaround possible except not registering events |
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1036 | for potentially C<dup ()>'ed file descriptors, or to resort to |
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1037 | C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>. |
|
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1038 | |
|
|
1039 | =head3 The special problem of fork |
|
|
1040 | |
|
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1041 | Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit |
|
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1042 | useless behaviour. Libev fully supports fork, but needs to be told about |
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1043 | it in the child. |
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1044 | |
|
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1045 | To support fork in your programs, you either have to call |
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1046 | C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child, |
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1047 | enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or |
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1048 | C<EVBACKEND_POLL>. |
947 | |
1049 | |
948 | |
1050 | |
949 | =head3 Watcher-Specific Functions |
1051 | =head3 Watcher-Specific Functions |
950 | |
1052 | |
951 | =over 4 |
1053 | =over 4 |
… | |
… | |
1388 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1490 | semantics of C<ev_stat> watchers, which means that libev sometimes needs |
1389 | to fall back to regular polling again even with inotify, but changes are |
1491 | to fall back to regular polling again even with inotify, but changes are |
1390 | usually detected immediately, and if the file exists there will be no |
1492 | usually detected immediately, and if the file exists there will be no |
1391 | polling. |
1493 | polling. |
1392 | |
1494 | |
|
|
1495 | =head3 Inotify |
|
|
1496 | |
|
|
1497 | When C<inotify (7)> support has been compiled into libev (generally only |
|
|
1498 | available on Linux) and present at runtime, it will be used to speed up |
|
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1499 | change detection where possible. The inotify descriptor will be created lazily |
|
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1500 | when the first C<ev_stat> watcher is being started. |
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1501 | |
|
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1502 | Inotify presense does not change the semantics of C<ev_stat> watchers |
|
|
1503 | except that changes might be detected earlier, and in some cases, to avoid |
|
|
1504 | making regular C<stat> calls. Even in the presense of inotify support |
|
|
1505 | there are many cases where libev has to resort to regular C<stat> polling. |
|
|
1506 | |
|
|
1507 | (There is no support for kqueue, as apparently it cannot be used to |
|
|
1508 | implement this functionality, due to the requirement of having a file |
|
|
1509 | descriptor open on the object at all times). |
|
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1510 | |
|
|
1511 | =head3 The special problem of stat time resolution |
|
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1512 | |
|
|
1513 | The C<stat ()> syscall only supports full-second resolution portably, and |
|
|
1514 | even on systems where the resolution is higher, many filesystems still |
|
|
1515 | only support whole seconds. |
|
|
1516 | |
|
|
1517 | That means that, if the time is the only thing that changes, you might |
|
|
1518 | miss updates: on the first update, C<ev_stat> detects a change and calls |
|
|
1519 | your callback, which does something. When there is another update within |
|
|
1520 | the same second, C<ev_stat> will be unable to detect it. |
|
|
1521 | |
|
|
1522 | The solution to this is to delay acting on a change for a second (or till |
|
|
1523 | the next second boundary), using a roughly one-second delay C<ev_timer> |
|
|
1524 | (C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01> |
|
|
1525 | is added to work around small timing inconsistencies of some operating |
|
|
1526 | systems. |
|
|
1527 | |
1393 | =head3 Watcher-Specific Functions and Data Members |
1528 | =head3 Watcher-Specific Functions and Data Members |
1394 | |
1529 | |
1395 | =over 4 |
1530 | =over 4 |
1396 | |
1531 | |
1397 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
1532 | =item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) |
… | |
… | |
1434 | =item const char *path [read-only] |
1569 | =item const char *path [read-only] |
1435 | |
1570 | |
1436 | The filesystem path that is being watched. |
1571 | The filesystem path that is being watched. |
1437 | |
1572 | |
1438 | =back |
1573 | =back |
|
|
1574 | |
|
|
1575 | =head3 Examples |
1439 | |
1576 | |
1440 | Example: Watch C</etc/passwd> for attribute changes. |
1577 | Example: Watch C</etc/passwd> for attribute changes. |
1441 | |
1578 | |
1442 | static void |
1579 | static void |
1443 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
1580 | passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) |
… | |
… | |
1456 | } |
1593 | } |
1457 | |
1594 | |
1458 | ... |
1595 | ... |
1459 | ev_stat passwd; |
1596 | ev_stat passwd; |
1460 | |
1597 | |
1461 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); |
1598 | ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.); |
1462 | ev_stat_start (loop, &passwd); |
1599 | ev_stat_start (loop, &passwd); |
|
|
1600 | |
|
|
1601 | Example: Like above, but additionally use a one-second delay so we do not |
|
|
1602 | miss updates (however, frequent updates will delay processing, too, so |
|
|
1603 | one might do the work both on C<ev_stat> callback invocation I<and> on |
|
|
1604 | C<ev_timer> callback invocation). |
|
|
1605 | |
|
|
1606 | static ev_stat passwd; |
|
|
1607 | static ev_timer timer; |
|
|
1608 | |
|
|
1609 | static void |
|
|
1610 | timer_cb (EV_P_ ev_timer *w, int revents) |
|
|
1611 | { |
|
|
1612 | ev_timer_stop (EV_A_ w); |
|
|
1613 | |
|
|
1614 | /* now it's one second after the most recent passwd change */ |
|
|
1615 | } |
|
|
1616 | |
|
|
1617 | static void |
|
|
1618 | stat_cb (EV_P_ ev_stat *w, int revents) |
|
|
1619 | { |
|
|
1620 | /* reset the one-second timer */ |
|
|
1621 | ev_timer_again (EV_A_ &timer); |
|
|
1622 | } |
|
|
1623 | |
|
|
1624 | ... |
|
|
1625 | ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.); |
|
|
1626 | ev_stat_start (loop, &passwd); |
|
|
1627 | ev_timer_init (&timer, timer_cb, 0., 1.01); |
1463 | |
1628 | |
1464 | |
1629 | |
1465 | =head2 C<ev_idle> - when you've got nothing better to do... |
1630 | =head2 C<ev_idle> - when you've got nothing better to do... |
1466 | |
1631 | |
1467 | Idle watchers trigger events when no other events of the same or higher |
1632 | Idle watchers trigger events when no other events of the same or higher |
… | |
… | |
1553 | |
1718 | |
1554 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1719 | It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) |
1555 | priority, to ensure that they are being run before any other watchers |
1720 | priority, to ensure that they are being run before any other watchers |
1556 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1721 | after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, |
1557 | too) should not activate ("feed") events into libev. While libev fully |
1722 | too) should not activate ("feed") events into libev. While libev fully |
1558 | supports this, they will be called before other C<ev_check> watchers did |
1723 | supports this, they will be called before other C<ev_check> watchers |
1559 | their job. As C<ev_check> watchers are often used to embed other event |
1724 | did their job. As C<ev_check> watchers are often used to embed other |
1560 | loops those other event loops might be in an unusable state until their |
1725 | (non-libev) event loops those other event loops might be in an unusable |
1561 | C<ev_check> watcher ran (always remind yourself to coexist peacefully with |
1726 | state until their C<ev_check> watcher ran (always remind yourself to |
1562 | others). |
1727 | coexist peacefully with others). |
1563 | |
1728 | |
1564 | =head3 Watcher-Specific Functions and Data Members |
1729 | =head3 Watcher-Specific Functions and Data Members |
1565 | |
1730 | |
1566 | =over 4 |
1731 | =over 4 |
1567 | |
1732 | |
… | |
… | |
2253 | runtime if successful). Otherwise no use of the realtime clock option will |
2418 | runtime if successful). Otherwise no use of the realtime clock option will |
2254 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2419 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
2255 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
2420 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
2256 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
2421 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
2257 | |
2422 | |
|
|
2423 | =item EV_USE_NANOSLEEP |
|
|
2424 | |
|
|
2425 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
|
|
2426 | and will use it for delays. Otherwise it will use C<select ()>. |
|
|
2427 | |
2258 | =item EV_USE_SELECT |
2428 | =item EV_USE_SELECT |
2259 | |
2429 | |
2260 | If undefined or defined to be C<1>, libev will compile in support for the |
2430 | If undefined or defined to be C<1>, libev will compile in support for the |
2261 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2431 | C<select>(2) backend. No attempt at autodetection will be done: if no |
2262 | other method takes over, select will be it. Otherwise the select backend |
2432 | other method takes over, select will be it. Otherwise the select backend |
… | |
… | |
2413 | than enough. If you need to manage thousands of children you might want to |
2583 | than enough. If you need to manage thousands of children you might want to |
2414 | increase this value (I<must> be a power of two). |
2584 | increase this value (I<must> be a power of two). |
2415 | |
2585 | |
2416 | =item EV_INOTIFY_HASHSIZE |
2586 | =item EV_INOTIFY_HASHSIZE |
2417 | |
2587 | |
2418 | C<ev_staz> watchers use a small hash table to distribute workload by |
2588 | C<ev_stat> watchers use a small hash table to distribute workload by |
2419 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2589 | inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), |
2420 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2590 | usually more than enough. If you need to manage thousands of C<ev_stat> |
2421 | watchers you might want to increase this value (I<must> be a power of |
2591 | watchers you might want to increase this value (I<must> be a power of |
2422 | two). |
2592 | two). |
2423 | |
2593 | |
… | |
… | |
2440 | |
2610 | |
2441 | =item ev_set_cb (ev, cb) |
2611 | =item ev_set_cb (ev, cb) |
2442 | |
2612 | |
2443 | Can be used to change the callback member declaration in each watcher, |
2613 | Can be used to change the callback member declaration in each watcher, |
2444 | and the way callbacks are invoked and set. Must expand to a struct member |
2614 | and the way callbacks are invoked and set. Must expand to a struct member |
2445 | definition and a statement, respectively. See the F<ev.c> header file for |
2615 | definition and a statement, respectively. See the F<ev.h> header file for |
2446 | their default definitions. One possible use for overriding these is to |
2616 | their default definitions. One possible use for overriding these is to |
2447 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2617 | avoid the C<struct ev_loop *> as first argument in all cases, or to use |
2448 | method calls instead of plain function calls in C++. |
2618 | method calls instead of plain function calls in C++. |
2449 | |
2619 | |
2450 | =head2 EXPORTED API SYMBOLS |
2620 | =head2 EXPORTED API SYMBOLS |
… | |
… | |
2519 | |
2689 | |
2520 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2690 | =item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) |
2521 | |
2691 | |
2522 | This means that, when you have a watcher that triggers in one hour and |
2692 | This means that, when you have a watcher that triggers in one hour and |
2523 | there are 100 watchers that would trigger before that then inserting will |
2693 | there are 100 watchers that would trigger before that then inserting will |
2524 | have to skip those 100 watchers. |
2694 | have to skip roughly seven (C<ld 100>) of these watchers. |
2525 | |
2695 | |
2526 | =item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) |
2696 | =item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers) |
2527 | |
2697 | |
2528 | That means that for changing a timer costs less than removing/adding them |
2698 | That means that changing a timer costs less than removing/adding them |
2529 | as only the relative motion in the event queue has to be paid for. |
2699 | as only the relative motion in the event queue has to be paid for. |
2530 | |
2700 | |
2531 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2701 | =item Starting io/check/prepare/idle/signal/child watchers: O(1) |
2532 | |
2702 | |
2533 | These just add the watcher into an array or at the head of a list. |
2703 | These just add the watcher into an array or at the head of a list. |
|
|
2704 | |
2534 | =item Stopping check/prepare/idle watchers: O(1) |
2705 | =item Stopping check/prepare/idle watchers: O(1) |
2535 | |
2706 | |
2536 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2707 | =item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) |
2537 | |
2708 | |
2538 | These watchers are stored in lists then need to be walked to find the |
2709 | These watchers are stored in lists then need to be walked to find the |
2539 | correct watcher to remove. The lists are usually short (you don't usually |
2710 | correct watcher to remove. The lists are usually short (you don't usually |
2540 | have many watchers waiting for the same fd or signal). |
2711 | have many watchers waiting for the same fd or signal). |
2541 | |
2712 | |
2542 | =item Finding the next timer per loop iteration: O(1) |
2713 | =item Finding the next timer in each loop iteration: O(1) |
|
|
2714 | |
|
|
2715 | By virtue of using a binary heap, the next timer is always found at the |
|
|
2716 | beginning of the storage array. |
2543 | |
2717 | |
2544 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2718 | =item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) |
2545 | |
2719 | |
2546 | A change means an I/O watcher gets started or stopped, which requires |
2720 | A change means an I/O watcher gets started or stopped, which requires |
2547 | libev to recalculate its status (and possibly tell the kernel). |
2721 | libev to recalculate its status (and possibly tell the kernel, depending |
|
|
2722 | on backend and wether C<ev_io_set> was used). |
2548 | |
2723 | |
2549 | =item Activating one watcher: O(1) |
2724 | =item Activating one watcher (putting it into the pending state): O(1) |
2550 | |
2725 | |
2551 | =item Priority handling: O(number_of_priorities) |
2726 | =item Priority handling: O(number_of_priorities) |
2552 | |
2727 | |
2553 | Priorities are implemented by allocating some space for each |
2728 | Priorities are implemented by allocating some space for each |
2554 | priority. When doing priority-based operations, libev usually has to |
2729 | priority. When doing priority-based operations, libev usually has to |
2555 | linearly search all the priorities. |
2730 | linearly search all the priorities, but starting/stopping and activating |
|
|
2731 | watchers becomes O(1) w.r.t. prioritiy handling. |
2556 | |
2732 | |
2557 | =back |
2733 | =back |
2558 | |
2734 | |
2559 | |
2735 | |
2560 | =head1 AUTHOR |
2736 | =head1 AUTHOR |