… | |
… | |
8 | |
8 | |
9 | =head2 EXAMPLE PROGRAM |
9 | =head2 EXAMPLE PROGRAM |
10 | |
10 | |
11 | // a single header file is required |
11 | // a single header file is required |
12 | #include <ev.h> |
12 | #include <ev.h> |
|
|
13 | |
|
|
14 | #include <stdio.h> // for puts |
13 | |
15 | |
14 | // every watcher type has its own typedef'd struct |
16 | // every watcher type has its own typedef'd struct |
15 | // with the name ev_TYPE |
17 | // with the name ev_TYPE |
16 | ev_io stdin_watcher; |
18 | ev_io stdin_watcher; |
17 | ev_timer timeout_watcher; |
19 | ev_timer timeout_watcher; |
… | |
… | |
41 | |
43 | |
42 | int |
44 | int |
43 | main (void) |
45 | main (void) |
44 | { |
46 | { |
45 | // use the default event loop unless you have special needs |
47 | // use the default event loop unless you have special needs |
46 | ev_loop *loop = ev_default_loop (0); |
48 | struct ev_loop *loop = ev_default_loop (0); |
47 | |
49 | |
48 | // initialise an io watcher, then start it |
50 | // initialise an io watcher, then start it |
49 | // this one will watch for stdin to become readable |
51 | // this one will watch for stdin to become readable |
50 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
52 | ev_io_init (&stdin_watcher, stdin_cb, /*STDIN_FILENO*/ 0, EV_READ); |
51 | ev_io_start (loop, &stdin_watcher); |
53 | ev_io_start (loop, &stdin_watcher); |
… | |
… | |
386 | For few fds, this backend is a bit little slower than poll and select, |
388 | For few fds, this backend is a bit little slower than poll and select, |
387 | but it scales phenomenally better. While poll and select usually scale |
389 | but it scales phenomenally better. While poll and select usually scale |
388 | like O(total_fds) where n is the total number of fds (or the highest fd), |
390 | like O(total_fds) where n is the total number of fds (or the highest fd), |
389 | epoll scales either O(1) or O(active_fds). |
391 | epoll scales either O(1) or O(active_fds). |
390 | |
392 | |
391 | The epoll syscalls are the most misdesigned of the more advanced event |
393 | The epoll mechanism deserves honorable mention as the most misdesigned |
392 | mechanisms: problems include silently dropping fds, requiring a system |
394 | of the more advanced event mechanisms: mere annoyances include silently |
393 | call per change per fd (and unnecessary guessing of parameters), problems |
395 | dropping file descriptors, requiring a system call per change per file |
|
|
396 | descriptor (and unnecessary guessing of parameters), problems with dup and |
394 | with dup and so on. The biggest issue is fork races, however - if a |
397 | so on. The biggest issue is fork races, however - if a program forks then |
395 | program forks then I<both> parent and child process have to recreate the |
398 | I<both> parent and child process have to recreate the epoll set, which can |
396 | epoll set, which can take considerable time (one syscall per fd) and is of |
399 | take considerable time (one syscall per file descriptor) and is of course |
397 | course hard to detect. |
400 | hard to detect. |
398 | |
401 | |
399 | Epoll is also notoriously buggy - embedding epoll fds should work, but |
402 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
400 | of course doesn't, and epoll just loves to report events for totally |
403 | of course I<doesn't>, and epoll just loves to report events for totally |
401 | I<different> file descriptors (even already closed ones, so one cannot |
404 | I<different> file descriptors (even already closed ones, so one cannot |
402 | even remove them from the set) than registered in the set (especially |
405 | even remove them from the set) than registered in the set (especially |
403 | on SMP systems). Libev tries to counter these spurious notifications by |
406 | on SMP systems). Libev tries to counter these spurious notifications by |
404 | employing an additional generation counter and comparing that against the |
407 | employing an additional generation counter and comparing that against the |
405 | events to filter out spurious ones. |
408 | events to filter out spurious ones, recreating the set when required. |
406 | |
409 | |
407 | While stopping, setting and starting an I/O watcher in the same iteration |
410 | While stopping, setting and starting an I/O watcher in the same iteration |
408 | will result in some caching, there is still a system call per such incident |
411 | will result in some caching, there is still a system call per such |
409 | (because the fd could point to a different file description now), so its |
412 | incident (because the same I<file descriptor> could point to a different |
410 | best to avoid that. Also, C<dup ()>'ed file descriptors might not work |
413 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
411 | very well if you register events for both fds. |
414 | file descriptors might not work very well if you register events for both |
|
|
415 | file descriptors. |
412 | |
416 | |
413 | Best performance from this backend is achieved by not unregistering all |
417 | Best performance from this backend is achieved by not unregistering all |
414 | watchers for a file descriptor until it has been closed, if possible, |
418 | watchers for a file descriptor until it has been closed, if possible, |
415 | i.e. keep at least one watcher active per fd at all times. Stopping and |
419 | i.e. keep at least one watcher active per fd at all times. Stopping and |
416 | starting a watcher (without re-setting it) also usually doesn't cause |
420 | starting a watcher (without re-setting it) also usually doesn't cause |
417 | extra overhead. A fork can both result in spurious notifications as well |
421 | extra overhead. A fork can both result in spurious notifications as well |
418 | as in libev having to destroy and recreate the epoll object, which can |
422 | as in libev having to destroy and recreate the epoll object, which can |
419 | take considerable time and thus should be avoided. |
423 | take considerable time and thus should be avoided. |
420 | |
424 | |
|
|
425 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
|
|
426 | faster than epoll for maybe up to a hundred file descriptors, depending on |
|
|
427 | the usage. So sad. |
|
|
428 | |
421 | While nominally embeddable in other event loops, this feature is broken in |
429 | While nominally embeddable in other event loops, this feature is broken in |
422 | all kernel versions tested so far. |
430 | all kernel versions tested so far. |
423 | |
431 | |
424 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
432 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
425 | C<EVBACKEND_POLL>. |
433 | C<EVBACKEND_POLL>. |
426 | |
434 | |
427 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
435 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
428 | |
436 | |
429 | Kqueue deserves special mention, as at the time of this writing, it was |
437 | Kqueue deserves special mention, as at the time of this writing, it |
430 | broken on all BSDs except NetBSD (usually it doesn't work reliably with |
438 | was broken on all BSDs except NetBSD (usually it doesn't work reliably |
431 | anything but sockets and pipes, except on Darwin, where of course it's |
439 | with anything but sockets and pipes, except on Darwin, where of course |
432 | completely useless). For this reason it's not being "auto-detected" unless |
440 | it's completely useless). Unlike epoll, however, whose brokenness |
433 | you explicitly specify it in the flags (i.e. using C<EVBACKEND_KQUEUE>) or |
441 | is by design, these kqueue bugs can (and eventually will) be fixed |
434 | libev was compiled on a known-to-be-good (-enough) system like NetBSD. |
442 | without API changes to existing programs. For this reason it's not being |
|
|
443 | "auto-detected" unless you explicitly specify it in the flags (i.e. using |
|
|
444 | C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough) |
|
|
445 | system like NetBSD. |
435 | |
446 | |
436 | You still can embed kqueue into a normal poll or select backend and use it |
447 | You still can embed kqueue into a normal poll or select backend and use it |
437 | only for sockets (after having made sure that sockets work with kqueue on |
448 | only for sockets (after having made sure that sockets work with kqueue on |
438 | the target platform). See C<ev_embed> watchers for more info. |
449 | the target platform). See C<ev_embed> watchers for more info. |
439 | |
450 | |
… | |
… | |
449 | |
460 | |
450 | While nominally embeddable in other event loops, this doesn't work |
461 | While nominally embeddable in other event loops, this doesn't work |
451 | everywhere, so you might need to test for this. And since it is broken |
462 | everywhere, so you might need to test for this. And since it is broken |
452 | almost everywhere, you should only use it when you have a lot of sockets |
463 | almost everywhere, you should only use it when you have a lot of sockets |
453 | (for which it usually works), by embedding it into another event loop |
464 | (for which it usually works), by embedding it into another event loop |
454 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and, did I mention it, |
465 | (e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> (but C<poll> is of course |
455 | using it only for sockets. |
466 | also broken on OS X)) and, did I mention it, using it only for sockets. |
456 | |
467 | |
457 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
468 | This backend maps C<EV_READ> into an C<EVFILT_READ> kevent with |
458 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
469 | C<NOTE_EOF>, and C<EV_WRITE> into an C<EVFILT_WRITE> kevent with |
459 | C<NOTE_EOF>. |
470 | C<NOTE_EOF>. |
460 | |
471 | |
… | |
… | |
1410 | else |
1421 | else |
1411 | { |
1422 | { |
1412 | // callback was invoked, but there was some activity, re-arm |
1423 | // callback was invoked, but there was some activity, re-arm |
1413 | // the watcher to fire in last_activity + 60, which is |
1424 | // the watcher to fire in last_activity + 60, which is |
1414 | // guaranteed to be in the future, so "again" is positive: |
1425 | // guaranteed to be in the future, so "again" is positive: |
1415 | w->again = timeout - now; |
1426 | w->repeat = timeout - now; |
1416 | ev_timer_again (EV_A_ w); |
1427 | ev_timer_again (EV_A_ w); |
1417 | } |
1428 | } |
1418 | } |
1429 | } |
1419 | |
1430 | |
1420 | To summarise the callback: first calculate the real timeout (defined |
1431 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1585 | =head2 C<ev_periodic> - to cron or not to cron? |
1596 | =head2 C<ev_periodic> - to cron or not to cron? |
1586 | |
1597 | |
1587 | Periodic watchers are also timers of a kind, but they are very versatile |
1598 | Periodic watchers are also timers of a kind, but they are very versatile |
1588 | (and unfortunately a bit complex). |
1599 | (and unfortunately a bit complex). |
1589 | |
1600 | |
1590 | Unlike C<ev_timer>'s, they are not based on real time (or relative time) |
1601 | Unlike C<ev_timer>, periodic watchers are not based on real time (or |
1591 | but on wall clock time (absolute time). You can tell a periodic watcher |
1602 | relative time, the physical time that passes) but on wall clock time |
1592 | to trigger after some specific point in time. For example, if you tell a |
1603 | (absolute time, the thing you can read on your calender or clock). The |
1593 | periodic watcher to trigger in 10 seconds (by specifying e.g. C<ev_now () |
1604 | difference is that wall clock time can run faster or slower than real |
1594 | + 10.>, that is, an absolute time not a delay) and then reset your system |
1605 | time, and time jumps are not uncommon (e.g. when you adjust your |
1595 | clock to January of the previous year, then it will take more than year |
1606 | wrist-watch). |
1596 | to trigger the event (unlike an C<ev_timer>, which would still trigger |
|
|
1597 | roughly 10 seconds later as it uses a relative timeout). |
|
|
1598 | |
1607 | |
|
|
1608 | You can tell a periodic watcher to trigger after some specific point |
|
|
1609 | in time: for example, if you tell a periodic watcher to trigger "in 10 |
|
|
1610 | seconds" (by specifying e.g. C<ev_now () + 10.>, that is, an absolute time |
|
|
1611 | not a delay) and then reset your system clock to January of the previous |
|
|
1612 | year, then it will take a year or more to trigger the event (unlike an |
|
|
1613 | C<ev_timer>, which would still trigger roughly 10 seconds after starting |
|
|
1614 | it, as it uses a relative timeout). |
|
|
1615 | |
1599 | C<ev_periodic>s can also be used to implement vastly more complex timers, |
1616 | C<ev_periodic> watchers can also be used to implement vastly more complex |
1600 | such as triggering an event on each "midnight, local time", or other |
1617 | timers, such as triggering an event on each "midnight, local time", or |
1601 | complicated rules. |
1618 | other complicated rules. This cannot be done with C<ev_timer> watchers, as |
|
|
1619 | those cannot react to time jumps. |
1602 | |
1620 | |
1603 | As with timers, the callback is guaranteed to be invoked only when the |
1621 | As with timers, the callback is guaranteed to be invoked only when the |
1604 | time (C<at>) has passed, but if multiple periodic timers become ready |
1622 | point in time where it is supposed to trigger has passed, but if multiple |
1605 | during the same loop iteration, then order of execution is undefined. |
1623 | periodic timers become ready during the same loop iteration, then order of |
|
|
1624 | execution is undefined. |
1606 | |
1625 | |
1607 | =head3 Watcher-Specific Functions and Data Members |
1626 | =head3 Watcher-Specific Functions and Data Members |
1608 | |
1627 | |
1609 | =over 4 |
1628 | =over 4 |
1610 | |
1629 | |
1611 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1630 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1612 | |
1631 | |
1613 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1632 | =item ev_periodic_set (ev_periodic *, ev_tstamp offset, ev_tstamp interval, reschedule_cb) |
1614 | |
1633 | |
1615 | Lots of arguments, lets sort it out... There are basically three modes of |
1634 | Lots of arguments, let's sort it out... There are basically three modes of |
1616 | operation, and we will explain them from simplest to most complex: |
1635 | operation, and we will explain them from simplest to most complex: |
1617 | |
1636 | |
1618 | =over 4 |
1637 | =over 4 |
1619 | |
1638 | |
1620 | =item * absolute timer (at = time, interval = reschedule_cb = 0) |
1639 | =item * absolute timer (offset = absolute time, interval = 0, reschedule_cb = 0) |
1621 | |
1640 | |
1622 | In this configuration the watcher triggers an event after the wall clock |
1641 | In this configuration the watcher triggers an event after the wall clock |
1623 | time C<at> has passed. It will not repeat and will not adjust when a time |
1642 | time C<offset> has passed. It will not repeat and will not adjust when a |
1624 | jump occurs, that is, if it is to be run at January 1st 2011 then it will |
1643 | time jump occurs, that is, if it is to be run at January 1st 2011 then it |
1625 | only run when the system clock reaches or surpasses this time. |
1644 | will be stopped and invoked when the system clock reaches or surpasses |
|
|
1645 | this point in time. |
1626 | |
1646 | |
1627 | =item * repeating interval timer (at = offset, interval > 0, reschedule_cb = 0) |
1647 | =item * repeating interval timer (offset = offset within interval, interval > 0, reschedule_cb = 0) |
1628 | |
1648 | |
1629 | In this mode the watcher will always be scheduled to time out at the next |
1649 | In this mode the watcher will always be scheduled to time out at the next |
1630 | C<at + N * interval> time (for some integer N, which can also be negative) |
1650 | C<offset + N * interval> time (for some integer N, which can also be |
1631 | and then repeat, regardless of any time jumps. |
1651 | negative) and then repeat, regardless of any time jumps. The C<offset> |
|
|
1652 | argument is merely an offset into the C<interval> periods. |
1632 | |
1653 | |
1633 | This can be used to create timers that do not drift with respect to the |
1654 | This can be used to create timers that do not drift with respect to the |
1634 | system clock, for example, here is a C<ev_periodic> that triggers each |
1655 | system clock, for example, here is an C<ev_periodic> that triggers each |
1635 | hour, on the hour: |
1656 | hour, on the hour (with respect to UTC): |
1636 | |
1657 | |
1637 | ev_periodic_set (&periodic, 0., 3600., 0); |
1658 | ev_periodic_set (&periodic, 0., 3600., 0); |
1638 | |
1659 | |
1639 | This doesn't mean there will always be 3600 seconds in between triggers, |
1660 | This doesn't mean there will always be 3600 seconds in between triggers, |
1640 | but only that the callback will be called when the system time shows a |
1661 | but only that the callback will be called when the system time shows a |
1641 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1662 | full hour (UTC), or more correctly, when the system time is evenly divisible |
1642 | by 3600. |
1663 | by 3600. |
1643 | |
1664 | |
1644 | Another way to think about it (for the mathematically inclined) is that |
1665 | Another way to think about it (for the mathematically inclined) is that |
1645 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1666 | C<ev_periodic> will try to run the callback in this mode at the next possible |
1646 | time where C<time = at (mod interval)>, regardless of any time jumps. |
1667 | time where C<time = offset (mod interval)>, regardless of any time jumps. |
1647 | |
1668 | |
1648 | For numerical stability it is preferable that the C<at> value is near |
1669 | For numerical stability it is preferable that the C<offset> value is near |
1649 | C<ev_now ()> (the current time), but there is no range requirement for |
1670 | C<ev_now ()> (the current time), but there is no range requirement for |
1650 | this value, and in fact is often specified as zero. |
1671 | this value, and in fact is often specified as zero. |
1651 | |
1672 | |
1652 | Note also that there is an upper limit to how often a timer can fire (CPU |
1673 | Note also that there is an upper limit to how often a timer can fire (CPU |
1653 | speed for example), so if C<interval> is very small then timing stability |
1674 | speed for example), so if C<interval> is very small then timing stability |
1654 | will of course deteriorate. Libev itself tries to be exact to be about one |
1675 | will of course deteriorate. Libev itself tries to be exact to be about one |
1655 | millisecond (if the OS supports it and the machine is fast enough). |
1676 | millisecond (if the OS supports it and the machine is fast enough). |
1656 | |
1677 | |
1657 | =item * manual reschedule mode (at and interval ignored, reschedule_cb = callback) |
1678 | =item * manual reschedule mode (offset ignored, interval ignored, reschedule_cb = callback) |
1658 | |
1679 | |
1659 | In this mode the values for C<interval> and C<at> are both being |
1680 | In this mode the values for C<interval> and C<offset> are both being |
1660 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1681 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1661 | reschedule callback will be called with the watcher as first, and the |
1682 | reschedule callback will be called with the watcher as first, and the |
1662 | current time as second argument. |
1683 | current time as second argument. |
1663 | |
1684 | |
1664 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1685 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, ever, |
1665 | ever, or make ANY event loop modifications whatsoever>. |
1686 | or make ANY other event loop modifications whatsoever, unless explicitly |
|
|
1687 | allowed by documentation here>. |
1666 | |
1688 | |
1667 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1689 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1668 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1690 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1669 | only event loop modification you are allowed to do). |
1691 | only event loop modification you are allowed to do). |
1670 | |
1692 | |
… | |
… | |
1700 | a different time than the last time it was called (e.g. in a crond like |
1722 | a different time than the last time it was called (e.g. in a crond like |
1701 | program when the crontabs have changed). |
1723 | program when the crontabs have changed). |
1702 | |
1724 | |
1703 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1725 | =item ev_tstamp ev_periodic_at (ev_periodic *) |
1704 | |
1726 | |
1705 | When active, returns the absolute time that the watcher is supposed to |
1727 | When active, returns the absolute time that the watcher is supposed |
1706 | trigger next. |
1728 | to trigger next. This is not the same as the C<offset> argument to |
|
|
1729 | C<ev_periodic_set>, but indeed works even in interval and manual |
|
|
1730 | rescheduling modes. |
1707 | |
1731 | |
1708 | =item ev_tstamp offset [read-write] |
1732 | =item ev_tstamp offset [read-write] |
1709 | |
1733 | |
1710 | When repeating, this contains the offset value, otherwise this is the |
1734 | When repeating, this contains the offset value, otherwise this is the |
1711 | absolute point in time (the C<at> value passed to C<ev_periodic_set>). |
1735 | absolute point in time (the C<offset> value passed to C<ev_periodic_set>, |
|
|
1736 | although libev might modify this value for better numerical stability). |
1712 | |
1737 | |
1713 | Can be modified any time, but changes only take effect when the periodic |
1738 | Can be modified any time, but changes only take effect when the periodic |
1714 | timer fires or C<ev_periodic_again> is being called. |
1739 | timer fires or C<ev_periodic_again> is being called. |
1715 | |
1740 | |
1716 | =item ev_tstamp interval [read-write] |
1741 | =item ev_tstamp interval [read-write] |
… | |
… | |
1927 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1952 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1928 | and sees if it changed compared to the last time, invoking the callback if |
1953 | and sees if it changed compared to the last time, invoking the callback if |
1929 | it did. |
1954 | it did. |
1930 | |
1955 | |
1931 | The path does not need to exist: changing from "path exists" to "path does |
1956 | The path does not need to exist: changing from "path exists" to "path does |
1932 | not exist" is a status change like any other. The condition "path does |
1957 | not exist" is a status change like any other. The condition "path does not |
1933 | not exist" is signified by the C<st_nlink> field being zero (which is |
1958 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1934 | otherwise always forced to be at least one) and all the other fields of |
1959 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1935 | the stat buffer having unspecified contents. |
1960 | least one) and all the other fields of the stat buffer having unspecified |
|
|
1961 | contents. |
1936 | |
1962 | |
1937 | The path I<must not> end in a slash or contain special components such as |
1963 | The path I<must not> end in a slash or contain special components such as |
1938 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1964 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1939 | your working directory changes, then the behaviour is undefined. |
1965 | your working directory changes, then the behaviour is undefined. |
1940 | |
1966 | |
… | |
… | |
1950 | This watcher type is not meant for massive numbers of stat watchers, |
1976 | This watcher type is not meant for massive numbers of stat watchers, |
1951 | as even with OS-supported change notifications, this can be |
1977 | as even with OS-supported change notifications, this can be |
1952 | resource-intensive. |
1978 | resource-intensive. |
1953 | |
1979 | |
1954 | At the time of this writing, the only OS-specific interface implemented |
1980 | At the time of this writing, the only OS-specific interface implemented |
1955 | is the Linux inotify interface (implementing kqueue support is left as |
1981 | is the Linux inotify interface (implementing kqueue support is left as an |
1956 | an exercise for the reader. Note, however, that the author sees no way |
1982 | exercise for the reader. Note, however, that the author sees no way of |
1957 | of implementing C<ev_stat> semantics with kqueue). |
1983 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1958 | |
1984 | |
1959 | =head3 ABI Issues (Largefile Support) |
1985 | =head3 ABI Issues (Largefile Support) |
1960 | |
1986 | |
1961 | Libev by default (unless the user overrides this) uses the default |
1987 | Libev by default (unless the user overrides this) uses the default |
1962 | compilation environment, which means that on systems with large file |
1988 | compilation environment, which means that on systems with large file |
… | |
… | |
1973 | to exchange stat structures with application programs compiled using the |
1999 | to exchange stat structures with application programs compiled using the |
1974 | default compilation environment. |
2000 | default compilation environment. |
1975 | |
2001 | |
1976 | =head3 Inotify and Kqueue |
2002 | =head3 Inotify and Kqueue |
1977 | |
2003 | |
1978 | When C<inotify (7)> support has been compiled into libev (generally |
2004 | When C<inotify (7)> support has been compiled into libev and present at |
1979 | only available with Linux 2.6.25 or above due to bugs in earlier |
2005 | runtime, it will be used to speed up change detection where possible. The |
1980 | implementations) and present at runtime, it will be used to speed up |
2006 | inotify descriptor will be created lazily when the first C<ev_stat> |
1981 | change detection where possible. The inotify descriptor will be created |
2007 | watcher is being started. |
1982 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1983 | |
2008 | |
1984 | Inotify presence does not change the semantics of C<ev_stat> watchers |
2009 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1985 | except that changes might be detected earlier, and in some cases, to avoid |
2010 | except that changes might be detected earlier, and in some cases, to avoid |
1986 | making regular C<stat> calls. Even in the presence of inotify support |
2011 | making regular C<stat> calls. Even in the presence of inotify support |
1987 | there are many cases where libev has to resort to regular C<stat> polling, |
2012 | there are many cases where libev has to resort to regular C<stat> polling, |
1988 | but as long as the path exists, libev usually gets away without polling. |
2013 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2014 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2015 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2016 | xfs are fully working) libev usually gets away without polling. |
1989 | |
2017 | |
1990 | There is no support for kqueue, as apparently it cannot be used to |
2018 | There is no support for kqueue, as apparently it cannot be used to |
1991 | implement this functionality, due to the requirement of having a file |
2019 | implement this functionality, due to the requirement of having a file |
1992 | descriptor open on the object at all times, and detecting renames, unlinks |
2020 | descriptor open on the object at all times, and detecting renames, unlinks |
1993 | etc. is difficult. |
2021 | etc. is difficult. |
|
|
2022 | |
|
|
2023 | =head3 C<stat ()> is a synchronous operation |
|
|
2024 | |
|
|
2025 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2026 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2027 | ()>, which is a synchronous operation. |
|
|
2028 | |
|
|
2029 | For local paths, this usually doesn't matter: unless the system is very |
|
|
2030 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2031 | as the path data is usually in memory already (except when starting the |
|
|
2032 | watcher). |
|
|
2033 | |
|
|
2034 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2035 | time due to network issues, and even under good conditions, a stat call |
|
|
2036 | often takes multiple milliseconds. |
|
|
2037 | |
|
|
2038 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2039 | paths, although this is fully supported by libev. |
1994 | |
2040 | |
1995 | =head3 The special problem of stat time resolution |
2041 | =head3 The special problem of stat time resolution |
1996 | |
2042 | |
1997 | The C<stat ()> system call only supports full-second resolution portably, |
2043 | The C<stat ()> system call only supports full-second resolution portably, |
1998 | and even on systems where the resolution is higher, most file systems |
2044 | and even on systems where the resolution is higher, most file systems |
… | |
… | |
2147 | |
2193 | |
2148 | =head3 Watcher-Specific Functions and Data Members |
2194 | =head3 Watcher-Specific Functions and Data Members |
2149 | |
2195 | |
2150 | =over 4 |
2196 | =over 4 |
2151 | |
2197 | |
2152 | =item ev_idle_init (ev_signal *, callback) |
2198 | =item ev_idle_init (ev_idle *, callback) |
2153 | |
2199 | |
2154 | Initialises and configures the idle watcher - it has no parameters of any |
2200 | Initialises and configures the idle watcher - it has no parameters of any |
2155 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2201 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2156 | believe me. |
2202 | believe me. |
2157 | |
2203 | |
… | |
… | |
2396 | some fds have to be watched and handled very quickly (with low latency), |
2442 | some fds have to be watched and handled very quickly (with low latency), |
2397 | and even priorities and idle watchers might have too much overhead. In |
2443 | and even priorities and idle watchers might have too much overhead. In |
2398 | this case you would put all the high priority stuff in one loop and all |
2444 | this case you would put all the high priority stuff in one loop and all |
2399 | the rest in a second one, and embed the second one in the first. |
2445 | the rest in a second one, and embed the second one in the first. |
2400 | |
2446 | |
2401 | As long as the watcher is active, the callback will be invoked every time |
2447 | As long as the watcher is active, the callback will be invoked every |
2402 | there might be events pending in the embedded loop. The callback must then |
2448 | time there might be events pending in the embedded loop. The callback |
2403 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2449 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2404 | their callbacks (you could also start an idle watcher to give the embedded |
2450 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2405 | loop strictly lower priority for example). You can also set the callback |
2451 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2406 | to C<0>, in which case the embed watcher will automatically execute the |
2452 | to give the embedded loop strictly lower priority for example). |
2407 | embedded loop sweep. |
|
|
2408 | |
2453 | |
2409 | As long as the watcher is started it will automatically handle events. The |
2454 | You can also set the callback to C<0>, in which case the embed watcher |
2410 | callback will be invoked whenever some events have been handled. You can |
2455 | will automatically execute the embedded loop sweep whenever necessary. |
2411 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2412 | interested in that. |
|
|
2413 | |
2456 | |
2414 | Also, there have not currently been made special provisions for forking: |
2457 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2415 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2458 | is active, i.e., the embedded loop will automatically be forked when the |
2416 | but you will also have to stop and restart any C<ev_embed> watchers |
2459 | embedding loop forks. In other cases, the user is responsible for calling |
2417 | yourself - but you can use a fork watcher to handle this automatically, |
2460 | C<ev_loop_fork> on the embedded loop. |
2418 | and future versions of libev might do just that. |
|
|
2419 | |
2461 | |
2420 | Unfortunately, not all backends are embeddable: only the ones returned by |
2462 | Unfortunately, not all backends are embeddable: only the ones returned by |
2421 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2463 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2422 | portable one. |
2464 | portable one. |
2423 | |
2465 | |
… | |
… | |
2654 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2696 | an C<EV_ASYNC> event on the watcher into the event loop. Unlike |
2655 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2697 | C<ev_feed_event>, this call is safe to do from other threads, signal or |
2656 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2698 | similar contexts (see the discussion of C<EV_ATOMIC_T> in the embedding |
2657 | section below on what exactly this means). |
2699 | section below on what exactly this means). |
2658 | |
2700 | |
|
|
2701 | Note that, as with other watchers in libev, multiple events might get |
|
|
2702 | compressed into a single callback invocation (another way to look at this |
|
|
2703 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
|
|
2704 | reset when the event loop detects that). |
|
|
2705 | |
2659 | This call incurs the overhead of a system call only once per loop iteration, |
2706 | This call incurs the overhead of a system call only once per event loop |
2660 | so while the overhead might be noticeable, it doesn't apply to repeated |
2707 | iteration, so while the overhead might be noticeable, it doesn't apply to |
2661 | calls to C<ev_async_send>. |
2708 | repeated calls to C<ev_async_send> for the same event loop. |
2662 | |
2709 | |
2663 | =item bool = ev_async_pending (ev_async *) |
2710 | =item bool = ev_async_pending (ev_async *) |
2664 | |
2711 | |
2665 | Returns a non-zero value when C<ev_async_send> has been called on the |
2712 | Returns a non-zero value when C<ev_async_send> has been called on the |
2666 | watcher but the event has not yet been processed (or even noted) by the |
2713 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
2669 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2716 | C<ev_async_send> sets a flag in the watcher and wakes up the loop. When |
2670 | the loop iterates next and checks for the watcher to have become active, |
2717 | the loop iterates next and checks for the watcher to have become active, |
2671 | it will reset the flag again. C<ev_async_pending> can be used to very |
2718 | it will reset the flag again. C<ev_async_pending> can be used to very |
2672 | quickly check whether invoking the loop might be a good idea. |
2719 | quickly check whether invoking the loop might be a good idea. |
2673 | |
2720 | |
2674 | Not that this does I<not> check whether the watcher itself is pending, only |
2721 | Not that this does I<not> check whether the watcher itself is pending, |
2675 | whether it has been requested to make this watcher pending. |
2722 | only whether it has been requested to make this watcher pending: there |
|
|
2723 | is a time window between the event loop checking and resetting the async |
|
|
2724 | notification, and the callback being invoked. |
2676 | |
2725 | |
2677 | =back |
2726 | =back |
2678 | |
2727 | |
2679 | |
2728 | |
2680 | =head1 OTHER FUNCTIONS |
2729 | =head1 OTHER FUNCTIONS |
… | |
… | |
2859 | |
2908 | |
2860 | myclass obj; |
2909 | myclass obj; |
2861 | ev::io iow; |
2910 | ev::io iow; |
2862 | iow.set <myclass, &myclass::io_cb> (&obj); |
2911 | iow.set <myclass, &myclass::io_cb> (&obj); |
2863 | |
2912 | |
|
|
2913 | =item w->set (object *) |
|
|
2914 | |
|
|
2915 | This is an B<experimental> feature that might go away in a future version. |
|
|
2916 | |
|
|
2917 | This is a variation of a method callback - leaving out the method to call |
|
|
2918 | will default the method to C<operator ()>, which makes it possible to use |
|
|
2919 | functor objects without having to manually specify the C<operator ()> all |
|
|
2920 | the time. Incidentally, you can then also leave out the template argument |
|
|
2921 | list. |
|
|
2922 | |
|
|
2923 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
2924 | int revents)>. |
|
|
2925 | |
|
|
2926 | See the method-C<set> above for more details. |
|
|
2927 | |
|
|
2928 | Example: use a functor object as callback. |
|
|
2929 | |
|
|
2930 | struct myfunctor |
|
|
2931 | { |
|
|
2932 | void operator() (ev::io &w, int revents) |
|
|
2933 | { |
|
|
2934 | ... |
|
|
2935 | } |
|
|
2936 | } |
|
|
2937 | |
|
|
2938 | myfunctor f; |
|
|
2939 | |
|
|
2940 | ev::io w; |
|
|
2941 | w.set (&f); |
|
|
2942 | |
2864 | =item w->set<function> (void *data = 0) |
2943 | =item w->set<function> (void *data = 0) |
2865 | |
2944 | |
2866 | Also sets a callback, but uses a static method or plain function as |
2945 | Also sets a callback, but uses a static method or plain function as |
2867 | callback. The optional C<data> argument will be stored in the watcher's |
2946 | callback. The optional C<data> argument will be stored in the watcher's |
2868 | C<data> member and is free for you to use. |
2947 | C<data> member and is free for you to use. |
… | |
… | |
2967 | Tony Arcieri has written a ruby extension that offers access to a subset |
3046 | Tony Arcieri has written a ruby extension that offers access to a subset |
2968 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3047 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2969 | more on top of it. It can be found via gem servers. Its homepage is at |
3048 | more on top of it. It can be found via gem servers. Its homepage is at |
2970 | L<http://rev.rubyforge.org/>. |
3049 | L<http://rev.rubyforge.org/>. |
2971 | |
3050 | |
|
|
3051 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3052 | makes rev work even on mingw. |
|
|
3053 | |
2972 | =item D |
3054 | =item D |
2973 | |
3055 | |
2974 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3056 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2975 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3057 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2976 | |
3058 | |
… | |
… | |
3152 | keeps libev from including F<config.h>, and it also defines dummy |
3234 | keeps libev from including F<config.h>, and it also defines dummy |
3153 | implementations for some libevent functions (such as logging, which is not |
3235 | implementations for some libevent functions (such as logging, which is not |
3154 | supported). It will also not define any of the structs usually found in |
3236 | supported). It will also not define any of the structs usually found in |
3155 | F<event.h> that are not directly supported by the libev core alone. |
3237 | F<event.h> that are not directly supported by the libev core alone. |
3156 | |
3238 | |
|
|
3239 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3240 | configuration, but has to be more conservative. |
|
|
3241 | |
3157 | =item EV_USE_MONOTONIC |
3242 | =item EV_USE_MONOTONIC |
3158 | |
3243 | |
3159 | If defined to be C<1>, libev will try to detect the availability of the |
3244 | If defined to be C<1>, libev will try to detect the availability of the |
3160 | monotonic clock option at both compile time and runtime. Otherwise no use |
3245 | monotonic clock option at both compile time and runtime. Otherwise no |
3161 | of the monotonic clock option will be attempted. If you enable this, you |
3246 | use of the monotonic clock option will be attempted. If you enable this, |
3162 | usually have to link against librt or something similar. Enabling it when |
3247 | you usually have to link against librt or something similar. Enabling it |
3163 | the functionality isn't available is safe, though, although you have |
3248 | when the functionality isn't available is safe, though, although you have |
3164 | to make sure you link against any libraries where the C<clock_gettime> |
3249 | to make sure you link against any libraries where the C<clock_gettime> |
3165 | function is hiding in (often F<-lrt>). |
3250 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3166 | |
3251 | |
3167 | =item EV_USE_REALTIME |
3252 | =item EV_USE_REALTIME |
3168 | |
3253 | |
3169 | If defined to be C<1>, libev will try to detect the availability of the |
3254 | If defined to be C<1>, libev will try to detect the availability of the |
3170 | real-time clock option at compile time (and assume its availability at |
3255 | real-time clock option at compile time (and assume its availability |
3171 | runtime if successful). Otherwise no use of the real-time clock option will |
3256 | at runtime if successful). Otherwise no use of the real-time clock |
3172 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3257 | option will be attempted. This effectively replaces C<gettimeofday> |
3173 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3258 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3174 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3259 | correctness. See the note about libraries in the description of |
|
|
3260 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3261 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3262 | |
|
|
3263 | =item EV_USE_CLOCK_SYSCALL |
|
|
3264 | |
|
|
3265 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3266 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3267 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3268 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3269 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3270 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3271 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3272 | higher, as it simplifies linking (no need for C<-lrt>). |
3175 | |
3273 | |
3176 | =item EV_USE_NANOSLEEP |
3274 | =item EV_USE_NANOSLEEP |
3177 | |
3275 | |
3178 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3276 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3179 | and will use it for delays. Otherwise it will use C<select ()>. |
3277 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3195 | |
3293 | |
3196 | =item EV_SELECT_USE_FD_SET |
3294 | =item EV_SELECT_USE_FD_SET |
3197 | |
3295 | |
3198 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3296 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3199 | structure. This is useful if libev doesn't compile due to a missing |
3297 | structure. This is useful if libev doesn't compile due to a missing |
3200 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3298 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3201 | exotic systems. This usually limits the range of file descriptors to some |
3299 | on exotic systems. This usually limits the range of file descriptors to |
3202 | low limit such as 1024 or might have other limitations (winsocket only |
3300 | some low limit such as 1024 or might have other limitations (winsocket |
3203 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3301 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3204 | influence the size of the C<fd_set> used. |
3302 | configures the maximum size of the C<fd_set>. |
3205 | |
3303 | |
3206 | =item EV_SELECT_IS_WINSOCKET |
3304 | =item EV_SELECT_IS_WINSOCKET |
3207 | |
3305 | |
3208 | When defined to C<1>, the select backend will assume that |
3306 | When defined to C<1>, the select backend will assume that |
3209 | select/socket/connect etc. don't understand file descriptors but |
3307 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3860 | =back |
3958 | =back |
3861 | |
3959 | |
3862 | |
3960 | |
3863 | =head1 AUTHOR |
3961 | =head1 AUTHOR |
3864 | |
3962 | |
3865 | Marc Lehmann <libev@schmorp.de>. |
3963 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3866 | |
3964 | |