… | |
… | |
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> |
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13 | |
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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); |
… | |
… | |
298 | If you don't know what event loop to use, use the one returned from this |
300 | If you don't know what event loop to use, use the one returned from this |
299 | function. |
301 | function. |
300 | |
302 | |
301 | Note that this function is I<not> thread-safe, so if you want to use it |
303 | Note that this function is I<not> thread-safe, so if you want to use it |
302 | from multiple threads, you have to lock (note also that this is unlikely, |
304 | from multiple threads, you have to lock (note also that this is unlikely, |
303 | as loops cannot bes hared easily between threads anyway). |
305 | as loops cannot be shared easily between threads anyway). |
304 | |
306 | |
305 | The default loop is the only loop that can handle C<ev_signal> and |
307 | The default loop is the only loop that can handle C<ev_signal> and |
306 | C<ev_child> watchers, and to do this, it always registers a handler |
308 | C<ev_child> watchers, and to do this, it always registers a handler |
307 | for C<SIGCHLD>. If this is a problem for your application you can either |
309 | for C<SIGCHLD>. If this is a problem for your application you can either |
308 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
310 | create a dynamic loop with C<ev_loop_new> that doesn't do that, or you |
… | |
… | |
384 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
386 | =item C<EVBACKEND_EPOLL> (value 4, Linux) |
385 | |
387 | |
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). The epoll design has a number |
391 | epoll scales either O(1) or O(active_fds). |
390 | of shortcomings, such as silently dropping events in some hard-to-detect |
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391 | cases and requiring a system call per fd change, no fork support and bad |
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392 | support for dup. |
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393 | |
392 | |
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393 | The epoll mechanism deserves honorable mention as the most misdesigned |
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394 | of the more advanced event mechanisms: mere annoyances include silently |
|
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395 | dropping file descriptors, requiring a system call per change per file |
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396 | descriptor (and unnecessary guessing of parameters), problems with dup and |
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397 | so on. The biggest issue is fork races, however - if a program forks then |
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398 | I<both> parent and child process have to recreate the epoll set, which can |
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399 | take considerable time (one syscall per file descriptor) and is of course |
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400 | hard to detect. |
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|
401 | |
394 | Epoll is also notoriously buggy - embedding epoll fds should work, but |
402 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
395 | 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 |
396 | I<different> file descriptors (even already closed ones) than registered |
404 | I<different> file descriptors (even already closed ones, so one cannot |
397 | in the set (especially on SMP systems). Libev tries to counter these |
405 | even remove them from the set) than registered in the set (especially |
398 | spurious notifications by employing an additional generation counter and |
406 | on SMP systems). Libev tries to counter these spurious notifications by |
399 | comparing that against the events to filter out spurious ones. |
407 | employing an additional generation counter and comparing that against the |
|
|
408 | events to filter out spurious ones, recreating the set when required. |
400 | |
409 | |
401 | 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 |
402 | 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 |
403 | (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 |
404 | 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 |
405 | very well if you register events for both fds. |
414 | file descriptors might not work very well if you register events for both |
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|
415 | file descriptors. |
406 | |
416 | |
407 | Best performance from this backend is achieved by not unregistering all |
417 | Best performance from this backend is achieved by not unregistering all |
408 | 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, |
409 | 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 |
410 | 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 |
411 | extra overhead. |
421 | extra overhead. A fork can both result in spurious notifications as well |
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|
422 | as in libev having to destroy and recreate the epoll object, which can |
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423 | take considerable time and thus should be avoided. |
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424 | |
|
|
425 | All this means that, in practice, C<EVBACKEND_SELECT> can be as fast or |
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426 | faster than epoll for maybe up to a hundred file descriptors, depending on |
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427 | the usage. So sad. |
412 | |
428 | |
413 | 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 |
414 | all kernel versions tested so far. |
430 | all kernel versions tested so far. |
415 | |
431 | |
416 | 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 |
417 | C<EVBACKEND_POLL>. |
433 | C<EVBACKEND_POLL>. |
418 | |
434 | |
419 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
435 | =item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) |
420 | |
436 | |
421 | 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 |
422 | 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 |
423 | 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 |
424 | completely useless). For this reason it's not being "auto-detected" unless |
440 | it's completely useless). Unlike epoll, however, whose brokenness |
425 | 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 |
426 | 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. |
427 | |
446 | |
428 | 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 |
429 | 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 |
430 | the target platform). See C<ev_embed> watchers for more info. |
449 | the target platform). See C<ev_embed> watchers for more info. |
431 | |
450 | |
432 | It scales in the same way as the epoll backend, but the interface to the |
451 | It scales in the same way as the epoll backend, but the interface to the |
433 | kernel is more efficient (which says nothing about its actual speed, of |
452 | kernel is more efficient (which says nothing about its actual speed, of |
434 | course). While stopping, setting and starting an I/O watcher does never |
453 | course). While stopping, setting and starting an I/O watcher does never |
435 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
454 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
436 | two event changes per incident. Support for C<fork ()> is very bad and it |
455 | two event changes per incident. Support for C<fork ()> is very bad (but |
437 | drops fds silently in similarly hard-to-detect cases. |
456 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
|
|
457 | cases |
438 | |
458 | |
439 | This backend usually performs well under most conditions. |
459 | This backend usually performs well under most conditions. |
440 | |
460 | |
441 | While nominally embeddable in other event loops, this doesn't work |
461 | While nominally embeddable in other event loops, this doesn't work |
442 | 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 |
443 | 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 |
444 | (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 |
445 | (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 |
446 | using it only for sockets. |
466 | also broken on OS X)) and, did I mention it, using it only for sockets. |
447 | |
467 | |
448 | 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 |
449 | 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 |
450 | C<NOTE_EOF>. |
470 | C<NOTE_EOF>. |
451 | |
471 | |
… | |
… | |
471 | might perform better. |
491 | might perform better. |
472 | |
492 | |
473 | On the positive side, with the exception of the spurious readiness |
493 | On the positive side, with the exception of the spurious readiness |
474 | notifications, this backend actually performed fully to specification |
494 | notifications, this backend actually performed fully to specification |
475 | in all tests and is fully embeddable, which is a rare feat among the |
495 | in all tests and is fully embeddable, which is a rare feat among the |
476 | OS-specific backends. |
496 | OS-specific backends (I vastly prefer correctness over speed hacks). |
477 | |
497 | |
478 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
498 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
479 | C<EVBACKEND_POLL>. |
499 | C<EVBACKEND_POLL>. |
480 | |
500 | |
481 | =item C<EVBACKEND_ALL> |
501 | =item C<EVBACKEND_ALL> |
… | |
… | |
638 | the loop. |
658 | the loop. |
639 | |
659 | |
640 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
660 | A flags value of C<EVLOOP_ONESHOT> will look for new events (waiting if |
641 | necessary) and will handle those and any already outstanding ones. It |
661 | necessary) and will handle those and any already outstanding ones. It |
642 | will block your process until at least one new event arrives (which could |
662 | will block your process until at least one new event arrives (which could |
643 | be an event internal to libev itself, so there is no guarentee that a |
663 | be an event internal to libev itself, so there is no guarantee that a |
644 | user-registered callback will be called), and will return after one |
664 | user-registered callback will be called), and will return after one |
645 | iteration of the loop. |
665 | iteration of the loop. |
646 | |
666 | |
647 | This is useful if you are waiting for some external event in conjunction |
667 | This is useful if you are waiting for some external event in conjunction |
648 | with something not expressible using other libev watchers (i.e. "roll your |
668 | with something not expressible using other libev watchers (i.e. "roll your |
… | |
… | |
1401 | else |
1421 | else |
1402 | { |
1422 | { |
1403 | // callback was invoked, but there was some activity, re-arm |
1423 | // callback was invoked, but there was some activity, re-arm |
1404 | // the watcher to fire in last_activity + 60, which is |
1424 | // the watcher to fire in last_activity + 60, which is |
1405 | // guaranteed to be in the future, so "again" is positive: |
1425 | // guaranteed to be in the future, so "again" is positive: |
1406 | w->again = timeout - now; |
1426 | w->repeat = timeout - now; |
1407 | ev_timer_again (EV_A_ w); |
1427 | ev_timer_again (EV_A_ w); |
1408 | } |
1428 | } |
1409 | } |
1429 | } |
1410 | |
1430 | |
1411 | To summarise the callback: first calculate the real timeout (defined |
1431 | To summarise the callback: first calculate the real timeout (defined |
… | |
… | |
1599 | |
1619 | |
1600 | =over 4 |
1620 | =over 4 |
1601 | |
1621 | |
1602 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1622 | =item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1603 | |
1623 | |
1604 | =item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) |
1624 | =item ev_periodic_set (ev_periodic *, ev_tstamp at, ev_tstamp interval, reschedule_cb) |
1605 | |
1625 | |
1606 | Lots of arguments, lets sort it out... There are basically three modes of |
1626 | Lots of arguments, lets sort it out... There are basically three modes of |
1607 | operation, and we will explain them from simplest to most complex: |
1627 | operation, and we will explain them from simplest to most complex: |
1608 | |
1628 | |
1609 | =over 4 |
1629 | =over 4 |
… | |
… | |
1651 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1671 | ignored. Instead, each time the periodic watcher gets scheduled, the |
1652 | reschedule callback will be called with the watcher as first, and the |
1672 | reschedule callback will be called with the watcher as first, and the |
1653 | current time as second argument. |
1673 | current time as second argument. |
1654 | |
1674 | |
1655 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1675 | NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, |
1656 | ever, or make ANY event loop modifications whatsoever>. |
1676 | ever, or make ANY other event loop modifications whatsoever>. |
1657 | |
1677 | |
1658 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1678 | If you need to stop it, return C<now + 1e30> (or so, fudge fudge) and stop |
1659 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1679 | it afterwards (e.g. by starting an C<ev_prepare> watcher, which is the |
1660 | only event loop modification you are allowed to do). |
1680 | only event loop modification you are allowed to do). |
1661 | |
1681 | |
… | |
… | |
1913 | |
1933 | |
1914 | |
1934 | |
1915 | =head2 C<ev_stat> - did the file attributes just change? |
1935 | =head2 C<ev_stat> - did the file attributes just change? |
1916 | |
1936 | |
1917 | This watches a file system path for attribute changes. That is, it calls |
1937 | This watches a file system path for attribute changes. That is, it calls |
1918 | C<stat> regularly (or when the OS says it changed) and sees if it changed |
1938 | C<stat> on that path in regular intervals (or when the OS says it changed) |
1919 | compared to the last time, invoking the callback if it did. |
1939 | and sees if it changed compared to the last time, invoking the callback if |
|
|
1940 | it did. |
1920 | |
1941 | |
1921 | The path does not need to exist: changing from "path exists" to "path does |
1942 | The path does not need to exist: changing from "path exists" to "path does |
1922 | not exist" is a status change like any other. The condition "path does |
1943 | not exist" is a status change like any other. The condition "path does not |
1923 | not exist" is signified by the C<st_nlink> field being zero (which is |
1944 | exist" (or more correctly "path cannot be stat'ed") is signified by the |
1924 | otherwise always forced to be at least one) and all the other fields of |
1945 | C<st_nlink> field being zero (which is otherwise always forced to be at |
1925 | the stat buffer having unspecified contents. |
1946 | least one) and all the other fields of the stat buffer having unspecified |
|
|
1947 | contents. |
1926 | |
1948 | |
1927 | The path I<should> be absolute and I<must not> end in a slash. If it is |
1949 | The path I<must not> end in a slash or contain special components such as |
|
|
1950 | C<.> or C<..>. The path I<should> be absolute: If it is relative and |
1928 | relative and your working directory changes, the behaviour is undefined. |
1951 | your working directory changes, then the behaviour is undefined. |
1929 | |
1952 | |
1930 | Since there is no standard kernel interface to do this, the portable |
1953 | Since there is no portable change notification interface available, the |
1931 | implementation simply calls C<stat (2)> regularly on the path to see if |
1954 | portable implementation simply calls C<stat(2)> regularly on the path |
1932 | it changed somehow. You can specify a recommended polling interval for |
1955 | to see if it changed somehow. You can specify a recommended polling |
1933 | this case. If you specify a polling interval of C<0> (highly recommended!) |
1956 | interval for this case. If you specify a polling interval of C<0> (highly |
1934 | then a I<suitable, unspecified default> value will be used (which |
1957 | recommended!) then a I<suitable, unspecified default> value will be used |
1935 | you can expect to be around five seconds, although this might change |
1958 | (which you can expect to be around five seconds, although this might |
1936 | dynamically). Libev will also impose a minimum interval which is currently |
1959 | change dynamically). Libev will also impose a minimum interval which is |
1937 | around C<0.1>, but thats usually overkill. |
1960 | currently around C<0.1>, but that's usually overkill. |
1938 | |
1961 | |
1939 | This watcher type is not meant for massive numbers of stat watchers, |
1962 | This watcher type is not meant for massive numbers of stat watchers, |
1940 | as even with OS-supported change notifications, this can be |
1963 | as even with OS-supported change notifications, this can be |
1941 | resource-intensive. |
1964 | resource-intensive. |
1942 | |
1965 | |
1943 | At the time of this writing, the only OS-specific interface implemented |
1966 | At the time of this writing, the only OS-specific interface implemented |
1944 | is the Linux inotify interface (implementing kqueue support is left as |
1967 | is the Linux inotify interface (implementing kqueue support is left as an |
1945 | an exercise for the reader. Note, however, that the author sees no way |
1968 | exercise for the reader. Note, however, that the author sees no way of |
1946 | of implementing C<ev_stat> semantics with kqueue). |
1969 | implementing C<ev_stat> semantics with kqueue, except as a hint). |
1947 | |
1970 | |
1948 | =head3 ABI Issues (Largefile Support) |
1971 | =head3 ABI Issues (Largefile Support) |
1949 | |
1972 | |
1950 | Libev by default (unless the user overrides this) uses the default |
1973 | Libev by default (unless the user overrides this) uses the default |
1951 | compilation environment, which means that on systems with large file |
1974 | compilation environment, which means that on systems with large file |
1952 | support disabled by default, you get the 32 bit version of the stat |
1975 | support disabled by default, you get the 32 bit version of the stat |
1953 | structure. When using the library from programs that change the ABI to |
1976 | structure. When using the library from programs that change the ABI to |
1954 | use 64 bit file offsets the programs will fail. In that case you have to |
1977 | use 64 bit file offsets the programs will fail. In that case you have to |
1955 | compile libev with the same flags to get binary compatibility. This is |
1978 | compile libev with the same flags to get binary compatibility. This is |
1956 | obviously the case with any flags that change the ABI, but the problem is |
1979 | obviously the case with any flags that change the ABI, but the problem is |
1957 | most noticeably disabled with ev_stat and large file support. |
1980 | most noticeably displayed with ev_stat and large file support. |
1958 | |
1981 | |
1959 | The solution for this is to lobby your distribution maker to make large |
1982 | The solution for this is to lobby your distribution maker to make large |
1960 | file interfaces available by default (as e.g. FreeBSD does) and not |
1983 | file interfaces available by default (as e.g. FreeBSD does) and not |
1961 | optional. Libev cannot simply switch on large file support because it has |
1984 | optional. Libev cannot simply switch on large file support because it has |
1962 | to exchange stat structures with application programs compiled using the |
1985 | to exchange stat structures with application programs compiled using the |
1963 | default compilation environment. |
1986 | default compilation environment. |
1964 | |
1987 | |
1965 | =head3 Inotify and Kqueue |
1988 | =head3 Inotify and Kqueue |
1966 | |
1989 | |
1967 | When C<inotify (7)> support has been compiled into libev (generally |
1990 | When C<inotify (7)> support has been compiled into libev and present at |
1968 | only available with Linux 2.6.25 or above due to bugs in earlier |
1991 | runtime, it will be used to speed up change detection where possible. The |
1969 | implementations) and present at runtime, it will be used to speed up |
1992 | inotify descriptor will be created lazily when the first C<ev_stat> |
1970 | change detection where possible. The inotify descriptor will be created |
1993 | watcher is being started. |
1971 | lazily when the first C<ev_stat> watcher is being started. |
|
|
1972 | |
1994 | |
1973 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1995 | Inotify presence does not change the semantics of C<ev_stat> watchers |
1974 | except that changes might be detected earlier, and in some cases, to avoid |
1996 | except that changes might be detected earlier, and in some cases, to avoid |
1975 | making regular C<stat> calls. Even in the presence of inotify support |
1997 | making regular C<stat> calls. Even in the presence of inotify support |
1976 | there are many cases where libev has to resort to regular C<stat> polling, |
1998 | there are many cases where libev has to resort to regular C<stat> polling, |
1977 | but as long as the path exists, libev usually gets away without polling. |
1999 | but as long as kernel 2.6.25 or newer is used (2.6.24 and older have too |
|
|
2000 | many bugs), the path exists (i.e. stat succeeds), and the path resides on |
|
|
2001 | a local filesystem (libev currently assumes only ext2/3, jfs, reiserfs and |
|
|
2002 | xfs are fully working) libev usually gets away without polling. |
1978 | |
2003 | |
1979 | There is no support for kqueue, as apparently it cannot be used to |
2004 | There is no support for kqueue, as apparently it cannot be used to |
1980 | implement this functionality, due to the requirement of having a file |
2005 | implement this functionality, due to the requirement of having a file |
1981 | descriptor open on the object at all times, and detecting renames, unlinks |
2006 | descriptor open on the object at all times, and detecting renames, unlinks |
1982 | etc. is difficult. |
2007 | etc. is difficult. |
1983 | |
2008 | |
|
|
2009 | =head3 C<stat ()> is a synchronous operation |
|
|
2010 | |
|
|
2011 | Libev doesn't normally do any kind of I/O itself, and so is not blocking |
|
|
2012 | the process. The exception are C<ev_stat> watchers - those call C<stat |
|
|
2013 | ()>, which is a synchronous operation. |
|
|
2014 | |
|
|
2015 | For local paths, this usually doesn't matter: unless the system is very |
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|
2016 | busy or the intervals between stat's are large, a stat call will be fast, |
|
|
2017 | as the path data is usually in memory already (except when starting the |
|
|
2018 | watcher). |
|
|
2019 | |
|
|
2020 | For networked file systems, calling C<stat ()> can block an indefinite |
|
|
2021 | time due to network issues, and even under good conditions, a stat call |
|
|
2022 | often takes multiple milliseconds. |
|
|
2023 | |
|
|
2024 | Therefore, it is best to avoid using C<ev_stat> watchers on networked |
|
|
2025 | paths, although this is fully supported by libev. |
|
|
2026 | |
1984 | =head3 The special problem of stat time resolution |
2027 | =head3 The special problem of stat time resolution |
1985 | |
2028 | |
1986 | The C<stat ()> system call only supports full-second resolution portably, and |
2029 | The C<stat ()> system call only supports full-second resolution portably, |
1987 | even on systems where the resolution is higher, most file systems still |
2030 | and even on systems where the resolution is higher, most file systems |
1988 | only support whole seconds. |
2031 | still only support whole seconds. |
1989 | |
2032 | |
1990 | That means that, if the time is the only thing that changes, you can |
2033 | That means that, if the time is the only thing that changes, you can |
1991 | easily miss updates: on the first update, C<ev_stat> detects a change and |
2034 | easily miss updates: on the first update, C<ev_stat> detects a change and |
1992 | calls your callback, which does something. When there is another update |
2035 | calls your callback, which does something. When there is another update |
1993 | within the same second, C<ev_stat> will be unable to detect unless the |
2036 | within the same second, C<ev_stat> will be unable to detect unless the |
… | |
… | |
2136 | |
2179 | |
2137 | =head3 Watcher-Specific Functions and Data Members |
2180 | =head3 Watcher-Specific Functions and Data Members |
2138 | |
2181 | |
2139 | =over 4 |
2182 | =over 4 |
2140 | |
2183 | |
2141 | =item ev_idle_init (ev_signal *, callback) |
2184 | =item ev_idle_init (ev_idle *, callback) |
2142 | |
2185 | |
2143 | Initialises and configures the idle watcher - it has no parameters of any |
2186 | Initialises and configures the idle watcher - it has no parameters of any |
2144 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2187 | kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, |
2145 | believe me. |
2188 | believe me. |
2146 | |
2189 | |
… | |
… | |
2385 | some fds have to be watched and handled very quickly (with low latency), |
2428 | some fds have to be watched and handled very quickly (with low latency), |
2386 | and even priorities and idle watchers might have too much overhead. In |
2429 | and even priorities and idle watchers might have too much overhead. In |
2387 | this case you would put all the high priority stuff in one loop and all |
2430 | this case you would put all the high priority stuff in one loop and all |
2388 | the rest in a second one, and embed the second one in the first. |
2431 | the rest in a second one, and embed the second one in the first. |
2389 | |
2432 | |
2390 | As long as the watcher is active, the callback will be invoked every time |
2433 | As long as the watcher is active, the callback will be invoked every |
2391 | there might be events pending in the embedded loop. The callback must then |
2434 | time there might be events pending in the embedded loop. The callback |
2392 | call C<ev_embed_sweep (mainloop, watcher)> to make a single sweep and invoke |
2435 | must then call C<ev_embed_sweep (mainloop, watcher)> to make a single |
2393 | their callbacks (you could also start an idle watcher to give the embedded |
2436 | sweep and invoke their callbacks (the callback doesn't need to invoke the |
2394 | loop strictly lower priority for example). You can also set the callback |
2437 | C<ev_embed_sweep> function directly, it could also start an idle watcher |
2395 | to C<0>, in which case the embed watcher will automatically execute the |
2438 | to give the embedded loop strictly lower priority for example). |
2396 | embedded loop sweep. |
|
|
2397 | |
2439 | |
2398 | As long as the watcher is started it will automatically handle events. The |
2440 | You can also set the callback to C<0>, in which case the embed watcher |
2399 | callback will be invoked whenever some events have been handled. You can |
2441 | will automatically execute the embedded loop sweep whenever necessary. |
2400 | set the callback to C<0> to avoid having to specify one if you are not |
|
|
2401 | interested in that. |
|
|
2402 | |
2442 | |
2403 | Also, there have not currently been made special provisions for forking: |
2443 | Fork detection will be handled transparently while the C<ev_embed> watcher |
2404 | when you fork, you not only have to call C<ev_loop_fork> on both loops, |
2444 | is active, i.e., the embedded loop will automatically be forked when the |
2405 | but you will also have to stop and restart any C<ev_embed> watchers |
2445 | embedding loop forks. In other cases, the user is responsible for calling |
2406 | yourself - but you can use a fork watcher to handle this automatically, |
2446 | C<ev_loop_fork> on the embedded loop. |
2407 | and future versions of libev might do just that. |
|
|
2408 | |
2447 | |
2409 | Unfortunately, not all backends are embeddable: only the ones returned by |
2448 | Unfortunately, not all backends are embeddable: only the ones returned by |
2410 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2449 | C<ev_embeddable_backends> are, which, unfortunately, does not include any |
2411 | portable one. |
2450 | portable one. |
2412 | |
2451 | |
… | |
… | |
2632 | =over 4 |
2671 | =over 4 |
2633 | |
2672 | |
2634 | =item ev_async_init (ev_async *, callback) |
2673 | =item ev_async_init (ev_async *, callback) |
2635 | |
2674 | |
2636 | Initialises and configures the async watcher - it has no parameters of any |
2675 | Initialises and configures the async watcher - it has no parameters of any |
2637 | kind. There is a C<ev_asynd_set> macro, but using it is utterly pointless, |
2676 | kind. There is a C<ev_async_set> macro, but using it is utterly pointless, |
2638 | trust me. |
2677 | trust me. |
2639 | |
2678 | |
2640 | =item ev_async_send (loop, ev_async *) |
2679 | =item ev_async_send (loop, ev_async *) |
2641 | |
2680 | |
2642 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
2681 | Sends/signals/activates the given C<ev_async> watcher, that is, feeds |
… | |
… | |
2848 | |
2887 | |
2849 | myclass obj; |
2888 | myclass obj; |
2850 | ev::io iow; |
2889 | ev::io iow; |
2851 | iow.set <myclass, &myclass::io_cb> (&obj); |
2890 | iow.set <myclass, &myclass::io_cb> (&obj); |
2852 | |
2891 | |
|
|
2892 | =item w->set (object *) |
|
|
2893 | |
|
|
2894 | This is an B<experimental> feature that might go away in a future version. |
|
|
2895 | |
|
|
2896 | This is a variation of a method callback - leaving out the method to call |
|
|
2897 | will default the method to C<operator ()>, which makes it possible to use |
|
|
2898 | functor objects without having to manually specify the C<operator ()> all |
|
|
2899 | the time. Incidentally, you can then also leave out the template argument |
|
|
2900 | list. |
|
|
2901 | |
|
|
2902 | The C<operator ()> method prototype must be C<void operator ()(watcher &w, |
|
|
2903 | int revents)>. |
|
|
2904 | |
|
|
2905 | See the method-C<set> above for more details. |
|
|
2906 | |
|
|
2907 | Example: use a functor object as callback. |
|
|
2908 | |
|
|
2909 | struct myfunctor |
|
|
2910 | { |
|
|
2911 | void operator() (ev::io &w, int revents) |
|
|
2912 | { |
|
|
2913 | ... |
|
|
2914 | } |
|
|
2915 | } |
|
|
2916 | |
|
|
2917 | myfunctor f; |
|
|
2918 | |
|
|
2919 | ev::io w; |
|
|
2920 | w.set (&f); |
|
|
2921 | |
2853 | =item w->set<function> (void *data = 0) |
2922 | =item w->set<function> (void *data = 0) |
2854 | |
2923 | |
2855 | Also sets a callback, but uses a static method or plain function as |
2924 | Also sets a callback, but uses a static method or plain function as |
2856 | callback. The optional C<data> argument will be stored in the watcher's |
2925 | callback. The optional C<data> argument will be stored in the watcher's |
2857 | C<data> member and is free for you to use. |
2926 | C<data> member and is free for you to use. |
… | |
… | |
2956 | Tony Arcieri has written a ruby extension that offers access to a subset |
3025 | Tony Arcieri has written a ruby extension that offers access to a subset |
2957 | of the libev API and adds file handle abstractions, asynchronous DNS and |
3026 | of the libev API and adds file handle abstractions, asynchronous DNS and |
2958 | more on top of it. It can be found via gem servers. Its homepage is at |
3027 | more on top of it. It can be found via gem servers. Its homepage is at |
2959 | L<http://rev.rubyforge.org/>. |
3028 | L<http://rev.rubyforge.org/>. |
2960 | |
3029 | |
|
|
3030 | Roger Pack reports that using the link order C<-lws2_32 -lmsvcrt-ruby-190> |
|
|
3031 | makes rev work even on mingw. |
|
|
3032 | |
2961 | =item D |
3033 | =item D |
2962 | |
3034 | |
2963 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
3035 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
2964 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
3036 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
2965 | |
3037 | |
… | |
… | |
3075 | |
3147 | |
3076 | #define EV_STANDALONE 1 |
3148 | #define EV_STANDALONE 1 |
3077 | #include "ev.h" |
3149 | #include "ev.h" |
3078 | |
3150 | |
3079 | Both header files and implementation files can be compiled with a C++ |
3151 | Both header files and implementation files can be compiled with a C++ |
3080 | compiler (at least, thats a stated goal, and breakage will be treated |
3152 | compiler (at least, that's a stated goal, and breakage will be treated |
3081 | as a bug). |
3153 | as a bug). |
3082 | |
3154 | |
3083 | You need the following files in your source tree, or in a directory |
3155 | You need the following files in your source tree, or in a directory |
3084 | in your include path (e.g. in libev/ when using -Ilibev): |
3156 | in your include path (e.g. in libev/ when using -Ilibev): |
3085 | |
3157 | |
… | |
… | |
3141 | keeps libev from including F<config.h>, and it also defines dummy |
3213 | keeps libev from including F<config.h>, and it also defines dummy |
3142 | implementations for some libevent functions (such as logging, which is not |
3214 | implementations for some libevent functions (such as logging, which is not |
3143 | supported). It will also not define any of the structs usually found in |
3215 | supported). It will also not define any of the structs usually found in |
3144 | F<event.h> that are not directly supported by the libev core alone. |
3216 | F<event.h> that are not directly supported by the libev core alone. |
3145 | |
3217 | |
|
|
3218 | In stanbdalone mode, libev will still try to automatically deduce the |
|
|
3219 | configuration, but has to be more conservative. |
|
|
3220 | |
3146 | =item EV_USE_MONOTONIC |
3221 | =item EV_USE_MONOTONIC |
3147 | |
3222 | |
3148 | If defined to be C<1>, libev will try to detect the availability of the |
3223 | If defined to be C<1>, libev will try to detect the availability of the |
3149 | monotonic clock option at both compile time and runtime. Otherwise no use |
3224 | monotonic clock option at both compile time and runtime. Otherwise no |
3150 | of the monotonic clock option will be attempted. If you enable this, you |
3225 | use of the monotonic clock option will be attempted. If you enable this, |
3151 | usually have to link against librt or something similar. Enabling it when |
3226 | you usually have to link against librt or something similar. Enabling it |
3152 | the functionality isn't available is safe, though, although you have |
3227 | when the functionality isn't available is safe, though, although you have |
3153 | to make sure you link against any libraries where the C<clock_gettime> |
3228 | to make sure you link against any libraries where the C<clock_gettime> |
3154 | function is hiding in (often F<-lrt>). |
3229 | function is hiding in (often F<-lrt>). See also C<EV_USE_CLOCK_SYSCALL>. |
3155 | |
3230 | |
3156 | =item EV_USE_REALTIME |
3231 | =item EV_USE_REALTIME |
3157 | |
3232 | |
3158 | If defined to be C<1>, libev will try to detect the availability of the |
3233 | If defined to be C<1>, libev will try to detect the availability of the |
3159 | real-time clock option at compile time (and assume its availability at |
3234 | real-time clock option at compile time (and assume its availability |
3160 | runtime if successful). Otherwise no use of the real-time clock option will |
3235 | at runtime if successful). Otherwise no use of the real-time clock |
3161 | be attempted. This effectively replaces C<gettimeofday> by C<clock_get |
3236 | option will be attempted. This effectively replaces C<gettimeofday> |
3162 | (CLOCK_REALTIME, ...)> and will not normally affect correctness. See the |
3237 | by C<clock_get (CLOCK_REALTIME, ...)> and will not normally affect |
3163 | note about libraries in the description of C<EV_USE_MONOTONIC>, though. |
3238 | correctness. See the note about libraries in the description of |
|
|
3239 | C<EV_USE_MONOTONIC>, though. Defaults to the opposite value of |
|
|
3240 | C<EV_USE_CLOCK_SYSCALL>. |
|
|
3241 | |
|
|
3242 | =item EV_USE_CLOCK_SYSCALL |
|
|
3243 | |
|
|
3244 | If defined to be C<1>, libev will try to use a direct syscall instead |
|
|
3245 | of calling the system-provided C<clock_gettime> function. This option |
|
|
3246 | exists because on GNU/Linux, C<clock_gettime> is in C<librt>, but C<librt> |
|
|
3247 | unconditionally pulls in C<libpthread>, slowing down single-threaded |
|
|
3248 | programs needlessly. Using a direct syscall is slightly slower (in |
|
|
3249 | theory), because no optimised vdso implementation can be used, but avoids |
|
|
3250 | the pthread dependency. Defaults to C<1> on GNU/Linux with glibc 2.x or |
|
|
3251 | higher, as it simplifies linking (no need for C<-lrt>). |
3164 | |
3252 | |
3165 | =item EV_USE_NANOSLEEP |
3253 | =item EV_USE_NANOSLEEP |
3166 | |
3254 | |
3167 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3255 | If defined to be C<1>, libev will assume that C<nanosleep ()> is available |
3168 | and will use it for delays. Otherwise it will use C<select ()>. |
3256 | and will use it for delays. Otherwise it will use C<select ()>. |
… | |
… | |
3184 | |
3272 | |
3185 | =item EV_SELECT_USE_FD_SET |
3273 | =item EV_SELECT_USE_FD_SET |
3186 | |
3274 | |
3187 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3275 | If defined to C<1>, then the select backend will use the system C<fd_set> |
3188 | structure. This is useful if libev doesn't compile due to a missing |
3276 | structure. This is useful if libev doesn't compile due to a missing |
3189 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout on |
3277 | C<NFDBITS> or C<fd_mask> definition or it mis-guesses the bitset layout |
3190 | exotic systems. This usually limits the range of file descriptors to some |
3278 | on exotic systems. This usually limits the range of file descriptors to |
3191 | low limit such as 1024 or might have other limitations (winsocket only |
3279 | some low limit such as 1024 or might have other limitations (winsocket |
3192 | allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, might |
3280 | only allows 64 sockets). The C<FD_SETSIZE> macro, set before compilation, |
3193 | influence the size of the C<fd_set> used. |
3281 | configures the maximum size of the C<fd_set>. |
3194 | |
3282 | |
3195 | =item EV_SELECT_IS_WINSOCKET |
3283 | =item EV_SELECT_IS_WINSOCKET |
3196 | |
3284 | |
3197 | When defined to C<1>, the select backend will assume that |
3285 | When defined to C<1>, the select backend will assume that |
3198 | select/socket/connect etc. don't understand file descriptors but |
3286 | select/socket/connect etc. don't understand file descriptors but |
… | |
… | |
3557 | loop, as long as you don't confuse yourself). The only exception is that |
3645 | loop, as long as you don't confuse yourself). The only exception is that |
3558 | you must not do this from C<ev_periodic> reschedule callbacks. |
3646 | you must not do this from C<ev_periodic> reschedule callbacks. |
3559 | |
3647 | |
3560 | Care has been taken to ensure that libev does not keep local state inside |
3648 | Care has been taken to ensure that libev does not keep local state inside |
3561 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3649 | C<ev_loop>, and other calls do not usually allow for coroutine switches as |
3562 | they do not clal any callbacks. |
3650 | they do not call any callbacks. |
3563 | |
3651 | |
3564 | =head2 COMPILER WARNINGS |
3652 | =head2 COMPILER WARNINGS |
3565 | |
3653 | |
3566 | Depending on your compiler and compiler settings, you might get no or a |
3654 | Depending on your compiler and compiler settings, you might get no or a |
3567 | lot of warnings when compiling libev code. Some people are apparently |
3655 | lot of warnings when compiling libev code. Some people are apparently |
… | |
… | |
3601 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3689 | ==2274== definitely lost: 0 bytes in 0 blocks. |
3602 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3690 | ==2274== possibly lost: 0 bytes in 0 blocks. |
3603 | ==2274== still reachable: 256 bytes in 1 blocks. |
3691 | ==2274== still reachable: 256 bytes in 1 blocks. |
3604 | |
3692 | |
3605 | Then there is no memory leak, just as memory accounted to global variables |
3693 | Then there is no memory leak, just as memory accounted to global variables |
3606 | is not a memleak - the memory is still being refernced, and didn't leak. |
3694 | is not a memleak - the memory is still being referenced, and didn't leak. |
3607 | |
3695 | |
3608 | Similarly, under some circumstances, valgrind might report kernel bugs |
3696 | Similarly, under some circumstances, valgrind might report kernel bugs |
3609 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3697 | as if it were a bug in libev (e.g. in realloc or in the poll backend, |
3610 | although an acceptable workaround has been found here), or it might be |
3698 | although an acceptable workaround has been found here), or it might be |
3611 | confused. |
3699 | confused. |
… | |
… | |
3849 | =back |
3937 | =back |
3850 | |
3938 | |
3851 | |
3939 | |
3852 | =head1 AUTHOR |
3940 | =head1 AUTHOR |
3853 | |
3941 | |
3854 | Marc Lehmann <libev@schmorp.de>. |
3942 | Marc Lehmann <libev@schmorp.de>, with repeated corrections by Mikael Magnusson. |
3855 | |
3943 | |