… | |
… | |
174 | =item ev_tstamp ev_time () |
174 | =item ev_tstamp ev_time () |
175 | |
175 | |
176 | Returns the current time as libev would use it. Please note that the |
176 | Returns the current time as libev would use it. Please note that the |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
177 | C<ev_now> function is usually faster and also often returns the timestamp |
178 | you actually want to know. Also interesting is the combination of |
178 | you actually want to know. Also interesting is the combination of |
179 | C<ev_update_now> and C<ev_now>. |
179 | C<ev_now_update> and C<ev_now>. |
180 | |
180 | |
181 | =item ev_sleep (ev_tstamp interval) |
181 | =item ev_sleep (ev_tstamp interval) |
182 | |
182 | |
183 | Sleep for the given interval: The current thread will be blocked until |
183 | Sleep for the given interval: The current thread will be blocked |
184 | either it is interrupted or the given time interval has passed. Basically |
184 | until either it is interrupted or the given time interval has |
|
|
185 | passed (approximately - it might return a bit earlier even if not |
|
|
186 | interrupted). Returns immediately if C<< interval <= 0 >>. |
|
|
187 | |
185 | this is a sub-second-resolution C<sleep ()>. |
188 | Basically this is a sub-second-resolution C<sleep ()>. |
|
|
189 | |
|
|
190 | The range of the C<interval> is limited - libev only guarantees to work |
|
|
191 | with sleep times of up to one day (C<< interval <= 86400 >>). |
186 | |
192 | |
187 | =item int ev_version_major () |
193 | =item int ev_version_major () |
188 | |
194 | |
189 | =item int ev_version_minor () |
195 | =item int ev_version_minor () |
190 | |
196 | |
… | |
… | |
435 | example) that can't properly initialise their signal masks. |
441 | example) that can't properly initialise their signal masks. |
436 | |
442 | |
437 | =item C<EVFLAG_NOSIGMASK> |
443 | =item C<EVFLAG_NOSIGMASK> |
438 | |
444 | |
439 | When this flag is specified, then libev will avoid to modify the signal |
445 | When this flag is specified, then libev will avoid to modify the signal |
440 | mask. Specifically, this means you ahve to make sure signals are unblocked |
446 | mask. Specifically, this means you have to make sure signals are unblocked |
441 | when you want to receive them. |
447 | when you want to receive them. |
442 | |
448 | |
443 | This behaviour is useful when you want to do your own signal handling, or |
449 | This behaviour is useful when you want to do your own signal handling, or |
444 | want to handle signals only in specific threads and want to avoid libev |
450 | want to handle signals only in specific threads and want to avoid libev |
445 | unblocking the signals. |
451 | unblocking the signals. |
… | |
… | |
499 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
505 | 0.1ms) and so on. The biggest issue is fork races, however - if a program |
500 | forks then I<both> parent and child process have to recreate the epoll |
506 | forks then I<both> parent and child process have to recreate the epoll |
501 | set, which can take considerable time (one syscall per file descriptor) |
507 | set, which can take considerable time (one syscall per file descriptor) |
502 | and is of course hard to detect. |
508 | and is of course hard to detect. |
503 | |
509 | |
504 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, but |
510 | Epoll is also notoriously buggy - embedding epoll fds I<should> work, |
505 | of course I<doesn't>, and epoll just loves to report events for totally |
511 | but of course I<doesn't>, and epoll just loves to report events for |
506 | I<different> file descriptors (even already closed ones, so one cannot |
512 | totally I<different> file descriptors (even already closed ones, so |
507 | even remove them from the set) than registered in the set (especially |
513 | one cannot even remove them from the set) than registered in the set |
508 | on SMP systems). Libev tries to counter these spurious notifications by |
514 | (especially on SMP systems). Libev tries to counter these spurious |
509 | employing an additional generation counter and comparing that against the |
515 | notifications by employing an additional generation counter and comparing |
510 | events to filter out spurious ones, recreating the set when required. Last |
516 | that against the events to filter out spurious ones, recreating the set |
|
|
517 | when required. Epoll also erroneously rounds down timeouts, but gives you |
|
|
518 | no way to know when and by how much, so sometimes you have to busy-wait |
|
|
519 | because epoll returns immediately despite a nonzero timeout. And last |
511 | not least, it also refuses to work with some file descriptors which work |
520 | not least, it also refuses to work with some file descriptors which work |
512 | perfectly fine with C<select> (files, many character devices...). |
521 | perfectly fine with C<select> (files, many character devices...). |
513 | |
522 | |
514 | Epoll is truly the train wreck analog among event poll mechanisms, |
523 | Epoll is truly the train wreck among event poll mechanisms, a frankenpoll, |
515 | a frankenpoll, cobbled together in a hurry, no thought to design or |
524 | cobbled together in a hurry, no thought to design or interaction with |
516 | interaction with others. |
525 | others. Oh, the pain, will it ever stop... |
517 | |
526 | |
518 | While stopping, setting and starting an I/O watcher in the same iteration |
527 | While stopping, setting and starting an I/O watcher in the same iteration |
519 | will result in some caching, there is still a system call per such |
528 | will result in some caching, there is still a system call per such |
520 | incident (because the same I<file descriptor> could point to a different |
529 | incident (because the same I<file descriptor> could point to a different |
521 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
530 | I<file description> now), so its best to avoid that. Also, C<dup ()>'ed |
… | |
… | |
558 | |
567 | |
559 | It scales in the same way as the epoll backend, but the interface to the |
568 | It scales in the same way as the epoll backend, but the interface to the |
560 | kernel is more efficient (which says nothing about its actual speed, of |
569 | kernel is more efficient (which says nothing about its actual speed, of |
561 | course). While stopping, setting and starting an I/O watcher does never |
570 | course). While stopping, setting and starting an I/O watcher does never |
562 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
571 | cause an extra system call as with C<EVBACKEND_EPOLL>, it still adds up to |
563 | two event changes per incident. Support for C<fork ()> is very bad (but |
572 | two event changes per incident. Support for C<fork ()> is very bad (you |
564 | sane, unlike epoll) and it drops fds silently in similarly hard-to-detect |
573 | might have to leak fd's on fork, but it's more sane than epoll) and it |
565 | cases |
574 | drops fds silently in similarly hard-to-detect cases |
566 | |
575 | |
567 | This backend usually performs well under most conditions. |
576 | This backend usually performs well under most conditions. |
568 | |
577 | |
569 | While nominally embeddable in other event loops, this doesn't work |
578 | While nominally embeddable in other event loops, this doesn't work |
570 | everywhere, so you might need to test for this. And since it is broken |
579 | everywhere, so you might need to test for this. And since it is broken |
… | |
… | |
599 | among the OS-specific backends (I vastly prefer correctness over speed |
608 | among the OS-specific backends (I vastly prefer correctness over speed |
600 | hacks). |
609 | hacks). |
601 | |
610 | |
602 | On the negative side, the interface is I<bizarre> - so bizarre that |
611 | On the negative side, the interface is I<bizarre> - so bizarre that |
603 | even sun itself gets it wrong in their code examples: The event polling |
612 | even sun itself gets it wrong in their code examples: The event polling |
604 | function sometimes returning events to the caller even though an error |
613 | function sometimes returns events to the caller even though an error |
605 | occurred, but with no indication whether it has done so or not (yes, it's |
614 | occurred, but with no indication whether it has done so or not (yes, it's |
606 | even documented that way) - deadly for edge-triggered interfaces where |
615 | even documented that way) - deadly for edge-triggered interfaces where you |
607 | you absolutely have to know whether an event occurred or not because you |
616 | absolutely have to know whether an event occurred or not because you have |
608 | have to re-arm the watcher. |
617 | to re-arm the watcher. |
609 | |
618 | |
610 | Fortunately libev seems to be able to work around these idiocies. |
619 | Fortunately libev seems to be able to work around these idiocies. |
611 | |
620 | |
612 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
621 | This backend maps C<EV_READ> and C<EV_WRITE> in the same way as |
613 | C<EVBACKEND_POLL>. |
622 | C<EVBACKEND_POLL>. |
… | |
… | |
783 | without a previous call to C<ev_suspend>. |
792 | without a previous call to C<ev_suspend>. |
784 | |
793 | |
785 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
794 | Calling C<ev_suspend>/C<ev_resume> has the side effect of updating the |
786 | event loop time (see C<ev_now_update>). |
795 | event loop time (see C<ev_now_update>). |
787 | |
796 | |
788 | =item ev_run (loop, int flags) |
797 | =item bool ev_run (loop, int flags) |
789 | |
798 | |
790 | Finally, this is it, the event handler. This function usually is called |
799 | Finally, this is it, the event handler. This function usually is called |
791 | after you have initialised all your watchers and you want to start |
800 | after you have initialised all your watchers and you want to start |
792 | handling events. It will ask the operating system for any new events, call |
801 | handling events. It will ask the operating system for any new events, call |
793 | the watcher callbacks, an then repeat the whole process indefinitely: This |
802 | the watcher callbacks, and then repeat the whole process indefinitely: This |
794 | is why event loops are called I<loops>. |
803 | is why event loops are called I<loops>. |
795 | |
804 | |
796 | If the flags argument is specified as C<0>, it will keep handling events |
805 | If the flags argument is specified as C<0>, it will keep handling events |
797 | until either no event watchers are active anymore or C<ev_break> was |
806 | until either no event watchers are active anymore or C<ev_break> was |
798 | called. |
807 | called. |
|
|
808 | |
|
|
809 | The return value is false if there are no more active watchers (which |
|
|
810 | usually means "all jobs done" or "deadlock"), and true in all other cases |
|
|
811 | (which usually means " you should call C<ev_run> again"). |
799 | |
812 | |
800 | Please note that an explicit C<ev_break> is usually better than |
813 | Please note that an explicit C<ev_break> is usually better than |
801 | relying on all watchers to be stopped when deciding when a program has |
814 | relying on all watchers to be stopped when deciding when a program has |
802 | finished (especially in interactive programs), but having a program |
815 | finished (especially in interactive programs), but having a program |
803 | that automatically loops as long as it has to and no longer by virtue |
816 | that automatically loops as long as it has to and no longer by virtue |
804 | of relying on its watchers stopping correctly, that is truly a thing of |
817 | of relying on its watchers stopping correctly, that is truly a thing of |
805 | beauty. |
818 | beauty. |
806 | |
819 | |
807 | This function is also I<mostly> exception-safe - you can break out of |
820 | This function is I<mostly> exception-safe - you can break out of a |
808 | a C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
821 | C<ev_run> call by calling C<longjmp> in a callback, throwing a C++ |
809 | exception and so on. This does not decrement the C<ev_depth> value, nor |
822 | exception and so on. This does not decrement the C<ev_depth> value, nor |
810 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
823 | will it clear any outstanding C<EVBREAK_ONE> breaks. |
811 | |
824 | |
812 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
825 | A flags value of C<EVRUN_NOWAIT> will look for new events, will handle |
813 | those events and any already outstanding ones, but will not wait and |
826 | those events and any already outstanding ones, but will not wait and |
… | |
… | |
943 | overhead for the actual polling but can deliver many events at once. |
956 | overhead for the actual polling but can deliver many events at once. |
944 | |
957 | |
945 | By setting a higher I<io collect interval> you allow libev to spend more |
958 | By setting a higher I<io collect interval> you allow libev to spend more |
946 | time collecting I/O events, so you can handle more events per iteration, |
959 | time collecting I/O events, so you can handle more events per iteration, |
947 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
960 | at the cost of increasing latency. Timeouts (both C<ev_periodic> and |
948 | C<ev_timer>) will be not affected. Setting this to a non-null value will |
961 | C<ev_timer>) will not be affected. Setting this to a non-null value will |
949 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
962 | introduce an additional C<ev_sleep ()> call into most loop iterations. The |
950 | sleep time ensures that libev will not poll for I/O events more often then |
963 | sleep time ensures that libev will not poll for I/O events more often then |
951 | once per this interval, on average. |
964 | once per this interval, on average (as long as the host time resolution is |
|
|
965 | good enough). |
952 | |
966 | |
953 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
967 | Likewise, by setting a higher I<timeout collect interval> you allow libev |
954 | to spend more time collecting timeouts, at the expense of increased |
968 | to spend more time collecting timeouts, at the expense of increased |
955 | latency/jitter/inexactness (the watcher callback will be called |
969 | latency/jitter/inexactness (the watcher callback will be called |
956 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
970 | later). C<ev_io> watchers will not be affected. Setting this to a non-null |
… | |
… | |
1010 | can be done relatively simply by putting mutex_lock/unlock calls around |
1024 | can be done relatively simply by putting mutex_lock/unlock calls around |
1011 | each call to a libev function. |
1025 | each call to a libev function. |
1012 | |
1026 | |
1013 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1027 | However, C<ev_run> can run an indefinite time, so it is not feasible |
1014 | to wait for it to return. One way around this is to wake up the event |
1028 | to wait for it to return. One way around this is to wake up the event |
1015 | loop via C<ev_break> and C<av_async_send>, another way is to set these |
1029 | loop via C<ev_break> and C<ev_async_send>, another way is to set these |
1016 | I<release> and I<acquire> callbacks on the loop. |
1030 | I<release> and I<acquire> callbacks on the loop. |
1017 | |
1031 | |
1018 | When set, then C<release> will be called just before the thread is |
1032 | When set, then C<release> will be called just before the thread is |
1019 | suspended waiting for new events, and C<acquire> is called just |
1033 | suspended waiting for new events, and C<acquire> is called just |
1020 | afterwards. |
1034 | afterwards. |
… | |
… | |
1376 | |
1390 | |
1377 | =over 4 |
1391 | =over 4 |
1378 | |
1392 | |
1379 | =item initialiased |
1393 | =item initialiased |
1380 | |
1394 | |
1381 | Before a watcher can be registered with the event looop it has to be |
1395 | Before a watcher can be registered with the event loop it has to be |
1382 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1396 | initialised. This can be done with a call to C<ev_TYPE_init>, or calls to |
1383 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1397 | C<ev_init> followed by the watcher-specific C<ev_TYPE_set> function. |
1384 | |
1398 | |
1385 | In this state it is simply some block of memory that is suitable for |
1399 | In this state it is simply some block of memory that is suitable for |
1386 | use in an event loop. It can be moved around, freed, reused etc. at |
1400 | use in an event loop. It can be moved around, freed, reused etc. at |
… | |
… | |
1761 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1775 | detecting time jumps is hard, and some inaccuracies are unavoidable (the |
1762 | monotonic clock option helps a lot here). |
1776 | monotonic clock option helps a lot here). |
1763 | |
1777 | |
1764 | The callback is guaranteed to be invoked only I<after> its timeout has |
1778 | The callback is guaranteed to be invoked only I<after> its timeout has |
1765 | passed (not I<at>, so on systems with very low-resolution clocks this |
1779 | passed (not I<at>, so on systems with very low-resolution clocks this |
1766 | might introduce a small delay). If multiple timers become ready during the |
1780 | might introduce a small delay, see "the special problem of being too |
|
|
1781 | early", below). If multiple timers become ready during the same loop |
1767 | same loop iteration then the ones with earlier time-out values are invoked |
1782 | iteration then the ones with earlier time-out values are invoked before |
1768 | before ones of the same priority with later time-out values (but this is |
1783 | ones of the same priority with later time-out values (but this is no |
1769 | no longer true when a callback calls C<ev_run> recursively). |
1784 | longer true when a callback calls C<ev_run> recursively). |
1770 | |
1785 | |
1771 | =head3 Be smart about timeouts |
1786 | =head3 Be smart about timeouts |
1772 | |
1787 | |
1773 | Many real-world problems involve some kind of timeout, usually for error |
1788 | Many real-world problems involve some kind of timeout, usually for error |
1774 | recovery. A typical example is an HTTP request - if the other side hangs, |
1789 | recovery. A typical example is an HTTP request - if the other side hangs, |
… | |
… | |
1849 | |
1864 | |
1850 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1865 | In this case, it would be more efficient to leave the C<ev_timer> alone, |
1851 | but remember the time of last activity, and check for a real timeout only |
1866 | but remember the time of last activity, and check for a real timeout only |
1852 | within the callback: |
1867 | within the callback: |
1853 | |
1868 | |
|
|
1869 | ev_tstamp timeout = 60.; |
1854 | ev_tstamp last_activity; // time of last activity |
1870 | ev_tstamp last_activity; // time of last activity |
|
|
1871 | ev_timer timer; |
1855 | |
1872 | |
1856 | static void |
1873 | static void |
1857 | callback (EV_P_ ev_timer *w, int revents) |
1874 | callback (EV_P_ ev_timer *w, int revents) |
1858 | { |
1875 | { |
1859 | ev_tstamp now = ev_now (EV_A); |
1876 | // calculate when the timeout would happen |
1860 | ev_tstamp timeout = last_activity + 60.; |
1877 | ev_tstamp after = last_activity - ev_now (EV_A) + timeout; |
1861 | |
1878 | |
1862 | // if last_activity + 60. is older than now, we did time out |
1879 | // if negative, it means we the timeout already occured |
1863 | if (timeout < now) |
1880 | if (after < 0.) |
1864 | { |
1881 | { |
1865 | // timeout occurred, take action |
1882 | // timeout occurred, take action |
1866 | } |
1883 | } |
1867 | else |
1884 | else |
1868 | { |
1885 | { |
1869 | // callback was invoked, but there was some activity, re-arm |
1886 | // callback was invoked, but there was some recent |
1870 | // the watcher to fire in last_activity + 60, which is |
1887 | // activity. simply restart the timer to time out |
1871 | // guaranteed to be in the future, so "again" is positive: |
1888 | // after "after" seconds, which is the earliest time |
1872 | w->repeat = timeout - now; |
1889 | // the timeout can occur. |
|
|
1890 | ev_timer_set (w, after, 0.); |
1873 | ev_timer_again (EV_A_ w); |
1891 | ev_timer_start (EV_A_ w); |
1874 | } |
1892 | } |
1875 | } |
1893 | } |
1876 | |
1894 | |
1877 | To summarise the callback: first calculate the real timeout (defined |
1895 | To summarise the callback: first calculate in how many seconds the |
1878 | as "60 seconds after the last activity"), then check if that time has |
1896 | timeout will occur (by calculating the absolute time when it would occur, |
1879 | been reached, which means something I<did>, in fact, time out. Otherwise |
1897 | C<last_activity + timeout>, and subtracting the current time, C<ev_now |
1880 | the callback was invoked too early (C<timeout> is in the future), so |
1898 | (EV_A)> from that). |
1881 | re-schedule the timer to fire at that future time, to see if maybe we have |
|
|
1882 | a timeout then. |
|
|
1883 | |
1899 | |
1884 | Note how C<ev_timer_again> is used, taking advantage of the |
1900 | If this value is negative, then we are already past the timeout, i.e. we |
1885 | C<ev_timer_again> optimisation when the timer is already running. |
1901 | timed out, and need to do whatever is needed in this case. |
|
|
1902 | |
|
|
1903 | Otherwise, we now the earliest time at which the timeout would trigger, |
|
|
1904 | and simply start the timer with this timeout value. |
|
|
1905 | |
|
|
1906 | In other words, each time the callback is invoked it will check whether |
|
|
1907 | the timeout cocured. If not, it will simply reschedule itself to check |
|
|
1908 | again at the earliest time it could time out. Rinse. Repeat. |
1886 | |
1909 | |
1887 | This scheme causes more callback invocations (about one every 60 seconds |
1910 | This scheme causes more callback invocations (about one every 60 seconds |
1888 | minus half the average time between activity), but virtually no calls to |
1911 | minus half the average time between activity), but virtually no calls to |
1889 | libev to change the timeout. |
1912 | libev to change the timeout. |
1890 | |
1913 | |
1891 | To start the timer, simply initialise the watcher and set C<last_activity> |
1914 | To start the machinery, simply initialise the watcher and set |
1892 | to the current time (meaning we just have some activity :), then call the |
1915 | C<last_activity> to the current time (meaning there was some activity just |
1893 | callback, which will "do the right thing" and start the timer: |
1916 | now), then call the callback, which will "do the right thing" and start |
|
|
1917 | the timer: |
1894 | |
1918 | |
|
|
1919 | last_activity = ev_now (EV_A); |
1895 | ev_init (timer, callback); |
1920 | ev_init (&timer, callback); |
1896 | last_activity = ev_now (loop); |
1921 | callback (EV_A_ &timer, 0); |
1897 | callback (loop, timer, EV_TIMER); |
|
|
1898 | |
1922 | |
1899 | And when there is some activity, simply store the current time in |
1923 | When there is some activity, simply store the current time in |
1900 | C<last_activity>, no libev calls at all: |
1924 | C<last_activity>, no libev calls at all: |
1901 | |
1925 | |
|
|
1926 | if (activity detected) |
1902 | last_activity = ev_now (loop); |
1927 | last_activity = ev_now (EV_A); |
|
|
1928 | |
|
|
1929 | When your timeout value changes, then the timeout can be changed by simply |
|
|
1930 | providing a new value, stopping the timer and calling the callback, which |
|
|
1931 | will agaion do the right thing (for example, time out immediately :). |
|
|
1932 | |
|
|
1933 | timeout = new_value; |
|
|
1934 | ev_timer_stop (EV_A_ &timer); |
|
|
1935 | callback (EV_A_ &timer, 0); |
1903 | |
1936 | |
1904 | This technique is slightly more complex, but in most cases where the |
1937 | This technique is slightly more complex, but in most cases where the |
1905 | time-out is unlikely to be triggered, much more efficient. |
1938 | time-out is unlikely to be triggered, much more efficient. |
1906 | |
|
|
1907 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
|
|
1908 | callback :) - just change the timeout and invoke the callback, which will |
|
|
1909 | fix things for you. |
|
|
1910 | |
1939 | |
1911 | =item 4. Wee, just use a double-linked list for your timeouts. |
1940 | =item 4. Wee, just use a double-linked list for your timeouts. |
1912 | |
1941 | |
1913 | If there is not one request, but many thousands (millions...), all |
1942 | If there is not one request, but many thousands (millions...), all |
1914 | employing some kind of timeout with the same timeout value, then one can |
1943 | employing some kind of timeout with the same timeout value, then one can |
… | |
… | |
1941 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1970 | Method #1 is almost always a bad idea, and buys you nothing. Method #4 is |
1942 | rather complicated, but extremely efficient, something that really pays |
1971 | rather complicated, but extremely efficient, something that really pays |
1943 | off after the first million or so of active timers, i.e. it's usually |
1972 | off after the first million or so of active timers, i.e. it's usually |
1944 | overkill :) |
1973 | overkill :) |
1945 | |
1974 | |
|
|
1975 | =head3 The special problem of being too early |
|
|
1976 | |
|
|
1977 | If you ask a timer to call your callback after three seconds, then |
|
|
1978 | you expect it to be invoked after three seconds - but of course, this |
|
|
1979 | cannot be guaranteed to infinite precision. Less obviously, it cannot be |
|
|
1980 | guaranteed to any precision by libev - imagine somebody suspending the |
|
|
1981 | process with a STOP signal for a few hours for example. |
|
|
1982 | |
|
|
1983 | So, libev tries to invoke your callback as soon as possible I<after> the |
|
|
1984 | delay has occurred, but cannot guarantee this. |
|
|
1985 | |
|
|
1986 | A less obvious failure mode is calling your callback too early: many event |
|
|
1987 | loops compare timestamps with a "elapsed delay >= requested delay", but |
|
|
1988 | this can cause your callback to be invoked much earlier than you would |
|
|
1989 | expect. |
|
|
1990 | |
|
|
1991 | To see why, imagine a system with a clock that only offers full second |
|
|
1992 | resolution (think windows if you can't come up with a broken enough OS |
|
|
1993 | yourself). If you schedule a one-second timer at the time 500.9, then the |
|
|
1994 | event loop will schedule your timeout to elapse at a system time of 500 |
|
|
1995 | (500.9 truncated to the resolution) + 1, or 501. |
|
|
1996 | |
|
|
1997 | If an event library looks at the timeout 0.1s later, it will see "501 >= |
|
|
1998 | 501" and invoke the callback 0.1s after it was started, even though a |
|
|
1999 | one-second delay was requested - this is being "too early", despite best |
|
|
2000 | intentions. |
|
|
2001 | |
|
|
2002 | This is the reason why libev will never invoke the callback if the elapsed |
|
|
2003 | delay equals the requested delay, but only when the elapsed delay is |
|
|
2004 | larger than the requested delay. In the example above, libev would only invoke |
|
|
2005 | the callback at system time 502, or 1.1s after the timer was started. |
|
|
2006 | |
|
|
2007 | So, while libev cannot guarantee that your callback will be invoked |
|
|
2008 | exactly when requested, it I<can> and I<does> guarantee that the requested |
|
|
2009 | delay has actually elapsed, or in other words, it always errs on the "too |
|
|
2010 | late" side of things. |
|
|
2011 | |
1946 | =head3 The special problem of time updates |
2012 | =head3 The special problem of time updates |
1947 | |
2013 | |
1948 | Establishing the current time is a costly operation (it usually takes at |
2014 | Establishing the current time is a costly operation (it usually takes |
1949 | least two system calls): EV therefore updates its idea of the current |
2015 | at least one system call): EV therefore updates its idea of the current |
1950 | time only before and after C<ev_run> collects new events, which causes a |
2016 | time only before and after C<ev_run> collects new events, which causes a |
1951 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
2017 | growing difference between C<ev_now ()> and C<ev_time ()> when handling |
1952 | lots of events in one iteration. |
2018 | lots of events in one iteration. |
1953 | |
2019 | |
1954 | The relative timeouts are calculated relative to the C<ev_now ()> |
2020 | The relative timeouts are calculated relative to the C<ev_now ()> |
… | |
… | |
1960 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
2026 | ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); |
1961 | |
2027 | |
1962 | If the event loop is suspended for a long time, you can also force an |
2028 | If the event loop is suspended for a long time, you can also force an |
1963 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
2029 | update of the time returned by C<ev_now ()> by calling C<ev_now_update |
1964 | ()>. |
2030 | ()>. |
|
|
2031 | |
|
|
2032 | =head3 The special problem of unsynchronised clocks |
|
|
2033 | |
|
|
2034 | Modern systems have a variety of clocks - libev itself uses the normal |
|
|
2035 | "wall clock" clock and, if available, the monotonic clock (to avoid time |
|
|
2036 | jumps). |
|
|
2037 | |
|
|
2038 | Neither of these clocks is synchronised with each other or any other clock |
|
|
2039 | on the system, so C<ev_time ()> might return a considerably different time |
|
|
2040 | than C<gettimeofday ()> or C<time ()>. On a GNU/Linux system, for example, |
|
|
2041 | a call to C<gettimeofday> might return a second count that is one higher |
|
|
2042 | than a directly following call to C<time>. |
|
|
2043 | |
|
|
2044 | The moral of this is to only compare libev-related timestamps with |
|
|
2045 | C<ev_time ()> and C<ev_now ()>, at least if you want better precision than |
|
|
2046 | a second or so. |
|
|
2047 | |
|
|
2048 | One more problem arises due to this lack of synchronisation: if libev uses |
|
|
2049 | the system monotonic clock and you compare timestamps from C<ev_time> |
|
|
2050 | or C<ev_now> from when you started your timer and when your callback is |
|
|
2051 | invoked, you will find that sometimes the callback is a bit "early". |
|
|
2052 | |
|
|
2053 | This is because C<ev_timer>s work in real time, not wall clock time, so |
|
|
2054 | libev makes sure your callback is not invoked before the delay happened, |
|
|
2055 | I<measured according to the real time>, not the system clock. |
|
|
2056 | |
|
|
2057 | If your timeouts are based on a physical timescale (e.g. "time out this |
|
|
2058 | connection after 100 seconds") then this shouldn't bother you as it is |
|
|
2059 | exactly the right behaviour. |
|
|
2060 | |
|
|
2061 | If you want to compare wall clock/system timestamps to your timers, then |
|
|
2062 | you need to use C<ev_periodic>s, as these are based on the wall clock |
|
|
2063 | time, where your comparisons will always generate correct results. |
1965 | |
2064 | |
1966 | =head3 The special problems of suspended animation |
2065 | =head3 The special problems of suspended animation |
1967 | |
2066 | |
1968 | When you leave the server world it is quite customary to hit machines that |
2067 | When you leave the server world it is quite customary to hit machines that |
1969 | can suspend/hibernate - what happens to the clocks during such a suspend? |
2068 | can suspend/hibernate - what happens to the clocks during such a suspend? |
… | |
… | |
2013 | keep up with the timer (because it takes longer than those 10 seconds to |
2112 | keep up with the timer (because it takes longer than those 10 seconds to |
2014 | do stuff) the timer will not fire more than once per event loop iteration. |
2113 | do stuff) the timer will not fire more than once per event loop iteration. |
2015 | |
2114 | |
2016 | =item ev_timer_again (loop, ev_timer *) |
2115 | =item ev_timer_again (loop, ev_timer *) |
2017 | |
2116 | |
2018 | This will act as if the timer timed out and restart it again if it is |
2117 | This will act as if the timer timed out, and restarts it again if it is |
2019 | repeating. The exact semantics are: |
2118 | repeating. It basically works like calling C<ev_timer_stop>, updating the |
|
|
2119 | timeout to the C<repeat> value and calling C<ev_timer_start>. |
2020 | |
2120 | |
|
|
2121 | The exact semantics are as in the following rules, all of which will be |
|
|
2122 | applied to the watcher: |
|
|
2123 | |
|
|
2124 | =over 4 |
|
|
2125 | |
2021 | If the timer is pending, its pending status is cleared. |
2126 | =item If the timer is pending, the pending status is always cleared. |
2022 | |
2127 | |
2023 | If the timer is started but non-repeating, stop it (as if it timed out). |
2128 | =item If the timer is started but non-repeating, stop it (as if it timed |
|
|
2129 | out, without invoking it). |
2024 | |
2130 | |
2025 | If the timer is repeating, either start it if necessary (with the |
2131 | =item If the timer is repeating, make the C<repeat> value the new timeout |
2026 | C<repeat> value), or reset the running timer to the C<repeat> value. |
2132 | and start the timer, if necessary. |
|
|
2133 | |
|
|
2134 | =back |
2027 | |
2135 | |
2028 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2136 | This sounds a bit complicated, see L<Be smart about timeouts>, above, for a |
2029 | usage example. |
2137 | usage example. |
2030 | |
2138 | |
2031 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
2139 | =item ev_tstamp ev_timer_remaining (loop, ev_timer *) |
… | |
… | |
3210 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3318 | C<ev_async_sent> calls). In fact, you could use signal watchers as a kind |
3211 | of "global async watchers" by using a watcher on an otherwise unused |
3319 | of "global async watchers" by using a watcher on an otherwise unused |
3212 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3320 | signal, and C<ev_feed_signal> to signal this watcher from another thread, |
3213 | even without knowing which loop owns the signal. |
3321 | even without knowing which loop owns the signal. |
3214 | |
3322 | |
3215 | Unlike C<ev_signal> watchers, C<ev_async> works with any event loop, not |
|
|
3216 | just the default loop. |
|
|
3217 | |
|
|
3218 | =head3 Queueing |
3323 | =head3 Queueing |
3219 | |
3324 | |
3220 | C<ev_async> does not support queueing of data in any way. The reason |
3325 | C<ev_async> does not support queueing of data in any way. The reason |
3221 | is that the author does not know of a simple (or any) algorithm for a |
3326 | is that the author does not know of a simple (or any) algorithm for a |
3222 | multiple-writer-single-reader queue that works in all cases and doesn't |
3327 | multiple-writer-single-reader queue that works in all cases and doesn't |
… | |
… | |
3321 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3426 | Unlike C<ev_feed_event>, this call is safe to do from other threads, |
3322 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3427 | signal or similar contexts (see the discussion of C<EV_ATOMIC_T> in the |
3323 | embedding section below on what exactly this means). |
3428 | embedding section below on what exactly this means). |
3324 | |
3429 | |
3325 | Note that, as with other watchers in libev, multiple events might get |
3430 | Note that, as with other watchers in libev, multiple events might get |
3326 | compressed into a single callback invocation (another way to look at this |
3431 | compressed into a single callback invocation (another way to look at |
3327 | is that C<ev_async> watchers are level-triggered, set on C<ev_async_send>, |
3432 | this is that C<ev_async> watchers are level-triggered: they are set on |
3328 | reset when the event loop detects that). |
3433 | C<ev_async_send>, reset when the event loop detects that). |
3329 | |
3434 | |
3330 | This call incurs the overhead of a system call only once per event loop |
3435 | This call incurs the overhead of at most one extra system call per event |
3331 | iteration, so while the overhead might be noticeable, it doesn't apply to |
3436 | loop iteration, if the event loop is blocked, and no syscall at all if |
3332 | repeated calls to C<ev_async_send> for the same event loop. |
3437 | the event loop (or your program) is processing events. That means that |
|
|
3438 | repeated calls are basically free (there is no need to avoid calls for |
|
|
3439 | performance reasons) and that the overhead becomes smaller (typically |
|
|
3440 | zero) under load. |
3333 | |
3441 | |
3334 | =item bool = ev_async_pending (ev_async *) |
3442 | =item bool = ev_async_pending (ev_async *) |
3335 | |
3443 | |
3336 | Returns a non-zero value when C<ev_async_send> has been called on the |
3444 | Returns a non-zero value when C<ev_async_send> has been called on the |
3337 | watcher but the event has not yet been processed (or even noted) by the |
3445 | watcher but the event has not yet been processed (or even noted) by the |
… | |
… | |
3392 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3500 | ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); |
3393 | |
3501 | |
3394 | =item ev_feed_fd_event (loop, int fd, int revents) |
3502 | =item ev_feed_fd_event (loop, int fd, int revents) |
3395 | |
3503 | |
3396 | Feed an event on the given fd, as if a file descriptor backend detected |
3504 | Feed an event on the given fd, as if a file descriptor backend detected |
3397 | the given events it. |
3505 | the given events. |
3398 | |
3506 | |
3399 | =item ev_feed_signal_event (loop, int signum) |
3507 | =item ev_feed_signal_event (loop, int signum) |
3400 | |
3508 | |
3401 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3509 | Feed an event as if the given signal occurred. See also C<ev_feed_signal>, |
3402 | which is async-safe. |
3510 | which is async-safe. |
… | |
… | |
3476 | { |
3584 | { |
3477 | struct my_biggy big = (struct my_biggy *) |
3585 | struct my_biggy big = (struct my_biggy *) |
3478 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3586 | (((char *)w) - offsetof (struct my_biggy, t2)); |
3479 | } |
3587 | } |
3480 | |
3588 | |
|
|
3589 | =head2 AVOIDING FINISHING BEFORE RETURNING |
|
|
3590 | |
|
|
3591 | Often you have structures like this in event-based programs: |
|
|
3592 | |
|
|
3593 | callback () |
|
|
3594 | { |
|
|
3595 | free (request); |
|
|
3596 | } |
|
|
3597 | |
|
|
3598 | request = start_new_request (..., callback); |
|
|
3599 | |
|
|
3600 | The intent is to start some "lengthy" operation. The C<request> could be |
|
|
3601 | used to cancel the operation, or do other things with it. |
|
|
3602 | |
|
|
3603 | It's not uncommon to have code paths in C<start_new_request> that |
|
|
3604 | immediately invoke the callback, for example, to report errors. Or you add |
|
|
3605 | some caching layer that finds that it can skip the lengthy aspects of the |
|
|
3606 | operation and simply invoke the callback with the result. |
|
|
3607 | |
|
|
3608 | The problem here is that this will happen I<before> C<start_new_request> |
|
|
3609 | has returned, so C<request> is not set. |
|
|
3610 | |
|
|
3611 | Even if you pass the request by some safer means to the callback, you |
|
|
3612 | might want to do something to the request after starting it, such as |
|
|
3613 | canceling it, which probably isn't working so well when the callback has |
|
|
3614 | already been invoked. |
|
|
3615 | |
|
|
3616 | A common way around all these issues is to make sure that |
|
|
3617 | C<start_new_request> I<always> returns before the callback is invoked. If |
|
|
3618 | C<start_new_request> immediately knows the result, it can artificially |
|
|
3619 | delay invoking the callback by e.g. using a C<prepare> or C<idle> watcher |
|
|
3620 | for example, or more sneakily, by reusing an existing (stopped) watcher |
|
|
3621 | and pushing it into the pending queue: |
|
|
3622 | |
|
|
3623 | ev_set_cb (watcher, callback); |
|
|
3624 | ev_feed_event (EV_A_ watcher, 0); |
|
|
3625 | |
|
|
3626 | This way, C<start_new_request> can safely return before the callback is |
|
|
3627 | invoked, while not delaying callback invocation too much. |
|
|
3628 | |
3481 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3629 | =head2 MODEL/NESTED EVENT LOOP INVOCATIONS AND EXIT CONDITIONS |
3482 | |
3630 | |
3483 | Often (especially in GUI toolkits) there are places where you have |
3631 | Often (especially in GUI toolkits) there are places where you have |
3484 | I<modal> interaction, which is most easily implemented by recursively |
3632 | I<modal> interaction, which is most easily implemented by recursively |
3485 | invoking C<ev_run>. |
3633 | invoking C<ev_run>. |
… | |
… | |
3498 | int exit_main_loop = 0; |
3646 | int exit_main_loop = 0; |
3499 | |
3647 | |
3500 | while (!exit_main_loop) |
3648 | while (!exit_main_loop) |
3501 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3649 | ev_run (EV_DEFAULT_ EVRUN_ONCE); |
3502 | |
3650 | |
3503 | // in a model watcher |
3651 | // in a modal watcher |
3504 | int exit_nested_loop = 0; |
3652 | int exit_nested_loop = 0; |
3505 | |
3653 | |
3506 | while (!exit_nested_loop) |
3654 | while (!exit_nested_loop) |
3507 | ev_run (EV_A_ EVRUN_ONCE); |
3655 | ev_run (EV_A_ EVRUN_ONCE); |
3508 | |
3656 | |
… | |
… | |
3688 | switch_to (libev_coro); |
3836 | switch_to (libev_coro); |
3689 | } |
3837 | } |
3690 | |
3838 | |
3691 | That basically suspends the coroutine inside C<wait_for_event> and |
3839 | That basically suspends the coroutine inside C<wait_for_event> and |
3692 | continues the libev coroutine, which, when appropriate, switches back to |
3840 | continues the libev coroutine, which, when appropriate, switches back to |
3693 | this or any other coroutine. I am sure if you sue this your own :) |
3841 | this or any other coroutine. |
3694 | |
3842 | |
3695 | You can do similar tricks if you have, say, threads with an event queue - |
3843 | You can do similar tricks if you have, say, threads with an event queue - |
3696 | instead of storing a coroutine, you store the queue object and instead of |
3844 | instead of storing a coroutine, you store the queue object and instead of |
3697 | switching to a coroutine, you push the watcher onto the queue and notify |
3845 | switching to a coroutine, you push the watcher onto the queue and notify |
3698 | any waiters. |
3846 | any waiters. |
… | |
… | |
3773 | with C<operator ()> can be used as callbacks. Other types should be easy |
3921 | with C<operator ()> can be used as callbacks. Other types should be easy |
3774 | to add as long as they only need one additional pointer for context. If |
3922 | to add as long as they only need one additional pointer for context. If |
3775 | you need support for other types of functors please contact the author |
3923 | you need support for other types of functors please contact the author |
3776 | (preferably after implementing it). |
3924 | (preferably after implementing it). |
3777 | |
3925 | |
|
|
3926 | For all this to work, your C++ compiler either has to use the same calling |
|
|
3927 | conventions as your C compiler (for static member functions), or you have |
|
|
3928 | to embed libev and compile libev itself as C++. |
|
|
3929 | |
3778 | Here is a list of things available in the C<ev> namespace: |
3930 | Here is a list of things available in the C<ev> namespace: |
3779 | |
3931 | |
3780 | =over 4 |
3932 | =over 4 |
3781 | |
3933 | |
3782 | =item C<ev::READ>, C<ev::WRITE> etc. |
3934 | =item C<ev::READ>, C<ev::WRITE> etc. |
… | |
… | |
3791 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3943 | =item C<ev::io>, C<ev::timer>, C<ev::periodic>, C<ev::idle>, C<ev::sig> etc. |
3792 | |
3944 | |
3793 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3945 | For each C<ev_TYPE> watcher in F<ev.h> there is a corresponding class of |
3794 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3946 | the same name in the C<ev> namespace, with the exception of C<ev_signal> |
3795 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3947 | which is called C<ev::sig> to avoid clashes with the C<signal> macro |
3796 | defines by many implementations. |
3948 | defined by many implementations. |
3797 | |
3949 | |
3798 | All of those classes have these methods: |
3950 | All of those classes have these methods: |
3799 | |
3951 | |
3800 | =over 4 |
3952 | =over 4 |
3801 | |
3953 | |
… | |
… | |
3934 | watchers in the constructor. |
4086 | watchers in the constructor. |
3935 | |
4087 | |
3936 | class myclass |
4088 | class myclass |
3937 | { |
4089 | { |
3938 | ev::io io ; void io_cb (ev::io &w, int revents); |
4090 | ev::io io ; void io_cb (ev::io &w, int revents); |
3939 | ev::io2 io2 ; void io2_cb (ev::io &w, int revents); |
4091 | ev::io io2 ; void io2_cb (ev::io &w, int revents); |
3940 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
4092 | ev::idle idle; void idle_cb (ev::idle &w, int revents); |
3941 | |
4093 | |
3942 | myclass (int fd) |
4094 | myclass (int fd) |
3943 | { |
4095 | { |
3944 | io .set <myclass, &myclass::io_cb > (this); |
4096 | io .set <myclass, &myclass::io_cb > (this); |
… | |
… | |
3995 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
4147 | L<http://hackage.haskell.org/cgi-bin/hackage-scripts/package/hlibev>. |
3996 | |
4148 | |
3997 | =item D |
4149 | =item D |
3998 | |
4150 | |
3999 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4151 | Leandro Lucarella has written a D language binding (F<ev.d>) for libev, to |
4000 | be found at L<http://proj.llucax.com.ar/wiki/evd>. |
4152 | be found at L<http://www.llucax.com.ar/proj/ev.d/index.html>. |
4001 | |
4153 | |
4002 | =item Ocaml |
4154 | =item Ocaml |
4003 | |
4155 | |
4004 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4156 | Erkki Seppala has written Ocaml bindings for libev, to be found at |
4005 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
4157 | L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. |
… | |
… | |
4053 | suitable for use with C<EV_A>. |
4205 | suitable for use with C<EV_A>. |
4054 | |
4206 | |
4055 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4207 | =item C<EV_DEFAULT>, C<EV_DEFAULT_> |
4056 | |
4208 | |
4057 | Similar to the other two macros, this gives you the value of the default |
4209 | Similar to the other two macros, this gives you the value of the default |
4058 | loop, if multiple loops are supported ("ev loop default"). |
4210 | loop, if multiple loops are supported ("ev loop default"). The default loop |
|
|
4211 | will be initialised if it isn't already initialised. |
|
|
4212 | |
|
|
4213 | For non-multiplicity builds, these macros do nothing, so you always have |
|
|
4214 | to initialise the loop somewhere. |
4059 | |
4215 | |
4060 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4216 | =item C<EV_DEFAULT_UC>, C<EV_DEFAULT_UC_> |
4061 | |
4217 | |
4062 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4218 | Usage identical to C<EV_DEFAULT> and C<EV_DEFAULT_>, but requires that the |
4063 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
4219 | default loop has been initialised (C<UC> == unchecked). Their behaviour |
… | |
… | |
4356 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4512 | If defined to be C<1>, libev will compile in support for the Linux inotify |
4357 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4513 | interface to speed up C<ev_stat> watchers. Its actual availability will |
4358 | be detected at runtime. If undefined, it will be enabled if the headers |
4514 | be detected at runtime. If undefined, it will be enabled if the headers |
4359 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4515 | indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. |
4360 | |
4516 | |
|
|
4517 | =item EV_NO_SMP |
|
|
4518 | |
|
|
4519 | If defined to be C<1>, libev will assume that memory is always coherent |
|
|
4520 | between threads, that is, threads can be used, but threads never run on |
|
|
4521 | different cpus (or different cpu cores). This reduces dependencies |
|
|
4522 | and makes libev faster. |
|
|
4523 | |
|
|
4524 | =item EV_NO_THREADS |
|
|
4525 | |
|
|
4526 | If defined to be C<1>, libev will assume that it will never be called |
|
|
4527 | from different threads, which is a stronger assumption than C<EV_NO_SMP>, |
|
|
4528 | above. This reduces dependencies and makes libev faster. |
|
|
4529 | |
4361 | =item EV_ATOMIC_T |
4530 | =item EV_ATOMIC_T |
4362 | |
4531 | |
4363 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4532 | Libev requires an integer type (suitable for storing C<0> or C<1>) whose |
4364 | access is atomic with respect to other threads or signal contexts. No such |
4533 | access is atomic and serialised with respect to other threads or signal |
4365 | type is easily found in the C language, so you can provide your own type |
4534 | contexts. No such type is easily found in the C language, so you can |
4366 | that you know is safe for your purposes. It is used both for signal handler "locking" |
4535 | provide your own type that you know is safe for your purposes. It is used |
4367 | as well as for signal and thread safety in C<ev_async> watchers. |
4536 | both for signal handler "locking" as well as for signal and thread safety |
|
|
4537 | in C<ev_async> watchers. |
4368 | |
4538 | |
4369 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4539 | In the absence of this define, libev will use C<sig_atomic_t volatile> |
4370 | (from F<signal.h>), which is usually good enough on most platforms. |
4540 | (from F<signal.h>), which is usually good enough on most platforms, |
|
|
4541 | although strictly speaking using a type that also implies a memory fence |
|
|
4542 | is required. |
4371 | |
4543 | |
4372 | =item EV_H (h) |
4544 | =item EV_H (h) |
4373 | |
4545 | |
4374 | The name of the F<ev.h> header file used to include it. The default if |
4546 | The name of the F<ev.h> header file used to include it. The default if |
4375 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
4547 | undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be |
… | |
… | |
4399 | will have the C<struct ev_loop *> as first argument, and you can create |
4571 | will have the C<struct ev_loop *> as first argument, and you can create |
4400 | additional independent event loops. Otherwise there will be no support |
4572 | additional independent event loops. Otherwise there will be no support |
4401 | for multiple event loops and there is no first event loop pointer |
4573 | for multiple event loops and there is no first event loop pointer |
4402 | argument. Instead, all functions act on the single default loop. |
4574 | argument. Instead, all functions act on the single default loop. |
4403 | |
4575 | |
|
|
4576 | Note that C<EV_DEFAULT> and C<EV_DEFAULT_> will no longer provide a |
|
|
4577 | default loop when multiplicity is switched off - you always have to |
|
|
4578 | initialise the loop manually in this case. |
|
|
4579 | |
4404 | =item EV_MINPRI |
4580 | =item EV_MINPRI |
4405 | |
4581 | |
4406 | =item EV_MAXPRI |
4582 | =item EV_MAXPRI |
4407 | |
4583 | |
4408 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
4584 | The range of allowed priorities. C<EV_MINPRI> must be smaller or equal to |
… | |
… | |
4444 | #define EV_USE_POLL 1 |
4620 | #define EV_USE_POLL 1 |
4445 | #define EV_CHILD_ENABLE 1 |
4621 | #define EV_CHILD_ENABLE 1 |
4446 | #define EV_ASYNC_ENABLE 1 |
4622 | #define EV_ASYNC_ENABLE 1 |
4447 | |
4623 | |
4448 | The actual value is a bitset, it can be a combination of the following |
4624 | The actual value is a bitset, it can be a combination of the following |
4449 | values: |
4625 | values (by default, all of these are enabled): |
4450 | |
4626 | |
4451 | =over 4 |
4627 | =over 4 |
4452 | |
4628 | |
4453 | =item C<1> - faster/larger code |
4629 | =item C<1> - faster/larger code |
4454 | |
4630 | |
… | |
… | |
4458 | code size by roughly 30% on amd64). |
4634 | code size by roughly 30% on amd64). |
4459 | |
4635 | |
4460 | When optimising for size, use of compiler flags such as C<-Os> with |
4636 | When optimising for size, use of compiler flags such as C<-Os> with |
4461 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4637 | gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of |
4462 | assertions. |
4638 | assertions. |
|
|
4639 | |
|
|
4640 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4641 | (e.g. gcc with C<-Os>). |
4463 | |
4642 | |
4464 | =item C<2> - faster/larger data structures |
4643 | =item C<2> - faster/larger data structures |
4465 | |
4644 | |
4466 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4645 | Replaces the small 2-heap for timer management by a faster 4-heap, larger |
4467 | hash table sizes and so on. This will usually further increase code size |
4646 | hash table sizes and so on. This will usually further increase code size |
4468 | and can additionally have an effect on the size of data structures at |
4647 | and can additionally have an effect on the size of data structures at |
4469 | runtime. |
4648 | runtime. |
4470 | |
4649 | |
|
|
4650 | The default is off when C<__OPTIMIZE_SIZE__> is defined by your compiler |
|
|
4651 | (e.g. gcc with C<-Os>). |
|
|
4652 | |
4471 | =item C<4> - full API configuration |
4653 | =item C<4> - full API configuration |
4472 | |
4654 | |
4473 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4655 | This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and |
4474 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4656 | enables multiplicity (C<EV_MULTIPLICITY>=1). |
4475 | |
4657 | |
… | |
… | |
4505 | |
4687 | |
4506 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4688 | With an intelligent-enough linker (gcc+binutils are intelligent enough |
4507 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4689 | when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by |
4508 | your program might be left out as well - a binary starting a timer and an |
4690 | your program might be left out as well - a binary starting a timer and an |
4509 | I/O watcher then might come out at only 5Kb. |
4691 | I/O watcher then might come out at only 5Kb. |
|
|
4692 | |
|
|
4693 | =item EV_API_STATIC |
|
|
4694 | |
|
|
4695 | If this symbol is defined (by default it is not), then all identifiers |
|
|
4696 | will have static linkage. This means that libev will not export any |
|
|
4697 | identifiers, and you cannot link against libev anymore. This can be useful |
|
|
4698 | when you embed libev, only want to use libev functions in a single file, |
|
|
4699 | and do not want its identifiers to be visible. |
|
|
4700 | |
|
|
4701 | To use this, define C<EV_API_STATIC> and include F<ev.c> in the file that |
|
|
4702 | wants to use libev. |
|
|
4703 | |
|
|
4704 | This option only works when libev is compiled with a C compiler, as C++ |
|
|
4705 | doesn't support the required declaration syntax. |
4510 | |
4706 | |
4511 | =item EV_AVOID_STDIO |
4707 | =item EV_AVOID_STDIO |
4512 | |
4708 | |
4513 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4709 | If this is set to C<1> at compiletime, then libev will avoid using stdio |
4514 | functions (printf, scanf, perror etc.). This will increase the code size |
4710 | functions (printf, scanf, perror etc.). This will increase the code size |
… | |
… | |
4894 | requires, and its I/O model is fundamentally incompatible with the POSIX |
5090 | requires, and its I/O model is fundamentally incompatible with the POSIX |
4895 | model. Libev still offers limited functionality on this platform in |
5091 | model. Libev still offers limited functionality on this platform in |
4896 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
5092 | the form of the C<EVBACKEND_SELECT> backend, and only supports socket |
4897 | descriptors. This only applies when using Win32 natively, not when using |
5093 | descriptors. This only applies when using Win32 natively, not when using |
4898 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
5094 | e.g. cygwin. Actually, it only applies to the microsofts own compilers, |
4899 | as every compielr comes with a slightly differently broken/incompatible |
5095 | as every compiler comes with a slightly differently broken/incompatible |
4900 | environment. |
5096 | environment. |
4901 | |
5097 | |
4902 | Lifting these limitations would basically require the full |
5098 | Lifting these limitations would basically require the full |
4903 | re-implementation of the I/O system. If you are into this kind of thing, |
5099 | re-implementation of the I/O system. If you are into this kind of thing, |
4904 | then note that glib does exactly that for you in a very portable way (note |
5100 | then note that glib does exactly that for you in a very portable way (note |
… | |
… | |
5037 | |
5233 | |
5038 | The type C<double> is used to represent timestamps. It is required to |
5234 | The type C<double> is used to represent timestamps. It is required to |
5039 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5235 | have at least 51 bits of mantissa (and 9 bits of exponent), which is |
5040 | good enough for at least into the year 4000 with millisecond accuracy |
5236 | good enough for at least into the year 4000 with millisecond accuracy |
5041 | (the design goal for libev). This requirement is overfulfilled by |
5237 | (the design goal for libev). This requirement is overfulfilled by |
5042 | implementations using IEEE 754, which is basically all existing ones. With |
5238 | implementations using IEEE 754, which is basically all existing ones. |
|
|
5239 | |
5043 | IEEE 754 doubles, you get microsecond accuracy until at least 2200. |
5240 | With IEEE 754 doubles, you get microsecond accuracy until at least the |
|
|
5241 | year 2255 (and millisecond accuracy till the year 287396 - by then, libev |
|
|
5242 | is either obsolete or somebody patched it to use C<long double> or |
|
|
5243 | something like that, just kidding). |
5044 | |
5244 | |
5045 | =back |
5245 | =back |
5046 | |
5246 | |
5047 | If you know of other additional requirements drop me a note. |
5247 | If you know of other additional requirements drop me a note. |
5048 | |
5248 | |
… | |
… | |
5110 | =item Processing ev_async_send: O(number_of_async_watchers) |
5310 | =item Processing ev_async_send: O(number_of_async_watchers) |
5111 | |
5311 | |
5112 | =item Processing signals: O(max_signal_number) |
5312 | =item Processing signals: O(max_signal_number) |
5113 | |
5313 | |
5114 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5314 | Sending involves a system call I<iff> there were no other C<ev_async_send> |
5115 | calls in the current loop iteration. Checking for async and signal events |
5315 | calls in the current loop iteration and the loop is currently |
|
|
5316 | blocked. Checking for async and signal events involves iterating over all |
5116 | involves iterating over all running async watchers or all signal numbers. |
5317 | running async watchers or all signal numbers. |
5117 | |
5318 | |
5118 | =back |
5319 | =back |
5119 | |
5320 | |
5120 | |
5321 | |
5121 | =head1 PORTING FROM LIBEV 3.X TO 4.X |
5322 | =head1 PORTING FROM LIBEV 3.X TO 4.X |