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75 | While this document tries to be as complete as possible in documenting |
75 | While this document tries to be as complete as possible in documenting |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
76 | libev, its usage and the rationale behind its design, it is not a tutorial |
77 | on event-based programming, nor will it introduce event-based programming |
77 | on event-based programming, nor will it introduce event-based programming |
78 | with libev. |
78 | with libev. |
79 | |
79 | |
80 | Familarity with event based programming techniques in general is assumed |
80 | Familiarity with event based programming techniques in general is assumed |
81 | throughout this document. |
81 | throughout this document. |
82 | |
82 | |
83 | =head1 ABOUT LIBEV |
83 | =head1 ABOUT LIBEV |
84 | |
84 | |
85 | Libev is an event loop: you register interest in certain events (such as a |
85 | Libev is an event loop: you register interest in certain events (such as a |
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192 | as this indicates an incompatible change. Minor versions are usually |
192 | as this indicates an incompatible change. Minor versions are usually |
193 | compatible to older versions, so a larger minor version alone is usually |
193 | compatible to older versions, so a larger minor version alone is usually |
194 | not a problem. |
194 | not a problem. |
195 | |
195 | |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
196 | Example: Make sure we haven't accidentally been linked against the wrong |
197 | version. |
197 | version (note, however, that this will not detect ABI mismatches :). |
198 | |
198 | |
199 | assert (("libev version mismatch", |
199 | assert (("libev version mismatch", |
200 | ev_version_major () == EV_VERSION_MAJOR |
200 | ev_version_major () == EV_VERSION_MAJOR |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
201 | && ev_version_minor () >= EV_VERSION_MINOR)); |
202 | |
202 | |
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705 | C<ev_resume> directly afterwards to resume timer processing. |
705 | C<ev_resume> directly afterwards to resume timer processing. |
706 | |
706 | |
707 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
707 | Effectively, all C<ev_timer> watchers will be delayed by the time spend |
708 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
708 | between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers |
709 | will be rescheduled (that is, they will lose any events that would have |
709 | will be rescheduled (that is, they will lose any events that would have |
710 | occured while suspended). |
710 | occurred while suspended). |
711 | |
711 | |
712 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
712 | After calling C<ev_suspend> you B<must not> call I<any> function on the |
713 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
713 | given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> |
714 | without a previous call to C<ev_suspend>. |
714 | without a previous call to C<ev_suspend>. |
715 | |
715 | |
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792 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
792 | C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or |
793 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
793 | C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. |
794 | |
794 | |
795 | This "unloop state" will be cleared when entering C<ev_loop> again. |
795 | This "unloop state" will be cleared when entering C<ev_loop> again. |
796 | |
796 | |
797 | It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. |
797 | It is safe to call C<ev_unloop> from outside any C<ev_loop> calls. |
798 | |
798 | |
799 | =item ev_ref (loop) |
799 | =item ev_ref (loop) |
800 | |
800 | |
801 | =item ev_unref (loop) |
801 | =item ev_unref (loop) |
802 | |
802 | |
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872 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
872 | usually doesn't make much sense to set it to a lower value than C<0.01>, |
873 | as this approaches the timing granularity of most systems. Note that if |
873 | as this approaches the timing granularity of most systems. Note that if |
874 | you do transactions with the outside world and you can't increase the |
874 | you do transactions with the outside world and you can't increase the |
875 | parallelity, then this setting will limit your transaction rate (if you |
875 | parallelity, then this setting will limit your transaction rate (if you |
876 | need to poll once per transaction and the I/O collect interval is 0.01, |
876 | need to poll once per transaction and the I/O collect interval is 0.01, |
877 | then you can't do more than 100 transations per second). |
877 | then you can't do more than 100 transactions per second). |
878 | |
878 | |
879 | Setting the I<timeout collect interval> can improve the opportunity for |
879 | Setting the I<timeout collect interval> can improve the opportunity for |
880 | saving power, as the program will "bundle" timer callback invocations that |
880 | saving power, as the program will "bundle" timer callback invocations that |
881 | are "near" in time together, by delaying some, thus reducing the number of |
881 | are "near" in time together, by delaying some, thus reducing the number of |
882 | times the process sleeps and wakes up again. Another useful technique to |
882 | times the process sleeps and wakes up again. Another useful technique to |
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1380 | |
1380 | |
1381 | For example, to emulate how many other event libraries handle priorities, |
1381 | For example, to emulate how many other event libraries handle priorities, |
1382 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1382 | you can associate an C<ev_idle> watcher to each such watcher, and in |
1383 | the normal watcher callback, you just start the idle watcher. The real |
1383 | the normal watcher callback, you just start the idle watcher. The real |
1384 | processing is done in the idle watcher callback. This causes libev to |
1384 | processing is done in the idle watcher callback. This causes libev to |
1385 | continously poll and process kernel event data for the watcher, but when |
1385 | continuously poll and process kernel event data for the watcher, but when |
1386 | the lock-out case is known to be rare (which in turn is rare :), this is |
1386 | the lock-out case is known to be rare (which in turn is rare :), this is |
1387 | workable. |
1387 | workable. |
1388 | |
1388 | |
1389 | Usually, however, the lock-out model implemented that way will perform |
1389 | Usually, however, the lock-out model implemented that way will perform |
1390 | miserably under the type of load it was designed to handle. In that case, |
1390 | miserably under the type of load it was designed to handle. In that case, |
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1404 | { |
1404 | { |
1405 | // stop the I/O watcher, we received the event, but |
1405 | // stop the I/O watcher, we received the event, but |
1406 | // are not yet ready to handle it. |
1406 | // are not yet ready to handle it. |
1407 | ev_io_stop (EV_A_ w); |
1407 | ev_io_stop (EV_A_ w); |
1408 | |
1408 | |
1409 | // start the idle watcher to ahndle the actual event. |
1409 | // start the idle watcher to handle the actual event. |
1410 | // it will not be executed as long as other watchers |
1410 | // it will not be executed as long as other watchers |
1411 | // with the default priority are receiving events. |
1411 | // with the default priority are receiving events. |
1412 | ev_idle_start (EV_A_ &idle); |
1412 | ev_idle_start (EV_A_ &idle); |
1413 | } |
1413 | } |
1414 | |
1414 | |
… | |
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1468 | |
1468 | |
1469 | If you cannot use non-blocking mode, then force the use of a |
1469 | If you cannot use non-blocking mode, then force the use of a |
1470 | known-to-be-good backend (at the time of this writing, this includes only |
1470 | known-to-be-good backend (at the time of this writing, this includes only |
1471 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
1471 | C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file |
1472 | descriptors for which non-blocking operation makes no sense (such as |
1472 | descriptors for which non-blocking operation makes no sense (such as |
1473 | files) - libev doesn't guarentee any specific behaviour in that case. |
1473 | files) - libev doesn't guarantee any specific behaviour in that case. |
1474 | |
1474 | |
1475 | Another thing you have to watch out for is that it is quite easy to |
1475 | Another thing you have to watch out for is that it is quite easy to |
1476 | receive "spurious" readiness notifications, that is your callback might |
1476 | receive "spurious" readiness notifications, that is your callback might |
1477 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1477 | be called with C<EV_READ> but a subsequent C<read>(2) will actually block |
1478 | because there is no data. Not only are some backends known to create a |
1478 | because there is no data. Not only are some backends known to create a |
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1737 | ev_tstamp timeout = last_activity + 60.; |
1737 | ev_tstamp timeout = last_activity + 60.; |
1738 | |
1738 | |
1739 | // if last_activity + 60. is older than now, we did time out |
1739 | // if last_activity + 60. is older than now, we did time out |
1740 | if (timeout < now) |
1740 | if (timeout < now) |
1741 | { |
1741 | { |
1742 | // timeout occured, take action |
1742 | // timeout occurred, take action |
1743 | } |
1743 | } |
1744 | else |
1744 | else |
1745 | { |
1745 | { |
1746 | // callback was invoked, but there was some activity, re-arm |
1746 | // callback was invoked, but there was some activity, re-arm |
1747 | // the watcher to fire in last_activity + 60, which is |
1747 | // the watcher to fire in last_activity + 60, which is |
… | |
… | |
1774 | callback (loop, timer, EV_TIMER); |
1774 | callback (loop, timer, EV_TIMER); |
1775 | |
1775 | |
1776 | And when there is some activity, simply store the current time in |
1776 | And when there is some activity, simply store the current time in |
1777 | C<last_activity>, no libev calls at all: |
1777 | C<last_activity>, no libev calls at all: |
1778 | |
1778 | |
1779 | last_actiivty = ev_now (loop); |
1779 | last_activity = ev_now (loop); |
1780 | |
1780 | |
1781 | This technique is slightly more complex, but in most cases where the |
1781 | This technique is slightly more complex, but in most cases where the |
1782 | time-out is unlikely to be triggered, much more efficient. |
1782 | time-out is unlikely to be triggered, much more efficient. |
1783 | |
1783 | |
1784 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
1784 | Changing the timeout is trivial as well (if it isn't hard-coded in the |
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… | |
3342 | ev::io iow; |
3342 | ev::io iow; |
3343 | iow.set <myclass, &myclass::io_cb> (&obj); |
3343 | iow.set <myclass, &myclass::io_cb> (&obj); |
3344 | |
3344 | |
3345 | =item w->set (object *) |
3345 | =item w->set (object *) |
3346 | |
3346 | |
3347 | This is an B<experimental> feature that might go away in a future version. |
|
|
3348 | |
|
|
3349 | This is a variation of a method callback - leaving out the method to call |
3347 | This is a variation of a method callback - leaving out the method to call |
3350 | will default the method to C<operator ()>, which makes it possible to use |
3348 | will default the method to C<operator ()>, which makes it possible to use |
3351 | functor objects without having to manually specify the C<operator ()> all |
3349 | functor objects without having to manually specify the C<operator ()> all |
3352 | the time. Incidentally, you can then also leave out the template argument |
3350 | the time. Incidentally, you can then also leave out the template argument |
3353 | list. |
3351 | list. |
… | |
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3988 | |
3986 | |
3989 | The highest supported signal number, +1 (or, the number of |
3987 | The highest supported signal number, +1 (or, the number of |
3990 | signals): Normally, libev tries to deduce the maximum number of signals |
3988 | signals): Normally, libev tries to deduce the maximum number of signals |
3991 | automatically, but sometimes this fails, in which case it can be |
3989 | automatically, but sometimes this fails, in which case it can be |
3992 | specified. Also, using a lower number than detected (C<32> should be |
3990 | specified. Also, using a lower number than detected (C<32> should be |
3993 | good for about any system in existance) can save some memory, as libev |
3991 | good for about any system in existence) can save some memory, as libev |
3994 | statically allocates some 12-24 bytes per signal number. |
3992 | statically allocates some 12-24 bytes per signal number. |
3995 | |
3993 | |
3996 | =item EV_PID_HASHSIZE |
3994 | =item EV_PID_HASHSIZE |
3997 | |
3995 | |
3998 | C<ev_child> watchers use a small hash table to distribute workload by |
3996 | C<ev_child> watchers use a small hash table to distribute workload by |
… | |
… | |
4653 | |
4651 | |
4654 | This is a simple rename - all other watcher types use their name |
4652 | This is a simple rename - all other watcher types use their name |
4655 | as revents flag, and now C<ev_timer> does, too. |
4653 | as revents flag, and now C<ev_timer> does, too. |
4656 | |
4654 | |
4657 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
4655 | Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions |
4658 | and continue to be present for the forseeable future, so this is mostly a |
4656 | and continue to be present for the foreseeable future, so this is mostly a |
4659 | documentation change. |
4657 | documentation change. |
4660 | |
4658 | |
4661 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4659 | =item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> |
4662 | |
4660 | |
4663 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |
4661 | The preprocessor symbol C<EV_MINIMAL> has been replaced by a different |