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75While this document tries to be as complete as possible in documenting 75While this document tries to be as complete as possible in documenting
76libev, its usage and the rationale behind its design, it is not a tutorial 76libev, its usage and the rationale behind its design, it is not a tutorial
77on event-based programming, nor will it introduce event-based programming 77on event-based programming, nor will it introduce event-based programming
78with libev. 78with libev.
79 79
80Familarity with event based programming techniques in general is assumed 80Familiarity with event based programming techniques in general is assumed
81throughout this document. 81throughout this document.
82 82
83=head1 ABOUT LIBEV 83=head1 ABOUT LIBEV
84 84
85Libev is an event loop: you register interest in certain events (such as a 85Libev is an event loop: you register interest in certain events (such as a
124this argument. 124this argument.
125 125
126=head2 TIME REPRESENTATION 126=head2 TIME REPRESENTATION
127 127
128Libev represents time as a single floating point number, representing 128Libev represents time as a single floating point number, representing
129the (fractional) number of seconds since the (POSIX) epoch (somewhere 129the (fractional) number of seconds since the (POSIX) epoch (in practise
130near the beginning of 1970, details are complicated, don't ask). This 130somewhere near the beginning of 1970, details are complicated, don't
131type is called C<ev_tstamp>, which is what you should use too. It usually 131ask). This type is called C<ev_tstamp>, which is what you should use
132aliases to the C<double> type in C. When you need to do any calculations 132too. It usually aliases to the C<double> type in C. When you need to do
133on it, you should treat it as some floating point value. Unlike the name 133any calculations on it, you should treat it as some floating point value.
134
134component C<stamp> might indicate, it is also used for time differences 135Unlike the name component C<stamp> might indicate, it is also used for
135throughout libev. 136time differences (e.g. delays) throughout libev.
136 137
137=head1 ERROR HANDLING 138=head1 ERROR HANDLING
138 139
139Libev knows three classes of errors: operating system errors, usage errors 140Libev knows three classes of errors: operating system errors, usage errors
140and internal errors (bugs). 141and internal errors (bugs).
191as this indicates an incompatible change. Minor versions are usually 192as this indicates an incompatible change. Minor versions are usually
192compatible to older versions, so a larger minor version alone is usually 193compatible to older versions, so a larger minor version alone is usually
193not a problem. 194not a problem.
194 195
195Example: Make sure we haven't accidentally been linked against the wrong 196Example: Make sure we haven't accidentally been linked against the wrong
196version. 197version (note, however, that this will not detect ABI mismatches :).
197 198
198 assert (("libev version mismatch", 199 assert (("libev version mismatch",
199 ev_version_major () == EV_VERSION_MAJOR 200 ev_version_major () == EV_VERSION_MAJOR
200 && ev_version_minor () >= EV_VERSION_MINOR)); 201 && ev_version_minor () >= EV_VERSION_MINOR));
201 202
345useful to try out specific backends to test their performance, or to work 346useful to try out specific backends to test their performance, or to work
346around bugs. 347around bugs.
347 348
348=item C<EVFLAG_FORKCHECK> 349=item C<EVFLAG_FORKCHECK>
349 350
350Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after 351Instead of calling C<ev_loop_fork> manually after a fork, you can also
351a fork, you can also make libev check for a fork in each iteration by 352make libev check for a fork in each iteration by enabling this flag.
352enabling this flag.
353 353
354This works by calling C<getpid ()> on every iteration of the loop, 354This works by calling C<getpid ()> on every iteration of the loop,
355and thus this might slow down your event loop if you do a lot of loop 355and thus this might slow down your event loop if you do a lot of loop
356iterations and little real work, but is usually not noticeable (on my 356iterations and little real work, but is usually not noticeable (on my
357GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence 357GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
567 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); 567 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568 568
569=item struct ev_loop *ev_loop_new (unsigned int flags) 569=item struct ev_loop *ev_loop_new (unsigned int flags)
570 570
571Similar to C<ev_default_loop>, but always creates a new event loop that is 571Similar to C<ev_default_loop>, but always creates a new event loop that is
572always distinct from the default loop. Unlike the default loop, it cannot 572always distinct from the default loop.
573handle signal and child watchers, and attempts to do so will be greeted by
574undefined behaviour (or a failed assertion if assertions are enabled).
575 573
576Note that this function I<is> thread-safe, and the recommended way to use 574Note that this function I<is> thread-safe, and one common way to use
577libev with threads is indeed to create one loop per thread, and using the 575libev with threads is indeed to create one loop per thread, and using the
578default loop in the "main" or "initial" thread. 576default loop in the "main" or "initial" thread.
579 577
580Example: Try to create a event loop that uses epoll and nothing else. 578Example: Try to create a event loop that uses epoll and nothing else.
581 579
583 if (!epoller) 581 if (!epoller)
584 fatal ("no epoll found here, maybe it hides under your chair"); 582 fatal ("no epoll found here, maybe it hides under your chair");
585 583
586=item ev_default_destroy () 584=item ev_default_destroy ()
587 585
588Destroys the default loop again (frees all memory and kernel state 586Destroys the default loop (frees all memory and kernel state etc.). None
589etc.). None of the active event watchers will be stopped in the normal 587of the active event watchers will be stopped in the normal sense, so
590sense, so e.g. C<ev_is_active> might still return true. It is your 588e.g. C<ev_is_active> might still return true. It is your responsibility to
591responsibility to either stop all watchers cleanly yourself I<before> 589either stop all watchers cleanly yourself I<before> calling this function,
592calling this function, or cope with the fact afterwards (which is usually 590or cope with the fact afterwards (which is usually the easiest thing, you
593the easiest thing, you can just ignore the watchers and/or C<free ()> them 591can just ignore the watchers and/or C<free ()> them for example).
594for example).
595 592
596Note that certain global state, such as signal state (and installed signal 593Note that certain global state, such as signal state (and installed signal
597handlers), will not be freed by this function, and related watchers (such 594handlers), will not be freed by this function, and related watchers (such
598as signal and child watchers) would need to be stopped manually. 595as signal and child watchers) would need to be stopped manually.
599 596
614name, you can call it anytime, but it makes most sense after forking, in 611name, you can call it anytime, but it makes most sense after forking, in
615the child process (or both child and parent, but that again makes little 612the child process (or both child and parent, but that again makes little
616sense). You I<must> call it in the child before using any of the libev 613sense). You I<must> call it in the child before using any of the libev
617functions, and it will only take effect at the next C<ev_loop> iteration. 614functions, and it will only take effect at the next C<ev_loop> iteration.
618 615
616Again, you I<have> to call it on I<any> loop that you want to re-use after
617a fork, I<even if you do not plan to use the loop in the parent>. This is
618because some kernel interfaces *cough* I<kqueue> *cough* do funny things
619during fork.
620
619On the other hand, you only need to call this function in the child 621On the other hand, you only need to call this function in the child
620process if and only if you want to use the event library in the child. If 622process if and only if you want to use the event loop in the child. If you
621you just fork+exec, you don't have to call it at all. 623just fork+exec or create a new loop in the child, you don't have to call
624it at all.
622 625
623The function itself is quite fast and it's usually not a problem to call 626The function itself is quite fast and it's usually not a problem to call
624it just in case after a fork. To make this easy, the function will fit in 627it just in case after a fork. To make this easy, the function will fit in
625quite nicely into a call to C<pthread_atfork>: 628quite nicely into a call to C<pthread_atfork>:
626 629
628 631
629=item ev_loop_fork (loop) 632=item ev_loop_fork (loop)
630 633
631Like C<ev_default_fork>, but acts on an event loop created by 634Like C<ev_default_fork>, but acts on an event loop created by
632C<ev_loop_new>. Yes, you have to call this on every allocated event loop 635C<ev_loop_new>. Yes, you have to call this on every allocated event loop
633after fork that you want to re-use in the child, and how you do this is 636after fork that you want to re-use in the child, and how you keep track of
634entirely your own problem. 637them is entirely your own problem.
635 638
636=item int ev_is_default_loop (loop) 639=item int ev_is_default_loop (loop)
637 640
638Returns true when the given loop is, in fact, the default loop, and false 641Returns true when the given loop is, in fact, the default loop, and false
639otherwise. 642otherwise.
640 643
641=item unsigned int ev_loop_count (loop) 644=item unsigned int ev_iteration (loop)
642 645
643Returns the count of loop iterations for the loop, which is identical to 646Returns the current iteration count for the loop, which is identical to
644the number of times libev did poll for new events. It starts at C<0> and 647the number of times libev did poll for new events. It starts at C<0> and
645happily wraps around with enough iterations. 648happily wraps around with enough iterations.
646 649
647This value can sometimes be useful as a generation counter of sorts (it 650This value can sometimes be useful as a generation counter of sorts (it
648"ticks" the number of loop iterations), as it roughly corresponds with 651"ticks" the number of loop iterations), as it roughly corresponds with
649C<ev_prepare> and C<ev_check> calls. 652C<ev_prepare> and C<ev_check> calls - and is incremented between the
653prepare and check phases.
650 654
651=item unsigned int ev_loop_depth (loop) 655=item unsigned int ev_depth (loop)
652 656
653Returns the number of times C<ev_loop> was entered minus the number of 657Returns the number of times C<ev_loop> was entered minus the number of
654times C<ev_loop> was exited, in other words, the recursion depth. 658times C<ev_loop> was exited, in other words, the recursion depth.
655 659
656Outside C<ev_loop>, this number is zero. In a callback, this number is 660Outside C<ev_loop>, this number is zero. In a callback, this number is
657C<1>, unless C<ev_loop> was invoked recursively (or from another thread), 661C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
658in which case it is higher. 662in which case it is higher.
659 663
660Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread 664Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
661etc.), doesn't count as exit. 665etc.), doesn't count as "exit" - consider this as a hint to avoid such
666ungentleman behaviour unless it's really convenient.
662 667
663=item unsigned int ev_backend (loop) 668=item unsigned int ev_backend (loop)
664 669
665Returns one of the C<EVBACKEND_*> flags indicating the event backend in 670Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666use. 671use.
700C<ev_resume> directly afterwards to resume timer processing. 705C<ev_resume> directly afterwards to resume timer processing.
701 706
702Effectively, all C<ev_timer> watchers will be delayed by the time spend 707Effectively, all C<ev_timer> watchers will be delayed by the time spend
703between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers 708between C<ev_suspend> and C<ev_resume>, and all C<ev_periodic> watchers
704will be rescheduled (that is, they will lose any events that would have 709will be rescheduled (that is, they will lose any events that would have
705occured while suspended). 710occurred while suspended).
706 711
707After calling C<ev_suspend> you B<must not> call I<any> function on the 712After calling C<ev_suspend> you B<must not> call I<any> function on the
708given loop other than C<ev_resume>, and you B<must not> call C<ev_resume> 713given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709without a previous call to C<ev_suspend>. 714without a previous call to C<ev_suspend>.
710 715
787C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 792C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
788C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 793C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
789 794
790This "unloop state" will be cleared when entering C<ev_loop> again. 795This "unloop state" will be cleared when entering C<ev_loop> again.
791 796
792It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. 797It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.
793 798
794=item ev_ref (loop) 799=item ev_ref (loop)
795 800
796=item ev_unref (loop) 801=item ev_unref (loop)
797 802
867usually doesn't make much sense to set it to a lower value than C<0.01>, 872usually doesn't make much sense to set it to a lower value than C<0.01>,
868as this approaches the timing granularity of most systems. Note that if 873as this approaches the timing granularity of most systems. Note that if
869you do transactions with the outside world and you can't increase the 874you do transactions with the outside world and you can't increase the
870parallelity, then this setting will limit your transaction rate (if you 875parallelity, then this setting will limit your transaction rate (if you
871need to poll once per transaction and the I/O collect interval is 0.01, 876need to poll once per transaction and the I/O collect interval is 0.01,
872then you can't do more than 100 transations per second). 877then you can't do more than 100 transactions per second).
873 878
874Setting the I<timeout collect interval> can improve the opportunity for 879Setting the I<timeout collect interval> can improve the opportunity for
875saving power, as the program will "bundle" timer callback invocations that 880saving power, as the program will "bundle" timer callback invocations that
876are "near" in time together, by delaying some, thus reducing the number of 881are "near" in time together, by delaying some, thus reducing the number of
877times the process sleeps and wakes up again. Another useful technique to 882times the process sleeps and wakes up again. Another useful technique to
1032=item C<EV_WRITE> 1037=item C<EV_WRITE>
1033 1038
1034The file descriptor in the C<ev_io> watcher has become readable and/or 1039The file descriptor in the C<ev_io> watcher has become readable and/or
1035writable. 1040writable.
1036 1041
1037=item C<EV_TIMEOUT> 1042=item C<EV_TIMER>
1038 1043
1039The C<ev_timer> watcher has timed out. 1044The C<ev_timer> watcher has timed out.
1040 1045
1041=item C<EV_PERIODIC> 1046=item C<EV_PERIODIC>
1042 1047
1375 1380
1376For example, to emulate how many other event libraries handle priorities, 1381For example, to emulate how many other event libraries handle priorities,
1377you can associate an C<ev_idle> watcher to each such watcher, and in 1382you can associate an C<ev_idle> watcher to each such watcher, and in
1378the normal watcher callback, you just start the idle watcher. The real 1383the normal watcher callback, you just start the idle watcher. The real
1379processing is done in the idle watcher callback. This causes libev to 1384processing is done in the idle watcher callback. This causes libev to
1380continously poll and process kernel event data for the watcher, but when 1385continuously poll and process kernel event data for the watcher, but when
1381the lock-out case is known to be rare (which in turn is rare :), this is 1386the lock-out case is known to be rare (which in turn is rare :), this is
1382workable. 1387workable.
1383 1388
1384Usually, however, the lock-out model implemented that way will perform 1389Usually, however, the lock-out model implemented that way will perform
1385miserably under the type of load it was designed to handle. In that case, 1390miserably under the type of load it was designed to handle. In that case,
1399 { 1404 {
1400 // stop the I/O watcher, we received the event, but 1405 // stop the I/O watcher, we received the event, but
1401 // are not yet ready to handle it. 1406 // are not yet ready to handle it.
1402 ev_io_stop (EV_A_ w); 1407 ev_io_stop (EV_A_ w);
1403 1408
1404 // start the idle watcher to ahndle the actual event. 1409 // start the idle watcher to handle the actual event.
1405 // it will not be executed as long as other watchers 1410 // it will not be executed as long as other watchers
1406 // with the default priority are receiving events. 1411 // with the default priority are receiving events.
1407 ev_idle_start (EV_A_ &idle); 1412 ev_idle_start (EV_A_ &idle);
1408 } 1413 }
1409 1414
1463 1468
1464If you cannot use non-blocking mode, then force the use of a 1469If you cannot use non-blocking mode, then force the use of a
1465known-to-be-good backend (at the time of this writing, this includes only 1470known-to-be-good backend (at the time of this writing, this includes only
1466C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file 1471C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467descriptors for which non-blocking operation makes no sense (such as 1472descriptors for which non-blocking operation makes no sense (such as
1468files) - libev doesn't guarentee any specific behaviour in that case. 1473files) - libev doesn't guarantee any specific behaviour in that case.
1469 1474
1470Another thing you have to watch out for is that it is quite easy to 1475Another thing you have to watch out for is that it is quite easy to
1471receive "spurious" readiness notifications, that is your callback might 1476receive "spurious" readiness notifications, that is your callback might
1472be called with C<EV_READ> but a subsequent C<read>(2) will actually block 1477be called with C<EV_READ> but a subsequent C<read>(2) will actually block
1473because there is no data. Not only are some backends known to create a 1478because there is no data. Not only are some backends known to create a
1538 1543
1539So when you encounter spurious, unexplained daemon exits, make sure you 1544So when you encounter spurious, unexplained daemon exits, make sure you
1540ignore SIGPIPE (and maybe make sure you log the exit status of your daemon 1545ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1541somewhere, as that would have given you a big clue). 1546somewhere, as that would have given you a big clue).
1542 1547
1548=head3 The special problem of accept()ing when you can't
1549
1550Many implementations of the POSIX C<accept> function (for example,
1551found in post-2004 Linux) have the peculiar behaviour of not removing a
1552connection from the pending queue in all error cases.
1553
1554For example, larger servers often run out of file descriptors (because
1555of resource limits), causing C<accept> to fail with C<ENFILE> but not
1556rejecting the connection, leading to libev signalling readiness on
1557the next iteration again (the connection still exists after all), and
1558typically causing the program to loop at 100% CPU usage.
1559
1560Unfortunately, the set of errors that cause this issue differs between
1561operating systems, there is usually little the app can do to remedy the
1562situation, and no known thread-safe method of removing the connection to
1563cope with overload is known (to me).
1564
1565One of the easiest ways to handle this situation is to just ignore it
1566- when the program encounters an overload, it will just loop until the
1567situation is over. While this is a form of busy waiting, no OS offers an
1568event-based way to handle this situation, so it's the best one can do.
1569
1570A better way to handle the situation is to log any errors other than
1571C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
1572messages, and continue as usual, which at least gives the user an idea of
1573what could be wrong ("raise the ulimit!"). For extra points one could stop
1574the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
1575usage.
1576
1577If your program is single-threaded, then you could also keep a dummy file
1578descriptor for overload situations (e.g. by opening F</dev/null>), and
1579when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
1580close that fd, and create a new dummy fd. This will gracefully refuse
1581clients under typical overload conditions.
1582
1583The last way to handle it is to simply log the error and C<exit>, as
1584is often done with C<malloc> failures, but this results in an easy
1585opportunity for a DoS attack.
1543 1586
1544=head3 Watcher-Specific Functions 1587=head3 Watcher-Specific Functions
1545 1588
1546=over 4 1589=over 4
1547 1590
1694 ev_tstamp timeout = last_activity + 60.; 1737 ev_tstamp timeout = last_activity + 60.;
1695 1738
1696 // 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
1697 if (timeout < now) 1740 if (timeout < now)
1698 { 1741 {
1699 // timeout occured, take action 1742 // timeout occurred, take action
1700 } 1743 }
1701 else 1744 else
1702 { 1745 {
1703 // callback was invoked, but there was some activity, re-arm 1746 // callback was invoked, but there was some activity, re-arm
1704 // the watcher to fire in last_activity + 60, which is 1747 // the watcher to fire in last_activity + 60, which is
1726to the current time (meaning we just have some activity :), then call the 1769to the current time (meaning we just have some activity :), then call the
1727callback, which will "do the right thing" and start the timer: 1770callback, which will "do the right thing" and start the timer:
1728 1771
1729 ev_init (timer, callback); 1772 ev_init (timer, callback);
1730 last_activity = ev_now (loop); 1773 last_activity = ev_now (loop);
1731 callback (loop, timer, EV_TIMEOUT); 1774 callback (loop, timer, EV_TIMER);
1732 1775
1733And when there is some activity, simply store the current time in 1776And when there is some activity, simply store the current time in
1734C<last_activity>, no libev calls at all: 1777C<last_activity>, no libev calls at all:
1735 1778
1736 last_actiivty = ev_now (loop); 1779 last_activity = ev_now (loop);
1737 1780
1738This technique is slightly more complex, but in most cases where the 1781This technique is slightly more complex, but in most cases where the
1739time-out is unlikely to be triggered, much more efficient. 1782time-out is unlikely to be triggered, much more efficient.
1740 1783
1741Changing the timeout is trivial as well (if it isn't hard-coded in the 1784Changing the timeout is trivial as well (if it isn't hard-coded in the
2080Example: Call a callback every hour, or, more precisely, whenever the 2123Example: Call a callback every hour, or, more precisely, whenever the
2081system time is divisible by 3600. The callback invocation times have 2124system time is divisible by 3600. The callback invocation times have
2082potentially a lot of jitter, but good long-term stability. 2125potentially a lot of jitter, but good long-term stability.
2083 2126
2084 static void 2127 static void
2085 clock_cb (struct ev_loop *loop, ev_io *w, int revents) 2128 clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2086 { 2129 {
2087 ... its now a full hour (UTC, or TAI or whatever your clock follows) 2130 ... its now a full hour (UTC, or TAI or whatever your clock follows)
2088 } 2131 }
2089 2132
2090 ev_periodic hourly_tick; 2133 ev_periodic hourly_tick;
2922C<ev_default_fork> cheats and calls it in the wrong process, the fork 2965C<ev_default_fork> cheats and calls it in the wrong process, the fork
2923handlers will be invoked, too, of course. 2966handlers will be invoked, too, of course.
2924 2967
2925=head3 The special problem of life after fork - how is it possible? 2968=head3 The special problem of life after fork - how is it possible?
2926 2969
2927Most uses of C<fork()> consist of forking, then some simple calls to ste 2970Most uses of C<fork()> consist of forking, then some simple calls to set
2928up/change the process environment, followed by a call to C<exec()>. This 2971up/change the process environment, followed by a call to C<exec()>. This
2929sequence should be handled by libev without any problems. 2972sequence should be handled by libev without any problems.
2930 2973
2931This changes when the application actually wants to do event handling 2974This changes when the application actually wants to do event handling
2932in the child, or both parent in child, in effect "continuing" after the 2975in the child, or both parent in child, in effect "continuing" after the
2966believe me. 3009believe me.
2967 3010
2968=back 3011=back
2969 3012
2970 3013
2971=head2 C<ev_async> - how to wake up another event loop 3014=head2 C<ev_async> - how to wake up an event loop
2972 3015
2973In general, you cannot use an C<ev_loop> from multiple threads or other 3016In general, you cannot use an C<ev_loop> from multiple threads or other
2974asynchronous sources such as signal handlers (as opposed to multiple event 3017asynchronous sources such as signal handlers (as opposed to multiple event
2975loops - those are of course safe to use in different threads). 3018loops - those are of course safe to use in different threads).
2976 3019
2977Sometimes, however, you need to wake up another event loop you do not 3020Sometimes, however, you need to wake up an event loop you do not control,
2978control, for example because it belongs to another thread. This is what 3021for example because it belongs to another thread. This is what C<ev_async>
2979C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you 3022watchers do: as long as the C<ev_async> watcher is active, you can signal
2980can signal it by calling C<ev_async_send>, which is thread- and signal 3023it by calling C<ev_async_send>, which is thread- and signal safe.
2981safe.
2982 3024
2983This functionality is very similar to C<ev_signal> watchers, as signals, 3025This functionality is very similar to C<ev_signal> watchers, as signals,
2984too, are asynchronous in nature, and signals, too, will be compressed 3026too, are asynchronous in nature, and signals, too, will be compressed
2985(i.e. the number of callback invocations may be less than the number of 3027(i.e. the number of callback invocations may be less than the number of
2986C<ev_async_sent> calls). 3028C<ev_async_sent> calls).
3141 3183
3142If C<timeout> is less than 0, then no timeout watcher will be 3184If C<timeout> is less than 0, then no timeout watcher will be
3143started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 3185started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144repeat = 0) will be started. C<0> is a valid timeout. 3186repeat = 0) will be started. C<0> is a valid timeout.
3145 3187
3146The callback has the type C<void (*cb)(int revents, void *arg)> and gets 3188The callback has the type C<void (*cb)(int revents, void *arg)> and is
3147passed an C<revents> set like normal event callbacks (a combination of 3189passed an C<revents> set like normal event callbacks (a combination of
3148C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> 3190C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMER>) and the C<arg>
3149value passed to C<ev_once>. Note that it is possible to receive I<both> 3191value passed to C<ev_once>. Note that it is possible to receive I<both>
3150a timeout and an io event at the same time - you probably should give io 3192a timeout and an io event at the same time - you probably should give io
3151events precedence. 3193events precedence.
3152 3194
3153Example: wait up to ten seconds for data to appear on STDIN_FILENO. 3195Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154 3196
3155 static void stdin_ready (int revents, void *arg) 3197 static void stdin_ready (int revents, void *arg)
3156 { 3198 {
3157 if (revents & EV_READ) 3199 if (revents & EV_READ)
3158 /* stdin might have data for us, joy! */; 3200 /* stdin might have data for us, joy! */;
3159 else if (revents & EV_TIMEOUT) 3201 else if (revents & EV_TIMER)
3160 /* doh, nothing entered */; 3202 /* doh, nothing entered */;
3161 } 3203 }
3162 3204
3163 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3205 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164 3206
3298 myclass obj; 3340 myclass obj;
3299 ev::io iow; 3341 ev::io iow;
3300 iow.set <myclass, &myclass::io_cb> (&obj); 3342 iow.set <myclass, &myclass::io_cb> (&obj);
3301 3343
3302=item w->set (object *) 3344=item w->set (object *)
3303
3304This is an B<experimental> feature that might go away in a future version.
3305 3345
3306This is a variation of a method callback - leaving out the method to call 3346This is a variation of a method callback - leaving out the method to call
3307will default the method to C<operator ()>, which makes it possible to use 3347will default the method to C<operator ()>, which makes it possible to use
3308functor objects without having to manually specify the C<operator ()> all 3348functor objects without having to manually specify the C<operator ()> all
3309the time. Incidentally, you can then also leave out the template argument 3349the time. Incidentally, you can then also leave out the template argument
3622define before including (or compiling) any of its files. The default in 3662define before including (or compiling) any of its files. The default in
3623the absence of autoconf is documented for every option. 3663the absence of autoconf is documented for every option.
3624 3664
3625Symbols marked with "(h)" do not change the ABI, and can have different 3665Symbols marked with "(h)" do not change the ABI, and can have different
3626values when compiling libev vs. including F<ev.h>, so it is permissible 3666values when compiling libev vs. including F<ev.h>, so it is permissible
3627to redefine them before including F<ev.h> without breakign compatibility 3667to redefine them before including F<ev.h> without breaking compatibility
3628to a compiled library. All other symbols change the ABI, which means all 3668to a compiled library. All other symbols change the ABI, which means all
3629users of libev and the libev code itself must be compiled with compatible 3669users of libev and the libev code itself must be compiled with compatible
3630settings. 3670settings.
3631 3671
3632=over 4 3672=over 4
3838fine. 3878fine.
3839 3879
3840If your embedding application does not need any priorities, defining these 3880If your embedding application does not need any priorities, defining these
3841both to C<0> will save some memory and CPU. 3881both to C<0> will save some memory and CPU.
3842 3882
3843=item EV_PERIODIC_ENABLE 3883=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
3884EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3885EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3844 3886
3845If undefined or defined to be C<1>, then periodic timers are supported. If 3887If undefined or defined to be C<1> (and the platform supports it), then
3846defined to be C<0>, then they are not. Disabling them saves a few kB of 3888the respective watcher type is supported. If defined to be C<0>, then it
3847code. 3889is not. Disabling watcher types mainly saves code size.
3848 3890
3849=item EV_IDLE_ENABLE 3891=item EV_FEATURES
3850
3851If undefined or defined to be C<1>, then idle watchers are supported. If
3852defined to be C<0>, then they are not. Disabling them saves a few kB of
3853code.
3854
3855=item EV_EMBED_ENABLE
3856
3857If undefined or defined to be C<1>, then embed watchers are supported. If
3858defined to be C<0>, then they are not. Embed watchers rely on most other
3859watcher types, which therefore must not be disabled.
3860
3861=item EV_STAT_ENABLE
3862
3863If undefined or defined to be C<1>, then stat watchers are supported. If
3864defined to be C<0>, then they are not.
3865
3866=item EV_FORK_ENABLE
3867
3868If undefined or defined to be C<1>, then fork watchers are supported. If
3869defined to be C<0>, then they are not.
3870
3871=item EV_SIGNAL_ENABLE
3872
3873If undefined or defined to be C<1>, then signal watchers are supported. If
3874defined to be C<0>, then they are not.
3875
3876=item EV_ASYNC_ENABLE
3877
3878If undefined or defined to be C<1>, then async watchers are supported. If
3879defined to be C<0>, then they are not.
3880
3881=item EV_CHILD_ENABLE
3882
3883If undefined or defined to be C<1> (and C<_WIN32> is not defined), then
3884child watchers are supported. If defined to be C<0>, then they are not.
3885
3886=item EV_MINIMAL
3887 3892
3888If you need to shave off some kilobytes of code at the expense of some 3893If you need to shave off some kilobytes of code at the expense of some
3889speed (but with the full API), define this symbol to C<1>. Currently this 3894speed (but with the full API), you can define this symbol to request
3890is used to override some inlining decisions, saves roughly 30% code size 3895certain subsets of functionality. The default is to enable all features
3891on amd64. It also selects a much smaller 2-heap for timer management over 3896that can be enabled on the platform.
3892the default 4-heap.
3893 3897
3894You can save even more by disabling watcher types you do not need 3898A typical way to use this symbol is to define it to C<0> (or to a bitset
3895and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> 3899with some broad features you want) and then selectively re-enable
3896(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify, 3900additional parts you want, for example if you want everything minimal,
3897eventfd and signalfd will further help, and disabling backends one doesn't 3901but multiple event loop support, async and child watchers and the poll
3898need (e.g. poll, epoll, kqueue, ports) will help further. 3902backend, use this:
3899 3903
3900Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to 3904 #define EV_FEATURES 0
3901provide a bare-bones event library. See C<ev.h> for details on what parts
3902of the API are still available, and do not complain if this subset changes
3903over time.
3904
3905This example set of settings reduces the compiled size of libev from 24Kb
3906to 8Kb on my GNU/Linux amd64 system (and leaves little in - there is also
3907an effect on the amount of memory used). With an intelligent-enough linker
3908further unused functions might be left out as well automatically.
3909
3910 // tuning and API changes
3911 #define EV_MINIMAL 2
3912 #define EV_MULTIPLICITY 0 3905 #define EV_MULTIPLICITY 1
3913 #define EV_MINPRI 0
3914 #define EV_MAXPRI 0
3915
3916 // OS-specific backends
3917 #define EV_USE_INOTIFY 0
3918 #define EV_USE_EVENTFD 0
3919 #define EV_USE_SIGNALFD 0
3920 #define EV_USE_REALTIME 0
3921 #define EV_USE_MONOTONIC 0
3922 #define EV_USE_CLOCK_SYSCALL 0
3923
3924 // disable all backends except select
3925 #define EV_USE_POLL 0 3906 #define EV_USE_POLL 1
3926 #define EV_USE_PORT 0
3927 #define EV_USE_KQUEUE 0
3928 #define EV_USE_EPOLL 0
3929
3930 // disable all watcher types that cna be disabled
3931 #define EV_STAT_ENABLE 0
3932 #define EV_PERIODIC_ENABLE 0
3933 #define EV_IDLE_ENABLE 0
3934 #define EV_FORK_ENABLE 0
3935 #define EV_SIGNAL_ENABLE 0
3936 #define EV_CHILD_ENABLE 0 3907 #define EV_CHILD_ENABLE 1
3937 #define EV_ASYNC_ENABLE 0 3908 #define EV_ASYNC_ENABLE 1
3938 #define EV_EMBED_ENABLE 0 3909
3910The actual value is a bitset, it can be a combination of the following
3911values:
3912
3913=over 4
3914
3915=item C<1> - faster/larger code
3916
3917Use larger code to speed up some operations.
3918
3919Currently this is used to override some inlining decisions (enlarging the
3920code size by roughly 30% on amd64).
3921
3922When optimising for size, use of compiler flags such as C<-Os> with
3923gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3924assertions.
3925
3926=item C<2> - faster/larger data structures
3927
3928Replaces the small 2-heap for timer management by a faster 4-heap, larger
3929hash table sizes and so on. This will usually further increase code size
3930and can additionally have an effect on the size of data structures at
3931runtime.
3932
3933=item C<4> - full API configuration
3934
3935This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3936enables multiplicity (C<EV_MULTIPLICITY>=1).
3937
3938=item C<8> - full API
3939
3940This enables a lot of the "lesser used" API functions. See C<ev.h> for
3941details on which parts of the API are still available without this
3942feature, and do not complain if this subset changes over time.
3943
3944=item C<16> - enable all optional watcher types
3945
3946Enables all optional watcher types. If you want to selectively enable
3947only some watcher types other than I/O and timers (e.g. prepare,
3948embed, async, child...) you can enable them manually by defining
3949C<EV_watchertype_ENABLE> to C<1> instead.
3950
3951=item C<32> - enable all backends
3952
3953This enables all backends - without this feature, you need to enable at
3954least one backend manually (C<EV_USE_SELECT> is a good choice).
3955
3956=item C<64> - enable OS-specific "helper" APIs
3957
3958Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
3959default.
3960
3961=back
3962
3963Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
3964reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
3965code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
3966watchers, timers and monotonic clock support.
3967
3968With an intelligent-enough linker (gcc+binutils are intelligent enough
3969when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3970your program might be left out as well - a binary starting a timer and an
3971I/O watcher then might come out at only 5Kb.
3939 3972
3940=item EV_AVOID_STDIO 3973=item EV_AVOID_STDIO
3941 3974
3942If this is set to C<1> at compiletime, then libev will avoid using stdio 3975If this is set to C<1> at compiletime, then libev will avoid using stdio
3943functions (printf, scanf, perror etc.). This will increase the codesize 3976functions (printf, scanf, perror etc.). This will increase the code size
3944somewhat, but if your program doesn't otherwise depend on stdio and your 3977somewhat, but if your program doesn't otherwise depend on stdio and your
3945libc allows it, this avoids linking in the stdio library which is quite 3978libc allows it, this avoids linking in the stdio library which is quite
3946big. 3979big.
3947 3980
3948Note that error messages might become less precise when this option is 3981Note that error messages might become less precise when this option is
3952 3985
3953The highest supported signal number, +1 (or, the number of 3986The highest supported signal number, +1 (or, the number of
3954signals): Normally, libev tries to deduce the maximum number of signals 3987signals): Normally, libev tries to deduce the maximum number of signals
3955automatically, but sometimes this fails, in which case it can be 3988automatically, but sometimes this fails, in which case it can be
3956specified. Also, using a lower number than detected (C<32> should be 3989specified. Also, using a lower number than detected (C<32> should be
3957good for about any system in existance) can save some memory, as libev 3990good for about any system in existence) can save some memory, as libev
3958statically allocates some 12-24 bytes per signal number. 3991statically allocates some 12-24 bytes per signal number.
3959 3992
3960=item EV_PID_HASHSIZE 3993=item EV_PID_HASHSIZE
3961 3994
3962C<ev_child> watchers use a small hash table to distribute workload by 3995C<ev_child> watchers use a small hash table to distribute workload by
3963pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more 3996pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3964than enough. If you need to manage thousands of children you might want to 3997usually more than enough. If you need to manage thousands of children you
3965increase this value (I<must> be a power of two). 3998might want to increase this value (I<must> be a power of two).
3966 3999
3967=item EV_INOTIFY_HASHSIZE 4000=item EV_INOTIFY_HASHSIZE
3968 4001
3969C<ev_stat> watchers use a small hash table to distribute workload by 4002C<ev_stat> watchers use a small hash table to distribute workload by
3970inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 4003inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3971usually more than enough. If you need to manage thousands of C<ev_stat> 4004disabled), usually more than enough. If you need to manage thousands of
3972watchers you might want to increase this value (I<must> be a power of 4005C<ev_stat> watchers you might want to increase this value (I<must> be a
3973two). 4006power of two).
3974 4007
3975=item EV_USE_4HEAP 4008=item EV_USE_4HEAP
3976 4009
3977Heaps are not very cache-efficient. To improve the cache-efficiency of the 4010Heaps are not very cache-efficient. To improve the cache-efficiency of the
3978timer and periodics heaps, libev uses a 4-heap when this symbol is defined 4011timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3979to C<1>. The 4-heap uses more complicated (longer) code but has noticeably 4012to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3980faster performance with many (thousands) of watchers. 4013faster performance with many (thousands) of watchers.
3981 4014
3982The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4015The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3983(disabled). 4016will be C<0>.
3984 4017
3985=item EV_HEAP_CACHE_AT 4018=item EV_HEAP_CACHE_AT
3986 4019
3987Heaps are not very cache-efficient. To improve the cache-efficiency of the 4020Heaps are not very cache-efficient. To improve the cache-efficiency of the
3988timer and periodics heaps, libev can cache the timestamp (I<at>) within 4021timer and periodics heaps, libev can cache the timestamp (I<at>) within
3989the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), 4022the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3990which uses 8-12 bytes more per watcher and a few hundred bytes more code, 4023which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3991but avoids random read accesses on heap changes. This improves performance 4024but avoids random read accesses on heap changes. This improves performance
3992noticeably with many (hundreds) of watchers. 4025noticeably with many (hundreds) of watchers.
3993 4026
3994The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4027The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3995(disabled). 4028will be C<0>.
3996 4029
3997=item EV_VERIFY 4030=item EV_VERIFY
3998 4031
3999Controls how much internal verification (see C<ev_loop_verify ()>) will 4032Controls how much internal verification (see C<ev_loop_verify ()>) will
4000be done: If set to C<0>, no internal verification code will be compiled 4033be done: If set to C<0>, no internal verification code will be compiled
4002called. If set to C<2>, then the internal verification code will be 4035called. If set to C<2>, then the internal verification code will be
4003called once per loop, which can slow down libev. If set to C<3>, then the 4036called once per loop, which can slow down libev. If set to C<3>, then the
4004verification code will be called very frequently, which will slow down 4037verification code will be called very frequently, which will slow down
4005libev considerably. 4038libev considerably.
4006 4039
4007The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be 4040The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4008C<0>. 4041will be C<0>.
4009 4042
4010=item EV_COMMON 4043=item EV_COMMON
4011 4044
4012By default, all watchers have a C<void *data> member. By redefining 4045By default, all watchers have a C<void *data> member. By redefining
4013this macro to a something else you can include more and other types of 4046this macro to something else you can include more and other types of
4014members. You have to define it each time you include one of the files, 4047members. You have to define it each time you include one of the files,
4015though, and it must be identical each time. 4048though, and it must be identical each time.
4016 4049
4017For example, the perl EV module uses something like this: 4050For example, the perl EV module uses something like this:
4018 4051
4071file. 4104file.
4072 4105
4073The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 4106The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4074that everybody includes and which overrides some configure choices: 4107that everybody includes and which overrides some configure choices:
4075 4108
4076 #define EV_MINIMAL 1 4109 #define EV_FEATURES 8
4077 #define EV_USE_POLL 0 4110 #define EV_USE_SELECT 1
4078 #define EV_MULTIPLICITY 0
4079 #define EV_PERIODIC_ENABLE 0 4111 #define EV_PREPARE_ENABLE 1
4112 #define EV_IDLE_ENABLE 1
4080 #define EV_STAT_ENABLE 0 4113 #define EV_SIGNAL_ENABLE 1
4081 #define EV_FORK_ENABLE 0 4114 #define EV_CHILD_ENABLE 1
4115 #define EV_USE_STDEXCEPT 0
4082 #define EV_CONFIG_H <config.h> 4116 #define EV_CONFIG_H <config.h>
4083 #define EV_MINPRI 0
4084 #define EV_MAXPRI 0
4085 4117
4086 #include "ev++.h" 4118 #include "ev++.h"
4087 4119
4088And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 4120And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4089 4121
4318maintainable. 4350maintainable.
4319 4351
4320And of course, some compiler warnings are just plain stupid, or simply 4352And of course, some compiler warnings are just plain stupid, or simply
4321wrong (because they don't actually warn about the condition their message 4353wrong (because they don't actually warn about the condition their message
4322seems to warn about). For example, certain older gcc versions had some 4354seems to warn about). For example, certain older gcc versions had some
4323warnings that resulted an extreme number of false positives. These have 4355warnings that resulted in an extreme number of false positives. These have
4324been fixed, but some people still insist on making code warn-free with 4356been fixed, but some people still insist on making code warn-free with
4325such buggy versions. 4357such buggy versions.
4326 4358
4327While libev is written to generate as few warnings as possible, 4359While libev is written to generate as few warnings as possible,
4328"warn-free" code is not a goal, and it is recommended not to build libev 4360"warn-free" code is not a goal, and it is recommended not to build libev
4364I suggest using suppression lists. 4396I suggest using suppression lists.
4365 4397
4366 4398
4367=head1 PORTABILITY NOTES 4399=head1 PORTABILITY NOTES
4368 4400
4401=head2 GNU/LINUX 32 BIT LIMITATIONS
4402
4403GNU/Linux is the only common platform that supports 64 bit file/large file
4404interfaces but I<disables> them by default.
4405
4406That means that libev compiled in the default environment doesn't support
4407files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
4408
4409Unfortunately, many programs try to work around this GNU/Linux issue
4410by enabling the large file API, which makes them incompatible with the
4411standard libev compiled for their system.
4412
4413Likewise, libev cannot enable the large file API itself as this would
4414suddenly make it incompatible to the default compile time environment,
4415i.e. all programs not using special compile switches.
4416
4417=head2 OS/X AND DARWIN BUGS
4418
4419The whole thing is a bug if you ask me - basically any system interface
4420you touch is broken, whether it is locales, poll, kqueue or even the
4421OpenGL drivers.
4422
4423=head3 C<kqueue> is buggy
4424
4425The kqueue syscall is broken in all known versions - most versions support
4426only sockets, many support pipes.
4427
4428Libev tries to work around this by not using C<kqueue> by default on
4429this rotten platform, but of course you can still ask for it when creating
4430a loop.
4431
4432=head3 C<poll> is buggy
4433
4434Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4435implementation by something calling C<kqueue> internally around the 10.5.6
4436release, so now C<kqueue> I<and> C<poll> are broken.
4437
4438Libev tries to work around this by not using C<poll> by default on
4439this rotten platform, but of course you can still ask for it when creating
4440a loop.
4441
4442=head3 C<select> is buggy
4443
4444All that's left is C<select>, and of course Apple found a way to fuck this
4445one up as well: On OS/X, C<select> actively limits the number of file
4446descriptors you can pass in to 1024 - your program suddenly crashes when
4447you use more.
4448
4449There is an undocumented "workaround" for this - defining
4450C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
4451work on OS/X.
4452
4453=head2 SOLARIS PROBLEMS AND WORKAROUNDS
4454
4455=head3 C<errno> reentrancy
4456
4457The default compile environment on Solaris is unfortunately so
4458thread-unsafe that you can't even use components/libraries compiled
4459without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
4460isn't defined by default.
4461
4462If you want to use libev in threaded environments you have to make sure
4463it's compiled with C<_REENTRANT> defined.
4464
4465=head3 Event port backend
4466
4467The scalable event interface for Solaris is called "event ports". Unfortunately,
4468this mechanism is very buggy. If you run into high CPU usage, your program
4469freezes or you get a large number of spurious wakeups, make sure you have
4470all the relevant and latest kernel patches applied. No, I don't know which
4471ones, but there are multiple ones.
4472
4473If you can't get it to work, you can try running the program by setting
4474the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4475C<select> backends.
4476
4477=head2 AIX POLL BUG
4478
4479AIX unfortunately has a broken C<poll.h> header. Libev works around
4480this by trying to avoid the poll backend altogether (i.e. it's not even
4481compiled in), which normally isn't a big problem as C<select> works fine
4482with large bitsets, and AIX is dead anyway.
4483
4369=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS 4484=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4485
4486=head3 General issues
4370 4487
4371Win32 doesn't support any of the standards (e.g. POSIX) that libev 4488Win32 doesn't support any of the standards (e.g. POSIX) that libev
4372requires, and its I/O model is fundamentally incompatible with the POSIX 4489requires, and its I/O model is fundamentally incompatible with the POSIX
4373model. Libev still offers limited functionality on this platform in 4490model. Libev still offers limited functionality on this platform in
4374the form of the C<EVBACKEND_SELECT> backend, and only supports socket 4491the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4375descriptors. This only applies when using Win32 natively, not when using 4492descriptors. This only applies when using Win32 natively, not when using
4376e.g. cygwin. 4493e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4494as every compielr comes with a slightly differently broken/incompatible
4495environment.
4377 4496
4378Lifting these limitations would basically require the full 4497Lifting these limitations would basically require the full
4379re-implementation of the I/O system. If you are into these kinds of 4498re-implementation of the I/O system. If you are into this kind of thing,
4380things, then note that glib does exactly that for you in a very portable 4499then note that glib does exactly that for you in a very portable way (note
4381way (note also that glib is the slowest event library known to man). 4500also that glib is the slowest event library known to man).
4382 4501
4383There is no supported compilation method available on windows except 4502There is no supported compilation method available on windows except
4384embedding it into other applications. 4503embedding it into other applications.
4385 4504
4386Sensible signal handling is officially unsupported by Microsoft - libev 4505Sensible signal handling is officially unsupported by Microsoft - libev
4414you do I<not> compile the F<ev.c> or any other embedded source files!): 4533you do I<not> compile the F<ev.c> or any other embedded source files!):
4415 4534
4416 #include "evwrap.h" 4535 #include "evwrap.h"
4417 #include "ev.c" 4536 #include "ev.c"
4418 4537
4419=over 4
4420
4421=item The winsocket select function 4538=head3 The winsocket C<select> function
4422 4539
4423The winsocket C<select> function doesn't follow POSIX in that it 4540The winsocket C<select> function doesn't follow POSIX in that it
4424requires socket I<handles> and not socket I<file descriptors> (it is 4541requires socket I<handles> and not socket I<file descriptors> (it is
4425also extremely buggy). This makes select very inefficient, and also 4542also extremely buggy). This makes select very inefficient, and also
4426requires a mapping from file descriptors to socket handles (the Microsoft 4543requires a mapping from file descriptors to socket handles (the Microsoft
4435 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ 4552 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4436 4553
4437Note that winsockets handling of fd sets is O(n), so you can easily get a 4554Note that winsockets handling of fd sets is O(n), so you can easily get a
4438complexity in the O(n²) range when using win32. 4555complexity in the O(n²) range when using win32.
4439 4556
4440=item Limited number of file descriptors 4557=head3 Limited number of file descriptors
4441 4558
4442Windows has numerous arbitrary (and low) limits on things. 4559Windows has numerous arbitrary (and low) limits on things.
4443 4560
4444Early versions of winsocket's select only supported waiting for a maximum 4561Early versions of winsocket's select only supported waiting for a maximum
4445of C<64> handles (probably owning to the fact that all windows kernels 4562of C<64> handles (probably owning to the fact that all windows kernels
4460runtime libraries. This might get you to about C<512> or C<2048> sockets 4577runtime libraries. This might get you to about C<512> or C<2048> sockets
4461(depending on windows version and/or the phase of the moon). To get more, 4578(depending on windows version and/or the phase of the moon). To get more,
4462you need to wrap all I/O functions and provide your own fd management, but 4579you need to wrap all I/O functions and provide your own fd management, but
4463the cost of calling select (O(n²)) will likely make this unworkable. 4580the cost of calling select (O(n²)) will likely make this unworkable.
4464 4581
4465=back
4466
4467=head2 PORTABILITY REQUIREMENTS 4582=head2 PORTABILITY REQUIREMENTS
4468 4583
4469In addition to a working ISO-C implementation and of course the 4584In addition to a working ISO-C implementation and of course the
4470backend-specific APIs, libev relies on a few additional extensions: 4585backend-specific APIs, libev relies on a few additional extensions:
4471 4586
4591involves iterating over all running async watchers or all signal numbers. 4706involves iterating over all running async watchers or all signal numbers.
4592 4707
4593=back 4708=back
4594 4709
4595 4710
4711=head1 PORTING FROM LIBEV 3.X TO 4.X
4712
4713The major version 4 introduced some minor incompatible changes to the API.
4714
4715At the moment, the C<ev.h> header file tries to implement superficial
4716compatibility, so most programs should still compile. Those might be
4717removed in later versions of libev, so better update early than late.
4718
4719=over 4
4720
4721=item C<ev_loop_count> renamed to C<ev_iteration>
4722
4723=item C<ev_loop_depth> renamed to C<ev_depth>
4724
4725=item C<ev_loop_verify> renamed to C<ev_verify>
4726
4727Most functions working on C<struct ev_loop> objects don't have an
4728C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
4729still called C<ev_loop_fork> because it would otherwise clash with the
4730C<ev_fork> typedef.
4731
4732=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4733
4734This is a simple rename - all other watcher types use their name
4735as revents flag, and now C<ev_timer> does, too.
4736
4737Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4738and continue to be present for the foreseeable future, so this is mostly a
4739documentation change.
4740
4741=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4742
4743The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4744mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4745and work, but the library code will of course be larger.
4746
4747=back
4748
4749
4596=head1 GLOSSARY 4750=head1 GLOSSARY
4597 4751
4598=over 4 4752=over 4
4599 4753
4600=item active 4754=item active
4621A change of state of some external event, such as data now being available 4775A change of state of some external event, such as data now being available
4622for reading on a file descriptor, time having passed or simply not having 4776for reading on a file descriptor, time having passed or simply not having
4623any other events happening anymore. 4777any other events happening anymore.
4624 4778
4625In libev, events are represented as single bits (such as C<EV_READ> or 4779In libev, events are represented as single bits (such as C<EV_READ> or
4626C<EV_TIMEOUT>). 4780C<EV_TIMER>).
4627 4781
4628=item event library 4782=item event library
4629 4783
4630A software package implementing an event model and loop. 4784A software package implementing an event model and loop.
4631 4785

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