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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
439of course I<doesn't>, and epoll just loves to report events for totally 439of course I<doesn't>, and epoll just loves to report events for totally
440I<different> file descriptors (even already closed ones, so one cannot 440I<different> file descriptors (even already closed ones, so one cannot
441even remove them from the set) than registered in the set (especially 441even remove them from the set) than registered in the set (especially
442on SMP systems). Libev tries to counter these spurious notifications by 442on SMP systems). Libev tries to counter these spurious notifications by
443employing an additional generation counter and comparing that against the 443employing an additional generation counter and comparing that against the
444events to filter out spurious ones, recreating the set when required. 444events to filter out spurious ones, recreating the set when required. Last
445not least, it also refuses to work with some file descriptors which work
446perfectly fine with C<select> (files, many character devices...).
445 447
446While stopping, setting and starting an I/O watcher in the same iteration 448While stopping, setting and starting an I/O watcher in the same iteration
447will result in some caching, there is still a system call per such 449will result in some caching, there is still a system call per such
448incident (because the same I<file descriptor> could point to a different 450incident (because the same I<file descriptor> could point to a different
449I<file description> now), so its best to avoid that. Also, C<dup ()>'ed 451I<file description> now), so its best to avoid that. Also, C<dup ()>'ed
567 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); 569 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
568 570
569=item struct ev_loop *ev_loop_new (unsigned int flags) 571=item struct ev_loop *ev_loop_new (unsigned int flags)
570 572
571Similar to C<ev_default_loop>, but always creates a new event loop that is 573Similar 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 574always 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).
575 575
576Note that this function I<is> thread-safe, and the recommended way to use 576Note 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 577libev with threads is indeed to create one loop per thread, and using the
578default loop in the "main" or "initial" thread. 578default loop in the "main" or "initial" thread.
579 579
580Example: Try to create a event loop that uses epoll and nothing else. 580Example: Try to create a event loop that uses epoll and nothing else.
581 581
583 if (!epoller) 583 if (!epoller)
584 fatal ("no epoll found here, maybe it hides under your chair"); 584 fatal ("no epoll found here, maybe it hides under your chair");
585 585
586=item ev_default_destroy () 586=item ev_default_destroy ()
587 587
588Destroys the default loop again (frees all memory and kernel state 588Destroys the default loop (frees all memory and kernel state etc.). None
589etc.). None of the active event watchers will be stopped in the normal 589of 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 590e.g. C<ev_is_active> might still return true. It is your responsibility to
591responsibility to either stop all watchers cleanly yourself I<before> 591either stop all watchers cleanly yourself I<before> calling this function,
592calling this function, or cope with the fact afterwards (which is usually 592or 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 593can just ignore the watchers and/or C<free ()> them for example).
594for example).
595 594
596Note that certain global state, such as signal state (and installed signal 595Note that certain global state, such as signal state (and installed signal
597handlers), will not be freed by this function, and related watchers (such 596handlers), will not be freed by this function, and related watchers (such
598as signal and child watchers) would need to be stopped manually. 597as signal and child watchers) would need to be stopped manually.
599 598
614name, you can call it anytime, but it makes most sense after forking, in 613name, 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 614the 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 615sense). 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. 616functions, and it will only take effect at the next C<ev_loop> iteration.
618 617
618Again, you I<have> to call it on I<any> loop that you want to re-use after
619a fork, I<even if you do not plan to use the loop in the parent>. This is
620because some kernel interfaces *cough* I<kqueue> *cough* do funny things
621during fork.
622
619On the other hand, you only need to call this function in the child 623On 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 624process 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. 625just fork+exec or create a new loop in the child, you don't have to call
626it at all.
622 627
623The function itself is quite fast and it's usually not a problem to call 628The 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 629it just in case after a fork. To make this easy, the function will fit in
625quite nicely into a call to C<pthread_atfork>: 630quite nicely into a call to C<pthread_atfork>:
626 631
628 633
629=item ev_loop_fork (loop) 634=item ev_loop_fork (loop)
630 635
631Like C<ev_default_fork>, but acts on an event loop created by 636Like 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 637C<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 638after fork that you want to re-use in the child, and how you keep track of
634entirely your own problem. 639them is entirely your own problem.
635 640
636=item int ev_is_default_loop (loop) 641=item int ev_is_default_loop (loop)
637 642
638Returns true when the given loop is, in fact, the default loop, and false 643Returns true when the given loop is, in fact, the default loop, and false
639otherwise. 644otherwise.
640 645
641=item unsigned int ev_loop_count (loop) 646=item unsigned int ev_iteration (loop)
642 647
643Returns the count of loop iterations for the loop, which is identical to 648Returns 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 649the number of times libev did poll for new events. It starts at C<0> and
645happily wraps around with enough iterations. 650happily wraps around with enough iterations.
646 651
647This value can sometimes be useful as a generation counter of sorts (it 652This value can sometimes be useful as a generation counter of sorts (it
648"ticks" the number of loop iterations), as it roughly corresponds with 653"ticks" the number of loop iterations), as it roughly corresponds with
649C<ev_prepare> and C<ev_check> calls. 654C<ev_prepare> and C<ev_check> calls - and is incremented between the
655prepare and check phases.
650 656
651=item unsigned int ev_loop_depth (loop) 657=item unsigned int ev_depth (loop)
652 658
653Returns the number of times C<ev_loop> was entered minus the number of 659Returns 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. 660times C<ev_loop> was exited, in other words, the recursion depth.
655 661
656Outside C<ev_loop>, this number is zero. In a callback, this number is 662Outside 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), 663C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
658in which case it is higher. 664in which case it is higher.
659 665
660Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread 666Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
661etc.), doesn't count as exit. 667etc.), doesn't count as "exit" - consider this as a hint to avoid such
668ungentleman behaviour unless it's really convenient.
662 669
663=item unsigned int ev_backend (loop) 670=item unsigned int ev_backend (loop)
664 671
665Returns one of the C<EVBACKEND_*> flags indicating the event backend in 672Returns one of the C<EVBACKEND_*> flags indicating the event backend in
666use. 673use.
700C<ev_resume> directly afterwards to resume timer processing. 707C<ev_resume> directly afterwards to resume timer processing.
701 708
702Effectively, all C<ev_timer> watchers will be delayed by the time spend 709Effectively, 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 710between 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 711will be rescheduled (that is, they will lose any events that would have
705occured while suspended). 712occurred while suspended).
706 713
707After calling C<ev_suspend> you B<must not> call I<any> function on the 714After 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> 715given loop other than C<ev_resume>, and you B<must not> call C<ev_resume>
709without a previous call to C<ev_suspend>. 716without a previous call to C<ev_suspend>.
710 717
787C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or 794C<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. 795C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
789 796
790This "unloop state" will be cleared when entering C<ev_loop> again. 797This "unloop state" will be cleared when entering C<ev_loop> again.
791 798
792It is safe to call C<ev_unloop> from otuside any C<ev_loop> calls. 799It is safe to call C<ev_unloop> from outside any C<ev_loop> calls.
793 800
794=item ev_ref (loop) 801=item ev_ref (loop)
795 802
796=item ev_unref (loop) 803=item ev_unref (loop)
797 804
867usually doesn't make much sense to set it to a lower value than C<0.01>, 874usually 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 875as this approaches the timing granularity of most systems. Note that if
869you do transactions with the outside world and you can't increase the 876you do transactions with the outside world and you can't increase the
870parallelity, then this setting will limit your transaction rate (if you 877parallelity, 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, 878need 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). 879then you can't do more than 100 transactions per second).
873 880
874Setting the I<timeout collect interval> can improve the opportunity for 881Setting the I<timeout collect interval> can improve the opportunity for
875saving power, as the program will "bundle" timer callback invocations that 882saving power, as the program will "bundle" timer callback invocations that
876are "near" in time together, by delaying some, thus reducing the number of 883are "near" in time together, by delaying some, thus reducing the number of
877times the process sleeps and wakes up again. Another useful technique to 884times the process sleeps and wakes up again. Another useful technique to
1375 1382
1376For example, to emulate how many other event libraries handle priorities, 1383For example, to emulate how many other event libraries handle priorities,
1377you can associate an C<ev_idle> watcher to each such watcher, and in 1384you 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 1385the normal watcher callback, you just start the idle watcher. The real
1379processing is done in the idle watcher callback. This causes libev to 1386processing is done in the idle watcher callback. This causes libev to
1380continously poll and process kernel event data for the watcher, but when 1387continuously 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 1388the lock-out case is known to be rare (which in turn is rare :), this is
1382workable. 1389workable.
1383 1390
1384Usually, however, the lock-out model implemented that way will perform 1391Usually, however, the lock-out model implemented that way will perform
1385miserably under the type of load it was designed to handle. In that case, 1392miserably under the type of load it was designed to handle. In that case,
1399 { 1406 {
1400 // stop the I/O watcher, we received the event, but 1407 // stop the I/O watcher, we received the event, but
1401 // are not yet ready to handle it. 1408 // are not yet ready to handle it.
1402 ev_io_stop (EV_A_ w); 1409 ev_io_stop (EV_A_ w);
1403 1410
1404 // start the idle watcher to ahndle the actual event. 1411 // start the idle watcher to handle the actual event.
1405 // it will not be executed as long as other watchers 1412 // it will not be executed as long as other watchers
1406 // with the default priority are receiving events. 1413 // with the default priority are receiving events.
1407 ev_idle_start (EV_A_ &idle); 1414 ev_idle_start (EV_A_ &idle);
1408 } 1415 }
1409 1416
1463 1470
1464If you cannot use non-blocking mode, then force the use of a 1471If 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 1472known-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 1473C<EVBACKEND_SELECT> and C<EVBACKEND_POLL>). The same applies to file
1467descriptors for which non-blocking operation makes no sense (such as 1474descriptors for which non-blocking operation makes no sense (such as
1468files) - libev doesn't guarentee any specific behaviour in that case. 1475files) - libev doesn't guarantee any specific behaviour in that case.
1469 1476
1470Another thing you have to watch out for is that it is quite easy to 1477Another thing you have to watch out for is that it is quite easy to
1471receive "spurious" readiness notifications, that is your callback might 1478receive "spurious" readiness notifications, that is your callback might
1472be called with C<EV_READ> but a subsequent C<read>(2) will actually block 1479be 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 1480because there is no data. Not only are some backends known to create a
1541somewhere, as that would have given you a big clue). 1548somewhere, as that would have given you a big clue).
1542 1549
1543=head3 The special problem of accept()ing when you can't 1550=head3 The special problem of accept()ing when you can't
1544 1551
1545Many implementations of the POSIX C<accept> function (for example, 1552Many implementations of the POSIX C<accept> function (for example,
1546found in port-2004 Linux) have the peculiar behaviour of not removing a 1553found in post-2004 Linux) have the peculiar behaviour of not removing a
1547connection from the pending queue in all error cases. 1554connection from the pending queue in all error cases.
1548 1555
1549For example, larger servers often run out of file descriptors (because 1556For example, larger servers often run out of file descriptors (because
1550of resource limits), causing C<accept> to fail with C<ENFILE> but not 1557of resource limits), causing C<accept> to fail with C<ENFILE> but not
1551rejecting the connection, leading to libev signalling readiness on 1558rejecting the connection, leading to libev signalling readiness on
1732 ev_tstamp timeout = last_activity + 60.; 1739 ev_tstamp timeout = last_activity + 60.;
1733 1740
1734 // if last_activity + 60. is older than now, we did time out 1741 // if last_activity + 60. is older than now, we did time out
1735 if (timeout < now) 1742 if (timeout < now)
1736 { 1743 {
1737 // timeout occured, take action 1744 // timeout occurred, take action
1738 } 1745 }
1739 else 1746 else
1740 { 1747 {
1741 // callback was invoked, but there was some activity, re-arm 1748 // callback was invoked, but there was some activity, re-arm
1742 // the watcher to fire in last_activity + 60, which is 1749 // the watcher to fire in last_activity + 60, which is
1769 callback (loop, timer, EV_TIMER); 1776 callback (loop, timer, EV_TIMER);
1770 1777
1771And when there is some activity, simply store the current time in 1778And when there is some activity, simply store the current time in
1772C<last_activity>, no libev calls at all: 1779C<last_activity>, no libev calls at all:
1773 1780
1774 last_actiivty = ev_now (loop); 1781 last_activity = ev_now (loop);
1775 1782
1776This technique is slightly more complex, but in most cases where the 1783This technique is slightly more complex, but in most cases where the
1777time-out is unlikely to be triggered, much more efficient. 1784time-out is unlikely to be triggered, much more efficient.
1778 1785
1779Changing the timeout is trivial as well (if it isn't hard-coded in the 1786Changing the timeout is trivial as well (if it isn't hard-coded in the
2118Example: Call a callback every hour, or, more precisely, whenever the 2125Example: Call a callback every hour, or, more precisely, whenever the
2119system time is divisible by 3600. The callback invocation times have 2126system time is divisible by 3600. The callback invocation times have
2120potentially a lot of jitter, but good long-term stability. 2127potentially a lot of jitter, but good long-term stability.
2121 2128
2122 static void 2129 static void
2123 clock_cb (struct ev_loop *loop, ev_io *w, int revents) 2130 clock_cb (struct ev_loop *loop, ev_periodic *w, int revents)
2124 { 2131 {
2125 ... its now a full hour (UTC, or TAI or whatever your clock follows) 2132 ... its now a full hour (UTC, or TAI or whatever your clock follows)
2126 } 2133 }
2127 2134
2128 ev_periodic hourly_tick; 2135 ev_periodic hourly_tick;
2960C<ev_default_fork> cheats and calls it in the wrong process, the fork 2967C<ev_default_fork> cheats and calls it in the wrong process, the fork
2961handlers will be invoked, too, of course. 2968handlers will be invoked, too, of course.
2962 2969
2963=head3 The special problem of life after fork - how is it possible? 2970=head3 The special problem of life after fork - how is it possible?
2964 2971
2965Most uses of C<fork()> consist of forking, then some simple calls to ste 2972Most uses of C<fork()> consist of forking, then some simple calls to set
2966up/change the process environment, followed by a call to C<exec()>. This 2973up/change the process environment, followed by a call to C<exec()>. This
2967sequence should be handled by libev without any problems. 2974sequence should be handled by libev without any problems.
2968 2975
2969This changes when the application actually wants to do event handling 2976This changes when the application actually wants to do event handling
2970in the child, or both parent in child, in effect "continuing" after the 2977in the child, or both parent in child, in effect "continuing" after the
3004believe me. 3011believe me.
3005 3012
3006=back 3013=back
3007 3014
3008 3015
3009=head2 C<ev_async> - how to wake up another event loop 3016=head2 C<ev_async> - how to wake up an event loop
3010 3017
3011In general, you cannot use an C<ev_loop> from multiple threads or other 3018In general, you cannot use an C<ev_loop> from multiple threads or other
3012asynchronous sources such as signal handlers (as opposed to multiple event 3019asynchronous sources such as signal handlers (as opposed to multiple event
3013loops - those are of course safe to use in different threads). 3020loops - those are of course safe to use in different threads).
3014 3021
3015Sometimes, however, you need to wake up another event loop you do not 3022Sometimes, however, you need to wake up an event loop you do not control,
3016control, for example because it belongs to another thread. This is what 3023for example because it belongs to another thread. This is what C<ev_async>
3017C<ev_async> watchers do: as long as the C<ev_async> watcher is active, you 3024watchers do: as long as the C<ev_async> watcher is active, you can signal
3018can signal it by calling C<ev_async_send>, which is thread- and signal 3025it by calling C<ev_async_send>, which is thread- and signal safe.
3019safe.
3020 3026
3021This functionality is very similar to C<ev_signal> watchers, as signals, 3027This functionality is very similar to C<ev_signal> watchers, as signals,
3022too, are asynchronous in nature, and signals, too, will be compressed 3028too, are asynchronous in nature, and signals, too, will be compressed
3023(i.e. the number of callback invocations may be less than the number of 3029(i.e. the number of callback invocations may be less than the number of
3024C<ev_async_sent> calls). 3030C<ev_async_sent> calls).
3336 myclass obj; 3342 myclass obj;
3337 ev::io iow; 3343 ev::io iow;
3338 iow.set <myclass, &myclass::io_cb> (&obj); 3344 iow.set <myclass, &myclass::io_cb> (&obj);
3339 3345
3340=item w->set (object *) 3346=item w->set (object *)
3341
3342This is an B<experimental> feature that might go away in a future version.
3343 3347
3344This is a variation of a method callback - leaving out the method to call 3348This is a variation of a method callback - leaving out the method to call
3345will default the method to C<operator ()>, which makes it possible to use 3349will default the method to C<operator ()>, which makes it possible to use
3346functor objects without having to manually specify the C<operator ()> all 3350functor objects without having to manually specify the C<operator ()> all
3347the time. Incidentally, you can then also leave out the template argument 3351the time. Incidentally, you can then also leave out the template argument
3660define before including (or compiling) any of its files. The default in 3664define before including (or compiling) any of its files. The default in
3661the absence of autoconf is documented for every option. 3665the absence of autoconf is documented for every option.
3662 3666
3663Symbols marked with "(h)" do not change the ABI, and can have different 3667Symbols marked with "(h)" do not change the ABI, and can have different
3664values when compiling libev vs. including F<ev.h>, so it is permissible 3668values when compiling libev vs. including F<ev.h>, so it is permissible
3665to redefine them before including F<ev.h> without breakign compatibility 3669to redefine them before including F<ev.h> without breaking compatibility
3666to a compiled library. All other symbols change the ABI, which means all 3670to a compiled library. All other symbols change the ABI, which means all
3667users of libev and the libev code itself must be compiled with compatible 3671users of libev and the libev code itself must be compiled with compatible
3668settings. 3672settings.
3669 3673
3670=over 4 3674=over 4
3882EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE, 3886EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3883EV_ASYNC_ENABLE, EV_CHILD_ENABLE. 3887EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3884 3888
3885If undefined or defined to be C<1> (and the platform supports it), then 3889If undefined or defined to be C<1> (and the platform supports it), then
3886the respective watcher type is supported. If defined to be C<0>, then it 3890the respective watcher type is supported. If defined to be C<0>, then it
3887is not. Disabling watcher types mainly saves codesize. 3891is not. Disabling watcher types mainly saves code size.
3888 3892
3889=item EV_FEATURES 3893=item EV_FEATURES
3890 3894
3891If you need to shave off some kilobytes of code at the expense of some 3895If you need to shave off some kilobytes of code at the expense of some
3892speed (but with the full API), you can define this symbol to request 3896speed (but with the full API), you can define this symbol to request
3912 3916
3913=item C<1> - faster/larger code 3917=item C<1> - faster/larger code
3914 3918
3915Use larger code to speed up some operations. 3919Use larger code to speed up some operations.
3916 3920
3917Currently this is used to override some inlining decisions (enlarging the roughly 3921Currently this is used to override some inlining decisions (enlarging the
391830% code size on amd64. 3922code size by roughly 30% on amd64).
3919 3923
3920When optimising for size, use of compiler flags such as C<-Os> with 3924When optimising for size, use of compiler flags such as C<-Os> with
3921gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of 3925gcc is recommended, as well as C<-DNDEBUG>, as libev contains a number of
3922assertions. 3926assertions.
3923 3927
3924=item C<2> - faster/larger data structures 3928=item C<2> - faster/larger data structures
3925 3929
3926Replaces the small 2-heap for timer management by a faster 4-heap, larger 3930Replaces the small 2-heap for timer management by a faster 4-heap, larger
3927hash table sizes and so on. This will usually further increase codesize 3931hash table sizes and so on. This will usually further increase code size
3928and can additionally have an effect on the size of data structures at 3932and can additionally have an effect on the size of data structures at
3929runtime. 3933runtime.
3930 3934
3931=item C<4> - full API configuration 3935=item C<4> - full API configuration
3932 3936
3969I/O watcher then might come out at only 5Kb. 3973I/O watcher then might come out at only 5Kb.
3970 3974
3971=item EV_AVOID_STDIO 3975=item EV_AVOID_STDIO
3972 3976
3973If this is set to C<1> at compiletime, then libev will avoid using stdio 3977If this is set to C<1> at compiletime, then libev will avoid using stdio
3974functions (printf, scanf, perror etc.). This will increase the codesize 3978functions (printf, scanf, perror etc.). This will increase the code size
3975somewhat, but if your program doesn't otherwise depend on stdio and your 3979somewhat, but if your program doesn't otherwise depend on stdio and your
3976libc allows it, this avoids linking in the stdio library which is quite 3980libc allows it, this avoids linking in the stdio library which is quite
3977big. 3981big.
3978 3982
3979Note that error messages might become less precise when this option is 3983Note that error messages might become less precise when this option is
3983 3987
3984The highest supported signal number, +1 (or, the number of 3988The highest supported signal number, +1 (or, the number of
3985signals): Normally, libev tries to deduce the maximum number of signals 3989signals): Normally, libev tries to deduce the maximum number of signals
3986automatically, but sometimes this fails, in which case it can be 3990automatically, but sometimes this fails, in which case it can be
3987specified. Also, using a lower number than detected (C<32> should be 3991specified. Also, using a lower number than detected (C<32> should be
3988good for about any system in existance) can save some memory, as libev 3992good for about any system in existence) can save some memory, as libev
3989statically allocates some 12-24 bytes per signal number. 3993statically allocates some 12-24 bytes per signal number.
3990 3994
3991=item EV_PID_HASHSIZE 3995=item EV_PID_HASHSIZE
3992 3996
3993C<ev_child> watchers use a small hash table to distribute workload by 3997C<ev_child> watchers use a small hash table to distribute workload by
4039will be C<0>. 4043will be C<0>.
4040 4044
4041=item EV_COMMON 4045=item EV_COMMON
4042 4046
4043By default, all watchers have a C<void *data> member. By redefining 4047By default, all watchers have a C<void *data> member. By redefining
4044this macro to a something else you can include more and other types of 4048this macro to something else you can include more and other types of
4045members. You have to define it each time you include one of the files, 4049members. You have to define it each time you include one of the files,
4046though, and it must be identical each time. 4050though, and it must be identical each time.
4047 4051
4048For example, the perl EV module uses something like this: 4052For example, the perl EV module uses something like this:
4049 4053
4348maintainable. 4352maintainable.
4349 4353
4350And of course, some compiler warnings are just plain stupid, or simply 4354And of course, some compiler warnings are just plain stupid, or simply
4351wrong (because they don't actually warn about the condition their message 4355wrong (because they don't actually warn about the condition their message
4352seems to warn about). For example, certain older gcc versions had some 4356seems to warn about). For example, certain older gcc versions had some
4353warnings that resulted an extreme number of false positives. These have 4357warnings that resulted in an extreme number of false positives. These have
4354been fixed, but some people still insist on making code warn-free with 4358been fixed, but some people still insist on making code warn-free with
4355such buggy versions. 4359such buggy versions.
4356 4360
4357While libev is written to generate as few warnings as possible, 4361While libev is written to generate as few warnings as possible,
4358"warn-free" code is not a goal, and it is recommended not to build libev 4362"warn-free" code is not a goal, and it is recommended not to build libev
4394I suggest using suppression lists. 4398I suggest using suppression lists.
4395 4399
4396 4400
4397=head1 PORTABILITY NOTES 4401=head1 PORTABILITY NOTES
4398 4402
4403=head2 GNU/LINUX 32 BIT LIMITATIONS
4404
4405GNU/Linux is the only common platform that supports 64 bit file/large file
4406interfaces but I<disables> them by default.
4407
4408That means that libev compiled in the default environment doesn't support
4409files larger than 2GiB or so, which mainly affects C<ev_stat> watchers.
4410
4411Unfortunately, many programs try to work around this GNU/Linux issue
4412by enabling the large file API, which makes them incompatible with the
4413standard libev compiled for their system.
4414
4415Likewise, libev cannot enable the large file API itself as this would
4416suddenly make it incompatible to the default compile time environment,
4417i.e. all programs not using special compile switches.
4418
4419=head2 OS/X AND DARWIN BUGS
4420
4421The whole thing is a bug if you ask me - basically any system interface
4422you touch is broken, whether it is locales, poll, kqueue or even the
4423OpenGL drivers.
4424
4425=head3 C<kqueue> is buggy
4426
4427The kqueue syscall is broken in all known versions - most versions support
4428only sockets, many support pipes.
4429
4430Libev tries to work around this by not using C<kqueue> by default on
4431this rotten platform, but of course you can still ask for it when creating
4432a loop.
4433
4434=head3 C<poll> is buggy
4435
4436Instead of fixing C<kqueue>, Apple replaced their (working) C<poll>
4437implementation by something calling C<kqueue> internally around the 10.5.6
4438release, so now C<kqueue> I<and> C<poll> are broken.
4439
4440Libev tries to work around this by not using C<poll> by default on
4441this rotten platform, but of course you can still ask for it when creating
4442a loop.
4443
4444=head3 C<select> is buggy
4445
4446All that's left is C<select>, and of course Apple found a way to fuck this
4447one up as well: On OS/X, C<select> actively limits the number of file
4448descriptors you can pass in to 1024 - your program suddenly crashes when
4449you use more.
4450
4451There is an undocumented "workaround" for this - defining
4452C<_DARWIN_UNLIMITED_SELECT>, which libev tries to use, so select I<should>
4453work on OS/X.
4454
4455=head2 SOLARIS PROBLEMS AND WORKAROUNDS
4456
4457=head3 C<errno> reentrancy
4458
4459The default compile environment on Solaris is unfortunately so
4460thread-unsafe that you can't even use components/libraries compiled
4461without C<-D_REENTRANT> (as long as they use C<errno>), which, of course,
4462isn't defined by default.
4463
4464If you want to use libev in threaded environments you have to make sure
4465it's compiled with C<_REENTRANT> defined.
4466
4467=head3 Event port backend
4468
4469The scalable event interface for Solaris is called "event ports". Unfortunately,
4470this mechanism is very buggy. If you run into high CPU usage, your program
4471freezes or you get a large number of spurious wakeups, make sure you have
4472all the relevant and latest kernel patches applied. No, I don't know which
4473ones, but there are multiple ones.
4474
4475If you can't get it to work, you can try running the program by setting
4476the environment variable C<LIBEV_FLAGS=3> to only allow C<poll> and
4477C<select> backends.
4478
4479=head2 AIX POLL BUG
4480
4481AIX unfortunately has a broken C<poll.h> header. Libev works around
4482this by trying to avoid the poll backend altogether (i.e. it's not even
4483compiled in), which normally isn't a big problem as C<select> works fine
4484with large bitsets, and AIX is dead anyway.
4485
4399=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS 4486=head2 WIN32 PLATFORM LIMITATIONS AND WORKAROUNDS
4487
4488=head3 General issues
4400 4489
4401Win32 doesn't support any of the standards (e.g. POSIX) that libev 4490Win32 doesn't support any of the standards (e.g. POSIX) that libev
4402requires, and its I/O model is fundamentally incompatible with the POSIX 4491requires, and its I/O model is fundamentally incompatible with the POSIX
4403model. Libev still offers limited functionality on this platform in 4492model. Libev still offers limited functionality on this platform in
4404the form of the C<EVBACKEND_SELECT> backend, and only supports socket 4493the form of the C<EVBACKEND_SELECT> backend, and only supports socket
4405descriptors. This only applies when using Win32 natively, not when using 4494descriptors. This only applies when using Win32 natively, not when using
4406e.g. cygwin. 4495e.g. cygwin. Actually, it only applies to the microsofts own compilers,
4496as every compielr comes with a slightly differently broken/incompatible
4497environment.
4407 4498
4408Lifting these limitations would basically require the full 4499Lifting these limitations would basically require the full
4409re-implementation of the I/O system. If you are into these kinds of 4500re-implementation of the I/O system. If you are into this kind of thing,
4410things, then note that glib does exactly that for you in a very portable 4501then note that glib does exactly that for you in a very portable way (note
4411way (note also that glib is the slowest event library known to man). 4502also that glib is the slowest event library known to man).
4412 4503
4413There is no supported compilation method available on windows except 4504There is no supported compilation method available on windows except
4414embedding it into other applications. 4505embedding it into other applications.
4415 4506
4416Sensible signal handling is officially unsupported by Microsoft - libev 4507Sensible signal handling is officially unsupported by Microsoft - libev
4444you do I<not> compile the F<ev.c> or any other embedded source files!): 4535you do I<not> compile the F<ev.c> or any other embedded source files!):
4445 4536
4446 #include "evwrap.h" 4537 #include "evwrap.h"
4447 #include "ev.c" 4538 #include "ev.c"
4448 4539
4449=over 4
4450
4451=item The winsocket select function 4540=head3 The winsocket C<select> function
4452 4541
4453The winsocket C<select> function doesn't follow POSIX in that it 4542The winsocket C<select> function doesn't follow POSIX in that it
4454requires socket I<handles> and not socket I<file descriptors> (it is 4543requires socket I<handles> and not socket I<file descriptors> (it is
4455also extremely buggy). This makes select very inefficient, and also 4544also extremely buggy). This makes select very inefficient, and also
4456requires a mapping from file descriptors to socket handles (the Microsoft 4545requires a mapping from file descriptors to socket handles (the Microsoft
4465 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */ 4554 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
4466 4555
4467Note that winsockets handling of fd sets is O(n), so you can easily get a 4556Note that winsockets handling of fd sets is O(n), so you can easily get a
4468complexity in the O(n²) range when using win32. 4557complexity in the O(n²) range when using win32.
4469 4558
4470=item Limited number of file descriptors 4559=head3 Limited number of file descriptors
4471 4560
4472Windows has numerous arbitrary (and low) limits on things. 4561Windows has numerous arbitrary (and low) limits on things.
4473 4562
4474Early versions of winsocket's select only supported waiting for a maximum 4563Early versions of winsocket's select only supported waiting for a maximum
4475of C<64> handles (probably owning to the fact that all windows kernels 4564of C<64> handles (probably owning to the fact that all windows kernels
4490runtime libraries. This might get you to about C<512> or C<2048> sockets 4579runtime libraries. This might get you to about C<512> or C<2048> sockets
4491(depending on windows version and/or the phase of the moon). To get more, 4580(depending on windows version and/or the phase of the moon). To get more,
4492you need to wrap all I/O functions and provide your own fd management, but 4581you need to wrap all I/O functions and provide your own fd management, but
4493the cost of calling select (O(n²)) will likely make this unworkable. 4582the cost of calling select (O(n²)) will likely make this unworkable.
4494 4583
4495=back
4496
4497=head2 PORTABILITY REQUIREMENTS 4584=head2 PORTABILITY REQUIREMENTS
4498 4585
4499In addition to a working ISO-C implementation and of course the 4586In addition to a working ISO-C implementation and of course the
4500backend-specific APIs, libev relies on a few additional extensions: 4587backend-specific APIs, libev relies on a few additional extensions:
4501 4588
4621involves iterating over all running async watchers or all signal numbers. 4708involves iterating over all running async watchers or all signal numbers.
4622 4709
4623=back 4710=back
4624 4711
4625 4712
4626=head1 PORTING FROM 3.X TO 4.X 4713=head1 PORTING FROM LIBEV 3.X TO 4.X
4627 4714
4628The major version 4 introduced some minor incompatible changes to the API. 4715The major version 4 introduced some minor incompatible changes to the API.
4629 4716
4717At the moment, the C<ev.h> header file tries to implement superficial
4718compatibility, so most programs should still compile. Those might be
4719removed in later versions of libev, so better update early than late.
4720
4630=over 4 4721=over 4
4631 4722
4723=item C<ev_loop_count> renamed to C<ev_iteration>
4724
4725=item C<ev_loop_depth> renamed to C<ev_depth>
4726
4727=item C<ev_loop_verify> renamed to C<ev_verify>
4728
4729Most functions working on C<struct ev_loop> objects don't have an
4730C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
4731still called C<ev_loop_fork> because it would otherwise clash with the
4732C<ev_fork> typedef.
4733
4632=item C<EV_TIMEOUT> replaced by C<EV_TIMER> in C<revents> 4734=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4633 4735
4634This is a simple rename - all other watcher types use their name 4736This is a simple rename - all other watcher types use their name
4635as revents flag, and now C<ev_timer> does, too. 4737as revents flag, and now C<ev_timer> does, too.
4636 4738
4637Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions 4739Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4638and continue to be present for the forseeable future, so this is mostly a 4740and continue to be present for the foreseeable future, so this is mostly a
4639documentation change. 4741documentation change.
4640 4742
4641=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES> 4743=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4642 4744
4643The preprocessor symbol C<EV_MINIMAL> has been replaced by a different 4745The preprocessor symbol C<EV_MINIMAL> has been replaced by a different

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