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Revision 1.277 by root, Thu Dec 31 06:50:17 2009 UTC vs.
Revision 1.292 by sf-exg, Mon Mar 22 09:57:01 2010 UTC

345useful to try out specific backends to test their performance, or to work 345useful to try out specific backends to test their performance, or to work
346around bugs. 346around bugs.
347 347
348=item C<EVFLAG_FORKCHECK> 348=item C<EVFLAG_FORKCHECK>
349 349
350Instead of calling C<ev_default_fork> or C<ev_loop_fork> manually after 350Instead 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 351make libev check for a fork in each iteration by enabling this flag.
352enabling this flag.
353 352
354This works by calling C<getpid ()> on every iteration of the loop, 353This 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 354and 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 355iterations 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 356GNU/Linux system for example, C<getpid> is actually a simple 5-insn sequence
374 373
375=item C<EVFLAG_SIGNALFD> 374=item C<EVFLAG_SIGNALFD>
376 375
377When this flag is specified, then libev will attempt to use the 376When this flag is specified, then libev will attempt to use the
378I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API 377I<signalfd> API for it's C<ev_signal> (and C<ev_child>) watchers. This API
379delivers signals synchronously, which makes is both faster and might make 378delivers signals synchronously, which makes it both faster and might make
380it possible to get the queued signal data. 379it possible to get the queued signal data. It can also simplify signal
380handling with threads, as long as you properly block signals in your
381threads that are not interested in handling them.
381 382
382Signalfd will not be used by default as this changes your signal mask, and 383Signalfd will not be used by default as this changes your signal mask, and
383there are a lot of shoddy libraries and programs (glib's threadpool for 384there are a lot of shoddy libraries and programs (glib's threadpool for
384example) that can't properly initialise their signal masks. 385example) that can't properly initialise their signal masks.
385 386
565 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE); 566 ev_default_loop (ev_recommended_backends () | EVBACKEND_KQUEUE);
566 567
567=item struct ev_loop *ev_loop_new (unsigned int flags) 568=item struct ev_loop *ev_loop_new (unsigned int flags)
568 569
569Similar to C<ev_default_loop>, but always creates a new event loop that is 570Similar to C<ev_default_loop>, but always creates a new event loop that is
570always distinct from the default loop. Unlike the default loop, it cannot 571always distinct from the default loop.
571handle signal and child watchers, and attempts to do so will be greeted by
572undefined behaviour (or a failed assertion if assertions are enabled).
573 572
574Note that this function I<is> thread-safe, and the recommended way to use 573Note that this function I<is> thread-safe, and one common way to use
575libev with threads is indeed to create one loop per thread, and using the 574libev with threads is indeed to create one loop per thread, and using the
576default loop in the "main" or "initial" thread. 575default loop in the "main" or "initial" thread.
577 576
578Example: Try to create a event loop that uses epoll and nothing else. 577Example: Try to create a event loop that uses epoll and nothing else.
579 578
581 if (!epoller) 580 if (!epoller)
582 fatal ("no epoll found here, maybe it hides under your chair"); 581 fatal ("no epoll found here, maybe it hides under your chair");
583 582
584=item ev_default_destroy () 583=item ev_default_destroy ()
585 584
586Destroys the default loop again (frees all memory and kernel state 585Destroys the default loop (frees all memory and kernel state etc.). None
587etc.). None of the active event watchers will be stopped in the normal 586of the active event watchers will be stopped in the normal sense, so
588sense, so e.g. C<ev_is_active> might still return true. It is your 587e.g. C<ev_is_active> might still return true. It is your responsibility to
589responsibility to either stop all watchers cleanly yourself I<before> 588either stop all watchers cleanly yourself I<before> calling this function,
590calling this function, or cope with the fact afterwards (which is usually 589or cope with the fact afterwards (which is usually the easiest thing, you
591the easiest thing, you can just ignore the watchers and/or C<free ()> them 590can just ignore the watchers and/or C<free ()> them for example).
592for example).
593 591
594Note that certain global state, such as signal state (and installed signal 592Note that certain global state, such as signal state (and installed signal
595handlers), will not be freed by this function, and related watchers (such 593handlers), will not be freed by this function, and related watchers (such
596as signal and child watchers) would need to be stopped manually. 594as signal and child watchers) would need to be stopped manually.
597 595
612name, you can call it anytime, but it makes most sense after forking, in 610name, you can call it anytime, but it makes most sense after forking, in
613the child process (or both child and parent, but that again makes little 611the child process (or both child and parent, but that again makes little
614sense). You I<must> call it in the child before using any of the libev 612sense). You I<must> call it in the child before using any of the libev
615functions, and it will only take effect at the next C<ev_loop> iteration. 613functions, and it will only take effect at the next C<ev_loop> iteration.
616 614
615Again, you I<have> to call it on I<any> loop that you want to re-use after
616a fork, I<even if you do not plan to use the loop in the parent>. This is
617because some kernel interfaces *cough* I<kqueue> *cough* do funny things
618during fork.
619
617On the other hand, you only need to call this function in the child 620On the other hand, you only need to call this function in the child
618process if and only if you want to use the event library in the child. If 621process if and only if you want to use the event loop in the child. If you
619you just fork+exec, you don't have to call it at all. 622just fork+exec or create a new loop in the child, you don't have to call
623it at all.
620 624
621The function itself is quite fast and it's usually not a problem to call 625The function itself is quite fast and it's usually not a problem to call
622it just in case after a fork. To make this easy, the function will fit in 626it just in case after a fork. To make this easy, the function will fit in
623quite nicely into a call to C<pthread_atfork>: 627quite nicely into a call to C<pthread_atfork>:
624 628
626 630
627=item ev_loop_fork (loop) 631=item ev_loop_fork (loop)
628 632
629Like C<ev_default_fork>, but acts on an event loop created by 633Like C<ev_default_fork>, but acts on an event loop created by
630C<ev_loop_new>. Yes, you have to call this on every allocated event loop 634C<ev_loop_new>. Yes, you have to call this on every allocated event loop
631after fork that you want to re-use in the child, and how you do this is 635after fork that you want to re-use in the child, and how you keep track of
632entirely your own problem. 636them is entirely your own problem.
633 637
634=item int ev_is_default_loop (loop) 638=item int ev_is_default_loop (loop)
635 639
636Returns true when the given loop is, in fact, the default loop, and false 640Returns true when the given loop is, in fact, the default loop, and false
637otherwise. 641otherwise.
638 642
639=item unsigned int ev_loop_count (loop) 643=item unsigned int ev_iteration (loop)
640 644
641Returns the count of loop iterations for the loop, which is identical to 645Returns the current iteration count for the loop, which is identical to
642the number of times libev did poll for new events. It starts at C<0> and 646the number of times libev did poll for new events. It starts at C<0> and
643happily wraps around with enough iterations. 647happily wraps around with enough iterations.
644 648
645This value can sometimes be useful as a generation counter of sorts (it 649This value can sometimes be useful as a generation counter of sorts (it
646"ticks" the number of loop iterations), as it roughly corresponds with 650"ticks" the number of loop iterations), as it roughly corresponds with
647C<ev_prepare> and C<ev_check> calls. 651C<ev_prepare> and C<ev_check> calls - and is incremented between the
652prepare and check phases.
648 653
649=item unsigned int ev_loop_depth (loop) 654=item unsigned int ev_depth (loop)
650 655
651Returns the number of times C<ev_loop> was entered minus the number of 656Returns the number of times C<ev_loop> was entered minus the number of
652times C<ev_loop> was exited, in other words, the recursion depth. 657times C<ev_loop> was exited, in other words, the recursion depth.
653 658
654Outside C<ev_loop>, this number is zero. In a callback, this number is 659Outside C<ev_loop>, this number is zero. In a callback, this number is
655C<1>, unless C<ev_loop> was invoked recursively (or from another thread), 660C<1>, unless C<ev_loop> was invoked recursively (or from another thread),
656in which case it is higher. 661in which case it is higher.
657 662
658Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread 663Leaving C<ev_loop> abnormally (setjmp/longjmp, cancelling the thread
659etc.), doesn't count as exit. 664etc.), doesn't count as "exit" - consider this as a hint to avoid such
665ungentleman behaviour unless it's really convenient.
660 666
661=item unsigned int ev_backend (loop) 667=item unsigned int ev_backend (loop)
662 668
663Returns one of the C<EVBACKEND_*> flags indicating the event backend in 669Returns one of the C<EVBACKEND_*> flags indicating the event backend in
664use. 670use.
1030=item C<EV_WRITE> 1036=item C<EV_WRITE>
1031 1037
1032The file descriptor in the C<ev_io> watcher has become readable and/or 1038The file descriptor in the C<ev_io> watcher has become readable and/or
1033writable. 1039writable.
1034 1040
1035=item C<EV_TIMEOUT> 1041=item C<EV_TIMER>
1036 1042
1037The C<ev_timer> watcher has timed out. 1043The C<ev_timer> watcher has timed out.
1038 1044
1039=item C<EV_PERIODIC> 1045=item C<EV_PERIODIC>
1040 1046
1536 1542
1537So when you encounter spurious, unexplained daemon exits, make sure you 1543So when you encounter spurious, unexplained daemon exits, make sure you
1538ignore SIGPIPE (and maybe make sure you log the exit status of your daemon 1544ignore SIGPIPE (and maybe make sure you log the exit status of your daemon
1539somewhere, as that would have given you a big clue). 1545somewhere, as that would have given you a big clue).
1540 1546
1547=head3 The special problem of accept()ing when you can't
1548
1549Many implementations of the POSIX C<accept> function (for example,
1550found in post-2004 Linux) have the peculiar behaviour of not removing a
1551connection from the pending queue in all error cases.
1552
1553For example, larger servers often run out of file descriptors (because
1554of resource limits), causing C<accept> to fail with C<ENFILE> but not
1555rejecting the connection, leading to libev signalling readiness on
1556the next iteration again (the connection still exists after all), and
1557typically causing the program to loop at 100% CPU usage.
1558
1559Unfortunately, the set of errors that cause this issue differs between
1560operating systems, there is usually little the app can do to remedy the
1561situation, and no known thread-safe method of removing the connection to
1562cope with overload is known (to me).
1563
1564One of the easiest ways to handle this situation is to just ignore it
1565- when the program encounters an overload, it will just loop until the
1566situation is over. While this is a form of busy waiting, no OS offers an
1567event-based way to handle this situation, so it's the best one can do.
1568
1569A better way to handle the situation is to log any errors other than
1570C<EAGAIN> and C<EWOULDBLOCK>, making sure not to flood the log with such
1571messages, and continue as usual, which at least gives the user an idea of
1572what could be wrong ("raise the ulimit!"). For extra points one could stop
1573the C<ev_io> watcher on the listening fd "for a while", which reduces CPU
1574usage.
1575
1576If your program is single-threaded, then you could also keep a dummy file
1577descriptor for overload situations (e.g. by opening F</dev/null>), and
1578when you run into C<ENFILE> or C<EMFILE>, close it, run C<accept>,
1579close that fd, and create a new dummy fd. This will gracefully refuse
1580clients under typical overload conditions.
1581
1582The last way to handle it is to simply log the error and C<exit>, as
1583is often done with C<malloc> failures, but this results in an easy
1584opportunity for a DoS attack.
1541 1585
1542=head3 Watcher-Specific Functions 1586=head3 Watcher-Specific Functions
1543 1587
1544=over 4 1588=over 4
1545 1589
1724to the current time (meaning we just have some activity :), then call the 1768to the current time (meaning we just have some activity :), then call the
1725callback, which will "do the right thing" and start the timer: 1769callback, which will "do the right thing" and start the timer:
1726 1770
1727 ev_init (timer, callback); 1771 ev_init (timer, callback);
1728 last_activity = ev_now (loop); 1772 last_activity = ev_now (loop);
1729 callback (loop, timer, EV_TIMEOUT); 1773 callback (loop, timer, EV_TIMER);
1730 1774
1731And when there is some activity, simply store the current time in 1775And when there is some activity, simply store the current time in
1732C<last_activity>, no libev calls at all: 1776C<last_activity>, no libev calls at all:
1733 1777
1734 last_actiivty = ev_now (loop); 1778 last_actiivty = ev_now (loop);
1865Returns the remaining time until a timer fires. If the timer is active, 1909Returns the remaining time until a timer fires. If the timer is active,
1866then this time is relative to the current event loop time, otherwise it's 1910then this time is relative to the current event loop time, otherwise it's
1867the timeout value currently configured. 1911the timeout value currently configured.
1868 1912
1869That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns 1913That is, after an C<ev_timer_set (w, 5, 7)>, C<ev_timer_remaining> returns
1870C<5>. When the timer is started and one second passes, C<ev_timer_remain> 1914C<5>. When the timer is started and one second passes, C<ev_timer_remaining>
1871will return C<4>. When the timer expires and is restarted, it will return 1915will return C<4>. When the timer expires and is restarted, it will return
1872roughly C<7> (likely slightly less as callback invocation takes some time, 1916roughly C<7> (likely slightly less as callback invocation takes some time,
1873too), and so on. 1917too), and so on.
1874 1918
1875=item ev_tstamp repeat [read-write] 1919=item ev_tstamp repeat [read-write]
2160In current versions of libev, the signal will not be blocked indefinitely 2204In current versions of libev, the signal will not be blocked indefinitely
2161unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces 2205unless you use the C<signalfd> API (C<EV_SIGNALFD>). While this reduces
2162the window of opportunity for problems, it will not go away, as libev 2206the window of opportunity for problems, it will not go away, as libev
2163I<has> to modify the signal mask, at least temporarily. 2207I<has> to modify the signal mask, at least temporarily.
2164 2208
2165So I can't stress this enough I<if you do not reset your signal mask 2209So I can't stress this enough: I<If you do not reset your signal mask when
2166when you expect it to be empty, you have a race condition in your 2210you expect it to be empty, you have a race condition in your code>. This
2167program>. This is not a libev-specific thing, this is true for most event 2211is not a libev-specific thing, this is true for most event libraries.
2168libraries.
2169 2212
2170=head3 Watcher-Specific Functions and Data Members 2213=head3 Watcher-Specific Functions and Data Members
2171 2214
2172=over 4 2215=over 4
2173 2216
3140 3183
3141If 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
3142started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 3185started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3143repeat = 0) will be started. C<0> is a valid timeout. 3186repeat = 0) will be started. C<0> is a valid timeout.
3144 3187
3145The 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
3146passed an C<revents> set like normal event callbacks (a combination of 3189passed an C<revents> set like normal event callbacks (a combination of
3147C<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>
3148value 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>
3149a 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
3150events precedence. 3193events precedence.
3151 3194
3152Example: 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.
3153 3196
3154 static void stdin_ready (int revents, void *arg) 3197 static void stdin_ready (int revents, void *arg)
3155 { 3198 {
3156 if (revents & EV_READ) 3199 if (revents & EV_READ)
3157 /* stdin might have data for us, joy! */; 3200 /* stdin might have data for us, joy! */;
3158 else if (revents & EV_TIMEOUT) 3201 else if (revents & EV_TIMER)
3159 /* doh, nothing entered */; 3202 /* doh, nothing entered */;
3160 } 3203 }
3161 3204
3162 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3205 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3163 3206
3450Erkki Seppala has written Ocaml bindings for libev, to be found at 3493Erkki Seppala has written Ocaml bindings for libev, to be found at
3451L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>. 3494L<http://modeemi.cs.tut.fi/~flux/software/ocaml-ev/>.
3452 3495
3453=item Lua 3496=item Lua
3454 3497
3455Brian Maher has written a partial interface to libev 3498Brian Maher has written a partial interface to libev for lua (at the
3456for lua (only C<ev_io> and C<ev_timer>), to be found at 3499time of this writing, only C<ev_io> and C<ev_timer>), to be found at
3457L<http://github.com/brimworks/lua-ev>. 3500L<http://github.com/brimworks/lua-ev>.
3458 3501
3459=back 3502=back
3460 3503
3461 3504
3616 libev.m4 3659 libev.m4
3617 3660
3618=head2 PREPROCESSOR SYMBOLS/MACROS 3661=head2 PREPROCESSOR SYMBOLS/MACROS
3619 3662
3620Libev can be configured via a variety of preprocessor symbols you have to 3663Libev can be configured via a variety of preprocessor symbols you have to
3621define before including any of its files. The default in the absence of 3664define before including (or compiling) any of its files. The default in
3622autoconf is documented for every option. 3665the absence of autoconf is documented for every option.
3666
3667Symbols marked with "(h)" do not change the ABI, and can have different
3668values when compiling libev vs. including F<ev.h>, so it is permissible
3669to redefine them before including F<ev.h> without breaking compatibility
3670to a compiled library. All other symbols change the ABI, which means all
3671users of libev and the libev code itself must be compiled with compatible
3672settings.
3623 3673
3624=over 4 3674=over 4
3625 3675
3626=item EV_STANDALONE 3676=item EV_STANDALONE (h)
3627 3677
3628Must always be C<1> if you do not use autoconf configuration, which 3678Must always be C<1> if you do not use autoconf configuration, which
3629keeps libev from including F<config.h>, and it also defines dummy 3679keeps libev from including F<config.h>, and it also defines dummy
3630implementations for some libevent functions (such as logging, which is not 3680implementations for some libevent functions (such as logging, which is not
3631supported). It will also not define any of the structs usually found in 3681supported). It will also not define any of the structs usually found in
3781as well as for signal and thread safety in C<ev_async> watchers. 3831as well as for signal and thread safety in C<ev_async> watchers.
3782 3832
3783In the absence of this define, libev will use C<sig_atomic_t volatile> 3833In the absence of this define, libev will use C<sig_atomic_t volatile>
3784(from F<signal.h>), which is usually good enough on most platforms. 3834(from F<signal.h>), which is usually good enough on most platforms.
3785 3835
3786=item EV_H 3836=item EV_H (h)
3787 3837
3788The name of the F<ev.h> header file used to include it. The default if 3838The name of the F<ev.h> header file used to include it. The default if
3789undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be 3839undefined is C<"ev.h"> in F<event.h>, F<ev.c> and F<ev++.h>. This can be
3790used to virtually rename the F<ev.h> header file in case of conflicts. 3840used to virtually rename the F<ev.h> header file in case of conflicts.
3791 3841
3792=item EV_CONFIG_H 3842=item EV_CONFIG_H (h)
3793 3843
3794If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 3844If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
3795F<ev.c>'s idea of where to find the F<config.h> file, similarly to 3845F<ev.c>'s idea of where to find the F<config.h> file, similarly to
3796C<EV_H>, above. 3846C<EV_H>, above.
3797 3847
3798=item EV_EVENT_H 3848=item EV_EVENT_H (h)
3799 3849
3800Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 3850Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
3801of how the F<event.h> header can be found, the default is C<"event.h">. 3851of how the F<event.h> header can be found, the default is C<"event.h">.
3802 3852
3803=item EV_PROTOTYPES 3853=item EV_PROTOTYPES (h)
3804 3854
3805If defined to be C<0>, then F<ev.h> will not define any function 3855If defined to be C<0>, then F<ev.h> will not define any function
3806prototypes, but still define all the structs and other symbols. This is 3856prototypes, but still define all the structs and other symbols. This is
3807occasionally useful if you want to provide your own wrapper functions 3857occasionally useful if you want to provide your own wrapper functions
3808around libev functions. 3858around libev functions.
3830fine. 3880fine.
3831 3881
3832If your embedding application does not need any priorities, defining these 3882If your embedding application does not need any priorities, defining these
3833both to C<0> will save some memory and CPU. 3883both to C<0> will save some memory and CPU.
3834 3884
3835=item EV_PERIODIC_ENABLE 3885=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
3886EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3887EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3836 3888
3837If undefined or defined to be C<1>, then periodic timers are supported. If 3889If undefined or defined to be C<1> (and the platform supports it), then
3838defined to be C<0>, then they are not. Disabling them saves a few kB of 3890the respective watcher type is supported. If defined to be C<0>, then it
3839code. 3891is not. Disabling watcher types mainly saves codesize.
3840 3892
3841=item EV_IDLE_ENABLE 3893=item EV_FEATURES
3842
3843If undefined or defined to be C<1>, then idle watchers are supported. If
3844defined to be C<0>, then they are not. Disabling them saves a few kB of
3845code.
3846
3847=item EV_EMBED_ENABLE
3848
3849If undefined or defined to be C<1>, then embed watchers are supported. If
3850defined to be C<0>, then they are not. Embed watchers rely on most other
3851watcher types, which therefore must not be disabled.
3852
3853=item EV_STAT_ENABLE
3854
3855If undefined or defined to be C<1>, then stat watchers are supported. If
3856defined to be C<0>, then they are not.
3857
3858=item EV_FORK_ENABLE
3859
3860If undefined or defined to be C<1>, then fork watchers are supported. If
3861defined to be C<0>, then they are not.
3862
3863=item EV_ASYNC_ENABLE
3864
3865If undefined or defined to be C<1>, then async watchers are supported. If
3866defined to be C<0>, then they are not.
3867
3868=item EV_MINIMAL
3869 3894
3870If 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
3871speed (but with the full API), define this symbol to C<1>. Currently this 3896speed (but with the full API), you can define this symbol to request
3872is used to override some inlining decisions, saves roughly 30% code size 3897certain subsets of functionality. The default is to enable all features
3873on amd64. It also selects a much smaller 2-heap for timer management over 3898that can be enabled on the platform.
3874the default 4-heap.
3875 3899
3876You can save even more by disabling watcher types you do not need 3900A typical way to use this symbol is to define it to C<0> (or to a bitset
3877and setting C<EV_MAXPRI> == C<EV_MINPRI>. Also, disabling C<assert> 3901with some broad features you want) and then selectively re-enable
3878(C<-DNDEBUG>) will usually reduce code size a lot. 3902additional parts you want, for example if you want everything minimal,
3903but multiple event loop support, async and child watchers and the poll
3904backend, use this:
3879 3905
3880Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to 3906 #define EV_FEATURES 0
3881provide a bare-bones event library. See C<ev.h> for details on what parts 3907 #define EV_MULTIPLICITY 1
3882of the API are still available, and do not complain if this subset changes 3908 #define EV_USE_POLL 1
3883over time. 3909 #define EV_CHILD_ENABLE 1
3910 #define EV_ASYNC_ENABLE 1
3911
3912The actual value is a bitset, it can be a combination of the following
3913values:
3914
3915=over 4
3916
3917=item C<1> - faster/larger code
3918
3919Use larger code to speed up some operations.
3920
3921Currently this is used to override some inlining decisions (enlarging the roughly
392230% code size on amd64.
3923
3924When optimising for size, use of compiler flags such as C<-Os> with
3925gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
3926assertions.
3927
3928=item C<2> - faster/larger data structures
3929
3930Replaces the small 2-heap for timer management by a faster 4-heap, larger
3931hash table sizes and so on. This will usually further increase codesize
3932and can additionally have an effect on the size of data structures at
3933runtime.
3934
3935=item C<4> - full API configuration
3936
3937This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3938enables multiplicity (C<EV_MULTIPLICITY>=1).
3939
3940=item C<8> - full API
3941
3942This enables a lot of the "lesser used" API functions. See C<ev.h> for
3943details on which parts of the API are still available without this
3944feature, and do not complain if this subset changes over time.
3945
3946=item C<16> - enable all optional watcher types
3947
3948Enables all optional watcher types. If you want to selectively enable
3949only some watcher types other than I/O and timers (e.g. prepare,
3950embed, async, child...) you can enable them manually by defining
3951C<EV_watchertype_ENABLE> to C<1> instead.
3952
3953=item C<32> - enable all backends
3954
3955This enables all backends - without this feature, you need to enable at
3956least one backend manually (C<EV_USE_SELECT> is a good choice).
3957
3958=item C<64> - enable OS-specific "helper" APIs
3959
3960Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
3961default.
3962
3963=back
3964
3965Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
3966reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
3967code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
3968watchers, timers and monotonic clock support.
3969
3970With an intelligent-enough linker (gcc+binutils are intelligent enough
3971when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3972your program might be left out as well - a binary starting a timer and an
3973I/O watcher then might come out at only 5Kb.
3974
3975=item EV_AVOID_STDIO
3976
3977If this is set to C<1> at compiletime, then libev will avoid using stdio
3978functions (printf, scanf, perror etc.). This will increase the codesize
3979somewhat, but if your program doesn't otherwise depend on stdio and your
3980libc allows it, this avoids linking in the stdio library which is quite
3981big.
3982
3983Note that error messages might become less precise when this option is
3984enabled.
3884 3985
3885=item EV_NSIG 3986=item EV_NSIG
3886 3987
3887The highest supported signal number, +1 (or, the number of 3988The highest supported signal number, +1 (or, the number of
3888signals): Normally, libev tries to deduce the maximum number of signals 3989signals): Normally, libev tries to deduce the maximum number of signals
3892statically allocates some 12-24 bytes per signal number. 3993statically allocates some 12-24 bytes per signal number.
3893 3994
3894=item EV_PID_HASHSIZE 3995=item EV_PID_HASHSIZE
3895 3996
3896C<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
3897pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more 3998pid. The default size is C<16> (or C<1> with C<EV_FEATURES> disabled),
3898than enough. If you need to manage thousands of children you might want to 3999usually more than enough. If you need to manage thousands of children you
3899increase this value (I<must> be a power of two). 4000might want to increase this value (I<must> be a power of two).
3900 4001
3901=item EV_INOTIFY_HASHSIZE 4002=item EV_INOTIFY_HASHSIZE
3902 4003
3903C<ev_stat> watchers use a small hash table to distribute workload by 4004C<ev_stat> watchers use a small hash table to distribute workload by
3904inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 4005inotify watch id. The default size is C<16> (or C<1> with C<EV_FEATURES>
3905usually more than enough. If you need to manage thousands of C<ev_stat> 4006disabled), usually more than enough. If you need to manage thousands of
3906watchers you might want to increase this value (I<must> be a power of 4007C<ev_stat> watchers you might want to increase this value (I<must> be a
3907two). 4008power of two).
3908 4009
3909=item EV_USE_4HEAP 4010=item EV_USE_4HEAP
3910 4011
3911Heaps are not very cache-efficient. To improve the cache-efficiency of the 4012Heaps are not very cache-efficient. To improve the cache-efficiency of the
3912timer and periodics heaps, libev uses a 4-heap when this symbol is defined 4013timer and periodics heaps, libev uses a 4-heap when this symbol is defined
3913to C<1>. The 4-heap uses more complicated (longer) code but has noticeably 4014to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3914faster performance with many (thousands) of watchers. 4015faster performance with many (thousands) of watchers.
3915 4016
3916The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4017The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3917(disabled). 4018will be C<0>.
3918 4019
3919=item EV_HEAP_CACHE_AT 4020=item EV_HEAP_CACHE_AT
3920 4021
3921Heaps are not very cache-efficient. To improve the cache-efficiency of the 4022Heaps are not very cache-efficient. To improve the cache-efficiency of the
3922timer and periodics heaps, libev can cache the timestamp (I<at>) within 4023timer and periodics heaps, libev can cache the timestamp (I<at>) within
3923the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>), 4024the heap structure (selected by defining C<EV_HEAP_CACHE_AT> to C<1>),
3924which uses 8-12 bytes more per watcher and a few hundred bytes more code, 4025which uses 8-12 bytes more per watcher and a few hundred bytes more code,
3925but avoids random read accesses on heap changes. This improves performance 4026but avoids random read accesses on heap changes. This improves performance
3926noticeably with many (hundreds) of watchers. 4027noticeably with many (hundreds) of watchers.
3927 4028
3928The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4029The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3929(disabled). 4030will be C<0>.
3930 4031
3931=item EV_VERIFY 4032=item EV_VERIFY
3932 4033
3933Controls how much internal verification (see C<ev_loop_verify ()>) will 4034Controls how much internal verification (see C<ev_loop_verify ()>) will
3934be done: If set to C<0>, no internal verification code will be compiled 4035be done: If set to C<0>, no internal verification code will be compiled
3936called. If set to C<2>, then the internal verification code will be 4037called. If set to C<2>, then the internal verification code will be
3937called once per loop, which can slow down libev. If set to C<3>, then the 4038called once per loop, which can slow down libev. If set to C<3>, then the
3938verification code will be called very frequently, which will slow down 4039verification code will be called very frequently, which will slow down
3939libev considerably. 4040libev considerably.
3940 4041
3941The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be 4042The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3942C<0>. 4043will be C<0>.
3943 4044
3944=item EV_COMMON 4045=item EV_COMMON
3945 4046
3946By default, all watchers have a C<void *data> member. By redefining 4047By default, all watchers have a C<void *data> member. By redefining
3947this macro to a something else you can include more and other types of 4048this macro to a something else you can include more and other types of
4005file. 4106file.
4006 4107
4007The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 4108The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4008that everybody includes and which overrides some configure choices: 4109that everybody includes and which overrides some configure choices:
4009 4110
4010 #define EV_MINIMAL 1 4111 #define EV_FEATURES 8
4011 #define EV_USE_POLL 0 4112 #define EV_USE_SELECT 1
4012 #define EV_MULTIPLICITY 0
4013 #define EV_PERIODIC_ENABLE 0 4113 #define EV_PREPARE_ENABLE 1
4114 #define EV_IDLE_ENABLE 1
4014 #define EV_STAT_ENABLE 0 4115 #define EV_SIGNAL_ENABLE 1
4015 #define EV_FORK_ENABLE 0 4116 #define EV_CHILD_ENABLE 1
4117 #define EV_USE_STDEXCEPT 0
4016 #define EV_CONFIG_H <config.h> 4118 #define EV_CONFIG_H <config.h>
4017 #define EV_MINPRI 0
4018 #define EV_MAXPRI 0
4019 4119
4020 #include "ev++.h" 4120 #include "ev++.h"
4021 4121
4022And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 4122And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4023 4123
4525involves iterating over all running async watchers or all signal numbers. 4625involves iterating over all running async watchers or all signal numbers.
4526 4626
4527=back 4627=back
4528 4628
4529 4629
4630=head1 PORTING FROM LIBEV 3.X TO 4.X
4631
4632The major version 4 introduced some minor incompatible changes to the API.
4633
4634At the moment, the C<ev.h> header file tries to implement superficial
4635compatibility, so most programs should still compile. Those might be
4636removed in later versions of libev, so better update early than late.
4637
4638=over 4
4639
4640=item C<ev_loop_count> renamed to C<ev_iteration>
4641
4642=item C<ev_loop_depth> renamed to C<ev_depth>
4643
4644=item C<ev_loop_verify> renamed to C<ev_verify>
4645
4646Most functions working on C<struct ev_loop> objects don't have an
4647C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
4648still called C<ev_loop_fork> because it would otherwise clash with the
4649C<ev_fork> typedef.
4650
4651=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4652
4653This is a simple rename - all other watcher types use their name
4654as revents flag, and now C<ev_timer> does, too.
4655
4656Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4657and continue to be present for the forseeable future, so this is mostly a
4658documentation change.
4659
4660=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4661
4662The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4663mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4664and work, but the library code will of course be larger.
4665
4666=back
4667
4668
4530=head1 GLOSSARY 4669=head1 GLOSSARY
4531 4670
4532=over 4 4671=over 4
4533 4672
4534=item active 4673=item active
4555A change of state of some external event, such as data now being available 4694A change of state of some external event, such as data now being available
4556for reading on a file descriptor, time having passed or simply not having 4695for reading on a file descriptor, time having passed or simply not having
4557any other events happening anymore. 4696any other events happening anymore.
4558 4697
4559In libev, events are represented as single bits (such as C<EV_READ> or 4698In libev, events are represented as single bits (such as C<EV_READ> or
4560C<EV_TIMEOUT>). 4699C<EV_TIMER>).
4561 4700
4562=item event library 4701=item event library
4563 4702
4564A software package implementing an event model and loop. 4703A software package implementing an event model and loop.
4565 4704

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