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Revision 1.282 by root, Wed Mar 10 08:19:39 2010 UTC vs.
Revision 1.293 by root, Wed Mar 24 18:27:13 2010 UTC

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).
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.
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
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
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_actiivty = ev_now (loop);
3141 3184
3142If C<timeout> is less than 0, then no timeout watcher will be 3185If C<timeout> is less than 0, then no timeout watcher will be
3143started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 3186started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
3144repeat = 0) will be started. C<0> is a valid timeout. 3187repeat = 0) will be started. C<0> is a valid timeout.
3145 3188
3146The callback has the type C<void (*cb)(int revents, void *arg)> and gets 3189The 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 3190passed 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> 3191C<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> 3192value 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 3193a timeout and an io event at the same time - you probably should give io
3151events precedence. 3194events precedence.
3152 3195
3153Example: wait up to ten seconds for data to appear on STDIN_FILENO. 3196Example: wait up to ten seconds for data to appear on STDIN_FILENO.
3154 3197
3155 static void stdin_ready (int revents, void *arg) 3198 static void stdin_ready (int revents, void *arg)
3156 { 3199 {
3157 if (revents & EV_READ) 3200 if (revents & EV_READ)
3158 /* stdin might have data for us, joy! */; 3201 /* stdin might have data for us, joy! */;
3159 else if (revents & EV_TIMEOUT) 3202 else if (revents & EV_TIMER)
3160 /* doh, nothing entered */; 3203 /* doh, nothing entered */;
3161 } 3204 }
3162 3205
3163 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0); 3206 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
3164 3207
3622define before including (or compiling) any of its files. The default in 3665define before including (or compiling) any of its files. The default in
3623the absence of autoconf is documented for every option. 3666the absence of autoconf is documented for every option.
3624 3667
3625Symbols marked with "(h)" do not change the ABI, and can have different 3668Symbols 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 3669values when compiling libev vs. including F<ev.h>, so it is permissible
3627to redefine them before including F<ev.h> without breakign compatibility 3670to redefine them before including F<ev.h> without breaking compatibility
3628to a compiled library. All other symbols change the ABI, which means all 3671to 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 3672users of libev and the libev code itself must be compiled with compatible
3630settings. 3673settings.
3631 3674
3632=over 4 3675=over 4
3838fine. 3881fine.
3839 3882
3840If your embedding application does not need any priorities, defining these 3883If your embedding application does not need any priorities, defining these
3841both to C<0> will save some memory and CPU. 3884both to C<0> will save some memory and CPU.
3842 3885
3843=item EV_PERIODIC_ENABLE 3886=item EV_PERIODIC_ENABLE, EV_IDLE_ENABLE, EV_EMBED_ENABLE, EV_STAT_ENABLE,
3887EV_PREPARE_ENABLE, EV_CHECK_ENABLE, EV_FORK_ENABLE, EV_SIGNAL_ENABLE,
3888EV_ASYNC_ENABLE, EV_CHILD_ENABLE.
3844 3889
3845If undefined or defined to be C<1>, then periodic timers are supported. If 3890If 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 3891the respective watcher type is supported. If defined to be C<0>, then it
3847code. 3892is not. Disabling watcher types mainly saves codesize.
3848 3893
3849=item EV_IDLE_ENABLE 3894=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 3895
3888If you need to shave off some kilobytes of code at the expense of some 3896If 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 3897speed (but with the full API), you can define this symbol to request
3890is used to override some inlining decisions, saves roughly 30% code size 3898certain subsets of functionality. The default is to enable all features
3891on amd64. It also selects a much smaller 2-heap for timer management over 3899that can be enabled on the platform.
3892the default 4-heap.
3893 3900
3894You can save even more by disabling watcher types you do not need 3901A 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> 3902with some broad features you want) and then selectively re-enable
3896(C<-DNDEBUG>) will usually reduce code size a lot. Disabling inotify, 3903additional parts you want, for example if you want everything minimal,
3897eventfd and signalfd will further help, and disabling backends one doesn't 3904but multiple event loop support, async and child watchers and the poll
3898need (e.g. poll, epoll, kqueue, ports) will help further. 3905backend, use this:
3899 3906
3900Defining C<EV_MINIMAL> to C<2> will additionally reduce the core API to 3907 #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 3908 #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 3909 #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 3910 #define EV_CHILD_ENABLE 1
3937 #define EV_ASYNC_ENABLE 0 3911 #define EV_ASYNC_ENABLE 1
3938 #define EV_EMBED_ENABLE 0 3912
3913The actual value is a bitset, it can be a combination of the following
3914values:
3915
3916=over 4
3917
3918=item C<1> - faster/larger code
3919
3920Use larger code to speed up some operations.
3921
3922Currently this is used to override some inlining decisions (enlarging the roughly
392330% code size on amd64.
3924
3925When optimising for size, use of compiler flags such as C<-Os> with
3926gcc recommended, as well as C<-DNDEBUG>, as libev contains a number of
3927assertions.
3928
3929=item C<2> - faster/larger data structures
3930
3931Replaces the small 2-heap for timer management by a faster 4-heap, larger
3932hash table sizes and so on. This will usually further increase codesize
3933and can additionally have an effect on the size of data structures at
3934runtime.
3935
3936=item C<4> - full API configuration
3937
3938This enables priorities (sets C<EV_MAXPRI>=2 and C<EV_MINPRI>=-2), and
3939enables multiplicity (C<EV_MULTIPLICITY>=1).
3940
3941=item C<8> - full API
3942
3943This enables a lot of the "lesser used" API functions. See C<ev.h> for
3944details on which parts of the API are still available without this
3945feature, and do not complain if this subset changes over time.
3946
3947=item C<16> - enable all optional watcher types
3948
3949Enables all optional watcher types. If you want to selectively enable
3950only some watcher types other than I/O and timers (e.g. prepare,
3951embed, async, child...) you can enable them manually by defining
3952C<EV_watchertype_ENABLE> to C<1> instead.
3953
3954=item C<32> - enable all backends
3955
3956This enables all backends - without this feature, you need to enable at
3957least one backend manually (C<EV_USE_SELECT> is a good choice).
3958
3959=item C<64> - enable OS-specific "helper" APIs
3960
3961Enable inotify, eventfd, signalfd and similar OS-specific helper APIs by
3962default.
3963
3964=back
3965
3966Compiling with C<gcc -Os -DEV_STANDALONE -DEV_USE_EPOLL=1 -DEV_FEATURES=0>
3967reduces the compiled size of libev from 24.7Kb code/2.8Kb data to 6.5Kb
3968code/0.3Kb data on my GNU/Linux amd64 system, while still giving you I/O
3969watchers, timers and monotonic clock support.
3970
3971With an intelligent-enough linker (gcc+binutils are intelligent enough
3972when you use C<-Wl,--gc-sections -ffunction-sections>) functions unused by
3973your program might be left out as well - a binary starting a timer and an
3974I/O watcher then might come out at only 5Kb.
3939 3975
3940=item EV_AVOID_STDIO 3976=item EV_AVOID_STDIO
3941 3977
3942If this is set to C<1> at compiletime, then libev will avoid using stdio 3978If this is set to C<1> at compiletime, then libev will avoid using stdio
3943functions (printf, scanf, perror etc.). This will increase the codesize 3979functions (printf, scanf, perror etc.). This will increase the codesize
3958statically allocates some 12-24 bytes per signal number. 3994statically allocates some 12-24 bytes per signal number.
3959 3995
3960=item EV_PID_HASHSIZE 3996=item EV_PID_HASHSIZE
3961 3997
3962C<ev_child> watchers use a small hash table to distribute workload by 3998C<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 3999pid. 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 4000usually more than enough. If you need to manage thousands of children you
3965increase this value (I<must> be a power of two). 4001might want to increase this value (I<must> be a power of two).
3966 4002
3967=item EV_INOTIFY_HASHSIZE 4003=item EV_INOTIFY_HASHSIZE
3968 4004
3969C<ev_stat> watchers use a small hash table to distribute workload by 4005C<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>), 4006inotify 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> 4007disabled), 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 4008C<ev_stat> watchers you might want to increase this value (I<must> be a
3973two). 4009power of two).
3974 4010
3975=item EV_USE_4HEAP 4011=item EV_USE_4HEAP
3976 4012
3977Heaps are not very cache-efficient. To improve the cache-efficiency of the 4013Heaps 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 4014timer 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 4015to C<1>. The 4-heap uses more complicated (longer) code but has noticeably
3980faster performance with many (thousands) of watchers. 4016faster performance with many (thousands) of watchers.
3981 4017
3982The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4018The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3983(disabled). 4019will be C<0>.
3984 4020
3985=item EV_HEAP_CACHE_AT 4021=item EV_HEAP_CACHE_AT
3986 4022
3987Heaps are not very cache-efficient. To improve the cache-efficiency of the 4023Heaps are not very cache-efficient. To improve the cache-efficiency of the
3988timer and periodics heaps, libev can cache the timestamp (I<at>) within 4024timer 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>), 4025the 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, 4026which 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 4027but avoids random read accesses on heap changes. This improves performance
3992noticeably with many (hundreds) of watchers. 4028noticeably with many (hundreds) of watchers.
3993 4029
3994The default is C<1> unless C<EV_MINIMAL> is set in which case it is C<0> 4030The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
3995(disabled). 4031will be C<0>.
3996 4032
3997=item EV_VERIFY 4033=item EV_VERIFY
3998 4034
3999Controls how much internal verification (see C<ev_loop_verify ()>) will 4035Controls how much internal verification (see C<ev_loop_verify ()>) will
4000be done: If set to C<0>, no internal verification code will be compiled 4036be 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 4038called. 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 4039called 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 4040verification code will be called very frequently, which will slow down
4005libev considerably. 4041libev considerably.
4006 4042
4007The default is C<1>, unless C<EV_MINIMAL> is set, in which case it will be 4043The default is C<1>, unless C<EV_FEATURES> overrides it, in which case it
4008C<0>. 4044will be C<0>.
4009 4045
4010=item EV_COMMON 4046=item EV_COMMON
4011 4047
4012By default, all watchers have a C<void *data> member. By redefining 4048By 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 4049this macro to a something else you can include more and other types of
4071file. 4107file.
4072 4108
4073The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file 4109The usage in rxvt-unicode is simpler. It has a F<ev_cpp.h> header file
4074that everybody includes and which overrides some configure choices: 4110that everybody includes and which overrides some configure choices:
4075 4111
4076 #define EV_MINIMAL 1 4112 #define EV_FEATURES 8
4077 #define EV_USE_POLL 0 4113 #define EV_USE_SELECT 1
4078 #define EV_MULTIPLICITY 0
4079 #define EV_PERIODIC_ENABLE 0 4114 #define EV_PREPARE_ENABLE 1
4115 #define EV_IDLE_ENABLE 1
4080 #define EV_STAT_ENABLE 0 4116 #define EV_SIGNAL_ENABLE 1
4081 #define EV_FORK_ENABLE 0 4117 #define EV_CHILD_ENABLE 1
4118 #define EV_USE_STDEXCEPT 0
4082 #define EV_CONFIG_H <config.h> 4119 #define EV_CONFIG_H <config.h>
4083 #define EV_MINPRI 0
4084 #define EV_MAXPRI 0
4085 4120
4086 #include "ev++.h" 4121 #include "ev++.h"
4087 4122
4088And a F<ev_cpp.C> implementation file that contains libev proper and is compiled: 4123And a F<ev_cpp.C> implementation file that contains libev proper and is compiled:
4089 4124
4591involves iterating over all running async watchers or all signal numbers. 4626involves iterating over all running async watchers or all signal numbers.
4592 4627
4593=back 4628=back
4594 4629
4595 4630
4631=head1 PORTING FROM LIBEV 3.X TO 4.X
4632
4633The major version 4 introduced some minor incompatible changes to the API.
4634
4635At the moment, the C<ev.h> header file tries to implement superficial
4636compatibility, so most programs should still compile. Those might be
4637removed in later versions of libev, so better update early than late.
4638
4639=over 4
4640
4641=item C<ev_loop_count> renamed to C<ev_iteration>
4642
4643=item C<ev_loop_depth> renamed to C<ev_depth>
4644
4645=item C<ev_loop_verify> renamed to C<ev_verify>
4646
4647Most functions working on C<struct ev_loop> objects don't have an
4648C<ev_loop_> prefix, so it was removed. Note that C<ev_loop_fork> is
4649still called C<ev_loop_fork> because it would otherwise clash with the
4650C<ev_fork> typedef.
4651
4652=item C<EV_TIMEOUT> renamed to C<EV_TIMER> in C<revents>
4653
4654This is a simple rename - all other watcher types use their name
4655as revents flag, and now C<ev_timer> does, too.
4656
4657Both C<EV_TIMER> and C<EV_TIMEOUT> symbols were present in 3.x versions
4658and continue to be present for the forseeable future, so this is mostly a
4659documentation change.
4660
4661=item C<EV_MINIMAL> mechanism replaced by C<EV_FEATURES>
4662
4663The preprocessor symbol C<EV_MINIMAL> has been replaced by a different
4664mechanism, C<EV_FEATURES>. Programs using C<EV_MINIMAL> usually compile
4665and work, but the library code will of course be larger.
4666
4667=back
4668
4669
4596=head1 GLOSSARY 4670=head1 GLOSSARY
4597 4671
4598=over 4 4672=over 4
4599 4673
4600=item active 4674=item active
4621A change of state of some external event, such as data now being available 4695A 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 4696for reading on a file descriptor, time having passed or simply not having
4623any other events happening anymore. 4697any other events happening anymore.
4624 4698
4625In libev, events are represented as single bits (such as C<EV_READ> or 4699In libev, events are represented as single bits (such as C<EV_READ> or
4626C<EV_TIMEOUT>). 4700C<EV_TIMER>).
4627 4701
4628=item event library 4702=item event library
4629 4703
4630A software package implementing an event model and loop. 4704A software package implementing an event model and loop.
4631 4705

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