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Revision 1.101 by root, Fri Dec 27 06:01:21 2013 UTC vs.
Revision 1.125 by sf-exg, Sun May 14 19:02:31 2023 UTC

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135.IX Title "LIBEV 3" 135.IX Title "LIBEV 3"
136.TH LIBEV 3 "2013-12-27" "libev-4.15" "libev - high performance full featured event loop" 136.TH LIBEV 3 "2021-01-11" "libev-4.33" "libev - high performance full featured event loop"
137.\" For nroff, turn off justification. Always turn off hyphenation; it makes 137.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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139.if n .ad l 139.if n .ad l
140.nh 140.nh
141.SH "NAME" 141.SH "NAME"
… …
240watchers\fR, which are relatively small C structures you initialise with the 240watchers\fR, which are relatively small C structures you initialise with the
241details of the event, and then hand it over to libev by \fIstarting\fR the 241details of the event, and then hand it over to libev by \fIstarting\fR the
242watcher. 242watcher.
243.SS "\s-1FEATURES\s0" 243.SS "\s-1FEATURES\s0"
244.IX Subsection "FEATURES" 244.IX Subsection "FEATURES"
245Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific \f(CW\*(C`epoll\*(C'\fR, the 245Libev supports \f(CW\*(C`select\*(C'\fR, \f(CW\*(C`poll\*(C'\fR, the Linux-specific aio and \f(CW\*(C`epoll\*(C'\fR
246BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port mechanisms 246interfaces, the BSD-specific \f(CW\*(C`kqueue\*(C'\fR and the Solaris-specific event port
247for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR interface 247mechanisms for file descriptor events (\f(CW\*(C`ev_io\*(C'\fR), the Linux \f(CW\*(C`inotify\*(C'\fR
248(for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner 248interface (for \f(CW\*(C`ev_stat\*(C'\fR), Linux eventfd/signalfd (for faster and cleaner
249inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative 249inter-thread wakeup (\f(CW\*(C`ev_async\*(C'\fR)/signal handling (\f(CW\*(C`ev_signal\*(C'\fR)) relative
250timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling 250timers (\f(CW\*(C`ev_timer\*(C'\fR), absolute timers with customised rescheduling
251(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status 251(\f(CW\*(C`ev_periodic\*(C'\fR), synchronous signals (\f(CW\*(C`ev_signal\*(C'\fR), process status
252change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event 252change events (\f(CW\*(C`ev_child\*(C'\fR), and event watchers dealing with the event
253loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and 253loop mechanism itself (\f(CW\*(C`ev_idle\*(C'\fR, \f(CW\*(C`ev_embed\*(C'\fR, \f(CW\*(C`ev_prepare\*(C'\fR and
… …
291When libev detects a usage error such as a negative timer interval, then 291When libev detects a usage error such as a negative timer interval, then
292it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism, 292it will print a diagnostic message and abort (via the \f(CW\*(C`assert\*(C'\fR mechanism,
293so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in 293so \f(CW\*(C`NDEBUG\*(C'\fR will disable this checking): these are programming errors in
294the libev caller and need to be fixed there. 294the libev caller and need to be fixed there.
295.PP 295.PP
296Via the \f(CW\*(C`EV_FREQUENT\*(C'\fR macro you can compile in and/or enable extensive
297consistency checking code inside libev that can be used to check for
298internal inconsistencies, suually caused by application bugs.
299.PP
296Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions, and also has 300Libev also has a few internal error-checking \f(CW\*(C`assert\*(C'\fRions. These do not
297extensive consistency checking code. These do not trigger under normal
298circumstances, as they indicate either a bug in libev or worse. 301trigger under normal circumstances, as they indicate either a bug in libev
302or worse.
299.SH "GLOBAL FUNCTIONS" 303.SH "GLOBAL FUNCTIONS"
300.IX Header "GLOBAL FUNCTIONS" 304.IX Header "GLOBAL FUNCTIONS"
301These functions can be called anytime, even before initialising the 305These functions can be called anytime, even before initialising the
302library in any way. 306library in any way.
303.IP "ev_tstamp ev_time ()" 4 307.IP "ev_tstamp ev_time ()" 4
… …
392.Sp 396.Sp
393You could override this function in high-availability programs to, say, 397You could override this function in high-availability programs to, say,
394free some memory if it cannot allocate memory, to use a special allocator, 398free some memory if it cannot allocate memory, to use a special allocator,
395or even to sleep a while and retry until some memory is available. 399or even to sleep a while and retry until some memory is available.
396.Sp 400.Sp
401Example: The following is the \f(CW\*(C`realloc\*(C'\fR function that libev itself uses
402which should work with \f(CW\*(C`realloc\*(C'\fR and \f(CW\*(C`free\*(C'\fR functions of all kinds and
403is probably a good basis for your own implementation.
404.Sp
405.Vb 5
406\& static void *
407\& ev_realloc_emul (void *ptr, long size) EV_NOEXCEPT
408\& {
409\& if (size)
410\& return realloc (ptr, size);
411\&
412\& free (ptr);
413\& return 0;
414\& }
415.Ve
416.Sp
397Example: Replace the libev allocator with one that waits a bit and then 417Example: Replace the libev allocator with one that waits a bit and then
398retries (example requires a standards-compliant \f(CW\*(C`realloc\*(C'\fR). 418retries.
399.Sp 419.Sp
400.Vb 6 420.Vb 8
401\& static void * 421\& static void *
402\& persistent_realloc (void *ptr, size_t size) 422\& persistent_realloc (void *ptr, size_t size)
403\& { 423\& {
424\& if (!size)
425\& {
426\& free (ptr);
427\& return 0;
428\& }
429\&
404\& for (;;) 430\& for (;;)
405\& { 431\& {
406\& void *newptr = realloc (ptr, size); 432\& void *newptr = realloc (ptr, size);
407\& 433\&
408\& if (newptr) 434\& if (newptr)
… …
536make libev check for a fork in each iteration by enabling this flag. 562make libev check for a fork in each iteration by enabling this flag.
537.Sp 563.Sp
538This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop, 564This works by calling \f(CW\*(C`getpid ()\*(C'\fR on every iteration of the loop,
539and thus this might slow down your event loop if you do a lot of loop 565and thus this might slow down your event loop if you do a lot of loop
540iterations and little real work, but is usually not noticeable (on my 566iterations and little real work, but is usually not noticeable (on my
541GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn sequence 567GNU/Linux system for example, \f(CW\*(C`getpid\*(C'\fR is actually a simple 5\-insn
542without a system call and thus \fIvery\fR fast, but my GNU/Linux system also has 568sequence without a system call and thus \fIvery\fR fast, but my GNU/Linux
543\&\f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). 569system also has \f(CW\*(C`pthread_atfork\*(C'\fR which is even faster). (Update: glibc
570versions 2.25 apparently removed the \f(CW\*(C`getpid\*(C'\fR optimisation again).
544.Sp 571.Sp
545The big advantage of this flag is that you can forget about fork (and 572The big advantage of this flag is that you can forget about fork (and
546forget about forgetting to tell libev about forking) when you use this 573forget about forgetting to tell libev about forking, although you still
547flag. 574have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR) when you use this flag.
548.Sp 575.Sp
549This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR 576This flag setting cannot be overridden or specified in the \f(CW\*(C`LIBEV_FLAGS\*(C'\fR
550environment variable. 577environment variable.
551.ie n .IP """EVFLAG_NOINOTIFY""" 4 578.ie n .IP """EVFLAG_NOINOTIFY""" 4
552.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4 579.el .IP "\f(CWEVFLAG_NOINOTIFY\fR" 4
… …
579want to handle signals only in specific threads and want to avoid libev 606want to handle signals only in specific threads and want to avoid libev
580unblocking the signals. 607unblocking the signals.
581.Sp 608.Sp
582It's also required by \s-1POSIX\s0 in a threaded program, as libev calls 609It's also required by \s-1POSIX\s0 in a threaded program, as libev calls
583\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified. 610\&\f(CW\*(C`sigprocmask\*(C'\fR, whose behaviour is officially unspecified.
611.ie n .IP """EVFLAG_NOTIMERFD""" 4
612.el .IP "\f(CWEVFLAG_NOTIMERFD\fR" 4
613.IX Item "EVFLAG_NOTIMERFD"
614When this flag is specified, the libev will avoid using a \f(CW\*(C`timerfd\*(C'\fR to
615detect time jumps. It will still be able to detect time jumps, but takes
616longer and has a lower accuracy in doing so, but saves a file descriptor
617per loop.
584.Sp 618.Sp
585This flag's behaviour will become the default in future versions of libev. 619The current implementation only tries to use a \f(CW\*(C`timerfd\*(C'\fR when the first
620\&\f(CW\*(C`ev_periodic\*(C'\fR watcher is started and falls back on other methods if it
621cannot be created, but this behaviour might change in the future.
586.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4 622.ie n .IP """EVBACKEND_SELECT"" (value 1, portable select backend)" 4
587.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4 623.el .IP "\f(CWEVBACKEND_SELECT\fR (value 1, portable select backend)" 4
588.IX Item "EVBACKEND_SELECT (value 1, portable select backend)" 624.IX Item "EVBACKEND_SELECT (value 1, portable select backend)"
589This is your standard \fIselect\fR\|(2) backend. Not \fIcompletely\fR standard, as 625This is your standard \fBselect\fR\|(2) backend. Not \fIcompletely\fR standard, as
590libev tries to roll its own fd_set with no limits on the number of fds, 626libev tries to roll its own fd_set with no limits on the number of fds,
591but if that fails, expect a fairly low limit on the number of fds when 627but if that fails, expect a fairly low limit on the number of fds when
592using this backend. It doesn't scale too well (O(highest_fd)), but its 628using this backend. It doesn't scale too well (O(highest_fd)), but its
593usually the fastest backend for a low number of (low-numbered :) fds. 629usually the fastest backend for a low number of (low-numbered :) fds.
594.Sp 630.Sp
… …
603\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the 639\&\f(CW\*(C`writefds\*(C'\fR set (and to work around Microsoft Windows bugs, also onto the
604\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform). 640\&\f(CW\*(C`exceptfds\*(C'\fR set on that platform).
605.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4 641.ie n .IP """EVBACKEND_POLL"" (value 2, poll backend, available everywhere except on windows)" 4
606.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4 642.el .IP "\f(CWEVBACKEND_POLL\fR (value 2, poll backend, available everywhere except on windows)" 4
607.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)" 643.IX Item "EVBACKEND_POLL (value 2, poll backend, available everywhere except on windows)"
608And this is your standard \fIpoll\fR\|(2) backend. It's more complicated 644And this is your standard \fBpoll\fR\|(2) backend. It's more complicated
609than select, but handles sparse fds better and has no artificial 645than select, but handles sparse fds better and has no artificial
610limit on the number of fds you can use (except it will slow down 646limit on the number of fds you can use (except it will slow down
611considerably with a lot of inactive fds). It scales similarly to select, 647considerably with a lot of inactive fds). It scales similarly to select,
612i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for 648i.e. O(total_fds). See the entry for \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR, above, for
613performance tips. 649performance tips.
… …
615This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and 651This backend maps \f(CW\*(C`EV_READ\*(C'\fR to \f(CW\*(C`POLLIN | POLLERR | POLLHUP\*(C'\fR, and
616\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR. 652\&\f(CW\*(C`EV_WRITE\*(C'\fR to \f(CW\*(C`POLLOUT | POLLERR | POLLHUP\*(C'\fR.
617.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4 653.ie n .IP """EVBACKEND_EPOLL"" (value 4, Linux)" 4
618.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4 654.el .IP "\f(CWEVBACKEND_EPOLL\fR (value 4, Linux)" 4
619.IX Item "EVBACKEND_EPOLL (value 4, Linux)" 655.IX Item "EVBACKEND_EPOLL (value 4, Linux)"
620Use the linux-specific \fIepoll\fR\|(7) interface (for both pre\- and post\-2.6.9 656Use the Linux-specific \fBepoll\fR\|(7) interface (for both pre\- and post\-2.6.9
621kernels). 657kernels).
622.Sp 658.Sp
623For few fds, this backend is a bit little slower than poll and select, but 659For few fds, this backend is a bit little slower than poll and select, but
624it scales phenomenally better. While poll and select usually scale like 660it scales phenomenally better. While poll and select usually scale like
625O(total_fds) where total_fds is the total number of fds (or the highest 661O(total_fds) where total_fds is the total number of fds (or the highest
… …
671All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or 707All this means that, in practice, \f(CW\*(C`EVBACKEND_SELECT\*(C'\fR can be as fast or
672faster than epoll for maybe up to a hundred file descriptors, depending on 708faster than epoll for maybe up to a hundred file descriptors, depending on
673the usage. So sad. 709the usage. So sad.
674.Sp 710.Sp
675While nominally embeddable in other event loops, this feature is broken in 711While nominally embeddable in other event loops, this feature is broken in
676all kernel versions tested so far. 712a lot of kernel revisions, but probably(!) works in current versions.
713.Sp
714This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
715\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
716.ie n .IP """EVBACKEND_LINUXAIO"" (value 64, Linux)" 4
717.el .IP "\f(CWEVBACKEND_LINUXAIO\fR (value 64, Linux)" 4
718.IX Item "EVBACKEND_LINUXAIO (value 64, Linux)"
719Use the Linux-specific Linux \s-1AIO\s0 (\fInot\fR \f(CWaio(7)\fR but \f(CWio_submit(2)\fR) event interface available in post\-4.18 kernels (but libev
720only tries to use it in 4.19+).
721.Sp
722This is another Linux train wreck of an event interface.
723.Sp
724If this backend works for you (as of this writing, it was very
725experimental), it is the best event interface available on Linux and might
726be well worth enabling it \- if it isn't available in your kernel this will
727be detected and this backend will be skipped.
728.Sp
729This backend can batch oneshot requests and supports a user-space ring
730buffer to receive events. It also doesn't suffer from most of the design
731problems of epoll (such as not being able to remove event sources from
732the epoll set), and generally sounds too good to be true. Because, this
733being the Linux kernel, of course it suffers from a whole new set of
734limitations, forcing you to fall back to epoll, inheriting all its design
735issues.
736.Sp
737For one, it is not easily embeddable (but probably could be done using
738an event fd at some extra overhead). It also is subject to a system wide
739limit that can be configured in \fI/proc/sys/fs/aio\-max\-nr\fR. If no \s-1AIO\s0
740requests are left, this backend will be skipped during initialisation, and
741will switch to epoll when the loop is active.
742.Sp
743Most problematic in practice, however, is that not all file descriptors
744work with it. For example, in Linux 5.1, \s-1TCP\s0 sockets, pipes, event fds,
745files, \fI/dev/null\fR and many others are supported, but ttys do not work
746properly (a known bug that the kernel developers don't care about, see
747<https://lore.kernel.org/patchwork/patch/1047453/>), so this is not
748(yet?) a generic event polling interface.
749.Sp
750Overall, it seems the Linux developers just don't want it to have a
751generic event handling mechanism other than \f(CW\*(C`select\*(C'\fR or \f(CW\*(C`poll\*(C'\fR.
752.Sp
753To work around all these problem, the current version of libev uses its
754epoll backend as a fallback for file descriptor types that do not work. Or
755falls back completely to epoll if the kernel acts up.
677.Sp 756.Sp
678This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as 757This backend maps \f(CW\*(C`EV_READ\*(C'\fR and \f(CW\*(C`EV_WRITE\*(C'\fR in the same way as
679\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR. 758\&\f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
680.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4 759.ie n .IP """EVBACKEND_KQUEUE"" (value 8, most \s-1BSD\s0 clones)" 4
681.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4 760.el .IP "\f(CWEVBACKEND_KQUEUE\fR (value 8, most \s-1BSD\s0 clones)" 4
682.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)" 761.IX Item "EVBACKEND_KQUEUE (value 8, most BSD clones)"
683Kqueue deserves special mention, as at the time of this writing, it 762Kqueue deserves special mention, as at the time this backend was
684was broken on all BSDs except NetBSD (usually it doesn't work reliably 763implemented, it was broken on all BSDs except NetBSD (usually it doesn't
685with anything but sockets and pipes, except on Darwin, where of course 764work reliably with anything but sockets and pipes, except on Darwin,
686it's completely useless). Unlike epoll, however, whose brokenness 765where of course it's completely useless). Unlike epoll, however, whose
687is by design, these kqueue bugs can (and eventually will) be fixed 766brokenness is by design, these kqueue bugs can be (and mostly have been)
688without \s-1API\s0 changes to existing programs. For this reason it's not being 767fixed without \s-1API\s0 changes to existing programs. For this reason it's not
689\&\*(L"auto-detected\*(R" unless you explicitly specify it in the flags (i.e. using 768being \*(L"auto-detected\*(R" on all platforms unless you explicitly specify it
690\&\f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a known-to-be-good (\-enough) 769in the flags (i.e. using \f(CW\*(C`EVBACKEND_KQUEUE\*(C'\fR) or libev was compiled on a
691system like NetBSD. 770known-to-be-good (\-enough) system like NetBSD.
692.Sp 771.Sp
693You still can embed kqueue into a normal poll or select backend and use it 772You still can embed kqueue into a normal poll or select backend and use it
694only for sockets (after having made sure that sockets work with kqueue on 773only for sockets (after having made sure that sockets work with kqueue on
695the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info. 774the target platform). See \f(CW\*(C`ev_embed\*(C'\fR watchers for more info.
696.Sp 775.Sp
697It scales in the same way as the epoll backend, but the interface to the 776It scales in the same way as the epoll backend, but the interface to the
698kernel is more efficient (which says nothing about its actual speed, of 777kernel is more efficient (which says nothing about its actual speed, of
699course). While stopping, setting and starting an I/O watcher does never 778course). While stopping, setting and starting an I/O watcher does never
700cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to 779cause an extra system call as with \f(CW\*(C`EVBACKEND_EPOLL\*(C'\fR, it still adds up to
701two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you 780two event changes per incident. Support for \f(CW\*(C`fork ()\*(C'\fR is very bad (you
702might have to leak fd's on fork, but it's more sane than epoll) and it 781might have to leak fds on fork, but it's more sane than epoll) and it
703drops fds silently in similarly hard-to-detect cases. 782drops fds silently in similarly hard-to-detect cases.
704.Sp 783.Sp
705This backend usually performs well under most conditions. 784This backend usually performs well under most conditions.
706.Sp 785.Sp
707While nominally embeddable in other event loops, this doesn't work 786While nominally embeddable in other event loops, this doesn't work
… …
785used if available. 864used if available.
786.Sp 865.Sp
787.Vb 1 866.Vb 1
788\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE); 867\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_KQUEUE);
789.Ve 868.Ve
869.Sp
870Example: Similarly, on linux, you mgiht want to take advantage of the
871linux aio backend if possible, but fall back to something else if that
872isn't available.
873.Sp
874.Vb 1
875\& struct ev_loop *loop = ev_loop_new (ev_recommended_backends () | EVBACKEND_LINUXAIO);
876.Ve
790.RE 877.RE
791.IP "ev_loop_destroy (loop)" 4 878.IP "ev_loop_destroy (loop)" 4
792.IX Item "ev_loop_destroy (loop)" 879.IX Item "ev_loop_destroy (loop)"
793Destroys an event loop object (frees all memory and kernel state 880Destroys an event loop object (frees all memory and kernel state
794etc.). None of the active event watchers will be stopped in the normal 881etc.). None of the active event watchers will be stopped in the normal
… …
810except in the rare occasion where you really need to free its resources. 897except in the rare occasion where you really need to free its resources.
811If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR 898If you need dynamically allocated loops it is better to use \f(CW\*(C`ev_loop_new\*(C'\fR
812and \f(CW\*(C`ev_loop_destroy\*(C'\fR. 899and \f(CW\*(C`ev_loop_destroy\*(C'\fR.
813.IP "ev_loop_fork (loop)" 4 900.IP "ev_loop_fork (loop)" 4
814.IX Item "ev_loop_fork (loop)" 901.IX Item "ev_loop_fork (loop)"
815This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations to 902This function sets a flag that causes subsequent \f(CW\*(C`ev_run\*(C'\fR iterations
816reinitialise the kernel state for backends that have one. Despite the 903to reinitialise the kernel state for backends that have one. Despite
817name, you can call it anytime, but it makes most sense after forking, in 904the name, you can call it anytime you are allowed to start or stop
818the child process. You \fImust\fR call it (or use \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the 905watchers (except inside an \f(CW\*(C`ev_prepare\*(C'\fR callback), but it makes most
819child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR. 906sense after forking, in the child process. You \fImust\fR call it (or use
907\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR) in the child before resuming or calling \f(CW\*(C`ev_run\*(C'\fR.
908.Sp
909In addition, if you want to reuse a loop (via this function or
910\&\f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR), you \fIalso\fR have to ignore \f(CW\*(C`SIGPIPE\*(C'\fR.
820.Sp 911.Sp
821Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after 912Again, you \fIhave\fR to call it on \fIany\fR loop that you want to re-use after
822a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is 913a fork, \fIeven if you do not plan to use the loop in the parent\fR. This is
823because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things 914because some kernel interfaces *cough* \fIkqueue\fR *cough* do funny things
824during fork. 915during fork.
… …
996\& \- Queue all expired timers. 1087\& \- Queue all expired timers.
997\& \- Queue all expired periodics. 1088\& \- Queue all expired periodics.
998\& \- Queue all idle watchers with priority higher than that of pending events. 1089\& \- Queue all idle watchers with priority higher than that of pending events.
999\& \- Queue all check watchers. 1090\& \- Queue all check watchers.
1000\& \- Call all queued watchers in reverse order (i.e. check watchers first). 1091\& \- Call all queued watchers in reverse order (i.e. check watchers first).
1001\& Signals and child watchers are implemented as I/O watchers, and will 1092\& Signals, async and child watchers are implemented as I/O watchers, and
1002\& be handled here by queueing them when their watcher gets executed. 1093\& will be handled here by queueing them when their watcher gets executed.
1003\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT 1094\& \- If ev_break has been called, or EVRUN_ONCE or EVRUN_NOWAIT
1004\& were used, or there are no active watchers, goto FINISH, otherwise 1095\& were used, or there are no active watchers, goto FINISH, otherwise
1005\& continue with step LOOP. 1096\& continue with step LOOP.
1006\& FINISH: 1097\& FINISH:
1007\& \- Reset the ev_break status iff it was EVBREAK_ONE. 1098\& \- Reset the ev_break status iff it was EVBREAK_ONE.
… …
1258with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher 1349with a watcher-specific start function (\f(CW\*(C`ev_TYPE_start (loop, watcher
1259*)\*(C'\fR), and you can stop watching for events at any time by calling the 1350*)\*(C'\fR), and you can stop watching for events at any time by calling the
1260corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR. 1351corresponding stop function (\f(CW\*(C`ev_TYPE_stop (loop, watcher *)\*(C'\fR.
1261.PP 1352.PP
1262As long as your watcher is active (has been started but not stopped) you 1353As long as your watcher is active (has been started but not stopped) you
1263must not touch the values stored in it. Most specifically you must never 1354must not touch the values stored in it except when explicitly documented
1264reinitialise it or call its \f(CW\*(C`ev_TYPE_set\*(C'\fR macro. 1355otherwise. Most specifically you must never reinitialise it or call its
1356\&\f(CW\*(C`ev_TYPE_set\*(C'\fR macro.
1265.PP 1357.PP
1266Each and every callback receives the event loop pointer as first, the 1358Each and every callback receives the event loop pointer as first, the
1267registered watcher structure as second, and a bitset of received events as 1359registered watcher structure as second, and a bitset of received events as
1268third argument. 1360third argument.
1269.PP 1361.PP
… …
1360bug in your program. 1452bug in your program.
1361.Sp 1453.Sp
1362Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for 1454Libev will usually signal a few \*(L"dummy\*(R" events together with an error, for
1363example it might indicate that a fd is readable or writable, and if your 1455example it might indicate that a fd is readable or writable, and if your
1364callbacks is well-written it can just attempt the operation and cope with 1456callbacks is well-written it can just attempt the operation and cope with
1365the error from \fIread()\fR or \fIwrite()\fR. This will not work in multi-threaded 1457the error from \fBread()\fR or \fBwrite()\fR. This will not work in multi-threaded
1366programs, though, as the fd could already be closed and reused for another 1458programs, though, as the fd could already be closed and reused for another
1367thing, so beware. 1459thing, so beware.
1368.SS "\s-1GENERIC WATCHER FUNCTIONS\s0" 1460.SS "\s-1GENERIC WATCHER FUNCTIONS\s0"
1369.IX Subsection "GENERIC WATCHER FUNCTIONS" 1461.IX Subsection "GENERIC WATCHER FUNCTIONS"
1370.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4 1462.ie n .IP """ev_init"" (ev_TYPE *watcher, callback)" 4
… …
1440therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function. 1532therefore a good idea to always call its \f(CW\*(C`ev_TYPE_stop\*(C'\fR function.
1441.IP "bool ev_is_active (ev_TYPE *watcher)" 4 1533.IP "bool ev_is_active (ev_TYPE *watcher)" 4
1442.IX Item "bool ev_is_active (ev_TYPE *watcher)" 1534.IX Item "bool ev_is_active (ev_TYPE *watcher)"
1443Returns a true value iff the watcher is active (i.e. it has been started 1535Returns a true value iff the watcher is active (i.e. it has been started
1444and not yet been stopped). As long as a watcher is active you must not modify 1536and not yet been stopped). As long as a watcher is active you must not modify
1445it. 1537it unless documented otherwise.
1446.IP "bool ev_is_pending (ev_TYPE *watcher)" 4 1538.IP "bool ev_is_pending (ev_TYPE *watcher)" 4
1447.IX Item "bool ev_is_pending (ev_TYPE *watcher)" 1539.IX Item "bool ev_is_pending (ev_TYPE *watcher)"
1448Returns a true value iff the watcher is pending, (i.e. it has outstanding 1540Returns a true value iff the watcher is pending, (i.e. it has outstanding
1449events but its callback has not yet been invoked). As long as a watcher 1541events but its callback has not yet been invoked). As long as a watcher
1450is pending (but not active) you must not call an init function on it (but 1542is pending (but not active) you must not call an init function on it (but
… …
1572.IX Subsection "WATCHER PRIORITY MODELS" 1664.IX Subsection "WATCHER PRIORITY MODELS"
1573Many event loops support \fIwatcher priorities\fR, which are usually small 1665Many event loops support \fIwatcher priorities\fR, which are usually small
1574integers that influence the ordering of event callback invocation 1666integers that influence the ordering of event callback invocation
1575between watchers in some way, all else being equal. 1667between watchers in some way, all else being equal.
1576.PP 1668.PP
1577In libev, Watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its 1669In libev, watcher priorities can be set using \f(CW\*(C`ev_set_priority\*(C'\fR. See its
1578description for the more technical details such as the actual priority 1670description for the more technical details such as the actual priority
1579range. 1671range.
1580.PP 1672.PP
1581There are two common ways how these these priorities are being interpreted 1673There are two common ways how these these priorities are being interpreted
1582by event loops: 1674by event loops:
… …
1676.IX Header "WATCHER TYPES" 1768.IX Header "WATCHER TYPES"
1677This section describes each watcher in detail, but will not repeat 1769This section describes each watcher in detail, but will not repeat
1678information given in the last section. Any initialisation/set macros, 1770information given in the last section. Any initialisation/set macros,
1679functions and members specific to the watcher type are explained. 1771functions and members specific to the watcher type are explained.
1680.PP 1772.PP
1681Members are additionally marked with either \fI[read\-only]\fR, meaning that, 1773Most members are additionally marked with either \fI[read\-only]\fR, meaning
1682while the watcher is active, you can look at the member and expect some 1774that, while the watcher is active, you can look at the member and expect
1683sensible content, but you must not modify it (you can modify it while the 1775some sensible content, but you must not modify it (you can modify it while
1684watcher is stopped to your hearts content), or \fI[read\-write]\fR, which 1776the watcher is stopped to your hearts content), or \fI[read\-write]\fR, which
1685means you can expect it to have some sensible content while the watcher 1777means you can expect it to have some sensible content while the watcher is
1686is active, but you can also modify it. Modifying it may not do something 1778active, but you can also modify it (within the same thread as the event
1779loop, i.e. without creating data races). Modifying it may not do something
1687sensible or take immediate effect (or do anything at all), but libev will 1780sensible or take immediate effect (or do anything at all), but libev will
1688not crash or malfunction in any way. 1781not crash or malfunction in any way.
1782.PP
1783In any case, the documentation for each member will explain what the
1784effects are, and if there are any additional access restrictions.
1689.ie n .SS """ev_io"" \- is this file descriptor readable or writable?" 1785.ie n .SS """ev_io"" \- is this file descriptor readable or writable?"
1690.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?" 1786.el .SS "\f(CWev_io\fP \- is this file descriptor readable or writable?"
1691.IX Subsection "ev_io - is this file descriptor readable or writable?" 1787.IX Subsection "ev_io - is this file descriptor readable or writable?"
1692I/O watchers check whether a file descriptor is readable or writable 1788I/O watchers check whether a file descriptor is readable or writable
1693in each iteration of the event loop, or, more precisely, when reading 1789in each iteration of the event loop, or, more precisely, when reading
… …
1721But really, best use non-blocking mode. 1817But really, best use non-blocking mode.
1722.PP 1818.PP
1723\fIThe special problem of disappearing file descriptors\fR 1819\fIThe special problem of disappearing file descriptors\fR
1724.IX Subsection "The special problem of disappearing file descriptors" 1820.IX Subsection "The special problem of disappearing file descriptors"
1725.PP 1821.PP
1726Some backends (e.g. kqueue, epoll) need to be told about closing a file 1822Some backends (e.g. kqueue, epoll, linuxaio) need to be told about closing
1727descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other means, 1823a file descriptor (either due to calling \f(CW\*(C`close\*(C'\fR explicitly or any other
1728such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some file 1824means, such as \f(CW\*(C`dup2\*(C'\fR). The reason is that you register interest in some
1729descriptor, but when it goes away, the operating system will silently drop 1825file descriptor, but when it goes away, the operating system will silently
1730this interest. If another file descriptor with the same number then is 1826drop this interest. If another file descriptor with the same number then
1731registered with libev, there is no efficient way to see that this is, in 1827is registered with libev, there is no efficient way to see that this is,
1732fact, a different file descriptor. 1828in fact, a different file descriptor.
1733.PP 1829.PP
1734To avoid having to explicitly tell libev about such cases, libev follows 1830To avoid having to explicitly tell libev about such cases, libev follows
1735the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev 1831the following policy: Each time \f(CW\*(C`ev_io_set\*(C'\fR is being called, libev
1736will assume that this is potentially a new file descriptor, otherwise 1832will assume that this is potentially a new file descriptor, otherwise
1737it is assumed that the file descriptor stays the same. That means that 1833it is assumed that the file descriptor stays the same. That means that
… …
1789reuse the same code path. 1885reuse the same code path.
1790.PP 1886.PP
1791\fIThe special problem of fork\fR 1887\fIThe special problem of fork\fR
1792.IX Subsection "The special problem of fork" 1888.IX Subsection "The special problem of fork"
1793.PP 1889.PP
1794Some backends (epoll, kqueue) do not support \f(CW\*(C`fork ()\*(C'\fR at all or exhibit 1890Some backends (epoll, kqueue, linuxaio, iouring) do not support \f(CW\*(C`fork ()\*(C'\fR
1795useless behaviour. Libev fully supports fork, but needs to be told about 1891at all or exhibit useless behaviour. Libev fully supports fork, but needs
1796it in the child if you want to continue to use it in the child. 1892to be told about it in the child if you want to continue to use it in the
1893child.
1797.PP 1894.PP
1798To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork 1895To support fork in your child processes, you have to call \f(CW\*(C`ev_loop_fork
1799()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to 1896()\*(C'\fR after a fork in the child, enable \f(CW\*(C`EVFLAG_FORKCHECK\*(C'\fR, or resort to
1800\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR. 1897\&\f(CW\*(C`EVBACKEND_SELECT\*(C'\fR or \f(CW\*(C`EVBACKEND_POLL\*(C'\fR.
1801.PP 1898.PP
… …
1806when writing to a pipe whose other end has been closed, your program gets 1903when writing to a pipe whose other end has been closed, your program gets
1807sent a \s-1SIGPIPE,\s0 which, by default, aborts your program. For most programs 1904sent a \s-1SIGPIPE,\s0 which, by default, aborts your program. For most programs
1808this is sensible behaviour, for daemons, this is usually undesirable. 1905this is sensible behaviour, for daemons, this is usually undesirable.
1809.PP 1906.PP
1810So when you encounter spurious, unexplained daemon exits, make sure you 1907So when you encounter spurious, unexplained daemon exits, make sure you
1811ignore \s-1SIGPIPE \s0(and maybe make sure you log the exit status of your daemon 1908ignore \s-1SIGPIPE\s0 (and maybe make sure you log the exit status of your daemon
1812somewhere, as that would have given you a big clue). 1909somewhere, as that would have given you a big clue).
1813.PP 1910.PP
1814\fIThe special problem of \fIaccept()\fIing when you can't\fR 1911\fIThe special problem of \f(BIaccept()\fIing when you can't\fR
1815.IX Subsection "The special problem of accept()ing when you can't" 1912.IX Subsection "The special problem of accept()ing when you can't"
1816.PP 1913.PP
1817Many implementations of the \s-1POSIX \s0\f(CW\*(C`accept\*(C'\fR function (for example, 1914Many implementations of the \s-1POSIX\s0 \f(CW\*(C`accept\*(C'\fR function (for example,
1818found in post\-2004 Linux) have the peculiar behaviour of not removing a 1915found in post\-2004 Linux) have the peculiar behaviour of not removing a
1819connection from the pending queue in all error cases. 1916connection from the pending queue in all error cases.
1820.PP 1917.PP
1821For example, larger servers often run out of file descriptors (because 1918For example, larger servers often run out of file descriptors (because
1822of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not 1919of resource limits), causing \f(CW\*(C`accept\*(C'\fR to fail with \f(CW\*(C`ENFILE\*(C'\fR but not
… …
1858.PD 0 1955.PD 0
1859.IP "ev_io_set (ev_io *, int fd, int events)" 4 1956.IP "ev_io_set (ev_io *, int fd, int events)" 4
1860.IX Item "ev_io_set (ev_io *, int fd, int events)" 1957.IX Item "ev_io_set (ev_io *, int fd, int events)"
1861.PD 1958.PD
1862Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to 1959Configures an \f(CW\*(C`ev_io\*(C'\fR watcher. The \f(CW\*(C`fd\*(C'\fR is the file descriptor to
1863receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR or 1960receive events for and \f(CW\*(C`events\*(C'\fR is either \f(CW\*(C`EV_READ\*(C'\fR, \f(CW\*(C`EV_WRITE\*(C'\fR, both
1864\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR, to express the desire to receive the given events. 1961\&\f(CW\*(C`EV_READ | EV_WRITE\*(C'\fR or \f(CW0\fR, to express the desire to receive the given
1962events.
1963.Sp
1964Note that setting the \f(CW\*(C`events\*(C'\fR to \f(CW0\fR and starting the watcher is
1965supported, but not specially optimized \- if your program sometimes happens
1966to generate this combination this is fine, but if it is easy to avoid
1967starting an io watcher watching for no events you should do so.
1968.IP "ev_io_modify (ev_io *, int events)" 4
1969.IX Item "ev_io_modify (ev_io *, int events)"
1970Similar to \f(CW\*(C`ev_io_set\*(C'\fR, but only changes the requested events. Using this
1971might be faster with some backends, as libev can assume that the \f(CW\*(C`fd\*(C'\fR
1972still refers to the same underlying file description, something it cannot
1973do when using \f(CW\*(C`ev_io_set\*(C'\fR.
1865.IP "int fd [read\-only]" 4 1974.IP "int fd [no\-modify]" 4
1866.IX Item "int fd [read-only]" 1975.IX Item "int fd [no-modify]"
1867The file descriptor being watched. 1976The file descriptor being watched. While it can be read at any time, you
1977must not modify this member even when the watcher is stopped \- always use
1978\&\f(CW\*(C`ev_io_set\*(C'\fR for that.
1868.IP "int events [read\-only]" 4 1979.IP "int events [no\-modify]" 4
1869.IX Item "int events [read-only]" 1980.IX Item "int events [no-modify]"
1870The events being watched. 1981The set of events the fd is being watched for, among other flags. Remember
1982that this is a bit set \- to test for \f(CW\*(C`EV_READ\*(C'\fR, use \f(CW\*(C`w\->events &
1983EV_READ\*(C'\fR, and similarly for \f(CW\*(C`EV_WRITE\*(C'\fR.
1984.Sp
1985As with \f(CW\*(C`fd\*(C'\fR, you must not modify this member even when the watcher is
1986stopped, always use \f(CW\*(C`ev_io_set\*(C'\fR or \f(CW\*(C`ev_io_modify\*(C'\fR for that.
1871.PP 1987.PP
1872\fIExamples\fR 1988\fIExamples\fR
1873.IX Subsection "Examples" 1989.IX Subsection "Examples"
1874.PP 1990.PP
1875Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well 1991Example: Call \f(CW\*(C`stdin_readable_cb\*(C'\fR when \s-1STDIN_FILENO\s0 has become, well
… …
2161.PP 2277.PP
2162The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR 2278The relative timeouts are calculated relative to the \f(CW\*(C`ev_now ()\*(C'\fR
2163time. This is usually the right thing as this timestamp refers to the time 2279time. This is usually the right thing as this timestamp refers to the time
2164of the event triggering whatever timeout you are modifying/starting. If 2280of the event triggering whatever timeout you are modifying/starting. If
2165you suspect event processing to be delayed and you \fIneed\fR to base the 2281you suspect event processing to be delayed and you \fIneed\fR to base the
2166timeout on the current time, use something like this to adjust for this: 2282timeout on the current time, use something like the following to adjust
2283for it:
2167.PP 2284.PP
2168.Vb 1 2285.Vb 1
2169\& ev_timer_set (&timer, after + ev_now () \- ev_time (), 0.); 2286\& ev_timer_set (&timer, after + (ev_time () \- ev_now ()), 0.);
2170.Ve 2287.Ve
2171.PP 2288.PP
2172If the event loop is suspended for a long time, you can also force an 2289If the event loop is suspended for a long time, you can also force an
2173update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update 2290update of the time returned by \f(CW\*(C`ev_now ()\*(C'\fR by calling \f(CW\*(C`ev_now_update
2174()\*(C'\fR. 2291()\*(C'\fR, although that will push the event time of all outstanding events
2292further into the future.
2175.PP 2293.PP
2176\fIThe special problem of unsynchronised clocks\fR 2294\fIThe special problem of unsynchronised clocks\fR
2177.IX Subsection "The special problem of unsynchronised clocks" 2295.IX Subsection "The special problem of unsynchronised clocks"
2178.PP 2296.PP
2179Modern systems have a variety of clocks \- libev itself uses the normal 2297Modern systems have a variety of clocks \- libev itself uses the normal
… …
2244.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)" 2362.IX Item "ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)"
2245.PD 0 2363.PD 0
2246.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4 2364.IP "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 4
2247.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)" 2365.IX Item "ev_timer_set (ev_timer *, ev_tstamp after, ev_tstamp repeat)"
2248.PD 2366.PD
2249Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds. If \f(CW\*(C`repeat\*(C'\fR 2367Configure the timer to trigger after \f(CW\*(C`after\*(C'\fR seconds (fractional and
2250is \f(CW0.\fR, then it will automatically be stopped once the timeout is 2368negative values are supported). If \f(CW\*(C`repeat\*(C'\fR is \f(CW0.\fR, then it will
2251reached. If it is positive, then the timer will automatically be 2369automatically be stopped once the timeout is reached. If it is positive,
2252configured to trigger again \f(CW\*(C`repeat\*(C'\fR seconds later, again, and again, 2370then the timer will automatically be configured to trigger again \f(CW\*(C`repeat\*(C'\fR
2253until stopped manually. 2371seconds later, again, and again, until stopped manually.
2254.Sp 2372.Sp
2255The timer itself will do a best-effort at avoiding drift, that is, if 2373The timer itself will do a best-effort at avoiding drift, that is, if
2256you configure a timer to trigger every 10 seconds, then it will normally 2374you configure a timer to trigger every 10 seconds, then it will normally
2257trigger at exactly 10 second intervals. If, however, your program cannot 2375trigger at exactly 10 second intervals. If, however, your program cannot
2258keep up with the timer (because it takes longer than those 10 seconds to 2376keep up with the timer (because it takes longer than those 10 seconds to
… …
2340Periodic watchers are also timers of a kind, but they are very versatile 2458Periodic watchers are also timers of a kind, but they are very versatile
2341(and unfortunately a bit complex). 2459(and unfortunately a bit complex).
2342.PP 2460.PP
2343Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or 2461Unlike \f(CW\*(C`ev_timer\*(C'\fR, periodic watchers are not based on real time (or
2344relative time, the physical time that passes) but on wall clock time 2462relative time, the physical time that passes) but on wall clock time
2345(absolute time, the thing you can read on your calender or clock). The 2463(absolute time, the thing you can read on your calendar or clock). The
2346difference is that wall clock time can run faster or slower than real 2464difference is that wall clock time can run faster or slower than real
2347time, and time jumps are not uncommon (e.g. when you adjust your 2465time, and time jumps are not uncommon (e.g. when you adjust your
2348wrist-watch). 2466wrist-watch).
2349.PP 2467.PP
2350You can tell a periodic watcher to trigger after some specific point 2468You can tell a periodic watcher to trigger after some specific point
… …
2355\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting 2473\&\f(CW\*(C`ev_timer\*(C'\fR, which would still trigger roughly 10 seconds after starting
2356it, as it uses a relative timeout). 2474it, as it uses a relative timeout).
2357.PP 2475.PP
2358\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex 2476\&\f(CW\*(C`ev_periodic\*(C'\fR watchers can also be used to implement vastly more complex
2359timers, such as triggering an event on each \*(L"midnight, local time\*(R", or 2477timers, such as triggering an event on each \*(L"midnight, local time\*(R", or
2360other complicated rules. This cannot be done with \f(CW\*(C`ev_timer\*(C'\fR watchers, as 2478other complicated rules. This cannot easily be done with \f(CW\*(C`ev_timer\*(C'\fR
2361those cannot react to time jumps. 2479watchers, as those cannot react to time jumps.
2362.PP 2480.PP
2363As with timers, the callback is guaranteed to be invoked only when the 2481As with timers, the callback is guaranteed to be invoked only when the
2364point in time where it is supposed to trigger has passed. If multiple 2482point in time where it is supposed to trigger has passed. If multiple
2365timers become ready during the same loop iteration then the ones with 2483timers become ready during the same loop iteration then the ones with
2366earlier time-out values are invoked before ones with later time-out values 2484earlier time-out values are invoked before ones with later time-out values
… …
2427In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being 2545In this mode the values for \f(CW\*(C`interval\*(C'\fR and \f(CW\*(C`offset\*(C'\fR are both being
2428ignored. Instead, each time the periodic watcher gets scheduled, the 2546ignored. Instead, each time the periodic watcher gets scheduled, the
2429reschedule callback will be called with the watcher as first, and the 2547reschedule callback will be called with the watcher as first, and the
2430current time as second argument. 2548current time as second argument.
2431.Sp 2549.Sp
2432\&\s-1NOTE: \s0\fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever, 2550\&\s-1NOTE:\s0 \fIThis callback \s-1MUST NOT\s0 stop or destroy any periodic watcher, ever,
2433or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly 2551or make \s-1ANY\s0 other event loop modifications whatsoever, unless explicitly
2434allowed by documentation here\fR. 2552allowed by documentation here\fR.
2435.Sp 2553.Sp
2436If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop 2554If you need to stop it, return \f(CW\*(C`now + 1e30\*(C'\fR (or so, fudge fudge) and stop
2437it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the 2555it afterwards (e.g. by starting an \f(CW\*(C`ev_prepare\*(C'\fR watcher, which is the
… …
2451It must return the next time to trigger, based on the passed time value 2569It must return the next time to trigger, based on the passed time value
2452(that is, the lowest time value larger than to the second argument). It 2570(that is, the lowest time value larger than to the second argument). It
2453will usually be called just before the callback will be triggered, but 2571will usually be called just before the callback will be triggered, but
2454might be called at other times, too. 2572might be called at other times, too.
2455.Sp 2573.Sp
2456\&\s-1NOTE: \s0\fIThis callback must always return a time that is higher than or 2574\&\s-1NOTE:\s0 \fIThis callback must always return a time that is higher than or
2457equal to the passed \f(CI\*(C`now\*(C'\fI value\fR. 2575equal to the passed \f(CI\*(C`now\*(C'\fI value\fR.
2458.Sp 2576.Sp
2459This can be used to create very complex timers, such as a timer that 2577This can be used to create very complex timers, such as a timer that
2460triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate the 2578triggers on \*(L"next midnight, local time\*(R". To do this, you would calculate
2461next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for this. How 2579the next midnight after \f(CW\*(C`now\*(C'\fR and return the timestamp value for
2462you do this is, again, up to you (but it is not trivial, which is the main 2580this. Here is a (completely untested, no error checking) example on how to
2463reason I omitted it as an example). 2581do this:
2582.Sp
2583.Vb 1
2584\& #include <time.h>
2585\&
2586\& static ev_tstamp
2587\& my_rescheduler (ev_periodic *w, ev_tstamp now)
2588\& {
2589\& time_t tnow = (time_t)now;
2590\& struct tm tm;
2591\& localtime_r (&tnow, &tm);
2592\&
2593\& tm.tm_sec = tm.tm_min = tm.tm_hour = 0; // midnight current day
2594\& ++tm.tm_mday; // midnight next day
2595\&
2596\& return mktime (&tm);
2597\& }
2598.Ve
2599.Sp
2600Note: this code might run into trouble on days that have more then two
2601midnights (beginning and end).
2464.RE 2602.RE
2465.RS 4 2603.RS 4
2466.RE 2604.RE
2467.IP "ev_periodic_again (loop, ev_periodic *)" 4 2605.IP "ev_periodic_again (loop, ev_periodic *)" 4
2468.IX Item "ev_periodic_again (loop, ev_periodic *)" 2606.IX Item "ev_periodic_again (loop, ev_periodic *)"
… …
2586The simplest way to ensure that the signal mask is reset in the child is 2724The simplest way to ensure that the signal mask is reset in the child is
2587to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will 2725to install a fork handler with \f(CW\*(C`pthread_atfork\*(C'\fR that resets it. That will
2588catch fork calls done by libraries (such as the libc) as well. 2726catch fork calls done by libraries (such as the libc) as well.
2589.PP 2727.PP
2590In current versions of libev, the signal will not be blocked indefinitely 2728In current versions of libev, the signal will not be blocked indefinitely
2591unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API \s0(\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces 2729unless you use the \f(CW\*(C`signalfd\*(C'\fR \s-1API\s0 (\f(CW\*(C`EV_SIGNALFD\*(C'\fR). While this reduces
2592the window of opportunity for problems, it will not go away, as libev 2730the window of opportunity for problems, it will not go away, as libev
2593\&\fIhas\fR to modify the signal mask, at least temporarily. 2731\&\fIhas\fR to modify the signal mask, at least temporarily.
2594.PP 2732.PP
2595So I can't stress this enough: \fIIf you do not reset your signal mask when 2733So I can't stress this enough: \fIIf you do not reset your signal mask when
2596you expect it to be empty, you have a race condition in your code\fR. This 2734you expect it to be empty, you have a race condition in your code\fR. This
… …
3048.IX Subsection "ev_prepare and ev_check - customise your event loop!" 3186.IX Subsection "ev_prepare and ev_check - customise your event loop!"
3049Prepare and check watchers are often (but not always) used in pairs: 3187Prepare and check watchers are often (but not always) used in pairs:
3050prepare watchers get invoked before the process blocks and check watchers 3188prepare watchers get invoked before the process blocks and check watchers
3051afterwards. 3189afterwards.
3052.PP 3190.PP
3053You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR or similar functions that enter 3191You \fImust not\fR call \f(CW\*(C`ev_run\*(C'\fR (or similar functions that enter the
3054the current event loop from either \f(CW\*(C`ev_prepare\*(C'\fR or \f(CW\*(C`ev_check\*(C'\fR 3192current event loop) or \f(CW\*(C`ev_loop_fork\*(C'\fR from either \f(CW\*(C`ev_prepare\*(C'\fR or
3055watchers. Other loops than the current one are fine, however. The 3193\&\f(CW\*(C`ev_check\*(C'\fR watchers. Other loops than the current one are fine,
3056rationale behind this is that you do not need to check for recursion in 3194however. The rationale behind this is that you do not need to check
3057those watchers, i.e. the sequence will always be \f(CW\*(C`ev_prepare\*(C'\fR, blocking, 3195for recursion in those watchers, i.e. the sequence will always be
3058\&\f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each kind they will always be 3196\&\f(CW\*(C`ev_prepare\*(C'\fR, blocking, \f(CW\*(C`ev_check\*(C'\fR so if you have one watcher of each
3059called in pairs bracketing the blocking call. 3197kind they will always be called in pairs bracketing the blocking call.
3060.PP 3198.PP
3061Their main purpose is to integrate other event mechanisms into libev and 3199Their main purpose is to integrate other event mechanisms into libev and
3062their use is somewhat advanced. They could be used, for example, to track 3200their use is somewhat advanced. They could be used, for example, to track
3063variable changes, implement your own watchers, integrate net-snmp or a 3201variable changes, implement your own watchers, integrate net-snmp or a
3064coroutine library and lots more. They are also occasionally useful if 3202coroutine library and lots more. They are also occasionally useful if
… …
3358.PP 3496.PP
3359.Vb 3 3497.Vb 3
3360\& struct ev_loop *loop_hi = ev_default_init (0); 3498\& struct ev_loop *loop_hi = ev_default_init (0);
3361\& struct ev_loop *loop_lo = 0; 3499\& struct ev_loop *loop_lo = 0;
3362\& ev_embed embed; 3500\& ev_embed embed;
3363\& 3501\&
3364\& // see if there is a chance of getting one that works 3502\& // see if there is a chance of getting one that works
3365\& // (remember that a flags value of 0 means autodetection) 3503\& // (remember that a flags value of 0 means autodetection)
3366\& loop_lo = ev_embeddable_backends () & ev_recommended_backends () 3504\& loop_lo = ev_embeddable_backends () & ev_recommended_backends ()
3367\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ()) 3505\& ? ev_loop_new (ev_embeddable_backends () & ev_recommended_backends ())
3368\& : 0; 3506\& : 0;
… …
3384.PP 3522.PP
3385.Vb 3 3523.Vb 3
3386\& struct ev_loop *loop = ev_default_init (0); 3524\& struct ev_loop *loop = ev_default_init (0);
3387\& struct ev_loop *loop_socket = 0; 3525\& struct ev_loop *loop_socket = 0;
3388\& ev_embed embed; 3526\& ev_embed embed;
3389\& 3527\&
3390\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE) 3528\& if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
3391\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE)) 3529\& if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
3392\& { 3530\& {
3393\& ev_embed_init (&embed, 0, loop_socket); 3531\& ev_embed_init (&embed, 0, loop_socket);
3394\& ev_embed_start (loop, &embed); 3532\& ev_embed_start (loop, &embed);
… …
3411of course. 3549of course.
3412.PP 3550.PP
3413\fIThe special problem of life after fork \- how is it possible?\fR 3551\fIThe special problem of life after fork \- how is it possible?\fR
3414.IX Subsection "The special problem of life after fork - how is it possible?" 3552.IX Subsection "The special problem of life after fork - how is it possible?"
3415.PP 3553.PP
3416Most uses of \f(CW\*(C`fork()\*(C'\fR consist of forking, then some simple calls to set 3554Most uses of \f(CW\*(C`fork ()\*(C'\fR consist of forking, then some simple calls to set
3417up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This 3555up/change the process environment, followed by a call to \f(CW\*(C`exec()\*(C'\fR. This
3418sequence should be handled by libev without any problems. 3556sequence should be handled by libev without any problems.
3419.PP 3557.PP
3420This changes when the application actually wants to do event handling 3558This changes when the application actually wants to do event handling
3421in the child, or both parent in child, in effect \*(L"continuing\*(R" after the 3559in the child, or both parent in child, in effect \*(L"continuing\*(R" after the
… …
3638is a time window between the event loop checking and resetting the async 3776is a time window between the event loop checking and resetting the async
3639notification, and the callback being invoked. 3777notification, and the callback being invoked.
3640.SH "OTHER FUNCTIONS" 3778.SH "OTHER FUNCTIONS"
3641.IX Header "OTHER FUNCTIONS" 3779.IX Header "OTHER FUNCTIONS"
3642There are some other functions of possible interest. Described. Here. Now. 3780There are some other functions of possible interest. Described. Here. Now.
3643.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 4 3781.IP "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)" 4
3644.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback)" 3782.IX Item "ev_once (loop, int fd, int events, ev_tstamp timeout, callback, arg)"
3645This function combines a simple timer and an I/O watcher, calls your 3783This function combines a simple timer and an I/O watcher, calls your
3646callback on whichever event happens first and automatically stops both 3784callback on whichever event happens first and automatically stops both
3647watchers. This is useful if you want to wait for a single event on an fd 3785watchers. This is useful if you want to wait for a single event on an fd
3648or timeout without having to allocate/configure/start/stop/free one or 3786or timeout without having to allocate/configure/start/stop/free one or
3649more watchers yourself. 3787more watchers yourself.
… …
3864.PP 4002.PP
3865First, you need to associate some data with the event loop: 4003First, you need to associate some data with the event loop:
3866.PP 4004.PP
3867.Vb 6 4005.Vb 6
3868\& typedef struct { 4006\& typedef struct {
3869\& mutex_t lock; /* global loop lock */ 4007\& pthread_mutex_t lock; /* global loop lock */
4008\& pthread_t tid;
4009\& pthread_cond_t invoke_cv;
3870\& ev_async async_w; 4010\& ev_async async_w;
3871\& thread_t tid;
3872\& cond_t invoke_cv;
3873\& } userdata; 4011\& } userdata;
3874\& 4012\&
3875\& void prepare_loop (EV_P) 4013\& void prepare_loop (EV_P)
3876\& { 4014\& {
3877\& // for simplicity, we use a static userdata struct. 4015\& // for simplicity, we use a static userdata struct.
3878\& static userdata u; 4016\& static userdata u;
3879\& 4017\&
3880\& ev_async_init (&u\->async_w, async_cb); 4018\& ev_async_init (&u.async_w, async_cb);
3881\& ev_async_start (EV_A_ &u\->async_w); 4019\& ev_async_start (EV_A_ &u.async_w);
3882\& 4020\&
3883\& pthread_mutex_init (&u\->lock, 0); 4021\& pthread_mutex_init (&u.lock, 0);
3884\& pthread_cond_init (&u\->invoke_cv, 0); 4022\& pthread_cond_init (&u.invoke_cv, 0);
3885\& 4023\&
3886\& // now associate this with the loop 4024\& // now associate this with the loop
3887\& ev_set_userdata (EV_A_ u); 4025\& ev_set_userdata (EV_A_ &u);
3888\& ev_set_invoke_pending_cb (EV_A_ l_invoke); 4026\& ev_set_invoke_pending_cb (EV_A_ l_invoke);
3889\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire); 4027\& ev_set_loop_release_cb (EV_A_ l_release, l_acquire);
3890\& 4028\&
3891\& // then create the thread running ev_run 4029\& // then create the thread running ev_run
3892\& pthread_create (&u\->tid, 0, l_run, EV_A); 4030\& pthread_create (&u.tid, 0, l_run, EV_A);
3893\& } 4031\& }
3894.Ve 4032.Ve
3895.PP 4033.PP
3896The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used 4034The callback for the \f(CW\*(C`ev_async\*(C'\fR watcher does nothing: the watcher is used
3897solely to wake up the event loop so it takes notice of any new watchers 4035solely to wake up the event loop so it takes notice of any new watchers
… …
4049files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files: 4187files, \fImy_ev.h\fR and \fImy_ev.c\fR that include the respective libev files:
4050.PP 4188.PP
4051.Vb 4 4189.Vb 4
4052\& // my_ev.h 4190\& // my_ev.h
4053\& #define EV_CB_DECLARE(type) struct my_coro *cb; 4191\& #define EV_CB_DECLARE(type) struct my_coro *cb;
4054\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb); 4192\& #define EV_CB_INVOKE(watcher) switch_to ((watcher)\->cb)
4055\& #include "../libev/ev.h" 4193\& #include "../libev/ev.h"
4056\& 4194\&
4057\& // my_ev.c 4195\& // my_ev.c
4058\& #define EV_H "my_ev.h" 4196\& #define EV_H "my_ev.h"
4059\& #include "../libev/ev.c" 4197\& #include "../libev/ev.c"
… …
4099The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the 4237The normal C \s-1API\s0 should work fine when used from \*(C+: both ev.h and the
4100libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0 4238libev sources can be compiled as \*(C+. Therefore, code that uses the C \s-1API\s0
4101will work fine. 4239will work fine.
4102.PP 4240.PP
4103Proper exception specifications might have to be added to callbacks passed 4241Proper exception specifications might have to be added to callbacks passed
4104to libev: exceptions may be thrown only from watcher callbacks, all 4242to libev: exceptions may be thrown only from watcher callbacks, all other
4105other callbacks (allocator, syserr, loop acquire/release and periodic 4243callbacks (allocator, syserr, loop acquire/release and periodic reschedule
4106reschedule callbacks) must not throw exceptions, and might need a \f(CW\*(C`throw 4244callbacks) must not throw exceptions, and might need a \f(CW\*(C`noexcept\*(C'\fR
4107()\*(C'\fR specification. If you have code that needs to be compiled as both C 4245specification. If you have code that needs to be compiled as both C and
4108and \*(C+ you can use the \f(CW\*(C`EV_THROW\*(C'\fR macro for this: 4246\&\*(C+ you can use the \f(CW\*(C`EV_NOEXCEPT\*(C'\fR macro for this:
4109.PP 4247.PP
4110.Vb 6 4248.Vb 6
4111\& static void 4249\& static void
4112\& fatal_error (const char *msg) EV_THROW 4250\& fatal_error (const char *msg) EV_NOEXCEPT
4113\& { 4251\& {
4114\& perror (msg); 4252\& perror (msg);
4115\& abort (); 4253\& abort ();
4116\& } 4254\& }
4117\& 4255\&
… …
4245\& void operator() (ev::io &w, int revents) 4383\& void operator() (ev::io &w, int revents)
4246\& { 4384\& {
4247\& ... 4385\& ...
4248\& } 4386\& }
4249\& } 4387\& }
4250\& 4388\&
4251\& myfunctor f; 4389\& myfunctor f;
4252\& 4390\&
4253\& ev::io w; 4391\& ev::io w;
4254\& w.set (&f); 4392\& w.set (&f);
4255.Ve 4393.Ve
… …
4281gets automatically stopped and restarted when reconfiguring it with this 4419gets automatically stopped and restarted when reconfiguring it with this
4282method. 4420method.
4283.Sp 4421.Sp
4284For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid 4422For \f(CW\*(C`ev::embed\*(C'\fR watchers this method is called \f(CW\*(C`set_embed\*(C'\fR, to avoid
4285clashing with the \f(CW\*(C`set (loop)\*(C'\fR method. 4423clashing with the \f(CW\*(C`set (loop)\*(C'\fR method.
4424.Sp
4425For \f(CW\*(C`ev::io\*(C'\fR watchers there is an additional \f(CW\*(C`set\*(C'\fR method that acepts a
4426new event mask only, and internally calls \f(CW\*(C`ev_io_modify\*(C'\fR.
4286.IP "w\->start ()" 4 4427.IP "w\->start ()" 4
4287.IX Item "w->start ()" 4428.IX Item "w->start ()"
4288Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the 4429Starts the watcher. Note that there is no \f(CW\*(C`loop\*(C'\fR argument, as the
4289constructor already stores the event loop. 4430constructor already stores the event loop.
4290.IP "w\->start ([arguments])" 4 4431.IP "w\->start ([arguments])" 4
… …
4491\& #include "ev.c" 4632\& #include "ev.c"
4492.Ve 4633.Ve
4493.PP 4634.PP
4494This will automatically include \fIev.h\fR, too, and should be done in a 4635This will automatically include \fIev.h\fR, too, and should be done in a
4495single C source file only to provide the function implementations. To use 4636single C source file only to provide the function implementations. To use
4496it, do the same for \fIev.h\fR in all files wishing to use this \s-1API \s0(best 4637it, do the same for \fIev.h\fR in all files wishing to use this \s-1API\s0 (best
4497done by writing a wrapper around \fIev.h\fR that you can include instead and 4638done by writing a wrapper around \fIev.h\fR that you can include instead and
4498where you can put other configuration options): 4639where you can put other configuration options):
4499.PP 4640.PP
4500.Vb 2 4641.Vb 2
4501\& #define EV_STANDALONE 1 4642\& #define EV_STANDALONE 1
… …
4515\& ev_vars.h 4656\& ev_vars.h
4516\& ev_wrap.h 4657\& ev_wrap.h
4517\& 4658\&
4518\& ev_win32.c required on win32 platforms only 4659\& ev_win32.c required on win32 platforms only
4519\& 4660\&
4520\& ev_select.c only when select backend is enabled (which is enabled by default) 4661\& ev_select.c only when select backend is enabled
4521\& ev_poll.c only when poll backend is enabled (disabled by default) 4662\& ev_poll.c only when poll backend is enabled
4522\& ev_epoll.c only when the epoll backend is enabled (disabled by default) 4663\& ev_epoll.c only when the epoll backend is enabled
4664\& ev_linuxaio.c only when the linux aio backend is enabled
4665\& ev_iouring.c only when the linux io_uring backend is enabled
4523\& ev_kqueue.c only when the kqueue backend is enabled (disabled by default) 4666\& ev_kqueue.c only when the kqueue backend is enabled
4524\& ev_port.c only when the solaris port backend is enabled (disabled by default) 4667\& ev_port.c only when the solaris port backend is enabled
4525.Ve 4668.Ve
4526.PP 4669.PP
4527\&\fIev.c\fR includes the backend files directly when enabled, so you only need 4670\&\fIev.c\fR includes the backend files directly when enabled, so you only need
4528to compile this single file. 4671to compile this single file.
4529.PP 4672.PP
… …
4574values when compiling libev vs. including \fIev.h\fR, so it is permissible 4717values when compiling libev vs. including \fIev.h\fR, so it is permissible
4575to redefine them before including \fIev.h\fR without breaking compatibility 4718to redefine them before including \fIev.h\fR without breaking compatibility
4576to a compiled library. All other symbols change the \s-1ABI,\s0 which means all 4719to a compiled library. All other symbols change the \s-1ABI,\s0 which means all
4577users of libev and the libev code itself must be compiled with compatible 4720users of libev and the libev code itself must be compiled with compatible
4578settings. 4721settings.
4579.IP "\s-1EV_COMPAT3 \s0(h)" 4 4722.IP "\s-1EV_COMPAT3\s0 (h)" 4
4580.IX Item "EV_COMPAT3 (h)" 4723.IX Item "EV_COMPAT3 (h)"
4581Backwards compatibility is a major concern for libev. This is why this 4724Backwards compatibility is a major concern for libev. This is why this
4582release of libev comes with wrappers for the functions and symbols that 4725release of libev comes with wrappers for the functions and symbols that
4583have been renamed between libev version 3 and 4. 4726have been renamed between libev version 3 and 4.
4584.Sp 4727.Sp
… …
4589typedef in that case. 4732typedef in that case.
4590.Sp 4733.Sp
4591In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR, 4734In some future version, the default for \f(CW\*(C`EV_COMPAT3\*(C'\fR will become \f(CW0\fR,
4592and in some even more future version the compatibility code will be 4735and in some even more future version the compatibility code will be
4593removed completely. 4736removed completely.
4594.IP "\s-1EV_STANDALONE \s0(h)" 4 4737.IP "\s-1EV_STANDALONE\s0 (h)" 4
4595.IX Item "EV_STANDALONE (h)" 4738.IX Item "EV_STANDALONE (h)"
4596Must always be \f(CW1\fR if you do not use autoconf configuration, which 4739Must always be \f(CW1\fR if you do not use autoconf configuration, which
4597keeps libev from including \fIconfig.h\fR, and it also defines dummy 4740keeps libev from including \fIconfig.h\fR, and it also defines dummy
4598implementations for some libevent functions (such as logging, which is not 4741implementations for some libevent functions (such as logging, which is not
4599supported). It will also not define any of the structs usually found in 4742supported). It will also not define any of the structs usually found in
… …
4640higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR). 4783higher, as it simplifies linking (no need for \f(CW\*(C`\-lrt\*(C'\fR).
4641.IP "\s-1EV_USE_NANOSLEEP\s0" 4 4784.IP "\s-1EV_USE_NANOSLEEP\s0" 4
4642.IX Item "EV_USE_NANOSLEEP" 4785.IX Item "EV_USE_NANOSLEEP"
4643If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available 4786If defined to be \f(CW1\fR, libev will assume that \f(CW\*(C`nanosleep ()\*(C'\fR is available
4644and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR. 4787and will use it for delays. Otherwise it will use \f(CW\*(C`select ()\*(C'\fR.
4788.IP "\s-1EV_USE_EVENTFD\s0" 4
4789.IX Item "EV_USE_EVENTFD"
4790If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4791available and will probe for kernel support at runtime. This will improve
4792\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
4793If undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
47942.7 or newer, otherwise disabled.
4795.IP "\s-1EV_USE_SIGNALFD\s0" 4
4796.IX Item "EV_USE_SIGNALFD"
4797If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`signalfd ()\*(C'\fR is
4798available and will probe for kernel support at runtime. This enables
4799the use of \s-1EVFLAG_SIGNALFD\s0 for faster and simpler signal handling. If
4800undefined, it will be enabled if the headers indicate GNU/Linux + Glibc
48012.7 or newer, otherwise disabled.
4802.IP "\s-1EV_USE_TIMERFD\s0" 4
4803.IX Item "EV_USE_TIMERFD"
4804If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`timerfd ()\*(C'\fR is
4805available and will probe for kernel support at runtime. This allows
4806libev to detect time jumps accurately. If undefined, it will be enabled
4807if the headers indicate GNU/Linux + Glibc 2.8 or newer and define
4808\&\f(CW\*(C`TFD_TIMER_CANCEL_ON_SET\*(C'\fR, otherwise disabled.
4645.IP "\s-1EV_USE_EVENTFD\s0" 4 4809.IP "\s-1EV_USE_EVENTFD\s0" 4
4646.IX Item "EV_USE_EVENTFD" 4810.IX Item "EV_USE_EVENTFD"
4647If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is 4811If defined to be \f(CW1\fR, then libev will assume that \f(CW\*(C`eventfd ()\*(C'\fR is
4648available and will probe for kernel support at runtime. This will improve 4812available and will probe for kernel support at runtime. This will improve
4649\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption. 4813\&\f(CW\*(C`ev_signal\*(C'\fR and \f(CW\*(C`ev_async\*(C'\fR performance and reduce resource consumption.
… …
4708If defined to be \f(CW1\fR, libev will compile in support for the Linux 4872If defined to be \f(CW1\fR, libev will compile in support for the Linux
4709\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime, 4873\&\f(CW\*(C`epoll\*(C'\fR(7) backend. Its availability will be detected at runtime,
4710otherwise another method will be used as fallback. This is the preferred 4874otherwise another method will be used as fallback. This is the preferred
4711backend for GNU/Linux systems. If undefined, it will be enabled if the 4875backend for GNU/Linux systems. If undefined, it will be enabled if the
4712headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled. 4876headers indicate GNU/Linux + Glibc 2.4 or newer, otherwise disabled.
4877.IP "\s-1EV_USE_LINUXAIO\s0" 4
4878.IX Item "EV_USE_LINUXAIO"
4879If defined to be \f(CW1\fR, libev will compile in support for the Linux aio
4880backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). If undefined, it will be
4881enabled on linux, otherwise disabled.
4882.IP "\s-1EV_USE_IOURING\s0" 4
4883.IX Item "EV_USE_IOURING"
4884If defined to be \f(CW1\fR, libev will compile in support for the Linux
4885io_uring backend (\f(CW\*(C`EV_USE_EPOLL\*(C'\fR must also be enabled). Due to it's
4886current limitations it has to be requested explicitly. If undefined, it
4887will be enabled on linux, otherwise disabled.
4713.IP "\s-1EV_USE_KQUEUE\s0" 4 4888.IP "\s-1EV_USE_KQUEUE\s0" 4
4714.IX Item "EV_USE_KQUEUE" 4889.IX Item "EV_USE_KQUEUE"
4715If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style 4890If defined to be \f(CW1\fR, libev will compile in support for the \s-1BSD\s0 style
4716\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime, 4891\&\f(CW\*(C`kqueue\*(C'\fR(2) backend. Its actual availability will be detected at runtime,
4717otherwise another method will be used as fallback. This is the preferred 4892otherwise another method will be used as fallback. This is the preferred
… …
4757handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR 4932handler \*(L"locking\*(R" as well as for signal and thread safety in \f(CW\*(C`ev_async\*(C'\fR
4758watchers. 4933watchers.
4759.Sp 4934.Sp
4760In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR 4935In the absence of this define, libev will use \f(CW\*(C`sig_atomic_t volatile\*(C'\fR
4761(from \fIsignal.h\fR), which is usually good enough on most platforms. 4936(from \fIsignal.h\fR), which is usually good enough on most platforms.
4762.IP "\s-1EV_H \s0(h)" 4 4937.IP "\s-1EV_H\s0 (h)" 4
4763.IX Item "EV_H (h)" 4938.IX Item "EV_H (h)"
4764The name of the \fIev.h\fR header file used to include it. The default if 4939The name of the \fIev.h\fR header file used to include it. The default if
4765undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be 4940undefined is \f(CW"ev.h"\fR in \fIevent.h\fR, \fIev.c\fR and \fIev++.h\fR. This can be
4766used to virtually rename the \fIev.h\fR header file in case of conflicts. 4941used to virtually rename the \fIev.h\fR header file in case of conflicts.
4767.IP "\s-1EV_CONFIG_H \s0(h)" 4 4942.IP "\s-1EV_CONFIG_H\s0 (h)" 4
4768.IX Item "EV_CONFIG_H (h)" 4943.IX Item "EV_CONFIG_H (h)"
4769If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override 4944If \f(CW\*(C`EV_STANDALONE\*(C'\fR isn't \f(CW1\fR, this variable can be used to override
4770\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to 4945\&\fIev.c\fR's idea of where to find the \fIconfig.h\fR file, similarly to
4771\&\f(CW\*(C`EV_H\*(C'\fR, above. 4946\&\f(CW\*(C`EV_H\*(C'\fR, above.
4772.IP "\s-1EV_EVENT_H \s0(h)" 4 4947.IP "\s-1EV_EVENT_H\s0 (h)" 4
4773.IX Item "EV_EVENT_H (h)" 4948.IX Item "EV_EVENT_H (h)"
4774Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea 4949Similarly to \f(CW\*(C`EV_H\*(C'\fR, this macro can be used to override \fIevent.c\fR's idea
4775of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR. 4950of how the \fIevent.h\fR header can be found, the default is \f(CW"event.h"\fR.
4776.IP "\s-1EV_PROTOTYPES \s0(h)" 4 4951.IP "\s-1EV_PROTOTYPES\s0 (h)" 4
4777.IX Item "EV_PROTOTYPES (h)" 4952.IX Item "EV_PROTOTYPES (h)"
4778If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function 4953If defined to be \f(CW0\fR, then \fIev.h\fR will not define any function
4779prototypes, but still define all the structs and other symbols. This is 4954prototypes, but still define all the structs and other symbols. This is
4780occasionally useful if you want to provide your own wrapper functions 4955occasionally useful if you want to provide your own wrapper functions
4781around libev functions. 4956around libev functions.
… …
4974called. If set to \f(CW2\fR, then the internal verification code will be 5149called. If set to \f(CW2\fR, then the internal verification code will be
4975called once per loop, which can slow down libev. If set to \f(CW3\fR, then the 5150called once per loop, which can slow down libev. If set to \f(CW3\fR, then the
4976verification code will be called very frequently, which will slow down 5151verification code will be called very frequently, which will slow down
4977libev considerably. 5152libev considerably.
4978.Sp 5153.Sp
5154Verification errors are reported via C's \f(CW\*(C`assert\*(C'\fR mechanism, so if you
5155disable that (e.g. by defining \f(CW\*(C`NDEBUG\*(C'\fR) then no errors will be reported.
5156.Sp
4979The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it 5157The default is \f(CW1\fR, unless \f(CW\*(C`EV_FEATURES\*(C'\fR overrides it, in which case it
4980will be \f(CW0\fR. 5158will be \f(CW0\fR.
4981.IP "\s-1EV_COMMON\s0" 4 5159.IP "\s-1EV_COMMON\s0" 4
4982.IX Item "EV_COMMON" 5160.IX Item "EV_COMMON"
4983By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining 5161By default, all watchers have a \f(CW\*(C`void *data\*(C'\fR member. By redefining
… …
4990.Vb 3 5168.Vb 3
4991\& #define EV_COMMON \e 5169\& #define EV_COMMON \e
4992\& SV *self; /* contains this struct */ \e 5170\& SV *self; /* contains this struct */ \e
4993\& SV *cb_sv, *fh /* note no trailing ";" */ 5171\& SV *cb_sv, *fh /* note no trailing ";" */
4994.Ve 5172.Ve
4995.IP "\s-1EV_CB_DECLARE \s0(type)" 4 5173.IP "\s-1EV_CB_DECLARE\s0 (type)" 4
4996.IX Item "EV_CB_DECLARE (type)" 5174.IX Item "EV_CB_DECLARE (type)"
4997.PD 0 5175.PD 0
4998.IP "\s-1EV_CB_INVOKE \s0(watcher, revents)" 4 5176.IP "\s-1EV_CB_INVOKE\s0 (watcher, revents)" 4
4999.IX Item "EV_CB_INVOKE (watcher, revents)" 5177.IX Item "EV_CB_INVOKE (watcher, revents)"
5000.IP "ev_set_cb (ev, cb)" 4 5178.IP "ev_set_cb (ev, cb)" 4
5001.IX Item "ev_set_cb (ev, cb)" 5179.IX Item "ev_set_cb (ev, cb)"
5002.PD 5180.PD
5003Can be used to change the callback member declaration in each watcher, 5181Can be used to change the callback member declaration in each watcher,
… …
5006their default definitions. One possible use for overriding these is to 5184their default definitions. One possible use for overriding these is to
5007avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use 5185avoid the \f(CW\*(C`struct ev_loop *\*(C'\fR as first argument in all cases, or to use
5008method calls instead of plain function calls in \*(C+. 5186method calls instead of plain function calls in \*(C+.
5009.SS "\s-1EXPORTED API SYMBOLS\s0" 5187.SS "\s-1EXPORTED API SYMBOLS\s0"
5010.IX Subsection "EXPORTED API SYMBOLS" 5188.IX Subsection "EXPORTED API SYMBOLS"
5011If you need to re-export the \s-1API \s0(e.g. via a \s-1DLL\s0) and you need a list of 5189If you need to re-export the \s-1API\s0 (e.g. via a \s-1DLL\s0) and you need a list of
5012exported symbols, you can use the provided \fISymbol.*\fR files which list 5190exported symbols, you can use the provided \fISymbol.*\fR files which list
5013all public symbols, one per line: 5191all public symbols, one per line:
5014.PP 5192.PP
5015.Vb 2 5193.Vb 2
5016\& Symbols.ev for libev proper 5194\& Symbols.ev for libev proper
… …
5248.PP 5426.PP
5249\fI\f(CI\*(C`select\*(C'\fI is buggy\fR 5427\fI\f(CI\*(C`select\*(C'\fI is buggy\fR
5250.IX Subsection "select is buggy" 5428.IX Subsection "select is buggy"
5251.PP 5429.PP
5252All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this 5430All that's left is \f(CW\*(C`select\*(C'\fR, and of course Apple found a way to fuck this
5253one up as well: On \s-1OS/X, \s0\f(CW\*(C`select\*(C'\fR actively limits the number of file 5431one up as well: On \s-1OS/X,\s0 \f(CW\*(C`select\*(C'\fR actively limits the number of file
5254descriptors you can pass in to 1024 \- your program suddenly crashes when 5432descriptors you can pass in to 1024 \- your program suddenly crashes when
5255you use more. 5433you use more.
5256.PP 5434.PP
5257There is an undocumented \*(L"workaround\*(R" for this \- defining 5435There is an undocumented \*(L"workaround\*(R" for this \- defining
5258\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR 5436\&\f(CW\*(C`_DARWIN_UNLIMITED_SELECT\*(C'\fR, which libev tries to use, so select \fIshould\fR
… …
5406Libev assumes not only that all watcher pointers have the same internal 5584Libev assumes not only that all watcher pointers have the same internal
5407structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also 5585structure (guaranteed by \s-1POSIX\s0 but not by \s-1ISO C\s0 for example), but it also
5408assumes that the same (machine) code can be used to call any watcher 5586assumes that the same (machine) code can be used to call any watcher
5409callback: The watcher callbacks have different type signatures, but libev 5587callback: The watcher callbacks have different type signatures, but libev
5410calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally. 5588calls them using an \f(CW\*(C`ev_watcher *\*(C'\fR internally.
5589.IP "null pointers and integer zero are represented by 0 bytes" 4
5590.IX Item "null pointers and integer zero are represented by 0 bytes"
5591Libev uses \f(CW\*(C`memset\*(C'\fR to initialise structs and arrays to \f(CW0\fR bytes, and
5592relies on this setting pointers and integers to null.
5411.IP "pointer accesses must be thread-atomic" 4 5593.IP "pointer accesses must be thread-atomic" 4
5412.IX Item "pointer accesses must be thread-atomic" 5594.IX Item "pointer accesses must be thread-atomic"
5413Accessing a pointer value must be atomic, it must both be readable and 5595Accessing a pointer value must be atomic, it must both be readable and
5414writable in one piece \- this is the case on all current architectures. 5596writable in one piece \- this is the case on all current architectures.
5415.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4 5597.ie n .IP """sig_atomic_t volatile"" must be thread-atomic as well" 4

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