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4 4
5=head1 SYNOPSIS 5=head1 SYNOPSIS
6 6
7 #include <ev.h> 7 #include <ev.h>
8 8
9=head1 EXAMPLE PROGRAM 9=head2 EXAMPLE PROGRAM
10 10
11 #include <ev.h> 11 #include <ev.h>
12 12
13 ev_io stdin_watcher; 13 ev_io stdin_watcher;
14 ev_timer timeout_watcher; 14 ev_timer timeout_watcher;
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53The newest version of this document is also available as a html-formatted 53The newest version of this document is also available as a html-formatted
54web page you might find easier to navigate when reading it for the first 54web page you might find easier to navigate when reading it for the first
55time: L<http://cvs.schmorp.de/libev/ev.html>. 55time: L<http://cvs.schmorp.de/libev/ev.html>.
56 56
57Libev is an event loop: you register interest in certain events (such as a 57Libev is an event loop: you register interest in certain events (such as a
58file descriptor being readable or a timeout occuring), and it will manage 58file descriptor being readable or a timeout occurring), and it will manage
59these event sources and provide your program with events. 59these event sources and provide your program with events.
60 60
61To do this, it must take more or less complete control over your process 61To do this, it must take more or less complete control over your process
62(or thread) by executing the I<event loop> handler, and will then 62(or thread) by executing the I<event loop> handler, and will then
63communicate events via a callback mechanism. 63communicate events via a callback mechanism.
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65You register interest in certain events by registering so-called I<event 65You register interest in certain events by registering so-called I<event
66watchers>, which are relatively small C structures you initialise with the 66watchers>, which are relatively small C structures you initialise with the
67details of the event, and then hand it over to libev by I<starting> the 67details of the event, and then hand it over to libev by I<starting> the
68watcher. 68watcher.
69 69
70=head1 FEATURES 70=head2 FEATURES
71 71
72Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the 72Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
73BSD-specific C<kqueue> and the Solaris-specific event port mechanisms 73BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
74for file descriptor events (C<ev_io>), the Linux C<inotify> interface 74for file descriptor events (C<ev_io>), the Linux C<inotify> interface
75(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers 75(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
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82 82
83It also is quite fast (see this 83It also is quite fast (see this
84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent 84L<benchmark|http://libev.schmorp.de/bench.html> comparing it to libevent
85for example). 85for example).
86 86
87=head1 CONVENTIONS 87=head2 CONVENTIONS
88 88
89Libev is very configurable. In this manual the default configuration will 89Libev is very configurable. In this manual the default configuration will
90be described, which supports multiple event loops. For more info about 90be described, which supports multiple event loops. For more info about
91various configuration options please have a look at B<EMBED> section in 91various configuration options please have a look at B<EMBED> section in
92this manual. If libev was configured without support for multiple event 92this manual. If libev was configured without support for multiple event
93loops, then all functions taking an initial argument of name C<loop> 93loops, then all functions taking an initial argument of name C<loop>
94(which is always of type C<struct ev_loop *>) will not have this argument. 94(which is always of type C<struct ev_loop *>) will not have this argument.
95 95
96=head1 TIME REPRESENTATION 96=head2 TIME REPRESENTATION
97 97
98Libev represents time as a single floating point number, representing the 98Libev represents time as a single floating point number, representing the
99(fractional) number of seconds since the (POSIX) epoch (somewhere near 99(fractional) number of seconds since the (POSIX) epoch (somewhere near
100the beginning of 1970, details are complicated, don't ask). This type is 100the beginning of 1970, details are complicated, don't ask). This type is
101called C<ev_tstamp>, which is what you should use too. It usually aliases 101called C<ev_tstamp>, which is what you should use too. It usually aliases
102to the C<double> type in C, and when you need to do any calculations on 102to the C<double> type in C, and when you need to do any calculations on
103it, you should treat it as such. 103it, you should treat it as some floatingpoint value. Unlike the name
104component C<stamp> might indicate, it is also used for time differences
105throughout libev.
104 106
105=head1 GLOBAL FUNCTIONS 107=head1 GLOBAL FUNCTIONS
106 108
107These functions can be called anytime, even before initialising the 109These functions can be called anytime, even before initialising the
108library in any way. 110library in any way.
… …
113 115
114Returns the current time as libev would use it. Please note that the 116Returns the current time as libev would use it. Please note that the
115C<ev_now> function is usually faster and also often returns the timestamp 117C<ev_now> function is usually faster and also often returns the timestamp
116you actually want to know. 118you actually want to know.
117 119
120=item ev_sleep (ev_tstamp interval)
121
122Sleep for the given interval: The current thread will be blocked until
123either it is interrupted or the given time interval has passed. Basically
124this is a subsecond-resolution C<sleep ()>.
125
118=item int ev_version_major () 126=item int ev_version_major ()
119 127
120=item int ev_version_minor () 128=item int ev_version_minor ()
121 129
122You can find out the major and minor version numbers of the library 130You can find out the major and minor ABI version numbers of the library
123you linked against by calling the functions C<ev_version_major> and 131you linked against by calling the functions C<ev_version_major> and
124C<ev_version_minor>. If you want, you can compare against the global 132C<ev_version_minor>. If you want, you can compare against the global
125symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the 133symbols C<EV_VERSION_MAJOR> and C<EV_VERSION_MINOR>, which specify the
126version of the library your program was compiled against. 134version of the library your program was compiled against.
127 135
136These version numbers refer to the ABI version of the library, not the
137release version.
138
128Usually, it's a good idea to terminate if the major versions mismatch, 139Usually, it's a good idea to terminate if the major versions mismatch,
129as this indicates an incompatible change. Minor versions are usually 140as this indicates an incompatible change. Minor versions are usually
130compatible to older versions, so a larger minor version alone is usually 141compatible to older versions, so a larger minor version alone is usually
131not a problem. 142not a problem.
132 143
133Example: Make sure we haven't accidentally been linked against the wrong 144Example: Make sure we haven't accidentally been linked against the wrong
134version. 145version.
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295=item C<EVBACKEND_SELECT> (value 1, portable select backend) 306=item C<EVBACKEND_SELECT> (value 1, portable select backend)
296 307
297This is your standard select(2) backend. Not I<completely> standard, as 308This is your standard select(2) backend. Not I<completely> standard, as
298libev tries to roll its own fd_set with no limits on the number of fds, 309libev tries to roll its own fd_set with no limits on the number of fds,
299but if that fails, expect a fairly low limit on the number of fds when 310but if that fails, expect a fairly low limit on the number of fds when
300using this backend. It doesn't scale too well (O(highest_fd)), but its usually 311using this backend. It doesn't scale too well (O(highest_fd)), but its
301the fastest backend for a low number of fds. 312usually the fastest backend for a low number of (low-numbered :) fds.
313
314To get good performance out of this backend you need a high amount of
315parallelity (most of the file descriptors should be busy). If you are
316writing a server, you should C<accept ()> in a loop to accept as many
317connections as possible during one iteration. You might also want to have
318a look at C<ev_set_io_collect_interval ()> to increase the amount of
319readyness notifications you get per iteration.
302 320
303=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows) 321=item C<EVBACKEND_POLL> (value 2, poll backend, available everywhere except on windows)
304 322
305And this is your standard poll(2) backend. It's more complicated than 323And this is your standard poll(2) backend. It's more complicated
306select, but handles sparse fds better and has no artificial limit on the 324than select, but handles sparse fds better and has no artificial
307number of fds you can use (except it will slow down considerably with a 325limit on the number of fds you can use (except it will slow down
308lot of inactive fds). It scales similarly to select, i.e. O(total_fds). 326considerably with a lot of inactive fds). It scales similarly to select,
327i.e. O(total_fds). See the entry for C<EVBACKEND_SELECT>, above, for
328performance tips.
309 329
310=item C<EVBACKEND_EPOLL> (value 4, Linux) 330=item C<EVBACKEND_EPOLL> (value 4, Linux)
311 331
312For few fds, this backend is a bit little slower than poll and select, 332For few fds, this backend is a bit little slower than poll and select,
313but it scales phenomenally better. While poll and select usually scale like 333but it scales phenomenally better. While poll and select usually scale
314O(total_fds) where n is the total number of fds (or the highest fd), epoll scales 334like O(total_fds) where n is the total number of fds (or the highest fd),
315either O(1) or O(active_fds). 335epoll scales either O(1) or O(active_fds). The epoll design has a number
336of shortcomings, such as silently dropping events in some hard-to-detect
337cases and rewiring a syscall per fd change, no fork support and bad
338support for dup.
316 339
317While stopping and starting an I/O watcher in the same iteration will 340While stopping, setting and starting an I/O watcher in the same iteration
318result in some caching, there is still a syscall per such incident 341will result in some caching, there is still a syscall per such incident
319(because the fd could point to a different file description now), so its 342(because the fd could point to a different file description now), so its
320best to avoid that. Also, dup()ed file descriptors might not work very 343best to avoid that. Also, C<dup ()>'ed file descriptors might not work
321well if you register events for both fds. 344very well if you register events for both fds.
322 345
323Please note that epoll sometimes generates spurious notifications, so you 346Please note that epoll sometimes generates spurious notifications, so you
324need to use non-blocking I/O or other means to avoid blocking when no data 347need to use non-blocking I/O or other means to avoid blocking when no data
325(or space) is available. 348(or space) is available.
326 349
350Best performance from this backend is achieved by not unregistering all
351watchers for a file descriptor until it has been closed, if possible, i.e.
352keep at least one watcher active per fd at all times.
353
354While nominally embeddeble in other event loops, this feature is broken in
355all kernel versions tested so far.
356
327=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones) 357=item C<EVBACKEND_KQUEUE> (value 8, most BSD clones)
328 358
329Kqueue deserves special mention, as at the time of this writing, it 359Kqueue deserves special mention, as at the time of this writing, it
330was broken on all BSDs except NetBSD (usually it doesn't work with 360was broken on all BSDs except NetBSD (usually it doesn't work reliably
331anything but sockets and pipes, except on Darwin, where of course its 361with anything but sockets and pipes, except on Darwin, where of course
332completely useless). For this reason its not being "autodetected" 362it's completely useless). For this reason it's not being "autodetected"
333unless you explicitly specify it explicitly in the flags (i.e. using 363unless you explicitly specify it explicitly in the flags (i.e. using
334C<EVBACKEND_KQUEUE>). 364C<EVBACKEND_KQUEUE>) or libev was compiled on a known-to-be-good (-enough)
365system like NetBSD.
366
367You still can embed kqueue into a normal poll or select backend and use it
368only for sockets (after having made sure that sockets work with kqueue on
369the target platform). See C<ev_embed> watchers for more info.
335 370
336It scales in the same way as the epoll backend, but the interface to the 371It scales in the same way as the epoll backend, but the interface to the
337kernel is more efficient (which says nothing about its actual speed, of 372kernel is more efficient (which says nothing about its actual speed, of
338course). While starting and stopping an I/O watcher does not cause an 373course). While stopping, setting and starting an I/O watcher does never
339extra syscall as with epoll, it still adds up to four event changes per 374cause an extra syscall as with C<EVBACKEND_EPOLL>, it still adds up to
340incident, so its best to avoid that. 375two event changes per incident, support for C<fork ()> is very bad and it
376drops fds silently in similarly hard-to-detect cases.
377
378This backend usually performs well under most conditions.
379
380While nominally embeddable in other event loops, this doesn't work
381everywhere, so you might need to test for this. And since it is broken
382almost everywhere, you should only use it when you have a lot of sockets
383(for which it usually works), by embedding it into another event loop
384(e.g. C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>) and using it only for
385sockets.
341 386
342=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8) 387=item C<EVBACKEND_DEVPOLL> (value 16, Solaris 8)
343 388
344This is not implemented yet (and might never be). 389This is not implemented yet (and might never be, unless you send me an
390implementation). According to reports, C</dev/poll> only supports sockets
391and is not embeddable, which would limit the usefulness of this backend
392immensely.
345 393
346=item C<EVBACKEND_PORT> (value 32, Solaris 10) 394=item C<EVBACKEND_PORT> (value 32, Solaris 10)
347 395
348This uses the Solaris 10 port mechanism. As with everything on Solaris, 396This uses the Solaris 10 event port mechanism. As with everything on Solaris,
349it's really slow, but it still scales very well (O(active_fds)). 397it's really slow, but it still scales very well (O(active_fds)).
350 398
351Please note that solaris ports can result in a lot of spurious 399Please note that solaris event ports can deliver a lot of spurious
352notifications, so you need to use non-blocking I/O or other means to avoid 400notifications, so you need to use non-blocking I/O or other means to avoid
353blocking when no data (or space) is available. 401blocking when no data (or space) is available.
402
403While this backend scales well, it requires one system call per active
404file descriptor per loop iteration. For small and medium numbers of file
405descriptors a "slow" C<EVBACKEND_SELECT> or C<EVBACKEND_POLL> backend
406might perform better.
354 407
355=item C<EVBACKEND_ALL> 408=item C<EVBACKEND_ALL>
356 409
357Try all backends (even potentially broken ones that wouldn't be tried 410Try all backends (even potentially broken ones that wouldn't be tried
358with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as 411with C<EVFLAG_AUTO>). Since this is a mask, you can do stuff such as
359C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>. 412C<EVBACKEND_ALL & ~EVBACKEND_KQUEUE>.
413
414It is definitely not recommended to use this flag.
360 415
361=back 416=back
362 417
363If one or more of these are ored into the flags value, then only these 418If one or more of these are ored into the flags value, then only these
364backends will be tried (in the reverse order as given here). If none are 419backends will be tried (in the reverse order as given here). If none are
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399Destroys the default loop again (frees all memory and kernel state 454Destroys the default loop again (frees all memory and kernel state
400etc.). None of the active event watchers will be stopped in the normal 455etc.). None of the active event watchers will be stopped in the normal
401sense, so e.g. C<ev_is_active> might still return true. It is your 456sense, so e.g. C<ev_is_active> might still return true. It is your
402responsibility to either stop all watchers cleanly yoursef I<before> 457responsibility to either stop all watchers cleanly yoursef I<before>
403calling this function, or cope with the fact afterwards (which is usually 458calling this function, or cope with the fact afterwards (which is usually
404the easiest thing, youc na just ignore the watchers and/or C<free ()> them 459the easiest thing, you can just ignore the watchers and/or C<free ()> them
405for example). 460for example).
461
462Note that certain global state, such as signal state, will not be freed by
463this function, and related watchers (such as signal and child watchers)
464would need to be stopped manually.
465
466In general it is not advisable to call this function except in the
467rare occasion where you really need to free e.g. the signal handling
468pipe fds. If you need dynamically allocated loops it is better to use
469C<ev_loop_new> and C<ev_loop_destroy>).
406 470
407=item ev_loop_destroy (loop) 471=item ev_loop_destroy (loop)
408 472
409Like C<ev_default_destroy>, but destroys an event loop created by an 473Like C<ev_default_destroy>, but destroys an event loop created by an
410earlier call to C<ev_loop_new>. 474earlier call to C<ev_loop_new>.
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455 519
456Returns the current "event loop time", which is the time the event loop 520Returns the current "event loop time", which is the time the event loop
457received events and started processing them. This timestamp does not 521received events and started processing them. This timestamp does not
458change as long as callbacks are being processed, and this is also the base 522change as long as callbacks are being processed, and this is also the base
459time used for relative timers. You can treat it as the timestamp of the 523time used for relative timers. You can treat it as the timestamp of the
460event occuring (or more correctly, libev finding out about it). 524event occurring (or more correctly, libev finding out about it).
461 525
462=item ev_loop (loop, int flags) 526=item ev_loop (loop, int flags)
463 527
464Finally, this is it, the event handler. This function usually is called 528Finally, this is it, the event handler. This function usually is called
465after you initialised all your watchers and you want to start handling 529after you initialised all your watchers and you want to start handling
… …
549Example: For some weird reason, unregister the above signal handler again. 613Example: For some weird reason, unregister the above signal handler again.
550 614
551 ev_ref (loop); 615 ev_ref (loop);
552 ev_signal_stop (loop, &exitsig); 616 ev_signal_stop (loop, &exitsig);
553 617
618=item ev_set_io_collect_interval (loop, ev_tstamp interval)
619
620=item ev_set_timeout_collect_interval (loop, ev_tstamp interval)
621
622These advanced functions influence the time that libev will spend waiting
623for events. Both are by default C<0>, meaning that libev will try to
624invoke timer/periodic callbacks and I/O callbacks with minimum latency.
625
626Setting these to a higher value (the C<interval> I<must> be >= C<0>)
627allows libev to delay invocation of I/O and timer/periodic callbacks to
628increase efficiency of loop iterations.
629
630The background is that sometimes your program runs just fast enough to
631handle one (or very few) event(s) per loop iteration. While this makes
632the program responsive, it also wastes a lot of CPU time to poll for new
633events, especially with backends like C<select ()> which have a high
634overhead for the actual polling but can deliver many events at once.
635
636By setting a higher I<io collect interval> you allow libev to spend more
637time collecting I/O events, so you can handle more events per iteration,
638at the cost of increasing latency. Timeouts (both C<ev_periodic> and
639C<ev_timer>) will be not affected. Setting this to a non-null value will
640introduce an additional C<ev_sleep ()> call into most loop iterations.
641
642Likewise, by setting a higher I<timeout collect interval> you allow libev
643to spend more time collecting timeouts, at the expense of increased
644latency (the watcher callback will be called later). C<ev_io> watchers
645will not be affected. Setting this to a non-null value will not introduce
646any overhead in libev.
647
648Many (busy) programs can usually benefit by setting the io collect
649interval to a value near C<0.1> or so, which is often enough for
650interactive servers (of course not for games), likewise for timeouts. It
651usually doesn't make much sense to set it to a lower value than C<0.01>,
652as this approsaches the timing granularity of most systems.
653
554=back 654=back
555 655
556 656
557=head1 ANATOMY OF A WATCHER 657=head1 ANATOMY OF A WATCHER
558 658
… …
883In general you can register as many read and/or write event watchers per 983In general you can register as many read and/or write event watchers per
884fd as you want (as long as you don't confuse yourself). Setting all file 984fd as you want (as long as you don't confuse yourself). Setting all file
885descriptors to non-blocking mode is also usually a good idea (but not 985descriptors to non-blocking mode is also usually a good idea (but not
886required if you know what you are doing). 986required if you know what you are doing).
887 987
888You have to be careful with dup'ed file descriptors, though. Some backends
889(the linux epoll backend is a notable example) cannot handle dup'ed file
890descriptors correctly if you register interest in two or more fds pointing
891to the same underlying file/socket/etc. description (that is, they share
892the same underlying "file open").
893
894If you must do this, then force the use of a known-to-be-good backend 988If you must do this, then force the use of a known-to-be-good backend
895(at the time of this writing, this includes only C<EVBACKEND_SELECT> and 989(at the time of this writing, this includes only C<EVBACKEND_SELECT> and
896C<EVBACKEND_POLL>). 990C<EVBACKEND_POLL>).
897 991
898Another thing you have to watch out for is that it is quite easy to 992Another thing you have to watch out for is that it is quite easy to
… …
908play around with an Xlib connection), then you have to seperately re-test 1002play around with an Xlib connection), then you have to seperately re-test
909whether a file descriptor is really ready with a known-to-be good interface 1003whether a file descriptor is really ready with a known-to-be good interface
910such as poll (fortunately in our Xlib example, Xlib already does this on 1004such as poll (fortunately in our Xlib example, Xlib already does this on
911its own, so its quite safe to use). 1005its own, so its quite safe to use).
912 1006
1007=head3 The special problem of disappearing file descriptors
1008
1009Some backends (e.g. kqueue, epoll) need to be told about closing a file
1010descriptor (either by calling C<close> explicitly or by any other means,
1011such as C<dup>). The reason is that you register interest in some file
1012descriptor, but when it goes away, the operating system will silently drop
1013this interest. If another file descriptor with the same number then is
1014registered with libev, there is no efficient way to see that this is, in
1015fact, a different file descriptor.
1016
1017To avoid having to explicitly tell libev about such cases, libev follows
1018the following policy: Each time C<ev_io_set> is being called, libev
1019will assume that this is potentially a new file descriptor, otherwise
1020it is assumed that the file descriptor stays the same. That means that
1021you I<have> to call C<ev_io_set> (or C<ev_io_init>) when you change the
1022descriptor even if the file descriptor number itself did not change.
1023
1024This is how one would do it normally anyway, the important point is that
1025the libev application should not optimise around libev but should leave
1026optimisations to libev.
1027
1028=head3 The special problem of dup'ed file descriptors
1029
1030Some backends (e.g. epoll), cannot register events for file descriptors,
1031but only events for the underlying file descriptions. That means when you
1032have C<dup ()>'ed file descriptors or weirder constellations, and register
1033events for them, only one file descriptor might actually receive events.
1034
1035There is no workaround possible except not registering events
1036for potentially C<dup ()>'ed file descriptors, or to resort to
1037C<EVBACKEND_SELECT> or C<EVBACKEND_POLL>.
1038
1039=head3 The special problem of fork
1040
1041Some backends (epoll, kqueue) do not support C<fork ()> at all or exhibit
1042useless behaviour. Libev fully supports fork, but needs to be told about
1043it in the child.
1044
1045To support fork in your programs, you either have to call
1046C<ev_default_fork ()> or C<ev_loop_fork ()> after a fork in the child,
1047enable C<EVFLAG_FORKCHECK>, or resort to C<EVBACKEND_SELECT> or
1048C<EVBACKEND_POLL>.
1049
1050
1051=head3 Watcher-Specific Functions
1052
913=over 4 1053=over 4
914 1054
915=item ev_io_init (ev_io *, callback, int fd, int events) 1055=item ev_io_init (ev_io *, callback, int fd, int events)
916 1056
917=item ev_io_set (ev_io *, int fd, int events) 1057=item ev_io_set (ev_io *, int fd, int events)
… …
927=item int events [read-only] 1067=item int events [read-only]
928 1068
929The events being watched. 1069The events being watched.
930 1070
931=back 1071=back
1072
1073=head3 Examples
932 1074
933Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well 1075Example: Call C<stdin_readable_cb> when STDIN_FILENO has become, well
934readable, but only once. Since it is likely line-buffered, you could 1076readable, but only once. Since it is likely line-buffered, you could
935attempt to read a whole line in the callback. 1077attempt to read a whole line in the callback.
936 1078
… …
969 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 1111 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
970 1112
971The callback is guarenteed to be invoked only when its timeout has passed, 1113The callback is guarenteed to be invoked only when its timeout has passed,
972but if multiple timers become ready during the same loop iteration then 1114but if multiple timers become ready during the same loop iteration then
973order of execution is undefined. 1115order of execution is undefined.
1116
1117=head3 Watcher-Specific Functions and Data Members
974 1118
975=over 4 1119=over 4
976 1120
977=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat) 1121=item ev_timer_init (ev_timer *, callback, ev_tstamp after, ev_tstamp repeat)
978 1122
… …
1032or C<ev_timer_again> is called and determines the next timeout (if any), 1176or C<ev_timer_again> is called and determines the next timeout (if any),
1033which is also when any modifications are taken into account. 1177which is also when any modifications are taken into account.
1034 1178
1035=back 1179=back
1036 1180
1181=head3 Examples
1182
1037Example: Create a timer that fires after 60 seconds. 1183Example: Create a timer that fires after 60 seconds.
1038 1184
1039 static void 1185 static void
1040 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents) 1186 one_minute_cb (struct ev_loop *loop, struct ev_timer *w, int revents)
1041 { 1187 {
… …
1074but on wallclock time (absolute time). You can tell a periodic watcher 1220but on wallclock time (absolute time). You can tell a periodic watcher
1075to trigger "at" some specific point in time. For example, if you tell a 1221to trigger "at" some specific point in time. For example, if you tell a
1076periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now () 1222periodic watcher to trigger in 10 seconds (by specifiying e.g. C<ev_now ()
1077+ 10.>) and then reset your system clock to the last year, then it will 1223+ 10.>) and then reset your system clock to the last year, then it will
1078take a year to trigger the event (unlike an C<ev_timer>, which would trigger 1224take a year to trigger the event (unlike an C<ev_timer>, which would trigger
1079roughly 10 seconds later and of course not if you reset your system time 1225roughly 10 seconds later).
1080again).
1081 1226
1082They can also be used to implement vastly more complex timers, such as 1227They can also be used to implement vastly more complex timers, such as
1083triggering an event on eahc midnight, local time. 1228triggering an event on each midnight, local time or other, complicated,
1229rules.
1084 1230
1085As with timers, the callback is guarenteed to be invoked only when the 1231As with timers, the callback is guarenteed to be invoked only when the
1086time (C<at>) has been passed, but if multiple periodic timers become ready 1232time (C<at>) has been passed, but if multiple periodic timers become ready
1087during the same loop iteration then order of execution is undefined. 1233during the same loop iteration then order of execution is undefined.
1088 1234
1235=head3 Watcher-Specific Functions and Data Members
1236
1089=over 4 1237=over 4
1090 1238
1091=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb) 1239=item ev_periodic_init (ev_periodic *, callback, ev_tstamp at, ev_tstamp interval, reschedule_cb)
1092 1240
1093=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb) 1241=item ev_periodic_set (ev_periodic *, ev_tstamp after, ev_tstamp repeat, reschedule_cb)
… …
1095Lots of arguments, lets sort it out... There are basically three modes of 1243Lots of arguments, lets sort it out... There are basically three modes of
1096operation, and we will explain them from simplest to complex: 1244operation, and we will explain them from simplest to complex:
1097 1245
1098=over 4 1246=over 4
1099 1247
1100=item * absolute timer (interval = reschedule_cb = 0) 1248=item * absolute timer (at = time, interval = reschedule_cb = 0)
1101 1249
1102In this configuration the watcher triggers an event at the wallclock time 1250In this configuration the watcher triggers an event at the wallclock time
1103C<at> and doesn't repeat. It will not adjust when a time jump occurs, 1251C<at> and doesn't repeat. It will not adjust when a time jump occurs,
1104that is, if it is to be run at January 1st 2011 then it will run when the 1252that is, if it is to be run at January 1st 2011 then it will run when the
1105system time reaches or surpasses this time. 1253system time reaches or surpasses this time.
1106 1254
1107=item * non-repeating interval timer (interval > 0, reschedule_cb = 0) 1255=item * non-repeating interval timer (at = offset, interval > 0, reschedule_cb = 0)
1108 1256
1109In this mode the watcher will always be scheduled to time out at the next 1257In this mode the watcher will always be scheduled to time out at the next
1110C<at + N * interval> time (for some integer N) and then repeat, regardless 1258C<at + N * interval> time (for some integer N, which can also be negative)
1111of any time jumps. 1259and then repeat, regardless of any time jumps.
1112 1260
1113This can be used to create timers that do not drift with respect to system 1261This can be used to create timers that do not drift with respect to system
1114time: 1262time:
1115 1263
1116 ev_periodic_set (&periodic, 0., 3600., 0); 1264 ev_periodic_set (&periodic, 0., 3600., 0);
… …
1122 1270
1123Another way to think about it (for the mathematically inclined) is that 1271Another way to think about it (for the mathematically inclined) is that
1124C<ev_periodic> will try to run the callback in this mode at the next possible 1272C<ev_periodic> will try to run the callback in this mode at the next possible
1125time where C<time = at (mod interval)>, regardless of any time jumps. 1273time where C<time = at (mod interval)>, regardless of any time jumps.
1126 1274
1275For numerical stability it is preferable that the C<at> value is near
1276C<ev_now ()> (the current time), but there is no range requirement for
1277this value.
1278
1127=item * manual reschedule mode (reschedule_cb = callback) 1279=item * manual reschedule mode (at and interval ignored, reschedule_cb = callback)
1128 1280
1129In this mode the values for C<interval> and C<at> are both being 1281In this mode the values for C<interval> and C<at> are both being
1130ignored. Instead, each time the periodic watcher gets scheduled, the 1282ignored. Instead, each time the periodic watcher gets scheduled, the
1131reschedule callback will be called with the watcher as first, and the 1283reschedule callback will be called with the watcher as first, and the
1132current time as second argument. 1284current time as second argument.
1133 1285
1134NOTE: I<This callback MUST NOT stop or destroy any periodic watcher, 1286NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
1135ever, or make any event loop modifications>. If you need to stop it, 1287ever, or make any event loop modifications>. If you need to stop it,
1136return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by 1288return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
1137starting a prepare watcher). 1289starting an C<ev_prepare> watcher, which is legal).
1138 1290
1139Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 1291Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
1140ev_tstamp now)>, e.g.: 1292ev_tstamp now)>, e.g.:
1141 1293
1142 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 1294 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
… …
1165Simply stops and restarts the periodic watcher again. This is only useful 1317Simply stops and restarts the periodic watcher again. This is only useful
1166when you changed some parameters or the reschedule callback would return 1318when you changed some parameters or the reschedule callback would return
1167a different time than the last time it was called (e.g. in a crond like 1319a different time than the last time it was called (e.g. in a crond like
1168program when the crontabs have changed). 1320program when the crontabs have changed).
1169 1321
1322=item ev_tstamp offset [read-write]
1323
1324When repeating, this contains the offset value, otherwise this is the
1325absolute point in time (the C<at> value passed to C<ev_periodic_set>).
1326
1327Can be modified any time, but changes only take effect when the periodic
1328timer fires or C<ev_periodic_again> is being called.
1329
1170=item ev_tstamp interval [read-write] 1330=item ev_tstamp interval [read-write]
1171 1331
1172The current interval value. Can be modified any time, but changes only 1332The current interval value. Can be modified any time, but changes only
1173take effect when the periodic timer fires or C<ev_periodic_again> is being 1333take effect when the periodic timer fires or C<ev_periodic_again> is being
1174called. 1334called.
… …
1177 1337
1178The current reschedule callback, or C<0>, if this functionality is 1338The current reschedule callback, or C<0>, if this functionality is
1179switched off. Can be changed any time, but changes only take effect when 1339switched off. Can be changed any time, but changes only take effect when
1180the periodic timer fires or C<ev_periodic_again> is being called. 1340the periodic timer fires or C<ev_periodic_again> is being called.
1181 1341
1342=item ev_tstamp at [read-only]
1343
1344When active, contains the absolute time that the watcher is supposed to
1345trigger next.
1346
1182=back 1347=back
1348
1349=head3 Examples
1183 1350
1184Example: Call a callback every hour, or, more precisely, whenever the 1351Example: Call a callback every hour, or, more precisely, whenever the
1185system clock is divisible by 3600. The callback invocation times have 1352system clock is divisible by 3600. The callback invocation times have
1186potentially a lot of jittering, but good long-term stability. 1353potentially a lot of jittering, but good long-term stability.
1187 1354
… …
1227with the kernel (thus it coexists with your own signal handlers as long 1394with the kernel (thus it coexists with your own signal handlers as long
1228as you don't register any with libev). Similarly, when the last signal 1395as you don't register any with libev). Similarly, when the last signal
1229watcher for a signal is stopped libev will reset the signal handler to 1396watcher for a signal is stopped libev will reset the signal handler to
1230SIG_DFL (regardless of what it was set to before). 1397SIG_DFL (regardless of what it was set to before).
1231 1398
1399=head3 Watcher-Specific Functions and Data Members
1400
1232=over 4 1401=over 4
1233 1402
1234=item ev_signal_init (ev_signal *, callback, int signum) 1403=item ev_signal_init (ev_signal *, callback, int signum)
1235 1404
1236=item ev_signal_set (ev_signal *, int signum) 1405=item ev_signal_set (ev_signal *, int signum)
… …
1247 1416
1248=head2 C<ev_child> - watch out for process status changes 1417=head2 C<ev_child> - watch out for process status changes
1249 1418
1250Child watchers trigger when your process receives a SIGCHLD in response to 1419Child watchers trigger when your process receives a SIGCHLD in response to
1251some child status changes (most typically when a child of yours dies). 1420some child status changes (most typically when a child of yours dies).
1421
1422=head3 Watcher-Specific Functions and Data Members
1252 1423
1253=over 4 1424=over 4
1254 1425
1255=item ev_child_init (ev_child *, callback, int pid) 1426=item ev_child_init (ev_child *, callback, int pid)
1256 1427
… …
1275 1446
1276The process exit/trace status caused by C<rpid> (see your systems 1447The process exit/trace status caused by C<rpid> (see your systems
1277C<waitpid> and C<sys/wait.h> documentation for details). 1448C<waitpid> and C<sys/wait.h> documentation for details).
1278 1449
1279=back 1450=back
1451
1452=head3 Examples
1280 1453
1281Example: Try to exit cleanly on SIGINT and SIGTERM. 1454Example: Try to exit cleanly on SIGINT and SIGTERM.
1282 1455
1283 static void 1456 static void
1284 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents) 1457 sigint_cb (struct ev_loop *loop, struct ev_signal *w, int revents)
… …
1325semantics of C<ev_stat> watchers, which means that libev sometimes needs 1498semantics of C<ev_stat> watchers, which means that libev sometimes needs
1326to fall back to regular polling again even with inotify, but changes are 1499to fall back to regular polling again even with inotify, but changes are
1327usually detected immediately, and if the file exists there will be no 1500usually detected immediately, and if the file exists there will be no
1328polling. 1501polling.
1329 1502
1503=head3 Inotify
1504
1505When C<inotify (7)> support has been compiled into libev (generally only
1506available on Linux) and present at runtime, it will be used to speed up
1507change detection where possible. The inotify descriptor will be created lazily
1508when the first C<ev_stat> watcher is being started.
1509
1510Inotify presense does not change the semantics of C<ev_stat> watchers
1511except that changes might be detected earlier, and in some cases, to avoid
1512making regular C<stat> calls. Even in the presense of inotify support
1513there are many cases where libev has to resort to regular C<stat> polling.
1514
1515(There is no support for kqueue, as apparently it cannot be used to
1516implement this functionality, due to the requirement of having a file
1517descriptor open on the object at all times).
1518
1519=head3 The special problem of stat time resolution
1520
1521The C<stat ()> syscall only supports full-second resolution portably, and
1522even on systems where the resolution is higher, many filesystems still
1523only support whole seconds.
1524
1525That means that, if the time is the only thing that changes, you might
1526miss updates: on the first update, C<ev_stat> detects a change and calls
1527your callback, which does something. When there is another update within
1528the same second, C<ev_stat> will be unable to detect it.
1529
1530The solution to this is to delay acting on a change for a second (or till
1531the next second boundary), using a roughly one-second delay C<ev_timer>
1532(C<ev_timer_set (w, 0., 1.01); ev_timer_again (loop, w)>). The C<.01>
1533is added to work around small timing inconsistencies of some operating
1534systems.
1535
1536=head3 Watcher-Specific Functions and Data Members
1537
1330=over 4 1538=over 4
1331 1539
1332=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1540=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1333 1541
1334=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval) 1542=item ev_stat_set (ev_stat *, const char *path, ev_tstamp interval)
… …
1369=item const char *path [read-only] 1577=item const char *path [read-only]
1370 1578
1371The filesystem path that is being watched. 1579The filesystem path that is being watched.
1372 1580
1373=back 1581=back
1582
1583=head3 Examples
1374 1584
1375Example: Watch C</etc/passwd> for attribute changes. 1585Example: Watch C</etc/passwd> for attribute changes.
1376 1586
1377 static void 1587 static void
1378 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents) 1588 passwd_cb (struct ev_loop *loop, ev_stat *w, int revents)
… …
1391 } 1601 }
1392 1602
1393 ... 1603 ...
1394 ev_stat passwd; 1604 ev_stat passwd;
1395 1605
1396 ev_stat_init (&passwd, passwd_cb, "/etc/passwd"); 1606 ev_stat_init (&passwd, passwd_cb, "/etc/passwd", 0.);
1397 ev_stat_start (loop, &passwd); 1607 ev_stat_start (loop, &passwd);
1608
1609Example: Like above, but additionally use a one-second delay so we do not
1610miss updates (however, frequent updates will delay processing, too, so
1611one might do the work both on C<ev_stat> callback invocation I<and> on
1612C<ev_timer> callback invocation).
1613
1614 static ev_stat passwd;
1615 static ev_timer timer;
1616
1617 static void
1618 timer_cb (EV_P_ ev_timer *w, int revents)
1619 {
1620 ev_timer_stop (EV_A_ w);
1621
1622 /* now it's one second after the most recent passwd change */
1623 }
1624
1625 static void
1626 stat_cb (EV_P_ ev_stat *w, int revents)
1627 {
1628 /* reset the one-second timer */
1629 ev_timer_again (EV_A_ &timer);
1630 }
1631
1632 ...
1633 ev_stat_init (&passwd, stat_cb, "/etc/passwd", 0.);
1634 ev_stat_start (loop, &passwd);
1635 ev_timer_init (&timer, timer_cb, 0., 1.01);
1398 1636
1399 1637
1400=head2 C<ev_idle> - when you've got nothing better to do... 1638=head2 C<ev_idle> - when you've got nothing better to do...
1401 1639
1402Idle watchers trigger events when no other events of the same or higher 1640Idle watchers trigger events when no other events of the same or higher
… …
1416Apart from keeping your process non-blocking (which is a useful 1654Apart from keeping your process non-blocking (which is a useful
1417effect on its own sometimes), idle watchers are a good place to do 1655effect on its own sometimes), idle watchers are a good place to do
1418"pseudo-background processing", or delay processing stuff to after the 1656"pseudo-background processing", or delay processing stuff to after the
1419event loop has handled all outstanding events. 1657event loop has handled all outstanding events.
1420 1658
1659=head3 Watcher-Specific Functions and Data Members
1660
1421=over 4 1661=over 4
1422 1662
1423=item ev_idle_init (ev_signal *, callback) 1663=item ev_idle_init (ev_signal *, callback)
1424 1664
1425Initialises and configures the idle watcher - it has no parameters of any 1665Initialises and configures the idle watcher - it has no parameters of any
1426kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 1666kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
1427believe me. 1667believe me.
1428 1668
1429=back 1669=back
1670
1671=head3 Examples
1430 1672
1431Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the 1673Example: Dynamically allocate an C<ev_idle> watcher, start it, and in the
1432callback, free it. Also, use no error checking, as usual. 1674callback, free it. Also, use no error checking, as usual.
1433 1675
1434 static void 1676 static void
… …
1486 1728
1487It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>) 1729It is recommended to give C<ev_check> watchers highest (C<EV_MAXPRI>)
1488priority, to ensure that they are being run before any other watchers 1730priority, to ensure that they are being run before any other watchers
1489after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers, 1731after the poll. Also, C<ev_check> watchers (and C<ev_prepare> watchers,
1490too) should not activate ("feed") events into libev. While libev fully 1732too) should not activate ("feed") events into libev. While libev fully
1491supports this, they will be called before other C<ev_check> watchers did 1733supports this, they will be called before other C<ev_check> watchers
1492their job. As C<ev_check> watchers are often used to embed other event 1734did their job. As C<ev_check> watchers are often used to embed other
1493loops those other event loops might be in an unusable state until their 1735(non-libev) event loops those other event loops might be in an unusable
1494C<ev_check> watcher ran (always remind yourself to coexist peacefully with 1736state until their C<ev_check> watcher ran (always remind yourself to
1495others). 1737coexist peacefully with others).
1738
1739=head3 Watcher-Specific Functions and Data Members
1496 1740
1497=over 4 1741=over 4
1498 1742
1499=item ev_prepare_init (ev_prepare *, callback) 1743=item ev_prepare_init (ev_prepare *, callback)
1500 1744
… …
1503Initialises and configures the prepare or check watcher - they have no 1747Initialises and configures the prepare or check watcher - they have no
1504parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 1748parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
1505macros, but using them is utterly, utterly and completely pointless. 1749macros, but using them is utterly, utterly and completely pointless.
1506 1750
1507=back 1751=back
1752
1753=head3 Examples
1508 1754
1509There are a number of principal ways to embed other event loops or modules 1755There are a number of principal ways to embed other event loops or modules
1510into libev. Here are some ideas on how to include libadns into libev 1756into libev. Here are some ideas on how to include libadns into libev
1511(there is a Perl module named C<EV::ADNS> that does this, which you could 1757(there is a Perl module named C<EV::ADNS> that does this, which you could
1512use for an actually working example. Another Perl module named C<EV::Glib> 1758use for an actually working example. Another Perl module named C<EV::Glib>
… …
1681portable one. 1927portable one.
1682 1928
1683So when you want to use this feature you will always have to be prepared 1929So when you want to use this feature you will always have to be prepared
1684that you cannot get an embeddable loop. The recommended way to get around 1930that you cannot get an embeddable loop. The recommended way to get around
1685this is to have a separate variables for your embeddable loop, try to 1931this is to have a separate variables for your embeddable loop, try to
1686create it, and if that fails, use the normal loop for everything: 1932create it, and if that fails, use the normal loop for everything.
1933
1934=head3 Watcher-Specific Functions and Data Members
1935
1936=over 4
1937
1938=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop)
1939
1940=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop)
1941
1942Configures the watcher to embed the given loop, which must be
1943embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1944invoked automatically, otherwise it is the responsibility of the callback
1945to invoke it (it will continue to be called until the sweep has been done,
1946if you do not want thta, you need to temporarily stop the embed watcher).
1947
1948=item ev_embed_sweep (loop, ev_embed *)
1949
1950Make a single, non-blocking sweep over the embedded loop. This works
1951similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1952apropriate way for embedded loops.
1953
1954=item struct ev_loop *other [read-only]
1955
1956The embedded event loop.
1957
1958=back
1959
1960=head3 Examples
1961
1962Example: Try to get an embeddable event loop and embed it into the default
1963event loop. If that is not possible, use the default loop. The default
1964loop is stored in C<loop_hi>, while the mebeddable loop is stored in
1965C<loop_lo> (which is C<loop_hi> in the acse no embeddable loop can be
1966used).
1687 1967
1688 struct ev_loop *loop_hi = ev_default_init (0); 1968 struct ev_loop *loop_hi = ev_default_init (0);
1689 struct ev_loop *loop_lo = 0; 1969 struct ev_loop *loop_lo = 0;
1690 struct ev_embed embed; 1970 struct ev_embed embed;
1691 1971
… …
1702 ev_embed_start (loop_hi, &embed); 1982 ev_embed_start (loop_hi, &embed);
1703 } 1983 }
1704 else 1984 else
1705 loop_lo = loop_hi; 1985 loop_lo = loop_hi;
1706 1986
1707=over 4 1987Example: Check if kqueue is available but not recommended and create
1988a kqueue backend for use with sockets (which usually work with any
1989kqueue implementation). Store the kqueue/socket-only event loop in
1990C<loop_socket>. (One might optionally use C<EVFLAG_NOENV>, too).
1708 1991
1709=item ev_embed_init (ev_embed *, callback, struct ev_loop *embedded_loop) 1992 struct ev_loop *loop = ev_default_init (0);
1993 struct ev_loop *loop_socket = 0;
1994 struct ev_embed embed;
1995
1996 if (ev_supported_backends () & ~ev_recommended_backends () & EVBACKEND_KQUEUE)
1997 if ((loop_socket = ev_loop_new (EVBACKEND_KQUEUE))
1998 {
1999 ev_embed_init (&embed, 0, loop_socket);
2000 ev_embed_start (loop, &embed);
2001 }
1710 2002
1711=item ev_embed_set (ev_embed *, callback, struct ev_loop *embedded_loop) 2003 if (!loop_socket)
2004 loop_socket = loop;
1712 2005
1713Configures the watcher to embed the given loop, which must be 2006 // now use loop_socket for all sockets, and loop for everything else
1714embeddable. If the callback is C<0>, then C<ev_embed_sweep> will be
1715invoked automatically, otherwise it is the responsibility of the callback
1716to invoke it (it will continue to be called until the sweep has been done,
1717if you do not want thta, you need to temporarily stop the embed watcher).
1718
1719=item ev_embed_sweep (loop, ev_embed *)
1720
1721Make a single, non-blocking sweep over the embedded loop. This works
1722similarly to C<ev_loop (embedded_loop, EVLOOP_NONBLOCK)>, but in the most
1723apropriate way for embedded loops.
1724
1725=item struct ev_loop *loop [read-only]
1726
1727The embedded event loop.
1728
1729=back
1730 2007
1731 2008
1732=head2 C<ev_fork> - the audacity to resume the event loop after a fork 2009=head2 C<ev_fork> - the audacity to resume the event loop after a fork
1733 2010
1734Fork watchers are called when a C<fork ()> was detected (usually because 2011Fork watchers are called when a C<fork ()> was detected (usually because
… …
1737event loop blocks next and before C<ev_check> watchers are being called, 2014event loop blocks next and before C<ev_check> watchers are being called,
1738and only in the child after the fork. If whoever good citizen calling 2015and only in the child after the fork. If whoever good citizen calling
1739C<ev_default_fork> cheats and calls it in the wrong process, the fork 2016C<ev_default_fork> cheats and calls it in the wrong process, the fork
1740handlers will be invoked, too, of course. 2017handlers will be invoked, too, of course.
1741 2018
2019=head3 Watcher-Specific Functions and Data Members
2020
1742=over 4 2021=over 4
1743 2022
1744=item ev_fork_init (ev_signal *, callback) 2023=item ev_fork_init (ev_signal *, callback)
1745 2024
1746Initialises and configures the fork watcher - it has no parameters of any 2025Initialises and configures the fork watcher - it has no parameters of any
… …
1962 2241
1963=item w->stop () 2242=item w->stop ()
1964 2243
1965Stops the watcher if it is active. Again, no C<loop> argument. 2244Stops the watcher if it is active. Again, no C<loop> argument.
1966 2245
1967=item w->again () C<ev::timer>, C<ev::periodic> only 2246=item w->again () (C<ev::timer>, C<ev::periodic> only)
1968 2247
1969For C<ev::timer> and C<ev::periodic>, this invokes the corresponding 2248For C<ev::timer> and C<ev::periodic>, this invokes the corresponding
1970C<ev_TYPE_again> function. 2249C<ev_TYPE_again> function.
1971 2250
1972=item w->sweep () C<ev::embed> only 2251=item w->sweep () (C<ev::embed> only)
1973 2252
1974Invokes C<ev_embed_sweep>. 2253Invokes C<ev_embed_sweep>.
1975 2254
1976=item w->update () C<ev::stat> only 2255=item w->update () (C<ev::stat> only)
1977 2256
1978Invokes C<ev_stat_stat>. 2257Invokes C<ev_stat_stat>.
1979 2258
1980=back 2259=back
1981 2260
… …
2001 } 2280 }
2002 2281
2003 2282
2004=head1 MACRO MAGIC 2283=head1 MACRO MAGIC
2005 2284
2006Libev can be compiled with a variety of options, the most fundemantal is 2285Libev can be compiled with a variety of options, the most fundamantal
2007C<EV_MULTIPLICITY>. This option determines whether (most) functions and 2286of which is C<EV_MULTIPLICITY>. This option determines whether (most)
2008callbacks have an initial C<struct ev_loop *> argument. 2287functions and callbacks have an initial C<struct ev_loop *> argument.
2009 2288
2010To make it easier to write programs that cope with either variant, the 2289To make it easier to write programs that cope with either variant, the
2011following macros are defined: 2290following macros are defined:
2012 2291
2013=over 4 2292=over 4
… …
2067Libev can (and often is) directly embedded into host 2346Libev can (and often is) directly embedded into host
2068applications. Examples of applications that embed it include the Deliantra 2347applications. Examples of applications that embed it include the Deliantra
2069Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe) 2348Game Server, the EV perl module, the GNU Virtual Private Ethernet (gvpe)
2070and rxvt-unicode. 2349and rxvt-unicode.
2071 2350
2072The goal is to enable you to just copy the neecssary files into your 2351The goal is to enable you to just copy the necessary files into your
2073source directory without having to change even a single line in them, so 2352source directory without having to change even a single line in them, so
2074you can easily upgrade by simply copying (or having a checked-out copy of 2353you can easily upgrade by simply copying (or having a checked-out copy of
2075libev somewhere in your source tree). 2354libev somewhere in your source tree).
2076 2355
2077=head2 FILESETS 2356=head2 FILESETS
… …
2167 2446
2168If defined to be C<1>, libev will try to detect the availability of the 2447If defined to be C<1>, libev will try to detect the availability of the
2169monotonic clock option at both compiletime and runtime. Otherwise no use 2448monotonic clock option at both compiletime and runtime. Otherwise no use
2170of the monotonic clock option will be attempted. If you enable this, you 2449of the monotonic clock option will be attempted. If you enable this, you
2171usually have to link against librt or something similar. Enabling it when 2450usually have to link against librt or something similar. Enabling it when
2172the functionality isn't available is safe, though, althoguh you have 2451the functionality isn't available is safe, though, although you have
2173to make sure you link against any libraries where the C<clock_gettime> 2452to make sure you link against any libraries where the C<clock_gettime>
2174function is hiding in (often F<-lrt>). 2453function is hiding in (often F<-lrt>).
2175 2454
2176=item EV_USE_REALTIME 2455=item EV_USE_REALTIME
2177 2456
2178If defined to be C<1>, libev will try to detect the availability of the 2457If defined to be C<1>, libev will try to detect the availability of the
2179realtime clock option at compiletime (and assume its availability at 2458realtime clock option at compiletime (and assume its availability at
2180runtime if successful). Otherwise no use of the realtime clock option will 2459runtime if successful). Otherwise no use of the realtime clock option will
2181be attempted. This effectively replaces C<gettimeofday> by C<clock_get 2460be attempted. This effectively replaces C<gettimeofday> by C<clock_get
2182(CLOCK_REALTIME, ...)> and will not normally affect correctness. See tzhe note about libraries 2461(CLOCK_REALTIME, ...)> and will not normally affect correctness. See the
2183in the description of C<EV_USE_MONOTONIC>, though. 2462note about libraries in the description of C<EV_USE_MONOTONIC>, though.
2463
2464=item EV_USE_NANOSLEEP
2465
2466If defined to be C<1>, libev will assume that C<nanosleep ()> is available
2467and will use it for delays. Otherwise it will use C<select ()>.
2184 2468
2185=item EV_USE_SELECT 2469=item EV_USE_SELECT
2186 2470
2187If undefined or defined to be C<1>, libev will compile in support for the 2471If undefined or defined to be C<1>, libev will compile in support for the
2188C<select>(2) backend. No attempt at autodetection will be done: if no 2472C<select>(2) backend. No attempt at autodetection will be done: if no
… …
2206wants osf handles on win32 (this is the case when the select to 2490wants osf handles on win32 (this is the case when the select to
2207be used is the winsock select). This means that it will call 2491be used is the winsock select). This means that it will call
2208C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise, 2492C<_get_osfhandle> on the fd to convert it to an OS handle. Otherwise,
2209it is assumed that all these functions actually work on fds, even 2493it is assumed that all these functions actually work on fds, even
2210on win32. Should not be defined on non-win32 platforms. 2494on win32. Should not be defined on non-win32 platforms.
2495
2496=item EV_FD_TO_WIN32_HANDLE
2497
2498If C<EV_SELECT_IS_WINSOCKET> is enabled, then libev needs a way to map
2499file descriptors to socket handles. When not defining this symbol (the
2500default), then libev will call C<_get_osfhandle>, which is usually
2501correct. In some cases, programs use their own file descriptor management,
2502in which case they can provide this function to map fds to socket handles.
2211 2503
2212=item EV_USE_POLL 2504=item EV_USE_POLL
2213 2505
2214If defined to be C<1>, libev will compile in support for the C<poll>(2) 2506If defined to be C<1>, libev will compile in support for the C<poll>(2)
2215backend. Otherwise it will be enabled on non-win32 platforms. It 2507backend. Otherwise it will be enabled on non-win32 platforms. It
… …
2252be detected at runtime. 2544be detected at runtime.
2253 2545
2254=item EV_H 2546=item EV_H
2255 2547
2256The name of the F<ev.h> header file used to include it. The default if 2548The name of the F<ev.h> header file used to include it. The default if
2257undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2549undefined is C<"ev.h"> in F<event.h> and F<ev.c>. This can be used to
2258can be used to virtually rename the F<ev.h> header file in case of conflicts. 2550virtually rename the F<ev.h> header file in case of conflicts.
2259 2551
2260=item EV_CONFIG_H 2552=item EV_CONFIG_H
2261 2553
2262If C<EV_STANDALONE> isn't C<1>, this variable can be used to override 2554If C<EV_STANDALONE> isn't C<1>, this variable can be used to override
2263F<ev.c>'s idea of where to find the F<config.h> file, similarly to 2555F<ev.c>'s idea of where to find the F<config.h> file, similarly to
2264C<EV_H>, above. 2556C<EV_H>, above.
2265 2557
2266=item EV_EVENT_H 2558=item EV_EVENT_H
2267 2559
2268Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea 2560Similarly to C<EV_H>, this macro can be used to override F<event.c>'s idea
2269of how the F<event.h> header can be found. 2561of how the F<event.h> header can be found, the dfeault is C<"event.h">.
2270 2562
2271=item EV_PROTOTYPES 2563=item EV_PROTOTYPES
2272 2564
2273If defined to be C<0>, then F<ev.h> will not define any function 2565If defined to be C<0>, then F<ev.h> will not define any function
2274prototypes, but still define all the structs and other symbols. This is 2566prototypes, but still define all the structs and other symbols. This is
… …
2340than enough. If you need to manage thousands of children you might want to 2632than enough. If you need to manage thousands of children you might want to
2341increase this value (I<must> be a power of two). 2633increase this value (I<must> be a power of two).
2342 2634
2343=item EV_INOTIFY_HASHSIZE 2635=item EV_INOTIFY_HASHSIZE
2344 2636
2345C<ev_staz> watchers use a small hash table to distribute workload by 2637C<ev_stat> watchers use a small hash table to distribute workload by
2346inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>), 2638inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2347usually more than enough. If you need to manage thousands of C<ev_stat> 2639usually more than enough. If you need to manage thousands of C<ev_stat>
2348watchers you might want to increase this value (I<must> be a power of 2640watchers you might want to increase this value (I<must> be a power of
2349two). 2641two).
2350 2642
… …
2367 2659
2368=item ev_set_cb (ev, cb) 2660=item ev_set_cb (ev, cb)
2369 2661
2370Can be used to change the callback member declaration in each watcher, 2662Can be used to change the callback member declaration in each watcher,
2371and the way callbacks are invoked and set. Must expand to a struct member 2663and the way callbacks are invoked and set. Must expand to a struct member
2372definition and a statement, respectively. See the F<ev.v> header file for 2664definition and a statement, respectively. See the F<ev.h> header file for
2373their default definitions. One possible use for overriding these is to 2665their default definitions. One possible use for overriding these is to
2374avoid the C<struct ev_loop *> as first argument in all cases, or to use 2666avoid the C<struct ev_loop *> as first argument in all cases, or to use
2375method calls instead of plain function calls in C++. 2667method calls instead of plain function calls in C++.
2668
2669=head2 EXPORTED API SYMBOLS
2670
2671If you need to re-export the API (e.g. via a dll) and you need a list of
2672exported symbols, you can use the provided F<Symbol.*> files which list
2673all public symbols, one per line:
2674
2675 Symbols.ev for libev proper
2676 Symbols.event for the libevent emulation
2677
2678This can also be used to rename all public symbols to avoid clashes with
2679multiple versions of libev linked together (which is obviously bad in
2680itself, but sometimes it is inconvinient to avoid this).
2681
2682A sed command like this will create wrapper C<#define>'s that you need to
2683include before including F<ev.h>:
2684
2685 <Symbols.ev sed -e "s/.*/#define & myprefix_&/" >wrap.h
2686
2687This would create a file F<wrap.h> which essentially looks like this:
2688
2689 #define ev_backend myprefix_ev_backend
2690 #define ev_check_start myprefix_ev_check_start
2691 #define ev_check_stop myprefix_ev_check_stop
2692 ...
2376 2693
2377=head2 EXAMPLES 2694=head2 EXAMPLES
2378 2695
2379For a real-world example of a program the includes libev 2696For a real-world example of a program the includes libev
2380verbatim, you can have a look at the EV perl module 2697verbatim, you can have a look at the EV perl module
… …
2421 2738
2422=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers) 2739=item Starting and stopping timer/periodic watchers: O(log skipped_other_timers)
2423 2740
2424This means that, when you have a watcher that triggers in one hour and 2741This means that, when you have a watcher that triggers in one hour and
2425there are 100 watchers that would trigger before that then inserting will 2742there are 100 watchers that would trigger before that then inserting will
2426have to skip those 100 watchers. 2743have to skip roughly seven (C<ld 100>) of these watchers.
2427 2744
2428=item Changing timer/periodic watchers (by autorepeat, again): O(log skipped_other_timers) 2745=item Changing timer/periodic watchers (by autorepeat or calling again): O(log skipped_other_timers)
2429 2746
2430That means that for changing a timer costs less than removing/adding them 2747That means that changing a timer costs less than removing/adding them
2431as only the relative motion in the event queue has to be paid for. 2748as only the relative motion in the event queue has to be paid for.
2432 2749
2433=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2750=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2434 2751
2435These just add the watcher into an array or at the head of a list. 2752These just add the watcher into an array or at the head of a list.
2753
2436=item Stopping check/prepare/idle watchers: O(1) 2754=item Stopping check/prepare/idle watchers: O(1)
2437 2755
2438=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE)) 2756=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2439 2757
2440These watchers are stored in lists then need to be walked to find the 2758These watchers are stored in lists then need to be walked to find the
2441correct watcher to remove. The lists are usually short (you don't usually 2759correct watcher to remove. The lists are usually short (you don't usually
2442have many watchers waiting for the same fd or signal). 2760have many watchers waiting for the same fd or signal).
2443 2761
2444=item Finding the next timer per loop iteration: O(1) 2762=item Finding the next timer in each loop iteration: O(1)
2763
2764By virtue of using a binary heap, the next timer is always found at the
2765beginning of the storage array.
2445 2766
2446=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2767=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2447 2768
2448A change means an I/O watcher gets started or stopped, which requires 2769A change means an I/O watcher gets started or stopped, which requires
2449libev to recalculate its status (and possibly tell the kernel). 2770libev to recalculate its status (and possibly tell the kernel, depending
2771on backend and wether C<ev_io_set> was used).
2450 2772
2451=item Activating one watcher: O(1) 2773=item Activating one watcher (putting it into the pending state): O(1)
2452 2774
2453=item Priority handling: O(number_of_priorities) 2775=item Priority handling: O(number_of_priorities)
2454 2776
2455Priorities are implemented by allocating some space for each 2777Priorities are implemented by allocating some space for each
2456priority. When doing priority-based operations, libev usually has to 2778priority. When doing priority-based operations, libev usually has to
2457linearly search all the priorities. 2779linearly search all the priorities, but starting/stopping and activating
2780watchers becomes O(1) w.r.t. prioritiy handling.
2458 2781
2459=back 2782=back
2460 2783
2461 2784
2785=head1 Win32 platform limitations and workarounds
2786
2787Win32 doesn't support any of the standards (e.g. POSIX) that libev
2788requires, and its I/O model is fundamentally incompatible with the POSIX
2789model. Libev still offers limited functionality on this platform in
2790the form of the C<EVBACKEND_SELECT> backend, and only supports socket
2791descriptors. This only applies when using Win32 natively, not when using
2792e.g. cygwin.
2793
2794There is no supported compilation method available on windows except
2795embedding it into other applications.
2796
2797Due to the many, low, and arbitrary limits on the win32 platform and the
2798abysmal performance of winsockets, using a large number of sockets is not
2799recommended (and not reasonable). If your program needs to use more than
2800a hundred or so sockets, then likely it needs to use a totally different
2801implementation for windows, as libev offers the POSIX model, which cannot
2802be implemented efficiently on windows (microsoft monopoly games).
2803
2804=over 4
2805
2806=item The winsocket select function
2807
2808The winsocket C<select> function doesn't follow POSIX in that it requires
2809socket I<handles> and not socket I<file descriptors>. This makes select
2810very inefficient, and also requires a mapping from file descriptors
2811to socket handles. See the discussion of the C<EV_SELECT_USE_FD_SET>,
2812C<EV_SELECT_IS_WINSOCKET> and C<EV_FD_TO_WIN32_HANDLE> preprocessor
2813symbols for more info.
2814
2815The configuration for a "naked" win32 using the microsoft runtime
2816libraries and raw winsocket select is:
2817
2818 #define EV_USE_SELECT 1
2819 #define EV_SELECT_IS_WINSOCKET 1 /* forces EV_SELECT_USE_FD_SET, too */
2820
2821Note that winsockets handling of fd sets is O(n), so you can easily get a
2822complexity in the O(n²) range when using win32.
2823
2824=item Limited number of file descriptors
2825
2826Windows has numerous arbitrary (and low) limits on things. Early versions
2827of winsocket's select only supported waiting for a max. of C<64> handles
2828(probably owning to the fact that all windows kernels can only wait for
2829C<64> things at the same time internally; microsoft recommends spawning a
2830chain of threads and wait for 63 handles and the previous thread in each).
2831
2832Newer versions support more handles, but you need to define C<FD_SETSIZE>
2833to some high number (e.g. C<2048>) before compiling the winsocket select
2834call (which might be in libev or elsewhere, for example, perl does its own
2835select emulation on windows).
2836
2837Another limit is the number of file descriptors in the microsoft runtime
2838libraries, which by default is C<64> (there must be a hidden I<64> fetish
2839or something like this inside microsoft). You can increase this by calling
2840C<_setmaxstdio>, which can increase this limit to C<2048> (another
2841arbitrary limit), but is broken in many versions of the microsoft runtime
2842libraries.
2843
2844This might get you to about C<512> or C<2048> sockets (depending on
2845windows version and/or the phase of the moon). To get more, you need to
2846wrap all I/O functions and provide your own fd management, but the cost of
2847calling select (O(n²)) will likely make this unworkable.
2848
2849=back
2850
2851
2462=head1 AUTHOR 2852=head1 AUTHOR
2463 2853
2464Marc Lehmann <libev@schmorp.de>. 2854Marc Lehmann <libev@schmorp.de>.
2465 2855

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