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39F<README.embed> in the libev distribution. If libev was configured without 39F<README.embed> in the libev distribution. If libev was configured without
40support for multiple event loops, then all functions taking an initial 40support for multiple event loops, then all functions taking an initial
41argument of name C<loop> (which is always of type C<struct ev_loop *>) 41argument of name C<loop> (which is always of type C<struct ev_loop *>)
42will not have this argument. 42will not have this argument.
43 43
44=head1 TIME AND OTHER GLOBAL FUNCTIONS 44=head1 TIME REPRESENTATION
45 45
46Libev represents time as a single floating point number, representing the 46Libev represents time as a single floating point number, representing the
47(fractional) number of seconds since the (POSIX) epoch (somewhere near 47(fractional) number of seconds since the (POSIX) epoch (somewhere near
48the beginning of 1970, details are complicated, don't ask). This type is 48the beginning of 1970, details are complicated, don't ask). This type is
49called C<ev_tstamp>, which is what you should use too. It usually aliases 49called C<ev_tstamp>, which is what you should use too. It usually aliases
50to the double type in C. 50to the double type in C.
51
52=head1 GLOBAL FUNCTIONS
53
54These functions can be called anytime, even before initialising the
55library in any way.
51 56
52=over 4 57=over 4
53 58
54=item ev_tstamp ev_time () 59=item ev_tstamp ev_time ()
55 60
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99An event loop is described by a C<struct ev_loop *>. The library knows two 104An event loop is described by a C<struct ev_loop *>. The library knows two
100types of such loops, the I<default> loop, which supports signals and child 105types of such loops, the I<default> loop, which supports signals and child
101events, and dynamically created loops which do not. 106events, and dynamically created loops which do not.
102 107
103If you use threads, a common model is to run the default event loop 108If you use threads, a common model is to run the default event loop
104in your main thread (or in a separate thrad) and for each thread you 109in your main thread (or in a separate thread) and for each thread you
105create, you also create another event loop. Libev itself does no locking 110create, you also create another event loop. Libev itself does no locking
106whatsoever, so if you mix calls to the same event loop in different 111whatsoever, so if you mix calls to the same event loop in different
107threads, make sure you lock (this is usually a bad idea, though, even if 112threads, make sure you lock (this is usually a bad idea, though, even if
108done correctly, because it's hideous and inefficient). 113done correctly, because it's hideous and inefficient).
109 114
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299 304
300As long as your watcher is active (has been started but not stopped) you 305As long as your watcher is active (has been started but not stopped) you
301must not touch the values stored in it. Most specifically you must never 306must not touch the values stored in it. Most specifically you must never
302reinitialise it or call its set method. 307reinitialise it or call its set method.
303 308
304You cna check whether an event is active by calling the C<ev_is_active 309You can check whether an event is active by calling the C<ev_is_active
305(watcher *)> macro. To see whether an event is outstanding (but the 310(watcher *)> macro. To see whether an event is outstanding (but the
306callback for it has not been called yet) you cna use the C<ev_is_pending 311callback for it has not been called yet) you can use the C<ev_is_pending
307(watcher *)> macro. 312(watcher *)> macro.
308 313
309Each and every callback receives the event loop pointer as first, the 314Each and every callback receives the event loop pointer as first, the
310registered watcher structure as second, and a bitset of received events as 315registered watcher structure as second, and a bitset of received events as
311third argument. 316third argument.
312 317
313The rceeived events usually include a single bit per event type received 318The received events usually include a single bit per event type received
314(you can receive multiple events at the same time). The possible bit masks 319(you can receive multiple events at the same time). The possible bit masks
315are: 320are:
316 321
317=over 4 322=over 4
318 323
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372=back 377=back
373 378
374=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 379=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375 380
376Each watcher has, by default, a member C<void *data> that you can change 381Each watcher has, by default, a member C<void *data> that you can change
377and read at any time, libev will completely ignore it. This cna be used 382and read at any time, libev will completely ignore it. This can be used
378to associate arbitrary data with your watcher. If you need more data and 383to associate arbitrary data with your watcher. If you need more data and
379don't want to allocate memory and store a pointer to it in that data 384don't want to allocate memory and store a pointer to it in that data
380member, you can also "subclass" the watcher type and provide your own 385member, you can also "subclass" the watcher type and provide your own
381data: 386data:
382 387
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409=head2 C<ev_io> - is this file descriptor readable or writable 414=head2 C<ev_io> - is this file descriptor readable or writable
410 415
411I/O watchers check whether a file descriptor is readable or writable 416I/O watchers check whether a file descriptor is readable or writable
412in each iteration of the event loop (This behaviour is called 417in each iteration of the event loop (This behaviour is called
413level-triggering because you keep receiving events as long as the 418level-triggering because you keep receiving events as long as the
414condition persists. Remember you cna stop the watcher if you don't want to 419condition persists. Remember you can stop the watcher if you don't want to
415act on the event and neither want to receive future events). 420act on the event and neither want to receive future events).
416 421
417In general you can register as many read and/or write event watchers oer 422In general you can register as many read and/or write event watchers oer
418fd as you want (as long as you don't confuse yourself). Setting all file 423fd as you want (as long as you don't confuse yourself). Setting all file
419descriptors to non-blocking mode is also usually a good idea (but not 424descriptors to non-blocking mode is also usually a good idea (but not
420required if you know what you are doing). 425required if you know what you are doing).
421 426
422You have to be careful with dup'ed file descriptors, though. Some backends 427You have to be careful with dup'ed file descriptors, though. Some backends
423(the linux epoll backend is a notable example) cannot handle dup'ed file 428(the linux epoll backend is a notable example) cannot handle dup'ed file
424descriptors correctly if you register interest in two or more fds pointing 429descriptors correctly if you register interest in two or more fds pointing
425to the same file/socket etc. description. 430to the same file/socket etc. description (that is, they share the same
431underlying "file open").
426 432
427If you must do this, then force the use of a known-to-be-good backend 433If you must do this, then force the use of a known-to-be-good backend
428(at the time of this writing, this includes only EVMETHOD_SELECT and 434(at the time of this writing, this includes only EVMETHOD_SELECT and
429EVMETHOD_POLL). 435EVMETHOD_POLL).
430 436
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444 450
445Timer watchers are simple relative timers that generate an event after a 451Timer watchers are simple relative timers that generate an event after a
446given time, and optionally repeating in regular intervals after that. 452given time, and optionally repeating in regular intervals after that.
447 453
448The timers are based on real time, that is, if you register an event that 454The timers are based on real time, that is, if you register an event that
449times out after an hour and youreset your system clock to last years 455times out after an hour and you reset your system clock to last years
450time, it will still time out after (roughly) and hour. "Roughly" because 456time, it will still time out after (roughly) and hour. "Roughly" because
451detecting time jumps is hard, and soem inaccuracies are unavoidable (the 457detecting time jumps is hard, and soem inaccuracies are unavoidable (the
452monotonic clock option helps a lot here). 458monotonic clock option helps a lot here).
453 459
454The relative timeouts are calculated relative to the C<ev_now ()> 460The relative timeouts are calculated relative to the C<ev_now ()>
455time. This is usually the right thing as this timestamp refers to the time 461time. This is usually the right thing as this timestamp refers to the time
456of the event triggering whatever timeout you are modifying/starting. If 462of the event triggering whatever timeout you are modifying/starting. If
457you suspect event processing to be delayed and you *need* to base the timeout 463you suspect event processing to be delayed and you *need* to base the timeout
458ion the current time, use something like this to adjust for this: 464on the current time, use something like this to adjust for this:
459 465
460 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 466 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
461 467
462=over 4 468=over 4
463 469
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471later, again, and again, until stopped manually. 477later, again, and again, until stopped manually.
472 478
473The timer itself will do a best-effort at avoiding drift, that is, if you 479The timer itself will do a best-effort at avoiding drift, that is, if you
474configure a timer to trigger every 10 seconds, then it will trigger at 480configure a timer to trigger every 10 seconds, then it will trigger at
475exactly 10 second intervals. If, however, your program cannot keep up with 481exactly 10 second intervals. If, however, your program cannot keep up with
476the timer (ecause it takes longer than those 10 seconds to do stuff) the 482the timer (because it takes longer than those 10 seconds to do stuff) the
477timer will not fire more than once per event loop iteration. 483timer will not fire more than once per event loop iteration.
478 484
479=item ev_timer_again (loop) 485=item ev_timer_again (loop)
480 486
481This will act as if the timer timed out and restart it again if it is 487This will act as if the timer timed out and restart it again if it is
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495state where you do not expect data to travel on the socket, you can stop 501state where you do not expect data to travel on the socket, you can stop
496the timer, and again will automatically restart it if need be. 502the timer, and again will automatically restart it if need be.
497 503
498=back 504=back
499 505
500=head2 C<ev_periodic> - to cron or not to cron it 506=head2 C<ev_periodic> - to cron or not to cron
501 507
502Periodic watchers are also timers of a kind, but they are very versatile 508Periodic watchers are also timers of a kind, but they are very versatile
503(and unfortunately a bit complex). 509(and unfortunately a bit complex).
504 510
505Unlike C<ev_timer>'s, they are not based on real time (or relative time) 511Unlike C<ev_timer>'s, they are not based on real time (or relative time)
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558In this mode the values for C<interval> and C<at> are both being 564In this mode the values for C<interval> and C<at> are both being
559ignored. Instead, each time the periodic watcher gets scheduled, the 565ignored. Instead, each time the periodic watcher gets scheduled, the
560reschedule callback will be called with the watcher as first, and the 566reschedule callback will be called with the watcher as first, and the
561current time as second argument. 567current time as second argument.
562 568
563NOTE: I<This callback MUST NOT stop or destroy the periodic or any other 569NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564periodic watcher, ever, or make any event loop modifications>. If you need 570ever, or make any event loop modifications>. If you need to stop it,
565to stop it, return C<now + 1e30> (or so, fudge fudge) and stop it afterwards. 571return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566 572starting a prepare watcher).
567Also, I<< this callback must always return a time that is later than the
568passed C<now> value >>. Not even C<now> itself will be ok.
569 573
570Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 574Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
571ev_tstamp now)>, e.g.: 575ev_tstamp now)>, e.g.:
572 576
573 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 577 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now)
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578It must return the next time to trigger, based on the passed time value 582It must return the next time to trigger, based on the passed time value
579(that is, the lowest time value larger than to the second argument). It 583(that is, the lowest time value larger than to the second argument). It
580will usually be called just before the callback will be triggered, but 584will usually be called just before the callback will be triggered, but
581might be called at other times, too. 585might be called at other times, too.
582 586
587NOTE: I<< This callback must always return a time that is later than the
588passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
589
583This can be used to create very complex timers, such as a timer that 590This can be used to create very complex timers, such as a timer that
584triggers on each midnight, local time. To do this, you would calculate the 591triggers on each midnight, local time. To do this, you would calculate the
585next midnight after C<now> and return the timestamp value for this. How you do this 592next midnight after C<now> and return the timestamp value for this. How
586is, again, up to you (but it is not trivial). 593you do this is, again, up to you (but it is not trivial, which is the main
594reason I omitted it as an example).
587 595
588=back 596=back
589 597
590=item ev_periodic_again (loop, ev_periodic *) 598=item ev_periodic_again (loop, ev_periodic *)
591 599
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601Signal watchers will trigger an event when the process receives a specific 609Signal watchers will trigger an event when the process receives a specific
602signal one or more times. Even though signals are very asynchronous, libev 610signal one or more times. Even though signals are very asynchronous, libev
603will try it's best to deliver signals synchronously, i.e. as part of the 611will try it's best to deliver signals synchronously, i.e. as part of the
604normal event processing, like any other event. 612normal event processing, like any other event.
605 613
606You cna configure as many watchers as you like per signal. Only when the 614You can configure as many watchers as you like per signal. Only when the
607first watcher gets started will libev actually register a signal watcher 615first watcher gets started will libev actually register a signal watcher
608with the kernel (thus it coexists with your own signal handlers as long 616with the kernel (thus it coexists with your own signal handlers as long
609as you don't register any with libev). Similarly, when the last signal 617as you don't register any with libev). Similarly, when the last signal
610watcher for a signal is stopped libev will reset the signal handler to 618watcher for a signal is stopped libev will reset the signal handler to
611SIG_DFL (regardless of what it was set to before). 619SIG_DFL (regardless of what it was set to before).
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633=item ev_child_set (ev_child *, int pid) 641=item ev_child_set (ev_child *, int pid)
634 642
635Configures the watcher to wait for status changes of process C<pid> (or 643Configures the watcher to wait for status changes of process C<pid> (or
636I<any> process if C<pid> is specified as C<0>). The callback can look 644I<any> process if C<pid> is specified as C<0>). The callback can look
637at the C<rstatus> member of the C<ev_child> watcher structure to see 645at the C<rstatus> member of the C<ev_child> watcher structure to see
638the status word (use the macros from C<sys/wait.h>). The C<rpid> member 646the status word (use the macros from C<sys/wait.h> and see your systems
639contains the pid of the process causing the status change. 647C<waitpid> documentation). The C<rpid> member contains the pid of the
648process causing the status change.
640 649
641=back 650=back
642 651
643=head2 C<ev_idle> - when you've got nothing better to do 652=head2 C<ev_idle> - when you've got nothing better to do
644 653
645Idle watchers trigger events when there are no other I/O or timer (or 654Idle watchers trigger events when there are no other events are pending
646periodic) events pending. That is, as long as your process is busy 655(prepare, check and other idle watchers do not count). That is, as long
647handling sockets or timeouts it will not be called. But when your process 656as your process is busy handling sockets or timeouts (or even signals,
648is idle all idle watchers are being called again and again - until 657imagine) it will not be triggered. But when your process is idle all idle
658watchers are being called again and again, once per event loop iteration -
649stopped, that is, or your process receives more events. 659until stopped, that is, or your process receives more events and becomes
660busy.
650 661
651The most noteworthy effect is that as long as any idle watchers are 662The most noteworthy effect is that as long as any idle watchers are
652active, the process will not block when waiting for new events. 663active, the process will not block when waiting for new events.
653 664
654Apart from keeping your process non-blocking (which is a useful 665Apart from keeping your process non-blocking (which is a useful
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664kind. There is a C<ev_idle_set> macro, but using it is utterly pointless, 675kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
665believe me. 676believe me.
666 677
667=back 678=back
668 679
669=head2 prepare and check - your hooks into the event loop 680=head2 C<ev_prepare> and C<ev_check> - customise your event loop
670 681
671Prepare and check watchers usually (but not always) are used in 682Prepare and check watchers are usually (but not always) used in tandem:
672tandom. Prepare watchers get invoked before the process blocks and check 683prepare watchers get invoked before the process blocks and check watchers
673watchers afterwards. 684afterwards.
674 685
675Their main purpose is to integrate other event mechanisms into libev. This 686Their main purpose is to integrate other event mechanisms into libev. This
676could be used, for example, to track variable changes, implement your own 687could be used, for example, to track variable changes, implement your own
677watchers, integrate net-snmp or a coroutine library and lots more. 688watchers, integrate net-snmp or a coroutine library and lots more.
678 689
679This is done by examining in each prepare call which file descriptors need 690This is done by examining in each prepare call which file descriptors need
680to be watched by the other library, registering C<ev_io> watchers for them 691to be watched by the other library, registering C<ev_io> watchers for
681and starting an C<ev_timer> watcher for any timeouts (many libraries provide 692them and starting an C<ev_timer> watcher for any timeouts (many libraries
682just this functionality). Then, in the check watcher you check for any 693provide just this functionality). Then, in the check watcher you check for
683events that occured (by making your callbacks set soem flags for example) 694any events that occured (by checking the pending status of all watchers
684and call back into the library. 695and stopping them) and call back into the library. The I/O and timer
696callbacks will never actually be called (but must be valid nevertheless,
697because you never know, you know?).
685 698
686As another example, the perl Coro module uses these hooks to integrate 699As another example, the Perl Coro module uses these hooks to integrate
687coroutines into libev programs, by yielding to other active coroutines 700coroutines into libev programs, by yielding to other active coroutines
688during each prepare and only letting the process block if no coroutines 701during each prepare and only letting the process block if no coroutines
689are ready to run. 702are ready to run (it's actually more complicated: it only runs coroutines
703with priority higher than or equal to the event loop and one coroutine
704of lower priority, but only once, using idle watchers to keep the event
705loop from blocking if lower-priority coroutines are active, thus mapping
706low-priority coroutines to idle/background tasks).
690 707
691=over 4 708=over 4
692 709
693=item ev_prepare_init (ev_prepare *, callback) 710=item ev_prepare_init (ev_prepare *, callback)
694 711
695=item ev_check_init (ev_check *, callback) 712=item ev_check_init (ev_check *, callback)
696 713
697Initialises and configures the prepare or check watcher - they have no 714Initialises and configures the prepare or check watcher - they have no
698parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set> 715parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
699macros, but using them is utterly, utterly pointless. 716macros, but using them is utterly, utterly and completely pointless.
700 717
701=back 718=back
702 719
703=head1 OTHER FUNCTIONS 720=head1 OTHER FUNCTIONS
704 721
705There are some other fucntions of possible interest. Described. Here. Now. 722There are some other functions of possible interest. Described. Here. Now.
706 723
707=over 4 724=over 4
708 725
709=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 726=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
710 727
711This function combines a simple timer and an I/O watcher, calls your 728This function combines a simple timer and an I/O watcher, calls your
712callback on whichever event happens first and automatically stop both 729callback on whichever event happens first and automatically stop both
713watchers. This is useful if you want to wait for a single event on an fd 730watchers. This is useful if you want to wait for a single event on an fd
714or timeout without havign to allocate/configure/start/stop/free one or 731or timeout without having to allocate/configure/start/stop/free one or
715more watchers yourself. 732more watchers yourself.
716 733
717If C<fd> is less than 0, then no I/O watcher will be started and events is 734If C<fd> is less than 0, then no I/O watcher will be started and events
718ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and C<events> set 735is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
719will be craeted and started. 736C<events> set will be craeted and started.
720 737
721If C<timeout> is less than 0, then no timeout watcher will be 738If C<timeout> is less than 0, then no timeout watcher will be
722started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and repeat 739started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
723= 0) will be started. 740repeat = 0) will be started. While C<0> is a valid timeout, it is of
741dubious value.
724 742
725The callback has the type C<void (*cb)(int revents, void *arg)> and 743The callback has the type C<void (*cb)(int revents, void *arg)> and gets
726gets passed an events set (normally a combination of C<EV_ERROR>, C<EV_READ>, 744passed an C<revents> set like normal event callbacks (a combination of
727C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> value passed to C<ev_once>: 745C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
746value passed to C<ev_once>:
728 747
729 static void stdin_ready (int revents, void *arg) 748 static void stdin_ready (int revents, void *arg)
730 { 749 {
731 if (revents & EV_TIMEOUT) 750 if (revents & EV_TIMEOUT)
732 /* doh, nothing entered */ 751 /* doh, nothing entered */;
733 else if (revents & EV_READ) 752 else if (revents & EV_READ)
734 /* stdin might have data for us, joy! */ 753 /* stdin might have data for us, joy! */;
735 } 754 }
736 755
737 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 756 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738 757
739=item ev_feed_event (loop, watcher, int events) 758=item ev_feed_event (loop, watcher, int events)
740 759
741Feeds the given event set into the event loop, as if the specified event 760Feeds the given event set into the event loop, as if the specified event
742has happened for the specified watcher (which must be a pointer to an 761had happened for the specified watcher (which must be a pointer to an
743initialised but not necessarily active event watcher). 762initialised but not necessarily started event watcher).
744 763
745=item ev_feed_fd_event (loop, int fd, int revents) 764=item ev_feed_fd_event (loop, int fd, int revents)
746 765
747Feed an event on the given fd, as if a file descriptor backend detected it. 766Feed an event on the given fd, as if a file descriptor backend detected
767the given events it.
748 768
749=item ev_feed_signal_event (loop, int signum) 769=item ev_feed_signal_event (loop, int signum)
750 770
751Feed an event as if the given signal occured (loop must be the default loop!). 771Feed an event as if the given signal occured (loop must be the default loop!).
752 772
753=back 773=back
754 774
775=head1 LIBEVENT EMULATION
776
777TBD.
778
779=head1 C++ SUPPORT
780
781TBD.
782
755=head1 AUTHOR 783=head1 AUTHOR
756 784
757Marc Lehmann <libev@schmorp.de>. 785Marc Lehmann <libev@schmorp.de>.
758 786

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