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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
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495state where you do not expect data to travel on the socket, you can stop 500state 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. 501the timer, and again will automatically restart it if need be.
497 502
498=back 503=back
499 504
500=head2 C<ev_periodic> - to cron or not to cron it 505=head2 C<ev_periodic> - to cron or not to cron
501 506
502Periodic watchers are also timers of a kind, but they are very versatile 507Periodic watchers are also timers of a kind, but they are very versatile
503(and unfortunately a bit complex). 508(and unfortunately a bit complex).
504 509
505Unlike C<ev_timer>'s, they are not based on real time (or relative time) 510Unlike 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 563In this mode the values for C<interval> and C<at> are both being
559ignored. Instead, each time the periodic watcher gets scheduled, the 564ignored. Instead, each time the periodic watcher gets scheduled, the
560reschedule callback will be called with the watcher as first, and the 565reschedule callback will be called with the watcher as first, and the
561current time as second argument. 566current time as second argument.
562 567
563NOTE: I<This callback MUST NOT stop or destroy the periodic or any other 568NOTE: I<This callback MUST NOT stop or destroy any periodic watcher,
564periodic watcher, ever, or make any event loop modifications>. If you need 569ever, 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. 570return C<now + 1e30> (or so, fudge fudge) and stop it afterwards (e.g. by
566 571starting 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.
569 572
570Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w, 573Its prototype is C<ev_tstamp (*reschedule_cb)(struct ev_periodic *w,
571ev_tstamp now)>, e.g.: 574ev_tstamp now)>, e.g.:
572 575
573 static ev_tstamp my_rescheduler (struct ev_periodic *w, ev_tstamp now) 576 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 581It 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 582(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 583will usually be called just before the callback will be triggered, but
581might be called at other times, too. 584might be called at other times, too.
582 585
586NOTE: I<< This callback must always return a time that is later than the
587passed C<now> value >>. Not even C<now> itself will do, it I<must> be larger.
588
583This can be used to create very complex timers, such as a timer that 589This 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 590triggers 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 591next midnight after C<now> and return the timestamp value for this. How
586is, again, up to you (but it is not trivial). 592you do this is, again, up to you (but it is not trivial, which is the main
593reason I omitted it as an example).
587 594
588=back 595=back
589 596
590=item ev_periodic_again (loop, ev_periodic *) 597=item ev_periodic_again (loop, ev_periodic *)
591 598
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601Signal watchers will trigger an event when the process receives a specific 608Signal watchers will trigger an event when the process receives a specific
602signal one or more times. Even though signals are very asynchronous, libev 609signal 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 610will try it's best to deliver signals synchronously, i.e. as part of the
604normal event processing, like any other event. 611normal event processing, like any other event.
605 612
606You cna configure as many watchers as you like per signal. Only when the 613You can configure as many watchers as you like per signal. Only when the
607first watcher gets started will libev actually register a signal watcher 614first watcher gets started will libev actually register a signal watcher
608with the kernel (thus it coexists with your own signal handlers as long 615with 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 616as 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 617watcher for a signal is stopped libev will reset the signal handler to
611SIG_DFL (regardless of what it was set to before). 618SIG_DFL (regardless of what it was set to before).
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633=item ev_child_set (ev_child *, int pid) 640=item ev_child_set (ev_child *, int pid)
634 641
635Configures the watcher to wait for status changes of process C<pid> (or 642Configures 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 643I<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 644at 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 645the status word (use the macros from C<sys/wait.h> and see your systems
639contains the pid of the process causing the status change. 646C<waitpid> documentation). The C<rpid> member contains the pid of the
647process causing the status change.
640 648
641=back 649=back
642 650
643=head2 C<ev_idle> - when you've got nothing better to do 651=head2 C<ev_idle> - when you've got nothing better to do
644 652
645Idle watchers trigger events when there are no other I/O or timer (or 653Idle watchers trigger events when there are no other events are pending
646periodic) events pending. That is, as long as your process is busy 654(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 655as your process is busy handling sockets or timeouts (or even signals,
648is idle all idle watchers are being called again and again - until 656imagine) it will not be triggered. But when your process is idle all idle
657watchers are being called again and again, once per event loop iteration -
649stopped, that is, or your process receives more events. 658until stopped, that is, or your process receives more events and becomes
659busy.
650 660
651The most noteworthy effect is that as long as any idle watchers are 661The most noteworthy effect is that as long as any idle watchers are
652active, the process will not block when waiting for new events. 662active, the process will not block when waiting for new events.
653 663
654Apart from keeping your process non-blocking (which is a useful 664Apart 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, 674kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
665believe me. 675believe me.
666 676
667=back 677=back
668 678
669=head2 prepare and check - your hooks into the event loop 679=head2 C<ev_prepare> and C<ev_check> - customise your event loop
670 680
671Prepare and check watchers usually (but not always) are used in 681Prepare and check watchers are usually (but not always) used in tandem:
672tandom. Prepare watchers get invoked before the process blocks and check 682prepare watchers get invoked before the process blocks and check watchers
673watchers afterwards. 683afterwards.
674 684
675Their main purpose is to integrate other event mechanisms into libev. This 685Their main purpose is to integrate other event mechanisms into libev. This
676could be used, for example, to track variable changes, implement your own 686could be used, for example, to track variable changes, implement your own
677watchers, integrate net-snmp or a coroutine library and lots more. 687watchers, integrate net-snmp or a coroutine library and lots more.
678 688
679This is done by examining in each prepare call which file descriptors need 689This 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 690to 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 691them and starting an C<ev_timer> watcher for any timeouts (many libraries
682just this functionality). Then, in the check watcher you check for any 692provide just this functionality). Then, in the check watcher you check for
683events that occured (by making your callbacks set soem flags for example) 693any events that occured (by checking the pending status of all watchers
684and call back into the library. 694and stopping them) and call back into the library. The I/O and timer
695callbacks will never actually be called (but must be valid nevertheless,
696because you never know, you know?).
685 697
686As another example, the perl Coro module uses these hooks to integrate 698As another example, the Perl Coro module uses these hooks to integrate
687coroutines into libev programs, by yielding to other active coroutines 699coroutines into libev programs, by yielding to other active coroutines
688during each prepare and only letting the process block if no coroutines 700during each prepare and only letting the process block if no coroutines
689are ready to run. 701are ready to run (it's actually more complicated: it only runs coroutines
702with priority higher than or equal to the event loop and one coroutine
703of lower priority, but only once, using idle watchers to keep the event
704loop from blocking if lower-priority coroutines are active, thus mapping
705low-priority coroutines to idle/background tasks).
690 706
691=over 4 707=over 4
692 708
693=item ev_prepare_init (ev_prepare *, callback) 709=item ev_prepare_init (ev_prepare *, callback)
694 710
695=item ev_check_init (ev_check *, callback) 711=item ev_check_init (ev_check *, callback)
696 712
697Initialises and configures the prepare or check watcher - they have no 713Initialises 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> 714parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
699macros, but using them is utterly, utterly pointless. 715macros, but using them is utterly, utterly and completely pointless.
700 716
701=back 717=back
702 718
703=head1 OTHER FUNCTIONS 719=head1 OTHER FUNCTIONS
704 720
705There are some other fucntions of possible interest. Described. Here. Now. 721There are some other functions of possible interest. Described. Here. Now.
706 722
707=over 4 723=over 4
708 724
709=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 725=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
710 726
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712callback on whichever event happens first and automatically stop both 728callback 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 729watchers. 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 730or timeout without havign to allocate/configure/start/stop/free one or
715more watchers yourself. 731more watchers yourself.
716 732
717If C<fd> is less than 0, then no I/O watcher will be started and events is 733If 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 734is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
719will be craeted and started. 735C<events> set will be craeted and started.
720 736
721If C<timeout> is less than 0, then no timeout watcher will be 737If 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 738started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
723= 0) will be started. 739repeat = 0) will be started. While C<0> is a valid timeout, it is of
740dubious value.
724 741
725The callback has the type C<void (*cb)(int revents, void *arg)> and 742The 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>, 743passed 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>: 744C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
745value passed to C<ev_once>:
728 746
729 static void stdin_ready (int revents, void *arg) 747 static void stdin_ready (int revents, void *arg)
730 { 748 {
731 if (revents & EV_TIMEOUT) 749 if (revents & EV_TIMEOUT)
732 /* doh, nothing entered */ 750 /* doh, nothing entered */;
733 else if (revents & EV_READ) 751 else if (revents & EV_READ)
734 /* stdin might have data for us, joy! */ 752 /* stdin might have data for us, joy! */;
735 } 753 }
736 754
737 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 755 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738 756
739=item ev_feed_event (loop, watcher, int events) 757=item ev_feed_event (loop, watcher, int events)
740 758
741Feeds the given event set into the event loop, as if the specified event 759Feeds 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 760had happened for the specified watcher (which must be a pointer to an
743initialised but not necessarily active event watcher). 761initialised but not necessarily started event watcher).
744 762
745=item ev_feed_fd_event (loop, int fd, int revents) 763=item ev_feed_fd_event (loop, int fd, int revents)
746 764
747Feed an event on the given fd, as if a file descriptor backend detected it. 765Feed an event on the given fd, as if a file descriptor backend detected
766the given events it.
748 767
749=item ev_feed_signal_event (loop, int signum) 768=item ev_feed_signal_event (loop, int signum)
750 769
751Feed an event as if the given signal occured (loop must be the default loop!). 770Feed an event as if the given signal occured (loop must be the default loop!).
752 771
753=back 772=back
754 773
774=head1 LIBEVENT EMULATION
775
776TBD.
777
778=head1 C++ SUPPORT
779
780TBD.
781
755=head1 AUTHOR 782=head1 AUTHOR
756 783
757Marc Lehmann <libev@schmorp.de>. 784Marc Lehmann <libev@schmorp.de>.
758 785

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