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Comparing libev/ev.pod (file contents):
Revision 1.19 by root, Mon Nov 12 09:02:16 2007 UTC vs.
Revision 1.26 by root, Tue Nov 13 03:11:57 2007 UTC

56 56
57=over 4 57=over 4
58 58
59=item ev_tstamp ev_time () 59=item ev_tstamp ev_time ()
60 60
61Returns the current time as libev would use it. 61Returns the current time as libev would use it. Please note that the
62C<ev_now> function is usually faster and also often returns the timestamp
63you actually want to know.
62 64
63=item int ev_version_major () 65=item int ev_version_major ()
64 66
65=item int ev_version_minor () 67=item int ev_version_minor ()
66 68
241 243
242=item ev_unloop (loop, how) 244=item ev_unloop (loop, how)
243 245
244Can be used to make a call to C<ev_loop> return early (but only after it 246Can be used to make a call to C<ev_loop> return early (but only after it
245has processed all outstanding events). The C<how> argument must be either 247has processed all outstanding events). The C<how> argument must be either
246C<EVUNLOOP_ONCE>, which will make the innermost C<ev_loop> call return, or 248C<EVUNLOOP_ONE>, which will make the innermost C<ev_loop> call return, or
247C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return. 249C<EVUNLOOP_ALL>, which will make all nested C<ev_loop> calls return.
248 250
249=item ev_ref (loop) 251=item ev_ref (loop)
250 252
251=item ev_unref (loop) 253=item ev_unref (loop)
417in each iteration of the event loop (This behaviour is called 419in each iteration of the event loop (This behaviour is called
418level-triggering because you keep receiving events as long as the 420level-triggering because you keep receiving events as long as the
419condition persists. Remember you can stop the watcher if you don't want to 421condition persists. Remember you can stop the watcher if you don't want to
420act on the event and neither want to receive future events). 422act on the event and neither want to receive future events).
421 423
422In general you can register as many read and/or write event watchers oer 424In general you can register as many read and/or write event watchers per
423fd as you want (as long as you don't confuse yourself). Setting all file 425fd as you want (as long as you don't confuse yourself). Setting all file
424descriptors to non-blocking mode is also usually a good idea (but not 426descriptors to non-blocking mode is also usually a good idea (but not
425required if you know what you are doing). 427required if you know what you are doing).
426 428
427You have to be careful with dup'ed file descriptors, though. Some backends 429You have to be careful with dup'ed file descriptors, though. Some backends
428(the linux epoll backend is a notable example) cannot handle dup'ed file 430(the linux epoll backend is a notable example) cannot handle dup'ed file
429descriptors correctly if you register interest in two or more fds pointing 431descriptors correctly if you register interest in two or more fds pointing
430to the same file/socket etc. description. 432to the same underlying file/socket etc. description (that is, they share
433the same underlying "file open").
431 434
432If you must do this, then force the use of a known-to-be-good backend 435If you must do this, then force the use of a known-to-be-good backend
433(at the time of this writing, this includes only EVMETHOD_SELECT and 436(at the time of this writing, this includes only EVMETHOD_SELECT and
434EVMETHOD_POLL). 437EVMETHOD_POLL).
435 438
449 452
450Timer watchers are simple relative timers that generate an event after a 453Timer watchers are simple relative timers that generate an event after a
451given time, and optionally repeating in regular intervals after that. 454given time, and optionally repeating in regular intervals after that.
452 455
453The timers are based on real time, that is, if you register an event that 456The timers are based on real time, that is, if you register an event that
454times out after an hour and youreset your system clock to last years 457times out after an hour and you reset your system clock to last years
455time, it will still time out after (roughly) and hour. "Roughly" because 458time, it will still time out after (roughly) and hour. "Roughly" because
456detecting time jumps is hard, and soem inaccuracies are unavoidable (the 459detecting time jumps is hard, and soem inaccuracies are unavoidable (the
457monotonic clock option helps a lot here). 460monotonic clock option helps a lot here).
458 461
459The relative timeouts are calculated relative to the C<ev_now ()> 462The relative timeouts are calculated relative to the C<ev_now ()>
460time. This is usually the right thing as this timestamp refers to the time 463time. This is usually the right thing as this timestamp refers to the time
461of the event triggering whatever timeout you are modifying/starting. If 464of the event triggering whatever timeout you are modifying/starting. If
462you suspect event processing to be delayed and you *need* to base the timeout 465you suspect event processing to be delayed and you *need* to base the timeout
463ion the current time, use something like this to adjust for this: 466on the current time, use something like this to adjust for this:
464 467
465 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.); 468 ev_timer_set (&timer, after + ev_now () - ev_time (), 0.);
466 469
467=over 4 470=over 4
468 471
476later, again, and again, until stopped manually. 479later, again, and again, until stopped manually.
477 480
478The timer itself will do a best-effort at avoiding drift, that is, if you 481The timer itself will do a best-effort at avoiding drift, that is, if you
479configure a timer to trigger every 10 seconds, then it will trigger at 482configure a timer to trigger every 10 seconds, then it will trigger at
480exactly 10 second intervals. If, however, your program cannot keep up with 483exactly 10 second intervals. If, however, your program cannot keep up with
481the timer (ecause it takes longer than those 10 seconds to do stuff) the 484the timer (because it takes longer than those 10 seconds to do stuff) the
482timer will not fire more than once per event loop iteration. 485timer will not fire more than once per event loop iteration.
483 486
484=item ev_timer_again (loop) 487=item ev_timer_again (loop)
485 488
486This will act as if the timer timed out and restart it again if it is 489This will act as if the timer timed out and restart it again if it is
677=back 680=back
678 681
679=head2 C<ev_prepare> and C<ev_check> - customise your event loop 682=head2 C<ev_prepare> and C<ev_check> - customise your event loop
680 683
681Prepare and check watchers are usually (but not always) used in tandem: 684Prepare and check watchers are usually (but not always) used in tandem:
682Prepare watchers get invoked before the process blocks and check watchers 685prepare watchers get invoked before the process blocks and check watchers
683afterwards. 686afterwards.
684 687
685Their main purpose is to integrate other event mechanisms into libev. This 688Their main purpose is to integrate other event mechanisms into libev. This
686could be used, for example, to track variable changes, implement your own 689could be used, for example, to track variable changes, implement your own
687watchers, integrate net-snmp or a coroutine library and lots more. 690watchers, integrate net-snmp or a coroutine library and lots more.
690to be watched by the other library, registering C<ev_io> watchers for 693to be watched by the other library, registering C<ev_io> watchers for
691them and starting an C<ev_timer> watcher for any timeouts (many libraries 694them and starting an C<ev_timer> watcher for any timeouts (many libraries
692provide just this functionality). Then, in the check watcher you check for 695provide just this functionality). Then, in the check watcher you check for
693any events that occured (by checking the pending status of all watchers 696any events that occured (by checking the pending status of all watchers
694and stopping them) and call back into the library. The I/O and timer 697and stopping them) and call back into the library. The I/O and timer
695callbacks will never actually be called (but must be valid neverthelles, 698callbacks will never actually be called (but must be valid nevertheless,
696because you never know, you know?). 699because you never know, you know?).
697 700
698As another example, the Perl Coro module uses these hooks to integrate 701As another example, the Perl Coro module uses these hooks to integrate
699coroutines into libev programs, by yielding to other active coroutines 702coroutines into libev programs, by yielding to other active coroutines
700during each prepare and only letting the process block if no coroutines 703during each prepare and only letting the process block if no coroutines
701are ready to run (its actually more complicated, it only runs coroutines 704are ready to run (it's actually more complicated: it only runs coroutines
702with priority higher than the event loop and one lower priority once, 705with priority higher than or equal to the event loop and one coroutine
703using idle watchers to keep the event loop from blocking if lower-priority 706of lower priority, but only once, using idle watchers to keep the event
704coroutines exist, thus mapping low-priority coroutines to idle/background 707loop from blocking if lower-priority coroutines are active, thus mapping
705tasks). 708low-priority coroutines to idle/background tasks).
706 709
707=over 4 710=over 4
708 711
709=item ev_prepare_init (ev_prepare *, callback) 712=item ev_prepare_init (ev_prepare *, callback)
710 713
725=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 728=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
726 729
727This function combines a simple timer and an I/O watcher, calls your 730This function combines a simple timer and an I/O watcher, calls your
728callback on whichever event happens first and automatically stop both 731callback on whichever event happens first and automatically stop both
729watchers. This is useful if you want to wait for a single event on an fd 732watchers. This is useful if you want to wait for a single event on an fd
730or timeout without havign to allocate/configure/start/stop/free one or 733or timeout without having to allocate/configure/start/stop/free one or
731more watchers yourself. 734more watchers yourself.
732 735
733If C<fd> is less than 0, then no I/O watcher will be started and events 736If C<fd> is less than 0, then no I/O watcher will be started and events
734is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and 737is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
735C<events> set will be craeted and started. 738C<events> set will be craeted and started.
738started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and 741started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
739repeat = 0) will be started. While C<0> is a valid timeout, it is of 742repeat = 0) will be started. While C<0> is a valid timeout, it is of
740dubious value. 743dubious value.
741 744
742The callback has the type C<void (*cb)(int revents, void *arg)> and gets 745The callback has the type C<void (*cb)(int revents, void *arg)> and gets
743passed an events set like normal event callbacks (with a combination of 746passed an C<revents> set like normal event callbacks (a combination of
744C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> 747C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
745value passed to C<ev_once>: 748value passed to C<ev_once>:
746 749
747 static void stdin_ready (int revents, void *arg) 750 static void stdin_ready (int revents, void *arg)
748 { 751 {
769 772
770Feed an event as if the given signal occured (loop must be the default loop!). 773Feed an event as if the given signal occured (loop must be the default loop!).
771 774
772=back 775=back
773 776
777=head1 LIBEVENT EMULATION
778
779Libev offers a compatibility emulation layer for libevent. It cannot
780emulate the internals of libevent, so here are some usage hints:
781
782=over 4
783
784=item * Use it by including <event.h>, as usual.
785
786=item * The following members are fully supported: ev_base, ev_callback,
787ev_arg, ev_fd, ev_res, ev_events.
788
789=item * Avoid using ev_flags and the EVLIST_*-macros, while it is
790maintained by libev, it does not work exactly the same way as in libevent (consider
791it a private API).
792
793=item * Priorities are not currently supported. Initialising priorities
794will fail and all watchers will have the same priority, even though there
795is an ev_pri field.
796
797=item * Other members are not supported.
798
799=item * The libev emulation is I<not> ABI compatible to libevent, you need
800to use the libev header file and library.
801
802=back
803
804=head1 C++ SUPPORT
805
806TBD.
807
774=head1 AUTHOR 808=head1 AUTHOR
775 809
776Marc Lehmann <libev@schmorp.de>. 810Marc Lehmann <libev@schmorp.de>.
777 811

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