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Revision 1.13 by root, Mon Nov 12 08:35:36 2007 UTC vs.
Revision 1.17 by root, Mon Nov 12 08:57:03 2007 UTC

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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
51 53
52=over 4 54=over 4
53 55
54=item ev_tstamp ev_time () 56=item ev_tstamp ev_time ()
55 57
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99An event loop is described by a C<struct ev_loop *>. The library knows two 101An 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 102types of such loops, the I<default> loop, which supports signals and child
101events, and dynamically created loops which do not. 103events, and dynamically created loops which do not.
102 104
103If you use threads, a common model is to run the default event loop 105If 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 106in 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 107create, you also create another event loop. Libev itself does no locking
106whatsoever, so if you mix calls to the same event loop in different 108whatsoever, 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 109threads, make sure you lock (this is usually a bad idea, though, even if
108done correctly, because it's hideous and inefficient). 110done correctly, because it's hideous and inefficient).
109 111
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299 301
300As long as your watcher is active (has been started but not stopped) you 302As 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 303must not touch the values stored in it. Most specifically you must never
302reinitialise it or call its set method. 304reinitialise it or call its set method.
303 305
304You cna check whether an event is active by calling the C<ev_is_active 306You 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 307(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 308callback for it has not been called yet) you can use the C<ev_is_pending
307(watcher *)> macro. 309(watcher *)> macro.
308 310
309Each and every callback receives the event loop pointer as first, the 311Each and every callback receives the event loop pointer as first, the
310registered watcher structure as second, and a bitset of received events as 312registered watcher structure as second, and a bitset of received events as
311third argument. 313third argument.
312 314
313The rceeived events usually include a single bit per event type received 315The 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 316(you can receive multiple events at the same time). The possible bit masks
315are: 317are:
316 318
317=over 4 319=over 4
318 320
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372=back 374=back
373 375
374=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER 376=head2 ASSOCIATING CUSTOM DATA WITH A WATCHER
375 377
376Each watcher has, by default, a member C<void *data> that you can change 378Each 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 379and 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 380to 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 381don'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 382member, you can also "subclass" the watcher type and provide your own
381data: 383data:
382 384
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409=head2 C<ev_io> - is this file descriptor readable or writable 411=head2 C<ev_io> - is this file descriptor readable or writable
410 412
411I/O watchers check whether a file descriptor is readable or writable 413I/O watchers check whether a file descriptor is readable or writable
412in each iteration of the event loop (This behaviour is called 414in each iteration of the event loop (This behaviour is called
413level-triggering because you keep receiving events as long as the 415level-triggering because you keep receiving events as long as the
414condition persists. Remember you cna stop the watcher if you don't want to 416condition persists. Remember you can stop the watcher if you don't want to
415act on the event and neither want to receive future events). 417act on the event and neither want to receive future events).
416 418
417In general you can register as many read and/or write event watchers oer 419In 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 420fd 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 421descriptors 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 497state 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. 498the timer, and again will automatically restart it if need be.
497 499
498=back 500=back
499 501
500=head2 C<ev_periodic> - to cron or not to cron it 502=head2 C<ev_periodic> - to cron or not to cron
501 503
502Periodic watchers are also timers of a kind, but they are very versatile 504Periodic watchers are also timers of a kind, but they are very versatile
503(and unfortunately a bit complex). 505(and unfortunately a bit complex).
504 506
505Unlike C<ev_timer>'s, they are not based on real time (or relative time) 507Unlike C<ev_timer>'s, they are not based on real time (or relative time)
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601Signal watchers will trigger an event when the process receives a specific 603Signal watchers will trigger an event when the process receives a specific
602signal one or more times. Even though signals are very asynchronous, libev 604signal 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 605will try it's best to deliver signals synchronously, i.e. as part of the
604normal event processing, like any other event. 606normal event processing, like any other event.
605 607
606You cna configure as many watchers as you like per signal. Only when the 608You can configure as many watchers as you like per signal. Only when the
607first watcher gets started will libev actually register a signal watcher 609first watcher gets started will libev actually register a signal watcher
608with the kernel (thus it coexists with your own signal handlers as long 610with 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 611as 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 612watcher for a signal is stopped libev will reset the signal handler to
611SIG_DFL (regardless of what it was set to before). 613SIG_DFL (regardless of what it was set to before).
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633=item ev_child_set (ev_child *, int pid) 635=item ev_child_set (ev_child *, int pid)
634 636
635Configures the watcher to wait for status changes of process C<pid> (or 637Configures 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 638I<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 639at 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 640the status word (use the macros from C<sys/wait.h> and see your systems
639contains the pid of the process causing the status change. 641C<waitpid> documentation). The C<rpid> member contains the pid of the
642process causing the status change.
640 643
641=back 644=back
642 645
643=head2 C<ev_idle> - when you've got nothing better to do 646=head2 C<ev_idle> - when you've got nothing better to do
644 647
645Idle watchers trigger events when there are no other I/O or timer (or 648Idle watchers trigger events when there are no other events are pending
646periodic) events pending. That is, as long as your process is busy 649(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 650as your process is busy handling sockets or timeouts (or even signals,
648is idle all idle watchers are being called again and again - until 651imagine) it will not be triggered. But when your process is idle all idle
652watchers are being called again and again, once per event loop iteration -
649stopped, that is, or your process receives more events. 653until stopped, that is, or your process receives more events and becomes
654busy.
650 655
651The most noteworthy effect is that as long as any idle watchers are 656The most noteworthy effect is that as long as any idle watchers are
652active, the process will not block when waiting for new events. 657active, the process will not block when waiting for new events.
653 658
654Apart from keeping your process non-blocking (which is a useful 659Apart 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, 669kind. There is a C<ev_idle_set> macro, but using it is utterly pointless,
665believe me. 670believe me.
666 671
667=back 672=back
668 673
669=head2 prepare and check - your hooks into the event loop 674=head2 C<ev_prepare> and C<ev_check> - customise your event loop
670 675
671Prepare and check watchers usually (but not always) are used in 676Prepare and check watchers are usually (but not always) used in tandem:
672tandom. Prepare watchers get invoked before the process blocks and check 677Prepare watchers get invoked before the process blocks and check watchers
673watchers afterwards. 678afterwards.
674 679
675Their main purpose is to integrate other event mechanisms into libev. This 680Their main purpose is to integrate other event mechanisms into libev. This
676could be used, for example, to track variable changes, implement your own 681could be used, for example, to track variable changes, implement your own
677watchers, integrate net-snmp or a coroutine library and lots more. 682watchers, integrate net-snmp or a coroutine library and lots more.
678 683
679This is done by examining in each prepare call which file descriptors need 684This 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 685to 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 686them and starting an C<ev_timer> watcher for any timeouts (many libraries
682just this functionality). Then, in the check watcher you check for any 687provide just this functionality). Then, in the check watcher you check for
683events that occured (by making your callbacks set soem flags for example) 688any events that occured (by checking the pending status of all watchers
684and call back into the library. 689and stopping them) and call back into the library. The I/O and timer
690callbacks will never actually be called (but must be valid neverthelles,
691because you never know, you know?).
685 692
686As another example, the perl Coro module uses these hooks to integrate 693As another example, the Perl Coro module uses these hooks to integrate
687coroutines into libev programs, by yielding to other active coroutines 694coroutines into libev programs, by yielding to other active coroutines
688during each prepare and only letting the process block if no coroutines 695during each prepare and only letting the process block if no coroutines
689are ready to run. 696are ready to run (its actually more complicated, it only runs coroutines
697with priority higher than the event loop and one lower priority once,
698using idle watchers to keep the event loop from blocking if lower-priority
699coroutines exist, thus mapping low-priority coroutines to idle/background
700tasks).
690 701
691=over 4 702=over 4
692 703
693=item ev_prepare_init (ev_prepare *, callback) 704=item ev_prepare_init (ev_prepare *, callback)
694 705
695=item ev_check_init (ev_check *, callback) 706=item ev_check_init (ev_check *, callback)
696 707
697Initialises and configures the prepare or check watcher - they have no 708Initialises 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> 709parameters of any kind. There are C<ev_prepare_set> and C<ev_check_set>
699macros, but using them is utterly, utterly pointless. 710macros, but using them is utterly, utterly and completely pointless.
700 711
701=back 712=back
702 713
703=head1 OTHER FUNCTIONS 714=head1 OTHER FUNCTIONS
704 715
705There are some other fucntions of possible interest. Described. Here. Now. 716There are some other functions of possible interest. Described. Here. Now.
706 717
707=over 4 718=over 4
708 719
709=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback) 720=item ev_once (loop, int fd, int events, ev_tstamp timeout, callback)
710 721
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712callback on whichever event happens first and automatically stop both 723callback 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 724watchers. 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 725or timeout without havign to allocate/configure/start/stop/free one or
715more watchers yourself. 726more watchers yourself.
716 727
717If C<fd> is less than 0, then no I/O watcher will be started and events is 728If 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 729is being ignored. Otherwise, an C<ev_io> watcher for the given C<fd> and
719will be craeted and started. 730C<events> set will be craeted and started.
720 731
721If C<timeout> is less than 0, then no timeout watcher will be 732If 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 733started. Otherwise an C<ev_timer> watcher with after = C<timeout> (and
723= 0) will be started. 734repeat = 0) will be started. While C<0> is a valid timeout, it is of
735dubious value.
724 736
725The callback has the type C<void (*cb)(int revents, void *arg)> and 737The 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>, 738passed an events set like normal event callbacks (with a combination of
727C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg> value passed to C<ev_once>: 739C<EV_ERROR>, C<EV_READ>, C<EV_WRITE> or C<EV_TIMEOUT>) and the C<arg>
740value passed to C<ev_once>:
728 741
729 static void stdin_ready (int revents, void *arg) 742 static void stdin_ready (int revents, void *arg)
730 { 743 {
731 if (revents & EV_TIMEOUT) 744 if (revents & EV_TIMEOUT)
732 /* doh, nothing entered */ 745 /* doh, nothing entered */;
733 else if (revents & EV_READ) 746 else if (revents & EV_READ)
734 /* stdin might have data for us, joy! */ 747 /* stdin might have data for us, joy! */;
735 } 748 }
736 749
737 ev_once (STDIN_FILENO, EV_READm 10., stdin_ready, 0); 750 ev_once (STDIN_FILENO, EV_READ, 10., stdin_ready, 0);
738 751
739=item ev_feed_event (loop, watcher, int events) 752=item ev_feed_event (loop, watcher, int events)
740 753
741Feeds the given event set into the event loop, as if the specified event 754Feeds 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 755had happened for the specified watcher (which must be a pointer to an
743initialised but not necessarily active event watcher). 756initialised but not necessarily started event watcher).
744 757
745=item ev_feed_fd_event (loop, int fd, int revents) 758=item ev_feed_fd_event (loop, int fd, int revents)
746 759
747Feed an event on the given fd, as if a file descriptor backend detected it. 760Feed an event on the given fd, as if a file descriptor backend detected
761the given events it.
748 762
749=item ev_feed_signal_event (loop, int signum) 763=item ev_feed_signal_event (loop, int signum)
750 764
751Feed an event as if the given signal occured (loop must be the default loop!). 765Feed an event as if the given signal occured (loop must be the default loop!).
752 766

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