[ViewVC] Diff of: cvs/EV/EV.pm

Comparing EV/EV.pm (file contents):
Revision 1.1 by root, Fri Oct 26 16:50:05 2007 UTC vs.
Revision 1.63 by root, Fri Dec 7 18:11:21 2007 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	EV - perl interface to libevent, monkey.org/~provos/libevent/	3	EV - perl interface to libev, a high performance full-featured event loop
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use EV;	7	use EV;
		8
		9	# TIMERS
		10
		11	my $w = EV::timer 2, 0, sub {
		12	warn "is called after 2s";
		13	};
		14
		15	my $w = EV::timer 2, 2, sub {
		16	warn "is called roughly every 2s (repeat = 2)";
		17	};
		18
		19	undef $w; # destroy event watcher again
		20
		21	my $w = EV::periodic 0, 60, 0, sub {
		22	warn "is called every minute, on the minute, exactly";
		23	};
		24
		25	# IO
		26
		27	my $w = EV::io *STDIN, EV::READ, sub {
		28	my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
		29	warn "stdin is readable, you entered: ", <STDIN>;
		30	};
		31
		32	# SIGNALS
		33
		34	my $w = EV::signal 'QUIT', sub {
		35	warn "sigquit received\n";
		36	};
		37
		38	# CHILD/PID STATUS CHANGES
		39
		40	my $w = EV::child 666, sub {
		41	my ($w, $revents) = @_;
		42	my $status = $w->rstatus;
		43	};
		44
		45	# STAT CHANGES
		46	my $w = EV::stat "/etc/passwd", 10, sub {
		47	my ($w, $revents) = @_;
		48	warn $w->path, " has changed somehow.\n";
		49	};
		50
		51	# MAINLOOP
		52	EV::loop; # loop until EV::unloop is called or all watchers stop
		53	EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
		54	EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
8		55
9	=head1 DESCRIPTION	56	=head1 DESCRIPTION
10		57
11	This module provides an interface to libevent	58	This module provides an interface to libev
12	(L<http://monkey.org/~provos/libevent/>).	59	(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
		60	below is comprehensive, one might also consult the documentation of libev
		61	itself (L<http://cvs.schmorp.de/libev/ev.html>) for more subtle details on
		62	watcher semantics or some discussion on the available backends, or how to
		63	force a specific backend with C<LIBEV_FLAGS>, or just about in any case
		64	because it has much more detailed information.
13		65
14	=cut	66	=cut
15		67
16	package EV;	68	package EV;
17		69
18	use strict;	70	use strict;
19		71
20	BEGIN {	72	BEGIN {
21	our $VERSION = '0.01';	73	our $VERSION = '1.71';
22	use XSLoader;	74	use XSLoader;
23	XSLoader::load "EV", $VERSION;	75	XSLoader::load "EV", $VERSION;
24	}	76	}
25		77
26	=head1 FUNCTIONAL INTERFACE	78	@EV::IO::ISA =
		79	@EV::Timer::ISA =
		80	@EV::Periodic::ISA =
		81	@EV::Signal::ISA =
		82	@EV::Child::ISA =
		83	@EV::Stat::ISA =
		84	@EV::Idle::ISA =
		85	@EV::Prepare::ISA =
		86	@EV::Check::ISA =
		87	@EV::Embed::ISA =
		88	@EV::Fork::ISA =
		89	"EV::Watcher";
27		90
28	=over 4	91	=head1 BASIC INTERFACE
29		92
30	=back
31
32
33	=head1 OBJECT-ORIENTED INTERFACE
34
35	The object oriented interface lets you configure your own encoding or
36	decoding style, within the limits of supported formats.
37
38	=over 4	93	=over 4
39		94
40	=back	95	=item $EV::DIED
41		96
42	=head1 BUGS	97	Must contain a reference to a function that is called when a callback
		98	throws an exception (with $@ containing thr error). The default prints an
		99	informative message and continues.
		100
		101	If this callback throws an exception it will be silently ignored.
		102
		103	=item $time = EV::time
		104
		105	Returns the current time in (fractional) seconds since the epoch.
		106
		107	=item $time = EV::now
		108
		109	Returns the time the last event loop iteration has been started. This
		110	is the time that (relative) timers are based on, and refering to it is
		111	usually faster then calling EV::time.
		112
		113	=item $method = EV::method
		114
		115	Returns an integer describing the backend used by libev (EV::METHOD_SELECT
		116	or EV::METHOD_EPOLL).
		117
		118	=item EV::loop [$flags]
		119
		120	Begin checking for events and calling callbacks. It returns when a
		121	callback calls EV::unloop.
		122
		123	The $flags argument can be one of the following:
		124
		125	0 as above
		126	EV::LOOP_ONESHOT block at most once (wait, but do not loop)
		127	EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
		128
		129	=item EV::unloop [$how]
		130
		131	When called with no arguments or an argument of EV::UNLOOP_ONE, makes the
		132	innermost call to EV::loop return.
		133
		134	When called with an argument of EV::UNLOOP_ALL, all calls to EV::loop will return as
		135	fast as possible.
		136
		137	=item $count = EV::loop_count
		138
		139	Return the number of times the event loop has polled for new
		140	events. Sometiems useful as a generation counter.
		141
		142	=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
		143
		144	This function rolls together an I/O and a timer watcher for a single
		145	one-shot event without the need for managing a watcher object.
		146
		147	If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
		148	must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
		149	\| EV::WRITE>, indicating the type of I/O event you want to wait for. If
		150	you do not want to wait for some I/O event, specify C<undef> for
		151	C<$fh_or_undef> and C<0> for C<$events>).
		152
		153	If timeout is C<undef> or negative, then there will be no
		154	timeout. Otherwise a EV::timer with this value will be started.
		155
		156	When an error occurs or either the timeout or I/O watcher triggers, then
		157	the callback will be called with the received event set (in general
		158	you can expect it to be a combination of C<EV:ERROR>, C<EV::READ>,
		159	C<EV::WRITE> and C<EV::TIMEOUT>).
		160
		161	EV::once doesn't return anything: the watchers stay active till either
		162	of them triggers, then they will be stopped and freed, and the callback
		163	invoked.
		164
		165	=back
		166
		167	=head2 WATCHER OBJECTS
		168
		169	A watcher is an object that gets created to record your interest in some
		170	event. For instance, if you want to wait for STDIN to become readable, you
		171	would create an EV::io watcher for that:
		172
		173	my $watcher = EV::io *STDIN, EV::READ, sub {
		174	my ($watcher, $revents) = @_;
		175	warn "yeah, STDIN should not be readable without blocking!\n"
		176	};
		177
		178	All watchers can be active (waiting for events) or inactive (paused). Only
		179	active watchers will have their callbacks invoked. All callbacks will be
		180	called with at least two arguments: the watcher and a bitmask of received
		181	events.
		182
		183	Each watcher type has its associated bit in revents, so you can use the
		184	same callback for multiple watchers. The event mask is named after the
		185	type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
		186	EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
		187	(which can set both EV::READ and EV::WRITE bits), and EV::timer (which
		188	uses EV::TIMEOUT).
		189
		190	In the rare case where one wants to create a watcher but not start it at
		191	the same time, each constructor has a variant with a trailing C<_ns> in
		192	its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
		193
		194	Please note that a watcher will automatically be stopped when the watcher
		195	object is destroyed, so you I<need> to keep the watcher objects returned by
		196	the constructors.
		197
		198	Also, all methods changing some aspect of a watcher (->set, ->priority,
		199	->fh and so on) automatically stop and start it again if it is active,
		200	which means pending events get lost.
		201
		202	=head2 COMMON WATCHER METHODS
		203
		204	This section lists methods common to all watchers.
		205
		206	=over 4
		207
		208	=item $w->start
		209
		210	Starts a watcher if it isn't active already. Does nothing to an already
		211	active watcher. By default, all watchers start out in the active state
		212	(see the description of the C<_ns> variants if you need stopped watchers).
		213
		214	=item $w->stop
		215
		216	Stop a watcher if it is active. Also clear any pending events (events that
		217	have been received but that didn't yet result in a callback invocation),
		218	regardless of whether the watcher was active or not.
		219
		220	=item $bool = $w->is_active
		221
		222	Returns true if the watcher is active, false otherwise.
		223
		224	=item $current_data = $w->data
		225
		226	=item $old_data = $w->data ($new_data)
		227
		228	Queries a freely usable data scalar on the watcher and optionally changes
		229	it. This is a way to associate custom data with a watcher:
		230
		231	my $w = EV::timer 60, 0, sub {
		232	warn $_[0]->data;
		233	};
		234	$w->data ("print me!");
		235
		236	=item $current_cb = $w->cb
		237
		238	=item $old_cb = $w->cb ($new_cb)
		239
		240	Queries the callback on the watcher and optionally changes it. You can do
		241	this at any time without the watcher restarting.
		242
		243	=item $current_priority = $w->priority
		244
		245	=item $old_priority = $w->priority ($new_priority)
		246
		247	Queries the priority on the watcher and optionally changes it. Pending
		248	watchers with higher priority will be invoked first. The valid range of
		249	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
		250	-2). If the priority is outside this range it will automatically be
		251	normalised to the nearest valid priority.
		252
		253	The default priority of any newly-created watcher is 0.
		254
		255	Note that the priority semantics have not yet been fleshed out and are
		256	subject to almost certain change.
		257
		258	=item $w->trigger ($revents)
		259
		260	Call the callback now with the given event mask.
		261
		262	=item $previous_state = $w->keepalive ($bool)
		263
		264	Normally, C<EV::loop> will return when there are no active watchers
		265	(which is a "deadlock" because no progress can be made anymore). This is
		266	convinient because it allows you to start your watchers (and your jobs),
		267	call C<EV::loop> once and when it returns you know that all your jobs are
		268	finished (or they forgot to register some watchers for their task :).
		269
		270	Sometimes, however, this gets in your way, for example when you the module
		271	that calls C<EV::loop> (usually the main program) is not the same module
		272	as a long-living watcher (for example a DNS client module written by
		273	somebody else even). Then you might want any outstanding requests to be
		274	handled, but you would not want to keep C<EV::loop> from returning just
		275	because you happen to have this long-running UDP port watcher.
		276
		277	In this case you can clear the keepalive status, which means that even
		278	though your watcher is active, it won't keep C<EV::loop> from returning.
		279
		280	The initial value for keepalive is true (enabled), and you cna change it
		281	any time.
		282
		283	Example: Register an I/O watcher for some UDP socket but do not keep the
		284	event loop from running just because of that watcher.
		285
		286	my $udp_socket = ...
		287	my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
		288	$udp_watcher->keepalive (0);
		289
		290	=back
		291
		292
		293	=head2 WATCHER TYPES
		294
		295	Each of the following subsections describes a single watcher type.
		296
		297	=head3 I/O WATCHERS - is this file descriptor readable or writable?
		298
		299	=over 4
		300
		301	=item $w = EV::io $fileno_or_fh, $eventmask, $callback
		302
		303	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
		304
		305	As long as the returned watcher object is alive, call the C<$callback>
		306	when at least one of events specified in C<$eventmask> occurs.
		307
		308	The $eventmask can be one or more of these constants ORed together:
		309
		310	EV::READ wait until read() wouldn't block anymore
		311	EV::WRITE wait until write() wouldn't block anymore
		312
		313	The C<io_ns> variant doesn't start (activate) the newly created watcher.
		314
		315	=item $w->set ($fileno_or_fh, $eventmask)
		316
		317	Reconfigures the watcher, see the constructor above for details. Can be
		318	called at any time.
		319
		320	=item $current_fh = $w->fh
		321
		322	=item $old_fh = $w->fh ($new_fh)
		323
		324	Returns the previously set filehandle and optionally set a new one.
		325
		326	=item $current_eventmask = $w->events
		327
		328	=item $old_eventmask = $w->events ($new_eventmask)
		329
		330	Returns the previously set event mask and optionally set a new one.
		331
		332	=back
		333
		334
		335	=head3 TIMER WATCHERS - relative and optionally repeating timeouts
		336
		337	=over 4
		338
		339	=item $w = EV::timer $after, $repeat, $callback
		340
		341	=item $w = EV::timer_ns $after, $repeat, $callback
		342
		343	Calls the callback after C<$after> seconds (which may be fractional). If
		344	C<$repeat> is non-zero, the timer will be restarted (with the $repeat
		345	value as $after) after the callback returns.
		346
		347	This means that the callback would be called roughly after C<$after>
		348	seconds, and then every C<$repeat> seconds. The timer does his best not
		349	to drift, but it will not invoke the timer more often then once per event
		350	loop iteration, and might drift in other cases. If that isn't acceptable,
		351	look at EV::periodic, which can provide long-term stable timers.
		352
		353	The timer is based on a monotonic clock, that is, if somebody is sitting
		354	in front of the machine while the timer is running and changes the system
		355	clock, the timer will nevertheless run (roughly) the same time.
		356
		357	The C<timer_ns> variant doesn't start (activate) the newly created watcher.
		358
		359	=item $w->set ($after, $repeat)
		360
		361	Reconfigures the watcher, see the constructor above for details. Can be called at
		362	any time.
		363
		364	=item $w->again
		365
		366	Similar to the C<start> method, but has special semantics for repeating timers:
		367
		368	If the timer is active and non-repeating, it will be stopped.
		369
		370	If the timer is active and repeating, reset the timeout to occur
		371	C<$repeat> seconds after now.
		372
		373	If the timer is inactive and repeating, start it using the repeat value.
		374
		375	Otherwise do nothing.
		376
		377	This behaviour is useful when you have a timeout for some IO
		378	operation. You create a timer object with the same value for C<$after> and
		379	C<$repeat>, and then, in the read/write watcher, run the C<again> method
		380	on the timeout.
		381
		382	=back
		383
		384
		385	=head3 PERIODIC WATCHERS - to cron or not to cron?
		386
		387	=over 4
		388
		389	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
		390
		391	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
		392
		393	Similar to EV::timer, but is not based on relative timeouts but on
		394	absolute times. Apart from creating "simple" timers that trigger "at" the
		395	specified time, it can also be used for non-drifting absolute timers and
		396	more complex, cron-like, setups that are not adversely affected by time
		397	jumps (i.e. when the system clock is changed by explicit date -s or other
		398	means such as ntpd). It is also the most complex watcher type in EV.
		399
		400	It has three distinct "modes":
		401
		402	=over 4
		403
		404	=item * absolute timer ($interval = $reschedule_cb = 0)
		405
		406	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
		407	will not adjust when a time jump occurs, that is, if it is to be run
		408	at January 1st 2011 then it will run when the system time reaches or
		409	surpasses this time.
		410
		411	=item * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
		412
		413	In this mode the watcher will always be scheduled to time out at the
		414	next C<$at + N * $interval> time (for some integer N) and then repeat,
		415	regardless of any time jumps.
		416
		417	This can be used to create timers that do not drift with respect to system
		418	time:
		419
		420	my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
		421
		422	That doesn't mean there will always be 3600 seconds in between triggers,
		423	but only that the the clalback will be called when the system time shows a
		424	full hour (UTC).
		425
		426	Another way to think about it (for the mathematically inclined) is that
		427	EV::periodic will try to run the callback in this mode at the next
		428	possible time where C<$time = $at (mod $interval)>, regardless of any time
		429	jumps.
		430
		431	=item * manual reschedule mode ($reschedule_cb = coderef)
		432
		433	In this mode $interval and $at are both being ignored. Instead, each
		434	time the periodic watcher gets scheduled, the reschedule callback
		435	($reschedule_cb) will be called with the watcher as first, and the current
		436	time as second argument.
		437
		438	I<This callback MUST NOT stop or destroy this or any other periodic
		439	watcher, ever>. If you need to stop it, return 1e30 and stop it
		440	afterwards.
		441
		442	It must return the next time to trigger, based on the passed time value
		443	(that is, the lowest time value larger than to the second argument). It
		444	will usually be called just before the callback will be triggered, but
		445	might be called at other times, too.
		446
		447	This can be used to create very complex timers, such as a timer that
		448	triggers on each midnight, local time (actually 24 hours after the last
		449	midnight, to keep the example simple. If you know a way to do it correctly
		450	in about the same space (without requiring elaborate modules), drop me a
		451	note :):
		452
		453	my $daily = EV::periodic 0, 0, sub {
		454	my ($w, $now) = @_;
		455
		456	use Time::Local ();
		457	my (undef, undef, undef, $d, $m, $y) = localtime $now;
		458	86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
		459	}, sub {
		460	print "it's midnight or likely shortly after, now\n";
		461	};
		462
		463	=back
		464
		465	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
		466
		467	=item $w->set ($at, $interval, $reschedule_cb)
		468
		469	Reconfigures the watcher, see the constructor above for details. Can be called at
		470	any time.
		471
		472	=item $w->again
		473
		474	Simply stops and starts the watcher again.
		475
		476	=back
		477
		478
		479	=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
		480
		481	=over 4
		482
		483	=item $w = EV::signal $signal, $callback
		484
		485	=item $w = EV::signal_ns $signal, $callback
		486
		487	Call the callback when $signal is received (the signal can be specified by
		488	number or by name, just as with C<kill> or C<%SIG>).
		489
		490	EV will grab the signal for the process (the kernel only allows one
		491	component to receive a signal at a time) when you start a signal watcher,
		492	and removes it again when you stop it. Perl does the same when you
		493	add/remove callbacks to C<%SIG>, so watch out.
		494
		495	You can have as many signal watchers per signal as you want.
		496
		497	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
		498
		499	=item $w->set ($signal)
		500
		501	Reconfigures the watcher, see the constructor above for details. Can be
		502	called at any time.
		503
		504	=item $current_signum = $w->signal
		505
		506	=item $old_signum = $w->signal ($new_signal)
		507
		508	Returns the previously set signal (always as a number not name) and
		509	optionally set a new one.
		510
		511	=back
		512
		513
		514	=head3 CHILD WATCHERS - watch out for process status changes
		515
		516	=over 4
		517
		518	=item $w = EV::child $pid, $callback
		519
		520	=item $w = EV::child_ns $pid, $callback
		521
		522	Call the callback when a status change for pid C<$pid> (or any pid if
		523	C<$pid> is 0) has been received. More precisely: when the process receives
		524	a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
		525	changed/zombie children and call the callback.
		526
		527	It is valid (and fully supported) to install a child watcher after a child
		528	has exited but before the event loop has started its next iteration (for
		529	example, first you C<fork>, then the new child process might exit, and
		530	only then do you install a child watcher in the parent for the new pid).
		531
		532	You can access both exit (or tracing) status and pid by using the
		533	C<rstatus> and C<rpid> methods on the watcher object.
		534
		535	You can have as many pid watchers per pid as you want, they will all be
		536	called.
		537
		538	The C<child_ns> variant doesn't start (activate) the newly created watcher.
		539
		540	=item $w->set ($pid)
		541
		542	Reconfigures the watcher, see the constructor above for details. Can be called at
		543	any time.
		544
		545	=item $current_pid = $w->pid
		546
		547	=item $old_pid = $w->pid ($new_pid)
		548
		549	Returns the previously set process id and optionally set a new one.
		550
		551	=item $exit_status = $w->rstatus
		552
		553	Return the exit/wait status (as returned by waitpid, see the waitpid entry
		554	in perlfunc).
		555
		556	=item $pid = $w->rpid
		557
		558	Return the pid of the awaited child (useful when you have installed a
		559	watcher for all pids).
		560
		561	=back
		562
		563
		564	=head3 STAT WATCHERS - did the file attributes just change?
		565
		566	=over 4
		567
		568	=item $w = EV::stat $path, $interval, $callback
		569
		570	=item $w = EV::stat_ns $path, $interval, $callback
		571
		572	Call the callback when a file status change has been detected on
		573	C<$path>. The C<$path> does not need to exist, changing from "path exists"
		574	to "path does not exist" is a status change like any other.
		575
		576	The C<$interval> is a recommended polling interval for systems where
		577	OS-supported change notifications don't exist or are not supported. If
		578	you use C<0> then an unspecified default is used (which is highly
		579	recommended!), which is to be expected to be around five seconds usually.
		580
		581	This watcher type is not meant for massive numbers of stat watchers,
		582	as even with OS-supported change notifications, this can be
		583	resource-intensive.
		584
		585	The C<stat_ns> variant doesn't start (activate) the newly created watcher.
		586
		587	=item ... = $w->stat
		588
		589	This call is very similar to the perl C<stat> built-in: It stats (using
		590	C<lstat>) the path specified in the watcher and sets perls stat cache (as
		591	well as EV's idea of the current stat values) to the values found.
		592
		593	In scalar context, a boolean is return indicating success or failure of
		594	the stat. In list context, the same 13-value list as with stat is returned
		595	(except that the blksize and blocks fields are not reliable).
		596
		597	In the case of an error, errno is set to C<ENOENT> (regardless of the
		598	actual error value) and the C<nlink> value is forced to zero (if the stat
		599	was successful then nlink is guaranteed to be non-zero).
		600
		601	See also the next two entries for more info.
		602
		603	=item ... = $w->attr
		604
		605	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		606	the values most recently detected by EV. See the next entry for more info.
		607
		608	=item ... = $w->prev
		609
		610	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		611	the previous set of values, before the change.
		612
		613	That is, when the watcher callback is invoked, C<< $w->prev >> will be set
		614	to the values found I<before> a change was detected, while C<< $w->attr >>
		615	returns the values found leading to the change detection. The difference (if any)
		616	between C<prev> and C<attr> is what triggered the callback.
		617
		618	If you did something to the filesystem object and do not want to trigger
		619	yet another change, you can call C<stat> to update EV's idea of what the
		620	current attributes are.
		621
		622	=item $w->set ($path, $interval)
		623
		624	Reconfigures the watcher, see the constructor above for details. Can be
		625	called at any time.
		626
		627	=item $current_path = $w->path
		628
		629	=item $old_path = $w->path ($new_path)
		630
		631	Returns the previously set path and optionally set a new one.
		632
		633	=item $current_interval = $w->interval
		634
		635	=item $old_interval = $w->interval ($new_interval)
		636
		637	Returns the previously set interval and optionally set a new one. Can be
		638	used to query the actual interval used.
		639
		640	=back
		641
		642
		643	=head3 IDLE WATCHERS - when you've got nothing better to do...
		644
		645	=over 4
		646
		647	=item $w = EV::idle $callback
		648
		649	=item $w = EV::idle_ns $callback
		650
		651	Call the callback when there are no other pending watchers of the same or
		652	higher priority (excluding check, prepare and other idle watchers of the
		653	same or lower priority, of course). They are called idle watchers because
		654	when the watcher is the highest priority pending event in the process, the
		655	process is considered to be idle at that priority.
		656
		657	If you want a watcher that is only ever called when I<no> other events are
		658	outstanding you have to set the priority to C<EV::MINPRI>.
		659
		660	The process will not block as long as any idle watchers are active, and
		661	they will be called repeatedly until stopped.
		662
		663	For example, if you have idle watchers at priority C<0> and C<1>, and
		664	an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
		665	and the I/O watcher will always run when ready. Only when the idle watcher
		666	at priority C<1> is stopped and the I/O watcher at priority C<0> is not
		667	pending with the C<0>-priority idle watcher be invoked.
		668
		669	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
		670
		671	=back
		672
		673
		674	=head3 PREPARE WATCHERS - customise your event loop!
		675
		676	=over 4
		677
		678	=item $w = EV::prepare $callback
		679
		680	=item $w = EV::prepare_ns $callback
		681
		682	Call the callback just before the process would block. You can still
		683	create/modify any watchers at this point.
		684
		685	See the EV::check watcher, below, for explanations and an example.
		686
		687	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
		688
		689	=back
		690
		691
		692	=head3 CHECK WATCHERS - customise your event loop even more!
		693
		694	=over 4
		695
		696	=item $w = EV::check $callback
		697
		698	=item $w = EV::check_ns $callback
		699
		700	Call the callback just after the process wakes up again (after it has
		701	gathered events), but before any other callbacks have been invoked.
		702
		703	This is used to integrate other event-based software into the EV
		704	mainloop: You register a prepare callback and in there, you create io and
		705	timer watchers as required by the other software. Here is a real-world
		706	example of integrating Net::SNMP (with some details left out):
		707
		708	our @snmp_watcher;
		709
		710	our $snmp_prepare = EV::prepare sub {
		711	# do nothing unless active
		712	$dispatcher->{_event_queue_h}
		713	or return;
		714
		715	# make the dispatcher handle any outstanding stuff
		716	... not shown
		717
		718	# create an I/O watcher for each and every socket
		719	@snmp_watcher = (
		720	(map { EV::io $_, EV::READ, sub { } }
		721	keys %{ $dispatcher->{_descriptors} }),
		722
		723	EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
		724	? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
		725	0, sub { },
		726	);
		727	};
		728
		729	The callbacks are irrelevant (and are not even being called), the
		730	only purpose of those watchers is to wake up the process as soon as
		731	one of those events occurs (socket readable, or timer timed out). The
		732	corresponding EV::check watcher will then clean up:
		733
		734	our $snmp_check = EV::check sub {
		735	# destroy all watchers
		736	@snmp_watcher = ();
		737
		738	# make the dispatcher handle any new stuff
		739	... not shown
		740	};
		741
		742	The callbacks of the created watchers will not be called as the watchers
		743	are destroyed before this cna happen (remember EV::check gets called
		744	first).
		745
		746	The C<check_ns> variant doesn't start (activate) the newly created watcher.
		747
		748	=back
		749
		750
		751	=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
		752
		753	Fork watchers are called when a C<fork ()> was detected. The invocation
		754	is done before the event loop blocks next and before C<check> watchers
		755	are being called, and only in the child after the fork.
		756
		757	=over 4
		758
		759	=item $w = EV::fork $callback
		760
		761	=item $w = EV::fork_ns $callback
		762
		763	Call the callback before the event loop is resumed in the child process
		764	after a fork.
		765
		766	The C<fork_ns> variant doesn't start (activate) the newly created watcher.
		767
		768	=back
		769
		770
		771	=head1 PERL SIGNALS
		772
		773	While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
		774	with EV is as the same as any other C library: Perl-signals will only be
		775	handled when Perl runs, which means your signal handler might be invoked
		776	only the next time an event callback is invoked.
		777
		778	The solution is to use EV signal watchers (see C<EV::signal>), which will
		779	ensure proper operations with regards to other event watchers.
		780
		781	If you cannot do this for whatever reason, you can also force a watcher
		782	to be called on every event loop iteration by installing a C<EV::check>
		783	watcher:
		784
		785	my $async_check = EV::check sub { };
		786
		787	This ensures that perl shortly gets into control for a short time, and
		788	also ensures slower overall operation.
		789
		790	=head1 THREADS
		791
		792	Threads are not supported by this module in any way. Perl pseudo-threads
		793	is evil stuff and must die. As soon as Perl gains real threads I will work
		794	on thread support for it.
		795
		796	=head1 FORK
		797
		798	Most of the "improved" event delivering mechanisms of modern operating
		799	systems have quite a few problems with fork(2) (to put it bluntly: it is
		800	not supported and usually destructive). Libev makes it possible to work
		801	around this by having a function that recreates the kernel state after
		802	fork in the child.
		803
		804	On non-win32 platforms, this module requires the pthread_atfork
		805	functionality to do this automatically for you. This function is quite
		806	buggy on most BSDs, though, so YMMV. The overhead for this is quite
		807	negligible, because everything the function currently does is set a flag
		808	that is checked only when the event loop gets used the next time, so when
		809	you do fork but not use EV, the overhead is minimal.
		810
		811	On win32, there is no notion of fork so all this doesn't apply, of course.
43		812
44	=cut	813	=cut
45		814
46	our $NPRI = 4;	815	our $DIED = sub {
47	our $BASE = init;	816	warn "EV: error in callback (ignoring): $@";
48	priority_init $NPRI;	817	};
		818
		819	default_loop
		820	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_METHODS}?';
49		821
50	1;	822	1;
		823
		824	=head1 SEE ALSO
		825
		826	L<EV::ADNS> (asynchronous dns), L<Glib::EV> (makes Glib/Gtk2 use EV as
		827	event loop), L<Coro::EV> (efficient coroutines with EV).
51		828
52	=head1 AUTHOR	829	=head1 AUTHOR
53		830
54	Marc Lehmann <schmorp@schmorp.de>	831	Marc Lehmann <schmorp@schmorp.de>
55	http://home.schmorp.de/	832	http://home.schmorp.de/

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing EV/EV.pm (file contents): Revision 1.1 by root, Fri Oct 26 16:50:05 2007 UTC vs. Revision 1.63 by root, Fri Dec 7 18:11:21 2007 UTC

Diff Legend

Comparing EV/EV.pm (file contents):
Revision 1.1 by root, Fri Oct 26 16:50:05 2007 UTC vs.
Revision 1.63 by root, Fri Dec 7 18:11:21 2007 UTC