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

Comparing EV/EV.pm (file contents):
Revision 1.22 by root, Fri Nov 2 11:02:22 2007 UTC vs.
Revision 1.162 by root, Wed Jan 22 23:17:31 2020 UTC

…		…
2		2
3	EV - perl interface to libev, a high performance full-featured event loop	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
8		39
9	# TIMERS	40	my $w = EV::child 666, 0, sub {
		41	my ($w, $revents) = @_;
		42	my $status = $w->rstatus;
		43	};
10		44
11	my $w = EV::timer 2, 0, sub {	45	# STAT CHANGES
12	warn "is called after 2s";	46	my $w = EV::stat "/etc/passwd", 10, sub {
		47	my ($w, $revents) = @_;
		48	warn $w->path, " has changed somehow.\n";
13	};	49	};
14		50
15	my $w = EV::timer 2, 1, sub {
16	warn "is called roughly every 2s (repeat = 1)";
17	};
18
19	undef $w; # destroy event watcher again
20
21	my $w = EV::periodic 0, 60, 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 get the watcher object 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	my $w = EV::signal 3, sub {
39	warn "sigquit received (this is GNU/Linux, right?)\n";
40	};
41
42	# CHILD/PID STATUS CHANGES
43
44	my $w = EV::child 666, sub {
45	my ($w, $revents, $status) = @_;
46	};
47
48	# MAINLOOP	51	# MAINLOOP
49	EV::loop; # loop until EV::loop_done is called	52	EV::run; # loop until EV::break is called or all watchers stop
50	EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled	53	EV::run EV::RUN_ONCE; # block until at least one event could be handled
51	EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block	54	EV::run EV::RUN_NOWAIT; # try to handle same events, but do not block
		55
		56	=head1 BEFORE YOU START USING THIS MODULE
		57
		58	If you only need timer, I/O, signal, child and idle watchers and not the
		59	advanced functionality of this module, consider using L<AnyEvent> instead,
		60	specifically the simplified API described in L<AE>.
		61
		62	When used with EV as backend, the L<AE> API is as fast as the native L<EV>
		63	API, but your programs/modules will still run with many other event loops.
52		64
53	=head1 DESCRIPTION	65	=head1 DESCRIPTION
54		66
55	This module provides an interface to libev	67	This module provides an interface to libev
56	(L<http://software.schmorp.de/pkg/libev.html>).	68	(L<http://software.schmorp.de/pkg/libev.html>). While the documentation
		69	below is comprehensive, one might also consult the documentation of
		70	libev itself (L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod> or
		71	F<perldoc EV::libev>) for more subtle details on watcher semantics or some
		72	discussion on the available backends, or how to force a specific backend
		73	with C<LIBEV_FLAGS>, or just about in any case because it has much more
		74	detailed information.
		75
		76	This module is very fast and scalable. It is actually so fast that you
		77	can use it through the L<AnyEvent> module, stay portable to other event
		78	loops (if you don't rely on any watcher types not available through it)
		79	and still be faster than with any other event loop currently supported in
		80	Perl.
		81
		82	=head2 PORTING FROM EV 3.X to 4.X
		83
		84	EV version 4 introduces a number of incompatible changes summarised
		85	here. According to the depreciation strategy used by libev, there is a
		86	compatibility layer in place so programs should continue to run unchanged
		87	(the XS interface lacks this layer, so programs using that one need to be
		88	updated).
		89
		90	This compatibility layer will be switched off in some future release.
		91
		92	All changes relevant to Perl are renames of symbols, functions and
		93	methods:
		94
		95	EV::loop => EV::run
		96	EV::LOOP_NONBLOCK => EV::RUN_NOWAIT
		97	EV::LOOP_ONESHOT => EV::RUN_ONCE
		98
		99	EV::unloop => EV::break
		100	EV::UNLOOP_CANCEL => EV::BREAK_CANCEL
		101	EV::UNLOOP_ONE => EV::BREAK_ONE
		102	EV::UNLOOP_ALL => EV::BREAK_ALL
		103
		104	EV::TIMEOUT => EV::TIMER
		105
		106	EV::loop_count => EV::iteration
		107	EV::loop_depth => EV::depth
		108	EV::loop_verify => EV::verify
		109
		110	The loop object methods corresponding to the functions above have been
		111	similarly renamed.
		112
		113	=head2 MODULE EXPORTS
		114
		115	This module does not export any symbols.
57		116
58	=cut	117	=cut
59		118
60	package EV;	119	package EV;
61		120
62	use strict;	121	use common::sense;
63		122
64	BEGIN {	123	BEGIN {
65	our $VERSION = '0.1';	124	our $VERSION = '4.31';
66	use XSLoader;	125	use XSLoader;
		126	local $^W = 0; # avoid spurious warning
67	XSLoader::load "EV", $VERSION;	127	XSLoader::load "EV", $VERSION;
68	}	128	}
69		129
70	@EV::Io::ISA =	130	@EV::IO::ISA =
71	@EV::Timer::ISA =	131	@EV::Timer::ISA =
72	@EV::Periodic::ISA =	132	@EV::Periodic::ISA =
73	@EV::Signal::ISA =	133	@EV::Signal::ISA =
		134	@EV::Child::ISA =
		135	@EV::Stat::ISA =
74	@EV::Idle::ISA =	136	@EV::Idle::ISA =
75	@EV::Prepare::ISA =	137	@EV::Prepare::ISA =
76	@EV::Check::ISA =	138	@EV::Check::ISA =
77	@EV::Child::ISA = "EV::Watcher";	139	@EV::Embed::ISA =
		140	@EV::Fork::ISA =
		141	@EV::Async::ISA =
		142	"EV::Watcher";
		143
		144	@EV::Loop::Default::ISA = "EV::Loop";
		145
		146	=head1 EVENT LOOPS
		147
		148	EV supports multiple event loops: There is a single "default event loop"
		149	that can handle everything including signals and child watchers, and any
		150	number of "dynamic event loops" that can use different backends (with
		151	various limitations), but no child and signal watchers.
		152
		153	You do not have to do anything to create the default event loop: When
		154	the module is loaded a suitable backend is selected on the premise of
		155	selecting a working backend (which for example rules out kqueue on most
		156	BSDs). Modules should, unless they have "special needs" always use the
		157	default loop as this is fastest (perl-wise), best supported by other
		158	modules (e.g. AnyEvent or Coro) and most portable event loop.
		159
		160	For specific programs you can create additional event loops dynamically.
		161
		162	If you want to take advantage of kqueue (which often works properly for
		163	sockets only) even though the default loop doesn't enable it, you can
		164	I<embed> a kqueue loop into the default loop: running the default loop
		165	will then also service the kqueue loop to some extent. See the example in
		166	the section about embed watchers for an example on how to achieve that.
		167
		168	=over 4
		169
		170	=item $loop = new EV::Loop [$flags]
		171
		172	Create a new event loop as per the specified flags. Please refer to
		173	the C<ev_loop_new ()> function description in the libev documentation
		174	(L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#GLOBAL_FUNCTIONS>,
		175	or locally-installed as F<EV::libev> manpage) for more info.
		176
		177	The loop will automatically be destroyed when it is no longer referenced
		178	by any watcher and the loop object goes out of scope.
		179
		180	If you are not embedding the loop, then Using C<EV::FLAG_FORKCHECK>
		181	is recommended, as only the default event loop is protected by this
		182	module. If you I<are> embedding this loop in the default loop, this is not
		183	necessary, as C<EV::embed> automatically does the right thing on fork.
		184
		185	=item $loop->loop_fork
		186
		187	Must be called after a fork in the child, before entering or continuing
		188	the event loop. An alternative is to use C<EV::FLAG_FORKCHECK> which calls
		189	this function automatically, at some performance loss (refer to the libev
		190	documentation).
		191
		192	=item $loop->verify
		193
		194	Calls C<ev_verify> to make internal consistency checks (for debugging
		195	libev) and abort the program if any data structures were found to be
		196	corrupted.
		197
		198	=item $loop = EV::default_loop [$flags]
		199
		200	Return the default loop (which is a singleton object). Since this module
		201	already creates the default loop with default flags, specifying flags here
		202	will not have any effect unless you destroy the default loop first, which
		203	isn't supported. So in short: don't do it, and if you break it, you get to
		204	keep the pieces.
		205
		206	=back
		207
78		208
79	=head1 BASIC INTERFACE	209	=head1 BASIC INTERFACE
80		210
81	=over 4	211	=over 4
82		212
83	=item $EV::DIED	213	=item $EV::DIED
84		214
85	Must contain a reference to a function that is called when a callback	215	Must contain a reference to a function that is called when a callback
86	throws an exception (with $@ containing thr error). The default prints an	216	throws an exception (with $@ containing the error). The default prints an
87	informative message and continues.	217	informative message and continues.
88		218
89	If this callback throws an exception it will be silently ignored.	219	If this callback throws an exception it will be silently ignored.
90		220
		221	=item $flags = EV::supported_backends
		222
		223	=item $flags = EV::recommended_backends
		224
		225	=item $flags = EV::embeddable_backends
		226
		227	Returns the set (see C<EV::BACKEND_*> flags) of backends supported by this
		228	instance of EV, the set of recommended backends (supposed to be good) for
		229	this platform and the set of embeddable backends (see EMBED WATCHERS).
		230
		231	=item EV::sleep $seconds
		232
		233	Block the process for the given number of (fractional) seconds.
		234
91	=item $time = EV::time	235	=item $time = EV::time
92		236
93	Returns the current time in (fractional) seconds since the epoch.	237	Returns the current time in (fractional) seconds since the epoch.
94		238
95	=item $time = EV::now	239	=item $time = EV::now
96		240
		241	=item $time = $loop->now
		242
97	Returns the time the last event loop iteration has been started. This	243	Returns the time the last event loop iteration has been started. This
98	is the time that (relative) timers are based on, and refering to it is	244	is the time that (relative) timers are based on, and referring to it is
99	usually faster then calling EV::time.	245	usually faster then calling EV::time.
100		246
101	=item $method = EV::ev_method	247	=item EV::now_update
102		248
		249	=item $loop->now_update
		250
		251	Establishes the current time by querying the kernel, updating the time
		252	returned by C<EV::now> in the progress. This is a costly operation and
		253	is usually done automatically within C<EV::run>.
		254
		255	This function is rarely useful, but when some event callback runs for a
		256	very long time without entering the event loop, updating libev's idea of
		257	the current time is a good idea.
		258
		259	=item EV::suspend
		260
		261	=item $loop->suspend
		262
		263	=item EV::resume
		264
		265	=item $loop->resume
		266
		267	These two functions suspend and resume a loop, for use when the loop is
		268	not used for a while and timeouts should not be processed.
		269
		270	A typical use case would be an interactive program such as a game: When
		271	the user presses C<^Z> to suspend the game and resumes it an hour later it
		272	would be best to handle timeouts as if no time had actually passed while
		273	the program was suspended. This can be achieved by calling C<suspend>
		274	in your C<SIGTSTP> handler, sending yourself a C<SIGSTOP> and calling
		275	C<resume> directly afterwards to resume timer processing.
		276
		277	Effectively, all C<timer> watchers will be delayed by the time spend
		278	between C<suspend> and C<resume>, and all C<periodic> watchers
		279	will be rescheduled (that is, they will lose any events that would have
		280	occured while suspended).
		281
		282	After calling C<suspend> you B<must not> call I<any> function on the given
		283	loop other than C<resume>, and you B<must not> call C<resume>
		284	without a previous call to C<suspend>.
		285
		286	Calling C<suspend>/C<resume> has the side effect of updating the event
		287	loop time (see C<now_update>).
		288
		289	=item $backend = EV::backend
		290
		291	=item $backend = $loop->backend
		292
103	Returns an integer describing the backend used by libev (EV::METHOD_SELECT	293	Returns an integer describing the backend used by libev (EV::BACKEND_SELECT
104	or EV::METHOD_EPOLL).	294	or EV::BACKEND_EPOLL).
105		295
106	=item EV::loop [$flags]	296	=item $active = EV::run [$flags]
		297
		298	=item $active = $loop->run ([$flags])
107		299
108	Begin checking for events and calling callbacks. It returns when a	300	Begin checking for events and calling callbacks. It returns when a
109	callback calls EV::loop_done.	301	callback calls EV::break or the flags are nonzero (in which case the
		302	return value is true) or when there are no active watchers which reference
		303	the loop (keepalive is true), in which case the return value will be
		304	false. The return value can generally be interpreted as "if true, there is
		305	more work left to do".
110		306
111	The $flags argument can be one of the following:	307	The $flags argument can be one of the following:
112		308
113	0 as above	309	0 as above
114	EV::LOOP_ONESHOT block at most once (wait, but do not loop)	310	EV::RUN_ONCE block at most once (wait, but do not loop)
115	EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)	311	EV::RUN_NOWAIT do not block at all (fetch/handle events but do not wait)
116		312
117	=item EV::loop_done [$how]	313	=item EV::break [$how]
118		314
		315	=item $loop->break ([$how])
		316
119	When called with no arguments or an argument of 1, makes the innermost	317	When called with no arguments or an argument of EV::BREAK_ONE, makes the
120	call to EV::loop return.	318	innermost call to EV::run return.
121		319
122	When called with an agrument of 2, all calls to EV::loop will return as	320	When called with an argument of EV::BREAK_ALL, all calls to EV::run will
123	fast as possible.	321	return as fast as possible.
124		322
125	=back	323	When called with an argument of EV::BREAK_CANCEL, any pending break will
		324	be cancelled.
126		325
127	=head2 WATCHER	326	=item $count = EV::iteration
		327
		328	=item $count = $loop->iteration
		329
		330	Return the number of times the event loop has polled for new
		331	events. Sometimes useful as a generation counter.
		332
		333	=item EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
		334
		335	=item $loop->once ($fh_or_undef, $events, $timeout, $cb->($revents))
		336
		337	This function rolls together an I/O and a timer watcher for a single
		338	one-shot event without the need for managing a watcher object.
		339
		340	If C<$fh_or_undef> is a filehandle or file descriptor, then C<$events>
		341	must be a bitset containing either C<EV::READ>, C<EV::WRITE> or C<EV::READ
		342	\| EV::WRITE>, indicating the type of I/O event you want to wait for. If
		343	you do not want to wait for some I/O event, specify C<undef> for
		344	C<$fh_or_undef> and C<0> for C<$events>).
		345
		346	If timeout is C<undef> or negative, then there will be no
		347	timeout. Otherwise an C<EV::timer> with this value will be started.
		348
		349	When an error occurs or either the timeout or I/O watcher triggers, then
		350	the callback will be called with the received event set (in general
		351	you can expect it to be a combination of C<EV::ERROR>, C<EV::READ>,
		352	C<EV::WRITE> and C<EV::TIMER>).
		353
		354	EV::once doesn't return anything: the watchers stay active till either
		355	of them triggers, then they will be stopped and freed, and the callback
		356	invoked.
		357
		358	=item EV::feed_fd_event $fd, $revents
		359
		360	=item $loop->feed_fd_event ($fd, $revents)
		361
		362	Feed an event on a file descriptor into EV. EV will react to this call as
		363	if the readyness notifications specified by C<$revents> (a combination of
		364	C<EV::READ> and C<EV::WRITE>) happened on the file descriptor C<$fd>.
		365
		366	=item EV::feed_signal_event $signal
		367
		368	Feed a signal event into the default loop. EV will react to this call as
		369	if the signal specified by C<$signal> had occured.
		370
		371	=item EV::feed_signal $signal
		372
		373	Feed a signal event into EV - unlike C<EV::feed_signal_event>, this works
		374	regardless of which loop has registered the signal, and is mainly useful
		375	for custom signal implementations.
		376
		377	=item EV::set_io_collect_interval $time
		378
		379	=item $loop->set_io_collect_interval ($time)
		380
		381	=item EV::set_timeout_collect_interval $time
		382
		383	=item $loop->set_timeout_collect_interval ($time)
		384
		385	These advanced functions set the minimum block interval when polling for I/O events and the minimum
		386	wait interval for timer events. See the libev documentation at
		387	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#FUNCTIONS_CONTROLLING_THE_EVENT_LOOP>
		388	(locally installed as F<EV::libev>) for a more detailed discussion.
		389
		390	=item $count = EV::pending_count
		391
		392	=item $count = $loop->pending_count
		393
		394	Returns the number of currently pending watchers.
		395
		396	=item EV::invoke_pending
		397
		398	=item $loop->invoke_pending
		399
		400	Invoke all currently pending watchers.
		401
		402	=back
		403
		404
		405	=head1 WATCHER OBJECTS
128		406
129	A watcher is an object that gets created to record your interest in some	407	A watcher is an object that gets created to record your interest in some
130	event. For instance, if you want to wait for STDIN to become readable, you	408	event. For instance, if you want to wait for STDIN to become readable, you
131	would create an EV::io watcher for that:	409	would create an EV::io watcher for that:
132		410
133	my $watcher = EV::io *STDIN, EV::READ, sub {	411	my $watcher = EV::io *STDIN, EV::READ, sub {
134	my ($watcher, $revents) = @_;	412	my ($watcher, $revents) = @_;
135	warn "yeah, STDIN should not be readable without blocking!\n"	413	warn "yeah, STDIN should now be readable without blocking!\n"
136	};	414	};
137		415
138	All watchers can be active (waiting for events) or inactive (paused). Only	416	All watchers can be active (waiting for events) or inactive (paused). Only
139	active watchers will have their callbacks invoked. All callbacks will be	417	active watchers will have their callbacks invoked. All callbacks will be
140	called with at least two arguments: the watcher and a bitmask of received	418	called with at least two arguments: the watcher and a bitmask of received
141	events.	419	events.
142		420
143	Each watcher type has its associated bit in revents, so you can use the	421	Each watcher type has its associated bit in revents, so you can use the
144	same callback for multiple watchers. The event mask is named after the	422	same callback for multiple watchers. The event mask is named after the
145	type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,	423	type, i.e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
146	EV::periodic sets EV::PERIODIC and so on, with the exception of IO events	424	EV::periodic sets EV::PERIODIC and so on, with the exception of I/O events
147	(which can set both EV::READ and EV::WRITE bits), and EV::timer (which	425	(which can set both EV::READ and EV::WRITE bits).
148	uses EV::TIMEOUT).
149		426
150	In the rare case where one wants to create a watcher but not start it at	427	In the rare case where one wants to create a watcher but not start it at
151	the same time, each constructor has a variant with a trailing C<_ns> in	428	the same time, each constructor has a variant with a trailing C<_ns> in
152	its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.	429	its name, e.g. EV::io has a non-starting variant EV::io_ns and so on.
153		430
154	Please note that a watcher will automatically be stopped when the watcher	431	Please note that a watcher will automatically be stopped when the watcher
155	object is returned, so you I<need> to keep the watcher objects returned by	432	object is destroyed, so you I<need> to keep the watcher objects returned by
156	the constructors.	433	the constructors.
157		434
158	=head2 WATCHER TYPES	435	Also, all methods changing some aspect of a watcher (->set, ->priority,
		436	->fh and so on) automatically stop and start it again if it is active,
		437	which means pending events get lost.
159		438
160	Now lets move to the existing watcher types and asociated methods.	439	=head2 COMMON WATCHER METHODS
161		440
162	The following methods are available for all watchers. Then followes a	441	This section lists methods common to all watchers.
163	description of each watcher constructor (EV::io, EV::timer, EV::periodic,
164	EV::signal, EV::child, EV::idle, EV::prepare and EV::check), followed by
165	any type-specific methods (if any).
166		442
167	=over 4	443	=over 4
168		444
169	=item $w->start	445	=item $w->start
170		446
…		…
174		450
175	=item $w->stop	451	=item $w->stop
176		452
177	Stop a watcher if it is active. Also clear any pending events (events that	453	Stop a watcher if it is active. Also clear any pending events (events that
178	have been received but that didn't yet result in a callback invocation),	454	have been received but that didn't yet result in a callback invocation),
179	regardless of wether the watcher was active or not.	455	regardless of whether the watcher was active or not.
180		456
181	=item $bool = $w->is_active	457	=item $bool = $w->is_active
182		458
183	Returns true if the watcher is active, false otherwise.	459	Returns true if the watcher is active, false otherwise.
184		460
		461	=item $current_data = $w->data
		462
		463	=item $old_data = $w->data ($new_data)
		464
		465	Queries a freely usable data scalar on the watcher and optionally changes
		466	it. This is a way to associate custom data with a watcher:
		467
		468	my $w = EV::timer 60, 0, sub {
		469	warn $_[0]->data;
		470	};
		471	$w->data ("print me!");
		472
185	=item $current_cb = $w->cb	473	=item $current_cb = $w->cb
186		474
187	=item $old_cb = $w->cb ($new_cb)	475	=item $old_cb = $w->cb ($new_cb)
188		476
189	Queries the callback on the watcher and optionally changes it. You cna do	477	Queries the callback on the watcher and optionally changes it. You can do
190	this at any time.	478	this at any time without the watcher restarting.
191		479
		480	=item $current_priority = $w->priority
		481
		482	=item $old_priority = $w->priority ($new_priority)
		483
		484	Queries the priority on the watcher and optionally changes it. Pending
		485	watchers with higher priority will be invoked first. The valid range of
		486	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
		487	-2). If the priority is outside this range it will automatically be
		488	normalised to the nearest valid priority.
		489
		490	The default priority of any newly-created watcher is 0.
		491
		492	Note that the priority semantics have not yet been fleshed out and are
		493	subject to almost certain change.
		494
192	=item $w->trigger ($revents)	495	=item $w->invoke ($revents)
193		496
194	Call the callback now with the given event mask.	497	Call the callback now with the given event mask.
195		498
		499	=item $w->feed_event ($revents)
		500
		501	Feed some events on this watcher into EV. EV will react to this call as if
		502	the watcher had received the given C<$revents> mask.
		503
		504	=item $revents = $w->clear_pending
		505
		506	If the watcher is pending, this function clears its pending status and
		507	returns its C<$revents> bitset (as if its callback was invoked). If the
		508	watcher isn't pending it does nothing and returns C<0>.
		509
		510	=item $previous_state = $w->keepalive ($bool)
		511
		512	Normally, C<EV::run> will return when there are no active watchers
		513	(which is a "deadlock" because no progress can be made anymore). This is
		514	convenient because it allows you to start your watchers (and your jobs),
		515	call C<EV::run> once and when it returns you know that all your jobs are
		516	finished (or they forgot to register some watchers for their task :).
		517
		518	Sometimes, however, this gets in your way, for example when the module
		519	that calls C<EV::run> (usually the main program) is not the same module
		520	as a long-living watcher (for example a DNS client module written by
		521	somebody else even). Then you might want any outstanding requests to be
		522	handled, but you would not want to keep C<EV::run> from returning just
		523	because you happen to have this long-running UDP port watcher.
		524
		525	In this case you can clear the keepalive status, which means that even
		526	though your watcher is active, it won't keep C<EV::run> from returning.
		527
		528	The initial value for keepalive is true (enabled), and you can change it
		529	any time.
		530
		531	Example: Register an I/O watcher for some UDP socket but do not keep the
		532	event loop from running just because of that watcher.
		533
		534	my $udp_socket = ...
		535	my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
		536	$udp_watcher->keepalive (0);
		537
		538	=item $loop = $w->loop
		539
		540	Return the loop that this watcher is attached to.
		541
		542	=back
		543
		544
		545	=head1 WATCHER TYPES
		546
		547	Each of the following subsections describes a single watcher type.
		548
		549	=head3 I/O WATCHERS - is this file descriptor readable or writable?
		550
		551	=over 4
196		552
197	=item $w = EV::io $fileno_or_fh, $eventmask, $callback	553	=item $w = EV::io $fileno_or_fh, $eventmask, $callback
198		554
199	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback	555	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
200		556
		557	=item $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
		558
		559	=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
		560
201	As long as the returned watcher object is alive, call the C<$callback>	561	As long as the returned watcher object is alive, call the C<$callback>
202	when the events specified in C<$eventmask>.	562	when at least one of events specified in C<$eventmask> occurs.
203		563
204	The $eventmask can be one or more of these constants ORed together:	564	The $eventmask can be one or more of these constants ORed together:
205		565
206	EV::READ wait until read() wouldn't block anymore	566	EV::READ wait until read() wouldn't block anymore
207	EV::WRITE wait until write() wouldn't block anymore	567	EV::WRITE wait until write() wouldn't block anymore
…		…
223		583
224	=item $old_eventmask = $w->events ($new_eventmask)	584	=item $old_eventmask = $w->events ($new_eventmask)
225		585
226	Returns the previously set event mask and optionally set a new one.	586	Returns the previously set event mask and optionally set a new one.
227		587
		588	=back
		589
		590
		591	=head3 TIMER WATCHERS - relative and optionally repeating timeouts
		592
		593	=over 4
228		594
229	=item $w = EV::timer $after, $repeat, $callback	595	=item $w = EV::timer $after, $repeat, $callback
230		596
231	=item $w = EV::timer_ns $after, $repeat, $callback	597	=item $w = EV::timer_ns $after, $repeat, $callback
232		598
233	Calls the callback after C<$after> seconds. If C<$repeat> is non-zero,	599	=item $w = $loop->timer ($after, $repeat, $callback)
234	the timer will be restarted (with the $repeat value as $after) after the	600
235	callback returns.	601	=item $w = $loop->timer_ns ($after, $repeat, $callback)
		602
		603	Calls the callback after C<$after> seconds (which may be fractional or
		604	negative). If C<$repeat> is non-zero, the timer will be restarted (with
		605	the $repeat value as $after) after the callback returns.
236		606
237	This means that the callback would be called roughly after C<$after>	607	This means that the callback would be called roughly after C<$after>
238	seconds, and then every C<$repeat> seconds. "Roughly" because the time of	608	seconds, and then every C<$repeat> seconds. The timer does his best not
239	callback processing is not taken into account, so the timer will slowly	609	to drift, but it will not invoke the timer more often then once per event
240	drift. If that isn't acceptable, look at EV::periodic.	610	loop iteration, and might drift in other cases. If that isn't acceptable,
		611	look at EV::periodic, which can provide long-term stable timers.
241		612
242	The timer is based on a monotonic clock, that is if somebody is sitting	613	The timer is based on a monotonic clock, that is, if somebody is sitting
243	in front of the machine while the timer is running and changes the system	614	in front of the machine while the timer is running and changes the system
244	clock, the timer will nevertheless run (roughly) the same time.	615	clock, the timer will nevertheless run (roughly) the same time.
245		616
246	The C<timer_ns> variant doesn't start (activate) the newly created watcher.	617	The C<timer_ns> variant doesn't start (activate) the newly created watcher.
247		618
248	=item $w->set ($after, $repeat)	619	=item $w->set ($after, $repeat = 0)
249		620
250	Reconfigures the watcher, see the constructor above for details. Can be at	621	Reconfigures the watcher, see the constructor above for details. Can be called at
251	any time.	622	any time.
252		623
253	=item $w->again	624	=item $w->again
254		625
		626	=item $w->again ($repeat)
		627
255	Similar to the C<start> method, but has special semantics for repeating timers:	628	Similar to the C<start> method, but has special semantics for repeating timers:
		629
		630	If the timer is active and non-repeating, it will be stopped.
256		631
257	If the timer is active and repeating, reset the timeout to occur	632	If the timer is active and repeating, reset the timeout to occur
258	C<$repeat> seconds after now.	633	C<$repeat> seconds after now.
259		634
260	If the timer is active and non-repeating, it will be stopped.
261
262	If the timer is in active and repeating, start it.	635	If the timer is inactive and repeating, start it using the repeat value.
263		636
264	Otherwise do nothing.	637	Otherwise do nothing.
265		638
266	This behaviour is useful when you have a timeout for some IO	639	This behaviour is useful when you have a timeout for some IO
267	operation. You create a timer object with the same value for C<$after> and	640	operation. You create a timer object with the same value for C<$after> and
268	C<$repeat>, and then, in the read/write watcher, run the C<again> method	641	C<$repeat>, and then, in the read/write watcher, run the C<again> method
269	on the timeout.	642	on the timeout.
270		643
		644	If called with a C<$repeat> argument, then it uses this a timer repeat
		645	value.
271		646
		647	=item $after = $w->remaining
		648
		649	Calculates and returns the remaining time till the timer will fire.
		650
		651	=item $old_repeat = $w->reapat ([$new_repeat])
		652
		653	Returns the current value of the repeat attribute and optionally sets a
		654	new one. Setting the new one will not restart the watcher - if the watcher
		655	is active, the new repeat value is used whenever it expires next.
		656
		657	=back
		658
		659
		660	=head3 PERIODIC WATCHERS - to cron or not to cron?
		661
		662	=over 4
		663
272	=item $w = EV::periodic $at, $interval, $callback	664	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
273		665
274	=item $w = EV::periodic_ns $at, $interval, $callback	666	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
275		667
276	Similar to EV::timer, but the time is given as an absolute point in time	668	=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
277	(C<$at>), plus an optional C<$interval>.
278		669
279	If the C<$interval> is zero, then the callback will be called at the time	670	=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
280	C<$at> if that is in the future, or as soon as possible if it is in the
281	past. It will not automatically repeat.
282		671
283	If the C<$interval> is nonzero, then the watcher will always be scheduled	672	Similar to EV::timer, but is not based on relative timeouts but on
284	to time out at the next C<$at + N * $interval> time.	673	absolute times. Apart from creating "simple" timers that trigger "at" the
		674	specified time, it can also be used for non-drifting absolute timers and
		675	more complex, cron-like, setups that are not adversely affected by time
		676	jumps (i.e. when the system clock is changed by explicit date -s or other
		677	means such as ntpd). It is also the most complex watcher type in EV.
285		678
286	This can be used to schedule a callback to run at very regular intervals,	679	It has three distinct "modes":
287	as long as the processing time is less then the interval (otherwise	680
288	obviously events will be skipped).	681	=over 4
		682
		683	=item * absolute timer ($interval = $reschedule_cb = 0)
		684
		685	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
		686	will not adjust when a time jump occurs, that is, if it is to be run
		687	at January 1st 2011 then it will run when the system time reaches or
		688	surpasses this time.
		689
		690	=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
		691
		692	In this mode the watcher will always be scheduled to time out at the
		693	next C<$at + N * $interval> time (for the lowest integer N) and then repeat,
		694	regardless of any time jumps. Note that, since C<N> can be negative, the
		695	first trigger can happen before C<$at>.
		696
		697	This can be used to create timers that do not drift with respect to system
		698	time:
		699
		700	my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
		701
		702	That doesn't mean there will always be 3600 seconds in between triggers,
		703	but only that the the callback will be called when the system time shows a
		704	full hour (UTC).
289		705
290	Another way to think about it (for the mathematically inclined) is that	706	Another way to think about it (for the mathematically inclined) is that
291	EV::periodic will try to run the callback at the next possible time where	707	EV::periodic will try to run the callback in this mode at the next
292	C<$time = $at (mod $interval)>, regardless of any time jumps.	708	possible time where C<$time = $at (mod $interval)>, regardless of any time
		709	jumps.
293		710
294	This periodic timer is based on "wallclock time", that is, if the clock	711	=item * manual reschedule mode ($reschedule_cb = coderef)
295	changes (C<ntp>, C<date -s> etc.), then the timer will nevertheless run at	712
296	the specified time. This means it will never drift (it might jitter, but	713	In this mode $interval and $at are both being ignored. Instead, each
297	it will not drift).	714	time the periodic watcher gets scheduled, the reschedule callback
		715	($reschedule_cb) will be called with the watcher as first, and the current
		716	time as second argument.
		717
		718	I<This callback MUST NOT stop or destroy this or any other periodic
		719	watcher, ever, and MUST NOT call any event loop functions or methods>. If
		720	you need to stop it, return 1e30 and stop it afterwards. You may create
		721	and start an C<EV::prepare> watcher for this task.
		722
		723	It must return the next time to trigger, based on the passed time value
		724	(that is, the lowest time value larger than or equal to to the second
		725	argument). It will usually be called just before the callback will be
		726	triggered, but might be called at other times, too.
		727
		728	This can be used to create very complex timers, such as a timer that
		729	triggers on each midnight, local time (actually one day after the last
		730	midnight, to keep the example simple):
		731
		732	my $daily = EV::periodic 0, 0, sub {
		733	my ($w, $now) = @_;
		734
		735	use Time::Local ();
		736	my (undef, undef, undef, $d, $m, $y) = localtime $now;
		737	Time::Local::timelocal_nocheck 0, 0, 0, $d + 1, $m, $y
		738	}, sub {
		739	print "it's midnight or likely shortly after, now\n";
		740	};
		741
		742	=back
298		743
299	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.	744	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
300		745
301	=item $w->set ($at, $interval)	746	=item $w->set ($at, $interval, $reschedule_cb)
302		747
303	Reconfigures the watcher, see the constructor above for details. Can be at	748	Reconfigures the watcher, see the constructor above for details. Can be called at
304	any time.	749	any time.
305		750
		751	=item $w->again
		752
		753	Simply stops and starts the watcher again.
		754
		755	=item $time = $w->at
		756
		757	Return the time that the watcher is expected to trigger next.
		758
		759	=item $old_offset = $w->offset ([$new_offset])
		760
		761	Returns the current value of the offset attribute and optionally sets a
		762	new one. Setting the new one will not restart the watcher - if the watcher
		763	is active, the new offset value is used whenever it expires next.
		764
		765	=item $old_interval = $w->interval ([$new_interval])
		766
		767	See above, for the interval attribute.
		768
		769	=item $old_reschedule_cb = $w->reschedule_cb ([$new_reschedule_xcb])
		770
		771	See above, for the reschedule callback.
		772
		773	=back
		774
		775
		776	=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
		777
		778	=over 4
306		779
307	=item $w = EV::signal $signal, $callback	780	=item $w = EV::signal $signal, $callback
308		781
309	=item $w = EV::signal_ns $signal, $callback	782	=item $w = EV::signal_ns $signal, $callback
310		783
		784	=item $w = $loop->signal ($signal, $callback)
		785
		786	=item $w = $loop->signal_ns ($signal, $callback)
		787
311	Call the callback when $signal is received (the signal can be specified	788	Call the callback when $signal is received (the signal can be specified by
312	by number or by name, just as with kill or %SIG).	789	number or by name, just as with C<kill> or C<%SIG>).
		790
		791	Only one event loop can grab a given signal - attempting to grab the same
		792	signal from two EV loops will crash the program immediately or cause data
		793	corruption.
313		794
314	EV will grab the signal for the process (the kernel only allows one	795	EV will grab the signal for the process (the kernel only allows one
315	component to receive a signal at a time) when you start a signal watcher,	796	component to receive a signal at a time) when you start a signal watcher,
316	and removes it again when you stop it. Perl does the same when you	797	and removes it again when you stop it. Perl does the same when you
317	add/remove callbacks to %SIG, so watch out.	798	add/remove callbacks to C<%SIG>, so watch out.
318		799
319	You can have as many signal watchers per signal as you want.	800	You can have as many signal watchers per signal as you want.
320		801
321	The C<signal_ns> variant doesn't start (activate) the newly created watcher.	802	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
322		803
323	=item $w->set ($signal)	804	=item $w->set ($signal)
324		805
325	Reconfigures the watcher, see the constructor above for details. Can be at	806	Reconfigures the watcher, see the constructor above for details. Can be
326	any time.	807	called at any time.
327		808
328	=item $current_signum = $w->signal	809	=item $current_signum = $w->signal
329		810
330	=item $old_signum = $w->signal ($new_signal)	811	=item $old_signum = $w->signal ($new_signal)
331		812
332	Returns the previously set signal (always as a number not name) and	813	Returns the previously set signal (always as a number not name) and
333	optionally set a new one.	814	optionally set a new one.
334		815
		816	=back
335		817
		818
		819	=head3 CHILD WATCHERS - watch out for process status changes
		820
		821	=over 4
		822
336	=item $w = EV::child $pid, $callback	823	=item $w = EV::child $pid, $trace, $callback
337		824
338	=item $w = EV::child_ns $pid, $callback	825	=item $w = EV::child_ns $pid, $trace, $callback
		826
		827	=item $w = $loop->child ($pid, $trace, $callback)
		828
		829	=item $w = $loop->child_ns ($pid, $trace, $callback)
339		830
340	Call the callback when a status change for pid C<$pid> (or any pid	831	Call the callback when a status change for pid C<$pid> (or any pid
341	if C<$pid> is 0) has been received. More precisely: when the process	832	if C<$pid> is 0) has been received (a status change happens when the
		833	process terminates or is killed, or, when trace is true, additionally when
		834	it is stopped or continued). More precisely: when the process receives
342	receives a SIGCHLD, EV will fetch the outstanding exit/wait status for all	835	a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
343	changed/zombie children and call the callback.	836	changed/zombie children and call the callback.
344		837
345	Unlike all other callbacks, this callback will be called with an	838	It is valid (and fully supported) to install a child watcher after a child
346	additional third argument which is the exit status. See the C<waitpid>	839	has exited but before the event loop has started its next iteration (for
347	function for details.	840	example, first you C<fork>, then the new child process might exit, and
		841	only then do you install a child watcher in the parent for the new pid).
348		842
		843	You can access both exit (or tracing) status and pid by using the
		844	C<rstatus> and C<rpid> methods on the watcher object.
		845
349	You can have as many pid watchers per pid as you want.	846	You can have as many pid watchers per pid as you want, they will all be
		847	called.
350		848
351	The C<child_ns> variant doesn't start (activate) the newly created watcher.	849	The C<child_ns> variant doesn't start (activate) the newly created watcher.
352		850
353	=item $w->set ($pid)	851	=item $w->set ($pid, $trace)
354		852
355	Reconfigures the watcher, see the constructor above for details. Can be at	853	Reconfigures the watcher, see the constructor above for details. Can be called at
356	any time.	854	any time.
357		855
358	=item $current_pid = $w->pid	856	=item $current_pid = $w->pid
359		857
360	=item $old_pid = $w->pid ($new_pid)
361
362	Returns the previously set process id and optionally set a new one.	858	Returns the previously set process id and optionally set a new one.
363		859
		860	=item $exit_status = $w->rstatus
		861
		862	Return the exit/wait status (as returned by waitpid, see the waitpid entry
		863	in perlfunc).
		864
		865	=item $pid = $w->rpid
		866
		867	Return the pid of the awaited child (useful when you have installed a
		868	watcher for all pids).
		869
		870	=back
		871
		872
		873	=head3 STAT WATCHERS - did the file attributes just change?
		874
		875	=over 4
		876
		877	=item $w = EV::stat $path, $interval, $callback
		878
		879	=item $w = EV::stat_ns $path, $interval, $callback
		880
		881	=item $w = $loop->stat ($path, $interval, $callback)
		882
		883	=item $w = $loop->stat_ns ($path, $interval, $callback)
		884
		885	Call the callback when a file status change has been detected on
		886	C<$path>. The C<$path> does not need to exist, changing from "path exists"
		887	to "path does not exist" is a status change like any other.
		888
		889	The C<$interval> is a recommended polling interval for systems where
		890	OS-supported change notifications don't exist or are not supported. If
		891	you use C<0> then an unspecified default is used (which is highly
		892	recommended!), which is to be expected to be around five seconds usually.
		893
		894	This watcher type is not meant for massive numbers of stat watchers,
		895	as even with OS-supported change notifications, this can be
		896	resource-intensive.
		897
		898	The C<stat_ns> variant doesn't start (activate) the newly created watcher.
		899
		900	=item ... = $w->stat
		901
		902	This call is very similar to the perl C<stat> built-in: It stats (using
		903	C<lstat>) the path specified in the watcher and sets perls stat cache (as
		904	well as EV's idea of the current stat values) to the values found.
		905
		906	In scalar context, a boolean is return indicating success or failure of
		907	the stat. In list context, the same 13-value list as with stat is returned
		908	(except that the blksize and blocks fields are not reliable).
		909
		910	In the case of an error, errno is set to C<ENOENT> (regardless of the
		911	actual error value) and the C<nlink> value is forced to zero (if the stat
		912	was successful then nlink is guaranteed to be non-zero).
		913
		914	See also the next two entries for more info.
		915
		916	=item ... = $w->attr
		917
		918	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		919	the values most recently detected by EV. See the next entry for more info.
		920
		921	=item ... = $w->prev
		922
		923	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		924	the previous set of values, before the change.
		925
		926	That is, when the watcher callback is invoked, C<< $w->prev >> will be set
		927	to the values found I<before> a change was detected, while C<< $w->attr >>
		928	returns the values found leading to the change detection. The difference (if any)
		929	between C<prev> and C<attr> is what triggered the callback.
		930
		931	If you did something to the filesystem object and do not want to trigger
		932	yet another change, you can call C<stat> to update EV's idea of what the
		933	current attributes are.
		934
		935	=item $w->set ($path, $interval)
		936
		937	Reconfigures the watcher, see the constructor above for details. Can be
		938	called at any time.
		939
		940	=item $current_path = $w->path
		941
		942	=item $old_path = $w->path ($new_path)
		943
		944	Returns the previously set path and optionally set a new one.
		945
		946	=item $current_interval = $w->interval
		947
		948	=item $old_interval = $w->interval ($new_interval)
		949
		950	Returns the previously set interval and optionally set a new one. Can be
		951	used to query the actual interval used.
		952
		953	=back
		954
		955
		956	=head3 IDLE WATCHERS - when you've got nothing better to do...
		957
		958	=over 4
364		959
365	=item $w = EV::idle $callback	960	=item $w = EV::idle $callback
366		961
367	=item $w = EV::idle_ns $callback	962	=item $w = EV::idle_ns $callback
368		963
369	Call the callback when there are no pending io, timer/periodic, signal or	964	=item $w = $loop->idle ($callback)
370	child events, i.e. when the process is idle.	965
		966	=item $w = $loop->idle_ns ($callback)
		967
		968	Call the callback when there are no other pending watchers of the same or
		969	higher priority (excluding check, prepare and other idle watchers of the
		970	same or lower priority, of course). They are called idle watchers because
		971	when the watcher is the highest priority pending event in the process, the
		972	process is considered to be idle at that priority.
		973
		974	If you want a watcher that is only ever called when I<no> other events are
		975	outstanding you have to set the priority to C<EV::MINPRI>.
371		976
372	The process will not block as long as any idle watchers are active, and	977	The process will not block as long as any idle watchers are active, and
373	they will be called repeatedly until stopped.	978	they will be called repeatedly until stopped.
374		979
		980	For example, if you have idle watchers at priority C<0> and C<1>, and
		981	an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
		982	and the I/O watcher will always run when ready. Only when the idle watcher
		983	at priority C<1> is stopped and the I/O watcher at priority C<0> is not
		984	pending with the C<0>-priority idle watcher be invoked.
		985
375	The C<idle_ns> variant doesn't start (activate) the newly created watcher.	986	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
376		987
		988	=back
		989
		990
		991	=head3 PREPARE WATCHERS - customise your event loop!
		992
		993	=over 4
377		994
378	=item $w = EV::prepare $callback	995	=item $w = EV::prepare $callback
379		996
380	=item $w = EV::prepare_ns $callback	997	=item $w = EV::prepare_ns $callback
		998
		999	=item $w = $loop->prepare ($callback)
		1000
		1001	=item $w = $loop->prepare_ns ($callback)
381		1002
382	Call the callback just before the process would block. You can still	1003	Call the callback just before the process would block. You can still
383	create/modify any watchers at this point.	1004	create/modify any watchers at this point.
384		1005
385	See the EV::check watcher, below, for explanations and an example.	1006	See the EV::check watcher, below, for explanations and an example.
386		1007
387	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.	1008	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
388		1009
		1010	=back
		1011
		1012
		1013	=head3 CHECK WATCHERS - customise your event loop even more!
		1014
		1015	=over 4
389		1016
390	=item $w = EV::check $callback	1017	=item $w = EV::check $callback
391		1018
392	=item $w = EV::check_ns $callback	1019	=item $w = EV::check_ns $callback
		1020
		1021	=item $w = $loop->check ($callback)
		1022
		1023	=item $w = $loop->check_ns ($callback)
393		1024
394	Call the callback just after the process wakes up again (after it has	1025	Call the callback just after the process wakes up again (after it has
395	gathered events), but before any other callbacks have been invoked.	1026	gathered events), but before any other callbacks have been invoked.
396		1027
397	This is used to integrate other event-based software into the EV	1028	This can be used to integrate other event-based software into the EV
398	mainloop: You register a prepare callback and in there, you create io and	1029	mainloop: You register a prepare callback and in there, you create io and
399	timer watchers as required by the other software. Here is a real-world	1030	timer watchers as required by the other software. Here is a real-world
400	example of integrating Net::SNMP (with some details left out):	1031	example of integrating Net::SNMP (with some details left out):
401		1032
402	our @snmp_watcher;	1033	our @snmp_watcher;
…		…
405	# do nothing unless active	1036	# do nothing unless active
406	$dispatcher->{_event_queue_h}	1037	$dispatcher->{_event_queue_h}
407	or return;	1038	or return;
408		1039
409	# make the dispatcher handle any outstanding stuff	1040	# make the dispatcher handle any outstanding stuff
		1041	... not shown
410		1042
411	# create an IO watcher for each and every socket	1043	# create an I/O watcher for each and every socket
412	@snmp_watcher = (	1044	@snmp_watcher = (
413	(map { EV::io $_, EV::READ, sub { } }	1045	(map { EV::io $_, EV::READ, sub { } }
414	keys %{ $dispatcher->{_descriptors} }),	1046	keys %{ $dispatcher->{_descriptors} }),
		1047
		1048	EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
		1049	? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
		1050	0, sub { },
415	);	1051	);
416
417	# if there are any timeouts, also create a timer
418	push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
419	if $event->[Net::SNMP::Dispatcher::_ACTIVE];
420	};	1052	};
421		1053
422	The callbacks are irrelevant, the only purpose of those watchers is	1054	The callbacks are irrelevant (and are not even being called), the
423	to wake up the process as soon as one of those events occurs (socket	1055	only purpose of those watchers is to wake up the process as soon as
424	readable, or timer timed out). The corresponding EV::check watcher will then	1056	one of those events occurs (socket readable, or timer timed out). The
425	clean up:	1057	corresponding EV::check watcher will then clean up:
426		1058
427	our $snmp_check = EV::check sub {	1059	our $snmp_check = EV::check sub {
428	# destroy all watchers	1060	# destroy all watchers
429	@snmp_watcher = ();	1061	@snmp_watcher = ();
430		1062
431	# make the dispatcher handle any new stuff	1063	# make the dispatcher handle any new stuff
		1064	... not shown
432	};	1065	};
433		1066
434	The callbacks of the created watchers will not be called as the watchers	1067	The callbacks of the created watchers will not be called as the watchers
435	are destroyed before this cna happen (remember EV::check gets called	1068	are destroyed before this can happen (remember EV::check gets called
436	first).	1069	first).
437		1070
438	The C<check_ns> variant doesn't start (activate) the newly created watcher.	1071	The C<check_ns> variant doesn't start (activate) the newly created watcher.
439		1072
440	=back	1073	=item EV::CHECK constant issues
441		1074
		1075	Like all other watcher types, there is a bitmask constant for use in
		1076	C<$revents> and other places. The C<EV::CHECK> is special as it has
		1077	the same name as the C<CHECK> sub called by Perl. This doesn't cause
		1078	big issues on newer perls (beginning with 5.8.9), but it means thatthe
		1079	constant must be I<inlined>, i.e. runtime calls will not work. That means
		1080	that as long as you always C<use EV> and then C<EV::CHECK> you are on the
		1081	safe side.
		1082
		1083	=back
		1084
		1085
		1086	=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
		1087
		1088	Fork watchers are called when a C<fork ()> was detected. The invocation
		1089	is done before the event loop blocks next and before C<check> watchers
		1090	are being called, and only in the child after the fork.
		1091
		1092	=over 4
		1093
		1094	=item $w = EV::fork $callback
		1095
		1096	=item $w = EV::fork_ns $callback
		1097
		1098	=item $w = $loop->fork ($callback)
		1099
		1100	=item $w = $loop->fork_ns ($callback)
		1101
		1102	Call the callback before the event loop is resumed in the child process
		1103	after a fork.
		1104
		1105	The C<fork_ns> variant doesn't start (activate) the newly created watcher.
		1106
		1107	=back
		1108
		1109
		1110	=head3 EMBED WATCHERS - when one backend isn't enough...
		1111
		1112	This is a rather advanced watcher type that lets you embed one event loop
		1113	into another (currently only IO events are supported in the embedded
		1114	loop, other types of watchers might be handled in a delayed or incorrect
		1115	fashion and must not be used).
		1116
		1117	See the libev documentation at
		1118	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
		1119	(locally installed as F<EV::libev>) for more details.
		1120
		1121	In short, this watcher is most useful on BSD systems without working
		1122	kqueue to still be able to handle a large number of sockets:
		1123
		1124	my $socket_loop;
		1125
		1126	# check wether we use SELECT or POLL _and_ KQUEUE is supported
		1127	if (
		1128	(EV::backend & (EV::BACKEND_POLL \| EV::BACKEND_SELECT))
		1129	&& (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
		1130	) {
		1131	# use kqueue for sockets
		1132	$socket_loop = new EV::Loop EV::BACKEND_KQUEUE \| EV::FLAG_NOENV;
		1133	}
		1134
		1135	# use the default loop otherwise
		1136	$socket_loop \|\|= EV::default_loop;
		1137
		1138	=over 4
		1139
		1140	=item $w = EV::embed $otherloop[, $callback]
		1141
		1142	=item $w = EV::embed_ns $otherloop[, $callback]
		1143
		1144	=item $w = $loop->embed ($otherloop[, $callback])
		1145
		1146	=item $w = $loop->embed_ns ($otherloop[, $callback])
		1147
		1148	Call the callback when the embedded event loop (C<$otherloop>) has any
		1149	I/O activity. The C<$callback> is optional: if it is missing, then the
		1150	embedded event loop will be managed automatically (which is recommended),
		1151	otherwise you have to invoke C<sweep> yourself.
		1152
		1153	The C<embed_ns> variant doesn't start (activate) the newly created watcher.
		1154
		1155	=back
		1156
		1157	=head3 ASYNC WATCHERS - how to wake up another event loop
		1158
		1159	Async watchers are provided by EV, but have little use in perl directly,
		1160	as perl neither supports threads running in parallel nor direct access to
		1161	signal handlers or other contexts where they could be of value.
		1162
		1163	It is, however, possible to use them from the XS level.
		1164
		1165	Please see the libev documentation for further details.
		1166
		1167	=over 4
		1168
		1169	=item $w = EV::async $callback
		1170
		1171	=item $w = EV::async_ns $callback
		1172
		1173	=item $w = $loop->async ($callback)
		1174
		1175	=item $w = $loop->async_ns ($callback)
		1176
		1177	=item $w->send
		1178
		1179	=item $bool = $w->async_pending
		1180
		1181	=back
		1182
		1183	=head3 CLEANUP WATCHERS - how to clean up when the event loop goes away
		1184
		1185	Cleanup watchers are not supported on the Perl level, they can only be
		1186	used via XS currently.
		1187
		1188
		1189	=head1 PERL SIGNALS
		1190
		1191	While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
		1192	with EV is as the same as any other C library: Perl-signals will only be
		1193	handled when Perl runs, which means your signal handler might be invoked
		1194	only the next time an event callback is invoked.
		1195
		1196	The solution is to use EV signal watchers (see C<EV::signal>), which will
		1197	ensure proper operations with regards to other event watchers.
		1198
		1199	If you cannot do this for whatever reason, you can also force a watcher
		1200	to be called on every event loop iteration by installing a C<EV::check>
		1201	watcher:
		1202
		1203	my $async_check = EV::check sub { };
		1204
		1205	This ensures that perl gets into control for a short time to handle any
		1206	pending signals, and also ensures (slightly) slower overall operation.
		1207
442	=head1 THREADS	1208	=head1 ITHREADS
443		1209
444	Threads are not supported by this in any way. Perl pseudo-threads is evil	1210	Ithreads are not supported by this module in any way. Perl pseudo-threads
445	stuff and must die.	1211	is evil stuff and must die. Real threads as provided by Coro are fully
		1212	supported (and enhanced support is available via L<Coro::EV>).
		1213
		1214	=head1 FORK
		1215
		1216	Most of the "improved" event delivering mechanisms of modern operating
		1217	systems have quite a few problems with fork(2) (to put it bluntly: it is
		1218	not supported and usually destructive). Libev makes it possible to work
		1219	around this by having a function that recreates the kernel state after
		1220	fork in the child.
		1221
		1222	On non-win32 platforms, this module requires the pthread_atfork
		1223	functionality to do this automatically for you. This function is quite
		1224	buggy on most BSDs, though, so YMMV. The overhead for this is quite
		1225	negligible, because everything the function currently does is set a flag
		1226	that is checked only when the event loop gets used the next time, so when
		1227	you do fork but not use EV, the overhead is minimal.
		1228
		1229	On win32, there is no notion of fork so all this doesn't apply, of course.
446		1230
447	=cut	1231	=cut
448		1232
449	our $DIED = sub {	1233	our $DIED = sub {
450	warn "EV: error in callback (ignoring): $@";	1234	warn "EV: error in callback (ignoring): $@";
451	};	1235	};
452		1236
453	init;	1237	default_loop
454		1238	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
455	push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
456		1239
457	1;	1240	1;
458		1241
459	=head1 SEE ALSO	1242	=head1 SEE ALSO
460		1243
461	L<EV::DNS>, L<EV::AnyEvent>.	1244	L<EV::MakeMaker> - MakeMaker interface to XS API, L<EV::ADNS>
		1245	(asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as event
		1246	loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient thread
		1247	integration), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
		1248	event-loop agnostic and portable event driven programming.
462		1249
463	=head1 AUTHOR	1250	=head1 AUTHOR
464		1251
465	Marc Lehmann <schmorp@schmorp.de>	1252	Marc Lehmann <schmorp@schmorp.de>
466	http://home.schmorp.de/	1253	http://home.schmorp.de/
467		1254
468	=cut	1255	=cut
469		1256

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Comparing EV/EV.pm (file contents): Revision 1.22 by root, Fri Nov 2 11:02:22 2007 UTC vs. Revision 1.162 by root, Wed Jan 22 23:17:31 2020 UTC

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Comparing EV/EV.pm (file contents):
Revision 1.22 by root, Fri Nov 2 11:02:22 2007 UTC vs.
Revision 1.162 by root, Wed Jan 22 23:17:31 2020 UTC