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

Comparing EV/EV.pm (file contents):
Revision 1.23 by root, Fri Nov 2 20:21:33 2007 UTC vs.
Revision 1.149 by root, Wed Apr 20 13:43:39 2016 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 = 4.22;
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::loop>.
		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::loop 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::loop 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 a 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	fro 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
…		…
157		434
158	Also, all methods changing some aspect of a watcher (->set, ->priority,	435	Also, all methods changing some aspect of a watcher (->set, ->priority,
159	->fh and so on) automatically stop and start it again if it is active,	436	->fh and so on) automatically stop and start it again if it is active,
160	which means pending events get lost.	437	which means pending events get lost.
161		438
162	=head2 WATCHER TYPES	439	=head2 COMMON WATCHER METHODS
163		440
164	Now lets move to the existing watcher types and asociated methods.	441	This section lists methods common to all watchers.
165
166	The following methods are available for all watchers. Then followes a
167	description of each watcher constructor (EV::io, EV::timer, EV::periodic,
168	EV::signal, EV::child, EV::idle, EV::prepare and EV::check), followed by
169	any type-specific methods (if any).
170		442
171	=over 4	443	=over 4
172		444
173	=item $w->start	445	=item $w->start
174		446
…		…
178		450
179	=item $w->stop	451	=item $w->stop
180		452
181	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
182	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),
183	regardless of wether the watcher was active or not.	455	regardless of whether the watcher was active or not.
184		456
185	=item $bool = $w->is_active	457	=item $bool = $w->is_active
186		458
187	Returns true if the watcher is active, false otherwise.	459	Returns true if the watcher is active, false otherwise.
		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!");
188		472
189	=item $current_cb = $w->cb	473	=item $current_cb = $w->cb
190		474
191	=item $old_cb = $w->cb ($new_cb)	475	=item $old_cb = $w->cb ($new_cb)
192		476
…		…
197		481
198	=item $old_priority = $w->priority ($new_priority)	482	=item $old_priority = $w->priority ($new_priority)
199		483
200	Queries the priority on the watcher and optionally changes it. Pending	484	Queries the priority on the watcher and optionally changes it. Pending
201	watchers with higher priority will be invoked first. The valid range of	485	watchers with higher priority will be invoked first. The valid range of
202	priorities lies between EV::MAXPRI (default 3) and EV::MINPRI (default	486	priorities lies between EV::MAXPRI (default 2) and EV::MINPRI (default
203	-3). If the priority is outside this range it will automatically be	487	-2). If the priority is outside this range it will automatically be
204	normalised to the nearest valid priority.	488	normalised to the nearest valid priority.
205		489
206	The default priority of any newly-created weatcher is 0.	490	The default priority of any newly-created watcher is 0.
207		491
		492	Note that the priority semantics have not yet been fleshed out and are
		493	subject to almost certain change.
		494
208	=item $w->trigger ($revents)	495	=item $w->invoke ($revents)
209		496
210	Call the callback now with the given event mask.	497	Call the callback now with the given event mask.
211		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::loop> 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::loop> 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::loop> (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::loop> 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::loop> 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
212		552
213	=item $w = EV::io $fileno_or_fh, $eventmask, $callback	553	=item $w = EV::io $fileno_or_fh, $eventmask, $callback
214		554
215	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback	555	=item $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
216		556
		557	=item $w = $loop->io ($fileno_or_fh, $eventmask, $callback)
		558
		559	=item $w = $loop->io_ns ($fileno_or_fh, $eventmask, $callback)
		560
217	As long as the returned watcher object is alive, call the C<$callback>	561	As long as the returned watcher object is alive, call the C<$callback>
218	when the events specified in C<$eventmask>.	562	when at least one of events specified in C<$eventmask> occurs.
219		563
220	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:
221		565
222	EV::READ wait until read() wouldn't block anymore	566	EV::READ wait until read() wouldn't block anymore
223	EV::WRITE wait until write() wouldn't block anymore	567	EV::WRITE wait until write() wouldn't block anymore
…		…
239		583
240	=item $old_eventmask = $w->events ($new_eventmask)	584	=item $old_eventmask = $w->events ($new_eventmask)
241		585
242	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.
243		587
		588	=back
		589
		590
		591	=head3 TIMER WATCHERS - relative and optionally repeating timeouts
		592
		593	=over 4
244		594
245	=item $w = EV::timer $after, $repeat, $callback	595	=item $w = EV::timer $after, $repeat, $callback
246		596
247	=item $w = EV::timer_ns $after, $repeat, $callback	597	=item $w = EV::timer_ns $after, $repeat, $callback
248		598
249	Calls the callback after C<$after> seconds. If C<$repeat> is non-zero,	599	=item $w = $loop->timer ($after, $repeat, $callback)
250	the timer will be restarted (with the $repeat value as $after) after the	600
251	callback returns.	601	=item $w = $loop->timer_ns ($after, $repeat, $callback)
		602
		603	Calls the callback after C<$after> seconds (which may be fractional). If
		604	C<$repeat> is non-zero, the timer will be restarted (with the $repeat
		605	value as $after) after the callback returns.
252		606
253	This means that the callback would be called roughly after C<$after>	607	This means that the callback would be called roughly after C<$after>
254	seconds, and then every C<$repeat> seconds. "Roughly" because the time of	608	seconds, and then every C<$repeat> seconds. The timer does his best not
255	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
256	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.
257		612
258	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
259	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
260	clock, the timer will nevertheless run (roughly) the same time.	615	clock, the timer will nevertheless run (roughly) the same time.
261		616
262	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.
263		618
264	=item $w->set ($after, $repeat)	619	=item $w->set ($after, $repeat = 0)
265		620
266	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
267	any time.	622	any time.
268		623
269	=item $w->again	624	=item $w->again
270		625
		626	=item $w->again ($repeat)
		627
271	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.
272		631
273	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
274	C<$repeat> seconds after now.	633	C<$repeat> seconds after now.
275		634
276	If the timer is active and non-repeating, it will be stopped.
277
278	If the timer is in active and repeating, start it.	635	If the timer is inactive and repeating, start it using the repeat value.
279		636
280	Otherwise do nothing.	637	Otherwise do nothing.
281		638
282	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
283	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
284	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
285	on the timeout.	642	on the timeout.
286		643
		644	If called with a C<$repeat> argument, then it uses this a timer repeat
		645	value.
287		646
		647	=item $after = $w->remaining
		648
		649	Calculates and returns the remaining time till the timer will fire.
		650
		651	=back
		652
		653
		654	=head3 PERIODIC WATCHERS - to cron or not to cron?
		655
		656	=over 4
		657
288	=item $w = EV::periodic $at, $interval, $callback	658	=item $w = EV::periodic $at, $interval, $reschedule_cb, $callback
289		659
290	=item $w = EV::periodic_ns $at, $interval, $callback	660	=item $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
291		661
292	Similar to EV::timer, but the time is given as an absolute point in time	662	=item $w = $loop->periodic ($at, $interval, $reschedule_cb, $callback)
293	(C<$at>), plus an optional C<$interval>.
294		663
295	If the C<$interval> is zero, then the callback will be called at the time	664	=item $w = $loop->periodic_ns ($at, $interval, $reschedule_cb, $callback)
296	C<$at> if that is in the future, or as soon as possible if it is in the
297	past. It will not automatically repeat.
298		665
299	If the C<$interval> is nonzero, then the watcher will always be scheduled	666	Similar to EV::timer, but is not based on relative timeouts but on
300	to time out at the next C<$at + N * $interval> time.	667	absolute times. Apart from creating "simple" timers that trigger "at" the
		668	specified time, it can also be used for non-drifting absolute timers and
		669	more complex, cron-like, setups that are not adversely affected by time
		670	jumps (i.e. when the system clock is changed by explicit date -s or other
		671	means such as ntpd). It is also the most complex watcher type in EV.
301		672
302	This can be used to schedule a callback to run at very regular intervals,	673	It has three distinct "modes":
303	as long as the processing time is less then the interval (otherwise	674
304	obviously events will be skipped).	675	=over 4
		676
		677	=item * absolute timer ($interval = $reschedule_cb = 0)
		678
		679	This time simply fires at the wallclock time C<$at> and doesn't repeat. It
		680	will not adjust when a time jump occurs, that is, if it is to be run
		681	at January 1st 2011 then it will run when the system time reaches or
		682	surpasses this time.
		683
		684	=item * repeating interval timer ($interval > 0, $reschedule_cb = 0)
		685
		686	In this mode the watcher will always be scheduled to time out at the
		687	next C<$at + N * $interval> time (for some integer N) and then repeat,
		688	regardless of any time jumps.
		689
		690	This can be used to create timers that do not drift with respect to system
		691	time:
		692
		693	my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
		694
		695	That doesn't mean there will always be 3600 seconds in between triggers,
		696	but only that the the callback will be called when the system time shows a
		697	full hour (UTC).
305		698
306	Another way to think about it (for the mathematically inclined) is that	699	Another way to think about it (for the mathematically inclined) is that
307	EV::periodic will try to run the callback at the next possible time where	700	EV::periodic will try to run the callback in this mode at the next
308	C<$time = $at (mod $interval)>, regardless of any time jumps.	701	possible time where C<$time = $at (mod $interval)>, regardless of any time
		702	jumps.
309		703
310	This periodic timer is based on "wallclock time", that is, if the clock	704	=item * manual reschedule mode ($reschedule_cb = coderef)
311	changes (C<ntp>, C<date -s> etc.), then the timer will nevertheless run at	705
312	the specified time. This means it will never drift (it might jitter, but	706	In this mode $interval and $at are both being ignored. Instead, each
313	it will not drift).	707	time the periodic watcher gets scheduled, the reschedule callback
		708	($reschedule_cb) will be called with the watcher as first, and the current
		709	time as second argument.
		710
		711	I<This callback MUST NOT stop or destroy this or any other periodic
		712	watcher, ever, and MUST NOT call any event loop functions or methods>. If
		713	you need to stop it, return 1e30 and stop it afterwards. You may create
		714	and start a C<EV::prepare> watcher for this task.
		715
		716	It must return the next time to trigger, based on the passed time value
		717	(that is, the lowest time value larger than or equal to to the second
		718	argument). It will usually be called just before the callback will be
		719	triggered, but might be called at other times, too.
		720
		721	This can be used to create very complex timers, such as a timer that
		722	triggers on each midnight, local time (actually 24 hours after the last
		723	midnight, to keep the example simple. If you know a way to do it correctly
		724	in about the same space (without requiring elaborate modules), drop me a
		725	note :):
		726
		727	my $daily = EV::periodic 0, 0, sub {
		728	my ($w, $now) = @_;
		729
		730	use Time::Local ();
		731	my (undef, undef, undef, $d, $m, $y) = localtime $now;
		732	86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
		733	}, sub {
		734	print "it's midnight or likely shortly after, now\n";
		735	};
		736
		737	=back
314		738
315	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.	739	The C<periodic_ns> variant doesn't start (activate) the newly created watcher.
316		740
317	=item $w->set ($at, $interval)	741	=item $w->set ($at, $interval, $reschedule_cb)
318		742
319	Reconfigures the watcher, see the constructor above for details. Can be at	743	Reconfigures the watcher, see the constructor above for details. Can be called at
320	any time.	744	any time.
321		745
		746	=item $w->again
		747
		748	Simply stops and starts the watcher again.
		749
		750	=item $time = $w->at
		751
		752	Return the time that the watcher is expected to trigger next.
		753
		754	=back
		755
		756
		757	=head3 SIGNAL WATCHERS - signal me when a signal gets signalled!
		758
		759	=over 4
322		760
323	=item $w = EV::signal $signal, $callback	761	=item $w = EV::signal $signal, $callback
324		762
325	=item $w = EV::signal_ns $signal, $callback	763	=item $w = EV::signal_ns $signal, $callback
326		764
		765	=item $w = $loop->signal ($signal, $callback)
		766
		767	=item $w = $loop->signal_ns ($signal, $callback)
		768
327	Call the callback when $signal is received (the signal can be specified	769	Call the callback when $signal is received (the signal can be specified by
328	by number or by name, just as with kill or %SIG).	770	number or by name, just as with C<kill> or C<%SIG>).
		771
		772	Only one event loop can grab a given signal - attempting to grab the same
		773	signal from two EV loops will crash the program immediately or cause data
		774	corruption.
329		775
330	EV will grab the signal for the process (the kernel only allows one	776	EV will grab the signal for the process (the kernel only allows one
331	component to receive a signal at a time) when you start a signal watcher,	777	component to receive a signal at a time) when you start a signal watcher,
332	and removes it again when you stop it. Perl does the same when you	778	and removes it again when you stop it. Perl does the same when you
333	add/remove callbacks to %SIG, so watch out.	779	add/remove callbacks to C<%SIG>, so watch out.
334		780
335	You can have as many signal watchers per signal as you want.	781	You can have as many signal watchers per signal as you want.
336		782
337	The C<signal_ns> variant doesn't start (activate) the newly created watcher.	783	The C<signal_ns> variant doesn't start (activate) the newly created watcher.
338		784
339	=item $w->set ($signal)	785	=item $w->set ($signal)
340		786
341	Reconfigures the watcher, see the constructor above for details. Can be at	787	Reconfigures the watcher, see the constructor above for details. Can be
342	any time.	788	called at any time.
343		789
344	=item $current_signum = $w->signal	790	=item $current_signum = $w->signal
345		791
346	=item $old_signum = $w->signal ($new_signal)	792	=item $old_signum = $w->signal ($new_signal)
347		793
348	Returns the previously set signal (always as a number not name) and	794	Returns the previously set signal (always as a number not name) and
349	optionally set a new one.	795	optionally set a new one.
350		796
		797	=back
351		798
		799
		800	=head3 CHILD WATCHERS - watch out for process status changes
		801
		802	=over 4
		803
352	=item $w = EV::child $pid, $callback	804	=item $w = EV::child $pid, $trace, $callback
353		805
354	=item $w = EV::child_ns $pid, $callback	806	=item $w = EV::child_ns $pid, $trace, $callback
		807
		808	=item $w = $loop->child ($pid, $trace, $callback)
		809
		810	=item $w = $loop->child_ns ($pid, $trace, $callback)
355		811
356	Call the callback when a status change for pid C<$pid> (or any pid	812	Call the callback when a status change for pid C<$pid> (or any pid
357	if C<$pid> is 0) has been received. More precisely: when the process	813	if C<$pid> is 0) has been received (a status change happens when the
		814	process terminates or is killed, or, when trace is true, additionally when
		815	it is stopped or continued). More precisely: when the process receives
358	receives a SIGCHLD, EV will fetch the outstanding exit/wait status for all	816	a C<SIGCHLD>, EV will fetch the outstanding exit/wait status for all
359	changed/zombie children and call the callback.	817	changed/zombie children and call the callback.
360		818
361	Unlike all other callbacks, this callback will be called with an	819	It is valid (and fully supported) to install a child watcher after a child
362	additional third argument which is the exit status. See the C<waitpid>	820	has exited but before the event loop has started its next iteration (for
363	function for details.	821	example, first you C<fork>, then the new child process might exit, and
		822	only then do you install a child watcher in the parent for the new pid).
364		823
		824	You can access both exit (or tracing) status and pid by using the
		825	C<rstatus> and C<rpid> methods on the watcher object.
		826
365	You can have as many pid watchers per pid as you want.	827	You can have as many pid watchers per pid as you want, they will all be
		828	called.
366		829
367	The C<child_ns> variant doesn't start (activate) the newly created watcher.	830	The C<child_ns> variant doesn't start (activate) the newly created watcher.
368		831
369	=item $w->set ($pid)	832	=item $w->set ($pid, $trace)
370		833
371	Reconfigures the watcher, see the constructor above for details. Can be at	834	Reconfigures the watcher, see the constructor above for details. Can be called at
372	any time.	835	any time.
373		836
374	=item $current_pid = $w->pid	837	=item $current_pid = $w->pid
375		838
376	=item $old_pid = $w->pid ($new_pid)
377
378	Returns the previously set process id and optionally set a new one.	839	Returns the previously set process id and optionally set a new one.
379		840
		841	=item $exit_status = $w->rstatus
		842
		843	Return the exit/wait status (as returned by waitpid, see the waitpid entry
		844	in perlfunc).
		845
		846	=item $pid = $w->rpid
		847
		848	Return the pid of the awaited child (useful when you have installed a
		849	watcher for all pids).
		850
		851	=back
		852
		853
		854	=head3 STAT WATCHERS - did the file attributes just change?
		855
		856	=over 4
		857
		858	=item $w = EV::stat $path, $interval, $callback
		859
		860	=item $w = EV::stat_ns $path, $interval, $callback
		861
		862	=item $w = $loop->stat ($path, $interval, $callback)
		863
		864	=item $w = $loop->stat_ns ($path, $interval, $callback)
		865
		866	Call the callback when a file status change has been detected on
		867	C<$path>. The C<$path> does not need to exist, changing from "path exists"
		868	to "path does not exist" is a status change like any other.
		869
		870	The C<$interval> is a recommended polling interval for systems where
		871	OS-supported change notifications don't exist or are not supported. If
		872	you use C<0> then an unspecified default is used (which is highly
		873	recommended!), which is to be expected to be around five seconds usually.
		874
		875	This watcher type is not meant for massive numbers of stat watchers,
		876	as even with OS-supported change notifications, this can be
		877	resource-intensive.
		878
		879	The C<stat_ns> variant doesn't start (activate) the newly created watcher.
		880
		881	=item ... = $w->stat
		882
		883	This call is very similar to the perl C<stat> built-in: It stats (using
		884	C<lstat>) the path specified in the watcher and sets perls stat cache (as
		885	well as EV's idea of the current stat values) to the values found.
		886
		887	In scalar context, a boolean is return indicating success or failure of
		888	the stat. In list context, the same 13-value list as with stat is returned
		889	(except that the blksize and blocks fields are not reliable).
		890
		891	In the case of an error, errno is set to C<ENOENT> (regardless of the
		892	actual error value) and the C<nlink> value is forced to zero (if the stat
		893	was successful then nlink is guaranteed to be non-zero).
		894
		895	See also the next two entries for more info.
		896
		897	=item ... = $w->attr
		898
		899	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		900	the values most recently detected by EV. See the next entry for more info.
		901
		902	=item ... = $w->prev
		903
		904	Just like C<< $w->stat >>, but without the initial stat'ing: this returns
		905	the previous set of values, before the change.
		906
		907	That is, when the watcher callback is invoked, C<< $w->prev >> will be set
		908	to the values found I<before> a change was detected, while C<< $w->attr >>
		909	returns the values found leading to the change detection. The difference (if any)
		910	between C<prev> and C<attr> is what triggered the callback.
		911
		912	If you did something to the filesystem object and do not want to trigger
		913	yet another change, you can call C<stat> to update EV's idea of what the
		914	current attributes are.
		915
		916	=item $w->set ($path, $interval)
		917
		918	Reconfigures the watcher, see the constructor above for details. Can be
		919	called at any time.
		920
		921	=item $current_path = $w->path
		922
		923	=item $old_path = $w->path ($new_path)
		924
		925	Returns the previously set path and optionally set a new one.
		926
		927	=item $current_interval = $w->interval
		928
		929	=item $old_interval = $w->interval ($new_interval)
		930
		931	Returns the previously set interval and optionally set a new one. Can be
		932	used to query the actual interval used.
		933
		934	=back
		935
		936
		937	=head3 IDLE WATCHERS - when you've got nothing better to do...
		938
		939	=over 4
380		940
381	=item $w = EV::idle $callback	941	=item $w = EV::idle $callback
382		942
383	=item $w = EV::idle_ns $callback	943	=item $w = EV::idle_ns $callback
384		944
385	Call the callback when there are no pending io, timer/periodic, signal or	945	=item $w = $loop->idle ($callback)
386	child events, i.e. when the process is idle.	946
		947	=item $w = $loop->idle_ns ($callback)
		948
		949	Call the callback when there are no other pending watchers of the same or
		950	higher priority (excluding check, prepare and other idle watchers of the
		951	same or lower priority, of course). They are called idle watchers because
		952	when the watcher is the highest priority pending event in the process, the
		953	process is considered to be idle at that priority.
		954
		955	If you want a watcher that is only ever called when I<no> other events are
		956	outstanding you have to set the priority to C<EV::MINPRI>.
387		957
388	The process will not block as long as any idle watchers are active, and	958	The process will not block as long as any idle watchers are active, and
389	they will be called repeatedly until stopped.	959	they will be called repeatedly until stopped.
390		960
		961	For example, if you have idle watchers at priority C<0> and C<1>, and
		962	an I/O watcher at priority C<0>, then the idle watcher at priority C<1>
		963	and the I/O watcher will always run when ready. Only when the idle watcher
		964	at priority C<1> is stopped and the I/O watcher at priority C<0> is not
		965	pending with the C<0>-priority idle watcher be invoked.
		966
391	The C<idle_ns> variant doesn't start (activate) the newly created watcher.	967	The C<idle_ns> variant doesn't start (activate) the newly created watcher.
392		968
		969	=back
		970
		971
		972	=head3 PREPARE WATCHERS - customise your event loop!
		973
		974	=over 4
393		975
394	=item $w = EV::prepare $callback	976	=item $w = EV::prepare $callback
395		977
396	=item $w = EV::prepare_ns $callback	978	=item $w = EV::prepare_ns $callback
		979
		980	=item $w = $loop->prepare ($callback)
		981
		982	=item $w = $loop->prepare_ns ($callback)
397		983
398	Call the callback just before the process would block. You can still	984	Call the callback just before the process would block. You can still
399	create/modify any watchers at this point.	985	create/modify any watchers at this point.
400		986
401	See the EV::check watcher, below, for explanations and an example.	987	See the EV::check watcher, below, for explanations and an example.
402		988
403	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.	989	The C<prepare_ns> variant doesn't start (activate) the newly created watcher.
404		990
		991	=back
		992
		993
		994	=head3 CHECK WATCHERS - customise your event loop even more!
		995
		996	=over 4
405		997
406	=item $w = EV::check $callback	998	=item $w = EV::check $callback
407		999
408	=item $w = EV::check_ns $callback	1000	=item $w = EV::check_ns $callback
		1001
		1002	=item $w = $loop->check ($callback)
		1003
		1004	=item $w = $loop->check_ns ($callback)
409		1005
410	Call the callback just after the process wakes up again (after it has	1006	Call the callback just after the process wakes up again (after it has
411	gathered events), but before any other callbacks have been invoked.	1007	gathered events), but before any other callbacks have been invoked.
412		1008
413	This is used to integrate other event-based software into the EV	1009	This can be used to integrate other event-based software into the EV
414	mainloop: You register a prepare callback and in there, you create io and	1010	mainloop: You register a prepare callback and in there, you create io and
415	timer watchers as required by the other software. Here is a real-world	1011	timer watchers as required by the other software. Here is a real-world
416	example of integrating Net::SNMP (with some details left out):	1012	example of integrating Net::SNMP (with some details left out):
417		1013
418	our @snmp_watcher;	1014	our @snmp_watcher;
…		…
421	# do nothing unless active	1017	# do nothing unless active
422	$dispatcher->{_event_queue_h}	1018	$dispatcher->{_event_queue_h}
423	or return;	1019	or return;
424		1020
425	# make the dispatcher handle any outstanding stuff	1021	# make the dispatcher handle any outstanding stuff
		1022	... not shown
426		1023
427	# create an IO watcher for each and every socket	1024	# create an I/O watcher for each and every socket
428	@snmp_watcher = (	1025	@snmp_watcher = (
429	(map { EV::io $_, EV::READ, sub { } }	1026	(map { EV::io $_, EV::READ, sub { } }
430	keys %{ $dispatcher->{_descriptors} }),	1027	keys %{ $dispatcher->{_descriptors} }),
		1028
		1029	EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
		1030	? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
		1031	0, sub { },
431	);	1032	);
432
433	# if there are any timeouts, also create a timer
434	push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
435	if $event->[Net::SNMP::Dispatcher::_ACTIVE];
436	};	1033	};
437		1034
438	The callbacks are irrelevant, the only purpose of those watchers is	1035	The callbacks are irrelevant (and are not even being called), the
439	to wake up the process as soon as one of those events occurs (socket	1036	only purpose of those watchers is to wake up the process as soon as
440	readable, or timer timed out). The corresponding EV::check watcher will then	1037	one of those events occurs (socket readable, or timer timed out). The
441	clean up:	1038	corresponding EV::check watcher will then clean up:
442		1039
443	our $snmp_check = EV::check sub {	1040	our $snmp_check = EV::check sub {
444	# destroy all watchers	1041	# destroy all watchers
445	@snmp_watcher = ();	1042	@snmp_watcher = ();
446		1043
447	# make the dispatcher handle any new stuff	1044	# make the dispatcher handle any new stuff
		1045	... not shown
448	};	1046	};
449		1047
450	The callbacks of the created watchers will not be called as the watchers	1048	The callbacks of the created watchers will not be called as the watchers
451	are destroyed before this cna happen (remember EV::check gets called	1049	are destroyed before this can happen (remember EV::check gets called
452	first).	1050	first).
453		1051
454	The C<check_ns> variant doesn't start (activate) the newly created watcher.	1052	The C<check_ns> variant doesn't start (activate) the newly created watcher.
455		1053
456	=back	1054	=item EV::CHECK constant issues
457		1055
		1056	Like all other watcher types, there is a bitmask constant for use in
		1057	C<$revents> and other places. The C<EV::CHECK> is special as it has
		1058	the same name as the C<CHECK> sub called by Perl. This doesn't cause
		1059	big issues on newer perls (beginning with 5.8.9), but it means thatthe
		1060	constant must be I<inlined>, i.e. runtime calls will not work. That means
		1061	that as long as you always C<use EV> and then C<EV::CHECK> you are on the
		1062	safe side.
		1063
		1064	=back
		1065
		1066
		1067	=head3 FORK WATCHERS - the audacity to resume the event loop after a fork
		1068
		1069	Fork watchers are called when a C<fork ()> was detected. The invocation
		1070	is done before the event loop blocks next and before C<check> watchers
		1071	are being called, and only in the child after the fork.
		1072
		1073	=over 4
		1074
		1075	=item $w = EV::fork $callback
		1076
		1077	=item $w = EV::fork_ns $callback
		1078
		1079	=item $w = $loop->fork ($callback)
		1080
		1081	=item $w = $loop->fork_ns ($callback)
		1082
		1083	Call the callback before the event loop is resumed in the child process
		1084	after a fork.
		1085
		1086	The C<fork_ns> variant doesn't start (activate) the newly created watcher.
		1087
		1088	=back
		1089
		1090
		1091	=head3 EMBED WATCHERS - when one backend isn't enough...
		1092
		1093	This is a rather advanced watcher type that lets you embed one event loop
		1094	into another (currently only IO events are supported in the embedded
		1095	loop, other types of watchers might be handled in a delayed or incorrect
		1096	fashion and must not be used).
		1097
		1098	See the libev documentation at
		1099	L<http://pod.tst.eu/http://cvs.schmorp.de/libev/ev.pod#code_ev_embed_code_when_one_backend_>
		1100	(locally installed as F<EV::libev>) for more details.
		1101
		1102	In short, this watcher is most useful on BSD systems without working
		1103	kqueue to still be able to handle a large number of sockets:
		1104
		1105	my $socket_loop;
		1106
		1107	# check wether we use SELECT or POLL _and_ KQUEUE is supported
		1108	if (
		1109	(EV::backend & (EV::BACKEND_POLL \| EV::BACKEND_SELECT))
		1110	&& (EV::supported_backends & EV::embeddable_backends & EV::BACKEND_KQUEUE)
		1111	) {
		1112	# use kqueue for sockets
		1113	$socket_loop = new EV::Loop EV::BACKEND_KQUEUE \| EV::FLAG_NOENV;
		1114	}
		1115
		1116	# use the default loop otherwise
		1117	$socket_loop \|\|= EV::default_loop;
		1118
		1119	=over 4
		1120
		1121	=item $w = EV::embed $otherloop[, $callback]
		1122
		1123	=item $w = EV::embed_ns $otherloop[, $callback]
		1124
		1125	=item $w = $loop->embed ($otherloop[, $callback])
		1126
		1127	=item $w = $loop->embed_ns ($otherloop[, $callback])
		1128
		1129	Call the callback when the embedded event loop (C<$otherloop>) has any
		1130	I/O activity. The C<$callback> is optional: if it is missing, then the
		1131	embedded event loop will be managed automatically (which is recommended),
		1132	otherwise you have to invoke C<sweep> yourself.
		1133
		1134	The C<embed_ns> variant doesn't start (activate) the newly created watcher.
		1135
		1136	=back
		1137
		1138	=head3 ASYNC WATCHERS - how to wake up another event loop
		1139
		1140	Async watchers are provided by EV, but have little use in perl directly,
		1141	as perl neither supports threads running in parallel nor direct access to
		1142	signal handlers or other contexts where they could be of value.
		1143
		1144	It is, however, possible to use them from the XS level.
		1145
		1146	Please see the libev documentation for further details.
		1147
		1148	=over 4
		1149
		1150	=item $w = EV::async $callback
		1151
		1152	=item $w = EV::async_ns $callback
		1153
		1154	=item $w = $loop->async ($callback)
		1155
		1156	=item $w = $loop->async_ns ($callback)
		1157
		1158	=item $w->send
		1159
		1160	=item $bool = $w->async_pending
		1161
		1162	=back
		1163
		1164	=head3 CLEANUP WATCHERS - how to clean up when the event loop goes away
		1165
		1166	Cleanup watchers are not supported on the Perl level, they can only be
		1167	used via XS currently.
		1168
		1169
		1170	=head1 PERL SIGNALS
		1171
		1172	While Perl signal handling (C<%SIG>) is not affected by EV, the behaviour
		1173	with EV is as the same as any other C library: Perl-signals will only be
		1174	handled when Perl runs, which means your signal handler might be invoked
		1175	only the next time an event callback is invoked.
		1176
		1177	The solution is to use EV signal watchers (see C<EV::signal>), which will
		1178	ensure proper operations with regards to other event watchers.
		1179
		1180	If you cannot do this for whatever reason, you can also force a watcher
		1181	to be called on every event loop iteration by installing a C<EV::check>
		1182	watcher:
		1183
		1184	my $async_check = EV::check sub { };
		1185
		1186	This ensures that perl gets into control for a short time to handle any
		1187	pending signals, and also ensures (slightly) slower overall operation.
		1188
458	=head1 THREADS	1189	=head1 ITHREADS
459		1190
460	Threads are not supported by this in any way. Perl pseudo-threads is evil	1191	Ithreads are not supported by this module in any way. Perl pseudo-threads
461	stuff and must die.	1192	is evil stuff and must die. Real threads as provided by Coro are fully
		1193	supported (and enhanced support is available via L<Coro::EV>).
		1194
		1195	=head1 FORK
		1196
		1197	Most of the "improved" event delivering mechanisms of modern operating
		1198	systems have quite a few problems with fork(2) (to put it bluntly: it is
		1199	not supported and usually destructive). Libev makes it possible to work
		1200	around this by having a function that recreates the kernel state after
		1201	fork in the child.
		1202
		1203	On non-win32 platforms, this module requires the pthread_atfork
		1204	functionality to do this automatically for you. This function is quite
		1205	buggy on most BSDs, though, so YMMV. The overhead for this is quite
		1206	negligible, because everything the function currently does is set a flag
		1207	that is checked only when the event loop gets used the next time, so when
		1208	you do fork but not use EV, the overhead is minimal.
		1209
		1210	On win32, there is no notion of fork so all this doesn't apply, of course.
462		1211
463	=cut	1212	=cut
464		1213
465	our $DIED = sub {	1214	our $DIED = sub {
466	warn "EV: error in callback (ignoring): $@";	1215	warn "EV: error in callback (ignoring): $@";
467	};	1216	};
468		1217
469	init;	1218	default_loop
470		1219	or die 'EV: cannot initialise libev backend. bad $ENV{LIBEV_FLAGS}?';
471	push @AnyEvent::REGISTRY, [EV => "EV::AnyEvent"];
472		1220
473	1;	1221	1;
474		1222
475	=head1 SEE ALSO	1223	=head1 SEE ALSO
476		1224
477	L<EV::DNS>, L<EV::AnyEvent>.	1225	L<EV::MakeMaker> - MakeMaker interface to XS API, L<EV::ADNS>
		1226	(asynchronous DNS), L<Glib::EV> (makes Glib/Gtk2 use EV as event
		1227	loop), L<EV::Glib> (embed Glib into EV), L<Coro::EV> (efficient thread
		1228	integration), L<Net::SNMP::EV> (asynchronous SNMP), L<AnyEvent> for
		1229	event-loop agnostic and portable event driven programming.
478		1230
479	=head1 AUTHOR	1231	=head1 AUTHOR
480		1232
481	Marc Lehmann <schmorp@schmorp.de>	1233	Marc Lehmann <schmorp@schmorp.de>
482	http://home.schmorp.de/	1234	http://home.schmorp.de/
483		1235
484	=cut	1236	=cut
485		1237

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Comparing EV/EV.pm (file contents): Revision 1.23 by root, Fri Nov 2 20:21:33 2007 UTC vs. Revision 1.149 by root, Wed Apr 20 13:43:39 2016 UTC

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Comparing EV/EV.pm (file contents):
Revision 1.23 by root, Fri Nov 2 20:21:33 2007 UTC vs.
Revision 1.149 by root, Wed Apr 20 13:43:39 2016 UTC