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Revision 1.142 by root, Tue May 27 02:34:30 2008 UTC vs.
Revision 1.247 by root, Sat Jul 18 22:24:17 2009 UTC

1	=head1 => NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
22		45
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	46	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		47
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	49	nowadays. So what is different about AnyEvent?
27		50
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	52	policy> and AnyEvent is I<small and efficient>.
30		53
31	First and foremost, I<AnyEvent is not an event model> itself, it only	54	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	55	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	56	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	57	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	58	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	59	cannot change this, but it can hide the differences between those event
		60	loops.
37		61
38	The goal of AnyEvent is to offer module authors the ability to do event	62	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	63	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	64	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	65	module users into the same thing by forcing them to use the same event
42	model you use.	66	model you use.
43		67
44	For modules like POE or IO::Async (which is a total misnomer as it is	68	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	69	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	70	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	71	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	72	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	73	module are I<also> forced to use the same event loop you use.
50		74
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	76	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if	77	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	78	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	79	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	80	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	81	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	82	to AnyEvent, too, so it is future-proof).
59		83
60	In addition to being free of having to use I<the one and only true event	84	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	85	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enormous amount of code and strict rules you have to	86	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	87	follow. AnyEvent, on the other hand, is lean and up to the point, by only
…		…
121	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
122	creating a watcher it will immediately "watch" for events and invoke the	146	creating a watcher it will immediately "watch" for events and invoke the
123	callback when the event occurs (of course, only when the event model	147	callback when the event occurs (of course, only when the event model
124	is in control).	148	is in control).
125		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
126	To disable the watcher you have to destroy it (e.g. by setting the	156	To disable the watcher you have to destroy it (e.g. by setting the
127	variable you store it in to C<undef> or otherwise deleting all references	157	variable you store it in to C<undef> or otherwise deleting all references
128	to it).	158	to it).
129		159
130	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
132	Many watchers either are used with "recursion" (repeating timers for	162	Many watchers either are used with "recursion" (repeating timers for
133	example), or need to refer to their watcher object in other ways.	163	example), or need to refer to their watcher object in other ways.
134		164
135	An any way to achieve that is this pattern:	165	An any way to achieve that is this pattern:
136		166
137	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
138	# you can use $w here, for example to undef it	168	# you can use $w here, for example to undef it
139	undef $w;	169	undef $w;
140	});	170	});
141		171
142	Note that C<my $w; $w => combination. This is necessary because in Perl,	172	Note that C<my $w; $w => combination. This is necessary because in Perl,
143	my variables are only visible after the statement in which they are	173	my variables are only visible after the statement in which they are
144	declared.	174	declared.
145		175
146	=head2 I/O WATCHERS	176	=head2 I/O WATCHERS
147		177
148	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
149	with the following mandatory key-value pairs as arguments:	179	with the following mandatory key-value pairs as arguments:
150		180
151	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	181	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
152	for events. C<poll> must be a string that is either C<r> or C<w>,	188	C<poll> must be a string that is either C<r> or C<w>, which creates a
153	which creates a watcher waiting for "r"eadable or "w"ritable events,	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
		190
154	respectively. C<cb> is the callback to invoke each time the file handle	191	C<cb> is the callback to invoke each time the file handle becomes ready.
155	becomes ready.
156		192
157	Although the callback might get passed parameters, their value and	193	Although the callback might get passed parameters, their value and
158	presence is undefined and you cannot rely on them. Portable AnyEvent	194	presence is undefined and you cannot rely on them. Portable AnyEvent
159	callbacks cannot use arguments passed to I/O watcher callbacks.	195	callbacks cannot use arguments passed to I/O watcher callbacks.
160		196
…		…
164		200
165	Some event loops issue spurious readyness notifications, so you should	201	Some event loops issue spurious readyness notifications, so you should
166	always use non-blocking calls when reading/writing from/to your file	202	always use non-blocking calls when reading/writing from/to your file
167	handles.	203	handles.
168		204
169	Example:
170
171	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
172	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
173	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
174	warn "read: $input\n";	210	warn "read: $input\n";
175	undef $w;	211	undef $w;
176	});	212	});
…		…
186		222
187	Although the callback might get passed parameters, their value and	223	Although the callback might get passed parameters, their value and
188	presence is undefined and you cannot rely on them. Portable AnyEvent	224	presence is undefined and you cannot rely on them. Portable AnyEvent
189	callbacks cannot use arguments passed to time watcher callbacks.	225	callbacks cannot use arguments passed to time watcher callbacks.
190		226
191	The timer callback will be invoked at most once: if you want a repeating	227	The callback will normally be invoked once only. If you specify another
192	timer you have to create a new watcher (this is a limitation by both Tk	228	parameter, C<interval>, as a strictly positive number (> 0), then the
193	and Glib).	229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
194		232
195	Example:	233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
196		236
197	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
198	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
199	warn "timeout\n";	240	warn "timeout\n";
200	});	241	});
201		242
202	# to cancel the timer:	243	# to cancel the timer:
203	undef $w;	244	undef $w;
204		245
205	Example 2:
206
207	# fire an event after 0.5 seconds, then roughly every second	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
208	my $w;
209		247
210	my $cb = sub {
211	# cancel the old timer while creating a new one
212	$w = AnyEvent->timer (after => 1, cb => $cb);	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		249	warn "timeout\n";
213	};	250	};
214
215	# start the "loop" by creating the first watcher
216	$w = AnyEvent->timer (after => 0.5, cb => $cb);
217		251
218	=head3 TIMING ISSUES	252	=head3 TIMING ISSUES
219		253
220	There are two ways to handle timers: based on real time (relative, "fire	254	There are two ways to handle timers: based on real time (relative, "fire
221	in 10 seconds") and based on wallclock time (absolute, "fire at 12	255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
233	timers.	267	timers.
234		268
235	AnyEvent always prefers relative timers, if available, matching the	269	AnyEvent always prefers relative timers, if available, matching the
236	AnyEvent API.	270	AnyEvent API.
237		271
		272	AnyEvent has two additional methods that return the "current time":
		273
		274	=over 4
		275
		276	=item AnyEvent->time
		277
		278	This returns the "current wallclock time" as a fractional number of
		279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		280	return, and the result is guaranteed to be compatible with those).
		281
		282	It progresses independently of any event loop processing, i.e. each call
		283	will check the system clock, which usually gets updated frequently.
		284
		285	=item AnyEvent->now
		286
		287	This also returns the "current wallclock time", but unlike C<time>, above,
		288	this value might change only once per event loop iteration, depending on
		289	the event loop (most return the same time as C<time>, above). This is the
		290	time that AnyEvent's timers get scheduled against.
		291
		292	I<In almost all cases (in all cases if you don't care), this is the
		293	function to call when you want to know the current time.>
		294
		295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
		301
		302	For a practical example of when these times differ, consider L<Event::Lib>
		303	and L<EV> and the following set-up:
		304
		305	The event loop is running and has just invoked one of your callback at
		306	time=500 (assume no other callbacks delay processing). In your callback,
		307	you wait a second by executing C<sleep 1> (blocking the process for a
		308	second) and then (at time=501) you create a relative timer that fires
		309	after three seconds.
		310
		311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		312	both return C<501>, because that is the current time, and the timer will
		313	be scheduled to fire at time=504 (C<501> + C<3>).
		314
		315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		317	last event processing phase started. With L<EV>, your timer gets scheduled
		318	to run at time=503 (C<500> + C<3>).
		319
		320	In one sense, L<Event::Lib> is more exact, as it uses the current time
		321	regardless of any delays introduced by event processing. However, most
		322	callbacks do not expect large delays in processing, so this causes a
		323	higher drift (and a lot more system calls to get the current time).
		324
		325	In another sense, L<EV> is more exact, as your timer will be scheduled at
		326	the same time, regardless of how long event processing actually took.
		327
		328	In either case, if you care (and in most cases, you don't), then you
		329	can get whatever behaviour you want with any event loop, by taking the
		330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		331	account.
		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
		348	=back
		349
238	=head2 SIGNAL WATCHERS	350	=head2 SIGNAL WATCHERS
239		351
240	You can watch for signals using a signal watcher, C<signal> is the signal	352	You can watch for signals using a signal watcher, C<signal> is the signal
241	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
242	be invoked whenever a signal occurs.	354	callback to be invoked whenever a signal occurs.
243		355
244	Although the callback might get passed parameters, their value and	356	Although the callback might get passed parameters, their value and
245	presence is undefined and you cannot rely on them. Portable AnyEvent	357	presence is undefined and you cannot rely on them. Portable AnyEvent
246	callbacks cannot use arguments passed to signal watcher callbacks.	358	callbacks cannot use arguments passed to signal watcher callbacks.
247		359
…		…
249	invocation, and callback invocation will be synchronous. Synchronous means	361	invocation, and callback invocation will be synchronous. Synchronous means
250	that it might take a while until the signal gets handled by the process,	362	that it might take a while until the signal gets handled by the process,
251	but it is guaranteed not to interrupt any other callbacks.	363	but it is guaranteed not to interrupt any other callbacks.
252		364
253	The main advantage of using these watchers is that you can share a signal	365	The main advantage of using these watchers is that you can share a signal
254	between multiple watchers.	366	between multiple watchers, and AnyEvent will ensure that signals will not
		367	interrupt your program at bad times.
255		368
256	This watcher might use C<%SIG>, so programs overwriting those signals	369	This watcher might use C<%SIG> (depending on the event loop used),
257	directly will likely not work correctly.	370	so programs overwriting those signals directly will likely not work
		371	correctly.
258		372
259	Example: exit on SIGINT	373	Example: exit on SIGINT
260		374
261	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	375	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
262		376
		377	=head3 Signal Races, Delays and Workarounds
		378
		379	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		380	callbacks to signals in a generic way, which is a pity, as you cannot do
		381	race-free signal handling in perl. AnyEvent will try to do it's best, but
		382	in some cases, signals will be delayed. The maximum time a signal might
		383	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		384	seconds). This variable can be changed only before the first signal
		385	watcher is created, and should be left alone otherwise. Higher values
		386	will cause fewer spurious wake-ups, which is better for power and CPU
		387	saving. All these problems can be avoided by installing the optional
		388	L<Async::Interrupt> module. This will not work with inherently broken
		389	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		390	currently, as POE does it's own workaround with one-second latency). With
		391	those, you just have to suffer the delays.
		392
263	=head2 CHILD PROCESS WATCHERS	393	=head2 CHILD PROCESS WATCHERS
264		394
265	You can also watch on a child process exit and catch its exit status.	395	You can also watch on a child process exit and catch its exit status.
266		396
267	The child process is specified by the C<pid> argument (if set to C<0>, it	397	The child process is specified by the C<pid> argument (if set to C<0>, it
268	watches for any child process exit). The watcher will trigger as often	398	watches for any child process exit). The watcher will triggered only when
269	as status change for the child are received. This works by installing a	399	the child process has finished and an exit status is available, not on
270	signal handler for C<SIGCHLD>. The callback will be called with the pid	400	any trace events (stopped/continued).
271	and exit status (as returned by waitpid), so unlike other watcher types,	401
272	you I<can> rely on child watcher callback arguments.	402	The callback will be called with the pid and exit status (as returned by
		403	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		404	callback arguments.
		405
		406	This watcher type works by installing a signal handler for C<SIGCHLD>,
		407	and since it cannot be shared, nothing else should use SIGCHLD or reap
		408	random child processes (waiting for specific child processes, e.g. inside
		409	C<system>, is just fine).
273		410
274	There is a slight catch to child watchers, however: you usually start them	411	There is a slight catch to child watchers, however: you usually start them
275	I<after> the child process was created, and this means the process could	412	I<after> the child process was created, and this means the process could
276	have exited already (and no SIGCHLD will be sent anymore).	413	have exited already (and no SIGCHLD will be sent anymore).
277		414
278	Not all event models handle this correctly (POE doesn't), but even for	415	Not all event models handle this correctly (neither POE nor IO::Async do,
		416	see their AnyEvent::Impl manpages for details), but even for event models
279	event models that I<do> handle this correctly, they usually need to be	417	that I<do> handle this correctly, they usually need to be loaded before
280	loaded before the process exits (i.e. before you fork in the first place).	418	the process exits (i.e. before you fork in the first place). AnyEvent's
		419	pure perl event loop handles all cases correctly regardless of when you
		420	start the watcher.
281		421
282	This means you cannot create a child watcher as the very first thing in an	422	This means you cannot create a child watcher as the very first
283	AnyEvent program, you I<have> to create at least one watcher before you	423	thing in an AnyEvent program, you I<have> to create at least one
284	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	424	watcher before you C<fork> the child (alternatively, you can call
		425	C<AnyEvent::detect>).
		426
		427	As most event loops do not support waiting for child events, they will be
		428	emulated by AnyEvent in most cases, in which the latency and race problems
		429	mentioned in the description of signal watchers apply.
285		430
286	Example: fork a process and wait for it	431	Example: fork a process and wait for it
287		432
288	my $done = AnyEvent->condvar;	433	my $done = AnyEvent->condvar;
289		434
290	my $pid = fork or exit 5;	435	my $pid = fork or exit 5;
291		436
292	my $w = AnyEvent->child (	437	my $w = AnyEvent->child (
293	pid => $pid,	438	pid => $pid,
294	cb => sub {	439	cb => sub {
295	my ($pid, $status) = @_;	440	my ($pid, $status) = @_;
296	warn "pid $pid exited with status $status";	441	warn "pid $pid exited with status $status";
297	$done->send;	442	$done->send;
298	},	443	},
299	);	444	);
300		445
301	# do something else, then wait for process exit	446	# do something else, then wait for process exit
302	$done->recv;	447	$done->recv;
		448
		449	=head2 IDLE WATCHERS
		450
		451	Sometimes there is a need to do something, but it is not so important
		452	to do it instantly, but only when there is nothing better to do. This
		453	"nothing better to do" is usually defined to be "no other events need
		454	attention by the event loop".
		455
		456	Idle watchers ideally get invoked when the event loop has nothing
		457	better to do, just before it would block the process to wait for new
		458	events. Instead of blocking, the idle watcher is invoked.
		459
		460	Most event loops unfortunately do not really support idle watchers (only
		461	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		462	will simply call the callback "from time to time".
		463
		464	Example: read lines from STDIN, but only process them when the
		465	program is otherwise idle:
		466
		467	my @lines; # read data
		468	my $idle_w;
		469	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		470	push @lines, scalar <STDIN>;
		471
		472	# start an idle watcher, if not already done
		473	$idle_w ||= AnyEvent->idle (cb => sub {
		474	# handle only one line, when there are lines left
		475	if (my $line = shift @lines) {
		476	print "handled when idle: $line";
		477	} else {
		478	# otherwise disable the idle watcher again
		479	undef $idle_w;
		480	}
		481	});
		482	});
303		483
304	=head2 CONDITION VARIABLES	484	=head2 CONDITION VARIABLES
305		485
306	If you are familiar with some event loops you will know that all of them	486	If you are familiar with some event loops you will know that all of them
307	require you to run some blocking "loop", "run" or similar function that	487	require you to run some blocking "loop", "run" or similar function that
308	will actively watch for new events and call your callbacks.	488	will actively watch for new events and call your callbacks.
309		489
310	AnyEvent is different, it expects somebody else to run the event loop and	490	AnyEvent is slightly different: it expects somebody else to run the event
311	will only block when necessary (usually when told by the user).	491	loop and will only block when necessary (usually when told by the user).
312		492
313	The instrument to do that is called a "condition variable", so called	493	The instrument to do that is called a "condition variable", so called
314	because they represent a condition that must become true.	494	because they represent a condition that must become true.
		495
		496	Now is probably a good time to look at the examples further below.
315		497
316	Condition variables can be created by calling the C<< AnyEvent->condvar	498	Condition variables can be created by calling the C<< AnyEvent->condvar
317	>> method, usually without arguments. The only argument pair allowed is	499	>> method, usually without arguments. The only argument pair allowed is
318	C<cb>, which specifies a callback to be called when the condition variable	500	C<cb>, which specifies a callback to be called when the condition variable
319	becomes true.	501	becomes true, with the condition variable as the first argument (but not
		502	the results).
320		503
321	After creation, the condition variable is "false" until it becomes "true"	504	After creation, the condition variable is "false" until it becomes "true"
322	by calling the C<send> method (or calling the condition variable as if it	505	by calling the C<send> method (or calling the condition variable as if it
323	were a callback, read about the caveats in the description for the C<<	506	were a callback, read about the caveats in the description for the C<<
324	->send >> method).	507	->send >> method).
…		…
370	after => 1,	553	after => 1,
371	cb => sub { $result_ready->send },	554	cb => sub { $result_ready->send },
372	);	555	);
373		556
374	# this "blocks" (while handling events) till the callback	557	# this "blocks" (while handling events) till the callback
375	# calls send	558	# calls -<send
376	$result_ready->recv;	559	$result_ready->recv;
377		560
378	Example: wait for a timer, but take advantage of the fact that	561	Example: wait for a timer, but take advantage of the fact that condition
379	condition variables are also code references.	562	variables are also callable directly.
380		563
381	my $done = AnyEvent->condvar;	564	my $done = AnyEvent->condvar;
382	my $delay = AnyEvent->timer (after => 5, cb => $done);	565	my $delay = AnyEvent->timer (after => 5, cb => $done);
383	$done->recv;	566	$done->recv;
		567
		568	Example: Imagine an API that returns a condvar and doesn't support
		569	callbacks. This is how you make a synchronous call, for example from
		570	the main program:
		571
		572	use AnyEvent::CouchDB;
		573
		574	...
		575
		576	my @info = $couchdb->info->recv;
		577
		578	And this is how you would just set a callback to be called whenever the
		579	results are available:
		580
		581	$couchdb->info->cb (sub {
		582	my @info = $_[0]->recv;
		583	});
384		584
385	=head3 METHODS FOR PRODUCERS	585	=head3 METHODS FOR PRODUCERS
386		586
387	These methods should only be used by the producing side, i.e. the	587	These methods should only be used by the producing side, i.e. the
388	code/module that eventually sends the signal. Note that it is also	588	code/module that eventually sends the signal. Note that it is also
…		…
401	immediately from within send.	601	immediately from within send.
402		602
403	Any arguments passed to the C<send> call will be returned by all	603	Any arguments passed to the C<send> call will be returned by all
404	future C<< ->recv >> calls.	604	future C<< ->recv >> calls.
405		605
406	Condition variables are overloaded so one can call them directly	606	Condition variables are overloaded so one can call them directly (as if
407	(as a code reference). Calling them directly is the same as calling	607	they were a code reference). Calling them directly is the same as calling
408	C<send>. Note, however, that many C-based event loops do not handle	608	C<send>.
409	overloading, so as tempting as it may be, passing a condition variable
410	instead of a callback does not work. Both the pure perl and EV loops
411	support overloading, however, as well as all functions that use perl to
412	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
413	example).
414		609
415	=item $cv->croak ($error)	610	=item $cv->croak ($error)
416		611
417	Similar to send, but causes all call's to C<< ->recv >> to invoke	612	Similar to send, but causes all call's to C<< ->recv >> to invoke
418	C<Carp::croak> with the given error message/object/scalar.	613	C<Carp::croak> with the given error message/object/scalar.
419		614
420	This can be used to signal any errors to the condition variable	615	This can be used to signal any errors to the condition variable
421	user/consumer.	616	user/consumer. Doing it this way instead of calling C<croak> directly
		617	delays the error detetcion, but has the overwhelmign advantage that it
		618	diagnoses the error at the place where the result is expected, and not
		619	deep in some event clalback without connection to the actual code causing
		620	the problem.
422		621
423	=item $cv->begin ([group callback])	622	=item $cv->begin ([group callback])
424		623
425	=item $cv->end	624	=item $cv->end
426
427	These two methods are EXPERIMENTAL and MIGHT CHANGE.
428		625
429	These two methods can be used to combine many transactions/events into	626	These two methods can be used to combine many transactions/events into
430	one. For example, a function that pings many hosts in parallel might want	627	one. For example, a function that pings many hosts in parallel might want
431	to use a condition variable for the whole process.	628	to use a condition variable for the whole process.
432		629
…		…
434	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	631	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
435	>>, the (last) callback passed to C<begin> will be executed. That callback	632	>>, the (last) callback passed to C<begin> will be executed. That callback
436	is I<supposed> to call C<< ->send >>, but that is not required. If no	633	is I<supposed> to call C<< ->send >>, but that is not required. If no
437	callback was set, C<send> will be called without any arguments.	634	callback was set, C<send> will be called without any arguments.
438		635
439	Let's clarify this with the ping example:	636	You can think of C<< $cv->send >> giving you an OR condition (one call
		637	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		638	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		639
		640	Let's start with a simple example: you have two I/O watchers (for example,
		641	STDOUT and STDERR for a program), and you want to wait for both streams to
		642	close before activating a condvar:
		643
		644	my $cv = AnyEvent->condvar;
		645
		646	$cv->begin; # first watcher
		647	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		648	defined sysread $fh1, my $buf, 4096
		649	or $cv->end;
		650	});
		651
		652	$cv->begin; # second watcher
		653	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		654	defined sysread $fh2, my $buf, 4096
		655	or $cv->end;
		656	});
		657
		658	$cv->recv;
		659
		660	This works because for every event source (EOF on file handle), there is
		661	one call to C<begin>, so the condvar waits for all calls to C<end> before
		662	sending.
		663
		664	The ping example mentioned above is slightly more complicated, as the
		665	there are results to be passwd back, and the number of tasks that are
		666	begung can potentially be zero:
440		667
441	my $cv = AnyEvent->condvar;	668	my $cv = AnyEvent->condvar;
442		669
443	my %result;	670	my %result;
444	$cv->begin (sub { $cv->send (\%result) });	671	$cv->begin (sub { $cv->send (\%result) });
…		…
464	loop, which serves two important purposes: first, it sets the callback	691	loop, which serves two important purposes: first, it sets the callback
465	to be called once the counter reaches C<0>, and second, it ensures that	692	to be called once the counter reaches C<0>, and second, it ensures that
466	C<send> is called even when C<no> hosts are being pinged (the loop	693	C<send> is called even when C<no> hosts are being pinged (the loop
467	doesn't execute once).	694	doesn't execute once).
468		695
469	This is the general pattern when you "fan out" into multiple subrequests:	696	This is the general pattern when you "fan out" into multiple (but
470	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	697	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
471	is called at least once, and then, for each subrequest you start, call	698	the callback and ensure C<end> is called at least once, and then, for each
472	C<begin> and for each subrequest you finish, call C<end>.	699	subrequest you start, call C<begin> and for each subrequest you finish,
		700	call C<end>.
473		701
474	=back	702	=back
475		703
476	=head3 METHODS FOR CONSUMERS	704	=head3 METHODS FOR CONSUMERS
477		705
…		…
493	function will call C<croak>.	721	function will call C<croak>.
494		722
495	In list context, all parameters passed to C<send> will be returned,	723	In list context, all parameters passed to C<send> will be returned,
496	in scalar context only the first one will be returned.	724	in scalar context only the first one will be returned.
497		725
		726	Note that doing a blocking wait in a callback is not supported by any
		727	event loop, that is, recursive invocation of a blocking C<< ->recv
		728	>> is not allowed, and the C<recv> call will C<croak> if such a
		729	condition is detected. This condition can be slightly loosened by using
		730	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		731	any thread that doesn't run the event loop itself.
		732
498	Not all event models support a blocking wait - some die in that case	733	Not all event models support a blocking wait - some die in that case
499	(programs might want to do that to stay interactive), so I<if you are	734	(programs might want to do that to stay interactive), so I<if you are
500	using this from a module, never require a blocking wait>, but let the	735	using this from a module, never require a blocking wait>. Instead, let the
501	caller decide whether the call will block or not (for example, by coupling	736	caller decide whether the call will block or not (for example, by coupling
502	condition variables with some kind of request results and supporting	737	condition variables with some kind of request results and supporting
503	callbacks so the caller knows that getting the result will not block,	738	callbacks so the caller knows that getting the result will not block,
504	while still supporting blocking waits if the caller so desires).	739	while still supporting blocking waits if the caller so desires).
505		740
506	Another reason I<never> to C<< ->recv >> in a module is that you cannot
507	sensibly have two C<< ->recv >>'s in parallel, as that would require
508	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
509	can supply.
510
511	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
512	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
513	versions and also integrates coroutines into AnyEvent, making blocking
514	C<< ->recv >> calls perfectly safe as long as they are done from another
515	coroutine (one that doesn't run the event loop).
516
517	You can ensure that C<< -recv >> never blocks by setting a callback and	741	You can ensure that C<< -recv >> never blocks by setting a callback and
518	only calling C<< ->recv >> from within that callback (or at a later	742	only calling C<< ->recv >> from within that callback (or at a later
519	time). This will work even when the event loop does not support blocking	743	time). This will work even when the event loop does not support blocking
520	waits otherwise.	744	waits otherwise.
521		745
522	=item $bool = $cv->ready	746	=item $bool = $cv->ready
523		747
524	Returns true when the condition is "true", i.e. whether C<send> or	748	Returns true when the condition is "true", i.e. whether C<send> or
525	C<croak> have been called.	749	C<croak> have been called.
526		750
527	=item $cb = $cv->cb ([new callback])	751	=item $cb = $cv->cb ($cb->($cv))
528		752
529	This is a mutator function that returns the callback set and optionally	753	This is a mutator function that returns the callback set and optionally
530	replaces it before doing so.	754	replaces it before doing so.
531		755
532	The callback will be called when the condition becomes "true", i.e. when	756	The callback will be called when the condition becomes "true", i.e. when
533	C<send> or C<croak> are called. Calling C<recv> inside the callback	757	C<send> or C<croak> are called, with the only argument being the condition
534	or at any later time is guaranteed not to block.	758	variable itself. Calling C<recv> inside the callback or at any later time
		759	is guaranteed not to block.
535		760
536	=back	761	=back
537		762
		763	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		764
		765	The available backend classes are (every class has its own manpage):
		766
		767	=over 4
		768
		769	=item Backends that are autoprobed when no other event loop can be found.
		770
		771	EV is the preferred backend when no other event loop seems to be in
		772	use. If EV is not installed, then AnyEvent will try Event, and, failing
		773	that, will fall back to its own pure-perl implementation, which is
		774	available everywhere as it comes with AnyEvent itself.
		775
		776	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		777	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		778	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		779
		780	=item Backends that are transparently being picked up when they are used.
		781
		782	These will be used when they are currently loaded when the first watcher
		783	is created, in which case it is assumed that the application is using
		784	them. This means that AnyEvent will automatically pick the right backend
		785	when the main program loads an event module before anything starts to
		786	create watchers. Nothing special needs to be done by the main program.
		787
		788	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		789	AnyEvent::Impl::Tk based on Tk, very broken.
		790	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		791	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		792
		793	=item Backends with special needs.
		794
		795	Qt requires the Qt::Application to be instantiated first, but will
		796	otherwise be picked up automatically. As long as the main program
		797	instantiates the application before any AnyEvent watchers are created,
		798	everything should just work.
		799
		800	AnyEvent::Impl::Qt based on Qt.
		801
		802	Support for IO::Async can only be partial, as it is too broken and
		803	architecturally limited to even support the AnyEvent API. It also
		804	is the only event loop that needs the loop to be set explicitly, so
		805	it can only be used by a main program knowing about AnyEvent. See
		806	L<AnyEvent::Impl::Async> for the gory details.
		807
		808	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		809
		810	=item Event loops that are indirectly supported via other backends.
		811
		812	Some event loops can be supported via other modules:
		813
		814	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		815
		816	B<WxWidgets> has no support for watching file handles. However, you can
		817	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		818	polls 20 times per second, which was considered to be too horrible to even
		819	consider for AnyEvent.
		820
		821	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		822	backend, so it can be supported through POE.
		823
		824	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		825	load L<POE> when detecting them, in the hope that POE will pick them up,
		826	in which case everything will be automatic.
		827
		828	=back
		829
538	=head1 GLOBAL VARIABLES AND FUNCTIONS	830	=head1 GLOBAL VARIABLES AND FUNCTIONS
539		831
		832	These are not normally required to use AnyEvent, but can be useful to
		833	write AnyEvent extension modules.
		834
540	=over 4	835	=over 4
541		836
542	=item $AnyEvent::MODEL	837	=item $AnyEvent::MODEL
543		838
544	Contains C<undef> until the first watcher is being created. Then it	839	Contains C<undef> until the first watcher is being created, before the
		840	backend has been autodetected.
		841
545	contains the event model that is being used, which is the name of the	842	Afterwards it contains the event model that is being used, which is the
546	Perl class implementing the model. This class is usually one of the	843	name of the Perl class implementing the model. This class is usually one
547	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	844	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
548	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	845	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
549		846	will be C<urxvt::anyevent>).
550	The known classes so far are:
551
552	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
553	AnyEvent::Impl::Event based on Event, second best choice.
554	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
555	AnyEvent::Impl::Glib based on Glib, third-best choice.
556	AnyEvent::Impl::Tk based on Tk, very bad choice.
557	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
558	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
559	AnyEvent::Impl::POE based on POE, not generic enough for full support.
560
561	There is no support for WxWidgets, as WxWidgets has no support for
562	watching file handles. However, you can use WxWidgets through the
563	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
564	second, which was considered to be too horrible to even consider for
565	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
566	it's adaptor.
567
568	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
569	autodetecting them.
570		847
571	=item AnyEvent::detect	848	=item AnyEvent::detect
572		849
573	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	850	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
574	if necessary. You should only call this function right before you would	851	if necessary. You should only call this function right before you would
575	have created an AnyEvent watcher anyway, that is, as late as possible at	852	have created an AnyEvent watcher anyway, that is, as late as possible at
576	runtime.	853	runtime, and not e.g. while initialising of your module.
		854
		855	If you need to do some initialisation before AnyEvent watchers are
		856	created, use C<post_detect>.
577		857
578	=item $guard = AnyEvent::post_detect { BLOCK }	858	=item $guard = AnyEvent::post_detect { BLOCK }
579		859
580	Arranges for the code block to be executed as soon as the event model is	860	Arranges for the code block to be executed as soon as the event model is
581	autodetected (or immediately if this has already happened).	861	autodetected (or immediately if this has already happened).
		862
		863	The block will be executed I<after> the actual backend has been detected
		864	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		865	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		866	other initialisations - see the sources of L<AnyEvent::Strict> or
		867	L<AnyEvent::AIO> to see how this is used.
		868
		869	The most common usage is to create some global watchers, without forcing
		870	event module detection too early, for example, L<AnyEvent::AIO> creates
		871	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		872	avoid autodetecting the event module at load time.
582		873
583	If called in scalar or list context, then it creates and returns an object	874	If called in scalar or list context, then it creates and returns an object
584	that automatically removes the callback again when it is destroyed. See	875	that automatically removes the callback again when it is destroyed. See
585	L<Coro::BDB> for a case where this is useful.	876	L<Coro::BDB> for a case where this is useful.
586		877
…		…
589	If there are any code references in this array (you can C<push> to it	880	If there are any code references in this array (you can C<push> to it
590	before or after loading AnyEvent), then they will called directly after	881	before or after loading AnyEvent), then they will called directly after
591	the event loop has been chosen.	882	the event loop has been chosen.
592		883
593	You should check C<$AnyEvent::MODEL> before adding to this array, though:	884	You should check C<$AnyEvent::MODEL> before adding to this array, though:
594	if it contains a true value then the event loop has already been detected,	885	if it is defined then the event loop has already been detected, and the
595	and the array will be ignored.	886	array will be ignored.
596		887
597	Best use C<AnyEvent::post_detect { BLOCK }> instead.	888	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		889	it,as it takes care of these details.
		890
		891	This variable is mainly useful for modules that can do something useful
		892	when AnyEvent is used and thus want to know when it is initialised, but do
		893	not need to even load it by default. This array provides the means to hook
		894	into AnyEvent passively, without loading it.
598		895
599	=back	896	=back
600		897
601	=head1 WHAT TO DO IN A MODULE	898	=head1 WHAT TO DO IN A MODULE
602		899
…		…
657		954
658		955
659	=head1 OTHER MODULES	956	=head1 OTHER MODULES
660		957
661	The following is a non-exhaustive list of additional modules that use	958	The following is a non-exhaustive list of additional modules that use
662	AnyEvent and can therefore be mixed easily with other AnyEvent modules	959	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
663	in the same program. Some of the modules come with AnyEvent, some are	960	modules and other event loops in the same program. Some of the modules
664	available via CPAN.	961	come with AnyEvent, most are available via CPAN.
665		962
666	=over 4	963	=over 4
667		964
668	=item L<AnyEvent::Util>	965	=item L<AnyEvent::Util>
669		966
670	Contains various utility functions that replace often-used but blocking	967	Contains various utility functions that replace often-used but blocking
671	functions such as C<inet_aton> by event-/callback-based versions.	968	functions such as C<inet_aton> by event-/callback-based versions.
672
673	=item L<AnyEvent::Handle>
674
675	Provide read and write buffers and manages watchers for reads and writes.
676		969
677	=item L<AnyEvent::Socket>	970	=item L<AnyEvent::Socket>
678		971
679	Provides various utility functions for (internet protocol) sockets,	972	Provides various utility functions for (internet protocol) sockets,
680	addresses and name resolution. Also functions to create non-blocking tcp	973	addresses and name resolution. Also functions to create non-blocking tcp
681	connections or tcp servers, with IPv6 and SRV record support and more.	974	connections or tcp servers, with IPv6 and SRV record support and more.
682		975
		976	=item L<AnyEvent::Handle>
		977
		978	Provide read and write buffers, manages watchers for reads and writes,
		979	supports raw and formatted I/O, I/O queued and fully transparent and
		980	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		981
683	=item L<AnyEvent::DNS>	982	=item L<AnyEvent::DNS>
684		983
685	Provides rich asynchronous DNS resolver capabilities.	984	Provides rich asynchronous DNS resolver capabilities.
686		985
		986	=item L<AnyEvent::HTTP>
		987
		988	A simple-to-use HTTP library that is capable of making a lot of concurrent
		989	HTTP requests.
		990
687	=item L<AnyEvent::HTTPD>	991	=item L<AnyEvent::HTTPD>
688		992
689	Provides a simple web application server framework.	993	Provides a simple web application server framework.
690		994
691	=item L<AnyEvent::FastPing>	995	=item L<AnyEvent::FastPing>
692		996
693	The fastest ping in the west.	997	The fastest ping in the west.
694		998
		999	=item L<AnyEvent::DBI>
		1000
		1001	Executes L<DBI> requests asynchronously in a proxy process.
		1002
		1003	=item L<AnyEvent::AIO>
		1004
		1005	Truly asynchronous I/O, should be in the toolbox of every event
		1006	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1007	together.
		1008
		1009	=item L<AnyEvent::BDB>
		1010
		1011	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1012	L<BDB> and AnyEvent together.
		1013
		1014	=item L<AnyEvent::GPSD>
		1015
		1016	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1017
695	=item L<Net::IRC3>	1018	=item L<AnyEvent::IRC>
696		1019
697	AnyEvent based IRC client module family.	1020	AnyEvent based IRC client module family (replacing the older Net::IRC3).
698		1021
699	=item L<Net::XMPP2>	1022	=item L<AnyEvent::XMPP>
700		1023
701	AnyEvent based XMPP (Jabber protocol) module family.	1024	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1025	Net::XMPP2>.
		1026
		1027	=item L<AnyEvent::IGS>
		1028
		1029	A non-blocking interface to the Internet Go Server protocol (used by
		1030	L<App::IGS>).
702		1031
703	=item L<Net::FCP>	1032	=item L<Net::FCP>
704		1033
705	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1034	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
706	of AnyEvent.	1035	of AnyEvent.
…		…
711		1040
712	=item L<Coro>	1041	=item L<Coro>
713		1042
714	Has special support for AnyEvent via L<Coro::AnyEvent>.	1043	Has special support for AnyEvent via L<Coro::AnyEvent>.
715		1044
716	=item L<AnyEvent::AIO>, L<IO::AIO>
717
718	Truly asynchronous I/O, should be in the toolbox of every event
719	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
720	together.
721
722	=item L<AnyEvent::BDB>, L<BDB>
723
724	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
725	IO::AIO and AnyEvent together.
726
727	=item L<IO::Lambda>
728
729	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
730
731	=back	1045	=back
732		1046
733	=cut	1047	=cut
734		1048
735	package AnyEvent;	1049	package AnyEvent;
736		1050
		1051	# basically a tuned-down version of common::sense
		1052	sub common_sense {
737	no warnings;	1053	# no warnings
738	use strict;	1054	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1055	# use strict vars subs
		1056	$^H |= 0x00000600;
		1057	}
739		1058
		1059	BEGIN { AnyEvent::common_sense }
		1060
740	use Carp;	1061	use Carp ();
741		1062
742	our $VERSION = '4.05';	1063	our $VERSION = 4.85;
743	our $MODEL;	1064	our $MODEL;
744		1065
745	our $AUTOLOAD;	1066	our $AUTOLOAD;
746	our @ISA;	1067	our @ISA;
747		1068
748	our @REGISTRY;	1069	our @REGISTRY;
749		1070
750	our $WIN32;	1071	our $WIN32;
751		1072
		1073	our $VERBOSE;
		1074
752	BEGIN {	1075	BEGIN {
753	my $win32 = ! ! ($^O =~ /mswin32/i);	1076	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
754	eval "sub WIN32(){ $win32 }";	1077	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
755	}
756		1078
		1079	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1080	if ${^TAINT};
		1081
757	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1082	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1083
		1084	}
		1085
		1086	our $MAX_SIGNAL_LATENCY = 10;
758		1087
759	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1088	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
760		1089
761	{	1090	{
762	my $idx;	1091	my $idx;
…		…
770	[Event:: => AnyEvent::Impl::Event::],	1099	[Event:: => AnyEvent::Impl::Event::],
771	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1100	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
772	# everything below here will not be autoprobed	1101	# everything below here will not be autoprobed
773	# as the pureperl backend should work everywhere	1102	# as the pureperl backend should work everywhere
774	# and is usually faster	1103	# and is usually faster
775	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
776	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers	1104	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
777	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1105	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1106	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
778	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1107	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
779	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1108	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
780	[Wx:: => AnyEvent::Impl::POE::],	1109	[Wx:: => AnyEvent::Impl::POE::],
781	[Prima:: => AnyEvent::Impl::POE::],	1110	[Prima:: => AnyEvent::Impl::POE::],
		1111	# IO::Async is just too broken - we would need workarounds for its
		1112	# byzantine signal and broken child handling, among others.
		1113	# IO::Async is rather hard to detect, as it doesn't have any
		1114	# obvious default class.
		1115	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1116	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1117	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
782	);	1118	);
783		1119
784	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1120	our %method = map +($_ => 1),
		1121	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
785		1122
786	our @post_detect;	1123	our @post_detect;
787		1124
788	sub post_detect(&) {	1125	sub post_detect(&) {
789	my ($cb) = @_;	1126	my ($cb) = @_;
…		…
794	1	1131	1
795	} else {	1132	} else {
796	push @post_detect, $cb;	1133	push @post_detect, $cb;
797		1134
798	defined wantarray	1135	defined wantarray
799	? bless \$cb, "AnyEvent::Util::PostDetect"	1136	? bless \$cb, "AnyEvent::Util::postdetect"
800	: ()	1137	: ()
801	}	1138	}
802	}	1139	}
803		1140
804	sub AnyEvent::Util::PostDetect::DESTROY {	1141	sub AnyEvent::Util::postdetect::DESTROY {
805	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1142	@post_detect = grep $_ != ${$_[0]}, @post_detect;
806	}	1143	}
807		1144
808	sub detect() {	1145	sub detect() {
809	unless ($MODEL) {	1146	unless ($MODEL) {
810	no strict 'refs';
811	local $SIG{__DIE__};	1147	local $SIG{__DIE__};
812		1148
813	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1149	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
814	my $model = "AnyEvent::Impl::$1";	1150	my $model = "AnyEvent::Impl::$1";
815	if (eval "require $model") {	1151	if (eval "require $model") {
816	$MODEL = $model;	1152	$MODEL = $model;
817	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1153	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
818	} else {	1154	} else {
819	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1155	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
820	}	1156	}
821	}	1157	}
822		1158
823	# check for already loaded models	1159	# check for already loaded models
824	unless ($MODEL) {	1160	unless ($MODEL) {
825	for (@REGISTRY, @models) {	1161	for (@REGISTRY, @models) {
826	my ($package, $model) = @$_;	1162	my ($package, $model) = @$_;
827	if (${"$package\::VERSION"} > 0) {	1163	if (${"$package\::VERSION"} > 0) {
828	if (eval "require $model") {	1164	if (eval "require $model") {
829	$MODEL = $model;	1165	$MODEL = $model;
830	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1166	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
831	last;	1167	last;
832	}	1168	}
833	}	1169	}
834	}	1170	}
835		1171
…		…
840	my ($package, $model) = @$_;	1176	my ($package, $model) = @$_;
841	if (eval "require $package"	1177	if (eval "require $package"
842	and ${"$package\::VERSION"} > 0	1178	and ${"$package\::VERSION"} > 0
843	and eval "require $model") {	1179	and eval "require $model") {
844	$MODEL = $model;	1180	$MODEL = $model;
845	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1181	warn "AnyEvent: autoprobed model '$model', using it.\n" if $VERBOSE >= 2;
846	last;	1182	last;
847	}	1183	}
848	}	1184	}
849		1185
850	$MODEL	1186	$MODEL
851	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1187	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
852	}	1188	}
853	}	1189	}
854		1190
		1191	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1192
855	unshift @ISA, $MODEL;	1193	unshift @ISA, $MODEL;
856	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1194
		1195	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
857		1196
858	(shift @post_detect)->() while @post_detect;	1197	(shift @post_detect)->() while @post_detect;
859	}	1198	}
860		1199
861	$MODEL	1200	$MODEL
…		…
863		1202
864	sub AUTOLOAD {	1203	sub AUTOLOAD {
865	(my $func = $AUTOLOAD) =~ s/.*://;	1204	(my $func = $AUTOLOAD) =~ s/.*://;
866		1205
867	$method{$func}	1206	$method{$func}
868	or croak "$func: not a valid method for AnyEvent objects";	1207	or Carp::croak "$func: not a valid method for AnyEvent objects";
869		1208
870	detect unless $MODEL;	1209	detect unless $MODEL;
871		1210
872	my $class = shift;	1211	my $class = shift;
873	$class->$func (@_);	1212	$class->$func (@_);
874	}	1213	}
875		1214
		1215	# utility function to dup a filehandle. this is used by many backends
		1216	# to support binding more than one watcher per filehandle (they usually
		1217	# allow only one watcher per fd, so we dup it to get a different one).
		1218	sub _dupfh($$;$$) {
		1219	my ($poll, $fh, $r, $w) = @_;
		1220
		1221	# cygwin requires the fh mode to be matching, unix doesn't
		1222	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1223
		1224	open my $fh2, $mode, $fh
		1225	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1226
		1227	# we assume CLOEXEC is already set by perl in all important cases
		1228
		1229	($fh2, $rw)
		1230	}
		1231
876	package AnyEvent::Base;	1232	package AnyEvent::Base;
877		1233
		1234	# default implementations for many methods
		1235
		1236	sub _time {
		1237	# probe for availability of Time::HiRes
		1238	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1239	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1240	*_time = \&Time::HiRes::time;
		1241	# if (eval "use POSIX (); (POSIX::times())...
		1242	} else {
		1243	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1244	*_time = sub { time }; # epic fail
		1245	}
		1246
		1247	&_time
		1248	}
		1249
		1250	sub time { _time }
		1251	sub now { _time }
		1252	sub now_update { }
		1253
878	# default implementation for ->condvar	1254	# default implementation for ->condvar
879		1255
880	sub condvar {	1256	sub condvar {
881	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1257	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
882	}	1258	}
883		1259
884	# default implementation for ->signal	1260	# default implementation for ->signal
885		1261
886	our %SIG_CB;	1262	our $HAVE_ASYNC_INTERRUPT;
		1263	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1264	our (%SIG_ASY, %SIG_ASY_W);
		1265	our ($SIG_COUNT, $SIG_TW);
887		1266
		1267	sub _signal_exec {
		1268	$HAVE_ASYNC_INTERRUPT
		1269	? $SIGPIPE_R->drain
		1270	: sysread $SIGPIPE_R, my $dummy, 9;
		1271
		1272	while (%SIG_EV) {
		1273	for (keys %SIG_EV) {
		1274	delete $SIG_EV{$_};
		1275	$_->() for values %{ $SIG_CB{$_} || {} };
		1276	}
		1277	}
		1278	}
		1279
		1280	# install a dumym wakeupw atcher to reduce signal catching latency
		1281	sub _sig_add() {
		1282	unless ($SIG_COUNT++) {
		1283	# try to align timer on a full-second boundary, if possible
		1284	my $NOW = AnyEvent->now;
		1285
		1286	$SIG_TW = AnyEvent->timer (
		1287	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1288	interval => $MAX_SIGNAL_LATENCY,
		1289	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1290	);
		1291	}
		1292	}
		1293
		1294	sub _sig_del {
		1295	undef $SIG_TW
		1296	unless --$SIG_COUNT;
		1297	}
		1298
888	sub signal {	1299	sub _signal {
889	my (undef, %arg) = @_;	1300	my (undef, %arg) = @_;
890		1301
891	my $signal = uc $arg{signal}	1302	my $signal = uc $arg{signal}
892	or Carp::croak "required option 'signal' is missing";	1303	or Carp::croak "required option 'signal' is missing";
893		1304
894	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1305	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1306
		1307	if ($HAVE_ASYNC_INTERRUPT) {
		1308	# async::interrupt
		1309
		1310	$SIG_ASY{$signal} ||= do {
		1311	my $asy = new Async::Interrupt
		1312	cb => sub { undef $SIG_EV{$signal} },
		1313	signal => $signal,
		1314	pipe => [$SIGPIPE_R->filenos],
		1315	;
		1316	$asy->pipe_autodrain (0);
		1317
		1318	$asy
		1319	};
		1320
		1321	} else {
		1322	# pure perl
		1323
895	$SIG{$signal} ||= sub {	1324	$SIG{$signal} ||= sub {
896	$_->() for values %{ $SIG_CB{$signal} || {} };	1325	local $!;
		1326	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1327	undef $SIG_EV{$signal};
		1328	};
		1329
		1330	# can't do signal processing without introducing races in pure perl,
		1331	# so limit the signal latency.
		1332	_sig_add;
897	};	1333	}
898		1334
899	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1335	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
900	}	1336	}
901		1337
		1338	sub signal {
		1339	# probe for availability of Async::Interrupt
		1340	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1341	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1342
		1343	$HAVE_ASYNC_INTERRUPT = 1;
		1344	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1345	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1346
		1347	} else {
		1348	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1349
		1350	require Fcntl;
		1351
		1352	if (AnyEvent::WIN32) {
		1353	require AnyEvent::Util;
		1354
		1355	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1356	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1357	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1358	} else {
		1359	pipe $SIGPIPE_R, $SIGPIPE_W;
		1360	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1361	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1362
		1363	# not strictly required, as $^F is normally 2, but let's make sure...
		1364	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1365	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1366	}
		1367
		1368	$SIGPIPE_R
		1369	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1370
		1371	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1372	}
		1373
		1374	*signal = \&_signal;
		1375	&signal
		1376	}
		1377
902	sub AnyEvent::Base::Signal::DESTROY {	1378	sub AnyEvent::Base::signal::DESTROY {
903	my ($signal, $cb) = @{$_[0]};	1379	my ($signal, $cb) = @{$_[0]};
904		1380
		1381	_sig_del;
		1382
905	delete $SIG_CB{$signal}{$cb};	1383	delete $SIG_CB{$signal}{$cb};
906		1384
907	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1385	$HAVE_ASYNC_INTERRUPT
		1386	? delete $SIG_ASY{$signal}
		1387	: # delete doesn't work with older perls - they then
		1388	# print weird messages, or just unconditionally exit
		1389	# instead of getting the default action.
		1390	undef $SIG{$signal}
		1391	unless keys %{ $SIG_CB{$signal} };
908	}	1392	}
909		1393
910	# default implementation for ->child	1394	# default implementation for ->child
911		1395
912	our %PID_CB;	1396	our %PID_CB;
913	our $CHLD_W;	1397	our $CHLD_W;
914	our $CHLD_DELAY_W;	1398	our $CHLD_DELAY_W;
915	our $PID_IDLE;
916	our $WNOHANG;	1399	our $WNOHANG;
917		1400
918	sub _child_wait {	1401	sub _sigchld {
919	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1402	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		1403	$_->($pid, $?)
920	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1404	for values %{ $PID_CB{$pid} || {} },
921	(values %{ $PID_CB{0} || {} });	1405	values %{ $PID_CB{0} || {} };
922	}	1406	}
923
924	undef $PID_IDLE;
925	}
926
927	sub _sigchld {
928	# make sure we deliver these changes "synchronous" with the event loop.
929	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
930	undef $CHLD_DELAY_W;
931	&_child_wait;
932	});
933	}	1407	}
934		1408
935	sub child {	1409	sub child {
936	my (undef, %arg) = @_;	1410	my (undef, %arg) = @_;
937		1411
938	defined (my $pid = $arg{pid} + 0)	1412	defined (my $pid = $arg{pid} + 0)
939	or Carp::croak "required option 'pid' is missing";	1413	or Carp::croak "required option 'pid' is missing";
940		1414
941	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1415	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
942		1416
943	unless ($WNOHANG) {	1417	# WNOHANG is almost cetrainly 1 everywhere
		1418	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1419	? 1
944	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1420	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
945	}
946		1421
947	unless ($CHLD_W) {	1422	unless ($CHLD_W) {
948	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1423	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
949	# child could be a zombie already, so make at least one round	1424	# child could be a zombie already, so make at least one round
950	&_sigchld;	1425	&_sigchld;
951	}	1426	}
952		1427
953	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1428	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
954	}	1429	}
955		1430
956	sub AnyEvent::Base::Child::DESTROY {	1431	sub AnyEvent::Base::child::DESTROY {
957	my ($pid, $cb) = @{$_[0]};	1432	my ($pid, $cb) = @{$_[0]};
958		1433
959	delete $PID_CB{$pid}{$cb};	1434	delete $PID_CB{$pid}{$cb};
960	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1435	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
961		1436
962	undef $CHLD_W unless keys %PID_CB;	1437	undef $CHLD_W unless keys %PID_CB;
963	}	1438	}
964		1439
		1440	# idle emulation is done by simply using a timer, regardless
		1441	# of whether the process is idle or not, and not letting
		1442	# the callback use more than 50% of the time.
		1443	sub idle {
		1444	my (undef, %arg) = @_;
		1445
		1446	my ($cb, $w, $rcb) = $arg{cb};
		1447
		1448	$rcb = sub {
		1449	if ($cb) {
		1450	$w = _time;
		1451	&$cb;
		1452	$w = _time - $w;
		1453
		1454	# never use more then 50% of the time for the idle watcher,
		1455	# within some limits
		1456	$w = 0.0001 if $w < 0.0001;
		1457	$w = 5 if $w > 5;
		1458
		1459	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1460	} else {
		1461	# clean up...
		1462	undef $w;
		1463	undef $rcb;
		1464	}
		1465	};
		1466
		1467	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1468
		1469	bless \\$cb, "AnyEvent::Base::idle"
		1470	}
		1471
		1472	sub AnyEvent::Base::idle::DESTROY {
		1473	undef $${$_[0]};
		1474	}
		1475
965	package AnyEvent::CondVar;	1476	package AnyEvent::CondVar;
966		1477
967	our @ISA = AnyEvent::CondVar::Base::;	1478	our @ISA = AnyEvent::CondVar::Base::;
968		1479
969	package AnyEvent::CondVar::Base;	1480	package AnyEvent::CondVar::Base;
970		1481
971	use overload	1482	#use overload
972	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1483	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
973	fallback => 1;	1484	# fallback => 1;
		1485
		1486	# save 300+ kilobytes by dirtily hardcoding overloading
		1487	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1488	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1489	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1490	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1491
		1492	our $WAITING;
974		1493
975	sub _send {	1494	sub _send {
976	# nop	1495	# nop
977	}	1496	}
978		1497
…		…
991	sub ready {	1510	sub ready {
992	$_[0]{_ae_sent}	1511	$_[0]{_ae_sent}
993	}	1512	}
994		1513
995	sub _wait {	1514	sub _wait {
		1515	$WAITING
		1516	and !$_[0]{_ae_sent}
		1517	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1518
		1519	local $WAITING = 1;
996	AnyEvent->one_event while !$_[0]{_ae_sent};	1520	AnyEvent->one_event while !$_[0]{_ae_sent};
997	}	1521	}
998		1522
999	sub recv {	1523	sub recv {
1000	$_[0]->_wait;	1524	$_[0]->_wait;
…		…
1019	}	1543	}
1020		1544
1021	# undocumented/compatibility with pre-3.4	1545	# undocumented/compatibility with pre-3.4
1022	*broadcast = \&send;	1546	*broadcast = \&send;
1023	*wait = \&_wait;	1547	*wait = \&_wait;
		1548
		1549	=head1 ERROR AND EXCEPTION HANDLING
		1550
		1551	In general, AnyEvent does not do any error handling - it relies on the
		1552	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1553	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1554	checking of all AnyEvent methods, however, which is highly useful during
		1555	development.
		1556
		1557	As for exception handling (i.e. runtime errors and exceptions thrown while
		1558	executing a callback), this is not only highly event-loop specific, but
		1559	also not in any way wrapped by this module, as this is the job of the main
		1560	program.
		1561
		1562	The pure perl event loop simply re-throws the exception (usually
		1563	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1564	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1565	so on.
		1566
		1567	=head1 ENVIRONMENT VARIABLES
		1568
		1569	The following environment variables are used by this module or its
		1570	submodules.
		1571
		1572	Note that AnyEvent will remove I<all> environment variables starting with
		1573	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1574	enabled.
		1575
		1576	=over 4
		1577
		1578	=item C<PERL_ANYEVENT_VERBOSE>
		1579
		1580	By default, AnyEvent will be completely silent except in fatal
		1581	conditions. You can set this environment variable to make AnyEvent more
		1582	talkative.
		1583
		1584	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1585	conditions, such as not being able to load the event model specified by
		1586	C<PERL_ANYEVENT_MODEL>.
		1587
		1588	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1589	model it chooses.
		1590
		1591	When set to C<8> or higher, then AnyEvent will report extra information on
		1592	which optional modules it loads and how it implements certain features.
		1593
		1594	=item C<PERL_ANYEVENT_STRICT>
		1595
		1596	AnyEvent does not do much argument checking by default, as thorough
		1597	argument checking is very costly. Setting this variable to a true value
		1598	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1599	check the arguments passed to most method calls. If it finds any problems,
		1600	it will croak.
		1601
		1602	In other words, enables "strict" mode.
		1603
		1604	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1605	>>, it is definitely recommended to keep it off in production. Keeping
		1606	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1607	can be very useful, however.
		1608
		1609	=item C<PERL_ANYEVENT_MODEL>
		1610
		1611	This can be used to specify the event model to be used by AnyEvent, before
		1612	auto detection and -probing kicks in. It must be a string consisting
		1613	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1614	and the resulting module name is loaded and if the load was successful,
		1615	used as event model. If it fails to load AnyEvent will proceed with
		1616	auto detection and -probing.
		1617
		1618	This functionality might change in future versions.
		1619
		1620	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1621	could start your program like this:
		1622
		1623	PERL_ANYEVENT_MODEL=Perl perl ...
		1624
		1625	=item C<PERL_ANYEVENT_PROTOCOLS>
		1626
		1627	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1628	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1629	of auto probing).
		1630
		1631	Must be set to a comma-separated list of protocols or address families,
		1632	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1633	used, and preference will be given to protocols mentioned earlier in the
		1634	list.
		1635
		1636	This variable can effectively be used for denial-of-service attacks
		1637	against local programs (e.g. when setuid), although the impact is likely
		1638	small, as the program has to handle conenction and other failures anyways.
		1639
		1640	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1641	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1642	- only support IPv4, never try to resolve or contact IPv6
		1643	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1644	IPv6, but prefer IPv6 over IPv4.
		1645
		1646	=item C<PERL_ANYEVENT_EDNS0>
		1647
		1648	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1649	for DNS. This extension is generally useful to reduce DNS traffic, but
		1650	some (broken) firewalls drop such DNS packets, which is why it is off by
		1651	default.
		1652
		1653	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1654	EDNS0 in its DNS requests.
		1655
		1656	=item C<PERL_ANYEVENT_MAX_FORKS>
		1657
		1658	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1659	will create in parallel.
		1660
		1661	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1662
		1663	The default value for the C<max_outstanding> parameter for the default DNS
		1664	resolver - this is the maximum number of parallel DNS requests that are
		1665	sent to the DNS server.
		1666
		1667	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1668
		1669	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1670	configuration) in the default resolver. When set to the empty string, no
		1671	default config will be used.
		1672
		1673	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1674
		1675	When neither C<ca_file> nor C<ca_path> was specified during
		1676	L<AnyEvent::TLS> context creation, and either of these environment
		1677	variables exist, they will be used to specify CA certificate locations
		1678	instead of a system-dependent default.
		1679
		1680	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1681
		1682	When these are set to C<1>, then the respective modules are not
		1683	loaded. Mostly good for testing AnyEvent itself.
		1684
		1685	=back
1024		1686
1025	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1687	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1026		1688
1027	This is an advanced topic that you do not normally need to use AnyEvent in	1689	This is an advanced topic that you do not normally need to use AnyEvent in
1028	a module. This section is only of use to event loop authors who want to	1690	a module. This section is only of use to event loop authors who want to
…		…
1062		1724
1063	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1725	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1064	condition variables: code blocking while waiting for a condition will	1726	condition variables: code blocking while waiting for a condition will
1065	C<die>. This still works with most modules/usages, and blocking calls must	1727	C<die>. This still works with most modules/usages, and blocking calls must
1066	not be done in an interactive application, so it makes sense.	1728	not be done in an interactive application, so it makes sense.
1067
1068	=head1 ENVIRONMENT VARIABLES
1069
1070	The following environment variables are used by this module:
1071
1072	=over 4
1073
1074	=item C<PERL_ANYEVENT_VERBOSE>
1075
1076	By default, AnyEvent will be completely silent except in fatal
1077	conditions. You can set this environment variable to make AnyEvent more
1078	talkative.
1079
1080	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1081	conditions, such as not being able to load the event model specified by
1082	C<PERL_ANYEVENT_MODEL>.
1083
1084	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1085	model it chooses.
1086
1087	=item C<PERL_ANYEVENT_MODEL>
1088
1089	This can be used to specify the event model to be used by AnyEvent, before
1090	auto detection and -probing kicks in. It must be a string consisting
1091	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1092	and the resulting module name is loaded and if the load was successful,
1093	used as event model. If it fails to load AnyEvent will proceed with
1094	auto detection and -probing.
1095
1096	This functionality might change in future versions.
1097
1098	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1099	could start your program like this:
1100
1101	PERL_ANYEVENT_MODEL=Perl perl ...
1102
1103	=item C<PERL_ANYEVENT_PROTOCOLS>
1104
1105	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1106	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1107	of auto probing).
1108
1109	Must be set to a comma-separated list of protocols or address families,
1110	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1111	used, and preference will be given to protocols mentioned earlier in the
1112	list.
1113
1114	This variable can effectively be used for denial-of-service attacks
1115	against local programs (e.g. when setuid), although the impact is likely
1116	small, as the program has to handle connection errors already-
1117
1118	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1119	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1120	- only support IPv4, never try to resolve or contact IPv6
1121	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1122	IPv6, but prefer IPv6 over IPv4.
1123
1124	=item C<PERL_ANYEVENT_EDNS0>
1125
1126	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1127	for DNS. This extension is generally useful to reduce DNS traffic, but
1128	some (broken) firewalls drop such DNS packets, which is why it is off by
1129	default.
1130
1131	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1132	EDNS0 in its DNS requests.
1133
1134	=item C<PERL_ANYEVENT_MAX_FORKS>
1135
1136	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1137	will create in parallel.
1138
1139	=back
1140		1729
1141	=head1 EXAMPLE PROGRAM	1730	=head1 EXAMPLE PROGRAM
1142		1731
1143	The following program uses an I/O watcher to read data from STDIN, a timer	1732	The following program uses an I/O watcher to read data from STDIN, a timer
1144	to display a message once per second, and a condition variable to quit the	1733	to display a message once per second, and a condition variable to quit the
…		…
1338	watcher.	1927	watcher.
1339		1928
1340	=head3 Results	1929	=head3 Results
1341		1930
1342	name watchers bytes create invoke destroy comment	1931	name watchers bytes create invoke destroy comment
1343	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1932	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1344	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1933	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1345	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1934	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1346	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1935	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1347	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1936	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1348	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1937	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1938	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1939	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1349	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1940	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1350	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1941	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1351	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1942	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1352	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1943	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1353		1944
1354	=head3 Discussion	1945	=head3 Discussion
1355		1946
1356	The benchmark does I<not> measure scalability of the event loop very	1947	The benchmark does I<not> measure scalability of the event loop very
1357	well. For example, a select-based event loop (such as the pure perl one)	1948	well. For example, a select-based event loop (such as the pure perl one)
…		…
1382	performance becomes really bad with lots of file descriptors (and few of	1973	performance becomes really bad with lots of file descriptors (and few of
1383	them active), of course, but this was not subject of this benchmark.	1974	them active), of course, but this was not subject of this benchmark.
1384		1975
1385	The C<Event> module has a relatively high setup and callback invocation	1976	The C<Event> module has a relatively high setup and callback invocation
1386	cost, but overall scores in on the third place.	1977	cost, but overall scores in on the third place.
		1978
		1979	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1980	when using its pure perl backend.
1387		1981
1388	C<Glib>'s memory usage is quite a bit higher, but it features a	1982	C<Glib>'s memory usage is quite a bit higher, but it features a
1389	faster callback invocation and overall ends up in the same class as	1983	faster callback invocation and overall ends up in the same class as
1390	C<Event>. However, Glib scales extremely badly, doubling the number of	1984	C<Event>. However, Glib scales extremely badly, doubling the number of
1391	watchers increases the processing time by more than a factor of four,	1985	watchers increases the processing time by more than a factor of four,
…		…
1469	it to another server. This includes deleting the old timeout and creating	2063	it to another server. This includes deleting the old timeout and creating
1470	a new one that moves the timeout into the future.	2064	a new one that moves the timeout into the future.
1471		2065
1472	=head3 Results	2066	=head3 Results
1473		2067
1474	name sockets create request	2068	name sockets create request
1475	EV 20000 69.01 11.16	2069	EV 20000 69.01 11.16
1476	Perl 20000 73.32 35.87	2070	Perl 20000 73.32 35.87
		2071	IOAsync 20000 157.00 98.14 epoll
		2072	IOAsync 20000 159.31 616.06 poll
1477	Event 20000 212.62 257.32	2073	Event 20000 212.62 257.32
1478	Glib 20000 651.16 1896.30	2074	Glib 20000 651.16 1896.30
1479	POE 20000 349.67 12317.24 uses POE::Loop::Event	2075	POE 20000 349.67 12317.24 uses POE::Loop::Event
1480		2076
1481	=head3 Discussion	2077	=head3 Discussion
1482		2078
1483	This benchmark I<does> measure scalability and overall performance of the	2079	This benchmark I<does> measure scalability and overall performance of the
1484	particular event loop.	2080	particular event loop.
…		…
1486	EV is again fastest. Since it is using epoll on my system, the setup time	2082	EV is again fastest. Since it is using epoll on my system, the setup time
1487	is relatively high, though.	2083	is relatively high, though.
1488		2084
1489	Perl surprisingly comes second. It is much faster than the C-based event	2085	Perl surprisingly comes second. It is much faster than the C-based event
1490	loops Event and Glib.	2086	loops Event and Glib.
		2087
		2088	IO::Async performs very well when using its epoll backend, and still quite
		2089	good compared to Glib when using its pure perl backend.
1491		2090
1492	Event suffers from high setup time as well (look at its code and you will	2091	Event suffers from high setup time as well (look at its code and you will
1493	understand why). Callback invocation also has a high overhead compared to	2092	understand why). Callback invocation also has a high overhead compared to
1494	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2093	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1495	uses select or poll in basically all documented configurations.	2094	uses select or poll in basically all documented configurations.
…		…
1558	=item * C-based event loops perform very well with small number of	2157	=item * C-based event loops perform very well with small number of
1559	watchers, as the management overhead dominates.	2158	watchers, as the management overhead dominates.
1560		2159
1561	=back	2160	=back
1562		2161
		2162	=head2 THE IO::Lambda BENCHMARK
		2163
		2164	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2165	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2166	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2167	shouldn't come as a surprise to anybody). As such, the benchmark is
		2168	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2169	very optimal. But how would AnyEvent compare when used without the extra
		2170	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2171
		2172	The benchmark itself creates an echo-server, and then, for 500 times,
		2173	connects to the echo server, sends a line, waits for the reply, and then
		2174	creates the next connection. This is a rather bad benchmark, as it doesn't
		2175	test the efficiency of the framework or much non-blocking I/O, but it is a
		2176	benchmark nevertheless.
		2177
		2178	name runtime
		2179	Lambda/select 0.330 sec
		2180	+ optimized 0.122 sec
		2181	Lambda/AnyEvent 0.327 sec
		2182	+ optimized 0.138 sec
		2183	Raw sockets/select 0.077 sec
		2184	POE/select, components 0.662 sec
		2185	POE/select, raw sockets 0.226 sec
		2186	POE/select, optimized 0.404 sec
		2187
		2188	AnyEvent/select/nb 0.085 sec
		2189	AnyEvent/EV/nb 0.068 sec
		2190	+state machine 0.134 sec
		2191
		2192	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2193	benchmarks actually make blocking connects and use 100% blocking I/O,
		2194	defeating the purpose of an event-based solution. All of the newly
		2195	written AnyEvent benchmarks use 100% non-blocking connects (using
		2196	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2197	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2198	generally require a lot more bookkeeping and event handling than blocking
		2199	connects (which involve a single syscall only).
		2200
		2201	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2202	offers similar expressive power as POE and IO::Lambda, using conventional
		2203	Perl syntax. This means that both the echo server and the client are 100%
		2204	non-blocking, further placing it at a disadvantage.
		2205
		2206	As you can see, the AnyEvent + EV combination even beats the
		2207	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2208	backend easily beats IO::Lambda and POE.
		2209
		2210	And even the 100% non-blocking version written using the high-level (and
		2211	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2212	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2213	in a non-blocking way.
		2214
		2215	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2216	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2217	part of the IO::lambda distribution and were used without any changes.
		2218
		2219
		2220	=head1 SIGNALS
		2221
		2222	AnyEvent currently installs handlers for these signals:
		2223
		2224	=over 4
		2225
		2226	=item SIGCHLD
		2227
		2228	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2229	emulation for event loops that do not support them natively. Also, some
		2230	event loops install a similar handler.
		2231
		2232	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2233	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2234
		2235	=item SIGPIPE
		2236
		2237	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2238	when AnyEvent gets loaded.
		2239
		2240	The rationale for this is that AnyEvent users usually do not really depend
		2241	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2242	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2243	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2244	some random socket.
		2245
		2246	The rationale for installing a no-op handler as opposed to ignoring it is
		2247	that this way, the handler will be restored to defaults on exec.
		2248
		2249	Feel free to install your own handler, or reset it to defaults.
		2250
		2251	=back
		2252
		2253	=cut
		2254
		2255	undef $SIG{CHLD}
		2256	if $SIG{CHLD} eq 'IGNORE';
		2257
		2258	$SIG{PIPE} = sub { }
		2259	unless defined $SIG{PIPE};
		2260
		2261	=head1 RECOMMENDED/OPTIONAL MODULES
		2262
		2263	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2264	it's built-in modules) are required to use it.
		2265
		2266	That does not mean that AnyEvent won't take advantage of some additional
		2267	modules if they are installed.
		2268
		2269	This section epxlains which additional modules will be used, and how they
		2270	affect AnyEvent's operetion.
		2271
		2272	=over 4
		2273
		2274	=item L<Async::Interrupt>
		2275
		2276	This slightly arcane module is used to implement fast signal handling: To
		2277	my knowledge, there is no way to do completely race-free and quick
		2278	signal handling in pure perl. To ensure that signals still get
		2279	delivered, AnyEvent will start an interval timer to wake up perl (and
		2280	catch the signals) with some delay (default is 10 seconds, look for
		2281	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2282
		2283	If this module is available, then it will be used to implement signal
		2284	catching, which means that signals will not be delayed, and the event loop
		2285	will not be interrupted regularly, which is more efficient (And good for
		2286	battery life on laptops).
		2287
		2288	This affects not just the pure-perl event loop, but also other event loops
		2289	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2290
		2291	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2292	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2293	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2294	does nothing for those backends.
		2295
		2296	=item L<EV>
		2297
		2298	This module isn't really "optional", as it is simply one of the backend
		2299	event loops that AnyEvent can use. However, it is simply the best event
		2300	loop available in terms of features, speed and stability: It supports
		2301	the AnyEvent API optimally, implements all the watcher types in XS, does
		2302	automatic timer adjustments even when no monotonic clock is available,
		2303	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2304	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2305	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2306
		2307	=item L<Guard>
		2308
		2309	The guard module, when used, will be used to implement
		2310	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2311	lot less memory), but otherwise doesn't affect guard operation much. It is
		2312	purely used for performance.
		2313
		2314	=item L<JSON> and L<JSON::XS>
		2315
		2316	This module is required when you want to read or write JSON data via
		2317	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2318	advantage of the ulta-high-speed L<JSON::XS> module when it is installed.
		2319
		2320	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2321	installed.
		2322
		2323	=item L<Net::SSLeay>
		2324
		2325	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2326	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2327	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2328
		2329	=item L<Time::HiRes>
		2330
		2331	This module is part of perl since release 5.008. It will be used when the
		2332	chosen event library does not come with a timing source on it's own. The
		2333	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2334	try to use a monotonic clock for timing stability.
		2335
		2336	=back
		2337
1563		2338
1564	=head1 FORK	2339	=head1 FORK
1565		2340
1566	Most event libraries are not fork-safe. The ones who are usually are	2341	Most event libraries are not fork-safe. The ones who are usually are
1567	because they rely on inefficient but fork-safe C<select> or C<poll>	2342	because they rely on inefficient but fork-safe C<select> or C<poll>
1568	calls. Only L<EV> is fully fork-aware.	2343	calls. Only L<EV> is fully fork-aware.
1569		2344
1570	If you have to fork, you must either do so I<before> creating your first	2345	If you have to fork, you must either do so I<before> creating your first
1571	watcher OR you must not use AnyEvent at all in the child.	2346	watcher OR you must not use AnyEvent at all in the child OR you must do
		2347	something completely out of the scope of AnyEvent.
1572		2348
1573		2349
1574	=head1 SECURITY CONSIDERATIONS	2350	=head1 SECURITY CONSIDERATIONS
1575		2351
1576	AnyEvent can be forced to load any event model via	2352	AnyEvent can be forced to load any event model via
…		…
1581	specified in the variable.	2357	specified in the variable.
1582		2358
1583	You can make AnyEvent completely ignore this variable by deleting it	2359	You can make AnyEvent completely ignore this variable by deleting it
1584	before the first watcher gets created, e.g. with a C<BEGIN> block:	2360	before the first watcher gets created, e.g. with a C<BEGIN> block:
1585		2361
1586	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2362	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1587		2363
1588	use AnyEvent;	2364	use AnyEvent;
1589		2365
1590	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2366	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1591	be used to probe what backend is used and gain other information (which is	2367	be used to probe what backend is used and gain other information (which is
1592	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2368	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2369	$ENV{PERL_ANYEVENT_STRICT}.
		2370
		2371	Note that AnyEvent will remove I<all> environment variables starting with
		2372	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2373	enabled.
		2374
		2375
		2376	=head1 BUGS
		2377
		2378	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2379	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2380	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2381	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2382	pronounced).
1593		2383
1594		2384
1595	=head1 SEE ALSO	2385	=head1 SEE ALSO
1596		2386
1597	Utility functions: L<AnyEvent::Util>.	2387	Utility functions: L<AnyEvent::Util>.
…		…
1600	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2390	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1601		2391
1602	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2392	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1603	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2393	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1604	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2394	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1605	L<AnyEvent::Impl::POE>.	2395	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1606		2396
1607	Non-blocking file handles, sockets, TCP clients and	2397	Non-blocking file handles, sockets, TCP clients and
1608	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2398	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1609		2399
1610	Asynchronous DNS: L<AnyEvent::DNS>.	2400	Asynchronous DNS: L<AnyEvent::DNS>.
1611		2401
1612	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2402	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2403	L<Coro::Event>,
1613		2404
1614	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2405	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2406	L<AnyEvent::HTTP>.
1615		2407
1616		2408
1617	=head1 AUTHOR	2409	=head1 AUTHOR
1618		2410
1619	Marc Lehmann <schmorp@schmorp.de>	2411	Marc Lehmann <schmorp@schmorp.de>
1620	http://home.schmorp.de/	2412	http://home.schmorp.de/
1621		2413
1622	=cut	2414	=cut
1623		2415
1624	1	2416	1
1625		2417

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