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Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC vs.
Revision 1.210 by root, Wed May 13 15:19:43 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, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
		11	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	12	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		13
		14	# one-shot or repeating timers
		15	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		16	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		17
		18	print AnyEvent->now; # prints current event loop time
		19	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		20
		21	# POSIX signal
		22	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		23
		24	# child process exit
		25	my $w = AnyEvent->child (pid => $pid, cb => sub {
		26	my ($pid, $status) = @_;
12	...	27	...
13	});	28	});
14		29
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	30	# called when event loop idle (if applicable)
16	...	31	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		32
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	33	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		34	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	35	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	36	# use a condvar in callback mode:
		37	$w->cb (sub { $_[0]->recv });
		38
		39	=head1 INTRODUCTION/TUTORIAL
		40
		41	This manpage is mainly a reference manual. If you are interested
		42	in a tutorial or some gentle introduction, have a look at the
		43	L<AnyEvent::Intro> manpage.
22		44
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	45	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		46
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	47	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	48	nowadays. So what is different about AnyEvent?
27		49
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	50	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	51	policy> and AnyEvent is I<small and efficient>.
30		52
31	First and foremost, I<AnyEvent is not an event model> itself, it only	53	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	54	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,	55	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,	56	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	57	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	58	cannot change this, but it can hide the differences between those event
		59	loops.
37		60
38	The goal of AnyEvent is to offer module authors the ability to do event	61	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	62	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	63	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	64	module users into the same thing by forcing them to use the same event
42	model you use.	65	model you use.
43		66
44	For modules like POE or IO::Async (which is a total misnomer as it is	67	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	68	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	69	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	70	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	71	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.	72	module are I<also> forced to use the same event loop you use.
50		73
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	74	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	75	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	76	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,	77	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	78	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	79	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	80	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).	81	to AnyEvent, too, so it is future-proof).
59		82
60	In addition to being free of having to use I<the one and only true event	83	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	84	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	85	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	86	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	87	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	88	technically possible.
66		89
		90	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		91	of useful functionality, such as an asynchronous DNS resolver, 100%
		92	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		93	such as Windows) and lots of real-world knowledge and workarounds for
		94	platform bugs and differences.
		95
67	Of course, if you want lots of policy (this can arguably be somewhat	96	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	97	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	98	model, you should I<not> use this module.
70
71	#TODO#
72
73	Net::IRC3
74	AnyEvent::HTTPD
75	AnyEvent::DNS
76	IO::AnyEvent
77	Net::FPing
78	Net::XMPP2
79	Coro
80
81	AnyEvent::IRC
82	AnyEvent::HTTPD
83	AnyEvent::DNS
84	AnyEvent::Handle
85	AnyEvent::Socket
86	AnyEvent::FPing
87	AnyEvent::XMPP
88	AnyEvent::SNMP
89	Coro
90		99
91	=head1 DESCRIPTION	100	=head1 DESCRIPTION
92		101
93	L<AnyEvent> provides an identical interface to multiple event loops. This	102	L<AnyEvent> provides an identical interface to multiple event loops. This
94	allows module authors to utilise an event loop without forcing module	103	allows module authors to utilise an event loop without forcing module
…		…
98	The interface itself is vaguely similar, but not identical to the L<Event>	107	The interface itself is vaguely similar, but not identical to the L<Event>
99	module.	108	module.
100		109
101	During the first call of any watcher-creation method, the module tries	110	During the first call of any watcher-creation method, the module tries
102	to detect the currently loaded event loop by probing whether one of the	111	to detect the currently loaded event loop by probing whether one of the
103	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	112	following modules is already loaded: L<EV>,
104	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	113	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
105	L<POE>. The first one found is used. If none are found, the module tries	114	L<POE>. The first one found is used. If none are found, the module tries
106	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	115	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
107	adaptor should always succeed) in the order given. The first one that can	116	adaptor should always succeed) in the order given. The first one that can
108	be successfully loaded will be used. If, after this, still none could be	117	be successfully loaded will be used. If, after this, still none could be
…		…
122	starts using it, all bets are off. Maybe you should tell their authors to	131	starts using it, all bets are off. Maybe you should tell their authors to
123	use AnyEvent so their modules work together with others seamlessly...	132	use AnyEvent so their modules work together with others seamlessly...
124		133
125	The pure-perl implementation of AnyEvent is called	134	The pure-perl implementation of AnyEvent is called
126	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	135	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
127	explicitly.	136	explicitly and enjoy the high availability of that event loop :)
128		137
129	=head1 WATCHERS	138	=head1 WATCHERS
130		139
131	AnyEvent has the central concept of a I<watcher>, which is an object that	140	AnyEvent has the central concept of a I<watcher>, which is an object that
132	stores relevant data for each kind of event you are waiting for, such as	141	stores relevant data for each kind of event you are waiting for, such as
133	the callback to call, the filehandle to watch, etc.	142	the callback to call, the file handle to watch, etc.
134		143
135	These watchers are normal Perl objects with normal Perl lifetime. After	144	These watchers are normal Perl objects with normal Perl lifetime. After
136	creating a watcher it will immediately "watch" for events and invoke the	145	creating a watcher it will immediately "watch" for events and invoke the
137	callback when the event occurs (of course, only when the event model	146	callback when the event occurs (of course, only when the event model
138	is in control).	147	is in control).
139		148
		149	Note that B<callbacks must not permanently change global variables>
		150	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		151	callbacks must not C<die> >>. The former is good programming practise in
		152	Perl and the latter stems from the fact that exception handling differs
		153	widely between event loops.
		154
140	To disable the watcher you have to destroy it (e.g. by setting the	155	To disable the watcher you have to destroy it (e.g. by setting the
141	variable you store it in to C<undef> or otherwise deleting all references	156	variable you store it in to C<undef> or otherwise deleting all references
142	to it).	157	to it).
143		158
144	All watchers are created by calling a method on the C<AnyEvent> class.	159	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
146	Many watchers either are used with "recursion" (repeating timers for	161	Many watchers either are used with "recursion" (repeating timers for
147	example), or need to refer to their watcher object in other ways.	162	example), or need to refer to their watcher object in other ways.
148		163
149	An any way to achieve that is this pattern:	164	An any way to achieve that is this pattern:
150		165
151	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	166	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
152	# you can use $w here, for example to undef it	167	# you can use $w here, for example to undef it
153	undef $w;	168	undef $w;
154	});	169	});
155		170
156	Note that C<my $w; $w => combination. This is necessary because in Perl,	171	Note that C<my $w; $w => combination. This is necessary because in Perl,
157	my variables are only visible after the statement in which they are	172	my variables are only visible after the statement in which they are
158	declared.	173	declared.
159		174
160	=head2 I/O WATCHERS	175	=head2 I/O WATCHERS
161		176
162	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	177	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
163	with the following mandatory key-value pairs as arguments:	178	with the following mandatory key-value pairs as arguments:
164		179
165	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	180	C<fh> is the Perl I<file handle> (I<not> file descriptor) to watch
		181	for events (AnyEvent might or might not keep a reference to this file
		182	handle). Note that only file handles pointing to things for which
		183	non-blocking operation makes sense are allowed. This includes sockets,
		184	most character devices, pipes, fifos and so on, but not for example files
		185	or block devices.
		186
166	for events. C<poll> must be a string that is either C<r> or C<w>,	187	C<poll> must be a string that is either C<r> or C<w>, which creates a
167	which creates a watcher waiting for "r"eadable or "w"ritable events,	188	watcher waiting for "r"eadable or "w"ritable events, respectively.
		189
168	respectively. C<cb> is the callback to invoke each time the file handle	190	C<cb> is the callback to invoke each time the file handle becomes ready.
169	becomes ready.
170		191
171	Although the callback might get passed parameters, their value and	192	Although the callback might get passed parameters, their value and
172	presence is undefined and you cannot rely on them. Portable AnyEvent	193	presence is undefined and you cannot rely on them. Portable AnyEvent
173	callbacks cannot use arguments passed to I/O watcher callbacks.	194	callbacks cannot use arguments passed to I/O watcher callbacks.
174		195
…		…
178		199
179	Some event loops issue spurious readyness notifications, so you should	200	Some event loops issue spurious readyness notifications, so you should
180	always use non-blocking calls when reading/writing from/to your file	201	always use non-blocking calls when reading/writing from/to your file
181	handles.	202	handles.
182		203
183	Example:
184
185	# wait for readability of STDIN, then read a line and disable the watcher	204	Example: wait for readability of STDIN, then read a line and disable the
		205	watcher.
		206
186	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	207	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
187	chomp (my $input = <STDIN>);	208	chomp (my $input = <STDIN>);
188	warn "read: $input\n";	209	warn "read: $input\n";
189	undef $w;	210	undef $w;
190	});	211	});
…		…
200		221
201	Although the callback might get passed parameters, their value and	222	Although the callback might get passed parameters, their value and
202	presence is undefined and you cannot rely on them. Portable AnyEvent	223	presence is undefined and you cannot rely on them. Portable AnyEvent
203	callbacks cannot use arguments passed to time watcher callbacks.	224	callbacks cannot use arguments passed to time watcher callbacks.
204		225
205	The timer callback will be invoked at most once: if you want a repeating	226	The callback will normally be invoked once only. If you specify another
206	timer you have to create a new watcher (this is a limitation by both Tk	227	parameter, C<interval>, as a strictly positive number (> 0), then the
207	and Glib).	228	callback will be invoked regularly at that interval (in fractional
		229	seconds) after the first invocation. If C<interval> is specified with a
		230	false value, then it is treated as if it were missing.
208		231
209	Example:	232	The callback will be rescheduled before invoking the callback, but no
		233	attempt is done to avoid timer drift in most backends, so the interval is
		234	only approximate.
210		235
211	# fire an event after 7.7 seconds	236	Example: fire an event after 7.7 seconds.
		237
212	my $w = AnyEvent->timer (after => 7.7, cb => sub {	238	my $w = AnyEvent->timer (after => 7.7, cb => sub {
213	warn "timeout\n";	239	warn "timeout\n";
214	});	240	});
215		241
216	# to cancel the timer:	242	# to cancel the timer:
217	undef $w;	243	undef $w;
218		244
219	Example 2:
220
221	# fire an event after 0.5 seconds, then roughly every second	245	Example 2: fire an event after 0.5 seconds, then roughly every second.
222	my $w;
223		246
224	my $cb = sub {
225	# cancel the old timer while creating a new one
226	$w = AnyEvent->timer (after => 1, cb => $cb);	247	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		248	warn "timeout\n";
227	};	249	};
228
229	# start the "loop" by creating the first watcher
230	$w = AnyEvent->timer (after => 0.5, cb => $cb);
231		250
232	=head3 TIMING ISSUES	251	=head3 TIMING ISSUES
233		252
234	There are two ways to handle timers: based on real time (relative, "fire	253	There are two ways to handle timers: based on real time (relative, "fire
235	in 10 seconds") and based on wallclock time (absolute, "fire at 12	254	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
247	timers.	266	timers.
248		267
249	AnyEvent always prefers relative timers, if available, matching the	268	AnyEvent always prefers relative timers, if available, matching the
250	AnyEvent API.	269	AnyEvent API.
251		270
		271	AnyEvent has two additional methods that return the "current time":
		272
		273	=over 4
		274
		275	=item AnyEvent->time
		276
		277	This returns the "current wallclock time" as a fractional number of
		278	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		279	return, and the result is guaranteed to be compatible with those).
		280
		281	It progresses independently of any event loop processing, i.e. each call
		282	will check the system clock, which usually gets updated frequently.
		283
		284	=item AnyEvent->now
		285
		286	This also returns the "current wallclock time", but unlike C<time>, above,
		287	this value might change only once per event loop iteration, depending on
		288	the event loop (most return the same time as C<time>, above). This is the
		289	time that AnyEvent's timers get scheduled against.
		290
		291	I<In almost all cases (in all cases if you don't care), this is the
		292	function to call when you want to know the current time.>
		293
		294	This function is also often faster then C<< AnyEvent->time >>, and
		295	thus the preferred method if you want some timestamp (for example,
		296	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		297
		298	The rest of this section is only of relevance if you try to be very exact
		299	with your timing, you can skip it without bad conscience.
		300
		301	For a practical example of when these times differ, consider L<Event::Lib>
		302	and L<EV> and the following set-up:
		303
		304	The event loop is running and has just invoked one of your callback at
		305	time=500 (assume no other callbacks delay processing). In your callback,
		306	you wait a second by executing C<sleep 1> (blocking the process for a
		307	second) and then (at time=501) you create a relative timer that fires
		308	after three seconds.
		309
		310	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		311	both return C<501>, because that is the current time, and the timer will
		312	be scheduled to fire at time=504 (C<501> + C<3>).
		313
		314	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		315	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		316	last event processing phase started. With L<EV>, your timer gets scheduled
		317	to run at time=503 (C<500> + C<3>).
		318
		319	In one sense, L<Event::Lib> is more exact, as it uses the current time
		320	regardless of any delays introduced by event processing. However, most
		321	callbacks do not expect large delays in processing, so this causes a
		322	higher drift (and a lot more system calls to get the current time).
		323
		324	In another sense, L<EV> is more exact, as your timer will be scheduled at
		325	the same time, regardless of how long event processing actually took.
		326
		327	In either case, if you care (and in most cases, you don't), then you
		328	can get whatever behaviour you want with any event loop, by taking the
		329	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		330	account.
		331
		332	=item AnyEvent->now_update
		333
		334	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		335	the current time for each loop iteration (see the discussion of L<<
		336	AnyEvent->now >>, above).
		337
		338	When a callback runs for a long time (or when the process sleeps), then
		339	this "current" time will differ substantially from the real time, which
		340	might affect timers and time-outs.
		341
		342	When this is the case, you can call this method, which will update the
		343	event loop's idea of "current time".
		344
		345	Note that updating the time I<might> cause some events to be handled.
		346
		347	=back
		348
252	=head2 SIGNAL WATCHERS	349	=head2 SIGNAL WATCHERS
253		350
254	You can watch for signals using a signal watcher, C<signal> is the signal	351	You can watch for signals using a signal watcher, C<signal> is the signal
255	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	352	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
256	be invoked whenever a signal occurs.	353	callback to be invoked whenever a signal occurs.
257		354
258	Although the callback might get passed parameters, their value and	355	Although the callback might get passed parameters, their value and
259	presence is undefined and you cannot rely on them. Portable AnyEvent	356	presence is undefined and you cannot rely on them. Portable AnyEvent
260	callbacks cannot use arguments passed to signal watcher callbacks.	357	callbacks cannot use arguments passed to signal watcher callbacks.
261		358
262	Multiple signal occurances can be clumped together into one callback	359	Multiple signal occurrences can be clumped together into one callback
263	invocation, and callback invocation will be synchronous. synchronous means	360	invocation, and callback invocation will be synchronous. Synchronous means
264	that it might take a while until the signal gets handled by the process,	361	that it might take a while until the signal gets handled by the process,
265	but it is guarenteed not to interrupt any other callbacks.	362	but it is guaranteed not to interrupt any other callbacks.
266		363
267	The main advantage of using these watchers is that you can share a signal	364	The main advantage of using these watchers is that you can share a signal
268	between multiple watchers.	365	between multiple watchers.
269		366
270	This watcher might use C<%SIG>, so programs overwriting those signals	367	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
277	=head2 CHILD PROCESS WATCHERS	374	=head2 CHILD PROCESS WATCHERS
278		375
279	You can also watch on a child process exit and catch its exit status.	376	You can also watch on a child process exit and catch its exit status.
280		377
281	The child process is specified by the C<pid> argument (if set to C<0>, it	378	The child process is specified by the C<pid> argument (if set to C<0>, it
282	watches for any child process exit). The watcher will trigger as often	379	watches for any child process exit). The watcher will triggered only when
283	as status change for the child are received. This works by installing a	380	the child process has finished and an exit status is available, not on
284	signal handler for C<SIGCHLD>. The callback will be called with the pid	381	any trace events (stopped/continued).
285	and exit status (as returned by waitpid), so unlike other watcher types,	382
286	you I<can> rely on child watcher callback arguments.	383	The callback will be called with the pid and exit status (as returned by
		384	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		385	callback arguments.
		386
		387	This watcher type works by installing a signal handler for C<SIGCHLD>,
		388	and since it cannot be shared, nothing else should use SIGCHLD or reap
		389	random child processes (waiting for specific child processes, e.g. inside
		390	C<system>, is just fine).
287		391
288	There is a slight catch to child watchers, however: you usually start them	392	There is a slight catch to child watchers, however: you usually start them
289	I<after> the child process was created, and this means the process could	393	I<after> the child process was created, and this means the process could
290	have exited already (and no SIGCHLD will be sent anymore).	394	have exited already (and no SIGCHLD will be sent anymore).
291		395
…		…
297	AnyEvent program, you I<have> to create at least one watcher before you	401	AnyEvent program, you I<have> to create at least one watcher before you
298	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	402	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
299		403
300	Example: fork a process and wait for it	404	Example: fork a process and wait for it
301		405
302	my $done = AnyEvent->condvar;	406	my $done = AnyEvent->condvar;
303		407
304	AnyEvent::detect; # force event module to be initialised
305
306	my $pid = fork or exit 5;	408	my $pid = fork or exit 5;
307		409
308	my $w = AnyEvent->child (	410	my $w = AnyEvent->child (
309	pid => $pid,	411	pid => $pid,
310	cb => sub {	412	cb => sub {
311	my ($pid, $status) = @_;	413	my ($pid, $status) = @_;
312	warn "pid $pid exited with status $status";	414	warn "pid $pid exited with status $status";
313	$done->broadcast;	415	$done->send;
314	},	416	},
315	);	417	);
316		418
317	# do something else, then wait for process exit	419	# do something else, then wait for process exit
318	$done->wait;	420	$done->recv;
		421
		422	=head2 IDLE WATCHERS
		423
		424	Sometimes there is a need to do something, but it is not so important
		425	to do it instantly, but only when there is nothing better to do. This
		426	"nothing better to do" is usually defined to be "no other events need
		427	attention by the event loop".
		428
		429	Idle watchers ideally get invoked when the event loop has nothing
		430	better to do, just before it would block the process to wait for new
		431	events. Instead of blocking, the idle watcher is invoked.
		432
		433	Most event loops unfortunately do not really support idle watchers (only
		434	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		435	will simply call the callback "from time to time".
		436
		437	Example: read lines from STDIN, but only process them when the
		438	program is otherwise idle:
		439
		440	my @lines; # read data
		441	my $idle_w;
		442	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		443	push @lines, scalar <STDIN>;
		444
		445	# start an idle watcher, if not already done
		446	$idle_w ||= AnyEvent->idle (cb => sub {
		447	# handle only one line, when there are lines left
		448	if (my $line = shift @lines) {
		449	print "handled when idle: $line";
		450	} else {
		451	# otherwise disable the idle watcher again
		452	undef $idle_w;
		453	}
		454	});
		455	});
319		456
320	=head2 CONDITION VARIABLES	457	=head2 CONDITION VARIABLES
321		458
		459	If you are familiar with some event loops you will know that all of them
		460	require you to run some blocking "loop", "run" or similar function that
		461	will actively watch for new events and call your callbacks.
		462
		463	AnyEvent is different, it expects somebody else to run the event loop and
		464	will only block when necessary (usually when told by the user).
		465
		466	The instrument to do that is called a "condition variable", so called
		467	because they represent a condition that must become true.
		468
322	Condition variables can be created by calling the C<< AnyEvent->condvar >>	469	Condition variables can be created by calling the C<< AnyEvent->condvar
323	method without any arguments.	470	>> method, usually without arguments. The only argument pair allowed is
324		471
325	A condition variable waits for a condition - precisely that the C<<	472	C<cb>, which specifies a callback to be called when the condition variable
326	->broadcast >> method has been called.	473	becomes true, with the condition variable as the first argument (but not
		474	the results).
327		475
328	They are very useful to signal that a condition has been fulfilled, for	476	After creation, the condition variable is "false" until it becomes "true"
		477	by calling the C<send> method (or calling the condition variable as if it
		478	were a callback, read about the caveats in the description for the C<<
		479	->send >> method).
		480
		481	Condition variables are similar to callbacks, except that you can
		482	optionally wait for them. They can also be called merge points - points
		483	in time where multiple outstanding events have been processed. And yet
		484	another way to call them is transactions - each condition variable can be
		485	used to represent a transaction, which finishes at some point and delivers
		486	a result.
		487
		488	Condition variables are very useful to signal that something has finished,
329	example, if you write a module that does asynchronous http requests,	489	for example, if you write a module that does asynchronous http requests,
330	then a condition variable would be the ideal candidate to signal the	490	then a condition variable would be the ideal candidate to signal the
331	availability of results.	491	availability of results. The user can either act when the callback is
		492	called or can synchronously C<< ->recv >> for the results.
332		493
333	You can also use condition variables to block your main program until	494	You can also use them to simulate traditional event loops - for example,
334	an event occurs - for example, you could C<< ->wait >> in your main	495	you can block your main program until an event occurs - for example, you
335	program until the user clicks the Quit button in your app, which would C<<	496	could C<< ->recv >> in your main program until the user clicks the Quit
336	->broadcast >> the "quit" event.	497	button of your app, which would C<< ->send >> the "quit" event.
337		498
338	Note that condition variables recurse into the event loop - if you have	499	Note that condition variables recurse into the event loop - if you have
339	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	500	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	501	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	502	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	503	as this asks for trouble.
343		504
344	This object has two methods:	505	Condition variables are represented by hash refs in perl, and the keys
		506	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		507	easy (it is often useful to build your own transaction class on top of
		508	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		509	it's C<new> method in your own C<new> method.
		510
		511	There are two "sides" to a condition variable - the "producer side" which
		512	eventually calls C<< -> send >>, and the "consumer side", which waits
		513	for the send to occur.
		514
		515	Example: wait for a timer.
		516
		517	# wait till the result is ready
		518	my $result_ready = AnyEvent->condvar;
		519
		520	# do something such as adding a timer
		521	# or socket watcher the calls $result_ready->send
		522	# when the "result" is ready.
		523	# in this case, we simply use a timer:
		524	my $w = AnyEvent->timer (
		525	after => 1,
		526	cb => sub { $result_ready->send },
		527	);
		528
		529	# this "blocks" (while handling events) till the callback
		530	# calls send
		531	$result_ready->recv;
		532
		533	Example: wait for a timer, but take advantage of the fact that
		534	condition variables are also code references.
		535
		536	my $done = AnyEvent->condvar;
		537	my $delay = AnyEvent->timer (after => 5, cb => $done);
		538	$done->recv;
		539
		540	Example: Imagine an API that returns a condvar and doesn't support
		541	callbacks. This is how you make a synchronous call, for example from
		542	the main program:
		543
		544	use AnyEvent::CouchDB;
		545
		546	...
		547
		548	my @info = $couchdb->info->recv;
		549
		550	And this is how you would just ste a callback to be called whenever the
		551	results are available:
		552
		553	$couchdb->info->cb (sub {
		554	my @info = $_[0]->recv;
		555	});
		556
		557	=head3 METHODS FOR PRODUCERS
		558
		559	These methods should only be used by the producing side, i.e. the
		560	code/module that eventually sends the signal. Note that it is also
		561	the producer side which creates the condvar in most cases, but it isn't
		562	uncommon for the consumer to create it as well.
345		563
346	=over 4	564	=over 4
347		565
		566	=item $cv->send (...)
		567
		568	Flag the condition as ready - a running C<< ->recv >> and all further
		569	calls to C<recv> will (eventually) return after this method has been
		570	called. If nobody is waiting the send will be remembered.
		571
		572	If a callback has been set on the condition variable, it is called
		573	immediately from within send.
		574
		575	Any arguments passed to the C<send> call will be returned by all
		576	future C<< ->recv >> calls.
		577
		578	Condition variables are overloaded so one can call them directly
		579	(as a code reference). Calling them directly is the same as calling
		580	C<send>. Note, however, that many C-based event loops do not handle
		581	overloading, so as tempting as it may be, passing a condition variable
		582	instead of a callback does not work. Both the pure perl and EV loops
		583	support overloading, however, as well as all functions that use perl to
		584	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		585	example).
		586
		587	=item $cv->croak ($error)
		588
		589	Similar to send, but causes all call's to C<< ->recv >> to invoke
		590	C<Carp::croak> with the given error message/object/scalar.
		591
		592	This can be used to signal any errors to the condition variable
		593	user/consumer.
		594
		595	=item $cv->begin ([group callback])
		596
348	=item $cv->wait	597	=item $cv->end
349		598
350	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	599	These two methods are EXPERIMENTAL and MIGHT CHANGE.
		600
		601	These two methods can be used to combine many transactions/events into
		602	one. For example, a function that pings many hosts in parallel might want
		603	to use a condition variable for the whole process.
		604
		605	Every call to C<< ->begin >> will increment a counter, and every call to
		606	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		607	>>, the (last) callback passed to C<begin> will be executed. That callback
		608	is I<supposed> to call C<< ->send >>, but that is not required. If no
		609	callback was set, C<send> will be called without any arguments.
		610
		611	Let's clarify this with the ping example:
		612
		613	my $cv = AnyEvent->condvar;
		614
		615	my %result;
		616	$cv->begin (sub { $cv->send (\%result) });
		617
		618	for my $host (@list_of_hosts) {
		619	$cv->begin;
		620	ping_host_then_call_callback $host, sub {
		621	$result{$host} = ...;
		622	$cv->end;
		623	};
		624	}
		625
		626	$cv->end;
		627
		628	This code fragment supposedly pings a number of hosts and calls
		629	C<send> after results for all then have have been gathered - in any
		630	order. To achieve this, the code issues a call to C<begin> when it starts
		631	each ping request and calls C<end> when it has received some result for
		632	it. Since C<begin> and C<end> only maintain a counter, the order in which
		633	results arrive is not relevant.
		634
		635	There is an additional bracketing call to C<begin> and C<end> outside the
		636	loop, which serves two important purposes: first, it sets the callback
		637	to be called once the counter reaches C<0>, and second, it ensures that
		638	C<send> is called even when C<no> hosts are being pinged (the loop
		639	doesn't execute once).
		640
		641	This is the general pattern when you "fan out" into multiple subrequests:
		642	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>
		643	is called at least once, and then, for each subrequest you start, call
		644	C<begin> and for each subrequest you finish, call C<end>.
		645
		646	=back
		647
		648	=head3 METHODS FOR CONSUMERS
		649
		650	These methods should only be used by the consuming side, i.e. the
		651	code awaits the condition.
		652
		653	=over 4
		654
		655	=item $cv->recv
		656
		657	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
351	called on c<$cv>, while servicing other watchers normally.	658	>> methods have been called on c<$cv>, while servicing other watchers
		659	normally.
352		660
353	You can only wait once on a condition - additional calls will return	661	You can only wait once on a condition - additional calls are valid but
354	immediately.	662	will return immediately.
		663
		664	If an error condition has been set by calling C<< ->croak >>, then this
		665	function will call C<croak>.
		666
		667	In list context, all parameters passed to C<send> will be returned,
		668	in scalar context only the first one will be returned.
355		669
356	Not all event models support a blocking wait - some die in that case	670	Not all event models support a blocking wait - some die in that case
357	(programs might want to do that to stay interactive), so I<if you are	671	(programs might want to do that to stay interactive), so I<if you are
358	using this from a module, never require a blocking wait>, but let the	672	using this from a module, never require a blocking wait>, but let the
359	caller decide whether the call will block or not (for example, by coupling	673	caller decide whether the call will block or not (for example, by coupling
360	condition variables with some kind of request results and supporting	674	condition variables with some kind of request results and supporting
361	callbacks so the caller knows that getting the result will not block,	675	callbacks so the caller knows that getting the result will not block,
362	while still suppporting blocking waits if the caller so desires).	676	while still supporting blocking waits if the caller so desires).
363		677
364	Another reason I<never> to C<< ->wait >> in a module is that you cannot	678	Another reason I<never> to C<< ->recv >> in a module is that you cannot
365	sensibly have two C<< ->wait >>'s in parallel, as that would require	679	sensibly have two C<< ->recv >>'s in parallel, as that would require
366	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	680	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
367	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	681	can supply.
368	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
369	from different coroutines, however).
370		682
371	=item $cv->broadcast	683	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
		684	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
		685	versions and also integrates coroutines into AnyEvent, making blocking
		686	C<< ->recv >> calls perfectly safe as long as they are done from another
		687	coroutine (one that doesn't run the event loop).
372		688
373	Flag the condition as ready - a running C<< ->wait >> and all further	689	You can ensure that C<< -recv >> never blocks by setting a callback and
374	calls to C<wait> will (eventually) return after this method has been	690	only calling C<< ->recv >> from within that callback (or at a later
375	called. If nobody is waiting the broadcast will be remembered..	691	time). This will work even when the event loop does not support blocking
		692	waits otherwise.
		693
		694	=item $bool = $cv->ready
		695
		696	Returns true when the condition is "true", i.e. whether C<send> or
		697	C<croak> have been called.
		698
		699	=item $cb = $cv->cb ($cb->($cv))
		700
		701	This is a mutator function that returns the callback set and optionally
		702	replaces it before doing so.
		703
		704	The callback will be called when the condition becomes "true", i.e. when
		705	C<send> or C<croak> are called, with the only argument being the condition
		706	variable itself. Calling C<recv> inside the callback or at any later time
		707	is guaranteed not to block.
376		708
377	=back	709	=back
378
379	Example:
380
381	# wait till the result is ready
382	my $result_ready = AnyEvent->condvar;
383
384	# do something such as adding a timer
385	# or socket watcher the calls $result_ready->broadcast
386	# when the "result" is ready.
387	# in this case, we simply use a timer:
388	my $w = AnyEvent->timer (
389	after => 1,
390	cb => sub { $result_ready->broadcast },
391	);
392
393	# this "blocks" (while handling events) till the watcher
394	# calls broadcast
395	$result_ready->wait;
396		710
397	=head1 GLOBAL VARIABLES AND FUNCTIONS	711	=head1 GLOBAL VARIABLES AND FUNCTIONS
398		712
399	=over 4	713	=over 4
400		714
…		…
406	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	720	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
407	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	721	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
408		722
409	The known classes so far are:	723	The known classes so far are:
410		724
411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).	725	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
414	AnyEvent::Impl::Event based on Event, second best choice.	726	AnyEvent::Impl::Event based on Event, second best choice.
		727	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
415	AnyEvent::Impl::Glib based on Glib, third-best choice.	728	AnyEvent::Impl::Glib based on Glib, third-best choice.
416	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
417	AnyEvent::Impl::Tk based on Tk, very bad choice.	729	AnyEvent::Impl::Tk based on Tk, very bad choice.
418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).	730	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.	731	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
420	AnyEvent::Impl::POE based on POE, not generic enough for full support.	732	AnyEvent::Impl::POE based on POE, not generic enough for full support.
421		733
…		…
434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	746	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
435	if necessary. You should only call this function right before you would	747	if necessary. You should only call this function right before you would
436	have created an AnyEvent watcher anyway, that is, as late as possible at	748	have created an AnyEvent watcher anyway, that is, as late as possible at
437	runtime.	749	runtime.
438		750
		751	=item $guard = AnyEvent::post_detect { BLOCK }
		752
		753	Arranges for the code block to be executed as soon as the event model is
		754	autodetected (or immediately if this has already happened).
		755
		756	If called in scalar or list context, then it creates and returns an object
		757	that automatically removes the callback again when it is destroyed. See
		758	L<Coro::BDB> for a case where this is useful.
		759
		760	=item @AnyEvent::post_detect
		761
		762	If there are any code references in this array (you can C<push> to it
		763	before or after loading AnyEvent), then they will called directly after
		764	the event loop has been chosen.
		765
		766	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		767	if it contains a true value then the event loop has already been detected,
		768	and the array will be ignored.
		769
		770	Best use C<AnyEvent::post_detect { BLOCK }> instead.
		771
439	=back	772	=back
440		773
441	=head1 WHAT TO DO IN A MODULE	774	=head1 WHAT TO DO IN A MODULE
442		775
443	As a module author, you should C<use AnyEvent> and call AnyEvent methods	776	As a module author, you should C<use AnyEvent> and call AnyEvent methods
…		…
446	Be careful when you create watchers in the module body - AnyEvent will	779	Be careful when you create watchers in the module body - AnyEvent will
447	decide which event module to use as soon as the first method is called, so	780	decide which event module to use as soon as the first method is called, so
448	by calling AnyEvent in your module body you force the user of your module	781	by calling AnyEvent in your module body you force the user of your module
449	to load the event module first.	782	to load the event module first.
450		783
451	Never call C<< ->wait >> on a condition variable unless you I<know> that	784	Never call C<< ->recv >> on a condition variable unless you I<know> that
452	the C<< ->broadcast >> method has been called on it already. This is	785	the C<< ->send >> method has been called on it already. This is
453	because it will stall the whole program, and the whole point of using	786	because it will stall the whole program, and the whole point of using
454	events is to stay interactive.	787	events is to stay interactive.
455		788
456	It is fine, however, to call C<< ->wait >> when the user of your module	789	It is fine, however, to call C<< ->recv >> when the user of your module
457	requests it (i.e. if you create a http request object ad have a method	790	requests it (i.e. if you create a http request object ad have a method
458	called C<results> that returns the results, it should call C<< ->wait >>	791	called C<results> that returns the results, it should call C<< ->recv >>
459	freely, as the user of your module knows what she is doing. always).	792	freely, as the user of your module knows what she is doing. always).
460		793
461	=head1 WHAT TO DO IN THE MAIN PROGRAM	794	=head1 WHAT TO DO IN THE MAIN PROGRAM
462		795
463	There will always be a single main program - the only place that should	796	There will always be a single main program - the only place that should
…		…
465		798
466	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	799	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
467	do anything special (it does not need to be event-based) and let AnyEvent	800	do anything special (it does not need to be event-based) and let AnyEvent
468	decide which implementation to chose if some module relies on it.	801	decide which implementation to chose if some module relies on it.
469		802
470	If the main program relies on a specific event model. For example, in	803	If the main program relies on a specific event model - for example, in
471	Gtk2 programs you have to rely on the Glib module. You should load the	804	Gtk2 programs you have to rely on the Glib module - you should load the
472	event module before loading AnyEvent or any module that uses it: generally	805	event module before loading AnyEvent or any module that uses it: generally
473	speaking, you should load it as early as possible. The reason is that	806	speaking, you should load it as early as possible. The reason is that
474	modules might create watchers when they are loaded, and AnyEvent will	807	modules might create watchers when they are loaded, and AnyEvent will
475	decide on the event model to use as soon as it creates watchers, and it	808	decide on the event model to use as soon as it creates watchers, and it
476	might chose the wrong one unless you load the correct one yourself.	809	might chose the wrong one unless you load the correct one yourself.
477		810
478	You can chose to use a rather inefficient pure-perl implementation by	811	You can chose to use a pure-perl implementation by loading the
479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	812	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
480	behaviour everywhere, but letting AnyEvent chose is generally better.	813	everywhere, but letting AnyEvent chose the model is generally better.
		814
		815	=head2 MAINLOOP EMULATION
		816
		817	Sometimes (often for short test scripts, or even standalone programs who
		818	only want to use AnyEvent), you do not want to run a specific event loop.
		819
		820	In that case, you can use a condition variable like this:
		821
		822	AnyEvent->condvar->recv;
		823
		824	This has the effect of entering the event loop and looping forever.
		825
		826	Note that usually your program has some exit condition, in which case
		827	it is better to use the "traditional" approach of storing a condition
		828	variable somewhere, waiting for it, and sending it when the program should
		829	exit cleanly.
		830
481		831
482	=head1 OTHER MODULES	832	=head1 OTHER MODULES
483		833
484	L<AnyEvent> itself comes with useful utility modules:	834	The following is a non-exhaustive list of additional modules that use
485		835	AnyEvent and can therefore be mixed easily with other AnyEvent modules
486	To make it easier to do non-blocking IO the modules L<AnyEvent::Handle>	836	in the same program. Some of the modules come with AnyEvent, some are
487	and L<AnyEvent::Socket> are provided. L<AnyEvent::Handle> provides	837	available via CPAN.
488	read and write buffers and manages watchers for reads and writes.
489	L<AnyEvent::Socket> provides means to do non-blocking connects.
490
491	Aside from those there are these modules that support AnyEvent (and use it
492	for non-blocking IO):
493		838
494	=over 4	839	=over 4
495		840
		841	=item L<AnyEvent::Util>
		842
		843	Contains various utility functions that replace often-used but blocking
		844	functions such as C<inet_aton> by event-/callback-based versions.
		845
		846	=item L<AnyEvent::Socket>
		847
		848	Provides various utility functions for (internet protocol) sockets,
		849	addresses and name resolution. Also functions to create non-blocking tcp
		850	connections or tcp servers, with IPv6 and SRV record support and more.
		851
		852	=item L<AnyEvent::Handle>
		853
		854	Provide read and write buffers, manages watchers for reads and writes,
		855	supports raw and formatted I/O, I/O queued and fully transparent and
		856	non-blocking SSL/TLS.
		857
		858	=item L<AnyEvent::DNS>
		859
		860	Provides rich asynchronous DNS resolver capabilities.
		861
		862	=item L<AnyEvent::HTTP>
		863
		864	A simple-to-use HTTP library that is capable of making a lot of concurrent
		865	HTTP requests.
		866
		867	=item L<AnyEvent::HTTPD>
		868
		869	Provides a simple web application server framework.
		870
496	=item L<AnyEvent::FastPing>	871	=item L<AnyEvent::FastPing>
497		872
		873	The fastest ping in the west.
		874
		875	=item L<AnyEvent::DBI>
		876
		877	Executes L<DBI> requests asynchronously in a proxy process.
		878
		879	=item L<AnyEvent::AIO>
		880
		881	Truly asynchronous I/O, should be in the toolbox of every event
		882	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		883	together.
		884
		885	=item L<AnyEvent::BDB>
		886
		887	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		888	L<BDB> and AnyEvent together.
		889
		890	=item L<AnyEvent::GPSD>
		891
		892	A non-blocking interface to gpsd, a daemon delivering GPS information.
		893
		894	=item L<AnyEvent::IGS>
		895
		896	A non-blocking interface to the Internet Go Server protocol (used by
		897	L<App::IGS>).
		898
498	=item L<Net::IRC3>	899	=item L<AnyEvent::IRC>
		900
		901	AnyEvent based IRC client module family (replacing the older Net::IRC3).
499		902
500	=item L<Net::XMPP2>	903	=item L<Net::XMPP2>
501		904
		905	AnyEvent based XMPP (Jabber protocol) module family.
		906
		907	=item L<Net::FCP>
		908
		909	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		910	of AnyEvent.
		911
		912	=item L<Event::ExecFlow>
		913
		914	High level API for event-based execution flow control.
		915
		916	=item L<Coro>
		917
		918	Has special support for AnyEvent via L<Coro::AnyEvent>.
		919
		920	=item L<IO::Lambda>
		921
		922	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
		923
502	=back	924	=back
503		925
504	=cut	926	=cut
505		927
506	package AnyEvent;	928	package AnyEvent;
507		929
508	no warnings;	930	no warnings;
509	use strict;	931	use strict qw(vars subs);
510		932
511	use Carp;	933	use Carp;
512		934
513	our $VERSION = '3.3';	935	our $VERSION = 4.41;
514	our $MODEL;	936	our $MODEL;
515		937
516	our $AUTOLOAD;	938	our $AUTOLOAD;
517	our @ISA;	939	our @ISA;
518		940
		941	our @REGISTRY;
		942
		943	our $WIN32;
		944
		945	BEGIN {
		946	my $win32 = ! ! ($^O =~ /mswin32/i);
		947	eval "sub WIN32(){ $win32 }";
		948	}
		949
519	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	950	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
520		951
521	our @REGISTRY;	952	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		953
		954	{
		955	my $idx;
		956	$PROTOCOL{$_} = ++$idx
		957	for reverse split /\s*,\s*/,
		958	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		959	}
522		960
523	my @models = (	961	my @models = (
524	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
525	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
526	[EV:: => AnyEvent::Impl::EV::],	962	[EV:: => AnyEvent::Impl::EV::],
527	[Event:: => AnyEvent::Impl::Event::],	963	[Event:: => AnyEvent::Impl::Event::],
528	[Glib:: => AnyEvent::Impl::Glib::],
529	[Tk:: => AnyEvent::Impl::Tk::],
530	[Wx:: => AnyEvent::Impl::POE::],
531	[Prima:: => AnyEvent::Impl::POE::],
532	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	964	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
533	# everything below here will not be autoprobed as the pureperl backend should work everywhere	965	# everything below here will not be autoprobed
		966	# as the pureperl backend should work everywhere
		967	# and is usually faster
		968	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		969	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
534	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	970	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
535	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	971	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
536	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	972	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		973	[Wx:: => AnyEvent::Impl::POE::],
		974	[Prima:: => AnyEvent::Impl::POE::],
537	);	975	);
538		976
539	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	977	our %method = map +($_ => 1),
		978	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		979
		980	our @post_detect;
		981
		982	sub post_detect(&) {
		983	my ($cb) = @_;
		984
		985	if ($MODEL) {
		986	$cb->();
		987
		988	1
		989	} else {
		990	push @post_detect, $cb;
		991
		992	defined wantarray
		993	? bless \$cb, "AnyEvent::Util::postdetect"
		994	: ()
		995	}
		996	}
		997
		998	sub AnyEvent::Util::postdetect::DESTROY {
		999	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1000	}
540		1001
541	sub detect() {	1002	sub detect() {
542	unless ($MODEL) {	1003	unless ($MODEL) {
543	no strict 'refs';	1004	no strict 'refs';
		1005	local $SIG{__DIE__};
544		1006
545	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1007	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
546	my $model = "AnyEvent::Impl::$1";	1008	my $model = "AnyEvent::Impl::$1";
547	if (eval "require $model") {	1009	if (eval "require $model") {
548	$MODEL = $model;	1010	$MODEL = $model;
…		…
578	last;	1040	last;
579	}	1041	}
580	}	1042	}
581		1043
582	$MODEL	1044	$MODEL
583	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1045	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
584	}	1046	}
585	}	1047	}
586		1048
		1049	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1050
587	unshift @ISA, $MODEL;	1051	unshift @ISA, $MODEL;
588	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1052
		1053	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1054
		1055	(shift @post_detect)->() while @post_detect;
589	}	1056	}
590		1057
591	$MODEL	1058	$MODEL
592	}	1059	}
593		1060
…		…
601		1068
602	my $class = shift;	1069	my $class = shift;
603	$class->$func (@_);	1070	$class->$func (@_);
604	}	1071	}
605		1072
		1073	# utility function to dup a filehandle. this is used by many backends
		1074	# to support binding more than one watcher per filehandle (they usually
		1075	# allow only one watcher per fd, so we dup it to get a different one).
		1076	sub _dupfh($$$$) {
		1077	my ($poll, $fh, $r, $w) = @_;
		1078
		1079	# cygwin requires the fh mode to be matching, unix doesn't
		1080	my ($rw, $mode) = $poll eq "r" ? ($r, "<")
		1081	: $poll eq "w" ? ($w, ">")
		1082	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
		1083
		1084	open my $fh2, "$mode&" . fileno $fh
		1085	or die "cannot dup() filehandle: $!,";
		1086
		1087	# we assume CLOEXEC is already set by perl in all important cases
		1088
		1089	($fh2, $rw)
		1090	}
		1091
606	package AnyEvent::Base;	1092	package AnyEvent::Base;
607		1093
		1094	# default implementations for many methods
		1095
		1096	BEGIN {
		1097	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1098	*_time = \&Time::HiRes::time;
		1099	# if (eval "use POSIX (); (POSIX::times())...
		1100	} else {
		1101	*_time = sub { time }; # epic fail
		1102	}
		1103	}
		1104
		1105	sub time { _time }
		1106	sub now { _time }
		1107	sub now_update { }
		1108
608	# default implementation for ->condvar, ->wait, ->broadcast	1109	# default implementation for ->condvar
609		1110
610	sub condvar {	1111	sub condvar {
611	bless \my $flag, "AnyEvent::Base::CondVar"	1112	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
612	}
613
614	sub AnyEvent::Base::CondVar::broadcast {
615	${$_[0]}++;
616	}
617
618	sub AnyEvent::Base::CondVar::wait {
619	AnyEvent->one_event while !${$_[0]};
620	}	1113	}
621		1114
622	# default implementation for ->signal	1115	# default implementation for ->signal
623		1116
624	our %SIG_CB;	1117	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1118
		1119	sub _signal_exec {
		1120	sysread $SIGPIPE_R, my $dummy, 4;
		1121
		1122	while (%SIG_EV) {
		1123	for (keys %SIG_EV) {
		1124	delete $SIG_EV{$_};
		1125	$_->() for values %{ $SIG_CB{$_} || {} };
		1126	}
		1127	}
		1128	}
625		1129
626	sub signal {	1130	sub signal {
627	my (undef, %arg) = @_;	1131	my (undef, %arg) = @_;
628		1132
		1133	unless ($SIGPIPE_R) {
		1134	require Fcntl;
		1135
		1136	if (AnyEvent::WIN32) {
		1137	require AnyEvent::Util;
		1138
		1139	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1140	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1141	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1142	} else {
		1143	pipe $SIGPIPE_R, $SIGPIPE_W;
		1144	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1145	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1146	}
		1147
		1148	$SIGPIPE_R
		1149	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1150
		1151	# not strictly required, as $^F is normally 2, but let's make sure...
		1152	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1153	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1154
		1155	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1156	}
		1157
629	my $signal = uc $arg{signal}	1158	my $signal = uc $arg{signal}
630	or Carp::croak "required option 'signal' is missing";	1159	or Carp::croak "required option 'signal' is missing";
631		1160
632	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1161	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
633	$SIG{$signal} ||= sub {	1162	$SIG{$signal} ||= sub {
634	$_->() for values %{ $SIG_CB{$signal} || {} };	1163	local $!;
		1164	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1165	undef $SIG_EV{$signal};
635	};	1166	};
636		1167
637	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1168	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
638	}	1169	}
639		1170
640	sub AnyEvent::Base::Signal::DESTROY {	1171	sub AnyEvent::Base::signal::DESTROY {
641	my ($signal, $cb) = @{$_[0]};	1172	my ($signal, $cb) = @{$_[0]};
642		1173
643	delete $SIG_CB{$signal}{$cb};	1174	delete $SIG_CB{$signal}{$cb};
644		1175
		1176	# delete doesn't work with older perls - they then
		1177	# print weird messages, or just unconditionally exit
		1178	# instead of getting the default action.
645	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1179	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
646	}	1180	}
647		1181
648	# default implementation for ->child	1182	# default implementation for ->child
649		1183
650	our %PID_CB;	1184	our %PID_CB;
651	our $CHLD_W;	1185	our $CHLD_W;
652	our $CHLD_DELAY_W;	1186	our $CHLD_DELAY_W;
653	our $PID_IDLE;
654	our $WNOHANG;	1187	our $WNOHANG;
655		1188
656	sub _child_wait {	1189	sub _sigchld {
657	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1190	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
658	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1191	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
659	(values %{ $PID_CB{0} || {} });	1192	(values %{ $PID_CB{0} || {} });
660	}	1193	}
661
662	undef $PID_IDLE;
663	}
664
665	sub _sigchld {
666	# make sure we deliver these changes "synchronous" with the event loop.
667	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
668	undef $CHLD_DELAY_W;
669	&_child_wait;
670	});
671	}	1194	}
672		1195
673	sub child {	1196	sub child {
674	my (undef, %arg) = @_;	1197	my (undef, %arg) = @_;
675		1198
676	defined (my $pid = $arg{pid} + 0)	1199	defined (my $pid = $arg{pid} + 0)
677	or Carp::croak "required option 'pid' is missing";	1200	or Carp::croak "required option 'pid' is missing";
678		1201
679	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1202	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
680		1203
681	unless ($WNOHANG) {
682	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1204	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
683	}
684		1205
685	unless ($CHLD_W) {	1206	unless ($CHLD_W) {
686	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1207	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
687	# child could be a zombie already, so make at least one round	1208	# child could be a zombie already, so make at least one round
688	&_sigchld;	1209	&_sigchld;
689	}	1210	}
690		1211
691	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1212	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
692	}	1213	}
693		1214
694	sub AnyEvent::Base::Child::DESTROY {	1215	sub AnyEvent::Base::child::DESTROY {
695	my ($pid, $cb) = @{$_[0]};	1216	my ($pid, $cb) = @{$_[0]};
696		1217
697	delete $PID_CB{$pid}{$cb};	1218	delete $PID_CB{$pid}{$cb};
698	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1219	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
699		1220
700	undef $CHLD_W unless keys %PID_CB;	1221	undef $CHLD_W unless keys %PID_CB;
701	}	1222	}
		1223
		1224	# idle emulation is done by simply using a timer, regardless
		1225	# of whether the process is idle or not, and not letting
		1226	# the callback use more than 50% of the time.
		1227	sub idle {
		1228	my (undef, %arg) = @_;
		1229
		1230	my ($cb, $w, $rcb) = $arg{cb};
		1231
		1232	$rcb = sub {
		1233	if ($cb) {
		1234	$w = _time;
		1235	&$cb;
		1236	$w = _time - $w;
		1237
		1238	# never use more then 50% of the time for the idle watcher,
		1239	# within some limits
		1240	$w = 0.0001 if $w < 0.0001;
		1241	$w = 5 if $w > 5;
		1242
		1243	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1244	} else {
		1245	# clean up...
		1246	undef $w;
		1247	undef $rcb;
		1248	}
		1249	};
		1250
		1251	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1252
		1253	bless \\$cb, "AnyEvent::Base::idle"
		1254	}
		1255
		1256	sub AnyEvent::Base::idle::DESTROY {
		1257	undef $${$_[0]};
		1258	}
		1259
		1260	package AnyEvent::CondVar;
		1261
		1262	our @ISA = AnyEvent::CondVar::Base::;
		1263
		1264	package AnyEvent::CondVar::Base;
		1265
		1266	use overload
		1267	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1268	fallback => 1;
		1269
		1270	sub _send {
		1271	# nop
		1272	}
		1273
		1274	sub send {
		1275	my $cv = shift;
		1276	$cv->{_ae_sent} = [@_];
		1277	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1278	$cv->_send;
		1279	}
		1280
		1281	sub croak {
		1282	$_[0]{_ae_croak} = $_[1];
		1283	$_[0]->send;
		1284	}
		1285
		1286	sub ready {
		1287	$_[0]{_ae_sent}
		1288	}
		1289
		1290	sub _wait {
		1291	AnyEvent->one_event while !$_[0]{_ae_sent};
		1292	}
		1293
		1294	sub recv {
		1295	$_[0]->_wait;
		1296
		1297	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1298	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1299	}
		1300
		1301	sub cb {
		1302	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1303	$_[0]{_ae_cb}
		1304	}
		1305
		1306	sub begin {
		1307	++$_[0]{_ae_counter};
		1308	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1309	}
		1310
		1311	sub end {
		1312	return if --$_[0]{_ae_counter};
		1313	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1314	}
		1315
		1316	# undocumented/compatibility with pre-3.4
		1317	*broadcast = \&send;
		1318	*wait = \&_wait;
		1319
		1320	=head1 ERROR AND EXCEPTION HANDLING
		1321
		1322	In general, AnyEvent does not do any error handling - it relies on the
		1323	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1324	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1325	checking of all AnyEvent methods, however, which is highly useful during
		1326	development.
		1327
		1328	As for exception handling (i.e. runtime errors and exceptions thrown while
		1329	executing a callback), this is not only highly event-loop specific, but
		1330	also not in any way wrapped by this module, as this is the job of the main
		1331	program.
		1332
		1333	The pure perl event loop simply re-throws the exception (usually
		1334	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1335	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1336	so on.
		1337
		1338	=head1 ENVIRONMENT VARIABLES
		1339
		1340	The following environment variables are used by this module or its
		1341	submodules:
		1342
		1343	=over 4
		1344
		1345	=item C<PERL_ANYEVENT_VERBOSE>
		1346
		1347	By default, AnyEvent will be completely silent except in fatal
		1348	conditions. You can set this environment variable to make AnyEvent more
		1349	talkative.
		1350
		1351	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1352	conditions, such as not being able to load the event model specified by
		1353	C<PERL_ANYEVENT_MODEL>.
		1354
		1355	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1356	model it chooses.
		1357
		1358	=item C<PERL_ANYEVENT_STRICT>
		1359
		1360	AnyEvent does not do much argument checking by default, as thorough
		1361	argument checking is very costly. Setting this variable to a true value
		1362	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1363	check the arguments passed to most method calls. If it finds any problems
		1364	it will croak.
		1365
		1366	In other words, enables "strict" mode.
		1367
		1368	Unlike C<use strict>, it is definitely recommended ot keep it off in
		1369	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1370	developing programs can be very useful, however.
		1371
		1372	=item C<PERL_ANYEVENT_MODEL>
		1373
		1374	This can be used to specify the event model to be used by AnyEvent, before
		1375	auto detection and -probing kicks in. It must be a string consisting
		1376	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1377	and the resulting module name is loaded and if the load was successful,
		1378	used as event model. If it fails to load AnyEvent will proceed with
		1379	auto detection and -probing.
		1380
		1381	This functionality might change in future versions.
		1382
		1383	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1384	could start your program like this:
		1385
		1386	PERL_ANYEVENT_MODEL=Perl perl ...
		1387
		1388	=item C<PERL_ANYEVENT_PROTOCOLS>
		1389
		1390	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1391	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1392	of auto probing).
		1393
		1394	Must be set to a comma-separated list of protocols or address families,
		1395	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1396	used, and preference will be given to protocols mentioned earlier in the
		1397	list.
		1398
		1399	This variable can effectively be used for denial-of-service attacks
		1400	against local programs (e.g. when setuid), although the impact is likely
		1401	small, as the program has to handle conenction and other failures anyways.
		1402
		1403	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1404	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1405	- only support IPv4, never try to resolve or contact IPv6
		1406	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1407	IPv6, but prefer IPv6 over IPv4.
		1408
		1409	=item C<PERL_ANYEVENT_EDNS0>
		1410
		1411	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1412	for DNS. This extension is generally useful to reduce DNS traffic, but
		1413	some (broken) firewalls drop such DNS packets, which is why it is off by
		1414	default.
		1415
		1416	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1417	EDNS0 in its DNS requests.
		1418
		1419	=item C<PERL_ANYEVENT_MAX_FORKS>
		1420
		1421	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1422	will create in parallel.
		1423
		1424	=back
702		1425
703	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1426	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
704		1427
705	This is an advanced topic that you do not normally need to use AnyEvent in	1428	This is an advanced topic that you do not normally need to use AnyEvent in
706	a module. This section is only of use to event loop authors who want to	1429	a module. This section is only of use to event loop authors who want to
…		…
740		1463
741	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1464	I<rxvt-unicode> also cheats a bit by not providing blocking access to
742	condition variables: code blocking while waiting for a condition will	1465	condition variables: code blocking while waiting for a condition will
743	C<die>. This still works with most modules/usages, and blocking calls must	1466	C<die>. This still works with most modules/usages, and blocking calls must
744	not be done in an interactive application, so it makes sense.	1467	not be done in an interactive application, so it makes sense.
745
746	=head1 ENVIRONMENT VARIABLES
747
748	The following environment variables are used by this module:
749
750	=over 4
751
752	=item C<PERL_ANYEVENT_VERBOSE>
753
754	By default, AnyEvent will be completely silent except in fatal
755	conditions. You can set this environment variable to make AnyEvent more
756	talkative.
757
758	When set to C<1> or higher, causes AnyEvent to warn about unexpected
759	conditions, such as not being able to load the event model specified by
760	C<PERL_ANYEVENT_MODEL>.
761
762	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
763	model it chooses.
764
765	=item C<PERL_ANYEVENT_MODEL>
766
767	This can be used to specify the event model to be used by AnyEvent, before
768	autodetection and -probing kicks in. It must be a string consisting
769	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
770	and the resulting module name is loaded and if the load was successful,
771	used as event model. If it fails to load AnyEvent will proceed with
772	autodetection and -probing.
773
774	This functionality might change in future versions.
775
776	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
777	could start your program like this:
778
779	PERL_ANYEVENT_MODEL=Perl perl ...
780
781	=back
782		1468
783	=head1 EXAMPLE PROGRAM	1469	=head1 EXAMPLE PROGRAM
784		1470
785	The following program uses an I/O watcher to read data from STDIN, a timer	1471	The following program uses an I/O watcher to read data from STDIN, a timer
786	to display a message once per second, and a condition variable to quit the	1472	to display a message once per second, and a condition variable to quit the
…		…
795	poll => 'r',	1481	poll => 'r',
796	cb => sub {	1482	cb => sub {
797	warn "io event <$_[0]>\n"; # will always output <r>	1483	warn "io event <$_[0]>\n"; # will always output <r>
798	chomp (my $input = <STDIN>); # read a line	1484	chomp (my $input = <STDIN>); # read a line
799	warn "read: $input\n"; # output what has been read	1485	warn "read: $input\n"; # output what has been read
800	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1486	$cv->send if $input =~ /^q/i; # quit program if /^q/i
801	},	1487	},
802	);	1488	);
803		1489
804	my $time_watcher; # can only be used once	1490	my $time_watcher; # can only be used once
805		1491
…		…
810	});	1496	});
811	}	1497	}
812		1498
813	new_timer; # create first timer	1499	new_timer; # create first timer
814		1500
815	$cv->wait; # wait until user enters /^q/i	1501	$cv->recv; # wait until user enters /^q/i
816		1502
817	=head1 REAL-WORLD EXAMPLE	1503	=head1 REAL-WORLD EXAMPLE
818		1504
819	Consider the L<Net::FCP> module. It features (among others) the following	1505	Consider the L<Net::FCP> module. It features (among others) the following
820	API calls, which are to freenet what HTTP GET requests are to http:	1506	API calls, which are to freenet what HTTP GET requests are to http:
…		…
870	syswrite $txn->{fh}, $txn->{request}	1556	syswrite $txn->{fh}, $txn->{request}
871	or die "connection or write error";	1557	or die "connection or write error";
872	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1558	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
873		1559
874	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1560	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
875	result and signals any possible waiters that the request ahs finished:	1561	result and signals any possible waiters that the request has finished:
876		1562
877	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1563	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
878		1564
879	if (end-of-file or data complete) {	1565	if (end-of-file or data complete) {
880	$txn->{result} = $txn->{buf};	1566	$txn->{result} = $txn->{buf};
881	$txn->{finished}->broadcast;	1567	$txn->{finished}->send;
882	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1568	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
883	}	1569	}
884		1570
885	The C<result> method, finally, just waits for the finished signal (if the	1571	The C<result> method, finally, just waits for the finished signal (if the
886	request was already finished, it doesn't wait, of course, and returns the	1572	request was already finished, it doesn't wait, of course, and returns the
887	data:	1573	data:
888		1574
889	$txn->{finished}->wait;	1575	$txn->{finished}->recv;
890	return $txn->{result};	1576	return $txn->{result};
891		1577
892	The actual code goes further and collects all errors (C<die>s, exceptions)	1578	The actual code goes further and collects all errors (C<die>s, exceptions)
893	that occured during request processing. The C<result> method detects	1579	that occurred during request processing. The C<result> method detects
894	whether an exception as thrown (it is stored inside the $txn object)	1580	whether an exception as thrown (it is stored inside the $txn object)
895	and just throws the exception, which means connection errors and other	1581	and just throws the exception, which means connection errors and other
896	problems get reported tot he code that tries to use the result, not in a	1582	problems get reported tot he code that tries to use the result, not in a
897	random callback.	1583	random callback.
898		1584
…		…
929		1615
930	my $quit = AnyEvent->condvar;	1616	my $quit = AnyEvent->condvar;
931		1617
932	$fcp->txn_client_get ($url)->cb (sub {	1618	$fcp->txn_client_get ($url)->cb (sub {
933	...	1619	...
934	$quit->broadcast;	1620	$quit->send;
935	});	1621	});
936		1622
937	$quit->wait;	1623	$quit->recv;
938		1624
939		1625
940	=head1 BENCHMARKS	1626	=head1 BENCHMARKS
941		1627
942	To give you an idea of the performance and overheads that AnyEvent adds	1628	To give you an idea of the performance and overheads that AnyEvent adds
…		…
944	of various event loops I prepared some benchmarks.	1630	of various event loops I prepared some benchmarks.
945		1631
946	=head2 BENCHMARKING ANYEVENT OVERHEAD	1632	=head2 BENCHMARKING ANYEVENT OVERHEAD
947		1633
948	Here is a benchmark of various supported event models used natively and	1634	Here is a benchmark of various supported event models used natively and
949	through anyevent. The benchmark creates a lot of timers (with a zero	1635	through AnyEvent. The benchmark creates a lot of timers (with a zero
950	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1636	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
951	which it is), lets them fire exactly once and destroys them again.	1637	which it is), lets them fire exactly once and destroys them again.
952		1638
953	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	1639	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
954	distribution.	1640	distribution.
…		…
971	all watchers, to avoid adding memory overhead. That means closure creation	1657	all watchers, to avoid adding memory overhead. That means closure creation
972	and memory usage is not included in the figures.	1658	and memory usage is not included in the figures.
973		1659
974	I<invoke> is the time, in microseconds, used to invoke a simple	1660	I<invoke> is the time, in microseconds, used to invoke a simple
975	callback. The callback simply counts down a Perl variable and after it was	1661	callback. The callback simply counts down a Perl variable and after it was
976	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1662	invoked "watcher" times, it would C<< ->send >> a condvar once to
977	signal the end of this phase.	1663	signal the end of this phase.
978		1664
979	I<destroy> is the time, in microseconds, that it takes to destroy a single	1665	I<destroy> is the time, in microseconds, that it takes to destroy a single
980	watcher.	1666	watcher.
981		1667
982	=head3 Results	1668	=head3 Results
983		1669
984	name watchers bytes create invoke destroy comment	1670	name watchers bytes create invoke destroy comment
985	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1671	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
986	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1672	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
987	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1673	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
988	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1674	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
989	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1675	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
990	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1676	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
991	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1677	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
992	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1678	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
993	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1679	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
994	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1680	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
995		1681
996	=head3 Discussion	1682	=head3 Discussion
997		1683
998	The benchmark does I<not> measure scalability of the event loop very	1684	The benchmark does I<not> measure scalability of the event loop very
999	well. For example, a select-based event loop (such as the pure perl one)	1685	well. For example, a select-based event loop (such as the pure perl one)
…		…
1041	file descriptor is dup()ed for each watcher. This shows that the dup()	1727	file descriptor is dup()ed for each watcher. This shows that the dup()
1042	employed by some adaptors is not a big performance issue (it does incur a	1728	employed by some adaptors is not a big performance issue (it does incur a
1043	hidden memory cost inside the kernel which is not reflected in the figures	1729	hidden memory cost inside the kernel which is not reflected in the figures
1044	above).	1730	above).
1045		1731
1046	C<POE>, regardless of underlying event loop (whether using its pure	1732	C<POE>, regardless of underlying event loop (whether using its pure perl
1047	perl select-based backend or the Event module, the POE-EV backend	1733	select-based backend or the Event module, the POE-EV backend couldn't
1048	couldn't be tested because it wasn't working) shows abysmal performance	1734	be tested because it wasn't working) shows abysmal performance and
1049	and memory usage: Watchers use almost 30 times as much memory as	1735	memory usage with AnyEvent: Watchers use almost 30 times as much memory
1050	EV watchers, and 10 times as much memory as Event (the high memory	1736	as EV watchers, and 10 times as much memory as Event (the high memory
1051	requirements are caused by requiring a session for each watcher). Watcher	1737	requirements are caused by requiring a session for each watcher). Watcher
1052	invocation speed is almost 900 times slower than with AnyEvent's pure perl	1738	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1739	implementation.
		1740
1053	implementation. The design of the POE adaptor class in AnyEvent can not	1741	The design of the POE adaptor class in AnyEvent can not really account
1054	really account for this, as session creation overhead is small compared	1742	for the performance issues, though, as session creation overhead is
1055	to execution of the state machine, which is coded pretty optimally within	1743	small compared to execution of the state machine, which is coded pretty
1056	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	1744	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		1745	using multiple sessions is not a good approach, especially regarding
		1746	memory usage, even the author of POE could not come up with a faster
		1747	design).
1057		1748
1058	=head3 Summary	1749	=head3 Summary
1059		1750
1060	=over 4	1751	=over 4
1061		1752
…		…
1072		1763
1073	=back	1764	=back
1074		1765
1075	=head2 BENCHMARKING THE LARGE SERVER CASE	1766	=head2 BENCHMARKING THE LARGE SERVER CASE
1076		1767
1077	This benchmark atcually benchmarks the event loop itself. It works by	1768	This benchmark actually benchmarks the event loop itself. It works by
1078	creating a number of "servers": each server consists of a socketpair, a	1769	creating a number of "servers": each server consists of a socket pair, a
1079	timeout watcher that gets reset on activity (but never fires), and an I/O	1770	timeout watcher that gets reset on activity (but never fires), and an I/O
1080	watcher waiting for input on one side of the socket. Each time the socket	1771	watcher waiting for input on one side of the socket. Each time the socket
1081	watcher reads a byte it will write that byte to a random other "server".	1772	watcher reads a byte it will write that byte to a random other "server".
1082		1773
1083	The effect is that there will be a lot of I/O watchers, only part of which	1774	The effect is that there will be a lot of I/O watchers, only part of which
1084	are active at any one point (so there is a constant number of active	1775	are active at any one point (so there is a constant number of active
1085	fds for each loop iterstaion, but which fds these are is random). The	1776	fds for each loop iteration, but which fds these are is random). The
1086	timeout is reset each time something is read because that reflects how	1777	timeout is reset each time something is read because that reflects how
1087	most timeouts work (and puts extra pressure on the event loops).	1778	most timeouts work (and puts extra pressure on the event loops).
1088		1779
1089	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	1780	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1090	(1%) are active. This mirrors the activity of large servers with many	1781	(1%) are active. This mirrors the activity of large servers with many
1091	connections, most of which are idle at any one point in time.	1782	connections, most of which are idle at any one point in time.
1092		1783
1093	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	1784	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1094	distribution.	1785	distribution.
…		…
1096	=head3 Explanation of the columns	1787	=head3 Explanation of the columns
1097		1788
1098	I<sockets> is the number of sockets, and twice the number of "servers" (as	1789	I<sockets> is the number of sockets, and twice the number of "servers" (as
1099	each server has a read and write socket end).	1790	each server has a read and write socket end).
1100		1791
1101	I<create> is the time it takes to create a socketpair (which is	1792	I<create> is the time it takes to create a socket pair (which is
1102	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	1793	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1103		1794
1104	I<request>, the most important value, is the time it takes to handle a	1795	I<request>, the most important value, is the time it takes to handle a
1105	single "request", that is, reading the token from the pipe and forwarding	1796	single "request", that is, reading the token from the pipe and forwarding
1106	it to another server. This includes deleting the old timeout and creating	1797	it to another server. This includes deleting the old timeout and creating
…		…
1140		1831
1141	=head3 Summary	1832	=head3 Summary
1142		1833
1143	=over 4	1834	=over 4
1144		1835
1145	=item * The pure perl implementation performs extremely well, considering	1836	=item * The pure perl implementation performs extremely well.
1146	that it uses select.
1147		1837
1148	=item * Avoid Glib or POE in large projects where performance matters.	1838	=item * Avoid Glib or POE in large projects where performance matters.
1149		1839
1150	=back	1840	=back
1151		1841
…		…
1180	speed most when you have lots of watchers, not when you only have a few of	1870	speed most when you have lots of watchers, not when you only have a few of
1181	them).	1871	them).
1182		1872
1183	EV is again fastest.	1873	EV is again fastest.
1184		1874
1185	The C-based event loops Event and Glib come in second this time, as the	1875	Perl again comes second. It is noticeably faster than the C-based event
1186	overhead of running an iteration is much smaller in C than in Perl (little	1876	loops Event and Glib, although the difference is too small to really
1187	code to execute in the inner loop, and perl's function calling overhead is	1877	matter.
1188	high, and updating all the data structures is costly).
1189
1190	The pure perl event loop is much slower, but still competitive.
1191		1878
1192	POE also performs much better in this case, but is is still far behind the	1879	POE also performs much better in this case, but is is still far behind the
1193	others.	1880	others.
1194		1881
1195	=head3 Summary	1882	=head3 Summary
…		…
1200	watchers, as the management overhead dominates.	1887	watchers, as the management overhead dominates.
1201		1888
1202	=back	1889	=back
1203		1890
1204		1891
		1892	=head1 SIGNALS
		1893
		1894	AnyEvent currently installs handlers for these signals:
		1895
		1896	=over 4
		1897
		1898	=item SIGCHLD
		1899
		1900	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		1901	emulation for event loops that do not support them natively. Also, some
		1902	event loops install a similar handler.
		1903
		1904	=item SIGPIPE
		1905
		1906	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		1907	when AnyEvent gets loaded.
		1908
		1909	The rationale for this is that AnyEvent users usually do not really depend
		1910	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		1911	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		1912	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		1913	some random socket.
		1914
		1915	The rationale for installing a no-op handler as opposed to ignoring it is
		1916	that this way, the handler will be restored to defaults on exec.
		1917
		1918	Feel free to install your own handler, or reset it to defaults.
		1919
		1920	=back
		1921
		1922	=cut
		1923
		1924	$SIG{PIPE} = sub { }
		1925	unless defined $SIG{PIPE};
		1926
		1927
1205	=head1 FORK	1928	=head1 FORK
1206		1929
1207	Most event libraries are not fork-safe. The ones who are usually are	1930	Most event libraries are not fork-safe. The ones who are usually are
1208	because they are so inefficient. Only L<EV> is fully fork-aware.	1931	because they rely on inefficient but fork-safe C<select> or C<poll>
		1932	calls. Only L<EV> is fully fork-aware.
1209		1933
1210	If you have to fork, you must either do so I<before> creating your first	1934	If you have to fork, you must either do so I<before> creating your first
1211	watcher OR you must not use AnyEvent at all in the child.	1935	watcher OR you must not use AnyEvent at all in the child.
1212		1936
1213		1937
…		…
1221	specified in the variable.	1945	specified in the variable.
1222		1946
1223	You can make AnyEvent completely ignore this variable by deleting it	1947	You can make AnyEvent completely ignore this variable by deleting it
1224	before the first watcher gets created, e.g. with a C<BEGIN> block:	1948	before the first watcher gets created, e.g. with a C<BEGIN> block:
1225		1949
1226	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1950	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1227		1951
1228	use AnyEvent;	1952	use AnyEvent;
		1953
		1954	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		1955	be used to probe what backend is used and gain other information (which is
		1956	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		1957	$ENV{PERL_ANYEGENT_STRICT}.
		1958
		1959
		1960	=head1 BUGS
		1961
		1962	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		1963	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		1964	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		1965	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		1966	pronounced).
1229		1967
1230		1968
1231	=head1 SEE ALSO	1969	=head1 SEE ALSO
1232		1970
1233	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	1971	Utility functions: L<AnyEvent::Util>.
1234	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	1972
		1973	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1235	L<Event::Lib>, L<Qt>, L<POE>.	1974	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1236		1975
1237	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	1976	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1238	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	1977	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1239	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	1978	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1240	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.	1979	L<AnyEvent::Impl::POE>.
1241		1980
		1981	Non-blocking file handles, sockets, TCP clients and
		1982	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.
		1983
		1984	Asynchronous DNS: L<AnyEvent::DNS>.
		1985
		1986	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,
		1987
1242	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	1988	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.
1243		1989
1244		1990
1245	=head1 AUTHOR	1991	=head1 AUTHOR
1246		1992
1247	Marc Lehmann <schmorp@schmorp.de>	1993	Marc Lehmann <schmorp@schmorp.de>
1248	http://home.schmorp.de/	1994	http://home.schmorp.de/
1249		1995
1250	=cut	1996	=cut
1251		1997
1252	1	1998	1
1253		1999

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